JPH07206905A - Methacrylic resin having resistance to thermal decomposition and its production - Google Patents

Abstract

PURPOSE:To obtain the subject resin having properties of less foaming, coloring and generating odor, by continuously polymerizing methyl methacrylate in a solution in the presence of a specific radical polymerization initiator and a specific chain transfer agent under specific conditions in respect to their concentrations in complete mixing vessels of two-step connected in a series. CONSTITUTION:By using complete mixing vessels of two-step connected in a series, methyl methacrylate alone or a composition containing 71-95wt.% of a monomer mixture consisting of 75wt.% or more of methyl methacrylate and 25wt.% or less of a 1-4C, alkylacrylate, and 29-5wt.% of a solvent, is adjusted to have a polymerization initiator concentration of 5.0X10<-4>-1.2 mole % and a chain transfer agent concentration of 1.0X10<-3>-1.0 mole %, and continuously polymerized at a polymerization temperature in first vessel of 100-170 deg.C, and in second vessel of 130-170 deg.C, with an average retention time set at 5-7000 fold of a half life of the polymerization initiator, by keeping a polymerization efficiency of 70-90%, to obtain a resin having 5% or less of a DW value before a history of after treatment, expressed by the formula [DW is decreasing weight ratio (wt.%); gammaWi is a content of a polymer having a double bond in its chain end in the i-th vessel (wt.%); RAi is a concentration of acrylate (mole %); and DELTAMi is a concentration of consumed monomer in the i-th vessel].

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventional methacrylic resins have transparency, weather resistance,
It has excellent mechanical strength and is widely used in various fields as building materials, furniture / upholstery materials, automobile parts, electric parts, and other molding materials. Generally, methacrylic resin is 2
Decomposition starts at around 30 ° C., and is particularly remarkable at around 270 ° C. 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 monomers thermally decomposed from the polymer remain in the molded product to cause silver streaks or foaming, coloring,
It is a problem in practical use due to deterioration of heat distortion resistance and deterioration of working environment due to odor. Until now, various measures have been made to improve the thermal decomposition resistance of methacrylic resin. For example, it was attempted to add an antioxidant in the initial stage and perform heat molding, but it had a defect that not only a sufficient effect was not obtained but also coloring was performed.

Recently, it has been shown that the thermal decomposition resistance is improved by producing a methacrylic resin by a continuous polymerization method. For example, in Japanese Examined Patent Publication No. 52-32665, a monomer satisfying a mercaptan concentration of 0.01 to 1.0 mol% and a following formula as a chain transfer agent is used in carrying out a one-stage complete mixing tank type continuous polymerization at a temperature of 130 to 160 ° C. The composition is continuously fed to obtain a monomer conversion of 50-
A method of maintaining 78% is disclosed. 10 ≧ A ^1/2 · B ^{−1 / 2} × 10 ³ 3 ≧ A · B × 10 ⁵ 2.9 ≧ A ⁻¹ · (B + 10.3) × 10 ^{−6 In the} above formula, A is a monomer The number of moles of the radical polymerization initiator in 100 g of the feed, and B represents the half-life (hour) at the polymerization temperature of the radical polymerization initiator.

Further, in JP-A-3-111408, in carrying out a one-stage complete mixing tank type continuous polymerization, an initiator having a half-life of 0.5 to 2 minutes at a polymerization temperature of 130 to 160 ° C. is used, The average residence time is set so 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 techniques, the thermal decomposition resistance in question is evaluated for a polymer that has undergone a vacuum devolatilization step or an extrusion molding step for removing residual volatile components such as unreacted monomers at high temperature. According to the studies by the present inventors, the thermal decomposition resistance of the polymer itself produced in the polymerization step was not always sufficient. Considering yield reduction due to thermal decomposition in the vacuum devolatilization step and extrusion molding step, coloring due to heat history, and the like, it is extremely important to improve the thermal decomposition resistance of the polymer produced in the polymerization step.

A multi-stage perfect mixing tank type continuous polymerization is also disclosed. JP-A-1-172401 describes that the quality such as thermal stability of the produced polymer is improved by dividing and feeding a part of a comonomer such as methyl acrylate or ethyl acrylate or a chain transfer agent, but specific details about this are given. No specific embodiments are mentioned. The inventors of the present invention filed an earlier application (Japanese Patent Application No.
-279861), methanol 5 to 29% by weight
An added continuous solution polymerization method was disclosed. According to this method, the gel effect can be suppressed in the relatively low concentration region of the polymer, so that the polymerization can be stabilized, but the thermal decomposition resistance of the obtained polymer is not always satisfactory. Not something.

Further, in JP-A-62-241905, the solubility parameter (δ) containing methanol is 10.5.
Although a method of carrying out the polymerization in the presence of 30 to 80% by weight of an aliphatic monohydric alcohol having a concentration of -14.5 (cal / cm ³ ) ^1/2 is disclosed, according to the test conducted by the present inventors. For example, in a large amount of alcohol addition system of 30 to 80% by weight, when a methacrylic resin having a molecular weight used as a molding material was produced, a polymer having extremely low thermal decomposition resistance was obtained.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and to reduce the occurrence of silver streaks, foaming, coloring and odor during thermoforming, and to obtain a methacrylic resin excellent in thermal decomposition resistance. , And its manufacturing method.

[0008]

[Means for Solving the Problems] As a result of intensive studies, the present inventors have found that the half-life of a certain radical polymerization initiator and its concentration, chain transfer agent concentration, monomer concentration and solvent concentration, polymerization temperature, average residence time. It was found that the above problems can be solved by reacting under the conditions of, and the present invention has been completed.

That is, according to the present invention, methyl methacrylate alone or 75% by weight or more of methyl methacrylate and 25% by weight or more of at least one of methyl acrylate, ethyl acrylate or butyl acrylate is used by using a two-stage serially connected complete mixing tank. The radical polymerization initiator concentration was 5.0 × 10 ^{−4 with} respect to the composition consisting of 71 to 95% by weight of the following monomer mixture and 29 to 5% by weight of the solvent.
Up to 1.2 mol% and a chain transfer agent concentration of 1.0 × 10 ⁻³
The polymerization temperature of the reaction composition prepared so as to be 1.0 to 1.0 mol% is 100 to 170 ° C. in the first tank and 130 to 120 in the second tank.
170 ° C. and an average residence time of 5 to 7,000 times the half-life of the polymerization initiator at the polymerization temperature, and polymerization was continuously carried out while maintaining the polymerization rate in the second tank at 70 to 90%. Further, the present invention relates to a methacrylic resin having thermal decomposition resistance having a thermal decomposition degree (DW) of 5 wt% or less defined by the following formula after the completion of the polymerization reaction and before being subjected to a thermal history in a post-treatment step.

[0010]

[Equation 4]

(In the formula, DW is a heating weight loss rate (wt%) when heated and heated from 30 ° C. to 300 ° C. at a rate of 2 ° C./min in a nitrogen stream, and γwi is a total of the i-th tank. Content of polymer having terminal double bond (w)
t%), RAi is the acrylate unit concentration (mol%) in the polymer produced in the i-th tank, and ΔMi is the monomer concentration consumed in the i-th tank, that is, (inflow monomer concentration-outflow monomer concentration). Show. )

The monomer component used in the present invention is methyl methacrylate alone or methyl methacrylate 7
It is a monomer mixture in which 5% by weight or more and at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate is 25% by weight or less. Generally, a methacrylic resin is a copolymer of methyl methacrylate and acrylates, and its composition ratio is determined by the molding purpose such as injection molding grade and extrusion molding grade, that is, the heat fluidity of the polymer. Usually, the concentration of acrylate units in the polymer is set to 20% by weight or less, but for this purpose, at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate needs to be 25% by weight or less.

The composition of the monomer mixture supplied is different from the copolymer composition of the polymer to be produced, but the relationship can be known in advance by a simple experiment, for example, the pyrolysis gas chromatography measurement of the polymer. Monomer mixture is first
Although it is supplied to the second tank, a part of it may be side-fed to the second tank. At that time, the composition of the monomer mixture supplied to the first and second tanks does not necessarily have to be the same. Second
The polymer is supplied so that the concentration of acrylate units in the polymer flowing out from the tank is the desired concentration. The side feed amount is preferably 1/50 to 1/5 with respect to the main feed amount.

Examples of the solvent usable in the present invention include toluene, xylene, acetone, methyl ethyl ketone, methanol and ethanol. Among these, use of methanol is particularly desirable in consideration of treatment after the polymerization reaction and the like. The solvent is used in an amount of 29 to 5% by weight with respect to 71 to 95% by weight of the monomer or monomer mixture.
Is. If the solvent concentration is less than 5% by weight, the radical polymerization of methyl methacrylate will have a remarkable automatic accelerating effect, that is, an abnormal acceleration phenomenon of the polymerization rate will occur due to an increase in viscosity in the system, and stable polymerization cannot be maintained. On the other hand, when the solvent concentration exceeds 29% by weight, the settable molecular weight range is narrowed, and the condition that the content γw of the polymer having a terminal double bond in the produced polymer can be set to 10 wt% or less becomes extremely narrow. .

As the polymerization initiator, di-t-butyl percarbonate, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxydineodecanoate, t-butyl peroxypyrone. Valate, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, acetyl peroxide, t-butylperoxy (2-ethylhexanoate), t-butylperoxyisobutyrate, t-butylperoxy Isopropyl carbonate, t-butyl peroxybenzoate, di-
organic peroxides such as t-amyl peroxide and di-t-butyl peroxide,

Alternatively, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2 '
-Azobisisobutyronitrile, dimethyl-2,2'-
Azo compounds such as azobisisobutyrate, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobisisobutyrate, 1,1′-azobis (1-cyclohexanecarbonitrile) Can be mentioned.

The concentration of the radical polymerization initiator in the composition of the monomer or the mixture of monomers and the solvent is 5.0 × 10 ⁻⁴ to
The amount is 1.2 mol%, preferably 5.0 × 10 ^{−4 to} 1.0 mol%. The polymerization initiator concentration is 5.0 × 10 above.
^If it is less than ^-4 mol%, an industrially advantageous polymerization rate, in other words, a polymer concentration cannot be achieved. On the other hand, when the amount exceeds 1.2 mol%, a high polymerization rate can be achieved but the settable molecular weight range is narrowed, and the content rate γw of the polymer having a terminal double bond in the produced polymer is 10 wt%.
The range of conditions that can be set below becomes extremely narrow. Also, the use of a large amount of polymerization initiator causes a problem in the transparency of the product polymer. The half-life and decomposition rate of the polymerization initiator are 13th edition of "Organic peroxide" published by NOF CORPORATION, "Technical data" published by Atochem Yoshitomi Co., Ltd. and Wako Pure Chemical Industries, Ltd.
Issued "Azo-based polymerization initiator (AZO POLYMERIZATION INITIAT
ORS) ”and other data.

As the chain transfer agent, t-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, isooctyl thioglycolate and the like which are commonly used in radical polymerization can be used. The concentration of the chain transfer agent in the composition such as the monomer or the mixture of monomers and the solvent is 1.0
× 10 ^{−3 to} 1.0 mol%, preferably 2.0 × 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 becomes difficult to reduce the content rate 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 amount exceeds 1.0 mol%, 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 that the desired concentrations are obtained with respect to the raw material composition to be fed.
It is desirable to dissolve the monomer or monomer mixture in advance or the solvent in advance and then continuously supply. Also, part of the second
You can also side feed to the tank. It is desirable to supply the polymers produced from the first tank and the second tank so that the molecular weights of the polymers are as equal as possible. The polymerization temperature of the present invention is 100 to 170 ° C. in the first tank and 130 to 1 in the second tank.
It is 70 ° C. The first tank and the second tank do not necessarily have to be matched. If the polymerization temperature is lower than 100 ° C, a thermally weak head-head bond that breaks at 200 ° C or lower may remain in the produced polymer chain. On the other hand, when the temperature exceeds 170 ° C., the oligomer is remarkably produced, and the polymer is colored. In the second tank, if the temperature is lower than 130 ° C., the viscosity of the reaction solution becomes high and sufficient stirring cannot be performed.

In the present invention, the average residence time is set to be 5 to 7,000 times the half-life of the polymerization initiator at the polymerization temperature, but the first tank and the second tank need not necessarily be the same. When the average residence time is less than 5 times the half-life of the polymerization initiator, a large amount of the polymerization initiator is required to obtain the desired polymerization rate, so the transparency of the product polymer is impaired. On the other hand, if it exceeds 7,000 times, the polymerization reaction tank becomes too large, which is industrially disadvantageous.

In the present invention, the polymerization rate is 70 in the second tank.
-90%, preferably 70-80%, continuously polymerizing. If the polymerization rate in the second tank is less than 70%, the polymer yield per unit time will be small, and the advantage of using two reaction tanks will be reduced. On the other hand, when the polymerization rate in the second tank is 90% or more, γw, that is, the content ratio of the polymer having a terminal double bond in the mixed polymer flowing out from the second tank is rapidly increased and set to 10 wt% or less. The range of possible conditions becomes extremely narrow.

In the present invention, the thermal decomposition degree DW is 5% or less, preferably 3% or less, more preferably 1.5% or less. The thermal decomposition degree DW is defined by the following equation.

[0023]

[Equation 5]

(In the formula, DW is the heating weight loss rate (wt%) when the temperature is raised from 30 ° C. to 300 ° C. at a rate of 2 ° C./min in the nitrogen stream, and γwi is the total of the i-th tank. Content of polymer having terminal double bond (w)
t%), RAi is the acrylate unit concentration (mol%) in the polymer produced in the i-th tank, and ΔMi is the monomer concentration consumed in the i-th tank, that is, (inflow monomer concentration-outflow monomer concentration). Show. )

Here, γw in the present invention, that is, the weight fraction of the polymer chains having a terminal double bond with respect to the total polymer chains flowing out from the second tank is calculated from the following formula. γw = 50Rtdν (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 2 (6) Rtc = (1-a) kt Q 2 (7) Q = (2fkdI / kt) 1 ^{/ 2} (8) These can be measured by the usual method.

The abbreviations used in equations (2) to (8) are explained below. γwi: γw of the polymer produced in the i-th tank ΔMi: Concentration of the monomer consumed in the i-th tank,
That is, (concentration of inflowing monomer)-(concentration of outflowing monomer) ν: kinetic chain length (ratio between the number of monomers grown and consumed per unit time and the number of terminations) [M]: monomer concentration (mol·L ^-1 ) [I]: Initiator concentration (mol.L- ¹ ) [X]: Chain transfer agent concentration (mol.L- ¹ ) [S]: Solvent concentration (mol.L- ¹ ) Q: Total radical concentration (mol · L ^-1) Rp: growth rate (mol · 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: All termination rate constants (L-mol ⁻¹ · sec ⁻¹ ) ktrx: Chain transfer rate constant to chain transfer agent X (L · mol
^-1 · sec ⁻¹ ) ktrs: Chain transfer rate constant to solvent S (L · mol ⁻¹ · sec)
^-1 ) ktrm: rate constant of 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 disproportionation termination reaction to total termination reaction f: Initiator efficiency

In the case of continuous polymerization in a two-stage serially coupled complete mixing tank, the polymer flowing out from the final tank is obtained as a mixture of the polymers produced in each tank, and therefore the reaction composition (monomer or monomer) in each tank for maintaining the polymerization is maintained. Concentrations of comonomer, radical polymerization initiator, chain transfer agent, solvent) and elementary reaction rate constants (start rate, growth rate, chain transfer rate, recombination termination rate and disproportionation termination rate) at a given polymerization temperature The heat of the polymer flowing out of the final tank using the equation (1) from γw of the polymer produced in each tank and RA (concentration of acrylate unit in the polymer) obtained by substituting (rate constant) into the equation (2). The operation may be designed so that the resolution Dw has a desired value.

The concentration of each reaction composition in the tank for maintaining the polymerization is determined by analysis such as gas chromatography, but the calculated value obtained from the mass balance formula of the complete mixing tank type continuous polymerization can also be used. (Tatsuya Imoto, Shu Yi:
"Polymerization reaction engineering", pp. 66, 121, published by Nikkan Kogyo Shimbun (1970)). In the region where the viscosity of the polymerization system increases and the auto-acceleration phenomenon appears, it is generally said that when γw is treated as if the termination rate constant is decreased, the thermal decomposition resistance is in good agreement. If the volume change of the reaction solution due to the difference in the density of the monomer and polymer cannot be ignored, each concentration term of the polymerization system can be corrected (Yasuo Hatate, Tadashi Hano, Takao Miyata,
Fumiyuki Nakashio, Wataru Sakai, Chemical Engineering, Volume 35, No. 8, No. 9
03 (1971), published by The Chemical Engineering Society). Further, in order to predict and design the thermal decomposition resistance of methacrylic resin by γw, oxygen in the reaction system must be sufficiently removed to 1 ppm or less. This is because methyl methacrylate and oxygen are copolymerized to form a thermally unstable peroxide bond in the chain.

In the present invention, γw is used to obtain DW.
It is necessary to obtain various elementary reaction rate constants and factors used in the relational expression of 1 in advance, but these can be easily obtained in the laboratory. Each of growth rate constant, termination rate constant, and polymer radical of a monomer mixture of 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. The chain transfer rate constant to the composition can be determined by a conventional method (Takayuki Otsu and Masae Kinoshita, "Experimental Method for Polymer Synthesis", published by Kagaku Dojin). In addition, the data on the elementary reaction rate constants of methyl methacrylate described in Polymer Handbook Second Edition (published by Willy Interscience) can also be used.

Determination of the proportion of disproportionation termination reaction and recombination termination reaction and evaluation of the polymer chain terminal double bond concentration obtained by calculation are possible by directly measuring the terminal structure by nuclear magnetic resonance spectroscopy. (Kouichi Hatada,
Polymer Journal, Volume 1, No. 5, p. 395 (1986), published by The Polymer Society of Japan. The molecular weight of the polymer can be measured by intrinsic viscosity measurement or gel permeation chromatography. The dynamic chain length ν was determined by dividing the number average molecular weight Mn by the average molecular weight of the monomer unit.

[0031]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. The physical properties of the polymer shown in this example were measured by the following methods. (1) Decomposition degree DW was determined by thermogravimetric analysis. Seiko Denshi Kogyo Co., Ltd. RTG220 type thermogravimetric analysis (TGA) device was used to place about 5 mg of methacrylic resin on a platinum pan, and from room temperature to 500 in a nitrogen stream of 300 ml / min.
The change in weight loss rate was measured by heating to 2 ° C / min at a heating rate of 2 ° C / min. The thermal decomposition degree was defined as the weight loss rate at the inflection point between the depolymerization type zipper decomposition peak and the random decomposition peak on the DTG curve. This inflection point is practically 3 under this TG condition.
It is 00 ° C.

(2) The polymerization rate is GC-produced by GL Science.
It was determined by measuring the concentration of unreacted monomer in the reaction liquid flowing out of the polymerization tank using 380 type gas chromatography. (3) The molecular weight of the polymer was measured by Tosoh 8010 gel permeation chromatography. The dynamic chain length ν 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 Σ80 NDH manufactured by Nippon Denshoku Industries Co., Ltd.

Example 1 A two-stage serially coupled complete mixing tank type continuous polymerization was carried out by using a 10-liter complete mixing tank equipped with a helical ribbon blade for both the first tank and the second tank. Methyl methacrylate 83.9
Parts, methyl acrylate 6.3 parts, and toluene 9.8 parts to a mixture of 0.14 n-dodecyl mercaptan.
9 mol%, di-t-amyl peroxide 0.006
The composition obtained by blending so as to have a concentration of mol% was continuously fed to the first tank at 1 Kg / Hr, extracted from the bottom of the tank with a gear pump and allowed to flow into the second tank. The amount of reaction liquid in each of the polymerization tanks was 5 kg, and the flow rate was adjusted so that the level was constant. Both average residence times were 5 hours. The jacket temperature was adjusted so that the polymerization temperature was 150 ° C. Therefore, the average residence time was 16.8 times the half life of the initiator (0.297 hours). First stage polymerization rate 61.5%, number average molecular weight 44.0
00, the second stage has a polymerization rate of 73.9%, a number average molecular weight of 44,
It was 000.

Table 1 shows the respective reaction rates of the first stage, the kinetic chain length ν, the consumed monomer concentration and the methyl acrylate unit concentration in the polymer in the steady operation of the two-stage continuous polymerization. By substituting these values into the equation (2), γw ₁ was found to be 3.1. Since the methyl acrylate unit concentration in the polymer is 7.1 mol%, the thermal decomposition degree DW ₁ is 1.0%. Table 2
Shows the elementary reaction rate in the second step, the kinetic chain length ν, the consumed monomer concentration and the methyl acrylate unit concentration in the polymer. The second stage thermal decomposition degree DW ₂ was 0.3%. Therefore, the thermal decomposition degree D of the polymer flowing out from the second stage
W was calculated as 0.9 from the equation (1). The elementary reaction rates in both tanks and the kinetic chain length ν, etc. are actually measured values obtained by a conventional method.

To examine the thermal decomposition resistance, a polymer was also obtained by extracting the reaction solution from the bottom of the second tank with a gear pump and purifying by precipitation. On the other hand, the reaction liquid extracted from the bottom of the second tank with a gear pump was heated to 250 ° 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 the volatile matter was removed was extracted as a strand from the bottom by a gear pump and cut into pellets. The results of examining the thermal decomposition resistance of the reprecipitated purified polymer (which has not undergone thermal history) and the polymer after vacuum devolatilization (which has undergone thermal history) are shown in FIGS. 1 and 2.
Respectively shown. Both have a thermal decomposition starting temperature of 300 ° C.
Therefore, almost no difference was observed in the TG and DTG curves, and it was found that a polymer having good thermal decomposition resistance was obtained regardless of the polymerization step and the devolatilization step. Vacuum devolatilized polymer using an Aburgh 45t injection molding machine 2
A 150 mmφ × 3 mm disk was molded at 60 ° C., but no silver streaks were found. The total light transmittance was 93%, and it had excellent transparency.

Table 1 Thermal decomposition rate of polymer produced in the first tank Growth rate Rp 0.292 (mmol·L ⁻¹ · sec ⁻¹ ) Disproportionation termination rate Rtd 4.08 × 10 ⁻⁵ (mmol · L ^-1 · sec ^-1 ) Kinetic chain length ν 439 Consumed monomer concentration ΔM ₁ 5.26 (mol · L ^-1 ) Unsaturated terminal polymer weight fraction γw ₁ 3.1 (wt%) Methyl acrylate unit concentration RA ₁ 7.1 (mol%) Thermal decomposition degree DW ₁ 1.0 (wt%)

Table 2 DW growth rate of polymer produced in the second tank Rp 4.07 × 10 ⁻² (mmol·L ⁻¹ · sec ⁻¹ ) Disproportionation termination rate Rtd 1.68 × 10 ⁻⁶ ( mmol·L ⁻¹ · sec ⁻¹ ) Dynamic chain length ν 466 Consumed monomer concentration ΔM ₂ 1.02 (mol·L ⁻¹ ) unsaturated terminal polymer weight fraction γw ₂ 1.0 (wt%) methyl acrylate Unit concentration RA ₂ 6.3 (mol%) Total unsaturated terminal polymer weight fraction γw 2.7 (wt%) Overall methyl acrylate unit concentration RA 7.0 (mol%) Thermal decomposition degree DW 1.0 (wt%) )

Examples 2 to 5 Continuous polymerization was carried out under various conditions by the same method as in Example 1. In each of the examples, the polymerization reaction was stably controlled, and a polymer having good thermal decomposition resistance was obtained. Tables 3 to 5 show raw material composition, polymerization conditions, polymerization rate, and resin characteristics (number average molecular weight, comonomer composition ratio in polymer, γw, thermal decomposition degree DW).

Table 3 Example No. 2 3 4 5 Raw material composition First tank main feed composition MMA (part) 82.7 87.4 85.6 81.7 Comonomer (part) MA MA EA MA 3.0 3.9 5.5 6.1 Solvent (part) Toluene Methanol Toluene Methanol 14.3 8.7 8.9 12.2 Polymerization initiator (10 ^-3 mol%) DTAP DTAP AIBN DTBP 2.1 2.7 4.3 5.2 Polymerization initiator half-life τ (10 ^-2 hours) 29.7 29.7 0.066 19.4 Chain transfer agent (mol%) DM DM DM OM 0.12 0.12 0.13 0.094 Second tank side feed composition MMA (part) 70.0 93.0 88.0-Comonomer (part) 30.0 7.0 12.0-Polymerization initiator (10 ^-2 mol%) 10.1 10.5 2.1 -Chain transfer agent (10 ^-2 mol%) 5.1 28.4 9.4 − Main feed / side feed 20.0 / 1 30.0 / 1 13.8 / 1 − (wt ratio)

Table 4 Example No. 2 3 4 5 Polymerization conditions 1st tank Polymerization temperature (° C) 150 150 155 160 Raw material composition supply rate (kg / hour) 1.0 1.67 1.67 1.67 Average residence time θ (hour) 5.0 3.0 3.0 3.0 θ / τ 16.8 10.1 4520 15.5 Second tank polymerization temperature (℃) 150 150 150 160 Average residence time θ (hours) 5.0 3.0 3.0 3.0 θ / τ 16.8 10.1 4520 15.5 Polymerization results First tank polymerization rate (%) 49.1 47.1 55.6 59.3 Growth rate Rp (mmol ・ L ^-1・ sec ^-1 ) 0.218 0.371 0.437 0.439 Stopping speed Rtd 1.48 3.40 5.92 7.11 (10 ⁵ mmol ・ L ^-1・ sec ^-1 ) Kinetic chain length ν 491 482 481 442 Consumption Monomer concentration ΔM ₁ (mol / L) 3.92 4.00 4.72 4.74 γw ₁ (wt%) 1.0 2.2 3.3 3.6 RA ₁ (mol%) 3.3 4.0 6.0 7.0 DW ₁ (wt%) 1.0 1.2 1.3 1.2

Table 5 Example No. 2 2 3 4 5 2nd tank Polymerization rate (%) 79.7 73.2 74.2 74.1 Growth rate Rp (mmol·L ⁻¹ · sec ⁻¹ ) 0.105 0.155 0.115 0.065 Stopping rate Rtd 1.83 2.17 0.995 0.317 ( 10 ⁵ mmol·L ⁻¹ · sec ⁻¹ ) Dynamic chain length ν 462 464 542 476 Consumed monomer concentration ΔM ₂ (mol / L) 2.62 2.30 1.75 0.97 γw ₂ (wt%) 4.0 3.3 2.4 1.2 RA ₂ (mol %) 5.5 4.1 6.0 6.3 DW ₂ (wt%) 2.1 1.7 0.9 0.4 Characteristics of resin Number average molecular weight (Mn × 10 ^-4 ) 4.8 4.8 5.0 4.5 Overall γw (wt%) 2.6 2.6 3.0 3.2 Overall RA (mol%) 4.2 4.0 6.0 6.9 Overall thermal decomposition DW (wt%) 1.4 1.4 1.2 1.1 Characteristics of molded product Silver streak generation None None None None None Total light transmittance (%) 93 93 93 93

Description of abbreviations in Tables 3-5 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 A mixture of 58.1 parts of methyl methacrylate, 2.1 parts of methyl acrylate and 39.8 parts of toluene was added with n-.
A composition obtained by blending dodecyl mercaptan at a concentration of 0.022 mol% and di-t-amyl peroxide at a concentration of 0.018 mol% was continuously fed to the first tank at 1.67 Kg / Hr. In a second tank, 0.023 mol% of n-dodecyl mercaptan and 0.011 mol% of di-t-amyl peroxide were added to a mixture consisting of 94.0 parts of methyl methacrylate and 6.0 parts of methyl acrylate. The composition obtained by blending so as to have a concentration of 167 g /
Side fed with Hr. Polymerization temperature 140 in both tanks
Continuous polymerization was carried out at a temperature of ℃ and an average residence time of 3 hours. Therefore,
The average residence time was 3.4 times the half life of the initiator. First stage polymerization rate 62.5%, number average molecular weight 49,600, 2
Operation was maintained at a polymerization rate of 80.8% at the stage and a number average molecular weight of 49,000.

Table 6 shows each elementary reaction rate, kinetic chain length ν, and methyl acrylate unit concentration in the polymer in the first-stage continuous polymerization steady-state operation. By substituting these values into the equation (2), γw1 was calculated to be 12.0. Since the methyl acrylate unit concentration in the polymer is 3.5 mol%, the thermal decomposition degree DW ₁ is 7.0%. Table 7 shows the elementary reaction rates in the second step, the kinetic chain length ν, the monomer consumption rate and the methyl acrylate unit concentration in the polymer. The thermal decomposition degree DW of the polymer flowing out from the second-stage outlet was found to be 6.2 from the equation (1). The elementary reaction rates and the dynamic chain length ν in both tanks are actually measured values obtained by a conventional method.

In order to investigate the thermal decomposition resistance in the same manner as in Example 1, a polymer was also obtained by subjecting the reaction solution flowing out of the second tank to precipitation purification 15 hours after the start of operation. on the other hand,
The reaction liquid was extracted from the bottom of the second tank with a gear pump, heated to 250 ° 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 the volatile matter was removed was extracted as a strand from the bottom by a gear pump and cut into pellets.
The results of measuring the thermal decomposition resistance of the polymer after the precipitation purification and after vacuum degassing are shown in FIGS. 3 and 4, respectively. In both DTG curves, two peaks appeared at about 280 and 370 ° C.
The peak at 280 ° C. became slightly smaller in the polymer after vacuum devolatilization. Although the terminal double bond-containing polymer was partially decomposed by vacuum devolatilization at 250 ° C., it was confirmed that a large amount of thermally weak polymer still remained. The vacuum devolatilized polymer was 260 using an Aburgh 45t injection molding machine.
When a disc of 150 mmφ × 3 mm was molded at 0 ° C., silver streaks occurred and became cloudy. The total light transmittance was 89%.

Table 6 Thermal decomposition rate of polymer produced in the first tank Growth rate Rp 0.318 (mmol·L ⁻¹ · sec ⁻¹ ) Disproportionation termination rate Rtd 1.54 × 10 ⁻⁴ (mmol · L ⁻¹ · sec ⁻¹ ) Kinetic chain length ν 496 Consumed monomer concentration ΔM ₁ 3.44 (mol·L ⁻¹ ) unsaturated terminal polymer weight fraction γw ₁ 12.0 (wt%) Methyl acrylate unit concentration RA ₁ 3.5 (mol%) Thermal decomposition degree DW ₁ 7.0 (wt%)

Table 7 Thermal decomposition degree of polymer flowing out from the second tank Growth rate Rp 9.48 × 10 ⁻² (mmol·L ⁻¹ · sec ⁻¹ ) Disproportionation termination rate Rtd 2.96 × 10 ^{− 5} (mmol·L ⁻¹ · sec ⁻¹ ) Kinetic chain length ν 466 Consumed monomer concentration ΔM ₂ 1.34 (mol·L ⁻¹ ) unsaturated terminal polymer weight fraction γw ₂ 7.3 (wt%) Methyl acrylate unit concentration RA ₂ 3.6 (mol%) Overall unsaturated terminal polymer weight fraction γw 10.7 (wt%) Overall methyl acrylate unit concentration RA 3.5 (mol%) Thermal decomposition degree DW 6.2 ( wt%)

Comparative Example 2 0.028 mol% of n-dodecyl mercaptan was added to a mixture of 60.2 parts of methyl methacrylate, 2.2 parts of methyl acrylate, and 37.7 parts of methanol.
The composition obtained by blending 2,2′-azobisisobutyronitrile to a concentration of 0.007 mol% was 1.67.
Continuously feed the first tank with Kg / Hr, and then feed the second tank.
In a mixture of 92.0 parts of methyl methacrylate and 8.0 parts of methyl acrylate, 0.116 mol% of n-dodecyl mercaptan and 0.053 mol% of 2,2'-azobisisobutyronitrile were added to the tank. The resulting composition was side fed at 110 g / Hr. Continuous polymerization was carried out in both tanks at a polymerization temperature of 130 ° C. and an average residence time of 3 hours. Therefore, the average residence time was 479 times the half life of the initiator. First-stage polymerization rate 59.9
%, Number average molecular weight 49,900, second stage polymerization rate 77.
The operation was maintained at 7% and a number average molecular weight of 49,300.

Table 8 shows the reaction rate of each element in the first stage, the kinetic chain length ν and the concentration of methyl acrylate unit in the polymer in the steady operation of the two-stage continuous polymerization. By substituting these values into the equation (2), γw1 was found to be 13.3. Since the methyl acrylate unit concentration in the polymer is 3.4 mol%, the thermal decomposition degree DW ₁ is 7.8%. Table 9 shows the elementary reaction rates in the second step, the kinetic chain length ν, the monomer consumption rate and the methyl acrylate unit concentration in the polymer. The thermal decomposition degree DW of the polymer flowing out from the outlet of the second stage was found to be 6.8 from the equation (1). The elementary reaction rates and the dynamic chain length ν in both tanks are actually measured values obtained by a conventional method.

To evaluate the thermal decomposition resistance, a polymer was obtained by subjecting the reaction solution flowing out from the second tank to precipitation purification. On the other hand, the reaction liquid was extracted from the bottom of the second tank with a gear pump and heated to 250 ° C. with a heat exchanger, and then the pressure was 10 to
It was continuously introduced into the devolatilization tank adjusted to rr and flushed. The molten polymer from which the volatile matter was removed was extracted as a strand from the bottom by a gear pump and cut into pellets. 15 hours after the start of operation, the thermal decomposition resistance of the polymer reprecipitated and purified from the resin liquid flowing out from the polymerization tank and the polymer after vacuum devolatilization at 250 ° C. were examined. In both DTG curves, two peaks appeared at about 280 and 370 ° C. The peak at 280 ° C. became slightly smaller in the polymer after vacuum devolatilization. Although the terminal double bond-containing polymer was partially decomposed by vacuum devolatilization at 250 ° C., it was confirmed that a large amount of thermally weak polymer still remained. Vacuum devolatilized polymer using an Aburgh 45t injection molding machine 2
When a disk of 150 mmφ × 3 mm was molded at 60 ° C., silver streaks were generated, and it became cloudy. The total light transmittance was 89%.

Table 8 Thermal decomposition rate of polymer produced in the first tank Growth rate Rp 0.305 (mmol·L ⁻¹ · sec ⁻¹ ) Disproportionation termination rate Rtd 1.63 × 10 ⁻⁴ (mmol · L ⁻¹ · sec ⁻¹ ) Dynamic chain length ν 498 Consumed monomer concentration ΔM ₁ 3.29 (mol·L ⁻¹ ) unsaturated terminal polymer weight fraction γw ₁ 13.3 (wt%) Methyl acrylate unit concentration RA ₁ 3.4 (mol%) Thermal decomposition degree DW ₁ 7.8 (wt%)

Table 9 Thermal decomposition rate of polymer flowing out from the second tank Growth rate Rp 7.75 × 10 ⁻² (mmol·L ⁻¹ · sec ⁻¹ ) Disproportionation termination rate Rtd 2.33 × 10 ^{− 5} (mmol·L ⁻¹ · sec ⁻¹ ) Kinetic chain length ν 467 Consumed monomer concentration ΔM ₂ 1.18 (mol·L ⁻¹ ) unsaturated terminal polymer weight fraction γw ₂ 7.0 (wt%) Methyl acrylate unit concentration RA ₂ 3.8 (mol%) Overall unsaturated terminal polymer weight fraction γw 11.6 (wt%) Overall methyl acrylate unit concentration RA 3.5 (mol%) Thermal decomposition DW 6.8 ( wt%)

[0053]

EFFECTS OF THE INVENTION According to the present invention, in a two-stage serially coupled complete mixing tank type continuous polymerization method, a certain half-life of radical polymerization initiator and its concentration, chain transfer agent concentration, monomer concentration and solvent concentration, polymerization temperature By conducting the reaction under the condition of the average residence time, the thermal decomposition degree DW of the polymer immediately after the polymerization step, that is, before passing through the vacuum devolatilization step and the extrusion molding step is 5
It is possible to produce a methacrylic resin having an excellent thermal decomposition resistance of not more than wt%.

[Brief description of drawings]

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

FIG. 2 shows TG and DTG curves of the polymer that was vacuum devolatilized 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 a polymer which was devolatilized in vacuum in Comparative Example 1.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masahiro Kurokawa 5-6-2 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Sanryo Gas Chemical Co., Ltd. Plastics Center

Claims (6)

[Claims] 1. A two-stage serially connected complete mixing tank is used, and methyl methacrylate alone or 75 wt% or more of methyl methacrylate and at least one or more selected from methyl acrylate, ethyl acrylate or butyl acrylate is 25 wt% or less. Monomer mixture 71-9
The radical polymerization initiator concentration is 5.0 × 10 ^{−4 to} 1.2 with respect to the composition composed of 5% by weight and 29 to 5% by weight of the solvent.
Mol% and chain transfer agent concentration 1.0 × 10 ^{−3 to} 1.0
The reaction composition prepared so as to have a mol% has a polymerization temperature of 100 to 170 ° C. in the first tank and 130 to 170 in the second tank.
C, and the average residence time is 5 to 7,000 times the half-life of the polymerization initiator at the polymerization temperature, and is obtained by continuously polymerizing while maintaining the polymerization rate in the second tank at 70 to 90%. And the thermal decomposition rate (DW) defined by the following formula after the completion of the polymerization reaction and before receiving the thermal history in the post-treatment step is 5 w
A methacrylic resin having a thermal decomposition resistance of t% or less. [Equation 1] (In the formula, DW is a heating weight loss rate (wt%) when heated and heated at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream, and γwi is relative to all produced polymers in the i-th tank. Content of polymer having terminal double bond (wt%), R
Ai is the acrylate unit concentration (mol%) in the polymer produced in the i-th tank, and ΔMi is the monomer concentration consumed in the i-th tank, that is, ((inflow monomer concentration-
The effluent monomer concentration) is shown. ) 2. The heat resistance according to claim 1, wherein the content ratio γw of the polymer having a terminal double bond is 10 wt% or less with respect to all the produced polymers after the completion of the polymerization reaction and before the thermal history in the post-treatment step. Degradable methacrylic resin. 3. A two-stage serially connected complete mixing tank is used, and methyl methacrylate alone or 75% by weight or more of methyl methacrylate and at least one selected from methyl acrylate, ethyl acrylate or butyl acrylate is 25% by weight or less. Monomer mixture 71-9
The radical polymerization initiator concentration is 5.0 × 10 ^{−4 to} 1.0 with respect to the composition composed of 5 wt% and the solvent of 29 to 5 wt%.
Mol% and chain transfer agent concentration is 2.0 × 10 ^{-2 to} 0.6
The polymerization temperature of the reaction composition prepared so as to be mol% was 100 to 170 ° C in the first tank and 130 to 170 ° C in the second tank.
And an average residence time of 5 to 7,000 times the half-life of the polymerization initiator at the polymerization temperature so as to continuously polymerize while maintaining the polymerization rate in the second tank at 70 to 80%, and The thermal decomposition rate (DW) defined by the following formula after the completion of the polymerization reaction and before the thermal history in the post-treatment step is 1.5 wt.
A methacrylic resin having a thermal decomposition resistance of not more than%. [Equation 2] (In the formula, DW is a heating weight loss rate (wt%) when heated and heated at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream, and γwi is relative to all produced polymers in the i-th tank. Content of polymer having terminal double bond (wt%), R
Ai is the acrylate unit concentration (mol%) in the polymer produced in the i-th tank, and ΔMi is the monomer concentration consumed in the i-th tank, that is, ((inflow monomer concentration-
The effluent monomer concentration) is shown. ) 4. The content γw of the polymer having a terminal double bond with respect to all the produced polymers before the thermal history before the post-treatment step after the completion of the polymerization reaction is 5 wt% or less. Methacrylic resin with thermal decomposition resistance. 5. A two-stage serially connected complete mixing tank is used, and methyl methacrylate alone or 75 wt% or more of methyl methacrylate and at least one or more selected from methyl acrylate, ethyl acrylate or butyl acrylate is 25 wt% or less. Monomer mixture 71-9
The radical polymerization initiator concentration is 5.0 × 10 ^{−4 to} 1.2 with respect to the composition composed of 5% by weight and 29 to 5% by weight of the solvent.
Mol% and chain transfer agent concentration 1.0 × 10 ^{−3 to} 1.0
When carrying out the polymerization reaction of the reaction composition prepared so as to be mol%, the polymerization temperature is 100 to 170 ° C. in the first tank, 130 to 170 ° C. in the second tank, and the average residence time is the polymerization initiator half-life at the polymerization temperature. 5 to 7,000 times that in the second tank to continuously polymerize while maintaining the polymerization rate in the second tank at 70 to 90%, and after receiving the heat history before the post-treatment step after the completion of the polymerization reaction. The method for producing a methacrylic resin having thermal decomposition resistance, characterized in that the reaction is carried out under the condition that the thermal decomposition degree DW of the polymer of 5 is 5 wt% or less. [Equation 3] (In the formula, DW is a heating weight loss rate (wt%) when heated and heated at a rate of 2 ° C./min from 30 ° C. to 300 ° C. in a nitrogen stream, and γwi is relative to all produced polymers in the i-th tank. Content of polymer having terminal double bond (wt%), R
Ai is the acrylate unit concentration (mol%) in the polymer produced in the i-th tank, and ΔMi is the monomer concentration consumed in the i-th tank, that is, ((inflow monomer concentration-
The effluent monomer concentration) is shown. ) 6. The method for producing a methacrylic resin having thermal decomposition resistance according to claim 5, wherein the solvent is methanol.