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...
Reexamination Certificate
1999-05-25
2001-03-06
Niland, Patrick D. (Department: 1714)
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...
C524S244000, C524S278000, C524S282000, C524S366000, C524S463000, C524S520000, C524S544000, C524S545000, C524S546000
Reexamination Certificate
active
06197866
ABSTRACT:
The present application claims priority to Italian Application Serial No. MI98A001736.
FIELD OF THE INVENTION
Painting composition based on fluoropolymers in an aqueous dispersion, comprising a partially fluorinated non ionic polymeric compound as an additive for the control of the viscosity and in general of the rheological characteristics of the composition itself.
PRIOR ART
It is known that every paint must have specific characteristics as a function of the application conditions, in order to guarantee the necessary final characteristics of the coating such as for example a minimum thickness vertically applicable, flow, superficial appearance and so on.
Therefore a fundamental characteristic of the paint is its “rheological profile” that is its viscous behaviour as a function of the slipping gradient to which it is submitted.
The rheology control as a function of the optimal profile for each specific application, may be obtained by different classes of inorganic (clays, bentonites, pyrogenic silica) or organic (acrylic, cellulosic, urethanic polymers) additives, used individually or in combination among them. The use of these additives takes on particular importance in the formulation of the systems in an aqueous emulsion, for which the control of the viscosity results more critical than in the case of solvent paints and in the majority of the cases the suitable rheological profile is obtained associating 2-4 additives having different characteristics. Each of these classes of additives shows however some limits and disadvantages.
The cellulose ethers cause in water viscous solutions of hydrated macromolecular aggregates not having an associative action but more simply increase the water viscosity. The behaviour of these products is clearly pseudo-plastic with very high viscosity at low gradient which is drastically reduced when this one increases and it comes back quickly to its original state as soon as the action of shear is interrupted. The obtained paint shows a good brushability while properties such as flow and antisplash are not optimal, negatively affecting properties such as the applicable thickness and the brightness, particularly in the case of spray or roll application.
The additives of acrylic kind are acid copolymers reinflatable with alkali and show, with respect to the cellulosic ethers, a greater Newtonian character (lower sensibility with respect to the applied gradient), resulting in better characteristics of the paint, in particular greater applicable thicknesses, better flow and quality of the film. As however the associative mechanism to which this behaviour is due depends on the presence in the polymeric chain of acid sites having salified form, the use of these additives is limited to paints having pH 8-10.
The polyether-polyurethane block polymers form the more recent innovation in the field of rheologic additives for emulsion paints. The associative action mechanism of these systems is linked to the different solubility in water of the portions of the chain PU and PE. They associate a behaviour more clearly Newtonian than the acrylic copolymers one and a substantial independence of the rheological characteristics from the pH of the paint.
The use of the polyurethanic additives is described for example in the U.S. Pat. Nos. 4,079,028 and 4,155,892.
Usually the inorganic additives show a behaviour more resistant against chemical agents vehiculated by the water (acids, bases, salts) but they need to be incorporated with a high shear and they give poorly reproducible results.
The most frequently used organic additives are hydrophilic polar polymers and they transfer these properties to the coatings obtained by the formulations containing them. In fact these coatings show a greater affinity for the water which represents the principal vehicle of the aggressive agents. This aspect is particularly important in the case of paints for application in aggressive environment where a high chemical resistance is required.
SUMMARY
We have found that using a partially fluorinated non ionic polymeric compound as thickening additive in aqueous painting compositions based on fluoropolymers, an improvement of the rheological behaviour of the compositions is obtained without affecting the coating hydrophilia.
Said partially fluorinated non ionic polymeric compound has the following general formula (I):
wherein
n is a number ranging from 4 to 60 and preferably ranging from 8 to 30; L and L′, equal or different between them, are selected from:
wherein
p is 0 or 1, Y is F or CF
3
and R′ is an alkyl radical C
1
-C
5
;
R
1
and R
2
are both H or one is H and the other one is CH
3
;
R
f
and R
f′
, equal or different between them, are perfluoropolyether radicals having a numerical average molecular weight ranging from 250 to 1500 and preferably ranging from 400 to 1000.
