JPS5867734A - Production of foamed product of crosslinked ethylenic resin with continuous foam structure - Google Patents

Abstract

PURPOSE:A trifunctional monomer and silicone oil are added to a composition containing an ethylenic resin, a foaming agent and a crosslinking agent to produce the titled foamed product with a fine and uniform structure, high gas permeability, water absorption and weather resistance through a one-step heating process, for example, for cushioning. CONSTITUTION:(A) A crosslinkable foaming composition consisting of 100pts.wt. of an ethylenic resin of 1 or more melt index, 1-20pts.wt. of a foaming agent with a foaming temperature (Tf) of 90-160 deg.C such as azobisbutyronitrile, 0.3- 10pts.wt. of a crosslinking agent of an organic peroxide with a half temperature (Tp) of 100-170 deg.C in 10min, wherein Tp-Tf is -10-50 deg.C is combined with (B) 0.1-10pts.wt. of a trifunctional monomer such as triallyl cyanurate and (C) 0.1-5pts.wt. of silicone oil or its derivative with a viscosity of less than 100 centistokes at room temperature. Then, the resultant composition is heated for 1-60min and the foamed product is cooled down to lower than 50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention contains an ethylene resin as a main component. Compositions and methods for producing open cell foam in a single step. More specifically, 'a crosslinking and foaming composition consisting of 100 parts by weight of an ethylene resin, 1 to 20 parts by weight of a blowing agent, and 5 to 10 parts by weight of an organic peroxide a, 1 trifunctional monomer, 11 to 1
0 parts by weight, 1 to 5 parts by weight of silicone oil or its derivative a, and the 10-minute half-life temperature (T, ) of the organic peroxide is 100 to 170°C, and the foaming temperature (T, ) of the blowing agent is 5. 110 to 160°C, and satisfies the following formula % formula %: an open cell cross-linked Edelene resin foam composition; and pellets of this composition.

As powder, films, sheets, and other molded products.

Method K is required for producing an open-cell warm cross-sectional ethylene resin composite by a single process of heating this.

The foam targeted by the present invention has excellent air permeability, water absorption, and weather resistance, and since it is an open cell type, it is more flexible than a closed cell type, and has an excellent texture and feel, and is a pure white foam. A feature of the method is that an open-cell foam can be obtained by a one-step heating method, and there is no need for a step of breaking the foam by applying pressure. This foam is used for cushions, pillows, mats, and anti-agitation clothing.

Cushioning materials, heat insulation materials, and sound absorbing materials for the lining of Carpella F, balls, toys, supporters, filters, etc.

Or used as furnace material.

Currently, foams made of ethylene resin are used as insulation materials.

Although they are used in large quantities as packaging materials, cushioning materials, etc., most of them are closed-cell foams and are not used for applications that require water absorption and breathability. Although some open-cell foams with air permeability can be found, they have large cell diameters, rough texture, poor texture, and are considered to have 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 producing closed-cell foams and then heating and expanding them. It causes "origami".

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 the closed cells were once molded and then compressed to break them, but the process involved two steps and
Although the obtained foam has a thinner thickness and the cells are continuous, the cell membrane is swollen and cannot be said to have good water absorption or air permeability. KIf to improve this! ! Kosho 47
-In 314?5, I'm independent! The Type I foam is first cooled to a temperature near or below the glass transition temperature;
Later, a method was proposed in which the bubble film was destroyed by compressing it, but this method required cooling polyethylene with an expensive refrigerant such as liquid nitrogen.

4. Equipment-wise. It becomes expensive.

On the other hand, Japanese Patent Publication No. 11855-42100 proposed a one-step pressurizing and hot pressing method in which a fairly large amount of amorphous polyethylene is 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 50 to 50% by weight of amorphous polypropylene, and that if the content is less than %zofrt-, 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 -1 amorphous polypropylene It is a clay-like material that is sticky even at room temperature, and it is difficult to obtain molded products by itself.

Traditionally, it has been added in small amounts as a filler in low-cost foams, and as shown in this patent, when mixed in large amounts it has a negative impact on the mechanical properties and feel of the foam.

