JPH1044251A - Cord-rubber composite and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a code/rubber composite excellent in cord dimensional stability and the adhesiveness of a cord and rubber. SOLUTION: A cord/rubber composite is obtained by treating a cord consisting of acrylic fibers with tensile strength of 5g/d or more with an aq. mixed soln. (RFL) and embedding this treated cord in an unvulcanized rubber compsn. and vulcunizing the whole to integrate the same. The cord/rubber composite is produced by adding at least RFL to the cord consisting of acrylic fibers with tensile strength of 5g/d or more and heat-treating this code to embed the same in an unvulcanized rubber compsn. to vulcanize and integrate the whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cord / rubber composite which can be used as rubber articles such as tires, conveyor belts, hoses, etc., and has excellent cord dimensional stability and adhesion between cord and rubber, and a method for producing the same. About.

[0002]

2. Description of the Related Art In a pneumatic tire, a carcass member having a skeleton structure is a cord / rubber composite, and polyester or rayon is conventionally used as the cord. In addition, this carcass cord has a tensile modulus, tensile strength, dimensional stability, adhesiveness with rubber,
From the viewpoint of manufacturing, characteristics such as productivity and economy are also required.

At present, the most widely used polyester cord is inexpensive as a raw material and has excellent strength and elastic modulus. However, conventionally, a so-called two-bath treatment in which, for example, an epoxy resin treatment is performed beforehand and then an RFL treatment is applied to the polyester cord in order to enhance adhesiveness with rubber is applied, so that productivity is poor and economic efficiency is poor. There's a problem.

On the other hand, rayon cords may be treated in a single bath, and have good adhesion to rubber, tensile modulus and dimensional stability, but have a large decrease in strength and modulus due to moisture absorption. Furthermore, the use of CS ₂ during the production of rayon has a problem that it has an adverse effect on the environment, and the production scale of rayon tends to be reduced worldwide. Therefore, development of new materials that can be substituted for these codes has been required. Acrylic fibers, which are the world's three largest synthetic fibers alongside polyester fibers and nylon fibers, have traditionally been poor in strength and have been rarely used as industrial materials. Is expected to be used.

For example, techniques for producing high-strength acrylic fibers are disclosed in JP-A-1-104816 and 1-104817.
Japanese Patent Application Laid-Open Nos. 1-104819, 1-108820, and JP-A-61-119710. However, no knowledge has been obtained on the method of bonding high-strength acrylic fibers to rubber and the dimensional stabilization technology essential for applying these high-strength acrylic fibers to tires, conveyor belts, hoses and the like.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a tire using a high-strength acrylic fiber, which has not been known at all in the art of compounding with rubber, that is, adhesion technology and dimensional stabilization technology. Carcass and belt materials,
Another object of the present invention is to provide a cord / rubber composite applicable to a reinforcing layer such as a conveyor belt and a method for producing the same.

The present inventors have conducted intensive studies on a cord / rubber bonding technique and a cord treatment method in order to apply a high-strength acrylic fiber to a cord / rubber composite. As a result, the present inventors have accomplished the present invention.

[0008]

The cord / rubber composite of the present invention comprises a cord composed of an acrylic fiber having a tensile strength of 5 g / d or more, and a precondensate (RF) of resorcinol (R) / formaldehyde (F). And treated with an aqueous mixed solution (RFL) of rubber latex (L), the treated cord is embedded in an unvulcanized rubber composition, and vulcanized and integrated.

Since the cord made of the acrylic fiber treated with RFL is used as described above, the adhesiveness between the cord and the rubber can be improved. In addition, the tensile strength is 5 g /
By using a cord made of an acrylic fiber of d or more, rubber can be sufficiently reinforced. In addition, the method for producing a cord / rubber composite of the present invention is characterized in that an aqueous mixed solution (RFL) of an initial condensate (RF) of resorcinol (R) / formaldehyde (F) and a rubber latex (L) has a tensile strength of 5%.
It is characterized in that the cord is made to adhere at least to a cord made of acrylic fiber of g / d or more, and then this cord is heat-treated, then embedded in an unvulcanized rubber composition, and vulcanized and integrated. As described above, it is only necessary to perform the one-bath treatment in which the RFL is attached to the cord, so that the productivity can be increased.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The high-strength acrylic fiber used in the present invention is acrylonitrile in a weight ratio of 40 to 100.
%, A fiber having a tensile strength of 5 g / d or more, preferably 7 g / d or more.
g / d or more. If the tensile strength is less than 5 g / d, the strength of the cord is reduced and it is not suitable as a reinforcing material.

The aqueous mixed solution (RF) used in the present invention
In the precondensate (RF) of resorcinol (R) / formaldehyde (F) in L), resorcinol (R) and an aqueous solution of formalin are dissolved in water, and an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is added thereto. There is a resol type in which R and F are reacted by adding a product as a catalyst, or a novolak type in which R and F are reacted in the presence of an acidic catalyst such as oxalic acid or hydrochloric acid, and any of them may be used. .
As the novolak-type precondensate (RF), Sumikanol 700 manufactured by Sumitomo Chemical Co., Ltd. and Adher RF manufactured by Hodogaya Chemical Industry Co., Ltd. are commercially available. When these novolak type RF resins are used, it is necessary to add a small amount of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to dissolve the RF resin in water. Usually, these novolak type RF
When a resin is used, it is necessary to add a formalin aqueous solution later.

The rubber latex (L) to be mixed with the precondensate (RF) is appropriately selected according to the type of rubber of the unvulcanized rubber composition in which the cord is embedded. For example, natural rubber (N
R), styrene-butadiene copolymer rubber (SBR),
For general-purpose rubbers such as isoprene rubber (IR) and butadiene rubber (BR), vinyl pyridine / styrene / butadiene terpolymer latex, SBR latex, natural rubber latex and the like are used. From the viewpoint of adhesion, it is desirable to use a vinylpyridine / styrene / butadiene terpolymer latex, but an SBR latex or a natural rubber latex can be appropriately mixed and used.
When the adhered rubber is chloroprene rubber (CR) or acrylonitrile-butadiene copolymer rubber (NBR), CR latex, NBR latex, or a mixture of these with vinyl pyridine / styrene / butadiene terpolymer latex may be used. it can. The choice of latex can be appropriately selected according to the type of rubber to be adhered.

Here, as the RFL, R, F, and L can be used in any ratio, but from the viewpoint of adhesion to rubber, the molar ratio of R to F is R / F = 0.28 to 0.67. And the weight ratio RF / L between RF and L = 0.25-0.35
It is preferred that When R / F is less than 0.28,
When it exceeds 0.67, the adhesion to rubber is inferior. Similarly, when RF / L is less than 0.25 or more than 0.35, the adhesion to rubber is significantly reduced.

The cord / rubber composite of the present invention is characterized in that the above-mentioned RF
A cord made of an acrylic fiber having a tensile strength of 5 g / d or more treated with L is embedded in an unvulcanized rubber composition and vulcanized and integrated. In order to manufacture this cord / rubber composite, first, the RFL is attached at least to a cord made of an acrylic fiber having a tensile strength of 5 g / d or more. At least, for example, the cord may be immersed in the RFL to impregnate or apply RFL to the cord.

Next, the cord to which the RFL is attached is heat-treated. This heat treatment is performed, for example, after drying the RFL adhesion cord at 80 to 150 ° C. and 150 to 215 ° C.
The heat treatment is performed at a temperature of As the heat treatment, for example, it is preferable to perform a heat setting process at a temperature of 150 to 215 ° C. and then perform a normalizing process at a temperature of 150 to 215 ° C. Here, it is preferable that the heat setting tension (HS) is HS ≧ 0.2 g / d and the normalizing tension (NL) is NL ≦ 0.2 g / d.
If the HS is less than 0.2 g / d, the strength of the obtained processing code is reduced. If the NL is larger than 0.2 g / d, the resulting treatment code is inferior in dimensional stability, which tends to shrink when heat is applied.

Here, the heat setting treatment means an operation of drawing while heating the fiber (heat drawing treatment). RFL
And to increase the dimensional stability and strength of the cord. The normalizing treatment refers to a second heat treatment performed with a slight reduction in tension next to the heat drawing treatment (heat setting treatment) in order to remove fiber distortion generated during heat drawing by the heat setting treatment. . The cord thus heat-treated is embedded in an unvulcanized rubber composition and vulcanized and integrated by a conventional method to obtain a cord / rubber composite.

[0017]

EXAMPLES RFL treatment liquids (adhesive liquids) having a solid content of 20% and varying R / F ratios and RF / L ratios were prepared according to the contents (parts by weight) shown in Tables 1 and 2. A 1100 d / 2 acrylic fiber cord obtained by adding a twist of 46 × 46 to a yarn having a tensile strength of 7.8 g / d was dipped in these adhesive liquids, and
After drying at 30 ° C., heat set treatment and normalization treatment were performed under the tension conditions shown in Tables 4, 5, and 6. The temperature and the processing time were set at 180 ° C. and 1 minute, respectively.

The rayon used for comparison was 1650 d /
The adhesive liquid D1 shown in Table 1 was impregnated and coated, dried at 130 ° C., and heat-set and normalized at 180 ° C. for 1 minute at a tension of 0.25 g / d. The polyester used for comparison was 1000d / 2, 46x46. The adhesive solution D10 shown in Table 2 was impregnated, dried at 130 ° C, heat-set at 235 ° C, and then impregnated with D1. Dry at 130 ° C, normalize at 235 ° C 2
A bath treatment was performed. The tension of the heat set and the normalizing treatment was 0.25 g / d, and the treatment time was 235 ° C., 1
Minutes.

The treated cord was subjected to a peeling test in accordance with JIS K6256. Further, the tensile strength of the cord was determined in accordance with JIS L1017 chemical fiber tire cord test method. Further, the elongation percentage E at 2.25 g / d of the treated cord and the dry heat shrinkage percentage S at 150 ° C. were respectively obtained, and the sum of these was calculated as an index of dimensional stability. The results of the peeling test are shown in Tables 4 and 5, and the results of the physical properties of the treated cord are shown in Table 6. In these tests, the treatment cords were arranged in parallel with the length direction of the test piece at intervals of 70 wires / 5 cm, embedded in the unvulcanized rubber composition shown in Table 3, and vulcanized at 148 ° C. for 30 minutes. Samples were used (Experimental Examples 1 to 14, Comparative Examples 1 and 2).

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

[Table 6]

From Tables 4 and 5, it can be seen that the adhesiveness between the acrylic fiber cord and the rubber is equal to or higher than that of the polyester cord by using RFL as the adhesive liquid. Also,
The effect of the mixing ratio of RFL on the adhesiveness is as follows: R / F =
It can be seen that the peeling force decreases when it is less than 0.28 and more than 0.67. When RF / L is less than 0.25 and when it is more than 0.35, the peeling force is also reduced. In order for the peel strength of the acrylic fiber cord to achieve a peel strength of rayon or more, R / F = 0.28 to 0.6.
7, and RF / L = 0.25 to 0.35,
Therefore, it is desirable that the R / F and the RF / L ratio be in this range.

From Table 6, it can be seen that the acrylic fiber cord is superior in both the strength and the elastic modulus when compared with the rayon cord and the polyester cord. As a tension condition at the time of heat treatment, heat set tension (HS) is HS <0.
In the case of 2 g / d, although both strength and modulus are superior to rayon and polyester, these values are all H
It is lower than the case where S ≧ 0.2 g / d. Further, the normalized tension (NL) at the time of heat treatment is set to NL ≦ 0.2 g / d
By doing so, it is understood that the sum E + S of the intermediate elongation E and the dry heat shrinkage S, which is an index of the dimensional stability, can impart dimensional stability that is clearly superior to polyester, comparable to rayon. As described above, in order to satisfy strength, elastic modulus and dimensional stability at a higher order, it is desirable that the tension conditions HS and NL at the time of heat treatment satisfy NL ≦ 0.2 g / d and HS ≧ 0.2 g / d, respectively. .

[0028]

As described above, according to the present invention, by applying a specific treatment to a high-strength acrylic fiber cord, an acrylic fiber which has not been obtained at all in the past in terms of compounding with rubber has been obtained. It is possible to provide a cord-rubber composite having high strength, high modulus, excellent dimensional stability of the cord, and excellent adhesion between the rubber and the cord, using the cord comprising:

Claims (6)

[Claims] 1. A cord composed of an acrylic fiber having a tensile strength of 5 g / d or more is prepared by using an initial condensate (RF) of resorcinol (R) / formaldehyde (F) and a rubber latex (L).
A cord / rubber composite obtained by treating with an aqueous mixed solution (RFL), embedding the treated cord in an unvulcanized rubber composition, and vulcanizing and integrating the cord. 2. The RF in the aqueous mixture (RFL)
The cord / rubber composite according to claim 1, wherein the weight ratio of R and F is RF / L = 0.25 to 0.35, and the molar ratio of R and F is R / F = 0.28 to 0.67. 3. In the RFL treatment, heat set treatment and normalization treatment are performed as heat treatment, and the heat set tension (HS) at that time is HS ≧ 0.2 g / d.
And the normalized tension (NL) is NL ≦ 0.2
The cord / rubber composite according to claim 1 or 2, wherein the cord / rubber composite is g / d. 4. A cord comprising an aqueous mixed solution (RFL) of an initial condensate (RF) of resorcinol (R) / formaldehyde (F) and a rubber latex (L), comprising an acrylic fiber having a tensile strength of 5 g / d or more. At least,
Then, the cord is subjected to a heat treatment, and then embedded in an unvulcanized rubber composition and vulcanized and integrated to produce a cord / rubber composite. 5. The RF in the aqueous mixture (RFL)
5. The cord / rubber composite according to claim 4, wherein the weight ratio of R and F is RF / L = 0.25 to 0.35, and the molar ratio of R and F is R / F = 0.28 to 0.67. Production method. 6. A heat setting treatment and a normalizing treatment are performed as the heat treatment, and the heat setting tension (HS) at that time is set to HS ≧ 0.2 g / d and the normalizing tension (NL) is set to NL ≦ 0.2 g. / D
Or a method for producing a cord / rubber composite according to item 5.