JP2005088310A - Method for producing thermoplastic resin plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a thermoplastic resin plate suppressing the occurrence of warpage in the flow direction during extrusion. <P>SOLUTION: In the method, an extruded sheet 17 which passed through a rolling roll 16 is fed to a take-over roll 19 with its width direction made horizontal. With the use of three warping rolls 20 arranged continuously in the flow direction y of the sheet 17, the shaft of a warping roll 20b arranged in the middle is arranged below a position connecting the shafts of the other warping rolls (20a and 20c), the roll 20b is brought into contact from the upper surface of the sheet 17, and the rolls (20a and 20c) are brought into contact from the lower surface of the sheet 17. Moreover, the temperature T<SB>warp</SB>(°C) of the lower surface of the sheet 17 in contact with the roll 20b of the middle is set up to meet formula (1): (wherein T<SB>VST</SB>is the Vicat softening point of the thermoplastic resin). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a thermoplastic resin plate, and more particularly to a method for producing a thermoplastic resin plate capable of suppressing or appropriately adjusting the occurrence of warpage in the flow direction during extrusion molding.

  Resin plates made of thermoplastic resins such as acrylic resins such as polymethyl methacrylate (PMMA), polyolefins such as polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polycarbonate (PC) are manufactured by extrusion. can do. That is, the thermoplastic resin introduced into the cylinder 11 of the extrusion molding machine 10 ′ is moved to the discharge hole 13 side by the propulsive force of the screw 12 while being melted by the heat of the heater 14, and extruded from the die 15 to be molded into a sheet shape. Thereafter, a sheet (extruded sheet) 17 of the thermoplastic resin is passed through the gap between the rolling rolls (16a to 16c) arranged at a predetermined interval, and is further cooled by being pulled by the take-up roll 19 through the transport roll 18. In addition, a resin plate whose thickness and surface roughness are appropriately adjusted can be obtained (see FIG. 5).

By the way, the resin plate 21 produced in this way has a problem that warpage occurs in which the upper surface side of the sheet is convex in both the sheet width direction x and the sheet flow direction y (FIG. 6). reference). This is because the extruded sheet 17 immediately after passing through the rolling roll 16 has a surface temperature equal to or higher than the Vicat softening point (T _VST ) and is allowed to cool to about room temperature in the vicinity of the take-up roll 19. Since the unextruded extruded sheet 17 is pulled by the take-up roll 19, contraction stress is generated, and further, the lower surface of the extruded sheet 17 whose cooling rate is slow because the radiant heat is likely to be trapped, and the radiant heat is easily diffused. This is due to the difference in shrinkage stress between the upper surface of the extruded sheet 17 where the cooling rate increases. Moreover, such a warp phenomenon occurs in the same manner regardless of the arrangement method and the total number of the rolling rolls 16. In general, warpage occurring in the flow direction y of the extruded sheet 17 is about 30 to 40 mm per 1 m.

  Conventionally, such warping has been corrected by a method such as pressing after a thermoplastic resin plate is cut to a desired size. However, since such correction processing takes time and cost, Depending on the use of the board, there is a case where the treatment is not performed. For example, a display device such as a rear projector type liquid crystal projector uses a screen in which a plurality of resin plates such as an acrylic resin are stacked, and a 100-inch screen (about 1.. There is a demand for a resin plate having a large size such as 5 m × 2 m and having a warp (curve) in only one direction. However, it is not easy to perform such correction processing itself. Therefore, at present, the thermoplastic resin plate obtained by extrusion molding is used as it is without being subjected to secondary processing, but the resin plate has a spherical warp, and the Since the degree of warpage varies from resin plate to resin plate, overlapping multiple resin sheets causes the resin sheets to come into contact with each other and rub against each other, resulting in problems such as scratches and wear. Yes.

