JP3319483B2 - Methacrylic resin having thermal decomposition resistance and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, methacrylic resin has high transparency, weather resistance,
It has excellent mechanical strength and is widely used in various fields as various molding materials such as building materials, furniture / upholstery materials, automobile parts, electric parts and the like. Generally, methacrylic resin is 2
Decomposition starts at around 30 ° C., and is particularly remarkable at around 270 ° C. On the other hand, 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, the monomer thermally decomposed from the polymer partially remains in the molded product, causing silver streaks and foaming, coloring,
The heat resistance is deteriorated and the working environment is deteriorated due to odor, which is a practical problem.

Various attempts have been made to improve the thermal decomposition resistance of methacrylic resins. For example, although an attempt was made to add an antioxidant and heat-mold at an early stage, it was not only insufficiently effective but also had disadvantages such as coloring. In recent years, it has been disclosed to improve the thermal decomposition resistance by producing a methacrylic resin by a continuous polymerization method. For example, Japanese Patent Publication No. 52-32665
In carrying out the one-stage complete mixing tank type continuous polymerization at a temperature of from 130 to 160 ° C., a monomer composition satisfying the following formula and a mercaptan concentration of 0.01 to 1.0 mol% as a chain transfer agent is continuously fed. To maintain the monomer conversion at 50-78%. 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 is a monomer feed The number of moles of the radical polymerization initiator in 100 g is shown, and B represents the half-life (time) at the polymerization temperature of the radical polymerization initiator.

Further, in Japanese Unexamined Patent Publication (Kokai) No. 3-111408, an initiator having a half-life of 0.5 to 2 minutes at a polymerization temperature of 130 to 160 ° C. is used for performing a one-stage complete mixing tank type continuous polymerization. The average residence time is set such that the ratio of the half life of the radical initiator to the average residence time is 1/200 to 1/10000, and the monomer conversion is 45 to 70.
% Is disclosed. In any of these inventions, the thermal decomposition resistance in question is evaluated for a polymer that has undergone a post-treatment step such as a vacuum devolatilization step or an extrusion molding step for removing residual volatile components such as unreacted monomers at a high temperature. . According to the study of the present inventors, the thermal decomposition resistance of the polymer itself produced in the polymerization step was not always sufficient. It is extremely important to improve the thermal decomposition resistance of the polymer generated in the polymerization step in consideration of a decrease in yield due to thermal decomposition in a post-treatment step such as a vacuum devolatilization step or an extrusion molding step, and coloring due to heat history. .

[0005] Also, an invention relating to a multistage complete mixing tank type continuous polymerization is disclosed. Japanese Patent Application Laid-Open No. 1-172401 describes that the quality such as the thermal stability of a produced polymer can be improved by split feed of a part of a comonomer such as methyl acrylate or ethyl acrylate or a chain transfer agent. No specific examples are disclosed. The present inventors have disclosed a continuous solution polymerization method in which 5-29% by weight of methanol is added in an earlier application (Japanese Patent Application No. 5-279861). According to this method, in the region where the polymer concentration is relatively low, the gel effect can be suppressed, so that the polymerization can be stabilized, but the obtained polymer is not necessarily satisfied with the thermal decomposition resistance. is not.

In Japanese Patent Application Laid-Open No. 62-241905, the solubility parameter (δ) containing methanol is 10.
A method is disclosed in which polymerization is carried out in the presence of 30 to 80% by weight of an aliphatic monohydric alcohol having a weight of 5 to 14.5 (cal / cm ³ ) ^1/2 . According to the results, it was found that, in the case of a large amount of an alcohol-added system of 30 to 80% by weight, when a methacrylic resin having a molecular weight used as a molding material was produced, only a polymer having extremely low thermal decomposition was obtained.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a methacrylic resin which is free from silver streaks, foaming, coloring and odor during thermoforming, and has excellent heat decomposition resistance. And a method for manufacturing the same.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a certain half-life of a radical polymerization initiator and its concentration, a chain transfer agent concentration, a monomer concentration and a solvent concentration, a polymerization temperature, and an average residence time. The inventors have found that the above-mentioned problems can be solved by polymerizing methyl methacrylate or a monomer mixture containing methyl methacrylate under the conditions of time, and completed the present invention.

That is, in the present invention, methyl methacrylate alone or at least 75% by weight of methyl methacrylate and 25% by weight of at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate are used in a one-stage complete mixing tank. % Of a monomer mixture consisting of 71 to 95% by weight and a composition consisting of 29 to 5% by weight of a solvent, wherein the concentration of the radical polymerization initiator in the composition is 1.0 × 10 ^{−3 to} 1.6 mol%, And a reaction composition prepared so that the concentration of the chain transfer agent is 1.0 × 10 ^{−3 to} 3.7 mol%, a polymerization temperature of 100 to 170 ° C., and an average residence time of the polymerization initiator half-life at the polymerization temperature. 5 to 700
It is obtained by continuously polymerizing while maintaining a polymerization rate of 40 to 80% so as to be 0 times, and is defined by the following formula after the completion of the polymerization reaction and before receiving the heat history in the post-treatment step. The invention relates to a methacrylic resin having a thermal decomposition resistance having a decomposition degree (DW) of 5 wt% or less. DW = γw · 0.87 ^RA (where DW is the heating weight loss rate (wt%) when heating and heating at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream, and γw is the total Content of polymer having terminal double bond (wt%) with respect to product polymer, and RA
Is the acrylate unit concentration (mol%) in the produced polymer
Is shown. )

As the monomer component used in the present invention, methyl methacrylate alone or methyl methacrylate 7
5 is a monomer or mixture of at least 25% by weight of at least one selected from methyl acrylate, ethyl acrylate and butyl acrylate at least 25% by weight. Generally, the methacrylic resin is a copolymer of methyl methacrylate and acrylates, and the composition ratio is determined by the molding purpose such as the injection molding grade and the extrusion molding grade, that is, the fluidity of the polymer. Usually, the concentration of the acrylate unit in the polymer is set to 20% by weight or less.
At least 5% by weight and at least one selected from methyl acrylate, ethyl acrylate and butyl acrylate must be 25% by weight or less. The composition of the monomer mixture supplied is different from the copolymer composition of the resulting polymer, but the relationship can be known in advance by simple experiments, for example, pyrolysis gas chromatography measurement of the polymer.

[0011] Solvents usable in the present invention include toluene, xylene, acetone, methyl ethyl ketone, methanol and ethanol. Among these, the use of methanol is particularly desirable in view of the treatment after the polymerization reaction and the like. The use ratio of the solvent is 29 to 5% by weight of the solvent based on 71 to 95% by weight of the monomer or the monomer mixture.
It is. If the solvent concentration is less than 5% by weight, a remarkable auto-promoting effect on the radical polymerization of methyl methacrylate, that is, an abnormal acceleration of the polymerization rate due to an increase in the viscosity in the system occurs, and a stable polymerization reaction cannot be maintained. On the other hand, when the solvent concentration exceeds 29% by weight, the settable molecular weight range is narrowed, and the conditions under which the content γw of the polymer having a terminal double bond in the produced polymer can be set to 10% by weight or less are extremely narrow. Become.

Examples of the polymerization initiator include di-t-butyl percarbonate, isobutyryl peroxide, diisopropyl peroxy dicarbonate, di-2-ethylhexyl peroxy dicarbonate, t-butyl peroxydineodenoate and t-butyl peroxy dicarbonate. -Butylperoxypivalate, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, acetyl peroxide, t-butylperoxy (2-ethylhexanoate), benzoyl peroxide, t-butylperoxy Organic peroxides such as isobutylate, t-butylperoxyisopropyl carbonate, t-butylperoxybenzoate, dicumyl peroxide, di-t-amyl peroxide, and di-t-butyl peroxide;

Alternatively, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), (1-phenylethyl) azodiphenylmethane, , 2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobisisobutyrate,
An azo compound such as 1,1′-azobis (1-cyclohexanecarbonitrile) is exemplified.

The concentration of a radical polymerization initiator in a composition such as a monomer or a monomer mixture and a solvent is 1.0 × 10 ⁻³ to 1.0 × 10 ⁻³ .
It is in the range of 1.6 mol%, preferably 1.0 × 10 ^{−3 to} 1.0 mol%. If the radical polymerization polymerization initiator concentration is less than 1.0 × 10 ⁻³ mol%, an industrially advantageous polymerization rate, in other words, the polymer concentration cannot be achieved. on the other hand,
If it exceeds 1.6 mol%, a high polymerization rate can be achieved, but the settable molecular weight range is narrowed and the content γw of the polymer having a terminal double bond in the produced polymer can be set to 10% by weight or less. Becomes extremely narrow. Further, the use of a large amount of the polymerization initiator causes a problem of lowering the transparency of the product polymer.

[0015] The half life and decomposition rate of the polymerization initiator are described in "Organic Peroxide" Data Collection, 13th Edition, published by NOF Corporation.
Azochem Yoshitomi Co., Ltd. technical data and azo polymerization initiator (AZO POLYMERIZATION INITIATORS) issued by Wako Pure Chemical Industries, Ltd.
) And so on.

As the chain transfer agent, t-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, isooctyl thioglycolate, etc. obtained by ordinary radical polymerization can be used. The concentration of the chain transfer agent in a composition such as a monomer or a monomer mixture and a solvent is 1.0 ×
10 ^{−3 to} 3.7 mol%, preferably 1.6 × 10 ⁻² to
It is in the range of 0.6 mol%. When the concentration of the chain transfer agent is less than 1.0 × 10 ⁻³ mol%, it is difficult to reduce the content γw of the polymer having a terminal double bond in the produced polymer to 10% by weight or less. On the other hand, when the content exceeds 3.7 mol%, the molecular weight of the produced polymer becomes small, so that sufficient mechanical properties cannot be obtained.

The polymerization initiator and the chain transfer agent may be supplied to the polymerization tank independently so as to have a desired concentration with respect to the raw material composition to be fed. It is desirable to supply after dissolving in a monomer mixture or a solvent.

The polymerization temperature of the present invention is from 100 to 170 ° C. When the polymerization temperature is lower than the above-mentioned 100 ° C., a thermally extremely weak head-to-head bond that breaks at a temperature of 200 ° C. or lower remains in the produced polymer chain. On the other hand, when the temperature exceeds 170 ° C., oligomers are remarkably generated, and the polymer is colored.

In the present invention, the average residence time is set to be 5 to 7000 times the half life of the polymerization initiator at the polymerization temperature. The average residence time is the above-mentioned 5 of the polymerization initiator half-life.
If the ratio is less than twice, a large amount of a polymerization initiator is required in spite of a low polymerization 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 the present invention, the polymerization rate is 40-80%,
Preferably, the polymerization is carried out continuously while maintaining the content at 40 to 70%. If the polymerization rate is less than 40%, the polymer yield per unit time becomes small, which is industrially disadvantageous. on the other hand,
If it exceeds 80%, γw, that is, the content of the polymer having a terminal double bond in the produced polymer increases rapidly, and the condition range that can be set to 10% by weight or less becomes extremely narrow.

In the present invention, the degree of thermal decomposition DW is 5% or less, preferably 3% or less, more preferably 1.5% or less. The thermal decomposition degree DW is defined by equation (1). DW = γw · 0.87 ^RA (1) (where DW indicates the degree of thermal decomposition (wt%), and when heated and heated at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream) Γw is the content of the polymer having a terminal double bond with respect to the total produced polymer (wt.
%) And RA represent the acrylate unit concentration (mol%) in the produced polymer, respectively. )

Here, γw in the present invention, that is, the weight fraction of the polymer chain having a terminal double bond with respect to all the stable polymer chains at a certain moment is obtained by the following equation. γw = 50Rtdν (2 + ν) / (Rp (1 + ν)) (2) where: ν = Rp / (Rtr + Rtd + Rtc / 2) (3) Rp = kp [M] Q (4) Rtr = (ktrx [X] + ktrs [ S] + ktrm [M] + ktri [I] Q (5) Rtd = akt Q (6) Rtc = (1-a) kt Q ² (7) Q = (2fkdI / kt) ^1/2 (8)

The abbreviations in the formulas (2) to (8) are as follows. ν: dynamic chain (ratio between the number of monomers grown and consumed per unit time and the number of stops) [M]: monomer concentration (mol·L ⁻¹ ) [I]: initiator concentration ( ^mol·L ) ^-1 ) [X]: Concentration of chain transfer agent (mol·L ^-1 ) [S]: Concentration of solvent (mol·L ^-1 ) Q: Total radical concentration (mol·L ^-1 ) Rp: Growth rate (mol·L ^-1 ) L ^-1 · sec ^-1) Rtd: disproportionation termination rate (mol · L ^-1 · sec ^-1) Rtc: recombination stop speed (mol · L ^-1 · sec ^-1) Rtr: total chain transfer rate ( Mol·L ^-1 · sec ^-1 ) kp: Growth rate constant (L · mol ^-1 · sec ^-1 ) kt: Total termination rate constant (L · mol ^-1 · sec ^-1 ) ktrx: To chain transfer agent X Chain transfer rate constant (L · mol
⁻¹ · sec ⁻¹ ) ktrs: Rate constant of chain transfer to solvent S (L · mol ⁻¹ · sec)
^-1 ) ktrm: Rate constant for chain transfer to monomer M (L · mol ^-1)
Sec- ¹ ) ktri: Chain transfer rate constant to initiator I (L mol- ¹
Sec- ¹ ) a: ratio of occurrence of disproportionation termination reaction to total termination reaction f: initiator efficiency

In order to produce a methacrylic resin having a desired γw value in a one-stage complete mixing tank type continuous polymerization method, a reaction composition (monomer or comonomer, radical polymerization initiator, chain transfer agent, etc.) in a tank for maintaining polymerization is required. , Solvent), and each elementary reaction rate constant (each rate constant of initiation rate, growth rate, chain transfer rate, recombination termination rate and disproportionation termination rate) at a predetermined polymerization temperature are substituted into the equation (2). Then, an operation design of polymerization conditions may be designed so as to obtain a desired γw value. For the concentration of each reaction composition in the tank to maintain the polymerization,
Determined by analysis such as gas chromatography,
It is also possible to use a calculated value obtained from a mass balance equation of a continuous mixing tank type continuous polymerization (for example, “Polymerization Reaction Engineering”, written by Tatsuya Imoto and Hidehide Lee, p. 66, p. 121 (1970),
Published by Nikkan Kogyo Shimbun).

In a region where the viscosity of the polymerization system increases and an auto-acceleration phenomenon appears, if γw is handled assuming that the stop rate constant kt has decreased as generally known, the thermal decomposition resistance is in good agreement. If the change in the volume of the reaction solution due to the difference in density between the monomer and the polymer cannot be ignored, the concentration terms in the polymerization system may be corrected (Yasuo Hatate, Tadashi Hano, Takao Miyata, Fumiyuki Nakashio, Wataru Sakai, " Chemical Engineering ”, Vol. 35, No. 8, 90
3 (1971)). Further, in order to predict and design the thermal decomposition resistance of the methacrylic resin based on γw, oxygen in the reaction system must be sufficiently removed to 1 ppm or less.
This is because methyl methacrylate and oxygen copolymerize to form a thermally unstable peroxide bond in the chain.

In the present invention, γw
Although various elementary reaction rate constants and factors used in the relational expression need to be obtained in advance, they can be easily obtained in a laboratory. Growth rate constant, stop rate constant, polymer radical of a monomer mixture consisting of methyl methacrylate alone or at least one of methyl methacrylate 75 and at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate at 25% by weight or less. The chain transfer rate constant for each composition can be determined by a conventional method (for example, Takayuki Otsu and Masayoshi Kinoshita, "Experimental Method for Polymer Synthesis", published by Kagaku Doujin). Further, each elementary reaction rate constant data of methyl methacrylate described in the Polymer Handbook, 2nd edition (published by Willy Inter, Science Inc.) can also be used.

It is possible to determine the ratio of the occurrence of the disproportionation termination reaction and the recombination termination reaction and to evaluate the concentration of the polymer chain terminal double bond obtained by calculation, by directly measuring the terminal structure by nuclear magnetic resonance spectroscopy. (Hatada, polymer
Journal, Vol. 1, No. 5, p. 395, published by The Society of Polymer Science, Japan, 1986).

The molecular weight of the polymer can be measured by limiting viscosity measurement or gel permeation chromatography. The dynamic chain length ν was determined by dividing the number average molecular weight by the average molecular weight of the monomer unit.

[0029]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” indicates “parts by weight”. The measurement of the physical properties of the polymer shown in this example was performed by the following methods. (1) Thermal decomposition DW was determined by thermogravimetric analysis. About 5 mg of methacrylic resin was placed on a platinum pan using a thermogravimetric analysis (TGA) apparatus manufactured by Seiko Electronic Industry Co., Ltd. (model: RTG220), and 2 ° C. from room temperature to 500 ° C. in a nitrogen stream of 300 ml / min. The sample was heated at a heating rate of / min and the change in weight loss was measured. The degree of thermal decomposition was defined as a weight loss rate at an inflection point between a peak of depolymerized zipper decomposition and a peak of random decomposition in a DTG curve. This inflection point is substantially at 300 ° C. under the present TG conditions. (2) The polymerization rate was determined by measuring the concentration of unreacted monomer in the reaction solution flowing out of the polymerization tank using GC-380 type gas chromatography manufactured by GL Sciences.

(3) The molecular weight of the polymer is determined by Tosoh Corporation.
Was measured by gel permeation chromatography, Model 8010. The dynamic chain length v was determined by dividing the number average molecular weight Mn by the average molecular weight of the monomer unit. (4) The total light transmittance of the polymer was measured by a transmission method using a model: Z-sensor # 80 NDH manufactured by Nippon Denshoku Industries.

Example 1 To a mixture consisting of 88.3 parts of methyl methacrylate, 5.2 parts of methyl acrylate and 6.2 parts of methanol,
0.15 mol% of n-dodecyl mercaptan, 2, 2 '
-Azobisisobutyronitrile in 4.2 × 10 ^-3 mol%
Was added to a 10-liter complete mixing tank with helical ribbon blades at a concentration of 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 polymerization rate was 60.3%, the number average molecular weight of the polymer was 45,000, and each became constant.
Driving was stable.

Table 1 shows the elementary reaction rates, the dynamic chain lengths ν, and the composition ratio of methyl acrylate in the polymer during the continuous operation of continuous polymerization. Substituting these values into equation (1) gives γw
Was determined to be 2.7. Since the mole fraction of methyl acrylate units in the polymer is 5.8, the degree of thermal decomposition DW is 1.
It was calculated as 2%. In addition, the value calculated | required by the conventional method was used for each elementary reaction rate. In order to examine the thermal decomposition resistance, the reaction liquid was withdrawn from the bottom with a gear pump so that the liquid level in the polymerization tank was constant, and the reaction liquid was precipitated and purified to obtain a polymer. On the other hand, the reaction solution was heated to 250 ° C. by a heat exchanger, and then continuously introduced into a devolatilization tank adjusted to a pressure of 10 torr and flushed. The molten polymer from which volatile components had been removed was drawn out as a strand from the bottom with a gear pump and cut into pellets.

The results of examining the thermal decomposition resistance of the reprecipitated purified polymer before receiving the thermal history and the polymer subjected to vacuum devolatilization after receiving the thermal history are shown in FIGS. 1 and 2, respectively. Both have a substantial thermal decomposition onset temperature of 300 ° C. and TG and D
Little difference was observed in the TG curve,
It was found that a polymer having good thermal decomposition resistance was obtained regardless of the devolatilization step. The polymer subjected to vacuum devolatilization was subjected to 150 mmφ at 260 ° C. using a 45 t injection molding machine manufactured by Aburg.
A × 3 mm disk was formed, but no silver streaks were generated. The total light transmittance was 93%, and it had excellent transparency.

Table 1 Elementary reaction rates in the polymerization tank (mmol·L ⁻¹ · second ⁻¹ ), kinetic chain length, methyl acrylate unit concentration in the polymer (mol%), γ w and thermal decomposition degree (wt%) ) Growth rate Rp 0.291 Disproportionation termination rate Rtd 3.56 × 10 ^-5 Kinetic chain length 449 γw 2.7 Methyl acrylate unit concentration 5.8 Thermal decomposition DW 1.2

Examples 2 to 5 Continuous polymerization was carried out in the same manner as in Example 1 under various conditions shown in Table 2. In each of the examples, the polymerization reaction was controlled stably, and a polymer having good thermal decomposition resistance was obtained. Table 2 shows the raw material composition, polymerization conditions, polymerization rate, and resin characteristics (number average molecular weight, comonomer in the polymer, composition ratio, γw, degree of thermal decomposition D
W).

Table 2 Example No. 2 3 4 5 Raw material composition MMA (parts) 82.9 79.4 89.3 82.6 Comonomer (parts) MA EA MA BA 3.6 7.2 4.6 6.8 Solvent (parts) ME ME TOL TOL 13.3 12.7 6.9 10.1 Polymerization initiator ( 10 ^-3 mol%) AIBN DTAP DTAP DTBP 1.3 7.7 4.7 3.8 initiator half-life (10 ^-2 h) 0.102 10.4 17.5 7.29 chain transfer agent (mol%) DM DM OM OM 0.13 0.12 0.15 0.13 polymerization conditions temperature (℃ ) 150 160 155 170 Feed rate of raw material composition (kg / hour) 0.77 0.83 0.91 1.0 Average residence time (hour) 6.5 6.0 5.5 5.0 Polymerization rate (%) 50.0 70.0 60.4 63.2 Characteristic of resin Number average molecular weight (Mn × 10 ^-4 ) 5.0 4.5 4.9 5.0 RA (comonomer in polymer 4.1 9.3 5.2 8.1 Unit concentration (mol%)) γw (wt%) 1.3 3.9 2.4 2.3 Thermal decomposition DW (wt%) 0.7 1.1 1.2 0.7 Molded product characteristics Occurrence None None None None Total light transmittance (%) 93 93 93 93

Description of Abbreviations in Table 2 MMA: Methyl methacrylate MA: Methyl acrylate EA: Ethyl acrylate BA: Butyl acrylate ME: Methanol TOL: Toluene 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 A mixture comprising 54.8 parts of methyl methacrylate, 4.0 parts of methyl acrylate, and 42.9 parts of methanol was added with n
The same polymerization tank as in Example 1 was obtained by mixing 1.67 kg / Hr of a composition obtained by mixing dodecyl mercaptan at a concentration of 2.3 mol% and di-t-amyl peroxide at a concentration of 0.002 mol%. When the polymerization was continuously performed at an average residence time of 3 hours and a polymerization temperature of 140 ° C., the polymerization rate was 65.7%, the number average molecular weight was 50,000, and RA4.
1 mol% of polymer was obtained. Table 3 shows the elementary reaction rates, kinetic chain lengths ν, and the methyl acrylate unit concentration ratio in the polymer during the continuous operation of continuous polymerization. These values are (2)
When substituted into the equation, γw was 16.0. Since the methyl acrylate unit concentration in the polymer was 3.5%, the thermal decomposition degree DW was 9.0%.

In the same manner as in Example 1, 15 hours after the start of the operation, a polymer reprecipitated and purified from the reaction solution flowing out of the polymerization tank (having no heat history) and a polymer subjected to vacuum devolatilization at 250 ° C. (heat history) 3 and FIG. 4 show the results of examining the thermal decomposition resistance of the sample (see FIG. 3). The pyrolysis temperature was 250 ° C. for both the polymer flowing out of the polymerization tank and the polymer after vacuum devolatilization at 250 ° C. The decomposition rate up to 300 ° C. at which the polymer flowing out of the polymerization tank was substantially zipper-decomposed was 8.8. The DTG curves are both about 280.
Although two peaks appeared at 370 ° C. and 370 ° C., the peak at 280 ° C. became slightly smaller in the polymer after vacuum devolatilization. It is considered that the terminal double bond-containing polymer was partially decomposed during vacuum devolatilization. The polymer subjected to vacuum devolatilization was heated at 260 ° C. for 150 mm using an Aburg 45 t injection molding machine.
A disk of φ × 3 mm was formed, but silver streaks occurred and the total light transmittance was 89%.

Table 3 Rate of each elementary reaction in the polymerization tank (mmol·L ⁻¹ · second ⁻¹ ), kinetic chain length, methyl acrylate unit concentration (mol%) in polymer, γ w and thermal decomposition degree (wt%) ) Growth rate Rp 0.477 Disproportionation stop rate Rtd 2.06 × 10 ^-4 Kinetic chain length 474 γw 16.0 Methyl acrylate unit concentration 4.1 Thermal decomposition DW 9.0

Comparative Example 2 A mixture consisting of 66.8 parts of methyl methacrylate, 1.8 parts of methyl acrylate and 31.4 parts of toluene was added to a mixture of
The composition obtained by blending t-butyl peroxide so as to have a concentration of 0.18 mol% was continuously fed into the same polymerization tank as in Example 1 at a rate of 1.47 kg / Hr, and the average residence time was 3 times. After continuous polymerization at a polymerization temperature of 130 ° C. for 0.0 hours, the polymerization rate was 75.7% and the number average molecular weight was 40,000.
0, 3.2 mol% of RA was obtained. The γw of the produced polymer was 32.3, and the methyl acrylate unit concentration in the polymer was 3.2 mol%, so that the DW was 20.7. As in Example 1, the thermal decomposition temperature of the polymer reprecipitated and purified from the reaction solution flowing out of the polymerization tank 15 hours after the start of operation and the polymer after vacuum devolatilization at 270 ° C. were measured. Met.

[0042]

According to the present invention, in a one-stage complete mixing tank type continuous polymerization method, the half-life and the concentration of a certain radical polymerization initiator, the concentration of a chain transfer agent, the concentration of a monomer and a solvent, the polymerization temperature, the average By reacting under the condition of residence time, a methacrylic resin having excellent heat resistance immediately after the polymerization step, that is, before the vacuum devolatilization step or the extrusion molding step, having a thermal decomposition degree DW of 5% by weight or less is obtained. Can be manufactured.

[Brief description of the drawings]

FIG. 1 shows TG and DTG curves of the polymer obtained by precipitation purification in Example 1.

FIG. 2 shows TG and DTG curves of the polymer subjected to vacuum devolatilization in Example 1.

FIG. 3 shows TG and DTG curves of a polymer obtained by precipitation purification in Comparative Example 1.

FIG. 4 shows TG and DTG curves of the polymer subjected to vacuum devolatilization in Comparative Example 1.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-294307 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 2/00-2/60

Claims (4)

(57) [Claims] 1. Using a one-stage complete mixing tank, methyl methacrylate alone or 75% by weight or more of methyl methacrylate and 25% by weight or less of at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate. Monomer mixture 71 to 95
% By weight and a composition comprising 29-5% by weight of a solvent,
The radical polymerization initiator concentration in the composition is 1.0 × 10 ⁻³ to
1.6 mol%, and a chain transfer agent concentration of 1.0 × 10 ⁻³ or more
The reaction composition prepared so as to have a concentration of 3.7 mol% was prepared by polymerization at a polymerization temperature of 100 to 170 ° C. and an average residence time of 5 to 7000 times the half life of the polymerization initiator at the polymerization temperature. It has a thermal decomposition degree (DW) of 5 as defined by the following formula, which is obtained by continuously polymerizing while maintaining at 80% and before receiving the heat history in the post-treatment step after the completion of the polymerization reaction.
A methacrylic resin having a thermal decomposition resistance of not more than wt%. DW = γw · 0.87 ^RA (where DW is the heating weight loss rate (wt%) when heating and heating at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream, and γw is the total Content of polymer having terminal double bond (wt%) with respect to product polymer, and RA
Is the acrylate unit concentration (mol%) in the produced polymer
Is shown. ) 2. Using a one-stage complete mixing tank, methyl methacrylate alone or 75% by weight or more of methyl methacrylate and 25% by weight or less of at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate. Monomer mixture 71 to 95
% By weight and a composition comprising 29-5% by weight of a solvent,
The radical polymerization initiator concentration in the composition is 1.0 × 10 ⁻³ to
1.0 mol%, and a chain transfer agent concentration of 1.6 × 10 ⁻² to
The reaction composition prepared to be 0.6 mol% is prepared by polymerization at a polymerization temperature of 100 to 170 ° C. and an average residence time of 5 to 7000 times the half life of the polymerization initiator at the polymerization temperature. The degree of thermal decomposition (DW) defined by the following equation obtained by continuously polymerizing while maintaining the temperature at 70% and receiving the heat history in the post-treatment step after the polymerization reaction is 1.5 wt% or less. A methacrylic resin having thermal decomposition resistance. DW = γw · 0.87 ^RA (where DW is the weight loss rate (wt%) when heating and heating at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream, and γw is the total Content of polymer having terminal double bond (wt%) with respect to produced polymer, and RA
Is the acrylate unit concentration (mol%) in the produced polymer
Is shown. ) 3. Using a one-stage complete mixing tank, methyl methacrylate alone or 75% by weight or more of methyl methacrylate and 25% by weight or less of at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate. In conducting the polymerization reaction of the monomer mixture, the reaction solvent is blended so as to be 71 to 95% by weight of the monomer or the monomer mixture and 29 to 5% by weight of the reaction solvent, and the radical polymerization in the reaction composition is started. concentration is 1.0 × 10 ^-3 to 1.6 mol%, and the reaction composition a chain transfer agent concentration was adjusted to 1.0 × 10 ^-3 to 3.7 mol%, a polymerization temperature of 100 １７０170 ° C., and an average residence time of the polymerization initiator half-life at the polymerization temperature of 5-70.
The thermal decomposition degree D of the polymer obtained by continuously polymerizing while maintaining the polymerization rate at 40 to 80% so as to be 00 times and before receiving the heat history in the post-treatment step after the polymerization reaction is completed.
W (2 ° C / min from 30 ° C to 300 ° C in a nitrogen stream)
Methacrylic resin having heat-decomposability, characterized in that the reaction is carried out under the condition that the heating loss at the time of heating at a rate of 5% is 5 wt% or less. 4. The method for producing a methacrylic resin having thermal decomposition resistance according to claim 3 , wherein the solvent is methanol.