JPH0729354B2 - Novel acrylic resin extruded plate and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel acrylic resin extruded plate having a small internal strain in the extruding direction which is optimum for heating secondary processing applications, and a method for producing the same.

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

By the way, in the secondary processing of these acrylic resin plates, there are cases where a cutting process and a bonding process are performed in a flat plate shape, and in addition thereto, a heating process such as bending, press molding, and vacuum forming is performed. Further, there is known a method of finishing by printing or the like to obtain a final product such as a signboard, a display or a lighting cover. At this time, as a method of manufacturing the acrylic resin plate, three methods, which are a cell casting method, a continuous casting method and an extrusion method, are usually performed. Among them, the cell casting method is a method of injecting a liquid resin raw material between two glass plates and polymerizing it, which has a low work efficiency, and its use has been limited to a special field. On the other hand, the continuous casting method
This is a method for continuously producing a plate by polymerizing a liquid resin raw material between continuously moving double belts, and has a much higher work efficiency than the cell casting method. However, this method requires large-scale manufacturing equipment and
Since it is an integrated process from the liquid resin raw material, it is not possible to improve efficiency sufficiently in the case of high-mix low-volume production.
The manufacturing cost is unavoidably high next to the cell casting method.

Finally, the extrusion method is a method widely applied to acrylic resins and other thermoplastic resins. That is, it is a method in which beads or powder obtained by a method such as suspension polymerization or emulsion polymerization is directly or pelletized, or bulk polymerization is performed, followed by pulverization or pelletization, and melt extrusion for processing according to each application. This method is superior to the above two methods in that the raw material can be supplied in the form of beads, pellets, granules, etc., and can be produced in a small lot according to each purpose. . According to this method, for example, in the case of acrylic resin, 20
A plate-like body can be obtained by extruding in a plate shape through a T-die at 0 to 300 ° C., imparting a surface texture with a forming roll having no substantial peripheral speed difference between the rolls, cooling and cutting. However, in order to ensure plate thickness accuracy and good surface properties, bank forming with forming rolls is essential. The extruded plate thus obtained has a significantly lower manufacturing cost than the above-mentioned two methods, and is superior to the cell cast plate and the continuous cast plate in terms of molding characteristics, so that it has been extremely used in recent years. It has increased.

(Problems to be Solved by the Invention) However, this extruded plate often has various non-uniformities in the extruding direction or the right angle direction due to its forming means, and in particular, a semi-molten resin is rolled between rolls. Further, the internal strain in the extrusion direction caused by being cooled and solidified while further closely adhering to the roll is considerably larger than that in the width direction. The internal strain of a commercially available acrylic resin extruded plate is 1% or less in the width direction in the case of a 2 mm plate, while the extruded direction is as large as about 5 to 10%. Therefore, when this extruded plate is heat-processed, it is large in the extruded direction. It has a drawback that shrinkage occurs, and causes various adverse effects as follows.

a) The dimensions of the plate to be subjected to the heat forming must be preliminarily set in consideration of the amount of shrinkage in the extrusion direction, and since there is a difference in the amount of shrinkage in the extrusion direction and the width direction, it must be clearly distinguished.

b) Since the internal strain in the extrusion direction is large, the variation in shrinkage is large and the shape of the molded product is distorted.

c) The surface is distorted due to shrinkage in the extrusion direction during heat processing, and the beautiful surface property is lost.

d) There is a discrepancy between the molding shape and the printing for the purpose of heating and molding on a flat plate.

Internal strain also occurs in acrylic resin cell cast plates and continuous cast plates, but the degree is much smaller than that in the extrusion direction of the extruded plate, and since it is almost the same in all directions, it is very useful for use. There is no obstacle.

Therefore, in the field of processing acrylic resins, it has been an important subject to obtain an extruded plate that does not leave the internal strain in the extruding direction and does not shrink during heating.

(Means for Solving the Problems) In view of such a current situation, the inventors of the present invention have earnestly studied to obtain an extruded plate having a small internal strain in the extruding direction, and as a result, have a peripheral speed difference between forming rolls. As a result, the inventors have found that the object can be achieved, and completed the present invention.

That is, the present invention is composed of a methyl methacrylate polymer having a molecular weight of 220,000 or less, the plate thickness is 3.2 mm or less and the internal strain in the extrusion direction is 2.0% or less and an acrylic resin extruded plate and a molecular weight of 220,000. Extruding the following methyl methacrylate polymer, in producing an acrylic resin plate by bank forming and surface finishing with a forming roll, between the forming roll to which the resin first adheres and the forming roll to which the resin finally adheres. The plate thickness is 3.2 mm or less and the internal strain in the extrusion direction is
The present invention provides a method for producing a novel acrylic resin extruded plate having a content of 2.0% or less.

(Function) The methyl methacrylate polymer in the present invention means a copolymer or homopolymer containing 75% or more of methyl methacrylate capable of being kneaded and melted by a screw extruder and extruded into a plate shape from a T-type die, It may contain a commonly used dye or pigment, a lubricant, an ultraviolet absorber, a whitening agent, a trace amount additive such as a heat stabilizer, or a modifier such as an impact resistance improver. Further, its molecular weight is characterized by being 220,000 or less, while the methyl methacrylate polymer obtained by the cell cast method or the continuous cast method which has been commercially available up to now is 600,000 or more.

The molecular weight (M) of the methyl methacrylate polymer in the present invention can be obtained, for example, from the following formula described on pages 150 to 152 of “Experimental Chemistry Lecture 8 Polymer Chemistry (above)” edited by The Chemical Society of Japan. .

[Η] = 4.85 × 10 ⁻³ × M ^0.8 However, [η] is the intrinsic viscosity in chloroform at 20 ° C.

The internal strain in the extrusion direction and the width direction of the acrylic resin extruded plate, the internal strain of the acrylic resin cell cast plate, and the internal strain of the continuous cast plate in the present invention are obtained by the following methods.

In other words, 100 mm x 1 for the acrylic resin extruded plate so that the two facing sides are parallel to the extruding direction and the width direction, respectively.
Cut out three 00mm sample pieces, and in each of them, as shown in Fig. 3, draw a standard line of about 25mm, which is a in the extrusion direction and b in the width direction, at right angles to each other. To measure.

Acrylic resin cell cast plates and continuous cast plates are also marked in the same manner as the extruded plate, but as described above, the internal strains of the cell cast plates and continuous cast plates are almost the same in any direction, so the marked lines a and It is not necessary to consider the directionality of b.

Then, in a constant temperature bath at 160 ° C, place a piece of talc powder on a flat metal plate to a thickness of about 3 mm, and place the sample piece so that the surface marked with a mark will contact the talc powder for 60 minutes. After heating, it is allowed to cool at room temperature. Since the extruded plate may be warped during heating, the sample piece is placed so that the warped state after heating is as shown in FIG.

After cooling, the lengths of the three marked lines a and b are re-measured, and for the extruded plate, the a and b directions and the respective average values are obtained, and the internal strain in the extruded direction and the width direction are calculated by the following formulas. Calculate the internal strain of.

Where Da: internal strain in extrusion direction (%) Db: internal strain in width direction (%) ao, bo: original length of marked lines a, b (mm) a ', b': marked line a, Length of b after heating (mm) For cell cast plates and continuous cast plates, the internal strains are almost the same in any direction, so the internal strains are calculated by the following formula.

Where Di: internal strain (%) ao, bo: original length of marked lines a, b (mm) a ′, b ′: length of marked lines a, b after heating (mm) According to the above method, the cell cast plate of each domestic company, the internal strain of the continuous cast plate, the internal strain of the extrusion direction of the extrusion plate of the domestic method of the conventional method and the result of measuring the internal strain of the extrusion direction of the extrusion plate of the present invention. It is shown in Table 1.

The extruded plate of the present invention is completely different from the conventional extruded plate as is clear from these results, has almost no internal strain in the extrusion direction, and is a novel one smaller than the internal strain of the cell cast plate / continuous cast plate. is there.

In order to obtain an acrylic resin extruded plate having extremely small internal strain in the extruding direction as described above in the present invention, an acrylic resin plate is produced by extruding a methyl methacrylate polymer, bank-forming with a forming roll and surface finishing. In that case, it is an essential requirement to provide a negative peripheral speed difference between the molding roll to which the resin first adheres and the molding roll to which the resin adheres last, and the peripheral speed difference is substantially provided between the molding rolls. It is completely different in concept from the conventional extrusion molding method.

In the present invention, the first closely adhering forming roll and the last closely adhering forming roll are, for example, the three and four forming rolls shown in FIG. 1 and the four and nine forming rolls shown in FIG. Each of the 11 forming rolls is closely attached to the forming roll, and the resin is wound as shown in FIGS.

Providing a negative peripheral speed difference between the molding rolls means slowing down the peripheral speed of the molding roll that is finally in contact with the resin relative to the peripheral speed of the molding roll that is in close contact with the resin first. The speed difference means a value obtained by the following equation.

For example, in the case of the four rolls shown in FIG. 2, when the peripheral speeds of the forming roll that comes into close contact first, the next forming roll, and the forming roll that comes into close contact last are V ₂ , V ₃ and V ₄ , respectively, The peripheral speed difference [%] is represented by (1-V ₄ / V ₂ ) × 100,
V ₂ = V ₃ > V ₄ or V ₂ > V ₃ = V ₄ may be satisfied, and V ₂
It may be ＞ V ₃ ＞ V ₄ . The peripheral speed difference is 1 to 15%, preferably the plate thickness is 1.4 mm or more and 3.2 mm or less, and the following formulas (I) and (I
I) r ≧ 0.8t ² −6t + 12 (I) r ≦ 15 (II) (where r is the peripheral speed difference (%) and t is the thickness (mm) of the acrylic resin extruded plate). The internal strain in the extrusion direction can be reduced to 2% or less by providing the peripheral speed difference in the range described above between the forming rolls. When the peripheral speed difference is less than 1.0%, the internal strain in the extrusion direction does not become 2.0% or less, while when it exceeds 15%, the smoothness of the resin surface and the beauty are lost, which is preferable. Absent.

Thus, in producing an acrylic resin plate-like body by extruding a methyl methacrylate polymer, bank forming and surface finishing with a forming roll, between the forming roll to which the resin first adheres and the forming roll to which the resin finally adheres. By providing a negative peripheral speed difference between the two, it is possible to obtain an acrylic resin extruded plate with extremely small internal strain in the extruding direction,
An acrylic resin extruded plate having an internal strain in the extruding direction of 2% or less can be obtained.

(Examples) The present invention will be described in more detail with reference to examples.

Example 1 and Comparative Example 1 Methyl methacrylate copolymer beads having a molecular weight of 160,000 composed of 6% by weight of methyl acrylate and 94% by weight of methyl methacrylate were mixed with a resin screw using a 120 mmφ vent type single screw extruder. Extruded into a flat plate with a T-shaped die with a width of 1100 mm at 260 ° C, 300 mmφ as shown in Fig. 1.
It was bank-formed by three forming rolls 3, 4 and 5 of (1), surface-finished, and taken up by the take-up roll 7 to obtain a flat plate having a thickness of 1.5 to 3.0 mm. At this time, the second roll 4 and the third roll 5 were subjected to plate making with a peripheral speed difference of X (%), the internal strain in the extrusion direction was measured, and the surface property was evaluated.
The results are shown in Table 2.

The peripheral speed difference X (%) is a value calculated by the following equation.

In addition, the surface property was evaluated by measuring the light from a 20W straight tube fluorescent lamp at 20 °.
The observation was performed by observing the contour of the fluorescent lamp reflected on the surface of the sample extruded plate with the naked eye, and the state is represented by the symbols shown below.

A: The outline of the fluorescent light looks straight.

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

C: The outline of the fluorescent lamp is clearly distorted.

Example 2 and Comparative Example 2 The same methyl methacrylate copolymer beads as in Example 1 were extruded into a flat plate shape with a T-type die having a width of 1100 mm at a resin temperature of 260 ° C. using a 150 mmφ bent type single screw extruder. As shown in FIG. 2, four rolls of 450 mmφ forming rolls 8, 9, 10 and 11 were used for bank forming, the surface was finished, and the take-up roll 7 was used to obtain a flat plate having a thickness of 1.5 to 3.0 mm. . At this time, the second roll 9 and the third roll
X on 10 and third roll 10 and fourth roll 11 respectively
(%) And Y (%) were provided with a peripheral speed difference, the plate was made, the internal strain in the extrusion direction was measured, and the surface property was evaluated. The results are shown in Table 3.

The peripheral speed differences X (%) and Y (%) are values calculated by the following equation.

Further, the surface property was evaluated by the same method as in Example 1.

As is clear from the results of Tables 2 and 3 as described above, according to the present invention, the internal strain in the extrusion direction can be 2% or less, or even a negative value, and the peripheral speed difference can be adjusted. As shown in Table 1, the internal strain in the extrusion direction is
Can be

(Effects of the invention) As described above, the present invention is a novel acrylic resin extrusion comprising a methyl methacrylate polymer having a quantity of 220,000 or less, a plate thickness of 3.2 mm or less and an internal strain in the extrusion direction of 2.0% or less. In producing an acrylic resin plate by extruding a plate and a methyl methacrylate polymer, and bank-forming and surface finishing with a forming roll, between the forming roll to which the resin first adheres and the forming roll to which the resin finally adheres. Since this is a method of manufacturing an acrylic resin extruded plate with a negative peripheral speed difference, the internal strain in the extruding direction is extremely small and there is almost no shrinkage due to heating. A product that has the effect of not distorting and losing its beautiful surface property, and is subject to heat processing such as signboards, displays, and lighting covers. It is possible to provide an acrylic resin plate which is excellent as a master plate.

[Brief description of drawings]

FIG. 1 is a schematic diagram of molding an extruded plate with three rolls, FIG. 2 is a schematic diagram of extruded plate with four rolls, and FIG. 3 is a diagram showing a reference line of an internal strain measurement sample piece, FIG. 4 is a diagram showing a state after heating during internal strain measurement. The following reference numerals in the drawings respectively indicate the following portions. 1: T-die provided in the extruder 2: bank 3,8: first roll 4,9: second roll 5,10: third roll 6: acrylic resin plate 7: take-up roll 11: fourth roll 12 : Sample piece after heating 13: Talc powder layer 14: Metal plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Sugimoto 4-7 Kyowa-machi, Nakajo-machi, Kitakanbara-gun, Niigata Inside Kyowa Gas Chemicals Co., Ltd. Nakajo factory (72) Masao Otaki Kyowa-cho, Nakajo-machi, Kitakanbara-gun, Niigata 4-7 Kyowa Gas Chemical Industry Co., Ltd. Nakajo Factory (56) References Japanese Patent Application Laid-Open No. 56-162625 (JP, A) Japanese Patent Application No. 53-5838 (Japanese Utility Model Application No. 54-110670) A microfilm (JP, U) that captures the contents of the description and drawings

Claims (4)

[Claims] 1. A novel acrylic resin extruded plate comprising a methyl methacrylate polymer having a molecular weight of 220,000 or less, a plate thickness of 3.2 mm or less, and an internal strain in the extrusion direction of 2.0% or less. 2. The novel acrylic resin extruded plate according to claim 1, which has a plate thickness of 1.4 mm or more. 3. When manufacturing an acrylic resin plate-like body by extruding a methyl methacrylate polymer having a molecular weight of 220,000 or less and performing bank molding and surface finishing with a molding roll, the molding roll to which the resin first adheres and the final molding roll. Negative peripheral speed difference is provided between the roll and the forming roll that is in close contact with the plate. The plate thickness is 3.2 mm or less and the internal strain in the extrusion direction is 2.0%.
The following is a method for producing a novel acrylic resin extruded plate. 4. The method for producing a novel acrylic resin extruded plate according to claim 3, wherein the peripheral speed difference is 1 to 15%.