JP2008018594A - Manufacturing method of polycarbonate resin pellet and housing feed container of silicon wafer or magnetic disk formed from pellet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polycarbonate resin material suitable for a housing feed container capable of reducing the surface contamination of a thin plate such as a silicon wafer or a magnetic disk. <P>SOLUTION: In a manufacturing method of a polycarbonate resin pellet, a twin-screw extruder having at least one water injection part on the upstream side of a vent is used as a twin-screw extruder not only to inject water from the water injection part but also to adjust the vacuum degree of the vent to 6.7 kPa or below. The screw of the kneading part just under the water injection part is constituted in the order of a seal ring, an orthogonal kneading disk or a successive feed kneading disk, a reverse feed kneading disk and a seal ring and the length of each screw element of the kneading part is set to 0.25-1.0 D while L<SB>2</SB>/D of the kneading part is set to 1-4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a polycarbonate resin pellet suitably used as a material for a storage and conveyance container such as a silicon wafer or a magnetic disk, and a molded product thereof.

In general, it is important that a container for storing and transporting a thin plate sensitive to surface contamination such as a silicon wafer or a magnetic disk can be transported while always keeping the surface of the silicon wafer normal.
Recently, with the increase in the diameter of silicon wafers, the demand for contamination from the container to the wafer surface has become stricter, and at the same time, a material with higher strength has been demanded. Similar demands exist not only for wafers but also for magnetic disk storage and transfer containers. Attempts have been made to use a polycarbonate resin or a resin composition containing this as a main component as a molding material suitable for this requirement.

  For example, Patent Documents 1 to 4 describe a method for preventing contamination of the surface of a silicon wafer by removing impurities in a polycarbonate resin or reducing the amount of volatile gas generated by heating at a high temperature. ing. However, storage containers for silicon wafers and magnetic disks are not used only once, but are repeatedly used after being washed with water. Therefore, the storage and transfer containers described in Patent Documents 1 to 4 can be made ionic by washing with water. There is a problem that impurities are eluted and ionic impurities adhering to the surface of the container contaminate the surface of the wafer or the like.

  On the other hand, a method for removing impurities in the polycarbonate resin by injecting water during melt extrusion has been proposed. Patent Documents 5 to 7 propose a method of extruding polycarbonate resin powder while injecting a small amount of water with an extruder equipped with a vent. However, although these methods can remove impurities and chlorine compounds in the polycarbonate resin to some extent, they are insufficient as materials for the storage and transfer container for wafers and the like as described above.

Japanese Patent Laid-Open No. 10-211686 Japanese Patent Laid-Open No. 11-241212 JP 2000-043436 A JP 2000-063505 A Japanese Examined Patent Publication No. 05-048162 Japanese Patent Publication No. 07-002364 JP 09-193230 A

  An object of this invention is to provide the polycarbonate resin material used suitably for the storage conveyance container which can reduce the surface contamination of thin plates, such as a silicon wafer and a magnetic disk which are sensitive to surface contamination.

  As a result of intensive studies to achieve the above object, the present inventor has improved the kneading performance immediately after water injection with a special screw structure of the twin screw extruder, and kneaded the polycarbonate resin efficiently to disperse and mix the water. If it is devolatilized after venting, the devolatilization efficiency is improved, and polycarbonate resin pellets with low chlorine compound content can be obtained. Molded products obtained using these pellets as materials are generated even when washed with water. The inventors have found that the amount of chlorine ions is small and can be suitably used as a storage and conveyance container for silicon wafers, magnetic disks and the like, and the present invention has been achieved.

That is, according to the present invention,
1. In a method of producing polycarbonate resin pellets by melt-extruding polycarbonate resin granules using a twin screw extruder and pelletizing to produce polycarbonate resin pellets, a mechanism for injecting at least one water upstream of the vent as the twin screw extruder (water injection) And a screw configuration of a kneading part immediately below the water injection part, while injecting water from the water injection part and adjusting the degree of vacuum of the vent to 6.7 kPa or less. In the order of the seal ring, the orthogonal kneading disk or the forward kneading disk, the reverse kneading disk, and the seal ring from the upstream side, and the length (L ₁ ) of each screw element of the kneading part is 0.25D in the range of; (inner diameter of the cylinder D), _L 2 / D of the kneading portion ～1.0D; to the _{(L 2} length of kneading zone) 1-4 range The method of producing a polycarbonate resin pellet, characterized in that,
2. The twin-screw extruder, that the entire screw configuration L _{3 / D;} method of producing a polycarbonate resin pellets (L 3 total length of the screw) is above 1, wherein in the range of 28 to 49,
3. The method for producing polycarbonate resin pellets according to the preceding item 1, wherein the twin-screw extruder has 2 to 6 vents and 1 to 5 water injection portions.
4). The method for producing polycarbonate resin pellets according to item 1 above, wherein the amount of water injected in each water injection part is 0.1 to 5 parts by weight per 100 parts by weight of the polycarbonate resin,
5. A silicon wafer or magnetic disk storage and conveyance container formed from the polycarbonate resin pellets obtained by the production method according to the preceding item 1,
6). 6. A polycarbonate resin molded product, wherein the amount of chlorine ions eluted from the molded product into water after heat treatment of the polycarbonate resin molded product in water at 80 ° C. for 24 hours is 7 ng / cm ² or less; The molded article according to the preceding item 6, wherein the molded article is a polycarbonate resin molded article that is a storage and transfer container for a silicon wafer or a magnetic disk,
Is provided.

Hereinafter, the present invention will be described in detail.
The polycarbonate resin used in the present invention is an aromatic polycarbonate resin obtained by reacting a dihydric phenol and a carbonate precursor by an interfacial polymerization method in the presence of a solvent. Examples of the dihydric phenol used here include hydroquinone, resorcin, 4,4′-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, and 2,2-bis (4 -Hydroxyphenyl) propane (commonly referred to as bisphenol A), 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane (commonly referred to as 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, 4,4'-dihydroxydipheny 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, 9,9-bis {(4-hydroxy-3-methyl) phenyl} fluorene, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, α, Examples include α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane. Among them, bisphenol A, bisphenol Z, 9,9-bis {(4-hydroxy-3-methyl) phenyl} fluorene, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene is preferred. These may be used alone or in combination of two or more.

As the carbonate precursor, carbonyl halide, haloformate or the like is used, and specific examples include phosgene or dihaloformate of dihydric phenol.
In producing a polycarbonate resin by reacting the dihydric phenol and the carbonate precursor by an interfacial polycondensation method, a terminal terminator, a dihydric phenol antioxidant or the like may be used as necessary. The polycarbonate resin may be a branched polycarbonate resin copolymerized with a trifunctional or higher polyfunctional aromatic compound, or may be a polyester carbonate resin copolymerized with an aromatic or aliphatic difunctional carboxylic acid, Moreover, the mixture which mixed 2 or more types of the obtained polycarbonate resin may be sufficient.

The reaction by the interfacial polycondensation method is usually a reaction between a dihydric phenol and phosgene, and is carried out in the presence of an acid binder, a catalyst 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.

  Examples of the organic solvent include halogenated hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane, 1,1-dichloroethane, bromoethane, butyl chloride, chloropropane and chlorobenzene, and methylene chloride is particularly preferably used. These solvents are used alone or in combination of two or more.

Examples of amine catalysts used for promoting the reaction include tertiary amines such as triethylamine, tetra-n-butylammonium bromide, and tetra-n-butylphosphonium bromide, quaternary ammonium compounds, and quaternary phosphonium compounds. In particular, triethylamine is preferably used.
The reaction temperature by the interfacial polycondensation method is preferably 0 to 40 ° C., the reaction time is about 10 minutes to 5 hours, and the pH during the reaction is preferably kept at 9 or more.

  In such a polymerization reaction, a terminal stopper is usually used. Monofunctional phenols can be used as such end terminators. Monofunctional phenols are commonly used as end terminators for molecular weight control, and the resulting polycarbonate resins are compared to those that do not because the ends are blocked by groups based on monofunctional phenols. Excellent thermal stability. Examples of such monofunctional phenols include phenol, p-tert-butylphenol, p-cumylphenol, and isooctylphenol.

  These end terminators are desirably introduced at the end of at least 5 mol%, preferably at least 10 mol%, based on all the ends of the obtained polycarbonate resin. You may mix and use.

The molecular weight of the polycarbonate resin is preferably 1 × 10 ⁴ to 4 × 10 ^{4 in} terms of viscosity average molecular weight (M), more preferably 1.3 × 10 ^{4 to} 3 × 10 ⁴ , and 1.6 × 10 ^{4 to} 2.4. × 10 ⁴ is particularly preferred. A polycarbonate resin having such a viscosity average molecular weight is preferable because sufficient strength can be obtained, and the melt fluidity at the time of molding is good and molding distortion does not occur. The viscosity average molecular weight is obtained by inserting the specific viscosity (η _sp ) obtained from a solution obtained by dissolving 0.7 g of a polycarbonate resin in 100 ml of methylene chloride at 20 ° C. 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

  The organic solvent solution of the polycarbonate resin obtained by the above reaction is usually washed with water. This washing step is preferably performed with water having an electric conductivity of 10 μS / cm or less, such as ion-exchanged water, and more preferably 1 μS / cm or less. The organic solvent solution and water are mixed and stirred, and then allowed to stand. Alternatively, the organic solvent solution phase and the aqueous phase are separated using a centrifuge or the like, and the organic solvent solution phase is removed repeatedly to remove water-soluble impurities. By performing water washing, water-soluble impurities are removed, and the hue of the obtained polycarbonate resin is improved.

The organic solvent solution of the polycarbonate resin described above is preferably subjected to acid cleaning or alkali cleaning in order to remove impurities such as a catalyst.
As the acid used for the acid cleaning, an aqueous solution of phosphoric acid, hydrochloric acid, sulfuric acid or the like is preferably used, and an aqueous solution having a concentration of 0.0004 to 40 g / liter (or pH 5 or less) is preferably used. Examples of the alkali used for the alkali cleaning include alkali metal compounds such as sodium hydroxide and potassium hydroxide, and alkaline earth metal compounds such as calcium hydroxide, barium hydroxide and magnesium hydroxide, and sodium hydroxide is particularly preferably used. Preferably, an aqueous solution having a concentration of 0.1 to 20 g / liter (or pH 11.5 or more) is used.

The ratio of the aqueous solution and the organic solvent solution used for alkali cleaning or acid cleaning is expressed as an aqueous solution / organic solvent solution (volume ratio) in the range of 0.2 to 1.5, so that the cleaning is performed efficiently. preferable.
The organic solvent solution that has been washed with water is then subjected to an operation of removing the solvent to obtain a polycarbonate resin powder.

  As a method (granulation process) for obtaining a polycarbonate resin granule, since the operation and post-treatment are simple, the agitation state is carried out in the granulation apparatus in which the polycarbonate granule and hot water (about 40 to 90 ° C.) are present. Then, a method of producing a slurry by continuously supplying an organic solvent solution of polycarbonate resin and evaporating the solvent is preferably employed. As the granulator, a mixer such as a stirring tank or a kneader is preferably employed.

  Such a slurry can then be hydrothermally treated. The hot water treatment step includes supplying the slurry to a hot water treatment container containing hot water at 90 to 100 ° C., or supplying the slurry to the hot water treatment vessel by blowing steam or the like to bring the water temperature to 90 to 100 ° C. The organic solvent to be removed is removed.

