RU2421477C2 - METHOD OF PRODUCING α-METHYL STYRENE, AND METHOD OF PRODUCING STYRENE-BASED HEAT-RESISTANT COPOLYMER USING α-METHYL STYRENE - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves the following steps: reaction of a polar substance containing a compound which contains a carbonyl group, and which is contained in α-methyl styrene, in the presence of a basic compound, wherein basicity of the basic compound is equal to or greater than 10 on acid dissociation constant pKa of the conjugated acid of the basic substance; separation of the component with low boiling point, obtained during the reaction, from the mixture of the product of reaction of the polar substance containing a compound which contains a carbonyl group and α-methyl styrene; and separation of α-methyl styrene from the mixture of the product of the reaction of the polar substance containing a compound which contains a carbonyl group and α-methyl styrene. Disclosed also is a method of producing α-methyl styrene (version) and a method of producing a styrene-based copolymer.

EFFECT: method enables to obtain α-methyl styrene of high purity.

9 cl, 26 ex, 3 tbl

Description

FIELD OF THE INVENTION

The present invention relates to a method for producing high-purity α-methylstyrene as a polymerization monomer. More specifically, the present invention relates to a method for purifying α-methylstyrene to high purity by removing polar substances such as aldehydes and ketones contained in trace amounts of α-methylstyrene by reaction in the presence of a basic substance, whereby effective removal can be achieved without the need for a complex process . In addition, the present invention relates to a styrene-based copolymer having a slight coloring and exceptional heat resistance, weather resistance, melting resistance, ductility, deformation resistance and rigidity, which can be obtained using this monomer.

State of the art

Styrene-based resins are used in an extremely wide range of applications, not only because they are made of high quality material in terms of transparency, stiffness, resistance to deformation and the like, but also as a result of the fact that they can be produced in various forms, such as rolled sheets, films, foam sheets, foam panels, and blow molded products, and since many styrene resins can be produced cheaply and in bulk through large-scale imerizatsii using radical polymerization, solution polymerization using a high monomer concentration, suspension polymerization or emulsion polymerization.

Although typical examples of styrene-based resins include polystyrene (GPPS), styrene / acrylonitrile (AS), styrene / methyl methacrylate (MS), styrene / methacrylic acid (SMAA), styrene / maleic anhydride (SMA) and the like similarly, styrene homopolymers (polystyrene (GPPS)) are used most universally.

Polystyrene has many excellent properties and, since it is cheap, it is of great importance to use, and it is used in various fields. Some key applications are listed below.

Use for packaging

Food containers (styrofoam: PSP), containers for dishes (styrofoam: PSP), colorless cups, spoons, forks, packing lists for vegetables and (biaxially oriented sheets), window cover.

Use in household electrical appliances

TV system, air conditioning and mainly equipment packaging, trays for an electric refrigerator, cassettes, MD and MO shells

Miscellaneous household items

Toys, stationery and supplies

Application in building materials

Insulation (foam panels), tatami mats (foam panels).

However, there were some applications that were not even satisfied with the properties of the resin, such as applications that limited the resin in use due to insufficient heat resistance. More specifically, since the heat resistance of GPPS is about 100 ° C (glass transition temperature), for applications involving contact with hot steam, for disinfection by boiling, applications for food packaging requiring heating in a microwave oven, or applications involving cast auto parts subject to high temperatures in summer, this resin cannot be used without risk of causing the cast products to deform.

One method for enhancing the heat resistance of polystyrene may include copolymerizing styrene with a monomer containing a polar functional group, examples of which may include copolymers of styrene and methacrylic acid (SMAA), copolymers of styrene and maleic anhydride (SMA), and copolymers of styrene and maleimide anhydride. Heat resistance can be arbitrarily changed by controlling the amount of monomer containing a polar functional group in the copolymer composition. For example, a typical example of a heat-resistant styrene-based resin in the form of SMAA has a Wick heat resistance temperature of 105 to 125 ° C. However, if polymers having a polar functional group are exposed to high temperatures, a crosslinking reaction of the polymer chain occurs due to side reactions of the polar groups, and as a result, gel-like substances are formed that cause a decrease in the processability of casting due to increased viscosity, thereby preventing satisfactory use these polymers by consumers in terms of quality and productivity.

In addition, an increased susceptibility to crosslinking reactions under conditions when the melt is at a high temperature implies an increased susceptibility of polymers with high molecular weight deformations during the casting process, thereby making it difficult to utilize and reuse resins. For example, when receiving a product by injection molding, the final materials (skeletons) are obtained in the process of forming the components of the central gate and the distributor and when receiving the molded products from biaxially oriented sheets, or foamed sheets. They are usually reused through partial mixing with the original granules after grinding or cutting, or are usually reused through partial mixing in universal resins such as polystyrene.

However, re-application becomes difficult if the flow characteristics of the resin change due to crosslinking of high molecular weight polymers during melt molding and there is a problem of limitations that apply to the use of these resins for processing into the original granules. In addition, copolymers containing a polar functional group usually have insufficient compatibility with polystyrene, and even when mixed by melting, they not only lead to a deterioration in mechanical properties, but also cause a loss of transparency, thereby preventing the processing of these copolymers with universal polystyrene.

Since increased emphasis is placed on the effective use of resins in recent years, various types of methods for returning to circulation have been developed and implemented. Resins that are able to be recycled, reconstituted and reused are a must on the resin markets of the future. Resins being developed in the future will certainly be resins that are able to efficiently return to circulation, almost without undergoing any reduction in molecular weight or the formation of monomers due to rupture of the polymer chain, even after passing through several molding cycles from the melt. Thus, there is a need to develop resins exhibiting higher resistance to melting than conventional styrene-based copolymers.

Another problem of conventional heat-resistant styrene-based resins was a narrow range of processing conditions during the casting process. Improving the heat resistance of the copolymer is tantamount to improving the temperature at which the polymer chain becomes fluid. Thus, if it is necessary to obtain flow characteristics similar to those of polystyrene during the casting process, then it is necessary to raise the temperature of the process, corresponding to the improvement of heat resistance. However, in the case of styrene-based copolymers containing a polar functional group, the corresponding decomposition onset temperature does not improve the heat resistance. Therefore, the temperature range of the casting process becomes narrow and, as a result, there were problems in terms of reducing productivity and quality.

There are also ways to improve the heat resistance of styrene-based resins, such as, for example, by using a monomer that does not contain a polar functional group. For example, a copolymer of styrene and α-methylstyrene, as is known, shows an increase in the glass transition temperature, as the content of α-methylstyrene increases (see, for example, non-patent document 1).

However, in the case of an attempt to copolymerize styrene and α-methylstyrene using the usual industrial production process in the form of radical polymerization in solution, none of these methods could be applied on an industrial scale due to the many problems that are listed below:

1) high molecular weight polymerization is difficult due to the low temperature of α-methyl styrene degradation at about 60 ° C;

2) the intended heat resistance cannot be obtained due to restrictions on the content of α-methylstyrene in the copolymer; and

3) the thermal decomposition of the copolymer easily occurs depending on the casting process conditions due to poor heat resistance during the melting process, thus leading to the formation of monomeric components and susceptibility to a decrease in molecular weight.

On the other hand, since α-methylstyrene can undergo live anionic polymerization by using a butyl lithium initiator, copolymers of styrene and α-methylstyrene can also be obtained by live anionic polymerization (see, for example, Patent Document 1).

Therefore, a method has been proposed to solve the problems of radical polymerization in solution by performing live anionic polymerization in accordance with a continuous live polymerization method using a type of polymerisation reactor with perfect mixing (see, for example, Patent Document 2). This method is characterized by the implementation of polymerization, using a continuous type of ideal mixing reactor, so that the concentrations of α-methyl styrene monomer, styrene monomer and live copolymer present in the living polymerization reaction system remain constant at any time, and offers the following effects:

1) high molecular weight polymerization is possible due to the application of the living polymerization method;

2) the content of α-methylstyrene in the copolymer can be controlled, since the concentration in the reaction system can be kept constant; and,

3) the heat resistance during the melting process is improved due to the absence of head-to-head bonds, tail-to-tail bonds and other unstable bonds in the main chain of the copolymer, due to the use of anionic polymerization.

However, living anionic polymerization is usually susceptible to the effects of impurities contained in the feed. In particular, active anions are known to readily react with polar substances such as water, aldehydes, ketones and alcohols. If polar substances are present in the anionic polymerization reaction system, even in trace amounts, the active anions react with polar substances, leading to the formation of stable bonds, thus causing the problem of interruption of polymerization. Therefore, when performing live anionic polymerization, it is necessary to reduce the amount of polar substances in the feed, and the influx of polar substances into the reaction system must be suppressed as much as possible.

In addition, the above polar substances and reaction products of active anions and polar substances decompose during the polymerization process, leading to the formation of colored substances. In this case, this can lead to coloring of the polymer or to a deterioration of the physical characteristics of the polymer, thus making it unacceptable. From this point of view, in addition, polar substances are removed from the feedstock preferably as much as possible.

However, the usual industrial production process for α-methylstyrene is a cumene-phenolic industrial production. This cumene-phenolic industrial production includes a stage in which cumene hydroperoxide obtained by oxidation of cumene feed concentrates to 80 to 85%, followed by acid decomposition into phenol and acetone and neutralization / washing. The resulting crude phenol contains substances such as acetone, water, cumene, α-methyl styrene and phenol, and the purified phenol is obtained from this crude phenol by distillation, while acetone and α-methyl styrene are separated and regenerated, respectively (see e.g. patent documents 3 and 4).

