JPS62223243A - Composition for open-cellular olefin resin foam - Google Patents

Abstract

PURPOSE:To obtain the titled composition which can give an open-cellular crosslinked foam having fine cells of a high uniformity and excelling in water absorptivity, air permeability and weathering resistance, by mixing an olefin resin with an olefin-modified surfactant, a specified blowing agent and an organic peroxide. CONSTITUTION:100pts.wt. olefin resin (A) (e.g., ethylene/vinyl acetate copolymer) of an MI>=5 is mixed with 0.1-10pts.wt. olefin-modified surfactant (B) (e.g., polyoxyethylene lauryl ether), 1-20pts.wt. blowing agent (C) having an initial decomposition temperature of 100-150 deg.C, which is higher than the m.p. of component A by 20-70 deg.C and having a final decomposition temperature of 150-210 deg.C (e.g., azodicarbonamide), said initial and final decomposition temperatures are controlled by the addition of a decomposition accelerator or a blowing said such as a urea compound, or zinc (compound), and 0.3-5pts. wt. organic peroxide (D) of a 1min half-life temperature of 150-190 deg.C [e.g., 1,1-bis(t-butylperoxy)cyclohexane].

Description

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

[Conventional technology]

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

Conventionally, as a method for producing an open-cell olefin resin foam, a method is known in which a closed-cell foam is once produced and the cell membrane is destroyed by heat expansion, pressure compression, or the like.

In this way, open-cell formation and foaming are performed in separate processes (,
A composition for open-cell ethylene-based resin foam suitable for producing open-cell ethylene-based resin foam in one step is proposed in Japanese Patent Publication No. 49657/1983.

This composition contains 100 parts by weight of ethylene resin, 1 part by weight of blowing agent,
~20 parts by weight, 0.3 to 10 parts by weight of an organic peroxide as a crosslinking agent, and 0.1 to 0.1 to 10 parts by weight of a trifunctional monomer.
10 parts by weight, 0.1 to 5 parts by weight of silicone oil, and the half-life temperature (T,) of the sufficient amount of organic peroxide is 100 to 170 °C, and the foaming temperature ('rr) of the blowing agent is
is 90 to 160°C, and satisfies the following formula: 0°C≦Tp Tt≦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 it fine and highly uniform,
It is assumed that uniform, 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 olefin resin foam of the present invention includes 100 parts by weight of olefin resin, 1 to 20 parts by weight of blowing agent, 0.3 to 5 parts by weight of organic peroxide, and 0.5 parts by weight of olefin-modified surfactant. The organic peroxide has a 1-minute half-life temperature of 150-190°C, and the blowing agent has a decomposition starting temperature of 100-190°C.
It is characterized in that the temperature is 150°C and 20 to 70°C higher than the melting point of the olefin resin, and the temperature at which the blowing agent completes decomposition is 150 to 210°C.

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

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

In addition, examples of the blowing agent include azobisisobutyronitrile, azodicarbonamide, P-toluenesulfonylhydrazide, dinitrosopentamethylenetetramine,
4.4°-Oxybisbenzenesulfonyl hydrazide or the like is used, but in the present invention, the decomposition initiation temperature is set to 20 to 20° below the melting point of the olefin resin as described above.
70°C high (and in the range of 100 to 150°C, and the decomposition completion temperature must be 150 to 210°C, so an appropriate amount of 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 compounds, lead-based compounds, calcium-based compounds (for example, 1
~5 parts by weight) is added and adjusted to satisfy the above conditions.

The melting point (hereinafter sometimes referred to as MP) of an olefin resin is the temperature at which there is a sudden change in the 1-hour temperature curve when the temperature is raised at a rate of 10°C/min using a differential thermal balance. Also, the decomposition start temperature (hereinafter sometimes referred to as TDs) and the decomposition completion temperature are l on a differential thermal balance.
It refers to the rise point and peak point measured at a heating rate of 0°C/min. Furthermore, the organic peroxide used as a crosslinking agent used in the composition of this invention has a half-life temperature of 150°C per minute.
-190°C, 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 (17
4), t-butylbaroxyallylcarbonate-1-(1
72), t-butylperoxyisopropyl carbonate (158), 2,5-dimethyl-2,5-di(penzoylveroxy)hexane (162), 2,2-bis(
t-Butylperoxy)octane (159), (-butylperoxyacetate (160), 2,2-bis(L
-butylperoxy)butane (1'60.5), t-butylperoxybenzoate (170), n-butyl-
4,4-bis(t-butylperoxy)berlate (1
66), di-t-butylshiba-oxyisophthalate (
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 (F9), 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 olefin-modified surfactant used in this invention has a function as a bubble regulator and has a carbon number of 4.
-16 olefin-modified surfactants, such as polyoxyethylene lauryl ether, oxyethylene/oxypropylene block copolymer, polyoxyethylene alkylamine, olefin-modified silicone oil, perfluoroalkyl ethylene oxide, and the like.

Next, to further explain the nature of the various additives added to the olefin resin, if the organic peroxide used as a crosslinking agent is less than 0.3 parts by weight, a sufficient degree of crosslinking cannot be obtained.
Since no improvement in crosslinking efficiency can be expected even if the number of overlays exceeds 5, 0.
It is used in a range of 3 to 5 parts.

