JP2012116258A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire that achieves improvement in water-resistant adhesion while excellently maintaining uniformity in a pneumatic radial tire in which cords made of lyocell fibers are used in a carcass layer.SOLUTION: The pneumatic radial tire is configured as follows. A cord is formed by twisting together three first-twist yarns made of lyocell fibers obtained by a solvent spinning method and subjecting it to heat treatment after immersing it in mixed liquid, comprising resorcin, formalin, and latex, in order to impart adhesion thereto. The cord is used in a carcass layer. The final-twist coefficient N1 is set to be in a range of 2,000≤N1≤3,500. The ratio N2/N1 between the final-twist coefficient N1 and the first-twist coefficient N2 is set to be in a range of N2/N1≤0.58.

Description

  The present invention relates to a pneumatic radial tire using a cord made of lyocell fiber for a carcass layer, and more particularly, to a pneumatic radial tire that can improve water-resistant adhesion and improve uniformity.

  Conventionally, rayon fiber cords have been used as carcass materials for high-performance tires. However, since harmful substances are used in the production process of rayon fibers, alternative materials are required. The lyocell fiber obtained by the solvent spinning method is a cellulosic highly elastic fiber like the rayon fiber, and is promising as a substitute for the rayon fiber. Therefore, various applications of lyocell fibers to carcass materials for high-performance tires have been proposed (for example, see Patent Document 1).

  However, when a lyocell fiber cord is used as a carcass material for a pneumatic radial tire, there is a problem that the lyocell fiber cord has poor adhesion retention (waterproof adhesion) after water resistance deterioration as compared with a rayon fiber cord.

JP 2004-66930 A

  An object of the present invention is to solve the above-described problems, and relates to a pneumatic radial tire using a cord made of lyocell fiber for a carcass layer, and more specifically, to improve water-resistant adhesion while maintaining good uniformity. An object of the present invention is to provide a pneumatic radial tire that makes it possible.

In order to achieve the above object, the pneumatic radial tire of the present invention is formed by twisting three plied yarns made of lyocell fiber obtained by a solvent spinning method, and applying a heat treatment with a mixed solution of resorcin, formalin and latex. In the pneumatic radial tire using the cord provided with adhesiveness for the carcass layer, the upper twist coefficient N1 represented by the following formula (1) of the cord is in the range of 2000 ≦ N1 ≦ 3500, and the upper twist coefficient A ratio N2 / N1 between N1 and a lower twisting coefficient N2 represented by the following formula (2) is in a range of N2 / N1 ≦ 0.58.
N1 = T1 × D1 ^1/2 (1)
N2 = T2 × D2 ^1/2 (2)
(In the formula, T1 is the number of upper twists [times / 10 cm], T2 is the number of lower twists [times / 10 cm], D1 is the total fineness [dtex] of the fiber cord, and D2 is the fineness [dtex] of the lower twisted yarn.)

  In the present invention, when the cord made of lyocell fiber is used for the carcass layer, the upper twist coefficient N1 of the cord is in the range of 2000 ≦ N1 ≦ 3500, and the ratio N2 / N1 between the upper twist coefficient N1 and the lower twist coefficient N2 is N2 / By setting the range of N1 ≦ 0.58, the number of upper twists becomes larger than the number of lower twists, and the angle formed by the cord direction and the filament of the lower twisted yarn becomes larger, so the anchoring effect between the rubber and the cord is high. Thus, the water-resistant adhesion can be improved. Moreover, since the three under-twisted yarns made of lyocell fibers are twisted together, it is possible to avoid an excessive increase in the elastic modulus of the cord, unlike the case of two-twisting. For this reason, even if the cord density is locally increased in the splice portion of the carcass layer, it is possible to suppress the depression of the portion at the time of filling with the internal pressure and improve the uniformity.

  In the present invention, the weight ratio RF / L of the total weight of resorcin and formalin to the weight of latex in the mixed solution is preferably in the range of 0.15 ≦ RF / L ≦ 0.45. Thereby, water-resistant adhesiveness can further be improved.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is a side view which shows an example of the code | cord | chord which comprises a carcass layer by this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic radial tire according to an embodiment of the present invention, and FIG. 2 shows a cord constituting a carcass layer according to the present invention.

  In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the tire inner side to the outer side around the bead core 5 disposed in each bead portion 3. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. A plurality of belt layers 7 are arranged on the outer peripheral side of the carcass layer 4.

  In the pneumatic radial tire described above, as a cord constituting the carcass layer 4, three mixed yarns made of lyocell fibers obtained by a solvent spinning method are twisted, and a mixed solution (RFL mixed solution) made of resorcin, formalin and latex Use a cord that has been heat treated to give adhesion. And the twist structure of this cord is set as follows.

When the upper twist number of the cord constituting the carcass layer 4 is T1 [times / 10 cm], the lower twist number is T2 [times / 10 cm], the total fineness is D1 [dtex], and the fineness of the lower twist yarn is D2 [dtex] N1 = T1 × D1 ^1/2 and the upper twist coefficient N1 is set in the range of 2000 ≦ N1 ≦ 3500, and the upper twist coefficient N1 and the lower twist coefficient N2 expressed by N2 = T2 × D2 ^1/2 The ratio N2 / N1 is set in a range of N2 / N1 ≦ 0.58, preferably 0.2 ≦ N2 / N1 ≦ 0.58. The upper twist direction and the lower twist direction are opposite to each other.

  By defining the twisted structure in this way, the angle θ (see FIG. 2) formed by the extending direction of the cord 8 and the filament of the lower twisted yarn 9 is increased, so that the anchoring effect between the rubber and the cord is improved. Water-resistant adhesion can be improved.

  When the upper twist coefficient N1 is smaller than 2000, the anchoring effect is lowered and the water-resistant adhesiveness is lowered. If the upper twist coefficient N1 is larger than 3500, the number of upper twists becomes too large, so that the elastic modulus of the cord is lowered. On the other hand, if the ratio N2 / N1 is larger than 0.58, the anchoring effect is lowered and the water-resistant adhesiveness is lowered. In this cord, the number of upper twists T1 is preferably 47 times / 10 cm or less. If the upper twist number T1 is larger than 47 times / 10 cm, it is difficult to set the upper twist coefficient N1 within the above range.

  Although the water-resistant adhesion can be improved by using the cord made of lyocell fiber configured as described above for the carcass layer 4, as this cord, two twisted yarns obtained by twisting together two lower twisted yarns made of lyocell fiber When a cord having a structure is used, since the elastic modulus of the cord becomes excessively high, a depression is likely to occur at a portion where the cord density of the splice portion is high at the time of internal pressure filling, and there is a problem that uniformity is lowered.

  Therefore, in this invention, the cord of the 3 strand structure which twisted together the 3 twisted yarns which consist of a lyocell fiber is used as this cord. Thus, by using the cord of the triple twist structure which consists of a lyocell fiber for the carcass layer 4, it can avoid that the elasticity modulus of a cord becomes high too much. As a result, even if the cord density is locally high in the splice portion of the carcass layer 4, it is possible to suppress the depression of the portion at the time of filling with the internal pressure and improve the uniformity.

  In the present invention, the cord made of lyocell fiber is preliminarily imparted with an adhesive by heat treatment with an RFL mixed solution (dip solution) in order to improve the adhesiveness with rubber. In this RFL mixture, the weight ratio RF / L of the total weight of resorcin and formalin to the weight of latex is preferably in the range of 0.15 ≦ RF / L ≦ 0.45. When RF / L is less than 0.15, the hardness of the RFL adhesive layer increases and the adhesion to rubber decreases. When RF / L is larger than 0.45, sufficient strength of the adhesive layer cannot be obtained, and the adhesion to rubber is lowered.

  Moreover, it is preferable to make the molar ratio (R / F ratio) of resorcin and formalin in a RFL liquid mixture into the range of 0.25-1.0. When the R / F ratio is less than 0.25, the ratio of formalin increases too much, so that cross-linking between resorcin and formalin proceeds, the hardness of the RFL adhesive layer increases, and the adhesion to rubber decreases. When the R / F ratio is larger than 1.0, sufficient strength of the adhesive layer cannot be obtained, and the adhesiveness to rubber is lowered.

  Moreover, it is preferable that the molar ratio (NaOH / R ratio) of sodium hydroxide and resorcin in the RFL mixed solution is 0.35 to 0.55. If the NaOH / R ratio is less than 0.35, the chemical stability of the RFL mixture is low and it is easy to gel, making it difficult to use as a dip solution. If the NaOH / R ratio is greater than 0.55, the crosslinking between resorcin and formalin proceeds, the hardness of the RFL adhesive layer increases, and the adhesion to rubber decreases.

