Chlorine-resistant water-resistant rubber composition and packing using the same

Abstract

This invention provides a packing used in water-stopping sections of water pipes and other applications that exhibits minimal deterioration of rubber properties, does not leach carbon black (known as the "ink phenomenon"), and offers excellent durability. [Solution] A chlorine-resistant water-soluble composition is used as the material for molding a packing, which is made by blending 100 parts by weight of EPDM with a high diene content and low to medium ethylene content with 3 parts by weight or less of carbon black, 15 to 65 parts by weight of silica, and 20 parts by weight or less of paraffinic oil.

Description

Technical Field

[0001] The present invention relates to a chlorine-resistant aqueous rubber composition and a packing formed using the composition as a material, and is particularly suitable for use in a water stop portion in a water supply pipe or the like.

Background Art

[0002] Conventionally, packings (such as O-rings and flat round packings) made of rubber such as NBR (acrylonitrile-butadiene copolymer) and EPDM (ethylene-propylene copolymer) have been used in water stop portions in water supply pipes and the like. However, NBR, EPDM, etc. are inferior in chlorine-resistant water resistance (durability against residual chlorine in tap water), and thus have a drawback that stable water stop performance cannot be obtained over a long period of time.

[0003] Therefore, recently, in order to improve chlorine-resistant water resistance, a rubber composition mainly composed of EPDM with a high diene content (see Patent Document 1) has been used for the packing in the water stop portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the EPDM composition with a high ethylene content as in Patent Document 1 has a drawback that the green strength of the rubber is too high and kneading with a roll or the like is difficult. In addition, when a packing made of EPDM is used under chlorinated water for a long time, carbon black blended as a reinforcing material may elute and black powder may be generated, and there is a problem that a so-called ink phenomenon may occur.

[0006] This invention has been made in view of the above problems, and aims to provide a rubber composition and a packing using the same that exhibits little deterioration in rubber properties and good durability without the leaching of carbon black, which is known as the "ink phenomenon," for use in packings used in water sealing parts of water pipes. [Means for solving the problem]

[0007] As a result of diligent research to achieve the aforementioned objectives, the inventors have discovered that by using a chlorine-resistant water-soluble composition as a material, comprising 100 parts by weight of EPDM with a high diene content and low to medium ethylene content, 3 parts by weight or less of carbon black, 15 to 65 parts by weight of silica, and 20 parts by weight or less of paraffinic oil, when forming a packing, the deterioration of rubber properties against chlorine water is minimal, and the phenomenon of carbon black leaching from deteriorated rubber, known as the "ink phenomenon," does not occur. Thus, the inventors have completed the present invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to obtain a packing used in the water-stopping parts of water pipes that exhibits excellent durability with minimal deterioration of rubber properties and no leaching of carbon black, known as the "ink phenomenon." [Modes for carrying out the invention]

[0009] The embodiments for carrying out the present invention will be described in detail below. The present invention relates to a rubber composition for packing suitably used in water-stopping parts of water pipes, and the ethylene-propylene copolymer rubber used as the base rubber refers to an ethylene-propylene-non-conjugated diene terpolymer (EPDM) obtained by introducing a non-conjugated diene as a third component having an unsaturated bond to an ethylene-propylene copolymer. Examples of the third component include dicyclopentadiene, dicyclooctadiene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, and 1,4-hexadiene.

[0010] In this invention, high-diene EPDM refers to the amount of non-conjugated diene, such as 5-ethylidene-2-norbornene, introduced as a third component in the ethylene-propylene copolymer. In EPDM, a higher diene content results in a faster crosslinking rate and lower compression set. In this invention, the amount of diene is 5 to 15 wt%, preferably 7 to 10 wt%.

[0011] Furthermore, the low-to-medium ethylene content of EPDM as used in this invention refers to the ethylene content among the saturated hydrocarbons introduced into the ethylene-propylene copolymer. Generally, in EPDM, the lower the ethylene content, the lower the tensile strength and rubber hardness, and the better the low-temperature properties. In this invention, the low-to-medium ethylene content of the EPDM is 40-60 wt%, preferably 45-55 wt%.

[0012] Specific grades of EPDM with high diene content and low to medium ethylene content (ethylene content / diene content in parentheses) include Mitsui EPT1045 (58 / 5.0), 3110L (56 / 5.0), 3090EM (48 / 5.2), X-4010M (54 / 7.6), 4021 (51 / 8.2), 4045M (45 / 7.6), 4070 (56 / 8.1), 8090M (47 / 9.5), 9090M (41 / 140) (all are product names manufactured by Mitsui Petrochemical Industries, Ltd.), Esprene 301A (5 0 / 5.0), 505A (50 / 9.5), 505 (50 / 10.0), 5206F (54 / 8.5), 5527F (54 / 8.5), 7456 (53 / 10.5) (all product names manufactured by Sumitomo Chemical Co., Ltd.), EPT7241 (52 / 7.7), EP33 (52 / 8.1), EP35 (52 / 8.1), EP65 (53.5 / 9), EP251 (53.5 / 9), EP342 (47 / 9), EP331 (47 / 11.3) (all product names manufactured by ENEOS Material Corporation), KEP 2380 (56 / 5.7), 6590 (53 / 6.5), 330 (57 / 7.9), 650L (59 / 8.7), 650 (59 / 8.7), 350 (57 / 7.9), 350F (59 / 8.1), 2480 (58 / 8.9), 9520 (56.5 / 9), 9590 (52 / 10.0), 9570E (55 / 10.0), 8521 (55 / 8.0) (all are product names of Kumho Polychem (South Korea)), Keltan 2650 (53 / 6.0), 2650C (46 / 6.0), 2750 (48 / 7.8), 3960 (56 / 11.0), 6950C (44 / 9.0), 6951C (44 / 9.0), 7752C (45 / 7.6), 8550C (48 / 5.5), 9650C (51 / 6.5), 9950C (44 / 9.0), 10660C (56 / 6.5), 10950C (52 / 9.0), 13561C (56 / 5.5), Eco6950 (48 / 9.0), Eco8550 (55 / 5.5) (all are product names from ARANXEO (Netherlands)), NORDEL Examples include 5565 (50 / 7.5) and 6530XFC (55 / 8.5) (all product names manufactured by DOW CHEMICAL (USA)).

[0013] The crosslinking (vulcanization) of the rubber composition of the present invention can be performed using a conventional sulfur crosslinking system. As sulfur, recovered sulfur is crushed into a fine powder and used. Examples include Kinka brand fine sulfur powder 150 mesh, 200 mesh, 300 mesh, 325 mesh, and precipitated sulfur (all product names of Tsurumi Chemical Industry Co., Ltd.). Surface-treated sulfur with improved dispersibility and other properties can also be used as appropriate, examples of which include Sulfax A, 5, 200S, 200SS, PS, PMC, SB, and PN (all product names of Tsurumi Chemical Industry Co., Ltd.). The sulfur used in this sulfur crosslinking is added in amounts of approximately 0.1 to 5 parts by weight per 100 parts by weight of base rubber.

[0014] In addition, insoluble sulfur may be used to avoid blooming from the uncrosslinked rubber. Examples include Seimi Sulfur, Seimi OT (product names of Tsurumi Chemical Industries, Ltd.), and Sanfer, Sanfer EX, and Sanfer Z (all product names of Sanshin Chemical Industries, Ltd.), which are added in amounts of approximately 0.1 to 5 parts by weight per 100 parts by weight of base rubber.

[0015] Furthermore, especially when low compression set is required, sulfur-containing organic compounds are used as crosslinking agents instead of using sulfur at all. Examples of these include morpholin disulfide such as Actor R (product name of Kawaguchi Chemical Industry Co., Ltd.), tetramethylthiram disulfide such as Accel TMT (product name of Kawaguchi Chemical Industry Co., Ltd.), tetraethylthiram disulfide such as Accel TET (product name of Kawaguchi Chemical Industry Co., Ltd.), and thiram compounds such as Accel TRA (product name of Kawaguchi Chemical Industry Co., Ltd.), which are added in amounts of approximately 0.5 to 5 parts by weight per 100 parts by weight of base rubber.

[0016] Furthermore, in sulfur crosslinking, to improve the properties of the crosslinked material, particularly its compression set and workability, typically 1 to 6 types of crosslinking accelerators are added in combination, each in an amount of approximately 0.5 to 3 parts by weight per 100 parts by weight of base rubber. Examples of these include thiraum compounds, thiazole compounds, thioureas, dithiocarbamates, and guanidines.

[0017] Examples of thiazoles include 2-mercaptobenzothiazole such as Accel M (product name of Kawaguchi Chemical Industry Co., Ltd.), dibenzothiazole disulfide such as Accel DM (product name of Kawaguchi Chemical Industry Co., Ltd.), N-cyclohexylbenzothiazole such as Accel CZ (product name of Kawaguchi Chemical Industry Co., Ltd.), N-oxydiethylene-2-benzothiazole sulfenamide such as Accel NS (product name of Kawaguchi Chemical Industry Co., Ltd.), Nt-butyl-2-benzothiazole sulfenamide such as Accel BNS-R (product name of Kawaguchi Chemical Industry Co., Ltd.), and N,N-dicyclohexyl-2-benzothiazole sulfenamide such as Accel DZ-G (product name of Kawaguchi Chemical Industry Co., Ltd.).

[0018] Examples of thioureas include diethylthiourea such as Accel EUR (product name manufactured by Kawaguchi Chemical Industry Co., Ltd.) and ethylenethiourea such as Accel 22-S (product name manufactured by Kawaguchi Chemical Industry Co., Ltd.). Examples of thiraums include tetramethylthiuram disulfide such as Accel TMT (product name manufactured by Kawaguchi Chemical Industry Co., Ltd.), tetraethylthiuram disulfide such as Accel TET (product name manufactured by Kawaguchi Chemical Industry Co., Ltd.), tetrabutylthiuram disulfide such as Accel TBT (product name manufactured by Kawaguchi Chemical Industry Co., Ltd.), dipentamethylenethiuram tetrasulfide such as Accel TRA (product name manufactured by Kawaguchi Chemical Industry Co., Ltd.), and tetramethylthiuram monosulfide such as Accel TS (product name manufactured by Kawaguchi Chemical Industry Co., Ltd.).

[0019] Examples of dithiocarbamates include zinc dimethyldithiocarbamate such as Accelerator PZ (trade name, manufactured by Kawaguchi Chemical Industry Co., Ltd.), zinc diethyldithiocarbamate such as Accelerator EZ (trade name, manufactured by Kawaguchi Chemical Industry Co., Ltd.), zinc dibutyldithiocarbamate such as Accelerator BZ (trade name, manufactured by Kawaguchi Chemical Industry Co., Ltd.), tellurium dithiocarbamate such as Accelerator TL-PT (trade name, manufactured by Kawaguchi Chemical Industry Co., Ltd.), and the like. Examples of guanidines include diphenylguanidine such as Accelerator D (trade name, manufactured by Kawaguchi Chemical Industry Co., Ltd.).

[0020] In the composition of the present invention, ordinary peroxides can be applied as a crosslinking agent. Examples of peroxides include dicumyl peroxide such as DiCup 40C (trade name, manufactured by Hercules (USA)), 1,1'-di(tert-butylperoxy)3,3,5-trimethylcyclohexane such as Perhexa 3M-40 (trade name, manufactured by NOF Corporation), di(tert-butylperoxy)diisopropylbenzene such as Pubtyl P-40 (trade name, manufactured by NOF Corporation), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane such as Perhexa 25B-40 (trade name, manufactured by NOF Corporation), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne such as Perhexyne 25B (trade name, manufactured by NOF Corporation), and the like. The addition amount is about 1 to 10 parts by weight in terms of 100% conversion of peroxide per 100 parts by weight of the base rubber.

[0021] When crosslinking with peroxide, triallyl isocyanurate (TAIC) such as Tyk (trade name, manufactured by Nippon Kasei Co., Ltd.) or methacrylic acid ester may be added as a crosslinking aid.

[0022] The carbon black incorporated in the present invention is 3 parts by weight or less with respect to 100 parts by weight of the base rubber. Using more than 3 parts by weight is not preferable because it may induce the ink phenomenon.

[0023] Examples of carbon black include SAF carbon (average particle size 18-22 μm) such as Asahi #90 (product name manufactured by Asahi Carbon Co., Ltd.), Show Black N110, N134 (product names manufactured by Showa Cabot Co., Ltd.), Seast 9 (product name manufactured by Tokai Carbon Co., Ltd.), and Dia Black-A (product name manufactured by Mitsubishi Chemical Co., Ltd.), as well as SAF-HS carbon (average particle size around 20 μm) such as Seast 9H (product name manufactured by Tokai Carbon Co., Ltd.), Asahi #80 (product name manufactured by Asahi Carbon Co., Ltd.), Show Black N220 (product name manufactured by Showa Cabot Co., Ltd.), Seast 6 (product name manufactured by Tokai Carbon Co., Ltd.), and Dia Black ISAF carbon (average particle size 19-29 μm) such as I, N220M (product names from Mitsubishi Chemical Corporation), N-339 carbon (average particle size around 24 μm) such as Asahi #75 (product name from Asahi Carbon Co., Ltd.), Show Black N339 (product name from Showa Cabot Co., Ltd.), Seest KH (product name from Tokai Carbon Co., Ltd.), Dia Black N339 (product name from Mitsubishi Chemical Corporation), ISAF-LS carbon (average particle size 21-24 μm) such as Asahi #80L (product name from Asahi Carbon Co., Ltd.), Show Black N219 (product name from Showa Cabot Co., Ltd.), Seest 600 (product name from Tokai Carbon Co., Ltd.), Dia Black LI (product name from Mitsubishi Chemical Corporation), Asahi #78 (product name from Asahi Carbon Co., Ltd.), Seest 5H (product name from Tokai Carbon Co., Ltd.), Dia Black I-ISAF-HS carbon (average particle size 21-31 μm) such as II (product name manufactured by Mitsubishi Chemical Corporation), HAF carbon (26-30 μm) such as Asahi #70 (product name manufactured by Asahi Carbon Co., Ltd.), Show Black N330 (product name manufactured by Showa Cabot Co., Ltd.), Seest S (product name manufactured by Tokai Carbon Co., Ltd.), Dia Black-H (product name manufactured by Mitsubishi Chemical Corporation), HAF-HS carbon (average particle size 22-30 μm) such as Asahi #70H (product name manufactured by Asahi Carbon Co., Ltd.), Seest 3H (product name manufactured by Tokai Carbon Co., Ltd.), Dia Black-SH (product name manufactured by Mitsubishi Chemical Corporation), N-351 carbon (average particle size around 29 μm) such as Asahi #70IH (product name manufactured by Asahi Carbon Co., Ltd.), Show Black N351 (product name manufactured by Showa Cabot Co., Ltd.), Seest NH (product name manufactured by Tokai Carbon Co., Ltd.), Asahi 70L (product name manufactured by Asahi Carbon Co., Ltd.),HAF-LS carbon (average particle size 25-29μm) such as Show Black N326 (product name manufactured by Showa Cabot), Seest 300 (product name manufactured by Tokai Carbon Co., Ltd.), Dia Black LH (product name manufactured by Mitsubishi Chemical Corporation), LI-HAF carbon (average particle size around 29μm) such as Asahi 70IN (product name manufactured by Asahi Carbon Co., Ltd.), Seest N (product name manufactured by Tokai Carbon Co., Ltd.), MAF carbon (average particle size 30-35μm) such as Asahi 60H (product name manufactured by Asahi Carbon Co., Ltd.), Show Black MAF (product name manufactured by Showa Cabot Co., Ltd.), Seest 116 (product name manufactured by Tokai Carbon Co., Ltd.), Dia Black N550M, SF, M (all product names manufactured by Mitsubishi Chemical Corporation), Asahi #60, #60U (both product names manufactured by Asahi Carbon Co., Ltd.), Show Black N550 Examples include FEF carbon (average particle size 40-52 μm) such as (product name manufactured by Showa Cabot Co., Ltd.), Seest SO, FM (product names manufactured by Tokai Carbon Co., Ltd.), Dia Black-E, EY (product names manufactured by Mitsubishi Chemical Corporation), SRF carbon (average particle size 58-94 μm) such as Asahi #50, #50U, #51 (product names manufactured by Asahi Carbon Co., Ltd.), Seest S (product name manufactured by Tokai Carbon Co., Ltd.), Dia Black R (product name manufactured by Mitsubishi Chemical Corporation), SRF-LM carbon such as Asahi #35 (product name manufactured by Asahi Carbon Co., Ltd.), Dia Black N760M, LR (product names manufactured by Mitsubishi Chemical Corporation), and GPF carbon (49-84 μm) such as Asahi #55 (product name manufactured by Asahi Carbon Co., Ltd.), Seest V (product name manufactured by Tokai Carbon Co., Ltd.).

[0024] Furthermore, activated calcium carbonate such as Shirotsuka CC, DD, O, U (all product names manufactured by Shiraishi Kogyo Co., Ltd.), special calcium carbonate such as Shirotsuka A, AA (all product names manufactured by Shiraishi Kogyo Co., Ltd.), magnesium silicate such as Mistron Paper (product name manufactured by Nippon Mistron Co., Ltd.), and magnesium silicate such as Hytron, Hytron A, Microlight, US-100, US-150S, US-150SS, Hylac, Hylac SS (all product names manufactured by Takehara Chemical Industry Co., Ltd.) may be used in combination as appropriate.

[0025] In the present invention, one of the important formulations is to use 15 to 65 parts by weight, preferably about 25 to 40 parts by weight, of weakly acidic to weakly alkaline silica as a reinforcing agent based on 100 parts by weight of the base rubber. Using more than 65 parts by weight will increase the rubber hardness and deteriorate the kneading property of the rubber. Also, strongly alkaline silica such as Carplex #1120 (product name manufactured by DSL Japan Co., Ltd. / pH 11.0) is not preferred because it increases the swelling property of EPDM in chlorine water. Moreover, strongly acidic silica such as Aerosil 300 (product name manufactured by Nippon Aerosil Co., Ltd. / pH 3.8) is not preferred because stickiness on the surface is observed in chlorine water.

[0026] Silica includes dry silica and wet silica. As the weakly acidic to weakly alkaline silica in the present invention, either dry silica or wet silica can be used. Examples of dry silica include Rheoseal QS-13 (pH 4.0 - 4.5), QS-30 (pH 4.0 - 4.5), QS-38 (pH 4.0 - 4.5), QS-102 (pH 4.0 - 4.5), DM-10 (pH 4.8), DM-20S (pH 4.8), DM-30 (pH 4.5) (product names manufactured by Tokuyama Corporation). Examples of wet silica include Carplex #67 (pH 7.6), #80 (pH 5.9), #101 (pH 6.1), XR (pH 6.2), CS-5 (pH 5.0), CS-7 (pH 5.8) (product names manufactured by DSL Japan Co., Ltd.), Silton A (pH 4.0 - 5.0), R-2 (pH 8.0) (product names manufactured by Mizusawa Chemical Industry Co., Ltd.), Tokushil U (pH 6.5), UR (pH 6.5), USG-T (ph 6.1) (product names manufactured by Oriental Silicas Corporation (Taiwan)), Nip Seal AQ (pH 6.0), ER (pH 8.5), LP (pH 6.0), VN3 (pH 6.0) (product names manufactured by Tosoh Silica Corporation), Ultrasil VN3 (product name manufactured by Evonik Industries (Germany). pH 6.2), Hi-Sil 233 (product name manufactured by PPG Silica Products) (USA). pH 6.9), etc.

[0027] Another crucial component in this invention is the use of paraffinic oil as a softening agent. Unlike naphthenic oils and aromatic oils, paraffinic oil does not readily adsorb chlorine in chlorinated water, making it an essential component of this invention.

[0028] Examples of paraffin-based oils include Diana Process Oil PW-32, PW-90, PW-150, PW-380, PS-32, PS-90, PS-430, PX-32, PX-90 (all product names manufactured by Idemitsu Kosan Co., Ltd.), Flexon 845 (all product names manufactured by Esso Petroleum Corporation), Syntac PA-95, PA-100, PA-140 (all product names manufactured by Kobe Oil Chemical Industry Co., Ltd.), and Cosmop Examples include Roces 10, 40, 40C (product names manufactured by Cosmo Oil Co., Ltd.), Sunper 110, 115, 120, 130, 150, 180, 2100, 2210, 2280 (product names manufactured by Nippon Sun Oil Co., Ltd.), Fukkol P-200, P-400, P-500 (product names manufactured by Fuji Kosan Co., Ltd.), and Mitsubishi 10, Mitsubishi 12 (product names manufactured by Mitsubishi Oil Co., Ltd.).

[0029] Paraffin-based oil is typically used in amounts of 20 parts by weight or less, preferably 10 to 20 parts by weight, per 100 parts by weight of base rubber. Using more than 10 parts by weight results in slightly greater swelling in chlorinated water, and using more than 20 parts by weight is undesirable because it lowers the rubber hardness and may induce stickiness of the rubber. The reason why increasing the amount of paraffin-based oil slightly worsens the physical properties in chlorinated water is unknown, but it is thought that this is probably because a small amount of chlorine is adsorbed onto the paraffin-based oil.

[0030] Furthermore, the rubber composition of the present invention may optionally contain an expanding filler in an amount of about 5 to 100 parts by weight per 100 parts by weight of the base rubber, for purposes such as dimensional stability and low cost.

[0031] The aforementioned bulk fillers include light calcium carbonate such as Green Ball (product name of Inoue Lime Industry Co., Ltd.), Tamapal TP-121, TP-121R, TP222H, TP-222HS, TP-123, TP-123CS (all product names of Okutama Industry Co., Ltd.), and Silver W (product name of Shiraishi Industry Co., Ltd.), Whitelon SSB, SB, S (all product names of Shiraishi Calcium Co., Ltd.), Sunlight #100, #300, #700, #800, #1000, #1500, #2000, #2200, #2500 (all product names of Takehara Chemical Industry Co., Ltd.), and NS #100, NS Heavy calcium carbonate such as #200, NS#400, NS#600, NS#1000, NS#2300, NS#2500, NS#2700, NS#3000, SS#30, SS#80, NN#200, NN#500 (all product names of Nitto Funka Kogyo Co., Ltd.) and Super S, SS, SSS, 4S, #1500, #1700, #2000 (all product names of Maruo Calcium Co., Ltd.), JET-S (product name of Asada Seifun Co., Ltd.), Crystallite AA, VX-S, VX-S-2, VX-SR (all product names of Ryumori Co., Ltd.), and Min-U-Sil 5, 10, 15, 30 (all product names of U.S. Silica (US)Quartz powder such as Silica (USA) company brand name, Imsil A-10, A-15, A-25, A-108 (all brand names from Illinois Minerals (USA) company), wollastonite (calcium metasilicate) such as JA-30W, 325M (all brand names from Asada Flour Milling Co., Ltd.), NYAD325, 400, 1250, G (all brand names from NYCO (USA) company), Celite 270, 281, 501, 503, 505, 535, 545, 560, 577, FC, SSC, Super Examples include diatomaceous earth products such as Floss, SnowFloss (product names from Johns-Manville, USA), and RadioLite #100, #200, #300, #500, #500S, #600, #700, #800, #800-S, #900, F, SPF, FineFlow A, and FineFlow B (product names from Showa Chemical Industry Co., Ltd.), zinc oxide such as two types of zinc oxide (product names from Sakai Chemical Industry Co., Ltd.), aluminum sulfate, barium sulfate, calcium sulfate, titanium dioxide, and molybdenum disulfide. Typically, one to several types are used in combination with reinforcing fillers.

[0032] Furthermore, the rubber composition of the present invention may optionally contain approximately 0.3 to 5 parts by weight of a lubricant or internal release agent per 100 parts by weight of the base rubber to improve its kneadability and extrusion properties. Adding too much can cause blooming, bleeding, or poor fusion, so depending on the type, it is usually added in amounts of approximately 0.5 to 1 part by weight.

[0033] Examples of lubricants and internal release agents include low molecular weight polyethylene such as Mitsui Highwax 100P, 110P, 200P, 210P, 220P, 320P, and 420P (all product names manufactured by Mitsui Petrochemical Industries, Ltd.), stearic acid such as Lunac S-20, S-30, and S-40 (all product names manufactured by Kao Corporation), FA-KR (product name manufactured by Nippon Oil & Fats Co., Ltd.), and Adeka fatty acid SA-20, SA-300, and SA-400 (all product names manufactured by Asahi Denka Co., Ltd.), fatty acid amides such as Plastrozine and Plastrozine S (both product names manufactured by Fujisawa Pharmaceutical Co., Ltd.), fatty acid nitrogen derivatives such as Armowax EBS (product name manufactured by Lion Akzo Co., Ltd.), and Leodol SP-L10 (Kao Corporation). Sorbitan monolaurate (sorbitan laurate ester) such as (company product name), sorbitan monopalmitate (sorbitan palmitate ester) such as Leodol SP-P10 (product name manufactured by Kao Corporation), sorbitan monostearate (sorbitan stearate ester) such as Leodol SP-S10 (product name manufactured by Kao Corporation), sorbitan monooleate (sorbitan oleate ester) such as Leodol SP-O10 (product name manufactured by Kao Corporation), sodium dialkyl sulfosuccinate (sodium di-2-ethylhexyl sulfosuccinate, etc.) such as Lipal 860K (product name manufactured by Lion Corporation), Aflex42 (Rein Chemie (Rein Mixtures of polar compounds and surfactants such as Chemi (product name from Germany), high-grade unsaturated zinc fatty acids such as Struktol A60, special zinc fatty acids such as Struktol EF44, mixtures of calcium fatty acids and fatty acid amides such as Struktol WB16, mixtures of fatty acid esters and fatty acid metal salts such as Struktol WB42, mixtures of high-grade fatty acid ester hydrates and inorganic carriers such as Struktol WB212, polyhydric alcohol fatty acid esters such as Struktol WB222 (product name from Schill & Co.), organosilicon condensates such as Struktol WS180 and WS280, mixtures of high molecular weight natural aliphatic alcohols and aliphatic soaps treated with inert fillers such as Struktol W33FL (all of the above are seal and lacquer (Schill & Co.)Examples include silicone oils such as Seillacher (product name from Germany) and KF96 (product name from Shin-Etsu Chemical Co., Ltd.), paraffin wax, and montan wax. Crosslinking of the composition of the present invention can be carried out by methods well known to those skilled in the art.

[0034] [Examples] More specific embodiments of the present invention are shown below, but the present invention is not limited to these. Example 1 100 parts by weight of Esprene 505A (product name manufactured by Sumitomo Chemical Co., Ltd.) as a high-diene-medium-ethylene EPDM, 6 parts by weight of DiCup 40C (product name manufactured by Hercules, Inc. (USA)) as a crosslinking agent, 4 parts by weight of Tyke (product name manufactured by Nippon Chemical Corporation) as a crosslinking accelerator, 3 parts by weight of Seest S (product name manufactured by Tokai Carbon Co., Ltd.) as carbon black (SRF carbon), 25 parts by weight of Nip Seal VN3 (product name manufactured by Tosoh Silica Co., Ltd.) as wet silica, 1 part by weight of Diana Process Oil PW-380 (product name manufactured by Idemitsu Kosan Co., Ltd.) as paraffinic oil, 5 parts by weight of Zinc Oxide 2 types (product name manufactured by Sakai Chemical Industry Co., Ltd.) as zinc oxide, and 1 part by weight of Lunac S-20 (product name manufactured by Kao Corporation) as stearic acid were weighed out, and each component was kneaded using a well-known rubber kneading roll to obtain an uncrosslinked rubber composition. Then, the rubber composition was cross-linked using a press molding machine to produce a packing (O-ring) with an inner diameter of 15.8 mm and a wire diameter of 2.4 mm. Example 2 From Example 1, the amount of carbon black was changed to 1 part by weight, and the amount of paraffin-based oil was changed to 5 parts by weight. Example 3 From Example 2, the amount of carbon black added was changed to 2 parts by weight. Example 4 In Example 3, the base rubber was changed to Keltan7752C (product name of ARANXEO, Netherlands), which is an EPDM with a high diene-low ethylene content. Example 5 In Example 3, the amount of paraffin-based oil was increased to 10 parts by weight. Example 6 In Example 5, the amount of paraffin-based oil was increased to 20 parts by weight. Example 7 From Example 3 onwards, the amount of wet silica used was changed to 15 parts by weight. Example 8 From Example 7 onwards, the amount of wet silica used was changed to 20 parts by weight. Example 9 From Example 8 onwards, the amount of wet silica used was changed to 30 parts by weight. Example 10 From Example 9 onwards, the amount of wet silica used was changed to 40 parts by weight. Example 11 From Example 10, the amount of wet silica used was changed to 65 parts by weight. Example 12 In Example 11, 25 parts by weight of dry silica, Rheoroseal DM-20S (product name manufactured by Tokuyama Corporation), was added instead of wet silica.

[0035] Next, comparative examples with the present invention are shown below. Comparative Example 1 100 parts by weight of Esprene 501A (product name of Sumitomo Chemical Co., Ltd.) as EPDM with a medium diene-to-ethylene content, 6 parts by weight of DiCup 40C (product name of Hercules Corporation (USA)) as a crosslinking agent, 4 parts by weight of Tyke (product name of Nippon Chemical Corporation) as a crosslinking accelerator, 2 parts by weight of Seast S (product name of Tokai Carbon Co., Ltd.) as carbon black (SRF carbon), 25 parts by weight of Nip Seal VN3 (product name of Tosoh Silica Co., Ltd.) as wet silica, 5 parts by weight of Diana Process Oil PW-380 (product name of Idemitsu Kosan Co., Ltd.) as paraffinic oil, 5 parts by weight of Zinc Oxide 2 types (product name of Sakai Chemical Industry Co., Ltd.) as zinc oxide, and 1 part by weight of Lunac S-20 (product name of Kao Corporation) as stearic acid were weighed out, and each component was kneaded using a well-known rubber kneading roll to obtain an uncrosslinked rubber composition. Then, the rubber composition was cross-linked using a press molding machine to produce a packing (O-ring) with an inner diameter of 15.8 mm and a wire diameter of 2.4 mm. Comparative Example 2 From Comparative Example 1, the amount of wet-processed silica was changed to 15 parts by weight. Comparative Example 3 From Comparative Example 1, the base rubber was changed to Esprene 505A (product name of Sumitomo Chemical Co., Ltd.) as a high-diene-medium-ethylene EPDM, and the amount of carbon black added was increased to 4 parts by weight. Comparative Example 4 Compared to Comparative Example 3, the amount of carbon black was increased to 30 parts by weight. Comparative Example 5 From Comparative Example 1, the base rubber was changed to Nordel IP3640 (product name of Dow Chemical Company (USA)) as an EPDM with a low diene-low ethylene content. Comparative Example 6 From Comparative Example 1, the base rubber was changed to Esprene 586 (product name of Sumitomo Chemical Co., Ltd.) as an EPDM with a high diene-high ethylene content. Comparative Example 7 From Comparative Example 1, the base rubber was changed to Esprene 505A (product name of Sumitomo Chemical Co., Ltd.) as an EPDM with a high diene-to-medium ethylene content, and the silica was changed to Carplex #1120 (product name of DSL. Japan Co., Ltd.), a strongly alkaline wet silica. Comparative Example 8 From Comparative Example 7, the silica was changed to Aerosil 300 (product name of Nippon Aerosil Co., Ltd.), which is a highly acidic dry silica. Comparative Example 9 From Comparative Example 1, the base rubber was changed to Esprene 505A (product name of Sumitomo Chemical Co., Ltd.) as an EPDM with a high diene-medium ethylene content, and the oil was changed to Sansen 450 (product name of Nippon Sun Oil Co., Ltd.), a naphthenic oil. Comparative Example 10 From Comparative Example 9, the oil was changed to JSO Aroma 90 (product name manufactured by Nippon Sun Oil Co., Ltd.), which is an aromatic oil.

[0036] [Evaluation Test] Packings manufactured with the compositions of Examples 1-12 and Comparative Examples 1-10 were immersed in 50 ppm hypochlorous acid solution at 60°C for 500 hours in accordance with the immersion test of JIS K6268. The volume change rate was measured, and changes in appearance, particularly the presence or absence of the "ink-like" phenomenon, were observed. The concentration of the 50 ppm hypochlorous acid solution was measured daily using a chlorine concentration meter, and hypochlorous acid was replenished to adjust the concentration to 50 ppm before continuing the immersion test. Furthermore, the kneadability of the rubber was also evaluated.

[0037] Table 1 shows the compositions and evaluation test results for Examples 1 to 12, and Table 2 shows the compositions and evaluation test results for Comparative Examples 1 to 10.

[0038] [Table 1]

[0039] [Table 2]

[0040] As is clear from the above results, the packings of Examples 1 to 12 of the present invention shown in Table 1 all exhibited a small volume change rate of less than 10% when exposed to chlorinated water, and no ink-like phenomenon (generation of black powder) was observed in terms of appearance. Furthermore, there were no problems with the kneadability of the rubber. Therefore, it was confirmed that the packings of Examples 1 to 12 of the present invention have good properties as water-stopping packings for water pipes and the like.

[0041] In contrast, while comparative examples 1, 2, 8, and 9 shown in Table 2 did not exhibit the "ink-like" phenomenon, they did become sticky on the surface. Furthermore, comparative examples 3, 4, 5, and 7 did exhibit the "ink-like" phenomenon. In addition, comparative examples 3, 4, 7, and 10 showed large volume changes of over 10%, and comparative example 6 was extremely difficult to mix due to the high green strength of the rubber. These results indicate that the packings of comparative examples 1 to 10 are unsuitable as water-stopping packings for water pipes and the like.

Claims

1. A chlorine-resistant aqueous rubber composition comprising 100 parts by weight of EPDM with a high diene content and low to medium ethylene content, 3 parts by weight or less of carbon black, 15 to 65 parts by weight of silica, and 20 parts by weight or less of paraffinic oil.

2. The chlorine-resistant water-resistant rubber composition according to claim 1, wherein the silica is a weakly acidic to weakly alkaline wet silica or dry silica.

3. A packing molded using the chlorine-resistant aqueous rubber composition described in claim 1 or 2 as a material.

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