JPH01235623A - New acrylic resin extruded sheet and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an extruded sheet, which is made of methyl methacrylate polymer having specified molecular weight and the internal strain in the extrusion direction of which is the specified amount or less and which does not shrink at hot processing, by a method wherein peripheral speed difference is realized between forming rolls. CONSTITUTION:The methyl methacrylate polymer concerned means copolymer or homopolymer containing 75% or more of methyl methacrylate having a molecular weight of 220,000 or less. The forming roll, which comes into close content firstly and that, which comes into close contact lastly, mean forming rolls 4 and 5 in case of a three-roll calendar, round which resin is wound closely. The provision of negative peripheral speed difference between forming rolls means to make the peripheral speed of the forming roll, which comes into close contact lastly, slower than that of the forming roll, which comes into close contact firstly. By providing the negative peripheral speed difference between the forming rolls, an acrylic resin extruded sheet, the internal strain in the extrusion direction of which is small or concretely 2% or less, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a novel extruded acrylic resin plate with small internal strain in the extrusion direction, which is suitable for use in heated secondary processing, and a method for manufacturing the same.

(Prior Art) Acrylic resin plates have excellent beauty, weather resistance, moldability, etc., and are subjected to various secondary processes and used in a wide range of applications.

By the way, in the secondary processing of these acrylic resin plates, there are cases where cutting and bonding are performed while the plate is still in the form of a flat plate, and cases where heat processing such as bending, press forming, and vacuum forming is performed in addition to these. Furthermore, a method is known in which the material is finished by printing or painting to produce a final product such as a signboard, display, or lighting cover. There are three methods for producing acrylic resin plates: cell casting, continuous casting, and extrusion.
! This is how it is usually done. Among these, the cell cast method is a method in which a liquid resin raw material is injected between two glass plates and polymerized, and its work efficiency is low, and its use has been limited to special fields.

On the other hand, the continuous casting method is a method in which a liquid resin raw material is polymerized between continuously moving double belts to continuously manufacture plates, and the work efficiency is much higher than that of the cell casting method described above. However, this method requires large-scale manufacturing equipment and is an integrated process starting from liquid resin raw materials, so it is not efficient enough for high-mix loft production. The disadvantage is that the cost is inevitably higher than the cell casting method.

Finally, extrusion is a method widely applied to acrylic resins and other thermoplastic resins.

That is, beads or powder obtained by a method such as suspension polymerization or emulsion polymerization are directly or pelletized, or after bulk polymerization, they are crushed or pelletized, and then processed by melt extrusion depending on the intended use. This method is superior to the above two methods in that raw materials can be supplied in the form of beads, pellets, granules, etc., and production can be done in small lots depending on the purpose. . According to this method, for example, in the case of acrylic resin, it is extruded into a plate through a T-die at 200 to 300°C, the surface texture is imparted using forming rolls with no substantial difference in circumferential speed between the rolls, and the material is cut after cooling. Although a plate-shaped body can be obtained by this method, bank forming using forming rolls is essential to ensure plate thickness accuracy and good surface properties. The extruded plate obtained in this way is much cheaper to manufacture than the above two methods, and its molding properties are also superior to cell cast plates and continuous cast plates, so its use has become extremely popular in recent years. It has increased.

(Problems to be Solved by the Invention) However, this extruded plate often has various non-uniformities in the extrusion direction or in the perpendicular direction due to its forming method, and in particular, semi-molten resin is rolled between rolls. The internal strain in the extrusion direction, which is caused by being cooled and solidified while being in close contact with the subsequent rolls, is greater than that in the middle direction. The internal strain of commercially available extruded acrylic resin plates is less than 1% in the middle direction for a 2mm plate, but is as large as 5 to 10% in the extrusion direction. It has the disadvantage that large shrinkage occurs, leading to various adverse effects as described below.

a) The dimensions of the plate to be subjected to thermoforming must take into account shrinkage in the extrusion direction, and since there is a difference in the amount of shrinkage between the extrusion direction and the middle direction, a clear distinction must be made.

b) The internal strain in the extrusion direction is large, and the shrinkage rate varies widely, causing distortion in the shape of the molded product.

C) Due to shrinkage in the extrusion direction during heat processing, distortion occurs on the surface and beautiful surface properties are lost.

d) For applications in which a flat plate is printed and then heat-formed, a misalignment occurs between the molded shape and the print.

Although internal strain occurs in acrylic resin cell cast plates and continuous cast plates, the degree of strain is much smaller than that in the extrusion direction of extruded plates, and it is almost the same in all directions, so it is a major problem in terms of use. Not a hindrance.

Therefore, in the field of processing acrylic resins, it has been an important issue to obtain an extruded plate that does not retain the above-mentioned internal strain in the extrusion direction and does not shrink during heat processing.

(Means for Solving the Problems) In view of the current situation, the present inventors have conducted extensive research in order to obtain an extruded plate with small internal strain in the extrusion direction, and as a result, the inventors have developed a method that creates a peripheral speed difference between forming rolls. By doing so, they discovered that the object could be achieved and came up with the present invention.

That is, the present invention is made of a methyl methacrylate polymer with a molecular weight of 220,000 or less, and has an internal strain of 2.0% in the extrusion direction.
In manufacturing an acrylic resin plate by extruding an acrylic resin extruded plate and a methyl methacrylate polymer, and performing bank forming and surface finishing with forming rolls, the resin is first molded in close contact with each other. The present invention provides a novel method for producing an extruded acrylic resin plate, which is characterized by providing a negative circumferential speed difference between the roll and the last forming roll that comes into close contact with it.

(Function) The methyl methacrylate polymer in the present invention refers to a copolymer or homopolymer containing 75% or more of methyl methacrylate that can be kneaded and melted in a screw extruder and extruded into a plate shape from a T-shaped die. It may contain trace additives such as commonly used dyes and pigments, lubricants, ultraviolet absorbers, brighteners, heat stabilizers, etc., or modifiers such as fiu resistance improvers.

Moreover, its molecular weight is characterized by being less than 220,000, whereas the molecular weight of methyl methacrylate polymers obtained by the cell casting method and continuous casting method which have been commercially available so far is more than 600,000.

The molecular weight (M
> can be determined, for example, from the following formula described on pages 150 to 152 of "Jitsugikagaku Kou FiS Polymer Chemistry (Part 1)" edited by the Chemical Society of Japan.

[η) = 4, 85 X 10-'XM0' However, [
η] is the intrinsic viscosity in chloroform at 20°C.

Extrusion direction and rjJ of the acrylic resin extrusion plate in the present invention
The internal strain in the direction, the internal strain of the acrylic resin cell cast board, and the internal strain of the continuous cast board were determined by the method shown below.

In other words, for the extruded acrylic resin board, the two sides facing each other are parallel to the extrusion direction and the middle direction, respectively, to 100n.
Cut out three sample pieces of t+X 100 nm, mark each with about 25 marked lines perpendicular to each other, a in the extrusion direction and b in the width direction, in the center as shown in Figure 3, and mark a and b in advance. Measure length.

Mark lines are drawn for acrylic resin cell-cast boards and continuous cast boards in the same way as for extruded boards, but as mentioned above, the internal strain of cell-cast boards and continuous cast boards is almost the same in all directions, so mark lines a and The directionality of b does not need to be considered.

Next, in a constant temperature bath at 160°C, talc powder was spread about 3 inches thick on a flat metal plate, and the sample piece was placed so that the side with the marked line was in contact with the talc powder. After heating for several minutes, the mixture is allowed to cool at room temperature.

Since the extruded plate may warp during heating, the sample piece was placed so that the warp after heating would be as shown in Figure 4.

After cooling, the lengths of each of the three gauge lines a and b are remeasured, and for the extruded plate, the average value of each direction is determined, and the internal strain in the extrusion direction and the middle direction are calculated using the following formula. Find the internal strain of.

O where Da = Internal strain in the extrusion direction (%) Db: Internal strain in the width direction (%) aOlbO: Original length of gauge lines a and b (,,) a-1b
-: Length of gauge lines a and b after heating (city) For cell cast plates and continuous cast plates, the internal strain is almost the same in all directions, so the internal strain is determined by the following formula.

Here, Di = internal strain (%) ao, bo: original length of gauge lines a, b (, m) a-, b
-: Length of marked lines a and b after heating (nII) Next, according to the above method, the internal strain of the cell cast plates and continuous cast plates of each domestic company, and the extrusion direction of the extruded plates of each domestic company using the conventional method were determined. Table 1 shows the results of measuring the internal strain and the internal strain in the extrusion direction of the extruded plate of the present invention.

Table 1 As is clear from the results, the extruded plate of the present invention is completely different from conventional extruded plates, and has almost no internal strain in the extrusion direction, which is even smaller than that of cell cast plates and continuous cast plates. It is something.

In the present invention, in order to obtain an extruded acrylic resin plate with extremely small internal strain in the extrusion direction as described above, the acrylic resin plate is manufactured by extruding a methyl methacrylate polymer, bank-forming it with forming rolls, and finishing the surface. In this case, the essential requirement is to provide a negative circumferential speed difference between the forming roll where the resin comes into close contact first and the forming roll where the resin comes into close contact last, and it is essential to create a negative circumferential speed difference between the forming rolls. The concept is completely different from conventional extrusion molding methods.

In the present invention, the forming rolls that come into close contact first and the forming rolls that come into close contact last include forming rolls 4 and 5 shown in FIG. 1 in the case of three rolls, and forming rolls 9 and 5 shown in FIG. 2 in the case of four rolls. Each of the 11 molding rolls is referred to as a molding roll, and the resin is tightly attached to the molding roll and wound around the molding roll as the first and second molding rolls.

Furthermore, providing a negative circumferential speed difference between the forming rolls means that the circumferential speed of the forming roll that comes into close contact with the resin last is slower than that of the forming roll that the resin first comes into close contact with. The speed difference refers to a value obtained from the following equation.

For example, in the case of the four rolls shown in Fig. 2, the circumferential speeds of the first forming roll that comes into close contact, the next forming roll, and the last forming roll that come into close contact are V2, V3,
When set to V4, the circumferential speed difference [%] is (1-V4 /V2)
Hail at X100, 2=V3 >V4 or V2
>Vs = V4, or V2 >V3
>V4 is also acceptable. The peripheral speed difference is 1 to 15%, preferably when the plate thickness is 1.4 mm or more and 3.2 mm or less, and the following formulas (I) and (II) r≧0.8t; 2-6t+12 (I
) r≦15 (II) (In the formula, r represents the peripheral speed difference (%), and t represents the thickness of the extruded acrylic resin plate). ), and when the plate thickness exceeds 3.2m+ and is 6 stops or less, it is 1 to 12%, and by providing this peripheral speed difference between the forming rolls, the internal strain in the extrusion direction can be reduced to 2% or less. be able to. Further, when the plate thickness exceeds 3.2++ on, the internal strain in the extrusion direction can be reduced to 1.5% or less as long as the circumferential speed difference satisfies 1.2% or more and 12% or less. If the peripheral speed difference is less than 1.0%, the internal strain in the extrusion direction will not be less than 2.0%, while if it exceeds 15%, the smoothness and beauty of the resin surface will be lost. This is not desirable because it causes

In this way, when manufacturing an acrylic resin plate by extruding a methyl methacrylate polymer, bank forming it with forming rolls, and finishing the surface, the forming roll where the resin comes into close contact first and the forming roll where the resin comes into close contact last. By providing a negative circumferential speed difference between the two, it is possible to obtain an acrylic resin extruded plate with extremely small internal strain in the extrusion direction.
It is possible to obtain an acrylic resin extruded plate having an internal strain in the extrusion direction of 2% or less, a thickness of the extruded plate exceeding 3.2111N and 6 degrees or less, and an internal strain in the extrusion direction of 1.5% or less.

(Example) The present invention will be explained in more detail with reference to Examples below.

Example 1 and Comparative Example 1 Methyl methacrylate copolymer beads with a molecular weight of 160,000, consisting of 6% by weight of methyl acrylate and 94% by weight of methyl methacrylate, were produced using a 120 mm diameter vent type single screw extruder. , resin temperature 260°C and medium 1100°C
It is extruded into a flat plate using a +m T-shaped die, bank-formed using three forming rolls 3, 4 and 5 with a diameter of 300 mm as shown in Fig. 1, the surface is finished, and a take-up roll 7 is formed.
A flat plate having a thickness of 1.5 to 5.0 raIN was obtained. At this time, X (%
), and the internal strain in the extrusion direction was measured and the surface properties were evaluated. The results are shown in Table 2.

Note that the circumferential speed difference×(%) is a value calculated using the following formula.

In addition, the surface quality was evaluated using light from a 20W straight tube fluorescent lamp.
This was done by observing the outline of the fluorescent light reflected on the surface of the sample extrusion plate with the naked eye by reflecting it at an angle of 0°, and the condition was expressed by the symbols shown below.

A: The outline of the fluorescent light appears to be a straight line.

B: The outline of the fluorescent light appears slightly distorted.

C: The outline of the fluorescent light appears clearly distorted.

Example 2 and Comparative Example 2 Methyl methacrylate copolymer beads similar to those in Example 1 were extruded using a 150 mm diameter bent type jingle screw extruder with a medium 1100 nn T-shaped die at a resin temperature of 260°C. Extrude it into a flat plate shape, 450 mm as shown in Figure 2.
Bank forming is performed using four forming rolls of diameter 8°9. A flat plate with a thickness of On++++ was obtained. At this time, the 20th rule, the 30th rule 10, and the 3rd rule
The 0-rule 10 and the 40th-rule 11 were manufactured with a peripheral speed difference of X (%) and Y (%), respectively, and the internal strain in the extrusion direction was measured and the surface properties were evaluated. The third
Shown in the table.

Note that the circumferential speed differences X (%) and Y (%) are values calculated using the following formula.

Furthermore, the surface properties were evaluated in the same manner as in Example 1.

As is clear from the results in Tables 2 and 3, the present invention makes it possible to reduce the internal strain in the extrusion direction to 2% or less, or even to a negative value, and to adjust the circumferential speed difference. As shown in Table 1, the internal strain in the extrusion direction is 0.
It can be done.

Margin below (effects of the invention) As stated above, the present invention is made of a methyl methacrylate polymer with an amount of 220,000 or less, and has an internal strain of 2 in the extrusion direction.
．． In manufacturing an acrylic resin plate by extruding a new acrylic resin extruded plate and methyl methacrylate polymer with a concentration of 0% or less, bank forming and surface finishing with forming rolls, the forming roll where the resin comes into close contact first and the last This is a manufacturing method for acrylic resin extruded plates that creates a negative circumferential speed difference between the molding roll and the molding roll that is in close contact with the plate, so the internal strain in the extrusion direction is extremely small and there is almost no shrinkage due to heating. We offer acrylic resin plates that do not require checking and do not suffer from distortion or loss of beautiful surface properties due to variations in shrinkage rate, and are excellent as base plates for products that require heat processing such as signboards, display displays, and lighting covers. be able to.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of forming an extruded plate with three rolls, Fig. 2 is a schematic diagram of forming an extruded plate with four rolls, Fig. 3 is a diagram showing the marked line of the sample piece for internal strain measurement, FIG. 4 is a diagram showing the state after heating when measuring internal strain. Note that the following symbols in the figure indicate the following parts, respectively. 1: T-die provided in the extruder 2: Bank 3.8: 10th-rule 4.9: 20th-rule 5, to: 30th-rule 6: Acrylic resin plate-shaped body 7: Take-up roll 11: No. 40-ru 12: Sample piece after heating 13: Talc powder layer 14: Metal plate Patent applicant Kyowa Gas Chemical Co., Ltd. Figure 1 Figure 2

Claims (5)

[Claims] (1) A novel extruded acrylic resin plate made of a methyl methacrylate polymer having a molecular weight of 220,000 or less and having an internal strain in the extrusion direction of 2.0% or less. (2) A new acrylic resin consisting of a methyl methacrylate polymer with a molecular weight of 220,000 or less, having a plate thickness of 1.4 mm or more and 3.2 mm or less, and an internal strain in the extrusion direction of 2.0% or less. Extrusion board. (3) A new acrylic resin extrusion made of a methyl methacrylate polymer with a molecular weight of 220,000 or less, with a plate thickness of more than 3.2 mm and 6 mm or less, and an internal strain in the extrusion direction of 1.5% or less. Board. (4) When producing an acrylic resin plate by extruding a methyl methacrylate polymer and performing bank forming and surface finishing with forming rolls, the forming rolls that the resin comes into close contact with first and the forming rolls where the resin comes into close contact with each other last. A method for manufacturing an extruded acrylic resin plate, characterized by providing a negative circumferential speed difference between the plates. (5) In the manufacturing method described in item 4, the circumferential speed difference is 1 to 1.
The internal strain in the extrusion direction, characterized by being 5%, is 2.
% or less.