JP7183665B2 - Method for manufacturing rubber products - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a rubber product, and more particularly, when vulcanizing an unvulcanized rubber molded body using a vulcanizing mold, vulcanization caused by air remaining inside the rubber molded body. The present invention relates to a method for manufacturing rubber products that can more effectively suppress the occurrence of failures.

BACKGROUND ART Rubber products such as tires are manufactured by vulcanizing an unvulcanized rubber molding placed in a vulcanizing mold. The molding surface of the vulcanization mold is formed with vent holes for air release. In the vulcanization process of the rubber molding, excess air is discharged from the inside to the outside of the vulcanization mold through the vent holes. Vent holes are effective in discharging air existing between the molding surface of the vulcanization mold and the surface of the rubber molded body to the outside of the vulcanization mold, but the air remains inside the rubber molded body. It does not work well enough to expel trapped air.

In order to prevent vulcanization failures during tire manufacturing, a method has been proposed in which threads are embedded inside a green tire, which is an unvulcanized rubber molding (see, for example, Patent Document 1). According to this method, the air remaining inside the green tire can be dispersed widely through the yarn during vulcanization of the green tire, so that vulcanization failure can be suppressed.

However, if a large amount of air remains even after the air is dispersed inside the green tire, vulcanization failures such as swelling due to the air remaining in the green tire occur in the vulcanized and manufactured tire. Therefore, there is room for improvement in suppressing the occurrence of such vulcanization failures.

JP 2016-182770 A

An object of the present invention is to more effectively suppress the occurrence of vulcanization failures caused by air remaining inside a rubber molded body when vulcanizing an unvulcanized rubber molded body using a vulcanizing mold. To provide a method for manufacturing a rubber product capable of

In order to achieve the above object, the method for producing a rubber product according to the present invention comprises vulcanizing an unvulcanized molded rubber article placed inside a vulcanizing mold having a vent hole on the molding surface, comprising: A thread is embedded in the vicinity of the surface at a predetermined depth of 2 mm to 5 mm from the surface of the rubber molded body, and the air remaining inside the rubber molded body is removed by the thread during vulcanization of the rubber molded body. It is characterized by guiding to the vent hole located in the vicinity of the yarn along.

According to the present invention, by embedding the thread in the vicinity of the surface at a predetermined depth from the surface of the unvulcanized rubber molded body, the thread remains inside the rubber molded body during vulcanization of the rubber molded body. It can move the air along the yarn. By guiding the air moved along the thread to the vent hole located near the thread, the air can be removed from the rubber product manufactured by vulcanizing the rubber molding. Therefore, it is possible to more effectively suppress the occurrence of vulcanization failures caused by air remaining inside the rubber molded body.

It is explanatory drawing which illustrates typically the tire width direction right side of a green tire by the cross-sectional view. 1. It is explanatory drawing which illustrates the state which closed the mold for vulcanization|mold which has arrange|positioned the green tire of FIG. 1 inside, in a cross-sectional view. FIG. 3 is an explanatory view exemplifying a partially enlarged side portion periphery of the green tire in FIG. 2 ; FIG. 4 is an explanatory diagram illustrating a part of a side portion cut away as viewed from the arrow A in FIG. 3 ; 4 is an explanatory diagram illustrating the state of the side portion of FIG. 3 during vulcanization; FIG. FIG. 6 is an explanatory view illustrating the state of the side portion of FIG. 5 when the vulcanization process has progressed further; FIG. 7 is an explanatory diagram illustrating the state of the side portion of FIG. 6 when the vulcanization process is completed; FIG. 8 is an explanatory diagram illustrating a state in which the spew in FIG. 7 is removed; It is explanatory drawing which illustrates typically the right side of the tire width direction of the manufactured tire by the cross-sectional view.

Hereinafter, the method for manufacturing a rubber product according to the present invention will be described based on the embodiment shown in the drawings, taking the case of manufacturing a tire as an example.

According to the present invention, the pneumatic tire T illustrated in FIG. 9 is manufactured by vulcanizing the green tire 9 illustrated in FIG. The green tire 9 in FIG. 1 is an unvulcanized rubber molding, and the tire T in FIG. 9 is in a vulcanized state.

In the green tire 9 of FIG. 1, a carcass 13 is laminated on the outer peripheral side of the innermost inner liner 12 . The carcass 13 is mounted between a pair of left and right bead portions 14 . The right and left end portions of the carcass 13 are folded back around the bead cores 14a of the respective bead portions 14 from the inside to the outside of the tire. The carcass 13 has many reinforcing wires extending in the tire radial direction. Two belt layers 15 are embedded in the outer peripheral side of the central portion in the tire width direction of the carcass 13, and a tread portion 18 is laminated on the outer peripheral side thereof. The number of layers of the belt layer 15 is appropriately set. Tire side portions 16 are laminated on the outer sides of the carcass 13 on both sides in the tire width direction. Shoulder portions 17 are laminated to the outside of the carcass 13 between the tread portion 18 and the respective tire side portions 16 .

For the green tire 9, in addition to the above-described members, necessary members such as a belt cover layer laminated on the outer peripheral side of the belt layer 15 to cover both ends of the belt layer 15 are used as appropriate. The members constituting the green tire 9 are mainly unvulcanized rubber and reinforcing material. In the present invention, the thread 11 is embedded near the surface of the green tire 9 at a predetermined depth d from the surface. This predetermined depth d is, for example, 2 mm to 5 mm. At least part of the entire length of the thread 11 is embedded in the range of this predetermined depth d. For example, 30% or more, 50% or more, or 100% of the total length of the thread 11 may be embedded in this range.

Although the thread 11 is embedded in the side portion 16 in this embodiment, it may also be embedded in the shoulder portion 17 or the tread portion 18 . A large number of threads 11 are scattered on the side portion 16, and each thread 11 extends in a direction (circumferential direction or radial direction) along the tire surface. In addition, the extending direction of the thread 11 is not particularly limited, and may be a circumferential direction, a radial direction, a width direction, or a direction inclined with respect to these directions.

The thread 11 has a very high flexibility since it does not function as a reinforcing material. The breaking strength of the thread 11 is, for example, 100 N or less, the outer diameter is, for example, 0.5 mm or less, and the length is, for example, 10 mm or more. The upper limit of the length of the thread 11 is not particularly limited as long as it can be embedded in the desired range of the green tire 9 without any problem. The outer diameter of the thread 11 is preferably smaller than the inner diameter of the vent hole 8, which will be described later. The material of the thread 11 is synthetic fiber or natural fiber such as cotton. For the thread 11, for example, a twisted thread formed by twisting one or more filaments is used.

A green tire 9 is vulcanized using a vulcanizing apparatus 1 illustrated in FIG. The vulcanizing device 1 includes an upper plate 2a, a lower plate 2b, a plurality of segments 2c, an annular container ring 3, and a central mechanism 4. A tire vulcanizing mold 6 (hereinafter referred to as a mold 6) is attached to the vulcanizing apparatus 1. As shown in FIG. The inner surface of the mold 6 becomes the molding surface 7 on which the green tire 9 is molded. A large number of vent holes 8 are formed in the molding surface 7 . The vent hole 8 communicates from the inside (molding surface 7) of the mold 6 to the outside. The inner diameter of the vent hole 8 is, for example, 0.5 mm to 2.0 mm.

In this embodiment, the mold 6 is composed of an annular upper side mold 6a, an annular lower side mold 6b, and a plurality of sector molds 6c. The upper surface of the upper side mold 6a is attached facing the lower surface of the upper plate 2a, and the lower surface of the upper side mold 6b is attached facing the upper surface of the lower plate 2b. The lower plate 2b is immovably fixed to the ground base.

A center post 4a that constitutes the center mechanism 4 is arranged at the annular center CL of the upper side mold 6a and the lower side mold 6b. A disk-shaped clamp portion 5a is attached to the central post 4a with a space therebetween in the vertical direction. Upper and lower ends of cylindrical vulcanizing bladders 5 (hereinafter referred to as bladders 5) are held by the respective clamping portions 5a.

Each segment 2c is annularly arranged around the central mechanism 4 (center CL). The outer peripheral surface of the sector mold 6c is attached facing the inner peripheral side of each segment 2c. The outer peripheral surface of each segment 2c has an upward inclination from the outer peripheral side toward the inner peripheral side.

Next, an example of a method of vulcanizing the green tire 9 to manufacture the pneumatic tire T using the vulcanizing apparatus 1 will be described.

When the green tire 9 is vulcanized, the green tire 9 lying sideways is passed through the center mechanism 4 while the mold 6 is opened. Then, the green tire 9 is held from the inside by the bladder 8 inflated by the shaping pressure. The green tire 9 is placed on the lower side mold 6b in a laid down state.

Next, the container ring 3, the upper plate 2a, and the upper side mold 6a are moved downward, and the inner peripheral inclined surface of the container ring 3 presses the outer peripheral inclined surface of each segment 2c placed on the lower plate 2b. . As a result, each segment 2c and each sector mold 6c are moved toward the annular center CL, and each sector mold 6c is assembled in an annular shape. The sector molds 6c assembled in an annular shape are vertically sandwiched between the upper side mold 6a and the lower side mold 6b, and the mold 6 is closed with the green tire 9 enclosed therein.

As illustrated in FIG. 2, in a state where the mold 6 is closed, a heating medium S such as steam and a pressurizing medium N such as nitrogen gas are sequentially injected into the bladder 8 to heat the bladder 8 and further Inflate. As a result, the inside of the green tire 9 is heated while being pressed mainly by the bladder 8, and the outside of the green tire 9 is heated while being pressed mainly by the mold 6, and the green tire 9 is vulcanized. The upper side portion 16 of the laid green tire 9 is vulcanized by the upper side mold 6a, and the lower side portion 16 is vulcanized by the lower side mold 6b. The shoulder portion 17 and the tread portion 18 are vulcanized by respective sector molds 6c.

In the vulcanization process of the green tire 9 , the air a existing between the surface of the green tire 9 and the molding surface 7 of the mold 6 is discharged to the outside of the mold 6 through the vent holes 8 . Also, the unvulcanized rubber forming the green tire 9 flows and part of it flows into the vent hole 8 . The air a remaining inside the unvulcanized rubber near the opening of the vent hole 8 also flows into the vent hole 8 together with the unvulcanized rubber and is discharged to the outside of the mold 6 .

To elaborate on the vulcanization process, in this embodiment, the thread 11 is embedded in the vicinity of the surface of the side portion 16, so that when the mold 6 is closed, the thread is placed in the vicinity of the molding surface 7 as illustrated in FIG. 11 is placed. The forming surface 7 and the thread 11 are spaced at a predetermined depth d. In this embodiment, as illustrated in FIG. 4, the thread 11 is open in a view normal to the opening defined by the opening edge in the molding surface 7 of the vent hole 8 (as viewed by arrow A in FIG. 3). It is arranged across the department.

After that, a pressing force for pressing the green tire 9 against the mold 6 (molding surface 7) is applied by the inflating vulcanizing bladder 5 . Due to this pressing force, unvulcanized rubber in the vicinity of the vent hole 8 flows into the vent hole 8, as illustrated in FIG. move toward the opening of the vent hole 8. Further, the air a remaining near the thread 11 inside the unvulcanized rubber of the side portion 16 moves along the thread 11 . As a result, the air a that has moved along the thread 11 is guided to the vent hole 8 located near the thread 11 together with the flowing unvulcanized rubber.

That is, the thread 11 embedded in the unvulcanized rubber functions as a guide for moving the air a remaining in the unvulcanized rubber near the thread 11 toward the vent hole 8 . Therefore, the air a remaining inside the unvulcanized rubber can be guided to the vent hole 8 over a wider range than when the thread 11 is not embedded.

However, the unvulcanized rubber at a position far from the molding surface 7 does not flow toward the vent hole 8, so the thread 11 needs to be arranged near the molding surface 7 to some extent. On the other hand, if the yarn 11 is positioned too close to the molding surface 7, the yarn 11 may be exposed on the surface of the manufactured tire T. Therefore, the thread 11 must be arranged at a predetermined depth d near the surface of the green tire 9 . In order to easily guide the air a moved along the thread 11 to the vent hole 8, the thread 11 should be arranged to cross the opening of the vent hole 8 as shown in FIG. Therefore, at least the position where the thread 11 crosses the opening of the vent hole 8 is preferably embedded near the surface of the green tire 9 at a predetermined depth d from the surface.

As the vulcanization process further progresses, air a is discharged from the unvulcanized rubber that has flowed into the vent hole 8 as illustrated in FIG. Some of the air a may remain inside the unvulcanized rubber that has flowed into the vent hole 8 .

