JPS6133696B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a heat insulating sheet reinforced with a mesh material.

Films with a large number of box-like protrusions of uniform depth are widely used as packaging containers and as materials for laminated films. Among these, a bent film with a structure in which box-like protrusions are lined up without gaps can be used as a bonded film to make an excellent heat-retaining sheet, so it is expected to have a wide range of uses.

A bent film with a structure in which a large number of box-like protrusions of uniform depth are lined up can be produced by passing a thermoplastic resin film between a pair of embossing rolls, or applying pressure or suction onto a perforated mold. This can be made by molding. However, with these methods, it is not possible to obtain a bent film with a structure in which the protrusions are arranged without gaps.

The inventor previously proposed a convenient method for making a bent film with a structure in which box-like protrusions of uniform depth are lined up without gaps. This method does not use the above-mentioned embossing roll or perforated die, but instead uses a net-like material. Specifically, a mesh is placed above a flat perforated plate,
The mesh is held parallel and taut away from the perforated plate, a thermoplastic resin film is placed on top of the mesh, the film is heated to soften it, and pressurized or vacuum air is applied to the film to tighten the film. A bending structure in which the film is closely placed on a perforated plate, the film located within the mesh of the mesh is made to protrude in a box shape, the film is folded back double at the mesh, and the side walls of the box are connected in a mesh pattern. It is made into a film. According to this method, a bent film having a structure in which box-like protrusions are successively arranged without gaps can be obtained. Since this film has a structure that includes a mesh material, it can be seen as a bent film reinforced with a mesh material.

According to the above-described method, even if the net-like material has some degree of elasticity, it is possible to easily produce a bent film having a relatively small area. However, it is difficult to obtain a bent film with a large area. This is because, in the case of large-area products, the suction or pressure during molding causes the net-like material, especially elastic net-like materials such as plastic nets, to be displaced together with the heat-softening film, and the box-like protrusions near the fulcrums at both ends are displaced. The depth is the desired value, but the depth of the box-like protrusion in the part far from the fulcrum is
This is because it becomes shallow.

This inventor inserted a grid-shaped support of a certain height between the mesh and the perforated plate in order to hold the elastic wide net in parallel with the perforated plate even during molding. I came up with something to do. This inventor is
The support in the form of a checkerboard is constructed from a large number of strips, each of which is made of a thin, strong material with equal width and thickness, and whose widths are oriented vertically and their longitudinal directions intersect vertically and horizontally. We decided to structure it as follows. Then, this support is placed on a perforated plate, the mesh is placed under tension on the support, and a polyethylene film that has been softened by heat is placed on top of it to absorb air from under the perforated plate. Then vacuum forming was performed.
In this way, the ends of the net and the support were folded back, and the side walls were fused together to form an adjacent box-shaped continuous body. Thereafter, the perforated plate was first removed from the box-like continuous body, and then the support was removed, and a box-like continuous body in which the film and the net-like material were integrated was obtained.
The inventor confirmed that the resulting box-like connected body was supported by a support, and thus became a box-like body in which all the side walls had substantially uniform heights. Further, the inventor has confirmed that this box-shaped continuous body can be easily separated from the support. This invention was made based on such confirmation.

In this invention, a large number of strips of equal width are arranged, their width directions are upright, and their longitudinal directions are crossed vertically and horizontally to form a grid-like support, and the support is made of a perforated plate. A net-like material is placed on top of the support and maintained in a tensioned state. A heat-softened thermoplastic resin film is placed on top of the net-like material and maintained in a tensioned state, and pressurized air is applied from the top surface of the film. The film is inserted into the mesh of the mesh and the gap of the support by suction from the bottom surface, or by using a combination of these, and the end of the film is brought into close contact with the perforated plate, so that the film can be connected in a large number of boxes. The invention relates to a method of making a heat insulating sheet by forming the film into a body, separating the film together with the net-like material from the support and the perforated plate, and then laminating a flat film to the thus obtained bent film.

The method of this invention will be explained with reference to the drawings as follows. FIG. 1 is a vertical cross-sectional view schematically showing a method of manufacturing a bent film according to the present invention. FIG. 2 is a partially cutaway perspective view of the process of manufacturing a bent film according to the present invention.
FIG. 3 is a partially cutaway perspective view of a bent film obtained by the present invention. FIG. 4 is a partially cutaway exploded perspective view of the support used in the present invention. FIG. 5 is a partially cutaway perspective view of a heat insulating sheet obtained by the present invention.

In FIG. 1, reference numeral 1 denotes a band-like body, and the band-like body 1 has its width upright and its longitudinal direction intersecting both vertically and horizontally to form a support in the form of a checkerboard. The support is placed on the perforated plate 2. 3 is a net-like material, and the net-like material 3 is placed on a support and maintained under tension. 4 is a thermoplastic resin film, and the film 4 is placed on the net-like material 3 and maintained under tension. The space between the film 4 and the perforated plate 2 is closed by a frame 5 to maintain an airtight state. 7 is a decompression chamber, and 8 is an air suction port.

As shown in FIG. 1, a support made of a strip 1 and a net-like material 3 are placed on a perforated plate 2, and a film 4 that has been softened by heating is placed thereon at another location. Next, air is removed from the suction port 8, and the pressure inside the decompression chamber 7 is reduced. Then, the film 4 enters into the mesh of the net-like material 3 and the grid pattern or gaps of the support, and the tip of the film that enters comes into close contact with the perforated plate 2. As a result, film 4
is formed into a box-like protrusion with the perforated plate 2 as the bottom within the mesh and the gap. At this time, the part of the film 4 in contact with the net-like material 3 is folded back along the net-like material 3 and hangs down to surround the net-like material 3, and the hanging portions are closely placed back to back to form a double wall. Further, the portion of the film 4 in contact with the strip 1 is bent along the strip 1 to form a narrow groove in which the strip 1 is accommodated. The height of the side wall of the box-like projection is equal to the width of the strip 1. In this way, the protruding film 4 becomes a series of box-like protrusions having a substantially uniform depth.

The state at this time is shown in FIG. FIG. 2 shows the state in which the lower part is formed into a series of box-like protrusions, and the upper part shows the state before that.
One box-shaped body 9 in FIG. 2 is connected to an adjacent box-shaped body 10
The tips of the side walls are folded back and connected in a continuous manner. A net-like material 3 is enclosed in the folded portion. Where the mesh 3 is enclosed, the side walls of the adjacent box-like bodies 9 and 10 are in close contact with each other, with almost no gap between them, forming a double wall. are doing. However, since the strip 1 is interposed where the box 9 contacts the adjacent box 11, the film is bent along the strip 1 to form a narrow groove that sandwiches the strip 1. become.

After forming the box-like continuous body in this way, the decompression chamber 7
is opened, and then the film 4 is cooled. Thereafter, when the film 4 is separated from the perforated plate 2, the film 4 is separated from the support consisting of the strip 1 and the net 3.
It is taken out with the contents still in it. The box-like connected body thus taken out has the bottom edge exposed at the end of the support made of the band-like body 1. When the support is removed from the exposed surface, the film 4 is obtained as a series of box-like protrusions in which the net-like material 3 is enclosed. This series of box-like protrusions is a bent film.

The bent film thus obtained is shown in FIG. In FIG. 3, between two adjacent box-shaped bodies 9 and 10, the side walls of each box-shaped body form a double wall that is in close contact with each other, and a mesh 3 is enclosed in the folded part of the double wall. There is. However, between the two adjacent box-like bodies 9 and 11, the side walls of each box-like body are folded back leaving a small gap, resulting in a narrow groove 12.
The groove is open at the bottom of the box.
This box-like connected body has a structure in which each box-like body is closely formed with no gaps, except for the portion where the groove 12 is formed.

The bent film thus obtained has a stable shape and is strong because the mesh material 3 is enclosed in the folded portion of the double wall, and the mesh material 3 acts as a reinforcing body. Moreover, since this bent film is made up of box-like bodies connected with almost no gaps, a film is pasted across the opening of the bent film box to make the box an independent bubble. Can be used as insulation and cushioning material. Therefore, this bent film formed into a box-like continuous body is useful.

In the above explanation, one embodiment of the method of the present invention has been described by taking the vacuum forming method as an example, but the method can be said to be an improvement on the conventional vacuum forming method. Conventional vacuum forming methods have not used the mesh 3 of this invention, but have instead used a mold. The type is
It has the shape to be formed and is either placed directly on the perforated plate 2 or made integrally with the perforated plate 2. However, the above-mentioned method of this invention does not use a mold, but instead uses the mesh 3. Moreover, the net-like material 3 is placed at a distance from the perforated plate 2 and parallel to the perforated plate 2. For this purpose, a support made of a strip 1 is used, which is interposed between the perforated plate 2 and the mesh 3 to ensure the maintenance of the spacing between them and the parallel relationship between them. There is. Moreover, by placing this support on the perforated plate 2, the lower end of the support can be removed from the molded body. In this respect, the method of the present invention differs from conventional molding methods.

The main points of this inventive method have been explained above regarding one embodiment of this inventive method, but below, detailed matters in this inventive method will be explained for each requirement.

An example of the support is shown in FIG.
The support is formed into a grid pattern in which a large number of strips 1 of the same width are combined. Each of the strips 1 has its width direction perpendicularly oriented and its longitudinal direction parallel to each other. A notch 13 extending in the width direction is formed at the intersection of the vertically facing strip and the horizontally facing strip.
are attached from the ends to the center of the width, making it convenient to combine with each other in the form of a cross. the result,
In the support, the upper edge and the lower edge of each strip 1 are on the same plane, and the plane connecting the upper edges and the plane connecting the lower edges are parallel to each other. Therefore, when this support is placed on the perforated plate 2, the lower edge of each strip 1 will come into close contact with the perforated plate 2, and the surface connecting the upper edge of each strip will be placed on the perforated plate 2. It becomes a plane parallel to 2.

The distance between the strips 1 on the support, ie, the size of the grid, is made larger than the distance between the meshes on the net-like material 3, usually several times as large. The distance should be as large as possible within a range that does not cause the net-like material placed on top of it to bend significantly. Further, the strip 1 is preferably made of a heat-resistant material and its thickness is made as thin as possible. A release agent is applied to the surface of the strip 1 to make it easier for the film to separate from the strip 1 after molding.

The support does not require that the grid formed between the strips be a right quadrilateral. The checkerboard-shaped gaps may be triangular, pentagonal, or circular.

Various thermoplastic resin films can be used as the film in this invention. Among them, ethylene resins, vinyl chloride resins, and styrene resins are most suitable. The thickness of the film is not limited to one as thin as about 0.02 to 0.1 mm, but may be as thick as about 1 mm or more, which is generally called a sheet.

The net-like material according to the present invention includes not only a net formed by tying threads together, but also any material formed by intersecting a large number of thread-like materials. That is, this net-like material may be of any kind as long as it has a mesh with gaps that allow the film to protrude from the mesh. The intersection of the threads does not necessarily need to be fixed. Yarns include natural fibers, synthetic fibers, synthetic resin fibers, glass fibers, metal wires, etc.
Various types can be used. As natural fibers, in addition to cotton and silk, recycled fibers such as rayon and Kyupura can be used. Further, as the synthetic fiber, polyester, polyamide, polyacrylonitrile, etc. can be used. Further, a net formed by making cuts in a medium-low pressure polyethylene film, a rotating die extrusion net, etc. can also be used as the net. Further, the shape of the mesh is not limited to a quadrangle, but may be a triangle or a polygon of pentagon or more. Moreover, the size of the mesh is preferably 3 to 30 mm in diameter, particularly preferably 5 to 15 mm, if this is expressed as the diameter of a circle with the same area. When synthetic fibers (including plastic nets) are used, the mesh is made of a material with a softening point higher than that of the film, preferably by about 10°C or more.

In the above explanation, an example was shown in which vacuum forming is performed by providing a decompression chamber 7 and sucking air in order to form the film 4 into a series of box-like protrusions, but the attachment of protrusions is not limited to this. . For example, pressurized air may be applied from above the film 4, or a combination of vacuum and pressurization may be used. The depth of the projections is between 2 and 10 mm, preferably between 3 and 6 mm. However, if it is used for packaging, it may be larger than this.

It is desirable to apply a mold release agent to the surface of the perforated plate 2 in order to facilitate the separation of the molded box-shaped projections.

This invention is a method for further manufacturing a heat insulating sheet from the bent film obtained as described above. The method for producing the heat insulation sheet is that a transparent thermoplastic resin film is selected and used in the above-mentioned method for producing a bent film, and a flat thermoplastic resin film is placed on the opening surface of the box-shaped body of the obtained bent film. This requires that the box-shaped body be made into one independent cell by bonding two films together.

In other words, the method for manufacturing a heat insulating sheet involves arranging a large number of strips of equal width, standing upright in the width direction, and crossing each other vertically and horizontally in the longitudinal direction to form a checkerboard-shaped support. It is placed on a perforated plate, a net is placed on a support to maintain it in tension, a transparent film made of thermoplastic resin that has been softened by heating is placed on top of the net and maintained in tension, and the upper surface of the film is Apply pressurized air from below, or suck from the bottom surface, or use a combination of these to push the film into the mesh of the net and the gap between the supports, bring the plunged end into close contact with the perforated plate, and then press the film. The film is formed into a large number of box-like continuous bodies, the film is separated from the support and the perforated plate together with the net-like material, and a flat transparent film made of thermoplastic resin is pasted on the opening surface of the box-like continuous body. It is something to do.

As shown in FIG. 5, the heat insulating sheet is made by laminating a flat film b to a film a formed into a box-like continuous body. The film a formed in the shape of a box-like continuous body is the above-mentioned bent film. Film a in FIG. 5 is the same as the bent film in FIG. 3, except that film a in FIG.
is located with the bottom of the box facing upwards, so
The bent film in Figure 3 is upside down.
Film b is attached to film a so as to cover the opening of the box-like body, and is adhered or welded at the opening of the box-like body. As a result, each box-like body is in the state of one independent bubble.

As the transparent film made of thermoplastic resin, the aforementioned ethylene resin, vinyl chloride resin, and styrene resin are used. In one sheet,
The bent film a and the flat film b are preferably made of the same type of thermoplastic resin. The reason for this is that if film a and film b are made of the same type of resin, it is convenient to bond or weld the two films together. The film b is said to be a flat film in the sense that the film b is flat to the extent that it can fit closely into the opening of each box-like body in the bent film a, and a slight embossed pattern is also permissible. That doesn't mean there aren't any.

Since the heat insulating sheet obtained by this invention is a bonded body of two transparent thermoplastic resin films, it is transparent and allows light to pass through it well. In addition, this sheet has a large number of independent box-like bodies formed without any gaps on one film a, and a flat film b is brought into contact with the box-like body so as to close the opening of the box-like body, making the sheet integral. Although it is a product made of only two sheets pasted together, independent air pockets are formed over the entire surface. Therefore, the insulation effect is good. Therefore, when used in greenhouse construction, this sheet allows light to pass through and warms the greenhouse interior well, and once the interior air is warmed, even when the outside air cools, the interior air is not cooled as much as traditional agricultural films. Therefore, energy for heating the greenhouse at night can be saved. Furthermore, since the sheet includes the net-like material 3, the opening is reinforced and the sheet becomes strong. Moreover, when this sheet is used in a film greenhouse, it is preferable to use the film a with its edges facing outward because the space in the grooves 12 becomes even narrower. In addition, it is easier to roll the sheet before application, and it is more convenient to use the film if the edges of the film are inward. The method of the present invention has an advantage in that it is possible to manufacture sheets with such special characteristics so that they always have a constant thickness.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view schematically showing a method of manufacturing a bent film according to the present invention. FIG. 2 is a partially cutaway perspective view of the process of manufacturing a bent film according to the present invention. FIG. 3 is a partially cutaway perspective view of a bent film obtained by the present invention. FIG. 4 is a partially cutaway exploded perspective view of the support used in the present invention. FIG. 5 is a partially cutaway perspective view of a heat insulating sheet obtained by the present invention.

Claims (1)

[Claims] 1 A large number of strips of equal width are arranged, their width directions are upright, and their longitudinal directions are crossed vertically and horizontally to form a checkerboard-shaped support, and the support is placed on a perforated plate. , Place a net-like material on a support and maintain it in a tensioned state, place a transparent film made of thermoplastic resin that has been softened by heat on top of the net-like material and maintain it in a tensioned state, and apply pressurized air from the top of the film. Alternatively, by suctioning from the bottom surface, or by using a combination of these, the film is plunged into the mesh of the mesh and the gap between the supports, and the thrust end is brought into close contact with the perforated plate, so that the film is formed into a large number of box-like connected bodies. reinforced with a net-like material, characterized in that the film is separated from the support and the perforated plate together with the net-like material, and a flat transparent film made of thermoplastic resin is pasted on the opening surface of the box-like connected body. A method of manufacturing a heat insulation sheet.