JP4977593B2 - Method for producing ultra-high molecular weight polyethylene porous sheet - Google Patents

Description

  The present invention relates to a method for producing an ultra high molecular weight polyethylene (hereinafter referred to as “UHMWPE”) porous sheet.

  Conventionally, when manufacturing a chip capacitor or the like, for example, a ceramic green sheet on which an electrode is printed is adsorbed by an adsorption plate and conveyed to a predetermined place. It is preferable to stick a porous sheet having air permeability as a buffer material on the adsorption surface of the adsorption plate. As such a porous sheet, a porous sheet made of UHMWPE having an average molecular weight of 500,000 or more may be used from the viewpoint of rigidity and cushioning properties.

As a method for producing a UHMWPE porous sheet, UHMWPE powder was filled into a mold, and this mold was put into a heating furnace maintained at a temperature equal to or higher than the melting point of UHMWPE to sinter the UHMWPE powder. Thereafter, a method is known in which a block-like porous body is taken out of a mold and cut into a predetermined thickness to form a sheet. In recent years, UHMWPE powder is preformed into a block shape in a mold, placed in a pressure vessel and sintered with heated steam, and the block-shaped porous body thus obtained has a predetermined thickness. A method of cutting into a sheet has also been proposed (see, for example, Patent Document 1).
Japanese Patent Publication No. 5-66855

  However, in any of the above methods, the block-shaped porous body is produced intermittently, and therefore the UHMWPE porous sheet cannot be produced continuously. In addition, a complicated operation of cutting the block-like porous body into a predetermined thickness is required.

  In view of such circumstances, an object of the present invention is to enable continuous production of a UHMWPE porous sheet.

  In order to achieve the above object, the present invention provides a coating process in which a dispersion obtained by mixing UHMWPE powder, a dispersant, and a surfactant is applied on a carrier sheet to form a coating film, A sintering step of sintering the UHMWPE powder by heating to obtain a sheet-like porous body, a peeling step of peeling the carrier sheet from the sheet-like porous body, and a residue in the sheet-like porous body There is provided a method for producing a UHMWPE porous sheet, comprising: a removing step of removing a dispersant and a surfactant; and a compressing step of obtaining the UHMWPE porous sheet by compressing the sheet-like porous body in the thickness direction. .

  According to the above configuration, since the sheet-like porous body can be directly and continuously produced by using the carrier sheet, all the steps can be continuously performed on the line. . That is, according to this invention, it becomes possible to produce a UHMWPE porous sheet continuously.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The following description relates to an example of the present invention, and the present invention is not limited to these.

  In FIG. 1, the block diagram of the production line for implement | achieving the manufacturing method which concerns on one Embodiment of this invention is shown. The manufacturing method of the present embodiment includes a coating process, a sintering process, a peeling process, a removing process, and a drying / compressing process. The production line shown in FIG. The UHMWPE porous sheet can be continuously produced by performing the above in order. Specifically, the production line includes a feeding unit 11 that feeds out the carrier sheet 1, a single-screw extruder 12 that performs a coating process, a heater 13 that performs a sintering process, a winding unit 14 that performs a peeling process, and a removing process. The extraction part 15 which performs this, and the compressor 16 which performs a drying and compression process are provided.

  As the carrier sheet 1, a plastic film having a softening point equal to or higher than the heating temperature described later in the sintering process may be used. Examples of the material include polyester and polyimide. Hereinafter, each process will be described in detail.

1) Coating process The extruder 12 applies a dispersion liquid by extrusion on the drawn-out carrier sheet 1, and forms the coating film 2a as shown to Fig.2 (a). The thickness of the coating film 2a is, for example, 1.0 to 2.0 mm. The dispersion is a mixture of UHMWPE powder, a dispersant, and a surfactant. The dispersion preferably has a viscosity of 150 to 250 poises. Therefore, the mixing ratio is 150 to 180 parts by weight of the dispersant and 4 to 8 parts by weight of the surfactant with respect to 100 parts by weight of the UHMWPE powder. Preferably there is. If the amount of the dispersant is too small, it is difficult to mix the UHMWPE powder and the dispersant. If the amount of the surfactant is too small, the sheet-like porous body described later is charged and dust tends to adhere.

  The UHMWPE powder preferably has an average particle size of 30 to 180 μm.

  The dispersant is preferably an organic material having a boiling point of 180 ° C. or higher. For example, glycerin, diethylene glycol, triethylene glycol, or the like can be used.

  The surfactant is for improving the stability of the dispersion and also functions as an antistatic agent. This surfactant is preferably a cationic or anionic one.

  In addition, the application | coating process of this invention can be performed by die coating other than the extrusion using the extruder 12. FIG.

2) Sintering Step The heater 13 sinters the UHMWPE powder by heating the coating film 2a to obtain a sheet-like porous body 2b as shown in FIG. In this embodiment, the heater 13a is arrange | positioned not only above the carrier sheet 1 but the inner side of the belt 13b which conveys the carrier sheet 1, and the coating film 2a is heated from both upper and lower sides. The heating conditions are preferably a heating temperature of 150 to 200 ° C. and a heating time of 3 to 60 minutes. In the sintering process, a part of the dispersant may be evaporated. When a low-boiling point dispersant is used, all the dispersant may be removed, but that may be used.

3) Peeling process The winding part 14 peels the carrier sheet 1 from the sheet-like porous body 2b by winding the carrier sheet 1. At this time, the charge generated when the carrier sheet 1 is peeled off is suppressed by the surfactant. In addition, before this process, it is preferable that the sheet-like porous body 2b is naturally cooled to about room temperature.

4) Removal step Distilled water 15a is stored in the extraction unit 15, and the sheet-like porous body 2b is allowed to pass through the distilled water 15a, thereby remaining in the sheet-like porous body 2b. Dispersant and surfactant are extracted and removed. In addition, the removal process of this invention may remove a dispersing agent and surfactant by evaporation instead of extraction.

5) Drying / Compression Step The compressor 16 has a pair of belts 16b and 16c that are transported with the sheet-like porous body 2b interposed therebetween, and a heater 16a that is disposed inside these belts 16b and 16c. . The sheet-like porous body 2b is heated by the heater 16a and conveyed while being compressed by the pair of belts 16b and 16c. Thereby, the sheet-like porous body 2b is dried and compressed in the thickness direction, and the UHMWPE porous sheet 2c as shown in FIG. 2C is manufactured. The conditions in this step are preferably a heating temperature of 150 to 200 ° C. and a compression time of 1 to 3 minutes.

Compression is performed not only to adjust the thickness but also to adjust the air flow. For example, when only drying is performed, a UHMWPE porous sheet with an air flow rate of 5 to 7 cm ³ / cm ² · s is obtained, but by performing compression, the air flow rate is reduced to, for example, 1 to ³ cm ³ / cm ² · s. Can be adjusted. The compression rate when compressing the sheet-like porous body 2b is preferably 20% or more and 40% or less. This is because if the compression ratio is too large, the air flow rate is low and the porous body is not made porous. If the compression ratio is too small, the porous body becomes porous but has no binding, and is fragile to bending.

  In addition, in this embodiment, although the sheet-like porous body 2b is dried with the compressor 16, when a removal process is performed by evaporation, drying is not especially required. Even if drying is required, the drying process can be performed separately before the compression process.

  According to the manufacturing method of this embodiment, as long as a dispersion liquid is supplied to the extruder 12, a UHMWPE porous sheet can be continuously produced. In the conventional manufacturing method, there is a limit in size because a mold or the like is used, but in the manufacturing method of the present embodiment, a long and long UHMWPE porous sheet that cannot be obtained by the conventional manufacturing method is obtained. be able to.

  In the production method of the present invention, it is not always necessary that each step is continuously performed on the same line, and individual steps can be performed separately. For example, using a carrier sheet 1 having a predetermined length that can be carried instead of a long one that can be traveled, a dispersion liquid is applied onto the carrier sheet 1 to form a coating film 2a. The carrier sheet 1 on which is formed may be put into a dryer to sinter UHMWPE powder. Further, after removing the remaining dispersant and surfactant from the sheet-like porous body 2b thus produced, it may be compressed by pressing at a predetermined temperature.

Example 1
100 parts by mass of UHMWPE powder (molecular weight 5 million, melting point 135 ° C., average particle size 60 μm), 160 parts by mass of glycerin as a dispersant, and 7.7 parts by mass of Elecnon N1711A manufactured by Dainichi Seika Kogyo Co., Ltd. as a surfactant To obtain a dispersion. This dispersion was 192 poise. This was extruded onto a carrier sheet at a discharge rate of 30 g / s using an extruder having a die slip thickness of 3 mm and a die width of 100 mm to form a coating film having a thickness of 2.5 mm and a width of 100 mm.

  This carrier sheet was placed in a dryer maintained at an internal temperature of 150 ° C. for 30 minutes to obtain a sheet-like porous body. After the carrier sheet carrying the sheet-like porous body is taken out of the dryer and naturally cooled to room temperature, the carrier sheet is peeled off from the sheet-like porous body, the sheet-like porous body is immersed in distilled water, a dispersant and an interface The active agent was extracted. At this time, in order to perform extraction efficiently, the sheet-like porous body was vibrated by ultrasonic waves. Thereafter, the sheet-like porous body was dried at 80 ° C., and then pressed at 150 ° C. for 1 minute so that the compression rate was 35%, to obtain a UHMWPE porous sheet having a thickness of 1.5 mm.

(Example 2)
A UHMWPE porous sheet having a thickness of 1.5 mm was obtained in the same manner as in Example 1 except that UHMWPE powder having an average particle diameter of 180 μm was used. The dispersion used in Example 2 was 230 poise.

(Comparative example)
The same UHMWPE powder (molecular weight 5 million, melting point 135 ° C., average particle size 180 μm) used in Example 2 was filled into a mold having an inner diameter of 500 mm and a depth of 1000 mm, and this was put into a metal pressure resistant container. The inside was depressurized to 30 mmHg. Thereafter, heated steam was introduced into the container and heated for 5 hours under the conditions of 160 ° C. and 6 atm to obtain a cylindrical porous body. This was cut into a thickness of 1.5 mm using a lathe to obtain a UHMWPE porous sheet.

(test)
With respect to the UHMWPE porous sheets of Example 1, Example 2, and Comparative Example, the porosity, the air flow rate, and the bending elasticity were measured.

The porosity was obtained from the equation {1- (bulk density / true density)} × 100, with the bulk density determined from the volume and weight, and the true density of UHMWPE being 0.93 g / cm ³ .

  The air flow rate was measured using a fragile tester manufactured by Toyo Seiki Co., Ltd. based on JIS L1096.

  The bending elasticity was measured by using KES-FB2S manufactured by Kato Tech Co., with the bending increase acceleration set to 0.5 cm / min.

  The obtained results were as shown in Table 1.

  As can be seen from Table 1, in the UHMWPE porous sheets of Example 1 and Example 2, even when the thickness was as thick as 1.5 mm, the bending elasticity was kept small. That is, since the UHMWPE porous sheets of Example 1 and Example 2 are soft, they are deformed along the uneven surface when attached to the uneven surface. Moreover, since the thickness is thick, the uneven surface is hardly reflected on the surface of the UHMWPE porous sheet (the surface opposite to the side attached to the uneven surface), and when used for adsorbing ceramic green sheets, etc. Moles are less likely to occur during the process.

  On the other hand, since the UHMWPE porous sheet of the comparative example has a large bending elasticity, there is a possibility that a gap is formed when it is attached to an uneven surface. In order to prevent this, it is necessary to reduce the thickness. However, when this is done, the uneven surface is reflected on the surface of the UHMWPE porous sheet, and leakage easily occurs during adsorption.

  Moreover, the UHMWPE porous sheet of Example 1 and Example 2 was able to ensure a large amount of airflow in the thickness direction, and good adsorptivity was obtained. On the other hand, in the UHMWPE porous sheet of the comparative example, the air flow rate in the thickness direction was small, and lateral leakage from the sheet cross section occurred. For this reason, although the amount of aeration became large, the actual adsorptivity was not so good as compared with the UHMWPE porous sheets of Example 1 and Example 2.

  As described above, the methods shown in Example 1 and Example 2 are not only suitable for continuous production of UHMWPE porous sheets, but are also useful as methods for obtaining UHMWPE porous sheets having excellent characteristics.

It is a lineblock diagram of a production line for realizing a manufacturing method concerning one embodiment of the present invention. (A)-(c) is sectional drawing which shows the state after a coating process, a sintering process, and a compression process, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carrier sheet 2a Coating film 2b Sheet-like porous body 2c Ultra high molecular weight polyethylene (UHMWPE) porous sheet 11 Feeding part 12 Extruder 13 Dryer 14 Winding part 15 Extraction part 16 Compressor

Claims (3)

A coating process for forming a coating film by applying a dispersion liquid obtained by mixing ultrahigh molecular weight polyethylene powder, a dispersant and a surfactant onto a carrier sheet;
A sintering step of obtaining a sheet-like porous body by sintering the ultrahigh molecular weight polyethylene powder by heating the coating film;
A peeling step of peeling the carrier sheet from the sheet-like porous body;
A removing step of removing the dispersant and the surfactant remaining in the sheet-like porous body;
Compressing the sheet-like porous body in the thickness direction to obtain an ultra-high molecular weight polyethylene porous sheet; and
The manufacturing method of the ultra high molecular weight polyethylene porous sheet containing this.   The method for producing an ultrahigh molecular weight polyethylene porous sheet according to claim 1, wherein in the coating step, the dispersion is applied onto the carrier sheet by extrusion.   The method for producing an ultrahigh molecular weight polyethylene porous sheet according to claim 1 or 2, wherein in the compression step, the sheet-like porous body is compressed at a compression rate of 40% or less.

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