Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Compound of indeterminate structure – prepared by reacting an...
Reexamination Certificate
2001-06-08
2003-06-17
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Compound of indeterminate structure, prepared by reacting an...
C508S464000, C521S155000
Reexamination Certificate
active
06579835
ABSTRACT:
The present invention relates to the use of polymer dispersions for the dry lubrication of hydrogenated polymer materials such for example rubbers, for example EPR, EPDM, SBR, or plastics, metals, glass having an improved friction coefficient. More specifically said polymer dispersions are aqueous dispersions of cationic fluorinated oligourethanes obtained from functional (per)fluoropolyethers (PFPE) which optionally can be formulated with other fluoropolymers.
Generally the dry lubrication is selected when it is necessary to maintain for long time the lubricant effect among the surfaces in contact, avoiding theyr damage by the friction. By this treatment therefore it is possible to maintain during the time the properties of said surfaces. The dry lubrication has a remarkable importance when the materials in contact are rubber or plastic materials, and therefore they generally have poor wear resistance. An example of dry lubrication is that which occurs on the rubber parts used as fittings for the mobile glass safety or not of cars for reducing the friction and noise. Said fittings, that besides friction are exposed to the action of the light and atmospheric agents, must be lubricated so that the rubber surface is not worn and maintains during the time the mechanical properties.
Dry lubrication systems for improving the friction coefficient are known in the prior art. Formulations based on polysiloxanes and silicon rubber, crosslinkable at 150° C. with hydrosoluble polyamines, able to form coatings having a thickness from 1 to 3 microns on rubbery surfaces EPDM type and to give a friction coefficient from 0.4 to 0.7 (1 Kg, 100 mm/min) are described in EP 761,791. The drawback of said formulations is that the friction coefficient is not satisfactory and besides thy are bicomponent systems wherefore the pot life is not high. In C.A. 131 300652t No. 22 1999, page 676, the Abstract of the patent JP 11 291769 is reported, wherein a coating for EPDM rubber is described, obtained by mixing with a polyurethane prepolymer based on polytetramethylenglycol (PTMG) a fluororesin in powder and a perfluoropolyether. Tests carried out by the Applicant with hydrogenated polyurethane prepolymers and a fluororesin in powder (PTFE) have shown that the obtained friction coefficient values are unsatisfactory. Compositions based on photocrosslinkable silicones (polyorganosiloxanes having epoxy functionality), particles of crosslinked silicone resin, having sizes from about 0.5 to 12 microns, able to give coatings having a low friction coefficient, are described in EP 903,385. Said formulations require the use of UV lamps for the photocrosslinking after the coating application and drying. From the industrial point of view this kind of crosslinking is an additional cost of the plant. In U.S. Pat. No. 5,115,007 formulations in solvent (toluene) for obtaining coatings on EPDM rubbers, formed by blocked isocyanic prepolymers formulated together with crosslinking agents and silicone oils, are described. The application of said formulations in solvent raises problems connected to the environmental impact and to the use in the work environment of organic solvents. Besides the obtained coatings have an high thickness, in the range 11-16 microns. U.S. Pat. No. 4,676,995 describes formulations is organic solvent, based on modified polyamides containing brominated and chlorinated groups on amidic nitrogen. Said formulations are applied on rubbers EPDM type in solutions at 4% of dry product in methylene chloride, forming coatings having a low friction coefficient. Also for said formulations in solvent it can be repeated what noticed above for the use of organic solvents in this kind of compositions. Similar formulations, that use organic solvents, are described in U.S. Pat. No. 4,720,518 and besides contain fillers such silica, PTFE powder, etc.
The need was felt to carry out dry lubricant treatments on rubbers, plastics, metals and glass, applying aqueous polymer systems, so as to avoid the use of organic solvents and to reduce the environmental impact, to eliminate the problems connected to the use of said solvents in the work environment, obtaining a dry lubricant layer showing the following combination of properties:
dynamic friction coefficient (ASTM D 1894-78) <0.4, preferably ≦0.3,
high adhesion to the treated surface (ASTM D 3359-87),
high resistance to photooxidative degradation,
high rubbing-resistance,
high resistance to water absorption,
dry lubricant layer having a reduced thickness, in the range 0.1-5 microns, preferably 1-3 microns.
The Applicant has unexpectedly and surprisingly found that it is possible to obtain said combination of properties by applying aqueous dispersions of thermocrosslinkable fluorinated oligourethanes having a cationic functionality.
An object of the present invention is the use of fluorinated polyurethanes thermally crosslinkable for obtaining coatings having an improved friction coefficient for the dry lubrication of rubbers, plastics, metals, glass, said crosslinkable polyurethanes obtainable from aqueous dispersions of cationic oligourethanes based on branched and thermocrosslinkable (per)fluoropolyethers (PFPE), said cationic oligourethanes having a number average molecular weight lower than or equal to 9,000, determined by vapour pressure osmometry and formed by the following monomers and macromers:
a) aliphatic, cycloaliphatic or aromatic polyisocyanates, having NCO functionality, determined by titration with dibutylamine-HCl (ASTM D2572), higher than 2, preferably in the range 3-4;
b) bifunctional hydrogenated monomers having the two functions chemically different from each other (hetero-functional monomers) having the general formula:
X
O
—(CR
1
A
R
2
A
)
b
—Y
0
(Ib)
wherein:
R
1
A
and R
2
A
, equal to or different from each other, are H, aliphatic radicals from 1 to 10 carbon atoms,
b is an integer in the range 1-20, preferably 1-10,
X
O
=X
A
H with X
A
=O, S,
Y
0
is a salifiable, anionic or cationic function,
when in the formula (Ib) X
O
=OH, b=1, R
1
A
=R
2
A
=H and
Y
0
is a hydrophilic group preferably having formula
—CH
2
O—(CH
2
—CH
2
O)
nT
—CH
3
(Ib1)
wherein nT is an integer in the range 3-20; and one or more of the following compounds:
c) bifunctional hydroxylated (per)fluoropolyethers (PFPE diols) having number average molecular weight in the range 400-3,000, preferably 700-2,000;
e) monofunctional hydroxyl or carboxylic (per)fluoropolyethers (e
0
) or monofunctional hydroxyl (per) fluoroalkanes (e′), said compounds (e
0
) and (e′) having number average molecular weight in the range 300-1,000, preferably 400-800.
and optionally the following compounds:
d) hydrogenated monomers with which it is possible to insert a crosslinkable chemical function in the oligourethane, said monomers having formula (Ib), wherein R
1
A
, R
2
A
, b and X
O
are as above and Y
0
, is selected from the following functional groups:
wherein
R
I
B
=H, CH
3
;
R
x
is a C
1
-C
5
, preferably C
1
-C
3
, saturated alkyl;
d
I
) hydrogen-active compounds, able to form with the NCO functions bonds which are stable to hydrolysis but thermolabile, said compounds known as blocking agents of the NCO group, and selected from those known in the prior art such as for example ketoximes, for example methylethylketoxime, phenols and mono-, di-alkyl substituted phenols wherein the alkyl chain contains from 1 to 8 carbon atoms, pyrazol, caprolactam, ethylmalonate, acetylacetone, ethylacetoacetate.
The preferred composition of the invention comprises a)+b)+c), optionally e).
Preferably the amounts of the components a)−c), monomers and macromers which constitute the oligourethanes according to the present invention are the following:
component a) polyisocyanate: 10-70% by weight based on the total of the dry oligourethane, preferably 20-40% by weight;
component b) ionic heterofunctional hydrogenated monomer: the amount by weight based on the total of the dry oligourethane is calc
Scicchitano Massimo
Trombetta Tania
Turri Stefano
Arent Fox Kintner & Plotkin & Kahn, PLLC
Ausimont S.p.A.
McAvoy Ellen M.
LandOfFree
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