JP2015229476A - tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire which has a cross-linked state of rubber optimized over the whole tire and is excellent in low heat generation performance.SOLUTION: A tire includes: a carcass ply which has a main body part extended in a toroidal shape between bead cores respectively embedded in a pair of bead parts and a ply edge part coupled to the main body part and is covered with a ply coating rubber; a belt part composed of a plurality of belt layers arranged on the outer side in a tire radial direction of the carcass ply; and a pair of side parts located on both edge parts of the belt part. Therein, all of Dvalues on following portions I,II,III and IV of the ply coating rubber satisfy D>0.75×Dwith respect to Dwhich is the Dvalue when a vulcanization torque gets to the maximum value.

Description

  The present invention relates to a tire excellent in low heat generation.

The demand for lower fuel consumption of automobiles is becoming more severe in connection with the global movement of carbon dioxide emission regulations due to the social demand for energy saving and the growing interest in environmental issues. In order to meet such demands, reduction of rolling resistance and improvement of durability have been demanded for tire performance.
When a pneumatic tire rolls under load, rolling resistance is generated due to deformation of the tread ground surface and the tire itself, and energy is mainly lost as heat energy. Since rolling resistance has a great influence on the fuel consumption of vehicles, various proposals have been made to reduce rolling resistance. For example, a rubber composition having a small loss tangent (tan δ) and low heat generation may be used in the tread portion.
Moreover, as an example of a method for obtaining a rubber composition having low exothermicity, an alkoxy containing a functional group that interacts with a filler in a polymerization active site of a conjugated diene (co) polymer obtained by anionic polymerization using organolithium Examples include a method of modifying with a silane derivative (see, for example, Patent Document 1 or 2).

In addition to these, as a method of reducing the rolling resistance of the tire, a method of blending a specific carbon black into the rubber composition forming the tread portion, a method of reducing the tire weight by reducing the thickness of the sidewall, etc. Is mentioned.
Furthermore, in recent years, it has been found that the rolling resistance of the tire can be reduced by setting the crosslinked state of the rubber to an appropriate condition. As a method for measuring the crosslinked state of rubber, a method for calculating the crosslinked state of rubber from a specific value (referred to as _Dres ) calculated from the results of NMR measurement has been proposed (see Non-Patent Document 1). By using this method, it became possible to detect the overvulcanized state, which was difficult to detect with the vulcanization torque.

Japanese Examined Patent Publication No. 6-57767 WO03 / 029299 pamphlet

Kay Saalwachter (2005) "Chain Order and Cross-Link Density of Elastomers As Investigated by Proton Multiple-Quantum NMR", Macromolecules 2005, 38, 9650-9660

Conventionally, in the vulcanization treatment of unvulcanized rubber, vulcanization conditions have been set such that the vulcanization torque measured using a curast meter is maximized. The vulcanization torque here is a value measured based on JIS K6300. However, when the vulcanization temperature, the vulcanization time, etc. exceed appropriate conditions, the crosslinked state of the rubber changes from an appropriate state to an inappropriate state. This improper state is called the overvulcanized state.
Further, it has been found that the maximum value of the vulcanization torque and the conditions under which the crosslink density is optimal do not exactly match. For this reason, if the crosslinked state of the rubber can be determined more accurately, the vulcanization conditions that make the crosslinked state of the rubber an appropriate state can be set wider. Moreover, if vulcanization conditions can be set widely, it can be set to the conditions where overvulcanization hardly occurs.
Accordingly, an object of the present invention is to provide a tire that is in an appropriate state of rubber cross-linking throughout the entire tire and is excellent in low heat generation even when the vulcanization conditions are set wider.

