JPS6038004A - Treatment of aqueous polymer emulsion by ultrafiltration membrane - Google Patents

Abstract

PURPOSE:To achieve the efficient removal of a surfactant, a polymerization initiator, an unreacted monomer, a low-molecular byproduct and an inorg. ion, by performing the treatment of an ultrafiltration membrane by using an aqueous polymer emulsion of which the coefficient of variation in its particle size is a specific value or less. CONSTITUTION:An aqueous polymer emulsion, of which the coefficient of variation in its particle size is about 23% or less, is treated by an ultrafiltration membrane. This coefficient of variation is calculated on the basis of formula sigmaN-1/dX100 after the particle diameter (d) of the aqueous polymer emulsion is practically measured with respect to N-numbers of particles from the photograph of said emulsion by an electronic microscope and the average value (d) and reference deviation sigmaN-1 thereof are calculated. In this case, a vinyl polymer emulsion, which is obtained by copolymerizing two or more of vinyl monomers, is used. The fractionation M.W. of the ultrafiltration membrane is pref. 500-500,000.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating an aqueous polymer emulsion with an ultrafiltration membrane.
This article relates to a method for efficiently purifying and concentrating aqueous polymer emulsions containing impurities such as polymerization initiators, unreacted monomers, low-molecular by-products, and inorganic ions using an ultrafiltration membrane treatment method. be.

Aqueous polymer emulsions are generally used to provide binder or coating functions to various fields such as adhesives, paints, leather processing, fiber processing, paper processing, civil engineering and construction materials, information recording paper, and antistatic properties. . Such aqueous polymer emulsions are generally produced from monomers by emulsion polymerization, but the emulsions after production contain impurities such as surfactants, polymerization initiators, unreacted monomers, low-molecular byproducts, and In many cases, the film contains inorganic ions and the like, resulting in bad odor and poor film performance, such as poor water resistance, which impairs commercial value.

Methods for removing the above-mentioned impurities from aqueous polymer emulsions include 1, a method using an ion exchange resin, 2 a dialysis method, 3 a method using a microfilter or an ultrafiltration membrane, but the method 1 above does not remove neutral molecules. Moreover, it takes too much time and effort to regenerate the ion exchange resin.

In the method 2 mentioned above, for example, Japanese Patent Application Laid-Open No. 57-30705 utilizes a diffusion phenomenon as the basic principle, which requires time and is inefficient. In addition, method 3 has conventional drawbacks such as a significant drop in water permeation rate due to concentration polarization, and in the worst case, a resin film is formed on the membrane surface and the water permeation rate is lost, so it has not been widely used industrially. do not have. In order to avoid these drawbacks, JP-A No. 52-96650 discloses the method of adding a protective colloid with a molecular weight larger than the cut-off molecular weight through concentration using an ultrafiltration membrane, and JP-A No. 52-147649 discloses the method of adding a protective colloid with a cina molecular weight larger than the cut-off molecular weight. The water permeation rate is restored by adding an activator or, in Japanese Patent Application Laid-open No. 123743/1983, by washing with a solvent. However, these methods involve a decrease in the protective colloid properties, such as a decrease in the water resistance of the film, and they also consume large amounts of cleaning solvent.
It is not favorable in terms of toxicity, health and safety, and economically.

In order to improve the above-mentioned drawbacks, the present inventors conducted intensive research and found that the problem could be solved by ultra-f membrane treatment using a specific aqueous polymer emulsion, thereby completing the present invention.

That is, the present invention has the following features: 1. The coefficient of variation of the particle diameter expressed by the following formula A is approximately 23%.
4. The following aqueous polymer emulsion is subjected to ultraf membrane treatment. A method for treating aqueous polymer emulsilon using an ultraf membrane.

A formula Two coefficient of variation of particle diameter = (F, -, /etX10
o(qQ, where σN-1 represents the average value and standard deviation value of the particle diameters of N particles obtained by actually measuring an aqueous polymer emulsion using an electron microscope photograph.

2. The ultra-f membrane treatment method for an aqueous polymer emulsion according to claim 1, wherein the aqueous polymer emulsion is a vinyl polymer emulsion.

3. The ultrafiltration membrane treatment method for an aqueous polymer emulsion as set forth in claim 1r, characterized in that the ultrafiltration membrane has a molecular weight cut-off of between 500,000 and 500,000.

It is. The method of the present invention will be explained in detail below.

The coefficient of variation of the particle size of the aqueous polymer emulsion applicable to the method of the present invention is about 23% or less.

Furthermore, one type of vinyl monomer listed below is a vinyl polymer emulsion obtained by copolymerizing two or more types. Specific examples of vinyl monomers include: (1) Styrenes such as styrene, divinylbenzene,
Methylstyrene, chloromethylstyrene, etc. (2) Vinyl acetate, ethylene, vinyl chloride, acrylonitrile,
Methacrylonitrile, chloroprene, isoprene, butadiene, vinylidene chloride, etc.

(3) Acrylic esters such as methyl acrylate.

Ethyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, etc.

(4) Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, glycidyl methacrylate, and the like.

(5) Amides, such as acrylic amide and methacrylic amide.

(6) Containing a hydroxyl group, such as 2-hydroxyethyl acrylate, methacrylate'rt12-hydroxyethyl,
2-hydroxypropyl acrylate, 2-methacrylate
such as hydroxypropyl.

(7) Carboxyl group-containing compounds such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid.

Further, it is necessary that the coefficient of variation of the particle diameter of the aqueous polymer emulsion obtained by copolymerizing one or more of the above-mentioned monomers is about 23 inches or less. If this coefficient of variation exceeds about 23 inches, the water permeation rate of the emulsion will drop significantly, for example, at a concentration of 5% by weight, the water permeation rate will become less than about 0.2r11/'8, which is undesirable.

This coefficient of variation is determined by measuring the particle diameter d of N particles from an electron micrograph of an aqueous polymer emulsion, calculating the average value d and standard deviation value cIM-1, and using the formula σN-
+ /cl x 100 (%J).

In addition, aqueous polymer emulsions are prepared using ordinary surfactants such as anionic surfactants such as alkylbenzene sulfonates, fatty acid salts, higher alcohol sulfates, alkylnaphthalene sulfonates, alkyl phosphates, and alkylphenyl polyoxyethylene sulfates. salt etc. Nonionic surfactants specifically used include polyoxyethylene alkyl ester, polyoxyethylene alkyl ether, and polyoxyethylene alkylphenyl ether.

Potassium persulfate, ammonium persulfate, etc. are usually used as the polymerization initiator.

Further, since the ultrafiltration membrane applied to the present invention has a typical aqueous polymer emulsion particle size of 0.01 to 5μ, all ultrafiltration membranes are applicable, but in particular, the molecular weight cutoff is 500 to 500μ.
500,000 is preferable. The molecular weight fraction was determined using a standard protein at xooppm # degree in a neutral buffer solution. In addition, ultraf membrane materials having the above-mentioned performance include polysalvon polymers, acetic acid cotton, cellulose polymers such as nitrified ISFT, acrylic polymers such as acrylic acid ester copolymers, and aliphatic or aromatic polyamides. , polyimide polymers, acrylonitrile polymers, polyester polymers, polyolefin polymers, polycarbonates, polyphenylene oxides, modified water-soluble polymers such as graft copolymers, crosslinked products, etc. It is not limited to these.

In the present invention, surfactants, polymerization initiators, unreacted monomers, low-molecular by-products, and
Inorganic ions are removed extremely efficiently, a highly pure aqueous polymer emulsion is obtained, and the water resistance of the emulsion film is improved. Furthermore, since special operations such as solvent washing and addition of surfactants are not required, there is no deterioration in the quality of the emulsion due to these contaminations, and there are no toxicity or health and safety problems, and it is also economical.

Further, the aqueous polymer emulsion purified according to the present invention showed no change in product performance for a long period of time, for example, 4 parts and 6 months, even after % purification.

In addition, the aqueous polymer emulsion purified by the present invention can be used in general fields such as adhesives, paints, leather processing, W2 fiber processing, paper processing, civil engineering and construction materials, information recording paper, and prevention of static 1. Particularly noticeable in paper processing is the reduction of odor and improvement in adhesive strength by removing unreacted monomers, the improvement in photographic performance in photocoat dyes, and the improvement in the aqueous property of films in adhesives and paints. It shows effectiveness. The method of the present invention includes:
The present invention can be applied not only to purification but also to the concentration of polymer emulsions by the ultra-laminar extraction method, which has been considered difficult in the past, and allows efficient concentration to be achieved.

