JPS62149977A - Treated carbon fiber cord for reinforcing rubber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Technical Field) The present invention is directed to carbon II for rubber reinforcement, which has excellent adhesion to rubber.
Regarding N code.

(Prior art) Traditionally, rubber reinforcing cords have been made of rayon, polyamide, polyester, etc., but recently organic fibers such as aramid have also been used, and inorganic fibers such as glass fibers and steel fibers have been used recently.
! i fiber is used.

In particular, rubber reinforcing cords used in tires are important for improving tire maneuverability, running stability, riding comfort, and tire durability.
From the viewpoint of fuel efficiency, high strength, high elasticity, and light tIa
Preferably, it is made of IIi material.

Carbon fibers are superior in specific elastic modulus and specific strength compared to the above reinforcing m-fibers, and have characteristics that allow extremely excellent rubber reinforcing cords to be made. However, carbon 11f
Since fl has the drawback of insufficient adhesion to rubber, various improvements have been made in the past. For example, a method of manufacturing a reinforcing cord by impregnating carbon fiber with an elastomer and twisting it (US Pat. No. 3,648,452)
No. specification) and carbon IIA miscellaneous are treated with an epoxy compound,
Next, treatment is performed with an adhesive such as a mixture of resorcin formaldehyde condensate and rubber latex (RFL) (Japanese Unexamined Patent Publication No. 50-102678), or with a first treatment bath containing polyisocyanate, followed by treatment with a first treatment bath containing RFL. According to the study of the present inventors, the cause of this problem is insufficient adhesive strength between the carbon fiber and the elastomer, epoxy resin, isocyanate, etc. Even if the adhesive strength is sufficient, it will become integrated with carbon mH and become a rigid cord lacking flexibility, and the carbon fibers will break when subjected to fatigue such as stretching, compression, and bending, resulting in poor fatigue properties. This is because it has the disadvantage of becoming.

(Object of the Invention) The present inventors have conducted studies to solve the above-mentioned drawbacks of the prior art, and as a result, have arrived at the present invention. An object of the present invention is to provide a cord that exhibits appropriate adhesive strength between carbon am and rubber, and that does not become excessively rigid when integrated with carbon fibers.

(Structure and operation of the invention) The structure of the present invention is to use glycidyl group-containing polybutadiene having an epoxy equivalent of 1000 to 2000 in a range of 0.1 to 1.
0 wt 1f)% and further a mixture of resorcin formaldehyde condensate and rubber latex (RFL)
This is a rubber-reinforcing carbon fiber treated cord with 25% by weight attached.

The glycidyl group-containing polybutadiene used in the present invention has a chemical structure represented by the general formula, where n is 4 to 22, and Q/
m = 2.3-9.

The epoxy equivalent is 1000-2000. If the 1 boxy equivalent is less than 1,000, the adhesion to carbon fibers is good, but the resulting cord after being served with RFL becomes hard, which is not preferable. Moreover, when it exceeds 2ooo, the adhesive force with carbon fiber becomes low, which is not preferable.

The amount of polybutadiene deposited is 0.1 to 1.0% by weight. If it is less than 0.1% by weight, adhesion is insufficient. If necessary, the polybutadiene used in the present invention may include other polybutadienes, such as those in which the terminal glycidyl ether group of formula (1) is replaced with a hydroxyl group or carboxyl ether group, and whose molecular weight is within the range of the compound of formula (1). Although polybutadiene can be mixed, the amount is preferably 30% by weight or less from the viewpoint of maintaining adhesive strength with carbon fibers.

In addition, if necessary, it is also possible to use a catalyst that causes the ring-opening reaction of the epoxy group to the polybutadiene of formula (1),
For example, imidazole catalysts such as dicyandiamide and 2-ethyl-4-methylimidazole, etc.
~5% by weight can also be used.

In the present invention, the method for adhering the polybutadiene (1) to the carbon IjJ may be a conventional dipping method, a transfer method from a roller surface, a spray method, etc., and will be explained below with an example.

Usually, a mixture of the polybutadiene of formula (1), other polybutadiene, and a catalyst if necessary is dissolved in ethyl acetate, methyl ethyl ketone, or acetone, which is a solvent for the polybutadiene of formula (1). After immersing the carbon fibers in the bath, the solvent is removed by heating above the boiling point of the solvent, and the polybutadiene of formula (1) is mixed with 1 μl of carbon.
The amount of adhesion is 0.1 to 1.0% by weight based on the total weight of the particles and the deposits. Preferably, it is preferable to use a polybutadiene system containing a catalyst and heat it at 120 to 140° C. for 1 to 10 minutes after deposition to improve adhesion.

In the present invention, the carbon fibers used are usually composed of 100 to 1,000 single fibers with a diameter of 5 to 10 μm, a tensile strength of 150 k (lr/11111' or more, and a tensile modulus of 10 x 10"). The strand has a weight of kgf/mm' or more.

