JP2004100059A - Fiber for reinforcing rubber product and method for producing the same - Google Patents

Abstract

Reinforcing fiber having excellent oil resistance, tackiness and bending fatigue resistance and suitable for manufacturing rubber products such as timing belts using highly saturated H-NBR using peroxide as a vulcanizing agent. And a method for producing the same.
A fiber having a first coating formed by a first coating agent and a second coating formed on the first coating by a second coating agent, wherein the first coating is a fiber. Contains 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 the second coating agent is uncoated. Contains cured phenolic resin and rubber.
[Selection diagram] None

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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reinforcing fiber for a rubber product used as a reinforcing material for various rubber products such as a rubber belt such as a timing belt for an automobile engine, a rubber hose, a rubber tire and the like, and a method for producing the same.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 1-221433
[Patent Document 2] Japanese Patent Application Laid-Open No. 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 product, and reduce the fibers themselves. In order to protect and enhance the durability of the rubber product, the rubber product is generally covered with a coating formed by various coating agents.
[0004]
As these coating agents, as disclosed in Patent Document 1 and Patent Document 2, etc., a coating agent containing a condensate of resorcinol 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 in which a rubber composition is dissolved in an organic solvent (hereinafter, also referred to as “rubber paste”) is known.
[0005]
In addition, a patent is made for the purpose of further strengthening the adhesiveness between a rubber substrate having 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, etc., the fiber coated with the first coating formed by the RFL coating agent is further treated with an organic diisocyanate, a rubber compound, a vulcanizing agent, and a vulcanizing agent. It is also known to cover with a second film formed of a rubber paste containing an auxiliary agent or the like, or to cover the outermost layer with a third film.
[0006]
[Problems to be solved by the invention]
However, the reinforcing fibers coated with the coatings formed by the above-mentioned various coating agents do not always have a sufficiently satisfactory performance particularly when used as a reinforcing material (core wire) for a timing belt for an engine of an automobile or the like. 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, ease of maintenance, etc., but transmit crankshaft power to camshafts, pumps, etc. If the power transmission mechanism is installed inside the engine block to make the engine more compact, the timing belt must be used in an environment that comes into 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 a moderate tackiness (adhesiveness) to the reinforcing fiber in order to prevent the function of the power transmission mechanism from being hindered by the elongation of the belt over time. Of the belt is required, and the belt is also required to have sufficiently high bending fatigue resistance.
[0008]
In response to these demands, the timing belt using the reinforcing fiber covered with the coating formed by the RFL coating disclosed in Patent Documents 1 and 2 described above has a relatively low oil resistance of rubber itself. Oil resistance is insufficient due to the low latex of vinylpyridine-styrene-butadiene copolymer. In addition, when a reinforcing fiber using only a rubber paste as a coating agent as disclosed in Patent Document 3 is used, the adhesiveness 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 on the surface of the fiber but also inside the fiber. The impregnation is insufficient and the durability of the resulting belt is not sufficient.
[0009]
Further, in a timing belt using a reinforcing fiber having two layers of a first coating and a second coating, as described in Patent Documents 4, 5 and 6 described above, The resulting oil resistance and flex fatigue resistance are not sufficient. Further, the conventional reinforcing fibers, among the H-NBR rubber compositions, show a certain degree of adhesion to a rubber composition mainly using sulfur as a vulcanizing agent, but in order to further improve heat resistance. In addition, the rubber composition using a peroxide as a vulcanizing agent, that is, a rubber composition having a high saturation of H-NBR, has insufficient adhesiveness, thereby deteriorating the properties of the resulting timing belt. Have a point.
[0010]
Further, since the modified phenol resin layer, which is a coating layer on the surface of the reinforcing fiber, described in Patent Document 6 described above, has poor flexibility, the coating layer is partially peeled off in the process of handling the reinforcing fiber. In addition, there is a problem that the timing belt obtained has an adverse effect on the bending fatigue resistance of the obtained timing belt.
[0011]
Therefore, the present invention has been made in order to solve the above problems, the object of which is excellent in oil resistance, heat resistance, bending fatigue resistance and the like, particularly suitable for engine timing belts, An object of the present invention is to provide a reinforcing fiber for a rubber product, which is suitable for a rubber product using highly saturated H-NBR, and a method for producing the same.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, a reinforcing fiber for a rubber product of the present invention comprises 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 agent is 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 the second coating agent comprises an uncured phenolic resin and a rubber.
[0013]
Further, the method for producing a reinforcing fiber for a rubber product of the present invention includes 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. Impregnating the fibers with the first coating agent to be dried and drying to produce a coated fiber having a first coating, and then twisting the coated fiber into a twisted yarn, wherein the twisted yarn contains an uncured phenolic 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 oil-resistant solid acrylonitrile-butadiene copolymer latex described above. Since the fibers are coated with the first coating formed by the coating agent of (1), the oil resistance of a rubber product using this as a reinforcing material can be improved. Good oil resistance.
[0015]
In addition, the liquid acrylonitrile-butadiene copolymer latex used in addition to the solid acrylonitrile-butadiene copolymer latex provides a high tackiness to the reinforcing fiber, and the fiber constituting the reinforcing fiber (primarily twisted yarn). This improves the adhesion between the two, greatly improving the performance of the power transmission mechanism due to belt elongation over time, and the strength of the belt due to oil contact and flex fatigue. Is also greatly improved.
[0016]
Further, the reinforcing fiber of the present invention comprises a second coating formed by a second coating containing an uncured phenolic resin and rubber on the first coating formed by the first coating. The first coating has a large adhesiveness to fibers, and the second coating is a rubber composition containing a rubber such as H-NBR, particularly a highly saturated H-NBR having excellent heat resistance. It has both strong adhesiveness to objects and flexibility. Therefore, the timing belt using the reinforcing fiber of the present invention as a core wire has good heat resistance and bending fatigue resistance as well as oil resistance.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. In the following description, unless otherwise specified, the unit “parts” means “parts by mass”, and the unit “%” means “mass percentage”.
[0018]
First, a first solution containing a water-soluble condensate of resorcinol and formaldehyde (hereinafter also referred to as “RF condensate”), a latex of a solid acrylonitrile-butadiene copolymer, and a latex of a liquid acrylonitrile-butadiene copolymer Will be described.
[0019]
The RF condensate to be incorporated in the first coating agent is rich in oxymethyl groups obtained by reacting resorcinol and formaldehyde in the presence of an alkali catalyst such as an alkali metal hydroxide, ammonia, or an amine. However, water-soluble addition condensates can be used. In particular, an RF condensate obtained by reacting resorcinol and formaldehyde at a molar ratio of 1: 0.3 to 2.5 is preferable.
[0020]
The latex of the solid acrylonitrile-butadiene copolymer (hereinafter, also referred to as “solid NBR latex”) to be mixed with the first coating agent is obtained by evaporating the dispersion medium at 110 ° C. for 2 hours to remove the dispersion medium, 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 when returned to the above. Here, the solid state includes a lump and a film. The acrylonitrile-butadiene copolymer forming the solid NBR latex preferably has an acrylonitrile content of 15 to 50%, particularly preferably 25 to 40%.
[0021]
In addition, since the oil resistance and heat resistance of the obtained rubber product such as a timing belt can be further improved, the solid NBR latex is a self-crosslinking acrylonitrile-butadiene copolymer latex (hereinafter, referred to as a “self-crosslinking type NBR latex), or a soap-free acrylonitrile-butadiene copolymer latex (hereinafter also referred to as a “soap-free NBR latex”), and particularly preferably a self-crosslinking NBR latex.
[0022]
The self-crosslinking type NBR latex is a latex of a copolymer in which an acrylonitrile-butadiene copolymer preferably contains 0.5 to 5% of a monomer capable of self-crosslinking. 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 with acrylonitrile and butadiene can be used.
