JPH10245446A - Production of foamed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamed body capable of forming a shape-recovering foamed body by compression in a short time by compressing a raw material foamed body in a state kept within a specific temperature range. SOLUTION: A raw material foamed body comprising an closed-cell resin foamed body is compressed in a state kept at a temp. 30 deg.C and the softening temperature of a resin forming the raw material foamed body, preferably, between 40 deg.C and (the softening temperature of the resin) -20 deg.C to provide a foamed body having delayed shape recovering properties. Thereby, the shape- recovering foamed body can be obtained in a shaft time while improving the productivity thereof. Furthermore, the foamed body having the thickness close to the objective one can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam having a delayed shape recovery property (hereinafter referred to as "shape recovery foam").
And a method for producing the same.

[0002]

2. Description of the Related Art The inventors of the present invention initially hold a bubble in a contracted state within the elastic limit of the resin, and gradually recover the original thickness while balancing the inner and outer pressures of the bubble by the elastic recovery force of the resin. A shape-recovery foam obtained by shrinking a raw material foam made of a closed-cell resin foam that recovers has already been proposed (see Japanese Patent Application No. 7-299654).

As a method of obtaining such a shape-recovery foam, a gas in closed cells (cells) is compressed while exhausting the gas through closed cell walls by sandwiching the raw material foam between press plates or the like. There is a way to do that. However, since the speed at which the gas in the gas bubbles permeates the cell wall is slow, the method using this compression requires a considerable amount of time to shrink the raw material foam to a predetermined thickness, resulting in poor productivity. There is.

[0004] Incidentally, a foaming ratio of 30 as a raw material foam is obtained.
In order to obtain a shape-recovered foam having a thickness of 2 mm by compressing a polyethylene foam having a thickness of 10 mm and a closed cell ratio of 80% (compressed thickness of 0.5 mm), it took about 40 minutes.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a method for producing a foam capable of obtaining a shape-recovered foam by compression in a short time.

[0006]

In order to achieve such an object, a method for producing a foam according to the first aspect of the present invention (hereinafter referred to as "a method for producing the first aspect") is independent. In a method for producing a foam having a delayed shape recovery property obtained by compressing a raw material foam made of a cellular resin foam,
The raw material foam was compressed while maintaining the temperature at 30 ° C. or higher and the softening temperature of the resin forming the raw material foam or lower.

According to a second aspect of the present invention, there is provided a method of producing a foam (hereinafter referred to as a “method of producing a second aspect”) obtained by compressing a raw material foam in the production method of the first aspect. Immediately after compression, the contracted body was cooled to 20 ° C. or less.

[0008] The method for producing a foam according to the invention according to claim 3 (hereinafter referred to as "the production method according to claim 2") is a method according to claim 1 or 2, wherein An air passage communicating with the inside of the cell was previously formed at a predetermined pitch in the raw material foam.

In the manufacturing method according to any one of claims 1 to 3, the method for compressing the raw material foam is not particularly limited. For example, two endless belts or rollers arranged with the raw material foam facing each other at a desired interval There is a method of compressing between endless belts and rollers for a predetermined period of time, or a method of compressing between two press plates for a predetermined period of time.

The method of heating the raw material foam is not particularly limited. For example, in the method of compressing using a press plate, a rod-shaped heater or a flow path of a heating medium such as heating oil is provided in the press plate. A method in which the press plate itself is heated by the heat of the heater or the heat medium to compress and simultaneously heat the raw material foam through the press plate, and in the method of compressing using the endless belt or roller, the endless belt or roller is used. Is heated first, and the raw material foam is heated by the heat of the endless belt or roller while being compressed between the endless belt or roller. Also, a method of installing a compression device itself having an endless belt, a roller or a press plate in a hot air heating device or an infrared heating device and compressing the raw material foam by the compression device and simultaneously heating the raw material foam by hot air or infrared light is also used. I do not care.

The temperature of the raw material foam at the time of compression is limited to 30 ° C. or higher but not higher than the softening temperature of the resin forming the raw material foam.
It is below ° C. If the temperature is lower than 30 ° C., the time required for compression is not much different from the conventional one. If the softening temperature is exceeded, the resin relaxes the stress during compression, and the shape recovery property of the obtained shape recovery foam deteriorates.

The raw material foam, that is, the resin forming the shape-recovery foam is not particularly limited, but the one having a compression set (according to JIS K 6767) of 20% or less, particularly 10% or less, is used for the shape recovery. For example, olefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polymethyl acrylate, polymethyl methacrylate, ethylene- Acrylic resins such as ethyl acrylate copolymer, butadiene-styrene, acrylonitrile-styrene, styrene, styrene-butadiene-
Styrene resins such as styrene, styrene-isoprene-styrene, styrene-acrylic acid, acrylonitrile-
Polyvinyl chloride resins such as polyvinyl chloride and polyvinyl chloride-ethylene; vinyl fluoride resins such as polyvinyl fluoride and polyvinylidene fluoride; amide resins such as 6-nylon, 6.6-nylon and 12-nylon; polyethylene Saturated ester resins such as terephthalate and polybutylene terephthalate, polycarbonate, polyphenylene oxide, polyacetal, polyphenylene sulfide,
Examples include thermoplastic resins such as silicone resins, thermoplastic urethane resins, polyetheretherketone, polyetherimide, various elastomers, and crosslinked products thereof.

The closed cell ratio of the raw material foam is determined by the amount of recovery required by the shape recovery foam to be obtained, and is 5%.
If it is above, it can be used, but a particularly preferred range is 30% to 100%. The method for producing the raw material foam includes known methods including the method described in the Plastic Foam Handbook, and any foaming method using a pyrolytic foaming agent and a physical foaming agent may be used.

The raw material foam may contain a filler, a reinforcing fiber, a coloring agent, an ultraviolet absorber, an antioxidant, a flame retardant, and the like, if necessary. Examples of the filler include calcium carbonate, talc, clay, magnesium oxide, zinc oxide, carbon black, silicon dioxide, titanium oxide, glass powder, glass beads and the like.

Examples of the reinforcing fibers include glass fibers and carbon fibers. Examples of the coloring agent include pigments such as titanium oxide. The antioxidant is not particularly limited as long as it is generally used,
For example, tetrakis [methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)] methane, dilauryl thiodipropionate, 1,1,3-tris (2-methyl-4-hydroxy-5- t-butylphenyl) butane and the like.

Examples of the flame retardant include brominated flame retardants such as hexabromophenyl ether and decabromodiphenyl ether, phosphoric acid-containing flame retardants such as ammonium polyphosphate, trimethyl phosphate and triethyl phosphate, melamine derivatives, inorganic flame retardants and the like. One type or a mixture of two or more types may be mentioned. The shape of the shape-recovery foam is not particularly limited, and examples thereof include a sheet-like shape, a rod-like shape, and a tube-like shape, and the shape before shape recovery and the shape after shape recovery may be non-similar. Absent.

In the manufacturing method according to the second aspect, the cooling temperature is limited to 20 ° C. or lower, but is preferably 10 ° C. or lower. If the cooling temperature is higher than 20 ° C., the shrinkable body shrunk by compression may recover its shape during winding by a winder or the like. Further, it is preferable to provide a heat insulating layer between the compression section and the cooling section.

In the manufacturing method according to the third aspect, the shape of the ventilation path is not limited to a straight line, but is not particularly limited to a spiral shape or an arc shape. The cross-sectional shape of the air passage is not particularly limited, for example, a circle, a triangle, a square, a star, a line,
Wavy lines and the like can be mentioned.

Although the size of the ventilation path is not particularly limited,
The cross-sectional area is preferably 7 mm ² (when the cross section is circular, about 3 mm in diameter) or less, and more preferably the maximum (width) thereof is equal to or less than the average cell diameter of the closed cells. That is, if it is too large, the bubble structure may be broken, and the original shape may not be recovered. The interval between the centers of the air passages is not particularly limited. When the cross section of the air passage is smaller than the bubble diameter, it is set to twice or more the bubble diameter. Is preferably not less than the bubble diameter.

The depth of the ventilation path is determined by the required recovery time, and is not particularly limited. It is preferable that the ventilation path reaches at least three or more internal closed cells from the surface. further,
The ventilation path may be provided perpendicular to the surface of the raw material foam, or may be provided at a predetermined angle to the surface. Moreover, you may make it provide spirally toward the inside of a shape recovery foam.

The method of forming the ventilation path is not particularly limited, but when a hole-shaped ventilation path is provided, a needle (Kenyama),
A method using a drill, an electron beam, a laser beam, or the like can be used. When a groove-shaped ventilation path is provided, a cutter (knife) is used.
And the like.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described in detail with reference to the drawings. FIG. 1 shows a first embodiment of a method for producing a foam according to the present invention.

In this manufacturing method, as shown in FIG. 1, a strip-shaped raw material foam 1 wound in a roll shape is compressed by a compression device 2a.
Continuously between the two press plates 21, 21 of
The press plates 21 and 21 are heated by a rod-shaped heater (not shown) provided inside the press plates 21 and 21, and the raw material foam 1 is heated between the press plates 21 and 21 at 30 ° C. or more. The raw material foam 1 is compressed while being heated to a temperature equal to or lower than the softening temperature of the resin forming the resin foam, thereby forming a contracted body 3 which is contracted to a predetermined thickness.

Next, the contracted body 3 is continuously introduced into the cooling chamber 4, and is cooled to 20 ° C. or less in the cooling chamber 4 by cold air sent from the cooler 5, and the shape-recovered foam 6 is cooled.
After that, the winding device 7 continuously winds. In FIG. 1, reference numeral 8 denotes a heat insulating material that prevents heat of the press plates 21 and 21 from being transmitted into the cooling chamber 4.

That is, according to this production method, the raw material foam 1 is compressed while being heated to a temperature not lower than the softening temperature of the resin forming the raw material foam 1 at 30 ° C. or more, so that the resin does not relax the stress. And the gas in the closed cells easily escapes through the cell wall. Therefore, the time required for compression can be reduced. In addition, since the contracted body contracted by the compression is cooled to 20 ° C. or less immediately after the compression, the shape recovery foam 6 does not recover its shape until it is wound by the winding device 7. That is, it is possible to reliably obtain the shape-recovery foam 6 having a predetermined thickness.

FIG. 2 shows a second embodiment of the method for producing a foam according to the present invention.

In this manufacturing method, two endless belts 22, 22 are provided between a press plate 21 provided with a rod-shaped heater inside and a press plate 21 as the compression device 2b as in the compression device 2a. The raw material foam 1 is placed between the upper press plate 21 and the upper endless belt 22 by the endless belt 22.
And the endless belt 22, and between the lower endless belt 22 and the lower press plate 21, in order, to compress and obtain the contracted body 3. It is similar.

That is, according to this manufacturing method, even if the width of the compression device 2b is reduced, the length of the compression section can be increased. That is, the installation space for the device is reduced.

FIG. 3 shows a third embodiment of the method for producing a foam according to the present invention.

In this manufacturing method, instead of the compression device 2a,
It has two endless belts 23 facing each other, and a flow path (not shown) for passing the heat medium through the drive rolls 24, 24 and the pressure rolls 5, ..., 25 of the endless belts 23, 23. Are heated by the heat of the drive rolls 24, 24 and the pressurizing rolls 25,..., 25, which are heated by the heat medium passed through the raw material foam 1 through the flow path, using the compression layer 2c provided with each. The configuration is the same as that of the first embodiment except that the raw material foam 1 is compressed while being heated by being passed between the endless belts 23, 23.

FIG. 4 shows a fourth embodiment of the method for producing a foam according to the present invention. In this manufacturing method, a plurality of cooling rolls 41, 41,
The structure is the same as that of the first embodiment except that the contracted body 3 is immediately cooled to 20 ° C. or lower at 42,.

[0032]

Embodiments of the present invention will be described below in more detail. (Example 1) Low density polyethylene (manufactured by Mitsubishi Chemical Corporation, LF
440HB, 100 parts by weight of Tm (melting point = 112.5 ° C.), 15 parts by weight of azodicarbonamide (AZ-HM, manufactured by Otsuka Chemical Co., Ltd.) as a foaming agent, 1 part by weight of zinc oxide as a foaming aid, peroxide 0.5 part by weight of dicumyl peroxide as a product is put into an extruder (φ = 50 mm, L / D = 22), kneaded, extruded as a raw material sheet having a thickness of 3 mm, and immediately after extruding the raw material sheet at 175 ° C. Crosslinking was performed by heating on a belt for 5 minutes to obtain a crosslinked sheet.

The crosslinked sheet was placed in a hot air oven at 250 ° C. and foamed to obtain a raw foam having a foaming ratio of 33 times (33 cc / g, a closed cell ratio of 88%, and a thickness of 10 mm. The raw foam had a diameter of 500 μm. After forming holes at a density of 8 holes / cm ² in the thickness direction with a needle, this raw material foam was heated to 40 ° C. from above and below from above and below while being heated to 40 ° C. by a press plate having a rod-shaped heater inside as in FIG. After being compressed to 5 mm and kept in a compressed state for 10 minutes to obtain a contracted body, the contracted body was left in a normal temperature atmosphere to obtain a shape-recovered foam.

Example 2 A shrinkable body obtained in the same manner as in Example 1 was immediately cooled to 3 ° C. with a cooling roll as shown in FIG. 4 to obtain a shape-recovered foam.

(Comparative Example 1) A shape-recovered foam was obtained in the same manner as in Example 1 except that heating was not performed during compression. (Comparative Example 2) While being heated to 120 ° C during compression,
A shape recovery foam was obtained in the same manner as in Example 1 except that the compression time was changed to 2 minutes.

The thickness of the shape-recovered foams obtained in Examples 1 and 2 and Comparative Examples 1 and 2, and the thickness after leaving the shape-recovered foams at room temperature and normal pressure for one month were measured. The results are shown in Table 1.

[0037]

[Table 1]

From the above Table 1, it can be seen that according to the production method of the first aspect of the present invention, the shape-recovered foam can be obtained by shrinking the raw foam in a short time. Further, it can be clearly understood that the shape-recovery foam having a thickness closer to the intended thickness can be obtained by using the manufacturing method of the second aspect.

[0039]

The method for producing a foam according to the present invention is configured as described above, so that a shape-recovery foam can be obtained in a short time. Therefore, the productivity of the shape recovery foam is improved.

Further, according to the manufacturing method of the second aspect, it is possible to obtain a shape-recovery foam having a thickness closer to a desired thickness. Further, according to the manufacturing method of the third aspect, the raw material foam can be brought into a contracted state in a shorter time.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a manufacturing apparatus showing a first embodiment of a method for manufacturing a foam according to the present invention.

FIG. 2 is a schematic explanatory view of a manufacturing apparatus showing a second embodiment of the method for manufacturing a foam according to the present invention.

FIG. 3 is a schematic explanatory view of a manufacturing apparatus showing a third embodiment of the method for manufacturing a foam according to the present invention.

FIG. 4 is a schematic explanatory view of a manufacturing apparatus showing a fourth embodiment of the method for manufacturing a foam according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material foam 2a, 2b, 2c Compressor 3 Shrink body 4 Cooling chamber 41, 42 Cooling roll 6 Shape recovery foam

Claims (3)

[Claims] 1. A method for producing a foam having delayed shape recovery by compressing a raw foam made of a closed-cell resin foam, wherein the raw foam is formed at a temperature of 30 ° C. or higher. A method for producing a foam, comprising compressing the foam while maintaining the temperature at or below the softening temperature of the foam. 2. The method for producing a foam according to claim 1, further comprising a step of cooling the contracted body obtained by compressing the raw material foam to 20 ° C. or lower immediately after the compression. 3. The method for producing a foam according to claim 1, wherein an air passage communicating from the surface to the inside of the closed cells is formed in the raw foam at a predetermined pitch in advance.