CA2096324A1

CA2096324A1 - Paint overspray protective coating and method of use

Info

Publication number: CA2096324A1
Application number: CA 2096324
Authority: CA
Inventors: Graham M. Brookes
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-05-14
Filing date: 1993-05-14
Publication date: 1994-11-15

Abstract

A B S T R A C T

A composition is disclosed for application to a surface to protect that surface from damage during processing of adjacent surfaces. The composition includes cellulosic thickener, a plasticizer, a surfactant, and water. The composition also includes an aliphatic polyol.

Description

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BACKGROUND OF THE INVENTION

This invention relates to the field of temporary coatings to be used to protect vehicles, buildings and spray booths from paint overspray, dirt and debris as well as mechanical operations such as painting, welding and grinding. Such usages are not however an exhaustive list, as other uses may exist for the temporary coating of the present invention.

In painting operations it is often necessary to prevent paint overspray from reaching all or certain areas of a vehicle, building, machinery or other surfaces. For example, a body shop may only want to paint the fender of a vehicle without getting paint overspray on the rest of this vehicle. This has usually been done by masking the vehicle with tape and masking paper or a plastic sheet.

Both these procedures are labour intensive and seldom prevent overspray from travelling under the paper or plastic sheeting on air currents that pass through the vehicles ventilation ducts and vents.
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Liquid masking agents have been developed, and are on the market. They contain varying amounts and types of alcohols.
This not only represents a health hazard due to inhalation or ingestion, but the alcohol can have a dulling effect on the paint surfaces. Alcohols can also attack certain car waxes, turning the waxed surfaces hazy.

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In one embodiment the formulation of the present invention provides an improved liquid masking agent for use by body shop repair facilities, superior in that when sprayed on a vehicle, the formulation has a tacky surface that traps dirt and dust that lands on the surface of the liquid mask. This ability to trap dust facilitates finishing paint application, since less dust is likely to drift onto freshly painted surfaces. Unlike other masking agents which are runny due to low viscosity, the masking agent of the present invention, which is of a higher viscosity, is able to trap dirt already on the surface of the vehicle, for instance in the wheel wells and engine bay, when it is sprayed over this dirt. This prevents dirt particles being dislodged by the air blast from a painter's spray gun and contaminating the wet paint surface.
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Unlike other liquid masks that are currently available, this preferred embodiment is non toxic if accidentally ingested and is not harmful to the environment.

SUMHARY OF THE INVENTION

The invention involves applying a continuousl, water soluble, masking film by brushing or spraying onto the surface of a vehicle2, spray booth, building3, machinery or other Continuouo ~l~an-- 4 non porou~ ~11~, ~reo o:e dol'octs or plnhola-: whlch would e~llow palnt or othor ~torl~lo to aont~at tho prot-atod undorlying our~!~ao.
Vahialo lo doPlnod ~ m a~to~aobllo, truak, bo/lt, ~hlp, alrar~lft or othor aoDvoyanco oL pa~enger or ~at~rlall~ .

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` 2~96324 surfaces that are to be protected against paint overspray, or dirt, sand, dust or salt contamination or during a mechanical operation such as welding, grinding or refinishing operations.

The masking material is unique, in that the surface of the film is tacky, which allows the trapping of dust and dirt that lands on the film. This results in a cleaner paint application, since less dust and dirt are likely to migrate to a wet paint surface.

~ . ;, In a preferred embodiment of the present invention for auto body repair facilities, this tackiness lasts for about eight hours. The surface then becomes dry, but the tackiness is re-activated when the vehicle is placed in a bake spray booth at a temperature about 100F. Since most vehicles are coated with liquid mask about one hour before painting, most dust is trapped by the tacky coating. When the vehicle is sprayed and left for long periods of time, usually in a dusty environment, the coating does not continue to trap dirt and dust. The surface does not `load up' until it can no longer trap any more dirt. This allows dirt and dust to be blown off the vehicle before it is placed in a bake spray booth. The surface now being relatively clean, re-tackifies and continues to traps dust and dirt.

In a preferred embodiment, the liquid mask is transparent.
This allows a body shop to spray over the glass ares of a vehicle and still maintain good visibility in order to drive this vehicle around the shop or into the spray booth.

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The masking materîal is, in one specific embodiment, a cellulosic thickener, a plasticizer (glycerine, sorbitol, polyethylene glyco, triethanolamine, triethylene glycol or propylene glycol), an aliphatic polyol, surfactant and water.

On a broad aspect, the present invention relates to a composition for application to a surface to protect that surface from damage during processing of adjacent surfaces, said compositlon including: (a) a cellulosic thickener; (b) a plasticizer; (c) a surfactant; and (d) water.

DESCRIPTION OF THE: PREFERRED ENBODIMENq'S

The method and composition of the present invention will produce a temporary coating of a viscosity thick enough to cling to vertical surfaces, and coat over dust and dirt to prevent dislodgement of these contaminants. The film will contain few if any pinholes.

One embodiment included hydroxypropyl methylcellulose, in the range of 4% to 14% by weight, 10% glycerine by volume, a surfactant and water.

A preferred embodiment includes water, hydroxyethyl cellulose, glycerine as a plasticizer at from 8% to 10% by volume, triethanolamine as an emulsifier, polyvinyl alcohol in the range of 0.05 to 0.8% by weight and a surfactant.

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A most preferred embodiment uses sodium carboxymethyl-cellulose in the range of 2% to 4% by weight, glycerin in the range of 4% to 10% by volume, sorbitol in the range of 4% to 10%
by volume, de-ionized water and a surfactant.

Another most preferred embodiment uses sodium carboxy- -~
methylcellulose in the range of 1% to 5~ by weight or hydroxyethyl cellulose in the range of 2% to 8% by weight, sorbitol in the range of 3% to 30% by volume, polyvinyl alcohol in the range of 0.05% to 0.8% by weight, de-ionized water and a surfactant.

Another preferred embodiment uses polyvinyl alcohol in the 0.1 to 0.4% range by weight. Unlike other liquid masks which use polyvinyl alcohol as the film forming coating itself, all preferred embodiments discussed in this application use PVA in ~ -a minor percentage to add varying degrees of tackiness to the coating. Other embodiments have substituted mono and poly saccarides such as sucrose, glucose, lactose, fructose and dextrose for the PVA with varying degrees of success. ~ ;

The li~uid mask also includes a surfactant. The surfactant in one embodiment is a nonionic mono(nonylphenyl) ether (such as Tergitol D-683). Another embodiment includes dodecyl thioethoxylate. In preferred embodiments, the formula includes an alkyl aryl surfactant (Triton CF10 & CF12), a silicone-polyether copolymer, (Silwet L-77), or an ethoxylated tetramethyldecyndiol (Surfynal SE-F).

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~ 2fl9~324 Other surfactants that may be utilized include poly~
alkoxylated aliphatic base surfactants (Makon NF-5 & NF-12), nonylphenol ethoxylates (Igepal C0-530,887,977), polyoxyalkylene glycols (Macol 18 ~ 19), acetylenic diols (Surfynal 104A). -Preferred embodiments include up to 11% surfactant. Most preferred compositions contain less than 3% surfactant, with one implementation using 0.1%.

The liquid mask includes substantial amounts of deionized water in the range of 400,000 to 600,000 ohms. In one embodiment the balance of the formula is water, although odorants and dyes may also be added.

The masking material is manufactured by conventional means at substantially atmospheric pressure. The components are blended together to form a homogeneous mixture. In some embodiments the mixture is heated above 120F. This decreases the length of the mixing time by about 70% while allowing better integration of the surfactant.

The masking material is applied by brush, conventional spray -guns or airless spray systems. When sprayed, the mask is applied in a single application, preferably using a 50% overlapping spray. Any overspray of the mask can be easily removed with water and a sponge or cloth.

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The liquid mask is usually permitted to dry at ambient temperatures and atmospheric pressures, although some auto body repair facilities choose to let the masked vehicle dry inside the bake booth at temperatures up to 160F. The mask will dry in 10 to 60 minutes approximately, depending on temperature and humidity.

If the mask is used to prevent paint overspray, as in a painting operation, the paint overspray is allowed to dry on the surface of the mask. After drying, the mask is washed with water, using a wash mitt, garden hose or a pressure washer.
Since the mask is highly water soluble, it washes off easily with no remaining residue on the surface to which it was applied.

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Thickeners Thickeners perform three functions in the formulation. They -act as the main barrier, preventing organic solvents and paint -:
overspray from reaching the underlying surface. They increase the viscosity of the formulation of the invention, allowing it ~ -~
to cling to vertical or partly vertical surfaces without running or sagging. They also act as rheology modifiers, allowing the mask to spray easily and level out to an even coat over the protected surface.

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The best results are obtained when the kinematic viscosity at 20 C is around 52 centistokes (MM2/S0).

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The thickener must also be highly water soluble and stable when exposed to ultra violet radiation. The thickener must not have any deleterious effect on the underlying protected surfaces and remain stable when exposed to temperatures up to 190F for up to 6 hours.

Over 100 different formulations were tested using about 30 different thickeners.

Several organic clay thickeners were tested including bentonite, as well as the organic thickeners used in the food industry, such as gaur gum, xanthin gum, carrageenin and calcium caseinate as well as different types of starches. A number of experiments were conducted with the colloidal thickeners such as colloidal magnesium aluminum silicate (Veegum PRO~, and the vinyl emulsions such as polyvinyl acetate emulsion and vinyl acetate ethylene emulsion (Airflex 400).

The thickeners which performed most satisfactorily, were the cellulosic thickeners such as sodium carboxymethylcellulose and hydroxyethylcellulose (Aqualon), ethyl hydroxyethylcellulose (Berol) and hydroxypropylmethylcellulose (Dow). The cellulose thickeners comprise from 7 % to 14% of the formulation of the present invention by weight.

One preferred embodiment uses sodium carboxymethylcellulose (7H, Aqualon) at 3.25% by weight.

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A most preferred embodiment uses hydroxypropyl methyl-cellulose (Methocel J75MS-N, Dow), at 9% by weight, while another preferred embodiment uses 8.7% of hydroxyethylcellulose t250 HR, Aqualon).

Plasti~izers Plasticizers perform three functions in the formulation of the present invention. They work in con~unction with the thickener to provide an effective barrier against paint overspray. ~hey aid in the washability of the mask, and give elasticity to the film so that it does not crack when drying on the surface to be protected.
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The plasticizer must also be stable in the presence of heat, oxygen, ultraviolet radiation and have no deleterious effect on the surfaces to be protected.

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Plasticizers such as glycerine, triethylene glycol, ~-propylene or polyethylene glycol, sorbitol, ethanolamines and -~
sulphonated oils were considered in the development of the present invention.

Plasticizers were used in the formulation from 5% to 30% by -~
volume.
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: ' ': ~' A preferred embodiment uses 15% sorbitol by volume, while ~:
another preferred embodiment uses propylene glycol at 10% by g ,: : -:
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volume. A most preferred embodiment uses 11% glycerine by volume and 0.04% by volume triethanolamine.

Polyvinyl Alcohol Polyvinyl alcohol is used in the formulation to give a tacky surface to the liquid mask. Since it is used in the formulation at between 0.1% to 0.4%, it does not form part of the barrier in the film.

Little difference has been noted between the different molecular weights of PVA. Any partially hydrolysed PVA such as Elvanol 5042 (DuPont) has worked with acceptable results.

It is to be understood that the examples described above are not meant to limit the scope of the present invention. It is expected that numerous variants will be obvious to the person skilled in the field of paint overspray mask formulation without any departure from the spirit of the invention. The appended claims, properly construed, form the only limitation upon the scope of the invention.

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Claims

1. A composition for application to a surface to protect that surface from damage during processing of adjacent surfaces, said composition including:
a) a cellulosic thickener;
b) a plasticizer;
c) a surfactant; and d) water.

2. A composition as claimed in Claim 1, further including an aliphatic polyol.

3. A composition as claimed in Claim 2, wherein said thickener is present in an amount of about 1% to 14% by weight of said composition, and is chosen from the group of cellulosic thickeners including sodium carboxymethylcellulose, hydroxyethyl-cellulose, ethylhydroxyethylcellulose, and hydroxypropyl-methylcellulose.

4. A composition as claimed in Claim 3, wherein said thickener is sodium carboxymethylcellulose, present in an amount of about 3.25% by weight.

5. A composition as claimed in Claim 3, wherein said thickener is hydroxypropylmethylcellulose, present in an amount of about 9% by weight.

6. A composition as claimed in Claim 3, wherein said thickener is hydroxyethylcellulose, present in an amount of about 8.7% by weight.

7. A composition as claimed in Claim 3, wherein said plasticizer is present in an amount of about 5% to 30% by volume, and is selected from the group including sorbitol, propylene glycol, glycerine and ethanolamines.

8. A composition as claimed in Claim 7, wherein said plasticizer is sorbitol, present in an amount of about 15% by volume.

9. A composition as claimed in Claim 7, wherein said plasticizer is propylene glycol present in an amount of about 10%
by volume.

10. A composition as claimed in Claim 7, wherein said plasticizer is a combination of glycerine present in an amount of about 11% by volume and triethanolamine present in an amount of about 0.04% by volume.

11. A composition as claimed in any of Claims 2 to 10, wherein said aliphatic polyol is a polyvinyl alcohol, present in an amount of about 0.1% to 0.4% by weight.

12. A composition as claimed in any of Claims 1 to 10, wherein said surfactant is present in an amount of from 0.1% to 11%, preferably 0.1% to 3%, and is selected from the group including nonionic mono(nonylphenyl) ether, dodecyl thioethoxylate, alkyl aryl surfactant, silicone-polyether copolymer, ethoxylated tetramethyldecyndiol, polyalkoxylated aliphatic base surfactants, nonylphenol ethoxylates, polyoxyalkylene glycols, and acetylenic diols.

13. A composition as claimed in any of Claims 2 to 10, wherein said surfactant is present in an amount of from 0.1% to 11%, preferably 0.1% to 3%, and is selected from the group including nonionic mono(nonylphenyl) ether, dodecyl thioethoxylate, alkyl aryl surfactant, silicone-polyether copolymer, ethoxylated tetramethyldecyndiol, polyalkoxylated aliphatic base surfactants, nonylphenol ethoxylates, polyoxyalkylene glycols, and acetylenic diols, and said aliphatic polyol is a polyvinyl alcohol, present in an amount of about 0.1% to 0.4% by weight.