JPH0825458A - Production of polycarbonate sheet - Google Patents

Abstract

PURPOSE:To obtain a polycarbonate sheet having a good surface state, free from warpage and not deformed by heating by cooling an extruded sheetlike article of polycarbonate resin while holding the same between a pair of polishing rolls set to specific surface temp. under pressure and subsequently cooling the same by a third roll. CONSTITUTION:The sheet like article 11 extruded from the die 1 of an extruder is supplied to the gap between a pair of polishing rolls consisting of first and second rolls 2, 3 and held between the polishing rolls under pressure to be cooled. The sheet like article is further cooled by a third roll 4 to be fed to a next apparatus through the third roll 4 to obtain a polycarbonate sheet 13. Herein, the surface temp. of the first roll 2 forming one of a pair of the polishing rolls is controlled to 120-140 deg.C and that of the second roll 3 is controlled to 120-145 deg.C and that of the third roll 4 is controlled to 135-150 deg.C. The temp. of the sheet 12 at the time of the release from the third roll 4 is controlled to 140-160 deg.C.

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 melt extrusion molding method of a polycarbonate sheet which has good flatness and surface condition and little heat deformation.

[0002]

2. Description of the Related Art Polycarbonate is a thermoplastic resin having excellent mechanical properties and electrical properties in a wide temperature range and excellent transparency, and is molded into a sheet and used in a wide variety of fields. There is. Usually, when a polycarbonate resin is formed into a sheet, raw materials in the form of powder or pellets are kneaded and melted using an extruder and extruded into a sheet through a T-die or the like, and the sheet is then polished with a polishing roll. A method of forming a sheet by cooling and solidifying is adopted. Polycarbonate sheets are used for window materials, nameplates, optical materials, etc. by taking advantage of their excellent transparency, so it is required that the sheets have good transparency and surface conditions. In many cases, gear marks, transfer marks, peel marks, and the like that occur in step S1 deteriorate the transparency and surface condition of the sheet.

As a method for solving such a problem, for example, Japanese Patent Publication No. 2-61899 discloses a polishing roll having a surface temperature of 30 to 80.degree. And a surface temperature of another polishing roll is maintained at 100 to 140 ° C. However, in this method, since the surface temperature of the polishing roll is too low, the sheet is overcooled, and horizontal streaks may be formed on the surface of the sheet, which may cause the surface of the sheet to be rough and reduce transparency.

Further, Japanese Patent Laid-Open No. 6-87151 discloses that
Polycarbonate sheet extruded from the extruder,
A method for producing a polycarbonate sheet having a thickness of less than 3 mm by sandwiching and pressing with a pair of polishing rolls composed of a first roll and a second roll, cooling, and then transporting to the next device through the second roll. , The surface temperature of the said 1st roll is 80-120 degreeC, and the surface temperature of the said 2nd roll is maintained at 100-140 degreeC, The manufacturing method of the polycarbonate sheet characterized by the above-mentioned is disclosed. The method is useful in that gear marks, transfer marks, peel marks, etc. are prevented from occurring on the surface of the sheet, and a polycarbonate sheet having excellent transparency can be produced, but the polycarbonate sheet is cooled on a polishing roll, Since this is a method in which solidification proceeds remarkably, warpage is likely to occur in the obtained sheet, and it is not necessarily a satisfactory method in that it is difficult to obtain a sheet having excellent flatness. Further, there is a problem that the sheet is deformed by heating.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a method for producing a polycarbonate sheet having a good surface condition, good warpage and flatness, and no heat deformation. Especially.

[0006]

As a result of intensive studies, the inventors of the present invention have controlled the surface temperature of a polishing roll used in a cooling step within a specific temperature range that does not result in supercooling, and from the final roll of the polishing roll. The present invention has been found that the above object can be achieved by maintaining the sheet temperature at the time of peeling in a specific temperature range near the glass transition point of polycarbonate.

That is, according to the present invention, a polycarbonate resin is kneaded and melt-extruded into a sheet by using an extruder, and the sheet is sandwiched by a pair of polishing rolls consisting of a first roll and a second roll. A method of producing a polycarbonate sheet, which is cooled while being pressed, is then cooled by a third roll, and is allowed to cool on a roller table while being shaped, wherein the surface temperature of the first roll is 120 to 140 ° C. The surface temperature of 2 rolls is 120 ~
145 ° C, the surface temperature of the third roll is 135 to 150 ° C
And the temperature of the surface to be cooled of the sheet at the time of peeling off the third roll is 140 to 160 ° C. in the method for producing a polycarbonate sheet.

The present invention will be described in detail below. The outline of the present invention is that a polycarbonate resin is kneaded using an extruder, melted and extruded into a sheet through a die, and then the sheet is nipped and pressed using a plurality of polishing rolls, and cooled. It is a method for producing a polycarbonate sheet which is shaped while being left to cool on a roller table.

The polycarbonate used in the present invention is
For example, a divalent phenol compound or glycol simple substance, or a resin obtained by a polycondensation reaction of a mixture thereof with a carbonic acid derivative, or a divalent phenol compound or glycol simple substance in the presence of an alkali, or a mixture thereof. An example is a resin obtained by reacting phosgene with. Among the above-mentioned polycarbonate sheets, the polystyrene reduced number average molecular weight is 25,000 to 42,000, the weight average molecular weight is 50,000 to 70,000, and the viscosity average molecular weight is 20,000 to 35.
A polycarbonate sheet having a melt viscosity of about 10 ⁶ to 10 ⁸ poise at 1,000 or 23 ° C. and a shear rate of 1 sec ⁻¹ is preferably used.

In the present invention, a stabilizer, a pigment, a release agent, an ultraviolet absorber, or an amount of another resin in a range that does not impair transparency even when mixed with the polycarbonate resin is added to the above polycarbonate resin. A polycarbonate resin composition added and mixed can also be used. The above-mentioned polycarbonate resin or polycarbonate resin composition may be used in powder form, or may be melt-extruded in advance and molded into pellet form.

The extruder used in the present invention is not particularly limited, and a screw type extruder used for usual melt extrusion molding of thermoplastic resin is used. To form a transparent sheet, extruder cylinders and screws, etc.
The main portion of the portion that directly contacts the polycarbonate resin is preferably, for example, hard chrome plating or the like.
The extrusion temperature is not particularly limited, and is usually extruded at a temperature at which the polycarbonate is molded, for example, in the temperature range of about 200 to 320 ° C., in order to improve the transparency of the obtained polycarbonate sheet, a die is used. The temperature of the sheet-like material extruded from the sheet and supplied to the pair of polishing rolls including the first roll and the second roll is 240 to
It is preferable to control in the range of 300 ° C. More preferably, it is 245 to 290 ° C.

In the present invention, the sheet-like material extruded from the die of the extruder is sandwiched, pressed and cooled by a pair of polishing rolls consisting of a first roll and a second roll, and then cooled by a third roll. Then, it is left to cool on a roller table, solidified and shaped. The surface temperature of the first roll, the second roll and the third roll affects the surface state and flatness of the obtained sheet. If the surface temperature of these polishing rolls is too low, the sheet-like material is overcooled, warpage is likely to occur in the obtained sheet, it is difficult to obtain a sheet having excellent flatness, and the sheet is easily deformed by heating. On the contrary, if it is too high, the adhesive force to the polishing roll increases, and the peeling property tends to decrease, so that the surface condition of the sheet tends to deteriorate. Considering this point comprehensively, the surface temperature of the first roll is 120 to 140 ° C.,
The surface temperature of the second roll is 120-145 ° C, and the third
The surface temperature of the roll is preferably in the range of 135 to 150 ° C.

Further, it is important to maintain the sheet temperature (the surface on the side cooled by the third roll) at 140 to 160 ° C. at the time of peeling from the third roll which is the final roll. Sheet temperature when peeled from the third roll is 140 ° C
If it is less than the above range, the sheet is excessively cooled and solidified on the polishing roll, so-called curling of the sheet occurs, and warpage occurs in the obtained sheet. Also, 160
If the temperature is higher than 0 ° C, the sheet-like material may not be sufficiently cooled, and the sheet may be deformed or may be difficult to be picked up due to tension or the like when conveyed to the next step, which is not preferable.

Surface temperature of polishing roll, and third
There is no particular limitation on the method of measuring and controlling the sheet temperature at the time of peeling from the roll, and a commonly used method, for example, hot water in a jacket installed inside the roll, pressurized steam, heating medium such as heating oil A method of automatically controlling while circulating is used. Examples of the measurement of these temperatures include a method using an infrared radiation thermometer.

In the present invention, the sheet peeled from the third roll is allowed to cool on the roller table to be solidified and shaped. The shape of the roller table used in the present invention is not particularly limited and a known one is used. For example, it is exemplified that a plurality of rolls having the same diameter are arranged horizontally in the traveling direction of the sheet, and the rolls constituting the roller table are arranged so that the surface in contact with the sheet is horizontal. It doesn't matter if you have it. The degree of cooling on the roller table may be such that the sheet is not deformed by an external force. Usually, it is in the range of room temperature to 100 ° C. If necessary, air may be blown upon cooling.

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of a cooling step used in the present invention. The sheet-like material 11 extruded from the extruder die 1 is supplied to a pair of polishing rolls composed of a first roll 2 and a second roll 3, sandwiched and pressed by the polishing rolls, and cooled. After being cooled, it is conveyed to the next device through the third roll 4, and the polycarbonate sheet 13 is obtained.

In the present invention, the surface temperature of the first roll 2 is 120 to 140 ° C. and the surface temperature of the second roll 3 is 120.
~ 145 ° C, the surface temperature of the third roll 4 is 135 ~ 150
It is preferable that the temperature is controlled at ° C. The temperature of the sheet 12 when peeled from the third roll 4 is preferably controlled to 140 to 160 ° C, more preferably 140 to 1
55 ° C. By controlling each temperature at the location under such a temperature condition, a polycarbonate sheet 13 having a good surface condition and transparency and without warping can be manufactured.

The thickness, width, etc. of the sheet produced by applying the present invention are not particularly limited, but the thickness is 0.5 to 10 m.
m, preferably 1-8 mm, more preferably 1-5 m
It is preferably applied to the production of a sheet of about m.

[0019]

EXAMPLES The present invention will be described in more detail below with reference to examples. The warpage rate and the appearance evaluation of the sheet shown in the examples were measured by the following methods.

(1) Method of measuring warp rate immediately after production and warp rate after heating <Preparation of measurement sample>: From the center portion in the width direction of the obtained sheet and from the positions 50 cm apart from the center portion to the left and right respectively. Three square sample pieces of 12 cm in each length and width are cut out to be used as measurement samples (3 samples). However, at the time of cutting, the longitudinal direction of the measurement sample is aligned with the length direction of the sheet, and the lateral direction of the measurement sample is aligned with the width direction of the sheet.

<Measurement method>: The vertical warp height of the sample is measured using a two-dimensional measuring machine (manufactured by Mitutoyo Corporation, type: CRYSTAL, μV606). Stand vertically on the sample table of a two-dimensional measuring machine with the vertical cross section as the base, and measure the length of the straight line connecting the vertical ends of the sample and the distance between the straight line and the center of the sample. To do. The maximum warp height after heating is measured by the same method after heating the sample at 140 ° C. for 40 minutes using an air oven.

<Calculation method>: The following mathematical expression (1) [Equation 1] described in JIS K-6911, Item 5.6.4.

[0023]

[Equation 1] [Wherein, W ₁₀₀₀ : warp rate (%), D: warp height (mm) relative to 1000 mm, L: distance between both longitudinal ends of the sample in the warp state (mm)]
The warp rate (%) per mm was calculated, and the average value is shown.

(2) Appearance of sheet According to the method defined in JIS K-6735, Section 5.1, the appearance is examined at a distance of about 60 cm from the sheet, and it is checked for scratches, color unevenness, and foreign matter that are harmful in use. To be good.

Examples 1 to 3, Comparative Examples 1 to 4 Polycarbonate resin [manufactured by Teijin Chemicals Ltd., trade name: Panlite K-1300Z (viscosity average molecular weight 29,50
0, or L-1250R (viscosity average molecular weight 24,
400)] is melt-extruded using a 90 mmφ vented single-screw extruder (T-die attached to the tip), setting the temperature of each part of the extruder cylinder and the die to each temperature in the range of 210 to 310 ° C. The first roll and the second roll set to each temperature of 120 to 145 ° C continuously sandwich, pressurize and cool, and then the third set to each temperature of 100 to 160 ° C.
A polycarbonate sheet was formed by cooling with a roll and then allowing it to cool on a roller table. The types of resin used, the die discharge resin temperature and the preset temperature of each polishing roll, the resin temperature of the cooled surface at the time of peeling the third roll, and the evaluation results of the obtained sheet are shown in [Table 1] and [Table 2].
Shown in

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

According to the present invention, there is no vertical warp,
A polycarbonate sheet having good flatness that does not deform even when heated can be obtained. Further, it is possible to prevent the occurrence of horizontal stripes that are likely to occur when peeling from the cooling roll, and a polycarbonate sheet having a good appearance can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a cooling step used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder die 2 1st roll 3 2nd roll 4 3rd roll 11 Extruded sheet-like material 12 Sheet peeled from 3rd roll 13 Polycarbonate sheet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Arimoto 2-1, Tango-dori, Minami-ku, Aichi Prefecture Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Hirotaka Wanibe 2 Tango-dori, Minami-ku, Aichi Prefecture 1-chome, Mitsui Toatsu Chemical Co., Ltd. (72) Inventor, Shuji Matsumura 1-6, Takasago, Takaishi City, Osaka Mitsui Toatsu Chemical Co., Ltd.

Claims (3)

[Claims] 1. A polycarbonate resin is kneaded using an extruder and melt-extruded to form a sheet-like material, which is cooled while being nipped and pressed by a pair of polishing rolls composed of a first roll and a second roll. A method of producing a polycarbonate sheet which is then cooled by a third roll and further shaped while being left to cool on a roller table, wherein the surface temperature of the first roll is 120 to 140 ° C.
The surface temperature of the second roll is 120 to 145 ° C., the surface temperature of the third roll is 135 to 150 ° C., and the third roll is
The temperature of the surface to be cooled of the sheet at the time of peeling the roll is 140 to 160
The method for producing a polycarbonate sheet is characterized in that the temperature is 0 ° C. 2. The take-up speed of the sheet from the third roll is 0.4 to 5 m / min.
A method for producing the polycarbonate sheet described. 3. The thickness of the polycarbonate sheet is 0.5.
It is 10 mm, The manufacturing method of the polycarbonate sheet of Claim 1 characterized by the above-mentioned.