JPH0725857B2 - Continuous bulk polymerization of impact-resistant styrenic resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a continuous bulk polymerization method for impact-resistant styrenic resin, and more specifically, it has a uniform particle size of the grafted rubbery polymer in the resin. In addition, the present invention relates to a continuous bulk polymerization method of an impact resistant styrene resin having excellent strength and gloss.

[Conventional technology]

In producing impact-resistant styrene-based resin by graft-polymerizing styrene-based monomer in the presence of rubbery polymer,
During the graft polymerization, how to control the atomization by the dispersion of the rubbery polymer and the stabilization of the rubber particles in the matrix resin is particularly important in determining the quality of the resin to be obtained, and the final resin The rubber particle size, its distribution, and the graft ratio have a great influence on impact strength and gloss.

Conventionally, as for the industrial production method of impact-resistant polystyrene, batch-type bulk-suspension polymerization method and continuous bulk-polymerization method are generally adopted, but the continuous method is superior because of its productivity and economy. The continuous bulk polymerization method is becoming the mainstream because of its excellent properties.

Usually, in the continuous bulk polymerization method, as proposed in JP-A-60-28407, several stirring tank type reactors are connected in series to continuously supply the raw material solution to proceed the polymerization. Some manufacturing methods are common.

More specifically, it is achieved by subjecting the grafted rubbery polymer to fine particles dispersed in the initial polymerization stage by applying a predetermined shearing action in a stirred tank reactor, and then a plurality of stirred tank reactions. A production method has been proposed in which it is continuously transferred to a vessel and polymerization is allowed to proceed.

However, in the case of the continuous bulk polymerization method using the above-mentioned tank type reactor, the drawbacks associated with the dynamic mixing with a stirrer have been pointed out. That is, as the polymerization progresses, the viscosity of the polymerization liquid in the tank increases, the power required to continue stirring increases and the one end of the polymerization conversion of the styrene-based monomer in the tank increases due to the strength design of the stirring blade. In addition, due to excessive stirring and mixing, excessive shearing force is applied to the grafted rubbery polymer that has been made into dispersed fine particles, so that the dispersed rubber fine particles are broken and the rubber particle diameter distribution is increased. Often results in a decrease in product strength. Further, as long as the stirring tank reactor is used, it has an excessively large volume in terms of its structure. Therefore, for example, when different products having different rubber particle diameters are produced, the time inferiority required for switching to different product brands is It is also a drawback that cannot be overlooked. Therefore, some improvements such as the influence of the structure of stirring blades on the stirring tank reactor, the implementation of prepolymerization, and the combination with a tubular reactor or a tower reactor have been made, but they are still insufficient. Absent.

[Problems to be Solved by the Present Invention]

In view of such a situation, the present inventors have not used any stirred tank reactor, and have a static mixing structure for mixing a polymerization liquid therein, for example, a shock resistance in a tubular reactor provided with a static mixer. The continuous production method of the functional styrene resin was examined.

Conventionally, regarding the use of such a tubular reactor in a continuous polymerization method,
For example, Japanese Patent Application Laid-Open No. 55-38893 proposes a process comprising an initial polymerization tank equipped with a stirring means and a tubular reactor for performing main polymerization. The disadvantages associated with (1) are not eliminated, excessive shear due to cooperative stirring and mixing is added, and the distribution of rubber particle diameters is widened, and the graft ratio is not improved either.

Then, as a result of the inventors' investigation on a method of polymerizing the rubbery polymer into fine particles by using a tubular reactor, the following things have been clarified. That is, in order to cause the dispersion of the rubber-like polymer, proper shearing is necessary at the initial stage of the polymerization, and therefore the presence of a mixer for providing mixing is indispensable. However, the degree of mixing by a static mixing structure in the tubular reactor, for example, a static mixer, is determined by the linear velocity of the polymerization liquid in the reactor, which depends on the flow rate and the pipe diameter, and therefore sufficient mixing is achieved. In order to perform, it is necessary to significantly increase the flow rate. However, increasing the flow rate significantly in the tubular reactor is technically limited because the viscosity increases remarkably as the polymerization proceeds and the pressure loss in the tube increases, and sufficient shearing cannot be obtained. Therefore, in the case of an ordinary tubular reactor, due to its weak shearing, for example, although it is possible to disperse the rubbery polymer into fine particles, the desired particle size cannot be obtained, or the grafted rubbery substance precipitated during the initial polymerization is obtained. Polymers often adhere to the walls inside the reactor. Especially when the adhered grafted rubbery polymer grows and mixes into the resin,
This is a problem that causes problems in the appearance of the product as fish eyes.

In order to solve these problems, at the stage of the initial polymerization in which the rubber-like polymer is dispersed into fine particles, a part or most of the initial polymerization liquid is refluxed, continuously joined with the feedstock solution, and then tubular. When the method of mixing simultaneously with the initial polymerization in a reactor was examined, it was possible to improve the rubber particle size and its distribution to some extent by increasing the reflux ratio and circulating mixing for a long time. As the amount increases, it becomes difficult to make the rubber particles finer and more uniform, and it is difficult to obtain an impact-resistant styrene resin having excellent strength and gloss.

[Means for solving problems]

In view of such a situation, as a result of intensive studies, the present inventors have conducted a bulk polymerization continuously using a tubular reactor having a structure for static mixing therein such as a static mixer, and the initial polymerization thereof. A part or most of the liquid is refluxed so as to be continuously merged with the feedstock, and then at the same time with initial polymerization by a tubular reactor and simultaneously mixed, at any position of a circulation line consisting of an initial polymerization line and a reflux line, Preferably, when a dynamic in-line mixer is incorporated in the initial polymerization line after merging and further mixing is carried out by this, the grafted rubbery polymer in the feed solution and the initial polymerization solution is easily made into fine particles to be uniform. Along with dispersion, the graft ratio is improved, and the impact-resistant styrenic resin having a uniform particle size and excellent strength and gloss of the grafted rubbery polymer can be easily obtained. Found the door, which resulted in the completion of the present invention.

That is, the present invention relates to an initial polymerization line that incorporates a tubular reactor having a static mixing structure inside, and a main polymerization that incorporates a tubular reactor having a static mixing structure inside subsequently. Using a polymerization line having a line and a reflux line branching from between the initial polymerization line and the main polymerization line and returning to the entrance of the initial polymerization line, the stin-based monomer is graft-polymerized in the presence of the rubbery polymer. In the continuous bulk polymerization method, at the time of initial polymerization, a part or most of the initial polymerization liquid is refluxed through a reflux line to continuously combine with the feedstock, and then mixed with the initial polymerization in a tubular reactor at the same time. Impact resistance characterized by incorporating a dynamic in-line mixer in the circulation line consisting of the initial polymerization line and the reflux line, and further mixing And it provides a continuous bulk polymerization process styrene-based resin.

Typical examples of the rubbery polymer used in the present invention are polybutadiene / rubber, styrene / butadiene copolymer rubber, styrene / butadiene / styrene block copolymer rubber, ethylene / propylene terpolymer rubber, butadiene / butadiene rubber. Conjugated 1,3-diene-based monomers such as isoprene or chloroprene, including acrylonitrile copolymer rubber, butyl rubber, acrylic rubber, styrene / isobutylene / butadiene copolymer rubber, or isoprene / acrylic ester copolymer rubber. There are rubbers obtained by using these, and these are used alone or in combination of two or more.

The styrene-based monomer used in the present invention includes styrene and α-
Methylstyrene, and benzene nucleus hydrogen atom is a generic name for styrene derivatives in which a halogen atom is substituted with an alkyl group of C _{1 to} C ₄ , and a typical example of such a styrene-based monomer is , Styrene, o-chlorostyrene, p-chlorostyrene, p-methylstyrene, 2,4-dimethylstyrene or t-butylstyrene.

In the present invention, another monomer copolymerizable with the styrene-based monomer (hereinafter abbreviated as “other monomer”) may be used in combination with the styrene-based monomer. Examples of the monomer include acrylonitrile, acrylic acid and methacrylic acid and their alkyl esters, maleic anhydride, and various maleimides.

Although the present invention employs bulk polymerization, it is possible to use an appropriate amount of a solvent for adjusting the viscosity of the polymerization solution, and the solvent is toluene, ethylbenzene, xylene or the like. The amount of the solvent used is usually 2 with respect to 100 parts by weight of the resin component composed of the rubbery polymer, the styrene-based monomer and the other monomer.
The amount does not exceed 0 part by weight.

In the polymerization liquid used as a feed material in the present invention, a known organic peroxide that releases a free radical when decomposed as a polymerization initiator if necessary, for example, benzoyl peroxide, di-t-butyl peroxide, dicumyl. A peroxide or the like can also be used. If necessary,
You may use together well-known additives, such as plasticity, an antioxidant, and a chain transfer agent.

