JP3340571B2 - Method for producing polycarbonate resin granules - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of granulating a polycarbonate resin (hereinafter sometimes abbreviated as PC) to obtain a solid. More specifically, a method of obtaining PC as a granulated solid from a solution of PC and an organic solvent, and re-dissolving in an organic solvent for use or re-melting to produce a PC granule suitable for molding Is to provide. In recent years, liquid crystal displays have attracted attention,
C is widely used as various members because of its excellent mechanical properties, electrical properties and transparency, and the present invention aims to provide PC granules suitable for the production thereof. I do.

[0002]

2. Description of the Related Art Polycarbonate resins are particularly required for members of liquid crystal displays that require transparency, for example, substrates for polarizing plates, substitutes for conductive glass, substrates for color filters,
Applications for retardation films and the like are expanding, and PCs used for them are required to have high optical characteristics. In addition, there is a demand for a PC having a high secondary dislocation temperature, which is easier to process when processing as a member. However, it has been difficult to obtain a granular solid of PC having a high molecular weight and high optical properties for use in such applications.

In order to obtain such a PC for re-melting and dissolving the solvent, various methods have been conventionally proposed, but each has the following problems. For example, a method of contacting a poor solvent such as methanol with an organic solvent solution of PC (Japanese Patent Laid-Open No.
JP-A-8-89956, JP-A-53-137297, etc.) show that since the obtained PC is in the form of pulp, the bulk density is extremely small, and not only large equipment is required for storage and transportation, but also re-melting or There is a problem that re-dissolution is extremely difficult.

Further, a method of spraying an organic solvent solution of PC into heated water to form a slurry (JP-A-59-133228)
JP-A-5-32793, etc.) has a drawback that when sprayed into heated water, the powder once forms a powder, but is immediately welded, making it difficult to obtain a slurry.

Further, a method of spraying an organic solvent solution of PC together with steam from a nozzle into the air or an insoluble gas (Japanese Patent Publication No. 2-65221, JP-A-54-1223)
No. 93) is extremely difficult to granulate when high molecular weight PC is used.

In addition, while the organic solvent solution of PC is treated by introducing steam or the like together with a large amount of heated water in a tank equipped with a twin-screw stirrer, while the PC that has become sticky is crushed. A method of granulating and drying (for example, Japanese Patent Publication No. 38-224)
No. 97, Japanese Patent Publication No. 40-12379).
In order to crush high molecular weight PC by this method, a large amount of power is required for the stirrer, and the obtained PC is being crystallized. A crystallized cloudy solution in which undissolved PC remains remains, and PC films and the like produced therefrom have high haze and cannot be used as liquid crystal display members at all.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to easily and industrially obtain PC granules suitable for producing crystal display members and the like.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to prepare PC granules from a solution of PC and an organic solvent, and to prepare the solution at 20 to 100 ° C. in the substantially absence of water. Concentrate to a solid and reduce the PC in the solid to 35-80.
% By weight, and obtained by crushing and drying the obtained solid as it is or by crushing the solid.

Hereinafter, the method of the present invention will be described in detail.

The target PC in the method of the present invention is an aromatic PC
As long as it is manufactured, any method may be used. For example, an interfacial polymerization method, a pyridine method, a transesterification method and the like are known, and any of them can be applied. Aromatic polycarbonate resin is a polymer or copolymer obtained by a phosgene method of reacting various dihydroxydiaryl compounds with phosgene, or a transesterification method of reacting a dihydroxydiaryl compound with a carbonate such as diphenyl carbonate, A typical example is 2,2-bis (4-hydroxyphenyl)
Polycarbonate resins produced from propane (bisphenol A) are mentioned.

Examples of the dihydroxydiaryl compounds include bisphenol A, bis (hydroxyaryl) alkanes such as bis (4-hydroxyphenyl) methane, and 1,1-bis (4-hydroxyphenyl) cyclopentane. Bis (hydroxyaryl) cycloalkanes, dihydroxydiarylethers such as 4,4-dihydroxydiphenylether, 4,4 '
-Dihydroxydiarylsulfoxides such as dihydroxydiarylsulfides such as dihydroxydiphenylsulfide, and dihydroxydiarylsulfones such as 4,4'-dihydroxydiphenylsulfone.

These may be used alone or in combination of two or more.

The method of the present invention can be advantageously carried out particularly when these polycarbonate resins have an average molecular weight of 40,000 or more. If the molecular weight is high, the solution viscosity of PC and the organic solvent is high, and it is difficult to granulate in the conventional method, requiring a large amount of energy.

The solution of PC and the organic solvent used in the present invention may be, for example, a reaction product obtained by a conventionally known method and separated from water. Even if less than 1% by weight of water is included, it is distilled off during the practice of the present invention and can be carried out in the substantial absence of water in the process of producing solids. Further, it can be carried out with a solution in which PC is once dissolved in an organic solvent. Usually, the PC content in the solution is 2 to 25% by weight, preferably 5 to 20% by weight.

The organic solvents for dissolving PC include 1,1,
2,2-tetrachloroethane, methylene chloride, 1,2-dichloroethylene, chloroform, 1,1,2-trichloroethane,
1,2-dichloroethane, thiophene, dioxane, tetrahydrofuran, dioxolane and the like can be used. Preferably, methylene chloride is used.

In the present invention, first, an organic solvent is distilled off from the PC solution to obtain a solid. A known method such as vacuum and / or heating can be employed for distilling off the organic solvent. At that time, the PC content in the solid is 35 to 80% by weight. Preferably, it is 35 to 70% by weight.

When the PC content exceeds the upper limit, the energy required for crushing in the next step (crushing pressure described later)
However, it is too economical because it requires excessive equipment.

If the upper limit is exceeded, the crystallization of PC proceeds further. For example, when the obtained PC particles are dissolved in methylene chloride or the like, the solution becomes cloudy and the resulting liquid crystal display member becomes transparent. This causes problems such as impairing the performance.

On the other hand, below the lower limit, the energy (pressure) of the crushing is low, but the particle size of the granulated material obtained from the crushed solid material is extremely small, which makes it difficult to handle in a subsequent step. Happens.

The concentration temperature is usually from 20 to 100 ° C., preferably from 30 to 80 ° C. It is not preferable to carry out the treatment at an excessively high temperature because crystallization of PC proceeds. The pressure in the system at the time of concentration may be any of normal pressure, reduced pressure, and increased pressure. Normal pressure is often sufficient. The time required for concentration is
Usually, the reaction is performed for 5 minutes to 3 hours, but is preferably performed for 10 minutes to 2 hours in order to minimize the progress of crystallization.
Concentration may be performed either batchwise or continuously.

The concentration can be performed using a conventionally known device. For example, a stirrer or a stirring tank with a scraping blade, a thin-film evaporator with a scraping blade, a two-axis kneader, and the like can be given. Concentration and crushing can be performed at the same time by performing the concentration treatment with these devices. If necessary, it may be further crushed after the concentration treatment.

The concentration is performed substantially in the absence of water. This is because, in the presence of water, the obtained solid becomes a sticky solid, so that crushing is substantially difficult, and the energy for crushing is extremely large.

The obtained solid can be crushed with low energy. The energy can be measured by the following method. That is, the crushing pressure is about 8 to 10 m on a platform scale.
m, place one solid object of approximately square or cylindrical shape,
A 10 mm × 10 mm × 1 mm thick stainless steel plate is placed on the plate, and a force is applied from above to read the scale on the platform scale when the solid material is broken and crushed to an average particle size of 5 mm or less.

The crushing is performed on a solid material in an amount of 0.1 to 20 k.
g Preferably, a crushing pressure of 0.5 to 10 kg is applied. If the amount is less than the above lower limit, sufficient crushing is not performed. On the other hand, if the amount exceeds the upper limit, not only crushing into fine particles, but also crystallization proceeds due to energy at the time of crushing or rapid heat between particles, which is not preferable. Crushing pressure is PC in solid matter
Depending on the content, the lower the PC content, the lower the pressure,
Since a higher pressure is required as the PC content is higher, the crushing pressure is selected according to the PC content.

By the crushing, particles having a particle size of 0.5 to 3 mm can be easily obtained.

Next, the crushed solid is dried. Drying is preferably performed by a conventionally known dryer having one stage and, if necessary, two or more stages. The drying temperature is 20 to 150 ° C., preferably 30 to 13 ° C. in order to suppress the progress of crystallization.
It is carried out as it is under a normal pressure and a reduced pressure of 0 ° C. or by introducing an inert gas. The drying time varies depending on the PC content (remaining amount of the organic solvent) in the crushed solid and the drying temperature.
The reaction is performed for 20 hours, preferably for 20 to 10 hours. In short, it is necessary to select drying conditions so as to minimize the progress of crystallization.

[0027]

EXAMPLES Examples will be described below, but the method of the present invention is not limited to these examples.

