JPS6068005A - Process for treating aqueous polymer dispersion using ultrafiltration membrane - Google Patents

Abstract

PURPOSE:To perform purification of aq. polymer dispersion contg. impurities such as surface active agent, polymerization initiator, unreacted monomer, low molecular by-products, and inorganic ions, etc. by treating with ultrafiltration membrane effectively. CONSTITUTION:Separation of aq. polymer dispersion such as dispersion of vinyl polymer obtd. by polymn. or copolymn. of one or >=two kinds of monomer and having >=15mV absolute value of zeta potential measured by electrophoretic method is possible by using ultrafiltration membrane. Preferred material for the ultrafiltration membrane is one having 500-500,000 fractionated molecular weight. Suitable material for the membrane is polysulphone type polymer, cellulosic polymer such as cellulose acetate, cellulose nitrate, etc., acrylic polymer such as polyacrylate or its copolymer, aliphatic or aromatic polyamide such as nylon, and polyimide type polymer, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of ultraf membrane treatment of an aqueous polymer emulsion. More specifically, a method for efficiently purifying or concentrating an aqueous polymer emulsion containing impurities such as surfactants, polymerization initiators, unreacted monomers, low-molecular by-products, and inorganic ions using an ultraf membrane treatment method. It is related to.

Aqueous polymer emulsions are generally used to impart binder or coating functions to various fields such as adhesives, paints, leather processing, fiber processing, paper processing, binder information recording paper for civil engineering and construction materials, and antistatic properties. Since such aqueous polymer emulsions contain surfactants, polymerization initiators, unreacted monomers, low-molecular by-products, inorganic ions, etc., they may cause problems in terms of odor and wandering, or may affect film performance, e.g. There are many cases where the water resistance is poor and the commercial value is lost. Methods for removing the above-mentioned impurities from the aqueous polymer emulsion include (1) a method using an ion exchange resin, (2) a dialysis method, and (3) a method using a microfilter or ultraf membrane.

However, in method 1 above, in addition to not being able to remove the neutral molecular force, it takes too much time and effort to regenerate the ion exchange resin.

The second method is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-30705, but it is time-consuming and inefficient because it relies entirely on the diffusion phenomenon as its basic principle.

In addition, the above method 3 has drawbacks such as a significant decrease in water permeation rate due to conventional concentration polarization, and in the worst case (a resin film is formed on the membrane surface and the water permeation rate is lost). Not widely used industrially 0 In order to avoid these drawbacks, in JP-A-52-96650, a protective colloid with a molecular weight larger than the molecular weight cut-off was added by concentration by ultraf filtration, and in JP-A-52-96650 147
In No. 649, the surfactant concentration j is added. Furthermore, in JP-A-50-123743, the water permeation rate was restored by solvent cleaning.

However, these methods are unfavorable from the viewpoint of toxicity, safety and hygiene, and economics because they involve a decrease in the water resistance of the film due to the presence of preserved colloids and surface activity, and consume a large amount of cleaning solvent.

As a result of intensive research, the present inventors have invented and completed a method for efficiently treating an aqueous polymer emulsion with an ultrafiltration membrane using a new treatment method.

That is, the present invention has the following features: 1. The absolute value of zeta potential measured by electrophoresis is l.
1. A method for treating an aqueous polymer emulsion with an ultrafiltration membrane, which comprises treating an aqueous polymer emulsion with a particle size of 5 m y or more using an ultraf filtration membrane.

2. The method according to claim 1, wherein the aqueous polymer emulsion is a vinyl polymer emulsion. 3. The ultrafiltration membrane is determined using a standard protein at a concentration of 100 in a neutral buffer solution. 2. The method according to claim 1, wherein the fractional molecular weight is between 500 and 500,000.

It is.

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

Polymer emulsions that can be applied to the method of the present invention are vinyl polymer emulsions obtained by copolymerizing one or more monomers listed below, and are generally used in adhesives, paints, and leather processing. It includes aqueous polymer emulsions that are used in various fields such as fiber processing, paper processing, civil engineering and construction materials, information recording paper, and antistatic, and have an absolute value of zeta potential of 15 mV or more as measured by electrophoresis. Specific examples of vinyl monomers include (11) Styrenes such as styrene, divinylbenzene, methylstyrene, chloromethylstyrene, etc.

(2) Vinyl acetate, ethylene, vinyl chloride, acrylonitrile, methacrylonitrile, chloroprene, isoprene, butadiene, vinylidene chloride, etc.

(3) Acrylic acid esters, such as methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, and glycidyl acrylate.

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

(5) Amides For example, acrylic acid amide, methacrylic acid amide, etc. 0 (6) Containing a hydroxyl group, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl meccrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, etc. 0 (carboxylic acid, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid,
such as fumaric acid.

On the other hand, since the particle size of a normal polymer emulsion is 0.01 to 5μ, any ultrafon membrane can be used as the ultrafine membrane to be applied to the present invention. ~500,000 is preferred. Ultrafiltration membrane materials that can have such performance include polysulfone polymers,
Cellulose polymers such as acetic acid cotton and nitrified cotton, acrylic polymers such as acrylic esters and their copolymers, aliphatic and aromatic polyamides such as nylon, polyimide polymers, acrylonitrile polymers, polyester polymers Examples include, but are not limited to, molecules, polyolefin-based polymers, polycarbonates, polyphenylene oxides, and modified water-soluble polymers (copolymers and crosslinked products).

The present invention is as described above, and the absolute value of zeta potential measured by electrophoresis is 15 mv or more, preferably lo
By ultrafiltration membrane treatment of aqueous polymer emulsions up to A molecular emulsion is obtained, and the emulsion film has excellent water resistance. In addition, it does not require special operations such as solvent cleaning or addition of surfactants, and is therefore economical, and there is no risk of toxicity or quality deterioration due to contamination with solvents or surfactants, and no health and safety issues. It is.

Surprisingly, the aqueous polymer emulsion purified by the present invention did not show any change in properties for a long period of time after purification. Also, the aqueous polymer emulsion purified by the present invention can be used, for example, in paper processing. It has remarkable effects such as reducing odor and improving adhesive strength when used as a photographic mordant, improving photographic performance when used as a photographic mordant, and improving the water resistance of films when used in adhesives and paints. The industrial utility value of the method of the present invention is enormous.

Furthermore, this method is not limited to mere purification, but can also be applied to concentration by ultraf-permeability of polymer emulsions, which has been considered difficult in the past, and efficient concentration can be achieved.

The present invention will be explained in more detail below with reference to Examples.

The water permeation rate is calculated by the formula Amount of permeated water (f7!”) It is defined as effective membrane area (fi2) x permeation time (days).

Further, the residual monomer was measured by gas chromatography under the following conditions.

Gas chromatography conditions equipment Takashi GC-4CPT column 20% FFAP/Crossorp 1016
0 mesh - 80 mesh 4m sedge x 2frL glass column temperature 80→200'C (heating rate 10°C/-j) Inlet temperature 150°C Detector temperature 250°C Flow rate 6 parts ml/mis (He) injection amount 10 ~
15μ! Internal label Dioxane sample 1 m of mixed solution of 1 g of dioxane and 100 d of water
About 2 g of emulsion and 4 tnl of water are added to 1. Parts and % are based on weight.

Example 1 Preparation of polymer emulsion and ultrafiltration treatment, 7 ml of water was placed in a polymerization tank equipped with a reflux condenser thermometer, a stirrer, and a dropping funnel.
3.4 parts of sodium polyoxyethylene alkyl sulfonate, 2 parts of sodium polyoxyethylene alkyl sulfonate, and 0.1 part of styrene were added, and then 0.5 part of a 2% aqueous solution of potassium persulfate as a polymerization initiator was added at about 60°C, and the mixture was stirred. Initial polymerization was carried out for 1 hour, and a mixed solution of 12 parts of a 2% potassium persulfate aqueous solution, 5 parts of chloromethylstyrene, 3 parts of styrene, and 1 part of divinylbenzene was added over 4 hours while stirring and maintaining the liquid temperature at 60°C. It was added dropwise to perform emulsion polymerization.

After the dropwise addition was completed, 3 parts of N-methylpiperidine as a neutralizing agent was added at 30°C, and the mixture was heated at 70°C for 1 hour to give a solid content of 13.5%, p.
A polymer emulsion of H7,7 was obtained. ◇To 100 parts of this polymer emulsion, a mixture of 0.3 parts of sodium bicarbonate and 12.5 parts of deionized water was added to pre-treat, resulting in a solid content of 10% and a pH of 7. ,01 Electrical conductivity 9.800 μ73/
art, residual amine 212%/polymer g1 chloride ion 3
．． 0X10 bow equivalent/polymer g1 sodium ion 47
A polymer emulsion with 0 PFD, 490 pJ of potassium ions, 0.5% ash, and 40% styrene was obtained.

This emulsion was diluted with commercially available purified water to a solid content of 1 to 5. This dilute aqueous solution (electrical conductivity 3-8μU/
cm ) using an electrophoretic zeta potential measuring device (lasersee model soo, manufactured by PEN KEM), the zeta potential was +3.5.cm at 20°C.
It was 9 mv.

A 16ky polymer emulsion with a solid content of 10% was filtered using a tube type ultrafiltration device using an acrylonitrile ultrafiltration membrane (DUY-L membrane manufactured by Daicel Chemical Industries, Ltd.) with a molecular weight cutoff of 40,000 kg/cli. The treatment was carried out by adding the same amount of ion-exchanged water as the permeate while increasing the pressure and ultrafiltering.The average water permeation rate was 0.23ff13/ff12 days, and the treatment was completed 6 hours after the start of operation. The resulting polymer emulsion had a solid content of 9%, pH 7.6, electrical conductivity 651) t7J/am, no residual amines detected, chlorine ions 2.0 x 10-3 equivalents/polymer I, sodium ions 23 reviews, potassium ions 6PPIIl. , ash content 0.0
2%, no styrene was detected (GC method), indicating that the purity of the polymer emulsion was extremely excellent.

