CN109422826B - Method for separating polymer product by using superfine polymer dispersion system with organic phase as dispersion medium - Google Patents
Method for separating polymer product by using superfine polymer dispersion system with organic phase as dispersion medium Download PDFInfo
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
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Abstract
The invention relates to the field of separation of superfine polymer disperse systems by taking an organic phase as a disperse medium, and discloses a method for separating a polymer product by using the superfine polymer disperse system by taking the organic phase as the disperse medium, which comprises the following steps: carrying out centrifugal separation on polymer mother liquor containing maleic anhydride-based copolymer, dispersion medium and polymerization monomer to obtain separated solid; mixing the separated solid with a washing solvent to obtain dispersed slurry; filtering the dispersed slurry through a filtering device with the filtering aperture of less than 6 mu m to obtain a filter cake and a separation liquid; drying the filter cake to obtain superfine polymer product particles; the total content of organic volatile components A1 in the filter cake is less than 10 mass%; the total content A2 of washing impurities in the separation liquid in the washing solvent is 1 mass% or less. Can realize the separation of high-purity superfine polymer product particles from a superfine polymer dispersion system taking an organic phase as a dispersion medium.
Description
Technical Field
The invention relates to the field of separation of superfine polymer dispersion systems with organic phases as dispersion media, in particular to a method for separating polymer products by using the superfine polymer dispersion systems with the organic phases as the dispersion media.
Background
Maleic anhydride and other monomers maleic anhydride copolymer microspheres (about 100-400nm in diameter) can be prepared by a self-stabilizing precipitation polymerization process. In most cases, poor solvent separation is required for the ultra-fine polymer particle dispersion system obtained after polymerization reaction to precipitate a polymer product, and then the polymer product is dried to obtain a relatively pure polymer product. The dispersion system of the ultrafine polymer particles may be a system in which water is used as a dispersion medium or a system in which an organic phase is used as a dispersion medium, and thus the separation of the polymerization products is different.
The separation, purification and drying techniques of the superfine polymer particle dispersion system using water as the dispersion medium are more and more researched and mature. In the aqueous phase, since stabilizers such as surfactants are present on the surface of polymer particles, the polymer is generally subjected to a demulsification process before being separated and purified from the aqueous phase. The demulsification method can be a chemical method of adding demulsifier, salt and the like, or a physical method of centrifugation, ultrasound, microwave, electrical method and the like. The demulsified product is generally washed through a plurality of washing processes to remove the demulsifier on the surface of the polymer particles and the residual stabilizer such as surfactant and the like so as to obtain a relatively pure polymer. Finally, a final drying process is required to obtain relatively pure polymer particle powder. Depending on the requirements of the final application for the morphology of the polymer particles, the polymer particles may be dried by taking them back to a converter, a fluidized bed or the like.
The superfine polymer dispersion system with organic phase as dispersing medium has certain specificity, specificity and complexity in separating, purifying and drying polymer particles owing to the variety of organic phases, various properties, complex action with polymer and other factors. Aiming at the purification, separation and drying methods of superfine micro-nano polymer particles in an organic phase, in particular to the purification, separation and drying of polymer particles in an organic dispersed phase with higher colloid stability, a technology and a process method with pertinence need to be developed.
In organic ester solvents, maleic anhydride and vinyl acetate, maleic anhydride and styrene, maleic anhydride and alpha methyl styrene, and the like undergo radical polymerization to form a self-stabilized dispersion system, and an organic medium suspension of polymer particles is obtained, and since organic polymer particles are well stabilized in organic ester solvents, the polymer particles are usually separated from the organic ester solvents by centrifugal separation methods (CN1247635C and CN 100579995C). However, in the prior art, the polymer is directly dried after being separated to obtain the polymer, and the polymer usually contains part of unreacted monomers and a dispersion medium, so that the product quality is influenced. The removal of these impurities is usually carried out under vacuum at a relatively high temperature, and the energy consumption is relatively high.
Therefore, for an ultrafine polymer dispersion system which is obtained by self-stabilizing precipitation polymerization of maleic anhydride and other monomers and takes an organic phase as a dispersion medium, how to improve the product separation effect and the quality of a polymer product needs to be improved.
Disclosure of Invention
The invention aims to overcome the defects that when a polymer product is obtained by separation, a separation effect is poor, and the product also contains partial unreacted monomers and a dispersion medium in an ultrafine polymer dispersion system which is obtained by self-stabilizing precipitation polymerization of maleic anhydride and other monomers and takes an organic phase as the dispersion medium.
In the course of the present invention, the inventors have found that it is difficult to achieve the desired effect if the separation and washing of small-sized particles are accomplished by a conventional suspension separation method such as a centrifugal operation or a filtering operation for the above-mentioned ultrafine polymer dispersion. Or repeated operations of centrifugation, washing, redispersion and recentrifugation are required, and the process takes longer time. Or the requirement on the filter apparatus and the material is higher, the penetration and the filtration often appear at the initial stage of the filtration operation, but the blockage phenomenon appears at the later stage of the filtration, and the filtration efficiency and the filtration effect are influenced. However, the inventors have found that if the suspension is centrifuged and the centrifuged solids are redispersed in a particular selected washing solvent, the resulting redispersed suspension can have a lower viscosity, the polymer particles can retain a larger agglomerate size in the washing solvent, and re-separation can be conveniently carried out using filtration means. At the moment, the phenomena of filter leakage and blockage are not easy to occur to the filter equipment, thereby obtaining the invention.
In order to achieve the above objects, the present invention provides a method for separating a polymer product from an ultrafine polymer dispersion using an organic phase as a dispersion medium, the method comprising: (1) carrying out centrifugal separation on polymer mother liquor containing maleic anhydride-based copolymer, dispersion medium and polymerization monomer to obtain separated solid; (2) mixing the separated solid with a washing solvent to obtain dispersed slurry; (3) filtering the dispersed slurry by a filtering device with the filtering aperture of less than 6 mu m to obtain a filter cake and a separation liquid; (4) drying the filter cake to obtain superfine polymer product particles; the total content A1 of organic volatile components in the filter cake is less than 10 mass%; the total content A2 of washing impurities in the washing solvent in the separation liquid is 1 mass% or less.
Preferably, in step (2), the washing solvent is selected from C4～C10Alkane, C1～C3Alcohol, C1～C2Halogenated hydrocarbons or C6～C7An aromatic hydrocarbon.
Preferably, the alkane is selected from at least one of butane, isobutane, pentane, isopentane, hexane, cyclohexane, heptane, octane, nonane and decane; the alcohol is selected from methanol and/or ethanol; the halogenated hydrocarbon is at least one of dichloromethane, chloroform and chloroethane; the aromatic hydrocarbon is selected from benzene and/or toluene.
Preferably, the weight ratio of the isolated solid to the washing solvent in step (2) is 1: (1-10).
Through the technical scheme, the invention combines centrifugal separation with the dispersed slurry obtained by using a special washing solvent, and then the dispersed slurry is filtered, so that a copolymer product with high purity is separated from an ultrafine polymer dispersion system taking an organic phase as a dispersion medium.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a method for separating polymer products by using an ultrafine polymer dispersion system with an organic phase as a dispersion medium, which comprises the following steps: (1) carrying out centrifugal separation on polymer mother liquor containing maleic anhydride-based copolymer, dispersion medium and polymerization monomer to obtain separated solid; (2) mixing the separated solid with a washing solvent to obtain dispersed slurry; (3) filtering the dispersed slurry by a filtering device with the filtering aperture of less than 6 mu m to obtain a filter cake and a separation liquid; (4) drying the filter cake to obtain superfine polymer product particles; the total content A1 of organic volatile components in the filter cake is less than 10 mass%; the total content A2 of washing impurities in the washing solvent in the separation liquid is 1 mass% or less.
The method provided by the invention is used for separating the superfine polymer product particles from the superfine polymer dispersion system which takes an organic phase as a dispersion medium, and the purity and the quality of the particles are improved. The content of organic volatile components in the finally obtained superfine polymer product particles is low.
In the invention, the centrifugal separation in the step (1) can be used for primary separation of the polymer mother liquor, and the product obtained by the centrifugal separation can be subjected to standing and layering, wherein the upper layer is supernatant and the lower layer is separated solid. Preferably, the rotation speed of the centrifugal separation is more than 3000rpm, and the time of the centrifugal separation is more than 10 min; preferably, the rotation speed of the centrifugal separation is 3000-5000 rpm, and the time of the centrifugal separation is 10-60 min.
In the method provided by the invention, the obtained separated solid is further passed through the washing solvent to form dispersed slurry, and the superfine polymer product particles can be dispersed in the washing solvent and keep larger agglomeration size, and are filtered by a filter device with a specific filter pore size to obtain pure superfine polymer product particles with reduced impurities (such as unreacted polymerization monomers and dispersion media).
In the process of the present invention, the total content of organic volatile components A1 in the filter cake obtained in step (3) and the total content of washing impurities in the separation liquid in the washing solvent A2 can be determined as monitoring aids in determining whether the impurities in the ultrafine polymer product particles are reduced. Preferably, the filter cake obtained in step (3) is returned to the steps (2) and (3) for a plurality of times, for example two or three times, so that the measured values of a1 and a2 satisfy the above-mentioned limits. Preferably, a1 is 7% by mass or less and a2 is 0.7% by mass or less.
According to the present invention, preferably, the organic volatile component comprises the polymerized monomer, a dispersion medium and a washing solvent; the wash impurities comprise the polymerized monomer and a dispersion medium. The separation liquid mainly contains the washing solvent, and the polymerized monomer and the dispersion medium are impurities therein. The measured values of A1 and A2 are reduced, which shows that the superfine polymer product particles separated by the method of the invention have high purity and good quality.
In the invention, the method for measuring the total content A1 of the organic volatile components can be a thermogravimetric analysis method, and the weight reduction part is the total weight of the various organic volatile components.
In the present invention, the method for determining the total content a2 of the washing impurities in the washing solvent may be a gas chromatography, and a gas chromatography analysis spectrum of the separation liquid is obtained, in which signal peaks corresponding to the polymerized monomer, the dispersion medium and the washing solvent are displayed. The size of the peak area indicates the relative content of each of the above substances in the separation liquid. The total content a2 of the total amount of washing impurities (the polymerization monomer and the dispersion medium) in the washing solvent can be converted by the sum of the peak areas corresponding to the polymerization monomer and the dispersion medium and the peak area corresponding to the washing solvent.
According to the invention, the method is provided for the superfine polymer dispersion system obtained by polymerizing the maleic anhydride-group-containing copolymer by adopting a self-stabilizing precipitation polymerization method aiming at maleic anhydride and other monomers, and the polymer mother liquor in the step (1) is the superfine polymer dispersion system. The monomer in the self-stabilizing precipitation polymerization may include maleic anhydride, and other monomer selected from styrene, alpha-methylstyrene, vinyl acetate and carbocatelene, preferably the other monomer may be alpha-methylstyrene or C4An olefin.
According to the present invention, preferably, the maleic anhydride group-containing copolymer in the step (1) is a copolymer of maleic anhydride and alpha-methylstyrene and/or maleic anhydride and C4An olefin copolymer; the polymerized monomer is selected from maleic anhydride, alpha-methyl styrene and C4An olefin; the dispersion medium is organic acid alkyl ester or a mixture of the organic acid alkyl ester and inert alkane, and preferably the dispersion medium is isoamyl acetate or a mixture of the isoamyl acetate and the inert alkane; in the polymer mother liquor, the content of the maleic anhydride group-containing copolymer is 5-25 wt%. Wherein the inert alkane may be selected from at least one of pentane, hexane, heptane, and octane. The process of the present invention provides for more efficient separation of the maleic anhydride group-containing copolymer with a dispersion medium and unreacted monomers minimized.
