JP3864129B2 - Fiber for reinforcing rubber products and method for producing the same - Google Patents

Description

【００７３】
表１に示したとおり、本発明のゴム製品の補強用繊維（実施例１〜３）は、加硫剤として過酸化物を用いる高飽和Ｈ−ＮＢＲを配合したゴム組成物との接着性に優れている。また、油浸漬後においても接着強さが大きく低下することがなく、注油屈曲疲労試験後の引張り強さ保持率が高いので、耐油性にも優れていることが分かる。特に、ＲＦＬ被覆剤における固形状ＮＢＲラテックスとして自己架橋型ＮＢＲラテックスを使用し、かつ、第２の被覆剤に未硬化エポキシ樹脂を配合した場合（実施例１）では、接着性及び耐油性の両方が極めて優れている。
【００７４】
これに対し、従来のＲＦＬ被覆剤を使用した比較例１と固形状ＮＢＲラテックスのみを配合して液状ＮＢＲラテックスを配合していない第１の被覆剤を使用した比較例２とでは、第２の被覆剤が本発明と同じであるので常態における接着性は同等であるが、油浸漬後の接着強さと注油屈曲疲労試験後の引張り強さ保持率との一方又は両方が低いので、耐油性が劣っていることが分かる。
【００７５】
また、従来の第２の被覆剤を用いた比較例３と従来の第２の被覆剤及び第３の被覆剤を用いた比較例４とでは、第１の被覆剤が本発明と同じであるにもかかわらず、常態及び油浸漬後の接着強さが低いばかりではなく、注油屈曲疲労試験後の引張り強さ保持率も少なからず悪い。
【００７６】
更に、固形状ＮＢＲラテックスのみを配合して液状ＮＢＲラテックスを配合していない第１の被覆剤及び従来の第２の被覆剤を用いた比較例５では、常態及び油浸漬後の接着強さと注油屈曲疲労試験後の引張り強さ保持率とが低いので、接着性及び耐油性の両方において劣っていることが分かる。
【００７７】
【発明の効果】
本発明のゴム製品の補強用繊維は、これを補強材として用いたゴム製品の耐油性、耐熱性及び耐屈曲疲労性を大きく改善する。また、本発明のゴム製品の補強用繊維は、高乾和Ｈ−ＮＢＲを配合したゴム組成物に対しても優れた接着性を有する。
【００７８】
従って、特に、本発明のゴム製品の補強用繊維を、特に、タイミングベルトの補強材として用いた場合には、タイミングベルトの耐油性、耐屈曲疲労性及び耐熱性を大幅に向上させることができるので、耐熱性及び耐屈曲疲労性が要求される用途のみならず、エンジンオイルと接触するような耐油性が要求されるタイミングベルト等の用途にも適用することができる。
【図面の簡単な説明】
【図１】注油屈曲疲労試験機の構造を示す概略図である。
【符号の説明】
１： 注油屈曲疲労試験機 ２： 往復運動部
３： スライドレール ４： エアーシリンダー
５： 平ベルト ６、７： 架台
８： 基盤 ９、１０、１１： プーリー
１２： ボルト １３： 錘
２１、２２、２３： 平プーリー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reinforcing fiber for rubber products used as a reinforcing material for various rubber products such as rubber belts such as timing belts for automobile engines, rubber hoses and rubber tires, and a method for producing the same.
[0002]
[Prior art]
[Patent Document 1]
JP-A-1-221433
[Patent Document 2]
JP-A-4-103634
[Patent Document 3]
JP-A 63-234075
[Patent Document 4]
JP-A-1-156535
[Patent Document 5]
JP-A-11-241275
[Patent Document 6]
JP-A-7-190149
[0003]
Reinforcing fibers used to increase the strength and durability of various rubber products such as rubber belts and rubber tires, including timing belts, increase the adhesion between the fibers and the rubber substrate in the rubber products, and the fibers themselves In order to protect and enhance the durability of the rubber product, it is generally coated with a coating formed of various coating agents.
[0004]
As these coating agents, as disclosed in Patent Document 1, Patent Document 2, and the like, a coating agent containing a condensate of resorcin and formaldehyde and a rubber latex as main components (hereinafter also referred to as “RFL coating agent”). )It has been known. Further, as disclosed in Patent Document 3 and the like, a coating agent (hereinafter also referred to as “rubber paste”) in which a rubber composition is dissolved in an organic solvent is known.
[0005]
Patented for the purpose of further strengthening the adhesion between a rubber substrate with high heat resistance such as hydrogenated nitrile rubber (hereinafter also referred to as “H-NBR”) and chlorosulfonated polyethylene and reinforcing fibers. As disclosed in Document 4, Patent Document 5, Patent Document 6 and the like, the fiber coated with the first film formed by the RFL coating agent is further mixed with an organic diisocyanate, a rubber compound, a vulcanizing agent, and a vulcanizing agent. It is also known to coat with a second coating formed of a rubber paste containing an auxiliary agent or the like, and to coat the outermost layer with a third coating.
[0006]
[Problems to be solved by the invention]
However, the reinforcing fibers covered with the coatings formed by the above-mentioned various kinds of conventional coating agents are sufficiently satisfactory particularly when used as a reinforcing material (core wire) for timing belts for engines such as automobiles. However, it has the following problems.
