JPH05186926A - Polyamide fiber cord for rubber reinforcement - Google Patents

Abstract

PURPOSE:To provide the subject cord causing no strength drop-off in its dipping and curing processes, also excellent in the fatigue resistance under repeated compressive strain. CONSTITUTION:The objective cord <=8.0g/d in the tenacity after cured in rubber, treated with a specific adhesive liquor. This adhesive liquor has the following characteristics: (1) each of the following parameters fall within a specified range: (a) molar ratio of the total resorcin to the total formaldehyde in the solution; (b) weight ratio of a total of the resorcin and formaldehyde to the total rubber latex solid fraction; (c) wt.% of the alkali metal hydroxide solid fraction based on the total solid in the RFL adhesive liquor; (d) wt.%, on a NH4OH basis, of the aqueous NH3 solution added based on the total solid; and (e) the total solid concentration (%); (2) the rubber as a component of the latex in this adhesive liquor is specified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-reinforced polyamide fiber cord having high strength.

[0002]

2. Description of the Related Art Polyamide fiber cords have excellent strength, durability and heat resistance among reinforcing cord materials for various rubber products such as tires. Therefore, they have been conventionally used for trucks / buses, construction vehicles and aircraft. It has been widely used as a reinforcing material for rubber industrial products such as large tires for automobiles, conveyor belts, hoses, and air springs.

On the other hand, for the purpose of reducing the weight of tires, reducing fuel consumption, saving resources, reducing costs, improving productivity, etc., the number of laminated reinforcing materials is reduced, the number of cords to be driven is reduced, and the thickness of cords is reduced. There is a strong demand for a reduction in the amount of reinforcing material.

In order to reduce the amount of the reinforcing material while maintaining the total strength as a rubber composite, higher strength fibers are required, but in recent years, ultra high strength polyamides having significantly improved strength compared with conventional ones. Fibers have been developed and disclosed (for example, JP-A-61-70008).

However, such a so-called ultra-high strength polyamide fiber cord is so-called "dip" in which it is soaked in an adhesive solution necessary for the adhesion between fibers and rubber, dried and heat-treated, and then heat-treated at a high temperature near the fiber melting point. It has been pointed out that a problem that the cord strength is significantly reduced when the "treatment process" is performed (Japanese Patent Laid-Open Nos. 63-17517 and 63-203841).
No.

In this publication, the cord tension when immersed in the adhesive liquid is set to 0.5 g / d or more, or pretreatment is performed at a high temperature of 100 ° C. or more to impregnate the inside of the cord with the adhesive liquid. It has been proposed to prevent such a code from being deteriorating.

Further, a technique similar to this has been disclosed before (Japanese Patent Laid-Open Nos. 60-71239 and 60-104580), and heat treatment under tension prior to adhesive treatment, and 3 It has been proposed to apply the adhesive under an elongation of at least%.

Further, when these dipping methods are used, the adhesion amount of the adhesive to the cord is small and the adhesive force between the rubber and the fiber is low. Therefore, the temperature and the tension in the tension heat treatment step before the immersion in the adhesive solution are used. At the same time as the relationship with resorcin-formaldehyde / rubber latex (so-called RFL), the solid content in the adhesive liquid, the ratio of the total weight of resorcin and formaldehyde to the latex, and the vinylpyridine latex to the total weight of vinylpyridine latex and styrene-butadiene latex. There is also disclosed a technique for improving the adhesiveness by also specifying the relationship of the ratio of the ratio (Japanese Patent Laid-Open No. 1-174627).
No. 1-174628).

Further, it has been found that the strength of the high-strength polyamide fiber is also reduced in the step of vulcanizing by embedding it in rubber after the dip treatment step (Japanese Patent Laid-Open No. 2-200,200).
This is also a problem that must be solved at the same time.

[Problems to be Solved by the Invention]

By the way, the present inventors have now found a second important problem. That is, when the cord is dipped in the adhesive liquid as in the prior art or before or after the heat treatment or tension is applied in the tension heat treatment step,
Certainly, the dip treatment process is prevented from being weakened, but
On the other hand, it was a new fact that the fatigue resistance of cords under repeated compressive strain in rubber was poor. Therefore, as a result of diligent studies on the cause of the problem, the present inventors have found that such a cord does not have an adhesive liquid impregnated into the inside of the cord, and bare filaments may come into contact with each other at the upper twisted interlaced surface to cause fatigue. Clarified the fact that it is the main cause.

Therefore, an object of the present invention is to provide the above first and second objects.
To solve all of the above problems simultaneously, and to provide a high-strength polyamide fiber cord for rubber reinforcement, which does not decrease in strength during dip treatment and vulcanization and has excellent fatigue resistance under repeated compression strain. ..

[0012]

Means for Solving the Problems The present inventors
We have extensively studied in order to solve the two important problems at the same time. First, in the cord subjected to the tension heat treatment before the immersion in the adhesive liquid as in the prior art, since the adhesive liquid is not impregnated inside the cord, the repeated stretching-compression causes the bare filaments to be twisted and twisted on each other. In order to prevent the cord from fatigue due to contact wear, the cord is not subjected to such a tension heat treatment step, and the cord is immersed in the adhesive solution under a relaxed state or under an extremely low tension as usual. It was considered necessary to impregnate the inside of the cord with an adhesive enough to cover the fiber filament surface of the twisted interlaced surface with an adhesive solid material.

However, although the second problem of fatigue property is solved by doing so, naturally the first problem is that the cord strength is lowered during dipping and vulcanization.

Then, the cause of the decrease in strength, which is the first problem, was further examined, and it was found in Japanese Patent Application Laid-Open No. 63-175179.
No. 63-203841, No. 60-71239 and No. 60-104580
As mentioned in each of the publications, the dip liquid impregnated inside the cord becomes a dry resin in the high temperature oven during the dipping process to bond the filaments, and the degree of freedom of each fiber filament constituting the cord It was found that the cords are constrained and the uniform stress distribution of each fiber filament when the cords are stretched is hindered, so that the cords are broken at a strength lower than that which should be originally exerted. Further, in order to produce a polyamide fiber having a higher strength, generally, drawing is performed at a higher ratio, so that a higher strength polyamide fiber has a higher terminal modulus at the time of breaking and is uniform with each fiber filament at the time of cord extension. We thought that it would be disadvantageous in stress sharing, and that the strength would easily decrease during dip processing.

Therefore, the inventors of the present invention have extensively studied various adhesive formulations. As a result, even if the cord is immersed in the adhesive liquid in a relaxed state or under an extremely low tension as in the conventional case, the cord is sufficiently impregnated. By making the adhesive liquid composition within a certain range, it was found that uniform stress sharing of each fiber filament at the time of cord elongation can be achieved, and the original strength of the high-strength polyamide fiber can be exhibited, and the present invention is completed. Came to.

[0016]

## EQU3 ## That is, according to the present invention, 1 / 2.3 ≦ R / F ≦ 1 / 1.1
, Preferably 1 / 2.0 ≦ R / F ≦ 1 / 1.3, more preferably 1 / 1.8 ≦ R / F ≦ 1 / 1.5 (molar ratio) 1/10 ≦ RF / L ≦ 1/4, preferably 1/8 ≤RF /
L ≤ 1/5 (solid content weight ratio) 0.05 ≤ S ≤ 0.8, preferably 0.1 ≤ S ≤ 0.5, more preferably 0.1 ≤ S ≤ 0.3 (wt%) 0 ≤ A ≤ 0.5, preferably 0 ≤ A ≤ 0.3 ( % By weight) 0.05 ≦ S + A ≦ 0.8, preferably 0.1 ≦ S + A ≦ 0.5
(Wt%) 10 ≦ C ≦ 24, preferably 14 ≦ C ≦ 22 (wt%) (where R / F is the molar ratio of resorcin / formaldehyde total amount, and RF / L is the total amount of resorcin / formaldehyde and rubber) Ratio to the total amount of latex solids, S is the weight% of alkali metal hydroxide (usually NaOH) or alkaline earth metal hydroxide to the total solids of RFL adhesive liquid, A is the total amount of RFL adhesive liquid NH ₄ OH-based weight% of NH ₃ aqueous solution based on solid content, C is RFL
All of the adhesive liquids represent the total solid content% by weight), and vinylpyridine (VP) latex (usually VP)
5-20% content and styrene-butadiene rubber (SB
R) latex and natural rubber (NR) and / or isoprene rubber (IR) latex solid content weight ratios to the total latex solid content weight% are a, b and c, respectively, ,

[Formula 4] VP latex: 10 ≦ a ≦ 80, preferably 30 ≦
a ≦ 60 (wt%) SBR latex: 0 ≦ b ≦ 70, preferably 10 ≦ b ≦ 50
(Wt%) IR and / or NR latex: embedded in rubber treated with an RFL adhesive solution that simultaneously satisfies 20 ≦ c ≦ 60, preferably 25 ≦ c ≦ 50 (wt%) The vulcanized polyamide fiber cord has a strength of 8.0 g / d or more. (However, latex other than the above may be contained as the latex component. In addition, SiO ₂ ,
Carbon black, a boron compound, etc. may be added. )

Polyamide fibers that can be used in the present invention include 6,6-nylon, 6-nylon and 4,6.
-Nylon, 6,10-nylon and copolymers or mixtures of aliphatic polyamides of these combinations are mentioned, but in particular, 6,6-nylon or 6-nylon-containing aliphatic polyamide is 80% by weight or more. Among them, 6,6-nylon is most preferable because of its high heat resistance. In addition, stabilizers composed of copper salts and other antioxidants are usually added to these polyamides in order to impart resistance to heat, light, oxygen and the like.

Further, by using such a polyamide fiber cord for rubber reinforcement, for example, the number of laminated reinforcing materials is reduced,
In order to achieve the objectives of sufficient weight reduction of tires, low fuel consumption, resource saving, cost reduction, productivity improvement, etc. by reducing the number of cords to be struck and making the cords thinner, the strength is 8.0g. / d or more, preferably 8.5 g / d or more, more preferably 9.5 g / d or more.

Further, the cord has a single yarn fineness of 1.5 to
10 denier is preferable and 3 denier or more and 8 denier or less is preferable. If it is less than 1.5 denier, the number of filaments constituting the cord is large and the surface area of the filament is too large. Therefore, the constraint of the adhesive layer on each fiber filament and the non-uniform stress distribution after the dry heat treatment increase, and the strength tends to decrease during the dip treatment. On the other hand, if it is greater than 10 denier, uniform cooling of the filament during spinning is hindered, which is not preferable for stable production of high-strength yarn.

In the range of the RFL adhesive liquid of the present invention,
When R / F is less than 1 / 2.3, the amount of F is too much relative to the amount of R, the crosslinking between R and F proceeds too much, and the final RF resin network after heat treatment becomes too dense. As RF
The hardness of the L adhesive layer becomes too hard, while the R / F is 1/1.
On the contrary, if it exceeds 1, the amount of F is too small relative to the amount of R, and R-
There is little cross-linking between F, the strength of the RFL layer is weakened, sufficient adhesion with rubber cannot be obtained, and the surface of the cord is sticky, which is not preferable in terms of workability.

Further, when RF / L exceeds 1/4, the RF amount is too much relative to the L amount, and as a result, the hardness of the RFL adhesive layer becomes too hard, while when RF / L is less than 1/10. On the contrary, the RF amount is too small with respect to the L amount, and sufficient adhesion with rubber cannot be obtained.

Further, when S exceeds 0.8% by weight, the amount of alkali metal hydroxide which is a reaction catalyst of F and R is too large,
Crosslinking between R and F is too advanced, and the final RF after heat treatment
Since the resin mesh is too dense, the hardness of the RFL adhesive layer becomes too hard as a result. On the other hand, when S is less than 0.05% by weight, on the contrary, the amount of alkali metal hydroxide is too small and the liquid tends to gel and is stable. The sex is bad. As the alkali metal hydroxide, NaOH is generally good, but other alkali metal hydroxides,
For example, KOH or the like may be used, or alkaline earth metal hydroxide may be used.

Furthermore, the adhesion to rubber is slightly improved by adding a small amount of NH ₃ aqueous solution, but if A exceeds 0.5% by weight, or if A is less than 0.5% by weight, S + A
If it exceeds 0.8% by weight, the crosslinking reaction between F and R proceeds too much, and the network of the RF resin after heat treatment becomes dense, and as a result, the hardness of the RFL adhesive layer becomes too hard.

Furthermore, if C is less than 10% by weight, it is not possible to adhere sufficient adhesive solids to the cord when it is dipped into the adhesive, while C is more than 24% by weight. If the concentration is too high, the RFL adhesive liquid easily gels and becomes unstable.

Next, regarding the latex component in the solution a
If it is less than 10% by weight, sufficient adhesion with rubber cannot be obtained, while if it exceeds 80% by weight, the adherence of the adhered rubber to the adherend becomes large, which is not preferable, and the cost of the RFL solution is too high. Further, when SBR latex is added as a latex component, the heat-resistant adhesive property is improved, which is preferable, but when b exceeds 70% by weight, the adhesive property with rubber decreases.

