Method for producing sheet, sheet, and device for producing packaged body and sheet

Abstract

According to this method for producing a sheet, a molten resin in the form of a sheet is cooled with water and fashioned into sheet (20), the sheet (20) is then transported upward from below, and porous, elastically deformable water-absorbent rolls (163A, 163B) rotating at the same circumferential rate as the rate at which the sheet (20) is transported are urged toward a surface of the sheet (20), whereby water droplets (W) adhering to the surface of the sheet (20) are removed.

Description

technical field [0001] The present invention relates to a method for manufacturing a sheet obtained by cooling molten resin with water to form a sheet, a sheet, a package, and an apparatus for manufacturing the sheet. Background technique [0002] As a method for producing a transparent polypropylene resin sheet, a method of rapidly cooling molten resin extruded from a die and then heat-treating it is known. [0003] For example, a method for producing a polypropylene resin sheet is proposed in which molten resin is rapidly cooled with water, and the surface and back of the obtained sheet are heat-treated (see Patent Documents 1, 2, and 3). In fact, using such a water cooling method, a highly transparent sheet can be produced at a high speed of 30 m / min or more. However, there is a problem that if water droplets remain on the surface of the sheet in the heat treatment stage after water cooling, it will cause a local defect in the appearance of the sheet surface and reduce t...

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Problems solved by technology

However, there is a problem that if water droplets remain on the surface of the sheet in the heat treatment stage after water cooling, it will cause a partial appearance defect on the surface of the sheet and reduce the value of the product.

[0016] However, in the methods of Patent Documents 4 and 5, there is a problem that, in a sheet having a large variation in absolute thickness in the TD direction (for example, a sheet thickness of 200 μm or more), a portion with a large difference in thickness occurs. Leakage of water not only fails to completely remove water droplets, but also causes impurities in water and leached substances from sheets to accumulate on the rollers during long-term operation, damaging the surface of the product and causing foreign matter to be mixed.

In addition, in the suction rollers of Patent Documents 6 and 7, there are the following disadvantages: if it is operated for a long time, the impurities contained in the absorbed water will accumulate in the fine and dense non-woven fabric or the many holes of the small holes, so that the water absorption Decreased capacity, not suitable for continuous operation

Furthermore, when the resin is directly water-cooled, there is a concern that leached substances from the resin are mixed in the water, which promotes clogging of the mesh and reduces the water absorption capacity.

[0017] In addition, it has been proposed that water is removed by hot air drying furnace, air nozzle, contact polyurethane sponge roller, etc., but there is a problem that the hot air drying furnace is large-scale and expensive, and the air nozzle and sponge roller cannot sufficiently remove water droplets.

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