According to the invention, step (2) is used to redisperse said isolated solid containing ultrafine copolymer particles, possibly with polymer particles, in said selected washing solventThe larger agglomerate size is maintained in the wash solvent, which in turn facilitates better separation of impurities from the separated solids using a filtration step. The washing solvent may serve to disperse the polymer particles and remove impurities and solvents adhered to the polymer surface, and preferably, in the step (2), the washing solvent is selected from the group consisting of C4～C10Alkane, C1～C3Alcohol, C1～C2Halogenated hydrocarbons or C6～C7An aromatic hydrocarbon.
Preferably, the alkane is selected from at least one of n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, heptane, octane, nonane and decane.
Preferably, the alcohol is selected from methanol and/or ethanol.
Preferably, the halogenated hydrocarbon is selected from at least one of dichloromethane, chloroform and ethyl chloride.
Preferably, the aromatic hydrocarbon is selected from benzene and/or toluene.
More preferably, the washing solvent is n-hexane or methanol. Better dispersion of the ultra-fine polymer product particles in the dispersed slurry can be provided, facilitating a more efficient separation of impurities by the filtration step.
According to the present invention, the mixing conditions in step (2) are such as to provide a better dispersion of the isolated solid in the washing solvent, providing a dispersion slurry suitable for subsequent filtration, and preferably the mixing temperature in step (2) is from-20 ℃ to 120 ℃, depending on the nature of the dispersion medium, unreacted monomers and washing solvent.
Preferably, the weight ratio of the isolated solid to the washing solvent in step (2) is 1: (1-10), more preferably 1: (5-9). Better dispersion of the isolated solids and better purification of the ultra-fine polymer product particles can be provided.
Preferably, the mixing in the step (2) is carried out by stirring the separated solid and the washing solvent at a rotating speed of 80-120 rpm for 45-75 min.
In the present invention, the dispersed slurry formed using the washing solvent may be filtered to separate impurities carried by the ultrafine polymer product particles. The filter means preferably used to meet the filter pore size requirements may be a sand-core funnel, a material known to be commercially available, such as G3 or G4 sand-core funnel from beijing-xinville glass instruments ltd. Preferably, the filtering pore size is 4-6 μm. The agglomerate size of the polymer product particles in the washing solvent can be matched.
According to the invention, step (4) provides a drying method suitable for ultrafine particles, further helps to effectively remove organic volatile components in the filter cake, and preferably, the drying in step (4) is vacuum drying or inert gas purging drying.
According to the present invention, preferably, the vacuum drying conditions include: the gauge pressure of the vacuum is not less than-0.01 MPa, the drying temperature is more than 50 ℃, and the drying time is more than 6 h. Preferably, the drying temperature is 80-120 ℃, and the drying time is 6-10 h.
According to the present invention, preferably, the average particle size of the ultrafine polymer product particles in step (4) is 500 to 1500 nm; the total content of organic volatile components A3 in the ultrafine polymer product particles is 3 mass% or less.
The average particle size of the polymer product of the present invention may be measured by scanning electron microscopy.
The determination method of the content of the organic volatile component A3 can be a thermogravimetric analysis method.
The present invention will be described in detail below by way of examples. In the following examples, A1 and A3 were measured by thermogravimetric analysis;
the determination method of a2 is gas chromatography, and a gas chromatography analysis spectrogram of the separation liquid is obtained, wherein signal peaks corresponding to a polymerized monomer, a dispersion medium and a washing solvent are shown, the size of a peak area shows the relative content of each substance in the separation liquid, and a2 can be obtained by converting the sum of the peak areas corresponding to the polymerized monomer and the dispersion medium and the peak area corresponding to the washing solvent.
The average particle size of the ultrafine polymer product particles was measured by a scanning electron microscope using a Hitachi S4800 instrument. The polymer powder is placed on the conductive adhesive of the testing platform a little, after gold spraying, the polymer powder is observed through S4800, and the size of the superfine polymer product particles obtained by a scanning electron microscope can be measured through S4800 self-contained testing software.
Example 1
(1) Self-stabilizing precipitation polymerization of maleic anhydride and alpha-methylstyrene
100g of maleic anhydride, 118g of alpha-methylstyrene, 1.6g of azobisisobutyronitrile and 1000ML of isoamyl acetate are subjected to polymerization reaction in a water bath at 70 ℃ for 5 hours to obtain milky white polymer mother liquor (an ultrafine polymer dispersion system, wherein the copolymer particles are copolymers of maleic anhydride and alpha-methylstyrene, and the dispersion medium is isoamyl acetate).
(2) Separating copolymer particles and washing impurities
a) Centrifuging the polymer mother liquor in a centrifuge at the rotating speed of 4000rpm for 30 min; standing the obtained product, and separating into supernatant and lower separated solid (containing copolymer solid);
b) and (3) mixing the separated solid with n-hexane according to the weight ratio of 1: 5, stirring at the stirring speed of 150rpm for 1h, and re-stirring and dispersing to obtain dispersed slurry;
c) filtering and separating the dispersed slurry by using a sand core funnel (the filtering aperture is about 5 mu m) to obtain a filter cake and a separation liquid; and measuring the content A1 of organic volatile components in the filter cake and the content A2 of washing impurities in the separation liquid;
the cake was subjected to the above steps b) and c) again three times, and the content of a2 in the separated liquid was measured to be 0.67 mass% (the content of isoamyl acetate was 0.07 mass%, the content of α -methylstyrene was 0.6 mass%); the a1 of the cake was 7 mass%;
d) vacuum drying the filter cake at 75 deg.C under vacuum degree gauge pressure of not less than-0.01 MPa for 6 hr to obtain superfine polymer product particles (average particle diameter 1000nm) with organic volatile component content A3 of 3 wt%.
Example 2
(1) Self-stabilizing precipitation polymerization of maleic anhydride and alpha-methylstyrene
100g of maleic anhydride, 118g of alpha-methylstyrene, 1.6g of azobisisobutyronitrile, 13g of divinylbenzene and 1000ML of isoamyl acetate are subjected to polymerization reaction in a water bath at 70 ℃ for 5 hours to obtain milky white polymer mother liquor (an ultrafine polymer dispersion system, wherein the copolymer particles are a copolymer of maleic anhydride and alpha-methylstyrene, and the dispersion medium is isoamyl acetate).
(2) Separating copolymer particles and washing impurities
a) Centrifuging the polymer mother liquor in a centrifuge at 3000rpm for 45 min; standing the obtained product, and separating into supernatant and lower separated solid (containing copolymer solid);
b) separating the solid from methanol according to the weight ratio of 1: 9, stirring at the stirring speed of 120rpm for 1 hour, and re-stirring and dispersing to obtain dispersed slurry;
c) filtering and separating the dispersed slurry by using a sand core funnel (the filtering aperture is about 6 mu m) to obtain a filter cake and a separation liquid; and measuring the content A1 of organic volatile components in the filter cake and the content A2 of washing impurities in the separation liquid;
the cake was again subjected to the above steps b) and c) three times, and the A2 content in the separated liquid was measured to be 0.4 mass% (only isoamyl acetate); the a1 of the filter cake was 6 mass%;
d) vacuum drying the filter cake at 50 deg.C under vacuum degree gauge pressure of not less than-0.01 MPa for 24 hr to obtain superfine polymer product particles (average particle diameter of 500nm), wherein the content of organic volatile component A3 is 2.8 wt%.
