JPH0131521B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in the continuous production method of styrenic resins, such as polystyrene, rubber-modified polystyrene, etc., using a radical polymerization catalyst. More specifically, the present invention relates to a continuous method for producing styrenic resins, which comprises treating recovered unreacted monomers prior to recycling and reusing them in the polymerization process. Conventionally, in the continuous polymerization of styrenic resins,
Non-catalytic thermal polymerization methods are generally carried out due to quality problems such as the color and transparency of the resulting polymers, or for economic reasons. However, in order to produce high molecular weight styrenic resin,
This method has a low polymerization rate and is not economical. As an improvement method, for example, JP-A-48-
No. 55981, Japanese Patent Application Publication No. 161587 (1977) and Special Publication No. 161587 (1977)
No. 138788, organic peroxide polymerization catalysts such as 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy) oxy)hexyne, 1,1-di-tert-butylperoxy-3,
3,5-trimethylcyclohexane or di-
A method for continuously producing high molecular weight styrenic resin using tert-butyl peroxide, dicumyl peroxide, and tert-butyl cumyl peroxide has been proposed. However, in these methods, recycling and reusing the recovered unreacted monomers in the polymerization process unexpectedly leads to a decrease in the polymerization rate and molecular weight, making it difficult to efficiently produce high-molecular-weight styrenic resins. It became clear that this would cause a major problem. The present invention aims to provide a method for producing a styrenic resin in which recovered unreacted monomers can be recycled and reused in the polymerization process without reducing the polymerization rate or molecular weight. The continuous production method of styrenic resin of the present invention includes:
When styrenic monomers are polymerized using a radical polymerization catalyst, and the unreacted monomers are separated by volatilization and reused as raw materials, the unreacted monomers are, prior to the cyclic reuse, It is characterized by treatment with an alkali metal or alkaline earth metal hydroxide, an aqueous solution thereof, a styrene-based or acrylic cation exchange resin, or a styrene-based chelate resin. In the present invention, styrene monomers include styrene, alkylstyrenes, halogenated alkylstyrenes, etc., and copolymerizable monomers such as acrylonitrile and methacrylonitrile are added to these styrene monomers. I can do it. Also,
The rubbery substance used in the rubber-modified polystyrene in the present invention includes polybutadiene, a copolymer of butadiene and styrene, acrylonitrile, methyl methacrylate, etc., natural rubber, polychloroprene, isoprene-isobutylene copolymer, or ethylene-propylene. Copolymers, etc. The amount of rubbery substance used is usually 1 to 15 parts by weight per 100 parts by weight of the styrene monomer. The radical polymerization catalysts used in the invention are, for example, benzoyl peroxide, tert-butyl perbenzoate, di-tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, and especially 2,5-dimethyl- 2,5
-di(benzoylperoxy)hexane, 2,5
-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, and the like. The amount of catalyst used is usually 0.01 to monomer.
It is 0.3% by weight. In addition, if necessary for polymerization,
Ethylbenzene, diekelbenzene, as a solvent
Methyl ethylbenzene, p-xylene, benzene or toluene, etc., based on the total weight of the reaction mixture.
It can be used in amounts less than % by weight. Furthermore, chain transfer agents,
Other materials known in the art to be useful in polymerization reactions to improve the properties of the final product may be included, such as lubricants. The processing in the present invention is performed as follows. That is, when using an aqueous solution of a hydroxide of an alkali metal or alkaline earth metal such as tonalium, potassium, or calcium, the recovered unreacted monomer is washed with it, or the unreacted monomer is mixed with the aqueous solution. A method of stirring and mixing the reacted monomers and then separating them into two layers, or an extraction method of bringing a liquid stream of these aqueous solutions into contact with a liquid stream of unreacted monomers, etc. are used. The amount of these aqueous solutions is not particularly limited, but
It is preferable to use 20% by weight or more of the unreacted monomer, and preferably 10 times the weight or less from the viewpoint of wastewater treatment and dissolution loss of the unreacted monomer. The concentration of these aqueous solutions must be such that the pH is 7.0 or higher, but in order to efficiently wash the unreacted monomer with the minimum amount of aqueous solution, the PH must be 10.0 or higher. It is preferable to set the concentration as follows. The processing temperature is preferably 0° to 100°C. In addition, in the present invention, solid hydroxides of alkali metals or alkaline earth metals such as sodium, potassium, and calcium, styrene-based (Na
Use a cation exchange resin (type) or acrylic (H type), or a chelate resin with a ligand structure in the polymer chain, that is, a styrene type (hexyl, iminodiacetic acid) (H type and Na type) chelate resin. You can also do that. In this case, the recovered unreacted monomer is brought into contact with the unreacted monomer in gaseous or liquid form, and the unreacted monomer is brought into contact with the solid hydroxide of alkali metal or alkaline earth metal or with the ion exchange resin. A method in which the unreacted monomers are brought into contact by stirring and mixed and then the unreacted monomers are separated, or a method in which the unreacted monomers are brought into contact with a gaseous or liquid stream of the unreacted monomers using a fixed bed or fluidized bed or column of an alkali or ion exchange resin. contact treatment using etc. The amount of solid alkali metal or alkaline earth metal hydroxide or ion exchange resin used is not particularly limited, but from the viewpoint of treatment efficiency, it is preferable to use 5% by weight or more of the unreacted monomer. Further, the treatment temperature is preferably 0 to 100° C. for both gaseous treatment and liquid treatment. Furthermore, the shape of the solid alkali metal or alkaline earth metal hydroxide is not limited at all. The recovered unreacted monomer purified by the treatment method described above can be reused as a raw material according to the required amount, either continuously in the polymerization process using a radical polymerization catalyst, or by storing it in a temporary storage tank. . According to the method of the present invention, polymerization can be carried out over a long period of time without deterioration in polymerization rate and molecular weight, and the quality is more stable than when unrefined recovered unreacted monomers are reused as raw materials. Enables the production of guaranteed, long-term stable styrenic resin. Examples and comparative examples are shown below. The effects of the present invention will be clear from the description of these Examples and Comparative Examples. Example 1 2,5-dimethyl-2,5 as a radical catalyst
- Put 3.0 of the unreacted monomer recovered from the continuous polymerization of polystyrene using di(tert-butylperoxy)hexane into the separating funnel in step 5, add 1.0 of a 25% aqueous sodium hydroxide solution, and shake for 5 minutes. After towing, the mixture was allowed to stand for 20 minutes and the oil layer was separated. This operation was repeated until the amount required for continuous polymerization was obtained. The resulting oil layer, i.e. styrene monomer, has 100%
A raw material liquid was prepared by dissolving 0.027 parts by weight of 2,5-dimethyl-2,5-di(benzoylperoxy)hexane based on parts by weight. Internal volume 3
The above raw material liquid was fed into the cylindrical stirring reactor from its inlet at a rate of 1.5 per hour so that the average residence time was 2 hours. It was operated at 130℃ for 200 hours, which is 100 times the average residence time, and 600 hours, which is 300 times the average residence time. The polymerization liquid continuously discharged from the reactor is continuously supplied to a heat exchanger, heated with a heating medium at 220°C, and continuously flashed into a vacuum chamber maintained under a reduced pressure of 50 mmHg, where it is volatilized. The unreacted monomers and the like were continuously collected from the upper part of the vacuum tank, and the molten polystyrene accumulated in the lower part of the vacuum tank was continuously extracted by a discharge pump and pelletized through an extruder. Unreacted monomers continuously recovered during this polymerization were washed with a 25% sodium hydroxide solution and recycled for reuse as described above. When 2 g of the polymerization liquid collected from the reaction tank is dissolved in 30 c.c. of methyl ethyl ketone and this is added dropwise into 300 c.c. of methyl alcohol, polystyrene is precipitated as a white precipitate. The yield (polymerization rate) of polystyrene obtained by drying this white precipitate was 46.6% for both 200 hours and 600 hours of operation.
(23.3%/Hr). Also, in toluene solution
The intrinsic viscosity of the above polystyrene measured at 30℃ is
It was 1.15 for both 200 hours and 600 hours of operation. In addition, the fluidity, which is one of the physical properties of the obtained pellets, was measured by the method according to ASTM D-1238-57T, and it was found to be 0.78 g / 5000 g at 200 ° C.
It was hot in 10 minutes. The tensile strength was measured according to ASTM D-638 and was found to be 565 Kg/cm ² . Furthermore, the yellowness according to JIS K-7103 was 0.41, and there was no difference in operating time and the product was stable. Example 2 2,5-dimethyl-2,5 as a radical catalyst
- Unreacted monomers recovered from continuous polymerization of polystyrene using di(tert-butylperoxy)hexane were placed in a cylindrical glass tube with a diameter of 50 mm and a length of 500 mm using an ion exchange resin (Na-type iminodiacetic acid chelate resin).
XE-318) from the top to a column filled with 1-5 c.c.
sec to contact the unreacted monomers. Polymerization was carried out in the same manner as in Example 1 using the unreacted monomers treated as above. Further, unreacted monomers continuously recovered during this polymerization were subjected to contact treatment with an ion exchange resin and recycled and reused. The yield (polymerization rate) of polystyrene in the polymerization solution obtained after 200 hours of operation and 600 hours of operation was 46.4% (23.2%).
%/Hr). Furthermore, the intrinsic viscosity of polystyrene was 1.13, which remained the same for a long time. On the other hand, the fluidity was also 0.78 g/10 min (200°C, 5000 g). The tensile strength was 565 Kg/cm ² and the yellowness was 0.39. It was stable with no difference due to operating time. Example 3 In place of the ion exchange resin column in Example 2, a stainless steel cylindrical tube with a diameter of 50 mm and a length of 500 mm containing sodium hydroxide particles with a particle size of 1 to 3 mm was used. , 1-5c.c./min
It was operated at a flow rate of The obtained purified unreacted monomer was polymerized in the same manner as in Example 1. The results after 200 hours and 600 hours of operation were as follows.

[Table] Example 4 The same procedure as in Example 3 was carried out except that calcium hydroxide tablets with a diameter of 8 mm and a thickness of 5 mm were used in place of the sodium hydroxide particles. The results after 200 hours and 600 hours of operation are as follows.

[Table] Comparative example 1 2,5-dimethyl-2,5 as a radical catalyst
The unreacted monomer recovered in the continuous polymerization of polystyrene using -di(tert-butylperoxy)hexane was used in its unpurified form and polymerized in exactly the same manner as in Example 1. Further, unreacted monomers continuously recovered during this polymerization were also reused in an unpurified state.

[Table] Example 5 2-5-dimethyl-2,5 as a radical catalyst
-The unreacted monomer recovered in the continuous polymerization of rubber-modified polystyrene using di(tert-butylperoxy)hexane was added to 97 parts by weight of unreacted monomer washed with an aqueous sodium hydroxide solution in the same manner as in Example 1. For 100 parts by weight of a solution obtained by dissolving 3 parts by weight of polybutadiene, 2,5-dimethyl-2,
5-di(tert-butylperoxy)hexane 0.040
A raw material liquid was prepared by dissolving the components in parts by weight. The above raw material solution was continuously polymerized in exactly the same manner as in Example 1. Further, unreacted monomers recovered during continuous polymerization were washed with an aqueous sodium hydroxide solution in the same manner as above and used again as a raw material. Sampled from the reactor in the same manner as in Example 1,
2 g of the sample was dissolved in 30 c.c. of toluene, and this was dropped into 300 c.c. of methyl alcohol, whereby polybutadiene and polystyrene precipitated out as a white precipitate. The yield of polystyrene obtained by drying this white precipitate was calculated. The dried product was dispersed in 50 c.c. of methyl ethyl ketone and centrifuged at 12,000 rpm for 30 minutes to separate polybutadiene and polystyrene grafted to the polybutadiene as an insoluble gel fraction.
When the supernatant liquid is dropped into 500 c.c. of methyl alcohol, a white precipitate of polystyrene from which the insoluble gel fraction has been separated is precipitated. This white precipitate was dried, and the intrinsic viscosity of the resulting polystyrene was measured. In addition, fluidity was measured as one of the physical properties of the product using a method according to ASTM D-1238-57T. Furthermore, the tensile strength is ASTM D-
638. The results were as follows.

[Table] Example 6 The recovered unreacted monomer obtained in Example 5 was treated by contacting with an ion exchange resin (XE-318), and polymerized in the same manner as in Example 6 as a raw material monomer.

[Table] Comparative Example 2 The recovered unreacted monomers obtained in Examples 5 and 6 were used as raw material monomers in an unpurified state, and Example 6
Polymerization was carried out in the same manner.

[Table] Example 7 The recovered unreacted monomer obtained in Example 5 was treated by contacting with a cation exchange resin Diaion WK20, and polymerized in the same manner as in Example 5 as a raw material monomer.

[Table] Diaion WK20 is manufactured by Mitsubishi Chemical Industries, Ltd.
The product name is an acrylic weakly acidic cation exchange resin. Example 8 The recovered unreacted monomer obtained in Example 5 was treated by contacting with a cation exchange resin Diaion SK1B, and polymerized in the same manner as in Example 5 as a raw material monomer.

[Table] Diaion SK1B is manufactured by Mitsubishi Chemical Industries, Ltd.
It is a Na-type styrene-based strongly acidic cation exchange resin.

Claims (1)

[Claims] 1. When styrenic monomers are polymerized using a radical polymerization catalyst and unreacted monomers are volatized and separated for recycling and reuse as raw materials, the unreacted monomers are , an alkali metal or alkaline earth metal hydroxide or an aqueous solution thereof, a styrenic or acrylic cation exchange resin, or a styrenic chelate resin. .