JPH06228203A - Production of methyl methacrylate-based polymer - Google Patents

Abstract

PURPOSE:To produce a methyl methacrylate-based polymer having no accumulation of impurities even in continuously recovering and reusing an unreacted monomer, forming a resin not different at all from one obtained by using a new monomer in producing the methyl methacrylate-based polymer by bulk polymerization or solution polymerization of a monomer consisting essentially of methyl methacrylate. CONSTITUTION:In producing a methyl methacrylate-based polymer by subjecting a monomer consisting essentially of methyl methacrylate to bulk polymerization or solution polymerization to give a liquid polymer composition containing an unreacted monomer, separating and recovering a volatile component from the liquid polymer composition, the unreacted monomers recovered from the volatile component are brought into contact with a sulfonic group-containing compound, then with an amine compound or a hydrazine and reused as monomers for raw materials for polymerization to produce the methyl methacrylate-based polymer.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a methyl methacrylate polymer. More specifically, a volatile component containing an unreacted monomer is separated and recovered from a methyl methacrylate-based polymer composition obtained by a methyl methacrylate-based bulk polymerization method or a solution polymerization method, and the volatile component is purified to prepare a polymerization raw material. The present invention relates to a method for producing a methyl methacrylate-based polymer including a so-called monomer recycling step of mixing with a new monomer as a part of and reusing it. As a method for polymerizing a methylmethacrylate monomer, a batch-type suspension polymerization method using an aqueous medium is generally adopted. Recently, the bulk polymerization method or the solution polymerization method, which has no problem of wastewater treatment associated with an aqueous medium and is excellent in productivity and energy, has come to be adopted. As a bulk polymerization method, Japanese Patent Publication No. 52-32665, Japanese Patent Publication No. 59-21325, Japanese Patent Publication No. 59-21326,
Japanese Patent Publication No. 1-49295, Japanese Patent Publication No. 2-26642, Japanese Patent Laid-Open No.
There are many proposals such as the 3-111408 publication. Further, as the solution polymerization method, Japanese Patent Publication No. 55-7845 and Japanese Patent Laid-Open No. 58-13
There are proposals such as 2002 and JP-A-63-57613. In these polymerization methods, not all the monomers are polymerized, but the content of the polymer is about 30 to 80% by weight, and the liquid is composed of unreacted monomer and solvent. It is common to take out the polymer composition as mentioned above from the polymerization system. From the liquid polymer composition, volatile components are evaporated and separated to take out the polymer. A method using a devolatilizing extruder to process this liquid polymer composition is known, for example, Japanese Patent Publication No. 51-29914, Japanese Patent Publication No. 52-17555, and Japanese Patent Publication No. 1-53682. JP-A-62-89710, JP-A-3-49925, and the like. The unreacted monomers separated and recovered from the liquid polymer composition as described above have a considerably large amount per polymer, and the monomers used as raw materials are reused. Will need to be reused as However, if reuse is continued, impurities are accumulated, and adverse effects such as polymerization itself and coloring of the produced polymer occur. Efficiently remove impurities contained in the unreacted monomers recovered there,
Provided is a method for producing a methyl methacrylic polymer in which the quality of the polymer produced is good even after purification and continuous polymerization for a long time. The present invention provides a liquid polymer composition containing unreacted monomers by bulk polymerization or solution polymerization of monomers containing methyl methacrylate as a main component. ,
In the method for producing a methyl methacrylate polymer by separating and recovering volatile components from the liquid polymer composition, the unreacted monomers recovered from the volatile components are contacted with a sulfonic acid group-containing compound and then amine A method for producing a methyl methacrylate-based polymer, which comprises reusing a compound or a hydrazine that has been brought into contact with it as a monomer for a polymerization raw material. The monomers containing methyl methacrylate as the main component in the present invention are methyl methacrylate alone or other vinyl monomers copolymerizable with methyl methacrylate. The methyl methacrylate may be any one that is industrially produced. It is produced by the acetone cyanohydrin method, isobutylene or tertiary butanol is catalytically oxidized to methacrylic acid, which is esterified with methanol. It is obtained by the method. Examples of the other vinyl monomer include methacrylic acid esters such as ethyl methacrylate, propyl methacrylate, butyl methacrylate and benzyl methacrylate: methyl acrylate, ethyl acrylate, propyl acrylate, acrylic acid. Acrylic esters such as butyl and 2-ethylhexyl acrylate: unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, acid anhydrides such as maleic anhydride and itaconic anhydride: acrylic acid 2-hydroxy Hydroxyl group-containing monomers such as ethyl, 2-hydroxypropyl acrylate, monoglycerol acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, monoglycerol methacrylate: acrylamide, methacrylamide,
Nitrogen-containing monomers such as acrylonitrile, methacrylonitrile, diacetone acrylamide, and dimethylaminoethyl methacrylate: allyl glycidyl ether, glycidyl acrylate, epoxy group-containing monomers such as glycidyl methacrylate: styrene, α-methylstyrene, etc. Styrene monomer: The bulk polymerization of the present invention is a well-known method, for example, JP-B-52-32665, JP-B-59-21325 and JP-B-59.
-21326 gazette, Japanese Patent Publication No. 1-49295 gazette, Japanese Patent Publication No. 2-26642
This is based on the method proposed in Japanese Patent Laid-Open No. 3-111408. That is, any method may be used as long as it is a method of polymerizing monomers having methyl methacrylate as a main component and taking out a liquid polymer composition containing unreacted monomers,
It is not further limited. The solution polymerization of the present invention is also well known, for example, JP-B-55-7845, JP-A-58-132002, JP-A-58-132002.
This is based on the method proposed in 63-57613. That is, a method of polymerizing monomers containing methyl methacrylate as a main component in the coexistence of a polymerization inert solvent, and extracting as a liquid polymer composition containing the solvent and unreacted monomers may be used. It is not further limited. Separation of the methyl methacrylate polymer and the volatile components consisting of monomers and solvents from the liquid polymer composition is a well-known method, for example, Japanese Patent Publication No. 51-29914.
JP-B-52-17555, JP-B1-53682, JP-A
62-89710, JP-A-3-49925 and the like. That is, the liquid polymer composition is heated to evaporate the volatile components by a disc-type or screw-type devolatilizing extruder to separate them from the polymer. The volatile components separated by evaporation, that is, the monomers and the monomers accompanied by the solvent (hereinafter referred to as unreacted monomers) are contact-treated with a sulfonic acid group-containing compound, and then, Contact treatment with amines or hydrazines. This treatment can be performed in a gaseous state, but it is preferable to once condense it into a liquid state. In the contact treatment of these unreacted monomers, the whole amount or a part of the recovered substance is continuously or intermittently carried out. The selection may be made based on the quality of the polymer to be produced, especially the color tone, that is, the degree of coloring. In operation, it is an easy method to continuously treat a part of the recovered unreacted monomers and adjust the treatment ratio. Since the unreacted monomers recovered are accompanied by dimers and oligomers and mercaptons which are chain transfer agents used in the polymerization, compounds having a sulfonic acid group and amines or Before or after the contact treatment with hydrazines, it is preferable to remove them as heavy components by distillation. In addition, since water accumulates, it can be separated from the distillate by liquid separation due to the difference in specific gravity and the like and then withdrawn. In the case of distilling before the contact treatment, gaseous unreacted monomers may be directly introduced into the distillation apparatus. Further, since polymerization of unreacted monomers in liquid form may proceed in the process of treatment, it is preferable to add a polymerization inhibitor at a proper time and in a proper place. Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, phenothiazine and benzophenothiazine. These are used at a concentration of about 10 to 100 ppm with respect to the unreacted monomers. The presence of the polymerization inhibitor has no particular adverse effect on the subsequent processing. The sulfonic acid group-containing compound used for the catalytic treatment of the unreacted monomers of the present invention includes sulfuric acid, benzenesulfonic acid, paratoluenesulfonic acid, dioctylsulfosuccinic acid, and styrene having a sulfonic acid group as a functional group. Various kinds of liquid or solid such as divinylbenzene copolymer, so-called strongly acidic cation exchange resin can be applied. The amount of these sulfonic acid group-containing compounds is 0.001 to sulfonic acid group per 1 kg of unreacted monomers.
It is about 0.1 equivalent. The contact time is about 10 to 120 minutes. The temperature is about 0 to 60 ° C., and if the temperature is low, the processability decreases, and if it is too high, the hydrolysis of the monomer easily occurs. Although these depend on the impurity concentration in the unreacted monomers, they can be easily determined by several trials. As a contact method, when the sulfonic acid group-containing compound is in a liquid state, the two are mixed in a stirring tank or the like, and then the unreacted unit amount is obtained by liquid-liquid separation operations such as liquid separation, distillation and evaporation. There is a method to separate the body. Alternatively, when the sulfonic acid group-containing compound is a solid such as an ion exchange resin and is insoluble in unreacted monomers, there is a method of packing this in a packed column and passing the unreacted monomers. This method is preferable because it is simple, and the corrosion of the apparatus and the hydrolysis of unreacted monomers are small. When the treatment is continuously carried out using this packed tower, it is suitable to flow at a space velocity of about 0.1 to 10 / Hr. Subsequently, it is treated by contact with an amine compound or hydrazines. The amine compound or hydrazines preferably have a boiling point higher than that of methyl methacrylate, and more preferably have a boiling point at atmospheric pressure of 150 ° C. or higher. The amine compound is a primary amine or a secondary amine, and examples thereof include aliphatic amines such as ethanolamine, hexamethylenediamine, octylamine, triethylenepentamine and tetraethylenepentamine. There are aromatic amines such as aniline and phenylenediamine. Examples of the hydrazines include hydrazine and phenylhydrazine. In order to contact-treat unreacted monomers with amine compounds or hydrazines, it is sufficient that they are in intimate contact with each other, and any method may be used as long as it is a so-called liquid-liquid mixing method. For example, a method of mixing in a vessel equipped with a stirrer, a method of passing through a tower containing a perforated plate or packing, and the like. The contact temperature is from room temperature to 80 ° C, and the time is 5
It is about 120 minutes. The amount of the amine compound is 1 kg of the unreacted monomer.
The amount is equivalent to 0.001 to 0.1 equivalents. In order to separate the unreacted monomers and the amine compound from the mixed liquid, any method of separating the constituents from the liquid-liquid solution may be used. Separate by distillation using a packed column. This distillation operation may be carried out alone, but it may be carried out also as distillation for removing the above-mentioned dimers and oligomers and mercaptans from the recovered unreacted monomers, or may be untreated. The unreacted monomers may be combined and distilled. The unreacted monomers treated in this way are mixed with new monomers for polymerization. According to the method of the present invention, when the methyl methacrylate polymer is continuously produced by the bulk polymerization method or the solution polymerization method, the unreacted monomers are reused for a long time. Even if there is no accumulation of impurities derived from the raw material methyl methacrylate and from the polymerization reaction, it is possible to produce the quality of the obtained methyl methacrylate-based polymer, in particular, the one with good color tone which is an important characteristic of the polymer. Is. EXAMPLES The present invention will be specifically described with reference to examples.
However, this is only one example and does not limit the present invention. The process used in the examples is shown in the flow chart of FIG. The outline specifications of the main equipment are as follows.・ Monomer mixing tank: 20L, SUS304, with paddle impeller agitator,
With jacket ・ Catalyst dissolution tank: 10L, SUS304, with paddle blade agitator, with jacket ・ Polymerization reactor: 10L, SUS304, with helical ribbon blade agitator, with jacket ・ Heating device: Inner diameter 16.7mm x length 3m, with jacket ・Devolatilizing extruder: Twin-screw extruder (TE) manufactured by Japan Steel Works, Ltd.
X-30), counter-rotating system, screw diameter 30 mm, cylinder length 1200 mm, rear vent 1 piece, fore vent 3 pieces / monomer recovery tower: inner diameter 100 mm, length 3 m, SUS304, 3
/ 8 inch SUS Raschig ring packing tower, concentration section length 0.
7m, collection section length 0.3m ・ Ion exchange resin tower: 3L, SUS304, sulfonic acid group strong acid cation exchange resin (Duolite C-26C Sumitomo Chemical Co., Ltd.) 2L filling ・ Amine treatment tank: 1L, SUS304, with paddle impeller agitator, with jacket [0028] Further, the evaluation method of the obtained polymer is as follows. (1) Measurement of melt flow rate (MFR) Using a melt indexer manufactured by Takara Industry Co., Ltd., JIS
It was determined under the conditions of 230 ° C. and a load of 3.8 kg based on −K7210. (2) Coloring degree A 40 mm extruder with a T-die (manufactured by Tanabe Plastic Co., Ltd.) was used to perform flat plate extrusion at a temperature of 250 ° C., and a 3 mm thick extruded plate was obtained via three polishing rolls at around 100 ° C. It was From this extruded plate, a plate-shaped sample measuring 5 cm in length and width is JIS-
The yellowness (YI) was measured using an SZ-Σ80 spectroscopic color difference meter manufactured by Nippon Denshoku Industries Co., Ltd. according to K7103. (3) A sunshine weather meter (WE-SUN-HCA-1 manufactured by Suga Test Instruments Co., Ltd.) was used as the same plate-shaped sample as used for the measurement of weather resistance coloring degree.
Type) and the YI measurement value after irradiation for 2000 hours at a black panel temperature of 63 ° C. was used to evaluate the weather resistance. Example 1 Methyl methacrylate (hereinafter referred to as MMA) manufactured by Nippon Methacrylic Monomer Co., Ltd. and methyl acrylate (hereinafter referred to as MA) manufactured by Toa Gosei Co., Ltd. were used as raw material monomers. Azobisisobutyronitrile (hereinafter referred to as AIBN) is used as a polymerization initiator, and n- is used as a chain transfer agent.
Octyl mercaptan (hereinafter referred to as OM) was used. Mainly MMA and MA of 6.2 in the catalyst dissolution tank.
The mixture was charged so that the weight% and AIBN would be 0.12% by weight, and mixed by stirring to completely dissolve AIBN to obtain a catalyst liquid. The refrigerant was passed through the jacket so that the temperature in the catalyst dissolution tank became 5 ° C. The catalyst solution thus prepared was continuously fed to the polymerization reactor at 1.47 Kg / Hr by a pump. In the monomer mixing tank, the concentrations of MMA, MA and OM were 93.65% by weight, 6.2% by weight and 0.
It was adjusted so as to be 15% by weight from the supply amount of new MMA, MA and OM, the recycling amount of the recovered unreacted monomer and its composition. The temperature was adjusted so that the temperature in the monomer mixing tank was 5 ° C. while stirring, and a refrigerant was passed through the jacket.
With a pump, the monomer mixture prepared in this way is
It was fed to the polymerization reactor at 13.279 Kg / Hr. The above catalyst liquid and monomer mixed liquid were fed from the bottom of the polymerization reactor, and the average residence time was 39 minutes and the temperature was 150.
Polymerization was carried out at an average polymerization rate of 45% by weight at ℃ ± 2 ℃, the resulting liquid polymer composition was taken out from the upper part of the polymerization reactor,
Then led to the heater. In the heater, a heating medium was passed through the jacket, and the liquid polymer composition was heated to 200 kg at 20 kg / cm ² G. Then, it was led to a devolatilizing extruder. Each vent of the devolatilizing extruder is depressurized, the temperature of the cylinder is set to about 250 ° C. to process the liquid polymer composition, and the volatile matter containing unreacted monomer as a main component is taken out from the vent. It was sent to the next monomer recovery tower. The polymer was extruded in the form of strands in a molten state, cooled with water and then shredded to obtain pellets having an average of 6.65 kg / hr. The volatile matter discharged from the rear vent of the devolatilizing extruder is supplied in a gaseous state to the recovery section of the monomer recovery tower, and the volatile matter discharged from the for vent of the devolatilizing extruder is cooled and condensed to be a liquid, It was supplied to the bottom of the monomer recovery column and continuously distilled at a reflux ratio of 1. From the distillate from the top of the monomer recovery tower, an average of 7.
98 Kg / Hr was recycled to the monomer mixing tank, and 1 Kg / Hr of the distillate was supplied to the next ion exchange resin column. An average of 147 g / waste liquid containing amine and a reaction product of an amine and impurities in the amine treatment described below from the bottom of the monomer recovery tower
Hr was extracted. In addition, about 0.5 g / Hr of hydroquinone as a polymerization inhibitor was continuously supplied from the top of the monomer recovery tower. The distillate from the monomer recovery column was continuously passed through the ion exchange resin column at an average of 1 kg / hr. The space velocity at this time was about 0.5 / Hr. To the distillate passing through the ion exchange resin tower, tetraethylenepentamine was continuously supplied at 2 g / Hr and allowed to flow into the amine treatment tank and heated at the jacket of the tank to an internal temperature of 50 ° C. The mixture was continuously and thoroughly mixed and contacted at an average residence time of about 1 hour. The liquid passed through the amine treatment tank was fed to the bottom of the monomer recovery tower. Continuous operation was continued for 30 days as described above,
The polymers obtained on the 10th, 20th and 30th days were evaluated. All the polymers had a melt flow rate of 1.5, a coloring degree of 0.4, and a weather resistance of 0.7. Example 2 Example 1 was repeated except that octylamine was used in place of tetraethylenepentamine placed in the amine treatment tank. As a result of evaluation, the melt flow rate of all the polymers was 1.5, the degree of coloring was 0.4, and the weather resistance was 0.7. Example 3 In Example 1, the concentration of MA was set to 1 in the catalyst dissolution tank.
0.5% by weight, MMA, MA in the monomer dissolution tank
And the OM were adjusted to be 89.03% by weight, 10.51% by weight, and 0.46% by weight, and the same procedure as in Example 1 was performed. As a result of evaluation, the melt flow rate was 20, the coloring degree was 0.4, and the weather resistance was 0.7 for all the resins.
Met. Comparative Example 1 In Example 1, the top distillate of the monomer recovery tower was not sent to the ion exchange resin tower and the amine treatment tank, but the entire amount was recycled as it was and sent to the monomer preparation tank. The procedure was the same as in Example 1 except for the above. The evaluation results of the obtained resin are shown in [Table 1].
Shown in. Comparative Example 2 The procedure of Example 1 was repeated, except that tetraethylenepentamine was not added to the liquid passing through the ion exchange resin tower, that is, no amine treatment was performed.
The evaluation results of the obtained resin are shown in [Table 1]. Comparative Example 3 The procedure of Example 1 was repeated except that the ion recovery resin column was bypassed, that is, the treatment with the ion recovery resin was not performed. The evaluation results of the obtained resin are shown in [Table 1]. [Table 1]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart of a process used in an embodiment of the present invention. FIG. 2 is a flowchart showing another aspect of the process for carrying out the present invention. [Explanation of symbols] Raw material methyl methacrylate Raw material methyl acrylate Chain transfer agent Polymerization initiator Polymer waste liquid Amines a Liquid polymer composition b Unreacted monomers c Recycle recovered monomers

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Gensuke Yoshikawa             Sumitomo Chemical 5-1, Soukai-cho, Niihama-shi, Ehime             Industry Co., Ltd.

Claims (1)

Claims: 1. Monomers mainly composed of methyl methacrylate are bulk-polymerized or solution-polymerized to obtain a liquid polymer composition containing unreacted monomers, In the method for producing a methyl methacrylate polymer by separating and recovering volatile components from the combined composition, the unreacted monomers recovered from the volatile components are contact-treated with a sulfonic acid group-containing compound, and then an amine compound or hydrazine is obtained. What was contact-treated with
A method for producing a methyl methacrylate polymer, which comprises reusing as a monomer for a polymerization raw material. 2. The method for producing a methyl methacrylate polymer according to claim 1, wherein the recovered unreacted monomers are contact-treated with an amine compound or hydrazine and then distilled. 3. The method for producing a methyl methacrylate polymer according to claim 1, wherein the sulfonic acid group-containing compound is a sulfonic acid group-containing cation exchange resin. 4. The boiling point of the amine compound at atmospheric pressure is 150.
The method for producing a methyl methacrylate polymer according to [claim 1] or [claim 2], which is a primary amine or secondary amine having a temperature of not less than ° C.