JPH0566859B2 - - Google Patents

Description

[Detailed description of the invention]

purpose of invention

[Industrial application field]

The present invention relates to a method for producing net-like bodies from plastics.

[Conventional technology]

For example, nets made from plastics such as polyethylene are widely used as packaging and construction materials. As known from Japanese Patent Publication No. 34-4185, a typical technology for manufacturing such plastic nets is an outer die with a plurality of notched resin channels on the inner periphery and corresponding notches on the outer periphery. Combine it with an inner die provided with a resin flow path, and while rotating both in opposite directions, discharge molten resin from the resin flow path, forming a mesh so that the points where the inner and outer resin flow paths meet serve as nodes. A cylindrical net is obtained. As a modification of this method, there is also a technique in which two flat dies are combined and a flat net is obtained by discharging molten resin while reciprocating the two in opposite directions. Although these technologies are widely adopted, the equipment used has a complex structure and the die must be made with high precision, resulting in high net costs and requiring skill in operation and maintenance. Another technique is to prepare an embossed film with many protrusions and heat the protrusions to open holes.
Method of enlarging holes by biaxial stretching (Special Publication 44-
There is also a method (Japanese Patent Publication No. 44-3879) in which the film is transferred while being in contact with a cooling drum, and a thin flame is ejected to make holes and then stretched in the longitudinal direction. With these, it is difficult to control the shape and size of the pores, and it is not possible to provide a net with a uniform appearance.

[Problems to be solved by the invention]

The object of the present invention is to go one step further than the current state of the art and to develop a method for producing plastic nets that do not require the use of sophisticated and complex equipment and that have a mesh of well-controlled shape and size. It is about providing. Composition of the invention

[Means to solve the problem]

The method for producing a plastic net of the present invention includes:
As shown schematically in FIGS. 1 and 2 and shown in detail in FIGS. 3 to 8, two rolls 2 each have a concave portion engraved with an arbitrary mesh pattern (diamond shape in the illustrated example). The molten plastic 6 is extruded and supplied between the embossing rolls provided so that the convex parts 21 and convex parts 21 and the concave parts 22 and concave parts 22 face each other. An embossed sheet 7 is formed in which the portion 72 is thin but has no holes, and then this embossed sheet is stretched by the biaxial stretching device 4 under heating to melt and open the thin portion between the meshes, This consists in obtaining a net 8 integrated into a thick mesh part. In forming the embossed sheet 7, the thin portions 7 between the mesh portions are formed using a so-called valley dyeing method.
It is desirable to provide material 2 that easily absorbs heat rays and to perform heating during biaxial stretching by irradiation with infrared rays. The method for producing a plastic net of the present invention includes:
All stretchable thermoplastic synthetic resins are applicable, but particularly suitable materials are crystalline polyolefins such as polyethylene and polypropylene.

[Effect]

The details of embossing roll 2 are shown in Figures 3 and 4.
As shown in the figure, the rolls 2 having concave portions 22 carved with a mesh pattern are provided so that the convex portions and concave portions face each other, so that the roll 2 is provided between the concave portions 22 by extrusion from the T-die. The molten plastic sheet 6 becomes an embossed sheet 7 consisting of a thick mesh portion 71 and a thin other portion 72, with the plastic in the portions sandwiched between the convex portions of the rolls transferred to the concave portions. For this purpose, it is preferable to operate in such a way that a bank 61 of molten plastic is always formed on the embossing roll, as shown in FIG. Although the mesh of the embossing roll can have any shape, it is advantageous for the recesses to be not parallel to the roll axis. This makes it easier for the air in the recesses to be expelled, smoothing the transition of the molten plastic, and making it easier to create a large difference in thickness between the thicker and thinner parts of the embossed sheet. . The roll 2 should be provided with suitable temperature control means so that its surface can be maintained at an optimum temperature for embossing depending on the physical properties of the plastic used. In order to provide the thin wall portion 72 between the mesh portions with a material that easily absorbs heat rays, an ink prepared by kneading carbon powder, metal powder such as aluminum or copper with a binder is prepared, and this is mixed as shown in FIG. As shown in the figure, the ink may be applied to the convex portions 21 of the embossing roll using the valley dyeing means 3, and the applied ink may be pressed against the plastic sheet during embossing. As will be readily understood, the heat-absorbing material thus provided helps rapidly raise the temperature of the thinned portion when subjected to infrared irradiation in the subsequent biaxial stretching step. Biaxial stretching under heating serves to melt the thinner portions with a relatively smaller heat capacity before the thinner portions with a larger heat capacity, as described above, and to apply tension to open the pores, thereby enlarging the pores. The situation can be understood by comparing FIGS. 5 and 6, which show the embossed sheet 7 before stretching, and FIGS. 7 and 8, which show the net 8 obtained by stretching. Although the mesh expands by stretching, its shape remains similar to that of the embossed sheet.

【Example】

An embossed roll was prepared by engraving orthogonal diagonal recesses at a pitch of 5 mm on the surface of a metal roll with an outer diameter of 300 mm and an effective width of 350 mm.Two rolls were provided with the protrusions facing each other and the recesses facing each other. Polypropylene (MI=1.0) was melted in an extruder, extruded through a T-die at a temperature of 240°C, and fed between the embossing rolls mentioned above. Aluminum alloy powder during embossing
Valley dyeing was carried out using an ink prepared by adding 100 parts by weight of a commercially available transparent lacquer as a binder to a mixture of 50 parts by weight and 50 parts by weight of carbon powder. Adjust the temperature of both embossing rolls to 55℃, and
The sheet was drawn at a speed of m/min to obtain an embossed sheet having a width of 300 mm, a thickness of 1.25 mm at the thick part of the mesh, and a thickness of 0.25 mm at the thin part in between. Subsequently, this embossed sheet was placed in a tenter device and biaxially stretched three times in length and width at an ambient temperature of 120°C. Except for the 50 mm selvedges on both sides, the thin-walled portions were evenly opened throughout, and a polypropylene net with a diamond-shaped mesh having a pitch of about 15 mm was obtained. This net was useful as a civil engineering and construction material. Effects of the Invention According to the manufacturing method of the present invention, a plastic net can be manufactured by using an ordinary stretched film manufacturing apparatus, provided that an embossing roll consisting of an engraved roll according to a desired mesh is prepared. can. Since it does not require a combination of sliding dies unlike the conventional technology, the device is not expensive and
Its operation and maintenance are also easy. The resulting net has a well-organized and beautiful appearance with precisely controlled mesh shape and dimensions. The mesh shape also depends on the selection of embossing roll.
In addition to the diamond shape shown in the figure, any other shape such as a lattice, triangle, or hexagon can be determined. FIG. 9 shows an example of a regular triangle, and FIG. 10 shows an example of a regular hexagon. The plastic net obtained by this manufacturing method can be suitably used for making water-permeable earth retaining nets for civil engineering works, various fences for building works, etc.

[Brief explanation of the drawing]

1 and 2 are schematic views of an apparatus for showing the plastic net manufacturing process of the present invention, with the former being a plan view and the latter being a side view. Third
The figure and FIG. 4 show details of the embossing roll portion, the former being a plan view and the latter being a sectional view. 5 and 6 show a part of the embossed sheet, the former being a plan view and the latter being a sectional view. 7 and 8 show a part of a plastic net obtained by biaxially stretching an embossed sheet, the former being a plan view and the latter a sectional view. 9 and 10 are plan views similar to FIG. 7, both showing other examples of plastic nets manufactured by the method of the present invention. 1...T die head, 2...emboss roll,
21... Convex portion, 22... Concave portion, 3... Valley dyeing means, 4... Biaxial stretching device, 6... Molten plastic, 7... Embossed sheet, 71... Thick part, 72... Thin wall Part 8... Plastic net, 81... Mesh, 82... Hole.

Claims (1)

[Claims] 1. Between the embossing rolls, two rolls having concave portions engraved with arbitrary mesh patterns are provided so that the convex portions and concave portions face each other,
By extruding and supplying molten plastic to form an embossed sheet with thick mesh portions and thin portions between them but without holes, this embossed sheet is then biaxially stretched under heating to achieve the above-mentioned properties. A method of manufacturing a plastic net, which comprises melting and opening the thin sections between the meshes and integrating them into the thicker mesh sections. 2. When forming the embossed sheet, a material that easily absorbs heat rays is applied to the thin parts between the mesh parts,
The manufacturing method according to claim 1, wherein heating during biaxial stretching is performed by irradiation with infrared rays. 3. The manufacturing method according to claim 1, wherein a crystalline thermoplastic resin is used as the plastic.