JP2000053709A - Continuous production of methacrylic polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain the subject methacrylic polymer that has excellent thermal stability and optical properties in high productivity by continuous solution polymerization under specific conditions using specific amounts of monomers, a specific amount of non-polymerizable solvent and a specific free-radical initiator. SOLUTION: (A) Methyl methacrylate monomer, (B) an acrylic alkyl ester monomer of a 1-8 alkyl carbon atoms and (C) a non-polymerizable solvent are purified by distillation so that the distillate mixture satisfies formula I and formula II [A is the parts by weight of the component A, B is the parts by weight of the component B and C is the parts by weight of the component C]. Then, the distillate mixture, (D) a free-radical initiator with a half-life of 5.55×10-5-0.12 hours and (E) a chain transfer agent are continuously fed into the reactor to effect continuous polymerization reaction, as the temperature in the reactor is kept at 130-170 deg.C, the mean residence time of the reaction mixture is controlled to 0.5-1.9 hour, the ratio of the half-life of the component D to the mean residence time of the reaction mixture is kept at 5.0×10-4-0.50, the polymer concentration is kept at 0.40-0.70 in weight fraction and the number- average molecular weight of the polymer is held at 2.5×104-12.0×104. Then, the reaction mixture is continuously driven away and treated under reduced pressure to remove the volatile components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing a methacrylic polymer which is excellent in thermal decomposition resistance, optical transparency and weather resistance and is suitable for materials for thermoforming such as injection molding and extrusion molding. About.

[0002]

2. Description of the Related Art An acrylic resin comprising a methyl methacrylate polymer or a methacrylic copolymer containing methyl methacrylate as a main component has excellent transparency, weather resistance, and excellent mechanical properties, surface hardness, and workability. Depending on the beauty of the appearance of the molded product, for example, optical applications such as various optical lenses, optical disks, and light guide plates, lighting equipment, signboards, various decorative products, nameplates, tableware, exterior parts such as tail lamps for automobiles, and exterior products Widely used for outdoor applications such as.

[0003] Conventionally, the problems that occur when this methacrylic resin is molded by injection molding include silver marks (silver streaks) of molded products, generation of bubbles, deterioration of heat-resistant deformation, and generation of gas. The work environment deteriorated. In general, these problems are often suppressed by lowering the temperature of the molten resin at the time of molding, but in that case, molding of large or thin-walled molded products becomes difficult due to a decrease in melt fluidity. In some cases, the use of the molded product is limited due to reasons such as a decrease in product quality due to residual distortion of the molded product.

[0004] These problems are caused by the fact that in the case of methacrylic polymers, the decomposition reaction of the polymer occurs during molding because the thermal decomposition temperature is close to the temperature at which the polymer exhibits the melt fluidity required for molding. It is considered to be a problem inherent to the methacrylic resin caused by the above. Therefore, it is considered that improving the thermal decomposition resistance of the polymer is effective for essentially solving the above problems, and a methacrylic polymer having improved heat stability and its production have been conventionally known. A way has been sought.

As a method for improving the thermal stability, bulk polymerization (JP-A-49-37993, JP-A-3-11
1408), a solution polymerization method (JP-A-63-576).
No. 13, JP-A-1-172401, etc.) and the like have been proposed. Generally, methacrylic polymers produced by bulk polymerization and solution polymerization can produce polymers with less impurities and good optical properties compared to methacrylic polymers produced by suspension polymerization. In addition, a continuous process with excellent productivity is possible.

[0006] For this reason, continuous bulk polymerization and continuous solution polymerization are particularly attracting attention as processes capable of producing high-quality polymers under high productivity conditions, and there is a demand for advanced techniques. However, as described below, at present, a method for producing a methacrylic polymer that can sufficiently satisfy both the productivity and the thermal stability of the polymer, which are features of these continuous polymerization methods, has not been found.

That is, the productivity in the continuous polymerization method depends on the scale of the polymerization equipment, the average residence time in the reactor, and the reaction conversion of the monomer at the final outlet of the reactor. It can be said that the production method is shorter and the higher the reaction conversion of the monomer at the final outlet of the reactor, the better the productivity. Further, when the polymer concentration at the final outlet of the reactor is compared under a constant condition, it can be said that the shorter the average residence time, the smaller the scale of the polymerization equipment and the more excellent the productivity.

Accordingly, the polymer concentration s at the final outlet of the reactor is
The value s / τ of the ratio between the (weight fraction) and the average residence time τ (time) in the reactor is an index representing the productivity under the same conditions of the polymerization reactor (the total weight of the reaction solution in the reactor). It is. In general, it is known that the polymerization reaction type, composition, and polymerization conversion rate under similar conditions, the residence time in the reactor, and the thermal stability of the polymer tend to be contradictory. There is little knowledge on methods for improving the balance of thermal stability, and the improvement is an important technical issue.

Japanese Patent Publication No. Hei 8-19193 discloses that a polymer produced by a continuous bulk polymerization method under specific conditions and having a double bond terminal content within a specific range is excellent in thermal decomposition resistance and optical properties. Is disclosed. However, the publication does not disclose the thermal decomposition resistance of the polymer and the conditions at the time of polymerization. For example, in Examples and Comparative Examples in the same bulletin,
The residence time in the reactor is 5,6.7 hours, and the degree of polymerization is 46 to 59.
Although examples of% are disclosed, no method is described for controlling thermal stability under general conditions where the rate of polymerization in the reactor is different. The maximum value of s / τ calculated from the embodiment is 0.11 (1 / hour).