On the other hand, the extrusion sheet 17 after passing through the rolling roll 16 is forcibly heated or cooled, and the temperature difference between the upper surface and the lower surface of the extrusion sheet 17 is controlled, thereby correcting the warp generated in the resin plate, or Attempts have been made to adjust the amount of warpage (see Patent Document 1).
However, according to the method described in Patent Document 1, although the warp can be eliminated in both the width direction x and the flow direction y of the resin plate 21 (see Example 1 of the same document), in this case, Such a resin plate used for a screen of a liquid crystal projector is not suitable for an application that requires warping only in one direction. Further, in the method described in Patent Document 1, the warpage disappears in the width direction x of the resin plate 21 and the amount of warpage can be appropriately adjusted in the flow direction y (see Example 2 of the same document), but the extruded sheet The warpage in the traveling direction (flow direction y) of 17 is not preferable because it causes a decrease in the handleability of the extruded sheet 17 after passing through the transport roll 18.
JP 2002-120249 A (Claim 1, paragraphs [0010] to [0012])

  Then, the objective of this invention is providing the method of manufacturing the thermoplastic resin board which has a curvature only in the width direction by extrusion molding.

The method for producing a thermoplastic resin plate according to the present invention for solving the above problems is as follows.
A method for producing a thermoplastic resin plate by extruding a thermoplastic resin into a sheet form from a die, passing through a rolling roll to obtain an extruded sheet, feeding the extruded sheet in a horizontal direction, and cooling it. ,
Using the three warping rolls arranged continuously in the flow direction of the extruded sheet, the axis of the warping roll arranged in the middle is connected from the position connecting the axes of the other two warping rolls. Also placed below,
A warping roll disposed in the middle is abutted from the upper surface side of the extruded sheet, and the other two warping rolls are abutted from the lower surface side of the extruded sheet;
The surface temperature T _warp (° C.) on the lower surface side of the extruded sheet at the time when it is in contact with the warping roll disposed in the middle is _expressed by the formula (1):

[In the formula (1), T _VST is the Vicat softening point of the thermoplastic resin. ]
It is characterized by setting to satisfy.
According to the method for producing a thermoplastic resin plate according to the present invention, it is possible to suppress the occurrence of warpage in the flow direction of the extruded sheet, and as a result, the warpage of the extruded sheet does not pass through processing such as secondary processing. A resin sheet generated only in the width direction can be obtained. Such a resin sheet has a warp only in one direction and is generally in the shape of a cylinder and does not have a spherical warp unlike conventional resin sheets. Even if there is some variation, it is possible to install a plurality of resin sheets in a stacked manner so that the resin sheets do not rub against each other, and there is a problem that the resin sheets are scratched or worn out. It can be prevented from occurring.

In addition, according to the method for manufacturing a thermoplastic resin plate according to the present invention, warpage disappears in the flow direction y of the resin plate 21 and the warpage amount is appropriately adjusted in the width direction x (see Examples described later). ) After the extruded sheet passes through the transport roll, there is no problem that the handleability of the extruded sheet is lowered.
In addition, in this invention, a thermoplastic resin board shape | molds a thermoplastic resin in the sheet form, Comprising: The thickness which can maintain the shape itself is provided. Specifically, the thickness is about 0.5 to 10 mm.

  In the method for producing a thermoplastic resin plate according to the present invention, the type of thermoplastic resin used as a raw material for the resin plate is not particularly limited, but an acrylic resin can be given as a specific example. Since the acrylic resin plate is highly transparent and has excellent mechanical strength, it is used, for example, as a screen in a display device such as a rear projector type liquid crystal projector. By reducing or appropriately adjusting the amount of warpage in the direction (flow direction), the handleability can be improved.

Next, a method for producing a thermoplastic resin plate according to the present invention will be described in detail with reference to the drawings.
In the method for producing a thermoplastic resin plate according to the present invention, a thermoplastic resin is extruded from a die 15 into a sheet shape, passed through a rolling roll 16 to form an extruded sheet 17, and then the take-up roll 19 with its width direction x being horizontal. It is a method of cooling while sending out to the side,
Using the three warping rolls 20 arranged continuously in the flow direction y of the extruded sheet 17, the shaft of the warping roll 20b arranged in the middle is used as the other two warping rolls 20a and 20c. Placed below the position connecting the axes of
The intermediate warping roll 20b is brought into contact with the upper surface side of the extruded sheet 17, and the other two warping rolls 20a and 20c are brought into contact with the lower surface side of the extruded sheet 17,
The surface temperature T _warp (° C.) on the lower surface side of the extruded sheet 17 at the time when it is in contact with the intermediate warp roll 20b is set so as to satisfy the above formula (1) (see FIG. 1). .

Of the three warping rolls 20 arranged continuously in the flow direction y of the extruded sheet 17, the warping roll 20 b arranged in the middle is convex on the lower surface side of the sheet 17 ( It is a roller for attaching a warp (opposite to a naturally occurring warp). By adjusting the positional relationship between the intermediate warp roll 20b and the other two warp rolls 20a and 20c and the temperature T _warp of the extruded sheet 17 when passing through the intermediate warp roll 20b, the extruded sheet The state of warping in the flow direction y of the resin plate 21 obtained by cooling and solidifying 17 can be appropriately adjusted.

The positional relationship between the intermediate warp roll 20b and the two warp rolls 20a and 20c arranged before and after the extruding sheet 17 in the flow direction y is sandwiched between the intermediate warp rolls 20b as described above. The shaft of 20b is arranged below the position connecting the shafts of the other two warping rolls 20a and 20c.
When the warping roll 20a and the warping roll 20c are at the same height (see FIG. 1), the warping roll 20a and the warping roll 20c are further intermediately warped with respect to the line connecting the two axes (dotted line i in FIG. 1). It is preferable to set the axis of the roll 20b so that it is 5 to 100 cm below, and it is more preferable to set it so that it is 20 to 80 cm below. If the amount by which the shaft position of the intermediate warp roll 20b is moved below the above range, the effect of suppressing or adjusting the warp in the flow direction y of the extruded sheet 17 may be insufficient. On the other hand, if the amount by which the shaft position of the intermediate warping roll 20b is moved downward exceeds the above range, the extruded sheet 17 exhibits rigidity as the cooling and solidification progresses. May become difficult. In FIG 1, it represents the distance between the axis of the dotted i and the intermediate warp with roll 20b by reference numeral L _2.

In the case where the warp with the roll 20a and the warp with roll 20c are at the same height, it is preferable distance _{L 1-2} of between axes of the warp with the roll 20a and the intermediate warp with roll 20b is 50 to 200 cm, More preferably, it is 50-150 cm. The distance L _2-3 between the axes of the intermediate warp roll 20b and the warp roll 20c is preferably 50 to 200 cm, and more preferably 50 to 150 cm. These distances _{L 1-2} and _{L 2-3,} the thickness of the extruded sheet 17, the conveyance speed may be set appropriately according to the amount of movement _{L 2,} etc. down the middle of the warp with the roll 20b. Incidentally, it is preferable substantially equal to the distance _{L 1-2} and _{L 2-3} between the axes, specifically, the ratio of the two _{(L 1-2:} L _2-3) is 1: 1.1 to 1 It is preferable to set the ratio to 1: 1.

An angle θ ₁ formed by a dotted line i in FIG. 1 and a line (dotted line ii in FIG. 1) along the traveling direction of the extruded sheet 17 between the warp roll 20a and the intermediate warp roll 20b is 10 It is preferable to set in the range of ˜50 °. Further, an angle θ ₂ formed by the dotted line i and a line along the traveling direction of the extruded sheet 17 between the intermediate warp roll 20b and the warp roll 20c (dotted line iii in FIG. 1) is 10 to 50 °. It is preferable to set in the range. Incidentally, substantially it is preferably equal to the theta ₁ and theta _2, specifically, their ratio of (θ _1: θ ₂₎ is 1: 1.1 to 1.1: to set to be 1 preferable.

The temperature T _warp (° C.) of the lower surface of the extruded sheet 17 that is in contact with the intermediate warping roll 20b is expressed by the formula (V) with respect to the Vicat softening point T _VST (° C.) for the thermoplastic resin forming the extruded sheet 17. 1):

Is set so as to satisfy the relationship represented by the formula (2), but within the range represented by the formula (1), the formula (2):

Is preferably set so as to satisfy the relationship represented by formula (3):

It is more preferable to set so as to satisfy the relationship represented by
When the temperature T _warp of the lower surface of the extruded sheet 17 in contact with the intermediate warping roll 20b exceeds the Vicat softening point T _VST + 20 ° C. for the thermoplastic resin forming the extruded sheet 17, the warpage of the extruded sheet 17 is corrected. Can no longer exert its effect. The upper limit of T _warp is preferably T _VST as shown in the above formula (2), and more preferably 6 ° C. lower than T _VST as shown in the above formula (3).

On the other hand, when the temperature T _warp of the lower surface of the extruded sheet 17 that is in contact with the intermediate warp roll 20b is lower than the Vicat softening point T _VST for the thermoplastic resin forming the extruded sheet 17 by more than 30 ° C., The solidification of the extruded sheet 17 has progressed too much at the point of contact with the warping roll 20b, and the effect of correcting the warpage of the extruded sheet 17 cannot be exhibited. The lower limit of T _warp is preferably a temperature 13 ° C. lower than T _VST , as shown in the above formulas (2) and (3).

Although not limited to this, the temperature T _{warp on} the lower surface of the extruded sheet 17 that is in contact with the intermediate warp roll 20b may be measured by, for example, a radiation thermometer.
In the present invention, the thickness of the thermoplastic resin plate 21 is not particularly limited, and as described above, it is set with an index that it can maintain its shape by itself. It is set to about 5 to 10 mm, preferably 1 to 5 mm. The resin plate 21 having a thickness of less than 0.5 mm is highly likely to exhibit flexibility, and the warping process may not make sense. Conversely, it is difficult to mold the resin plate 21 having a thickness exceeding the above range by the method of the present invention.

In the present invention, the material of the warping roll 20 is not particularly limited, and the same material as that used for manufacturing a resin plate by ordinary extrusion molding may be used. For example, metals such as SUS and aluminum, hard rubber, heat-resistant rubber, fluororesin, and the like can be used.
The diameter of the warping roll 20 is not particularly limited, and the same diameter as that used for manufacturing a resin plate by ordinary extrusion molding may be used. Usually, the diameter is set in the range of 1 to 30 cm.

  In the present invention, the conveyance speed of the extruded sheet 17 adjusted by the take-up roll 19 and the conveyance roll 18 is not particularly limited, but is usually set in the range of 1 to 10 m / min. When the conveyance speed is below the above range, the productivity of the extruded sheet 17 may be reduced. On the other hand, if the conveying speed exceeds the above range, there is a possibility that production of the extruded sheet 17 and warping processing cannot be performed.

  In the present invention, the arrangement of the rolling rolls 16 is such that the extruded sheet 17 that has passed through the rolling rolls 16 is sent to the conveying roll 18 (or the warping roll 20 is the take-up roll 19) with its width direction x being horizontal. Other than the above, there is no particular limitation, and various conventionally known arrangements such as a so-called vertical type and horizontal type can be employed. Further, the number of rolling rolls 16 is not particularly limited.

  Examples of the resin to which the method for producing a thermoplastic resin plate according to the present invention can be applied include acrylic resins such as polymethyl methacrylate (PMMA), polyolefins such as polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS). Styrene-methyl methacrylate copolymer resin, polycarbonate (PC) and the like.

Next, an example and a comparative example are given and the manufacturing method of the thermoplastic resin board of the present invention is explained.
[Manufacture of thermoplastic resin plates]
(Example 1)
A plate having a length in the width direction x of 95 cm and a length in the flow direction y of 125 cm by using the acrylic resin composition having a Vicat softening point T _VST of 104 to 105 ° C. and the extruder 10 shown in FIG. A 2.0 mm thick acrylic resin plate (acrylic sheet) was molded.

  Among the warp rolls 20 of the extrusion molding machine 10, the second warp roll 20b disposed in the middle is arranged with its axis in the position of the first warp roll 20a and the third warp roll 20c. The line is arranged below the line (indicated by a dotted line i in FIG. 1) connecting the two axes. As the first to third warping rolls 20, SUS rollers having a diameter of 50 mm were used.

Distance _{L 1-2} between axial center of the first warp with roll 20a and the second warp with roll 20b is such that the 1240 mm, the second warp with roll 20b and the third warp with roll 20c The distance L _2-3 between the shaft centers is 1255 mm, and the amount of downward movement of the second warp roll 20b (the line connecting the axes of the first and third warp rolls 20a and 20c ( The distance L ₂ ) between the dotted line i) and the axis of the second warping roll 20b was set to 600 mm. In this case, the angle θ ₁ formed by the dotted line i and the dotted line ii is about 28.9 °, and the angle θ ₂ formed by the dotted line i and the dotted line iii is about 28.6 °. Become.

The temperature T _{warp on} the lower surface of the extruded sheet 17 passing through the second warping roll 20b was adjusted to 95 to 98 ° C. In this case, the difference between the Vicat softening point T _VST at most 10 ° C., was minimal at 6 ° C.. The temperature of the lower surface of the extruded sheet 17 is 109 to 112 ° C. (T ₁ ) when passing through the first warping roll 20a, and 77 to 79 ° C. (T when passing through the third warping roll 20c). ₃ ). The line speed between the first to third warping rolls 20 was 3.0 m / min.

(Example 2)
In addition to adjusting the temperature T _warp of the lower surface of the extruded sheet 17 passing through the second warping roll 20b to 89 to 90 ° C., the difference from the Vicat softening point T _VST is 16 ° C. at maximum and 14 ° C. at minimum. In the same manner as in Example 1, an acrylic resin plate (acrylic sheet) having a thickness of 2.0 mm and a length of 95 cm in the width direction x and a length of 125 cm in the flow direction y was molded.

(Comparative Example 1)
Using the same acrylic resin composition as in Example 1 having a Vicat softening point T _VST of 104 to 105 ° C., the length in the width direction x is 95 cm and the length in the flow direction y is measured by the extruder 10 ′ shown in FIG. An acrylic resin plate (acrylic sheet) having a thickness of 125 cm and a thickness of 2.0 mm was molded.

All of the four conveying rolls (18a to 18d) of the extrusion molding machine 10 ′ were arranged so that the extruded sheet 17 that passed through the roll 16c could be conveyed horizontally. As the transport roll 18, a SUS product having a diameter of 50 mm was used. The line speed between the first to third warping rolls 20 was 3.0 m / min.
(Measurement of warpage)
-Warpage amount in the flow direction y As shown in Fig. 2 for the acrylic resin plates obtained in the examples and comparative examples, two suspension holes 22b are provided at the side end (long side) of the resin plate 21, respectively. It was. This hole 22b was disposed at a position obtained by dividing the side end of the long side into three equal parts in the flow direction y. Next, the resin plate 21 is suspended by using the two holes 22b for hanging, and a thread 24 is stretched between both ends 23 in the flow direction y of the resin plate 21 so as to be horizontal with the flow direction y. . Further, in the central portion 25 in the flow direction y of the resin plate 21, the distance is measured perpendicularly from the surface to the yarn 24, and the distance L _warp (y) at this time is the amount of warpage of the resin plate 21 in the flow direction y ( mm).

On the other hand, as shown in FIG. 2, two suspension holes 22 a are provided in the side end (short side) of the resin plate 21. The hole 22a was disposed at a position where the side end portion on the short side was equally divided into three in the width direction x. Next, the resin plate 21 is suspended by using the hole 22a for hanging, and a thread is stretched between both ends in the width direction x of the resin plate 21 so as to be horizontal to the width direction x (not shown). . Further, in the central portion in the width direction x of the resin plate 21, the distance is measured perpendicularly from the surface to the yarn, and the distance L _warp (x) at this time is the amount of warpage (mm) of the resin plate 21 in the width direction x. It was.

When the warp amount L _warp is “+”, it indicates that it is convex on the upper surface side of the resin plate 21, and when it is “−”, it indicates that it is convex on the lower surface side of the resin plate 21. .
[Measurement of residual stress]
When the resin plate has residual stress, warpage corresponding to the residual stress occurs over time. The degree of this residual stress can be detected by, for example, performing a so-called heating acceleration test that is left for a predetermined time in an atmosphere of a certain high temperature and measuring the amount of warping thereafter. Therefore, for the acrylic resin plates 21 obtained in Examples and Comparative Examples, as shown in FIG. 3, a sample 30 cut out along the width direction x and a sample 31 cut out along the flow direction y It produced and used for the heating acceleration test.

The sample 30 was a sample of 400 mm in the width direction x of the resin plate 21 and 30 mm in the flow direction y. The sample 31 was a sample having a thickness of 30 mm in the width direction x of the resin plate 21 and 400 mm in the flow direction y. The heating conditions for the heating acceleration test were heating at 80 ° C. for 30 minutes in an air oven.
As shown in FIG. 4, the sample 30 is set so that its long side (width direction x of the resin plate 21) is left and right, and its short side (flow direction y of the resin plate 21) is up and down. The lower end side was fixed with a clip. One sample 31 is also set so that its long side (flow direction y of the resin plate 21) is left and right, and its short side (width direction x of the resin plate 21) is up and down, and its lower end is clipped. Fixed with 32. When the sample shown in FIG. 4A is the sample 30, the horizontal direction in the figure is the width direction x of the resin plate 21, and the vertical direction in the figure is the flow direction y of the resin plate 21. On the other hand, in the case of the sample 31, the left and right direction and the up and down direction are opposite to the case of the sample 30. The fixing position of the clip 32 was a position (two places) divided into three equal parts on the long side of the samples 30 and 31. Next, a plate 34 processed so that the end surface thereof is exactly a flat surface is brought into contact between both end portions 33 on the long side of the samples 31 and 32, and the samples 31 and 32 are started from the end 34 a of the plate 34. The distance D was measured perpendicularly to the central portion 35 on the long side. In FIG. 4, reference numeral 36 denotes a flat base for installing the plate 34.

This measurement was conducted twice after being subjected before and the test to be subjected to heat acceleration test to determine the variation of the distance D _a after heating the distance D _b before heating [Delta] D (mm).
When the distance D and the change amount ΔD are “+”, it indicates that it is convex on the upper surface side of the resin plate 21, and when it is “−”, it is convex on the lower surface side of the resin plate 21. Indicates.
The results are shown in Table 1.

  As is apparent from Table 1, in Examples 1 and 2, the amount of warpage in the flow direction y could be extremely reduced. Moreover, in Example 1, the variation | change_quantity of the curvature amount by a heating acceleration test was also able to be suppressed. Since the resin plates obtained in Examples 1 and 2 generally have warpage only in one direction (width direction), they are particularly suitable for applications in which a plurality of resin plates are used in an overlapping manner.

On the other hand, in Comparative Example 1, the amount of warpage in the flow direction y was large, and the entire resin plate was spherical.
In the above embodiment, the present invention has been described with an example of manufacturing an acrylic resin plate. However, the present invention is not limited to the above embodiment, and various design changes can be made without changing the gist of the present invention.

It is a typical side view which shows the arrangement | positioning state of a conveyance roll. It is a schematic diagram which shows the method of measuring the curvature amount of a resin board, Comprising: (a) is a perspective view, (b) is a top view. It is a top view of the resin board 21 which shows the place which takes out the sample for a heating test. It is a schematic diagram which shows the method of measuring the curvature amount of the sample for a heating test, Comprising: (a) is a perspective view, (b) is a rear view. It is a schematic diagram which shows an example of the manufacturing process of the resin board by the conventional extrusion molding. It is a schematic diagram for demonstrating the state of the curvature which arose in the resin board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Extruder 15 Die 16 Rolling roll 17 Extrusion sheet 20 Warp roll 21 Resin plate

Claims (2)

A method for producing a thermoplastic resin plate by extruding a thermoplastic resin into a sheet form from a die, passing through a rolling roll to obtain an extruded sheet, feeding the extruded sheet in a horizontal direction, and cooling it. ,
Using the three warping rolls arranged continuously in the flow direction of the extruded sheet, the axis of the warping roll arranged in the middle is connected from the position connecting the axes of the other two warping rolls. Also placed below,
Abutting the warping roll arranged in the middle from the upper surface side of the extruded sheet, and abutting the other two warping rolls from the lower surface side of the extruded sheet;
The surface temperature T _warp (° C.) on the lower surface side of the extruded sheet at the time when it is in contact with the warping roll disposed in the middle is _expressed by the formula (1):
[In the formula (1), T _VST is the Vicat softening point of the thermoplastic resin. ]
It sets so that it may satisfy | fill. The manufacturing method of the thermoplastic resin board characterized by the above-mentioned.   The method for producing a thermoplastic resin plate according to claim 1, wherein the thermoplastic resin is an acrylic resin.