JPH05155940A - Production of styrene copolymer - Google Patents

Abstract

PURPOSE:To prevent the growth of scales deposited on the inside wall of a polymerizer by performing a specified agitation operation before starting the polymerization in the production of a styrene copolymer by an aqueous suspension polymerization. CONSTITUTION:This process is to polymerize a monomer mixture comprising an aromatic vinyl monomer, a vinyl cyanide monomer and other vinyl monomers copolymerizable therewith in an aqueous suspension system, wherein the mixture and water are first fed and agitated, and the monomer is then dispersed in the water by feeding a suspension stabilizer. The agitation is desirably performed at 0-65 deg.C for 5-120min after at least 80wt.% monomer mixture and at least 90wt.% water are fed to the system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a styrenic copolymer by aqueous suspension polymerization, and more particularly to a suspension polymerization method for preventing the growth of adhered scale.

[0002]

BACKGROUND OF THE INVENTION Acrylonitrile-styrene copolymer resins are excellent in transparency and oil resistance, and are used as raw materials for ABS resins in various applications and fields. The turbid polymerization method, emulsion polymerization method and the like are known as known methods.

Among them, the aqueous suspension polymerization method is generally adopted as a production method which is suitable for small-quantity multi-product production and has a relatively small amount of impurities. In the conventional aqueous suspension polymerization method, the following procedure is usually performed. That is, in the order of supply, water is supplied, the suspension stabilizer is added, and then the monomer is supplied with stirring. Then, other additives such as a polymerization initiator are supplied to start the polymerization reaction. In the above procedure, since the suspension stabilizer is added in advance before supplying the monomer, the supplied monomer has an advantage that it can be quickly dispersed in water and a stable dispersion state can be obtained.

However, this method has a problem that the scale is likely to adhere to the inner wall of the polymerization vessel, and the scale adhered grows as the reaction is repeated, and the scale must be removed at last.

As a method for solving this, conventionally, a glass-lined polymerization vessel is used, or a silicone-based anti-adhesion agent is applied to the inner wall of the polymerization vessel in advance (JP-A-55-21488). Etc. have been proposed.

[0006]

However, the former method has a problem that the lining portion is damaged because the glass layer is easily broken by thermal shock during long-term use. In addition, the latter method has problems such as complexity and environmental pollution because the anti-adhesion agent is mixed in the product and is repeatedly discharged because it flows out into the drainage.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for preventing the growth of adhered scale in the suspension polymerization method.

[0008]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the growth of the adhered scale can be prevented by carrying out a specific stirring treatment operation before the initiation of polymerization. Heading The invention has been reached. That is, in the present invention, when a monomer mixture consisting of an aromatic vinyl monomer, a vinyl cyanide monomer and another vinyl monomer copolymerizable with these monomers is polymerized in an aqueous suspension system. The present invention provides a polymerization method in which at least 80% by weight of the monomer mixture and at least 90% by weight of water are supplied and a stirring treatment operation is performed at a temperature of 0 to 65 ° C. for 5 to 120 minutes. Hereinafter, the present invention will be described in detail.

Examples of the aromatic vinyl monomer used in the present invention include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, chlorostyrene, dichlorostyrene and bromostyrene. Examples include α-ethylstyrene.

As the vinyl cyanide-based monomer used in the present invention, for example, acrylonitrile, methacrylonitrile, chloroacrylonitrile and the like can be mentioned, but acrylonitrile is particularly preferable.

Further, as the other vinyl monomer copolymerizable with the aromatic vinyl monomer and the vinyl cyanide monomer used in the present invention, acrylic acid,
Examples thereof include unsaturated carboxylic acid monomers such as methacrylic acid, unsaturated carboxylic acid alkyl ester monomers such as methyl methacrylate, ethyl methacrylate, methyl acrylate, and butyl acrylate.

These monomers are preferably 50 to 95% by weight of an aromatic vinyl type monomer, 5 to 50% by weight of a vinyl cyanide type monomer, and 0 to 50% by weight of a monomer copolymerizable therewith. Three
Used in a proportion of 0% by weight. If the amount of the vinyl cyanide-based monomer is less than 5% by weight, the oil resistance is insufficient, while if it is 5
If it exceeds 0% by weight, workability and thermal stability are deteriorated.

Examples of the suspension stabilizer used in the present invention include inorganic suspension stabilizers such as tricalcium phosphate, magnesium phosphate, calcium carbonate, sodium silicate and magnesium carbonate, polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone. And organic suspension stabilizers such as methylcellulose. Among them, the inorganic suspension stabilizer is more preferable because it is easy to remove and collect and does not easily remain in the product. Among them, since tricalcium phosphate is dissolved and extracted in the aqueous phase by washing with acid,
It is extremely easy to remove and collect. In the case of an inorganic suspension stabilizer, it is more preferable to use an anionic surfactant such as sodium dodecylbenzenesulfonate as an auxiliary agent.

As the polymerization initiator used in the present invention, an organic peroxide or an azo compound is used.
It is preferable that the 0 hour half-life temperature is 55 ° C or higher. 10
If the time half-life temperature is less than 55 ° C, polymerization may start during the stirring treatment operation.

Examples of the polymerization initiator used in the present invention include organic compounds such as benzoyl peroxide, t-butylperoxylaurate, t-butylperoxybutyrate, lauroyl peroxide and t-butylperoxyisopropyl carbonate. Examples include azo compounds such as peroxides, 1,1′-azobiscyclohexanecarbonitrile, 1,1′-azobisisobutyronitrile, and 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile.

The chain transfer agent used in the polymerization is also not particularly limited, and examples thereof include alkyl mercaptan,
Examples thereof include alkyl halides, alkyl sulfides and α-methylstyrene dimers, and alkyl mercaptans are particularly preferable.

In the polymerization method of the present invention, the monomer mixture and water are supplied to a polymerization vessel, a stirring treatment operation is performed for a certain period of time, and then a suspension stabilizer is supplied to disperse the monomers. It is a method of post-polymerization.

More preferably, the stirring treatment operation is performed by supplying at least 80% by weight of the monomer mixture and at least 90% by weight of water and stirring at a temperature of 0 to 65 ° C. for 5 to 120 minutes.

[0019]

According to the method of the present invention, since the suspending / dispersing agent is not present on the surface of the monomer, it is considered that the monomer dissolves the scale attached to the vessel wall.

[0020]

EXAMPLES Next, the present invention will be described more specifically by way of examples. The scale preventive property is measured by measuring the thickness of the adhered scale before and after the polymerization, and the increase in the thickness is 0.2
Less than mm is represented by O, 0.2 mm to 0.4 mm is represented by Δ, and more than 0.4 mm is represented by X. The dispersed state during the reaction was visually observed. All parts used below are parts by weight.

Example 1 100 parts of water, 75 parts of styrene and 2 parts of acrylonitrile were placed in a 10 liter polymerization vessel having a deposition scale thickness of 0.3 mm.
5 parts and 0.5 part of lauroyl peroxide, t-
0.16 parts of butyl peroxylaurate and 0.27 part of t-dodecyl mercaptan are fed, and the stirring speed is 320.
Stirring operation was carried out at rpm and temperature of 20 ° C. for 30 minutes.

Next, 0.4 parts of tricalcium phosphate and 0.002 part of sodium dodecylbenzene sulfonate were added as suspension stabilizers. 3 hours at 80 ° C, then 12
The temperature was raised to 0 ° C. in 1 hour, and the reaction was further performed at 120 ° C. for 2 hours to complete the polymerization operation. The dispersion state during the reaction was good. The thickness of the attached scale of the polymerization vessel after the completion of the polymerization was 0.3 mm.

Example 2 Using the monomer mixture whose type and quantity are shown in Table 1, stirring treatment was carried out at a temperature of 60 ° C. for 20 minutes, and then a polymerization reaction was carried out in the same manner as in Example 1. The dispersed state during the reaction was good, and the thickness of the adhered scale before and after the reaction was 0.6 mm and 0.7 mm, respectively. Example 3 After using a monomer mixture whose type and quantity are shown in Table 1 and performing a stirring treatment operation at a temperature of 40 ° C. for 20 minutes,
A polymerization reaction was carried out in the same manner as in Example 1. The dispersed state during the reaction was good, and the thickness of the adhered scale before and after the reaction was 0.5 mm and 0.6 mm, respectively.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the monomer mixture was supplied after the suspension dispersant was added and the stirring treatment operation was omitted. The thickness of the deposited scale before and after the reaction was 0.
It was 5 mm and 0.9 mm.

Comparative Example 2 The reaction was carried out in the same manner as in Example 1 except that the stirring treatment was carried out at a temperature of -5 ° C for 3 minutes. The deposited scale thickness before and after the reaction was 0.5 mm and 1.0 mm, respectively.

Comparative Example 3 The reaction was carried out in the same manner as in Example 1 except that the stirring treatment operation was carried out at a temperature of 70 ° C. for 6 minutes. The reaction was stopped because agglomeration occurred during the reaction. The above results are summarized in Table 1.

[0027]

[Table 1]

[0028]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a method for preventing the growth of adhered scale on the vessel wall in aqueous suspension polymerization.

Claims (3)

[Claims] 1. When polymerizing a monomer mixture comprising an aromatic vinyl monomer, a vinyl cyanide monomer and another vinyl monomer copolymerizable with these monomers in an aqueous suspension system. A method for producing a styrene-based copolymer, which comprises supplying the monomer mixture and water, performing a stirring treatment operation, and then supplying a suspension stabilizer to disperse the monomer. 2. The aromatic vinyl monomer is 50 to 95% by weight.
And a vinyl cyanide monomer in an amount of 5 to 50% by weight, and another vinyl monomer copolymerizable with these monomers in an amount of 0 to 30% by weight. Item 1. The manufacturing method according to Item 1. 3. Feeding at least 80% by weight of the monomer mixture and at least 90% by weight of water, 0 to 65.
The production method according to claim 1, wherein the stirring treatment operation is carried out at a temperature of ° C for 5 to 120 minutes.