JP2000034303A - Manufacture of polymethylmethacrylate polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of obtaining polymethyl- methacrylates in high productivity having high heat decomposition resistance and heat distortion temperature, excellent in molding properties by polymerizing monomers mainly comprising methylmethacrylate in a specific continuous bulk polymerization. SOLUTION: In this bulk polymerization method, polymerizing methylmethacrylate monomer, or copolymerizing methylmethacrylate and an alkyl(meth)acrylate, monomers including 1.0×10-4 to 1.0×10-2 mole of a mercaptan as a chain transfer agent, and 5.0×10-6 to 5.0×10-5 mole of a radical initiator selected from 1,1-bis(t-butylperoxy)cyclohexane and 1,1-bis(t-butylperoxy)3,3,5- trimethylcyclohexane per 1 mole of monomer is continuously supplied to the reaction zone. This reaction zone is uniformly agitated at 120 to 150 deg.C and polymerized so that the polymer content in the reaction zone is 40 to 65 wt.% and the reaction mixture is continuously taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for continuously producing a methacrylic polymer by bulk polymerization.

[0002]

2. Description of the Related Art Polymethyl methacrylate (PMMA)
The continuous bulk polymerization method is excellent in productivity as compared with batch suspension polymerization, and is extremely excellent in transparency because it does not require an auxiliary agent such as a dispersant. Separation is not required, the polymer after removal of volatile components has no residual solvent, it is very excellent in transparency, and the radical polymerization initiator supplied to the reaction zone is very small. For a reason such as obtaining a polymer having excellent thermal decomposition resistance, studies have been conducted for a long time.

[0003] For example, Japanese Patent Publication No. 52-32665 discloses a method in which the half-life and the amount of a radical polymerization initiator to be added at a polymerization temperature are specified, and the monomer conversion rate is 50 to 70% at a polymerization reaction temperature of 130 to 160 ° C. It has been disclosed.

Japanese Patent Application Laid-Open No. 3-111408 discloses a method using a short-lived radical polymerization initiator having a half-life at a polymerization temperature of 0.5 to 120 seconds at 130 to 160 ° C.
Discloses a method of polymerizing so that the monomer conversion is 45 to 70%.

In Japanese Patent Application Laid-Open No. 7-126308, a half-life at a polymerization temperature of 1 is used as a radical polymerization initiator.
Min.
A production method is shown in which the monomer conversion is 40 to 70% by weight at 0 ° C.

[0006]

However, according to the method described in Japanese Patent Publication No. 52-26565, the inventors conducted additional examinations and found that, under the manufacturing conditions described in this publication, the heat distortion temperature was not necessarily high and the heat resistance was high. It was not always possible to produce a methacrylic polymer having excellent decomposability.

Further, the methods described in the above-mentioned JP-A-3-111408 and JP-A-7-126308 are
To use a very short-lived radical polymerization initiator,
Most of the supplied radical polymerization initiator is decomposed before being uniformly dispersed in the reaction tank. Therefore, it is necessary to use a large amount of a radical polymerization initiator, and as a result,
There is a drawback that a large amount of low molecular weight substances such as oligomers are generated, and that the number of terminal double bonds accompanying the disproportionation termination reaction is increased, so that the thermal decomposition resistance is reduced. Decreasing the thermal decomposition resistance means lowering the upper limit of the molding temperature range, and in order to secure a certain degree of the molding temperature range, be aware that the thermal deformation temperature will decrease. And an alkyl acrylate having an effect of improving thermal decomposition resistance.

That is, as a method for producing a methacrylic polymer, a continuous bulk polymerization method is more advantageous than the suspension polymerization method and the solution polymerization method in the above point, but the conventional continuous bulk polymerization technique has a sufficient heat resistance. It has been difficult to produce a polymer having decomposability and high heat distortion temperature with good productivity.

Accordingly, the present invention has been made in view of such conventional problems, and is intended to provide a methacrylic polymer having high thermal decomposition resistance, excellent moldability, and a high heat distortion temperature with good productivity. It is intended to provide a method of manufacturing.

[0010]

SUMMARY OF THE INVENTION The present invention provides a method for producing a homopolymer of methyl methacrylate or a copolymer containing a methyl methacrylate unit and an alkyl acrylate or alkyl methacrylate unit (excluding a methyl methacrylate unit) by bulk polymerization. Wherein the mercaptan compound is used as a chain transfer agent in an amount of 1.0 × 10 ^{−4 to} 1.0 × ^10-4 per 1 mol of the monomer or the monomer mixture.
^-2 mol, and at least one selected from 1,1-bis (t-butylperoxy) cyclohexane and 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane as a radical polymerization initiator From 5.0 × 10 ⁻⁶ to 5.0 per 1 mol of monomer or monomer mixture.
A monomer-containing mixture containing × 10 ⁻⁵ mol is continuously supplied to the reaction zone, and the reaction zone is substantially uniformly stirred and mixed at 120 to 150 ° C., so that the polymer content of the reaction zone is 40%. ~
The present invention relates to a method for producing a methacrylic polymer, wherein polymerization is carried out so as to satisfy 65% by weight, and a reaction mixture is continuously taken out from the reaction zone.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The production method of the present invention uses a methyl methacrylate homopolymer or a methyl methacrylate unit and an alkyl acrylate unit or an alkyl methacrylate unit (excluding a methyl methacrylate unit).
It is applied to the production of a copolymer containing Preferably, the copolymer is a polymer containing 80% by weight or more of methyl methacrylate units and 20% by weight or less of alkyl acrylate units or alkyl methacrylate (excluding methyl methacrylate units) units.

Each is obtained by homopolymerization using methyl methacrylate alone as a monomer or copolymerization using methyl methacrylate and alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) as a monomer mixture.

When copolymerization is performed, the alkyl acrylate used together with methyl methacrylate has 1 to 1 carbon atoms.
It is selected from those having an alkyl group of 18 and includes, for example, an alkyl acrylate having an alkyl group such as methyl, ethyl, n-propyl, n-butyl, 2-ethylhexyl, dodecyl, stearyl and the like.

The alkyl methacrylate used together with methyl methacrylate is selected from those having an alkyl group having 2 to 18 carbon atoms, and includes, for example, an alkyl methacrylate having the same alkyl group as described above except for a methyl group.

The methacrylic polymer obtained by the present invention is particularly preferably a homopolymer, ie, polymethyl methacrylate, or a copolymer of methyl methacrylate and an alkyl acrylate selected from methyl, ethyl and butyl acrylate.

Methyl methacrylate has a different polymerization activity from other alkyl methacrylates and alkyl acrylates to be copolymerized therewith. Therefore, when it is desired to obtain a copolymer having the above composition, the composition of the charged monomer mixture is changed to those of these. It is appropriately selected according to the polymerization activity. For example, when methyl methacrylate is copolymerized with methyl acrylate or ethyl acrylate, the composition of the charged monomer mixture is preferably 70% by weight or more of methyl methacrylate and 30% by weight or less of methyl acrylate or ethyl acrylate.

In the present invention, a monomer-containing mixture mainly composed of methyl methacrylate containing a mercaptan compound and a radical polymerization initiator is continuously supplied to one reaction zone.

The mercaptan compound used in the present invention includes, for example, an alkyl group or a substituted alkyl group such as n-butyl, isobutyl, n-octyl, n-dodecyl, sec-butyl, sec-dodecyl and tert-butyl mercaptan. Primary, secondary, tertiary mercaptans having the formula: phenylmercaptan, thiocresol, 4-
aromatic mercaptans such as tert-butyl-o-thiocresol; thioglycolic acid and its esters; and mercaptans having 3 to 18 carbon atoms such as ethylenethioglycol. These can be used alone or in combination of two or more. Among these mercaptans,
Tert-butyl, n-butyl, n-octyl, n-dodecyl mercaptan are preferred.

The polymer terminated by a mercaptan chain transfer reaction is excellent in thermal decomposition resistance. As the ratio of the number of mercaptan terminated terminals to the total number of polymer terminals increases,
A polymer having excellent thermal decomposition resistance is obtained. However,
If the amount is too large, the degree of polymerization of the polymer will decrease, and the tensile strength and bending strength of the molded product obtained by molding the polymer will decrease.Therefore, appropriate polymerization that can be molded while maintaining the tensile strength and bending strength In order to obtain a polymer having excellent thermal decomposition resistance while obtaining a degree, the amount of the mercaptan to be used is 1.0 × 10 ⁻⁴ to 1.0 × 10 ⁻⁴ to 1 mol of the monomer or the monomer mixture.
× 10 ⁻² mol, preferably 5.0 × 10 ^{−4 to} 5.0 × 1
0 ^-3 mol.

The radical polymerization initiator used in the production method of the present invention is 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) 3,
It is at least one selected from 3,5-trimethylcyclohexane, and is 5.0 × 10 ⁻⁶ to 5.0 × 10 ⁻⁵ mol, preferably 1.0 × 10 ⁻⁵ mol, per 1 mol of the monomer or the monomer mixture. × 10 ^{−5 to} 3.0 × 10 ⁻⁵ mol is continuously supplied to the reaction zone.

The present inventors have found that the above-mentioned specific radical polymerization initiator is used in combination with a mercaptan compound in a specific amount at a polymerization temperature of 120 to 150 ° C., whereby a heat distortion temperature is high and heat resistance is excellent in thermal decomposition. The present inventors have found that a methacrylic polymer having no coloring can be produced, and have completed the present invention.

That is, it was found that these radical polymerization initiators can efficiently perform polymerization at a very small concentration at a polymerization temperature of 120 to 150 ° C.
For this reason, it was possible to suppress the formation of low molecular weight products such as oligomers and to suppress the number of terminal double bonds of the polymer generated by the disproportionation termination reaction between radicals.
As a result, it has become possible to produce a methacrylic polymer having excellent thermal decomposition resistance.

In order to obtain a polymer having excellent thermal decomposition resistance, it is preferable that the amount of the radical polymerization initiator used is small. Therefore, the upper limit of the amount used is preferably 5 mol / mol of the monomer or the monomer mixture. 0 × 10 ⁻⁵ mol, preferably 3.0 × 10 ⁻⁵ mol, and the lower limit is 5.0 × 10 ^{−6 in} consideration of industrial productivity.
Molar preferably 1.0 × 10 ⁻⁵ mol.

The reason why the use of these radical polymerization initiators enables efficient polymerization in a very small amount is as follows.
In the range of 50 ° C., the half-life is about 50 to 1000 seconds, and after being fed into the reaction zone, most of it is uniformly dispersed throughout the reaction zone without being decomposed while being uniformly mixed with stirring. It has an appropriate decomposition rate. Therefore, since the reaction zone can be regarded as a complete mixing tank, the utilization efficiency of the radical polymerization initiator is improved. In order to further improve the utilization efficiency of these radical polymerization initiators, it is preferable to set the polymerization temperature at which the half-life of these radical polymerization initiators is 120 seconds or more.

More surprisingly, it has been found that the same monomer conversion can be achieved at very low concentrations compared to other radical polymerization initiators having almost the same decomposition rate, such as peroxyesters. is there. This is considered to be due to the polymerization initiation efficiency of each radical polymerization initiator.

The present invention, in addition to using such a specific initiator at a specific concentration, satisfies the following conditions, thereby exhibiting more excellent effects as compared with the conventional method.

First, in the present invention, it is important that the whole reaction mixture supplied to the reaction zone is substantially uniformly stirred and mixed at 120 to 150 ° C. for polymerization. When the temperature of the reaction mixture is lower than 120 ° C., the viscosity increases, and it becomes difficult to achieve sufficient mixing or heat transfer, and it is difficult to control the reaction stably. Therefore, the polymer content φ in the reaction mixture (hereinafter referred to as It is called "polymerization rate" and expressed in "% by weight". On the other hand, when the polymerization temperature is increased, the viscosity decreases, which is advantageous in terms of reaction control.However, by-products such as methyl methacrylate dimer are increased, and the syndiotacticity of the polymer stereoregularity is increased. The reason for the decrease in the ratio of tics is accompanied by a decrease in the heat distortion temperature, moldability and the like of the polymer. The polymerization temperature is preferably from 120 to 140 ° C., more preferably 13 to 140 ° C.
0-140 ° C. It is desirable that the polymerization temperature be constant. When the polymerization temperature is constant, the polymerization rate is also constant, and more stable operation is possible.

Since heat is generated in the reaction zone by the polymerization reaction and stirring and mixing, the heat is removed, and in some cases, the temperature is controlled by heating to a predetermined polymerization temperature. Temperature control can be performed by a known method. For example, methods such as heat transfer heat removal or heating by circulating a heat medium to a draft tube or a coil installed in a jacket, a reaction zone, or the like, cooling supply of a monomer-containing mixture, reflux cooling, and the like can be adopted.

Further, in the present invention, it is preferable that the polymerization rate φ in the reaction mixture in the reaction zone is maintained at a substantially constant value in the range of 40 to 65% by weight. When the polymerization rate φ exceeds the specified upper limit, it is difficult to achieve sufficient mixing and heat transfer, and stable operation becomes difficult. If the polymerization rate φ is lower than the specified lower limit, the cost required for separating volatiles mainly composed of unreacted monomers increases, and the industrial merit decreases. Therefore, it is necessary to maintain the polymerization rate φ within the specified range. This polymerization rate φ is preferably 40 to 60% by weight. To maintain the polymerization rate φ, the residence time 2
In 5 to 5 hours, mixing may be performed uniformly so that there is no temperature unevenness in the reactor, and the polymerization initiator may be quantitatively supplied so as to obtain a desired polymerization rate.

The reactor used for carrying out the present invention is preferably a tank-type reactor provided with a stirrer having a supply port and an outlet, and the stirrer has a mixing performance over the entire reaction zone. It is preferable to have.

The monomer-containing mixture to be supplied to the reaction zone is subjected to an operation such as introducing an inert gas such as nitrogen, or maintaining the mixture under a reduced pressure for a certain period of time to reduce the dissolved oxygen concentration to 2 ppm or less. , Preferably 1 ppm or less.

In the present invention, after such a polymerization step,
Usually, it has a volatile matter separation step mainly composed of unreacted monomers, and heats a reaction mixture having a predetermined polymerization rate which is continuously sent to 200 to 290 ° C. under reduced pressure. Most of the volatiles mainly composed of monomers are continuously separated and removed, and the residual monomer content in the obtained polymer is preferably 1.0% by weight or less, more preferably 0.1% by weight or less. 3% by weight
Make sure that:

In the volatile matter separation step, residual dimers are also removed. It is preferable that the amount of the residual dimer is small because it causes coloring during heating and a reduction in heat distortion temperature. The residual dimer content in the obtained polymer is preferably 0.1% by weight.
Or less, more preferably 0.05% by weight or less.

When the methacrylic polymer thus produced is used as a molding material, a lubricant such as a higher alcohol or a higher fatty acid ester can be added. Further, if necessary, an ultraviolet absorber, a heat stabilizer, a coloring agent, an antistatic agent and the like can be added.

The methacrylic polymer obtained in the present invention is
When used as a molding material, it is characterized by excellent quality, especially excellent moldability. The quality of the moldability can be determined by the temperature range in which the moldability is possible, and the larger the width is, the better.

The lower limit temperature of this temperature range is mainly determined by the fluidity of the molding material, and can be relatively easily controlled by changing the average degree of polymerization, the amount of the copolymer component, and the amount of the plasticizer. However, when the fluidity is increased and the lower limit temperature is lowered, the lowering of the lower limit temperature is actually difficult because the heat deformation temperature and the mechanical strength are lowered at the same time.

On the other hand, the upper limit temperature of the above temperature range depends on the thermal decomposition resistance and the volatile matter content of the molding material. Further, the thermal decomposition resistance of the polymer is mainly determined by the number of double bonds at the terminal of the polymer accompanying the termination reaction of the polymer radical and the copolymerization amount of the alkyl acrylate. It is preferable that the amount of the radical polymerization initiator added is small because the smaller the double bond, the better the thermal decomposition resistance. The higher the ratio of the number of polymer terminals terminated by the mercaptan chain transfer reaction, the higher the thermal decomposition resistance. In addition, the higher the copolymerization amount of the alkyl acrylate, the better the thermal decomposition resistance, but the higher the copolymerization amount of the alkyl acrylate, the lower the glass transition temperature of the copolymer and the lower the heat distortion temperature, and thus the higher the molding material. When a heat distortion temperature is required, the copolymerization amount is limited. Therefore, in order to increase the copolymerization amount of the alkyl acrylate without impairing the heat distortion temperature, the glass transition temperature is increased by lowering the polymerization temperature and making the stereoregularity of the resulting polymer syndiotactic rich, thereby increasing the glass transition temperature. The copolymerization amount of the alkyl acrylate can be increased.

[0038] For these reasons, it is preferable that the amount of the radical polymerization initiator used is small and the polymerization temperature is low. Therefore, according to the present invention, the moldability having both a high heat deformation temperature and a high thermal decomposition resistance. A methacrylic polymer excellent in the above can be produced.

According to the present invention, a methacrylic polymer having a high upper limit temperature for molding can be obtained due to its excellent thermal decomposition resistance, so that a molding material having a wide molding temperature range and excellent moldability can be obtained. .

[0040]

The present invention will be described in more detail with reference to the following examples, which do not limit the present invention.

The thermal decomposition resistance of the examples was evaluated using a differential thermal electronic balance (SSC50) manufactured by Seiko Instruments Inc.
0) shows the bending temperature (° C.) when the polymer pellets were heated to 400 ° C. in air at a rate of 5 ° C./min.

Example 1 1.57 × 10 ⁻³ mol% of n-octyl mercaptan (0.25 mol%) was added to 1 mol of a monomer mixture consisting of 98% by weight of purified methyl methacrylate and 2% by weight of methyl acrylate. % By weight) and 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane as a radical polymerization initiator 1.0 × 1
0 ^-5 mol (0.003 wt%) monomer containing mixture was mixed and continuously supplied to the reaction zone which is stirred and mixed at a polymerization temperature of 140 ° C..

The half life at the polymerization temperature is 230 seconds. The polymerization was carried out with the average residence time in the reaction zone being 3.0 hours.

The reaction mixture was continuously taken out of the reaction zone and continuously supplied to a vent extruder-type extruder to separate and remove volatiles mainly composed of unreacted monomers to obtain a polymer. .

When the physical properties of the polymer in each step were examined,
The polymer content in the reaction mixture after the polymerization reaction is 48% by weight.
And the dimer content was as low as 0.04% by weight. Further, the residual monomer content of the polymer obtained after separating the volatile components was 0.03% by weight, and the residual dimer content was 0.02% by weight or less.

When the thermal decomposition resistance of this polymer was evaluated, the results shown in Table 1 were obtained, and the polymer was very excellent in thermal decomposition resistance.

In a continuous operation for 360 hours,
There was no problem with the control of the polymerization, and no observation of the inside of the reaction tank after the completion of the operation showed any formation of deposits or foreign substances on the apparatus.

Examples 2 to 4 Polymers having the physical properties shown in Table 2 were obtained in the same manner as in Example 1 except that the raw materials and conditions shown in Table 1 were used. In all of Examples 2 to 4, the control of polymerization was good in the continuous operation for 360 hours, and no observation of the inside of the reaction tank after the completion of the operation showed any formation of deposits or foreign substances on the apparatus.

Comparative Examples 1 to 3 Polymers having the physical properties shown in Table 2 were obtained in the same manner as in Example 1 except that the raw materials and conditions shown in Table 1 were used. From these results, it is clear that under these conditions, the thermal decomposition resistance is poor.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

According to the production method of the present invention, a monomer-containing mixture containing methyl methacrylate as a main component is subjected to continuous bulk polymerization under specific conditions using a complete mixing reaction apparatus, so that a high heat-resistant decomposition property is obtained. A methacrylic polymer having excellent processability and a high heat distortion temperature can be produced.

Continued on the front page (72) Inventor Tatsuyuki Takayanagi 3rd Kaigan-dori, Toyama City, Toyama Prefecture Mitsubishi Rayon Co., Ltd. Toyama Works (72) Inventor Wataru Hatano 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. F-term in the laboratory (reference) 4J011 AA05 AB02 AB07 BB01 BB02 BB04 BB10 FA02 FA03 FA05 FB05 FB09 FB10 FB19 NA25 NB04 4J015 BA10 4J100 AL03P AL03Q AL04Q AL05Q CA01 CA04 FA03 FA04 FA18 FA27 FA28

Claims (2)

[Claims] 1. A method for producing a methyl methacrylate homopolymer or a copolymer containing a methyl methacrylate unit and an alkyl acrylate unit or an alkyl methacrylate unit (excluding a methyl methacrylate unit) by bulk polymerization, wherein the mercaptan compound is used as a chain transfer agent. Of 1.0 × 10 ^{−4 to} 1.0 × 1 with respect to 1 mol of the monomer or the monomer mixture.
0 ^-2 mol, and 1,1-bis (t-butylperoxy) cyclohexane and 1,1-bis (t-butylperoxy) as a radical polymerization initiator 3,3,5 least a selected trimethyl cyclohexane From 5.0 × 10 ⁻⁶ to 5.0 with respect to 1 mol of monomer or monomer mixture.
A monomer-containing mixture containing × 10 ⁻⁵ mol is continuously supplied to the reaction zone, and the reaction zone is substantially uniformly stirred and mixed at 120 to 150 ° C., so that the polymer content of the reaction zone is 40%. ~
A method for producing a methacrylic polymer, wherein polymerization is carried out so as to satisfy 65% by weight, and a reaction mixture is continuously taken out from the reaction zone. 2. The polymerization is carried out at a temperature at which the half-life of the radical polymerization initiator is at least 120 seconds.
A method for producing the methacrylic polymer according to the above.