[0023]
Further, the soap-free NBR latex is a latex that does not contain a surfactant as an emulsifier or has a very small content. As such a soap-free NBR latex, an acrylonitrile-butadiene copolymer latex obtained by emulsion-polymerizing a monomer using an alkali-soluble oligomer as an emulsifier can be used.
[0024]
The liquid acrylonitrile-butadiene copolymer latex (hereinafter referred to as liquid NBR latex) to be mixed with the first coating agent is obtained by evaporating at 110 ° C. for 2 hours to remove the dispersion medium, and then returning to room temperature. It means a latex that produces a liquid or viscous acrylonitrile-butadiene copolymer (weight average molecular weight: 1,000 to 70,000) as an evaporation residue. The acrylonitrile-butadiene copolymer forming the liquid NBR latex preferably has an acrylonitrile content of 15 to 50%, particularly preferably 25 to 40%.
[0025]
In addition to the above-mentioned RF condensate, solid NBR latex and liquid NBR latex, if necessary, the first coating agent may contain the same additives as those used in conventional RFL coating agents such as antioxidants. Agents, other rubber latexes, or resin emulsions. Examples of the anti-aging agent include a liquid emulsion of mineral oil, and examples of the other rubber latex include a latex of a halogen-containing polymer, a latex of an acrylate polymer, a latex of a styrene-butadiene copolymer, and a latex of polybutadiene. 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, they 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. The acrylate polymer in the latex of the acrylate polymer is, for example, a polymer obtained by introducing a carboxyl group, an acrylonitrile group, or a styrene group into a polymer of an alkyl acrylate or an alkyl methacrylate, and having 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 novolak type epoxy resin.
[0027]
Among the above-mentioned components that are optionally added to the first treating agent, one or more components selected from a latex of a halogen-containing polymer, a latex of an acrylate-based polymer, and an epoxy resin emulsion may be blended. preferable. In such a case, the adhesion to the second coating formed by the second coating agent described later is improved, or a small amount of metal oxide mixed into the engine oil with the elapse of the operation time of the automobile engine. Resistance to the effects of substances, nitrogen oxides or sulfur oxides.
[0028]
The first coating agent in the present invention is a mixture of the above-mentioned RF condensate, solid NBR latex, liquid NBR latex and the above-mentioned components to be blended as required, and water as a dispersion medium, in a uniform manner in a conventional manner. It can be obtained by mixing. In the first coating agent, the liquid NBR latex is preferably blended in a ratio of 10 to 900 parts, and more preferably in a ratio of 30 to 300 parts, with respect to 100 parts of the solid NBR latex. It is preferable that the composition is further blended at a ratio of 65 to 150 parts. When the ratio of the liquid NBR latex is less than 10 parts, the tackiness (the degree of tackiness) of the obtained reinforcing fiber becomes low, and the finally obtained timing belt elongates with the elapse of use time. Problems may occur. On the other hand, when the ratio of the liquid NBR latex exceeds 900 parts, the tackiness of the obtained reinforcing fiber becomes extremely high, which may hinder the production of the reinforcing fiber. The ratio between the solid NBR latex and the liquid NBR latex is the mass ratio of each as an evaporation residue.
[0029]
Further, as a ratio of the above-mentioned components to be added to the first coating agent as needed with respect to 100 parts of the solid NBR latex, the other rubber latex is preferably from 10 to 400 parts, particularly preferably from 30 to 300 parts. More preferred. The resin emulsion is preferably used in an amount of 2 to 70 parts, more preferably 5 to 18 parts. It should be noted that this ratio is a ratio as an evaporation residue similarly to the above.
[0030]
Further, based on the total evaporation residue of the first coating agent, the content of the RF condensate is preferably 0.5 to 15%, more preferably 1 to 10%, as the evaporation residue. On the other hand, the content as the total latex of the solid NBR latex, the liquid NBR latex, and other rubber latex or resin emulsion blended as necessary is preferably 85 to 99.5% as an evaporation residue, Particularly, 90 to 99% is more preferable. If the content of all the latex is out of the above range, there may be a problem in the adhesiveness between the obtained reinforcing fiber and rubber and the bending fatigue resistance of the finally obtained timing belt.
[0031]
Further, the concentration of the first coating agent, in other words, the total of components such as the RF condensate, the solid NBR latex, the liquid NBR latex, and the components blended as necessary in the first treatment agent The content is preferably 10 to 50%, more preferably 20 to 40%, as an evaporation residue. 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. In some cases, gelation may occur.
[0032]
Next, the second coating agent containing an 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 phenolic resin used herein is a resin obtained from a phenol and an aldehyde that has not been cured yet, that is, a resin having reactivity for curing. The uncured phenolic resin preferably includes novolak and / or resole. It is preferable to use novolak in that the adhesiveness between the obtained reinforcing fiber and H-NBR can be increased, and in that the adhesion at the interface between the first coating and the second coating can be improved. It is preferred to use resole. In order to take advantage of both of these advantages, it is preferable to use a novolak / resole ratio of preferably 10/4 to 10/1 as an 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 the rubber composition serving as a base material of the rubber product to be reinforced such as a timing belt. Preferred 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 film formed by the second coating agent can be improved, and the oil resistance of the rubber itself can be improved. For this reason, it is preferable to use acrylonitrile-butadiene copolymer rubber.
[0034]
Further, the adhesiveness between the obtained reinforcing fiber and H-NBR, particularly the adhesiveness between H-NBR using a peroxide as a vulcanizing agent and the reinforcing fiber can be improved, It is preferable that an uncured epoxy resin is blended in the second coating agent in that good adhesiveness can be maintained also in the above. This uncured epoxy resin is a state in which the epoxy resin has not been cured yet, and has reactivity for curing. Preferred examples of the epoxy resin include a bisphenol A epoxy resin, a bisphenol F epoxy resin, a phenol novolak epoxy resin, and a cresol novolak epoxy resin.
[0035]
The content ratio of the uncured phenol resin to the rubber in the second coating agent is preferably from 10 to 60 parts, more preferably from 30 to 40 parts, based on 100 parts of the uncured phenol resin. If the ratio of the rubber is less than 10 parts, the flexibility of the second coating formed by the second coating agent may be poor. Conversely, if it exceeds 60 parts, the adhesiveness between the rubber composition as the base material of the rubber product and the fiber may be adversely affected. When an uncured epoxy resin is blended, 2 to 20 parts of the uncured epoxy resin is preferable with respect to 100 parts of the uncured phenol resin, and more preferably 5 to 10 parts. If the content of the uncured epoxy resin is less than 2 parts, it is difficult to obtain the effect of improving the adhesiveness between the rubber composition 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, the content ratio of each of the above components is a ratio as an evaporation residue.
[0036]
In addition to the above components, an inorganic filler, a vulcanizing agent or an additive may be added to the second coating agent, if necessary. As the inorganic filler, general fillers for rubber compositions such as silica and carbon black can be used. As the additives, general softeners, anti-aging agents, vulcanization accelerators and the like can be used as additives for the rubber composition.
[0037]
As the solvent for dissolving or dispersing the above components in the second coating agent, those used in conventional rubber pastes can be used alone or in combination of two or more. It is preferable to use a system solvent. Preferred examples include methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), ethyl acetate and the like.
[0038]
Furthermore, the concentration of the second coating agent, in other words, the total content of the uncured phenolic resin, rubber, and optionally the uncured epoxy resin compounded in the second coating agent is determined by the evaporation residual Is preferably 3 to 20%, and particularly preferably 5 to 15%. If the concentration is less than 3%, it may be difficult to apply the second coating agent to the fiber in a sufficient amount. 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 and organic fibers used for conventional rubber reinforcing fibers. Glass fibers and carbon fibers can be used as the inorganic fibers, and aramid fibers, PBO (polyparaphenylenebenzoxazole) 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 being coated with the first coating agent in order to enhance the adhesion between the first coating formed by the first coating agent and the fibers themselves. Preferably.
[0040]
Among the above fibers, it is preferable to use glass fibers in terms of versatility, price, and ease of application to the manufacturing process of the timing belt. As the glass fiber, for example, one obtained by bundling 200 to 600 glass monofilaments having a diameter of 7 to 9 μm can be used. Further, the composition of the glass fiber is not particularly limited, and examples thereof include E glass and S glass. In the case of glass fiber, it is preferable to pre-treat with a sizing agent containing an existing silane coupling agent, film-forming agent and the like.
[0041]
Next, a method for producing a reinforcing fiber for a rubber product of the present invention will be described, but the present invention is not limited to the described production method.
[0042]
First, the fibers to be coated are continuously immersed in a liquid tank filled with a first coating agent, and the first coating agent is attached to and impregnated with the fibers. Is heated continuously in a hot air oven or the like to dry and solidify the first coating agent to form a first coating, thereby obtaining a coated fiber having the first coating.
[0043]
At this time, the amount of the first coating adhered to the coated fibers is preferably 12 to 25%, more preferably 16 to 22%, as an evaporation residue based on the mass of the coated fibers. When the adhesion amount is less than 12%, the individual monofilaments of the coated fiber are difficult to be sufficiently covered with the first coating, so that the monofilaments come into contact with each other and are liable to be worn due to their friction, and finally obtained. It is not preferable because the bending fatigue resistance of the timing belt or the like may deteriorate. 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 undesirably reduced.
[0044]
Next, the above-mentioned coated fibers are twisted by a twisting machine such as a ring twisting machine, one by one, or a plurality of the coated fibers are combined to form a lower twisted yarn. The number of twists in the lower twisting step is preferably 0.5 to 4 turns / 25 mm. In addition, the coated fiber once wound in a non-twisted state may be twisted as a lower twist yarn, but the winding device in the above step of obtaining the coated fiber is used as a twisting machine, and the step of obtaining the coated fiber and the lower twisting step are performed. A ply-twisted yarn may be obtained by performing the combination.
[0045]
Subsequently, 5 to 20 of the above-described lower twisted yarns are combined and twisted by a twisting machine such as a ring twisting machine or a flyer twisting machine to form an upper twisted yarn. The number of twists in the first twisting step is preferably 0.5 to 4 times / 25 mm, and the twisting direction in the first twisting step is opposite to the twisting direction in the first twisting step, like the conventional rubber reinforcing fiber. Direction.
[0046]
Finally, the above-mentioned twisted yarn is continuously immersed in a liquid tank filled with the above-mentioned second coating agent, or the second coating agent is sprayed or coated on the surface of the above-mentioned twisted yarn to form the second twisted yarn. After the coating agent is applied to the twisted yarn, subsequently, the twisted yarn is continuously heated in a hot-air oven at 120 to 200 ° C. to dry and solidify the second coating agent. Is formed to obtain a reinforcing fiber of the rubber product of the present invention.
[0047]
At this time, the amount of the second coating adhered to the reinforcing fibers is preferably 1 to 15%, more preferably 3 to 10%, as the evaporation residue based on the mass of the reinforcing fibers. If the amount is less than 1%, the effect of increasing the adhesion between the reinforcing fiber and the rubber composition serving as the base of the rubber product may be insufficient. Even if the amount of adhesion exceeds 15%, the effect of enhancing the adhesiveness is not so large, and may rather impair the adhesiveness.
[0048]
The rubber composition used as the base material of the rubber product to be reinforced by the reinforcing fiber of the rubber product of the present invention is not particularly limited, but a timing belt having good oil resistance and heat resistance can be obtained. The rubber composition preferably contains a hydrogenated nitrile rubber, an acrylic rubber or a fluorine rubber as a main component, and particularly preferably contains a hydrogenated nitrile rubber as a main component.
[0049]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples.
[Example 1]
31.1 parts of self-crosslinking type NBR latex (trade name “Nipol AF1001”, manufactured by Zeon Corporation, weight average molecular weight of NBR: about 300,000, evaporation residue: 45%) as solid NBR latex, liquid NBR latex (product Name "Nipol 1312", manufactured by Zeon Corporation, 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 having a diameter of 7 μm made of high-strength glass (S glass) were bundled while applying a sizing agent having an aminosilane coupling agent as a main component, and dried to obtain glass fibers. While arranging three of these glass fibers, they were continuously immersed in a liquid tank filled with the first coating agent, to adhere and impregnate the first coating agent on the glass fibers. 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]
Furthermore, the above-mentioned coated glass fibers were twisted one by one using a ring twisting machine so that the number of twists was 2 turns / 25 mm to obtain a twisted yarn. Subsequently, while the above-mentioned 11 lower twisted yarns are being aligned, the upper twisted yarn is obtained by using another ring twisting machine so that the number of twists is 2 turns / 25 mm in the twisting direction opposite to the lower twisting. 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 a solvent described below Was mixed to obtain a second coating agent having a concentration of 10%. In addition, the ratio of each component described above is a ratio as an evaporation residue. The solvent used was a mixture of methyl isobutyl ketone, methyl ethyl ketone and ethyl acetate at a mass ratio of 8: 1: 4.
[0053]
The twisted yarn obtained above was continuously immersed in a liquid tank filled with the second coating agent to apply the second coating agent to the twisted yarn. Next, the first twisted yarn is continuously heated in a hot air oven at a temperature of 130 ° C. for one minute, and the second coating agent is dried and solidified to form a second coating film. Obtained. The amount of the second coating agent adhered was set to 7% as the residual evaporation based on the mass of the reinforcing fiber.
[0054]
[Example 2]
A second coating having a concentration of 10% obtained by mixing 60 parts of novolak and 40 parts of resol as uncured phenolic 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 using the same glass fiber and the first coating agent as in Example 1 but using the same manufacturing method as in Example 1 except that the agent was used.
[0055]
[Example 3]
In place of 31.1 parts of the self-crosslinking type NBR latex blended in the first coating agent of Example 1, a 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%) The same glass fiber and glass fiber as in Example 1 were used except that 33.3 parts of a first coating agent having a concentration of 29% obtained by mixing and mixing was used. Using the coating agent of No. 2, 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.
[0056]
[Example 4]
Instead of 31.1 parts of the self-crosslinking type NBR latex blended in the first coating agent of Example 1, solid NBR latex (trade name “Nipol 1562”, manufactured by Zeon Corporation, weight average molecular weight of NBR: about 300000) The same glass fibers and the second coating agent as in Example 1 were used except that 34.1 parts of the first coating agent having a concentration of 29% obtained by mixing and mixing 34.1 parts were used. Thus, 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.
[0057]
[Comparative Example 1]
60.0 parts of latex of vinyl pyridine-styrene-butadiene terpolymer (trade name “Pyratex”, manufactured by A & L Japan, 41% evaporation residue) as rubber latex, latex of chlorosulfonated polyethylene (product) 10.6 parts of "CSM450", manufactured by Sumitomo Seika Co., Ltd., evaporation residue 40%), 21.9 parts of RF condensate (evaporation residue 7%), 2.4 parts of ammonia water (concentration 18%), and And using the same glass fiber and the second coating agent as in Example 1 under the same conditions as in Example 1 except that the first coating agent having 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]
62.2 parts of a self-crosslinking type NBR latex (trade name “Nipol AF1001”, manufactured by Zeon Corporation, evaporation residue 45%) as solid NBR latex, 14.3 parts of RF condensate (evaporation residue 7%), Glass fiber and second coating same as in Example 1 except that 0.5 part of aqueous ammonia (concentration: 18%) and a first coating agent having a concentration of 29% obtained by mixing ion-exchanged water were used. Using the agent, a reinforcing fiber for a rubber product was obtained by a 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 Elastomers), 5 parts of polyisocyanate (trade name "MR-200", manufactured by Nippon Polyurethane), p, p as vulcanizing agents Example 1 except that 2 parts of '-dibenzoylbenzoquinonedioxime, 5 parts of carbon black as an inorganic filler, and 10% of a second coating agent 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 a rubber product was obtained by the production method under the same conditions as in Example 1.
