JP4362051B2 - Stable rubber composition for chlorine water - Google Patents

Description

The present invention relates to (A) one or more rubbers substantially free of double bonds in the main chain, (B) a polyisoprene maleic acid monomethyl ester adduct, and a polyisoprene maleic anhydride. Including a chlorine resistance improver selected from the group consisting of an adduct, phthalic anhydride, maleic anhydride and mixtures thereof, (C) a filler, (D) a vulcanizing agent, and (E) an anti-aging agent. The present invention relates to a rubber composition stable in chlorine water.

The present invention relates to a water-stable rubber composition containing chlorine-based substances such as chlorine (Cl ₂ ), hypochlorous acid (HClO), hypochlorite ion (ClO ⁻ ), and more particularly The present invention relates to a chlorine-resistant rubber composition used for equipment in contact with tap water containing a chlorine-based disinfectant.

Conventional technology The sterilization of tap water in Japan is mainly based on a chlorine-based sterilization method using Cl ₂ (chlorine) or NaClO (sodium hypochlorite). And the residual effective chlorine density | concentration in this water supply is generally the range of 0.5-1.0 ppm, but the area | region with a high density | concentration with about 1.5 ppm is also seen. In recent years, pollution of rivers, lakes, and the like that are water sources has progressed, and the amount of chlorinated fungicides used for sterilization tends to increase. On the other hand, with the improvement of our standard of living, various types of hot water supply equipment, dishwashing equipment, solar systems, etc. have become widespread, and these equipment are used in various places. Furthermore, the use of pressure-reducing valve devices and pumping devices used in high-rise houses and the like, and the use of connecting devices for connecting distribution pipes at various locations are increasing.

  Many rubber products are built into these devices, and since these rubber parts were initially made of rubber materials such as NBR, EPM, EPDM, H-NBR, etc., it was estimated that they had sufficient practical durability. Has been used in the direction. However, these rubber products are exposed to chlorinated disinfectants remaining in tap water and water leakage occurs, or the affected rubber products tear off and float in the water to contaminate tap water. Currently, the related industry is struggling with countermeasures.

  In order to solve such a problem, an ethylene-propylene-diene terpolymer, a chlorine-resistant water-resistant rubber (Japanese Patent Laid-Open No. 9-249778) made of a phenol formaldehyde resin and a phthalic acid-based prepolymer, an ethylene-propylene rubber, Chlorine-resistant water-resistant rubber blended with hydrogenated acrylonitrile-butadiene rubber (Japanese Patent Laid-Open No. 9-157464), and chlorine-resistant water-resistant water in which diphenylamine and mercaptobenzimidazole are added to ethylene-propylene rubber and hydrogenated acrylonitrile-butadiene rubber Chlorine-resistant water-resistant rubber (Japanese Patent Laid-Open No. 5-230300) in which a fluororesin fine powder is blended with rubber (Japanese Patent Laid-Open No. 10-60198) or ethylene propylene-based rubber has been proposed.

  In addition, a rubber sheet for a butterfly valve using a water-resistant rubber (Japanese Patent Laid-Open No. 6-200080) in which a hydrotalcite is added to a rubber member or an ethylene-propylene-ethylidene norbornene copolymer rubber (Japanese Patent Laid-Open No. No. 5-44857) has been proposed. Further, a chlorine-resistant water-based rubber composition in which a silica-based filler is added to a blend rubber composed of ethylene propylene rubber and butyl rubber has been proposed (Japanese Patent Laid-Open No. 4-353543).

However, the conventional chlorine-resistant rubber described above does not actually have sufficient chlorine resistance. For this reason, in recent years, an example of using fluorine-based rubber having excellent weather resistance such as chemical resistance has increased. However, this fluorine-based rubber is expensive and may have inferior physical properties of rubber other than chemical resistance.
Japanese Patent Application Laid-Open No. 2003-96253 discloses one or more kinds of rubbers that do not substantially have a double bond in the main chain, a rubber material having a double bond in the main chain, and / or a double bond in the main chain. A rubber composition that is stable in chlorinated sterilized water containing a synthetic resin is described. The present invention is very unlikely to be deteriorated by a chlorine-based disinfectant even in cold water, hot water, hot water and long-term indirect corrosion or immersed, and has durability comparable to that of a fluorine-based rubber, and The purpose is to reduce the chemical oxygen demand (COD) with high physical properties, low cost and high chlorine resistance.

Problems to be Solved by the Invention The present inventor has added a polyisoprene maleic acid monomethyl ester adduct, a polyisoprene maleic anhydride adduct, to one or more rubbers substantially free of double bonds in the main chain. By adding a chlorine resistance improver selected from the group consisting of phthalic anhydride, maleic anhydride and a mixture thereof, a rubber composition stable in chlorine water was successfully developed.

The present invention comprises (A) one or more rubbers having no double bond in the main chain, one or more rubbers having almost no double bond in the main chain, or a mixture thereof;
(B) (i) To the adjacent carbon of the side chain (a)

Or a carboxylic acid group represented by (b) a carboxylic acid group and

Wherein R is an alkyl group, it is preferably a C ₁ -C ₆ alkyl group:
Or a polymer having a carboxylic acid ester group represented by (ii)

(Iii) a chlorine resistance improver selected from the group consisting of a compound having a carboxylic anhydride group represented by:
The present invention relates to a chlorine water-stable rubber composition comprising (C) a filler, (D) a vulcanizing agent, and (E) an anti-aging agent.

  Each element of the present invention will be described in detail. (A) Saturated synthetic rubber having substantially no double bond in the main chain, which constitutes the present invention, is responsible for basic physical properties as a vulcanized rubber, such as the elongation and tensile strength of the rubber after vulcanization. It is effective to use a rubber material that does not contain unsaturated groups as much as possible so as not to be deteriorated by chlorine contained in tap water or the like.

  Specific examples of the rubber having no double bond in the main chain are ethylene propylene rubber (EPM) and ethylene / propylene / diene rubber (EPDM). Examples of EPDM include the following

And ethylidene norbornene (ENB type)

And dicyclopentadiene (DCPD type) shown in FIG. The ENB type is mainly used. In any case, there is no double bond in the main chain. However, there are double bonds in the side chains.

  An example of a rubber having few double bonds in the main chain is hydrogenated acrylonitrile butadiene rubber (H-NBR), which is prepared by hydrogenating acrylonitrile butadiene rubber. In the hydrogenation, most (but not all) of the acrylonitrile-butadiene butadiene units are hydrogenated. In one part, it is not hydrogenated.

    In addition to these rubber materials, chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CPE), epichlorohydrin rubber (CHR, CHC), and acrylic rubber (ACM, ANM) are substantially unsaturated. Even if it does not have a group or has a group, it can be used in combination if it is a very small amount.

  The polyisoprene maleic acid monomethyl ester adduct that can be used as the component (B) (i) of the present invention is represented by the following formula.

  The polyisoprene maleic anhydride adduct is represented by the following formula.

  In the general formulas representing the maleic acid monomethyl ester adduct of polyisoprene and the maleic anhydride adduct of polyisoprene, m and p are preferably several hundreds, and n and q are preferably about 3 to 5. The molecular weight of these compounds may be from oligomers to polymers.

  As the component (B) (ii) of the present invention, in addition to phthalic anhydride and maleic anhydride, isobutyric anhydride, itaconic anhydride, glycolic anhydride, glutaconic anhydride, glutaric anhydride, succinic anhydride, acetic anhydride, etc. Acid anhydrides can also be used. Most preferred are phthalic anhydride and maleic anhydride.

  The blending amount of the polyisoprene maleic acid monomethyl ester adduct and / or polyisoprene maleic anhydride adduct which is the chlorine resistance improver (B) (i) is such that a double bond is added to the main chain which is the component (A). The amount is 3 to 30 parts by weight, preferably 10 to 25 parts by weight, based on 100 parts by weight of one or more kinds of rubber that is substantially absent. When the blending amount of the component (B) is less than 3 parts by weight, effective chlorine resistance cannot be obtained, and even if it exceeds 30 parts by weight, the effect of improving chlorine resistance is recognized, but the physical properties are greatly lowered.

  Component chlorine resistance improver (B) (ii) phthalic anhydride and / or maleic anhydride and the like are blended in one or more kinds substantially free of double bonds in the main chain of component (A). 2 to 10 parts by weight per 100 parts by weight of rubber. If the blending amount is less than 2 parts by weight, effective chlorine resistance cannot be obtained, and if it exceeds 10 parts by weight, a vulcanization (crosslinking) failure occurs and a rubber elastic body that can withstand practical use cannot be obtained.

  As the filler (C) that can be used in the present invention, conventionally known fillers can be used. Specifically, inorganic fillers such as carbon black, silicic acid, silicate, calcium carbonate, magnesium carbonate, clay, talc, bentonite, sericite, mica, asbestos, calcium silicate, alumina hydrate, barium sulfate, Examples of the organic filler include polyethylene resin, polypropylene resin, styrene resin, coumarone-indene resin, melamine resin, phenol resin, and cork powder. The amount of the filler is 0.1 to 200 parts by weight with respect to 100 parts by weight of the saturated synthetic rubber (A) having substantially no double bond in the main chain. Depending on the case, it may be blended even outside the above range. What is necessary is just to determine the kind and compounding quantity of these fillers arbitrarily according to the objective.

  The (D) vulcanizing agent system that can be used in the present invention is generally used in combination with a vulcanizing agent (crosslinking agent) and a vulcanization accelerator, but an organic peroxide as a vulcanizing agent. When used, it is not always necessary to use a vulcanization accelerator. Conventionally known vulcanizing agent systems can be used. Examples of the vulcanizing agent include sulfur compounds such as sulfur, powdered sulfur, sulfur white, precipitated sulfur, colloidal sulfur, sulfur chloride, inorganic compounds such as selenium, tellurium, zinc oxide, magnesium oxide, lead monoxide, morpholine disulfide, Organic sulfur compounds such as alkylphenol disulfide and thiuram disulfide, organic vulcanizing agents such as dithiocarbamates, oximes, dinitroso compounds, polyamines and organic peroxides. Examples of the vulcanization accelerator include metal oxides such as zinc oxide and magnesium oxide, metal hydroxides such as calcium hydroxide, fatty acids such as stearic acid, oleic acid and lauric acid, and fatty acid derivatives such as zinc stearate. And amines such as diethanolamine, triethanolamine and dicyclohexylamine, and various organic compounds such as thiazole, sulfinamide, thiuram and dithioate. These vulcanizing agents and vulcanization accelerators can be used in combination of two or more, and conventionally known vulcanizing aids may be used in combination as required. The addition amount of the vulcanizing agent or vulcanization accelerator may be within the range of conventionally known addition amounts, and is appropriately determined depending on the type of rubber material or other compound.

In the present invention, known vulcanization aids, processing aids, anti-aging agents, reinforcing agents, softeners, colorants, fillers and the like which are added to ordinary rubber compositions may be added.
The rubber composition of the present invention is usually made into a product by kneading the above-mentioned components and forming them into a desired shape, followed by vulcanization. As a specific molding vulcanization method, conventionally known methods such as injection molding, pressure (press) molding, extrusion molding, and calendar molding can be used. For example, when performing pressure molding at 130 to 180 ° C., It can be molded by pressurizing to 5 to 30 MPa and vulcanizing for 2 to 30 minutes. Other methods can be easily molded by appropriately selecting conditions. Moreover, you may perform secondary vulcanization | cure as needed.
As the anti-aging agent (E), known anti-aging agents can be used.

On the basis of the following examples embodiments of the invention The present invention is described in detail.
Examples 1-50 and Comparative Examples 1-5
Each component was kneaded at a blending ratio shown in Tables 1 to 7 to obtain a vulcanized rubber composition in a uniform state. Next, this vulcanized rubber composition is subjected to arbitrary conditions (temperature: 160 to 175 ° C., time: about 7 to 10 minutes, pressure: 10 to 20 Mpa, and this molding vulcanization condition depends on the type of rubber material, the crosslinking agent, and the amount added The rubber sheet of t2 (thickness 2 mm) and 250 □ (250 mm × 250 mm) was obtained. A 35 mm × 35 mm sample was taken from this rubber sheet, immersed in 70 ° C. warm water with a chlorine concentration of 200 ppm, and the state of change of the sample piece after a predetermined time elapsed as shown in Tables 1 to 7 was visually and finger touched. The deterioration and the state of the immersion liquid were evaluated.

Claims (3)

(A) one or more rubbers having no double bond in the main chain, one or more rubbers having almost no double bond in the main chain, or a mixture thereof;
(B) To adjacent carbon of side chain
Carboxylic acid groups and

( Wherein R is an alkyl group )
Salt-containing enhancer is a polymer having represented Ru carboxylic acid ester group in,
(C) Filler (D) Vulcanizing agent, and (E) Anti-aging agent, A chlorine composition stable in chlorine water. The salt-containing enhancer, stable rubber compositions chlorine water according to claim 1, wherein the maleic acid monomethyl ester wipe of polyisoprene. The one or more rubbers having no double bond in the main chain or the one or more rubbers having almost no double bond in the main chain are ethylene-propylene rubber, ethylene-propylene-diene rubber or hydrogenated acrylonitrile butadiene rubber. The rubber composition stable to chlorine water according to claim 1 or 2.