Example 3
(1) Self-stabilizing precipitation polymerization of maleic anhydride and alpha-methylstyrene
50g of maleic anhydride, 59g of alpha-methylstyrene, 1g of azobisisobutyronitrile and 1000ML of isoamyl acetate are subjected to polymerization reaction in a water bath at 70 ℃ for 5 hours to obtain milky white polymer mother liquor (an ultrafine polymer dispersion system, wherein the copolymer particles are a copolymer of maleic anhydride and alpha-methylstyrene, and the dispersion medium is isoamyl acetate).
(2) Separating copolymer particles and washing impurities
a) Centrifuging the polymer mother liquor in a centrifuge at 3000rpm for 45 min; standing the obtained product, and separating into supernatant and lower separated solid (containing copolymer solid);
b) and (3) mixing the separated solid with n-hexane according to the weight ratio of 1: 8, stirring at the stirring speed of 140rpm for 1h, and re-stirring and dispersing to obtain dispersed slurry;
c) filtering and separating the dispersed slurry by using a sand core funnel (the filtering aperture is about 4 mu m) to obtain a filter cake and a separation liquid; and measuring the content A1 of organic volatile components in the filter cake and the content A2 of washing impurities in the separation liquid;
the cake was again subjected to the above steps b) and c) three times, and the A2 content in the separated liquid was measured to be 0.3 mass% (only isoamyl acetate); the a1 of the cake was 5 mass%;
d) vacuum drying the filter cake at 50 deg.C under vacuum degree gauge pressure of not less than-0.01 MPa for 12 hr to obtain superfine polymer product particles (average particle diameter of 1500nm), wherein the content of organic volatile component A3 is 2.7 wt%.
Example 4
(1) Maleic anhydride and C4Olefin self-stabilizing precipitation polymerization
Carrying out polymerization reaction on 100g of maleic anhydride, 300g of mixed carbon, 1.6g of azodiisobutyronitrile and 1000ML of isoamyl acetate in a water bath at 70 ℃ for 5 hours to obtain milky polymer mother liquor (an ultrafine polymer dispersion system, wherein copolymer particles are maleic anhydride and C4Copolymers of olefins, dispersion medium isoamyl acetate).
(2) Separating copolymer particles and washing impurities
a) Centrifuging the polymer mother liquor in a centrifuge at 3000rpm for 45 min; standing the obtained product, and separating into supernatant and lower separated solid (containing copolymer solid);
b) and (3) mixing the separated solid with n-hexane according to the weight ratio of 1: 10, stirring at the stirring speed of 150rpm for 1h, and re-stirring and dispersing to obtain dispersed slurry;
c) filtering and separating the dispersed slurry by using a sand core funnel (the filtering aperture is about 6 mu m) to obtain a filter cake and a separation liquid; and measuring the content A1 of organic volatile components in the filter cake and the content A2 of washing impurities in the separation liquid;
the cake was again subjected to the above steps b) and c) three times, and the A2 content in the separated liquid was measured to be 0.75 mass% (only isoamyl acetate); the a1 of the filter cake was 8 mass%;
d) vacuum drying the filter cake at 50 deg.C under vacuum degree gauge pressure of not less than-0.01 MPa for 10 hr to obtain superfine polymer product particles (average particle diameter of 1300nm), wherein the content of organic volatile component A3 is 3.1 wt%.
Example 5
The procedure of example 1 was followed except that "cyclohexane" was used in place of "n-hexane" in step (2) b), and a cake and a separated liquid were separated.
The content of a2 in the separated liquid was 0.8 mass% (only isoamyl acetate); the a1 of the filter cake was 9 mass%; ultrafine polymer product particles (average particle diameter 1100nm) were obtained, and A3 was 3.1% by mass.
Example 6
Following the procedure of example 1, except that "dichloroethane" was used in place of "n-hexane" in step (2) b), the cake and the separated liquid were separated.
The content of a2 in the separated liquid was 0.9 mass% (only isoamyl acetate); the a1 of the filter cake was 9 mass%; ultrafine polymer product particles (average particle diameter 900nm) were obtained, and A3 was 3.4% by mass.
Example 7
Following the procedure of example 1 except that "toluene" was used in place of "n-hexane" in step (2) b), the cake and the separated liquid were separated.
The content of a2 in the separated liquid was 1.0 mass% (only isoamyl acetate); the a1 of the filter cake was 10 mass%; ultrafine polymer product particles (average particle diameter 600nm) were obtained, and A3 was 3.2% by mass.
Example 8
Following the procedure of example 1 except substituting "xylene" for "n-hexane" in step (2) b), the cake and the separated liquid were separated.
The content of a2 in the separated liquid was 1.1 mass% (only isoamyl acetate); the a1 of the filter cake was 12 mass%; ultrafine polymer product particles (average particle diameter 1200nm) were obtained, A3 being 4.0 mass%.
Example 9
Following the procedure of example 1 except that "diethyl ether" was used in place of "n-hexane" in step (2) b), the cake and the separated liquid were separated.
The content of a2 in the separated liquid was 1.2 mass% (only isoamyl acetate); the a1 of the filter cake was 11 mass%; ultrafine polymer product particles (average particle diameter 700nm) were obtained, and A3 was 3.8% by mass.
Example 10
The procedure is as in example 1, except that, in step (2) c), the "filter pore size of about 2 μm" is used instead of the "filter pore size of about 5 μm". The sand core funnel is blocked and cannot complete the filtration separation.
Comparative example 1
(1) Self-stabilizing precipitation polymerization of maleic anhydride and alpha-methylstyrene
100g of maleic anhydride, 118g of alpha-methylstyrene, 1.6g of azobisisobutyronitrile and 1000ML of isoamyl acetate are subjected to polymerization reaction in a water bath at 70 ℃ for 5 hours to obtain milky white polymer mother liquor (an ultrafine polymer dispersion system, wherein the copolymer particles are copolymers of maleic anhydride and alpha-methylstyrene, and the dispersion medium is isoamyl acetate).
(2) Separation of copolymer microparticles and isoamyl acetate
Centrifuging the polymer mother liquor in a centrifuge at the rotating speed of 4000rpm for 30 min; and the resulting product was allowed to stand, and separated into a supernatant of the upper layer and a separated solid (containing a copolymer solid) of the lower layer.
Vacuum drying the separated solid at 75 deg.C under vacuum degree gauge pressure of not less than-0.01 MPa for 24 hr to obtain superfine polymer product particles (average particle diameter of 1500nm), wherein the content of organic volatile component A3 is 3 wt%.
Comparative example 2
(1) Self-stabilizing precipitation polymerization of maleic anhydride and alpha-methylstyrene
100g of maleic anhydride, 118g of alpha-methylstyrene, 1.6g of azobisisobutyronitrile and 1000ML of isoamyl acetate are subjected to polymerization reaction in a water bath at 70 ℃ for 5 hours to obtain milky white polymer mother liquor (an ultrafine polymer dispersion system, wherein the copolymer particles are copolymers of maleic anhydride and alpha-methylstyrene, and the dispersion medium is isoamyl acetate).
(2) Separation of copolymer microparticles and isoamyl acetate
a) Centrifuging the polymer mother liquor in a centrifuge at the rotating speed of 4000rpm for 30 min; standing the obtained product, and separating into supernatant and lower separated solid (containing copolymer solid);
b) the separated solid was separated by filtration using a sand-core funnel (filter pore size about 5 μm), and the funnel was quickly clogged, failing to complete the separation.
Comparative example 3
The procedure of example 1 was followed except that "the filtration pore size was about 8 μm" was used in place of "the filtration pore size was about 5 μm" in step (2) b), and a cake and a separation liquid were separated.
The content of a2 in the separated liquid was 1.2 mass% (only isoamyl acetate); the a1 of the filter cake was 17 mass%; ultrafine polymer product particles (average particle diameter 900nm) were obtained, A3 being 4.5% by mass.
It can be seen from the results of the above examples that the ultrafine polymer product particles having an organic volatile content of less than 3% by mass can be obtained by the examples of the method provided by the present invention, the impurity content in the ultrafine polymer product particles is reduced, and the purity and quality of the product are improved.
