JPS6410172B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously producing extruded plates, and more particularly to a method for continuously producing extruded plates from methyl methacrylate monomers.

Conventionally, thermoplastic resin extrusion plates are produced by suspension polymerizing vinyl monomers to produce a polymer, then melting and extruding the resulting polymer from an extruder equipped with a die, and then forming the plate using rolls or the like. A method of forming it into a shaped body is adopted.

Such a method has the advantage that as long as an extrusion molding machine is available, various thermoplastic polymers can be extruded into desired plate-shaped products.

However, since the thermoplastic polymer used for extrusion molding in the above production method is mainly produced by a suspension polymerization method using water as a medium, the dispersion used for polymerization may be present in the obtained polymer. Auxiliary agents such as additives remain, reducing quality, and post-processing requires washing with a large amount of water and subsequent drying.
Furthermore, since the polymerization operation is carried out batchwise, quality variations occur, and the operation becomes inefficient and complicated, and at the same time, the required costs such as equipment costs and operating costs are high. Furthermore, now that pollution regulations are becoming stricter,
It is undesirable to release a large amount of water used for polymerization or washing water that contains auxiliary agents such as dispersants and unreacted monomers, and if treatment equipment is provided, the required cost will increase, making it difficult for industrial use. This is inevitably a disadvantageous manufacturing method. In addition, the methyl methacrylate-based polymer produced by the above method generally does not have sufficient thermal decomposition resistance, so when molded by extruding at high temperatures, the polymer decomposes in the extruder and volatile matter is released. In many cases, this produced foaming in the extruded molding plate, making it impossible to obtain a satisfactory molded product.

In view of this situation, the inventors of the present invention have conducted extensive studies on the manufacturing method of extruded plates in order to eliminate the above-mentioned drawbacks, and have discovered that the above-mentioned drawbacks can be eliminated by adopting a special process, and have developed the present invention. completed.

The first object of the present invention is to provide a method for manufacturing a thermoplastic resin extruded plate of constant quality.

A second object of the present invention is to provide an industrially advantageous method for manufacturing an extruded plate, in which the extruded plate is manufactured from monomers all at once.

A third object of the present invention is to provide a method for continuously producing an extruded plate that has excellent heat decomposition resistance and is free of bubbles due to foaming even when passed through an extruder at high temperatures.

That is, the gist of the present invention is a polymethyl methacrylate or a methacrylic copolymer containing 80% by weight or more of methyl methacrylate units and 20% by weight or less of alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) units. In the method of producing an extruded plate, 0.01 to 1.0% by weight of mercaptan and the following formula 40≧A ^1/2・B ^-1/2 ×10 ³ 3≧A・B×10 ⁵ and 2.0≧A ⁻¹・(B + 10 .3)×10 ^-6 [In the formula, A is the number of moles of the polymerization initiator in 100 g of the feed monomer, and B is the half-life (hours) of the radical polymerization initiator at the polymerization temperature]. A monomer mixture of the above polymer containing a radical polymerization initiator is continuously fed into one reaction zone, and the reaction mixture in the reaction zone is stirred and mixed substantially uniformly at a temperature of 130 to 200°C. , and the viscosity of the reaction mixture is 10 to 500 at the reaction temperature of the reaction mixture.
Polymerization is carried out while maintaining a constant poise value, and then the reaction mixture is continuously taken out from the reaction zone, and after separating the polymer and unreacted monomers in a devolatilizing extruder, the polymer is Provided is a continuous method for producing an extruded plate, characterized in that the extruded plate is formed into a plate by extrusion through a die of an extruder.

The extruded plate obtained by the method of the present invention is a homopolymer of methyl methacrylate or a copolymer ( Hereinafter, these are simply referred to as methacrylic polymers). The alkyl acrylate that can be used for copolymerization with methyl methacrylate is selected from those having an alkyl group having 1 to 18 carbon atoms, such as methyl, ethyl, n
-propyl, n-butyl, 2-ethylhexyl,
Alkyl acrylates having alkyl groups such as dodecyl and stearyl are included. Further, the alkyl methacrylate which is a copolymerization component of methyl methacrylate is selected from those having an alkyl group having 2 to 18 carbon atoms, and includes, for example, alkyl methacrylate having the same alkyl group as described above except for a methyl group. Particularly preferred are homopolymers, ie polymethyl methacrylate, and copolymers of methyl methacrylate and alkyl acrylates selected from methyl and ethyl.

The present invention can be roughly divided into three steps: polymerization, volatile matter separation, and plate forming step. The polymerization process is a process in which monomers or monomer mixtures are continuously polymerized in bulk. In the volatile matter separation step, volatile matter mainly composed of unreacted monomers is continuously separated and removed from the reaction mixture containing the polymer produced in the polymerization step, and if necessary, additives are added to extrude the extruded plate of the desired quality. This is the process of obtaining materials. The plate forming process is a process in which a polymer extruded from a die of a degassing extruder is rolled and formed using rollers to produce a plate of a desired thickness.

In the polymerization step, a monomer mixture containing a radical polymerization initiator and a mercaptan is continuously supplied to the reaction zone and polymerized.

The mercaptans used in the present invention include primary mercaptans having an alkyl group or a substituted alkyl group.
mercaptans such as n-butyl, isopropyl, n-octyl, n-dodecyl, sec-butyl, sec-dodecyl, tert-butyl mercaptan; aromatic mercaptans such as phenyl mercaptan, thiocresol , 4-tert-
Examples include mercaptans having 2 to 18 carbon atoms such as butyl-o-thiocresol; thioglycolic acid and its alkyl esters; β-mercaptopropionic acid and its alkyl esters; and ethylene thioglycol. These can be used alone or in combination of two or more. Among these mercaptans, tert-butyl, n-butyl, n-octyl and n-dodecyl mercaptan are preferred.

The amount of mercaptan used is 0.01 to 1.0% by weight, based on the monomer mixture. If the amount used is less than 0.01% by weight, the reaction rate becomes abnormally high and the polymerization reaction may not be controlled, making it difficult to obtain a polymer of constant quality and excellent heat decomposition resistance. Moreover, if it exceeds 1.0% by weight, the degree of polymerization will decrease and the mechanical properties of the product will decrease. The preferred amount used depends on the type of mercaptan, but is between 0.05 and 0.5.
% by weight.

Examples of the radical polymerization initiator used in the method of the present invention include di-tert.butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, di-tert.butyl perphthalate, di-tert.butyl perbenzoate, and tert.・Butyl peracetate, 2,5-dimethyl-2,5-di-(tert・butylperoxy)
Organic peroxides such as hexane, di-tert-amyl peroxide, and 2,5-dimethyl-2,2-di(tert-butylperoxy)hexyne, and azobisisobutanol diacetate, 1,
1-azobiscyclohexanecarbonitrile, 2
Examples include azo compounds such as -phenylazo-2,4-dimethyl-4-methoxyvaleronitrile and 2-cyano-2-propylazoformamide. These radical polymerization initiators can be used alone or in combination of two or more.

The amount of radical polymerization initiator in the monomer mixture is A
When is the number of moles of the radical polymerization initiator in 100 g of monomer feed, and B is the half-life (hours) of the radical polymerization initiator at the polymerization temperature, A and B are expressed by the following formulas (1), (2), and It must be controlled to satisfy (3).

40≧A ^1/2・B ^-1/2 ×10 ³ ...(1) 3≧A・B×10 ⁵ ......(2) and 2.0≧A ^-1・(B+10.3)×10 ^-6 ... ...(3) The method of the present invention can yield an extruded plate with excellent heat decomposition resistance, which is the object of the present invention, if the concentration of the radical polymerization initiator used satisfies the above three formulas. I can do it.

Here, "the half-life of a radical polymerization initiator at the polymerization temperature" means the half-life in a dilute benzene solution having the same temperature as the polymerization temperature, and this is described in Modern Plastics magazine, February 1952 issue, page 144. It can be easily measured according to the method.

The entire reaction mixture in the reaction zone is stirred and mixed substantially uniformly at a temperature of 130°C or higher and 200°C or lower. If the temperature of the reaction mixture is less than 130°C, the viscosity of the system will be high, and mixing or heat transfer will be insufficient, making it difficult to stably control the reaction. Increasing the polymerization reaction temperature to 200°C or higher reduces the viscosity and is advantageous in terms of reaction control, but it also reduces the thermal decomposition resistance of the resulting polymer, worsens moldability, and increases the production of side reaction products. The amount of produced will increase. Therefore, the polymerization temperature of the present invention is 130°C or higher and lower than 200°C, preferably 160°C or higher and 185°C or lower.