When the vulcanization process of the green tire 9 is completed, as illustrated in FIG. 7, the unvulcanized rubber loses fluidity and becomes hardened, and the tire T is manufactured. The manufactured tire T is taken out from the mold 6 . The unvulcanized rubber that has flowed into the vent hole 8 during the vulcanization step protrudes from the surface of the manufactured tire T as a so-called spew 10 . In this embodiment, air a remains in spew 10 .

The tire T taken out from the mold 6 has the spew 10 cut off from the tire surface in the finishing process, as illustrated in FIG. 8 . Therefore, the air a remaining in the spew 10 is removed from the tire T. Thus, the tire T illustrated in FIG. 9 is completed.

As described above, by using the thread 11 embedded near the surface of the green tire 9 , the air a remaining inside the unvulcanized rubber over a wider range can be guided to the vent hole 8 . Accordingly, it becomes possible to more effectively suppress the occurrence of vulcanization failures caused by the air a remaining inside the green tire 9 . In the manufactured tire T, the air a remaining inside the green tire 9 is removed, which contributes to improvement in tire quality.

Appropriate specifications of the thread 11 and appropriate embedding positions (depth and placement) in the green tire 9 vary depending on the specifications of the green tire 9 and vulcanization conditions. Therefore, test vulcanization and simulation are performed in advance, and the appropriate specification of the thread 11 and the appropriate embedding position of the thread 11 in the green tire 9 are grasped for each tire specification and vulcanization condition, and the allowable range is set. do it. Then, it is preferable to vulcanize the green tire 9 in a state in which the specification of the yarn 11 and the position where the yarn 11 is embedded in the green tire 9 are within the set allowable range.

If a twisted yarn formed by twisting one or more filaments is used as the yarn 11, the air a remaining inside the green tire 9 moves along the yarn 11 compared to untwisted yarn. becomes easier. Accordingly, it is more advantageous to suppress the occurrence of vulcanization failures caused by the air a.

The rubber molded body to which the present invention can be applied is not limited to the green tire 9, and may be an unvulcanized rubber molded body for manufacturing rubber products other than tires (for example, tire vulcanizing bladders, etc.). That is, the present invention can be used when vulcanizing an unvulcanized rubber molding 9 using a mold 6 having vent holes 8 on the molding surface 7 .

When the thread 11 is embedded in the side portion 16 of the green tire 9, the thread 11 remains in the side portion 16 of the manufactured tire T. Since the side portion 16 is not substantially worn even when the tire T is used, the remaining thread 11 is not exposed from the tire T. Therefore, it is possible to avoid the problem that the thread 11 is exposed due to the use of the tire T over time and the appearance quality is deteriorated.

In this embodiment, a so-called sectional type mold 6 is used to vulcanize the green tire 9, but the mold 6 may be a so-called split type.

1 Vulcanizing device 2a Upper plate 2b Lower plate 2c Segment 3 Container ring 4 Center mechanism 4a Center post 5 Vulcanizing bladder 6 Mold 6a Upper side mold 6b Lower side mold 6c Sector mold 7 Molding surface 8 Vent hole 9 Green tire ( Unvulcanized rubber molding)
10 spew 11 thread 12 inner liner 13 carcass 14 bead portion 14a bead core 15 belt layer 16 side portion 17 shoulder portion 18 tread portion T tire (manufactured tire)

Claims (5)

In a method for producing a rubber product, vulcanizing an unvulcanized rubber molding placed inside a vulcanization mold having vent holes on the molding surface,
A thread is embedded in the vicinity of the surface at a predetermined depth of 2 mm to 5 mm from the surface of the rubber molded body, and the air remaining inside the rubber molded body is removed by the thread during vulcanization of the rubber molded body. A method for manufacturing a rubber product, characterized in that the yarn is guided to the vent hole located in the vicinity of the yarn along. 2. The method of manufacturing a rubber product according to claim 1, wherein a twisted yarn formed by twisting one or more filaments is used as said yarn. When the mold with the rubber molded body arranged inside is closed, the thread crosses the opening in the normal direction to the opening defined by the opening edge of the vent hole on the molding surface. 3. The method for manufacturing a rubber product according to claim 1 or 2, wherein the arrangement is such that The method for producing a rubber product according to any one of claims 1 to 3, wherein the rubber molding is a green tire, and a tire is produced as the rubber product. 5. The method of manufacturing a rubber product according to claim 4, wherein the thread is embedded in the side portion of the green tire.

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