JPH0713154B2 - Method for producing olefin resin open-cell crosslinked foam - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an open-cell crosslinked resin foam containing an olefin resin as a main component.

[Conventional technology]

Olefin resin foams are used in a wide range of fields, but most of them are closed-cell foams. This closed-cell type foam is naturally unsuitable for applications requiring water absorption or air permeability. Further, the impact cushioning material has a large impact resilience, so that the usage method needs to be devised, and the usage range is limited.

With regard to the open-cell foam made of olefin resin, its application is expanding due to the characteristics of olefin resin. As a method for producing an open-cell foam made of this olefin resin, a method of once producing a closed-cell foam and then expanding it by heat or mechanically compressing it to break the cell membrane into open cells It has been known.

As described above, a method suitable for producing an open-cell type olefin-based resin foam in one step, rather than performing foaming and open-cell formation in separate steps, is disclosed in JP-B-60-49657, 6
2-89738, 62-89739.

This composition contains 100 parts by weight of an olefin resin and 1 blowing agent.
To 20 parts by weight, and 0.3 to 10 parts by weight of an organic peroxide as a cross-linking agent, 0.1 to 10 parts by weight of a silicone oil, a silicone block copolymer, or a silicone oil modified with an alkyl group or a phenyl group is added to a crosslinked foaming composition. And that the 10-minute half-life temperature (Tp) of the organic peroxide is 100 to 170 ° C,
The foaming agent has a foaming temperature (Tf) of 90 to 160 ° C. and satisfies the following formula −10 ° C. ≦ Tp−Tf ≦ 50 ° C.

[Problems to be Solved by the Invention]

The known composition reverses the relative relationship between the decomposition temperature of the foaming agent and the decomposition temperature of the cross-linking agent as compared with the conventional foaming technology, and modifies the trifunctional monomer and the silicone oil or the silicone block copolymer, or the alkyl or phenyl group. By adding silicone oil to make the bubble diameter after foaming fine and highly uniform, a uniform and fine open-cell foam can be obtained.

However, the degree of cross-linking of the open-cell body obtained using these compositions is low, and when it is attempted to increase the degree of cross-linking by increasing the addition amount of the trifunctional monomer and the addition amount of the organic peroxide, foaming It becomes difficult to match the timing of cross-linking with each other, the cells become rough, and the variation in the cell diameter in the thickness direction becomes large.

When the degree of cross-linking of the foam is low, it is likely to be deformed by heat and easily set due to repeated compression, which causes many practical restrictions.

In order to solve such a problem and to make a practically good open-cell foam, the degree of crosslinking must be 30%, preferably 50% or more. However, increasing the degree of cross-linking during foaming has the above-mentioned problems.

[Means for Solving the Problems]

The present inventor has conducted diligent studies to eliminate such drawbacks, and as a result, at the same time as making the alkoxysilane function as a surfactant in the foaming process, grafting it onto an olefin resin and condensing and crosslinking the alkoxysilane to solve the problem. I found that I could do it.

That is, an alkoxysilane is blended with an olefin resin together with a foaming agent and an organic peroxide, and the alkoxysilane is graft-reacted with an organic peroxide that generates a free radical site in the olefin resin in the foaming step. Is subjected to condensation reaction and cross-linking to form an open-cell type olefin resin cross-linked foam.

According to the method of the present invention, an open-cell foam having a high degree of cross-linking can be obtained, and since the grafting reaction and the condensation reaction cross-linking of the alkoxysilane can be performed in the foaming step, no special equipment is required. The alkoxysilane also has a function as a surfactant for controlling the growth and breakage of generated bubbles.

The present invention has been completed based on these findings.

