Cord for rubber reinforcement

Abstract

To provide a cord for rubber reinforcement that exhibits excellent tensile strength, strong adhesion to rubber, superior abrasion resistance between fibers, and also exhibits high processability during weaving or knitting of the reinforcement cord.SOLUTION: A cord for rubber reinforcement comprises spun yarn of an aromatic polyamide fiber with a surface treatment agent adhered thereto, the surface treatment agent being silicone oil and wax, and a total adhesion amount of the surface treatment agent being 0.1 to 20 wt.% relative to the weight of the aromatic polyamide fiber spun yarn.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber reinforcing cord. [Background technology]

[0002] Due to the trend towards more efficient and powerful automobile engines and the downsizing of engine compartments, there is an increasing demand for improved heat resistance and durability of heat-resistant hoses such as air hoses for turbocharger systems and oil cooling hoses. At the same time, as engine compartments become more complex, there is also an increasing demand for improved flexibility to accommodate complex layouts.

[0003] The rubber reinforcing cords used in these highly heat-resistant, highly durable hoses have traditionally been made of aromatic polyamide (aramid) fibers, which have excellent heat resistance, because general-purpose synthetic fibers such as ordinary polyamide and polyester do not have sufficient heat resistance. However, filament (long fiber) type rubber reinforcing cords often lack sufficient adhesive strength with the rubber because of their smooth surface, and there is a problem that the rubber and rubber reinforcing cord can peel off when subjected to repeated pressure fluctuations. To address this problem, a method has been proposed in which stretch-cut aramid fiber yarn or spun yarn is used to improve the adhesive strength between the rubber and the rubber reinforcing cord.

[0004] In order to achieve both durability and flexibility for the rubber hose, the rubber reinforcing cord is often used for reinforcement in the form of a braid. In this case, during the knitting process of the rubber reinforcing cord in the molding of the hose, the stretch-break processed yarn or single fibers on the surface of the spun yarn of the rubber reinforcing cord fall off due to contact between the knitting needle and the rubber reinforcing cord, and these fall off and accumulate on the guides of the process. In this case, frequent cleaning is required, and the process passability becomes significantly worse. In addition, the fluff on the surface falls off during the process, and sufficient adhesiveness cannot be achieved.

[0005] Furthermore, when a rubber hose is used repeatedly, wear occurs between the stretch-break processed yarn and the spun yarn at the intertwined portions of the yarn, which further accelerates the fuzzing on the surface, making the rubber reinforcing cord more susceptible to damage and resulting in insufficient abrasion resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-37240 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a rubber-reinforcing cord which is excellent in strength, adhesion to rubber and abrasion resistance, and which exhibits high processability during weaving and knitting of the rubber-reinforcing cord. [Means for solving the problem]

[0008] The present invention relates to a rubber-reinforcing cord including a spun yarn of an aromatic polyamide fiber having a surface treatment agent attached thereto, characterized in that the surface treatment agent is silicone oil and wax, and the amount of the surface treatment agent attached is 0.1 to 20% by weight in total, based on the weight of the spun yarn of the aromatic polyamide fiber. Effect of the Invention

[0009] According to the present invention, it is possible to provide a rubber-reinforcing cord which is excellent in strength, adhesion to rubber and abrasion resistance, and further has high processability during weaving and knitting of the rubber-reinforcing cord. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below.

[0011] [Aromatic polyamide fiber] The aromatic polyamide fiber in the present invention is a fiber made of an aromatic polyamide, and specific examples thereof include polyparaphenylene terephthalamide fiber, which is a para-type aromatic polyamide fiber (e.g., "Twaron" (registered trademark) manufactured by Teijin Aramid BV), copolyparaphenylene-3,4'-oxydiphenylene-terephthalamide fiber, which is a copolymer type aromatic polyamide fiber (e.g., "Technora" (registered trademark) manufactured by Teijin Limited), and polymetaphenylene isophthalamide fiber, which is a meta-type aromatic polyamide fiber (e.g., "Conex" (registered trademark) manufactured by Teijin Limited).

[0012] As the aromatic polyamide fiber, copolyparaphenylene-3,4'-oxydiphenylene-terephthalamide fiber, which is a copolymer type para-aromatic polyamide fiber, is preferred. Copolyparaphenylene-3,4'-oxydiphenylene-terephthalamide fiber has high tensile strength and excellent flex fatigue resistance, making it possible to provide rubber molded products with higher durability.

[0013] [Spun yarn] The spun yarn of aromatic polyamide fiber in the present invention is composed of short fibers. The average fiber length of the short fibers is preferably 0.1 to 40 mm, more preferably 0.1 to 30 mm, further preferably 2 to 20 mm, and particularly preferably 3 to 15 mm. If the average fiber length is less than 0.1 mm, the strength as a rubber reinforcing cord decreases, and sufficient durability of the rubber product cannot be ensured, which is undesirable. On the other hand, if it exceeds 40 mm, the fluff on the surface of the spun yarn is insufficient, and the adhesion to the rubber decreases, which is undesirable.

[0014] [Rubber reinforcing cord] The rubber reinforcing cord of the present invention includes a spun yarn of aromatic polyamide fiber with a surface treatment agent attached thereto. The content of the spun yarn of aromatic polyamide fiber with a surface treatment agent attached thereto in the rubber reinforcing cord of the present invention is 10% by weight or more, preferably 20% by weight or more, and more preferably 30% by weight or more, based on the total weight of the rubber reinforcing cord. If it is less than 10% by weight, the rubber adhesive strength and abrasion resistance may decrease. The upper limit of the content of the spun yarn of aromatic polyamide fiber with a surface treatment agent attached thereto in the rubber reinforcing cord of the present invention is, for example, 70% by weight, preferably 90% by weight, and more preferably 100% by weight.

[0015] So long as the content of the spun yarn of the surface-treatment-agent-adhered aromatic polyamide fiber is within the above range, the rubber-reinforcing cord of the present invention may contain a portion of fibers other than the surface-treatment-agent-adhered aromatic polyamide fiber.

[0016] For example, by incorporating general-purpose synthetic fibers that have lower fiber strength and elastic modulus than aromatic polyamide fibers, it is possible to increase the durability of the rubber product against repeated extension and compression when it is used.

[0017] Examples of general-purpose synthetic fibers include polyurethane fibers, aliphatic polyamide fibers known as nylon 6, nylon 66, and nylon 46, polyester fibers known as polyethylene terephthalate and polytrimethylene terephthalate, polyvinyl alcohol fibers known as vinylon, and rayon fibers.

[0018] In the present invention, of the staple fibers constituting the spun yarn, preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 30% by weight or more are staple fibers obtained by cutting and opening used continuous fibers of aromatic polyamide fibers with a surface treatment agent attached thereto. By containing them in this range, the amount of energy used in the production of the continuous fibers and the amount of waste of used products can be reduced, and the burden on the environment can be reduced.

[0019] The rubber-reinforcing cord of the present invention is preferably a plied cord obtained by twisting together two or more spun yarns of aromatic polyamide fiber with a surface treatment agent in the direction opposite to the twisting direction of the spun yarn. By pliedly twisting two or more spun yarns in this manner, the durability of rubber products can be further improved. In the case of a ply-twisted cord, it is more preferable that the cord is a ply-twisted cord in which the cord is ply-twisted in the opposite direction to the twist direction of the spun yarn.

[0020] The rubber reinforcing cord of the present invention may contain a yarn in a form other than spun yarn in part depending on the application. For example, by further containing a multifilament type aromatic polyamide fiber, the strength as a fiber is improved and the processability during weaving and knitting of the reinforcing cord is also improved.

[0021] The rubber reinforcing cord of the present invention may contain a portion of aromatic polyamide fiber to which no surface treatment agent is applied, which allows the aromatic polyamide fiber used for purposes other than ropes and sling belts to be reused, thereby further reducing the burden on the environment.

[0022] When the rubber reinforcing cord of the present invention is a ply-twisted cord, the twist factor TM of the ply-twisted cord, represented by the following formula, is preferably 1 to 7, and more preferably 2 to 6. If the twist factor TM is less than 1 or exceeds 7, the strength and tenacity of the rubber reinforcing cord decreases, which is undesirable. TM=T / √D Here, T is the number of twists (turns / inch) and D is the total fineness (count) of the rubber reinforcing cord. From the viewpoint of durability of the rubber molded product, the strength of the rubber reinforcing cord of the present invention is preferably 10 cN / dtex or more, and more preferably 12 cN / dtex or more.

[0023] [Surface treatment agent] In the present invention, the surface treatment agent is a silicone oil or a wax. In the present invention, it is necessary to use both of them in combination.

[0024] The amount of the surface treatment agent attached is 0.1 to 20% by weight, preferably 1 to 15% by weight, based on 100% by weight of the spun aromatic polyamide fiber. If the amount is less than 0.1% by weight, the effect of controlling the friction coefficient of the fiber surface cannot be sufficiently obtained, and the abrasion resistance between the fibers decreases. On the other hand, if the amount of the surface treatment agent attached exceeds 20% by weight, the effect of controlling the friction coefficient does not change, and it becomes a factor that inhibits adhesion to rubber.

[0025] Examples of silicone oils include polyalkylsiloxanes and polyetheralkylsiloxanes. These may be used in combination. Examples of the wax include petroleum wax, natural wax, and synthetic wax. Specifically, Fischer-Tropsch wax, Sasol wax, paraffin wax, polyethylene wax, polypropylene wax, and oxidized polyethylene wax are preferred.

[0026] The spun yarn of aromatic polyamide fiber with surface treatment agent attached has excellent abrasion resistance between fibers and adhesion to rubber because of both silicone oil and wax attached, compared to when each is attached alone. Although the mechanism is unclear, the inventor speculates that it is because the silicone oil controls the friction coefficient, and the wax increases the affinity with rubber, including the silicone oil.

[0027] The weight ratio of silicone oil to wax is preferably 10:90 to 90:10, more preferably 10:90 to 60:40, and particularly preferably 10:90 to 40:60, from the viewpoint of the friction coefficient and adhesion to the fiber surface achieved by using them in combination.

[0028] In addition to the silicone oil and wax, the spun yarn of the aromatic polyamide fiber having a surface treatment agent may further have an oil agent generally used for fibers, such as a surfactant, attached thereto.

[0029] [Manufacturing method] The spun yarn of the aromatic polyamide fiber with the surface treatment agent attached can also be obtained from waste yarn containing aromatic polyamide fiber generated in an aromatic polyamide fiber manufacturing plant or a plant using aromatic polyamide fiber and / or from used products containing aromatic polyamide fiber. In these cases, the aromatic polyamide fiber is cut to a predetermined length to obtain short fibers, which are then spun into spun yarn.

[0030] Silicone oil and wax can reduce the friction coefficient of the surface of spun yarn, improve abrasion resistance, and do not easily fall off due to water, etc. Therefore, silicone oil and wax can be applied to continuous aromatic polyamide fibers used for applications such as ropes and sling belts.

[0031] Therefore, the continuous fiber of aromatic polyamide fiber with silicone oil and wax attached thereto is first used for rope or sling belt, then the part that is worn or deteriorated by ultraviolet rays and located on the surface of the rope or ring belt is removed, and the continuous fiber of aromatic polyamide fiber with surface treatment agent attached thereto is recovered from the continuous fiber of aromatic polyamide fiber located inside with less deterioration, and can be used as the raw material for the spun yarn of aromatic polyamide fiber with surface treatment agent attached thereto.The preferred embodiment of the present invention is to use the spun yarn of aromatic polyamide fiber with surface treatment agent attached thereto obtained from the continuous fiber recovered.

[0032] When the amount of the surface treatment agent adhering to the continuous fibers is large, the continuous fibers may be washed to reduce the amount of the surface treatment agent adhering to within a range of 0.1 to 20% by weight, and then the fibers may be cut to a predetermined length to obtain short aromatic polyamide fibers adhering to the surface treatment agent.

[0033] The silicone oil and wax can be applied to the spun yarn of aromatic polyamide fiber by a known method, such as application to the surface of the spun yarn by a kiss roll, nozzle, or spray, or dipping the spun yarn in the treatment agent.

[0034] The silicone oil may be emulsified in water to be used as a silicone oil emulsion for attachment to spun yarn of aromatic polyamide fiber. The wax may be emulsified in water to provide an emulsion of the wax for attachment to the spun aromatic polyamide fiber yarn. To inhibit static electricity, antistatic agents may be added to the emulsion.

[0035] The silicone oil and the wax may be applied to the aromatic polyamide fibers separately or together. When they are applied together, it is preferable to use an emulsion obtained by mixing a silicone oil emulsion and a wax emulsion, apply the mixture to the spun yarn of aromatic polyamide fiber, and then dry the water to allow the two to adhere to each other. EXAMPLES

[0036] The present invention will now be described in more detail with reference to examples. (1) Average fiber length The staple fibers constituting the spun yarn were randomly taken out one by one, and the length of each staple fiber was measured in a straight state without being stretched. The lengths of 50 staple fibers were measured and the average value was calculated. (2) Amount of silicone oil and wax attached The amount of silicone oil or wax attached was calculated from the difference in the fiber weight before and after the treatment. (3) Tensile strength and tensile strength The tensile strength was measured according to JIS L 1017. The tensile strength was calculated by dividing the tensile strength by the fineness of the sample including the attached silicone oil and the attached wax. (4) Rubber adhesion 25 samples were embedded near the surface of an unvulcanized rubber sheet made mainly of acrylic rubber, and subjected to a stress of 1N / mm at 150°C for 30 minutes. 2 The force required to peel the rubber sheet in a direction at an angle of 90 degrees to the rubber sheet surface at a speed of 200 mm / min was measured. (5) Process passability The sample was rubbed against a pin guide having a diameter of 1 mm at a speed of 100 m / min, and the weight of the fluff that fell off in 10 minutes was measured. (6) Abrasion resistance The samples were abraded against each other under a load of 500 g, and the number of abrasions until the sample broke was measured.

[0037] Example 1 A surface-treated aromatic polyamide fiber was prepared, which was a multifilament of para-aramid fiber (manufactured by Teijin Limited, Technora (registered trademark)) with 1670 dtex and 1000 filaments, to which 0.8% by weight of silicone oil and 2.3% by weight of paraffin wax were attached relative to 100% by weight of the fiber. This was not wound on a paper tube but was randomly packed in a cardboard box.

[0038] The aromatic polyamide fibers with the surface treatment agent attached were cut by a guillotine cutter into cut pieces with an average fiber length of 40 mm. The cut pieces were passed through a carding machine with metal needles three times to open the fibers, and then a sliver was obtained using a carding machine, after which a spun yarn with a British cotton count of 10 (590 dtex) and a twist of 10.0 turns / inch (twist factor TM = 3.2) was obtained using a ring spinning machine.

[0039] Two of these spun yarns were then bundled together, and wound while being second-twisted in the Z direction at 6.9 turns / inch (twist factor TM = 3.1) to obtain a ply-twisted rubber reinforcing cord. The evaluation results of the obtained rubber reinforcing cord are shown in Table 1.

[0040] Example 2 A surface treatment agent-attached aromatic polyamide fiber was prepared, which was a multifilament of para-aramid fiber (manufactured by Teijin Limited, Technora (registered trademark)) of 1670 dtex 1000 filament, to which 3.0% by weight of silicone oil and 9.0% by weight of paraffin wax were attached relative to 100% by weight of the fiber.

[0041] A spun yarn of British cotton count 10 (590 dtex) having a twist of 10.0 turns / inch (twist factor TM = 3.2) was obtained in the same manner as in Example 1, and then a ply-twisted rubber reinforcing cord was obtained in the same manner as in Example 1. The evaluation results of the obtained rubber reinforcing cord are shown in Table 1.

[0042] Example 3 A surface treatment agent-attached aromatic polyamide fiber was prepared, which was a multifilament of para-aramid fiber (manufactured by Teijin Limited, Technora (registered trademark)) of 1670 dtex 1000 filament, to which 0.8 wt% silicone oil and 1.0 wt% paraffin wax were attached relative to 100 wt% fiber.

[0043] A spun yarn of British cotton count 10 (590 dtex) having a twist of 10.0 turns / inch (twist factor TM = 3.2) was obtained in the same manner as in Example 1, and then a ply-twisted rubber reinforcing cord was obtained in the same manner as in Example 1. The evaluation results of the obtained rubber reinforcing cord are shown in Table 1.

[0044] Comparative Example 1 A surface treatment agent-attached aromatic polyamide fiber was prepared, which was a multifilament of para-aramid fiber (manufactured by Teijin Limited, Technora (registered trademark)) of 1670 dtex 1000 filament, to which 0.8% by weight of silicone oil was attached relative to 100% by weight of the fiber.

[0045] A spun yarn of British cotton count 10 (590 dtex) having a twist of 10.0 turns / inch (twist factor TM = 3.2) was obtained in the same manner as in Example 1, and then a ply-twisted rubber reinforcing cord was obtained in the same manner as in Example 1. The evaluation results of the obtained rubber reinforcing cord are shown in Table 1.

[0046] Comparative Example 2 A surface treatment agent-attached aromatic polyamide fiber was prepared, which was a multifilament of para-aramid fiber (manufactured by Teijin Limited, Technora (registered trademark)) of 1670 dtex 1000 filament, to which 2.3% by weight of paraffin wax was attached relative to 100% by weight of the fiber.

[0047] A spun yarn of British cotton count 10 (590 dtex) having a twist of 10.0 turns / inch (twist factor TM = 3.2) was obtained in the same manner as in Example 1, and then a ply-twisted rubber reinforcing cord was obtained in the same manner as in Example 1. The evaluation results of the obtained rubber reinforcing cord are shown in Table 1.

[0048] Comparative Example 3 An aromatic polyamide fiber was prepared, which was a multifilament para-aramid fiber (manufactured by Teijin Limited, Technora (registered trademark)) of 1670 dtex 1000 filament, containing no silicone oil or paraffin wax and having 2 wt% fatty acid ester-based oil applied thereto relative to 100 wt% fiber.

[0049] A spun yarn of British cotton count 10 (590 dtex) having a twist of 10.0 turns / inch (twist factor TM = 3.2) was obtained in the same manner as in Example 1, and then a ply-twisted rubber reinforcing cord was obtained in the same manner as in Example 1. The evaluation results of the obtained rubber reinforcing cord are shown in Table 1.

[0050] [Table 1] [Industrial Applicability]

[0051] The rubber reinforcing cord of the present invention can be used to reinforce rubber molded products, and is particularly suitable for reinforcing heat-resistant rubber hoses.

Claims

1. A rubber reinforcing cord comprising a spun yarn of an aromatic polyamide fiber having a surface treatment agent attached thereto, the surface treatment agent being silicone oil and wax, and the amount of the surface treatment agent attached being 0.1 to 20% by weight in total relative to the weight of the spun yarn of the aromatic polyamide fiber.

2. 2. The rubber reinforcing cord according to claim 1, wherein the spun yarn of aromatic polyamide fiber is composed of short fibers, and the short fibers have an average fiber length of 0.1 to 40 mm.

3. 2. The rubber reinforcing cord according to claim 1, which is a ply-twisted cord obtained by twisting together two or more spun yarns of the aromatic polyamide fiber with a surface treatment agent in a direction opposite to the twisting direction of the spun yarns.

4. 4. The rubber reinforcing cord according to claim 3, wherein the twist factor TM of the plying is 1 to 7, as represented by the following formula: TM = T / √D (where T is the number of twists (turns / inch), and D is the total fineness (count) of the rubber reinforcing cord.)

5. The rubber reinforcing cord according to claim 4, having a strength of 10 cN / dtex or more.

6. 3. The rubber reinforcing cord according to claim 2, wherein 5% by weight or more of the short fibers are short fibers obtained by cutting and opening continuous fibers of used aromatic polyamide fibers having a surface treatment agent attached thereto.

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