JPH0253928A - Treated high-tenacity polyvinyl alcohol fiber cord and pneumatic tire reinforced with the same cord - Google Patents

Abstract

PURPOSE:To obtain the title product providing pneumatic tire having improved durability free from reduction in tenacity of cord even after traveling on road by coating polyvinyl alcohol fiber cord with a water-soluble polymer and treating the cord with a resorcin-formalin/latex adhesive. CONSTITUTION:Polyvinyl alcohol fiber cord is coated with a water-soluble polymer and treated with a resorcin-formalin/latex adhesive to give the aimed product. The coating of the water-soluble polymer is preferably carried out by immersing high-tenacity PVA fiber filament or high-tenacity PVA fiber cord in an aqueous solution of the water-soluble polymer such as PVA and drying and heat-treating under tension. The concentration of the water-soluble polymer in the immersion is preferably >=2% at 30 deg.C.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to high-strength polyvinyl alcohol-based synthetic fibers (hereinafter abbreviated as rPVA fibers) for rubber reinforcement that have significantly improved fatigue resistance, and the PVA fiber cords. This relates to pneumatic tires reinforced by

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

However, as seen in JP-A-59-130314 and JP-A-59-100710, it has now 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, by making the PVA polymer have a molecular weight slightly larger than that of conventional PVA fibers,
Industrially, a method for supplying high-strength PVA fibers in large quantities was discovered relatively easily (for example, in Japanese Patent Laid-Open No. 60-12
No. 6311 and No. 60-126312), the prospect of industrial and commercial use as tire cords has been established. Although the high-strength PVA fibers supplied in this way are not comparable to aramid fibers in terms of strength and elastic modulus, they have significantly improved strength compared to conventional fibers such as nylon and polyester. It was considered to be fully usable. Furthermore, as described in JP-A No. 61-108713, the high-strength PVA fibers obtained by this method have significantly improved resistance to mechanical strain input compared to conventional PVA fibers. 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 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 up), making it completely unsuitable for practical use in terms of tire safety. 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 in comparison 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, the strength of high-strength PVA fibers decreased to 20 to 40%, and in some cases, CBU occurred and the tire was on the verge of puncture.

The above practical driving test was conducted with the test tires mounted on a normal vehicle and at normal internal pressure (usually 1.7 kg/cm2), but this is only a controlled condition for tire usage conditions. In the general market, overloading and sometimes internal pressure of 1.0 kg / cm
Since it may be used in an abnormal state of 2 or less,
The fact that the cord strength retention rate was 20-40% after 50,000 miles of actual driving under controlled conditions means that we cannot guarantee safety at all in the general market. It was judged that it could not be put to practical use.

Furthermore, the following tests were conducted regarding the heald.

A passenger car tire with a tire puncture P235/75R15 having a fault belt structure as shown in FIG. 2 was experimentally manufactured using various fiber materials shown in Table 2 below as a heald cord under the conditions shown in the same table. For these tires, the strength retention rate of the hert cord after actual driving was evaluated as described above. The obtained results are also listed in Table 2. The location where the strength retention rate of the heald 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, the 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,
The object of the present invention is to improve the durability of pneumatic tires by using the high strength PVA fiber as a tire reinforcing cord.

(Means for Solving the Problems) The present inventors have intensively investigated the cause of the decrease in the strength of the high-strength PVA fiber cord after the above-mentioned actual running, and have obtained the following knowledge.

First, when we embedded the cord taken out from the tire in an epoxy resin after actual driving and observed the cross section of the cord cut with a microtome, we found that the filaments near the intersecting plane of the first and second twists were significantly deformed, and more than 10 filaments were found. was found to be concentrated in Tohoku. Normally, the filament has the role of distributing the strain caused by the cord to the filament - book - book = 10, so if the filament aggregates and the strain cannot be evenly distributed, the strength of the filament or cord will decrease. It will end up being put away.

Next, in order to further clarify such a filament aggregate phenomenon, the first twist and first twist were removed, and the cord interface where the first twist and first twist were in contact was observed using a microscope. As a result, it was found that the filaments were formed into a film-like shape in units of several to several tens of filaments, as if they had been pressed, and it was impossible to alleviate the strain input, which is thought to be the original role of filaments. I understand. 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 runs, strong cord retention rate 60)
%), although some of the above filament aggregation phenomenon 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, CBU occurs after 4,700 km of drum running with conventional PVA fibers, but the high-strength PVA fibers have a residual strength of 60% even after 20,000 km, and are significantly more resistant to fatigue than conventional PVA fibers. It can be seen that the properties have been improved. However, even with this improved high-strength PVA fiber, the strength of the cord decreases significantly after being run on the ground, a phenomenon that could not have been predicted based on conventional knowledge.

The inventors of the present invention have found the following differences by closely observing the cord and filament after actual running and after running on a drum. That is, (1) during actual running, the vehicle repeatedly runs and stops, so it is repeatedly subjected to an irregular temperature history from 100° C. to room temperature.

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

(3) On the other hand, the cord during drum running is constantly exposed to high temperatures of 100° C. or higher, and the filaments themselves soften, which tends to ease the rubbing force between the filaments.

The above findings indicate that the filament of the cord after running on a drum has a so-called bias-cut surface due to the rubbing between the filaments concentrating on one place in the filament, whereas the filament surface of the cord after running on a drum has many places on the filament surface. This can also be explained by the fact that rubbing scratches between the filaments can be seen, and that there are several rubbing scars within the bias cut when looking only at the bias cut surface.

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, the hydrogen bonds have an affinity for water molecules even in the presence of a small amount of water, and this has the disadvantage that PVA fibers themselves tend to aggregate. It is thought that it has become. Furthermore, it is thought that so-called water molecules penetrate into the amorphous portion of the PVA fiber and cause the amorphous portion of the PVA fiber to swell, resulting in, for example, a decrease in the glass transition point.

In the above-mentioned high-strength PVA fiber, high strength is achieved by making the amorphous part denser and highly oriented as a means of achieving high strength. Although it has been reported that the vapor pressure resistance is also improved, it is clear from the above results that it is still impossible to improve the fatigue resistance of the cord after actual running with this alone.

Therefore, the present inventors have investigated the possibility of friction and abrasion between filaments.
As a result of further careful consideration, we believe that filling a polymer compound between the filaments to prevent adhesion can substantially prevent the strength of high-strength PVA fibers from decreasing during actual running. High tenacity P with yarn strength of 15 g/d or more
After adhering a water-soluble polymer to VA fiber filaments or a cord made by twisting them together, adhesive treatment with ordinary resorcinol-formalin/latex (hereinafter abbreviated as rRFL) reduces the strength of the cord after running on a tire. The present inventors have discovered that this can be largely prevented, and have completed the present invention.

That is, the present invention provides RF
This invention relates to a high-strength PVA fiber cord characterized by being treated with an adhesive, and to a pneumatic tire reinforced with the cord.

Previously, it was thought that if foreign matter got between the filaments, the strength of the cord would generally decrease or the adhesive force would decrease.
The fact that a rubber reinforcing cord with satisfactory strength and adhesive strength can be obtained through appropriate treatment as in the present invention is a finding discovered for the first time by the present inventors.

In addition, water-soluble polymers react well with the OH groups on the surface of high-strength PVA fibers, which increases the rigidity of the cord and seems to reduce fatigue resistance. It was revealed that a tire cord with good fatigue resistance can be obtained without any adverse effects.

Furthermore, since the processing agent used in the present invention is water-soluble,
It also has great advantages in industrial production in terms of safety and workability.

The present invention will be explained in detail below.

The general manufacturing method for high-strength PVA fibers with a fiber strength of 15 g/d or more, which is required for the present invention, uses a polymer with a significantly increased molecular weight compared to that used in the production of conventional PVA fibers. This can be achieved by a method of increasing the draw ratio, 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 method.

In the present invention, high-strength PVA extracted from tires
The strength S of the fiber cord is expressed by the following formula, S≧14.5-12 N a (g/d) (NT in the formula is Nt = Nxi Gofufu II plane XIO-3
is the twist coefficient expressed as , where N is the number of twists of the cord (twists/10
cm), D is the token denier number of the cord (2), and ρ is the specific gravity of the cord).

The water-soluble polymer adhesion treatment in the present invention is performed using high-strength PV
A Since the purpose is to attach a water-soluble polymer to the surface of the fiber filaments, either the fiber filaments 1 to 1 or the twisted cords may be treated. As a method for adhesion treatment of water-soluble polymers, an aqueous solution of water-soluble polymers is applied to high-strength PV.
Although a treatment method such as spraying the A fiber filament or its twisted cord is also possible, it is preferable to immerse the high-strength PVA fiber filament or its twisted cord in an aqueous solution of a water-soluble polymer and then perform a dry heat treatment. The same effect can also be obtained by attaching a water-soluble polymer to the filament immediately after spinning.

Examples of the water-soluble polymer used in the present invention include polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, polyethyloxazoline, water-soluble polyamide, and copolymers containing these monomers.

Polyvinyl alcohol has the following formula, The degree of polymerization is preferably from 200 to 3000.

Alternatively, polyvinyl alcohol modified with pyrrolidone may be used.

Polyethylene oxide has the following formula, It is highly soluble in water.

Polyethyloxazoline has the following formula, C21 (5 The molecular weight is preferably 50,000.

The water-soluble polyamide is represented by the following formula, where X in the formula includes 10C0N114, a hydroxyl group, or a halogen atom.

