JPH04218512A - Production of styrene-based resin - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject high-molecular and high-strength resin by carrying out polymerization of a styrene-based monomer, etc., in a complete mixing and stirred type polymerization vessel and a plug flow type reactor in multistage under specific conditions, then adding a solvent thereto and subsequently performing flash type volatilizing treatment. CONSTITUTION:A complete mixing and stirred type polymerization vessel and a plug flow type reactor are used to carry out continuous bulk polymerization of a raw material containing a styrene-based monomer. In the process, an organic peroxide as a polymerization initiator is added into the raw material and polymerization is performed to 35-55% conversion rate in the complete mixing and stirred type polymerization vessel in the former stage. Thereby, a polymer having 1.4-2.0 reduced viscosity is produced. In the latter stage, polymerization is carried out to 50-90% conversion rate under conditions of 100-140 deg.C temperature in the plug flow type reactor. To the resultant polymerization solution, is added >=10% solvent. The obtained solution is then subjected to volatilizing treatment by a flash type volatilizing method constructed from a heating step and a vapor-liquid separating step following the heating step. In the process, the objective styrene-based resin is obtained by performing the volatilizing treatment without producing low-molecular polymers.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a styrenic resin, and more particularly, to a method for efficiently producing a styrenic resin having a high average molecular weight and high strength.

0002

[Prior art] Styrenic resins generally have low strength, but
It is known that high molecular weight materials have relatively high strength. A method using a complete mixing stirring type polymerization tank is known as one of the methods suitable for producing a high molecular weight styrene resin. However, in the case of a completely mixed stirring type polymerization tank, the higher the conversion rate of the polymerization liquid, the higher the viscosity of the polymerization liquid and the difficulty of stirring, so it was not possible to carry out the polymerization reaction to a high conversion rate. In operation under low temperature conditions and low conversion rates, high molecular weight styrene resin can be obtained, but the production efficiency is poor and it is difficult to remove volatile substances such as unreacted components from the polymerization solution. Furthermore, when a polymerization solution is subjected to devolatilization treatment at a low temperature, there is a problem that a low molecular weight polymer is likely to be produced in the heating step. Therefore, there is a method to prevent the viscosity from increasing even if the conversion rate of the polymerization solution increases by adding a solvent to the raw material solution. A method of further polymerization reaction using a static mixer that can be operated (Japanese Patent Application Laid-Open No. 60-28407),
A method using a reaction device in which a plurality of tubular reactors are connected in series (Japanese Unexamined Patent Application Publication No. 1988-70507), an organic peroxide is used as a polymerization initiator, and when polymerizing using a plurality of reactors, the final A method has been proposed in which the polymerization temperature in the first reactor is 20° C. or more higher than the polymerization temperature in the preceding reactor (Japanese Patent Application Laid-open No. 173107/1983).

However, when a solvent is added to the raw material solution, there are disadvantages such as a decrease in the reaction rate, resulting in poor production efficiency, and a difficulty in increasing the molecular weight of the polymer due to the chain transfer effect of the solvent. In addition, in the case of the method described in JP-A-60-28407, the polymerization reaction in a static mixer is carried out adiabatically to prevent uneven temperature conditions, but as a result, the temperature ℃ or higher, and especially when the conversion rate of the polymer introduced into the static mixer is low, the temperature tends to rise, and as the temperature rises, low molecular weight polymers are likely to be generated, so try to obtain high molecular weight polymers. This is not preferable if Furthermore, in the case of the method described in JP-A-64-70507, when attempting to obtain a high molecular weight polymer, the pressure drop in the reactor tends to increase, making stable operation difficult. In the method described in JP-A-58-173107, the polymerization temperature in the final reactor is set as high as 140 to 180°C, so that low molecular weight polymers are likely to be generated.

0004

[Problems to be Solved by the Invention] The object of the present invention is to enable operation at a high conversion rate, to improve production efficiency, to prevent a decrease in the molecular weight of the polymer, and to achieve a low average content of low molecular weight polymers. The object of the present invention is to provide a manufacturing method suitable for obtaining a styrenic resin having a high molecular weight.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventor conducted various studies, and after polymerizing raw materials to a certain extent in a completely mixed stirred polymerization tank, the present inventors conducted a plug-flow type reaction. In this method, the polymerization reaction is carried out in a plug flow type reactor at a relatively low temperature of 100 to 140°C.
The present invention was completed by discovering that carrying out the devolatilization treatment under the following conditions and adding a solvent to the polymerization solution during the devolatilization treatment are effective in preventing the generation of low molecular weight polymers.

That is, the present invention involves the continuous bulk polymerization of a raw material containing a styrenic monomer using a completely mixed stirred polymerization tank and a plug flow reactor. However, in the completely mixed stirred polymerization tank in the previous stage, polymerization is carried out to a conversion rate of 35 to 55%, and the reduced viscosity is 1.4 to 1.4.
A conversion rate of 50 to 90 was produced at a temperature of 100 to 140°C in the plug flow reactor in the latter stage.
%, and after adding 10% or more of solvent to the obtained polymerization liquid, styrene is devolatilized by a flash devolatilization method consisting of a heating step and a gas-liquid separation step following the heating step. This is a method for producing a styrene-based resin, which is characterized by obtaining a styrene-based resin. Note that "%" here means "% by weight" (the same applies hereinafter).

The present invention will be explained in detail below. The polymerization raw materials used in the present invention include styrene, α-methylstyrene,
It contains one or more styrenic monomers such as substituted styrene such as p-methylstyrene and an organic peroxide that acts as a polymerization initiator. It may contain one or more monomers copolymerizable with styrene monomers such as methyl chloride, and it may also contain various additives other than organic peroxides, if necessary. The styrenic resin that can be produced by the present invention is polystyrene, AS
resin, styrene copolymer resin such as MS resin, etc.
Since an organic peroxide is used as a polymerization initiator, the average molecular weight is as high as about 40,000 to 50,000. The molecular weight and other properties of the polymer obtained by polymerizing raw materials can be determined by changing the temperature conditions of the polymerization reaction as well as the types and amounts of additives added to the raw materials, including organic peroxides. It can be adjusted by The organic peroxide that can be used as a polymerization initiator in the present invention is preferably one having a difunctional reactive group, such as 1,1-di-t-butylperoxycyclohexane, di-t-butylperoxycyclohexane, and di-t-butylperoxycyclohexane. Oxytrimethyl adipate, tris-t-butylperoxyvinylsilane, 2,5-dimethyl-2,5-di-t
-butylperoxyhexane, 1,3-bis-t-butylperoxyisopropylbenzene, benzoyl peroxide, and lauroyl peroxide, among which 1,1-di-t-
Butylperoxycyclohexane has excellent properties as a polymerization initiator.

In the present invention, polymerization raw materials are subjected to continuous bulk polymerization using two or more stages of reactors connected in series. As the reactor, a complete mixing type stirring type polymerization tank and a plug flow type reactor are used, and the conversion rate in the first completely mixing type stirring type polymerization tank is 35 to 55%, preferably 40 to 55%, more preferably 40 to 50%. After the polymerization reaction reaches a conversion rate of 50 to 90%, preferably 60 to 80%, more preferably 60 to 70%, in a subsequent plug flow reactor. The polymer obtained at this time has a large molecular weight because an organic peroxide is used as a polymerization initiator. The viscosity of the liquid becomes very high and stirring tends to be insufficient, making it difficult to control the polymerization reaction. Furthermore, it is not preferable to polymerize a polymer solution with a conversion rate of less than 35% in a plug flow reactor because the reaction efficiency is poor and it is difficult to produce a high molecular weight polymer. The complete mixing stirred polymerization tank and the plug flow reactor may each have one stage, but if necessary, two or more of each may be connected in series to have two or more stages. According to the findings of the present inventor, a complete mixing type stirring type polymerization tank It is most effective to use two or three reactors and one or two plug flow reactors.

[0009] As the complete mixing type stirring type polymerization tank, a boiling heat removal type is preferable because it is easy to control the reduced viscosity of the produced polymer and can operate stably even when the production amount is changed. In addition, the temperature of the polymerization reaction in a completely mixed stirred polymerization tank is about 100 to 140°C, preferably 105 to 130°C.
to produce a polymer with a reduced viscosity of 1.4 to 2.0. At this time, if the temperature is less than 100°C, the polymerization reaction rate is low and the viscosity of the polymerization solution tends to increase, which is undesirable. If the temperature exceeds 140°C, the action of the organic peroxide as a polymerization initiator becomes weak and This is not preferable for obtaining high molecular weight polymers because molecular weight polymers are likely to be generated. The present invention is suitable for producing a polymer with a reduced viscosity of 1.4 or more, especially 1.6 or more in a completely mixed stirred polymerization tank, and ultimately obtaining a styrenic resin with a high average molecular weight. It is.

Polymerization in a plug flow reactor is carried out at a temperature of 100-140°C, preferably 110-135°C. If the temperature is less than 100°C, the polymerization reaction rate will be low and the viscosity of the polymerization liquid will be high, which is not preferable. Furthermore, if the temperature exceeds 140°C, low molecular weight polymers tend to be generated, which is not preferable. Temperature control and maintenance of polymerization in a plug-flow type reactor can be carried out efficiently by heating or cooling each section divided in the flow direction of the plug-flow type reactor. Plug flow reactors include, but are not particularly limited to, static mixers and vertical column type reactors with stirring blades that are made up of elongated reactors that are used under relatively weak stirring conditions. , can be used alone or in combination. At this time, a portion of a hydrocarbon solvent, particularly a mixed solvent of ethylbenzene and a styrene monomer, may be added as necessary.

Furthermore, in the present invention, 10% or more of a solvent, preferably a hydrocarbon solvent, particularly preferably an aromatic hydrocarbon solvent such as benzene, toluene, xylene, or ethylbenzene, is added to the polymerization liquid obtained in the plug flow reactor. is added after being appropriately preheated to a temperature close to that of the polymerization solution, and then devolatilized by a flash devolatilization method to obtain a styrenic resin. The flash type devolatilization method consists of a heating step and a gas-liquid separation step following the heating step, and generally a vacuum chamber is used for the gas-liquid separation step. If unreacted monomers are included in the polymerization solution to be devolatilized, unreacted monomers tend to polymerize during this heating process and produce low molecular weight polymers. However, in the present invention, by adding 10% or more of a solvent to the polymerization solution, the fluidity of the highly viscous polymer is increased and at the same time the residence time is shortened. It is thought that the polymerization reaction is suppressed because the content of unreacted monomers in the liquid is reduced. A suitable amount of solvent added is 10-40%, preferably 15-30%. If the amount is too small, the effect of suppressing the polymerization reaction will be small, and if it is too large, the devolatilization treatment will become difficult, which is not preferable.

[0012] The volatile substances recovered during this devolatilization process can be used as a solvent to be added to the polymerization liquid at the outlet of the plug-flow type reactor, or added to the polymerization liquid as necessary in the plug-flow type reactor. It can also be used as a solvent. In this case, since the solvent is recycled, there is an advantage that the amount of waste liquid to be treated can be small. In addition, if the volatile substance recovered during the devolatilization treatment contains an oligomer component, it is preferable to remove the oligomer component by distillation or the like before use.

[0013]

[Operation] In the present invention, the polymerization reaction is carried out in a plug-flow reactor at a temperature of 100 to 140°C, and a solvent is added to the polymerization liquid during the devolatilization process, so that low molecular weight polymers are generated less. It is suitable for obtaining high molecular weight polymers, and can be operated at high conversion rates, resulting in good production efficiency.

[0014]

EXAMPLES Examples and comparative examples of the present invention will be described below in accordance with the flowchart of the present invention shown in FIG. Figure 1
Inside, 1 and 3 are complete mixing stirring type polymerization tanks, 5 is a static mixer equivalent to a plug flow reactor, 7 is a flash type devolatilization heating device, and 9 is a flash type devolatilization gas-liquid separation device. This is a vacuum chamber.

Example 1 Styrene to which an appropriate amount of organic peroxide was added as a polymerization initiator was introduced into the complete mixing type stirring type polymerization tank 1 from a pipe 2 installed on the side wall of the completely mixing type stirring type polymerization tank 1. Piping that connects the bottom of the complete mixing type stirring type polymerization tank 1 and the side wall of the complete mixing type stirring type polymerization tank 3, through which the polymerization reaction is carried out continuously at a temperature of 105°C to a conversion rate of 21%. 4 into the complete mixing type stirring type polymerization tank 3, and the temperature was increased to 11.
The polymerization reaction was carried out at 0° C. to a conversion rate of 40%. The reduced viscosity of the polymer contained in the obtained polymerization liquid was 1.7. Furthermore, the polymerization liquid obtained in the complete mixing type stirring type polymerization tank 3 is passed through the static mixer 5 through a pipe 6 that connects the bottom of the complete mixing type stirring type polymerization tank 3 and the lower inlet of the static mixer 5 installed vertically. to 115-1
The polymerization reaction is carried out to a conversion rate of 62% while maintaining the temperature within the range of 25° C., and the resulting polymerization liquid is passed through a pipe 8 that connects the upper outlet of the static mixer 5 and the heating device 7 for flash type devolatilization to the heating device 7. and heated to 180°C and placed in vacuum chamber 9.
devolatilization treatment is carried out by separating gas and liquid with extruder 1.
0 to obtain polystyrene. Note that the polymerization liquid obtained by the static mixer 5 is passed through a pipe 8 to a heating device 9.
When introducing ethylbenzene into the polymerization liquid, 24% by weight of ethylbenzene was added to the polymerization liquid through the pipe 11, mixed uniformly with the line mixer 12, and then introduced into the heating device 7. In addition, the residence time in the complete mixing type stirring type polymerization tank 1 is 180 minutes, the residence time in the complete mixing type stirring type polymerization tank 3 is 170 minutes, the residence time in the static mixer 5 is 100 minutes, and the temperature conditions etc. are shown in Table 1. The reduced viscosity of the obtained polystyrene was 1.54.

Comparative Example 1 Polystyrene was obtained by directly introducing the polymerization liquid obtained in the complete mixing type stirring type polymerization tank 3 into the heating device 7 and performing devolatilization treatment without using the static mixer 5. is Example 1
When conducted in the same manner as above, the production amount per hour was 65% compared to the case of Example 1 using static mixer 5.
%, and production efficiency was poor.

Examples 2 to 3 The temperature conditions and conversion rate of the polymerization reaction in the completely mixed stirring type polymerization tanks 1 and 3, and the temperature conditions and conversion rate of the polymerization reaction in the static mixer 5 were changed, and the polymerization initiator was changed. The same procedure as in Example 1 was carried out except that the amount added was adjusted to change the reduced viscosity of the polymer produced in the complete mixing type stirring type polymerization tank 3. Table 2 shows the conditions and results of each example. Comparative Examples 2 to 3 Comparative examples except that the temperature conditions and conversion rates of the polymerization reaction in the fully mixed stirring type polymerization tanks 1 and 3, and the amount of polymerization initiator added and the conversion rate were the same as in Examples 2 to 3, respectively. This was done in the same manner as in step 1. Table 2 shows the conditions and results of each comparative example.

Comparative Example 4 The temperature conditions for the polymerization reaction in the static mixer 5 were set to 17
The procedure was the same as in Example 1 except that the temperature was 5 to 185°C. The conditions and results are shown in Table 1. Comparative Example 5 The same procedure as in Example 1 was carried out except that ethylbenzene was not added to the polymerization liquid obtained in static mixer 5, and the reduced viscosity of the obtained polystyrene was 1.50.
Met.

*Note: Relative production efficiency indicates the ratio of the production amount per hour in the comparative example, which was conducted under the same conditions except that no static mixer was used, to the production amount per hour in the example.

[0020]

[0021]

[Effects of the Invention] According to the present invention, styrenic resins can be produced by continuous bulk polymerization at relatively low temperatures and high conversion rates, resulting in good production efficiency, and low molecular weight polymers can also be produced using conventional methods. This is particularly effective in producing high-strength styrenic resins that have a low content of low molecular weight polymers and a high average molecular weight.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of an embodiment of the present invention.

[Explanation of symbols]

1 Complete mixing type stirring type polymerization tank 3 Complete mixing type stirring type polymerization tank 5 Plug flow type reactor (static mixer) 7 Flash type devolatilization heating device 9
Flash type devolatilization gas-liquid separation device (vacuum tank) 11 Solvent addition piping

Claims (1)

[Claims] Claim 1: When performing continuous bulk polymerization of raw materials containing styrenic monomers using a completely mixed stirred polymerization tank and a plug flow reactor, an organic peroxide is added to the raw materials and In a completely mixed stirred polymerization tank, the conversion rate is 35 to 5.
Polymerize up to 5% to produce a polymer with a reduced viscosity of 1.4 to 2.0, and in the plug flow reactor in the latter stage, the temperature is 100%.
Polymerize to a conversion rate of 50 to 90% at ~140°C,
After adding 10% or more of a solvent to the obtained polymerization liquid, a styrenic resin is obtained by performing a devolatilization treatment using a flash type devolatilization method consisting of a heating step and a gas-liquid separation step following the heating step. A method for producing styrenic resin characterized by: