JP3090793B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having improved durability by preventing the occurrence of cords generated during tire molding and vulcanization.

[0002]

Conventionally, and ply coating rubber of air Ri tire, in a rubber layer between the plies Sukijigomu, the rubber composition composed mainly of isoprene rubber with an emphasis on fracture properties have been found using. In general, isoprene rubber has a higher green modulus than synthetic rubber, but has a lower absolute level, and the ply cord used to reinforce the tire during molding and vulcanization of the tire is a so-called cord that cuts into the inner liner. It had the drawback that it caused out. When such a cord emerges, the gauge between the inner liner and the cord becomes thinner, so that not only can the tire pressure not be maintained for a long period of time, but also the concentration of stress occurs at the cord emergence portion when the tire rolls, and The durability was significantly reduced.

[0003] Several methods have been proposed to prevent such code output. For example,
There is a method in which the inner liner is preliminarily cross-linked by irradiating an electron beam during tire molding. Further, as other methods, Japanese Patent Application Laid-Open No. 50-74643 and
As disclosed in Japanese Patent Application Publication No. 109104, syndiotactic-1,2-polybutadiene (hereinafter referred to as “syn-1,
2PB ") to increase the green modulus. Further, Japanese Patent Application Laid-Open No. 61-11060
As disclosed in Japanese Patent Laid-Open No. 2 (1999) -1995, there is a method of dispersing a short fiber reinforced resin in a matrix rubber of a squeegee to increase a green modulus and prevent cords from appearing.

[0004]

However, the above-mentioned method of preventing the occurrence of a code, which has been conventionally proposed, has not always been satisfactory. That is, although the method of irradiating an electron beam at the time of molding a tire has a great effect in terms of preventing the occurrence of cords, it requires large-scale equipment and is not practical.

In addition, the rubber composition for the inner liner has a
The method of blending yn-1 and 2PB to increase the green modulus is effective in preventing the occurrence of cords, but since syn-1 and 2PB are present as crystals after vulcanization, the physical properties of the rubber such as modulus are reduced by temperature. Has a major drawback that it changes rapidly.

Further, a method of dispersing a short fiber reinforcing resin in a matrix rubber of a squeegee and increasing a green modulus to prevent the occurrence of cords involves a method of dispersing such a resin in a matrix fiber in the form of a short fiber. operation of kneading the resin at a high temperature into the rubber is required, it lacked versatility.

Accordingly, an object of the present invention is to increase the green modulus of the unvulcanized rubber, prevent the occurrence of cords generated during molding and vulcanization of the tire, increase the durability of the tire, and improve the physical properties of the rubber after vulcanization. In order to minimize the temperature dependence.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, a rubber component system in which isoprene-based rubber is present has syn-1 having a specific melting point.
By using a rubber composition containing a specific amount of 2PB as a ply coating rubber and / or a squeegee rubber, syn-1,2PB is completely or partially compatible with the polyisoprene rubber during vulcanization of the tire. It has been found that the crystallinity of syn-1,2PB after vulcanization by co-vulcanization is greatly reduced, the temperature dependence of the vulcanized rubber properties is reduced, and the above object can be achieved. It was completed.

[0009] That is, the pneumatic tire of the present invention, the rubber Ingredients 1 including natural rubber and / or isoprene rubber
A rubber composition comprising 3 to 30 parts by weight of syn-1,2PB having a melting point in the range of 60 to 110 ° C. with respect to 00 parts by weight is used for the ply coating rubber and / or the squeegee rubber. Things.

The melting point used in the present invention is 60 to 11
As syn-1,2 PB of polymerization catalyst is within the range of 0 ° C., the soluble cobalt, such as cobalt octoate, cobalt 1- Nafute ne over preparative, cobalt benzoate,
Organoaluminum compounds such as trimethylaluminum, triethylaluminum, tri-butyl aluminum, triphenyl aluminum, can be cited the catalysts system or the like consisting of a two-vulcanized carbon. Specific polymerization methods include JP-B-53-39917 and JP-B-54-543.
No. 6 and Japanese Patent Publication No. 56-18005 can be used, but the syn method used in the present invention can be used.
The polymerization method of -1,2PB is not particularly limited to the methods described above.

The method of mixing the rubber composition according to the present invention is not particularly limited, and the same effect can be obtained by a wet blending method in a solvent or a dry blending method using a Banbury mixer or the like.

The rubber composition according to the present invention contains an inorganic filler such as carbon black and silica, a softener such as aroma oil and spindle oil, an antioxidant, a vulcanizing agent, a vulcanization accelerator, and a vulcanizing agent. It goes without saying that a proper amount of a compounding agent usually compounded such as an accelerating aid can be appropriately compounded.

[0013]

The rubber composition for ply coating rubber and / or squeegee rubber of the pneumatic tire according to the present invention contains 3 parts of syn-1,2 PB having a melting point in the range of 60 to 110 ° C. per 100 parts by weight of the rubber component. It is necessary to mix up to 30 parts by weight.

It is the vulcanization temperature of the tire that defines the melting point range of syn-1 and 2PB in such a range.
At ~ 180 ° C, the syn-1,2PB is completely compatible with the polyisoprene rubber, or partially compatible and co-vulcanized. This is because the temperature dependency of the vulcanized rubber can be kept low. In other words, syn-
If the melting point of 1,2PB is higher than 110 ° C., the temperature dependency of the modulus becomes large due to the crystal of syn-1,2PB present after vulcanization, and the object of the present invention cannot be achieved. It is. On the other hand, syn-1,2
If the melting point of PB is lower than 60 ° C., no increase in the green modulus of the unvulcanized rubber is observed, and a sufficient effect of preventing cord release cannot be obtained.

The reason why the compounding amount of syn-1 and 2PB is specified in the above range is that if the compounding amount is less than 3 parts by weight, the green modulus of the unvulcanized rubber is relatively low, and the cord is not drawn. On the other hand, a sufficient prevention effect cannot be obtained, while if it is more than 30 parts by weight, the bending fatigue resistance of the rubber composition is inferior.

In the present invention, as described above, syn-
In view of the compatibility with 1,2PB, the presence of an isoprene-based rubber is essential as a rubber component, and it is preferable that the rubber component be present in an amount of 50 parts by weight or more. However, even if a conjugated diene rubber such as a butadiene-styrene copolymer is blended, the effects of the present invention are not lost.

As described above, the rubber composition for ply coating rubber and / or squeegee rubber of the pneumatic tire of the present invention is such that syn-1,2PB is completely compatible with polyisoprene rubber at the time of vulcanization, or one of them is not. Because of partial compatibility and co-vulcanization, the crystallinity of syn-1 and 2PB after vulcanization is greatly reduced. Therefore, according to the present invention, it is possible to increase the green modulus of the unvulcanized rubber and effectively prevent the occurrence of cords, and at the same time, suppress the temperature dependence of physical properties such as the modulus of the vulcanized rubber. .

[0018]

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. First, various syn-
A 1,2PB resin was prepared. In a 2-liter autoclave in which air was replaced with nitrogen gas, dehydrated benzene 760 was added.
cc was added, and 74 g of 1,3-butadiene was dissolved. To this, cobalt octoate 1 mmol (concentration 1 mmol / cc)
Was added, and after 1 minute, 2 mmol of triethylaluminum (a benzene solution having a concentration of 1 mmol / cc) was added thereto, followed by stirring, and then 1 minute later, the amount of acetone shown in Table 1 below was added. One minute later, carbon disulfide 0.6m
mol (a benzene solution having a concentration of 0.3 mmol / cc) was added thereto, followed by stirring at 10 ° C. for 60 minutes to polymerize 1,3-butadiene.

[0019] The resulting syn-1,2 PB resin product solution was added 2,4 Jitasha butyl -p- cresol 0.75 g. Then, 1000 cc of methanol
Then, syn-1 and 2PB resin production liquid were added thereto, and syn-
The 1,2PB resin was precipitated. This syn-1,2
The PB was further washed with methanol, filtered, and then dried in vacuum. The melting points of the obtained syn-1 and 2PB are also shown in Table 1 below.

[0020]

[Table 1]

A rubber composition for ply coating rubber and / or squeegee rubber was prepared by using the above-mentioned various syn-1 and PBs according to the formulation shown in Table 2 below. In addition, the rubber components in the table were adjusted to be 100 parts by weight in total.

[0022]

Table 2 Compounding agent parts by weight natural rubber (NR) variable amount styrene butadiene rubber (SBR) ¹⁾ variable amount butadiene rubber (BR) ²⁾ variable amount syn-1,2PB variable amount carbon black (HAF) 40 spindle oil 10 stearic acid 2 aging Inhibitor ³⁾ 1 ZnO 3 vulcanization accelerator (Nobs) ⁴⁾ 0.7 sulfur 3 soda 0.5 1) SBR # 1500 manufactured by Nippon Synthetic Rubber Co., Ltd. 2) BR01 manufactured by Nippon Synthetic Rubber Co., Ltd. 3) Large Nocrack 810-NA manufactured by Uchi Shinko Chemical Industry Co., Ltd. 4) Noccellar MSA-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

The rubber compositions shown in Table 2 were vulcanized at 165 ° C. for 15 minutes to prepare various test pieces. Further, such a rubber composition is used for a ply coating rubber and / or a squeegee rubber of a tire, and has a size of PSR165S.
Various test tires of R13 were prepared and evaluated for cord output. In this example, various measurements were performed according to the following methods.

