JPS6125735B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has excellent solvent resistance, moldability,
The present invention relates to a method for producing an acrylic resin plate that is excellent in transparency and heat deformation resistance. More specifically, the present invention relates to a method of copolymerizing a higher alkyl ester of acrylic acid, methyl acrylate, and methyl methacrylate in a specific ratio, and extruding this into a plate shape. The resulting acrylic resin plate has excellent solvent resistance, with no cracks occurring even when solvents such as methylene dichloride come into contact with areas where internal distortion has occurred due to heat bending, etc., and it also has excellent solvent resistance. Like the plate, it has excellent molding process, transparency, and heat deformation resistance. Generally, acrylic resin plates are manufactured by two methods: casting and extrusion. The cast method involves injecting methyl methacrylate monomer or its partial polymer with a catalyst into the gap between two pieces of tempered glass that are combined via a gasket, heating it to polymerize as it is, and then removing the glass. It is a method of obtaining an acrylic resin board,
This method usually results in polymers with an average molecular weight of 1 million to 4 million. The acrylic plate obtained by this method has no particular dissatisfaction with its physical properties, but due to its high molecular weight, it is difficult to become fluid even when heated, making it difficult to obtain sufficient mold reproducibility in vacuum forming and other thermal processing. Moreover, the production method requires a batch system, and the disadvantage is that the productivity is low because polymerization takes a long time. On the other hand, the extrusion method uses an extruder and a T-tie to supply acrylic resin, which is a molding material prepared in advance, to the extruder and sufficiently melt it inside the extruder. This is a method of continuously manufacturing resin plates by extruding the resin, polishing it with metal rolls, taking it off at a constant speed, and cooling it. The acrylic resin used in this method is mainly produced by a suspension polymerization method and supplied in granular form. It has a molecular weight and is usually copolymerized with a few percent of methyl acrylate or ethyl acrylate. This method is much better in terms of productivity than the casting method, and the properties of the resulting resin plate itself are also very good. In other words, the acrylic resin board obtained by this extrusion method has various properties such as weather resistance, light transmittance, and surface hardness that rank among the highest among various synthetic resins.
These properties are not inferior to resin plates produced by the cast method. In addition, resin plates made by extrusion have excellent fluidity when heated, so they exhibit excellent mold reproducibility in vacuum forming and other thermal processing, and are capable of deep drawing and forming with acute angles, which are impossible with resin plates made by casting. It has properties suitable for use in fields of application that involve molding, such as signboards and displays. However, the acrylic resin plate produced by this extrusion method has a disadvantage in that it has inferior solvent resistance compared to the plate produced by the cast method. In addition, solvent resistance in this case refers to cracks that occur when a solvent such as methylene dichloride, which is commonly used as an adhesive, comes into contact with the part where the plate has been heated and subjected to forming processes such as bending. Judgment is made based on the presence or absence of phenomena that occur. Vacuum-formed and heat-processed acrylic resin plates are used as signboards, displays, and the like by further assembling or gluing them to a higher degree of processing. However, extruded acrylic plates suffer from solvent cracks caused by the adhesive, which limits their use and makes it impossible to fully demonstrate the characteristics of an extruded plate. The present inventors conducted various studies to develop an acrylic resin plate with good solvent resistance that does not cause solvent cracks in molded products, and found that by first using a specific acrylic resin as an extrusion material, I discovered that the purpose could be achieved (Japanese Patent Application Laid-open No. 1973-
12381), and subsequent research revealed that the boards obtained in this way were slightly cloudy, which could impair the marketability of acrylic boards, which are characterized by excellent transparency. Another drawback is that acrylic resins with low molecular weights and good productivity cannot be used. As a result of further research, it was discovered that turbidity could be eliminated by using an acrylic resin with a specific composition consisting of higher alkyl esters of acrylic acid, methyl acrylate, and methyl methacrylate as an extrusion molding material. What is more surprising is that when methyl methacrylate is constant,
It has been found that a composition in which a higher alkyl ester of acrylic acid and methyl acrylate coexist has a higher heat distortion temperature than a composition in which a higher alkyl ester of acrylic acid or methyl acrylate is present alone. Therefore, it is possible to use an acrylic resin with a low molecular weight, which could not be used with conventional techniques, and productivity can be significantly improved. The present invention mainly contains at least one type of higher alkyl ester of acrylic acid derived from an alcohol having 3 to 8 carbon atoms and acrylic acid, and at least three types of monomers consisting of methyl acrylate and methyl methacrylate. This is a method of manufacturing a plate by polymerizing a mixture of components and extruding the copolymer. These compositions are shown as shaded areas in the ternary composition diagram of the accompanying drawings. In the present invention,
Components of the mixture other than these main monomers include other copolymerizable monomers, plasticizers, heat stabilizers for imparting various functions, light stabilizers, flame retardants,
It may contain additives such as antistatic agents, polymerization initiators, and molecular weight regulators. Examples of other copolymerizable monomers include ethyl acrylate, stearyl methacrylate, styrene, acrylonitrile, and vinyl acetate. Furthermore, examples of the plasticizer include dibutyl phthalate, dioctyl phthalate, cetyl alcohol, stearyl alcohol, and the like. Furthermore, during extrusion molding, a colored plate can also be produced by blending a conventionally known coloring agent such as a pigment or dye with the copolymer composition. Similarly, copolymers include heat stabilizers, light stabilizers,
