JP2000177845A - Carrying method for thermoplastic resin powder and granule, and manufacture of thermoplastic resin pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrying method to obtain thermoplastic resin powder and granule without the increase of a foreign material amount, and an effective and stable manufacturing method for thermoplastic resin pellet excellent in hue with reduced foreign material by melting and extruding the thermoplastic resin powder and granule carried by the carrying method. SOLUTION: A carrying method for thermoplastic resin powder and granule uses inert carrier gas having moisture from 50% in relative humidity to 1.5 times of saturated steam. A manufacturing method for thermoplastic resin pellet melts and extrudes the thermoplastic resin powder and granule. The manufacturing method for thermoplastic resin pellet uses the thermoplastic resin powder and granule carried by airflow of the inert carrier gas having moisture from 50% in relative humidity to 1.5 times of saturated steam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for transporting thermoplastic resin powder and granular material and a method for producing thermoplastic resin pellets. More specifically, a method of transporting airflow with a gas whose moisture content has been adjusted to obtain a thermoplastic resin powder having no increase in the amount of foreign matter, and a method of melt-extruding the thermoplastic resin powder transported by the transport method. The present invention relates to a method for producing a thermoplastic resin pellet having an excellent hue and containing few foreign substances. In the present invention, the powdery material includes both powder and pellets, and the powdery material means powder.

[0002]

2. Description of the Related Art In a method for producing thermoplastic resin pellets by melt-extruding a thermoplastic resin powder, conventionally, (1) pneumatic transportation of the thermoplastic resin powder to an extruder hopper using air. The method of melt-extruding this powdery material or (2) while passing an inert gas through an extruder hopper,
In general, a method of supplying a pulverized thermoplastic resin powder and melt-extruding the powder is generally adopted. However, in the method (1), at the time of melt extrusion, the air used for the pneumatic transport together with the powder is taken into the melt extruder, and the oxygen in the air causes the thermoplastic resin to be oxidized and decomposed, thereby deteriorating the hue and physical properties. Cause unfavorable. The method (2) is a method of suppressing the oxidative decomposition of the thermoplastic resin and preventing deterioration of the hue and physical properties. However, if the residence time of the inert gas in the extruder hopper is short, the replacement with the inert gas is completely completed. It is not possible and its effect on the amount of inert gas used is low and not sufficient. In addition, both methods have a problem that the amount of foreign matters in the pellets obtained is large.

Further, in order to improve the hue of thermoplastic resin pellets, a method has been proposed in which water is injected and added to a molten polycarbonate resin at the time of melt extrusion (Japanese Patent Application Laid-Open No. 62-294528). However, such a method requires an extruder for injecting and adding water to the polycarbonate resin in a molten state, and is not sufficient for reducing the amount of foreign matters in the obtained pellets.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for transporting thermoplastic resin particles without increasing the amount of foreign matter, and a method of melting and extruding the thermoplastic resin powder transported by this method to obtain a hue. It is an object of the present invention to provide a method for efficiently and stably producing thermoplastic resin pellets excellent in heat resistance and containing few foreign substances.

The inventor of the present invention has conducted intensive studies in order to achieve this object. As a result, the present inventors have found that an inert gas whose moisture content has been adjusted is used as a transport gas when transporting thermoplastic resin powder particles by air flow. The present inventors have found that there is no increase in the amount of foreign substances, and that a thermoplastic resin pellet excellent in hue and containing few foreign substances can be obtained by melt-extruding a thermoplastic resin powder transported by such a method.

[0006]

That is, according to the present invention, there is provided a thermoplastic resin granule characterized by using an inert transport gas having a water content of 50% relative humidity to 1.5 times saturated steam. A method of transporting a body is provided.

The inert gas is usually supplied in a substantially dry state. Therefore, when the thermoplastic resin particles are transported using the inert gas in a completely dry state, fine powder is generated or the transportation tube wall is crushed at the time of collision between the particles or between the particles and the transportation tube wall. It is presumed that dropouts occur, which causes foreign matter to increase.

[0008] Therefore, when the amount of water in the transport gas is adjusted to a certain range, the impact at the time of the collision described above is reduced, the generation of foreign substances can be suppressed, and the aging of the transport pipe due to rust can be prevented.

The thermoplastic resin in the present invention includes polycarbonate resin, polyester resin, polymethyl methacrylate resin, polyarylate resin, polyamide resin, polyolefin resin and the like, and polycarbonate resin is particularly preferably used.

Such a polycarbonate resin is usually obtained by reacting a dihydric phenol with a carbonate precursor by a solution method or a melting method. Representative examples of the dihydric phenol used here include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl) Phenyl @ methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol A ), 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis} (3 , 5-Dibromo-4-hydroxy) phenyl} propane, 2,2
-Bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2-bis} (4-hydroxy-3-
Phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4
-Hydroxyphenyl) -3,3-dimethylbutane,
2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) -4-
Methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-
Bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis {(4-hydroxy-3-methyl) phenyl} fluorene, α , Α'-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -m
-Diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,
3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfoxide, 4,4'-dihydroxydiphenylsulfide,
4,4'-dihydroxydiphenyl ketone, 4,4'-
Examples thereof include dihydroxydiphenyl ether and 4,4'-dihydroxydiphenyl ester, which can be used alone or as a mixture of two or more.

Among them, bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane,
2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl)-
3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4
A homopolymer obtained from at least one bisphenol selected from the group consisting of -hydroxyphenyl) -3,3,5-trimethylcyclohexane and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene, or Copolymers are preferred. In particular, bisphenol A homopolymer and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and bisphenol A, 2,2-bis {(4-hydroxy- Copolymers with 3-methyl) phenyl} propane or α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene are preferably used.

As the carbonate precursor, carbonyl halide, carbonate ester or haloformate is used, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol and the like.

In producing the polycarbonate resin by reacting the above-mentioned dihydric phenol with the carbonate precursor by a solution method or a melting method, a catalyst, a terminal stopper, an antioxidant for the dihydric phenol and the like may be used, if necessary. May be used. Further, the polycarbonate resin may be a branched polycarbonate resin obtained by copolymerizing a trifunctional or higher polyfunctional aromatic compound, or a polyester carbonate resin obtained by copolymerizing an aromatic or aliphatic bifunctional carboxylic acid. Alternatively, a mixture of two or more of the obtained polycarbonate resins may be used.

The reaction by the solution method is usually a reaction between dihydric phenol and phosgene, and is carried out in the presence of an acid binder and an organic solvent. As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an amine compound such as pyridine is used. As the organic solvent, for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. Further, for promoting the reaction, for example, a catalyst such as a tertiary amine such as triethylamine, tetra-n-butylammonium bromide, or tetra-n-butylphosphonium bromide, a quaternary ammonium compound, or a quaternary phosphonium compound may be used. it can. At that time, the reaction temperature is usually 0 to 40 ° C., the reaction time is preferably about 10 minutes to 5 hours, and the pH during the reaction is preferably maintained at 9 or more.

In such a polymerization reaction, a terminal terminator is usually used. Monofunctional phenols can be used as such a terminal stopper. Monofunctional phenols are commonly used as molecular terminators for molecular weight control, and the resulting polycarbonate resins are capped by groups based on monofunctional phenols, so that Excellent heat stability. Such a monofunctional phenol is generally a phenol or a lower alkyl-substituted phenol, and may be a monofunctional phenol represented by the following general formula (1).

[0016]

Embedded image

[Wherein A is a hydrogen atom or a carbon number of 1 to 9]
And r is an integer of 1 to 5, preferably 1 to 3. ]

Specific examples of the above monofunctional phenols include phenol, p-tert-butylphenol, p-cumylphenol and isooctylphenol.

From the organic solvent of the polycarbonate resin obtained by the solution method, known methods such as a method of adding this solution to warm water, a method of contacting with steam, a method of concentrating or cooling, and a method of adding a non-solvent or a poor solvent are used. According to the method, a polycarbonate resin powder can be obtained. Such a polycarbonate resin powder is suitably used in the transportation method and the pellet production method of the present invention described below.

The reaction by the melting method is usually a transesterification reaction between a dihydric phenol and a carbonate ester,
The method is carried out by a method in which a dihydric phenol and a carbonate ester are mixed while heating in the presence of an inert gas to distill off the produced alcohol or phenol. The reaction temperature varies depending on the boiling point of the produced alcohol or phenol, but is usually in the range of 120 to 350 ° C.
In the latter stage of the reaction, the pressure of the system is reduced to about 10 to 0.1 Torr to facilitate the distillation of the alcohol or phenol produced. The reaction time is usually about 1 to 4 hours.

The polycarbonate resin melt obtained by the melting method can be extruded into, for example, a strand, cooled, and cut into polycarbonate resin pellets. Such polycarbonate resin pellets are suitably used in the transportation method of the present invention described below.

The molecular weight of the polycarbonate resin is preferably 10,000 to 50,000, more preferably 12,000 to 40,000, and more preferably 1 to 40,000 in terms of viscosity average molecular weight (M).
3,000 to 30,000 are particularly preferred. A polycarbonate resin having such a viscosity average molecular weight is preferable because sufficient strength is obtained and the melt fluidity during molding is good. The viscosity average molecular weight referred to in the present invention is methylene chloride 1
The specific viscosity (η _sp ) obtained from a solution obtained by dissolving 0.7 g of a polycarbonate resin in 00 ml at 20 ° C. was inserted into the following equation. η _sp /c=[η]+0.45×[η] ² c (where [η]
Is the intrinsic viscosity) [η] = 1.23 × 10 ⁻⁴ M ^0.83 c = 0.7

As the inert transport gas used in the present invention, nitrogen gas, carbon dioxide gas and a mixed gas thereof are preferably used, and nitrogen gas is particularly preferably used. The used inert transport gas can be reused.

In the transport method of the present invention, the inert transport gas has a relative humidity of 50% or more, preferably 60% or more.
% Or more, more preferably 80% or more, and 1.5 times or less, preferably 1.4 times or less of the saturated steam. When an inert transport gas having a relative humidity of less than 50% is used, metal particles generated from the pipe increase due to contact between the thermoplastic resin powder and the inner wall of the pipe, which is not preferable. In addition, when an inert transport gas containing more than 1.5 times the water content of the saturated steam is used, when the thermoplastic resin powder or the like is constantly transported for a long period of time, corrosion on the inner wall of the pipe due to the water content may occur. It is easy to generate, especially in the case of polycarbonate resin, the hydrochloric acid generated by the reaction between the chlorine compound remaining in the polycarbonate resin and the water causes the corrosion to the inner wall of the pipe more easily, and the amount of foreign substances increases due to this corrosion, which is preferable. Absent. Water vapor or water is used to adjust the amount of water in the inert transport gas, and water vapor is particularly preferably used.

The oxygen concentration in the inert transport gas is preferably 5% by volume or less.
The thermoplastic resin pellets obtained by melt extrusion molding described later have better hue, which is preferable.

In the transportation method of the present invention, the temperature in the transportation pipe is preferably from 10 to 100 ° C., particularly preferably from 15 to 80 ° C. The shape of the transport pipe includes a cylinder, an ellipse, a prism, and the like, and a cylindrical shape is particularly preferably used.
The diameter of the cylindrical pipe is preferably 30 to 250 mm. For the length of the pipe,
The length is preferably 10 m or more, because the effect of the present invention that the amount of foreign matters of the thermoplastic resin particles does not increase in the transport pipe as the length becomes longer is easily exhibited.
A pipe length of 500 m is preferred. Further, as for the material of the pipe, austenitic stainless steel, ferritic stainless steel, chromium-molybdenum steel, nickel-chromium iron, aluminum, titanium, and other alloy steel pipes can be used, and in particular, mechanical properties such as strength and hardness and cost. Austenitic stainless steel and its sanitary specification are preferably used from the viewpoint of excellent balance with the surface. In addition, the transfer speed of the thermoplastic resin particles is from 15 to 40 m from the viewpoint of preventing crushing of the particles.
/ S range is desirable.

According to the present invention, there is further provided a method for producing thermoplastic resin pellets by melt-extruding a thermoplastic resin powder, wherein the water content is from 50% relative humidity to 1.5 times the saturated steam. A method for producing thermoplastic resin pellets, comprising using a thermoplastic resin powder that has been transported in a gas stream by a transport gas.

The thermoplastic resin powder used in the method for producing thermoplastic resin pellets of the present invention is prepared by a method of transporting with an inert transport gas having a water content of 50% relative humidity to 1.5 times saturated steam. And transported thermoplastic resin powder.

In the method for producing thermoplastic resin pellets of the present invention, the water content of the inert transport gas is 50
% Or more, preferably 60% or more, more preferably 80%
Above, 1.5 times or less of saturated steam, preferably 1.4 times
Less than twice. When an inert transport gas having a relative humidity of less than 50% is used, metal foreign matter generated from the pipe increases due to contact between the thermoplastic resin powder and the inner wall of the pipe, which is obtained by melt extrusion. The hue of the thermoplastic resin pellets deteriorates and the amount of foreign substances increases, which is not preferable. In addition, when an inert transport gas containing more than 1.5 times the saturated steam is used, the transported powder is melt-extruded as it is, and the molten resin is transferred to the vent of the melt extruder (vent up). ) Occurs violently and the extruder cannot operate normally, which is not preferable.

The thermoplastic resin powder is heated and melted by using a melt extruder to produce thermoplastic resin pellets. As such a melt extruder, a vented extruder is preferably used, and as a type, a twin-screw extruder is preferable.
Extrusion conditions do not need to be special conditions, and ordinary melt extrusion conditions are used. For example, the resin temperature is preferably in the range of 280 to 340 ° C. in the case of a polycarbonate resin obtained from bisphenol A and a carbonate precursor.

The thermoplastic resin pellets obtained by the present invention can be formed by any method such as injection molding, compression molding, extrusion molding, and solution casting. In particular, the molded article molded from the polycarbonate resin pellets obtained by the production method of the present invention has an extremely small amount of foreign matter, and has a small amount of foreign matter in optical applications such as optical disk substrates, optical fibers, lenses, and retardation films, and particularly in optical disk substrates. Is small, which has the advantage of reducing the error rate when used as an optical disc, and is preferably used.

The obtained thermoplastic resin pellets may contain, if necessary, a heat stabilizer, a releasing agent, an antioxidant, an ultraviolet absorber (weathering agent), a coloring agent, a whitening agent, an antistatic agent, a lubricant. And additives such as antibacterial agents.

[0033]

EXAMPLES Examples will be further described below with reference to examples. In addition,
The evaluation was performed by the following method. (1) Hue Pellets were injected at a cylinder temperature of 340 ° C. using an injection molding machine (Nihon Steel Works Co., Ltd .: Nikko Anchor V17-65).
A sample plate having a size of 50 mm square and a thickness of 2 mm was formed. The b value of these sample plates was measured using a color difference meter (Z-1001DP type manufactured by Nippon Denshoku Co., Ltd.). The smaller the b value, the better the hue without yellow.

(2) Foreign matter amount The foreign matter amount was determined by dissolving 100 g of powder and 100 g of pellets in 1000 ml of methylene chloride, respectively, and measuring the amount of foreign matter having a particle size of 0.5 μm or more using a foreign matter measuring device manufactured by Hiac Leuco.

(3) Viscosity average molecular weight Polycarbonate resin 0.7 in 100 ml of methylene chloride
g was calculated from the specific viscosity obtained from a solution obtained by dissolving g at 20 ° C.

(4) A polycarbonate resin powder is put into a metal cylindrical container having a bulk density of 1000 cm ³ using a funnel, and the excess is ground off and weighed to determine the weight W (g) of the content. It was calculated by the following equation. Bulk density (g / cm ³ ) = W / 1000

Example 1 Solution supply port, steam inlet,
In a kneader having a content of 500 l having a steam outlet and an overflow port, a bulk density of 0.5 g / cm ³ and a viscosity average molecular weight of 235 were added.
100 kg of polycarbonate resin powder and hot water 2
And put the pressure of 2.7kg under stirring of the kneader.
/ Cm ² , and when the water temperature reached 65 ° C., the viscosity average molecular weight was 2350 while stirring was continued.
Methylene chloride solution having a polycarbonate resin concentration of 15% by weight at a rate of 10 kg / min.
The feed was started continuously at a rate of 7 kg / min, and at the same time, the water temperature in the kneader was maintained at 65 ° C. at a pressure of 2.7.
kg / cm ² of water vapor was continuously introduced. A water slurry having a water temperature of 65 ° C. and a polycarbonate resin concentration of 33% by weight was continuously discharged from the overflow port. The discharged polycarbonate water slurry continuously separated the polycarbonate powder by a centrifugal separator, and was continuously supplied to a jacketed horizontal dryer having an overflow port, and the internal temperature of the dryer was 140 ° C. It was dried for 6 hours and continuously discharged from the overflow. The discharged polycarbonate powder had a bulk density of 0.5 g / cm ³ and an amount of foreign substances of 2800 / g.

