JPH0539323A - Acrylonitrile/styrene copolymer resin and its production - Google Patents

Abstract

PURPOSE:To obtain at good productivity an acrylonitrile/styrene copolymer resin having a sharp compositional distribution, good hue, and excellent transparency, rigidity and chemical resistance. CONSTITUTION:The objective acrylonitrile/styrene copolymer resin containing 30-50wt.% acrylonitrile units and a very sharp compositional distribution is produced by using 1.0wt.% or below radical polymerization initiator having a 10hr half-life temperature of 60-120 deg.C, continuously feeding the initiator together with other feedstocks to a liquid-phase reaction zone kept at 100-160 deg.C, condensing the volatile component evaporated from the liquid-phase reaction zone in a vapor-phase zone, recirculating the condensate from the vapor-phase zone to the liquid-phase reaction zone, and continuously removing the volatile component from the reaction mixture discharged from the reaction zone.

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 relates to an acrylonitrile-styrene copolymer resin having a narrow copolymer composition distribution, good color tone, excellent transparency, and excellent rigidity and chemical resistance, and excellent The present invention relates to a method for producing an acrylonitrile-based copolymer having excellent physical properties with high productivity.

[0002]

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

However, in the suspension polymerization method or emulsion polymerization method which is an integral polymerization method, acrylonitrile (AN) / styrene (S) which is an azeo composition of a monomer and a polymer is used because of the copolymerization reactivity of acrylonitrile and styrene.
T) It is difficult to obtain a transparent resin over a wide composition range except the composition having a weight ratio of 25/75.

On the other hand, in the continuous polymerization method which is a differential polymerization method, since the heat of polymerization of acrylonitrile is large,
In order to maintain the desired polymerization temperature, the productivity is inevitably lowered, and the copolymers having AN / ST weight ratios near 15 and around 45, which greatly deviate from the azeo composition, are difficult to control the composition distribution. However, there is a drawback that it is difficult to obtain a transparent product.

By the way, when an acrylonitrile-styrene type copolymer resin is produced by a continuous solution polymerization method, a solvent is usually used as a solvent having a solubility parameter [SP value, (J / m ³ )
X 1/2 x 10 ^-3 ] ("Polymer Handbook" published by Willy International Co.) is 17 to 19,
SP value of acrylonitrile-styrene copolymer 20 to
A solvent different from 25 is used. In this case, although the viscosity of the polymerization system is lowered and the reaction product is easily transferred into the system, there is a problem that the solubility of the copolymer in the polymerization reaction solution is lowered. As a method of improving the solubility, it is conceivable to raise the polymerization temperature, but raising the polymerization temperature leads to a decrease in heat removal efficiency, making it difficult to control the polymerization temperature, resulting in deterioration of product quality and polymerization runaway reaction. In addition to the possibility of causing an unfavorable situation, an acrylonitrile-styrene copolymer having a high content of acrylonitrile units has a drawback that it is colored by an intramolecular reaction due to heat or an oxidation reaction involving oxygen and heat.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The present invention is directed to the 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 resin due to copolymer composition distribution Acrylonitrile-styrene copolymer, which solves the problems of opacity and resin coloring, has a narrow copolymer composition distribution, good color tone and excellent transparency, and also has excellent rigidity and chemical resistance. The present invention provides a method for producing a polymerized 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 proposed a method of copolymerizing acrylonitrile and other monomers to produce an acrylonitrile copolymer having excellent physical properties containing 30 to 50% by weight of acrylonitrile units. As a result of repeated intensive research on acrylonitrile-based copolymers having excellent transparency, mechanical strength, and chemical resistance by using a specific polymerization initiator and polymerizing by a specific reaction means including devolatilization conditions. It was found that this method can be obtained, and 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 completed based on this finding.

That is, the present invention is a copolymer containing 30 to 50% by weight of acrylonitrile units, where 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 ratio of 5
It has a narrow copolymer composition distribution of 1% by weight or less of the content of the copolymer containing acrylonitrile outside the range of 10% by weight or less (X ± 10)% by weight, and 25 ° C. when it is used as a 10% methyl ethyl solution. Solution viscosity at 4.5-13
Acrylonitrile-styrene copolymer resin characterized by being centipoise and a copolymer resin containing 30 to 50% by weight of acrylonitrile unit by copolymerizing acrylonitrile and other copolymerizable monomer The decomposition temperature for obtaining a half-life of 10 hours is 60 to 120
A liquid phase reaction in which a radical polymerization initiator at ℃ is used at a ratio of 1.0% by weight or less with respect to the total amount of raw material monomers, and is kept at a constant temperature in the range of 100 ° C to less than 160 ° C with other charged components. The polymerization reaction is carried out while continuously supplying to the zone, and during this period, the volatile components are condensed and recovered from the gas phase zone containing the volatile components formed during the reaction formed above the liquid phase reaction zone, and the liquid phase is obtained. An acrylonitrile-based copolymer resin characterized by being continuously separated and removed from the reaction mixture continuously extracted from the liquid-phase reaction zone along with the reaction zone, and the low-boiling components mainly consisting of unreacted monomers are continuously removed. The present invention provides a method of manufacturing the same.

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 hitherto been considered difficult to obtain a good product. It has a very narrow polymer composition and has excellent transparency, mechanical strength and chemical resistance. Such a novel acrylonitrile-styrene copolymer resin uses a radical polymerization initiator having a decomposition temperature of 60 to 120 ° C. to obtain the above-mentioned 10-hour half-life, and is acrylonitrile-treated with 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 and styrene and another monomer such as alkyl acrylate, alkyl methacrylate, N-phenylmaleimide, It can also be used for production of an acrylonitrile-styrene-alkyl acrylate copolymer, an acrylonitrile-styrene-alkyl methacrylate copolymer, an acrylonitrile-styrene-N-phenylmaleimide copolymer and the like.

Acrylonitrile polymerization heat value is 347k.
cal / kg, styrene 170 kcal / k
g, methylmethacrylate is extremely larger than 130 kcal / kg. Therefore, in the present invention, this heat generation amount of polymerization is suppressed by the latent heat of vaporization of the reaction mixture, and the volatile components evaporated in the reaction zone are condensed and recovered by a heat exchanger. The process of returning the reaction zone to the reaction zone is used.

Therefore, as a reactor for carrying out this process, a tank reactor equipped with a supply port, an outlet port, and a stirring means having a mixing function over the entire reaction zone is preferable, and a uniform reaction is conducted over the entire reaction zone. Plug flow type reactors in which no significant mixing occurs are not suitable for the practice of the invention. Further, the tank type reactor has a gas phase zone in the upper part under the reaction operation conditions, and removes a part of the heat value of polymerization by latent heat of vaporization of volatile components in the reaction mixture,
A type in which evaporated volatile components are condensed and circulated by an external heat exchanger is used.

Since the monomer in the condensate is mainly composed of acrylonitrile and its monomer composition is different from that in the reaction zone, the stirring in the liquid phase reaction zone is sufficiently uniform. If this is not the case, the copolymer composition of the polymerization product will become more uneven, and the transparency and mechanical properties will deteriorate.

In order to make the copolymer composition uniform, the stirring strength of the tank reactor, the introduction position of the condensate into the reaction zone, and the prevention of post-polymerization in the volatile component separation step are extremely important. By sufficiently satisfying these conditions, an acrylonitrile-styrene copolymer resin having a uniform composition excellent in 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 factor, ρ: Stirring fluid density,
d: stirring blade diameter].

As the return position of the condensate to the liquid phase reaction zone, it is advantageous to select a position where diffusion of the condensate is the fastest in the liquid phase reaction zone due to the rotation of the stirring blade and to return it to the reaction liquid instead of the gas phase zone. .. In particular, it is preferable to connect the main raw material to a pipe immediately before it is supplied to the reactor and to return it to the liquid phase reaction zone together with the main raw material from the viewpoint of the mixing property.

Further, in order to make the composition distribution of the copolymer as uniform as possible, it is important to prevent the post-polymerization in the step of separating the volatile components, as described above. In addition, the polymerization initiator such as a radical polymerization initiator should not be present in a high concentration in the reaction mixture in the volatile component separation step, and the concentration of acrylonitrile, which is a highly reactive monomer, should be low. preferable.
In order to satisfy such conditions, the polymerization initiator supplied to the liquid phase reaction zone must be selected so that it is sufficiently consumed within the residence time of the reaction liquid, and the volatile component separation step Therefore, it is necessary to raise the temperature after the acrylonitrile concentration becomes low.Therefore, after separating acrylonitrile under low temperature and low vacuum, the separation operation should be performed under high temperature and high vacuum to obtain the desired volatile component concentration. It is desirable to carry out.

In the method of the present invention, for such a reason, a radical polymerization initiator having a decomposition temperature of 60 to 120 ° C., which gives a half-life of 10 hours, is used as the polymerization initiator. As such a radical polymerization initiator,
Butyl peroxy-2-ethylhexanoate, for example,
Benzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-bis (t-butyl peroxy)-
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) valeate, dicumyl peroxide, t-butylcumyl peroxide, etc. Organic peroxides and even general formulas

[Chemical 1] (1 and n in the formula are integers of 1 to 20, m is 0 or 1 to 5
And 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

[Chemical 2] (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 has a decomposition temperature of 60 hours and a half-life of 10 hours. An organic peroxide having a temperature of up to 120 ° C. may be mentioned.

Further, 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-butylperoxyisopropyl carbonate is particularly preferable because it gives a colorless and transparent acrylonitrile-styrene copolymer resin.

The amount of these polymerization initiators used is 1.0% by weight or less, preferably 0.01-% by weight based on the raw material monomers.
It is necessary to select in the range of 0.5% by weight. When this amount exceeds 1.0% by weight, the molecular weight of the copolymer resin obtained 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, etc. are preferably used. These may be used alone or in combination of two or more. Further, if desired, as a chain transfer agent, for example, mercaptans such as octyl mercaptan and dodecyl mercaptan, α-
Methylstyrene dimer or 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, lubricants such as monoglycerin higher fatty acid ester, etc. Etc. can be used.

An embodiment of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a schematic view of an example of a reaction apparatus for carrying out the method of the present invention. A charge liquid comprising a solvent, a polymerization initiator, and optionally a chain transfer agent and other additives is continuously supplied from the charge liquid storage tank 1 to the reaction tank 3 via the pump 2,
The polymerization reaction is carried out at a temperature of ~ 160 ° C. The reaction tank 3 is a complete mixing tank with a stirrer equipped with a two-stage inclined turbine blade, and has a jacket and a gas phase gas extraction line connected to the 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 by the type of polymerization initiator and chain transfer agent used, the type of reaction vessel, and the like.
Further, in order to make the composition of the copolymer uniform, it is necessary to prevent the post-polymerization by setting the concentration of the polymerization initiator in the reaction mixture continuously withdrawn from the reaction tank to 5 ppm or less. For this purpose, it is necessary to appropriately select the combination of the polymerization initiator and the polymerization temperature or 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 in the range of 10 to 100 poise. Furthermore, the solubility of the copolymer in the polymerization solution is also an extremely important factor for making the composition of the copolymer uniform, and this solubility is included in the content of the acrylonitrile unit in the copolymer and in the polymerization solution. It is determined by the amount of acrylonitrile monomer 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 in the reaction tank and narrow the composition distribution of the copolymer. It is also important to do.

When the polymerization temperature is less than 100 ° C., the polymerization rate is too slow to be practical, the solubility of the copolymer in the polymerization solution is low, and the viscosity of the reaction system is high, so that the uniformity of stirring can be sufficiently maintained. If it exceeds 160 ° C., a low polymer (oligomer having a molecular weight of 1,000 or less) is likely to be produced, 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 40 to 60.
Advantageously, it is in the weight% range.

The reaction mixture is continuously withdrawn from the discharge port of the reaction tank 3, passes through the pump 6 and the heat exchanger 7 at 100 ° C.
After being heated and maintained at a temperature of up to 160 ° C., it is supplied to the separation tank 8 and a part of the volatile components is removed under the condition of a vacuum degree of about 500 to 900 Torr. The temperature of the reaction mixture and the degree of vacuum in the separation tank are important factors that control the volatilization amount of the volatile components, and by this volatilization operation, the polymer concentration in the reaction mixture is changed from 40 to 60% by weight to 70 to 90% by weight. %, The temperature is 100 to 160 ° C. and the degree of vacuum is 500 to
A condition of 900 Torr is suitable.

In the first separation tank, unreacted acrylonitrile having a particularly low vapor pressure is devolatilized, the concentration in the reaction mixture is lowered, and as a result, the polymerization reactivity is extremely lowered, resulting in a copolymer by post-polymerization. It is possible to prevent the nonuniformity of the composition from expanding, and to suppress gelation and coloring due to heating due to acrylonitrile. The amount of volatile components in the reaction mixture discharged from the first separation tank is preferably in the range of 10 to 30% by weight. If this amount is less than 10% by weight, the reaction may not be performed when transferring to the second separation tank. Since the viscosity of the mixture is high, the tube wall resistance is large, which is not preferable. When 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 220 to 280 in the heat exchanger 10.
After being heated to a temperature of about C, it is supplied to the second separation tank 11 and the volatile components are removed under the condition of a vacuum degree 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, the apparatus used for separating such volatile components is generally called a devolatizer [a device described in "Devolatization", published by Hanser Co. (1983), For example, U.S. Pat. No. 2,434,707 and U.S. Pat.
No. 851, No. 2,736,058, No. 2,753,595, No. 2,774,10
5, which corresponds to the device described in Japanese Patent Publication No. 5-30848, etc.].

The copolymer from which the volatile components have been removed in the second separation tank 11 is discharged in a molten state through the gear pump 12 and becomes 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 wt% solution of methyl ethyl ketone.
When the average value of the acrylonitrile units is in the range of up to 13 centipoise (X ± 5), the content of the copolymer containing acrylonitrile units outside the range of 5% by weight is 5% by weight or less (X ± 5). 10) It is necessary that the content ratio of the copolymer containing an acrylonitrile unit outside the range of 1% by weight is 1% by weight or less. When the copolymer composition distribution is wider than the above range, an acrylonitrile-styrene copolymer resin excellent in transparency and mechanical properties cannot be obtained.

[0032]

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

[0033]

EXAMPLES The present invention will be described in more detail with reference to 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) Compositional distribution of copolymer 0.05 g of a sample was dissolved in 40 ml of THF (tetrahydrofuran) and the compositional distribution of AN in the copolymer was measured using a high performance liquid chromatograph. As a column packing material, Zolvac CN manufactured by Shimadzu Corporation was used.

(2) Yellow Index Injection molding was carried out under the following conditions, and the obtained test piece was measured for yellow index (YI) by using SM color computer SM-S of Suga Test Machine (ASTMD-19.
25). Injection molding machine; Toshiba IS80 mold; 50x90x3mm Cylinder temperature; 220,230,240 ° C Mold temperature; 40 ° C Injection molding residence time; 2 minutes

Example 1 Acrylonitrile 43.4 parts by weight, styrene 32.5 parts by weight, ethylbenzene 24.1 parts by weight, α-methylstyrene dimer 0.3 parts by weight, t-butylperoxyisopropyl carbonate 0.01 parts by weight. A monomer mixture consisting of was prepared without contact with air and continuously fed to the reactor. The polymerization temperature was adjusted to 142 ° C. The stirring rotation speed was 95 rotations and sufficient mixing was performed, and the 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. After heating to 160 ° C. in a heat exchanger and devolatilization at a vacuum degree of 60 Torr to make the polymer concentration in the reaction mixture 65 wt%, it was 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 degree of 32 Torr to make the content of volatile components in the reaction mixture 0.7 wt% and the polymer component 99.4 wt%, and then discharged. The pelletized product was obtained.

The copolymer resin thus obtained is
As a volatile component, styrene 480 ppm, acrylonitrile 80 ppm, ethylbenzene 150 ppm, acrylonitrile-styrene dimer, oligomer 5000 ppm consisting of trimer are contained, the yellow index thereof is 15, and the content of acrylonitrile unit is 45. Styrene unit content is 54.7 at 3 wt%.
At wt%, the distribution of acrylonitrile units in the copolymer was sharp. The content of the copolymer containing 40.3% by weight of the acrylonitrile unit was 0.1% by weight, and the content of the copolymer containing 50.3% by weight of the acrylonitrile unit was 0.3% by weight.

Examples 2 to 5 A copolymer resin was produced by using the monomer mixture having the composition shown in Table 1 and performing the same operation as in Example 1 under the conditions shown in Table 1. The results are shown in Table 1. The symbols in Table 1 mean the following. A-1: t-butylperoxyisopropyl carbonate A-2: 1,1′-azobis (1-cyclohexanecarbonitrile) A-3: a 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-
(Parts by weight of monomer) and 0.3 parts 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 from the average value of acrylonitrile units by 10 wt%

[Brief description of drawings]

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

[Explanation of symbols]

 1 Charged liquid storage tank 2, 5, 6 Pump 3 Reaction tank 4, 7, 10 Heat exchanger 8 1st separation tank 9, 12 Gear pump 10 2nd separation tank

[Chemical 3]

Claims (3)

[Claims] 1. Acrylonitrile unit 30 to 50% by weight
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 ± 1).
0) The content of the copolymer containing acrylonitrile outside the range of 1% by weight has a narrow copolymer composition distribution of 1% by weight or less, and 25% in a 10% methylethyl solution.
An acrylonitrile-styrene copolymer resin having a solution viscosity at 4.5 ° C. of 4.5 to 13 centipoise. 2. A half-life of 10 hours is obtained in producing a copolymer resin containing 30 to 50% by weight of acrylonitrile unit by copolymerizing acrylonitrile and styrene or other copolymerizable monomers thereof. Decomposition temperature is 60 ~
A liquid phase in which a radical polymerization initiator at 120 ° C. is used in a ratio of 1.0% by weight or less with respect to the total amount of raw material monomers and is kept at a constant temperature in the range of 100 ° C. or higher and less than 160 ° C. together with other charged components. The polymerization reaction is carried out while continuously supplying to the reaction zone, and during this period, the volatile component is condensed and recovered from the gas phase zone containing the volatile component formed during the reaction formed above the liquid phase reaction zone, and the liquid is obtained. Along the vertical reaction zone,
A method for producing an acrylonitrile-based copolymer resin, which comprises continuously separating and removing low-boiling components mainly containing unreacted monomers from a reaction mixture continuously withdrawn from a liquid phase reaction zone. 3. The acrylonitrile copolymer resin is a copolymer of acrylonitrile and styrene, a copolymer of acrylonitrile and styrene and an alkyl acrylate or alkyl methacrylate, or a copolymer of acrylonitrile and styrene and N-phenylmaleimide. The manufacturing method according to claim 2.