JP2003128826A - Polyolefin resin crosslinked foam and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin crosslinked foam comprising cells having uniform and fine inner diameters on the surface of and inside the foam. SOLUTION: A polyolefin resin having a boiling point of lower than 120 deg.C is mixed with a blowing agent composition at least consisting of azodicarbonamide and p,p'-oxybis(benzenesulfonyl hydrazide), the compounding ratio being 98-20 pts.wt. of the azodicarbonamide and 2-80 pts.wt. of the p,p'- oxybis(benzenesulfonyl hydrazide), at a kick-off temperature of the blowing agent or below, molded to a long sheet form, irradiated with ionizing radiation to be crosslinked, and heated to the kick-off temperature of the blowing agent composition or above to be foamed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyolefin resin crosslinked foam and a method for producing the same. More specifically, for example, it can be used as a heat insulating material for building materials, industrial materials, adhesive tape base materials, furniture, household appliances, cushioning agents such as heat and cold insulating agents, heat insulating materials, etc. The present invention relates to a polyolefin resin cross-linked foam having a smoothed surface and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a crosslinked foam of a polyolefin resin, a method of heating a polyolefin resin molded product containing a crosslinking agent and a foaming agent under atmospheric pressure to form a crosslinked foam, and electron beam etc. There is known a method of heating a molded product composed of a mixture of a polyolefin resin and a foaming agent which has been cross-linked in advance by ionizing radiation under normal pressure to form a cross-linked foam. These methods are well known as a method for producing a polyolefin resin crosslinked foam, but particularly when the obtained foam is subjected to adhesion processing, an adhesive is uniformly and efficiently applied to the surface thereof. For,
It was desired that the surface of the foam be smoother than that of the conventional product.

However, in the above-mentioned conventional polyolefin resin cross-linked foam, the cells present in the obtained foam have large cell diameters or the cell diameters of the surface layer portion and the central portion vary, and However, there was a problem in that the amount of adhesive applied was uneven, and peeling from the adherend occurred. On the other hand, a foam produced by block foaming under reduced pressure can obtain uniform fine cells, but a block foam cannot obtain a long foam, and continuous production on a line is difficult.
Further, slicing is performed in a post-processing step to obtain an appropriate thickness, but there is a problem that unevenness of bubbles appears on the slicing surface and a smooth surface cannot be obtained.

In order to meet such a problem, Japanese Patent Laid-Open No. 58-58
No. 29636 discloses a method for producing a crosslinked foam under normal pressure so that the foam has a good appearance and the cells are uniformly fine, and a part of the mixed foaming agent is intended prior to the heat foaming. There is known a method of producing a foam in which uniform fine bubbles are grown by using a large number of these bubbles as a nucleating agent in the subsequent heat-foaming step.

[0005]

In any case, according to the above-mentioned prior art, the foam having uniform bubble diameters existing inside the obtained foam and having sufficiently miniaturized foam. I couldn't get a body.

The present invention solves the above problems of the prior art,
It is an object of the present invention to provide a polyolefin resin crosslinked foam having a smooth surface and having a smooth surface by having uniform fine cells throughout, and a method for producing the same.

[0007]

Means for Solving the Problems As a result of intensive research to solve the above-mentioned problems, the present inventors have found that thermoplastic resins include azodicarbonamide and P, P'-oxybis (benzenesulfonylhydrazide). The inventors have found that such an object can be achieved by kneading a foaming agent composition consisting of the above and crosslinking-foaming, and reached the present invention. That is, the polyolefin resin crosslinked foam of the present invention comprises a polyolefin resin having a melting point of less than 120 ° C. and at least azodicarbonamide and P, P′-oxybis (benzenesulfonylhydrazide). Is 98 to 20 parts by weight, and P, P'-oxybis (benzenesulfonylhydrazide) is added to the foam composition having a compounding ratio of 2 to 80 parts by weight.

In the method for producing a crosslinked foamed polyolefin resin according to the present invention, azodicarbonamide and P, P'are added to a polyolefin resin having a melting point of less than 120 ° C.
A foaming agent composition composed of oxybis (benzenesulfonylhydrazide) is mixed at a temperature equal to or lower than the decomposition start temperature of the foaming agent, molded into a long sheet shape, and then irradiated with ionizing radiation to be crosslinked to form a foaming agent composition. It is characterized in that it is heated to a temperature not lower than its decomposition temperature to cause foaming.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below.

The polyolefin resin used in the cross-linked polyolefin resin foam of the present invention is not particularly limited, and examples thereof include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, Examples thereof include ethylene-α-olefin copolymers, propylene-α-olefin copolymers, ethylene-ethyl acrylate copolymers and ethylene-vinyl acetate copolymers. These may be used alone or in combination of two or more when used. Can be used. Of these olefin-based resins, the polyolefin-based resin having a crystal melting peak (melting point Tm ₁ ) having a melting point of less than 120 ° C. is not particularly limited, and examples thereof include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, Copolymers such as ethylene-diene copolymer, ethylene-propylene-diene terpolymer, ethylene-octene copolymer, high-pressure low density polyethylene, new polyolefin (linear low density polyethylene, ultra low density polyethylene,
Examples thereof include cyclic olefin (co) polymers.

The "melting point" represented here is the crystal melting peak temperature of the DSC curve obtained by differential scanning calorimetry, and the measuring condition is from -10 ° C to 200 ° C.
The temperature was raised at a rate of C / min, the temperature was held for 5 minutes, the temperature was lowered at a rate of 10 ° C / min between 200 ° C and -10 ° C, and the temperature was further held for 5 minutes, and the temperature was set between 10 ° C and 200 ° C for 10 minutes. When the temperature is raised at a rate of ° C / min, the melting point is the crystal melting peak temperature of the DSC curve obtained by the second heating. The polyolefin resin used in the present invention is mixed below the decomposition temperature of the foaming agent, and in order to form a long sheet shape,
It is necessary that the melting point be less than 120 ° C. However, if the melting point is less than 50 ° C., it is possible to knead or extrude the foaming agent without decomposing it, but when it is heat-processed into a foamed product, the heat resistance is remarkably reduced, which may be impractical. . Therefore, the preferable melting point of the polyolefin resin is in the range of 50 to 120 ° C., and more preferably in the range of 60 to 100 ° C. in terms of production stability such as increase in production capacity and defects due to decomposition of the blowing agent during production. preferable.

In the present invention, as described above,
It is necessary to use a polyolefin resin having a melting point of less than 120 ° C, but depending on the application requiring physical properties such as heat resistance, mechanical properties (strength / elongation), and moldability, melting of crystals with a melting point of 120 ° C or higher is possible. You may mix the polyolefin resin which has a peak with 1 type (s) or 2 or more types.

As the polyolefin resin having a crystal melting peak (melting point Tm ₂ ) having a melting point of 120 ° C. or more, linear polyethylene obtained by copolymerizing ethylene and α-olefin having 4 to 12 carbon atoms, high density Polyethylene, polypropylene, novel polyolefin (cyclic olefin (co) polymer, isotactic polypropylene, syndiotactic polypropylene, syndiotactic polystyrene, ethylene-carbon monoxide alternating polymer), ethylene-propylene copolymer, ethylene-1 -Butene copolymer, ethylene-propylene-non-conjugated diene copolymer, ethylene-ethyl acrylate copolymer, ethylene-
Glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate copolymer and ethylene-
Examples include propylene-g-maleic anhydride copolymer, ABS, and olefin-based thermoplastic elastomer, which may be used alone or in combination of two or more kinds.

In the olefin resin crosslinked foam of the present invention, the resin raw material having a melting point of at least less than 120 ° C.
It is preferably composed of 100 parts by weight. When the content of the polyolefin resin having a melting point of less than 120 ° C. is less than 20 parts by weight, the amount of the resin melted at the decomposition start temperature of the foaming agent is small, so that a foam having an appropriate cell shape may not be obtained. Yes, and the appearance may deteriorate.

The blowing agent used in the present invention is azodicarbonamide (hereinafter referred to as ADC) which is a pyrolytic chemical blowing agent.
A) and P, P′-oxybis (benzenesulfonylhydrazide) (hereinafter abbreviated as OBSH). Since ADCA has a decomposition starting temperature of around 175 ° C and a decomposition temperature of around 200 ° C, and has a small amount of heat generated during decomposition, a large amount of generated gas, and nontoxic and odorless excellent properties, it is used as a foaming agent for thermoplastic resins. Widely used. OBS
H has a decomposition start temperature of around 120 ° C and a decomposition temperature of 160 ° C
It is in the vicinity, does not cause coloring, and has excellent characteristics of nontoxic and odorless. The blending ratio of these foaming agent compositions is ADC
A is 20 to 98 parts by weight, OBSH is 2 to 80 parts by weight, and more preferably ADCA is 95 to 70 parts by weight and OB.
SH is 5 to 30 parts by weight. If the ADCA is more than 98 parts by weight and the OBSH is less than 2 parts by weight, it may not be possible to obtain sufficiently fine bubbles, and the mixing ratio is ADCA.
Is less than 20 parts by weight and OBSH exceeds 80 parts by weight, the resulting foam may be colored blackish brown or the resin may be carbonized, which may cause problems in appearance and safety. The blending ratio of these foaming agent compositions to 100 parts by weight of the polyolefin resin can be appropriately added in an amount necessary to obtain a desired expansion ratio, but is preferably in the range of 2 to 25 parts by weight. If the amount of the foaming agent composition is less than 2 parts by weight with respect to 100 parts by weight of the polyolefin resin, a predetermined expansion ratio may not be obtained, and uniform bubbles may not be formed. On the other hand, if the compounding ratio of the foaming agent composition exceeds 25 parts by weight, the expansion ratio increases, the flexibility increases, and it is preferable in terms of buffering property, but the resin portion in the volume decreases, so the mechanical strength and heat resistance are reduced. May decrease. In addition, the diameter of each cell inside the foam may be large. Further, in the case of lowering the foaming temperature at the time of production to improve the production efficiency, a known decomposition accelerator such as a compound containing urea or a metal may be used for ADCA to obtain a decomposition temperature close to that of OBSH.

The "decomposition start temperature" and "decomposition temperature" of the thermal decomposition type chemical foaming agent in the present invention are represented by the following measuring methods. A sample of 1 g of the chemical foaming agent was sampled in a polyethylene film, put in a test tube, 10 ml of liquid paraffin was added, and the test tube was immersed in a liquid paraffin bath and connected to a gas guide tube connected to a gas buret. To do.
After that, the liquid paraffin bath is kept at 25 ° C to 250 ° C for 2 ° C.
The temperature is raised at a rate of / minute, and the amount of gas introduced into the buret is measured every minute. The curve obtained by subtracting the expansion amount of air that does not contain the sample measured in advance is taken as the decomposition curve of the thermal decomposition type chemical blowing agent. In the decomposition curve of the thermal decomposition type chemical foaming agent obtained from this, the temperature at which gas generation was observed was taken as the decomposition start temperature, and the total amount of gas finally generated was 70%.
If the amount of gas generated is more than%, the amount of gas increase is 1
The temperature at which the concentration is less than 0% is the decomposition temperature.

In the present invention, the above-mentioned polyolefin resin is added to a composition of azodicarbonamide having a specific mixing ratio and P,
By selecting a foaming agent composition composed of P′-oxybis (benzenesulfonylhydrazide), a foam having a smooth surface and uniform fine cells can be obtained, and its application is, for example, from its surface smoothness to adhesive processing. It is possible to obtain a polyolefin resin cross-linked foam having improved adhesive coatability.

Next, a method for producing the polyolefin resin crosslinked foam of the present invention will be described.

The method for producing a polyolefin resin composition having a foaming ability according to the present invention is once kneaded in a molten state at a temperature not lower than the melting point of the polyolefin resin component using a general-purpose kneading device such as an extruder or a mixing roll. Prepare raw materials, and then mix the blowing agent composition and optional crosslinking aids, additives, etc. below the decomposition start temperature of the blowing agent composition, and decompose above the melting point of the polyolefin resin and the blowing agent composition. This is a method of kneading using a general-purpose kneading device such as an extruder or a mixing roll in a temperature range below the starting temperature. By such a method, the polyolefin resin composition having the foaming ability of the present invention is formed into a long product having a shape such as a sheet or a strand.

In the present invention, a crosslinked structure is introduced into the foam.
The cross-linking can be carried out as necessary if the degree of cross-linking is 20% by weight or less. For example, when it is necessary to carry out the cross-linking before foaming as in the electron beam cross-linking method, a long product such as a sheet or a strand. The cross-linking treatment is performed in As the electron beam crosslinking method, any conventionally known radiation crosslinking method of irradiating ionizing radiation can be applied. For crosslinking by electron beam irradiation, a crosslinking aid can be used if necessary.

The crosslinking aid is not particularly limited, but
Divinylbenzene, trimethylolpropane trimethacrylate, 1,6-hexanediol methacrylate,
1,9-nonanediol dimethacrylate, 1,10-
Examples are decanediol dimethacrylate, trimellitic acid triallyl ester, triallyl isocyanate, neopentyl glycol dimethacrylate, 1,2,4-benzenetricarboxylic acid triallyl ester, tricyclodecane dimethacrylate, polyethylene glycol diacrylate, and the like. Two or more of these may be used in combination.

The foam having a crosslinked structure introduced by the above-mentioned crosslinking method preferably has a crosslinking degree of 10 to 50% by weight, which is measured by the method described below. Degree of crosslinking is 1
When the content is less than 0% by weight, the foaming gas holding force is weak during the production of the foam, and the foaming gas escapes from the surface so that the foaming ratio does not become a predetermined expansion ratio, the bubbles become large, and the surface morphology deteriorates. There are cases. On the other hand, if it exceeds 50% by weight, the crosslinking becomes dense, which is preferable from the viewpoint of foaming property and surface smoothness, but the crosslinking becomes too dense and the holding power of the foaming gas becomes excessive, causing partial destruction of bubbles. , It may become a void.

A known method may be used as the foaming method according to the present invention. Specifically, a vertical hot air foaming method, a horizontal hot air foaming method,
What can be produced as a continuous sheet form such as a horizontal chemical bath foaming method is preferable.

The processing temperature for heat-foaming the polyolefin resin composition having the foaming ability of the present invention is necessary to obtain a target expansion ratio with a uniform cell shape and a high closed cell ratio. For the resin component with the highest melting point at (resin melting point −10) to (resin melting point +7
A temperature range of 0 ° C. is preferable, and (resin melting point +1)
The temperature range of 0) to (resin melting point + 50) ° C. is more preferable. When the processing temperature for foaming by heating is lower than (resin melting point −10), it is a temperature at which the polyolefin resin is not sufficiently softened, gas generated by decomposition of the foaming agent is suppressed, and low strength in the bubble film is obtained. A good foam may not be obtained due to non-uniform cell shape or a decrease in the closed cell ratio due to destruction of the part. When the decomposition peak temperature is higher than (resin melting point + 70) ° C. with respect to the highest melting point,
Since the viscosity of the olefin resin decreases significantly and the foaming agent decomposes rapidly, the gas holding force of the resin weakens due to the gas pressure, the foaming gas escapes, the bubble film is destroyed, and the uneven bubble shape and closed cell ratio May not be a good foam due to a decrease in

The expansion ratio of the crosslinked foam of the present invention is 2 to 40.
Times, preferably 7 to 20 times. If the expansion ratio is less than 2 times, the resin portion in the volume is large and the strength increases, which is preferable in terms of mechanical properties, but the flexibility as a foam deteriorates. On the other hand, when it exceeds 40 times, the flexibility is increased and it is preferable from the viewpoint of buffering property, but the resin portion in the volume is reduced, so that mechanical strength and heat resistance may be lowered.

As described above, the method for producing a crosslinked polyolefin resin foam of the present invention is a polyolefin resin having a melting point of less than 120 ° C. and a decomposition temperature of ADCA and OBSH as a foaming agent composition. By using two kinds of thermally decomposable foaming agent compositions different in the above, a foam having a uniform and fine cell structure can be obtained.

[0027]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

The measuring methods and evaluation criteria in the present invention are as follows. 1. Crosslinking degree The foam is shredded and 0.2 g is precisely weighed. This is immersed in tetralin at 130 ° C. and heated for 3 hours with stirring to dissolve the dissolved portion, the insoluble portion is taken out, washed with acetone to remove tetralin, and then washed with pure water to remove acetone. Next, after removing water with a hot air dryer at 120 ° C., it is naturally cooled to room temperature. Weight of this item W ₁
(G) was measured and the degree of crosslinking was determined by the following formula.

Crosslinking degree = [(0.2-W ₁ ) /0.2] ×
100 (%) 2. Expansion ratio Cut out a sample piece of 10 × 10 cm from the foam,
The thickness t ₁ (cm) and the weight W ₂ (g) were measured, and the apparent density was calculated by the following formula.

Apparent density = W ₂ / (10 × 10 × t ₁ ) (g / cm ³ ) The expansion ratio is calculated from the apparent density by the following formula.

Expansion ratio = 1 / apparent density 3. Measured temperature 1 by the method according to MFR JIS K-6922-2.
It was measured at 90 ° C. 4. Average foam diameter of foam cut a foam sample piece with a sharp blade so that the bubbles do not collapse, enlarge the cross section with a microscope, draw a vertical line in the thickness direction, and measure the inner diameter of the bubble on the vertical line To do. The inner diameters of 120 arbitrarily selected bubbles were measured, and the average value was defined as the average bubble diameter (μm). The obtained foams having an average cell diameter of less than 300 μm were passed (combined), and those having an average cell diameter of 300 μm or more were rejected (fail). 5. Appearance of the composition The resin composition and the foaming agent composition are kneaded with a mixing roll, molded into a long sheet shape, irradiated with an electron beam and crosslinked, and the flatness of the surface of the foam foamed by heating and discoloration. The presence or absence was visually determined. If the foam had no distortion, the surface was smooth, and discoloration was not seen, it was judged as acceptable (pass), and if the foam was markedly defective, it was judged as rejected (fail). 6. Comprehensive evaluation: Foams with uniform and fine inner diameter and excellent appearance were passed (combined) in the comprehensive evaluation, uniform and fine cells were not obtained, or problems in appearance (distortion or discoloration) Those that were seen, and those that had any one of the corresponding items were judged as rejected (failed).

Example 1 As a polyolefin resin having a melting point of less than 120 ° C., ethylene-vinyl acetate copolymer (melting point 76 ° C., MFR 4.0 g / 10 min) 100
By weight, as a heat stabilizer, "Irganox 1010"
0.4 part by weight was thoroughly mixed with a mixing roll set at 180 ° C., and ADCA was further added as a decomposition type foaming agent.
(Manufactured by Eiwa Chemical Industry Co., Ltd., product name: Vinyl Hall AC # 3, decomposition starting temperature 175 ° C., decomposition temperature 208 ° C.) 10 parts by weight, O
BSH (decomposition start temperature 120 ° C, decomposition temperature 159 ° C) 2
A part by weight was added and the mixture was kneaded with a mixing roll set at 110 ° C. to obtain a foaming composition.

The foaming composition was pressed at a temperature at which the foaming agent was not decomposed, specifically, at 110 ° C. to a thickness of 1.
A 2 mm sheet was created. This sheet has a gel fraction of 3
An electron beam was irradiated at an accelerating voltage of 800 kV so that the concentration was 0 ± 2% by weight, and crosslinking was imparted. This sheet was heated and foamed in a hot air oven at 240 ° C. to obtain a foamed sheet having a closed cell structure with a thickness of 5.3 mm. The expansion ratio of this foam was 18, the gel fraction was 28% by weight, and the average cell diameter of the foam was 120 μm.

Example 2 As a polyolefin resin having a melting point of less than 120 ° C., ethylene-vinyl acetate copolymer (melting point 76 ° C., MFR 4.0 g / 10 min) 100
By weight, as a heat stabilizer, "Irganox 1010"
After thoroughly mixing 0.4 parts by weight with a mixing roll set to 180 ° C., ADCA (manufactured by Eiwa Chemical Industry Co., Ltd., trade name: Vinylhole FZ # 80, decomposition start temperature 126 ° C., decomposition temperature 143 ° C.) is further used as a decomposition type foaming agent. ) 10 parts by weight, OB
2 parts by weight of SH (decomposition starting temperature 120 ° C., decomposition temperature 159 ° C.) was added and kneaded with a mixing roll set at 110 ° C. to obtain a foaming composition.

The foaming composition was pressed at a temperature at which the foaming agent was not decomposed, specifically, at 110 ° C. to a thickness of 1.
A 2 mm sheet was created. This sheet has a gel fraction of 3
An electron beam was irradiated at an accelerating voltage of 800 kV so that the concentration was 0 ± 2% by weight, and crosslinking was imparted. This sheet was heated and foamed in a hot air oven at 180 ° C. to obtain a foamed sheet having a closed cell structure with a thickness of 4.4 mm. The foaming ratio of this foam was 13 times, the gel fraction was 31% by weight, and the average cell diameter of the foam was 90 μm.

Example 3 ADC was used as a foaming agent composition.
A (manufactured by Eiwa Chemical Industry Co., Ltd., product name: Vinyl Hall FZ # 80,
Decomposition start temperature 126 ° C, decomposition temperature 143 ° C) 5 parts by weight,
OBSH (decomposition start temperature 120 ° C, decomposition temperature 159 ° C)
A foamed sheet was prepared in the same manner as in Example 2 except that the compounding ratio was 2 parts by weight. The expansion ratio of this foam was 11, the gel fraction was 27% by weight, and the average cell diameter of the foam was 90 μm.

Example 4 As a polyolefin resin having a melting point of less than 120 ° C., 60 parts by weight of an ethylene-vinyl acetate copolymer (melting point of 76 ° C., MFR 4.0 g / 10 minutes), a melting point of 120 ° C. or higher. Ethylene-propylene random copolymer (melting point 13
8 parts by weight, MFR 2.0 g / 10 minutes) 40 parts by weight, as a foaming agent composition, ADCA (manufactured by Eiwa Chemical Industry Co., Ltd., trade name: Vinylhole FZ # 80, decomposition starting temperature 126 ° C., decomposition peak temperature 143 ° C.) 10 parts by weight , OBSH (decomposition start temperature 1
A foamed sheet was prepared in the same manner as in Example 2 except that the amount was 2 parts by weight (20 ° C., decomposition temperature 159 ° C.). The expansion ratio of this foam was 10 times, the gel fraction was 29% by weight, and the average cell diameter of the foam was 85 μm.

Example 5 100 parts by weight of high-pressure low-density polyethylene (melting point 105 ° C., MFR 8.0 g / 10 minutes) was used as a polyolefin resin having a melting point of less than 120 ° C., and ADCA (Nagawa) was used as a foaming agent composition. Made by Kasei Kogyo, trade name: Vinylhole FZ # 80, decomposition start temperature 12
A foamed sheet was prepared in the same manner as in Example 2 except that the content was 6 ° C., decomposition temperature 143 ° C.) 10 parts by weight, and OBSH (decomposition start temperature 120 ° C., decomposition temperature 159 ° C.) 2 parts by weight. The expansion ratio of this foam was 12 times, the gel fraction was 30% by weight, and the average cell diameter of the foam was 95 μm.

Comparative Example 1 ADC was used as a foaming agent composition.
A foamed sheet was prepared in the same manner as in Example 1 except that 12% by weight was used only for A (manufactured by Eiwa Kasei Co., Ltd., trade name: Vinylhol AC # 3, decomposition starting temperature 175 ° C., decomposition temperature 208 ° C.). The foaming ratio of this foam was 10 times, the gel fraction was 28% by weight, and the foam had an average cell diameter of 460 μm.

Comparative Example 2 OBS was used as a foaming agent composition.
H (decomposition start temperature 120 ° C, decomposition temperature 159 ° C) only 1
A foamed sheet was prepared in the same manner as in Example 1 except that 2% by weight was used. The expansion ratio of this foam was 12.5 times, the gel fraction was 32% by weight, and the average cell diameter of the foam was 95 μm.

[Comparative Example 3] An ethylene-propylene random copolymer (melting point: 13) was used as an olefin resin having a temperature of 120 ° C or higher without using a polyolefin resin having a temperature of less than 120 ° C.
A foamed sheet was prepared in the same manner as in Example 1 except that the amount was 100 parts by weight (8 ° C., MFR 2.0 g / 10 min). The expansion ratio of this foam was 14 times, the gel fraction was 25% by weight, and the average cell diameter of the foam was 350 μm.

Tables 1 and 2 below show the compositions of the foaming compositions in the above Examples and Comparative Examples and the physical properties of the foams obtained.

[0043]

[Table 1]

[0044]

[Table 2]

Regarding the physical properties of the foams obtained in Examples 1 to 5, as shown in Table 2, all have uniform and fine cell diameters, the foams have no distortion and the surface is smooth and the appearance is beautiful. It was a thing.

On the other hand, although the foam of Comparative Example 1 had a smooth surface, it had a large cell diameter of 460 μm and no fine cells were obtained. Although the foam according to Comparative Example 2 provided uniform fine cells, the resin was partially carbonized due to the heat of decomposition of the foaming agent, and a brown discoloration was observed in the foam. Also,
In the foam according to Comparative Example 3, the melting point of the resin was higher than the decomposition temperature of the foaming agent composition, large bubbles were occasionally generated in the foam due to gas release, and the bubble diameter was found to vary. Also, there was a problem in the appearance of the smoothness of the surface.

As described above, the polyolefin resin crosslinked foams of the present invention shown in Examples 1 to 5 are foaming agents obtained by blending ADCA and OBSH in a thermoplastic resin in a blending ratio within a specific range. It is a polyolefin resin crosslinked foam obtained by mixing and foaming a composition, and thereby a foam having a uniform and fine cell diameter is obtained.

[0048]

According to the foam of the present invention as set forth in claim 1, in a foam which requires post-processing, the surface is smooth and has a good appearance, and the surface is smoothed by having uniform fine cells throughout. The obtained polyolefin resin crosslinked foam can be obtained. Therefore, particularly in the bonding process, the adhesive can be applied uniformly and evenly, and workability and adhesiveness are improved.

According to the manufacturing method of the present invention as set forth in claim 4, a foaming agent composition comprising ADCA and OBSH is kneaded with a thermoplastic resin at a temperature not higher than the decomposition start temperature of the foaming agent, and this is kneaded into a long sheet shape. It is possible to continuously produce a foam having fine cells by molding, cross-linking, and heating above the decomposition temperature of the foaming agent composition to foam.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F074 AA16 AA22 AD12 AG03 BA13                       BA19 CA29 CC04Y CC06X                       DA02 DA03 DA04 DA32 DA37                       DA47 DA53                 4F212 AA03 AB02 AE02 AE07 AG01                       AG20 UA09 UB02 UC05 UG02                       UN03 UN06

Claims (5)

[Claims] 1. A polyolefin resin having a melting point of less than 120 ° C., at least azodicarbonamide, P,
A foam composition composed of P'-oxybis (benzenesulfonylhydrazide), 98 to 20 parts by weight of the azodicarbonamide, and 2 to 80 parts by weight of P, P'-oxybis (benzenesulfonylhydrazide). A polyolefin-based resin crosslinked foam comprising: 2. The blending ratio of the foaming agent composition is in the range of 2 to 25 parts by weight with respect to 100 parts by weight of the polyolefin resin having a melting point of less than 120 ° C. Polyolefin resin crosslinked foam. 3. The polyolefin resin crosslinked foam according to claim 1, wherein the average cell diameter of the foam is in the range of 50 to 300 μm. 4. A foaming agent composition comprising azodicarbonamide and P, P′-oxybis (benzenesulfonylhydrazide) is mixed with a polyolefin resin having a melting point of less than 120 ° C. at a temperature not higher than the decomposition initiation temperature of the foaming agent. A method for producing a cross-linked polyolefin resin foam, which comprises forming into a long sheet shape, then irradiating with ionizing radiation to cross-link, and heating to a temperature not lower than the decomposition temperature of the foaming agent composition for foaming. 5. The polyolefin resin crosslinked foam according to claim 3, wherein the degree of crosslinking of the foam is in the range of 5 to 50% by weight.