DE102014105343B4 - MANUFACTURING PROCESS FOR TIRES AND TIRES - Google Patents

Abstract

A manufacturing method for a pneumatic tire with a tread, the method comprising: (A) a step of molding an unvulcanized rubber composition for a tread to obtain a concave tread raw extrudate; (B) a step of laminating the tire in step (A ) obtained tread raw extrudate with other unvulcanized rubber compositions to obtain an unvulcanized raw cover; and (C) a step of vulcanizing the unvulcanized raw cover obtained in the step (B) in a vulcanization mold, the steps (A), (B) and (C) being carried out so that the tread of the tire is formed from a rubber composition for a tread which, based on 100 parts by mass of the rubber component, 2.5 to 8.0 parts by mass of at least one selected from the group consisting of stearic acid, a metal salt of a saturated fatty acid and a mold release agent which comprises at least one selected from the group consisting of a metal salt of a fatty acid, a fatty acid amide and an amide ester, and which has an initial vulcanization rate t10 as measured by a vulcanization elastometer of 2.0 to 5.0 minutes at 160 ° C, the one provided in the tread raw extrudate concave profile is positioned at a point in which the convexity of the main groove of the K rone of the vulcanization form which forms the main groove of the crown, in which step (C) is pressed, the cross-sectional area of the concave profile perpendicular to the circumferential direction of the tire is set to be 30 to 100% of the cross-sectional area of the convexity for the main groove of the crown the width of the concave profile is set to be 100 to 300% of the width of the convexity of the convex portion of the crown, provided that when the distance from the center of the crown of the tread to the shoulder edge is 1, the The center of the convexity of the main groove of the crown is provided at a position from 0 to 1/2 from the origin of the crown, and the width of the main groove of the crown on the surface of the manufactured tire is adjusted to be not less than 7.0 mm.

Description

TECHNICAL AREA

The present invention relates to a manufacturing method for a pneumatic tire and a pneumatic tire manufactured by this manufacturing method.

BACKGROUND OF THE INVENTION

To ensure the mileage of a pneumatic tire on wet roads (wet braking performance), it is important to prevent the formation of a water film between the tread and the road and to increase the area with which the tread is in contact with the road. To this end, a method of widening the effective area of the tread that is in contact with the road by providing a plurality of grooves (tread grooves) in the tread to water caused by the road contact pressure of the rotating tire from the road contact area has been widely adopted the tread is pressed through main grooves around a crown section. It is also known that by providing one or more main grooves with a large cross-sectional area perpendicular to the circumferential direction of the tire as a tread groove in the crown portion, the road contact area is effectively increased and the wet braking performance can be ensured.

However, when main grooves with a large cross-sectional area are provided in the crown portion, there arises a problem that during the tire vulcanization step, corrugations occur on a breaker layer within or near the breaker layer (see 7a and 7b) , the tread is not inflated evenly during inflation and there is a slight possibility of deformation of the contact surface. Such pneumatic tires with a fault on the contact surface have a deteriorated movement control, in particular wet braking performance.

Furthermore, in the crown portion of the tread, there is a problem that the rubber flows with difficulty and easily shrinks when it is pressed by the vulcanization mold, because the bonding force between the breaker and the band is strong and the rubber composition, which is pressed by a vulcanization mold, has a small space to dodge. These shrinkage points occur primarily in an edge section between the road contact surface and the main groove (710 in 7b) as well as in a section of a wear indicator. It should be noted that shrinkage is a phenomenon in which there is an intermediate air space between the unvulcanized rubber composition and the vulcanization mold due to insufficient adhesion between them, and after vulcanization, the rubber composition in this section is pressed in in a semi-finished state and has a gloss.

The JP 5153961 B describes a manufacturing method for a pneumatic tire having a tread made of a predetermined rubber composition in which a tread raw extrudate having a predetermined concave profile is provided at a portion where a convexity for shoulder main grooves is pressed. However, this method is designed to prevent tread groove breaks in a shoulder main groove, and applications of this technique to the crown main grooves and prevention of shrinkage and curl are not disclosed.

In the JP 51-53961 B1 discloses a method of making a tread of a tire from a rubber composition containing 2.5 to 6 parts by mass of at least one compound selected from the group consisting of stearic acid, metal salt of saturated fatty acid and mold release agent, the cross-sectional area of the concave profile of the tread being perpendicular to the circumferential direction of the tire is 30 to 100% of the cross-sectional area of the convexity for the shoulder main groove and the cross-sectional area of the convexity of the shoulder main groove perpendicular to the circumferential direction of the tire is not less than 5% of the total cross-sectional area of the groove.

From the US 4,308,083 a method of manufacturing a pneumatic tire is known in which the tread portion of the pneumatic tire is preformed before vulcanization to avoid unevenness of the belt pack.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a manufacturing method for a pneumatic tire in which the formation of corrugations on a breaker layer or in the vicinity of a breaker layer and shrinkage in the crown portion of a tread are prevented without deteriorating the productivity of the vulcanization, and one To provide pneumatic tires, which was produced by this manufacturing method.

1. (A) einen Schritt des Formens einer unvulkanisierten Kautschukzusammensetzung für eine Lauffläche, um ein mit einem konkaven Profil versehenes Laufflächenrohextrudat zu erhalten;
2. (B) einen Schritt des Laminierens des in Schritt (A) erhaltenen Laufflächenrohextrudats mit anderen unvulkanisierten Kautschukzusammensetzungen, um eine vulkanisierte Rohabdeckung zu erhalten; und
3. (C) einen Schritt des Vulkanisierens der unvulkanisierten Rohabdeckung, welche in dem Schritt (B) erhalten worden ist, in einer Vulkanisationsform,

wobei das in dem Laufflächenrohextrudat vorgesehene konkave Profil an einer Stelle positioniert wird, in welche die Konvexität der Hauptrille der Krone der Vulkanisationsform, welche die Hauptrille der Krone ausbildet, in dem Schritt (C) gepresst wird,
die Querschnittsfläche des konkaven Profils senkrecht zu der Umlaufsrichtung des Reifens 30 bis 100% der Querschnittsfläche der Konvexität für die Hauptrille der Krone beträgt,
die Breite des konkaven Profils 100 bis 300% der Breite der Konvexität des konvexen Abschnitts der Krone beträgt,
mit der Maßgabe, dass der Abstand von der Mitte der Krone der Lauffläche zu der Schulterkante 1 beträgt, die Mitte der Konvexität der Hauptrille der Krone an einer Stelle von 0 bis 1/2 von dem Ursprung der Krone vorgesehen ist und die Breite der Hauptrille der Krone auf der Oberfläche des hergestellten Reifens nicht weniger als 7,0 mm beträgt.The present invention relates to a manufacturing method for a pneumatic tire having a tread which contains a rubber composition for a tread which, based on 100 parts by mass of the rubber component, 2.5 to 8.0 parts by mass of at least one selected from the group consisting of Stearic acid, a metal salt of a saturated fatty acid and a mold release agent which comprises at least one selected from the group consisting of a metal salt of a fatty acid, a fatty acid amide and an amide ester, and which have an initial vulcanization rate t10 of 2.0 to 5 measured with a vulcanization elastometer , 0 minutes at 160 ° C, the method comprising:

1. (A) a step of molding an unvulcanized rubber composition for a tread to obtain a concave tread raw extrudate;
2. (B) a step of laminating the tread raw extrudate obtained in step (A) with other unvulcanized rubber compositions to obtain a vulcanized raw cover; and
3. (C) a step of vulcanizing the unvulcanized raw cover obtained in the step (B) in a vulcanization mold,

wherein the concave profile provided in the tread raw extrudate is positioned at a position into which the convexity of the main groove of the crown of the vulcanization mold which forms the main groove of the crown is pressed in step (C),
the cross-sectional area of the concave profile perpendicular to the circumferential direction of the tire is 30 to 100% of the cross-sectional area of the convexity for the main groove of the crown,
the width of the concave profile is 100 to 300% of the width of the convexity of the convex section of the crown,
with the proviso that the distance from the center of the crown of the tread to the shoulder edge is 1, the center of the convexity of the main groove of the crown is provided at a position from 0 to 1/2 of the origin of the crown and the width of the main groove of the Crown on the surface of the manufactured tire is not less than 7.0 mm.

It is preferred that the profile provided in the tread raw extrudate has a convexity at its bottom which has a height of 0.1 to 2.0 mm in at least a portion of the direction of the circumference of the tire.

It is preferred that the rubber composition for a tread, based on 100 parts by mass of the rubber component, comprises 30 to 130 parts by mass of silica with a specific BET surface area of 40 to 300 m ² / g.

It is preferable that the preset temperature of the vulcanization mold in step (C) is not less than 165 ° C.

The present invention also relates to a pneumatic tire manufactured by the above-mentioned manufacturing method.

According to the present invention, a manufacturing method for a pneumatic tire, in which the formation of corrugations on a breaker layer or in the vicinity of a breaker layer as well as shrinkage at the crown portion of a tread without reducing the vulcanization productivity can be provided by providing a rubber composition for a tread is used which, based on 100 parts by mass of the rubber component, 2.5 to 8.0 parts by mass of at least one selected from the group consists of stearic acid, a metal salt of a saturated fatty acid and a mold release agent which consists of at least one selected from the group comprising a metal salt of a fatty acid, a fatty acid amide and an amide ester, and which has an initial vulcanization rate t10 of 2.5 to 5.0 minutes at 160 ° C measured with a vulcanization elastometer, and by in the forming step (Sc Step A) the unvulcanized A rubber composition for a tread of a concave profile is provided in a predetermined shape at a location where the convexity for the main groove of the crown of the vulcanization mold which forms the main groove of the crown is pressed. According to the present invention, there can also be provided a pneumatic tire manufactured by the manufacturing method.

