Paints comprising aqueous dispersions of hydroxylated...

Details Paints comprising aqueous dispersions of hydroxylated... Paints comprising aqueous dispersions of hydroxylated...

1995-05-30

2002-09-10

Reddick, Judy M. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S544000, C524S545000, C524S546000

Reexamination Certificate

active

06448328

ABSTRACT:

FIELD OF THE INVENTION
The subject of the present invention is a stable aqueous dispersion comprising one or a number of hydroxylated fluorinated copolymers and optionally one or a number of acrylic copolymers. These dispersions have the advantage of being stable on storage, of being suitable for forming films with excellent adhesion to various substrates, and of having good chemical properties and good mechanical strength. In general they have the additional advantage of possessing a high solids content, that is to say greater than 30% by weight. These dispersions can be used as paints or coatings which can be applied in a number of ways to a variety of substrates.
BACKGROUND OF THE INVENTION
Aqueous dispersions are described in EP 212,508 and EP 224,870, assigned to Daikin, EP 341,716, assigned to Asahi Glass, and EP 508,229, assigned to Central Glass. All of these dispersions contain an alcohol and a tertiary amine, such as triethylamine. The presence of amine in a paint composition has the disadvantage of leading to yellowing of the paint during the film-forming heat treatment or even the appearance of small holes at the surface of the said paint.
EP 360,575, assigned to JSR, describes solvent-free and amine-free aqueous dispersions in the vinylidene fluoride copolymer latex form prepared as an emulsion and seeded with an acrylic copolymer with a low glass transition temperature; the main defect of these dispersions is their lack of hardness, which is particularly injurious to paint applications.
Fluorinated polymers are known for their chemical resistance, especially to solvents, their excellent thermal behavior and resistance to bad weather and to radiation, for example ultraviolet radiation, their impermeability to gases and to liquids, and their property as electrical insulators. They nevertheless have the disadvantage of being rather difficult to use, in particular for film-forming, with adhesion, transparency, and impact resistance properties which are in general inferior to other thermoplastic polymers such as polyamides.
SUMMARY OF THE INVENTION
The present invention provides a stable aqueous dispersion comprising an emulsifying agent and a hydroxylated fluorinated copolymer, wherein said hydroxylated fluorinated copolymer is the result of copolymerization of the following monomers: (a) tetrafluoroethylene, (b) a member selected from the group consisting of vinylidene fluoride, trifluoro-ethylene, and mixtures thereof, and (c) a member selected from the group consisting of allylic alcohol, allylic ethers, and mixtures thereof. The monomers are copolymerized in molar ratios such that (b)=45 to 95% of (a)+(b) and (c)=2 to 25% of (a)+(b). Optionally, the hydroxylated fluorinated copolymer may be the result of copolymerization of monomers (a), (b), and (c), and of (d) a member selected from the group consisting of nonhydroxylated vinyl ethers; fluorinated monomers other than vinylidene fluoride, trifluoroethylene, and tetrafluoroethylene; non-salified allylic ethers and esters which are optionally carboxylated and/or substituted with —(CF
2
)
n
—CF
3
having 4<n>10; and mixtures thereof. In this case, the monomers are copolymerized in molar ratios such that (b)=45 to 95% of (a)+(b), (c)=2 to 25% of (a)+(b), and (d)=>0 to 10% of (a)+(b).
In another aspect of the present invention, the stable aqueous dispersion may further comprise an acrylic copolymer wherein said acrylic copolymer is the result of copolymerization of the following monomers: from 40 to 70% (by mass) of methyl methacrylate; from 30 to 60% (by mass) of an alkyl (meth)acrylate, and from 0 to 15% (by mass) of a functionalized or substituted alkyl (meth)acrylate monomers. The ratio by weight of the acrylic copolymer(s) to the hydroxylated fluorinated copolymer(s) in the stable aqueous dispersion is less than 50%.
The stable aqueous dispersions according to the present invention are preferably characterized by solids contents of at least 30% by weight.
The present invention also contemplates processes for the manufacture of a stable aqueous dispersions. One such process comprises preparing a solution of hydroxylated fluorinated copolymer(s) in an organic solvent, dispersing the solution thus obtained in an aqueous solution of emulsifying agent(s), and removing the organic solvent, either simultaneously by distillation or after dispersion. Another such process comprises copolymerizing the acrylic monomers in the presence of the hydroxylated fluorinated copolymer(s) in solution or in emulsion in an organic solvent, dispersing the solution thus obtained in an aqueous solution of emulsifying agent(s), and removing the organic solvent, either simultaneously by distillation or after dispersion.
The stable aqueous dispersions of the present invention are useful for making aqueous-phase paints and varnishes.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The Hydroxylated Fluorinated Copolymers
The hydroxylated fluorinated copolymers which can be used for the aqueous dispersions according to the invention are known. They are described, for instance, in U.S. Pat. Nos. 5,231,155, 5,166,284, and 5,200,479. They derive from the following monomers:
1. from 45 to 95% (molar) of vinylidene fluoride (VF2) and/or of trifluoroethylene (VF3),
2. from 5 to 55% (molar) of tetrafluoroethylene (C
2
F
4
)
3. from 2 to 25 mol, per 100 mol of monomers 1+2, of one or a number of hydroxylated allylic monomers chosen from allylic alcohol and hydroxylated allylic ethers such as
CH
2
═CH—CH
2
—O—CH
2
—CHOH—CH
2
—OH
CH
2
═CH—CH
2
—O—CH
2
—C(CH
2
OH)
2
(CH
2
CH
3
)
 CH
2
═CH—CH
2
—O—(CH
2
)
n
—OH with
3
≦n≦
8
CH
2
═CH—CH
2
—O—(CH
2
—CH
2
—O)
n
—H with 1≦n≦14
CH
2
═CH—CH
2
—O—(CH
2
—CH(CH
3
)—O)
n
—H with 1≦n≦14
4. and from 0 to 10 mol, per 100 mol of monomers 1+2, of one or a number of monomers chosen from non-hydroxylated vinyl ethers, such as butyl vinyl ether, other fluorinated monomers (i.e., other than VF2, VF3, or C
2
F
4
), such as C
3
F
6
or C
2
F
3
Cl, or non-salified allylic ethers and esters which are optionally carboxylated and/or substituted with —(CF
2
)
n
—CF
3
with 4≦n≧10, such as:
CH
2
═CH—CH
2
—O—CO—C
2
H
4
—COOH,
CH
2
═CH—CH
2
—O—CO—C
6
H
10
—COOH
CH
2
═CH—CH
2
—O—C
2
H
4
—(CF
2
)
n
CF
3
,
CH
2
═CH—CH
2
—CO—O—C
2
H
4
—(CF
2
)
n
CF
3
,
CH
2
═C(CH
3
)—CO—O—CH
2
—CF
3
The stable aqueous dispersions contain at least 30% by weight of hydroxylated fluorinated copolymer(s).
The Acrylic Copolymers
The acrylic copolymer(s) according to the invention derive from the following monomers:
from 40 to 70% (by weight) of methyl methacrylate (MMA),
from 30 to 60% (by weight) of one or a number of alkyl (meth)acrylate(s), such as butyl acrylate (BuA) or the ethyl (meth)acrylates,
and from 0 to 15% (by weight) of one or a number of alkyl (meth)acrylate monomers which are functionalized or substituted, for example, with hydroxyl groups or CF
3
—(CF
2
)
n
—groups with 4≦n≦10, such as hydroxyethyl (meth)acrylate (HEA), 2,2,2-trifluoroethyl methacrylate (TRIFEMA), CH
2
═CR—COO—C
2
H
4
—(CF
2
)
n
—CF
3
with R═H or CH
3
(CFnA), the (meth)acrylic acids (AA and MAA), the salts of 2-acrylamido-2-methylpropanesulphonic acid, in particular CH
2
═CH—CO—NH—C(CH
3
)
2
—CH
2
—SO
3
—N
+
(C
2
H
5
)
3
(AMPS/TEA), dimethylacrylamide (DMA) or dimethylaminoethyl methacrylate CH
2
═C(CH
3
)—COO—CH
2
—CH
2
—N(CH
3
)
2
(MADAME).
The presence of some of the above monomers in the acrylic copolymer(s) improves certain mechanical, physical and/or chemical properties of the dispersion according to the invention. By way of example, hydroxy (meth)acrylates improve the crosslinking properties, TRIFEMA and the (CFnA)s have anti-graffiti properties, acrylic and methacrylic acids improve the adhesion properties, AMPS/TFA and DRA have properties of mechanical stabilization of the dispersion and MADAME makes it possible to coat substrates by cataphoresis.
The ratio by weight of the acrylic

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