JPH0688251B2 - Polycarbonate resin pellet and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polycarbonate resin pellet having a special shape excellent in plasticization and metering property, and a method for producing the same. INDUSTRIAL APPLICABILITY The polycarbonate resin pellets of the present invention are excellent in plasticizing and metering properties, and are suitable for manufacturing optical precision molded products such as compact disks by injection molding with high temperature, high back pressure and high speed screw rotation.

[Conventional technology and its problems]

Compact discs made of polycarbonate resin and other precision molded products for optics that require transparency, low dust, and low birefringence are lower in birefringence than conventional polycarbonate resin molding materials for general molding. Using a viscous material, a so-called high flow material, at a high resin temperature of about 340 ° C, with a high back pressure to suppress the generation of silver,
High cycle molding is performed by high-speed screw rotation to improve productivity.

For this purpose, it is necessary as a molding material that the weighing be performed with high precision in order to reduce the variation in weight between shots, and that the plasticization time be short in order to shorten the molding cycle. Furthermore, if the shear friction resistance of the molten resin in the cylinder during plasticization fluctuates, oxidative deterioration and thermal decomposition due to partial frictional heating will be promoted, which will cause burns, black spots, and silver. For this reason, it is necessary to achieve the screw rotation with plasticization and smooth metering.

However, when high-flow materials are used and injection molding is performed at high temperature, high back pressure, and high-speed screw rotation, high-flow materials require longer time for plasticization, weighing, and screw rotation than general molding materials. Need to be overly fast.

Further, sometimes smooth screw rotation may not be achieved, which causes an increase in dust in the molded product, and there are drawbacks such that the molding cycle cannot be shortened.

[Means for solving problems]

As a result of earnestly studying the above-mentioned drawbacks from various viewpoints, the present invention has surprisingly found that the above-mentioned drawbacks can be largely solved by using a pellet having a special shape, and completed the present invention.

That is, the present invention has a viscosity average molecular weight Mv of 1.3 × 10 ⁴ to 1.
Regarding polycarbonate resin pellets for substantially curved cylindrical precision injection molding made of 9 × 10 ⁴ polycarbonate resin,
In a preferred embodiment, the diameter D, the length L and the height H of the polycarbonate resin pellet in the shape of a substantially curved column from the geodesic curve are 0.5 mm ≦ D ≦ 3.0 mm (1) 2.0 mm ≦ L ≦ 6.0 mm (2) 1.5 ≦ L / D ≦ 10 (3) H ≦ L (4) Polycarbonate resin pellets with viscosity average molecular weight Mv of 1.3 × 10 ^{4 to} 1.9 × 10 ⁴ When a polycarbonate resin melt is extruded from a nozzle of an extruder to produce resin pellets by hot cutting in water, an effective nozzle diameter D'of an extrusion die and an extrusion length L'of a strand are 0.4 mm ≤ D '≤ 2.8 mm. (1) ′ 1.5 ≦ L ′ / D ′ ≦ 10 (2) ′ The present invention relates to the production of a polycarbonate resin pellet having a curved columnar shape by cutting a strand.

The polycarbonate resin pellet having a substantially curved columnar shape according to the present invention has a high plasticity, a high plasticity required for injection molding at a high temperature, a high back pressure, and a high speed screw rotation, and a highly accurate metering property.

In the specially shaped polycarbonate resin pellets of the present invention, a substantially curved columnar shape means that its outer shape corresponds to a curved columnar shape, and as the shape of the cross section,
It may be circular, elliptical, triangular or other polygonal shape,
Further, the way of bending need not be uniform.

In FIG. 1 of the accompanying drawings, a is a schematic view showing an example of a substantially curved columnar pellet of the present invention, b is a schematic view of a spherical pellet by a hot cut method, and c is a schematic view of a pellet by strand cutting. It is a figure. It can be seen from FIG. 1 that the shape of the pellet according to the present invention is a special shape as compared with the conventionally known pellet.

In FIG. 1a, D: diameter, L: length, H: height from the geodesic line 1 and l: L geodesic line, respectively. These values are in the ranges represented by the above formulas (1) to (4), but preferably 1.0 mm ≦ D ≦ 3.0 mm (1) 3.0 mm ≦ L ≦ 5.0 mm (2) 2.0 ≦ L / D ≦ 6.0 (3) H ≦ 9 / 10L (4)

In the known extruded underwater hot-cut method, the polycarbonate resin pellets having a substantially curved columnar shape according to the present invention have a slower tamping for cutting the hot strand than usual (longer outflow molten strand length for cutting).
Is preferably manufactured by

That is, the relationship between the strand cutting timing and the effective nozzle diameter D'mm of the extruder die and the molten resin outflow length L'mm from the nozzle is 0.4 mm≤D'≤2.8 mm (1). ′ 1.5 ≦ L ′ / D ′ ≦ 10 (2) ′ More preferably, 0.8 mm ≦ D ′ ≦ 2.3 mm (1) ′ 2.0 ≦ L ′ / D ′ ≦ 6.0 (2) ′ It is manufactured by The effective nozzle diameter D'herein is a value that takes into account the fact that the die nozzle hole is partially blocked by the resin, and usually represents a value of about 50 to 80% of the die nozzle diameter.

In this case, the degree of curvature changes depending on the flow and temperature of the cooling water flow, the temperature at which the resin flows out, and can also be changed by changing the shape of the nozzle to a polygon such as a triangle or its flat shape. Therefore, it may be appropriately selected depending on the extruding material used and the like.

The curved columnar pellet of the present invention is preferably produced by the above method, but the production method of the curved columnar pellet of the present invention is not limited to the above method, for example,
This can be done by subjecting the tip of the nozzle of the die to work in the air extrusion.

The substantially curved columnar pellet of the present invention is suitable for producing a transparent low birefringence optical polycarbonate precision molded article by precision injection molding with high back pressure and high speed screw rotation, Shaped pellets, that is, a polycarbonate resin having a viscosity average molecular weight Mv of 1.3 × 10 ^{4 to} 1.9 × 10 ⁴ as described above, satisfying the conditions of the above formulas (1) to (4), and a precision injection molding machine screw Pellets that satisfy L ≦ 4 / 5C (5) with respect to the groove depth C of the feed part of
℃, especially high temperature of 320-360 ℃, high back pressure more than double the usual injection molding, precision injection molding by high cycle by high-speed screw rotation to produce transparent low birefringence optical polycarbonate precision molded products be able to.

〔Example〕

 Hereinafter, a specific description will be given with reference to examples.

Pellets of various shapes were manufactured using an optical polycarbonate resin having a viscosity average molecular weight Mv of 1.5 × 10 ⁴ (trade name: Iupilon H4000, manufactured by Mitsubishi Gas Chemical Co., Inc.).

Table 1 shows the shapes of these pellets and the manufacturing method thereof.

In the table, a normal product having a viscosity average molecular weight of 2.5 × 10 ⁴ (Mitsubishi Gas Chemical Co., Ltd., trade name: Iupilon S2000) is also described.

Precision injection molding machine (Mitsubishi Heavy Industries, Ltd., / 75MS, screw diameter 28mm) using various pellets obtained by the above method
Tests of plasticizing and metering ability by the method were carried out under various conditions. The results are shown in the attached FIG. 2 and Table 2 below.

The plasticizing ability is defined as follows, and the larger the value, the better the ability.

Q / N: Plasticization capacity, plasticization amount per screw rotation.

-Plastification amount Q = W x (3600 / tp) [kg / H] [W: weight of one shot, tp: time required for plasticization] -rotation speed N [rpm] From Fig. 2, the curve of the present invention It is clear that the cylindrical pellets have a plasticizing capacity of about 2 cups as compared with the pellets of other shapes, and Table 2 shows that the weighing accuracy is comparable.

As a reference, Table 3 shows the results of testing the sub-refractivity of the compact disc substrate obtained by injection molding using the pellets A and C.

[Operations and Effects of the Invention] As is clear from the above, the substantially curved columnar pellet of the present invention is extremely fast in plasticizing / measuring as compared with the conventional ordinary pellets, because it is achieved by smooth screw rotation. High-cycle molding is possible without difficulty, and deterioration due to local heat generation due to shearing is extremely unlikely to occur, so that a precision molded product with low birefringence and low dust can be easily obtained.

[Brief description of drawings]

1A to 1C are schematic views showing the shape of polycarbonate resin pellets, and FIG. 2 is a graph showing the measurement results of the plasticizing ability of various pellets. In FIG. 1, reference numerals indicate geodesic curves for measuring D: diameter, L: length, H: height, and l: height L, respectively, and in FIG. Curved cylindrical pellet, B: Spherical pellet by hot cut method, C: Normal shape pellet,
CL: Large diameter pellet, DS: Small diameter pellet, D: Normal product pellet.

Claims (4)

[Claims] 1. A polycarbonate resin pellet for precision injection molding of a substantially curved columnar shape, which is made of a polycarbonate resin having a viscosity average molecular weight Mv of 1.3 × 10 ^{4 to} 1.9 × 10 ⁴ . 2. The diameter D, the length L, and the height H of the length from the geodesic curve of the polycarbonate resin pellet having a substantially curved columnar shape are 0.5 mm ≦ D ≦ 3.0 mm (1) 2.0 mm ≦ L ≦ 6.0 mm (2) 1.5 ≦ L / D ≦ 10 (3) H ≦ L (4) The polycarbonate resin pellet according to claim 1. 3. When a polycarbonate resin melt is extruded from a nozzle of an extruder to produce resin pellets by hot cutting in water, an effective nozzle diameter D'of an extrusion die,
The extruded length L'of the strand is 0.4 mm ≤ D'≤ 2.8 mm (1) '1.5 ≤ L' / D '≤ 10 (2)' A method for producing substantially curved cylindrical polycarbonate resin pellets. 4. A viscosity average molecular weight Mv of a polycarbonate resin
Is 1.3 × 10 ^{4 to} 1.9 × 10 ⁴ , the method for producing a substantially curved columnar polycarbonate resin pellet according to claim 3.