Compositions for aqueous delivery of fluorinated silanes

Details Compositions for aqueous delivery of fluorinated silanes Compositions for aqueous delivery of fluorinated silanes

2001-11-15

2003-07-15

Moore, Margaret G. (Department: 1712)

Compositions: coating or plastic

Coating or plastic compositions

Silicon containing other than solely as silicon dioxide or...

C106S287140, C106S287270, C428S447000, C428S421000, C427S387000

Reexamination Certificate

active

06592659

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to aqueous delivery of fluorinated silanes to a substrate. More particularly, the present invention is a dilutable, non-aqueous concentrate comprising at least one fluorinated silane and at least one fluorinated surfactant, which together with water or an aqueous solvent mixture form an aqueous dilution that may be coated and cured on a substrate.
BACKGROUND OF THE INVENTION
Good oil-repellent and water-repellent coatings may be provided to certain substrates by applying to a substrate fluorinated silanes in the molten state or dissolved in volatile organic solvents. The applied fluorinated silanes are cured by heating with a catalyst to chemically affix the fluorinated silanes to the substrates. (See, for example, U.S. Pat. No. 3,012,006 (Holbrook et al.)). However, the use of volatile organic solvents is generally harmful to the environment, and may be hazardous due to the flammability of the solvents. Therefore, an alternative means to apply fluorinated silanes to substrates was developed, which is to use aqueous delivery. (See, for examples, U.S. Pat. No. 5,274,159 (Pellerite et al.), U.S. Pat. No. 5,702,509 (Pellerite et al.), and U.S. Pat. No. 5,550,184 (Halling)).
One problem with known compositions for the aqueous delivery of fluorinated silanes to substrates is that they may not have long shelf lives. Another problem is that they may require high-shear mixing before they are coated on a substrate. Known compositions have high solids content, which result in thick coatings
Although using aqueous delivery of fluorinated silanes to substrates is known in the art, there continues to be a desire to provide compositions for aqueous delivery of fluorinated silanes that: 1) can be stored for relatively long periods of time; 2) do not require high-shear mixing or other input of mechanical energy; 3) have relatively low solids content, making them easier to coat thinly on glass and other substrates; and 4) at the same time, once applied to a substrate and cured, can provide durable coatings.
SUMMARY OF THE INVENTION
The present invention provides compositions for the aqueous delivery of fluorinated silanes. One type of composition is a dilutable, non-aqueous concentrate and another type is an aqueous dilution comprising the dilutable, non-aqueous concentrate and a diluting medium that comprises water or an aqueous solvent mixture.
The dilutable, non-aqueous concentrate comprises a non-aqueous, homogeneous mixture comprising: (a) at least one fluorinated silane of the formula I:
R
f
1
—[—Q—[SiY
3-x
R
1
x
]
z
]
y
  (I)
wherein R
f
1
represents a monofunctional or difunctional fluorinated group; Q independently represents an organic difunctional or trifunctional linking group; R
1
independently represents a C
1
-C
4
alkyl group; Y independently represents a hydrolyzable group; x is 0 or 1; y is 1 or 2; and z is 1 or 2; and (b) at least one fluorinated surfactant. The dilutable, non-aqueous concentrate may optionally further comprise one or both of at least one organic cosolvent and at least one additive.
The dilutable, non-aqueous concentrate must be diluted with water or an aqueous solvent mixture before being coated on a substrate. Advantageously, the dilutable, non-aqueous concentrate has a relatively long shelf life that is greater than about 1 day, preferably greater than about 14 days, and most preferably greater than about 6 months under proper storage conditions. The dilutable, non-aqueous concentrate may be shipped and stored more economically than in diluted form. The dilutable, non-aqueous concentrate may be diluted at the location where it is to be coated, which advantageously allows for greater flexibility in choices of the dilution and hence thickness of the coatings being applied. The dilutable, non-aqueous concentrate is dispersed in water or an aqueous solvent mixture (to form the aqueous dilution) simply by shaking by hand a mixture of the dilutable, non-aqueous concentrate and either water or an aqueous solvent mixture. No additional mechanical processing, such as high-shear mixing or ultrasonication, is required.
The aqueous dilution comprises: (a) a diluting medium comprising water or an aqueous solvent mixture comprising water and at least one water miscible cosolvent; and (b) a dilutable, non-aqueous concentrate comprising a non-aqueous, homogeneous mixture comprising: (i) at least one fluorinated silane of the formula I:
R
f
1
—[—Q—[SiY
3-x
R
1
x
]
z
]
y
  (I)
wherein R
f
1
represents a monofunctional or difunctional fluorinated group; Q independently represents an organic difunctional or trifunctional linking group; R
1
independently represents a C
1
-C
4
alkyl group; Y independently represents a hydrolyzable group; x is 0 or 1; y is 1 or 2; and z is 1 or 2; and (ii) at least one fluorinated surfactant.
The aqueous dilution may be coated on a substrate to provide a durable coating. Advantageously, the aqueous dilution of the present invention has a relatively low solids content, which makes it easier to coat thinly on glass or other siliceous substrates that may have, for example, optical properties that are sensitive to thickness. The inventive aqueous dilution allows for the elimination of or the substantial reduction in the use of organic solvents in the process that may be flammable and/or harmful to the environment. The aqueous dilution also has a shelf life that is at least several hours under proper storage conditions.
Other embodiments of the present invention include a method of treating a substrate, and an article comprising a substrate and a coating that is formed by coating and curing the aqueous dilution.
DETAILED DESCRIPTION OF THE INVENTION
Dilutable, Non-aqueous Concentrate
The dilutable, non-aqueous concentrate of the present invention comprises a non-aqueous, homogeneous mixture that comprises at least one fluorinated silane and at least one fluorinated surfactant. The dilutable, non-aqueous concentrate may optionally further comprise at least one organic cosolvent, and/or at least one additive.
A “homogeneous mixture,” when referring to the dilutable, non-aqueous concentrate, is defined as the dilutable, non-aqueous concentrate being stable, i.e., no substantial precipitation or substantial phase separation occurs for at least the time necessary to prepare an aqueous dilution from the dilutable, non-aqueous concentrate, however, preferably, and for the purpose of being commercially practical, the dilutable concentrate is stable for a period of at least about one hour, and preferably up to about six months or longer, under proper storage conditions (closed container, no water, room temperature). The dilutable, non-aqueous concentrate may be clear or somewhat hazy.
By the term “non-aqueous” it is meant that water is not added as a component of the dilutable, non-aqueous concentrate. However, there may be adventitious water in the other components of the composition, but the total amount of water does not adversely affect the shelf life or the stability of the dilutable, non-aqueous concentrate (i.e., preferably less than about 0.1 wt % of the dilutable, non-aqueous concentrate).
Fluorinated Silane
The fluorinated silane of the dilutable, non-aqueous concentrate has the formula
R
f
1
—[—Q—[SiY
3-x
R
1
x
]
z
]
y
  (I)
wherein R
f
1
represents a monofunctional or difunctional fluorinated group, optionally containing one or more ether oxygen atoms, Q independently represents an organic difunctional or trifunctional linking group, R
1
independently represents a C
1
-C
4
alkyl group, Y independently represents a hydrolyzable group, x is 0 or 1, y is 1 or 2, and z is 1 or 2. Fluorinated silanes of Formula I are incompatible with water (meaning, the fluorinated silanes cannot substantially combine with water to form a single phase blend) and immiscible with water (meaning, the fluorinated silanes cannot substantially combine with water so as to result in the combination or blend exhibiting a single T
g

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