[0007]
In other words, timing belts for automobile engines are superior to metal silent chains in terms of lightness, quietness and ease of maintenance, but transmit crankshaft power to camshafts and pumps. When installing the power transmission mechanism to the inside of the engine block in order to make the engine compact, a timing belt must be used in an environment in contact with engine oil, etc., and extremely high oil resistance is required. Is done. In addition to the above oil resistance, the timing belt has an appropriate tackiness (adhesiveness) for the reinforcing fiber so as not to hinder the function of the power transmission mechanism due to the elongation of the belt as the usage time elapses. The degree of flexibility is required, and the belt is required to have sufficiently high bending fatigue resistance.
[0008]
In response to these requirements, the timing belt using the reinforcing fiber covered with the coating formed by the RFL coating agent disclosed in Patent Document 1 and Patent Document 2 described above has relatively low oil resistance of the rubber itself. Oil resistance is insufficient due to the inclusion of low vinylpyridine-styrene-butadiene copolymer latex. Moreover, when using the reinforcing fiber which uses only the rubber paste as disclosed in Patent Document 3 as a coating agent, the adhesion to inorganic fibers such as glass fibers is insufficient. In addition, since the reinforcing fiber (core wire) is generally a filament yarn, the coating agent needs to be impregnated not only into the surface of the fiber but also into its interior, but the rubber paste has a high viscosity and is suitable for the fiber. The impregnation is insufficient and the durability performance of the resulting belt is not sufficient.
[0009]
Further, in the timing belt using the reinforcing fiber having two layers of the first coating and the second coating as described in Patent Document 4, Patent Document 5, and Patent Document 6 described above, The oil resistance and bending fatigue resistance are not sufficient. Furthermore, the conventional reinforcing fiber shows a temporary adhesion to a rubber composition mainly using sulfur as a vulcanizing agent among H-NBR rubber compositions, but in order to further improve heat resistance. Inadequate adhesion to a rubber composition using a peroxide as a vulcanizing agent, that is, a highly saturated H-NBR rubber composition, resulting in deterioration of the properties of the resulting timing belt Has a point.
[0010]
Furthermore, since the modified phenolic resin layer, which is a covering layer on the surface of the reinforcing fiber described in Patent Document 6, has poor flexibility, the covering layer partially peels off during the handling of the reinforcing fiber. In addition, there is a problem that the bending fatigue resistance of the obtained timing belt is adversely affected.
[0011]
Therefore, the present invention has been made to solve the above problems, and its purpose is suitable for rubber products excellent in oil resistance, heat resistance and bending fatigue resistance, particularly for engine timing belts, It is an object of the present invention to provide a reinforcing fiber for rubber products and a method for producing the same, which are also suitable for rubber products using highly saturated H-NBR.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problems, a reinforcing fiber for a rubber product according to the present invention includes a first coating formed by a first coating agent, and a second coating formed on the first coating by a second coating agent. 2, wherein the first coating agent is a water-soluble condensate of resorcin and formaldehyde, a solid acrylonitrile-butadiene copolymer latex, and a liquid acrylonitrile-butadiene copolymer latex. And the second coating agent contains an uncured phenol resin and rubber.
[0013]
The rubber fiber reinforcing fiber manufacturing method of the present invention includes a water-soluble condensate of resorcinol and formaldehyde, a solid acrylonitrile-butadiene copolymer latex, and a liquid acrylonitrile-butadiene copolymer latex. The first coating agent is impregnated into the fiber and dried to produce a coated fiber having the first coating, and then the coated fiber is twisted to form a twisted yarn, and the twisted yarn contains an uncured phenol resin and rubber A second coating agent is applied and dried to form a second coating on the first coating.
[0014]
According to the reinforcing fiber of the rubber product of the present invention, the first fiber containing a liquid acrylonitrile-butadiene copolymer latex in addition to the solid acrylonitrile-butadiene copolymer latex having oil resistance as described above. Since the fiber is covered with the first coating formed by the coating agent, the oil resistance of the rubber product using this as a reinforcing material can be improved. Particularly, the timing belt using this as a core wire is remarkably used. Good oil resistance.
[0015]
Further, the liquid acrylonitrile-butadiene copolymer latex used in addition to the solid acrylonitrile-butadiene copolymer latex brings high tackiness to the reinforcing fibers, and the fibers constituting the reinforcing fibers (primary twisted yarn) This improves the adhesion between the belts, greatly improving the belt's elongation over time and hindering the function of the power transmission mechanism, and the strength of the belt due to contact with oil and bending fatigue. This also greatly improves the point of decrease.
[0016]
Furthermore, the reinforcing fiber of the present invention has a second coating formed by a second coating containing uncured phenolic resin and rubber on the first coating formed by the first coating. The first coating has a high adhesion to the fiber, and the second coating is a rubber composition in which a rubber such as H-NBR, in particular, a highly saturated H-NBR excellent in heat resistance is blended. It has both strong adhesion and flexibility to objects. Therefore, the timing belt using the reinforcing fiber of the present invention as a core wire has not only oil resistance but also heat resistance and bending fatigue resistance.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. In the following description, unless otherwise specified, the unit “part” means “part by mass”, and the unit “%” means “mass percentage”.
[0018]
First, a water-soluble condensate of resorcinol and formaldehyde (hereinafter also referred to as “RF condensate”), a solid acrylonitrile-butadiene copolymer latex, and a liquid acrylonitrile-butadiene copolymer latex The coating agent will be described.
[0019]
The RF condensate to be blended with the first coating agent is rich in oxymethyl groups obtained by reacting resorcin and formaldehyde in the presence of an alkaline catalyst such as an alkali metal hydroxide, ammonia or amine. However, water-soluble addition condensates can be used. In particular, an RF condensate obtained by reacting resorcin and formaldehyde in a molar ratio of 1: 0.3 to 2.5 is preferable.
[0020]
The solid acrylonitrile-butadiene copolymer latex (hereinafter, also referred to as “solid NBR latex”) to be blended with the first coating agent is a normal temperature after removing the dispersion medium by evaporating at 110 ° C. for 2 hours. Means a latex that produces a solid acrylonitrile-butadiene copolymer (having a weight average molecular weight of 150,000 or more) as an evaporation residue. Here, the solid form includes a solid form or a film form. The acrylonitrile-butadiene copolymer forming the solid NBR latex preferably has an acrylonitrile content of 15 to 50%, particularly 25 to 40%.
[0021]
In addition, since the oil resistance and heat resistance of rubber products such as timing belts obtained can be further increased, the solid NBR latex may be a self-crosslinking acrylonitrile-butadiene copolymer latex (hereinafter referred to as “self-crosslinking type”). NBR latex ”or soap-free acrylonitrile-butadiene copolymer latex (hereinafter also referred to as“ soap-free NBR latex ”), and self-crosslinking type NBR latex is particularly preferable.
[0022]
The self-crosslinking type NBR latex is a latex of a copolymer in which a monomer capable of self-crosslinking is preferably contained in an acrylonitrile-butadiene copolymer in an amount of 0.5 to 5%. As such a self-crosslinking type NBR latex, an acrylonitrile-butadiene copolymer latex obtained by copolymerizing an ethylenic monomer such as N-methylol (meth) acrylamide together with acrylonitrile and butadiene can be used.
[0023]
The soap-free NBR latex is a latex that does not contain a surfactant as an emulsifier or has a very low content. As such soap-free NBR latex, latex of acrylonitrile-butadiene copolymer obtained by emulsion polymerization of a monomer using an alkali-soluble oligomer as an emulsifier can be used.
[0024]
The liquid acrylonitrile-butadiene copolymer latex blended in the first coating agent (hereinafter referred to as “liquid NBR latex”) is obtained by removing the dispersion medium by evaporating at 110 ° C. for 2 hours and then returning to normal temperature. It means a latex that produces a liquid or viscous acrylonitrile-butadiene copolymer (weight average molecular weight 1000 to 70000) as an evaporation residue. The acrylonitrile-butadiene copolymer forming the liquid NBR latex preferably has an acrylonitrile content of 15 to 50%, particularly 25 to 40%.
[0025]
In addition to the above RF condensate, solid NBR latex, and liquid NBR latex, the first coating agent may be added in the same manner as used in conventional RFL coating agents such as anti-aging agents, if necessary. An agent, other rubber latex, or a resin emulsion may be blended. Anti-aging agents include liquid emulsions of mineral oil, and other rubber latexes include halogen-containing polymer latexes, acrylate polymer latexes, styrene-butadiene copolymer latexes, and polybutadiene latexes. Examples of the resin emulsion include an epoxy resin emulsion, an acrylic resin emulsion, and a phenoxy resin emulsion. In addition, since these components are compositions in which the first coating agent uses water as a dispersion medium, these components need to be in any form of a water-soluble solid, an aqueous solution, a latex, or an emulsion.
[0026]
Examples of the halogen-containing polymer in the latex of the halogen-containing polymer include chlorinated rubber, chloroprene rubber, and chlorosulfonated polyethylene, and chlorosulfonated polyethylene is preferable. Examples of the acrylate polymer in the latex of the acrylate polymer include, for example, a polymer in which a carboxyl group, an acrylonitrile group, or a styrene group is introduced into a polymer of alkyl acrylate or alkyl methacrylate and has elasticity. Can be mentioned. Furthermore, examples of the epoxy resin in the epoxy resin emulsion include a bisphenol A type epoxy resin and a phenol novolac type epoxy resin.
[0027]
Among the above-mentioned components blended in the first treatment agent as necessary, one or more components selected from a halogen-containing polymer latex, an acrylate polymer latex, and an epoxy resin emulsion may be blended. preferable. In such a case, the adhesion to the second film formed by the second coating agent to be described later is improved, or the metal oxide mixed in a small amount into the engine oil with the passage of time of operation of the automobile engine. It is possible to increase the resistance to the influence of substances, nitrogen oxides or sulfur oxides.
[0028]
The first coating agent in the present invention is prepared by uniformly mixing the above-described RF condensate, solid NBR latex, liquid NBR latex and the above-described components blended as necessary, and water as a dispersion medium according to a conventional method. It can be obtained by mixing. In the first coating agent, the liquid NBR latex is preferably blended at a ratio of 10 to 900 parts, more preferably at a ratio of 30 to 300 parts, with respect to 100 parts of the solid NBR latex. It is preferable to further blend at a ratio of 65 to 150 parts. When the ratio of the liquid NBR latex is less than 10 parts, the tackiness (adhesion degree) of the obtained reinforcing fiber is lowered, and the finally obtained timing belt is extended with the passage of use time. Problems may occur. Moreover, when the ratio of liquid NBR latex exceeds 900 parts, the tackiness of the reinforcing fiber obtained may become extremely high, which may hinder the production of the reinforcing fiber. In addition, the ratio of the said solid NBR latex and liquid NBR latex is a mass ratio as each evaporation residue.