On the other hand, Japanese Patent Application Laid-Open No. Hei 8-253507 discloses a method for producing a methacrylic resin which is less likely to generate silver streaks, foaming, coloring and odor during thermoforming and which is excellent in thermal decomposition resistance. The amount of the solvent 29 to 5 with the half-life, average residence time, radical initiator concentration, chain transfer agent concentration and monomer conversion of
A production method using a one-stage complete mixing tank, which is a percentage by weight, is disclosed.

It is stated that as a reason for limiting the amount of the solvent, if the amount is less than 5% by weight, the phenomenon of abnormal acceleration of the polymerization rate due to the effect of automatic promotion of the polymerization is likely to occur, and the polymerization cannot be stably maintained. However, there is no description other than the amount of solvent for stably controlling the polymerization. The maximum value of s / τ calculated from the embodiment is 0.132 (1 / hour).
It is.

As exemplified above, it is obvious that the smaller the value of s / τ, the higher the industrial value, but in the range of the prior art, in order to keep the thermal stability at a practicable level, It can be said that τ was limited to a certain range value or less.

On the other hand, when there is no restriction on the level of thermal stability, it is considered that there is little restriction on productivity, and a continuous bulk polymerization method having a large s / τ and excellent productivity is disclosed in JP-A-7-12.
No. 6308. The same publication discloses a production method in which the inside of a complete mixing type reaction tank is filled with water, and is in an adiabatic state where heat does not flow in and out, and continuous bulk polymerization is performed under specific conditions. / Τ is 0.33 ~
Production conditions of 1.34 (1 / hour) and higher productivity than the conventional ones are described.
The thermal stability of the polymer is not described at all and is unknown.

As is apparent from the above description, the production technology for stably producing a methacrylic polymer having excellent thermal decomposition resistance by a continuous solution polymerization method is limited in a limited condition range in which productivity is greatly limited. Was only known about. In particular, a continuous solution polymerization technique for producing a polymer having a high productivity of s / τ of 0.2 (1 / hour) or more, and having excellent thermal stability, optical transparency, and weather resistance is required. At present it has not been obtained. From the above viewpoints, it has been desired to establish a continuous solution polymerization technique capable of producing a high-quality polymer excellent in thermal stability, optical properties, and weather resistance with higher productivity than before.

[0015]

SUMMARY OF THE INVENTION The present invention meets the above-mentioned demand and provides a continuous solution polymerization method capable of producing a methacrylic polymer excellent in thermal decomposition resistance and optical characteristics with high productivity. The task is to provide.

[0016]

Means for Solving the Problems The present inventors have conducted intensive studies to find a method for solving the above-mentioned problems, and have found that a specific amount of monomer, a specific amount of non-polymerizable solvent, and a specific range of half-life are determined. By using a free radical generator having a continuous solution polymerization method under specific conditions, a methacrylic polymer having excellent heat stability and optical properties can be stably and continuously produced with higher productivity than before. The present invention has been completed.

That is, the present invention provides: A methyl methacrylate monomer, an alkyl acrylate monomer having an alkyl group having 1 to 8 carbon atoms, and a non-polymerizable solvent were respectively expressed by the following formula: 0.70 ≦ A / (A + B) ≦ 0.998. 001 <C / (A + B + C) <0.050 (where A is the weight part of the methyl methacrylate monomer, B is the weight part of the alkyl methacrylate monomer, and C is the weight part of the non-polymerizable solvent. ), A free radical generator having a half-life in the reactor of 5.55 × 10 ^{−5 to} 0.12 hours, and a chain transfer agent are continuously supplied to the reactor. While maintaining the inside at 130 to 170 ° C. and stirring and mixing uniformly, the average residence time of the reaction solution in the reactor is 0.5 to 1.9 hours, the half-life of the free radical generator and the reaction time of the reaction solution in the reactor. The ratio of the average residence time is 5.0 × 10 ⁻⁴ or more.
0.50, the polymer concentration (weight fraction) in the reactor was 0.4
0 to 0.70, the ratio of the generated free radical generator concentration (mol · g ⁻¹ ) of the free radical generator in the whole supply liquid to the polymer concentration (weight fraction) of the polymerization liquid in the reactor is 0.5 × 10 ^{-6 to} 3.0 × 1
0 ^-6 mol · g ^-1 , and the number average molecular weight of the polymer is 2.
The polymerization reaction is controlled continuously within the range of 5 × 10 ^{4 to} 12.0 × 10 ⁴ , and the polymerization reaction is continuously performed. Then, the reaction solution is continuously discharged from the reactor, followed by heating under reduced pressure and devolatilization. Of producing a methacrylic polymer.

2. Distillation and purification of methyl methacrylate, acrylate and specific polymerizable solvent used for the feed solution,
2. The method for producing a methacrylic polymer according to 1 above, wherein the solid foreign matter is removed by making the dissolved oxygen content in the supply liquid 1 ppm or less and passing through a filter having a transmission particle size of 2 μm or less.

3. 3. The method for producing a methacrylic polymer according to 1 or 2, wherein the non-polymerizable solvent is at least one solvent selected from ethylbenzene, toluene, o-xylene, m-xylene, and p-xylene. .

