WO2005061766A1

WO2005061766A1 - Rubber reinforcing cord and rubber product using same

Info

Publication number: WO2005061766A1
Application number: PCT/JP2004/018404
Authority: WO
Inventors: Keisuke Kajihara
Original assignee: Nippon Sheet Glass Company, Limited
Priority date: 2003-12-18
Filing date: 2004-12-09
Publication date: 2005-07-07
Also published as: US20070144134A1; JPWO2005061766A1; CA2548207A1; EP1698720A1; CN1894451A

Abstract

Disclosed is a rubber reinforcing cord comprising a reinforcing fiber. The reinforcing fiber contains a polyarylate fiber (11) and a plurality of outer strands (12) arranged around the polyarylate fiber (11), and the outer strands (12) contain a fiber other than the polyarylate fiber. This rubber reinforcing cord is high in strength, elasticity and flex fatigue resistance. Also disclosed is a rubber product using such a rubber reinforcing cord.

Description

Specification

Rubber reinforcing cord and rubber product using the same

Technical field

The present invention relates to a rubber reinforcing cord and a rubber product reinforced with the rubber reinforcing cord.

Background art

[0002] Reinforcing fibers such as glass fiber peramide fibers have been used as reinforcing materials for rubber products such as rubber belts and tires. However, these rubber products are subject to bending fatigue due to repeated bending stress, resulting in reduced performance, peeling between the reinforcing fibers and the rubber matrix, and a reduction in strength due to wear of the reinforcing fibers. Occurs and is sore. On the other hand, a toothed rubber belt used for driving a camshaft of an internal combustion engine of an automobile requires a high degree of dimensional stability in order to maintain appropriate timing. In addition, rubber belts used for auxiliary drives such as injection pumps that are driven only by camshafts and for power transmission of industrial machines are required to have high strength and high elasticity that can withstand high loads.

[0003] Under such circumstances, new materials are being studied as reinforcing fibers for rubber belts. For example, recently, polyarylate fibers have been proposed (see JP-A-2003-294086).

[0004] As described above, rubber reinforcing cords are required to have high strength, high elasticity, flexibility with respect to bending, and abrasion resistance, but conventional cords balance strength and flexibility. It was difficult. For example, when polyarylate fiber is used as a reinforcing fiber, a cord having high strength and high elasticity can be obtained, but this cord has a problem that the strength tends to decrease easily due to bending fatigue. .

Disclosure of the invention

[0005] In view of such circumstances, an object of the present invention is to provide a rubber reinforcing cord having high strength, elasticity and bending fatigue resistance, and a rubber product using the same.

[0006] As a result of investigations by the present inventors to achieve the above object, it has been found that a combination of polyarylate fibers and glass fibers in a specific arrangement provides a more remarkable effect than expected. Was. Then, based on this new knowledge, the following invention has been achieved. It was.

[0007] A rubber reinforcing cord according to the present invention is a rubber reinforcing cord including reinforcing fibers, wherein the reinforcing fibers include a polyarylate fiber and a plurality of outer fibers arranged around the polyarylate fiber. And a strand, wherein the outer strand contains fibers other than polyarylate fibers. In this specification, the term "strand" refers to a bundle obtained by bundling a plurality of filament fibers without twisting, a bundle obtained by bundling a plurality of filament fibers and twisting the strand, or a plurality of strands without twisting. And bundles of multiple strands and twists.

[0008] A rubber product of the present invention includes the rubber reinforcing cord of the present invention.

According to the present invention, a rubber reinforcing cord having high strength, elasticity, and high bending fatigue resistance and excellent dimensional stability can be obtained. In particular, by combining the polyarylate fiber strand and the glass fiber strand in a specific arrangement, a rubber reinforcing cord having remarkably high bending fatigue resistance can be obtained. Since the rubber product of the present invention contains the cord, it has excellent strength, elasticity and bending fatigue resistance, and excellent dimensional stability.

Brief Description of Drawings

FIG. 1 is a cross-sectional view schematically showing one example of a rubber reinforcing cord of the present invention.

FIG. 2 is a schematic view showing a bending test method in an example.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described.

(Embodiment 1)

In Embodiment 1, a rubber reinforcing cord of the present invention will be described. The rubber reinforcing cord of the present invention contains reinforcing fibers. The reinforcing fibers include polyarylate fibers and a plurality of strands (outer strands) arranged around the polyarylate fibers. The outer strand contains other fibers other than polyarylate fibers (hereinafter, may be referred to as “second fibers”).

[0013] The polyarylate fiber is a wholly aromatic polyester fiber, and is obtained by polycondensation of a divalent phenol (for example, bisphenol A) and an aromatic dicarboxylic acid (for example, phthalic acid-isophthalic acid). [0014] The second fiber is preferably a fiber having higher bending resistance than the polyarylate fiber. For example, as the second fiber, a glass fiber, a polyparaphenylene-benzobenzoxazole fiber, a carbon fiber, an aramide fiber such as a polyparaphenylene-terephthalamide fiber, or a mixed fiber thereof can be used. The outer strand is at least one fiber selected from glass fiber, polyparaphenylene benzobisoxazole fiber, carbon fiber, and aramide fiber (preferably polyparaphenylene-lentephthalamide fiber; the same applies hereinafter). It is particularly preferred to be made of glass fiber or aramide fiber, which is preferable.

[0015] When the proportion of the polyarylate fiber in the reinforcing fiber is increased, the elastic modulus and dimensional stability are improved, but the dynamic flexibility is reduced. Conversely, when the ratio is low, the elastic modulus and dimensional stability decrease. Accordingly, the ratio of the polyarylate fibers to the entire reinforcing fiber is 20 vol ^_0/0 - preferably a range of - 80 vol ^_0/0 (70 vol ^_0/0 and more preferably 30 volume ^_0/0) .

[0016] In the rubber reinforcing cord of the present invention, it is preferable that the polyarylate fiber strength constitutes a strand of polyarylate fiber. In this case, the rubber reinforcing cord includes a core strand of polyarylate fiber and a plurality of outer strands arranged around the core strand. The core strand is preferably substantially composed of polyarylate fibers. Typically, only the polyarylate fibers are strong.

In the cord of the present invention, a polyarylate fiber having a high elastic modulus (preferably, a strand of the polyarylate fiber) is arranged near the center of the cord, and the outer strand having excellent flexibility and abrasion resistance is formed of the polystrand. It is particularly preferred to arrange around the arylate fibers. Polyarylate fibers located near the center of the cord, by virtue of their properties, provide the cord with high strength, modulus and excellent dimensional stability. Further, the outer strand may have a lower elastic modulus than that of the polyarylate fiber, and may be made of fiber (for example, glass fiber). By using such an outer strand, a rubber reinforcing cord having high strength, elasticity, and bending fatigue resistance can be obtained.

The diameter and elastic modulus of the polyarylate fiber are not particularly limited, and are selected according to the characteristics required for the reinforcing cord. For example, density of ^{1. 2g / cm 3 -2. OgZcm} 3 about Po Realate fibers may be used. It is also possible to use polyarylate fibers with an elastic modulus (Young's modulus) of about 70GPa-120GPa! ヽ.

[0019] The polyarylate fiber may be non-twisted and untreated, but may be coated with an adhesive or twisted to improve adhesiveness and prevent fraying. Adhesives are not particularly limited V. However, treatment liquids mainly composed of an initial condensate of resorcinol and formaldehyde and rubber latex (hereinafter sometimes referred to as RFL treatment liquids), epoxy compounds, isocyanate compounds, etc. Can be used. The number of twists of the polyarylate fiber (core strand) is not particularly limited, and is usually within a range of 8.0 times Z25mm or less, for example, 0.5 times Z25mm-5.0 times Z25mm. When twisting is applied, it is preferable to apply the treatment liquid and then knit the twist. When the treatment liquid is applied with twist and force, the strands of the polyarylate fiber may be easily frayed.