[0029]
Moreover, as a ratio with respect to 100 parts of solid NBR latex of the above-mentioned component mix | blended as needed with respect to a 1st coating material, 10-400 parts are preferable, and especially 30-300 parts of other rubber latexes. More preferred. The resin emulsion is preferably 2 to 70 parts, more preferably 5 to 18 parts. In addition, this ratio is a ratio as an evaporation residue similarly to the above.
[0030]
Further, when the total evaporation residue of the first coating agent is used as a reference, the content of the RF condensate is preferably 0.5 to 15% as evaporation residue, and particularly preferably 1 to 10%. On the other hand, the total latex content of solid NBR latex, liquid NBR latex and other rubber latex or resin emulsion blended as necessary is preferably 85 to 99.5% as an evaporation residue, In particular, 90 to 99% is more preferable. If the total latex content is out of the above range, there may be a problem with the adhesion between the reinforcing fiber and the rubber obtained and the bending fatigue resistance of the finally obtained timing belt.
[0031]
Furthermore, the concentration of the first coating, in other words the first Coating The total content of components such as the above-mentioned RF condensate, solid NBR latex, liquid NBR latex, and components blended as necessary in the agent is preferably 10 to 50% as an evaporation residue, In particular, 20 to 40% is more preferable. If the concentration is less than 10%, it may be difficult to impregnate the glass fiber with a sufficient amount of the first coating agent, and if it exceeds 50%, the stability of the first coating agent is poor. It may become easy to gel.
[0032]
Next, the second coating agent containing uncured phenol resin and rubber will be described. The second coating agent is obtained by mixing an uncured phenol resin, rubber, and a solvent. The uncured phenol resin used here is a resin that is not yet cured among resins obtained from phenols and aldehydes, that is, has reactivity for curing. Preferred examples of the uncured phenol resin include novolak and / or resol. It is preferable to use a novolac in that the adhesion between the resulting reinforcing fiber and H-NBR can be increased, and in that the adhesion state at the interface between the first film and the second film can be improved. It is preferred to use resole. Further, in order to take advantage of both of these advantages, it is preferable that the novolak / resole ratio is preferably 10/4 to 10/1 as the evaporation residue.
[0033]
As the rubber in the second coating agent, it is preferable to use a rubber having a high affinity with the rubber composition in consideration of compatibility with a rubber composition that is a base material of a rubber product to be reinforced such as a timing belt. Preferable examples include chloroprene rubber, chlorosulfonated polyethylene, acrylonitrile-butadiene copolymer rubber (so-called “NBR”), H-NBR, and the like. Among these, the adhesiveness with H-NBR can be improved, the flexibility of the second coating formed by the second coating agent can be improved, and the oil resistance of the rubber itself can be improved. In particular, it is preferable to use acrylonitrile-butadiene copolymer rubber.
[0034]
Further, the adhesion between the obtained reinforcing fiber and H-NBR, in particular, the adhesion between H-NBR using a peroxide as a vulcanizing agent and the reinforcing fiber can be improved. It is preferable to blend an uncured epoxy resin with the second coating agent in that good adhesiveness can be maintained. This uncured epoxy resin is in an uncured state among the epoxy resins and has reactivity for curing. Preferred examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, and cresol novolac type epoxy resin.
[0035]
10-60 parts of rubber | gum is preferable with respect to 100 parts of uncured phenol resin, and, as for the content ratio of uncured phenol resin and rubber | gum in a 2nd coating agent, 30-40 parts is more preferable. If the rubber ratio is less than 10 parts, the flexibility of the second coating formed by the second coating agent may be poor. On the other hand, when it exceeds 60 parts, the adhesion between the rubber composition as a base material of the rubber product and the fiber may be adversely affected. Moreover, when mix | blending an uncured epoxy resin, 2-20 parts of uncured epoxy resin is preferable with respect to 100 parts of uncured phenol resin, and 5-10 parts are especially more preferable. When the content ratio of the uncured epoxy resin is less than 2 parts, it is difficult to obtain the effect of improving the adhesion between the rubber composition serving as the base material of the rubber product and the fiber. Conversely, if it exceeds 20 parts, the flexibility of the second coating formed by the second coating agent may be poor. In addition, all the content ratio of said each component is a ratio as an evaporation residue.
[0036]
In addition to the above components, the second coating material may contain an inorganic filler, a vulcanizing agent, or an additive as necessary. As the inorganic filler, general fillers for rubber compositions such as silica and carbon black can be used. As the additive, general softeners, anti-aging agents, vulcanization accelerators and the like can be used as additives for the rubber composition.
[0037]
The solvent for dissolving or dispersing each component in the second coating agent can be used alone or in combination of two or more of those used in conventional rubber pastes. It is preferable to use a solvent of the system. Preferred examples include methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), ethyl acetate and the like.
[0038]
Further, the concentration of the second coating agent, in other words, the total content of components such as uncured phenol resin, rubber, and uncured epoxy resin blended as necessary in the second coating agent is determined as an evaporation residue. 3 to 20% is preferable, and 5 to 15% is more preferable. If the concentration is less than 3%, it may be difficult to apply a sufficient amount of the second coating agent to the fibers. On the other hand, if it exceeds 20%, the stability of the second coating agent may deteriorate.
[0039]
In the present invention, the fibers coated with the first coating agent and the second coating agent may be any of inorganic fibers or organic fibers used in conventional rubber reinforcing fibers. Glass fibers and carbon fibers can be used as the inorganic fibers, and aramid fibers, PBO (polyparaphenylene benzoxazole) fibers, PET (polyethylene terephthalate) fibers, PEN (polyethylene naphthalate) fibers, and the like can be used as the organic fibers. These fibers are provided with a sizing agent or a sizing agent before coating with the first coating agent in order to enhance the adhesion between the first coating formed by the first coating agent and the fiber itself. It is preferable to keep it.
[0040]
Among the above-mentioned fibers, it is preferable to use glass fibers in terms of versatility, price, and easy application to the timing belt manufacturing process. As a glass fiber, what obtained by converging 200-600 glass monofilaments with a diameter of 7-9 micrometers can be used, for example. Moreover, there is no restriction | limiting in particular as a composition of glass fiber, E glass, S glass, etc. are mentioned. Further, in the case of glass fiber, it is preferable to pre-treat with a sizing agent containing an existing silane coupling agent or film forming agent.
[0041]
Next, although the manufacturing method of the fiber for reinforcement of the rubber product of this invention is demonstrated, it is not limited to the described manufacturing method.
[0042]
First, the fiber to be coated is continuously immersed in a liquid tank filled with the first coating agent, and the first coating agent is attached to and impregnated on the fiber, and then the fiber is heated to 200 to 350 ° C. In the hot air furnace or the like, the first coating agent is dried and solidified by continuously heating in a hot air oven or the like to obtain a coated fiber having the first coating.
[0043]
At this time, the adhesion amount of the first film to the coated fiber is preferably 12 to 25%, more preferably 16 to 22% as an evaporation residue based on the mass of the coated fiber. If the adhesion amount is less than 12%, the individual monofilaments of the coated fiber are not easily covered with the first coating, so that the monofilaments tend to come into contact with each other and wear due to their friction. Further, the bending fatigue resistance of a timing belt or the like may be lowered, which is not preferable. On the other hand, if the adhesion amount exceeds 25%, the flexibility of the coating film becomes poor, and the bending fatigue resistance of the finally obtained rubber belt or the like may be lowered.
[0044]
Next, the above coated fibers are twisted by a twisting machine such as a ring twisting machine one by one or a plurality of the coated fibers to make a lower twisted yarn. The number of twists in this lower twisting step is preferably 0.5 to 4 times / 25 mm. The coated fiber once wound in an untwisted state may be twisted to form a lower twisted yarn, but the winding device of the above process for obtaining the coated fiber is used as a twisting machine to obtain the coated fiber and the lower twisted process. You may obtain a twisted yarn by carrying out together.
[0045]
Subsequently, while twisting 5 to 20 of the above-mentioned lower twist yarns, they are twisted with a twisting machine such as a ring twisting machine or a flyer twisting machine to obtain an upper twisted yarn. The number of twists in the upper twisting process is preferably 0.5 to 4 times / 25 mm, and the twisting direction in the upper twisting process is opposite to the twisting direction in the lower twisting process, as in the case of conventional rubber reinforcing fibers. In the direction.
[0046]
Finally, the upper twisted yarn is continuously immersed in the liquid tank filled with the second coating agent, or the second coating agent is sprayed or applied on the surface of the upper twisted yarn to obtain the second Is then applied to the upper twisted yarn, and then the upper twisted yarn is continuously heated in a hot air oven at 120 to 200 ° C. to dry and solidify the second coating agent. The reinforcing fiber of the rubber product of the present invention is obtained.
[0047]
At this time, the adhesion amount of the second film to the reinforcing fiber is preferably 1 to 15%, more preferably 3 to 10% as an evaporation residue based on the mass of the reinforcing fiber. If the adhesion amount is less than 1%, the effect of enhancing the adhesion between the reinforcing fiber and the rubber composition as the base material of the rubber product may be insufficient. Even if the adhesion amount exceeds 15%, the effect of improving the adhesiveness is not so great, and the adhesiveness may be hindered.
[0048]
There is no particular limitation on the rubber composition that is the base material of the rubber product to be reinforced by the reinforcing fiber of the rubber product of the present invention, but a timing belt having good oil resistance and heat resistance can be obtained. The rubber composition is preferably mainly composed of hydrogenated nitrile rubber, acrylic rubber or fluororubber, and particularly preferably composed mainly of hydrogenated nitrile rubber.
[0049]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples.
[Example 1]
Self-crosslinking type NBR latex (trade name “Nipol AF1001”, manufactured by Nippon Zeon Co., Ltd., NBR weight average molecular weight: about 300,000, evaporation residue: 45%) 31.1 parts, liquid NBR latex (product) Name “Nipol 1312”, manufactured by Nippon Zeon Co., Ltd., NBR weight average molecular weight: about 9000, evaporation residue: 33%) 42.4 parts, RF condensate (evaporation residue: 7%) 14.3 parts, ammonia water (Concentration 18%) 0.5 parts and ion-exchanged water were mixed to obtain a first coating agent having a concentration of 29%.
[0050]
Next, 200 glass monofilaments made of high-strength glass (S glass) having a diameter of 7 μm were focused while applying a sizing agent mainly composed of an aminosilane coupling agent, and then dried to obtain glass fibers. While aligning the three glass fibers, the glass fibers were continuously immersed in a liquid tank filled with the first coating agent, and the first coating agent was adhered and impregnated on the glass fiber. Next, the glass fiber was continuously heated in a hot air oven at a temperature of 250 ° C. for 1 minute to dry and solidify the first coating agent to form a first coating, thereby obtaining a coated glass fiber. In addition, the adhesion amount of the first coating agent was set to 18% as an evaporation residue based on the mass of the coated glass fiber.
[0051]
Further, the above-mentioned coated glass fibers were twisted one by one using a ring twisting machine so that the number of twists was 2 times / 25 mm, thereby obtaining a bottom twisted yarn. Subsequently, while aligning the 11 lower twisted yarns, the upper twisted yarn is obtained by twisting with another ring twisting machine so that the number of twists is 2 times / 25 mm in the twisting direction opposite to the lower twisting. It was.
[0052]
Next, 60 parts of novolak and 40 parts of resol as uncured phenol resin, 35 parts of acrylonitrile-butadiene copolymer rubber as rubber, 7 parts of bisphenol A type epoxy resin as uncured epoxy resin, and the following solvent Were mixed to obtain a second coating agent having a concentration of 10%. In addition, the ratio of each said component is a ratio as an evaporation residue. Moreover, as said solvent, what mixed methyl isobutyl ketone, methyl ethyl ketone, and ethyl acetate by mass ratio 8: 1: 4 was used.
[0053]
The upper twisted yarn obtained above was continuously immersed in the liquid tank filled with the second coating agent to give the second coating agent to the upper twisted yarn. Next, the upper twisted yarn is continuously heated in a hot air oven having a temperature of 130 ° C. for 1 minute to dry and solidify the second coating agent to form the second coating, and the reinforcing fiber of the rubber product is formed. Obtained. The adhesion amount of the second coating agent was 7% as an evaporation residue based on the mass of the reinforcing fiber.
[0054]
[Example 2]
Second coating 10% in concentration obtained by mixing 60 parts of novolak and 40 parts of resole as uncured phenol resin, 35 parts of acrylonitrile-butadiene copolymer rubber as rubber, and the same solvent as in Example 1 A reinforcing fiber for a rubber product of the present invention was obtained by the production method under the same conditions as in Example 1 using the same glass fiber and the first coating agent as in Example 1 except that the agent was used.
[0055]
[Example 3]
Instead of 31.1 parts of the self-crosslinking NBR latex blended in the first coating agent of Example 1, soap-free NBR latex (trade name “Nipol SX1503”, manufactured by Nippon Zeon Co., Ltd., NBR) (Weight average molecular weight: about 300,000, evaporation residue 42%) 33.3 parts) was mixed and mixed, and the same glass fiber and the same as in Example 1 were used except that the first coating agent having a concentration of 29% was used. Using the coating agent of No. 2, a reinforcing fiber of the rubber product of the present invention was obtained by the production method under the same conditions as in Example 1.
[0056]
[Example 4]
Instead of 31.1 parts of the self-crosslinking NBR latex blended in the first coating agent of Example 1, solid NBR latex (trade name “Nipol 1562”, manufactured by Nippon Zeon Co., Ltd., weight average molecular weight of NBR: about 300000 The same glass fiber and second coating agent as in Example 1 were used except that 34.1 parts of the evaporation residue (41%) were mixed and mixed, and the first coating agent having a concentration of 29% was used. Thus, the reinforcing fiber of the rubber product of the present invention was obtained by the production method under the same conditions as in Example 1.
[0057]
[Comparative Example 1]
60.0 parts of a vinylpyridine-styrene-butadiene terpolymer latex (trade name “Pyratex”, manufactured by Nippon A & L Co., Ltd., 41% evaporation residue) as a rubber latex, latex of chlorosulfonated polyethylene (product) Name "CSM450", manufactured by Sumitomo Seika Co., Ltd., evaporation residue 40%) 10.6 parts, RF condensate (evaporation residue 7%) 21.9 parts, ammonia water (concentration 18%) 2.4 parts, and Production of the same conditions as in Example 1 using the same glass fiber and second coating as in Example 1, except that the first coating with a concentration of 30% obtained by mixing ion-exchanged water was used. Fibers for reinforcing rubber products were obtained by the method.
[0058]
[Comparative Example 2]
Self-crosslinking type NBR latex (trade name “Nipol AF1001” manufactured by Nippon Zeon Co., Ltd., evaporation residue 45%) 62.2 parts, RF condensate (evaporation residue 7%) 14.3 parts as solid NBR latex The same glass fiber and second coating as in Example 1 except that 0.5 part of ammonia water (concentration 18%) and a first coating agent having a concentration of 29% obtained by mixing ion-exchanged water were used. Using the agent, reinforcing fibers for rubber products were obtained by the production method under the same conditions as in Example 1.
[0059]
[Comparative Example 3]
10 parts of chlorosulfonated polyethylene (trade name “Hypalon 40”, manufactured by DuPont Dow Elastomer), 5 parts of polyisocyanate (trade name “MR-200”, manufactured by Nippon Polyurethane), p, p as vulcanizing agents Example 1 except that 2 parts of '-dibenzoylbenzoquinone dioxime, 5 parts of carbon black as an inorganic filler, and a second coating agent having a concentration of 10% obtained by mixing toluene as a solvent were used. Using the same glass fiber and the first coating agent as in Example 1, a reinforcing fiber for rubber products was obtained by the production method under the same conditions as in Example 1.
[0060]
[Comparative Example 4]
A modified phenolic resin (trade name “Sumilite Resin PR12687”, manufactured by Sumitomo Durez) was mixed and dissolved with methyl ethyl ketone as a solvent to obtain a third coating agent having a concentration of 25%.
