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United States Patent m
US005688864A [ii] Patent Number:  Date of Patent:
 AUTOPHOBIC WATER REPELLENT SURFACE TREATMENT
 Inventor: George B. Goodwin. Mars, Pa.
 Assignee: PPG Industries, Inc., Pittsburgh. Pa.
 Appl. No.: 734,156
 Filed: Oct 21, 1996
Related U.S. Application Data
 Continuation of Ser. No. 458,149, Jun. 1, 1995, abandoned, which is a continuation-in-part of Set. No. 220353, Mar. 30, 1994, abandoned, which is a continuation-in-part of Ser. No. 589,235, Sep. 28, 1990, Pat No. 5,308,705, which is a continuation-in-part of Ser. No. 503,587, Apr. 3, 1990, Pat No. 4,983,459.
 Int. CI.6 C08G 77/24
 U.S. CI 524/858; 106/287.14; 106/287.16;
427/387; 428/447; 428/429
 Field of Search 524/858; 106/287.14,
106/287.16; 427/387; 428/447, 429
 References Cited
U.S. PATENT DOCUMENTS
3,859,320 1/1975 Atherton 260/448.2 N
3,950,588 4/1976 McDougal 442/80
4,024,306 5/1977 Takamizawa et al 427/387
4^63,371 4/1981 Franz 428/432
4,276,350 6/1981 Franz 428/410
4,301,197 11/1981 Franz et al 427/353
4,529,657 7/1985 Franz 428/410
4,617,057 10/1986 Plueddemann 106/2
4,724,022 2/1988 Armstrong 156799
4,879,345 11/1989 Connelly et al 525/104
4,944,962 7/1990 Furutaetal 427/164
4,983,459 1/1991 Franz et al 428/410
4,997,684 3/1991 Franz et al 427/384
5266,358 11/1993 Uemuraetal 427/376.2
5294252 3/1994 Gun 106/287.13
5,308,705 5/1994 Franz et al 428/421
5,314,731 5/1994 Yoneda et al 428/429
5,314,947 5/1994 Sawaragi 524/780
5,328,768 7/1994 Goodwin 428/428
5,368,892 11/1994 Berquier 427/299
5.413.865 5/1995 Nakamura et al 428/432
5.421.866 6/1995 Stark-Kasley et al 106/2
5,424,130 6/1995 Nakanishi et al 428/410
5,425,804 6/1995 Shinohara et al 106/2
5,489,328 2/1996 Ono et al 106/2
5.523.161 6/1996 Goodwin 428/421
5.523.162 6/1996 Franz et al 428/421
FOREIGN PATENT DOCUMENTS
0 476 510 3/1992 European Pat. Off. .
0 492 545 7/1992 European Pat. Off. .
0 513 727 11/1992 European Pat. Off. .
0 545 201 6/1993 European Pat. Off. .
0 548 775 6/1993 European Pat. Off. .
0 719 743 7/1996 European Pat. Off. .
4218657 12/1992 Germany.
58-172244 10/1983 Japan.
61-278574 12/1986 Japan .
1-275674 11/1989 Japan.
Miall & Sharp, "A New Dictionary of Chemistry", 4th edition, p. 440.
Primary Examiner—Margaret W. Glass
Attorney, Agent, or Firm—Raymond J. Harmufh
a composition and method are disclosed whereby a substrate such as glass, plastic, metal, inorganic polymer coated substrate or inorganic coated substrate is provided with a durable non-wetting surface by treatment with a perfluoroalkylalkyl silane in a solvent which together form a composition which initially wets the surface. As the perfluoroalkylalkyl silane reacts with the surface, the remaining composition is repelled by the perfluoroalkylalkyl silane treated surface due to the difference between the surface tension of the solvent and the free energy of the treated surface, for expedient removal of the remaining composition from the treated surface.
45 Claims, 2 Drawing Sheets
AUTOPHOBIC WATER REPELLENT
CROSS REFERENCE TO RELATED
This application is a continuation of U.S. application Ser. No. 08/458.149, filed Jun. 1, 1995, now abandoned, which is a continuation-in-part of U.S. application Ser. No. 08/220, 353, filed Mar. 30, 1994, now abandoned, which is a continuation-in-part of U.S. application Ser. No. 07/589,235 filed Sep. 28, 1990, now U.S. Pat. No. 5308,705, which is a continuation-in-part of U.S. application Ser. No. 07/503, 587 filed Apr. 3, 1990, now U.S. Pat. No. 4,983,459.
The present invention relates generally to the art of surface treatment and, more particularly, to the art of producing a water repellent surface on various substrates, and most particularly to producing such a water repellent surface without applying excess material which must be removed.
U.S. Pat No. 4,724,022 to Armstrong discloses an improved method of preparing a glass release surface useful in the manufacture of anti-lacerative window assemblies by treating the glass surface with (heptadecafluoro-1,1,2,2tetrahydrodecyl)-l-trichlorosilane.