The present inventor has found that rubber vulcanized under vulcanization conditions set based on the D _res value calculated from the NMR measurement results is excellent in low heat buildup and can improve tire performance. The present invention has been completed based on such knowledge.
That is, the present invention relates to a carcass ply having a main body portion extending in a toroidal shape between bead cores embedded in a pair of bead portions and a ply end portion connected to the main body portion and covered with ply coating rubber, and the carcass ply. A tire including a belt portion composed of a plurality of belt layers arranged on the outer side in the tire radial direction of the ply, and a pair of side portions located at both ends of the belt portion, the following portion I of the ply coating rubber , II, with respect to D _max is a D _res value when D _res value in III and IV which are both vulcanization torque becomes a maximum value, satisfy D _res> 0.8 × D _max.
However, the part I is in the vicinity of the tire center line, the part II is in the vicinity of the maximum width part where the tire width is maximum in the cross section in the tread width direction and the tire radial direction, and the part III is the end of the carcass ply. The portion IV is a carcass ply near the end of the belt portion, and the D _res value is a value measured under a temperature of 40 ° C. using a TD-NMR apparatus.

  According to the present invention, even if the vulcanization conditions are set wider, it is possible to provide a tire that is in an appropriate state of rubber cross-linking throughout the tire and has excellent low heat buildup.

It is sectional drawing of the tire width direction and tire radial direction of the tire which concerns on embodiment of this invention. It is sectional drawing explaining the base tire A and the precure tread B of the tire which concerns on embodiment of this invention.

[tire]
A tire according to an embodiment of the present invention includes a carcass ply covered with a ply coating rubber having a main body portion extending in a toroid shape between bead cores embedded in a pair of bead portions and a ply end portion connected to the main body portion. And a pair of side portions located at both ends of the belt portion, the ply coating rubber comprising: a belt portion comprising a plurality of belt layers disposed on the outer side in the tire radial direction of the carcass ply; The D _res values in the following sites I, II, III and IV are all D _res values when the vulcanization torque reaches the maximum value, D _max
D _res > 0.75 × D _max is satisfied.
Parts I to IV in the present embodiment will be described in detail with reference to the drawings.
The D _res value is based on the description of Kay Saalwachter (2005) “Chain Order and Cross-Link Density of Elastomers As Investigated by Proton Multiple-Quantum NMR”, Macromolecules 2005, 38, 9650-9660. This is a value measured under the condition of a temperature of 40 ° C. using a minispec mq20).

<Tire configuration>
Hereinafter, the tire 1 which concerns on embodiment of this invention is demonstrated in detail with reference to drawings. FIG. 1 is a cross-sectional view of the tire 1 in the tire width direction and the tire radial direction.
The tire 1 has a pair of bead portions N and a side portion M continuous to the bead portion N. In each of the bead portions N, bead cores 2 and 2 ′ are embedded. Stiffeners 3 and 3 ′ extend on the radially outer sides of the pair of bead cores 2 and 2 ′, respectively.
The tire 1 has a carcass ply 4 that is covered with ply coating rubber. The carcass ply 4 has a main body portion extending in a toroidal shape between the bead cores 2 and 2 ′, and a ply end portion connected to the main body portion. The carcass ply 4 is folded at the bead core 2 from the outside of the stiffener 3 to form a horseshoe-shaped tire case shape, folded at the opposite bead core 2 ', and locked at the outside of the stiffener 3'.
An inner liner 10 is disposed inside the carcass ply 4 as an air permeation preventive layer.
The tire 1 has a belt portion 5 outside the carcass ply 4 in the tire radial direction. The belt portion 5 includes a plurality of belt layers (four layers 5a to 5d in FIG. 1). An inter-belt seat rubber 6 is disposed between the end of the belt layer 5a and the end of the belt layer 5b. A tread portion 8 is disposed outside the tire radius of the belt portion 5.
A sidewall rubber 9 is disposed outside the carous ply 4 and between the tread portion 8 and the stiffener 3.

In the tire 1 shown in FIG. 1, each part mentioned above is defined as follows.
Part I is in the vicinity of the tire center line. “Near the tire center line” is an area of 20% of the tread width in the tread width direction around the tire center line.
Part II is in the vicinity of the maximum width portion where the tire width is maximum in the cross section in the tread width direction and the tire radial direction. “Near the maximum width portion” is an area of 50 mm in the tire radial direction centering on the maximum width portion where the tire width is maximum in the cross section in the tread width direction and the tire radial direction.
Site III is near the end of the carcass ply. “Near the end of the carcass ply” is an area of 20 mm from the end of the carcass ply to the inside in the tire radial direction.
The portion IV is a region corresponding to the end portion of the belt portion in the carcass ply, and is a region of 5% of the tread width in the tread width direction from the end portion of the belt portion.

