JPS5936922B2 - Method for producing rubber-modified impact-resistant polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing rubber-modified impact polymers.

More specifically, the present invention provides a method for producing a polymer having improved impact resistance and improved properties such as tensile strength, heat resistance, and hardness.

Rubber components such as styrene-butene copolymer rubber and polyptadiene are uniformly dissolved in a monovinyl aromatic monomer such as styrene, and this solution is prepolymerized with stirring to a polymerization rate of 10 to 40%, and the rubber component is added to the resin phase. It is best to precipitate and disperse as fine particles (referred to as microgels) in water and then polymerize or suspend in water and continue the polymerization to produce rubber-modified impact-resistant polymers with high impact strength. Are known.

(Special Publication No. 43-19749). However, performance such as impact resistance, tensile strength, heat resistance, hardness, etc. is affected by the rubber content, and there has been a problem in that the balance between both performances cannot be maintained, especially when the amount of the expensive rubber component is reduced.

In these cases, when the rubber-modified polymer is observed under an electron microscope, it is found that the rubber component is dispersed as a microgel in the resin phase forming the continuous phase, and that the resin component is further included in the microgel as particles.

The amount of microgel in the rubber-modified polymer is measured as a gel content, although not all according to the analysis method described in the notes (Table 1*1), together with the rubber component and the resin component grafted to the rubber component. It is generally known that the larger the gel content contained in a rubber-modified polymer, the higher the impact strength.

The higher the amount of rubber component used (or the lower the polymerization rate in the polymerization step following prepolymerization, the higher the rubber content in the polymer obtained by removing volatiles). It is possible to increase the gel content in the modified polymer and improve the impact resistance of the rubber modified polymer, but this results in the use of more expensive rubber components, which is economically disadvantageous. In addition, there is a drawback that the properties such as tensile strength, heat resistance, hardness, etc. of the rubber-modified polymer obtained are impaired.

The object of the present invention is to reduce the amount of rubber components used in the rubber-modified polymer obtained by the conventional method, yet maintain performance such as impact resistance and elongation, and improve tensile strength, heat resistance, hardness, etc. It is possible to produce a rubber-modified polymer with improved performance, or even when the amount of rubber components contained in the rubber-modified polymer obtained by conventional methods is the same, it is possible to produce a rubber-modified polymer with improved performance such as impact resistance and elongation. The point is to produce a combination.

In the present invention, a raw material solution containing a monovinyl aromatic monomer and a rubber component is prepolymerized, and the reaction rate of the monovinyl aromatic monomer is 40 to 80C! ) The first step is to proceed with polymerization until
During the polymerization process, unreacted monopynyl aromatic monomer is evaporated from the resulting polymerization solution, and at least 10% by weight of the resulting polymer is removed.
and at least 10 of the produced polymer.
An intermediate step of volatilizing and removing the unreacted monovinyl aromatic monomer so that an amount corresponding to the amount by weight remains, and the polymerization solution after volatilizing and removing unreacted monovinyl aromatic monomer is further polymerized at 150°C until the polymerization is substantially completed. It consists of a second polymerization step in which polymerization is continued at the above temperature. Representative examples of monovinyl aromatic monomers used in the present invention include styrene, α-methylstyrene,
Examples include nuclear methylated styrene (for example, o- or p-pinyltoluene), nuclear halogenated styrene (for example, o- or p-chlorostyrene), and two or more of these may be used as a mixture.

The rubber component used in the present invention needs to be dissolved in the monopynyl aromatic monomer, so it is generally desirable to have no crosslinks, and typical examples include polyptadiene, butadiene-styrene copolymer rubber, Isoprene, etc., and two or more of these may be used as a mixture. A raw material solution containing a rubber component and a monovinyl aromatic monomer is obtained by dissolving the rubber component in the monovinyl aromatic monomer.
The rubber component is preferably used in an amount of 2 to 20 parts by weight per 100 parts by weight of the monovinyl aromatic monomer. If the rubber component in the rubber-modified polymer is less than 2% by weight, the performance as an impact-resistant polymer is poor. Therefore, for example, when using 1.5 parts by weight of the rubber component, it is necessary to reduce the amount in the volatilization removal step.
In both cases, it is necessary to volatilize and remove about 26.5 parts by weight of unreacted monovinyl aromatic monomer, which creates a restriction that the polymerization rate in the first polymerization step must be kept below about 66.71:f), and the polymerization conditions must be adjusted. The disadvantage is that there is less freedom in selection. On the other hand, if more than 20 parts by weight is used, the viscosity of the prepolymerization liquid becomes too high, causing poor stirring, making it difficult to precipitate and disperse the rubber component as fine particles in the resin phase.