[0061]
The reinforcing fiber obtained in Comparative Example 3 was continuously immersed in a liquid tank filled with the third coating agent to give the third coating agent to the reinforcing fiber. Next, the reinforcing fiber is continuously heated in a hot air oven at a temperature of 130 ° C. for 1 minute to dry and solidify the third coating agent to form a third coating, thereby reinforcing the reinforcing fiber of the rubber product. Got. In addition, the adhesion amount of the 3rd coating agent was 2% as solid content on the basis of the mass of the reinforcing fiber.
[0062]
[Comparative Example 5]
Solid NBR latex (trade name “Nipol 1562”, manufactured by Nippon Zeon Co., Ltd., 41% evaporation residue), 68.3 parts, RF condensate (7% evaporation residue), aqueous ammonia (concentration 18%) The same glass fiber as in Example 1 and the same second coating as in Comparative Example 3 except that 0.5 part and the first coating with a concentration of 29% obtained by mixing ion-exchanged water were used. By using the same manufacturing method as in Example 1, a reinforcing fiber for rubber products was obtained.
[0063]
[Test example]
About the reinforcing fiber of each rubber product obtained by the above Examples 1 to 3 and Comparative Examples 1 to 4, the adhesiveness and oil resistance of the rubber product based on the rubber composition having the following composition were evaluated. The following method was used. The results are shown in Table 1.
[0064]
・ Rubber composition
Hydrogenated nitrile rubber (trade name: Zetpol 2000, manufactured by Zeon Corporation): 100 parts, zinc oxide: 10 parts, zinc methacrylate: 15 parts, zinc salt of 2-mercaptobenzimidazole: 1 part, substituted diphenylamine: 1 part Parts, carbon black [HAF]: 3 parts, silica hydrate: 30 parts, dicumyl peroxide: 10 parts, 1,3-bis (t-butylperoxyisopropyl) benzene: 5 parts, sulfur: 0.3 Parts, TMTD [tetramethylthiuram disulfide]: 1 part, MBT [2-mercaptobenzothiazole]: 0.5 part.
[0065]
・ Adhesion evaluation method
On the rubber sheet having a thickness of 3 mm, a width of 25 mm, and a length of 100 mm obtained by processing the rubber composition, the reinforcing fibers are arranged without gaps along the length direction, and the same rubber sheet as above is placed. Thus, a reinforcing fiber was sandwiched between the upper and lower rubber sheets. This was heated and pressurized for 20 minutes under the conditions of a temperature of 170 ° C. and a pressure of 42 kgf using a heating press device to obtain a test piece.
The test piece was peeled between the reinforcing fiber and the rubber sheet using an autograph at a tensile speed of 50 mm / min, and the adhesive strength between the reinforcing fiber and the rubber sheet was measured.
[0066]
・ Evaluation method of oil resistance
(1) Adhesion after oil immersion
A test piece prepared in the same manner as the above-described evaluation of adhesiveness is put in a liquid tank filled with engine oil for automobiles at a temperature of 100 ° C., immersed for 500 hours, taken out, wiped off the oil, and then using an autograph. Peeling was performed between the reinforcing fiber and the rubber sheet at a pulling speed of 50 mm / min, and the adhesive strength between the reinforcing fiber and the rubber sheet was measured.
(2) Tensile strength retention after lubrication flex fatigue test
A flat belt having a width of 9 mm, a thickness of 2 mm, and a length of 400 mm was prepared using the reinforcing fiber of each rubber product and the rubber composition. The flat belt has a structure in which one reinforcing fiber is embedded in the center of a strip-shaped flat rubber plate, and the embedded reinforcing fiber extends from both ends of the flat rubber plate. The portion of the flat rubber plate is the belt portion having the above dimensions. About this flat belt, oil resistance was evaluated by the method shown below.
[0067]
The test was conducted using an oil lubrication bending fatigue tester having the structure shown in FIG. In FIG. 1, three flat pulleys 21, 22, and 23 having a diameter of 30 mm are fixed to the reciprocating motion unit 2 in a rotatable state, and the reciprocating motion unit 2 is joined to the slide rail 3 in a slidable state. Has been. The reciprocating unit 2 is driven by the cylinder shaft 41 of the air cylinder 4 joined thereto, and reciprocates in the direction of the arrow in the figure. The slide rail 3 is fixed to the bases 6 and 7, the air cylinder 4 is fixed to the base 6, and the bases 6 and 7 are fixed to the base 8.
[0068]
First, the flat belt 5 was attached to the above-described lubrication bending fatigue tester 1 as shown in FIG. That is, the belt portion 51 of the flat belt 5 is hung along the flat pulleys 21, 22 and 23, and one of the reinforcing fibers 52 extending from the end of the flat belt 5 is connected to the pulleys 9 and 10. After being hung, it is fixed to the bolt 12 fixed to the base 8, and the other of the reinforcing fibers 52 is hung on the pulley 11 and then joined to the weight 13 (mass 11.5 kg) for applying tension to the flat belt 5. .
[0069]
The reciprocating motion unit 2 has a one-way travel distance of 180 mm while dripping the engine oil for automobiles in an amount of 100 cc per hour from the upper side to the portion where the flat belt 5 and the flat pulley 21 are in contact with each other by an unshown supply device. The flat belt 5 was subjected to a lubrication bending fatigue test by moving the portion where the flat belt 5 and the flat pulleys 21, 22, and 23 are in contact with each other, and bending the belt portion 51. . In addition, the atmospheric temperature was maintained at 120 ° C. by a thermostat (not shown) installed so as to surround the reciprocating unit 2, the flat pulleys 21, 22 and 23, and the flat belt 5.
[0070]
In the test, one reciprocation of the reciprocating motion part 2 is counted as one time, moved at a speed of 60 times per minute, reciprocated 1 million times to cause the flat belt 5 to bend and fatigue, and then the lubrication bending fatigue testing machine 1 The flat belt 5 was removed from the belt, and the tensile strength was measured under the condition that the tensile speed of the measuring machine was 250 mm / min.
[0071]
The evaluation was made by dividing the value of the tensile strength of the flat belt after the lubrication bending fatigue test by the value of the tensile strength of the flat belt not subjected to the lubrication bending fatigue test prepared under the same conditions using the same reinforcing fiber. The value was converted into percentage to obtain the tensile strength retention rate, and this was used as an index for evaluating the degree of decrease in tensile strength by the lubrication bending fatigue test of the flat belt.
[0072]
[Table 1]

[0073]
As shown in Table 1, the reinforcing fibers (Examples 1 to 3) of the rubber product of the present invention have an adhesive property with a rubber composition containing a highly saturated H-NBR using a peroxide as a vulcanizing agent. Are better. In addition, it can be seen that even after immersion in oil, the adhesive strength is not significantly reduced, and the tensile strength retention after the oil-bending bending fatigue test is high, so that the oil resistance is also excellent. In particular, when self-crosslinking type NBR latex is used as the solid NBR latex in the RFL coating and an uncured epoxy resin is blended in the second coating (Example 1), both adhesion and oil resistance are obtained. Is very good.
[0074]
On the other hand, in Comparative Example 1 using the conventional RFL coating and Comparative Example 2 using only the solid NBR latex and using the first coating without liquid NBR latex, the second Since the coating agent is the same as in the present invention, the adhesion in the normal state is the same, but one or both of the adhesion strength after oil immersion and the tensile strength retention after the oil bending bending fatigue test are low, so that the oil resistance is low. It turns out that it is inferior.
[0075]
Further, in Comparative Example 3 using the conventional second coating agent and Comparative Example 4 using the conventional second coating agent and the third coating agent, the first coating agent is the same as that of the present invention. Nevertheless, not only the adhesion strength after immersion in the normal state and after oil immersion is low, but also the tensile strength retention after the oil bending bending fatigue test is not bad.
[0076]
Further, in Comparative Example 5 in which only the solid NBR latex was blended and the liquid NBR latex was not blended and the conventional second coating agent was used, the adhesive strength and lubrication after normal and oil immersion It can be seen that both the adhesiveness and oil resistance are inferior because the tensile strength retention after the bending fatigue test is low.
[0077]
【The invention's effect】
The reinforcing fiber for rubber products of the present invention greatly improves the oil resistance, heat resistance, and bending fatigue resistance of rubber products using this as a reinforcing material. Moreover, the reinforcing fiber of the rubber product of the present invention has excellent adhesiveness even to a rubber composition containing high dryness H-NBR.
[0078]
Therefore, especially when the reinforcing fiber of the rubber product of the present invention is used as a reinforcing material for the timing belt, the oil resistance, bending fatigue resistance and heat resistance of the timing belt can be greatly improved. Therefore, it can be applied not only to applications that require heat resistance and bending fatigue resistance, but also to applications such as timing belts that require oil resistance to come into contact with engine oil.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the structure of a lubrication bending fatigue testing machine.
[Explanation of symbols]
1: Lubrication bending fatigue testing machine 2: Reciprocating motion part
3: Slide rail 4: Air cylinder
5: Flat belt 6, 7: Mount
8: Base 9, 10, 11: Pulley
12: Bolt 13: Weight
21, 22, 23: Flat pulley

Claims (8)

A fiber having a first coating formed by a first coating and a second coating formed by a second coating on the first coating, wherein the first coating is A water-soluble condensate of resorcin and formaldehyde, a latex of solid acrylonitrile-butadiene copolymer, and a latex of liquid acrylonitrile-butadiene copolymer, and the second coating agent comprises an uncured phenol resin and A reinforcing fiber for rubber products characterized by containing rubber. 2. The reinforcing fiber for rubber products according to claim 1, wherein the latex of the solid acrylonitrile-butadiene copolymer contained in the first coating agent is a latex of a self-crosslinking acrylonitrile-butadiene copolymer. The reinforcing fiber for rubber products according to claim 1 or 2, wherein the latex of the solid acrylonitrile-butadiene copolymer contained in the first coating agent is a soap-free acrylonitrile-butadiene copolymer latex. The first coating agent further comprises at least one component selected from the group consisting of a latex of a halogen-containing polymer, a latex of an acrylate polymer, and an epoxy resin emulsion. Fiber for reinforcing rubber products as described in 1. The rubber for reinforcing a rubber product according to any one of claims 1 to 4, wherein the rubber contained in the second coating agent is acrylonitrile-butadiene copolymer rubber. The fiber for reinforcing rubber products according to any one of claims 1 to 5, wherein the second coating agent further contains an uncured epoxy resin. The fiber for reinforcing rubber products according to any one of claims 1 to 6, wherein the fiber is a glass fiber. A fiber is impregnated with a first coating agent containing a water-soluble condensate of resorcinol and formaldehyde, a latex of a solid acrylonitrile-butadiene copolymer, and a latex of a liquid acrylonitrile-butadiene copolymer, and dried. A coated fiber having a coating of 1, and then twisting the coated fiber into a twisted yarn, applying a second coating agent containing an uncured phenolic resin and rubber to the twisted yarn, and drying, A method for producing a reinforcing fiber for rubber products, wherein a second coating is formed on the coating.

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