JPH06228213A - Production of acrylic resin - Google Patents

Abstract

PURPOSE:To efficiently produce an acrylic resin by a simple method by using methyl methacrylate produced from a new raw material as a monomer. CONSTITUTION:Methyl methacrylate produced from methylacetylene, etc., contains methyl crotonate as a by-product. The by-product is not removed and optionally methyl crotonate is used as a solvent for solution polymerization to produce an acrylic polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing an acrylic resin useful as a plastic material having excellent transparency.

[0002]

Acrylic resins are plastics with excellent transparency, weather resistance, mechanical strength, moldability and processability.
It is used for signboards, lighting equipment, vehicle parts, and various decorative items. In recent years, applications in the optical field such as lenses, optical disks, and optical fibers are expanding, and there is a demand for a method of producing an acrylic resin of superior quality with a simple device and a simple process.

Conventionally, a method for producing methyl methacrylate, which is a raw material for an acrylic resin, is a method in which acetone cyanohydrin obtained by adding hydrogen cyanide to acetone is treated with sulfuric acid and then esterified (acetone cyanohydrin method). , A method using a direct oxidation reaction of isobutylene, a method of oxidizing t-butanol obtained by hydrating isobutylene in a naphtha C ₄ fraction spent BB, and a sulfuric acid treatment of methacrylonitrile obtained by ammoxidation of isobutylene. Known methods include esterification, dehydrogenation of methyl isobutyrate obtained by reacting propylene with carbon monoxide and methanol.

[0004]

By the way, recently, as a new method for producing methyl methacrylate, a method for obtaining methyl methacrylate in a single step by reaction with carbon monoxide and methanol by using methylacetylene as a raw material, and by using propylene as a raw material, A method of reacting this with carbon monoxide and hydrogen fluoride to give isobutyric acid fluoride, and obtaining methyl methacrylate through hydrolysis, oxidation and esterification, and using ethylene as a raw material, reacting carbon monoxide and hydrogen Has been developed into propionaldehyde, dehydrogenated with formaldehyde, oxidized and esterified to obtain methyl methacrylate, and the like, which has been developed and has been attracting attention as an efficient production method.

However, in each of the production steps using these methylacetylene, propylene, and ethylene as raw materials, methyl crotonic acid is produced as an impurity (by-product) different from the above-mentioned conventional methods, so this methyl methacrylate is used as an acrylic acid. When it is used as a raw material for a system resin, it is considered necessary to remove methyl crotonate.

[0006]

DISCLOSURE OF THE INVENTION The present invention uses the above methyl acetylene, propylene, and methyl methacrylate prepared from ethylene as raw materials to produce an acrylic resin without the extremely troublesome operation of removing by-products. The task is to do.

[0007]

Means for Solving the Problems In the present invention, when an acrylic resin having methyl methacrylate as a constituent unit is produced by radical polymerization, methyl methacrylate containing methyl crotonic acid is homopolymerized or otherwise copolymerized. It relates to a method for producing an acrylic resin by copolymerizing with a possible vinyl compound.

Methyl methacrylate used in the method for producing an acrylic resin of the present invention is produced by using methyl acetylene, propylene and ethylene as raw materials.
These raw materials usually contain about 0.001 to 1% by weight of methyl crotonate as a by-product. In the method for producing an acrylic resin of the present invention, the methyl methacrylate is subjected to polymerization without removing any of these methyl crotones. In the present invention, the meaning of containing methyl crotonate includes not only the above byproducts but also methyl crotonate added to the reaction system as a solvent in the case of solution polymerization. Methyl crotonate present in the polymerization reaction system may be bonded to the end of the polymer molecule by chain transfer reaction, but even if it is bonded, the quality of the polymer does not deteriorate, and coloring and heat resistance Will not be reduced.

Methyl methacrylate containing methyl crotonate may be polymerized alone or may be copolymerized with 0.1 to 20% by weight of another monomer based on methyl methacrylate. Other copolymerizable monomers include methyl acrylate, ethyl acrylate, propyl acrylate,
Acrylic acid-n-hexyl, chloroethyl acrylate,
Examples thereof include vinyl compounds such as stearyl acrylate, -n-butyl methacrylate, -n-octyl methacrylate, styrene, α-methylstyrene, and acrylonitrile.

The method for producing the acrylic resin of the present invention is carried out by a polymerization method such as suspension polymerization, bulk polymerization or solution polymerization using a radical polymerization initiator, and the solution polymerization method is preferred. The solvent used for the solution polymerization may be any solvent that is soluble in the polymer to be produced and is inert to the polymerization reaction, but the solvent has a boiling point under normal pressure of 50 to 150 ° C. Is preferred. Examples of such a solvent include benzene, toluene, xylene, ethylbenzene,
Acetone, tetrahydrofuran, methyl acetate, ethyl acetate, methyl ethyl ketone, hexane, heptane, octane, cyclohexane, isooctane and the like can be mentioned. It is also possible to use methyl crotonate as described above. These may be used alone or in combination of two or more. These solvents are used after removing dissolved oxygen to an amount that does not affect the polymerization reaction.

If the boiling point of the solvent used exceeds 150 ° C., it is difficult to remove the solvent when purifying the polymer, which is not preferable. On the other hand, when the boiling point of the solvent is less than 50 ° C., a sufficient polymerization rate cannot be obtained, and when the temperature of the reaction solution is higher than the boiling point, the polymerization rate becomes large, but for that purpose, significant pressurization is required. Not practical. Further, when carrying out the recycling of the mixture of the monomer and the solvent, in order to avoid the need for intermediate separation of these, it is preferable to use a solvent having a boiling point close to that of methyl methacrylate. . The mixtures will have a narrow boiling range, reducing the risk of impurities being incorporated into the recycled mixture.

The amount of the solvent used is usually selected in the range of 5 to 70% by weight in the reaction mixture in consideration of the phenomenon of automatically accelerating the polymerization reaction, the viscosity of the reaction mixture produced, and the like. When the amount of the solvent is less than 5% by weight, the viscosity of the reaction mixture becomes high and the phenomenon of automatically accelerating the polymerization reaction easily occurs, which is not preferable. On the other hand, when the amount of the solvent exceeds 70% by weight, the polymerization rate becomes small and it takes a long time to complete the polymerization reaction, which is not practical, and when the solvent is removed from the polymerization reaction system, a multi-step removal operation is required. Is required, which is not preferable.

In the production method of the present invention, a radical polymerization initiator, a chain transfer agent, and other additives are added to a monomer solution, the mixture is polymerized in a polymerization reactor, and then the solvent is removed from the obtained reaction mixture. It is carried out by separating. The polymerization temperature is such that the boiling point of methyl methacrylate at atmospheric pressure is 100 ° C.
50 to 1 in relation to the polymerization initiator used and
The range is 50 ° C. The reaction pressure depends on the kind or amount of the solvent used, but is normal pressure or relatively easy to put into practical use.
The range is up to 30 kg / cm ² . When the polymerization temperature is lower than 50 ° C, it is needless to say that when the amount of the solvent is large, for example, 5 to 10
Even in a small amount such as wt%, the polymerization completion time becomes extremely long, which is not practical. On the other hand, when the polymerization temperature exceeds 150 ° C., the initial polymerization rate becomes remarkably high, and heat cannot be removed by a practical device.

As the radical polymerization initiator used for initiating the polymerization, a radical polymerization initiator having a decomposition rate constant in the temperature range of 50 to 150 ° C. in the range of 0.003 to 0.07 / min.
It is used at a rate of 02 to 0.0001 mol / liter. Examples of such a polymerization initiator include lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxyisopropyl carbonate,
Peroxides such as benzoyl peroxide or 2,2 '
-Azobisisobutyronitrile, 2,2'-azobis-
Examples thereof include azo initiators such as 2,4-dimethylvaleronitrile, methyl 2,2′-azobisisobutyrate, and 1,1′-azobis (cyclohexane-1-carbonitrile).

As a polymerization initiator, the decomposition rate constant is 0.0
If the amount used is less than 03 / min, the initial polymerization rate will be remarkably low at the time of low polymerization temperature, the reaction will take a long time, and an automatic acceleration phenomenon will occur in the final reaction stage, which is not preferable. Also, when a decomposition rate constant of more than 0.07 / min is used, the initial polymerization rate becomes remarkably high, which makes reaction control extremely difficult and is not preferable. Furthermore, the concentration of the polymerization initiator is 0.000.
When the amount is less than 1 mol / liter, it depends on the decomposition rate of the polymerization initiator, but the polymerization rate is generally very low and the polymerization yield is low, which is not practical. On the other hand, when the concentration of the polymerization initiator exceeds 0.02 mol / liter, in general, the initial heat generation due to the decomposition of the initiator is remarkable, but it is difficult to remove the heat from the reaction system, although it depends on the decomposition rate of the polymerization initiator. Is not preferable.

In the production method of the present invention, the molecular weight of the polymer is adjusted to a preferable range (50,000 to 200,000) as a thermoplastic molding material, and further, a molecule having a thermally unstable unsaturated bond carbon at the terminal is used. In order to reduce the ratio, it is desirable to use a chain transfer agent having a concentration of 0.04 to 0.001 mol / liter in addition to the above polymerization initiator. As a chain transfer agent,
Amyl mercaptan, heptyl mercaptan, isooctyl mercaptan, decyl mercaptan, n-dodecyl mercaptan, phenylethyl mercaptan, hexadecyl mercaptan, stearyl mercaptan and other sulfur compounds such as alkyl or arylalkyl mercaptans, benzene , Toluene, ethylbenzene, xylene, propylbenzene, isobutylbenzene, etc., alkyl substituted aromatic compounds having about 6 to 18 carbon atoms, carbon tetrachloride, dichloroethane, trichloroethane, difluoropropane, methylamine, isopropylamine, t-butylamine, dodecyl Halogen-, amino- or imide-substituted hydrocarbons or aromatizations of amines, anilines, piperosines, pyridines, pyridylidenes, dimethylsulfoxides, etc. Things and the like.

Further, in the production method of the present invention, additives which do not inhibit the polymerization at the start of the reaction or during the reaction, for example, plasticizers, lubricants, dyes, pigments or various stabilizers may be added. As the polymerization reaction type, a general type such as a tank type or a tower type and a combination thereof may be used, and either a batch type or a continuous type may be applied.
After the completion of the polymerization reaction, residual monomers, methyl crotonate, volatile components such as a solvent are removed from the reaction mixture, and the polymer is recovered. As a method for removing the volatile component, for example, a method using flash can be mentioned. According to this method, the reaction mixture is preliminarily heated to 200 to 300 ° C., preferably 2
The volatile components are removed by heating to a temperature range of 40 to 270 ° C. and spraying this in a devolatilization tank. When the heating temperature of the reaction mixture exceeds 300 ° C., the polymer is discolored and depolymerization is likely to cause loss of the polymer, which is not preferable. On the other hand, if the heating temperature is less than 200 ° C, the devolatilization efficiency is lowered, which is not preferable. The devolatilization tank is maintained under reduced pressure so that all of the above volatile components can be removed. The degree of pressure reduction is maintained at an absolute pressure of 10 to 150 mmHg, preferably about 50 mmHg. The method for producing an acrylic resin of the present invention can be industrially advantageously carried out by combining it with a step for producing methyl methacrylate using methylacetylene, propylene or ethylene as a raw material.

[0018]

According to the method for producing an acrylic resin of the present invention,
It is used in the polymerization reaction without removing the by-product methyl crotonic acid from methyl methacrylate produced from methylacetylene, propylene or ethylene. Therefore, the monomer separation and purification treatment is not required, and the methyl crotonic acid can be easily removed together with the residual monomer in the reaction mixture and the volatile components such as the solvent, a simple apparatus, and a simple method. The acrylic resin can be efficiently obtained by the method.

Hereinafter, the present invention will be described in more detail with reference to Examples.

【Example】

Example 1 A 300 ml glass four-neck round bottom flask equipped with a stirring blade, a cooling tube and a thermometer was placed in a glass four-necked round-bottomed flask containing methacrylic acid containing 0.05% by weight of methyl crotonate produced from methylacetylene as a raw material. Methyl 80.0 g (4.2
Mol / liter), toluene 80.0 as solvent
g, 0.08 g of lauryl mercaptan as a chain transfer agent
(Corresponding to 2.1 mmol / liter), 300
80 with stirring under a nitrogen atmosphere while stirring at a rotation speed of rpm.
Heated to ° C. When the temperature reached 80 ° C., 2,2′-azobisisobutyronitrile 0.0 was added as a polymerization initiator.
64 g (corresponding to 2.0 mmol / l) was added. Stirring was continued for 8 hours while maintaining the solution at this temperature. After heating the resulting reaction mixture to 240 ° C., 50
It sprayed in the devolatilization tank decompressed to mmHg. The obtained molten polymer was extruded and collected as a strand. The polymerization yield was 75% from the weight of the polymer after drying under reduced pressure. Also,
The number average molecular weight of the polymer measured by GPC is 74,000,
The molecular weight distribution was 2.0. As a result of analysis of volatile components by GLC, the amount of methyl crotonate remaining in the polymer was 20 ppm. The residual amount of toluene used as a solvent was 500 ppm. Furthermore, when analyzed by TGA, ¹ H-NMR and ¹³ C-NMR,
This methyl crotonate was not contained in the polymer main chain as a copolymer component.

Example 2 A methyl methacrylate polymer was produced in the same manner as in Example 1 except that methyl crotonate was used instead of toluene as the solvent. As a result, the polymerization yield was 73%, the number average molecular weight of the polymer was 74,000, and the molecular weight distribution was 2.0. As a result of analysis of volatile components, methyl crotonate remaining in the polymer was 580 ppm, which was not much different from the residual amount of toluene used as a solvent in Example 1 of 500 ppm. In addition, as a result of analysis by NMR and the like, it was found that methyl croutonate was not substantially contained in the main chain of the polymer even in this example in which a large amount of methyl croutonate was used as the solvent.

Claims (1)

[Claims] 1. When producing an acrylic resin containing methyl methacrylate as a constituent unit by radical polymerization,
A method for producing an acrylic resin, which comprises using methyl methacrylate containing methyl crotonate.