Figure list

• 1A shows a schematic partial cross-sectional view of a vulcanization mold and an unvulcanized raw cover according to an embodiment of the present invention.
• 1B shows a schematic partial cross-sectional view of a vulcanization mold and a tire according to an embodiment of the present invention.
• 2A and 2 B show a schematic partial cross-sectional view of a convexity for a main groove of a crown and a concave profile according to an embodiment of the present invention.
• 3A and 3B FIG. 4 shows a schematic cross-sectional view of a convexity for a main groove of a crown and a concave profile according to a reference embodiment of the present invention.
• 4th shows a schematic cross-sectional view for a convexity for a main groove of a crown, which is provided on the inner surface of a vulcanization mold.
• 5 shows a schematic partial cross-sectional view for a tire according to an embodiment of the present invention.
• 6 FIG. 12 shows a schematic partial cross-sectional view for a tire, a vulcanization mold and a vulcanization bellows in the vulcanization step of the present invention.
• 7A shows a schematic partial cross-sectional view of a conventional vulcanization mold and an unvulcanized raw cover in a flat shape (without a concave profile).
• 7B shows a schematic partial cross-sectional view for a conventional vulcanization mold and a tire

DETAILED DESCRIPTION

The manufacturing method for a pneumatic tire of the present invention is a manufacturing method for a pneumatic tire that has a tread formed from a predetermined rubber composition for a tread and is characterized in that a concave profile is provided at a position where a convexity for a main groove of the crown of the vulcanization mold, which forms the main groove of the crown from the tread raw extrudate.

A tread of a pneumatic tire made by the manufacturing method of the present invention is composed of a rubber composition for a tread having a predetermined initial vulcanization rate and comprises a predetermined amount of at least one selected from the group consisting of stearic acid, a metal salt of a saturated fatty acid and a mold release agent which comprises at least one selected from the group consisting of a metal salt of a fatty acid, a fatty acid amide and an amide ester, based on the rubber component.

Examples of the rubber component include diene rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene Rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) and butyl rubber (IIR). These diene rubbers can be used alone or in combination of two or more thereof. Among them, it is preferable to use NR, BR and SBR, since grip and abrasion resistance can then be obtained in an advantageous balance, and it is particularly preferable to use SBR, since even better grip can be obtained.

The SBR is not particularly limited and, for example, an emulsion-polymerized styrene-butadiene rubber (E-SBR) and a solution-polymerized styrene-butadiene rubber (S-SBR) and the like can be used. In addition, a terminal-modified S-SBR (modified S-SBR) or an E-SBR (modified E-SBR) can also be used, and examples of the modified S-SBR and the modified E-SBR include one that has been modified with an organic silicon compound having an alkoxy group, such as an alkoxy group, having an amino group, or one having only one amino group.

The styrene content in the SBR is preferably not less than 20% by mass, and particularly preferably not less than 25% by mass. If the styrene content in the SBR is less than 20% by mass, there is a tendency that a sufficient grip cannot be obtained. On the other hand, the styrene content in the SBR is preferably not more than 60% by mass and particularly preferably not more than 50% by mass. If the styrene content in the SBR is more than 60% by mass, there is a tendency that the abrasion resistance decreases and the temperature dependency is increased, and therefore the change in performance with respect to a change in temperature is increased.

In the case where the rubber composition comprises SBR as a diene rubber component, the content of the SBR is preferably not less than 20% by mass and particularly preferably not less than 30% by mass. If the content of the SBR is less than 20% by mass, there is a tendency that a sufficient heat resistance and a good grip cannot be obtained. On the other hand, the content of SBR is preferably not more than 90 mass% and particularly preferably not more than 80 mass%. If the content of SBR is more than 90 mass%, heat build-up property and crack growth resistance tend to be deteriorated.

Examples of the BR include a high cis-1,4-polybutadiene rubber (high-cis BR), a butadiene rubber containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), a modified butadiene rubber (modified BR) and a rare earth-catalyzed BR, and these can be used singly or in combination of two or more thereof.

The high-cis BR is a butadiene rubber in which the content of cis-1,4 bonds is not less than 90% by mass.

It is preferred that the SPB-containing BR is not the one in which 1,2-syndiotactic polybutadiene crystals (SPB) are simply dispersed in the BR, but the one in which 1,2-syndiotactic polybutadiene crystals (SPB) are chemically attached to the BR are bound and dispersed because it is even more excellent in crack growth resistance.

The melting point of the 1,2-syndiotactic polybutadiene crystals is preferably not less than 180 ° C and particularly preferably not less than 190 ° C. If the melting point of the 1,2-syndiotactic polybutadiene crystals is less than 180 ° C, there is a tendency that the crystals melt during the vulcanization of the tire and the hardness of the rubber compound decreases. On the other hand, the melting point of the 1,2-syndiotactic polybutadiene crystals is preferably not more than 220 ° C. and particularly preferably not more than 210 ° C. If the melting point of the 1,2-syndiotactic polybutadiene crystals is more than 220 ° C, there is a tendency that the dispersibility in the rubber composition and the extrusion processability are deteriorated due to an increase in the molecular weight of the BR.

The content of the boiling n-hexane-insoluble material in the SPB-containing BR is preferably not less than 2.5% by mass and particularly preferably not less than 8% by mass. If the content is less than 2.5 mass%, the hardness of the rubber composition tends to be insufficient. On the other hand, the content of material insoluble in boiling n-hexane is preferably not more than 22% by mass, particularly preferably not more than 20% by mass and very particularly preferably not more than 18% by mass. If the content exceeds 22 mass%, the viscosity of the BR itself becomes high and the dispersibility of the BR and a filler in the rubber composition tend to deteriorate. Here, the boiling n-hexane insoluble material denotes 1,2-syndiotactic polybutadiene in the SPB-containing BR.

The content of 1,2-syndiotactic polybutadiene crystals in the SPB-containing BR is preferably not less than 2.5% by mass and particularly preferably not less than 10% by mass. If the content is less than 2.5 mass%, the hardness of the rubber composition tends to be insufficient. On the other hand, the content of 1,2-syndiotactic polybutadiene crystals in the BR is preferably not more than 20 mass% and particularly preferably not more than 18 mass%. If the content exceeds 20% by mass, the BR becomes difficult to disperse in the rubber composition and the processability tends to deteriorate.

Examples of the modified BR include terminal-modified BR coupled with tin and terminal-modified BR which has an alkoxysilyl group and / or an amino group. Among these, preferred are the modified BR, which are obtained by carrying out the polymerization of 1,3-butadiene with a lithium initiator and then adding a tin compound, and in addition the terminal molecules are bound by a tin-carbon bond.

Examples of the lithium initiator include lithium compounds such as alkyl lithium, aryllithium, vinyl lithium, organotin lithium compounds and organo nitrogen lithium compounds, lithium metal and the like. When using the lithium initiator as an initiator for a modified BR, a modified BR with a high vinyl content and a low cis content can be produced.

Examples of the tin compound include tin tetrachloride, butyltin trichloride, dibutyltin dichloride, dioctyltin dichloride, tributyltin chloride, triphenyltin chloride, diphenyldibutyltin, triphenyltin ethoxide, diphenyldimethyltin, ditoloyltin chloride, diphenyltindiethyldistyltin, diethenyltin diethyltin, diethenyltin dextrin, dithenyltin diethyltin, dithenyltin diethyltin, dithenyltin, diethenyltin, diethenyltin, diethenyltin, diethenyltin, diethenyltin, diethenyltin, diethenyltin, diethenyltin, diethyltin, diethyltin, diethyltin, diethyltin, diethyltin. These tin compounds can be used alone or in combination of two or more thereof.

The content of tin atoms in the modified BR is preferably not less than 50 ppm, and particularly preferably not less than 60 ppm. If the tin atom content is less than 50 ppm, the effect of accelerating the dispersion of carbon black in the modified BR tends to be small and, in addition, tan δ tends to increase. On the other hand, the tin atom content is preferably not more than 3000 ppm, particularly preferably not more than 2500 ppm and very particularly preferably not more than 250 ppm. When the tin atom content exceeds 3000 ppm, the cohesion of the kneaded product tends to be poor, the edges thereof tend to be misaligned, and therefore the extrusion processability of the kneaded product tends to be deteriorated.

The molecular weight distribution (Mw / Mn) of the modified BR is preferably not more than 2.0 and particularly preferably not more than 1.5. When the Mw / Mn of the modified BR exceeds 2.0, the dispersibility of carbon black tends to deteriorate and the tan δ tends to increase. Note that Mw and Mn in the present invention are a value calculated with polystyrene standards using gel permeation chromatography (GPC).

The content of vinyl bonds in the modified BR is preferably not less than 5% by mass and particularly preferably not less than 7% by mass. If the vinyl bond content of the modified BR is less than 5 mass%, it tends to be difficult to polymerize (produce) a modified BR. On the other hand, the content of vinyl bonds in the modified BR is preferably not more than 50% by mass and particularly preferably not more than 20% by mass. When the content of vinyl bonds in the modified BR exceeds 50 mass%, the heat build-up properties tend to increase and the rolling resistance deteriorates.

The rare earth-catalyzed BR is a butadiene rubber, which was synthesized with a rare earth element-containing catalyst, and is characterized by a high cis content and a low vinyl content. As the rare earth-catalyzed BR, there can be used those which are generally used in the manufacture of tires.

