JPH047989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an open-cell plastic foam having an open-cell structure.

[Conventional technology]

Plastic foams obtained by conventional manufacturing methods, such as crosslinked olefin resin foams, often have a closed cell structure and are unsuitable for applications requiring water absorption or air permeability.

Therefore, in the case of crosslinked olefin resin foams and the like, methods for producing foams with an open cell structure are being considered.

For example, a method of mixing a water-soluble powder such as starch with a resin and eluting and removing the water-soluble powder, or a method of producing a foam with a closed cell structure and using physical means such as compressing it between rolls. Methods for destroying bubble membranes have been proposed (Japanese Patent Publication No. 10850/1985, Japanese Patent Application Laid-open No. 63172/1983, Japanese Patent Application Laid-Open No. 56-1988).
Publication No. 121739)).

[Problem that the invention seeks to solve]

However, the method of eluting and removing the water-soluble powder has a fatal drawback in that only a foam can be obtained with an extremely low expansion ratio of several times.

In addition, in the latter method using roll pressure compression,
It is difficult to destroy the bubbles by simply applying pressure and compression, and it is necessary to cool the foam to below its embrittlement temperature before compressing it, or to add a specific filler or a specific crosslinking agent.

In view of the above points, it is an object of the present invention to provide a method that can easily and reliably produce open-cell plastic foam regardless of whether the expansion ratio is high or low.

[Means for solving problems]

The method for producing an open-cell plastic foam of the present invention is a method of creating an open-cell structure by compressing and passing a plastic foam sheet between rolls to destroy the cell membrane, and in which the interval between the rolls is set to the thickness of the foam sheet. A plastic foam sheet with many pores punched in advance with a punching needle is placed between the rolls and compressed and passed through the rolls, or a plastic foam sheet is compressed and passed between the rolls at the same time with a punching needle. It is characterized by having a large number of pores.

In this invention, the plastic foam sheet refers to a thermoplastic resin foam sheet that becomes a closed cell structure by a normal foaming method, such as an olefin resin foam sheet with a closed cell structure.

Examples of the thermoplastic resin include polymers such as medium-low pressure polyethylene, high pressure polyethylene, linear low density polyethylene (LLDPE), or polymers containing ethylene as a main component, such as ethylene-acetic acid. A resin mainly composed of a copolymer such as a vinyl copolymer, an ethylene-propylene copolymer, an ethylene-α-olefin copolymer, or a mixture of two or more of these polymers or copolymers is used.

Foamed sheets are manufactured from these thermoplastic resins by conventional methods.

As a method for providing a large number of perforations in advance in this foam sheet, for example, there is a method in which the foam sheet is perforated by passing it between a rotating roll and a receiving roll on which a large number of perforation needles are implanted on the peripheral surface.

In addition, if the foam sheet is not perforated in advance,
A perforation needle is provided on one of the rolls for compressing the foam sheet to rupture the membrane, similar to the perforation roll described above, and the perforation needle is inserted between the rolls and passed through the rolls to perforate the foam sheet simultaneously with the compression rupture.

There may be multiple pairs of rolls for compression membrane rupture, and the passage may be repeated two or more times.

In the method of this invention, it is preferable that the foamed sheet is compressed and then annealed by heating to a temperature higher than the softening point of the thermoplastic resin used.

If this annealing is not performed, the bubbles compressed between the rolls will recover from their crushed state;
This is because elasticity etc. may not be sufficient.

However, if a flexible open-cell plastic foam is required, it may be better not to perform annealing.

[Function] In the method for producing an open-cell plastic foam of the present invention, the plastic foam sheet is perforated in advance, so that the cell membrane can be easily crushed when the plastic foam sheet is compressed between rolls.

Furthermore, after the formation of open cells, air quickly enters the cells through the perforations, so that the elasticity recovers quickly and returns to its original shape.

〔Example〕

A perforated foam sheet was manufactured by perforating a 40 times expanded cross-linked polyethylene sheet (8 mm thick) to a depth of 5 mm on each side of a 40 times foamed cross-linked polyethylene sheet (8 mm thick) using a perforated roll with hot needles (0.5 mmφ) implanted at 4 mm pitch on the circumference. .

This perforated foam sheet was passed between 3 pairs of rolls (each 400 mmφ) with a roll interval of 2 mm, then annealed by passing it through a 150°C oven for 3 minutes, cooled with a cooling roll, and then wound into an open-cell polyethylene sheet. I got it.

This foam sheet has excellent cushioning properties, and
The elastic recovery was quick and it was suitable as a carpet underlay sheet.

〔Effect of the invention〕

In the method for producing open-cell plastic foam of the present invention, the plastic foam sheet is perforated in advance or perforated at the same time as it is compressed, so that the cell membrane can be easily crushed when the plastic foam sheet is compressed between rolls. Become.

Furthermore, after the formation of open cells, air quickly enters the cells through the perforations, so that the elasticity recovers quickly and returns to its original shape.

Therefore, it is suitably used as an underlay material, joint material, and breathable foam for this carpet.

Claims (1)

[Claims] 1. In a method of creating an open cell structure by passing a plastic foam sheet while compressing it between rolls to destroy the cell membrane, the distance between the rolls is set to 1/2 or less of the thickness of the foam sheet, and there is a gap between the rolls. , insert a plastic foam sheet with many pores punched in advance with a perforation needle and press it through;
Alternatively, a method for producing an open-cell plastic foam, characterized in that the plastic foam is compressed and passed between the rolls, and at the same time, a large number of pores are punched with a punching needle.