JPH0367539B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention is a mixed latex mainly composed of a copolymer latex obtained by emulsion polymerization of a monomer mixture consisting of α-methylstyrene, acrylonitrile, and other copolymerizable vinyl monomers. The present invention relates to a method for recovering 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> A copolymer consisting of α-methylstyrene, acrylonitrile, and other copolymerizable vinyl monomers such as styrene and methyl methacrylate is a heat-resistant copolymer having a high heat distortion temperature. Are known. 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, since they have good miscibility with coalescence. (Tokuko Akira
44-15902, 18016, 18016, 33304, 33304, 33661, 37415, 46472,
JP-A-54-122389, etc. ) The above-mentioned copolymers of α-methylstyrene and other vinyl monomers are usually industrially polymerized by emulsion polymerization, and the resulting copolymer latex is diene-based rubber-like. A graft copolymer latex is obtained by emulsion graft copolymerizing a polymer with an aromatic vinyl compound such as styrene or α-methylstyrene, and acrylonitrile, methyl methacrylate, etc. in a latex state, and then solidified to form a powder. A copolymer mixture is obtained by recovering the copolymer mixture of 100% or coagulating it separately from the graft copolymer latex, recovering the powdered copolymer once, and then mixing them. etc., are mainly used to produce impact-resistant resins. <Problems to be Solved by the Invention> However, a copolymer latex consisting of α-methylstyrene and other vinyl monomers, or a mixed latex of this copolymer latex and the above-mentioned graft copolymer latex, is subjected to normal coagulation conditions. , i.e.
When solidified under normal pressure at temperatures below 100°C, the particle size of the recovered powdered copolymer particles is extremely small, which may cause clogging of the filter cloth in the subsequent separation process or scattering of the powdered copolymer during the drying process. There is a problem in that the yield decreases and the productivity and operability are extremely poor. Conventional 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 coagulation of α-methylstyrene and other vinyl monomers. A method of mixing and coagulating a copolymer latex with a low softening point containing acrylonitrile and/or methyl methacrylate as an essential component in addition to a copolymer latex consisting of
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 reduces the mixing of other components. Therefore, the original purpose of obtaining a heat-resistant resin cannot be achieved in either method because a significant decrease in heat distortion temperature is unavoidable. Therefore, with conventional coagulation methods, it has been difficult to maintain a high heat distortion temperature and recover a powdery copolymer having a large particle size. Therefore, the present inventors have developed a copolymer latex consisting of α-methylstyrene and other copolymerizable vinyl monomers, or a copolymer latex and a diene-based rubbery polymer by emulsion grafting of vinyl monomers. As a result of intensive studies aimed at recovering a powdered copolymer with a sufficiently large particle size, excellent productivity, and a high heat distortion temperature from a mixed latex with a graft copolymer latex obtained by polymerization, we found that: The inventors have discovered that the above object can be achieved by heat-treating the coagulation reaction system after coagulation at a certain temperature range, and have thus arrived at the present invention. <Means for solving the problems> That is, the present invention provides (A) α-methylstyrene 40-85
40 to 95 parts by weight (solid content equivalent) of a copolymer latex obtained by emulsion polymerization of a monomer mixture consisting of 5 to 35 weight % of acrylonitrile and 0 to 40 weight % of other copolymerizable vinyl monomers. ) and (B) 20 to 80 parts by weight of an aromatic vinyl compound and 0 to 80 parts by weight of a diene rubber polymer.
