JP2000281716A - Method for concentrating polymer latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To concentrate a polymer latex to a high degree of concentration effectively with a vibration type membrane separation apparatus by vibrating its separation membrane at a specific torsional vibration frequency and a specific torsional vibration angle and applying a specific temperature and a specific operation pressure for separation to keep a high permeation flux. SOLUTION: A polymer latex is concentrated with a vibration type membrane separation apparatus using a torsional vibration frequency of 40-80 Hz and a torsional vibration angle of 4-12 degree for membrane vibration at a temperature of 10-50 deg.C and an operation pressure of 2-15 kg/cm2G. A nano filter, a reverse osmosis membrane or the like is used for the separation membrane. If the particle size distribution of the polymer latex has only one frequency local maximum, the concentration is preferably carried out at 30-45 deg. and an operation pressure of 2.3-3.5 kg/cm2G. If the particle size distribution of the polymer latex has two frequency local maximums, the concentration is preferably carried out at 35-45 deg. and an operation pressure of 3.0-4.0 kg/cm2G. The polymer latex is preferably a vinyl chloride polymer latex having a glass transition temperature of not less than 60 deg.C or a methyl methacrylate polymer latex.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for concentrating a polymer latex. More specifically, the present invention can use a vibrating membrane separation device to maintain a high permeation flux and efficiently concentrate to a high concentration without generating aggregates and clogging the separation membrane. The present invention relates to a method for concentrating a polymer latex.

[0002]

2. Description of the Related Art A polymer latex is often provided with a concentration step following a polymerization reaction for the purpose of producing a concentrated latex, reducing drying costs, and improving productivity.
Conventionally, ultrafiltration membranes are often used for concentrating polymer latex. When performing a concentration operation using a membrane separation device, because a concentration polarization layer is formed near the separation membrane,
It is known that there is a critical flux at which the permeation flux does not increase even if the operating pressure is increased above a certain limit. Since this critical flux decreases as the concentration of the stock solution increases, there is a limit to the concentration. In addition, in the concentration of the polymer latex, there is a problem that agglomerates are generated due to the high concentration, and the module is clogged, so that stable operation cannot be performed for a long period of time. On the other hand, attempts have been made to vibrate the separation membrane to prevent the occurrence of blockage, maintain a high permeation flux, and enable high concentration. For example,
Japanese Patent Application Laid-Open No. 2-241524 discloses a device for separating selected components from a colloidal suspension without causing clogging or contamination of a filter membrane, and includes means for vibrating a leaf-shaped element connected to the separation membrane. Devices have been proposed. Further, Japanese Patent Application Laid-Open No. 10-128083 proposes a membrane separation device provided with a vibrating membrane as a concentration device that maintains a high permeation flux of a separation membrane and enables high concentration of slurry. However, even when these devices are applied to polymer latex, clogging occurs in the separation membrane due to aggregates, and it has been difficult to achieve long-term stable operation and high concentration. For this reason, there has been a demand for a method for concentrating a polymer latex that enables a stable concentration operation without generating aggregates.

[0003]

SUMMARY OF THE INVENTION The present invention uses a vibrating membrane separation device to maintain a high permeation flux without generating aggregates and clogging of the separation membrane, and to efficiently achieve a high concentration. The purpose of the present invention is to provide a method for concentrating a polymer latex that can be concentrated.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the polymer latex was subjected to torsional vibration using a vibrating membrane separation device while applying torsional vibration to the separation membrane. By allowing moisture to permeate under specific temperature and operating pressure conditions, it is possible to concentrate to a high concentration while maintaining a high permeation flux without generating aggregates, clogging the separation membrane And completed the present invention based on this finding. That is, the present invention provides (1) a method of concentrating a polymer latex using a vibration type membrane separation device, wherein the separation membrane of the device is vibrated at a torsional vibration frequency of 40 to 80 Hz and a torsional vibration angle of 4 to 12 degrees, Temperature 10-50 ° C, operating pressure 2-15kg
/ Cm ² G, and a method for concentrating the polymer latex. Further, as a preferred embodiment of the present invention, (2) the method for concentrating a polymer latex according to (1), wherein the separation membrane of the vibration type membrane separation device is a nanofilter or a reverse osmosis membrane, (3) a polymer latex Wherein the polymer latex is a vinyl chloride polymer latex, and (4) the polymer latex is a methyl methacrylate polymer latex.
(5) The method for concentrating a polymer latex according to (1), wherein the polymer latex has one frequency maximum in the particle size distribution, (6) the temperature of 30 to 45. (5) The method for concentrating a polymer latex according to (5), wherein the polymer latex is condensed at a temperature of 2.3 to 3.5 kg / cm < ² > G.
(7) The method for concentrating a polymer latex according to (1), wherein the polymer latex has two or more frequency maxima in the particle size distribution, and (8) a temperature of 30 to 47 ° C. and an operating pressure of 2.5. The method for concentrating a polymer latex according to the item (7), in which the polymer latex is concentrated at 4.5 kg / cm ² G, may be used.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The method for concentrating a polymer latex according to the present invention is a method for concentrating a polymer latex using a vibrating membrane separation apparatus.
z, the separation membrane of the apparatus is vibrated at a torsional vibration angle of 4 to 12 degrees to concentrate at a temperature of 10 to 50 ° C. and an operating pressure of ^{2 to} 15 kg / cm ² G. The method of the present invention is preferably applied to the concentration of a polymer latex, particularly to the concentration of a thermoplastic polymer latex having a glass transition temperature (Tg) of 60 ° C. or more,
In particular, it can be particularly suitably applied to the concentration of a vinyl chloride polymer latex and a methyl methacrylate polymer latex. The vinyl chloride polymer latex which can be concentrated by the method of the present invention comprises vinyl chloride homopolymer or vinyl chloride at 50% by weight or more, preferably 75% by weight or more, and an unsaturated monomer copolymerizable with vinyl chloride. Is a latex of a polymer having a glass transition temperature (Tg) of 60 ° C. or higher. Examples of unsaturated monomers copolymerizable with vinyl chloride include, for example, acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, cinnamic acid, unsaturated monocarboxylic acids such as maleic anhydride, unsaturated dicarboxylic acids and the like. Acid anhydride; monoalkyl fumarate,
Monoalkyl esters of unsaturated dicarboxylic acids such as monoalkyl esters of itaconic acid; unsaturated monocarboxylic esters such as methyl, ethyl, propyl and benzyl esters of acrylic acid or methacrylic acid; dimethyl and diethyl esters of maleic acid and fumaric acid; Unsaturated dicarboxylic acid diesters such as dipropyl ester; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and propyl vinyl ether; olefins such as ethylene, propylene, butene-1 and pentene-1; fragrances such as styrene and α-methylstyrene An aromatic monovinyl compound;
Vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; unsaturated amide compounds such as acrylamide and methacrylamide; vinyl carboxylate esters such as vinyl acetate and vinyl propionate; and vinylidene chloride. One of these copolymerizable monomers can be used alone, or two or more can be used in combination. The methyl methacrylate polymer latex which can be concentrated by the method of the present invention is a homopolymer of methyl methacrylate or 40% by weight or more, preferably 60% by weight of methyl methacrylate.
And a glass transition temperature (Tg) of 6% by weight or more and an unsaturated monomer copolymerizable with methyl methacrylate.
It is a polymer latex at 0 ° C. or higher. Examples of the unsaturated monomer copolymerizable with methyl methacrylate include alkyl acrylates and / or alkyl methacrylates having an alkyl group having 1 to 8 carbon atoms such as ethyl acrylate, propyl acrylate, and n-butyl acrylate ( (Hereinafter referred to as (meth) acrylate-based monomer) (meth) acrylate-based monomer; unsaturated halogen compound such as vinyl chloride and vinylidene chloride; aromatic vinyl-based compound such as styrene, vinyltoluene, and α-methylstyrene Vinyl cyanide compounds such as (meth) acrylonitrile and vinylidene cyanide; vinyl ester compounds such as vinyl acetate and vinyl propionate; vinyl ether compounds such as ethyl vinyl ether, cetyl vinyl ether and hydroxybutyl vinyl ether; 2-hydroxyethyl (methyl ) Acrylates, (meth) acrylic acid, 2-
Hydroxyethyl fumarate, monobutyl maleate and the like can be mentioned. The method for producing a polymer latex that can be concentrated by the method of the present invention is not particularly limited. For example, the average particle diameter of a single particle produced by an emulsion polymerization method is as small as about several hundred nm, and a sharp particle diameter distribution is obtained. A polymer latex having a single frequency maximum in the particle size distribution, a single particle size produced by the fine suspension polymerization method is widely distributed over several tens nm to several μm, and the frequency maximum in the particle size distribution is One latex, and a single particle size obtained by mixing a latex produced by an emulsion polymerization method with a latex produced by a seeded emulsion polymerization method or a fine suspension polymerization method or a seeded fine suspension polymerization method. Has one frequency maximum in a small particle size region of 100 to 500 nm and 1 to 3 frequency maxima in a large particle size region of 1 to 5 μm, and the frequency maximum in the particle size distribution is 2
Latex or the like. Here, the particle size distribution of a single particle can be obtained by a centrifugal sedimentation turbidity method, and refers to a particle size distribution in a range of 100 nm to 8 μm in particle size. The polymer latex having a frequency maximum of 2 or more in a preferable particle size distribution preferably has a polymer particle ratio of 5 to 40% by weight in a small particle size region of 500 nm or less. Among these, the polymer latex whose frequency maximum in the preferred particle size distribution is 2 or more is easy to increase the temperature and the operating pressure during concentration, and is efficient up to a high concentration without generating aggregates. Therefore, the method of the present invention can be particularly suitably applied.

The vibration type membrane separation apparatus used in the method of the present invention comprises:
There is no particular limitation as long as the disc-shaped separation membrane vibrates torsional about the axis.For example, a horizontally installed disc-shaped separation membrane has a torsional vibration mechanism, Shinko Pantech Co., Ltd. "VSEP" or the like can be used. There is no particular limitation on the separation membrane used in the method of the present invention, and examples thereof include a microfiltration membrane, an ultrafiltration membrane, a nanofilter, and a reverse osmosis membrane. Among these, the nanofilter and the reverse osmosis membrane reduce the flow of latex auxiliary materials into the permeate, maintain the stability of the latex, and reduce the load on the environment of the permeate treated as waste. Since it is small, it can be used particularly preferably. According to the method of the present invention, even a separation membrane having a small molecular weight cut-off such as a nanofilter or a reverse osmosis membrane can be efficiently concentrated while maintaining a high permeation flux, and particularly has a high rejection rate. When the NaCl rejection is high, preferably 70% or more, the removal of water-soluble auxiliary materials such as an emulsifier is small,
Variations in polymer quality can be suppressed. In the method of the present invention, the separation membrane of the vibrating membrane type separation device is vibrated at a torsional vibration frequency of 40 to 80 Hz, more preferably 45 to 60 Hz, and a torsional vibration angle of 4 to 12 degrees, more preferably 8 to 10 degrees. When the separation membrane is a disk having a diameter of 275 mm, the torsional vibration angle of 4 degrees is 9.7 mm in amplitude at the periphery of the separation membrane.
The torsional vibration angle of 12 degrees corresponds to an amplitude of 28.7 mm at the periphery of the separation membrane. 40H torsional vibration frequency
If it is less than z, the polymer particles may adhere to the membrane surface of the separation membrane and blockage may occur. 8 torsional vibration frequency
When the frequency exceeds 0 Hz, the energy required for giving the torsional vibration becomes excessive, and the economic efficiency may be lost.
If the torsional vibration angle is less than 4 degrees, agglomerates are generated, and polymer particles may adhere to the membrane surface of the separation membrane, resulting in blockage. If the torsional vibration angle exceeds 12 degrees, the energy required for giving the torsional vibration becomes excessive, and the economic efficiency may be lost.

