JP4977786B1 - Method for producing polycarbonate resin pellets - Google Patents

Abstract

Disclosed is a polycarbonate resin pellet that has an extremely small content of impurities such as a chlorine compound, little deterioration of the resin, does not cause yellowing, has a good pellet appearance, and can be used free of resin additives.
[MEANS FOR SOLVING PROBLEMS] (1) Using a polycarbonate resin having a specific granular shape, (2) dropping and moving by 50 cm or more in an inert gas atmosphere having an oxygen concentration of 3% by volume or less, (3) in the kneading zone of an extruder A specific amount of water having a conductivity of 30 μS / cm or less is injected, 4) the suction is performed with the vent port in a reduced pressure state, the water concentration in the resin is adjusted to 10 to 200 ppm, and 5) the strand extruded from the die. Cooled in water having an electric conductivity of 30 μS / cm or less, 6) cutting the strands at 70 ° C. to 130 ° C. to obtain pellets containing 10 to 200 ppm, and 7) allowing the pellets to contain water in a humid atmosphere. The manufacturing method of the polycarbonate resin pellet characterized by adjusting the moisture content to 1300 ppm or less.
[Selection] Figure 1

Description

  The present invention relates to a method for producing polycarbonate resin pellets. More specifically, the content of impurities such as chlorine compounds is extremely small, the resin is hardly deteriorated, yellowing does not occur, the pellet appearance is good, and resin additives are free. The present invention relates to a method for producing polycarbonate resin pellets that can be used in the above.

Polycarbonate resin is a general-purpose engineering plastic that excels in transparency, impact resistance, heat resistance, dimensional stability, etc., and its excellent characteristics make it an excellent choice in a wide range of fields such as electrical / electronic / OA equipment parts, machine parts, and vehicle parts. in use.
Various electrical and electronic equipment parts such as a silicon wafer, a disk substrate, a data storage hard disk, an optical storage disk, an IC chip, and a high-performance substrate glass for LCD are used as parts in the electrical and electronic equipment. In the manufacture of electrical and electronic equipment, these parts must be transported and transported in order to be used in an assembly line, and a transport case for this purpose is used. Various thermoplastic resins have been used.

  In recent years, with the miniaturization, high density, and high integration of electrical and electronic equipment components, the pollutants that are generated and contacted during the manufacturing environment, storage, and movement are affected by the yield of electrical and electronic equipment products. The quality and reliability have been greatly influenced, and as the electrical and electronic equipment components have been miniaturized, densified, and highly integrated, a higher degree of cleanliness has become necessary.

  Polycarbonate resins, especially those obtained by reacting aromatic dihydroxy compounds and phosgene in a methylene chloride solvent, by so-called interfacial polymerization, contain methylene chloride and other chlorinated compounds to a small extent. The compound decomposes upon melting to generate an acidic substance. By removing these contaminants from the polycarbonate resin material, it is expected to improve the reliability of the transport case using the same.

  In order to solve such problems relating to the polycarbonate resin, a method of removing impurities by adding water at the time of melt extrusion (for example, see Patent Document 1) is known. In Patent Document 2, foamed water is added. There is a proposed method. However, with these methods alone, the degree of cleanliness is not sufficient for transport cases that require a high level, and a polycarbonate resin molding material having a higher level of cleanliness is more efficient. A method of manufacturing well has been desired.

Japanese Patent Publication No. 5-48162 Japanese Patent No. 3776746

  In view of the above-mentioned problems of the prior art, the object of the present invention is that the content of impurities such as chlorine compounds is extremely small, the resin is hardly deteriorated, yellowing does not occur, the pellet appearance is good, and the resin additive is free. It is providing the method of manufacturing the polycarbonate resin pellet which can be used.

  As a result of intensive studies in order to achieve the above-mentioned problems, the present inventors use a polycarbonate resin having a specific specific surface area and particle size, respectively, specific inert gas treatment process, water injection process, vacuum suction process, respectively. It was found that by combining the cooling step, the cutting step, and the aging step, polycarbonate resin pellets having an extremely low level of impurity content that could not be achieved until now can be obtained, and the present invention has been completed.

That is, according to the first invention of the present invention, a method for producing a polycarbonate resin pellet having a reduced methylene chloride content from a polycarbonate resin containing a small amount of methylene chloride,
1) As a polycarbonate containing a small amount of methylene chloride, a polycarbonate resin in the form of a granular material having a specific surface area of 0.008 m ² / g or more and 50% by mass or more having a particle size of 200 to 2,000 μm is used.
2) An inert gas treatment step in which a polycarbonate resin in the form of granules is dropped and moved by 50 cm or more in an inert gas atmosphere having an oxygen concentration of 3% by volume or less,
3) The inert gas-treated polycarbonate resin in the form of granules is supplied to a vent-type extruder, and in the kneading zone, water having an electric conductivity of 30 μS / cm or less is added to 0.1 parts by mass of 100 parts by mass of the polycarbonate resin. Injecting 1 to 2 parts by mass;
4) By suctioning the vent port provided on the downstream side of the water injection portion of the extruder under reduced pressure, the methylene chloride is sucked and removed together with the water from the molten resin, and the water concentration in the resin is 10 Adjusting to ˜200 ppm,
5) A step of introducing and cooling the strand-shaped molten resin extruded from the die of the extruder into water having an electric conductivity of 30 μS / cm or less,
6) A step of cutting the strand in the range of 70 ° C to 130 ° C to obtain pellets containing 10 to 200 ppm of water,
7) including a aging step of further hydrating the obtained pellets containing 10 to 200 ppm of moisture in a wet atmosphere and adjusting the moisture content to exceed the original moisture content of the pellets and to 1300 ppm or less. A method for producing a polycarbonate resin pellet is provided.

  According to the second invention of the present invention, there is provided a method for producing polycarbonate resin pellets, characterized in that in the first invention, a drying step of drying the moisture-containing pellets obtained through the aging step is further performed. Provided.

  According to the third invention of the present invention, in the first or second invention, when the polycarbonate resin in the form of a granule is treated with an inert gas, the powder fluid is supplied in a falling state, and the inert gas is supplied. A method for producing a polycarbonate resin pellet is provided, which is supplied from below so as to be countercurrent to the granular material.

  According to a fourth invention of the present invention, in any one of the first to third inventions, the polycarbonate resin pellets characterized in that the oxygen concentration in the barrel of the vented extruder is 3% by volume or less. A manufacturing method is provided.

  According to the fifth invention of the present invention, in any one of the first to fourth inventions, the kneading zone for injecting water is a resin-filled region, and the resin pressure is in the range of 0.5 to 10 MPa. A method for producing polycarbonate resin pellets is provided.

  According to the sixth invention of the present invention, in any one of the first to fifth inventions, the length of the region where the resin filling rate in the decompression section of the extruder is 5 to 30% by volume is 8. There is provided a method for producing polycarbonate resin pellets, characterized in that it is 0D (D is the cylinder inner diameter of the extruder) or more.

  According to a seventh aspect of the present invention, there is provided the method for producing polycarbonate resin pellets according to any one of the first to sixth aspects, wherein the temperature of water for cooling the strand is 30 to 90 ° C. Provided.

  Moreover, according to the 8th invention of this invention, the polycarbonate resin pellet manufactured with the manufacturing method of the invention in any one of the 1st-7th is provided.

  Furthermore, according to the ninth aspect of the present invention, there is provided an electric / electronic equipment component carrying case using the polycarbonate resin pellet of the eighth aspect.

  According to the method for producing a thermoplastic resin composition molded body of the present invention, the content of impurities such as chlorine compounds is extremely small, the resin is hardly deteriorated, yellowing does not occur, the pellet appearance is good, and particularly the electric and electronic A polycarbonate resin pellet that can be used without using a resin additive, which is suitable for a case for conveying equipment parts, can be produced.

It is a figure which shows the structural example of the feeder-hopper-extruder applicable to this invention. (A) And (b) is a figure explaining the definition of the fall distance in this invention, (c) is a figure which shows the example of the member provided in a hopper chute | shoot in order to drop polycarbonate resin in steps. It is a figure which shows the screw structure of the extruder used in the Example of this invention.

Hereinafter, although an embodiment and an example thing are shown and explained in detail about the present invention, the present invention is limited to the embodiment, an example thing, etc., and is not interpreted.
In the specification of the present application, “to” is used in the sense of including the numerical values described before and after the lower limit and the upper limit unless otherwise specified. "Ppm" means mass ppm.

The present invention is a method for producing polycarbonate resin pellets having a reduced methylene chloride content from a polycarbonate resin containing a small amount of methylene chloride,
1) As a polycarbonate containing a small amount of methylene chloride, a polycarbonate resin in the form of a granular material having a specific surface area of 0.008 m ² / g or more and 50% by mass or more having a particle size of 200 to 2,000 μm is used.
2) An inert gas treatment step in which a polycarbonate resin in the form of granules is dropped and moved by 50 cm or more in an inert gas atmosphere having an oxygen concentration of 3% by mass or less,
3) The inert gas-treated polycarbonate resin in the form of granules is supplied to a vent-type extruder, and in the kneading zone, water having an electric conductivity of 30 μS / cm or less is added to 0.1 parts by mass of 100 parts by mass of the polycarbonate resin. Injecting 1 to 2 parts by mass;
4) By suctioning the vent port provided on the downstream side of the water injection portion of the extruder under reduced pressure, the methylene chloride is sucked and removed together with the water from the molten resin, and the water concentration in the resin is 10 Adjusting to ˜200 ppm,
5) A step of introducing and cooling the strand-shaped molten resin extruded from the die of the extruder into water having an electric conductivity of 30 μS / cm or less,
6) A step of cutting the strand in the range of 70 ° C to 130 ° C to obtain pellets containing 10 to 200 ppm of moisture. 7) Further placing the obtained pellets containing 10 to 200 ppm of moisture in a humid atmosphere And an aging step of adjusting the moisture content to exceed the original moisture content of the pellets and to 1300 ppm or less.

  Examples of the polycarbonate resin (A) used in the present invention include an aromatic polycarbonate resin, an aliphatic polycarbonate resin, and an aromatic-aliphatic polycarbonate resin, preferably an aromatic polycarbonate resin. A thermoplastic aromatic polycarbonate polymer or copolymer obtained by reacting an aromatic dihydroxy compound with phosgene or a diester of carbonic acid is used.

Aromatic dihydroxy compounds include 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), tetramethylbisphenol A, α, α'-bis (4-hydroxyphenyl) -p-diisopropylbenzene, hydroquinone, resorcinol 4,4'-dihydroxydiphenyl and the like. Further, as a part of the dihydroxy compound, when the above-mentioned aromatic dihydroxy compound is combined with one or more tetraalkylphosphonium sulfonates, or a polymer or oligomer containing both terminal phenolic OH groups having a siloxane structure, A highly flame-retardant polycarbonate resin can be obtained.
Preferred examples of the polycarbonate resin used in the present invention include 2,2-bis (4-hydroxyphenyl) propane as a dihydroxy compound, or 2,2-bis (4-hydroxyphenyl) propane and another aromatic dihydroxy compound. The polycarbonate resin used together is mentioned.

  The method for producing the polycarbonate resin is not particularly limited, but it is usually produced by an interfacial polymerization method (phosgene method) or a melting method (transesterification method).

  In the interfacial polymerization method, the polymerization reaction is usually carried out in the presence of an organic solvent inert to the reaction and an aqueous alkaline solution, and the pH is usually kept at 9 or higher. And an antioxidant for preventing oxidation of the aromatic dihydroxy compound, and after reacting with phosgene, a polymerization catalyst such as a tertiary amine or a quaternary ammonium salt is added, and interfacial polymerization is carried out to obtain a polymer. A sulfonate resin is obtained. The addition of the molecular weight regulator is not particularly limited as long as it is from the time of phosgenation to the start of the polymerization reaction. In addition, reaction temperature is 0-40 degreeC, for example, and reaction time is several minutes (for example, 10 minutes)-several hours (for example, 6 hours), for example.

  Here, examples of the organic solvent inert to the reaction include chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane, chloroform, monochlorobenzene and dichlorobenzene. Examples of the alkali compound used in the alkaline aqueous solution include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide.

  Examples of the molecular weight regulator include compounds having a monovalent phenolic hydroxyl group, such as m-methylphenol, p-methylphenol, m-propylphenol, p-propylphenol, and p-tert. Preferred examples include -butylphenol and p-long chain alkyl-substituted phenol. The amount of the molecular weight regulator used is preferably 50 to 0.5 mol, more preferably 30 to 1 mol, per 100 mol of the aromatic dihydroxy compound.

  Polymerization catalysts include tertiary amines such as trimethylamine, triethylamine, tributylamine, tripropylamine, trihexylamine, pyridine, and quaternary ammonium salts such as trimethylbenzylammonium chloride, tetramethylammonium chloride, and triethylbenzylammonium chloride. Etc.

  Explaining the melting method, the polymerization reaction in this production method is, for example, a transesterification reaction between a carbonic acid diester and an aromatic dihydroxy compound. Examples of the carbonic acid diester include dialkyl carbonate compounds such as dimethyl carbonate, diethyl carbonate and di-tert-butyl carbonate, and substituted diphenyl carbonates such as diphenyl carbonate and ditolyl carbonate. An example is a bonate. The carbonic acid diester is preferably diphenyl carbonate or substituted diphenyl carbonate, more preferably diphenyl carbonate.

  In the melt transesterification reaction, usually, the mixing ratio of the carbonic acid diester and the aromatic dihydroxy compound and the degree of pressure reduction during the transesterification reaction are adjusted to obtain an aromatic polycarbonate resin having the desired molecular weight and terminal hydroxyl group content adjusted. be able to. Usually, in the melt transesterification reaction, the carbonic acid diester is used in an equimolar amount or more with respect to 1 mol of the aromatic dihydroxy compound. preferable. Further, as a more aggressive adjustment method, there is a method of adding a terminal terminator separately at the time of reaction, and examples of the terminal terminator in this case include monohydric phenols, monovalent carboxylic acids, and carbonic acid diesters. It is done.

  The polycarbonate resin used in the present invention may be produced by any of the above interfacial polymerization method and melt polymerization method. However, as described above, in the polycarbonate resin produced by the interfacial polymerization method, methylene chloride derived from a polymerization solvent, a catalyst, a catalyst deactivator, a reaction by-product and the like, and chloroformate which is an unreacted residue are included. It contains not a few chlorine compounds such as group-containing compounds and is preferable for the purpose of the present invention. Therefore, the method of the present invention is suitable for using a polycarbonate resin produced by an interfacial polymerization method.

  The molecular weight of the polycarbonate resin is a viscosity average molecular weight converted from the solution viscosity measured at a temperature of 25 ° C. using methylene chloride as a solvent, and is usually in the range of 10,000 to 50,000, and 15,000 to 30,000. The thing of the range of this is suitable, and the thing of the range of 17,500-27,000 is more suitable. If the viscosity average molecular weight is less than 10,000, the mechanical strength is inferior, and if it exceeds 50,000, the moldability is inferior.

  The polycarbonate resin used in the present invention is intended to contain a trace amount of methylene chloride. Here, the trace amount means that it contains 200 ppm or less of a chlorine-containing compound in terms of the amount of chlorine atoms. The polycarbonate resin obtained by the interfacial polymerization method usually contains 20 ppm or more of a chlorine-containing compound when taken out from the polymerization system. The normal content of methylene chloride in the raw material polycarbonate resin is 10 to 100 ppm. In addition, in a polycarbonate resin containing a chlorine-containing compound that significantly exceeds 200 ppm in terms of the amount of chlorine atoms, it is difficult to reduce it to about 3 ppm or less suitable for the purpose of the present invention even if the method of the present invention is applied. .

In the present invention, the polycarbonate resin is used as having a granular shape.
Specifically, 50% by mass or more of the polycarbonate resin is 200 to 2,000 μm, preferably 300 to 2,000 μm, more preferably, in a particle size distribution measured by a method based on JIS K0069 (screening test method). Is a granular material in the range of 400 to 2,000 μm. If a resin having a particle size of less than 200 μm or more than 2,000 μm is contained in an amount exceeding 50% by mass, components having a particle size of less than 200 μm are likely to rise, making it difficult to quantitatively supply from the feeder to the extruder. Become. Moreover, about the component which has a particle size exceeding 2,000 micrometers, the effect of the process by the following inert gas becomes scarce.

Further, the polycarbonate resin further has a specific surface area as determined by BET multipoint method 0.008 m ² / g or more, preferably 0.01 m ² / g or more, more preferably 0.012 m ² / g or more . When the specific surface area is as small as less than 0.008 m ² / g, the effect of the treatment with the next inert gas is hardly exhibited.

  The shape of the granular material in the present invention is not particularly limited as long as it has a fine particle size distribution as described above, so-called powder, granular material such as fine pellets, granular material, flakes, etc. It refers to the shape.

  Polycarbonate resin should not be added as much as possible of additives that may become pollutants when used in applications that require a low amount of semiconductor pollutants such as chlorine, such as containers for semiconductor substrates. In addition, so-called "additive-free", depending on the application, heat stabilizer, antioxidant, mold release agent, UV absorber, fluorescent whitening agent, pigment, dye, other polymers, flame retardant, resistance Additives such as impact modifiers, antistatic agents, plasticizers and compatibilizers can be included. These additives may be used alone or in combination of two or more. Among these, it is particularly preferable to use a heat stabilizer and an antioxidant.

  Although there is no restriction | limiting in particular as a heat stabilizer, For example, a phosphorus compound is mentioned preferably. Any known phosphorous compound can be used. Specific examples include phosphorus oxo acids such as phosphoric acid, phosphonic acid, phosphorous acid, phosphinic acid, polyphosphoric acid, acidic pyrophosphoric acid metal salts such as acidic sodium pyrophosphate, acidic potassium pyrophosphate, acidic calcium pyrophosphate, and phosphoric acid. Examples include Group 1 or Group 10 metal phosphates such as potassium, sodium phosphate, cesium phosphate, and zinc phosphate, organic phosphate compounds, organic phosphite compounds, and organic phosphonite compounds.

  Among them, triphenyl phosphite, tris (monononylphenyl) phosphite, tris (monononyl / dinonyl phenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, monooctyl diphenyl phosphite, Dioctyl monophenyl phosphite, monodecyl diphenyl phosphite, didecyl monophenyl phosphite, tridecyl phosphite, trilauryl phosphite, tristearyl phosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) ) Organic phosphites such as octyl phosphite are preferred.

  The content of the heat stabilizer is usually 0.001 part by mass or more, preferably 0.01 part by mass or more, more preferably 0.03 part by mass or more, based on 100 parts by mass of the polycarbonate resin. It is not more than part by mass, preferably not more than 0.7 part by mass, more preferably not more than 0.5 part by mass. If the amount of the heat stabilizer is too small, the heat stabilization effect may be insufficient. If the amount of the heat stabilizer is too large, the effect may reach a peak and may not be economical.

  Moreover, as an antioxidant, a hindered phenolic antioxidant is mentioned preferably, for example. Specific examples thereof include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl). ) Propionate, thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N, N′-hexane-1,6-diylbis [3- (3,5-di-) tert-butyl-4-hydroxyphenylpropionamide), 2,4-dimethyl-6- (1-methylpentadecyl) phenol, diethyl [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl ] Methyl] phosphoate, 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″ (Mesitylene-2,4,6-triyl) tri-p-cresol, 4,6-bis (octylthiomethyl) -o-cresol, ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4 -Hydroxy-m-tolyl) propionate], hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-tris (3,5-di-tert) -Butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2,6-di-tert-butyl-4- (4,6-bis (Octylthio) -1,3,5-triazin-2-ylamino) phenol and the like.

Among them, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate preferable. Specific examples of such phenolic antioxidants include “Irganox 1010” (registered trademark, the same shall apply hereinafter) manufactured by Ciba Specialty Chemicals, “Irganox 1076”, and “Adeka Stub” manufactured by Adeka. AO-50 "," ADK STAB AO-60 "and the like.
In addition, 1 type may contain antioxidant and 2 or more types may contain it by arbitrary combinations and a ratio.

  The content of the antioxidant is usually 0.001 part by mass or more, preferably 0.01 part by mass or more, and usually 1 part by mass or less, preferably 0.5 part by mass with respect to 100 parts by mass of the polycarbonate resin. Or less. When the content of the antioxidant is less than or equal to the lower limit of the range, the effect as an antioxidant may be insufficient, and when the content of the antioxidant exceeds the upper limit of the range, There is a possibility that the effect reaches its peak and is not economical.

  Furthermore, as the polycarbonate resin in the present invention, not only a virgin raw material but also a polycarbonate resin regenerated from a used product, a so-called material recycled polycarbonate resin may be used. It is also possible to use a pulverized product obtained from the above or a granular material obtained by melting them. The regenerated polycarbonate resin is used by mixing with a non-recycled granule-shaped polycarbonate resin, and the mixing amount is preferably 80% by mass or less, more preferably 50% by mass of the total polycarbonate resin component. % Or less, in particular 30% by mass.

The polycarbonate resin in the form of a granular material is first treated with an inert gas.
The treatment with the inert gas is performed with the polycarbonate resin in a specific shape and in a specific state.
Specifically, as a polycarbonate containing a small amount of methylene chloride, a polycarbonate resin in the form of a granular material having a specific surface area of 0.008 m ² / g or more and a particle size of 50 to 50% by mass of 200 to 2,000 μm is prepared. Then, such a granular-shaped polycarbonate resin is dropped and moved in an inert gas atmosphere having an oxygen concentration of 3% by volume or less by 50 cm or more.

The reason why the polycarbonate resin has such a special shape is to increase the area (surface) in contact with the inert gas, and to efficiently remove oxygen remaining on the surface of the granular material by the inert gas, Further, the reason why the particles are moved down is to increase the processing efficiency by moving the powder particles in the inert gas.
By the way, it has been obtained that it is difficult to perform sufficient treatment with a method in which a granular polycarbonate resin is accommodated in a container and the atmosphere in the container is replaced with an inert gas.
In the drop movement, an inert gas is flowed from below into a tubular member in which a granular polycarbonate resin is placed vertically, and the granular polycarbonate resin is supplied from above using a quantitative feeder, etc. What is necessary is just to move by making it fall.
Specifically, a simple method is a method in which a polycarbonate resin in the form of a granular material is supplied and dropped from above a hopper having a height of 50 cm or more (a hopper of an extruder) and an inert gas is supplied from the base of the hopper. Can be mentioned.

Hereinafter, specific examples will be described with reference to the drawings.
Such a polycarbonate resin in the form of a granular material is stored in a raw material supply machine, and is supplied from there to a hopper chute installed on the extruder by a feeder (quantitative supply machine).
FIG. 1 is a diagram showing a configuration example of a feeder-hopper-extruder applicable to the present invention. The bottom of the hopper chute is connected to the supply port of the extruder, and the polycarbonate resin is sequentially supplied to the extruder via the hopper chute, and melted and kneaded in the extruder to become a resin molding material such as pellets.

  In the case of blending other components other than the polycarbonate resin, the mixing can be blended at an arbitrary stage before being charged into the extruder. For example, after all components are blended by a tumbler, a Henschel mixer, and a blender, they may be fed into a hopper chute via a feeder and supplied to an extruder as necessary. As the extruder, a single screw extruder, a twin screw extruder or the like can be used. Moreover, you may supply to a hopper chute | shoot with the path | route different from polycarbonate resin.

  First, in the present invention, the atmosphere inside the hopper chute for supplying the material to the extruder is replaced with an inert gas. In the present invention, the inert gas means not only a rare gas but also a gas inert to the polycarbonate resin powder to be used. As the inert gas, for example, nitrogen gas, carbon dioxide gas, rare gas or the like is used, and nitrogen gas is particularly preferably used.

  In the present invention, the inert gas supplied to the hopper chute to replace the atmosphere in the hopper chute is preferably in a dry state and a purity of 99% by volume or more. In addition, as shown by a dotted line in FIG. 1, the inert gas can be supplied from the vicinity of the supply port of the hopper chute extruder or from the upper part of the hopper chute, but is supplied from the vicinity of the supply port (lowermost part). It is preferable to do. This is because it is desirable to maintain a high inert gas concentration in the atmosphere below the hopper chute when replacing the air in the resin with the inert gas in the atmosphere while dropping the polycarbonate resin.

The hopper chute preferably has an airtightness enough to discharge the substituted air to the outside while maintaining a high inert gas concentration in the internal atmosphere. The inert gas is continuously supplied at a flow rate that maintains the low oxygen concentration in the internal atmosphere while discharging the air substituted in the hopper chute. The specific flow rate can be appropriately determined according to the size and airtightness of the hopper chute.
Further, in the present invention, when treating the polycarbonate resin in the form of a granular material with an inert gas, the powdered fluid is supplied in a falling state so that the inert gas is counterflowed to the granular material from below. It is preferable to supply to.

In the present invention, the oxygen concentration in the atmosphere inside the hopper chute is 3% by volume or less, preferably 1% by volume or less, more preferably 0.5% by volume or less, and most preferably 0.1% by volume or less. It is preferable to supply gas. The oxygen concentration can be measured, for example, in the lower part of the hopper chute and in the vicinity of the supply port of the extruder. When the oxygen concentration exceeds 3% by volume, the effect of suppressing yellowing due to oxidative degradation or the like and the effect of removing chlorine compounds cannot be sufficiently obtained.
The inert gas can be supplied not only into the hopper chute but also into the barrel of the extruder.
As described above, when other components are blended in the polycarbonate resin, the polycarbonate resin is supplied to the extruder after passing through an inert gas atmosphere in a dispersed state. Specifically, the inside of the hopper chute where the internal atmosphere is replaced with an inert gas is dropped and supplied to the extruder.

  As described above, in the present invention, it is preferable to supply the polycarbonate resin in the form of granular material so as to fall in the hopper chute in a dispersed state. Here, the “dispersed state” means a state in which the surface of each resin particle can sufficiently come into contact with the atmosphere, but a special supply method is not required, and the granular shape of the present invention is not necessary. The polycarbonate resin can be dropped in a dispersed state by continuously (or intermittently) supplying the polycarbonate resin from the upper part of the hopper using a screw-type quantitative supply device or the like. It is not preferable in the case of falling in a dense state or a lump rather than in a dispersed state.

However, in order to sufficiently replace the air held in the depressions on the surface of the polycarbonate resin with an inert gas, the polycarbonate resin in the form of a granular material falls in an inert gas atmosphere at a vertical distance of 50 cm or more, preferably 80 cm or more. After that, feed it to reach the feed port of the extruder.
For example, as shown in FIG. 1, when a polycarbonate resin is supplied to a hopper chute using a feeder, as shown in FIG. 2 (a), the height of the feeder outlet and the material supply port of the extruder (hopper chute bottom) The vertical distance h is set to 50 cm or more. However, as shown in FIG. 2B, when the material to be melt-kneaded accumulates in the hopper chute, the vertical distance h between the height of the feeder outlet and the apex of the deposited material is set to 50 cm or more.

  For example, when using a twin-screw extruder as an extruder, when performing a starvation supply (starvation feed) called a starvation material supply method in which materials are supplied in small amounts into the cylinder of the extruder, FIG. It will be in the state of a). Moreover, when the starvation supply is not performed, such as when a single screw extruder is used, the state shown in FIG. Therefore, the type of the extruder, the presence / absence of the starvation feed, the extrusion speed, and the supply amount of the material are determined so that the polycarbonate resin in the form of granular material falls 50 cm or more in the hopper chute. It has been confirmed that stable extrusion can be performed by using a starvation feed.

  In the present invention, the polycarbonate resin in the form of a granular material may be dropped by 50 cm or more in an inert gas atmosphere at a substantial vertical distance, and the dropping process is not particularly limited. It is not necessary to drop more than 50 cm at a time. Also, for example, as shown in FIG. 2 (c), the tip of the polycarbonate resin in the form of a granule falls on the inner surface of the hopper chute so as to fall stepwise (zigzag) and reach the material supply port of the extruder. One or more plate-shaped members (baffle plates) inclined toward the surface may be provided. For example, when a baffle plate is provided in the hopper chute, the total distance (zigzag distance) dropped in a plurality of steps may be 50 cm or more. Note that the fall is not limited to free fall, and may be any downward movement. Therefore, the distance dropped while sliding on the baffle plate is also included in the fall distance.

It is considered that the replacement of the air contained in the resin with the inert gas progresses when the time in contact with the atmosphere (inert gas) is longer in the dispersed state than in the state in which the particles are accumulated. When the baffle plate is provided, the air drops into the hopper chute more slowly than in the case of dropping 50 cm or more in one free fall, so that the replacement efficiency of air and inert gas is increased.
However, since the polycarbonate resin targeted by the present invention has a granular shape with a small particle size, the air resistance is larger than the shape like a pellet and the speed of free fall is small. Is replaced with an inert gas.

The polycarbonate resin in the form of a granular material that has been treated with an inert gas in this manner is supplied to a vent-type extruder. In the kneading zone, water is injected and added, and the polycarbonate resin is melt-extruded while degassing with a vent.
As water to be injected, water having an electric conductivity of 30 μS / cm or less is used. When the electrical conductivity exceeds 30 μS / cm, the cleanliness of the obtained polycarbonate resin pellets deteriorates. The mechanism that affects the cleanliness of polycarbonate resin pellets from which electrical conductivity is obtained is not yet clear, but it is presumed to be due to the interaction of ionic components with polycarbonate and impurities.
The electrical conductivity of water is preferably 20 μS / cm or less, more preferably 10 μS / cm or less, further preferably 5 μS / cm or less, particularly preferably 3 μS / cm or less, and most preferably 1 μS / cm or less.
The electrical conductivity is measured at a measurement temperature of 25 ° C. using a conductivity meter.

  Moreover, the injection amount of water is 0.1 to 2 parts by mass with respect to 100 parts by mass of the polycarbonate resin. inject. If the amount of water injected is less than 0.1 parts by mass, the effect of adding water will not be exhibited, and the chlorine compound in the polycarbonate resin will be less than 3 ppm in terms of chlorine atoms, and more than 2 parts by mass. If it becomes, deaeration in a vent part will become inadequate and it will come to have a bad influence of hydrolysis etc. with respect to polycarbonate resin. In addition, a large amount of generated steam causes resin vent-up. The preferable amount of water to be injected is 0.15 to 1.8 parts by mass, more preferably 0.2 to 1.5 parts by mass, and further 0.3 to 1.2 parts by mass with respect to 100 parts by mass of the polycarbonate resin. In particular, it is 0.4 to 1.0 part by mass.

The extruder with a vent used in the present invention may be a single screw extruder or a twin screw extruder, but a twin screw extruder is preferred. Further, the number of vents may be one or two or more, and preferably 2 to 6. There may be two or more places where water is injected and added.
As L / D of the screw of an extruder, 10-80 are preferable, More preferably, it is 15-70, More preferably, it is 20-60. If it is too short, deaeration tends to be insufficient, and if it is too long, the color tone tends to deteriorate.

  The kneading zone for injecting water is preferably performed when the molten polycarbonate resin is fully filled (filled area). The filling area is 95% by volume or more, preferably expressed by the ratio of the amount of resin (capacity by true density) to the space capacity per pitch of the screw in the kneading zone (referred to as the filling rate. Unit: volume%), preferably 98% by volume or more, more preferably 99% by volume or more, particularly 100% by volume is preferable.

  The resin pressure in the water injection portion (in-cylinder pressure in the kneading portion) is preferably 0.5 to 10 MPa, more preferably 1 to 8 MPa, and more preferably 2 to 7 MPa. The pressure of the polycarbonate resin is increased and water is dispersed in the molten polycarbonate resin. If the resin pressure is too small, the effect of removing methylene chloride is small, and if it is too large, the resin deteriorates and the color tone tends to deteriorate.

It is preferable to provide a region where the resin pressure is high on the upstream side of the water injection point in the kneading zone and provide the water injection point on the downstream side. Specifically, the screw configuration of the extruder is as follows: 1) a water injection point is provided immediately after the location where the seal ring is provided on the upstream side, or 2) a progressive kneading element is provided from the upstream side, followed by reverse feed kneading. It is recommended that the element be installed and then watered.
In the method 1), the seal ring is a ring shape fitted to a screw, and closes about 70 to 90% of the flow path to retain the resin flow, thereby increasing the resin pressure. A water injection point is provided on the downstream side immediately after this.
Further, in the method 2), a forward kneading element for feeding the resin to the downstream side when rotated is provided, and then a reverse kneading element for returning the resin to the upstream side when rotated is provided. In this method, the resin pressure is increased and water is injected after this.

The oxygen concentration in the barrel (cylinder) of the vent type extruder is preferably 3% by volume or less. It becomes easy to prevent yellowing of the polycarbonate resin pellet obtained by setting it as 3 volume% or less.
In order to reduce the oxygen concentration in the barrel to 3% by volume or less, an inert gas may be injected from the hopper side (screw base) of the extruder. If it is difficult to directly measure the oxygen concentration in the barrel, a significant difference cannot be considered, so the oxygen concentration at the bottom of the hopper is substituted.

