CA1330288B - Solid Absorbent Containing Paint Removing Compositions - Google Patents

Abstract

ABSTRACT

Novel paint removing compositions, a method for their production, and methods for using the same, are described, which employ conventional active paint removing ingredients, in combination with auxiliary ingredients, which aid in lifting paint from a painted surface, such as an automobile body and which act to prevent re-adhesion of the paint, and to convert the paint-paint-removing composition mixture to a dry, friable mass, which is easily removed to expose the bare substrate, and produce a dry easily handled and disposable waste product.

Description

1080-1(R) SOLID ABSORBENT CONTAINING PAINT REMOVING COMPOSITIONS

Back~round and PriorArt The present invention relates to paint removal and, more particularly, to the stripping of paint and other finishes from automobiles prior to repainting.

It i8 well-known to those in the automobile body repair and refinishing art that removal of the old automotive f~nish iB the most difficult, time-consuming,and messiest part of the work. Automotive finishes can be removed by sanding and/or with the aid of chemical strippers. When u~ing a chemical etripper, typically a liquid, or more usually, a semi-liquid thin paste, containing the active paint stripper is applied to the auto body to be stripped and allowed to stand until the paint has been lifted from the surface. This may require several hours or even standing overnight. When the paint iB at its loosest, it is removed by scraping.This produces a messy deposit on the floor of the work place consisting of strips or scraps of paint film swollen with the still wet paint remover. Inasmuch a~ the active paint removing agents in the paint remover are irritating to the skin andeyes, protective gloves and goggles are preferably worn for this work. In any event, it is a difficult and unpleasant task to clean up and dispose of the wet paint strippings.

Another disadvantage of commercially available paint removers, particularly for automotive use, is that they have varying degrees of effectiveness, removingmost of the paint in some cases, but only part of the paint or hardly any of it in others. Previously available paint removers are particularly ineffective on epoxy, urethane and lacquer finishes, and some automotive undercoats.

Still another disadvantage of currently available chemical paint strippers B 3~

i8 that the paint tends to re-adhere to the stripped surface if the paint remover is allowed to stand too long. Therefore, the scraping operation must be conducted at the optimun time to avoid the need to re-apply paint remover with consequent 1086 of time. This presents a scheduling problem and necessarily reduces efficiency. ~
~ ~' The deficiencies of presently available chemical paint removers are 80 great that some auto body shops resort to the more time-consuming and therefore, expensive sand-blasting and grinding techniques. These methods of paint removal also have the disadvantage of creating a dust problem, -requiring the workers towear protective masks and clothing. Also, as with any operation that creates a dust-laden atmosphere, there i~ always the possibility of a dust explosion.

In view of the very large volume of automotive refinishing work, and thc obvious disadvantages ofthe currentmethods of paintremoval, itis apparentthat there is a pressing need in the art for an improved method of paint removal and improved chemical composition~ for this purpose.

It is a primary object of the present invention to seek to provide an improved method for ~emoving paint, and particularly automotive paint, and improved chemical compositions for this purpose, which are not subject to the disadvantages of the prior art.

It is another aspect of the invention to seek to provide an improved method and compositions for paint removal, which reduce labor, increase efficiency, do not require protective clothing during the stripping operation, and which permit easy clean up ofthe stripped paint.

It is still another aspect of the invention to seek to provide a method and compositions for paint removal, which prevent re-adhesion of stripped paint to the treated surface.

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~ -It is yet another aspect of the invention to seek to provide a method and composition~ for paint removal which are not only more efflcient and convenient than those of the prior art, but which are also less expensive.

It is still another aspect of the invention to seek to provide a method and compositions capable of completely removing all commercial automotive finishes, including acrylics, synthetics, epoxies, urethanes, lac~uers and undercoatings, down to the bare metal with minimal effort in the stripping operation.
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It is another aspect of the invention to seek to provide a method and compositions for automotive paint removal in which the paint is removed in dry flake form without the need for heavy manual scraping.

It is another aspect of the invention to seek to provide a method and compositions for the removal of automotive paint in which the stripped paint i~
converted to a dry, frangible mass, which can be removed from the treated surface by compressed air from an air gun to form a dry flaky material easily swept up for disposal.

It is yet another aspect of the invention to seek to provide paint removing compositions which have good flow and adhesion, long shelflife, non-flammability, good color and low odor.

