JPH09227608A - Production of styrene-acrylonitrile resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an AS copolymer further excellent in surface appearance, heat stability and transparency while reducing the formation of a gel polymer and realizing continuous operation for a long time. SOLUTION: A monomer mixture comprising 10-50 pts.wt. vinyl cyanide monomer and 90-50 pts.wt. aromatic vinyl monomer is fed into a polymerizer to polymerize to a conversion of 40-90wt.%, a radical scavenger is then added thereto in an amount of 0.005-3 pts.wt. based on 100 pts.wt. of the resin, and this mixture is deaerated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an improved method for producing a styrene-acrylonitrile copolymer by a continuous polymerization method. More specifically, when a styrene-acrylonitrile-based copolymer is produced, a silver-like (silver streak) that prevents the formation of a gel-like polymer and causes a poor appearance of the molded product during the molding process of the resulting copolymer is described. Reduce
In addition, it has excellent thermal stability (discoloration resistance), chemical resistance, and transparency during molding, and also reduces the amount of gel-like polymer to the devolatilization device, enabling the continuous operation for a long time. It relates to a manufacturing method.

[0002]

BACKGROUND OF THE INVENTION Copolymers containing styrene and acrylonitrile as main components, so-called AS resins, are used in a wide variety of fields because of their excellent properties such as transparency, chemical resistance, rigidity and moldability. ing. As the method for producing these copolymers, solution polymerization, bulk polymerization, emulsion polymerization,
It can be produced by various polymerization methods such as suspension polymerization.

However, in the case of emulsion polymerization, since an emulsifier is used, there are problems in terms of transparency and discoloration of the polymerization product, and since acrylonitrile is easily dissolved in water, a polymerization product having a uniform composition is produced. It is difficult to get things. In the case of suspension polymerization, the same problems as above are encountered because the polymerization is carried out in an aqueous system by using a dispersant or the like. On the other hand, in the case of bulk polymerization, since the raw material monomer is basically heated as it is, there is no problem as described above. Further, in the case of solution polymerization, the raw material monomer is dissolved in an organic solvent to carry out the polymerization, but since the organic solvent is removed after the polymerization to take out the polymerization product, there is no problem as described above.

Therefore, in the industrial production of the styrene-acrylonitrile copolymer, bulk polymerization or solution polymerization is adopted, and it is continuously carried out. However, when a styrene-acrylonitrile-based copolymer is continuously produced by solution or bulk polymerization, a degassing step of volatilizing and separating unreacted monomers and other solvents is required. Polymer formation is significantly accelerated, and stable long-term operation becomes impossible. In addition, a part of the gel-like polymer is mixed in the product, and silver (silver streaks) occurs on the surface of the molded product, especially during the molding process.
Then, the thermal stability and the transparency are lowered, and as a result, the commercial value is lowered. For this reason, it takes a lot of time and labor such as washing and removing the gelled polymer by shortening the continuous operation time, and it is inevitable that productivity is lowered.

[0005] For the purpose of improving silver streaks, for example, the amount of water contained in the raw material is set to 200.
A method of carrying out continuous bulk polymerization while controlling to 520 ppm (Japanese Patent Application Laid-Open No. 57-25310) or 100 parts by weight of a reaction mixture of a monomer mixture, and 0.1 to 3.
A method has been proposed in which 0 part by weight is added to carry out continuous bulk or solution polymerization (JP-A-60-250605). However, these methods require dehydration operation of water in the monomer, impair the transparency of the copolymer from which higher fatty acid amides are obtained, and the like, which does not always satisfy the simplification of the polymerization operation and the improvement of quality. I can't say. Also, 2
Using a polymerization device in which at least one polymerization group is connected, when supplying to at least one polymerization group after the second group, an aromatic vinyl compound and a radical scavenger are added to carry out solution or bulk polymerization. A method (Japanese Patent Laid-Open No. 6-329703) has been proposed, but it focuses on the suppression of gel-like polymer formation in the reactor, and aims at suppressing the formation of gel-like polymer in the degassing step. Not a thing.

[0006]

The present invention has been made against the background of the above problems of the prior art. When the styrene-acrylonitrile-based copolymer is continuously produced, the formation of a gel-like polymer is prevented. Of the styrene-acrylonitrile-based copolymer that can be continuously operated for a long period of time, and can produce a copolymer having excellent surface appearance, thermal stability and transparency of the molded product. A manufacturing method is provided.