European Patent Application No. 92107814.3 (Publication Number 0 513 690 A2) of Yoneda et aL describes a surface-treated substrate having at least two treated surface layers wherein the first outermost layer is obtained by treatment with a compound forming a surface having a contact angle of at least 70° against water and the second underlayer is obtained by treatment with at least one reactive silane compound selected from isocyanate silane compounds and hydrolyzable silane compounds.
U.S. Pat. Nos. 4,983.459 and 4,997.684 to Franz et al. disclose an article and method respectively for providing a durable nonwetting surface on glass by treatment with a perfluoroalkylalkyl silane and a fluorinated olefin telomer.
U.S. Pat. No. 5308,705 to Franz et al. describe providing nonwetting surface properties to substrates other than glass by treatment with a perfluoroalkylalkyl silane and a fluorinated olefin telomer.
U.S. Pat. No. 5328.768 to Goodwin discloses a glass substrate the surface of which is treated with first a silica primer layer and second a perfluoroalkylalkyl silane.
U.S. Pat. No. 5368.892 to Berquier describes a nonwettable glass sheet comprising a hydrophobic, oleophobic. UV resistant layer and a process for manufacturing the same, which includes cleaning the glass, contacting the glass with a solution containing a fluorinated organosilane in a nonpolar solvent system at a temperature ranging between -10° C. and 25° C. for at least 5 minutes, and rinsing.
DESCRIPTION OF THE DRAWING
FIG. 1 illustrates the contact angle of a liquid drop as a function of solvent surface tension in dynes per centimeter on substrates having various surface free energies, measured in dynes per centimeter.
FIG. 2 illustrates the contact angle of a liquid drop as a function of surface free energy in dynes per centimeter of various fluids, the surface tensions of which are measured in dynes per centimeter.
SUMMARY OF THE INVENTION The present invention provides a substrate surface with high water repellency and high lubricity. Durable water and
dirt repellency of a substrate surface are provided by applying to the substrate surface a composition comprising a perfluoroalkylalkyl silane compound and a solvent which renders the surface treatment autophobic, i.e. the composi
5 tion initially wets the substrate surface, and as the substrate surface becomes treated with the perfluoroalkylalkyl silane, the composition is repelled by the treated substrate surface. The composition comprises at least one solvent for the perfluoroalkylalkyl silane. The composition comprises at
10 least one solvent having a boiling point sufficiently high to prevent complete evaporation of solvent upon application of the perfluoroalkylalkyl silane, and a surface tension at least 5 dynes per centimeter higher than the surface free energy of the perfluoroalkylalkyl silane treated surface. The compo
15 sition may comprise a single solvent or a mixture of solvents.
Description of the Preferred Embodiment
A composition comprising perfluoroalkylalkyl silane and
20 solvent in accordance with the present invention is applied to the surface of a substrate to produce a surface treatment article. The perfluoroalkylalkyl silane and solvent composition is preferably employed as a suspension or solution, preferably in a solvent for the perfluoroalkylalkyl silane. The
25 preferred solution of the present invention is applied to a substrate surface by any conventional technique such as dipping, flowing, wiping or spraying. The composition initially wets the surface, usually for about 0.2 to 2 seconds until the treated surface becomes sufficiently nonwetting to
30 repel the remaining composition. As the perfluoroalkylalkyl silane reacts with the surface, and the treated surface repels the remaining composition, any excess composition can be easily removed, for example by wiping, without deposition of any excess silane as a thin hazy film which is difficult to
35 remove and requires significant effort to eliminate.
Preferred perfluoroalkylalkyl silanes have the general formula R^'nSiX,^^^,, wherein R is a perfluoroalkylalkyl radical; m is typically one, n is typically zero or one, and
4Q m+n is not greater than 3; R' is a vinyl or alkyl radical, preferably methyl, ethyl or propyl; and X is preferably a radical such as halogen, acyloxy, and/or alkoxy. Preferred perfluoroalkylalkyl radicals preferably comprise perfluoroalkyl moieties which range from CF3 to ... preferably
45 Qfjj to C18F37, and most preferably C8F17 to Cl2F25. The alkyl moiety of the perfluoroalkylalkyl radical is preferably ethyl. Preferred radicals for X include chloro, bromo, iodo, methoxy, ethoxy and acetoxy radicals. Preferred perfluoroalkylethylsilanes in accordance with the present invention
50 include perfluoroalkylethyltrichlorosilane, perfluoroalkylethyltrimethoxysilane, perfluoroalkylethyltriacetoxysilane, perfluoroalkylethyldichloro(methyl)silane and perfluoroalkylethyldiethoxy(methyl)silane.
55 These perfluoroalkylethylsilanes appear to react with bonding sites at the substrate surface on a molecular basis. Strong surface bonding of the perfluoroalkylethylsilanes produces a durable substrate surface which exhibits a high contact angle with a drop of water, indicating high water
60 repellency. The perfluoroalkylalkyl silane composition may further comprise a hydrolyzable silane capable of hydrolytic condensation to form a silica gel which acts as an integral primer. Preferred hydrolyzable silanes include fully hydrolyzable organosilanes, such as tetrahalosilanes. particularly
65 tetrachlorosilane, SiCl4.
Suitable solvents include those with relatively high boiling points, preferably above 65° C, and surface tensions