JP6134471B2 - Method for producing unvulcanized tire and method for producing pneumatic tire - Google Patents

Description

  The present invention relates to an unvulcanized tire and a pneumatic tire using an inner liner that can flexibly cope with a tire size having a high inner expansion rate while effectively preventing joint cracking that may occur during or after molding. .

  Conventionally, a rubber composition mainly composed of butyl rubber, halogenated butyl rubber or the like is used for an inner liner disposed as a gas barrier layer on the inner surface of the tire in order to maintain the internal pressure of the tire. However, these rubber compositions using butyl rubber as the main raw material have low gas barrier properties, and therefore when the rubber composition is used for an inner liner, the thickness of the inner liner has to be about 1 mm. Therefore, the weight of the inner liner in the tire is about 5%, which is an obstacle to improving the fuel efficiency of automobiles, agricultural vehicles, construction vehicles, etc. by reducing the weight of the tires.

  On the other hand, an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) is known to have excellent gas barrier properties. Since the EVOH has an air permeation amount of 1/100 or less of the butyl rubber, when used for the inner liner, the internal pressure retention of the tire can be greatly improved even with a thickness of 100 μm or less. It is possible to reduce the weight of the tire.

  Here, there are many resins having a lower air permeability than the butyl rubber, but if the air permeability is about one-tenth of that of the butyl rubber, the effect of improving the internal pressure retention is required unless the thickness exceeds 100 μm. Is small. On the other hand, when the thickness exceeds 100 μm, the effect of reducing the weight of the tire is small, and the inner liner is broken or cracked in the inner liner due to deformation at the time of bending of the tire, so that the gas barrier property is maintained. It becomes difficult.

  As means for solving this, Patent Document 1 discloses a tire in which a terminal rubber portion is disposed on a side facing the inner liner at a circumferential joint portion of a carcass ply, and prevents inner cracks. Thin gauge has been realized. Patent Document 2 discloses an inner liner in which a gas barrier layer is formed by applying an unmodified or modified EVOH solution, and the uniformity of the tire is deteriorated by eliminating the joint portion between the gas barrier layers. While improving, it is trying to achieve both weight reduction and gas barrier properties. Further, Patent Documents 3 to 4 also disclose tires provided with an inner liner layer formed on a cylindrical film.

JP 2006-224853 A JP 2007-112000 A Japanese Patent No. 3159886 International Publication No. 2004/110735

  However, even when the inner liner as described above is employed, when unvulcanized tires are expanded at the time of molding, the robustness tends to be low for tire sizes with a high inner expansion rate, and the existing In some cases, it is not possible to effectively utilize these facilities, and there is still room for improvement.

  Therefore, the present invention effectively eliminates joint cracks that may occur during or after molding so that it can flexibly cope with tire sizes with a high inner expansion rate while contributing to cost reduction by effectively utilizing existing equipment. An object of the present invention is to provide an unvulcanized tire and a pneumatic tire using an inner liner that can be effectively prevented to improve the uniformity and internal pressure retention of the tire.

In order to solve the above-mentioned problems, the present inventors have found an unvulcanized tire using a specific inner liner and wound around a molding drum so that the joint surfaces at both end portions have a specific mode. It came to complete.
That is, the unvulcanized tire of the present invention is
In the both ends of the inner liner composed of a laminate having a resin layer and a rubber layer, including the step of winding around the molding drum while joining the other end on the one end,
Before joining one said edge part and the other edge part, a part of rubber layer is previously arrange | positioned to the side wall of one edge part, It is characterized by the above-mentioned.

A part of the rubber layer may be a rubber piece made of a rubber layer, and when placing a part of the rubber layer on the side wall of the one end, the side wall of the one end applied with an adhesive A rubber piece made of a rubber layer may be joined.
In addition, when a part of the rubber layer is disposed on the side wall of the one end, a part of the rubber layer may be folded so as to cover a part of the resin layer at the one end.

The pneumatic tire of the present invention includes an inner liner in which a part of a rubber layer is disposed on a side wall of one end portion at one end portion of an inner liner composed of a laminate having a resin layer and a rubber layer. It is characterized by.
A part of the rubber layer may be a rubber piece made of a rubber layer, and a part of the rubber layer disposed on the side wall of the one end is a part of the resin layer at one end. A part of the rubber layer may be folded so as to cover the part.

  According to the unvulcanized tire of the present invention, since an inner liner that can effectively prevent joint cracking that may occur at the time of molding or after molding is used, a pneumatic tire having excellent uniformity and high internal pressure retention is provided. realizable. In addition, it is possible to flexibly cope with tire sizes having a high inner expansion rate, and it is possible to contribute to cost reduction by effectively utilizing existing equipment.

FIG. 1 is a cross-sectional view of the green case at the molding stage. FIG. 2 is a schematic cross-sectional view showing a state in which both end portions of the inner liner are overlapped and joined in the joint portion I included in the H portion of the inner liner of FIG. 1, and FIG. 2 (b) shows the state after joining. In the joint part I included in the H portion of the inner liner in FIG. 1, when the rubber piece made of the rubber layer is arranged, the rubber piece made of the rubber layer is joined to the side wall of one end portion to which the adhesive is applied. FIG. 4A to 4C are schematic cross-sectional views of the inner liner showing a state in which a part of the rubber layer is folded so as to cover a part of the resin layer at one end and then both ends are overlapped and joined. 4 (a) is before joining and the end is folded, FIG. 4 (b) is before joining and the end is folded, and FIG. 4 (c) is both ends. It shows after overlapping and joining the parts. 5 (a) to 5 (b), a part of the rubber layer is folded so as to cover a part of the resin layer at one end, and the resin layer is extended at the other end, FIG. 5A is a schematic cross-sectional view of an inner liner showing a state in which both ends are overlapped and joined, and FIG. 5A shows a state in which both ends are folded before one end is folded before joining. After overlapping and joining. FIG. 6 is a schematic cross-sectional view showing a state in which both end portions of the inner liner of the comparative example are overlapped and joined.

Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.
The unvulcanized of the present invention is
In the both ends of the inner liner composed of a laminate having a resin layer and a rubber layer, including the step of winding around the molding drum while joining the other end on the one end,
Before joining one said edge part and the other edge part, a part of rubber layer is previously arrange | positioned to the side wall of one edge part, It is characterized by the above-mentioned.

  First, a general molding process of an unvulcanized tire for obtaining a pneumatic tire will be described with reference to FIG. Unvulcanized tires usually undergo a two-stage molding process. In the first first molding stage, the inner liner 1 and the carcass ply 2 are pasted on the molding drum, a pair of bead cores 5 are driven in, the carcass ply 2 is folded around, and the bead portion reinforcing cord layer 6 is formed as necessary. Paste together. The bead portion reinforcing cord layer 6 may be bonded to the carcass ply 2 in advance. Next, a sidewall rubber 7 is attached to obtain a cylindrical green case 3.

  In the subsequent second molding stage, the green case 3 is narrowed toward the center C of the cross section while the devices for clamping the pair of bead portions 10 are narrowed toward each other, and the mutual distance between the pair of bead portions 10 is reduced. It is filled with low-pressure air and expanded in the outer diameter direction. At this time, a composite member in which an unvulcanized tread rubber 11 is pasted on the outer periphery of the belt member 4 is pasted on the surface of a cylindrical drum whose diameter can be reduced and expanded in advance, and this is aligned with the center C of the cross section of the green case 3. However, the green case 3 expanded while folding the unvulcanized tread rubber 11 as necessary is brought into contact with the inner peripheral surface of the belt member 4 to obtain an unvulcanized tire. Then, a pneumatic tire is obtained by taking out the unvulcanized tire which passed through the molding process from a molding machine, and performing a vulcanization treatment.

  Here, when the inner liner 1 is attached to the molding drum, the inner liner 1 is wound around the molding drum while overlapping both ends of the inner liner 1 and joining them. That is, one end of the inner liner 1 is disposed inside the tire diameter, and the other end is overlapped from above. Both end portions of the overlapped inner liner 1 are generally referred to as joint portions. However, if the adhesion of these portions is insufficient, stress is caused when the green case 3 is expanded in the second molding stage or when the tire is used. When added, there is a possibility that peeling or cracking (joint cracking) may occur at the joint portion or the uniformity may be reduced.

  The inner liner 1 used in the present invention is composed of a laminate having a resin layer 21 (21x, 21y) and a rubber layer 22 (22x, 22y) as shown in the schematic cross-sectional view of FIG. In the method for producing an unvulcanized tire according to the present invention, the inner end 1 is wound around the molding drum A while the other end y is overlapped and joined on the one end x. Here, before joining the end part x and the end part y, a part 22z of the rubber layer is disposed in advance on the side wall of the one end part x. In the joint part I between the wound one end x and the other end y, a part 22z of the disposed rubber layer is the same quality as the rubber layer 22x and the rubber layer 22y. When it is pressed from the pressing direction B in the expansion process, it is integrated with the rubber layer 22y of the end portion y and firmly bonded.

  Conventionally, as the pressing process and the expansion process are performed, there is a possibility that the rubber layer 22y at the end part y extends or thins more than necessary at the joint part I, and in particular, the rubber layer 22y and the molding drum A There is a possibility that a slight gap may occur between the joint and the joint part, so that the reinforcement of the joint part is reduced and peeling and cracks (joint cracks) are generated and uniformity is sufficiently avoided. Was difficult. However, according to the present invention, by arranging the rubber layer part 22z on the side wall of the end portion x, the expansion and thinning of the rubber layer 22y can be effectively relieved and the both end portions x and y can be firmly fixed. It is possible to improve uniformity while effectively preventing the occurrence of peeling and cracking (joint cracking) in the joint portion I and the occurrence of slight voids.

  As described above, as the part 22z of the rubber layer disposed on the side wall of the end portion x, for example, a rubber piece 22z made of the rubber layer 22 may be used. By using a rubber piece 22z of the same quality as the rubber layer 22, integration with the rubber layer 22y can be further promoted. The rubber piece 22z made of the rubber layer 22 may be produced by once forming the rubber layer 22 and cutting out a part thereof to a desired size.

  The size of a part of the rubber layer is not particularly limited as long as at least the average gauge thickness is equal to the average gauge thickness of the inner liner 1.

  Further, when the rubber piece 22z made of the rubber layer 22 is disposed, it is desirable to apply an adhesive to the side wall of the end portion x as shown in FIG. By applying the adhesive, the adhesive layer 23 can be interposed on the side wall of the end portion x, and the adhesiveness between the rubber piece 22z and the end portion x can be improved by using the adhesive layer 23. It becomes easy and it can also prevent effectively that peeling and a crack generate | occur | produce between these.

  The adhesive is not particularly limited as long as it is usually used for a tire member. For example, a maleimide derivative such as 1,4-phenylene dimaleimide or a rubber component such as butyl rubber, halogenated butyl rubber, or diene rubber may be used. An adhesive blended with poly-p-dinitrosobenzene is preferred. In addition, from the viewpoint of improving physical properties such as weather resistance, ozone resistance, and heat resistance, chlorosulfonated polyethylene may be further added to the rubber component.

  Furthermore, when the rubber layer part 22z is disposed on the side wall of the end part x, a part of the rubber layer 22 may be folded so as to cover a part of the resin layer 21 at the end part x. Specifically, as shown in FIG. 4 (a), the rubber layer 22x is extended to the tip of the end portion x, and the extended rubber layer 22x is folded in the E direction to obtain the state shown in FIG. 4 (b). To. Next, both end portions x and y are joined and pressed in the B direction to obtain an inner liner 1 shown in FIG. As shown in FIG. 4C, the folded portion of the extended rubber layer 22 corresponds to a part 22z of the rubber layer, and can be sufficiently integrated with the rubber layer 22y. . Note that the rubber layer 22x at the tip of the folded end portion x and the rubber layer 22y at the end portion y are also pressed from the pressing direction B, so that these homogeneous rubber layers are integrated and firmly bonded. Therefore, the stress concentration generated in the joint portion I is further relaxed even under a low internal pressure / high load environment, and delamination of the inner liner 1 can be effectively prevented.

  At this time, as shown in FIG. 5A, it is desirable that the resin layer 21y be extended by an area equivalent to the portion joined to the end x at the tip of the end y. By doing in this way, when it joins with the rubber layer 22x by which the edge part x was folded, it can prevent effectively that the gauge thickness of the joint part I increases more than necessary, and the obtained pneumatic There is no possibility that the uniformity of the tire will be hindered.

  The inner liner 1 used in the present invention comprises a laminate having a resin layer 21 and a rubber layer 22, and each of the resin layer 21 and the rubber layer 22 may be a laminate having only one layer, each having two or more layers. The laminated body which has this may be sufficient.

  The resin that forms the resin layer 21 is preferably one that exhibits good gas barrier properties, such as nylon 6, nylon 6,6, polybutadiene resin, maleic anhydride-modified polyethylene, maleic anhydride-modified polybutadiene, Examples include ethylene-vinyl alcohol copolymer (EVOH), modified EVOH, polyethylene, polypropylene, polyethylene terephthalate (PET), vinylidene chloride, polybutylene terephthalate (PBT), and vinyl acetate resin. These may be used alone or in combination of two or more. Of these, ethylene-vinyl alcohol copolymers and modified ethylene-vinyl alcohol copolymers are desirable from the viewpoints of excellent gas barrier properties and greatly improving the internal pressure retention of the tire. If necessary, fillers such as carbon black and silica, crosslinking agents such as sulfur, diphenylguanidine (DPG), tetramethylthiuram disulfide (TMTD), tetramethylthiuram monosulfide (TMTM), 2-mercaptobenzo Thiazole zinc salt (ZnBDC), 2-mercaptobenzothiazole (MBT), 2-benzothiazolyl disulfide (MBTS), N-cyclohexyl-2-benzothiazolesulfenamide (CBS) and Nt-butyl-2- The barrier layer may be formed by blending a crosslinking accelerator such as benzothiazole sulfenamide (BBS) and a crosslinking accelerator such as zinc white (zinc oxide).

  The average gauge thickness of the resin layer 21 may vary depending on the layer configuration of the inner liner 1 and the like, but is usually 50 to 300 μm, preferably 50 to 150 μm. Therefore, even if the inner liner 1 is a laminated body including a plurality of resin layers 21, it is possible to easily realize a thin layer.

  The rubber composition for forming the rubber layer 22 is preferably one that can exhibit a good protective function and reinforcement, such as natural rubber, synthetic isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile- In addition to rubber components such as butadiene rubber, ethylene-propylene rubber, butyl rubber, chloroprene rubber, acrylic rubber, urethane rubber, chlorinated polyethylene, and ethylene-acrylic rubber, olefin-based, styrene-based, ester-based, urethane-based, ionomer-based, 1 , 2-polybutadiene-based, polyamide-based thermoplastic elastomers and the like. Of these, butyl rubber is preferred from the viewpoint of more effectively suppressing the generation and extension of cracks.

  Further, the rubber layer 22 may be formed by further blending the above-described filler, cross-linking agent, cross-linking accelerator, and cross-linking accelerating aid with the rubber composition as necessary.

  The average gauge thickness of the rubber layer 22 may vary depending on the layer configuration of the inner liner 1 and the like, but is usually 0.01 to 2 mm, preferably 1 to 2 mm. Therefore, even if the inner liner 1 is a laminated body including a plurality of rubber layers 22, it is possible to easily realize a thin layer.

  Furthermore, if necessary, an adhesive layer (not shown) may be further provided at a desired location, for example, the innermost side in the tire radial direction, from the viewpoint of further improving the adhesion at the joint portion I of the inner liner 1. When such an adhesive layer is included, it becomes easy to immediately bond the inner liner 1 and the adjacent member to effectively prevent peeling between the members at the time of tire molding. Specifically, for example, it is effective when the inner liner 1 is stuck on the molding drum A via a rubber member that is easy to stick to the molding drum A while avoiding the damage or the like of the thinned inner liner 1. .

  The layer forming the adhesive layer is preferably a layer made of an adhesive composition that can also be used for an adhesive applied to the side wall of the end x.

  The average gauge thickness of the inner liner 1 may vary depending on the layer structure of the inner liner 1, but is usually 140 μm or less, preferably 120 μm or less. When the average gauge thickness exceeds 140 μm, the adhesive strength between both ends of the inner liner 1 in the joint portion I becomes insufficient, and peeling or cracking occurs in the joint portion I when expanded toward the outer diameter direction during molding. May occur.

  As shown in FIG. 1, the pneumatic tire of the present invention is characterized by using the inner liner or the unvulcanized tire. As described above, in the normal first molding stage, for example, one end of the inner liner 1 on the molding drum with the through-hole z formed therein is disposed on the inner side in the tire radial direction, and the upper surface thereof. Overlap the other end. Next, a desired adjacent member is pasted and expanded to obtain an unvulcanized tire. At this time, the inner liner 1 of the present invention is pressed from the pressing direction B and is firmly fixed at the joint portion, and there is no possibility of peeling.

  Thereafter, in the second molding stage, the vulcanized tire is vulcanized under known vulcanization conditions. As the conditions for the vulcanization treatment, for example, the vulcanization treatment is performed at a temperature of 100 ° C. or higher, preferably 125 to 200 ° C., more preferably 130 to 180 ° C. Even at this stage, the inner liner will be further expanded, but since the joint part is firmly fixed as described above, there is no risk of cracks occurring in such a part, and the uniformity with the desired size is achieved. The tire can be high. Next, the pneumatic tire of the present invention is obtained by filling with air, nitrogen, helium or the like.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Examples 1-3)
As Examples 1-3, as shown in FIG. 2, a resin layer 21 (21x, 21y) having a thickness of 100 μm made of a modified EVOH and a thermoplastic urethane elastomer layer, and a thickness made of natural rubber and brominated butyl rubber. It is a laminated body having a rubber layer 22 (22x, 22y) of 500 μm, and when it is wound around the molding drum A while the other end y is overlapped and joined on one end x, it is preliminarily applied to the one end x. A sample of the inner liner 1 in which a part 22z of the rubber layer was arranged was produced.

  In addition, about the said rubber piece 22z, in Example 1, as shown in FIG. 2, the rubber piece 22z is arrange | positioned at the side wall of the edge part x. In Example 2, as shown in FIG. 4, the rubber layer 22x is extended at the tip of the end portion x (FIG. 4A), and the extended rubber layer 22x is folded in the E direction (FIG. b)), rubber pieces 22z are formed by joining both ends x and y and pressing in the B direction (FIG. 4C). In Example 3, as shown in FIG. 5, the rubber layer 22x is extended in the E direction in the state where the resin layer 21y is extended by an area equivalent to the portion joined to the end x at the tip of the end y. The rubber piece 22z is formed by joining and pressing both ends x and y (FIG. 4 (c)).

(Comparative example)
As a comparative example, as shown in FIG. 6, when the other end y is overlapped on one end x and wound around the molding drum A, a part of the rubber layer is preliminarily placed on the one end x. A sample of the inner liner was produced under the same conditions as in Examples 1 to 3 except that the bonding was performed without arranging 22z.

(Evaluation)
The inner liner produced in each Example and each Comparative Example was subjected to a winding process around a molding drum in the tire manufacturing process together with other members, and then left for one day with the case expanded in the second molding stage. Evaluation was performed by confirming whether or not the inner liner was peeled off at the joint portion of the film. The evaluation results are shown in Table 1.

(result)
From Table 1, it turned out that about the inner liner of Examples 1-3 concerning this invention, the joint part of the film after leaving for one day was not peeled, but the joint crack could be suppressed effectively. On the other hand, it was found that the inner liner of the comparative example was peeled off and the joint cracking was not sufficiently suppressed.

  According to the present invention, since an inner liner capable of effectively preventing joint cracking that may occur at the time of molding or after molding can be obtained, it is possible to realize a pneumatic tire having excellent uniformity and high internal pressure retention. It becomes possible. As a result, it is possible to flexibly cope with a tire size having a high inner expansion rate, and it is possible to effectively utilize existing facilities and contribute to cost reduction.

1: Inner liner 2: Carcass ply 3: Green case 5: Bead core 6: Bead portion reinforcing cord layer 7: Side wall rubber 10: Bead portion 11: Unvulcanized tread rubber 21x: Resin layer of end portion 21y: End portion y resin layer 22x: rubber layer at end x 22y: rubber layer at end y 22z: part of rubber layer 23: adhesive A: molding drum B: pressing direction C: center of cross section of green case E: rubber layer Folding direction of 22x I: Joint part x: One end of the inner liner y: The other end of the inner liner

Claims (2)

A inner liner made of the modified EVOH layer and a thermoplastic urethane-based resin layer of elastomeric layer and laminate with one rubber layer made form the surface of the resin layer, the rubber layer, the inner liner The rubber layer extends at the tip of one end of the resin layer, and the inner liner of the one surface of the resin layer is overlapped with the other end on the one end. A step of preparing an inner liner, which is formed at least on the entire surface other than the surface in contact with the one end when wound around a molding drum;
Wherein the inner liner, so as to bond overlapping the other end portion on one end of the inner liner, the resin layer on the outer side in the tire radial direction, so that the rubber layer is on the inner side in the tire radial direction And before placing the one end and the other end together, placing a part of the rubber layer on the side wall of one end in advance ,
In the step of placing a portion of the rubber layer on the side walls of the one end, the so as to cover the side walls and the other side end portion of the resin layer at one end, extending to the tip of one end Zaisa performs an operation for folding said rubber layer were, and wherein the method of manufacturing a green tire. A inner liner made of the modified EVOH layer and a thermoplastic urethane-based resin layer of elastomeric layer and laminate with one rubber layer made form the surface of the resin layer, the rubber layer, the inner liner The rubber layer extends at the tip of one end of the resin layer, and the inner liner of the one surface of the resin layer is overlapped with the other end on the one end. A step of preparing an inner liner, which is formed at least on the entire surface other than the surface in contact with the one end when wound around a molding drum;
The inner liner is joined with the other end overlapped on one end of the inner liner so that the resin layer is on the outer side in the tire radial direction and the rubber layer is on the inner side in the tire radial direction. The process of winding on a molding drum, and
Before joining the one end and the other end , a step of arranging a part of the rubber layer on the side wall of the one end in advance ,
In the step of placing a portion of the rubber layer on the side walls of the one end, the so as to cover the side walls and the other side end portion of the resin layer at one end, extending to the tip of one end Zaisa perform tatami no operation folding the rubber layer was, characterized in that, the pneumatic tire manufacturing method.