Thus, according to the present invention, (A) olefin resin 10
0 parts by weight, (B) a blowing agent having a decomposition starting temperature of 100 to 150 ° C., a melting temperature of 20 to 70 ° C. higher than the melting point of the olefin resin, and a decomposition completion temperature of 150 to 210 ° C. 20 parts by weight, (C) 0.3 to 5 parts by weight of an organic peroxide having a one-minute half-life temperature of 150 to 190 ° C., and (D) a general formula RnSi (O
R) _4- n Alkoxysilane represented by 0.1 to 5 parts by weight (wherein R is vinyl group, chloro group, amino group, mercapto group, epoxy group or methacrylo group, OR is methoxy group or ethoxy group, n Is 1 or 2.) An open-cell type olefin resin crosslinked foam composition containing the following is molded into a sheet at a temperature not higher than the decomposition temperature of the foaming agent and the organic peroxide, and then the foaming agent and the organic peroxide are added. An open-cell type olefin resin characterized by being heated to a temperature equal to or higher than a decomposition temperature to cause foaming, and in the process of the foaming, an alkoxysilane is grafted to an olefin resin to cause condensation reaction crosslinking by the alkoxysilane. A method of making a crosslinked foam is provided.

The alkoxysilane used in the present invention assists the generation, growth, and bubble breaking of bubbles by foaming, and at the same time acts as a surfactant for maintaining the shape of the bubbles that have been broken, part of which is formed by the organic peroxide. The generated radicals are graft-reacted with the olefin-based resin to bond with the olefin-based resin, and finally most of them are grafted onto the olefin-based resin, and the grafted alkoxysilane is condensed and crosslinked to form an open-cell olefin-based resin. Form a resin crosslinked foam.

In this series of foaming steps, particularly in the steps from foaming to foam breaking, it is preferable to increase the resin viscosity after foam breaking in order to keep the foam in a stable state. It is necessary to act on the cross-linking, and therefore, the organic peroxide needs to be added in an amount sufficient for both the cross-linking of the resin and the silane graft reaction.

Further, for the alkoxysilane, since the graft reaction and the condensation reaction crosslinking proceed in parallel with the progress of foaming,
The amount added is required to maintain a sufficient effect as a surfactant.

Examples of the olefin resin used in the present invention include medium- and low-pressure method polyethylene, high-pressure method polyethylene, linear low-density polyethylene (LLDPE), linear ultra-low-density polyethylene (VLDPE), and other polymers containing ethylene as a main component. Polymers, for example, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-α olefin copolymer, copolymers such as ethylene-ethyl acrylate copolymer, chlorinated polyethylene, ionomer, chlorsulfone Examples thereof include derivatives of polyolefin polymers such as polyethylene, and mixtures of two or more of these polymers.

The foaming agent used in the present invention has a decomposition initiation temperature of 100 to 150.
℃ and the melting point of the olefin resin is 20 ~
70 ℃ higher and decomposition completion temperature 150-210 ℃
Any foaming agent may be used, and the decomposition start temperature and decomposition completion temperature may be adjusted using a foaming auxiliary.

Examples of the foaming agent include azobisisobutyronitrile, azodicarbonamide, p-toluenesulfonyl hydrazide, dinitrosopentamethylenetetramine, 4,
Although 4'-oxybisbenzenesulfonyl hydrazide and the like are used, among these, azodicarbonamide is the most preferable in terms of the amount of generated gas, the effect of the foaming aid, the economical efficiency and the like. The blowing agent is 100 parts by weight of the olefin resin,
Usually, a proportion of 1 to 20 parts by weight is suitable, and the amount to be used is determined within this range from the target expansion ratio, the amount of gas generated by the foaming agent used, and the like.

If the decomposition start temperature of this foaming agent is less than 100 ° C, processing is difficult, and there is a risk that the foaming agent will decompose in the kneading step of the composition. Conversely, if it exceeds 150 ° C, the The viscosity is not balanced, the molten resin film is broken by the pressure of the generated gas, and the generated bubbles cannot be held, and the bubbles become coarse. Further, if the decomposition start temperature is lower than the melting point of the olefin resin used + 20 ° C., the viscosity of the resin cannot follow the foaming, the resin film is broken, and it becomes difficult to generate bubbles. When the decomposition start temperature exceeds the melting point of the olefin resin used + 70 ° C, the resin flows and it becomes difficult to generate bubbles.

Note that the above temperature condition range may be difficult to satisfy with a single foaming agent, so a urea compound, zinc oxide,
It is desirable to control the temperature range by adding 1 to 10 parts by weight of a decomposition accelerator such as a zinc compound or a lead compound. Moreover, you may use together 2 types of foaming agents as needed.

The decomposition start temperature and the decomposition completion temperature of the foaming agent refer to each point of the temperature-time curve when measured at a temperature rising rate of 10 ° C / min on a differential thermal balance, and the decomposition start temperature is the temperature of the rising point. Yes, the decomposition completion temperature is at its peak point.

The organic peroxide used in the present invention has a 1-minute half-life temperature.
The temperature may be 150 to 190 ° C., and it may be appropriately selected from among them in view of process convenience and economical efficiency. When a specific example is shown together with a half-minute temperature for 1 minute, 1,1-bis (t-butylperoxy) cyclohexane (154 ° C), t-butylperoxymaleic acid (167 ° C), t-butylperoxy-3,
5,5-Trimethylhexane (165 ° C), Cyclohexane peroxide (174 ° C), t-Butylperoxyallylcarbonate (172 ° C), t-Butylperoxyisopropylcarbonate (158 ° C), 2,5-Dimethyl-2 , 5-
Di (benzoylperoxy) hexane (162 ° C), 2,2-
Bis (t-butylperoxy) octane (159 ° C), t
-Butylperoxyacetate (160 ° C), 2,2-bis (t-butylperoxy) butane (160.5 ° C), t-butylperoxybenzoate (170 ° C), n-butyl-4,4
-Bis (t-butylperoxy) vellate (166
C), di-t-butylperoxyisophthalate (168
℃), methyl ethyl ketone peroxide (171 ℃),
Dicumyl peroxide (171 ° C), 2,5-dimethyl-2,
5-di (t-butylperoxy) hexane (179 ° C),
α, α′-bis (t-butylperoxy-m-isopropyl) benzene (179 ° C.), t-butylcumyl peroxide (176 ° C.), di-t-butyl peroxide (186
℃) and the like.

The organic peroxide is usually added in a proportion of 0.3 to 5 parts by weight with respect to 100 parts by weight of the olefin resin.

It is also possible to improve graftability by adding a polyfunctional monomer and a chain transfer agent.

The alkoxysilane used in the present invention is a dimethylsilicone-based one in which the Si side chain is modified with α-olefin, and those represented by the general formula RnSi (OR) _4- n are used. , Vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, 3-aminopropyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane are more preferable. The alkoxysilane is usually added in a proportion of 0.1 to 5 parts by weight with respect to 100 parts by weight of the olefin resin. If it is less than 0.1 part by weight, the effect cannot be expected sufficiently, and if it is more than 5 parts by weight, the effect is not increased and it is uneconomical, and the bleeding phenomenon may occur.

In addition, the resin composition of the present invention includes a fungicide, a fungicide,
It is also possible to add flame retardants, extenders, deodorants, odorants, etc.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Example-1] Ethylene vinyl acetate copolymer (density 0.93, MI 17.0) 10
0 part by weight, azodicarbonamide 10 parts by weight, zinc oxide 1.0
Parts by weight, urea 0.5 parts by weight, antioxidant 0.5 parts by weight, dicumyl peroxide (DCP) 1.0 parts by weight, vinyl tris (2-
(Methoxyethoxy) silane 1.0 part by weight is mixed, 65 mmφ
A sheet having a thickness of 1.0 mm was prepared by an extruder.

The decomposition start temperature of the foaming agent in this kneaded material is 140 ° C,
The decomposition completion temperature was 165 ° C.

Next, this sheet was placed in a hot air circulation furnace at 180 ° C. for 5 minutes for foaming, then taken out of the furnace and cooled to obtain a good foam. The measurement results of this foam are shown in Table-1.

[Example-2] Ethylene vinyl acetate copolymer (density 0.93, MI 17.0) 10
0 part by weight, azodicarbonamide 10 parts by weight, zinc oxide 1.0
6 parts by weight of 6 parts by weight, 0.5 parts by weight of urea, 0.5 parts by weight of antioxidant, 1.0 part by weight of DCP, 1.0 part by weight of vinyltriethoxysilane.
Create a 1.0 mm thick sheet with a 5 mmφ extruder and
It was placed in a hot air circulation furnace at 0 ° C. for 5 minutes for foaming, then taken out of the furnace and cooled to obtain a good foam. This foam was placed at 65 ° C. and 90% humidity for 24 hours.

The measurement results of this foam are shown in Table-1.

[Comparative Example-1] Ethylene vinyl acetate copolymer (density 0.93, MI 17.0) 10
0 part by weight, azodicarbonamide 10 parts by weight, zinc oxide 1.0
65 parts by weight, by mixing parts by weight, 0.5 parts by weight of urea, 0.5 parts by weight of antioxidant, 1.0 part by weight of dimethyl silicone, 1.0 part by weight of DCP.
A 1.0 mm thick sheet was prepared by an extruder, put in a hot air circulation furnace at 180 ° C. for 5 minutes for foaming, and then taken out of the furnace and cooled to obtain a good foam. The measurement results of this foam are shown in Table-1.

[Comparative Example-2] Ethylene vinyl acetate copolymer (density 0.93, MI 17.0) 10
0 part by weight, azodicarbonamide 10 parts by weight, zinc oxide 1.0
Parts by weight, antioxidant 0.5 parts by weight, vinylethoxysilane 1.0
1 part by mixing 65 parts by weight and DCP 2.0 parts by weight, and a 65 mmφ extruder.
A 0 mm thick sheet was created.

The decomposition start temperature of the foaming agent in this sheet was 160 ° C, and the decomposition completion temperature was 195 ° C.

This was placed in a hot air circulation furnace at 210 ° C. for 5 minutes for foaming, then taken out of the furnace and cooled to obtain a foam. However, looking at the cross section of this foam, the foam diameter was large and the foam was non-uniform as a whole. The measurement results of this foam are shown in Table-1.

[Effect of the Invention] According to the present invention, it is possible to obtain an open-cell foam having a higher degree of cross-linking than a foam obtained by a conventionally proposed method. Further, since the grafting reaction and the condensation reaction crosslinking of the alkoxysilane according to the present invention are performed in the foaming step, no special equipment is required.

The foam according to the method of the present invention is an open-cell foam of an olefin resin, which is excellent in water absorption, air permeability, and weather resistance, is flexible, and has a good texture. It is excellent and is preferably used for sealing materials, pad materials, cushioning materials, carpet underlays and the like.

Claims (1)

[Claims] (A) 100 parts by weight of an olefin resin, (B) a decomposition start temperature of 100 to 150 ° C., which is 20 to 70 ° C. higher than the melting point of the olefin resin, and a decomposition completion temperature. 1 to 20 parts by weight of a foaming agent having a temperature of 150 to 210 ° C, (C) an organic peroxide having a half-life of 1 minute to 150 to 190 ° C 0.3 to
5 parts by weight, and (D) 0.1 to 5 parts by weight of an alkoxysilane represented by the general formula RnSi (OR) _4- n (wherein R is a vinyl group, a chloro group, an amino group, a mercapto group, an epoxy group or a methacrylyl group. , OR is a methoxy group or an ethoxy group, and n is 1 or 2.) at a temperature lower than the decomposition initiation temperature of the foaming agent and the organic peroxide. Molded into a sheet, then heated to a temperature not lower than the decomposition temperature of the foaming agent and the organic peroxide to foam, and in the process of foaming, alkoxysilane is grafted onto an olefin resin and condensed by the alkoxysilane. A method for producing an open-cell type olefin-based resin crosslinked foam, which comprises performing reactive crosslinking.