JP2010023412A - Method for producing soft sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing a soft sheet, especially a method for producing the soft sheet wherein a rolling process is shortened. <P>SOLUTION: A mixture which is a raw material of the soft sheet and a die having a cross-sectional hole through which a molten mixture passes are prepared. The method for producing the soft sheet has: an extrusion process for making the mixture pass through the cross-sectional hole of the die to mold a long object; a cutting process for cutting the long object molded in the extrusion process to obtain a predetermined cut object; and a rolling process for rolling the predetermined cut object obtained in the cutting process to mold the sheet of a uniform property. A material of the mixture is a composition obtained by compounding a fluororesin with an inorganic filler and a cross-sectional shape of the long object molded in the extrusion process is annular. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a soft sheet such as a sheet gasket, and more particularly to a method for producing a soft sheet having uniform properties obtained by cutting and rolling a mixture extruded by an extruder.

  Filled fluororesin sheet is a sheet made by filling fluororesin with a filler. In addition to the chemical resistance, heat resistance, non-adhesiveness, and low friction properties of fluororesin, It is often used for sealing materials by adding the unique functions and characteristics of, or improving the wear resistance and creep resistance, which are disadvantages of fluororesin.

  As a method for producing a flexible sheet typified by this filler-containing fluororesin sheet, the material is stirred and mixed, and the mixture obtained by heating the mixture is extruded into a flat plate shape by an extruder, and then cut. A forming method of rolling into a sheet is employed.

  4 and 5 are explanatory diagrams of a method for manufacturing a flexible sheet according to the conventional technique. FIG. 4 shows an extrusion process in which the material 110 is extruded as a flat plate-like long object 120 by the extruder 100, and FIG. 5 shows a continuous flat plate-like long piece 120 cut and rolled. The process of forming the flexible sheet 130 is shown.

  As shown in FIG. 4, the material 110 charged from the hopper 104 is heated and pressurized in the cylinder 108 and integrated. The integrated material 110 is extruded in the direction of the tip of the extruder 100 and passes through the die 102 provided at the tip. The die 102 is a so-called flat die that extrudes the mixture, that is, the mixed material 110 into a flat plate shape, and the mixture passes through the cross-sectional hole 102a of the die 102 so that a continuous flat plate-like long object 120 is obtained. Is extruded.

  Next, the continuous flat plate-like long object 120 formed by the extruder 100 is cut by cutting the continuous flat plate-like long object 120 into a predetermined size by the cutting step shown in FIG. An object 122 is obtained. Then, the cut product 122 is folded back by the rolling process shown in FIG. 5B, and then repeatedly rolled until it reaches a predetermined thickness. At this time, the cut product 122 is folded and then rolled in order to remove internal voids and to give strength by orienting molecular chains, that is, to promote the fiberization of the fluororesin. This is because the number of rolling is necessary. Further, as shown in FIG. 5 (C), the sheet end portion 124 that has been dried and deteriorated by repeated rolling is cut, and thereafter, the respective steps such as drying, baking, and correction (not shown) are performed, and FIG. ) Is produced.

  By the way, in the above forming method, since the rolling process occupies a large weight in the soft sheet manufacturing process, in order to improve the efficiency of the soft sheet manufacturing process, how to shorten this rolling process is realized. It is a problem to do.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for producing a flexible sheet that is more efficient than conventional and has uniform properties.

The present invention has been invented in order to achieve the problems and objects in the prior art as described above, and the method for producing a flexible sheet of the present invention includes:
Preparing a mixture that is a raw material of the flexible sheet and a die having a cross-sectional hole through which the mixture passes, and an extrusion process for forming a long product by passing the mixture through the cross-sectional hole of the die; and
A cutting step of obtaining a predetermined cut product by cutting the long product formed by the extrusion step;
Rolling a predetermined cut product obtained by the cutting step to form a sheet having a uniform property,
The material of the mixture is a composition in which an inorganic filler is blended with a fluororesin,
The long product formed by the extrusion process has a circular cross-sectional shape.

  By constructing the present invention as described above, by increasing the extrusion ratio in the extrusion process, fiberization of the fluororesin in the extrusion process can be promoted, so that the number of rolling in the rolling process can be reduced. Moreover, it becomes possible to produce a soft sheet more efficiently than before, such as an improvement in yield rate.

In the above invention, the fluororesin is preferably a polytetrafluoroethylene resin.
By configuring the present invention as described above, the effect of the present invention that a soft sheet having a uniform property can be produced with a small number of rollings is remarkably exhibited.

Moreover, in the said invention, it is preferable that the ratio of the inorganic filler to the material of the said mixture is 20 weight% or more.
By configuring the present invention as described above, the effect of the present invention that a soft sheet having a uniform property can be produced with a small number of rollings is more remarkably exhibited.

Moreover, in the said invention, it is preferable that the extrusion ratio in the said extrusion process is 5-10.
By configuring the present invention as described above, it is possible to produce a soft sheet more efficiently than before with a small number of rolling operations without deteriorating the efficiency in the extrusion process.

  According to the method for producing a flexible sheet of the present invention, by increasing the extrusion ratio in the extrusion process, the fiberization of the fluororesin in the extrusion process can be promoted, so that the rolling process can be shortened compared to the conventional method. In addition, it is possible to produce a soft sheet with uniform properties more efficiently than in the past, such as improving the yield rate.

Hereinafter, the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.
1 and 2 are explanatory views of a method for producing a flexible sheet according to the present invention. FIG. 1 shows an extrusion process in which a material 10 is extruded as an annular long object 20 by an extruder 1, and FIG. 2 shows a continuous annular long object 20 cut and rolled. The process of forming the flexible sheet 30 is shown.

  As shown in FIG. 1, the material 10 charged from the hopper 4 is heated in the cylinder 8 to be mixed. The material 10 is preferably a composition in which an inorganic filler is blended with a polytetrafluoroethylene resin.

The mixed material 10 is extruded toward the tip of the extruder 1 and passes through the die 2 provided at the tip. The die 2 is a so-called circular die that extrudes the mixture, that is, the mixed material 10 into an annular shape. By passing the mixture through the cross-sectional hole 2a of the die 2, the continuous annular long object 20 is obtained. Is extruded.

  Next, the continuous annular long object 20 formed by the extruder 1 is cut by cutting the continuous annular long object 20 into a predetermined dimension by the cutting step shown in FIG. An object 22 is obtained. Then, after the cut product 22 is expanded into a flat plate shape by the rolling process shown in FIG. 2 (B), it is repeatedly rolled until it reaches a predetermined thickness. Thereafter, the flexible sheet 30 shown in FIG. 2C is manufactured through steps such as drying, baking, and correction (not shown).

  As the extruder used in the above-described extrusion process, conventionally used extruders such as a hydraulic press type extruder and a screw type extruder can be used. Moreover, as a rolling mill used at said rolling process, the conventionally used rolling mill can be used. In addition, you may integrally perform a cutting process and an extrusion process by cut | disconnecting the elongate object 20 in the extruder 1 immediately after passage of the cross-sectional hole 2a.

  In the above-described extrusion process, by extruding the elongated object 20 in an annular shape, it becomes possible to perform extrusion molding at a higher extrusion ratio as compared to the case of extruding the elongated object 120 in a flat plate shape as in the past. The fiberization of the fluororesin in the process can be promoted. This is because it is necessary to increase the extrusion ratio and increase the shearing force acting at the time of extrusion in order to promote the fiberization of fluororesin in the extrusion process. This is because it is indispensable to extrude.

  When extruding into a flat plate shape as in the past, the shearing force acting on the end portion is larger than that in the central portion. Further, when the extrusion ratio is increased, the shearing force that acts during extrusion increases. Therefore, when extrusion molding is performed in a flat plate shape with a high extrusion ratio, the difference in shearing force acting between the central portion and the end portion increases, and the progress of fiberization differs between the central portion and the end portion.

  By the way, as fiberization progresses, malleability is lost and resistance to the die contact surface during extrusion increases. Therefore, if extrusion is performed in a flat plate shape with a high extrusion ratio, the resistance during extrusion will be different between the center and the end, so it will not be possible to extrude uniformly or cracks will occur in the center. Will occur.

  On the other hand, when extruding in an annular shape as in the present invention, since there is no end portion (cut), a shearing force acts uniformly regardless of the cross-sectional position, and the progress of fiberization becomes similar. Therefore, since there is no difference in resistance during extrusion, the conventional problem does not occur, and extrusion molding at a high extrusion ratio becomes possible.

  From this, the long product 20 of the present invention that has been extrusion molded at a high extrusion ratio is more fiberized as a whole than the conventional long product 120, and therefore the number of rolling operations in the rolling process is reduced. And there is no need to wrap. Therefore, since the sheet edge portion does not dry and deteriorate as in the prior art, a step of cutting the sheet edge portion is unnecessary, and the yield rate is improved.

  The extrusion ratio is defined as (cross-sectional area in the cylinder of the extruder) / (cross-sectional area of the cross-sectional hole of the die). As described above, the higher the extrusion ratio, the smaller the number of rollings in the rolling process. On the other hand, if the extrusion ratio is too high, extrusion becomes difficult and the efficiency in the extrusion process deteriorates. The extrusion ratio in the present invention is preferably 5 or more, particularly preferably 5 to 10.

In the said embodiment, although the cross-sectional shape of the elongate thing made the circular thing the example, the cross-sectional shape of the elongate thing concerning this invention is not limited to an annular shape. For example, an elliptical shape 40 as shown in FIG. 3 (A), a shape 60 where two circles overlap as shown in FIG. 3 (B), and three circles as shown in FIG. 3 (C) overlap. Shape 80 etc. may be sufficient. That is, it is sufficient that the cross-sectional shape has no break so that a density difference does not occur in any part of the long product when being extruded from the extruder. In the present specification, “annular” means a shape having no break.

  As mentioned above, although preferable embodiment of this invention was described to the example of the manufacturing method of a soft sheet, this invention is not limited to the said embodiment. Various modifications can be made without departing from the object of the present invention.

  Examples of the present invention will be described below in comparison with comparative examples. In the following description, the method for producing a soft sheet according to the present invention shown in FIGS. 1 and 2 is used as an example, and the method for producing a soft sheet according to the prior art shown in FIGS. 4 and 5 is used as a comparative example.

In addition, these Examples and Comparative Examples are for describing the present invention more specifically, and the present invention is not limited only to the scope of the Examples.
(material)
The raw materials of the material 10 of the example and the material 110 of the comparative example are as shown in Table 1.

（押出比）
本実施例では、実施例の押出比を７．５、比較例の押出比を５．０とする。

(Extrusion ratio)
In this example, the extrusion ratio of the example is 7.5, and the extrusion ratio of the comparative example is 5.0.

(Dimensions of the cut product before rolling)
As shown in Table 2, the dimensions of the cut product 22 before rolling in the example are 305 mm in width, 20 mm in thickness, and 490 mm in length. On the other hand, as shown in Table 2, the dimensions of the cut piece 122 before rolling in the comparative example are 365 mm wide, 15 mm thick, and 620 mm long. The cut pieces 22 and 122 are rolled until the sheet thickness of the finished product is 1.5 mm.

(Number of rolling)
As shown in Table 2, the number of rollings in the example is 15 times, which is half the number of rollings of 30 in the comparative example. This is because in the examples, fiberization of polytetrafluoroethylene resin (PTFE) proceeds in the extrusion process. Further, in the embodiment where the number of rolling operations is small, the sheet end portion is not deteriorated by drying, so that the step of cutting the sheet end portion is not necessary. By reducing the number of rolling operations and omitting the step of cutting the sheet edge, it was confirmed in the examples that the rolling time per sheet can be significantly shortened as shown in Table 2.

（製品物性）
上記の成形方法により製造された軟質シートの物性を表３に示す。なお、表３における実施例のNo.1〜No.8に示す物性値は、１枚の製品シート（１１００mm×１１００mm）から８個の試験片を押し抜き加工によって取り出して、各々のガスケットの物性を測定したものである。

(Product properties)
Table 3 shows the physical properties of the flexible sheet produced by the above molding method. The physical property values shown in No. 1 to No. 8 of the examples in Table 3 are the physical properties of each gasket obtained by punching out eight test pieces from one product sheet (1100 mm × 1100 mm). Is measured.

［評価基準］
・引張強度（縦）：10.8Kgf/mm２以上で良好
・引張強度（横）：10.8Kgf/mm２以上で良好
・圧縮率：４〜１０％で良好
・復元率：４０％以上で良好
・柔軟性：３倍以下で良好
・比重：２．２０〜２．４０g/mm²で良好
・シール性：温度２００℃の環境下で３０分間放置し、漏洩量を測定
・外観：限度見本により判定
表３より、実施例の軟質シートは比較例の軟質シートと同等の物性を有することを確認した。

[Evaluation criteria]
・ Tensile strength (longitudinal): 10.8Kgf / mm2 or more is good ・ Tensile strength (horizontal): 10.8Kgf / mm2 or more is good ・ Compression rate: 4-10% is good ・ Restoration rate: 40% or more is good ・ Flexibility : Good at 3 times or less ・ Specific gravity: Good at 2.20 to 2.40 g / mm ²・ Sealability: Leave in an environment of 200 ° C. for 30 minutes and measure leakage amount ・ Appearance: Determined by limit sample Table 3 From the results, it was confirmed that the soft sheets of the examples had the same physical properties as the soft sheets of the comparative examples.

(Yield rate)
Table 4 shows the yield rates of the examples and comparative examples. In the example, since the sheet edge portion is not cut during the rolling process, the yield rate of the example is 85% with respect to the yield rate of 65% of the comparative example, and it was confirmed that the yield rate was significantly improved in the example.

以上の実施例および比較例より、本発明の軟質シートの製造方法によれば、従来よりも圧延工程を短縮することができ、また、歩留り率も向上するなど、従来よりも効率的に均一な性状の軟質シートを製造することが可能となることを確認した。

From the above examples and comparative examples, according to the method for producing a soft sheet of the present invention, the rolling process can be shortened compared to the conventional method, and the yield rate is also improved. It was confirmed that it was possible to produce a soft sheet with properties.

FIG. 1 is a view showing an extrusion process, which is a method for producing a flexible sheet according to the present invention. FIG. 2 is a view showing a process for forming a soft sheet by cutting and rolling, which is a method for producing a soft sheet according to the present invention. FIG. 3 is a diagram showing a cross-sectional shape of another long object according to the present invention. FIG. 4 is a view showing an extrusion process, which is a method for producing a flexible sheet according to the prior art. FIG. 5 is a view showing a process for forming a soft sheet by cutting and rolling, which is a method for manufacturing a soft sheet according to the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 Extruder 2,102 Die 2a, 102a Section hole 4,104 Hopper 8,108 Cylinder 10,110 Mixed material 20,120 Long material 22,122 Cut material 30,130 Soft sheet 40 Ellipse shape 60 Two circles Overlapping shape 80 Three circles overlapping shape 124 Sheet edge

Claims (4)

A method for producing a flexible sheet, comprising:
Preparing a mixture that is a raw material of the flexible sheet and a die having a cross-sectional hole through which the mixture passes, and an extrusion process for forming a long product by passing the mixture through the cross-sectional hole of the die; and
A cutting step of obtaining a predetermined cut product by cutting the long product formed by the extrusion step;
Rolling a predetermined cut product obtained by the cutting step to form a sheet having a uniform property,
The material of the mixture is a composition in which an inorganic filler is blended with a fluororesin,
The method for producing a flexible sheet, wherein the long article formed by the extrusion step has an annular cross-sectional shape.   The method for producing a soft sheet according to claim 1, wherein the fluororesin is a polytetrafluoroethylene resin.   The method for producing a flexible sheet according to claim 1 or 2, wherein the proportion of the inorganic filler in the material of the mixture is 20% by weight or more.   The method for producing a flexible sheet according to any one of claims 1 to 3, wherein an extrusion ratio in the extrusion step is 5 to 10.

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