JPS5824453B2 - How do you know what to do? - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing a sheet material in which the pores are restored when heated to a predetermined temperature range (referred to as heat permeability).

The novel sheet-like material obtained by the present invention does not have through holes in its normal state and is airtight and insulating, but when a certain amount of heat is applied, it becomes transparent, especially a large number of fine through holes from the front surface to the back surface. It is capable of passing through materials with air permeability, water permeability, etc., and can be applied to packaging and various other uses.

In the present invention, the sheet-like material includes even a thin material called a film.

In other words, if a plastic film of an appropriate thickness, in which a large number of pores penetrating from the front surface to the back surface are drilled in advance, is heated and pressed if necessary using a pressure press machine or a rolling roll, and then cooled, the apparent appearance is The above-mentioned pores are collapsed, occluded, and erased, and this state is maintained at room temperature.

Then, when the film is treated again by applying an appropriate temperature, the collapsed pores open again and penetrate through the front and back sides, restoring the original porous film.

This is due to the fact that the pores are apparently compressed upward due to stress (not fused), and the residual strain at that time is recovered by heat treatment, and is based on the memory phenomenon of plastics.

In order to ensure this effect, the pores of the porous film must not be fused together when the porous film is pressed, so it is necessary to heat the film at a temperature below the melting point.

In addition, even if heating is not used, it is necessary to carry out the pressure treatment at a temperature above the glass transition point of the material used.The key point varies depending on the type of thermoplastic film or sheet used, but the pressure treatment should be carried out within the temperature range above the glass transition point and below the melting point. This is important, and it is virtually impossible to maintain the restoring effect outside this temperature range.

It is necessary that the heating temperature for restoring the pores be within the same range, but it is desirable to set it at least higher than the temperature during the above-mentioned pressing.

Materials for the sheet-like material used in the present invention include:
Polyolefin resins such as polyethylene, polystyrene, and polypropylene; vinyl resins such as polyvinyl alcohol, polyvinyl acetate, and polyvinyl chloride; acrylic resins such as polymethyl acrylate and polymethyl methacrylate; other polyvinyritine chloride, polyester resins, cellulose resins, Examples include polyamide resins, polycarbonate resins, copolymers or mixtures thereof, and gelatin, casein, etc. are also used.

Methods for forming through holes by pre-drilling holes in sheet materials made of such materials include mechanical means using a perforator using a needle or mold, chemical means using corrosive liquid, etc., and electrical means such as electrical discharge destruction. Other known methods such as partially heating and melting may be used.

Moreover, instead of perforating a sheet-like material, a sheet-like structure having through-holes in advance may be used.

For example, it is also possible to use a structure made of a thermoplastic glass material, such as a cloth or net-like structure, a nonwoven fabric, or a net-like structure whose intersections are fused by melt extrusion.

In order to close the pores of these materials and apparently erase them, uniform pressure is applied to the surface, but the pressure can be lowered if the temperature at this time is higher. If it is low, a relatively high pressure is required.

In addition, it is not limited to a specific one because it depends on the type and thickness of the material used, the size of the through hole, etc.

As mentioned above, it is important to keep the temperature within a predetermined range so that the through holes do not fuse together.

In addition, the heat treatment temperature for restoring the transparent pores to the sheet-like material obtained in this way can be gradually reproduced if it is close to the glass transition point, but in reality it is When heated at a temperature higher than the heating temperature and lower than the melting temperature, the through-holes are quickly and accurately restored to the original openings.Thus, the sheet-like material obtained by the present invention can be Even though it has no pores, when it is heated it develops many pores that pass through the front and back, or it becomes like a net or cloth and becomes air permeable or water permeable, so it is not airtight during storage. When used by heating etc., it is suitable as a packaging material that requires water permeability, ventilation, properties, etc.

For example, when used in so-called tea pack bags used to hold black tea, other teas, or coffee, etc., or bags containing seasonings for instant foods, etc., it prevents the contents from absorbing moisture during storage, and when used, for example, by pouring boiling water into them. The bag has a large number of pores of a predetermined size, allowing hot water to enter therein, thereby facilitating the dissolution and extraction of the contents, which can then be leached out of the bag.

In addition, in the sheet-like material obtained by the above-mentioned nine present inventions, by selectively heating only the desired portions, it is possible to prevent minute holes from forming only in the heated portions, so that various materials can pass through the desired portions. It can be applied to plate materials for various types of printing and textile printing based on the stencil format, for example, which require barrier properties in other areas and barrier properties in other areas.

It has a wide range of applications, including various other recording materials.

Example 1 Thread width (cross-sectional diameter) 0.5 mm, mesh size 1 mvt
x 1, a polyethylene network (melting point 115°C, glass transition point -30°C) obtained by melt extrusion method with a thickness of 1 mm was
It was pressed at 100 kg/c4 while heating to 05° C. to close the mesh and form a film.

When this was heat-treated at 110° C., it was restored to its original network shape within 5 seconds.

Example 2 A nonwoven fabric with a thickness of 300μ made of fibers of polyethylene terephthalate (melting point 265°C, glass transition point 81°C) was
Pressing was carried out at 00° C. and 280 ky/cn to obtain a film-like product in which the voids between the fibers were closed.

When a bag was made from this film-like material and water was poured into it, it was watertight with no leakage. However, when the bag was heat-treated at 240°C for 10 seconds and water was poured in again, the water leaked out of the bag. passed through and leaked out.

Example 3 A crosslinked polyethylene film with a glass transition point of -25°C
．． A needle with a diameter of 5 m and 7 ft was used to make many pores penetrating the front and back sides, and this was heated at 130°C with Nilagol at 100 kg/
CNT was treated under heating and pressurizing conditions to obtain a film in which the pores were closed.

As a result of heat-treating this film at 150° C., the film had the same pores as before.

Example 4 A cheesecloth-like fabric with a mesh size of about 2 mm x 2 mm and a thickness of about 1 m71 L made of polyvinyl chloride (melting point: about 200°C, glass transition point: 70°C) yarn with a thread width (cross-sectional diameter) of ITtn was made into Niragroll. Heating at 80℃ and 40kg/cl,
The eyes were closed and formed into a film by processing under pressure conditions.

When this was heat-treated at 90°C, the original mesh was restored within 2 seconds.

Claims (1)

[Claims] 1. Heat-permeable holes characterized in that a sheet-like material made of a thermoplastic resin having a large number of through-holes penetrating from the front surface to the back surface is pressurized at a temperature above the glass transition point and below the melting point to close the through-holes. A method for producing a sheet-like product.