JPH02249705A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To restrict any reduction in the strength of a cord in practical travelling in the case of polyvinylalcohol synthetic fiber cord for reinforcing pneumatic tires by setting the strength of the cord so as to meet a specific relationship of a specific twist coefficient. CONSTITUTION:A pneumatic tire is provided with a polyvinylalcohol synthetic fiber (PVA fiber) cord reinforced belt 1 and a steel cord reinforced belt 2. In this case, filaments of the PVA fiber cord are bridged by a bridging material. When a specific twist coefficient of the PVA fiber cord is expressed by NT, the strength S of the PVA fiber cord taken out from a tire is set to meet the following relationship: S>=14.5-12 NT. Further, when the PVA fiber cord is melted in dimethylsulfoxide at temperature of 120 deg.C, insoluble matters are set at above 5 weight %. As a result, any reduction in the strength of the PVA fiber cord can be restricted even after paratical travelling.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention is a high-strength "polyvinyl alcohol-based synthetic fiber" (hereinafter abbreviated as rPVA fiber) for reinforcing rubber, especially for pneumatic tires, which has significantly improved fatigue resistance. This relates to pneumatic tires reinforced by .). The present invention also relates to a method for producing the above-mentioned high-strength "PVA fiber."

(Prior Art) Conventionally, PVA fibers have been widely used for industrial purposes as rubber reinforcing materials. However, this fiber has the disadvantage of poor fatigue resistance and poor hot water resistance because it has a polymer property of being inherently soluble in water. Therefore, at present, this fiber is only partially used as a belt material for radial tires, which has a relatively low input strain, as a tire reinforcing cord that is subjected to a large amount of bending strain.

However, today, JP-A-59-130314 and JP-A-59
As seen in each publication of No. 9100710, it has become possible to increase the strength of PVA fibers by increasing the molecular weight (for example, average molecular weight of 400,000 or more). However, it is difficult to industrially produce such ultra-high molecular weight PVA polymer, and due to manufacturing difficulties, the cost is significantly higher than that of fibers used in general tire cords such as polyester and nylon. It was expensive and could not be commercially competitive.

From the above background, PVA polymer has been replaced with conventional PVA.
A method was discovered that was industrially relatively easy and could supply a large amount of high-strength PVA fiber by making the molecular weight slightly larger than the molecular weight of the fiber (for example, JP-A-60-1
No. 26311 and No. 60-126312), there is a prospect of industrial and commercial use as tire cords. Although the high-strength PVA fibers supplied in this way are not comparable to aramid fibers in both strength and elastic modulus, their strength is significantly improved over conventional fibers such as nylon and polyester, so they are sufficient for tire cords. It looked usable. In addition, the high-strength PVA fibers obtained by this method have significantly improved resistance to mechanical strain input compared to conventional PVA fibers, as described in JP-A-61-108713. Therefore, it was thought that the fatigue resistance as a tire cord would be sufficient for practical use.

(Problems to be Solved by the Invention) However, the present inventors have revealed that the high-strength PVA fiber obtained by the above method has a serious drawback in terms of fatigue resistance. In other words, it is clear that if the tire cord remains as it is, it will not have enough fatigue resistance as a tire cord, and the cord will break even during normal driving (hereinafter referred to as rCBUJ: cord breaking amplifier), making it unsuitable for practical use as a device for tire safety reasons. I made it. This point will be explained in more detail below.

Tire size 19 using various fiber materials shown in Table 1 below as carcass ply cord under the conditions shown in the same table.
5/70 SR14 passenger car tires were prototyped, and the cord strength retention rate of the carcass ply was evaluated by comparing with the cord strength when new after drum running and actual running. The obtained results are also listed in Table 1. The strength retention rate of the carcass ply cord was measured at the part marked with an x on the tire shown in FIG.

As is clear from Table 1, the strength retention rate of high-strength PVA fibers after drum running was almost the same as that of polyester fibers, but the cord strength retention rate after actual running was 90% or more for polyester fibers. In contrast, high-strength PVA
The fiber content decreased to 20-40%, and in some cases, CBU occurred, and the tire was on the verge of puncture.

In the above practical driving test, test tires were installed on a normal vehicle, and the internal pressure was normal (usually 1.7 kg/aa).
”), but this is just a controlled condition for tire usage conditions, and in the general market, overloading and sometimes internal pressure of 1.0kg /
It is possible that it is used under abnormal conditions such as Cl11" or less. Therefore, the fact that the cord strength retention rate was 20 to 40% after 50,000 actual driving under controlled conditions indicates that it is safe in the general market. It must be concluded that the accuracy cannot be guaranteed at all, and such a code cannot be put to practical use in the device as it is.

Furthermore, the following tests were conducted on the belt.

A passenger car tire with a tire size of P235/75R15 having the folded belt structure shown in FIG. 2 was experimentally manufactured using various fiber materials shown in Table 2 below as a belt cord under the conditions shown in the same table. Regarding these tires, the strength retention rate of the belt cord after actual running was evaluated as described above. The obtained results are also listed in Table 2. The location where the strength retention rate of the belt cord was measured was the part marked with an x in FIG. 2.

As is clear from Table 2, even when high-strength PVA fibers are used as belt cords, the strength retention rate of the cords decreases to about 60% compared to when they were new, indicating that there is still a major problem in fatigue resistance. found.

Therefore, an object of the present invention is to establish a high-strength PVA fiber that hardly causes a decrease in the strength of the cord even after running on the road, and to improve the durability of pneumatic tires by using the high-strength PVA fiber as a tire reinforcing cord. The goal is to improve.

(Means for Solving the Problems) The inventors of the present invention conducted extensive studies on the cause of the decrease in the strength of the high-strength PVA fiber cord after the above-mentioned actual running, and as a result, the following findings were obtained.

First, when we embedded the cord taken out from the tire after actual driving into epoxy resin and observed the cross section of the cord cut with a microtome, we found that the filaments near the intersection of the first twist and second twist were significantly deformed, and 10 filaments were removed. It was found that the above areas were clustered together in Tohoku. Normally, the filament has the role of dispersing the strain caused by the cord between the filament and the cord, so if the filament aggregates and the strain cannot be evenly distributed, the strength of the filament or cord will decrease. It turns out.

Next, in order to further clarify such a filament aggregate phenomenon, the top twist and bottom twist were loosened, and the cord interface where the top twist and bottom twist were in contact was observed under a microscope. As expected, there was evidence that the filaments were shaped into a film, as if they had been pressed, in units of several to dozens of filaments.
It was found that it was impossible to alleviate the strain input, which is considered to be the original role of the filament. Such a phenomenon of aggregation between filaments was not observed in polyester or aramid fibers, but was a phenomenon observed only in PVA fibers.

On the other hand, drum running (20,000 i running, strong cord retention rate 60
%), although some of the filament aggregation phenomenon described above is observed in some areas, the extent of the filament aggregation phenomenon is extremely small, and it is considered that the strain input is still uniformly distributed to each filament during drum running. In addition, with conventional PVA fibers, CBU occurs at 4,700 klIl even when running on a drum, but with the high-strength PVA fibers, the residual strength is 60% even after 20,000 klIl, compared to conventional PVA fibers.
It can be seen that the fatigue resistance is significantly improved compared to fiber.

However, even with such improved high-strength PVA fibers, the strength of the cord decreases significantly after being run on the ground, a phenomenon that could not be predicted by the equipment based on conventional knowledge.

Therefore, the present inventors observed the following differences in detail by observing the cord and filament after actual running and after running on a drum. In other words, (1) during actual running, the cord is heated to 100°C because running and stopping are repeated.
Subject to repeated irregular temperature history up to room temperature.

(2) During actual running, the strain input received by the cord constantly changes irregularly, and accordingly, the locations where the filaments rub against each other and the rubbing input also change.

(3) On the other hand, the cord during drum running is constantly exposed to a high temperature of 100'C or more, and the rubbing force between the filaments is easily alleviated by softening of the filaments themselves.

The above findings indicate that the filament of the cord after running on the drum is
While the filaments have a so-called bias-cut surface due to the strain between the filaments being concentrated in one place in the filament, the filament surface of the cord after actual running shows scratches where the filaments rub against each other in many places. This can also be explained by the fact that when looking only at the bias-cut surface, there are several rubbing marks within the bias-cut.

Based on the knowledge that it is sufficient to prevent filament aggregation in order to reduce the filament input due to filament aggregation and bundling as described above and increase the fatigue resistance of the cord of high-strength PVA fibers, the present invention has been developed as follows. This was done after careful consideration.

In other words, since PVA fibers originally have hydrogen bonds within their molecules, even the presence of a small amount of water causes the hydrogen bonds to have an affinity for water molecules, which explains the disadvantage that PVA fibers themselves tend to aggregate. This is thought to be the cause. Further, it is considered that water molecules penetrate into the amorphous part of the PVA fiber and cause the amorphous part of the PVA fiber to swell, which causes, for example, a decrease in the glass transition point.

Furthermore, it is said that densification of the amorphous portion and high orientation are effective means for achieving high strength in the above-mentioned high strength PVA fibers, and Japanese Patent Application Laid-open No. 108713/1983 discloses that such high strength PVA fibers are Although it has been reported that the steam heat resistance of cords is also improved, it is clear from the above results that it is still impossible to improve the fatigue resistance of cords after actual running.

Therefore, in order to prevent the strength loss due to filament compression and rubbing, the present inventors have found that if the filament is cross-linked and hardened, the strength loss of high-strength PVA fibers during actual running can be substantially prevented. After careful consideration, we found that either high-strength PVA filaments with a fiber strength of 15 g/d or more or cords made by twisting these filaments are swollen to allow the crosslinking agent to penetrate into the inside of the filaments, or a PVA solution can be used. After adding a cross-linking agent to the mixture and uniformly dispersing the cross-linking agent, PVA is spun, subjected to a dry heat treatment to carry out a cross-linking reaction, and then treated with ordinary resorcinol-formalin-latex (hereinafter abbreviated as rRFLJ). The present inventors have found that by crosslinking PVA through adhesive treatment and using such a cord, it is possible to significantly prevent a decrease in the strength of the cord after running on a tire, leading to the completion of this invention.

That is, the present invention provides a pneumatic retired tire reinforced with a PVA fiber cord, in which the filaments of the cord are crosslinked with a crosslinking agent, and the cord taken out from the tire has the following formula: % formula % (in the formula, N7 is Nv-Nxi maD/pX10-'' is the twisting coefficient, where N is the number of twists of the cord (twists/l0CII
+), D is the token denier number of the cord 172, ρ
indicates the chord specific gravity).
d) is a high-strength PVA fiber cord, and the pneumatic tire has an insoluble component of 5% by weight or more when the cord is dissolved in dimethyl sulfoxide at 120°C.

A method for producing a high-strength PVA fiber cord having the above-mentioned properties for use in the pneumatic tire of the present invention is also provided as a second invention, and this method is applied to a raw yarn of high-strength polyvinyl alcohol-based synthetic fiber or to this raw yarn. A cord made by twisting together multiple underburned threads is treated with a crosslinking agent,
This is a method for producing a high-strength polyvinylnarcohol-based synthetic fiber cord for rubber reinforcement, which is then bonded and heat-treated with a resorcinol-formalin-latex adhesive.

Furthermore, a third invention, which is another method for manufacturing the cord,
In the spinning process of polyvinyl alcohol-based synthetic fibers or the subsequent coagulation bath process, a crosslinking agent is infiltrated into the inside of polyvinyl alcohol, and a crosslinking reaction of polyvinyl alcohol is performed during heating and stretching of the coagulated polyvinyl alcohol filament. This is a method for producing a high-strength polyvinyl alcohol-based synthetic fiber cord for rubber reinforcement, which involves subjecting filaments having a crosslinked structure to a twisting process to produce a green cord, and subjecting the cord to an adhesive treatment with resorcinol-formalin-latex under heating.

Conventionally, it was thought that crosslinking the filament to the inside would immediately reduce the strength of the cord. Furthermore, crosslinking only the surface layer did not cause a decrease in strength, and although it was effective against friction fatigue like belt materials, it did not improve fatigue resistance when compressive strain was applied like carcass plies.

The present inventors succeeded for the first time in obtaining a carcass ply tire cord with no loss in strength and good fatigue resistance by selecting a preferable crosslinking agent for high-strength PVA fibers and devising crosslinking treatment conditions. It is. Furthermore, we have also succeeded in using such cross-linked high-strength PVA fiber cords as belt materials in place of steel cords.

(for production) This invention will be specifically explained below.

The general method for producing high-strength PVA fibers with a fiber strength of 15 g/d or more, as required by this invention, uses a polymer with a higher molecular weight than that used in the production of conventional PVAN fibers.
This can be achieved by increasing the draw ratio during spinning, or by spinning an ultra-high molecular weight polymer from a dilute solution and stretching it at a high draw ratio, generally known as gel spinning. .

The crosslinking agent used in this invention is preferably one that reacts with the hydroxyl group in the PVA molecule and causes a crosslinking reaction.
Any other method may be used as long as it crosslinks the A molecular chains. Examples of crosslinking agents include phosphoric acid compounds, aldehydes, methylol compounds, epoxy compounds, isocyanate compounds, peroxides, crosslinking agents containing metals or phosphorus, and inorganic acid compounds other than phosphoric acid compounds that cause dehydration reactions. .

The phosphoric acid compound used in this invention refers to phosphoric acid or phosphates containing metal ions, and in addition to orthophosphoric acid, it also includes metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, and ammonium phosphate. , phosphorus oxychloride, etc. have a similar effect, but orthophosphoric acid is preferable because it is used as orthophosphoric acid in an aqueous solution. Examples of the compound include at least one selected from the group consisting of compounds represented by the following structural formulas.

1) Hanging occurs like in glycerol polyglycidyl ether, and then by applying heat, crosslinks are formed between molecules as shown in the following formula: -P-OH 00H -CH-CH-CH-CH-.

Examples of the aldehydes used in this invention include formaldehyde, glyoxal, and terephthalaldehyde, and examples of the methylol compound include N-methylolacrylamide.

2) Trimethylolpropane polyglycidyl ether 2) 3) Diglycerol polyglycidyl ether CH3 4) Sorbitol polyglycidyl ether H υ (n in the formula represents 1, 2.3) 7) Neopentyl glycol diglycidyl ether I3 5 ) Ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether 8) Olympus cresol novolac type epoxy resin 25χ emulsion (n in the formula represents 1, 2.3) 6) Propylene glycol diglycidyl ether or polypropylene glycidyl ether Glycidyl ether (in the formula, a represents 0.3 to 16, b represents 1.7 to 4.4) 9) As the terephthalic acid diglycidyl ester ortho-phthalic acid diglycidyl ester isocyanate compound, diphenylmethane diisocyanate is used. (MDI), naphthylene-1,5-diisocyanate (NDI), o-)
Examples include tylene diisocyanate (TODI).

In addition, peroxides include dicumyl peroxide,
Examples include 2,5-dimethylhexane-2,5-dihydroperoxide and dilauroyl peroxide. The crosslinking agent containing metal or phosphorus is AI! ,, Ti.

A compound containing P, Cr, Cu, etc., for example,
These include alkyl titanates, titanium raftate, and aluminum tris (acetylacetonate).

Examples of the inorganic acid compound that causes the dehydration reaction include hydrochloric acid and formic acid.

Next, a method for reacting a crosslinking agent with a PVA fiber cord will be described.

When the crosslinking agent is infiltrated into the PVA fiber cord or yarn in a bath diluted with a solvent, it is recommended to use the same solvent as the spinning solvent in order for the crosslinking agent to penetrate into the inside of the filament. Preferred spinning solvents include dimethyl sulfoxide, glycerin, ethylene glycol, propylene glycol, triethylene glycol, dimethyl formamide, methyl alcohol, ethyl alcohol, phenol, n-propyl alcohol, 1so-propyl alcohol, water and combinations of these solvents. A mixed solvent may be used, but dimethyl sulfoxide and water are particularly preferred. When the temperature of a bath in which a crosslinking agent is dissolved in dimethyl sulfoxide or water is set to about 50°C to 90°C, the amorphous part of the PVA fiber swells and flows into the inside of the filament. helps the crosslinking agent penetrate.

In this case, the longer the immersion time, the better, but about 30 minutes is sufficient.

Thereafter, excess crosslinking agent adhering between the cords and on the surface of the filament is washed away with water or alcohol, and a dry heat treatment is performed to carry out the crosslinking reaction.

To specifically explain the above method in terms of the treatment of phosphoric acid compounds in this invention, high strength PVA fibers are treated with phosphoric acid compounds.
% or more, the amorphous part of the PVA fiber is swollen by raising the temperature, and the crosslinking agent penetrates into the inside.

Therefore, the higher the temperature, the more the crosslinking agent penetrates into the interior.

This temperature is preferably 50°C or more and 80°C or less, and the immersion time is preferably 10 minutes or more and 40 minutes or less. If the temperature is higher than this for a long time, there is a risk that the strength will decrease.

Then, wash with water to remove excess crosslinking agent and catalyst attached to the surface. Thereafter, it is preferable to force dry at a temperature of 50 DEG to 120 DEG C., then heat-treat under tension at a temperature of 100 DEG to 240 DEG C., and then perform a conventional RFL adhesive treatment.

Further, to explain an example of epoxy compound treatment, it is preferable that the epoxy compound is dissolved in water or an organic solvent and used at a concentration of 5% or less. The reason for this is that if the concentration exceeds 5%, there is a need to worry about a decrease in adhesive strength.

Furthermore, it is preferable to immerse the yarn or twisted cord of high-strength PVA fibers in the solution to which a catalyst has been added, and then perform a dry heat treatment under tension. This drying is carried out at 100°C or higher, and then at 150°C or higher.
Epoxy compound and PV by heat treatment at a temperature of ~240°C
React with A fiber. This is preferably followed by a conventional RFL adhesive treatment.

Furthermore, in the present invention, it is of course possible to allow the crosslinking agent to penetrate into the interior of the filament during the spinning process or the coagulation bath process after spinning, and this method is rather preferable from an industrial perspective. Specifically, the method of adding a crosslinking agent to a spinning dope is to prepare a spinning dope in which 2 to 50% by weight of PVA is dissolved, and add a crosslinking agent to this dope by weight of PVA10.
Input so that the ratio is 1 or less compared to 0. The spinning method may be either a dry method or a wet method, or a dry/wet method that is a combination of both methods. Generally, after spinning, the fiber is passed through a coagulation bath of methanol or the like, then stretched, subjected to heat treatment, and further stretched while performing a crosslinking reaction. It is also possible to adopt a method in which the crosslinking agent is not added to the above-mentioned spinning dope and the crosslinking agent is allowed to penetrate inside the fibers in this coagulation bath. The temperature required for this crosslinking reaction varies depending on the crosslinking agent, but is generally preferably 120° C. or higher and lower than the melting point of the filament. Further, ultraviolet rays, far infrared rays, microwaves, etc. may be used for the crosslinking reaction. After crosslinking, when the fiber cord is dissolved in dimethyl sulfoxide at 120°C, the amount of insoluble components must be 5% by weight or more, preferably 10% by weight or more, more preferably 30% by weight or more.
% by weight or more. After a crosslinking reaction is performed on the PVA filament, in which the amount of insoluble components is an indicator of the degree of intermolecular crosslinking, the PVA filament is subjected to a twisting process to form a green cord. After that, convert this raw code to normal RFL
Subject to adhesive treatment.

High-strength PVA crosslinked by the method of this invention
Pneumatic tires reinforced with fiber cords subjected to normal RFL treatment have a lower cord strength after actual tire running than pneumatic tires reinforced with ordinary PVA fiber cords that have not been subjected to such treatment. The strength retention rate of the high strength PVA fiber cord taken out from the tire is 80% or more in the carcass ply, and the strength retention rate of 80% or more can be obtained in the belt material.

Such high-strength PVA fibers that satisfy the conditions of the present invention can have significantly improved strength and elastic modulus compared to conventional nylon and polyester fibers. As a result, the amount of cord used can be significantly reduced compared to conventional fiber cords, resulting in lighter tires and lower drying resistance, and when such cords are used as belt material, they can replace steel cords. As a result, it is possible to reduce road noise and significantly improve ride comfort due to vibration.

(Example) Next, the present invention will be explained with reference to Examples and Comparative Examples.

The codes for Examples 1 to 15 and Comparative Examples 3 and 6.7 below are JP-A-61-10871.1 and JP-A-61-108.
High tenacity PVA with yarn strength of 17.5 g/d obtained by the method described in No. 712, No. 61-108713, etc.
Yar: A 1500 d/2 cord obtained by applying a certain number of underburnings to a 1,500 denier cord, plucking the two underburning cords together, and then twisting the yarn a certain number of times was used. In other comparative examples, conventional PVA cords shown in Tables 5 and 6 were used.

The crosslinking treatment with a phosphoric acid compound was carried out by immersing the twisted cord in a mixed aqueous solution of orthophosphoric acid and urea having a formulation shown in Table 3 below, and leaving it at 60°C for 30 minutes.

After that, the cross-linked twisted cord was washed with water and
After drying at °C for 1 minute, tension heat treatment was performed at a tension of 0.5 g/d. The cord was then subjected to RFL dip processing. This dip treatment was performed using the RFL adhesive shown in Table 4 below, and after dipping in the RFL adhesive, the cord was subjected to tension heat treatment in a dry zone, hot zone, and norm zone. The processing temperature, time and tension conditions for these zones are as follows: dry zone 150
°CX120secX0.1g/d, hot zone 200'
CX 40 seconds x 1 g/d and norm zone 200°C
x 40 seconds x 0.5 g/d.

The cord obtained by this method (number of twists: 31 x 31) was embedded in a rubber composition for cord embedding, and JISL 10
17-1983 Reference Standard 3.2.1. A fatigue test sample was prepared based on the Section 6 method, and a belt bending fatigue test was conducted.

At this time, the pulley diameter was set to 20 nua, and the load was 100 nua.
kg, and the bending was repeated 10,000 times at a temperature of 00°C.

For comparison, we used a conventional PVA fiber cord (twist count: 2).
8.3×28.3) was subjected to the belt bending fatigue test as described above (Comparative Example 1°2 in Table 5 below).

The test results are shown in Table 5 below.

From Table 5 above, the following was confirmed.

In Comparative Example 3 and Examples 1 to 8, high strength PVA was used as the sample.
As examples using fiber cords, since Examples 1 to 8 were treated with phosphoric acid, the fatigue resistance was significantly improved compared to Comparative Example 3, which was not subjected to such treatment.

Further, in Examples 1 to 8, the heat treatment temperature and time were varied, but the effect of improving fatigue resistance was confirmed in each case. In particular, the higher the heat treatment temperature or the longer the treatment time, the more the fatigue resistance is improved. However, as in Examples 5 and 8, it was confirmed that if the heat treatment is applied too much, the strength decreases.

Examples 7.9 to 11 are examples in which the phosphoric acid concentration was varied, but the fatigue resistance improvement effect was 1i at any concentration.
! ! ! ! It was done.

Next, the treated cord obtained by the adhesive treatment as described above is made into a sudare weave, and then covered with a rubber sheet in the usual manner to make a rubberized cloth, which is used as a carcass ply or belt member, and various A test tire was manufactured. The tire size was 195/70 SR1 for the prototype tires for carcass ply examination of Comparative Examples 4 to 6 and Example 12.13.
4, and 185/70 R13 size for the trial tires for belt examination of Comparative Example 7 and Example 14.15. Further, the number of cords inserted in the crown center part of the trial tire was 33 cords (15cn+) for the carcass ply, and 40 cords (15c11) for the belt.

In Comparative Examples 4 and 5, conventional PVA fibers were applied to the carcass monobly for comparison.

Regarding the above prototype tire, a strength measurement test of the cord taken out from the tire, a drum running test for evaluating the durability of the bead part (
Hereinafter abbreviated as "bead section durability drum running test") and a field running test were carried out as follows. The measurement position is the first one for the prototype tire for carcass ply examination.
The test was conducted at the part where the strength reduction rate was the largest, which is the bead folded part marked with an X in the figure. In addition, the prototype tire for belt examination has a high-strength PVAtI belt structure with a folding structure.
! This tire has a two-layer structure consisting of an A-fiber cord reinforcing belt 1 and a steel cord reinforcing belt 2, and the test was conducted at the belt fold-back portion marked with an X in FIG.

1 Cord (S) Weight Belt bending test After removing the attached rubber from the sample and the cord taken out from the tire with scissors, the cord was pulled at room temperature with a distance of 10 cm between chucks according to JIS L1017, and the strength at break was measured. The value obtained by dividing the breaking strength by the torque denier number before twisting was defined as the strength S (g/d). The torque denier is the denier before twisting, but this is complicated because the cord expands and contracts slightly during the cord processing process and tire vulcanization process, and the cord taken out from the tire has some rubber adhesion. This is to avoid confusion.

Bead Dome - The prototype tire was heated indoors at 25°C ± 2°C with an internal pressure of 3.0.
kg/CTII” and leave it for 24 hours.
The air pressure was readjusted, a load twice the JIS load was applied to the tire, and the tire was run for 20,000 rounds at a speed of 60 am/hour on a drum approximately 3 m in diameter. Thereafter, the cord was removed from the tire, and the strength of the cord was measured according to JIS L1017 as described above. The test results were expressed as a percentage retention rate, with the strength before running being 100.

After assembling the Sara 11 Sooka Hachiten prototype tire with the specified rim, it was installed on a general passenger car and driven in general, and the 195/70 SR14 size carcass ply trial tire was used for approximately 50,000 hours of actual driving.
In addition, the cord strength of the 185/70 R13 belt cord test prototype tire was measured in accordance with JIS L1017 after traveling 320,000 km as described above.

The strength retention rate was expressed as a percentage in the same manner as in the door section durability drum running test.

The results obtained are shown in Table 6.

From Table 6 above, the following was confirmed.

Comparative Example 4.5 is an example using a conventional PVA fiber cord, but these examples show that even conventional PVA fiber cords that have been subjected to the above crosslinking treatment can have high performance when used as a carcass ply material. It was found that strength and fatigue resistance were improved.

Comparative Example 6 is an example in which a high-strength PVA fiber cord was used as a carcass ply material without undergoing the above-mentioned crosslinking treatment,
On the other hand, Examples 12 and 13 are examples in which such cords subjected to the above-mentioned crosslinking treatment were used as carcass ply materials.

From these examples, it was confirmed that fatigue resistance was significantly improved when a high-strength PVA fiber cord subjected to the above-mentioned crosslinking treatment was used for the carcass ply.

Comparative Example 7 is an example in which a high-strength PVA fiber cord is used as a belt material without undergoing the above-mentioned cross-linking treatment, while Examples 14 and 15 are examples in which such a cord is subjected to the above-mentioned cross-linking treatment and is used as a belt material. This is an example. From these examples,
It has been found that even when a high-strength PVA fiber cord subjected to the above-mentioned crosslinking treatment is used as a belt material, the fatigue resistance is improved.

16-32 6 8-12 The codes of Examples 16-32 and Comparative Examples 9-12 below are all JP-A-61-108711, JP-A-61-108712,
High tenacity PVA yarn 150 with a yarn strength of 17.5 g/d obtained by the method described in Publication No. 61-108713 etc.
Using 0 denier or 1800 denier, after applying a certain number of underburning cords, two underburning cords are combined and twisted a certain number of times to obtain 1500d/2 or 180 denier.
0d/2 was used.

After immersing the cord obtained as described above in an epoxy compound solution having the formulation shown in Table 7 below for about 10 seconds,
Dry and heat treated.

However, since terephthalic acid diglycidyl ester is insoluble in water, the formulation shown in Table 7-2 below was used.

The temperature was 150°C, the exposure time was 120 minutes, and the tension was 0.
The test was carried out under a tension of 1 g/d +200° (x120 minutes xo, 45 g/d).

Thereafter, the cord was subjected to RFL dip processing.

This dip treatment was performed using the RFL adhesive shown in Table 4 above, and after dipping in the RFL adhesive, the cord was subjected to tension heat treatment in a dry zone, hot zone, and norm zone. The processing temperature, time and tension conditions in these zones were the same as in Examples 1-15 and Comparative Examples 1-7.

The treated cord obtained by the adhesive treatment as described above was made into a sudare weave, and then covered with a rubber sheet in the usual manner to make a rubberized cloth, which was used as a carcass ply or belt member, and was used to fabricate various test tires. We made a prototype. The tire size was 195/70 SR14 for the trial tires for carcass ply examination of Comparative Examples 8 to 10 and Examples 16 to 20, and 185/70 R13 for the trial tires for belt examination of Comparative Example IL 12 and Examples 21 to 32. Size. Further, in the drying and heat treatment of the trial tire, the number of cords in the crown center using a dip machine was 33 cords/5 cm for the carcass ply, and 40 cords/5 cm for the belt.

In Comparative Examples 8 and 9, conventional PVA fibers were applied to the carcass monoply for comparison.

For the above prototype tires, a strength measurement test of the cord taken out from the tire, a bead durability drum running test, and a field running test were carried out in the same manner as described in Examples 1 to 15 and Comparative Examples 1 to 7.

The results obtained are shown in Table 8.

From Table 8 above, the following was confirmed.

First, carcass ply application examples (Comparative Examples 8 to 10, Examples 16 to 20) will be described.

Comparative Example 8 is an example using a conventional PVA fiber cord, but this example has poor fatigue resistance and the bead part durability drum 4
After driving 600km, the cord broke at the bead and the tire broke.

Comparative Example 9 and Example 16 are both examples in which high-strength PVA fiber cords were used, but whereas Example 16 was subjected to epoxy treatment, Comparative Example 9 was not subjected to such treatment. As a result, in Comparative Example 9, the cord broke after traveling 10,000 km on the bead durability drum, but in Example 16, the cord broke after traveling 20,000 km.

Comparative Example 10 and Example 17 use DMSO as the spinning solvent.
These are examples of high-strength PVA fiber cords using DMSO, which have improved fatigue resistance by using DMSO.
Both cars completed 20,000km on the bead section of the endurance drum.

However, in Example 17, in which such a high-strength PVA fiber cord was subjected to epoxy treatment, the fatigue resistance was further improved compared to Comparative Example 10, in which such treatment was not performed.

A practical 50,000 kilometer running test was conducted on the above-mentioned Examples 16 to 20 and Comparative Example 10, and all of them were able to complete the run. However, the strong code retention rate was 3 in Example 16.
In Comparative Example 10, it was 30%, and in Comparative Example 10, some cords were on the verge of breaking. On the other hand, in Example 17, the cord strength retention rate was 95%, and it was confirmed that the cord was sufficiently usable.

Examples 17 to 19 are examples in which the temperature conditions when treating high-strength PVA fiber cords with diglycerol polyglycidyl ether were changed. In all of these examples, good results were obtained in the drum running test and the actual running test.

In Example 20, an epoxy compound different from the above-mentioned epoxy compound was used, but the same effect as that of the above-mentioned Example was still observed.

Next, application examples of PSR tire belts (Comparative Examples 11 and 12 and Examples 21 to 32) will be described.

Comparative Example 11 and Example 21 are examples of cases in which epoxy treatment was not performed and cases in which epoxy treatment was applied. When epoxy treatment was applied according to these examples, the cord strength retention rate after 32,000 km of actual driving was 4 g. % to 65%.

Comparative Example 12 and Examples 22 to 32 are both examples in which DMSO was used as a spinning solvent, but Examples 22 to 32 were subjected to epoxy treatment, whereas Comparative Example 12 was not subjected to such treatment. As a result, in both cases, the actual running test resulted in a completion of 32,000 kII+, but in Comparative Example 12, the cord strength retention rate at this time was 60.
%, whereas in Examples 22 to 32, it was 87% or more, indicating that any epoxy treatment in Table 8 was effective. In addition, Examples 22, 31, and 32 are examples in which the temperature conditions when treating high-strength PVA fiber cords with diglycerol polyglycidyl ether were changed, but in all of these examples, drum running tests were performed. Good results were obtained in field tests.

33-40. 13-15 In the following Examples 33-40 and Comparative Examples 14.15, 1500 d/2 or 1800 d/2 obtained in the same manner as the fiber cord manufacturing method of Examples 16-32 and Comparative Examples 9-12 was used as the cord. The code was used.

As a crosslinking agent, A-codihydroxybislacta=totitanium (Ti(OH)z (OCH(CH3)COOH)
(OCR(CHj)COONH4) ”) (TLA
), B: 4.4'-diisocyanatodiphenylmethane (MDI), C diglycerol polyglycidyl ether, and D: formalin were diluted with water in the proportions shown below.

A: TLA 5g 50g B: MDl 5g 50g C Nidiglycerol polyglycidyl ether 5g 50g D: Formalin 5g NazS0435 g HzSOa 35g 50g In Examples 33.34.36 to 40, the PVA fiber cord was wound into a skein shape. This was immersed in various crosslinking treatment solutions at 60°C for 30 minutes, washed with water, and subjected to dry heat treatment under tension. The dry heat treatment conditions include a treatment temperature of 15
0'CXi exit time 120 seconds x tension 0.1g/d +20
The temperature was 0°C x 120 seconds x 0.5 g/d.

In Example 35, completely saponified type (saponification degree of 99.5% or more) polyvinyl alcohol with a polymerization degree of 3500 was used.
A 2% by weight dimethyl sulfoxide (DMSO) solution was prepared, and TLA was added thereto at a ratio of 0.006 to 100 of the polymer, which was used as a spinning dope, and wet-dry spinning was carried out in a methyl alcohol coagulation solution. The resulting coagulated thread was washed in a methanol bath to remove DMSO and stretched three times. Thereafter, the dried coagulated yarn was heated to 230° C., stretched five times, and simultaneously subjected to a crosslinking reaction. A raw cord was obtained by doubling and twisting the raw yarns thus obtained.

Thereafter, each of the above cords was subjected to RFL dip processing.

This dip treatment was performed using the RFL adhesive shown in Table 4 above, and after dipping in the RFL adhesive, the cord was subjected to tension heat treatment in a dry zone, hot zone, and norma zone. The processing temperature of these zones,
The time and tension conditions are Examples 1 to 5 and Comparative Examples 1 to 7.
It was the same.

The treated cord obtained by the adhesive treatment was made into a sudare weave, and then covered with a rubber sheet in the usual manner to make a rubberized cloth, which was used as a carcass ply member in the structure shown in Table 9. , various test tires were manufactured. The tire size is 1 as a prototype tire for carcass ply examination.
It was set to 95/70R14.

In addition, the number of cords inserted in a portion of the crown center of this prototype tire was 33 cords/5 c+m.

In Comparative Example 13, conventional PVA fibers were applied to the carcass ply for comparison.

For the above prototype tire, (1) a strength measurement test of the cord taken out from the tire, (2) a bead durability drum running test, (3) a field running test, and (4) a crosslinking degree measurement test were conducted as follows. .

(1) Cord strength (S) measurement test (2) Bead section durability drum running test The above test items (1) and (2) were performed using the same method as described in Examples 1 to 15 and Comparative Examples 1 to 7. By line again.

(6) After assembling the 4-narrow prototype tires of IU Kono-Sado with the specified rims, they were installed on general passenger cars and driven in general, and the test tires were driven approximately 50,000 times in the field using 195/70 SR14 size carcass ply trial tires. JIS L101 code strength as mentioned above
Measurement was carried out according to 7. The test results were expressed as a percentage retention rate in the same manner as the bead section durability drum running test.

(9) The solubility of PVA fibers in DMSO was measured in order to measure the degree of constant crosslinking.

Uncrosslinked PVA fibers dissolve in DMSO, but
Insoluble components are formed by the formation of crosslinks. The proportion of this insoluble matter was measured as the degree of crosslinking. in particular,
0.05g of PVA fiber cut into approximately 3M pieces
It was dissolved in 0 cc of DMSO at 120°C, and the proportion of insoluble content, that is, gel content, was measured.

The test results obtained are also listed in Table 9.

From the test results shown in Table 9, the following was confirmed.

Comparative Example 13 uses a conventional PVA fiber cord and has low cord strength, with a bead part durability drum running test of 4600
I woke up CBU at km.

Comparative Example 14 uses high-strength PVA fibers, so the cord strength when new is high, but since water is used as the spinning solvent, the fatigue resistance is not very good, and in the bead section durability drum test, the CBU did not reach 10,000 km. I woke you up.

The reinforced cord of Example 33 was obtained by swelling the raw cord of Comparative Example 14 and crosslinking it with TLA, and in this case, it was able to complete 20,000 km in the bead section durability drum running test.

In addition, the strength retention rate of the cord after running on the drum was 65%, and in the actual running test, the cord completed 11 runs at 50,000 km, and the strength retention rate at that time was 55%.

Comparative Example I5 and Examples 34 to 40 contain DMS in the spinning solvent.
These are examples using O, and fatigue resistance is improved in all of these cases. However, in Comparative Example 15, in which the cord was not cross-linked, although it completed the run in the bead durability drum test, the strength retention rate after 50,000 runs was 3.
It decreased to 0%.

Examples 36, 39 and 40 use an isocyanate compound as a crosslinking agent, and Examples 37 and 38 use an epoxy compound and formalin as a crosslinking agent, respectively. In all of these cases, since the filaments were crosslinked, a slight decrease in cord strength due to formalization was observed in Example 38, but the effect of improving fatigue resistance was high in all cases.

(Effect of the invention).

As explained above, by the production method of the present invention, high-strength PVA fibers can be advantageously crosslinked,
In the pneumatic tire of the present invention reinforced with the cross-linked high-strength PVA fiber cord, it is possible to suppress a decrease in the strength of the cord even after actual driving, and as a result, the durability of the tire is improved. This has the effect of significantly improving the In addition, when such a cord is used as a belt material, it can be used as a substitute for a steel cord, and it is possible to reduce road noise and significantly improve vibration riding comfort.

[Brief explanation of drawings]

Figure 1 is a partial sectional view of a prototype tire for examining carcass ply fatigue, and Figure 2 is a partial sectional view of a trial tire for examining belt fatigue. 1...High strength PVA fiber cord reinforcement belt 2...Steel cord reinforcement belt

Claims (1)

[Claims] 1. In a pneumatic tire reinforced with a polyvinyl alcohol synthetic fiber cord, the filaments of the cord are crosslinked with a crosslinking agent, and the cord taken out from the tire has the following formula: S≧14. 5-12N_T (N_T in the formula is N_T=N×√(0.139×D/ρ
)×10^-^3, where N is the number of twists of the cord (twists/10cm), D is 1/2 of the total denier of the cord, and ρ is the cord specific gravity. A high-strength polyvinyl alcohol-based synthetic fiber cord having a strength S (g/d) of tire. 2. The pneumatic tire according to claim 1, wherein the insoluble component when dissolved in dimethyl sulfoxide at 120° C. is 10% by weight or more. 3. The pneumatic tire according to claim 2, wherein the insoluble component when dissolved in dimethyl sulfoxide at 120° C. is 30% by weight or more. 4.Claim 1, wherein the crosslinking agent is a phosphoric acid compound, an aldehyde, a methylol compound, an epoxy compound, an isocyanate compound, a peroxide, a metal or a crosslinking agent containing phosphorus, or an inorganic acid compound other than a phosphoric acid compound that causes a dehydration reaction. A pneumatic tire according to any one of claims 1 to 3. 5. A cord made by twisting a raw thread of high-strength polyvinyl alcohol synthetic fiber or a plurality of underburned threads obtained by applying underburning to this raw yarn is treated with a crosslinking agent, and then treated with resorcinol.
A method for producing a high-strength polyvinyl alcohol-based synthetic fiber cord for rubber reinforcement, characterized by adhesive heat treatment using a formalin-latex adhesive. 6. In the spinning process of polyvinyl alcohol-based synthetic fibers or the subsequent coagulation bath process, a crosslinking agent is infiltrated into the interior of the polyvinyl alcohol, and a crosslinking reaction of the polyvinyl alcohol is performed during heating and stretching of the coagulated polyvinyl alcohol filament, High-strength polyvinyl alcohol-based synthesis for rubber reinforcement, characterized in that filaments having a cross-linked structure of polyvinyl alcohol are subjected to a twisting process to produce a green cord, and the cord is subjected to adhesive treatment with resorcinol-formalin-latex under heating. Method of manufacturing fiber cord.