JPH0119816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rubber composition, and particularly to a rubber composition that is heat resistant and less likely to stain molds, and is mainly composed of polyolefin synthetic rubber. (Prior art) Various types of synthetic rubber are already on the market, but these rubber products suffer from aging phenomena due to oxidation, contact with heat, light, ozone, and mechanical fatigue during use. Ru. For this reason, an anti-aging agent is usually added, but the anti-aging agent is selected in accordance with the cause of aging depending on the use of the rubber product, and the effect on vulcanization rate, blooming property, etc. However, in rubber compositions to which this anti-aging agent has been added, the anti-aging agent may migrate from inside the composition onto the mold during molding, causing mold fouling.
Countermeasures against this problem are being considered because this results in disadvantages in that the peeling of the molded product from the mold becomes difficult and furthermore, the surface of the molded product loses its luster. (Structure of the Invention) The present invention relates to a rubber composition mainly composed of polyolefin-based synthetic rubber that solves the above-mentioned disadvantages. parts by weight, (2) 0.1 to 10 parts by weight of an anti-aging agent, and (3) 1 to 30 parts by weight of calcium oxide. That is, the present inventors have conducted various studies on methods for preventing mold fouling of synthetic rubber, particularly rubber compositions in which an antiaging agent is added to a mixture of polyolefin-based synthetic rubber and organopolysiloxane. Adding calcium oxide to a product prevents the anti-aging agent from migrating to the mold during molding of this composition, significantly reducing mold fouling, making continuous molding possible, and resulting molded products with less surface staining. They discovered that it gave a glossy appearance, and conducted research on the type and amount of calcium oxide used, and completed the present invention. The rubber component as the first component constituting the rubber composition of the present invention is a mixture of a polyolefin-based synthetic rubber and an organopolysiloxane, but this may be any known one, and this polyolefin-based synthetic rubber is an ethylene- Propylene copolymer, ethylene-propylene-diene copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene copolymer, isobutylene-isoprene copolymer Examples include coalescence, but this is used as a mixture with organosiloxane to improve heat resistance. This organopolysiloxane may be a known organopolysiloxane, and is represented by the general formula (RSiO _1.5 ) _l (R ₂ SiO) _n −(R ₃ SiO _1.5 ) _o (SiO ₂ ) _k , where R is a methyl group or an ethyl group. group, alkyl groups such as propyl group, butyl group, alkenyl group such as vinyl group, allyl group, aryl group such as phenyl group, tolyl group, cycloalkyl group such as cyclohexyl group, or bonded to the carbon atom of these groups. Chloromethyl groups, trifluoropropyl groups, cyanomethyl groups, mercaptomethyl groups, etc. in which part or all of the hydrogen atoms are substituted with halogen atoms, cyano groups, mercapto groups, etc., and alkoxy groups such as methoxy groups, ethoxy groups, propoxy groups, etc. a group selected from the same or different unsubstituted or substituted monovalent hydrocarbon groups exemplified by hydroxyl groups, alkoxy groups, hydroxyl groups, l, m, n, k
are each independently 0 or an integer, and may be substantially linear, cyclic, or three-dimensional network structure, but preferably the formula (p is 10 or more). If the amount of this organopolysiloxane added to the polyolefin synthetic rubber is less than 1 part by weight per 100 parts by weight of the polyolefin synthetic rubber, sufficient heat resistance will not be obtained from the composition, and if it is more than 70 parts by weight, the amount obtained from the polyolefin synthetic rubber will be less than 1 part by weight. Since the resulting molded product will have low strength, the amount should be in the range of 1 to 70 parts by weight, but the preferred range is 20 to 50 parts by weight. The anti-aging agent as the second component constituting the composition of the present invention may be any known anti-aging agent, including naphthylamine-based agents such as phenyl-β-naphthylamine,
Diphenylamine series such as N-N'-diphenylethylenediamine, N,N'-diphenyl-p-
p-phenylenediamine series such as phenylenediamine, 6-ethoxy-2,2,4-trimethyl-
Hydroquinone derivatives such as 1,2-dihydroquinoline, monophenols such as 2,6-di-tert-butyl-4-methylphenol, 2,2'-methylene-bis-(4-ethyl-6-t-butyl polyphenols such as 4,4′-thiobis-(6-t-butyl-3-methylphenol)
Examples include thiobisphenols such as, 2-mercaptobenzimidazole, etc., and these may be optionally blended according to their respective properties. However, the amount of this anti-aging agent is the first ingredient mentioned above.
If it is less than 0.1 part by weight per 100 parts by weight, it will not provide sufficient anti-aging effect, and if it is more than 10 parts by weight, vulcanization failure or significant blooming will occur in the composition, so the content should be in the range of 0.1 to 10 parts by weight. Although it is necessary,
The preferred range is 1 to 5 parts. In addition, these anti-aging agents may be used in combination of two or more thereof, and according to this, the anti-aging effect can also be improved. The composition of the present invention has calcium oxide added as a third component to the first and second components described above, but this does not adversely affect the mechanical strength of molded products made from this composition. Therefore, it is preferable to use a fine powder with an average particle diameter of 2 μm or less, such as Airlock (trade name, manufactured by Sun Chemical Co., Ltd.).
If the amount of calcium oxide added is less than 1 part per 100 parts by weight of the mixture of polyolefin-based synthetic rubber and organopolysiloxane as the first component, a sufficient mold stain prevention effect cannot be obtained, and if it is more than 30 parts by weight, Since no significant improvement in effect can be obtained by increasing the amount, the amount may be in the range of 1 to 30 parts by weight, but the preferred range is 5 to 15 parts. The rubber composition of the present invention can be obtained by uniformly mixing predetermined amounts of the first to third components described above, and this mixing can be carried out using a Banbury mixer, a kneader,
The kneading may be carried out using ordinary rubber compounding equipment such as a two-roll machine. In addition, appropriate amounts of reinforcing agents such as silica, carbon black, process oil, fillers, various carbon functional silanes, etc. may be added to this composition as required. The composition of the present invention has excellent heat resistance and less mold staining due to the above-mentioned combination of calcium oxide, but in order to obtain a cured molded product from this composition, organic peroxide or sulfur;
It is preferable to add a sulfur-based vulcanizing agent. Examples of this organic peroxide include dicumyl peroxide,
t-Butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy) ) hexyne, etc., and examples of accelerators when curing with sulfur include 2-mercaptobenzothiazole, tetramethylthyuram monosulfide, etc., but the addition of this type of curing aid is as described above. Since kneading may be carried out under heat, in that case it is necessary to cool down the temperature of the composition to below its decomposition temperature. Next, examples of the present invention will be given, and parts in the examples indicate parts by weight. Example 1, Comparative Examples 1 to 3 70 parts of polyolefin synthetic rubber EDPM/EP43 [trade name manufactured by Japan EP Rubber Co., Ltd.],
( _CH3 ) ₂ SiO units 99.5 mol%, ( _CH3 )( _CH2 =CH)
30 parts of dimethylvinylpolysiloxane raw rubber with an average degree of polymerization of 8000, consisting of 0.5 mol% of SiO units, 30 parts of precipitated silica Nipsil LP (trade name manufactured by Nippon Silica Co., Ltd.) with a specific surface area of 230 m ² /g, zinc oxide 5 parts and 1 part of stearic acid were added and kneaded using a pressure kneader to prepare a rubber compound. Next, 100 parts of this rubber compound was added with an anti-aging agent, Nokratsuku MB (trade name, manufactured by Ouchi Shinko Kagaku Co., Ltd.).
2 parts of dicumyl peroxide, 10 parts of calcium oxide aerox (mentioned above), and then 2.8 parts of dicumyl peroxide.
170℃ after adding 100% of
Heat and pressurize for 10 minutes at 100Kg/ ^cm2 to a thickness of 2mm.
The initial physical properties of this sheet are 180
When the heat resistance and mold staining after heating at ℃ for 168 hours were examined, the results shown in Table 1 were obtained. In addition, Comparative Example 1 in Table 1 is the above composition in which calcium oxide was not added, Comparative Example 2 was a composition in which neither an anti-aging agent nor calcium oxide was added, and Comparative Example 3 was a composition in which neither an anti-aging agent nor calcium oxide was added. The test results are shown for a composition in which barium oxide was added instead of calcium oxide and calcium oxide, and when an infrared spectrum of the mold stain was taken for Comparative Example 1, it was found that the first
The results shown in the figure were obtained, and this is similar to the infrared spectrum shown in Figure 2 of Nokrac MB added as an anti-aging agent (see above), so the cause of mold staining is migration of the anti-aging agent. It was confirmed that the barium oxide stains the mold in Comparative Example 3. 【table】

[Brief explanation of drawings]

Figure 1 is an infrared spectrum diagram of the mold stain area of the composition of Comparative Example 1, and Figure 2 is an infrared spectrum diagram of the mold stain area of the composition of Comparative Example 1.
This is an infrared spectrum diagram of Nokrac MB.

Claims (1)

[Scope of Claims] 1 (1) 100 parts by weight of a mixture of polyolefin-based synthetic rubber and organopolysiloxane (2) 0.1 to 10 parts by weight of an anti-aging agent (3) 1 to 30 parts by weight of calcium oxide Characteristic rubber composition. 2 Polyolefin synthetic rubber is ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-
The rubber composition according to claim 1, which is selected from ethyl acrylate copolymer, acrylonitrile-butadiene copolymer, and isobutene-isobrene copolymer. 3. A patent in which the anti-aging agent is selected from naphthylamine, diphenylamine, p-phenylenediamine, quinoline, hydroquinone derivatives, monophenol, bis, tris, polyphenol, and thiobisphenol. A rubber composition according to claim 1. 4. The rubber composition according to claim 1, wherein the calcium oxide has an average particle size of 2 μm or less.