JPH07300508A - Production of alpha-methyl-styrene-base copolymer of low volatile matter content - Google Patents

Abstract

PURPOSE:To control pyrolysis of alpha-methyl-styrene-base copolymer containing volatile matter and evaporate it to a high level by kneading it with water in a specific screw extruder and removing the volatile matter. CONSTITUTION:A method for producing alpha-methyl-styrene-base copolymer of low volatile matter content, in which the copolymer solution containing 1wt.% or more of volatile matter (2) is supplied from the hopper (1) to the screw extruder whose barrel is kept at 180 to 300 deg.C, and is transferred to the downstream unit by means of the screw (100,) while being kneaded. The volatile matter is released through the vacuum line (8) kept at a vacuum of 200Torr. or less from the vents (3), (4) and (5), while water is added through the water nozzles (6) and (7) to the copolymer to 0.01 to 20wt.% on the copolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a volatile component such as an unreacted monomer or a solvent from an α-methylstyrene copolymer resin which has a high melt viscosity and is easily decomposed by heat using a screw extruder. To obtain an excellent α-methylstyrene copolymer resin as a molding material.

[0002]

2. Description of the Related Art Generally, when synthesizing a resin, it is necessary to separate volatile components such as unreacted monomers and solvents from a polymer at the outlet of a reactor. For that purpose, the point is how to remove the volatile matter efficiently in a short time. Therefore, various methods for removing the volatile matter have been conventionally proposed. Typical examples of these devolatilization methods include the following three types.

(1) Flash Drum with Heat Exchanger Japanese Patent Publication No. 48-29797 discloses a method of devolatilizing a volatile component by exposing a polymer solution from a polymerization apparatus to a decompression tank. There is. However, in this method, the temperature of the polymer solution is lowered when the volatile components are evaporated and vaporized, and therefore the temperature of the pressure reducing tank must be kept high. In addition, the viscous polymer after removing the volatile components is extracted from the bottom of the vacuum tank, but because the flow rate is low,
In the case of α-methylstyrene-based copolymer resin, which is likely to be thermally decomposed for a long time in a decompression tank heated to a high temperature, a new volatile component is generated due to thermal decomposition of the resin. , Phenomenon such as a significant decrease in molecular weight occurs,
This causes adverse effects such as deterioration of mechanical properties and heat resistance of the finally obtained resin. Furthermore, since this method does not have a structure in which the surface of the polymer solution is mechanically forcibly renewed, the removal of volatile components from the inside of the solution is not effective,
In particular, it was not suitable for devolatilization of volatile components from a highly viscous α-methylstyrene copolymer resin solution.

(2) Centrifugal thin film evaporator In Japanese Patent Laid-Open No. 1-99601, a polymer solution is introduced into a heated tube, a thin film is formed on the inner wall of the tube by a rotating blade, and volatile components are evaporated. A devolatilization method of discharging later has been proposed. However, if the gap between the inner wall of the pipe and the blade is not adjusted accurately, the surface renewal of the thin film is obstructed and the devolatilization efficiency is reduced, or large mechanical shearing acts on the polymer solution, and the molecular weight of the resin decreases. This causes the generation of new volatile components.
Furthermore, when the polymer solution was introduced into a heated tube, it rapidly foamed before forming a thin film, and the scattered foam sometimes adhered to the rotary shaft of the inclined blade, but adhered to the rotary shaft. Since a mechanical force for flowing down is not transmitted to the foam, long-term heat history acts, and in the case of α-methylstyrene-based copolymer resin that is easily thermally decomposed, new volatile components are not generated or It causes adverse effects such as a decrease in molecular weight.

(3) Screw Extruder Japanese Patent Publication No. Sho 63-30921 discloses a devolatilization method for polymethylmethacrylate using a screw extruder. However, the extruder in this method
Since the pressure is applied in the devolatilization section, the devolatilization efficiency decreases, and
Since it does not have a kneading part adjacent to the devolatilizing part and because it does not add water, the surface of the resin is not sufficiently renewed, and it is difficult to devolatilize the α-methylstyrene-based resin having a high melt viscosity. It is not suitable for the devolatilization of the polymerized resin, and no satisfactory devolatilization result was obtained even if the method described in this Example was applied. Thus, it has a high viscosity, and
There is no method for efficiently volatilizing volatile components to a high level from an α-methylstyrene copolymer resin which is easily decomposed by heat.

[0006]

SUMMARY OF THE INVENTION The present invention was devised from such a viewpoint, and its object is to devolatilize an α-methylstyrene copolymer resin containing 1% by weight or more of volatile matter. In carrying out the process, the thermal decomposition of the resin can be suppressed, and the volatile components can be devolatilized efficiently to a high level, which reduces the residual volatile components as much as possible.
-To provide a method for producing a methylstyrene copolymer resin.

[0007]

That is, the present invention uses a screw extruder having a plurality of vent holes to provide 1% by weight.
In the method for removing volatile matter from the α-methylstyrene-based copolymer resin containing the above volatile matter, the screw extruder has a plurality of kneading section and devolatilizing section adjacent to each other, the barrel temperature of the kneading section It is a method for producing a low volatile content α-methylstyrene copolymer resin, which is kept at 50 ° C. or more lower than the barrel temperature of the devolatilization section, and water is added in the second and subsequent kneading sections.

In the present invention, the α-methylstyrene copolymer resin contains α-methylstyrene units in an amount of 5% by weight or more,
The content is preferably 10 to 40% by weight, and the vinyl-based monomer to be copolymerized is not particularly limited. Typical examples of vinyl monomers used for industrial polymerization include, for example,
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, methacrylic acid i
-Butyl, t-butyl methacrylate, cyclohexyl methacrylate, methacrylic acid esters such as benzyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, i acrylate
-Butyl, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate, and other acrylic esters, styrene, acrylonitrile, methacrylonitrile, N-phenylmaleimide, N-phenylmethacrylamide, methacrylic acid, acrylic acid, maleic anhydride Acid etc. are mentioned. Preferred is methyl methacrylate.

The .alpha.-methylstyrene copolymer resin may be a polymer obtained by any of bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization, but is preferably a bulk polymerization in which impurities are not mixed in the copolymer. Is used. Further, organic polymerization oxides, initiator polymerization using an azo compound as a polymerization initiator at the time of polymerization, or thermal polymerization without an initiator may be used, and a chain such as an alkyl mercaptan for controlling the molecular weight may be used. It is also possible to add a suitable amount of the transfer agent.

Further, as the conversion rate increases, the viscosity of the polymer also increases and a large load is applied to the rotor blades of the polymerization tank.
It may be difficult to transfer in the pipe. In order to prevent this, a solvent may be added to the system as needed. Examples of the solvent added include ethylbenzene, toluene, xylene, methyl ethyl ketone, benzene, isopropanol and the like.

A screw extruder is used for devolatilization of the α-methylstyrene copolymer resin of the present invention. The extruder may be either a single screw extruder or a twin screw extruder. In the case of a twin-screw extruder, the two screws rotate in the same direction and in different directions, but any type of devolatilization of the α-methylstyrene-based copolymer resin of the present invention is possible. A twin screw extruder can also be used.

This screw extruder is provided with a plurality of vent holes for depressurizing the inside of the barrel to remove volatile components in the resin. The vent holes are provided with a long vent having a large opening area or a material supply port. A rear vent having a vent hole on the rear side may be included.

Further, in order to improve the devolatilization efficiency, it is necessary for the barrel to have a plurality of kneading parts for renewing the surface of the resin and devolatilizing parts for removing volatile components through the vent holes. However, in order to efficiently remove volatiles from the resin whose surface has been sufficiently renewed in the kneading section, the devolatilizing section should be present immediately after the kneading section, and in order to eliminate extra residence time. It is preferable that the kneading section is present again immediately after the devolatilization section. As a result, the kneading section and the devolatilizing section need to be adjacent to each other.

The barrel temperature of the screw extruder is 180 to 3
The temperature is 00 ° C, preferably 200 to 280 ° C. When the barrel temperature is lower than 180 ° C., not only the volatile matter cannot be efficiently removed, but also the viscosity of the resin becomes large, which imposes a great load on the motor and the like. Further, when the barrel temperature is higher than 300 ° C., the thermal decomposition of the resin becomes remarkable, so that the molecular weight of the resin is lowered or a low molecular weight product is generated, which adversely affects the thermal physical properties and the mechanical physical properties.

Here, the barrel temperature of the kneading section and the devolatilizing section subsequent to the kneading section adjacent to each other must be kept lower than the barrel temperature of the devolatilizing section subsequent thereto by 50 ° C. or more.
Unless the barrel temperature of the kneading section is lower than the barrel temperature of the devolatilizing section by 50 ° C. or more, the abnormal shearing heat generation in the kneading section is not cooled, which leads to a decrease in the molecular weight of the resin and the generation of new volatile components. . On the contrary, unless the barrel temperature of the devolatilization section is higher than the barrel temperature of the kneading section by 50 ° C. or more, the devolatilization efficiency is lowered and it becomes difficult to reduce the residual volatile content.

In the present invention, the barrel temperatures of the kneading section and the devolatilizing section are preferably controlled independently of each other, and, for example, the first kneading section and the first degassing section connected immediately after the first kneading section. Between the volatile unit, between the second kneading unit and the second devolatilizing unit connected immediately thereafter, and between the third kneading unit and the third devolatilizing unit connected immediately thereafter, and so on. The kneading section and the devolatilizing section which are adjacent to each other are maintained so as to have a temperature difference of 50 ° C. or more.

Each vent hole is connected to an exhaust device such as a vacuum pump. The evacuation speed of the vacuum pump depends on the volume of the extruder used and the amount of volatile matter contained in the resin, but is 200 torr or less, preferably 100 torr or less, and more preferably 50 torr during volatile matter removal. It is desirable that the following vacuum degree can be achieved. If the degree of vacuum exceeds 200 torr, the devolatilization efficiency decreases, and the amount of residual volatile components in the resin increases.

When there are a plurality of kneading sections and devolatilizing sections, it is desirable that all of the kneading sections and the devolatilizing sections following the kneading sections satisfy the above relationship, but they may be part.

In the method for producing a low volatile content α-methylstyrene copolymer resin of the present invention, it is necessary to add water to the resin when removing the volatile content from the copolymer resin. Addition of water to the resin promotes foaming of the resin and has the effect of renewing the surface, which improves the efficiency of volatile matter removal. Further, the water becomes water vapor, and the partial pressure of the volatile matter is lowered, so that the volatile matter is more effectively evaporated. Since this effect becomes large when the volatile content is small, it is preferable to add water after the second vent hole of the extruder. In addition, when the boiling point of the volatile component is high, it has an effect of forming an azeotropic mixture with water and lowering the boiling point of the volatile component. The amount of water added is 0.01 to 20% by weight, preferably 0.0 to 20% by weight, from each addition hole to the resin.
It is 5 to 10% by weight. If the amount of water added is less than 0.01% by weight, the effect of removing volatile matter as described above does not appear.
Further, if the amount of water added exceeds 20% by weight, a large amount of heat is required to remove the water or the water remains in the final product.

Further, in the method for producing a low volatile content α-methylstyrene copolymer resin of the present invention, various additives may be added within a range not impairing the properties of the resin. Examples of this additive include n-octadecyl-3- (3 ', 5'-di-tert-butyl-4'- as an antioxidant.
Hydroxyphenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyl) propionate] and other hindered phenolic compounds, and 2,2-methylenebis (4,4)
Phosphite compounds such as 6-di-tert-butylphenyl) octylphosphite and tris (2,4-di-tert-butylphenyl) phosphite, and tetrakis [methylene-3- (dodecylthio) propionate] methane and the like. Examples thereof include thioether compounds, flame retardants include bromine compounds such as tetrabromobisphenol A and decabromodiphenyl oxide, and antistatic agents such as Electrostopper series [Kao Corporation] and Dasper series. Examples include [Miyoshi Oil & Fats Co., Ltd.], TB-123, TB-128 [Matsumoto Yushi-Seiyaku Co., Ltd.], and the like. Further, an ultraviolet absorber such as a benzotriazole compound and a light stabilizer such as a hindered amine compound can be added if necessary. Further, various improving agents, release agents, dyes, pigments and the like can be added.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to these examples and comparative examples.

Examples 1-7 and Comparative Examples 1-7 Weight average molecular weight 105,000 and residual volatiles of about 5
A devolatilization treatment of 0000 ppm of methyl methacrylate-α-methylstyrene copolymer resin (containing 20 mol% of α-methylstyrene) under the conditions shown in Tables 1 and 2 using the twin-screw extruder shown in FIG. did.

The resin solution 2 is introduced into the extruder from the hopper 1 at the upstream portion of the extruder and is transferred downstream by the screw 10. The volatile components in the resin solution are vent holes 3, 4, and 5.
Was evaporated and removed through a vacuum line 8. Further, during the transfer of the resin solution, 2% by weight of water was added to the resin through the water addition holes 6 and 7 into the extruder. The copolymer resin from which the volatile components were removed was shaped into a strand through the die 9. In the figure, a1, a2 and a3 indicate barrels of the kneading section, and b1, b2 and b3 indicate barrels of the devolatilizing section.

The residual volatile matter and the weight average molecular weight of the devolatilized α-methylstyrene-methyl methacrylate copolymer resin obtained in each of the above Examples and Comparative Examples were measured. The results are shown in Tables 1 and 2.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

EFFECTS OF THE INVENTION According to the present invention, the volatile matter can be efficiently devolatilized to a high level from the hardly devolatilized α-methylstyrene copolymer resin containing the volatile matter. At the same time, it is possible to suppress the decrease in the molecular weight due to the thermal decomposition of the resin and prevent the expansion of the molecular weight distribution, and it is possible to produce an α-methylstyrene-based copolymer resin excellent as a molding material.

[Brief description of drawings]

FIG. 1 is an illustration of a screw extruder used to remove volatile components.

[Explanation of symbols]

1 ... Hopper, 2 ... Resin solution, 3, 4, 5 ... Vent hole,
6, 7 ... Water addition hole, 8 ... Decompression line, 9 ... Die, 10 ...
Screw, a1, a2, a3 ... kneading section, b1, b2, b
3 ... Devolatilization section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Yamamoto 1618 Ida, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, inside the Advanced Technology Research Laboratories, Nippon Steel Corporation (72) Inventor, Ikuo Yamaoka 1618 Ida, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Address, Nippon Steel Corporation Advanced Technology Research Center

Claims (1)

[Claims] 1. A method of removing volatile components from an α-methylstyrene-based copolymer resin containing 1% by weight or more of volatile components using a screw extruder having a plurality of vent holes, wherein the screw extruders are adjacent to each other. To have a plurality of matching kneading parts and devolatilizing parts, keep the barrel temperature of the kneading parts lower than the barrel temperature of the subsequent devolatilizing parts by 50 ° C. or more, and add water in the kneading parts after the second kneading part. Low volatile content α-
A method for producing a methylstyrene copolymer resin.