Examples 1-3, using the most preferred conditions, provide better separation with fewer impurities (low a3 content) in the ultra-fine polymer product particles. The amount of washing solvent used in example 4 is not in the most preferred range and affects the purity of the ultra fine polymer product particles. Examples 5-8 use less preferred washing solvents and the purification of the ultra fine polymer product particles is less effective than examples 1-3. Example 9 the separation of impurities was less effective using a solvent that was conventional but not the solvent of choice in the present invention. The sand core funnel selected in example 10 had a filter pore size outside the preferred range, resulting in a clogged funnel that did not allow filtration separation.
The purity improvement of the ultrafine polymer product particles cannot be achieved using only centrifugal separation in comparative example 1.
In comparative example 2, the centrifugal separation and filtration were directly and simply combined, and the solid was separated without redispersion of a washing solvent, and the separation and purification of the ultrafine polymer product particles could not be accomplished by filtration due to clogging of a sand core funnel.
The sand core funnel selected in comparative example 3 has too large filter pore size and cannot effectively separate and purify ultrafine polymer product particles.
The method and the optimized conditions provided by the invention can realize the effective separation of the superfine polymer dispersion system and improve the purity of superfine polymer product particles.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (7)
1. A method for separating a polymer product from an ultra-fine polymer dispersion having an organic phase as a dispersion medium, the method comprising:
(1) carrying out centrifugal separation on polymer mother liquor containing maleic anhydride-based copolymer, dispersion medium and polymerization monomer to obtain separated solid;
(2) mixing the separated solid with a washing solvent to obtain dispersed slurry;
(3) filtering the dispersed slurry through a filtering device with the filtering aperture of 4-6 microns to obtain a filter cake and a separation liquid;
(4) drying the filter cake to obtain superfine polymer product particles;
the total content A1 of organic volatile components in the filter cake is less than 10 mass%;
a total content A2 of washing impurities in the separation liquid in the washing solvent is 1 mass% or less;
the washing solvent is n-hexane or methanol; the weight ratio of the isolated solid to the washing solvent is 1: (5-9).
2. The method of claim 1, wherein the organic volatile component comprises the polymerized monomer, a dispersion medium, and a wash solvent; the wash impurities comprise the polymerized monomer and a dispersion medium.
3. The method according to claim 1 or 2, wherein the maleic anhydride group-containing copolymer in step (1) is a copolymer of maleic anhydride and α -methylstyrene and/or maleic anhydride and C4An olefin copolymer; the polymerized monomer is selected from maleic anhydride, alpha-methyl styrene and C4An olefin; the dispersion medium is organic acid alkyl ester or a mixture of the organic acid alkyl ester and inert alkane; in the polymer mother liquor, the content of the maleic anhydride group-containing copolymer is 5-25 wt%.
4. The method according to claim 1, wherein the mixing temperature in the step (2) is-20 ℃ to 120 ℃.
5. The method according to claim 1, wherein the mixing in step (2) is carried out by stirring the separated solid and the washing solvent at a rotation speed of 80-120 rpm for 45-75 min.
6. The method according to claim 1, wherein the drying in step (4) is vacuum drying; the gauge pressure of the vacuum is not less than-0.01 MPa, the drying temperature is more than 50 ℃, and the drying time is more than 6 h.
7. The process according to claim 1 or 2, wherein the average particle size of the ultrafine polymer product particles in step (4) is 500 to 1500 nm; the total content of organic volatile components A3 in the ultrafine polymer product particles is 3 mass% or less.
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| CN102302904A (en) * | 2011-05-17 | 2012-01-04 | 清华大学 | Method for preparing polystyrene maleimide membrane for gasoline desulfurization by pervaporation |
| CN102250273A (en) * | 2011-06-02 | 2011-11-23 | 北京化工大学 | Preparation method of styrene-maleic anhydride random copolymer |
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