[0007]

That is, the present invention provides:
(A) 10 to 50 parts by weight of vinyl cyanide-based monomer,
(B) A monomer comprising 90 to 50 parts by weight of an aromatic vinyl monomer is supplied to a polymerization vessel and the polymerization conversion rate is 40 to 90% by weight.
The method for producing a styrene-acrylonitrile-based copolymer is characterized in that 0.005 to 3 parts by weight of a radical scavenger is added to 100 parts by weight of a resin, and a deaeration step is performed after the polymerization is performed until .

The present invention will be described in more detail below. The components of the monomer of the present invention will be described. Examples of the (a) vinyl cyanide-based monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, and the like. Generally, acrylonitrile is used, but two or more kinds are used. It can be used as a mixture.

As the above-mentioned (b) aromatic vinyl monomer,
For example, styrene, α-methyl styrene, p-methyl styrene, alkyl substituent styrene having a substituent such as 3,5-dimethylstyrene, 4-methoxystyrene, 2-hydroxystyrene, α-bromostyrene, 2,4-dichlorostyrene, etc. Examples thereof include styrene, 1-vinylnaphthalene, divinylbenzene, and the like. Generally, styrene is used, but two or more kinds can be used as a mixture.

As (c), if necessary (a),
Other copolymerizable vinyl compound may be added to (b) within 30 parts by weight. Examples of (c) include acrylic acid esters such as methyl methacrylate, ethyl methacrylate, ethyl acrylate and butyl acrylate, unsaturated acids such as acrylic acid and methacrylic acid, unsaturated anhydrides such as maleic anhydride and itaconic acid, N- Phenylmaleimide, N
There are maleimide compounds such as cyclohexylmaleimide.

Specific examples of the radical scavenger are as follows. Examples of the radical scavenger include hindered phenol-based and hindered amine-based agents, and specific examples include:
Hindered phenol compounds include 2,6-di-t-butyl-4-methylphenol, octadodecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) -2-propionate, 2,6-di-t-butylphenol, triethylene glycol Bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] and the like are preferable, and a compound represented by the following general formula (1) is preferable, and specific examples thereof include 2
-T-butyl-6- (3'-t-butyl-5'-methyl-2'-hydroxybenzyl) -4-methylphenyl acrylate (Sumitomo Chemical Co., Ltd., registered trademark Sumilizer GS), 2,4-g-t-amyloo 6- [1- ( 3,5
G-t-Amylou 2-hydroxyphenyl) ethyl]
Phenyl acrylate (registered trademark Sumilizer GM, manufactured by Sumitomo Chemical Co., Ltd.) can be used.

[0012]

Embedded image

(R ₁ is hydrogen or methyl group, R ₂ is methyl group, t-butyl group or t-amyl group, R ₃ is t-butyl group or t-amyl group, R ₄ is hydrogen or methyl group) Then, the monomer supplied is (a) 10 to 50 parts by weight of vinyl cyanide-based monomer, preferably 20 to 45 parts by weight, (b) 90 to 50 parts by weight of aromatic vinyl monomer,
It is preferably composed of 80 to 55 parts by weight, and these mixed monomers are fed to a polymerization vessel, and the polymerization conversion rate is 40 to 9
The polymerization reaction is carried out so as to be 0% by weight, preferably 45 to 80% by weight. If the conversion rate is less than 40%, the amount of resin produced is reduced, which is not preferable. Further, if it exceeds 90%, it becomes difficult to suppress the gelled polymer, which is not preferable. Further, as (c), (a) and (b) are provided as necessary.
It may be added within 30 parts by weight of another vinyl compound monomer copolymerizable with.

The addition amount of the radical scavenger is 0.005 to 3 parts by weight based on 100 parts by weight of the resin, and 0.00
If the amount is 5 parts by weight or less, a large amount of gel-like polymer will be produced. Similarly, if the amount is 3 parts by weight or more, the gel-like polymer will decrease, but the color tone of the resin deteriorates, which is not preferable. In addition,
Two or more kinds of radical scavengers that can be used in the present invention can be mixed and used.

The method of adding the radical scavenger is not particularly limited, but a method of adding the radical scavenger in a solvent is preferable, and it is preferable to add the radical scavenger just before the degassing step. The initiator used in the polymerization reaction is not particularly limited, but an organic peroxide is usually used. Moreover, it is also possible to carry out thermal polymerization without using an initiator. The solvent used in the solution polymerization is an inert polymerization solvent usually used in radical polymerization, for example, ethylbenzene, aromatic hydrocarbons such as toluene, other, chloroform, dichloromethylene, halogenated carbon such as carbon tetrachloride, Ketones such as methyl ethyl ketone,
Other examples include acetonitrile and dimethylformamide. The amount of solvent used is usually 0 with respect to the total amount of monomers.
Use up to 50 parts by weight. The polymerization reaction temperature is usually 60 ° C to 1
It is preferably carried out at a temperature range of 70 ° C, preferably 80 ° C to 160 ° C.

