Film-forming method and metal material

Details Film-forming method and metal material Film-forming method and metal material

1999-01-19

2001-05-29

Beck, Shrive (Department: 1762)

Electrolysis: processes, compositions used therein, and methods

Electrolytic coating

Treating substrate prior to coating

C205S210000, C205S147000, C427S240000, C427S327000, C427S421100, C427S428010, C427S435000

Reexamination Certificate

active

06238541

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a film-forming method, and in particular a method for forming an organic film or and inorganic/organic composite film having excellent adhesion properties and anti-corrosion properties in surface treatment of a metal material, and to a metal material on which such a film is formed.
DESCRIPTION OF THE RELATED ARTS
Conventionally, when a metal surface is coated, the surface is first degreased, surface treatment is performed and then paint is applied. In the prior art, the surface was first treated with zinc phosphate or a chromate to impart anti-corrosion properties to the metal surface and improve adhesion between the surface and the coated film on the surface.
However, in the case of zinc phosphate, the phosphorus contained in effluent may cause water eutrophication and contamination, and gives rise to sludge in the surface treatment bath. On the other hand in the case of chromate treatment, the chromium in wash water is harmful, and can have a detrimental effect on the environment and human beings. This requires expensive waste water treatment equipment, which was rather uneconomical.
In recent years, therefore, there has been a need for a film-forming method which does not use surface treatment fluids containing harmful materials such as phosphorus or chromate, does not produce sludge, but which confers excellent anti-corrosion properties.
The following light curing composition having the general formula (II) shown below is disclosed in “Radiation Sensitive Ethylenic Unsaturated Sulfonium Salts Capable of Copolymerization”, Japan patent laid-open publication No. 2-264756.
[(R)
a
(R
1
)
b
(R
2
)
c
S
⊕
]A
⊖
  (II)
(in the formula, R is a monovalent aromatic group which may or may not be substituted,
R
1
is a monovalent organic aliphatic group which may or may not be substituted, and is one group chosen from alkyl, cycloalkyl and substituted alkyl groups,
R
2
is a bivalent or trivalent aliphatic or aromatic organic group which may or may not be substituted and which has a complex ring structure or a condensed ring structure.
a is an integer from 0 to 3 (including 3),
b is an integer from 0 to 2 (including 2),
c is an integer equal to 0 or 1, such that a+b+c=3.
A
−
is an acid anion.
At least one of R-R
2
contains one of the groups shown below in combination:
W in the formula is a single bond or one of the groups shown below:
X in the above formula is a bivalent alkylene group having the structure shown below which may or may not be substituted,
R′ and R″ are identical or different aryl, C
1
-C
4
alkyl, H, COOH, COOCH
3
, COOCH
2
CH
3
groups or, perfluoroalkylene groups —(CF
2
)
m
(m=1-10), oxyalkylene groups —(CH
2
)
n
—O—(CH
2
)
p
— (n=1-5 and p=1-5), perfluorooxyalkylene groups, one of the following polyoxyalkylene groups which may be perfluorinated comprising 2-20 oxygen atoms, these oxygen atoms being linked via at least one —CH
2
—,
—CF
2
or —CH
2
—CH(CH
3
)— group,
—(CH
2
)
m
—O—CO—O—(CH
2
)
n
—,
—(CH
2
)
m
—O—CO—NH—(CH
2
)
n
—,
—(CH
2
)
m
—NH—CO—O—(CH
2
)
n
—,
—(CH
2
)
m
—O—CO—(CH
2
)
n
— or
—(CH
2
)
m
—CO—O—(CH
2
)
n
— (m=1-10, n=1-10), or
a phenylene group substituted in the o-, m- or p- positions by an alkyl group comprising 1-4 carbon atoms, OH, OCH
3
, OC
2
H
5
, SH, SCH
3
or SC
2
H
5
.
Y is hydrogen, an alkyl or phenyl group comprising 1 to 6 carbon atoms, and Z is O or NY.
In “A Novel Acrylate Compound” in Japan patent laid-open publication No. 5-32618, a novel acrylate derivative having the structure shown below is disclosed as starting material of a functional polymer used as a carrier for clinical diagnosis agents.
(in the formula, R is hydrogen, a C
1
-C
4
alkyl group or a phenyl group,
R
1
is hydrogen or a C
1
-C
4
alkyl group,
R
2
, R
3
are separately hydrogen, halogen or C
1
-C
4
alkyl groups,
R
4
, R
5
are separately C
1
-C
4
alkyl groups,
X is an alkyl sulfate ion, halogen ion, perchlorate ion, bisulphate ion or p-toluenesulfonic ion.
U.S. Pat. No. 4,528,384 describes ethylenic unsaturated aromatic sulfonium salts having for example the structure shown below as starting materials for new polymers used as cationic surfactants.
(in the formula, X
⊖
is an anion such as Cl
−
or CH
3
COO
−
).
However, all of the ethylenic unsaturated aromatic sulfenium salts described in the aforesaid Japanese patent laid-open publication No. 2-264756, Japanese patent laid-open publication No. 5-32618 and U.S. Pat. No. 4,528,384 are used as light curing compositions, as carriers for clinical diagnosis agents or as cationic surfactants, and there are no examples of their use as surface treatments prior to the painting of metal materials.
Until now, no method had been found for forming an organic film or organic/inorganic film on a metal surface, and treatment of metal surfaces had to be performed while taking precautions against environmental pollution and sludge prevention. This required costly effluent treatment equipment and metal surface treatment equipment, which was uneconomical.
SUMMARY OF THE INVENTION
It is therefore an object of this invention, which was conceived in view of the above problems in the prior art, to provide a method of forming an organic film or an organic/inorganic composite film having excellent adhesive properties and anticorrosive properties on a metal surface in the surface treatment of metal materials.
To achieve the above object, the film-forming method according to this invention is a method comprising a film-forming step wherein a film is formed by bringing an aqueous solution comprising at least one of the following compositions (A), (B), (C) or (D) into contact with a metal material.
(A) A monomer comprising a sulfonium group at one end of the molecule,
(B) A water-soluble polymer obtained by homopolymerization or copolymerization of the monomer (A),
(C) An emulsion or water-soluble polymer comprising a sulfonium group obtained by copolymerization of the monomer (A) and a radical-polymerizable unsaturated monomer excluding the monomer (A),
(D) A composite emulsion comprising a sulfonium group wherein inorganic particle core are coated by a layer comprising a copolymer of the aforesaid monomer (A) and a radical-polymerizable unsaturated monomer excluding the monomer (A).
In another film-forming method according to this invention, the aforesaid monomer (A) is a monomer comprising a sulfonium group at the end of the molecule, and having the following general formula (a).
Y−W·X  (a)
(in the formula, Y is an aromatic ring comprising a benzene ring, a naphthalene ring or a pyridine ring having a polymerizable unsaturated group and/or active hydrogen, and/or a straight chain or branched aliphatic group having a polymerizable unsaturated group and/or active hydrogen, W is a sulfonium group and X is a counter anion shown by the following formulae).
The sulfonium group in the aforesaid compositions (A), (B), (C) or (D) of the film-forming step is highly reactive to metals, and as it is a cation, the sulfonium group arranges itself on the metal surface when a metal material is brought in contact with it by, for example, spraying, spin coating, roll coating, bar coating, dipping or electrolysis during dipping, and removes an electron pair from the metal surface to form a metal-S bond. This permits an organic film or organic film/inorganic film to be formed on the metal surface comprising the aforesaid compositions (A), (B), (C) or (D), and having excellent adhesive properties and anticorrosive properties.
Further, in another film-forming method according to this invention, the monomer (A) is a monomer having the general formula (I) comprising a sulfonium group at one end of the molecule, and an active ester group in the same molecule.
(in the formula, W is a sulfonium group and X is the counter anion X
2
shown above).
The active ester of the monomer (A) is a highly reactive functional group which reacts rapidly at normal temperature with —OH

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