In the method of the present invention, the polymer latex is concentrated at a temperature of 10 to 50 ° C. and an operating pressure of ^{2 to} 15 kg / cm ² G. Here, the operating pressure is a pressure obtained by subtracting the pressure of the permeated liquid from the arithmetic mean of the pressure at the inlet of the vibrating membrane separator for polymer latex and the pressure at the outlet of the concentrated latex. When the temperature is lower than 10 ° C., the permeation flux is small, and it may take a long time for concentration. When the temperature increases, the permeation flux increases, but when the temperature exceeds 50 ° C., aggregates may be easily generated. Operating pressure is 2kg / cm
^If it is less than ² G, the permeation flux is small, and it may take a long time for concentration. If the operation pressure exceeds 15 kg / cm ² G, aggregates may be generated, and the polymer may adhere to the membrane surface of the separation membrane, which may cause blockage. In the method of the present invention,
When the polymer latex has one frequency maximum in the particle size distribution, the temperature is 30 to 45 ° C, the operating pressure is 2.3 to 3.5.
It is preferred to concentrate at kg / cm ² G, temperature 35-38.
More preferably, it is concentrated at a temperature of 2.5 ° C. and an operating pressure of 2.5 to 3.0 kg / cm ² G. The polymer latex having a particle size distribution having one frequency maximum can be produced by fine suspension polymerization, emulsion polymerization, or the like. By concentrating at a temperature of 30 to 45 ° C. and an operating pressure of 2.3 to 3.5 kg / cm ² G, it is possible to efficiently maintain the high permeation flux without generating aggregates and clogging the separation membrane. To a solids concentration of 50
High concentrated latexes of up to 70% by weight can be obtained.

In the method of the present invention, when the polymer latex has two or more frequency maxima in the particle size distribution, it can be concentrated at a temperature of 30 to 47 ° C. and an operating pressure of 2.5 to 4.5 kg / cm ² G. It is more preferable to concentrate at a temperature of 35 to 45 ° C. and an operating pressure of 3.0 to 4.0 kg / cm ² G. There is no particular limitation on the method for producing a polymer latex having a particle size distribution having two or more frequency maxima. For example, the method has a gentle particle size distribution obtained by fine suspension polymerization and the like, and has a frequency maxima of about 1 μm. A polymer latex having
It can be produced by mixing a polymer latex having a sharp particle size distribution obtained by emulsion polymerization or the like and having a frequency maximum at several hundred nm. By concentrating at a temperature of 30-47 ° C. and an operating pressure of 2.5-4.5 kg / cm ² G,
It is possible to obtain a concentrated latex having a high solids content of 55 to 75% by weight while maintaining a high permeation flux and efficiently concentrating without generating aggregates and clogging the separation membrane. A polymer latex having a particle size distribution having two or more frequency maxima is less likely to generate agglomerates than a polymer latex having a particle size distribution having one frequency maxima,
Since the concentration can be performed by applying a higher temperature and a higher operating pressure, the concentration can be performed more efficiently and the concentration can be increased to a higher concentration. In the method of the present invention, if necessary, a surfactant can be further added to the polymer latex for concentration. The surfactant to be added is not particularly limited, and examples thereof include soap and sodium dodecylbenzenesulfonate. The addition of a surfactant to the polymer latex can stabilize the latex, but the addition of an excess of the surfactant may rather increase the viscosity. According to the method of the present invention, a polymer latex can be efficiently concentrated to easily produce a concentrated latex having a solid content of not less than 60% by weight containing no aggregate.

[0009]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Production Example 1 125 parts by weight of deionized water, 0.06 parts by weight of sodium lauryl sulfate and 0.01 parts by weight of sodium formaldehyde sulfoxylate were charged into a stainless steel stirrer and a jacketed pressure-resistant reactor, and degassing was performed under reduced pressure. Repeated twice. Next, 100 parts by weight of vinyl chloride were charged, and the temperature was raised to 63 ° C. with stirring, 0.6 parts by weight of sodium dodecylbenzenesulfonate and 30% by weight of hydrogen peroxide.
0.03 parts by weight of the aqueous solution was diluted with water, and the emulsion polymerization reaction was performed while continuously adding the solution until the end of the reaction. When the polymerization conversion reached 83%, unreacted vinyl chloride was removed.
The resulting vinyl chloride polymer latex has a solids concentration of 4
It was 0% by weight, and had a sharp primary particle size distribution having a frequency maximum at 0.3 μm as measured by a particle size distribution measurement by a centrifugal sedimentation turbidity method. Further, the glass transition temperature determined by differential thermal analysis was 79 ° C. Production Example 2 90 parts by weight of deionized water, 0.8 part by weight of sodium lauryl sulfate, 1.2 parts by weight of lauryl alcohol and 0.06 parts by weight of diisopropyl peroxydicarbonate were placed in a stainless steel stirrer and a jacketed pressure-resistant reactor. , And the atmosphere was replaced with nitrogen. Then, degassing under reduced pressure was repeated twice. Next, 100 parts by weight of vinyl chloride were charged and stirred.
Mixed. After homogenizing the mixture using a homogenizer, the mixture was transferred to another degassed stainless steel stirrer and jacketed pressure-resistant reactor, and heated to 47 ° C. to perform fine suspension polymerization. When the polymerization conversion reaches 90%,
Unreacted vinyl chloride was removed to obtain a vinyl chloride polymer latex A. The resulting latex A has a solid content of 5
1% by weight, and the particle size of single particles was widely distributed from 0.02 μm to 5 μm in the particle size distribution measurement by the centrifugal sedimentation turbidity method, the frequency maximum was 1.0 μm, and the average particle size was 1.0 μm.
Met. The glass transition temperature determined by differential thermal analysis was 80 ° C.

