JP6850644B2 - How to manufacture high-strength dip cord - Google Patents

Description

The present invention relates to a method for manufacturing a high-strength dip cord. More specifically, the present invention relates to a method for manufacturing a high-strength dip cord that can minimize the strong loss generated in the dip cord manufacturing process and bring out the maximum strength in the cord structure.

High-strength and low-elongation aramid fiber cords are embedded in rubber products such as power transmission belts, rubber hoses, and tires to reinforce the rubber. As the rubber reinforcing aramid fiber cord, a plurality of aramid fiber raw yarns are aligned to form a twisted yarn, which is immersed in an adhesive treatment liquid such as resorcin, formalin, and rubber latex (hereinafter referred to as "RFL") solution. , Those with adhesiveness to rubber are known.

However, since aramid fibers (particularly para-aramid fibers) have a high elastic modulus, there is a problem that the strength of the cord after twisting and the dip cord after the adhesive treatment is remarkably lowered when filament alignment failure occurs. Therefore, according to Patent Document 1, a high-strength plying cord can be obtained by drying the raw yarn of the aramid fiber to the official moisture content or less and then twisting the yarn so that the twist coefficient T becomes 1.0 to 10. Has been proposed.

Further, since the aramid fiber generally has very low fatigue characteristics, the running performance of the tire may be deteriorated. Therefore, in Patent Document 2, when the aramid twisted yarn is dipped in the adhesive solution, the strong retention rate after the disc fatigue test is increased by applying a tension of 0.2 to 5 kg / cord to the aramid twisted yarn. Has been proposed. In this case, it has been reported that when the tension exceeds 5 kg / cord, the strength at a 3% elongation rate exceeds 8 g / d, the penetration rate of the adhesive into the plyed yarn is low, and the strength retention rate is low. There is.

The method of Patent Document 1 improves the poor alignment between filaments due to the high water content of the aramid fiber, thereby suppressing a strong decrease after twisting. The method of Patent Document 2 suppresses a strong decrease in the dip cord by preventing the yarn from being scratched or twisted due to excessive tension during dipping. However, there are other possible causes for the strong drop in the dip code. For example, it is possible to suppress the strong decrease of the dip cord by suppressing the strong decrease due to the thermal history of the aramid fiber and the poor alignment of the under-twisted cord at the time of twisting.

Japanese Unexamined Patent Publication No. 9-67730 (Claims, Examples, etc.) Japanese Patent Application Laid-Open No. 2014-530302 (Claim 8, Tables 1 to 2, paragraph [0064], etc.)

The present invention has been made in view of the above problems, and is a method for manufacturing a high-strength dip cord capable of minimizing the strong loss generated in the dip cord manufacturing process and drawing out the maximum strength in the cord structure. The purpose is to provide.

As a result of diligent studies in order to achieve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by examining in detail the drying conditions, the upper twisting conditions, the dip conditions, etc. of the lower twisted cord. , The present invention has been completed.
That is, the present invention is as follows.

1) The first step of applying a single twist (lower twist) to the aramid fiber (raw yarn), and
In the second step of combining a plurality of the lower twist cords and applying the upper twist,
A method for manufacturing an aramid dip cord, which comprises a third step of applying an adhesive to the upper twisted cord to obtain a dip cord.
A method for producing an aramid dip cord, which comprises drying the lower twisted cord in an atmosphere of a temperature of 50 ° C. or lower until the moisture content becomes 7% or less in the first step.
2) The aramid dip cord according to 1) above, wherein in the second step, a cord obtained by combining a plurality of lower twisted cords is subjected to an upper twist by applying a tension of 0.15 g / dtex or less. Production method.
3) In the third step, when the adhesive is applied, dried, and heat-treated, tension heat treatment is performed by applying a tension of 0.15 g / dtex to 0.60 g / dtex. Alternatively, the method for manufacturing an aramid dip cord according to 2).
4) The method for producing an aramid dip cord according to any one of 1) to 3) above, wherein the adhesive is an adhesive containing resorcin, formalin, and latex (RFL) as a main component.
5) The method for producing an aramid dip cord according to any one of 1) to 4) above, wherein the aramid fiber is a polyparaphenylene terephthalamide fiber.

According to the present invention, the strong loss generated in the dip cord manufacturing process can be minimized, and the maximum strength can be obtained in the cord structure.

Examples of the aramid fiber in the aramid fiber cord of the present invention include para-based aramid fiber and meta-based aramid fiber, but para-based aramid fiber having excellent tensile strength is preferable. Examples of the para-aramid fiber include polyparaphenylene terephthalamide fiber (manufactured by DuPont in the United States and Toray DuPont Co., Ltd., trade name "Kevlar" (registered trademark)), and copolyparaphenylene-3,4'-oxydi. Phenylene terephthalamide fibers (manufactured by Teijin Co., Ltd., trade name "Technora" (registered trademark)) and the like can be mentioned, and among these para-aramid fibers, polyparaphenylene terephthalamide fibers are particularly preferable.
As these aramid fibers, those produced by a known method can be used. The aramid fiber is a fiber having at least one divalent aromatic group which may be usually substituted in the repeating unit of the polymer forming the fiber, and is particularly a fiber having at least one amide bond. There is no limitation, and it may be referred to as a total aromatic polyamide fiber or an aramid fiber, and the "divalent aromatic group which may be substituted" has one or more substituents which are the same as or different from each other. It means a divalent aromatic group that may be used.

In the high-strength dip cord of the present invention, the total fineness of the aramid fiber (raw yarn) to be twisted under is not particularly limited, but is preferably in the range of 200 to 5,000 dtex, more preferably in the range of 500 to 3,500 dtex. The range of 1,000 to 3,500 dtex is more preferable.

(First step)
In the method for producing a high-strength dip cord of the present invention, in the first step, an appropriate single twist (lower twist) is applied to an aramid fiber (raw yarn) to produce a lower twist cord. The bottom twisted cord can have a single twisted structure in which one or two or more aramid fibers (raw yarns) are aligned and appropriately twisted.

In the present invention, it is important to dry the produced bottom twisted cord to a moisture content of 7% or less in an atmosphere of a temperature of 50 ° C. or less. The relative humidity in a dry atmosphere is preferably 60% RH or less. Here, the official water content of polyparaphenylene terephthalamide (specified by JIS) is 6.5%. The bottom twisted cord is preferably dried to a moisture content of 5 to 7%.

The reason why the drying atmosphere of the lower twisted cord is set to a temperature of 50 ° C. or lower is that when the temperature exceeds 50 ° C., the aramid fiber undergoes a thermal history by drying at a high temperature, and as a result, the strength of the twisted cord is likely to decrease. Because. Further, the reason why the dry atmosphere is preferably a relative humidity of 60% RH or less is that when the relative humidity exceeds 60%, it may be difficult to reduce the moisture content of the aramid fiber to 7% or less. The temperature of the drying atmosphere is preferably 20 ° C. or higher, more preferably 25 ° C. or higher in consideration of drying efficiency.

The lower twisted cord may be dried after the twisted yarn or in the twisted yarn. It is necessary to perform the twisting in the dry atmosphere and store the twisted cord in the same atmosphere for a certain period of time in order to shorten the drying time. More preferable.

(Second step)
Next, in the second step, a plurality of lower twist cords produced in the first step are combined and twisted upward. The number of yarns to be combined is preferably in the range of 2 to 9, more preferably in the range of 2 to 6, and even more preferably in the range of 3 to 6. The larger the number of single-twisted cords, the stronger the dip cord can be manufactured. The twisting direction (S direction or Z direction) of the upper twisted cord is not particularly limited, but is preferably the direction opposite to that of the lower twisted cord.

In the present invention, it is preferable to combine a plurality of bottom twisted cords dried to a moisture content of 7% or less under the above conditions and apply a tension of 0.15 g / dtex or less to perform top twisting. By applying an upper twist with such a low tension, it is possible to impart structural elongation to the aramid twisted yarn cord having a high elastic modulus, so that damage to the yarn due to the tension load after dipping can be suppressed. .. As a result, it is possible to prevent a strong decrease in the aramid dip cord.

In the second step, the upper twist may be performed by applying a tension exceeding 0.15 g / dtex, and the conditions can be selected according to the target quality. Even in this case, it is preferable to apply a tension of 0.50 g / dtex or less to perform the top twist, and it is more preferable to apply a tension of 0.30 g / dtex or less to perform the top twist.

