JPS6026147B2 - Manufacturing method of vinyl chloride paste foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a vinyl chloride-based foam having a high closed foam ratio and a high expansion ratio.

The method of producing a foam by adding a chemical blowing agent to a polyvinyl chloride base has been practiced for a long time and is still widely practiced today.

Foams are required to have various physical properties depending on their use. Among these, obtaining a foam with a high expansion ratio and a foam with a high closed cell ratio are the biggest themes that have been pursued from the past to the present. There are two main types of methods for producing vinyl chloride paste foams using chemical blowing agents: one is high-pressure two-stage foaming, and the other is normal-pressure foaming.

Although high-pressure two-stage foaming can produce a foam with a high expansion ratio and a high closed cell ratio, it is limited to a specific shape, is expensive, and has poor efficiency. Therefore, the problem here is normal pressure foaming. Various methods have been studied to obtain foams with a high expansion ratio and a high closed cell ratio in normal pressure foaming.
If you use a foam with a high expansion ratio, it will become an open-cell foam.
Furthermore, if the closed cell ratio is increased, the foaming ratio must be lowered.

For example, if you try to obtain a foam with a high expansion ratio by increasing the amount of blowing agent added, the cells will become larger and the open cell ratio will increase.
This results in a foam that cannot be put to practical use.

This is mainly caused by the decomposition gas pressure of the added blowing agent and the viscosity of polyvinyl chloride when it is melted. In order to obtain a foam with a high expansion ratio, it is necessary to add a large amount of blowing agent, and therefore the decomposition gas pressure of the blowing agent also increases. Therefore, the most appropriate way to efficiently retain this cracked gas is to increase the viscosity of polyvinyl chloride when it is heated and melted. (Using a thermosetting plasticizer is also one method. However, the use of a thermosetting plasticizer may cause the viscosity of the polyvinyl chloride base to change over time, making it inconvenient to handle.) In view of the circumstances,
In order to increase the viscosity of polyvinyl chloride base when melted by heating, the present inventor conducted extensive research into additives and discovered that a specific ethylene-vinyl acetate copolymer was extremely effective, leading to the completion of the present invention. It was. For the ethylene-vinyl acetate copolymer to be used effectively, it must be uniformly dispersed in the polyvinyl chloride paste.

As a method for this, before preparing the polyvinyl chloride base, the polyvinyl chloride base may be heated and dissolved in a plasticizer in advance, and the dissolved plasticizer may be used to prepare the polyvinyl chloride base by a known method. Due to this solubility, polyethylene homopolymer is not suitable, and ethylene-vinyl acetate copolymer containing 5 to 50% vinyl acetate is preferred. If the vinyl acetate content exceeds 50%, foaming will be adversely affected. Also, in ethylene-vinyl acetate copolymer,
The melt index must be between 20 and 150. If the melt index is less than 20, the solubility in the plasticizer will be poor, and if it is more than 150, the viscosity of the polyvinyl chloride base when melted by heating will be reduced. The amount of ethylene-vinyl acetate copolymer added is determined in order to maintain the paste properties of the polyvinyl chloride base, and to more effectively produce a foam with a high expansion ratio and closed cell ratio. , 2 parts by weight or more and 15 parts by weight or less.

Therefore, in the present invention, when a polychlorinated pinyl base to which an organic blowing agent is added is prepared by a conventional method, 2 parts by weight or more and 15 parts by weight or less of an ethylene-vinyl acetate copolymer (with a pinyl acetate content of 5 to 50 parts by weight) is added to the plasticizer in advance. %, melt index 2
The most suitable manufacturing method is to manufacture a foam by a conventional method using a polyvinyl chloride base obtained by dissolving polyvinyl chloride (0 to 150). According to this invention, the ethylene-vinyl acetate copolymer is inexpensive, and the simple operation of pre-dissolving a small amount of this copolymer in a plasticizer does not impair its characteristics as a polyvinyl chloride paste. It is possible to obtain a foam that has a high expansion ratio and a high closed cell ratio without any problems.

Next, the present invention will be explained by examples.

Example 1 Ethylene-vinyl acetate copolymer (trade name, Evatate M
5011, 35% vinyl acetate content Melt Index 60) 8 parts by weight are heated and dissolved in 75 parts by weight of dioctyl phthalate.

A base was prepared by mixing this solution with 100 parts by weight of polyvinyl chloride base resin, 3 parts by weight of Ca×Zn-Mg stabilizer, and 7 parts by weight of a blowing agent (Azodicarbonamide). do. This paste was uniformly applied to a thickness of 0.25mm on another aluminum slope to a thickness of 0.5mm, and heated and foamed in a 200mm oven for 3 minutes.
(moss with a foaming ratio of 1) to obtain a foam having a high closed cell ratio and fine cells. As a comparative example, a foam was obtained in the same manner using the above paste composition with the ethylene-vinyl acetate copolymer removed, but the cells were large and all were open cells, and the foaming ratio was 7 times. there were.
Example 2 Ethylene monovinyl acetate copolymer (trade name, Sumitate D
B-10, 10% vinyl acetate content Melt Index 70) 5 parts by weight are heated and dissolved in 75 parts by weight of dioctyl phthalate.

A paste is prepared by mixing this solution with 100 parts by weight of a polyvinyl chloride base resin, 3 parts by weight of a Cd--Zn stabilizer, and 6 parts by weight of a blowing agent (azodicarbonamide). This paste is uniformly applied to the inner surface of a ceramic tank with a thickness of 1.5 mm using a slash molding method. By heating and foaming in a 200° C. oven for 1 minute, a tank with a heat insulating material having a foam layer of 10 willow thickness is obtained.

Although this foaming rate is 7 times higher, the foamed layer has a high closed cell rate and is effective as a heat insulating material. As a comparative example, a foam layer was formed on the inner surface of the tank using the same method using a paste obtained by removing the ethylene-vinyl acetate copolymer from the above paste composition. It is something that is lacking. As described above, according to the present invention, it is possible to inexpensively and easily produce a foam with a high expansion ratio and fine non-open cells, whereas conventionally it has been difficult to produce a foam with a high expansion ratio and non-open cells. Because it can be obtained, it has excellent effects such as improved thermal insulation properties, better resilience, and less materials, so it is easy to obtain a thick insulation layer at a low price.

Claims (1)

[Claims] 1 Add an organic blowing agent to polyvinyl chloride paste,
When producing foam, the ethylene-vinyl acetate copolymer is mixed with a vinyl acetate content of 5 to 50% and a melt index of 2.
0 or more and 150 or less, and the method for producing a polyvinyl chloride foam is characterized in that the polyvinyl chloride foam is used after being heated and dissolved in a plasticizer in advance from 2 parts by weight to 15 parts by weight.