JPH01201307A - Production of methacrylate polymer - Google Patents

Abstract

PURPOSE:To obtain a methacrylate polymer excellent in optical properties, thermal decomposition resistance, etc., by mixing a methyl methacrylate monomer with a specified mixed solvent, an MW modifier and a polymerization initiator and continuously polymerizing the mixture at a specified temperature. CONSTITUTION:Methyl methacrylate alone or a monomer mixture of methyl methacrylate with other alkyl (meth)acrylates (e.g., methyl acrylate) (A) is mixed with 5-30wt.% mixed solvent (B) composed of 5-50wt.% monohydric alkyl alcohol (e.g., methyl alcohol) and 95-50wt.% (alkyl)benzene. The mixture is homogeneously mixed with an MW modifier (e.g., n-octyl mercaptan) and 3X10<-4>g.mol., per 100g of a mixture of components A and B, of a polymerization initiator (e.g., di-t-butyl peroxide), and the obtained mixture is continuously polymerized at 60-170 deg.C to obtain a methacrylate polymer.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a continuous method for producing methacrylic polymers.

[Conventional technology]

Methacrylic polymers are not only transparent but also have excellent weather resistance and mechanical properties, so they are useful resins used in high-performance optical materials, decorative materials, automobile and electrical product parts, etc.

Suspension polymerization is widely used as a method for producing methacrylic polymers. A disadvantage of this method is that the suspending agent used remains partially in the polymer, which deteriorates the polymer properties, especially the optical properties.

In recent years, bulk polymerization has been considered as a method for improving the disadvantages of suspension polymerization. According to this method, since no suspending agent is used, it is possible to produce a polymer with excellent optical properties. However, a drawback of the bulk polymerization method is that it is extremely difficult to control a stable polymerization reaction, which sometimes leads to runaway reactions. This is due to the well-known self-accelerating effect of the polymerization reaction called the "gel effect" or "Tromsdorff effect", and as the viscosity of the polymerization system increases, the diffusion of polymer molecules is restricted and stopped. This is due to a decrease in reaction. This gel effect is a phenomenon that is widely observed in the bulk radical polymerization of vinyl compounds, but is particularly noticeable in the polymerization reaction of methyl methacrylate.

As another method for improving the drawbacks of the suspension polymerization method, a polymerization method called a solution polymerization method in which polymerization is performed in a solvent is also considered. According to this method, since the viscosity of the reaction system is reduced by the solvent, the gel effect can be minimized and a stable polymerization reaction can be performed. However, the use of solvents creates additional problems. This is a decrease in the thermal decomposition resistance of the polymer. If the thermal decomposition resistance decreases, when the polymer is molded at high temperatures, silver streaks called "silver streaks" will occur due to the decomposition products of the polymer, so the molding temperature cannot be raised too high, and the molding processability will be greatly reduced. I will let you do it.

If the amount of solvent used is reduced in an attempt to improve the thermal decomposition resistance of the polymer, the gel effect increases, making it difficult to control a stable polymerization reaction.

[Problem to be solved by the invention]

In view of the above-mentioned circumstances, an object of the present invention is to provide a method for producing a methacrylic polymer with excellent quality, particularly a methacrylic polymer with excellent optical properties and thermal decomposition resistance, by a stably controlled polymerization reaction. be.

[Means to solve the problem]

The method for producing a methacrylic polymer of the present invention involves continuous polymerization of methyl methacrylate alone or a monomer mixture of methyl methacrylate and other alkyl methacrylates or alkyl acrylates. 100g of a mixture of alcohol and the above monomer containing a mixed solvent consisting of 95 to 50% by weight of benzene or alkylbenzene in a range of 5% by weight or more and less than 30% by weight, a molecular weight regulator and the above monomer. It is characterized by polymerization at a temperature of 60 DEG to 170 DEG C. in a substantially uniformly mixed reaction zone with not more than 3.times.10@-4 g-mol of polymerization initiator per polymerization initiator.

Examples of alkyl methacrylates copolymerized with methyl methacrylate include ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, and examples of alkyl acrylates include methyl acrylate. , ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, and the like. There is no particular restriction on the amount of these alkyl methacrylates or alkyl acrylates used when making a copolymer, but usually 3
It is 0% by weight or less.

The solvent used in the present invention is a mixed solvent of monohydric alkyl alcohol and benzene or alkylbenzene. Examples of polymerizing methyl methacrylate using benzene or alkylbenzene as a solvent are already known.

The present inventors have discovered that the viscosity of the methyl methacrylate polymerization solution can be significantly reduced by using a mixed solvent containing monovalent alkyl alcohol in combination with these solvents. The use of this mixed solvent brings about the following effects. In other words, by lowering the viscosity of the polymerization solution, the self-acceleration effect of the polymerization reaction, that is, the gel effect, is minimized and stable polymerization is possible, and the amount of solvent used can be reduced, making it possible to There should be no reduction in heat decomposition resistance.

Preferred monohydric alkyl alcohols include alcohols having an alkyl group having 4 or less carbon atoms, i.e., methyl alcohol, ethyl alcohol, n-propyl alcohol,
These are isopropyl alcohol, n-butyl alcohol and isobutyl alcohol. The amount of these alcohols used is 5 to 50 parts per mixed solvent. If it is less than 5% by weight, no effect can be expected, and if it exceeds 50% by weight, the solubility of the polymer will decrease. The preferred amount used is 10 to 40% by weight.

Preferred alkylbenzenes include toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, and the like having an alkyl group having 4 or less carbon atoms.

The amount of the mixed solvent used is 5% by weight or more and less than 30% by weight based on the mixture with a monomer such as methyl methacrylate. If the amount is less than 5% by weight, the viscosity of the polymerization solution will not be sufficiently reduced, and the polymerization reaction will likely become unstable. If it exceeds 30% by weight, the thermal decomposition resistance of the polymer will decrease.゛Preferably,
It is 7 to 25% by weight.

As the polymer molecular weight regulator, commonly used mercaptans are used. Specific examples include primary, secondary and tertiary mercaptans having alkyl groups or substituted alkyl groups, such as n-butyl, isobutyl, n-octyl, n-dodecyl, 5ec-butyl, 5ec-dodecyl, Mention may be made of mercaptans such as tert-butyl mercaptan; aromatic mercaptans such as phenyl mercaptan, thiocresol; thioglycolic acid and its esters; and ethylene thioglycol.

These may be used alone or in combination of two or more. The amount of the polymer molecular weight regulator used is appropriately determined depending on the desired molecular weight of the polymer.

Polymerization initiators are those that actively decompose at the reaction temperature and generate radicals, such as G-tert-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, G-tert-butyl perphthalate, and G-tert-butyl peroxide. rhubarbenduate, tert
・Butyl peracetate, 2,5-dimethyl-2,5-
Di(tert-butylperoxy)hexane, di-t
Organic peroxides such as amyl peroxide, benzoyl peroxide and lauryl peroxide, and azobisisobutanol diacetate, 1,
Examples include 1'-azobiscyclohexanecarbonitrile, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, 2-cyano-2-propylazoformacide and 2,2'-azobisisobutyronitrile. It will be done. These polymerization initiators can be used alone or in combination of two or more. The amount of polymerization initiator used is 3X10-4g per 100g of the mixture of mixed solvent and monomer.
Less than a mole. If the amount of the polymerization initiator exceeds this amount, a polymer with excellent heat decomposition resistance cannot be obtained. Preferably, it is not more than 2.5×10 −4 g-mol per 100 g of said mixture.

A mixture of a mixed solvent and a monomer, a polymer molecular weight regulator, and a polymerization initiator are mixed separately or in advance, and then introduced into the reaction zone where they are substantially uniformly mixed to carry out a polymerization reaction. If there is an unmixed portion in the reaction zone, the accumulation of polymerization heat may trigger a runaway reaction due to the automatic acceleration effect of the reaction, which not only makes stable polymerization difficult, but also makes it difficult to obtain a polymer of consistent quality. I can't get it.

A substantially uniformly mixed reaction zone is achieved, for example, by a vessel-type reactor equipped with stirring blades such as anchor type, double spiral type, and screw type.

The polymerization temperature is 60 to 170°C. Polymerization temperature is 60℃
If it is less than this, the polymerization rate decreases and is not economical, and the viscosity of the polymerization solution increases, making it difficult to operate the polymerization reaction. When the polymerization temperature exceeds 170°C, the generation of oligomers increases,
This causes a yellowish color when the polymer is heated, leading to a decrease in optical properties.

Preferably, the temperature is 70 to 160°C.

In the reaction zone, usually after polymerization to at least 50% of the initial monomer, volatile components such as the solvent and unreacted i-mer are removed to obtain the desired polymer. As a method for removing volatile components from the polymerization solution, a method of heating to 200 to 300° C. under reduced pressure is usually adopted, and a device such as a screw extruder or a devolatizer is used. The volatile content remaining in the polymer is 1% by weight or less, preferably 0.5% by weight or less.

[Effects of the Invention] According to the present invention, methyl methacrylate monomers are polymerized using a mixed solvent consisting of alkyl alcohol and benzene or alkylbenzene in the presence of a radical polymerization initiator limited to a specific amount or less. , the automatic acceleration effect and gel effect of the polymerization reaction peculiar to the polymerization of vinyl monomers are suppressed, the polymerization reaction becomes stable, and a methacrylic polymer particularly excellent in heat decomposition resistance and optical properties can be obtained.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the Examples. All "parts" and "%" used in the examples are by weight.

In the following examples, the physical properties of the polymer were measured by the following method.

(1) The intrinsic viscosity of a polymer is determined by Delow-Bishop (De
The flow time (t
) and the flow time (to) of dimethylformamide were measured at a temperature of 25 ± 0.1 °C, to / to 4 direct force 1
The relative viscosity η, ..., l of the polymer was calculated from the following formula.

Intrinsic viscosity = (In η, , ri/C (wherein, C is the number of polymers per 100 mm of solvent) (2) The total light transmittance (%) of the molded product is ASTM D 10
It was measured by the 03 method.

(3) The thermal decomposition rate of the polymer was determined from the difference in weight before and after heating 100 cm of a sample at 290° C. for 30 minutes in a nitrogen atmosphere. Note that the sample used was one that had been vacuum dried at 80° C. for 24 hours before measurement.

Example 1 83 parts of methyl methacrylate, 2 parts of methyl acrylate, 0.025 parts of 1,1'-azobis-1-cyclohexanecarbonitrile (1,OX 10-4 g-mol/10
0 g-monomer mixture), n-octyl mercaptan 0.
25 parts and toluene-methanol mixed solvent (weight ratio 7
:3) After mixing 15 parts, the internal volume is 2 at a rate of 31/h.
It was supplied to the ON reaction tank. The reaction vessel was equipped with a jacket for circulating a heat medium, and the reaction temperature was maintained at 115°C. Also,
The inside of the reaction tank was sufficiently stirred to achieve substantially uniform mixing. The polymerization rate immediately after leaving the reaction tank was 77±2% for 3 days after reaching a steady state, and it was possible to maintain the polymerization reaction extremely stably. This polymerization solution was heated to 230° C. and then continuously supplied to a degassing extruder under reduced pressure. This degassing extruder has a single screw with an outer diameter of 30 mm and a vacuum level of 10 mH.
The reactor was equipped with three vent openings for degassing which were maintained at a reduced pressure of 1.5 g and a die for shaping the polymer into strands, and heated to 260°C. The polymer that has been sufficiently degassed at the vent section is taken out in the form of strands from the die.
After cooling with water, it was pelletized using a pelletizer. It was confirmed that the volatile content contained in the obtained polymer was 0.1% or less. The physical properties of this polymer are as follows.

Intrinsic viscosity 0.32 Total light transmittance 93% Thermal decomposition rate 2.1% Example 2, 90 parts of methyl methacrylate, 0.004 parts of di-tert-butyl peroxide (2.7 x 10-4 g-mol/100 g-unit) Polymerization was carried out in the same manner as in Example 1 using 10 parts of tert-butyl mercaptan solvent (weight ratio 8:2). However, the polymerization temperature was 150°C.

The polymerization rate was 78 parts and 2% for 3 days after reaching a steady state, and it was possible to maintain the polymerization reaction extremely stably. This polymerization solution was pelletized in the same manner as in Example 1. It was confirmed that the volatile content contained in the obtained polymer was 0.1% or less.

The physical properties of this polymer are as follows.

Intrinsic viscosity 0.35 Total light transmittance 92.5% Thermal decomposition rate 1.9% Example 3 65 parts of methyl methacrylate, 10 parts of methyl acrylate
parts, 2.2'-azobisisobutyronitrile 0.039
Same as Example 1, using 2,4 parts of 10-4 g-mol/100 g-monomer mixture, 0.31 parts of n-octyl mercaptan and 25 parts of benzene-methanol mixed solvent (weight ratio 7:3). Polymerization was carried out by the method of However, the polymerization temperature was 95°C.

The polymerization rate was 72 parts and 2% for 3 days after reaching a steady state, and it was possible to maintain the polymerization reaction extremely stably. This polymerization solution was pelletized in the same manner as in Example 1. It was confirmed that the volatile content contained in the obtained polymer was 0.1% or less.

The physical properties of this polymer are as follows.

Intrinsic viscosity 0.30 Total light transmittance 93% Thermal decomposition rate 2.5% Example 4 80 parts of methyl methacrylate, 0.031 parts of dicumyl peroxide (1,1x 10-4 g-mol/100
g-monomer mixture), n-dodecyl mercaptan 0.2
Polymerization was carried out in the same manner as in Example 1 using 8 parts and 20 parts of an ethylbenzene-isopropyl alcohol mixed solvent (weight ratio 6:4). However, the polymerization temperature was 140°C. Three days after reaching steady state, the polymerization rate was 81 parts and 2%.
Therefore, it was possible to maintain the polymerization reaction extremely stably. This polymerization solution was pelletized in the same manner as in Example 1. The volatile content contained in the obtained polymer was 0.1
% or less. The physical properties of this polymer are as follows.

Intrinsic viscosity 0.32 Total light transmittance 93% Thermal decomposition rate 2.4%

Claims (1)

[Claims] 1. When continuously polymerizing methyl methacrylate alone or a monomer mixture of methyl methacrylate and other alkyl methacrylate or alkyl acrylate, 5 to 50% by weight of monohydric alkyl alcohol and 95%
3 to 50% by weight of a mixture with the monomer containing benzene or alkylbenzene in a range of 5% by weight or more and less than 30% by weight per 100g of the mixture with the molecular weight regulator and the monomer. ×10^-^4g
- A method for producing a methacrylic polymer, characterized in that the polymerization is carried out at a temperature of 60 to 170° C. in a substantially uniformly mixed reaction zone with less than mol of a polymerization initiator. 2. The method according to claim 1, wherein the alkyl group of the monovalent alkyl alcohol and alkylbenzene has 4 or less carbon atoms.