JPH0618890B2 - Polycarbonate molding material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low molecular weight polycarbonate molding material suitable for a molding material for optical discs, which is less likely to produce silver.

[Conventional technology]

Polycarbonate resin is excellent in transparency, heat resistance, and low water absorption, and therefore, it has recently begun to be used as a molding material for optical applications, especially for optical disks. Since it is necessary to read and write signals of micron order with a laser beam in the optical disk, if there is a defect of micron order or more in the substrate of the optical disk, reading and writing cannot be performed and the error rate deteriorates. Black spots due to heat deterioration of the resin are well known as such defects, but there are other linear defects called silver. Regarding black spots, measures have been taken by incorporating an organic phosphite into a polycarbonate resin (JP-A-58-58).
126119).

On the other hand, silver has been regarded as a problem because it generally has a large shape, but the cause is considered to be insufficient drying of the moisture content of the pellet immediately before molding of 0.01% or more, or improper molding conditions. Most of the various measures have been taken. However, the current situation is that it has not been possible to reduce the defective rate due to silver to 1% or less.

[Object of the Invention]

The inventors of the present invention have conducted a cause investigation to suppress the generation of silver particularly in the molding of an optical disk substrate. Surprisingly, it is caused by the presence of fine powder having a particle diameter of 1 mm or less in the granular body. The present invention has been discovered and the present invention has been reached.

That is, a molding material composed of polycarbonate pellets having a molecular weight of 10,000 to 18,000, wherein the content of the powdery weight material having an average particle diameter of 0.5 mm or less in the molding material is 2.0% by weight or less, It was found that the generation of silver can be suppressed by using a polycarbonate molding material characterized by having a radius of 1 mm or less.

[Structure of Invention]

 The present invention will be specifically described below.

The polycarbonate resin of the present invention is a polymer or copolymer obtained by a phosgene method in which various dihydroxydiaryl compounds are reacted with phosgene, or a transesterification method in which dihydroxydiaryl compounds are reacted with a carbonic acid ester such as diphenyl carbonate. A typical example of the union is a polycarbonate resin produced from 2,2-bis (4-hydroxyphenyl) propane (bisphenol A).

Examples of the dihydroxydiaryl compound include bisphenol A, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, and 2,2
-Bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) octane, bis (4-hydroxyphenyl) phenylmethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane 1,1-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-hydroxy-3,5dibromophenyl) Enenyl) propane, 2,2-bis (4-hydroxy-
Bis (hydroxyaryl) alkanes such as 3,5 dichlorophenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclopentane, such as 1,1-bis (4-hydroxyphenyl) cyclohexane Dihydroxy diaryl ethers such as bis (hydroxyaryl) cycloalkanoic acid, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether, 4,4'-dihydroxy Diphenyl disulfides such as diphenyl sulfide, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide, 4,4'-dihydroxy diphenyl sulfoxide, 4,4'-dihydroxy Dihydroxydiaryl sulfoxides such as -3,3'-dimethyldiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfoxide Sulfone, 4,
Examples thereof include dihydroxydiarylsulfones such as 4'-dihydroxy-3,3'-dimethyldiphenyl sulfone.

These may be used alone or in combination of two or more,
In addition to these, piperazine, dipiperidyl, hydroquinone, resorcin, 4,4′-dihydroxydiphenyl and the like may be mixed and used.

Since optical components such as optical discs are required to have no optical distortion, the molecular weight is 10,000 to 18,000, preferably
Must be in the range 11000-17000. The molecular weight (M) as used herein is determined from the Schnell's viscosity formula [η] = 1.23 × 10 ^-5 M ^0.83 by determining the intrinsic viscosity [η] of a solution using methylene chloride as a solvent using an Ostwald viscometer.

Polycarbonate molding materials for optical parts such as optical discs have low viscosity, so there is little shear heat generation by the screen of the molding machine, and it is usually 1 mm in granules (pellets) with a particle size of 2-4 mm. A finely divided polymer having a diameter not larger than that can be melted only by heat from the cylinder. However, since a polymer such as polycarbonate has a low thermal conductivity, a finely divided polymer is injection-molded in an unmelted state and is observed as a silver-like defect in a molded product. Therefore, if the content of the powdery polymer is more than 2.0% by weight, unmelted powder is likely to occur and silver is often generated. If 2.0% by weight or less, preferably 1.0% by weight or less, For example, the defective rate due to silver can be suppressed to 1 to 2% or less, and the target required for optical applications can be achieved.

