JP2002283367A - Method for manufacturing silicone rubber sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a thin and large silicone rubber sheet having uniform thickness and a smooth outer surface free from minute unevenness. SOLUTION: A centrifugal molding machine equipped with a mold 11 is used and a liquid silicone rubber is injected in the mold 11 and cured along the inner peripheral surface of the mold 11 while rotating the mold 11 and a cylindrical silicone rubber object 21 is centrifugally formed so that the surface not being in contact with the mold of the silicone rubber becomes smooth by self-leveling and peeled from the inner peripheral surface of the mold 11 to be taken out of the mold and cut to manufacture a sheetlike silicone rubber sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicone rubber sheet, and more particularly to a method for producing a silicone rubber sheet having a smooth surface used as a blanket for precision printing or an intermediate transfer member for OA equipment. It is.

[0002]

2. Description of the Related Art Conventionally, silicone rubber has been used as a surface material of an intermediate transfer member of OA equipment and a blanket for offset printing of a fine pattern, etc., utilizing the property that its surface tension is small. It is desired to improve the thickness accuracy and to smooth the outer surface. Examples of the method for producing such a silicone sheet include a method using a coater, a method by casting, a method by extrusion, a method by casting, and a method by pressing.

For example, Japanese Patent Application Laid-Open No. 60-260308 discloses a method for producing a sheet having a uniform thickness, a small amount of entangled bubbles, and high transparency. That is, a thermosetting silicone rubber is injected and cured in a cylindrical mold to form a release surface, then a liquid elastomer is injected and centrifugally formed, only the elastomer is peeled and taken out, and cut into a sheet to produce a sheet. A method has been proposed.

[0004]

However, in any method such as the above-mentioned method using a coater,
It is difficult to produce a thin, uniform and smooth sheet. Also, since more silicone rubber than necessary must be injected, the loss of rubber is large. Furthermore, it is difficult to produce a material having a small surface roughness, and there is also a problem that bubbles may enter the sheet depending on the production method.
In particular, in recent years, the demand for a large-sized silicone sheet has increased with the increase in size of a machine. However, when a large sheet is manufactured, problems such as a large amount of energy required for heating are noticeable.

Further, in the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 60-260308, since a silicone rubber is used as a release layer and a urethane sheet on the release layer is taken out, only the silicone rubber layer is taken out of the mold and transferred. Cannot be used on the body. In addition, since the sheet is formed as a two-layer structure of the release layer and the sheet layer, it takes time and effort to inject the material to be centrifugally molded into the mold in two separate steps and to cure by centrifugation. In addition, since the release layer cannot be used as a product, productivity is deteriorated. Further, there is a problem that the surface roughness is large.

The present invention has been made in view of the above-mentioned problems, and it is possible to obtain a silicone rubber sheet which is large, thin and uniform, and has a smooth outer surface without fine irregularities. It is another object of the present invention to provide a method for producing a silicone rubber sheet that makes the production process efficient.

[0007]

In order to solve the above-mentioned problems, the present invention uses a centrifugal molding machine equipped with a mold, injects liquid silicone rubber into the mold, and rotates the mold while rotating the mold. Along the inner peripheral surface of the mold, the liquid silicone rubber is cured, and the cylindrical silicone rubber body is centrifugally formed so that the surface not in contact with the mold is smoothed by self-leveling. The present invention provides a method for producing a silicone rubber sheet, wherein the silicone rubber body is cut into a sheet shape after the rubber body is peeled and taken out from the inner peripheral surface of the mold.

As described above, since the surface not in contact with the mold is centrifugally molded so as to be smooth by self-leveling, the inner peripheral surface of the cylindrical silicone rubber body can be smoothed, When the body is cut into a sheet, at least one surface of the sheet can be smoothed. Further, the thickness can be made uniform by the self-leveling action. That is, according to the production method of the present invention, regardless of the surface roughness of the mold, it is possible to produce a silicone rubber sheet having a very smooth surface without minute irregularities and a uniform thickness. Also, since only silicone rubber is formed by centrifugal molding, it can be manufactured accurately and easily.

As the liquid silicone rubber to be injected into the mold, RTV (room temperature curing type), LTV (heat curing type) and the like can be mentioned, and either one liquid type or two liquid type can be used. Can be.

Prior to injecting the liquid silicone rubber into the mold, a material of the same or different type as the liquid silicone rubber is injected into the mold, and the material is rotated along the inner peripheral surface of the mold while rotating the mold. Then, after the substrate made of the above material is centrifugally molded as an outer layer, the silicone rubber body can be centrifugally molded as an inner layer along the inner peripheral surface of the outer layer made of the above substrate. In this way, the silicone rubber sheet to be manufactured has a two-layer structure of an inner layer made of a silicone rubber body and an outer layer made of a base material of the same or different material as the liquid silicone rubber. Strength can be improved.

