Multi-purpose paint and varnish stripper

This invention provides a paint stripping composition comprising N-methyl-2-pyrrolidone and lower alkyl ethers of propylene glycol and dipropylene glycol. The composition does not include any toluene, halogenated hydrocarbons, acids, caustics or waxes and is not harmful to a wide variety of substrates.

BACKGROUND OF THE INVENTION 
This invention relates to compositions and methods for chemically removing 
paint and varnish from wood, metal, glass, fiberglass and many plastics 
surfaces. Prior to the realization of the various health hazards caused by 
halogenated hydrocarbon chemicals, the cornerstone of the paint stripping 
industry was methylene chloride. With the discovery of the hazards 
connected with the use of such materials, many proposals have been made 
for paint and varnish stripping compositions that do not include 
halogenated hydrocarbons. Hitherto, the most successful of these 
developments required the use of acids, thereby creating the problems of 
neutralization and/or harming the surface to be stripped. A recent patent, 
U.S. Pat. No. 4,965,010 to Ralph R. Swett, proposes to solve the problem 
by employing approximately equal parts of methyl ethyl ketone, methyl 
alcohol, toluene and acetone. The volatile nature of such compositions can 
create severe ventilation problems when working in confined spaces and 
further requires the use of large amounts of thickeners to assist in 
keeping the stripping compositions in place long enough to do a thorough 
stripping job. 
U.S. Pat. No. 5,089,164 describes and claims multi-purpose paint and 
varnish strippers comprising N-methyl-2-pyrrolidone, toluene, lower 
aliphatic alcohols and ketones, propylene glycol, mineral spirits, 
surfactants and thickeners. While such compositions are very effective 
paint and varnish strippers, it has been found that they are not 
environmentally acceptable due to the suspected carcinogenic activity of 
toluene. 
SUMMARY OF THE INVENTION 
This invention provides an improved composition and method for stripping 
paint or varnish from a variety of substrates such as, for example, wood, 
metal, glass, fiberglass and plastics which comprises at least one member 
of the group consisting of N-methyl-2-pyrrolidone and dipropylene glycol 
dimethyl ether, ethyl 3-ethoxypropionate, lower alipathic ketones, 
surfactants and at least one member of the group consisting of lower alkyl 
ethers of propylene glycol and dipropylene glycol wherein the lower alkyl 
groups comprise 1 to 4 carbon atoms. Odorants, such as d-limonene and 
thickeners, may be added if desired. The compositions of this invention 
have improved stripping efficiency, improved flash points, reduced 
evaporation and improved environmental safety. They are safe to handle and 
do not harm the surface to be stripped.

DETAILED DESCRIPTION OF THE INVENTION 
The compositions of this invention are preferably prepared by first 
blending the desired amounts of N-methyl-2-pyrrolidone or dipropylene 
glycol dimethyl ether and the lower alkyl ethers of propylene glycol and 
dipropylene glycol. After blending or thoroughly mixing the 
N-methyl-2-pyrrolidone and lower alkyl ethers of propylene glycol and 
dipropylene glycol, the remaining ingredients comprising ethyl 
3-ethoxypropionate, acetone, surfactants such as Igepal (Reg. TM) CO-730 
(nonylphenoxypoly(ethyleneoxy)ethanol), odorants such as, for example, 
d-limonene and thickeners, if desired, such as, for example, hydroxypropyl 
cellulose, and others known in the art, can be added and mixed as desired. 
When properly mixed, these components remove the paint and/or varnish 
without the development of air bubbles which serve to prevent the 
stripping composition from penetrating all layers of the paint or varnish 
to be removed. As used herein, propylene glycol refers to both the 1,2 and 
1,3 hydroxy substitution on the propylene moiety. 
Compositions in accordance with the present invention advantageously 
comprise the following materials and amounts, the weight percentages all 
being based on the total weight of the composition: 
______________________________________ 
Wt. % 
______________________________________ 
Mixture of propylene glycol n-butyl 
2-35 
ether (80%) and dipropylene glycol 
dimethyl ether (20%) 
N-methyl-2-pyrrolidone 10-25 
Ethyl 3-ethoxypropionate 
5-10 
Isopropyl alcohol 5-15 
Lower aliphatic ketones 
10-25 
Surfactant 1-5 
Odorant 1-5 
Thickener 0-5 
______________________________________ 
A preferred composition in accordance with the present invention comprises 
the following materials and approximate amounts, the weight percentages 
all being based on the total weight of the composition: 
______________________________________ 
Wt. % 
______________________________________ 
N-methyl-2-pyrrolidone 20 
Mixture of propylene glycol n-butyl 
20 
ether (80%) and dipropylene glycol 
dimethyl ether (20%) 
Mixture of 1-Methoxy-2-propanol (98%) 
10 
and 2-Methoxy-1-propanol (2%) 
Ethyl 3-ethoxypropionate 
10 
Isopropyl alcohol 10 
Acetone 25 
Igepal (Reg. TM) CO-730 2 
Odorant 4 
______________________________________ 
If a semi-paste is desired, a thickener may be added in an amount of about 
4% and the amount of acetone decreased accordingly. 
In the most preferred compositions, hydroxypropyl cellulose is employed as 
the thickener and d-limonene is a preferred odorant. 
The compositions of this invention are environmentally safe, do not burn 
the skin, do not raise the grain or fur the wood, do not harm veneers, 
patina, glue joints, glass, fiberglass, most plastics or metal and do not 
require neutralizing or a water wash. Because of their reduced volatility, 
the compositions of this invention have increased effectiveness without 
requiring excessive amounts of thickeners. Further, a wax sealer is not 
needed to reduce evaporation. Wax sealers generally leave a residue or 
film on stripped surfaces and thus interfere with finishes that are to be 
re-applied. 
The compositions of the invention can be applied as a liquid or can be 
thickened sufficiently to form a semi-paste like product. No acids or 
caustics are employed and no halogenated hydrocarbons. The compositions 
will soften most paints and varnishes in from 1 to 3 minutes, at which 
time the residue can be readily removed with a scraper or a rag or brush 
moistened with further stripping composition. Urethane finishes require a 
somewhat longer time to soften and the use of the semi-paste formulation 
rather than the liquid formulation is suggested. These compositions will 
stay moist for up to 24 hours without leaving an oily residue. 
Various modifications may be made in the present invention without 
departing from the spirit or scope thereof, as will be understood by those 
skilled in the art.