JP7720728B2 - Hydrogenated block copolymer, elastomer composition containing hydrogenated block copolymer, seal member, stopper and medicine stopper each made of elastomer composition - Google Patents

Description

The present invention relates to hydrogenated block copolymers, elastomer compositions containing hydrogenated block copolymers, and sealing members, stoppers, and drug stoppers made from the elastomer compositions.

Block copolymers composed of vinyl aromatic monomer units and conjugated diene monomer units have elasticity at room temperature similar to that of vulcanized natural or synthetic rubber, even without vulcanization, and at high temperatures they have moldability similar to that of thermoplastic resins. Therefore, they are widely used in fields such as footwear, plastic modification, asphalt modification, adhesives, household products, packaging materials for home appliances and industrial parts, toys, etc. Furthermore, hydrogenated products of these block copolymers (hydrogenated block copolymers) have excellent weather resistance and heat resistance, and are therefore widely used in automotive parts, medical devices, and other applications in addition to the above-mentioned fields.

In particular, high-molecular-weight hydrogenated block copolymers have excellent mechanical properties in addition to the various properties mentioned above, and are therefore used in combination with liquid softeners such as oil, plasticizers, and thermoplastic resins such as polypropylene as materials for various industrial parts such as electric wires and cables, automobile parts, medical stoppers, syringe gaskets, and more.

Of the polymers used in these applications, linear triblock polymer SEBS (styrene-ethylene-butylene-styrene) (polystyrene-equivalent molecular weight of approximately 200,000 to 500,000) is widely used due to its particularly excellent heat resistance and mechanical strength.

For example, Patent Document 1 describes the production of a crumb-like product from high-molecular-weight SEBS with a main peak molecular weight of 200,000 to 600,000.

For example, Patent Document 2 describes SEBS with a number average molecular weight of 50,000 to 600,000.

Furthermore, Patent Document 3 describes a composition containing an SEBS structure with a number average molecular weight of 250,000 or more.

Patent Document 4 also describes a coupling-type polymeric SEBS in which the molecular weight of the coupling moiety is essentially between 15,000 and 300,000.

Patent Document 5 also describes a coupling-type, radially structured polymeric SEBS with a diblock peak molecular weight of 230,000 to 275,000.

Patent Document 6 also describes a medical rubber stopper molded from a resin composition containing a hydrogenated block copolymer, a hydrocarbon-based rubber softener, and a polyolefin-based resin.

Furthermore, Patent Document 7 describes a composition that has an excellent balance of resealability, coring resistance, and needle puncture resistance.

Patent Document 8 also describes a composition that, by incorporating special surface-treated silica, achieves an excellent balance of resealability, coring resistance, and needle puncture resistance.

Patent No. 5591346 Patent No. 2764746 Japanese Patent Application Laid-Open No. 2001-240720 Patent No. 3378582 Patent No. 5324426 Patent No. 5703990 International Publication No. 2018/139122 Japanese Patent Application Laid-Open No. 2020-19947

However, linear polymer triblock SEBS has an extremely high viscosity, which reduces its mixability with other resins, resulting in issues such as residual melting during compound processing (i.e., the formation of lumps), poor appearance during injection molding, and poor thin-film formability.

Furthermore, high viscosity is undesirable even during the manufacturing stage of SEBS.

Specifically, when linear triblock SEBS with a molecular weight of 250,000 or more is produced using typical living anionic polymerization in the polymerization process, the amount of polymerization initiator is extremely small. Trace amounts of deactivating components (impurities) contained in the solvent and monomer significantly affect the molecular weight, resulting in low yields. Avoiding this requires extensive purification of the solvent and monomer, but this is economically disadvantageous. Furthermore, during the hydrogenation reaction, the efficiency of hydrogen diffusion within the system decreases, potentially requiring an extremely long time to achieve the desired hydrogenation rate, resulting in reduced productivity. Furthermore, during the desolvation process, which consists of a typical steam stripping and dehydration extrusion process, excessive loads on the driving equipment can cause equipment damage, polymer chain scission, and even fire. Furthermore, since the product is often powdery after drying, it adheres to the process, resulting in reduced yields and contamination.

Furthermore, Patent Document 1 also shows that a crumb-like product was successfully obtained from high-molecular-weight SEBS with a main peak molecular weight of 200,000 to 600,000, but that the manufacturing method is not easy, requiring ingenuity in the finishing process.

In particular, the aforementioned issues that occur during processing and molding must be resolved as a priority, and measures such as adding oil or increasing the amount added have been taken to improve compounding and molding processability, but maintaining heat resistance and mechanical strength is difficult, and this is not sufficient from the perspective of balancing compounding and molding processability with high heat resistance and high mechanical strength, nor is it sufficient from the perspective of reducing particles. To resolve these issues, it would be preferable to use a high-molecular-weight SEBS of the coupling type rather than a linear type, but this has not been fully explored.

Furthermore, while Patent Document 2 describes coupling types in the specification for SEBS with a number average molecular weight of 50,000 to 600,000, there is no mention of these types in the examples, and the maximum number average molecular weight is approximately 300,000.

Furthermore, Patent Document 3 also describes a coupling type in the specification for compositions containing an SEBS structure with a number average molecular weight of 250,000 or more, but, like Patent Document 2, there is no mention of this in the examples, and the maximum number average molecular weight of the SEBS structure is 280,000.

Furthermore, in Patent Document 4, in coupling-type polymer SEBS, the coupling portion is limited to a linear type, and there is no mention of a radial structure.

Furthermore, in Patent Document 5, the diblock content in the coupling-type radial structure polymer SEBS is extremely low, and in the examples, there is also little radial structure component with three or more branches, so essentially no structural optimization focusing primarily on the radial structure has been performed.

Therefore, there is still room for improvement in conventional coupling-type polymer SEBS, particularly polymer SEBS primarily based on a radial structure, in terms of the balance between processability, heat resistance (low compression set), and the lack of particles when formed into a composition.

In addition, when used as a medicine stopper, in addition to the balance of the above-mentioned compounding and molding processability, high heat resistance, high mechanical strength, and low particle generation, an excellent balance of resealability, coring resistance, needle puncture resistance, oil bleed resistance, and low odor is required.

In Patent Document 6, sealing tests were conducted using sealed PET bottles with a small amount of liquid, but sealing performance when using bag-shaped containers was not verified. Furthermore, the resealability of containers using stoppers when a needle is pierced for a long period of time under atmospheric pressure conditions with an air hole opened in the stopper, and when the amount of liquid was large, was still insufficient.

Furthermore, the composition described in Patent Document 7 must contain polyphenylene ether resin, and a relatively large amount of non-aromatic softener must be blended in to adjust hardness, which raises concerns about oil bleeding and odors derived from the polyphenylene ether resin.

Furthermore, the composition described in Patent Document 8 requires the incorporation of a relatively large amount of a non-aromatic softener due to its high hardness, which raises concerns about oil bleeding and requires special silica, making it unsuitable for general use.

In view of the above-mentioned problems with the conventional technology, the present invention aims to provide a hydrogenated block copolymer and an elastomer composition containing a hydrogenated block copolymer that exhibit an excellent balance between processability and low compression set, and that, when used in medicine stoppers, exhibit an excellent balance of resealability, coring resistance, and needle puncture resistance.

As a result of extensive research into resolving the problems of the prior art, the inventors discovered that coupling-type hydrogenated block copolymers having specific structures and elastomer compositions containing hydrogenated block copolymers effectively resolve the problems described above, leading to the completion of the present invention.

That is, the present invention is as follows.
[1]
A hydrogenated block copolymer (P) obtained by hydrogenating a coupling polymer represented by the following formula (1):
(A-B)n-X (1)
[In formula (1), A is a polymer block mainly composed of vinyl aromatic monomer units, B is a polymer block mainly composed of conjugated diene monomer units, n is an integer of 1 or more, and X is a residue of a coupling agent or a residue of a polymerization initiator.]
the content of vinyl aromatic monomer units in the hydrogenated block copolymer (P) is 10% by mass to 40% by mass,
The peak top molecular weight of the diblock component corresponding to (A-B) in the above formula (1) is 160,000 to 225,000,
the proportion of the bibranched component corresponding to the case where n is 2 in the above formula (1) is 10% by mass to 30% by mass of the total hydrogenated block copolymer (P),
the proportion of the three-branched component corresponding to the case where n in the above formula (1) is 3 is 40% by mass to 70% by mass of the total hydrogenated block copolymer (P),
A hydrogenated block copolymer, wherein the ratio M of tri-branched components to di-branched components (mass of tri-branched components/mass of di-branched components) is 2 or more.
[2]
The hydrogenated block copolymer according to [1], wherein the proportion of the diblock component is 10% by mass to 40% by mass of the entire hydrogenated block copolymer (P).
[3]
The hydrogenated block copolymer according to [1] or [2], wherein the proportion of components with 4 or more branches, corresponding to the case where n in formula (1) is an integer of 4 or more, is 10% by mass or less of the total hydrogenated block copolymer (P).
[4]
The hydrogenated block copolymer according to any one of [1] to [3], wherein the weight average molecular weight of the entire hydrogenated block copolymer (P) is 350,000 to 500,000.
[5]
The hydrogenated block copolymer according to any one of [1] to [4], wherein the ratio of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units in the hydrogenated block copolymer (P) is 50 mol % to 80 mol %.
[6]
The hydrogenated block copolymer according to any one of [1] to [5], wherein the hydrogenation rate of the conjugated diene monomer units in the hydrogenated block copolymer (P) is 80 mol % or more.
[7]
An elastomer composition comprising the hydrogenated block copolymer according to any one of [1] to [6].
[8]
The elastomer composition according to [7], comprising 10 to 50 parts by mass of a polypropylene resin and 30 to 200 parts by mass of a non-aromatic softener relative to 100 parts by mass of the hydrogenated block copolymer.
[9]
The elastomer composition according to [7] or [8], wherein when an elastomer composition sheet produced under the following conditions is cut into a 10 cm x 10 cm piece and both surfaces are observed under a microscope, the number of particles having a diameter of 200 μm or more calculated by the following formula is 0;
[Production of elastomer composition sheet]
The sheet material containing the hydrogenated block copolymer is melt-kneaded in a twin-screw extruder at a set temperature of 230°C, and a 500 µm-thick elastomer composition sheet is produced using a T-die at a screw rotation speed of 300 rpm [calculation formula for the number of particles]
Number of bumps = total number of bumps with a diameter of 200 μm or more observed [number] * Y/X
(In the formula, X is the weight (g) of the composition sheet, Y is the amount (g) of the hydrogenated block copolymer in the composition sheet, and the calculated value is rounded to one decimal place to obtain the number of particles.)
[10]
The elastomer composition according to any one of [7] to [9], which does not contain a polyphenylene ether resin.
[11]
The elastomer composition according to any one of [7] to [10], which does not contain surface-treated silica.
[12]
The elastomer composition according to any one of [7] to [9], which does not contain a polyphenylene ether resin or surface-treated silica.
[13]
A sealing member made of the elastomer composition according to any one of [7] to [12].
[14]
A plug made of the elastomer composition according to any one of [7] to [12].
[15]
A drug stopper for medical use, comprising the elastomer composition according to any one of [7] to [12].

The hydrogenated block copolymer of the present invention has an excellent balance of processability and low compression set, and when used in medicine stoppers, it has an excellent balance of resealability, coring resistance, and needle puncture resistance.

FIG. 1 shows a schematic diagram of an example of a plug. FIG. 2 shows a schematic diagram of an example of a jig.

The following provides a detailed description of an embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to the following description and can be modified in various ways within the scope of its gist.

[Hydrogenated Block Copolymer]
The hydrogenated block copolymer of the present embodiment is a hydrogenated block copolymer (P) obtained by hydrogenating a coupling polymer represented by the following formula (1):
(A-B)n-X (1)
[In formula (1), A is a polymer block mainly composed of vinyl aromatic monomer units, B is a polymer block mainly composed of conjugated diene monomer units, n is an integer of 1 or more, and X is a residue of a coupling agent or a residue of a polymerization initiator.]
the content of vinyl aromatic monomer units in the hydrogenated block copolymer (P) is 10% by mass to 40% by mass,
The peak top molecular weight of the diblock component corresponding to (A-B) in the above formula (1) is 160,000 to 225,000,
the proportion of the bibranched component corresponding to the case where n is 2 in the above formula (1) is 10% by mass to 30% by mass of the total hydrogenated block copolymer (P),
the proportion of the three-branched component corresponding to the case where n in the above formula (1) is 3 is 40% by mass to 70% by mass of the total hydrogenated block copolymer (P),
The ratio M of the three-branched component to the two-branched component (mass of the three-branched component/mass of the two-branched component) is 2 or more.

Conventionally, when viscosity is reduced to improve processability, mechanical properties such as low compression set typically decrease. However, the hydrogenated block copolymer of this embodiment, with the above-described configuration, can achieve a balanced improvement in both processability and low compression set.

In this embodiment, the naming of each monomer unit constituting the block copolymer follows the naming of the monomer from which the monomer unit is derived.

For example, a "vinyl aromatic monomer unit" refers to a structural unit of a polymer resulting from the polymerization of a vinyl aromatic compound monomer. A vinyl aromatic monomer unit is bonded to other monomer units via the vinyl group of the vinyl aromatic compound.

Furthermore, "conjugated diene monomer unit" refers to a structural unit of a polymer resulting from the polymerization of a conjugated diene compound as a monomer. A conjugated diene monomer unit is bonded to another monomer unit through one of the two double bonds of the conjugated diene compound (1,2-bond or 3,4-bond), or is bonded to another monomer unit through both of the two double bonds of the conjugated diene compound (1,4-bond).

The hydrogenated block copolymer (P) of this embodiment includes a polymer block A (hereinafter also simply referred to as "polymer block A") primarily composed of vinyl aromatic monomer units, and a polymer block B (hereinafter also simply referred to as "polymer block B") primarily composed of conjugated diene monomer units.

Here, "mainly composed of vinyl aromatic monomer units" means that the amount of vinyl aromatic monomer units contained in polymer block A is 75% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more, based on polymer block A. Also, "mainly composed of conjugated diene monomer units" means that the amount of conjugated diene monomer units contained in polymer block B is 90% by mass or more, preferably 96% by mass or more, and more preferably 99% by mass or more, based on polymer block B.

The "vinyl aromatic compound" constituting the "vinyl aromatic monomer unit" is not limited to the following, but examples include styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, and N,N-diethyl-p-aminoethylstyrene. Of these, styrene, α-methylstyrene, and p-methylstyrene are preferred from the standpoints of availability and productivity. Of these, styrene is particularly preferred. These compounds may be used alone or in combination of two or more.

The "conjugated diene compound" that constitutes the "conjugated diene monomer unit" is a diolefin having one pair of conjugated double bonds. Examples of conjugated diene compounds include, but are not limited to, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, and farnesene. Preferred diolefins include 1,3-butadiene and isoprene. These may be used alone or in combination of two or more.

(structure)
The structure of the hydrogenated block copolymer (P) of this embodiment is a structure obtained by hydrogenating a coupling polymer represented by the following formula (1).
(A-B)n-X (1)
[In formula (1), A is a polymer block mainly composed of vinyl aromatic monomer units, B is a polymer block mainly composed of conjugated diene monomer units, n is an integer of 1 or more, and X is a residue of a coupling agent or a residue of a polymerization initiator.]

A hydrogenated block copolymer (P) having such a structure can be obtained, for example, by polymerizing polymer block A and polymer block B in that order, and then hydrogenating the resulting coupling polymer.

In addition, in the hydrogenated block copolymer (P) of this embodiment, the proportion of bibranched components, which corresponds to n = 2 in the above formula (1), is 10% to 30% by mass, preferably 10% to 20% by mass, and more preferably 12% to 18% by mass of the total hydrogenated block copolymer (P). In addition, in the hydrogenated block copolymer (P) of this embodiment, the proportion of tribranched components, which corresponds to n = 3 in the above formula (1), is 40% to 70% by mass, preferably 45% to 65% by mass, and more preferably 50% to 60% by mass of the total hydrogenated block copolymer (P). In addition, in the hydrogenated block copolymer (P) of this embodiment, the ratio of tribranched components to bibranched components (tribranched component mass/bibranched component mass) is 2 or more, preferably 2 to 7, and more preferably 2 to 6.

By ensuring that the ratio of each component in the hydrogenated block copolymer (P) of this embodiment is within the above range, it is possible to increase the molecular weight while suppressing an increase in viscosity, thereby improving the compression set and, when molded into a medicine stopper, tending to have an excellent balance of resealability, coring resistance, and needlestick resistance.

From the perspective of balancing improved compression set and increased viscosity, hydrogenated block copolymer (P) preferably contains more multi-branched structures with three or more branches. It may also contain higher-branched structures with four or more branches. However, from the perspective of improving the balance between increased viscosity and compression set, it is preferable for the hydrogenated block copolymer (P) to contain more tri-branched components. While containing four or more branches in the hydrogenated block copolymer (P) slightly improves compression set, it also tends to result in a significant increase in viscosity, worsening the performance balance and making it difficult to stably control the degree of branching. Furthermore, when hydrogenated block copolymer (P) with four or more branches is molded into a medicine stopper, its coring resistance tends to be significantly impaired. Therefore, it is preferable for the hydrogenated block copolymer (P) to be primarily tri-branched components. More preferably, the proportion of four or more branches is 10% by mass or less of the total hydrogenated block copolymer (P), more preferably 9% by mass or less, and even more preferably 8% by mass or less. The lower limit of the proportion of four or more branches is not particularly limited, but is, for example, 1% by mass of the total hydrogenated block copolymer (P). On the other hand, it is preferable to reduce as much as possible the bibranched components produced in the process primarily consisting of tribranched components. However, reducing the proportion of bibranched components, particularly to less than 10% by mass, requires thorough control of deactivated components (impurities) in the solvent and monomer, and strict control of the purity of the coupling agent, as described below, which is not economical. From the perspectives of practicality, a good balance of viscosity and compression set, and a balance of resealability and needle puncture resistance when molded into a medicine stopper, the ratio of tribranched components to bibranched components (tribranched component mass/bibranched component mass) is 2 or greater.

Furthermore, in the hydrogenated block copolymer (P) of this embodiment, when n = 1 in the above formula (1), i.e., the diblock component corresponding to (A-B) (hereinafter also referred to simply as "diblock component"), is preferably contained in 10% to 40% by mass of the entire hydrogenated block copolymer (P), more preferably 15% to 35% by mass, and even more preferably 20% to 30% by mass, from the viewpoint of the balance between compression set and viscosity. Furthermore, when molded into a medicine stopper, an excellent balance between resealability and needlestick resistance is achieved by having the diblock component amount within the above range. When the diblock component amount is equal to or greater than the lower limit, needlestick resistance tends to be good, and when the diblock component amount is equal to or less than the upper limit, resealability tends to be good.

Coupling agents are not particularly limited as long as they achieve the above-mentioned mass ratios of each branching component, but examples include polyalkenyl coupling agents. Suitable polyalkenyl coupling agents are not particularly limited, but examples include divinylbenzene, with m-divinylbenzene being preferred. Coupling agents are also not particularly limited, but examples include tetraalkoxysilanes such as tetraethoxysilane and tetramethoxysilane, alkyltrialkoxysilanes such as methyltrimethoxysilane, dialkyldialkoxysilanes such as dimethyldimethoxysilane, carboxylic acid ester compounds such as ethyl benzoate and methyl benzoate, tetrafunctional halogenated alkanes such as carbon tetrachloride, carbon tetrabromide, and tetrachloroethane, and diglycidyl aromatic epoxy compounds such as diglycidyl ether derived from the reaction of bisphenol A with epichlorohydrin. These agents may be used alone or in combination; however, to obtain the desired branched structure alone, it is preferable to use tetramethoxysilane or tetraethoxysilane.

The proportion of each of the above branched components can be controlled by adjusting the amount of coupling agent added relative to the amount of polymerization initiator added and the temperature during the coupling reaction, depending on the type of coupling agent. Furthermore, when the terminal structure during coupling is a vinyl aromatic monomer, branching tends to be suppressed and the amount of bibranched components tends to increase compared to when the terminal structure is a conjugated diene monomer. Therefore, it is preferable to adjust the terminal structure to be a conjugated diene monomer.

The proportion of each branched component can be determined by, for example, vertically dividing each peak obtained by gel permeation chromatography (GPC) (solvent: tetrahydrofuran, temperature: 40°C) at the inflection point between each peak. Detailed measurement conditions are shown in the examples.

(molecular weight)
The peak top molecular weight of the diblock component in the hydrogenated block copolymer (P) of this embodiment is 160,000 to 225,000, preferably 170,000 to 200,000. When the peak top molecular weight of the diblock component is within this range, the balance between low compression set and processability tends to be excellent. Furthermore, when the peak top molecular weight of the diblock component is within this range, the balance between resealability and needlestick resistance also tends to be excellent when used as a medicine stopper. When the peak top molecular weight of the diblock component is equal to or greater than the lower limit, the needlestick resistance tends to be good, and when the peak top molecular weight of the diblock component is equal to or less than the upper limit, the resealability tends to be good.

In addition, the weight-average molecular weight of the entire hydrogenated block copolymer (P) of this embodiment is preferably 350,000 to 500,000, more preferably 370,000 to 470,000, and even more preferably 400,000 to 450,000. When the weight-average molecular weight of the hydrogenated block copolymer (P) of this embodiment is equal to or greater than the lower limit, the compression set is improved. When the weight-average molecular weight is equal to or less than the upper limit, the processability is improved by reducing the viscosity while maintaining the improved compression set. Furthermore, when the weight-average molecular weight of the entire hydrogenated block copolymer (P) is within the above range, an excellent balance is achieved between resealability and needlestick resistance when used as a medicine stopper. When the weight-average molecular weight of the entire hydrogenated block copolymer (P) is equal to or greater than the lower limit, the needlestick resistance tends to be good, and when the weight-average molecular weight of the entire hydrogenated block copolymer (P) is equal to or less than the upper limit, the resealability tends to be good.

The peak top molecular weight of the diblock component can be determined by calculating the molecular weight corresponding to the top of the peak obtained by gel permeation chromatography (GPC) (solvent: tetrahydrofuran, temperature: 40°C) from a standard polystyrene calibration curve. The weight average molecular weight of the entire hydrogenated block copolymer (P) can also be determined using the same instrument. Detailed measurement conditions are shown in the Examples.

(Vinyl aromatic monomer unit content)
The content of the vinyl aromatic monomer unit in the hydrogenated block copolymer (P) of this embodiment is 10% by mass to 40% by mass, preferably 15% by mass to 35% by mass, and more preferably 20% by mass to 30% by mass. When the content of the vinyl aromatic monomer unit in the hydrogenated block copolymer (P) of this embodiment is equal to or greater than the lower limit, the compression set is improved and blocking of the hydrogenated block copolymer itself can be suppressed. When the content of the vinyl aromatic monomer unit in the hydrogenated block copolymer (P) of this embodiment is equal to or less than the upper limit, the viscosity is reduced and the compression set is also good. Furthermore, by setting the content of the vinyl aromatic monomer unit in the hydrogenated block copolymer (P) within the above range, an excellent balance of coring resistance, needlestick resistance, and oil-bleed resistance is achieved when the copolymer is molded into a medicine stopper. When the content of the vinyl aromatic monomer unit in the hydrogenated block copolymer (P) is equal to or greater than the above-mentioned lower limit, the needle puncture resistance is improved, and when the content of the vinyl aromatic monomer unit in the hydrogenated block copolymer (P) is equal to or less than the above-mentioned upper limit, the needle puncture resistance is good, and the core resistance tends to be improved, and the oil bleed resistance is also further improved.

The content of vinyl aromatic monomer units in the hydrogenated block copolymer (P) can be measured using an ultraviolet spectrophotometer as described in the Examples below.

The content of vinyl aromatic monomer units in the hydrogenated copolymer composition can be controlled within the above-mentioned specified numerical range by adjusting the amount of vinyl aromatic compound added in the polymerization process.

(Content of conjugated diene monomer units)
The content of the conjugated diene monomer units in the hydrogenated block copolymer (P) of the present embodiment is preferably 60% by mass to 90% by mass, more preferably 65% by mass to 85% by mass, and even more preferably 70% by mass to 80% by mass.

(Proportion of 1,2-bonds and 3,4-bonds in conjugated diene monomer units)
In the hydrogenated block copolymer (P) of this embodiment, the conjugated diene monomer units before hydrogenation are incorporated into the copolymer via a 1,2-bond, a 3,4-bond, or a 1,4-bond. The ratio of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units in the hydrogenated block copolymer (P) of this embodiment, i.e., the total ratio of conjugated diene monomer units incorporated via a 1,2-bond or a 3,4-bond, is preferably 50 mol% to 80 mol%, more preferably 55 mol% to 75 mol%, and even more preferably 60 mol% to 70 mol%, based on the total of conjugated diene monomer units incorporated via a 1,2-bond, a 3,4-bond, or a 1,4-bond. When the ratio of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units in the hydrogenated block copolymer (P) of this embodiment is equal to or greater than the lower limit, crystallinity after the hydrogenation reaction described below is suppressed, maintaining low viscosity. Furthermore, the composition exhibits moderate compatibility with the polypropylene-based resin, thereby reducing the formation of particles (i.e., undissolved hydrogenated block copolymers) and preventing excessive oil bleed-through from being released into the polypropylene-based resin. The term "pimples" used herein refers to protrusions primarily composed of the hydrogenated block copolymer that appear on the smooth surface of a thermoplastic elastomer composition sheet produced according to the method described in the Examples below. While "pimples" can vary in size, the issue here is those with a diameter of 200 μm or greater in a thermoplastic elastomer composition sheet obtained under the production conditions described in the Examples below. Pimples with a diameter of 200 μm or greater may cause deterioration in resealability and coring resistance when the sheet is molded into a medicine stopper. Here, "diameter" is defined as the maximum diameter of the object.
The proportions of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units can be controlled by adjusting the Lewis base (for example, ether, amine, etc.), the amount thereof used, and the polymerization temperature. When the proportions of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units are 80 mol % or less, there is no need to adjust the polymerization temperature to a low temperature in order to obtain the hydrogenated block copolymer (P), and this is economical in terms of production.

In this embodiment, the ratio of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units can be measured by nuclear magnetic resonance spectroscopy ( ¹ H-NMR) or the like. The ratio of 1,2-bonds and 3,4-bonds may be measured either before or after hydrogenation. Specifically, the ratio can be measured by the method described in the Examples below.

(Hydrogenation rate in conjugated diene monomer units)
The double bonds of the conjugated diene monomer units contained in the hydrogenated block copolymer (P) of this embodiment are hydrogenated. The proportion of hydrogenated double bonds in the conjugated diene monomer units (hereinafter also referred to as the "hydrogenation rate in the conjugated diene monomer units") is 80 mol% or more, preferably 85 mol% or more, and more preferably 90 mol% or more. In the hydrogenated block copolymer (P) of this embodiment, if the hydrogenation rate in the conjugated diene monomer units is 80 mol% or more, the compression set tends to be good and, when formed into a composition, a suitably good compatibility with polypropylene-based resins can be obtained. The upper limit of the hydrogenation rate in the conjugated diene monomer units is 100 mol%.

The hydrogenation rate of the conjugated diene monomer units can be controlled, for example, by adjusting the amount of catalyst and the amount of hydrogen fed during the hydrogenation reaction. The hydrogenation reaction rate can be controlled, for example, by adjusting the amount of catalyst, the amount of hydrogen fed, the pressure, the temperature, etc. during hydrogenation.

The hydrogenation rate of the conjugated diene monomer units can be measured by the method described in the Examples below.

[Method for producing hydrogenated block copolymer (P)]
The hydrogenated block copolymer (P) of the present embodiment can be produced, for example, by carrying out polymerization in an organic solvent using an organic alkali metal compound as a polymerization initiator to obtain a copolymer, and then carrying out a hydrogenation reaction.

The polymerization method may be batch polymerization, continuous polymerization, or a combination of these. From the viewpoint of obtaining a copolymer with a narrow molecular weight distribution, batch polymerization is preferred.

The polymerization temperature is generally 0°C to 150°C, preferably 20°C to 120°C, more preferably 40°C to 100°C, and even more preferably 40°C to 80°C.

The polymerization time varies depending on the desired polymer, but is usually within 24 hours, preferably 0.1 to 10 hours. From the perspective of obtaining a copolymer with a narrow molecular weight distribution and high strength, a time of 0.5 to 3 hours is more preferable.

The polymerization pressure is not particularly limited, as long as it is within a range of pressure sufficient to maintain the nitrogen and solvent in a liquid phase.

It is preferable that the polymerization system be free of impurities that may inactivate the polymerization initiator and living polymer, such as water, oxygen, and carbon dioxide.

The organic solvent is not particularly limited, but examples include aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclohexane, cycloheptane, and methylcyclopentane; and aromatic hydrocarbons such as benzene, xylene, toluene, and ethylbenzene.

Organolithium compounds are preferred as the organic alkali metal compound used as the polymerization initiator.

The organolithium compound is not particularly limited, but examples thereof include organomonolithium compounds, organodilithium compounds, and organopolylithium compounds. Examples of organolithium compounds include, but are not limited to, ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, phenyllithium, hexamethylenedilithium, butadienyllithium, and isopropenyldilithium. Among these, n-butyllithium and sec-butyllithium are preferred from the viewpoint of polymerization activity.

The amount of organic alkali metal compound used as a polymerization initiator varies depending on the molecular weight of the desired polymer, but is generally preferably in the range of 0.01 phm to 0.5 phm (parts by mass per 100 parts by mass of monomer), more preferably in the range of 0.03 phm to 0.3 phm, and even more preferably in the range of 0.05 phm to 0.15 phm.

The total amount of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units of the hydrogenated block copolymer (P) before hydrogenation can be controlled by using a Lewis base (e.g., ether, amine, etc.). The amount of Lewis base used is adjusted depending on the desired ratio of 1,2-bonds and 3,4-bonds. Furthermore, by adding the Lewis base and the metal alkoxide described below under two or more separate conditions, it is possible to produce a polymer primarily composed of conjugated diene monomer units with different ratios of 1,2-bonds and 3,4-bonds.

Examples of Lewis bases include, but are not limited to, ether compounds, ether compounds having two or more oxygen atoms, and tertiary amine compounds.

Tertiary amine compounds include, but are not limited to, pyridine, N,N,N',N'-tetramethylethylenediamine, tributylamine, tetramethylpropanediamine, 1,2-dipiperidinoethane, bis[2-(N,N-dimethylamino)ethyl]ether, etc. These may be used alone or in combination of two or more.

Preferred tertiary amine compounds are compounds containing two amines. Furthermore, among these, compounds with a symmetrical structure within the molecule are more preferred, with N,N,N',N'-tetramethylethylenediamine, bis[2-(N,N-dimethylamino)ethyl]ether, and 1,2-dipiperidinoethane being even more preferred.

In the production process for the hydrogenated block copolymer (P) of this embodiment, polymerization may be carried out in the coexistence of the above-mentioned Lewis base, organolithium compound, and alkali metal alkoxide. Here, the alkali metal alkoxide is a compound represented by the general formula MOR (where M is an alkali metal and R is an alkyl group).

The alkali metal in the alkali metal alkoxide is preferably sodium or potassium, from the viewpoints of a high ratio of 1,2-bonds and 3,4-bonds, a narrow molecular weight distribution, and a high polymerization rate.

Although alkali metal alkoxides are not limited to the following, preferred examples include sodium alkoxides, lithium alkoxides, and potassium alkoxides having an alkyl group containing 2 to 12 carbon atoms, more preferred are sodium alkoxides and potassium alkoxides having an alkyl group containing 3 to 6 carbon atoms, and even more preferred are sodium t-butoxide, sodium t-pentoxide, potassium t-butoxide, and potassium t-pentoxide. Of these, the sodium alkoxides sodium t-butoxide and sodium t-pentoxide are even more preferred.

In the production process of the hydrogenated block copolymer (P) of the present embodiment, when polymerization is performed in the coexistence of a Lewis base, an organolithium compound, and an alkali metal alkoxide, it is preferable that the molar ratios of the Lewis base to the organolithium compound (Lewis base/organolithium compound) and the molar ratio of the alkali metal alkoxide to the organolithium compound (alkali metal alkoxide/organolithium compound) be as follows:
Lewis base/organolithium compound: 0.2 to less than 3.0 Alkali metal alkoxide/organolithium compound: 0.3 or less

In the polymerization step, the molar ratio of Lewis base to organolithium compound is preferably 0.5 or more from the viewpoints of a high proportion of 1,2-bonds and 3,4-bonds and a high polymerization rate, and is more preferably 2.5 or less from the viewpoints of a narrow molecular weight distribution and high hydrogenation activity, with a range of 0.8 to 2.0 being even more preferred.

Furthermore, from the viewpoint of narrow molecular weight distribution and high hydrogenation activity, the molar ratio of alkali metal alkoxide to organolithium compound is preferably 0.2 or less, even more preferably 0.1 or less, and even more preferably 0.08 or less.

Furthermore, from the viewpoint of achieving a narrow molecular weight distribution and obtaining high hydrogenation activity, the molar ratio of alkali metal alkoxide to Lewis base is preferably 0.1 or less, even more preferably 0.08 or less, even more preferably 0.06 or less, and even more preferably 0.05 or less.

In the production process of the hydrogenated block copolymer (P) of this embodiment, the hydrogenation method is not particularly limited. For example, the copolymer obtained as described above can be hydrogenated by supplying hydrogen in the presence of a hydrogenation catalyst to obtain a hydrogenated block copolymer in which the double bond residues of the conjugated diene monomer units have been hydrogenated.

When the polymerization step and hydrogenation step are carried out in an inert hydrocarbon solvent, the hydrogenated block copolymer can be isolated, for example, by removing the inert hydrocarbon solvent. Specific methods for removing the solvent are not particularly limited, but include, for example, steam stripping. Hydrous crumbs are obtained by steam stripping, and the resulting hydrous crumbs can be dried to obtain the hydrogenated block copolymer.

In steam stripping, it is preferable to use a surfactant as a crumbing agent. Examples of such surfactants include, but are not limited to, the same anionic surfactants, cationic surfactants, and nonionic surfactants as described above. These surfactants can generally be added to the water in the stripping zone in amounts of 0.1 ppm to 3000 ppm. In addition to surfactants, water-soluble salts of metals such as Li, Na, Mg, Ca, Al, and Zn can also be used as crumb dispersing agents.

The concentration of the crumb-like hydrogenated block copolymer (P) dispersed in water obtained through the hydrogenated block copolymer (P) polymerization process and the steam stripping is generally 0.1% to 20% by mass (ratio to the water in the stripping zone). Within this range, crumbs with good particle size can be obtained without causing operational problems. It is preferable to dehydrate the hydrogenated block copolymer (P) crumbs to adjust the moisture content to 1% to 30% by mass, and then dry them until the moisture content is 1% by mass or less.

In the dehydration process for the crumbs, dehydration can be carried out using a compression dehydrator such as a roll, Banbury dehydrator, or screw extruder-type dehydrator, or dehydration and drying can be carried out simultaneously using a conveyor or box-type hot air dryer.

The method for producing the hydrogenated block copolymer (P) of this embodiment may, if necessary, employ a step of deashing metals derived from the polymerization initiator, etc. Furthermore, the method for producing the hydrogenated block copolymer (P) of this embodiment may further employ a step of adding an antioxidant, a neutralizing agent, a surfactant, etc., if necessary.

Antioxidants include, but are not limited to, hindered phenol compounds, phosphorus compounds, sulfur compounds, etc., which may be used alone or in combination of two or more. Specific examples of hindered phenol compounds include, but are not limited to, 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, [octadecyl-3-(3,5-dibutyl-t-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl- 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]acrylate, and the like. Specific examples of phosphorus-based compounds and sulfur-based compounds include, but are not limited to, 3,3'-thiodipropionate, 2-mercaptobenzimidazole, 4,6-bis(octylthiomethyl)-o-cresol, thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dilauryl thiodipropionate, lauryl stearyl thiodipropionate pentaerythritol-tetrakis(6-laurylthiopropionate), tris(nonylphenyl)phosphite, and tris(2,4-di-t-butylphenyl)phosphite.

The amount of antioxidant added is preferably 0.01 to 1 part by mass, more preferably 0.05 to 0.5 parts by mass, and even more preferably 0.1 to 0.4 parts by mass, per 100 parts by mass of hydrogenated block copolymer.

Neutralizing agents are not particularly limited, but examples include various metal stearates, hydrotalcite, benzoic acid, etc.

Surfactants are not particularly limited, but examples include anionic surfactants, nonionic surfactants, cationic surfactants, etc. Anionic surfactants are not particularly limited, but examples include fatty acid salts, alkyl sulfate ester salts, and alkylaryl sulfonate salts. Nonionic surfactants are not particularly limited, but examples include polyoxyethylene alkyl ethers and polyoxyethylene alkylaryl ethers. Cationic surfactants are not particularly limited, but examples include alkylamine salts and quaternary ammonium salts.

If necessary, the hydrogenated block copolymer (P) of this embodiment can be blended with an anti-blocking agent in its crumb to prevent blocking.

Examples of anti-blocking agents include, but are not limited to, calcium stearate, magnesium stearate, zinc stearate, polyethylene, polypropylene, ethylene bisstearylamide, talc, and amorphous silica.

The amount of anti-blocking agent to be added is preferably 500 to 10,000 ppm relative to the hydrogenated block copolymer (P), and more preferably 1,000 to 7,000 ppm relative to the hydrogenated block copolymer (P). The anti-blocking agent is preferably added in a state where it adheres to the crumb surface, but a portion of the agent may also be contained within the crumb.

The hydrogenated block copolymer of this embodiment also includes copolymers containing the above additives.

[Elastomer composition]
The elastomer composition of the present embodiment contains the hydrogenated block copolymer (P) described above.
The elastomer composition of the present embodiment contains the hydrogenated block copolymer (P) described above, and therefore has few particles. Therefore, the elastomer composition of the present embodiment can be suitably used particularly for sealing members, especially for medicine stoppers.

In the elastomer composition of the present embodiment, when an elastomer composition sheet produced under the following conditions is cut into a 10 cm × 10 cm piece and both surfaces are observed under a microscope, it is preferable that the number of bumps with a diameter of 200 μm or more, calculated by the following formula, is 0. When the number of bumps is within the above range, the appearance of the elastomer composition sheet is excellent, and when used for medicine stoppers, the resealability and coring resistance tend to be excellent.
[Production of elastomer composition sheet]
The sheet material containing the hydrogenated block copolymer is melt-kneaded in a twin-screw extruder at a set temperature of 230° C., and a 500 μm thick elastomer composition sheet is produced using a T-die at a screw rotation speed of 300 rpm.
[Formula for calculating the number of items]
Number of bumps = total number of bumps with a diameter of 200 μm or more observed [number] * Y/X
(In the formula, X is the weight (g) of the composition sheet, Y is the amount (g) of the hydrogenated block copolymer in the composition sheet, and the calculated value is rounded to one decimal place to obtain the number of particles.)

The elastomer composition of this embodiment may contain a polypropylene-based resin.

Examples of polypropylene-based resins include, but are not limited to, propylene homopolymers, block copolymers or random copolymers of propylene and an olefin other than propylene, preferably an α-olefin having 2 to 20 carbon atoms, or blends thereof.

Examples of α-olefins having 2 to 20 carbon atoms include, but are not limited to, ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene. α-olefins having 2 to 8 carbon atoms are preferred, and ethylene, 1-butene, 1-hexene, and 4-methyl-1-pentene are even more preferred.

The polypropylene-based resins may be used alone or in combination of two or more types.

The polypropylene resin preferably has a melt flow rate (MFR) of 0.1 g/10 min to 50 g/10 min, more preferably 0.5 g/10 min to 45 g/10 min, and even more preferably 1.0 g/10 min to 40 g/10 min, measured at a temperature of 230°C and a load of 2.16 kg. An MFR within this range tends to further improve moldability.

Methods for producing polypropylene-based resins include, but are not limited to, polymerizing the above-mentioned monomers using a Ziegler-Natta catalyst that combines a titanium-containing solid transition metal component and an organometallic component.

Transition metal components used in Ziegler-Natta catalysts include, but are not limited to, solid components containing titanium, magnesium, and a halogen as essential components, with an electron donor compound as an optional component, or titanium trichloride. Organometallic components include, but are not limited to, aluminum compounds.

In addition, polymerization methods used to produce polypropylene-based resins include, but are not limited to, slurry polymerization, gas-phase polymerization, bulk polymerization, solution polymerization, and multi-stage polymerization methods that combine these.

In these polymerization methods, to obtain a propylene homopolymer, only propylene is polymerized, and to obtain a copolymer, propylene and a monomer other than propylene are polymerized.

In the elastomer composition of this embodiment, the content of the polypropylene resin is preferably 10 to 100 parts by mass, more preferably 13 to 75 parts by mass, and even more preferably 15 to 50 parts by mass, per 100 parts by mass of the hydrogenated block copolymer (P).

When the polypropylene resin content is 10 parts by mass or more, the elastomer composition of this embodiment exhibits good fluidity and excellent moldability. When the polypropylene resin content is 100 parts by mass or less, the elastomer composition of this embodiment exhibits good impact resilience and flexibility. When used as a medicine stopper, a polypropylene resin content of 10 parts by mass or more results in excellent moldability, reduces the formation of particles resulting from residual hydrogenated block copolymer (P), and provides excellent resealability and coring resistance. When the polypropylene resin content is 50 parts by mass or less, excellent needlestick resistance and resealability are achieved.

The elastomer composition of this embodiment may further contain a non-aromatic softener.

The non-aromatic softener is not particularly limited as long as it does not exhibit aromaticity and is capable of softening the elastomer composition of this embodiment, and examples include paraffinic oil, naphthenic oil, paraffin wax, liquid paraffin, white mineral oil, and plant-based softeners. Of these, paraffinic oil, liquid paraffin, and white mineral oil are preferred from the standpoint of the low-temperature properties and elution resistance of a stopper for a medical container containing the elastomer composition of this embodiment.

The kinematic viscosity of the non-aromatic softener at 40° C. is preferably 500 mm ² /sec or less. There is no particular lower limit to the kinematic viscosity of the non-aromatic softener at 40° C., but it is preferably 10 mm ² /sec or more.

When the kinematic viscosity of the non-aromatic softener at 40° C. is 500 mm ² /sec or less, the flowability of the elastomer composition of this embodiment tends to be further improved, and the molding processability tends to be further improved.

The kinematic viscosity of non-aromatic softeners can be measured using a glass capillary viscometer.

If the elastomer composition of this embodiment contains a non-aromatic softener whose kinematic viscosity at 40°C is within the above range, it will have good non-aromatic softener retention, i.e., good oil-bleed resistance.

In the elastomer composition of this embodiment, the content of the non-aromatic softener is preferably 75 to 300 parts by mass, more preferably 85 to 250 parts by mass, and even more preferably 90 to 200 parts by mass, per 100 parts by mass of the hydrogenated block copolymer (P).

When the content of the non-aromatic softener is within the above range, an elastomer composition having excellent retention of the non-aromatic softener can be obtained, and when used as a medicine stopper, the composition tends to have excellent oil-bleed resistance. Furthermore, when used as a medicine stopper, it is preferable to use a small amount of non-aromatic softener to reduce the risk of bacterial growth, etc., but by using the hydrogenated block copolymer (P) of this embodiment, it is possible to eliminate or reduce the amount of polyphenylene ether resin and inorganic filler described below, and it is possible to reduce the amount of non-aromatic softener used.
Specifically, when an inorganic filler is used without using a polyphenylene ether resin, the amount of the non-aromatic softener added is preferably 30 to 250 parts by mass, more preferably 50 to 200 parts by mass, and even more preferably 70 to 180 parts by mass, relative to 100 parts by mass of the hydrogenated block copolymer (P).
When a polyphenylene ether resin is used without using an inorganic filler, the amount of the non-aromatic softener added is preferably 30 parts by mass to 250 parts by mass, more preferably 50 parts by mass to 230 parts by mass, and even more preferably 70 to 200 parts by mass, relative to 100 parts by mass of the hydrogenated block copolymer (P).
When neither a polyphenylene ether resin nor an inorganic filler is used, the amount of the non-aromatic softener added is preferably 20 parts by mass to 150 parts by mass, more preferably 30 to 120 parts by mass, and even more preferably 40 to 100 parts by mass, relative to 100 parts by mass of the hydrogenated block copolymer (P).
Furthermore, the amount of polypropylene-based resin added can be adjusted to adjust the balance between moldability, resealability, needle puncture resistance, and coring resistance. For example, when the amount of non-aromatic softener added is small, the flowability, i.e., processability, can be adjusted by increasing the amount of polypropylene-based resin. From the viewpoint of adjusting the balance between moldability, resealability, needle puncture resistance, and coring resistance, the amount of polypropylene-based resin added is preferably 10 parts by mass to 100 parts by mass, more preferably 13 parts by mass to 75 parts by mass, and even more preferably 15 parts by mass to 50 parts by mass, per 100 parts by mass of the hydrogenated block copolymer (P).

From the above perspective, the elastomer composition of this embodiment preferably contains 10 to 50 parts by mass of polypropylene resin and 30 to 200 parts by mass of non-aromatic softener per 100 parts by mass of hydrogenated block copolymer.

The elastomer composition of this embodiment may further contain an inorganic filler.

Inorganic fillers include, but are not limited to, talc, calcium carbonate, calcium oxide, zinc carbonate, wollastonite, zeolite, wollastonite, silica, alumina, clay, titanium oxide, magnesium hydroxide, magnesium oxide, sodium silicate, calcium silicate, magnesium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, zinc oxide, potassium titanate, hydrotalcite, barium sulfate, titanium black, and carbon blacks such as furnace black, thermal black, and acetylene black.

These inorganic fillers may be used alone or in combination of two or more. Among these, from the viewpoint of the resealability of the drug stopper containing the elastomer composition of this embodiment, talc, calcium carbonate, silica, and clay are preferred, with talc and calcium carbonate being more preferred.

When the elastomer composition is used as a material for rubber stoppers (medicinal stoppers) for medical containers, it is expected that the stoppers will be subjected to steam sterilization at approximately 110°C to 121°C while assembled into a cap or holder. If the dimensions of the stoppers change due to heating, there is a risk that a sufficient crimping effect will not be achieved.

The use of surface-treated inorganic fillers can further improve the resealability of stoppers for medical containers after steam sterilization. However, by using the hydrogenated block copolymer (P) of this embodiment, no special surface treatment is required, the amount of inorganic filler added can be reduced, or even the addition of inorganic filler can be eliminated altogether, and the amount of non-aromatic softener added to adjust hardness can also be reduced.

One method for surface treating inorganic fillers is to bring a surface treatment agent and/or its solution into contact with the surface of the inorganic filler.

For example, when the surface treatment agent is a fatty acid, resin acid, oil or surfactant, dry treatment involves mixing the powdered surface treatment agent with an inorganic filler and pulverizing it in a pulverizer such as a heated ball mill or roller mill, or in a mixer such as a ribbon blender or Henschel mixer, while melting and causing a chemical reaction.

When using a surface treatment agent that has a high melting point and is water-insoluble, the surface treatment is carried out by making it into an emulsion or dissolving it in alcohol, pouring it into a grinder or mixer, stirring and mixing it with the inorganic filler, and then drying it.

In wet treatment, the surface of the inorganic filler is treated by adding a surface treatment agent to the slurry produced during the synthesis of the inorganic filler and stirring it in a mixer while heating. When a surface treatment agent with a high melting point is used, it is used in an emulsion state and similarly added to the inorganic filler during synthesis and stirred to perform the surface treatment.

When using a coupling agent as a surface treatment agent, if it is water-soluble, the pH is usually adjusted to a mixture of water and ethanol, the coupling agent is added to the solution, and the solution is sprayed into a heated high-speed agitating mixer such as a Henschel mixer containing inorganic filler, causing a chemical reaction with the surface of the inorganic filler, thereby achieving surface treatment. When using a water-insoluble coupling agent as a surface treatment agent, the coupling agent is dissolved in acetone, alcohol, etc., and sprayed into a heated high-speed agitating mixer containing inorganic filler, as described above, to achieve surface treatment of the inorganic filler.

Typical surface treatment agents include fatty acids, resin acids, oils and fats, surfactants, and coupling agents (silane-based, titanium-based, phosphoric acid-based, carboxylic acid-based, etc.), but are not limited to these as long as they can act on the surface of the inorganic filler.

Fatty acids include, but are not limited to, saturated fatty acids such as caproic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, as well as their metal salts and modified products; and unsaturated fatty acids such as oleic acid, linoleic acid, erucic acid, eicosadienoic acid, docosadienoic acid, linolenic acid, eicosatetraenoic acid, tetracosapentaenoic acid, and docosahexaenoic acid, as well as their metal salts and modified products.

Resin acids include, but are not limited to, rosins whose main components are abietic acid, neoabietic acid, palustric acid, pimaric acid, isopimaric acid, dehydroabietic acid, etc., and derivatives thereof.

Examples of fats and oils include, but are not limited to, soybean oil, linseed oil, coconut oil, safflower oil, etc.

Surfactants include, but are not limited to, fatty acid anionic surfactants such as sodium stearate and potassium stearate; sulfate ester anionic surfactants such as polyoxyethylene alkyl ether sulfate esters and long-chain alcohol sulfate esters, and their sodium and potassium salts; sulfonic acid anionic surfactants such as alkylbenzenesulfonic acid, alkylnaphthalenesulfonic acid, paraffin sulfonic acid, α-olefinsulfonic acid, alkylsulfosuccinic acid, and their sodium and potassium salts; and nonionic surfactants such as polyethylene glycol, polyvinyl alcohol, and derivatives thereof.

Silane coupling agents include, but are not limited to, alkyl group-containing silane coupling agents such as dimethyldichlorosilane, trimethylchlorosilane, dimethyldimethoxysilane, trimethylmethoxysilane, dimethyldiethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, and polydimethylsiloxane; phenyl group-containing silane coupling agents such as phenyltrichlorosilane, phenyltrimethoxysilane, and phenyltriethoxysilane; vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltriethoxysilane; Examples include vinyl group-containing silane coupling agents such as p-styryltriethoxysilane; styryl group-containing silane coupling agents such as p-styryltrimethoxysilane; epoxy group-containing silane coupling agents such as 3-glycidoxypropylmethyldimethoxysilane; methacryl group-containing silane coupling agents such as 3-methacryloxypropylmethyldimethoxysilane; acrylic group-containing silane coupling agents such as 3-acryloxypropylmethyldimethoxysilane; and amino group-containing silane coupling agents such as hexamethyldisilazane and N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane.

Titanium-based coupling agents include, but are not limited to, titanium isostearate, tetrastearyl titanate, tetraisopropyl titanate, isopropyl triisostearoyl titanate, titanium octylene glycolate compound, titanium diethanolamine, titanium aminoethyl aminoethanolate, bis(dioctyl pyrophosphate) oxyacetate titanate, tris(dioctyl pyrophosphate) ethylene titanate, isopropyl dioctyl paprika Examples include pyrophosphate titanate, isopropyl tris(dioctyl pyrophosphate) titanate, isopropyl tris(dodecylbenzenesulfonyl)titanate, titanium tetra-n-butoxide, titanium tetra-2-ethylhexoxide, tetraoctyl bis(ditridecyl phosphite) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, and tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate.

Examples of phosphoric acid coupling agents include, but are not limited to, phosphate triesters such as tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, and xylenyl diphenyl phosphate; monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monoisopropyl ... Nononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, dibutyl acid phosphate, Dipentyl acid phosphate, dihexyl acid phosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate acidic phosphate esters such as tributyl phosphorothioate, tripentyl phosphorothioate, trihexyl phosphorothioate, triheptyl phosphorothioate, trioctyl phosphorothioate, trinonyl phosphorothioate, tridecyl phosphorothioate, triundecyl phosphorothioate, tridodecyl phosphorothioate, tritridecyl phosphorothioate, phosphorothioate, tritetradecyl phosphorothioate, tripentadecyl phosphorothioate, trihexadecyl phosphorothioate, triheptadecyl phosphorothioate, trioctadecyl phosphorothioate, trioleyl phosphorothioate, triphenyl phosphorothioate, tricresyl phosphorothioate, trixylenyl phosphorothioate, cresyl diphenyl phosphorothioate, xylenyl diphenyl phosphorothioate thiophosphate esters such as tris-dichloropropyl phosphate, tris-chloroethyl phosphate, tris-chlorophenyl phosphate, and polyoxyalkylene bis[di(chloroalkyl)]phosphate; and phosphite esters such as dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, and tricresyl phosphite.

Examples of carboxylic acid coupling agents include, but are not limited to, carboxylated polybutadiene and its hydrogenated products, carboxylated polyisoprene and its hydrogenated products, carboxylated polyolefin, carboxylated polystyrene, carboxylated styrene-butadiene copolymer and its hydrogenated products, and carboxylated nitrile rubber.

Among these, when the elastomer composition of this embodiment is used as a material for stoppers for medical containers, from the viewpoint of resealability after steam sterilization, fatty acids and modified products thereof, and silane coupling agents are preferred as surface treatment agents, and among silane coupling agents, trimethylsilyl silane coupling agents and dimethylsilyl silane coupling agents are more preferred.

Furthermore, from the viewpoint of resealability after steam sterilization, preferred combinations with inorganic fillers include calcium carbonate surface-treated with a fatty acid or a modified product thereof, and silica surface-treated with a silane coupling agent (hereinafter also referred to as "surface-treated silica"). More preferred is silica surface-treated with a silane coupling agent, and even more preferred is silica surface-treated with a trimethylsilyl silane coupling agent or a dimethylsilyl silane coupling agent.
The elastomer composition of this embodiment may not contain surface-treated silica.

As mentioned above, the inclusion of an inorganic filler can improve resealability when used as a medicine stopper. However, by using the hydrogenated block copolymer (P) of this embodiment, the amount of inorganic filler added can be reduced or even eliminated, and the amount of non-aromatic softener added for hardness adjustment can also be reduced. In other words, the elastomer composition of this embodiment may or may not contain an inorganic filler. In applications requiring higher resealability, an inorganic filler may be contained. In such cases, the total content of the inorganic filler is preferably 10 to 200 parts by weight, more preferably 50 to 150 parts by weight, even more preferably 10 to 100 parts by weight, and even more preferably 15 to 90 parts by weight, per 100 parts by weight of the hydrogenated block copolymer (P).

When the inorganic filler content is within the above range, the stopper used in a medical container containing the elastomer composition of this embodiment tends to have excellent resealability.

The average primary particle size of the inorganic filler is preferably 0.01 μm to 5 μm, more preferably 0.01 μm to 4 μm, and even more preferably 0.01 μm to 3 μm.
When the average primary particle size of the inorganic filler is 0.01 μm or more, the flexibility of the elastomer composition can be improved, and when it is 5 μm or less, the uniform dispersion in the elastomer composition can be improved.

The elastomer composition of this embodiment may further contain a polyphenylene ether resin. The inclusion of a polyphenylene ether resin can improve heat resistance, i.e., low compression set, and improve resealability when used as a medicine stopper. However, the use of the hydrogenated block copolymer (P) of this embodiment can reduce the amount of polyphenylene ether resin added or even eliminate the need for adding a polyphenylene ether resin, and can also reduce the amount of non-aromatic softener added for adjusting hardness. Furthermore, it can reduce or eliminate the odor characteristic of polyphenylene ether resin.
The elastomer composition of the present embodiment may not contain the polyphenylene ether resin and the surface-treated silica.

The polyphenylene ether resin is preferably a homopolymer and/or copolymer having a repeating structural unit represented by the following general formula (I):

In the general formula (I), O represents an oxygen atom.
^R2 to ^R5 each independently represent hydrogen, halogen, a primary or secondary C1 to C7 alkyl group, a phenyl group, a C1 to C7 haloalkyl group, a C1 to C7 aminoalkyl group, a C1 to C7 hydrocarbyloxy group, or a halohydrocarbyloxy group (wherein at least two carbon atoms separate the halogen atom from the oxygen atom).

The method for producing polyphenylene ether resin is not particularly limited, and known methods can be used. Examples include the production methods described in U.S. Pat. Nos. 3,306,874, 3,306,875, 3,257,357, 3,257,358, JP-A Nos. 50-51197, 52-17880, and 63-152628.

Examples of polyphenylene ether resins include, but are not limited to, homopolymers such as poly(2,6-dimethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-6-phenyl-1,4-phenylene ether), and poly(2,6-dichloro-1,4-phenylene ether), as well as polyphenylene ether copolymers such as copolymers of 2,6-dimethylphenol with other phenols (for example, copolymers with 2,3,6-trimethylphenol and copolymers with 2-methyl-6-butylphenol, as described in JP-B No. 52-17880).

Among these, poly(2,6-dimethyl-1,4-phenylene ether), a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol, or a mixture thereof is preferred from the standpoint of industrial productivity and heat resistance.

Furthermore, the polyphenylene ether resin may be a modified polyphenylene ether resin that has been completely or partially modified.

Here, modified polyphenylene ether resin refers to a polyphenylene ether resin that has been modified with at least one modifying compound that has at least one carbon-carbon double bond or triple bond and at least one carboxylic acid group, acid anhydride group, amino group, hydroxyl group, or glycidyl group within its molecular structure.

Examples of modified compounds having at least one carbon-carbon double bond and a carboxylic acid group or anhydride group within their molecular structure include, but are not limited to, maleic acid, fumaric acid, chloromaleic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, and their anhydrides.

Among these, from the viewpoint of compatibility between the hydrogenated block copolymer (P) and the polyphenylene ether resin, fumaric acid, maleic acid, and maleic anhydride are preferred, and fumaric acid and maleic anhydride are more preferred.

Compounds in which one or both of the two carboxyl groups of these unsaturated dicarboxylic acids are esterified can also be used.

Modified compounds having at least one carbon-carbon double bond and a glycidyl group in their molecular structure include, but are not limited to, allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, and epoxidized natural fats and oils. Of these, glycidyl acrylate and glycidyl methacrylate are preferred.

Examples of the modified compound having at least one carbon-carbon double bond and a hydroxyl group in its molecular structure include, but are not limited to, unsaturated alcohols represented by the general formula C _n H _2n-3 OH (n is a positive integer), such as allyl alcohol, 4-penten-1-ol, and 1,4-pentadiene-3-ol, as well as unsaturated alcohols represented by the general formula C _n H _2n-5 OH and C _n H _2n-7 OH (n is a positive integer).

The above-mentioned various modified compounds may be used alone or in combination of two or more.

The addition rate of the modifying compound in the modified polyphenylene ether resin is preferably 0.01% by mass to 5% by mass, and more preferably 0.1% by mass to 3% by mass. Note that unreacted modifying compound and/or polymer of the modifying compound may remain in the modified polyphenylene ether resin in an amount of less than 1% by mass.

The reduced viscosity ηsp/C of the polyphenylene ether resin (0.5 g/dL, chloroform solution, measured at 30°C) is preferably in the range of 0.15 dL/g to 0.70 dL/g, more preferably in the range of 0.20 dL/g to 0.60 dL/g, and even more preferably in the range of 0.25 dL/g to 0.50 dL/g.

When the reduced viscosity of the polyphenylene ether resin is 0.15 dL/g or higher, the elastomer composition of this embodiment tends to have good compression set, and when it is 0.70 dL/g or lower, it tends to have excellent processability.

The reduced viscosity of polyphenylene ether resin can be controlled within the above numerical range by adjusting the type of catalyst, polymerization time, and polymerization temperature during the polyphenylene ether resin production process.

In this embodiment, two or more polyphenylene ether resins with different reduced viscosities may be blended and used as a polyphenylene ether resin as a whole. In this case, the reduced viscosity of the mixture obtained by mixing the multiple polyphenylene ether resins is preferably in the range of 0.15 dL/g to 0.70 dL/g, and the reduced viscosity of each individual polyphenylene ether resin does not have to be in the range of 0.15 dL/g to 0.70 dL/g.

The reduced viscosity of polyphenylene ether resin can be measured by the method described in the Examples below.

The number-average molecular weight Mn of the polyphenylene ether resin is preferably 1,000 to 50,000, more preferably 1,500 to 50,000, and even more preferably 1,500 to 30,000. If the number-average molecular weight of the polyphenylene ether resin is within this range, an elastomer composition with superior compression set tends to be obtained.

The number average molecular weight of the polyphenylene ether resin, as with the hydrogenated block copolymer (a) described above, can be determined based on the molecular weight of the peak in the chromatogram measured by GPC using a calibration curve (prepared using the peak molecular weight of the standard polystyrene) obtained from measurements of commercially available standard polystyrene.

The polyphenylene ether resin may be used alone, or may be modified by blending with a resin such as a polystyrene-based resin or a polypropylene-based resin to improve processability.

Examples of polystyrene resins include, but are not limited to, general-purpose polystyrene (GPPS), rubber-reinforced high-impact polystyrene (HIPS), styrene-butadiene copolymers, hydrogenated styrene-butadiene copolymers other than the hydrogenated block copolymer (P) used in this embodiment, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-acrylonitrile-butadiene copolymers, and styrene-methyl methacrylate copolymers. These copolymers may be random copolymers or block copolymers.

Examples of polypropylene-based resins include, but are not limited to, block or random copolymers of propylene and an olefin other than propylene, preferably an α-olefin having 2 to 20 carbon atoms, or blends thereof.

As mentioned above, the inclusion of polyphenylene ether resin can improve heat resistance, i.e., low compression set, and improve resealability when used as a medicine stopper. However, by using the hydrogenated block copolymer (P) of this embodiment, the amount of polyphenylene ether resin added can be reduced or even eliminated, making it possible to reduce the amount of non-aromatic softener added for hardness adjustment. It also makes it possible to reduce or eliminate the odor characteristic of polyphenylene ether resin. That is, the elastomer composition of this embodiment may or may not contain polyphenylene ether resin. However, polyphenylene ether resin may be contained in applications where the odor derived from polyphenylene ether resin is not an issue or where highly low compression set is required. In such cases, the content of polyphenylene ether resin is 5 to 100 parts by weight, preferably 10 to 90 parts by weight, more preferably 20 to 85 parts by weight, and even more preferably 30 to 85 parts by weight, per 100 parts by weight of the hydrogenated block copolymer (P).

When the polyphenylene ether resin content is within the above range, the elastomer composition tends to have good compression set properties.

The elastomer composition of this embodiment may contain a hydrogenated styrene-based elastomer other than the hydrogenated block copolymer (P). Representative examples of the hydrogenated styrene-based elastomer include, but are not limited to, styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene (SEBS), and styrene-ethylene-propylene-styrene (SEPS), which are styrene-isoprene-styrene saturated by hydrogenation.

Other examples include elastomers with structures such as styrene-ethylene-butylene (SEB) and styrene-ethylene-propylene (SEP).

In addition, reactive elastomers in which various functional groups have been added to the hydrogenated styrene-based elastomer may also be used.

Examples of the functional group include, but are not limited to, a hydroxyl group, a carboxyl group, a carbonyl group, a thiocarbonyl group, an acid halide group, an acid anhydride group, a thiocarboxylic acid group, an aldehyde group, a thioaldehyde group, a carboxylic acid ester group, an amide group, a sulfonic acid group, a sulfonate ester group, a phosphoric acid group, a phosphoric acid ester group, an amino group, an imino group, a nitrile group, a pyridyl group, a quinoline group, an epoxy group, a thioepoxy group, a sulfide group, an isocyanate group, an isothiocyanate group, a silicon halide group, an alkoxy silicon group, a tin halide group, a boronic acid group, a boron-containing group, a boronate salt group, an alkoxy tin group, and a phenyl tin group.

The elastomer composition of this embodiment may be partially crosslinked in the presence of an organic peroxide from the standpoint of compression set.

Organic peroxides include, but are not limited to, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxybenzoate, t-butylcumyl peroxide, diisopropylbenzenehydroxyperoxide, 1,3-bis(t-butylperoxyisopropyl)benzene, benzoyl peroxide, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, Examples include hexane, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, di-t-butyl peroxide, 1,1-di-t-butylperoxycyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, n-butyl-4,4-bis(t-butylperoxy)valerate, t-butylperoxyisobutyrate, t-butylperoxy-2-ethylhexanoate, and t-butylperoxyisopropyl carbonate.

These organic peroxides may be used alone or in combination of two or more.

The amount of organic peroxide used is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 4 parts by mass, and even more preferably 0.3 to 3 parts by mass, per 100 parts by mass of the hydrogenated block copolymer (P).

When the amount of organic peroxide used is within the above range, an elastomer composition with excellent recovery properties, particularly compression set, tends to be obtained without reducing processability.

Furthermore, when the elastomer composition of this embodiment is partially crosslinked, a crosslinking aid can be used as needed to adjust the degree of crosslinking.

Examples of crosslinking aids include, but are not limited to, trimethylolpropane triacrylate, triallyl isocyanurate, triallyl cyanurate, triallyl formal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalamide, triallyl phosphate, divinylbenzene, ethylene dimethacrylate, diallyl phthalate, quinone dioxime, ethylene glycol dimethacrylate, polyfunctional methacrylate monomers, polyhydric alcohol methacrylates and acrylates, and unsaturated silane compounds (e.g., vinyltrimethoxysilane, vinyltriethoxysilane, etc.).

These may be used alone or in combination of two or more types as needed.

The amount of crosslinking aid used is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 8 parts by mass, and even more preferably 0.5 to 7 parts by mass, per 100 parts by mass of hydrogenated block copolymer (P).

The elastomer composition of this embodiment may contain other additives in addition to the components described above, as long as the purpose of this embodiment is not impaired.

Such other additives include heat stabilizers, antioxidants, ultraviolet absorbers, antioxidants, plasticizers, light stabilizers, crystal nucleating agents, impact modifiers, pigments, lubricants, antistatic agents, flame retardants, flame retardant aids, compatibilizers, and tackifiers.

In particular, adding silicone oil as a lubricant improves sliding properties, reduces needle puncture resistance, and is effective in improving coring properties.

Examples of silicone oils include common dimethylpolysiloxane and phenyl-methylpolysiloxane, with dimethylpolysiloxane being particularly preferred.

The amount of silicone oil added is preferably 0.5 to 10 parts by mass, more preferably 0.7 to 7 parts by mass, and even more preferably 1.0 to 5 parts by mass, per 100 parts by mass of the hydrogenated block copolymer (a). The kinematic viscosity of the silicone oil is not particularly limited, but is preferably 10 mm ² /sec to 10,000 mm ² /sec, more preferably 50 mm ² /sec to 7,000 mm ² /sec, and even more preferably 100 mm ² /sec to 5,000 mm ² /sec.

These additives may be used alone or in combination of two or more.

(Method for producing elastomer composition)
The method for producing the elastomer composition of the present embodiment is not particularly limited, and any conventionally known method can be applied.

Examples include melt-kneading methods using common mixers such as pressure kneaders, Banbury mixers, internal mixers, Labo Plastomills, Mix Labs, single-screw extruders, twin-screw extruders, co-kneaders, and multi-screw extruders, and methods in which the components are dissolved or dispersed and mixed and then the solvent is removed by heating.

When the elastomer composition of this embodiment is partially crosslinked using the organic peroxide described above, the components may be combined and partially crosslinked using the organic peroxide (and a crosslinking aid, if necessary) simultaneously, or the components may be combined and then partially crosslinked by adding the organic peroxide and, if necessary, a crosslinking aid.

Alternatively, a portion of each component may be mixed with an organic peroxide and, if necessary, a crosslinking aid, followed by crosslinking, followed by mixing with the remaining components.

Partial crosslinking can be carried out at a temperature at which the organic peroxide used decomposes, generally between 150°C and 250°C.

When compounding some or all of the components and crosslinking with an organic peroxide (and a crosslinking aid, if added as needed) are carried out simultaneously, compounding can be carried out using the melt kneader, etc., at a temperature at which the organic peroxide used decomposes.

(Application)
The sealing member of this embodiment is made of the above-described elastomer composition. The stopper of this embodiment is made of the above-described elastomer composition. The drug stopper used for medical purposes of this embodiment is made of the above-described elastomer composition.

(Plug use)
When the elastomer composition of the present embodiment is used for a stopper, it is preferably used in a medical airtight container or a sealed container. When it is used for inserting an injection needle, a typical form is that a cylindrical stopper is fitted into a roughly cylindrical lid or a predetermined jig and used as an integral part of the lid or the jig.

Examples of the jig include, but are not limited to, a specific framework, cap, housing, sealant, etc. Specific examples include those used as caps for infusion bags.

On the other hand, cylindrical stoppers can also be used alone, fitting into the mouth of a glass bottle to function as a sealing stopper.

For applications that do not require the insertion of a syringe needle, fitting a disc-shaped stopper onto the inner surface of a container lid that can be sealed with a screw or other means contributes to improved sealing.

The stopper containing the elastomer composition of this embodiment is preferably used as a stopper for a container, particularly a medical container.

Medical containers are preferably airtight or sealed containers, and examples include, but are not limited to, infusion bags, peritoneal dialysis bags, infusion bottles, soft infusion bottles, glass vials, and plastic vials.

The shape of the stopper is not particularly limited, but examples include truncated cones, cylinders, and disks, and its diameter is typically about 5 mm to 25 mm. The thickness of the stopper, i.e., the thickness in the direction of needle insertion when used with an injection needle, is also not particularly limited, but is typically about 2 mm to 10 mm.

(Method for manufacturing plug)
The plug can be produced by, but not limited to, injection molding, compression molding, punching from extrusion molding, or the like.

From the standpoint of dimensional accuracy and reproducibility of surface roughness, manufacturing by injection molding is preferable.

The present embodiment will be described in detail below with specific examples and comparative examples, but the present embodiment is not limited to the following examples. For example, in this embodiment, a composition is prepared using a hydrogenated block polymer and then formed into a stopper of a specific shape. However, the stopper may be melted once and remolded into the shape given in the examples, after which a similar evaluation may be performed. In this case, the method for quantifying the composition of the composition is not particularly limited, but may be a combination of general quantification techniques, such as GPC or NMR.

First, the evaluation methods and physical property measurement methods used in the examples and comparative examples are described below.

[Physical properties of hydrogenated block copolymer]
(Peak-top molecular weight of diblock component in hydrogenated block copolymer and weight-average molecular weight of entire hydrogenated block copolymer)
Each molecular weight was measured by gel permeation chromatography (GPC) (apparatus: manufactured by Waters) under the following conditions. From the obtained chromatogram, the molecular weight of the peak top corresponding to the diblock component in the hydrogenated block copolymer was determined using a calibration curve (prepared using the peak molecular weight of the standard polystyrene) obtained from the measurement of commercially available standard polystyrene. In addition, a baseline including all peaks was set, and the weight average molecular weight of the entire hydrogenated block copolymer was calculated in the same manner.
(Measurement conditions)
GPC: ACQUITY APC system (manufactured by Nihon Waters Co., Ltd.)
System (measurement and analysis) software: Empower3
Detector: Differential refractive index (RI) detector Refractive index unit full scale: 500 μRIU
Output full scale: 2000mV
Sampling rate: 10 points/sec
Column: ACQUITY APC XT125 (4.6 mm x 150 mm); 1
ACQUITY APC XT200 (4.6mm x 150mm); 1 piece
ACQUITY APC XT900 (4.6mm x 150mm); 1 piece
ACQUITY APC XT450 (4.6 mm x 150 mm); 1 bottle Solvent; tetrahydrofuran (THF)
Flow rate: 1.0mL/min Concentration: 0.1mg/mL
Column temperature: 40°C
Injection volume: 20μL

(Ratio of diblock component, ratio of dibranched component, ratio of tribranched component, ratio of quadruple or more branched component in hydrogenated block copolymer)
The inflection points of each inter-peak curve obtained from the GPC were vertically divided, and the ratio of each divided area to the total area was defined as the mass ratio of each component. When no inflection points were observed between peaks, the ratio of the divided area from the position of 1.5 times the peak top molecular weight of the diblock component to the position of 2.5 times the molecular weight of the diblock component to the total peak area was defined as the 2-branched component ratio. Similarly, the ratio of the divided area from the position of 2.5 times the peak top molecular weight of the diblock component to the position of 3.5 times the molecular weight of the diblock component to the total peak area was defined as the 3-branched component ratio, and the ratio of the divided area of components with molecular weights equal to or greater than 3.5 times the peak top molecular weight of the diblock component was defined as the 4- or more-branched component ratio.

(Total vinyl aromatic monomer unit content (total styrene content) in hydrogenated block copolymer)
A certain amount of hydrogenated block copolymer (P) was dissolved in chloroform and measured with an ultraviolet spectrophotometer (Shimadzu Corporation, UV-2450). The content of vinyl aromatic monomer units (styrene) was calculated using a calibration curve from the peak intensity at the absorption wavelength (262 nm) attributable to the vinyl aromatic compound component (styrene).

(Proportion of 1,2-bonds and 3,4-bonds in conjugated diene monomer units in hydrogenated block copolymer)
The proportions of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units in the hydrogenated block copolymer (P) were measured using a nuclear magnetic resonance (NMR) spectrometer under the following conditions.
After all reactions were completed (after the hydrogenation reaction for the hydrogenated block copolymer), a large amount of methanol was added to the reaction solution to precipitate and recover the hydrogenated block copolymer (P). The recovered hydrogenated block copolymer (P) was then extracted with acetone, and the extract was dried under vacuum and used as a sample for ^1H -NMR measurement. The conditions for ^1H -NMR measurement are as follows:
(Measurement conditions)
Measuring equipment: JNM-LA400 (manufactured by JEOL)
Solvent: Deuterated chloroform Sample concentration: 50 mg/ml
Observation frequency: 400 MHz
Chemical shift reference: TMS (tetramethylsilane)
Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45°
Measurement temperature: 26℃
The proportion of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units in the hydrogenated block copolymer was determined as the ratio of the total peak area of 1,2-bonds and 3,4-bonds to the total area of all peaks associated with the conjugated diene monomer units (1,2-bonds, 3,4-bonds, 1,4-bonds) among the obtained peaks.

(Content of total vinyl aromatic monomer units in hydrogenated block copolymer)
The content of all vinyl aromatic monomer units in the hydrogenated block copolymer (P) was measured using a nuclear magnetic resonance (NMR) spectrometer under the same conditions as in the measurement method for the above (ratio of 1,2-bonds and 3,4-bonds).

(Hydrogenation rate (hydrogenation rate) of conjugated diene monomer units in hydrogenated block copolymer)
The hydrogenation rate of double bonds in the conjugated diene monomer units in the hydrogenated block copolymer (P) was measured using a nuclear magnetic resonance (NMR) apparatus under the same conditions as in the measurement method for the above (ratio of 1,2-bonds and 3,4-bonds).
The hydrogenation rate of the double bonds in the conjugated diene monomer units in the hydrogenated block copolymer (P) was determined by calculating the ratio of the total area of the peaks of the hydrogenated 1,2-bonds, the hydrogenated 3,4-bonds, and the hydrogenated 1,4-bonds to the total area of all peaks (1,2-bonds, 3,4-bonds, 1,4-bonds) associated with the double bonds in the conjugated diene monomer units among the obtained peaks.

[Evaluation of hydrogenated block copolymers]
(70°C Compression Set of Hydrogenated Block Copolymer (P))
The 70°C compression set of the hydrogenated block copolymer (P) was determined in accordance with JIS K6301 compression set test as follows. A 2 mm thick press sheet of the hydrogenated block copolymer (P) was punched into a circle with a diameter of 29 mm, and six of these were stacked to form a test specimen. The initial thickness of the six stacked test specimens was measured at 23°C. The test specimens were then left in an oven at 70°C for 22 hours while compressed by 25%. The test specimens were then removed from the oven, and after releasing the compression, they were left at 23°C for 30 minutes. The residual strain (70°C compression set) of the test specimens was then calculated using the following formula:
70°C compression set = (t ₀ - _{t 1} )/(t ₀ ×0.25) × 100
t ₀ : Initial thickness of the test piece (mm)
_t1 : Thickness (mm) of the test piece after releasing the compression and leaving it at 23°C for 30 minutes
The lower the residual distortion rate, the better the heat resistance and mechanical properties. A residual distortion rate of 25% or less was evaluated as being excellent for practical use.

(Shear Melt Viscosity of Hydrogenated Block Copolymer (P))
The shear melt viscosity (hereinafter also referred to as "Capillary viscosity") of the hydrogenated block copolymer (P) was determined in accordance with ISO 11443 as follows. Measurement was carried out under conditions of a temperature of 240°C and a shear rate of 122 sec ^-1 . This Capillary viscosity is a value measured in accordance with ISO 11443, but is a so-called "apparent viscosity" without Burley correction or Rabinowich correction, and the measured value varies significantly depending on the conditions of the measuring device. Therefore, the conditions of the measuring device were specified as follows.
Capillary die inner diameter: φ1.0 mm
Capillary die length: 10.0 mm
・Inflow angle: 180°
Piston diameter: φ9.510 mm
・Furnace diameter: φ9.55mm
The lower the shear melt viscosity, the better the processability, and under these conditions, a viscosity of 4000 mP·s or less was evaluated as being excellent for practical use.

[Evaluation of Elastomer Composition]
[Production of Thermoplastic Elastomer Composition]
The raw material components were uniformly mixed and melt-kneaded at a set temperature of 230°C using a twin-screw extruder (TEX-30αII manufactured by The Japan Steel Works, Ltd., cylinder diameter 30 mm) to produce pellets of a thermoplastic elastomer composition.

[Seat manufacturing]
The components of the raw materials were uniformly mixed and melt-kneaded at a set temperature of 230°C using a twin-screw extruder ("TEX-30αII" manufactured by The Japan Steel Works, Ltd., cylinder diameter 30 mm). A thermoplastic elastomer composition sheet having a thickness of 500 μm was produced using a T-die at a screw rotation speed of 300 rpm.

(Quantity of particles)
The thermoplastic elastomer composition sheet thus prepared was cut into a 10 cm x 10 cm piece, both sides of which were observed under a microscope, the number of lumps was counted, and the sheet was evaluated according to the following criteria.
Since the amount of hydrogenated block copolymer in the composition sheet was not constant, when the weight of the composition sheet was X g and the amount of hydrogenated block copolymer in the composition sheet was Y g, the evaluation criterion was the total number of particles * Y/X [pieces], rounded to the first decimal place.
Evaluation criteria for the amount of bumps ◎: 0 bumps with a diameter of 50 μm or more.
Good: The number of bumps with a diameter of 50 μm or more and less than 200 μm is 1 to 2, and the number of bumps with a diameter of 200 μm or more is 0.
△: The number of bumps with a diameter of 50 μm or more and less than 200 μm is 3 or more, and the number of bumps with a diameter of 200 μm or more is 0.
▽: There are 1 to 2 particles with a diameter of 200 μm or more.
×: The number of particles having a diameter of 200 μm or more is 3 or more.
Since the number of bumps affects the resealability and coring resistance, the evaluation was made with ⊚ representing extremely excellent, ◯ representing excellent, and Δ representing good for practical use.

[Manufacturing of plug]
Using the pellets of the thermoplastic elastomer composition obtained in the above [Production of Thermoplastic Elastomer Composition], a cylindrical plug 1 having a diameter of 20 mm and a thickness of 4 mm was molded using an injection molding machine FE120S18A (manufactured by Nissei Plastic Industrial Co., Ltd.).
FIG. 1(A) shows a schematic top view of the plug 1, and FIG. 1(B) shows a schematic cross-sectional view of the plug 1.
The injection molding conditions were as follows: resin temperature: 240°C, injection speed: 45 cm ³ /sec, injection time: 10 seconds, mold temperature: 40°C, cooling time: 40 seconds.

(Resealability after steam sterilization)
First, the plug 1 shown in FIG. 1 was fitted into a predetermined jig 2 as shown in FIG.
Next, the retaining ring 23 was fixed with another jig so that it was in complete contact with the holder 22 into which the stopper body 1 was fitted, and the stopper body 1 was steam sterilized at 121°C for 20 minutes at a steam pressure of 0.104 MPa in an autoclave SN500 manufactured by Yamato Scientific Co., Ltd.
Thereafter, the bottle was cooled in the device for 2 hours, and then the stopper 1 was removed and further cooled at room temperature of 23°C for 2 hours. Then, in the same manner as in (needlestick resistance) described below, the stopper 1 shown in Figure 1 was fitted into the jig 2 shown in Figure 2, and the stopper 1 was attached to the mouth of a PET bottle filled with 500 mL of water, and the jig 2 was fixed in place.
The bottle was turned upside down with the stopper facing downwards, and the height from the inner surface of the stopper to the liquid level was 18.5 cm.
A hole with a diameter of 3 mm was drilled in the bottom (upper side) of the bottle, and a resin needle (plastic bottle needle) with a diameter (maximum diameter at the base) of 5 mm was inserted into the center of the stopper 1 up to the maximum diameter of the needle.
After leaving it as it was for 4 hours, the needle was removed from the stopper 1 and the mass of water leaking from the pinhole was measured.
The smaller the mass of leaked water, the better the resealability was judged to be.
The number of measurements was eight, and the simple average was taken as the measured value. Based on the measured values, the resealability was evaluated according to the following criteria.
◎: Mass of leaked water is 0g,
○: The mass of the leaked water is more than 0 g and 0.1 g or less.
△: The mass of the leaked water is more than 0.1 g and 1.0 g or less.
▽: The mass of the leaked water is more than 1.0 g and 5.0 g or less,
×: The mass of the leaked water exceeds 5.0 g.
The evaluation was made as follows: ◎ is extremely excellent, ○ is excellent, and △ is good for practical use.

(needle stick resistance)
The plug 1 shown in FIG. 1 was fitted into a predetermined jig as shown in FIG.
FIG. 2A shows a schematic top view of the jig 2, and FIG. 2B shows a schematic cross-sectional view of the jig 2.
The jig 2 had a tubular holder 22 that could be attached to the opening of a predetermined container via a thread pitch portion 21 .
The plug 1 was fitted into the open end of the jig 2 and fixed with a retaining ring 23 .
Next, the jig 2 with the stopper 1 fitted therein was attached and fixed to the mouth of a PET bottle filled with 500 mL of water.
The above-mentioned PET bottle was fixed to a tensile tester TG-5kN (manufactured by Minebea Co., Ltd.) with the stopper 1 facing upward, and a resin needle (plastic bottle needle) with a diameter (maximum diameter at the base) of 5 mm was penetrated from above into the center of the stopper 1 at a speed of 200 mm/min. The maximum load at this time was measured.
The needle used was a Terufusion infusion set (TK-U200L) manufactured by Terumo Corporation.
It was judged that the smaller the maximum load, the lower the needle puncture resistance and the better the result.
The number of measurements was four, and the simple average was used as the measurement value. Based on the measurement values, the needlestick resistance was evaluated according to the following criteria.
◎: Maximum load is 3.0 kgf or less,
○: Maximum load is more than 3.0 kgf and 3.5 kgf or less,
△: Maximum load is more than 3.5 kgf and 4.0 kgf or less,
×: Maximum load exceeds 4.0 kgf. ⊚ is extremely excellent, ◯ is excellent, and Δ is good for practical use.

(coring resistance)
As in the above (needlestick resistance), the stopper 1 of FIG. 1 was fitted into the jig 2 of FIG. 2, and attached and fixed to the mouth of a PET bottle filled with 500 mL of water.
A resin needle (plastic bottle needle) with a diameter (maximum diameter at the base) of 5 mm was pierced five times through the center of the PET bottle stopper 1, and then the presence or absence of stopper shavings was visually confirmed in the water or on the surface of the needle.
Those with no or little shavings were judged to have good coring resistance.
The number of measurements was 5, and the simple average was used as the measured value. Based on the measurement results, the coring resistance was evaluated according to the following criteria.
◎: No shavings of the stopper are observed.
○: 1 to 3 pieces of stopper shavings of 0.5 mm or less were observed, and no stopper shavings of more than 0.5 mm were observed.
△: 4 to 5 pieces of shavings of the plug less than 0.5 mm were observed, and no shavings of the plug more than 0.5 mm were observed.
▽: Six or more pieces of stopper shavings of 0.5 mm or less are observed, and no stopper shavings of more than 0.5 mm are observed.
×: One or more pieces of plug shavings larger than 0.5 mm are observed.
The evaluation was made as follows: ⊚: particularly excellent, ◯: excellent, and △: good for practical use.

(Odor sensory test)
The stopper 1 shown in FIG. 1 was placed in a 500 mL pressure-resistant glass bottle, which was then sealed and heated at 70° C. for 1 hour, and then allowed to stand at room temperature for 48 hours.
Thereafter, 10 subjects checked the odor from the opening of the glass bottle and rated it according to the <Odor Intensity> below.
The odor intensity was determined by calculating the average value and rating according to the following criteria.
(standard)
An odor intensity of less than 3 was evaluated as being good for practical use.
<Odor Intensity>
0: No odor, 1: Barely detectable odor, 2: Weak odor that is recognizable, 2.5: Between 2 and 3, 3: Easily detectable odor, 3.5: Between 3 and 4, 4: Strong odor, 5: Overpowering odor.

(oil bleeding resistance)
The plug 1 shown in Figure 1 was placed on kraft paper, a 250 g load was applied from above, and the plug was left to stand for 72 hours in a gear oven at 180°C. Thereafter, the lightness L* was measured before and after the test using a colorimeter ZE6000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and the difference ΔL* (lightness L* before the test - lightness L* after the test) was calculated and evaluated according to the following criteria.
⊚: -1.0 or more ◯: -1.5 or more but less than -1.0 △: -2.0 or more but less than -1.5 ×: less than -2.0 ⊚ is particularly excellent, ◯ is excellent, and △ is good for practical use.

