Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Liquid composition
Reexamination Certificate
2002-06-03
2004-08-03
Webb, Gregory (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Liquid composition
C510S177000, C510S273000, C510S410000, C252S067000, C252S364000, C134S038000, C134S040000
Reexamination Certificate
active
06770614
ABSTRACT:
BACKGROUND OF THE INVENTION
Precision cleaning is a term used to describe the removal of soil from sensitive electrical and electronic components. For example, electrical, telecommunication and electronic components, including switches, circuits, boards, etc., are often cleaned during their manufacturing process in order to ensure proper electrical conductivity of these components. In addition, during repair and maintenance situations, it is often desirable to perform spot cleaning of electrical and electronic parts.
Ten years ago, the exclusive material for such precision cleaning applications was 1,1,2-trichloro,1,2,2-trifluoroethane, also known as CFC-1 13, which is marketed by E. I.du Pont Nemours & Co. under the trademark Freon TF®, by Allied Signal under the trademark Genesolv D® and by Imperial Chemical Industries under the trademark Arklone P®. However, in 1996 CFC-113 was phased out due to its ozone-depleting characteristics, forcing the development of alternative products. Numerous alternatives have been developed because not one single product has been able to duplicate all of the characteristics of CFC-113.
During the past ten years, a subset of the precision cleaning category has emerged. In particular, in some precision cleaning applications, the soil, which may include grease, sludge and oil, is very heavy and tenacious. It has been found that most CFC-113 alternative products are ineffective on these types of soils. Therefore, HCFC-141b became widely accepted as the product of choice for cleaning grease-like soils from electrical and electronic components. HCFC-141b was a preferred cleaner because it is strong enough to attack heavy soil, yet is gentle enough that it will not damage some sensitive plastics. In addition, 141b is nonflammable and evaporates quickly. The only disadvantage is that it is an ozone-depleting chemical. Consequently, the manufacture of 141b will cease at the end of 2002. Therefore, there remains a need in the art for an environmentally friendly precision cleaner which is strong enough to destroy heavy soil, yet mild enough for use on plastic components.
The application of precision cleaners during manufacturing of the electrical/electronic components may be performed in a cleaning machine, such as a vapor degreaser or cleaning tank. In contrast, often after an electrical or electronic component becomes part of a larger machine, it is no longer possible to clean it using a vapor degreaser or cleaning machine. Therefore, when performing spot cleaning during repair and maintenance situations, aerosol cans are often preferred by maintenance technicians because they are portable, and the aerosol stream may be easily directed to a specific area on the substrate. All propellants are not equivalent and the choice of a proper propellant depends on a given cleaner and a particular situation.
A further desirable feature of a precision cleaning product is that it leave no residue on the substrate. Not only might residue interfere with the performance of the electrical or electronic component, but it could also damage the component.
Consequently, a desirable precision cleaner would be a non-ozone depleting, non-flammable composition which would be applicable as an aerosol, would leave no residue, and would be strong enough to tackle tenacious soil, while at the same time being gentle enough for use on plastic substrates.
BRIEF SUMMARY OF THE INVENTION
According to the present invention, a cleaning composition which meets the above objectives comprises a blend of:
(a) at least one halogenated, saturated or unsaturated hydrocarbon other than cis-1,2-dichloroethylene;
(b) at least one fluorinated, saturated or unsaturated hydrocarbon having the formula C
n
H
m
F
p
, wherein 3≦n≦6, 0≦m≧9 and p≧5;
(c) at least one fluorinated, saturated or unsaturated ether having the formula C
a
H
b
O
c
F
d
, wherein 3≦a≦6, 0≦b≦9, c≧1, and d≧5;
(d) methylal; and
(e) at least one simple alcohol.
According to a preferred embodiment of the invention, an aerosol cleaning composition comprises a blend of about 40 to about 70 weight percent trans-1,2-dichloroethylene, about 20 to about 55 weight percent 1,1,1,3,3-pentafluorobutane, greater than 0 percent but not more than about 20 weight percent methyl nonafluorobutyl ether, greater than 0 percent but not more than about 20 weight percent ethyl nonafluoroisobutyl ether, greater than 0 percent but not more than about 5 weight percent methylal, about 3 to about 8 weight percent carbon dioxide, and greater than 0 percent but not more than about 5 weight percent isopropanol.
According to the present invention, a method for cleaning a substrate, particularly an electronic or electrical component, having a soiled surface comprises applying to the surface one of the above cleaning compositions and removing the composition from the surface, along with the soil.
DETAILED DESCRIPTION OF THE INVENTION
The cleaning compositions according to the present invention are particularly useful for precision cleaning of electronic and electrical components, and in particular for spot cleaning during repair and maintenance situations. As will be described in further detail below, a preferred embodiment of the invention is directed to aerosol cleaning compositions, which are advantageous because they are portable and easy to direct to a specific area. Further, the cleaning compositions according to the present invention are effective on heavy soil such as grease, sludge and oil, yet usable on plastics, leave no residues and are non-ozone depleting.
The compositions are non-aqueous and comprise five essential components as follows: (a) at least one halogenated saturated or unsaturated hydrocarbon; (b) at least one fluorinated saturated or unsaturated hydrocarbon; (c) at least one saturated or unsaturated fluorinated ether; (d) methylal; and (e) at least one simple alcohol. The compositions may optionally comprise a propellant for aerosol application.
The halogenated saturated or unsaturated hydrocarbon preferably has low PEL (personal exposure limit, established by OSHA) and TLV (threshold limit value, established by American Conference of Governmental Industrial Hygienists (ACGIH)), good cleaning ability, and is non-flammable. The halogenated saturated or unsaturated hydrocarbon is preferably trans-1,2-dichloroethylene, trichloroethylene, perchloroethylene or n-propyl bromide, and more preferably is 1,2-trans-dichloroethylene, because its inclusion results in a cleaning composition with desirable cleaning properties, as will be explained in further detail below. However, other halogenated saturated or unsaturated hydrocarbons, either branched or linear, which contain chlorine, fluorine, bromine, or iodine are also within the scope of the invention, as well as halogenated hydrocarbons containing oxygen and/or nitrogen heteroatoms. However, 1,2-cis-dichloroethylene is not an appropriate halogenated hydrocarbon for the cleaning composition. The halogenated hydrocarbon is preferably present in an amount of about 40 to about 70 weight percent of the total weight of the composition, and more preferably about 53 to about 62 weight percent.
The second essential component of the cleaning compositions is a fluorinated hydrocarbon having the formula C
n
H
m
F
p
, wherein 3≦n≦6, 0≦m≦9 and p is at least 5. The fluorinated hydrocarbon may be branched, linear or cyclic, and may be saturated or unsaturated. Although perfluorinated hydrocarbons are within the scope of the invention, they are not preferred because they may have high global warming potential (GWP). Preferred fluorinated hydrocarbons include 1,1,1,3,3-pentafluoropropane and 1,1,1,2,3,4,4,5,5,5-decafluoropentane. A more preferred compound is 1,1,1,3,3-pentafluorobutane, which has a more desirable boiling point. The fluorinated hydrocarbon compound is preferably present in an amount of about 20 to about 55 weight percent of the total weight of the composition, and more preferably about 25 to about 50 weight percent.
The compositions also contain at least one
Miller Richard L.
Nemeth Melodee A.
Akin Gump Strauss Hauer & Feld & LLP
CRC Industries, Inc.
Webb Gregory
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