JP3125892B2 - Acrylonitrile-styrene copolymer resin and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel acrylonitrile-styrene copolymer resin and a method for producing an improved acrylonitrile copolymer resin. More specifically, the present invention provides an acrylonitrile-styrene copolymer resin having a narrow composition distribution of a copolymer, and having a good color tone, excellent transparency, and excellent rigidity and chemical resistance. The present invention relates to a method for producing an acrylonitrile copolymer having excellent physical properties with high productivity.

[0002]

2. Description of the Related Art Conventionally, an acrylonitrile-styrene copolymer resin is known as a resin which has good transparency and processability and can be obtained at a low cost. This acrylonitrile-styrene copolymer resin usually has a large heat of polymerization,
Industrially, it is produced by an aqueous dispersion polymerization method, that is, a suspension polymerization method or an emulsion polymerization method.

[0003] However, in the suspension polymerization method and the emulsion polymerization method, which are integral polymerization methods, acrylonitrile (AN) / styrene (S
T) Except for the composition having a weight ratio of 25/75, there is a disadvantage that it is difficult to obtain a transparent resin over a wide composition range.

On the other hand, in the continuous polymerization method as a differential polymerization method, acrylonitrile generates a large amount of heat due to polymerization.
In order to maintain the desired polymerization temperature, the productivity is inevitably reduced, and it is difficult to control the composition distribution of the copolymer having an AN / ST weight ratio near 15 and 45, which is greatly deviated from the azeo composition. However, there is a disadvantage that it is difficult to obtain a transparent material.

When an acrylonitrile-styrene copolymer resin is produced by a continuous solution polymerization method, a solvent usually has a solubility parameter [SP value, (J / m ³ )].
× 1/2 × 10 ⁻³ ] (“Polymer Handbook” published by Willy International) is 17 to 19,
SP value of acrylonitrile-styrene copolymer is 20 to
A solvent different from 25 is used. In this case, although the viscosity of the polymerization system decreases and the transfer of the reaction product into the system becomes easy, there arises a problem that the solubility of the copolymer in the polymerization reaction solution decreases. As a method of improving solubility, raising the polymerization temperature can be considered.However, raising the polymerization temperature causes a decrease in heat removal efficiency, making it difficult to control the polymerization temperature, resulting in deterioration of product quality and polymerization runaway reaction. An acrylonitrile-styrene-based copolymer having a high content of acrylonitrile unit has a disadvantage that it may be colored by an intramolecular reaction due to heat or an oxidation reaction involving oxygen and heat.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a problem of solubility of a copolymer in a polymerization reaction solution in such a continuous solution polymerization method, a problem of efficient removal of heat of polymerization, and a problem of resin distribution due to copolymer composition distribution. Acrylonitrile-styrene copolymer with a narrow copolymer distribution, good color tone, excellent transparency, and excellent rigidity and chemical resistance. An object of the present invention is to provide a method for producing a polymer resin with high productivity and a novel acrylonitrile-styrene copolymer resin obtained by such a method.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have prepared a method for producing an acrylonitrile-based copolymer having excellent physical properties containing 30 to 50% by weight of an acrylonitrile unit by copolymerizing acrylonitrile with another monomer. As a result of intensive studies on acrylonitrile-based copolymers with good transparency, mechanical strength, and chemical resistance, polymerization was conducted using specific polymerization initiators and specific reaction means including devolatilization conditions. The present inventors have found that a novel acrylonitrile-styrene copolymer resin having a very narrow copolymer composition distribution can be obtained by this method, and the present invention has been accomplished based on this finding.

That is, the present invention relates to a copolymer containing 30 to 50% by weight of acrylonitrile units and, when the average value of the acrylonitrile units is X% by weight, the copolymer containing acrylonitrile units outside the range of (X ± 5)% by weight. Content of 5
% By weight of the copolymer containing acrylonitrile out of the range of not more than 1% by weight (X ± 10). Solution viscosity is 4.5
Acrylonitrile-styrene copolymer resin having a molecular weight of about 13 to about 13 centipoise, and copolymer containing acrylonitrile unit in an amount of 30 to 50% by weight by copolymerizing acrylonitrile with styrene or other copolymerizable monomers. In producing the coalesced resin, a radical polymerization initiator giving a half-life of 10 hours and having a decomposition temperature of 60 to 120 ° C. is used at a ratio of 1.0% by weight or less based on the total amount of the raw material monomers. The polymerization reaction is carried out while continuously supplying the components together with the components to the liquid phase reaction zone in a complete mixing tank reactor maintained at a constant temperature in the range of 100 ° C. or more and less than 160 ° C. The volatile component is condensed and recovered from the gas phase zone containing the volatile component generated during the formed reaction and circulated to the liquid phase reaction zone. There is provided a method for producing acrylonitrile copolymer resin characterized by a low-boiling component mainly unreacted monomers from the extracted reaction mixture is removed continuously separated.

The novel acrylonitrile-styrene copolymer resin of the present invention comprises a copolymer containing an acrylonitrile unit in the range of 30 to 50% by weight, which has heretofore been considered difficult to obtain good quality. It has a very narrow polymer composition distribution and has excellent transparency, mechanical strength and chemical resistance. Such a novel acrylonitrile-styrene copolymer resin is prepared by using a radical polymerization initiator having a decomposition temperature of 60 to 120 ° C., which gives the above-mentioned 10-hour half-life, with acrylonitrile according to a specific reaction means including devolatilization conditions. It can be produced by copolymerizing with styrene.

In this method, in addition to the above-mentioned copolymer of acrylonitrile and styrene, a copolymer of acrylonitrile with styrene and other monomers such as alkyl acrylate, alkyl methacrylate, N-phenylmaleimide, etc. It can also be used for the production of acrylonitrile-styrene-alkyl acrylate copolymer, acrylonitrile-styrene-alkyl methacrylate copolymer, acrylonitrile-styrene-N-phenylmaleimide copolymer and the like.

[0011] The heating value of polymerization of acrylonitrile is 347 k
cal / kg, styrene 170 kcal / k
g, methyl methacrylate 130 kcal / kg, which is extremely large. Therefore, in the present invention, this polymerization heat generation is suppressed by the latent heat of vaporization of the reaction mixture, and volatile components evaporated in the reaction zone are condensed and recovered by a heat exchanger. A process is used to return to the reaction zone.

As a reactor for carrying out this process, a complete mixing tank type reactor is used. Among them, a reactor equipped with a mixing function having a mixing function over the supply port, the discharge port and the entire reaction zone is preferable. Plug flow type reactors that do not provide uniform mixing throughout the reaction zone are not suitable for the practice of the present invention. In addition, the complete mixing tank type reactor has a gas phase zone at the top under the reaction operation conditions, and a part of the heat generated by polymerization is removed by the latent heat of evaporation of the volatile components in the reaction mixture. Is used in the form of condensing and circulating through an external heat exchanger.

The monomer in the condensate is mainly composed of acrylonitrile, and its monomer composition is different from the monomer composition in the reaction zone. Therefore, the stirring in the liquid phase reaction zone is sufficiently uniform. Otherwise, the copolymer composition unevenness of the polymerization product will increase, and the transparency and mechanical properties will decrease.

In order to make the copolymer composition uniform, the stirring strength of the tank reactor, the position where the condensate is introduced into the reaction zone, and the prevention of post-polymerization in the volatile component separation step are extremely important. By satisfying these conditions sufficiently, an acrylonitrile-styrene copolymer resin having a uniform composition and excellent transparency and mechanical properties can be obtained.

The stirred strength of the tank reactor is in the range of 3.0~10.0kw / ^{m 3} is preferably represented by the required power Pv agitation per liquid unit volume (kw / ^{m 3)} [However, Pv = (Np / gc) ρn ³ d ⁵ / d ³ , Np:
Power number, gc: gravity conversion coefficient, ρ: stirred liquid density,
d: stirring blade diameter].

The return position of the condensate to the liquid phase reaction zone is selected at the position where diffusion in the liquid phase reaction zone by the rotation of the stirring blade is the fastest, and it is advantageous to return the condensate to the reaction solution instead of the gas phase zone. . In particular, it is preferable to connect the main raw material to the pipe just before supplying it to the reactor and return it to the liquid phase reaction zone together with the main raw material from the viewpoint of mixing properties.

Further, in order to make the composition distribution of the copolymer as uniform as possible, it is important to prevent post-polymerization in the volatile component separation step as described above. In other words, the polymerization initiator such as a radical polymerization initiator must not be present in a high concentration in the reaction mixture in the volatile component separation step, and the lower the concentration of the highly reactive monomer acrylonitrile, the better. preferable.
In order to satisfy such a condition, it is necessary to select a polymerization initiator supplied to the liquid phase reaction zone that is sufficiently consumed within the residence time of the reaction solution, and it is necessary to select a volatile component separation step. Therefore, it is necessary to raise the temperature after the acrylonitrile concentration is diluted.Therefore, after separating acrylonitrile at a low temperature and a low vacuum, a separation operation is performed at a high temperature and a high vacuum to obtain a desired volatile component concentration. It is desirable to implement.

In the method of the present invention, for such a reason, a radical polymerization initiator having a decomposition temperature giving a half-life of 10 hours in the range of 60 to 120 ° C. is used as the polymerization initiator. As such a radical polymerization initiator,
For example, butylperoxy-2-ethylhexanoate,
Benzoyl peroxide, t-butylperoxyisobutyrate, 1,1-bis (t-butylperoxy)-
3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, t-butylperoxylaurate, t-butylperoxy-3
5,5-trimethylhexanoate, cyclohexanone peroxide, t-butylperoxyallyl carbonate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,2 -Bis (t-butylperoxy) octane, t-butylperoxyacetate, 2,
2-bis (t-butylperoxy) butane, t-butylperoxybenzoate, n-butyl-4,4-bis (t-butylperoxy) valate, dicumyl peroxide, t-butylcumyl peroxide, etc. Organic peroxides and even general formulas

Embedded image (Wherein l and n are integers of 1 to 20, m is 0 or 1 to 5
R ¹ , R ² , R ³ and R ⁴ are each a hydrogen atom, an alkyl group, a phenyl group or a cyclohexyl group) and

Embedded image (Wherein R ⁵ is a cyclohexylene group or a methylcyclohexylene group, and R ⁶ is an ethylene group, a vinylene group or a phenylene group), and the decomposition temperature giving a half-life of 10 hours is 60. And organic peroxides at a temperature of up to 120 ° C.

Organic azo compounds such as 1,1'-azobis (1-cyclohexanecarbonitrile), 2-carbamoylazoisobutyronitrile, and 2,2'-azobis (2,4,4-trimethylpentane) Can also be used.

Among these polymerization initiators, t-butyl peroxyisopropyl carbonate is particularly preferable because it gives a colorless and transparent acrylonitrile-styrene copolymer resin.

The amount of these polymerization initiators to be used is 1.0% by weight or less, preferably 0.01 to
It is necessary to select in the range of 0.5% by weight. If this amount exceeds 1.0% by weight, the molecular weight of the obtained copolymer resin tends to decrease.

As the solvent in the present invention, those having the SP value in the range of 17 to 19, for example, benzene, toluene, xylene, ethylbenzene, methyl isobutyl ketone and the like are preferably used. These may be used alone or in combination of two or more. If desired, as a chain transfer agent, for example, mercaptans such as octyl mercaptan and dodecyl mercaptan, α-
Methylstyrene dimer and the like can be used. Further, if desired, various additives, for example, antioxidants such as hindered phenolic antioxidants, ultraviolet absorbers such as benzotriazole ultraviolet absorbers, plasticizers such as mineral oil, and lubricants such as monoglycerin higher fatty acid esters Etc. can be used.

Next, an example of an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of an example of a reaction apparatus for carrying out the method of the present invention. A charged solution comprising a solvent, a polymerization initiator, and a chain transfer agent and other additives used as necessary is continuously supplied from a charged solution storage tank 1 to a reaction tank 3 via a pump 2 to obtain a 100
The polymerization reaction is performed at a temperature of ~ 160 ° C. The reaction tank 3 is a complete mixing tank equipped with a stirrer equipped with a two-stage inclined turbine blade, and has a gas phase gas extraction line connected to a jacket and a heat exchanger 4. The liquid condensed in the heat exchanger 4 is returned to the reaction tank 3 via the pump 5.

The optimum polymerization temperature is determined according to the type of the polymerization initiator and the chain transfer agent used, the type of the reaction tank, and the like.
Further, in order to make the composition of the copolymer uniform, it is necessary to prevent the post-polymerization by making the concentration of the polymerization initiator in the reaction mixture continuously withdrawn from the reaction tank 5 ppm or less. For this purpose, it is necessary to appropriately select a combination of the polymerization initiator, the polymerization temperature and the residence time so that the concentration decay behavior due to the decomposition of the polymerization initiator satisfies the above condition.

The viscosity of the reaction mixture under the reaction conditions depends on the molecular weight and concentration of the copolymer, the polymerization temperature, etc., and is a very important factor for making the composition of the copolymer uniform. It is desirable to operate so as to be in the range of 10 to 100 poise. Furthermore, the solubility of the copolymer in the polymerization solution is also a very important factor for making the composition of the copolymer uniform, and this solubility is included in the content of acrylonitrile units in the copolymer and in the polymerization solution. Is determined by the amount of acrylonitrile monomer used and the polymerization temperature. An appropriate polymerization rate is industrially necessary, and the solubility of the copolymer in the polymerization solution and the appropriate viscosity of the reaction system ensure uniform stirring of the reaction tank and narrow the composition distribution of the copolymer. It is also important to do.

If the polymerization temperature is less than 100 ° C., the polymerization rate is too slow to be practical, and the copolymer has low solubility in the polymerization solution and the viscosity of the reaction system is high, so that the uniformity of stirring is sufficiently maintained. When the temperature exceeds 160 ° C., a low polymer (oligomer having a molecular weight of 1,000 or less) is easily generated, and it becomes difficult to obtain a copolymer having a desired molecular weight. Further, the average residence time is preferably in the range of 0.5 to 4.5 hours, and the polymer concentration in the reaction mixture is preferably 40 to 60 hours.
Advantageously, it is in the range of weight percent.

The reaction mixture is continuously withdrawn from the outlet of the reaction vessel 3, passed through a pump 6 and heat-exchanged by a heat exchanger 7.
After being heated to and maintained at a temperature of about 160 ° C., it is supplied to the separation tank 8 and a part of the volatile component is removed under a condition of a degree of vacuum of about 500 to 900 Torr. The temperature of the reaction mixture and the degree of vacuum in the separation tank are important factors for controlling the devolatilization amount of volatile components. By this devolatilization operation, the polymer concentration in the reaction mixture is reduced from 40 to 60% by weight to 70 to 90% by weight. %, The above-mentioned temperature of 100 to 160 ° C. and the degree of vacuum of 500 to
A condition of 900 Torr is appropriate.

In this first separation tank, unreacted acrylonitrile having a particularly low vapor pressure is devolatilized, and the concentration in the reaction mixture is reduced. As a result, the polymerization reactivity is extremely reduced and the copolymer obtained by post-polymerization is reduced. The nonuniformity of the composition is prevented from expanding, and gelation and coloring due to heating caused by acrylonitrile are also suppressed. The amount of volatile components in the reaction mixture discharged from the first separation tank is desirably in the range of 10 to 30% by weight, and if the amount is less than 10% by weight, the reaction mixture may not be transferred to the second separation tank. Since the viscosity of the mixture is high, the tube wall resistance is large, which is not preferable. If it exceeds 30% by weight, the residual amount of acrylonitrile is large, and coloring is not preferable.

The reaction mixture discharged from the first separation tank 8 via the gear pump 9 is passed through the heat exchanger 10 to 220-280.
After being heated to a temperature of about ° C., it is supplied to the second separation tank 11 to remove volatile components under the condition of a degree of vacuum of about 20 to 100 Torr. By this devolatilization operation, the polymer concentration in the reaction mixture becomes 99% by weight or more.

In the present invention, an apparatus used for separating such volatile components is generally referred to as a devolatizer ["Deboratization", described in Hanser Co. (1983), For example, U.S. Pat. Nos. 2,434,707 and 2,834,
No. 851, No. 2,736,058, No. 2,753,595, No. 2,774,10
No. 5, Japanese Patent Publication No. 1-30848, etc.].

The copolymer from which volatile components have been removed in the second separation tank 11 is discharged in a molten state through a gear pump 12 to obtain a product having a desired shape. The acrylonitrile-styrene copolymer resin of the present invention has a viscosity of 4.5% at a temperature of 25 ° C. of a 10% by weight solution of methyl ethyl ketone.
When the average value of acrylonitrile units is in the range of 平均 13 centipoise and the average value of acrylonitrile units is X% by weight, the content of the copolymer containing acrylonitrile units outside the range of (X ± 5)% by weight is 5% by weight or less (X ± 10) It is necessary that the content of the copolymer containing an acrylonitrile unit out of the range of 1% by weight is 1% by weight or less. If the copolymer composition distribution is wider than the above, an acrylonitrile-styrene copolymer resin having excellent transparency and mechanical properties will not be obtained.

[0032]

According to the continuous solution polymerization method of the present invention, the heat of polymerization is easily removed, the composition distribution of the copolymer is narrow,
An acrylonitrile-styrene copolymer resin which is uniform, has a good color tone, and is excellent in transparency, rigidity and chemical resistance can be produced with high productivity.

[0033]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. The composition distribution and the yellow index (YI) of the copolymer were determined as follows.

(1) Composition distribution of copolymer 0.05 g of a sample was dissolved in 40 ml of THF (tetrahydrofuran), and the AN composition distribution in the copolymer was measured using a high performance liquid chromatograph. In addition, Zolvac CN manufactured by Shimadzu Corporation was used as a column packing material.

(2) Yellow Index Injection molding was carried out under the following conditions, and the obtained test pieces were measured for yellow index (YI) using SM color computer SM-S of Suga Test Machine (ASTMD-19).
25). Injection molding machine; Toshiba IS80 mold; 50 × 90 × 3 mm Cylinder temperature; 220, 230, 240 ° C. Mold temperature; 40 ° C. Injection molding residence time: 2 minutes

Example 1 43.4 parts by weight of acrylonitrile, 32.5 parts by weight of styrene, 24.1 parts by weight of ethylbenzene, 0.3 part by weight of α-methylstyrene dimer, 0.01 part by weight of t-butylperoxyisopropyl carbonate Was prepared in the absence of air and continuously fed to the reactor. The polymerization temperature was adjusted to 142 ° C. Sufficient mixing was performed at a stirring rotation speed of 95 rotations, and P / V was 4.0 kW / m ³ . The average residence time was 1.65 hours. A solution having a polymerization rate of 60% and a polymer concentration of 50 wt% was continuously withdrawn from the reactor and transferred to the first separation tank. The mixture was heated to 160 ° C. in a heat exchanger, devolatilized at a degree of vacuum of 60 Torr to make the polymer concentration in the reaction mixture 65% by weight, and then discharged from the first separation tank and transferred to the second separation tank. The reaction mixture was heated to 260 ° C. in a heat exchanger, devolatilized at a vacuum of 32 Torr to reduce the content of volatile components in the reaction mixture to 0.7 wt% and the polymer component to 99.4 wt%, and then discharged. Thus, a pellet product was obtained.

The copolymer resin thus obtained is
As volatile components, 480 ppm of styrene, 80 ppm of acrylonitrile, 150 ppm of ethylbenzene, 5000 ppm of oligomers composed of dimers and trimers of acrylonitrile-styrene are contained, the yellow index is 15, and the content of acrylonitrile units is 45. At 3 wt%, the content of styrene units is 54.7.
At wt%, the distribution of acrylonitrile units in the copolymer was sharp. The content of the copolymer containing 40.3% by weight of acrylonitrile units was 0.1% by weight, and the content of the copolymer containing 50.3% by weight of acrylonitrile units was 0.3% by weight.

Examples 2 to 5 Copolymer resins were produced by using the monomer mixture having the composition shown in Table 1 and performing the same operations as in Example 1 under the conditions shown in Table 1. Table 1 shows the results. The symbols in Table 1 mean the following. A-1: t-butylperoxyisopropyl carbonate A-2: 1,1'-azobis (1-cyclohexanecarbonitrile) A-3: peroxide having 7 repeating units represented by [Chemical Formula 3], 10 Time half-life 63.5 ° C B-1: butyl acrylate B-2: N-phenylmaleimide

[Table 1] Note 1) Ethylbenzene (100 parts by weight-
Monomer) and 0.3 part by weight of α-methylstyrene dimer as a chain transfer agent. 2) W ₁ : 5 wt% from the average value of acrylonitrile units
Content of distant copolymer W ₂ : Content of copolymer distant by 10 wt% from the average value of acrylonitrile units

[Brief description of the drawings]

FIG. 1 is a flow sheet of a reactor for carrying out the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charged liquid storage tank 2, 5, 6 Pump 3 Reaction tank 4, 7, 10 Heat exchanger 8 First separation tank 9, 12 Gear pump 10 Second separation tank

Embedded image

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-5808 (JP, A) JP-A-61-276807 (JP, A) JP-A-58-29807 (JP, A) JP-A-3-3 205411 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 2/00 C08F 212/10 C08F 220/44

Claims (3)

(57) [Claims] 1. An acrylonitrile unit of 30 to 50% by weight.
When the average value of acrylonitrile units is X% by weight, the content of the copolymer containing acrylonitrile units outside the range of (X ± 5)% by weight is 5% by weight or less (X ± 1%).
0) It has a narrow copolymer composition distribution in which the content of the copolymer containing acrylonitrile out of the range of 1% by weight is 1% by weight or less, and the solution viscosity at 25 ° C. of a 10% methyl ethyl ketone solution is 4.5. An acrylonitrile-styrene copolymer resin having a molecular weight of about 13 centipoise. 2. A half-life of 10 hours for producing a copolymer resin containing 30 to 50% by weight of acrylonitrile by copolymerizing acrylonitrile with styrene or other copolymerizable monomers. Decomposition temperature is 60
A radical polymerization initiator at a temperature of 100 ° C. to less than 160 ° C. is used with a radical polymerization initiator at a temperature of 100 ° C. or more and less than 160 ° C. together with other charged components using a radical polymerization initiator at a temperature of −120 ° C. The polymerization reaction is carried out while continuously supplying the liquid phase reaction zone in the mixing tank type reactor. During the polymerization reaction, a gas phase zone containing volatile components generated during the reaction formed above the liquid phase reaction zone is used. Condensing and recovering volatile components and circulating them in the liquid phase reaction zone, and continuously separating and removing low boiling components mainly composed of unreacted monomers from the reaction mixture continuously extracted from the liquid phase reaction zone A method for producing an acrylonitrile-based copolymer resin, comprising: 3. The acrylonitrile copolymer resin is a copolymer of acrylonitrile and styrene, a copolymer of acrylonitrile and styrene and alkyl acrylate or alkyl methacrylate, or a copolymer of acrylonitrile, styrene and N-phenylmaleimide. 3. The method according to claim 2, wherein: