JPH089676B2 - Method for producing crosslinked foamed vinyl chloride polymer - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a vinyl chloride-based crosslinked foam, and more particularly to have a uniform foam cell from a vinyl chloride-based polymer containing a carbon monoxide copolymer. The present invention relates to a method for producing a vinyl chloride-based crosslinked foam.

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION Conventionally, foamed polyurethane or polyolefin cross-linked foam has been mainly used for cushion materials such as crash pad and door panel for automobile interior parts made of skin / cushion / aggregate. Came.

However, since a vinyl chloride-based sheet is usually used as the skin material of the panel, recently, a vinyl chloride-based sheet that can be easily bonded to the vinyl chloride-based sheet by a high-frequency welder and that can be molded by vacuum molding is used. The use of vinyl-based crosslinked foam as a cushioning material for automobile interior parts has been studied.

Conventional vinyl chloride cross-linked foams are made by adding a chemical foaming agent to a vinyl chloride polymer together with a liquid plasticizer and uniformly kneading the resulting kneaded product into a sheet at a temperature below the decomposition temperature of the chemical foaming agent. After molding, electron beam or γ
It is produced by irradiating a wire or the like to crosslink it, and then heating it to decompose and foam a chemical foaming agent.

In this case, a radical cross-linking agent is added together with a chemical foaming agent, a liquid plasticizer, etc. without being cross-linked by irradiation with electron beams, γ-rays, etc., and the vinyl chloride polymer is cross-linked in the above heating step. Sometimes.

However, the conventional method for producing a vinyl chloride-based crosslinked foam has a problem that a side reaction such as dehydrochlorination is likely to occur in the crosslinking step, and the resulting composition is colored and deteriorated. This coloring and deterioration proceed more easily as the irradiation of the electron beam or the like is stronger and the amount of the radical crosslinking agent used is larger, and the color shifts from brown to black.

Therefore, as a method of solving such a problem, without using a liquid plasticizer, instead, it is well compatible with a vinyl chloride polymer and acts as a polymer plasticizer, and also an electron beam irradiation or a radical crosslinking agent. To facilitate cross-linking with ethylene, or self-crosslinking with chemical blowing agents, ethylene, carbon monoxide,
Vinyl acetate copolymer, or ethylene / carbon monoxide /
A method of blending a (meth) acrylic acid alkyl ester copolymer has been proposed (see JP-A-59-80444, JP-A-61-225225, and JP-A-61-276835).

However, when the vinyl chloride polymer is blended with a carbon monoxide copolymer as described above in place of the conventional liquid plasticizer, the viscosity of the obtained vinyl chloride polymer composition at the time of melting increases, When molding into a sheet in an unfoamed state by calender molding, T-die extrusion molding, etc., the composition heats up due to shearing force, so that the temperature rises above the decomposition temperature of the chemical foaming agent and the chemical foaming agent partially decomposes and foams. I had to do it. If even a part of the chemical foaming agent is decomposed and foamed in this step, it is not possible to finally obtain a uniform vinyl chloride-based crosslinked foam. Therefore, in the past, in order to prevent this temperature rise, the molding speed at the time of molding an unfoamed sheet-like material had to be extremely slowed.

That is, in order to produce a vinyl chloride-based crosslinked foam having a uniform foam cell, a vinyl chloride-based polymer, a carbon monoxide copolymer, an unfoamed chemical foaming agent before crosslinking / foaming,
In addition, it is necessary to obtain an unfoamed sheet in which the undecomposed cross-linking agent and other compounding ingredients are uniformly dispersed. However, since the carbon monoxide copolymer is a high molecular weight plasticizer, in order to knead the vinyl chloride polymer and the carbon monoxide copolymer with a kneader, a high shear at a high temperature of 160 to 180 ° C is required. In contrast to this, chemical foaming agents, cross-linking agents, etc. are partially decomposed at 150 ° C or higher. Therefore, unfoamed chemical foaming agents, other undecomposed cross-linking agents, and other compounding components are uniform. It was extremely difficult to obtain a vinyl chloride-based unfoamed product dispersed in.