Since the copolymer obtained by the present invention has excellent quality, it is suitable as a molding material requiring chemical resistance, either alone or as a mixed resin blended with another resin such as ABS resin. used.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the Examples, Comparative Examples and Tables 1 and 2, parts and% are based on weight.

[0018]

Example 1 Styrene 49 parts by weight, acrylonitrile 2
A mixture of 5 parts by weight and 26 parts by weight of toluene in a total of 100 parts by weight is prepared. This solution was continuously supplied to a reactor having a volume of 3 liters for 1.5 kg / hour for polymerization to carry out polymerization so that the conversion rate of the polymerization would be 71% by weight, and the polymerized product was continuously withdrawn. The reactor residence time was 2.2.
It was time. The conditions such as the polymerization temperature are shown in Table 1.

The reaction liquid extracted is 250 ° C., 10 mmH
g, a port for adding a radical scavenger is installed in a pipe to be introduced into the devolatilization device kept in a high vacuum, and the solution in which the radical scavenger shown in Table 1 is dissolved is added and mixed with the reaction liquid by a pump. After that, the product was introduced into a devolatilizer, and after removing the devolatilizer, it was taken out from the die in a strand form. The calculation of the polymerization conversion rate is as follows. The reaction liquid extracted from the reactor was sampled, and the reaction liquid was thoroughly evaluated at about 10 g (g). The reaction liquid was dried under reduced pressure at 120 ° C. for 3 hours to obtain the unreacted monomer,
The solvent was removed, the weight thereof was evaluated (g), and the polymerization conversion rate was calculated by the following calculation formula.

Polymerization conversion rate (%) = / [× (+)
/ 100] × 100 where, and represent the weight parts of styrene and acrylonitrile, respectively. In addition, the amount of gel polymer produced was continuously operated for 30 days, and the polymer obtained from the devolatilization device was sampled and evaluated at 10 g (g). This was dissolved in 300 ml of methyl ethyl ketone, and this solution was prepared in advance. Well-established quantitative filter paper (JISP 3801 5 types C
Weight g) and filtered, and the filter paper is kept at 120 ° C for 1
After drying under reduced pressure for an hour, evaluate the weight after drying (
g), the amount of gel polymer produced was calculated by the following formula.

Gel polymer (ppm) = [(-)
/] × 1000000 The amount of gel-like polymer calculated by this calculation formula is shown in Table 2. After the polymerization, the AN content in the resin is
1H-NMR (JEOL, GX-270, 270MH
z, solvent: deuterated chloroform), and the results are shown in Table 2. Regarding the color tone of the resin, after degassing the solvent and the unreacted monomer, the color tone of the obtained resin was visually evaluated, and the results are shown in Table 2. The molecular weight of the resin was calculated using a GPC device (manufactured by Tosoh Corporation, HLC-8020, solvent: chloroform) with reference to standard polystyrene, and the results are shown in Table 2.

[0022]

Examples 2 and 3, Comparative Examples 1 and 2 Using the same apparatus as in Example 1, the composition of the mixture of styrene, acrylonitrile, toluene, etc. fed to the reactor, the polymerization temperature, etc. are as shown in Table 1. It evaluated similarly to 1. Table 2 shows the results.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

The method for producing a styrene-acrylonitrile-based copolymer of the present invention enables continuous operation for a long period of time, and the obtained copolymer is excellent as a molded product with less silver streaks. And its industrial significance is extremely large.

Claims (2)

[Claims] 1. (a) Vinyl cyanide type monomers 10 to 5
A monomer comprising 0 to 50 parts by weight of (b) 90 to 50 parts by weight of an aromatic vinyl monomer is supplied to a polymerization vessel and the polymerization conversion rate is 40 to 40%.
A method for producing a copolymer, characterized in that, after polymerizing to 90% by weight, 0.005 to 3 parts by weight of a radical scavenger is added to 100 parts by weight of a resin to carry out a deaeration step. 2. The method for producing a copolymer according to claim 1, wherein the radical scavenger is a compound selected from the general formula (1). Embedded image (R ₁ represents hydrogen or methyl group, R ₂ represents methyl group, t-butyl group or t-amyl group, R ₃ represents t-butyl group or t-amyl group, and R ₄ represents hydrogen or methyl group.)