  The slurry discharged in the granulation step or the slurry after the hydrothermal treatment is preferably removed to some extent water and organic solvent by filtration, centrifugation, etc., and a wet paste of polycarbonate resin is recovered.

  The polycarbonate resin wet paste is then dried. The dryer may be a conduction heating method or a hot air heating method, and the polycarbonate resin may be allowed to stand, be transferred, or stirred. Of these, a grooved or cylindrical dryer in which the polycarbonate resin is stirred by a conductive heating method is preferable, and a grooved dryer is particularly preferable. The drying temperature is preferably in the range of 130 ° C to 150 ° C.

  In the present invention, the shape of the aromatic polycarbonate resin supplied to the kneading and extrusion treatment may be any of powder, fine particles, flakes, and pellets, preferably powder, fine particles, or flakes. Is.

  In the present invention, the aromatic polycarbonate resin supplied to the kneading extrusion treatment preferably has a chlorine atom content of 5 to 2000 ppm, and more preferably 5 to 1500 ppm. When the chlorine atom content is in the above range, the object of the present invention is effectively achieved.

In the present invention, the extruder used for kneading and extruding the aromatic polycarbonate resin granules is a commonly used twin-screw extruder with a vent. The number of vents is preferably 2 or more, more preferably 2 to 6 and even more preferably 3 to 5. When the number of vents is one, the amount of residual chlorine ions in the obtained polycarbonate resin molded product tends to increase, and when the number of vents increases too much, L ₃ / D (L ₃ ; Since the entire length of the screw (D: inner diameter of the cylinder) becomes longer, adverse effects such as resin burns and resin deterioration tend to occur.

The twin-screw extruder is provided with a mechanism (water injection part) for injecting at least one water upstream of the vent, and the water injection part may be smaller than the number of vents, and 1 to 5 points. Is preferable, and 2-3 places are more preferable. When the number of water injection points is two or more, it is easy to achieve a reduction in the amount of residual chlorine ions in the polycarbonate resin molded product, which is the object of the present invention. In addition, it is not necessary to install the water injection location on the upstream side of the vent in all the vents, and the water injection position may be determined as necessary. L ₃ / D of the entire screw configuration of such an extruder is preferably in the range of 28 to 49, more preferably in the range of 31.5 to 45.5.

  In the present invention, the screw configuration of the kneading portion immediately below the location (water injection portion) where water is injected is important. Such a screw configuration is configured in the order of a seal ring, an orthogonal kneading disc or a forward feed kneading disc, a reverse feed kneading disc, and a seal ring from the upstream side.

  The kneading disc used here is preferably a double thread type. The kneading angle of the kneading disk is preferably 15 to 90 degrees, more preferably 45 to 90 degrees. Each kneading disk is composed of a plurality of disks, and the number of disks is preferably 3 to 7, more preferably Preferably 4-6 sheets.

The length (L ₁ ) of each screw element in the kneading part is in the range of 0.25D to 1.0D, preferably in the range of 0.5D to 0.75D.
Furthermore, L ₂ / D (L ₂ ; length of the kneading part) of the kneading part having the material seal mechanism from the seal ring to the seal ring is in the range of 1 to 4, preferably 1.5 to 3.5. Range.

  By setting the kneading part immediately below the water injection part to the screw configuration as described above, the content of the chlorine compound in the polycarbonate resin is reduced, and the molded product formed from the obtained pellet is eluted with chlorine ions by water. The amount is small, and it is suitably used as a storage and transfer container for silicon wafers and magnetic disks.

  If the water injection amount added from the water injection part is too small, the effect of water injection addition will not be exhibited, the chlorine atom content in the resulting polycarbonate resin pellets will not be reduced, and if it is too large, the deaeration in the vent part will be prevented. Is insufficient, and the polycarbonate resin is adversely affected by hydrolysis and the like. Therefore, the water injection amount in each water injection portion is preferably 0.1 to 5 parts by weight per 100 parts by weight of the polycarbonate resin. 2 to 4 parts by weight is more preferable.