However, in the case of an attempt to appropriately separate and regenerate acetone and α-methylstyrene simultaneously with obtaining purified phenol using the process described above, the following problems arise. Namely, substances having a boiling point close to that of α-methylstyrene, for which separation by distillation is difficult, are present among polar substances such as aldehydes and ketones obtained as by-products during the phenol production process. Thus, polar substances cease pollution of α-methylstyrene as impurities in the case of only distillation purification.

In addition, the method is carried out in order to remove impurities containing polar substances, including the delivery of crude α-methylstyrene to an alkaline wash tank before distillation and washing in a tank, followed by delivery to a distillation column in order to regenerate the product α-methylstyrene (see e.g. patent documents 5 and 6). However, in the case of washing in an alkaline washing tank according to the aforementioned method, since the solubility of the polar substances in the alkaline solution is unsatisfactory, the polar substances cease to remain in α-methyl styrene, thereby preventing the removal of trace amounts of polar substances. In addition, although methods have also been considered that include reacting polar substances in an alkaline wash tank in order to obtain substances with low volatility, and increasing the difference in relative volatility between these substances and α-methylstyrene, followed by distillation, in this case, polar substances cannot be removed unless the reaction is nearly 100% complete.

On the other hand, an example of a conventional method for purifying styrene polymerization monomers in a laboratory may include washing with an alkaline substance such as an aqueous solution of sodium thiosulfate or an aqueous solution of sodium hydroxide and water, followed by drying and distillation (see, for example, non-patent document 2 ) However, although the above method makes it possible to exclude the use of a polymerization inhibitor, peroxide and polymer, it is not possible to completely remove polar substances from α-methylstyrene for the same reasons as in the case of washing in an alkaline washing tank, as described above.

In addition, although a method was indicated that included adding alkyl lithium and the like to the monomers before polymerization in order to deactivate the polar substances, followed by distillation, in this case, since significant amounts of polymers, oligomers and the like are formed, accompanying the reaction, then this method is considered industrially unsuitable. In addition, the monomers can become contaminated oligomers depending on the distillation conditions, thus having the potential to adversely affect the polymerization.

Another example of a method for purifying α-methyl styrene may include purification using a column filled with silica gel, alumina or ion exchange resin and the like (see, for example, Patent Document 2 and Non-Patent Document 3). However, these excipients usually contain acidic or basic components. Namely, in the aforementioned method, there is the possibility of the presence of an acid component in the filler, causing the formation of low molecular weight α-methyl styrene oligomers, or the presence of the main component in the filler, which causes the decomposition of polar substances to high molecular weight condensates. High molecular weight oligomers or condensates formed contaminate the monomers in the column, and if the polymerization is carried out using these contaminated monomers, there is a risk that the polymerization will be interrupted or the reaction will be slowed down otherwise. In addition, since these oligomers and high molecular weight condensates have low volatility, they cannot be removed from the polymerised polymer solution and they no longer contaminate the final polymer obtained. As a result, problems arise that lead to a deterioration in the operational parameters of the polymer in the form of a decrease in the heat resistance of the obtained polymer or yellowing.

As described above, none of the methods of the prior art is effectively applied on an industrial scale as a method of purification of α-methylstyrene.

Patent Document 1: Japanese Patent Publication No. H6-10219.

Patent Document 2: Japanese Patent Application Publication No. 2006052346.

Patent Document 3: Japanese Patent Application Publication No. S55-94326.

Patent Document 4: Japanese Patent Publication No. S64-7058.

Patent Document 5: Japanese Patent Application Published No. 200086559.

Patent Document 6: Japanese Patent Application Publication No. H3-258733.

Non-Patent Document 1: Journal of Applied Polymer Science, T. 41, p. 383 (1990).

Non-Patent Document 2: R.H. Boundry, R.F. Boyer, "Styrene, its Polymers, Copolymers and Derivatives", Reinhold (1952).

Non-Patent Document 3: Journal of Applied Polymer Science, T. 40, p. 41 (1990).

Disclosure of invention

The tasks solved by this invention

An object of the present invention is to provide a method for purifying α-methylstyrene, providing high purity α-methylstyrene containing almost no polar substances, by effectively removing polar substances contained in trace amounts in α-methylstyrene by a method for purifying α-methylstyrene. In addition, it is an object of the present invention to provide a copolymer containing a styrene-based copolymer that improves the heat and weather resistance, which are disadvantages of SMAA and SMA, and also has excellent melting resistance, ductility, strength, stiffness and recyclability. applications, at the same time preventing the coloring of the polymer and leaving excellent characteristics of conventional styrene-based resins, as, for example, as transparent STI, dimensional stability and molding processability, by using this α-methylstyrene.

Means for solving problems

As a result of extensive research to solve the above problems, the inventors of the present invention found that certain polar substances contained in trace amounts in α-methyl styrene cause polymer staining and hinder polymerization control, and that oligomers obtained by conventional purification methods also cause polymer staining and worsen his physical characteristics. In order to eliminate these problems, the inventors of the present invention have found that the purification method of α-methylstyrene can effectively remove polar substances without the formation of oligomers by using the method of removing these polar substances, so as to control the content of polar substances and oligomers within a fixed range by reacting polar substances contained in α-methyl styrene, in the presence of a basic substance, and then separation of low temperature by-products boiling formed by this reaction from the reaction products of polar substances, thus leading to the refinement of the present invention.

Namely, the present invention is described below and provides a process for the purification of α-methylstyrene, α-methylstyrene for live anionic polymerization and a styrene-based copolymer.

In a first aspect, the present invention provides:

[1] a method for purifying α-methylstyrene, comprising the steps of:

reacting a polar substance contained in α-methylstyrene in the presence of a basic substance; and

separation of the reaction product of the polar substance and α-methylstyrene.

[2] a method for purifying α-methylstyrene in accordance with paragraph [1], comprising the steps of:

reacting a polar substance contained in α-methylstyrene in the presence of a basic substance; and

the separation of the component with a low boiling point obtained by the reaction, α-methylstyrene and the reaction product of a polar substance.

[3] a method for purifying α-methylstyrene according to [1] or [2], the process comprising the steps of:

1) the reaction of a polar substance contained in α-methylstyrene in the presence of a basic substance;

2) the separation of the component with a low boiling point obtained by reaction from a mixture of the reaction product of a polar substance and α-methylstyrene; and

3) the separation of α-methylstyrene from a mixture of the reaction product of a polar substance and α-methylstyrene.

[4] a method for purifying α-methylstyrene according to [1] or [2], the process comprising the steps of:

1) the reaction of a polar substance contained in α-methylstyrene in the presence of a basic substance;

2) separating the mixture of the component with a low boiling point obtained by the reaction and α-methylstyrene from the reaction product of the polar substance; and

3) the separation of α-methylstyrene from a mixture of a component with a low boiling point obtained by the reaction and α-methylstyrene.

[5] a purification method according to any one of paragraphs [1] to [4], wherein the polar substance contains a compound containing a carbonyl group.

[6] a purification method according to any one of [1] to [5], wherein the polar substance comprises a compound containing a carbonyl group and a mixture of phenol and catechol.

[7] a purification method according to [5] or [6], wherein the carbonyl group-containing compound is a compound represented by the following general formula (1) or general formula (2):

(wherein each of R ¹ , R ³ and R ⁴ independently represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, and R ² represents an alkyl group having from 1 to 6 carbon atoms).

[8] the purification method according to [7], wherein the compound containing the carbonyl group contains at least one compound selected from acetonylacetone, 3-methyl-2-cyclopentenone, benzaldehyde and acetophenone.

[9] a purification method according to any one of paragraphs [1] to [8], wherein the basicity of the basic substance is 10 or more in terms of the acid dissociation constant pKa of the acid conjugated with the given basic substance.

[10] a cleaning method according to [9], wherein the base material is a base compound containing an alkali metal or alkaline earth metal.

In a second aspect, the present invention also provides:

[11] α-methylstyrene for anionic polymerization, wherein the combination of an aliphatic carbonyl compound represented by the following general formula (1) and its intramolecular dehydration condensate is 100 ppm by mass or less, and an aromatic carbonyl compound represented by the following general formula (2) is present at 30 ppm by weight or less:

(wherein each of R ¹ , R ³ and R ⁴ independently represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, and R ² represents an alkyl group having from 1 to 6 carbon atoms).

[12] α-methylstyrene for anionic polymerization according to [11], wherein the alcohol, phenol and catechol content is 10 ppm by weight or less.

[13] α-methylstyrene for anionic polymerization according to [11] or [12], wherein the α-methylstyrene dimer is less than 5 ppm.

[14] α-methylstyrene for anionic polymerization according to any one of [11] to [13], wherein the benzofuran content is from 5 to 5000 ppm by weight.

In a third aspect, the present invention further provides:

[15] a styrene-based copolymer obtained by copolymerizing α-methylstyrene according to any one of items 11 to 14 and a vinyl aromatic monomer represented by the following general formula (3) using anionic polymerization:

(wherein R ⁵ represents a hydrogen atom, an alkyl group having 2 or more carbon atoms, or a phenyl group, and R ⁶ represents a hydrogen atom, a halogen, a hydroxyl group, an alkyl group, an alkoxy group, a carboxyl group or a haloalkyl group).

[16] a styrene-based copolymer according to [15], wherein the yellowness index value is 3 or less.

The beneficial effects of this invention

The present invention is applicable as a method for producing high-purity α-methylstyrene for anionic polymerization without the need for a complex process that allows removal by distillation of trace amounts of polar substances, which usually cannot be removed by distillation, by efficient modification to high molecular weight condensates by reacting the polar substance with α-methylstyrene in the presence of a basic substance and separation from the reaction by-products from the bottom oh boiling. In addition, the use of α-methyl styrene purified by the purification method of the present invention makes it possible to obtain a copolymer containing a styrene-based copolymer which improves the heat and weather resistance, which were disadvantages of SMAA and SMA, and also has excellent melting resistance, ductility, strength, rigidity and the possibility of processing for reuse, at the same time preventing the polymer from staining and leaving excellent characteristics of the generally accepted styrene-based resins, as, for example, according to the state of transparency, resistance to deformation and manufacturability of castings.

Best Mode for Carrying Out the Invention

The following provides a detailed explanation of the present invention.

Examples of polar substances present in α-methylstyrene that must be removed by the purification process of the present invention may include compounds containing a carbonyl group, phenol and catechol mixtures containing t-butylcatechol polymerization inhibitors. Specific examples of polar substances in the form of compounds containing a carbonyl group may include aliphatic carbonyl compounds in the form of a compound represented by the following general formula (1) and aromatic carbonyl compounds in the form of compounds represented by the following general formula (2):

(wherein each of R ¹ , R ³ and R ⁴ independently represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, and R ² represents an alkyl group having from 1 to 6 carbon atoms).

The term “alkyl group having from 1 to 6 carbon atoms”, as used herein, refers to a linear or branched alkyl group having from 1 to 6 carbon atoms, specific examples of which may include a methyl group, an ethyl group, a n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1 ethyl propyl group, n-hexyl group , 1-ethyl-2-methylpropyl group, 1,1,2-trimethylpropyl group, 1-ethylbutyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, 2 , 2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyl group, 3-methylpentyl group and the like. Preferred examples may include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, and the like.

In the present invention, more specific examples of compounds containing a carbonyl group may include acetonyl acetone, 3-methyl-2-cyclopentenone, benzaldehyde, acetophenone and the like. Since these polar substances inhibit the polymerization or cause the polymer to stain during the production of poly-α-methylstyrene and its copolymers by anionic polymerization and the like, they are preferably removed as much as possible. Since polar substances, with the exception of water, such as tert-butylcatechol, acetonylacetone, 3-methyl-2-cyclopentenone, benzaldehyde and acetophenone, have boiling points close to the temperature of α-methylstyrene, their content cannot be reduced above a certain level by using ordinary distillation.

The inventors of the present invention made it possible to remove trace amounts of these polar substances that could not be removed by conventional distillation, by distillation by reacting in the presence of specific basic substances, and by effectively converting polar substances that reacted in the presence of basic substances into compounds with high boiling points , in order to increase the difference in relative volatility of these compounds with α-methylstyrene. In addition, the inventors of the present invention also found a method for producing high purity α-methylstyrene by separating the reaction products of the polar substance from α-methylstyrene and low boiling point components containing side reaction products, followed by additional separation of α-methylstyrene from low boiling points.

In the present invention, there are two possible reactions for producing high boiling compounds by reacting polar substances in the presence of a basic substance. The first method involves the reaction of producing a high boiling point compound by reacting phenol or catechols having active hydrogen to form a salt, while the other method involves increasing the molecular weight by forcing an aldehyde or ketone having one or more hydrogen atoms at the α position , undergo a reaction of intramolecular or intermolecular condensation in the presence of a basic substance. In the case of the latter reaction, in particular, since water or alcohol is obtained by condensation, as will be described later, and if we take into account that the reaction is an equilibrium reaction, it is extremely difficult to carry out the reaction and increase the molecular weight, since the concentration of reagents is extremely low.

In addition, although there are compounds that undergo an intermolecular reaction depending on the particular compound, in this case, since the boiling point is extremely close to the temperature of the starting polar substance, the compounds cannot be separated by distillation. The inventors of the present invention have found that the boiling point can be increased by converting these compounds to intermolecular condensation by treatment under specific conditions.

Examples of aldehydes and ketones having a hydrogen atom in the α position may include acetonyl acetone, 3-methyl-2-cyclopentenone and acetophenone. At the first stage, the main substance removes the hydrogen atom in the α position, leading to the formation of enolate and polar matter. Since this reaction is an equilibrium reaction, and the equilibrium is usually biased towards the reactants, the formation of enolate is difficult. Therefore, in the second stage, the formed enolate undergoes an intermolecular addition reaction with the polar substance. As a result, since two or more polar substances increase in molecular weight and the difference in relative volatility with α-methylstyrene increases, they can be separated by distillation. The polar substance to which the enolate was added may or may not have a hydrogen atom in the α position, and even benzaldehyde that does not have a hydrogen atom in the α position may increase in molecular weight.

In particular, it is important in the present invention that the formation of the enolate in the first step is effectively carried out in order to carry out the condensation reaction in a trace concentration, which usually proceeds with difficulty. Therefore, by-products with a low boiling point, such as water and alcohol, obtained through a condensation reaction, are removed from the reaction system during the condensation reaction in the presence of a basic substance. As a result of the removal of by-products with a low boiling point from the reaction system, the first stage of the equilibrium reaction shifts toward the formation of enolate, thus allowing condensation reactions to proceed efficiently and making it possible to recover high-purity α-methyl styrene. Low boiling point by-products at the same time indicate products having a boiling point lower than the temperature of α-methyl styrene. The removal of low boiling point by-products from the reaction system can be carried out continuously or sequentially within the reaction system.

The separation only need to be that which separates the low boiling point by-products from the reaction system, and usually consists of evaporating the low boiling point by-products by heating the reaction system to a temperature equal to or higher than the boiling point of the low boiling point by-products. like distillation. Examples of methods for removing low boiling point by-products from the reaction system may include a method in which low-boiling point by-products are separated from the reaction system and the remaining α-methyl styrene and the polar reaction product are separated by a method such as distillation; a method in which a mixture of α-methylstyrene and low boiling point by-products is removed from the reaction system, in addition, at the same time, separating α-methylstyrene from low boiling point by-products by distillation; and a method in which a mixture of α-methylstyrene and low boiling point by-products is separated from the reaction system, followed by separation of α-methylstyrene and low boiling point by-products by distillation or adsorption using a column and the like. Any of these methods may be used in the present invention. What is important in the context of this document is that by-products with a low boiling point are effectively removed from the reaction system and that, as a result, a condensation reaction can proceed efficiently.

There are no particular restrictions on the basic substance used in the present invention, provided that it has a degree of basicity which allows it to remove a hydrogen atom in the α position of the polar substances. As an indicator of the basicity of its pKa, the acid conjugated to the base is preferably 10 or more. Examples of basic substances that can be used may include basic substances containing alkali metals or alkaline earth metals, including metal alkoxides such as sodium ethoxide, potassium ethoxide (conjugate acid: ethanol, pKa: 17) or sodium methoxide (conjugate acid: methanol, pKa: 16), metal hydroxides (conjugated acid: water, pKa: 16), such as sodium hydroxide, potassium hydroxide or magnesium hydroxide, metal oxides (conjugated acid: water, pKa: 16), such as sodium oxide, potassium oxide or magnesium oxide, metal amides, e as sodium amide (conjugated acid: ammonia, pKa: 35) or lithium diisopropylamide (conjugated acid: diisopropylamine, pKa: 36), and metal alkyls such as butyllithium (conjugated acid: butane, pKa: 45) or methyl lithium (conjugated acid : methane, pKa: 40).

These basic substances preferably have high solubility and dispersibility in α-methylstyrene. Although basic substances having high solubility and dispersibility in α-methylstyrene can be used as is, there are cases in which they are preferably used as a solution by using a suitable solvent. In this case, there are no particular restrictions on the solvent which is mixed with the basic substance, provided that it is capable of dissolving the basic substance, and water, alcohol or a mixed solution thereof can be used.

In this case, although water and alcohol inhibit the condensation reaction following the dispersion of the basic substance, this does not cause problems, provided that water and alcohol can be removed outside the reaction system along with by-products with a low boiling point. Thus, alcohols preferably have a boiling point of at least lower than α-methylstyrene.

The concentration of the basic substance is preferably from 0.01 to 10% by weight and more preferably from 0.02 to 5% by weight, based on α-methylstyrene. Despite the dependence on the concentration of the basic substance, there are no specific restrictions on the reaction time, provided that it is long enough to allow condensation reactions to take place, and it is preferable to give a certain amount of time for conversion to high boiling point intermolecular condensation products . Although the reaction time is presented as the average retention time in the case of a flow reaction system or as the sum of the reaction time and the distillation rate in the case of a batch reaction system, in the case of the basic substance at the concentrations indicated above, the preferred reaction time is at least 15 minutes more preferably from 15 minutes to 4 hours and even more preferably from 30 minutes to 3 hours.

Any kind of reaction system can be used in the present invention, provided that it allows you to essentially maintain the balance of air and liquid within the system. Operating pressure can be arbitrarily selected from a range of atmospheric pressure up to 5 kg / cm ² . In addition, there are also no specific problems, even if the procedure is carried out under reduced pressure. Although the temperature within the reaction system can be arbitrarily determined in accordance with the pressure, it is preferably from 40 to 200 ° C and more preferably from 60 to 150 ° C. The degradation temperature is 60 ° C or higher, taking into account the inhibition of polymerization of α-methylstyrene and 150 ° C or lower, taking into account the energy conservation of the heat source.

There are no particular restrictions on the form in which α-methyl styrene and the base material are fed, provided that low boiling point by-products such as water and alcohol obtained by condensation can be removed sequentially and can be fed by a batch process or continuous process.

The α-methyl styrene obtained in accordance with the purification method of the present invention can be purified from impurities in the form of polar substances such as phenol, tert-butyl catechol, acetonyl acetone, 3-methyl-2-cyclopentenone or benzaldehyde and controlled within a fixed range. Controlling these polar substances within a fixed range is extremely effective in controlling the polymerization and preventing yellowing of the polymer.

Although a small amount of polar substances is better, the total amount of acetonylacetone and its intramolecular condensation product as 3-methyl-2-cyclopentenone is preferably 100 ppm by mass or less and more preferably 50 ppm by mass or less, and the amount of benzaldehyde is preferably 30 ppm by weight or less and more preferably 20 ppm by weight or less. If the total amount of acetonylacetone and its intramolecular condensation product in the form of 3-methyl-2-pentenone exceeds 100 ppm by mass or the amount of benzaldehyde exceeds 30 ppm by mass, the yellowing of the resulting polymer becomes noticeable, and live polymerization can be inhibited depending on the case.

The following provides a description of the styrene-based copolymer of a component that contains a heat-resistant styrene-based copolymer in accordance with the present invention. The heat-resistant styrene-based copolymer in the present invention comprises an α-methylstyrene unit obtained by purification in accordance with the purification method in accordance with the present invention, and a vinyl aromatic unit. The copolymer containing a vinyl aromatic unit mentioned in the present invention is a copolymer obtained by polymerization using a vinyl aromatic monomer represented by the following formula (3) as a feed:

(wherein R ⁵ represents a hydrogen atom, an alkyl group having 2 or more carbon atoms, or a phenyl group, and R ⁶ represents a hydrogen atom, a halogen, a hydroxyl group, an alkyl group having from 1 to 6 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, a carboxyl group or a haloalkyl group having from 1 to 6 carbon atoms).

The term “alkoxy group having 1 to 6 carbon atoms” as used herein refers to an oxy group to which a predetermined “alkyl group having 1 to 6 carbon atoms” is attached, specific examples of which may include a methoxy group, an ethoxy group, n a propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an n-pentyloxy group, an isopentyloxy group, a sec-pentyloxy group, an n-hexyloxy group, isohexyloxy group, 1,1 -hexyloxy group, 1,1 ethyl propoxy group, 2,2-dimethylpropoxy group, 2-methylbutoxy group, 1-ethyl-2-methylpropoxy group, 1,2,2-trimethylpropoxy group, 1,1-dimethylbutoxy group, 1,2-dimethylbutoxy group, 2,2-dimethylbutoxy group, 2,3- dimethyl butoxy group, 1,3-dimethyl butoxy group, 2-ethyl butoxy group, 2-methyl pentyloxy group, 3-methyl pentyloxy group and the like. Preferred examples may include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group and the like, and even more preferred examples may include a methoxy group and an ethoxy group.

The term "alkyl group having 2 or more carbon atoms", as used herein, refers to a linear or branched alkyl group having from 2 to 6 carbon atoms, specific examples of which may include an ethyl group, an n-propyl group, an isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, n -hexyl group, 1-ethyl-2-methylpr sawn group, 1,1,2-trimethylpropyl group, 1-ethylbutyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1 , 3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyl group, 3-methylpentyl group and the like. Preferred examples may include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, and the like.

The term “halogen atom” as used herein refers to a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

The term “haloalkyl group having from 1 to 6 carbon atoms” as used herein refers to a group in which a predefined “halogen atom” is attached to a predefined “alkyl group having from 1 to 6 carbon atoms”.

The vinyl aromatic monomer used in the present description refers, for example, styrene; alkyl substituted styrene such as p-methyl styrene, m-methyl styrene, o-methyl styrene, 2,4-dimethyl styrene, 2,5-dimethyl styrene, 3,4-dimethyl styrene, 3,5-dimethyl styrene, p-ethyl styrene, m-ethyl styrene or o-ethyl styrene; or another styrene derivative such as p-hydroxystyrene, p-methoxystyrene, p-chlorostyrene or 1,1-diphenylethylene. Styrene is the preferred vinyl aromatic monomer. One type of each α-methyl styrene and vinyl aromatic monomer may be used, or a mixture of two or more types may be used. In the present invention, the most preferred combination is a combination of styrene and α-methylstyrene obtained by purification in accordance with the purification method of the present invention.

The content of the α-methyl styrene unit in the styrene-based copolymer is from 5 to 70% by weight, preferably from 7 to 68% by weight, and more preferably from 10 to 65% by weight. If the content of the α-methylstyrene unit is less than 5% by mass, then practical effects on improving the heat resistance are practically not observed. On the other hand, if the content of the α-methylstyrene unit exceeds 70% by mass, the susceptibility to thermal decomposition during melting and casting increases, while also increasing the amount of gas obtained during casting. In addition, the amount of monomer components in the resin enhances the concomitant decomposition, thus leading to an increase in the occurrence of excess binder on the surface of cast products.

Other polymerizable monomers can be used, besides the monomers described above, within a range that does not impair the object of the present invention. Examples of other polymerizable monomers may include diene monomers with conjugated double bonds, such as butadiene or isoprene; methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate or butyl methacrylate; and acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate or butyl acrylate. These monomers are used in case of improvement or regulation of impact strength, extensibility or chemical resistance and the like of the resin.

The styrene-based copolymer of the present invention is synthesized by living anionic polymerization. For carrying out live anionic polymerization, a known method can be used. For example, an organic lithium compound is used as an initiator, specific examples of which may include n-butyllithium, sec-butyl lithium, tert-butyl lithium, ethyl lithium, benzyl lithium, 1,6-dilithiohexane, styryl lithium, butadiene lithium and the like. Preferred examples may include n-butyllithium and sec-butyl lithium.

A heteroatom-free hydrocarbon-based compound is preferred as a polymerization solvent, specific examples of which may include aliphatic hydrocarbon compounds such as n-hexane, cyclohexane or heptane, and aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene or xylene. One type or two or more types of these hydrocarbon compounds may be used. In particular, a preferred compound is cyclohexane.

In addition, benzofuran may be added in the present invention to control polymerization. The inventors of the present invention have found that the polymerization efficiency of α-methylstyrene can be significantly improved by containing benzofuran in the living anionic polymerization system of a monomer containing α-methylstyrene.

Typically, in a living anionic polymerization system of styrene and diene with conjugated double bonds, any compound, such as tetrahydrofuran, is known to be added in order to increase the rate of polymerization and help to randomize the copolymerization process. However, since tetrahydrofuran, for example, readily reacts with lithium compounds, which are often used as initiators of living anionic polymerization systems depending on the polymerization temperature, there was a problem of reducing the effectiveness of the initiator as a result of acting as an inhibitor.

On the other hand, the benzofuran used in the present invention contributes to an increase in the polymerization rate and the reactivity of the monomer without causing the above problems, and effectively influences the production of a heat-resistant high molecular weight styrene polymer copolymer. In the present invention, benzofuran is added to α-methylstyrene in an amount of 5 to 5000 ppm, preferably 10 to 4800 ppm, and more preferably 20 to 4500 ppm. If the added amount is less than 5 ppm, the effect on the growing polymer particles is reduced. Namely, the effects on the polymerization rate and the polymerization conversion coefficient are reduced, thereby hindering the preparation of an object of the present invention. Even if benzofuran is present in excess of 5000 ppm, slight changes are observed in the polymerization rate or conversion rate. In addition, since benzofuran is yellow in color, the characteristic yellowing of benzofuran becomes noticeable during the granulation process following the removal of unreacted monomer and solvent, thus making this unacceptable depending on the application.

Benzofuran is not necessary to add and mix with α-methylstyrene before polymerization, but can be mixed with other monomers and solvents.

The polymerization temperature preferably lies within the range of 40 to 110 ° C, more preferably within the range of 50 to 100 ° C, and even more preferably within the range of 55 to 95 ° C. If the polymerization temperature is lower than 40 ° C, then the reaction rate decreases, thus making the process impractical for industrial production. In addition, if the polymerization temperature is higher than 110 ° C, the yellowing of the copolymer becomes noticeable, at the same time also causing a decrease in weather resistance and heat resistance of the copolymer during the melting process.

The styrene-based copolymer according to the present invention can be obtained by, for example, continuous live polymerization using a complex mixed type of polymerization reactor. Alternatively, the type of perfect mixing of the polymerization reactor and the type of imperfect mixing of the polymerization reactor can be combined. In order to obtain a random copolymer, in particular, the type of perfect mixing of the polymerization reactor is preferred. Perfect blend type polymerization refers to a polymerization process that uses a continuous type of perfect mix reactor, such that the concentrations of α-methyl styrene, vinyl aromatic monomer and living copolymer present in the living polymerization reaction system remain constant at all times.

If it is necessary to increase productivity by increasing the concentration of monomer in the feed solution, it is advisable to attach a condenser to the polymerization reactor and to remove the polymerization heat with the latent heat of vaporization of the solvent to effectively remove heat from the polymerization reaction. When mainly cyclohexane (which may also contain n-hexane) is used as a solvent, in particular, it becomes easy to control the polymerization temperature in the region from 80 to 90 ° C, since the boiling point of cyclohexane is 82 ° C.

In the case of using a tubular polymerization reactor of the type of non-ideal mixing, if it is difficult to obtain a perfect mixing state in the polymerization reactor, as, for example, in the case of a ratio (L / D) of the length (L) to the inner diameter (D) of the reactor 1 or more or in case of poor mixing efficiency, the styrene-based copolymer in accordance with the present invention can be obtained by adding a solution of vinyl aromatic monomer from an intermediate location in the reactor.

In addition, the copolymer of the present invention can also be obtained by combining two or more polymerization reactors of the type of non-perfect mixing in series and adding a solution of vinyl aromatic monomer to the second polymerization reactor, followed by polymerization in the first polymerization reactor. In addition, a block copolymer of a homopolymer and a copolymer of a vinyl aromatic unit can be obtained by only polymerizing a vinyl aromatic monomer unit in a first polymerization reactor, and then copolymerizing α-methyl styrene and a vinyl aromatic monomer unit in a second polymerization reactor.

The yellowness index of the styrene-based copolymer according to the present invention is preferably 3 or less, more preferably 2 or less, and even more preferably 1.5 or less. As previously described, it is effective to reduce the content of polar substances in α-methylstyrene purified by the purification method of the present invention in order to reduce the yellowness index. In the production process of biaxially oriented sheet (OPS) or foam sheet (PSP) used in the field of packaging for food products, in particular, there are cases in which yellowing of the resin becomes noticeable, causing problems in terms of quality, as a result of the restoration of the sheet by drying on air. Thus, for consumers of these types of applications, yellowing of the resin is particularly critical, thus making this an important operational requirement.

The ratio of (Mz / Mw) Z - average molecular weight (Mz) to weight average molecular weight (Mw) of a styrene-based copolymer containing α-methylstyrene, purified by the purification method in accordance with the present invention, lies within the range from 1.4 to 3.0, preferably within the range of 1.42 to 2.9, and even more preferably within the range of 1.45 to 2.8. If the Mz / Mw ratio is less than 1.4, then the balance between fluidity and mechanical strength of the resin becomes unsatisfactory, leading to a problem making it difficult to increase the degree of drawing in biaxial orientation. In addition, if the ratio exceeds 3.0, then the balance between fluidity and thermal decomposability becomes unsatisfactory, thereby making it difficult to cast large cast products, thin-walled cast products, and the like.

Examples of methods for controlling the Mz / Mw value may include a method in which the molecular weight distribution range is increased by performing polymerization in a reactor in which polymerization times are distributed; and a method in which two or more types of copolymers having different molecular weights are repeatedly dispersed by melting or stirring a solution. Z-average molecular weight (Mz) and weighted average molecular weight (Mw) can be determined by polystyrene conversion using gel permeation chromatography (GPC).

The glass transition temperature in the present invention can be determined by DSC, and the temperature determined in accordance with the method specified in JIS-K7121 is used as the glass transition temperature.

Although there are no particular restrictions on the type of binding of the α-methyl styrene unit and the vinyl aromatic monomer unit of the styrene-based copolymer according to the present invention, the most preferred type of binding is a copolymer consisting of arbitrary bonds. Typically, thermal decomposition tends to increase more chains of the α-methylstyrene units present. Thus, depending on the application, it is preferable to control the number of chains of α-methylstyrene units to from 2 to 4 chains.

Since there is no risk of deterioration in the heat resistance of vinyl aromatic units even if they are in the form of chains, they can also be in the form of a long chain structure. The inventors of the present invention have found that if the vinyl aromatic units are AB type, in which long chains of vinyl aromatic units are present at the end of the molecular chain of the copolymer or are in the form of block copolymers of type ABA (in which A is a homopolymer component, mainly consisting of components of vinyl aromatic units, while B is an arbitrary copolymer component containing α-methyl styrene units and vinyl aromatic units), For more operational characteristics including heat resistance, thermal stability, mechanical properties and fluidity are the same as those of the random copolymer, and such compatibility with homopolymers composed of the same structure as the block component in the form of vinyl aromatic units is extremely favorable. In the case of repeated use of the styrene-based copolymer in accordance with the present invention, such as, for example, returning the material into circulation, taking advantage of such characteristics as, for example, in the case of repeated use by melting and plasticizing with polystyrene, a copolymer in which polystyrene chains can be used blocked at the ends of the polymer chains of the copolymer.

There are no particular restrictions on the chain length of a block of vinyl aromatic units, and the number average molecular weight of a part of the block chain can lie within the range of 1000 to 300,000. In addition, the ratio Mw / Mn of the portion of the block consisting of vinyl aromatic units is preferably within the range of 1.0 to 3.5.

The ratio of Mz / Mw Z — the average molecular weight (Mz) to the weight average molecular weight (Mw) of the vinyl aromatic unit as a block component must necessarily lie within the range from 1.4 to 3.0, preferably within the range from 1.42 to 2.9 and more preferably within the range of 1.45 to 2.8. If the Mz / Mw ratio is less than 1.4, the balance between fluidity and mechanical properties of the resin becomes unsatisfactory, thereby making it difficult to show satisfactory performance, such as, for example, a molded resin product. In addition, if the Mz / Mw ratio exceeds 3.0, then the fluidity becomes unsatisfactory, thereby making it difficult to cast large cast products, thin-walled cast products, and the like.

In the process of producing a copolymer having a vinyl aromatic unit as a block component, a homopolymer consisting of vinyl aromatic units is obtained, for example, in a batch reactor, a continuous tube reactor, a continuous static mixing reactor, a tank type continuous reactor with a stirrer, or a continuous ring reactor, followed by a supply of α-methylstyrene, a vinyl aromatic monomer and a living homopolymer consisting of and vinyl aromatic units in a continuous stirred tank reactor and continuous copolymerization, in order to obtain a block copolymer of type AB. In the case of obtaining a block copolymer of type ABA, vinyl aromatic units are subjected to live polymerization in another reactor after obtaining a block copolymer of type AB. Alternatively, an ABA type block copolymer can be obtained by adding a bifunctional compound that reacts with the growing living polymer particles in another reactor after obtaining an AB type block copolymer.

As a result of further extensive research, the inventors of the present invention found that a styrene-based copolymer consisting of at least two types of copolymers containing an α-methylstyrene unit and a vinyl aromatic unit, obtained by continuous live polymerization, and in which the composition ratio in copolymers obtained by feeding into the polymerization reactor, differs as a result of continuous or periodic changes in the compositional ratio of α-methylstyrene and the vinyl aromatic monomer represented by formula (3) in the feedstock shows additional performance characteristics, including heat resistance, heat resistance, mechanical characteristics and fluidity, the same as the characteristics of arbitrary copolymers, and compatibility with copolymers having a vinyl aromatic component as Their main component is extremely favorable.

This fact suggests that in the case of the return to circulation of molded products of this copolymer, polymers consisting mainly of vinyl aromatic units, such as polystyrene, can also be used repeatedly as recoverable materials by mixing. Various copolymers refer to copolymers in which their glass transition temperature differs by at least 3 ° C.

Providing in the polymerization reactor a continuous or periodic change in the compositional ratio of α-methylstyrene and vinyl aromatic monomer along with monomers implies that the concentration of each monomer introduced into the polymerization reaction system changes either continuously or periodically, and as a result, the compositional ratio of each aromatic unit of the resulting copolymer changes, leading to sequential production of copolymers consisting of at least two different mpozitsionnyh relations.

Copolymers having two or more different composition ratios can be mixed into a solution in a batch tank, followed by rinsing in a tank heated under vacuum to remove the solvent, or can be reconstituted as granules by removing the solvent using an extruder or plasticizer. Alternatively, they can also be recovered in the form of granules directly without being held in a tank of periodic action, and the granules can then be mixed and made homogeneous in a batch or continuous mixer. Alternatively, after bringing the granules into a homogeneous state in the mixer, the granules can also be melted and mixed using an extruder.

As a specific preparation example, after feeding a feed having a compositional ratio of M1 / M2 α-methylstyrene (M1) to a vinyl aromatic monomer (M2) 50/50 (wt%), into a reactor and polymerization, the feed is switched to a feed having a different composition a ratio such as M1 / M2 40/60 (wt%), which is also introduced into the reactor, followed by polymerization. In this case, they say that the raw material composition changes periodically. When polymerizing in this way, copolymers are sequentially obtained having compositions that continuously change from a copolymer composition obtained by polymerization at a ratio of M1 / M2 50/50 (wt%) to a copolymer composition obtained by polymerization at a ratio of M1 / M2 40/60 (wt%) . The resulting copolymers are then mixed into the solution or mixed and mixed in the form of granules in a batch reactor, followed by melting and mastication, in order to obtain a copolymer having a defined constant composition.

We can assume that the copolymers obtained in accordance with a similar method have a copolymer composition in which the composition ratios of the components of the α-methylstyrene unit and the vinyl aromatic unit are different. The copolymers obtained as a result of this have extremely good compatibility with homopolymers of vinyl aromatic monomers, and since they are able to maintain transparency without causing deterioration in mechanical characteristics, it was determined that they are polymers having an extremely high coefficient of use as recoverable materials.

In live anionic polymerization serving as the process for preparing the copolymer of the present invention, completion of the polymerization reaction is preferably carried out if the reactivity of the vinyl aromatic monomer reaches 99% or more and α-methyl styrene can be left in the reaction system. The termination of the polymerization reaction is carried out by adding a reagent terminating the reaction in the form of a compound having an oxygen-hydrogen bond, such as water, alcohol, phenol or carboxylic acid, and similar effects can be expected for epoxy compounds, ester compounds, ketone compounds, carboxylic anhydrides and compounds having a carbon-halogen bond. The amount of these additives used is preferably about one to ten equivalents of growing particles. If the amount of data of the additives used is excessively large, then this is not only unfavorable in terms of cost, but there are also many cases in which this affects the mixing of the remaining additives.

The molecular weight of the polymer can be increased, and the polymer chain can be made to have a branched structure by carrying out a coupling reaction with a multifunctional compound using growing living polymer particles. As a multifunctional compound, a known compound used in this type of coupling reaction can be selected. Examples of multifunctional compounds may include polyhalogen compounds, polyepoxy compounds, esters of mono- or polycarboxylic acids, polyketone compounds, anhydrides of mono- or polycarboxylic acids, and the like. Specific examples may include silicon tetrachloride, di (trichlorosilyl) ethane, 1,3,5-tribromobenzene, epoxidized soybean oil, tetra glycidyl-1,3-bisaminomethylcyclohexane, dimethyl oxalate, tri-2-ethylhexyltrimellitate, pyromellitic acid dianhydride, and diethyl.

After completion of the polymerization, the unreacted monomer and solvent are removed by evaporation from the polymer for reduction and regeneration. A known method can be used to remove by evaporation. A method including rinsing in a vacuum tank and / or a method including heating until vaporization under vacuum using an extruder or plasticizer, can preferably be used for the evaporation removal device. Despite the variability depending on the volatility of the solvent, volatile components such as the solvent and other monomers are usually removed by evaporation at a temperature of from 180 to 300 ° C and a vacuum of 100 Pa to 50 kPa.

The method in which the vapor removal devices are connected in series and arranged in two or more steps is also effective. In addition, a method can also be applied in which water is added between the first step and the second step in order to increase the ability to vaporize the monomer in the second step. In addition, after removing volatile components in the wash tank, an extruder equipped with ventilation can be used to remove other volatile components. The styrene-based copolymer, which has been purified from the solvent, can be processed into granules using a known method.

Known compounds used in styrene-based resins can be added to the styrene-based copolymer in accordance with the present invention in order to improve thermal and mechanical stability, fluidity and coloring if necessary. Examples of such additives may include primary antioxidants in the form of 2,4,6-tri-substituted phenols, such as 2,6-di-tert-butyl-4-methylphenol, triethylene glycol bis [3- (3-tert-butyl- 5-methyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis [- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl ) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5, -di-tert-butyl-4-hydroxybenzyl) benzene, n-octadecyl-3- (3,5-di-tert -butyl-4-hydroxyphenyl) propionate, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate, 2 [1- (2-hydroxy-3,5- di et-pentylphenyl)] - 4,6-di-tert-pentylphenylacrylate, tetrakis [methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane, 3,9-bis [2- { 3- (tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraox [5.5] undecane, 1,3,5-tris (3 ', 5'-di-tert-butyl-4'-hydroxybenzyl) -s-triazine-2,4,6 (1H, 2H, 3H) -trion, 1,1,4-tris (2-methyl-4- hydroxy-5-tert-butylphenyl) butane, 4,4'-butylidenebis (3-methyl-6-tert-butylphenol) and the like.

In addition, phosphorus-based antioxidants or sulfur-based antioxidants can be added as secondary antioxidants, and sterically hindered amine stabilizers or UV absorbers can be added as weathering agents. In addition, plasticizers such as mineral oils, lubricants such as long chain aliphatic carboxylic acids and / or metal salts thereof, coloring improvers such as organic dyes or organic pigments can also be added.

Anthraquinone-based organic dyes to improve staining are particularly preferred due to a slight deterioration in the heat resistance of the copolymer.

Silicon and fluorine based lubricants, antistatic agents and other known technologies used in styrene resins can also be directly applied.

These stabilizers can be added and mixed into the polymer solution after completion of the polymerization, or they can be melted and mixed using an extruder after polymer recovery.

The styrene-based copolymer according to the present invention is preferably suitable for incorporation into molded articles. In particular, it can be used in building materials and containers that require transparency, heat resistance and high rigidity, as well as in molded products and electric lighting coatings that require resistance to weathering.

EXAMPLES

The following provides a more detailed explanation of the distillation conditions of the present invention by way of examples thereof. In addition, the present invention is not limited to these examples.

First, the following provides a description of the analysis methods used in the examples and comparative examples.

Analysis Methods

(1) Solubility of basic substances in α-methyl styrene

The solubility of the basic substances in α-methylstyrene was evaluated visually and analyzed based on the following criteria. If the basic substance is a solution, the state of α-methylstyrene in the reaction furnace was observed after the solvent was recovered from the basic substance in the form of the initial fraction.

Ο: Uniformly dissolved and clear.

Δ: Slightly dispersed or suspended.

×: Completely divided.

(2) Purification effects of α-methylstyrene

Polar substances contained in the recovered base fraction were quantified by gas chromatography (GC-14A, Shimadzu Corp.). The amount of polar substances was taken equal to the total amount of acetonylacetone, 3-methyl-2-cyclopentenone, benzaldehyde and acetophenone. The removal rate of the polar substance was determined based on the following formula 1.

The removal rate (%) = The amount of reduction of polar substances (ppm) / The content of polar substances before cleaning (ppm) × 100

◎: Removal rate above 99%.

○: The removal rate is higher from 90% to 99%.

△: The removal rate is higher from 80% to 90%.

×: The removal rate is 80% or lower.

Receipt process

Technological Example 1

(1) Raw materials

After the storage of styrene (St: Sumitomo Chemical Co., Ltd.) and cyclohexane (CH: Idemitsu Petrochemical Co., Ltd.) in a nitrogen storage and bubbling tank, the solution was passed through a treatment column filled with activated alumina (KHD-24, Sumika Alchem Co., Ltd.) having a volume of 5 liters in order to remove the polymerization inhibitor in the form of tert-butylcatechol.

α-Methylstyrene (aMeSt: Mitsui Chemicals, Inc.) was purified under the conditions specified in the examples and comparative examples described below.

(2) Initiator

n-butyllithium (15 wt% n-hexane solution, Wako Pure Chemical Industries, Ltd.) was diluted with 1/61 cyclohexane.

(3) Interruption Agent

Methanol (chemically pure, Wako Pure Chemical Industries, Ltd.) was diluted with cyclohexane to a concentration of 3 wt%.

(4) Polymerization Method

A jacketed 5 liter reactor (R1) connected to a stirrer (Maxblend Impeller, Sumitomo Heavy Industries, Ltd.) and a condenser and additionally equipped with a raw material inlet, an initiator inlet and a polymerization solution outlet valve was used as a polymerization reactor. The condenser outlet was isolated with nitrogen gas in order to prevent atmospheric air from entering. The volume of the polymerization solution in the polymerization reactor was controlled to 3 liters at any time. Part of the polymerization solution was constantly kept in a boiling state and the internal temperature was controlled from 82 to 84 ° C. The speed of the stirrer was 320 rpm. Gear pumps were respectively connected to the feed inlet and the outlet of the polymerization reactor, and the polymerization solution was controlled so that the solution mixed in the ratio St / αMeSt / CH 10/21/69 (wt%) was allowed to flow at a constant flow rate 1.5 l / h In addition, an initiator was introduced into the polymerization reactor at 0.07 l / h.

The living polymer solution discharged from the polymerization reactor was further fed to the inlet of the solution of the polymerization terminating agent through a tube having a diameter of 10 mm by means of a gear pump. The length of the pipe from the reactor to the place of mixing with the polymerization terminating agent was about 2 m, and the pipe was maintained at a temperature of 65 to 70 ° C. The solution of the polymerization terminating agent was introduced into the polymerization reaction solution at a flow rate of 0.1 l / h, and then the polymerization reaction was terminated after passing through a static mixer having a volume of 1.2 liters (Model SMX, Sulzer Corp.). In addition, the polymer solution was heated to 260 ° C with a pre-heater, and then washed in approximately 50 L of a reactor heated to an initial temperature of 260 ° C under a reduced pressure of 60 torr, followed by separation and reduction of the solvent and unreacted monomer from the polymer. The polymer temperature in the wash tank was about 240 to 250 ° C., and the polymer retention time in the tank was about 20 to 30 minutes. After the volatiles were sufficiently removed, the polymer was then released as a tow, cooled with water, and then granules were formed using a cutting machine in order to recover the styrene-based copolymer.

Technological Example 2

The styrene-based copolymer was obtained by polymerization under the same conditions and using the same method as in Technological Example 1, except for creating a flow rate of the initiator solution in the polymerization reactor of 0.16 l / h.

Analysis Methods

(1) Molecular Weight Measurement (Mn, Mw, Mz, Mz / Mw)

Molecular weights were measured using a gel permeation chromatography (GPC) system consisting of connecting two columns (TSKgel SuperHZM-H, 40 ° C) with HLC-8220 manufactured by Toray Industries, Inc., and provided with a refractive index detector (PP). THF was used as the mobile phase. Molecular weights were calculated by preparing calibration curves using polystyrene standards (Toray Industries, Inc.) and then transforming relative to polystyrene.

(2) Measurement of polymerization rates

Samples of the polymer solution were collected after termination of the polymerization, followed by determining the amount of styrene monomer and α-methylstyrene remaining in the solution by gas chromatography gas chromatography (GC-14B, Shimadzu Corp.). Each polymerization rate was determined based on formula (a) below.

Formula (a):

Polymerization rate (%) = (1- (concentration of monomer remaining in the polymer solution after polymerization / concentration of monomer in the feed solution before polymerization)) × 100.

Casting method

Casting was carried out under the following conditions using an injection molding machine manufactured by Funac, Ltd. (AUTO SHOT 15A). The cylinder temperatures were set to 215 ° C, 225 ° C, 230 ° C, and 230 ° C, moving away from the loading funnel. The mold temperature was set at 60 ° C, the injection time was 10 seconds, and the cooling time was 20 seconds. The molten resin was poured into the mold by providing a pressure of 5 MPa higher than the casting pressure at which the resin was poured into the mold. Dumbbell ASTM No. 4, having a thickness of 3 mm, was cast and used as a sample for measuring the yellowness index.

Analysis Methods

(1) Determination of polar content in α-methylstyrene

The polar substances contained in the selected α-methylstyrene were quantified by gas chromatography (GC-1700, Shimadzu Corp.). The column temperature (HR-20 manufactured by Shinwa Chemical Industries, Ltd.) was maintained at 110 ° C for 10 minutes, and then raised to 160 ° C at a rate of 5 ° C / min, and then further raised to 230 ° C at a speed of 20 ° C / min, followed by measurement.

(2) Determination of dimer content in α-methyl styrene

The polar substances contained in the selected α-methylstyrene were quantified by gas chromatography (GC-1700, Shimadzu Corp.). The measurement was carried out under the following conditions.

Column: HR-1 (0.32 mm × 30 m × 0.25 μm), non-polar.

Carrier gas: He (1 ml / min, dilution ratio: 1:10).

Column temperature: 200 ° C → (3 ° C / min) → 290 ° C (40 ° C / min) → 300 ° C (maintained for 20 minutes).

Sample inlet opening temperature: 250 ° C.

Detector temperature: 280 ° C.

(3) Determination of the rate of living polymerization

The living polymerization index is an indicator that expresses proximity to ideal living polymerization. In the case of perfect living polymerization, since the concentration of active particles does not change before and after polymerization, the number average molecular weight (Mn) calculated from the resulting polymer is represented by the following formula (b).

Formula (b):

Ideal Mn = Weight of all reacted monomers (g) / total amount of initiator (mol)

The living polymerization rate is taken to be the difference between the above-mentioned ideal Mn and Mn of the polymer obtained in reality, is determined based on the following formula (c), and is determined as indicated below.

Formula (C):

The rate of living polymerization = ideal Mp / Mp of the resulting polymer

○: The rate of live polymerization is greater than 0.8 to 1.2.

△: The rate of live polymerization is greater than 0.7 to 0.8, or greater than 1.2 to 1.3.

×: The rate of live polymerization of 0.7 or less or more than 1.3.

(4) Glass transition temperature (Tg)

The glass transition temperature (TD) was determined in accordance with JIS-K-7121 using DSC-7 manufactured by Perkin-Elmer Corp. More specifically, the temperature was raised to 250 ° C at a rate of 10 ° C / min, returned to room temperature at a speed of 10 ° C / min and again raised to 250 ° C at a rate of 10 ° C / min in a nitrogen atmosphere. The glass transition temperature measured during the second temperature rise was used as the value of Tg.

(5) Yellowness Index

The yellowness index was measured in accordance with JIS-K7103 using SM-5-CH-H2 manufactured by Suga Test Instruments Co., Ltd.

©: Yellowness Index 1.5 or lower.

o: The yellowness index is higher than 1.5 to 2.0.

Δ: The yellowness index is higher than 2.0 to 3.0.

×: Yellowness Index 3.0 or more.

Example 1

Distillation was carried out by simple distillation. More specifically, a thermometer for measuring the temperature of the liquid was attached to a 300 ml reaction flask containing an anchor, and in addition, a K-shaped tube connected to a thermometer for measuring the temperature of water vapor, a Liebig refrigerator, a double-sided allonge, and a flask for temporary storage were attached . In addition, a vacuum pump was connected to the allonge through a vacuum regulator (VC-30S, Okano Works, Ltd.) in order to allow regulation of the degree of pressure drop. An oil bath was used as a heat source.

200 ml of α-methyl styrene (Mitsui Chemicals, Inc.) was placed in a reaction flask, and the temperature of the liquid was raised to 80 ° C. Then, a basic substance in the form of 0.08% by weight of sodium ethoxide (20% by weight of ethanol solution, Wako Pure Chemical Industries, Ltd.) was added to the reaction flask with stirring. The degree of pressure drop was adjusted to 230 mm Hg, and the liquid temperature was slowly raised from 120 to 125 ° C.

The fraction with a low boiling point, which condenses after reaching the boiling point during heating, is returned back as the initial fraction.

The main fraction is returned back when the temperature of the liquid reached from 120 to 125 ° C, and the temperature of the water vapor also reached from 120 to 125 ° C. The content of phenol and tert-butylcatechol in the purified α-methylstyrene was below the sensitivity limit (2 ppm by weight).

Example 2

Example 2 was carried out in the same manner as Example 1, except for adding an additional amount of sodium ethoxide (20% by weight ethanol solution, Wako Pure Chemical Industries, Ltd.) 0.4% by weight. The content of phenol and tert-butylcatechol in the purified α-methylstyrene was below the sensitivity limit (2 ppm by weight).

Example 3

A thermometer for measuring the temperature of the liquid was attached to a 160 ml 5-crucible reaction flask containing an anchor, and in addition, a K-shaped tube connected to a thermometer for measuring the temperature of water vapor, a Liebig refrigerator, a two-way allonge, and a flask for temporary storage. In addition, a vacuum pump was connected to the allonge through a vacuum regulator (VC-30S, Okano Works, Ltd.) in order to allow regulation of the degree of pressure drop. In addition, α-methyl styrene was introduced into the flask at a rate of 1.99 ml / min by pump A. In addition, sodium ethoxide (20% by weight ethanol solution, Wako Pure Chemical Industries, Ltd.) was supplied to the flask at a rate of 0.008 ml / min by micropower (pump B). The liquid inside the flask was discharged at a rate of 0.1 ml / min using pump C. The pressure inside the system was maintained at 230 mm Hg. Art., and distillation was carried out at a speed of 1.9 ml / min. An oil bath was used as a heat source. After the conditions were stabilized, the distilled monomer liquid was analyzed. The content of phenol and tert-butylcatechol in the purified α-methylstyrene was below the sensitivity limit (2 ppm by weight).

Example 4

Example 4 was carried out in the same manner as Example 2, except for the use of sodium hydroxide (50% by weight aqueous solution, Wako Pure Chemical Industries, Ltd.) as the main substance.

Example 5

Purification of α-methyl styrene was carried out by adding 0.8% by weight of the basic substance in the form of sodium ethoxide (20% by weight of ethanol solution, Wako Pure Chemical Industries, Ltd.), distilling at a pressure drop of 230 mm Hg. Art. and a liquid temperature of 120 to 125 ° C, and restoring the basic fraction when the temperature of the water vapor reaches 120 to 125 ° C. The content of phenol and tert-butylcatechol in the purified α-methylstyrene was below the sensitivity limit (2 ppm by weight). The preparation of a styrene-based resin copolymer was carried out in accordance with the process described in Technological Example 1.

The number average molecular weight Mn of the resulting styrene-based copolymer was 98,000. In addition, the polymerization rates were 99.7% for St and 48.9% for α-MeSt.

Example 6

Purification of α-methylstyrene was carried out in the same manner as in Example 1. The content of phenol and tert-butylcatechol in the purified α-methylstyrene was below the sensitivity limit (2 ppm by weight). The preparation of a styrene-based copolymer was carried out in accordance with the process described in Technological Example 2.

The number average molecular weight Mn of the resulting styrene-based copolymer was 62,000 and the polymerization rates were 99.8% for St and 47.5% for α-MeSt.

Example 7

Purification of α-methylstyrene was carried out in the same manner as in Example 2. The content of phenol and tert-butylcatechol in the purified α-methylstyrene was below the sensitivity limit (2 ppm by weight). The preparation of a styrene-based copolymer was carried out in accordance with the process described in Technological Example 2.

The number average molecular weight Mn of the resulting styrene-based copolymer was 61,000 and the polymerization rates were 99.7% for St and 46.5% for α-MeSt.

Example 8

Purification of α-methylstyrene was carried out in the same manner as in Example 3. The content of phenol and tert-butylcatechol in the purified α-methylstyrene was below the sensitivity limit (2 ppm by weight). The preparation of a styrene-based copolymer was carried out in accordance with the process described in Technological Example 2.

The number average molecular weight Mn of the resulting styrene-based copolymer was 60,000, and the polymerization rates were 99.6% for St and 46.3% for α-MeSt.

Example 9

Purification of α-methylstyrene was carried out in the same manner as in Example 3. The content of phenol and tert-butylcatechol in the purified α-methylstyrene was below the sensitivity limit (2 ppm by weight). The preparation of a styrene-based copolymer was carried out in accordance with the process described in Technological Example 2.

The number average molecular weight Mn of the resulting styrene-based copolymer was 61,000 and the polymerization rates were 99.7% for St and 46.4% for α-MeSt.

Reference Example ]

The polymerization was carried out in accordance with Technological Example 2 by adding benzofuran to a solution of a polymerization feed (a mixed solution of styrene, α-methylstyrene and cyclohexane) to a concentration of 65 ppm based on α-methylstyrene.

Reference Examples 2 to 7

Benzofuran in the amounts shown in Table 3 was added to the polymerization feed solution. Other conditions were the same as in Example 10 (link to an example that is not in the revised version).

Comparative Example 1

Reference Example 1 was carried out in the same manner as Example 2, except for the use of diethanolamine (chemically pure, Wako Pure Chemical Industries, Ltd.) as the main substance.

Comparative Example 2

Reference Example 2 was carried out in the same manner as Example 2, except for the use of pyridine (chemically pure, Wako Pure Chemical Industries, Ltd.) as the main substance.

Comparative Example 3

200 ml of α-methyl styrene (Mitsui Chemicals, Inc.) was placed in a 300 ml separatory funnel, followed by the addition of 50 ml of sodium hydroxide (10% by weight aqueous solution, Wako Pure Chemical Industries, Ltd.) and shaking 100 times. After the mixture was allowed to stand intact, the procedure for removing only the aqueous layer was repeated five times. Then, instead of an aqueous solution of sodium hydroxide, 50 ml of distilled water was added and the same procedure was repeated until the aqueous layer became neutral. Then the oil layer was removed and the distillation procedure was carried out in the same manner as in Example 2 without the addition of a basic substance.

Comparative Example 4

The distillation procedure was carried out in the same manner as in Example 2 without the addition of a basic substance.

Comparative Example 5

Purification of α-methylstyrene was carried out by containing α-methylstyrene in a nitrogen storage and bubbling tank, followed by passing through a purification column having an inner diameter of 76.3 mm, a height of 600 mm and a volume of 2.5 liters filled with activated alumina (KHD) -24, Sumika Alchem Co., Ltd.).

The content of basic substances in α-methylstyrene was measured by taking a sample of α-methylstyrene, which was eluted from the treatment column 200 hours after the passage of α-methylstyrene through the column.

The preparation of a styrene-based copolymer was carried out using the method described in Technological Example 2, except for the use of a sample of α-methylstyrene taken 200 hours after the start of passage of α-methylstyrene through the column.

The number average molecular weight Mn of the resulting styrene-based copolymer was 61,000 and the polymerization rates were 99.5% for St and 46.2% for α-MeSt.

Comparative Example 6

Purification of α-methylstyrene was carried out in the same manner as in Comparative Example 5.

The content of polar substances in α-methylstyrene was measured by taking a sample of α-methylstyrene, which was suirable from the treatment column 300 hours after the passage of α-methylstyrene through the column.

The preparation of the styrene-based copolymer was carried out using the method described in Technological Example 2, except for the use of a sample of α-methylstyrene taken 300 hours after the passage of α-methylstyrene through the column.

The number average molecular weight Mn of the resulting styrene-based copolymer was 60,000, and the polymerization rates were 80.8% for St and 5.7% for α-MeSt.

Reference Examples 6 and 7

Benzofuran was added to the polymerization feedstock solution in the amounts shown in Table 3. Other conditions were the same as in Example 10 (link to an example that is not in the revised version).

Analysis results

The results of the analysis, examples and comparative examples are shown in Table 1.

Table 1 Example 1 Example 2 Example 3 Example 4 Main substance NaOEt EtOH solution NaOEt EtOH solution NaOEt EtOH solution NaOH H ₂ O solution pKa conjugate acid 17 17 17 16 Catalyst concentration 0.08 0.4 0.08 0.4 Low molecular weight by-product removal Yes Yes Yes Yes Solubility Ο Ο Ο Δ Cleaning effects Ο

Ο Δ Compares. Example 1 Compares. Example 2 Compares. Example 3 Compares. Example 4 Main substance (EtOH) ₂ NH Pyridine NaOH H ₂ O solution No pKa conjugate acid 9 6 16 - Catalyst concentration 0.4 0.4 - 0 Low molecular weight by-product removal Yes Yes No - Solubility Δ Ο - - Cleaning effects × × × ×

table 2 Receipt process The content of the main substance in α-methylstyrene Styrene Based Copolymer Analysis Results Acetonylacetone and 3-methyl-2-cyclopentenone (wt. Ppm) Benzaldehyde (wt. Ppm) Living Polymer Index Glass transition temperature Tg (° C) IL yellowness index Example 5 Technological Example 1 <2 <2 Ο 131

Example 6 Technological Example 2 <2 <2 Ο 131

Example 7 Technological Example 2 <2 <2 Ο 130

Example 8 Technological Example 2 36 fifteen Ο 130 Ο Example 9 Technological Example 2 72 21 Ο 130 Δ Comparative Example 5 Technological Example 2 105 32 Ο 130 × Comparative Example 6 Technological Example 2 185 52 × 106 ×

Table 3 Amount of benzofuran added to α-methylstyrene (ppm) Conversion Molecular weight DSC Yellowness index Styrene α-MeSt Mw × 10 ^-4 Mn × 10 ^-4 Reference Example 1 65 > 99.9 fifty 28.3 11.3 125 Ο Reference Example 2 210 > 99.9 65 26.3 12.5 131 Ο Reference Example 3 500 > 99.9 72 28.7 fourteen 133 Ο Reference Example 4 1000 > 99.9 75 28.7 fourteen 134 Δ Reference Example 5 4000 > 99.9 76 28.7 14.1 134 Δ Reference Example 6 10,000 > 99.9 74 28.5 13.8 134 × Reference Example 7 0 > 99.9 44 21,2 10,2 121 Ο

Industrial applicability

In accordance with the present invention, high-purity α-methylstyrene can be achieved by effectively removing trace amounts of polar substances contained in α-methylstyrene that were not able to remove in the prior art without the need for a complex process. The resulting α-methylstyrene is used as a monomer for the industrial production of polymers and allows to obtain polymers with high molecular weight without staining.

Claims (9)

1. A method of producing α-methylstyrene, comprising the steps of:
reacting a polar substance which contains a compound containing a carbonyl group and which is contained in α-methylstyrene in the presence of a basic compound, the basicity of the basic compound being 10 or more in terms of the acid dissociation constant pKa of the conjugated acid of the basic substance;
separating the component with a low boiling point obtained by the reaction from a mixture of the reaction product of a polar substance containing a compound containing a carbonyl group and α-methylstyrene; and
separating α-methylstyrene from a mixture of a reaction product of a polar substance containing a compound containing a carbonyl group and α-methylstyrene. 2. A method of producing α-methylstyrene, comprising the steps of:
reacting a polar substance which contains a compound containing a carbonyl group and which is contained in α-methylstyrene in the presence of a basic compound, the basicity of the basic compound being 10 or more in terms of the acid dissociation constant pKa of the conjugated acid of the basic substance;
separating a mixture of the low boiling point component obtained by the reaction and α-methylstyrene from the reaction product of a polar substance containing a compound containing a carbonyl group and α-methylstyrene; and
separating α-methylstyrene from a mixture of a reaction product of a polar substance containing a compound containing a carbonyl group and α-methylstyrene. 3. The method of producing α-methylstyrene according to claim 1 or 2, in which the basic substance is a basic compound containing an alkali metal or alkaline earth metal. 4. The method of producing α-methylstyrene according to claim 1 or 2, in which the polar substance containing a compound containing a carbonyl group contains a compound containing a carbonyl group and a mixture of phenol and catechol. 5. The method of producing α-methylstyrene according to claim 4, in which the compound containing a carbonyl group is a compound represented by the following general formula (1) or general formula (2):

moreover, each of R ¹ , R ³ and R ⁴ independently represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, and R ² represents an alkyl group having from 1 to 6 carbon atoms. 6. The method of producing α-methylstyrene according to claim 5, in which the compound containing a carbonyl group contains at least one compound selected from acetonylacetone, 3-methyl-2-cyclopentenone, benzaldehyde and acetophenone. 7. A method of producing a styrene-based copolymer by live anionic polymerization using α-methylstyrene obtained in accordance with the method according to claim 1 or 2, and a vinyl aromatic monomer represented by the following general formula (3)

where R ⁵ represents a hydrogen atom, an alkyl group having 2 or more carbon atoms, or a phenyl group, and R ⁶ represents a hydrogen atom, a halogen, a hydroxyl group, an alkyl group, an alkoxy group, a carboxyl group or a haloalkyl group,
moreover, the total content of α-methylstyrene aliphatic carbonyl compounds represented by the following General formula (1) and its condensate intramolecular dehydration is 100 wt. mn ^-1 or less and the content of the aromatic carbonyl compound represented by the following general formula (2) is 30 wt. mn ^-1 or less:

wherein each of R ¹ , R ³ and R ⁴ independently represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, and R ² represents an alkyl group having from 1 to 6 carbon atoms. 8. The method of producing a styrene-based copolymer according to claim 7, in which the content of alcohol, phenol and catechols contained in α-methylstyrene is 10 wt. mn ^-1 or less. 9. A method for producing a styrene-based copolymer according to claim 7 or 8, wherein the content of α-methylstyrene dimer in α-methylstyrene is less than 5 wt. ppm ^-1 .