JPS58170502A - Removal of contaminant of membrane - Google Patents

Abstract

PURPOSE:To restore the membrane capacity well, by contacting a permeable membrane used in membrane separation of an anionic electrodeposition paint containing liquid with a mixed liquid having a specific component. CONSTITUTION:A contaminated permeable membrane used in recovering an anionic electrodeposition paint is contacted with a mixed liquid consisting of 100pt.wt. water, at least 1pt.wt., org. solvent compatible with water and capable of dissolving said paint such as butyl cellosolve or isopropyl alcohol and at least 1pt.wt. aminoalcohols such as dimethylaminoethanol to remove the contaminant adhered to the surface thereof. In this case, because a small amount of an org. solvent is contained in a permeate obtained by subjecting the anionic electrodeposition paint containing liquid to membrane separation, it is preferable from an industrial standpoint that the org. solvent and amino-alcohol are added thereto to contact the same with the contaminated membrane. By this inventive method, membrane capacity can be restored without imparting any influence to a membrane substrate or an electrodeposition painting process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing contaminants adhering to a permeable membrane used for membrane separation treatment of a liquid containing anionic electrodeposition paint.

Electrodeposition painting, which has traditionally been carried out using electrodeposition paint in automobile factories, home appliance manufacturing factories, etc., involves dipping the object in a paint bath and applying electricity to coat the surface with paint resin. After that, it is pulled up and the excess paint that has adhered to it is washed away with water.0 Since the washing water after this washing contains a large amount of paint that has a high recovery value, the permeable membrane A method is used in which water as a solvent, amines, other metal salts, metal ions, etc. are removed from the washing water using a rinsing water, valuable paint is recovered, and the obtained permeate is reused as washing water.

However, when such a permeable membrane is used for a long period of time, contaminants such as electrodeposited paint particles adhere to the membrane surface, resulting in a decrease in the amount of permeated water.
Other inconvenient problems arise, such as increased pressure loss.

In order to eliminate such inconveniences, proposals have been made to clean the membrane surface by bringing a surfactant into contact with the surface of the membrane to which contaminants have adhered, but satisfactory results have not yet been obtained.

The present invention has been made to solve the drawbacks of the prior art, and is a method for removing contaminants adhering to a permeable membrane used for membrane separation of a liquid containing anionic electrodeposition paint. , by contacting the contaminated membrane with a mixed solution consisting of 1[0 parts by weight of water, at least 1 part by weight of an organic solvent compatible with water, and at least 1 part by weight of an amino alcohol, the membrane contaminants are effectively removed. The present invention provides a method that can remove these substances.

The organic solvent used in the present invention is one that is compatible with water, dissolves the solid content of the electrodeposition paint, and does not dissolve the permeable membrane, such as propyl alcohol, methanol, ethanol, methyl cellosolve, ethyl cellosolve, Examples include butyl cellosolve, acetic acid cellosolve, acetone, etc., butyl cellosolve and/or acetone are preferred.
Or isopropyl alcohol is used.

The above-mentioned organic solvent is required to be used in an amount of at least 1 part by weight per 100 parts by weight of water, and normally 1 to 20 parts by weight is used.If the amount of the organic solvent is less than 11 parts by weight, the removal effect of membrane contaminants will not be sufficient. It is.

The amino alcohol used in the present invention has a prime number of 1 to 5.
is an aliphatic hydrocarbon group, R', R'' is H or an alkyl group having 1 to 4 carbon atoms, n and m are positive integers of 1 to 3), such as dimethyl- 1minoethanol, 2-aminoethanol, 37minopropanol, 2-aminobutan-3-ol, 2-aminobentan-4-ol, 3-nonalaminopropan-2-ol, 2-methylamino-2-methylpentanol, etc. However, dimethylaminoethanol is preferably used.The above amino alcohol is
At least 1 part by weight, usually 1 to 20 parts by weight, is practically used.

The present invention removes membrane contaminants by bringing the above-mentioned mixed solution consisting of an organic solvent, an amino alcohol, and water into contact with a contaminated membrane, and furthermore, an industrially preferred mode of use in the present invention is anionic electrocoating paint. This is a method in which an organic solvent and an amino alcohol are added to the permeate obtained by membrane separation of the contained liquid, and the mixture is brought into contact with a contaminated membrane. This is because the permeate obtained by membrane separation of a liquid containing anionic electrodeposition paint contains a small amount of an organic solvent such as butyl cellosolve or isopropyl alcohol.

As described above, according to the present invention, membrane contaminants are removed by bringing a mixed solution consisting of water, an organic solvent, and an amino alcohol into contact with the contaminated membrane. Membrane performance degraded by -2 due to contaminants can be recovered to a high degree without any adverse effects.

Hereinafter, the present invention will be specifically explained using Examples and Comparative Examples.

Example 1 In an electrocoating paint recovery system, as a tubular module, ultra-f ultra-module NTU-2020- manufactured by Tokyo Denko Corporation was used.
M4 (1 (area 0.39'77k, fractionated molecule lid 200
Using 80 bottles of 00), an oil-modified alkyd resin-containing liquid (solid content 10% by weight) was membrane-separated for half a year at a pressure of 5 kg/c#/ and a liquid temperature of 30°C as an anionic electrodeposition paint-containing liquid. Processed. The amount of permeated water obtained at the time of keratin was at the initial stage (
During the first day), it was 16 tn and -7, but after half a year of treatment it was 10'/min, which was 63% of the initial rate.

In order to wash the permeable membrane in this state, butyl cellosolve and dimethylaminoethanol were added to the obtained permeate so that the concentration of each was 15% by weight, and the liquid was mixed under the conditions of pressure 4 and 9/Qwt. The membrane was cleaned by circulating the membrane for 1 hour, and the permeated water recovery rate was 971, indicating that the membrane performance was well recovered.

The permeated water recovery rate is defined by the following formula. When the membrane was cleaned in the same manner as in Example 1 except for the above, the permeated water recovery rate was 92 cm.
, 〇 Example 3 The contaminated membrane before cleaning in Example 1 was prepared in the same manner as in Example 1, except that the concentration of butyl cellosolve in the permeate was 5% by weight and the concentration of dimethylamine ethanol was 5% by weight.
When the membrane was washed, the permeate water recovery rate was 80 cm.

Comparative Example 1 The contaminated membrane before cleaning in Example 1 was cleaned in the same manner as in Example 1 except that butyl cellosolve was not added to the permeate and the dimethylamine ethanol concentration was 10% by weight. The recovery rate was 72.

Comparative Example 2 The contaminated membrane in Example 1 before cleaning was washed in the same manner as in Example 1 except that dimethylaminoethanol was not added to the permeate and the butyl cellosolve concentration was 1O w/f%. The water recovery rate is 70%, and the patent applicant: Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] When removing contaminants adhering to a permeable membrane used for membrane separation treatment of a solution containing anionic electrodeposition paint, add 100 parts by weight of water and at least 1 part of an organic solvent compatible with water to the contaminated membrane.
Membrane contaminant removal method 0 characterized by contacting a mixed solution consisting of at least 1 part by weight and amino alcohol at least 1 part by weight.