CA1332329C

CA1332329C - Method for hydrophilic treatment of aluminum using an amphoteric polymer

Info

Publication number: CA1332329C
Application number: CA000555524A
Authority: CA
Inventors: Ryosuke Sako; Takao Ogino; Motoki Kanazawa; Akira Nishihara; Hiroshi Okita; Yoshinori Sakamoto
Original assignee: Nihon Parkerizing Co Ltd
Current assignee: Nihon Parkerizing Co Ltd
Priority date: 1986-12-29
Filing date: 1987-12-29
Publication date: 1994-10-11
Anticipated expiration: 2011-10-11
Also published as: AU8299387A; EP0274738A1; US4783224A; JP2523114B2; AU588149B2; MX168763B; JPS63171684A; DE3744006A1

Abstract

ABSTRACT OF THE DISCLOSURE

A hydrophilic coating is formed on an aluminum surface by the application of an aqueous solution of an amphoteric acrylamide polymer which is dried in place. The polymer solution may contain a cross-linking agent and the dried coating may be subsequently treated to form a water-glass coating.

Description

~332~2~ ~
~EIIIOD F~R E~YDROPHILIC TREAl~E23T OF ALUMINt~M
USING AN AklPHarERIC P0~YMER

Background of the Invention -~

The present invention concerns a method for the hydrophilic treatment of an aluminum surface. More specifically, it concerns a method for hydrophilic treatment of the surface of the heat transfer ~-fins of aluminum heat exchangers.

In the past technology for the surface treatment of heat exchangers made of aluminum or aluminum alloy (hereinunder referred to as (aluminum)) for the purpose of preventing white rust develop-ment, employed anodic oxidation coating, Boehmite coating, resin treatment etc. However, the coating formed by such methods provide the surface with almost no water wettability. For the purpose of preventing white rust development, chromate conversion coating is also used in practice, which also gives water wettability but to a slight extent and only for a short period after the formation of coating. Therefore, chromating alone cannot provide sufficient hydro-philic quality. Further, a chromate conversion coating has a tendency to lose its hydrophilic property as time passes, particu-larly under heating/drying conditions. merefore, chromate coating for the surfa¢e treatment of heat-exchanger fins is not satisfactory.

It is of course, desirable that the efficiency of heat radia-tion/cooling of the heat exchanger be as high as possible. For this purpose, the radiation and cooling parts are designed to have as large a surface area as possible for the majority of cases and consequently the interfin distance is made extremely narrow. This causes atmospheric moisture to condense on the surface of the heat exchanger when used for cooling, particularly at the inteffin spaces.
Water thus condensed forms water droplets to a greater and greater extent the more hydrophobic the fin surface is. Such water droplets fill up the interfin spaces resulting in increased air flow resist-ance and the heat exchange efficiency is thereby reduced.

:: *

~L33~32~
Moreover, due to the air flow, water droplets in the interfin spaces are subject to spattering the area around the heat exchanger.

Various methods have been proposed for the purpose of preventing water droplets from forming at interfin spaces. Treatment of the surface with a silicate such as water glass is effective for improv-ing the water wettability and heat resistance with low cost, in view of which a number of methods have been proposed.

In summary, the methods hitherto used involving both inorganic and organic compounds for coating formation can be classified as follows:

a : Phosphate treated aluminum surface is processed directly with aqueous silicate coating and then dried. This method is exemplified by the Japanese Laid-Open Patent Sho 50-38645 (1975).

b : This method is exemplified by the Japanese Laid-Open Patent Sho 60-221582 (1985) which discloses that a hydrophilic inorganic coating comprising silicate, Boehmite etc. is formed on the aluminum sheet, over which a hydrophilic organic polymer having a ratio of polymerization more than 50 is coated.

c : The aluminum surface treated with an organic polymer coating is followed by silicate liquid coating and drying, one example of which is described in Japanese Laid-Open Patent Sho 59-205596 (1984) which discloses a fin material where aluminum sheet is coated with an organic resin film having corrosion resistance over which a hydrophilic coat-ing consisting of silicates such as silica sol, silicic acid and water glass is formed.

d : The aluminum surface is coated with a mixture of organic polymer and inorganic silicate. m is is exemplified by the following Laid-Open patents.

. .~.. - . ~ . .
~,."~
r~
'~

~ ~ 3~23~9 Japanese Laid-Open Patent Sho 61-8593 (1986) discloses a fin material which is coated with a mixture consisting of styrene/maleic acid copolymer, polyacrylamide, butylene/
maleic acid copolymer, polyacrylic acid or their salts and silicates as represented by xM20 ySiO~ (M = Li, Na or R, ~;
y/x ~ 2). Japanese Laid-Open Patent Sho 60-101156 (1985) discloses a chemical for forming hydrophilic coating on aluminum which contains alkali silicate and carbonyl comçounds (aldehydes, esters, amides etc.).

With regard to other conventional methods that use organic compounds for the hydrophilic treatment of aluminum, Japanese Laid-Open Patent Sho 53-205596 discloses a method of using an organic solvent. Organic compounds disclosed therein are acrylic resins, epoxy base resins, urethane base resins, vinyl type resins such as polyvinyl chloride-vinyl acetate, polyethylene, polypropylene and the like, stylol base resins, phenolic resins, fluoro-resins, silicone resins, diaryl phthalate resins, polycarbonate resins, polyamide resins, alkyd resins, polyester resins, urea melamine resins, polyacetal resins, cellulose resins etc. These compounds may be combined with an organic solvent. On the other hand, the abovementioned Laid-Cpen Sho 60-101156 describes low molecular organic compounds having the carbonyl group (e.g. glyoxal) together with a water-soluble ~rganic polymer (e.g. copolymer of acrylamide and acrylic acid~ diluted with water and used for coating aluminum followed by heating and drying.

The past technologies which use polyacrylamide as an organic compound for hydrophilic treatment have been further reviewed.
, As described in Japanese Laid-Open Patents Sho 60-101156 and Sho 61-8598, the use of a polyacrylamide as a chemical for hydrophilic treatment is known. Such cDmpound can be uniformly mixed in water when the content is low. However, with increasing concentration caused during the drying ~3~232~
process, the alkali silicate and polymer become separated into two phases, often resulting in non-reproducibility of the quality. This is a major drawback.

Japanese Laid-Open Patent Sho 60-221582 proposes a method that, over the film of a hydrophilic inorganic coating, polyacrylamide as hydrophilic organic coating former is applied wherein the degree of polymerization is adjusted so that solvent degreasing of press oil used for press working can be done with ease and the organic polymer layer remain-ing after degreasing can serve to fill pinholes of the inorganic coating. According to this patent, further, a cross-linking agent consisting of compounds of Zr, Ti etc.
can provide said polyacrylamide with cross-linking of hydrophilic group in a range that such group is not entirely all cross-linked. According to said patent, the hydrophilic coating remaining as a final coating after solvent cleaning is a layer of inorganic, hydrophilic coating obtained by silicate treatment or Boehmite treat-ment as the undermost layer.

The first category (a) of conventional methods for hydrophilic film formation, provides the coating with a hydrophilic property but not with corrosion resistance. For this reason, such coating forma-tion may lead on the contrary to degraded corrosion resistance and exhibits a disadvantage that white rust tends to occur.
~,. .
In the case of the second category (b) of conventional methods for hydrophilic treatment, the hydrophilic property is mainly given by the inorganic components such as Boehmite and silicate. m e main purpose of the organic coating is to prevent the abovementioned inorganic coating from being contaminated with press oil and thereby being made water repellent; after having performed this role, such organic coating is removed together with press oil in the subsequent ;~ degreasing stage. As a result, the performance is not satisfactory in the corrosion resistance nor in the hydrophilicity.
.

~' :

.

-` ~L3~329 :~ ~
The third category (c) is satisfactory for aorrosion resistance and for the hydrophilic performanoe during the incipient period, its disadvantage being, however, that the silicate of the top layer tends to be washed away as water condenses on the surface during operation resulting in degradation of the hydrophilic property.

In the fourth category ~d), since silicate is a~ntained in the coating it tends to be washed away and the fin treated with such method has a tendency to increasingly undergo white rusting.
Further, the drying stage may cause the silicate and the organic polymer to separate into different layers and as a result the perfor-mance beaomes variable largely depending on manufacture conditions, and in many cases the fin thereby treated exhibits insufficient hydrophilicity.

The method of Japanese Laid-Open Patent Sho 59-205596 uses an organic polymer coating having resistance to water and corrosion as the base coating. Since this method uses organic solvent in many cases, problems arise from fire hazard and environmental safety as well as from the low hydrophilicity of the thereby formed base film, which makes it difficult to use aqueous water-glass solution for forming a thin and uniform top aoat over the base ooat.

It is notable here that the method of Japanese Laid-Open Patent Sho 60-221582 where polyacrylamide etc. are also described should be regarded as equivalent to the aonventional technology classified into the first category in regard to the way of constituting the coating layer for the reason that polyacrylamide doe s no~ remain on the fin to any significant extent, meaning that no suggestion is made of using water-soluble organic polymer like polyacrylamide as a perma-, nent coa~ing of the fin.

The inventors hypothesized that a single layer of organic polymer that constitutes the coating, provided that the coating thusformed be given sufficient corrosion resistance and hydrophilicity (including durability resistance to running water) might be capable of overaoming the disadvantages mentioned in the first category.

` .

r . ~

~33232~
Further, such a layer of organic polymer as abovementioned may then be coated with a silicate film by making use of the technology as mentioned in the 2nd category. It is also possible to form an organic coating of high hydrophilicity over a double-layered structure consisting of a base coat with high corrosion resistance and a uniform top coat with sufficient hydrophilicity. In this way, exposure of a hydrophilic layer former such as silica gel and water glass can be avoided thereby minimizing tool abrasion during subse-quent working.

SummarY of the Invention The present invention is characterized in that, at least one material from (A) and (B) is selected to prepare an aqueous solution, and such a solution is applied to aluminum, and dried.

(A) : amphoteric polymer obtained by the copolymerization of monomer (I) which is represented by the empirical formula, Rl R2 CH2 = C - C - N (I) where Rl represents H or CH3 and R2 and R3 represent H, alkyl radical of Cl - C4, benzyl radical or alkanol group .; of C2 ~ C3 -together with an unsaturated cationic m~nomer (II) and an unsaturated anionic monamer (III).

(B) : amphoteric polymer obtained by the post treatment of homopolymer or copolymer of the abovementioned monomer (I).
, It may be desirable to include a water-soluble cross-link-ing agent (C) in the aqueous solution.
:

::`

t ,."~
"~

: ': " ~ .. '' ., ,,~' " . " ' In some cases, it may also be desirable to apply an aqueous water-glass solution over the above coatings and dry it to form a hydrophilic film.

Detailed Description of the Invention It is publicly-known that polymers of acrylamide (corresponding to the said general formula (I) where Rl, R2 and R3 are H) are of excellent hydrophilicity. However, such polymers having a linear structure, and being water soluble, are not suitable for forming a hydrophilic film on a heat exchanger. However, when an acrylamide is formed into an amphoteric polymer, or is cross-linked with cross-link-ing agent so as to achieve a network structure, it becomes water-insoluble and therefore usable as a coating former. Accord-ingly, the present invention can make use of a water-soluble cross-linking agent to provide the formed coating with water-insolu-lS bility. The coating remains durable without being washed away in running water and exhibits resistance to organic solvents such as ~;
trichloroethane which, dep*nding on the case, may be used in a subsequent cold working process. In order to attain such excellent performance, it is necessary to either use amphoteric polymer (A) or (B) or to uniformly mix the water soluble acrylamide polymer with a water-soluble cross-linking agent to make the cross-linking reaction proceed sufficiently.

Further, where addition of chromic acid or a dichromate is made for the purpose of providing corrosion resistance to the aluminum ~ 25 surface, the polymer produced from the abovementioned m~nomers, (I),- (II) and (III) has a sufficient mixing stability, so tbat it is ~; possible to perform chromate conversion coating simultaneously with , polymer fiIm formation. Further the two treatments can yield a synergistic effect, providing superior surface quality.

As the water-soluble cross-linking agent (C) there may be employed those based on inorganic constituents or those based on organic constituents. Of the inorganic types, metal compounds capable of forming complex compounds with polymer (A) or (B) are usable. As such compounds, those having coordination number more ~`:
~::

;~ ~3323~9 than 4 as listed in Table 1 are preferred. Amongst the compounds of Cr, Ti, Al and Zr, specifically effective are the compounds having particularly high water-solubility such as chromic acid, dichromates, di-isopropoxy-titanium-bis-acetylacetone, reaction product of lactic acid and titanium alcoholoxide, zirconyl nitrate, zirconyl acetate, zirconyl-ammonium carbonate, fluorozirconic acid and its salts and aluminum sulphate.

Table 1 Coordination 10Number __ Metal Ion 2 Cu(I) Ag(I~Hg(I) Hg(II) 4 Li(I) Ee(II)B(III) Z~(II) Cd(II) Hg(II) Al(III) Co(II) Ni(II) Cu(II) Ag(II) Au(III) Pd(II) Pt(II) 6 Ca(II) Sr(II)Ba(II) Ti(IV) V(III) V(rV) Cr(III) Mn(II) Mn(III) Fe(II) Fe(III) Co(II) Co(III) Ni(II) Pd(IV) ~-Pt(IV) Cd(II)Al(III) Sc(III) Y(III) Si(rV) Sn(II)Sn(IV) Pb(II) Pb(rV) Ru(III) Rh(III) Os(III) Ir(III) Lanthanide 8 Zr(IV) Hf(rV)Mo(rV) W(rV) ~ U(rV) Actinide :~
.
As water-soluble organic cross-linking agents, water-soluble blocked polyisocyanate and/or water-soluble compounds of poly-methylol, polyglycidyl, polyaziridyl are usable. T~ mention them inconcrete terms, they are polyisocyanate blocked with NaHS03 (e.g.
~ ELASTRON product of DAI-ICHI KOGYO SEIYAKU CO., LTD.), methylol `;~ melamine, methylol urea, methyloled polyacrylamide, diglycidyl-ether of polyethylene oxide and diaziridyl-polyethylene oxide.
i ~
Of course, combined use of organic and inorganic agents is also possible, for example, compounds of Cr, Ti, Al and Zr as inorganic water-soluble compounds and blocked polyisocyanate, polymethylol/
polyglycidyl/polyaziridyl compounds as organic water-soluble compounds.
.
* Trade mark ~ .
A

... , .. . . i ~ ~, .. .. .. ,.. ~ .~
,~
..

~33232~
The appropriate amount of cross-linking agent differs depending on the specific agent employed. It also differs depending whether the polymer is used as a thicker base coat primarily aiming at the corrosion resistance or is used as a thinner monolayer type coa~ing.
Still it may be said in ~eneral that the amount of cross-linking agent per 100 weight parts of polymer used is 1-400 weight parts, preferably 5-200 weight parts.

The amphoteric polymer which is used in the present invention has the empirical generic formula~ - (II)m - (III)n - (IV)o, in which l, m, n and o are mole % in the oopolymer, (II) is a cationic monomer, (III) is an anionic monomer, 1 ~40, m = 1 - 59, n = 1-59, 0~ o<30 and l + m + n + o = 100.

(I) is as described previously and preferably is acrylamide, ~ -methacrylamide, N-methylacrylamide, or N-dimethylacrylamide and (IV) is a nonionic monomer capable of copolymerization and examples are:
- , ~
2-hydroxy methacrylate Diacetone acrylamide Methylol acrylamide Acryloyl morpholine Acrylonitrile Methacrylic ester Styrene Vinyl acetate R
~' I
(II) has the general formula: CH2 = C
M
where M is one of the following:
0 IRa 1) - C - NH ~t-cH2)r - I - Rb x _9_ ~ .
, .
. , , : :, :, ~33232~

2) - C - O - CH2 ~ C~ - Rb ~3 3) - C - O - CH2 - I - CH2 - ~ - Rb x9 H Rc Ra 4) ~ CH2 - ~ - Rb Rc 105) ~ ~ - Ra ~a Wherein Ra~ Rb, Rc = H, alkyl, hydroxyalkyl~ phenyl, benzyl.
r = 1 to 3 ~3 = acid radical of inorganic or organic acid.
15(III) has the general formula:

Q 2 = I or its copolymer with an unsaturated N

compound having carbonic group of maleic anhydride, itaconic aFid or sulpho (phospho) group-where N is one of the following:
a) - COOH (or its salt) . `
b) - S03H (or its salt) C) ~ (or its salt) C OH
d) ~ (or its salt) ~ -10-::

-o e) - C - NH - CH2 - S03H (or its salt) Il I .
) C NH 7 CH2 ~ S03H (or ltS sa1t) CH3 ::.

CH3 H (or CH3)/ H
g) CH2 = C - COO - CH2 - CH - O - P = O
0~3 ' ..
(or its salt) The polymer post-treatment referred to in (B) may be accomp-lished as follows:

i) Conversion of amide radical to carboxyl radical by -hydrolysis.

ii) Conversion of amide radical to ' ~R4 R5 ~ :
: ~R4 by Mannich reaction with HN~
: 20 Rs and formaldehyde wherein R4, Rs are alkyl radical of C1 -; C4, alkanol group of C2 - C3 or benzyl.

iii) Introduction of - CONH - R6 ~ NH2 by the Hofmann reaction between side-chain ester radical and alkylenediamine (H2N -25 ~ R6 ~ NH2), wherein R6 is alkylene radical of C2 - C6.

iv) Conversion to quaternary amino compound, by alkylating the amino radical of the reaction product of ii) or iii).

,- ~

32~2~
The coating may be applied by dipping, spraying, brushing, roll coating, flow coating etc., adjusting the molecular weight to less than 2,000,000, preferably 1,000,000, is advisable in order to suppress stringiness of the polymer. As to the selection of the concentration and viscosity, appropriate levels are established according to the coating method to be used and the required paint film thickness. As to the film thickness for the aluminum heat .,~.....
exchanger, in order to improve the thermal efficiency and to be capable of contributing to the corrosion resistance, about 0.1 to 10 microns, preferably 0.2 to 2 microns is advisable.

As to the coating of aluminum, which has been previously degreased, either direct coating or coating after; Boehmite treat-ment, or chemical conversion treatment like chromating is available.
In the case of direct coating, however, addition of chromic acid or lS dichromate is particularly effective.

~ s to other agents such as rust preventive, filler, pigment, surface-active agent, antifoam, levelling-effective agent, antibac-terial/fungal agent etc., addition is possible to the extent that it does not imPair the performance of the coating as intended in the present invention.

As described earlier, water is used as the paint solvent, but for the purpose of accelerating the drying and improving the paint film quality, the combination use of water-soluble solvent, such as alcohol, ketone, CELLOSOLVEis also possibly available though not re~uired in the present invention.

The stability of the coating solution varies depending on the composition. Use of the amphoteric polymer in the vicinity of the isoelectric point should be avoided as the polymer undergoe s deposi-tion/separation there. In general, it is preferable for the cationic polymer to be used on the neutral - acidic side and for anionic polymer to be used on the neutral - alkaline side.

* Trade mark 3~232~

If a cross-linking agent is used, in the case metallic compound except special cclpounds such as zirconyl-ammonium carbonate, acidic side is generally preferable, while, in the case of organic cross-linking agent, the acidic side is preferable for isocyanate type, and the alkaline side for methylol, glycidyl and aziridyl types.
. .
Where a water glass solution is also applied, water glass having a SiO2/h20 ratio (M indicates Na, K or Li) of 2 to 5 is generally used, on which, however, no specific limit is placed. me concentra-tion of the aqueous silicate solution is without restriction as torange from the performance aspect of hydrophilic surface.

As to the a unt of aqueous silicate solution, it is desirable to design the process so as to form a silicate coating of 0.1 - 5Jum thickness after heating/drying. A thickness less than 0.1JIn cannot yield sufficiently durable hydrophilicity, while over 5,um often gives rise to insufficient hardening (non-water-solubilization) or development of fissures on the coating which may affect the perfor-mance of the heat exchanger. Addition of a polymer, e.g.
water-soluble acrylate, to the water glass solution is effective for preventing fissure development.

As to heating/drying of the silicate, selection should be made within the range: 100 - 250C and 20 sec. - 10 min., employing shorter time at higher temperature.
.

The present invention hais made it possible to use an amphoteric polymer for coating aluminum, since the dried film becomes water-insoluble. Further it has been made known that, besides the ; hydLu~hilicity provided by polyacrylamide, which is oommon knowledge, excellent corrosion resistance can be thereby obtained.

;In the following, the present invention is explained in more ; 30 detail by citing practical examples.

~, . .. .....

~3~232~
The test method used in the Examples is as follows:
. ~ .. .
o Contact angle A water droplet of 1-2 mm diameter was placed on a ooated surface and its contact angle was measured by face contact angle measuring apparatus, Model CA-P, product of Kyowa Kaimenkagaku Co., Ltd. Both a freshly coated surface and one subjected to marine water immersion for 1 week were tested.

o Corrosion resistance In accordance with JIS Z-2371 for salt spray test, the t~me for white rust development on 5% surfaoe area was indicated.

o Running water resistance The test piece was immersed in running water at room temperature for 8 hr. and then dried at 80C for 16 hr.
After repeating this cycle 5 times, the contact angle of water was measured, Example 1 Aluminum sheet pretreated with chromic chromate was ooated with an a~ueous solution containing 10 g/l of a polymer which was obtained by dimethyl-aminomethylation of the co-polymer of 95 mol % acrylamide and 5 l % acrylic acid to the extent of about 11%. The work was put in an electric oven of 250C and heat-dried. The ooating weight thus obtained was 0.3 g/m2.
i i Examples 2 and 3 In the same way as in Example 1 but with varied oonditions. The results are indicated in Table 3.

- ~

, ,., ~ . ~ . ; .: i. . :~ . . i ~3323`2~
~----I
~ ~ ~ ~o~

o _ ' :

, ~C~ I
e ~ O a ~ 5 11 ~

. ~ ~ ~ a ~ ~ O c ~ O ~ ~ ~ _ ~ ~

.~

~33232~

0 ~ .

~ I

, . _ .

9~ 8 N

~D 1~' 10 _ D O ~ I ~ ^
. ~: y ~ Q ~ U_ _ _ O~ ~_ ~: . ~ O
. j ~t~ ~ . : .

I ~
~ ~ -16~
''~
:::
.~ff . . ~

~ 33232~
Table 3 Contact angle (degree) Example Corrosion No. Incipient After running Resistance period _ water test(hr) 1 15 - 20 35 - 45 ~ 240 :

2 ~ 5 20 - 25 ~ 240 20 - 25 30 - 40 ~ 216 (Effect of the present invention) Coating with superior hydrophilicity and corrosion resistan oe can be obtained.

l ~
-;
~,~
.~
~;, .
:,~
~:
-~:

::

~L~

Claims

1. A method for forming a hydrophilic coating on an aluminum surface comprising contacting said surface with an aqueous solution comprising at least one polymer or copolymer selected from the group consisting of (1) an amphoteric copolymer having the empirical formula (I)l - (II)m - (III)n - (IV)o in which (I) is wherein R1 represents H or CH3 and R2 and R3 represent H, alkyl radical of C1-C4, benzyl radical or alkanol group of C2-C3 (II) is an unsaturated cationic monomer;

(III) is an unsaturated anionic monomer;

(IV) is a nonionic monomer capable of copolymerization;

and wherein l, m, n and o represent mole % and l + m +
n + o = 100 l ? 40; m = 1-59; n = 1-59 and o = 0-30 and (2) an amphoteric polymer obtained by the reaction of a homopolymer or copolymer of monomer (I) by i) Conversion of amide radical to carboxyl radical by hydrolysis.

ii) Conversion of amide radical to by Mannich reaction with and formaldehyde wherein R4, R5 are alkyl radical of C1 - C4, alkanol group of C2 - C3 or benzyl.
iii) Introduction of - CONH - R6 - NH2 by the Hofmann reaction between side-chain ester radical and alkylenediamine (H2N - R6 - NH2), wherein R6 is alkylene radical of C2 - C6.

iv) Conversion to quaternary amino compound, by alkylating the amino radical of the reaction product of ii) or iii).

and thereafter drying the solution on the surface.

2. The method of Claim 1 wherein monomer (II) has the general formula wherein M is one of the following:
1) 2)

3)

4)

5) Wherein Ra, Rb, Rc = H, alkyl, hydroxyalkyl, phenyl, benzyl.
r = 1 to 3 x? = acid radical of inorganic or organic acid.

3. The method of Claim 1 wherein monomer (III) has the general formula or its copolymer with an unsaturated compound having carbonic group of maleic anhydride, itaconic acid or sulpho (phospho) group.

where N is one of the following:

a) - COOH (or its salt) b) - SO3H (or its salt) c) (or its salt) d) (or its salt) e) - ? - NH - CH2 - SO3H (or its salt) f) (or its salt) g) (or its salt) 4. The method of Claim 1 wherein the monomer (IV) is at least one monomer selected from the group consisting of 2-hydroxy methacrylate, diacetone acrylamide, methylol acrylamide, acryloyl morpholine, acrylonitrile, methacrylic ester, styrene and vinyl acetate.

5. The method of Claim 1 wherein the aqueous polymeric solution additionally oomprises a cross-linking agent.

6. The method of Claim 5 wherein the cross-linking agent comprises at least one metal ion having a coordination number of more than 4.

7. The method of Claim 5 wherein the cross-linking agent oomprises at least one water soluble organic compound selected from blocked polyisocyanates, polymethylol, polyglycidyl and polyaziridyl compounds.

8. The method of Claim 7 wherein the organic compound is selected from polyisocyanate blocked with NaHSO3, methylolmelamine, methylolurea, methyloled polyacrylamide, diglycidylether of poly-ethyleneoxide, and diaziridyl-polyethyleneoxide.

9. The method of Claim 1, 2, 3, 4, 5, 6, 7 or 8, comprising the additional subsequent steps of apply-ing a water-glass solution to the dried organic coating and drying it on the surface.