JPH044109A - Manufacture of pneumatic tire - Google Patents

Abstract

PURPOSE:To enable the read patterns of a tire to be developed in a short time and at low cost by casting a material (gypsum) having fluidity and rigidity after curing into a rubber mold, and curing it for manufacturing tire patterns, and then manufacturing a mold from the tire patterns, and thereafter using the mold for manufacturing tires. CONSTITUTION:The composite of a mold material is injected into mold material filling parts 4, 4 until it reaches above the width directional center of a model tire 1. After the completion of curing, the vacuum of a vacuum case is broken for removing an assembly therefrom and then the cured rubber mold is separated from the model tire 1. In the next place, the upper and lower parts of the model tire 1 wherein a center clamping device 8 or the like is disengaged therefrom are reversed and the assembly is constructed repeatedly and the half- remained rubber mold of the model tire 1 is manufactured similarly. An upper and lower split-type molding mold is manufactured from these two rubber molds in accordance with the process of a conventional gypsum molding (tire pattern), aluminum alloy casting, flash removing, sizing, and machining.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a pneumatic tire. More specifically, when manufacturing a tire, a tire pattern is molded into a mold prototype (rubber mold) using a material that is made of injection-curable fluid resin and has rubber-like elasticity after curing. ), producing a tire mold from this rubber mold, and manufacturing a pneumatic tire using this mold.

[Conventional technology]

In the development of automobile sales strategies, there is a strong demand for the development of tire tread patterns in a short period of time and at low cost, along with demands for a wide variety of tire tread patterns and shortening of development and delivery times.

Conventionally, the tire molding molds required for the development of new pneumatic tires, especially pneumatic tires with new tread patterns, have been made by making a partial full-size mold of a model tire, making a rubber impression, placing sipes, and plastering. Making the mold - Cutting and assembling the plaster mold
It was manufactured using a process of aluminum alloy casting, sizing, and machining.

That is, first, using plaster, wood, etc., 200 to 400
A plurality of partial full-size molds (usually 2 to 3 pieces) are produced from a tire model obtained by carving a trend pattern of mm.

As shown in Fig. 2, the molding surface of this partial full-size mold M is
A polystyrene foam core 6 is covered with a hack core 2 hardened with plaster and the whole is surrounded by an outer wall board 3 so that a molding material (injection hardening type fluid composition) filling part 4 is formed on the outer peripheral side surface of the core 6. Create a mold for making the impression.

A molding material is injected into the molding material filling part 4 from the injection hole 5 of this mold for making a rubber mold, and is cured to form a rubber mold. After implanting sipes into the rubber mold as desired, a plaster mold is made. As shown in FIG. 3, several C2 plaster molds 12 are cut and assembled on a plaster base 1) to form a tire model for casting. After casting an aluminum alloy using this tire model, the plaster mold was removed, removed, sized, rounded, and finished by machining to produce a mold.

The above-described method for manufacturing a tire mold has the drawback of repeatedly making rubber molds and plaster molds, resulting in large process losses and significantly lengthening the development period. Also,
The disadvantage was that the work was complicated and required skill because duplicate plaster molds were made and the necessary parts were cut and assembled.

On the other hand, compositions containing thiocol resin as a main component are generally known as injection-curing fluid compositions used for manufacturing the above-mentioned tire molds. However, although this thiocol resin has a low viscosity, has a long pot life, is easy to use, and has excellent rubber molding properties, it is difficult to perform multiple rubber moldings on partial full-size models.
Due to its low elasticity, it easily loses its shape. Furthermore, rubber molds cannot be stored for long periods of time because they shrink over time and lose their shape. For this reason, it cannot be reused or stored as a mold sample, so there is a drawback that the rubber mold must be made again. Furthermore, since highly active organic peroxides and metal peroxides are used for vulcanization, they are dangerous and have the disadvantage of emitting a bad odor. In addition, when used for molding an integral comb, since the initial elastic modulus is low, there is a risk that it may be bent and deformed by the construction pressure during tire model manufacturing. For this reason, it is necessary to prevent this bending with a sawing material, making it difficult to use it for making integral rubber molds.

[Problem to be solved by the invention]

The purpose of the present invention is to create a rubber mold by directly molding the entire tire from an actual tire such as a developed product or prototype, without going through the process of manufacturing multiple partial full-size models. The object of the present invention is to provide a method for manufacturing tires using a mold made from this rubber mold. Another object of the present invention is that, in the above-described tire manufacturing method, there are no disadvantages such as deformation, shrinkage, catalyst poisoning, moisture absorption, foaming, etc., and it is possible to advantageously make an integral rubber mold directly from a model tire. The object of the present invention is to provide an injection-curable flowable composition that forms a rubber mold that can be stored and reused.

[Means to solve the problem]

The above purpose is to create a rubber mold (mold prototype) by casting a material that has fluidity into a tire prototype and has rubber-like elasticity after curing, and then having this rubber mold have fluidity. Achieved by casting a material (gypsum) that has rigidity after hardening, allowing it to harden to create a tire model, then creating a mold from this tire model, and then using this mold to manufacture tires. can do. That is, the mold used in the present invention is manufactured through a shortened process of making a rubber mold from a model tire, making a plaster mold, casting an aluminum alloy, sizing, and finishing it by machining, so it can be manufactured in a short period of time and at low cost. Allows to develop tire tread patterns.

An example of a method for manufacturing a mold used in the tire manufacturing method of the present invention will be described below based on the drawings.

FIG. 1 is a half-sectional explanatory diagram showing an example of an assembly for making a rubber mold from a model tire. As shown in the figure, a model tire 1 is filled with air, and a model tire 1 is filled with air.
After attaching the wheel 7 to the bottom plate 10 with a center fastener 8, the model tire l is set on a tire stand 9. The tire stand 9 is in close contact with the rim attachment part of the bead part of the model tire l and the sidewall part.

As shown in the right half of FIG. 1, the outer peripheral side of the model tire 1 is surrounded by a tapered outer wall plate 3 attached to the bottom plate 10, and the trend of the model tire 1 is the inner side and the outer wall plate 3 is the outer side. An assembly is formed in which the shaped mold material filling part 4 serves as a mold. That is, the molding material filling portion 4 is a half of the model tire 1 centered on the equatorial plane, and is designed to be a mold into which molding material can be poured over the entire circumference in the tire circumferential direction. Also,
As shown in the left half of FIG. 1, a styrofoam core 6 is covered with a bank core 2 hardened with plaster so that a 4° filled part of the molding material is formed on the outer circumferential side of the model tire 1, and then the outer circumferential side is By surrounding it with the tapered outer wall plate 3, it is possible to form an assembly in which the trend of the model tire l is the inner surface and the outer wall plate 3 is the outer surface of the doughnut-shaped mold material filling part 4'' (formwork). .

In order to facilitate the operation of demolding the rubber mold from this assembly, the inner surfaces of the bottom plate 10 and the outer wall plate 3 can be subjected to a mold release treatment.

The entire assembly is then placed in a vacuum case (not shown) having an injection hole with pulp, and the inside of the case is evacuated. Through this injection hole, the composition of the molding material of the present invention, which has been completely defoamed in advance, is poured at a distance of 10 to 15 mm from the center in the width direction (-dotted chain line) of the model tire 1.
The mold material is injected into the filling part 4.4'' until it reaches the upper part. After curing is completed, the vacuum in the vacuum case is broken and the assembly is taken out, and the cured rubber mold is separated from the model tire 1.

Next, the model tire 1 from which the center fastener 8 and the like have been removed is turned upside down and reassembled, and a rubber mold for the remaining half of the model tire 1 is produced in the same manner. From these two rubber molds, a top and bottom split mold for tire molding can be manufactured according to conventional methods: plaster molding (tire model), aluminum alloy casting, firming, sizing, and machining finishing.

The outer periphery of the mold material filling part 4.4° (hereinafter referred to as the mold) may have any shape, but generally it is annular to save the amount of the composition to be cast. It is advantageous. However, when a flange is erected on the outer shell to make it into an assembled form, a cylindrical side surface may be used.

In manufacturing the mold of the present invention, the model tire may be set vertically or horizontally in the assembly. Moreover, the number of times of casting can be set from one to an arbitrary number of times. Common sense suggests that when placed horizontally, it can be placed once or twice, that is, it can be placed in one piece as referred to in the present invention. When making one impression with this horizontal placement, it is necessary to set the partition film on the center line of the tire.

Furthermore, even in the case of vertical placement, it is possible to perform integral molding once or twice. In this case of vertical placement, making the mold twice is not realistic because it creates an unnatural situation. In the case of one-time molding in the vertical setting, it is necessary to centrate the partition film as in the case of the horizontal setting. Further, the bottom plate 10 of the form frame 4.4° is preferably a removable flat plate, and is preferably fixed or disposed using a flange or fitting method. By removing the bottom plate 10 first, the rubber mold can be easily removed from the model tire 1.

Further, even if the shrinkage rate of the mold material during molding is 0.1χ, there is a dimensional change after curing due to shape curing of the rubber-like elastic body. For this reason, the outer diameter and roundness of an annular tire must be carefully examined at each stage of molding, but in the case of integral rubber molding, the shape must be corrected during the intermediate transfer process. . Additionally, in the case of partial rubber molding, this correction process can be incorporated in the form of circumference correction.

In the production method of the present invention, examples of the material having fluidity and rubber elasticity after curing include compositions containing urethane bond-containing epoxy resins, silicone resins, and urethane resins as main components.

In particular, it is preferable to use a composition containing a urethane bond-containing epoxy resin and a curing agent as main components.

The urethane bond-containing epoxy resin has a main skeleton having a molecular structure represented by the following formula (1).

The characteristics of the main skeleton shown in the above formula (1) are that the alkyl main chain R
A bifunctional isocyanate was placed at the end of the molecule, and the open residue was reacted with glycidol to form an epoxy group at the end, thereby removing traces of the isocyanate. The activity of the oxysilane ring can be adjusted in various ways depending on the type of alkyl main chain R, the degree of polymerization, and the isocyanate skeleton.

In the above formula (I), preferred examples of the alkyl main chain R include polypropylene glycol having a molecular weight of 500 to 4,000 and polytetramethylene glycol having a molecular weight of 500 to 1,500. Moreover, the epoxy equivalent is usually in the range of 500 to 2,000, preferably the average epoxy equivalent is in the range of 800 to 1,200. The epoxy equivalent does not necessarily have to be within a narrow range, and the equivalent distribution is determined by the balance between fluidity, initial elastic modulus, tear resistance, etc. In particular, epoxy resin, which forms a castable rubber-like elastic body, has a higher initial elasticity than silicone resin for the purpose of large-scale casting, and also provides the cut-cutting properties that are characteristic of cast molds. It is better to have lower rigidity than urethane resin.

Further, as the curing agent, one that slowly crosslinks and cures the urethane bond-containing epoxy resin at room temperature is preferable. For example, those having a molecular structure represented by the following formula (II), which is a substantially equivalent reaction product of 13-bisaminomethylcyclohexane and phenylglycidyl ether, are preferred.

H2 In the above formula (II), the amine component is ■, 3
In addition to -bisaminomethylcyclohexane, it is preferable to use tetrafunctional amines such as isophorone diamine, 1,6-hexane diamine, and trimethylhexamethylene diamine. Moreover, as the glycidyl component of the above formula (II), it is preferable to use butyl glycidyl ether in addition to phenyl glycidyl ether.

A composition containing such a urethane bond-containing epoxy resin and a curing agent as main components may contain flow improvers, antifoaming agents, curing accelerators, softeners, mold release modifiers, fillers, colorants, etc. They can be blended as appropriate.

The mixing ratio of the urethane bond-containing epoxy resin and the curing agent is 0.5 of the curing agent to the urethane bond-containing epoxy resin.
It is preferable to set it in the range of ~1.5.

Rubber elasticity varies depending on this blending ratio. For example, if the blending ratio is 1:1, the tensile strength specified in JIS K 6301 is 50 Kg/cm, the elongation is 400!, the initial elastic modulus is 8-10 Kg/cm, and the tearing force is A 8 Kg/c.
m, tearing force 815Kg/cm, hardness 40(A),
65(C), permanent elongation 1% or less, JIS K 691
), molding shrinkage rate of 0.1% or less as specified in
40°C).

Furthermore, it does not generate heat during curing, and its pot life is approximately 5 hours. If the curing agent is vacuum degassed during mixing, about 4 hours can be used for casting, so even large capacity tires can be cast without problems. Since a curing time of 15 to 20 hours is required, it is desirable to complete the reaction by heating and curing at 80°C.

In the present invention, an elongation of 300 to 400[chi] of a composition containing a urethane bond-containing epoxy resin and a curing agent as main components is sufficient for making rubber molds of model tires. However, by adjusting the formulation, the elongation of thiocol resin was 7.
It is possible to set it to 1000% or more. Moreover, since the above composition has high opening stability, it does not require strict management unlike conventional compositions, and maintenance can be simplified. Although it has good mold releasability from tires (rubber) and plaster, it may adhere to metal materials, so it is desirable to apply a mold release agent. but,
Since the amine does not volatilize even when vacuum suction is applied, there is no need to worry about pollution.

As the silicone resin used in the present invention, those generally used as rubber molding materials can be used. A typical example is an additive type deep-curing silicone resin that hardens uniformly inside the wall, such as silicone resin KE-1300 manufactured by Shin-Etsu Chemical. The performance of this resin is viscosity 1200 voise (25℃), pot life 90 minutes, curing time 24 hours (25℃), hardness 40
(A), strength 45 Kg/cm", elongation 300X, tear strength 20 Kg/cm (A, B).

Linear shrinkage rate 0. It is engineering χ.

This silicone resin is sensitively affected by the material of the surface it comes into contact with due to catalyst poison. In particular, when it comes into contact with tires, it is affected by metals, plasticizers, stabilizers, vulcanization accelerators, etc. contained in the tires. Therefore, during use, it is desirable to apply an acrylic paint or the like to the above-mentioned contact surface to prevent the influence of catalyst poison.

The urethane resin used in the present invention is physically more suitable as a tire mold original material than thiocol resins and silicone resins. Among them, urethane resins with improved molding shrinkage properties have recently been developed as casting resins, such as Quinnate manufactured by Nippon Zeon ■.
RA-60 is preferred. The characteristics of this urethane resin are:
Urethane prepolymer 52.5 to polyol 47.
It is a resin obtained by reacting at a mixing ratio (weight ratio) of 5, with a pot life of 7 to 10 minutes and a viscosity of 2 o voids or less (25°C).
, hardness 60(A), tensile strength 50Kg/cm2. Initial elastic modulus 10Kg/cm2. Elongation 270E, tear strength 3
0Kg/cm (B). Curing time is 2 at 60'c.
The curing shrinkage rate is about 0.1χ.

When using this urethane resin, please keep in mind that both the uncured urethane resin (base resin) and the curing agent dislike moisture, so they must be sealed with high-pressure nitrogen or stored with air removed. It is. If it is stored open for a long period of time, it will absorb moisture and foam, making it unusable for making molds. In addition, since urethane prepolymers can cause harm to humans, it is necessary to strictly control the work and pay attention to workability and safety.

Furthermore, when casting large capacity objects such as rubber molds,
Since a mixer with a large discharge rate will be used, when using urethane resin as a mold material, RIM
It is recommended to use a type of injection machine. Also, the mold of the assembly should be poured as quickly as possible.

Examples of the material used in the present invention that have fluidity and have rigidity after hardening include casting gypsum that is used in the production of ordinary tire molds. Specifically, αC
A plaster with a low drying shrinkage rate, which is made by adding a polymer emulsion to a mixture of a5O</CaO, and which has the ability to accurately transfer model dimensions and transfer a design of 3 to 20 μm is preferable.

