JPH055255B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composition for producing an open-cell foam in a single step, the main component of which is an ethylene resin. More particularly, the present invention relates to a composition for producing open cell foam in a single step comprising an ethylene resin, a blowing agent and a silicone block copolymer.

An object of the present invention is to provide a composition for an ethylene resin open-cell foam that has air permeability, water absorption, and weather resistance. Because of this, it is a foam that is more flexible than closed-cell foam, and has a superior texture and feel.
A feature of the manufacturing method is that an open-cell foam can be obtained by a one-stage heating method, and there is no need for a step of breaking the foam by applying pressure. This foam is used as a cushioning material, a heat insulating material, a sound absorbing material, or a furnace material for cushions, pillows, mats, winter clothing, carpet linings, balls, toys, supporters, filters, etc.

Currently, foams made of ethylene resin are used as insulation materials,
Although they are used in large quantities for packaging materials, cushioning materials, etc., most of them are closed-cell foams and are not used for applications that require water absorption, breathability, etc. Although some open-cell foams with air permeability can be found, they are limited to those with large cell diameters, rough texture, poor texture, and low commercial value. On the other hand, rubber or polyurethane open-cell foams are rapidly degraded by ultraviolet rays or ozone.

Conventional open-cell foams made of ethylene resin are produced by first manufacturing closed-cell foams and then heating and expanding them. Causes "sagging",
There is no elasticity, it is difficult to break the bubbles uniformly, and the bubble diameter is large. In order to solve this problem, a method was developed in which closed cells were first molded and then broken by pressure, but the process was two-step, the resulting foam was thinner, and the cells became open. However, the bubble membranes overlap and cannot be said to have good water absorption or air permeability. In order to improve this problem, Japanese Patent Publication No. 47-31695 proposes a method in which the closed-cell foam is first cooled to a temperature near or below the glass transition temperature, and then compressed to destroy the cell membrane. Although this method has been proposed, in the case of polyethylene, it is necessary to cool it with an expensive refrigerant such as liquid nitrogen, and the equipment becomes expensive.

On the other hand, Japanese Patent Publication No. 55-42100 proposed a one-step pressurizing and hot-pressing method in which polyethylene is mixed with a crosslinking agent in a considerable amount of amorphous polypropylene as a method for obtaining open-cell polyethylene foam in a one-step process. However, in this method, it is said that it is preferable to mix 30 to 50% by weight of amorphous polypropylene, and if it is less than 20% by weight, the open cell ratio will be low. Amorphous polypropylene is a by-product during the production of crystalline polypropylene, and it has no use value and has been discarded, so it makes sense to utilize it, but on the other hand, amorphous polypropylene is sticky even at room temperature. It is a clay-like substance that uses the properties of clay, and is difficult to make into molded products by itself, and has traditionally been added in small amounts as an extender to low-cost foams, as disclosed in this patent. Mixing in large quantities will adversely affect the mechanical properties and feel of the foam.

The technical content of Japanese Patent Publication No. 54-63172 is to disperse and mix 30 to 300 parts by weight of inorganic powder with 100 parts by weight of polyolefin resin, foam it to form a closed-cell foam, and then deform it to break the foam. It is characterized by Moreover, in this method, it is said that the communication of air bubbles is made even more effective by subjecting the inorganic powder to a surface treatment that actively reduces the adhesive force between the inorganic material interface and the polymer. In other words, this foam requires mixing a large amount of inorganic material simply to break the foam. It is easy to imagine that the presence of the inorganic substance causes the mechanical properties and tactile sensation of the foam to be different from those of the original polyethylene foam. More importantly, it shows how difficult it is to manufacture with open cell foam and polyolefin.

The inventors of the present application have conducted intensive studies to solve the many problems contained in these prior art technologies, and have found that
a) A single process that is as simple as possible, in other words, without using a separate process for foam breaking, and b) The characteristic of the ethylene resin itself is not lost due to large amounts of additives, and the water absorption and We have developed a method for producing open-celled ethylene resin foam with excellent weather resistance and texture, and by adding a small amount of silicone block copolymer, the cell diameter before and after bursting can be made fine and highly uniform. It is characterized by the fact that it can be made into something. d) Therefore, not only batch-type production in a heating furnace but also endless-type production is possible, and e) the composition before foaming is not limited to shapes such as pellets, powder, film, and sheets.

That is, the present invention provides a foamable composition comprising 100 parts by weight of an ethylene resin and 1 to 30 parts by weight of a blowing agent. or ₍ In _the above formula, R is a monovalent hydrocarbon _group , P is 0 or 1, Y is (CnH ₂ nO) _t -R', m is 0 to 300, n is 2 to 10, s is 1 to 30, q is 1 to 300, t is 1 to 100, and (CnH ₂ nO) is an oxyalkylene group, or a mixture of such groups.
The present invention relates to a thermoplastic resin open-cell foam composition which has excellent mold releasability from a base material after heat molding and has uniform and fine cells, which is characterized by adding 0.1 to 5 parts by weight.

These features of the present invention will be specifically explained below. The fact that the form of the foaming composition does not matter means that open-cell foams can be obtained from pellets, powders, films, and sheets, and furthermore, online molding of these materials is also possible. . For example, to obtain a thin foam sheet, it can be produced by forming it into a thin film and then passing it through a heating furnace, or in the case of a thick sheet, pellets can be spread in a single layer and passed through a heating furnace. It is also possible to manufacture the foam by a method, and productivity can be improved compared to the conventional method of once manufacturing a bulk foam and slicing it. Of course, even if an extruder, kneader, or other mixing method is used to obtain these compositions, the temperature must be such that the blowing agent does not substantially decompose. In addition, a powdered composition is obtained by using a powdered ethylene resin and mixing other additive components in powdered or liquid form, and by heating this, an open-cell foam is formed. You can also do that.

The foam obtained by this invention has a fine and uniform foam structure. This is because it is known that even with many conventional methods in which closed cells are formed once and then broken, the fine cells do not become uniform, fine, open cells at the stage of breaking the closed cells.
Furthermore, the foaming method in which the foam is heated and expanded in one stage only yields a foam containing many coarse cells. For example, as shown in Example 1, the average bubble diameter is 80 to 120μ.
It has been impossible to obtain such an open-cell body consisting of microscopic cells using conventional methods.

One of the features of the present invention is that a foam with excellent weather resistance can be obtained. For example, even if it is left outdoors for 6 months, it will not discolor or deteriorate.

In the present invention, ethylene resin is a polymer whose main component is ethylene, such as high-pressure polyethylene, low-pressure low-density polyethylene, linear low-density polyethylene (LLDPE), ethylene-vinyl ester copolymer, ethylene-acrylic. Refers to acid alkyl copolymers, ethylene-propylene copolymers, ethylene-α/olefin copolymers, and others.

The foaming agent used in the present invention preferably has a foaming temperature of 90°C or higher. The decomposition temperature can also be adjusted by using a promoter or an auxiliary agent.
Examples include:

Azobisisobutyronitrile, cyazocarbonamide (with auxiliary agent), P-toluenesulfonyl hydrazide (with auxiliary agent), 4,4'-oxybis(benzenesulfonyl hydrazide) (with auxiliary agent), n-heptane, n -Octane, n-nonane, n-decane.

The silicone block copolymer used in the present invention has the general formula or ₍ In _the above formula, R is a monovalent hydrocarbon _group , P is 0 or 1, Y is (CnH ₂ nO) _t -R', m is 0 to 300, n is 2 to 10, s is 1 to 30, q is 1 to 300, t is 1 to 100, and Here, (CnH ₂ nO) is an oxyalkylene group or a mixture of such groups.) The silicone block copolymer preferably has a molecular weight of 500 or more.
If it is smaller than 500, it may evaporate during processing. Those with a molecular weight of 20,000 or more may become solid at room temperature, but can be used in the present invention.
In addition, if it is solid and dispersion is a concern, it is possible to use it by dissolving it in a solvent.

By using a silicone block copolymer, when the composition is foamed by heating and then cooled, the adhesion between the resulting foam and a metal plate, plastic film, etc. is weak. When foamed, the foam can be easily peeled off from the metal plate after cooling.