The technical content of Japanese Patent Publication No. 54-65172 is to disperse and mix 30 to 500 parts by weight of inorganic powder with 100 parts by weight of polyolefin resin, and then foam the mixture to form a closed-cell foam.
It is characterized by deforming the foam and causing it to burst. Moreover, in this method, it is suitable for the inorganic world and poly! It is said that the communication of air bubbles can be made more effective by subjecting the inorganic powder to a surface treatment that actively reduces its adhesion to -. 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 produce open-cell foams from polyolefins.

As a result of intensive studies to solve the many problems contained in the prior art, the inventors of the present application found that (a) a single process as simple as possible, in other words, a separate process for breaking the bubbles; 0) Developed a method for producing open-cell ethylene resin foam that does not lose its characteristics due to large amounts of additives and has excellent compression properties, water absorption, weather resistance, and feel. c) The first technical component is that the relative relationship between the decomposition temperature of the blowing agent and the decomposition temperature of the crosslinking agent is reversed from that of conventional foaming technology, and the second one is that It is characterized by the fact that by adding a trifunctional group and a small amount of silicone oil or a derivative, the bubble diameter before and after foam breakage can be made fine and highly uniform. e) For this reason, batch-type manufacturing methods in heating furnaces are not required,
Endless production is possible;)) The composition before foaming can be pellets, powders, films, sheets or other shaped articles. 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 seeds, and furthermore, online molding of these materials is also possible. . For example, in order to obtain a thin foam sheet, it can be manufactured by forming it into a thin film and then passing it through a heating furnace, and in the case of a thick sheet, it can be manufactured by spreading pellets in a single layer and passing it 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, a nylon, or other mixing method is used at the stage of obtaining these compositions, it is necessary that the temperature is such that the crosslinking agent and the blowing agent do not substantially decompose. Furthermore, by using powdered ethylene resin and mixing other additive components in powdered or liquid form, a powdered composition can be obtained, which is then heated to form an open-cell foam. can.

The foam obtained by this invention has an extremely fine and uniform foam structure. It is known that even with many conventional methods in which closed cells are formed once and then broken, the fine bubbles do not turn into uniform, fine, open cells at the stage of breaking the closed cells. In the foaming method of heating and expanding, only a foam containing many coarse cells can be obtained.For example, the average cell diameter is 12 as shown in Example 1.
U±IIL03 It has been impossible to obtain open-cell bodies consisting of microscopic cells by conventional methods.

The principle behind how it became possible to produce such uniform, fine, open-celled cells is not necessarily clear, but if we consider the factors, it is likely that the addition of silicone oil or its derivatives and the Increasing the rate of building by functional groups and using a reaction mechanism that is completely opposite to the conventional method of selecting blowing and crosslinking agents to foam after building all combine organically to achieve this goal. It is assumed that this has become possible.

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 (LLDPI).
), ethylene-vinyl ester copolymer, ethylene-alkyl acrylate copolymer, ethylene-propylene copolymer, ethylene-a/olefin copolymer, and others.

The organic peroxide used in the present invention has a decomposition temperature of 100°C to 170°C with a half-life of 10 minutes, and the following are examples. However, the value in parentheses is the decomposition temperature (°C).

Succinic acid heroxide (110)% pensoyl peroxide (110), t-butylperoxy-2-ethylhexanony) (115) hp-chlorobenzoyl peroxide (11s), t-butylperoxyisobutyrate (115), t- Butyl peroxybutyrucarbonate (1s5), t-butyl silacrate (14G)% 2.5-dimethyl-2,5-di(benzoylperoxy)hexane (140), t-butyl peroxyacetate (140) hsheet- Butyl diperoxyphthalate (140), t-butylperoxymaleic acid (140)% cyclohexanone peroxide (1
45), t-butyl peroxybenzoate (145)
% Methyl ethyl ketone peroxide (150)b dicune luberoxide (1SO), 2.5-dimethyl-2,
5-di(i-butylperoxy)hexane (1SS),
t-Butylcumyl peroxide (155)% in -butyl hydroperoxide (1s8L di-t-butyl peroxide (160), 2,5-dimethyl-2,5-di(t)
-butylperoxy)hexyne 5 (170).

The foaming agent used in the present invention has a foaming temperature of 90°C to 140°C, and is used in combination with an accelerator or auxiliary agent to maintain the decomposition temperature within this range! ! The following examples include those with IK adjustment.