The process for producing a methacrylic polymer of the present invention comprises the steps of reacting a methyl methacrylate monomer, an alkyl acrylate monomer having an alkyl group having 1 to 8 carbon atoms and a non-polymerizable solvent with the following formula: 0.70 ≦ A / (A + B) ≦ 0.998 0.001 <C / (A + B + C) <0.050 (where A is the weight part of methyl methacrylate monomer, B is alkyl acrylate monomer) And C is a part by weight of the non-polymerizable solvent.) And a free radical generator having a half-life of 5.55 × 10 ^{−5 to} 0.12 hours in a reactor. And the chain transfer agent is continuously supplied to the reactor.

The alkyl acrylate monomer having 1 to 8 carbon atoms in the alkyl group in the liquid supplied to the reactor is a component for imparting heat decomposition resistance and melt fluidity of the polymer to be produced. is there.

The composition of the feed solution is as follows: when A is a part by weight of a methyl methacrylate monomer and B is a part by weight of an alkyl acrylate monomer having an alkyl group having 1 to 8 carbon atoms. It is necessary to satisfy 70 ≦ A / (A + B) ≦ 0.998. The above A / (A + B) represents the ratio of the methyl methacrylate monomer to the total monomer components in the obtained feed solution, and is obtained when the value of A / (A + B) is less than 0.70. Since the characteristics of the polymer as a methacrylic polymer are impaired, it is not preferable. On the other hand, if the value of A / (A + B) exceeds 0.998, the effect of copolymerizing the alkyl ester monomer is small, which is not preferable.

Examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, sec-propyl acrylate, tert-propyl acrylate, and acryl acrylate. N-butyl acid, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, sec-propyl acrylate, and the like.
Of these, methyl acrylate, ethyl acrylate,
Is particularly preferred in view of the effects of improving the thermal decomposition resistance and the melt fluidity by copolymerization.

In the present invention, the non-polymerizable solvent in the liquid supplied to the reactor is a component necessary for improving the thermal stability of the polymer and controlling the stability of the polymerization reaction. Organic compounds having no copolymerizability in radical polymerization.
Specific examples of the non-polymerizable solvent used in the present invention include toluene, o-xylene, m-xylene, p-xylene, aromatic compounds such as ethylbenzene, octane, decane, aliphatic compounds such as cyclohexane, decalin and the like. Alicyclic compounds, butyl acetate, ester compounds such as pentyl acetate,
Examples include alcohols such as methanol and ethanol. Particularly, from the viewpoint of polymerization stability, toluene, o-xylene, m-xylene, p-xylene and ethylbenzene are preferred.

In the present invention, A in the feed to the reactor
Is a weight part of a methyl methacrylate monomer, B is a weight part of an alkyl acrylate monomer having an alkyl group having 1 to 8 carbon atoms, and C is a weight part of a non-polymerizable solvent. 001 ≦ C / (A + B + C) ≦ 0.050 Preferably, it is necessary that 0.003 ≦ C / (A + B + C) ≦ 0.035.

In the present invention, C / (A + B + C) is not more than 0.
If it exceeds 050, not only the effect of improving the polymerization stability is not observed, but also the thermal stability of the polymer decreases in comparison at the same production rate, which is not preferable. On the other hand, if the value of C / (A + B + C) is less than 0.001, the effect of improving the polymerization stability is not seen, and the thermal decomposability of the polymer is lowered in comparison at the same production rate, which is not preferable. When the value of C / (A + B + C) is 0.003 to 0.035, the effect of using a solvent, that is, the effect of improving the thermal stability of the polymer and the effect of controlling the stability of the polymerization reaction, is more preferable.

The free radical generator supplied to the reactor of the present invention is a component which initiates the radical polymerization of the acrylic polymer, and has a half life of 5. in the polymerization reactor.
It needs to be 55 × 10 ^{−5 to} 0.12 hours.
If the half-life is less than 5.55 × 10 ⁻⁵ hours, the thermal stability of the polymer obtained under the same production rate conditions tends to decrease, which is not preferable. If the time is exceeded, the stability controllability of the polymerization reaction tends to decrease, which is not preferable.

Examples of the free radical generator used in the present invention include, for example, di-tert-butyl peroxide, di-cumyl peroxide, methyl ethyl ketone peroxide, di-tert-butyl perphthalate, di-tert-butyl peroxide.
t-butyl perbenzoate, tert-butyl peracetate, 2,5-dimethyl-2,5-di (tert-butyl perbenzoate)
Butylperoxy) hexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, di-tert-amyl peroxide, benzoyl peroxide, cumene hydroperoxide and lauryl peroxide. Organic peroxide, azobisisobutanol diacetate, 1,1′-azobiscyclohexanecarbonitrile, 2-phenylazo 2,4-dimethyl-
Examples include azo compounds such as 4-methoxyvaleronitrile, 2-cyano-2,2-propylazoformamide and 2,2′-azobisisobutyronitrile. These can be used alone or in combination of two or more.

As the polymerization reactor for the present invention, a reactor equipped with a mixing device and a temperature control device and having a supply port and a discharge port capable of continuously supplying raw materials and discharging the reaction solution is provided. Is used. The reactor in the present invention needs to be provided with a stirrer in order to stir and mix uniformly, and examples of stirring blades that can be used include a double helical ribbon blade, a pitched paddle, a turbine, and an anchor type.

As a method for removing the reaction heat in the present invention, a condenser is provided at the upper part of the reactor, the pressure inside the reactor is controlled to boil the reaction solution, and the above is condensed and circulated by the condenser to evaporate. A method of removing the heat of reaction by latent heat,
A method of removing the reaction heat by sensible heat of the supply liquid by controlling the temperature of the supply liquid supplied to the reactor to a low temperature, and circulating the reaction liquid to an external cooling device provided outside the reaction liquid to react by heat exchange Any method such as a method of cooling a liquid may be used, and a plurality of heat removal methods may be used in combination.

The pressure in the polymerization reactor in the present invention is not particularly limited as long as it is within the upper limit of the design of the reactor and within the limit, and under the condition that the internal pressure is appropriately adjusted according to the heat removal method of the reaction solution. The reaction can take place.

In the present invention, the temperature in the polymerization reactor is 1
It needs to be 30 to 170 ° C, preferably 135 to 160 ° C. If the temperature in the reactor is lower than 130 ° C., the stability of the polymerization control decreases due to an increase in the viscosity in the reactor,
Further, the thermal stability of the obtained polymer tends to decrease, which is not preferable. On the other hand, if the temperature in the reactor exceeds 170 ° C., the thermal stability of the polymer tends to decrease, and the chromaticity tends to deteriorate.

In the present invention, the average residence time of the reaction solution in the reactor is 0.5 to 1.9 hours, preferably 0.7 to 1.
It needs to be 8 hours. Average residence time 0.5
When the time is less than the time, the thermal stability of the obtained polymer tends to decrease, and on the other hand, when the average residence time exceeds 1.9 hours, the productivity decreases, which is not preferable.

In the present invention, the weight fraction of the polymer in the reaction solution in the reactor is 0.40 to 0.70, preferably 0.1 to 0.70.
It is necessary to control in the range of 45 to 0.65. When the weight fraction of the polymer is less than 0.40, the production rate of the polymer is inferior, and the load at the time of devolatilization and recovery after polymerization and the recovery of unreacted components required per unit weight of the polymer are required. Energy consumption becomes excessive, which is not preferable.

In general, in a continuous polymerization method, the scale of the polymerization equipment, the average residence time in the reactor, and the reaction conversion of the monomer at the final outlet of the reactor are important.
It can be said that the shorter the average residence time and the higher the reaction conversion of the monomer at the final outlet of the reactor, the better the productivity. Further, when the polymer concentration at the final outlet of the reactor is compared under a constant condition, it can be said that the shorter the average residence time, the smaller the scale of the polymerization equipment and the more excellent the productivity.

Accordingly, the ratio of the polymer concentration (weight fraction) at the final outlet of the reactor to the average residence time in the reactor is determined under the condition that the scale of the polymerization reactor (total weight of the reaction solution in the reactor) is the same. It is considered to be an index indicating productivity in The ratio s / τ of the polymer concentration s (weight fraction) in the reactor and the residence time τ (time) in the reactor in the present invention is in the range of 0.21 to 1.40 (1 / hour). According to the invention, it is possible to manufacture with higher productivity as compared with the manufacturing method according to the prior art.

In the present invention, the play in the liquid supplied to the reactor is
Half-life of the radical generator in the reactor and average residence time in the reactor
Is 5.0 × 10^-Four~ 0.50, preferably 1.0x
10 ^-3It needs to be 〜0.10. Of the above ratio
Value is 5.0 × 10^-FourIf less than the thermal stability of the resulting polymer
The qualitative tendency tends to decrease, while when it exceeds 0.50,
There is a tendency for polymerization stability to decrease, i.e., poor control of conversion.
Is not preferred.

In the present invention, the ratio I / s of the concentration I (mol · g ⁻¹ ) of the generated free radical in the feed liquid to the concentration s (weight fraction) of the polymerization liquid in the reactor is 0. .5 × 10 ^-6
~ 3.0 × 10 ⁻⁶ mol · g ⁻¹ , preferably 0.6 ×
A concentration within the range of 10 ^{-6 to} 2.8 × 10 ^-6 mol · g ^-1 is supplied to the reactor.

Here, the concentration in terms of the generated free radical of the free radical generator refers to an amount defined as follows. It can be determined from the concentration of the free radical generator based on the whole in the feed solution and the amount of active oxygen of the free radical generator, and [concentration in terms of generated free radical (mol
G- ¹ )] = [free radical generator concentration (mol.g- ¹ )]. Times.
It is calculated by [(amount of active oxygen of free radical generator / 16) / 100]. Here, [the amount of active oxygen (%)] is defined as [weight of RO / radical O atom generated per unit weight of free radical generator] × 100 (%). These can be determined by calculation from the chemical structure and purity of the free radical generator used, or by analysis of the product at the time of complete decomposition of the initiator. In the case of azo-based compounds and other cases, they can be similarly determined based on the number of moles of free radicals generated per mole of the compound.

The above ratio I / s is important as an index of the thermal decomposability of the polymer, and is 0.5 × 10 ⁻⁶ mol · g ^−1.
Less than the To, it is necessary to control the polymerization reaction to low productivity conditions not preferable, whereas, 3.0 × 10 ^-6 m
When ol · g ^-1 is exceeded, the thermal stability is reduced, and the tendency to generate defects such as silver streaks increases in high-temperature molding, thin-wall large-sized molding, etc., as compared with conventional methacrylic polymers. Is not preferred.

In the method for producing a methacrylic polymer of the present invention, the chain transfer agent is a component supplied to the reactor for controlling the molecular weight of the polymer, and the content contained in the liquid supplied to the reactor is as follows: The number average molecular weight of the polymer in the reactor is 2.
5 × 10 ^{4 to} 12 × 10 ⁴ , preferably 3.0 × 10 ⁴ to
The addition concentration is adjusted according to the target molecular weight of the polymer so as to fall within the range of 10 × 10 ⁴ .

In the present invention, the number average molecular weight of the polymer is:
It is a numerical value measured by a gel permeation (GPC) method, and the PM of the sample is determined by a gel permeation chromatograph calibrated using standard polymethyl methacrylate (PMMA) having a narrow molecular weight distribution as a standard sample.
It is a numerical value calculated from data obtained by measuring the molecular weight distribution in terms of MA.

The number average molecular weight of the polymer in the reactor is 2.5
If it is less than × 10 ⁴ , the mechanical strength of the product obtained by molding the polymer tends to decrease, which is not preferable,
On the other hand, if it exceeds 12 × 10 ⁴ , the condition range in which the polymerization reaction can be stably controlled becomes narrow, which is not preferable.

Examples of the chain transfer agent include methyl mercaptan, ethyl mercaptan, propyl mercaptan, isopropyl, n-butyl mercaptan, isobutyl mercaptan, t-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-dodecyl mercaptan, Primary, secondary and tertiary mercaptans having an alkyl group or a substituted alkyl group such as t-butyl mercaptan, aromatic mercaptans such as phenyl mercaptan, thiocresol, thioglycolic acid and its esters, ethylene thioglycol, etc. No. These can be used alone or in combination of two or more. Of these, use of n-butyl, t-butyl and n-octyl mercaptan is particularly preferred in view of the color tone of the polymer and the ease of separation and removal from the reaction mixture.

In the present invention, the reaction solution continuously discharged from the reactor is devolatilized to remove the polymer, and at the same time, a monomer and a solvent mainly composed of unreacted methyl methacrylate, which is a volatile component, are removed. To separate. As the devolatilizing device, an extruder with a multi-stage vent, a devolatilizing tank, or the like can be used.
In particular, the reaction solution is heated to a temperature of 200 to 290 ° C., and a polymer is taken out by feeding it to a devolatilization tank having a sufficient space above and having a temperature of 200 to 280 ° C. and a pressure of 100 torr or less under vacuum. At the same time, a method of separating a volatile component composed of a monomer having unreacted methyl methacrylate as a main component and a non-polymerizable solvent is preferable.

The method of introducing the polymerization solution into the devolatilization tank held under reduced pressure involves the instantaneous volatilization of volatile components and the resulting foaming, forming an extremely large evaporation area and removing the solvent having a high boiling point. Even when used, volatile components are efficiently removed in a short time, and unreacted monomers, dimers,
This is an excellent devolatilization method in that the amount of the oligomer and the non-polymerizable solvent is small, and a polymer having excellent optical transparency is obtained. In this devolatilization step, the content of the non-polymerizable solvent contained in the polymer is 2 to 500 ppm, preferably 2 to 3 ppm.
It can be controlled within the range of 00 ppm.

In the method for producing a polymer according to the present invention, when supplying a supply liquid to a reactor, a mixture of methyl methacrylate, acrylate and non-polymerizable solvent is purified by distillation, and the concentration of dissolved oxygen in the supply liquid is adjusted. To 1 ppm or less,
In addition, by passing the supply liquid through a filter having a transmission particle size of 2 μm or less, solid foreign matters can be removed.
By the above operation, the optical properties and weather resistance of the polymer can be further improved.

The distillation purification of the feed solution is effective for removing impurities and foreign substances contained in the monomer and the non-polymerizable solvent.
It has the effect of removing the foreign matter contained in the polymer and the optical transparency of the polymer. At that time, the distillation and purification of the monomer and the non-polymerizable solvent are carried out, for example, by a distillation column such as a packed column type or a tray type. The distillation method supplies the raw material mixture from the middle or upper stage of the distillation column, distills while heating the distillation column bottom liquid with a heater such as a reboiler, and mainly contains methyl methacrylate flowing out from the top of the distillation column. It is carried out by condensing the vapors of the monomer and the non-polymerizable solvent in a condenser.

At this time, when the boiling point of the non-polymerizable solvent used is higher than that of the monomer, the non-polymerizable solvent is added to stabilize the storage of the high boiling point impurities, foreign substances and monomer concentrated in the bottom liquid of the distillation column. The polymerization inhibitor and the like are particularly preferable because they can be removed by continuously or intermittently removing the bottom liquid of the distillation column and simultaneously adding the removed solvent.

When the unreacted monomer and the non-polymerizable solvent devolatilized and separated from the reaction solution after the polymerization reaction are recycled for use as a part of the raw materials, the recovered unreacted monomer is distilled off. By purifying, methyl methacrylate dimer and oligomer can be removed.

The feed liquid material purified by distillation is further replaced with an inert gas by bringing it into countercurrent contact with a countercurrent contact tower to reduce the concentration of dissolved oxygen in the feed liquid to 1 ppm or less.
Although the dissolved oxygen concentration is 10 to 20 ppm by the inert gas bubbling method in the tank, the dissolved oxygen concentration can be reduced to 1 ppm or less by the countercurrent contact method.

In the present invention, when the feedstock is purified by distillation, solid foreign matter is reduced, but the dissolved oxygen concentration is reduced to 1 pp.
m or less, it is necessary to remove the remaining foreign matter by filtering through a filter having a transmission particle size of 2 μm or less. The type of the filter is not particularly limited as long as it is chemically stable to the supply liquid, does not contaminate the supply liquid, and has a structure capable of removing solid foreign matter from the supply liquid. Vessel, ultrafiltration membrane and the like. By such a filtration treatment, the content of solid foreign substances having a particle diameter of 2 μm or more in the obtained polymer can be reduced, and the yellowness and weather resistance of the polymer can be improved.

One example of a process diagram of a continuous polymerization apparatus used in the continuous polymerization process of the present invention described in detail above is shown in FIG. 1 (first half) and FIG. 2 (second half).

In the method for producing a methacrylic polymer of the present invention, a releasing agent, an antioxidant, a light diffusing agent, a dye, a pigment, a fluorescent brightener, a lubricant,
Impact modifiers and the like can be added to the polymer at each stage of the manufacturing process.

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to examples, but the present invention is not limited by these examples. In addition, the number average molecular weight, the thermal decomposability, and the occurrence rate of silver streaks of the polymers in Examples and Comparative Examples were measured according to the methods described below.

(1) Number average molecular weight of polymer The reaction solution was taken out of the polymerization reactor during the polymerization reaction, and determined by gel permeation chromatography (GPC) as follows. After completely dissolving 2 g of the reaction solution in 20 g of acetone, the polymer was separated by reprecipitation in 2,000 g of n-hexane, and dried under vacuum to obtain a polymer sample. 20 mg of a polymer sample was dissolved in 40 cm ³ of tetrahydrofuran: THF to obtain a sample solution. The obtained chromatogram was converted into a molecular weight distribution using a calibration line created by standard PMMA (manufactured by Polymer Laboratories), and the number average molecular weight was calculated.

[GPC Measurement Conditions] Apparatus: Tosoh HLC8120, Column: Tosoh TSKgel, superHM-M two in series, solvent: tetrahydrofuran (THF), column temperature: 40 ° C., flow rate: 0.2 cm ³ / min.

(2) Thermal Decomposition of Polymer A Curie Point Pyrolyzer (manufactured by Nippon Kagaku Kogyo Co., Ltd.) is connected to a gas chromatograph, and monomers generated during pyrolysis are analyzed by a method of analyzing and quantifying pyrolysis gas generated by the Pyrolyzer. By quantifying, the thermal decomposition property was evaluated. A sample (1 g) was completely dissolved in methylene chloride (20 cm ³ ), 25 μL of the solution was uniformly applied to pyrofoil (Curie point: 315 ° C., manufactured by Nippon Kagaku Kogyo), and dried under reduced pressure at 200 ° C. for 1 hour using a vacuum dryer. Removed.

After setting the pyrofoil in the Curie Point Pyrolyzer and completely replacing the inside of the apparatus with nitrogen, the sample was heated at a heating time of 10 seconds, and the generated MMA monomer and alkyl acrylate were analyzed by gas chromatography. The quantification and the total amount were calculated.

(3) Generation rate of silver streaks The generation rate of silver streaks generated during high-temperature molding was evaluated by the following method. The polymer pellets were dried by a hot air dryer until the water concentration in the pellets became 300 ppm, and an injection molding test was performed under the following conditions.
Foaming by gas generated by thermal decomposition during high-temperature molding was evaluated by the following method. FANUC injection molding machine T-10
Using 0D mold, cylinder temperature 300 ° C, mold temperature 55
At a filling temperature of 750 kgf / cm ² at 250 ° C. for a spiral flow length (SFD) evaluation.
m) was molded. After the SFD was stabilized, 50 shots were molded further, and the molded product was observed for the presence of silver streaks and foaming. The measurement was performed twice by the same method, and a total of 10
The number of times silver streaks were observed on the molded piece during 0 shot was recorded, and was defined as a silver generation rate (%).

(4) Injection molding of polymer and evaluation of chromaticity of molded piece A 3 × 20 × 220 mm test piece was molded at 250 ° C. cylinder temperature using an injection molding machine IS-75S manufactured by Toshiba Machine Co., Ltd. After the molding cycle was stabilized, four shots were formed after the molding cycle was stabilized. Four test pieces were stacked in the thickness direction, and the yellowness ΔYI based on air in the length direction (no test piece)
(Optical path length 220 mm) using a color difference meter (TC-
1500MC type).

(5) Evaluation of weather resistance of molded product The molded piece molded in (4) was subjected to a sunshine weatherometer (SWOM) at 56 ° C. under rainfall conditions.
The yellowness (ΔYI) after exposure for 00 hours was measured in the same manner as in (4).

[0063]

EXAMPLE 1 A mixture of 97.8% by weight of methyl methacrylate, 2.0% by weight of methyl acrylate, and 0.2% by weight of ethylbenzene was mixed with 1,1-bis (t- 96 ppm of butylperoxy) -3,3,5-trimethylcyclohexane and 204 ppm of n-octylmercaptan
0 ppm was continuously added and mixed and continuously supplied to a 10-L complete mixing type polymerization reactor equipped with a pitched paddle blade stirrer, the liquid temperature in the reactor was 155 ° C, and the average residence time (τ) in the reactor was 1.00 hours. The polymerization liquid was continuously discharged from the reactor, and then the polymerization liquid was passed through the gap between the heating plates to exchange heat, heated to 260 ° C., and cast and dropped into a devolatilization tank.

Since the half-life (θ) of the free radical generator in the reactor is 0.0083 hr and the average residence time (τ) in the reactor is 1.00 hr, θ / τ is 0.00
83. The devolatilization tank reduces the internal pressure to 3 by vacuum devolatilization.
At 0 torr and the temperature was maintained at 230 ° C., the unreacted monomer and the polymerization solvent were separated and recovered. The polymer was discharged by a gear pump below the devolatilizing tank, extruded from an extrusion die, and the strand was pelletized by a strand cutter and collected as pellets. When the weight fraction of the polymer in the reactor was calculated from the ratio of the weight of the pellets produced per unit time to the weight of the feed liquid supplied to the reactor per unit time, the steady value was 0.57. Met. The concentration (I) of the free radical generator calculated from the molecular weight of the free radical generator and the amount of active oxygen is 1.26.
5 mol · g ⁻¹ and I / s is 2.22 × 10 ⁻⁶ mo
It was 1 · g ^-1 . Table 1 shows the composition of the liquid supplied to the polymerization reactor, the reaction conditions, and the characteristics of the polymer.

Examples 2 to 5 The same operation as in Example 1 was carried out except that the composition of the liquid supplied to the polymerization reactor and the reaction conditions in Example 1 were changed as shown in Table 1, to obtain a polymer. . Table 1 shows the results.

Example 6 After the operation of Example 3, a mixture (hereinafter, referred to as a recycle liquid) 4 composed of an unreacted monomer, a non-polymerizable solvent, and the like collected.
A mixture consisting of 3.0% by weight, 55.8% by weight of new methyl methacrylate and 1.2% by weight of new methyl acrylate was continuously fed to the distillation column, and the bottom temperature was 90 ° C.
Continuous simple distillation was carried out under a pressure of 70 torr. The composition of the mixture mainly composed of the distilled monomers is 96.0% by weight of methyl methacrylate, 2.0% by weight of methyl acrylate,
The content of ethylbenzene was 2.0% by weight.

To this mixture, 107 ppm of 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane and 193 of n-octylmercaptan were added.
0 ppm was continuously added and mixed to form a feed solution, which was then deoxygenated by a nitrogen countercurrent contact tower, passed through a filter having a permeation particle size of 2 μm, and continuously fed to the polymerization reactor. Polymerization was carried out under the conditions of a liquid temperature of 155 ° C. and an average residence time in the reactor of 1.00 hour, the polymer solution was continuously discharged from the reactor, and then the polymer solution was passed through the gap between the heating plates to exchange heat and heated to 260 ° C. Then, it was cast and dropped into a devolatilization tank.

The oxygen concentration in the feed solution immediately before being fed to the reactor was 0.2 ppm or less. The devolatilization tank maintained the internal pressure at 30 Torr and the temperature at 230 ° C. by vacuum devolatilization to separate the unreacted monomer and the polymerization solvent. The polymer was discharged by a gear pump below the devolatilization tank, extruded from an extrusion die, and the strands were pelletized by a strand cutter and collected as pellets.

The compositions of the unreacted monomer and the solvent separated and recovered by devolatilization were the same as in Example 3. The collected recycle solution was stored in a tank, and after operating continuously for 10 days by a method of reusing as a recycle solution, a polymer was produced and sampled. At that time, according to the change in the composition of the recycle solution, the mixing ratio of the recycle solution and the new monomer was adjusted, and the composition of the supply solution was maintained equal to that in Example 3. No increase in viscosity due to polymer formation at the bottom of the distillation column was observed during the operation period, and the reboiler at the bottom of the rectification column was capable of continuous stable operation. Table 1 shows the evaluation results of the polymers. The polymer characteristics were excellent in the initial ΔYI and the ΔYI after exposure as compared with those of Example 3.

Example 7 After the implementation of Example 4, 43.0% by weight of the recycled liquid containing the unreacted monomer recovered and fresh methyl methacrylate 5
5.8% by weight and 1.2% by weight of new methyl acrylate
Was continuously fed to a distillation column, and was continuously subjected to simple distillation under the conditions of a bottom temperature of 90 ° C. and a pressure of 70 torr. The composition of the mixture mainly composed of the distilled monomer was 94.6% by weight of methyl methacrylate and 1.66% by weight of methyl acrylate.
9% by weight and 3.5% by weight of ethylbenzene.

To this mixture, 117 ppm of 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane and 183 ppm of n-octylmercaptan were added.
0 ppm was continuously added and mixed to form a feed solution, which was then deoxygenated by a nitrogen countercurrent contact tower, passed through a filter having a permeation particle size of 2 μm, and continuously fed to the polymerization reactor. Polymerization was carried out under the conditions of a liquid temperature of 155 ° C. and an average residence time in the reactor of 1.00 hour, the polymer solution was continuously discharged from the reactor, and then the polymer solution was passed through the gap between the heating plates to exchange heat and heated to 260 ° C. Then, it was cast and dropped into a devolatilization tank. The oxygen concentration in the supply liquid immediately before being supplied to the reactor was 0.2 ppm or less. The devolatilization tank maintained the internal pressure at 30 Torr and the temperature at 230 ° C. by vacuum devolatilization, and separated and recovered the unreacted monomer and the polymerization solvent.

The polymer was discharged by a gear pump below the devolatilizing tank, extruded from an extrusion die, and the strand was pelletized by a strand cutter and collected as pellets. The unreacted monomer and polymerization solvent are condensed by a condenser connected to a devolatilization tank, stored in a recycling tank as a recycle liquid for reuse, and continuously reused as a recycle liquid for 10 days. Was carried out to produce a polymer. At that time, according to the change in the composition of the recycle solution, the mixing ratio of the recycle solution and the new monomer was adjusted, and the composition of the supply solution was maintained equal to that in Example 4. Table 1 shows the evaluation results of the polymers. Polymerization characteristics were ΔYI initial and ΔYI after exposure as compared to those of Example 4.
Excellent in

Comparative Examples 1 and 2 The operation was carried out under the same conditions as in Example 1 except that the composition of the feed solution in Example 1 was changed as shown in Table 1. Table 1 shows the results. As shown in Table 1, the polymerization characteristics are inferior to Examples 1 to 7 in thermal decomposability, silver generation rate, ΔYI value at initial stage and after exposure, and the like.

Examples 8 to 12 In order to examine the conditions in which the residence time in the reactor was changed, the same as in Example 6 except that the composition of the liquid to be fed to the reactor and the reaction conditions were changed as shown in Table 2. The operation was performed. 1 continuously
A stable operation was performed for 0 days, and a polymer was produced and sampled to obtain a polymer. Table 2 shows the evaluation results of the polymer. As well as excellent polymerization characteristics, s / τ as an index of productivity was in the range of 0.263 to 0.316 hr ^-1 , and a result excellent in productivity was obtained.

Comparative Example 3 A polymerization reaction was started in the same manner as in Example 8, except that the composition of the liquid supplied to the reactor and the reaction conditions were changed as shown in Table 2. After the start of the reaction, the operation was stopped because the polymer concentration in the reactor became unstable and the steady operation became difficult.

Comparative Example 4 A polymerization reaction was carried out in the same manner as in Example 8, except that the composition of the liquid supplied to the reactor and the reaction conditions were changed as shown in Table 2. A stable operation was continuously performed for 10 days to produce a polymer, which was sampled. Table 2 shows the evaluation results of the polymer. Thermal decomposition of polymer, silver generation rate, initial ΔY
I, ΔYI value after exposure to weather test was inferior.

[0077]

[Table 1]

[0078]

[Table 2]

[0079]

According to the present invention, a methacrylic polymer which is excellent in thermal decomposition resistance, optical transparency and weather resistance, and is suitable for thermoforming materials such as injection molding and extrusion molding is excellent in stability and productivity. An effect is provided that a manufacturing method is provided.

[Brief description of the drawings]

FIG. 1 is a process diagram (first half) showing an example of a continuous polymerization apparatus in a solution polymerization process of the present invention.

FIG. 2 is a process diagram (second half) showing an example of a continuous polymerization apparatus in the solution polymerization process of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 New monomer supply line 2 Recovered volatiles storage tank 3 Recovered volatiles supply line 4 Metering pump 5 Rectification tower 6 Condenser 7 High boiling point discharge line 8 Chain transfer agent supply line 9 Countercurrent contact tower 10 Nitrogen supply Line 11 Buffer tank 12 Free radical generator supply line 13 Filter 14 Complete mixing type reactor 15 Dispense pump 16 Polymer heating plate 17 Devolatilization tank 18 Condenser 19 Recovered volatile liquid sending line 20 Vacuum pump 21 Polymer extrusion die 22 Strand bath 23 Strand cutter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08F 220/14 C08F 220/14 // (C08F 220/14 220: 10) F-term (Reference) 4J011 AA04 AA05 AB02 AB05 AB08 BA01 BA06 BB01 BB04 HA03 HA10 HB02 HB05 HB06 HB10 HB12 HB22 4J015 AA01 BA03 4J100 AL03P AL03Q CA04 DA01 FA03 FA04 FA19 FA28 FA30 FA37 FA39 FA41 GB05 GD01

Claims (3)

[Claims] 1. A methyl methacrylate monomer, an alkyl acrylate monomer having an alkyl group having 1 to 8 carbon atoms and a non-polymerizable solvent are each represented by the following formula: 0.70 ≦ A / (A + B) ≦ 0.998 0.001 <C / (A + B + C) <0.05 (where A is the weight part of the methyl methacrylate monomer, B is the weight part of the alkyl acrylate monomer, C is the non-polymerizable solvent ), A free radical generator having a half-life in the reactor of 5.55 x 10 ^{-5 to} 0.12 hours, and a chain transfer agent are continuously fed into the reactor. While supplying and keeping the inside of the reactor at 130 to 170 ° C. while stirring and mixing uniformly, the average residence time of the reaction solution in the reactor is 0.5 to 1.9 hours, the half-life of the free radical generator and the reactor The ratio of the average residence time of the reaction solution in the mixture is from 5.0 × 10 ^{−4 to} 0.
50, the polymer concentration (weight fraction) in the reactor is 0.40 to
0.70, the ratio of the concentration of the generated free radicals (mol · g ⁻¹ ) of the free radical generator in the whole supply liquid to the polymer concentration (weight fraction) of the polymerization liquid in the reactor was 0.5 × 10 ^{-6 to} 3.0 x ^10-6 m
ol · g ⁻¹ , and the number average molecular weight of the polymer is 2.5 × 1
Methacrylic acid characterized in that the polymerization reaction is controlled continuously within the range of 0 ^{4 to} 12.0 × 10 ⁴ , the polymerization reaction is continuously performed, the reaction liquid is continuously discharged from the reactor, and then the mixture is heated and devolatilized under reduced pressure. A method for producing a polymer. 2. Methyl methacrylate used for the feed liquid,
Acrylic ester and non-polymerizable solvent are purified by distillation,
2. The method for producing a methacrylic polymer according to claim 1, wherein the solid foreign matter is removed by passing a dissolved oxygen content in the supply liquid of 1 ppm or less and passing through a filter having a transmission particle size of 2 μm or less. . 3. The method for producing a methacrylic polymer according to claim 1, wherein the non-polymerizable solvent is at least one solvent selected from ethylbenzene, toluene, o-xylene, m-xylene, and p-xylene. .