JP6130742B2 - Pneumatic tire manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a pneumatic tire capable of suppressing waviness deformation of a composite sheet obtained by combining a sheet-shaped inner liner and a sheet-shaped chafer, and suppressing generation loss.

  In a general pneumatic tire manufacturing method, a cylindrical carcass is formed by sequentially winding a composite sheet in which a sheet-like inner liner and a sheet-like chafer are combined, and a sheet-like carcass ply on the outer peripheral surface of a cylindrical molding drum. A step of forming a laminated body, a step of setting a bead core on the outer peripheral surface and both ends, a step of shaping the carcass laminated body in a toroid shape between the bead cores, and the like are included.

  As shown in FIGS. 10A and 10B, the composite sheet a is formed by rolling a first rubber sheet b formed by rolling a butyl rubber-based first rubber b1 and an NR-based second rubber c1. A step of superimposing the second rubber sheet c formed in this way to form a sheet-like inner liner d, and inner edge portions of the sheet-like chafer e on both side edges in the tire axial direction of the sheet-like inner liner d. It is formed through a splicing step for lap splicing.

  In the splicing step, the sheet-shaped inner liner d and the sheet-shaped chafer e are overlapped with the same length. However, after the splicing step, a shrink (shrinkage) larger than that of the sheet-shaped chafer e occurs in the sheet-shaped inner liner d over time. On the other hand, since the fiber material (for example, campus cloth etc.) for preventing rim displacement is embedded in the rubber in the sheet-shaped chafer e, shrinkage does not substantially occur.

  As a result, as shown in FIG. 10C, a wavy deformation f occurs in the composite sheet a. In the case of the composite sheet a having a large wavy deformation f, it cannot be used from the viewpoint of tire quality, resulting in a manufacturing loss.

  Therefore, in the following Patent Document 1, in the production line of the sheet-like inner liner d, the undulation deformation f is suppressed by adding a device to the number of rotations of the roll in each part and forcibly shrinking before the lap joint. Proposed. However, a satisfactory effect has not been achieved.

JP 2010-173223 A

  The present invention adopts the MSR of the stress relaxation test of rubber as a shrink parameter, and based on the determination of the MSR of the second rubber prior to rolling, the occurrence of wavy deformation in the composite sheet can be suppressed, and the tire An object of the present invention is to provide a method for manufacturing a pneumatic tire capable of improving production efficiency.

The present invention relates to a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, an air non-permeable inner liner disposed on a radially inner side of the carcass, and an anti-rim shift extending along the bottom surface of the bead. A pneumatic tire manufacturing method comprising:
Including a composite sheet forming step of forming a composite sheet obtained by combining an unvulcanized sheet-like inner liner and a sheet-like chafer,
Moreover, this composite sheet forming process
A first rubber rolling step of rolling a butyl rubber-based first rubber to form a first rubber sheet;
A second rubber rolling step of rolling an NR-based second rubber to form a second rubber sheet;
An overlapping step of forming the sheet-shaped inner liner by overlapping the first rubber sheet and the second rubber sheet;
And a joining step for forming the composite sheet by overlapping and joining the inner edge portions of the sheet-shaped chafers on both side edges in the tire axial direction of the sheet-like inner liner,
In the composite sheet forming step, prior to the second rubber rolling step, the MSR (Mooney stress-relaxation rate) of the stress relaxation test of the second rubber is measured, and only when the measured MSR value is equal to or higher than a reference value, It is characterized by including an MSR determination step to be put into the two rubber rolling step.

  In the method for manufacturing a pneumatic tire according to the present invention, the reference value is preferably 0.45 or more.

  In the method for manufacturing a pneumatic tire according to the present invention, it is preferable that the composite sheet forming step includes a re-kneading step of lowering the MSR value by kneading the second rubber when the MSR value is less than a reference value. .

  The “MSR (Mooney stress-relaxation rate) of stress relaxation test” is a value at 130 ° C. measured in accordance with ISO 289-4: 2003.

  The mechanism of shrinkage of unvulcanized rubber is as follows. As conceptually shown in FIG. 6, the rubber molecule g is rounded and in a stable state in the heated state J1. However, in the state J2 immediately after rolling, the rubber molecule g is stretched in the rolling direction by a calender roll or the like, and thus becomes unstable. Then, in the time lapse state J3 after rolling, the rubber molecule g gradually returns to a stable state due to molecular motion, and the stretched portion is gradually rounded. The unstable rubber molecules g thus stretched into a sheet by rolling gradually return to a stable state by molecular motion, and the process is observed as rubber shrinkage.

Such a phenomenon is known as one of the relaxation phenomena of rubber and can be expressed by the following formula (1).
Change in shrinkage with time A = A ₀ × exp (−t / B) −−− Expression (1)
“A ₀ ” in the formula is a value indicating how much the rubber shrinks, and affects the type of rubber, the blending ratio of different types of rubber, the molecular weight of the rubber, and the like. “B” is a shrinking speed, which affects the temperature of rubber, the molecular weight of rubber, and the like. “T” is time.

  As understood from the above formula (1), the shrinkage of rubber is related to the molecular weight of rubber, and MSR is an index related to the molecular weight of rubber. This MSR is an index of the speed of stress relaxation of rubber. As conceptually shown in FIG. 7, when the rubber G is first deformed by applying a force F and is maintained, it is necessary to maintain the deformation. The effective force F gradually decreases. The index of the speed at which the force F decreases is “MSR”, and the greater the MSR, the faster the speed at which the force F decreases.

  Here, when the molecular weight of rubber is large, the molecular chain becomes long. Therefore, it is considered that both the amount of rubber expansion and the amount of shrinkage (shrink amount) increase. This is also confirmed by the experiment results of the present inventor shown in FIG. That is, using a Banbury mixer, a plurality of unvulcanized rubbers (in this example, NR was used) with different molecular weights were formed by changing the kneading time, and the shrink amounts (ratio) thereof were measured. As a result, it was confirmed that there was a strong correlation between the molecular weight and the shrink amount (ratio). Further, the MSR of the plurality of unvulcanized rubbers having different molecular weights was measured, and the relationship between the MSR and the shrink amount (ratio) was investigated. As a result, as shown in FIG. 8B, there is also a strong correlation between the MSR and the shrink amount (ratio), and the shrink amount (ratio) can be grasped by using this MSR as a parameter. It was investigated.

  On the other hand, FIG. 9 shows an example of the change of the shrinkage amount with time in the first rubber sheet, the second rubber sheet, and the sheet-like inner liner obtained by the present inventors through experiments. As shown in the figure, the NR type second rubber has a larger shrink amount than the butyl rubber type first rubber. Therefore, it is possible to reduce the amount of shrinkage in the sheet-like inner liner by keeping the amount of shrinkage of the second rubber low.

  Therefore, in the present invention, prior to the second rubber rolling step, the MSR of the second rubber is measured, and only when the MSR value is equal to or higher than the reference value, the second rubber rolling step is input. Thereby, the amount of shrinkage in the sheet-like inner liner can be kept low, and the occurrence of undulating deformation in the composite sheet can be suppressed.

It is sectional drawing which shows one Example of the pneumatic tire formed by the manufacturing method of this invention. (A) is sectional drawing explaining the winding process of a composite sheet. It is a side view which shows notionally the 1st rubber rolling step in the composite sheet formation process, the 2nd rubber rolling step, and the superposition step. It is a perspective view which shows notionally the splicing step in a composite sheet formation process. It is a graph which shows the generation | occurrence | production state of a wavy deformation. It is a conceptual diagram explaining the generation | occurrence | production mechanism of shrink. It is a conceptual diagram which grasps MSR with an image. (A) is a graph showing the relationship between the molecular weight of rubber and the shrink amount (ratio), and (B) is a graph showing the relationship between the MSR value and the shrink amount (ratio). It is a graph which shows the change by the elapsed time of the shrinkage amount in a 1st rubber sheet, a 2nd rubber sheet, and a sheet-like inner liner. (A), (B) is sectional drawing which shows the conventional sheet-like inner liner and a composite sheet, (C) is a perspective view which shows the wavy deformation in a composite sheet.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a cross-sectional view showing one embodiment of a pneumatic tire 1 formed by the manufacturing method of the present invention.

