JP2006183167A - Cord for reinforcing rubber and pneumatic radial tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cord consisting of polyolefin ketone fibers, a cord for reinforcing rubber, improved in the bonding property with the rubber, and a pneumatic radial tire by using the cord. <P>SOLUTION: This cord obtained by immersing twisted yarns consisting of the polyolefin ketone fibers having a chemical structure expressed by formula (1): (CH<SB>2</SB>CH<SB>2</SB>CO)<SB>n</SB>(R'CO)<SB>m</SB>(1) [wherein, 1.05≥(n+m)/n≥1.00; and R' is a ≥3C alkylene], in a mixed liquid containing resorcinol, formalin, latex and sodium hydroxide for imparting a bonding property is provided by setting 0.35≤NaOH/R≤0.55 molar ratio of the sodium hydroxide (NaOH) to the resorcinol (R), 0.25≤R/F≤1.0 molar ratio of the resorcinol (R) to the formalin (F) and 0.1≤RF/L≤0.4 weight ratio of the total amount of the resorcinol and formalin (RF) to the latex (L) in the mixed liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber reinforcing cord made of polyolefin ketone fiber and a pneumatic radial tire using the cord, and more particularly, a rubber reinforcing cord having improved adhesion to rubber and a pneumatic radial tire using the cord. About.

  A cord made of polyolefin ketone fiber is a new material having high strength and high elastic modulus, and is expected as a reinforcing material for rubber products such as tires, belts and hoses. In particular, a cord made of polyolefin ketone fiber is promising as a substitute for rayon because it can be dipped with a mixed solution containing resorcin, formalin, and latex in the same manner as nylon and rayon (for example, Patent Document 1). To 3).

However, the conventional dip treatment method does not always sufficiently enhance the adhesion of cords made of polyolefin ketone fibers to rubber. For this reason, it has been demanded to search for an optimum dip liquid composition for the polyolefin ketone fiber cord. In addition, since the polyolefin ketone fiber cord has high dimensional stability and small heat shrinkage stress, it is difficult to embed it without causing loosening in the tire. Therefore, there is also a disadvantage that the high elastic modulus characteristic of the polyolefin ketone fiber cord cannot be fully utilized.
JP 2002-307908 A JP 2003-145645 A JP 2003-55855 A

  An object of the present invention is to provide a cord made of polyolefin ketone fiber, a cord for reinforcing rubber having improved adhesion to rubber, and a pneumatic radial tire using the cord.

In order to achieve the above object, the rubber reinforcing cord of the present invention comprises a twisted yarn comprising a polyolefin ketone fiber having a chemical structure represented by the following formula (1) in a mixed solution containing resorcin, formalin, latex and caustic soda. In cords that have been dipped to give adhesion,
_{- (CH 2 -CH 2 -CO)} n- (R'-CO) m- ··· (1)
However, 1.05 ≧ (n + m) /n≧1.00
R ′: an alkylene group having 3 or more carbon atoms The molar ratio of caustic soda (NaOH) and resorcin (R) in the mixed solution is 0.35 ≦ NaOH / R ≦ 0.55, and resorcin (R) and formalin (F ) And 0.25 ≦ R / F ≦ 1.0, and the weight ratio of the total amount of resorcin and formalin (RF) to latex (L) is 0.1 ≦ RF / L ≦ 0.4. It is characterized by this.

  As a result of diligent research on the adhesiveness of polyolefin ketone fiber cords, the present inventor has found an optimal blend of resorcin, formalin, latex, and caustic soda in a mixed solution (dip solution) for imparting adhesiveness to polyolefin ketone fiber cords. The present invention has been reached. That is, by defining the composition of the dip solution as described above, the adhesion of the polyolefin ketone fiber cord to rubber can be greatly improved. In particular, it is preferable that 50% by weight or more of the latex contained in the mixed solution is vinylpyridine latex.

  The rubber reinforcing cord of the present invention is suitable as a reinforcing material for rubber products such as tires, belts and hoses. In particular, the rubber reinforcing cord of the present invention is preferably used for a carcass layer of a pneumatic radial tire.

That is, the pneumatic radial tire of the present invention is characterized in that the rubber reinforcing cord is used for at least one carcass layer. In particular, the pneumatic radial tire of the present invention uses the above-mentioned rubber reinforcing cord and a cord having an elongation of 2.0% or less at a load of 2.0 cN / dtex for at least one carcass layer. It should be good. Furthermore, in the pneumatic radial tire of the present invention, when performing the heat setting process and the normalizing process on the rubber reinforcing cord, the tension T _HS in the heat setting process is set to 0.7 cN / dtex or more, The ratio of the tension T _HS in heat set processing to the tension T _{NL in} normalization processing (T _HS / T _NL ) is set to 2 or less, and the rate of increase in the code length after processing relative to the code length before processing It is preferable that the processed cords having a value of 0.9% or more be used for at least one carcass layer.

  When the polyolefin ketone fiber cord is subjected to the prescribed heat-setting and normalizing treatment, and the intermediate elongation of the cord is defined as described above, the polyolefin ketone fiber cord is embedded without causing any looseness in the tire. Is possible. This makes it possible to fully utilize the high elastic modulus characteristics of the polyolefin ketone fiber cord.

  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. 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, and an end portion of the carcass layer 4 is folded around the bead core 5 from the inside to the outside of the tire. The carcass layer 4 is composed of a plurality of reinforcing cords extending in the tire radial direction. On the outer peripheral side of the carcass layer 4 in the tread portion 1, a belt layer 6 is disposed over the entire tire circumference. These belt layers 6 include reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged such that the reinforcing cords cross each other between the layers. A belt cover layer 7 is disposed on the outer peripheral side of the belt layer 6 so as to cover at least the edge portion of the belt layer 6.

In the pneumatic radial tire, a cord made of polyolefin ketone fiber (POK) is used as a reinforcing cord for the carcass layer 4. The polyolefin ketone fiber has a chemical structure represented by the following formula (1).
_{- (CH 2 -CH 2 -CO)} n- (R'-CO) m- ··· (1)

  Here, 1.05 ≧ (n + m) /n≧1.00, R ′ is an alkylene group having 3 or more carbon atoms. By reducing the fraction of m, a cord having high strength, high dimensional stability, and high heat resistance can be obtained. In particular, it is preferable to use an alternating copolymer consisting essentially of ethylene and carbon monoxide, where m = 0. The alkylene group includes, for example, a propylene group.

The method for twisting the polyolefin ketone fiber cord is not particularly limited, and may be a cord formed by twisting two strands, twisting three strands, or twisting four or more fiber bundles. The polyolefin ketone fiber cord preferably has a twist coefficient K represented by K = T × (D / 1.111) ^1/2 in the range of 1300 to 2500. Here, T is the number of twists of the cord (times / 10 cm), and D is the total number of decitex of the cord. If the twist coefficient K is less than 1300, the fatigue property of the cord decreases, and if it exceeds 2500, the strength of the polyolefin ketone fiber cannot be utilized. Further, the total decitex number D of the cord is preferably 500 to 6000 dtex.

  The polyolefin ketone fiber cord is subjected to the following dipping treatment. That is, a twisted yarn made of polyolefin ketone fiber (multifilament) is immersed in a mixed solution (dip solution) containing resorcin, formalin, latex and caustic soda in order to obtain excellent adhesion to rubber. At that time, in the dip solution, the molar ratio of caustic soda (NaOH) to resorcin (R) is set to 0.35 ≦ NaOH / R ≦ 0.55, and the molar ratio of resorcin (R) to formalin (F) is 0.25 ≦ R / F ≦ 1.0, and the weight ratio of the total amount of resorcin and formalin (RF) to latex (L) is set to 0.1 ≦ RF / L ≦ 0.4.

  Here, when the NaOH / R ratio is less than 0.35, the chemical stability of the dip solution is low and it is easy to gel, so that it is difficult to use it as a dip solution. On the other hand, when the NaOH / R ratio is larger than 0.55, 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 less than 0.25, the ratio of formalin increases so much that crosslinking between resorcin and formalin advances, the hardness of the RFL adhesive layer increases, and the adhesion to rubber decreases. On the other hand, 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.

  When the RF / L ratio is less than 0.1, the hardness of the RFL adhesive layer increases and the adhesion to rubber decreases. On the other hand, when the RF / L ratio is larger than 0.4, sufficient adhesive layer strength cannot be obtained, and the adhesiveness to rubber is lowered.

  Examples of the latex contained in the dip liquid 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. The selection of the vinyl pyridine latex can effectively improve the adhesion of the polyolefin ketone fiber cord to the rubber. In particular, the total amount of latex (100% by weight) is most preferably vinylpyridine latex.

  The polyolefin ketone fiber cord is subjected to the following heat setting treatment and normalization treatment. That is, the polyolefin ketone fiber cord subjected to the dip treatment is subjected to drying treatment at a temperature of 80 to 130 ° C. for 45 to 160 seconds, and then at a temperature of 210 to 260 ° C. for 45 seconds or more, preferably 45 to 140 seconds. A heat setting process is performed, and then a normalizing process is performed at a temperature of 210 to 260 ° C. for 45 seconds or more, preferably 45 to 140 seconds.