As the rare earth element-containing catalyst for the synthesis of rare earth-catalyzed BR, known ones can be used, and examples thereof include catalysts which include a lanthanoid-containing compound, an organoaluminum compound, an aluminoxane or a halogen-containing compound and optionally comprise a Lewis base. Of these, Nd-containing catalysts using a neodymium (Nd) -containing compound as a lanthanoid-containing compound are particularly preferred.

Examples of the compound containing lanthanoids include halides, carboxylates, alcoholates, thioalcoholates and amides of rare earth metals, which have an atomic number of 57 to 71. Among them, the Nd-containing catalysts are preferred because a BR having a high cis content and a low vinyl content can be obtained.

As the organoaluminum compound, compounds represented by AIR ^a R ^b R ^c (wherein R ^a , R ^b and R ^{c are the} same or different and each represents hydrogen or a hydrocarbon group having 1 to 8 carbon atoms) can be used. Examples of the aluminoxanes include Chain aluminoxanes and cyclic aluminoxanes. Examples of the halogen-containing compound include aluminum halides represented by AIX _k R ^d _3-k (where X is halogen, R ^{d is} an alkyl, aryl or aralkyl group having 1 to 20 carbon atoms and k is 1, 1.5 , 2 or 3) are shown, strontium halides such as Me ₃ SrCl, Me ₂ SrCl ₂ , MeSrHCl ₂ and MeSrCl ₃ , and metal halides such as silicon tetrachloride, tin tetrachloride and titanium tetrachloride. The Lewis base can be used to complex a lanthanoid-containing compound, and suitable examples thereof include acetylacetone, ketone, alcohol and the like.

In the polymerization of butadiene, the rare earth element-containing catalyst can be used while dissolved in an organic solvent (such as n-hexane, cyclohexane, n-heptane, toluene, xylene or benzene) or while on a suitable support such as Silica, magnesia or magnesium chloride. The polymerization condition can be either that of solution polymerization or that of bulk polymerization. The polymerization temperature is preferably -30 to 150 ° C and the polymerization pressure can optionally be set depending on the other conditions.

The rare earth-catalyzed BR has a Mooney viscosity ML _{1 + 4} (100 ° C) of preferably not less than 35 and particularly preferably not less than 40. A Mooney viscosity of less than 35 tends to cause the unvulcanized rubber composition to have a low viscosity, and an appropriate thickness after vulcanization tends to be unsafe. Further, the Mooney viscosity is preferably not more than 55, and particularly preferably not more than 50. When the Mooney viscosity exceeds 55, the unvulcanized rubber composition tends to become so hard that it is difficult to extrude with smooth edges. It is noted that the Mooney viscosity is measured in accordance with ISO289 or JIS K6300.

The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) of the rare earth-catalyzed BR is preferably not less than 1.2 and particularly preferably not less than 1.5. If the Mw / Mn is less than 1.2, processability tends to be significantly degraded. Further, the Mw / Mn is preferably not more than 5, and particularly preferably not more than 4. When the Mw / Mn exceeds 5, the heat build-up property tends to deteriorate.

The Mw of the rare earth-catalyzed BR is preferably not less than 300,000 and particularly preferably not less than 320,000. On the other hand, the Mw is preferably not more than 1,500,000 and particularly preferably not more than 1,300,000. Furthermore, the Mn of the rare earth-catalyzed BR is preferably not less than 100,000 and particularly preferably not less than 150,000. On the other hand, the Mn is preferably not more than 1,000,000, and particularly preferably not more than 800,000. If the Mw or Mn is less than the preferred lower limits, heat buildup properties and elongation at break tend to deteriorate. On the other hand, if the Mw or Mn is more than the preferred upper limits, deterioration in processability becomes a concern. In the present invention, the Mw and Mn can be calculated using polystyrene standards using gel permeation chromatography (GPC).

The content of cis-1,4-bonds of the rare earth-catalyzed BR is preferably not less than 90% by mass, particularly preferably not less than 93% by mass and very particularly preferably not less than 95% by mass. If the content is less than 90 mass%, elongation at break and abrasion resistance tend to deteriorate.

The vinyl content of the rare earth-catalyzed BR is preferably not more than 1.8% by mass, particularly preferably not more than 1.0% by mass, very particularly preferably not more than 0.5% by mass and even more preferably not more than 0.3%. If the content exceeds 1.8 mass%, elongation at break and abrasion resistance tend to deteriorate. It should be noted that the vinyl content (amount of butadiene units with 1,2-bond) and the cis-1,4-bond content of the high-cis BR, modified BR and rare earth-catalyzed BR can be measured by analysis of the infrared absorption spectrum.

Among these various BRs, it is preferred to use rare earth-catalyzed BRs due to its excellent abrasion resistance and excellent heat build-up properties. Among the rare earth-catalyzed BR, in view of the even better abrasion resistance and the even better heat build-up property, it is preferable to use a BR which has been synthesized with an Nd-containing catalyst.

When the rubber composition comprises the BR as a diene rubber component, the content thereof is preferably not less than 10% by mass, and particularly preferably not less than 15% by mass. If the BR content is less than 10 mass%, abrasion resistance and crack growth resistance tend to be insufficient. On the other hand, the BR content is preferably not more than 80% by mass, particularly preferably not more than 70% by mass and very particularly preferably not more than 60% by mass. If the BR content exceeds 80% by mass, the grip tends to be insufficient. In addition, when two or more kinds of BRs are used together, the total content of the combined BRs is considered as the content of BR.

The NR is not particularly limited and those generally used in the manufacture of tires can be used, and examples thereof include SIR20, RSS # 3, TSR20 and the like.

When the rubber composition comprises NR as a diene rubber component, the content thereof is preferably not less than 10% by mass, and particularly preferably not less than 15% by mass. If the content of the NR is less than 10 mass%, the elongation at break and the resistance to break tend to be insufficient. On the other hand, the content of NR is preferably not more than 60% by mass, particularly preferably not more than 50% by mass and very particularly preferably not more than 40% by mass. If the content of NR exceeds 60 mass%, crack growth resistance and reversion resistance tend to be insufficient.

When using the rubber composition for a tread, which comprises at least one selected from the group consisting of stearic acid, a metal salt of a saturated fatty acid and a specific mold release agent, the sliding property of the rubber composition (the sliding of the rubber) for a tread, which by a in the internal surface of the vulcanization mold is pressed in a vulcanization step (step C) described below, improved, the flow of the rubber becomes uniform and the formation of shrinkage points can be suppressed.

The stearic acid is not particularly limited and those which are generally used in the manufacture of tires can be used. By using the rubber composition comprising stearic acid, the working viscosity can be reduced and an appropriate vulcanization rate can be ensured. Since zinc stearate bound to zinc oxide also blooms on the surface of the rubber, as described below, high sliding properties and high dispersibility of the zinc oxide can be obtained. Furthermore, when used together with the mold release agent, high sliding properties with respect to the vulcanization mold can be obtained.

As metal salts of the saturated fatty acids, those which are generally used in the manufacture of tires can be used. Examples include zinc stearate and a mixture of zinc soaps saturated fatty acids with different numbers of carbon atoms.

The zinc stearate is not particularly limited and those which are generally used in the manufacture of tires can be used. There is a case where zinc stearate is used as an anti-adhesion agent in a tire molding machine, and therefore, when the rubber composition comprises zinc stearate, it blooms on the surface and can improve the sliding property.

Examples of the mixture of zinc soaps of saturated fatty acids with different numbers of carbon atoms include Aktiplast PP (mainly composed of zinc soaps of saturated fatty acids with 17 carbon atoms) manufactured by Rhein Chemie Corporation and the like. By preparing the rubber composition comprising such a mixture, the sliding property can be improved without deteriorating the adhesion of the tread to the formwork.

The specific mold release agent is a mold release agent which comprises at least one selected from the group consisting of a metal salt of a fatty acid, a fatty acid amide and an amide ester. Examples of a metal in the metal salt of the fatty acid include calcium, zinc, potassium and sodium. Among them, a calcium salt of the fatty acid is preferred because it is inexpensive, does not cause pollution and does not affect the rate of vulcanization.

Examples of the specific mold release agent include WB16 manufactured by Struktol Co., Ltd., which is a mixture of a calcium salt of a fatty acid and a fatty acid amide, Aflux16 manufactured by Rhein Chemie Corporation, which is a mixture of a calcium salt of a fatty acid and an amide ester, and Aflux37, manufactured by Rhein Chemie Corporation, which comprises an amide ester.

The total content of at least one selected from the group consisting of stearic acid, a metal salt of a saturated fatty acid and a specific mold release agent is based on 100 parts by mass of the rubber component, not less than 2.5 parts by mass, preferably not less than 3.5 parts by mass, and particularly preferably not less than 4.0 parts by mass. If the total content is less than 2.5 parts by mass, the sliding properties of the rubber composition in the vulcanization step tend to be insufficient and the processability tends to deteriorate. On the other hand, the total content is not more than 8.0 parts by mass, and preferably not more than 5.5 parts by mass. If the total content exceeds 8.0 parts by mass, the adhesion of the tread to the formwork tends to deteriorate, the processability deteriorates (due to insufficient viscosity) and the molding into the profile shape tends to become difficult.

In the case where the rubber composition comprises stearic acid, the content thereof based on 100 parts by mass of the rubber component is preferably not less than 2.2 parts by mass and particularly preferably not less than 2.5 parts by mass. If the stearic acid content is less than 2.2 parts by mass, processability and abrasion resistance tend to deteriorate. On the other hand, the stearic acid content is preferably not more than 4.0 parts by mass, and particularly preferably not more than 3.5 parts by mass. If the stearic acid content exceeds 4.0 parts by mass, the adhesion of the tread to the formwork tends to deteriorate.

In the case where the rubber composition comprises zinc stearate as the metal salt of a saturated fatty acid, the content thereof, based on 100 parts by mass of the rubber component, is preferably not less than 0.5 parts by mass, and particularly preferably not less than 1.0 parts by mass. If the zinc stearate content is less than 0.5 parts by mass, the sliding property of the rubber composition in the vulcanization step tends not to be improved enough. On the other hand, the content of zinc stearate is preferably not more than 2.0 parts by mass, and particularly preferably not more than 1.5 parts by mass. If the zinc stearate content exceeds 2.0 parts by mass, an excess blooms on the rubber surface and there is a tendency that the tread adhesion to the formwork and the abrasion resistance deteriorate.

In the case where the rubber composition comprises a mixture of zinc soaps of saturated fatty acids having a varying number of carbon atoms as the metal salt of the saturated fatty acid, the content thereof based on 100 parts by mass of the rubber component is preferably not less than 0, 5 parts by mass and particularly preferably not less than 1.0 part by mass. If the content in the mixture is less than 0.5 part by mass, the sliding property tends to be insufficient in shape and the shrinkage tends to occur. On the other hand, the content of the mixture is preferably not more than 2.0 parts by mass, and particularly preferably not more than 1.5 parts by mass. If the content of the mixture exceeds 2.0 parts by mass, the adhesion of the tread to the formwork tends to deteriorate, and a blistered rubber (a rubber composition in which an interface adhesion thereof is peeled in a bump shape) tends to be made. generated.

In the case where the rubber composition comprises the specific mold releasing agent, the content thereof based on 100 parts by mass of the rubber component is preferably not less than 0.1 part by mass and particularly preferably not less than 0.5 part by mass. If the content is less than 0.1 part by mass, the sliding property of the rubber composition in the vulcanization step tends not to be improved enough. On the other hand, the content is preferably not more than 4.0 parts by mass, and particularly preferably not more than 3.5 parts by mass. If the content exceeds 4.0 parts by mass, the adhesion of the tread to the formwork tends to be deteriorated.

In addition to the above components, the tread rubber composition can suitably use blending agents conventionally used in the tire industry, and examples thereof include a reinforcing filler such as silica or carbon black, a silane coupling agent, zinc oxide, an anti-aging agent, oil , Wax, a vulcanizing agent such as sulfur, a vulcanization accelerator, a crosslinking agent and the like.

It is preferred that the rubber composition comprise silica because this improves the wet braking performance. Examples of silica include through a dry process (silica anhydride) silica produced and silica (hydrogenated silica) manufactured by a wet process. The silica produced by the wet process is preferred because it has more silanol groups on the surface and has many reaction sites with a silane coupling agent.

The specific BET surface area of silica is preferably 40 to 300 m ² / g, particularly preferably 60 to 280 m ² / g and very particularly preferably 80 to 260 m ² / g. If the BET specific surface area is less than 40 m ² / g, the abrasion resistance tends to be insufficient. On the other hand, if the specific BET surface area exceeds 300 m ² / g, the processability tends to deteriorate. It should be noted that the BET specific surface area of silica of the present invention is a value measured by the BET method according to ASTM D3037-81.

In the case where the rubber composition comprises silica, the content thereof is preferably not less than 30 parts by mass, and particularly preferably not less than 40 parts by mass. If the silica content is less than 30 parts by mass, the effect of improving the wet braking performance obtained by using silica tends to be insufficient. On the other hand, the silica content is preferably not more than 130 parts by mass, and particularly preferably not more than 125 parts by mass. If the silica content exceeds 130 parts by mass, the processability tends to deteriorate.

In the case where the rubber composition comprises silica, it is preferable to use a silane coupling agent therewith. Any commonly used silane coupling agent can be used, and examples include: sulfide silane coupling agents such as bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysetryl) tetrasulfyl, bis (3-trimethoxysetryl) tetrasulfyl -trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trisulfide, bis (3 ) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, disulfide , Bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfid, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfid, 2-triethoxysilylethyl-Nocarbamoyl-N, N-dim sulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide and 3-trimethoxysilylpropyl methacrylate monosulfide; Mercaptosilane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane and 8-mercaptooctanoyltriethoxysilane; Vinyl silane coupling agents such as vinyl triethoxysilane and vinyl trimethoxysilane; Aminosilane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane and 3- (2-aminoethyl) aminopropyltrimethoxysilane; Glycidylsilane coupling agents such as γ-glycidylpropyltriethoxysilane, γ-glycidylpropyltrimethoxysilane, γ-glycidylpropylmethyldiethoxysilane and γ-glycidylpropylmethyldimethoxysilane; Nitrogen silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane and chlorosilane coupling agents such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane and 2-chloroethylaniethoxane. These silane coupling agents can be used singly or can be used as combinations of two or more thereof. Among them, bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are preferred in view of their good processability. Furthermore, sulfide silane coupling agents and mercaptosilane coupling agents are preferred in view of the strong binding force with silica and excellent heat build-up property. In addition, mercaptosilane coupling agents are particularly preferred because they suitably improve fuel efficiency and wear resistance. Examples of mercaptosilane coupling agents include NXT-Z100, NXT-Z45 and NXT manufactured by Momentive Performance Materials INC.

In the case where the rubber composition comprises a silane coupling agent, the content thereof based on 100 parts by mass of silica is preferably not less than 4.0 parts by mass and particularly preferably not less than 6.0 parts by mass. If the content of the silane coupling agent is less than 4.0 parts by mass, the effect of improved dispersibility and the like tend not to be sufficiently achieved. On the other hand, the silane coupling agent content is preferably not more than 12 parts by mass, and particularly preferably not more than 10 parts by mass. If the content of the silane coupling agent exceeds 12 parts by mass, there is a tendency that the sufficient coupling effect and the sufficient dispersibility effect of silica are not obtained and the reinforcing property is deteriorated.

It is preferable that the rubber composition comprises zinc oxide because the processability and the resistance to reversion can be improved.

Further, when used together with the above stearic acid, the heating in the vulcanization step causes a reaction to produce the zinc stearate, and this zinc stearate can further improve the sliding properties of the rubber composition for a tread.

In the case where the rubber composition comprises zinc oxide, the content thereof based on 100 parts by mass of the rubber component is preferably not less than 0.5 parts by mass and particularly preferably not less than 1.0 parts by mass. If the zinc oxide content is less than 0.5 parts by mass, the processability tends to deteriorate (due to the high viscosity). On the other hand, the zinc oxide content is preferably not more than 2.5 parts by mass and particularly preferably not more than 2.0 parts by mass. If the zinc oxide content exceeds 2.5 parts by mass, the abrasion resistance tends to deteriorate.

It is preferred that the rubber composition include carbon black because it can improve reinforcing properties, resistance to ultraviolet damage, and crack growth resistance of the rubber composition. Examples of the carbon black include those which are generally used in the manufacture of tires such as SAF, ISAF, HAF, FF, FEF and GPF, and these carbon blacks can be used alone or can be used in combination of two or more of them.

In the case where the rubber composition comprises carbon black, the content thereof, based on 100 parts by mass of the rubber composition, is preferably not less than 5 parts by mass, particularly preferably not less than 10 parts by mass and very particularly preferably not less than 20 parts by mass. If the content of the carbon black is less than 5 parts by mass, the resistance to ultraviolet damage and the durability tend to deteriorate. On the other hand, the content of carbon black is preferably not more than 100 parts by mass, particularly preferably not more than 80 parts by mass and very particularly preferably not more than 60 parts by mass. If the content of the carbon black exceeds 100 parts by mass, the heat build-up tends to be excessively increased and therefore the rolling resistance is deteriorated.

Crosslinking agents which are generally used in the production of tires can be used. Among them, it is preferable that the rubber composition contains a compound represented by the following general formula (1) and / or contains a compound represented by the following general formula (2).

In the general formula (1), each of R ¹ to R ⁴ , each independently, is a linear or branched alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 5 to 12 carbon atoms.

In the general formula (2), x is an integer of 1 or more, and each of R ⁵ to R ⁸ is, independently of one another, a linear or branched alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 5 to 12 carbon atoms.

In the case where the rubber composition comprises a compound represented by the general formula (1) and / or represented by the general formula (2), the content thereof, based on 100 parts by mass of the rubber component, is preferably 0.1 to 4, 0 parts by mass and particularly preferably 0.5 to 3.0 parts by mass. If the content of the compound is less than 0.1 part by mass, the effect of accelerating the vulcanization tends to be insufficient. On the other hand, if the content of the compound is more than 4.0 parts by mass, the crosslinking density tends to become too high and the abrasion resistance deteriorates.

In view of the productivity of the kneading step, the extrusion step and the vulcanization step and prevention of shrinkage, it is preferred that the rubber composition for a tread have an initial vulcanization speed t10 (the time to reach ML + 0.1ME, with the minimum value of the torque being the vulcanization rate curve is shown as ML, the maximum value is shown as MH and the difference thereof (MH-ML) is shown as ME) measured at 160 ° C using a vulcanization elastomer from 2.0 to 5.0 minutes is. The initial vulcanization rate t10 is more preferably 2.5 to 4.0 minutes, and most preferably 2.7 to 3.8 minutes, to avoid shrinkage and to effectively maintain a good balance of productivity between the extrusion step and the vulcanization step.

The manufacturing method for a pneumatic tire of the present invention comprises a step (A) of molding the unvulcanized rubber composition into a tread using the above rubber composition for a tread to obtain a tread raw extrudate which is provided with a concave profile, a step (B) laminating the tread raw extrudate with other unvulcanized rubber compositions to obtain an unvulcanized raw cover, and a step (C) of vulcanizing the unvulcanized raw cover obtained in step (B) in a vulcanization mold.

In step (A), an unvulcanized rubber composition is kneaded by kneading the rubber components of at least one selected from the group consisting of stearic acid, a metal salt of a saturated fatty acid and a specific mold release agent, and other blending agents with a Banbury mixer, a kneader or one open roller is extruded into a predetermined shape to provide a tread raw extrudate with a concave profile.

While the kneading step is not particularly limited as long as it does not interfere with the effects of the present invention, it is preferred that the kneading step include: a kneading step X of kneading the rubber components, half the amount of silica (50 mass% of the silica containing) ) when silica is included and all of the carbon black when carbon black is included; a kneading step Y of adding components other than the vulcanizing agents (sulfur, vulcanization accelerator, vulcanization accelerator aid, crosslinking aid) and then kneading; and a kneading step F of further adding the vulcanizing agents and kneading since the carbon black and silica can be sufficiently dispersed, and a rubber composition excellent in abrasion resistance, fuel efficiency and elongation at break can be obtained.

Among the components of the tread rubber composition, there are those which may cause reaction with other components or those which decompose during heating in the kneading step and vulcanization step to produce a substance which is relatively volatile, such as water, Ethanol or aniline. It is preferred not to include such substances as they can cause shrinkage; however, even if they are contained, shrinkage can be prevented by volatilizing the volatile substances by repeatedly moving a punch up and down during the kneading step or by suspending the kneaded rubber sheets in rooms without laminating them.

Although the concave profile of the present invention will be explained with reference to the accompanying drawings, the present invention is not limited to this.

In the 1A is the inner surface of a tread portion of a vulcanization mold 20th which is used in the manufacturing method for a pneumatic tire according to the present invention, and a tread portion 11 an unvulcanized raw cover 10th before pressing through the vulcanization mold 20th shown. In the 1B becomes the unvulcanized raw cover 10th through the vulcanization form 20th pressed.

Like in the 1A shown is the vulcanization form used in the present invention 20th with convexities for a main groove Q fitted. The convexities for the main groove Q are convexities serially provided in the circumferential direction of the tread portion in the vulcanization mold, and are provided for forming main grooves of the crown in the crown portion of the tread of the tire to be vulcanized.

The convexity for the main groove Q the crown is a convexity in which the center line thereof, which is obtained by a weighted average, is at a distance of 0 to 1/2 from the center the crown (between q1 and q2 in the 1A) , assuming that the distance from the center C of the crown portion of the tread to the corresponding shoulder edges Se1 and Se2 in the vulcanization form 20th 1 is. It should be noted that in the 1A the intersection of an imaginary elongated line on the outer surface of the shoulder portion of the tread and an imaginary elongated line on the outer surface of the sidewall is defined as the shoulder edge.

The effect of the present invention can be exerted if the width of the main groove of the crown on the surface of the manufactured tire (referring to the width of the bottom portion of the convexity for the main groove of the crown (Qw in the 2A) ) is not less than 7.0 mm, preferably the width is not less than 8.0 mm and particularly preferably is not less than 9.0 mm. If the width of the bottom portion is less than 7.0 mm, the effect of draining water through the tire when it is rain is small, and an aquaplanin phenomenon tends to occur.

Although the number of convexities for the main groove Q of the crown is not limited, so long as the effect of the present invention is not impaired, a number of 1 to 4 is preferred in view of an excellent aquaplanin prevention effect, an excellent abrasion resistance and an excellent stability in handling, and a number from 2 to 3 is particularly preferred.

Like in the 1A shown is the tread portion 11 the unvulcanized raw cover 10th of the present invention with a concave profile P fitted. The concave profile P is serially provided in the circumferential direction of the tire in the crown portion of the tread of the unvulcanized raw cover obtained in the step (B) and is provided at a position which leads to the convexity for the main groove of the crown Q which corresponds in the vulcanization form 20th is provided and is pressed in step (C). By providing the concave profile P in the unvulcanized raw cover and the formation of the tread portion from the predetermined rubber composition, curls near the breaker layer and shrinkage in the crown portion can be prevented. That is, by providing the concave profile P is the sliding of the rubber of the unvulcanized rubber composition, which is caused by the convexity of the main groove Q the crown is pressed, evenly, and the profile of convexity for the main groove Q The crown in the vulcanization mold can be formed without deforming the rubber composition. As a result, undulations near the breaker layer and shrinkage in the crown portion can be prevented.

On the other hand, as in the 7A shown a pneumatic tire by pressing a tire 70 with a tread section 71 without a concave profile against the inner surface of the with convexities for the main grooves Q the crown-equipped vulcanization form 20th is pressed, shrinkage points easily appear on the edge portion 710 the main groove of the crown. Like in the 7B there is also a tendency for corrugations to occur near the breaker layer.

The cross-sectional area perpendicular to the circumferential direction of the tire in the concave profile is with respect to the cross-sectional area perpendicular to the circumferential direction of the tire in the convexity for the main groove of the crown in the vulcanization mold 30th to 100 %, preferably 30 to 70% and particularly preferably 40 to 60%. If the cross-sectional area of the concave profile is less than 30%, there is a tendency that the effect of preventing curl and shrinkage becomes insufficient. On the other hand, if the cross-sectional area exceeds 100%, more of the unvulcanized rubber composition is lost than the volume of the convexity for the main groove of the crown; this creates a space between the unvulcanized raw cover and the vulcanization mold during the vulcanization, and there is a tendency that corrugations or are considerable.

The ratio of the cross-sectional area of the convex profile with respect to the cross-sectional area of the convexity for the main groove of the crown can be calculated in the present invention by aligning the center line of the convexity for the main groove of the crown obtained by a weighted average and the center line of the concave profile and further by placing the bottom of the convexity for the main groove at the position spaced from the surface of the tape layer under the profile 1.5 mm and by calculating the ratio of the area in the cross-sectional area of the convexity for the main groove of the Crown which does not overlap with the unvulcanized raw cover in the cross-sectional area for the convexity for the main groove of the crown.

The comparison between the cross-sectional area of the convexity for the main groove of the crown and that for the concave profile is explained using FIGS. 2A, 2B, 3A and 3B.

Figures 2A and 3A are enlarged views of the convexity for the main groove of the crown in the vulcanization form 20th and the concave profile P the tread portion 11 before pressing through the convexity. FIGS. 2B and 3B show the state in which the corresponding center lines are aligned and the bottom of the convexity for the main groove Q is located at the position (S in FIGS. 2B and 3B) from the surface of the tape layer 12 is spaced apart by 1.5 mm in the tread side. In FIGS. 2B and 3B, there is a section in the cross-sectional area of the convexity for the main groove of the crown Q , which does not overlap with the unvulcanized rubber composition, indicated by the symbol T.

In the case where the concave profile is provided as shown in FIGS. 2A and 2B, since the cross-sectional area of the concave profile with respect to the cross-sectional area of the convexity is sufficient for the main groove of the crown, which is caused by the convexity for the main groove of the crown pressed rubber composition flow evenly to the both sides and undulations near the breaker layer and shrinkage in the crown section can be avoided.

In the case where, on the other hand, the concave profile is provided as shown in FIGS. 3A and 3B, the cross-sectional area of the concave profile is small with respect to the cross-sectional area of the convexity for the main groove of the crown, and further the width of the concave profile narrow, which therefore worsens an even flow of the rubber and can cause curls and shrinkage.

The width of the concave profile (Pw in FIGS. 2A and 3A) with respect to the width of the convexity for the main groove of the crown to be pressed is not less than 100% and preferably not less than 120%. If the width of the concave profile is less than 100%, the convexity for the main groove of the crown in the vulcanization mold tends to be difficult to fit in the concave profile. The width of the concave profile of not less than 120% is particularly preferred since the convexity and the profile will fit easily, and if the position in which the tread is located is a little misaligned, the convexity of the main groove can add to that concave profile fit. On the other hand, the width of the concave profile with respect to the width of the convexity for the main groove of the crown to be pressed is not more than 300%, and particularly preferably not more than 200%. If the width of the concave profile exceeds 300%, the rubber flow does not become small during vulcanization, which can cause shrinkage. It should be noted that the width of the convexity for the main groove of the crown in the present invention is the width of the bottom portion of the convexity (Qw in FIGS. 2A and 3A). It should also be noted that the width of the convexity for the main groove of the crown refers to the distance between the intersection of an imaginary elongated line of the surface of the tread crown section and an imaginary elongated line from both groove walls.

The depth of the concave profile (Pd in FIGS. 2A and 3A) is preferably not less than 10% and particularly preferably not less than 20 in relation to the corresponding height of the convexity for the main groove of the crown (Qd in FIGS. 2A and 3A) %. If the depth of the concave profile is less than 10%, the effect of causing the rubber to slide will tend to be small. On the other hand, the depth of the concave profile is preferably not more than 100% and particularly preferably not more than 80%. If the depth of the concave profile exceeds 100%, it tends to cause flaws.

It is preferable that the position of the concave profile is provided so that the center line of convexity for the main groove of the crown, which is obtained by a weighted average, becomes the center line of the concave profile. It should be noted that, as in the 4th shown, the center line of convexity for the main groove of the crown obtained by a weighted average is a vertical line Y extending from the intersection X of the imaginary elongated lines of the two groove walls to the surface of the vulcanization mold.

Examples of the shape of the concave profile include square shape, U shape and V shape, and these can be properly selected to match the shape of the convexity for the main groove of the vulcanization shape. Regarding the shape of the convexity for the main groove of the crown, a square shape close to that of a U-shape of the convexity or a U-shape is preferred because a U-shape as shown in FIGS. 2A and 3A is preferred because the water drainage performance and the wet braking performance are continuous.

It is further preferred to provide convexity (R in FIGS. 2A and 3A) in at least a portion of the groove bottom of the concave profile. By providing this convexity on the groove bottom, flaws on the portion of a wear indicator can occur 14 , like in the 5 shown to be effectively prevented. In addition, the shape of the concave profile, in which the convexity of the groove bottom is provided, is provided as a W shape.

Here, the wear indicator is a portion in which the depth of the groove is shallow, owing to providing a predetermined height from the deepest point of the main groove in the tread of a pneumatic tire (1.6 mm for passenger car tires), and the like generates an indication of when to replace with a new tire due to wear on the tread of the tire. The position of the wear indicator 14 is through a wear indicator position marker 15 displayed. In the area of the wear indicator 14 the rubber flow is not uniform and shrinkage points appear in different sections, even if the above concave profile P (without the groove bottom convexity) is provided. However, by providing the groove bottom convexity, shrinkage at the area of the wear indicator can be prevented.

The shape of the convexity of the groove bottom of the concave profile can be a triangular shape (inverted V shape), a pentagonal shape or a circular shape (semicircular shape), as shown in FIGS. 2A and 3A, and this can be selected appropriately. It should be noted that a rectangular or square shape is preferably avoided in view of a uniform rubber flow.

The height of the convexity of the groove bottom from the bottom of the groove of the concave profile (Rd in FIGS. 2A and 3A) is preferably 0.1 to 2.0 mm and particularly preferably 0.2 to 1.5 mm. If the height of the convexity is less than 1.0 mm, the effect of avoiding shrinkage on the wear indicator portions tends to be small. On the other hand, if the height of the convexity exceeds 2.0 mm, fading points in the area of the wear indicator tend to be serious.

It should be noted that the convexity of the bottom of the groove of the concave tread may be provided only in the area of the wear indicator or may be provided serially in the circumferential direction of the tire. Since pneumatic tires generally have six wear indicators placed on the circumference of the tire, it is simple and therefore preferred to provide the convexity of the groove bottom in series.

Examples of a method of molding the tread raw extrudate having the concave profile include a method of extruding and molding an unvulcanized rubber composition into a tread mold having the concave profile with an extruder, or a method of strip wrap molding in which the unvulcanized rubber composition is added a rubber strip is formed into a long belt-like shape (for example, about 1 mm thick and about 10 mm wide), and this rubber strip is wrapped around a tread shape in which the concave profile is provided. In view of excellent productivity, extrusion molding is preferred, and strip wrap molding is preferred, since the concave profile can be introduced in detail, the problem of aging shrinkage after extrusion molding is not caused and a tire in which the thickness of the Tread is uniform in the circumferential length of the tire, can be easily obtained.

The above step (B) is a step of laminating the raw tire extrudate obtained in the step (A) with other unvulcanized rubber compositions in a tire molding machine to obtain an unvulcanized raw cover. Step (B) is not particularly limited, and an unvulcanized raw cover manufacturing step commonly used in the manufacture of tires can be used. In the case where a strip wrap molding is used as the step (A), the step (B) is carried out simultaneously with the step (A) because the belt-like rubber strip is layered and a tread with a predetermined profile is made in the molding machine .

The above step (C) is a step of vulcanizing the unvulcanized raw cover obtained in the step (B) in the vulcanization mold, and a step of manufacturing a pneumatic tire by heating and vulcanizing the unvulcanized raw cover positioned in the vulcanization mold.

The unvulcanized raw cover, which is heated in the vulcanization mold, is thereby pressed against the inner surface of the vulcanization mold by vulcanizing and inflating it through a vulcanization bellows, which will be described below. Here, the portion within the vulcanization mold that presses the tread of the unvulcanized raw cover is provided with a convexity for forming predetermined tread grooves.

While the vulcanization molds are used, those in the tire manufacturing in general can be used, in the present invention, as described above, a vulcanization mold is used in which the position of the convexity which constitutes the main groove of the crown is provided so that assuming that the distance from the center C of the crown section of the Tread to the two shoulder edges Se1 and Se2 in the vulcanization form 1 is the center line of convexity for the main groove of the crown, obtained by a weighted average, at a distance of 0 to 1/2 from the center of the crown (between q1 and q2 in 1A) is provided and the width of the bottom portion of the convexity for the main groove of the crown is not less than a predetermined size.

In step (C), for example, as in the 6 shown the unvulcanized raw cover 10th within the vulcanization form 20th arranged and the vulcanization step can be an internal heating c1 , heating the unvulcanized raw cover 10th from the inner recess with a heating medium, which is in the inner recess of the unvulcanized raw cover 10th is filled, and an external heating c2 heating the unvulcanized raw cover 10th from the outer surface through the vulcanization mold 20th include. On the inner surface of the depression of the unvulcanized raw cover 10th becomes a vulcanization bellows 30th clamped to conduct the heat of the heating medium and to provide a molding pressure.

The internal heating c1 It is preferable to internally heat the unvulcanized raw cover from the inside of the recess by filling a heating medium at 180 to 210 ° C for 20 seconds to 5 minutes into the inner recess of the unvulcanized raw cover, since the crosslink density of each component of the tire can be ensured and reversion can be prevented.

Further, since reversion can be prevented and it can be ensured that the rubber can enter a steel cord of the breaker, it is preferable that the internal heating c1 comprises a first heating step using a first heating medium and a second heating step using a second heating medium.

It is preferable in the first heating step that the internal pressure of the vulcanization bladder is set to 14 to 15 MPa by filling steam with 180 to 210 ° C as a first heating medium, and the filling time for the steam, that is, the time from The start of filling until the start of the second heating step is 20 seconds to 5 minutes, since the rubber can easily flow into the groove (between the convexities) of the vulcanization mold during the second heating step, in which the rubber is pressed under high pressure.

In the second heating step, it is further preferred that nitrogen gas as the second heating medium is filled into the vulcanization bellows at normal temperature and the internal pressure of the vulcanization bellows is 21 to 28 MPa. In particular, since the tire can be strongly pressed into the vulcanization mold during the vulcanization, the temperature is maintained and a rubber rubber for a breaker or a cover other than the tread can be used with the space between the twisted strands of the cord and a very small adhesive surface of the cord be contacted; it is preferred that the internal pressure of the vulcanization bellows is greater than that of the first heating step. If oxygen of not less than 250 ppm is present in the second heating medium, oxidative degradation of the vulcanization bellows also occurs and the life of the vulcanization bellows is significantly shortened. Therefore, it is preferable to fill in purity-controlled nitrogen gas. In addition, the second heating step begins immediately after the first heating step has ended. The vulcanizer is opened at the same time as the start of venting the heating medium in the vulcanization bellows.

External heating c2 it is preferable to externally heat the unvulcanized raw cover from the outer surface side by setting the preset temperature of the vulcanization mold to not less than 165 ° C, and particularly preferably to not less than 170 ° C in view of the vulcanization productivity. If the preset temperature for the vulcanization mold is high, such as at least 165 ° C, the crosslinking of the unvulcanized rubber composition which is in contact with the vulcanization mold is generally accelerated to quickly cure the rubber composition, thereby easily causing shrinkage; however, by using the rubber composition for a tread and the concave profile of the present invention, the formation of flaws can be prevented even if the preset temperature of the vulcanization mold is not less than 165 ° C. The heating time for external heating refers here c2 preferably for a time from the start of filling the first heating medium to the start of venting the heating medium in the vulcanization bellows.

Since the pneumatic tire manufactured by the manufacturing method for a tire of the present invention has a main groove of the crown, which is a width of not less than one has a predetermined width, and the wet braking performance is excellent, it can be suitably used for cars or trucks.

EXAMPLE

Although the present invention is explained based on examples, the present invention is not limited to them.

Different types of chemicals used in the examples and comparative examples are described below.
High-cis BR: CB 25, manufactured by Lanxess AG (Nd-catalyzed high-cis BR, Mooney viscosity ML _{1 + 4} : 44, Mw / Mn: 1.78, Mw: 500,000, Mn: 280,000, cis-1 , 4-bond content: 96.2% by mass, trans-1,4-bond content: 3.1% by mass, vinyl content: 0.7% by mass)
Modified S-SBR: Modified S-SBR (styrene content: 37% by mass), produced according to the following manufacturing example for modified S-SBR
Carbon black: SHOBLACK N220, manufactured by CABOT Japan KK (N220, BET: 114 m ² / g)
Silica 1: ULTRASIL VN3, manufactured by Evonik Degussa GmbH (BET: 175 m ² / g)
Silica 2: ULTRASIL U9000Gr, manufactured by Evonik Degussa GmbH (BET: 235 m ² / g)
Silane coupling agent 1: Si75 (bis (3-triethoxysilylpropyl) disulfide), manufactured by Evonik Degussa GmbH
Resin C10: NOVARES C10 (liquid coumarone in resin, softening point: 5 to 15 ° C) manufactured by Rutgers Chemicals
Aromatic vinyl polymer: SYLVARES SA 85 (copolymer of α-methylstyrene and styrene, softening point: 85 ° C, Mw: 1000), manufactured by Arizona Chemical Corporation
Oil: VIVATEC500 (TDAE-ÖI) manufactured by H&R Co., Ltd.
Wax: OZOACE 355, manufactured by Nippon Seiro Co., Ltd.
Anti-aging agent 6PPD: Antigen 6C (N-phenyl-N '- (1,3-dimethylbutyl) -p-phenylenediamine) manufactured by Sumitomo Chemical Co. LTD. TMQ anti-aging agent: Nocrac 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD. Zinc oxide: Ginrei R, manufactured by TOHO ZINC CO., LTD.
Stearic acid: Stearic acid Tsubaki manufactured by NOF Corporation mold release agent 1: WB16 (a mixture of a metal salt of a fatty acid (calcium fatty acid) and fatty acid amide) manufactured by Struktol Co., Ltd. Mold Release Agent 2: Aflux37 (contains amide ester) manufactured by Rhein Chemie Corporation
Mold Release Agent 3: Aflux16 (a mixture of a fatty acid calcium salt and amide ester) manufactured by Rhein Chemie Corporation
Sulfur: HK200-5 (sulfur powder containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd.
Vulcanization accelerator TBBS: Nocceler NS manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD. (N-tert-Butyl-2-benzothiazylsulfenamide) vulcanization accelerator DPG: Nocceler D (1,3-diphenylguanidine) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD.

Crosslinking aid SDT-50: SDT-50 (compound represented by the general formula (2), x: not less than 1, R ⁵ to R ⁸ : 2-ethylhexyl group, content of active ingredients: 50% by mass) by Rhein Chemie Corporation

The manufacturing example for the modified S-SBR and an analytical method for it are described in detail.

Preparation of the terminal modifier

In a 100 ml volumetric flask, 23.6 g of 3- (N, N-dimethylamino) propyltrimethoxysilane (manufactured by AZmax Co. Ltd.) and anhydrous hexane (manufactured by KANTO CHEMICAL CO., INC.) Were mixed under a nitrogen atmosphere to make a To get total amount of 100 ml. A terminal modifying agent was thus obtained.

Production of the modified S-SBR

To a 30 L pressure-resistant vessel replaced with sufficient nitrogen, 18 L of n-hexane (manufactured by KANTO CHEMICAL CO., INC.), 740 g of styrene (manufactured by KANTO CHEMICAL CO., INC.), 1260 g of butadiene (available from TAKACHIHO TRADING CO., LTD) and 10 mmol of tetramethylethylene diamine (manufactured by KANTO CHEMICAL CO., INC.) Were added and the temperature was raised to 40 ° C. Then 10 ml of butyllithium (manufactured by KANTO CHEMICAL CO., INC.) Was added and the Temperature was raised to 50 ° C, followed by stirring for three hours. Then 11 ml of the terminal modifier was added, followed by stirring for 30 minutes. To the reaction mixture, 15 ml of methanol (manufactured by KANTO CHEMICAL CO., INC.) And 0.1 g Nocrac 200 (manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD.) Were added, and the reaction solution was placed in a stainless steel vessel, in which contained 18 L of methanol to collect an aggregate. The obtained aggregate was dried under reduced pressure for 24 hours to obtain a copolymer (1). As a result of the analysis, Mw was 270,000, the styrene content was 37 mass%, and the vinyl content was 56 mass%.

Measurement method for the weight average molecular weight Mw

The weight average molecular weight Mw for the copolymer was determined with polystyrene standards based on the measured values using Gel Permeation Chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation) have been obtained.

Process of structural recognition of the copolymer

The structure elucidation for the copolymer was carried out using a JNM-ECA series apparatus manufactured by JEOL Ltd. From the measurement results, the styrene content and the vinyl content in the copolymer were calculated.

The characteristics for the main groove of the crown of the vulcanization mold used are now shown.

Number of main grooves in the crown: 3
Shape of the main groove of the crown: U shape
Width of the bottom portion of the main groove of the crown (center): 13.0 mm
Height of the main groove of the crown (middle): 8.2 mm
Position of the main groove of the crown (center): 0.25 (distance from the center of the crown, assuming that the distance from the center of the crown to the switch edge is 1)

EXAMPLES 1 to 25 and COMPARATIVE EXAMPLES 1 to 10

Kneading step

Using the various types of chemicals shown in Tables 1 to 3, a kneading step X of kneading the rubber components, all of the carbon black and half the content of silica (composition temperature at the time of discharge of the mixer: 150 ° C, four minutes) , a kneading step Y of adding other components other than vulcanizing agents (sulfur, vulcanization accelerator, crosslinking aid) and then kneading (composition temperature at the time of discharge of the mixer: 150 ° C., three minutes) and a kneading step F of further adding the vulcanizing agents and then kneading (Composition temperature at the time of discharge of the mixer: 100 ° C, three minutes) was carried out to obtain unvulcanized rubber compositions.

Tread extrusion step (step A)

The obtained unvulcanized rubber composition was molded by extrusion with a predetermined extruder to obtain a tread raw extrudate with a predetermined profile. In each tread raw extrudate, the cross-sectional area, width, depth and height of the convexity of the bottom of the groove of the concave profile groove shown in Tables 1 to 3 with respect to the convexity for the main groove of the crown were provided. It should be noted that the convexity of the bottom of the groove is provided contiguously in the circumferential direction of the tire.

Tire forming step (step B)

The raw tread extrudates obtained were laminated with other components of a tire in a molding machine to produce unvulcanized raw covers.

Vulcanization step (step C)

The unvulcanized raw covers were press-vulcanized using a vulcanization bellows to make tires for testing (belt tires for cars, size: 225 / 45R17).

The first heating step was carried out using steam of 200 ° C, which was filled in the vulcanization bellows, as the first heating medium and the second heating step was carried out using nitrogen gas with normal temperature (23 ° C), as the second heating medium. The time of the first heating step was 2.5 minutes, the internal pressure of the vulcanization bellows was 15 MPa and the internal pressure of the vulcanization bellows in the second heating step was 24 MPa. The preset temperature of the vulcanization mold is shown in Tables 1 to 3.

The following tests were carried out using each unvulcanized rubber composition and tire obtained for tests.

<Initial vulcanization rate>

Using an oscillating vulcanizer (vulcanization elastomer) described in JIS K 6300, the vulcanization tests were carried out at a preset temperature of 160 ° C for each unvulcanized rubber composition to obtain a vulcanization speed curve plotted with time and torque. The time t10 (minute) to reach ML + 0.1ME, the lowest value for the torque on the vulcanization rate curve is shown as ML, the maximum value is shown as MH and the difference thereof (MH-ML) is shown as ME , got calculated. It should be noted that a target value for t10 is 2.0 to 5.0 minutes in view of the protection against the burning of the rubber and the protection of the productivity. If t10 exceeds 5.0 minutes, the vulcanization rate is slow and productivity is deteriorated.

<Tread adhesion to formwork>

After each tread raw extrudate was laminated to the breaker layer in the molding machine, the tackiness was evaluated with the breaker rubber composition. If this stickiness is insufficient, a space is created between the tread and the breaker layer and air pockets and vulcanization adhesion defects are created. Even if the adhesion deteriorates if zinc stearate is formed on the surface of the tread raw extrudate, the stickiness is due to the mixing in of petroleum C5 Resin and the like improved. This stickiness was rated on a scale of up to 5. The marking +, which was added to the evaluation, stands for a slightly better tread adhesion to the formwork than for those for which the marking has not been added. The higher the rating, the more excellent the adhesive property with the rubber composition that forms the seamless tape or the breaker. In addition, a target value for this liability is not less than 3.

<Assessment of shrink points>

The main grooves of the crown for each tire to test ( 10th for each example and comparative example) were visually observed and the formation of flaws was evaluated based on the presence of the semi-vulcanized state, bitings and a rough surface. The evaluation was made with respect to corresponding edge portions of the main grooves of the crown and areas of wear indicators. Those where flaws did not occur were considered 100, those in which flaws were not found, even if consumers closely examined them, were considered 80 and those where flaws were created were considered less than 80 and those less than 80 were rated based on the number of shrinkage sections generated. Note that a target value is not less than 80.

<Breaker layer corrugations>

Each tire was cut perpendicular to the circumferential direction of the tire for inspection, and the cross-sectional area thereof was optically related to the height of the corrugation (U in 7B) near the breaker layer. This corrugation was rated on a scale of up to 5. The mark +, which was added to the evaluation, stands for a somewhat better effect of preventing the curl than in those for which this mark was not added. The higher the rating, the more the less curl is generated and the more excellent the curl prevention effect is. It should be noted that a target value for the evaluation of the curl is not less than 3+. TABLE 1 EXAMPLE COMPARATIVE EXAMPLE 1 2nd 3rd 4th 5 6 1 2nd 3rd 4th Interference content (parts by mass) Kneading step X High-cis BR 30th 30th 30th 30th 30th 30th 30th 30th 30th 30th Modified S-SBR 70 70 70 70 70 70 70 70 70 70 soot 20th 20th 20th 20th 20th 20th 20th 20th 20th 20th Kneading step X / Y Silica 1 75 75 75 75 75 75 75 75 75 75 Silica 2 - - - - - - - - - Kneading step Y Silane coupling agent 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 Resin C10 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th Aromatic vinyl polymer 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th oil 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th wax 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti aging agent 6PPD 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd Anti-aging agent TMQ 1 1 1 1 1 1 1 1 1 1 zinc oxide 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd I mold release agent 1 (WB16) - - - - - - - - - II mold release agent 2 (Aflux37) - - 2.0 - 2.0 - - - - III mold release agent 3 (Aflux16) 1.0 - 2.0 1.0 2.0 2.0 - 1.0 1.0 IV zinc stearate - - - - - - - - - V stearic acid 3.0 2.5 2.5 3rd 2.5 2.5 2.0 3.0 3.0 2.0 Total content of I to V 4.0 2.5 6.5 4.0 6.5 4.5 2.0 4.0 4.0 2.0 Interference content (parts by mass) Kneading step F sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator TBBS 2.0 2.0 2.0 1.5 1.5 1.5 2.0 1.2 2.5 2.5 Vulcanization accelerator DPG 2.0 2.0 2.0 3.5 3.5 2.0 2.0 5.0 0.5 0.5 Networking aid SDT-50 - - - - - 2.0 - - - - Vulcanization condition Mold temperature (° C) 183 183 183 183 183 183 183 183 183 183 Concave profile Cross sectional area (%) 60 60 60 60 60 60 60 60 60 60 Width (%) 150 150 150 150 150 150 150 150 150 150 Depth (%) 35 35 35 35 35 35 35 35 35 35 Groove bottom convex height (mm) 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Evaluation results t10 (minute) 3.4 3.8 4.3 2.2 2.9 2.2 3.7 1.8 5.5 5.2 Tread tack on formwork 4th 4th 3rd 4th 3rd 3rd 4+ 4th 4th 5 Assessment of the shrinkage points Edge section of the main groove 100 80 100 90 95 100 70 65 100 75 Wear indicator area 100 100 100 95 95 100 90 75 100 95 Curl 4th 3+ 4th 4th 4th 4th 3rd 2nd 4th 3+ TABLE 2 EXAMPLE COMPARATIVE EXAMPLE 7 8th 9 10th 11 12 13 14 15 16 5 6 7 Interference content (parts by mass) Kneading step X High-cis BR 30th 30th 30th 30th 30th 30th 30th 30th 30th 30th 30th 30th 30th Modified S-SBR 70 70 70 70 70 70 70 70 70 70 70 70 70 soot 20th 20th 20th 20th 20th 20th 20th 20th 20th 20th 20th 20th 20th Kneading step X / Y Silica 1 75 75 75 75 75 75 75 75 75 75 75 75 75 Silica 2 - - - - - - - - - - - - - Kneading step Y Silane coupling agent 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 Resin C10 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th Aromatic vinyl polymer 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th oil 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th wax 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti aging agent 6PPD 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd Anti-aging agent TMQ 1 1 1 1 1 1 1 1 1 1 1 1 1 zinc oxide 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd I mold release agent 1 (WB16) - - - - - - - - - - - - - II mold release agent 2 (Aflux37) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 - 1.0 III mold release agent 3 (Aflux16) - - - - - - - - - - - - - IV zinc stearate - - - - - - - - - - - - - V stearic acid 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 2.0 3.0 Total content of I to V 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 2.0 4.0 Interference content (parts by mass) Kneading step F sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator TBBS 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Vulcanization accelerator DPG 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Networking aid SDT-50 - - - - - - - - - - - - - Vulcanization conditions Mold temperature (° C) 183 183 183 183 183 183 183 183 183 183 183 183 183 Concave profile Cross sectional area (%) 60 60 60 58 57 57 30th 45 80 100 27th 27th 0 Width (%) 150 150 150 150 150 150 160 160 150 200 160 160 0 Depth (%) 35 35 35 35 35 35 20th 28 52 48 15 15 0 Groove bottom convex height (mm) 0 0.1 0.5 1.5 2.0 2.5 0.3 0.3 0.3 0.3 0.3 0.3 0 Evaluation results t10 (minute) 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.7 3.4 Tread tack on formwork 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th 4+ 4th Assessment of the shrinkage points Edge section of the main groove 100 100 100 100 90 85 85 95 90 80 70 60 50 Wear indicator area 80 85 100 90 80 65 100 100 95 90 100 90 90 Curl 4th 4th 4th 4th 4th 4th 3+ 3+ 5 4th 3rd 3rd 1 TABLE 3 EXAMPLE COMPARATIVE EXAMPLE 17th 18th 19th 20th 21st 22 23 24th 25th 8th 9 10th Interference content (parts by mass) Kneading step X High-cis BR 30th 30th 30th 30th 30th 30th 30th 30th 30th 30th 30th 30th Modified S-SBR 70 70 70 70 70 70 70 70 70 70 70 70 soot 20th 20th 20th 20th 20th 20th 20th 20th 20th 20th 20th 20th Kneading step X / Y Silica 1 75 75 75 75 75 75 95 60 - 75 75 75 Silica 2 - - - - - - - - 65 - - - Kneading step Y Silane coupling agent 6.0 6.0 6.0 6.0 6.0 6.0 7.6 4.8 6.0 6.0 6.0 6.0 Resin C10 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th 4th Aromatic vinyl polymer 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th 10th oil 10th 10th 10th 10th 10th 10th 15 10th 10th 10th 10th 10th wax 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti aging agent 6PPD 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd 3rd Anti-aging agent TMQ 1 1 1 1 1 1 1 1 1 1 1 1 zinc oxide 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd I mold release agent 1 (WB16) 2.0 1.5 - - - - - - - - 3.0 1.5 II mold release agent 2 (Aflux37) - - 1.0 - - - - - - - - - III mold release agent 3 (Aflux16) 2.0 2.0 2.0 1.0 1.0 1.0 1.0 2.0 1.0 1.0 3.0 3.0 IV zinc stearate - 0.5 - - - - - - - - - - V stearic acid 2.5 2.5 3.5 3.0 3.0 3.0 3.0 3.0 3.0 3.0 2.5 4.0 Total content of I to V 6.5 6.5 6.5 4.0 4.0 4.0 4.0 5.0 4.0 4.0 8.5 8.5 Interference content (parts by mass) Kneading step F sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.2 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator TBBS 2.0 2.0 2.0 1.5 1.5 1.5 1.5 2.5 2.0 2.0 2.0 2.0 Vulcanization accelerator DPG 2.0 2.0 2.0 3.5 3.5 3.5 3.0 1.8 2.0 2.0 2.0 2.0 Networking aid SDT-50 - - - - - - - - - - - - Vulcanization condition Mold temperature (° C) 183 183 183 160 170 193 183 183 183 183 183 183 Concave profile Cross sectional area (%) 60 60 60 60 60 60 60 60 60 50 60 60 Width (%) 150 150 150 150 150 150 150 150 150 80 150 150 Depth (%) 35 35 35 35 35 35 35 35 35 60 35 35 Groove bottom convex height (mm) 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Evaluation results t10 (minute) 4.2 3.9 3.8 2.2 2.2 2.2 3.5 3.1 3.5 3.4 5.2 4.5 Tread tack on formwork 3rd 3rd 3rd 4th 4th 4th 4th 5 4th 4th 2nd 1 Assessment of the shrinkage points Edge section of the main groove 100 90 95 100 100 80 95 100 100 50 80 70 Wear indicator area 100 100 100 100 100 85 100 100 100 100 75 80 Curl 4+ 5 4th 4th 4th 4th 4th 4th 4th 2nd 4+ 4+

As shown in Tables 1 to 3, it can be seen that in examples using a predetermined rubber composition and having a concave profile with a predetermined shape at a predetermined position, it is possible to manufacture pneumatic tires in which undulation occurs the breaker layer or in the vicinity of the breaker layer and shrinkage points on the crown section of the tread are avoided.

Reference symbol list

10th

unvulcanized cover

11

Tread section

12

Strip layer

13

Breaker layer

14

Wear indicator

15

Wear indicator marking

20th

Vulcanization form

30th

Vulcanization bellows

P

concave profile

Q

Convexity for the main groove

Claims (5)

A method of manufacturing a pneumatic tire with a tread, the method comprising: (A) a step of molding an unvulcanized rubber composition for a tread to obtain a concave tread raw extrudate; (B) a step of laminating the tread raw extrudate obtained in step (A) with other unvulcanized rubber compositions to obtain an unvulcanized raw cover; and (C) a step of vulcanizing the unvulcanized raw cover obtained in the step (B) in a vulcanization mold, the steps (A), (B) and (C) being carried out so that the tread of the tire is formed from a rubber composition for a tread which, based on 100 parts by mass of the rubber component, 2.5 to 8.0 parts by mass of at least one selected from the group consisting of stearic acid, a metal salt of a saturated fatty acid and a mold release agent which comprises at least one selected from the group consisting of a metal salt of a fatty acid, a fatty acid amide and an amide ester, and which has an initial vulcanization rate t10 as measured by a vulcanization elastometer of 2.0 to 5.0 minutes at 160 ° C, the one provided in the tread raw extrudate concave profile is positioned in a position in which the convexity of the main groove of the Crown of the vulcanization mold which forms the main groove of the crown, in which step (C) is pressed, the cross-sectional area of the concave profile perpendicular to the circumferential direction of the tire is set to be 30 to 100% of the cross-sectional area of the convexity for the main groove of the crown amounts to the width of the concave profile is set to be 100 to 300% of the width of the convexity of the convex portion of the crown, provided that when the distance from the center of the tread crown to the shoulder edge is 1, the center of the Convexity of the main groove of the crown is provided at a position from 0 to 1/2 from the origin of the crown and the width of the main groove of the crown on the surface of the tire manufactured is adjusted so that it is not less than 7.0 mm. Manufacturing process according to Claim 1 , wherein the concave profile provided in the tread raw extrudate has a convexity on its bottom with a height of 0.1 to 2.0 mm in at least a portion of the circumferential direction of the tire. Manufacturing process according to Claim 1 or 2nd , wherein the rubber composition for the tread, based on 100 parts by mass of the rubber component, comprises 30 to 130 parts by mass of silica with a specific BET surface area of 40 to 300 m ² / g. Manufacturing process according to one of the Claims 1 to 3rd , wherein the preset temperature of the vulcanization mold in step (C) is not less than 165 ° C. Pneumatic tire, which by a manufacturing method according to one of the Claims 1 to 4th has been manufactured.

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