Azobisisobutytetranitrile, diazocarmenamide (
(auxiliary formula), p-sylenesulfonylhydrazide (auxiliary formula), 44'-oxybis(benzenesulfonylhydrazide (auxiliary formula), 1-hebutane, -1-octane, turtle-nonane, m-fitton.

Trifunctional mono used in the present invention! Examples of - include triallyl cyasate, triallyl isocyanurate, triallyl trimellitate, and others.

The silicone oil used in the present invention has a strength of 100 centistokes or less at room temperature.

In the present invention, the decomposition temperature i of the organic peroxide at a half-life of 10 minutes is the foaming temperature of the blowing agent T.

When h Tp-T1=ΔT, -1ot:<Δ'r
A combination of an organic peroxide and a blowing agent that satisfies the condition <50°C is desirable. In other words, by combining a crosslinking agent and a blowing agent that satisfy the above conditions, we can create a trifunctional product! When a composition in which a combination of - and silicone oil is added to an ethylene resin is heated under normal pressure, crosslinking begins at the same time or slightly after foaming occurs, and crosslinking slowly progresses until foaming is completed. The crosslinking density sharply increases after or just before the completion of foaming, and the resulting homogeneous open cells or open cells containing some closed cells are stabilized and fixed by cooling.

If ΔT<-10°C, when the composition is heated, crosslinking will preferentially proceed and foaming will not occur at all.
Even if it happens, it will be a closed cell type.

Further, when ΔT>50°C, foaming proceeds preferentially and the bubbles are not stabilized.

In the present invention, trifunctional heptamers have the effect of rapidly increasing the degree of crosslinking, and further improve the heat resistance temperature and increase the modulus of elasticity of the resulting foam.

Silicone oil has the effect of providing a foam with uniform, fine cells.

The melt index of the ethylene resin used in the present invention is 1 or more.

If it is less than 1, the composition may not melt when heated, and burning spots or discoloration may occur.

The composition ratio of each component of the composition used in the present invention will be listed.

For 100 parts by weight of ethylene resin, 5 to 10 parts by weight of organic peroxide is required. If the amount is less than 13 parts by weight, the viscosity of the composition will hardly increase during foaming, even if the composition is trifunctional! Even if - is added, the foam will collapse and even if the amount is more than 5 stol parts, there will be little improvement in the efficiency of the structure.

The amount of blowing agent required is 1 to 20 parts by weight. If the amount is less than 1 part by volume, the foaming effect will be negligible, and if it is more than 20 parts, the amount of foaming agent decomposition products wastefully escaping into the atmosphere during foaming will increase, resulting in poor efficiency.

The amount of trifunctional monomer is required (L1 to 10 parts by weight. If it is less than 11 parts by weight, the effect will hardly be seen and
If the amount is more than 10 parts by weight, it will ooze out onto the surface of the composition, causing adverse effects such as slipping during processing.

The amount of silicone oil or its rust conductor is required to be a1 to 5 parts by weight. If it is less than 1 part by weight per liter, there is no effect of providing a gas with a uniform fine structure, and if it is more than 5 parts, K oozes out significantly.

In this invention 1ji, the composition may contain oxidation stabilizers, ultraviolet 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 necessary for foaming and structural formation, and specifically is between 120 and 250°C.

In the present invention, the decomposition temperature of the organic peroxide is indicated by the temperature at which the pure product has a half-life of 10 minutes, so the structure proceeds even below this temperature.

In the present invention 1jl, the heating time is the time necessary to generate a foam having open cells, specifically 1 to 6
It is in the range of 0 minutes.

In the present invention, when the foam is cooled after heating, the structure is fixed by K. The cooling temperature is desirably 50°C or less.

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

Furthermore, depending on the purpose, heating can be performed under normal pressure or under increased pressure.

Examples are given below.

Example 1 Mel) index 100, vinyl acetate content 28 weight -
Ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar) 1
00 parts, 5 parts of azobisuitronitrile (foaming temperature 100°C), 1 part of t-butylperoxyisobutyl carginide (decomposition temperature 155°C), triallyl trimellitate 11S, sig. Add 1 part of corn oil (10 centistokes: made by Nippon Tool Car) to 70℃ in a Banbury mixer.
The mixture was kneaded for 5 minutes and turned into Beretsu F.

This pellet was formed into a 1 mm thick sheet by compression molding at 70°C. Pressure 1 hour is 50 to 915II respectively
Th2 minutes. When this sea F was made of 200 mesh metal steel and placed in an open air at 130℃, it was found that 10
It foamed uniformly in minutes. KI to expose this foam as it is.
After leaving it for D minutes, I took it out and left it to cool to room temperature, and the thickness was 5.
%Bubble size L2(a17~&2!i)m Apparent secant modulus S OIIg/eII
&"A white foam with 30 flexible open cells was obtained using a hardness tester (type C). The apparent density of this foam was 165 J97S8, and when water was absorbed, the foam had a density of 1 am" Contains CL45t of water with K.

I left this sheet outside for 6 months, but it changed color.

No deterioration phenomena such as cracks occurred.

Example 2 7 tons of pellets obtained in Example 1 were placed in a Petri dish and 15
When heated for 10 minutes in an open environment at 0°C, foaming occurred uniformly. After leaving this foam for another 15 minutes, it was taken out and allowed to cool to room temperature K. Example 1 had a diameter of 7es and a thickness of 2α.
A foam similar to that obtained was obtained.

Example 3 Put the 7t pellet used in Example 1 into a petri dish and
After heating for 5 minutes in an open environment at .degree. C., foaming started when the mixture was heated for 3 minutes using a high-frequency heating device (frequency 2450 MHm output IKW: JEOL Ltd.). When it was taken out after 1 minute and allowed to cool, a foam similar to that of Example 2 was obtained.

Example 4 Melt index 20, vinyl acetate component 2
An ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar) was pulverized to obtain a powder with an average particle size of 40 pieces. For 100 parts of this powder, 7 parts of azoshicar pump containing auxiliary agent (foaming temperature 135°C), 1 part of 1-butylperoxyisopropyl carbonate (decomposition temperature [1ss°C), triallylinocyanurate) IIB, One piece of silicone oil (20 centistokes; manufactured by Nippon Unicar) was stirred in a Super Mi medium for 10 minutes and left for one day.

When this powder composition 6f was placed in a Petri dish and heated in an open air at 140° C. for 7 minutes, it foamed uniformly. When the mixture was left to stand for 10 minutes and cooled, a uniform white foam with a diameter of 7 mm and a thickness of 2 mm was obtained.

This foam has a cell size of 12 ((Ll y~a
25) 5 on w hardness tester (type C)
It had 5 soft open cells. The foam had an apparent density of 1551 q/m''.

Example 5 To 100 parts of ethylene-ethyl acrylate copolymer (Nippon Unicar 11 [) with a melt index of 6 and an ethyl acrylate component of 20% by weight, 10 parts of azodicarbonate containing auxiliary agent (foaming temperature 135°C), 1 part of kunluver oxide (decomposition temperature 150°C).

One part of triallyl cyanurate and one part of silicone (10-Ni-Stokes; Nippon Eni*-If) were kneaded in a Banbury mixer at 90°C for 5 minutes, and the mixture was pelletized.

This pellet was heated to 50 kg/aIM for 5 minutes at 90'C.
It was compression molded at a pressure of 1 u.

Place this sheet on top of 200mm gold copper and heat to 180℃.
I boiled it for 7 minutes in the open air.

Foamed uniformly. When I left it for 15 minutes and left it to cool, it turned out to be thick (S sw & air bubbles). S' a 4 ((L
4-a8), a white foam with 55 open cells in a Th hardness tester (type C) was obtained. The foam had an apparent density of 1504 F/Il&'' and absorbed IL6 of water per inch of foam.

Example 6 Melt index & O, density a? 18 low-tubularity polyethylene (Nippon Tools*-ml) 1o O@ to 511,
5 parts of azodicarbonate containing auxiliary agent (foaming temperature 145°C), 1 part of 2.5-dimethyl, 2.5-tabit-t-butylperoxy)hexane (decomposition temperature 155°C), 1 part of triallyl trimellitate, Add 1 part of silicone oil (10 centistokes: manufactured by Nippon Unicar) to 110 ml in a Banbury mixer.
The mixture was kneaded at ℃ for 5 minutes and pelletized.

Is this beret 120t? :100 by/- for 5 minutes
A sheet with a thickness of 2 mm was obtained by compression molding under a pressure of 2 mm. I bought this sea F for 200 meters.

When placed in an open air at 190°C, foaming occurred in 10 minutes. When left to cool for 10 minutes, the thickness was 61 m, and the average bubble size was αB (16 to 10).

A foam sheet of 70 was obtained in a hardness tester (type C) with open cells. The apparent density of this foam is 118 to 9/1, which is comparable to that of foam 131 (L5F
absorbed water.

Comparative Example 1 10 G parts of low density polyethylene with melt index cLs, can degree a, 920, 5 parts of auxiliary-containing azocycarbonand (foaming temperature 145°C), 2.5-dimethyl-2
, 1 part of 5-di(t-butylperoxy)hexane (decomposition temperature 155°C), 1 part of triallyl tritate, and 1 part of silicone oil (10 centistorium, manufactured by Nippon Unicar) were heated at 120°C in a pampaline xer. The mixture was kneaded for 5 minutes and pelletized.

This pellet was heated to 120℃ for 5 minutes,
A sheet with a thickness of 1M was obtained by compression molding under a pressure of 1M. Place this sea F on the gold steel of 200 mesh, and 230
When the polyethylene was placed in an open state at ℃, foaming started while the polyethylene was still semi-molten, and the boundaries of the original pellets appeared on the surface of the sheath.

So I put it in the open air at 260 degrees Celsius and it got burnt.

Note that when the sample was left at 230° C. for 40 minutes and cooled, a slight KR ponding occurred, although it was uneven.

Comparative Example 2 Melt index 28. Ethylene-vinyl acetate copolymer with vinyl acetate content of 28 weight tS (manufactured by t3 Honko Uni) 1
00 parts, 5 parts of auxiliary-containing azocycal amide (foaming temperature 150°C), cyisoglobyl carbonate in t-butyl peroxide (decomposition temperature 135°C) 11S,) 9allylisocyanurate 1 part, Add 1 part of silicone oil (10 centistokes: manufactured by Nippon Unicar) to 90% in a Banbury mixer.
The mixture was kneaded at 0° C. for 5 minutes and pelletized.

When this pellet was heated in an open air at 160°C, only a hard pellet was obtained without foaming at all. (80 on Hardness Tester Type C) Comparative Example 3 Ethylene-ethyl acrylate copolymer 1001SK with melt index 6 and acrylic ethyl content 20 volume.
On the other hand, asobis isopti tetranitrile (foaming temperature 100
5 parts of λ5-di(t-butylperoxy)hexane (decomposition temperature 155°C), 1 part of triallyl trimellitate, and 1 part of silicone oil (10 centistokes; Nippon Unicar 11i1) at 90°C. The mixture was kneaded for 5 minutes and pelletized.

When this pellet 7f was placed in a petri dish and heated in an open air at 180℃, it started foaming at 3 degrees, but 15 degrees.
When I left it for a minute and cooled it down, it was flattened (
Only solid or non-uniform foams were obtained from L4-15.0 cells.

Comparative Example 4 The composition was the same as in Example 3, except that seriallyl trimellitate was not blended, and foaming was carried out under the same conditions. The size of the bubbles in the foam was widely distributed (L! 12 to 16B), and a cavity with a diameter of about 151 g was formed in the center.

Comparative Example 5 Foaming was carried out using the composition and conditions of Example 5, except that no silicone oil was mixed. The size of the foam bubbles is A24 ~
It has a wide fiK distribution of 162 votes, has a low bubble breakage rate, and has a water absorption amount of only α28t (lam"@su), which makes it impossible to achieve the object of the present invention.

Claims (1)

Scope of Claims t A crosslinking and foaming composition consisting of 100 parts by weight of an ethylene resin, 1 to 20 parts by weight of a blowing agent, and 3 to 10 parts by weight of an organic peroxide α as a crosslinking agent is added with a trifunctional monomer α1 to 10 parts by weight. 1 to 5 parts by weight of silicone oil or its derivative α, and the 10-minute half-life temperature (T) of the organic peroxide.
is 100-170℃, and the foaming temperature (T, ) of one blowing agent is 100-170℃.
90 to 140° C., and satisfies the following formula %: 2. A method for producing an open-cell crosslinked ethylene resin foam by a single step of forming the composition according to claim 1 into pellets, powder, or films, sheets, or other molded products and heating the product. .