JPH0217578B2 - - 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, impact resilience, heat resistance, 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. 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 to it during the punching and deburring process, and then silicone was applied to it to improve its sliding properties 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 and 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. Additionally, gaskets obtained by this method have sulfur, vulcanization accelerators, etc. added during manufacturing, so if they come into contact with medical solutions such as injections or 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 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, its productivity was improved, and it also exhibited good compression set and excellent rubber elasticity. (Problems to be Solved by the Invention) However, although the syringe gasket obtained by this proposal has excellent rubber elasticity, its sliding properties are still insufficient. At present, it is virtually impossible to obtain. (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 syringe gasket that has excellent rubber elasticity (compression set) and excellent sliding properties while being processable and recyclable. A gasket for syringes with excellent rubber elasticity, sliding properties, and safety, achieved by a thermoplastic elastomer material made of a specific component using a hydrogenated block copolymer with a specific structure. It was discovered that That is, the present invention has (a) a polymer block A mainly composed of at least two vinyl aromatic compounds and a polymer block B mainly composed of at least two conjugated diene compounds; Hydrogenated block copolymer obtained by hydrogenating a block copolymer characterized in that at least one block B is arranged at the end of the polymer chain 100 parts by weight (b) Paraffin oil 30 to 300 parts by weight (c) A gasket for a syringe is provided which is molded from a thermoplastic elastomer material comprising 10 to 200 parts by weight of a polyolefin resin and/or a polystyrene resin. 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 two vinyl aromatic compounds and a polymer block A mainly composed of at least two conjugated diene compounds. B, and has a specific structure in which at least one polymer block B is arranged at the end of the polymer chain, so it has the effect of improving the sliding properties of the syringe gasket obtained by the present invention. The structure is represented by the general formula as follows. (B-A) - _o n≧2 (B-A) - _o B n≧2 (B-A) - _n X (-B-A) _o m, n≧1, m+
n≧2 (B-A)― _n X(-A-B-A) _o m, n≧1,
m+n≧2 (here, X is a coupling agent or a polyfunctional polymerization initiator residue having a functional group number of 2 or more) To give some more specific examples, B-A-B-A, B-A -B-A-B, (B-
A) _-4Si , and a hydrogenated block copolymer consisting of a mixture thereof. As mentioned above, the hydrogenated block copolymer always has a hydrogenated structure in which at least one of the polymer chain ends is a polymer block B mainly composed of a conjugated diene compound, and the polymer chain ends always have a vinyl aromatic structure. Polymer blocks mainly composed of group compounds, such as A-B-A, A-B-A-B-A, (A-B
)-- ₄ Compared to a hydrogenated vinyl aromatic-conjugated diene compound block copolymer having a structure such as Si, when combined as a composition, the sliding properties and rubber elasticity (compression set ) has outstanding characteristics of balance. The hydrogenated block copolymer provided as component (a) contains 5 to 60% by weight, preferably 10 to 50% by weight of a vinyl aromatic compound. Polymer block A is a vinyl aromatic compound polymer block or a copolymer of a vinyl aromatic compound containing more than 50% by weight and preferably 70% by weight or more and a hydrogenated conjugated diene compound. The polymer block B, which has the structure of a hydrogenated conjugated diene compound as a main component, is a hydrogenated conjugated diene compound polymer block, or a hydrogenated conjugated diene compound Preferably more than % by weight
It has a structure of a copolymer block of a hydrogenated conjugated diene compound and a vinyl aromatic compound containing 70% by weight or more. In addition, polymer block A mainly composed of these vinyl aromatic compounds and polymer block B mainly composed of hydrogenated conjugated diene compounds are composed of hydrogenated conjugated diene in the molecular chain of each polymer block. The distribution of the 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. The polymer blocks A mainly composed of vinyl aromatic compounds may have the same structure as described above, or may have different structures. In addition, at least one polymer block mainly composed of a hydrogenated conjugated diene compound is arranged at the end of the polymer chain, and the above-mentioned polymer chain end is always a polymer block mainly composed of a vinyl aromatic compound. A hydrogenated block copolymer having a structure (for example, A-
When molded into a syringe gasket, it improves the balance between sliding properties and rubber elasticity (compression set) when molded as a syringe gasket. Therefore, the polymer block B mainly consists of a hydrogenated conjugated diene compound located at the end of the polymer chain.
It is preferably 3 to 30 wt% based on the total amount of the polymer,
More preferably, it is 5 to 15 wt%. When there are two or more polymer blocks B mainly composed of other hydrogenated conjugated diene compounds in the polymer chain, they may each have the same structure as described above or may be different. 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, 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 can be 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) of the hydrogenated block copolymer to The block copolymer before hydrogenation may be produced by any method as long as it has the above-mentioned structure. A vinyl aromatic compound having the above structure may be prepared using a lithium catalyst or the like in an inert solvent.
Conjugated diene compound block copolymers can be synthesized. Next, as a method for producing a hydrogenated product of such a vinyl aromatic compound-conjugated diene compound block copolymer, it may be obtained by the method described in, for example, Japanese Patent Publication No. 42-8704 and Japanese Patent Publication No. 43-6636. However, hydrogenated block copolymers synthesized using titanium-based hydrogenation catalysts are most preferred because they exhibit excellent weather resistance and heat deterioration resistance, such as Unexamined Japanese Patent Publication 1987
The hydrogenated block copolymer used in the present invention is obtained by hydrogenation in the presence of a titanium-based hydrogenation catalyst in an inert solvent by the method described in JP-A-133203 and JP-A-60-79005. Can be synthesized. 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,
A polymer block mainly composed of a conjugated diene compound can be morphologically converted into an olefinic compound 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 listed in 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. In addition to the above-mentioned liquid paraffin, petroleum-based softeners approved by the FDA (US Food and Drug Administration) may 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 polyolefin resin used as component (c) of the present invention is effective in increasing the hardness of the resulting syringe gasket, as well as improving processability during molding. , such as polyethylene, isotactic polypropylene, copolymers of propylene with small amounts of other α-olefins, such as propylene/ethylene copolymers, propylene/1-hexene copolymers, propylene/4-methyl-pentene copolymers, etc. Examples include polymers, poly-4-methyl-1-pentene, polybutene-1, and the like. When using isotactic polypropylene or its copolymer as a polyolefin resin
MFR (ASTM-D-1238L condition 230℃) is 0.1 to 50
g/10 minutes, particularly those in the range of 0.5 to 30 g/10 minutes can be suitably used. In addition, the polystyrene resin that can be used as component (c) is effective in increasing the hardness of the resulting syringe gasket and improving processability, and those obtained by known radical polymerization methods and ionic polymerization methods are preferred. Can be used, and its number average molecular weight is 5000~
500,000, preferably from the range of 10,000 to 200,000, and the molecular weight distribution [ratio of weight average molecular weight (w) to number average molecular weight (n) (w/n)] is 5.
The following are preferred. Examples of the polystyrene resin include polystyrene, poly α-methylstyrene, poly p-tert-butylstyrene, etc.
Two or more types of these may be used. Similarly, it may be a copolymer obtained by polymerizing a mixture of monomers constituting these polymers. The polyolefin resin of component (c) listed here,
Polystyrene resin can also be blended together as component (c). 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 (c) components can be selected at any blending ratio. In the case of mixing, the ratio of polyolefin resin/polystyrene resin is 95/5 to 5/95.
(weight ratio). The amount of component (c) described above can be suitably selected in the range of 10 to 200 parts by weight, with 15 to 200 parts by weight based on 100 parts by weight of the hydrogenated block copolymer of component (a).
100 parts by weight is preferred. If the amount exceeds 200 parts by weight, the hardness of the resulting syringe gasket will become too high and the rubber elasticity (compression set) will deteriorate, 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. In addition to the above-mentioned components (a) to (c) that are provided for the present invention, ingredients that can be added as necessary to the syringe gasket of the present invention include antioxidants, hindered amine light stabilizers, etc. , ultraviolet absorbent,
Examples include inorganic fillers, colorants, silicone oils, and the like. The method for producing a thermoplastic elastomer that can be used as a material for the syringe gasket of the present invention is to process the above-mentioned components (a) to (c) and optionally addable components by, for example, a single-screw extruder or a twin-screw extruder. 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 is injection molded in a short time to obtain a syringe gasket. Further, 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 hydrogenated block copolymer having a specific structure that has not been seen in the past. ) and sliding properties are improved, and since it is a thermoplastic elastomer that does not contain sulfur like vulcanized rubber, there is no elution of sulfur into chemicals or blood that come into contact with the gasket, and there is no zinc Since it does not contain heavy metals such as, there is no elution of heavy metals, 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 those that involve a conventional vulcanization process, and the mold release property is also good, so mass production is possible. 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 [%] 1 JIS-K6301, the sample is a 2 mm thick in-die extension sheet, and the test piece is A size 3 dumbbell was used. (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 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) <Component (a-1)> Hydrogenated polybutadiene-polystyrene-hydrogenated polybutadiene-polystyrene structure, bound styrene content 30% by weight, number average molecular weight 172000, molecular weight distribution 1.05, hydrogenated A hydrogenated block copolymer with a 1,2-vinyl bond content of the previous polybutadiene portion of 39%, an amount of hydrogenated polybutadiene placed at the end of the polymer chain of 8% by weight, and a hydrogenation rate of 99% was produced in JP-A-1989-1999. It was synthesized using the Ti-based hydrogenation catalyst described in Publication No. 79005, and was used as component (a-1). <Component (a-2)> Has a polystyrene-hydrogenated polybutadiene-polystyrene structure, with a combined styrene content of 30
JP-A-60-79005 discloses a hydrogenated block copolymer having a weight% number average molecular weight of 176,000, a molecular weight distribution of 1.04, a 1,2-vinyl bond content of the polybutadiene portion before hydrogenation of 37%, and a hydrogenation rate of 99%. It was synthesized using the Ti-based hydrogenation catalyst described in Component (a-2). <Component (a-3)> (Hydrogenated polybutadiene-polystyrene-hydrogenated polybutadiene) - ₄ Si structure, bound styrene content 15% by weight, number average molecular weight 116000, molecular weight distribution 1.38, hydrogenated A hydrogenated block copolymer in which the amount of 1,2-vinyl bonds in the previous polybutadiene portion is 30%, the amount of hydrogenated polybutadiene placed at the end of the polymer chain is 15% by weight, and the hydrogenation rate is 98% is produced in JP-A-59- Component (a-3) was synthesized using the Ti-based hydrogenation catalyst described in Publication No. 133203. <Component (a-4)> It has a structure of polystyrene-hydrogenated polybutadiene-polystyrene, and the amount of bound styrene is 33
Kraton-G1651 (manufactured by Ciel Chemical Co., Ltd.) in weight%
was used as the component (a-4). <Component (a-5)> has a structure of hydrogenated polybutadiene-polystyrene-hydrogenated polybutadiene-polystyrene-hydrogenated polybutadiene,
Bound styrene content 21% by weight, number average molecular weight 213000,
Hydrogenation block with a molecular weight distribution of 1.16, a 1,2-vinyl bond content of the polybutadiene moiety before hydrogenation of 43%, a total amount of hydrogenated polybutadiene placed at both ends of the polymer chain of 23% by weight, and a hydrogenation rate of 97%. A copolymer was synthesized using a Ti-based hydrogenation catalyst described in JP-A-60-79005, and was used as component (a-5). (2) Component (b) Liquid paraffin manufactured by Matsumura Sekiyu Co., Ltd.; Smoyl P-
350 [Kinematic viscosity (37.8℃) 75.8cst, Naphthene component 37
%, paraffin component 63%] (3) Component (c-1) Polypropylene resin manufactured by Asahi Kasei Corporation, M-1600
[MFR (230°C) 14 g/10 minutes] Component (c-2) Asahi Kasei Kogyo Co., Ltd. polystyrene resin, Styron-685 [MFR (200°C) 3 g/10 minutes] Examples 1 to 3, Comparative Examples 1 to 2 As a hydrogenated block copolymer, component (a-1),
Using (a-2), (a-3), (a-4), and (a-5), each component shown in Table 1 was mixed in a Henschel mixer, and then 220 The pellets of thermoplastic elastomer were obtained by melt-kneading under the condition of ℃. Using this pellet, 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 of 190°C to 220°C. 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, 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 these results, it can be seen that the syringe gasket of the present invention has better sliding properties and compression set than the thermoplastic elastomer composed of a hydrogenated block copolymer having a known structure (Comparative Examples 1 and 2). It became clear.

【table】

[Table] Examples 4 to 7 As a hydrogenated block copolymer, components (a-1),
Using (a-3), each component shown in Table 2 was prepared in Examples 1 to 1.
A syringe gasket and a test piece were obtained by molding in the same manner as in 3. The sliding characteristics and physical properties of this material were measured and listed in Table 2. From these results, it was found that the syringe gasket of the present invention has excellent compression set and sliding properties even if the thermoplastic elastomer that constitutes the material contains polystyrene resin.

【table】

[Table] Example 8 Component (a-1) as a hydrogenated block copolymer
100 parts by weight, liquid paraffin (Smoil P-350)
120 parts by weight, 40 parts by weight of polypropylene (M-1300)
Parts by weight were heated and kneaded by the method shown in Examples 1 to 3 to obtain a thermoplastic elastomer. This is then molded into a syringe gasket using an injection molding machine.
Material and leachate tests were conducted in accordance with the test method for rubber stoppers for infusions in the 10th edition of the Japanese Pharmacopoeia. Table 3 shows the results.
Shown below. 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. 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)

[Scope of Claims] 1 (a) a polymer block A mainly composed of at least two vinyl aromatic compounds;
The block copolymer is obtained by hydrogenating a block copolymer characterized in that it has a polymer block B mainly composed of conjugated diene compounds, and at least one polymer block B is arranged at the end of the polymer chain. 100 parts by weight of hydrogenated block copolymer (b) 30 to 300 parts by weight of paraffin oil (c) 10 to 200 parts by weight of polyolefin resin and/or polystyrene resin.