JP3901700B2 - Method for producing methacrylic resin - Google Patents

Description

  The present invention relates to a method for producing a methacrylic resin. More specifically, the present invention relates to a method for producing a methacrylic resin having excellent thermal decomposition resistance.

  Methacrylic resin has excellent transparency, weather resistance, and mechanical strength, and is widely used in various fields as various molding materials such as building materials, furniture, interior decoration materials, automobile parts, and electrical parts. Conventionally, a suspension polymerization method is generally employed as a method for producing a methacrylic resin used as a molding material. However, this method has a high purity because a secondary material such as a suspension dispersant used is mixed in the polymer. Polymers are difficult to obtain and are not suitable for applications such as optical materials. Furthermore, the post-treatment process of the polymer is complicated with filtration, washing, and drying, and also involves a large amount of waste water treatment, leaving problems as an industrial process.

In recent years, continuous bulk polymerization methods and solution polymerization methods have attracted attention as methods for improving the disadvantages of this suspension polymerization method. According to these methods, since a suspension dispersant or the like is not used, it is possible to produce a high-quality resin having excellent optical characteristics.
However, since the former method is an automatic acceleration effect called "gel effect", it is very difficult to stably control the polymerization reaction while maintaining a high monomer conversion rate, and it is difficult to obtain a final polymer having a high polymer concentration. It is difficult.

  There has been proposed a continuous bulk polymerization method in which a homogeneous reaction is carried out at a relatively low monomer conversion rate using a tank reactor, and unreacted monomers are continuously separated and removed (see Patent Document 1). In this method, a large amount of unreacted monomer remains, and a large amount of energy must be spent in the devolatilization process for recovery and reuse and concentration of the polymer. There is a drawback that it is easy to cause. According to the solution polymerization method using benzene or alkylbenzene as the solvent, the viscosity of the reaction solution is reduced by the solvent, so that it is known that the gel effect is suppressed and a stable polymerization reaction is possible at a high monomer conversion rate. (See Patent Document 2).

  In such a solution polymerization method, there is a limit in reducing the amount of solvent used, and even if the monomer conversion rate is increased and the amount of unreacted monomer remaining in the reaction solution is reduced, the volatile content including the solvent is reduced. In addition, the energy consumed for removing the volatile components may not be different from the bulk polymerization method, and in addition, there are problems such as a decrease in the thermal decomposition resistance of the polymer and a complicated method for recovering and reusing the solvent and monomer components. Also have. On the other hand, a method of performing radical polymerization of a monomer mixture containing methyl methacrylate as a main component using an aliphatic monohydric alcohol such as methanol as a solvent and precipitating the obtained polymer into a slurry and separating it is shown. Slurry when 80 to 30 parts of solvent and a large amount of solvent are used for 20 to 70 parts of monomer component, cooling, precipitation, filtration and drying steps are required to separate the polymer, and a continuous process is used. There are also many problems that must be solved industrially, such as the need to uniformly transfer and process the polymer solution (see Patent Document 3).

  Then, according to this method, when a methacrylic resin having a molecular weight suitable for a molding material is produced, it has been found by experiments of the present inventors that only a polymer having extremely low heat decomposability can be obtained (see Comparative Example 2). In addition, a method of performing solution polymerization of a monomer mixture containing methyl methacrylate as a main component by using a mixed solvent composed of monovalent alkyl alcohol and benzene or alkylbenzene in an amount of 5% by weight to less than 30% by weight is shown. These alkyl alcohols occupy only 5 to 50% by weight in the mixed solvent, and do not drastically change the method using general benzene or alkylbenzene as a solvent (see Patent Document 4).

  The present inventors have solved the above-mentioned problems of the conventional method, and as a method for producing a methacrylic resin economically and advantageously through a stably controlled polymerization reaction (Japanese Patent Application No. 5-279611). ) Disclosed a continuous solution polymerization method in which 5-29% by weight of methanol was added. According to this method, since the polymer concentration at which the gel effect appears can be increased, the polymerization can be stabilized. By the way, in general, methacrylic resin starts to decompose around 230 ° C., and is particularly noticeable around 270 ° C. This thermal decomposition is due to the fact that the carbon-carbon single bond adjacent to the double bond remaining at the polymer terminal is thermally weak and is cleaved at around 230 to 270 ° C. to become the starting point of so-called zipper decomposition (non- (See Patent Document 1).

  On the other hand, the methacrylic resin is injection-molded or extruded at 230 ° C. to 250 ° C. Since the methacrylic resin molded at this time is close to the thermal decomposition temperature, some of the monomer thermally decomposed from the polymer remains in the molded product, causing silver streaks and foaming, coloring, and heat-resistant deformation. The work environment has deteriorated due to reduction and odor, which is a practical problem. Various attempts have been made so far to improve the thermal decomposition resistance of methacrylic resins. For example, an attempt has been made to heat-mold by adding an antioxidant at an early stage, but it has not only a sufficient effect but also a disadvantage of coloring.

In recent years, it has been shown that the thermal decomposition resistance is improved by producing a methacrylic resin by a continuous polymerization method. For example, in Patent Document 1 described above, in carrying out one-stage complete mixing type continuous polymerization at a temperature of 130 to 160 ° C., a mercaptan concentration of 0.01 to 1.0 mol% as a chain transfer agent and the following formula
10 ≧ A ^1/2・ B ^-1/2 × 10 ³
3 ≧ A ・ B × 10 ⁵
2.9 ≧ A ⁻¹ · (B + 10.3) × 10 ⁻⁶
Where A = number of moles of radical polymerization initiator in 100 g of monomer feed
B = half-life (time) of polymerization temperature of radical polymerization initiator
A monomer composition that satisfies the above conditions is continuously fed to maintain a monomer conversion rate of 50 to 78%, and a half-life at a polymerization temperature of 130 to 160 ° C. is zero when performing a one-stage fully mixed continuous polymerization. Using an initiator of .5 to 2 minutes, setting the average residence time so that the ratio between the half-life of the radical initiator at the polymerization temperature and the average residence time is 1/200 to 1/10000, the monomer conversion rate is A method of 45 to 70% is disclosed (see Patent Document 5).

  In any of these techniques, the thermal decomposition resistance in question is evaluated for a polymer that has been subjected to a vacuum devolatilization process or an extrusion process in which residual volatile components such as unreacted monomers are removed at a high temperature. According to the study by the present inventors, the thermal decomposition resistance of the polymer itself produced in the polymerization process is not always sufficient. Considering yield reduction due to thermal decomposition in the devolatilization process and extrusion molding process, coloring due to thermal history, etc., it is extremely important to improve the thermal decomposition resistance of the polymer produced in the polymerization process.

  Furthermore, in the continuous polymerization method of methacrylic resin, there is a description that a methacrylic resin having a thermal decomposition index α of 3.0 or less has good thermal decomposition resistance (see Patent Document 6). However, although the definition of the thermal decomposition index α is shown, there is no mention of the production conditions of the methacrylic resin having the thermal decomposition index α of 3.0 or less. A specific method of the multi-stage complete mixing tank type continuous polymerization method, although it is described that the quality such as the thermal stability of the produced polymer is improved by split-feeding a part of a comonomer such as methyl acrylate or ethyl acrylate or a chain transfer agent. No examples are described (see Patent Document 7).

In the above-mentioned Japanese Patent Application No. 5-279661, the present inventors can stabilize the polymerization because the polymer concentration at which the gel effect is exhibited can be increased by the continuous solution polymerization method in which 5-29% by weight of methanol is added. However, the thermal decomposition resistance of the resulting polymer was not always satisfactory. The above-described prior art does not necessarily provide a method for producing a methacrylic resin having excellent thermal decomposition resistance even if the polymerization reaction operation stability and production efficiency can be improved.
Japanese Patent Publication No.52-32665 Japanese Patent Publication No.55-7845 JP-A-62-241905 Japanese Patent Laid-Open No. 1-201307 Japanese Patent Laid-Open No. 3-111408 JP-A-6-239938 JP-A-1-172401 Oak, Inabe, Brown, Kitayama, Masuda, Macromolecules, 19, 2160 (1986) (T. Kashiwagi, A. Inaba, E. Brown, K. Hatada, T. Kitayama, E. Masuda, Macromolecules)

      An object of the present invention is to solve the above-mentioned problems and to provide a method for producing a methacrylic resin excellent in heat-resistant decomposability with less generation of silver streaks, foaming, coloring, odor and the like during thermoforming.

  As a result of intensive studies, the present inventors have determined that in continuous solution polymerization, the half-life and concentration of a specific radical polymerization initiator, the chain transfer agent concentration, the monomer concentration and the solvent concentration, the polymerization temperature, and the average residence time. It was found that the above-mentioned problems can be solved by reacting, and the present invention was completed.

That is, the present invention
Using a single-stage complete mixing tank (hereinafter sometimes referred to as “Method A”), methyl methacrylate alone, or at least one selected from methyl methacrylate 75% by weight and methyl acrylate, ethyl acrylate or butyl acrylate is 25% by weight. % Of a monomer mixture 71 to 95% by weight and a solvent 29 to 5% by weight,
(1) A radical polymerization initiator having a half-life of 0.05 to 20 minutes at a polymerization temperature of 90 to 180 ° C. is used, and the average residence time is 5 to 7000 times the half-life of the radical polymerization initiator. Prepared,
(2) The radical polymerization initiator concentration with respect to the composition is 1.0 × 10 ^{−4 to} 0.16 mol / liter, and the chain transfer agent concentration is 1.0 × 10 ^{−4 to} 0.37 mol / liter. Prepared to
(3) Further, the reaction composition is continuously polymerized while maintaining a monomer conversion rate of 40 to 90%, and the thermal decomposition rate of the polymer obtained by the polymerization reaction (after completion of the polymerization reaction, devolatilization step or extrusion molding step) Production of a methacrylic resin characterized in that the polymer before heating is heated in a nitrogen stream from 30 ° C. to 300 ° C. at a rate of 2 ° C./min. Method

Using a two-stage serially coupled complete mixing tank (hereinafter also referred to as “Method B”), methyl methacrylate alone, or at least one selected from methyl methacrylate, 75 wt% or more and methyl acrylate, ethyl acrylate or butyl acrylate A mixture consisting of 71 to 95% by weight of a monomer mixture and 25 to 5% by weight of a solvent and 29 to 5% by weight of a solvent.
(1) Using a radical polymerization initiator having a half-life of 0.05 to 20 minutes at a first tank polymerization temperature of 100 to 170 ° C and a second tank polymerization temperature of 130 to 170 ° C,
(2) And the average residence time is set to be 5 to 7000 times the half-life of the radical polymerization initiator,
(3) The radical polymerization initiator concentration for the composition is 5.0 × 10 ^{−5 to} 0.12 mol / liter, and the chain transfer agent concentration is 1.0 × 10 ^{−4 to} 0.1 mol / liter. Prepared to
(4) The reaction composition is continuously polymerized while maintaining the second tank monomer conversion rate of 70 to 90%, and the thermal decomposition rate of the polymer obtained by the polymerization reaction (after completion of the polymerization reaction, devolatilization step) And the polymer before being subjected to the extrusion molding step is heated to 30 ° C. to 300 ° C. at a rate of 2 ° C./min. Method for producing methacrylic resin and

Using a complete mixing tank of the first stage reactor connected in series in two stages and a plug flow reactor of the second stage reactor (hereinafter also referred to as method C), methacrylate alone or methacrylate A mixture comprising 71 to 95% by weight of a monomer mixture of 75% by weight or more and at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate being 25% by weight or less and 29 to 5% by weight of a solvent,
(1) The polymerization temperature is 100 to 170 ° C. in the first stage complete mixing tank 100 to 170 ° C. in the second stage plug flow reactor 100 to 170 ° C.
(2) The average residence time in the first stage complete mixing tank is 5 to 7000 times the half life of the initiator at the polymerization temperature, and the residence time in the second stage plug flow reactor is 5 to 50 times the half life of the initiator. Set to be
(3) Radical polymerization initiator concentration with respect to the composition of 1.0 × 10 ^{−4 to} 0.16 mol / liter,
(4) and the reaction composition prepared so as to have a chain transfer agent concentration of 1.0 × 10 ^{−4 to} 0.1 mol / liter, (5) the monomer conversion rate at the outlet of the second-stage plug flow reactor While maintaining at 70 to 90%, the polymer is continuously polymerized, and the thermal decomposition rate of the polymer obtained by the polymerization reaction (after the completion of the polymerization reaction, the polymer before passing through the devolatilization step and the extrusion step, in a nitrogen stream, 30 It is an invention relating to a method for producing a methacrylic resin, characterized in that the thermal decomposition rate when heated from 2 ° C. to 300 ° C. at a rate of 2 ° C./min is 5% by weight or less.

  According to the present invention, a single-stage complete mixing tank type continuous polymerization method (Method A), a complete mixing tank type continuous polymerization method (Method B) connected in series in two stages, a complete mixing tank and a plug flow reactor In a continuous polymerization method (Method C) coupled in series, by reacting under the conditions of half-life and concentration of a specific radical polymerization initiator, chain transfer agent concentration, monomer concentration and solvent concentration, polymerization temperature, and average residence time. A methacrylic resin having excellent heat decomposability can be produced immediately after the polymerization step, that is, the polymer before passing through the vacuum devolatilization step and the extrusion molding step.

(A) Method A According to the case of using a one-stage complete mixing tank (Method A), methyl methacrylate alone, or at least 75% by weight of methyl methacrylate and at least selected from methyl acrylate, ethyl acrylate or butyl acrylate A raw material composition comprising a mixture of 71 to 95% by weight of a monomer mixture of not less than 25% by weight and 29 to 5% by weight of a solvent, a radical polymerization initiator and a chain transfer agent, and a radical polymerization initiator in the composition The concentration was adjusted to 1.0 × 10 ^{−4 to} 0.16 mol / liter and the chain transfer agent concentration was 1.0 × 10 ^{−4 to} 0.37 mol / liter, and the polymerization temperature was 90 to 180 ° C. Use a radical polymerization initiator having a half-life of 0.05 to 20 minutes at the polymerization temperature and 5 to 7000 times the half-life The polymer is continuously polymerized while maintaining a monomer conversion rate of 40 to 90% at an average residence time, so that the polymer before the devolatilization step and the extrusion step is generated in the polymerization step. A methacrylic resin having a thermal decomposition rate of 5% by weight or less when heated at a rate of 2 ° C./min from 30 ° C. to 300 ° C. can be produced.

  Among the conditions in the method A, particularly preferable conditions satisfy the following expressions (1) to (3).

Formula (1)
7.0 × 10 ⁷ ≦ [C ² (τ + θ) e ^{4529 / T} ] / (I · θ ² ) ≦ 3.0 × 10 ⁹
Formula (2)
100 ≤ M / (D + E + F) ≤ 40000
Formula (3)
4.0 × 10 ^-7 ≦ (I ・ G) / [M ・ θ / (τ + θ)] ≦ 1.0 × 10 ^-4

  Where C is the monomer conversion (%), τ is the half-life of the radical polymerization initiator (min), θ is the average residence time (min), T is the polymerization temperature (absolute temperature), and I is the radical polymerization start to be fed Agent concentration (mol / liter), M represents the monomer concentration (mol / liter) to be fed. D, E, F, and G are defined by the following equations, respectively.

D = (7.75 × 10 ³ e ^{−3674 / T}・ X) / [ ¹⁰⁰⁺ (7.75 × 10 ³・ e ^{−3674 / T} −1) C]
E = (423e− ^{6021 / T} · S) / [ ¹⁰⁰⁺ (423e− ^{6021 / T} −1) · C]
F = (1.13 × 10 ⁻⁴ e ^{4529 / T} · C) / [θ · (100−C) ² ]
G = 2.0 × 10 ⁻³ · H ² −8.5 × 10 ⁻² · H + 1

  Here, X represents the chain transfer agent concentration (mol / liter) to be fed, S represents the solvent concentration (mol / liter) to be fed, and H is a constant derived from the monomer conversion and the acrylate concentration in the feed monomer. It is defined by the following formula.

H = m · (3.7 × 10 ⁻³ · C + 0.63)
(M is the acrylate concentration in the feed monomer (mol%))
The heat decomposability referred to in the present invention means that a polymer that has not been subjected to a heat history before passing through a devolatilization step or an extrusion step obtained in a polymerization tank is 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream. It is represented by the thermal decomposition rate when the temperature is raised by heating. In the present invention, the thermal decomposition rate is 5% or less, preferably 3% or less, more preferably 2% or less. When the thermal decomposition rate exceeds 5%, molding defects such as silver streaks and voids occur during molding.

In the method A of the present invention, as described above, the monomer component used is a monomer mixture composed of methyl methacrylate alone or methyl methacrylate 75% by weight or more and methyl acrylate, ethyl acrylate or butyl acrylate 25% by weight or less.
Examples of the solvent used in the present invention include toluene, methanol, acetone, ethyl acetate, and the like. Particularly, the use of methanol is particularly desirable in consideration of the treatment after the polymerization reaction. The use ratio of the solvent is 29 to 5% by weight of the solvent with respect to 71 to 95% by weight of the monomer or the monomer mixture.

  When the solvent concentration is less than 5% by weight, a remarkable autoaccelerating effect in radical polymerization of methyl methacrylate, that is, an abnormal acceleration phenomenon of the polymerization rate due to an increase in the viscosity of the system tends to occur, and the polymerization cannot be stably maintained. On the other hand, when the solvent concentration exceeds 29% by weight, the molecular weight range that can be set is narrowed, and the production rate of the polymer having terminal double bonds that are easily thermally decomposed is increased, so that the polymer having excellent thermal decomposition resistance is produced. Setting range is extremely narrow.

  Examples of the polymerization initiator include di-t-butyl percarbonate, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxydineodecanoate, t-butyl peroxypivalate, 3 , 5,5-trimethylhexanoyl peroxide, lauroyl peroxide, acetyl peroxide, t-butylperoxy (2-ethylhexanoate), t-butylperoxyisobutyrate, t-butylperoxyisopropyl carbonate, organic peroxides such as t-butyl peroxybenzoate, di-t-amyl peroxide, di-t-butyl peroxide, or 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl Relonitrile), 2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis Examples include azo compounds such as isobutyrate and 1,1′-azobis (1-cyclohexanecarbonitrile), and these can be used alone or in combination of two or more.

In Method A, the concentration of the radical polymerization initiator in the raw material composition is in the range of 1.0 × 10 ^{−4 to} 0.16 mol / liter, preferably 1.0 × 10 ^{−4 to} 0.10 mol / liter. It is. When the radical polymerization initiator concentration is less than 1.0 × 10 ⁻⁴ mol / liter, an industrially advantageous monomer conversion cannot be achieved, and the production efficiency is lowered. When the radical polymerization initiator concentration exceeds 0.16 mol / liter, high monomer conversion can be achieved, but the molecular weight range that can be set is narrowed, and the content of the polymer having terminal double bonds in the produced polymer is extremely It becomes larger and the thermal decomposition resistance is remarkably lowered. In addition, the use of a large amount of polymerization initiator causes a problem in the transparency of the product polymer.

It can be found from data such as “Organic Peroxide” 13th Edition and “Azo Polymerization Initiators”.
As the chain transfer agent, t-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and the like used in usual radical polymerization can be used.
In Method A, the chain transfer agent concentration in the raw material composition is in the range of 1.0 × 10 ^{−4 to} 0.37 mol / liter. When the chain transfer agent concentration is less than 1.0 × 10 ⁻⁴ mol / liter, the content of the polymer having a terminal double bond in the produced polymer becomes extremely large, and the thermal decomposition resistance is lowered.
On the other hand, when the chain transfer agent concentration exceeds 0.37 mol / liter, the molecular weight of the produced polymer becomes small, and mechanical properties that can withstand use as a molding material cannot be obtained.

The polymerization initiator and the chain transfer agent may be supplied to the polymerization tank individually so as to have a desired concentration with respect to the raw material composition to be fed. It is desirable to supply continuously after dissolving.
The polymerization temperature in Method A is 90 to 180 ° C, preferably 100 to 170 ° C, more preferably 110 to 170 ° C. When the polymerization temperature is too low, a thermally weak head-head bond that breaks at 200 ° C. or less remains in the polymer chain formed (K. Hatada, T. Kitayama, E. Masuda). , Polymer Journal, Vol. 1, No. 5,395 (1986) and the aforementioned, Macromolecules, 19, 2160 (1986)). On the other hand, when the polymerization temperature is too high, oligomers that are considered to color the polymer are remarkably produced (Fumio Ide, Polymer, Vol. 27, November, 819 (1978)).

  In Method A, the average residence time is set to 5 to 7000 times the half-life of the polymerization initiator at the polymerization temperature. If the average residence time is less than 5 times the half-life of the polymerization initiator, a large amount of polymerization initiator is required despite the low monomer conversion rate, and the transparency of the product polymer is impaired. On the other hand, if it exceeds 7000 times, the polymerization reaction tank becomes too large, which is industrially disadvantageous. In Method A, the polymerization is continuously carried out while maintaining the monomer conversion rate at 40 to 90%, preferably 40 to 80%, more preferably 50 to 80%. When the monomer conversion is less than 40%, the polymer yield per unit time is small, which is industrially disadvantageous. On the other hand, if it exceeds 90%, the content of the polymer having a terminal double bond in the produced polymer increases rapidly, and the thermal decomposition resistance is remarkably lowered.

(B) Method B Next, when the present invention is carried out using a complete mixing tank connected in series in two stages (Method B), the concentration of the radical polymerization initiator in the composition is changed as described above. 5.0 × 10 ^{−5 to} 0.12 mol / liter and the chain transfer agent concentration is adjusted to 1.0 × 10 ^{−4 to} 0.1 mol / liter. The first tank polymerization temperature is 90 to 170 ° C., the second tank polymerization temperature is 130 to 180 ° C., and a radical polymerization initiator having a half life of 0.05 to 20 minutes at the polymerization temperature is used. It is produced in the polymerization step by continuously polymerizing the monomer while maintaining the monomer conversion rate in the second tank at 40 to 90% at an average residence time of ˜7000 times. The polymer before passing through the extrusion process is placed in a nitrogen stream. It is possible to produce a methacrylic resin having a heat decomposability having a thermal decomposition rate of 5% by weight or less when heated from 0 ° C. to 300 ° C. at a rate of 2 ° C./min.

  Among the conditions in the method B, particularly preferable conditions satisfy the following expressions (4) to (6).

Formula (4)
7.0 × 10 ⁷ ≦ [(C ₂ −C ₁ ) ²・ (τ ₁ + θ ₁ ) ・ (τ ₂ + θ ₂ ) e ^{4529 / T} ] / (
I ・ τ ₁・ θ ₂ ² ) ≦ 1.0 × 10 ¹⁰
Formula (5)
100 ≦ M / (D ′ + E ′ + F ′) ≦ 40000
Formula (6)
4 × 10 ^-7 ≦ (I ・ G ′ ・ θ ₁ ) / [M ・ (τ ₁ + θ ₁ )] ≦ 1.0 × 10 ^-4

  Where Ci (i = 1 or 2) is the monomer conversion rate (%) in the i-th tank, τ i is the half-life (min) of the radical polymerization initiator in the i-th tank, and θ i is the average residence time in the i-th tank ( Min), T represents the polymerization temperature (absolute temperature) of the first tank, I represents the concentration of the radical polymerization initiator fed (mol / liter), and M represents the concentration of the monomer fed (mol / liter).

D ′, E ′, F ′ and G ′ are defined by the following equations, respectively.
D ′ = (7.75 × 10 ³ e ^{−3674 / T} · X) / [100+ (7.75 × 10 ³ e ^{−3674 / T} −1) C ₁ ]
E ′ = (423e− ^{6021 / T} · S) / [100+ (423e− ^{6021 / T} −1) · C ₁ ]
F ′ = (1.13 × 10 ⁻⁴ e ^{4529 / T} · C ₁ ) / [θ ₁ · (100 −C ₁ ) ² ]
G ′ = 2.0 × 10 ⁻³ · H ₁ ² −8.5 × 10 ⁻² · H ₁ +1

Here, X represents the chain transfer agent concentration to be fed (mol / liter), S represents the solvent concentration to be fed (mol / liter), and H1 represents the monomer conversion rate in the first tank and the acrylate concentration in the feed monomer. It is a derived constant and is defined by the following equation.
H1 = m · (3.7 × 10 ^-3 · C ₁ +0.63)
(M is the acrylate concentration in the feed monomer (mol%))
In Method B, the monomer mixture in the raw material composition is supplied to the first tank, but a part of the monomer mixture can be side-fed to the second tank. In that case, the composition of the monomer mixture supplied to the 1st and 2nd tanks does not necessarily need to match. It supplies so that the acrylate unit density | concentration in the polymer which flows out out of a 2nd tank may become a desired density | concentration. The side feed amount is preferably 1/50 to 1/5 of the main feed amount.

In Method B, the concentration of the radical polymerization initiator in the raw material composition is 5.0 × 10 ^{−5 to} 0.12 mol / liter, preferably 5.0 × 10 ^{−5 to} 0.10 mol / liter. Range. When the radical polymerization initiator concentration is less than 5.0 × 10 −5 mol / liter, an industrially advantageous monomer conversion cannot be achieved, and the production efficiency is lowered. When the radical polymerization initiator concentration exceeds 0.12 mol / liter, a high monomer conversion can be achieved, but the molecular weight range that can be set is narrowed, and the content of the polymer having a terminal double bond in the produced polymer is extremely low. It becomes larger and the thermal decomposition resistance is remarkably lowered. In addition, the use of a large amount of polymerization initiator causes a problem in the transparency of the product polymer.

In the method B, the chain transfer agent concentration in the raw material composition is 1.0 × 10 ^{−4 to} 0.10 mol / liter, preferably 2.0 × 10 ^{−3 to} 0.06 mol / liter. The range is in liters. When the chain transfer agent concentration is less than 1.0 × 10 ⁻⁴ mol / liter, the content of the polymer having a terminal double bond in the produced polymer becomes extremely large, and the thermal decomposition resistance is lowered. On the other hand, if it exceeds 0.10 mol / liter, the molecular weight of the produced polymer becomes small, and sufficient mechanical properties cannot be obtained.
The polymerization initiator and the chain transfer agent may be supplied to the polymerization tank individually so as to have a desired concentration with respect to the raw material composition to be fed. It is desirable to supply continuously after dissolving.

A part of the chain transfer agent can also be side-fed into the second tank. It is desirable to supply the polymers generated from the first tank and the second tank so that their molecular weights are as equal as possible. The polymerization temperature in Method B is 90 to 170 ° C. in the first tank, preferably 100 to 170 ° C., more preferably 110 to 170 ° C., 120 to 180 ° C., preferably 120 to 170 ° C., more preferably 130 in the second tank. ~ 170 ° C. It is not always necessary to match the first tank and the second tank. If the polymerization temperature is too low, there is a possibility that a very weak head-to-head bond thermally broken at 200 ° C. or lower may remain in the polymer chain formed (Polymer Journal, Vol. 1, No. 5). , 395 (1986) and Macromolecules, 19, 2160 (1986)).
On the other hand, when the polymerization temperature is too high, oligomers that are considered to color the polymer are remarkably produced (the above-mentioned polymer, 27, November, 819 (1978)). On the other hand, when the polymerization temperature in the second tank is less than 120 ° C., the viscosity of the reaction solution becomes high, and sufficient stirring cannot be performed.

In Method B, the average residence time is set to 5 to 7000 times the half-life of the polymerization initiator at the polymerization temperature, but it is not always necessary to match the first tank and the second tank. If the average residence time is less than 5 times the half-life of the polymerization initiator, a large amount of polymerization initiator is required to obtain the desired monomer conversion, and the transparency of the product polymer is impaired. On the other hand, if it exceeds 7000 times, the polymerization reaction tank becomes too large, which is industrially disadvantageous.
In Method B, the polymerization is continuously carried out while maintaining the monomer conversion rate in the second tank at 70 to 90%, preferably 70 to 80%. When the monomer conversion rate in the second tank is less than 70%, the polymer yield per unit time becomes small and the advantage of using two reaction tanks is lost. On the other hand, when the monomer conversion rate in the second tank exceeds 90%, the content of the polymer having a terminal double bond in the produced polymer increases rapidly, and the thermal decomposition resistance is remarkably lowered.

(C) Method C Further, when the method of the present invention is carried out using a complete mixing tank of a first stage reactor and a plug flow reactor of a second stage reactor connected in series in two stages (Method C) ), The above-mentioned raw material composition, the radical polymerization initiator concentration in the composition is 1.0 × 10 ^{−4 to} 0.16 mol / liter and the chain transfer agent concentration is 1.0 × 10 ^{−4 to} 0. In the complete mixing tank of the first stage reactor and the plug flow type reactor of the second stage reactor which are prepared to be 1 mol / liter and are connected in series in two stages, the complete mixing which is the first stage reactor Polymerization temperature 90 to 180 ° C. in the tank, average residence time in the complete mixing tank 5 to 7000 times the polymerization initiator half-life in the polymerization time, polymerization start in the plug flow reactor at the polymerization temperature So that the half-life of the agent is 5 to 50 times. By continuously polymerizing the monomer while maintaining the monomer conversion rate at 70 to 90% at the outlet of the raw reactor, the polymer before the devolatilization step and the extrusion step is generated in the polymerization step. A methacrylic resin having a heat decomposability having a thermal decomposition rate of 5% by weight or less when heated at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream can be produced.

Of the conditions in Method C above, particularly preferred conditions are those that satisfy the following formulas (7) to (9):
7.0 × 10 ⁷ ≦ [C ² (τ + θ) e ^{4529 / T} ] / (I · θ ² ) ≦ 3.0 × 10 ⁹
Formula (8)
100 ≤ M / (D + E + F) ≤ 40000
Formula (9)
4.0 × 10 ^-7 ≦ (I ・ G ・ θ) / [M ・ (τ + θ)] ≦ 1.0 × 10 ^-4

  Where C is the monomer conversion rate (%) in the first stage complete mixing tank, τ is the half-life (minutes) of the radical polymerization initiator in the first stage complete mixing tank, and θ is the average residence time in the first stage complete mixing tank. Time (minutes), T is the polymerization temperature (absolute temperature) of the first stage complete mixing tank, I is the concentration of the feed radical polymerization initiator (mol / liter), and M is the concentration of the feed monomer (mol / liter).

D, E, F, and G are defined by the following equations, respectively.
D = (7.75 × 10 ³ e ^{−3674 / T} · X) / [100+ (7.75 × 10 ³ e ^{−3674 / T} −1) C]
E = (423e− ^{6021 / T} · S) / [ ¹⁰⁰⁺ (423e− ^{6021 / T} −1) · C]
F = (1.13 × 10 ⁻⁴ e ^{4529 / T} · C) / [θ · (100−C) ² ]
G = 2.0 × 10 ⁻³ · H ² −8.5 × 10 ⁻² · H + 1

Here, X represents the chain transfer agent concentration (mol / liter) to be fed, S represents the solvent concentration (mol / liter) to be fed, and H is a constant derived from the monomer conversion and the acrylate concentration in the feed monomer. It is defined by the following formula.
H = m · (3.7 × 10 ^-3 · C + 0.63)
(M is the acrylate concentration (mol%) in the feed monomer)

In Method C, the entire amount of monomer or monomer mixture as a raw material is usually supplied to the first-stage complete mixing tank, but a part of the monomer or monomer mixture is introduced into the second-stage plug flow reactor and / or in the middle. You can also feed.
At that time, the composition of the monomer mixture supplied to the first stage and the second stage is not necessarily matched. It supplies so that the acrylate unit density | concentration in the polymer flowing out from a 2nd stage may become a desired density | concentration. The side feed amount is preferably 1/50 to 1/5 of the main feed amount. In Method C, the radical polymerization initiator concentration in the raw material composition is 1.0 × 10 ^{−4 to} 0.16 mol / liter, preferably 1.0 × 10 ^{−4 to} 0.12 mol / liter. Range. When the radical polymerization initiator concentration is less than 1.0 × 10 ⁻⁴ mol / liter, the monomer conversion rate in the first stage complete mixing tank is low, and as a result, the polymer produced in the second stage plug flow reactor Increases the molecular weight distribution.

On the other hand, if it exceeds 0.16 mol / liter, a high monomer conversion can be achieved, but the molecular weight range that can be set is narrowed, and the content of the polymer having a terminal double bond in the resulting polymer becomes extremely large, Thermal decomposition resistance is significantly reduced. In addition, the use of a large amount of polymerization initiator causes a problem in the transparency of the product polymer. In the method C, the chain transfer agent concentration in the raw material composition is 1.0 × 10 ^{−4 to} 0.1 mol / liter, preferably 1.6 × 10 ^{−3 to} 0.1 mol / liter. The range is in liters. When the chain transfer agent concentration is less than 1.0 × 10 ⁻⁴ mol / liter, the content of the polymer having a terminal double bond in the produced polymer becomes extremely large, so that the thermal decomposition resistance is remarkably lowered. . On the other hand, if it exceeds 0.1 mol / liter, the molecular weight of the produced polymer becomes small, and sufficient mechanical properties cannot be obtained. A part of the chain transfer agent can also be side-fed to the second stage plug flow reactor inlet and / or in the middle. It is desirable to supply the polymer so that the molecular weights of the polymer flowing out from the first stage complete mixing tank outlet and the second stage plug flow reactor outlet are as equal as possible.

  In Method C, the polymerization temperature is 90 to 180 ° C, preferably 100 to 170 ° C, more preferably 110 to 170 ° C in the first stage complete mixing tank. It is 100-180 degreeC by a 2nd stage | paragraph plug flow type | mold reactor, Preferably it is 100-170 degreeC, More preferably, it is 110-170 degreeC. It is not always necessary to match the first and second stages. When the polymerization temperature is too low, there is a possibility that a very weak head-head bond thermally ruptured at 200 ° C. or less may remain in the produced polymer chain (described in Polymer Journal, Vol. 1, No. 5). , 395 (1986) and Macromolecules, 19, 2160 (1986)). On the other hand, when the polymerization temperature is too high, the formation of oligomers that are considered to color the polymer is remarkable (described above, Polymer, Vol. 27, November, 819 (1978)).

  In this method C, the average residence time of the first stage complete mixing tank is set to 5 to 7000 times the half-life of the polymerization initiator at the polymerization temperature. If the average residence time is less than 5 times the half-life of the polymerization initiator, a large amount of polymerization initiator is required to obtain the desired monomer conversion, and the transparency of the product polymer is impaired. On the other hand, if it exceeds 7000 times, the polymerization reaction tank becomes too large, which is industrially disadvantageous. The residence time of the second stage plug flow reactor is set to 5 to 50 times the initiator half-life at the polymerization temperature. When the residence time is less than 5 times the half-life of the polymerization initiator, the monomer conversion cannot be increased. On the other hand, if it exceeds 50 times, the plug flow reactor becomes too large, and the advantage of using two reactors becomes small.

  In Method C, the polymerization is continuously carried out so that the monomer conversion is 70 to 90% at the outlet of the second-stage plug flow reactor. When the monomer conversion rate at the outlet of the second-stage plug flow reactor is less than 70%, the polymer yield per unit time becomes small and the merit of using two reactors becomes small. On the other hand, in order for the monomer conversion rate in the second stage to exceed 90%, it is necessary to make the reactor extremely large, or to increase the polymerization temperature or the initiator concentration, resulting in many problems.

  In order to produce a methacrylic resin having excellent thermal decomposition resistance by the methods A, B and C, the above-mentioned conditions may be selected, but it is preferable to sufficiently remove oxygen in the reaction system ( The aforementioned polymer, 27, November, 819 (1978)).

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all. The physical properties of the polymer shown in this example were measured by the following method.
In the examples and comparative examples, “parts” represents “parts by weight”.
(1) The thermodegradability was measured by thermogravimetric analysis. Using an RTG220 type thermogravimetric analysis (TGA) apparatus manufactured by Seiko Denshi Kogyo Co., Ltd., about 5 mg of methacrylic resin is placed on a platinum pan, and a temperature of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream of 300 ml / min. The weight loss change was measured by heating at a heating rate.
(2) The monomer conversion was determined by measuring the unreacted monomer concentration in the reaction solution flowing out from the polymerization tank using GC-380 gas chromatography manufactured by GL Science.

(3) The molecular weight of the polymer was measured by Tosoh 8010 type gel permeation chromatography.
(4) The total light transmittance of the polymer was measured by a transmission method using a Z-Sensor Σ80NDH manufactured by Nippon Denshoku Industries Co., Ltd. Hereinafter, the first-stage complete mixing tank type continuous polymerization will be described in Reference Examples 1 to 5 and Comparative Examples 1 and 2. In Reference Examples 6 to 10 and Comparative Examples 3 to 4, two-stage serially coupled complete mixing tank type continuous polymerization was performed. In Examples 1 to 5 and Comparative Examples 5 to 6, a complete mixing tank and a plug flow reactor were used. The continuous polymerization performed by two-stage series connection will be described respectively.

Reference example 1
A reference example of single-stage complete mixing tank type continuous polymerization is shown.
Methyl methacrylate 88.3 parts (8.11 mol / liter), methyl acrylate 5.5 parts (0.69 mol / liter), methanol 6.2 parts (1.79 mol / liter), n-dodecyl mercaptan 0.7. 15 mol% (0.016 mol / liter), 2,2′-azobisisobutyronitrile was blended to a concentration of 4.2 × 10 −3 mol% (0.45 mmol / liter). The obtained composition was continuously fed to a 10 liter complete mixing tank equipped with a helical ribbon blade at 1 Kg / Hr for continuous polymerization. The amount of the reaction solution in the polymerization tank was 5 kg. Therefore, the average residence time was 5 hours. The jacket temperature was adjusted so that the polymerization temperature was 150 ° C. The monomer conversion was 61.5%, and the weight average molecular weight of the polymer was 85,000.

The reaction liquid is extracted from the bottom with a gear pump so that the liquid level in the polymerization tank is constant, heated to 270 ° C. with a heat exchanger, and then continuously introduced into a devolatilization tank whose pressure is adjusted to 10 torr and flushed. It was. The molten polymer from which volatile components had been removed was extracted as a strand from the bottom with a gear pump and cut into pellets (polymer P _H that had undergone a thermal history). Also, to obtain a polymer by precipitation purification from the reaction solution flowing out from a polymerization vessel (polymer P _P that is not subjected to thermal _history).

Monomer concentration used in Table 1, acrylate concentration in monomer, methanol concentration, polymerization initiator concentration, chain transfer agent concentration, half-life of polymerization initiator used, set average residence time, polymerization temperature, reached monomer conversion rate, The values obtained by substituting these into the equations (1) to (3) and the thermal decomposition rate of the resulting polymer measured by thermogravimetric analysis are shown. The results of examining the thermal decomposition resistance of the precipitated purified polymer (P _P ) before receiving the thermal history and the polymer (P _H ) receiving the thermal history after heating vacuum devolatilization are shown in FIGS. 1 and 2, respectively. In both cases, the substantial pyrolysis start temperature was 300 ° C. Thermal decomposition rate is 0.5% P _P, a 0.2% P _H, the polymerization step, the thermal decomposition resistance good polymer regardless devolatilization step was found to be obtained. A vacuum devolatilized polymer was used to form a 150 mmφ × 3 mm disc at 260 ° C. using an Aburg 45t injection molding machine, but no silver streaks or voids were observed. The total light transmittance was 93% and had excellent transparency.

Table 1

Raw material concentration (mol / liter)
Methyl methacrylate 8.11
Methyl acrylate 0.69
Methanol 1.79
n-dodecyl mercaptan 0.016
2,2′-Azobisisobutyronitrile 4.5 × 10 ⁻⁴
Polymerization initiator half-life τ (min) 0.06
Average residence time θ (min) 300
θ / τ 4910
Polymerization temperature (° C) 150
Ultimate monomer conversion (%) 61.5
Value of equation (1) 1.3 × 10 ⁹
(2) Value of formula 9.9 × 10 ³
(3) Expression value 2.0 × 10 ⁻⁵
Thermal decomposition rate of polymer before receiving thermal history (%) 0.5

Reference Examples 2-5
A one-stage complete mixing tank type continuous polymerization was carried out under various conditions in the same manner as in Reference Example 1. In any of the reference examples , the polymerization reaction was stably controlled, and a polymer having good thermal decomposition resistance was obtained. Table 2 shows the raw material composition, polymerization conditions, monomer conversion rate, and resin properties (weight average molecular weight, thermal decomposition rate).

Table 2
Reference example number 2 3 4 5
Raw material composition MMA (part) 82.9 71.0 83.9 82.8
(Mol / l) 7.54 6.20 7.72 7.35
Comonomer MA EA MA BA
Comonomers (parts) 3.8 6.8 6.3 7.0
(Mol / l) 0.46 0.80 0.78 0.85
Solvent CH ₃ OH CH ₃ OH CH ₃ OH CH ₃ OH
(Part) 13.3 22.2 3.6 3.6
(Mol / l) 3.81 6.25 1.00 1.02
Polymerization initiator AIBN DTAP DTAP DTBP
Polymerization initiator (10 ^-3 mol%) 1.3 9.8 10.5 3.8
(Mmol / liter) 0.2 1.3 1.0 0.4
Polymerization initiator half-life τ (min) 0.06 5.26 15.0 4.4
Chain transfer agent DM DM OM OM
Chain transfer agent (mol%) 0.13 0.03 0.14 0.13
(Mmol / liter) 15.4 4.0 13.0 12.0
Polymerization conditions Polymerization temperature (℃) 150 160 150 170
Average residence time θ (min) 390 250 330 300
θ / τ 6373 48 22 69
Monomer conversion (%) 52.0 70.7 70.0 62.6
Resin properties Weight average molecular weight (Mw x 10 ^-4 ) 7.8 9.0 8.9 8.1
Thermal decomposition rate (wt%) 0.6 1.4 1.4 0.5
Molded product characteristics
Occurrence of silver streak None None None None
Generation of voids None None None None
Total light transmittance (%) 93 93 93 93

Explanation of abbreviations in Table 2 (similar abbreviations are used in the following tables)
MMA: methyl methacrylate MA: methyl acrylate EA: ethyl acrylate BA: butyl acrylate AIBN: 2,2′-azobisisobutyronitrile DTAP: di-t-amyl peroxide DTBP: di-t-butyl peroxide DM: n -Dodecyl mercaptan OM: n-octyl mercaptan

Comparative Example 1
This is an example of a single-stage complete mixing tank type continuous polymerization.
4. Methyl methacrylate 50.1 parts (4.29 mol / liter), methyl acrylate 1.8 parts (0.21 mol / liter), methanol 48.1 parts (12.91 mol / liter), n-dodecyl mercaptan A composition 1.67 Kg / Hr composed of 7 × 10 −4 mol% (0.1 mmol / liter) and di-t-amyl peroxide 0.017 mol% (3.0 mmol / liter) was used as Reference Example 1 When continuous polymerization was carried out at an average residence time of 180 minutes (θ / τ = 4.0) and a polymerization temperature of 140 ° C. while continuously feeding to the same polymerization tank, the monomer conversion was 67.7% and the weight average molecular weight was The operation was maintained at 73,000. The monomer concentration used in Table 3, the acrylate concentration in the monomer, the methanol concentration, the polymerization initiator concentration, the chain transfer agent concentration, the half-life of the polymerization initiator used, the set average residence time, the polymerization temperature, the monomer conversion reached, The values obtained by substituting these into the equations (1) to (3) and the thermal decomposition rate of the resulting polymer measured by thermogravimetric analysis are shown.

As in Reference Example 1, the heat resistance of the polymer (P _P ) before receiving the heat history precipitated and purified from the reaction solution flowing out of the polymerization tank and the polymer (P _H ) receiving the heat history after vacuum devolatilization at 270 ° C. The results of examining the decomposability are shown in FIGS. 3 and 4, respectively. The thermal decomposition starting temperature was 250 ° C. for both the polymer flowing out from the polymerization tank (P _P ) and the polymer (P _H ) after vacuum devolatilization at 270 ° C. The decomposition rate of the polymer flowing out from the polymerization tank up to 300 ° C. was 9.0%.
A vacuum devolatilized polymer was used to form a 150 mmφ × 3 mm disk at 260 ° C. using an Aburg 45t injection molding machine, but silver streaks occurred and the total light transmittance was 91%.

Table 3

Raw material concentration (mol / liter)
Methyl methacrylate 4.29
Methyl acrylate 0.21
Methanol 12.9
n-dodecyl mercaptan 1.0 × 10 ⁻⁴
Di-t-amyl peroxide 0.003
Polymerization initiator half-life (minutes) 44.9
Average residence time (min) 180
Polymerization temperature (° C) 140
Achievable monomer conversion (%) 67.7
Value of equation (1) 6.7 × 10 ⁸
Value of formula (2) 1.9 × 10 ³
Value of equation (3) 2.8 × 10 ⁻⁴
Thermal decomposition rate of polymer before receiving thermal history (%) 9.0

Comparative Example 2
This is an example of a single-stage complete mixing tank type continuous polymerization.
Methyl methacrylate 44.8 parts (3.85 mol / liter), methyl acrylate 5.0 parts (0.50 mol / liter), methanol 50.2 parts (13.43 mol / liter), n-dodecyl mercaptan A composition consisting of 011 mol% (2.0 mmol / liter) and lauroyl peroxide 0.028 mol% (5.0 mmol / liter) was continuously fed to the polymerization tank and an average residence time of 300 minutes (θ / When continuous polymerization was performed at 90 ° C. at a polymerization temperature of τ = 6.7), stable operation could be maintained at a monomer conversion of 64.0% and a weight average molecular weight of 80,000. The thermal decomposition temperature of the polymer (P _P ) before receiving the thermal history precipitated and purified from the reaction solution flowing out of the polymerization tank and the polymer (P _H ) receiving the thermal history after devolatilization at 270 ° C. are both It was 250 ° C. The decomposition rate of the polymer (P _P ) flowing out from the polymerization tank to 300 ° C. was 12.6.

Reference Example 6
In conducting the complete mixing tank type continuous polymerization coupled in series in two stages, a 10 liter complete mixing tank with helical ribbon blades was used for both the first tank and the second tank. A composition comprising 84.6 parts of methyl methacrylate, 6.3 parts of methyl acrylate, 9.1 parts of methanol, 0.148 mol% of n-dodecyl mercaptan, and 0.006 mol% of di-t-amyl peroxide is added to the first tank. The eye is continuously fed at 1 Kg / Hr and extracted from the bottom with a gear pump so that the first tank liquid level is constant, and then flows into the second tank, and the liquid level in the second tank is constant. Was extracted from the bottom of the second tank with a gear pump. The amount of the reaction solution in the polymerization tank was 5 kg in both tanks, and the average residence time was 5 hours. The jacket temperature was adjusted so that the polymerization temperature was 150 ° C. Therefore, the average residence time was 16.9 times the initiator half-life. The first stage monomer conversion was 61.5%, and the second stage monomer conversion was 73.4% and the weight average molecular weight was 85,000.

The reaction liquid extracted from the bottom of the second tank was heated to 270 ° C. with a heat exchanger, and then continuously introduced into a devolatilization tank whose pressure was adjusted to 10 torr and flushed. The molten polymer from which volatile components were removed was extracted as a strand from the bottom with a gear pump and cut to obtain pellets (P _H ). The polymer was also obtained by precipitation purification from the reaction solution flowing out from the second tank (P _P ). Monomer concentration used in Table 4, acrylate concentration in monomer, methanol concentration, polymerization initiator concentration, chain transfer agent concentration, half-life of polymerization initiator used, set average residence time, polymerization temperature, reached monomer conversion rate, The values obtained by substituting these into the equations (4) to (6) and the thermal decomposition rate of the resulting polymer measured by thermogravimetric analysis are shown.

The results of examining the thermal decomposition resistance of the precipitated purified polymer (P _P ) before receiving the thermal history after the polymerization step and the polymer (P _H ) receiving the thermal history after the devolatilization step are shown in FIGS. 5 and 6, respectively. . In both cases, the substantial pyrolysis start temperature was 300 ° C. Thermal decomposition rate is 0.5% P _P, a 0.2% P _H, the polymerization step, the thermal decomposition resistance good polymer regardless devolatilization step was found to be obtained. A vacuum devolatilized polymer was used to form a 150 mmφ × 3 mm disk at 260 ° C. using an Aburg 45t injection molding machine, but no generation of silver streaks or voids was observed. The total light transmittance was 93% and had excellent transparency.

Table 4

Raw material composition 1st tank main feed composition (mol / liter)
Methyl methacrylate 7.82
Methyl acrylate 0.68
Methanol 2.61
n-dodecyl mercaptan 0.014
G-tamyl peroxide 5.4 × 10 ⁻⁴
Second tank side feed composition No side feed
1st tank
Polymerization temperature (° C) 150
Average residence time θ (min) 300
First tank monomer conversion (%) 60.5
Second tank
Polymerization temperature (° C) 150
Average residence time θ (min) 300
Second tank monomer conversion (%) 74.0
(4) Value 7.7 × 10 ⁸
(5) Value of equation 9.8 × 10 ³
(6) Value of expression 3.0 × 10 ⁻⁵
Thermal decomposition rate of polymer before receiving thermal history (%) 0.5

Reference Examples 7-10
In the same manner as in Reference Example 6, complete mixing tank type continuous polymerization was performed in two stages in series under various conditions. In any of the reference examples , the polymerization reaction was stably controlled, and a polymer having good thermal decomposition resistance was obtained. Tables 5 and 6 show the raw material composition, polymerization conditions, monomer conversion, and resin properties (weight average molecular weight, thermal decomposition rate).

Table 5
Reference example number 7 8 9 10
Raw material composition
1st tank main feed composition
MMA (part) 82.7 88.4 88.7 85.0
(Mol / liter) 7.68 8.18 8.23 7.65
Comonomer MA MA EA BA
Comonomer (part) 3.0 3.0 5.4 5.2
(Mol / liter) 0.32 0.32 0.57 0.55
Solvent CH ₃ OH CH ₃ OH CH ₃ OH CH ₃ OH
Solvent (parts) 13.2 8.6 5.2 9.7
(Mol / liter) 3.78 2.47 1.51 2.79
Polymerization initiator DTAP DTAP AIBN DTBP
Polymerization initiator (mmol / liter) 0.21 0.27 0.32 0.36
Chain transfer agent DM DM DM OM
Chain transfer agent (mmol / liter) 12.0 11.0 17.0 9.4
Second tank side feed composition
MMA (part) 70.0 73.1 90.0 90.0
(Mol / liter) 6.60 6.89 8.29 8.09
Comonomer (part) 30.0 26.9 10.0 10.0
(Mol / liter) 3.29 2.95 1.07 1.04
Polymerization initiator (mmol / liter) 10.2 10.2 3.1 2.1
Chain transfer agent (mmol / liter) 51.5 28.0 32.0 30.0
Main / side-feed weight ratio 20.0 / 1 33.4 / 1 13.9 / 1 13.9 / 1

Table 6
Reference example number 7 8 9 10
Polymerization conditions
1st tank
Polymerization temperature (℃) 150 150 155 160
Average residence time θ (min) 300 180 180 180
Polymerization initiator half-life τ (min) 17.8 17.8 1.2 22.8
Tank 1 monomer conversion (%) 49.1 47.1 56.2 54.3
Second tank
Polymerization temperature (℃) 150 150 155 160
Average residence time θ (min) 300 180 180 180
Polymerization initiator half-life τ (min) 17.8 17.8 1.2 22.8
Second tank monomer conversion (%) 80.2 71.0 77.4 74.1
Resin characteristics
Weight average molecular weight (Mw × 10 ⁻⁴ ) 7.8 9.0 8.9 8.1
Thermal decomposition rate (wt%) 0.9 1.4 1.4 0.5
Molded product characteristics
Occurrence of silver streak None None None None
Generation of voids None None None None
Total light transmittance (%) 93 93 93 93

Comparative Example 3
Complete mixing tank type continuous polymerization connected in series in two stages was carried out.
A composition comprising 58.3 parts of methyl methacrylate, 2.0 parts of methyl acrylate, 39.7 parts of methanol, 3.2 mmol / liter of n-dodecyl mercaptan, and 2.0 mmol / liter of di-t-amyl peroxide was used. Feed continuously to the first tank at .67 Kg / Hr, and further to the second tank 90.0 parts methyl methacrylate, 10.0 parts methyl acrylate, 1.2 mmol / l n-dodecyl mercaptan, di-t-amyl A composition consisting of 1.9 mmol / liter of peroxide was side-fed at 120 g / Hr. In both tanks, continuous polymerization was carried out at a polymerization temperature of 140 ° C. and an average residence time of 3 hours. Therefore, the average residence time was 3.4 times the initiator half-life. Operation was maintained at a monomer conversion of the first stage of 63.8%, a monomer conversion of the second stage of 82.2%, and a weight average molecular weight of 86,000.

