JPS6059862B2 - Transparent soft synthetic resin foam sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transparent flexible synthetic resin foam sheet.

More specifically, this invention involves pasting a non-foamed transparent soft synthetic resin film on a flat surface obtained by cutting the skin of a transparent soft synthetic resin foam sheet obtained by a foaming operation. This relates to the sheet obtained by applying the same method.

That is, this invention consists of a bonded body of a foamed sheet of synthetic resin and a non-foamed film of synthetic resin. A foam sheet that occupies 60% or more of the area and is made of a thin cell wall with a cell wall of 0.1 or less, and is a transparent soft synthetic resin foam sheet with a sheet thickness of 2 to 107 Joa, and a non-foamed film has a thickness of 0.2 to 107 Joa. O, 02wgR transparent soft synthetic resin film,
The present invention relates to a transparent flexible synthetic resin foam sheet in which a non-foamed film is adhered to the cut surface of the foam sheet.

Closed-cell foam sheets made of synthetic resin have large heat insulating properties and good cushioning properties, and are therefore widely used as heat insulating materials or cushioning materials. However, conventional closed-cell foam sheets are almost opaque, and even thin ones are translucent, and there are hardly any sheets with good transparency. This is natural considering that when a large number of bubbles are present in the resin, the number of refraction of light increases and the transparency decreases. If a transparent synthetic resin foam sheet can be obtained, it will allow sunlight to pass through and warm things inside, while at the same time preventing heat dissipation due to its insulating properties, it can be used as a greenhouse sheet or Useful as an agricultural film.

Moreover, it is very convenient because it protects the internal items as a packaging material and at the same time allows the internal items to be seen from the outside.
Therefore, I thought it would be possible to make a transparent synthetic resin foam sheet.It is also desirable that such a sheet be flexible and bendable.Based on this idea, We set out to create a synthetic resin foam sheet that is both transparent and flexible.Until now, when it comes to synthetic resin foams, we have only thought about uniformly and finely foaming it.For example, polyethylene is originally a translucent resin. However, if the thickness is set to about 17lgR in the non-foamed state,
It looks almost transparent. However, commercially available foamed products have fine bubbles, and therefore have a thickness of about 1 wn after foaming, and are already opaque.
Therefore, with commercially available sheets, if you try to see what's on the other side through the sheet, you can hardly see anything, and it also cannot allow light to pass through. The inventor attempted to produce a foam sheet by pressurizing a mixed gas of propane and butane into molten polyethylene in an extruder and extruding it through an annular slit.

In that case, conventionally a small amount of foaming cores such as calcium carbonate was added in order to make the bubbles uniform and fine, but by chance the foaming cores were removed and a foamed sheet with a thickness of about 6 Tfn was made. As a result, the product thus obtained is a closed-cell foam with a coarse cell diameter of 2 to 4 m, and a thin cell wall of 0.1W1i.
It was confirmed that the thickness was as follows, so that the foam appeared to be transparent and that objects on the other side could be seen through it. This invention was born based on such confirmation. The foam sheet according to the present invention has coarse, closed-cell cells, and 60% or more of the cells have an average diameter of 2 or more, and the cell walls are thin and have a cell wall of 0.1 size or less. The sheet is a transparent soft synthetic resin foam sheet with a thickness of 2 to 10 Tf.
The sheet according to the present invention is made of soft synthetic resin.

Among the soft synthetic resins, soft vinyl chloride resins and olefin resins are preferred. The soft vinyl chloride resin may be made by blending a vinyl chloride homopolymer with a plasticizer such as dioctyl phthalate to give it flexibility, or it may be made by blending vinyl chloride with vinyl acetate or other monomers. It may also be made flexible by polymerization. Examples of olefin 5 resins include polyethylene, polypropylene,
A copolymer of ethylene and propylene, a copolymer of ethylene and vinyl acetate, etc. can be used. The sheet according to the present invention is a closed cell sheet4.

Closed cell property refers to a structure in which each cell does not inherently communicate with adjacent cells. Closed-cell foams are produced by using a liquid or gaseous blowing agent, or a solid blowing agent that decomposes and generates gas when heated, press-fitting or kneading it into a resin, and then leaving the resin in a softened state. It is most commonly obtained by rapid transfer of the resin under low pressure conditions and generation of gas from the blowing agent. The foam sheet of this invention has coarse cells. Coarse bubbles have an average diameter of 2W! Refers to more than l. The average diameter here means that the shape of the bubble is not a true sphere;
Since it has an ellipsoidal shape or an irregular polyhedral shape, it refers to the diameter when the volume of one bubble is adjusted to a roughly spherical shape. Also,
Bubbles do not necessarily all have the same size. Therefore, even though it has coarse air bubbles, there may be a small amount of fine air bubbles mixed into the air bubbles. Therefore, to indicate that the sheet has large air bubbles, it is necessary to use an expression such as when the sheet is viewed from the front or back side, air bubbles with an average diameter of 2 m or more occupy 60% or more of the sheet's total surface area. I don't get it. Conventional foam sheets all had an average diameter of 1 WI or less because, as mentioned above, fine cells were valued.

Therefore, if even a small amount of material with an average diameter of 2 WR or more is present in a foam sheet, cavities are formed there, and the foam sheet cannot be said to be of good quality as a heat insulating material or a cushioning material. However, when the sheet of the present invention is viewed from the front or back side, the majority of the cells are coarse, with more than 60% of the cells having an average diameter of 2Tmn or more. The state of the bubbles is different from that of foam sheets. The sheet according to the invention is a foam sheet with a uniform thickness in the range of 2 to 10 m.

Most of the bubbles present therein are coarse bubbles with an average diameter of 2 or more. Therefore, in the direction from the front surface to the back surface, the majority of the cell walls are overlapped 4 to 61 times, and at most, the cell walls overlap 7 or 8 times.
You can hardly see any places where the bubble walls overlap. Moreover, the cell wall thickness is a thin film with a thickness of 0.1 Tgt or less. Therefore, when the sheet of the present invention is viewed from the front side to the back side, it appears almost transparent, and the shape of objects on the other side of the sheet can be clearly seen through.
Among these, particularly preferred is a sheet in which cell walls overlap in most of the sheets in five or less layers, particularly four or less layers. The sheet of this invention is manufactured by extrusion molding. Specifically, a thermoplastic resin is impregnated with a foaming agent, the softened resin is extruded through slits, and foamed to create a thick foam base plate, which is then sliced into foam sheets. In this way, if you do not make a foam base plate with a large thickness, the thickness will be 2
In a thin sheet with an average diameter of 2 to 1
This is because it is difficult to obtain a foam sheet with coarse cells of m or more. As the blowing agent, an aliphatic hydrocarbon with a low boiling point such as propane, butane, or pentane, or an aliphatic halogenated hydrocarbon with a low boiling point such as methylene chloride is used. In the case of aliphatic hydrocarbons, the amount used is about 1% by weight for polyethylene and about 5% by weight for polypropylene. The foamed original plate thus obtained is usually foamed to 20 to 8 pores. In the present invention, foams within this range can be used, but among them, foams with a diameter of 50 to 60 f8 are preferred. The foam sheet as obtained as described above does not have a smooth surface. The reason is that in order to increase the size of the bubbles, the bubbles must be allowed to expand freely, but when the bubbles are allowed to expand freely, the top surface of the bubbles becomes spherical. For this reason,
The surface of the foam sheet becomes a continuous surface of small spheres and is therefore not smooth. Thus, non-smooth surfaces are undesirable. Therefore, the surface of the foamed sheet obtained in this manner is cut to make the surface smooth. When the surface is cut, air bubbles are released at the surface. Therefore, a transparent film is attached to the cut surface to close the open air bubbles and create a smooth surface. Then, the foamed sheet thus obtained maintains its transparency and has good heat retention and cushioning properties. In the foamed sheet, it is preferable to cut the skin portion generated during foaming on both sides and apply a transparent film to both cut surfaces.

However, pasting a transparent sheet on both sides increases the price, so it is used by pasting a transparent sheet on only one side. Use a transparent film that is not breathable.

As the film, one made of soft thermoplastic resin and as thin as possible is used. It is desirable to use the same resin as the resin constituting the foam sheet. The thickness of the film is 0.2 to 0.05m.
Those within the range are suitable. This film may be adhered to the surface of the foam sheet made by thinly slicing with an adhesive, or it may be pressed onto the surface of the foam sheet while the film is softened and heat-sealed. It may also be pasted. The foamed sheet according to the present invention will be explained with reference to the drawings as follows.

FIG. 1 is a partially exploded perspective view of a hand-supported foam sheet according to the invention. FIG. 2 is a perspective view schematically showing the method for manufacturing a foam sheet according to the present invention. 1st
In the figure, the foam sheet of the present invention has a foam sheet 1 made of a copolymer of ethylene and vinyl acetate, on both sides.
It is made by laminating non-foamed films 2 and 3 made of the same copolymer. The cells in the foam sheet 1 are coarse, closed cells, and have an average diameter of about 5
Almost all of them were ugly, and those with an average diameter of less than 3 meters were hardly recognized. The foam sheet 1 was made as follows.

1 part by weight of an equal mixture of butane and propane as a blowing agent is added to 100 parts by weight of a copolymer of ethylene and vinyl acetate, and this is extruded through an annular gap with a gap width of 1.2 and a diameter of 130 mm to foam. A foam base plate with a thickness of approximately 9WR was made. This foam base plate foams to about 6@, and the cell wall is 0.0
The thickness was between 2 and 0.04 m. This foam base plate has a thickness of 3T1r! It was sliced into n-thin slices to form a foam sheet.
The state of slicing is shown in FIG. The foam base plate 4 was sliced into three foam sheets 5, 1, and 6.
The foam sheet 1 shown in FIG. 1 uses the foam sheet 1 located in the center of the foam base plate 4. The foam sheet 1 shown in FIG. The foam sheet 1 is an inner sheet made by thinly slicing a foam base plate 4 made of coarse cells.
Therefore, one air bubble was cut on the front and back sides, and therefore, there was a large air permeability from the front side to the back side. Therefore, films 2 and 3 having a thickness of about 0.057 rn were attached to both the front and back sides of the foam sheet 1 in a heated and molten state to obtain the foam sheet of the present invention. The foam sheet 1 shown in FIG. 1 is made of a copolymer of ethylene and vinyl acetate, which is inherently transparent.

Therefore, films 2 and 3 attached to both the front and back sides
The foam sheet 1 is transparent, and since the foam sheet 1 has coarse bubbles and some of the bubbles are cut on both the front and back sides, objects on the other side can be clearly seen through the bubbles. In this way, the foam sheet 1, which is clearly visible, and the film 2,
Since the foam sheet of the present invention is made by fusing together the foam sheet and the foam sheet, the object on the other side can be clearly seen through the foam sheet, even though the foam sheet of the present invention is as thick as approximately 37T01t. As a result, as shown in FIG. 1, the hands supporting the foam sheet can be seen as they are. Because it has the property of being transparent, it allows light, including sunlight, to pass through it well. As mentioned above, the foam sheet of the present invention allows light to pass through well and has heat retaining properties, so it is suitable for use in greenhouses and other agricultural applications.

It is also suitable as a transparent packaging material because it is transparent and has cushioning properties. Furthermore, this foam sheet has closed-cell cells within the sheet, and the openings of the cells are covered by films attached to both the front and back sides, so it has good heat conduction insulation and cushioning properties. It is. Moreover, since the trunk is made of a soft synthetic resin, it is flexible and can be rolled up and stored, making it convenient for use, transportation and storage. Thus, the foam sheet of the present invention can be used as a film or sheet for greenhouses or agriculture, or as a packaging or cushioning sheet;
suitable for Moreover, this foam sheet can be manufactured by the above-mentioned manufacturing method, so it has the feature of being easy to manufacture. The sheet of this invention has the above-mentioned advantages. In addition, in FIGS. 1 and 2, sheet 1 located inside the thinly sliced sheet was used, so non-foamed films 2 and 3 were attached to both the front and back sides, but the thinly sliced sheet Sheet 5 located on the outside of the
Or when using No. 6, it is sufficient to attach the non-foamed film only to the cut surface created by thin slicing.

This is because the surface of the foam base plate does not have air permeability since the air bubbles are not open. When using a foam sheet with a transparent film attached to only one side as a transparent heat-retaining sheet for a greenhouse, it is preferable to use the sheet with the film attached facing the outside.

This is because the attached film is thicker than the cell walls in the skin of the foam sheet, making it stronger, and when it is turned outward, the surface becomes stronger. be.

[Brief explanation of drawings]

FIG. 1 is a partially exploded perspective view of a foam sheet according to the present invention supported by hand.

Claims (1)

[Claims] 1 Consists of a bonded body of a foamed synthetic resin sheet and a non-foamed synthetic resin film.The foamed sheet has coarse, closed-cell cells, with the cells having an average diameter of 2 mm or more occupying 60% or more of the total surface area. occupies, bubble wall is 0.1mm
A foam sheet made of the following thin sheets, with a sheet thickness of 2
It is a transparent soft synthetic resin foam sheet with a thickness of 0.2 to 10 mm, and the non-foamed film is a transparent soft synthetic resin film with a thickness of 0.2 to 0.02 mm, and the non-foamed film is pasted on the cut surface of the foamed sheet. Transparent soft synthetic resin foam sheet.