JP2000281827A - Production of polyolefin crosslinked foamed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of sublimates attributable to decomposition residues of a decomposition-type chemical foaming agent, decrease the amount of the sublimable compound remaining in a foamed body and widely decrease the generation of sublimates when a foamed body product is heated again. SOLUTION: When a crosslinked foamed body is produced from a polyolefin resin by azodicarbonamide and a high-decomposition exothermic type foaming agent whose calorific value is twice or more that of azodicarbonamide and whose gas generation value is equal to or more than that of azodicarbonamide is used as a heat decomposition-type chemical foaming agent, and 0.5-20 wt.% of an alkali metal chloride and/or an oxide of a 2A-group element in the periodic table is used together, based on the heat decomposition-type chemical foaming agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing a sublimate generated from a crosslinked foam at the time of heating in a process for producing or processing a polyolefin crosslinked foam.

[0002]

2. Description of the Related Art Recently, polyolefin cross-linked foams have been used as cushioning materials for automobile interiors because of their excellent heat resistance, light weight, heat insulating properties, sound insulation properties, etc., and their ease of molding by various processing methods. As a heat insulating material in the construction field,
Further, it is widely used as an adhesive tape or packing in the field of industrial materials. However, a polyolefin-based cross-linked foam is generally produced using a decomposition-type chemical blowing agent. For example, an azo-based blowing agent generates a sublimable substance such as ammonia and a urea compound, which is a nitrogen-based decomposition residue. A part of the foaming agent decomposition residue generated in the foaming step is scattered as a sublimate, but the rest remains in the crosslinked foam of the product.

[0003] If a foaming agent decomposition residue remains inside the product foam, the foam is removed from the foam by a heating step in post-processing the foam or by being continuously used in a heating atmosphere. Sublimates are generated and scatter. The sublimate generated due to the decomposition residue of the foaming agent contains some unfavorable substances in terms of safety and quality stability of the final product after processing. It is desirable to remove the foaming agent residue in the production process, but it has been considered difficult to remove the residue in the foam production process in the conventional method.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a method for producing a crosslinked polyolefin foam using a decomposable chemical foaming agent, the generation of sublimates resulting from decomposition residues from the decomposable chemical foaming agent. It is a main object of the present invention to suppress the occurrence of sublimates in the foam and to reduce the amount of the sublimable compound remaining in the foam to significantly reduce the occurrence of sublimates when the product foam is reheated.

[0005]

In order to achieve the above-mentioned object, according to the present invention, there is provided a method for producing a crosslinked foam from a polyolefin resin by using a pyrolytic chemical foaming agent. It is characterized by using a plurality of different types of chemical blowing agents having different calorific values and using 0.5 to 20% by weight of an alkali metal chloride and / or a Group 2A element oxide in the periodic table with respect to the pyrolytic type chemical blowing agent. And In the method of the present invention according to claims 2 and 3, azodicarbonamide is used as a thermal decomposition type chemical foaming agent, and the amount of heat generated by decomposition is twice or more and the amount of generated gas is equal to or more than that of azodicarbonamide. The method of the present invention according to claim 4 further comprises using a high-decomposition exothermic type chemical blowing agent in a predetermined amount, and further comprising the step of reducing the wavelength from 2 nm to 2 μm in the presence of moisture on the surface of the foam after completion of foaming. Irradiation up to the wave region is performed at a density of 2 to 12 KW / cm ³ .

The present invention has been made by repeatedly examining the decomposition mechanism of the blowing agent, the characteristics of the generated decomposition residue, or the possibility of its reaction. When a plurality of specific foaming agents are used in combination, the decomposition of the foaming agent can be completely prevented at low temperature during foaming without decomposing the foaming agent at the time of foaming sheet molding. Can be suppressed. Furthermore, the sublimability can be suppressed by using a specific inorganic compound in combination. Although the mechanism of the significant suppression of the amount of sublimable decomposition residue generated is not clear, for example, when azodicarbonamide is used, it is assumed that the initial decomposition time, which is presumed to form a bubble nucleus in the decomposition, or from that to rapid decomposition At the same time, since the combined blowing agent starts to decompose and generates high heat at the same time, the decomposition of azodicarbonamide progresses more rapidly than in the case of a single composition, so before the urea compound considered as a sublimate is formed It is considered that a nitrogen compound having extremely low sublimability is generated.