In accordance with the present invention, up to 30% by weight of diluent, based on the total of rubber component and monopynyl aromatic monomer, can be used.

The diluent reduces the viscosity of the polymerization solution and facilitates mixing, stirring, reaction heat removal, etc., and is therefore preferably used in an amount of 5 to 20% by weight. If more than 30% by weight is used, the production amount of polymer per unit reaction volume will decrease, leading to an increase in the size of the reaction equipment, and economic disadvantages such as increased costs for recovery and reuse will become noticeable. This is not desirable.

Examples of usable diluents include aromatic hydrocarbon compounds such as benzene, toluene, and ethylbenzene.Prepolymerization of the raw material solution is usually continued with stirring until the reaction rate is 40 to 80%.

When the polymerization rate is less than 40%, the cost of the volatilization removal process is uneconomical, and at the same time, the inclusion of the resin component into the rubber particles, that is, the microgel, is insufficient, resulting in a low gel content, that is, the formation of gel, which reduces the impact resistance. I have bad sex. If it exceeds 80%, the amount of unreacted monovinyl aromatic monomer to be volatilized and removed in the volatilization removal step will be small, and gel formation will also be small, so that the effects of the present invention will not be noticeable. Polymerization is carried out using organic peroxides such as t-butyl peroxybenzoate, t-butyl peroxyacetate, di-t-butyl peroxide, dicumyl peroxide, benzoyl peroxide, etc., or in the absence of these initiators. It is carried out by thermal polymerization, which proceeds thermally. The polymerization conditions are closely related to the performance of the resulting product; for example, to obtain a product with good fluidity, the polymerization temperature may be increased, the amount of initiator used may be increased, or t-dodecylmercabutane, Conditions such as the use of more chain transfer agents such as n-dodecyl mercaptan and α-methylstyrene dimer are not strictly defined, but for example, when using a raw material solution in which linear polybutadiene is dissolved in styrene, In prepolymerization using an organic peroxide initiator, polymerization proceeds in a temperature range of 60 to 110°C, and in prepolymerization by thermal initiation, polymerization proceeds in a temperature range of 120 to 160°C, and the polymerization time usually takes 1 to 20 hours. This is the condition.

In addition, as a reactor, a stirring tank equipped with a screw-type stirrer suitable for mixing and stirring highly viscous liquids and equipped with a jacket to remove reaction heat is suitably used. Polymerization is normally carried out under stirring, and rubber components is dispersed as a microgel. Such polymerization can also be carried out continuously as follows.

One reactor, or two or more reactors connected in series, are used, and the feed liquid is continuously supplied to the reactor, and substantially the same weight of the discharge liquid is continuously taken out from the reactor. Continuous polymerization takes place. In such a case, in order to fully utilize the efficiency of the present invention, the prepolymerization step is carried out continuously using a stirring tank equipped with the above-mentioned screw type stirrer and jacket as a reactor. The polymerization liquid obtained in the prepolymerization step is subjected to an intermediate volatilization removal step.

Here, unreacted monomers contained in the polymerization solution are volatilized,
At least 10% of the rubber-modified polymer produced in the first polymerization step
The volatilization removal is adjusted so that a weight percent of unreacted monomer is removed and at least 10 weight percent of unreacted monomer remains in the polymerization solution. If the amount of unreacted monomer removed by volatilization is less than 10% of the produced polymer, the polymerization completion step will be carried out at high temperatures, resulting in an increased amount of low-molecular-weight polymer produced, resulting in a modified final rubber. The average molecular weight of the polymer decreases too much, resulting in a decrease in impact resistance.

In addition, if the amount of unreacted monomer remaining in the polymerization solution after the volatilization removal step is 10% by weight or less based on the produced polymer, the amount of unreacted monomer polymerized at high temperature in the polymerization completion step will be small. As a result, a decrease in the molecular weight of the obtained rubber-modified polymer is suppressed, but no significant increase in gel content is observed, and the effects of the present invention become difficult to manifest. For removal by volatilization, use an evaporator such as a multi-tubular evaporator or thin film evaporator, or connect a condenser to the polymerization reactor to volatilize unreacted monomers contained in the polymerization liquid and guide it to the condenser. It is also possible to condense and remove it.

The operating conditions for devolatilization, such as temperature and degree of vacuum, are determined by the content of volatile components contained in the polymerization solution, temperature, and supply rate. An example of how to devolatilize the liquid will be explained below.

The shell-and-tube evaporator used here has a shell-and-tube preheater connected to the top of a vacuum chamber.

The polymerization liquid obtained in the prepolymerization step is continuously supplied to a multi-tubular preheater. This preheater is heated with a heating medium and maintained at a temperature higher than the temperature of the supplied polymerization liquid and lower than the temperature at which thermal deterioration of the rubber-modified polymer substantially occurs, for example, 290° C. or lower. In order to achieve more volatilization removal, it is necessary to heat to a higher temperature within this temperature range. The pressure inside the multi-tubular preheater is adjusted by adjusting the aperture of a pressure regulating valve installed at the connection between the vacuum tank and the multi-tubular preheater, and the pressure is lower than the vapor pressure of the polymerization liquid in the preheater. If it is high, the preheater is filled with liquid,
Conversely, if it is low, volatile components (unreacted monomers and solvent, if used) in the polymerization solution will evaporate, resulting in a partially foamed state. In order to facilitate removal by volatilization, it is necessary to adjust the amount so that excessive unreacted monomers are not removed by volatilization. on the other hand,
The amount removed by volatilization can be adjusted by adjusting the heating temperature of the preheater in the same manner.

The polymerization liquid supplied to the multi-tubular preheater is thus continuously supplied in its entirety through the pressure regulating valve to a vacuum tank maintained at a pressure lower than the pressure of the preheater. Volatile components (unreacted monomers, solvent, etc.) remaining in the polymerization solution are partially evaporated here. The vacuum tank is heated to a temperature above which the polymerization liquid after volatilization substantially flows by flowing a heat medium through the outer shell. A gas exhaust pipe connected to a recovery system for recovering unreacted monomers is provided at the top of the vacuum chamber to guide the volatilized components to the recovery system. The polymerization liquid after volatilization is stored in the lower part of the vacuum chamber, and is continuously discharged from the vacuum chamber by a discharge pump to be used in the next polymerization completion step.

The pressure within the vacuum chamber is regulated in a conventional manner by providing a vacuum source such as a vacuum pump or a vacuum sector in the recovery system.

Although the amount removed by volatilization from the polymerization solution can be adjusted by adjusting this pressure and the heating temperature of the vacuum chamber, it is easier to control the operating conditions of the multi-tube preheater. In the intermediate volatilization step, since heating is performed using a heating medium or the like, polymerization generally proceeds at the same time as the monovinyl aromatic monomer contained in the polymerization solution is removed by volatilization.

It would be advantageous if such polymerization occurred primarily during the latter half of the volatilization step at temperatures above 150°C. Ru.

The polymerization liquid after volatilization is carried out to the polymerization completion step. Polymerization in this process is generally carried out using a reactor such as a stirred tank reactor or a tower reactor, but the polymerization of the polymer solution may also proceed in the supply piping from the intermediate volatilization removal process to the polymerization completion process. Yes, this supply piping can also be used as a means for completing the polymerization process. Furthermore, in order to produce a rubber-modified polymer with extremely low volatile content, a volatilization removal process is installed again after the completion of the polymerization process, and when the polymerization liquid is heated and supplied to the volatilization removal equipment, this supply piping or preheating is used. Polymerization can also proceed in a container or the like. In addition, in the polymerization completion step, the unreacted monomer remaining in the final polymer after the polymerization completion step is evaporated and the unreacted monomer remaining in the polymerization solution after the previous step is
It is necessary to proceed with polymerization so that the molecular weight becomes less than 6.

If 50% or more of unreacted monomer remains, the increase in gel content will be insufficient and the effect of the present invention will not be significant.The smaller the residual amount, the greater the effect of the present invention. It is necessary to carry out the polymerization at a fast rate, and the higher the polymerization temperature, the greater the effect of the present invention.
Polymerization proceeds at the above temperature.

When the rubber-modified polymer obtained in the polymerization completion step is sent to an ordinary vented extruder or multi-tube devolatilizer and the volatile components are further removed by volatilization, a rubber-modified polymer with extremely low volatile content can be obtained. The rubber-modified polymer thus obtained becomes an excellent molding material for extrusion molding or injection molding as an impact-resistant resin. On the other hand, when the rubber modified polymer according to the present invention is compared with the rubber modified polymer produced by the conventional method with the same amount of rubber components, it has a high gel content; this is estimated to be a major factor in bringing about the effects of the present invention, According to the method of the present invention, even if the polymerization completion step is carried out at a high temperature, the molecular weight of the rubber-modified polymer does not decrease significantly and the gel content increases, which is considered to be one of the factors contributing to the effects of the present invention. .

Examples and comparative examples will be described below.

The outline of the reactor and devolatilizer in the example is as follows.
Reactor: Jacket using a screw type stirrer,
No. 1 and No. 2 in a normal stirring reaction tank with a draft tube.
The internal volumes of the third and fourth reactors are 3, 3, 5, and 51, respectively. Volatization remover A vertical sleeve type at the head of a vacuum chamber with a jacket connected to a vacuum pump through a horizontal sleeve type condenser. Example 1 A raw material solution consisting of 5% by weight of polyptadiene and 95% by weight of styrene was supplied to the first reactor at a rate of 3.0 K9/Hr. The polymerization was carried out at 129° C. by continuously supplying the heat medium at a high speed and controlling the temperature of the heat medium to disperse the rubber.

The entire amount of the polymerization liquid flowing out from the first reactor was continuously supplied to the second reactor, and polymerization was carried out while maintaining the internal temperature at 150°C. The polymerization rate of styrene at the outlet of the second reactor was 58%.
The entire amount of this polymerization liquid was continuously introduced into an intermediate volatilization remover. The polymerization solution was heated by flowing a heating medium at 190° C. through a vertical sleeve type heater and flashed while flowing down into a vacuum tank maintained under a reduced pressure of 400 mmH9. The polymerization liquid collected at the bottom of the vacuum chamber was immediately and continuously discharged by a discharge pump, and the entire amount was continuously supplied to the third reactor. The amount of unreacted styrene monomer condensed in the jacket condenser was 0.6K7/Hr. The third reactor was kept at 180°C to complete the polymerization. The polymerization liquid continuously discharged from the third reactor was fed to a vented extruder, volatile components were removed by a conventional method, and then pelletized. The amount of unreacted styrene monomer recovered from the vent was 0.1 instant/Hr. Table 1 shows the analysis and performance evaluation results of the pellets obtained. Example 2 An experiment similar to Example 1 was conducted using a raw material solution consisting of 7% by weight of polyptadiene and 93% by weight of styrene.

The feed rate of the raw material solution was 3.0 Kf/Hr, and the polymerization temperatures of the first and second reactors were maintained at 132°C and 150°C, respectively. The polymerization rate of styrene at the outlet of the second reactor is 60 (
I! It was hot. The unreacted monomer was removed by volatilization in exactly the same manner as in Example 1, but the amount of unreacted styrene monomer removed was 0.5 KV/Hr. The polymerization temperature in the third reactor was maintained at 180°C to complete the polymerization. The amount of unreacted monomer recovered from the vented extruder is 0.1
It was K7/Hr. Table 1 shows the analysis and performance evaluation results of the pellets obtained. Comparative Example 1 Using a raw material solution consisting of 8% by weight of polybutadiene and 92% by weight of styrene, the same experiment as in Example 2 was carried out, except that part of the unreacted monomer was not removed by volatilization during the polymerization process. Summer.

The feed rate of the raw material solution was 3.0K9/Hr, and
and the polymerization temperature of the third reactor was 132°C and 15°C, respectively.
It was kept at 0°C and 180°C. This polymerization solution was fed to a vented extruder, volatile components were removed by a conventional method, and pelletized. Table 1 shows the analysis and performance evaluation results of the pellets obtained. Without intermediate volatilization, the Izot impact value was low despite the rubber content being higher than in Example 1.
In addition, compared to Example 2, which has almost the same rubber content, the Izot impact value is naturally inferior, and the elongation is also inferior.
Polymerization was carried out under the conditions shown in .

In this comparative example, since the prepolymerization rate is insufficient,
Two stages of polymerization reactors were used for the complete polymerization. The results are shown in Table 1. If the prepolymerization rate was too low, the gel content was insufficient and the Izot impact value was low even though the rubber concentration of the obtained polymer was the same as in Example 2. Comparative Example 3 In Example 2, the preliminary polymerization rate was increased to 83% and polymerization was carried out under the conditions shown in Table 1 below.

The results are shown in Table 1. If the prepolymerization rate is too high, the Izo3 impact value will be low, as will the case if the prepolymerization rate is too low.

Example 3 A raw material solution prepared by adding 20 parts by weight of ethylbenzene as a diluent to 13 parts by weight of the rubber component and 87 parts by weight of styrene was mixed with 2.7 parts by weight.
A feed rate of K7/Hr was fed to the first reactor.

Tests were conducted under the conditions shown in Table 1 below. The results are shown in Table 1.
Furthermore, the amount of monomer recovered in the intermediate volatilization and vented extruder was determined by gas chromatography analysis.

Comparative Example 4 A test was attempted in the same manner as in Example 3 except that the rubber component was changed to 20 parts by weight and the styrene was changed to 80 parts by weight, but the viscosity in the first reactor was high. However, the test was discontinued due to poor rubber dispersion.

Comparative Example 5 Example 1 with a rubber component amount of 1% by weight based on styrene.
It was tested in the same way.

The results are shown in Table 1. Since the amount of rubber component is small, the Izod impact value is extremely low. Comparative Example 6 40 parts by weight of ethylbenzene was further added as a diluent to 100 parts by weight of the raw material composition of Example 2, and prepolymerization was carried out.

After this prepolymerization, the monomer was removed in an intermediate volatilization step, but the amount of monomer removed did not reach 10% by weight of the polymer produced in the prepolymerization even when the temperature of the heating medium in the heater was 205°C. No tests were conducted. That is, it can be seen that if too much diluent is used, a large amount of energy is required to remove the monomer.

Comparative Example 7 According to Example 2, the temperature for complete polymerization was set at 140°C (3rd
The test was carried out in the same manner as in Example 2, except that the temperature was 145°C (4th reactor) and 2 stages.

The results are shown in Table 1. Even though the amount of rubber was greater than in Example 2, the Izot impact value was low.

Claims (1)

[Claims] 1 100 parts by weight of monovinyl aromatic monomer, rubber component 2
In a method for producing a rubber-modified impact-resistant polymer by polymerizing a raw material solution consisting of ~20 parts by weight and a diluent of 30% by weight or less based on the total of monovinyl aromatic monomer and rubber component, (1) Prepolymerizing a raw material solution containing a monovinyl aromatic monomer and a rubber component and proceeding with the polymerization until the reaction rate of the monovinyl aromatic monomer reaches 40 to 80%, (2)
Next, the unreacted monovinyl aromatic monomer is evaporated from the obtained polymerization liquid, and an amount corresponding to at least 10% by weight of the produced polymer obtained in the prepolymerization is removed, and at least the amount of the produced polymer is removed. A method for producing a rubber-modified impact-resistant polymer, which comprises adjusting volatilization removal so that an amount equivalent to 10% by weight remains, and (3) subsequently completing polymerization at a high temperature of 150° C. or higher.