Therefore, the inventors of the present invention have earnestly studied a method of uniformly kneading a vinyl chloride-based polymer, a carbon monoxide copolymer, and a chemical foaming agent at low temperature without undecomposition, and as a result, have found that the vinyl chloride-based polymer and the monoxide are mixed. The component (A) was prepared by preliminarily kneading with the carbon copolymer sufficiently under high temperature and high shear to prepare the component (A). On the other hand, the chemically unstable chemical blowing agent was mixed with a small amount of the carbon monoxide copolymer. When the component (B) is sufficiently kneaded at a low temperature to prepare the component (B), and then the component (A) and the component (B) are kneaded and molded at a low temperature, the component (A) is chlorinated by the carbon monoxide copolymer. The softening point of the vinyl-based polymer is lowered so that the vinyl chloride-based polymer and the carbon monoxide copolymer can be uniformly mixed, and the carbon monoxide copolymer in the component (B) is carbon monoxide. Acts as a binder when kneading and molding the copolymer and chemical blowing agent The carbon monoxide copolymer and the chemical foaming agent can be mixed very smoothly at a temperature lower than the decomposition temperature of the chemical foaming agent, and when the components (A) and (B) are kneaded, (B) The present invention has been completed by finding that the carbon monoxide copolymer contained in the component can function as an internal lubricant to suppress heat generation during kneading.

OBJECT OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and to melt a vinyl chloride polymer composition containing a carbon monoxide copolymer and a chemical blowing agent. It is possible to produce an unfoamed sheet-like product in which each component is uniformly kneaded while reducing the viscosity and leaving the chemical foaming agent undecomposed.
Therefore, it is an object of the present invention to provide a method for producing a vinyl chloride-based crosslinked foam capable of obtaining a vinyl chloride-based crosslinked foam having uniform foam cells from this unfoamed sheet.

SUMMARY OF THE INVENTION A method for producing a vinyl chloride-based crosslinked foam according to the present invention,
In producing a vinyl chloride copolymer crosslinked foam containing a vinyl chloride polymer and a carbon monoxide copolymer, on the other hand, 100 parts by weight of the vinyl chloride polymer and 40 to 150 parts by weight of the carbon monoxide copolymer are used. To prepare a homogeneous pre-kneaded product (A) component obtained by kneading with 10 parts by weight at a temperature of 160 to 180 ° C., on the other hand, 10 to 50 parts by weight of a carbon monoxide copolymer, a chemical blowing agent, and optionally a crosslinking agent To prepare a component (B) obtained by kneading at a temperature not higher than the decomposition temperature of the chemical foaming agent, and then kneading the components (A) and (B), followed by extrusion molding or calender molding to obtain an unfoamed molded product. Is produced, and then cross-linked and foamed.

According to the method for producing a vinyl chloride-based crosslinked foam according to the present invention, the component (A) is prepared by uniformly pre-kneading a vinyl chloride-based polymer and a carbon monoxide copolymer under high temperature and high shear. A component (B) is prepared by kneading a carbon monoxide copolymer and a chemical foaming agent at a temperature not higher than the decomposition temperature of the chemical foaming agent, and then kneading the components (A) and (B). After the unfoamed sheet-like material is created, this sheet-like material is heated for foaming, so the melt viscosity of the vinyl chloride polymer composition when creating the unfoamed sheet-like object is reduced. Therefore, a vinyl chloride-based crosslinked foam having uniform foam cells can be obtained.

DETAILED DESCRIPTION OF THE INVENTION The method for producing the vinyl chloride-based crosslinked foam according to the present invention will be specifically described.

In the present invention, the component (A) obtained by uniformly pre-kneading 100 parts by weight of a vinyl chloride polymer and 40 to 150 parts by weight of a carbon monoxide copolymer at a high temperature of 160 to 180 ° C. and under high shear is used. 10 to 50 parts by weight of a carbon monoxide copolymer and a chemical foaming agent are kneaded at a temperature not higher than the decomposition temperature of the chemical foaming agent (B).
After the components are prepared, and then the components (A) and (B) are kneaded, an unfoamed molded product, for example, a sheet-like product is prepared by extrusion molding or calender molding, and this molded product is heated to foam. Thus, a vinyl chloride-based crosslinked foam is manufactured.

 First, each component will be described below.

