JPH09193230A - Production of polycarbonate resin molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence of the corrosion of a mold in melt molding by injecting and adding water from two or more places just in front of vents by using a twin-screw extruder fitted with a multistage vent and kneading and extruding a polycarbonate resin while degassing the resin from the vents. SOLUTION: Water is injected and added from two or more places by using a twin-screw extruder fitted with a multistage vent having two or more places where water is injected and added just in front of vents and a polycarbonate resin is kneaded and extruded while degassed through the vents. The polycarbonate resin pref. contains 5-2000ppm of a chlorine compd. in terms of a chlorine atom. The injection addition amt. of water at the respective injection addition position is pref. 0.2-4 pts.wt. per 100 pts.wt. of the polycarbonate resin and resin temp. is pref. 260-320 deg.C. Further, the filling amt. of the polycarbonate resin in the spatial vol. of the screw parts corresponding to vent positions is pref. 20vol.% or less.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polycarbonate resin molded article. More specifically, a method for producing a polycarbonate resin molded product having an extremely low content of chlorine compounds, particularly a molded product such as a polycarbonate resin pellet, in which corrosion of a mold used during molding and corrosion of a recording film such as an optical disk or a magnetic disk are extremely low Regarding

[0002]

2. Description of the Related Art Polycarbonate resins are excellent in transparency, heat resistance, impact resistance, etc., and are therefore melt-molded by injection molding, compression molding, extrusion molding, rotational molding, etc. It is used for purposes. Such a polycarbonate resin, particularly a polycarbonate resin produced by a so-called interfacial polymerization method in which a dihydric phenol and phosgene are reacted in the presence of methylene chloride is a compound having a small amount of methylene chloride or a chloroformate group which is an unreacted residue. And the like, and these chlorine compounds are decomposed at the time of melt molding to generate an acidic substance, which causes corrosion of molds and corrosion of recording films such as optical disks and magnetic disks. Particularly in recent years, the problem of mold corrosion has been largely addressed by shortening the molding cycle. In addition, the recording film of optical disks and magnetic disks is also shifting to high density, and the corrosion of the recording film becomes a big problem.

On the other hand, a method has been proposed in which water is added during melt extrusion to remove impurities in the polycarbonate resin. Japanese Patent Publication No. 5-48162 proposes a method of adding a small amount of water to a polycarbonate resin powder separated and recovered from a methylene chloride solution and extruding the powder with a vented extruder. Further, the present inventors have used one or more extruders with a vacuum vent to provide a pressure ratio of 0.1% per 100 parts by weight of the polycarbonate resin between the compression-melting part and the farthest vent port.
It has been proposed to inject 1 to 5 parts by weight of water (Japanese Patent Publication No. 7-2364). However, although these methods can remove impurities and chlorine compounds in the polycarbonate resin to some extent, they are not sufficiently effective in suppressing mold corrosion and recording film corrosion.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polycarbonate resin molded product having a very low chlorine compound content. The term "molded product" as used herein refers to all extrusion molded products, including molding materials such as pellets.
Molding materials such as pellets of polycarbonate resin that have an extremely low content of chlorine compounds, for example, 5 ppm or less in terms of chlorine atoms, have extremely low corrosion of the mold used during injection molding. Corrosion of the recording film of the obtained optical disk or magnetic disk is extremely small.

The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, when kneading and extruding the polycarbonate resin obtained by the interfacial condensation method, water has a function of injecting and adding water at two or more positions immediately before the vent. Using a twin-screw extruder equipped with a multi-stage vent, by injecting and adding water from two or more locations and kneading and extruding the polycarbonate resin while degassing at the vent, the chlorine compound contained in the polycarbonate resin is converted into chlorine atoms. Less than 5ppm,
It has been found that corrosion of the mold and recording film is extremely reduced. The present invention has been achieved as a result of further studies based on this finding.

[0006]

DISCLOSURE OF THE INVENTION In the present invention, in kneading and extruding a polycarbonate resin obtained by an interfacial condensation method, a twin-screw with a multistage vent having two or more portions having a function of injecting and adding water immediately before the vent. A method for producing a polycarbonate resin molded article, which comprises using an extruder to inject and add water from two or more locations and kneading and extruding a polycarbonate resin while degassing with a vent.