  The water to be injected preferably has an electric conductivity measured at 25 ° C. of 1 μS / cm or less, and more preferably 0.5 μS / cm or less. Use of water having an electric conductivity of 1 μS / cm or less is preferable because hydrolysis of the polycarbonate resin is less likely to occur, and a decrease in the molecular weight of the resin is suppressed.

Furthermore, the degree of vacuum in each vent of the twin screw extruder is 6.7 kPa or less, and preferably 2.0 kPa or less. If the degree of vacuum is within the range, it is preferable that the injected and added water is sufficiently removed at the vent, the amount of chlorine atoms is reduced, and the aromatic polycarbonate resin is not adversely affected by hydrolysis or the like.
Moreover, the resin temperature at the time of kneading and extruding the polycarbonate resin is appropriately set depending on the molecular weight of the polycarbonate resin, and about 270 to 320 ° C. is preferably used.

The polycarbonate resin pellet obtained by the above-described method is molded by a usual method such as extrusion molding or injection molding. Molded articles formed from such polycarbonate resin pellets have a marked decrease in the amount of chloride ions eluted with water. Specifically, 80 ° C. The polycarbonate resin molded article in water after 24 hours of heat treatment, and the amount of chlorine ions eluted from the molded article in water 10 ng / cm ² or less, preferably 9 ng / cm ² or less is there. Although a minimum is not specifically limited, It is difficult to make it 0.5 ng / cm < ² > or less. Such a molded article is suitably used as a container for storing and transporting silicon wafers and magnetic disks.

  According to the present invention, in the kneading part of the water injection part, by using a twin screw extruder with a vent having a material seal mechanism having a screw having an excellent water dispersion effect, a polycarbonate resin is melt-extruded to obtain a silicon wafer. Polycarbonate resin pellets suitably used as a material for forming a storage and conveyance container that can reduce surface contamination such as magnetic disks and magnetic disks can be obtained.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. In addition, the part in an Example is a weight part and% shows weight% unless there is particular notice. Evaluation was performed by the following method.

(1) Chlorine ion amount: A sample plate having a thickness of 1 mm obtained by injection molding of polycarbonate resin pellets is cut into a size of 20 mm in length and 25 mm in width, put in an extraction pack and sealed with 15 cm ³ of ultrapure water. After heating at 80 ° C. for 24 hours, the mixture was allowed to cool to room temperature, and then Cl ⁻ in water was quantified by ion chromatography to determine the amount of Cl ⁻ extracted per 1 cm ³ of the surface area of the molded product. The apparatus and conditions used are as shown in Table 1 below.

(2) Chlorine atom content: Polycarbonate resin pellets are completely burned, and the generated hydrogen chloride (HCl) is titrated with silver ions (Ag ⁺ ), and the chlorine atom content is determined from the amount of electricity required for this potential titration. It was.

(3) Hue (b value of pellet): The b value was measured using a hue meter (Nippon Denshoku Co., Ltd. Z-II). The higher the b value, the more yellowish it is, indicating that the thermal stability at the time of melt extrusion of the polycarbonate resin was inferior.

[Examples 1 to 7 and Comparative Examples 1 to 4]
Screw diameter with three vents (V1, V2, V3 from the vent near the hopper) and a water injection part (referred to as W1, W2 from the water injection point close to the raw material supply hopper) just before the vents V2, V3 30 mmφ twin screw extruder [manufactured by Nippon Steel Works, TEX30α, L ₃ /D=45.5 of the entire screw configuration] is supplied with the raw material resin described in Table 2, and in the form of a strand under the extrusion conditions described in Table 2 To produce pellets. The evaluation results are shown in Table 3.
In addition, the symbol of the raw material resin in Table 2 and the screw of a water injection | pouring part shows the following.

Resin raw material A: Polycarbonate resin powder having a viscosity average molecular weight of 18500 (chlorine atomic weight 50 ppm) obtained by reacting bisphenol A and phosgene in methylene chloride by a conventional method.
Resin raw material B: Polycarbonate resin powder having a viscosity average molecular weight of 18500 (chlorine atom weight 236 ppm) obtained by reacting bisphenol A and phosgene in methylene chloride by a conventional method.

Screw A: Extruder water injection part A seal ring (length 0.5D) is arranged at a location 1.0D upstream from the nozzle hole, and an orthogonal kneading disk (length 0.5D; length 0) is provided downstream from the ring. .2 discs (consisting of 5 1D discs) and 2 reverse kneading discs (length 0.5D; comprising 5 discs of length 0.1D), followed by a seal ring (length 0. 5D) screw shape of the water injection part (the twist angle of the screw element of the kneading part is 90 degrees for the orthogonal kneading disk and 45 degrees for the reverse feeding kneading disk, and L ₂ / D is 3.0D ).

Screw B: A seal ring (length 0.5D) is arranged at a location 1.0D upstream from the nozzle hole of the water injection portion of the extruder, and a kneading disc (length 0.5D; length 0) is fed forward from the ring. .3 discs (consisting of 5 1D discs), 1 reverse disc kneading disc (length 0.5D; consisting of 5 discs of length 0.1D), and seal ring (length 0. 5D) is the screw shape of the water injection part (the twist angle of the screw element in the kneading part is 45 degrees for the forward kneading disk and 45 degrees for the reverse kneading disk, and L ₂ / D is 3.0D. ).

[Example 8 and Comparative Example 5]
Using the pellets obtained in the examples and comparative example 1, a storage transfer container for silicon wafers was formed. This silicon wafer storage and conveyance container was immersed in warm water at 80 ° C. for 24 hours. After that, the container was dried, a predetermined number of silicon wafers were inserted into this container, kept at room temperature for one week in a sealed container, the silicon wafer was taken out, and the contact angle between water and the wafer surface was measured at five locations on the surface. . The average contact angle measured is shown in Table 4.

Claims (7)

In a method of producing polycarbonate resin pellets by melt-extruding polycarbonate resin granules using a twin screw extruder and pelletizing to produce polycarbonate resin pellets, a mechanism for injecting at least one water upstream of the vent as the twin screw extruder (water injection) And a screw configuration of a kneading part immediately below the water injection part, while injecting water from the water injection part and adjusting the degree of vacuum of the vent to 6.7 kPa or less. In the order of the seal ring, the orthogonal kneading disk or the forward kneading disk, the reverse kneading disk, and the seal ring from the upstream side, and the length (L ₁ ) of each screw element of the kneading part is 0.25D in the range of; (inner diameter of the cylinder D), _L 2 / D of the kneading portion ～1.0D; to the _{(L 2} length of kneading zone) 1-4 range Method for producing a polycarbonate resin pellet, characterized in that. The twin-screw extruder, the entire screw configuration L _{3 / D;} the production method of the polycarbonate resin pellets according to claim 1 wherein (L 3 total length of the screw) is in the range of 28-49.   The method for producing a polycarbonate resin pellet according to claim 1, wherein the biaxial extruder has 2 to 6 vents and 1 to 5 water injection portions.   The method for producing a polycarbonate resin pellet according to claim 1, wherein the amount of water injected in each water injection part is 0.1 to 5 parts by weight per 100 parts by weight of the polycarbonate resin.   A container for transporting silicon wafers or magnetic disks formed from polycarbonate resin pellets obtained by the manufacturing method according to claim 1. A polycarbonate resin molded product, wherein the amount of chlorine ions eluted from the molded product into water after heating the polycarbonate resin molded product in water at 80 ° C. for 24 hours is 10 ng / cm ² or less.   A molded article of polycarbonate resin, wherein the molded article according to claim 6 is a storage / container for a silicon wafer or a magnetic disk.