GB2377710A

GB2377710A - A paint stripper

Info

Publication number: GB2377710A
Application number: GB0117517A
Authority: GB
Inventors: Paul Barney; Brian Huxted; Bernhard Schottmer
Original assignee: Henkel AG and Co KGaA; Henkel Loctite Adhesives Ltd
Current assignee: Henkel AG and Co KGaA; Henkel Loctite Adhesives Ltd
Priority date: 2001-07-18
Filing date: 2001-07-18
Publication date: 2003-01-22
Anticipated expiration: 2021-07-18
Also published as: GB2377710B; GB0117517D0

Abstract

A paint and varnish stripper comprises one or more active paint and varnish removing solvents that blister and/or soften aged paint and 1 to 10% by weight of linseed oil, preferably boiled linseed oil. The paint stripper is particularly suitable for use in stripping paint and varnish from wood surfaces. The solvent is preferably dichloromethane and other components of the stripper may include an accelerant, e.g. methanol.

Description

Title: A Paint Stripper This invention relates to a paint stripper and, more particularly, to a paint stripper which is particularly suitable for removing paint or varnish from wooden substrates.

Dissolving paint strippers are known. For example, commercially available paint strippers are known which contain dichloromethane and methanol. Other paint strippers are known which are based on dimethylsulfoxide (DMSO) and may contain an alkyl glycol ether or an alkyl diglycol ether. Paint strippers based on dichloromethane have the advantage that they are extremely effective having a fast stripping action. Paint strippers based on DMSO have a slower stripping action but have the advantage of low health risk due to toxicity as compared to dichloromethane based paint removers. These known paint strippers are generally available for use in removing paint or varnish from all types of substrates including plaster, metal and wood.

When used on wooden substrates conventional paint strippers have the problem that the stripped wood has a dull washed-out appearance and the grain of the wood is not clearly evident.

The object of the present invention is to provide a paint stripper which has the advantages of conventional paint strippers and in addition, when used on wooden substrates results in stripped wood which has an improved appearance both when bare and after re-coating.

The invention provides a paint stripper comprising 90 to 99% by weight of one or more active paint and varnish removing solvents that blister and/or soften aged paint and varnish optionally with one or more accelerants and I to 10% by weight of linseed oil.

According to a preferred embodiment the paint stripper comprises 93 to 96% by weight of the paint and varnish removing solvent or solvents optionally with one or more accelerants and 4 to 7% by weight of linseed oil.

According to the present invention linseed oil is incorporated in a paint stripper based on a conventional paint-removing solvent or solvent combination.

Linseed oil is extracted from flax and consists mainly of CI8 fatty acids. It is known for use in paints, varnishes and lacquers and is available commercially as both raw linseed oil and boiled linseed oil, which has been thickened by boiling and dries rapidly on exposure to air. Boiled linseed oil can contain chemical accelerators which speed up curing time. In the present invention, the use of boiled linseed oil is preferred.

The linseed oil is preferably incorporated in the paint stripper according to the invention in an amount of 4 to 7% by weight.

Examples of solvents which will blister or soften aged paint and varnish and are commonly used as active solvents in paint and varnish stripper formulations are: dichloromethane, alkyl glycol or alkyl diglycol ethers such as ethyl diglycol and butyl diglycol; benzyl alcohol; dimethyl sulfoxide (DMSO) ; dibasic ester blends, typically blend of dimethyl glutarate (55-65% w/w), dimethyl succinate (15-25% w/w), dimethyl adipate (10-25% w/w); ethyl-3-ethoxypropionate; ethyl acetate; butyl acetate; gamma butyrolactone; ketones, such as methyl ethyl ketone (butan-2-one) and acetone; N-methyl-2-pyrrolidone (NMP); 1, 3 dioxolane ; and toluene.

According to a particular embodiment, there is provided a paint stripper comprising 90 to 99% by weight, more particularly 93 to 96% by weight of active paint and varnish solvents consisting of dichloromethane and up to 10% by weight of methanol and 1 to 10% by weight linseed oil.

A particular formulation comprises 86 to 91% by weight dichloromethane, 5 to 7% by weight methanol and 4 to 7% by weight linseed oil.

The paint stripper according to the invention may include one or more optional conventional components of paint strippers as described below (percentages by weight are based on the sum of the active paint and varnish removing solvents and linseed oil).

An accelerant for the paint and varnish stripping may be incorporated, that is a solvent which acts as accelerant for paint and varnish stripping, for example methanol or ethanol in the format of industrial methylated spirit. The accelerant is preferably incorporated in an amount of 4 to 10% by weight, more particularly 5 to 7% by weight. The incorporation of methanol in the paint stripper is particularly desirable when the composition is based on dichloromethane.

An extending solvent that does not blister or soften paint and varnish, for example, white spirit, in an amount of up to 5% by weight, preferably up to 2% by weight may be incorporated.

An evaporation retardant such as i. e. wax or vegetable ester derivative may be incorporated for example, in an amount of up to 2% by weight. For example, the paint stripper may contain 0 to 2% by weight, preferably 1.0 to 1.5% of paraffin wax as an evaporation retardant; The paint stripper may contain a thickener which must be compatible with linseed oil.

The function of the thickener is generally to increase the viscosity of the solution.

Suitable thickeners are inorganic thickeners, for example polysilicic acids and clay minerals, such as zeolites and silicas. Suitable organic modified natural substances may include carboxymethylcellulose, cellulose ether, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethoxyethyl cellulose and hydroxy propyl methyl cellulose. Suitable organic natural thickeners are starch, gum arabic, dextrins, gelatine and alginates.

For example the paint stripper may contain up to 3%, more particularly 0.5 to 1.5% of at least one thickener. When the paint stripper is based on dichloromethane the thickener is preferably based on a cellulose derivative such as hydroxy propyl methyl cellulose.

The paint stripper may contain a conventional surfactant to improve wetting and washability, for example in an amount of 0.2 to 0.7%.

The paint stripper may contain an in-can corrosion inhibitor in an amount of, for example, up to 1 % by weight.

The components of the paint stripper according to the invention may readily be mixed together.

The paint stripper of the invention has a broad application spectrum. Paints or varnishes based on the following organic binders may be removed with the stripper according to the invention: alkyd resin, chlorinated rubber, epoxy resin, acrylate resin, polyester, polyurethane, polyvinyl acetate, chlorinated polypropylene and cyclo rubber.

We have surprisingly found that the invention stripper has noticeably improved performance, i. e. greater penetration through paint and varnish layers compared to similar conventional paint strippers without the inclusion of linseed oil.

It was also surprising to find that after removing paint and varnish with the invention stripper from wood items constructed from a range of variety of timbers (e. g. pine, oak, mahogany, beech etc). and after removing residual paint and varnish with solvent such as white spirit or methylated spirit, and after drying off residual solvent, the stripped wood contains a light coating of absorbed linseed oil that gives the bare wood a bright and rejuvenated appearance compared to the same wood that has been stripped with conventional chemical paint and varnish strippers.

Wood from which paint and varnish has been stripped with the paint and varnish stripper according to the invention, can, after cleaning with solvent as above and after drying, be successfully re-coated with both solvent based and water based wood coatings such as varnishes, paints, stains, finishing waxes, oils polishes etc.

The paint stripper according to the invention has good application properties being particularly easy to apply by brush using dabbing action and is particularly adapted for use on vertical surfaces.

For transparent coatings such as varnish, the re-coated wood that has been stripped with the paint and varnish stripper according to the invention has a noticeably brighter and superior appearance when compared to the same wood that has been stripped with conventional paint and varnish strippers and re-coated with the same transparent coating.

We have also found that the light coat of linseed oil absorbed into wood stripped with the invention paint stripper results in a reduction in coating application weight when re-coating with paints and varnishes etc. , compared to the coating weight required when re-coating wood stripped with conventional paint stripper.

The paint stripper of the invention thus has the advantages and positive effects of conventional paint stripper with additional advantages that, when applied to a wooden substrate, the appearance of the stripped wood both when bare and after re-coating is improved.

The composition, properties and results achieved by the paint stripper according to the present invention as compared with a commercially available paint stripper are set out in the following table.

The commercially available paint stripper (1) consisted of

Component % by weight Dichloromethane 85.40 Methanol 9.30 White Spirit 1. 50 Cellulose derivative thickener 1. 00 Surfactant (30% by weight aqueous 1.30 solution) Paraffin Wax 0. 80 Water* 0. 60 Sodium Carbonate Decahydrate* 0. 04 Sodium tetraborate* 0.06 T m can corrosion innibitor solution The paint stripper of the invention (2) consisted of

Component % by weight Dichloromethane 86. 30 Methanol 5. 80 Single Boiled Linseed Oil 5. 00 Cellulose derivative thickener 0. 90 Paraffin Wax 1. 30 Water* 0. 60 Sodium Carbonate Decahydrate* 0. 04 Sodium tetraborate* 0. 06 * In can corrosion inhibitor solution

Commercially Paint Available Stripper of Paint Stripper Invention (1) (2) General Properties Appearance &commat;20 C Smooth colourless Smooth straw clear viscous semi-coloured clear gel highly structured semi-gel Odour Characteristic sweet Characteristic dichloromethane sweet dichloromethan e Viscosity &commat;20 C (Rotothinner) 2. 5 Poise 4.2 Poise Viscosity &commat;20 C (Brookfield DV-II+ spindle 3200cPs 7100cPs RV5/20rpm) SG (density) &commat;20 C1. 220L232 Application Properties (* Poor, ** Satisfactory, ### Good, #### Very Good ***** Excellent) Suitability for vertical surfaces ? Easy to apply by ***** Easy to brush using dabbing apply by brush action. Very little using dabbing sagging action. Excellent Very little saggmg Suitability for intricate surfaces (furniture, #/## A little difficult #/## A little mouldings etc). to get into intricate difficult to get into mouldings etc. Easy to intricate mouldings apply by brush using etc. Easy to apply dabbing action. Very by brush using little sagging dabbing action.

Very little sagging Paint & Varnish Removal Time taken to fully rerupt old paint/ varnish Up to 5 mins 3 to 5 mins Time after which paint/varnish can be Approx. 30 mins Approx. 25 stripped mins Method of neutralisation Detergent in cold water. Wipe with white Wipe with white spirit or spirit or methylated methylated spirit to spirit avoid raising grain

Commercially Paint Available Stripper of Paint Stripper Invention (1) (2) Appearance of Stripped Wood (# Poor, ## Satisfactory, ### Good, #### Very Good ##### Excellent) Bare Wood ### ##### Re-coated with : # # Solvent based varnishes ### ##### Water based varnish ### ##### Finishing Wax ### ##### Finishing oils ### ##### Solvent based gloss paints ##### ##### Test Results Linseed oil absorbed after stripping: Pine 0 10g/m2 Beech 0 20g/m2 Oak 0 109/m2 Mahogany 0 5g/m2 Ash 0 5g/m2 Cedar 0 30 m2 Coating weight after stripping softwood : 33g/m2 (28% lower than after stripping with Solvent based varnish 46g/m2 (1)) 46g/m2 (21 % lower than after stripping with Wood primer (1)) Weight increase of wood panels (approx.

0. 015m2) stripped with remover, dried and immersed in water for 1 hour: Softwood 7. 5g 5. 5g Oak 21g 8g

Claims

CLAIMS: 1. A paint stripper comprising 90 to 99% by weight of one or more active paint and varnish removing solvents that blister and/or soften aged paint and varnish optionally with one or more accelerants and 1 to 10% by weight of linseed oil.
2. A paint stripper according to claim 1 comprising 93 to 96% by weight of the paint and varnish removing solvent or solvents optionally with one or more accelerants and 4 to 7% by weight of linseed oil.
3. A paint stripper according to claim 1 or 2, wherein the linseed oil is boiled linseed oil.
4. A paint stripper according to any of claims 1 to 3, wherein the paint and varnish removing solvent is selected from one or more of dichloromethane, alkyl glycol or alkyl diglycol ethers; benzyl alcohol, dimethyl sulfoxide (DMSO), dibasic ester blends, ethyl-3-ethoxypropionate, ethyl acetate, butyl acetate, gamma butyrolactone, ketones, N-methyl-2-pyrrolidone (NMP); 1,3-dioxolane ; and toluene
5. A paint stripper according to any of claims 1 to 4, which comprises 4 to 10% by weight of an accelerant.
6. A paint stripper according to claim 5, which comprises 5 to 7% by weight of the accelerant.
7. A paint stripper according to claim 5 or 6, wherein the accelerant is methanol.
8. A paint stripper according to any of claims 1 to 6, comprising dichloromethane and methanol.
9. A paint stripper according to claim 8 comprising 86 to 91 % by weight dichloromethane, 5 to 7% by weight methanol and 4 to 7% by weight linseed oil.

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10. Use of linseed oil as a wood conditioning agent incorporated in an amount of 1 to 10% by weight in a paint stripper comprising 90 to 99% by weight of one or more active paint and varnish removing solvents that blister and/or soften aged paint and varnish optionally with one or more accelerants.