Further, as disclosed in JP-A-2-91276, by using an appropriate amount of NR and / or IR latex, it is possible to suppress the decrease in strength during vulcanization, but c is 20% by weight. If it is less than%, there is no sufficient effect of suppressing the reduction in strength during vulcanization, while if c exceeds 60% by weight, sufficient adhesion with rubber cannot be obtained.

The above-mentioned requirements can be obtained only when all the requirements are satisfied at the same time, and the RFL adhesive layer within the scope of the present invention is not achieved even if only one of the requirements is satisfied.

Further, when the novolak RF resin of the acid catalyst pre-condensation type is used, since R and F are linearly condensed, the RF network of the final RF resin after heat treatment becomes slightly rough, The RFL adhesive layer tends to be relatively flexible, but even in this case, if the above requirements such as the ratio of R, F, and L, the amount of alkali metal hydroxide, the type of latex, and the fraction are not satisfied at the same time, It does not fall within the scope of the present invention, and the strength of the fiber cannot be sufficiently exhibited.

However, the precondensation type Novorax RF
When a resin is used, the surface of the cord is sticky, and the stability of the liquid is slightly inferior to that of an alkali-catalyzed resol-based resin. Therefore, the alkali-catalyzed resol-based resin is usually preferable.

In treating the adhesive, the RF
If the cord tension T when immersed in the L liquid is 0.3 g / d or more, the adhesive liquid is not sufficiently impregnated inside the cord, and the filament contact wear fatigue at the twisted crossing surface is poor. T is preferably 0.
It is 2 g / d or less, more preferably 0.1 g / d or less.

In the polyamide fiber cord treated with the RFL adhesive of the present invention and embedded in rubber, the RF
Since the L adhesive layer is more flexible than the conventional one, and the adhesive layer restrains less to each fiber filament constituting the cord, it is possible to achieve uniform stress sharing of each fiber filament when the cord is stretched. It is thought that it can exert its original high strength.

[0032]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. As a polyamide raw yarn to be tested,
(A) Conventional 6-10-nylon of general strength, single yarn fineness 6d (denier), original yarn strength of 9.5 g / d,
(A) High strength 6,6-nylon 1890d, single yarn fineness 6d,
Original yarn strength 10.2 g / d, (c) Ultra high strength 6,6-nylon 1890d, Single yarn fineness 4d, Original yarn strength 12.2 g / d, and (d) Ultra high strength 6-nylon 1260d, A total of four types each having a single yarn fineness of 3d and a raw yarn strength of 13.0 g / d were used. For the yarns (a), (a), and (c), the twisted structure
With 1890d / 2, the number of twists is 32 times / 10 cm.
The twist structure was 1260d / 2 and the number of twists was 39 times / 10 cm.

As a method for preparing the RFL adhesive solution in this example and the comparative example, first, resorcin was dissolved in soft water, then an aqueous NaOH solution was added, and then formalin was added, followed by aging at room temperature for 6 hours. and then after adding NH ₃ aqueous solution in the case of compounding adding NH ₃ aqueous solution, a latex was added, was used in the adhesive treatment after being left for 24 hours further aged at room temperature.

FIG. 1 shows an outline of the method for treating the adhesive liquid in this embodiment. In addition, FIG. 2 shows an outline of a treatment method for performing cord tension heat treatment before dipping the adhesive, which is performed for comparison. 1 and 2, in each of the pre-tension heat treatment zone 1, the drying zone 2, the hot zone 3, and the normalizing zone 4, the temperature applied to the cord, the exposure time, and the tension are 190 ° C. for 6,6-nylon fiber, respectively. × 40
Seconds × 1.0 g / d, 130 ° C × 120 seconds × 0.8 g / d, 235 ° C × 40 seconds ×
0.8g / d, 230 ℃ × 40sec × 0.5g / d, 6-nylon fiber 160 ℃ × 40sec × 1.0g / d, 130 ℃ × 12
0 seconds × 0.8g / d, 200 ° C × 40 seconds × 0.8g / d, 195 ° C × 40 seconds ×
It was set to 0.5 g / d.

The measuring method of each physical property value is as follows. 1) Breaking strength, strength Raw yarn, raw cord, dip cord, and cord after vulcanization were all subjected to a tensile test using an autograph manufactured by Shimadzu Corporation in accordance with JIS L1017 to determine the strength (kg) at break. Further, the strength (g / d) was calculated according to the following formula, and the cord denier at this time was the true-density fineness of JIS L1017 for the raw yarn. Strength = Breaking strength / Positive fineness For the cords in the rubber after vulcanization, 10 filaments are extracted from the collected cords, the diameter of each filament is determined with an optical microscope, and the cross section is calculated from the average filament diameter. The filament cross-sectional area was obtained by regarding it as a perfect circle. The volume per unit length was calculated from this and the total number of filaments counted by observing the cross-section, and this was calculated using the density ρ of polyamide fiber (ρ = 1.14 for 6,6-nylon and 6-nylon). The weight per length (denier) was converted, the estimated denier number was calculated, and the strength was calculated according to the following formula. Strength = breaking strength / estimated denier

2) Adhesive strength The adhesive-treated cord was embedded in an unvulcanized compounded rubber composition shown in Table 1 below, vulcanized at 153 ° C. for 20 minutes, and the cord was dug up from the obtained vulcanized product, The cord was peeled from the vulcanized product by pulling at a speed of 300 mm / min, and the peeling resistance per cord was determined, and this was taken as the adhesive force (kg / bar).

[0037]

[Table 1]

3) After vulcanization, the strong test dip cord in rubber was embedded in the unvulcanized compounded rubber composition shown in Table 1, both ends of the cord were fixed and vulcanized at 153 ° C. for 40 minutes in a constant length state. .. After that, the vulcanized sample was taken out after it was naturally cooled in the fixed length state, and in order to avoid fluffing when peeling off the cord, cut the cord with the rubber around it with scissors and scrape the surface rubber as much as possible. Dropped. The breaking strength of the cord with the surface rubber attached was measured by the above method.

4) Strength retention after fatigue test Adhesive-treated cords, 1890d / 2 are 50 cords / 5 cm, 1260
d / 2 is lined up with the number of punches of 60 pieces / 5 cm, and 0.4 mm sheets of the same unvulcanized compound rubber used in the above-mentioned adhesion test are stuck from both sides to create a rubber topping sheet with a width of 5 cm and a length of 60 cm. did. Such topping sheet 2
A non-vulcanized rubber sheet with a thickness of 3 mm is sandwiched between the sheets, and the unvulcanized rubber sheet is attached to the upper and lower surfaces so that the total thickness of the sample is 15 mm, and both ends of the cord are fixed to a fixed length. It was vulcanized under a pressure of 20 kg / cm ² at 145 ° C. for 40 minutes to prepare a sample for flex fatigue resistance test. next,
This sample is hung on a pulley with a diameter of 60 mm and 15
5000 kg / h at a temperature of 120 ° C with a load of 0 kg.
Repeated flexions were added. Remove after bending 1 million times, take out the cord of the two layers of polyamide fiber cord that is in contact with the pulley (the side that is subjected to repeated compressive strain), measure the breaking strength, and measure the value of the new one before bending test. The retention rate (%) against the strength was used to express the fatigue resistance of the cord.

[0040]

[Table 2]

In Comparative Example 1 of Table 2, 6,6-
Since the nylon cord is treated with the conventional general RFL compounding which is out of the compounding range of the present invention and by the conventional general adhesive treatment step as shown in FIG. 1, the strength retention during dipping is 82.2%. The decline was remarkable.

On the other hand, in Comparative Example 2, since the same raw cord was immersed in the adhesive liquid under high tension after passing through the tension heat treatment zone as shown in FIG. 2, the adhesive liquid did not impregnate the inside of the cord, The strength retention rate during dipping was also high. However, the strength was significantly reduced by repeated compression in the fatigue test.
After observing the cords in detail after fatigue, it was found that the bare filaments were contacted and worn at the crossing of the twisted strands, causing fatigue.

Next, in Examples 1 and 2, since the RFL adhesive compounding liquid within the scope of the present invention was used, the adhesive layer was soft and the conventional general adhesive treatment step as shown in FIG. It can be seen that the strength retention rate at the time of dipping is high despite the treatment. Also, the strength during vulcanization is kept high. Further, in Examples 1 and 2, since the tension at the time of immersion in the adhesive solution is low, the cord is sufficiently impregnated, and the fiber filament surface of the crossed surface of the upper twist is covered and protected by the adhesive solid material, so that the fatigue test is strongly retained. Was very good. That is, it is understood that the two problems of dipping, reduction of strength during vulcanization, and fatigue resistance under low compression could be solved at the same time.

Next, Examples 3 and 4 are high-strength 6,6-nylon having a raw yarn strength of 10.2, but since the adhesive liquid of the present invention is also used, the strength retention and fatigue resistance are improved. I was able to balance the two. On the other hand, Comparative Example 3 is 6,6-nylon having the conventional strength, and therefore the conventional RFL
Even if the composition is used and the conventional general adhesive treatment step as shown in FIG. 1 is used, the strength reduction is small. At this time, the medium strength of the rubber after vulcanization was 7.9.

In Example 5, 6-nylon having an extremely high strength is used, but since an adhesive solution having a composition within the scope of the present invention is used, the dip, the strength retention during vulcanization and the fatigue resistance are good. Met. In Comparative Example 4, a precondensation type novolak resin is used, but the range of the compounding of the adhesive solution is outside the range of the present invention and the hardness of the RFL layer is too hard. The strength was greatly reduced and the original strength could not be exhibited. On the other hand, Example 6 also uses the same pre-condensation type novolak RF resin, but good results were obtained because the blending of the adhesive liquid was within the scope of the present invention.

[0046]

As described above, according to the present invention, by controlling the RFL adhesive composition within an appropriate range, the high strength polyamide fiber cord is a problem which has been incompatible until now. A polyamide fiber cord for rubber reinforcement, which can overcome both the problem of reduction in strength during agent treatment and vulcanization and the problem of deterioration in repeated compression fatigue resistance, and which also has excellent adhesion to rubber. be able to. As a result, the amount of reinforcing material can be reduced by reducing the number of laminated reinforcing materials and the number of cords to be driven, and the objects such as weight reduction of tires, low fuel consumption, resource saving, cost reduction, and productivity improvement can be achieved.

[Brief description of drawings]

FIG. 1 is a process diagram showing an outline of an adhesive treatment method.

FIG. 2 is a process diagram showing an outline of an adhesive treatment method in which a cord tension heat treatment is performed before the adhesive is immersed.

[Explanation of symbols]

 1 Pre-tension heat treatment zone 2 Drying zone 3 Hot zone 4 Normalizing zone

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location D01F 6/60 311 C 7199-3B D02G 3/40 D06M 15/693 // C08J 5/12 CFG 9267 -4F

Claims (3)

[Claims] 1. 1 / 2.3 ≤ R / F ≤ 1/1. 1 (molar ratio) 1/10 ≤ RF / L ≤ 1/4 (solid content weight ratio) 0.05 ≤ S ≤ 0.8 (wt%) 0 ≦ A ≦ 0.5 (wt%) 0.05 ≦ S + A ≦ 0.8 (wt%) 10 ≦ C ≦ 24 (wt%) (However, in the above formula, R / F is the molar ratio of the total amount of resorcin / formaldehyde, and RF / L is The ratio of the total amount of resorcinol and formaldehyde to the total amount of rubber latex solids, S is the weight% of the alkali metal hydroxide relative to the total solids of the RFL adhesive liquid, and A is the NH ₃ aqueous solution relative to the total solids of the RFL adhesive liquid. Wt% based on NH ₄ OH base, C represents wt% of total solid content of RFL adhesive solution) at the same time, and vinyl pyridine (VP) latex, styrene butadiene rubber (SBR) latex and natural rubber ( NR) and / or isoprene Beam the weight ratio% relative to the total latex solids by weight of the solid weight of each (IR) latices when a, b, and c respectively,
The following formula, VP latex: 10 ≦ a ≦ 80 (wt%) SBR latex: 0 ≦ b ≦ 70 (wt%) IR and / or NR latex: 20 ≦ c ≦ 60 (wt%) at the same time A polyamide fiber cord after being treated with an adhesive using an RFL adhesive liquid as described above, embedded in rubber and vulcanized, wherein the cord has a strength of 8.0 g / d or more. Polyamide fiber cord for rubber reinforcement. 2. The strength of the polyamide fiber cord is 8.5 g.
/ d or more, preferably 9.5 g / d or more, and a single yarn fineness of 1.5 to
The polyamide fiber cord for rubber reinforcement according to claim 1, which is in the range of 10 denier. 3. The rubber-reinforced polyamide fiber cord according to claim 1, wherein the polyamide fiber is 6,6-nylon.