After water injection in the kneading zone, the vent port provided near the tip of the extruder, that is, near the tip of the extruder, is sucked in a reduced pressure state, so that methylene chloride and the like are melted together with water from the molten resin. Remove volatile components by suction. After the kneaded portion filled with the resin by this suction, the non-filled region between the full region of the screw tip is in a reduced pressure state (depressurized portion).
The vent port is connected to a vacuum exhaust device (not shown), and decompressed exhaust is performed. The polycarbonate resin in the high-temperature and high-pressure state in which water is dispersed in the previous process is vaporized and expanded by rapid decompression at the vent part, and foams to expand the surface area of the polycarbonate resin. From the surface together with water, methylene chloride, etc. Volatile components are volatilized.
The degree of vacuum at the vent port is −0.05 MPa or less, more preferably −0.07 MPa or less, and still more preferably −0.09 MPa or less.
The moisture concentration in the polycarbonate resin in the molten state cannot be directly measured with the molten resin in the extruder, so that the moisture concentration in the pellets described later is substituted. It is considered that there is little difference between the moisture concentration in the molten resin in the die and the moisture concentration in the pellet.

  The length of the decompression part is preferably 8.0D (D is the cylinder inner diameter of the extruder) or more in the screw direction, and more preferably 12D or more. Moreover, it is preferable that the resin filling rate of this pressure reduction part is 5-30 volume%. This is because it is preferable to sufficiently reduce the filling rate of the molten polycarbonate resin and sufficiently perform deaeration. A more preferable resin filling rate is 8 to 25% by volume, and more preferably 10 to 20% by volume. When the resin filling rate is lower than 5% by volume, the amount of resin that can be processed decreases, and thus productivity decreases.

Then, the moisture concentration in the polycarbonate resin after extrusion (immediately after) is adjusted to 10 to 200 ppm. The reason for setting the moisture concentration in such a range is to remove methylene chloride and the like well without deteriorating the polycarbonate resin. When kneading and venting so that the moisture concentration is less than 10 ppm, the polycarbonate resin tends to deteriorate. If the amount exceeds 200 ppm, methylene chloride and the like also remain. Moreover, by setting it as the water content of such a range, the effect that a strand cut is stabilized by the plasticization effect of water can also be expected.
The water concentration in the polycarbonate resin is preferably 15 to 150 ppm, more preferably 20 to 100 ppm. The moisture content in the polycarbonate immediately after extrusion is measured by placing only the surface adsorbed water by placing it in a vacuum dryer within 3 minutes and drying at room temperature for about 5 minutes after the strand is cooled and cut. It can be measured with a trace moisture measuring device.

Next, the polycarbonate resin is extruded as a strand from the die of the extruder, introduced into water, and cooled. There is no restriction | limiting in particular in the shape of an extrusion die, A well-known thing is used. The diameter of the die of the discharge nozzle is usually about 2 to 5 mm, although it depends on the extrusion pressure and the desired pellet size. The temperature of the polycarbonate resin immediately after being extruded is usually about 300 ° C.
The strand is taken up by a take-up roller and cooled in such a manner that it is transported through the water stored in the cooling tank. In order to reduce the deterioration of the resin, it is better that the time from when the strand is pushed out of the die until entering the water is shorter. Normally, it is better to enter the water within 1 second after being pushed out of the die.

In the present invention, at this time, it is introduced into water having an electric conductivity of 30 μS / cm or less. If the electrical conductivity of the water used exceeds 30 μS / cm, the cleanliness of the resulting polycarbonate resin pellets deteriorates. The electrical conductivity of water is preferably 20 μS / cm or less, more preferably 10 μS / cm or less, further preferably 5 μS / cm or less, particularly preferably 3 μS / cm or less, and most preferably 1 μS / cm or less.
The water stored in the cooling tank deteriorates with time, and the electrical conductivity increases. However, the electrical conductivity is kept within a predetermined range (30 μS / cm or less) by constantly supplying cooling water and causing the water to overflow from the tank. Can be kept in. Further, the temperature of the water tank varies depending on the position, and the temperature is usually highest when the strand enters the water tank, and the temperature of the water tank decreases as it cools. If the temperature of the water tank is too low, the strand is supercooled, and if the temperature of the water tank is high, the temperature of the strand is too high. A preferable range of the temperature of the water tank is 30 ° C to 90 ° C, and a more preferable range is 40 ° C to 70 ° C.

The strand cooled in this way is sent to a pelletizer by a take-up roller, and is cut into pellets. Cutting is performed when the strand temperature is in the range of 70-130 ° C, preferably 75-125 ° C. And the water-containing pellet which contains a water | moisture content 10-200 ppm, Preferably 15-150 ppm is obtained. Since the obtained water-containing pellet has not undergone an excessive shearing history by the extruder, it becomes a pellet having a high cleanliness without causing a significant molecular weight reduction or hydrolysis.
If the strand temperature falls below 70 ° C, the strand becomes too hard, and breakage and chipping are likely to occur when cutting with a pelletizer. If the strand temperature exceeds 130 ° C, the strand becomes soft, whiskers are generated on the cut surface, and the pellet is easily deformed. Become.
The strand temperature at this time may be measured with a non-contact type thermometer, but it is substituted by simply inserting a thermometer into the pellets in the bag or container containing the pellets cut by the cutter. Just do it.

Furthermore, it is preferable that the pellets cut by the cutter are put in a paper bag, a paper drum can, a metal container or the like and brought into contact with moist air to be aged. If the pellet cut by the cutter is left as it is, static electricity is charged, and it is easy to adsorb dust and floor dust in the air. In order to reduce this static electricity, there is a method of positively removing static electricity with a static eliminator (for example, ionizer SJ-M02: manufactured by Keyence Corporation), but simply put the pellet in a metal container etc. and contact with wet air. Can be reduced. Touching wet air increases the amount of moisture adsorbed on the pellet, improving the electrical conductivity of the pellet surface, increasing the rate of charge leakage, or improving the overall electrical conductivity of the pellet due to the volumetric moisture absorption of the pellet. The reason is to do. It is considered that the neutralization effect is more effective by using a metal pellet container.
In any case, the aging step can obtain a pellet with less dust and dust adhesion.

By extending this aging step for a long time, the moisture content increases, charge leakage proceeds, the amount of charge of the pellets decreases, and a pellet with less dust and dust adhesion can be obtained.
As a long-term aging method, pellets cut with a cutter are stored in polyethylene bags with a relatively high water vapor transmission rate before being polluted with dust, etc., and placed in a room on a daily or monthly basis for aging. Is the method. The temperature and humidity in this long-time treatment may be room temperature and normal humidity, but of course, it is preferable to control the moisture content by adjusting the date and time in a temperature-controlled and humidity-controlled environment.
However, there is a limit to the length of the aging step and the amount of water to be hydrated, and the moisture content after aging is preferably 1300 ppm or less. If the water content is exceeded, the resin is easily hydrolyzed when a desired molded product is molded using the water-containing pellets, causing a problem that the strength of the molded product is lowered. Moreover, even if it is dried before the molding of the pellets, it takes time to dry and the productivity is lowered. A preferable moisture content is 1000 ppm or less. More preferably, it is 700 ppm or less. Although charging is prevented by containing the pellets with water, the target charge amount is preferably 10 kV or less, more preferably 8 kV or less.

Next, a drying step of drying the water-containing pellets obtained through the aging step is further performed. The purpose of the water-containing step is to eliminate static electricity and suppress the adsorption of dust. However, when a pellet is formed into a molded product, if the water content is high, the polycarbonate is hydrolyzed, causing yellowing and the like. For this reason, the water content in the pellet is adjusted again before molding the molded product.
The pellets containing water are subjected to a drying treatment, and the water content is adjusted to 50 to 200 ppm. The drying treatment is performed in a hot air drier at a temperature of about 100 to 130 ° C, preferably in the range of 105 to 125 ° C, and usually in the range of 2 to 10 hours, preferably 3 to 7 hours.

The polycarbonate resin pellets (pellets after drying treatment) obtained by the present invention are molded into an arbitrary shape and used as a molded body. There is no restriction | limiting in the shape of a molded object, a pattern, a color, a dimension, etc., What is necessary is just to set arbitrarily according to the use of the molded object.
The manufacturing method of a molded object is not specifically limited, The molding method generally employ | adopted about the polycarbonate resin composition can be employ | adopted arbitrarily. For example, injection molding method, ultra-high speed injection molding method, injection compression molding method, two-color molding method, hollow molding method such as gas assist, molding method using heat insulating mold, rapid heating mold were used. Molding method, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating molding) molding method, extrusion molding method, sheet molding method, thermoforming method, rotational molding method, laminate molding method, press molding method, etc. Is mentioned. A molding method using a hot runner method can also be used.

  In particular, the polycarbonate resin pellet of the present invention has a very low content of impurities such as chlorine compounds, is less deteriorated in resin, does not cause yellowing, and can be used free of resin additives. It can be widely used in electrical and electronic equipment and the like that require a high degree of cleanness of the molded body, and is particularly useful for a case for conveying parts of electrical and electronic equipment.

In order to manufacture a case for conveying electrical and electronic equipment parts, resin pellets are formed into a case having a desired shape by injection molding or the like by a known method. The transfer case includes various magazines, trays, boxes, containers, and the like.
Here, the electric / electronic device components are not particularly limited, but include components for various electric / electronic devices such as silicon wafers, hard disks, various disk substrates, IC chips, and high-functional substrate glass for LCD.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not construed as being limited to the following examples.

  In the following examples and comparative examples, the following polycarbonate resins (PC-1) to (PC-3) were used as polycarbonate resins.

PC-1:
(Manufacture of polycarbonate resin (PC-1))
An aqueous solution in which bisphenol-A is dissolved in a caustic soda solution in which hydrosulfite is dissolved at 35 ° C. and then cooled to 25 ° C. and methylene chloride cooled to 5 ° C. are continuously added to a stainless steel pipe having an inner diameter of 6 mm. And the mixture was passed through a homomixer and emulsified to prepare an emulsion. The feed rates to the pipe are bisphenol-A 16.31 kg / hr, caustic soda 5.93 kg / hr, water 101.1 kg / hr, hydrosulfite 0.018 kg / hr and methylene chloride 68.0 kg / hr.
The produced emulsion was passed through a pipe reactor having an inner diameter of 6 mm and a polytetrafluoroethylene resin pipe reactor having an inner diameter of 6 mm and a length of 34 m. At the same time, liquefied phosgene cooled to 0 ° C. was supplied to the pipe reactor at 7.5 kg / hr to cause reaction to produce oligomers. The flow rate of the pipe reactor is 1.7 m / sec.
In the pipe reactor, the temperature rose to 60 ° C., but was 35 ° C. at the outlet due to external cooling. The reaction mixture was allowed to stand and separate into an aqueous phase and an oil phase. The resulting oligomer had a chloroformate concentration of 0.47 N, an OH terminal concentration of 0.23 N, and an oligomer concentration of 27.7%. 40 kg was fractionated from the obtained oil phase and charged into a reaction vessel with an internal volume of 200 liters equipped with a Faudler blade. Next, a catalyst of 25 kg of methylene chloride, 5.75 kg of 25% aqueous sodium hydroxide solution, 41 kg of water and 0.87 g of pyridine hydrochloride (0.020 mol% with respect to bisphenol-A) was added to this, and 360 rpm at 10 ° C. for 60 minutes in a nitrogen atmosphere. The polymerization reaction was carried out with stirring to produce a polycarbonate resin with all OH terminals (OH terminal group concentration: 60 μeq / g).

  Next, 175 g (3.92 mol% to bisphenol-A) of pt-butylphenol (end-capping agent), 105 g of 25 wt% aqueous sodium hydroxide solution, 218 g of 2 wt% aqueous triethylamine (0.10 mol%) was added to the reaction mixture. The bisphenol-A) was added and the reaction continued for an additional hour under stirring at 360 rpm. Thereafter, 30 kg of methylene chloride and 7 kg of water were added, and the mixture was stirred for 20 minutes at room temperature and allowed to stand to separate the aqueous phase and the organic phase. The organic phase was added with 20 kg of 0.1N aqueous sodium hydroxide solution, stirred for 15 minutes, and then allowed to stand to separate into an aqueous phase and an organic phase three times. 20 kg of 0.1 N hydrochloric acid was added to the organic phase after alkali washing, and the mixture was stirred for 15 minutes and then allowed to stand to separate the aqueous phase and the organic phase. The organic phase was added with 20 kg of pure water, stirred for 15 minutes, and then left to stand and separated into an aqueous phase and an oil phase three times. As a result, chlorine ions were not detected in the aqueous phase. Therefore, the washing operation was stopped. The methylene chloride was removed by evaporation from the organic phase with a kneader, and the resulting powder was dried to obtain a polycarbonate resin (PC-1).

PC-2:
PC-1 was pulverized at 650 rpm with a granulator HB189 manufactured by Furukawa Otsuka Steel.
PC-3:
A granular material obtained by extruding the PC-1 with Nippon Steel Works TEX30α at a discharge rate of 50 kg / hr and a screw rotation speed of 200 rpm, cooling in a water tank, and strand cutting.

The specific surface area of the polycarbonate resin was determined by subjecting the sample to 110 ° C. under vacuum (about 1.3 Pa or less) for 3 hours under reduced pressure, and then using a powder meter autosorb 1MP manufactured by Canterchrome at liquid nitrogen temperature. Then, the adsorption isotherm (adsorption gas: krypton) was measured by the BET multipoint method using the obtained adsorption isotherm.
The particle size was determined as follows.
The particle size distribution of 1 mm or more using a mesh of 1 mm or more, and 1 mm or less, the particle size distribution (wet method) is obtained by a laser diffraction scattering type particle size distribution measuring instrument (LMS-2000e manufactured by Seishin Enterprise Co., Ltd.) Asked.
The viscosity average molecular weight is determined by measuring the intrinsic viscosity [η] at 20 ° C. using an Ubbelohde viscometer,
[Η] = 1.23 × 10 ⁻⁴ × (Mv) ^{Obtained from} the equation ^0.83 .
Further, the amount of methylene chloride was measured by the method described later.
Table 1 shows the amount of methylene chloride, particle size, and viscosity average molecular weight of the polycarbonate resins PC-1 to PC-3.

Example 1
A mesh configuration same direction twin screw vent type extruder (TEX30α manufactured by Nippon Steel Works, cylinder length 52.5D (D is cylinder inner diameter)) was used, and screw configuration A shown in FIG. 3 was used.
As shown in FIG. 3, for the sake of explanation, C1 to C15 are divided into the same length from the hopper side of the extruder toward the die.
The screw configuration A is configured as follows for each zone shown in FIG.
a) Melting zone: A forward feed screw having a length of 31.5D and a lead of 1.5D was connected.
b) Kneading zone: Length 4.0D
The feed kneading element 1D, the reverse feed kneading element 0.5D, the forward feed kneading element 1.0D, the orthogonal kneading element 1.0D, and the reverse feed screw 0.5D are formed in the feed direction. A liquid injection plug was attached to the C10 cylinder, and water was added with a plunger pump.
c) Decompression zone: A forward screw having a length of 17.0D and a lead of 1.5D was connected. This 17.0D was taken as the length of the decompression section.
The C14 cylinder was provided with a vacuum vent, and the degree of vacuum was -0.090 MPa.

In the configuration shown in FIG. 1, the distance (height) from the material supply port of the quantitative feeder (belt weighing feeder wide range B-WF manufactured by Kubota Corporation) to the material supply port of the twin screw extruder was set to 85 cm. 35 liters of nitrogen gas (purity 99.9% by volume) using a hopper chute having substantially airtightness, facing upward from the vicinity of the material supply port of the twin-screw extruder so as to counter flow with the polycarbonate resin granules. / Min. In the vicinity of the material supply port of the twin screw extruder, in the hopper chute (lower hopper) by an oxygen concentration meter (zirconia oxygen concentration meter LC-750L manufactured by Toray Industries, Inc.) provided at a position corresponding to the nitrogen gas supply port The oxygen concentration was measured and it was confirmed that the oxygen concentration was 0.3% by volume.
The said polycarbonate resin granular material (PC-1) was supplied to the nitrogen-substituted hopper chute | shoot with the fixed quantity feeder. The polycarbonate resin has a measuring feeder provided at the lower part of the hopper, and was supplied to the extruder at 50 kg / hr in a starved state.

The barrel set temperature of the extruder is 270 ° C., the screw rotation speed is 400 rpm, and the electric conductivity is 1 using a plunger pump from the liquid injection plug installed in the C10 cylinder of the screw configuration A in FIG. 3 in the kneading zone. 0.5 parts by mass of ion-exchanged water produced by a 2-bed, 3-tower pure water apparatus of 5 μS / cm was injected with respect to 100 parts by mass of the polycarbonate resin. The electrical conductivity was measured at 25 ° C. using a conductivity meter manufactured by Electrochemical Instruments.
The resin filling rate in the reduced pressure zone was 13% by volume, and the resin filling rate in the kneading zone was 99% by volume.
In addition, the filling rate of resin was calculated | required with the following formula | equation.
Discharge rate (kg / hour) / {resin specific gravity × (cylinder cross-sectional area−two screw cross-sectional area) × lead length × screw rotation speed (/ hour)}
Further, when the resin pressure in the water injection portion was measured with a resin pressure sensor, it was 2.0 MPa.

Next, the water concentration in the resin is adjusted to 38 ppm by sucking and removing water and volatile components from the vent opening of the C14 cylinder with a vacuum pump so that the degree of vacuum is -0.09 MPa. It was adjusted.
Next, it extruded from the extrusion nozzle of the front-end | tip of an extruder as a strand of a circular cross section with a diameter of 4 mm. The strand temperature immediately after extrusion was 310 ° C.
The extruded strand was introduced into a water tank containing ion-exchanged water produced by a two-bed / three-column pure water apparatus having an electric conductivity of 1.5 μS / cm and cooled. The water tank was adjusted to a temperature range of 40 ° C. to 70 ° C. by overflowing water.
The strand was cooled to 103 ° C., inserted into a pelletizer and cut. When the strand temperature exceeded 130 ° C., a good pet wound around the cutter could not be obtained. Beard was also seen on the cut surface. On the other hand, when the temperature is lower than 70 ° C., the pellets are broken at the time of cutting, and the design is lowered. The pellets cut at 103 ° C. had a beautiful and good cut surface. Within 3 minutes after cutting, the pellets were placed in a vacuum dryer at room temperature for 5 minutes at room temperature to remove the water adhering to the pellet surface, and the moisture content of the pellets was measured.

Next, 3 kg of this pellet was placed in a stainless round tank (10 L capacity, model ST-24: purchased from Shonan Scientific Co., Ltd.), the lid was opened, and the pellet was aged by being exposed to wet air for 3 hours. The moisture content and charge amount of the pellets taken out after 3 hours were measured. The results are shown in Table 3.
The moisture content was measured using a trace moisture measuring device (CA-100, manufactured by Mitsubishi Chemical Corporation).
The charge amount was measured with a handy sensor SK-030 (manufactured by Keyence Corporation).

Further, the methylene chloride content and the eluted chlorine concentration of the obtained pellets were measured by the following methods.
(Measurement method of methylene chloride)
Under a flow of 70 ml / min of nitrogen gas, set 4 g or more of pellets in a heating furnace of a vaporizer (UA-21 manufactured by MCI) set at 300 ° C., and generate 20 ml of dioxane and an internal standard for the generated gas and nitrogen gas. (Chloroform 0.08 mg / ml dioxane solution) introduced into an absorption tube (cooled to 13 ± 1 ° C.) containing 5 ml for 60 minutes. The obtained absorbing solution was measured (internal standard method) with a gas chromatography with a Frame Ionization Detector (GC-14A manufactured by Shimadzu Corporation).
The measurement conditions are as follows.
Column ・ SUS column 3mmφ × 2m
・ Filler silicon DC-550 25%
80/100 mesh
Celite545 sk DMCS
・ Column temperature 60 ℃
Injection temperature 250 ℃
Detector temperature 250 ℃
・ Gas air 0.60kg / cm ²
Hydrogen 0.60kg / cm ²
Carrier gas (helium) 1.15 kg / cm ²
・ Sample injection volume 3μL

(Measurement method of elution chlorine concentration)
A polypropylene container with a lid that has been washed with pure water is charged with 50 g of pellets and 100 g of pure water, kept in a clean oven at 50 ° C. for 3 hours, and then the pellets and the aqueous phase are separated. A chloride ion component in the liquid phase was measured (absolute calibration curve method) using an ion chromatograph (Nippon Dionex Corporation's ion chromatograph DX-AQ) equipped with a sample concentration module SPU-300 manufactured by Nippon Dionex. The measurement conditions are as follows.
・ Column Analytical column AS12A manufactured by Nippon Dionex
Guard column AG12A made by Nippon Dionex
Concentrated column AG4A-SC manufactured by Nippon Dionex
・ Suppressor Nippon Dionex Suppressor ASRS300 4mm
・ Eluent: 2.7 mM sodium carbonate + 0.3 mM sodium bicarbonate ・ Eluent flow rate: 1.5 ml / min ・ Sample injection volume (concentrator setting conditions) Flow and concentrate in the concentration column at 1.5 ml / min for 4 minutes Detection sensitivity RANGE: 3 μS Temperature correction: 1.7 / ° C
・ Suppressor current value 50mA

  Furthermore, the obtained pellet was heat-dried at 120 ° C. for 5 hours, and a flat plate shape of 100 mm × 100 mm × 3 mm was used under the conditions of a cylinder temperature of 290 ° C. and a mold temperature of 80 ° C. using an injection molding machine SH100 manufactured by Sumitomo Heavy Industries. The molded product was molded. A good molded article free from silver (silver strip) and air bubbles was obtained.

The color tone (yellow index (YI value)) was measured using the obtained flat molded article.
The yellow index (YI value) was measured according to JIS K-7105, using the above-mentioned 3 mm-thick flat plate as a test piece, with a SE2000 type spectral colorimeter manufactured by Nippon Denshoku Industries Co., Ltd.
The above evaluation results are shown in Table 3.

(Example 2)
Pellets were produced in the same manner as in Example 1 except that PC-2 was used instead of PC-1. The results are shown in Table 3.
Example 3
A pellet was manufactured in the same manner as in Example 1 except that the supply amount of nitrogen gas was increased and the oxygen concentration in the hopper chute was 0.1% by volume or less. The results are shown in Table 3.
Example 4
A pellet was manufactured in the same manner as in Example 1 except that the supply amount of nitrogen gas was reduced and the oxygen concentration in the hopper chute was 2.1% by volume. The results are shown in Table 3.

(Example 5)
Except that the distance (height) from the material supply port of the quantitative feeder (Belt Weighing Feeder Wide Range B-WF manufactured by Kubota) to the material supply port of the twin screw extruder was set to 60 cm, the same as in Example 1. The pellets were manufactured. The results are shown in Table 3.

(Example 6)
A pellet was produced in the same manner as in Example 1 except that the amount of water injected was 0.2 parts by mass. The results are shown in Table 3.
(Example 7)
A pellet was produced in the same manner as in Example 1 except that the amount of water injected was 1.5 parts by mass. The results are shown in Table 3.

(Example 8)
Pellets were produced in the same manner as in Example 1 except that pure water having an electric conductivity of 0.5 μS / cm made with a mixed bed pure water apparatus was poured. The results are shown in Table 3.

Example 9
Pellets were produced in the same manner as in Example 1 except that pure water and tap water were mixed using a two-bed / three-column type pure water apparatus, and water having an electric conductivity of 9 μS / cm was injected. The results are shown in Table 3.
(Example 10)
Pellets were produced in the same manner as in Example 1 except that pure water and tap water were mixed with a two-bed / three-column type pure water apparatus, and water having an electric conductivity of 17 μS / cm was injected. The results are shown in Table 3.

(Example 11)
Pellets were produced in the same manner as in Example 1 except that the water tank was filled with pure water having an electric conductivity of 0.5 μS / cm made with a mixed bed pure water device and the strand was cooled. The results are shown in Table 3.
(Example 12)
The pellets were produced in the same manner as in Example 1 except that the water tank was mixed with pure water and tap water by a two-bed / three-column pure water device, filled with water having an electric conductivity of 9 μS / cm, and cooled in the strand. went. The results are shown in Table 3.
(Example 13)
The pellets were produced in the same manner as in Example 1 except that the water tank was mixed with pure water and tap water by a two-bed / three-column type pure water device, filled with water having an electric conductivity of 17 μS / cm, and the strand was cooled. went. The results are shown in Table 3.

(Example 14)
Pellets were produced in the same manner as in Example 1 except that the water bath cooling distance was shortened and the strand temperature during cutting was increased to 118 ° C. The results are shown in Table 3.
(Example 15)
Pellets were produced in the same manner as in Example 1 except that the water bath cooling distance was increased and the strand temperature during cutting was lowered to 79 ° C. The results are shown in Table 3.
(Example 16)
Pellets were produced in the same manner as in Example 1 except that the aging step was 7 hours. The results are shown in Table 3.

In Table 3 and below, “X” in the columns of “pellet shape” and “overall evaluation” were determined according to the criteria in Table 2 below.

(Comparative Example 1)
Pellets were produced in the same manner as in Example 1 except that PC-3 was used instead of PC-1. The results are shown in Table 4.

(Comparative Example 2)
A pellet was produced in the same manner as in Example 1 except that the supply amount of nitrogen gas was reduced and the oxygen concentration in the hopper chute was 4.0% by volume. The results are shown in Table 4.
(Comparative Example 3)
A pellet was produced in the same manner as in Example 1 except that the supply of nitrogen was stopped and the oxygen concentration in the hopper chute was changed to 21% by volume. The results are shown in Table 4.

(Comparative Example 4)
The same as Example 1 except that the distance (vertical height) from the material supply port of the quantitative feeder (Belt Weighing Feeder Wide Range B-WF manufactured by Kubota) to the material supply port of the twin screw extruder was set to 40 cm. The pellets were manufactured. The results are shown in Table 4.

(Comparative Example 5)
Pellets were produced in the same manner as in Example 1 except that pure water and tap water were mixed using a two-bed / three-column type pure water apparatus, and water having an electric conductivity of 33 μS / cm was injected. The results are shown in Table 4.
(Comparative Example 6)
The pellets were produced in the same manner as in Example 1 except that the water tank was mixed with pure water and tap water by a two-bed / three-column pure water device, filled with water having an electric conductivity of 33 μS / cm, and cooled in the strand. went. The results are shown in Table 4.

(Comparative Example 7)
Pellets were produced in the same manner as in Example 1 except that the water injection was stopped. The results are shown in Table 4.
(Comparative Example 8)
Pellets were produced in the same manner as in Example 1 except that the amount of water injected was 0.05 parts by mass. The results are shown in Table 4.

(Comparative Example 9)
Pellets were produced in the same manner as in Example 1 except that the amount of water injected was 2.5 parts by mass. The results are shown in Table 4.
When the vent was opened at the end of extrusion, the resin had risen (vent up. In a long-term continuous production, the vacuum system could be blocked by the resin, and it was judged that stable production was impossible).

(Comparative Example 10) Pellets were produced in the same manner as in Example 1 except that the screw rotation speed was 900 rpm. The results are shown in Table 4.

(Comparative Example 11)
Pellets were produced in the same manner as in Example 1 except that the water tank cooling distance was shortened and the strand temperature during cutting was increased to 132 ° C. The results are shown in Table 4.
(Comparative Example 12)
Pellets were produced in the same manner as in Example 1 except that the water tank cooling distance was increased and the strand temperature during cutting was lowered to 65 ° C. The results are shown in Table 4.
(Comparative Example 13)
In Example 1, the charge amount of the pellet was measured without going through the aging process. The charge amount was 10.2 kV, and dust in the air was easily adsorbed. The results are shown in Table 4.

(Example 17)
Pellets were produced in the same manner as in Example 1 except that the screw rotation speed was 700 rpm.
The results are shown in Table 5.
(Example 18)
Pellets were produced in the same manner as in Example 1 except that the discharge amount was 70 kg / hr and the screw rotation speed was 300 rpm. The results are shown in Table 5.

(Example 19)
Pellets were produced in the same manner as in Example 18 except that the screw configuration was changed to the screw configuration B in FIG. The screw configuration B is a configuration in which the screw lead in the decompression zone of the screw configuration A is 1.0D. The results are shown in Table 5.

(Example 20)
Pellets were produced in the same manner as in Example 1 except that the screw configuration was changed to the screw configuration C in FIG.
The screw configuration C has the following configuration.
a) Melting zone: A forward feed screw having a length of 31.5D and a lead of 1.5D was connected.
b) Kneading zone: Length 4.5D
The feed kneading element 1.0D, the reverse feed kneading element 0.5D, the forward feed kneading element 1.0D, the orthogonal kneading element 1.0D, and the reverse feed kneading 1.0 are formed in the feed direction.
c) Depressurization zone: A forward screw having a length of 16.5D and a lead of 1.5D was connected.
The results are shown in Table 5.

(Example 21)
Pellets were produced in the same manner as in Example 1 except that the screw configuration was changed to the screw configuration D in FIG.
a) Melting zone: A forward feed screw having a length of 41.5D and a lead of 1.5D was connected.
b) Kneading zone: Length 4.0D
The feed kneading element 1D, the reverse feed kneading element 0.5D, the forward feed kneading element 1.0D, the orthogonal kneading element 1.0D, and the reverse feed screw 0.5D are formed in the feed direction. In addition, the liquid injection plug was attached to C13 cylinder, and water was added with the plunger pump.
c) Decompression zone: A forward feed screw having a length of 7.0D and a lead of 1.5D was connected. This resin feed zone was the length of the decompression section.
The results are shown in Table 5.

(Example 22)
In Example 1, a plate-shaped molded product of 100 mm × 100 mm × 3 mm was used without drying the pellets, using an injection molding machine SH100 manufactured by Sumitomo Heavy Industries, Ltd. under conditions of a cylinder temperature of 290 ° C. and a mold temperature of 80 ° C. Molded. Although very slightly silver (silver strip) was seen, it was in a range where there was no problem.

  According to the production method of the present invention, the content of impurities such as chlorine compounds is extremely low, the resin is hardly deteriorated, yellowing does not occur, the pellet appearance is good, and the resin can be used free of resin additives. Since pellets can be manufactured and a high-quality molded product with extremely high cleanliness can be obtained, it can be applied to a wide range of fields such as electrical and electronic parts, and industrial applicability is very high.

Claims (9)

A method for producing a polycarbonate resin pellet having a reduced methylene chloride content from a polycarbonate resin containing a small amount of methylene chloride,
1) As a polycarbonate containing a small amount of methylene chloride, a polycarbonate resin in the form of a granular material having a specific surface area of 0.008 m ² / g or more and 50% by mass or more having a particle size of 200 to 2,000 μm is used.
2) An inert gas treatment step in which a polycarbonate resin in the form of granules is dropped and moved by 50 cm or more in an inert gas atmosphere having an oxygen concentration of 3% by volume or less,
3) The inert gas-treated polycarbonate resin in the form of granules is supplied to a vent-type extruder, and in the kneading zone, water having an electric conductivity of 30 μS / cm or less is added to 0.1 parts by mass of 100 parts by mass of the polycarbonate resin. Injecting 1 to 2 parts by mass;
4) By suctioning the vent port provided on the downstream side of the water injection portion of the extruder under reduced pressure, the methylene chloride is sucked and removed together with the water from the molten resin, and the water concentration in the resin is 10 Adjusting to ˜200 ppm,
5) A step of introducing and cooling the strand-shaped molten resin extruded from the die of the extruder into water having an electric conductivity of 30 μS / cm or less,
6) A step of cutting the strand in the range of 70 ° C to 130 ° C to obtain pellets containing 10 to 200 ppm of water,
7) including a aging step of further hydrating the obtained pellets containing 10 to 200 ppm of moisture in a wet atmosphere and adjusting the moisture content to exceed the original moisture content of the pellets and to 1300 ppm or less. A method for producing polycarbonate resin pellets.   The method for producing a polycarbonate resin pellet according to claim 1, further comprising a drying step of drying the moisture-containing pellet obtained through the aging step.   When processing a polycarbonate resin in the form of a granular material with an inert gas, the powdered fluid is supplied in a falling state, and the inert gas is supplied from below so as to be countercurrent to the granular material. The manufacturing method of the polycarbonate resin pellet of Claim 1 or 2.   The method for producing a polycarbonate resin pellet according to any one of claims 1 to 3, wherein the oxygen concentration in the barrel of the vent type extruder is 3% by volume or less.   The method for producing polycarbonate resin pellets according to any one of claims 1 to 4, wherein the kneading zone for injecting water is a resin-filled region and the resin pressure is in the range of 0.5 to 10 MPa.   The length of the region where the resin filling rate in the decompression part of the extruder is 5 to 30% by volume is 8.0 D or more (D is the cylinder inner diameter of the extruder) or more. The manufacturing method of the polycarbonate resin pellet in any one.   The temperature of the water which cools a strand is 30-90 degreeC, The manufacturing method of the polycarbonate resin pellet in any one of the Claims 1 thru | or 6 characterized by the above-mentioned.   The polycarbonate resin pellet manufactured with the manufacturing method of any one of Claims 1 thru | or 7.   A case for conveying parts of electrical and electronic equipment, wherein the polycarbonate resin pellet according to claim 8 is used.

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