FIG. 2 is a cross-sectional view in the tire width direction and the tire radial direction for explaining the case where the tire 1 is composed of a base tire A and a precure tread B.
The base tire A of the tire 1 is obtained by vulcanizing a tire case including a carcass ply 4 and a belt portion 5 including a plurality of belt layers 5a to 5d disposed on the outer side in the tire radial direction of the carcass ply 4. It is a thing.
Precure tread B is obtained by vulcanizing a tread member having at least a tread portion 8. The tire 1 may be a tire obtained by vulcanizing after the above base tire A and the precure tread B are bonded together.
The tire 1 according to this embodiment described with reference to FIGS. 1 and 2 can be suitably used as a heavy load tire. The heavy duty tire represents a tire for a large vehicle used in a truck tire, a bus tire, a construction site, a port, a mine, or the like.

[Ply coating rubber]
The D _res value at the parts I, II, III and IV of the ply coating rubber of the carcass ply is D _res > 0.75 × with respect to D _max which is the D _res value when the vulcanization torque reaches the maximum value. _Satisfy D _max . When the above relational expression is not satisfied, the cross-linked state of the ply coating rubber is not uniform over the entire tire, and the low heat build-up is deteriorated.
From the above viewpoint, the D _res value in the parts I, II, III, and IV of the ply coating rubber of the carcass ply is D _res > with respect to D _max that is the D _res value when the vulcanization torque reaches the maximum value. 0.75 × D _max is preferable, and D _res > 0.8 × D _max is more preferable.
By setting the conditions as described above, it is possible to prevent performance degradation of the entire tire due to overvulcanization, and it is possible to improve low rolling resistance of the tire.

<Rubber composition>
In the tire according to the present invention, the rubber composition used for the ply coating rubber covering the carcass ply 4 contains a rubber component and a vulcanizing agent. In addition, various vulcanization accelerating components usually used in rubber compositions may be blended.

<Rubber component>
As the rubber component, natural rubber and / or synthetic polyisoprene rubber (IR) is preferable, and natural rubber is more preferable. Even in the case of combined use with other synthetic rubbers, the natural rubber in the rubber component is preferably 60% by mass or more, more preferably 70% by mass or more, and 80% by mass or more. Further preferred is natural rubber alone.
Examples of other synthetic rubbers include polybutadiene rubber (BR), styrene-butadiene copolymer (SBR), and styrene-isoprene copolymer (SIR).

<Vulcanizing agent>
The vulcanizing agent is preferably contained in the rubber composition in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. If the content of the vulcanizing agent is 0.1 parts by mass or more, sufficient vulcanization can be achieved, and if it is 10 parts by mass or less, the overvulcanized state can be prevented and the rubber composition can be prevented from becoming hard and brittle. . From the above viewpoint, the vulcanizing agent is preferably blended in 7.0 parts by mass or less. In particular, the range is 3.0 parts by mass or more and 7.0 parts by mass or less, more preferably 4.0 parts by mass or more and 6.0 parts by mass or less. When the blending amount of the vulcanizing agent is 7.0 parts by mass or less, it is possible to prevent the deterioration of the aging resistance of the rubber composition. Moreover, if 3.0 mass parts or more of vulcanizing agents are blended, the initial adhesiveness can be improved, which is more preferable. Sulfur is preferred as the vulcanizing agent for the rubber composition.

<Filler>
In addition to the above components, fillers such as carbon black and inorganic fillers may be blended as necessary. The filler is preferably contained in the rubber composition in an amount of 40 to 80 parts by mass with respect to 100 parts by mass of the rubber component. If the content of the filler is 40 parts by mass or more, sufficient crack resistance can be obtained, and the durability of the tire can be improved. Moreover, it can prevent that a tire becomes weak as it is 80 mass parts or less, and can prevent a deterioration of durability.

(Carbon black)
Examples of the carbon black used in the rubber composition constituting the ply coating rubber of the carcass ply 4 include, for example, HAF (nitrogen adsorption specific surface area: 75 to 80 m ² / g), HS-HAF (nitrogen adsorption specific surface area: 78 to 83 m). ² / g), LS-HAF (nitrogen adsorption specific surface area: 80 to 85 m ² / g), FEF (nitrogen adsorption specific surface area: 40 to 42 m ² / g), GPF (nitrogen adsorption specific surface area: 26 to 28 m ² / g) ), N339 (nitrogen adsorption specific surface area: 88 to 96 m ² / g), LI-HAF (nitrogen adsorption specific surface area: 73 to 75 m ² / g), IISAF (nitrogen adsorption specific surface area: 97 to 98 m ² / g), HS -IISAF (nitrogen adsorption specific surface area: 98 to 99 m ² / g) and the like.
Of these, HAF (nitrogen adsorption specific surface ^{area: 75~80m 2 / g), HS} -HAF ( nitrogen adsorption specific surface ^{area: 78~83m 2 / g), LS} -HAF ( nitrogen adsorption specific surface area: 80~85m ² / g), FEF (nitrogen adsorption specific surface area: 40 to 42 m ² / g), and LI-HAF (nitrogen adsorption specific surface area: 73 to 75 m ² / g) are preferable.

(silica)
In the present invention, the rubber composition constituting the ply coating rubber of the carcass ply 4 may be blended with silica as desired in addition to carbon black. It is preferable to contain 10 parts by mass or less of silica with respect to 100 parts by mass of the rubber component of the rubber composition.
As silica, wet silica, dry silica, and colloidal silica are preferably used, and wet silica is particularly preferably used. The BET specific surface area (measured in accordance with ISO 5794/1) of silica is preferably 40 to 350 m ² / g. Silica having a BET surface area within this range has an advantage that both rubber reinforcement and dispersibility in a rubber component can be achieved. In this respect, BET surface area is more preferably silica in the range of 80~350m ² / g, silica BET surface area in the range of 120~350m ² / g is particularly preferred. Examples of such silicas are those manufactured by Tosoh Silica Co., Ltd., trade names “Nipsil AQ” (BET specific surface area = 220 m ² / g), “Nipsil KQ”, and Degussa's trade name “Ultra Gil VN3” (BET specific surface area = 175 m ^2. / G) and other commercial products can be used.

(Other ingredients)
The rubber composition constituting the ply coating rubber of the carcass ply 4 in the present invention includes, in addition to the above-mentioned compounding agents, for example, a vulcanization activator such as a cross-linking component other than sulfur, zinc white, organic acid (stearic acid, etc.) Chemicals usually used in the rubber industry such as vulcanization accelerators, inorganic fillers other than silica, anti-aging agents, anti-ozone degradation agents, and softeners (oils) can be appropriately blended.

[Tire manufacturing method]
As a method for manufacturing a tire according to an embodiment of the present invention, the following first to third methods may be mentioned.
<First method>
The following method is mentioned as a 1st method among the manufacturing methods of the tire which concerns on embodiment of this invention. That is, when the base tire A is manufactured by vulcanizing the case portion, the unvulcanized case portion is first formed. The case portion is formed in the same manner as the green tire forming step in a known tire manufacturing method. For example, a carcass ply in which unvulcanized rubber is rubberized is wound on a molding drum, bead cores are set on both ends thereof, the both end portions are folded back, and unvulcanized rubber on a sidewall portion is further attached. Next, the central portion in the width direction is expanded to form an annular shape having a horseshoe cross section, and then an unvulcanized belt layer is provided on the outer periphery of the carcass layer, and preferably the same rubber composition as the inner layer of the tread portion 8 thereon. A case layer can be obtained by sticking a thin layer.
By setting the case part in a vulcanization mold (mold) and performing vulcanization molding, a base tire A having a part of the tread part 8 or no tread part 8 can be obtained.

