JPH11291304A - Manufacture of polycarbonate resin molding material and transparent molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of a gelled material in a method for producing a polycarbonate resin molding material by extruding a polycarbonate resin powder in a molten state. SOLUTION: In a method for producing a polycarbonate resin molding material by extruding a polycarbonate resin powder in a molten state, the interior of the cylinder of an extruder and/or the housing and metal element of the resin filter provided to the extruder is filled and replaced with nitrogen and, thereafter, the molten resin is passed through the extruder to substantially suppress the generation of a gelled material caused by the resin filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polycarbonate resin molding material and a transparent molded article obtained by molding the obtained molding material. The invention relates to a resin filter in an extruder cylinder and / or an extruder. The present invention relates to a method for producing a resin in which the generation of a gelled substance caused by passing a molten resin through a resin filter after a specific pretreatment is performed, and a transparent molded article having no gelled substance or having little effect on the appearance.

[0002]

2. Description of the Related Art As a method of producing a molding material from a polycarbonate resin solution, a method of separating a resin from a solution, drying the resin, and pelletizing the resin with an extruder has been used.

However, since extrusion of the polycarbonate resin is performed under high temperature conditions, it has been considered that a part of the raw material is thermally decomposed to generate a gel, a carbide, and the like.

Polycarbonate resins are used for optical and medical applications and as sheets for building materials because of their excellent transparency. For optical discs, foreign matter on the order of microns causes errors in signal writing and reading, resulting in information reliability. In addition, foreign substances that can be seen in medical supplies and building material sheets reduce the strength of the product and the commercial value of the product due to its transparent appearance.
A resin filter is installed for filtering the molten resin.

[0005]

However, it takes more than 20 hours from the start of the extrusion to the time when the operating condition is stabilized and the generation of foreign substances such as gels and carbides becomes less than a predetermined amount. Production efficiency was significantly deteriorated. Of these, the gelled material that remains in the extruded polycarbonate resin without being caught and removed by the resin filter is different from a foreign material having a clear nucleus such as a metal foreign material or a resin or carbonized carbide in a subsequent molded product, and is visually or microscopically. There was no nucleus in the observation, but when it was made into a molded product, the phenomenon of light scattering (silver) occurred, which was a cause of failure of signal errors of optical discs and poor appearance of medical supplies and building material sheets. .

Japanese Patent Application Laid-Open No. Hei 2-135222 discloses a method for controlling the occurrence and increase of gelation due to an extrusion operation by adjusting the degree of depressurization of a vent so as not to make it too high. The vent is for removing impurities such as low molecular weight substances and solvents contained in the polycarbonate resin.If the degree of pressure reduction is not too high, the removal of impurities becomes insufficient, and as a result, the molded product is injected. This is not a complete solution because it causes poor appearance of the molded article and mold contamination during molding, causing a significant decrease in productivity in the production of the molded article.

Therefore, the present inventors studied an extruder, a resin filter, and the like in order to reduce the generation of a gelled product.
The air that has accumulated in the extruder cylinder and in the resin filter comes into contact with the molten resin and causes thermal decomposition of the resin, which causes the formation of gelled substances, and the treatment of the extruder cylinder and resin filter in a specific manner The present inventors have found that the formation of a gelled substance is substantially suppressed by carrying out the method, and arrived at the present invention.

[0008]

That is, the present invention relates to a method for producing a polycarbonate molding material by melt-extruding a raw material powder of a polycarbonate resin, comprising a resin filter housing mounted in an extruder cylinder and / or mounted on the extruder. This is a method for producing a polycarbonate resin molding material in which generation of a gelled substance by passing a molten resin when a metal element is filled with nitrogen is substantially suppressed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polycarbonate resin comprises bisphenol as a monomer,
Aromatic polycarbonate resin produced by transesterification, pyridine method, or the like, by bonding bisphenol to carbonic acid ester.

[0010] Representative examples of bisphenols include:
2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenol) ethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 1,1-bis ( 4-hydroxyphenyl) cyclohexane and the like. Preferred bisphenols are bis (4-hydroxyphenyl) alkane-based compounds, particularly 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A). Bisphenols can be used alone or in combination of two or more. Further, the present invention can be applied to a transparent resin such as a graft copolymer of the polycarbonate resin and another resin.

In the present invention, for example, in the case of the phosgene method, the polycarbonate resin powder is obtained by separating the polycarbonate resin solution from the polymerization solution, washing and purifying, and further removing foreign substances and ionic impurities by microfiltration, centrifugation and the like. To obtain a solution of the purified polycarbonate resin.

[0012] The following resin separation method includes:
A method of concentrating and gelling a resin solution as it is or a resin solution to which a poor solvent is added to such an extent that precipitation does not occur ("
"Gel concentration method": solvent evaporation gelation, flash concentration gelation, etc.), or "hot water dropping method" in which the resin solution is dropped into warm water to evaporate the solvent and gel. For example, a "precipitation method", which is a method of dropping or adding a poor solvent to the resin solution, is employed.

[0013] Polycarbonate resin powder is defined as a method in which water is added to a wet powder obtained by the "hot water dropping method" or a powder obtained by the precipitation method, and the solvent is distilled off by heating while appropriately performing wet grinding. It is a wet powder produced.
A method in which the wet powder is introduced into an extruder from which a volatile component can be easily removed from the vent portion and the solvent is distilled off together with the extrusion is preferable from the viewpoint of preventing thermal deterioration since there is no heat history in the drying step.

In the present invention, various extruders such as a single-screw extruder with a vent, a twin-screw extruder with a vent, a multi-screw extruder with a vent, or a special extruder such as a co-kneader or a planetary screw extruder are used. Can be used.

The inner surface of the extruder barrel used in the present invention is made of chrome tungsten steel (SKS) or chrome vanadium steel (S
KD), nickel chrome steel (SNC), nickel chrome molybdenum steel (SNCM), chromium molybdenum steel (SC
M) or aluminum chrome molybdenum steel (SACM)
And the like. Nitriding of a high-strength steel material such as Stellite, Hastelloy, or Colmonoy is particularly preferable. Further, as the screw, chromium tungsten steel (SKS), chromium vanadium steel (SKD), nickel chrome steel (SNC), nickel chromium molybdenum steel (SNCM), and chromium molybdenum steel (SCM) were hard chromium plated or Ni Kanigen plated. Steel, heat-treated martensitic stainless steel, or chrome tungsten steel (SK
S), chrome vanadium steel (SKD), nickel chrome steel (SNC), nickel chrome molybdenum steel (SNC)
M), chromium molybdenum steel (SCM) as a base material, and stellite overlaid on a mountain material is used. In particular, chrome vanadium steel (SKD), nickel chrome steel (SN)
C), preferably, hard chromium plating or Ni Kanigen plating on chromium molybdenum steel (SCM) or nickel chromium molybdenum steel (SNCM).

Austenitic stainless steel is usually used for the resin filter element of the present invention. For example, SUS304, SUS304L, SUS316, S
US316L, SUS309S, SUS310S, SU
S317 and SUS317L can be mentioned. Nominal filter diameter of resin filter is usually 1-100μ
m, preferably 1 to 60 μm, more preferably 2 to 4
0 μm. Examples of the filter include various types such as a disk filter, a leaf disk filter, a cylindrical filter, and a tube type filter, and a leaf disk filter and a disk filter are particularly preferable. The filter medium is desirably a metal fiber sintered body in which a metal fiber is formed into a nonwoven fabric and the nonwoven fabric is sintered to be a porous body.

In the case of a resin filter, the filter element is fixed in a housing, and before or after being mounted on the extruder, nitrogen is flowed and filled at normal pressure or slightly pressurized. Even if the porosity is high, even if nitrogen is circulated in the cylinder and displaces the remaining air, even if the molten polycarbonate resin subsequently comes into the extruder cylinder or the filter part, it will come into contact with the air. In addition, gelation due to thermal decomposition is suppressed.

The determination of the gelled product is performed by forming a film of 50 kg to 200 μm from 1 kg of the polycarbonate resin pellets, detecting a foreign material of 50 μm or more by a CCD optical camera, and discriminating the gelled product by visual or microscopic observation. How to confirm. Although the number of gelled substances slightly differs depending on the thickness of the film,
Pcs / Kg or less, preferably 10 pcs / Kg or less, more preferably 5 pcs / Kg or less.

[0019]

Hereinafter, the present invention will be described with reference to examples and the like.
The present invention is not limited in any way by these examples.

In the measurement of the gelled product in Examples and the like, 1 kg of the polycarbonate resin pellet was measured at 150 to 200 μm.
Of 50μ with a CCD optical camera
m or more foreign substances were detected, and among them, those which were visually identified as gelled substances were confirmed.

Example 1 Using a 50 mmφ vented extruder (barrel inner surface: spraying Colmonoy, screw: hard chrome plating on chromium molybdenum steel), using a filter element made of SUS316L having a nominal filtration diameter of 40 μm as a resin filter, and mounting it on the housing After setting, the inside of the filter element and the housing were replaced with nitrogen, and then attached to an extruder.
Further, after flowing nitrogen to replace the voids in the extruder cylinder with nitrogen, the polycarbonate resin powder is extruded at a high temperature (330 ° C.), and the degree of vacuum of the vent is reduced to 20 Torr or less. The number of gelled materials was measured by molding and foreign matter inspection. In addition, the above-mentioned pellet was prepared by an injection molding machine to have a diameter of 120 mm and a thickness of 1.2 mm.
200 mm disks were molded, and the number of generated silver due to the gel was measured. Table 1 shows the results.

COMPARATIVE EXAMPLE 1 For the purpose of comparison, the pellets obtained in the same manner as in Example 1 except that nitrogen replacement in the filter element, the housing, and the extruder cylinder were not performed, and the pellets were subjected to injection molding. A silver test was performed in the same manner as in Example 1 due to the gelation of the obtained disk. The results are shown in Table 1.

[0023]

[Table 1] Number of nitrogen-substituted gels (pieces / kg) Silver generation rate (sheets / sheet) ──────────────────────────── ─────── Example 1 Yes 5 1.5% Comparative Example 1 No 299 13%

[0024]

According to the present invention, in a method for producing a polycarbonate resin molding material by melt-extruding a polycarbonate resin powder, a gelled material which cannot be removed by a resin filter by a very simple operation is substantially contained. Polycarbonate resin molding materials can be manufactured, and are suitably used as molding materials for optical disks, medical supplies, or sheets for building materials.

Claims (4)

[Claims] 1. A method for producing a polycarbonate resin molding material by melt-extruding a polycarbonate resin powder, wherein a housing and a metal element of a resin filter mounted in an extruder cylinder and / or the extruder are filled and replaced with nitrogen. A method for producing a polycarbonate resin molding material, wherein the generation of a gelled substance by a filter is substantially suppressed by passing a molten resin. 2. The method according to claim 1, wherein the resin filter element is austenitic stainless steel. 3. The resin filter element is made of SUS30.
4, SUS304L, SUS316, SUS316L,
The method for producing a polycarbonate resin molding material according to claim 2, wherein the method is at least one selected from SUS309S, SUS310S, SUS317, and SUS317L. 4. A transparent molded article obtained by molding the polycarbonate resin molding material obtained by the production method according to claim 1 by at least one of injection molding, extrusion molding and compression molding.