Further, when the surface of the foam is subjected to infrared treatment in the presence of moisture as in the present invention, the sublimable compound remaining on the surface of the foam or a relatively shallow portion can be removed. Even if the product foam is heated again to the generation temperature, the generation of sublimates can be further reduced. As a result, according to the method of the present invention, it is possible to greatly reduce the occurrence of sublimates when the foam is reheated without deteriorating the quality of the foam.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin resin used for cross-linking and foaming in the method of the present invention is a polymer obtained by random or block copolymerization of propylene with 2 to 15% by weight of ethylene or an α-olefin having 4 to 8 carbon atoms. Is 125
Polypropylene resin (A) having an MFR of 0.5 to 10 g / 10 min and a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms at a density of 0.915 to 155 ° C.
0.940 g / cm ³ , MFR 1.0 to 30 g / 10
And a polyethylene-based polymer having a different polymerization composition from the polyethylene-based resin (B), having a density of 0.915 to 950 g / cm ³ ,
A polyethylene-based resin (C) having an MFR of 1 to 20 g / 10 minutes.

The polypropylene resin (A) is a copolymer obtained by random or block copolymerization of propylene with a predetermined amount of the above-mentioned α-olefin by a Ziegler-type catalyst or a metallocene-type catalyst. 125-155 ° C, MFR is 0.5-10 g / 10 min. Ethylene or 4-8 carbon atoms to be copolymerized
The number of species of the α-olefin is not particularly limited, and examples thereof include ethylene, butene, hexene, ethylene and butene, and ethylene and hexene. In order to maintain the mechanical strength of the foam, an α-olefin having as large a carbon number as possible is preferable, and a terpolymer is preferable.

[0010] Ethylene or 4 carbon atoms to be copolymerized
To 8 to 8 to 15% by weight, preferably 3 to
８8% by weight. If the copolymerization ratio is too low, the crystallinity of the resin will increase and the melting point will also increase, so the foam obtained will be hardened, the buffering properties will decrease, and the impact resistance at low temperatures will deteriorate, or the foam sheet It is not preferable because the foaming agent is easily decomposed due to heat generated by shearing during the production, and coarse bubbles are easily generated. On the other hand, if it is too large, it is preferable in terms of buffering properties and impact resistance, but it is not preferable because the melting point is lowered and the heat resistance is lowered.

[0011] The melting point of the resin is from 125 to 155 ° C, preferably from 130 to 145 ° C. If the melting point is lower than 125 ° C., it is not preferable because the application is restricted from the viewpoint of heat resistance. Conversely, if the melting point is so high that it exceeds 155 ° C,
Although it can cover a wide range of uses, it is not preferable because the foaming agent is easily decomposed due to heat generated by shearing during the production of the foaming sheet, and coarse bubbles are easily generated. Further, if the melting point is too high, it is difficult to remove the sublimate from the foam, which is not preferable. The MFR is 0.5 to 10 g / 10 minutes, preferably 1.0 to 3 g / 10 minutes. MFR is 0.5
When the viscosity is less than g / 10 minutes, the melt viscosity of the resin becomes high, so that the shearing heat generated during the production of the sheet for foaming tends to cause the decomposition of the foaming agent and the generation of coarse bubbles, which is not preferable. On the other hand, when the melt viscosity exceeds 10 g / 10 minutes, the melt viscosity becomes low, so that it is preferable in sheet production. However, the elongation of the foam is reduced, and the shape holding force is deteriorated at the time of heat forming such as vacuum forming, and a good molded product is obtained. It is not preferable because it becomes difficult to obtain.

The polyethylene resin (B) is a copolymer obtained by copolymerizing ethylene with a specific α-olefin, and has a density of 0.915 to 0.940 g / cm ³ and an MF
R is 1.0 to 30 g / 10 minutes. The number of species of the α-olefin to be copolymerized with ethylene is not particularly limited, but generally a binary copolymer of ethylene and an α-olefin is preferable, and the number of carbon atoms in the α-olefin having 4 to 12 carbon atoms is preferable. However, those obtained by copolymerizing 4 to 6 are advantageous in terms of both price and physical properties.

The density is 0.915 to 0.940 g / c
m ³ , preferably 0.920 to 0.935 g / cm ³ . If the density is less than 0.915 g / cm ³ , the flexibility of the resin is remarkable, stickiness is caused, and if the foam is used, blocking occurs and the mechanical strength is unfavorably reduced. On the other hand, if it exceeds 0.940 g / cm ³ , it is preferable in terms of mechanical strength, but it is not preferable because elongation is reduced and the compression recovery of the foam is reduced. MF
R is 1.0 to 30 g / 10 min, preferably 2 to 15 g /
10 minutes. If the MFR is less than 1.0 g / 10 minutes, the melt viscosity of the resin becomes high, so that the foaming agent is liable to be decomposed due to the heat generated by shearing during the production of the foaming sheet, and coarse bubbles are easily generated, which is not preferable. On the other hand, 30g /
If the time is longer than 10 minutes, the melt viscosity becomes low, which is preferable in the production of sheets. However, the tensile strength of the resin at high temperature is reduced, and the uneven thickness tends to occur during molding, which is not preferable.

When the polypropylene resin (A) is used, it is preferable to use it in combination with the polyethylene resin (B), and the mixing ratio (A) / (B) is 85/1.
5-15 / 85, more preferably 30 / 70-70 / 30. If (A) / (B) is less than (15/85), the properties of the polyethylene resin (B) are dominant, and heat resistance is deteriorated and moldability is deteriorated. On the other hand, when it exceeds (85/15), the mechanical strength, heat resistance and moldability are good, but the rigidity of the foam is remarkable, the buffering property is deteriorated, and the influence of the polyethylene resin component is large, and the effect of the present invention is large. Although it is convenient in terms of removing sublimates, it is not preferable because heating is not sufficient under a heating condition for a polyethylene resin because it is a mixed system with a polypropylene resin.

When the polypropylene resin (A) and the polyethylene resin (B) are used in combination as described above, the degree of crosslinking of the obtained foam is 20 to 70%, preferably 30 to 60%.
%. If the degree of cross-linking is less than 20%, the foaming gas easily escapes from the foam surface at the time of heating and foaming, and a predetermined foaming ratio cannot be obtained, the foam surface is roughened, and the foam is oriented in the length direction during foaming. Is not preferred because the properties tend to be remarkable and anisotropy occurs in the physical properties, and the surface of the foam is easily roughened by heating. On the other hand, the degree of crosslinking is 70
%, The cell diameter becomes small and the shape becomes almost spherical, so that the resin becomes hard and the buffering property decreases, the elongation decreases, the heat moldability deteriorates, or the foaming agent is contained in the crosslinked network chain. It is not preferable because the residue is taken in and hinders decomposition and sublimation of the residue into the air.

In this case, the expansion ratio of the foam is 5 to 5.
It is 40 times, preferably 5 to 30 times. If the expansion ratio is less than 5 times, a high degree of deep drawing can be performed and the final processed product is excellent in formability, but hard and has poor buffering properties, which is not preferable. On the other hand, if it exceeds 40 times, it is preferable in terms of buffering property, but it is not preferable because the mechanical strength is reduced due to high foaming and the moldability is deteriorated, and the addition amount of the foaming agent increases as the foaming degree increases. It is necessary to increase the amount, and the amount of the foaming agent residue also increases in proportion, which is not preferable for reducing the sublimate according to the present invention.

The polyethylene resin (C) used as the resin component used in the method of the present invention is a high-pressure low-density polyethylene or a polyethylene resin obtained by copolymerizing ethylene with vinyl acetate or an alkyl (meth) acrylate. And the density is 0.915 to 950 g / c
m ³ , MFR is 1 to 20 g / 10 min, preferably density is 0.920 to 940 g / cm ³ , and MFR is 2 to 10 g / min.
Should be 10 minutes. If the density is less than 0.915 / cm ³ , the high-pressure low-density polyethylene is not preferable because the stickiness and mechanical properties of the resin, specifically the strength, are greatly reduced. It is not preferable because it becomes the same as the density polyethylene. On the other hand, if it exceeds 0.950 g / cm ³ , the high-pressure method low-density polyethylene becomes hard and the elastic restorability is greatly reduced, which is not preferable. In the latter copolymer, the copolymerization amount of the comonomer increases and the melting point decreases. It is not preferable because heat resistance is reduced and blocking occurs, and products cannot be stored in piles. That is, the products cannot be stored in a roll shape.

