JPS6197340A - Production of polyvinyl chloride resin foam - Google Patents

Abstract

PURPOSE:To obtain easily and continuously the title foam which has excellent heat resistance, dimensional stability and closed cell properties, is rigid and has a desired shape, by heating a foaming crosslinked molding obtd. by irradiating a foaming molding with ionizing radiation to expand it. CONSTITUTION:100pts.wt. PVC having an average degree of polymn. of 800-1,600 or PVC resin such as vinyl chloride/ethylene copolymer having an average degree of polymn. of 500-2,000 and an ethylene content of 10wt% or below, 20-100pts.wt. polyfunctional epoxy compd. cong. at least two epoxy groups per molecule (e.g. bisphenol A), 0.5-20pts.wt. polyfunctional compd. contg. at least two unsaturated bonds per molecule, 1-30pts.wt. decomposition type blowing agent and 0.01-2pts.wt. stabilizer such as organotin stabilizer are blended together. The resin compsn. is melt-kneaded at a temp. of not higher than the decomposition temp. (610 deg.C) of said blowing agent to obtain a foaming molding. The molding is crosslinked by irradiating it with ionizing radiation such as electron beams at a dose of 0.05-10 Mrad to obtain a foaming crosslinked molding having a gel fraction of 10-50%. The molding is then heated at 180-240 deg.C to expand it.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a rigid polyvinyl chloride resin foam.

(Prior art) Hard polyvinyl chloride foam is manufactured by
The product name Klegecell was obtained by the K15ber method described in Japanese Patent No. 2370 and Japanese Patent Publication No. 41-12632.
It can be manufactured as According to this, polyisocyanate and acid anhydride are added to polyvinyl chloride powder obtained by emulsion polymerization to form a paste, which is then placed in a mold.
The desired foam is obtained by foaming by repeating pressurization, heating, and cooling. According to this method, a foam with relatively excellent heat resistance can be obtained. Japanese Patent Publication No. 34-4989 discloses that a solvent and a foaming agent are added to polyvinyl chloride powder obtained by an emulsion polymerization method to form a paste, and this is foamed by a high-pressure two-step process to produce a rigid polyvinyl chloride foam. It describes how to obtain it. However, in any of the above methods, the raw material polyvinyl chloride is emulsified),
Since it is manufactured legally, it is expensive and the manufacturing process is complicated, so one foam cannot be provided at a low price. Furthermore, it is difficult to produce elongated sheet-like foams with a wide width, for example, by such a method.

Japanese Patent Publication No. 55-65241. 55-71727. 55
-139435゜55-149328.55-1527
25 and 55-152726, using inexpensive polyvinyl chloride obtained by a suspension polymerization method, adding volatile foaming agents and processing aids to it, and then producing hard polyvinyl chloride foam by an extrusion foaming method. It describes how to obtain the body. According to this method, yL! Since polyvinyl chloride obtained by the turbidity polymerization method is inexpensive and the manufacturing process is simple, the foam can be supplied at low cost. However, the foam obtained by this method has poor heat resistance. As an improvement to such a method, the present inventors have studied a method of obtaining a foam using chlorinated polyvinyl chloride. As a result of various research, a foam with excellent heat resistance was obtained.
Due to the lack of stability of extrusion foam molding, it was not possible to commercialize the product.

JP-A-58-1729 discloses a method of forming a soft polyvinyl chloride resin foam into a desired shape, for example, by forming a sheet-like two-foaming molded product and foaming it to obtain a foam having the desired shape. The manufacturing method is described.

In this method, first, a resin composition containing a polyvinyl chloride resin 1 plasticizer, a crosslinking aid, and a stabilizer is kneaded at a temperature equal to or higher than the gelling temperature of the polyvinyl chloride resin. Once the plasticizer is uniformly dispersed throughout the composition.

It melts even at temperatures below the melting point of polyvinyl chloride resin. Therefore, the foaming agent can be used at a temperature below the melting point of the polyvinyl chloride resin without the foaming agent decomposing and foaming.
It becomes possible to knead.

This is molded into a desired shape using an extruder or calender roll. The obtained foaming molded product is irradiated with an electron beam to crosslink the polyvinyl chloride resin of the molded product, and then heated and foamed. Since the obtained foam is crosslinked, it has excellent heat resistance. but.

This method is applicable only to soft foams containing a relatively large amount of plasticizer, and cannot be applied to the production of rigid polyvinyl chloride resin foams.

Furthermore, JP-A-57-180645 discloses that a polyvinyl chloride resin, a plasticizer, a stabilizer, a crosslinking aid, a foaming agent, etc. are heated and kneaded, formed into a sheet shape, and irradiated with ionizing radiation. A method is disclosed in which a polyvinyl chloride resin is crosslinked and then heated and foamed to obtain a vinyl chloride resin foam sheet. In this method, a compound such as dibutyl phthalate that easily volatizes when heated is used as a plasticizer.

Although the plasticizer is continuously lost during heating and foaming, and the resulting foam becomes hard, it is not practical for industrial use because the equipment becomes complicated and the volatilized plasticizer pollutes the environment.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned drawbacks, and its purpose is to provide a method for manufacturing a rigid polyvinyl chloride resin foam with excellent heat resistance at a low cost. be. Another object of the present invention is to provide a method for continuously producing a rigid polyvinyl chloride resin foam in a desired shape, particularly in the form of a long and wide sheet, through simple steps.

(Means for solving the problem) The method for producing the polyvinyl chloride resin foam of the present invention is (1)
) A polyfunctional epoxy compound having two or more epoxy groups in nine molecules of a polyvinyl chloride resin.A polyfunctional compound having two or more unsaturated bonds in two molecules.

a step of obtaining a resin composition containing a decomposable blowing agent and a stabilizer; (2) a step of melt-kneading the resin composition at a temperature below the decomposition temperature of the decomposable blowing agent to obtain a molded article for foaming; A step of irradiating the foaming molded product with ionizing radiation to obtain a foaming crosslinked molded product, and (4) a step of heating the foaming crosslinked molded product to a temperature higher than the decomposition temperature of the decomposable foaming agent to obtain a hard foamed product. , thereby achieving the above object.

The polyvinyl chloride resin used in the method of the present invention is a resin containing 50% by weight or more of a vinyl chloride component, such as polyvinyl chloride, chlorinated polyvinyl chloride, and vinyl chloride-ethylene copolymer.

There are graft polymers in which vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, and ethylene-vinyl acetate copolymer are grafted with vinyl chloride. Furthermore, acrylonitrile-butadiene-styrene copolymer (ABS), methyl methacrylate-butadiene-styrene copolymer (MBS), acrylic rubber, etc. are added to the above polymer.

It is also possible to mix the vinyl chloride component within a range in which the content of the vinyl chloride component is not less than 50% of the total resin.

Among these, the average degree of polymerization is 500 to 2000. Preferably polyvinyl chloride of 800 to 1600 and an average degree of polymerization of 500 to 2000 with ethylene as a constituent component of 10
A vinyl chloride-ethylene copolymer containing less than % by weight is preferably used. If the average degree of polymerization of these polymers is less than 500, the viscosity necessary for foaming cannot be obtained even if the polyvinyl chloride resin is crosslinked.

If it exceeds 2000, the viscosity becomes too high due to crosslinking, making it impossible to obtain a foam with a high expansion ratio. Regarding vinyl chloride-ethylene copolymers, when the ethylene content exceeds 20% by weight, the resulting foam becomes soft.

Polyfunctional epoxy compounds have two or more functional groups 1-1- in the molecule.
It has a Si group and functions as a plasticizer and stabilizing agent for polyvinyl chloride resin in the composition. Examples of polyfunctional epoxy compounds include 2,2-bis(4-hydroxyphenyl)propane diglycidyl ether (-ship name: bisphenol A) and its hydrogenated product, 2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether (-ship name: bisphenol A). Glycidyl ethers or low molecular weight polymers thereof; polyglycidyl ethers of novolac type phenols; low molecular weight aliphatic polyols such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, trimethylolpropane, 1,4-butanediol Polyglycidyl ethers of , pentaerythritol, neopentyl glycol, 1,6-hexanediol; polyfunctional carboxylic acids 2 such as phthalic acid and its hydrogenated products, isophthalic acid and its hydrogenated products, terephthalic acid and its hydrogenated products Additive, polyglycidyl ester of trimellitic acid; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carbonate-1, obtained by peracetic acid method.
Bis(3,4-epoxycyclohexyl)azibe 1-
．． 2- (3,4-epoxycyclohexyl-5,5-
spiro-3,4-epoxy)cyclohexane-meta-dioxane, and the like. Among these, aromatic compounds and their hydrogenated compounds have a high function as a desensitizing agent, and the resulting foam has excellent heat resistance. In particular, 2
- Diglycidyl ethers of 2-bis(4-hydroxyphenyl)propane and its derivatives and polyglycidyl esters of aromatic polyfunctional carboxylic acids are preferably used.

Two or more of the above polyfunctional epoxy compounds may be used as a mixture, if necessary.

The polyfunctional epoxy compound is polyvinyl chloride resin 100
10 to 100 parts by weight, preferably 20 to 100 parts by weight
It is contained in the resin composition in a proportion of 80 parts by weight. If the content is too small, the polyvinyl chloride resin will not be sufficiently plasticized, making it impossible to knead the resin composition at a temperature below the decomposition temperature of one blowing agent. If it is in excess, the viscosity of the foaming molded product becomes too low during heating and foaming, making it impossible to obtain a good foam, and the resulting foam becomes expensive, which is undesirable.

Polyfunctional compounds having two or more unsaturated bonds in the molecule are
As a crosslinking aid for polyvinyl chloride resin.

Contained in the resin composition. Such polyfunctional compounds include ethylene glycol dimethacrylate.

Diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate,
1,3 butanediol dimethacrylate, tris-(2
-Hydroxyethyl) isocyanuric acid tri(meth)
Acrylic acid ester, triallyl isocyanurate, triallyl cyanurate, triallyl trimellitate.

Examples include diallylphthalene rhodivinylbenzene. The content of such a polyfunctional compound having two or more unsaturated bonds in the molecule varies depending on the amount of components in the composition, but it may be 0 to 100 parts by weight of the polyvinyl chloride resin in the resin composition.
．． It ranges from 5 to 20 parts by weight, preferably from 1 to IO parts by weight. If it is too small, the resin viscosity necessary for foaming will not be obtained.
If it is in excess, the crosslinking reaction will proceed too much, making it impossible to obtain a good foam.

Such polyfunctional compounds may also be used in combination of two or more.

In order to ensure the thermal stability of the polyvinyl chloride resin, the resin composition contains a stabilizer. Stabilizers include lead-based, organic tin-based, and barium-zinc-based stabilizers.

Calcium-zinc based stabilizers can be used, with organotin based stabilizers being preferred. The resin composition contains a polyfunctional epoxy compound. This polyfunctional epoxy compound functions as a stabilizing agent for polyvinyl chloride resin, so even if the content of the stabilizer is small, polyvinyl chloride is The thermal stability of the system resin is good. The content of the stabilizer is 0.01 to 2 parts by weight per 100 parts by weight of the vinyl chloride resin. If the amount exceeds 2 parts by weight, the foaming agent may decompose during kneading of the resin composition, or the polyfunctional epoxy compound may undergo side reactions, making it impossible to obtain a good foamable molded product.

The decomposable blowing agent is one that decomposes when heated to generate gas, and azodicarbonamide, dinitrone pentamethylene tetramine, p'p"-oxybisbenzenesulfonyl hydrazide, etc. are used. Among these, the blowing agent decomposition temperature Azodicarbonamide is most suitable from the viewpoints of gas generation and amount of gas generated.A lubricant may be added to the resin composition as required.

Epoxy curing agent, flame retardant 1 foaming aid, impact modifier,
Pigments and the like may be added. In particular, acrylic foaming aids are effective in stabilizing foaming during heating and foaming.

The resin composition containing each of the above components is below the decomposition temperature of the blowing agent.
The mixture is preferably melt-kneaded at 160° C. or lower, more preferably 150° C. or lower, and then molded into a desired shape using an extruder, calender roll, or the like. Since the polyfunctional epoxy compound in the composition acts as a plasticizer for the polyvinyl chloride resin, the resin composition can be kneaded at a temperature below the decomposition temperature of the blowing agent.

The obtained molded article for foaming can be made of a polyfunctional epoxy compound.
It is essentially a soft polyvinyl chloride-based resin molded article because it acts as an agent. In the case of a sheet, it is soft and can be rolled up, so even a wide and long molded product can be easily manufactured.

In conventional techniques using phthalate ester or polyester plasticizers, a relatively large amount of stabilizer is required to prevent the polyvinyl chloride resin from decomposing during heat kneading or foaming. This stabilizer acts as a decomposition aid for the foaming agent, and foaming occurs during kneading. On the other hand, since the polyfunctional epoxy compound contained in the resin composition of the present invention acts as a stabilizing agent for polyvinyl chloride resin, the amount of the stabilizer may be small. The foaming agent inside will not decompose and cause foaming. Furthermore, the polyvinyl chloride resin hardly decomposes to generate hydrogen chloride gas or become colored twice.

Next, the foamed molded article is irradiated with ionizing radiation to crosslink the polyvinyl chloride resin. As ionizing radiation,
T-rays, β-rays, neutron beams, electron beams, etc. are used, and from an industrial perspective, electron beams generated by accelerators are preferred. Irradiation of ionizing radiation ■ differs depending on the blending ratio of each component of the resin composition.

If the absorbed dose is in the range of 0.5 to 10 Mrad, the desired crosslinking can be achieved. The gel fraction (the weight fraction of insoluble matter after being immersed in tetrahydrofuran for 24 hours at room temperature) of the crosslinked foamed body thus obtained is the blending ratio of each component in the resin composition.

Although it varies depending on the type of polyvinyl chloride resin and the type and amount of the polyfunctional epoxy compound, it is preferably in the range of 10 to 50%. If the gel fraction is 10% or less, the resin viscosity during heat foaming will be too low, resulting in degassing, making it impossible to obtain a foam with a high expansion ratio. In addition, in the case of vertical foaming, the resin becomes thicker, making it extremely difficult to maintain the foam shape.If the gel fraction is higher than 50%, the viscosity of the resin during heat foaming will increase. Because it's too much,
A foam with a high expansion ratio cannot be obtained.

The foaming agent is decomposed by heating the obtained crosslinked foaming molded body to 180 to 240°C, gas is generated, and a foamed body is obtained. At this time, since the polyfunctional epoxy compound is partially cured, the obtained foam becomes hard. This is thought to be because the decomposition gas and decomposition residue of the blowing agent act as a curing catalyst, and the polyfunctional epoxy compound is cured by heat. On the other hand.

Since the polyfunctional epoxy compound acts as a stabilizing agent, even if the polyvinyl chloride resin is exposed to heat for a long time in a foaming furnace during heating and foaming, it will hardly decompose and become colored. The resulting foam has excellent heat resistance and dimensional stability. Furthermore, it has a uniform cell structure, excellent independent foaming properties, and a good appearance. According to the method of the present invention, it is possible to continuously produce a rigid polyvinyl chloride resin foam of any shape, particularly in the form of a long and wide sheet, by an atmospheric foaming method.

(Example) The invention will be explained below with reference to examples.

Polyvinyl chloride with an average degree of polymerization of 1400 as a polyvinyl chloride resin on Daichung charcoal (Tokuyama Sekisui Kogyo Sumi I TS-1400K)
10031, 40 parts by weight of a polyfunctional epoxy compound mainly composed of diglycidyl ether of 2,2-bis(4-hydroxyphenyl)propane (Epicote 828; manufactured by Shell Chemical ■), and 2 or more unsaturated bonds. Triacrylate ester of tris-(2-hydroxyethyl)isocyanuric acid (FA-731
(manufactured by Hitachi Kasei Jun) 3 parts by weight 2 20 parts by weight of azodicarbonamide as a blowing agent, organic tin mercaptide stabilizer as a stabilizer (JP-95B i manufactured by Sankyo Organic Synthesis 9 Kiku)
A resin composition containing 0.5 parts by weight was uniformly mixed using a Henschel mixer. This was melt-kneaded using a calendar roll at 140°C to obtain a foamed molded product with a thickness of 1 mm. This foaming molded article had a smooth surface and almost no small bubbles caused by the primary decomposition of the foaming agent. Next, this foaming molded article was irradiated with an electron beam of 5 Mrad using an accelerating tube to crosslink the polyvinyl chloride. The gel fraction of the obtained foam crosslinked molded article was measured. This foamed crosslinked molded body was suspended in a hot air stove and heated at 210° C. for 5 minutes.

Foamed. The appearance of the obtained rigid foam is density.

The closed cell ratio, average cell diameter, and bending strength at room temperature were measured. Further, the nine foams were placed in a gear oven at 80°C and 120°C, and the volume reduction rate was measured after 24 hours. Table 1 shows each measured value.

Big Flag 1 A foam was prepared in the same manner as in Example 1 except that the electron beam irradiation amount was 2 Mrad. Gel fraction of the crosslinked molded product for foaming; The apparent density, closed cell ratio, average cell diameter, and bending strength at room temperature of the foam were measured. Table 1 shows each value.
Shown below.

Example 2 except that the cold storm main electron beam irradiation dose was set to 3 Mrad.
It is similar to

Okimasu ↓ Example 2 except that the electron beam irradiation amount was 11 Mrad.
It is similar to

A foam was prepared in the same manner as in Example 1 except that polyvinyl chloride having an average degree of polymerization of 1050 was used as the polyvinyl chloride resin. Gel fraction of the crosslinked molded product for foaming; apparent density, closed cell ratio, and bending strength at room temperature of the foamed product were measured. The respective values are shown in Table 1.

The procedure was the same as in Example 5 except that polyvinyl chloride having an average degree of polymerization of 1900 was used as the Hitachi Tantan polyvinyl chloride resin.

A vinyl chloride-ethylene copolymer (degree of polymerization 1300) containing 3.6% by weight of ethylene as a constituent component is used as the polyvinyl chloride resin, and the amount of electron beam irradiation is 4 Mrad. A foam was prepared in the same manner as in Example 1 except for the following. Gel fraction of the crosslinked molded product for foaming; apparent density, closed cell ratio, and bending strength at room temperature of the foamed product were measured. Furthermore, the foam was placed in a gear oven at 80°C and 120°C, and the volume reduction rate was measured after 24 hours. Table 1 shows each measured value.

j at a ratio of 4.1% by weight with ethylene as a constituent component,
The procedure was the same as in Example 5, except that the vinyl chloride-ethylene copolymer (polymerization degree 1'7 QO) contained therein was used as the polyvinyl chloride resin, and the electron beam irradiation amount was 4 Mrad.

A vinyl chloride-ethylene copolymer (degree of polymerization 2100) containing 4.0% by weight of ethylene as a constituent component was used as the polyvinyl chloride resin, and the electron beam irradiation amount was set to 4 Mrad. The rest is the same as in Example 5.

Vinyl chloride-ethylene copolymer containing 11.0% by weight of ethylene for cold war history (degree of polymerization 1300)
Example 5 is the same as Example 5, except that the polyvinyl chloride resin was used and the electron beam irradiation amount was 2.5 Mrad.

The apparent density and closed cell ratio of the rigid polyvinyl chloride foam manufactured by another company using the carbonaceous clay polyisocyanate-acid anhydride method were measured.

Furthermore, the volume reduction rate was measured after 24 hours in a gear oven at 80°C and 120°C. Table 1 shows the values.
Shown below.

This! 24 Regarding rigid polyvinyl chloride foam produced by other companies using the shadow extrusion foaming method, the apparent density of the foam is:

The closed cell ratio was measured. Furthermore, the volume reduction rate was measured after 24 hours in a gear oven at 80°C and 120°C. The values are shown in Table 1.

(The following is a blank space) A foam was prepared in the same manner as in Example 7, except that polyglycidyl ether of novolac type phenol (Epicor 152; manufactured by Shell Chemical ■) was used as the polyfunctional epoxy compound. Table 2 shows the moldability with a calendar roll, the apparent density of the obtained foam, and the bending strength at room temperature.

Daitosai U Example 11 except that 1,6-hexanediol diglycidyl ether was used as the polyfunctional epoxy compound
It is similar to

Daiarashimasu U Same as Example 11 except that diethylene glycol diglycidyl ether was used as the polyfunctional epoxy compound.

The procedure was the same as in Example 11 except that phthalic acid diglycidyl ester was used as the polyfunctional epoxy compound.

Comparative Example 3 A foam was prepared in the same manner as in Example 7, using dioctyl phthalate as a plasticizer instead of the polyfunctional epoxy compound. The resin composition was colored brown by heating, and gas release during one foaming was severe, so that a foam with a high expansion ratio could not be obtained. On the other hand, in Example 7 produced by the method of the present invention, the color of the foam was pale yellow, but a foam with a high expansion ratio and excellent closed cell properties was obtained.

↓ Adipic acid polyester (8DK-C1zer PN-40) is used as a plasticizer instead of a polyfunctional epoxy compound.
A foam was prepared in the same manner as in Example 7 using Adeka Argus Co., Ltd.). The resin composition was colored brown by heating, and gas release during one foaming was severe, so that a foam with a high expansion ratio could not be obtained.

A foam was prepared in the same manner as in Example 7 except that the amount of light entry length stabilizer was 0.2 parts by weight. Calendar Roll Formability 1 The foamed state and the apparent density of the resulting foam are shown in Table 3.

Example 15 except that the amount of Otachimunuki stabilizer was 1.2 parts by weight
It is similar to

Example 15 except that the amount of stabilizer was 2.5 parts by weight
It is similar to

The procedure was the same as in Example 15 except that 0.5 parts by weight of dibutyltin dilaurate was used as the Ohata Yukou stabilizer.

Example 15 The procedure was the same as in Example 15 except that 0.5 parts by weight of tribasic lead nitrate was used as a stabilizer.

The procedure was the same as in Example 15, except that 0.5 parts by weight of lead stearate was used as a stabilizer.

1H Barium-lead stabilizer (11AI'lK) was used as a stabilizer.
The procedure was the same as in Example 15 except that 0.5 parts by weight of AC-169 (manufactured by Adeka Argus ■) was used.

(Effects of the Invention) According to the method of the present invention, a rigid polyvinyl chloride resin foam having far superior heat resistance than before can be produced continuously and through a simple process using the normal pressure foaming method. Can be manufactured on a large scale. Since the raw material polyvinyl chloride resin can be obtained by a normal suspension polymerization method and the manufacturing process is simple, the 9 foam can be provided at low cost. According to the method of the present invention, since a soft foaming molded body is molded and then turned into a hard foamed body, it becomes easy to manufacture a sheet-like foamed body of any shape, especially a long and wide-radius sheet-like foamed body. The resulting foam has a high expansion rate, a uniform cell structure, and excellent independent foaming properties. It also has excellent dimensional stability at high temperatures, making it suitable for use in high-temperature environments.

that's all

Claims (1)

[Claims] 1. (1) Polyvinyl chloride resin, polyfunctional epoxy compound having two or more epoxy groups in the molecule, polyfunctional compound having two or more unsaturated bonds in the molecule, decomposition type Obtaining a resin composition containing a blowing agent and a stabilizer. (2) Melting and kneading the resin composition at a temperature below the decomposition temperature of the decomposable blowing agent to obtain a foamable molded product; (3) irradiating the foamable molded product with ionizing radiation to obtain a foamable crosslinked molded product. and (4) heating the crosslinked foam to a temperature higher than the decomposition temperature of the decomposable blowing agent to obtain a hard foam. 2. The resin composition contains 20 to 100 parts by weight of the polyfunctional epoxy compound, 0.5 to 20 parts by weight of the polyfunctional compound, and the decomposable blowing agent based on 100 parts by weight of the polyvinyl chloride resin. The manufacturing method according to claim 1, wherein each of these components is contained in a proportion of 1 to 30 parts by weight. 3. The polyvinyl chloride resin has a polymerization degree of 800 to 160.
The manufacturing method according to claim 1, which is polyvinyl chloride with a polyvinyl chloride of 0. 4. The polyvinyl chloride resin contains 10% by weight of ethylene.
The manufacturing method according to claim 1, which is a vinyl chloride-ethylene copolymer containing the following proportions and has a degree of polymerization of 500 to 2,000. 5. The manufacturing method according to claim 1, wherein the polyfunctional epoxy compound is an aromatic polyfunctional epoxy compound or an aromatic hydrogenated polyfunctional epoxy compound. 6. The production according to claim 1, wherein the stabilizer is an organotin stabilizer and is contained in a proportion of 0.01 to 2 parts by weight based on 100 parts by weight of the polyvinyl chloride resin. Method.