1) Melting point Using a differential thermal analyzer (DSC200) manufactured by Seiko Co., Ltd., the temperature was lowered from 20 ° C. to 10 ° C. at a nitrogen flow rate of 20 ml / min.
/ Min at a heating rate of / min.

2) Breaking rate due to bending fatigue After performing a demashing test for 100 hours, the breaking rate (%) of the test piece was determined by the following equation. Rupture rate (%) = ｛(fracture length of test piece after bending fatigue) /
(Length of initial test piece)｝ × 100

3) Gauge between ply cord and inner liner A gauge of 10 cords was measured at the boundary position between the tread portion and the sidewall portion of the test tire, and the average value (mm)
I asked.

4 ) Modulus temperature change rate Measurement was performed in accordance with JIS K6301, and the modulus was determined by the following equation. Modulus temperature change rate (%) = ｛(100% elongation modulus at 100 ° C.) /
(Modulus at 100% elongation at 50 ° C.)｝ × 10
0

5 ) Drum Durability A test tire was loaded with an internal pressure of 1.0 kg / cm ² and a load of 470 kg.
Under the conditions described above, was run up to 10,000 km on a drum having a diameter of about 3 m. After the drum test, cut the tire,
The cross section was observed. The evaluation was performed according to the following criteria. ：: No abnormality △ 1: Cracking around the cord in the shoulder part (small) ２2: Cracking around the cord in the shoulder part (large) ×: Cracking along the cord in the shoulder part The following results were obtained. The results are shown in Tables 3, 4 and 5. In addition,
Table 3 shows the results of applying the rubber composition shown in Table 2 to squeegee rubber, Table 4 shows the results of applying the rubber composition to ply coating rubber, and Table 5 shows the results of applying the rubber composition to both squeegee rubber and ply coating rubber. .

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

First, Comparative Examples 1 to 3 and Examples 1 to 3 shown in Table 3 and Comparative Examples 6 to 8 and Example 8 shown in Table 4
10 to 10 confirm the following. syn-1,2
If the melting point of PB is lower than 60 ° C., no effect is obtained on the prevention of cords. On the other hand, if the melting point is higher than 110 ° C., there is an effect on the cords, but the modulus has a large temperature dependence. In addition, it is inferior in flex fatigue, and in any case, the effect of improving the durability of the tire is not recognized.

Next, Examples 4 and 5 and Comparative Examples 4 and 5 shown in Table 3 and Examples 11 and 12 and Comparative Examples 9 and 10 shown in Table 4 show that syn with respect to 100 parts by weight of the rubber component.
It was confirmed that there was an optimum range for the blending number of -1,2PB. That is, if the blending amount is less than 3 parts by weight, no effect on prevention of cord outgrowth is recognized, while if it exceeds 30 parts by weight, the effect on prevention of cord outgrowth becomes large, but the temperature dependence of the modulus becomes large. In addition, the flex fatigue was also poor. Therefore, in such a case, no improvement in tire durability is observed.

Examples 6 and 7 shown in Table 3 and Table 4
From Examples 13 and 14, it was confirmed that the effect of the present invention can be obtained in a blend system with another diene rubber as long as the isoprene rubber is present.

As can be seen from the examples shown in Tables 3 and 4, when a rubber composition containing a specific amount of syn-1,2PB having a specific melting point range is used for one of squeegee rubber and ply coating rubber, As a result, as shown in Table 5, the same effect can be obtained by using the rubber composition for both the squeegee rubber and the ply coating rubber.

[0036]

As described above, in the pneumatic tire of the present invention, as the rubber composition for the ply coating rubber and / or squeegee rubber of the tire, the rubber component in which isoprene-based rubber is present has a specific melting point. By using a rubber composition containing a specific amount of syn-1,2PB, the occurrence of cords occurring during molding and vulcanization of the tire is prevented, the durability of the tire is improved, and a crystalline resin is used. Nevertheless, the effect is obtained that the temperature dependence of the rubber properties such as modulus after vulcanization is minimized.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-109104 (JP, A) JP-A-56-166240 (JP, A) JP-A-52-72743 (JP, A) JP-A-2- 114002 (JP, A) JP-A-55-114606 (JP, A) JP-A-53-126050 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 7/00 B60C 1 / 00 C08L 9/00

Claims (1)

(57) [Claims] Respect 1. A natural rubber and / or rubber component per 100 parts by weight comprising isoprene rubber, mp 60-1
A pneumatic tire, wherein a rubber composition containing 3 to 30 parts by weight of syndiotactic-1,2-polybutadiene within a temperature range of 10 ° C. is used for a ply coating rubber and / or a squeegee rubber.