The present invention relates to a glass fiber coating composition, a rubber-reinforcing glass fiber product coated with the coating composition, and a rubber article such as a rubber belt, a tire and the like, formed using the glass fiber product as a reinforcing material, and a process for treating the glass fiber.
Reinforcing fibers such as a glass fiber have been conventionally widely used as a reinforcing material for rubber articles such as a rubber belt, a tire and the like.
The rubber articles such as the rubber belt may be repeatedly subjected to a flexing stress to cause a flex fatigue, resulting in a reduced performance, a peel-off between the reinforcing material and a rubber matrix and a wearing of the reinforcing fiber. Further, the strength is liable to be reduced. Such phenomena tend to be particularly accelerated by a heat and water. In order to prevent a peel-off due to such a flex fatigue and to provide a sufficient reinforcing effect, it is necessary to increase the conformity and adhesion between the reinforcing fiber and the rubber and to provide the rubber article with heat and water resistances. For this purpose, various treating agents may be applied onto the surface of the reinforcing fiber.
For example, in Japanese Patent Application Laid-open No. 221433/89, a treating agent has been proposed which employs, in combination, a water-soluble resorcinol-formaldehyde condensate, a vinylpyridine/butadiene/styrene terpolymer latex, a dicarboxylated butadiene/styrene copolymer latex and a chlorosulfonated polyethylene latex.
The use of such a treating agent makes it possible to satisfy the adhesion between the reinforcing fiber and the rubber matrix and the heat and flex resistances of the treating agent itself to a certain extent, but is accompanied by a disadvantage that when a reinforcing fiber coated with such treating agent is used, sufficiently satisfactory heat, water and flex resistances cannot be obtained because of a insufficient water resistance of the treating agent itself and hence, it is difficult to provide an excellent rubber article.
The present inventors have previously invented and proposed a rubber-reinforcing glass fiber cord coated with a composition consisting essentially of a water-soluble resorcinol/formaldehyde condensate having an improved adhesive strength to a heat-resistant rubber, and a nitrile group-containing highly saturated polymer rubber having an iodine value of 120 or less (see Japanese Patent Application Laid-open No. 270877/88). This invention and proposal have been accomplished by finding that the strength of a rubber film and the adhesive strength to the matrix rubber are enhanced by using a nitrile group-containing highly saturated polymer rubber having an iodine value of 120 or less, preferably 0 to 100.
Even in the above-described invention by the present inventors, a scope for improvement for water and flex resistances has been left.
It is an object of the present invention to provide a reinforcing fiber product in which the disadvantages associated with the prior art are overcome, and which exhibits a large bonding force between a reinforcing fiber and a rubber matrix, and which cannot be reduced in strength, even if it is repeatedly subjected to a flexing stress, and which cannot produce a peel-off between the reinforcing fiber product and the rubber matrix and moreover, has sufficient heat and water resistances.
The present invention embraces following aspects (1) to (7):
(1) A glass fiber coating composition comprising a nitrile group-containing highly saturated polymer rubber latex (A) having an iodine value of 120 or less, a rubber latex (B) other than the highly saturated polymer rubber latex, and a water-soluble resorcinol/formaldehyde condensate in amounts of 15 to 80%, 5 to 70% and 2 to 15%, all by weight in terms of solids, respectively.
(2) A rubber-reinforcing glass fiber product which is coated with a treating agent comprising a nitrile group-containing highly saturated polymer rubber latex (A) having an iodine value of 120 or less, a rubber latex (B) other than the highly saturated polymer rubber latex, and a water-soluble resorcinol/formaldehyde condensate in amounts of 15 to 80%, 5 to 70% and 2 to 15%, all by weight in terms of solids, respectively.
(3) A rubber-reinforcing glass fiber product, which is coated with a treating agent comprising a nitrile group-containing highly saturated polymer rubber latex (A) having an iodine value of 120 or less, a rubber latex (B) other than the highly saturated polymer rubber latex, and a water-soluble resorcinol/formaldehyde condensate in amounts of 15 to 80%, 5 to 70% and 2 to 15%, all by weight in terms of solids, respectively, and which is further coated with a halogen-containing polymer-based adhesive solution.
(4) A rubber article made using a glass fiber product which is coated with a treating agent comprising a nitrile group-containing highly saturated polymer rubber latex (A) having an iodine value of 120 or less, a rubber latex (B) other than the highly saturated polymer rubber latex, and a water-soluble resorcinol/formaldehyde condensate in amounts of 15 to 80%, 5 to 70% and 2 to 15%, all by weight in terms of solids, respectively.
(5) A rubber article made using a glass fiber product which is coated with a treating agent comprising a nitrile group-containing highly saturated polymer rubber latex (A) having an iodine value of 120 or less, a rubber latex (B) other than the highly saturated polymer rubber latex, and a water-soluble resorcinol/formaldehyde condensate in amounts of 15 to 80%, 5 to 70% and 2 to 15%, all by weight in terms of solids, respectively, and which is further coated with a halogen-containing polymer-based adhesive solution.
(6) A process for coating a rubber-reinforcing glass fiber product, comprising the step of coating the rubber-reinforcing glass fiber product with a treating agent which comprises a nitrile group-containing highly saturated polymer rubber latex (A) having an iodine value of 120 or less, a rubber latex (B) other than the highly saturated polymer rubber latex, and a water-soluble resorcinol/formaldehyde condensate in amounts of 15 to 80%, 5 to 70% and 2 to 15%, all by weight in terms of solids, respectively.
(7) A process for coating a rubber-reinforcing glass fiber product, comprising the steps of coating the rubber-reinforcing glass fiber product with a treating agent which comprises a nitrile group-containing highly saturated polymer rubber latex (A) having an iodine value of 120 or less, a rubber latex (B) other than the highly saturated polymer rubber latex, and a water-soluble resorcinol/formaldehyde condensate in amounts of 15 to 80%, 5 to 70% and 2 to 15%, all by weight in terms of solids, respectively, and coating the resulting product with a halogen-containing polymer-based adhesive solution.
The present invention will now be described in further detail.
The nitrile group-containing highly saturated polymer rubber latex (A) used in the present invention is required to have an iodine value of 120 or less, preferably, in a range of 0 to 100 from the viewpoints of strength of a rubber film and adhesive strength to the matrix rubber. A preferred example of the latex which may be used is Zetpole Latex 2020 (which has an iodine value of 28, and which is made by Nippon Zeon Co., Corp.). It should be noted that the iodine value was determined according to JIS K0070. The nitrile group-containing highly saturated polymer rubbers (A) includes a rubber made by hydrogenating a conjugated diene unit moiety of an unsaturated nitrile/conjugated diene copolymer rubbers; an unsaturated nitrile/conjugated diene/ethylenically unsaturated monomer tridimensional copolymer rubber and the derivatives made by hydrogenation thereof; an unsaturated nitrile/ethylenically unsaturated monomer based copolymer rubber. The unsaturated nitrile/ethylenically unsaturated monomer based copolymer rubber may be a rubber made by substituting a portion of the unsaturated monomer by a non-conjugated diene such as vinyl-norbornene, dicyclopentadiene, and 1,4-hexadiene, and then subjecting the resulting substance to a copolymerization.
Specified examples of these nitrile group-containing highly saturated polymer rubbers (A) are those made by hydrogenating a butadiene/acrylonitrile copolymer rubber, an isoprene/butadiene/acrylonitrile copolymer rubber, an isoprene/acrylonitrile copolymer rubber; a butadiene/methylacrylate/acrylonitrile copolymer rubber, a butadiene/acrylic acid/acrylonitrile copolymer rubber, etc., and the derivatives made by hydrogenation thereof; a butadiene/ethylene/acrylonitrile copolymer rubber, a butylacrylate/ethoxyethyleacrylate/vinylchloroacetate/acrylonitrile copolymer rubber, a butylacrylate/ethoxyethylacrylate/vinylnorbornene/acrylonitrile copolymer rubber, and the like. They may be produced using a usual polymerizing technique and a usual hydrogenating process.
Preferred examples of the rubber latices (B) other than the highly saturated rubber latex, which may be used, are a butadiene/styrene copolymer latex, a dicarboxylated butadiene/styrene copolymer latex, a vinylpyridine/butadiene/styrene terpolymer latex, a chlorosulfonated polyethylene latex, an acrylonitrile/butadiene copolymer latex having an iodine value of 200 or more, and the like. If a mixture of a vinylpyridine/butadiene/styrene terpolymer latex and a chlorosulfonated polyethylene latex, among them, is used, a particularly appropriate effect can be provided. Preferred examples of the latex which may be used are J9040 (which is a trade name and made by Sumitomo Norgatta Co., Corp.), Nipol LX 110 (which is a trade name and made by Nippon Zeon Co., Corp.), and the like.
Particularly suitable examples of the dicarboxylated butadiene/styrene copolymer latex are those containing 20 to 80% by weight of butadiene, 5 to 70% by weight of styrene, and 1 to 10% by weight of an ethylenically unsaturated dicarboxylic acid, including Nipol 2570X5 (which is a trade name and is made by Nippon Zeon Co., Corp.), JSR 0668 (which is a trade name and is made by Nippon Gousei Gomu K.K.) and the like.
The vinylpyridine/butadiene/styrene terpolymer latex which can be used include a large number of such terpolymers well known to those skilled in the art. For example, a terpolymer containing vinylpyridine, butadiene and styrene in a proportion of polymerization of 10-20:60-80:10-20 is particularly preferred, such as Nipol 2518FS (which is a trade name and is made by Nippon Zeon Co., Corp.), Pyratex (which is a trade name and is made by Sumitomo Norgatta Co., Corp.) and the like.
Particularly suitable examples of the chlorosulfonated polyethylene latex are those containing 25 to 43% by weight of chlorine and 1.0 to 1.5% by weight of sulfur, such as Esprene (which is a trade name and is made by Sumitomo Chemical Co., Ltd.).
Particularly suitable examples of the acrylonitrile/butadiene copolymer latex having an iodine value of 200 or more are those having a bound-acrylonitrile content of 36 to 43% by weight, such Nipol 1561 (which is a trade name and is made by Nippon Zeon Co., Corp.), and the like.
Suitable examples of the water-soluble resorcinol-formaldehyde condensate (which will be referred to as RF hereinafter) which may be used in the present invention are resorcinol-based water-soluble addition condensate produced from a reaction of resorcinol and formaldehyde in the presence of an alkaline catalyst such as alkali hydroxide and an amine. Particularly, it is desirable to use a condensate produced from a reaction of resorcinol (R) and formaldehyde (F) at a reaction mole ratio R/F of 1:0.53-3.
According to the present invention, a nitrile group-containing highly saturated polymer rubber latex (A) having an iodine value of 120 or less, a rubber latex (B) and a water-soluble resorcinol/formaldehyde condensate are mixed homogeneously in amounts of 15 to 80%, 5 to 70% and 2 to 15% by weight in terms of solids, respectively. A more preferable proportion of incorporation is such that the amount of the component (A) is of 30 to 70% by weight; the amount of the component (B) is of 20 to 60% by weight, and the amount of the condensate is of 3 to 12% by weight. If the proportion of the nitrile group-containing highly saturated polymer rubber latex in the treating agent is less than 15% by weight or exceeds 80% by weight, the resulting treating agent will have unimproved heat-, water- and flex-resistances. If the amount of RF exceeds 12% by weight, a coating of the resulting treating agent of the present invention will be hardened and hence, sufficient flex-fatigue resistance cannot be obtained. If the amount of RF is less than 3% by weight, a sufficient adhesion between the reinforcing fiber and the rubber matrix cannot be obtained. If the amount of the rubber latex (B) exceeds 70% by weight, a sufficient heat and flex resistances cannot be obtained. If the amount of the rubber latex (B) is less than 3% by weight, a sufficient water resistance cannot be obtained.
The solid concentration of the treating agent according to the present invention is suitable to be 10 to 40% by weight, preferably, 20 to 30% by weight. If the concentration is too low, the treating agent may be insufficiently deposited on the reinforcing fiber. On the other hand, if the concentration is too high, it is difficult to control the amount of treating agent deposited on the reinforcing fiber, resulting in a difficulty to provide a reinforcing fiber product with the treating agent deposited thereon in a uniform amount.
According to the present invention, the treating agent comprises the nitrile group-containing highly saturated polymer rubber latex (A), the rubber latex (B) and the RF as essential components, but if required, a base for adjusting pH, e.g., ammonia, may be incorporated into the treating agent and further, other additives such as a stabilizer, an age resistor and the like may be incorporated into the treating agent.
According to the present invention, the essential components of the treating agent are coated onto a glass fiber strand by immersing a glass fiber, particularly, a strand-like glass fiber into the treating agent, removing an excessive treating agent and then, if required, drying the resulting material. In this case, greige goods, which are usually applied in spinning of a glass fiber, may be either applied, or not applied to the glass fiber strand. Then, a desired number of glass fiber strands are collected and subjected to a twisting to provide a glass fiber cord. The glass fiber cord is embedded into an unvulcanized rubber substrate in a known manner and then heated and vulcanized under pressurization.
According to the present invention, the treating agent is applied to the glass fiber cord, usually in an amount of 10 to 30% by weight in terms of solids based on the glass fiber cord.
The type of the rubber to be reinforced with the glass fiber cord according to the present invention is particularly not limited, but illustrative of such rubbers are a chloroprene rubber, an acrylonitrile/butadiene rubber, a chlorosulfonated polyethylene rubber, a hydrogenated nitrile rubber and the like. When these rubbers are used, an extremely appropriate effect can be obtained.
When a chlorosulfonated polyethylene rubber or a hydrogenated nitrile rubber is used as a rubber to be reinforced, the glass fiber cord according to the present invention, preferably, is further coated with an adhesive solution containing a halogen-containing polymer such as described above, an isocyanate compound, carbon black, a vulcanizing agent and the like, prior to application to such rubbers, in order to further enhance the adhesive property.
More specifically, according to the present invention, if the treating agent is used as a primary coating agent, a halogen-containing polymer based adhesive solution can be further used as a secondary coating agent on the glass fiber treated with such primary coating agent. The halogen-containing polymer based adhesive solution comprises a mixture containing an organic di-isocyanate, a chlorosulfonated polyethylene and an aromatic nitroso compound.
A secondary coating layer made by application of the secondary coating agent can be formed by applying, for example, a solution of an organic di-isocyanate, a chlorosulfonated polyethylene and an aromatic nitroso compound dissolved in an organic solvent onto a glass fiber cord coated with a primary coating agent such as described above.
Preferred examples of the organic di-isocyanates are hexamethylene di-isocyanate, isophoron di-isocyanate, methylene-bis-(4-cyclohexyl isocyanate), toluene di-isocyanate, xylene di-isocyanate, naphthalene di-isocyanate, methylene-bis-(phenyl isocyanate) and the like. They may be used in a combination of two or more of them. If the organic di-isocyanates have isomers with substituent groups, as is the case with toluene di-isocyanate and methylene-bis-(phenyl isocyanate), a mixture of such isomers may be used. These organic di-isocyanates can be also used in the form with the isocyanate group protected by phenol or lactum. The organic di-isocyanate in the form protected in such a manner is advantageously used, when the secondary coating agent is used in the form of a mixture in an aqueous medium such as an aqueous emulsion.
A chlorosulfonated polyethylene having, for example, a chlorine content of 20 to 45% by weight and a sulfonyl sulfur content of 1 to 2.5% by weight, can be usually used as the above-described chlorosulfonated polyethylene. Particularly, a chlorosulfonated polyethylene having, for example, a chlorine content of 25 to 45% by weight and a sulfonyl sulfur content of 1.0 to 1.5% by weight, is advantageously used. In addition, a preferred chlorosulfonated polyethylene exhibits Mooney viscosity of 20 to 50 ML1+4 (at 100xc2x0 C.). The chlorosulfonated polyethylene is soluble very well in aromatic hydrocarbons such as benzene, toluene and xylene, and a halogenated hydrocarbons such as trichloroethylene.
The aromatic nitroso compound may be any of hydrocarbons such as benzene, naphthalene, anthracene and biphenyl which have at least two nitroso groups directly bonded to non-adjacent carbon atoms in a ring. More specifically, such a nitroso compound is represented as an aromatic poly-C-nitroso compound which has one or three aromatic nuclei including condensed aromatic nuclei and has two or six nitroso groups directly bonded to non-adjacent nucleus carbon atoms. Preferred poly-C-nitroso compounds are aromatic di-nitroso compounds, particularly, di-nitroso benzenes or di-nitroso naphthalenes such as aromatic meta- or para-di-nitroso benznen or aromatic meta- or para-di-nitroso naphthalene. The hydrogen atom in an aromatic nucleus can be substituted by a substituent such as alkyl, alkoxy, cycloalkoxy, aryl, aryl alkyl, alkyryl, arylamines, arylnitroso, amine, halogens (fluorine, chlorine, bromine and iodine) and the like. The presence of such a substituent on the aromatic nucleus exerts little influence to the active effect of the poly-C-nitroso compound used in the present invention. Insofar as being presently known, the nature of the substituent is not limited in any way, whether the substituent is an organic or inorganic group. It should be understood that when the poly-C-nitroso benzene or poly-C-nitroso naphthalene is referred to, it embraces both of a substituted nitroso compound and a non-substituted nitroso compound, unless otherwise defined.
An especially preferred poly-C-nitroso compound is a compound represented by a general formula:
(R1)pxe2x80x94Arxe2x80x94(NO)2 
wherein Ar is selected from a group consisting of phenylenes and naphthalenes; R1 is a monovalent organic radical selected from a group consisting of alkyl, cycloalkyl, aryl, arylalkyl, alkyryl, arylamine, alkoxy groups having 1 to 20 carbon atoms, amino group and halogens (fluorine, chlorine, bromine and iodine), and preferably, an alkyl group having 1 to 6 carbon atoms; and p is 0, 1, 2, 3 or 4, preferably, 0.
Preferred partial and non-limited examples of the poly-C-nitroso compounds suitable in carrying out the present invention are m-di-nitroso benzene, p-di-nitroso benzene, m-di-nitroso naphthalene, p-di-nitroso naphthalene, 2,5-di-nitroso-p-cymene, 2-methyl-1,4-di-nitroso benzene, 2-methyl-5-chloro-1,4-di-nitroso benzene, 2-fluoro-1,4-di-nitroso benzene, 2-methoxy-1,3-di-nitroso benzene, 5-chloro-1,3-di-nitroso benzene, 2-benzyl-1,4-di-nitroso benzene, and 2-cyclohexyl-1,4-di-nitroso benzene.
The secondary coating agent may contain an isocyanate, a chlorosulfonated polyethylene and an aromatic nitroso compound. The secondary coating agent further may contain, or rather desirably contains inorganic filler or fillers. Illustrative of the inorganic fillers are carbon black, magnesium oxide, silica, lead oxides, and magnesium carbonate. Among them, carbon black is especially preferred.
The secondary coating agent may be prepared in the form of a solution or a dispersion having a solid content of 3 to 25% by weight, more preferably, 5 to 15% by weight. The organic di-isocyanate occupies a solid content of preferably 10 to 50%, more preferably, 25 to 45% by weight. The chlorosulfonated polyethylene occupies a solid content of preferably 10 to 60%, more preferably, 20 to 50% by weight. The aromatic nitroso compound occupies a solid content of preferably 1 to 20%, more preferably, 2 to 15% by weight. The inorganic filler occupies a solid content of preferably at most 30%, more preferably, 5 to 20% by weight.
The secondary coating agent is applied usually in the form of a solution or a dispersion having a solid content of 1 to 5% by weight (preferably 2 to 4% by weight onto a glass fiber cord having a primary coating layer thereon, and then dried for 0.1 to 1 minute at a temperature of 80 to 150xc2x0 C. to provide a secondary coating layer on the primary coating layer of the glass fiber cord.
A rubber article produced using a glass fiber product according to the present invention as a reinforcing material has excellent resistances to heat, flex-fatigue and water. Therefore, the glass fiber product according to the present invention can be used extremely appropriately as a reinforcing fiber used, for example, for a timing belt, a toothed belt, a rubber tire and the like in an automobile, which may be subjected to a flexing stress under an environment influenced by a heat and water.