DETAILED DESCRIPTION OF THE INVENTION
The characteristics and the advantages of the use of an additive consisting of a partially fluorinated non ionic polymeric compound in aqueous painting compositions based on fluoropolymers, will be mostly pointed out during the following detailed description.
Said polymeric compound has the following general formula (I)
wherein:
n is a number ranging from 4 to 60 and preferably ranging from 8 to 30; L and L′, equal or different between them, are selected from:
wherein
p is 0 or 1, Y is F or CF
3
and R′ is an alkyl radical C
1
-C
5
;
R
1
and R
2
are both H or one is H and the other one is CH
3
;
R
f
and R
f′
, equal or different between them, are perfluoropolyether radicals having a numerical average molecular weight ranging from 250 to 1500 and preferably ranging from 400 to 1000.
The perfluoropolyether radicals R
f
and R
f
′ comprise a T terminal and repetitive units statistically distributed along the polymer chain selected from:
wherein X is F or —CF
3
,
—CF
2
(CF
2
)
z
O wherein z is a number equal to 2 or 3;
—CF
2
CF(OR
f″
)O— or —CF(OR
f″
)O— wherein R
f″
is —CF
3
, —C
2
F
5
or —C
3
F
7
.
The T terminal of the perfluoropolyether radical is selected from: —CF
3
, —C
2
F
5
, C
3
F
7
, ClCF
2
CF(CF
3
)—, CF
3
CFClCF
2
—, ClCF
2
CF
2
— and ClCF
2
—.
In particular the following perfluoropolyether radicals R
f
and R
f′
may be cited as preferred:
(a) T—O (CF
2
CF(CF
3
)O)
a
(CFXO)
b
—
wherein: X is F or CF
3
, a and b are numbers such that the molecular weight is ranging in the above shown range, the ratio a/b is ranging from 10 to 100 and T is one of the above cited terminals;
(b) T—O(CF
2
CF
2
O)
c
(CF
2
O)
d
(CF
2
(CF
2
)
z
CF
2
O)
h
—
wherein: c, d and h are numbers such that the molecular weight is ranging in the above shown range, the ratio c/d is ranging from 0.1 to 10, the ratio h/(c+d) is ranging from 0 to 0.05, z is a number equal to 2 or 3, and T is one of the above cited terminals;
(c) T—O(CF
2
CF(CF
3
)O)
e
(CF
2
CF
2
O)
f
(CFXO)
g
—
wherein: X is F or CF
3
; e, f, g are numbers such that the molecular weight is ranging in the above shown range; the ratio e/(f+g) is ranging from 0.1 to 10, the ratio f/g is ranging from 2 to 10 and T is one of the above cited terminals;
(d) T—O(CF
2
O)
j
(CF
2
CF(OR
f″
)O)
k
(CF(OR
f″
)O)
l
—
wherein: R
f″
is —CF
3
, —C
2
F
5
, —C
3
F
7
; j, k, l are numbers such that the molecular weight is ranging in the above shown range; k+l and j+k+l are at least equal to 2, the ratio k/(j+l) is ranging from 0.01 to 1000, the ratio l/j is ranging from 0.01 to 100 and T is one of the above cited terminals;
(e) T—O—(CF
2
(CF
2
)
z
CF
2
O)
s
—
wherein s is such a number to give the above shown molecular weight, z has the above defined meaning and T is one of the above cited terminals;
(f) T—O(CR
4
R
5
CF
2
CF
2
O)
j′
—
wherein R4 and R5 are equal or different between them and selected from H, Cl or perfluoroalkyl having for example 1-4 C atoms, j′ is such a number to give the above indicated molecular weight;
(g) T—O(CF(CF
3
)CF
2
O)
j″
—
wherein j″ is such a number to give the above indi
Lenti Daria
Poggio Tiziana
Ausimont S.p.A.
Hedman & Costigan ,P.C.
Niland Patrick D.
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