The same kind of material means a material used as the above-mentioned liquid silicone rubber, and the same liquid silicone rubber as that forming the silicone rubber body may be used. The different kind of material means a rubber or resin other than the above liquid silicone rubber, and includes a thermosetting resin, a thermoplastic resin, a thermoplastic elastomer, a known rubber component, and a mixture thereof. Among them, a thermosetting resin is preferable, and a polyimide resin and a polyamideimide resin are particularly preferable because of excellent heat resistance. In addition, a polyurethane resin, a polybenzimidazole resin, or the like can be used.

When a substrate made of the same or a different material as the liquid silicone rubber is provided as an outer layer, it is preferable to apply a primer to the inner peripheral surface of the substrate after molding the substrate. Thereby, the adhesion between the inner layer made of the silicone rubber body and the outer layer made of the base material of the same or different material as the liquid silicone rubber can be improved. As the primer, a commercially available primer for silicone rubber can be used. For example, Shin-Etsu Chemical Co., Ltd.
"Primer A", "Primer T" and the like can be mentioned.
In order to provide the base material, the base material may be formed by centrifugal molding as described above, or the liquid silicone rubber may be integrally formed by placing the film-shaped material in close contact with a mold in advance. It may be molded.

The viscosity of the liquid silicone rubber before curing is 1 P or more and 1000 P or less at room temperature. Thereby, a sheet having a uniform thickness can be accurately manufactured. The reason for setting the above range is that if the viscosity is more than 1000P, there is a problem that the fluidity of the rubber during centrifugation becomes poor and a uniform belt cannot be obtained. Although the lower limit of the viscosity is 1P, the lower the viscosity, the more preferable.

In the liquid silicone rubber, if necessary,
The viscosity can be adjusted by adding a solvent and a viscosity modifier. As the solvent, an organic solvent such as xylene, toluene, and benzene can be used. Silicone oil or the like can be used as the viscosity modifier. Further, a filler such as silica may be mixed if necessary. Further, a curing agent is indispensable, and the curing agent is mixed into the liquid silicone rubber and then injected into a mold.

According to the production method of the present invention, the thickness of the silicone rubber body is 0.01 mm or more and 3 mm or less, preferably 0.05 mm or more and 2 mm or less, depending on the rotational speed of the mold, the viscosity of the silicone rubber, and the like. More preferably 0.1
A silicone rubber sheet having a thickness of 1 mm or more and 1 mm or less can be suitably manufactured. By calculating the required amount of the liquid silicone rubber and injecting it into the mold, the thickness can be easily controlled, which is particularly suitable for the production of a thin silicone rubber sheet. Further, since the sheet is formed by centrifugal molding, even a large sheet can be accurately and uniformly formed.

As a method of centrifugal molding, first, a silicone rubber layer is formed uniformly while rotating the mold at room temperature for a certain period of time, and then the silicone rubber layer is cured by heating and rotating the mold to form a silicone rubber layer. It is preferable to get a body. As described above, a sheet having a uniform thickness can be obtained by performing centrifugal molding while changing the temperature stepwise. Further, the rubber can be efficiently cured by heating during rotation.

If the rotation speed during rotation is too low, a uniform layer may not be produced due to dripping of the liquid silicone rubber, and therefore, a uniform silicone may be formed according to the viscosity of the liquid silicone rubber before curing. It is preferable that the rotation speed is set to an appropriate value at which a rubber body can be produced. Specifically, 5
rpm or more and 3000 rpm or less, preferably 100 rpm
m and 2500 rpm or less. The reason for setting the above range is that if the number of rotations is smaller than the above range, a uniform sheet cannot be produced due to the dripping of the silicone rubber. This is because there is a problem that it becomes difficult. The rotation of the mold may be started after injecting the liquid silicone rubber, or the mold may be rotated (during rotation).
Liquid silicone rubber may be injected into the liquid.

The temperature at the time of rotation can be appropriately set to an appropriate temperature for curing depending on the type of the silicone rubber and the like.
C. or lower, preferably 40 ° C. or higher and 120 ° C. or lower. The reason why the above range is set is that if the temperature is lower than the above range, it takes time to cure the silicone rubber, and if the temperature is higher than the above range, the silicone rubber deteriorates or it takes time to cool down. Because there is. Further, it is desirable that the temperature be raised after a certain time has elapsed after the liquid silicone rubber has been injected and rotated. This is because if the temperature is increased immediately after the rotation, the silicone rubber may be cured before it becomes a silicone rubber having a uniform thickness.

The rotation time of the mold can be appropriately set according to the type and temperature of the silicone rubber, but specifically, 5 minutes or more and 6 hours or less, preferably 10 minutes or less.
It is preferable to set the time between minutes and 3 hours. The reason for setting the above range is that if the rotation time is shorter than the above range, molding of the silicone rubber body is insufficient, and if the rotation time is longer than the above range, the performance after molding is not affected. .
In addition, when centrifugal molding is performed by changing the temperature stepwise,
The rotation time at room temperature is preferably from 3 minutes to 2 hours, and the rotation time while heating is preferably from 5 minutes to 6 hours.

When the centrifugally formed silicone rubber body is cut, the cutting position, cutting direction, number of cuts and the like can be appropriately set according to the size of the silicone rubber sheet to be produced. In order to obtain one large sheet, it is preferable to cut in the depth direction.

The required amount of liquid silicone rubber to be injected into the mold can be calculated from the size of the mold of the centrifugal molding machine to be used and the required thickness of the silicone rubber body. There is no need to use silicone rubber, which improves productivity and is advantageous in cost.

According to the method for producing a silicone rubber sheet of the present invention, it is possible to provide a silicone rubber sheet which is large, thin and uniform, and has a smooth outer surface without fine irregularities. As a result, a large and thin silicone rubber sheet having the above-mentioned excellent properties can be easily obtained, and can be suitably used as a precision printing-like blanket, a surface material of an intermediate transfer body of OA equipment, and the like.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a silicone rubber sheet 20 produced by the method for producing a silicone rubber sheet according to the first embodiment of the present invention.

Hereinafter, a method of manufacturing the silicone rubber sheet 20 using the centrifugal molding machine 10 shown in FIG. 2 will be described. First, a solvent, a diluent, and a curing agent are added to the liquid silicone rubber (RTV) as necessary, and the viscosity is adjusted to 50P to prepare a silicone rubber solution. Next, the required amount of liquid silicone rubber is calculated from the size of the mold 11 of the centrifugal molding machine 10 and the required thickness of the belt, and the liquid silicone rubber is injected into the cylindrical mold 11 of the centrifugal molding machine 10. . After the injection, while rotating the mold 11 at a constant rotation speed of 1500 rpm for 0.5 hour at room temperature, the inner peripheral surface 11 of the mold 11 is rotated.
a, the cylindrical silicone rubber body 2 is formed so that the surface not in contact with the mold 11 becomes smooth by self-leveling.
After the temporary molding of No. 1, the temperature was further raised to 40 ° C., and the mold 11 was centrifugally formed for 5 hours while rotating to completely cure the mold. Thus, as shown in FIGS. 3A and 3B, a cylindrical silicone rubber body 21 in which the inner peripheral surface 21a not touching the mold 11 is smoothed by self-leveling is obtained.

After the cylindrical silicone rubber body 21 is peeled off from the mold 11 and taken out, as shown in FIGS. 4A, 4B and 4C, in the depth direction (along the dotted line in the figure). The silicone rubber body 21 is cut to obtain a silicone rubber sheet 20. The silicone rubber sheet 20 has an inner peripheral surface 21a smoothed by self-leveling of a cylindrical silicone rubber body 21 as a front side, and an outer peripheral surface 21b of the silicone rubber body 21 as a back side, and has a uniform thickness by self-leveling. I have. As described above, by using the inner peripheral surface 21a not in contact with the mold 11 as the surface (use surface) of the silicone rubber sheet 20, the silicone rubber sheet is used as a printing blanket or the like that requires a uniform thickness and a smooth surface. Sheet 20 can be used.

The size of the mold 11 of the centrifugal molding machine 10 is 30 cm in diameter × 40 cm in depth. Therefore, the obtained silicone rubber sheet 20 has a width of 40 cm.
× about 90 cm.

Next, a method for manufacturing the silicone rubber sheet 30 of the second embodiment will be described. FIGS. 5A and 5B show a silicone rubber sheet 30 produced by the method for producing a silicone rubber sheet of the second embodiment.

First, the polyimide resin solution is adjusted to a viscosity of 10 P, poured into a cylindrical mold 11, and the mold 11 is rotated at a constant rotation speed of 1500 rpm and heated to 130 ° C. for 1 hour. After rotating at 500 rpm for 1 hour at 200 ° C., the polyimide resin is cured along the inner peripheral surface 11 a of the mold 11 while further rotating at 500 rpm for 1 hour at 300 ° C., and the base material 32 made of polyimide is used as an outer layer. Centrifugal molding. Then, as in the first embodiment, liquid silicone rubber is injected into the mold 11 and
The silicone rubber is cured while rotating at room temperature for 3 hours at a constant speed of 500 rpm, and the silicone rubber body 31 is formed as an inner layer by centrifugal formation along an inner peripheral surface 32a of a base material 32 made of a polyimide resin as an outer layer.

