JPH045058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention (Technical Field) The present invention relates to rubber molded articles. Specifically, the present invention relates to a rubber molded product that has extremely low compression set and is suitable, for example, as a stopper for a closed container. (Prior Art) Conventionally, plugs have sufficient elasticity, small compression set, and low gas permeability to close the openings of various closed containers, especially containers that require airtightness such as vacuum blood collection tubes. Those made of vulcanized butyl rubber (IIR) are widely used. However, in the case of vulcanized butyl rubber, there are problems such as the complexity of the vulcanization process, the elution of chemicals such as vulcanization accelerators, and blooming, and there is a desire to develop a product to replace this. From this point of view, for example, ethylene-propylene copolymer elastomers, which do not require vulcanization,
Thermoplastics such as polyester elastomers, nylon elastomers, ethylene-vinyl acetate copolymers, styrene-isoprene block copolymers, styrene-butadiene block copolymers, polybutadiene, thermoplastic polyurethanes, hydrogenated styrene-butadiene block copolymers, etc. The use of elastomers is being considered. However, the thermoplastic elastomer has poor compression set compared to vulcanized rubber such as vulcanized butyl rubber, and when used as a stopper, for example, permanent deformation occurs so that the shape matches the opening of a container into which it is fitted. If the entire container is kept at a low temperature, for example -30°C, a gap will be created between the container and the stopper due to the difference in the thermal expansion coefficients of the materials that make up the container and the stopper, making it impossible to seal the inside of the container. It becomes something that cannot be maintained. In addition, instead of the general vulcanization method, X-rays, γ-rays,
It has also been done to crosslink polymers by irradiating them with radiation such as particle beams to impart rubber elasticity, but in the case of butyl rubber polymers, the polymer decomposes when irradiated with radiation.
Such crosslinking methods have not been applicable to butyl rubber polymers. OBJECTS OF THE INVENTION Therefore, an object of the present invention is to provide a novel rubber molded product. Another object of the present invention is to provide a rubber molded product with extremely small compression set. A further object of the present invention is to provide a rubber molded product which, when used as a closure for a sealed container, does not create a gap between the container and the closure even at low temperatures, and is suitable as the closure. do. The above objects are achieved by a rubber molded article, which is characterized in that the compression set is improved by crosslinking a molded article of an elastomer compound made of a polymer composition containing partially crosslinked butyl rubber by irradiating it with radiation. Ru. The present invention also provides a rubber molded article in which partially crosslinked butyl rubber is contained in the elastomer compound in an amount of 20 to 90% by weight of the polymer composition (components excluding inorganic components such as fillers and pigments). It shows.
The present invention further provides a rubber molded article, wherein the elastomer compound contains unvulcanized chlorinated butyl rubber or unvulcanized brominated butyl rubber in an amount of 0 to 70% by weight of the polymer composition. It is. The invention also provides a rubber molding in which the elastomer formulation contains 0 to 70% by weight of the polymer composition of unvulcanized butyl rubber or polyisobutylene. The present invention also provides a rubber molded product in which the cyclohexane soluble portion of the partially crosslinked butyl rubber is 60% by weight or less of the partially crosslinked butyl rubber. The present invention further provides that the radiation dose is
This shows a rubber molded product crosslinked at 0.1 to 5.0 Mrad. The present invention further provides a rubber molded article in which radiation irradiation is performed in air. The present invention also provides a rubber molded product, in which the molded product is a stopper for a closed container. Specific Structure of the Invention The present invention will be explained in detail below. The rubber molded product of the present invention is characterized in that an elastomer compound made of a polymer composition containing partially crosslinked butyl rubber is crosslinked by irradiation with radiation to improve compression set. Surprisingly, butyl rubber is known to be a radiation-degradable type, but when an elastomer compound made of a polymer composition containing partially crosslinked butyl rubber is irradiated with radiation, the crosslinking reaction progresses. Moreover, it has become clear that even when the elastomer blend contains a butyl rubber polymer as a component other than partially crosslinked butyl rubber, the crosslinking reaction proceeds and the permanent compression set of the elastomer is improved. The partially crosslinked butyl rubber contained in the elastomer formulation used in the present invention is a butyl rubber, that is, an isobutylene-isoprene copolymer that is partially crosslinked using a divinyl monomer system, such as divinylbenzene, during the manufacturing process. The isobutylene-isoprene copolymer is crosslinked to such an extent that 60% by weight or less, preferably 20 to 50% by weight thereof, is soluble in cyclohexane, which is a good solvent for the isobutylene-isoprene copolymer. Examples of such partially cross-linked butyl rubber include Polysar Butyl XL-50 and Polysar Butyl XL.
-20 etc. are available commercially. Such partially crosslinked butyl rubber is contained in the elastomer formulation used in an amount of 20 to 90%, preferably 40 to 80% by weight of the polymer composition. That is, if the partially crosslinked butyl rubber is less than 20% by weight, there is a risk that the crosslinking reaction will not proceed sufficiently when the elastomer compound is irradiated with radiation, and the compression set in the elastomer compound may not be sufficiently improved.
On the other hand, if it exceeds 90% by weight, problems will arise in processability. Constituent components other than the partially crosslinked butyl rubber of the polymer composition in the elastomer blend include butyl rubber polymers, other thermoplastic resins, etc., and several of these can also be used in combination. In addition to unvulcanized butyl rubber, butyl rubber-based polymers include polyisobutylene, unvulcanized chlorinated butyl rubber, unvulcanized brominated butyl rubber, etc., and these may be used not only alone but in combination. . Examples of unvulcanized butyl rubber include Exxon Butyl 065 and Exxon Butyl 268 from Exxon Chemical Co., Polyservyl 400 from Polysar Co., Ltd.
Examples of unvulcanized chlorinated butyl rubber include chlorobutyl 1066 manufactured by Exxon Chemical Co., Ltd.; examples of unvulcanized brominated butyl rubber include polyservomobutyl X2 manufactured by Polycer; As isobutylene,
For example, Exxon Chemical's Vistanetx MML-
100, Vistanetx MML-80, etc. are commercially available. These butyl rubber-based polymers are contained in the elastomer formulation in an amount of 0 to 70% by weight, preferably 0 to 40% by weight of the polymer composition. In addition, thermoplastic resins include polyethylene,
Polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyester elastomer, nylon elastomer, styrene-isoprene block copolymer, styrene-
butadiene block copolymer, polybutadiene,
Examples include thermoplastic polyurethane and hydrogenated styrene-butadiene block copolymer. These thermoplastic resins may be present in the elastomer formulation in an amount of 2 to 60% by weight of the polymer composition, preferably 5 to 60% by weight of the polymer composition.
Contains 40% by weight. In addition to the polymer composition, inorganic fillers such as mica and clay, antioxidants, colorants, etc. may be added to the elastomer compound used in the rubber molded product of the present invention, if necessary. The rubber molded product of the present invention is prepared by thoroughly kneading the above-mentioned components using a kneading machine such as a Henshil mixer or a Banbury mixer to prepare an elastomer compound in the form of a sheet, pellet, etc.; The elastomer compound is obtained by molding it into a predetermined shape by injection molding, extrusion molding, etc., and then irradiating it with radiation to crosslink the elastomer compound. The radiation used during crosslinking includes electron beams, X-rays, gamma rays, and particle beams, but gamma rays are preferred, and ⁶⁰ Co, ¹³⁷ Cs, etc. are mainly used as the gamma ray source. Therefore, the amount of radiation irradiated to the elastomer compound is 0.1 to 5.0 Mrad,
Preferably it is 0.5 to 3.0 Mrad. i.e.
If it is less than 0.1 Mrad, there is a risk that the crosslinking reaction will not proceed sufficiently, while if it exceeds 5.0 Mrad, there is a risk that the elastomer compound will deteriorate. Note that the radiation irradiation may be performed in an inert gas or water, but is sufficiently effective even if it is performed in the air. As shown in FIG. 1, the rubber molded product of the present invention is used, for example, as a stopper 4 of a vacuum blood collection tube 1. That is, the vacuum blood collection tube 1 includes a tubular part 2 made of glass or low gas permeable synthetic resin that is closed at one end and open at the other end, and a rubber molded article of the present invention in which the open end 3 of the tubular part 2 is sealed. The internal space 5 of the thus sealed tubular portion 2 is filled with a predetermined gas and maintained in a reduced pressure state. Here, since the stopper 4 has an extremely small compression set, even if the reduced pressure blood collection tube 1 is kept at a low temperature, for example, -30°C, there is a difference in thermal expansion coefficient between the stopper 4 and the material constituting the tubular part 2. This prevents the creation of a gap between the plug body 2 and the tubular portion 4 and the depressurized state of the internal space 5 being disrupted. This vacuum blood collection tube is used as follows. That is, as shown in FIG. 1, a vacuum blood collection tube 1 filled with a predetermined gas and maintained at a predetermined degree of vacuum is closed at one end and opened at the other end as shown in FIG. The blood collection needle 8 is inserted into the blood collection tube holder 9 screwed into the screw hole 7 of the blood collection tube 6 through the opening. This blood collection needle 8 is composed of, for example, a blood vessel piercing part 8a and a plug puncturing part 8b, and the plug puncturing part 8b is wrapped with a rubber chip 10 made of synthetic resin or natural rubber. Next, when the blood vessel puncture part 8a of the blood collection tube 8 is pierced into a blood vessel, for example, a vein, and the vacuum blood collection tube 1 is further pressed and inserted into the closed end 6 of the blood collection tube holder 9, the stopper puncture part 8b of the blood collection tube 8 is inserted into the rubber tip 10. Since the tip of the stopper 4 reaches the internal space 5 of the blood collection tube 1, the blood vessel and the internal space 5 communicate with each other, and the blood in the blood vessel is decompressed due to the negative pressure in the internal space 5. The liquid flows into the internal space 5 of the blood collection tube 1 in an amount corresponding to the amount of water. Next, the blood vessel piercing portion 8a of the blood collection tube 8
Blood collection is completed by removing the tube from the blood vessel. The above description has been made using the case of a stopper for a vacuum blood collection tube as an example, but the rubber molded product of the present invention can also be used as a stopper for other closed containers, as a connecting member (connector) for a tubular body, or as a packing material. Used for various purposes such as materials. The present invention will be explained in more detail below with reference to Examples. Examples 1 to 4 and Comparative Examples 1 to 2 The mixtures were kneaded at 150 DEG C. in a Banbury mixer according to the compounding ratios shown in Table 1, formed into sheets with rolls, and pellets of elastomer compounds were obtained using a sheet pelletizer. The pellets were molded into cylindrical compression set test pieces with a diameter of 29.0 mm and a thickness of 12.7 mm using an injection molding machine. The test piece formed in this way
Gamma rays using ⁶⁰ Co as a radiation source were irradiated with a dose of 2.0 Mrad. Then compressed by 25% according to JIS K 6301, 70
Compression set was measured at ℃ for 22 hours. The results are shown in Table 1. Example 5 Same as Example 1 except that the γ-ray irradiation dose was 4.0 Mrad. The results are shown in Table 1. Comparative Examples 3-8 Compression set was measured for test pieces prepared in the same manner as Examples 1-4 and Comparative Examples 1-2 except that γ-rays were not irradiated. The results are shown in Table 1. Comparative Example 9 Diameter manufactured using vulcanized butyl rubber manufactured under vulcanization conditions of 170°C and 5 minutes with the composition shown in Table 2.
The compression set of a cylindrical compression set test piece having a size of 29.0 mm and a thickness of 12.7 mm was measured in the same manner as in Examples 1 to 4. The results are shown in Table 2.

[Table] Table 2 Compounding ratio (parts by weight) Butyl rubber 80 Ethylene propylene terpolymer 20 Sulfur 0.9 Inorganic filler 50 Stearic acid 0.5 Zinc white 3 Vulcanization accelerator 1 Compression set (%) 27% Extractables test Example 1 Then, 30 g of the rubber composition prepared in Comparative Example 9 was placed in 300 ml of distilled water and extracted in an autoclave at 121°C for 20 minutes. Extractables tests were conducted in accordance with the Japanese Pharmacopoeia's ``Test Methods for Rubber Stainless Steel Infusions'' (Awadachi, ultraviolet absorption spectrum, zinc). The results are shown in Table 3.

[Table] Specific Effects of the Invention As described above, the rubber molded product of the present invention is produced by irradiating a molded product of an elastomer compound made of a polymer composition containing partially cross-linked butyl rubber with radiation to crosslink it, thereby making it compression permanent. Since it is characterized by improved distortion, it eliminates problems such as the complexity of the vulcanization process, the elution of chemicals such as vulcanization accelerators, and blooming, which are associated with conventional rubber molded products made of vulcanized butyl rubber. As an excellent rubber molded product with sufficient elasticity, low gas permeability, and small compression set, it can be used as closures for various containers, especially for medical devices such as vacuum blood collection tubes, infusion bottles, and medical solution mixture injection parts. Furthermore, it is suitably used in various other applications such as connectors between pipe bodies and packing materials. In addition, the rubber molded product contains partially crosslinked butyl rubber in the elastomer compound in an amount of 20 to 90% by weight of the polymer composition, and unvulcanized chlorinated butyl rubber or unvulcanized brominated butyl rubber as other components. 0 of the polymer composition
~70% by weight of the polymer composition, or if the unvulcanized butyl rubber or polyisobutylene comprises 0 to 70% by weight of the polymer composition, and the thermoplastic resin comprises 2 to 60% by weight of the polymer composition; When using a crosslinked butyl rubber in which the cyclohexane soluble portion is 60% by weight or less of the partially crosslinked butyl rubber, and when the radiation dose is 0.1 to 5.0 Mrad, the above effects are even more excellent. becomes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a vacuum blood collection tube using a rubber molded product according to the present invention as a stopper, and FIG.
The figure is a sectional view showing the state in which the reduced pressure blood collection tube is used. 1... Decompression blood collection tube, 2... Tubular part, 3... Open end, 4
...Plug body, 5...Inner space.

Claims (1)

[Scope of Claims] 1. A rubber molded article, characterized in that the compression set is improved by crosslinking a molded article of an elastomer compound made of a polymer composition containing partially crosslinked butyl rubber by irradiating it with radiation. 2. The rubber molded article according to claim 1, wherein the partially crosslinked butyl rubber is contained in the elastomer compound in an amount of 20 to 90% by weight of the polymer composition. 3. According to claim 2, the elastomer compound contains unvulcanized chlorinated butyl rubber or unvulcanized brominated butyl rubber in an amount of 0 to 70% by weight of the polymer composition. Rubber molded products. 4. Unvulcanized butyl rubber or polyisobutylene in the elastomer formulation is present in the polymer composition.
The rubber molded article according to claim 1 or 2, which contains ~70% by weight. 5. The rubber molded product according to any one of claims 1 to 4, wherein the cyclohexane soluble portion of the partially crosslinked butyl rubber is 60% by weight or less of the partially crosslinked butyl rubber. 6. The rubber molded article according to any one of claims 1 to 5, which is crosslinked at a radiation dose of 0.1 to 5.0 Mrad. 7. The rubber molded article according to any one of claims 1 to 6, wherein the radiation irradiation is performed in air. 8. The rubber molded article according to any one of claims 1 to 7, wherein the molded article is a stopper for a closed container.