The twist coefficient of the twisted cord of the aramid fiber (raw yarn) is preferably in the range of 1 to 10 for both the lower twist and the upper twist, and more preferably in the range of 2 to 6. The durability of the cord is improved by adding twist to the fiber, but if the twist coefficient is too small, the fatigue resistance of the twisted cord tends to decrease. On the other hand, if the twist coefficient is too large, the strength of the fiber cord tends to decrease. The twist coefficient (K) is a value obtained by the following formula.

Twist coefficient (K) = [D ^1/2 x T] / 2840
T: Number of twists (t / 10 cm)
D: Total fineness of aramid fiber (dtex)

In the first step and the second step, known twisting machines such as a ring twisting machine, a double twister twisting machine, and an aroma twisting machine can be used as the twisting method. Even if the method is to twist the aramid fiber yarns once, then wind them up, and then combine two or more of the obtained lower twisted yarns and twist them upwards, two or more aramid fiber yarns are twisted separately. A method may be used in which the obtained lower twisted yarns are not wound up and then twisted upward with each other.

(Third step)
Next, in the third step, an adhesive is applied to the upper twisted cord obtained in the second step to produce a dip cord. The treatment with the adhesive may be performed once, but may be performed twice or more, and is preferably performed on the twisted yarn cord to which the upper twist is added. Further, after applying the adhesive, it is preferable to perform drying and heat treatment under the same conditions as before.

The type of adhesive is not particularly limited, and known rubber adhesives can be used. Among them, an adhesive containing resorcin, formalin, and latex (RFL) as a main component is preferable because it is excellent in permeability / adhesion to a twisted cord and adhesiveness to rubber.
Examples of the latex include vinylpyridine-styrene-butadiene copolymer latex, styrene-butadiene latex, acrylonitrile-butadiene latex, chloroprene latex, chlorosulfonated polyethylene latex, acrylate latex and natural rubber latex. Resolcin and formaldehyde can be used alone, or a novolac-type condensate obtained by pre-condensing resorcin-formaldehyde under an acid catalyst or an alkali catalyst can be used. The adhesive may be mixed with one or more compounds selected from an epoxy compound, a blocked polyisocyanate compound, an ethyleneimine compound, a reaction product of polyisocyanate and ethyleneimine, and the like.

The solid content concentration of the adhesive is preferably in the range of 2 to 20% by mass. A known adhesive viscosity modifier can also be added.

As a method for applying the adhesive, a known dip treatment method may be adopted in which an adhesive containing RFL as a main component is dipped and applied to the upper twisted cord using a dipping machine, and then dried and heat-treated under tension conditions. it can. The dip process from the immersion of the adhesive to the heat treatment may be completed only once, or may be completed in two steps. In order to obtain high strength, a single dip treatment with a small heat history is preferable, and in order to obtain high adhesive strength, after performing the dip treatment with at least a first adhesive treatment liquid containing an epoxy compound, RFL is applied. It is preferable to perform a double dip treatment in which the dip treatment is performed with the second adhesive treatment liquid as the main component. The adhesive component when the dip treatment is performed twice may be the same component or different from each other.

The heat treatment conditions are preferably a drying temperature of 100 to 160 ° C., a residence time of 0.5 to 5 minutes, a heat treatment temperature of 200 to 260 ° C., and a residence time of 0.5 to 5 minutes.

In the present invention, when the adhesive is applied to dry and heat-treat, it is preferable to apply a tension of 0.15 g / dtex to 0.60 g / dtex to perform the tension heat treatment. By applying tension heat treatment with a tension of 0.15 g / dtex or more, the aligned state of the filaments of the upper twisted cord can be optimized, and the strength can be enhanced. On the other hand, by applying tension at 0.60 g / dtex or less and performing tension heat treatment, an excessive tension load is not applied to the upper twisted cord, so damage to the yarn due to scratching during the process is minimized and the cord is used. The strength can be maintained at a higher price. The tension during the tensile heat treatment is more preferably in the range of 0.15 g / dtex to 0.50 g / dtex, and further preferably in the range of 0.15 g / dtex to 0.30 g / dtex.

The high-strength dip cord of the present invention thus obtained can bring out the maximum strength in the cord structure because the strong loss generated in the dip cord manufacturing process is minimized in each process. Taking advantage of these characteristics, it is suitable for reinforcing rubber products such as various tires for automobiles and aircraft; various belts such as transmission belts, V-belts and timing belts; various hoses such as radiator hoses, heater hoses and power steering hoses; Can be used for.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Further, in the following examples and the like, "mass%" is abbreviated as "%" unless otherwise specified. The evaluation method of the aramid fiber cord described in the examples is as follows.

(1) Strong under-twist cord, top-twist cord and dip cord JIS L 1017: 2002 Chemical fiber tire cord test method 8.5 a) Measured based on the standard time test.
(2) Strong retention rate Calculated by the following formula. Strong retention rate = (strong dip cord / strong top twist cord)

(Examples 1 to 4, Comparative Examples 1 to 2)
After applying single twist (Z direction) to polyparaphenylene terephthalamide fiber (trade name Kevlar (R), fineness 1,670 dtex, number of filaments 1,000, strong 360 N) manufactured by Toray DuPont Co., Ltd. The bottom twisted cord was dried under the temperature and humidity conditions shown in Table 1 until the moisture content shown in Table 1 was reached.
Three lower twisted cords were aligned and twisted in the S direction using a ring twisting machine while applying the tension shown in Table 1 to prepare an upper twisted cord.
The above twisted cord is immersed in an adhesive treatment liquid containing RFL as a main component and heat-treated at 140 ° C. for 2 minutes to remove water, and then 1 at 230 ° C. while applying the dip tension shown in Table 1. A dip cord was prepared by tension heat treatment for 1 minute.

(Example 5, Comparative Example 3)
After applying single twist (Z direction) to polyparaphenylene terephthalamide fiber (trade name Kevlar (R), fineness 1,670 dtex, number of filaments 1,000, strong 360 N) manufactured by Toray DuPont Co., Ltd. The bottom twisted cord was dried under the temperature and humidity conditions shown in Table 1 until the moisture content shown in Table 1 was reached.
Two of the lower twisted cords were aligned and twisted in the S direction using a ring twisting machine while applying the tension shown in Table 1 to prepare an upper twisted cord.
The above twisted cord is immersed in an adhesive treatment liquid containing RFL as a main component and heat-treated at 140 ° C. for 2 minutes to remove water, and then 1 at 230 ° C. while applying the dip tension shown in Table 1. A dip cord was prepared by tension heat treatment for 1 minute.

The above results are shown in Table 1.

From Table 1, the aramid dip cord produced in this example shows a high value of the dip cord's strength and strong retention rate as compared with the aramid dip cord produced in the comparative example, and the upper twist is performed with low tension. It can be seen that a dip cord having a strong strength and a high retention rate can be obtained by hanging the dip cord and further producing the dip cord within a predetermined tension range.

The aramid dip cord of the present invention is useful for reinforcing rubber products such as tires, belts and hoses.

Claims (5)

The first step of applying a single twist (lower twist) to the aramid fiber (raw yarn), and
In the second step of combining a plurality of the lower twist cords and applying the upper twist,
A method for manufacturing an aramid dip cord, which comprises a third step of applying an adhesive to the upper twisted cord to obtain a dip cord.
A method for producing an aramid dip cord, which comprises drying the lower twisted cord in an atmosphere of a temperature of 50 ° C. or lower until the moisture content becomes 7% or less in the first step. The method for producing an aramid dip cord according to claim 1, wherein in the second step, a cord obtained by applying a tension of 0.15 g / dtex or less to a cord obtained by combining a plurality of lower twisted cords is subjected to upper twisting. .. Claim 1 or 2 is characterized in that, in the third step, when an adhesive is applied to dry and heat-treat, tension heat treatment is performed by applying a tension of 0.15 g / dtex to 0.60 g / dtex. A method for manufacturing an aramid dip cord described in 1. The method for producing an aramid dip cord according to any one of claims 1 to 3, wherein the adhesive is an adhesive containing resorcin, formalin, latex (RFL) as a main component. The method for producing an aramid dip cord according to any one of claims 1 to 4, wherein the aramid fiber is a polyparaphenylene terephthalamide fiber.