Further, even if the amount of the blowing agent exceeds 20 parts by weight, the foaming gas efficiency is poor, so the foaming agent is selected in the range of L 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 olefin-modified surfactant added as a foam regulator is less than 0.1 parts by weight, a sufficient foam regulating effect will not be obtained, and if it exceeds the ■θ important part, no further foam regulating effect will be obtained. Since it is not obtained and bleeds, it is used selectively in the range of 0.1-10 parts by weight.

As with conventional foamable compositions, heat stabilizers, ultraviolet stabilizers, inorganic fillers, pigments, flame retardants, or other additives can be added to the composition of the present invention, if necessary.

Further, this foamable resin composition may be in any form such as pellets, powder, film, or sheet.

[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. In addition, olefin-modified surfactants have good affinity with olefin resins, and the viscosity of the molten resin is well adjusted, allowing bubble breakage to proceed while maintaining the fine cell structure, making it difficult to use during 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 To 100 parts by weight of an ethylene-vinyl acetate copolymer having an Ml of 15 and a vinyl acetate content of 19% by weight (MP; 85°C), 10 parts by weight of azodicarbonamide, 1 part by weight of dicumyl peroxide, A foaming composition was prepared by adding a foaming agent consisting of two parts by weight of urea and one part by weight of zinc oxide (Tos; 135°C), and further adding one part by weight of olefin-modified silicone oil KF-412 (Shin-Etsu Chemical Co., Ltd.). Surface temperature 10
Knead for 5 minutes with a mixing roll at 0°C, then mix at 100°C.
It was molded into a sheet with a thickness of 1 dragon using a press molding machine at °C.

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 good texture was obtained. This foam has a thickness of 2
0 mm, the size of the bubbles was 0.15 to 0.25 mm, and the density was O, (15 (< /crl).This foam absorbed 0.81 g of water per 1 c11+. From this, 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 One piece of cotton cloth was placed on both sides of the press-formed sheet produced in Example 1.
When it was attached using a press molding machine at 00°C and suspended in an oven at 180°C, it foamed uniformly in 4 minutes. When this was taken out and left to cool at room temperature, the foam layer was the same as above.
It was made of open cells that were flexible and had a good feel.

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 Low density polyethylene 100 with MI23 and density 0.916
Parts by weight include 8 parts of azodicarbonamide, 2 parts by weight of α,α-bis(t-butylbaroxym-isopropyl)benzene, 2 parts by weight of urea, 1 part of zinc oxide, and olefin-modified silicone oil KF-412 ( Add 1 part by weight of Shin-Etsu Chemical Co., Ltd. and mix with a mixing roll at a surface temperature of 110°C.
Knead for 1 minute, then knead in a press molding machine at 110°C.
A sheet with a thickness of 0 am was prepared.

When this sheet was placed on a Teflon sheet and heated in an oven at 190°C for 5 minutes, the thickness was 14 mm and the bubble diameter was 0.
-2~0.4 as, apparent density 0.068g/cIi
A white foam of I was obtained.

The absorption rate of this foam was 0.75 g/ct, and it was confirmed that it was an open cell type.

Comparative Example 1 100 parts by weight of ethylene-vinyl acetate copolymer with M I 2.5 and 119% by weight of vinyl acetate (MP; 86°C
), 10 parts of azodicarbonamide (Tns; 19
8°C), 0.5 part of dicumyl peroxide, and 1 part by weight of olefin-modified silicone oil KF-412 (Shin-Etsu Chemical Co., Ltd.) were kneaded for 5 minutes using a mixing roll with a surface temperature of 110'C, and then kneaded in a press at 120'C. A sheet with a thickness of one dragon was produced using a molding machine.

When this sheet was placed on a Teflon sheet and placed in a 190t oven, it started foaming after 3 minutes and completed foaming after 5 minutes, but this sheet was not a smooth foam sheet and the closed cell ratio was 35%. However, the foam was not sufficiently open-celled.

Comparative Example 2 M instead of the ethylene-vinyl acetate copolymer of Comparative Example 1
I 2. Low-density polyethylene (MP; 112°C) with 0.921 parts of O11 was used, but a foam was produced in the same manner as in Example 1, but the cells became coarse and a satisfactory foam could not be obtained. .

〔Effect of the invention〕

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 ([8 peroxide) also has a specific half-life temperature range. Since it is added, the increase in the degree of crosslinking from the start of foaming to the completion of foaming is controlled, and the viscosity of the molten resin is well adjusted by adding a small amount of an olefin-modified surfactant that has good compatibility with the resin. Cell bursting progresses while maintaining the microcellular 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.

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

Further, if this composition is used, an olefin resin foam with excellent water absorption, air permeability, weather resistance, etc., flexibility, and good texture can be obtained.

Claims (1)

[Claims] 1. Consists of 100 parts by weight of an olefin resin, 1 to 20 parts by weight of a blowing agent, 0.3 to 5 parts by weight of an organic peroxide, and 0.1 to 10 parts by weight of an olefin-modified surfactant; The blowing agent has a one-minute half-life temperature of 150 to 190°C, and the blowing agent has a decomposition starting temperature of 100 to 190°C.
150°C and 20 to 70°C higher than the melting point of the olefin resin, and the temperature at which the blowing agent completes decomposition is 150 to 210°C. Composition.