Itis still another aspect ofthe invention to provide such compo~itions which are capable of removing multiple coats of paint in a single operation. ~ ~;

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Summarv ofthe Invention The foregoing and other aspects of the invention which will become apparent below are sought to be achieved by incorporating one or more ingredients in a paint stripping composition which aid the primary active paint removing I '~.. j!l.
agent, such as methylene chloride, to achieve complete paint removal and to convert the 6tripped paint and paint remover to a dry, friable mass, which i8 not only easily removed from the treated surface to leave bare metal, but which iB also safely handled without gloves or other protective clothing.

According to the present invention there is provided a paint removing composition comprising at least one active paint removing material and other auxiliary materials and which is a flowable composition adapted to be applied toa painted surface, said paint removing composition including an effective amountof an inert absorbent, particulate material which, after lifting of the paint from the painted surface by said active paint removing material, functions to dry the paint removing composition and the removed paint to form a dry, frangible mass on the treated surface, which is readily removable therefrom as a dry powder or flake material.

A preferred paint remover contains methylene chloride in the range offrom 70 to 82% by weight, paraffin refined wax in the range of from 1.5 to 4% by weight, mineral spirits in the range of from 1 to 5% by weight, ethyl alcohol, denatured in the range of from 0 to 6% by weight, aqua ammonia in the range of from 0 to 8% by weight, hydroxypropylmethyl cellulose or the equivalent, in the range of from 1 to 4% by weight, methanol in the range of from 1 to 8% by weight, and diatomaceous earth or equivalent, in the range of from 3 to 10% by weight.

According to a further preferred aspect of the invention there is provided a method of making the preferred paint remover comprising blending slowly into themethylene chloride the paraffin wax pre-dissolved, if desired with heating, in the mineral spirits followed by the other ingredients in the sequence .. ~
hydroxypropylmethyl cellulose, diatomaceous earth, ammonia, ethanol, and methanol.

This invention relies on the discovery that the addition of from about 3% to about 10% by weight of certain dry, particulate absorbent materials, such as diatomeceous earth, to the paint remover causes the formation, from the strippedpaint and paint remover residue, of a dry, friable, easily removed mass, which can be handled without gloves or other protective clothing without irritation of theskin of the operator.

Furthermore, this invention also contemplates inclusion in the paint remover composition certain thickening agents which operate in combination with the diatomaceous earth or equivalent to produce the de~ired friable dry mass of paint and paint remover. Various thickening agents known to the art ~er se and previously employed in the paint remover not containing a material providing a dry mass may be used. These include, among others, modified cellulose compositions such as Methocel (Trademark), which may suitably have a viscosity of from about 2000 to about 6000 cps., perferably about 4000 cps.
: .-While not essential for all automotive finishes, it has been found that it isnecessary to include from about 1% to about 4% ammonia in the new compositions in order to succe~sfully remove lacquer type automotive finishes. The ammonia ;
may be added in any suitable form, but concentrated aqua ammonia is preferred for ease of handling. Again, while ethanol is not an essential ingredient for some automotive finishes, it is necessary to add about 3 to about 6% to successfully remove epoxy and urethane automotive finishes. Other optional, but desirable, ingredients are a~ follows: refined paraffin wax; mineral spirits or the equivalent and methanol.

In a preferred embodiment the new paint removers have the following composition~:

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Ingredient Percent BY Wei~ht Min Max Preferred Methylene chloride 70 82 75-78 Paraffin refined wax 1.5 4 2 Mineral Spirits 1 5 2 Ethyl alcohol, denatured 0 6 3 Aqua ammonia 0 8 4 Hydroxypropylmethyl cellulose 1 4 2 Methanol 1 8 4 Diatomaceous earth 3 10 5 It should be understood that the foregoing proportions are approximate and that they are based on the weight of the total composition. ~ ~ `

The preferred act*e paint stripping agent, methylene chloride, is commonly used for this purpose in chemical paint removers. While less than about 70% --. .. -methylene chloride may be used, if desired, there is a consequent loss of paint stripping effectiveness. It is preferred to use about 75 to about 78% to provide a composition which will have the desired effect*eness. While more than 82%
methylene chloride could be used, it has not been found necessary to do so, and ~;
such large amounts increase the rate of evaporation from the composition, and consequently its odor.
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The ethyl alcohol is not an essential ingredient, but is desirable, since it aids in the penetration of various paint surfaces, and particularly automotive lacquer finishes. -The aqua ammonia or its equivalent is an essential ingredient, particularly for lacquer removal, since it creates a bubbling effect in use which helps to lift the paint from the treated surface. While anhydrous ammonia could be used, it is more convenient to handle aqua ammonia. Any suitable concentration of aqua :'"~ . ' -A
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ammonia may be used up to about 36 Baumé, which is an aqueous solution containing about 30% ammonia, by weight. Other substances having the same effects as ammonia may also be employed, such as organic amines. Wbile somewhat more than about 8% aqua ammonia may be employed, it has not been found to be necessary and it is undesirable to add more water to the compositionthan i~ contained in that amount of aqua ammonia.
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A thickening agent is added to lend body to the composition, not only to aid in holding it in place on the surface to be treated, but to aid in the formation of the dry frangible mass. Any suitable thickening agent known to the art may be employed. Modified cellulose available under the tradenames "Methocel"
(Trade,mark) and "Cellosize" (Trademark) are suitable. Carboxymethylcellulose, methj~ellulose and hydroxyethyl cellulose are also very effective. The preferredthickening agent is hydroxypropylmethyl cellulose, suitably having a viscosity of about 4000 to about 5000 cps. VVhile less than 1% thickening agent may be employed the resulting compositions are thin and difficult to use. More than 4%
of the thickening agent may be used but is seldom necessary. Other thickening agents are operable at viscosities of from about 2000 to about 6000 cps.; 4000 cps.
being preferred.

The methanol is also an optional, but desirable ingredient, since it swells the modified cellulose thickening agent and enhances its thickening properties.
Less than about 1% methanol may be used, but with reduced effect. More than about 4% methanol may also be used, but is seldom necessary, and would require labèlling the composition as a poison.

Any suitable refined paraffin wax may be employed in amounts from about 1.5% to about 4% by weight. The wax serves several functions, i.e., it reduces evaporation of the volatile ingredients and for this reason also reduces the odor of ammonia. The wax also form~ a film on a surface to be treated. The wax film aids in holding the other ingredients in place while the composition is working.
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,~ .` ~ : . , , While less than about 1.5% wax may be employed, such small amounts reduce control of evaporation. More than about 4% is undesirable, since it reduces the bubbling effect of the ammonia.

The mineral spirits are employed to dissolve the solid paraffin wax for addition to the composition. The preferred mineral spirits are a hydrocarbon cuthaving a boiling point in the range from about 200 F. to about 400 F. Other wax solvents such as xylene or toluene, for example, may also be employed. From about 1% to about 5% wax solvent may be employed depending on the amount of ; ~-wax used. The solid wax is placed in the solvent in a container and the solvent is heated sufficiently to dissolve the wax, typically to about 130 F. ~ ~
''' :' The most important ingredient and the one which iB primarily responsible for the advantages of the new paint stripping compositions is a dry, inert, ~ ~
particulate absorbent material. The preferred material for this purpose is -- -diatomaceous earth. This material absorbs the paint remover and stripped paint, prevents the stripped paint from re-adhering to the treated surface and dries the mixture to form an easily removable, dry, frangible mass. Certain materials other than diatomaceous earth also serve this purpose, expanded perlite, for example.
However, a number of commonly available absorbent particulate materials which might suggest themselves for this purpose are, in fact, inoperable. Such inoperable materials include saw dust, or wood flour, talc, bentonite, potato stQrch, and clay among many others. However, having disclosed the utility of diatomaceous earth for this purpose, those skilled in the art will be able to find other operable materials by routine trial and error, and, therefore, it is the co~ncept which constitutes the invention and not the use of diatomaceous earth ~er se. The diatomaceous earth or other operable absorbent is added to the paint remover in an efflctive amount which is typically an amount of from about 3% to about 10%
by weight. Less than 3% may be employed, but with reduction in the desired properties of preventing re-adhesion of the paint and drying of the mixture to an easily removed frangible mass. More than 10% by weight of the absorbent may ~:
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- ` 1 330288 g be used, but to do 80 i8 unnecessary to achieving the de~ired properties and, ofcourse, reduces the proportion of active ingredients. For diatomaceous earth, a preferred amount i~ about 5% by weight.

As noted above, some of the ingredients are optional. However, three of the ingredients have been found desirable for achieving the complete removal of an automotive finish as a dry frangible or friable mass easily separated from the treated surface. These three ingredients, diatomaceous earth, thickener and ammonia, or their equivalents, work in combination to produce the novel properties of the new compositions.

The invention also includes the method of making the new compositions, since it has been found that the order of addition of at least some of the ingredients is critical to achieving compositions having the desired properties.
The preferred method of making new compositions is as follows. The methylene chloride is stirred in a suitable container with conventional blendingequipment. In a separate container, the wax is dissolved in the mineral ~pirits or other wax solvent by heating and melting the wax in the solvent. The solution ofwax and solvent is then added to the methylene chloride, slowly with continued stirring. Next, while the stirring continues, the hydroxypropylmethyl cellulose is slowly added followed by the diatomaceous earth or equivalent. The aqua ammonia is added next, followed by the ethyl alcohol. The methanol is then addedas the last ingredient.
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In this way a paint stripping composition is made which has long shelf life, is non-flammable, has good color and a low odor, and which is capable of completely removing any automotive finish down to the bare metal.

The new compo~itions may be applied to the surface to be treated by techniques known in the art, such as by brushing or rolling, or even spraying, if :

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desired. The new compositions lift the paint from the metal and dry in about 4 to about 6 hours, in most cases. If desired the compositions may be removed by ~ -`
scraping or WipiIlg while still wet after the paint has been lifted. This is notpreferred however, since the primary advantages of dry stripping and clean up are lost. It is preferred to wait until the paint and paint remover mixture has fully ;
dried to a friable, dry mass. This mass is then very easily removed by any suitable mechanical method with minimal effort, as by scraping or brushing, either manually or by the use of a power tool. The easiest method of all is to use ~ -compressed air from commercially available hand held air guns, which direct a jet of air at the friable mass to swif~ly and fully remove it from the bare metal. The flaked or powdered mass containing the removed paint is then simply swept up - ~
and discarded as clean dry, easily handled loose material. ~ ;

The preferred practice is to apply the compositions to the surfaces to be treated at the end of the work day and to let the composition work and dry overnight for removal in the morning. This leaves the remainder of the work day -~
for refinishing the auto body. The new compositions are very economical, since they are made from inexpensive ingredients, and usually only one gallon is needed to strip most automobiles.

The invention will now be described in greater detail in the following examples.
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Example I
Production of a Paint Stripping Composition :.
Place 2 lbs of solid, refined paraffin wax into a metal pot containing 2 lbs of mineral spirits, the wax should be cut or chopped into small pieces to facilitate melting. Heat the pot with occasional mild stirring, until the mineral spirits reach the melting point of the wax, i.e., about 130F., and continue stirring until all of the wax has melted and dissolved.
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Add the mineral spirits - wax solution very slowly to 78 lbs of methylene chloride in a vessel fitted with a conventional stirrer. Stir the mixture 810wly, during the gradual addition of the wax solution, until all of the wax has been added and the solution in the vessel is homogeneous. While continuing mild~
stirring, add 2 lbs of hydroxypropylmethyl cellulose followed by 5 lbs of diatomaceous earth ("Celatom Diatomite," Trademark) to form a suspension ofthe particles of diatomaceous earth in the liquid vehicle. Then, while continuing mild stirring, add 4 lbs of 36 Baumé aqua ammonia followed by 3 lbs of denatured ethyl alcohol. Lastly, add 4 lbs of methanol and continue stirring until the mixture is homogeneous. Continue stirring while fillingthe finished paint stripper into drums or gallon cans in order to insure the uniformity of the composition.

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Example II
Use of the Paint StriDDine ComDosition The paint stripping composition of Example I is preferably poured onto the surfiace of sn automobile to be stripped and brushed in one direction using an ordinary paint brush. Use about one gallon of the composition to coat a full-sized :
automobile. Allow the paint stripper to stand in contact with the auto body for from 4 to 6 hours or preferably overnight, until the lifted paint and paint stripper is thoroughly dry to the touch.

Then remove the dry, friable paint-paint stripper mass from the auto body by any suitable mechanical means, such as a scraper, a common scrub brush or, preferably and most easily, by the use of a commercially available compressed air gun. Then sweep up the flaky and powdered residue and dispose of it as clean rubbish or Sll.

No protective clothing or breathing device is required either during the application of the paint stripper or during its removal as a dry safely handled ~:

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It will be apparent to those skilled in the art that the foregoing description and examples are merely illu~trative, and that other composition~, and other methods of making and using them are included in the scope of the invention. Forexample, and without limitation, any known active paint stripping ingredient other than the preferred methylene chloride may be used. While diatomaceous earth is pre~ently the preferred inert, particulate absorbent material, which provides the major advantage~ of the new compositions, the invention resides in the concept of using such a material in a paint stripper and any functional equivalent of the diatomaceous earth may be employed. Indeed, functional equivalents of any of the ingredients may be used, and any other ingredients commonly employed in such compositions may also be added 80 long as they do not alter the character of the claimed compositions.

Claims (24)

1. A paint removing composition containing at least one active paint removing material, which is a flowable composition adapted to be applied to a painted surface, the paint removing composition including an effective amount ofdiatomaceous earth or expanded perlite particulate which, after lifting of the paint from the painted surface by the active paint removing material, functions to dryboth the paint removing composition and the removed paint to form a dry, frangible mass on the treated surface, which is readily removable therefrom as adry powder or flake material.

2. A composition according to claim 1 wherein the inert particulate material is chosen from diatomaceous earth.

3. A composition according to claim 1 containing in addition an effective amount of a thickening agent which acts in conjunction with the inert absorbent material to form the dry frangible mass.

4. A composition according to claim 3 wherein the inert absorbent material is diatomaceous earth, and the thickening agent is a modified cellulose.

5. A composition according to claim 4 wherein the modified cellulose is selected from carboxy methyl cellulose, methyl cellulose, hydroxy ethyl cellulose, and hydroxypropylmethyl cellulose.

6. A composition according to claim 5 wherein the modified cellulose has a viscosity of from about 2000 to about 6000 cps.

7. A composition according to claim 5 wherein the modified cellulose is a hydroxypropylmethyl cellulose having a viscosity of from about 2000 cps to about 6000 cps, and which comprises from about 1% to about 4% by weight of the composition.

8. A composition according to claim 1 which contains in addition from about 1% to about 4% of anhydrous ammonia by weight based on the total weight of the composition.

9. A composition according to claim 1 which contains in addition from about 3% to about 6% ethanol by weight.

10. A composition according to claim 5 which contains from about 1% to about 4% methanol by weight.

11. A paint remover composition which contains in percentages by weight to a total of 100%:
methylene chloride: from about 70 to about 82;
paraffin refined wax: from about 1.5 to about 4;
mineral spirits: from about 1 to about 5;
ethanol, denatured: from about 0 to about 6;
concentrated aqueous ammonia: from about 4 to about 8;
thickening agent: from about 1 to about 4;
methanol: from about 0 to about 4;
diatomaceous earth or expanded perlite: from about 3 to about 10.

wherein the thickening agent is a modified cellulose.

12. A composition according to claim 11 which contains from about 3% to about 6% by weight ethanol denatured.

13. A composition according to claim 11 which contains from about 1% to about 4% by weight methanol.

14. A composition according to claim 11 which contains diatomaceous earth.

15. A composition according to claim 11 wherein the thickening agent is then selected from carboxy methyl cellulose, methyl cellulose, hydroxy ethyl cellulose, and hydroxypropylmethyl cellulose.

16. A composition according to claim 15 which contains in percent by weight, to a total of 100%:
Methylene chloride: about 78;
Paraffin refined wax: about 2;
Mineral spirits: about 2;
Ethanol, denatured: about 3;
Concentrated aqueous ammonia: about 4;
Hydroxypropylmethyl cellulose: about 2;
Methanol: about 4;
Diatomaceous earth: about 5;
wherein the mineral spirits comprises a hydrocarbon material having a boiling point in the range of from about 200°F to about 400°F.

17. A method for the production of a paint removing composition as claimed in claim 11, wherein diatomaceous earth is used, which comprises blending slowly into the methylene chloride the paraffin wax pre-dissolved in the mineral spirits followed by the other ingredients in the sequence hydroxypropylmethyl cellulose,diatomaceous earth, ammonia, ethanol, and methanol.

18. A method for removing paint from a painted surface which comprises applying to the painted surface a composition as claimed in claim 1; allowing the composition and loosened paint to dry to a frangible mass; and removing the massas a dry, flaky, material.

19. A method for removing paint from a painted surface which comprises applying to the painted surface a composition as claimed in claim 11; allowing the composition and loosened paint to dry to a frangible mass; and removing the massas a dry, flaky, material.

20. A method for removing paint from a painted surface which comprises applying to the painted surface a composition as claimed in claim 16; allowing the composition and loosened paint to dry to a frangible mass; and removing the massas a dry, flaky, material.

21. A method for removing a lacquer-type automotive finish from a painted surface which comprises applying to the painted surface a composition as claimedin claim 16; allowing the composition and loosened paint to dry to a frangible mass;
and removing the mass as a dry, flaky, material.

22. A method for removing epoxy and urethane automotive finishes from a painted surface which comprises applying to the painted surface a composition asclaimed in claim 16; allowing the composition and loosened paint to dry to a frangible mass; and removing the mass as a dry, flaky, material.

23. A method according to claim 17 wherein the paraffin wax is predissolved in the mineral spirit with heating.

24. A composition according to claim 11 wherein the mineral spirits are chosen from a hydrocarbon cut having a boiling point in the range form about 200°F to 400°F., toluene, and xylene.