  As shown in FIG. 1, the pneumatic tire 1 includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and an air non-circulation disposed on the radially inner side of the carcass 6. A permeable inner liner 11 and a chafer 12 for preventing rim deviation extending along the bead bottom surface 4S are provided. In this example, although the case where the said pneumatic tire 1 is a tire for passenger cars is shown, for example, it is not limited to this, For example, it can apply to various tires of other categories, such as a tire for motorcycles.

  The carcass 6 is composed of one or more, in this example, one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 80 to 90 degrees with respect to the tire equator C. The carcass ply 6A includes a ply main body portion 6a that extends between the bead cores 5 and 5, a ply folding portion 6b that extends from the ply main body portion 6a and is folded from the inner side to the outer side in the tire axial direction around the bead core 5. Have A bead apex 8 made of hard rubber having a triangular cross section extending from the bead core 5 to the outer side in the tire radial direction is disposed between the ply main body portion 6a and the ply folding portion 6b.

  A tread reinforcing layer 7 is disposed outside the carcass 6 in the radial direction and inside the tread portion 2. The tread reinforcing layer 7 includes a belt layer 9 and / or a band layer 10. In this example, the tread reinforcing layer 7 includes both the belt layer 9 and the band layer 10.

  The belt layer 9 is composed of one belt ply 9A and 9B in this example, one on which the belt cord is arranged at an angle of, for example, 10 to 35 degrees with respect to the tire equator C. In the belt layer 9, the belt cords cross each other between the plies, so that the belt rigidity is enhanced and the tread portion 2 is strongly reinforced.

  The band layer 10 is formed of one band ply in which a band cord is spirally wound in the tire circumferential direction. As the band ply, a pair of left and right edge band plies that covers only the outer end in the tire axial direction of the belt layer 9 and a full band ply that covers substantially the entire width of the belt layer 9 can be used as appropriate. A case of the band ply 10A is shown. In addition, as a carcass cord, a belt cord, and a band cord, a well-known tire cord similar to the conventional one is appropriately employed.

  The inner liner 11 has a two-layer structure of an inner layer portion 11a along the tire lumen surface TS and an outer layer portion 11b disposed on the outer side thereof. Of these, the inner layer portion 11a is formed of an air-impermeable butyl rubber-based first rubber G1. As the butyl rubber-based first rubber G1, butyl rubber, a halogenated butyl rubber that is a derivative thereof, and a blend rubber containing 60% by mass or more of the butyl rubber or halogenated butyl rubber in a rubber component are employed. In the case of blend rubber, diene rubbers such as NR (natural rubber), SBR (styrene-butadiene rubber), BR (butadiene rubber), IR (isoprene rubber) are suitably employed as the remaining rubber.

  The outer layer portion 11b is formed of an NR-based second rubber G2 having excellent adhesiveness, and increases the adhesive strength between the inner layer portion 11a and the carcass 6. As the NR-based second rubber G2, NR (natural rubber) and a blend rubber containing 60% by mass or more of the NR in a rubber component are employed. In the case of blend rubber, diene rubbers such as SBR (styrene butadiene rubber), BR (butadiene rubber), IR (isoprene rubber) can be suitably used as the remaining rubber.

  The chafer 12 has at least a base portion 12A extending along the bead bottom surface 4S. The chafer 12 of this example is bent at the inner end in the tire axial direction of the base portion 12A, and rises along the tire cavity surface TS, and is bent at the outer end in the tire axial direction of the base portion 12A, and the outer surface of the ply folded portion 6b. And an outer rising portion 12o that rises along.

  The chafer 12 has a rubber sheet shape reinforced with a fiber material to prevent rim displacement. In this example, a case where the chafer 12 is made of a so-called canvas chafer in which a canvas cloth made of organic fibers is covered with rubber is shown, but various types reinforced with a fiber material such as those in which a cord array body is covered with rubber are employed. Yes. As the fiber material, organic fibers such as aramid, nylon and rayon are suitably employed. In the chafer 12 of this example, the upper end of the inner raised portion 12 i is abutted with the lower end of the inner layer portion 11 a of the inner liner 11 and terminates. Further, the outer layer portion 11b of the inner liner 11 is interposed between the upright portion 12i and the base portion 12A, and the carcass ply 6A, thereby increasing the adhesive strength therebetween.

Next, a method for manufacturing the pneumatic tire 1 will be described.
This manufacturing method includes at least a composite sheet forming step SA, and in this example, further includes a composite sheet winding step SB, a carcass ply winding step SC, a bead core mounting step SD, and a shaping step SE that are performed thereafter.

  The composite sheet forming step SA is a step of forming a composite sheet 13N (shown in FIG. 3B) in which the unvulcanized sheet-like inner liner 11N and the sheet-like chafer 12N are composited. This composite sheet forming step SA includes a first rubber rolling step SA1, a second rubber rolling step SA2, an overlapping step SA3, and a splicing step SA4.

  As shown in FIG. 2A, in the first rubber rolling step SA1, the first rubber sheet 11aN is formed by rolling the first rubber G1 using a known calendar device 20. In the second rubber rolling step SA2, the second rubber sheet 11bN is formed by rolling the second rubber G2 using a known calendar device 20. In the overlapping step SA3, the first rubber sheet 11aN and the second rubber sheet 11bN are overlapped to form a sheet-like inner liner 11N.

  Reference numeral 21 in the drawing denotes a cooling region in which a plurality of cooling drums 21A are arranged, and the sheet-like inner liner 11N is cooled by passing between the plurality of cooling drums 21A. As shown in FIG. 2B, the second rubber sheet 11bN is wider than the first rubber sheet 11aN, and the second rubber sheet 11bN is disposed on both sides of the sheet-like inner liner 11N. A protruding portion 14 that protrudes out is formed.

  In this example, the cooled sheet-like inner liner 11N is once wound up in a roll shape and then sent to the next splicing step SA4. However, the sheet-like inner liner 11N can be conveyed to the splicing step SA4 in the form of a sheet.

  As shown in FIGS. 3 (A) and 3 (B), in the joining step SA4, for example, the pressure roller 24 is used, and the sheet-shaped inner liner 11N has both the side edges in the tire axial direction, strictly speaking, the protruding portion 14. The inner edge of the sheet-shaped chafer 12N is overlapped, thereby forming a composite sheet 13N.

  As shown in FIG. 4A, in the composite sheet winding step SB, the composite sheet 13N is wound on the outer peripheral surface of the molding drum 25 having a known structure. As shown in FIG. 4B, in the carcass ply winding step SC, a sheet-like carcass ply 6AN is wound further outside the composite sheet 13N to form a cylindrical carcass laminate 15. In the bead core mounting step SD, the bead cores 5 are set on the outer peripheral surface of the carcass laminate 15 and on both end sides. A bead apex 8 is bonded to the bead core 5 of the present example in advance on the outer circumferential surface in the radial direction.

  Further, as shown in FIG. 4C, in the shaping step SE, the carcass laminate 15 is shaped in a toroid shape between the bead cores 5 and 5 while the bead cores 5 and 5 are brought close to each other. As a result, the expanded portion of the carcass laminate 15 and the tread ring 16 for forming a tread that has been previously waited radially outward are joined to form an unvulcanized green tire 1N. Various conventional methods can be adopted as the composite sheet winding step SB, the carcass ply winding step SC, the bead core mounting step SD, and the shaping step SE.

  And in this invention, the said composite sheet formation process SA measures MSR of the stress relaxation test of the said 2nd rubber | gum G2 prior to said 2nd rubber rolling step SA2, and only when the measured MSR value is more than a reference value, 2 includes an MSR determination step (not shown) for feeding the rubber G2 into the second rubber rolling step SA2.

  As described above, there is a strong correlation as shown in FIG. 8B between the MSR value of unvulcanized rubber and the shrinkage amount. By using this MSR as a parameter, the shrinkage amount (ratio As a result of the inventor's research, it was revealed that

  Therefore, the MSR determination step measures the MSR of the second rubber that has a great influence on the shrink amount of the sheet-like inner liner 11N, and only enters the second rubber rolling step SA2 when the MSR value is equal to or greater than the reference value. Further, the amount of shrinkage in the sheet-like inner liner 11N can be kept low, and the wavy deformation in the composite sheet 13N can be suppressed.

  The reference value is preferably 0.45 or more, and if it is less than this, the wavy deformation tends not to be sufficiently suppressed. The upper limit of the reference value is not particularly restricted.

As described above, the MSR value is related to the rubber molecular weight, that is, the length of the molecular chain. For example, the MSR value can be increased by increasing the rubber kneading time and cutting the rubber molecular chain. Accordingly, the composite sheet forming step SA of the present embodiment, for the second rubber G2 is less than the reference value MSR values, it is preferable to comprise the upper gel reconsidered step the MSR value by Nerinaosu the second rubber .

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  In order to confirm the effect of the present invention, a plurality of second rubbers G2 having different MSR values are prepared, and a composite sheet having the structure shown in FIG. The occurrence of deformation was investigated. As for the occurrence of undulation deformation, the composite sheet is wound into a roll and stored (storage time 3 to 5 hours). Thereafter, when the composite sheet is used in a tire production line, the composite sheet Therefore, the occurrence rate of rolls that could not be used was compared. The result is shown in FIG.

  The MSR value of the second rubber G2 is adjusted by the rubber kneading time by a rubber kneader (Banbury mixer), and the rubber composition is the same. In this example, the first rubber is made of 100% by weight of butyl rubber, and the second rubber is made of a blend rubber of 70% by weight of NR and 30% by weight of SBR. Known additives such as vulcanizing agents, vulcanization accelerators, and carbon black are blended in the same manner as before. As the chafer, a canvas chafer in which a nylon canvas cloth is covered with rubber is used.

   The MSR value is based on ISO 289-4: 2003, and the second rubber G2 kneaded with a rubber kneader (Banbury mixer) is heated at a temperature of 130 ° C. using a Mooney viscometer (SMV-300RT manufactured by Shimadzu Corporation). MSR was measured.

  As shown in FIG. 5, by using the second rubber having a high MSR value, it can be confirmed that the number of composite sheets that cannot be used due to undulation deformation can be reduced. In particular, by setting the MSR value to 0.45 or more. It is confirmed that the effect is exerted highly.

2 Tread portion 3 Side wall portion 4 Bead portion 4S Bead bottom surface 5 Bead core 6 Carcass 11 Inner liner 11N Sheet-like inner liner 11aN First rubber sheet 11bN Second rubber sheet 12 Chafer 12N Sheet-like chafer 13N Composite sheet 25 Molding drum G1 First Rubber G2 Second rubber SA Composite sheet forming step SA1 First rubber rolling step SA2 Second rubber rolling step SA3 Overlapping step SA4 Joint step SB Composite sheet winding step

Claims (3)

A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, an air-impermeable inner liner disposed inside the carcass in the radial direction, and a chafer for preventing rim misalignment extending along the bottom surface of the bead. A pneumatic tire manufacturing method comprising:
Including a composite sheet forming step of forming a composite sheet obtained by combining an unvulcanized sheet-like inner liner and a sheet-like chafer,
Moreover, this composite sheet forming process
A first rubber rolling step of rolling a butyl rubber-based first rubber to form a first rubber sheet;
A second rubber rolling step of rolling an NR-based second rubber to form a second rubber sheet;
An overlapping step of forming the sheet-shaped inner liner by overlapping the first rubber sheet and the second rubber sheet;
And a joining step for forming the composite sheet by overlapping and joining the inner edge portions of the sheet-shaped chafers on both side edges in the tire axial direction of the sheet-like inner liner,
In the composite sheet forming step, prior to the second rubber rolling step, the MSR (Mooney stress-relaxation rate) of the stress relaxation test of the second rubber is measured, and only when the measured MSR value is equal to or higher than a reference value, (2) A method for manufacturing a pneumatic tire, comprising an MSR determination step to be put into a rubber rolling step.   The method for manufacturing a pneumatic tire according to claim 1, wherein the reference value is 0.45 or more. The composite sheet forming step, if MSR value is less than the reference value, according to claim 1 or 2, wherein the pneumatic characterized in that it comprises a reconsidered on gel step the MSR value by Nerinaosu the second rubber Tire manufacturing method.

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