Rubber reinforcing cord and rubber products using the same

Abstract

To provide a rubber-reinforcing cord comprising a coating layer, wherein the rubber-reinforcing cord can achieve excellent adhesion to a matrix rubber of a rubber product, particularly a matrix rubber comprising an ethylene-propylene-diene rubber.SOLUTION: A rubber-reinforcing cord 12 comprises at least one strand. The strand comprises at least one filament bundle, and a coating layer provided to cover at least a part of the surface of the filament bundle. The coating layer comprises a resorcin-formaldehyde condensate, and a modified polyolefin comprising at least one selected from the group consisting of acid radicals and acid radical derivative groups.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rubber reinforcing cord and a rubber product using the same. [Background technology]

[0002] Rubber belts or metal chains are used to drive camshafts in automotive internal combustion engines, drive accessories such as injection pumps, and transmit power in industrial machinery. In recent years, with growing interest in energy conservation, the use of rubber belts, which offer excellent power transmission efficiency, has been attracting attention from the perspective of improving fuel efficiency. Rubber belts also have the advantage of being stronger and more elastic than metal chains, allowing them to be used under high-load conditions. However, rubber belts can experience a decrease in strength when subjected to repeated stress, limiting their applications.

[0003] Generally, rubber products such as rubber belts include a matrix rubber and a rubber reinforcing cord embedded in the matrix rubber. The strength of the rubber belt depends on the strength of the rubber reinforcing cord. Therefore, the rubber reinforcing cord is an important component that determines the lifespan of the rubber belt.

[0004] A rubber reinforcing cord is generally formed of a reinforcing fiber (a filament bundle containing a plurality of filaments) and a coating that protects the surface of the reinforcing fiber. Such a coating can also improve the adhesion between the rubber reinforcing cord and the matrix rubber when the rubber reinforcing cord is embedded in the matrix rubber of a rubber product.

[0005] In rubber products that require heat resistance, for example, ethylene-propylene-diene rubber (EPDM), which has excellent heat resistance, is used as the matrix rubber. Conventionally, when EPDM is used as the matrix rubber, RFL (a mixed liquid of a resorcinol-formaldehyde condensate and latex) is usually used to prepare the coating of a rubber-reinforcing cord (for example, Patent Document 1). Examples of common RFLs used to prepare coatings for rubber-reinforcing cords include a mixed liquid of a resorcinol-formaldehyde condensate (RF) and a rubber latex of 2-vinylpyridine (VP), chlorosulfonated polyethylene rubber (CSM), and / or styrene-butadiene rubber (SBR). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-177068 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional rubber reinforcing cords with coatings made using general RFLs have insufficient adhesion to EPDM. Therefore, for rubber reinforcing cords used in rubber products that use EPDM as the matrix rubber, it has been necessary to provide an additional coating on the coating made using RFLs to improve adhesion to EPDM.

[0008] Therefore, one object of the present invention is to provide a rubber reinforcing cord having a coating made from RFL, which can achieve excellent adhesion to the matrix rubber of a rubber product, particularly to a matrix rubber containing EPDM.Furthermore, another object of the present invention is to provide a highly reliable rubber product reinforced with such a rubber reinforcing cord, which is less likely to peel off from the matrix rubber. [Means for solving the problem]

[0009] The present invention provides a rubber reinforcing cord for reinforcing a rubber product, comprising: The rubber reinforcing cord comprises at least one strand, The strand includes at least one filament bundle and a coating provided so as to cover at least a portion of a surface of the filament bundle, The coating contains a resorcinol-formaldehyde condensate and a modified polyolefin containing at least one group selected from the group consisting of an acid group and a derivative group of an acid group. A rubber reinforcing cord is provided.

[0010] The present invention also provides a rubber product reinforced with the rubber-reinforcing cord of the present invention.

[0011] The present invention also provides a method for producing a rubber reinforcing cord, comprising: The manufacturing method includes: bundling a plurality of filaments to form at least one filament bundle; and supplying a treatment agent to at least a portion of the surface of the filament bundle and drying the treatment agent to produce a strand having a coating formed on the surface of the filament bundle; Including, The treating agent comprises a resorcinol-formaldehyde condensate and a latex of a modified polyolefin containing at least one group selected from the group consisting of an acid group and a derivative group of an acid group. A method for manufacturing a rubber reinforcing cord is provided. [Effects of the Invention]

[0012] According to the present invention, a rubber-reinforcing cord having a coating made from an RFL can be provided, which can achieve excellent adhesion to the matrix rubber of a rubber product, particularly to a matrix rubber containing EPDM.Furthermore, the present invention can provide a highly reliable rubber product in which peeling between the matrix rubber and the rubber-reinforcing cord is unlikely to occur. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a partially exploded perspective view schematically illustrating an example of a rubber product of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a strand of an embodiment. [Figure 3] FIG. 1 is a cross-sectional view showing a rubber reinforcing cord according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail.

[0015] [Rubber reinforcement cord] The rubber reinforcing cord of this embodiment is a cord for reinforcing rubber products. This rubber reinforcing cord has at least one strand. This strand includes at least one filament bundle (reinforcing fiber) and a coating provided so as to cover at least a portion of the surface of the filament bundle. The coating contains a resorcinol-formaldehyde condensate and a modified polyolefin. The rubber reinforcing cord of this embodiment has a coating containing a resorcinol-formaldehyde condensate and a modified polyolefin, thereby achieving excellent adhesion to the matrix rubber of a rubber product, particularly to a matrix rubber containing EPDM. Here, in this specification, modified polyolefin means a polyolefin containing at least one group selected from the group consisting of an acid group and an acid group derivative group.

[0016] The method for producing the reinforcing cord of this embodiment will be described in more detail below.

[0017] In the rubber reinforcement cord of this embodiment, the filament bundle constituting the strand includes a plurality of filaments. The material of the filaments is not particularly limited. Examples of filaments that can be used for the rubber reinforcement cord of this embodiment include glass fiber filaments, polyvinyl alcohol fiber filaments typified by vinylon fiber, polyester fiber filaments, polyamide fiber filaments such as nylon and aramid fiber (aromatic polyamide), carbon fiber filaments, and polyparaphenylene benzobisoxazole (PBO) fiber filaments. Among these, it is preferable to use filaments of fibers that have excellent dimensional stability, tensile strength, modulus, and flexural fatigue resistance. For example, it is preferable to use at least one fiber filament selected from glass fiber filaments, aramid fiber filaments, polyparaphenylene benzobisoxazole fiber filaments, and carbon fiber filaments, with glass fiber filaments being particularly preferred. The filament bundle may be composed of one type of filament or multiple types of filaments.

[0018] There is no particular limit to the number of filaments contained in the filament bundle, and the filament bundle may contain, for example, 200 to 24,000 filaments.

[0019] The surfaces of the filaments contained in the filament bundle may be pretreated to enhance adhesive strength. A preferred example of a pretreatment agent is a compound containing at least one functional group selected from the group consisting of an epoxy group and an amino group. Examples of pretreatment agents include aminosilane, epoxysilane, novolac-type epoxy resin, bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, brominated epoxy resin, bisphenol AD-type epoxy resin, and glycidylamine-type epoxy resin. Specific examples include the Denacol series from Nagase ChemteX Corporation, the Epiclon series from DIC Corporation, and the Epicoat series from Mitsubishi Chemical Corporation. Polyurethane resins and isocyanate compounds can also be used as pretreatment agents. For example, a pretreatment agent containing at least one selected from the group consisting of an epoxy resin, a urethane resin, and an isocyanate compound may be used. Pretreatment with such a treatment agent further provides a resin layer containing at least one selected from the group consisting of an epoxy resin, a urethane resin, and an isocyanate compound between the filament bundle and the coating. By pretreating the surface, it is possible to improve the adhesion between the matrix rubber and the rubber reinforcing cord, even when using fiber filaments that are difficult to bond, such as polyparaphenylene terephthalamide fiber filaments. Note that the coating (pretreatment agent film) made of a pretreatment agent formed on the filament surface by pretreatment of the filament is different from the coating that covers at least a portion of the surface of the filament bundle as specified in this embodiment, and is not included in the coating specified in this embodiment.

[0020] There is no limitation on the number of filament bundles included in the rubber reinforcing cord, and it may be one or more. The filament bundle may be a bundle of multiple filament bundles. In this case, each of the multiple filament bundles may or may not be twisted. Furthermore, the multiple filament bundles may or may not be twisted together.

[0021] The coating is provided so as to cover at least a portion of the surface of the filament bundle. The coating may be provided directly on the surface of the filament bundle, or may cover the surface of the filament bundle via another layer. The rubber-reinforcing cord of this embodiment may not be provided with any other coating besides this coating. As mentioned above, the "further coating" here does not include the above-mentioned pretreatment agent coating. Therefore, even if this coating is provided on the surface of a filament bundle containing filaments on which a pretreatment agent film is provided, it can still be considered a "rubber-reinforcing cord on which no other coating is provided besides this coating."

[0022] In the rubber-reinforcing cord of this embodiment, the coating containing the resorcinol-formaldehyde condensate and modified polyolefin may be located on the outer surface of the rubber-reinforcing cord. That is, the coating may be the outermost layer exposed on the surface of the rubber-reinforcing cord of this embodiment. In this case, when the rubber-reinforcing cord of this embodiment is embedded in the matrix rubber of a rubber product, the coating comes into direct contact with the matrix rubber. The coating containing the resorcinol-formaldehyde condensate and modified polyolefin has excellent adhesion to the matrix rubber of the rubber product, particularly to matrix rubber containing EPDM. Therefore, even if the matrix rubber of the rubber product contains EPDM, the rubber-reinforcing cord of this embodiment can achieve strong adhesion to the matrix rubber without providing a separate coating on top of the coating to improve adhesion to the matrix rubber.

[0023] The coating is formed by supplying a coating treatment agent, described below, to at least a portion of the surface of the filament bundle and drying it by heat treatment. Supplying the treatment agent to the surface of the filament bundle can be carried out, for example, by impregnating the filament bundle with the coating treatment agent, or by applying the coating treatment agent to at least a portion of the surface of the filament bundle. The heat treatment removes most of the moisture contained in the filaments themselves and the solvent (e.g., water) of the treatment agent. The method of supplying and drying the coating treatment agent to the filament bundle is not particularly limited, but it is preferable to supply the treatment agent so that it penetrates into the interior of the fiber bundle.

[0024] The coating comprises a resorcinol-formaldehyde condensate and a modified polyolefin.

[0025] The resorcinol-formaldehyde condensate (RF) is not particularly limited. Suitable examples include resol-type RF obtained by reacting resorcinol with formaldehyde in the presence of an alkaline catalyst such as an alkali hydroxide or an amine, and novolac-type RF obtained by reacting resorcinol with formaldehyde in the presence of an acid catalyst. A mixture of resol-type RF and novolac-type RF may also be used. It is particularly preferable to use RF obtained by reacting resorcinol (R) with formaldehyde (F) in a molar ratio of R:F = 2:1 to 1:3. The content of the RF component in the coating is preferably 1% by mass or more, more preferably 5% by mass or more. The content of the RF component in the coating is preferably 20% by mass or less, more preferably 15% by mass or less. A content of the RF component in the coating of 1% by mass or more improves adhesion of the coating to matrix rubber, particularly to matrix rubber containing EPDM. By ensuring that the content of the RF component in the coating is 20% by mass or less, the adhesion of the coating to the matrix rubber, particularly to a matrix rubber containing EPDM, is improved.

[0026] The modified polyolefin is a polyolefin containing an acid group and / or an acid group derivative group in the molecule. The acid group contained in the modified polyolefin molecule is at least one selected from the group consisting of a carboxyl group and a carboxylic acid anhydride group. The acid group derivative group contained in the modified polyolefin molecule is at least one acid group derivative group selected from the group consisting of a carboxyl group and a carboxylic acid anhydride group. That is, the modified polyolefin is a modified product obtained by modifying a polyolefin with at least one selected from the group consisting of an unsaturated carboxylic acid, an unsaturated carboxylic acid anhydride, a derivative of an unsaturated carboxylic acid, and a derivative of an unsaturated carboxylic acid anhydride. In the modified polyolefin, the acid group and / or the acid group derivative group may be contained in the polyolefin molecule. The acid group and / or the acid group derivative group may be introduced into the molecular chain of the polyolefin or may be introduced into the molecular terminal of the polyolefin. In this embodiment, examples of modified polyolefins include those obtained by addition reaction of polyolefin with unsaturated carboxylic acid, unsaturated carboxylic anhydride, unsaturated carboxylic acid derivative, and / or unsaturated carboxylic anhydride derivative, and copolymers of polyolefin with unsaturated carboxylic acid, unsaturated carboxylic anhydride, unsaturated carboxylic acid derivative, and / or unsaturated carboxylic anhydride derivative. The copolymer may be an alternating copolymer or a random copolymer in which polyolefin and unsaturated carboxylic acid, unsaturated carboxylic anhydride, unsaturated carboxylic acid derivative, and / or unsaturated carboxylic anhydride derivative are arranged alternately or randomly, a graft copolymer obtained by graft polymerization of unsaturated carboxylic acid, unsaturated carboxylic anhydride, unsaturated carboxylic acid derivative, and / or unsaturated carboxylic anhydride derivative onto polyolefin, or a block copolymer of polyolefin with unsaturated carboxylic acid, unsaturated carboxylic anhydride, unsaturated carboxylic acid derivative, and / or unsaturated carboxylic anhydride derivative.

[0027] The unsaturated carboxylic acid used to modify the polyolefin refers to an unsaturated compound containing a carboxyl group. The unsaturated carboxylic acid anhydride used to modify the polyolefin refers to an anhydride of an unsaturated compound containing a carboxyl group. Examples of unsaturated carboxylic acids and unsaturated carboxylic acid anhydrides include acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, aconitic acid, nadic acid, and anhydrides thereof, with itaconic anhydride and maleic anhydride being preferred. The derivative of the unsaturated carboxylic acid used to modify the polyolefin refers to, for example, mono- or diesters, amides, or imides of the unsaturated carboxylic acid. Examples of unsaturated carboxylic acid derivatives and unsaturated carboxylic acid anhydride derivatives used to modify polyolefins include methyl fumarate, ethyl fumarate, propyl fumarate, butyl fumarate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, dibutyl fumarate, methyl maleate, ethyl maleate, propyl maleate, butyl maleate, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, maleimide, N-phenylmaleimide, and anhydrides thereof.

[0028] The polyolefin may be a homopolymer of an olefin made from one type of monomer, a copolymer made from multiple types of olefin monomers, or a copolymer of an olefin monomer and a monomer other than an olefin. Examples of olefins include ethylene and α-olefins. The monomer other than an olefin is not particularly limited. The polyolefin may be, for example, a polymer obtained by homopolymerizing one selected from ethylene and an α-olefin, or a polymer obtained by copolymerizing two or more selected from ethylene and an α-olefin. When polymerizing the monomer, a known polymerization catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst can be used. Specific examples of polyolefins include polypropylene, ethylene-propylene copolymer, propylene-butene copolymer, and ethylene-propylene-butene copolymer. The modified polyolefin used in this embodiment may be one type, or multiple types may be mixed and used.

[0029] In this embodiment, the modified polyolefin contained in the coating is preferably, for example, a maleic anhydride modified polyolefin or an itaconic anhydride modified polyolefin.

[0030] The weight-average molecular weight of the modified polyolefin is, for example, 15,000 or more, preferably 30,000 or more, more preferably 70,000 or more, and more preferably 100,000 or more. The weight-average molecular weight of the modified polyolefin is, for example, 200,000 or less. In this specification, the molecular weight of the acid-modified polyolefin is a value measured by gel permeation chromatography (GPC).

[0031] The polar group content in the modified polyolefin is, for example, 0.02 mmol / g or more, preferably 0.5 mmol / g or more. The polar group content in the modified polyolefin is, for example, 3.3 mmol / g or less, preferably 1.8 mmol / g or less, more preferably less than 1.3 mmol / g, and particularly preferably less than 0.9 mmol / g. The polar group content in the modified polyolefin is a theoretical value calculated from the amount of the compound used for the acid modification of the polyolefin.

[0032] The modified polyolefin preferably satisfies at least one selected from the group consisting of the following (A) and (B), and more preferably satisfies both of the following (A) and (B). (A) The weight average molecular weight is 100,000 or more and 200,000 or less. (B) The polar group content is 0.5 mmol / g or more and less than 0.9 mmol / g.

[0033] The polar group contained in the modified polyolefin herein refers to an acid group introduced into the polyolefin, that is, a carboxyl group or an acid anhydride group of a carboxylic acid.

[0034] When the coating contains a modified polyolefin that satisfies at least one of the above (A) and (B), the adhesion of the coating to the matrix rubber of a rubber product, particularly to a matrix rubber containing EPDM, is further improved, thereby enabling the rubber-reinforcing cord of this embodiment to achieve stronger adhesion to the matrix rubber.

[0035] When the coating contains a modified polyolefin that satisfies both of the above (A) and (B), the adhesion of the coating to the matrix rubber of the rubber product, particularly to a matrix rubber containing EPDM, is further improved, thereby enabling the rubber-reinforcing cord of this embodiment to achieve even stronger adhesion to the matrix rubber.

[0036] The melting point of the modified polyolefin is not particularly limited. The melting point of the modified polyolefin is, for example, 20°C or higher, or may be 60°C or higher, or 65°C or higher. The melting point of the modified polyolefin is, for example, 100°C or lower, or may be 75°C or lower, or may be 70°C or higher. In this specification, the melting point of the modified polyolefin is a value determined by differential scanning calorimetry (DSC).

[0037] As described above, the modified polyolefin may contain a derivative group of an acid group. The modified polyolefin may contain both an acid group and a derivative group of the acid group. For example, the modified polyolefin may contain a derivative group of the acid group formed by a neutralization reaction between a neutralizing agent and a carboxyl group or an acid anhydride group of a carboxylic acid, which is an acid group. The neutralizing agent is preferably at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine. That is, the modified polyolefin may contain a derivative group of the acid group formed by a neutralization reaction between the acid group contained in the modified polyolefin and at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine. When the modified polyolefin contained in the coating contains the derivative group of the acid group formed by a neutralization reaction between the acid group and at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine, the adhesion of the coating to the matrix rubber of the rubber product, particularly to matrix rubber containing EPDM, is further improved. This allows the rubber-reinforcing cord of this embodiment to achieve stronger adhesion to the matrix rubber.

[0038] The modified polyolefin more preferably contains a derivative group of the acid group formed by a neutralization reaction between the acid group contained in the modified polyolefin and at least one selected from the group consisting of a secondary amine and a tertiary amine. When the coating contains a modified polyolefin containing such a derivative group, the adhesion of the coating to the matrix rubber of the rubber product, particularly to a matrix rubber containing EPDM, is further improved. This allows the rubber-reinforcing cord of this embodiment to achieve even stronger adhesion to the matrix rubber.

[0039] The content of the modified polyolefin in the coating is, for example, 30% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more. The content of the modified polyolefin in the coating is, for example, 99% by mass or less, preferably 95% by mass or less, and more preferably 93% by mass or less. When the content of the modified polyolefin in the coating is 30% by mass or more, the adhesion of the coating to the matrix rubber, particularly to a matrix rubber containing EPDM, is improved. When the content of the modified polyolefin in the coating is 99% by mass or less, the adhesion of the coating to the matrix rubber, particularly to a matrix rubber containing EPDM, is improved.

[0040] In the coating, the solid content mass ratio of the resorcinol-formaldehyde condensate to the modified polyolefin is, for example, preferably in the range of 1:99 to 20:80 (resorcinol-formaldehyde condensate:modified polyolefin), and more preferably 5:95 to 15:85.

[0041] In the coating, the total content of the resorcinol-formaldehyde condensate and the modified polyolefin is preferably 10% by mass or more, and more preferably 30% by mass or more. By making the total content of the resorcinol-formaldehyde condensate and the modified polyolefin 10% by mass or more, the adhesion of the coating to the matrix rubber, particularly to a matrix rubber containing EPDM, is further improved. This allows the rubber-reinforcing cord of this embodiment to achieve stronger adhesion to the matrix rubber.

[0042] The coating may consist essentially of a resorcinol-formaldehyde condensate and a modified polyolefin. "The coating consists essentially of a resorcinol-formaldehyde condensate and a modified polyolefin" means that the coating does not contain any components other than the resorcinol-formaldehyde condensate and the modified polyolefin, except for unavoidable components. Specifically, this means that the total content of the resorcinol-formaldehyde condensate and the modified polyolefin in the coating is 95% by mass or more, preferably 98% by mass or more. The coating may consist solely of a resorcinol-formaldehyde condensate and a modified polyolefin. By having the coating consist essentially of a resorcinol-formaldehyde condensate and a modified polyolefin, the adhesion of the coating to the matrix rubber, particularly to a matrix rubber containing EPDM, is further improved. This allows the rubber-reinforcing cord of this embodiment to achieve even stronger adhesion to the matrix rubber.

[0043] The coating may further contain other components in addition to the resorcinol-formaldehyde condensate and the modified polyolefin.

[0044] The coating may contain, as the other component, for example, a rubber component. Examples of the rubber component include chlorosulfonated polyethylene rubber, nitrile rubber, hydrogenated nitrile rubber, carboxyl-modified nitrile rubber (X-NBR), carboxyl-modified hydrogenated nitrile rubber (X-HNBR), butadiene-styrene copolymer latex, dicarboxylated butadiene-styrene copolymer rubber, vinylpyridine-styrene-butadiene terpolymer rubber, isoprene rubber, chloroprene rubber, acrylonitrile-butadiene copolymer rubber, hydrogenated acrylonitrile-butadiene copolymer rubber, and ethylene-propylene-non-conjugated diene terpolymer rubber.

[0045] The coating may further contain other components such as a stabilizer, a thickener, and an anti-aging agent.

[0046] Because the coating contains a resorcinol-formaldehyde condensate and a modified polyolefin, the coating alone can achieve excellent adhesion to the matrix rubber. In particular, when the reinforcing cord of this embodiment is applied to a rubber product in which the matrix rubber contains EPDM, good adhesion between the coating and the matrix rubber is achieved. Thus, when the modified polyolefin is used in combination with a resorcinol-formaldehyde condensate, adhesion to the matrix rubber can be dramatically improved. Furthermore, when the modified polyolefin is used in combination with a resorcinol-formaldehyde condensate, further improvement in adhesion to the matrix rubber can be achieved by appropriately adjusting the weight-average molecular weight, polar group content, and / or melting point, as described above, in addition to including acid groups and / or derivative groups.

[0047] The mass of the coating applied to at least the surface of the filament bundle is not particularly limited and may be adjusted as appropriate. For example, the coating is preferably applied in a range of 5 to 30 mass % of the entire reinforcing cord, more preferably in a range of 10 to 25 mass %, and particularly preferably in a range of 13 to 19 mass %. If the mass % of the coating is too high, problems such as a decrease in the dimensional stability of the rubber reinforcing cord in the rubber product or a decrease in the elastic modulus of the rubber reinforcing cord may occur. On the other hand, if the mass of the coating is too low, the strands may become more susceptible to fraying or the coating's ability to protect the fibers may be reduced, resulting in a shortened lifespan of the rubber product.

[0048] The number of twists in the rubber reinforcing cord of this embodiment is not particularly limited. The number of twists applied to one strand (hereinafter also referred to as first twists) may be in the range of 1 to 6 times per 25 mm, for example. Furthermore, the number of twists applied to multiple strands (hereinafter also referred to as final twists) may be in the range of 1 to 8 times per 25 mm, for example. The twist may be a rung twist in which the first twist direction and the final twist direction are the same, or a moro twist in which the first twist direction and the final twist direction are opposite. There are no limitations on the twist direction, and it may be either the S direction or the Z direction.