〔Example〕

Conventional Example As a material that has fluidity and elasticity after curing, thiocol resin FMC (Flexible Mold C) manufactured by SmoothOn Corp.
A composition was prepared by blending 8 parts by weight of a curing agent with 100 parts by weight of 200 (abbreviation for "pound") and defoaming at 10° C. for 10 minutes.

Three partial full-size models were made using plaster, and as shown in FIG. 2, the composition was cast between the partial full-size models and the hack core, and immediately defoamed under vacuum. After being left at room temperature for one day to cure and harden, the mold was removed to prepare a rubber mold. A total of 24 plaster molds were made from the three rubber molds using casting plaster. It took 24 hours for the primary drying of the plaster mold.

Next, cut the plaster mold and assemble it to make a tire model.
Second drying time. Aluminum alloy casting was performed using the obtained tire model, and a mold was fabricated by removing firmness, sizing, and mechanical finishing. A tire was manufactured using this mold.

In this case, rubber molding and plaster molding are repeated, plaster molding is duplicated, and the necessary parts are cut and assembled into the tire model, so it takes an extremely long time to make the mold, and the model It took 45 days from production to completion of the tire.

In addition, it was difficult to cut and assemble the complicated plaster molds without skill. Furthermore, the lifespan of the rubber mold is only about 10 days, making it impossible to reuse it.

Example 1 The composition shown in the table was prepared as a material having fluidity and elasticity after curing, and after defoaming and mixing at 40°C for 30 minutes, it was cast into the assembly shown in Figure 1, and I took a look at my body shape. That is, the composition was poured into the mold 7 to have an average thickness of 50 mm, and after being degassed in vacuum for 30 minutes, the pressure was returned to normal and left for 20 minutes. The composition in the mold is approx.
Time held its fluidity. Then at 80℃ for 24
After curing for a period of time, the mold was removed and a rubber mold was prepared. A bubble-free rubber mold with high transfer accuracy was obtained. I turned the model tire over and made a rubber mold in the same way again.

The entire tire obtained was molded using two rubber molds, and then a plaster cast was made using casting plaster, and the tire was heated and dried for 24 hours. Next, an aluminum alloy was cast on this plaster tire model, and a mold was fabricated by performing firming, sizing, and mechanical finishing. A tire was molded using this mold.

The number of days required from manufacturing the model tire to completing the tire was 10 days. Additionally, the process of cutting and assembling plaster molds could be omitted, and the plaster only needed to be dried once, resulting in a significant reduction in man-hours. Furthermore, the comb type had good dimensional stability and could be used repeatedly and stored.

In the above table, urethane bond-containing epoxy resin A has a molecular weight of 20.
00 polypropylene glycol and tolylene diisocyanate with an epoxy equivalent weight of 1250, urethane bond-containing epoxy resin B is a resin with an epoxy equivalent weight of 720 using polytetramethylene glycol with a molecular weight of 850 and isophorone diisocyanate, and bisphenol A. The type epoxy resin (ELA1) B) manufactured by Jumen Kagaku ■ is a mixture of bisphenol A type epoxy resin and monoepoxide, the antifoaming agent is 070 manufactured by BYK Hiemi, and the curing agent is 1 mol of 1,3-bisaminomethylcyclohexane and phenyl. The reaction product with 1 mole of glycidyl ether, the colorant, is Pipalast Green 8ON. Moreover, the blending amount is in parts by weight.

Example 2 A mold was manufactured according to Example 1, and a tire was manufactured using this mold.

However, as a material that has fluidity and elasticity after curing,
Silicone resin manufactured by Shin-Etsu Chemical (product name KE-1300)
)It was used. The blending ratio of this resin and curing agent is resin 100.
In contrast, a hardening agent of 10 was used, and both were degassed and mixed at 20° C. for 10 minutes. Additionally, when injecting into the assembly, a thin layer of acrylic paint was applied to the surface of the model tire to prevent catalyst poisoning, and the top surface of the bank core made of styrofoam hardened with plaster was opened. The average filling thickness of the composition is 10-12
It was made to be about mm.

The number of days required from manufacturing the model tire to completing the tire was 10 days. The obtained rubber mold had good transferability and molding accuracy.

Example 3 A mold was manufactured according to Example 1, and a tire was manufactured using this mold.

However, as a material that has fluidity and elasticity after curing,
Urethane resin manufactured by Nippon Zeon (product name Quinnat)
e RA-60) was used. The blending ratio of this resin and curing agent was 52.5% of the resin and 47.5% of the curing agent, and the mixture was quickly mixed and then cast.

The number of days required from manufacturing the model tire to completing the tire was 10 days. The obtained rubber mold had good transferability and molding accuracy.

Comparative Example A mold was manufactured according to Example 1, and a tire was manufactured using this mold.

However, as a material that has fluidity and elasticity after curing,
A composition containing the thiocol resin as the main component used in the conventional example was used. The top surface of the bank core made of Styrofoam plastered with plaster was left open. The filling thickness of the composition was adjusted to be about 10 to 12 mm on average.

The number of days required from manufacturing the model tire to completing the tire was 10 days. Although the rubber mold was reinforced with a hack core, the surface of the mold began to warp within 10 days after demolding, and the dimensional accuracy deteriorated, making it unusable as a rubber mold.

〔Effect of the invention〕

According to the present invention, a material that has fluidity and has rubber-like elasticity after curing is cast into a tire prototype, and is cured to produce a rubber mold. After creating a tire model by casting and curing a rigid material, a tire molding mold is created from this tire model, and the resulting mold is used to manufacture tires, so the mold manufacturing process The tire development period can be significantly shortened.

[Brief explanation of the drawing]

Fig. 1 is a half-sectional explanatory view showing an example of an assembly used for making a rubber impression of a model tire of the present invention, Fig. 2 is a perspective view of an assembly for making a rubber impression from a conventional partial full-size model, and Fig. 3 is a perspective view of a tire model assembled from a plurality of plaster molds. 1...Model tire, 3...Outer wall board, 4,4'...
・Mold material filling part, 8...Center fastener, 9・
...Tire stand, 10...Bottom plate.

Claims (10)

[Claims] (1) A material that has fluidity and rubber-like elasticity after curing is poured into a tire prototype, and is cured to produce a mold prototype, and then the mold prototype has fluidity and rigidity after curing. A method for manufacturing a pneumatic tire, comprising: casting a material and curing it to produce a tire model; then producing a tire mold from the tire model; and using the obtained tire mold. (2) The method for manufacturing a pneumatic tire according to claim (1), wherein the material having fluidity and having rubber-like elasticity after curing is a composition containing an urethane bond-containing epoxy resin and a curing agent as main components. (3) The method for manufacturing a pneumatic tire according to claim (1), wherein the material having fluidity and rigidity after hardening is gypsum. (4) The method for manufacturing a pneumatic tire according to claim 1, wherein the material has fluidity and rubber-like elasticity after curing and has a shrinkage rate of less than 3% after molding. (5) Claim (1) wherein the material that has fluidity and has rubber-like elasticity after curing is a silicone resin or a urethane resin.
The method of manufacturing the pneumatic tire described. (6) Urethane bond-containing epoxy resin has an epoxy equivalent of 5
The method for manufacturing a pneumatic tire according to claim 2, wherein the epoxy resin has a urethane bond at a position adjacent to a terminal oxirane ring of 00 to 2000. (7) The method for manufacturing a pneumatic tire according to claim (2), wherein the curing agent is an amine compound. (8) The method for manufacturing a pneumatic tire according to claim (2), wherein the curing agent is a reaction product of substantially equivalent amounts of a tetrafunctional amine and a glycidyl ether. (9) The air according to claim (8), wherein the tetrafunctional amine is at least one selected from the group consisting of 1,3-bisaminomethylcyclohexane, isophorone diamine, 1,6-hexane diamine, and trimethylhexamethylene diamine. A method of manufacturing tires. (10) The method for manufacturing a pneumatic tire according to claim (8), wherein the glycidyl ether is at least one selected from the group consisting of phenyl glycidyl ether and butyl glycidyl ether.