JPH0419246B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for suspension polymerizing vinyl chloride or a mixture of vinyl chloride as a main component and monomers copolymerizable with vinyl chloride (hereinafter collectively referred to as vinyl chloride monomers). More specifically, the present invention relates to a polymerization method that can extremely reduce the possibility that a part of the produced polymer becomes scale and adheres to the walls of the polymerization vessel used for polymerization and the surfaces of attached equipment of the polymerization vessel. The properties of the polymer obtained by polymerizing vinyl chloride monomers are greatly influenced by the degree of polymerization, and the degree of polymerization is also greatly controlled by the polymerization conditions, particularly the polymerization temperature. Generally, the degree of polymerization is less than 1000, and the polymerization temperature is 57 to 70℃.
Vinyl chloride polymers obtained by suspension polymerization have optimal properties for films, sheets, etc., and are therefore widely used industrially. During suspension polymerization of vinyl chloride monomers, scale adhesion to the walls of the polymerization vessel reduces the cooling efficiency of the jacket provided to remove the generated polymerization heat, impeding temperature control, and impeding the stirring effect. decrease. Furthermore, this scale mixes into the product, causing so-called "fisheye" and deteriorating the quality of the product. Conventionally, many methods have been proposed to prevent such scale adhesion. These methods can be roughly divided into () methods of chemically treating the surface of the polymerization vessel, () methods of adding chemicals into the polymerization system, and () methods of adding chemicals into the polymerization system.
The method is summarized as () a method using a specific dispersant, and () a method using an azo polymerization initiator or a combination of an azo polymerization initiator and an organic peroxide polymerization initiator. However, although the above-mentioned methods () to () have been found to be effective to some extent, further improvements are desired. In the method (), for example, the method using azobisdimethylvaleronitrile as a polymerization initiator, the polymerization initiator used therein is suitable for exhibiting polymerization activity in the above polymerization temperature range, but the initial coloration of the resulting polymer is Significantly inferior. On the other hand, methods using known dialkyl peroxy dicarbonates or tertiary-butyl peroxy neodecanoate are industrially useful polymerization initiators, but in the above polymerization temperature range. Since the polymerization activity is too high, the sustainability of the polymerization activity until the late stage of polymerization is poor, and for example, the method using tertiary-butyl peroxypivalate is superior in terms of polymerization activity and initial coloration of the polymer. However, scale adhesion is a problem. The present inventors have synthesized vinyl chloride monomers at a polymerization temperature of 57
Degree of polymerization of polymer obtained by suspension polymerization at ~70℃
In order to obtain a polymer with a molecular weight of 1000 or less, scale does not occur in the polymerization reaction system, the polymerization activity of the polymerization initiator is sustained even in the late stage of polymerization, and the obtained polymer has almost no stickiness and has good initial coloring property. As a result of research in search of a method to provide a polymer with excellent properties, the present invention was completed. The polymerization method of the present invention has a polymerization temperature range of 57 to 70°C,
Preferably, when suspension polymerizing vinyl chloride monomers at 60 to 67°C to obtain a polymer with a degree of polymerization of 1000 or less, tertiary-hexyl peroxy pivalate and a specific polymerization initiator are used in combination with vinyl chloride monomers. It is characterized in that suspension polymerization is carried out by adding 0.03 to 0.15 weight percent of the monomer to the total amount charged. The specific polymerization initiator used in combination for the purpose of shortening the production cycle is at least one type of oil-soluble polymerization initiator selected from oil-soluble polymerization initiators that have a 10-hour half-life within a range of more than 40.5°C and less than 65°C. It is a compound. Examples of such compounds include di2
Examples include peroxydicarbonates such as -ethylhexylperoxydicarbonate, peroxyesters such as tertiary-butylperoxyneodecanoate, diacyl peroxides such as dilauroyl peroxide, and azo compounds such as azobisdimethylvaleronitrile. Ru. In addition, monomers that can be copolymerized with vinyl chloride monomers include vinyl ether, acrylic acid or methacrylic acid and its esters, vinyl acetate, ethylene, etc., and are used in an amount of 50% by weight or less based on the vinyl chloride monomer. Ru. The polymerization method of the present invention uses a tertiary polymer as a polymerization initiator.
Hexyl peroxypivalate and a specific polymerization initiator are used together, and the polymerization temperature is 57-70℃, preferably 60-70℃.
The same method as normal suspension polymerization can be applied except for the 67°C condition. That is, a stainless steel autoclave is used as the polymerization vessel, and examples of the suspending agent include cellulose derivatives such as methyl cellulose, partially saponified polyvinyl acetate, and the like. Other additives such as a buffer, a scale inhibitor, a chain transfer agent, etc. may be added. According to the method of the present invention, tertiary-hexyl peroxypivalate is used as a polymerization initiator when carrying out suspension polymerization of a vinyl chloride monomer at a polymerization temperature of 57 to 70°C, preferably 60 to 67°C. By using alone or in combination with a specific polymerization initiator,
It can prevent scale adhesion, including in the interior space of the polymerization vessel, maintains polymerization activity even in the late stages of polymerization, and provides a polymer with almost no stickiness and excellent initial coloring properties. be able to. The present invention will be explained below with reference to Examples and Comparative Examples. Note that parts in the text indicate parts by weight unless otherwise specified. Example 1 In the stainless steel autoclave of 3, 1400 ml of deionized exchange water in which 2.1 g of partially saponified polyvinyl acetate (GH-17) was dissolved, 0.10 g of di-2-ethylhexyl peroxydicarbonate, and 0.25 g of tertiary-hexyl peroxypivalate. Furthermore, 700 g of vinyl chloride monomer was added, and polymerization was carried out at 60° C. for 5 hours with stirring. After the obtained polymer was filtered, it was dried under reduced pressure at 40°C until a constant weight was reached. The degree of polymerization obtained was 950. This polymerization operation was repeated 10 times to determine the amount of scale adhering to the walls of the polymerization vessel and stirring blades. On the other hand, 100 parts of the obtained polymer, 50 parts of dioctyl phthalate, 1.0 parts of diptyltin malate
After mixing, add 0.5 parts of stearic acid and knead with a roll at 160℃ for 5 minutes, then 160Kg/cm ² , 160
℃, by heating pressing for 3 minutes to a thickness of 5 mm.
A sheet was prepared and the initial colorability was visually observed. The results obtained are shown in Table 1. In Table 1, the scale adhesion amount is the total value of 10 polymerization operations, and the polymer yield and initial coloration are the average values of 10 times. Comparative Example 1 The same procedure as in Example 1 was carried out except that 0.35 g of tertiary-butyl peroxypivalate was used as a polymerization initiator. The results obtained are shown in Table 1. Comparative Example 2 The same procedure as in Example 1 was carried out except that 0.35 g of azobisdimethylvaleronitrile was used as a polymerization initiator. The results obtained are shown in Table 1. Comparative Example 3 Diisobutyryl peroxide as a polymerization initiator
Example 1 was repeated except that 0.10 g and 0.25 g of tertiary-hexyl peroxypivalate were used. The results obtained are shown in Table 1. However, many hard eyes were observed during sheet production.

[Table] As is clear from Table 1, the polymerization method using tertiary-hexyl peroxypivalate in combination with a specific polymerization initiator was found to significantly improve the amount of scale deposited without impairing the initial coloring properties. It was done.

Claims (1)

[Claims] 1. In obtaining a polymer with a degree of polymerization of 1000 or less by suspension polymerizing a vinyl chloride monomer alone or a mixture of a vinyl chloride monomer as a main component and a monomer that can be copolymerized with it at 57 to 70°C. , at least one compound selected from tertiary-hexyl peroxypivalate as a polymerization initiator and an oil-soluble polymerization initiator with a 10-hour half-life temperature of more than 40.5°C and less than 65°C, and the vinyl chloride monomer. Alternatively, a method for polymerizing vinyl chloride monomers, characterized in that the amount is used in an amount of 0.03 to 0.15% by weight based on the charged amount of a mixture mainly consisting of vinyl chloride monomers.