After the mold 11 has cooled, the inner layer made of the silicone rubber body 31 and the outer layer made of the polyimide resin base material 32 are taken out of the mold 11 as a single piece, cut in the depth direction, and cut to a depth of 0.3 mm. Silicone rubber sheet 30
Have gained. The silicone rubber sheet 30 has an inner peripheral surface 31a smoothed by self-leveling of a cylindrical silicone rubber body 31 as an inner layer as a front (use surface) side, and an outer peripheral surface 32b of a base material 32 as an outer layer as a back side.

As described above, by providing a heat-resistant polyimide resin base material 32 along the outer peripheral surface of the silicone rubber body to form a two-layer structure, a silicone film having a uniform thickness and a very smooth surface is obtained. The strength of the rubber sheet 30 can be improved.

Hereinafter, Examples and Comparative Examples of the method for producing a silicone rubber sheet of the present invention will be described in detail.

(Example 1) Liquid silicone rubber (RT
V) 110 g was dissolved in xylene. After adding 11 g of a curing agent and adjusting the viscosity to 50 P, 300 g of this silicone rubber solution was poured into a mold of a centrifugal molding machine. In addition, this silicone rubber solution was adjusted by calculating a necessary amount, assuming that the thickness of the obtained silicone rubber sheet was 0.3 mm. The size of the mold was 30 cm in diameter × 40 cm in depth. After the rotation of the mold was started, the rotation speed was gradually increased. When the rotation speed reached 300 rpm, the rotation speed was kept constant at room temperature for 0.5 hour, and then at 40 ° C. for 5 hours. Stopped. After the mold was cooled, the cylindrical silicone rubber body was taken out and cut in the depth direction.
Was obtained (width 40 cm × about 90 cm).

Example 2 100 parts of a polyimide resin solution
g After pouring into the cylindrical mold 11, the mold 11 was rotated at a rotation speed of 1500 rpm at 130 ° C. for 1 hour, and then rotated at 200 ° C. for 1 hour at 500 rpm.
Further, the polyimide resin was cured while rotating at 500 rpm for 1 hour at 300 ° C. Next, 300 g of the same liquid silicone rubber as in Example 1 was injected, and while rotating at room temperature for 1 hour while being kept constant at 1500 rpm, the rotation was continued at 40 ° C. for 2 hours, and then the rotation was stopped. After the mold was cooled, the integrated silicone rubber body was taken out and cut in the depth direction to obtain the silicone rubber sheet of Example 2 (width 40 cm × about 90 cm).

(Comparative Example 1) On a biaxially stretched 90 cm long belt, using a coater, a width of 40 cm and a thickness of 0.1 cm were used.
Liquid silicone rubber 200g, curing agent 20g in 3mm
Was coated once with a rubber solution in which was dissolved in xylene, the coater was released, and after curing, the silicone rubber belt was removed. In addition, 400 g of the rubber solution having the above composition was used for producing the silicone rubber sheet.

The following evaluations were performed on the silicone rubber sheet of the above example and the silicone rubber sheet of the comparative example. For the sheet of the example and the sheet of the comparative example, the thickness was measured at 24 points in the width direction and the length direction, respectively.
The difference between the maximum value and the minimum value was determined. Further, the surface roughness (10-point roughness Rz [μm]) of the outer surface of the belt was measured (average of 6 locations) (a product manufactured by Tencor Corporation was used). Furthermore, the presence or absence of bubbles was visually observed. The results of each of the above evaluations are shown in Table 1 below.

[0036]

[Table 1]

As shown in Table 1, the average thickness of the silicone rubber sheet of Example 1 was 0.30 mm, the difference between the maximum and minimum thicknesses was as small as 0.02 mm, and the thickness variation was small. Was. Also, no air bubbles entered the sheet. That is, by the production method of the present invention, it was possible to obtain a silicone rubber sheet having a predetermined thickness uniformly with high accuracy. Further, the surface roughness Rz of the outer surface of the sheet could be about 0.1 μm, and a smooth surface could be obtained.

The average thickness of the silicone rubber sheet of Example 2 was 0.40 mm (the thickness of the polyimide resin substrate was 0.10 mm), and the difference between the maximum value and the minimum value of the thickness was also small. The thickness was as small as 0.02 mm, and the thickness variation was small. Also, no air bubbles entered the sheet.
As in the first embodiment, the manufacturing method of the present invention provides a highly accurate
A silicone rubber sheet having a predetermined thickness uniformly was obtained. Furthermore, the surface roughness Rz of the outer surface of the sheet
Was 0.2 μm, and a smooth surface was obtained.

On the other hand, the silicone rubber sheet of the comparative example
Despite being coated to a thickness of 0.3 mm, the average thickness is 0.29 mm, and the difference between the maximum and minimum thicknesses is as large as 0.06 mm. Was inferior. Further, it was observed that air bubbles were contained in the sheet.

[0040]

As is apparent from the above description, according to the present invention, a liquid silicone rubber is injected into a mold and the surface not in contact with the mold is smoothed by self-leveling to form a cylindrical silicone rubber body. By forming and then cutting to produce a silicone rubber sheet, it is possible to accurately and easily manufacture a large, thin, uniform thickness and smooth surface silicone rubber sheet, which has been difficult until now. .

As described above, by setting the inner peripheral surface of the silicone rubber body not in contact with the mold as the surface of the silicone rubber sheet, the silicone rubber having a very smooth outer surface can be obtained regardless of the surface roughness of the mold. Sheets can be manufactured. Furthermore, since a sheet can be manufactured with a single layer of silicone rubber, heating during molding can be performed efficiently, and the molding time can be shortened.

Accordingly, the silicone rubber sheet produced according to the present invention has excellent properties as described above, and therefore can be very suitably used particularly as a blanket for precision printing and a surface material for an intermediate transfer member of OA equipment. .

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a silicone rubber sheet manufactured by a manufacturing method according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a centrifugal molding machine.

FIG. 3A is a perspective view and FIG. 3B is a cross-sectional view of a mold in a state of being subjected to centrifugal molding by the manufacturing method of the embodiment.

4 (A) is a perspective view of a silicone rubber body, and FIG. 4 (B) is a sectional view of the silicone rubber body cut along a dotted line in FIG. 4 (A) in a process of the silicone rubber sheet manufactured by the manufacturing method according to the embodiment of the present invention. FIG. 2C is a perspective view of the state, and FIG.

5A and 5B are cross-sectional views of a silicone rubber manufactured by the manufacturing method according to the second embodiment of the present invention, wherein FIG. 5A is a cross-sectional view when centrifugally molded, and FIG. 5B is a perspective view of a silicone rubber sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Centrifugal molding machine 11 Die 20 Silicone rubber sheet 21 Silicone rubber body

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B29L 9:00 B29L 9:00 C08L 83:04 C08L 83:04 (72) Inventor Katsumi Terakawa Wakihama, Chuo-ku, Kobe City, Hyogo Prefecture Sumitomo Rubber Industries Co., Ltd. 3-6-9, Sumitomo Rubber Industries, Ltd. (72) Inventor Jun Nishibayashi 3-6-9, Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo F-term in Sumitomo Rubber Industries, Ltd. 4F071 AA67 AA88 AF27 AH16 AH17 BB13 BC01 4F205 AA33 AA40 AA45 AG01 AG03 GA02 GB01 GB26 GC04 GN29 GW23

Claims (5)

[Claims] 1. A liquid silicone rubber is injected into a mold using a centrifugal molding machine equipped with a mold, and the liquid silicone rubber is cured along the inner peripheral surface of the mold while rotating the mold. Then, a cylindrical silicone rubber body is centrifugally formed so that the surface not in contact with the mold is smoothed by self-leveling, and the tubular silicone rubber body is peeled off from the mold inner peripheral surface and taken out. A method for producing a silicone rubber sheet, comprising cutting the silicone rubber body into a sheet. 2. Before injecting the liquid silicone rubber into the mold, a material of the same or different type as the liquid silicone rubber is injected into the mold, and the inner peripheral surface of the mold is rotated while rotating the mold. 2. The method according to claim 1, wherein after the base material made of the material is centrifugally formed as an outer layer, the silicone rubber body is formed as an inner layer along the inner peripheral surface of the outer layer made of the base material. A method for producing a silicone rubber sheet. 3. The method for producing a silicone rubber sheet according to claim 1, wherein the silicone rubber injected into the mold is of a two-part liquid type. 4. The method for producing a silicone rubber sheet according to claim 1, wherein the viscosity at room temperature of the liquid silicone rubber before curing, which is injected into the mold, is 1000 P or less. 5. A silicone rubber sheet produced by the method for producing a silicone rubber sheet according to claim 1.