[0060]
[Comparative Example 4]
A modified phenol 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 apply 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 material to form a third coating film, and the reinforcing fiber for rubber products Got. In addition, the adhesion amount of the third coating agent was set to 2% as a solid content based on the mass of the reinforcing fiber.
[0062]
[Comparative Example 5]
68.3 parts of solid NBR latex (trade name "Nipol 1562", manufactured by Zeon Corporation, evaporation residue 41%), 14.3 parts of RF condensate (evaporation residue 7%), ammonia water (concentration 18%) The same glass fiber as in Example 1 and the same second coating as in Comparative Example 3 were used except that 0.5 part and the first coating having a concentration of 29% obtained by mixing ion-exchanged water were used. Thus, a reinforcing fiber for a rubber product was obtained by a production method under the same conditions as in Example 1.
[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 evaluation of the adhesiveness and oil resistance of the rubber product based on the rubber composition having the following composition was performed. The procedure was as follows. Table 1 shows the results.
[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 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 Part, TMTD [tetramethylthiuram disulfide]: 1 part, MBT [2-mercaptobenzothiazole]: 0.5 part.
[0065]
・ Adhesion evaluation method
On a rubber sheet having a thickness of 3 mm, a width of 25 mm and a length of 100 mm obtained by processing the above rubber composition, 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 at a temperature of 170 ° C. and a pressure of 42 kgf using a heating press device to obtain a test piece.
Using an autograph, the test piece was peeled between the reinforcing fiber and the rubber sheet at a tension rate of 50 mm / min, and the adhesive strength between the reinforcing fiber and the rubber sheet was measured.
[0066]
・ Oil resistance evaluation method
(1) Adhesion after oil immersion
A test piece prepared in the same manner as in the evaluation of the adhesiveness described above was put into a liquid tank filled with automobile engine oil at a temperature of 100 ° C., immersed for 500 hours, taken out, and the oil was wiped off. 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 bending test
A flat belt having a width of 9 mm, a thickness of 2 mm, and a length of 400 mm was produced using the reinforcing fiber of each rubber product and the above 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 fibers extend from both ends of the flat rubber plate. The flat rubber plate portion is a belt portion having the above dimensions. The oil resistance of this flat belt was evaluated by the following method.
[0067]
The test was performed using a lubricating and 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 rotatably fixed to a reciprocating unit 2, and the reciprocating unit 2 is slidably joined to a slide rail 3. Have been. The reciprocating unit 2 is driven by a cylinder shaft 41 of an air cylinder 4 joined to the reciprocating unit 2, and reciprocates in a direction indicated by an arrow in FIG. The slide rail 3 is fixed to the gantry 6 and 7, the air cylinder 4 is fixed to the gantry 6, and the gantry 6 and 7 are fixed to the base 8.
[0068]
First, a flat belt 5 was mounted on the above-described lubricating bending fatigue tester 1 as shown in FIG. That is, the belt portion 51 of the flat belt 5 is hung along each of the flat pulleys 21, 22, and 23, and one of the reinforcing fibers 52 extending from the end of the flat belt 5 is applied to the pulleys 9 and 10. After hanging, it was fixed to the bolt 12 fixed to the base 8, the other of the reinforcing fibers 52 was 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]
Then, while the engine oil for a vehicle is dropped from above from a supply device (not shown) at a rate of 100 cc per hour to a portion where the flat belt 5 and the flat pulley 21 are in contact with each other, the one-way moving distance is set to 180 mm, and the reciprocating portion 2 is moved. The flat belt 5 was subjected to a lubrication bending fatigue test by moving a portion where the flat belt 5 and the flat pulleys 21, 22 and 23 were in contact with the reciprocating motion so as to bend the belt portion 51. . The ambient temperature was kept 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 unit 2 was counted as one time, the reciprocating unit 2 was moved at a speed of 60 times per minute, and was reciprocated 1 million times to bend and fatigue the flat belt 5. , And the tensile strength was measured at a tensile speed of a measuring machine of 250 mm / min.
[0071]
The evaluation was obtained 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 manufactured under the same conditions using the same reinforcing fiber. The value was converted into a percentage to obtain a tensile strength retention rate, which was used as an index for evaluating the degree of decrease in tensile strength in a flat belt lubrication bending fatigue test.
[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 improved adhesiveness to a rubber composition containing highly saturated H-NBR using a peroxide as a vulcanizing agent. Are better. Further, it can be seen that the adhesive strength is not significantly reduced even after oil immersion, and the tensile strength retention rate after the oiling flex fatigue test is high, so that the oil resistance is also excellent. In particular, when a self-crosslinking type NBR latex is used as the solid NBR latex in the RFL coating agent and an uncured epoxy resin is blended in the second coating agent (Example 1), both the adhesiveness and the oil resistance are improved. Is extremely excellent.
[0074]
In contrast, Comparative Example 1 using the conventional RFL coating agent and Comparative Example 2 using only the solid NBR latex and using the first coating agent not containing the liquid NBR latex had the second problem. Since the coating agent is the same as that of the present invention, the adhesiveness in the normal state is the same, but one or both of the adhesive strength after oil immersion and the tensile strength retention rate after lubrication and 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 and third coating agents, the first coating agent is the same as the present invention. Nevertheless, not only the adhesion strength under normal conditions and after oil immersion is low, but also the retention of tensile strength after lubrication and bending fatigue tests is not bad.
[0076]
Further, in Comparative Example 5 in which the first coating agent containing only the solid NBR latex but not the liquid NBR latex and the conventional second coating agent were used, the adhesive strength and the lubrication under normal conditions and after oil immersion were used. Since the tensile strength retention after the bending fatigue test is low, it can be seen that both the adhesiveness and the oil resistance are inferior.
[0077]
【The invention's effect】
The reinforcing fiber for a rubber product of the present invention greatly improves oil resistance, heat resistance and bending fatigue resistance of a rubber product using the same as a reinforcing material. Further, the reinforcing fiber of the rubber product of the present invention has excellent adhesiveness 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 a timing belt, the oil resistance, bending fatigue resistance and heat resistance of the timing belt can be significantly improved. Therefore, the present invention can be applied not only to applications requiring heat resistance and bending fatigue resistance, but also to applications such as timing belts requiring oil resistance to be in contact with engine oil.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the structure of a lubricating bending fatigue tester.
[Explanation of symbols]
1: Lubrication bending fatigue tester 2: Reciprocating part
3: Slide rail 4: Air cylinder
5: Flat belt 6, 7: Stand
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 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 wherein the second coating agent is an uncured phenolic resin and Fiber for reinforcing rubber products, characterized by containing rubber. The reinforcing fiber for a rubber product according to claim 1, wherein the solid acrylonitrile-butadiene copolymer latex contained in the first coating agent is a self-crosslinking acrylonitrile-butadiene copolymer latex. The reinforcing fiber for a rubber product 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 material according to any one of claims 1 to 3, further comprising at least one component selected from the group consisting of a halogen-containing polymer latex, an acrylate-based polymer latex, and an epoxy resin emulsion. A fiber for reinforcing rubber products according to claim 1. The reinforcing fiber for a rubber product according to any one of claims 1 to 4, wherein the rubber contained in the second coating agent is an acrylonitrile-butadiene copolymer rubber. The reinforcing fiber for a rubber product according to any one of claims 1 to 5, wherein the second coating agent further contains an uncured epoxy resin. The reinforcing fiber for a rubber product according to any one of claims 1 to 6, wherein the fiber is a glass fiber. The 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 is impregnated into fibers, dried and dried. Producing a coated fiber having a coating of 1 and then twisting the coated fiber into a twisted yarn, applying a second coating agent containing uncured phenolic resin and rubber to the twisted yarn, drying, and drying A method for producing a reinforcing fiber for a rubber product, comprising forming a second coating on the coating.

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