In the following, the present invention will be described in more detail by way of examples. 73.4 parts of water, 2 parts of sodium polyoxyethylene alkyl sulfonate, and 0.1 part of styrene were charged, and then about 6 parts of a 2% aqueous solution of potassium persulfate as a polymerization initiator was added.
The mixture was added at 0°C and initial polymerization was carried out for 1 hour while stirring, and while stirring was continued to maintain the liquid temperature at 60°C, 12 parts of a 2% potassium persulfate aqueous solution, 5 parts of chloromethylstyrene, and 3 parts of styrene were added at 0°C. A mixed solution of 1 part of divinylbenzene was added dropwise over 4 hours to carry out emulsion polymerization. After completing the dropping, remove the neutralizing agent with N at 30°C.
73 parts of -methylbiperidine were added and heated for 70'CI hours to obtain a polymer emulsion with a solid content of 13.5% and a pH of 7.7. This polymer emulsion lo.

0.3 parts of sodium bicarbonate and 12.5 parts of deionized water
The solid content was 10%, the coefficient of variation of the particle diameter was 17.5%, the pH was 7.0, and the mixture was pretreated. x-, -1
')-+t high molecular weight polymer t1 chloride ion 3. OX1
0-8 equivalent i:/high molecular polymer f, sodium ion 47
0 ppm, potassium ion 490 ppm, ash 0.
A polymer emulsion containing 5% styrene and 40 ppm (GC method) was obtained. This latex 16 ~ was passed through a tube-type ultrafiltration device using an acrylonitrile-based ultraf filtration membrane (DUY-L membrane manufactured by Daicel Chemical Industries, Ltd.) with a molecular weight cutoff of 40,000 for 3 hours.
The treatment was carried out by applying a pressure of /cr&, ultrafiltering, and adding the same amount of ion-exchanged water as the permeate. The average water permeation rate is 0.23 m''/m', and the operation will start in 1 day)
Treatment was terminated in the 6 hour layer. The obtained polymer emulsion had a solid content of 9%, a pH of 7,e, and an electrical conductivity of 651μ'.
a/cm, no residual amine detected, chlorine ions 2. ．． 0X
IF8 Tosaku/High molecular polymer, sodium ion 23pp
It was found that the purity of the polymer emulsilon was extremely excellent, with potassium ions of 6 ppm, ash content of 0.02 mm, and no styrene detected (GC method).

Production Example 1 In a polymerization can, 48.8 parts of water and 2 parts of polyoxyethylene nonylfer ether (15 moles of added polyoxyethylene) were added.
A mixture of 46 parts of styrene and 3 parts of methacrylic acid and 0.2 parts of ammonium persulfate were added separately to this mixture.
The mixture was added over a period of 2.3 hours at 0° C., and an emulsion polymerization layer was formed, and ammonia was neutralized to obtain a polymer emulsion having a solid content of 49%, a viscosity of 50 cps, and a pH of 8.4.

Production Example 2 In a polymerization can, 13.38 parts of water, 2 parts of polyoxyethylene lauryl ether sodium sulfate, 2.4 parts of styrene, 1 part of methyl methacrylate, and 0.1 part of acrylic acid were mixed and heated at 75°C to produce 0 potassium persulfate. Add 0.02 parts, to this 45 parts of water,
Polyoxyethylene lauryl ether sodium sulfate 5.2
A mixture of 21 parts of styrene, 9 parts of methyl methacrylate, 0.7 parts of acrylic acid, and 0.2 parts of potassium persulfate were separately added at 80°C over 3 hours to conduct emulsion polymerization and neutralize ammonia to form a solid. Minute 36 cm, viscosity 80 cps,
A polymer emulsion with a pH of 8.0 was obtained.

Examples 2 to 3 The polymer emulsions obtained in Production Examples 1 and 2 above were diluted with ion-exchanged water to a solid content of 5% by weight, and an acrylonitrile-based ultra-e-filter membrane DUY- manufactured by Daicel Chemical Industries, Ltd.
All samples were treated by ultrafiltration under a pressure of 5 Kr/crl using a batch-type electromagnetic stirring Nipei membrane measuring device using an L membrane.

This treatment was carried out while supplementing each batch with the same amount of ion-exchanged water as the amount of permeated water.

The properties of the shoulder of the polymer emulsion before membrane treatment are shown in Table 1.

In Table 1, the water extractables are the water extractables of a film prepared from an emulsion with a concentration of 5% by weight, and the measurement method is in accordance with JIS K6828. Also, the water permeation rate is the initial performance of each batch. In both cases, a high water permeation rate is maintained, and although the amount of ion-exchanged water supplied is only about 1.5 to 2 times that of the prepared elm, the amount of water extracted is significantly reduced. In the test, all purified products showed 6
It showed water resistance of 0 minutes or more. Therefore, the water resistance of the film was significantly improved by the ultra-t coating treatment. Further, the amount of unreacted monomer measured by gas chromatography under the following conditions was 0.01% or less in all purified products.

Moreover, the gas chromatography conditions are as follows.

Equipment Shimadzu GC-4CPT Column 2 parts% FFAP/Chromosolve 10160
Mesh ~ 80 mesh, 4 x 2m glass column Temperature: 80 → 200℃ Temperature ramp type (10℃/min) Inlet temperature: 150℃ Detector temperature: 250℃ Flow rate: 1 (e60/-) Injection volume JO ~ 15μ! Internal standard Dioxane sample Mixed solution 11 of dioxane 1f and water 100-
nt plus about 2 tons of emulsilon and 4 fnt of water.

Example 4 Emulsilon of the ultrafiltration membrane of Example 2 was further subjected to ultraf filtration treatment under the same conditions as Example 2 except that ion exchange water was not replenished. Water permeation rate was 1.527 n''/71'l'', and efficient concentration could be performed in days. The solid content of the emulsilon thus obtained was 1.4.4%, and the electrical conductivity was 482μυ/
The water extractable content of the film was 0.26%, and the water resistance of the film was significantly improved.

Comparative Example 1 49 parts of water and 2 parts of partially saponified poval were mixed in 75 parts in a polymerization mill.
℃ for 1 hour, 5 parts of polyethylene glycol alkyl ether was added thereto, and 45 parts of vinyl acetate and 0.1 part of ammonium persulfate were added at 80℃ for 3 hours to carry out emulsion polymerization to reduce the solid content. 49%, viscosity 12,000
cps, PH 5,'' vinyl acetate f (obtained from a coalesced emulsion. This 17/l/l) diluted with ion-exchanged water to approximately 5 ml has a coefficient of variation in particle diameter of 24.4%,
Solid content 4.9%, water extractable content 0.99%, electrical conductivity summer 42
It was 1 μU/ctn.

When this was subjected to ultrafiltration membrane treatment in the same manner as in Example 2, the water permeation rate at the start was 0.15 m''/m'', but the water permeation rate decreased significantly during the treatment. When the total amount of water permeation reaches a certain level, the water permeation rate virtually disappears,
The emulsion was not refined.

patent applicant Daicel Chemical Industries, Ltd.

Claims (1)

[Claims] 1. The coefficient of variation of the particle diameter expressed by the following formula A is approximately 23%.
A method for ultra-e membrane treatment of an aqueous polymer emulsion characterized by subjecting an aqueous polymer emulsion to the following ultra-e membrane treatment Formula A Two Coefficient of variation of particle diameter = σN-1/τX100 (%
1 However, d and σH−r represent the average value and standard deviation value of particle diameters of N particles obtained by actually measuring an aqueous polymer emulsion using an electron microscope photograph. 2. The ultra i5 membrane treatment method for an aqueous polymer emulsion according to claim 1, wherein the aqueous polymer emulsion is a vinyl polymer emulsilon. 3. Fraction of the ultra-f membrane - The molecular weight of claim 11, 1P ##, 7-N Kakie day-half emul, di, characterized in that the molecular weight is between 500,000 and 500,000. (-Membrane treatment method.