In the resin component used in the present invention, in addition to the above-mentioned polypropylene resin (A), polyethylene resin (B) and polyethylene resin (C), 30% by weight or less of other polyolefin resin is mixed. May be.
Specifically, ethylene-propylene rubber-diene rubber (E
PDM), high-density polyethylene and the like, and terpolymers obtained by copolymerizing maleic anhydride as a third component with a copolymer with ethylene, and the like. Above all, maleic anhydride was copolymerized as a third component with ethylene-propylene rubber (EPM), ethylene-propylene rubber-diene rubber (EPDM), ethylene- (meth) alkyl acrylate copolymer or a copolymer with these ethylenes. Tertiary copolymers are preferred. If the amount exceeds 30% by weight, heat resistance,
It is not preferable because mechanical strength and moldability are reduced.

In addition, if necessary, a heat stabilizer, a weathering agent, a flame retardant aid (for example, an antimony compound), a dispersant, a crosslinking agent, and a crosslinking aid may be added.

In the method of the present invention, it is important to use a plurality of types of pyrolytic chemical foaming agents having different calorific values, especially azodicarbonamide, which has a different structure from azodicarbonamide. It is preferable to use a high-decomposition type chemical foaming agent having a calorific value twice or more and an amount of generated gas equal to or more than an equivalent amount. Examples of the high-decomposition type chemical blowing agent include N, N'-dinitrosopentamethylenetetramine or a tetrazole-based compound, specifically, 5-phenyltetrazole, and P, P having a lower decomposition temperature than azodicarbonamide. '-Oxybenzenesulfonyl hydrazide and the like and inorganic foaming agents are not suitable.
The mixing ratio between azodicarbonamide and a high-resolution chemical blowing agent having a different structure is 90:10 to 99.
5: 0.5 is preferred. If the amount of the high-decomposition type chemical blowing agent to be mixed is too large, the high-decomposition type chemical blowing agent has a high calorific value, so that the temperature at the center of the foam at the time of completion of foaming is significantly increased, and discoloration due to thermal deterioration, This is not preferred because it causes so-called burning.

It is necessary to use an alkali metal chloride and / or an oxide of a Group 2A element of the periodic table in addition to the above-mentioned thermal decomposition type chemical blowing agent. As the alkali metal chloride, a chloride of a lithium compound containing lithium is preferable. The oxide of a Group 2A element in the periodic table is an oxide containing a metal element selected from Group 2A elements in the periodic table from magnesium to barium. These contain, in total, 0.5% to 20% by weight, preferably 1% to 10% by weight, of those having a moisture content of 0.1% or less, preferably 0.5% by weight.
When the amount is less than 20% by weight, the effect of preventing the sublimation is not sufficiently increased. However, when the amount exceeds 20% by weight, the effect as a filler is increased, and the mechanical strength of the foam is lowered.

In the present invention, it is necessary that the resin portion of the foam is cross-linked. As a cross-linking method, a so-called chemical cross-linking method, which is performed by adding a peroxide such as peroxide, is used. A radiation crosslinking method performed by irradiation can be exemplified. In the case of the chemical crosslinking method, a known method of adding a peroxide compound such as dicumyl peroxide, t-butyl per-benzoate, ditertiary butyl peroxide, etc. to the resin component in an amount of 0.5 to 5 parts by weight and performing crosslinking is applied. do it. In the case of the radiation crosslinking method performed by irradiating with ionizing radiation, a known method by electron beam irradiation may be applied, and the degree of electron beam irradiation is such that the degree of crosslinking when the foam is formed is 25 to 70%. Good degree.

Known foaming methods can be applied to the foaming method according to the present invention, and specific examples thereof include those which can be produced as a continuous sheet such as a vertical hot air foaming method, a horizontal hot air foaming method, and a horizontal chemical liquid foaming method. For example, a continuous sheet cross-linked by electron beam irradiation is heated to a temperature of 30 to 100 ° C. below the decomposition temperature of the foaming agent.
It is continuously introduced into a horizontal foaming furnace of the chemical heating system heated to a high temperature, foamed, and then out of the foaming tank, introduced into a water cooling tank for the purpose of primary cleaning and cooling of the chemical, and further complete After being introduced into a water washing tank heated to 30 to 80 ° C. for washing, the quartz tube type infrared heater and 100 to 120 ° C. are placed at a position 100 mm from the surface of the foam while the surface is wet. After being introduced into a dryer equipped with a hot-air nozzle, the surface and the surface of the foam were removed to 100 to 140 ° C. from the surface to 100 ° C. to remove the surface moisture and sublimates near the surface. It can be carried out by a winding method.

The sublimate obtained in this manner is reduced.
The expanded polyolefin-based cross-linked foam is
(For example, after the completion of foaming in the foam manufacturing process, or
The wavelength from 2 nm on both sides of the foam (when processing the foam)
It is preferable to irradiate infrared rays up to the microwave range.
is there. For example, about 50 to 400 mm from the surface of the foam
Is made of quartz, ceramic, zirconia, etc.
A heater that generates infrared light of the wavelength is placed, and the width and length
The irradiation density is 2 to 12 KW / cm^ThreeAdjusted to be
To irradiate infrared rays, the temperature of the foam is 100-140 ° C
Is applied so that when reheating
Can be reduced to a level close to almost no sublimation
You. At this time, in order to rapidly raise the surface temperature of the foam, 1
Hot air of 00 to 120 ° C may be used in combination. In addition, the present invention
In order to reduce the amount of sublimate,
Moisture, specifically the foam itself is the one with the water film
Is effective, for example, by suppressing the deterioration of the shape and by preventing the form from changing.
In the present invention, the irradiation density of infrared rays is 2 KW / cm^ThreeNot yet
When full, the temperature of the sublimate itself due to infrared rays rises sufficiently
It is difficult to remove the sublimate sufficiently,
On the other hand, 12KW / cm ^ThreeBeyond the temperature of the sublimate itself
Degree of temperature rises rapidly and is preferable in removing sublimates
However, due to the radiant heat generated by the heater, the foam surface
It is not preferable because it melts and becomes rough.

[0025]

Next, the present invention will be described based on embodiments. The measuring method and evaluation criteria in the present invention are as follows.

1. Sublimate Confirmation Test Using a fogging tester manufactured by Hacke Co., the foam is heated at a heating temperature of 110 ° C. for 3 hours, and what adheres to the glass plate surface is visually observed with a microscope to check for the occurrence of sublimate. Further, the haze (surface) is also measured. A sample in which no crystal was observed by visual observation of a substance attached to the glass plate surface and a sample whose haze measurement value was 60% or more were judged to be acceptable.

2. Degree of crosslinking of foam The foam is cut into small pieces and precisely weighed at 0.2 g. This is 130
Immersed in tetralin at room temperature and heated with stirring for 3 hours to dissolve the dissolved part. The insoluble part was taken out and washed with acetone to remove tetralin. Moisture is removed with a dryer, and the mixture is naturally cooled to room temperature. The weight (W ₁ ) g of this product is measured, and the degree of crosslinking is determined by the following equation. Degree of crosslinking = [(0.2−W ₁ ) /0.2] × 100 (%)

3. Formability Formed by a vacuum forming machine equipped with a cup-shaped mold having a diameter (D) and depth (L), and the maximum L / D ratio that could be formed into a cup without breaking the foam. The value is used as an index of moldability. An L / D of 0.5 or more is considered acceptable. 4. Mechanical strength, elongation Measured according to JIS K-6767.

5. Melting point The largest peak of the melting endothermic curve measured by a differential scanning calorimeter (DSCII manufactured by PerkinElmer) is defined as the melting point. 6. MFR polypropylene resin conforms to JIS K-6758,
The polyethylene resin is measured according to JIS K-6760. 7. Density The polyethylene resin is measured according to JIS K-6760.

Example 1 propylene obtained by random copolymerization of propylene with 4% by weight of ethylene has a melting point of 136.degree.
The density obtained by copolymerizing 0.8 g / 10 min of the polypropylene resin (A) and hexene with ethylene is 0.930.
g / cm ³ , and a polyethylene resin (B) having an MFR of 6.0 g / 10 minutes so that (A) :( B) is 75:25 to obtain a composition. Further, 0.2 kg of Irgnox1010 as a heat stabilizer
Mix and put into a pressure kneader, knead the first stage,
Disperse the resin, flame retardant, and stabilizer sufficiently in the molten state.
Further, 3 kg of pentaerythritol triacrylate is added as a crosslinking aid, and the mixture is kneaded in the second stage to finely disperse the crosslinking aid. Further, 6 kg of azodicarbonamide, 0.3 kg of N, N'-dinitrosopentamethylenetetramine and 90 g of magnesium oxide are added as decomposable foaming agents, and the mixture is kneaded in the third stage to obtain a foaming resin composition. This is passed through a roll kneader, formed into a sheet having a thickness of 2 mm, and taken out, and pelletized into a 2 mm square with a pelletizer.

This mixed raw material is introduced into a vented extruder heated to a temperature of 150 to 180 ° C. at a temperature at which the foaming agent is not decomposed, and is extruded from a set T-die. 0.5mm, width 550mm
Into a continuous sheet and wound up. 6.3
It was irradiated with an electron beam of Mrad to cause crosslinking. The sheet was introduced into a silicone chemical solution foaming apparatus heated in the order of 220 ° C. → 225 ° C. → 235 ° C. to form a foam, then passed through a water tank, and then 100 ° C. of 2 m long for the purpose of removing water droplets adhering to the surface. Was passed through an apparatus equipped with a twin-tube type infrared heater provided with a gold-plated reflection layer on a quartz ring manufactured by Heraeus Co., Ltd. in a hot-air drying furnace, and wound into a roll as a continuous sheet-like foam.

The foam thus obtained was a smooth foam having a thickness of 3.3 mm, a width of 1250 mm and an expansion ratio of 18 times. As a result of confirming the state of sublimate generation of this foam using a fogging tester manufactured by Hacke Co., sublimate did not adhere to the glass plate surface, and sublimate generation was reduced to a level that was not observed by visual observation.

Example 2 Ethylene is added to propylene.
8% by weight random copolymerized, melting point 134 ° C, MFR
0.8 g / 10 min of polypropylene resin (A) and ethylene with octene copolymerized with a density of 0.935 g / c
A polyethylene resin (B) having m ³ and MFR of 6.0 g / 10 min was prepared and mixed so that (A) :( B) was 80:20. To 100 kg of this mixed resin, 0.2 kg of Irgnox1010 as a heat stabilizer was mixed and charged into a Henschel mixer, and dispersed and mixed in the first stage. Further, 4 kg of divinylbenzene was charged as a crosslinking aid and uniformly mixed. Furthermore, 12 kg of azodicarbonamide and 0.3 kg of 5-phenyltetrazole are used as decomposition-type foaming agents.
And magnesium oxide and lithium chloride 1:
(1) 120 g of the inorganic mixture is charged and mixed to obtain a foaming resin composition.

This mixed raw material is introduced into a vented extruder heated to a temperature of 150 to 180 ° C. at a temperature at which the foaming agent is not decomposed, and extruded from a set T-die. 0.7mm, width 430mm
Into a continuous sheet and wound up. 9.0 on this sheet
It was irradiated with an electron beam of Mrad to cause crosslinking. This sheet is introduced into a silicone chemical solution foaming apparatus heated in the order of 220 ° C. → 230 ° C. → 235 ° C. to foam the foam, and then passed through a water tank, and then a 100 m 2 m long sheet for removing water droplets adhering to the surface. In a hot air drying oven at ℃, a device provided with a twin tube type infrared heater provided with a gold-plated reflection layer on a quartz ring manufactured by Heraeus Co., Ltd. was continuously passed through and wound up as a continuous sheet-like foam.

[Comparative Example] The type of resin, the type of foaming agent, the conditions of sheet thickness and width, the amount of electron beam irradiation were changed as shown in Table 1, and the addition of an inorganic compound and the irradiation with far infrared rays were not performed. Was carried out in the same manner as in Examples.

As can be seen from the results shown in Tables 1 and 2, the crosslinked foam obtained by the method of the present invention has good moldability,
The required properties such as mechanical strength and elongation were excellent, and no sublimate generation was observed in a sublimate confirmation test using a Hagge fogging tester, and the haze was as good as 82%. On the other hand, the conventional polypropylene-based cross-linked foam shown in the comparative example generates sublimates containing urea, and a post-processed product and a laminate with a PVC skin for an automobile interior were evaluated by a Hakke fogging tester. As a result, sublimates were confirmed, and the haze was 51%, which was extremely unsatisfactory.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

According to the method of the present invention, the decomposition foaming agent of a specific composition and a specific inorganic compound are used in combination, so that the amount of sublimable decomposition residues generated can be greatly suppressed, and the sublimation decomposition residues remain. Sublimation of the decomposition residue is suppressed. Moreover, since the obtained foam does not deteriorate in mechanical properties, moldability, and the like, the occurrence of sublimates during production can be suppressed, and the occurrence of sublimates during reheating during post-processing of products is greatly suppressed. Thus, a foam having excellent quality can be manufactured. Since the foam obtained by the method of the present invention has significantly reduced the generation of sublimates due to the foam decomposition residue, it may be used for pipe cover applications where there is a concern about the harmful effects of sublimable urea-based materials, or when heated. It is particularly useful in applications involving several steps of processing (for example, in the field of cushioning materials for automobile interiors bonded to various skins) or in the field of packing.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F074 AA17A AA20A AA25B AB03 AB05 AC13 AC19 BA13 BA16 BA20 CA29 CC04Y CC28Z CC46 CC49 4J002 BB052 BB141 BB151 BP021 DD057 DE067 DE077 DE087 EQ016 ES006 EU156 FD207 FD00 GG326

Claims (5)

[Claims] 1. When a crosslinked foam is produced from a polyolefin resin using a pyrolytic chemical foaming agent, a plurality of pyrolytic chemical foaming agents having different calorific values are used as the pyrolytic chemical foaming agent. A method for producing a crosslinked polyolefin foam, characterized in that 0.5 to 20% by weight of an alkali metal chloride and / or an oxide of a Group 2A element of the periodic table are used in combination. 2. A thermal decomposition type chemical foaming agent comprising: an azodicarbonamide; and a high decomposition heat generation type chemical foaming agent having an amount of generated gas equal to or more than twice that of the azodicarbonamide. The method for producing a polyolefin-based crosslinked foam according to claim 1, which is used in combination. 3. The high-decomposition exothermic chemical blowing agent is contained in an amount of 0.5 to 10% based on the total amount of the blowing agent.
The method for producing a crosslinked polyolefin-based foam according to the above. 4. An infrared ray having a wavelength of from 2 nm to a microwave region is irradiated on the surface of the foam after completion of foaming in the presence of moisture.
Method for producing a polyolefin-based crosslinked foam according to any one of claims 1 to 3, characterized in that irradiation at a density of ~12KW / cm ^3. 5. The polyolefin-based resin is obtained by adding ethylene or α-olefin having 4 to 8 carbon atoms to propylene.
15% by weight random or block copolymerized,
Melting point 125-155 ° C, MFR 0.5-10 g / 1
0-minute polypropylene resin (A), ethylene is copolymerized with an α-olefin having 4 to 12 carbon atoms, has a density of 0.915 to 0.940 g / cm ³ and an MFR of 1.0 to 1.0.
30 g / 10 min of the polyethylene resin (B), and the compounding ratio (A) / (B) is 15 / 85-85 / 1.
5, and the degree of crosslinking of the crosslinked foam is 20 to 70%,
The foaming ratio is 5 to 40 times.
5. The method for producing a polyolefin-based crosslinked foam according to any one of items 4 to 4.