The polycarbonate resin referred to in the present invention is an aromatic polycarbonate resin obtained by reacting a dihydric phenol with a carbonate precursor such as phosgene in the presence of a solution, and includes methylene chloride, 1,2.
-Powder, fine particles, or flakes separated and recovered from a solution of a chlorine-based organic solvent such as dichloroethylene or chloroform. Examples of the dihydric phenol used here include hydroquinone, resorcin, 4,4'-dihydroxydiphenyl, and bis (4-hydroxyphenyl).
Methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane (commonly called bisphenol Z), 2,2-bis (3-phenyl-4-hydroxyphenyl) propane, 2,2-bis (3-isopropyl-4-hydroxyphenyl) Propane 2,2
-Bis (4-hydroxyphenyl) butane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane, 4, 4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfide, 3,3'-dimethyl-4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl oxide, 9,9-bis (4-hydroxyphenyl) fluorene, 1,1-bis (4-hydroxyphenyl)-
Examples include 3,3,5-trimethylcyclohexane and 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane. Among them, bisphenol A, bisphenol Z, 9,9-bis (4-hydroxyphenyl) fluorene, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 1, in terms of great improvement effect. 3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane is preferred. These may be used alone or in combination of two or more. Also, a small amount of a trifunctional compound may be used as a branching agent, or a small amount of an aliphatic bifunctional compound may be copolymerized.

As the polycarbonate resin targeted by the present invention, a chlorine compound is 5 to 200 in terms of chlorine atom.
Those containing 0 ppm are preferable. More preferably 5 to 1
It is 500 ppm. It is less necessary to apply the present invention to a polycarbonate resin having a chlorine atom of less than 5 ppm.
If it exceeds 00 ppm, it will be difficult to achieve 5 ppm or less in terms of chlorine atoms even if the present invention is applied, and the object of the present invention cannot be achieved. The polycarbonate resin containing such a chlorine compound is a polycarbonate resin produced by an interfacial polymerization method and contains a small amount of a chlorine compound such as methylene chloride or a compound having a chloroformate group which is an unreacted residue. However, it is preferable to be the subject of the present invention.

The interfacial polymerization method for producing a polycarbonate resin will be briefly described. In the interfacial polymerization method using phosgene as a carbonate precursor, the reaction is usually performed 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, a catalyst such as a tertiary amine or a quaternary ammonium salt can be used to promote the reaction, and a terminal stopper such as an alkyl-substituted phenol such as phenol or p-tert-butylphenol can be used as a molecular weight regulator. It is desirable to use. The reaction temperature is usually 0 to 40 ° C., the reaction time is several minutes to 5 hours, and the pH during the reaction is preferably 10 or more.

The twin-screw extruder with multi-stage vents used in the present invention requires two or more vents, preferably two vents.
~ 6 places. The number of locations where water is injected and added may be less than the number of vents, but two or more locations are required, and preferably two to six locations. If the number of vents and the water injection point are one, there will be a large amount of residual chlorine in the obtained polycarbonate resin molded product, and if the number of vents is too large, the L / D of the extruder will become long and adverse effects such as resin burns will occur. Is likely to occur. The water injection / addition position immediately before venting does not need to be installed in each vent portion, and two or more injection / addition positions may be determined as necessary.

If the amount of water added is too small, the effect of water addition will not be exhibited, and the chlorine compound in the polycarbonate resin will be less than 5 ppm in terms of chlorine atoms. Since deaeration becomes insufficient and the polycarbonate resin is adversely affected by hydrolysis and the like, the amount of water to be added at each injection addition position should be 0.2 to 4 parts by weight per 100 parts by weight of the supplied polycarbonate resin. Is preferred.

The polycarbonate resin filling amount in the space volume of the screw portion corresponding to the vent position of the multi-screw twin-screw extruder is preferably 20% by volume or less. If the polycarbonate resin is packed too densely, the degassing efficiency will be poor, and the chlorine compound in the resulting polycarbonate resin will be less than 5 ppm in terms of chlorine atoms, making it difficult to achieve the object of the present invention. Become.

The degree of vacuum of each vent is preferably 50 Torr or less. More preferably, it is 30 Torr or less.
If the degree of vacuum is not sufficient, the water added by injection cannot be sufficiently removed at the vent portion, which adversely affects the polycarbonate resin such as hydrolysis, which is not preferable.

The resin temperature of the polycarbonate resin during kneading is preferably 260 to 320 ° C. When the resin temperature is less than 260 ° C., the melt viscosity of the polycarbonate resin is high and it becomes difficult to knead. On the other hand, if the temperature exceeds 320 ° C., the thermal decomposition of the polycarbonate resin becomes severe, which is not preferable.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to examples. In addition, the part in an Example is a weight part and evaluation was performed by the following method. (1) Resin filling rate: After the extrusion has reached a steady state under each condition, the raw material supply and the screw are stopped at the same time, the screw is removed from the cylinder, and then the resin is retained in the part corresponding to the vent part. The resin filling rate was calculated from the weight of. (2) Resin temperature: The temperature of the molten resin extruded from the nozzle of the extruder was measured using a Yokogawa digital pocket thermometer. (3) Amount of chlorine atom: Silver ion (Ag) generated by coulometrically generating hydrogen chloride (HCl) generated by completely burning the sample
+) And titrated. (4) Specific viscosity (ηsp): A solution prepared by dissolving 0.7 g of polycarbonate resin in 100 ml of methylene chloride was measured at 20 ° C. (5) Mold corrosion: using a carbon steel (S50C) mold,
An injection molding machine [Toshiba Machine Co., Ltd.]
Manufactured by IS-150EN], the cylinder temperature is 300 ° C,
Mold temperature 50 ℃, molding cycle 20 seconds 70mm length, 5 width
800 pieces of flat plates having a thickness of 0 mm and a thickness of 2 mm were continuously formed, and the state of the surface of the die was visually observed when the used die was allowed to stand at 50 ° C. × 90% RH for 2 hours. The evaluation index was 0 for no rust, 1 for spotted rust, 2 for partially reddish brown rust, and 3 for reddish rust on the entire surface.

[Examples 1 to 13 and Comparative Examples 1 to 7] The number of vents was 3 (referred to as vents closer to the hopper), and water injection addition points (referred to as vents closer to the hopper) were provided immediately before each vent section. Screw diameter 46mm
φ twin-screw extruder [HYPERKTX manufactured by Kobe Steel, Ltd.
-46], the raw material resin (polycarbonate resin) shown in Table 1 was used to extrude into a strand shape under the extrusion conditions shown in Table 1, and cut into pellets. The chlorine atom amount in the pellet and the specific viscosity of the pellet are shown in Table 1. In addition,
The water injection addition amount in the table is the amount per 100 parts of the resin. The obtained pellets were dried with a hot air circulation dryer at 120 ° C. for 5 hours and then subjected to a mold corrosion test. The mold corrosion results are shown in Table 1.

[0017]

[Table 1]

The symbols of the raw material resins in Table 1 are as follows. A: Polycarbonate resin having a specific viscosity of 0.285 obtained by reacting bisphenol A and phosgene in methylene chloride by a conventional method and containing a chlorine compound of 410 ppm as a chlorine atom. B: A polycarbonate resin having a specific viscosity of 0.285 obtained by reacting bisphenol A and phosgene in methylene chloride by a conventional method and containing 970 ppm of a chlorine compound as a chlorine atom. C: Polycarbonate resin having a specific viscosity of 0.285 obtained by reacting bisphenol A and phosgene in methylene chloride by a conventional method and containing a chlorine compound of 1480 ppm as a chlorine atom. D: A polycarbonate resin having a specific viscosity of 0.285 obtained by reacting bisphenol A and phosgene in methylene chloride by a conventional method and containing a chlorine compound of 2520 ppm as a chlorine atom. E: A polycarbonate resin having a specific viscosity of 0.406 obtained by reacting bisphenol A and phosgene in methylene chloride by a conventional method and containing 1270 ppm of a chlorine compound as a chlorine atom. F: A polycarbonate resin having a specific viscosity of 0.392 obtained by reacting bisphenol Z and phosgene in methylene chloride by a conventional method and containing a chlorine compound of 100 ppm as a chlorine atom.

[0019]

As is clear from Table 1, the polycarbonate resin produced by the production method of the present invention has the effect that the occurrence of mold corrosion during melt molding is extremely small.

Claims (5)

[Claims] 1. When kneading and extruding a polycarbonate resin obtained by an interfacial condensation method, a twin-screw extruder with a multi-stage vent having two or more places having a function of injecting and adding water immediately before the vent is used, and two places are used. From the above, a method for producing a polycarbonate resin molded article, which comprises kneading and extruding a polycarbonate resin while injecting and adding water and degassing with a vent. 2. The method for producing a polycarbonate resin molded article according to claim 1, wherein the number of vents of the twin-screw extruder with a multi-stage vent is 2 to 6, and the location where water is injected and added is 2 to 6. 3. The water injection addition amount at each injection addition location is 0.2 per 100 parts by weight of the supplied polycarbonate resin.
To 4 parts by weight, The method for producing a polycarbonate resin molded article according to claim 1 or 2. 4. A polycarbonate resin filling amount in a space volume of a screw portion corresponding to a vent position of a multi-screw twin-screw extruder is 20% by volume or less.
4. The method for producing a polycarbonate resin molded article according to any one of 3 to 3. 5. The method for producing a polycarbonate resin molded article according to claim 1, wherein the degree of vacuum of each vent is 50 Torr or less.