JPH0412900B2 - - 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 expressed by compression set at high temperatures (100° C.), sliding properties and safety, 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, oil, vulcanization accelerator, sulfur, etc. as a filler and reinforcing agent to this. 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, and then a molded body in which multiple gaskets are connected is taken out from the mold, and this molded body is The gaskets were obtained by cutting them into individual gaskets by punching them out. This gasket was further cleaned to remove rubber pieces and foreign matter that had adhered during the punching and burring process, and then coated with silicone to improve sliding performance with the syringe outer cylinder. As described above, since conventional gaskets are mainly made of vulcanizate, they go through a complicated process to obtain a molded product, requiring large-scale equipment, and requiring adjustment and management of additives and the acquisition of many additives during 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. 56-53173 discloses a syringe gasket obtained by injection molding an off-in thermoplastic elastomer.
No. 58-25172 proposes a gasket for a syringe made of a colorable and injection moldable elastomer 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 it no longer functions as a restraining segment, so the compression set at 100°C is extremely poor. Therefore, a syringe gasket made of a thermoplastic elastomer made of this hydrogenated block copolymer was not suitable for being exposed to a high temperature of substantially 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 desire for a syringe gasket that has excellent sliding characteristics and excellent sliding characteristics, and this desire was fully achieved by using a thermoplastic elastomer, which was not previously known as a syringe gasket material. It was discovered that the gasket for syringes has excellent rubber elasticity and sliding properties under high temperatures, as well as excellent safety. That is, the present invention provides (1)(a) a block copolymer comprising a polymer block A mainly composed of at least two vinyl aromatic compounds and a polymer block B mainly composed of at least one conjugated diene compound; Hydrogenated block copolymer obtained by hydrogenating the polymer or the block copolymer 100 parts by weight (b) Bonding unit (where R ₁ , R ₂ , R ₃ , and R ₄ are each selected from the group consisting of hydrogen, halogen, hydrocarbon group, and substituted hydrocarbon group), and has a reduced viscosity (0.5 g/ dl chloroform solution,
Polyphenylene ether resin, which is a homopolymer and/or copolymer whose temperature (measured at 30°C) is in the range of 0.15 to 0.70 (c) 10 to 250 parts by weight (c) Paraffin oil 10 to 300 parts by weight (d) Polyolefin resin The present invention provides a gasket for a syringe having excellent heat resistance, which is molded using a thermoplastic elastomer material obtained by partially crosslinking the mixture and/or polystyrene resin in the presence of an organic peroxide. The present invention will be described in detail below. The block copolymer or hydrogenated block copolymer used as component (a) and (i) in the present invention comprises at least two polymer blocks A mainly composed of vinyl aromatic compounds and at least one polymer block A mainly composed of vinyl aromatic compounds. A block copolymer consisting of a polymer block B mainly composed of a conjugated diene compound, or a block copolymer obtained by hydrogenating the block copolymer.
-B-A, B-A-B-A, (A-B-) ₄ Si, A-
It is a vinyl aromatic compound-conjugated diene compound block copolymer having a structure such as B-A-B-A, or a hydrogenated product of the block copolymer. This block copolymer contains 5 to 60% by weight, preferably 10 to 50% by weight of a vinyl aromatic compound.
means a vinyl aromatic compound polymer block (homopolymer) or 50% by weight vinyl aromatic compound
The polymer block B has a structure of a copolymer block of a vinyl aromatic compound and a conjugated diene compound containing preferably 70% by weight or more, and furthermore, the polymer block B mainly consists of a conjugated diene compound.
Conjugated diene compound polymer block (homopolymer),
Alternatively, it has a structure of a copolymer block of a conjugated diene compound and a vinyl aromatic compound containing more than 50% by weight, preferably 70% by weight or more of the conjugated diene compound. Furthermore, polymer block A mainly composed of vinyl aromatic compounds and polymer block B mainly composed of conjugated diene compounds are based on the distribution of conjugated diene compounds or vinyl aromatic compounds in the molecular chains of each polymer block. but,
It may be random, tapered (monomer component increases or decreases along the molecular chain), partially block-like, or any combination thereof, and is a polymer block mainly composed of the vinyl aromatic compound. When there are two or more polymer blocks A and B mainly composed of the conjugated diene compound, each polymer block has the same structure (molecular weight, weight ratio of the vinyl aromatic compound to the conjugated diene compound, molecular chain (distribution of conjugated diene compounds or vinyl aromatic compounds), and may have different structures. As the vinyl aromatic compound constituting the block copolymer, one or more types can be selected from, for example, styrene, α-methylstyrene, vinyltoluene, p-tert-butylstyrene, and the like, with styrene being preferred. In addition, examples of conjugated diene compounds include butadiene, isoprene, 1.
