JPH0623827A - Production of polycarbonate sheet - Google Patents

Abstract

PURPOSE:To obtain polycarbonate sheet good in surface conditions and excellent in transparency by a method wherein a sheet-like material is cooled by a polishing roll having a plating layer of a specific thickness on its surface. CONSTITUTION:Polycarbonate or polycarbonate composition is kneaded, melted and extruded by using an extruder into the form of a sheet. The resulting sheet-like material is then cooled by using a specific polishing roll to obtain a polycarbonate sheet. This polishing roll has a hard chrome plating layer having a thickness of 20-80mum on its surface. The polycarbonate is the resin which is obtained by the condensation polymerization of divalent phenol compound, glycol monomer or the mixture thereof and carbonic acid derivative or by allowing phosgene to react with divalent phenol compound, glycol monomer or the mixture thereof in the presence of alkali.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a polycarbonate sheet by a melt extrusion method. More specifically, the present invention relates to a method for producing a polycarbonate sheet, in which a polycarbonate sheet extruded by a melt extrusion molding method is cooled using a polishing roll plated with hard chrome to a specific thickness.

[0002]

2. Description of the Related Art Polycarbonate sheet is a thermoplastic resin which has excellent mechanical and electrical properties in a wide temperature range, excellent transparency, and the highest impact resistance. It is molded and used in a wide range of fields.

Usually, when a polycarbonate resin is molded into a sheet, raw materials in the form of powder or pellets are kneaded using an extruder, melt-extruded into a sheet through a T-die or the like, and cooled using a polishing roll. Then, a method of manufacturing a sheet is adopted.

Polycarbonate sheets are used for window materials, nameplates, optical materials and the like by taking advantage of their excellent transparency, so that the die line generated in the extrusion process, gear marks, transfer marks, peel marks, etc. generated in the cooling process are transparent. , It is often the cause of impairing the see-through property (the sharpness of the image seen through the sheet).

As a method for solving such a problem, for example, Japanese Patent Publication No. 25450/51 discloses a polycarbonate sheet extruded from an extruder at 155 to 190.
A method has been proposed in which a pair of rolls having a surface temperature of ℃ holds and pressurizes them to cool them.

Further, Japanese Patent Publication No. 2-61899 discloses that
A method has been proposed in which the surface temperature of one of the pair of rolls is kept at 30 to 80 ° C. and the surface temperature of the other roll is kept at 100 to 140 ° C. to cool it.

However, when a polycarbonate sheet is manufactured according to these methods, plate-out (dirt on the surface of the roll) is gradually generated on the surface of the polishing roll, the surface roughness of the polycarbonate sheet is deteriorated, and the transparency of the obtained sheet is increased. The problem arises that This phenomenon is particularly remarkable when an ultraviolet absorber or the like is added to the raw material polycarbonate.

Conventionally, the surface contamination of the polishing roll is
A method of preventing the plate out of the roll is employed by removing it by wiping it off manually or mechanically with a cloth or the like. However, this method is not a satisfactory method because the fibrous material such as the cloth used as the wiping material adheres to the surface of the polishing roll as a foreign matter and is mixed into the polycarbonate sheet.

Conventionally, as a polishing roll, a roll having a surface plated with hard chrome having a thickness of about 100 μm has been used. However, a roll having a thick plating layer is made of iron as a base material layer of the roll. Due to the difference in coefficient of linear expansion from that of chromium, which is the plating layer, large cracks of 50 μm or more are likely to occur in the plating layer. When a polishing roll having a crack of 50 μm or more in the plating layer is used, the plate out phenomenon of the roll becomes severe, the surface of the obtained polycarbonate sheet is roughened, and a sheet having a good surface condition cannot be obtained.

[0010]

The object of the present invention is to solve the above technical problems, prevent the plate-out phenomenon of the polishing roll in the cooling step, and produce a polycarbonate sheet having a good surface condition and excellent transparency. To provide a method.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, the above object was achieved by using a polishing roll having a hard chrome plating layer of a specific thickness on the surface. They have found that they can do so and have completed the present invention.

That is, according to the present invention, a method for producing a polycarbonate sheet by kneading a polycarbonate or a polycarbonate composition using an extruder and melt-extruding to form a sheet, and cooling the sheet with a polishing roll, 20-80 μm thickness on roll surface
There is provided a method for producing a polycarbonate sheet, which comprises using a polishing roll having a hard chrome plated layer.

According to the present invention, a polycarbonate sheet having a good surface condition and excellent transparency can be produced.

The present invention will be described in detail below. The outline of the present invention is that a polycarbonate sheet or a polycarbonate composition is kneaded using an extruder, melted and extruded into a sheet through a die, and then the sheet is cooled using a specific polishing roll to form a polycarbonate sheet. It is a manufacturing method.

The polycarbonate used in the present invention is
For example, a resin obtained by a polycondensation reaction of a divalent phenol compound or glycol simple substance, or a mixture thereof with a carbonic acid derivative, or a divalent phenol compound or glycol simple substance or a mixture thereof in the presence of an alkali, An example is a resin obtained by reacting phosgene.

Of the above polycarbonates, those preferably used in the present invention are those represented by the following general formula (1)

[0017]

[Chemical 1] Is a polymer compound having a repeating structural unit represented by:

The polycarbonate is synthesized by reacting phosgene with 2,2-bis (4-hydroxyphenyl) propane in the presence of alkali, has a high glass transition temperature, and has high heat resistance, weather resistance, acid resistance and the like. It is excellent.

Among them, the number average molecular weight converted to polystyrene is 25,000 to 42,000, the weight average molecular weight is 50,000 to 70,000, and the viscosity average molecular weight is 2,0.
Polycarbonate having a melt viscosity of 10 ⁶ to 10 ⁸ poise at a temperature of 230 ° C. and a shear rate of 1 sec ⁻¹ is more preferably used.

Further, in the present invention, for the purpose of improving the weather resistance of the above polycarbonate, an ultraviolet absorber such as 2-
If necessary, additives such as (2′-hydroxy-5′-t-octylphenyl) benzotriazole and other stabilizers and antioxidants may be appropriately added. Alternatively, it is also possible to use a polycarbonate composition in which other additives, resins and the like are added and mixed in an amount within a range that does not impair transparency when mixed with polycarbonate.

The above-mentioned polycarbonate or polycarbonate composition may be used in the form of powder, or may be melt-extruded in advance and molded into pellets for use.

The type of extruder used in the present invention is not particularly limited, and a screw type extruder used for ordinary melt extrusion molding of thermoplastic resin is used. In order to form a transparent sheet, the main part of the cylinder, screw, etc. of the extruder, which is in direct contact with the polycarbonate,
For example, it is preferably plated with hard chrome.

The extrusion temperature is not particularly limited, and is usually a temperature at which polycarbonate is extruded, for example, 250 to
It is extruded in a temperature range of about 300 ° C.

In the present invention, the sheet material extruded from the die of the extruder is cooled by using a polishing roll. The surface temperature of the polishing roll may be a temperature which is usually carried out, but when a plurality of polishing rolls are used, the surface temperature of the first roll is 80 to
It is preferable to maintain in the range of 110 ° C. By maintaining the surface temperature of the roll in such a range, the surface state of the sheet does not become, for example, rippled, and a smooth sheet can be obtained.

In the polishing roll used in the present invention, the base material of the main body is not particularly limited, and a commonly used one, for example, iron-based main component may be used, but hard chromium plating is applied over the entire surface thereof. Is given,
It is necessary to have a hard chrome plating layer having a thickness of 20 to 80 μm on the roll surface. The preferable thickness of the plated layer is 30 to 60 μm.

When the thickness of the plating layer is less than 20 μm,
The strength of the roll surface is insufficient, and not only the plating layer but also the base material may be damaged when a mechanical shock or the like is applied, which is not preferable.

When the polycarbonate sheet is cooled by using the polishing roll, the surface temperature of the polishing roll is not generally used at room temperature, but is used in a state of being heated to about 100 ° C. When heated, cracks occur in the plating layer due to the difference in linear expansion coefficient between the base material layer of the roll such as iron and the plating layer of chromium. When the thickness of the plating layer exceeds 80 μm, the cracks are large and the gap between the cracks may reach a size of about 50 μm. If a polishing roll having a plating layer with such large cracks is used, the resin is likely to adhere to the surface of the roll, which causes plate-out. Therefore, the surface roughness of the obtained sheet deteriorates,
A sheet with good transparency cannot be obtained.

Since the polishing roll used in the present invention has a hard chrome plating layer having a thickness of 20 to 80 μm on the surface thereof, it is satisfactory in terms of the strength of the roll surface and also in terms of preventing the occurrence of large cracks.

The plate-out phenomenon of the roll is apt to occur especially when an ultraviolet absorber is added to polycarbonate, but by adopting the constitution of the present invention, this phenomenon can be prevented, and transparency and the like can be prevented. A sheet having excellent optical properties can be obtained.

The sheet cooled according to the method of the present invention is further cooled by a known method, for example, after further cooling on a roller table, laminated with a surface protective film in a masking unit for the purpose of surface protection, and then trimmed. It is cut into a predetermined size to obtain a polycarbonate sheet.

[0031]

EXAMPLES The present invention will be described more specifically below with reference to examples. The surface roughness of the rolls and sheets shown in the examples was measured by the following method.

(1) Method of measuring surface roughness Measuring instrument: Surface roughness meter (manufactured by Kosaka Laboratory Ltd.) Model: Stylus type detector Stylus: Tip R 0.5 μm Measuring force: 1-50 mgf variable Measurement speed: 2 μm / sec. Measuring distance: 30mm Recording pitch: 1mm Enlarging magnification: 50,000 times

(2) Method for measuring parallel light transmittance Measuring instrument: Haze meter (manufactured by Toyo Seiki Co., Ltd.) Light wavelength: 375 to 700 nm Sheet thickness: 2 mm Parallel light transmittance = total light transmittance-scattered light transmittance

Examples 1 to 3, Comparative Example 1 Polycarbonate pellets (trade name: Panlite 1285Z, manufactured by Teijin Kasei Co., Ltd.) were melt extruded at 270 to 285 ° C. using a single screw extruder with a 90 mmφ vent.
Polishing roll whose surface temperature was adjusted to the following temperature (The thickness of the hard chrome plating layer on the roll surface is [Table 1]
(Shown in FIG. 4).

At this time, the sheet-like melt extruded from the extruder die is sandwiched and cooled by the first polishing roll and the second polishing roll continuously, and then the second melt is formed.
It was conveyed to the third polishing roll via the polishing roll. It should be noted that only the cooling was performed without sandwiching by the second polishing roll and the third polishing roll. The sheet cooled by the third polishing roll was conveyed to the next device through the roll.

Thus, a polycarbonate sheet having a thickness of 2 mm was formed. The molding conditions are as follows. Extruder cylinder temperature: 270-285 ° C Adapter: 285 ° C Die: 300 ° C 1st polishing roll temperature: 100 ° C 2nd polishing roll temperature: 110 ° C 3rd polishing roll temperature: 140 ° C Screw rotation speed: 75rpm Take-up speed: 1 .2 m / min.

The sheet obtained by cooling with a polishing roll having a plating layer having a thickness of 80 μm or less had a surface roughness Rmax of 0.1 μm or less and was excellent in transparency.

When the plating thickness was 100 μm, a severe plate-out phenomenon was observed on the roll surface, and the roughness and light transmittance of the obtained sheet surface were also extremely low.

The thickness and surface roughness of the plating layer on the surface of the polishing roll used, and the surface roughness and parallel light transmittance of the obtained sheet are shown in Table 1.

[0040]

[Table 1]

[0041]

According to the present invention, it is possible to prevent plate-out of the polishing roll in the cooling step. Therefore, the obtained polycarbonate sheet has a good surface condition and excellent transparency. Therefore, it is useful as various name plates, daylighting materials for windows, etc., building materials, etc.

Front Page Continuation (72) Inventor I-saki Kenharu 2-1, Tango-dori, Minami-ku, Nagoya-shi, Aichi Mitsui Toatsu Chemicals, Inc. (72) Inventor Shoji Arimoto 2 Tango-dori, Minami-ku, Nagoya-shi, Aichi 1-chome, Mitsui Toatsu Chemical Co., Ltd. (72) Inventor, Naohiro Furukaku 2-1-1, Tango-dori, Minami-ku, Aichi Prefecture Nagoya Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A method for producing a polycarbonate sheet by kneading and melt-extruding a polycarbonate or a polycarbonate composition using an extruder to form a sheet, and cooling the sheet with a polishing roll to obtain a polycarbonate sheet having a thickness of 20. A method for producing a polycarbonate sheet, which comprises using a polishing roll having a hard chrome plating layer of ˜80 μm.