As the tubular reactor used in the present invention, any known tubular reactor having a static mixing structure inside can be used, but among them, a tubular reaction having a static mixing structure consisting of a large number of mixing elements and the like. A vessel such as a Sulzer type static mixer, a Kenix type static mixer, a Toray type static mixer or the like is preferable.

The number of tubular reactors used in the present invention, for example, in the case of the static mixer as described above, varies depending on the length of the static mixer, the number of mixing elements, etc. and is not particularly limited, but usually 5 or more mixing elements, preferably 10 Normally, 4 to 15, preferably 6 to 10, static mixers having -40 are used in combination.

As the dynamic in-line mixer used in the present invention, a housing part of a lock and a dynamic mixing structure part for forcing in the housing part, for example, a propeller type, turbine type, anchor type stirring blade and the like for supporting the stirring blade Any known dynamic in-line mixer consisting of the shaft part of The clearance between the inner wall of the housing and the stirring blade is usually in the range of 0.1 to 2 mm, but preferably in the range of 0.2 to 1 mm.

Specific examples of the dynamic in-line mixer used in the present invention include special anchor type mixers of Satake Chemical Industry Co., Ltd., angle mixers of Chemineer type, pipeline mixers of Greerco type, and Kurimoto Iron Works type. A kneader type mixer or the like is preferable.

The polymerization apparatus used in the present invention comprises a raw material supply unit, an initial polymerization line which is continuous with the raw material supply unit and incorporates a tube-locking reactor having a static mixing structure inside, and a static polymerization system which continues from the initial polymerization line. A main polymerization line incorporating a tubular reactor having a structure for dynamic mixing, and a reflux line branched from between the initial polymerization line and the main polymerization line to return to the initial polymerization line inlet, and the initial stage Examples include a dynamic in-line mixer incorporated at an arbitrary position in a circulation line formed by combining a polymerization line and a reflux line, preferably in an initial polymerization line after joining with a raw material solution.

A transfer pump is preferably provided between the raw material supply section and the initial polymerization line.

Here, the raw material solution supplied from the raw material supply section into the circulation line is the rubbery polymer and the styrene-based monomer, and further other monomers added as necessary, a solvent, a polymerization initiator,
Other known additives and the like are contained.

The proportion of the rubbery polymer used here is the content of the rubbery polymer in 100% by weight of the resin component composed of the rubbery polymer, the styrene monomer and the other monomer (a% by weight). )
Is preferably in the range of 3 to 15% by weight, because the viscosity of the polymerization liquid in the circulation line does not increase so much, the particle size can be easily controlled, and a rubber-modified styrene resin having excellent impact resistance can be obtained. .

The raw material solution supplied from the raw material supply section is continuously merged and mixed with the initial polymerization liquid circulating in the circulation line,
While being circulated while being appropriately sheared by a dynamic in-line mixer, initial polymerization is usually carried out at a reaction temperature of 110 to 140 ° C. in a tubular reactor, and further mixed and dispersed.

At this time, the tubular reactor installed in the circulation line is extremely effective in mixing the circulating polymer solution with a newly supplied raw material solution while receiving an appropriate shearing force. Further, the dynamic in-line mixer is extremely effective in uniformly dispersing the rubber-like polymer without generating giant particles, and the particle diameter can be controlled in a short time.

That is, under appropriate shearing in the tubular reactor, the circulating rubbery polymer solution and the raw material solution to be newly supplied are mixed, and without causing generation of giant particles by a dynamic in-line mixer. It is a method of instantaneously forming fine rubber particles, and the effects of the present invention are beneficially achieved by combining a tubular reactor and a dynamic in-line mixer. In addition, controlling the rotational speed of the dynamic in-line mixer when controlling the rubber particle size brings about a very powerful effect.

The reflux ratio (R) of the polymerization solution in the circulation line, the flow rate of the initial polymerization solution refluxed in the circulation line was F ₁ l / hour, and the flow rate of the raw material solution supplied in the circulation line was F ₂ l / hour. In this case, the range of R = F ₁ / F ₂ = 1 to 20 is usually satisfied. Above all, the reflux can be stably carried out, wall poly is not generated, and fine particles of a rubber polymer having a uniform particle size can be obtained. And R = 1.5-10
Is preferred.

The degree of initial polymerization in the circulation line is the polymerization conversion rate of the monomer component consisting of the styrene-based monomer at the exit of the circulation line, that is, the main polymerization line inlet and other monomer added as necessary. (B weight%) is usually b = 0. 0 in relation to the content (a weight%) of the rubber chamber polymer.
9a to 5a, and preferably b = 1.5a to 3a,
Within these ranges, it is easy to make the rubbery polymer phase into fine particles and to disperse it uniformly. Therefore, a rubber-modified styrene resin in which a rubbery polymer having an average particle diameter of 0.3 to 6.0 μm, preferably 0.6 to 3.0 μm is uniformly dispersed. Is obtained.

The initial polymerization liquid thus obtained is partially or mostly refluxed to join the raw material solution again, but the rest is supplied to the main polymerization line and is usually styrene-based at a reaction temperature of 130 to 170 ° C. It is polymerized until the polymerization conversion rate of the monomer component consisting of the monomer and other monomer added as necessary is usually 70 to 90% by weight, and then, for example, in a devolatilization tank under reduced pressure. After removing the reaction monomer and the solvent, pelletizing is performed to obtain an impact resistant stin resin.

〔The invention's effect〕

According to the method of the present invention, a rubbery polymer grafted by a tubular continuous bulk polymerization obtained by combining a tubular tablet reactor having a structure for static mixing and a dynamic in-line mixer under specific conditions. However, it is possible to easily produce fine particles in a short time, improve the graft ratio, and produce an impact-resistant styrene-based resin having a uniform strength of rubber particles and an excellent gloss.

INDUSTRIAL APPLICABILITY The present invention can switch to products having different average particle diameters, rubber contents and / or different kinds of rubber in a short time as compared with a continuous bulk polymerization process using a stirred tank reactor, resulting in low cost production. It is a continuous bulk polymerization method that supplies a great deal of industrial utility value to meet the demand.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. All parts and% in the examples are based on weight, and various physical properties in the examples were measured as follows.

(1) Rubbery polymer content The infrared absorption is determined by an infrared spectrophotometer, and the intensity of the absorption is compared with a calibration curve prepared in advance.

(2) Izod impact value Based on JIS K-6871.

(3) Surface gloss Based on JIS Z-8471.

(4) A resin having a graft ratio of 1 g is added to 50 ml of a mixed solvent of methyl ethyl ketone / acetone = 1/1 (weight ratio) and vigorously shaken for 1 hour to dissolve and swell. Next, after insoluble matter is settled by a centrifuge, the supernatant is discarded by decantation. The methyl ethyl ketone / acetone insoluble matter thus obtained is dried under reduced pressure at 50 ° C., cooled in a desiccator, weighed, and the graft ratio is calculated by the following formula.

(5) Average particle size of rubbery polymer in resin and its distribution A weight average and number average are obtained by using a Coulter counter (TA-II type manufactured by Coulter, Inc.) using an electrolytic solution composed of dimethylformamide and ammonium thiocyanate. The 50% median diameter was calculated, and these were defined as the weight average particle diameter and the number average particle diameter, respectively, and the ratio was defined as the particle distribution. The smaller the value of the ratio, the narrower the particle size distribution.

Example 1 In this example, a tube lock reactor having an inner diameter of 2 inches and a length of 1 m (Kenix type static mixer N10 manufactured by Noritake Co., Ltd.)
Type, 12 built-in mixing elements) were connected in series, and an initial polymerization line with a dynamic in-line mixer (6 turbines, Gleaco, USA, clearance 0.5 mm) installed between them and the main polymerization line that follows A continuous polymerization apparatus having a polymerization region consisting of and a reflux line for refluxing a part or most of the initial polymerization liquid was used.

The initial polymerization line is a raw material supply part for supplying the raw material solution sent by the gear pump to the circulation line, and subsequent four tube lock reactors (I) to (IV) connected in series.
[However, (I), (I
I), (III), and (IV)], and a dynamic in-line mixer installed in series between the tube lock reactors (II) and (III).

The reflux line consists of a line connecting the outlet of the tube-lock reactor (IV) and the inlet of the tubular reactor (I), and a reflux gear pump is provided in the line. (In addition, the initial polymerization line and the reflux line are collectively called a circulation line.) The main polymerization line is a tubular reactor (IV) in the circulation line.
Of four tubular reactors (V) connected in series following the outlet of
(VIII) [however, (V), (VI), (VII), and (VIII) in order from the side closer to the tubular reactor (IV)], and the outlet of the tubular reactor (VIII) is Further heat exchanger,
It continues to the post-treatment area consisting of the devolatilization tank and extruder.

Polybutadiene [Asahi Kasei Co., Ltd. diene NF35A] 6
Content of polybutadiene consisting of 100 parts of styrene and 94 parts of styrene a
= 6% raw material solution was prepared, and bulk polymerization was continuously performed under the following conditions.

Flow rate returned to circulation line (F ₁ ): 25l / hour (flow rate of reflux line) Flow rate of raw material solution supplied to circulation line (F ₂ ): 5l / hour Reflux ratio (R = F ₁ / F ₂ ) : 5 Reaction temperature in circulation line: 130 ℃ At the outlet of tubular reactor (IV): 24% Polymerization conversion rate of monomer component (b) Reaction temperature in main polymerization line: 155 ℃ Rotation of dynamic in-line mixer Number: 700 rpm The obtained polymerization solution is heated to 230 ° C in a heat exchanger and heated to 50 mmHg.
After removing the volatile components under the pressure sensitive condition of No. 1, the resin was melted by an extruder, kneaded, and pelletized to obtain an impact-resistant styrene resin of the present invention, and then various physical properties were measured. The measurement results are shown in Table-1.

Example 2 The impact resistant styrene resin of the present invention was prepared in the same manner as in Example 1 except that the reflux ratio (R) in the circulation line was changed to 7 and the rotation speed of the dynamic in-line mixer was changed to 1500 Rrpm. After being obtained, various physical properties were similarly measured. The results are shown in Table-1.

Example 3 Using a raw material solution consisting of 12 parts of polybutadiene, 88 parts of styrene and 5 parts of ethylbenzene, the reflux ratio (R) in the circulation line was set to 8, and the rotation speed of the dynamic in-line mixer was set to 1800.
The impact-resistant styrene-based resin of the present invention was obtained in the same manner as in Example 1 except that the rpm was changed, and various physical properties were measured in the same manner. The results are shown in Table-1.

Example 4 The reflux ratio (R) in the circulation line was 8, the reaction temperature was 127 ° C. so that the polymerization conversion rate (b) of the monomer component was 18%,
An impact-resistant styrenic resin of the present invention was obtained in the same manner as in Example 3 except that the respective properties were changed, and then various physical properties were similarly measured. The results are shown in Table-1.

Comparative Example 1 The polymerization reaction was carried out using a continuous reaction apparatus comprising two 20-liter tank type reactors equipped with helical stirring blades, a heat exchanger, and a devolatilization tank. Example 1 in the first tank reactor
A raw material solution having the same composition as the above was continuously supplied at 5 l / hour with stirring to carry out initial polymerization at 130 ° C., and the initial polymerization solution was continuously withdrawn at 5 l / hour from the bottom of the reactor, It is supplied to the tank-type reactor, and then the second tank-type reactor is used for 15
An impact-resistant styrene-based resin for comparison was obtained in the same manner as in Example 1 except that the polymerization was carried out at 5 ° C., and then various physical properties were measured in the same manner. The results are shown in Table-1.

Comparative Example 2 An impact-resistant styrene-based resin for comparison was obtained in the same manner as in Example 1 except that initial polymerization was carried out using the first tank reactor used in Comparative Example 1 instead of the circulation line. Then, various physical properties were measured in the same manner. The results are shown in Table-1.

Comparative Example 3 An impact-resistant styrenic resin for comparison was obtained in the same manner as in Example 4 except that the dynamic inline mixer was stopped.
Then, various physical properties were measured in the same manner. Table of results
Shown in 1.

Comparative Example 4 An impact-resistant styrene-based resin for comparison was obtained in the same manner as in Example 1 except that a tubular reactor having no built-in static mixing structure was used, and then various physical properties were similarly measured. I went. The results are shown in Table-1.

Claims (1)

[Claims] 1. An initial polymerization line incorporating a raw material supply part, a tubular reactor having a static mixing structure part inside from the raw material supply part, and a static mixing structure inside from the initial polymerization line. Using a polymerization device having a main polymerization line incorporating a tubular reactor having a portion and a reflux line that divides between the initial polymerization line and the main polymerization line and returns to the entrance of the initial polymerization line. Is a continuous bulk polymerization method in which a styrene-based monomer is graft-polymerized in the presence of, and at the time of initial polymerization, a part or most of the initial polymerization liquid is refluxed through a reflux line to continuously join the feedstock. And then mixing at the same time as the initial polymerization by the tubular reactor, and incorporating a dynamic in-line mixer in the circulation line consisting of the initial polymerization line and the reflux line, Continuous bulk polymerization of high impact styrene resin which comprises bringing together.