JPH0622932B2 - Process for producing thermoplastic plastic sheet or film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to sheets of a thermoplastic plastic sheet or film (hereinafter referred to as sheets) in which a difference in thickness between both ends and a central portion in the width direction is improved. Manufacturing method.

(Prior art and its problems) Conventionally, sheets in calendering method, extrusion method, inflation method, etc. have various temperature control rolls such as bored rolls, drilled rolls, double pipes while their surfaces are in a molten state. It is manufactured by contacting with a fin type roll, a spiral fin type roll, etc., cooling and solidifying while annealing, and winding up on a paper tube. However, since these conventionally known temperature control rolls try to make the temperature distribution in the width direction of the roll itself as uniform as possible, in other words, the temperature difference between the both ends and the center of the roll should be set to zero. As a result, a remarkable thickness difference and unevenness occur between the both end portions and the central portion of the finished sheets in the width direction. As shown in), when the winding side rises and the product width is trimmed with BT in the same figure, when secondary forming such as vacuum forming, embossing, laminating etc. is performed using these sheets, the boundary part in the figure Since stress at the time of rewinding concentrates on C, and various problems such as meandering, tearing, and tearing occur, the trimming width must be set with AT in the figure, and the width of the AT and BT The difference is large, simply Not only say that wide of the sheet can not be manufactured, it has been a cause of this product rate greatly reduced (down 30-40%) is. There is a problem that this tendency becomes more remarkable as the thickness of the sheets to be manufactured is smaller and the width of the sheets is larger (in other words, the length of the roll is longer).

As a result of various investigations by the present inventors to solve the above-mentioned problems, the above-mentioned phenomenon is caused by the fact that the temperature distribution in the width direction of the sheets in the molten state becomes higher in the central portion as compared with the both end portions. The adhesiveness of the central part of the roll to the roll is higher than that of both ends, the peeling from the roll is worse than the other parts, and as a result, the central part of the sheets is removed on the roll. At the boundary between the two ends, the tensile stress concentrates and the thickness becomes thinner than the central part (see FIG. 4 (b)), which causes a meandering phenomenon that the sheets swing, and the thickness difference between the central part and both ends and unevenness occur. It was found that the temperature would be further increased, and it was found that all the above problems could be solved by lowering the temperature of the central portion of the sheets to be lower than that of both end portions, and completed the present invention.

(Structure of the invention) That is, the present invention is characterized in that the surface of the thermoplastic plastic sheet or film immediately after being formed is brought into contact with rolls in which the temperature of both end portions is set higher than the temperature of the central portion to take it up. A method of manufacturing a plastic sheet or film.

Hereinafter, the present invention will be described in more detail with reference to FIGS. 1 to 3 of the accompanying drawings.

FIG. 1 is a schematic view showing an embodiment of the present invention, which is PVC, PE, ABS, MBS, EPDM immediately after being formed by a molding machine (not shown) such as a calender roll or an extruder.
At least one roll 2 (three in the drawing) whose both end portions are set to have a temperature higher than that of the central portion of the thermoplastic sheet 1 is wound with a winder (not shown). At this time, since the temperature of the roll 2 is set as described above, the central portion 1'of the sheets as shown by the broken line in FIG. 1 does not stick to the roll longer than both ends of the sheets. Therefore, there is no difference in the pulling force or the winding force applied to the central portion and both end portions of the sheets, and as a result, the thickness difference and unevenness of the sheets are reduced. FIG. 2 (a) is a schematic cross-sectional view showing a heat medium passage of the rolls 2 used in the present invention, and FIG. 2 (b) is a conceptual diagram showing a temperature gradient in the length direction of each roll. Figure (a-1) shows
The heat medium central outflow type is shown in Fig. (A-2), and the heat medium central outflow type is shown. In all of these, the heat medium is introduced from the center of the end face center of the rolls, At the center of the center in the length direction, the flow path is changed by 90 ° by a baffle plate or partition wall, and the surface of the rolls is heated from the inside through directly below the outer wall of the rolls, and then discharged from the inflow end or the other end. In each case, the temperature distribution is such that the central portion of the rolls is higher than both ends of the rolls, as shown in (b-1) and (b-2) of FIG.

Example According to the present invention, the temperature of the heat transfer medium introduced was set to 154 ° C. by the calendering method using the metal temperature control roll (diameter 150 mm, length 1700 mm) of the heat transfer medium outflow system shown in FIG. 2 (a). Approximately 80 cm wide polyvinyl chloride resin, standard thickness 200
The sheet was pulled out as a sheet of μm, and the respective temperatures at the central portion and both end portions of the sheet on the temperature control roll in the steady state and the roll surface temperature of each corresponding portion were measured. The results are shown in Table 1. Also, measure the thickness of the obtained sheet over the entire width direction,
Each measured value was plotted in FIG. 3 (a) and shown as a thickness distribution diagram in the width direction.

For comparison, the same operation was performed except that a conventional ordinary temperature control roll was used, and the respective measured temperatures are also shown in Table 1. Further, the thickness of the obtained sheet over the entire width direction was measured, and similarly, a thickness distribution chart in the width direction was shown in FIG. 3 (b).

As can be seen by comparing FIGS. 3 (a) and 3 (b), the sheet obtained according to the present invention has a significantly uniform thickness over the entire width even when the measurement error is taken into consideration. You can see that

In fact, the conventional method, for example, provided a sheet product having a width of 58 cm by trimming both sides of a vinyl chloride resin sheet squeezed to a length of 80 cm by about 11 cm, but according to the method of the present invention. The trimmed sheet is trimmed by about 1 cm on each side.
It could be commercialized as a good sheet having a width of 78 cm. Further, in the conventional method, the maximum thickness is 208 μm and the minimum thickness is 198 μm with respect to the 200 μm standard (set) thickness, the variation is 10 μm, and the average thickness of the product is 205 μm. According to the method of the present invention,
The maximum thickness was 202 μm, the minimum thickness was 198 μm, the variation was as small as 4 μm, and the average thickness was 200.5 μm. It was recognized that such a remarkable reduction in the variation can save 2.3% of the material resin when the same width of the sheet is compared.

[Advantages of the Invention] From the above, it is clear that the thickness of the thermoplastic sheets according to the present invention is highly uniform in the width direction, and the present invention is a significantly improved industrially desirable sheet. It will be understood that this is a manufacturing method of a class.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention, and FIG.
The schematic cross-sectional views of the temperature control rolls of the heat medium central outflow system and the heat medium central outflow system used in the present invention, and FIGS. 3 (a) and 3 (b) are obtained by the present invention and the conventional method. Fig. 4 (a) is a winding distribution diagram of the sheets obtained by the conventional method, and Fig. 4 (b) is a distribution diagram of the thickness of each sheet in the width direction. It is a conceptual diagram which shows the adhesive state to a roll.

Claims (1)

[Claims] 1. A thermoplastic sheet or film, characterized in that the surface of the thermoplastic sheet or film immediately after being formed is brought into contact with a roll whose temperature at both ends is set higher than the temperature at the central portion. Production method.