JPS6289739A - Ethylenic resin composition for open-cell foam - Google Patents

Abstract

PURPOSE:The titled composition that is obtained by adding a specific silicone block copolymer and a foaming agent, thus giving foamed products with uniform fine cells despite no additional defoaming process, which has good air permeation, water absorption, weather resistance and mold release after molding. CONSTITUTION:The objective composition is obtained by adding 1-30pts.wt. of a foaming agent and 0.5-5pts.wt. of a silicone block copolymer of formula I or II [R is monovalent hydrocarbon; X is -(O)p-(CnH2nO)t-R'; R' is H, alkyl, aryl, aralkyl, carbamyl; p is 0, 1; Y is (CnH2nO)t-R'; m is 0-300; n is 2-10; s is 1-30; q is 1-300; t is 1-100; (CnH2nO) is oxyalkylene].

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 and has a better texture and feel than closed-cell foams, and its production method is characterized by the fact that open-cell foams can be obtained using a one-step heating method.
There is no need for a process of breaking bubbles by applying pressure. This foam is used as a cushioning material, a heat insulating material, a sound absorbing material, or a door material for cushions, pillows, mats, winter clothing, carpet linings, balls, toys, supporters, filters, etc.

Currently ethylene-based! Foams made from Ig resin are used in large quantities as insulation materials, packaging materials, cushioning materials, etc., but most of them are closed-cell foams, and are not suitable for applications that require water absorption, breathability, etc. not being used. Although some open-cell foams with air permeability can be found, they are limited to those with large cell diameters, rough texture, and confusing texture, and low product 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 producing closed-cell foams and then heating and expanding them. It has 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 compressed to break them, but the process involved two steps, the thickness of the resulting foam was thin, and the cells became compliant. However, the bubble membranes overlap and cannot be said to have good water absorption or air permeability. In order to improve this, in Japanese Patent Publication No. 47-51695, 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. A method has been proposed, but in the case of polyethylene, this method requires cooling with an expensive refrigerant such as liquid nitrogen, and the equipment is also expensive.

On the other hand, Japanese Patent Publication No. 55-42100 proposed a one-step hot pressing method in which a fairly large amount of amorphous polypropylene was mixed with polyethylene together with a crosslinking agent as a method for obtaining an 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 - universally shaped polypropylene is sticky even at room temperature. It is a clay-like material that uses adhesive properties 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. When mixed in large amounts, the mechanical properties and feel of the foam are adversely affected.

The technical answer in Japanese Patent Publication No. 54-65172 is to mix 100 parts by weight of polyolefin resin with 30 to 300 parts of inorganic powder and foam it to form a closed cell foam, which is then deformed and ruptured. It is characterized by foaming.

Moreover, in this method, the communication of air bubbles is made 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 must be mixed with a large amount of inorganic material simply to break the foam.

It is easy to imagine that the presence of the inorganic material causes the mechanical properties and tactile sensation of the foam to differ from those of the original polyethylene foam. More importantly, it shows how difficult it is to produce open-cell foams from polyolefins.

As a result of intensive studies in order to solve the many problems contained in these prior art technologies, the present inventors found that (a) a single process as simple as possible, in other words, a separate process for foam breaking; We have developed a method for producing open-cell ethylene resin foam that has excellent water absorption, weather resistance, and texture without using a large amount of additives and without losing the characteristics of the ethylene resin itself. It is characterized by the fact that by adding a small amount of silicone block copolymer, the cell diameter before and after the bubble breakage can be made fine and highly uniform.

2) Therefore, not only a batch-type production method in a heating furnace but also an endless-type production method is possible, and e) the composition before foaming is not limited to shapes such as pellets, powder, films, and sheets.

That is, the present invention provides a foamable composition comprising 100 parts of an ethylene resin and 1 to 30 parts of a blowing agent of the general formula (in the above formula, R is a monovalent hydrocarbon group, and X is -(0)).
p -(Cn H* n O) t -R'R1 is H
, alkyl, aryl, aralkyl or carbamyl group, P is 0 me is 1 Y is (CnHtnO) t-R' m is 0 to 300 n is 2 to 10 3 is 1 to 30 q is 1 to 300 t is from 1 to 100, and (CnH, no) is an oxyalkylene group or a mixture of such groups. ) Silicone block copolymers α1-5 selected from
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, in which the present invention has added parts by weight.

These features of the present invention will be specifically explained below. The form of the foaming composition does not matter, simply pellets,
It is possible to obtain open-cell foams from powders, films, and sheets, and it also enables continuous online molding of them. For example, to obtain a thin foam sheet, it can be manufactured by forming it into a thin film and passing it through a heating furnace, and in the case of a thick sheet, it can be manufactured by passing pellets spread in a single layer through a heating furnace. It is also possible to do this, and the productivity can be increased compared to the conventional method of once producing a bulk foam and slicing it. Of course, even if an extruder, kneader 1, or other mixing method is used at the stage of obtaining these compositions, the temperature must be such that the blowing agent does not substantially decompose.

It is also possible to obtain a powder composition by using powdered ethylene resin and mixing other additive components in powder or liquid form, and by heating this, it is possible to make an open-cell foam. .

The foam obtained by this invention is fine and uniform! I have a 2m structure. It is known that even with many conventional methods in which closed cells are formed once and then broken, the tiny cells do not turn into uniform, fine, open cells at the stage of cell breaking. The foaming method in which the foam is heated and expanded only yields a foam containing many coarse cells. For example, as shown in Example 1, the average bubble diameter is 80~
It has been impossible to obtain open-cell bodies consisting of microscopic cells of 120 microns by 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 six months, it will not discolor or deteriorate.

In the present invention, the ethylene resin is a polymer whose main component is ethylene, including high-pressure polyethylene, low-pressure low-density polyethylene, and linear low-density polyethylene (LLDPE).
), ethylene-vinyl ester copolymer, ethylene-alkyl acrylate copolymer, ethylene-propylene copolymer, ethylene-α/olefin copolymer, and others.

The foaming agent used in the present invention has a foaming temperature of 90°C.
The above is desirable. The decomposition temperature can also be adjusted by using a promoter or an auxiliary agent.

Examples include:

Azobisisobutyronitrile, diazocarbonamide (
(with auxiliary agent), P-toluenesulfonyl hydrazide (with auxiliary agent), 4,4'-oxybis(benzenesulfonylhydrazide) (with auxiliary agent), n-hebutane, n-octane, n-
Nonane, n-decane.

The silicone block copolymer used in the present invention has the general formula % (in the above formula, R is a monovalent hydrocarbon group, and X is -(0)
-(CnHlnO)t-R'R' is a group selected from H, alkyl, aryl, aralkyl, or carbamyl group, P is 0 or 1 Y is (Cn H! n O) t-R'm is 0 to 30
0 n is from 2 to 10 S is from 1 to 30 q is from 1 to 300 t is from 1 to 100 In this case, (CnH, no) is an oxyalkylene group or a mixture of such groups. ) is a silicone block copolymer selected from
Its molecular weight is preferably 500 or more.

If it is less than 500, it may volatilize 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 a solid and dispersion is a concern, it is also possible to use it as a solvent.

By using silicone block copolymer,
When the composition is foamed by heating and then cooled, the resulting foam has poor adhesion to metal plates, plastic films, etc.; The foam can then be peeled off the metal plate.

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

The blowing agent is 1 to 3 parts by weight per 100 parts by weight of ethylene resin.
ON remains are necessary.

If the amount 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 products wastefully escaping into the atmosphere during foaming increases, resulting in poor efficiency.

The amount of silicone block copolymer required is 5 to 5 parts α. If the amount is less than 0.5 parts by weight, there will be 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 contain oxidation stabilizers, ultraviolet leg stabilizers, inorganic photonic agents, pigments, flame retardants, plasticizers, other additives, other resins, rubbers, etc., if necessary. .

In the present invention, the temperature at which the composition is heated is at least the temperature g required for foaming, specifically between about 120 and 250°C.

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

The cooling temperature is desirably 50°C or less.

Heating methods include heating gas such as electricity, direct or indirect 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. .

Furthermore, depending on the purpose, heating can be carried out under normal pressure or under pressure. Examples are given below.

Example 1 Ethylene-vinyl acetate copolymer with a melt index of 20 and a vinyl acetate component of 28% by weight (manufactured by Nippon Unicar) 10
0 parts, Azocica-bonamide with auxiliary agent "Cellmic CAP149J (foaming temperature 125°C; manufactured by Sankyo Kasei)
10 parts and 1 m of a silicone block copolymer represented by the formula (a) (Nippon Unicar G; 1sooC8) were kneaded at 80° C. for 5 minutes using a pant (Lee mixer), and then pelletized.

(-)Si(0((CHs)*S'i0)m (C
tyaO)Special(cm几0)! IC4 horse].

(a) This pellet was compression-molded into a 1-fin-thick sheet, placed on a polyester film, placed on an aluminum plate, heated in an open air at 190°C for 4 minutes, and then taken out and allowed to cool. The resulting foam was easily peeled off from the polyester film. This foam has a thickness of 7s++a
It had uniform, void-free, and fine cells with a cell diameter of 80 to 120 μe, and the appearance was an open-cell foam with a density of 1.10 g/cIL3. Maximum water absorption is α7597c
It was "m".

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 a silicone block copolymer adhered to a polyester film, and when it was peeled off, the foam suffered cohesive failure. Foam thickness: 71it, cell diameter: 1-3 Bg
It has rough air bubbles with an apparent density of I111 l/am”
It was an open cell foam.

The maximum water absorption amount was 0.66-g/cm''.

Comparative Example 2 Similar to Example 1, but instead of using silicone block copolymer, dimethyl silicone oil (10,000
0CSp (manufactured by Nippon Unicar), the foam adhered to the polyester film, and when it was peeled off, the foam suffered cohesive failure. This foam is 71m thick.
With a cell diameter of 100-200μ, the cross-sectional area of the foam is cm”
An average of one void (Q, 5 to 1 mB) was observed per sample. The appearance was an open-cell foam with a density (L 109/CrrL" and a maximum water absorption of 173 fi/cm").

Example 3 In the same manner as in Example 1, magnesium silicate powder Micron White φs, o o was used as an additive.

The foam obtained by further adding 20 parts of S (manufactured by Hayashi Kasei) was easily peeled off from the polyester film.

This foam has a thickness of 7 mm and a bubble diameter of 280 to 230 μC.
It was uniform and void-free. The apparent density is α131
It was an open cell foam with a maximum water absorption α of 2711 parts cm".

Example 4 In the same manner as in Example 3, a sheet was placed directly on a stainless steel plate and heated. Peeling of 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. To 100 parts of ethylene-ethyl acrylate copolymer (Nippon Unicar 3Q) containing 20% by weight of ethyl acrylate component, azocica-bonamide foaming agent "Celmic CAP124J (foaming temperature 130°C:
(manufactured by Sankyo Kasei) 5 parts, silicone block copolymer represented by formula (b) (Japan Unicar family; 500C8)
After kneading 5 parts of t in a Banbury mixer at 80°C for 5 minutes, it was pelletized.

(CHs ) S i (0((CHs )t S 1o
t4 (Ct mountain 0) tscaH*]s (b) This pellet was compression molded into a sheet with a thickness of I II+, placed on a copper plate, heated in an open air at 190°C for 5 minutes, and then taken out and left to cool. did. 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 μ2, uniform, void-free, and fine bubbles, and an apparent density of α21. ! It was an open cell foam of 9/clIL3.

Maximum water absorption is α25! i'/cm".

Example 6 An azodicarbonamide foaming agent [Celmic CAP 500 J (foaming temperature 1
50°C: 10 parts (manufactured by Sankyo Kasei), silicone block copolymer represented by formula (e) (Nippon Unicar;
1 part of the mixture was kneaded in a Banbury mixer at 125° C. for 10 minutes, and then pelletized.

(CL)St(O((C mountain)msio)s(Ct mountain 0
)1゜(C, LE0)1゜QL)m(c) This pellet was compression-molded into a sheet with a thickness of 2 MN, placed on an aluminum plate, and heated in a Matsufuru furnace at 200°C for 5 minutes. It was taken out and left to cool. The obtained foam is
It was easily peeled off from the aluminum plate.

This foam has a thickness of 8m and a cell diameter of 150-200μ.
Uniform and void-free, with an apparent density of 0.2411/am”
It was an open cell foam. Maximum water absorption is 0.299
It was 77 cm.

Example 7 A foam was obtained in the same manner as in Example 6, using polyethylene DNDJ-0405R (Nippon Unicar) having a melt index of 25 and a density of 0.9145 instead of DFDA-1138. This foam has a thickness of 8 mm and a cell diameter of 20 mm.
0~500μC1 It was an open-cell foam with an apparent density of 0.289/Cm. The maximum water absorption was 0.5697.
Met.

r″--t ; 1 Name of agent: Motohiro Kurauchi
Hiroshi Kazama, 1 (,~/ Procedural amendment dated February 4, 1985, Director General of the Patent Office, Ubuya Michibe Case, 1985 Patent Application No. 227744Fi, Name of the invention, For ethylene resin open-cell foams Relationship with the composition amendment case Patent applicant name Nippon Unicar Co., Ltd.

Claims (1)

[Claims] A foamable composition consisting of 100 parts by weight of ethylene resin and 1 to 30 parts by weight of a blowing agent has a general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the above formula, R is a monovalent hydrocarbon group, X is -(O)_p-(CnH_2_nO)_t-R^1
R^1 is a group selected from H, alkyl, aryl, aralkyl, or carbamyl group, P is 0 or 1 Y is (CnH_2nO)_t-R^1 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_2nO) is an oxyalkylene group or a mixture of such groups. ) Silicone block copolymer selected from 0.1 to
5 parts by weight of a thermoplastic resin open-cell foam composition having excellent mold releasability from a base material after heat molding and having uniform and fine cells.