JPH0966524A - Manufacture of polycarbonate resin pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polycarbonate resin pellet which contains a small low- molecular-weight material or residual solvent amount in the pellet and is useful for an optical grade having high transparency or a lens for a vehicle. SOLUTION: This method for manufacturing a pellet has the steps of melting and extruding a polycarbonate resin powder, and comprises the steps of enhancing the resin filling ratio by using a screw provided with a material sealing mechanism, melting and kneading it, degassing an organic solvent and/or low- molecular weight volatile material at the bent part, and pelletizing it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polycarbonate resin pellets which have excellent heat resistance and color tone and generate little gas during molding. More specifically, it is possible to increase the resin filling rate during the production of polycarbonate resin pellets. By melting and kneading with a screw with a special shape that can, devolatilization of the organic solvent and low molecular weight substances remaining in the powder,
It is intended to improve the hue by purging air, and is useful as a method for producing a light-colored transparent polycarbonate resin which is particularly suitable as a material for optics and automobile parts.

[0002]

2. Description of the Related Art Polycarbonate resins are used in a wide range of fields because of their transparency, mechanical properties, flame retardancy, dimensional stability and electrical properties. However, the polycarbonate resin has the property of being colored yellow when it is melt-processed into pellets or formed into a sheet, which deteriorates the appearance.

Most of the polycarbonate resin powders used as raw materials are currently produced by an interfacial polymerization method using an organic solvent, and therefore contain residual organic solvents and low molecular weight substances.
The organic solvent and low-molecular-weight volatiles remain in the pellets obtained by melt-extruding the product, and when processed into a molded product, bubbles are generated in the molded product, or low-molecular-weight volatiles are generated.
In particular, when molding an optical disc substrate, such low-molecular-weight volatiles cause stains on the stamper, resulting in a significant decrease in productivity due to maintenance and a decrease in pit transferability. The low-molecular-weight volatile material is an oligomer in which the raw material monomer and the endcapping agent are reacted in a ratio of 1: 1 or a monomer oligomer or a dimer of the endcapping agent which is reacted in a ratio of 1: 2. However, it is known that the most problematic one among them is a monomer oligomer having a high content in the polymer.

Polycarbonate resins are currently generally produced by reaction polymerization by an interfacial polymerization method. In the interfacial polymerization method, since the polycarbonate resin is obtained as an organic solvent solution, a method for isolating and obtaining a solid is to add a polymer organic solvent solution to warm water under stirring to evaporate the solvent, or a jacket. A large number of methods have been disclosed so far, such as a method of charging into a heating paddle type kneader to perform granulation and drying.

However, in the above-mentioned conventional method, since a solvent represented by methylene chloride has a high affinity with polycarbonate, it is difficult to remove the solvent with a general dryer or a large dryer is required. did. Various methods for solving such a problem have been proposed.

That is, a drying method using a paddle type dryer having a spiral blade group for progressive feeding and a spiral blade group for backward feeding (Japanese Patent Publication No. 53-15899, Japanese Patent Publication No. 55-33966, and Japanese Patent Publication No. 53-137298). However, when such a horizontal dryer is used, the fluidity of the powder in the dryer becomes uneven, so burnt dust is generated due to overheating, and the paddle blade and the powder are forcibly brought into contact with each other. Occurrence of dust is observed. In addition, there is a method of filtering and drying the polycarbonate solid particles in the same dryer using a filter dryer (Japanese Patent Laid-Open No. 61-250025). However,
When this dryer is used, a long drying time is required, and since the structure of the dryer allows only batch processing, it cannot be applied to continuous production.

So far, several methods have been proposed for reducing the amount of residual organic solvent during extrusion and improving the hue of pellets. For example, before and / or during the mixing of the polycarbonate resin powder, the polycarbonate 100
A method of adding 0.2 to 20 parts by weight of water per part by weight and extruding while degassing under conditions that do not cause hydrolysis (Japanese Patent Publication No. 5-27647), a high theoretical surface renewal of wet powder containing water and solvent. A method of directly pelletizing by charging into an extruder having a frequency (Japanese Patent Laid-Open No. 1-149827), and during melt extrusion, 0.1 to 5 per 100 parts by weight of polycarbonate between the compression melting part and the farthest vent port. A method of press-fitting water by weight (Japanese Patent Publication No. 7-2364) is disclosed, but even if a conventionally known method is used, the contact between the added water and the molten resin and the degree of kneading are insufficient. Therefore, the effect of reducing the residual solvent in the pellet was small. Also,
While adding phosphorous acid to the polycarbonate resin,
A method in which water is added to adjust the water content of the resin to 500 to 5000 ppm and then pelletized (JP-A-4-8145).
In 7), the addition of phosphorous acid causes a reduction in hydrolysis resistance and a reduction in long-term reliability of the optical disc.

[0008]

Conventionally, it is possible to remove residual solvent and low molecular weight volatiles to some extent during extrusion pelletization, and a method of adding water during extrusion has been used to further increase the removal rate. Came. However, the residual amount of residual solvent and low-molecular-weight volatiles has not reached the target level even by using the conventionally used methods. As a cause of this, it was found that the shape of the screw that has been conventionally used is not a shape that contributes to devolatilization and that the added water and the molten resin are not sufficiently kneaded.

The inventors of the present invention have designed the screw shape of the extruder to have a special structure to increase the residence time of the molten resin in the portion and to increase the filling rate of the molten resin, that is, by performing so-called material sealing. It is possible to prevent air from flowing from the hopper part to the vent part and keep the vacuum level of the vent part high, and increase the pressure of the molten resin in the material seal part to knead it, and then devolatilize it with the vent to degas It has been found that the effect is improved, and that the effect is remarkably improved by adding a specific amount of water to the portion having the material sealing mechanism.

The present invention significantly reduces the amount of organic solvent and low molecular weight volatiles remaining in the polycarbonate resin solid particles,
It is a method of manufacturing polycarbonate resin molding materials that improve the hue of molded products and generate less gas from molded products.By reducing the load in the drying process, product costs can be reduced.Residual solvents and low molecular weight volatiles The purpose is to provide a removal method.

[0011]

Means for Solving the Problems The present inventors have solved the above-mentioned problems by providing a screw structure capable of improving the residence time of molten resin in an extruder and performing sufficient kneading. Has reached the present invention.

That is, the present invention relates to a method for producing pellets by melt-extruding a polycarbonate resin powder with an extruder having a screw with a vent, in which a screw having a material sealing mechanism is used to increase the resin filling rate in the cylinder and melt kneading. Then, the organic solvent and / or the low-molecular-weight volatile matter is devolatilized in the vent portion .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as an embodiment, a screw having a material seal mechanism is used, and a resin filling rate in a cylinder is at least 50% of a space portion filled with a molten resin in the material seal mechanism portion.
Is melt-kneaded, and then the organic solvent and / or low-molecular-weight volatile matter is devolatilized in the vent portion to pelletize.

The above-mentioned material sealing method in the present invention is selected from a reverse screw and a dam ring. Further, in the present invention, a method of adding water corresponding to 0.05 to 5.0 parts by weight to 100 parts by weight of a polycarbonate resin, kneading and pelletizing the portion having a material sealing mechanism in order to improve the devolatilizing effect. Is.

The polycarbonate resin in the present invention is
An interfacial polymerization method, a pyridine method, a solution method such as a chloroformate method, a dihydric phenol-based compound as a main component, a small amount of a molecular weight modifier and if desired by reacting with phosgene using a branching agent, Aromatic homo- or copolycarbonate resins obtained by using usual bisphenols, further branched ones, viscosity average molecular weights of those having long-chain alkyl groups introduced at the terminals of 5,000 to 100,000, Preferably 13,00
It is from 0 to 90,000, especially from 15,000 to 35,000.

The polycarbonate resin applied to the present invention includes a polycarbonate resin having a double bond or other graft-polymerizable active site at the molecular end, and a resin such as styrene, methallylic acid, acrylic acid, meacrylate or acrylate. A grafted polycarbonate resin obtained by reacting with a polymerizable monomer can also be used.

Preferred examples of the bisphenol compound as a raw material of the polycarbonate resin used in the present invention include bis (4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) ether and bis (4-hydroxy). Phenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ketone, 1,1-bis (4-hydroxyphenyl)
Ethane, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A; BPA), 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane (TBA), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl)
Cyclohexane (bisphenol Z; BPZ), 2,2
-Bis (4-hydroxy-3,5-dichlorophenyl)
Propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-hydroxy-)
3-chlorophenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-
Bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,1-bis (4-hydroxyphenyl) -1
-Phenylethane, bis (4-hydroxyphenyl) diphenylmethane, α, ω-bis [3- (O-hydroxyphenyl) propyl] polydimethylsiloxane (PD
S) and biphenol are exemplified. You may use these in combination of 2 or more types. Among them, those selected from bisphenol A, bisphenol Z, TBA and PDS are preferable.

Examples of the terminal terminator or molecular weight regulator include compounds having a monovalent phenolic hydroxyl group,
Other than ordinary phenol, P-tert-butylphenol, tribromophenol, etc., long-chain alkylphenol, aliphatic carboxylic acid chloride, aliphatic carboxylic acid, aromatic carboxylic acid, aromatic acid chloride, hydroxybenzoic acid alkyl ester, alkyl ether Examples include phenol.

A compound having a reactive double bond can also be used as a terminal stopper. Examples of such compounds include unsaturated carboxylic acids such as acrylic acid, vinyl acetic acid, 2-pentenoic acid, 3-pentenoic acid, 5-hexenoic acid, 9-undecenoic acid; acrylic acid chloride, sorbic acid chloride, allyl alcohol. Acid chlorides or chloroformates such as chlorochloroformate, isopropenylphenol chloroformate or hydroxystyrene chloroformate; isopropenylphenol,
Hydroxystyrene, hydroxyphenylmaleimide,
Examples thereof include phenols having an unsaturated group such as hydroxybenzoic acid allyl ester and hydroxybenzoic acid methylallyl ester. These compounds may be used in combination with a compound having a usual monovalent phenolic hydroxyl group.

The terminator or molecular weight regulator is usually used in an amount of 1 mol based on 1 mol of the above dihydric phenol compound.
It is used in the range of .about.25 mol%, preferably 1.5 to 10 mol%.

The organic solvent used in the reaction is a solvent inert to the reaction, for example, dichloromethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chloroform,
Chlorinated hydrocarbons such as 1,1,1-trichloroethane, carbon tetrachloride, monochlorobenzene and dichlorobenzene; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; ether compounds such as diethyl ether These can be used, and two or more kinds of these organic solvents can be mixed and used. In addition, if desired, solvents other than the above, such as ethers, ketones, esters, and nitriles, which have an affinity for water may be used within the limit that the mixed solvent system is not completely compatible with water.

Further, a branching agent may be used, and the amount of the branching agent is based on the above dihydric phenol compound.
It can be used as a branched polycarbonate in combination in the range of 0.01 to 3.0 mol%, particularly 0.1 to 1.0 mol%. As a branching agent, phloroglucin, 2,6-dimethyl-2,4,6-tri (4-hydroxyphenyl)
Heptene-3,4,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) heptene-2,1,3,5
-Tri (2-hydroxyphenyl) benzol, 1,
1,1-tri (4-hydroxyphenyl) ethane, 2,
6-bis (2-hydroxy-5-methylbenzyl) -4
-A polyhydroxy compound exemplified by methylphenol, α, α ′, α ″ -tri (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, and 3,
Examples thereof include 3-bis (4-hydroxyphenyl) oxindole (= isatin bisphenol), 5-chloroisatin bisphenol, 5,7-dichloroisatin bisphenol, and 5-bromoisatin bisphenol.

Examples of the polycarbonate resin include a polycarbonate containing bisphenol A as a main raw material, and a polycarbonate copolymer obtained by using, for example, bisphenol Z or tetrabromobisphenol A (TBA) in combination therewith, and a branch thereof. A modified product or a product modified with a long-chain alkyl group is preferable.

The polycarbonate resin powder used in the present invention is a powder obtained by solidifying a polycarbonate resin from a refined polycarbonate resin solution. The method for making powder is to distill off the solvent from the polycarbonate resin solution. The method of concentrating and granulating the product, adding a poor solvent to the polycarbonate resin solution, adding the resin solution in warm water under heating and suspending it in warm water to distill the solvent and poor solvent to solidify There are various methods such as a method of circulating a liquid in a solidification process in a wet crusher while generating a water slurry liquid, and crushing it. In the present invention, a powder obtained by any method can be used. . The powder thus obtained varies depending on whether or not it is dried, the type of dryer, and the drying conditions, but in general, the powder has a residual water content of 0.01
10 to 10% by weight, and 0.01 to 4% by weight as a residual solvent.

In the present invention, the polycarbonate resin powder is melt extruded by an extruder equipped with a screw having a material sealing mechanism with a vent to produce pellets. Specifically, the extruder is a single-stage or multi-stage vent. A single-screw extruder or a multi-screw extruder equipped with the same can be used. Among these, a twin-screw extruder having two or more vents is preferable.

The material sealing mechanism uses a screw element having a special shape to regulate the moving speed of the resin inside the cylinder, increase the filling rate of the molten resin in the portion, and degas the remaining solvent. This refers to a mechanism that prevents backflow of low-molecular-weight volatiles and subsequently reduces the filling rate to flush and degas residual solvent and low-molecular-weight volatiles all at once at the vent. It is possible to have one or more material sealing mechanisms in one extruder.

The material sealing method may be any structure having the above mechanism as a screw element, but it is preferable to use a structure selected from a reverse screw and a dam ring as the structure of the screw element. Furthermore, a vent for promoting degassing is provided on the die side (outlet side) of these screw elements, and the degree of vacuum of the vent is 60 torr in order to reduce the amount of residual solvent and the amount of low molecular weight volatiles remaining. The following are preferable, and by using a mechanical booster,
It is more preferable to set it to 30 torr or less.

The polycarbonate resin powder as the raw material is
It is supplied directly into the cylinder through the hopper or by the side hood. The powder is melted by heating the cylinder. Normally, the screw is provided with a forward screw, so by rotating the screw,
The molten resin moves toward the outlet and is guided to the material seal portion. In the material seal part, depending on the structure, not the screw in the forward direction but the screw in the reverse direction may be provided, or the dam ring may be provided to prevent the flow of the molten resin. The filling rate increases significantly. In the material seal portion, the temperature rises due to heat from the barrel or shear heat generation due to friction between the resins and between the resin and the barrel, and volatilization of the residual solvent and low molecular weight volatiles is promoted. Since the resin filling rate is high and the pressure is high in this portion, backflow of these gaseous volatiles toward the rear of the screw, that is, toward the hopper can be prevented.

In this material seal portion, the resin filling rate is at least 5 of the space portion to be filled with the molten resin.
It needs to be 0%. If the filling rate of molten resin is 50
If it is less than%, the sealing effect becomes insufficient and back evaporation of the vaporized gaseous substance occurs to reduce the degassing effect. The molten resin that has been compressed in the material seal portion moves to the vent portion, the pressure is suddenly released, and the devolatilization of the residual solvent and low molecular weight volatile matter is promoted.

In the present invention, water may be added to the raw material powder or the molten portion in order to accelerate the devolatilization of the residual solvent and the low molecular weight volatile matter. It is particularly preferable to use a method of adding 0.05 to 5.0 parts by weight of water per 100 parts by weight of polycarbonate to the portion having the material sealing mechanism. The added water rapidly gasifies and tries to flow back to the powder feed port, but does not flow back due to the material sealing mechanism, which prevents the powder backflow phenomenon. Further, due to the high resin filling rate, the degree of kneading of the gasified water and the molten resin can be improved to further promote the devolatilization.

The addition position of the water is added to the portion having the material seal mechanism, specifically, part of the resin filling ratio was increased by dam ring and hand thread screw, or that its is immediately after preferable. When added to the part closer to the hopper side than the dam ring or the reverse screw, the gasified water flows out to the powder feed port.
And the supply troubles and the powder due to the back flow, it is impossible to satisfactorily perform kneading with gasified water with molten resin. Further, when water is added after the portion having the material sealing mechanism, the gasified water is not preferable because it will escape from the vent without making sufficient contact with the molten resin.

With respect to the kneading time of water and the molten resin, the gasified water and the molten resin are mixed for a few seconds to a few tens of seconds, specifically 2 to.
It is preferable to knead for 30 seconds. Kneading time is 2
If it is less than 2 seconds, the kneading of the molten resin and water will be insufficient and the effect of water addition will not be fully exerted, and if the kneading time is more than 30 seconds, hydrolysis of polymer molecules due to water vapor will occur and coloring will occur. Cause of. The kneading time of gasified water and molten resin is determined by the distance from the position where water is added to the vent, the discharge amount of resin, and the screw rotation speed, and the kneading time can be controlled by changing these conditions. it can.

The kneading time of the molten resin and the gasified water is
Specifically, a tracer response test is performed for each resin discharge amount and screw rotation speed to obtain an average residence time (T) in which the molten resin moves along the screw length (L), and the average residence time (T) from the water addition position to the vent is determined. When the distance is (d), the kneading time (t) can be approximated by the calculation formula of t = Td / L.

The water added in the present invention is preferably pure water, and has a conductivity of 5 μS / cm or less, particularly preferably 1 μS / cm or less. Water usually contains inorganic salts, and even if these are present in trace amounts,
Since the vapor resistance and heat resistance of the molded product are reduced, it is necessary to reduce the conductivity as much as possible.

In the melt extrusion of the present invention, additives generally added to polycarbonate resins may be added. For example, flame retardants, light stabilizers, antistatic agents, plasticizers, lubricants, compatibilizers, foaming agents, glass fibers, glass beads, glass powder, carbon fibers, reinforcing agents such as ceramic whiskers, fillers, dyes, pigments. Is exemplified. Further, resins other than polycarbonate resin, for example, polyethylene,
Polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polymethylmethacrylate, AB
If desired, S resin, polyester, polyphenylene oxide, and other elastomers can be mixed.

[0036]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto as long as the scope of the present invention is not exceeded.

Reference Example (Representative Polycarbonate Powder Production Method) A methylene chloride solution of a polycarbonate resin produced from bisphenol A was purified to obtain a solution having a resin concentration of 20% and a viscosity average molecular weight of 2.1 × 10 ⁴ . This resin liquid 200
To the liter, 40 liters of n-heptane, which was also microfiltered, was added under stirring and uniformly mixed, and then this solution was dropped into warm water under stirring for 10 minutes and pulverized by a wet pulverizer. The temperature of the liquid in the container is 40 ℃ and the internal pressure is 0.1 k.
It was maintained below gG / cm ² . After dripping, the temperature inside the container is about 1
The temperature was raised to 00 ° C., the solvent was distilled off in about 15 minutes, the obtained aqueous slurry of polycarbonate resin was taken out, filtered and drained to obtain a wet powder, which was then dried using a hot air circulation dryer. , Spend 4 hours at 140 ℃ to dry,
The amount of residual organic solvent is 4530 ppm of n-heptane content,
A dry powder having a methylene chloride content of 11 ppm and a monomer oligomer content of 0.94% was obtained.

Method for measuring the amount of residual solvent in pellets: 1 g of polycarbonate resin pellets was dissolved in dioxane,
A 20 ml solution was prepared and quantitative analysis was performed by gas chromatography.

Content of monomer / oligomer in pellet: 100 mg of pellet was dissolved in 20 ml of chloroform, and Waters
GPC (column: Shodex K803L x 2, detector: 4
90 UV detector, 254 nm, AUFS1.0), sample volume: 100 μl, solvent flow rate: 1.0 ml / min, and the peak area around the retention time of 1925 minutes indicates the monomer oligomer in the pellet. The content rate (%) was calculated.

Hue evaluation method: Each pellet was injected into an injection molding machine (Sumitomo Heavy Industries, Ltd .: Neomat 350/12).
0) resin temperature 320 ° C, mold temperature 80 ° C, holding pressure 10
5 pieces of 50 mm x 60 mm and 3 mm thick test pieces were continuously molded at 00 kg / cm2, and the color of the test pieces was measured with a Nippon Denshoku Co., Ltd. color difference meter, and the YI value (index indicating yellowness) was obtained. I asked.