35% by weight and 0-80% by weight of methyl methacrylate
60 to 5 parts by weight (solid content equivalent) of a graft copolymer latex obtained by emulsion polymerization of 60 to 20 parts by weight of a monomer mixture consisting of (A) and (B) of 100 parts by weight (solid content equivalent) ) When recovering a powdered copolymer from a copolymer latex mixture mixed at a ratio of
First, the copolymer latex mixture is coagulated at a temperature of 20 to 110 °C in the presence of a coagulant, and then the temperature of the coagulation reaction system is raised to 120 to 145 °C, and the temperature is maintained for 1 minute to 5 hours. The present invention provides a method for recovering a copolymer from a copolymer latex mixture, which comprises separating and recovering the copolymer powder mixture. In the copolymer of the present invention consisting of α-methylstyrene, acrylonitrile, and other copolymerizable vinyl monomers (hereinafter referred to as copolymer (A)), other copolymerizable vinyl monomers include Styrene and methyl methacrylate are commonly used, but are not limited to these. The copolymer composition of copolymer (A) is 40 to 80% by weight of α-methylstyrene, 5 to 35% by weight of acrylonitrile, and 0 to 40% by weight of other copolymerizable vinyl monomers. A high heat distortion temperature and excellent mechanical properties can be obtained only within the polymerization composition range; however, outside the above copolymer composition range, either or both of the heat distortion temperature and mechanical properties are poor and it cannot be put into practical use. Therefore, it is undesirable. On the other hand, a graft copolymer is obtained by emulsion polymerizing a monomer mixture consisting of an aromatic vinyl compound, methyl methacrylate, and acrylonitrile in the presence of a diene rubber-like polymer (hereinafter referred to as graft copolymer (B)). As the diene rubber polymer, polybutadiene rubber, acrylonitrile-butadiene copolymer (NBR), styrene-butadiene copolymer rubber (SBR), etc. can be used. In order to realize good miscibility between this graft copolymer (B) and the above copolymer (A) and obtain a resin composition with excellent impact resistance and other mechanical properties, The composition of the monomer mixture to be polymerized into the diene-based rubbery polymer is 20 to 80% by weight of an aromatic vinyl compound,
It is necessary that methyl methacrylate be 0 to 80% by weight and acrylonitrile be 0 to 35% by weight,
Outside this composition range, the graft copolymer (B) and copolymer (A) will have poor miscibility, and a resin composition with excellent impact resistance and mechanical properties will not be obtained. Furthermore, when polymerizing the graft copolymer (B), it is necessary to polymerize 60 to 20 parts by weight of the monomer mixture having the above composition in the presence of 40 to 80 parts by weight of the diene rubber-like polymer. If the diene rubbery polymer is less than 40 parts by weight, high impact strength cannot be obtained even if the graft copolymer (B) is mixed with the copolymer (A); on the contrary, the diene rubbery polymer If the amount is more than 80 parts by weight, the graft copolymer (B) and the copolymer (A) will not be sufficiently miscible and impact resistance and other mechanical properties will deteriorate, which is not preferable. The emulsion polymerization method for copolymer (A) and graft copolymer (B) may be carried out by a commonly used method, and there are no particular restrictions on emulsifiers, initiators, other polymerization aids, etc., and those commonly used. What you have is fine. That is, as the emulsifier, sodium oleate, sodium laurate, sodium lauryl sulfate, etc. may be used, and as the initiator, hydrogen peroxide, hydroperoxide type, persulfate type, etc. may be used. Since the above copolymer (A) and graft copolymer (B) are produced as latex by emulsion polymerization, the mixed composition of copolymer (A) and graft copolymer (B) is recovered in powder form. In order to do this, it is necessary to coagulate the latex. Therefore, the target latex to which the recovery method of the present invention is applied is the above-mentioned graft copolymer (B) latex 5.
It is a mixed copolymer latex consisting of ~60 parts by weight (in terms of solid content) and 95 to 40 parts by weight (in terms of solid content) of copolymer (A) latex. When graft copolymer (B) latex and copolymer (A) latex are mixed and used to obtain an impact-resistant resin composition, the mixing ratio of graft copolymer (B) is 5% by weight. If the amount is less than 60 parts by weight, the desired impact resistance cannot be obtained, and if it is more than 60 parts by weight, the impact resistance of the composition decreases, which is not preferable. When recovering powdered copolymers from these copolymer latex mixtures, a coagulant is first added to the latex, and the mixture is heated to 20-110°C, preferably 60-110°C.
Coagulation is performed at a coagulation temperature of 100°C. The coagulant used here is not limited to the coagulant that is normally used to break the emulsified state of latex, and examples include inorganic salts such as sodium chloride, magnesium sulfate, magnesium chloride, and aluminum sulfate, and hydrochloric acid. , inorganic acids such as sulfuric acid are used. There is no particular limit to the amount of these coagulants added, but it is usually about 0.5 to 10% of the solid content of the latex.
Weight % is appropriate. To coagulate latex, add a coagulant to latex heated to 20-110℃, or add coagulant to latex heated to 20-110℃.
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 step, heating treatment, is carried out. However, the particle size of the powdered copolymer cannot be sufficiently increased at 110° C. or higher, and on the other hand, the particle size of the powdered polymer becomes large at 110° 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 temperature of the coagulation reaction system (slurry) after completion of coagulation is raised to 120 to 145 °C, preferably 130 to 140 °C, and the temperature is maintained for 1 minute to 5 hours, preferably 20 °C.
It is important to hold the copolymer powder for a minute to two hours, and during this step, appropriate agglomeration of the solidified copolymer particles occurs, allowing recovery of copolymer powder with a high heat distortion temperature and a desirable large particle size. becomes. If the holding temperature in this heating and holding step is 120°C or lower, not only will it not be possible to obtain a powdery copolymer with a sufficiently large particle size, but the heat deformation temperature of the copolymer will not be high enough to reach 145°C.
This is not preferable because the copolymer is fused to the coagulation device and difficult to recover. Furthermore, if the heating holding time is less than 1 minute, a powdery copolymer with a sufficiently large particle size cannot be obtained, and if it exceeds 5 hours, the above-mentioned fusion of the copolymer and a decrease in the heat distortion temperature may occur. This is not desirable because it happens. In this way, the heat deformation temperature of the copolymer in the copolymer slurry that has undergone the coagulation-heat-holding process of the present invention does not decrease, and the copolymer particles aggregate to an appropriate size. As a result, there is no clogging of the filter cloth in the subsequent separation processes such as filtration and centrifugation, and no scattering loss during the drying process, and it is significantly improved by applying the normal separation-washing-drying process. Desired powdered copolymers can be recovered with productivity and ease of operation. The powdered copolymer mixture recovered by the method of the present invention may optionally contain stabilizers,
Common additives such as lubricants, reinforcing agents, fillers, flame retardants, colorants, and pigments can be added to the composition for practical use. <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 BS2782/102°C. 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) Copolymer (A) latex, graft copolymer (B) latex, and copolymer (A) were prepared by the following method.
A latex (C) was produced by mixing the latex and the graft copolymer (B) latex. Production of copolymer (A) latex: Latex A-1: 200 parts of water, 3.0 parts of sodium lauryl 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 60°C. Then, 65 parts of α-methylstyrene,
A mixture of 15 parts of methyl methacrylate, 20 parts of acrylonitrile and 0.3 parts of cumene hydroperoxide was added dropwise at a constant rate over 8 hours, and after the addition was completed, the temperature was raised to 70°C and maintained for 2 hours to produce latex A-1. Latex A-2: Latex A62 was produced by polymerizing in the same manner as Latex A-1 except that the monomer components were 5 parts of α-methylstyrene and 25 parts of acrylonitrile. Latex A-3: Polymerization was carried out in the same manner as Latex A-1 except that 2.0 parts of potassium olefinate was used as an emulsifier and the monomer components were 70 parts of α-methylstyrene, 10 parts of styrene, and 20 parts of acrylonitrile. -3 was manufactured. Latex A-4: 50 parts of α-methylstyrene,
30 parts of methyl methacrylate, 20 parts of acrylonitrile
A mixture of 2.0 parts of sodium laurate, 0.5 parts of potassium persulfate, and 200 parts of water was charged into a reaction vessel.
After purging with nitrogen, the temperature was raised to 65°C and polymerization was carried out for 10 hours to produce latex A-4. Production of graft copolymer (B) 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. Latex B-2: 60 parts of polybutadiene latex (solid content), styrene as a monomer component
Latex B-2 was produced by polymerizing in the same manner as latex B-1, except that 18 parts of methyl methacrylate, 4 parts of acrylonitrile, and 0.2 parts of n-dodecyl mercaptan were used. Production of mixed latex (C) The copolymer (A) latex produced above and the graft copolymer (B) latex were mixed in the proportions (solid content weight ratio) shown in Table 1 to produce mixed latex (C). did.

[Table] Example 2 (Measurement of property values of copolymer powder recovered from latex) Each latex produced in Example 1 was coagulated using an autoclave. Magnesium sulfate (MgSO ₄ ) or salt and hydrochloric acid (NaCl/
Coagulation was performed using HCl) at a slurry concentration of 10%. The temperature conditions are as shown in Table 2. That is, first, solidification is performed at each temperature between 60 and 105°C, and then the temperature is raised to each temperature between 125 and 140°C.
The heat treatment was carried out by controlling the temperature while stirring thoroughly.
After holding for a certain period of time, filtration and washing were performed to recover the powdered copolymer. The characteristic values of the recovered copolymer are heat distortion temperature (BS-HDT) and particle size (cumulative weight).
The particle size D50%) was measured and the results are summarized in Table 2. In all cases, the heat distortion temperature is high, and the particle size (D50%) is large, even for small particles.
Since it has a diameter of 450μ, filtration performance and operability are good. Comparative Example 1 Using the same autoclave as in Example 2, coagulation was carried out under the conditions shown in Table 2. The results are also shown in Table 2.
summarized in.

【table】

[Table] From the results in Table 2, only when the temperature was raised to 120°C to 145°C after solidification at 20°C to 110°C and held for 1 minute to 5 hours, a high heat distortion temperature and a large It is clear that a powder copolymer having a combined particle size is obtained. In addition, if only coagulation is performed without heat treatment at elevated temperature, 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 (90℃), it is difficult to recover the copolymer by filtration. Have difficulty. Even if heat treatment is carried out after solidification, if the above conditions are not met, either the particle size or the heat distortion temperature, or both, will be poor, and it will not be possible to achieve both a large particle size and a high heat distortion temperature. <Effects of the Invention> As explained above, the method of recovering a copolymer from a copolymer latex mixture of the present invention produces particles that have a high heat distortion temperature and are excellent in operability and productivity in the separation process and drying process. A powdered copolymer with a sufficiently large diameter can be recovered.

Claims (1)

[Claims] 1 Copolymer latex 40 obtained by emulsion polymerization of a monomer mixture consisting of 40 to 85% by weight of α-methylstyrene, 5 to 35% by weight of acrylonitrile, and 0 to 40% by weight of other copolymerizable vinyl monomers. ~95 parts by weight (solid content equivalent) and (B) 40 parts by weight of diene-based rubbery polymer
In the presence of 80 parts by weight, 20 to 80 parts by weight of an aromatic vinyl compound
60 to 5 parts by weight of a graft copolymer latex obtained by emulsion polymerization of 60 to 20 parts by weight of a monomer mixture consisting of 0 to 35 parts by weight of acrylonitrile and 0 to 80 parts by weight of methyl methacrylate (in terms of solid content) of
When recovering a powdered copolymer from a copolymer latex mixture in which (A) and (B) are mixed at a ratio of 100 parts by weight (solid content equivalent), the copolymer latex mixture is first treated with a coagulant. After coagulating at a temperature of 20 to 110 °C in the presence of a coagulating reaction system, and then raising the temperature of the coagulation reaction system to 120 to 145 °C and maintaining the temperature for 1 minute to 5 hours,
A method for recovering a copolymer from a copolymer latex mixture, comprising separating and recovering the copolymer powder mixture.