Reference example 1゜(1) 48.8 parts of water (2+ polyoxyethylene nonylphenyl ether
2.0 (added 15 moles of polyoxyethylene) (3) Styrene 46.0 (4) Methacrylic acid 3.0 (5) Catalyst (ammonium persulfate) 0.2100 parts Mix (1) and (2) in a polymerization can Then, a mixture of (3) and (4) and (5) were added separately at 80°C over 3 hours, emulsion polymerized, and ammonia neutralized to give a solid content of 49%, a viscosity of 50 cps, and a pH of 8.4. Obtained.

Reference example 2゜ (1) Water 13.38 parts (2) Polyoxyethylene lauryl ether sodium sulfate 2.0 (3) Styrene 2.4 parts (4) Methyl methacrylate 1.0 (5) Acrylic acid 0.1 (6) Catalyst (potassium persulfate) 0.02 (power water 4
5.0 (8) Polyoxyene 7-tyrene lauryl 5.2 Sodium ether sulfate (9) Styrene 21.0 (ICI) Methyl methacrylate/I/ 9.00υ Acrylic acid 07 (12) Catalyst (potassium persulfate) 0.2 ioo , Add (1) to (5) to o part polymerization can, mix and heat (6) at 75°C.
(7) αD and a2 at about 83°C for 3 hours.
were added separately, emulsion polymerization was performed, and ammonia neutralization was performed to obtain I) H8.0 with a solid content of 36% and a viscosity of 80 cps.

Examples 2 to 3 The various emulsions produced in Reference Examples 1 and 2 were diluted with ion-exchanged water to a solid content of 5%, and Daicel Chemical Industry ■
The produced acrylonitrile ultrafiltration membrane DUY-L was subjected to ultrafiltration using a batch type electromagnetic stirring type flat membrane measuring device under a pressure of 5 kg/m'. The treatment was carried out while replenishing the same amount of ion-exchanged water as the amount of permeated water for each batch. The properties of various emulsions before and after membrane treatment are shown in Table 1.

In Table 1, the water extractable content is the water extractable content of a film made from an emulsion with a depth of 5%, and the measurement method is JISK6.
828.

In addition, the water permeation rate is the initial performance of each batch. In both cases, a high water permeation rate is maintained, and even though the amount of ion-exchanged water supplied is only about 1.5 to 2 times the amount of preparation,
The water extractable content was significantly reduced, and in a water drop test of the film according to JIS K6828, all purified products showed water resistance of 60 minutes or more. Therefore, the ultrafiltration membrane treatment significantly improved the water resistance of the film. Furthermore, the residual monomer content was 0.01% or less in all refined products.

Example 4 The emulsion after ultrafiltration in Example 2 was further subjected to ultrafiltration membrane treatment following Example 2 under the same conditions as Example 2, except that ion exchange water was not replenished. Efficient concentration could be performed at an average water permeation rate of 1.52 m37 in for 2 days. The resulting emulsion had a solid content of 14.4%, an electrical conductivity of 4B2 μU/am, and a water extractable content of 0.26'X, and the water resistance of the film was significantly improved.

Comparative Example 1゜(1) Water 49.9 parts (21m portion) Saponified polyvinyl alcohol 2(3) Polyethylene glycol alkyl ether 50(4) Vinyl acetate/l/4.5 (5) Catalyst (ammonium persulfate) OlIQO, 0 parts Dissolve the above (1) and (2) at 75°C for 1 hour in a polymerization can,
Add (3), heat at 80℃ for 3 hours, add (4) and (5), emulsion polymerize, solid content 49%, viscosity 12000cp
gpH 5.0 was obtained. This emulsion diluted to about 5% with ion-exchanged water had a solid content of 4.9%, a water extractable content of 099%, and an electrical conductivity of 421 μU/cIrL. Further, the zeta potential measured in the same manner as in Example 1 was -12.9 mV (calculated at 20°C)◇An attempt was made to treat this with an ultrafiltration membrane in the same manner as in Example 2. The water permeation rate at the beginning was O, 15 m37 m2 days, but the water permeation rate decreased significantly during treatment and when the total water permeation amount reached about half of the amount of the preparation, the water permeation rate virtually disappeared and purification was not possible.

patent applicant Daicel Chemical Industries, Ltd.

Claims (3)

[Claims] (1) The absolute value of zeta potential measured by electrophoresis is 1
Ultra-r of aqueous polymer emulsion characterized by ultra-f membrane treatment of aqueous polymer emulsion of 5mv or more
Transmembrane treatment method. (2) The method according to claim 1, wherein the aqueous polymer emulsion is a vinyl polymer emulsion. (3) Claim 1, characterized in that the ultrafiltration membrane has a molecular weight cutoff between 500 and 500,000, determined using a standard protein at a concentration of 100F in a neutral buffer solution.
The method described in section.