Coating processes – With post-treatment of coating or coating material – Swelling agent or solvent applied to treat coating
Reexamination Certificate
2000-05-08
2001-03-13
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Swelling agent or solvent applied to treat coating
C427S388100, C427S389700, C427S389900, C427S393400, C427S393500, C427S393600, C427S394000, C427S435000, C427S439000
Reexamination Certificate
active
06200637
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to treating surfaces of substrates. More particularly, the invention relates to treating the surfaces using a carbon dioxide fluid. The method is particularly useful for imparting stain resistance to fabrics.
BACKGROUND OF THE INVENTION
In a number of industrial applications, it is often desirable to treat the surface of an article or substrate in order to protect the substrate from contaminants. This typically includes controlling and enhancing the barrier properties of a surface to, for example, oils, grease, lipophilic materials, water, hydrophilic solutions, and dirt. Examples of such applications include SCOTCH GUARD® and STAIN MASTER® surface coating materials for textile articles such as furniture, clothing, and carpets to impart resistance to staining, and also treating articles formed from metal such as precision parts. It is often desirable to apply a surface treatment to an article in order to protect an article from foreign matter while also preserving the desirable physical properties of the article. With respect to textile-related articles for example, it is particularly desirable to maintain aesthetic properties relating to hand, drape, and texture.
For the most part, organic solvents such as hydrocarbons, chlorinated solvents, and chlorofluorocarbons (CFCs) have been employed in treating various substrates. Recently, however, the use of these solvents has been increasingly disfavored due to heightened environmental concerns. As one alternative, aqueous-based systems have been proposed for treating various articles. The use of the aqueous-based systems, however, also suffers from possible drawbacks, For example, contacting an article with water often adversely affects the physical properties of the article. For example, the texture and drape of a textile can be negatively impacted, or flash rusting of metal parts may occur due to water contact. Additionally, many low surface energy materials are largely insoluble in water, and must be formulated into emulsions or suspensions (an inherent disadvantage of aqueous systems). Moreover, water of suitable quality for use in coating and impregnation is becoming less available and more expensive.
CO
2
-based dry cleaning systems that contain surfactant molecules (particularly molecules having a CO
2
-philic group are described in, for example, U.S. Pat. Nos. 5,683,473; 5,676,705; and 5,683,977, all to Jureller. The purpose of the surfactant molecule proposed in the Jureller patents is to carry away soil from the fabrics, rather than to become deposited upon, and seal soil to, the fabric. Surface treatment is, accordingly, neither suggested nor disclosed.
In view of the above, it is an object of the present invention to provide a method of treating and/or impregnating a substrate which does not require the use of organic solvents or water.
It is also an object of the present invention to provide a method of impregnating a substrate which minimizes adverse affects to the physical properties of the substrate.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a method of treating a substrate. The method comprises contacting, preferably by immersing, a surface of the substrate with a pressurized fluid comprising carbon dioxide and a surface treatment component. The surface treatment component is entrained in the pressurized fluid and contacts the surface so that the surface treatment component lowers the surface tension of the surface of the substrate and treats the substrate. Surface treatment components comprising fluoroacrylate polymers (including copolymers thereof) are preferred. The fluid is preferably a liquid or supercritical fluid.
In another aspect, the invention provides a method of imparting stain resistance to a fabric. The method comprises immersing the fabric in a pressurized fluid containing carbon dioxide and a surface treatment component. The surface treatment component is entrained in the pressurized fluid and contacts the fabric to lower the surface tension of the fabric. The surface treatment component is deposited on the fabric, and the carbon dioxide separated from the fabric so that the surface treatment component remains deposited on the fabric, thus rendering the fabric stain resistant.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be further described by the preferred embodiments presented herein. It should be understood however that the embodiments are to be interpreted as being illustrative of the invention and not as limiting the invention.
The invention relates to a method of treating a substrate in a pressurized system. The method includes the step of contacting a surface of the substrate with a fluid comprising carbon dioxide and a surface treatment component. The surface treatment component is entrained in the fluid and contacts the surface so that the surface treatment component lowers the surface tension of the substrate, In this instance, the “entrainment of the surface treatment component in the fluid” refers to a surface treatment component which may be solubilized, dissolved, emulsified, or dispersed in the bulk fluid during transport of the fluid to the substrate surface and also upon the interaction of the fluid with the substrate surface. Entrainment may also include surface treatment components which are insoluble in the carbon dioxide containing fluid but which may be physically dispersed in the fluid with or without the aid or a dispersing agent or the like. For the purposes of the invention, the term “lowers the surface tension” can be understood as reducing the surface tension of the substrate to the extent such that in end use commercial applications contaminant materials (aqueous, organics, solids, liquids, etc.) exhibit a reduced tendency to adhere or absorb onto the substrate surface. For illustrative purposes, the invention is to be differentiated from processes in which surface treatments are applied in a transient manner for treating materials. Such an instance involves sizing of textile yarns as set forth in Bowman et al.,
Textile Res. J.
66 (12), 795-802 (1996), in which coating materials are applied to the yarns and then removed. In contrast to the claimed invention, properties imparted by the sizing would render the substrate unusable.
Moreover, the surface treatment component is entrained in the fluid upon contacting the substrate. Such a process is distinguishable from spraying applications in which a fluid containing a coating material is emitted from an apparatus and thereafter undergoes a phase change, and is propelled by the fluid to the substrate. The surface treatment component of the present invention is entrained in the pressurized fluid upon contacting the substrate.
As described above, the surface tension is lowered as a result of applying the surface treatment component. Preferably, the surface tension is lowered by a value of 10 percent, and more preferably the surface tension is lowered by a value of 25 percent. The level of reduction can be on the order of 1 dyne/sq cm.
The fluid employed in the method of the invention is pressurized fluid, which is defined to be greater than ambient, typically at least 20 bar. For the purposes of the invention, the fluid contains carbon dioxide in a liquid, gaseous, or supercritical phase. If liquid CO
2
is used, the temperature employed during the process is preferably below 31° C. If gaseous CO
2
is used, it is preferred that the phase be employed at high pressure. As used herein, the term “high pressure” generally refers to CO
2
having a pressure from about 20 to about 500 bar. With respect to CO
2
, the pressure of the gas is typically greater than 20 bar and less than its critical pressure.
In the preferred embodiment, the CO
2
is utilized in a dense (i.e., “supercritical” or “liquid” or “compressed gas”) phase. Such a phase typically employs CO
2
at a density greater than the critical density, typically greater than 0.5 g/cc. As used herein, “supercritical” means that a fluid medium is at a temperature that is sufficiently high that
DeYoung James P.
McClain James B.
Romack Timothy J.
Cameron Erma
MiCell Technologies, Inc.
Myers Bigel & Sibley & Sajovec
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