JP2634263B2 - Method for producing olefin-based resin open-cell foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing an open-cell olefin-based resin foam having a smooth surface without wrinkles or irregularities, in which a skin and an open-cell foam are integrated.

[Conventional technology]

By laminating a film as a skin on the surface of the olefin resin foam, a foam having a smooth surface is obtained,
Also, if you use printing film or functional film,
Production of high value-added foams becomes possible.

Conventionally, for laminating an olefin-based resin foam and a plastic film, a heat fusion method, an adhesive method, or the like is generally used.

The heat fusion method is mainly used for closed cell foams.
In closed-cell foams, the air in the cells effectively acts as a repellent material against the compression during thermal fusion, so that the foam and foam thickness can be sufficiently maintained even after the thermal fusion of the film. However, in the case of an open-cell foam, resistance to heating and compression during thermal fusion is small, so that destruction of cells and reduction in thickness of the foam occur. For this reason, a method of laminating the open-cell foam and the film using an adhesive is used.

However, in the case of the adhesive method, there are drawbacks in that the processing steps are complicated, the yield is reduced, and the overall cost is increased due to the cost of the adhesive.

Pressure-sensitive adhesives have also been used as a method to prevent breakage of open cells and decrease in foam thickness, but also the overall cost due to the complexity of processing steps, lower yields, adhesive costs, etc. In addition to high, it has the disadvantage of insufficient adhesive strength.

In the method for producing an open-cell foam that has already been proposed (JP-A-56-121739, JP-A-57-191027),
The surface of the foam obtained is a sliced surface, and there is the above-mentioned problem in laminating the skin on the sliced surface.

When the composition for open-cell foams proposed in Japanese Patent Publication No. 60-49657 is used, an open-cell foam having a skin is obtained. With uneven surface, insufficient surface smoothness,
The mechanical strength is also small.

[Problems to be solved by the present invention]

An object of the present invention is to provide an olefin-based resin open-cell foam having a smooth surface without wrinkles or irregularities, in which a skin made of a plastic film and an open-cell foam are integrated.

Also, the purpose of the present invention, without using an adhesive,
It is an object of the present invention to provide an efficient method of integrating and laminating a film serving as a skin with an open-cell foam.

The present inventors have conducted intensive studies to overcome the problems of the prior art, and as a result, when laminating a film as an outer skin on an open-cell foam, for an open-cell foam containing an olefin resin and a foaming agent. In a method in which the composition is molded into a sheet and then heated and foamed on a support, a film made of an olefin resin is fusion-laminated in advance to a foamable sheet, and then heated and foamed, whereby the film is completely adhered to the surface. It has been found that an olefin-based resin open-cell foam sheet having a smooth surface without any wrinkles or irregularities can be efficiently produced.

Further, it has been found that according to this method, a better foaming efficiency can be achieved than before.

Furthermore, as a support, for example, an endless belt is used, and on the foamable sheet continuously extruded from the extruder, a film that becomes a skin is continuously supplied before the foamable sheet is cooled and solidified. It has been found that a series of operations can be efficiently and continuously performed by pressure bonding with a pressing roll or the like and fusion lamination.

The present invention has been completed based on these findings.

[Means for solving the problem]

Thus, according to the present invention, the composition for an open-cell foam containing an olefin-based resin and a foaming agent is molded into a sheet, and one surface of the foamable sheet is pressure-bonded to a support having a smooth surface, In the method for producing an olefin-based resin open-cell foam that is heated and foamed at a temperature equal to or higher than the decomposition temperature of the foaming agent, and then cooled after the obtained open-cell foam is released from the support, the foam is in contact with the support surface of the expandable sheet. The present invention provides a method for producing an olefin-based resin open-cell foam, which comprises laminating a film made of an olefin-based resin on another surface which has not been melted, and then heating the film to a temperature not lower than a decomposition temperature of a foaming agent.

 Hereinafter, the present invention will be described in detail.

(Composition for Open Cell Foam) The composition for open cell foam used in the present invention is not particularly limited, and includes conventionally known compositions.

 Among them, the following compositions are particularly preferable.

A composition comprising an olefin resin, a foaming agent, and an α-olefin-modified surfactant.

A composition containing an olefin resin, a foaming agent, an α-olefin-modified surfactant, and an organic peroxide.

A composition containing an olefin resin, a foaming agent, an α-olefin-modified surfactant, an organic peroxide, and a process oil.

A composition containing an olefin resin, a foaming agent, a methylphenyl-modified surfactant, and an organic peroxide.

As the olefin-based resin, for example, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-acrylate copolymer, and high-molecular weight blends of these copolymers , Medium and low density polyethylene, chlorinated polyethylene,
Examples include polypropylene.

These compositions may contain a zinc compound, a urea compound, a zinc chloride compound or the like for adjusting the decomposition temperature of the foaming agent, or a bactericidal agent, a fungicide, or a deodorant.

Such an olefin-based resin open-cell foam composition is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-223243 filed by the present inventors.
JP-A-63-159448, JP-A-63-268748, JP-A-3-309535 and the like can be used for the composition for an open-cell olefin-based resin foam, and these compositions If the product sheet is heated and foamed under normal pressure, an open-cell foam having a uniform cell structure can be obtained.

(Olefin-Based Resin Film) The olefin-based resin film used in the present invention has a heat-fusing property with respect to the olefin-based resin used in the composition for an open-cell foam, or has been modified to have a heat-fusing property. Any film may be used as long as it is a surface-treated material.

Specific examples include an ethylene-vinyl acetate copolymer,
High, medium and low density polyethylene, polypropylene and other films can be mentioned.

The olefin resin film preferably has a dimensional change of (±) 5.0% or less, more preferably 2.0% or less, from the melting point of the film material to room temperature.
If the dimensional change is larger than 5.0%, a good foam is obtained by curling the entire foam due to shrinkage of the film upon cooling after foaming, causing unevenness in thickness, and deforming the support. It becomes difficult. In particular, the dimensional change rate 0.3 ~
A range of 5.0% is preferable for obtaining a smooth foam sheet.

There is no particular limitation on the thickness of the film,
If it is too thin, it is difficult to obtain a smooth surface, and if it is too thick, it is difficult to fuse it to the foamable sheet, so that preheating is required.

(Production Method) In the present invention, the composition for an open-cell foam containing an olefin-based resin and a foaming agent is melt-kneaded at a temperature not lower than the melting point of the resin and not higher than the decomposition temperature of the foaming agent using an extruder or a calender roll. And form into a sheet.

One side of the foamable sheet obtained in this way is pressed against the surface of the support having a smooth surface and usually not air-permeable so that air does not intervene, and the film is heat-fused to the other side. And laminate.

When heat-sealing a film, a foamable sheet, a support,
It is preferable to press the film on a foamable sheet with a pressing roll or the like after heating the film in advance, since it is possible to easily perform pressure contact and to obtain a tightly adhered state.

Further, in order to perform the production more efficiently, an extruder is used for molding the foamable sheet, the composition for the foam is melt-extruded from a slit-shaped die into a sheet, and is transferred onto a support. Prior to cooling and solidifying, a heat-fusible film is pressed on the surface using a pressing roll, an air knife, or the like, and then introduced into a heating furnace for heating and foaming.

When a film made of an olefin resin is fusion-laminated on the foamable sheet surface, the size of the film is usually preferably the entire width and the entire length of the foamable sheet. Thereby, the foaming gas is confined inside by the film, and the foaming ratio can be increased.

Examples of the material of the support used in the present invention include steel, fluorocarbon resin, silicone rubber, fluorocarbon resin-coated cloth, fluorocarbon resin-coated glass cloth, and the like, which have a smooth surface and no air permeability, and furthermore have heat resistance, peelability, and mechanical properties. Those having good durability are preferable. Although a mesh-type air-permeable support can be used, it is not preferable because of problems such as releasability and a specific pattern remaining on the surface of the foam.

Further, in order to obtain a long foam, it is preferable to use a support made of an endless conveyor belt.

1 and 2 are views showing an embodiment of the manufacturing method of the present invention.

FIG. 1 is a schematic view showing a method for continuously producing an olefin-based resin open-cell foam using an extruder. The foamable sheet melt-extruded from the extrusion die is transported onto an endless conveyor belt, a film is supplied on the surface thereof, and pressed on the foamable sheet surface by a pressing roll. Thereafter, the laminated foamable sheet is introduced into a heating furnace and heated and foamed.

FIG. 2 is a view showing a method of heating a foamable sheet, a support, and a film in advance by using a heater, and then pressing the film on the foamable sheet with a pressing roll or the like.
Foamable sheets, endless conveyor belts and films are preheated by a heater,
It is pressed and pressed by a pressing roll.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.

[Example 1] The melt index MI was 7.
0, 100 parts by weight of ethylene-vinyl acetate copolymer having an acetic acid content of 6% by weight, 8 parts by weight of azodicarbonamide as a foaming agent, 2 parts by weight of urea and 2 parts by weight of zinc oxide, α-olefin-modified surfactant 2 parts by weight (silicone modified by 50% by C ₁₀ H ₂₀ ) were mixed by a roll mill at 110 ° C. to form pellets.

Using a 50 mm extruder, the pellets are 0.5 mm thick and 5 mm wide.
The sheet was formed into a 00 mm sheet, and this sheet was continuously introduced into a foaming machine having a polytetrafluoroethylene endless belt and a heating furnace using the apparatus shown in FIG.

At this time, the foamable sheet is transferred to the endless belt, and at the same time, an ethylene-vinyl acetate copolymer resin (vinyl acetate content of 5%) is placed between the pressing roll and the foamable sheet.
A film having a thickness of 0.1 mm and a width of 600 mm was supplied, and foaming was performed by passing through a heating furnace at an ambient temperature of 200 ° C. while continuously pressing. After cooling, the foam was peeled off from the endless belt to obtain an open-cell foam in which the skin film was integrated.

The obtained foam had a uniform cell structure with an average cell diameter of 0.35 mm, and the film surface of the skin was very smooth and completely integrated with the foam.

The expansion ratio was 17.0 cc / g without the film. The closed cell rate measured by an air comparison hydrometer was almost 0%.

The dimensional change of the used ethylene-vinyl acetate copolymer resin film from the melting point to room temperature was -1.8%.

Example 2 Instead of the ethylene-vinyl acetate copolymer resin film used in Example 1, a linear low-density polyethylene (density was
A skin film was prepared in the same manner as in Example 1 except that a film having a thickness of 0.05 mm, a width of 600 mm, and a dimensional change rate of -1.1% from the melting point to room temperature made of 2.0) was used. To produce an open cell foam having

The obtained foam had a uniform cell structure with an average cell diameter of 0.35 mm, and the film surface of the skin was very smooth and completely integrated with the foam.

The expansion ratio was 17.0 cc / g without the film, and the thickness was 8.5 mm. In addition, the closed cell ratio measured by an air comparison hydrometer was almost 0%.

[Comparative Example 1] In the method performed in Example 1, without using a film,
Foaming was performed only with the foamable sheet.

Although the obtained foam was a good foam having a uniform cell structure, the surface of the foam was seemingly smooth, but when observed in detail, it had small irregularities due to the cells.

The expansion ratio was 15 cc / g, and the thickness was 7.5 mm.

[Comparative Example 2] Instead of the ethylene / vinyl acetate copolymer resin film used in Example 1, a high-density polyethylene (density: 0.95
4. In the same manner as in Example 1, except that a film made of 1.1) having a thickness of 0.05 mm, a width of 600 mm, and a dimensional change rate of -5.5% from the melting point to room temperature was used. An open cell foam with a film was produced.

The obtained foam was a good foam with a uniform cell structure, the film and the foam were completely integrated, and the film surface of the skin was very smooth, but the dimensional change of the film Since the rate was large, shrinkage in the width direction occurred during cooling, and the endless belt made of polytetrafluoroethylene was deformed, and the thickness of the foam in the width direction became uneven.

The foaming ratio at a portion where the thickness of the obtained foam was relatively uniform was 17.00 cc / g, and the thickness was 8.5 mm.

〔The invention's effect〕

According to the present invention, when laminating the skin film on the open-cell foam, by previously heat-sealing the foamable sheet and then foaming, the skin and the foam are completely integrated,
It is possible to easily provide a long continuous open-cell foam having a smooth surface without any wrinkles or irregularities and with good production efficiency.

Further, according to the method of the present invention, it is possible to produce a foam having high added value by using a printing film and a functional film.

Furthermore, the decomposition gas of the foaming agent is confined between the support and the skin film and is effectively used for foaming, and a foam having a high foaming efficiency and a high magnification can be easily obtained.

The open-cell foam obtained by the present invention has excellent water absorption, weather resistance, water resistance, flexibility, good compression recovery, and excellent tactile sensation. Therefore, cushioning material, heat insulating material, sound absorbing material, filtering material Used as etc.

[Brief description of the drawings]

1 and 2 are views showing an embodiment of the manufacturing method of the present invention. … Extrusion mold,… foamable sheet,… heater,
… Endless belt made of polytetrafluoroethylene,
... Skin film, ... Press roll, ... Heating furnace.

Claims (3)

(57) [Claims] 1. A composition for an open-cell foam containing an olefinic resin and a foaming agent is molded into a sheet, and one side of the foamable sheet is pressed against a smooth surface of a support. In the method for producing an olefin-based resin open-cell foam which is heated at a decomposition temperature or higher to cause foaming, and the obtained open-cell foam is cooled and then separated from the support, the foam-sheet is not in contact with the support surface. A method for producing an olefin-based resin open-cell foam, comprising: laminating a film made of an olefin-based resin on the surface of the above-mentioned item by fusion bonding, and then heating the film to a temperature not lower than the decomposition temperature of a foaming agent. 2. The method according to claim 1, wherein the olefin resin film has a dimensional change of 5.0% or less from its melting point to room temperature. 3. The composition for an open-cell foam is melt-extruded by an extruder to form a sheet, and the foamable sheet is transferred onto a support and pressed, and before the foamable sheet is cooled and solidified. 3. The method according to claim 1, wherein a film made of an olefin resin is continuously supplied onto the surface, and the film is pressure-bonded and fusion-laminated.