Results of examining the thermal decomposition resistance of the polymer (P _P ) that has been subjected to precipitation purification from the reaction solution flowing out of the polymerization tank and the polymer (P _H ) that has undergone the thermal history after vacuum devolatilization at 270 ° C. Are shown in FIGS. 7 and 8, respectively. The thermal decomposition starting temperature was 250 ° C. for both the polymer flowing out from the polymerization tank and the polymer after devolatilization at 270 ° C. The decomposition rate of the polymer flowing out from the polymerization tank up to 300 ° C. was 7.0. A vacuum devolatilized polymer was used to form a 150 mmφ × 3 mm disk at 260 ° C. using an Aburg 45t injection molding machine, but silver streaks occurred and the total light transmittance was 91%.

Table 7

Raw material composition
1st tank main feed composition (mol / liter)
Methyl methacrylate 5.10
Methyl acrylate 0.20
Methanol 10.82
n-dodecyl mercaptan 0.003
G-tamyl peroxide 0.002
Second tank rhino domain feed composition (mol / liter)
Methyl methacrylate 8.47
Methyl acrylate 1.10
n-dodecyl mercaptan 0.001
G-tamyl peroxide 0.002
Main / side-feed weight ratio 14.0 / 1
First tank polymerization temperature (° C) 150
Average residence time θ (min) 300
First tank monomer conversion (%) 61.5
Second tank polymerization temperature (° C) 150
Average residence time θ (min) 300
Second tank monomer conversion (%) 73.2
(4) Value 3.4 × 10 ⁸
The value of the formula (5) 2.9 × 10 ³
(6) Value of formula 2.0 × 10 ⁻⁴
Thermal decomposition rate of polymer before undergoing thermal history (%) 7.0

Comparative Example 4
It is an example of a complete mixing tank type continuous polymerization connected in series in two stages.
Methyl methacrylate 62.0 parts (5.44 mol / liter), methyl acrylate 0.6 parts (0.06 mol / liter), methanol 37.4 parts (10.24 mol / liter), 2,2′-azo A composition comprising 0.007 mol% (1.1 mmol / liter) of bisisobutyronitrile was continuously fed at 1.67 Kg / Hr to the same first tank as in Reference Example 6, and further to the second tank. Methyl methacrylate 95.0 parts (8.93 mol / liter), methyl acrylate 5.0 parts (0.55 mol / liter), 2,2′-azobisisobutyronitrile 0.12 mol% (11.5 The composition consisting of (mmol / liter) was side fed at 120 g / Hr. Both tanks were continuously polymerized at a polymerization temperature of 130 ° C. and an average residence time of 3 hours. Therefore, the average residence time was 479 times the initiator half-life. The first stage monomer conversion was 60.3%, the second stage monomer conversion was 82.7%, and the weight average molecular weight was 79.000.

As a result of examining the thermal decomposition resistance of the polymer (P _P ) precipitated and purified from the reaction solution flowing out of the second tank and the polymer (P _H ) after vacuum devolatilization at 270 ° C., the thermal decomposition initiation temperature of each polymer is It was 250 ° C. The thermal decomposition rate of the polymer (P _P ) before receiving the thermal history was 8.2%.
A vacuum devolatilized polymer was used to form a 150 mmφ × 3 mm disk at 260 ° C. using an Aburg 45t injection molding machine, but silver streaks occurred and the total light transmittance was 91%.

Example 1
For continuous polymerization using a first-stage complete mixing tank and a second-stage plug flow reactor connected in series, a 10-liter complete mixing tank with a helical ribbon blade in the first stage and a heating medium jacket in the second stage A static mixer (inner diameter 3/4 inch) was used. Methyl methacrylate 84.6 parts (7.82 mol / liter), methyl acrylate 6.4 parts (0.68 mol / liter), methanol 9.1 parts (2.61 mol / liter), n-dodecyl mercaptan 0.8. While continuously feeding a composition comprising 148 mol% (0.14 mol / liter) and 6 mmol% (6 mmol / liter) of di-t-amyl peroxide to the first stage complete mixing tank at 1 kg / hr. It extracted with the gear pump from the tank bottom part, and was made to flow in into the 2nd stage static mixer.
The amount of the reaction liquid in the first stage tank was 5 kg, the flow rate was adjusted so that the level was constant, and the average residence time was 5 hours. The residence time of the second stage static mixer was 2 hours. The jacket temperature was adjusted so that the polymerization temperature was 150 ° C. As a result, the first stage monomer conversion was 61.3%, and the second stage monomer conversion was 80.7%, and the weight average molecular weight was 85,000.

The reaction liquid from the static mixer outlet was introduced into a heat exchanger and heated to 270 ° C., and then continuously introduced into a devolatilizing tank whose pressure was adjusted to 10 torr and flushed. The molten polymer from which volatile components were removed was extracted as a strand from the bottom of the devolatilization tank with a gear pump, and cut into pellets (P _H ). Moreover, the polymer was obtained also by carrying out the precipitation refinement | purification of the reaction liquid which flows out out of a static mixer (P _P ). Monomer concentration used in Table 8, acrylate concentration in monomer, methanol concentration, polymerization initiator concentration, chain transfer agent concentration, half-life of polymerization initiator used, set average residence time, polymerization temperature, reached monomer conversion rate, The values obtained by substituting these into the equations (7) to (9) and the thermal decomposition rate of the polymer produced by thermogravimetric analysis are shown.
The results of examining the thermal decomposition resistance of the precipitated purified polymer (P _P ) before receiving the heat history and the polymer receiving the heat history after the devolatilization step are shown in FIGS. 9 and 10, respectively. Substantial thermal decomposition temperature both are 300 ° C., their thermal decomposition rate was 0.6% in the P _P, 0.2% in the PH, the polymerization step, the thermal decomposition resistance regardless devolatilization step It was found that a good polymer was obtained. A vacuum devolatilized polymer was used to form a 150 mmφ × 3 mm disk at 260 ° C. using an Aburg 45t injection molding machine, but no generation of silver streaks or voids was observed. The total light transmittance was 93% and had excellent transparency.

Table 8

Raw material composition 1st tank main feed composition (mol / liter)
Methyl methacrylate 7.82
Methyl acrylate 0.68
Methanol 2.61
n-dodecyl mercaptan 0.14
G-tamyl peroxide 6.0 × 10 ⁻⁴
Second stage plug flow reactor side feed composition No side feed
First tank polymerization temperature (° C) 150
Average residence time θ (min) 300
Polymerization initiator half-life τ (min) 17.8
First tank monomer conversion (%) 61.3
Second stage plug flow reactor
Polymerization temperature (° C) 150
Residence time (min) 120
Polymerization initiator half-life τ (min) 17.8
Second stage plug flow reactor
Outlet monomer conversion (%) 81.5
(7) Expression value 1.1 × 10 ⁹
(8) Value 3.7 × 10 ³
Value of equation (9) 2.3 × 10 ⁻⁵
Thermal decomposition rate of polymer before thermal history (%) 0.6

Examples 2-5
Continuous polymerization using a complete mixing tank and a plug flow reactor, which were serially coupled in two stages under various conditions, in the same manner as in Example 1 , was performed. A 10-liter complete mixing tank with a helical ribbon blade was used in the first stage, and a static mixer was used in the second stage. In any of the examples, the polymerization reaction was stably controlled, and a polymer having good thermal decomposition resistance was obtained. Tables 9 and 10 show the raw material composition, polymerization conditions, monomer conversion, and resin properties (weight average molecular weight, thermal decomposition rate).

Table 9
Example No. 2 3 4 5
Raw material composition
1st tank main feed composition
MMA (part) 82.8 85.4 90.0 86.9
(Mol / liter) 7.58 7.89 8.17 7.87
Comonomer MA MA EA BA
Comonomer (part) 3.0 5.6 4.0 4.1
(Mol / liter) 0.32 0.61 0.43 0.43
Solvent CH ₃ OH CH ₃ OH CH ₃ OH CH ₃ OH
Solvent (parts) 14.3 9.0 7.1 9.1
(Mol / liter) 4.05 2.58 2.04 2.60
Polymerization initiator DTAP DTAP AIBN DTBP
Polymerization initiator (mmol / liter) 0.21 0.23 0.43 0.36
Chain transfer agent DM OM OM DM
Chain transfer agent (mmol / liter) 12.0 11.0 17.0 9.4

Table 10
Example No. 2 3 4 5
Second stage plug flow reactor side feed composition
MMA (part) 93.8 93.5 90.0 80.0
(Mol / liter) 8.82 8.79 8.29 6.90
Comonomer (parts) 6.2 6.5 10.0 20.0
(Mol / liter) 0.68 0.71 1.07 2.00
Polymerization initiator DTAP DTAP DTAP DTBP
Polymerization initiator (mmol / liter) 21.0 10.5 10.5 10.3
Chain transfer agent (mmol / liter) 0 10.5 2.1 20.6
Main / side-feed weight ratio 10.0 / 1 10.0 / 1 20.0 / 1 20.0 / 1
Polymerization conditions and monomer conversion 1st tank
Polymerization temperature (℃) 150 150 155 160
Average residence time θ (min) 300 180 180 300
Polymerization initiator half-life τ (min) 17.8 17.8 4.0 11.6
Tank 1 monomer conversion (%) 49.0 45.7 56.4 56.6
Second stage plug flow reactor
Polymerization temperature (℃) 150 150 155 160
Residence time (min) 120 120 120 120
Polymerization initiator half-life τ (min) 17.8 17.8 4.0 11.6
Second stage static mixer
Outlet monomer conversion (%) 90.5 86.0 83.0 87.1
Resin properties
Weight average molecular weight (Mw × 10 ⁻⁴ ) 9.1 9.0 8.9 9.3
Thermal decomposition rate (wt%) 1.8 1.4 1.4 0.9
Molded product characteristics
Occurrence of silver streak None None None None
Generation of voids None None None None
Total light transmittance (%) 93 93 93 93

Comparative Example 5
Continuous polymerization was carried out by connecting a complete mixing tank and a plug flow reactor in series.
Methyl methacrylate 59.6 (5.23 mol / liter), methyl acrylate 2.6 parts (0.27 mol / liter), methanol 37.7 parts (10.32 mol / liter), di-t-amyl peroxide A composition comprising 0.021 mol% (2.0 mmol / liter) and n-dodecyl mercaptan 0.021 mol% (2.0 mmol / liter) was continuously added to the first stage complete mixing tank at 1.67 kg / hr. Fed to the static mixer of the second stage reactor. Further, 80.0 parts of methyl methacrylate (7.53 mol / liter), 20.0 parts of methyl acrylate (2.19 mol / liter), 0.051 mol% of di-t-amyl peroxide (5.0 mmol / liter) Liter) and a composition comprising 0.051 mol% (5.0 mmol / liter) of n-dodecyl mercaptan was side-feeded at 167 g / hr at the static mixer inlet.

Both reactors were polymerized at a polymerization temperature of 140 ° C., an average residence time of 3 hours, and a residence time of 2 hours. Therefore, the average residence time of the complete mixing tank was 3.4 times the initiator half-life, and the residence time of the static mixer was 2.3 times.
As a result, the monomer conversion rate in the first stage was 58.3%, the monomer conversion ratio at the second stage static mixer outlet was 88.2%, and the weight average molecular weight was 79,000. The thermal decomposition resistance of the polymer (P _P ) that was subjected to precipitation history purification from the reaction solution flowing out from the static mixer outlet and the polymer (P _H ) that was subjected to heat history after vacuum devolatilization at 270 ° C. was examined. The results are shown in FIGS. 11 and 12, respectively. The thermal decomposition starting temperature was 250 ° C. for both the polymer flowing out from the polymerization tank and the polymer after devolatilization at 270 ° C. The thermal decomposition rate of the polymer (P _P ) flowing out from the polymerization tank up to 300 ° C. was 7.0.
When a vacuum devolatilized polymer was used to form a 150 mmφ × 3 mm disc at 260 ° C. using an Aburg 45t injection molding machine, silver streaks were generated and clouded. The total light transmittance was 91%.

Table 11

Raw material composition 1st tank main feed composition (mol / liter)
Methyl methacrylate 5.23
Methyl acrylate 0.27
Methanol 10.32
n-dodecyl mercaptan 2.0 × 10 ⁻³
G-tamyl peroxide 2.0 × 10 ^-3
Plug flow reactor side feed
Methyl methacrylate 7.53
Methyl acrylate 2.19
n-dodecyl mercaptan 5.0 × 10 ⁻³
G-tamyl peroxide 5.0 × 10 ^-3
Main / side-feed ratio 10/1
First tank polymerization temperature (℃) 140
Average residence time θ (min) 180
First tank monomer conversion (%) 58.3
Plug flow reactor Polymerization temperature (℃) 140
Residence time (min) 120
Second stage static mixer outlet monomer conversion (%) 88.2
The value of equation (7) 9.2 × 10 ⁸
Value of formula (8) 2.8 × 10 ³
The value of equation (9) 1.5 × 10 ⁻⁴
Thermal decomposition rate of polymer before undergoing thermal history (%) 7.0

Comparative Example 6
Continuous polymerization was performed using a complete mixing tank and a plug flow reactor connected in series in two stages. 5.70 mol / liter methyl methacrylate, 0.20 mol / liter methyl acrylate, 9.95 mol / liter methanol, 2.1 mmol / liter n-dodecyl mercaptan, 3.2 mmol / liter di-t-butyl peroxide The composition consisting of the following is continuously fed to the first tank at 1.67 Kg / Hr, and further to the second stage static mixer: 8.47 l / liter of methyl methacrylate, 1.09 mol / liter of methyl acrylate, n-dodecyl mercaptan A composition consisting of 5.0 mmol / L and di-t-butyl peroxide 5.0 mmol / L was side-fed at 110 g / Hr.

Both reactors were continuously polymerized at a polymerization temperature of 140 ° C., an average residence time of 3 hours in the first tank, and a residence time of 2 hours in the second stage static mixer. The first stage monomer conversion was 62.7%, the second stage monomer conversion was 88.0%, and the weight average molecular weight was 100,000. As a result of examining the thermal decomposition resistance of the polymer (P _P ) precipitated and purified from the reaction solution flowing out of the second stage static mixer and the polymer (P _H ) after vacuum devolatilization at 270 ° C., thermal decomposition of all polymer samples was started. The temperature was 250 ° C.
The thermal decomposition rate of the polymer flowing out from the polymerization tank up to 300 ° C. was 9.5.
When the devolatilized polymer was formed into a disc of 150 mmφ × 3 mm at 260 ° C. using an Aburg 45t injection molding machine, silver streaks occurred and became cloudy. The total light transmittance was 91%.

The heat decomposability of the polymer (P _P ) before receiving the heat history subjected to precipitation purification in Reference Example 1 is shown. Shows the thermal decomposition resistance of the polymer (P _H) which has received the thermal history of the heating vacuum devolatilization in Reference Example 1. The heat-decomposability of the polymer (P _P ) before receiving the heat history subjected to precipitation purification in Comparative Example 1 is shown. Shows the thermal decomposition resistance of the polymer subjected to thermal history of the heating vacuum devolatilization in Comparative Example 1 (P _H). The heat-decomposability of the polymer (P _P ) before receiving the heat history subjected to precipitation purification in Reference Example 6 is shown. Shows the thermal decomposition resistance of the polymer (P _H) which has received the thermal history of the heating vacuum devolatilization in Reference Example 6. The heat-decomposability of the polymer (P _P ) before receiving the heat history subjected to precipitation purification in Comparative Example 3 is shown. Shows the thermal decomposition resistance of the polymer subjected to thermal history of the heating vacuum devolatilization in Comparative Example 3 (P _H). The heat decomposability of the polymer (P _P ) before receiving the heat history subjected to precipitation purification in Example 1 is shown. Shows the thermal decomposition resistance of the polymer subjected to thermal history of the heating vacuum devolatilization in Example 1 (P _H). The heat decomposability of the polymer (P _P ) before receiving the heat history subjected to precipitation purification in Comparative Example 5 is shown. Shows the thermal decomposition resistance of the polymer subjected to thermal history of the heating vacuum devolatilization in Comparative Example 5 (P _H).

Claims (3)

Using a complete mixing tank of the first stage reactor connected in series in two stages and a plug flow type reactor of the second stage reactor, methacrylate alone or 75% by weight or more of methyl acrylate and ethyl acrylate or at least one or more is 25 wt% or less of the monomer mixture from 71 to 95 wt% selected from butyl acrylate and mixtures of solvents 29-5 wt%,
(1) The polymerization temperature is 100 to 170 ° C. in the first stage complete mixing tank 100 to 170 ° C. in the second stage plug flow reactor 100 to 170 ° C.
(2) The average residence time in the first stage complete mixing tank is 5 to 7000 times the half life of the initiator at the polymerization temperature, and the residence time in the second stage plug flow reactor is 5 to 50 times the half life of the initiator. Set to be
(3) Radical polymerization initiator concentration with respect to the composition of 1.0 × 10 ^{−4 to} 0.16 mol / liter,
(4) and the reaction composition prepared so as to have a chain transfer agent concentration of 1.0 × 10 ^{−4 to} 0.1 mol / liter, (5) the monomer conversion rate at the outlet of the second-stage plug flow reactor While maintaining at 70 to 90%, the polymer is continuously polymerized, and the thermal decomposition rate of the polymer obtained by the polymerization reaction (after the completion of the polymerization reaction, the polymer before passing through the devolatilization step and the extrusion step, in a nitrogen stream, 30 A method for producing a methacrylic resin, characterized in that the thermal decomposition rate when heated at a rate of 2 ° C./min from 5 ° C. to 300 ° C. is 5% by weight or less. After completion of the polymerization reaction, the thermal decomposition rate of the polymer before passing through the devolatilization step and extrusion molding step (thermal decomposition rate when heated at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream) The method for producing a methacrylic resin according to claim 1, wherein the content is 2% by weight or less. The method for producing a methacrylic resin according to claim 1, wherein the solvent is methanol.

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