In the manufacturing method of the present invention, the vulcanization method of the case portion (the untired base tire A) is a method of surrounding the case portion from the outside with a vulcanization mold, and the bead portion side of the case portion Is heated by the first heating means, the belt portion side of the case portion is heated by the second means, and the amount of heat per unit volume given to the belt portion side by the second heating means is the bead portion by the first heating means. It is preferable to perform vulcanization molding so that the amount of heat per unit volume given to the side is smaller.
In ordinary heavy duty tires (for example, pneumatic radial tires for trucks and buses), the thickness of the belt portion side of the case portion is thinner than the maximum thickness of the bead portion N. There is a slow point. As described above, if the amount of heat per unit volume is reduced on the belt portion side and the amount of heat per unit volume is increased on the bead portion side, the belt portion side will not be overvulcanized and the carcass ply 4 covering rubber composition This is preferable because the adhesion to steel cord (both initial adhesion and adhesion after long-time use) is improved, and tan δ is lowered and low heat build-up is also improved.
As a means for reducing the amount of heat per unit volume on the belt side and increasing the amount of heat per unit volume on the bead side, when producing the base tire A by vulcanizing the case part, for example, in the vulcanization mold The case part is put in and pressure and heat are applied from the inside of the case part by a vulcanization bladder, but at this time, it is higher than the first heating means of the vulcanization mold part facing the bead part N of the case part. What is necessary is just to heat at a temperature lower than a 1st heating means from the 2nd heating means of the part of a vulcanization metal mold | die facing the belt part side of a case part.

In the manufacturing method of the present invention, the vulcanization temperature reached by the carcass ply 4 (particularly, the latest vulcanization point of the innermost layer 5a) at the time of vulcanization of the case portion is 110 to 160 ° C., and the bead portion N The vulcanization temperature reached by (particularly the latest vulcanization point of the bead portion N) is 125 to 180 ° C., and the vulcanization temperature reached by the latest vulcanization point of the carcass ply 4 is increased by the bead portion N. The temperature is preferably 2 to 25 ° C higher than the sulfur temperature, more preferably 4 to 25 ° C lower, and still more preferably 4 to 20 ° C lower.
The belt portion side is prevented from being overvulcanized, and the steel cord initial adhesiveness and low heat build-up of the coated rubber composition of the carcass ply 4 are improved.
If the vulcanization temperature reached by the carcass ply 4 (particularly the latest vulcanization point of the carcass ply 4) is 110 ° C. or higher, vulcanization proceeds preferably, and if it is 160 ° C. or lower, the steel cord Since initial adhesiveness improves, it is preferable. Further, if the vulcanization temperature reached by the bead part N (particularly the latest vulcanization point of the carcass ply 4) is 125 ° C. or higher, the vulcanization time of the base tire A can be shortened, and if it is 180 ° C. or lower, It is preferable because the durability of the bead portion is improved.

On the other hand, when producing the precure tread B, a tread material made of unvulcanized rubber having a substantially trapezoidal cross section in the width direction is extruded from an extruder (not shown), and then cut into a predetermined length. Then, the cut strip-shaped tread material is set in a vulcanization mold having an upper mold and a lower mold, and vulcanized to obtain a ring-shaped precure tread B. At this time, a plurality of grooves extending in the longitudinal direction of the ring-shaped outer surface of the precure tread B are formed.
The vulcanization conditions are preferably about 100 to 185 ° C. and the time until the vulcanization of the precured tread B is completed.

In the base tire A and the pre-cured tread B obtained as described above, the tire casing surface that is in contact with the mold surface during vulcanization has a property that it is difficult to co-crosslink with the unvulcanized rubber. For the purpose of ensuring, it is preferable to remove (shave off) the surface rubber on the outer surface which is the bonding surface between the base tire A and the precure tread B. However, as the surface rubber to be scraped off, an extremely thin layer having a thickness of 0.001 mm or less is sufficient for the purpose.
The method of scraping off the surface rubber is not particularly limited as long as the surface roughness can be adjusted to a suitable range, and the adhesive surface may be polished using a grindstone, a metal polishing tool, a non-woven fabric abrasive, etc. In order to make the thickness of the surface rubber as extremely thin as 10 nm to 1 mm, it is preferable to use a nonwoven fabric abrasive. Non-woven abrasives are preferred for polishing (roughening) the surface layer uniformly and thinly as described above, because the force applied for polishing is dispersed by the spring effect, so that no excessive cutting or deep scratches are generated. It is a material. In addition, it can grind | polish by attaching the said nonwoven fabric abrasive material to the existing buffing machine. Specific examples of the non-woven abrasive include “Scotch Bright” manufactured by Sumitomo 3M Limited.

As described above, the outer surface, which serves as an adhesive surface between the base tire A and the precure tread B, is preferably roughened uniformly as described above in order to enhance the adhesiveness by the anchoring effect (also referred to as an anchor effect).
Next, the tire 1 is obtained by bonding the base tire A and the precure tread B and vulcanizing them integrally. At this time, it is preferable to vulcanize and mold the base tire A and the precure tread B through an unvulcanized cushion rubber layer.
Next, the base tire A to which the precure tread B is affixed is carried into a vulcanizer (not shown) (for example, a vulcanizing can), and the unvulcanized cushion rubber layer is vulcanized to obtain the tire 1. At this time, the precure tread B is co-vulcanized and bonded to the outer periphery of the crown portion of the base tire A. As vulcanization conditions, it is preferable to carry out at about 60-140 degreeC.
In this vulcanization, the ultimate temperature of the vulcanization latest point of the carcass ply 4 when the base tire A and the precure tread B are bonded and integrally vulcanized is the carcass ply when the case portion is vulcanized. It is preferable that the temperature is lower than the temperature reached at the latest vulcanization point of 4. The vulcanization degree of the case portion vulcanization and the vulcanization degree of the vulcanization of the base tire A and the precure tread B are optimized so as not to be excessive, and the covering rubber composition of the carcass ply 4 is This is to improve the initial adhesion to steel cord, low heat generation and durability.

<Second method>
The second method is a method of vulcanizing at an ultra-low temperature. If the temperature is extremely low, the difference in the amount of heat applied to the member can be reduced, so that the entire tire can be uniformly vulcanized.
<Third method>
The third method is a method of changing the composition of the ply coating rubber that covers the carcass ply according to the position in the tire. That is, a ply coating rubber blending that requires a long vulcanization time is used at a position where heat is easily transmitted, and a ply coating rubber blending that can be crosslinked in a short vulcanization time is used at a position where heat is difficult to transmit.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.
[Measuring method]
<D _res value>
The D _res value is based on the description of Kay Saalwachter (2005) “Chain Order and Cross-Link Density of Elastomers As Investigated by Proton Multiple-Quantum NMR”, Macromolecules 2005, 38, 9650-9660. It was measured using a minispec mq20).
From the parts I, II, III, and IV of the ply coating rubber, 0.5 g of a rubber piece that was confirmed to be uniform visually was taken out and finely cut to obtain a measurement sample.
A measurement apparatus MQ-NMR apparatus was prepared, measurement samples extracted from each part were measured under a temperature of 40 ° C., and each D _res value was measured. The parameters related to signal acquisition were as follows.
Scans: 64
dummy_shots: 1
rd [s]: 0.5
det_mode: complex
The pulse sequence conditions were as follows.
Initial Cycle Time [ms]: 0
Cycle Time Increment [ms]: 0.035
Number of Cycles: 2
Number of DQ Build-Up Points: 60
Double Increment after Points: 10
FID Evaluation Interval [ms]: 0.02
Further, the D _res value (referred to as D _max value) of the tire crosslinked under the vulcanization condition that maximizes the vulcanization torque was calculated by a conventional method. The minimum value of the D _res value in each part was compared with the above D _max value, and displayed as an index. Those having an index exceeding 0.75 were regarded as acceptable.
D _res index = (minimum value of D _res value at each part / D _max )

<Low rolling resistance>
The resistance to the traveling direction generated on the tire ground contact surface during running at 80 km / hour was measured for each prototype tire in a drum test, and the value of Comparative Example 1 was set to 100, and displayed as an index according to the following formula. The larger this value, the smaller the rolling resistance and the better. The results are shown in Table 2.
Low rolling resistance index = {(rolling resistance of tire of Comparative Example 1) / (rolling resistance of test tire)} × 100

[Production method]
<Method A>
An unvulcanized case portion using a rubber composition described later as a ply coating rubber was prepared with a common tire size of 11R22.5. These case parts are each vulcanized by a method in which the case part is surrounded from the outside by a vulcanization mold and pressurized and heated by a vulcanization bladder from the inside (pressurized with high-pressure steam at 150 ° C.) Manufactured.
At this time, the first heating means of the vulcanization mold block facing the bead part side of the case part is kept at 170 ° C., and the second heating means of the vulcanization mold block facing the belt part side of the case part is 140 ° C. Kept. Thus, the amount of heat per unit volume given to the belt portion side by the second heating means is made smaller than the amount of heat per unit volume given to the bead portion side by the first heating means. The vulcanization temperature at which the latest vulcanization point of the innermost belt layer reached was 150 ° C., and the vulcanization temperature at which the latest vulcanization point of the bead portion reached was 155 ° C. All vulcanization times were 30 minutes.
Separately, a precure tread that was vulcanized and molded by heating at 160 ° C. so as to mold the tread pattern in advance was prepared.
The adhesion surface of these base tires and precure tread was polished by a buffing machine. Next, the base tire and the precure tread member were bonded together using a cushion rubber, and then vulcanized at 120 ° C. for 2 hours using a vulcanizer (vulcanized can). Each tire was obtained by bonding the base tire and the precure tread. At this time, the vulcanization temperature at which the latest vulcanization point of the innermost belt layer reached was 120 ° C.

<Method B>
Next, the tire size is the same for 11R22.5, an unvulcanized case portion using a rubber composition described later is prepared for the ply coating rubber, and an unvulcanized tread member is attached to the outer side in the tire radial direction. To get a raw tire. These tires were vulcanized by ordinary one-stage vulcanization.

[Examples and Comparative Examples]
A tire was manufactured by the method A or B described above according to the formulation of the rubber composition of the ply coating rubber shown in Table 1. The manufactured tire was evaluated by the above method. The results are shown in Table 2.

[note]
* 1: HAF (N-330), manufactured by Asahi Carbon Co., Ltd., trade name “Asahi # 70” (nitrogen adsorption specific surface area: 77 m ² / g)
* 2: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”

From the above results, a tire having rolling resistance with no practical problems if the vulcanization conditions such that the D _res values at the following parts I, II, III and IV of the ply coating rubber exceed 0.75 are followed. Was found to be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Tire, 2, 2 '... Bead core, 3, 3' ... Stiffener, 4 ... Carcass ply, 5 ... Belt part, 5a ... Innermost belt layer (inner belt layer which forms a crossing layer), 5b ... Crossing layer Outer belt layer to be formed, 5c ... outermost belt layer, 6 ... belt wedge rubber, 8 ... tread portion, 9 ... sidewall rubber, 10 ... inner liner, M ... side portion, N ... bead portion, A ... stand tire, B ... Precure tread

Claims (4)

A carcass ply having a main body portion extending in a toroidal shape between bead cores embedded in a pair of bead portions and a ply end portion connected to the main body portion and covered with ply coating rubber; and an outer side in the tire radial direction of the carcass ply A tire comprising a belt portion composed of a plurality of belt layers disposed on the belt portion and a pair of side portions located at both ends of the belt portion,
Following site I of the ply coating rubber, II, also D _res value either in III and IV, with respect to D _max is a D _res value when the vulcanization torque becomes the maximum value,
D _res > 0.75 × D _max
Satisfy tires.
However,
Part I: In the vicinity of the tire center line Part II: In the vicinity of the maximum width part where the tire width becomes maximum in the cross section in the tread width direction and the tire radial direction Part III: In the vicinity of the end part of the carcass ply Part IV: End of the belt part Carcass ply near
The D _res value is a value measured using a TD-NMR apparatus at a temperature of 40 ° C.   The tire according to claim 1, which is for heavy loads.   The tire according to claim 1, wherein the rubber composition constituting the ply-coating rubber contains 0.1 to 10 parts by mass of a vulcanizing agent with respect to 100 parts by mass of the rubber component.   The tire according to claim 1, wherein the rubber composition constituting the ply-coating rubber contains 40 to 80 parts by mass of a filler with respect to 100 parts by mass of the rubber component.

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