JPH0217579B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a gasket for a syringe that has excellent rubber elasticity, sliding properties, and stability as expressed by compression set at high temperatures (100° C.), and is thermoplastic. (Prior Art) Conventionally, gaskets for syringes have been made by masticating natural rubber, isoprene rubber, styrene-butadiene rubber, etc., and adding carbon black as a filler and reinforcing agent, oil, vulcanization accelerator, sulfur, etc. Other auxiliary agents are added and kneaded, and the sheet is formed into a sheet using rolls, which is then fed into a gasket mold, heated, pressurized, and vulcanized. A molded body in which multiple gaskets are connected is taken out from the metal, and this molded body is It was obtained by cutting into individual gaskets by punching. This gasket was further cleaned to remove rubber pieces and foreign matter that had adhered to it during the punching and burring process, etc., and then coated with silicone to improve sliding performance with the syringe outer cylinder. In this way, conventional gaskets are mainly made of vulcanized materials, which require large-scale equipment as they go through a complicated process to obtain a molded product, and require a lot of manpower during the adjustment and management of additives and manufacturing. Therefore, it was expensive and had poor productivity. In particular, the vulcanization process in a press mold for gaskets takes about 10 to 30 seconds, compared to injection molding of thermoplastic polymers.
The vulcanization time was approximately 10 minutes, which required a long time, which inevitably limited productivity. In addition, the gasket obtained by this vulcanization method has many unnecessary burrs, and since it is a vulcanized product, it cannot be reused, making it an economically costly manufacturing method. In addition, since gaskets obtained by this method have sulfur, vulcanization accelerators, etc. added during manufacture, when they come into contact with medical solutions such as injections and blood, these additives may be eluted into the medical solutions and blood. Not only that, but also the coefficient of static friction and dynamic friction are large and sliding properties are poor, so coating with a lubricant such as silicone oil is required. Furthermore, when this gasket is disposed of and then burned during disposal, sulfur dioxide gas is generated, which is undesirable. For this reason, in recent years, several proposals have been made for syringe gaskets made of thermoplastic elastomers with the aim of improving productivity and safety as described above. For example, JP-A-55-36236
No. 1 discloses a gasket for a syringe obtained by injection molding an olefinic thermoplastic elastomer, and also discloses a gasket for a syringe obtained by injection molding an olefin thermoplastic elastomer.
No. 53173 and JP-A No. 58-25172 propose a gasket for a syringe made of a colorable and injection moldable elastomeric material made of a hydrogenated block copolymer or polyolefin having a specific structure. Among the syringe gaskets proposed here, the syringe gaskets molded from an elastomer material containing a hydrogenated block copolymer with a specific structure have a thermoplastic characteristic compared to those molded from conventional vulcanized rubber. As a result, the productivity was improved, and the compression set (rubber elasticity) at 70°C was good. (Problems to be Solved by the Invention) However, in the syringe gasket obtained by this proposal, the hydrogenated block copolymer with a specific structure used as its material has thermoplasticity, and Since the restraining segment is composed of polystyrene chains, its cohesive force effect decreases at high temperatures such as 100°C, and the compression set at 100°C is currently extremely poor as it no longer functions as a restraining segment. Therefore, a syringe gasket molded from a thermoplastic elastomer made of this hydrogenated block copolymer is substantially
It was inappropriate to expose it to high temperatures of 100°C. Furthermore, when trying to improve the sliding properties, which are important for the performance of syringe gaskets, conventional thermoplastic elastomers made of hydrogenated block copolymers have the undesirable result of deteriorating rubber elasticity (compression set). At present, it has been virtually impossible to obtain a gasket for a syringe that has an excellent balance of both properties. (Means for Solving the Problems) The present invention has been made to solve the problems that were difficult to solve with the elastomer molding materials presented in the above-mentioned conventional proposals. Rubber elasticity (compression set) at 100°C while having good properties and recyclability
This was made based on the demand for a gasket for syringes that has excellent sliding properties and excellent properties.This demand was fully achieved by using a thermoplastic elastomer, which was not previously known as a material for gaskets for syringes. It was discovered that the gasket for syringes has excellent rubber elasticity and sliding properties under the surface, as well as excellent safety. That is, the present invention provides a block copolymer comprising (a) a polymer block A mainly composed of at least one vinyl aromatic compound and a polymer block B mainly composed of at least one conjugated diene compound. Hydrogenated block copolymer obtained by hydrogenation: 100 parts by weight (b) Paraffin oil: 30 to 400 parts by weight (c) Monoolefin copolymer rubber and/or conjugated diene rubber: 10 to 200 parts by weight (d) The object of the present invention is to provide a gasket for a syringe having excellent heat resistance and molded from a thermoplastic elastomer material comprising 20 to 500 parts by weight of a polyolefin resin and/or a polystyrene resin and partially crosslinked in the presence of an organic peroxide. The present invention will be described in detail below. The hydrogenated block copolymer used as component (a) in the present invention consists of a polymer block A mainly composed of at least one vinyl aromatic compound and a polymer block mainly composed of at least one conjugated diene compound. It is obtained by hydrogenating a block copolymer consisting of A-B, A-B
-A, B-A-B-A, (A-B-) ₄ Si, (B-A
-B-) ₄ It is a hydrogenated vinyl aromatic compound-conjugated diene compound block copolymer having a structure such as Si. The hydrogenated block copolymer contains 5 to 95% by weight of vinyl aromatic compounds, preferably 10 to 85% by weight of vinyl aromatic compounds;
At 60% by weight or less, preferably 55% by weight or less, such a hydrogenated block copolymer exhibits properties as a thermoplastic elastomer. Furthermore, referring to the block structure, the polymer block A mainly composed of a vinyl aromatic compound is a vinyl aromatic compound polymer block or a vinyl aromatic compound containing more than 50% by weight and preferably 70% by weight or more of a vinyl aromatic compound. The polymer block B has a structure of a copolymer block of a hydrogenated conjugated diene compound and a hydrogenated conjugated diene compound. More than 50% by weight of the compound polymer block or hydrogenated conjugated diene compound, preferably 70% by weight
It has a structure of a copolymer block of a hydrogenated conjugated diene compound and a vinyl aromatic compound containing at least % by weight. In addition, polymer block A mainly composed of these vinyl aromatic compounds,
Polymer block B mainly composed of hydrogenated conjugated diene compounds has a random distribution of hydrogenated conjugated diene compounds or vinyl aromatic compounds in the molecular chains of each polymer block.
It may be tapered (the monomer component increases or decreases along the molecular chain), partially block-shaped, or any combination thereof, and the polymer block mainly composed of the vinyl aromatic compound and the hydrogen When there are two or more polymer blocks each consisting mainly of the added conjugated diene compound, each of the polymer blocks may have the same structure or may have different structures. As the vinyl aromatic compound constituting the hydrogenated block copolymer, one or more types can be selected from, for example, styrene, α-methylstyrene, vinyltoluene, P-tert-butylstyrene, etc.
Among them, styrene is preferred. Further, as the conjugated diene compound before hydrogenation constituting the hydrogenated conjugated diene compound, for example, one selected from butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc. species or two
Among these, butadiene, isoprene and combinations thereof are preferred. The microstructure of a polymer block mainly composed of a conjugated diene compound before being hydrogenated can be arbitrarily selected. For example, in a polybutadiene block, 1,2-vinyl bonds have 20 to 50
%, preferably 25-45%. Further, the number average molecular weight of the hydrogenated block copolymer used in the present invention having the above structure is 5000 to 5000.
1000000, preferably 10000 to 800000, more preferably 30000 to 500000, and the molecular weight distribution [weight average molecular weight (w) and number average molecular weight (n)]
(w/n)] is 10 or less. Furthermore, the molecular structure of the hydrogenated block copolymer may be linear, branched, radial, or any combination thereof. These block copolymers may be produced by any method as long as they have the above structure. For example, a vinyl aromatic compound-conjugated diene compound block copolymer is synthesized in an inert solvent using a lithium catalyst or the like by the method described in Japanese Patent Publication No. 40-23798, and then, for example,
In an inert solvent by the method described in Japanese Patent Publication No. 8704 and Japanese Patent Publication No. 43-6636, particularly preferably by the method described in Japanese Patent Application Publication No. 59-133203 and Japanese Patent Application Publication No. 60-79005. The hydrogenated block copolymer used in the present invention can be synthesized by hydrogenation in the presence of a hydrogenation catalyst. At that time, at least 80% of the aliphatic double bonds based on the conjugated diene compound of the vinyl aromatic compound-conjugated diene compound block copolymer are hydrogenated, and the polymer block mainly composed of the conjugated diene compound is transformed into an olefin in morphology. The compound can be converted into a polymer block. In addition, hydrogen of an aromatic double bond based on a vinyl aromatic compound copolymerized into a polymer block A mainly composed of a vinyl aromatic compound and, if necessary, a polymer block B mainly composed of a conjugated diene compound. Although there is no particular restriction on the addition rate, it is preferable that the hydrogenation rate is 20% or less. The amount of unhydrogenated aliphatic double bonds contained in the hydrogenated block copolymer can be easily determined using an infrared spectrophotometer, nuclear magnetic resonance apparatus, or the like. Next, the paraffinic oil that can be used as component (b) of the present invention is useful for adjusting the hardness and imparting flexibility to the resulting syringe gasket. The paraffinic oil used here can be called liquid paraffin, which is purified by removing impurities such as aromatic hydrocarbons and sulfur compounds contained in petroleum lubricating oil fractions with sulfuric anhydride or fuming sulfuric acid. Colorless and transparent, made of hydrogen.
It is a tasteless and odorless oil, and is classified by the Japanese Pharmacopoeia (JP).
Liquid paraffin that has passed food additive standards, cosmetic raw material standards, ultraviolet absorbance tests (260-350 nm), etc. can be used. Further, in the present invention, as component (b), in addition to the above-mentioned liquid paraffin, petroleum-based softeners approved by the FDA (US Food and Drug Administration) can also be useful. The amount of paraffinic oil used is 30 to 400 parts by weight, preferably 50 to 300 parts by weight, per 100 parts by weight of the hydrogenated block copolymer (a).
If the amount exceeds 400 parts by weight, oil bleed-out tends to occur, which is undesirable because it may impart stickiness to the final product, and furthermore, mechanical strength is undesirably lowered. In addition, if the amount is less than 30 parts by weight, it is not preferable from the viewpoint of imparting flexibility and economical efficiency. Next, the monoolefin copolymer rubber used as component (c) of the present invention has an olefin as a main component, such as an ethylene/propylene copolymer rubber or an ethylene/propylene/non-conjugated diene copolymer rubber. An elastomer of an amorphous random copolymer which mainly causes a crosslinking reaction by heat treatment in the presence of an organic peroxide is preferably used. The above ethylene/propylene/non-conjugated diene copolymer rubber is generally
It is called EPDM, and the non-conjugated diene includes dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylnorbornene, ethylidenenorbornene, etc.
Among them, ethylidene norbornene is preferred. Among these monoolefin copolymer rubbers,
EPDM can be more preferably used in the present invention, and the degree of unsaturation indicated by its iodine value is 30.
Mooney viscosity ML ₁₊₄ (100℃) is 10-120, preferably 35-20, preferably 5-20.
It is 100. The propylene content in the copolymer is 25 to 25% due to its flexibility as an elastomer.
50% by weight is preferred. Further, the conjugated diene rubber that can be used as the component (c) of the present invention can be arbitrarily selected from natural rubber or synthetic rubber. Examples of the synthetic rubber include polybutadiene, polyisoprene,
Styrene-butadiene random copolymer rubber, styrene-isoprene random copolymer rubber, styrene-butadiene block copolymer rubber, styrene-isoprene block copolymer rubber, acrylonitrile-butadiene copolymer rubber, polychloroprene, etc. . Furthermore, hydrogenated rubbers in which the aliphatic double bonds contained in these conjugated diene rubbers are partially hydrogenated to reduce the degree of unsaturation can also be used. For example, hydrogenated rubbers with a hydrogenation rate of 80 Partially hydrogenated rubber of less than 1% can also be provided as a conjugated diene rubber. The monoolefin copolymer rubber and the conjugated diene rubber can be selected at any blending ratio. The amount of monoolefin copolymer rubber and/or conjugated diene rubber used as component (c) shown above is the same as that of the hydrogenated block copolymer of component (a).
It is 10 to 200 parts by weight per 100 parts by weight, and if it is less than 10 parts by weight, compression set at high temperatures (100°C) will be poor.
Further, if the amount exceeds 200 parts by weight, mechanical strength and elongation deteriorate, which is not preferable. Next, the polyolefin resin used as component (d) of the present invention is an olefin resin that is thermally decomposed by heat treatment in the presence of peroxide, reducing the molecular weight of the resin and increasing the fluidity of the resin. For example, isotactic polypropylene, poly(4-methyl-1-pentene),
Polybutene-1, propylene and other small amounts of α-
Examples of copolymers of olefins include propylene/ethylene copolymers, propylene/1-butene copolymers, propylene/4-methyl-1-pentene copolymers, and the like. For example,
In the case of polypropylene resin, MFR (ASTM-
D-1238-L condition, 230℃) is 0.1 to 50g/10
minutes, particularly preferably in the range of 0.5 to 30 g/10 minutes. The polystyrene resin that can be used as component (d) of the present invention is preferably one obtained by a known radical polymerization method or ionic polymerization method, and has a number average molecular weight of 5,000 to 500,000, preferably It can be selected from the range of 10,000 to 200,000, and preferably has a molecular weight distribution [ratio of weight average molecular weight (w) to number average molecular weight (n) (w/n)] of 5 or less. Specifically, for example, polystyrene, rubber-reinforced polystyrene, polyα-methylstyrene,
Poly p-tert-butylstyrene, styrene-butadiene block copolymer with a styrene content of 60% by weight or more, etc., and two or more types of these may be used, or a mixture of monomers constituting these polymers. It may be a copolymer obtained by polymerizing. The polyolefin resin of component (d) listed here,
Polystyrene resin can also be blended together as component (d). In the present invention, when polyolefin resin is blended alone, the hardness of the resulting thermoplastic elastomer material tends to be higher than when polystyrene resin is blended alone. These two types of (d) components can be selected at any blending ratio. In this case, polyolefin resin/
The ratio of polystyrene resin is preferably selected from 95/5 to 5/95 (weight ratio). The amount of component (d) mentioned above can be suitably selected in the range of 20 to 500 parts by weight, with 50 to 300 parts by weight based on 100 parts by weight of the hydrogenated block copolymer of component (a).
Parts by weight. If the amount exceeds 500 parts by weight, the hardness of the resulting syringe gasket will become too high, resulting in poor rubber elasticity (compression set), which is not preferable. This is to prevent the syringe gasket from creating a gap between the syringe outer cylinder and the gasket.
Gaskets are usually molded with an outer diameter slightly larger than the inner diameter of the syringe outer cylinder, so if they do not have rubber elasticity, they cannot be inserted into the syringe, and if the gasket contains more than 500 parts by weight, this rubber elasticity cannot be maintained. It's for a reason. In addition, if the amount is less than 20 parts by weight, although the rubber elasticity of the resulting gasket is good, the processability during molding and the sliding properties of the gasket when inserted into the syringe barrel deteriorate, which is not preferable. The above-mentioned components (a) to (d) are partially crosslinked by heating, melting and kneading in the presence of an organic peroxide and a crosslinking aid, and are the material for the syringe gasket with excellent heat resistance of the present invention. Thermoplastic elastomers can be obtained. In the partial crosslinking of the present invention, 1 g of thermoplastic elastomer is extracted with boiling xylene using a Soxhlet extractor for 10 hours, and the residue is passed through an 80-mesh wire gauze.
The crosslinking is adjusted so that the value obtained by dividing the amount of component (a)+component (c) contained in g divided by 100 is preferably in the range of 20 to 95%, more preferably 30 to 90%. Organic peroxides that can be used here include, for example, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, 2,5-dimethyl-
2,5-di(benzoylperoxy)-hexane, t-butylperoxybenzoate, dicumyl peroxide, t-butylcumyl peroxide, diisopropylbenzohydroperoxide, 1,3-bis-(t-butylperoxy) isopropyl)-benzene, benzoyl peroxide, 1,1-di(t-butylperoxy)-
3,3,5-trimethylcyclohexane, etc., and useful crosslinking aids include, for example, divinylbenzene, trimethylolpropane triacrylate, ethylene dimethacrylate, diallyl phthalate, quinone dioxime, phenylene bismaleimide, polyethylene Examples include glycol dimethacrylate. These organic peroxides and crosslinking aids can be suitably used in the range of 0.1 to 5 parts by weight per 100 parts by weight of components (a) to (d).
These organic peroxides and crosslinking aids can be used in combination of two or more types, if necessary. Furthermore, as a component of the syringe gasket of the present invention, a hindered amine light stabilizer, an ultraviolet absorber, an antioxidant, an inorganic filler,
Coloring agents, silicone oil, etc. can be added. The method for producing a thermoplastic elastomer that can be used as a material for the syringe gasket of the present invention includes the above-mentioned components (a) to (d) and components that can be added as necessary, for example, by a single-screw extruder or a twin-screw extruder. Melt and knead using various heating kneaders such as mills, rolls, Banbury mixers, Brabenders, and kneaders, and then add organic peroxide and crosslinking aids and melt and knead, or mix these necessary components simultaneously and heat. It can be easily obtained by melt-kneading. The thermoplastic elastomer obtained here is further supplied to an injection molding machine equipped with a mold for a syringe gasket, and can be injection molded in a short time to obtain a syringe gasket. Furthermore, since the unnecessary burrs, runner parts, and spool parts of the injection molded product are made of thermoplastic elastomer, they can be recycled and can be reused as materials for syringe gaskets. (Effects of the Invention) The syringe gasket obtained by the present invention uses a thermoplastic elastomer material containing a partially crosslinked product of a specific component that has not been seen before.
°C) has an improved balance of rubber elasticity (compression set) and sliding properties, and since it is a thermoplastic elastomer that does not contain sulfur like vulcanized rubber, it will not be absorbed by chemicals or blood that come into contact with the gasket. There is no elution of sulfur, and since it does not contain heavy metals such as zinc, there is no elution of sulfur, and free sulfur and metals do not react with the chemical solution. Furthermore, since the gasket of the present invention can be injection molded, the molding time is greatly shortened compared to conventional gaskets that involve a vulcanization process, and the mold releasability is also good, allowing for mass production. Since the spool part is made of thermoplastic elastomer, it can be injection molded again to form a gasket, which is economical as there is no waste of raw materials. [Examples] The present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, in these Examples and Comparative Examples,
The test methods used for various evaluations are as follows. (1) Hardness [-] JIS-K6301, A type (2) Tensile strength [Kg/cm ² ] and elongation [%] JIS-K6301, the sample is a 2 mm thick in-die extension sheet, and the test piece is 3 I used size dumbbells. (3) Compression set [%] JIS-K6301, strain residual rate after 25% deformation at 100°C for 22 hours (4) Sliding properties A gasket having the structure shown in the attached drawing was injection molded, After obtaining the 5c.c. and 10c.c. syringe gaskets, attach them to the syringe pusher.
Furthermore, it was inserted into a syringe outer cylinder, and the load (g) during the initial movement and sliding of the syringe pusher was measured. In the attached drawings, the shaded area in Figure 1 shows the cross section of the entire gasket;
It consists of a cylindrical body 1 having a hollow hole 5 made of thermoplastic elastomer. The tip 2 of this cylindrical body has a conical shape, and the outer peripheral surface of this cylindrical body 1 has two annular ribs 3 and 4. Also, Fig. 2 shows the cylindrical hollow hole 5 of this gasket.
A tip 7 of a cylinder pusher 6 is attached to the cylinder. In addition, the ingredients blended are as follows. (1) <Component (a-1)> Hydrogenated polybutadiene-polystyrene-hydrogenated polybutadiene-polystyrene structure, bound styrene content 15% by weight, number average molecular weight 139000, molecular weight distribution 1.04, before hydrogenation The amount of 1,2-vinyl bonds in the polybutadiene part of is 44%, and the hydrogenation rate is
99% hydrogenated block copolymer published in JP-A-60-79005
Synthesized using the Ti-based water catalyst described in the publication,
(a-1) component. <Component (a-2)> It has a structure of polystyrene-hydrogenated polybutadiene-polystyrene, and the amount of bound styrene is 30
Weight%, number average molecular weight 161000, molecular weight distribution 1.05,
A hydrogenated block copolymer with a 1,2-vinyl bond content of 33% in the polybutadiene moiety before hydrogenation and a hydrogenation rate of 98% was synthesized using a Ti-based hydrogenation catalyst described in JP-A-59-133203. This was used as component (a-2). <Component (a-3)> Hydrogenated polybutadiene-polystyrene-hydrogenated polybutadiene-polystyrene structure, bound styrene content 41% by weight, number average molecular weight 157000, molecular weight distribution 1.05, polybutadiene before hydrogenation A hydrogenated block copolymer with a 1,2-vinyl bond content of 39% and a hydrogenation rate of 99% was obtained.
It was synthesized using a Ti-based hydrogenation catalyst described in Publication No. 133203, and was used as component (a-3). <Component (a-4)> (Polystyrene-hydrogenated polybutadiene-) Has a structure of ₄ Si, with a bound styrene content of 60% by weight,
Number average molecular weight 127,000, molecular weight distribution 1.39, 1,2-vinyl bond content in the polybutadiene part before hydrogenation is 41%,
A hydrogenated block copolymer with a hydrogenation rate of 99% was published in 1980-
It was synthesized using the Ti-based hydrogenation catalyst described in Publication No. 79005, and was used as component (a-4). (2) Component (b) Liquid paraffin manufactured by Matsumura Sekiyu Co., Ltd.; Smoyl P-
350 [Kinematic viscosity (37.8℃) 75.5cst, Naphthene component 37
%, paraffin component 63%] (3) <Ingredient (c-1)> EPDM manufactured by Japan EP Rubber Co., Ltd.; EP-57P,
Mooney viscosity 88, third component is ethylidene norbornene, iodine value 15 <Component (c-2)> Polybutadiene manufactured by Asahi Kasei Corporation; diene
NF55A, Mooney viscosity 57 <Component (c-3)> Number average molecular weight 87000, molecular weight distribution 1.23, 1,2-vinyl bond amount in polybutadiene part before hydrogenation is 32
% of polybutadiene was hydrogenated using a Ti-based hydrogenation catalyst described in JP-A-59-133203 to obtain a hydrogenated polymer (c-3) with a hydrogenation rate of 68%. (4) <Component (d-1)> Asahi Kasei Industries, Ltd. polypropylene; Asahi Polypro E-
1100, MFR0.5g/10min <Component (d-2)> Asahi Kasei Polystyrene; Styron 685,
MFR3g/10min Examples 1-4, Comparative Examples 1-2 Organic peroxide [2,5-dimethyl-2,
Each component shown in Table 1 except 5-di[tert-butylperoxy)hexane] and the crosslinking aid (trimethylolpropane triacrylate) was prepared in advance.
The mixture was heated and kneaded at 220°C using a 50 mm diameter twin-screw extruder to obtain a polymer before partial crosslinking. Thereafter, to 100 parts by weight of the obtained polymer, the above-mentioned organic peroxide and crosslinking aid were added in the equivalent amounts shown in Table 1, and 0.2 parts by weight of an antioxidant (Irganox 1010; manufactured by Ciba Geigy) was added. After mixing in a shell mixer, the mixture was reacted in a 50 mm diameter twin screw extruder at 220°C to obtain a partially crosslinked thermoplastic elastomer. Using the thermoplastic elastomer pellets obtained here, syringe gaskets were made using an injection molding machine equipped with 5 c.c. and 10 c.c. syringe gasket molds at a temperature setting of 190 to 220°C. Molded. Then, the syringe pusher fitted with the gasket obtained here was inserted into a polypropylene syringe outer cylinder to produce 5 c.c. and 10 c.c. syringes.
On the other hand, 150 mm for making test pieces for measuring physical properties.
Injection molding was performed at a set temperature of 190°C to 220°C using an injection molding machine equipped with a flat mold of 150 mm x 2 mm (thickness). Various performance tests were conducted using the syringe and test piece obtained here, and the results are listed in Table 1. From this result, the syringe gasket of the present invention has excellent rubber elasticity as shown by compression set at 100°C,
In addition, it was revealed that it has excellent sliding properties.
On the other hand, gaskets for syringes made of thermoplastic elastomers other than those of the present invention had poor compression set at 100° C. and still had insufficient sliding properties.

【table】

[Table] Examples 5 to 6 As a hydrogenated block copolymer, components (a-1),
Using (a-2), each component shown in Table 2 was prepared in Example 1.
A syringe gasket and a test piece were obtained by molding in the same manner as in 4. The sliding characteristics and physical properties of this material were measured and listed in Table 2. The syringe gasket of the present invention obtained here has excellent sliding properties even though it contains polystyrene.
It has become clear that the material has excellent compression set at 100℃.

【table】

[Table] Example 7 The syringe gasket obtained in Example 1 was subjected to material and eluate tests according to the rubber stopper test method for infusion according to the 10th edition of the Japanese Pharmacopoeia. The results are shown in Table 3. From this result, it was found that the syringe gasket of the present invention cleared the standards.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of a syringe gasket part obtained by injection molding of a thermoplastic elastomer provided in Examples and Comparative Examples of the present invention. The shaded area shows the entire gasket. FIG. 2 is a sectional view of an example in which a syringe pusher is attached to the gasket of FIG. 1. 1: cylindrical body with gasket structure, 2: conical tip of gasket cylindrical body, 3: and 4: annular rib,
5: Hollow hole for attaching a syringe pusher,
6: Cylinder pusher, 7: Cylinder pusher tip.

Claims (1)

[Scope of Claims] 1 (a) a polymer block A mainly composed of at least one vinyl aromatic compound; and at least one
Hydrogenated block copolymer obtained by hydrogenating a block copolymer consisting of a polymer block B mainly composed of a conjugated diene compound: 100 parts by weight (b) Paraffin oil: 30 to 400 parts by weight (c) Thermoplastic material made by partially crosslinking a blend consisting of 10 to 200 parts by weight of monoolefin copolymer rubber and/or conjugated diene rubber (d) 20 to 500 parts by weight of polyolefin resin and/or polystyrene resin in the presence of organic peroxide. A syringe gasket with excellent heat resistance molded from elastomer material.