KR950008508B1 - Polyacrylic process - Google Patents

Abstract

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Description

Continuous Solution Polymerization of Acrylic Monomer

1 is a schematic process flow diagram illustrating a method according to the present invention.

* Explanation of symbols for main parts of the drawings

10, 20: continuous stirred tank reactor 11, 21: propeller shaft

12, 22: motor assembly 14: propeller wing

15, 25: gear pump 17, 27: inlet line

18, 28: steam leader 30: solvent recycle line

32: feed mixture introduction line 34: reactant feed line to the second reactor

36: delayed wire 38: reactant feeder to volatile removal preheater

39: transfer line to volatile eliminator 40: vacuum device

50, 51: cell tube condenser 58, 59: reflux line

60, 62: steamer 61, 63: pressure regulating valve

70: volatile removal preheater 71: hot oil fluid introduction line

72: rear pressure regulating valve 75: polymer pull-out pump

76: volatile removal container 78: spray sparger

80: steam recirculation line 81: reflux distillation

82: reflux condenser 83, 85: packing area

84: reflux condenser 86, 91: recycled condensate flow line

87: reboiler 88: injection nozzle

89: additive introduction line 90: static mixer

92: screen 93: leaking fluid removal ship

94: extrusion die 96: water bath

98: moisture stripper 100: polymer strand

102: pellet place 104: pellet

The present invention relates to a solution polymerization method of acryl monomer.

One of the difficulties experienced with the polymerization of methyl methacrylate is that it is not possible to control the polymerization when the final polymerization product exceeds the critical polymerization solids concentration. For this reason, conventional polymerization processes have avoided bulk polymerization and the poly (methyl methacrylate) commercially available today is mostly produced by suspension polymers.

In general, methyl methacrylate is copolymerized with limited amounts of copolymerizable monomers (comonomers) such as methyl acrylate and ethyl acrylate. These comonomers stabilize the polymer, particularly against depolymerization, which can occur when the polymer chain terminates at unsaturated carbon atoms. Since this result is obtained from the termination by disproportionation reaction, the conventional objective was to achieve chain termination by free group bonding rather than disproportionation reaction. This object is achieved by incorporating a limited amount of chain transfer agent, such as alkyl mercaptans, for example n-dodecyl mercaptan, into the polymerization zone. However, chain termination by free group bonding to alkyl mercaptans forms mercaptan free groups that allow the polymerization to proceed again, so that the polymer chains have mercaptan end groups.

Usually poly (methyl methacrylate) is produced by suspension polymerization because of the difficulties experienced through solution polymerization or bulk polymerization of methyl methacrylate. One of the main difficulties in limiting the use of bulk polymerization is that when the polymerization product is in the gel state, typically when the solid concentration value of 30 to 40% by weight or more is reached, the polymerization cannot be controlled. Although solvent polymerization could not be used conventionally to avoid this difficulty, conventional researchers have found it a desirable alternative to using methods such as suspension polymerization or block polymerization, which indicate a lack in efficiency and / or product consistency. No effective method or apparatus has been developed for the volatile removal of large amounts of solvents from prepolymerisations. When the solvent is present in the polymerisation before completion, severe foaming occurs during the devolatileing process and this foaming prevents effective heat transfer and volatile removal. Furthermore, the polymer easily discolors when in contact with a heat transfer surface at temperatures in excess of approximately 270 ° C. These properties hinder effective heat transfer and have conventionally ruled out the successful commercialization of continuous solution polymerization of acrylate esters such as methyl methacrylate.

The present invention includes a continuous block polymerization process of methyl methacrylate in the presence of a limited amount of comonomers such as ethyl acrylate and methyl acrylate. The polymerization is carried out as a plurality of stages, most of which is carried out in the first stage, in the latter stage serving to complete the polymerization and to remove the residual initiator and / or denaturant. The polymerization is also carried out in the presence of a chain transfer agent which improves the properties of the final product and preferably these additives are introduced in every step carried out. The prepolymerization from the last stage is heated in the preheater under sufficient pressure to enter the preheater in the volatile removal section to maintain a liquid phase and to suppress the formation of solid debris on the heat transfer surface of the heater. The polymerisation product before completion is heated sufficiently in the preheater to provide the heat of vaporization necessary for effective volatile removal of solvents, unreacted monomers and low boiling polymerization products. The preheated prepolymerisation is passed to a volatile scrubber where the pressure is reduced to remove solvent, unreacted monomers and low molecular weight polymer from the polymerization product. The vaporized solvents and monomers are reclaimed for the first reaction step on a continuous basis after the contaminants have been removed, cooled and condensed, thereby ending the cycle of recycled solvents and monomers. The main part used in the process, for example 75% of methyl acrylate or ethyl acrylate comonomer and chain transfer additive, is introduced with the methyl methacrylate feed in the first stage. The remainder is introduced into the latter polymerization stage so that the polymerization in the latter stage proceeds under conditions that help to form a homogeneous copolymer with good properties such as thermal stability and heat distortion temperature.

Preferably the polymerization is carried out in continuous stirred tank reactors (CSTRs) with sufficient agitation so that a uniform reactant is obtained in each reactor. The exothermic heat of polymerization, preferably by reflux cooling, is removed, in order to achieve this, the reactor is maintained at a precisely controlled pressure so that the boiling of the polymerization product continues. The vapor is withdrawn from the reactor, cooled, condensed and returned as reflux fluid. The polymerization method ensures precise control of the polymerization conditions such as temperature and can produce a product having a desired molecular weight (molecular weight distribution) within a relatively narrow range of change limits.

The present invention relates to a process for the polymerization of acrylic monomers, in particular monomers such as acrylate and methacrylate esters of halogen substituted alkanols having from 1 to about 18 carbon atoms, for example homopolymers or copolymers. Methyl acrylate, ethyl acrylate, methyl methacrylate, propyl acrylate, n-butyl methacrylate, n-hexyl acrylate, chloroethyl acrylate, n-octyl methacrylate, or stearyl acrylate for production It relates to the polymerization of. Other common comonomers that may be included in amounts of about 1 to about 60 weight percent include acrylonitrile, styrene, male anhydride, alpha-methylstyrene, and mixtures thereof.

The polymerization is carried out in the presence of sufficient solvent to avoid the viscosity of the polymerization product before completion to rise above the uncontrollable value. This is expressed as a term of solids content and sufficient solvent is used to maintain the prepolymerisation product having a solids content of up to 50% by weight, preferably up to 40% by weight. For this purpose, any low boiling point solvent may be used, examples of which are hexane, heptane, octane, benzene, toluene, silane, chlorohexane, cyclodecane, isooctane, and mixtures thereof (e.g. naphtha) Saturated aromatic hydrocarbons such as these. Generally solvents having an atmospheric boiling point of about 40 to about 225 ° C., preferably about 60 to about 150 ° C., are useful. In order to eliminate the necessity of the fractionation of the recycle mixture of monomers and solvents, it is preferred to use a solvent having a boiling point temperature similar to the boiling point temperature of the main monomers, for example methyl methacrylate. If they have similar boiling point temperatures, the mixture will have a narrow boiling point range to reduce the contaminants contained in the recycle mixture.

It is also desirable to perform the polymerization in the presence of free group chain transfer agents in order to minimize concentration of polymer chains containing terminal unsaturated carbons. For this purpose, free radical chain transfer agents are used. Useful free radical chain transfer agents release hydrogen atoms on polymer chains that form free radicals which can terminate its polymerization and resume polymerization at a saturated carbon end group or combine with another free radical to form a stable byproduct. Compounds. Examples of suitable chain transfer agents include alkyl and arylalkyl mercaptans having 5 to 18 carbon atoms, such as amyl mercaptan, heptyl mercaptan, iso-octyl ercaptan, decyl ercaptan, n-dodecyl mercaptan, Sulfur compounds such as phenylethyl mercaptan, hexadecyl mercaptan, stearyl mercaptan and the like.

Other compounds useful as chain transfer agents are those having structures that stabilize free radicals, examples of which include aromatic hydrocarbons having from 6 to about 18 carbon atoms and halo, amino or already substituted alkanes having from 1 to about 18 carbon atoms or Aromatic compounds. Examples of suitable aromatic hydrocarbons include benzene and C ₁ -C ₆ alkylbenzenes such as toluene, ethylbenzene, xylene, propylbenzene, isobutylbenzene, isopropyl toluene, diisopropyl benzene, triethyl benzene and the like. .

Examples of substituted hydrocarbons include compounds having 1 to about 18 carbon atoms and C ₁ -C ₆ halo, amino or imido groups such as carbon tetrachloride, dichloroethane, trichloroethane, difluoro- Propane, fluorodichlorobutane, dichloro-isopentane, bromo cyclohexane, methylamine, isopropylamine, t-butylamine, dodecylamine, 2,4-di aminooctane, cyclopentylamine, methylcyclohexylamine, Aniline, pyridylidene, pyrerozine, pyridine, dimethyl sulfoxide and the like.

Particularly useful among the chain transfer agents are compounds having a low boiling point, for example, a boiling point of from 60 to about 150 ° C., because these compounds may act as solvents alone or in combination with the abovementioned solvents. Because.

The concentration of chain transfer agent used depends on the type of transfer agent selected. Sulfur compounds or mercaptans are used at concentrations of from about 0.1 to about 1.0 weight, preferably from about 0.2 to about 0.3 weight percent, based on the monomer and comonomer feed mixture. However, alkylbenzenes are used in very large amounts because these components may act as solvents alone or as a mixture with other solvents.

In addition, the modifier may be included in a concentration of 2 to 50% by weight in order to improve the impact strength of the finished polymer. These modifiers are elastomers such as ethylene-propylene diamine copolymer (EPDM), polybutadiene, styrene-butadiene copolymer, polyurethane, and ethylene propylene copolymer rubber (ETR). These polymers may be included in the finished polymer, preferably by being added to the polymerization zone. These modifiers may also be blended into the molten polymer or the finished polymer during the product finishing process step.

The present invention provides methyl meta in the presence of a limited amount of comonomers such as ethyl acrylate or methyl acrylate in an amount of 0.1 to about 12% by weight, preferably about 1 to about 6% by weight, based on the copolymer obtained. It is particularly suitable for the polymerization of acrylates.

The polymerization of the monomers mentioned above is initiated by the free group initiator, for which disclosure any of a number of free group precursors may be used as the free group initiator. Examples of free radical initiators include dibenzoyl peroxide, dicumyl peroxide, 2, 2'-azo (bis) isobutylnitrile, 2, 2'-azobis (dimethylvaleronitrile), diethylperoxide, distearyl per Oxide, t-butylperoxide, di (2,4-dichlorobenzoyl) peroxide, diacetyl peroxide, t-butyl perbenzoate, t-amylperoctoate, 1,1-di (t-butylperoxy Chlorohexane, di (t-butyl) peroxide, dicumylperoxide and the like. Of these, 2,2'-azo (bis) isobutyl-nitrile is preferred. The initiator may be used at a concentration of about 0.01 to about 1.0 weight percent, preferably about 0.03 to about 0.5 weight percent, and most preferably 0.07 to 0.10 weight percent, based on the monomer feed mixture.

As other useful additives for the process, peroxyfree group scanbingers are included to exclude any formation of polymers that will contain oxy groups. The presence of any negligible amount of polymer containing an oxy group is undesirable because such polymers have poor wind resistance and heat resistance and are easily discolored. Insignificant oxy-substituted polymers can be eliminated by including the following limited amounts of peroxyfree radicals as additives in the process: Negative free phenolic antioxidants, tetrakis [methylene (3,5-di-tertiary) -Butyl-4-hydroxyhydrocinnamate] methane, thiodiethylene bis (3,5-di-tert-butyl-4-hydroxy) hydrocinnamate, 1,6-hexamethylenebis (3,5- Di-tert-butyl-4-hydroxyhydrocinnamate, di-t-butyl-p-cresol, octadecyl 3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) Propionate, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 2,2'-methylene bis (4-methyl-6-t-butylphenol), and 3-methyl 3: 1 condensate of -6-t-butylphenol and crotonaldehyde.

Of these, octadecyl 3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) pyropyionate and tris (3,5-di-t-butyl-4-hydroxybenzyl) Isocyanurate is a preferred additive because it does not interfere with the polymerization. The aforementioned peroxyfree radical scavenger is used at a concentration of about 0.1 to about 0.2% by weight, based on the monomer feed mixture.

The drawings will be described. The process according to the invention is carried out in two or more continuous stirred tank reactors 10 and 20. Each reactor includes a steel vessel having propeller shafts 11 and 21 disposed in the center extending from the propeller drive motor assemblies 12 and 22 placed thereon. Each propeller shaft, such as (11), may be entirely radial, i.e., with a plurality of radial vanes 13, which may not have an axial pitch, or may have an axial pitch, as seen from the side of the propeller blade 14. Support one or more propellers formed. The propeller mixes well the polymerization medium to form a homogeneous material in each reactor.

Each tank reactor has a bottom discharge nozzle that directly drains the polymer before completion into closely coupled gear pumps 15 and 25, such as commercially available gear pumps. Each tank reactor has supply lines 17 and 27 for the introduction of reactants which can be polymerized. The recycle mixture consisting primarily of solvent is introduced via solvent recycle line 30 and a new feed mixture consisting of methyl methacrylate, a limited amount of comonomers, chain transfer agents, peroxide group scavengers, etc. Is introduced through.

The final polymerization reactant enters the first tank reactor 10, passes through the polymer gear pump 15, and enters the second tank reactor 20 through the transfer line 34. Additional amounts of comonomers, and optionally chain transfer, are also introduced into the tank reactor 20 via the delayed addition line 36.

Heat generated during the polymerization is removed from the reactors 10 and 20 by reflux cooling. By this, the tank reactors 10 and 20 are completely enclosed and maintained at a predetermined pressure. When auxiliary pressure is required, a vacuum device is used, as indicated by (40). Each tank reactor has steam take-offs 18 and 28 which discharge steam to the cell tube condensers 50 and 51. Cooling water is fed to the condenser via lines 54 and 56 and the condensed reflux liquid is fed into their corresponding reactors via reflux lines 58 and 59.

Heat exchangers 50 and 51 are with the pressure regulator by steam lines 60 and 62 with pressure regulating valves 61 and 63. These valves are controlled by appropriate pressure regulators maintained at predetermined pressures in each reactor, so that precise temperature control within these tank reactors is achieved by precisely adjusting the pressure in each of the tank reactors 10 and 20. As a practical matter, the temperature in the first and second tank reactors can be controlled within an error limit of 0.5 ° C., and this accuracy provides very precise control over the molecular weight and molecular weight denominator of the polymers produced in these reactors.

As mentioned earlier, most of the polymerization is carried out in the first tank reactor 10. Typically, a polymerization rate of 20 to 90%, preferably 65 to 95%, is desorbed in the first tank reactor. In general, the temperature in the first reactor is from 60 ° C. to about 130 ° C., and the particular temperature is selected depending on the molecular weight and other properties required by the final polymer product.

The second tank reactor is used for the purpose of completing the polymerization and excluding any residue or pre-completion of the unconsumed initiator. This object is achieved by providing an extended residence time so that all initiators are practically consumed. Because of the optimal nature of the final polymer, an additional amount of copolymer, such as ethyl acrylate or methyl acrylate, is introduced into the second tank reactor together with the final polymer transferred from the first tank reactor 10. 5 to about 50%, preferably 25%, of the total comonomer used in this process is introduced into the second tank reactor 20 via line 36. As mentioned above, an additional amount of chain transfer additive, such as n-dodecyl mercaptan, is also introduced into the second tank reactor 20.

About 5 to about 50%, preferably about 25%, of the total chain transfer agent used in this process is introduced into the second tank reactor 20 via line 36. In addition, the temperature range for the second tank reactor 20 is about 60 ℃ to 130 ℃.

The finished polymer drawn out from the second tank reactor 20 is transferred to the devolatile preheater 70 through the transfer line 38 through the polymer pump 25. Preferably the complete polymer passes through the tubes of the cell tube heat exchanger and with the heating fluid. For example, heat transfer with hot oil fluid introduced into the cell side of the heat exchanger via line 71 raises the raw material temperature in the heat exchanger to about 220-260 ° C. The finished polymer heated in the heat exchanger 70 is transferred to a new vessel 76 at the devolatile end via transfer line 39. The feed line 39 has a rear pressure regulating valve 72 that responds to the discharge pressure of the polymer gear pump 25. The pressure maintained in the polymerisation before completion is sufficient to maintain two phases of mixed liquid and vapor. As a practical matter, the actual portion of the solvent remains in the liquid phase in the preheater 70 to avoid the formation of debris on the surface of the heat exchanger and to allow sufficient heat transfer to occur in the devolatile preheater. When excess vaporization occurs in the heat exchanger, a solid phase is formed which quickly forms debris on the surface of the heat exchanger, so that the polymer before completion can be cooled to its melting point or below. The problem that the bubble is formed can be solved by maintaining the polymer before completion in the preheater 70 at a sufficient back pressure.

The back pressure required for the final polymer with any combination of monomers, comonomers, and solvents ensures that the sample is at a sufficient pressure to ensure that no actual vaporization occurs and to completion of the supply temperature from the experimental pressure spring to the preheater. It can be determined experimentally by heating the polymer sample. The pressure is then slowly removed from the sample while observing the liquid phase of the sample to determine the pressure at which initial solidification occurs. This pressure is the minimum pressure to be maintained at the supply pressure to the preheater 70.

Care should be taken not to heat the polymer before completion to temperatures above about 270 ° C., such as increased temperatures that discolor the product. However, for efficient volatile removal, it is necessary to heat the prepolymer to a temperature of about 240-250 ° C. to narrow the temperature range between the effective effective operating temperature and the product discoloration operating temperature very much.

The final polymer flows into the volatile removal vessel 76 where it is maintained at a sufficient atmospheric pressure to strip almost all solvents, unreacted monomers, comonomers and low-boiling polymerization byproducts from the final polymerization product. Spray sparger 78 is preferably used to disperse the polymer well in the form of fine sheets or droplets for effective volatile removal. Typically, the volatile eliminator is maintained at an absolute pressure of 10 to about 150 mmHg, preferably about 50 mmHg. Vapor is removed from the vessel 76 via a nozzle on the tower and passes through line 80 to recycle distillation 81 which is a column with two zones of packing 83 and 85 and a reboiler 87 underneath. Enter Hot steam is introduced under the lower packing region 85 and partially condenses in contact with the recycle condensate from lines 86 and 91. The velocity of the recycle condensate through line 86 is controlled by valve 79 to maintain the preselected liquid level in reboiler 87. The solvent, some monomers and the low boiling polymerization byproducts are collected in the reboiler 87 and the discharge flow therefrom is removed at 93.

Steam exiting recycle distillation unit 81 passes through line 95 and enters reflux condenser 82. The reflux condenser 82 is a cell tube heat exchanger and the solvent vapor is condensed and collected in the reflux condenser 84. Steam, which cannot be condensed, passes through line 97 and enters vacuum device 40 through control valve 99. Some of the condensed solvent is returned to reflux as reflux via line 86 and the remaining condensation solvent is recycled to the process via line 30 to complete the solvent circulation of the process. Typically, a finished polymer having residual monomer and a solvent content of about 1.0% by weight or less, preferably 0.1% by weight or less, is withdrawn from the devolatile vessel 76 through the polymer pump 75 and enters a finishing step. . In the finishing treatment, the polymer is blended with the additives introduced via line 89 and through injection nozzle 88 and then passed through static mixer 90 to evenly mix. This static mixer is a unit having a plurality of continuous and fixed blades bent opposite each other. At this time, the above-mentioned elastic modifier may be added, or other additives such as ultra-ultraviolet stabilizer, antioxidant, internal lubricant / processing accelerator, thermal stabilizer, dye / light emitting agent and plasticizer may be added as usual concentrations. have. The polymer passes through the screen 92 to remove particulate contaminants and the filtered polymer is extruded through the die 94 in the form of a plurality of molten threaded polymer to pass through the water bath 96 to solidify the polymer. . The solidified polymer is then passed through a water stripper 98 to remove residual moisture, while further cooling there, and then through a pelletization site 102, suitable for use in plastic molding equipment such as extrusion and injection molding equipment, It is cut in the form of pellets 104.

The present invention has been described on the basis of representative and preferred embodiments today. The invention is not limited to the scope of the preferred embodiments. The invention will be limited to the means and steps described in the following claims and to those apparently similar thereto.

Claims (22)

(a) introducing a monomer, initiator and chain transfer agent into the solvent mixture to prepare a polymerization medium containing less than about 40% by weight of a solvent; (b) maintaining a polymerization medium at a temperature of 60 to about 130 ° C. and sufficient residence time in at least one polymerization reactor to achieve a monomer polymerization rate of 20 to 95% and to form an intermediate polymerization reactor before completion; (c) withdrawing the intermediate polymerization product before completion, introducing the intermediate polymerization product to at least one subsequent polymerization reactor, including the final polymerization reactor; (d) intermediate polymerization before completion in at least one subsequent polymerization reactor comprising the final polymerization reactor, while maintaining polymerization conditions of a temperature of 60 to about 90 ° C. and a residence time sufficient to substantially remove the initiator in the final polymerization polymer; Stirring the reactants to maintain a well-mixed prepolymer, forming a prepolymer which contains solvent, unreacted monomers and less than about 50% by weight of polymer and pumping it from the final polymerizer; (e) The prepolymer is heated in a devolatile preheater to a temperature of 200 ° C. to 270 ° C., and the preheated prepolymerization is withdrawn from the devolatile preheater and sprayed into the volatile remover via a transfer line to the volatile remover. And flash distillation thereon to remove volatile fluid consisting of solvent, unreacted monomer, and oligomer; And mixing the vapor and liquid phases in the preheater with sufficient heating of the prepolymer in the preheater to provide sufficient heat to provide preheated polymer to produce the molten polymer and pump it out of the volatile eliminator. Maintaining the pressure of the complete crystallization reactant at the transfer line to a sufficient pressure to prevent the initial solidification of the liquid phase in the transfer line to allow vaporization to form a gas to avoid the formation of debris on the heat exchange surface of the volatile preheater. A continuous solution polymerization of monomers comprising at least 40% of the monomers comprising acrylate esters of C ₁ -C ₈ alkanols. The method of claim 1 wherein the acrylate ester is methyl methacrylate. The method of claim 2 wherein the monomer is 80 to 99% methyl methacrylate and 1 to 20% ethyl acrylate, methyl acrylate, or a mixture thereof. The method of claim 1 wherein the solvent is toluene. The method of claim 1, wherein the solvent is selected from the group consisting of benzene, C ₆ -C ₁₀ alkyl, and mixtures thereof. The method of claim 1, wherein the chain transfer agent is n-dodecyl mercaptan. The method of claim 1, wherein the polymerization medium is well mixed to form thermally and chemically uniform materials in all polymerization zones. The method of claim 1, wherein a portion of the vapor formed in the first polymerization zone is withdrawn, cooled and condensed such that the condensate thus obtained is returned to the first polymerization zone to maintain its temperature. The method of claim 9, wherein a vacuum device is used for the first polymerization zone and includes maintaining the pressure of the first polymerization zone by passing steam drawn out from the first polymerization reactor through the throttle valve. The method of claim 1 wherein the prepolymerization is heated by indirect heat exchange with a heat transfer surface in a devolatile preheater. The method of claim 10, wherein the prepolymerisation is maintained under pressure while being heated to prevent the formation of a solid phase to prevent the formation of solid debris on the heat transfer surface. The method of claim 1, comprising adding 5 to about 30% of the comonomer used for this process to the pre-finished intermediate polymerization product in at least one subsequent polymerization zone including the final polymerization zone. 13. The method of claim 12, comprising adding 5 to about 30% of the chain transfer agent used for this process to the pre-finished intermediate polymerization product in at least one subsequent polymerization zone including the final polymerization zone. The method of claim 1, comprising adding a peroxyfree group scavenger to the polymerization medium in an amount of 0.05 to 5.0 wt% based on the amount of polymerization medium. (a) condensing the volatile fluid to obtain a condensate comprising a solvent and an unreacted monomer; And (b) recycling the condensate of said step to a first polymerization reactor as a solvent source. (a) heating the prepolymerization product by indirect heat exchange to a temperature of about 200 to about 270 ° C. in a devolatile preheater; (b) the pre-polymerization reaction in the devolatile preheater at a pressure sufficient to prevent vaporisation of the liquid phase and to prevent the formation of debris on the heat exchanger surface of the preheater at a pressure that allows vaporization to form a vapor-liquid mixed phase; While controlling the pressure of the catalyst, the crystalline prepolymer in the devolatile preheater is sufficient to provide a preheated prepolymer with sufficient heat to produce the molten polymer and to provide the heat of vaporization necessary to allow it to be pumped from the devolatile preheater. Heating; (c) introducing the preheated polymerization product into the devolatile vessel via a transfer line and flash distilling the polymerization product therein to remove volatile fluids including solvents, unreacted monomers and oligomers; And (d) withdrawing the molten polymer containing up to 1.0% by weight of solvent and unreacted monomer from the volatile eliminator, the poly (acrylate) containing solvent, unreacted monomer and less than about 50% by weight of polymer. Volatile removal of the polymerization reaction prior to completion of the ester). The method of claim 16 including condensing the volatile fluid to obtain a condensate comprising a solvent and an unreacted monomer. 17. The method of claim 16, wherein the prepolymerisation is heated in a preheater to a temperature of about 220 ° C to 260 ° C. 17. The process of claim 16, wherein the polymer before completion is discharged into the volatile remover via spray spargers in a well dispersed form of fine sheets or droplets. The method of claim 16 including maintaining the volatile remover at an absolute pressure of 10 to about 150 mmHg. The method of claim 16 wherein the polymer is a copolymer of 80-99% methyl methacrylate with 1-20% methyl acrylate, ethyl acrylate, and mixtures thereof. The method of claim 16, wherein the solvent is selected from the class consisting of benzene, C ₆ -C ₁₀ alkylbenzenes, and mixtures thereof.

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