Examples 1, 2 and 3 10 parts by weight of a polycarbonate resin (average molecular weight 62,000) were dissolved in 90 parts by weight of methylene chloride to prepare a polycarbonate resin solution.

The above solution was charged into a 500 cc flask, and heated and heated in a warm water bath at 50 ° C., and methylene chloride was distilled off at normal pressure and concentrated until the content of the polycarbonate resin in the precipitated solid became as shown in Table 1. did.

A part of the obtained solid was crushed and the crushing pressure was measured. The crushing pressure is about 8 to 1 on a platform scale.
0 mm, place a single solid having a roughly square or cylindrical shape, place a 10 mm × 20 mm × 1 mm thick stainless steel plate on it, and apply a force from above with a finger or hand to apply the solid. The measurement was carried out by measuring the scale of the platform scale at the moment when the shape of the product was broken and crushed to an average particle size of 5 mm or less. Table 1 shows the results. Next, the remaining solid was placed in a mortar and crushed. Thereafter, the solid obtained by crushing was dried in a hot-air dryer maintained at 80 ° C. for 8 hours to obtain a granulated PC. The particle size of the granular material obtained in each of Examples 1, 2, and ^{3 was} 0.5 to ³ mm visually with a microscope, and the bulk density was 0.41 to 0.50 g / cm ³ measured by a measuring cylinder method.
Met.

The time required for dissolving the granules again in methylene chloride until the polycarbonate content was reduced to 15% by weight was determined at 20 ° C. in Example 1,
The granular materials obtained in steps 2 and 3 were treated for 50 minutes and 6 minutes, respectively.
It took 0 minutes and 75 minutes.

The dissolving time of the polycarbonate resin as the starting material used in the concentration treatment of Example 1 was 30 minutes. According to the present invention, the time required for re-dissolution was remarkably reduced, and re-dissolution was excellent.

The solution thus obtained was formed into a film on a ferro-plate and dried to obtain a 100 μm film. The haze of the dried film was 0.4 to 0.6%.

[0034]

[Table 1]

[Comparative Examples 1 and 2] The same operation as in Example 1 was carried out, and the solvent was concentrated by distillation until the PC content in the solid became as shown in Table 1. The crushing pressure of the obtained solid was as shown in Table 1.

A portion was placed in a mortar and crushed, but crushing was extremely difficult and time-consuming. The particle size of the granular material obtained by drying the crushed solid in the same manner as in Example 1 is as follows:
It was 0.1 to 4 mm, and the particle size distribution was wide.

The granules were dissolved in methylene chloride in the same manner as in Example 1, and the time required for dissolution until the PC content became 15% by weight was measured. It was 180 minutes and 300 minutes, and the solution in which the granular material of Comparative Example 1 was dissolved was slightly cloudy, and that of Comparative Example 2 was cloudy. The haze of the film obtained by forming a film from this solution in the same manner as in Example 1 was 1.
9% and 5.7%.

Comparative Example 3 To 100 parts by weight of the PC solution prepared in Example 1 was added 10 parts by weight of water, and PC: methylene chloride = 50: 50 while refluxing only water into the system during the distillation of methylene chloride. (Weight ratio). A sticky solid was obtained, which could not be crushed only by applying pressure to spread the sticky shape.

[0039]

According to the method of the present invention, a granular product of PC excellent in resolubility, remeltability and the like can be easily produced industrially. Such a granular material can be used for manufacturing a liquid crystal display member requiring high optical characteristics. In addition, the present invention can perform the concentration treatment and the drying of the crushed granules substantially in the presence of water, so that the reaction of generating hydrochloric acid from methylene chloride and water does not occur, and the material of the apparatus is titanium or the like. It can be implemented with industrially inexpensive equipment without requiring advanced materials.

Claims (2)

(57) [Claims] In producing a granular material of a polycarbonate resin from a solution of a polycarbonate resin and an organic solvent, the solution is prepared in the absence of water in the presence of 20 to 10 g.
A process for producing polycarbonate resin granules , comprising concentrating at 0 ° C. to form a solid, making the polycarbonate resin in the solid 35 to 80% by weight, and drying the obtained solid as it is or by crushing it. Law. 2. The method according to claim 1, wherein the solid is crushed at a crushing pressure of 0.1 to 20 kg. (Here, the crushing pressure is about 8 to 10 mm on a platform scale,
A solid material having a roughly square or columnar shape is placed, and a stainless steel plate of 10 mm × 20 mm × 1 mm thickness is placed on the solid material, and a force is applied from above on the stainless steel plate. It refers to the scale of the platform scale at the moment of crushing to 5 mm or less. )