[0020] The thickness of the outer strand, the number and diameter of the fibers constituting the outer strand, and the like are selected according to the characteristics required for the reinforcing cord, which is not particularly limited. The number of outer strands arranged around the polyarylate fiber is usually about 3 to 20.

[0021] Like the outer strand, a strand arranged near the outer periphery of the cord is required to relieve a tensile stress and a compressive stress generated when the cord is bent. As a strand satisfying such requirements, a glass fiber strand and an aramide fiber strand are preferable. By arranging glass fiber strands whose main fibers are glass fibers (50% by volume or more, preferably 60% by volume or more and, for example, 100% by volume) around the core strand which also has polyarylate fiber strength, strength, elasticity and resistance to A rubber reinforcing cord with particularly high flex fatigue can be obtained. Also, by using a glass fiber strand as the outer strand, a reinforcing cord that strongly adheres to the rubber in which the reinforcing cord is embedded can be obtained. As the glass fiber, for example, an E glass filament or a high-strength glass filament is preferably used. As the glass fiber strand, a strand of about 20 to 480 tex in which about 200 to 2400 glass filaments each having a diameter of 7 to 9 / z m are bundled and twisted, and are preferably used.

[0022] The outer strands may be twisted. By twisting (primarily twisting) the outer strand disposed near the outer periphery of the cord, the bending fatigue resistance of the cord can be improved. Twist The number is not particularly limited, but is preferably about 0.25 times Z25mm-5.0 times Z25mm.

[0023] Further, the plurality of outer strands may be spirally wound (ie, twisted) with the polyarylate fiber as a core. The number of twists of the first twist can be, for example, about 0.5 times Z25 mm—about 10 times Z25 mm. When the outer strands are ply-twisted and ply-twisted, the direction of the ply-twist may be the same as or different from the direction of the ply-twist. By setting the direction of the first twist and the direction of the first twist to be the same, a cord having particularly high bending resistance can be obtained. Further, by setting the direction of the first twist and the direction of the first twist to different directions, high dimensional stability can be obtained.

[0024] The rubber reinforcing cord of the present invention preferably has a surface coated with a coating film containing rubber. The coating is usually selected according to the rubber (matrix rubber) in which the cord is embedded. As a method for forming the coating film, a known method without any particular limitation can be applied. For example, a coating film can be formed by applying a treatment liquid containing rubber, followed by heat treatment or drying. As the treatment liquid, for example, an RFL treatment liquid can be used. Examples of the rubber latex used in the RFL treatment solution include acrylic rubber-based latex, urethane-based latex, chlorosulfonated polyethylene-based latex, modified latex thereof, and mixtures thereof.

[0025] The coating film may be formed of different materials around the fiber strand and the outer peripheral portion of the cord. For example, in order to increase the adhesiveness between the matrix rubber of the rubber product and the cord of the present invention, the outer periphery of the cord may be overcoated. The overcoat treatment can be performed with a treatment liquid containing a rubber such as hydrogenated kato-tolyl rubber, chlorosulfonated polyethylene rubber (CSM), chloroprene rubber, natural rubber, or urethane rubber and a crosslinking agent. The rubber used for the overcoat treatment is usually selected according to the type of the matrix rubber. The amount of the overcoat is not particularly limited. For example, the amount may be 2.0 to 10.0 parts by mass with respect to 100 parts by mass of the code before the overcoating.