3-pentadiene, 2,3-dimethyl-1,3-
One or more types are selected from butadiene and the like, and among them, butadiene, isoprene, and a mixture thereof are preferred. In a polymer block mainly composed of a conjugated diene compound, the bond type based on the conjugated diene in the block can be arbitrarily selected. For example, in a polymer block mainly composed of butadiene, the bond type of butadiene is 1. - 2-vinyl bonds account for 5-50%, preferably 10-45%. 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 [ratio of weight average molecular weight (w) to number average molecular weight (n) (w/n)] teeth
10 or less. Furthermore, the molecular structure of the block copolymer may be linear, branched, radial, or any combination thereof. Hydrogenated block copolymers are produced by subjecting block copolymers having the above structure to a hydrogenation reaction, and compared to block copolymers, hydrogenated block copolymers have superior heat resistance and weather resistance. has. These block copolymers may be produced by any method as long as they have the above structure. For example, by the method described in Japanese Patent Publication No. 40-23798, a vinyl aromatic compound-conjugated diene compound block copolymer is synthesized in an inert solvent using a lithium catalyst, etc., and the (a) component of the present invention is synthesized. , a block copolymer of component (i), and a hydrogenated product (hydrogenated block copolymer) of such a vinyl aromatic compound-conjugated diene compound block copolymer.
For example, the manufacturing method of
Although it can be obtained by the method described in JP-A No. 20814, for example, the titanium-based waterborne catalyst can be obtained by the method described in JP-A-59-133203 and JP-A-60-79005. Hydrogenated block copolymers of component (a) and component (i) to be used in the present invention can be synthesized by hydrogenation in the presence of. At this 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. 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 measured using an infrared spectrophotometer,
It can be easily determined using a nuclear magnetic resonance apparatus or the like. Next, the polyphenylene ether resin used as component (b) and component (ii) of the present invention is an essential component for improving the compression set of the resulting composition,
bonding unit (Here, R ₁ , R ₂ , R ₃ , and R ₄ are each selected from the group consisting of hydrogen, halogen, and hydrocarbon groups, and may be the same or different from each other.) and or copolymer at 30°C in 0.5g/dl chloroform solution.
Those having a reduced viscosity measured in the range of 0.15 to 0.70 are used, and those having a reduced viscosity of 0.20 to 0.60 are more preferably used. A known polyphenylene ether resin is used as this polyphenylene ether resin. Specifically, poly(2,6-dimethyl-1,4-phenylene ether), poly(2-methyl-6ethyl-1,4-phenylene ether), poly(2,
6-diphenyl-1,4-phenyleneniter),
Poly(2-methyl-6-phenylene-1,4-phenylene ether), poly(2,6-dichloro-
1,4-phenylene ether), and copolymers of 2,6-dimethylphenol and valent phenols (for example, 2,3,6-trimethylphenol and 2-methyl-6-butylphenol). Also included are polyphenylene ether copolymers such as polyphenylene ether copolymers. Among them, poly(2,6-dimethyl-
1,4-phenylene) ether, a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol is preferred, and furthermore, poly(2,
6-dimethyl-1,4-phenylene) ether is preferred. In the case of poly(2,6-dimethyl-1,4-phenylene ether), its reduced viscosity (0.5 g/dl,
(chloroform solution, measured at 30°C) preferably ranges from 0.15 to 0.70, more preferably from 0.30 to 0.70.
It is in the range of 0.60. The blending amount of component (b) and component (ii) is the block copolymer or hydrogenated block copolymer of component (a) and component (i).