Production Example 3 A stainless steel stirrer and a jacketed pressure-resistant reactor were charged with 105 parts by weight of deionized water, 0.6 parts by weight of sodium dodecylbenzenesulfonate, and 1.5 parts by weight of lauryl alcohol.
Parts by weight and 0.06 parts by weight of diisopropyl peroxydicarbonate were charged and purged with nitrogen, and then degassing under reduced pressure was repeated twice. Next, 100 parts by weight of vinyl chloride were charged, stirred and mixed. After homogenizing the mixture using a homogenizer, the mixture was transferred to another degassed stainless steel stirrer and jacketed pressure-resistant reactor, and subjected to 62 ° C.
To carry out fine suspension polymerization. 90% polymerization conversion
, Unreacted vinyl chloride was removed. The obtained vinyl chloride polymer latex has a solid content concentration of 47% by weight, the particle size of single particles is widely distributed from 0.2 μm to 5.0 μm, the frequency maximum is 1.7 μm, and the average particle size is 1.7%. Was 1.8 μm. Latex B was prepared by mixing 80 parts by weight of this latex and 20 parts by weight of the latex obtained in Production Example 1. Latex B has a solid concentration of 46
% By weight, and the particle size of a single particle was widely distributed from 0.02 μm to 5 μm in the particle size distribution measurement by the centrifugal sedimentation turbidity method.
It had a sharp maximum at 0.3 μm and a gentle maximum at 1.0 μm, the average particle size was 1.4 μm, and the proportion of polymer particles in the small particle size region of 500 nm or less was 12% by weight.
The glass transition temperature determined by differential thermal analysis was 79
° C. Production Example 4 125 parts by weight of deionized water and sodium lauryl sulfate 1.2 were placed in a stainless steel stirrer and a jacketed reactor.
Parts by weight, 0.8 parts by weight of lauryl alcohol, 0.6 parts by weight of t-dodecylmercaptan, 0.3 parts by weight of lauroyl peroxide, and 100 parts by weight of methyl methacrylate, followed by purging with nitrogen and then degassing under reduced pressure twice. repetition,
Stir and mix. After homogenizing the mixture using a homogenizer, the mixture was transferred to another degassed stainless steel stirrer and jacketed reactor, and heated to 65 ° C. to perform fine suspension polymerization. When the polymerization conversion reached 92%, unreacted methyl methacrylate was removed to obtain a methyl methacrylate polymer latex. The obtained latex had a solid content of 43% by weight, and the particle size of a single particle was 0.02 μm to 2.0% by particle size distribution measurement by centrifugal sedimentation turbidity method.
It was widely distributed at 5 μm, had a frequency maximum at 0.6 μm, and the average particle size was 0.7 μm. The weight average molecular weight of the polymer determined by gel permeation using a mixed gel column and tetrahydrofuran as an eluent with reference to standard polystyrene was 280,000. The glass transition temperature of the polymer determined by differential thermal analysis was 105 ° C.

Example 1 Using a vibrating membrane separation device [VSEP Series L, Shinko Pantech Co., Ltd., membrane area 0.045 m ² ] equipped with a nano filter [NTR-7450, Nitto Denko Corporation]. Then, a concentration test was performed. Using vinyl chloride polymer latex A, torsional vibration frequency 60 Hz, torsional vibration angle 8.0 degrees, latex temperature 30 ° C, operating pressure 3 kg / cm ² G
The solid content concentration of the latex is from 53% by weight to 70%.
Weight percent. The permeation flux was constant at 25 liters / m ² / hr, and the concentration could be increased without any problem up to a solid concentration of 70% by weight. Comparative Example 1 The vinyl chloride polymer latex A was concentrated in the same manner as in Example 1 except that the operation pressure was changed to 16 kg / cm ² G. When the solid content concentration of the latex before concentration was 53% by weight, the permeation flux was 60 l / m ² / hr. However, as the solid content concentration was increased, the permeation flux decreased, and the solid content concentration was 70% by weight. When the permeation flux is 30 l / m ² / hr
And aggregates were generated. Example 1 and Comparative Example 1
1 are shown in FIG. From these results, it can be seen that in the concentration of the polymer latex having one frequency maximum in the particle size distribution, when the operating pressure is set to 3 kg / cm ² G, the solid content concentration is stably maintained without generation of aggregates. It can be concentrated up to 70% by weight, but the operating pressure is 16 kg / cm ² G
It can be seen that when the solid content concentration exceeds 65% by weight, the operation becomes unstable and agglomerates are easily generated.

Example 2 Using the same apparatus as in Example 1, a concentration test of vinyl chloride polymer latexes A and B was conducted. Torsional vibration frequency 6
The operation pressure was increased from 2.8 kg / cm ² G at 0 Hz, a torsional vibration angle of 8.0 degrees, and a latex temperature of 40 ° C. When the solid content concentration of the concentrated latex is made constant at 51% by weight using the vinyl chloride polymer latex A, the operating pressure is 2.8 kg / cm ² G, 6.3 kg / cm ² G and 10 kg / cm ² G. When the permeation flux is 39 l / m ² / hr,
69 l / m ² / hr and 71 l / m ² / hr. When the solid concentration of the latex after concentration is kept constant at 55% by weight, the operating pressure is 2.8 kg / cm ² G, 6.3 kg / cm ²
G and 10 kg / cm ² G, the permeation flux was 4
3 l / m ² / hr, 52 l / m ² / hr and 54
Liter / m ² / hr. When the solid content of the latex after concentration was 65% by weight and the operating pressure was 2.8 kg / cm ² G, the permeation flux was 12 liter / m ² / hr.
When vinyl chloride polymer latex B was used and the solid content concentration of the concentrated latex was kept constant at 47% by weight, the operating pressure was 2.8 kg / cm ² G, 6.3 kg / cm ² G, 10 kg / cm ² G and The permeation flux at 13.4 kg / cm ² G was 30
Liters / m ² / hr, 66 liters / m ² / hr, 66 liters / m ² / hr and 78 liters / m ² / hr. When the solids concentration of the concentrated latex is kept constant at 52% by weight, the operating pressure is 2.8 kg / cm ² G, 6.3 kg / cm ² G and 1
The permeation flux at 0 kg / cm ² G was 40 l / m ² / hr, 64 l / m ² / hr and 70 l / m ² / hr, respectively. When the solid content concentration of the latex after concentration is constant at 65% by weight, the operating pressure is 2.8 kg / cm.
The permeation flux at ² G, 6.3 kg / cm ² G and 10 kg / cm ² G was 25 l / m ² / hr, 35 l / m ² / hr and 38 l / m ² / hr, respectively. Was. FIG. 2 shows the results when the vinyl chloride polymer latex B was used. From the test results for the vinyl chloride polymer latexes A and B, when the solids concentration of the concentrated latex is relatively low, the permeation flux increases with increasing operating pressure, but the solids content of the concentrated latex is increased. If the concentration exceeds 60% by weight, the permeation flux does not change significantly even when the operating pressure is increased. Further, the polymer latex A having one frequency maximum in the particle size distribution is affected by the high temperature of 40 ° C., and when concentrated to a concentration of 65% by weight, the permeation flux is considerably reduced. In the case of the polymer latex B having the maximum frequency of
Even at 5% by weight, a smooth concentration operation can be performed.

Example 3 Using the same apparatus as in Example 1, a vinyl chloride polymer latex was used.
A concentration test of Cousin A was performed. Latex solids after concentration
53% by weight, torsional vibration frequency 60Hz, torsion
Vibration angle 5.2 degrees or 10.6 degrees, latex temperature 25 ° C
did. When the torsional vibration angle is fixed at 5.2 degrees, the operating pressure
3.0 kg / cm^TwoG, 6.3 kg / cm ^TwoG, 10.5 kg / cm^TwoG and
And 13.7kg / cm^TwoThe permeation flux at G is 26
Liter / m^Two/ Hr, 47 liters / m^Two/ Hr, 47 lit
Torr / m^Two/ Hr and 48 l / m^Two/ Hr. Right
When the torsional vibration angle is constant at 10.6 degrees, the operating pressure is 3.0
kg / cm^TwoG, 6.3 kg / cm^TwoG, 10.5 kg / cm^TwoG and 1
3.7kg / cm^TwoThe permeation flux at G is 54 litres.
Torr / m^Two/ Hr, 68 liters / m^Two/ Hr, 75 liters
/ M^Two/ Hr and 77 l / m^Two/ Hr. Comparative Example 2 Same as Example 3 except that no torsional vibration was applied to the separation membrane
The operation was repeated. Operating pressure 3.0kg / cm^TwoG, 6.3kg
/cm^TwoG, 10.5 kg / cm^TwoG and 13.7 kg / cm^TwoG's
Permeation flux is 11 liters / m^Two/ Hr, 1
3 liters / m^Two/ Hr, 12 liters / m^Two/ Hr and 12
Liter / m^Two/ Hr. Example 3 and Comparative Example 2
The results are shown in FIG. From the results in Fig. 3, torsional vibration was applied.
In the case of Comparative Example 2 where
Example 3 has a larger permeation flux and a higher torsional vibration angle.
When the torsional vibration angle is 10.6 degrees compared to 5.2 degrees
It can be seen that is higher in the permeation flux.

Example 4 Using the same apparatus as in Example 1, a vinyl chloride polymer latex was used.
A concentration test of Cousin B was performed. Latex solids after concentration
Partial concentration 74% by weight, torsional vibration frequency 60Hz,
The temperature was 30 ° C. The torsional vibration angle is fixed at 5.2 degrees.
When operating pressure is 4.2kg / cm^TwoG, 7.7 kg / cm ^TwoG and
14.8 kg / cm^TwoThe permeation flux at G is 19 l each.
Tol / m^Two/ Hr, 19 liters / m^Two/ Hr and 20 liters
Torr / m^Two/ Hr. Constant torsional vibration angle of 10.6 degrees
And the operating pressure is 4.2 kg / cm^TwoG, 7.7 kg / cm
^TwoG, 11.2 kg / cm^TwoG and 14.8 kg / cm^TwoWhen G
The permeation flux is 23 liters / m each^Two/ Hr, 29 l
Tol / m^Two/ Hr, 30 liters / m^Two/ Hr and 30 liters
Torr / m^Two/ Hr. Comparative Example 3 Same as Example 4 except that no torsional vibration was applied to the separation membrane
The operation was repeated. Operating pressure 4.2kg / cm^TwoG, 7.7kg
/cm^TwoG and 14.8 kg / cm^TwoAt G, the permeation flux is
3 liters / m each^Two/ Hr, 4 liters / m^Two/ Hr and
4 liters / m^Two/ Hr. Example 4 and Comparative Example 3
Comparing the results, the results for the comparative example without torsional vibration
In the embodiment in which the torsional vibration is applied, the permeation flux is larger.
And the torsional vibration angle is 5.2 degrees.
When the vibration angle is 10.6 degrees, the transmitted flux is larger.
I understand.

Example 5 Using the same apparatus as in Example 1, a concentration test of the vinyl chloride polymer latex A was performed. 60Hz torsional vibration frequency,
The torsional vibration angle was 10.6 degrees, the latex temperature was 40 ° C, and the operating pressure was 2.8 kg / cm ² G. When the temperature is constant at 40 ° C., the latex concentration after concentration is 48% by weight, 53% by weight,
The permeation flux at 60% by weight and 68% by weight was 40 liter / m ² / hr, 40 liter / m ² / hr,
^{They were} 5 l / m ² / hr and 30 l / m ² / hr. Example 6 A concentration test was performed using an apparatus in which a nanofilter [NaCl rejection: 75%] was attached to a vibrating membrane separator [VSEP Series L, Shinko Pantech Co., Ltd., membrane area: 0.045 m ² ]. . Using vinyl chloride polymer latex B, torsional vibration frequency 60 Hz, torsional vibration angle 8.0 degrees,
The latex temperature was 35 ° C., the operating pressure was 3 kg / cm ² G, and the solid content concentration of the latex after concentration was 55% by weight. The permeate flux was 30 l / m ² / hr and the evaporation residue of the permeate was 130 mg / l. Example 7 A concentration test of a vinyl chloride polymer latex B was carried out in the same manner as in Example 6, except that the separation membrane was a reverse osmosis membrane [NaCl rejection 97%]. 20 liter / m permeate flux
² / hr, and the evaporation residue of the permeate was 100 mg / l. Comparative Example 4 A concentration test of vinyl chloride polymer latex B was performed in the same manner as in Example 6, except that no torsional vibration was applied to the separation membrane. The permeate flux was 7 liters / m ² / hr, and the evaporation residue of the permeate was 390 mg / liter. Comparative Example 5 A concentration test of a vinyl chloride polymer latex B was performed in the same manner as in Example 7, except that no torsional vibration was applied to the separation membrane. The permeate flux was 4 l / m ² / hr and the residue of evaporation of the permeate was 250 mg / l. Comparative Example 6 A concentration test of vinyl chloride polymer latex B was performed in the same manner as in Example 6, except that the separation membrane was an ultrafiltration membrane [fraction molecular weight: 13,000]. The permeate flux was 50 l / m ² / hr, and the evaporation residue of the permeate was 920 mg / l. Comparative Example 7 A concentration test of vinyl chloride polymer latex B was performed in the same manner as in Comparative Example 6, except that no torsional vibration was applied to the separation membrane. The permeate flux was 30 l / m ² / hr, and the evaporation residue of the permeate was 1,550 mg / l. The results of Examples 6 to 7 and Comparative Examples 4 to 7 are collectively shown in Table 1.

[0016]

[Table 1]

As shown in Table 1, even when a nanofilter or a reverse osmosis membrane is used as a separation membrane, a permeation flux equivalent to that of a conventional method using an ultrafiltration membrane without vibration can be obtained.
In addition, when a nanofilter or a reverse osmosis membrane is used, as seen from the small amount of the evaporation residue in the permeate, there is little escape of auxiliary materials such as emulsifiers in the latex, and the stability of the latex is maintained. Thus, high concentration can be performed. This can prevent fluctuations in properties such as thermal stability and color tone of the dried polymer. Example 8 The methyl methacrylate polymer latex produced in Production Example 4 was subjected to a torsional vibration frequency of 60 Hz and a torsional vibration angle of 8.0 degrees using the same vibration type membrane separation device as in Example 1.
Assuming a latex temperature of 35 ° C. and an operating pressure of 3 kg / cm ² G,
The solid content of the latex was gradually increased from 43% by weight to 63% by weight. The permeation flux is 24 l / m ²
/ Hr, and could be concentrated to a solid concentration of 63% by weight without any problem.

[0018]

According to the method for concentrating a polymer latex of the present invention, it is possible to maintain a high permeation flux and to efficiently concentrate to a high concentration without generating aggregates and clogging a separation membrane. it can.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a solid content concentration and a permeation flux with operating pressure as a parameter.

FIG. 2 is a graph showing the relationship between operating pressure and permeation flux with the solid content concentration as a parameter.

FIG. 3 is a graph showing a relationship between an operating pressure and a permeation flux with a torsional vibration angle as a parameter.

FIG. 4 is a graph showing a relationship between a solid concentration and a permeation flux and a solid concentration and an operating pressure at a temperature of 40 ° C.

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Claims (1)

[Claims] In a method for concentrating a polymer latex using a vibrating membrane separation device, a torsional vibration frequency of 40 to 8 is used.
The separation membrane of the apparatus is vibrated at 0 Hz and a torsional vibration angle of 4 to 12 degrees, the temperature is 10 to 50 ° C., and the operating pressure is ^{2 to} 15 kg / cm ² G.
A method for concentrating a polymer latex, comprising concentrating the polymer latex.