Within the reaction zone, the viscosity of the reaction mixture is controlled within the viscosity range of 10 to 500 poise at the reaction temperature. If the viscosity in the reaction zone is less than 10 poise, the resulting polymer will have poor thermal decomposition resistance, and the acceleration of the reaction due to the gel effect will not be fully utilized. On the other hand, if the viscosity exceeds 500 poise, the resulting polymer has excellent thermal decomposition resistance, but mixing and heat transfer cannot be performed sufficiently, making stable control impossible.

A preferable reaction apparatus used in carrying out the present invention is a tank-type reaction apparatus equipped with an inlet and an outlet, such as described in Japanese Patent Publication No. 56-15641, Utility Model Publication No. 54-38625, etc. It has the function of sufficiently mixing the entire contents.

In the volatile matter separation process, which consists mainly of unreacted monomers, a continuously fed reaction mixture with a predetermined polymerization rate is heated to 200 to 290°C under reduced pressure to continuously remove most of the volatile matter. Separate and remove. The residual monomer content in the final molded plate is 1% by weight or less, preferably 0.3% by weight or less. As the device used for volatile matter separation, a general single-screw or multi-screw vented extruder can preferably be used. The volatilized and separated polymer is extruded from a die in a molten state.

The plate forming process is a process in which a molten polymer extruded from a die of a devolatilizing extruder at a temperature of 220 to 260°C is formed into a plate having a required thickness (for example, 0.5 to 12 mm) and width using a plurality of rollers. Conventional equipment and methods can be applied to this plate process.

The following additives can be added depending on the type of extruded board and the requirements for the type. Examples include plasticizers and lubricants such as dioctyl phthalate and stearyl alcohol; ultraviolet absorbers such as Tinuvin-P (Ciba Geigy) and methyl salicylate; colorants, pigments; and high molecular weight polymers such as synthetic rubber. These can be added during the polymerization step or the volatile matter separation step. In many cases it is preferred to add it after the polymerization step.

The extruded plate obtained by the present invention has a [η] of 0.04 to 1.0.
It has excellent quality, especially transparency and moldability.

Next, a typical apparatus used to carry out the present invention will be described with reference to FIG.

A monomer mixture containing a radical polymerization initiator and a polymerization regulator passes from a storage tank 1 through a line 2 and is sent to a heat exchanger 5 through a line 4 by a pump 3. Here, the temperature-controlled monomer mixture is fed into a reaction tank 7 via a line 6. The reaction tank 7 is equipped with, for example, a spiral ribbon stirrer 8 and a jacket 9 through which a heat medium flows. The reaction mixture in the reaction vessel 7 is discharged through the discharge line 10 and the pump 1.
1. The molten polymer is sent to a volatile separator 13 via a line 12, where volatile components are removed, and the molten polymer is discharged from a die 14. The volatile separator 13 is equipped with screws, vents, means for heating or cooling, and an additive injection system. The volatile components, mainly composed of monomers, separated from the vent are supplied to the heat exchanger 20 through the line 19, and after removing impurities, the volatile component vapor is recovered in full by the total condenser 21, and stored in the holder 22. The recovered monomer is recycled to the raw material system via pump 23 and line 24. The molten polymer extruded from the die 14 of the volatile matter separator 13 is transferred to the roller 1
6, 16', 16'', molded and cooled, roller 17,
The extruded plate 18 is manufactured by taking it off at 17'. The continuously produced extruded plate 18 is cut into a predetermined length by a cutting machine (not shown).

The manufacturing method of the present invention can be used to manufacture not only a general flat plate but also a laminated product stuck to a film or the like, or a corrugated extruded plate by adding an apparatus.

Examples are shown below. These examples are not intended to limit the invention. All parts and percentages used below are by weight.

Note that the examples were carried out using the apparatus system shown in FIG. The specifications of the equipment used are as follows.

Reaction tank internal volume: 300 Volatile separator: Twin-screw vent extruder Screw: 90 mmφ It was carried out using the method shown in .

That is, the sample was dissolved in chloroform and 0.5% by weight
This solution was maintained at 25° C., and the number of seconds t of flow between the marks of an Ostwald viscometer and the number of seconds t ₀ of chloroform flow were measured, and the intrinsic viscosity [η] was calculated using the following formula.

[η] = 3 {(t/to) ^1/3 -1}/C where C is the sample concentration (g/) Example 1 100 parts of methyl methacrylate, 0.15 parts of n-octyl mercaptan, di-tert-butylper A polymerization stock solution consisting of 0.0017 parts of oxide was prepared under nitrogen and fed continuously to the reactor at 15/hour. The inside of the reaction tank was pressurized with nitrogen, the internal pressure was 8 Kg/cm ² G, and the polymerization temperature was 170°C. After about 8 hours, steady operation was reached, and the raw solution supply was changed to 25/hour, and the stirring blade rotation speed was increased.
Sufficient mixing was carried out at 90 rpm and the residence time was about 5 hours. The viscosity inside the reaction tank in this steady state was 100 poise. The viscosity in the reaction tank was measured using a viscometer attached to a pipe provided at the bottom of the reaction tank and continuously sending the reaction mixture to the volatile matter removal device (the same applies hereinafter).

On the other hand, the temperature of the vent extruder is 230℃, and the extrusion part is 240℃.
℃, die 250℃, vent vacuum degree 9mmHg
It was called abs. The polymer was extruded into a sheet form from a hanger coat die and molded through a roller having a roller surface temperature of 95°C to continuously produce a 2 mm thick methacrylic resin plate having an [η] of approximately 0.065. The obtained extruded plate has excellent transparency,
It had no uneven thickness.

Example 2 90 parts of methyl methacrylate, 10 parts of methyl acrylate, 0.20 parts of n-dodecylmercaptan, di-
An extruded plate was produced in the same manner as in Example 1 using a polymerization stock solution containing 0.002 part of tert-butyl peroxide. However, the polymerization temperature was 160°C. The temperature of the vent extruder is 230℃, the extrusion section is 230℃, and the die is 240℃.
The degree of vacuum at the vent section was set to 9 mmHg abs.
The viscosity immediately after leaving the reaction tank was 80 poise, and the [η] of the polymer was 0.075.

The operation was continued for 120 hours, and each step was extremely stable, and the obtained methacrylic resin plate was colorless and had excellent transparency.

Example 3 Raw materials for polymerization consisting of 100 parts of methyl methacrylate, 0.002 parts of di-tert-butyl peroxide, and 0.25 parts of tert-butyl mercaptan were continuously charged into a polymerization tank, and the polymerization of Example 1 was carried out using the following conditions. The process was repeated to produce an extruded plate with [η] 0.066. The obtained extruded plate was colorless and had excellent transparency.

Polymerization reaction tank temperature 160℃ Reaction mixture viscosity 150 poise Extruder temperature 240℃ Dice temperature 250℃ Vent vacuum level 8mmHg abs

[Brief explanation of drawings]

FIG. 1 diagrammatically shows one specific example of the apparatus used to carry out the invention. In the figure, 7 is a reaction device, 13 is a volatile matter separator, 14 is a die, 16
The roller 18 is an extrusion plate.

Claims (1)

[Claims] 1. Consisting of polymethyl methacrylate or
A method for producing an extruded plate made of a methacrylic polymer containing 80% by weight or more of methyl methacrylate units and 20% by weight or less of alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) units, wherein 0.01% to 1.0% by weight of Mercaptan and the following formula 40≧A ^1/2・B ^-1/2 ×10 ³ 3≧A・B×10 ⁵ and 2.0≧A ^-1・(B+10.3)×10 ^-6 A=monomer feed 100g Number of moles of radical polymerization initiator in B = half-life (time) of radical polymerization initiator at polymerization temperature. The above monomer mixture containing a radical polymerization initiator in an amount satisfying the above is supplied to a reaction zone, and the reaction mixture in the reaction zone is stirred and mixed substantially uniformly at a temperature of 130 ° C. or more and 200 ° C. or less, The polymerization is carried out while maintaining the viscosity of the reaction mixture at a constant value of 10 to 500 poise at the reaction temperature, and then the reaction mixture is continuously taken out from the reaction zone, and the polymer and unreacted monomers are separated in a devolatilizing extruder. 1. A continuous method for producing an extruded plate, characterized in that after separating the polymer from the polymer, the polymer is extruded through a die of the extruder to form a plate-shaped body.