JP7590638B2 - Resin composition and method for producing resin composition - Google Patents

Description

The present invention relates to a resin composition containing polymethylpentene and a thermoplastic elastomer, and a method for producing the resin composition.

Resin materials are used in a wide range of fields, and there is a demand for the development of resin materials that meet the increasingly diverse and complex required characteristics. In recent years, there are many cases in which contradictory characteristics are required. For example, automotive resins are required to be lightweight, as well as heat resistance, chemical resistance, toughness, and processability.
However, it is difficult for a single existing resin to combine multiple properties. For example, the toughness and heat resistance of a resin are often in a trade-off relationship, and improving one can result in a significant decrease in the other.

For example, polyolefin resins such as polypropylene are lightweight, general-purpose resins with a variety of excellent properties, and are therefore used in a wide range of applications, including home appliance parts, food packaging, medical supplies, and automotive parts. However, depending on the application, they can have issues such as insufficient heat resistance and relatively poor elasticity and elongation.

Polymethylpentene, a polyolefin resin, has the chemical resistance and water resistance that are characteristic of polyolefins, and also has the lowest specific gravity of all thermoplastic resins and a melting point of 200-250°C, making it highly heat-resistant. However, it still has issues with its relatively poor elasticity and elongation.

On the other hand, thermoplastic elastomers have excellent rubber elasticity, sufficient flexibility and large elongation, and because they are thermoplastic, they can be processed relatively easily, but they have poor heat resistance and chemical resistance.

As mentioned above, it is becoming difficult to meet the complex needs of recent years with a single material, and there is a demand for resin materials that have improved tensile properties in addition to the light weight, heat resistance, and chemical resistance unique to polyolefins. As one solution to this problem, efforts are being made to develop new materials that combine multiple properties that cannot be achieved with a single material by mixing multiple resins or resins with thermoplastic elastomers. When expecting improved tensile properties by mixing resins, the compatibility of the mixed materials, such as resins and resins or resins and elastomers, is important, and in the case of complete compatibility, the properties are expressed in an additive manner according to the addition ratio. On the other hand, if the main material and the additive material are not compatible and form a dispersion structure, a synergistic effect that cannot be achieved by each material alone can be expected. However, the synergistic effect is not expressed unconditionally, and in many cases, the compatibility between the two is poor, resulting in the formation of a large dispersion phase, or the physical properties are lower than those of the single material due to poor interfacial adhesion. Therefore, in order to express the synergistic effect of mixing, it is desirable to develop a resin material with a controlled dispersion structure.

For example, Patent Document 1 discloses a thermoplastic elastomer composition having a continuous phase in which a thermoplastic resin and a rubber are mixed together, and describes that a thermoplastic elastomer composition having an excellent balance of tensile strength, elongation, etc. can be provided.

Patent Document 2 describes how adding a specified amount of thermoplastic elastomer to 4-methyl-1-pentene makes it possible to provide a packaging film that has high heat sealability without impairing the gas permeability of 4-methyl-1-pentene.

JP 2019-70079 A JP 2012-201392 A

In Patent Document 1, it is described that the mechanism for providing a thermoplastic elastomer composition with an excellent balance of tensile strength, elongation, etc. is that the resin and rubber have a continuous phase in which they are partially compatible. However, it is not difficult to imagine that the partially compatible continuous phase makes the composition soft overall, and the tensile strength of the provided thermoplastic elastomer is lower than that of the added thermoplastic resin. In addition, kneading is required in a high-temperature environment until the partially compatible continuous phase is formed. According to the example in Patent Document 1, this is 180°C for 30 minutes, but depending on the resin or rubber components used, thermal degradation due to kneading cannot be avoided. Furthermore, the additive material is limited to rubber, that is, a material that requires the separate addition of a crosslinking agent, so while a composition mainly composed of a thermoplastic resin is obtained, the rubber component does not have plasticity and moldability becomes an issue.

Patent Document 2 aims to improve the heat sealability of the film while maintaining gas permeability, but does not improve tensile strength or elongation. In many cases, the compatibility between resins or between resins and elastomers is poor. As a result, large dispersed phases are formed, and the physical properties are often lower than those of simple materials due to poor interfacial adhesion, so tensile properties are not easily improved by resin blending. In addition, the addition of a propylene (co)polymer as a third additive is mentioned, but it is described as being compatible with the thermoplastic elastomer that constitutes the dispersed phase, and the purpose of adding it is to suppress blocking during kneading of the raw materials or film formation, and to improve film formability.

The present invention was made in consideration of the above problems, and its purpose is to provide a resin composition that uses a polyolefin resin with the above-mentioned excellent properties and has improved tensile properties.

After thorough investigation into the conditions necessary to solve this problem, we discovered that in order to achieve better properties through the synergistic effect of a resin blend than either material alone, it is important to form a phase-separated structure and to maintain good interfacial adhesion by having partially compatible sites at the interface between the dispersed phase and the continuous phase.

In other words, it was found that a partially compatible portion in the continuous phase as described in Patent Document 1 is not necessarily required, but that it is important that there is a partially compatible phase at the interface between the continuous phase and the dispersed phase, and as a result, the stress propagating from the continuous phase reaches the elastomer, which is the dispersed phase, and the stress is dispersed within the elastomer, which is believed to subsequently suppress the growth of cracks and improve tensile strength and elongation. These findings led to the invention.

The gist of the present invention is as follows.
[1] A resin composition containing polymethylpentene and a thermoplastic elastomer,
A continuous phase consisting of the polymethylpentene;
A dispersed phase consisting of the thermoplastic elastomer;
a compatible phase in which the polymethylpentene and the thermoplastic elastomer are compatible with each other and is present at the interface between the continuous phase and the dispersed phase;
The resin composition has an area ratio of a dispersed phase of 0.6 to 12.0%.
[2] The resin composition according to [1], wherein the thermoplastic elastomer is at least one selected from the group consisting of styrene-ethylene-butylene-styrene (SEBS), styrene-butadiene-styrene (SBS), and styrene-butadiene rubber (SBR).
[3] The tensile strength A (MPa) of the polymethylpentene alone, the tensile strength B (MPa) of the thermoplastic elastomer alone, the tensile strength C (MPa) of the resin composition, and the area ratio X (%) of the dispersed phase in the resin composition are C>(B-A)X/100+A
The resin composition according to [1] or [2], which satisfies the above.
[4] A method for producing a resin composition, comprising:
A step of melt-kneading polymethylpentene and a thermoplastic elastomer;
and cooling the melt-kneaded resin to room temperature.
In the melt-kneading step, the thermoplastic elastomer is added in an amount of 1 to 18% based on the total volume ratio of the polymethylpentene and the thermoplastic elastomer;
A continuous phase of the polymethylpentene, a dispersed phase of the thermoplastic elastomer, and a compatible phase in which the polymethylpentene and the thermoplastic elastomer are dissolved and which exists at the interface between the continuous phase and the dispersed phase are formed.
A method for producing a resin composition.
[5] The method for producing a resin composition according to [4], wherein the thermoplastic elastomer is at least one selected from the group consisting of styrene-ethylene-butylene-styrene (SEBS), styrene-butadiene-styrene (SBS), and styrene-butadiene rubber (SBR).
[6] The tensile strength A (MPa) of the polymethylpentene alone, the tensile strength B (MPa) of the thermoplastic elastomer alone, the tensile strength C (MPa) of the resin composition, and the area ratio X (%) of the dispersed phase in the resin composition are C>(B-A)X/100+A
The method for producing a resin composition according to [4] or [5],

The present invention makes it possible to improve the tensile properties of a polyolefin resin that has excellent light weight, heat resistance, chemical resistance, and ease of processing due to its thermoplasticity.

FIG. 2 is an explanatory diagram illustrating a phase-separated structure of a resin composition according to an embodiment of the present invention. FIG. 2 is an example of a binarized contrast image of a resin composition according to an embodiment of the present invention, showing a binarized image of a visual field of 100 μm square. FIG. 1 is an example of visualization of the compatible phase of a resin composition according to an embodiment of the present invention by STXM, showing an STXM image with a field of view of 5 μm square. 1 is an example of a K-shell X-ray absorption near-edge fine structure spectrum of a resin composition according to an embodiment of the present invention.

An example of an embodiment of the resin composition of the present invention will be described with reference to FIG. 1. The resin composition in this embodiment has a continuous phase 11 made of polymethylpentene and a dispersed phase 13 made of a thermoplastic elastomer, and has a phase separation structure in which the thermoplastic elastomer is dispersed as domains in the polymethylpentene matrix. The above phase separation structure is also called a sea-island structure, in which the continuous phase is the sea and the dispersed phase are the islands.

The resin composition in this embodiment has a compatible phase 12 at the interface between the continuous phase and the dispersed phase. The compatible phase refers to a phase in which the molecular chains of the polymethylpentene and the thermoplastic elastomer penetrate and dissolve in each other.

The phase separation structure and the presence or absence of compatible phases can be examined using STXM (Scanning Transmission X-ray Microscopy).

The resin composition is adjusted to a thin film of about 100 nm using an ultramicrotome and measured, and the phase separation structure and compatible phase can be identified from the obtained contrast image. The area ratio of the dispersed phase is calculated by binarizing the contrast image of a field of view of 100 μm square obtained by STXM under the condition of 100 nm/pixel. When the continuous phase is black and the dispersed phase is white and binarized under the above conditions, the area ratio shown in white relative to the entire contrast image of a field of view of 100 μm square is the area ratio of the dispersed phase. An example is shown in Figure 2. Furthermore, the presence or absence of a compatible phase can be determined from the binarized image, but it can be further clarified by obtaining a fine structure spectrum near the K-shell X-ray absorption edge. For example, in the case of a resin composition having aromatic rings only in the thermoplastic elastomer, the absorption energy of the aromatic ring of 285 eV is irradiated to obtain a contrast image of a field of view of 5 μm square, and the regions of the continuous phase 31, the dispersed phase 33, and the compatible phase 32 are identified. An example is shown in Figure 3. The wavelength of the incident X-ray is scanned within each region. Then, an X-ray absorption spectrum can be obtained for each phase. An example is shown in FIG. 4. Comparing the spectra obtained for each phase (spectrum 41 of the continuous phase, spectrum 42 of the compatible phase, and spectrum 43 of the dispersed phase in FIG. 4), a spectrum having both the characteristics of the continuous phase and the dispersed phase is obtained for the compatible phase. From this, it is clear that a compatible phase exists. In the resin composition of this embodiment, it is not possible to obtain a sufficient effect simply by including a continuous phase made of polymethylpentene and a dispersed phase made of a thermoplastic elastomer, and it is important that a compatible phase exists at the interface between these phases. The presence of a compatible phase improves interfacial adhesion, and as a result, the stress propagated from the continuous phase reaches the elastomer, which is the dispersed phase, and the stress is dispersed within the elastomer, which is thought to suppress the progression of cracks and improve tensile strength and elongation.

The addition ratio of the thermoplastic elastomer is preferably 1 to 18 vol% relative to the total 100 vol% of the polymethylpentene and the thermoplastic elastomer, and a resin composition is obtained that exhibits a superadditive tensile strength that exceeds the additive tensile strength predicted from the tensile strength of each of the polymethylpentene and the thermoplastic elastomer alone. In addition, the improvement in tensile elongation is also remarkable. A particularly preferred addition ratio of the thermoplastic elastomer is 1 to 15 vol% or 4 to 10 vol% relative to the total 100 vol% of the polymethylpentene and the thermoplastic elastomer. Here, the superadditive tensile strength that exceeds the additive tensile strength predicted from the tensile strength of each of the polymethylpentene and the thermoplastic elastomer alone means that the following formula (1-1) is established.
C>(B-A)X/100+A... Formula (1-1)
In the above formula (1-1), A is the tensile strength (MPa) of the polymethylpentene alone, B is the tensile strength (MPa) of the thermoplastic elastomer alone, C is the tensile strength (MPa) of the resin composition, and X is the area ratio (%) of the dispersed phase in the resin composition. C is preferably 101% or more of A or B, more preferably 105% or more of A, even more preferably 110% or more of A, and most preferably 120% or more of A.

The area ratio of the dispersed phase calculated by the above method is 0.6 to 12.0% relative to the entire contrast image of the resin composition in a field of view of 100 μm square. If the area ratio of the dispersed phase is too small, even if the stress propagated from the continuous phase reaches the elastomer, which is the dispersed phase, the stress is not dispersed within the elastomer, and the crack growth cannot be stopped, so that the tensile strength and elongation are not improved. Therefore, the area ratio of the dispersed phase is 0.6% or more, and may be 1.0% or more, 1.5% or more, 2.0% or more, or 2.5% or more. On the other hand, if the area ratio of the dispersed phase is too high, the adhesion between the continuous phase and the dispersed phase decreases, so that improvement in the tensile strength and elongation cannot be expected. Therefore, the area ratio of the dispersed phase is 12.0% or less, and may be 11.0% or less, 10.0% or less, 9.0% or less, or 8.0% or less.

The thermoplastic elastomer in this embodiment is not particularly limited as long as it can form a compatible phase with polymethylpentene, but examples include olefin-based elastomers and/or styrene-based elastomers. The thermoplastic elastomer is preferably a styrene-based elastomer, and more preferably at least one selected from the group consisting of styrene-ethylene-butylene-styrene (SEBS), styrene-butadiene-styrene (SBS), and styrene-butadiene rubber (SBR).

In this embodiment, the resin composition may be composed of only polymethylpentene and a thermoplastic elastomer, or may further contain other additives within a range that does not impair the purpose. Examples of these other additives include talc, mica, clay, basic magnesium carbonate, aluminum hydroxide, glass flakes, glass fibers, glass beads, carbon fibers, aramid fibers, boron fibers, silicon carbide fibers, steel fibers, PBO fibers, alumina fibers, high-strength polyethylene fibers, calcium carbonate, silica sand, barium sulfate, titanium oxide, antioxidants, flame retardants, flame retardant assistants, ultraviolet absorbers, antibacterial agents, heat stabilizers, antistatic agents, colorants, foaming agents, crosslinking agents, coupling agents, compatibilizers, etc. The content of other additives other than polymethylpentene and a thermoplastic elastomer is preferably 10% by mass or less, and may be 8% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less.

The presence of polymethylpentene or a thermoplastic elastomer in a resin composition can be identified by solid-state NMR measurement, particularly ¹ H and ¹³ C measurement, of the resin composition.

Polymethylpentene and thermoplastic elastomer are blended by melt kneading in a heated environment. The kneading temperature is a temperature equal to or higher than the melting points of the thermoplastic resin and the thermoplastic elastomer, for example, 180°C or higher or 220°C or higher, and kneading is performed under conditions suitable for the materials, for example, a kneading time of 1 minute or more or 2 minutes or more, and a mixer rotation speed of 80 rpm or more or 90 rpm or more, and the resin composition is removed from the kneading mixer and cooled. The kneading temperature may be 300°C or lower or 280°C or lower, and the kneading time may be 10 minutes or lower or 5 minutes or less. The mixer rotation speed may be 150 ppm or lower or 120 ppm or lower. In order to prevent thermal deterioration due to long-term exposure to the high temperature of the kneading mixer, the resin composition is removed from the kneading mixer after kneading, but since a phase separation structure is formed during melt kneading, the subsequent cooling rate does not matter. Kneading can be performed with a known kneading mixer.

The resin composition of this embodiment is a resin composition that has good tensile properties that show the superadditivity law while mainly using a polyolefin resin that has excellent lightness, heat resistance, and chemical resistance as described above. Therefore, this resin composition can be used for a wide range of applications such as home appliance parts, food packaging applications, medical supplies, and automotive parts.

The following are examples of the present invention, but the present invention is not limited to these examples. The methods for producing and measuring various resin compositions in these examples are as follows. The raw materials for each example and comparative example are shown in Table 1.

Example 1
Polymethylpentene (A1) and SEBS (B1) previously dried in a vacuum at 70 ° C. for 24 hours were weighed so that A1:B1 was 96:4 vol%, and melt-kneaded at 225 ° C. in a kneader. A Toyo Seiki R-30 was used as the kneading mixer, and the raw materials were charged so that the filling rate was 80% for a kneading mixer volume of 30 cm ^3. After the entire amount of the raw materials was charged, the kneading time was 3 minutes and the rotation speed was 100 rpm, and the resin composition was taken out of the kneading mixer and naturally cooled. Thereafter, a hot press (Toyo Seiki, tabletop mini hot press) was used to press at 250 ° C., 5 minutes, and 4 MPa, and then water-cooled to prepare a sheet with a thickness of 0.2 mm, and evaluation was performed by a tensile test. The results are shown in Table 2.

Example 2
A1 and B1, which had been previously dried in a vacuum at 70° C. for 24 hours, were weighed out so that A1:B1 was 95:5 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

Example 3
A1 and B1, which had been previously dried in a vacuum at 70° C. for 24 hours, were weighed out so that A1:B1 was 90:10 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

Example 4
A1 and B1, which had been previously dried in a vacuum at 70° C. for 24 hours, were weighed out so that A1:B1 was 85:15 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

Example 5
A1 and SEBS (B2), which had been previously dried in a vacuum at 70° C. for 24 hours, were weighed out so that A1:B2 was 90:10 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

Example 6
A1 and SBS (B3), which had been previously dried in a vacuum at 70° C. for 24 hours, were weighed out so that A1:B3 was 90:10 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 7)
A1, which had been previously dried in a vacuum at 70° C. for 24 hours, and SBR (B4) were weighed out so that A1:B4 was 90:10 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 1)
A1, which had been previously dried in a vacuum at 70° C. for 24 hours, was weighed and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 2)
A1 and B1, which had been previously dried in a vacuum at 70° C. for 24 hours, were weighed out so that A1:B1 was 80:20 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 3)
A1, which had been previously dried in a vacuum at 70° C. for 24 hours, and styrene-isoprene-styrene (SIS) (B5) were weighed out so that A1:B5 was 90:10 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 4)
A1, which had been previously dried in a vacuum at 70° C. for 24 hours, and Bondfast (B6), a glycidyl methacrylate-modified polyethylene copolymer, were weighed out so that A1:B6 was 90:10 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 5)
A1, which had been previously dried in a vacuum at 70° C. for 24 hours, and the thermoplastic polyester elastomer Hytrel (B7) were weighed out so that A1:B7 was 90:10 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 6)
Polypropylene (A2) and B1, which had been previously dried in a vacuum at 70° C. for 24 hours, were weighed out so that A2:B1 was 95:5 vol %, and kneaded in the same manner as in Example 1. Furthermore, the tensile properties were evaluated in the same manner as in Example 1. The results are shown in Table 2.

Tensile tests were performed using a Shimadzu AGS-H to evaluate the tensile strength (MPa) and tensile elongation at break (%). The resin composition was cut into a size of 75 x 10 x 0.2 mm and measured with a gauge length of 10 mm and a crosshead speed of 500 mm/min.

Visualization of the miscible phase and confirmation of the dispersed phase were performed using an STXM. The equipment used was an STXM manufactured by BRUKER ASC installed at beamline BL4U of the Extreme Ultraviolet Research Facility (UVSOR) of the Institute for Molecular Science, National Institutes of Natural Sciences. Thin films of approximately 100 nm were prepared using an ultramicrotome and measurements were performed. Energy of 285 eV was used to obtain the images.

The manufacturing conditions and the verification results obtained for Examples 1 to 7 and Comparative Examples 1 to 6 are summarized in Table 2.

As shown in Table 2, the resin composition of the present invention has a continuous phase composed of polymethylpentene, but contains a thermoplastic elastomer as a dispersed phase, and further has a compatible phase in which polymethylpentene and thermoplastic elastomer are compatible at the interface between them, thereby satisfying formula (1-1) and achieving tensile properties that show superadditivity. In addition, the resin composition of the present invention also achieved good results in terms of tensile elongation at break, specifically, even the lowest tensile elongation at break of 8% was achieved in Examples 6 and 7, and tensile elongation at break of 15% was achieved in Examples 3 and 5. In addition, since the resin composition of the present invention uses polymethylpentene as the main component, it has the light weight, heat resistance, and chemical resistance characteristic of polyolefin resins, as well as ease of processing due to thermoplasticity, and in fact, all of the resin compositions produced had thermoplasticity and were easy to process. On the other hand, the tensile properties of the resin compositions of Comparative Examples 1 to 6 were inferior to the additivity law.

The resin composition of the present invention combines the excellent characteristics of polyolefins with superadditive tensile strength, making it suitable for a wide range of applications, including home appliance parts, food packaging, medical supplies, and automotive parts.

11: Continuous phase 12: Compatible phase 13: Dispersed phase 31: Continuous phase 32: Compatible phase 33: Dispersed phase 41: Spectrum of 31 42: Spectrum of 32 43: Spectrum of 33

Claims (6)

A resin composition comprising polymethylpentene and a thermoplastic elastomer,
The thermoplastic elastomer is at least one selected from the group consisting of styrene-ethylene-butylene-styrene (SEBS) and styrene-butadiene-styrene (SBS);
A continuous phase consisting of the polymethylpentene;
A dispersed phase consisting of the thermoplastic elastomer;
a compatible phase in which the polymethylpentene and the thermoplastic elastomer are compatible with each other and is present at the interface between the continuous phase and the dispersed phase;
The resin composition has an area ratio of a dispersed phase of 0.6 to 12.0%. The tensile strength A (MPa) of the polymethylpentene alone, the tensile strength B (MPa) of the thermoplastic elastomer alone, the tensile strength C (MPa) of the resin composition, and the area ratio X (%) of the dispersed phase in the resin composition are C>(B-A)X/100+A
The resin composition according to claim 1, which satisfies the above. 3. The resin composition according to claim 1, which has a phase-separated structure in which the dispersed phase is dispersed in the continuous phase which serves as a matrix. A method for producing a resin composition, comprising:
A step of melt-kneading polymethylpentene and a thermoplastic elastomer;
and cooling the melt-kneaded resin to room temperature.
In the melt-kneading step, the thermoplastic elastomer is added in an amount of 1 to 18% based on the total volume ratio of the polymethylpentene and the thermoplastic elastomer;
A continuous phase of the polymethylpentene, a dispersed phase of the thermoplastic elastomer, and a compatible phase in which the polymethylpentene and the thermoplastic elastomer are dissolved and which exists at the interface between the continuous phase and the dispersed phase are formed ,
The thermoplastic elastomer is at least one selected from the group consisting of styrene-ethylene-butylene-styrene (SEBS) and styrene-butadiene-styrene (SBS).
A method for producing a resin composition. The tensile strength A (MPa) of the polymethylpentene alone, the tensile strength B (MPa) of the thermoplastic elastomer alone, the tensile strength C (MPa) of the resin composition, and the area ratio X (%) of the dispersed phase in the resin composition are C>(B-A)X/100+A
The method for producing a resin composition according to claim 4, which satisfies the above. The method for producing a resin composition according to claim 4 or 5, which has a phase separation structure in which the dispersed phase is dispersed in the continuous phase which serves as a matrix.