Coatings based on fluoropolyethers

Details Coatings based on fluoropolyethers Coatings based on fluoropolyethers

1996-12-12

2002-02-26

Wilson, Donald R. (Department: 1713)

Compositions: coating or plastic

Coating or plastic compositions

O-containing organic compound

C106S287240, C106S287280, C106S287300, C568S615000, C252S182150

Reexamination Certificate

active

06350306

ABSTRACT:

The present invention relates to “high dry” formulations for preparing paints and coatings in general. It relates in particular to “high dry” compositions based on fluorine containing polymers. As “high dry” we mean formulations wherein the solvent is 20% by weight at most, preferably 10% by weigh. More particularly the object of the present invention relates to compositions suited for top coating, in particular in the car field, endowed with optimal capacity of adhesion to pigment ed bases, high hardness, protective an d antispot properties, scratch resistance, weather-proof and in particular resistant to UV radiation. Moreover the compositions must be usable in field applications, that is outside, assuring high aesthetic qualities, such as high gloss, image definition (DOI), together with the protective function and utilize a little solvent thus reducing the environmental impact. High dry formulations can be used in a range of temperatures generally from 10° C. to 50° C. This however depends on the crosslinking system, as well known, for instance melamines and blocked diisocyanates require higher temperatures.
The use of fluorine containing polymers for preparing coatings is known. These polymers are endowed with very good chemical, thermal and UV resistance and oleo- and water repellence. Known formulations for coating, having a fluorine containing basis, are for instance chlorotrifluoroethylene (CTFE) copolymers with hydrogenated vinylether or vinylesters; or VDF (vinylidenefluoride) polymer or copolymers with tetrafluoroethylene and/or hexafluoropropylene. The former are for instance LUMIFLON® and CEFRAL®, the latter are commercialized for instance as KYNAR® and TECNOFLON®. The main drawback of these fluoropolymers is that they are employed at high dilutions, even of 90% by weight of solvent. This leads to high costs for eliminating the solvents, since the solvents needed for preparing the formulations of these fluorine containing polymers have a high environmental impact.
In the case of TECNOFLON®-based coatings, chlorofluorocarbon solvents, which will be no longer used according to the laws of all countries, are presently used. In conclusion, these fluorine containing polymers even though endowed with the indicated excellent properties, cannot be used for high dry formulations.
The use of partially fluorinated copolymers is also known in the art, for instance perfluoropolyethers of elastomeric or filming type, are crosslinkable depending on the molecular weight and on the ratio between fluorine containing part and hydrogenated part.
However these products need to be used at high dilutions. Moreover, weather stability is not good. Therefore it is not possible to prepare high dry formulations from these products.
Coatings based on polyesters from perfluoropolyethers and coatings based on perfluoropolyethers containing acrylic groups are also known. One can see European patent applications 622353 and 622391 in the name of the Applicant. These products give good coatings and allow the use of less solvent than the products of the art indicated above. However it is not possible to obtain high dry formulations from these products since they require an amount of solvent of about 50% by weight.
The use of water coatings is also known. These formulations contain a low amount of solvent, of about 10%, whereby they could fall within high dry formulations, however they are endowed with low chemical resistance and moreover do not show the high aesthetic and mechanical properties, such as the gloss and the hardness that the high quality coatings must have.
Solvent-less coatings are also known, that is homogeneous bicomponent compositions without solvents or having a limited amount of solvents, applicable by means of traditional techniques and therefore endowed of minimum environmental impact. Epoxy resins can be mentioned. These resins however lead to poor coatings (coatings of inferior quality) from the aesthetic point of view. For instance the gloss of the coatings is of the order of 10-20 at 60° C. according to ISO 2813 standard. These compositions, however, do not yield reduced coating thicknesses, lower than 50 &mgr;, as required for top coating. Moreover the finishing of these products is not very good.
Object of the present invention is obtaining “high dry” formulations based on fluorine containing polymers capable of giving crosslinked films having the combination of properties indicated above: very good chemical, mechanical, thermal properties and resistance to UV radiations, usable also for applications on the field, very good aesthetic and durability properties, scratch and spot resistance.
The Applicant has unexpectedly and surprisingly found that it is possible to prepare “high dry” formulations based on fluoropolyethers if functionalized fluoropolyethers, as defined hereinunder, are used.
It has been surprisingly found that the polymers based on fluoropolyethers as defined be low do give “high dry” formulations since they require the addition of small amounts of solvent, of about 10% by weight and generally lower than 20% by weight.
Object of the present invention are high dry formulations of fluorine containing polymers for preparing paints and coatings wherein the fluorine containing polymers are based on fluoropolyethers comprising a fluorine containing part R
F
and optionally a hydrogen containing part R
H
, the bonds joining the fluorine containing part to the hydrogen containing one being an ether, C—O—C, bond the terminals T′ being such as to render bi or polyfunctional the structure and thus making possible the crosslinking reaction, the hydrogen containing part R
H
not containing groups capable of linking by means of hydrogen bonds to basic acceptors.
More in detail, preferred are the fluorine containing products which can be represented with the formula
T′—(R
H
)
x
—R
F
—(R
H
)
x
—T′  (I)
wherein
R
F
is
wherein R
f
is a fluoropolyether chain, Y and Y′ being same or different from each other and being F or CF
3
x is 0 or an integer from 1 to 10, preferably from 1 to 3;
R
H
is a linking bivalent radical, of linear aliphatic type—(CH
2
)
m
—, m being an integer from 1 to 20, or of (alkylene)cycloaliphatic type or of (alkylene)aromatic type, optionally having also heteroatoms on the ring or in chain, the number of carbon atoms being from 3 to 20 for the cycloaliphatic compounds, and from 5 to 30 for the aromatic ones; the R
H
group can also be a mixture of the types indicated:
T′=—(CH
2
CH
2
O)
n
—R
H
)
x′
—T, wherein n is 0 or an integer from 1 to 6, preferably from 1 to 2;
x′ is 0 or an integer from 1 to 10, preferably from 1 to 3, x′ can be different from x; and
T being hydrogen or a terminal capable of rendering bior polyfunctional the structure such as to make it reactive towards both ionic and radical crosslinking agents.
In particular terminals T are preferably of the type:
In particular the following groups must be absent from the hydrogen containing part R
H
: —COOH, —NH—COO—; —NH—CO—NH—; —OH; —NH
2
; —NH—; CO—NH—.
The radical R
f
of number average molecular weight M
n
comprised, preferably, from 500 to 5000, more preferably from 700 to 1500, represents a fluoropolyether chain bifunctional radical, comprising as repetitive units sequences of one or more oxyfluoroalkylene units of the type
wherein R
4
and R
5
have the meaning indicated hereafter.
It was unexpectedly found that the fluoropolymers of the present invention by addition of small amounts of solvent lead to the formation of solutions having an extremely low viscosity, generally of the order of 50-300 cPoise at room temperature.
It is even more surprising that amounts of about 2-3% by weight of solvents, selected from those generally used in the paints field are sufficient for obtaining solutions having very low viscosities such as to render them easily utilizable.
The preferred compounds of the formula I are the following:
 R
F
[(CH
2
)
6
—CH(CH
2
O—CH
2
—CH═CH
2
)
2
]
2
Generally utilizable solven

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