When the heat treatment and the normalization treatment are performed on the polyolefin ketone fiber cord, the tension T _HS in the heat setting treatment is set to 0.7 cN / dtex or more, preferably 0.7 to 1.4 cN / dtex. the ratio of the tension T _NL at the tension T _HS and Norma rise process in the setting process (T _HS / T _NL) is 2 or less, preferably set to 1.2 to 2, after the process to the code length of the pre-treatment The code length increase rate is set to 0.9% or more, preferably 0.9 to 2.0%. In general, the cord expands in the heat setting process and contracts in the normalizing process, but the increase rate is the total stretch ratio of the cord before and after performing both the heat setting process and the normalizing process. By setting the above processing conditions, the elongation of the polyolefin ketone fiber cord when loaded with 2.0 cN / dtex is 2.0% or less.

  When the polyolefin ketone fiber cord is subjected to the prescribed heat set treatment and normalization treatment, thereby reducing the intermediate elongation of the cord, the cord is used when the polyolefin ketone fiber cord is used for the carcass layer of the pneumatic radial tire. Can be buried in tension without causing meandering due to loosening. As a result, it is possible to make full use of the characteristics of the high elastic modulus of the polyolefin ketone fiber cord. For example, the cornering power of a pneumatic radial tire can be increased to improve steering stability.

Here, when the tension T _HS in the heat setting process is less than 0.7 cN / dtex, it becomes difficult to prevent the cord from meandering. Further, if the ratio (T _HS / T _NL ) between the tension T _HS in the heat setting process and the tension T _NL in the normalizing process is larger than 2, it becomes difficult to prevent the meandering of the cord. Furthermore, when the rate of increase in the code length after processing relative to the code length before processing is less than 0.9%, it becomes difficult to prevent the meandering of the code. If the elongation of the polyolefin ketone fiber cord at a load of 2.0 cN / dtex is larger than 2.0%, it becomes difficult to prevent the cord from meandering.

  In the above-described embodiment, the case where the polyolefin ketone fiber cord is used for the carcass layer of the pneumatic radial tire has been described. However, in the present invention, the polyolefin ketone fiber cord is used as a tire reinforcing material other than the carcass cord or a rubber product reinforcing material other than the tire. Can be used as Moreover, the structure of a pneumatic radial tire is not limited to the said embodiment, It is possible to employ | adopt various structures known conventionally.

  Polyolefin ketone fiber cords of Examples 1 to 9 and Comparative Examples 1 to 15 were produced by varying only the dip treatment conditions. The polyolefin ketone fiber cord had a thickness of 1670 dtex / 2, and the number of lower twists and the number of upper twists were 38 times / 10 cm, respectively. For comparison, a rayon fiber cord was prepared as a conventional example.

  In the dip solution, the molar ratio of caustic soda and resorcin (NaOH / R), the molar ratio of resorcin and formalin (R / F), the total amount of resorcin and formalin and the weight ratio of latex (RF / L) are varied. It was. However, the weight ratio of latex was vinylpyridine (Vp): styrene-butadiene rubber (SBR): natural rubber (NR) = 55: 40: 5. The solid content ratio (TSC) of the dip solution was 18.0%.

  After the dipping process, a drying process is performed for 144 seconds at a temperature of 130 ° C. with a tension of 0.147 cN / dtex, and then a heat setting process is performed for 120 seconds at a temperature of 220 ° C. with a tension of 0.734 cN / dtex. Was 0.367 cN / dtex, and a normalizing treatment was performed at a temperature of 220 ° C. for 120 seconds.

  Two cords having a width of 25 mm formed by embedding the cord obtained in this manner in rubber at a driving density of 50/50 mm were vulcanized and bonded together to produce a test sample.

About these test samples, the peeling force in 100 degreeC and the peeling force after water immersion were measured, and the result was shown in Table 1 and Table 2. The peeling force at 100 ° C. is the force required to peel both the test samples while being heated to 100 ° C. The peeling force after immersion is the force required to peel the test sample after immersing it in water for 3 days. The measurement results are indicated by an index with the conventional example being 100. The larger the index value, the greater the peeling force, which means that the cord has better adhesion to rubber.

  As shown in Table 1 and Table 2, all of the polyolefin ketone fiber cords of Examples 1 to 9 exhibited adhesiveness equal to or higher than that of the rayon fiber cord. On the other hand, the polyolefin ketone fiber cords of Comparative Examples 1 to 15 in which the conditions of the dip solution deviated from the specified range of the present invention were inferior in adhesiveness to the rayon fiber cord.

  Next, polyolefin ketone fiber cords of Examples 10 to 14 were produced by varying only the dip treatment conditions. Here, the composition of the latex was mainly varied, and the other processing conditions were the same as those in the above test.

Two cords having a width of 25 mm formed by embedding the cord thus obtained in a density of 50/50 mm in rubber were vulcanized and bonded to each other to prepare a test sample. And about the test sample, the peeling force in 100 degreeC was measured, and the result was shown in Table 3. However, the measurement results are shown as an index with Example 12 as 100.

  As is apparent from Table 3, it can be seen that the adhesiveness at high temperature is increased when the ratio of the vinylpyridine latex in the latex contained in the dip solution is increased.

  Next, in the pneumatic radial tires of the tire size 205 / 65R15, tires of Examples 15 to 17 in which the polyolefin ketone fiber cord is used for the carcass layer and the conditions in the heat setting process and the normalizing process are variously changed. Produced.

  The thickness of the polyolefin ketone fiber cord was 1670 dtex / 2, the number of lower twists and the number of upper twists were 38 times / 10 cm, respectively, and the driving density in the carcass layer was 50/50 mm. For comparison, a pneumatic radial tire using a rayon fiber cord for the carcass layer was prepared as a conventional example. The thickness of the rayon fiber cord was 1840 dtex / 2, the number of lower twists and the number of upper twists were 49 times / 10 cm and 47 times / 10 cm, respectively, and the driving density in the carcass layer was 48/50 mm.

As conditions for heat setting and normalizing, tension T _HS in heat setting, tension T _{NL in normalizing} , ratio of tension T _HS to tension T _NL (T _HS / T _NL ), before processing The increase rate (total stretch rate) of the cord length after the treatment with respect to the cord length was varied. Regarding the dip solution, NaOH / R = 0.0.4, R / F = 0.65, and RF / L = 0.17.

  The test tires thus obtained were evaluated for carcass cord meandering and steering stability by the following test methods, and the results are shown in Table 4. Table 4 also shows the intermediate elongation of the cord when the load is 2.0 cN / dtex.

Carcass cord meander:
The carcass cord was pulled out from the carcass layer of the test tire, and the arrangement state of the carcass cord between one bead portion and the other bead portion was visually confirmed to check for the presence of the carcass cord meandering.

Steering stability:
The cornering power of the test tire was measured. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the greater the cornering power and the better the steering stability.

  As shown in Table 4, in the tires of Examples 15 to 17, no carcass cord meandering occurred, and the steering stability was superior to the case where rayon fiber cords were used for the carcass layer.

1 is a meridian half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 7 Belt cover layer

Claims (5)

In a cord in which a twisted yarn made of a polyolefin ketone fiber having a chemical structure represented by the following formula (1) is immersed in a mixed solution containing resorcin, formalin, latex, and caustic soda to provide adhesion,
_{- (CH 2 -CH 2 -CO)} n- (R'-CO) m- ··· (1)
However, 1.05 ≧ (n + m) /n≧1.00
R ′: an alkylene group having 3 or more carbon atoms The molar ratio of caustic soda (NaOH) and resorcin (R) in the mixed solution is 0.35 ≦ NaOH / R ≦ 0.55, and resorcin (R) and formalin (F ) And 0.25 ≦ R / F ≦ 1.0, and the weight ratio of the total amount of resorcin and formalin (RF) to latex (L) is 0.1 ≦ RF / L ≦ 0.4. Cord for rubber reinforcement. The rubber reinforcing cord according to claim 1, wherein 50% by weight or more of the latex contained in the mixed solution is vinylpyridine latex. A pneumatic radial tire in which the rubber reinforcing cord according to claim 1 or 2 is used for at least one carcass layer. 3. An air using the rubber reinforcing cord according to claim 1 or 2, wherein the cord has an elongation of 2.0% or less at a load of 2.0 cN / dtex for at least one carcass layer. Entering radial tire. When the heat reinforcing treatment and the normalizing treatment are applied to the rubber reinforcing cord according to claim 1 or 2, the tension T _HS in the heat setting treatment is set to 0.7 cN / dtex or more, and the heat setting is performed. The ratio (T _HS / T _NL ) between the tension T _{HS in the} processing and the tension T _NL in the normalization processing is set to 2 or less, and the increase rate of the code length after the processing to the code length before the processing is 0 A pneumatic radial tire using a treated cord set to 9% or more for at least one carcass layer.

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