The ratio of each component of the foamable composition of the present invention is shown below.

The blowing agent is required in an amount of 1 to 30 parts by weight per 100 parts by weight of the ethylene resin.

If it is less than 1 part by weight, there is almost no foaming effect, and if it is more than 30 parts by weight, the amount of foaming agent decomposition product that wastefully escapes into the atmosphere during foaming increases, resulting in poor efficiency.

The amount of silicone block copolymer ranges from 0.5 to
5 parts by weight are required. If it is less than 0.5 parts by weight, there is no effect of providing cells with a uniform fine structure, and if it is more than 5 parts by weight, oozing will be significant and the physical properties of the foam will be adversely affected.

In the present invention, the composition may optionally include oxidation stabilizers, ultraviolet stabilizers, inorganic fillers, pigments, flame retardants, plasticizers, other additives, or other resins,
Rubbers and the like can be added.

In the present invention, the temperature at which the composition is heated is:
The temperature is higher than that required for foaming, specifically about 120°C.
~250℃.

In the present invention, the structure is fixed by cooling the foam after heating.

The cooling temperature is preferably 50℃ or less.

Heating methods include heating gas such as electricity, direct or joint contact with heated metals such as iron or aluminum, external heating using infrared rays, burners, electric heat, etc., as well as internal heating such as high frequency heating. can.

Furthermore, depending on the purpose, it may be heated under normal pressure.
Heating under pressure is also possible. Examples are given below.

Example 1 100 parts of an ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar) with a melt index of 20 and a vinyl acetate component of 28% by weight was mixed with auxiliary-containing azodicarbonamide "Cellmic CAP149" (foaming temperature 125°C; 10 parts (manufactured by Kyokasei) and 1 part of a silicone copolymer represented by formula (a) (manufactured by Nippon Unicar; 1300CS) were kneaded at 80°C for 5 minutes in a Banbury mixer, and then pelletized.

(CH ₃ )Si[O {(CH ₃ ) ₂ SiO} ₃ (C ₂ H ₄ O) ₂₀
(C ₃ H ₆ O) ₂₃ C ₄ H ₉ 〕 ₃ (a) This pellet was compression molded into a 1 mm thick sheet, placed on a polyester film, placed on an aluminum plate, and placed in an oven at 190℃. After heating for 4 minutes, it was taken out and left to cool. The resulting foam was easily peeled off from the polyester film. This foam has a thickness of 7mm and a cell diameter of 80~120μφ.
It was a uniform open-cell foam with no voids, fine bubbles, and an apparent density of 0.10 g/cm ³ . The maximum water absorption amount was 0.75 g/cm ³ .

Example 2 In the same manner as in Example 1, a sheet was placed directly on an aluminum plate and heated. The foam was easily peeled off from the aluminum plate. The physical properties of the foam were similar to those obtained in Example 1.

Comparative Example 1 A foam obtained in the same manner as in Example 1 without using the silicone block copolymer adhered to the polyester film, and when it was peeled off, the foam suffered cohesive failure. Foam thickness 7
It was an open-cell foam having rough cells with a cell diameter of 1 to 3 mmφ and an apparent density of 0.11 g/cm ³ .
The maximum water absorption amount was 0.66 g/cm ³ .

Comparative Example 2 In the same manner as in Example 1, a foam using dimethyl silicone oil (10000CS; manufactured by Nippon Unicar) instead of silicone block copolymer adhered to the polyester film.
When it was peeled off, the foam suffered cohesive failure. This foam had a thickness of 7 mm, a cell diameter of 100 to 200 μφ, and an average of one void (0.5 to 1 mmφ) per 5 cm ² of cross-sectional area of the foam. Apparent density 0.10g/
cm ³ and a maximum water absorption of 0.73 g/cm ³ .

Example 3 In the same manner as in Example 1, magnesium silicate powder Micron White #5000S was added as an additive.
(manufactured by Hayashi Kasei), the foam obtained by adding 20 parts of
It was easily peeled off from the polyester film. This foam had a thickness of 7 mm, a cell diameter of 280 to 230 μΦ, and was uniform and void-free. Apparent density 0.13
g/cm ³ and a maximum water absorption of 0.27 g/cm ³ .

Example 4 In the same manner as in Example 3, a sheet was placed directly on a stainless steel plate and heated. Peeling the foam from the stainless steel plate was easy.

Comparative Example 3 In the same manner as in Comparative Example 2, when a foam obtained by placing a sheet directly on a stainless steel plate and heating it was attempted to be peeled off from the stainless steel plate, the foam suffered cohesive failure.

Example 5 Melt index 20, ethyl acrylate component
For 100 parts of 20% by weight ethylene-ethyl acrylate copolymer (manufactured by Nippon Unicar), 5 parts of azodicarbonamide foaming agent "Cellmic CAP124" (foaming temperature 130°C; manufactured by Sankyo Kasei), (b) 1.5 parts of silicone block copolymer (manufactured by Nippon Unicar; 500CS) represented by the formula was heated at 80°C in a Banbury mixer.
After kneading for 5 minutes, the mixture was pelletized.

(CH ₃ )Si[O {(CH ₃ ) ₂ SiO} ₄ (C ₂ H ₄ O) ₁₅ C ₄ H ₉ ] ₃ (b) Compression mold this pellet into a 1 mm thick sheet and place it on a copper plate. and put it in the oven at 190℃ for 5 minutes.
After heating for a minute, it was taken out and allowed to cool. The resulting foam was easily peeled off from the copper plate. This foam has a thickness of 3.5 mm, a bubble diameter of 100 to 150 μφ, uniform, void-free, and fine bubbles, and an apparent density of 0.21.
It was an open cell foam of g/cm ³ . The maximum water absorption amount was 0.25 g/cm ³ .

Example 6 100 parts of ethylene-α-olefin copolymer DFDA-1138 (manufactured by Union Carbide) with a melt index of 0.4 and a density of 0.894 was mixed with an azodicarbonamide foaming agent "Celmic CAP500" (foaming temperature
150°C; manufactured by Sankyo Kasei) 10 parts, silicone block copolymer represented by formula (c) (manufactured by Nippon Unicar;
1000CS) in a Banbury mixer at 125℃ for 10 minutes.
After kneading for a minute, it was pelletized.

(CH ₃ )Si[O {(CH ₃ ) ₂ SiO} ₆ (C ₂ H ₄ O) ₂₀
(C ₃ H ₆ O) ₂₀ C ₄ H ₉ 〕 ₃ (c) This pellet was compression molded into a 2 mm thick sheet, placed on an aluminum plate, heated in a Matsufuru furnace at 200℃ for 5 minutes, and then taken out. It was left to cool. The resulting foam was easily peeled off from the aluminum plate.
This foam has a thickness of 8 mm and a cell diameter of 100 to 200 μφ.
It was a uniform open-cell foam with no voids and an apparent density of 0.24 g/cm ³ . Maximum water absorption is 0.29g/
It was warm at ^cm3 .

Example 7 A foam was obtained in the same manner as in Example 6, using polyethylene DNDJ-0405R (manufactured by Nippon Unicar) having a melt index of 25 and a density of 0.9145 instead of DFDA-1138. This foam was an open-cell foam with a thickness of 8 mm, a cell diameter of 200 to 500 μΦ, and an apparent density of 0.28 g/cm ³ . The maximum water absorption amount was 0.56 g/cm ³ .

Claims (1)

[Scope of Claims] 1. A foamable composition comprising 100 parts by weight of an ethylene resin and 1 to 30 parts by weight of a blowing agent has the general formula or ₍ In _the above formula, R is a monovalent hydrocarbon _group , P is 0 or 1, Y is (CnH ₂ nO) _t -R', m is 0 to 300, n is 2 to 10, s is 1 to 30, q is 1 to 300, t is 1 to 100, and (CnH ₂ nO) is an oxyalkylene group, or a mixture of such groups.
1. A thermoplastic resin open-cell foam composition having excellent mold releasability from a base material after heat molding and having uniform and fine cells, the composition containing 0.1 to 5 parts by weight.