These polymers can be endowed with various functional groups at the ends and within the molecule to make them covulcanizable with rubber, and can also be copolymerized with monomers with other functions. Polymers modified in this way can also be used in the present invention.

In the present invention, the above-mentioned water-soluble polymer is preferably dissolved in water or warm water and used as a fiber treatment agent. The concentration of such a treatment agent is preferably 2% or more at 30°C. Further, in the present invention, it is preferable to immerse the yarn or twisted cord of high-strength PVA fibers in the above-mentioned treatment agent, perform a dry heat treatment under tension, and then perform a normal RFL adhesive treatment.

(Function) When the high-strength PVA fiber cord treated with the present invention is used for tire reinforcement, the tire strength is improved compared to when the high-strength PVA fiber cord treated with the present invention is used for reinforcing a tire with a normal PVA fiber cord that has not been surface-treated with a water-soluble polymer. The effect of significantly suppressing the decrease in cord strength after driving is obtained, and the high strength PV removed from the tire
The strength retention rate of A fiber cord is 80% in carcass ply.
This is the above, and it is also possible to obtain a strong retention rate of 80% or more even with 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 or polyester fibers.

As a result, the amount of cord used can be significantly reduced compared to conventional fiber cords, making tires lighter and with lower drying resistance.Furthermore, when bulky cords are used as belt material, steel cords can be used. As an alternative, it will be possible to reduce road noise and significantly improve vibration and riding comfort.

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

The codes for Examples 1 to 10 and Comparative Examples 2 to 6 below are JP-A-61-108711 and JP-A-61-108712.
A high-strength PVA filament with a raw strength of 17.5 g/d obtained by the method described in No. 61-108713, etc., is spun to make a 1,500-denier or 1,800-denier yarn, which is then twisted a certain number of times. After twisting, two first-twisted cords were combined, and a 1,500 d/2 or 1,800 d/2 cord was used, which was obtained by ply-twisting a certain number of times.

For adhesion treatment of water-soluble polymers, polyvinyl alcohol,
Solid content of polyvinylpyrrolidone, polyethyloxazoline or water-soluble polyamide dissolved in water or hot water 1
A 0% aqueous solution was used as the treatment agent.

The twisted cord was immersed in the treatment agent for 2 seconds, and then subjected to a dry heat treatment under tension. The dry heat treatment conditions are: treatment temperature 150°C x exposure time 120 seconds x tension 0.1g/d
+200°C x 120 seconds x 0.5 g/d. Thereafter, the cord was subjected to RFL dip processing.

This dip treatment was performed using the RFL adhesive shown in Table 3 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: dry zone 150°C x 120 seconds x O, 1 g/d, hot zone 200°C x 40 seconds x l g/d, and norm zone 200'C x 40 seconds x O, 5 g/d. did.

3: RFL 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 SR14 for the trial tires for carcass ply examination of Comparative Examples 1 to 3 and Examples 1 to 2, and 185/70 for the trial tires for belt examination of Comparative Examples 4 to 6 and Examples 3 to 10. It was set to R13 size. Further, the number of cords inserted in the crown center of the trial tire was 33 cords/5 cm for the carcass ply and 40 cords/5 cm for the belt.

In Comparative Example 1, conventional PVA fibers were applied to a carcass monoply 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 (
An IBF drum running test] and a field running test were carried out as follows.

1 Cord S'' After removing the attached rubber from the cord taken out from the tire with scissors, put the cord through JI with a distance of 10 cm between the chucks.
The strength at break was measured by pulling at room temperature in accordance with S L1017, and the value obtained by dividing the breaking strength by the torque denier before twisting was defined as the strength S (g/d). The total denier number used was the denier number before twisting, but this is 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 complexity. Furthermore, the measurements were made at the bead folded portion shown in FIG. 1 for the carcass ply and at the belt folded portion shown in FIG. 2 for the belt.

2BF Dome a.

The prototype tire was heated indoors at 25°C ± 2°C at an internal pressure of 3.0k.
g/cm2, and after leaving it for 24 hours, readjust the air pressure, load the tire with twice the JIS load, and run it on a drum with a diameter of about 3 m at a speed of 60 kg/hour for 20,000 hours. Ta. Thereafter, the cord was removed from the tire, and the strength of the cord was measured in accordance with JIS L1017 as described above. The test results were expressed as a retention rate in %, with the strength before running being 100%.

After assembling the prototype tire with the specified rim, it was mounted on a general passenger car and driven in general, and the prototype tire for carcass ply examination of 195/70 SR1.4 size was used for about 50,000 hours of actual driving. The cord strength of the 185/70 R13 prototype tire for testing the heald cord was measured in accordance with JIS LLO17 after traveling for 32,000 km as described above. The test results were expressed as retention rates in % in the same manner as the BF drum running test. The results obtained are shown in Tables 4 and 5 below.

-1-1□=,1 From the test results shown in Tables 4 and 5, the following was confirmed.

First, carcass ply application examples (Comparative Examples 1 to 3, Examples)
, 2) will be discussed.

Comparative Example 1 is an example in which conventional PVA fibers were used as carcass ply, but in this case, both strength and fatigue resistance were not satisfactory, and in the BF drum test, C at 4600 km
A BU occurred and the product could no longer be put to practical use. Comparative Example 2 is an example of a high-strength PVA fiber cord using water as the spinning solvent, but was not subjected to the treatment of the present invention. In this case, both strength and fatigue resistance were improved, but in the BF tram test, 10,000 km
I woke up CBU at m. On the other hand, Example J is an example in which a high-strength PVA fiber cord is impregnated with a polyvinyl alcohol aqueous solution. In this example, fatigue resistance was significantly improved, and the vehicle completed 20,000 km in the BF drum test. In addition, when it was put into practice, the cord strength retention rate was 55% after driving 50,000 km.

Comparative Example 3 is an example in which dimethyl sulfoxide (DMSO) was used as a spinning solvent, but the treatment of the present invention was not performed. In this example, high strength, improved fatigue resistance,
The cord strength retention rate after 50,000 km of actual driving was 30%, which was by no means satisfactory. On the other hand, Example 2 is an example in which such a cord was impregnated with an aqueous polyvinyl alcohol solution. In this example, even after actual use, the cord strength retention rate was 95%, indicating that it is sufficiently durable for use.

Next, heald application examples (Comparative Examples 4 to 5, Examples 4 to 11) will be described.

Comparative Example 4 is an example in which water was used as the spinning solvent but the treatment of the present invention was not applied, whereas Example 3 is an example in which the same cord was treated with an aqueous polyvinyl alcohol solution. By comparing these examples, it was possible to confirm the effectiveness of the present invention in terms of cord strength retention rate after 32,000 km of actual driving.

Comparative Example 5 and Examples 4 to 8 are both examples in which DMSO was used as the spinning solvent, but Comparative Example 5 was not subjected to the treatment of the present invention, whereas Examples 4 to 8 were not subjected to the treatment of the present invention. The fibers were impregnated with various water-soluble polymers.

As a result, the effects of polyvinyl alcohol, polyethyloxazoline, polyvinylpyrrolidone, and water-soluble nylon were all significant, and the actual mileage was 32,000 km.
Even after m, a cord strength retention rate of 90% or more could be obtained.

On the other hand, Comparative Example 5 and Example 9.10.11. 4, the concentration of the water-soluble polymer treatment solution is 0%, 1%, 3%, and 5%.
, is also an example of 10%. From these examples, it was confirmed that when the solution concentration is 1%, the effect is small, but when it exceeds 3%, the effect becomes remarkable, and the higher the concentration, the greater the effect.

(Effects of the Invention) As explained above, the pneumatic tire of the present invention reinforced with a high-strength PVA fiber cord treated with a water-soluble polymer and then treated with an REL adhesive can be used in actual driving. It is possible to suppress a decrease in the strength of the cord even later, and as a result, it is possible to obtain the effect that the durability of the tire can be significantly improved. In addition, when such a cord is used as a heald material, it can be used as a substitute for a steel cord, reducing road noise and significantly improving vibration riding comfort.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a trial tire for carcass ply examination, and FIG. 2 is a partial sectional view of a trial tire for belt examination. 1...High strength PVA fiber cord reinforcement belt 2...Steel cord reinforcement belt Patent applicant Brideston Co., Ltd. Daiichi 1

Claims (1)

[Claims] 1. A high-strength polyvinyl alcohol fiber cord, characterized in that it is treated with a resorcinol-formalin/latex adhesive after being treated with a water-soluble polymer. 2. The treated high-strength fiber according to claim 1, wherein the water-soluble polymer treatment is performed by immersing the high-strength polyvinyl alcohol fiber filament or the high-strength polyvinyl alcohol fiber cord in an aqueous solution of the water-soluble polymer and then subjecting it to dry heat treatment. Polyvinyl alcohol fiber cord. 3. The water-soluble polymer is at least one selected from polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, polyethyloxazoline, water-soluble polyamide, and copolymers containing these monomers. A treated high tenacity polyvinyl alcohol fiber cord according to claim 1 or 2. 4. A pneumatic tire reinforced with a treated high-strength polyvinyl alcohol fiber cord according to any one of claims 1 to 3. 5. The strength S of the high-strength polyvinyl alcohol fiber cord taken out from the pneumatic tire is the following formula, S≧14.5-1
2N_T(g/d) (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 pneumatic tire characterized by: