JPH10217315A - Manufacture of thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermoplastic resin sheet in which thickness spots are small and flat die stripe tracks are reduced. SOLUTION: In a method for producing a thermoplastic resin sheet in which a molten resin sheet extruded from the flat die of a melting extruder is contacted with a cooling casting roll by a static application contacting method, a cooling casting roll in which an air shutting-off plate is installed upstream in the rotational direction from the landing line of the molten resin sheet and close to the surface is used, and the length of the sheet from the lip end of the flat die to the landing line in the surface of the cooling casting roll is regulated to be 100-200mm.

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 thermoplastic resin sheet, and more particularly, to a method for producing a thermoplastic resin sheet having a small thickness unevenness and a small flat die trace.

[0002]

2. Description of the Related Art A thermoplastic resin sheet is manufactured by extruding a molten resin sheet from a flat die of a melt extruder onto a casting roll for cooling. At this time, in order to increase the adhesion between the molten resin sheet and the casting roll, an electrostatic application adhesion method is employed. The electrostatic application adhesion method generally involves applying an application electrode in the direction perpendicular to the flow of the sheet near the molten resin sheet, and applying the applied electrode to the electrode at about 5 to 10 kV.
Is applied to the molten resin sheet by applying a DC voltage, and the adhesion to a casting roll is improved by electrostatic force.

By the way, in order to effectively perform the above-mentioned electrostatic application and adhesion method, the length of the molten resin sheet from the lip tip line of the flat die of the molten resin to the landing line on the cooling casting roll (hereinafter referred to as the molten resin The sheet length is abbreviated). However, when the length of the molten resin sheet is increased, the occurrence of flat die traces in the molten resin sheet is suppressed accordingly, but the molten resin sheet swings and the amount of neck-in increases, resulting in a result. There is a problem that the thickness unevenness becomes large.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a thermoplastic resin sheet having a small thickness unevenness and a small flat die trace. It is in.

[0005]

That is, the gist of the present invention is to provide a thermoplastic resin sheet in which a molten resin sheet extruded from a flat die of a melt extruder is brought into close contact with a cooling casting roll by an electrostatic application contact method. In the method of manufacturing, using a cooling casting roll provided with an air blocking plate close to the surface on the upstream side in the rotation direction from the landing line of the molten resin sheet, and cooling casting roll from the lip tip of the flat die The length of the molten resin sheet up to the landing line on the surface is 100 to 2
The method for producing a thermoplastic resin sheet is characterized in that it is adjusted to a range of 00 mm.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The production method of the present invention is basically the same as a conventionally known method, in which a molten resin sheet extruded from a flat die of a melt extruder is brought into close contact with a cooling casting roll by an electrostatic application contact method. Manufacture a thermoplastic resin sheet. That is, an application electrode is stretched in the direction orthogonal to the flow of the sheet near the molten resin sheet, and about 5 to 5
An electrostatic charge is applied to the molten resin sheet by applying a DC voltage of 10 kV, and the adhesion to the casting roll is improved by electrostatic force.

[0007] Examples of the thermoplastic resin targeted in the present invention include polyesters such as polyethylene terephthalate, polyamides and polyolefins.

[0008] As the melt extrusion apparatus used in the present invention, a known apparatus can be used. that time,
As the flat die of the melt extruder, it is preferable to use a flat die having neck down plates at both ends. The above-mentioned neck down plate is a plate provided so as to extend both end surfaces of the resin extruding port. By cooling the neck down plate, both ears of the extruded molten resin sheet become the neck down plate. And is cooled first. By this contact and cooling, neck-in of the molten resin sheet is suppressed.

As a material for the neck-down plate, a metal plate such as aluminum can be usually used, but it is not limited to such a metal plate. The width of the neck down plate itself is usually 10 to 20 mm, and the length is
Usually, it is about 20 to 40 mm. In addition, by suppressing the shape of the neck down plate so as to spread slightly outward from the direction of the extension of the width of the extrusion opening, it is possible to more effectively suppress neck-in.

The above-mentioned neck-down plate is maintained at a temperature which is usually 5 to 20 ° C., preferably 7 to 15 ° C. lower than the extrusion temperature of the molten resin sheet. Although the cooling method is not particularly limited, for example, a method of laminating a metal block in which cooling water circulates on the back surface of the neck down plate and cooling the metal block can be used.

It is preferable to use a flat die capable of adjusting the gap at both ends of the lip. By adjusting the gap, even when neck-in of the molten resin sheet occurs, unevenness in the thickness of the film to be manufactured in the width direction can be reduced.

As the main body of the casting roll for cooling (hereinafter abbreviated as cooling roll) in the present invention, a known body can be used. At this time, the accompanying air is turned into a molten resin sheet by rotation of the cooling roll. In order to avoid the influence of the above, the air-blocking plate provided on the surface is used on the upstream side in the rotation direction from the landing line of the molten resin sheet.

The height and width of the dimensions of the air-blocking plate are determined as appropriate so that the accompanying air due to the rotation of the cooling roll does not affect the molten resin sheet. For example, the height when provided in the vertical direction in the vicinity immediately below the flat die,
The height is about the height of the flat die, and the width is about 200 mm or more wider than the width of the molten resin sheet and is equal to or less than the width of the cooling roll.

The position where the above-mentioned air shut-off plate is provided is not particularly limited as long as the above-mentioned accompanying air does not affect the molten resin sheet, but it is usually a position 10 to 50 mm upstream from immediately below the flat die. And the bottom edge is provided parallel to the axis of the cooling roll and close to the surface of the cooling roll. In addition, when the landing line of the molten resin sheet is on the downstream side immediately below the flat die, and when the distance is large, for example, when it is 130 mm or more and the air blocking plate is inclined upstream, The position can be further downstream than the above position.

Further, since the air blocking plate cannot be fixed to the surface of the cooling roll, it is provided close to the surface. At that time, the gap between the surface of the cooling roll and the bottom edge of the air blocking plate is preferably as small as possible, for example, 0.5 mm or less. In order to further improve the air blocking effect, a turn-back portion can be provided on the periphery of the air blocking plate toward the upstream side of the roll rotation.

The ratio of the extrusion speed from the melt extruder to the peripheral speed of the cooling roll, that is, the draft ratio of the molten resin sheet is usually 5 to 15 times, preferably 8 to 12 times.
Doubled. When the draft ratio is less than 5 times, the draft ratio of the molten resin sheet due to the above-mentioned ratio is small, so that it is difficult to exert the uniform thickness effect. If the draft ratio exceeds 15 times, spots due to the draft are likely to occur.

When the thermoplastic resin is melt-extruded, the length of the molten resin sheet is adjusted in order to effectively perform the electrostatic application adhesion method.
In the range of 100 to 200 mm, preferably 130 to 170
It is necessary to adjust it to be within the range of mm. When the length of the molten resin sheet is less than 100 mm, the electrostatic application and adhesion method does not work effectively, and the thickness unevenness increases, and furthermore, traces due to the flat die are generated. On the other hand, if the length of the molten resin sheet exceeds 200 mm, the molten resin sheet is likely to sway under the influence of the vibration of the flat die, so that the effect of improving the uneven thickness of the present invention is not sufficiently exhibited.

The length of the molten resin sheet can be adjusted by adjusting the rotational surface speed of the cooling roll, but is usually adjusted by adjusting the height of the flat die position from the surface of the cooling roll. .

A known method can be applied to the method of melt-extruding a thermoplastic resin by the above-mentioned melt-extrusion apparatus. The extrusion speed at that time is not particularly limited,
The effect of the present invention is remarkable when the thickness of the thermoplastic resin sheet obtained after stretching, landing on the surface of the cooling roll, and cooling is 700 μm or less.

The above-mentioned thermoplastic resin sheet is usually further stretched in the longitudinal direction by a roll stretching machine, and then stretched in the width direction by a tenter stretching device to form a thermoplastic resin film.

[0021]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 A polyethylene terephthalate resin was melt-extruded from a flat die of a melt extruder, and had a width of 2200 mm and a diameter of 1 mm.
It is landed on a cooling roll surface of 300 mm, adhered by an electrostatic adhesion method and cooled, and has a thickness of 200 μm and a width of 1600.
mm of a thermoplastic resin sheet was obtained. At this time, the melting temperature of the resin was 285 ° C., the extrusion width was 1800 mm, the extrusion speed was 7 m / min, and the peripheral speed of the cooling roll was 70 m / m.
in, and the cooling temperature was 30 ° C. The obtained thermoplastic resin sheet was biaxially stretched by a roll stretching machine and a tenter stretching machine in order to confirm the properties of the film after stretching, to obtain a biaxially stretched polyethylene terephthalate film having a thickness of 12 μm.

The gap at both ends of the extrusion port of the flat die is adjusted so as to cancel the change in thickness due to neck-in, and the both sides of the extrusion port have a thickness of 1 mm.
A neck down plate made of an aluminum plate having a width of 10 mm and a length of 20 mm was connected. The neck down plate was cooled to 275 ° C. by an internal water-cooled metal block laminated on the back surface. The height of the flat die was adjusted so that the length of the molten resin sheet became 150 mm.

The above-mentioned cooling roll has an air width equal to the roll width and a height of 900 mm on the surface thereof and at a position 10 mm upstream of the rotation direction from immediately below the flat die. A blocking plate was used in which the bottom edge was parallel to the axis, was provided so as to be close to the surface almost in close contact, and the surface was vertical.

From the thermoplastic resin sheet and the stretched film manufactured as described above, three test pieces each having a width of 30 mm and a length of 15 m were sampled in a longitudinal direction, and a film thick nest tester (“KG601A” manufactured by Anritsu Corporation) was obtained. )), The maximum thickness, the minimum thickness, and the average thickness were determined by continuously measuring the test piece length of 15 m at a transport speed of 3 m / min. From the above values of maximum thickness, minimum thickness and average thickness,
Thickness unevenness (%) for each test piece (= (maximum thickness-minimum thickness)
/ Average thickness × 100), and the average of the three values obtained was taken as the average thickness unevenness of the thermoplastic resin sheet and the stretched film, and is shown in Table 2.

The state of the trace of the thermoplastic resin sheet obtained by the flat die was evaluated according to the following criteria.

[0027]

[Table 1] A: No trace of trace was observed. ：: Traces of traces were slightly observed, but were not practically problematic. C: Traces were scattered and the commercial value was low.

Comparative Example 1 A molten resin sheet was cooled and stretched biaxially in the same manner as in Example 1 except that the length of the molten resin sheet was adjusted to 50 mm. A thermoplastic resin film was manufactured, and the maximum thickness, the minimum thickness, and the average thickness of the thermoplastic resin sheet and the thermoplastic resin film were obtained, and the thickness unevenness was obtained. Further, the state of traces on the surface of the thermoplastic resin sheet due to the flat die was evaluated. Table 2 shows the results.

Comparative Example 2 The procedure of Example 1 was repeated, except that the air blocking plate provided on the cooling roll was removed, and the molten resin sheet was cooled and stretched biaxially in the same manner as in Example 1. A resin film was manufactured. In the above production, the molten resin sheet was unstable due to swinging by the accompanying air due to the rotation of the cooling roll. The maximum thickness, minimum thickness, and average thickness of the above-mentioned thermoplastic resin sheet and thermoplastic resin film were obtained, and uneven thickness was obtained. Further, the state of traces on the surface of the thermoplastic resin sheet due to the flat die was evaluated. Table 2 shows the results.

[0030]

[Table 2] Item Example 1 Comparative Example 1 Comparative Example 2有無 Presence / absence of air blocking plate Yes Yes No Length of molten resin sheet (mm) 150 50 150 Thickness of thermoplastic resin sheet Spot unevenness (%) 0.9 2.5 3.1 Thickness unevenness of stretched film (%) 2.25 5.00 5.80 Streaks by flat die ◎ △ △ ────────── ────────────────────

[0031]

According to the present invention described above, a film having a small thickness unevenness and a small trace of a flat die can be manufactured, and the industrial value of the present invention is great.

Claims (3)

[Claims] 1. A method for producing a thermoplastic resin sheet by adhering a molten resin sheet extruded from a flat die of a melt extrusion device onto a cooling casting roll by an electrostatic application adhesion method, wherein a landing line of the molten resin sheet is provided. Use a cooling casting roll provided with an air blocking plate closer to the surface on the more upstream side in the rotation direction, and the length of the molten resin sheet from the lip tip of the flat die to the landing line on the cooling casting roll surface Is adjusted to a range of 100 to 200 mm. 2. The manufacturing method according to claim 1, wherein neck down plates are provided on both side ends of the lip of the flat die. 3. The thickness of the thermoplastic resin sheet is 700 μm.
The method according to claim 1, wherein: