JPS5824454B2 - Netsuto Kosei Plastics - Tojiyouseikebutsu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-permeable plastic sheet-like molded article, and more specifically, a heat-permeable plastic sheet-like molded article, which does not have any pores in its normal state (apparently), but which has a temperature above its glass transition point and below its melting point. The present invention relates to a novel sheet-shaped molded product made of a thermoplastic resin in which a large number of fine pores are restored when heated in a temperature range of .

In the present invention, the sheet-like molded product mainly refers to a film or a sheet-like product.

In addition, the term "through hole" refers to a fine hole or small hole that penetrates from the surface to the back surface of a molded product.

2. Description of the Related Art Heat-expandable or shrinkable films are known as conventional plastic film processed products.

In other words, when stress is applied at an appropriate temperature, the resulting strain remains, and this residual strain is recovered by appropriate heat treatment to return to its original state.

This is also referred to as the memory effect or memory phenomenon of plastics; for example, some types of stretched plastic film shrink when heated, and certain types of stretched plastic tubes expand when heated. There are some, but all of these utilize the above properties.

The present invention utilizes the wall-like properties of plastics to provide a completely new and extremely useful sheet-like molded product.

That is, the present invention involves providing a sheet-like material made of a thermoplastic resin with a large number of fine holes, for example, a sheet-like material formed by a known method, with a large number of perforations penetrating from the front surface to the back surface thereof by any means, or Or a structure in which a large number of through holes penetrating the front and back are evenly distributed, such as a knitted fabric or woven fabric such as a net or cloth made of fibers or threads made of thermoplastic resin, or a structure made of thermoplastic resin. A nonwoven fabric made of a large number of fibers fused or bonded at their intersection points, or a net made of a thermoplastic resin whose intersections are fused by melt extrusion, at a temperature above the glass transition point and below the melting point of the resin. It can be easily obtained by pressing to close the through hole and cooling it.

In this case, the term "blockage" refers to the state in which the through-hole portion is crushed and the hole walls come into close contact with each other, and is not a state in which the hole walls melt and flow and come into close contact with each other, as in fusion.

The temperature range during pressurization when closing the through hole is as described above, but it varies depending on the resin material used.

For example, the temperature range is -30 to 115°C for polyethylene, and 70 to 200°C for polyvinyl chloride.

Pressing can be done using a flat plate or a roll (
The key is to press the entire surface uniformly and without fusion.

The pressure may also be appropriately determined within the above-mentioned conditions depending on the temperature, material, thickness, etc. of the sheet-like object.

Generally, the higher the temperature, the lower the pressure.

In the sheet-like molded product of the present invention, the pores are apparently closed (not fused) due to pressing (stress), so the melting point is higher than the glass transition point again. When the sheet is heated to a temperature below, the residual strain is released and the through holes that penetrate the front and back of the sheet appear as before.

The temperature for restoring the pores is that the pores are restored slowly even near the above glass transition point, but preferably the pores are sharpest if the apparent temperature is higher than the temperature at which the upper pores are closed, that is, higher than the temperature during pressing and below the melting point. will be restored to.

Examples of thermoplastic resins used in the present invention include polyolefin resins such as polyethylene, polystyrene, and polypropylene, vinyl resins such as polyvinyl alcohol, polyvinyl chloride, and polyvinyl acetate, and acrylic resins such as polymethyl acrylate and polymethyl methacrylate. , polyvinylidene chloride resin, polyester resin, polyamide resin, polycarbonate resin, or copolymers or mixtures thereof, and gelatin, casein, etc. may also be used.

The sheet-like molded product of the present invention is used as a printing plate material for printing or textile printing by stencil formation, and as a packaging material.

For example, if the sheet-like material of the present invention is partially heat-treated, fine through-holes penetrating the front and back sides will be restored only in the heated part, so if a desired image is applied to it by heat, it will be The through holes are restored only at the corresponding positions, and an image is formed by a group of fine through holes.

Therefore, it can be used as a base paper for stencil printing or as a screen printing mold.

In other words, first make small holes corresponding to the mesh of the screen in the film, or use a net to heat press the film as described above to close the small holes, and then place the specified original into this. When they are stacked closely together and irradiated with heat rays (from either side, preferably from the document side if the material is opaque, or from the material side if the document is opaque), only the image area will be exposed. It is selectively heated, and first small holes are opened in the area corresponding to the image.

Instead of the contact copying type heat ray irradiation, the purpose can be similarly achieved by writing with a hot iron pen, a heat laser beam, a light pen, or the like.

When a film or sheet with an image formed by a group of fine perforations obtained by the above operation is printed or textile-printed using a known stencil printing machine or textile printing device, ink passes through the image area and is blocked from the non-image area. Clear prints can be obtained.

In this way, when the sheet-shaped molded product of the present invention is applied to a stencil printing material, etc., it can be made extremely easily in a normal working environment and in a dry process, and does not require special photosensitive materials or irradiation light. The sheet-like molded product of the present invention exhibits excellent effects such as a sharp image and high printing resistance.

In addition to the above, it has a wide range of applications as a variety of recording materials.

In addition, by selecting the plastic to be used, it can maintain airtightness and watertightness under normal conditions, and can be used as a packaging material that is breathable and water permeable when necessary, making it extremely suitable for so-called tea bags such as black tea. You can get something.

That is, if a predetermined amount of black tea or the like is sealed in the bag, there is no risk of deterioration during storage, and if necessary, if the bag is placed directly into hot water, holes will be formed in the bag so that the black tea or the like can be easily leached out.

Example 1 A polyethylene network (melting point: 115°C; glass transition point: -30°C) made by melt extrusion method with thread width (cross-sectional diameter) of 0.5 tnrn, mesh size of 1 mm x 1 mm, and thickness of 1 mm was
It was heated to 05°C and pressed at 100 kg/ctyt to close the mesh and form a film.

When this film was recorded with a hot pen heated to 110° C., holes were formed in the recorded area.

When this film was used to print using mimeograph ink in a conventional manner, very clear prints were obtained.

Example 2 Thread width (cross-sectional diameter) is 0.1 mm, mesh size is 0
A polyvinyl chloride (melting point: about 200° C., glass transition point: 70° C.) net made of polyvinyl chloride (melting point: about 200° C., glass transition point: 70° C.), 5 mm×O, 5 mrIL, and 1 mm thick was pressed at 40 kg/c4 with nip rolls at 80° C. to form a film.

Next, a manuscript (printed material) was placed on this film and exposed using a discharge flash irradiation device TU-250 manufactured by Riso Kagaku Kogyo Co., Ltd. (estimated temperature: 75 to 120°C).

When this film was used as an original plate and printed with mimeograph ink, clear prints faithful to the original were obtained.

Example 3 A cross-linked polyethylene film with a thickness of 100 μm and a glass transition point of -25° C. was made with numerous holes penetrating from the front surface to the back surface using a needle with a diameter of 0.5 mm. The pores were closed by applying pressure at kg/cm.

The original was placed on top of this film and exposed using a 3M Model 288 exposure machine (estimated temperature 90-150°C).

When this film was printed using mimeograph ink, clear prints were obtained.

Example 4 A 300μ thick nonwoven fabric of polyethylene terephthalate (melting point 265°C, glass transition point 81°C) was heated at 200°C for 2 hours.
It was pressed at 80 kg/crtt to close the voids and form a film.

This film was irradiated with a laser beam modulated into characters with signals (estimated temperature: 215°C), and this was used as an original to print with mimeograph ink, resulting in clear printed matter.

Example 5 A nonwoven fabric with a thickness of 300μ made of fibers of polyethylene terephthalate (melting point 265°C, glass transition point 81°C) was
It was pressed at 00°C and 280 kg/c4 to form a film-like product in which the voids between the fibers were closed.

When a bag was made from this film and filled with water, no leakage was observed.

When this bag was heat-treated at 240° C. for 10 seconds and water was added again, the water passed through the bag and flowed out.

Claims (1)

[Claims] 1. Sheet-like molding of thermoporous plastic made of thermoplastic resin, characterized in that a large number of through holes penetrating the front and back sides of a molded article are closed with residual strain that restores the through holes by heating. thing.