In the polycarbonate molding material of the present invention, in order to reduce the content of the polycarbonate powder having an average particle diameter of 0.5 mm or less to 2% or less, the cutting conditions in the cutting process of cooling the molten polymer into pellets are optimized to obtain powder. It is necessary to minimize the amount of generation and to suppress the generation of powder as much as possible even after pelletization, by reducing the mechanical shearing force applied to the pellet as much as possible throughout the entire process. In particular, it minimizes collisions between pellets, pellets in the pellet transporting process such as drying process, compounding process, packaging process, and pellet transporting process connecting these processes, and rotation in all unit operations. It is important not to use means such as a mechanical stirrer to provide a strong shear history. Since the polycarbonate having a relatively low molecular weight of 10,000 to 18,000 as used in the present invention has low strength, powder is likely to be generated in the cutting process for pelletizing. Therefore, wear of the cutter blade during pelletization, temperature of the strand, etc. are major factors in the generation of powder. Further, regarding the polycarbonate powder which is inevitably generated in the manufacturing process, it is possible to reduce the powder at the final stage of the manufacturing process. A mechanical method such as a vibrating screen is well known as a method for removing powder. However, it is difficult to satisfactorily remove the fine powder adhering to the pellet surface by a mechanical method, and when performing special powder removal such as washing with water, the process becomes complicated and the production efficiency is lowered. Therefore, it is more preferable to minimize the amount of powder generated in the manufacturing process and further reduce the amount of powder in the final process.

The total amount of powder in the polycarbonate pellet of the present invention is measured by the following method. After weighing 100 to 200 g of polycarbonate pellets, the pellets are placed in a stainless steel mesh container of 30 mesh and shaken well in 300 to 400 cc of methanol to wash the pellets, and the powder is separated in methanol. The powder separated here usually has a particle size of 1 mm or less.

Separate this wash with a G4 glass filter. This operation is repeated until no suspended substance is observed in methanol. Usually, the weight of the residue taken in 4 to 5 times reaches a constant weight. The weight of this residue is the powder weight.

The above is the case where the additive is not surface-adhered to the pellet, but usually the additive is often mixed in polycarbonate, and especially the cleanliness of the molding chamber, such as optical disk, is set to class 1000 or less. In order to keep it, it is preferable that all the additives are kneaded. When the additive is surface-attached, the additive also migrates into methanol, so the additive must be qualitatively and quantitatively determined.
Since the specific method of analysis differs depending on the type of additive, it is only necessary to select the optimum quantification method for each additive.

Polycarbonate pellets are usually spherical particles with a diameter of 2.0 to 3.5 mm or cylindrical granules with a diameter and length of 2.0 to 4.0 mm. If the diameter or length is 2.0 mm or more, the shape is Is not particularly a problem.

To measure the average particle size of the powder, the powder having a particle size of 1 mm or less collected as described above is used in the visual field of 200 to
The maximum width of the particles (the maximum distance when the projected image of the particles is sandwiched by the two parallel lines in the plane) is measured for 1000 powder particles, and the arithmetic mean is taken.

INDUSTRIAL APPLICABILITY The molding material of the present invention is effective in a molding machine that is plasticized by a shearing force such as a screw, that is, an injection molding machine, an injection compression molding machine, an extrusion molding machine, and can be used in various materials such as a disk, a lens, a mirror, a nameplate, a sheet, and a plate. Processed into a thing.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1, 2 and Comparative Example 1 Bisphenol A and phosgene were polymerized by an interfacial polymerization method by a conventional method to obtain a polycarbonate powder having a molecular weight of 15,000 and organic phosphite (trisnonylphenylphosphite, ADEKA Mark 1178 made by Argus Co., Ltd.
After blending 05%, use a 40mmφ vent extruder to 250
It was extruded in a strand form at ℃ and cut for pelletization to obtain a cylindrical pellet having a diameter of 2.5 mm and a length of 3.0 mm. The average particle size and content of the powdery polymer of this granular material were measured by the method described above. The results are 0.
It was 41 mm and 2.8% by weight. The pellet was further shaken by shaking or washed with water to obtain a pellet containing powder as shown in Table 1.

These pellets were dried by the Karl Fisher method until the water content became 50 ppm, and a 120 mm diameter, 1.2 mm thick compact disk was molded by an injection molding machine (M-100DM manufactured by Meiki). Conditions are resin temperature 340
C., mold temperature 95.degree. C., injection rate 105 cc / sec.

200 sheets of this compact disk were continuously molded, the disks in which silver was generated were visually observed, the number of disks was measured, and the ratio of the disks in which silver was generated was measured as a defective rate. The results are shown in Table-1.

From this, it is shown that the generation of silver decreases sharply as the amount of fine powder decreases.

[Effect of the Invention] The molding material according to the present invention can prevent the generation of silver,
The utility value is extremely high because the defect rate can be significantly reduced.

Claims (3)

[Claims] 1. A molding material comprising polycarbonate pellets having a molecular weight of 10,000 to 18,000, wherein the content of the powdery polymer having an average particle diameter of 0.5 mm or less in the molding material is 2.0% by weight or less. Characteristic polycarbonate molding material. 2. The polycarbonate molding material according to claim 1, wherein the polycarbonate pellet is a granular body having a particle size of substantially 2 mm or more. 3. The polycarbonate molding material according to claim 1, wherein the powdery polymer has a particle diameter of 1 mm or less.