The vinyl chloride polymer used in the present invention is not only a vinyl chloride homopolymer, but also vinyl chloride and other monomers, for example, α-olefins such as ethylene and propylene, vinyl esters such as vinyl acetate. , Unsaturated carboxylic acid esters such as acrylic acid esters, vinyl ethers such as alkyl vinyl ethers, other vinyl halides such as vinyl bromide and vinyl fluoride, and other vinyl compounds such as styrene, acrylonitrile and vinylidene chloride Alternatively, a copolymer with a vinylidene compound or the like is used. In some cases, an ethylene / vinyl acetate copolymer, a carbon monoxide copolymer, or a thermoplastic urethane polymer may be used as a trunk polymer, and a vinyl chloride-based graft polymer obtained by graft-polymerizing vinyl chloride on it may also be used.

The degree of polymerization of this vinyl chloride polymer is preferably 300 to 5000, particularly preferably 500 to 2000.

The carbon monoxide copolymer used in the present invention,
A copolymer composed of ethylene, an ethylenically unsaturated organic monomer, and carbon monoxide.

The ethylenically unsaturated organic monomer used when producing the carbon monoxide copolymer used in the present invention,
Vinyl ester of saturated carboxylic acid having an acid group of 2 to 18 carbon atoms, unsaturated mono- or dicarboxylic acid having 3 to 20 carbon atoms, unsaturated mono- or dicarboxylic acid ester, alkyl group of 1 to 18 A compound selected from vinyl alkyl ethers having 4 carbon atoms, vinyl or vinylidene halides, acrylonitrile, methacrylonitrile, norbornene, α-olefins having 3 to 12 carbon atoms, and vinyl aromatic compounds. Preferred organic monomers include vinyl acetate, methyl (meth) acrylate, ethyl (meth) acrylate,
Examples include n-butyl (meth) acrylate, isobutyl (meth) acrylate, and t-butyl (meth) acrylate.

The ethylene / ethylenically unsaturated organic monomer / carbon monoxide-based copolymer used in the present invention are all 40 to 80% by weight of ethylene, preferably 60 to 70% by weight, and the unsaturated organic monomer is about 15 to 60%. Preferably about 20 to 35%, and carbon monoxide is copolymerized at a ratio of about 5 to 30%, preferably 5 to 15%, and if necessary, further other monomers are copolymerized. It is also possible to polymerize. The details of the method for producing such a carbon monoxide copolymer are described, for example, in Japanese Examined Patent Publication No. 55-50063.

In the vinyl chloride-based crosslinked foam according to the present invention, the amount of the carbon monoxide copolymer as described above is arbitrary, but generally 50 to 200 parts by weight with respect to 100 parts by weight of the vinyl chloride-based polymer. , Preferably 70 to 150 parts by weight. When the blending amount of the carbon monoxide copolymer is less than 50 parts by weight, the obtained crosslinked foam tends to be hard and the elasticity characteristic of the vinyl chloride-based crosslinked foam becomes poor. On the other hand, if the blending amount of the carbon monoxide copolymer exceeds 200 parts by weight, the heat resistance of the obtained crosslinked foam is deteriorated, so that it cannot be used for applications such as cushion layers of automobile interior materials.

Examples of the chemical foaming agent used in the vinyl chloride crosslinked foam according to the present invention include azodicarbonamide, (1,1-azobisformamide), sulfonylhydraside, p, p ′.
-Oxy-bis- (benzenesulfonylhydrazide),
Examples thereof include sulfonyl semicarbazide, p-toluenesulfonyl semicarbazide, trihydrazine triazine, 5-phenyltetrazole, mono- and polyazoformamide, and dinitrosomethyleneamine.

These chemical foaming agents are used in an amount of 5 to 40 parts by weight based on 100 parts by weight of the vinyl chloride polymer and the carbon monoxide copolymer.
It is preferably blended in an amount of 10 to 30 parts by weight.

In order to produce the vinyl chloride-based crosslinked foam according to the present invention, it is necessary to crosslink the vinyl chloride-based foam, and therefore, the following crosslinking agent is generally added to the vinyl chloride-based polymer composition. To be done.

Examples of such a cross-linking agent include organic peroxides such as dicumyl peroxide (see JP-A-59-80444),
Diamines such as p-phenylenediamine, a chemical foaming agent that also functions as a cross-linking agent (JP-A-58-204033),
Sulfur-based vulcanizing agents (JP-A-48-28544) are used.

In producing the vinyl chloride-based crosslinked foam according to the present invention, the vinyl chloride-based polymer composition can be foamed by irradiating with an electron beam or γ-ray without using the above-mentioned crosslinking agent. .

Further, as the crosslinking aid, a polyfunctional co-crosslinking agent such as divinylbenzene, triallyl cyanurate, trimethylolpropane triacrylate or the like can be added to the vinyl chloride polymer composition.

The vinyl chloride-based crosslinked foam according to the present invention may contain a small amount of a liquid plasticizer, a stabilizer and the like in addition to the above components.

As the liquid plasticizer, dioctyl phthalate, trioctyl trimellitate, polyester plasticizer and the like are used.

As the stabilizer, metal soaps such as metal stearates such as zinc, barium and calcium are generally used.

Next, a method for producing a vinyl chloride-based crosslinked foam using each of the above components will be described.

In the present invention, first, 100 parts by weight of a vinyl chloride polymer and 40 to 150 parts by weight of a carbon monoxide copolymer are uniformly pre-kneaded at a high temperature of 160 to 180 ° C. and under high shear (A). On the other hand, the component (B) is prepared by kneading the carbon monoxide copolymer, preferably 10 to 50 parts by weight, and the chemical foaming agent at a temperature not higher than the decomposition temperature of the chemical foaming agent.

To prepare the component (A), vinyl chloride polymer, carbon monoxide copolymer and, if necessary, each component such as a stabilizer are mixed in a blending ratio as described above by a ribbon blender or a Henschel mixer. After premixing using the device, using a batch type kneader such as a roll or Banbury mixer, or a twin-screw extruder, a high shear continuous kneader such as FCM, at a high kneading temperature of 160 to 180 ° C. Just knead. By doing so, the component (A) in which the respective components are uniformly dispersed is obtained. The component (A) has a softening temperature lower than the softening temperature of the vinyl chloride polymer alone, and can be kneaded with the component (B) at a low temperature.

To prepare the component (B), the carbon monoxide copolymer as described above, a chemical foaming agent and, if necessary, various cross-linking agents, cross-linking aids, etc. are mixed in the above-mentioned mixing ratio in rolls. Alternatively, a kneader such as a twin-screw extruder may be used to knead at a temperature lower than the decomposition temperature of the chemical foaming agent, for example, a temperature of 100 to 120 ° C. By doing so, the component (B) in which the respective components are uniformly dispersed is obtained.

The carbon monoxide copolymer contained in the component (B) is
When the component (B) and the component (A) are kneaded, they act as one kind of internal lubricant and suppress shear heat generation during kneading to enable molding of an unfoamed sheet material at a low temperature. Further, since the component (B) can be sufficiently kneaded as a masterbatch of a chemical foaming agent or a cross-linking agent using a carbon monoxide copolymer as a binder, it can be kneaded with the component (A). A small amount of chemical foaming agent or cross-linking agent can be uniformly dispersed throughout the unfoamed sheet material. By doing so, the chemical foaming agent or the like can be added to the vinyl chloride composition within a limited time without applying too much shearing force to the unfoamed T-die sheet or the like using a continuous kneader such as a single screw extruder. Effective to disperse evenly.

In addition, the blending amount of the carbon monoxide copolymer in the component (B) is 40 to 40 times the amount of the carbon monoxide copolymer in the component (A).
When the amount is 150 parts by weight, if the amount is less than 10 parts by weight, the amount of the foaming agent as a binder is too small, and it tends to be difficult to uniformly disperse the foaming agent. When the amount of the carbon monoxide copolymer is more than 50 parts by weight, the following step of kneading the component (A) and the component (B) cannot be completed in a short time, resulting in a uniform unfoamed sheet material. Is difficult to create, which is not preferable.

Next, the components (A) and (B) are uniformly kneaded using a kneader such as a roll, a Banbury mixer, or an extruder at a temperature lower than the decomposition temperature of the foaming agent, and then extrusion-molded by a T-die or A non-foamed sheet is formed by calendering.

In order to obtain a vinyl chloride crosslinked foam by crosslinking / foaming the unfoamed sheet material (raw sheet) thus obtained, (1) irradiating with an electron beam or γ ray After crosslinking the polymer, it is heated to decompose the chemical foaming agent and foamed by the decomposition gas generated at that time, or (2) it is heated and crosslinked with an organic peroxide, a diamine or a sulfur-based vulcanizing agent. The reaction may be performed and the chemical foaming agent may be decomposed to foam. The foaming conditions are higher than the decomposition temperature of the foaming agent, for example, in the case of using azodicarbonamide, a temperature of about 200 ° C. to 230 ° C.
Heat for 5 minutes.

Effect of the Invention According to the method for producing a vinyl chloride-based crosslinked foam according to the present invention, the component (A) obtained by uniformly pre-kneading a vinyl chloride-based polymer and a carbon monoxide copolymer under high temperature and high shear. Is prepared, and the carbon monoxide copolymer and the chemical foaming agent are kneaded at a temperature not higher than the decomposition temperature of the chemical foaming agent to prepare a component (B), and then the components (A) and (B) are mixed. After kneading to create an unfoamed sheet material, this sheet material is heated to cause foaming, so the vinyl chloride polymer composition melts when creating the unfoamed sheet material. The viscosity can be reduced, and thus a vinyl chloride-based crosslinked foam having a uniform foam cell can be obtained.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example Vinyl chloride polymer (Mitsui Toatsu Chemical Co., Ltd., Vinylon 2000)
M number average degree of polymerization 1100) 100 parts by weight, ethylene-vinyl acetate-carbon monoxide copolymer (vinyl acetate content 28% by weight,
Carbon monoxide content 9% by weight, MFR 35dg / min) 80 parts by weight,
4 parts by weight of trimethylolpropane triacrylate,
Preblend with 4 parts by weight of epoxidized soybean oil, 3 parts by weight of Ba-Zn stabilizer, 1.5 parts by weight of phosphite, and 0.5 parts by weight of polyethylene wax using a 20 Henschel mixer, and then in the same direction. Using a twin-screw extruder (PCM-30, Ikegai Tekko Co., Ltd., L / D = 25), kneading at a screw speed of 200 min ^-1 and a die temperature of 160 ° C, and vinyl chloride composition (component A) at about 7 kg / hour. Pellets were prepared. The component A had a smooth strand surface, gloss, and good transparency.

Then, the composition was met by two rolls at 150 ° C., a press sheet having a thickness of 1 mm was prepared by hot pressing at 180 ° C., and a tensile test was conducted according to JIS K 6723.
The results are shown in Table 2. The tensile strength and elongation at break of the component (A) were 18.5 MPa and 400%, respectively, and the vinyl chloride polymer was sufficiently melted and each component was uniformly dispersed.

On the other hand, 20 parts by weight of the ethylene-vinyl acetate-carbon monoxide copolymer and 15 parts by weight of azodicarbonamide (Uniform AZ manufactured by Otsuka Chemical Co., Ltd.) were used, and the screw rotation speed was 80 min using the same-direction twin-screw extruder. ^-1 , and the mixture was kneaded at a die temperature of 100 ° C to prepare pellets of a foaming agent composition (component B) in which yellow azodicarbonamide was uniformly dispersed at about 5 Kg / hour.

Then, after pre-blending the pellets of each of the components (A) and (B) with a tumbler, a single-screw extruder (L / D) having a coat hanger type T-die (die width 300 mm) is used.
= 28 CR = 3.0 full flight screw), the die set temperature is 130 ° C, the screw rotation speed is 30 min ^-1 ,
Screen mesh, 30/60/30 mesh, take-up speed 50cm
A sheet with a width of 250 mm and a thickness of 0.5 mm was created at a speed of / min. The resin temperature measured by die lip was 140 ° C. The obtained sheet was yellow and glossy, and no bubbles were observed in the cross section of the sheet.

Next, the obtained sheet was irradiated with 3 Mrad of an electron beam by an electron beam acceleration irradiation device (manufactured by Nisshin High Voltage Co., Ltd.), and the electron beam irradiation sheet was further left to stand in an air oven at 230 ° C. for 3 minutes to foam. It was

The obtained crosslinked foam was a light brown and elastic foam having uniform cells and had a density of 0.075 g / cm ³ .

Comparative Example 1 After the components (A) and (B) in Example 1 were not prepared respectively and all the components (A) and (B) were combined and pre-blended using a 20 Henschel mixer, Screw rotation speed 20 using the same direction twin screw extruder
The mixture was kneaded at 0 min ⁻¹ and a die temperature of 160 ° C. to obtain a vinyl chloride composition at about 7 kg / hour. The strand of this composition was yellow and had a good surface gloss, but the surface of the strand was rough and a large number of small bubbles were observed in the cross section.

A T-die sheet was prepared from the obtained vinyl chloride-based composition in the same manner as in Example 1, but a large number of small bubbles were observed in the cross section of the sheet-shaped product.

Then, in the same manner as in Example 1, the sheet-like material in the unfoamed state was subjected to electron beam irradiation treatment and foaming treatment by heating to prepare a crosslinked foam sheet.

The obtained foam sheet was light brown, its surface was corrugated, the size of the foam cells was uneven, and the elasticity was inferior to that of the crosslinked foam of Example 1. Density is 0.09
It was 6 g / cm ³ .

Comparative Example 2 In Comparative Example 1, the die temperature of the same-direction twin-screw extruder was changed to
A crosslinked foam sheet was obtained by the same method except that the temperature was changed to 130 ° C.

The surface of the obtained T die sheet had a rough and dull yellow color, and the melting of the vinyl chloride polymer was clearly incomplete.

The finally obtained foam was light brown, had a very low tensile rate, and was brittle.

Examples 2 to 3 Comparative Example 3 In Example 1, in place of the vinyl chloride polymer, a vinyl chloride-ethylene copolymer (Toyo Soda's Litron E-
1050, the number average degree of polymerization is 1050), and a crosslinked foam comprising the components (A) and (B) as shown in Table 1 was prepared in Example 1.
Created in the same manner as. At this time, the resin temperature at the die lip at the time of producing the T die sheet, the dispersion state of the foaming agent in the obtained T die sheet, the appearance of the finally obtained crosslinked foam, the uniformity and density of foam cells were evaluated. .

 The results are shown in Table 1.

Comparative Example 4 Pellets of a vinyl chloride composition (component A) were prepared in the same manner as in Example 1 except that the die temperature of the co-direction twin-screw extruder was changed to 150 ° C.
In the obtained component (A), the surface of the strand was rough and was not glossy.

Then, a tensile test was performed in the same manner as in Example 1. The results are shown in Table 2. The tensile strength and elongation at break of the component (A) were poor, and the melting of the vinyl chloride polymer was clearly incomplete.

Then, a crosslinked foam sheet was obtained in the same manner as in Example 1. The obtained foam sheet was light brown, and its surface was wavy, and the size of the foam cells varied.

In Example 2 and Example 3, T-die sheets were obtained which were yellow and shiny and had no bubbles observed in the cross section. The crosslinked foam of this sheet was light yellow, had uniform cells, and was elastic.

On the other hand, in Comparative Example 3, undispersed particles of azodicarbonamide, which is a foaming agent, clogged the breaker plate, and T die sheet molding was impossible.

Claims (1)

[Claims] 1. When producing a crosslinked foam of a vinyl chloride polymer containing a vinyl chloride polymer and a carbon monoxide copolymer, 100 parts by weight of the vinyl chloride polymer and the carbon monoxide copolymer are used. A uniform pre-kneaded product (A) component prepared by kneading 40 to 150 parts by weight of the combined product at a temperature of 160 to 180 ° C.,
On the other hand, 10 to 50 parts by weight of a carbon monoxide copolymer, a chemical foaming agent, and optionally a cross-linking agent are kneaded at a temperature not higher than the decomposition temperature of the chemical foaming agent to prepare a component (B). A method for producing a crosslinked foamed vinyl chloride polymer, which comprises kneading the above-mentioned components (A) and (B), and then forming an unfoamed molded product by extrusion molding or calendering, and then crosslinking and foaming.