Then, charcoal mIa attached with polybutadiene of formula (1)
A mixture of resorcin formaldehyde condensate and rubber latex (RFL) is applied to m. RFL usually has a molar ratio of resorcin and formaldehyde of 1:0, 1 to 1.
:8, preferably in the range of 1:0.5 to 1:5,
In addition, natural rubber latex, styrene/butadiene copolymer latex, vinylpyridine/styrene/butadiene terpolymer latex, nitrile rubber latex, etc. may be used alone or in combination as rubber latex. Vinylpyridine-styrene-butadiene terpolymer latex is preferred because it has excellent adhesion to rubber.

The amount of RFL deposited may be as long as it can achieve adhesion to the rubber, but is preferably 10 to 25% by weight. When the amount is less than 10% by weight, the single fibers of the carbon fiber strand tend to be difficult to be sufficiently coated, and tend to become hard and have lower resistance to bending. The blending ratio of the resorcin formaldehyde condensate and the rubber latex is 1:1:1 to -1+15 for the solid content type, preferably 1:3.
~1:12.

A method for preparing carbon fibers to which RFL is attached is, for example, as follows. 1 for a 10-35% weight dispersion of RFL.
After soaking the carbon fibers with the polybutadiene of formula (1) attached at 0 to 25°C, adjust the amount of adhesion with a squeezing roller if desired, then drying in air at 80 to 110°C for 2 to 3 minutes, and further It can be obtained by heat treatment at 200 to 230°C for 1 to 2 minutes, but preferably, after drying, it is immersed in the same RFL liquid again and subjected to dry heat treatment under the same conditions to obtain the carbon gimm and the formula (1). RFL is applied in an amount of 10 to 25 wt % with respect to the total amount of polybutadiene adhesion m and RFL adhesion.

(Effects of the Invention) The carbon fiber treated cord of the present invention has a structure that has a layer that properly adheres to carbon fibers and maintains flexibility, and a layer that has good adhesion between the layer and rubber. It is possible to make a rubber reinforcing material with excellent resistance to repeated fatigue, especially a reinforced tire that takes advantage of the high specific strength and specific modulus of carbon fiber.

(Example and comparative example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Unless otherwise specified, "%" and "part" are expressed by weight.

In the Examples, the adhesive strength between carbon fiber and rubber was measured by a pull-out test and a two-ply peel force test as described below.

In addition, in order to measure the bending fatigue properties of carbon fibers, a bending fatigue test was conducted in the manner described below.

Pull-out test After vulcanization at ℃ for 30 minutes, the adhesive strength was determined by a pull-out test in which the force of pulling the cord from the vulcanized rubber was measured.

2-ply Sesame test Width 25 mm, length 2 of the unvulcanized rubber compound shown in Table 1 below
00III111 On the surface layer of a rubber sheet with a thickness of 1.0 mm, 20 cords are arranged in parallel in the longitudinal direction of the rubber sheet, covered with the above rubber sheet, and then 20 cords are similarly placed on top of the rubber sheet. After arranging them in parallel in the longitudinal direction, they are covered again with a rubber sheet to produce a laminate of rubber/cord/rubber/cord/rubber with a so-called two-ply structure.
After vulcanization at 150°C for 30 minutes under a pressure of 30 kg/am', a peel test was conducted to peel off the cord layers to determine the adhesive strength of each cord, and the state of the peeled interface was observed.

Figure 1 shows the shape of the sample used here. In Figure 1, a
is a rubber layer, b is a cord layer, and peeling is performed between the cord layers along the longitudinal direction of the cord.

Bending fatigue test In order to measure the bending fatigue properties of the cord in rubber, a so-called demature bending fatigue test was conducted in which the cord was embedded in rubber and bent with a constant stroke.

The compounded rubber shown in Table 1 was used as the rubber.

The rubber blocks that were subjected to the demarcher type flexural fatigue test had a width of 25 mm. b 5 mm, three cords were embedded therein in the longitudinal direction of the rubber block at intervals of 6.35 mm, and prepared by vulcanizing at 148° C. for 30 minutes.

After bending this rubber block 100,000 times with a stroke of 30 mm, the rubber block was divided into three equal parts, a rubber block with a cord was collected, and the rubber block with a cord was pulled and bent at a pulling speed of 300 mm/min and a chuck opening of 930 mm. The bending fatigue resistance of the cord was determined by determining the tensile strength after that and determining the 100% of the tensile strength when not fatigued.

Table 1 Rubber compound natural rubber R8
S#3 100 parts zinc flower
5-part stearic acid
2 parts carbon black (GPF
) 50 parts anti-aging agent *1
1 part aromatic oil 7 parts sulfur 2.2
5 parts vulcanization accelerator o+v+*2 1 part (
Note): 1τ1 Zantflex 13 (manufactured by Ryo Mon Sando Co., Ltd.) *2 Dibenzothiazyl disulfide Examples 1 to 2 and Comparative Examples 1 to 2 2 to 18 g of polybutadiene with an epoxy equivalent m of 1400 was dissolved in methyl ethyl ketone (MEK). A solution of /β was prepared and added to it was a 3600 denier carbon from a 6000 filament with a diameter of 7 μm. Klt (tensile strength 380kgf/ml'
, tensile modulus of elasticity 24 x 10'kgf/mm', Besphite 1'' FA, Toho Rayon Format) was continuously immersed to adhere the resin as shown in Table 3, and dried at 60°C.

The obtained carbon fibers were continuously immersed at 25°C in a bath with a 20% concentration of RFL having the composition shown in Table 2 to coat them with RF L. After drying at 85°C for 2 minutes, they were heat-treated at 215°C for 2 minutes to form RFL.
A bonded carbon fiber treated cord was obtained.

When this material was subjected to a pull-out test, a two-ply peel test, and a bending fatigue test, the results shown in Table 3 were obtained.

According to the results, it can be seen that within the range of the present invention, excellent adhesion to rubber and fatigue resistance are exhibited.

Table 2 RFL softening water 3
87.6 parts Sodium hydroxide (10% aqueous solution) 6.3 parts Resorcinol 23.1 parts Formalin (37%) 25.6 parts Bipol 2518F S (40%)*1 543.5 parts Aqueous ammonia (28%) 13.9 copies total
1000.0 parts (Note) *1 Vinylpyridine/l-styrene/butadiene copolymer rubber latex (manufactured by Nippon Zeon Co., Ltd.) Table 3 (Note) 2-ply peeling force ( ) indicates the fractured interface state, and 100 is 100% The value is the best for rubber breakage, and 0 indicates the worst for adhesive layer breakage.

Example 3 and Comparative Examples 3 to 4 Epoxy equivalents are 800.1500.2800, respectively.
The MEK bath concentration was increased to 11o/
R, and the carbon fiber is 3000 made of 7 μm single #A fiber.
Filament, 1800 denier carbon fiber II (tensile strength 390 kgf/l11 m', tensile modulus 23.9X
■ 101k (If /am2, Best Fight l-I T
RFI-
A carbon fiber treated cord was created by adhering 17% of the carbon fiber.

The obtained cord was made into a double yarn with 7 twists of 10 times/Ill on the bottom side and S twists of 10 times/m on the top side, and then it was subjected to drawing, 2-ply peeling, and bending fatigue tests. As shown in Table 4, the cords according to the present invention exhibited excellent adhesion to rubber and fatigue resistance.

Note that the cord using epoxy equivalent of 800 was very hard, and the cord using 2800 was found to be flexible, but
Test results with rubber were poor.

Table 4 (Note) The values in parentheses for 2-ply peeling force are the same as those in Table 3 (Note) Example 4 M1 was prepared by mixing 0.3% of 2-ethyl-4-methylimidazole with the polybutadiene used in Example 1. A bath was prepared by dissolving aI BQ/Q in 3K, and the carbon fibers used in Example 1 were immersed in the bath at 60°C.
The carbon IJi fibers with an adhesion amount of 0.4% are removed, and this is 1
It was heat-treated in air at 50° C. for 3 minutes, and then treated in the same manner as in Example 2 to obtain an RFI-attached carbon fiber cord.

The obtained cord had 18.3% RFL attached and was pulled out.
In each of the braking peeling and bending fatigue tests, the results were 18.
2k(1,24,8(90)), 87%, indicating excellent adhesive strength and high bending fatigue resistance.

Example 5 A carbon fiber cord was produced in the same manner as in Example 4 except that 1.0% of dicyandiamide was used instead of 2-ethyl-4-methylimidazole.

The pull-out force, 2-ply peeling force, and flexural fatigue strength retention rate of this product were measured and found to be 18.5 kQ.

A value of 25.3 (89), 88% was obtained, and the product showed high adhesive strength and flex fatigue resistance.

Example 6 and Comparative Examples 5 and 6 Except for setting RFL side dishes to 8%, 21%, and 21%,
A carbon fiber treated cord was created in exactly the same manner as in Example 3.

When the pulling force, 2-ply peeling force, and bending fatigue strength retention rate of the obtained cord were measured, as shown in Table 5, excellent values were shown within the range of the present invention.

Table 5 (Note) The value in parentheses for 2-ply peeling force is the same as the note in Table 3.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the shape of a sample used in a 2-ply peel test. a...Rubber layer, b...Cord layer. Figure 1 Procedural Amendments December 5, 1986

Claims (3)

[Claims] (1) 0.1 to 1.0% by weight of glycidyl group-containing polybutadiene having an epoxy equivalent of 1000 to 2000 is attached, and a mixture of resorcin formaldehyde condensate and rubber latex (hereinafter, this mixture is referred to as "RFL") Carbon fiber treated cord for rubber reinforcement. (2) The carbon fiber treated cord for rubber reinforcement according to claim (1), wherein the amount of RFL attached is 10 to 25% by weight. (3) The carbon fiber treated cord for rubber reinforcement according to claim (1), wherein the polybutadiene is a mixture of 0.1 to 5% by weight of 2-ethyl-4methylimidazole or dicyandiamide.