JP5888206B2 - Method for forming irregularities on the rubber surface - Google Patents

Description

  The present invention relates to a method for forming a stamp, a pattern, or a specific pattern shape on a rubber surface, and particularly relates to a method for precisely forming unevenness with a fine height or a complicated pattern shape on a rubber surface.

In order to accurately form irregularities on the rubber surface, it is usually necessary to form a predetermined irregular shape on the surface of the mold, pressurize and fill the uncured rubber material in this, and cure the rubber material by heating etc. A method of transferring the uneven shape of the mold to the rubber surface is performed. In this case, it takes time to form a predetermined uneven shape on the mold, and a large mold manufacturing cost is required. Furthermore, it is necessary to produce a mold every time the uneven shape changes.
In order to improve this point, various methods have been proposed in which a plate having a concavo-convex shape is separately prepared, a plate is attached to a mold, and then a rubber material is filled and cured.

In Japanese Utility Model Laid-Open No. 58-66930, a removable engraving plate having a flange with a flat contact surface with a mold is mounted in a shallow groove with a step of the mold, and the inner surface of the mold and the plate are connected to each other. A rubber vulcanization mold having almost the same plane has been proposed. Japanese Patent Application Laid-Open No. 58-81149 proposes a method of vulcanizing unvulcanized rubber in a state in which a thin stamped plate with irregularities is in contact with the inner surface of a rubber ball vulcanizing mold. Japanese Patent Application Laid-Open No. 2004-98621 proposes a molding method in which a mark forming body cut into a mark shape is interposed between the surface of an unvulcanized rubber and a molding surface of a mold.
In these proposals, there are problems that it takes time and cost to produce a plate having a concavo-convex shape, and that a rubber material flows into an interface where the plate is attached to a mold at the time of molding, thereby generating burrs.
In order to solve the problem of burrs, in Japanese Utility Model Laid-Open No. 4-1263838, when a mark plate is attached to a mold, a rubber product molding is provided with a packing made of rubber or a synthetic resin material on the outer peripheral edge of the plate. Molds have been proposed.

  As a molding method that does not generate burrs, Japanese Patent Application Laid-Open No. 53-22578 discloses a method in which a porous plate provided with a large number of holes is placed on a sheet made of a rubber compound via a thermoplastic film, and is pressed and heated. Thus, a manufacturing method has been proposed in which hemispherical protrusions are formed on a rubber sheet and then the thermoplastic film is peeled off. This method has a drawback that the shape of the rubber hemispherical protrusion cannot be accurately formed.

  As a method for forming irregularities on the rubber surface without using a metal mold, Japanese Patent Publication No. 33-6489 discloses a paper plate, a fabric or a metal foil plate on which an irregular pattern is formed together with a rubber sheet, A manufacturing method has been proposed in which the mold plate is removed after vulcanization. In this method, it is difficult to adjust the height of the unevenness on the rubber surface, and there is a problem that the rubber bites into the unevenness of the template and the vulcanized rubber and the template are exfoliated.

  Japanese Patent Application Laid-Open No. 2004-351836 discloses an uneven forming member selected from a wire net, punching metal, fiber net, etc. on one side of a sheet made of a polymer material such as a thermoplastic elastomer or a rubber composition. There has been proposed a method of forming irregularities on a sheet material by placing the molds on top of each other, pressurizing and heating them, and then removing the irregularity forming member and the sheet-like mold release body. This method has the disadvantage that it is difficult to adjust the height of the irregularities on the rubber surface and that only simple irregularities can be provided.

Japanese Utility Model Publication No. 58-66930 JP 58-81149 A JP 2004-98621 A Japanese Utility Model Publication No. 4-12638 JP-A-53-22578 Japanese Patent Publication No.33-6489 JP 2004-351836 A

  The present invention has been made in view of the above circumstances, and it is possible to form precise unevenness on the rubber surface at low cost without producing a mold or a plate having an uneven shape, and the unevenness can be formed without generating burrs. It is an object of the present invention to provide a method for forming irregularities on a rubber surface that can be formed, can adjust irregularities with a fine height, and can further form irregularities with complicated pattern shapes.

