JPH0423646B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention provides a copolymer produced by emulsion polymerization of a monomer mixture consisting of styrene and/or α-methylstyrene, acrylonitrile, N-substituted phenylmaleimide, and other copolymerizable vinyl monomers. The present invention relates to a method for recovering from a polymer latex a powdery copolymer having a sufficiently large particle size that has a high heat distortion temperature, excellent operability and productivity in separation steps, drying steps, etc. <Prior art> Copolymers consisting of styrene, α-methylstyrene, acrylonitrile, N-substituted phenylmaleimide, and other copolymerizable vinyl monomers such as methylmetallic acid are heat-resistant and have a high heat distortion temperature. It is known that it is a copolymer.
-39651 Publication, JP-A-57-31914, JP-A-Sho
57-55901). This copolymer is a graft copolymer obtained by polymerizing a monomer mixture of an aromatic vinyl compound such as styrene or α-methylstyrene and methyl methacrylate and/or acrylonitrile in the presence of a diene rubber-like polymer. It is also a well-known fact that a thermoplastic resin composition with excellent heat resistance and impact resistance can be obtained by mixing the two, as they have good miscibility with the polymer. -39651, JP 58-129043, JP 58-162616, JP 59-11322
Publication No.). The above-mentioned copolymer consisting of N-substituted phenylmaleimide and other vinyl monomers can be produced in the form of lumps, suspensions,
It can be produced by any polymerization method such as emulsification. As a method for recovering a polymer from a copolymer latex, for example, a copolymer latex made of α-methylstyrene and other vinyl monomers produced by an emulsion polymerization method can be efficiently coagulated into a powder form by two-stage coagulation. Methods of obtaining polymers are known. (Japanese Patent Publication No. 60-56726) <Problems to be solved by the invention> Copolymer consisting of N-substituted phenylmaleimide and other vinyl monomers introduced for the purpose of improving the heat resistance of styrene resins can be produced by a normal emulsion polymerization method, but if this copolymer latex is coagulated under normal coagulation conditions, that is, under normal pressure at 100°C or less, the powdered copolymer particles recovered Because the diameter is extremely small, the yield decreases due to clogging of the filter cloth in the subsequent separation process and scattering of the powdered copolymer during the drying process, which reduces productivity.
There is a problem that the operability is extremely poor. Conventionally, methods for increasing the particle size of powdered copolymer particles recovered from latex and improving productivity generally involve coagulation under pressure at 100°C or higher, and methods for coagulating N-substituted phenylmaleimide and other vinyl A method of mixing and coagulating a latex of a copolymer with a low softening point containing acrylonitrile and/or methyl methacrylate as an essential component in addition to a copolymer latex consisting of a monomer (Japanese Patent Laid-Open No. 122389/1989), etc. However, although the former method increases the particle size of the recovered copolymer particles, the heat distortion temperature of the copolymer decreases, and the latter method lowers the heat distortion temperature by mixing other components. Since a significant decrease in the temperature is unavoidable, the original purpose of obtaining a heat-resistant resin cannot be achieved in either method. In addition, in the case of a copolymer containing N-substituted phenylmaleimide, the usual two-stage coagulation method results in the resulting powdery copolymer having a small particle size, a wide particle size distribution, and poor heat resistance. There were problems such as a decline in productivity and insufficient productivity. Therefore, the present inventors developed a method using N-substituted phenylmaleimide and other latexes with sufficiently large particle sizes.
As a result of intensive studies aimed at recovering a powdered copolymer with excellent productivity and a high heat distortion temperature, we succeeded in coagulating it within a certain temperature range and then heating the coagulation reaction system under high-speed stirring. The present inventors have discovered that the above objects can be achieved through treatment, and have arrived at the present invention. <Means for solving the problems> That is, the present invention, styrene and/or α
- 20-80% by weight of methylstyrene, 5-40% by weight of acrylonitrile, 1 N-substituted phenylmaleimide
When recovering a powdered copolymer from a copolymer latex obtained by emulsion polymerization of a monomer mixture consisting of ~45% by weight and 0~40% by weight of other vinyl monomers copolymerizable with these, First, the copolymer latex is coagulated at a temperature of 20 to 120°C in the presence of a coagulant, and then the coagulation reaction system is stirred at a temperature of 130 to 195 °C under strong stirring with an average circulation time θc of 10 seconds or less as shown by the following formula. ℃
The present invention provides a method for recovering a polymer from a copolymer latex, which comprises holding the copolymer powder for 5 seconds to 3 hours and then separating and recovering the copolymer powder. θc=V/Nqd [1+0.16 {(D/d) ² -1}]nd ³ where θc: Average circulation time (seconds) V: Total liquid volume (m ³ ) Nqd: Discharge flow rate (-) D : Diameter of tank (m) d: Stirring blade span (m) n: Number of rotations (times/sec) Styrene and/or α-methylstyrene, acrylonitrile, N-substituted phenylmaleimide, and other copolymers of the present invention In the copolymer consisting of possible vinyl monomers (hereinafter referred to as copolymer (A)), methacrylonitrile and methyl methacrylate are usually used as other copolymerizable vinyl monomers. , but not limited to these. The copolymer composition of the copolymer (A) is 20 to 80% by weight of styrene and/or α-methylstyrene, 5 to 40% by weight of acrylonitrile, 1 to 45% by weight of N-substituted phenylmaleimide, and other copolymers. The possible vinyl monomer content is 0 to 40% by weight, and only within this copolymer composition range can a high heat distortion temperature and excellent mechanical properties be obtained, but outside the above copolymer composition range can the heat distortion temperature and It is not preferred because one or both of the mechanical properties are inferior and it cannot be put to practical use. The emulsion polymerization method of the copolymer (A) may be a commonly used method, and there are no particular restrictions on the emulsifier, initiator, other polymerization aids, etc., and commonly used ones may be used. In other words, the emulsifiers include sodium oleate, sodium laurate,
Hydrogen peroxide, hydroperoxide type, persulfate type, etc. may be used as the initiator, such as sodium lauryl sulfate. Since the above copolymer (A) is produced as a latex by emulsion polymerization, it is necessary to coagulate the latex in order to recover the copolymer (A) in powder form. When recovering a powdered copolymer from these copolymer latexes, a coagulant is first added to the latex, and coagulation is carried out at a coagulation temperature of 20 to 120°C, preferably 60 to 110°C. The coagulant used here is not limited to coagulants that are normally used to break the emulsified state of latex, such as sodium chloride, magnesium sulfate, etc.
Inorganic salts such as magnesium chloride and aluminum sulfate, and inorganic acids such as hydrochloric acid and sulfuric acid are used. There is no particular limit to the amount of these coagulants added, but the appropriate amount is usually about 0.5 to 10% by weight based on the solid content of the latex. To coagulate latex, add a coagulant to latex heated to 20-120℃, or add coagulant to latex heated to 20-120℃
This is carried out by pouring the latex into a coagulant aqueous solution heated and kept warm, and preferably by stirring the coagulation reaction system. However, if the coagulation temperature is below 20 °C, the next stage of heating treatment is carried out. However, the particle size of the powdered copolymer cannot be sufficiently increased at 120° C. or higher, and on the other hand, the particle size of the powdered polymer becomes large at 120° C. or higher, which is not preferable because a high heat distortion temperature cannot be obtained. The coagulation of latex is completed in about 1 second to 5 minutes after adding the coagulant or charging the latex.
In the present invention, the average circulation time θc of the coagulation reaction system (slurry) after completion of coagulation is 10
130~ under strong stirring for less than seconds, preferably less than 7 seconds
195℃, preferably 135-180℃ for 5 seconds to 3 hours,
It is important to hold the temperature preferably for 1 minute to 2 hours. θc=V/Nqd [1+0.16 {(D/d) ² -1}]nd ³ where θc: Average circulation time (seconds) V: Total liquid volume (m ³ ) Nqd: Discharge flow rate (-) D : Diameter of the tank (m) d: Stirring blade span (m) n: Number of revolutions (times/second) The above formula is based on the Revised Third Edition Chemical Engineering Handbook (edited by the Chemical Engineering Society), page 1075 (18.4) ) and (18.5), where θc represents the average circulation time required for the liquid to circulate within the tank. Appropriate agglomeration of the copolymer particles coagulated during this step is achieved, making it possible to recover a copolymer powder having a high heat distortion temperature and a desired particle size. If the average circulation time θc exceeds 10 seconds, the particle size will become non-uniform, which is unfavorable from the viewpoint of productivity and heat resistance. In addition, the holding temperature in the heating and holding process is 130℃.
If the temperature is below 195°C, not only will it not be possible to obtain a powdered copolymer with a sufficiently large particle size, but the heat distortion temperature of the copolymer will not be high, and if the temperature exceeds 195°C, the copolymer will fuse to the coagulation equipment. This is not preferable because it makes recovery difficult. Furthermore, even if the heating and holding time is less than 5 seconds, a powdery copolymer with a sufficiently large particle size cannot be obtained.
If the heating time exceeds 3 hours, it is not preferable because the above-mentioned fusion of the copolymer and a decrease in the heat distortion temperature occur. In this way, the heat deformation temperature of the copolymer in the copolymer slurry that has undergone the coagulation heating and holding step of the present invention does not decrease, and the copolymer particles aggregate to an appropriate size. Therefore, there is no clogging of the filter cloth in the subsequent separation processes such as filtration and centrifugation, and there is no scattering loss in the drying process, and by applying the normal separation-washing-drying process, production is significantly improved. The desired powdered copolymer can be recovered under reasonable conditions and operability. In addition, by applying the method of recovering the copolymer (A) latex alone through the above steps, for example, a rubber component-containing graft copolymer latex or a styrene/acrylonitrile copolymer latex may be recovered as necessary, or a powdered copolymer may be recovered. It is also possible to perform a coagulation treatment after addition for the purpose of controlling the particle size. Examples of graft copolymers include, for example, 20 to 80 parts by weight of an aromatic vinyl compound and 0 parts by weight of acrylonitrile in the presence of 40 to 80 parts by weight of a diene-based rubbery polymer.
Examples include graft copolymer latexes obtained by emulsion polymerization of 60 to 20 parts by weight of a monomer mixture consisting of ~35% by weight and 0 to 80% by weight of methyl methacrylate. By blending the obtained copolymer (A) powder with a graft copolymer or the like, an impact-resistant resin composition with excellent heat resistance can be obtained. Thus, the powdered copolymer or the resin mixture containing the copolymer recovered by the method of the present invention may contain stabilizers, lubricants, reinforcing agents, fillers, flame retardants, colorants, pigments, etc. as necessary. It can be put into practical use by blending the usual additives. <Function> Although the function of the present invention is not clear, by employing a specific two-stage coagulation method, the degree of polymer coalescence can be controlled, and components other than the polymer, such as emulsifiers, can be easily removed. It is presumed that this was the case. <Examples> The details of the present invention will be explained below using Examples.
In addition, in the examples, the heat distortion temperature (BS-HDT) is
Measured according to BS2782, 102C. The particle size of the powdered resin was determined by measuring the particle size distribution using a light transmission type particle size distribution analyzer, and the particle size at which the cumulative weight was 50% (D50%) was representative as the particle size of the powdered resin. The numbers in the examples represent parts by weight. Example 1 (Manufacture of latex) A copolymer (A) latex was manufactured by the method shown below. Production of copolymer (A) latex: Latex A-1: 200 parts of water, 3.0 parts of sodium laurium sulfate, 0.4 parts of ascorbic acid, 0.005 parts of ferrous sulfate, sodium ethylenediaminetetraacetate.
0.01 part was charged into a reaction vessel, and after purging with nitrogen, the mixture was heated and stirred at 70°C. Thereafter, a mixture of 15 parts of styrene, 35 parts of α-methylstyrene, 20 parts of acrylonitrile, 30 parts of N-substituted phenylmaleimide, and 0.3 parts of cumene hydroperoxide was added dropwise at a constant rate over 8 hours, and the temperature was raised to 90°C after the addition was completed. Keep it warm for 2 hours and make latex A.
-1 was manufactured. The latex was solidified using an autoclave. Magnesium sulfate ( _MgSO4 ) as coagulant
Coagulation was performed at a slurry concentration of 11%. The temperature conditions are as shown in Table 1. That is, first, solidification is performed at various temperatures between 60 and 115°C,
Subsequently, the temperature was raised to 135 to 195℃, and θc: 1 to 195℃.
The heat treatment was carried out for 7 seconds while thoroughly stirring and controlling the temperature. After holding for a certain period of time, filtration and washing were performed to recover the powdered copolymer. The heat distortion temperature (BS-HDT) and particle size (particle size D50% of cumulative weight 50%) were measured as characteristic values of the recovered copolymer, and the results are summarized in Table 1. In all cases, the heat distortion temperature is high, and the particle size (D50%) is large, even for small particles.
Since it had a diameter of 450μ, filtration performance and operability were good. Examples 2 to 4 Production of copolymer (A) latex: Polymerization was carried out in the same manner as latex A-1 except for the composition and conditions shown in Table 2 to produce latex A-2.
~A-4 was manufactured. Production of graft copolymer latex Latex B-1: Polybutadiene latex (solid content) 60 parts sodium formaldehyde sulfoxylate
0.4 parts Sodium ethylenediaminetetraacetate 0.1 parts Ferrous sulfate 0.01 parts Sodium phosphate 0.1 parts Water 180 parts were charged into a reaction vessel, the temperature was adjusted to 65°C after purging with nitrogen, and 22.5 parts of styrene, 7.5 parts of acrylonitrile and n-dodecyl mercaptan were added. 0.2 parts of the mixture 4
Continuously dripped over time. At the same time, a mixture of 0.2 parts of cumene hydroperoxide, 2.0 parts of sodium dodecylbenzenesulfonate and 20 parts of water was continuously added dropwise over a period of 5 hours, and polymerization was carried out for a total of 6 hours to produce latex B-1. The produced copolymer (A) latex was used alone or mixed with latex B-1, and after coagulating under the conditions shown in Table 3, the characteristic values of the recovered polymer were measured. The results are summarized in Table 3. In both cases, high heat distortion temperatures are shown.
Moreover, the particle size was large, and the filterability and operability were good. Comparative Example 1 Solidification was carried out under the conditions shown in Table 4 using the same autoclave as in Example 1. The results are summarized in Table 4. The recovered copolymer had drawbacks such as a low heat distortion temperature and a significantly low amount of copolymer recovered. Comparative Examples 2 to 4 The copolymer latexes obtained in Examples 1 to 4 were coagulated individually or as a mixture under the conditions shown in Table 4. The results are also summarized in Table 4.

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[Table] From the results in Tables 1, 3, and 4, after solidification was performed at 20°C to 120°C, the temperature was raised to 130°C to 195°C under high-speed stirring and held for 5 seconds to 3 hours. It is clear that a powder copolymer having both a high heat distortion temperature and a large particle size can only be obtained. In addition, if only coagulation is performed without heat treatment at elevated temperatures, not only the particle size is small, but the heat distortion temperature is extremely low, and especially if it is only coagulated under normal pressure (95°C), it is difficult to recover the copolymer by filtration. It was also difficult. If the above conditions are not met even if heat treatment is performed to raise the temperature after solidification, either the particle size or the heat distortion temperature,
Or both were bad, making it impossible to achieve both large grain size and high heat distortion temperature. <Effects of the Invention> As explained above, the method of the present invention is a method for efficiently recovering a polymer from a copolymer latex containing N-substituted phenylmaleimide,
In addition, this method can provide a copolymer with particularly excellent heat resistance.

Claims (1)

[Claims] 1. Styrene and/or α-methylstyrene
20-80% by weight, acrylonitrile 5-40% by weight,
1 to 45% by weight of N-substituted phenylmaleimide and 0 to 40% of other vinyl monomers copolymerizable with these
When recovering a powdered copolymer from a copolymer latex obtained by emulsion polymerization of a monomer mixture consisting of Then, after holding the coagulation reaction system at 130 to 195°C for 5 seconds to 3 hours under strong stirring with an average circulation time θ of 10 seconds or less as shown by the following formula, the copolymer powder is separated and recovered. A method for recovering polymers from copolymer latexes. θc=V/Nqd [1+0.16 {(D/d) ² -1}]nd ³ where θc: Average circulation time (seconds) V: Total liquid volume (m ³ ) Nqd: Discharge flow rate (-) D : Diameter of tank (m) d: Stirring blade span (m) n: Number of rotations (times/second)