JPH0523297B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a resin composition suitable for producing an open-cell resin foam containing an olefinic resin as a main component.

[Conventional technology]

Most olefin resin foams are closed-cell foams, but these foams are naturally unsuitable for applications that require water absorption or air permeability.

Conventionally, the method for producing open-cell olefin resin foam is to first produce a closed-cell foam,
A known method is to destroy the cell membrane by heating, expanding, pressurizing, or the like.

In this way, an open-cell ethylene resin foam composition suitable for producing an open-cell ethylene resin foam in one step, instead of performing open-cell formation and foaming in separate steps, is It was proposed in Special Publication No. 60-49657.

This composition consists of 100 parts by weight of an ethylene resin, 1 to 20 parts by weight of a blowing agent, and 0.3 to 0.3 parts by weight of an organic peroxide as a crosslinking agent.
Adding 0.1 to 10 parts by weight of a trifunctional monomer and 0.1 to 5 parts by weight of silicone oil to a crosslinked foaming composition consisting of 10 parts by _weight ; and It is characterized in that the foaming temperature (T _f ) of the blowing agent is 90 to 160°C and satisfies the following formula -10°C≦T _P -T _f <50°C.

[Problem that the invention seeks to solve]

The above-mentioned known composition reverses the relative relationship between the decomposition temperature of the blowing agent and the decomposition temperature of the crosslinking agent compared to conventional foaming technology, and increases the cell diameter before and after foam breakage by adding a small amount of trifunctional monomer and silicone oil. By making the foam fine and highly uniform, uniform and fine open cells can be obtained.

By the way, dimethyl silicone oil, which is generally widely known as silicone oil, used in this composition has poor compatibility with olefin resins and is extremely difficult to knead. For this reason, products made from this composition had drawbacks such as unstable foaming, rough foaming, and restrictions on the setting of foaming conditions. In addition, the trifunctional monomer added at the same time in this composition tends to bleed after addition.
There were drawbacks that often adversely affected the life of the kneaded composition.

This invention aims to solve the above problems.

[Means for solving problems]

The composition for open-cell olefinic resin foam of the present invention includes 100 parts by weight of olefinic resin, 1 to 20 parts by weight of a blowing agent, 0.3 to 5 parts by weight of an organic peroxide,
It consists of 0.1 to 5 parts by weight of a methylphenyl-modified surfactant, the organic peroxide has a 1-minute half-life temperature of 150 to 190°C, and the blowing agent includes:
The decomposition starting temperature is 100 to 150°C and 20 to 70°C higher than the melting point of the olefin resin, and the blowing agent has a decomposition completion temperature of 150 to 150°C.
It is characterized by a temperature of 210℃.

Here, the olefin resin is a polymer such as medium-low-pressure polyethylene, high-pressure polyethylene, linear low-density polyethylene (LLDPE), linear very-low-density polyethylene, or a polymer whose main component is ethylene. Polymers such as copolymers such as ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, ethylene-α-olefin copolymers, or mixtures of two or more of these polymers are used.

It should be noted that if the melt index (MI) of these polymers is less than 5, the closed cell ratio tends to increase, so those having a melt index (MI) of 5 or more are preferable.

Further, as the blowing agent, for example, azobisisobutyronitrile, azodicarbonamide, P-toluenesulfonylhydrazide, dinitrosopentamethylenetetramine, 4,4'-oxybisbenzenesulfonylhydrazide, etc. are used, but the present invention As mentioned above, the decomposition start temperature is set to be 20 to 70°C higher than the melting point of the olefin resin.
In addition to keeping the temperature within the range of 100 to 150℃, the temperature at which decomposition is completed is
Since the temperature must be 150 to 210°C, an appropriate amount of a urea compound (for example, 1 to 20 parts by weight) or an appropriate amount of a decomposition accelerator or foaming aid such as zinc, zinc compound, lead compound, calcium compound, etc. (For example, 1 to 5 parts by weight) is added to adjust the above conditions.

The melting point (hereinafter referred to as MP) of an olefin resin is the temperature at which there is a sudden change in the temperature-time curve when the temperature is raised at a rate of 10°C/min using a differential thermobalance. Also, the decomposition start temperature (hereinafter sometimes referred to as _TDS ) and the decomposition completion temperature refer to the rise point and peak point measured at a temperature increase rate of 10°C/min using a differential thermal balance.

Further, the organic peroxide used as a crosslinking agent in the composition of the present invention has a half-life temperature of 150 to 190°C in 1 minute, and for example, the following are used.

1,1-bis(t-butylperoxy)cyclohexane (154), t-butylperoxymaleic acid (167), t-butylperoxy 3,5,5-trimethylhexane (165), cyclohexane peroxide (174) ), t-butylperoxyallyl carbonate (172), t-butylperoxyisopropyl carbonate (158), 2,5-dimethyl-
2,5-di(benzoylperoxy)hexane (162), 2,2-bis(t-butylperoxy)
Octane (159), t-butylperoxyacetate (160), 2,2-bis(t-butylperoxy)butane (160.5), t-butylperoxybenzoate (170), n-butyl-4,4- screw (t
-butylperoxy)berlate (166), di-t
-Butyl diperoxyisophthalate (168), methyl ethyl ketone peroxide (171), dicumyl peroxide (171), 2,5-dimethyl-
2,5-di(t-butylperoxy)hexane (179), α,α'-bis(t-butylperoxy-
m-isopropyl)benzene (179), t-butylcumyl peroxide (176), di-t-butyl peroxide (186). Note that the numbers in parentheses indicate the half-life temperature (° C.) for 1 minute.

The methylphenyl-modified surfactant used in this invention acts as a foam regulator and is represented by the following formula () or ().

() (CH ₃ )SiO [(CH ₃ ) ₂ SiO] _X (CH ₃・C ₆ H ₅・
SiO) _Y Si(CH ₃ ) () (CH ₃ ) SiO [(CH ₃ ) ₂ SiO] _X [(C ₆ H ₅ ) ₂・
SiO] _Y Si(CH ₃ ) ₃ However, X represents 0 or a positive integer, and Y represents a positive integer.

Next, to further explain the amounts of the various additives added to the olefin resin, if the organic peroxide as a crosslinking agent is less than 0.3 parts by weight, a sufficient degree of crosslinking cannot be obtained, and if it exceeds 5 parts by weight, However, since no improvement in crosslinking efficiency can be expected, it is used in the range of 0.3 to 5 parts by weight.

Moreover, if the blowing agent exceeds 20 parts by weight, the efficiency of the foaming gas will be poor, so the blowing agent should be selected in the range of 1 to 20 parts by weight in relation to the expansion ratio of the foam to be obtained.

On the other hand, if the amount of the methylphenyl-modified surfactant added as a foam regulator is less than 0.1 part by weight, a sufficient foam regulating effect will not be obtained, and if it exceeds 5 parts by weight, an even greater foam regulating effect will not be obtained. Since it may bleed, it should be used in a range of 0.1 to 5 parts by weight.

The composition of the present invention may optionally contain heat stabilizers, ultraviolet stabilizers,
Inorganic fillers, pigments, flame retardants or other additives can be added.

Furthermore, the composition of this invention can be used in the form of pellets, powder,
It is made into a film, sheet, etc. and foamed to form the desired foam.

[Effect]

In the composition of this invention, the blowing agent added to the olefin resin has a specific decomposition temperature range as described above, and the crosslinking agent (organic peroxide) is also added in a specific half-life temperature range. Therefore, the increase in the degree of crosslinking from the start of foaming to the completion of foaming is controlled, and as foaming progresses, crosslinking also progresses.

Furthermore, methylphenyl-modified surfactants have good affinity with olefin resins, and the viscosity of the molten resin can be well adjusted, allowing bubble breakage to proceed while maintaining the fine cell structure, which makes it difficult to use at the stage of the heating and foaming process. , an open-cell crosslinked foam with fine cell diameter and high uniformity can be obtained without the cell structure being crushed or collapsed.

〔Example〕

Example 1 100 parts by weight of an ethylene-vinyl acetate copolymer with an MI of 15 and a vinyl acetate content of 19% (MP; 85
A blowing agent consisting of 10 parts by weight of azodicarbonamide, 1 part by weight of dicumyl peroxide, 2 parts by weight of urea and 1 part by weight of zinc oxide (T _DS ; 135°C) was added to A foamable composition containing 1 part by weight of a modified surfactant (Toray Silicone Co., Ltd.) was kneaded for 5 minutes using a mixing roll with a surface temperature of 100°C, and then formed into a 1 mm thick sheet using a press molding machine at 100°C. Molded.

(CH ₃ )SiO [(CH ₃ ) ₂ SiO] ₂₀ (CH ₃・
C ₆ H ₅ .SiO) ₆₀ Si(CH ₃ ) ₃ When this sheet was placed on a Teflon sheet and heated in a hot air oven at 180°C, it foamed uniformly in 5 minutes.

When this foam sheet was left to cool at room temperature for 10 minutes, a soft foam with a good feel was obtained. This foam had a thickness of 20 mm, a bubble size of 0.15 to 0.25 mm, and a density of 0.05 g/cm ² .
Since this foam absorbed 0.80 g of water per cm ³ , it was confirmed that it was an open-cell foam.

Although this foam was left outdoors for 6 months, no deterioration phenomena such as discoloration or cracking were observed.

Example 2 Cotton cloth was attached to both sides of the press-molded sheet produced in Example 1 using a press molding machine at 100°C, and when the sheet was hung in an oven at 180°C, it foamed uniformly in 4 minutes. When this was taken out and allowed to cool at room temperature, the foam layer was found to be open-celled and soft and pleasant to the touch, as described above.

Example 3 The press-formed sheet produced in Example 1 was placed on a Teflon sheet, placed in a household microwave oven preheated to 180°C, and subjected to high-frequency heating for 2 minutes. An open-cell foam with a soft and pleasant feel similar to that obtained in the above case was obtained.

Example 4 MI23, 100 parts by weight of low density polyethylene with a density of 0.916, 8 parts of azodicarbonamide, α,α'-bis(t-butylperoxy-m-isopropyl)
2 parts by weight of benzene, 2 parts by weight of urea, 1 part by weight of zinc oxide
1 part by weight of a methyl phenyl surfactant (Shin-Etsu Chemical Co., Ltd.) represented by the following formula was added, and kneaded for 5 minutes using a mixing roll with a surface temperature of 110°C.
A sheet with a thickness of 1.0 mm was created using a press molding machine.

(CH ₃ )SiO [(CH ₃ ) ₂ SiO] ₁₀ [(C ₆ H
₅ ) _2SiO ) ₄₀・Si( _CH3 ) _3Place this sheet on a Teflon sheet and heat at 190℃.
When heated in the oven for 5 minutes, the thickness was 14 mm.
A white foam with a cell diameter of 0.2 to 0.4 mm and an apparent density of 0.068 g/cm ³ was obtained.

The absorption rate of this foam was 0.73 g/cm ³ and it was confirmed that it was an open cell type.

Comparative Example 1 100 parts by weight of ethylene-vinyl acetate copolymer with MI2.5 and vinyl acetate content of 19% (MP; 86°C)
and 10 parts by weight of azodicarbonamide (T _DS ; 198
℃), 0.5 part of dicumyl peroxide, and 1 part by weight of a methyl phenyl surfactant represented by the following formula (Shin-Etsu Chemical Co., Ltd.) were added, kneaded for 5 minutes using a mixing roll with a surface temperature of 110℃, and then press-molded at 120℃. A sheet with a thickness of 1 mm was produced using a machine.

(CH ₃ )SiO [(CH ₃ ) ₂ SiO] ₁₀ [C ₆ H ₅
) ₂ SiO] ₄₀・Si(CH ₃ ) ₃ When this sheet was placed on a Teflon sheet and placed in an oven at 190℃, it started foaming after 3 minutes.
After several minutes, foaming was completed, but the foam sheet was not smooth and the closed cell ratio was 35%.
The foam was not sufficiently open-celled.

Comparative Example 2 Low density polyethylene (MP; 112°C) with an MI of 2.0 and a density of 0.921 was used in place of the ethylene-vinyl acetate copolymer in Comparative Example 1, but a foam was produced in the same manner as in Example 1. However, the cells became coarse and a satisfactory foam could not be obtained.

〔Effect of the invention〕

Since the composition of the present invention has the above-mentioned structure, the increase in the degree of crosslinking from the start of foaming to the completion of foaming is controlled, and furthermore, a small amount of methylphenyl-modified surfactant having good compatibility with the resin is added. The viscosity of the molten resin is well adjusted by
Cell bursting progresses while maintaining the fine cell structure generated during foaming and crosslinking.

Therefore, an open-cell crosslinked foam with fine cell diameter and high uniformity can be obtained in one step of the heating and foaming process without the cell structure being crushed or collapsed.

Further, this foamable resin composition is suitable not only for the batch-type production method but also for the endless-type, normal-pressure or open-type foam production.

Further, by using this composition, an olefin resin foam having excellent water absorption, air permeability, weather resistance, etc., flexibility, and good texture can be obtained.

Claims (1)

[Claims] 1 100 parts by weight of olefin resin, blowing agent 1-20
parts by weight, 0.3 to 5 parts by weight of organic peroxide, and 0.1 to 5 parts by weight of methylphenyl-modified surfactant,
The organic peroxide has a 1 minute half-life temperature of 150~
190°C, and the blowing agent has a decomposition start temperature of 100 to 150°C, a melting point of 20 to 70°C higher than the melting point of the olefin resin, and a decomposition completion temperature of the blowing agent. 150~210℃
A composition for open-cell olefin resin foam, characterized in that: