CN1605593A - Production method of (methyl) acrylic acid polymer - Google Patents

Abstract

The present invention provides a method for producing a recyclable (meth)acrylic polymer in which unreacted (meth)acrylic monomers are not self-polymerized. The method is to continuously supply a raw material composition of a (meth)acrylic monomer, a free radical polymerization agent and a chain transfer agent containing at least 50% by mass of methyl methacrylate to a polymerization tank, and The reaction mixture of the (meth)acrylic polymer in which the acrylic monomer is at least partially polymerized is continuously extracted from the polymerization tank, and separated to remove the volatile methyl methacrylate dimer and unreacted (meth)acrylic monomer. After the degassing treatment of the components, the above-mentioned volatile components separated and removed are introduced into a distillation tower, and the above-mentioned methyl methacrylate dimer content is controlled under the condition of 0.1 to 1.0% by mass, and the di-polymer containing the above-mentioned methyl methacrylate dimer is recovered. Process for recovering components of polymers and unreacted (meth)acrylic monomers.

Description

Method for producing (meth)acrylic polymer

technical field

The present invention relates to a method for producing (meth)acrylic polymers by continuous polymerization.

Background technique

(Meth)acrylic polymers made by polymerizing (meth)acrylic monomers mainly composed of methyl methacrylate have the characteristics of transparency, weather resistance and excellent appearance, and can be used in lighting, Billboards, vehicles and many other fields. It is also widely used in optical lenses, disk substrates, plastic optical fibers and other optical applications.

As a method for producing a (meth)acrylic polymer, generally, a suspension polymerization method is often used. However, it is not suitable for optical applications because the suspending agent and other auxiliary agents used are mixed into the (meth)acrylic polymer to reduce its transparency. In addition, productivity is reduced due to complicated steps such as filtration, washing, and drying required in the manufacturing process.

As a method for producing a (meth)acrylic polymer, there are known bulk polymerization methods and solution polymerization methods in addition to the suspension polymerization method described above. By these methods, (meth)acrylic polymers having excellent properties without lowering the transparency can be obtained. Recently, it has been attracting attention to use bulk polymerization or solution polymerization with a small amount of solvent for continuous production to improve productivity. However, when these methods are used to produce (meth)acrylic polymers, once the content of the polymer becomes high, the so-called "gel effect" will occur, which will cause a phenomenon in which the polymerization reaction rate increases sharply, that is, when the polymer content is low In a high state, it is difficult to control the occurrence of a stable polymerization reaction.

Therefore, in order to achieve a stable polymerization reaction, the next step of the degassing treatment step is often performed at a stage where the polymer content is low. That is, since the polymerization reaction is terminated with a low polymerization rate, there is a large amount of unreacted (meth)acrylic monomers in the volatile components, and there is a problem of increasing raw material costs if they are discarded as they are.

Then, a method of recovering unreacted (meth)acrylic monomers from the volatile components using a distillation tower or the like and reusing the unreacted (meth)acrylic monomers has been considered. However, the recovered (meth)acrylic monomers also contain many other components. If these (meth)acrylic monomers are reused, the transparency and heat resistance of the manufactured (meth)acrylic polymers will decrease. The problem. In addition, due to conditions such as environment or management, (meth)acrylic monomers self-polymerize to form polymers, which are firmly attached to the piping or recovery tanks before and after the distillation tower, making the production of (meth)acrylic polymers difficult. Difficult to perform stably.

For example, Japanese Patent Application Laid-Open No. 10-87705 discloses that by removing acidic substances generated in the system, a highly transparent (meth)acrylic polymer can be obtained even if the recovered (meth)acrylic monomer is reused. Methods. However, the removal of acidic substances requires specialized equipment, which raises the problem of increased manufacturing costs. In addition, the problem of self-polymerization that occurs when the (meth)acrylic monomer is recovered cannot be prevented. There is still a problem that it is difficult to stably perform the production of (meth)acrylic polymers.

Contents of the invention

In view of the above circumstances, an object of the present invention is to provide a method for producing a (meth)acrylic polymer that can be recovered and reused without self-polymerization of unreacted (meth)acrylic monomers.

The present invention is a method for producing a (meth)acrylic polymer, which has

and

(B) In the polymerization tank, at least a part of the (meth)acrylic monomer is polymerized to obtain an at least partially polymerized (meth)acrylic polymer containing the above (meth)acrylic monomer. mixture process and

(C) The reaction mixture is continuously extracted from the above-mentioned polymerization tank, and the degassing treatment is carried out to separate and remove the volatile components containing methyl methacrylate dimer and unreacted (meth)acrylic monomer to obtain the above-mentioned (meth) ) process of acrylic polymer,

It is characterized in that it further has

(D) introducing the above-mentioned volatile components through separation and removal into a distillation column, and at least a part of the above-mentioned methyl methacrylate dimer contained in the above-mentioned volatile components and the above-mentioned unreacted ( A step of recovering at least a part of the recovered component of the meth)acrylic monomer under the condition that the content of the above-mentioned methyl methacrylate dimer in the recovered component is controlled to be 0.1 to 1.0% by mass. According to this method for producing a (meth)acrylic polymer, unreacted (meth)acrylic monomers can be recovered and reused in a state where self-polymerization does not occur.

In the above-mentioned step (D), it is preferable to maintain a constant pressure in the above-mentioned distillation column, and to adjust the reflux ratio of the distillation column and/or the temperature of the heating medium in the liquid phase part in the above-mentioned distillation column, while the pressure is reduced under reduced pressure. The gas temperature at the top of the tower is controlled within the range of 48-60°C while distillation is carried out. In addition, if there is further provided (E) a step of mixing at least a part of the above-mentioned recovered components with the above-mentioned (meth)acrylic monomer contained in the above-mentioned raw material composition, and recycling as at least a part of the raw material composition, it will be further improved. good.

The manufacturing method of the said (meth)acryl-type polymer is suitable when the said chain transfer agent is a thiol compound.

According to the method for producing a (meth)acrylic polymer of the present invention, it is possible to recover and reuse unreacted (meth)acrylic monomers in a state where self-polymerization does not occur.

Detailed ways

The method for producing a (meth)acrylic polymer of the present invention is very suitable for bulk polymerization or solution polymerization of (meth)acrylic monomers. As a (meth)acrylic monomer, at least 50% by mass of methyl methacrylate should be contained, and methyl methacrylate alone is also acceptable, and (meth)acrylate other than methyl methacrylate (meth) ) mixtures of alkyl acrylates are also possible. Alkyl (meth)acrylates other than methyl methacrylate are not particularly limited, and for example, methyl methacrylates other than methyl methacrylate among alkyl (meth)acrylates having an alkyl group having 1 to 18 carbon atoms can be used. For alkyl (meth)acrylates. Specifically, methyl acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexanoate (meth)acrylate, (meth)acrylate base) lauryl acrylate, octadecyl (meth) acrylate, etc. These may be used alone or in combination of two or more. In addition, "(meth)acrylic acid" here means methacrylic acid or acrylic acid (the same applies hereinafter).

The present invention is suitable for the production of a (meth)acrylic polymer containing 80% by mass or more of a methyl methacrylate unit and further containing an alkyl (meth)acrylate unit other than a methyl methacrylate unit. At this time, since the polymerization activities of methyl methacrylate and alkyl (meth)acrylates other than methyl methacrylate are generally different, in the case of obtaining the above-mentioned (meth)acrylic polymer, it is necessary to The component of the (meth)acrylic monomer is appropriately selected according to its polymerization activity. For example, when preparing a (meth)acrylic polymer containing 80% by mass of methyl methacrylate units and 20% by mass of methyl acrylate units or ethyl acrylate units, the amount of (meth)acrylic monomers Although the composition varies depending on the type of radical polymerization initiator, polymerization temperature and other conditions, it is desirable to have about 75% by mass of methyl methacrylate and about 25% by mass of methyl acrylate or ethyl acrylate.

The radical polymerization initiator of the present invention is not particularly limited, and known radical polymerization initiators such as known organic peroxides and azo compounds may be used alone or in combination of two or more. It is preferable to use a radical polymerization initiator whose half-life is 10 seconds to 1 hour at the polymerization temperature of the polymerization tank. A free radical initiator with a short half-life will reduce the uniformity of the reaction, and a free radical initiator with a long half-life will easily produce polymer blocks in the polymerization tank, making it difficult to run stably. It is most preferable to use a radical polymerization initiator whose half-life is 120 seconds to 30 minutes at the polymerization temperature of the polymerization tank. In addition, the value of the "half-life" of the above-mentioned radical polymerization initiator is a numerical value described in a well-known catalog such as NOF Co., Ltd. or Wako Pharmaceutical Co., Ltd. or the like. Examples of such free radical initiators include tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl monocarbonate, tert-hexylperoxyisopropyl monocarbonate, tert-butylperoxyacetate, 1,1-bis(tert-butylperoxy)3,5,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy)cyclohexane, tert-butylperoxy 2-ethylhexanoate, tert-butylperoxyisobutyrate, tert-hexylperoxy 2-ethylhexanoate, di-tert-butyl Organic peroxides such as peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; 2-(carbamoyl azo)-isobutyronitrile, 1,1' -Azobis(1-cyclohexanenitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobisisobutyronitrile Azo compounds such as dimethyl butyrate, 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane).

The usage amount of the radical polymerization initiator can be appropriately selected according to the requirements of polymerization temperature and productivity. For example, 5.0×10 ^-6 to 5.0×10 ^-5 can be used relative to 1 mole of (meth)acrylic monomer. The amount of about moles.

The chain transfer agent of the present invention is not particularly limited, and known chain transfer agents such as chlorine-containing compounds, alkylbenzene compounds, and mercaptan compounds can be used alone or in combination of two or more, but the efficiency of the chain transfer agent , From the viewpoint of good thermal decomposition resistance for producing (meth)acrylic polymers, thiol compounds are preferable.

As thiol compounds: n-butanethiol, isobutylmercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-butyl mercaptan, sec-dodecyl mercaptan, tert-butyl mercaptan, etc. have alkyl or substituted alkanes Primary, secondary, and tertiary thiol compounds; aromatic thiophenol compounds such as thiophenol, cresylthiol, 4-tert-butyl-o-cresylthiol, thioglycolic acid and its esters, and carbon atoms such as hydroxyethylthiol Thiol compounds with numbers 3 to 18, etc. Among these thiol compounds, t-butylmercaptan, n-butylmercaptan, n-octylmercaptan, n-dodecylmercaptan and the like are particularly suitable.

About the usage-amount of a chain transfer agent, an appropriate amount can be selected in consideration of the physical property of the objective (meth)acrylic-type polymer. For example, the usage-amount which can make the weight average molecular weight (standard polystyrene conversion value) of a (meth)acrylic-type polymer into the range of 70000-150000 is suitable. Specifically, the chain transfer agent is used in an amount of 0.01 to 1.0 mol, preferably 0.05 to 0.5 mol, per 100 mol of the (meth)acrylic monomer. When used too much, the degree of polymerization of the (meth)acrylic polymer is low and the strength of the product decreases. If the amount used is too small, there is a problem that the thermal decomposability of the (meth)acrylic polymer decreases.

The form as at least a part of the polymerized (meth)acrylic monomer of the present invention is suitable for both bulk polymerization without an inert solvent and solution polymerization using an inert solvent. Particular preference is given to bulk polymerization. If solution polymerization is used, the amount of the inert solvent preferably used is less than 5% by mass of the whole reaction mixture, so that, like bulk polymerization, a small amount of free radical polymerization initiator can effectively improve the polymerization rate and make resistant A (meth)acrylic polymer with excellent thermal decomposition properties. If it is used in a solution polymerization system using an inert solvent amount of 5% by mass or more, a large amount of inert solvent exists in recovered unreacted (meth)acrylic monomers, so an additional separation step is sometimes required. As the inert solvent, known organic solvents such as methanol, ethanol, toluene, xylene, acetone, methyl isobutyl ketone, ethylbenzene, methyl ethyl ketone, and butyl acetate can be used. Particularly preferred are methanol, toluene, ethylbenzene, butyl acetate. An inert solvent may be added to the above-mentioned raw material composition containing a (meth)acrylic monomer, a radical polymerization initiator, and a chain transfer agent.

The polymerization kettle used in the present invention can use a tank type reaction device provided with a raw material composition feed port, a reaction mixture extraction port and a stirring device. The stirring device preferably has the performance of keeping the whole polymerization tank mixed. In addition, if necessary, it is preferable to provide a mechanism capable of removing heat or controlling heating to a set polymerization temperature. Temperature control can be performed by known methods. For example, a jacket can be used for temperature control, temperature control can be carried out by circulation of a heating medium such as a draft tube or a coil installed in the polymerization tank, and temperature control can also be carried out by adjusting the temperature of the raw material composition. By controlling the set polymerization temperature by temperature, an appropriate temperature can be selected according to the type of raw material, the mixture ratio, and the like.

The present invention has the reaction mixture containing at least part of (meth)acrylic monomer polymerized (meth)acrylic polymer derived from the polymerization tank, in order to separate and remove the unreacted (meth)acrylic monomer as the main The process of degassing the volatile components of the ingredients to obtain (meth)acrylic polymers. It is better to control the average residence time of the reaction mixture in the polymerization tank within the range of 1 to 6 hours. Within this range, polymerization can be stably controlled and a (meth)acrylic polymer having good molding processability can be produced. If the residence time is too short, it is necessary to increase the usage amount of the free radical initiator, because the increase of the free radical initiator makes it difficult to control the polymerization reaction and increases the terminal double bond content of the (meth)acrylic polymer, making it difficult to obtain heat-resistant Decomposable polymer. Therefore the residence time is preferably at least 2 hours. However, if the above-mentioned average residence time is too long, the productivity will be reduced and the dimer of (meth)acrylic monomers will increase. It is best to control the time to be at most 5 hours.

In addition, it is preferable to control the polymer content in the reaction mixture drawn out from the polymerization tank within a range of 35 to 65% by mass. If the polymer content is too high, the mixing and heat transfer efficiency will be lowered and the stability will be poor. If the polymer content is too low, the cost of separating volatile matter mainly composed of unreacted (meth)acrylic monomers will increase and the industrial value will decrease.

The implementation of degassing treatment is under reduced pressure (for example, when processing on a degassing device with two outlets, the upper outlet pressure is adjusted at about -0.01 ~ -0.04Mpa (gauge pressure), and the lower outlet pressure is adjusted At -0.09～-0.1Mpa (gauge pressure) or so), the continuously sent reaction mixture is heated to 200～290°C, and the macromolecules mainly composed of unreacted (meth)acrylic monomers are continuously separated and removed. Some volatile components. For example, for the degassing treatment, a vent extruder type degassing extruder such as TEX (trade name) manufactured by Nippon Steel Works can be used. The number of outlets is not particularly limited, but a degassing device with 2 to 4 outlets is preferable in view of degassing efficiency and operating cost. The methyl methacrylate dimer remaining in the obtained (meth)acrylic polymer is preferably 1000 mass ppm or less, and the (meth)acrylic monomer is 3000 mass ppm or less. Thus, a (meth)acrylic polymer having a high heat distortion temperature and excellent molding processability can be formed. In addition, the remaining chain transfer agent is preferably 50 mass ppm or less. This suppresses the problem of coloring due to heating when molding (meth)acrylic polymers. These can be achieved by appropriately setting the pressure and temperature conditions of the degassing treatment.

Simultaneously with or after the above-mentioned degassing treatment, lubricants such as higher alcohols and higher fatty acid esters, ultraviolet absorbers, heat stabilizers, colorants, and antistatic agents can be added to (meth)acrylic polymers as needed. agent etc.

The volatile components separated and removed by the above-mentioned degassing treatment are introduced into the distillation column. The distillation column is not particularly limited, and a known one may be used. For example: the inner diameter is 700mm×height 3600mm (the recovery part is 1800mm, the cooling part is 1800mm), the number of trays is about 6 to 20, and the reflux ratio is about 0.4 to 2.0. Multi-stage distillation tower is better.

The volatile components separated and removed by the above-mentioned degassing treatment contain unreacted (meth)acrylic monomers as main components, and usually also contain methyl methacrylate dimers represented by the following formula (1) (hereinafter also referred to as called MMA dimer)

In addition, it may also contain chain transfer agents, inert solvents or impurities contained in raw materials, other reactants such as methanol, methyl propionate, methyl isobutyrate, methyl acrylate, methyl α-hydroxyisobutyrate, etc. ingredients.

Generally speaking, since the boiling point of the unreacted (meth)acrylic monomer is lower than that of the MMA dimer, the gas obtained from the top of the distillation column in the present invention is recovered through condensation as a recovery component. The recovered components contain MMA dimers and unreacted (meth)acrylic monomers (and sometimes chain transfer agents, inert solvents, and the above-mentioned various components, etc.). But the present invention carries out distillation under the condition of 0.1～1.0 mass % with controlling the content of the MMA dimer in the reclaimed component after distillation, and reclaims the recovered component as the greatest feature. Recycling under this condition, even if no additional polymerization inhibitor is added to the recovered components, the phenomenon that monomers such as methyl methacrylate will polymerize and the polymer will firmly adhere to the piping before and after the distillation tower and the recovery tank , so that the production of (meth)acrylic polymers can be carried out continuously and stably. When the amount of MMA dimer is less than 0.1% by mass, the polymer will firmly adhere to the piping before and after the distillation tower, and in the recovery tank, so that the production of (meth)acrylic polymer cannot be carried out stably, and from the distillation The amount of waste liquid exported from the bottom of the tower increases and loses economic efficiency. When it is more than 1.0% by mass, the (meth)acrylic polymer has problems such as coloring and a decrease in heat resistance after recycling. It is best to control it within the range of 0.2 to 0.5% by mass. The mechanism by which the polymerized polymer does not adhere firmly has not been clarified in detail, but it is generally speculated that the MMA dimer controls the self-polymerization of the (meth)acrylic monomer. The MMA dimer represented by the above formula (1) is a compound having a boiling point of 236°C and a viscosity of 4.1 MPa·S (25°C). For example, gas chromatography can be used to measure the content of its recovered components.

The adjustment of the MMA dimer content contained in the above-mentioned recovered components can usually be realized by controlling the gas temperature at the top of the distillation column. That is to say, the content of MMA dimer in the recovery component can be reduced by reducing the temperature of the distillation tower top gas, and the content of MMA dimer in the recovery component can be increased by increasing the temperature of the tower top gas. Although controlling the content of the MMA dimer in the recovered components to be 0.1 to 1.0% by mass depends on the composition of the (meth)acrylic monomer, production conditions, etc., it can be obtained by, for example, passing through a distillation tower under reduced pressure. The top gas is controlled at 48-60°C. The control of the gas temperature at the top of the tower can be achieved by keeping the pressure in the distillation tower and the gas piping before and after it at a constant state by means of a vacuum pump, etc., and adjusting the reflux ratio and the temperature of the heat carrier in the liquid phase part of the distillation tower.

As described above, the present invention is a method for producing a (meth)acrylic polymer having

and

(B) In the polymerization tank, at least a part of the above-mentioned (meth)acrylic monomer is polymerized to obtain a reaction mixture containing a (meth)acrylic polymer in which the above-mentioned (meth)acrylic monomer is at least partially polymerized process and

(C) The reaction mixture is continuously extracted from the above-mentioned polymerization tank, and the volatile components containing methyl methacrylate dimer and unreacted (meth)acrylic monomer are separated and removed through degassing treatment. The process of the above-mentioned (meth)acrylic polymer,

It is characterized in that it further has

(D) introducing the above-mentioned volatile components that have been separated and removed into a distillation column, and at least a part of the above-mentioned methyl methacrylate dimer contained in the above-mentioned volatile components and the above-mentioned (methyl) A step of recovering at least a part of recovered components of acrylic monomers under recovery conditions that control the content of the above-mentioned methyl methacrylate dimer contained in the recovered components to 0.1 to 1.0% by mass. The method for producing a (meth)acrylic polymer enables recovery and reuse of unreacted (meth)acrylic monomers in a state where self-polymerization does not occur.

Although some or all of the recovered components can be discarded, at least some of them can be reused in the manufacture of (meth)acrylic polymers. That is, the method for producing a (meth)acrylic polymer of the present invention preferably further comprises

(E) A step of mixing at least a part of the recovered component with the (meth)acrylic monomer contained in the raw material composition, and recycling as at least a part of the raw material composition. In particular, it is preferable to control the recovered content to 10 to 50% by mass of the total amount of methacrylic monomers used in the production of (meth)acrylic polymers. If there are too many recovered components, the produced (meth)acrylic polymer may be colored. Too little recycled content will cause the storage period of the recycled content to be too long to be used, and increase the waste of recycled content and increase the cost of raw materials.

Furthermore, in the production method of the (meth)acrylic polymer of the present invention, the chain transfer agent which has a large influence on the physical properties of the (meth)acrylic polymer in the raw material composition is divided into two components Addition to the polymerization tank is also a preferred embodiment. That is, at least two components of an adjustment component containing at least a part of the chain transfer agent and a main raw material component other than the adjustment component are supplied to a polymerization tank. When mixing in a polymerization tank, the raw material composition should be supplied in a predetermined mixing ratio. At this time, the concentration of the chain transfer agent in the adjustment component is adjusted to be higher than that in the main raw material component, and the adjustment component can be used as a so-called masterbatch. In this way, the chain transfer agent in the raw material composition is finely adjusted by adjusting the supply amount to the polymerization tank for adjusting the components as needed, thereby adjusting the physical properties of the produced (meth)acrylic polymer.

In addition, one or more physical properties (such as melt flow rate, molecular weight, etc.) of at least a part of the produced (meth)acrylic polymer are continuously or discontinuously measured. With the step of adjusting the supply rate to the polymerization tank of the adjusted components based on the measured physical properties, the variation in the physical properties of the produced (meth)acrylic polymer can be reduced.

The (meth)acrylic polymer prepared by the production method of the present invention has excellent transparency and weather resistance and is widely used in many fields such as lighting, billboards, and vehicles. At the same time, it is also suitable for optical applications such as optical lenses, disk substrates, and plastic optical fibers. In addition, it is also suitable for large-sized moldings that require a long residence time in the barrel and thin-walled moldings that set a high resin temperature during extrusion molding.

[Example]

Below, describe the present invention in detail with embodiment

(manufacturing example 1)

In the tank reaction device equipped with a stirring device, replace the dissolved oxygen with nitrogen to lower than 1ppm, put in the raw material composition 1 mixed according to the following ratio, set the polymerization temperature to 135°C, and the average residence time to be 3 hours to carry out polymerization reaction.

<Raw material composition 1>

Methyl methacrylate (MMA) 98.0 parts by mass

Methyl acrylate (MA) 2.0 parts by mass

N-octyl mercaptan 0.25 parts by mass

tert-butylperoxy-3,5,5-trimethylhexanoate (relative to the total amount of MMA and MA)

70 ppm by mass

The reaction mixture extracted from the tank reactor was introduced into an outlet extruder type degassing outlet (TEX65 (trade name) manufactured by Nippon Steel Works, number of outlets: 2), and degassed (250°C, upper outlet pressure -0.02MPa (gauge pressure), lower outlet pressure -0.097MPa (gauge pressure) ) to produce (meth)acrylic polymers. The obtained (meth)acrylic polymer was transparent, HDT was 100 degreeC, the residual (meth)acrylic monomer was 2400 mass ppm, and the residual MMA dimer was 500 mass ppm. HDT is evaluated by JIS K7191-1, 2, and the content of residual components is evaluated by gas chromatography.

(Example 1)

It is 700mm * 3600mm (recovery section 1800mm, condensing section (1800mm), column plate number 8 sections, tower top pressure-0.084MPa (gauge pressure) to import the volatile component removed through the degassing treatment in the manufacture example 1. In the multi-stage distillation tower. At this time, the reflux ratio of the distillation tower is adjusted to be 0.55 so that the temperature of the distillation tower top is 52 ° C. Under this condition, the gas from the top of the tower is condensed, and the liquid obtained is recovered as the following recovery Ingredient 1.

<Recycled Component 1>

Methyl methacrylate (MMA) 97.5 parts by mass

Methyl acrylate (MA) 2.5 parts by mass

N-octyl mercaptan 0.11 parts by mass

Next, polymerization reaction and degassing treatment were carried out under the same conditions as above using the following raw material composition 2, and a (meth)acrylic polymer was produced continuously. In addition, raw material composition 2 was obtained by mixing recovered components with other raw material components, and the raw material composition 2 was used after replacing with nitrogen to reduce the dissolved oxygen content to less than 1 ppm.

<Raw material composition 2>

Methyl methacrylate (MMA) 68.75 parts by mass

Methyl acrylate (MA) 1.25 parts by mass

Recycled component 1 30.0 parts by mass

N-octylthiol 0.217 parts by mass

tert-butylperoxy-3,5,5-trimethylhexanoate (compared to the total amount of MMA and MA that also includes recovered components) 70 mass ppm

The operation was carried out using the raw material composition 2, and the volatile components removed by the degassing treatment were distilled and condensed under the above conditions, and the liquid obtained after distillation and condensation was used repeatedly to produce (meth)acrylic acid continuously for 10 days. polymer. Manufacturing can be carried out stably and continuously for 10 days. The polymerization rate 10 days after the start of production was 51% by mass, and the content of MMA dimer contained in the recovered fraction was confirmed by gas chromatography to be 0.2% by mass. The obtained (meth)acrylic polymer is transparent, the weight average molecular weight converted to standard polystyrene is 98000, the mass ratio of each monomer unit in the polymer is MMA/MA=98.5/1.5, HDT is 100 °C, the residual (meth)acrylic monomer was 2400 mass ppm, and the residual MMA dimer was 700 mass ppm.

(Example 2)

The following recovery component 2 was recovered as a liquid in the same manner as in Example 1 except that the reflux ratio of the distillation column was adjusted so that the temperature of the column top gas was 55°C.

<Recycled Component 2>

Methyl methacrylate (MMA) 97.6 parts by mass

Methyl acrylate (MA) 2.4 parts by mass

N-octylthiol 0.12 parts by mass

Secondly, use the following raw material composition 3 to remove the volatile components after degassing treatment, and carry out distillation and condensation under the condition that the temperature of the gas at the top of the distillation tower is controlled at 55 ° C to obtain a liquid, except that it is used instead of the recovered component 2 for repeated use , Carry out the manufacture of methacrylic acid polymer in the same method as in Example 1 for 10 consecutive days.

<Raw material composition 3>

Methyl methacrylate (MMA) 68.72 parts by mass

Methyl acrylate (MA) 1.28 parts by mass

Recycled component 2 30.0 parts by mass

N-octylthiol 0.214 parts by mass

tert-butylperoxy-3,5,5-trimethylhexanoate (compared to the total amount of MMA and MA that also includes recovered components) 70 mass ppm

Manufacturing can be carried out stably and continuously for 10 days. The polymerization rate after 10 days from the start of production was 51% by mass, and the content of the MMA dimer contained in the recovered fraction was confirmed to be 0.4% by mass by gas chromatography. The obtained (meth)acrylic polymer was transparent, the weight average molecular weight in terms of standard polystyrene was 98000, the mass ratio of each monomer unit in the polymer was MMA/MA=98.5/1.5, and the HDT was 100°C residual The (meth)acrylic monomer was 2500 mass ppm, and the residual MMA polymer was 800 mass ppm.

(comparative example 1]

By adjusting the reflux ratio of the distillation tower to control the temperature of the gas at the top of the distillation tower to be 45°C, the same method as in Example 1 was used to reclaim the following recovery component 3 as a liquid.

<Recycled Component 3>

Methyl methacrylate (MMA) 97.3 parts by mass

Methyl acrylate (MA) 2.7 parts by mass

N-octylthiol 0.09 parts by mass

Next, using the following raw material composition 4, the volatile components removed by degassing treatment are distilled and condensed under the condition that the temperature of the gas at the top of the distillation tower is controlled at 45°C to obtain a liquid, except that it is used instead of the recovered component 3 for repeated use Besides, a (meth)acrylic polymer was produced in the same manner as in Example 2.

<Raw material composition 4>

Methyl methacrylate (MMA) 68.81 parts by mass

Methyl acrylate (MA) 1.19 parts by mass

Recycled component 3 30.0 parts by mass

N-octylthiol 0.223 parts by mass

tert-butylperoxy-3,5,5-trimethylhexanoate (compared to the total amount of recovered components MMA and MA) 70 mass ppm

Six days after the start of production, the polymer was firmly adhered to the gas piping from the top of the distillation column to the total condenser, clogging the piping, and the production could not be continued. The content of the MMA dimer contained in the recovered fraction immediately before the pipe was blocked was confirmed by gas chromatography to be 0.05% by mass.

(comparative example 2)

Except adjusting the reflux ratio of the distillation column to control the temperature of the distillation column top gas at 64° C., the following recovered component 4 was recovered as a liquid in the same manner as in Production Example 1.

<Recycled Component 4>

Methyl methacrylate (MMA) 97.8 parts by mass

Methyl acrylate (MA) 2.2 parts by mass

N-octyl mercaptan 0.13 parts by mass

Next, using the following raw material composition 5, the volatile components removed by degassing treatment were distilled under the condition that the temperature of the gas at the top of the distillation tower was 64°C, and the liquid obtained by condensation was used instead of the recovered component 4 and repeated for use. , Continuously manufacture (meth)acrylic polymer in the same manner as in Example 1.

<Raw material composition 5>

Methyl methacrylate (MMA) 68.66 parts by mass

Methyl acrylate (MA) 1.34 parts by mass

Recycled component 4 30.0 parts by mass

n-octyl mercaptan 0.211 parts by mass of tert-butylperoxy-3,5,5-trimethylhexanoate (compared to the total amount of MMA and MA which also contains recovered components) 70 ppm by mass

Manufacturing can be carried out stably and continuously for 10 days. The polymerization ratio 10 days after the start of production was 50% by mass, and the content of the MMA polymer contained in the recovered fraction was confirmed to be 1.5% by weight by gas chromatography. The obtained (meth)acrylic polymer is slightly yellow, and the weight average molecular weight in terms of standard polystyrene is 97000. The mass ratio of each monomer unit in the polymer is: MMA/MA=98.5/1.5, HDT is 98°C, residual The (meth)acrylic monomer content was 2800 mass ppm, and the residual MMA dimer was 2400 mass ppm.

From the above results, the content of methyl methacrylate dimer contained in the recovered components is in the range of 0.1 to 1.0% by mass, and the unreacted (meth)acrylic monomer is in a state where self-polymerization does not occur. Recycling is possible under conditions, and a high-quality (meth)acrylic polymer can be stably produced.

Claims (4)

1. The manufacture method of (meth)acrylic polymer, it has and (B) In the polymerization tank, at least a part of the (meth)acrylic monomer is polymerized to obtain an at least partially polymerized (meth)acrylic polymer containing the above (meth)acrylic monomer. mixture process and (C) The reaction mixture is continuously extracted from the above-mentioned polymerization tank, and the degassing treatment is carried out to separate and remove the volatile components containing methyl methacrylate dimer and unreacted (meth)acrylic monomer to obtain the above-mentioned (meth) ) process of acrylic polymer, It is characterized in that it further has (D) introducing the above-mentioned volatile components through separation and removal into a distillation column, and at least a part of the above-mentioned methyl methacrylate dimer contained in the above-mentioned volatile components and the above-mentioned unreacted ( A step of recovering at least a part of the recovered component of the meth)acrylic monomer under the condition that the content of the above-mentioned methyl methacrylate dimer in the recovered component is controlled to be 0.1 to 1.0% by mass. 2. The method for producing a (meth)acrylic polymer according to claim 1, wherein in said step (D), a constant pressure is maintained in said distillation tower, and the pressure is adjusted by adjusting the reflux ratio of the distillation tower and/or said distillation The temperature of the heating medium in the liquid phase part in the column was distilled while controlling the temperature of the gas at the top of the column to 48 to 60°C under reduced pressure. 3. The method for producing (meth)acrylic polymers according to claim 1 or 2, further comprising (E) mixing at least a part of the above-mentioned recycled components into the above-mentioned (meth)acrylic acid contained in the above-mentioned raw material composition. ) in the acrylic monomer, a step of recycling as at least a part of the raw material composition. 4. The method for producing a (meth)acrylic polymer according to any one of claims 1 to 3, wherein the chain transfer agent is a thiol compound.