JPH06344417A - Manufacture of polycarbonate sheet - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a polycarbonate(PC) sheet wherein thermal contraction is little even by reheating in postforming, and dimensional precision of a molded product has been improved. CONSTITUTION:While PC resin is extruded in a molten sheet state from a die 16 of an extruder and received with pitch rolls 17, the extruded PC sheet 14 is introduced between the first polishing roll 11 and the second polishing roll 12, and advanced on a peripheral surface of the second polishing roll 12. In a method for manufacturing the PC sheet wherein it is successively introduced between the second polishing roll 12 and the third polishing roll 13 to carry out sheeting, temperature of the first polishing roll is set at 130 to 140 deg.C, and temperature of the second and third polishing rolls is set at 180 to 190 deg.C. Besides, the PC sheet 14 is extruded at 260 to 280 deg.C. Further, the PC sheet 14 is heated before being introduced so that surface temperature of the PC sheet 14 in the introduction onto the third polishing roll can reach 190 to 200 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing a polycarbonate sheet by extrusion molding and polishing rolls.

[0002]

2. Description of the Related Art Polycarbonate resins are widely used as windshields for motorcycles, face plates for vending machines, etc. as a substitute for glass because of their excellent impact resistance and transparency.

Generally, a polycarbonate sheet is manufactured by heating and melting a resin raw material, extruding it into a sheet form from a die, and subsequently cooling and solidifying it while taking it out by a polishing roll, a pinch roll or the like. For example, as shown in FIG. 2, a polycarbonate sheet (14) extruded into a sheet form in a molten state from a die (16) of an extruder has three upright polishing rolls (1).
It is cooled and solidified while advancing between 1), (12) and (13) in an S shape, and taken up by the pinch roll (17). At this time, the first polishing roll (11) is 110
~ 120 ° C, Second and Third Polishing Roll (12)
(13) is set to 165 to 175 ° C, and the polycarbonate sheet (14) extruded from the die (16) at 240 to 250 ° C is the third polishing roll (1).
When it is introduced into 3), it is cooled to about 180 to 185 ° C.

When the polycarbonate sheet produced as described above is used as a material to be secondarily processed into a molded article such as a windshield of a motorcycle, first the polycarbonate sheet is cut into a required size and, if necessary, characters, patterns, etc. To print.
And, the surface temperature of the polycarbonate sheet is 180 ° C.
After heating to a certain degree to give flexibility, this is put between a male mold and a female mold, bent into a required shape by embossing, taken out from the mold and cooled to obtain a product.

[0005]

However, when the polycarbonate sheet is reheated and secondarily molded as described above,
Since the sheet shrinks during cooling, there is a problem that the finished dimensions of the product vary. Of course, when the material sheet is cut, the shrinkage is taken into consideration so that the desired dimension can be finally obtained, but there is a problem that the yield of the product is poor because the shrinkage is not constant.

[0006] The present invention provides a method for producing a polycarbonate sheet, which has a small heat shrinkage even by reheating at the time of secondary molding and can improve the dimensional accuracy of a molded article, for the purpose of solving such problems. Is what you are trying to do.

[0007]

As a result of intensive studies on the cause of heat shrinkage during secondary processing, the inventors of the present invention have found that internal strain generated during extrusion of a polycarbonate sheet remains after cooling, Focusing on the fact that shrinkage occurs due to reheating and cooling during molding, it was found that the internal strain can be relaxed and the thermal shrinkage can be suppressed by setting the temperature condition in the manufacturing process of the polycarbonate sheet to a specific range.

That is, in the method for producing a polycarbonate sheet of the present invention, the polycarbonate resin extruded while the polycarbonate resin is extruded from the die (16) of the extruder into a molten sheet and taken by the pinch roll (17). (14) to the first polishing roll (1
1) and the second polishing roll (12) are introduced to advance on the peripheral surface of the second polishing roll (12), and then the first and second polishing rolls (11) (1)
Third polishing roll (13) arranged in series with 2)
In the method for manufacturing a polycarbonate sheet, which is introduced between the second polishing roll (12) and the second polishing roll (12), the temperature of the first polishing roll (11) is set to 130 to 140 ° C., and the second and third polishing rolls are set. (12) The temperature of (13) is set to 180 to 190 ° C., the polycarbonate sheet (14) is extruded to 260 to 280 ° C., and the polycarbonate sheet (14) when the third polishing roll (13) is introduced.
The polycarbonate sheet (14) is heated before its introduction so that the surface temperature of the polycarbonate sheet becomes 190 to 200 ° C.

In the method for producing a polycarbonate sheet according to the present invention, the polycarbonate sheet (1
If the temperature of 4) is less than 260 ° C, the heat shrinkage becomes large, and 2
If the temperature exceeds 80 ° C, the sheet sags and does not follow the second polishing roll (12) and sheeting cannot be performed. Therefore, it is necessary to extrude the polycarbonate resin to 260 to 280 ° C.
The sheet temperature in this range can be achieved by melt-plasticizing the raw material resin under normal extrusion molding conditions and extruding it into a sheet.

If the temperature of the first polishing roll (11) is less than 130 ° C. with respect to the polycarbonate sheet (14) extruded at 260 to 280 ° C., cooling will be too fast and heat shrinkage will increase. If it exceeds, the polycarbonate sheet (14) will be the first because it will not be cooled sufficiently.
It cannot be seated because it is taken by the polishing roll (11). Therefore, it is necessary to set the temperature of the first polishing roll (11) to 130 to 140 ° C. If the second and third polishing rolls (12) and (13) are less than 180 ° C., cooling is too fast and heat shrinkage increases.
Further, when the temperature exceeds 190 ° C., the polycarbonate sheet (14) is not sufficiently cooled and is taken by the second or third polishing rolls (12) and (11) to prevent sheeting. Therefore, the second and third polishing rolls (1
2) It is necessary to set the temperature of (13) to 180 to 190 ° C. The temperature control of the first to third polishing rolls (11) (12) (13) can be easily performed by the conventional roll temperature control means.

Further, it is necessary to heat the polycarbonate sheet (14) so that the surface temperature of the polycarbonate sheet (14) when introduced into the third polishing roll (13) becomes 190 to 200 ° C. This is because if it is lower than 190 ° C, the heat shrinkage becomes large, and if it exceeds 200 ° C, the polycarbonate sheet (14) is taken by the third polishing roll (13) and cannot be sheeted.
The heating method of the polycarbonate sheet (14) is not particularly limited, but as shown in FIG. 1, for example, a heater (15) or the like is provided on the side of the second polishing roll (12). By arranging the equipment, the polycarbonate sheet (14) can be easily heated to a predetermined temperature.

If the pulling speed of the polycarbonate sheet (14) by the pinch rolls (17) is slowed down to reduce the speed difference between the polishing rolls (11) (12) (13) and the pinch rolls (17). Since the cooling progresses slowly and the internal strain is easily alleviated, the heat shrinkage during the secondary molding is also suppressed. However, on the other hand, the polycarbonate sheet (14) may be taken up by the third polishing roll (13) and hinder good sheeting. Therefore, it is not always a good idea to make the speed difference too small. If the sheeting temperature conditions of the present invention described above are set, thermal contraction can be sufficiently suppressed even if the polycarbonate sheet (14) is pulled at a speed difference similar to that in the conventional case. Specifically, the peripheral speed of the pinch roll (17) is set to the peripheral speed of the second polishing roll (12), which is set to a constant peripheral speed regardless of the thickness of the sheet. It suffices to set the speed difference between and about 50 mm / min. However, the present invention does not prevent the pulling speed by the pinch rolls (17) from being slowed to reduce the speed difference as long as the sheeting can be performed well.

[0013]

Function: From the extruder die (16) to 260-280 ° C
The polycarbonate sheet (14) extruded in
The first polishing roll (1
1) and a second polishing roll (12) set at 180 to 190 ° C. to have a predetermined sheet thickness, and the second polishing roll (1) while being gradually cooled.
Proceed on the circumference of 2). Then, the polycarbonate sheet (14) is the second polishing roll (12).
And the third polishing roll (13) set at 180 to 190 ° C., the polycarbonate sheet (14) is heated before being introduced into the third polishing roll (13). It is introduced between the second and third polishing rolls (12) (13) at 0 ° C. and then taken up by the pinch rolls (17). The internal strain generated during extrusion during such a gradual cooling process is gradually alleviated, and the internal strain is almost eliminated in the sheeted polycarbonate sheet (14). For this reason, when the polycarbonate sheet (14) is molded and processed, thermal shrinkage hardly occurs even if it is heated and cooled again.

[0014]

EXAMPLES Next, specific examples of the method for producing a polycarbonate sheet of the present invention will be described.

In this example, "Iupilon (trade name)" manufactured by Mitsubishi Gas Chemical Co., Inc. was used as a polycarbonate resin as a sheet material and continuously extruded to a predetermined thickness by an extruder, as shown in FIG. A polycarbonate sheet was produced with a sheeting machine (1).

In the sheeting apparatus (1) shown in FIG. 1, reference numeral (11) is a first polishing roll, (12) is a second polishing roll, and (13) is a third polishing roll.
The second polishing roll (1
A heater (15) for heating the polycarbonate sheet (14) is installed on the side of 2).

A polycarbonate sheet (14) in a melt-softened state which is continuously extruded from a die (16) of an extruder.
Is guided between the first polishing roll (11) and the second polishing roll (12) and advances along the 1/2 peripheral surface of the second polishing roll (12), and the outer surface side of the polycarbonate sheet (14) is It is heated to a predetermined surface temperature by the heater (15). Then, the polycarbonate sheet (14) is attached to the second polishing roll (12) and the third polishing roll (12).
It is guided to the polishing roll (13), advances along the ½ circumferential surface of the third polishing roll (13), and is continuously taken up by the pinch roll (17).

The polycarbonate sheet (1
In the manufacturing process of 4), the resin temperature immediately after extrusion, the temperatures of the first to third polishing rolls (11), (12) and (13), when the third polishing roll (13) shown by (P) in FIG. 1 is introduced. The surface temperature of the polycarbonate sheet (14) is set to the temperature shown in Table 1 below, and the thickness is set to 3.0.
Three types of polycarbonate sheet (14) of mm, 2.0 mm and 1.5 mm were manufactured. In addition, as a comparative example, FIG.
With the heater-free type sheeting device (2) shown in Fig. 3, the resin temperature immediately after extrusion and the respective polishing roll temperatures were set to the conventional conditions shown in Table 1, and the thicknesses of 3.0 mm, 2.0 mm and Three types of 1.5 mm polycarbonate sheet (14) were produced. In the comparative example, the temperature of the polycarbonate sheet (14) before introduction of the third polishing roll (13) in Table 1 was not the set temperature, and was obtained as a result of not heating before introduction (P ′). ) Is the temperature at.

The peripheral speed of the pinch roll (17) was set to be 50 mm / min faster than the peripheral speed of the second polishing roll (12) in both the present invention example and the comparative example. This speed is as fast as the conventional manufacturing method.

The shrinkage rate of each polycarbonate sheet thus manufactured was evaluated. Evaluation is JIS K
Applying the heat expansion / contraction test method of 6735, 180 ° C x 10
It was performed under the heating condition for a minute. The shrinkage rate of each sheet is also shown in Table 1.

[0021]

[Table 1] As is clear from Table 1, in the examples of the present invention, it was possible to obtain a polycarbonate sheet having a small shrinkage rate even when the conventional take-up speed was maintained.

[0022]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, while the polycarbonate resin is extruded from a die of an extruder into a sheet in a molten state and taken by a pinch roll, the extruded polycarbonate sheet is treated with a first polishing roll and a first polishing roll. Between the second polishing roll and the third polishing roll arranged in series with the first and second polishing rolls by introducing between the second polishing roll and the second polishing roll. In the method for producing a polycarbonate sheet, which is introduced by inserting between the sheets, the temperature of the first polishing roll is 130 to 140 ° C., and the temperatures of the second and third polishing rolls are 180 to 1
While setting the temperature to 90 ° C, which is higher than before,
The polycarbonate sheet is extruded to 260 to 280 ° C., and the polycarbonate sheet is heated before the introduction so that the surface temperature of the polycarbonate sheet at the time of introducing the third polishing roll becomes 190 to 200 ° C. Cooling in the sheeting process proceeds slowly, and the internal strain of the polycarbonate sheet generated during extrusion is sufficiently relaxed. Therefore, when the polycarbonate sheet produced by the method of the present invention is used as a material for secondary molding, thermal contraction due to reheating and cooling is suppressed, and the dimensional accuracy of the molded product is improved.

Furthermore, since the method of the present invention can be easily carried out only by controlling the temperature condition of the sheeting process, the sheeting speed can be maintained at the conventional speed and the productivity is excellent.

[Brief description of drawings]

FIG. 1 is a schematic view of a sheeting device used for manufacturing a polycarbonate sheet in an example of the present invention.

FIG. 2 is a schematic view of a sheeting device used for manufacturing a polycarbonate sheet in a comparative example.

[Explanation of symbols]

 11 ... 1st polishing roll 12 ... 2nd polishing roll 13 ... 3rd polishing roll 14 ... Polycarbonate sheet 16 ... Die 17 ... Pinch roll

Claims (1)

[Claims] 1. While the polycarbonate resin is extruded from a die (16) of an extruder into a molten sheet and taken by a pinch roll (17), the extruded polycarbonate sheet (14) is fed to a first polishing roll (11). )
Between the second polishing roll (12) and the second polishing roll (12)
It advances on the peripheral surface of the polishing roll (12), and then the first and second polishing rolls (11) (12).
In the method for producing a polycarbonate sheet, which is introduced between a third polishing roll (13) and a second polishing roll (12) arranged in series with each other, the temperature of the first polishing roll (11) is set to 13
The temperature of the second and third polishing rolls (12) and (13) is set to 0 to 140 ° C., and the temperature of the polycarbonate sheet (14) is set to 26.
The polycarbonate sheet (14) is extruded at 0 to 280 ° C. and heated so that the surface temperature of the polycarbonate sheet (14) at the time of introducing the third polishing roll (13) becomes 190 to 200 ° C. A method for producing a polycarbonate sheet, comprising: