Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2000-10-12
2003-09-02
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S035000, C528S042000, C528S401000, C427S387000, C427S393400
Reexamination Certificate
active
06613860
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of treating substrates, in particular substrates having a hard surface such as ceramics, to render them water, oil, stain and dirt repellent. The present invention also relates to compositions for use in such a method.
BACKGROUND OF THE INVENTION
The use of fluorinated silanes, i.e. silane compounds that have one or more fluorinated groups for rendering substrates such as glass and ceramics oil and water repellent have been long known. For example such silanes have been described in U.S. Pat. No. 5,274,159. This latter document describes destructable fluorinated alkoxysilane surfactants that can be applied from an aqueous solution.
Commercial products are also available that comprise a silane having one or more hydrolysable groups and at least one non-hydrolysable fluorinated alkyl group. One such commercially available product is FC 405, available from 3M Company. This product comprises a solution in ethanol of a silane having a non-hydrolysable fluorinated alkyl group. The product is used to treat ceramic or glass surfaces and is generally applied in the presence of an acid such as acetic acid. Although good results are obtained with such products, there continues to be a desire to further improve them, in particular the abrasion resistance.
Fluorinated polyether silanes are also known in the art. For example, EP 789050 discloses the use thereof for making composite film coatings. U.S. Pat. No. 3,646,085 teaches fluorinated polyether silanes for rendering glass or metal surfaces oil and water repellent. The surfaces are rendered oil and/or water repellent by treating them with a solution of the fluorinated polyether silane in ethanol or in 1,2,2-trichloro-1,1,2-trifluoroethane. WO 99/37720 discloses fluorinated polyether silanes for providing an antisoiling coating to antireflective surfaces on substrates such as glass or plastic. It is taught to apply the fluorinated polyether silane from a solution in an aprotic solvent. The necessary amount of water for the condensation reaction is supplied by allowing the treated substrates to cure in an environment of sufficient humidity.
U.S. Pat. No. 3,950,588 discloses the use of fluorinated polyether silanes to render ceramic surfaces such as bathroom tiles or cookware water and/or oil repellent. It is taught in this document that care should be taken that the coating composition is contained in an anhydrous state prior to application. Also, it is recommended in this document that the surface to be treated be free of water as a separate phase. The necessary water for the polycondensation reaction at the surface is derived from adsorbed water in the ceramic and/or the environment.
Although many fluorinated silane compositions are known in the art for treating substrates to render them oil and water repellent, there continues to be a desire to provide further compositions for the treatment of substrates, in particular substrates having a hard surface such as ceramics, in order to render them water and oil repellent. Desirably, such compositions and methods employing them can yield coatings that have improved properties. In particular, it would be desirable to improve the durability of the coating, including an improved abrasion resistance of the coating. The compositions can preferably be applied in an easy, convenient and safe way and are compatible with existing manufacturing methods. Preferably, the compositions will fit easily in the manufacturing processes that are practiced to produce the substrates to be treated. The compositions preferably also avoid the use of ecologically objectionable components.
SUMMARY OF THE INVENTION
The present invention provides in one aspect a composition for treating a substrate comprising a homogeneous mixture of
(a) a fluorinated polyether silane of the formula:
R
f
1
—[—Q—SiY
3−x
R
1
x
]
y
(I)
wherein R
f
1
represents a monovalent or divalent polyfluoropolyether group, Q represents an organic divalent linking group, R
1
represents a C
1
-C
4
alkyl group, Y represents a hydrolysable group; x is 0 or 1 and y is 1 or 2;
(b) an organic or an inorganic acid;
(c) water; and
(d) an organic solvent.
It has been found that when a fluorinated polyether silane of formula (I) is applied from a homogeneous mixture that includes an organic or inorganic acid as well as water, oil and water repellent coatings can be obtained that have improved abrasion resistance relative to similar fluorinated polyether silanes that have been applied in accordance with the methods of the prior art that use compositions that do not include water and the acid. Furthermore, the compositions spread well on the substrate to be treated with the result that uniform properties can be achieved over the whole surface of the treated substrate.
By the term ‘homogeneous mixture’ in connection with the present invention is meant that the composition is stable, i.e. no precipitation or phase separation occurs, for at least the amount of time necessary to prepare the composition and to apply it to the substrate. Generally, this means that the composition should be stable for at least one hour. Compositions of the invention were found to have generally a stability of 1 to 3 days or even longer despite the fact that the compositions contain water as well as an acid catalyst. The compositions suitable for use in this invention may be clear solutions as well as somewhat turbid mixtures.
Advantageously, the compositions of the invention are prepared by diluting a concentrated solution of the fluorinated polyether silane of formula (I). Accordingly, in a further aspect, the invention provides a method for making a composition for the treatment of a substrate, the method comprising diluting a concentrated solution of at least 25% by weight of a fluorinated polyether silane of formula (I) in an organic solvent by adding to said solution an organic solvent, water, and an organic or inorganic acid so as to prepare a homogeneous mixture containing between 0.01 and 5% by weight inclusive of the fluorinated polyether silane.
In a still further aspect, the present invention also provides a method for treating a substrate, comprising the step of applying the composition of the invention as defined above to the substrate. Preferably, the obtained coating on the substrate is cured, generally at an elevated temperature of 40 to 300° C. The heat for curing can be supplied either through an initial preheat of substrates having sufficient heat capacity to provide the heat for curing, or through heating of coated substrates by an external heat source subsequent to coating.
DETAILED DESCRIPTION OF THE INVENTION
The monovalent or divalent polyfluoropolyether group R
f
in the above Formula I, representing the fluorinated polyether silane, can include linear, branched, and/or cyclic structures, that may be saturated or unsaturated. It is preferably a perfluorinated group (i.e., all C—H bonds are replaced by C—F bonds). More preferably, it includes perfluorinated repeating units selected from the group of —(C
n
F
2n
)—, —(C
n
F
2n
O)—, —(CF(Z))—, —(CF(Z)O)—, —(CF(Z)C
n
F
2n
O)—, —(C
n
F
2n
CF(Z)O)—, —(CF
2
CF(Z)O)—, and combinations thereof. In these repeating units Z is a perfluoroalkyl group, an oxygen-substituted perfluoroalkyl group, a perfluoroalkoxy group, or an oxygen-substituted perfluoroalkoxy group, all of which can be linear, branched, or cyclic, and preferably have about 1 to about 9 carbon atoms and 0 to about 4 oxygen atoms. Examples of polyfluoropolyethers containing polymeric moieties made of these repeating units are disclosed in U.S. Pat. No. 5,306,758 (Pellerite). For the monovalent polyfluoropolyether group (wherein y is 1 in Formula I above), the terminal groups can be (C
n
F
2n+1
)—, (C
n
F
2n+1
O)— or (X′C
n
F
2n
O)—, wherein X′ is H, Cl, or Br, for example. Preferably, these terminal groups are perfluorinated. In these repeating units or terminal groups, n is I or more, and preferably 1 to 4.
Preferred approximate average
Dams Rudolf J.
Fieuws Franceska M.
Martin Steven J.
Pellerite Mark J.
Terrazas Michael S.
Moore Margaret G.
Zimmer Marc
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