FIG. 1 shows a cross-sectional view of a preferred example of the rubber reinforcing cord of the present invention. The cord 10 in FIG. 1 is composed of a polyarylate fiber (core strand) 11 arranged in the center of the cord 10, a plurality of outer strands 12 arranged around the polyarylate fiber 11, a polyarylate fiber 11 and the like. And a coating film 13 for coating both the outer strands 12 (hatching is omitted). The plurality of outer strands 12 are spirally wound around the polyarylate fibers 11. The coating film 13 contains rubber.

Hereinafter, a method for manufacturing the code 10 will be described. The outer strands 12 can be formed by bundling fibers. If necessary, a coating film may be formed on the polyarylate fiber (core strand) and the Z or outer strand by performing an RFL treatment or the like. If necessary, the polyarylate fiber (core strand) and the Z or outer strand may be twisted. Further, if necessary, a plurality of strands may be twisted into one strand.

Next, the outer strands 12 are arranged around the polyarylate fibers 11. This step can be performed, for example, using a guide having a central portion guide hole and a plurality of outer peripheral portion guide holes arranged on the same circumference as the center portion guide hole. One or more untwisted or bottom-twisted polyarylate fibers 11 are passed through the center guide hole, and the outer strands 12 are passed through the plurality of outer guide holes. It is also possible to apply a tension 1.2 times or more higher than the outer fiber to the center fiber without using a guide. By applying a higher tension to the center fiber than to the outer fibers, the center fiber can be easily arranged, and the same effect as that obtained by using a guide can be obtained. The outer strand 12 is sub-twisted as required. The apparatus used for the combination and twisting of the strand is not particularly limited. For example, a ring twisting machine, a flyer single twisting machine, a stranded wire machine, and the like can be used.

Finally, a covering film 13 is formed so as to coat the entire polyarylate fiber 11 and the outer strands 12. Thus, the code 10 is manufactured.

[0030] The cord of the present invention may be used alone (rope structure). Further, the cord of the present invention may be used in a cord structure, that is, a structure in which a plurality of cords are arranged in a plane and loosely adhered to each other.

(Embodiment 2)

Embodiment 2 describes a rubber product of the present invention. The rubber product of the present invention includes at least one rubber reinforcing cord described in the first embodiment. The rubber reinforcing cord may have a rope structure. In addition, a plurality of rubber reinforcing cords are It may be embedded.

[0032] The rubber product of the present invention is not particularly limited as long as the rubber product is effectively reinforced by a rubber reinforcing cord. Representative examples of the rubber product of the present invention include, for example, a toothed belt and a moving belt, a tied rubber belt, and a rubber crawler.

[0033] In the rubber product of the present invention, the ratio of the rubber reinforcing cord in the rubber product is, for example, about 10 to 170 mass%.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. In this example, rubber reinforcing cords of the present invention and a comparative example were produced, and their characteristics were evaluated.

[0035] (Sample 1)

The rubber reinforcing cord of the present invention was produced by the following method. First, a resorcinol-formaldehyde condensate (solid content 8% by mass), vinylpyridine styrene butadiene latex (solid content 40% by mass), and CSM (solid content 40% by mass) were mixed at a solid content ratio of 2:13. : 6 to prepare an RFL treatment solution. This RFL treatment solution was applied to a strand (diameter of about 0.8 mm, non-woven) composed of polyarylate fiber (Kuraray Co., Ltd., Vectran (trade name), elastic modulus of 106 GPa, density of about 1.41 g / cm ³ ). After being applied to the twisted product, it was dried by heat treatment (at 180 ° C. for 120 seconds). Thus, an RFL-treated core strand (RFL adhesion amount: 20% by mass) was obtained.

On the other hand, a bundle of 600 glass fibers (Nippon Sheet Glass Co., Ltd., E-glass, diameter 9 μm, elastic modulus 70 GPa, density about 2.5 gZcm ³ ) was impregnated with the RFL treatment solution, It was dried by heat treatment (at 180 ° C. for 120 seconds). Thereafter, the strand was twisted 2.0 times in the S direction at a ratio of Z25 mm to obtain a glass fiber strand of about 100 tex (RFL adhesion amount: 20% by mass).

[0037] Next, nine glass fiber strands were arranged around the core strand after the RFL treatment so as to have the arrangement shown in Fig. 1, and further twisted 2.0 times in the Z direction at a rate of Z25mm. And got Code 1A. Cord 1A had a diameter of about 1.20 mm. The ratio of the cross-sectional area of the polyarylate fiber to the total cross-sectional area of the fiber was 45%.

[0038] Next, a treatment solution for overcoating of the components shown in Table 1 below was applied to Code 1A. Dry to obtain Code IB. The solids deposition rate of the overcoat treatment liquid on Code 1B was 5% by mass. Also, the count (weight (g) per 1000 m length) of the cord 1B was 1 580 tex (gZl000m). The tensile strength and elongation at break (%) of the obtained cord 1B were measured. The tensile strength (initial) per cord 1B was 1250NZ cord, and the elongation at break was 3.2%.

[table 1]

[0040] Also, a rubber sheet (width 10 mm, length 300 mm, thickness lmm) having the components shown in Table 2 below was used.

Two sheets were prepared.

[Table 2]

[0042] Then, one cord 1B having a length of 300 mm was arranged on one rubber sheet, and another rubber sheet was stacked thereon. These were press-vulcanized from above and below at 150 ° C for 20 minutes. Thus, a strip-shaped test piece was produced.

Next, this test piece was subjected to a bending test using a bending test machine 20 shown in FIG. The bending tester 20 has one flat pulley 21 having a diameter of 25 mm, a motor (not shown), and four guides. And a pulley 22. First, the manufactured test piece 23 was hung on five pulleys. Then, a weight was attached to one end 23a of the test piece 23 to give the test piece 23 an initial tension of 9.8N. In this state, the other end 23b of the test piece 23 was reciprocated 10,000 times in the direction of the arrow in FIG. 2 with a movement width of 10 cm, and the test piece 23 was repeatedly bent at the flat pulley 21. The bending test was performed at room temperature. After performing the bending test on the test piece 23 in this way, the tensile strength of the test piece after the bending test was measured. Then, when the tensile strength of the test piece before the bending test was set to 100%, the retention rate (%) of the tensile strength of the test piece after the bending test was determined. The higher the value of the retention ratio of the tensile strength, the better the flex fatigue resistance. The bow I tension strength retention of the test piece of sample 1 was 85%.

[0044] (Sample 2)

Sample 2 is different from Sample 1 in that the core strand is knitted with a lower twist. Here, the RFL treatment solution was applied to the strand of the polyarylate fiber used in Sample 1, 2.0 times of twisting was applied at a rate of Z25 mm, and heat treatment was performed to produce a core strand. A code 2A was produced in the same manner as the code 1A of the sample 1, except that the obtained core strand was used.

[0045] The obtained code 2A was subjected to an overcoat treatment in the same manner as in sample 1, to obtain code 2B. The tensile strength and elongation at break (%) of the cord 2B were measured. The tensile strength (initial) per cord 2B is 1200NZ code, and the elongation at break is 3.0%.

Further, a test piece for a bending test was prepared using the cord 2B in the same manner as in the sample 1, and a bending test was performed. The tensile strength retention (%) of the test piece after the bending test was determined.

[0047] (Comparative sample 1)

After bundling and twisting 11 glass fiber strands prepared in Sample 1, overcoat treatment was performed in the same manner as in Sample 1 to prepare a cord of Comparative Sample 1. For this cord, the initial tensile strength and elongation at break (%) were measured. In addition, using the cord of Comparative Sample 1, a test piece for a bending test was prepared and a bending test was performed in the same manner as in Sample 1, and the tensile strength retention (%) of the test piece after the bending test was determined. .

[0048] (Comparative sample 2) Two strands of the polyarylate fiber used in Sample 1 were prepared, subjected to RFL treatment, and then twisted. Next, the obtained two strands were bundled and twisted. The cord thus obtained was subjected to an overcoat treatment in the same manner as in Sample 1 to prepare a cord of Comparative Sample 2. The initial tensile strength and elongation at break (%) of this cord were measured. Also, using the cord of Comparative Sample 2, a test piece for the bending test was prepared and a bending test was performed in the same manner as Sample 1, and the bow I tensile strength retention (%) of the test piece after the bending test was determined. I asked.

[0049] (Comparative sample 3)

The polyarylate fiber and glass fiber used in Sample 1 were mixed without being divided into a core strand and an outer strand, and twisted. The number of twists was 2.0 times Z25mm. The cord thus obtained was subjected to an overcoat treatment in the same manner as in Sample 1 to prepare a cord of Comparative Sample 3. For this cord, the initial tensile strength and the elongation at break (%) were measured. Also, using the cord of Comparative Sample 3, a test piece for a bending test was prepared and a bending test was performed in the same manner as in Sample 1, and the tensile strength retention (%) of the test piece after the bending test was determined.

[0050] Table 3 shows the evaluation results of the five types of samples thus obtained.

[Table 3]

As shown in Table 3, with the cord using only polyarylate fiber or glass fiber as the reinforcing fiber, the initial strength and the strength after the bending test were low. In Comparative Sample 3 where glass fiber strands were not arranged around the polyarylate fiber strand, , The elongation at break and the strength after the bending test were not sufficient. In particular, in Comparative Sample 3, the elongation at break was large. A cord having a large elongation at break has a problem that the dimensional stability is low and the tooth portion is likely to be damaged when used for a toothed belt. Therefore, it is preferable that the elongation at break is as small as possible. In sample 2 in which the polyarylate fiber strand was ply-twisted, the elongation at break could be particularly reduced.

On the other hand, the reinforcing cord of the present invention in which the glass fiber strand was disposed around the polyarylate fiber strand had a high initial strength, a small elongation at break, and a high tensile strength retention after the bending test. These values were significantly higher than Comparative Sample 3, which simply combined polyarylate fiber and glass fiber.

Industrial applicability

INDUSTRIAL APPLICABILITY The present invention can be applied to a rubber reinforcing cord suitable for reinforcing various rubber products. The present invention can be applied to various rubber products reinforced by the rubber reinforcing cord of the present invention, and can be applied to, for example, a rubber belt such as a toothed belt or a moving belt, or a rubber crawler.

Claims

The scope of the claims

[I] A rubber reinforcing cord including a reinforcing fiber,

The reinforcing fibers include polyarylate fibers, and a plurality of outer strands disposed around the polyarylate fibers,

A rubber reinforcing cord in which the outer strands include fibers other than polyarylate fibers.

[2] The rubber reinforcing cord according to claim 1, wherein a ratio of the polyarylate fiber to the reinforcing fiber is in a range of 20% by volume to 80% by volume.

[3] The rubber reinforcing cord according to [1], wherein the polyarylate fiber comprises a strand of polyarylate fiber.

4. The rubber reinforcing cord according to claim 3, wherein the outer strand is a glass fiber strand.

[5] The rubber reinforcing cord according to claim 1, wherein the outer strand is twisted.

[6] The rubber reinforcing cord according to claim 5, wherein the plurality of outer strands are twisted around the polyarylate fiber as a core.

7. The rubber reinforcing cord according to claim 1, wherein the outer strand has a lower elastic modulus than the polyarylate fiber and is made of fiber.

[8] The rubber reinforcing cord according to claim 1, wherein the surface is coated with a coating film containing rubber.

[9] A rubber product comprising the rubber reinforcing cord according to claim 1.

10. The rubber product according to claim 9, wherein a plurality of the rubber reinforcing cords are arranged in a plane and embedded.

[II] The rubber product according to claim 9, which is a rubber belt or a rubber crawler.