JPH089650B2 - Method for producing styrenic polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a styrene polymer, and more particularly to a method for producing a styrene polymer which is amorphous and has a syndiotactic structure. .

[Conventional technology]

Conventionally, as a method for producing a styrene-based polymer, methods such as radical polymerization, cationic polymerization, anionic polymerization, polymerization with a transition metal complex catalyst, and radiation polymerization are known. However, a normal styrene-based polymer is a radical polymerization method. Is manufactured by.

The styrenic polymer produced by this radical polymerization method has an atactic structure in its stereoregularity, and various molding methods such as injection molding, extrusion molding, hollow molding, vacuum molding, injection molding and the like. It is molded into various shapes according to various types, and is widely used as, for example, household electric appliances, office equipment, household products, packaging containers, toys, furniture, synthetic paper, and other industrial materials.

By the way, the present inventors polymerize a styrene-based monomer using a catalyst composed of a special transition metal compound and an organoaluminum compound, so that the crystalline and stereoregularity is substantially a syndiotactic structure. It was found that a styrenic polymer was obtained. However, the styrene-based polymer having such a syndiotactic structure is remarkably different from the one having the atactic structure in the physical and chemical properties thereof and has various excellent properties, but as it is, , Because of its high crystallinity, its melting point is extremely high, and it is necessary to carry out thermoforming at a higher temperature, which may lead to thermal deterioration, and the solubility characteristics in a solvent are significantly different from those having a conventional atactic structure. However, there is a problem that it is difficult to handle the molding method in the same manner as the conventional method, such as requiring a special solvent molding method.

[Problems to be solved by the invention]

The object of the present invention is, under the above circumstances, a polystyrene polymer having a syndiotacticity of 50% or more in racemic pentad, and an excellent molding method such as thermoforming at a relatively low temperature. To provide a manufacturing method of.

[Means for solving problems]

The present inventors have conducted various studies to mold a styrene-based polymer having a syndiotactic structure at a lower temperature. As a result, the styrene-based polymer is dissolved in a solvent under specific conditions and then the polymer is dissolved. By recovering, it is possible to easily obtain a styrene-based polymer which is amorphous and can be molded under mild conditions and has a syndiotacticity of 50% or more in racemic pentad, and the above object can be achieved. The present invention has been completed, and the present invention has been completed based on this finding.

That is, the present invention provides a styrene-based polymer having a syndiotacticity of 50% or more in racemic pentad,
Disclosed is a method for producing a styrene-based polymer having an amorphous and syndiotactic structure, which comprises dissolving the polymer in a solvent at a temperature of not higher than 0 ° C. and then recovering the polymer from the solution.

 Hereinafter, the present invention will be described in detail.

The styrene polymer used in the method of the present invention has a syndiotacticity of 50% or more in racemic pentad. Here, a styrene-based polymer having a syndiotacticity of 50% or more in racemic pentad is a racemic pentad by nuclear magnetic resonance ( ¹³ C-NMR) analysis of isotope carbon and 50% or more in syndiotactic structure. Means a styrenic polymer having Examples of the styrene-based polymer include styrene homopolymers such as styrene, p-methylstyrene, m-methylstyrene, p-chlorostyrene, p-fluorostyrene, and copolymers thereof. In addition, the syndiotacticity
If it is less than 50%, the heat resistance is not sufficient.

The styrene-based polymer having a racemic pentad of 50% or more in the syndiotacticity used in the method of the present invention can be produced, for example, by the following method. That is, it can be produced by polymerizing a styrene-based monomer in an inert hydrocarbon solvent or in the absence of a solvent, using a titanium compound and a condensation product of water and a trialkylaluminum as a catalyst.

In the method of the present invention, the syndiotacticity is 50% or more of racemic pentad in the styrene-based polymer as a solvent, aromatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, cyclic amides and cyclic ethers. At least one solvent selected from the above is used.

Examples of the aromatic hydrocarbon include benzene, toluene, xylene, ethylbenzene, methylnaphthalene, and tetralin, and examples of the alicyclic hydrocarbon include cyclohexane, cyclohexene, methylcyclohexane,
Ethylcyclohexane, decahydronaphthalene, etc.
Examples of the halogenated hydrocarbon include dichloromethane,
Chloroform, carbon tetrachloride, dichloroethane, trichloroethane, tetrachloroethane, trifluoroethane,
Examples of the cyclic amide include trichlene, chlorobenzene, dichlorobenzene, trichlorobenzene, and the like.
-Methylpyrrolidone, N-ethylpyrrolidone and the like, and examples of the cyclic ether include tetrahydrofuran and dioxane. These solvents may be used alone or in combination of two or more.

In the method of the present invention, first, the above syndiotacticity is 50% in these solvents in racemic pentad.
The above styrene-based polymer is dissolved to prepare a polymer solution. The melting operation and the temperature of the solution are 200 ° C. or lower, preferably 180 ° C. or lower. If this temperature exceeds 200 ° C, the molecular weight of the polymer may decrease. The concentration of the polymer in this solution is not particularly limited,
Usually, the range of 1 to 20% by weight is suitable. If this concentration is too low, the amount of solvent is large and it is economically disadvantageous, while if it is too high, a polymer excellent in the target moldability cannot be obtained, or the viscosity of the solution becomes high, and a gel-like substance is formed. It becomes difficult to handle such as generation and non-uniformity.

To this solution, various kinds of additives which are generated as desired and can be dissolved in the solvent used, for example, antioxidants, ultraviolet absorbers, heat stabilizers, flame retardants, antistatic agents, colorants and the like can be added.

In the present invention, the solution thus prepared may be used as it is, or if necessary, after removal of insoluble matters present in the solution by means such as filtration,
You may use.

This filtration is usually done with cotton cloth, flannel,
It is carried out by a pressure method using glass wool, kanakin and a combination thereof. When bubbles are present in the solution, if necessary, the bubbles may be removed by an appropriate method before use.

In the method of the present invention, the solvent is removed from the polymer solution, and the polymer is separated and recovered. The method for separating and recovering the polymer is not particularly limited, and various commonly used methods can be used. As such a method, for example,
Examples thereof include a method of reprecipitation, a precipitation method by cooling, a method of volatilizing or distilling off a solvent, a centrifugal separation method and the like, or a combination thereof.

As the method of the reprecipitation, a usual method of mixing or contacting the polymer solution with a liquid or a compound capable of precipitating or precipitating the polymer is used, and specifically, for example, methanol, A method in which the polymer solution is added to ethanol, isopropyl alcohol, hexane, heptane or a liquid mixture thereof to reprecipitate or precipitate the polymer is preferably used.

The precipitation method by cooling is a method in which the polymer is precipitated by cooling the solution to reduce the solubility. In this method, the precipitation recovery rate of the polymer can be increased by selecting conditions such as the type of solvent, the concentration of the polymer, and the temperature after cooling.

In the reprecipitation method and the precipitation method by cooling, the polymer precipitated or precipitated is separated from the liquid by an ordinary liquid-solid separation method such as filtration and centrifugation, and if necessary, an appropriate washing liquid is added. It can be recovered by washing after use and drying. Examples of the cleaning solution include methanol, ethanol, isopropyl alcohol, pentane, hexane, heptane, water, and the like, or a mixed solution thereof. Of these, methanol is particularly preferable. The drying method is not particularly limited, and a commonly used method can be used. Examples of such a method include a reduced pressure drying method, a blast drying method, a heat drying method and the like, and a method combining these. However, in any of the drying methods, it is desirable to set the operating temperature so that it is usually 150 ° C. or lower, preferably 100 ° C. or lower.

Examples of the method of volatilizing or distilling the solvent include a reduced pressure drying method, a blast drying method, a heat drying method, a natural drying method, a reduced pressure distillation method, an atmospheric distillation method and the like, or a combination thereof. A method such as heating under reduced pressure is preferred.

In any method such as drying by heating, the operating temperature is preferably in the range of 150 ° C or lower.

More specifically explaining the method for recovering the styrene-based polymer, for example, the polymer solution is dropped into a poor solvent of the polymer such as methanol to be deposited as particles, and dried under reduced pressure to form a resin in particles, Further, a method in which the polymer solution is dried under reduced pressure to obtain a plate-shaped body, and the resin body is shredded to obtain a particulate resin is also exemplified.

The styrene-based polymer can be recovered as an amorphous styrene-based polymer having a syndiotacticity of 50% or more in racemic pentad by using the above method. Since the recovered styrene polymer is amorphous, it can be molded at a temperature above the glass transition temperature, and therefore, thermoforming can be performed at a relatively low temperature, that is, at a temperature at which thermal deterioration of the polymer does not occur. it can.

Further, since the recovered styrene-based polymer has improved solubility in a solvent, it can be suitably used in a molding method using a solvent, if necessary.

That is, the amorphous and syndiotacticity of the styrenic polymer having a racemic pentad of 50% or more produced by the method of the present invention is various molding methods such as a thermoforming method or a molding method using a solvent. Various molding methods such as thermoforming method used for molding of a styrene-based polymer having an atactic structure, more specifically, for example, press molding, injection molding, extrusion molding, hollow molding, vacuum molding, injection molding, It can be suitably formed by methods such as casting, casting, coating, spinning, dipping, brush coating, and spraying, and various shapes, such as castings, Film, sheet,
Easily molded into laminates, coatings, melt-molded products, etc., for example, appliances such as household appliances, various equipment or machine parts such as office equipment, daily necessities such as household products, packaging containers, toys, It can be suitably used as furniture, synthetic paper, and various other industrial materials.

When performing this molding, various additives such as an antioxidant, an ultraviolet absorber, a heat stabilizer, a flame retardant, an antistatic agent, a colorant, and a plasticizer are added to the styrene-based polymer as desired. can do.

〔Example〕

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Production Example 1 Production of polystyrene having syndiotactic structure Toluene 2 as a solvent, 20 mmol of cyclopentadienyl titanium trichloride as a catalyst component, and 0.8 mol of methylaluminoxane as an aluminum atom were added to a reaction vessel, and styrene was added at 20 ° C. 3.6 was added and the polymerization reaction was performed for 1 hour. After the reaction was completed, the product was treated with hydrochloric acid-
The catalyst component was decomposed and removed by washing with a mixed solution of methanol.
Then, it was dried to obtain 330 g of a polymer. Next, this polymer was Soxhlet extracted with methyl ethyl ketone as a solvent,
An extraction residue of 95% by weight was obtained. This polymer had a weight average molecular weight of 280000, a number average molecular weight of 57,000, and a melting point of 270 ° C. In addition, this polymer has a nuclear magnetic resonance ( ¹³ C
-NMR) analysis showed absorption at 145.35 ppm due to the syndiotactic structure, and the syndiotacticity in the pentad calculated from the peak area was 96.
%.

Example 1 2.5 g of the polystyrene powder obtained in Production Example 1 and 47.5 g of chloroform were placed in a flask having an internal volume of 300 ml and dissolved at 60 ° C. to obtain a transparent solution having a concentration of 5% by weight. This solution was added dropwise to 200 ml of methanol stirred in a beaker at a dropping rate of 2-3 drops per second. The particles thus precipitated were separated by filtration and dried under reduced pressure at room temperature to obtain semitransparent polystyrene particles having a diameter of 2 to 3 mm.

Next, the polystyrene particles were held at 150 ° C. for 5 minutes, and then press-molded by a press molding machine at a pressure of 50 kg / cm ² G for 5 minutes and then at 200 kg / cm ² G for 10 minutes.
As a result, a semitransparent film was obtained.

Example 2 5 g of the polystyrene powder obtained in Production Example 1 was mixed with para-xylene.
It was added to 95 g and dissolved at 138 ° C. The obtained solution having a concentration of 5% by weight was poured into a 5 cm square box made of copper, cooled to room temperature, and dried under reduced pressure to obtain a semitransparent plate-shaped body having a thickness of 2 mm. The plate-shaped compact was chopped into small particles, and the small particles were press-molded in the same manner as in Example 1. As a result, a semitransparent film was obtained.

Example 3 1 g of the polystyrene powder obtained in Production Example 1 was added to 99 g of tetrahydrofuran and dissolved at 65 ° C. Got 1
A solution having a weight% concentration was poured into a petri dish having a diameter of 5 cm and dried at room temperature to obtain a translucent plate-shaped molded body having a wall thickness of 0.5 mm. The plate-shaped compact was chopped into small particles, and the small particles were press-molded in the same manner as in Example 1. As a result, a semitransparent film was obtained.

Production Example 2 Production of Polystyrene Copolymer with Syndiotactic Structure 60 ml of toluene as a reaction solvent, 0.05 mmol of tetraethoxytitanium and 5 mmol of methylaluminoxane as an aluminum atom were placed in a reaction vessel, and 0.45 mol of styrene and p-methyl at 50 ° C. 0.05 mol of styrene was added and a polymerization reaction was carried out for 2 hours.

After completion of the reaction, the product was washed with a mixed solution of hydrochloric acid and methanol to decompose and remove the catalyst component. Then, by drying, 6.4 g of a copolymer was obtained. Next, this copolymer was subjected to Soxhlet extraction using methylethylken as a solvent to obtain an extraction residue of 80% by weight. This extraction residual copolymer had a weight average molecular weight of 440,000 and a number average molecular weight of 240,000 and a melting point of 227 ° C. The content rate of the p-methylstyrene unit of this copolymer was 18 mol%. Further, this copolymer was found to have an absorption at 145.35 ppm by analysis by ¹³ C-NMR, and the syndiotacticity of the styrene unit in the pentad was 72%, which was calculated from the peak area.

Example 4 2.5 g of the powder of the polystyrene copolymer obtained in Production Example 2 was added to 47.5 g of decahydronaphthalene and dissolved at 180 ° C. The resulting 5 wt% strength solution was added dropwise to 250 ml of stirred hexane at a rate of 2-3 drops per second.
The particles thus precipitated were collected by filtration and dried under reduced pressure at room temperature to obtain white small particles having a diameter of 2 to 3 mm. Next, as a result of press molding in the same manner as in Example 1, a semitransparent film was obtained.

Comparative Example 1 The polystyrene powder obtained in Production Example 1 was press-molded under the same conditions as in Example 1 without being dissolved in a solvent. In this case, no film was obtained, and an aggregate of polystyrene powder was obtained. It was

〔The invention's effect〕

According to the present invention, it is possible to perform molding at a relatively low temperature, and therefore, the syndiotacticity which is remarkably improved in moldability such that there is no risk of causing thermal deterioration (such as decrease in molecular weight) during thermoforming is racemic pentad. A styrene-based polymer of 50% or more can be easily obtained, and its industrial value is extremely large.

Claims (1)

[Claims] 1. A styrene-based polymer having a racemic pentad having a syndiotacticity of 50% or more is dissolved in a solvent at a temperature of 200 ° C. or less, and then the polymer is separated and recovered from the solution. A method for producing a styrene-based polymer having an amorphous and syndiotactic structure.