  Here, examples of the latex contained in the RFL mixed solution include vinyl pyridine latex, natural rubber latex, styrene-butadiene rubber latex, and the like. It is preferable that 50% by weight or more of the total latex is vinyl pyridine latex. By selecting the vinylpyridine latex, the adhesion of the cord made of lyocell fiber to rubber can be effectively improved. In particular, it is most preferable that the total amount of latex (100% by weight) is vinylpyridine latex.

  The tire size is the same for 205 / 55ZR16, and the specifications of the cord constituting the carcass layer, specifically the total fineness D1 of the cord, the fineness D2 of the lower twisted yarn, the number of twists, the number of lower twists T2, the lower twist factor N2, the upper twist As shown in Table 1, the number T1, the upper twist coefficient N1, the ratio N2 / N1 of the upper twist coefficient and the lower twist coefficient, and the weight ratio RF / L of the total weight of resorcin and formalin and the weight of latex in the RFL mixed solution are different as shown in Table 1. The tires of Comparative Examples 1 to 3 and Examples 1 to 7 were manufactured.

  In Comparative Examples 1 to 3 and Examples 1 to 7, the R / F ratio in the RFL mixed solution was set to 1 / 2.5, the NaOH / R ratio was set to 0.5 / 1, and the latex had a total solid content. 18% vinyl pyridine latex was used.

  About these test tires, tire uniformity and water-resistant adhesiveness were evaluated by the following evaluation method, and the results are also shown in Table 1.

Tire uniformity When the tire was filled with normal internal pressure, the average value of the tire maximum width at the splice portion of the carcass layer and the maximum width at four locations on the tire circumference excluding the splice portion was measured, and the difference was obtained. The evaluation results are shown as an index with Comparative Example 1 being 100, using the reciprocal of the measured value. The greater the index value, the better the tire uniformity.

Water Resistance Adhesion The tires were conditioned for 30 days under conditions of humidity 80% and temperature 70 ° C., and then an endurance test was performed to measure the travel distance. More specifically, the durability test was performed according to the following procedure. The evaluation tire after humidity control is assembled on a wheel with a rim size of 16 × 61 / 2JJ, the running speed is constant at 81 km / h, and the maximum load corresponding to the pneumatic condition specified by JATMA is set on a drum with a diameter of 1707 mm. 4 hours at 85%, then 6 hours at 90% of the maximum load, then 2 hours at 130% of the maximum load, then 4 hours at 145% of the maximum load, then 160% of the maximum load, and measure the distance traveled until breaking did. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the water-resistant adhesion.

  Comparative example 1 is the standard. In Comparative Example 2, the value of N2 / N1 was reduced, so that the water-resistant adhesion was improved. However, since the number of twists of the lower twisted yarn was two, the elastic modulus of the cord was too high and the uniformity was lowered. In Comparative Example 3, since the ratio N2 / N1 was too large, the effect of improving water-resistant adhesion could not be obtained.

  On the other hand, Examples 1-7 were able to improve water-resistant adhesion while maintaining uniformity. In particular, Examples 2 to 7 in which the number of lower twists T2 and the ratio N2 / N1 were further reduced as compared with Example 1 were able to achieve both higher uniformity and water-resistant adhesion.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Cord 9 Lower twisted yarn

Claims (2)

Pneumatic radials using cords with twisted three plied yarns made of lyocell fiber obtained by solvent spinning and heat treated with a mixture of resorcin, formalin and latex to give adhesion to the carcass layer In the tire,
The upper twist coefficient N1 represented by the following expression (1) of the cord is in the range of 2000 ≦ N1 ≦ 3500, and the ratio N2 // of the upper twist coefficient N1 and the lower twist coefficient N2 represented by the following expression (2) A pneumatic radial tire characterized in that N1 is in a range of N2 / N1 ≦ 0.58.
N1 = T1 × D1 ^1/2 (1)
N2 = T2 × D2 ^1/2 (2)
(In the formula, T1 is the number of upper twists [times / 10 cm], T2 is the number of lower twists [times / 10 cm], D1 is the total fineness [dtex] of the fiber cord, and D2 is the fineness [dtex] of the lower twisted yarn.)   2. The pneumatic according to claim 1, wherein a weight ratio RF / L of a total weight of resorcin and formalin to a weight of latex in the mixed solution is in a range of 0.15 ≦ RF / L ≦ 0.45. Radial tire.

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