  As a means for achieving the above object, the present inventors installed an unevenness forming film processed into a predetermined shape through a release film having a thickness in the range of 5 to 150 μm on the uncured rubber surface. It was found that the method of forming irregularities on the rubber surface by pressing the plate with a plate-like material having a flat surface, curing the rubber, and peeling the irregularity-forming film from the release film is effective. Invented the invention.

That is, this invention provides the method of forming an unevenness | corrugation on the following rubber | gum surface.
[1]
After coating the release film with a coating solution prepared by dissolving and diluting the rubber material in an organic solvent, the organic solvent is volatilized to produce an uncured rubber sheet, and then thickened on the uncured rubber surface. An unevenness forming film processed into a predetermined shape through a release film having a thickness of 5 to 150 μm is placed, and they are pressed with a plate-like material having a flat surface, and the uncured rubber surface is subjected to the above A method of forming irregularities on the rubber surface by transferring irregularities corresponding to the shape of the irregularity-forming film, then curing the uncured rubber, and peeling the irregularity-forming film and the release film.
[2]
The unevenness forming film is a flat film in which a portion where the rubber surface is a convex portion is formed as a through hole portion having a shape corresponding to the convex portion, and a portion which is a concave portion is a region other than the through hole portion. The method for forming irregularities on the rubber surface as described in [1].
[3]
The method for forming unevenness on the rubber surface according to [1] or [2], wherein the unevenness forming film is formed of a resin film, a metal foil or a composite film thereof.
[4]
The method for forming irregularities on the rubber surface according to any one of [1] to [3], wherein the thickness of the irregularity-forming film is 1 mm or less.
[5]
The method for forming irregularities on the rubber surface according to any one of [1] to [4], wherein the irregularity-forming film is processed into a predetermined shape by punching.
[6]
The method for forming irregularities on the rubber surface according to any one of [1] to [4], wherein the irregularity-forming film is processed into a predetermined shape by a cutting plotter.
[7]
The method for forming irregularities on the rubber surface according to any one of [1] to [6], wherein the release film is a heat-resistant and flexible resin film.
[8]
The method for forming irregularities on the rubber surface according to any one of [1] to [7], wherein the release film is subjected to silicone treatment or fluorine treatment.
[9]
An uncured rubber, a release film, a concavo-convex film, and a plate-like material having a flat surface are sequentially laminated, and then a hot press molding machine is used for the step of pressurizing and thermosetting the rubber [1. ] The method of forming an unevenness | corrugation in the rubber surface in any one of [8].

  Since the method for forming fine irregularities on the rubber surface of the present invention does not require the production of a mold or a plate having an irregular shape, an irregularity-forming film can be produced with a relatively short delivery time and at a low cost. It is possible to precisely adjust the height of the unevenness and form unevenness with a complicated pattern shape.

It is sectional drawing which shows an example of the uneven | corrugated formation method which concerns on this invention, (A) is a member structure, (B) is a member lamination process, (C) is a process and rubber curing process, (D) is the obtained uneven | corrugated rubber | gum. Indicates. It is the top view which showed the shape of the uneven | corrugated formation film used in Examples 1-4 and Comparative Examples 1 and 2. FIG. It is the top view which showed the shape of the uneven | corrugated formation film used in Examples 5-8 and Comparative Example 3. FIG.

  As shown in FIG. 1, the method for forming precise unevenness on the rubber surface according to the present invention is such that the release film 2 is laminated on the surface of the uncured rubber 1, and the unevenness forming film 3 is laminated thereon. In this state, the plate-like material 4 having a flat surface is pressed from above the unevenness-forming film 3 [see (A), (B)]. As a result, as shown in FIG. 1 (C), unevenness corresponding to the shape of the unevenness forming film 3 is transferred and formed on the surface of the uncured rubber 1, and the uncured rubber 1 is cured in this state. After the rubber is cured, the concavo-convex-forming film 3 and the release film 2 are peeled off to obtain a cured rubber 1 ′ having concavo-convex formed on the surface as shown in FIG.

  Here, the rubber material in the present invention may be a general material. Specifically, silicone rubber (Q), acrylic rubber (ACM), nitrile rubber (NBR), isoprene rubber (IR), urethane rubber (U ), Ethylene propylene rubber (EPM, EPDM), chlorosulfonated polyethylene (CSM), epichlorohydrin rubber (CO, ECO), chloroprene rubber (CR), styrene-butadiene rubber (SBR), butadiene rubber (BR), fluoro rubber ( FKM), butyl rubber (IIR), etc., can be variously selected according to characteristics and applications.

  As the curing agent for the rubber material, those usually used for the respective rubber materials may be used. If a curing agent that accelerates curing by heat is used, the molding cycle can be increased.

For example, in the case of silicone rubber, a filler, particularly reinforcing silica, can be used for the organopolysiloxane. In this case, the organopolysiloxane has the following average composition formula (1):
R _n SiO _{(4-n) / 2} (1)
(N is a positive number from 1.95 to 2.05)
In the formula, R is unsubstituted or substituted, preferably represents a monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 8 carbon atoms, specifically a methyl group, an ethyl group, a propyl group, or the like. Alkyl groups such as alkyl groups, cyclopentyl groups and cyclohexyl groups, alkenyl groups such as vinyl groups and allyl groups, aryl groups such as phenyl groups and tolyl groups, or hydrogen atoms thereof are partially chlorine atoms, fluorine atoms, etc. Substituted halogenated hydrocarbon groups and the like are exemplified. Generally, the main chain of the organopolysiloxane is composed of dimethylsiloxane units, or the main chain of the organopolysiloxane is vinyl, phenyl, trifluoro. What introduced the propyl group etc. is preferable. The molecular chain terminal may be blocked with a triorganosilyl group or a hydroxyl group. Examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group, and a trivinylsilyl group.

  This organopolysiloxane preferably has an alkenyl group bonded to at least two silicon atoms in one molecule, and 0.001 to 5 mol%, particularly 0.01 to 1 mol% of vinyl groups in R. It is preferable to contain.

Reinforcing silica is intended to be formulated in order to obtain a good silicone rubber in mechanical strength, BET method specific surface area of 50 m ² / g or more, particularly preferably 100 to 400 m ² / g. Examples of the reinforcing silica include fumed silica (dry silica) and precipitated silica (wet silica). Further, the surface of the reinforcing silica may be hydrophobized with organopolysiloxane, organosilazane, chlorosilane, alkoxysilane, or the like.

  The amount of the reinforcing silica added is not particularly limited, but if it is less than 5 parts by mass relative to 100 parts by mass of the organopolysiloxane, a sufficient reinforcing effect may not be obtained. Since moldability may deteriorate, the range is 5 to 100 parts by mass, preferably 20 to 80 parts by mass.

  In addition to reinforcing silica, this silicone rubber composition includes thermally conductive fillers such as alumina, aluminum hydroxide and boron nitride, conductive fillers such as carbon black and silver powder, fillers such as color pigments, heat resistance improvers, Add various additives such as flame retardant improver, acid acceptor, fluorine mold release agent, reinforcing silica dispersant, various alkoxysilanes, diphenylsilanediol, carbon functional silane, silanol group-containing siloxane, etc. May be.

  The curing agent that cures the silicone rubber composition to form a rubber elastic body may be a conventionally known one that is usually used for curing the silicone rubber composition, which is di-t-butyl used for radical reaction. When the organopolysiloxane has an alkenyl group as an organic peroxide such as peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, or addition reaction curing agent, When the organopolysiloxane contains a silanol group as a condensation reaction curing agent, consisting of an organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to a silicon atom in one molecule and a platinum group metal catalyst, Organic having two or more hydrolyzable groups such as alkoxy group, acetoxy group, ketoxime group, propenoxy group Although Lee-containing compound and the like, the amount of the curing agent may be the same as ordinary silicone rubber compositions.

  The release film in the present invention is a heat-resistant and flexible resin film, specifically, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyetherimide (PEI). Characteristics from polyethylene naphthalate (PEN), poly-4-methylpentene-1 (PMP), polyethylene sulfide (PPS), polyimide (PI), polyetheretherketone (PEEK), fluororesin (PTFE, FEP, PFA), etc. Various selections can be made according to Among these, polyethylene terephthalate (PET) is suitable because it is relatively inexpensive and easily available in various thicknesses.

  If the thickness of the release film is less than 5 μm, the strength of the film may be insufficient and may break when forming irregularities. If the thickness exceeds 150 μm, the shape of the irregularity-formed film cannot be successfully transferred to the rubber surface, so the range is from 5 to 150 μm. , Preferably in the range of 10-100 μm, especially 10-80 μm.

  Furthermore, the surface of the release film that comes into contact with the rubber is treated with silicone or fluorine to improve the release property between the rubber and the film, and the fine film on the cured rubber surface has a defect that can be removed by the release film. Can be prevented.

  The unevenness-forming film in the present invention is a heat-resistant sheet-like material selected from a resin film, a metal foil, and a composite film thereof. Specifically, the resin film is the same material as the release film. Examples of the metal foil include aluminum foil, copper foil, and stainless steel foil. Among these, the resin film is excellent in that it is easy to process and is less likely to be wrinkled by bending.

  Here, as shown in FIG. 1 (A), as the unevenness forming film, a portion where the rubber surface is a convex portion is formed as a through-hole portion 11 having a shape corresponding to the convex portion, and the rubber surface is What was formed in the flat film shape from which the part used as a recessed part becomes the area | region (land part) 12 other than the said through-hole part 11 can be used. In this case, the shape of the through-hole part 11 should just respond | correspond to the convex part shape which should be formed in the rubber | gum surface, for example, in the example of the uneven | corrugated film shown in FIG. In the shape of the ring-shaped long hole, the example of the unevenness forming film shown in FIG. 3, the through-hole portion 11 has a circular hole shape.

  In this invention, the rubber | gum surface corresponding to the land part 12 which an unevenness | corrugation formation film contact | abuts via a release film becomes a concave surface, and the height of an unevenness | corrugation can be adjusted with the thickness of an unevenness formation film. The thickness of the concavo-convex film and the release film is related to the height of the concavo-convex formed on the rubber surface and the transfer accuracy.If a thin release film is used, the height of the concavo-convex is close to the thickness of the concavo-convex film, The shape of the uneven film is accurately transferred. On the contrary, when a thick release film is used, the height of the unevenness becomes smaller than the thickness of the unevenness forming film, and the shape of the transferred unevenness becomes unclear.

  The convex part on the rubber surface is formed by the mold release film being deformed and entering together with the rubber at the cutout part (through hole part) of the concave-convex forming film. When the thickness of the concavo-convex film is increased, the release film cannot follow the concavo-convex film, and there is a risk that the concavo-convex edge portion of the rubber surface cannot be formed cleanly. In order to form the uneven edge portion neatly, the thickness of the unevenness forming film should be thin, preferably 1 mm or less, more preferably 0.5 mm or less, still more preferably 150 μm or less, particularly 80 μm or less. is there. The thickness is preferably 10 μm or more.

  As a method of processing the concavo-convex film into a predetermined shape, a method using a punching die is the simplest and inexpensive. For die cutting, a type with a steel blade embedded in a plywood or resin plate called Thomson type or Bic type, and a blade (corrosion blade) are formed by etching a metal called pinnacle type, and the cutting edge is sharpened There is a type. The Thomson type is fast and relatively inexpensive, and the Pinnacle type has excellent punching accuracy.

  As another method for processing the concavo-convex film, there is a method using a cutting plotter. The cutting plotter is almost the same as the pen-type plotter in terms of equipment, but a sharp knife is attached instead of the pen, and the film can be cut into an arbitrary shape. A complicated pattern shape can be produced from CAD data or the like in a short time, and the introduction of the apparatus is expensive. However, it is not necessary to produce a mold for each pattern shape as in the case of die cutting.

  As a method of forming precise unevenness on the rubber surface of the present invention, an unevenness-forming film processed into a predetermined shape via a release film is installed on the surface of an uncured rubber sheet to which a curing agent is added, Achieved by pressurizing with a plate material with a flat surface to transfer the pattern shape of the concavo-convex film to the rubber surface through the release film, curing the rubber, and peeling the concavo-convex film from the release film Is done. Since there is a release film between the rubber material and the concavo-convex film, no burrs are generated, and the concavo-convex film can be used multiple times.

  In addition, an uncured rubber sheet, a release film, a concavo-convex forming film, and a plate-like material having a flat surface are sequentially laminated, and then a pressure and temperature are applied using a hot press molding machine in the process of pressurizing and thermosetting. By adjusting, irregularities can be formed on the rubber surface accurately in a short time.

  In order to dispense uncured rubber to a certain thickness, a two-roll or calendar roll is usually used. Furthermore, in order to dispense the rubber thinly, an uncured rubber is prepared by coating the release film with a coating solution prepared by dissolving and diluting an uncured rubber material in an organic solvent to a predetermined thickness, and then volatilizing the organic solvent. A sheet may be produced.

  As a plate-like material having a flat surface used in the molding of the present invention, a metal plate material such as iron, stainless steel, aluminum alloy or the like having a thickness of 2 mm or more is preferable. If the thickness is less than 2 mm, the strength is insufficient and the plate material may be deformed. Further, it is preferable to use a plate material having good flatness without warping or distortion, and polishing the surface to eliminate fine irregularities.

  When the metal plate and rubber are bonded together and the rubber surface is further uneven, a primer suitable for each rubber material is applied to the metal plate, and then the uncured rubber component to which a curing agent is added is sequentially applied. Adhesion of metal plate and rubber by setting plate material such as feeding sheet, release film, concavo-convex forming film, stainless steel plate, etc., then applying pressure and temperature using a hot press molding machine to cure the rubber In addition, it is possible to simultaneously form irregularities on the rubber surface.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited by these Examples.

[Examples 1 to 4, Comparative Examples 1 and 2]
An organopolysiloxane (composition: methylvinylpolysiloxane having an average degree of polymerization of 8,000 consisting of 99.85 mol% of dimethylsiloxane units and 0.15 mol% of methylvinylsiloxane units) is added to reinforcing silica Aerosil200 [trade name] , Nippon Aerosil Co., Ltd.] 20 parts by mass, spherical alumina Admafine A041R [trade name, manufactured by Admatex Co., Ltd.] 250 parts by mass, organic peroxide 2,5-dimethyl-2,5- 300 parts by mass of toluene is added to a thermally conductive silicone rubber composition containing 1 part by mass of di (t-butylperoxy) hexane, and the mixture is uniformly dissolved with a homogenizer, and then filtered through a 400 mesh wire mesh for coating. A liquid was prepared. After coating this coating solution on a release film made of fluorine-treated polyethylene terephthalate (PET) with the thickness shown in Table 1, with a bar coat, toluene is volatilized in a heating oven at 60 ° C. A silicone rubber sheet was prepared.

  Next, a polyethylene terephthalate film having the thickness shown in Table 1 was punched into a shape shown in FIG.

  2 is installed on the release film side of an uncured silicone rubber sheet having a thickness of 300 μm, and a polyethylene terephthalate film having a thickness of 100 μm is installed on the silicone rubber sheet side as a process film. It was sandwiched between stainless steel plates with a thickness of 3 mm. Next, after the silicone rubber is cured by pressurizing and heating for 10 minutes under the conditions of a pressure of 5 MPa and a temperature of 160 ° C. using a 50-ton hot press molding machine, the concavo-convex film, release film and process film are peeled off. Thus, irregularities were formed on the surface of the silicone rubber.

  Table 1 shows the measurement results of the depth of the unevenness and the width of the recessed portions at the locations A to D, and the sharpness of the uneven shape of each silicone rubber sheet on which the unevenness was formed.

比較例１及び２は凹凸形状のエッジ部が不鮮明のため、箇所Ａ〜Ｄの凹部の幅を測定できない。

In Comparative Examples 1 and 2, since the uneven-shaped edge portion is unclear, the width of the recesses in the locations A to D cannot be measured.

[ Reference Examples 1 to 4 , Comparative Example 3]
Silicone rubber compound KE-951-U [trade name, manufactured by Shin-Etsu Chemical Co., Ltd.] containing reinforcing silica and 100 parts by mass of organic peroxide paste C-8 [trade name, Shin-Etsu Chemical Co., Ltd.] [Product] 2 parts by mass were added, kneaded with two rolls, and then dispensed to a thickness of 2.1 mm to prepare an uncured silicone rubber sheet.

  Silicone-modified ethylene propylene rubber (EPDM) SEP-1411-U [trade name, manufactured by Shin-Etsu Chemical Co., Ltd.] 100 parts by weight of organic peroxide paste C-11 [trade name, Shin-Etsu Chemical Co., Ltd.] Manufactured] After adding 2 parts by mass and kneading with two rolls, it was dispensed to a thickness of 2.1 mm to prepare an uncured silicone-modified ethylene propylene rubber sheet.

  Next, a polyethylene terephthalate film having a thickness of 50 μm was cut into the shape shown in FIG. 3 using a cutting plotter to produce a concavo-convex film. The shape of FIG. 3 has many φ3 mm holes and the distance between the holes is short, so that the Thomson mold itself cannot be produced.

  Opulan X-88B [trade name, manufactured by Mitsui Chemicals, Inc., Cello Co., Ltd.], which is a film of poly-4-methylpentene-1 (PMP) having a thickness of 50 μm, as a release film on one side of each uncured silicone rubber sheet, 3 were sequentially stacked on top of each other, placed in a stainless steel frame plate having a thickness of 2 mm, and sandwiched between two stainless steel plates having a thickness of 3 mm. Next, the rubber is cured by pressurizing and heating for 10 minutes under the conditions of a pressure of 5 MPa and a temperature of 160 ° C. using a 50-ton hot press molding machine, and then the concavo-convex film and the release film are peeled off. Unevenness was formed on the surface.

  Next, using the uncured silicone rubber sheet of KE-951-U [above], the Opulan X-88B [above] was placed on top of each other as two, three, and four sheets as a release film. Thereafter, irregularities were formed on the rubber surface by the same molding method.

  Table 2 shows the measurement results of the unevenness depth of each silicone rubber sheet on which the unevenness was formed, the diameter of the protrusion at the hole portion of φ3 mm, and the sharpness of the unevenness shape.

比較例３は凹凸形状のエッジ部が不鮮明のため、φ３ｍｍの穴箇所の凸部の径を測定できない。

In Comparative Example 3, since the concavo-convex edge portion is unclear, the diameter of the convex portion at the hole portion of φ3 mm cannot be measured.

DESCRIPTION OF SYMBOLS 1 Uncured rubber 1 'Cured rubber 2 Release film 3 Concavity and convexity formation film 4 Plate-shaped material 11 Through-hole part 12 Land part

Claims (9)

After coating the release film with a coating solution prepared by dissolving and diluting the rubber material in an organic solvent, the organic solvent is volatilized to produce an uncured rubber sheet, and then thickened on the uncured rubber surface. An unevenness forming film processed into a predetermined shape through a release film having a thickness of 5 to 150 μm is placed, and they are pressed with a plate-like material having a flat surface, and the uncured rubber surface is subjected to the above A method of forming irregularities on the rubber surface by transferring irregularities corresponding to the shape of the irregularity-forming film, then curing the uncured rubber, and peeling the irregularity-forming film and the release film.   The unevenness forming film is a flat film in which a portion where the rubber surface is a convex portion is formed as a through hole portion having a shape corresponding to the convex portion, and a portion which is a concave portion is a region other than the through hole portion. The method for forming irregularities on a rubber surface according to claim 1.   The method for forming irregularities on a rubber surface according to claim 1 or 2, wherein the irregularity-forming film is formed of a resin film, a metal foil or a composite film thereof.   The method for forming irregularities on a rubber surface according to any one of claims 1 to 3, wherein the thickness of the irregularity-forming film is 1 mm or less.   The method for forming irregularities on a rubber surface according to any one of claims 1 to 4, wherein the irregularity-forming film is processed into a predetermined shape by punching.   The method for forming irregularities on a rubber surface according to any one of claims 1 to 4, wherein the irregularity-forming film is processed into a predetermined shape by a cutting plotter.   The method for forming irregularities on a rubber surface according to any one of claims 1 to 6, wherein the release film is a heat-resistant and flexible resin film.   The method for forming irregularities on a rubber surface according to any one of claims 1 to 7, wherein the release film is subjected to silicone treatment or fluorine treatment.   A heat press molding machine is used for the step of laminating uncured rubber, a release film, a concavo-convex forming film, and a plate-like material having a flat surface in order, and then applying pressure to thermally cure the rubber. The method of forming an unevenness | corrugation in the rubber | gum surface of any one of 1-8.

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