[0049] [Manufacturing method for rubber reinforcing cord] An example of a method for manufacturing the rubber-reinforcing cord of this embodiment (hereinafter referred to as the manufacturing method of this embodiment) will be described below. Note that, since the matters described for the rubber-reinforcing cord of this embodiment can be applied to the manufacturing method below, duplicated explanations may be omitted. Furthermore, the matters described for the manufacturing method of this embodiment below can be applied to the rubber-reinforcing cord of this embodiment.

[0050] The manufacturing method of this embodiment includes bundling a plurality of filaments to form at least one filament bundle, and supplying a treatment agent to at least a portion of the surface of the filament bundle and drying it to form a strand having a coating formed on the surface of the filament bundle. The treatment agent includes a resorcinol-formaldehyde condensate and a modified polyolefin latex containing at least one group selected from the group consisting of an acid group and an acid group derivative group.

[0051] As described above, at least one filament bundle is prepared by bundling a plurality of filaments, and a treatment agent (coating treatment agent) to be used for preparing the coating is prepared. Next, the coating treatment agent is applied to at least a portion of the surface of the filament bundle. Thereafter, the coating treatment agent is dried, i.e., the solvent in the coating treatment agent is removed. To dry the coating treatment agent, the coating treatment agent applied to the surface of the filament bundle is subjected to, for example, heat treatment.

[0052] By the above method, a coating is formed on at least a portion of the surface of the filament bundle. The method for supplying the coating treatment agent to at least a portion of the surface of the filament bundle is not limited, and for example, the coating treatment agent may be applied to the surface of the filament bundle, or the filament bundle may be immersed in the coating treatment agent.

[0053] The conditions for the heat treatment to remove the solvent from the coating treatment agent are not particularly limited, but one example is drying in an atmosphere at 80°C to 280°C for 0.1 to 2 minutes.

[0054] The coated filament bundle may be twisted in one direction. The twisting direction may be either the S direction or the Z direction. The number of filaments contained in the filament bundle and the number of twists of the filament bundle have been described above, so further explanation will be omitted. In this manner, the rubber reinforcing cord of this embodiment can be manufactured. Note that multiple coated filament bundles may be formed, and these multiple filament bundles may be bundled and then twisted. The direction of the final twist may be the same as or different from the twist direction of the filament bundle (direction of the primary twist). Alternatively, multiple coated filament bundles may be formed, and the bundle of multiple filament bundles may be twisted without twisting each filament bundle individually.

[0055] The coating may be formed after twisting the filament bundle, with the type, number and twisting degree of the filaments being as described above.

[0056] In a preferred example of the manufacturing method of this embodiment, a rubber reinforcing cord is formed by coating or impregnating a filament bundle with a coating treatment agent and then twisting the bundle in one direction.

[0057] Next, the coating treatment agent will be described.

[0058] The coating treatment agent contains a resorcinol-formaldehyde condensate and a modified polyolefin latex containing at least one group selected from the group consisting of an acid group and an acid group derivative group. That is, in this embodiment, the RFL used to prepare the coating contains a modified polyolefin latex (aqueous dispersion) as the latex, rather than the rubber latex that has been used in conventional RFLs. Note that, when preparing a coating containing a rubber component, the RFL latex may further contain a rubber latex.

[0059] When the modified polyolefin contained in the coating treatment agent contains acid groups, the coating treatment agent may further contain a neutralizing agent that neutralizes with the acid groups of the modified polyolefin. For example, the coating treatment agent preferably further contains at least one selected from the group consisting of primary amines, secondary amines, and tertiary amines, and more preferably at least one selected from the group consisting of secondary amines and tertiary amines. Primary amines, secondary amines, and tertiary amines function as neutralizing agents that neutralize with the acid groups of the modified polyolefin, i.e., carboxyl groups or carboxylic acid anhydride groups. The neutralization of the acid groups of the modified polyolefin with the amine forms a salt (a derivative group of the acid group), thereby improving the water solubility of the modified polyolefin. This improves the uniformity of the modified polyolefin in the coating treatment agent, thereby improving the performance of the resulting coating. That is, a coating with superior adhesion to the matrix rubber of a rubber product can be formed, resulting in a rubber-reinforcing cord that achieves stronger adhesion to the matrix rubber.

[0060] The coating treatment agent may further contain other components in addition to those described above, such as a plasticizer, an antioxidant, a stabilizer, a filler, and the like.

[0061] [Rubber products] The rubber product of this embodiment is a rubber product reinforced with the rubber reinforcing cord of this embodiment. There are no particular limitations on the rubber product. Examples of the rubber product of this embodiment include automobile and bicycle tires and power transmission belts. Examples of power transmission belts include meshing power transmission belts and friction power transmission belts. Examples of meshing power transmission belts include toothed belts, such as automotive timing belts. Examples of friction power transmission belts include flat belts, round belts, V-belts, and V-ribbed belts. That is, the rubber product of this embodiment may be a toothed belt, flat belt, round belt, V-belt, or V-ribbed belt.

[0062] The rubber product of this embodiment is formed by embedding the rubber reinforcing cord of this embodiment in a rubber composition (matrix rubber). The method for embedding the rubber reinforcing cord in the matrix rubber is not particularly limited, and any known method may be applied. The rubber product of this embodiment (e.g., a rubber belt) has the rubber reinforcing cord of this embodiment embedded therein. As a result, the rubber product of this embodiment has high flex fatigue resistance. Therefore, the rubber product of this embodiment is particularly suitable for applications such as timing belts for vehicle engines and belts for driving vehicle accessories.

[0063] The rubber contained in the rubber composition in which the rubber-reinforcing cord of this embodiment is embedded is not particularly limited, but it preferably contains EPDM, because, as described above, the coating of the rubber-reinforcing cord of this embodiment has particularly excellent adhesion when used in combination with a matrix rubber containing EPDM.

[0064] As an example of a rubber product, a toothed belt is shown in Fig. 1. The toothed belt 1 shown in Fig. 1 includes a belt body 11 and a plurality of rubber reinforcing cords 12. The belt body 11 includes a belt portion 13 and a plurality of tooth portions 14 protruding from the belt portion 13 at regular intervals. The rubber reinforcing cords 12 are embedded inside the belt portion 13 so as to be parallel to the longitudinal direction of the belt portion 13. The rubber reinforcing cords 12 are the rubber reinforcing cords of this embodiment. [Example]

[0065] Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples and comparative examples.

[0066] [Manufacturing of rubber reinforcing cords] Examples 1 to 8 A glass fiber (filament bundle) consisting of 200 glass filaments (E-glass composition, average diameter 9 μm) was prepared. Three of these glass fibers were aligned and coated with a coating treatment agent (RFL) having a mass ratio of the solid content composition (solid content mass ratio) shown in Table 1 below. The modified polyolefin latex shown in Table 2 was used as the RFL latex. The fiber was then dried for 1 minute in a drying oven set at 150°C. A strand was thus formed.

[0067] The formed strand had a cross section as shown in FIG. 2. That is, a coating 22 was provided so as to cover the surfaces of three bundles of glass fibers 21 made of a large number of glass filaments, thereby forming a strand 20. The three glass fibers 21 were bonded to each other by the coating 22. The strand thus obtained was pre-twisted at a rate of 2 times per 25 mm. Then, 11 of the pre-twisted strands were aligned and then second-twisted at a rate of 2 times per 25 mm. In this way, a rubber reinforcing cord 30 having a cross section as shown in FIG. 3 was obtained. The proportion of the coating in the obtained cord was 20% by mass. In this way, the reinforcing cords of Examples 1 to 8 were obtained.

[0068] (Comparative Example 1) A reinforcing cord of Comparative Example 1 was obtained in the same manner as in Examples 1 to 8, except that RFL having a mass ratio of the solid content composition (solid content mass ratio) as shown in Table 3 was used to form the coating.

[0069] [Table 1]

[0070] [Table 2]

[0071] Modified polyolefins A to H were all modified products obtained by modifying polypropylene, a polyolefin, with maleic anhydride. Modified polyolefin C contained the primary amine 2-amino-2-methyl-1-propanol as a neutralizing agent, modified polyolefin D contained the secondary amine morpholine as a neutralizing agent, and modified polyolefin E contained the tertiary amine dimethylaminoethanol as a neutralizing agent.

[0072] [Table 3]

[0073] [Adhesion evaluation (adhesion strength with matrix rubber and fracture morphology)] First, two rubber pieces (25 mm wide x 50 mm long x 5 mm thick) each having the composition shown in Table 4 were prepared. Next, the rubber reinforcing cord was sandwiched between the two test pieces so that the rubber reinforcing cord was parallel to the longitudinal direction of the rubber pieces, and the pieces were heated at 165°C for 30 minutes to bond them together. The test pieces thus obtained were pulled in the longitudinal direction using a tensile tester, and the peel strength between the matrix rubber and the rubber reinforcing cord of each Example and Comparative Example was measured.

[0074] The failure mode of the test specimens was also examined to determine whether it was "rubber failure," in which the rubber reinforcing cord and matrix rubber remained bonded, "interfacial delamination," in which delamination occurred at the interface between the matrix rubber and the rubber reinforcing cord, or "spot," a state between "rubber failure" and "interfacial delamination." More specifically, "rubber failure" refers to a state in which cracks develop within the matrix rubber rather than delamination at the interface between the matrix rubber and the rubber reinforcing cord, and indicates a state in which 90% or more of the delamination interface in the rubber reinforcing cord is covered by the matrix rubber. "Spot 1" refers to a state in which 50% to less than 90% of the delamination interface in the rubber reinforcing cord is covered by the matrix rubber. "Spot 2" refers to a state in which 20% to less than 50% of the delamination interface in the rubber reinforcing cord is covered by the matrix rubber. On the other hand, "interfacial delamination" refers to a state in which delamination occurs between the matrix rubber and the rubber reinforcing cord, but rubber failure does not occur, and indicates that the presence of broken rubber is less than 20% on the surface of the delaminated rubber reinforcing cord.

[0075] Here, the proportion of rubber present at the peel interface was determined using a printed photograph of the peel interface. Specifically, a photograph was first taken so that the entire peel interface of the test piece was included, and the entire test piece was cut out from the printed image of the photograph, and the weight W of the printed image of the entire cut test piece was measured. Next, the rubber portion was cut out from the printed image of the entire test piece, and the total weight w of the cut rubber portion was measured. The proportion of remaining rubber ((w / W) x 100%) was calculated from the obtained weights W and w. The results are shown in Table 5.

[0076] [Table 4]

[0077] [Table 5]

[0078] The rubber-reinforcing cords of Examples 1 to 8 had better adhesion to the matrix rubber than the rubber-reinforcing cord of Comparative Example 1. The rubber-reinforcing cords of Examples 1 and 2 obtained good adhesion, designated "Spot-2." The rubber-reinforcing cords of Examples 3 and 6 to 8 obtained even better adhesion, designated "Spot-1." The rubber-reinforcing cords of Examples 4 and 5 obtained the best adhesion, designated "rubber failure."

[0079] In contrast, the rubber-reinforcing cord of Comparative Example 1 exhibited "interface peeling" at the peel interface, and had poor adhesiveness. [Industrial Applicability]

[0080] The present invention can be used for a rubber reinforcing cord for reinforcing rubber products. [Explanation of symbols]

[0081] 1 Toothed belt 11 Belt body 12 Rubber reinforcement cord 13 Belt section 14 Tooth 20 strands 21 Glass Fiber 22 Coating 30 Rubber reinforcement cord

Claims

1. A rubber reinforcing cord for reinforcing a rubber product, The rubber reinforcing cord comprises at least one strand, The strand includes at least one filament bundle and a coating provided so as to cover at least a portion of a surface of the filament bundle, the coating film essentially consists of a resorcinol-formaldehyde condensate and a modified polyolefin containing at least one group selected from the group consisting of an acid group and a derivative group of an acid group; Rubber reinforcement cord.

2. The modified polyolefin satisfies at least one selected from the group consisting of the following (A) and (B): The rubber reinforcing cord according to claim 1. (A) The weight average molecular weight is 100,000 or more and 200,000 or less. (B) The polar group content is 0.5 mmol / g or more and less than 0.9 mmol / g.

3. The modified polyolefin satisfies both of (A) and (B). The rubber reinforcing cord according to claim 2.

4. The derivative group is a group formed by a neutralization reaction between the acid group and at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine. The rubber reinforcing cord according to any one of claims 1 to 3.

5. the derivative group is a group formed by a neutralization reaction between the acid group and at least one selected from the group consisting of the secondary amine and the tertiary amine; The rubber reinforcing cord according to claim 4.

6. the coating is located on the outer surface of the rubber reinforcing cord, The rubber reinforcing cord according to any one of claims 1 to 5.

7. In the coating, the content of the modified polyolefin is 30% by mass or more and 95% by mass or less. The rubber reinforcing cord according to any one of claims 1 to 6.

8. A rubber product reinforced with the rubber-reinforcing cord according to any one of claims 1 to 7.

9. A rubber belt including a matrix rubber and the rubber reinforcing cord embedded in the matrix rubber. The rubber product according to claim 8.

10. The matrix rubber includes an ethylene-propylene-diene rubber. The rubber product according to claim 9.

11. A method for manufacturing a rubber reinforcing cord, comprising: The manufacturing method includes: bundling a plurality of filaments to form at least one filament bundle; and supplying a treatment agent to at least a portion of the surface of the filament bundle and drying the treatment agent to produce a strand having a coating formed on the surface of the filament bundle; Including, the treating agent comprises a resorcinol-formaldehyde condensate and a latex of a modified polyolefin containing at least one group selected from the group consisting of an acid group and a derivative group of an acid group; the coating consists essentially of the resorcinol-formaldehyde condensate and the modified polyolefin; A method for manufacturing a rubber reinforcing cord.

12. The treatment agent further includes at least one selected from the group consisting of a primary amine, a secondary amine, and a tertiary amine. The method for producing the rubber reinforcing cord according to claim 11.

13. The treatment agent includes at least one selected from the group consisting of the secondary amine and the tertiary amine. A method for producing the rubber reinforcing cord according to claim 12.

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