(Production of hydrogenated block copolymer)
Example 1
<Preparation of hydrogenation catalyst>
In the examples and comparative examples described later, the hydrogenation catalysts used in producing the hydrogenated block copolymer compositions were prepared by the following method.
A reaction vessel equipped with a stirrer was purged with nitrogen, and 1 L of dried and purified cyclohexane was placed in the vessel.
Next, 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added.
While thoroughly stirring, an n-hexane solution containing 200 mmol of trimethylaluminum was added, and the mixture was allowed to react at room temperature for about 3 days to obtain a hydrogenation catalyst.
<Production of hydrogenated block copolymer>
A 100 L tank reactor equipped with a stirrer and a jacket was washed, dried, and purged with nitrogen, and then batch polymerization was carried out as follows to produce a hydrogenated block copolymer.
In a first step, 38 L of cyclohexane and a cyclohexane solution containing 20.0 parts by mass of styrene monomer were added, and then 1.2 moles of N,N,N',N'-tetramethylethylenediamine (hereinafter also referred to as "TMEDA") were added per mole of n-butyllithium (hereinafter also referred to as "Bu-Li").
In the second step, the temperature was adjusted to 40° C., and then 0.056 parts by mass of Bu—Li was added to 100 parts by mass of the total monomers, followed by polymerization at a reactor temperature of 45° C. for 30 minutes.
In the third step, a cyclohexane solution containing 80.0 parts by mass of a conjugated diene monomer (butadiene monomer) was added, and then polymerization was carried out for another 60 minutes while adjusting the reaction temperature to 80°C.
In the fourth step, tetramethoxysilane (hereinafter also referred to as "TMS") was added so that the molar ratio of Si to Li (Si/Li) was 0.24 mol, and after stirring for 20 minutes, 0.1 mol of methanol was added per 1 mol of Bu-Li to obtain a styrene-butadiene coupling polymer.
In the fifth step, the resulting coupling polymer was continuously hydrogenated at 95°C using the hydrogenation catalyst prepared as described above, to obtain hydrogenated block copolymer 1. The catalyst amount was 100 ppm, the hydrogen pressure in the hydrogenation polymerization reactor was 0.95 MPa, and the average residence time was 120 minutes. After completion of the reaction, 0.25 parts by mass of an antioxidant (octadecyl-3-(3,5-dibutyl-t-butyl-4-hydroxyphenyl)propionate) was added per 100 parts by mass of hydrogenated block copolymer 1, to obtain polymer 1. The physical properties and characteristics of the resulting polymer 1 were measured by the methods described above. The measurement results are shown in Table 1.

[Examples 2, 3, and 8, and Comparative Examples 4, 5, 10, and 11]
Polymers 2, 3, 8, 14, 15, 20, and 21 were obtained in the same manner as in Example 1, except that the amount of TMS added in the fourth step was adjusted as shown in Tables 1 and 2. The physical properties and characteristics of the obtained polymers were measured by the methods described above. The measurement results are shown in Tables 1 and 2.

[Examples 4 and 5, and Comparative Examples 6 and 7]
Polymers 4, 5, 16, and 17 were obtained in the same manner as in Example 1, except that the amount of Bu—Li added in the second step was adjusted as shown in Tables 1 and 2. The physical properties and characteristics of the obtained polymers were measured by the methods described above. The measurement results are shown in Tables 1 and 2.

[Examples 6 and 7, and Comparative Examples 8 and 9]
Polymers 6, 7, 18, and 19 were obtained in the same manner as in Example 1, except that the amount of styrene monomer in the first step was adjusted as shown in Tables 1 and 2, and the amount of conjugated diene monomer (butadiene monomer) in the third step was adjusted as shown in Tables 1 and 2. The physical properties and characteristics of the obtained polymers were measured by the methods described above. The measurement results are shown in Tables 1 and 2.

[Examples 9 and 10, and Comparative Example 12]
Polymers 9, 10, and 22 were obtained in the same manner as in Example 1, except that the amount of TMEDA in the first step was adjusted as shown in Tables 1 and 2. The physical properties and characteristics of the obtained polymers were measured by the methods described above. The measurement results are shown in Tables 1 and 2.

Comparative Example 1
Polymer 11 was obtained in the same manner as in Example 1, except that the amount of TMEDA added in the first step was adjusted as shown in Table 2, the amount of Bu—Li added in the second step was adjusted as shown in Table 2, and the amount of TMS added in the fourth step was changed to 0.45 as shown in Table 2. The physical properties and characteristics of the obtained polymer were measured by the methods described above. The measurement results are shown in Table 2.

Comparative Examples 2 and 3
Polymers 12 and 13 were obtained in the same manner as in Example 1, except that in the first step, the amount of TMEDA added and the amount of styrene monomer were adjusted as shown in Table 2, in the second step, the amount of Bu—Li added was adjusted as shown in Table 2, in the third step, the amount of conjugated diene monomer (butadiene monomer) was adjusted as shown in Table 2, and in the fourth step, TMS was changed to styrene monomer. The physical properties and characteristics of the obtained polymers were measured by the methods described above. The measurement results are shown in Table 2.

Comparative Example 13
Polymer 23 was obtained in the same manner as in Example 1, except that the average residence time in the fifth step was changed to 90 minutes. The physical properties and characteristics of the obtained polymer were measured by the methods described above. The measurement results are shown in Table 2.

Comparative Example 14
Polymer 24 was obtained in the same manner as in Example 1, except that in the first step, the amount of styrene monomer was adjusted as shown in Table 2, in the second step, the amount of Bu—Li added was adjusted as shown in Table 2, and in the third step, 30 parts of butadiene monomer and 30 parts of isoprene monomer were added as conjugated diene monomers. The physical properties and characteristics of the obtained polymer were measured by the methods described above. The measurement results are shown in Table 2.

[Production of Thermoplastic Elastomer Composition]
The following components were used as raw materials for the thermoplastic elastomer composition.

<Hydrogenated Block Copolymer (a)>
As the hydrogenated block copolymer (a), the polymers polymerized in the above Examples and Comparative Examples were used.

<Polypropylene Resin (b)>
The following commercially available polypropylene resin (b) was used.
Polypropylene resin (b): PM801A from SunAllomer Co., Ltd., propylene homopolymer, MFR (230°C, 2.16 kg) 13 g/10 min

<Non-aromatic softener (c)>
The following commercially available products were used as the non-aromatic softener (c).
Non-aromatic softener (c-1): Diana Process Oil PW380 manufactured by Idemitsu Kosan Co., Ltd., paraffinic oil, weight average molecular weight 750, kinematic viscosity (40°C) = 380 mm ² /sec. Non-aromatic softener (c-2): Diana Process Oil PW90 manufactured by Idemitsu Kosan Co., Ltd., paraffinic oil, weight average molecular weight 530, kinematic viscosity (40°C) = 90.5 mm ² /sec.

<Inorganic filler (d)>
As the inorganic filler (d), the following commercially available products were used.
Inorganic filler (d): Aerosil R972V manufactured by Nippon Aerosil Co., Ltd., average primary particle size 16 nm, specific surface area by BET method 110 m ² /g, dimethylsilyl surface-treated silica

<Silicone oil (e)>
The following commercially available silicone oil was used:
Silicone oil (e): SH200-100Cs, manufactured by Toray Dow Corning Co., Ltd., dimethylpolysiloxane, kinematic viscosity 100 mm ² /sec

<Polyphenylene ether resin (f)>
The polyphenylene ether resin (f) was produced according to the following method.
According to a known method, polyphenylene ether was polymerized by oxidative coupling polymerization of 2,6-dimethylphenol, and purified to obtain polyphenylene ether resin (f).
The reduced viscosity (ηsp/c) (0.5 g/dL chloroform solution, measured at 30° C.), number average molecular weight, and average particle size of the obtained polyphenylene ether resin (f) are shown below.
Polyphenylene ether resin (f): reduced viscosity = 0.45 dL/g, number average molecular weight = 17,400, average particle size = 290 μm

(Examples 11 to 42 and Comparative Examples 15 to 34)
As shown in Tables 3 to 11, the polymers obtained in Examples 1 and 3 and Comparative Examples 1, 2, 4, 5, and 14 were blended as hydrogenated block copolymer (a) with the above-mentioned components (b) to (f) to produce pellets of thermoplastic elastomer composition by the above-mentioned method. Using the obtained pellets of thermoplastic elastomer composition, sheets with a thickness of 500 μm and cylindrical stoppers 1 with a diameter of 20 mm and a thickness of 4 mm as shown in FIG. 1 were produced by the above-mentioned method. The amount of particles in each obtained sheet and the properties of each stopper were evaluated as described above. The evaluation results are shown in Tables 3 to 11.

The hydrogenated block copolymer of the present invention has a low shear melt viscosity, excellent processability, and good 70°C compression set, which is characteristic of polymers, making it suitable for a wide range of applications. Furthermore, its high compatibility with polypropylene and fine crystal structure suppress gel formation, thereby minimizing the degradation of design and physical properties due to granules. Furthermore, for example, medical container closures made using the hydrogenated block copolymer of the present invention have an excellent balance of needlestick resistance, resealability, coring resistance, and oil-bleed resistance, even without the addition of polyphenylene ether resin or inorganic fillers. Therefore, they do not emit odors associated with polyphenylene ether resins, and have industrial applicability as closures for various medical containers, such as infusion bags.

1 Plug 2 Jig 21 Thread pitch portion 22 Holder 23 Retaining ring

Claims (14)

A hydrogenated block copolymer (P) obtained by hydrogenating a coupling polymer represented by the following formula (1):
(A-B)n-X (1)
[In formula (1), A is a polymer block mainly composed of vinyl aromatic monomer units, B is a polymer block mainly composed of conjugated diene monomer units, n is an integer of 1 or more, and X is a residue of a coupling agent or a residue of a polymerization initiator.]
the content of vinyl aromatic monomer units in the hydrogenated block copolymer (P) is 10% by mass to 40% by mass,
The peak top molecular weight of the diblock component corresponding to (A-B) in the above formula (1) is 160,000 to 225,000,
the proportion of the bibranched component corresponding to the case where n is 2 in the above formula (1) is 10% by mass to 30% by mass of the total hydrogenated block copolymer (P),
the proportion of the three-branched component corresponding to the case where n in the above formula (1) is 3 is 40% by mass to 70% by mass of the total hydrogenated block copolymer (P),
a ratio M of the three-branched component to the two-branched component (the mass of the three-branched component/the mass of the two-branched component) is 2 or more;
A hydrogenated block copolymer (P), in which the ratio of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units in the hydrogenated block copolymer (P) is 50 mol % to 80 mol % . The hydrogenated block copolymer according to claim 1, wherein the proportion of the diblock component is 10% by mass to 40% by mass of the entire hydrogenated block copolymer (P). The hydrogenated block copolymer according to claim 1 or 2, wherein the proportion of 4- or more branched components corresponding to the case where n in formula (1) is an integer of 4 or greater is 10% by mass or less of the total hydrogenated block copolymer (P). The hydrogenated block copolymer according to any one of claims 1 to 3, wherein the weight-average molecular weight of the entire hydrogenated block copolymer (P) is 350,000 to 500,000. The hydrogenated block copolymer according to any one of claims 1 to 4 , wherein the hydrogenation rate of the conjugated diene monomer units in the hydrogenated block copolymer (P) is 80 mol % or more. An elastomer composition comprising the hydrogenated block copolymer according to any one of claims 1 to 5 . 7. The elastomer composition according to claim 6 , comprising 10 to 50 parts by mass of a polypropylene resin and 30 to 200 parts by mass of a non-aromatic softener relative to 100 parts by mass of the hydrogenated block copolymer. The elastomer composition according to claim 6 or 7, wherein when an elastomer composition sheet produced under the following conditions is cut into a 10 cm x 10 cm piece and both surfaces are observed under a microscope, the number of particles having a diameter of 200 μm or more calculated by the following formula is 0:
[Production of elastomer composition sheet]
The sheet material containing the hydrogenated block copolymer is melt-kneaded in a twin-screw extruder at a set temperature of 230°C, and a 500 µm-thick elastomer composition sheet is produced using a T-die at a screw rotation speed of 300 rpm [calculation formula for the number of particles]
Number of bumps = total number of bumps with a diameter of 200 μm or more observed [number] × Y/X
(In the formula, X is the weight (g) of the composition sheet, Y is the amount (g) of the hydrogenated block copolymer in the composition sheet, and the calculated value is rounded to one decimal place to obtain the number of particles.) The elastomer composition according to any one of claims 6 to 8 , which does not contain a polyphenylene ether resin. The elastomer composition according to any one of claims 6 to 9 , which does not contain surface-treated silica. The elastomer composition according to any one of claims 6 to 8 , which does not contain a polyphenylene ether resin or surface-treated silica. A sealing member comprising the elastomer composition according to any one of claims 6 to 11 . A plug made of the elastomer composition according to any one of claims 6 to 11 . A drug stopper for medical use, comprising the elastomer composition according to any one of claims 6 to 11 .