It can be suitably selected in the range of 10 to 250 parts by weight relative to 100 parts by weight. If the blending amount is less than 10 parts by weight, the effect of adding the polyphenylene ether resin is that the rubber elasticity (compression set) of the syringe gasket at high temperatures (100°C) cannot be improved, which is undesirable. In addition, if the amount exceeds 250 parts by weight, the hardness of the thermoplastic elastomer material obtained will be too high, making it unsuitable for use as a material for syringe gaskets due to loss of flexibility, and more importantly, high temperature performance. This is not preferred because the rubber elasticity [compression set (100°C x 22 hours)] is poor. Next, the paraffinic oil that can be used as components (c) and (iii) of the present invention is advantageous in adjusting the hardness and imparting flexibility to the resulting syringe gasket. The paraffin oil provided here can be called liquid paraffin, which is purified by removing impurities such as aromatic hydrocarbons and sulfur compounds contained in the lubricating oil fraction of petroleum with sulfuric anhydride or fuming sulfuric acid, and then purifying it with saturated carbonized oil. It is a colorless, transparent, tasteless, and odorless oil made of hydrogen, and liquid paraffin that has passed the Japanese Pharmacopoeia (JP), food additive standards, cosmetic raw material standards, ultraviolet absorbance test (260-350 nm), etc. can be used. In addition to the above-mentioned liquid paraffin, petroleum-based softeners approved by the FDA (US Food and Drug Administration) can also be useful as components (c) and (iii) in the present invention. The amount of paraffin oil used is (a) component,
The amount is 10 to 300 parts by weight, preferably 30 to 250 parts by weight, per 100 parts by weight of the block copolymer or hydrogenated block copolymer of component (i). If the amount exceeds 300 parts by weight, the oil tends to bleed out and the final product, the syringe gasket, may become sticky, which is undesirable, and the mechanical strength is also undesirably lowered. Also
If the amount is less than 10 parts by weight, it is not preferable from the viewpoint of imparting flexibility and economical efficiency. Next, the polyolefin resin and/or polystyrene resin used as the component (d) and (iv) of the present invention are effective in improving the processability and/or heat resistance of the resulting syringe gasket, and as a polyolefin resin, For example, polyethylene, isotactic polypropylene, copolymers of propylene with small amounts of other α-olefins, such as propylene-ethylene copolymers, propylene/4-methyl-1-pentene copolymers, and poly-4-methyl- Examples include 1-pentene and polybutene-1. When using isotactic polypropylene or its copolymer as the polyolefin resin, its MFR (ASTM-D1238
-L condition, 230℃) is 0.1 to 50g/10 minutes, especially
Those in the range of 0.5 to 30 g/10 minutes can be suitably used. Further, polystyrene resin can be suitably used by either radical polymerization or ionic polymerization as long as it can be obtained by a known manufacturing method, and its number average molecular weight is 5000 to 500000, preferably 10000 to 10000.
The molecular weight distribution [ratio (w)/(n) of weight average molecular weight (w) to number average molecular weight (n)] is preferably 5 or less. Examples of this polystyrene resin include polystyrene, styrene containing 60% by weight or more of styrene,
Examples include butadiene block copolymer, rubber-reinforced polystyrene, polyα-methylstyrene, polyp-tert-butylstyrene, etc. Two or more types of these may be used, and furthermore, these polymers may be composed of It may be a copolymer obtained by polymerizing a mixture of monomers. The polyolefin resins and polystyrene resins listed here as components (d) and (iv) can also be blended together in the components (d) and (iv). 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, the ratio of polyolefin resin/polystyrene resin is 95/5.
It is preferable to select from among 5/95 (weight ratio). The amount of ingredients (d) and (iv) is the same as that of ingredients (a) and (i).
The amount is 10 to 200 parts by weight, preferably 30 to 150 parts by weight, per 100 parts by weight. If the amount exceeds 200 parts by weight, the hardness of the resulting elastomeric composition becomes too high and flexibility is lost, and although the sliding properties of the syringe gasket are improved, a product with a rubber-like feel cannot be obtained. However, the balance between rubber elasticity (compression set) and sliding properties at high temperatures deteriorates, which is undesirable. This is because the gasket for a syringe is usually molded with an outer diameter slightly larger than the inner diameter of the syringe outer barrel so that there is no gap between the syringe outer barrel and the gasket. This is because rubber elasticity cannot be maintained if the amount exceeds 200 parts by weight. In addition, if the amount is less than 10 parts by weight, although the rubber elasticity of the resulting gasket is good, the processability during molding and the sliding characteristics of the gasket when inserted into the syringe barrel deteriorate, which is not preferable. 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) or (i) to (iv) and optionally addable components. , for example, by melt-kneading using various heating kneaders such as a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, a Brabender, a kneader, etc., and further adding an organic peroxide and a crosslinking aid that are essential in the second invention. It can be easily obtained by adding and melt-kneading, or by mixing these necessary components simultaneously and heating and melt-kneading. In the partial crosslinking of the second invention, 1 g of thermoplastic elastomer is extracted with boiling xylene in a Soxhlet extractor for 10 hours, and then the residue is removed.
The value obtained by dividing the weight of the solid obtained by filtration through an 80-mesh wire mesh by the amount of component (i) contained in 1 g of the same sample multiplied by 100 is preferably 20-95%, more preferably 30-95%. Adjust crosslinking to within 90% range. The organic peroxide that can be provided in this second invention is, 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 -butylperoxyisopropyl)-benzene, benzoyl peroxide, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, etc., and useful crosslinking aids include:
Examples include divinylbenzene, trimethylolpropane triacrylate, ethylene dimethacrylate, diallyl phthalate, quinone dioxime, phenylene bismaleimide, polyethylene glycol dimethacrylate, and unsaturated silane compounds. These organic peroxides and crosslinking aids can be suitably used from 0.1 to 5 parts by weight per 100 parts by weight of components (i) to (iv), and the degree of crosslinking can be adjusted as desired. These organic peroxides and crosslinking aids may be used in combination of two or more, if necessary. In addition, when an unsaturated silane compound is used as a crosslinking aid, crosslinking can be further progressed by contacting with moisture in the presence of a silanol condensation catalyst. The thermoplastic elastomer of the present invention 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 specific component that has not been seen before, or a thermoplastic elastomer material containing a partially crosslinked product of the specific component. At high temperatures required for gaskets (100
°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 syringe gaskets of 5 c.c. and 10 c.c., attach them to the syringe pusher, insert them into the syringe outer cylinder, and measure the load (g) during the initial movement and sliding of the syringe pusher. did. In the accompanying drawings, the shaded area in FIG. 1 shows the cross section of the entire gasket, which consists of a cylindrical body 1 having a hollow hole 5 formed 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. In addition, FIG. 2 shows that the tip 7 of a cylinder pusher 6 is attached to the cylindrical hollow hole 5 of this gasket. In addition, the ingredients blended are as follows. (1) <(Synthesis a-1)> (Polystyrene-polybutadiene-) Has a structure of ₄ Si, the amount of bound styrene is 35% by weight, and the number average molecular weight
103000, a molecular weight distribution of 1.29, and a 1,2-vinyl bond content of 14% in the polybutadiene moiety, a styrene-butadiene block copolymer was synthesized in an inert solvent using a butyllithium catalyst and tetraterminated silicon. ). <Component (a-2)> Hydrogenated polybutadiene-polystyrene-hydrogenated polybutadiene-polystyrene structure, bound styrene content 30% by weight, number average molecular weight 143000, molecular weight distribution 1.06, polybutadiene before hydrogenation 1,2-vinyl content of 41%, hydrogenation rate
99% hydrogenated block copolymer published in JP-A-60-79005
Component (a-2) was synthesized using the Ti-based hydrogenation catalyst described in the publication. <Component (a-3)> It has a structure of polystyrene-hydrogenated polybutadiene-polystyrene, and the amount of bound styrene is 43
Weight%, number average molecular weight 177000, molecular weight distribution 1.05,
A hydrogenated block copolymer with a 1,2-vinyl bond content of 34% in the polybutadiene moiety before hydrogenation and a hydrogenation rate of 99% was prepared using a Ti-based hydrogenation catalyst described in JP-A-59-133203. This was synthesized to obtain component (a-3). <Component (a-4)> It has a structure of polystyrene-hydrogenated polybutadiene-polystyrene, and the amount of bound styrene is 33
% by weight of KRATON-G1651 (manufactured by Shell Chemical Co., USA) was used as component (a-4). <Component (a-5)> (Polystyrene - hydrogenated polybutadiene) has a structure of ₄ Si, with a bound styrene content of 20% by weight,
Number average molecular weight 136,000, molecular weight distribution 1.43, 1,2-vinyl bond amount in the polybutadiene part before hydrogenation is 37
%, a hydrogenated block copolymer with a hydrogenation rate of 99%
Component (a-5) was synthesized using the Ti-based hydrogenation catalyst described in Japanese Patent No. 59-133203. In addition, as component (-1), component (-2), component (-3), and component (-4), component (a-2), component (a-3), component (a-4), and
Component (a-5) was used. (2) <Component (b-1>) Poly(2,6-dimethyl-1,4-phenylene) ether (ring base viscosity: 0.58) was synthesized as a polyphenylene ether resin. <Component (b-2) 〉 As polyphenylene ether resin, 2.3.
2.6 containing 5 mol% 6-trimethylphenol
- A 2,6-dimethylphenol/2,3,6-trimethylphenol copolymer (ring base viscosity: 0.37) was synthesized from dimethylphenol. In addition, as component (-1) and component (-2),
Component (b-1) and component (b-2) were used, respectively. (3) Component (c) Liquid paraffin manufactured by Matsumura Sekiyu Co., Ltd.; Smoyl P-
350 [Kinematic viscosity (37.8℃) 75.5cst, naphthene component 37
%, paraffin component 63%] Note that component (c) was used as component (iii). (4) <Component (d-1)> As a polyolefin resin, Asahi Polypro M-
1300 (isotactic polypropylene, MFR
4 g/10 minutes, manufactured by Asahi Kasei Co., Ltd.) was used as the component (d-1). In addition, as the component (-1), this (d-1)
using the ingredients. <Component (d-2)> As a polystyrene resin, Stylon 685 (polystyrene, MFR 3 g/10 minutes, manufactured by Asahi Kasei Corporation) was used as the component (d-2). In addition, as component (-2), this (d-2)
using the ingredients. (5) Organic peroxide; Perhexa 25B (2,5-dimethyl-2,5-di(t-
butylperoxy)hexane> (6) Crosslinking aid; trimethylolpropane triacrylate (manufactured by Seiko Kagaku Co., Ltd.) (7) Inorganic filler: Talc Examples 1 to 5, Comparative Examples 1 and 2 Each component shown in Table 1 was The mixture was mixed in a Henschel mixer and melt-kneaded in a 50 mm diameter twin screw extruder at 240°C to obtain thermoplastic elastomer pellets. Using the thermoplastic elastomer pellets obtained here, syringe gaskets were made at a temperature setting of 200 to 250°C using an injection molding machine equipped with 5 c.c. and 10 c.c. syringe gasket molds. Molded. Then, the syringe pusher equipped 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, 150mm×
Injection molding was carried out using an injection molding machine equipped with a flat plate mold of 150 mm x 2 mm (thickness) at a set temperature of 200 to 250°C. Various performance tests were conducted using the syringe and test piece obtained here, and the results are listed in Table 1. From these results, it was found that the syringe gasket of the present invention was excellent in high-temperature compression set at 100°C and also had excellent sliding properties. In addition, it was found that a comparative example of a syringe gasket molded from a thermoplastic elastomer other than the one according to the invention had poor high-temperature compression set and poor sliding properties.

【table】

[Table] Example 6 The runner parts that were no longer used during injection molding in Example 2 were collected and heated again at 230°C using a 30mmφ twin-screw extruder.
The mixture was kneaded to obtain granulated pellets. This product was again injection molded under the same conditions as in Example 2 to obtain a syringe gasket and a test piece for physical property testing.The physical properties and sliding characteristics were measured in the same manner as in Example 2.The hardness was 64. , tensile strength 176Kg/cm ² , elongation 720%, compression set at 100℃ 48%, syringe initial motion value of 5 c.c. 156 g, sliding value 58 g, syringe initial motion value of 10 c.c. 118 g, sliding value 51 g It has been found that the thermoplastic elastomer that is the material for the syringe gasket of the present invention has reworkability and is excellent in heat resistance and sliding properties. Examples 7 to 10, Comparative Examples 3 and 4 Table 2 excluding organic peroxide and crosslinking aid
Thermoplastic elastomer pellets were obtained by mixing the components shown in the following in a Henschel mixer and heating and kneading the mixture in advance at 240°C in a 50 mm diameter twin screw extruder. Thereafter, to 100 parts by weight of the obtained polymer, organic peroxide and crosslinking aid were added in the equivalent amounts shown in Table 1, and an antioxidant (Irganox
1330 (manufactured by Ciba Geigy) was added and mixed in a Henschel mixer, followed by reaction at 240°C in a 50 mm diameter twin screw extruder to obtain a partially crosslinked thermoplastic elastomer. Using the thermoplastic elastomer pellets obtained here, an injection molding machine equipped with a syringe gasket mold of 5 c.c. and 10 c.c.
A gasket for a syringe was molded at a set temperature of 200-250°C. Then, the syringe pusher fitted with this gasket was inserted into a polypropylene syringe outer cylinder to produce 5 g and 10 c.c. syringes. On the other hand, for making test pieces for measuring physical properties.
Injection molding was carried out using an injection molding machine equipped with a flat plate mold of 150 mm x 150 mm x 2 mm (thickness) at a set temperature of 200 to 250°C. Various performance tests were conducted using the syringe and test piece obtained here, and the results are shown in Table 2.
I posted it on. From these results, it was found that the syringe gasket of the present invention was excellent in high-temperature compression set at 100°C and also had excellent sliding properties. On the other hand, it was revealed that the syringe gasket of the comparative example made of a thermoplastic elastomer other than the one according to the present invention was inferior in compression set at 100° C. and poor balance in sliding properties.

【table】

[Table] Examples 11 and 12 The syringe gaskets obtained in Examples 2 and 9 were subjected to material and eluate tests in accordance with the rubber stopper test method for infusions of 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] Example 13 Styrene-butadiene block copolymer having a polystyrene-polybutadiene-polystyrene structure, with a bound styrene content of 30%, a number average molecular weight of 144,000, a molecular weight distribution of 1.07, and a 1,2-vinyl bond content of the polybutadiene portion of 11%. The combination was synthesized in an inert solvent using a butyllithium catalyst. This block copolymer
100 parts by weight, component (b-1) 100 parts by weight, component (c) 110 parts by weight
A thermoplastic elastomer was prepared using 40 parts by weight of component (d-2) in the same manner as in Example 1, and injection molded in the same manner to obtain a gasket for a syringe and a test piece for measuring physical properties. After various performance tests were conducted, the hardness was 68, and the tensile strength was 68.
126Kg/cm ² , elongation 610%, compression set (100℃) 61
%, initial movement value of 5 c.c. syringe 168 (g), sliding value 64
(g), initial movement value of 10 c.c. syringe 127 (g), sliding value
It was 57 (g).

[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. DESCRIPTION OF SYMBOLS 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)

[Claims] 1(a) A polymer block A mainly composed of at least two vinyl aromatic compounds; and at least one
100 parts by weight (b) of a block copolymer consisting of a polymer block B mainly composed of a conjugated diene compound, or a hydrogenated block copolymer obtained by hydrogenating the block copolymer. (wherein R ₁ , R ₂ , R ₃ and R ₄ are each selected from the group consisting of hydrogen, halogen, hydrocarbon group, substituted hydrocarbon group) and has a reduced viscosity (0.5 g/dl chloroform solution,
Polyphenylene ether resin, which is a homopolymer and/or copolymer whose temperature (measured at 30°C) is in the range of 0.15 to 0.70 (c) 10 to 250 parts by weight (c) Paraffin oil 10 to 300 parts by weight (d) Polyolefin resin Gasket 2 for a syringe with excellent heat resistance molded from a thermoplastic elastomer material comprising 10 to 200 parts by weight of polystyrene resin and/or polystyrene resin (i) At least two polymer blocks A mainly composed of vinyl aromatic compounds;
100 parts by weight of a block copolymer consisting of a polymer block B mainly composed of a conjugated diene compound, or a hydrogenated block copolymer obtained by hydrogenating the block copolymer (ii) Bonding unit (wherein R ₁ , R ₂ , R ₃ and R ₄ are each selected from the group consisting of hydrogen, halogen, hydrocarbon group, substituted hydrocarbon group) and has a reduced viscosity (0.5 g/dl chloroform solution,
Polyphenylene ether resin, which is a homopolymer and/or copolymer whose temperature (measured at 30°C) is in the range of 0.15 to 0.70 10 to 250 parts by weight (iii) Paraffin oil 10 to 300 parts by weight (iv) Polyolefin resin A gasket for syringes with excellent heat resistance molded from a thermoplastic elastomer material obtained by partially crosslinking a mixture of 10 to 200 parts by weight of polystyrene resin and/or polystyrene resin in the presence of organic peroxide.