Molten resin filling rate: When the space portion volume (V) of the screw groove portion in the material seal portion and the discharge amount (E), the molten resin residence time (t) in this portion [shown above by the tracer response test] Formula t =
Td / L], and the specific gravity of the polycarbonate is 1.19, and can be approximately calculated by the following formula. f = E × t / (V × 1.19)

Examples 1 to 5 As a raw material powder, a polycarbonate resin powder containing 4530 ppm of n-heptane and 11 ppm of methylene chloride was used, and a twin-screw extruder manufactured by Bear Stoof (screw diameter: 40 mm, L / D = 32) was used as an extruder. , L: total screw length, D: screw diameter,) were used. As the screw shape, a screw having a double thread was used except that a dam ring was provided at the 16D portion from the tip, and a barrel having a vent port (vacuum degree 40 torr) was provided at the 14D portion from the tip. (Note that the space volume (V) of the screw groove portion in the material seal portion is about 50 cm ^3. ) Discharge rate 20 kg / h (Example 1), 30 kg / h (Example 2),
40 kg / h (Example 3), 50 kg / h (Example 4), 70 kg
/ h (Example 5), screw rotation speed 250 r.p.m.
Was extruded. The residual solvent concentration in the pellet, the monomer oligomer content, and the YI value were measured and the results are shown in Table 1.

Comparative Examples 1 to 3 The screw rotation speed was 250 r.p.m., except that a screw having no dam ring was used. p. m. Discharge rate is 30 kg / h
(Comparative Example 1), 50 kg / h (Comparative Example 2) and 70 kg / h (Comparative Example 3) were extruded and pelletized, and the residual solvent concentration in the pellet, the content of the monomer oligomer, and the hue after plate molding were measured. The measurement results are shown in Table 1.

[0044]

[Table 1] Table-1 ──────────────────────────────────── Discharge rate Screw fill rate Hue remaining Dissolved monomer (kg / h) Rotation speed Medium content (rpm) (%) (YI value) (ppm) (%) ──────────────────── ───────────────── Example 1 20 250 53 1.33 24 0.16 Example 2 30 250 62 1.25 25 0.17 Example 3 40 250 70 1.22 25 0.17 Example 4 50 250 81 1.21 26 0.18 Example 5 70 250 95 1.24 26 0.18 Comparative Example 1 30 250 23 2.21 130 0.66 Comparative Example 2 50 250 35 2.12 234 0.69 Comparative Example 3 70 250 43 2.15 318 0.75 ─────────── ─────────────────────────

Examples 6-8 18030 ppm n-heptane, 10 methylene chloride
Polycarbonate resin powder containing 50 ppm was used as the raw material powder, the extruder used in Examples 1 to 5 was used, and the screw shape was a double thread type except that it had a dam ring at the 16D portion from the tip, 1 from the tip
Barrel with 2D vent (vacuum 40 torr)
Use a polycarbonate resin 1 from the tip to the 16D part
Discharge amount of 30 kg / h (Example 6), 50 kg / h (Example 7), 70 kg / h (Example 8), screw rotation while adding 1 part by weight of pure water to 00 parts by weight Number 300
Extrusion was carried out at r.p.m. The residual solvent concentration, monomer oligomer content, and YI value of the extruded pellets were measured, and the results are shown in Table 2.

Comparative Examples 4 to 5 Extrusion pelletization was carried out in the same manner as in Examples 6 and 8 except that a double thread screw having no dam ring was used.
The residual solvent of the pellet, the content of the monomer oligomer, and the hue after plate molding were measured, and the results are shown in Table 2.

[0047]

[Table 2] Table-2 ──────────────────────────────────── Discharge rate Screw fill rate Hue remaining Dissolved monomer (kg / h) Rotation speed Medium content (rpm) (%) (YI value) (ppm) (%) ──────────────────── ───────────────── Example 6 30 300 60 1.13 35 0.14 Example 7 50 300 79 1.15 37 0.14 Example 8 70 300 92 1.21 41 0.15 Comparative Example 4 30 300 20 2.15 430 0.66 Comparative Example 5 70 300 40 2.29 550 0.75 ─────────────────────────────────────

Examples 9 to 11 Extrusion pelletization was performed in the same manner as in Examples 6 to 8 except that the reverse screw was used instead of the dam ring, and the residual solvent concentration in the pellet, the content of the monomer oligomer, and the The hue after plate molding was measured and the results are shown in Table 3.

Example 12 Extrusion pelletization was carried out in the same manner as in Example 7 except that the amount of pure water added was 2.7 parts by weight, and the residual solvent concentration in the pellets, the monomer oligomer content, and the plate molding. The subsequent hue was measured and the results are shown in Table 3.

