JPH03136903A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To enhance the mechanical properties and heat resistance of a pneumatic tire having an organic fiber carcass layer and a belt layer by using a fiber made of the predetermined polymerization degree of polyvinyl alcohol and having the predetermined single yarn woven degree, tensile strength, initial elastic modulus and hot water resistance. CONSTITUTION:As an organic fiber constituting a carcass ply layer 1 and a belt layer 2, a polyvinyl alcohol fiber is used after preparation in such a way that the polyvinyl alcohol having the polymerization degree of 1,500 to 7,000 is dissolved in a solvent and 0.05 to 30wt.% of an organic peroxide selected from dialkyl peroxide generally expressed as R-O-O-R (R shows an alkyl group) and a peroxiketar having alkyl groups R, R1 and R2, and expressed by the formula I. Also, the single yarn woven degree of thereof is taken at 10 deniers or more, tensile strength at 10g/d or more, initial elastic modulus at 200g/d or more and hot water resistance at 120 deg.C, respectively. According to the aforesaid construction, the mechanical properties and heat resistance of a pneumatic tire can be enhanced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a pneumatic radial tire comprising a carcass layer and/or a belt layer made of organic fibers, particularly a pneumatic radial tire comprising polyvinyl alcohol fibers with improved mechanical properties and heat resistance. The present invention relates to a pneumatic radial tire comprising a carcass layer and/or a belt layer.

(Prior art) Conventionally, polyvinyl alcohol synthetic fiber (rPVA)
IJ], abbreviated as "IJ") have been widely used as industrial fibers, mainly as rubber reinforcing materials. However, this fiber
It has poor fatigue resistance, and because it has a polymer property of being inherently soluble in water, it has the disadvantage of poor hot water resistance. Therefore, among the tire reinforcing cords that are subjected to a large amount of bending strain, this fiber is only partially used as a belt material for radial tires that have relatively little input strain.

However, today, as seen in JP-A-59-130314 and JP-A-59-100710, PV
It has become possible to increase the strength of Am fiber. However, such ultra-high molecular weight PVA polymers are difficult to produce industrially, and due to manufacturing difficulties, they are less expensive than fibers used in general tire cords such as polyester and nylon. This made the product significantly more expensive, making it commercially uncompetitive.

From the above background, PVA polymer has been replaced with conventional PVA.
By making the molecular weight slightly larger than the molecular weight of the fiber, it is relatively easy to produce high-strength PVA1 in large quantities industrially.
A method for supplying fibers was discovered (for example, in JP-A-Sho 6).
No. 0-126311 and No. 60-126312), the prospect of industrial and commercial use as tire cords has been established. High strength P supplied in this way
Although VA fibers are not comparable to aramid fibers in terms of strength and elastic modulus, they are significantly stronger than conventional fibers such as nylon and polyester, and are considered to be suitable for use as tire cords. Ta. In addition, the high strength PVA fiber obtained by this method is disclosed in Japanese Patent Application Laid-Open No. 611087
As described in Publication No. 13, it is greatly improved against mechanical strain input compared to conventional PVAm fibers.
The fatigue resistance as a tire cord was also considered to be sufficient for practical use.

(Problems to be Solved by the Invention) However, the present inventors have revealed that the high-strength PVAl1i fiber obtained by the above method has a serious drawback in terms of fatigue resistance. In other words, as it is, this fiber lacks fatigue resistance as a tire cord, and even during normal driving, the fiber will break (hereinafter referred to as rcBU).
(referred to as code breaking up) occurred, and it was revealed that this was completely unsuitable for practical use in terms of tire safety. This point will be explained in more detail below.

Various fiber materials shown in Table 1 below were used as carcass ply cords under the conditions shown in the same table to form tire size 20.
5/60 R15 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. In addition,
The strong retention rate of the carcass ply cord is measured at the first point.
The x mark on the tire shown in the diagram (approximately 3 cm above the bead baseline)
position).