The polycarbonate resin powder discharged from the overflow port of the dryer was adjusted to a relative humidity of 95% and an oxygen concentration of less than 0.01% by volume in terms of nitrogen, oxygen and steam shown in Table 1. Stainless steel (SU)
S304) through a 150 m long pipe of a cylindrical mold 32A (outer diameter 42.7 mm, inner diameter 35.5 mm).
The polycarbonate resin powder was steadily pneumatically transported at a rate of 90 kg / hr to a melt extruder hopper at 90 ° C. The gas flow rate was measured by an FHGN type flow meter manufactured by Nippon Flow Cell Co., Ltd., the oxygen concentration was measured by an OX-571 type oxygen concentration meter manufactured by Riken Keiki Co., Ltd., and the moisture content was measured by an MX-9-H type humidity controller manufactured by Nippo Co., Ltd. did. One month after the start of transport, the amount of foreign substances in the polycarbonate resin powder transported by airflow was 450
It was 0 / g. Next, the polycarbonate resin powder was melt extruded (TEM-70 manufactured by Toshiba Machine Co., Ltd.).
The mixture was melt-extruded into strands at 300 ° C. using a mold, cooled and cut to obtain polycarbonate resin pellets. The foreign material amount of the polycarbonate resin pellets was 4,800 / g, and the b value of the molded product was 0.1. Table 2 shows the results.

Example 2 Polycarbonate resin pellets were prepared in the same manner as in Example 1 except that a nitrogen gas transport gas adjusted to a relative humidity of 60% and an oxygen concentration of less than 0.01% by volume was used. I got Table 2 shows the evaluation results.

Example 3 Polycarbonate resin pellets were obtained in the same manner as in Example 1, except that a nitrogen gas transport gas adjusted to a relative humidity of 95% and an oxygen concentration of 5% by volume was used. . Table 2 shows the evaluation results.

Example 4 Example 1 was the same as Example 1 except that a nitrogen gas transport gas having a water content adjusted to 1.4 times that of saturated steam and an oxygen concentration of less than 0.01% by volume was used. Thus, polycarbonate resin pellets were obtained. Table 2 shows the evaluation results.

Comparative Example 1 A polycarbonate resin pellet was obtained in the same manner as in Example 1, except that a nitrogen gas transport gas having a relative humidity of 0% and an oxygen concentration of less than 0.01% by volume was used. Was. Table 2 shows the evaluation results.

[Comparative Example 2] Same as Example 1 except that a nitrogen gas transport gas whose water content was adjusted to 1.8 times that of saturated steam and oxygen concentration was less than 0.01% by volume was used. According to the method described above, the polycarbonate resin powder was pneumatically transported to a melt extruder hopper. One month after the start of transport, the amount of foreign substances in the polycarbonate resin powder transported by air was 8,000 particles / g. Further, when the polycarbonate resin powder was melt-extruded with a melt extruder (TEM-70 manufactured by Toshiba Machine Co., Ltd.) in the same manner as in Example 1, the molten resin was sharply transferred to the vent of the melt extruder. Normal operation has been disabled.

Comparative Example 3 Polycarbonate resin pellets were obtained in the same manner as in Example 1, except that air having a relative humidity of 60% was used as the transport gas. Table 2 shows the evaluation results.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

According to the present invention, it is possible to efficiently produce a thermoplastic resin powder having an excellent hue and a small amount of foreign matter, and its industrial effect is remarkable.

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Claims (3)

[Claims] 1. A method for transporting thermoplastic resin particles, wherein an inert transport gas having a water content of 50% relative humidity to 1.5 times saturated steam is used. 2. The method according to claim 1, wherein the thermoplastic resin is a polycarbonate resin. 3. A method for producing a thermoplastic resin pellet by melt-extruding a thermoplastic resin powder, wherein the powder is transported by an inert transport gas having a water content of 50% relative humidity to 1.5 times saturated steam. A method for producing thermoplastic resin pellets, comprising using a thermoplastic resin powder.