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
1999-06-24
2001-02-13
Szekely, Peter A. (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...
C524S456000, C524S492000, C524S493000, C524S520000, C524S544000, C524S545000, C428S421000
Reexamination Certificate
active
06187851
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the surface treatment of materials, in particular of stony materials, marble, sandstone, bricks, concretes and the like, and of metals, and to aqueous compositions employed therein.
1. Description of the Related Art
As is known, stony materials, marble, sandstone, bricks and concretes, usually employed in building industry, and also metals, suffer from a progressive decay owing to the atmospheric agents and pollutants. Such decay is determined by a series of phenomena both of physical and chemical nature which mainly occur in the presence of water. In order to eliminate or at least meaningfully reduce, such phenomena, it is known to apply on the surface of such materials protective substances of various kinds (see “Stone Decay and Conservation”, of Amoroso e Fassina, Elsewier Ed., Amsterdam, 1983).
If these decay phenomena have induced the formation of a surface layer having poor cohesion, it is essential that the applied substances, besides acting as protective agents, also exert a surface aggregating action.
Briefly, a good aggregating/protective agent, to perform the desired action and not to contemporanteously induce side decay phenomena or other undesired secondary effects, must show the following characteristics:
1. to markedly reduce the inlet and the penetration rate of water inside the material to be protected and consolidated;
2. to re-establish the cohesion between the particles of the surface layer of the decayed material, as well as the adhesion between the surface layer and the integral underlying part;
3. to impart an oil-repellence effect so as to reduce the penetration of oils and hydrocarbons, commonly present as atmospheric pollutants, or at least to make their removal from the material easier;
4. to show suitable chemical stability with respect to the action of the atmospheric agents, of light and of heat;
5. to maintain elasticity properties in order to avoid the formation of a stiff surface layer with mechanical properties different with respect to the subtratum;
6. to show chemical inertia towards the material to be treated;
7. not to alter, where required, the chromaticity of the material to be treated;
8. to maintain over time its own characteristics of solubility to assure the treatment reversibility;
9. to maintain a sufficient permeability to air and to steam, in order to avoid, because of the condensate, alteration phenomena under the protected surface layer.
In the class of fluorinated polymers, the use of perfluoropolyoxyalkylenes as protective agents for stony and cement manufactured articles, as described in U.S. Pat. No. 4,499,146 and U.S. Pat. No. 4,745,009, is known. Such products, even though they solve the problem of the protection, cannot however exert an effective consolidating action because of their nature of fluids.
A substantial improvement has been obtained by using elastomeric polymers based on vinylidene fluoride (VDF), which effectively exert both a protective and aggregating function (see for instance U.S. Pat. No. 4,764,431). A further improvement has been obtained by using as aggregating/protective agents, mixtures consisting of a fluoroelastomer based on VDF and of a VDF non elastomeric homopolymer or copolymer, as described in EP patent EP-A-479,240.
The use of silica and inorganic silicates as reinforcing agents for both non fluorinated and fluorinated resins is also known. For instance, in U.S. Pat. No. 4,680,331 aqueous compositions are described, consisting of a fluorinated resin, in particular polytetrafluoroethylene (PTFE), a silicone emulsion, a flocky inorganic material and a non ionic surfactant, optionally in admixture with an anionic surfactant. Among the inorganic flocky materials SiO
2
, TiO
2
, Al
2
O
3
and others are indicated. Such compositions are employed for the coating of glass or metal. To obtain a stable coating, the fluorinated resin must be submitted after the application to a sintering process at a temperature higher than the melting point of the resin itself, (for example higher than 320° C. in case of PTFE. The use of so high temperatures is a true drawback, both as it makes the process applicable only on manufactured thermally resistant articles of small sizes, and because of unavoidable decay phenomena of the silicone material.
The Applicant has now surprisingly found that the application of an aqueous composition, as defined hereinunder, comprising both a fluoreoelastomer and an inorganic compound of the silicon, allows one to obtain a remarkable improvement in surface protection and consolidation compared to the individual components when used separately. The synergistic effect of the combination of an inorganic compound of silicon and a fluoroelastomer is particularly surprising since, on the basis of experiments carried out by the Applicant, the application of an inorganic compound of silicon, for example sodium silicate, on a stony material while exerting a discrete consolidating action, does not produce any protective effect, since the silicate does not possess water-repellent properties.
SUMMARY OF THE INVENTION
An object of the present invention is therefore a process for the surface treatment of materials, in particular of stony materials, marble, sandstone, bricks, concretes and the like, and of metals, which comprises applying on the surface of said materials an aqueous composition comprising:
(a) from 2 to 95% by weight, preferably from 2 to 60%, even more preferably from 2 to 30% by weight based on the weight of the dry product of an inorganic compound selected from colloidal silica, silicates, of sodium, potassium, ammonium, alkali or alkaline-earth metals or mixtures thereof; and
(b) from 5 to 98%, preferably from 40 to 98%, even more preferably from 70 to 98% by weight based on the weight of dry product of a fluoroelastomer based on vinylidene fluoride (VDF).
A further object of the present invention consists in the aqueous compositions as defined above.
By weight % on the dry product it is meant the amount of product present in the solid residue obtained after complete evacuation of the water and of other solvents optionally present.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The total content of the components (a) and (b) in the aqueous composition is generally comprised between 1 and 15%, preferably between 2 and 10%, by weight/volume (grams per 100 ml of aqueous phase).
The silicates (a) are preferably sodium or potassium silicates, having a ratio by weight SiO
2
/Me
3
O (Me═Na, K) comprised between 1.6 and 3.6, preferably from 2.8 and 3.6.
The fluoroelastomers based on VDF (b) are well known products in the art (see for instance Kirk-Othmer, “Encyclopedia of Chemical Technology”, Vol. 8, pg. 500-515 (1979)). They are elastomeric copolymers comprising VDF, in amounts generally comprised between 35 and 85% by moles, preferably between 40 and 70% by moles, and at least another fluorinated comonomer ethylenically unsaturated. Examples of such comonomers are: trifluoroethylene, tetrafluoroethylene (TFE), trifluoropropene, hexafluoropropene (HFP), pentafluoropropene, chlorotrifluoroethylene (CTFE), perfluoroalkylvinylethers (PAVE), in particular perfluoromethylvinylether (PMVE) and perf luoropropylvinylether (PPVE). The copolymers comprising, by moles, from 55 to 85% of VDF, from 15 to 45% of HFP, from 0 to 30% of TFE, are particularly preferred. They are available on the market with different trade names, such as TECHNOFLON® (Ausimont), VITON® (DuPont), FLUOREL® (3M), DAIEL® (Daikin). Fluoroelastomers having high molecular weight, having a ponderal average molecular weight higher than 20,000, are particularly preferred. Ponderal average molecular weight is synonymous with weight-average molecular weight.
The aqueous phase of the compositions of the present invention can comprise, besides water, a polar organic solvent, in amounts generally comprised between 2 and 25% by weight, preferably between 3 and 10% by weight, with respect to the total weight of the composition
Di Carlo Camillo
Netti Stefano
Ausimont S.p.A.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Szekely Peter A.
LandOfFree
Surface protective layer for materials does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Surface protective layer for materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Surface protective layer for materials will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2591217