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. On the other hand, with high-strength PVA fibers, it decreased to 20 to 40%, and in some cases, CBU occurred, which was on the verge of tire 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/cm2).
However, this is only a controlled condition for tire use, and in the general market tires are often used under abnormal conditions such as overloading or internal pressure of less than 1.0 kg/cm2. Therefore, since the cord retention rate was 20-40% after 50,000 km of actual driving under controlled conditions, we have to judge that safety in the general market cannot be guaranteed at all. However, it was determined that this structure could not be put to practical use as a basolateral device.

The present inventors conducted extensive research into the cause of the decrease in strength of the high-strength PVA fiber cord after the actual running, and as a result, the following knowledge was obtained.

First, the cord taken out from the tire after actual driving was embedded in epoxy resin, cut with a microtome, and when the cross section of the cord was observed, the filaments near the intersecting plane of the first and second twists were significantly deformed. It was found that the above is agglomerated to the east. Normally, the filament has the role of dispersing the strain applied to the cord between the filament and the cord, so if the filament aggregates and the strain cannot be uniformly distributed, the strength of the filament or cord will be reduced. become.

Next, in order to further clarify such filament agglomeration phenomenon, the upper twist and lower twist were loosened, and the cord interface where the upper twist and the lower twist were in contact was observed under 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, although some of the above-mentioned filament aggregation phenomenon is observed in some parts of cords that have been run on drums (20,000km run, cord strength retention rate 60%), the extent of this is extremely small, and each filament is strained when running on drums. It is assumed that the input is still evenly distributed. In addition, the conventional PVAl 1ll fiber can travel 5300km on a drum.
CBU has occurred in the above-mentioned high-strength PVA.
The residual strength of the fiber is 60% even at 20,000 liters (m), which shows that the fatigue resistance is significantly improved compared to conventional PVA fiber.

However, even with this improved high-strength PVAwa fiber, the phenomenon that the strength of the cord decreases significantly after actual running is a phenomenon that could not be predicted based on conventional knowledge.

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

(2) During actual running, the strain input received by the cord also 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 high temperatures of 100° C. or higher, and the rubbing force between the filaments is likely to be alleviated due to the softening of the filaments themselves.

The above findings indicate that the filament of the cord after running on a drum shows a so-called bias-cut surface due to the strain between the filaments concentrating on one specific part of the filament, whereas the filament surface of the cord after running on the drum shows a so-called bias cut surface. This is supported by the fact that rubbing scratches between the filaments are seen at many places, and even on the bias cut surface, there are several rubbing scratches within the bias cut.

From the knowledge explained above, it was found that in order to reduce the concentration of filament input due to filament aggregation and bunching and increase the fatigue resistance of the cord of high-strength PVA fibers, it is sufficient to prevent filament aggregation. Based on this, the following considerations were made.

In other words, since PVAl1i 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 the PVA fibers themselves tend to aggregate. This is thought to be the cause.

In addition, water molecules invade the amorphous part of PVA fibers, causing PVA
Swelling of the amorphous portion of the fiber is considered to be a cause of, for example, a decrease in the glass transition point.

In addition, in the above-mentioned high-strength PVA fiber, high strength is made possible by densification of the amorphous part and high orientation 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.

(Means for Solving the Problems) The present inventors have conducted various studies to obtain PVA fibers that prevent the strength from decreasing due to filament compression and rubbing and have excellent fatigue resistance. This invention was achieved by confirming that by using cross-linked filaments made from polyvinyl alcohol with a high degree of polymerization and increasing the single filament fineness, it was possible to improve cohesiveness and obtain PVA fibers with excellent fatigue resistance. I ended up doing it.

That is, the present invention includes a carcass ply layer in which the cords are arranged in a substantially radial arrangement, and one or more belt layers surrounding the outer periphery of the crown portion of the carcass ply layer,
and at least one layer of the carcass ply layer and the belt layer is made of organic fiber, and the organic fiber is made of polyvinyl alcohol with a degree of polymerization of 1500 to 7000, has a single fiber fineness of 10 denier or more, and has a tensile strength. Strength is 10g/d or more, initial elastic modulus is 200g
/d or more, and a pneumatic radial tire made of polyvinyl alcohol fibers having hot water resistance of 120° C. or more.