Example 13 Extrusion pelletization was performed in the same manner as in Example 7 except that the amount of pure water added was changed to 5 parts by weight, and the residual solvent concentration in the pellet, the monomer oligomer, and the hue after plate molding were measured. The measurement results are shown in Table 3.

Comparative Example 6 Extrusion pelletization was carried out in the same manner as in Example 12 except that a double thread screw having no dam ring was used. The hue was measured and the results are shown in Table 3.

Comparative Example 7 Extrusion pelletization was performed in the same manner as in Example 13 except that a double-threaded screw having no dam ring was used. The hue was measured and the results are shown in Table 3.

Example 14 A polycarbonate resin powder containing 3% of n-heptane and 4500 ppm of methylene chloride was used as a raw material powder, and the same extruder as that used in Examples 1 to 5 was used as an extruder, and a screw shape was used. Is a double thread type except that it has a dam ring in the 16D and 24D portions from the tip, and uses a barrel (vacuum degree 40 torr) with a vent port in the 12D and 24D portions from the tip, and 1 from the tip
While adding pure water equivalent to 1 part by weight to 100 parts by weight of the polycarbonate resin to the 6D and 24D parts, the discharge rate was 50 kg / h and the screw rotation speed was 200 r.p.
Extrusion was carried out at m. The residual solvent concentration, monomer oligomer content, and YI value of the extruded pellets were measured and the results are shown in Table 3.

Example 15 Extrusion was carried out in the same manner as in Example 14 except that the amount of pure water added was 1.5 parts by weight with respect to 100 parts by weight of the polycarbonate resin, and the results are shown in Table 3.

Example 16 Extrusion was carried out in the same manner as in Example 14 except that the amount of pure water added was 2.5 parts by weight relative to 100 parts by weight of the polycarbonate resin, and the results are shown in Table 3.

Comparative Example 8 Extrusion was performed in the same manner as in Example 14 except that the amount of pure water added was 3 parts by weight with respect to the polycarbonate resin, and the results are shown in Table 3.

[0057]

[Table 3] Table-3 ──────────────────────────────────── Discharge rate Screw fill rate Hue remaining Dissolved monomer (kg / h) Rotation speed Medium content (rpm) (%) (YI value) (ppm) (%) ──────────────────── ───────────────── Example 9 30 300 60 1.21 23 0.13 Example 10 50 300 80 1.14 34 0.15 Example 11 70 300 92 1.16 40 0.14 Example 12 50 300 80 1.08 12 0.16 Example 13 50 300 79 1.07 10 0.15 Example 14 50 200 95 1.20 ND 0.13 Example 15 50 200 95 1.16 ND 0.13 Example 16 50 200 94 1.13 ND 0.13 Comparative Example 6 50 300 32 2.33 320 0.86 Comparative Example 7 50 300 30 2.42 230 0.88 Comparative Example 8 50 200 95 2.88 ND 0.15 ─────────────────────────────────── ──

[0058]

INDUSTRIAL APPLICABILITY As described above, by extruding a molten resin using an extruder equipped with a screw having a material sealing mechanism according to the method of the present invention, the amount of residual solvent in pellets and low molecular weight volatiles are reduced. It is possible to prevent the generation of bubbles during molding and the contamination of the stamper, and it is possible to obtain a transparent material with good color tone and high transparency and low dust such as optical grade and automobile lenses. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Mori 2-12, Shinshu-cho, Toyonaka-shi, Osaka Mitsubishi Gas Chemical Co., Ltd. Osaka Plant

Claims (4)

[Claims] 1. A method of melt-extruding a polycarbonate resin powder by an extruder having a screw with a vent to produce pellets, wherein a screw having a material sealing mechanism is used to increase the resin filling rate in a cylinder and melt-kneading. Next, a method for producing a polycarbonate resin pellet, which comprises devolatilizing an organic solvent and / or low-molecular-weight volatile matter in a vent portion. 2. The resin filling rate is at least 5 of the volume of the space portion filled with the molten resin in the material seal mechanism portion.
The method of claim 1, which is 0%. 3. The method of claim 1, wherein the material seal mechanism is a method selected from the group consisting of a reverse screw and a dam ring. 4. A portion having a material sealing mechanism, 0.05 to 5.5 parts per 100 parts by weight of a polycarbonate resin.
2. Melt kneading is carried out by adding water corresponding to 0 part by weight.
the method of.