JPH043777B2 - - 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 compression set, rebound resilience, slidability 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. Auxiliary agents are added and kneaded, and the material is formed into a sheet using rolls. The material is fed into a gasket mold, heated and pressurized to vulcanize it, and then a molded product in which multiple gaskets are connected is taken out from the mold, and this molded product 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 during the punching and burring process, 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 using a gasket press mold takes a long time, with the vulcanization time being approximately 10 minutes, compared to the injection molding time of approximately 10 to 30 seconds when injection molding thermoplastic polymers. This 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
The publication discloses a gasket for a syringe obtained by injection molding an olefinic thermoplastic elastomer.
53173 and Japanese Patent Application Laid-open No. 58-25172,
Gaskets for syringes have been proposed that are molded from a colorable and injection moldable elastomeric material comprising 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, its productivity was improved, and it also exhibited good compression set and excellent rubber elasticity. (Problems to be Solved by the Invention) However, since the syringe gasket obtained by this proposal uses a polyolefin resin such as polypropylene, ethylene, which is the so-called soft segment of the hydrogenated block copolymer provided, is Since the copolymerized portion of and butylene has good compatibility with the polyolefin, there is a drawback that the soft segment region is substantially hardened, and as a result, the rubber elasticity (compression set) of the syringe gasket is reduced.
The balance between hardness, hardness, and sliding properties is still insufficient, and when emphasis is placed on sliding properties, rubber elasticity tends to deteriorate, making it virtually impossible to obtain thermoplastic gaskets for syringes with an excellent balance of both performances. That was the current situation. (Means for Solving the Problems) The present invention was made to solve the problems that were difficult to solve with the elastomer molding materials presented in the above-mentioned conventional proposals. This was created based on the need for a thermoplastic gasket for syringes that has excellent rubber elasticity (compression set) and excellent sliding properties while being processable and recyclable. It has been discovered that this thermoplastic gasket for syringes has excellent rubber elasticity, sliding properties, and safety, and is fully achieved by using a thermoplastic elastomer material made of unknown specific components. . That is, the present invention has (a) a polymer block A mainly composed of at least two vinyl aromatic compounds, the polymer chain terminal is constituted by the polymer block A, and further includes at least one conjugated diene compound. Hydrogenated block copolymer obtained by hydrogenating a block copolymer consisting of intermediate polymer block B mainly composed of 100 parts by weight (b) Paraffin oil 30 to 300 parts by weight (c) Polystyrene resin 10 The present invention provides a thermoplastic gasket for a syringe molded from an elastomeric material comprising ~200 parts by weight. The present invention will be described in detail below. The hydrogenated block copolymer used as component (a) in the present invention has at least two polymer blocks A mainly composed of vinyl aromatic compounds, and the polymer chain terminals are composed of the polymer blocks A. , and further an intermediate polymer block B mainly composed of at least one conjugated diene compound, such as A-B-A, (A-B-) ₄ Si, A-B-A-B-
This is a hydrogenated vinyl aromatic compound-conjugated diene compound block copolymer having a structure such as A. This hydrogenated block copolymer contains 5 to 60% by weight, preferably 10 to 60% by weight of a vinyl aromatic compound.
Containing 50% by weight, and referring to the block structure, polymer block A mainly composed of a vinyl aromatic compound is a vinyl aromatic compound polymer block or contains more than 50% by weight, preferably 70% by weight of a vinyl aromatic compound. It has the structure of a copolymer block of the above-contained vinyl aromatic compound and a hydrogenated conjugated diene compound, and furthermore, an intermediate polymer block B mainly composed of a hydrogenated conjugated diene compound, A hydrogenated conjugated diene compound polymer block or a copolymer block of a hydrogenated conjugated diene compound and a vinyl aromatic compound containing more than 50% by weight and preferably 70% by weight or more of a hydrogenated conjugated diene compound. It has a structure. In addition, polymer block A mainly composed of these vinyl aromatic compounds and intermediate polymer block B mainly composed of hydrogenated conjugated diene compounds are composed of hydrogenated conjugates in the molecular chains of each polymer block. The distribution of the diene compound or vinyl aromatic compound may be random, tapered (monomer component increases or decreases along the molecular chain), partially block-like, or any combination thereof, and the vinyl aromatic When there are two or more polymer blocks each consisting mainly of a group compound and the hydrogenated conjugated diene compound, each polymer block may have the same structure or may have different structures. It may be a structure. As the vinyl aromatic compound constituting the hydrogen 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, examples of the conjugated diene compound before hydrogenation constituting the hydrogenated conjugated diene compound include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-
One or more types are selected from 1,3-butadiene and the like, and among them, butadiene, isoprene, and a combination 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)]
The ratio (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. 40-2798, and then, for example, 8704
Publication No. 43-6636, or Japanese Patent Publication No. Sho 43-6636, or
The hydrogenated block copolymer used in the present invention is synthesized by hydrogenation in the presence of a hydrogenation catalyst in an inert solvent by the method described in JP-A No. 59-133203 and JP-A No. 60-79005. can do.
In this case, 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,
A polymer block mainly composed of a conjugated diene compound can be morphologically converted into an olefinic compound polymer block. In addition, hydrogenation of aromatic double bonds based on vinyl aromatic compounds copolymerized into polymer block A mainly composed of vinyl aromatic compounds and, if necessary, polymer block B mainly composed of conjugated diene compounds. Although there is no particular restriction on the hydrogenation 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 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 petroleum lubricating oil fraction 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 to 350 nm), etc. can be used. In addition to the liquid paraffin described above, petroleum-based softeners approved by the FDA (US Food and Drug Administration) can also be useful as component (b) in the present invention. The amount of paraffin oil used is 30 to 300 parts by weight per 100 parts by weight of the hydrogenated block copolymer (a).
Parts by weight, preferably 50 to 150 parts by weight.
If the amount exceeds 300 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 polystyrene resin used as component (c) of the present invention is used not only to improve the processing method during molding but also to adjust the hardness of the resulting syringe gasket. This polystyrene resin has a characteristic that the resulting syringe has a softer hardness than the known method of adding a polyolefin resin. As the polystyrene resin provided here, those obtained by known radical polymerization methods and ionic polymerization methods can be suitably used, and the number average molecular weight of
It can be selected from the range of 5,000 to 500,000, preferably 10,000 to 200,000, and the molecular weight distribution [weight average molecular weight (
w) and number average molecular weight (n) (w/
n] is preferably 5 or less. Specifically, examples include polystyrene, rubber-reinforced polystyrene, poly-alpha-methylstyrene, poly-p-tert-butylstyrene, and styrene-butadiene block copolymer with a styrene content of 60% by weight or more. You may use it. Similarly,
It may be a copolymer obtained by polymerizing a mixture of monomers constituting these polymers. The amount of the component (c) mentioned above can be suitably selected in the range of 10 to 200 parts by weight, with 15 to 100 parts by weight based on 100 parts by weight of the hydrogenated block copolymer of component (a). preferable. If the formulation exceeds 200 parts by weight,
The hardness of the obtained syringe gasket becomes too high and the rubber elasticity (compression set) deteriorates, which is not preferable. 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 is 200 parts by weight or more. In addition, if the amount is less than 10 parts by weight, although the resulting syringe gasket has good rubber elasticity, the processability during molding and the sliding properties of the gasket when inserted into the syringe barrel deteriorate, which is not preferable. (a) ~ which can be provided for the present invention listed above
In addition to component (c), ingredients that can be added as necessary to the syringe gasket of the present invention include hindered amine light stabilizers, ultraviolet absorbers, antioxidants, inorganic fillers, colorants, and silicone oil. Furthermore, polyolefin resins such as polypropylene, polyethylene, propylene/α-olefin copolymers, etc. can also 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 (c) and components that can be added as necessary, for example, by single-screw extrusion or twin-screw extrusion. It can be easily obtained by melt-kneading using various heating kneaders such as mills, rolls, Banbury mixers, Brabenders, and kneaders.
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 used again as materials for syringe gaskets. (Effects of the Invention) The syringe gasket obtained by the present invention uses a thermoplastic elastomer material consisting of specific components that have not been seen before, so it has the rubber elasticity (compression set) required for a syringe gasket.
The balance of sliding characteristics has been improved.
Furthermore, since it is a thermoplastic elastomer that does not contain sulfur like vulcanized rubber, there is no elution of sulfur into the chemical solution or blood that comes into contact with the gasket, and since it does not contain heavy metals such as zinc, there is no elution of sulfur. 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 70°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)> It has a polystyrene-hydrogenated polybutadiene-polystyrene structure, with a bound styrene content of 25% by weight, a number average molecular weight of 147,000, and a molecular weight distribution.
1.05, the amount of 1,2-vinyl bonds in the polybutadiene moiety before hydrogenation is 41%, and the hydrogenation rate is 99% using the Ti-based hydrogenation catalyst described in JP-A-59-133203 It was synthesized using Component (a-1). <Component (a-2)> (Polystyrene-hydrogenated polybutadiene) - has a structure of ₄ Si, the amount of bound styrene is 18% by weight, the number average molecular weight is 139000, the molecular weight distribution is 1.43,
A hydrogenated block copolymer with a 1,2-vinyl bond content of 35% in the polybutadiene moiety before hydrogenation and a hydrogenation rate of 99% was prepared using a Ti-based hydrogenation catalyst described in JP-A-60-79005. This was synthesized to obtain component (a-2). <Component (a-3)> Kraton-G1651 (manufactured by Ciel Chemical Co., Ltd.) having a polystyrene-hydrogenated polybutadiene-polystyrene structure and containing 33% by weight of bound styrene was used as component (a-3). (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) <Component (c)> Polystyrene resin manufactured by Asahi Kasei Industries, Ltd., Styron-685 [MFR (200°C) 3 g/10 minutes] Examples 1 to 3, Comparative Examples 1 to 3 As a hydrogenated block copolymer, component (a-1),
Using (a-2) and (a-3), each component shown in Table 1 was mixed in a Henschel mixer, and melted and kneaded at 220°C in a 50 mm diameter twin screw extruder to form a thermoplastic elastomer. of pellets were obtained. In the comparative example, isotactic polypropylene (Asahi Polypro M-1600; manufactured by Asahi Kasei Corporation) was used instead of polystyrene resin. 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 temperature setting of 0.degree. C. to 220.degree. 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, in order to prepare a test piece for measuring physical properties, injection molding was carried out at a set temperature of 190°C to 220°C using an injection molding machine equipped with a flat plate mold of 150 mm x 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 a higher
It was found that although the hardness is soft and the compression set is excellent, the sliding properties are excellent.

[Table] Examples 4 to 6 Using component (a-1) as the hydrogenated block copolymer, each component shown in Table 2 was molded in the same manner as in Examples 1 to 3, and syringe gaskets and test pieces were made. I got it. The physical properties and sliding characteristics of this material were measured and listed in Table 2. These results revealed that the syringe gasket within the scope of the present invention has excellent sliding properties and rubber elasticity.

【table】

[Table] Example 7 Component (a-1) as a hydrogenated block copolymer
100 parts by weight, liquid paraffin (Smoil P-350)
120 parts by weight, polystyrene (Styron-685)
A thermoplastic elastomer was obtained by heating and kneading 40% of the mixture by the method shown in Examples 1 to 3. This was further molded into a syringe gasket using an injection molding machine, and material and eluate tests were conducted in accordance with the test method for rubber stoppers for infusions in the 10th edition of the Japanese Pharmacopoeia. The results are listed 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 cylinder; 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) It has at least two polymer blocks A mainly composed of vinyl aromatic compounds, the polymer chain terminal is constituted by the polymer blocks A, and further comprises at least one conjugated diene. Hydrogenated block copolymer obtained by hydrogenating a block copolymer consisting of compound-based intermediate polymer block B (b) 100 parts by weight (b) Paraffin oil 30 to 300 parts by weight (c) Polystyrene resin A thermoplastic gasket for syringes made of 10 to 200 parts by weight of elastomer material.