The polyvinyl alcohol fiber has a degree of polymerization of 1500 to 7.
(a) A dialkyl peroxide represented by the general formula R-0-0-R and (b) a peroxyketal represented by the general formula (R, R, , R, in the formulas (a) and (b) represent an alkyl group.) At least one organic peroxide selected from the group consisting of: It can be produced by adding 05 to 30% by weight, dry/wet spinning, and hot stretching the obtained undrawn yarn, and the obtained polyvinyl alcohol fiber is suitably used in the pneumatic radial tire of the present invention. be able to.

(Function) In the pneumatic radial tire of the present invention, PVA fibers having the above characteristics can be used in all or one of the carcass ply layers, and can also be used in at least one of the one or more belt layers. If necessary, the above method can be used for both the carcass layer and the belt layer. Here, the belt layer refers to a "cap layer" which is a protective layer used to protect the belt as the outermost layer of the belt in addition to a normal belt, and a "0 degree belt" which is a belt that wraps a cord approximately parallel to the tire equator direction. Including "belt".

The degree of polymerization of PVA constituting the organic fiber of the tire of this invention needs to be 1,500 to 7,000, preferably 3,000 or more, and more preferably 4,500 or more. Here, "degree of polymerization" refers to P before crosslinking treatment.
It means the degree of polymerization of VA. The upper limit of the degree of polymerization is required to be 7000 or less from the viewpoint of polymer cost. When the degree of polymerization is less than 1500, the strength of the obtained fiber is 108
/d, and the object of this invention cannot be achieved.

Moreover, the degree of saponification of PVA is preferably 99% or more.

Next, if the single yarn fineness of the PVA fiber used in this invention is less than 10 deniers, the pneumatic radial tire using the same will not have sufficient strength retention during actual running, and the fatigue resistance will be poor, so the single yarn fineness will not be sufficient. 10 denier or more is required.

Furthermore, the tensile strength of the PVA fiber used in this invention is Lo
g/d or more, the initial elastic modulus is 200 g/d or more, and the hot water resistance is 120 or more, which are naturally required standards under the usage conditions of the tire for use as carcass layer and belt layer materials of pneumatic radial tires. It is a value.

Such PVA fibers can be produced by dissolving PVA having the above-described degree of polymerization in a solvent to prepare a spinning stock solution as described below.

As a solvent, a saturated aliphatic polyhydric alcohol such as glycerin, ethylene glycol, propylene glycol, etc.
MSO, dimethylformamide, 1゜3-dimethyl-2
It may be selected from -imidazolidinone, water, etc., and mixtures thereof, among which DMSO, water, or mixtures thereof are particularly preferably used. In the present invention, a PVA heat resistant agent, a pigment, etc. may be appropriately mixed into this solvent.

The PVA concentration in the spinning stock solution is preferably adjusted to a range of 2 to 35% by weight. If the concentration is less than 2% by weight, the spinnability will decrease, while if it exceeds 35% by weight, the drawability of the undrawn yarn will tend to decrease, which is not preferable.

The organic peroxide may be added to the spinning solution either before or after heating and dissolving PVA, but it is preferably added after heating and dissolving PVA for the following reason.

In other words, organic peroxide decomposes and generates radicals when it receives heat above a certain window. At that time, if a PVA molecule exists near the radical, hydrogen atoms (protons) other than the hydroxyl group in the PVA molecule ) is extracted to become PVA radicals, and these PVA radicals are cross-linked with each other.

Therefore, if the organic peroxide is added and then dissolved by heating, crosslinking will occur at the same time as the dissolution, which may make spinning difficult.

When adding an organic peroxide after dissolving PVA, it may be added before the spinning stock solution is discharged from the spinneret.
For example, preparation of spinning dope (heating and dissolving PVA in solvent)
When this is carried out using a dissolving device capable of stirring and heating, the spinning dope may be added in a conduit that is transported from the dissolving device to the spinneret. In this case, if a static stirring device is provided in the conduit after the addition section, uniform dispersion of the organic peroxide into the spinning dope can be promoted.

The organic peroxide to be added to the spinning dope must have a half-life of 30 minutes or more at the maximum temperature that the organic peroxide is exposed to during the process up to obtaining an undrawn yarn, and It is preferable that the half-life at the maximum temperature to which it is subjected is 2 minutes or less. Specifically, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 and α,α′-bis(1-butylperoxy-m-isopropyl)benzene are used as dialkyl peroxides. etc., and 2,2-bis(butylperoxy) as a peroxyketal.
Examples include octene and 2,2-bis(t-butylperoxy)butene, but the present invention is not limited to these.

The amount of organic peroxide added is: 0.05 to 3 to PVA
It must be 0% by weight, and the amount of organic peroxide added must be P
If it is less than 0.05% by weight based on VA, too few radicals will be generated, and the crosslinking reaction will not occur sufficiently and the apparent degree of polymerization of PVA will not increase, resulting in insufficient improvement in hot water resistance. On the other hand, the amount of organic peroxide added is P
If the amount is more than 30% by weight based on VA, a crosslinking reaction occurs rapidly, making stretching difficult, and the cost of the organic peroxide increases, which is not preferable.

In this invention, the spinning dope to which the organic peroxide has been added is dry/wet-spun into a coagulation bath or cooling bath using a spinneret having one or more discharge holes to form yarn. Then, the solvent of the PVA is extracted in an extraction bath to form an undrawn yarn.

As the coagulation bath and extraction bath, alcohols such as methanol, ethanol, propatool, butanol, etc., which are miscible with the solvent that dissolves PVA, or ketones such as acetone, methyl ethyl ketone, diethyl ketone, or a solvent of these and PVA are used. A mixed solvent etc. with

Alternatively, a cooling bath made of decalin, paraffin oil, etc. that is immiscible with the solvent may be used, and only cooling and gelation may be performed in this cooling bath, and then the solvent may be extracted in the above-mentioned extraction bath.

In this invention, the undrawn yarn obtained above is wound up once or continuously supplied to a drawing step and drawn.

In the present invention, other processes such as drying, oil treatment, etc. may be appropriately introduced during the dry/wet spinning process or between this process and the stretching process, if necessary.

Various methods can be applied as the stretching method, for example, a method in which the PVA fiber is stretched while being in contact with a heating body such as a heat plate, a method in which the PVA fiber is stretched in a hot air bath such as a heat oven, and a method in which the PVA fiber is stretched in a hot air bath such as a heat oven. Examples include a method of stretching and a method of stretching using a dielectric heating method.

In this invention, heat is applied to the added organic peroxide to generate radicals, and the PVA molecular chains are crosslinked by these radicals, so the stretching temperature, stretching speed, and It is necessary to set the stretching time, preferably at a temperature of 250°C or higher, from 4 to
It is preferable to set the stretching time to 10 seconds to 2 minutes at a stretching speed of about 80 m/min.

Further, when hot-stretching the undrawn yarn, it can be drawn in one stage or in multiple stages of two or more stages, but it is preferable to stretch in multiple stages of two or more stages. In this case, it is preferable to set the stretching temperature, stretching speed, and stretching time at the final stretching to the above values.

Furthermore, in the case of multi-stage stretching, the n-th stage stretching and the (n+1
) Moisture application, oil agent application, etc. may be performed between stage stretching (n is an integer of 1 or more).

In order to obtain PVA fibers with excellent strength, initial elastic modulus, and hot water resistance, which are the objects of this invention, the total draw ratio is preferably 10 times or more, more preferably 15 times or more.

According to this invention, the commercially available degree of polymerization is 150.
PVA fibers having high strength, high initial elastic modulus, and high hot water resistance can be manufactured with high productivity at low cost using PVA with a molecular weight of 0 or more and 7000 or less.

Furthermore, the PVA fiber of the present invention obtained in this manner has a tensile strength of 10 g/d or more and an initial elastic modulus of 200 g/d or more, and has a large single yarn fineness of 1O denier or more. , when used for tire reinforcement,
Excellent durability.

In addition, when the PVA fiber is used in the belt layer, the range of 100% modinilas of the embedded rubber is preferably 40 to 70 kg/cm2, more preferably 50 to 60 kg/cm2.
g/cm2 is chosen.・1 for less than 40kg/cm2
The rigidity of the belt layer (belt composite layer) is not sufficient, and the steering stability is deteriorated, which is not preferable. Also, 7. O
If it exceeds "kg/cm", it is undesirable because it is too hard and causes problems of cracking growth and belt edge separation.

On the other hand, when this PVA fiber is used as a carcass ply layer reinforcing agent, the range of 100% modulus of the embedded rubber is preferably 10 kg/cm2 or more and less than 40 kg/co+2, and more preferably 20 to 30 kg/cm2.

If it is less than lQkg/cm2, there is a problem in running durability, and 4
If it exceeds 0 kg/cm2, it is not preferable because there is a risk of cracking growth and separation.

It is known that the higher the degree of polymerization of PVA as a raw material, the higher the hot water resistance of the resulting fiber. Therefore, if PVA with a high degree of polymerization is used, PVA fibers with excellent hot water resistance can be obtained, which prevents filament agglomeration and improves fatigue resistance, and can be used for tire cords. PV with ultra-high degree of polymerization such as
A has problems in that it is not only difficult to use commercially, but also difficult to spin due to its poor solubility in solvents.

In this invention, while PVA with a relatively low degree of polymerization is used as a raw material, the PVA molecular chains are cross-linked in the drawing process to increase the apparent degree of polymerization, thereby achieving the same performance as fibers made from PVA with an ultra-high degree of polymerization. It is now possible to grant PVA
It can also improve the hot water resistance of fibers.

That is, when the organic peroxide added to the spinning stock solution decomposes and generates radicals during hot stretching, it induces the generation of PVA radicals. For this reason, the generated PVA radicals cross-link with each other, resulting in PV with a higher apparent degree of polymerization.
A, resulting in a PVA fiber with improved hot water resistance.

In addition, the tensile strength and initial elastic modulus in this invention are measured according to the method of JIS L-1013, and the hot water resistance is measured by the following method. 100 mg of sample cut into 5 mm length,
Seal it in a glass tube with an inner diameter of gmm along with 5 ml of water. This glass tube is immersed in a silicone oil bath, and the temperature of the silicone oil bath is raised at a rate of 5° C./min, and the temperature at which the sample is completely dissolved is defined as hot water resistance.

As mentioned above, the PVA fiber used in the pneumatic tire of the present invention can be used for the carcass ply layer and the belt layer, and the belt layer includes use as the cap layer layer and the 0 degree belt. Similar effects were observed in both cases.

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

3 in Example 1, Comparative Example 1 As shown in Table 2, the degree of polymerization was 1300.1700.51.
A DMSO solution of PVA of
- Made of stainless steel with 25% by weight of dimethyl-2,5-di(t-butylperoxy)hexyne-3 added to PVA and an inner diameter of 0.7 mm on the exit side of the spinning dope.

Using a spinneret in which 100 cylindrical thin tubes were embedded to form a 3 mm protrusion from the spinneret side, the discharge linear velocity was 4.
After dry/wet spinning in methanol at m/min and draft 5.0, DMSO was extracted with methanol and dried to obtain an undrawn yarn.

Next, the obtained undrawn yarn was subjected to a first-stage drawing temperature of 180°C.
The PVA fibers were obtained by drawing at a second stage drawing temperature of 255°C.

Table 2 shows the manufacturing conditions and the properties of the obtained PVA fibers.

Next, the cord was set to 15006/2, the first twist and the second twist were applied 31 times/10cm each, and the resultant was subjected to the usual resorcinol, formalin, and latex treatments, and was then dry heat treated to form a tire carcass ply as shown in Figure 2. 1 was used to manufacture tires. After assembling this prototype tire with the specified rim, it was mounted on a general passenger car and driven for general use.205/
60 After running approximately 50,000 km on an R15 size tire, remove the cord from the tire, pull the bead part of the cord at room temperature with a distance between chucks of 10 cm according to JIS 1017, measure the strength at break, and then The retention rate was expressed in %, with the previous strength being 100, and was used as the fatigue resistance of the cord. The measurement position is the part marked with an x in FIG. 2 (a position approximately 3 cm above the bead baseline). Second test result
Shown in the table. Examples 1 to 3 have good yarn properties and high cord strength retention, giving good results. Although the cord strength retention rate after running in Comparative Example 1 is high, the initial cord strength is low, which is not preferable in terms of tire safety and strength design.

Example 4. Comparative Example 2 Spinning and stretching were carried out in the same manner as in Example 2 except that the organic peroxide to be added was changed to α,α'-bis(1-butylperoxy-m-isopropyl)benzene.

Moreover, as Comparative Example 2, spinning and drawing were performed in the same manner as in Example 4 except that no organic peroxide was added.

Table 2 shows the yarn quality of the PVA fibers obtained. Tires were manufactured and tested in the same manner as in Examples 1 to 3 using these fibers in the carcass ply layer. The results are shown in Table 2. Example 4 has good yarn physical properties and sufficient cord strength retention, but Comparative Example 2 has poor fatigue resistance because there is no crosslinking with organic peroxide and hot water resistance is as low as 118°C. For this reason,
Comparative Example 2 had a low card strength retention rate, and there were concerns about tire durability.

Comparative Example 3 Using the same spinning solution as in Example 2, spinning was carried out in the same manner while adding 35% by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3 to PVA. An undrawn yarn was obtained.

An attempt was made to draw the obtained undrawn yarn in the same manner as in Example 2, but the drawing ratio was only 12 times.

The yarn quality of the obtained PVA fiber is shown in Table 2, and the tensile strength was as low as that of Comparative Example 1, which was also unfavorable from the standpoint of tire safety and strength design.

Incidentally, the tire was made by applying this fiber to the carcass, and the tire manufacturing and testing methods were the same as in Examples 1 to 3.

Comparative Example 4 The same spinning dope and organic peroxide as in Comparative Example 3 were used, but the amount of organic peroxide added was 25% by weight based on PVA.
VA fibers were produced. This fiber had a single yarn fineness of about 7.9 denier. Using this fiber for the carcass ply layer, tires were manufactured and tested in the same manner as in Examples 1 to 3. Although it has the effect of improving the fatigue resistance of the cord, considering that the retention rate has decreased by almost half to 60%, there is concern as a reinforcing fiber for tires.

Example 5, Comparative Example 5 Example 5 uses the same raw yarn as Example 2, and Comparative Example 5 uses the same yarn as Comparative Example 2, and the number of twists is changed to make a passenger car tire size 185 as shown in FIG. /60 R14 fold belt 3 was subjected to a practical durability test as shown in Examples 1 to 3, and a fatigue resistance measurement of the cord taken out after the test was conducted. The measurement position is the folded part of the belt indicated by the X mark in FIG. The results are shown in Table 2. The cord of Example 5 has durability, but the cord of Comparative Example 5 has extremely low durability.

Example 6, Comparative Example 6 Example 6 uses the same yarn as Example 2, and Comparative Example 5 uses the same yarn as Comparative Example 2, and the number of twists is changed to 185 as shown in FIG.
/60 R14 was applied to cap layer 4, and a practical durability test and fatigue resistance measurement were conducted in the same manner as in the previous example. The measurement position was approximately at the center of the cap layer indicated by the X mark in FIG. The results are shown in Table 2. The cord of Example 6 has sufficient durability, but the cord of Comparative Example 6 has significantly inferior durability.

Example 7, Comparative Example 7 Example 7 uses the same raw yarn as Example 2, and Comparative Example 7 uses the same raw yarn as Comparative Example 2, and three 1500 denier plied cords are twisted together and the number of twists is 26 times. /10 Cm, and a practical durability test was conducted by applying it to a tire 00 degree belt 5 of size 170/60R18 for motorcycles as shown in FIG.

The fatigue resistance of the cord was tested in the same manner as for the carcass ply layer. The measurement position was a part of the center of the tire indicated by the X mark in FIG. As shown in Table 2, the cord durability of Example 7 was sufficient, but that of Comparative Example 7 was significantly inferior.

(Effects of the Invention) As shown in the above Examples and Comparative Examples, the present invention is made of polyvinyl alcohol with a degree of polymerization of 1500 to 7000, has a single yarn fineness of 10 deniers or more, has specific tensile strength, initial elastic modulus, and hot water resistance. The present invention provides a pneumatic radial tire using PVA fibers having a carcass ply layer or a belt layer, which enables the conventional PVAI fibers with a polymerization degree of this level to be used.
In addition, the PVA fibers used in this invention are much easier to commercially produce than ultra-high molecular weight PVA fibers, and are therefore significantly less costly than ultra-high molecular weight PVA fibers. has advantages that are advantageous.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a conventional pneumatic radial tire, Fig. 2 is a schematic cross-sectional view of a pneumatic radial tire showing an embodiment of the present invention, and Fig. 3 is a schematic cross-sectional view of a pneumatic radial tire showing an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a pneumatic radial tire having a cap layer layer according to an embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a pneumatic radial tire having a pneumatic radial tire. 1...Carcass ply layer 2...Belt layer 3...Fold belt layer 4...Cap layer layer 5...0 degree belt layer

Claims (1)

[Claims] 1. A carcass ply layer in which the cords are arranged in a substantially radial manner, and one or more belt layers surrounding the outer periphery of the crown portion of the carcass ply layer, and the carcass ply layer and the belt layer A pneumatic radial tire in which at least one layer is made of organic fibers, wherein the organic fibers are made of polyvinyl alcohol with a degree of polymerization of 1500 to 7000, have a single fiber fineness of 10 denier or more, and have a tensile strength of 10
A pneumatic radial tire comprising polyvinyl alcohol fibers having an initial elastic modulus of 200 g/d or higher, and a hot water resistance of 120° C. or higher. 2. The polyvinyl alcohol fiber has a polymerization degree of 1500 to
The spinning stock solution prepared by dissolving 7000 polyvinyl alcohol in a solvent contains (a) dialkyl peroxide represented by the general formula R-O-O-R and (b) general formula▲mathematical formula, chemical formula, table, etc.▼ At least one organic peroxide selected from the group consisting of peroxyketal (R, R_1, R_2 in the formulas (a) and (b) represent an alkyl group) represented by polyvinyl alcohol 2. The air-filled polyvinyl alcohol fiber according to claim 1, which is a polyvinyl alcohol fiber with excellent hot water resistance, which is produced by adding 0.05 to 30% by weight of the polyvinyl alcohol fiber to the polyvinyl alcohol fiber, dry-spinning and hot-stretching the resulting undrawn yarn. radial tire. 3. The cord of the carcass ply layer is made of organic fiber, and the 100% modulus of the embedded rubber is 10 kg/cm^2 or more and less than 40 kg/cm^2.
Pneumatic radial tires listed. 4. The pneumatic radial tire according to claim 1 or 2, wherein the cords of the belt layer are made of organic fibers, and the embedded rubber has a 100% modulus of 40 to 70 kg/cm^2.