Acrylic plates with various functions can also be manufactured by blending additives such as flame retardants and antistatic agents and extrusion molding. Specific examples of higher alkyl esters of acrylic acid derived from alcohols having 3 to 8 carbon atoms and acrylic acid include n-butyl acrylate, isobutyl acrylate, n-proyl acrylate, isoproyl acrylate, and n-acrylic acid. -amyl, hexyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, etc. If the total amount of the acrylic acid higher ester and methyl acrylate is less than 10% by weight of the monomer containing methyl methacrylate, the resulting plate will not have satisfactory solvent resistance. Furthermore, if the total amount exceeds 20% by weight, the heat deformation resistance will not be satisfactory. As for heat deformation resistance, ASTM648-56 (load stress
It is practically inconvenient if the heat distortion temperature measured at 264psi) is less than 85℃. In addition, the amount of acrylic acid higher ester must not exceed the amount of methyl acrylate; if it exceeds the amount, the obtained board will become cloudy and lose its transparency, which is one of the characteristics of acrylic board. . Turbidity can be easily determined by polishing both ends of boards cut to lengths of 10 cm or more to allow light to pass through them, or by stacking boards cut to appropriate sizes 10 cm or more and observing them. Furthermore, higher alkyl ester of acrylic acid and methyl acrylate must coexist. In a composition in which either one of them is copolymerized alone with methyl methacrylate, the resulting board becomes cloudy and the productivity is lower than 100,000~
When the molecular weight is 150,000, the heat deformation resistance is not satisfactory. The molecular weight of the composition used in the present invention is 10
Preferably, it is in the range of 600,000 to 600,000. If the molecular weight does not reach 100,000, the mechanical strength of the obtained plate will decrease and the heat distortion temperature will also decrease, which is not preferable. Furthermore, if the molecular weight exceeds 600,000, the extrusion rate will be extremely reduced, making it impossible to form a plate. A copolymer composition with controlled molecular weight can be obtained by adding an appropriate amount of a known chain transfer agent to the monomer mixture and polymerizing the mixture in the presence of a known polymerization initiator. Although it is possible to control the molecular weight by controlling the concentration of the polymerization initiator and the polymerization temperature without using a chain transfer agent, using a chain transfer agent makes it possible to reproducibly create a composition with a desired molecular weight. It is advantageous because it can be easily obtained. That is, the concentration of the polymerization initiator and the polymerization temperature are set within predetermined ranges, and the molecular weight is adjusted by adjusting the amount of the chain transfer agent added, as is commonly done. The concentration of the polymerization initiator is selected within the range of 0.1% to 0.5% for commonly used organic peroxides, and the polymerization temperature does not exceed the boiling point of methyl methacrylate, 100°C, or the boiling point of methyl acrylate, 80°C. With consideration to
It is usually selected within the range of 60 to 80°C. As the chain transfer agent, mercaptans such as n-dodecyl mercaptan and n-butyl mercaptan, carbon tetrachloride, alkylthioglycolate, pendyl chloride, etc. can be used, but mercaptans are preferable in terms of the physical properties of the resulting composition. It is preferable to use To obtain a copolymer composition having a molecular weight of 100,000 to 600,000, taking n-dodecyl mercaptan as an example, an amount of 1.00 to 0.08% by weight of the monomer mixture is added. In the case of other chain transfer agents, for example, "Polymer Handboock", published by Interscience Publishers, edited by J. Brandrup et al., pages 100-105 and pages 126-128, published by Asakura Shoten, The amount to be used can be easily determined by referring to the chain transfer constant described on page 325 of "Modern Industrial Chemistry 16" edited by Imoto and Takemoto, Polymer Industrial Chemistry, page 325. That is, in general, when a substance with a high chain transfer constant is used, the amount may be reduced, and when a substance with a low chain transfer constant is used, the amount may be increased. The molecular weight shown in the specification of the present invention was determined from the intrinsic viscosity [η] at 25°C of the above-mentioned polymer in chloroform using the following relational expression. Measured using Intrinsic viscosity [η] = KM = where K = ^4.85 Moreover, productivity,
An extruded acrylic resin plate with excellent heat processability, transparency, thermal deformability, etc., is produced like conventional extruded plates. The present invention will be specifically explained below using Examples. Examples First, a polymer is produced by suspension polymerization. Pure water
150 Sodium polyacrylate 1.5Kg Disodium hydrogen phosphate 850g Sodium dihydrogen phosphate 50
g and stir while heating to 30-35°C until the liquid becomes transparent to form an aqueous phase. On the other hand, a monomer mixture consisting of methyl methacrylate, methyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate was weighed according to the combinations shown in Table 2 so that the total weight was 50 kg; Appropriate amount of n-dodecyl mercaptan and 500g of benzoyl peroxide
After adding and stirring well to adjust the monomer phase,
Add this monomer phase to the aqueous phase and stir well to suspend. While maintaining this state, the air in the container is replaced with nitrogen, and the temperature is maintained at 76 to 78°C for 3 hours to carry out polymerization. In order to further complete the reaction, the reaction temperature was increased to 95%.
After raising the temperature to 0.degree. C. and maintaining it for 2 hours, and then cooling the reaction mixture to room temperature, the copolymer was collected by filtration, washed several times with distilled water, and dried. Note that the amount of n-dodecyl mercaptan and the molecular weight of the copolymer are
As shown in the table.

[Table] The obtained copolymer was extruded using an extruder manufactured by Japan Steel Works (P40-30AB-V type) and a T-die, and cooled with a metal roll to produce a plate with a width of 20 cm and a thickness of 3 mm. The extruder cylinder temperature and T-die temperature are
The temperature of the metal roll was controlled within the range of 210°C to 250°C, and the temperature of the metal roll was controlled within the range of 80°C to 100°C. The amount of extrusion per hour was calculated from the weight of the plate manufactured per unit time and is shown in Table 2. The heat distortion temperature of the obtained plate was measured according to ASTM648-56 (load stress 264 psi), and the results were
Shown in the table. Also, cut the board into 10cm x 10cm pieces, and
The plates were stacked and visually observed to test for turbidity. Then, heat it from one side using a pipe-shaped electric heater, and when the back side reaches 120℃, bend it at right angles with the heated side outside and cool it to room temperature.
Methylene dichloride was applied and the presence or absence of cracks was observed. These results are shown in Table 2.

[Table] Comparative Example A copolymer consisting of methyl methacrylate, methyl acrylate, and n-butyl acrylate was produced in the same manner as in the example, and a plate was produced using an extruder. The presence or absence of turbidity and the occurrence of cracks when methylene dichloride was applied to the bent pipe heater were observed. The results are shown in Table 3.

【table】 [Brief explanation of the drawing]

The drawing is a ternary system composition diagram showing the components of a monomer mixture consisting of higher alkyl esters of acrylic acid (A), methyl acrylate (B), and methyl methacrylate (C), and the hatched areas in the drawing are is within the scope of the present invention.

Claims (1)

[Claims] 1 (A) At least one higher alkyl ester of acrylic acid, (B) methyl acrylate and (C) methyl methacrylate, (A) component is 1% by weight or more, (B) component is
Same as or more than component (A), component (C) is 80% by weight
Production of a solvent-resistant acrylic resin board characterized by copolymerizing a monomer mixture mixed at a ratio of 90% by weight or less, and then extruding the obtained copolymer into a board shape. Method.