WO1996032451A1

WO1996032451A1 - A paint stripper

Info

Publication number: WO1996032451A1
Application number: PCT/EP1996/001575
Authority: WO
Inventors: Bryan Huxted; Paul Barney; Werner Haller; Bernhard Schottmer
Original assignee: Henkel Kommanditgesellschaft Auf Aktien; Henkel Limited
Priority date: 1995-04-13
Filing date: 1996-04-11
Publication date: 1996-10-17
Also published as: GB9507909D0; GB2299812B; GB2299812A

Abstract

A paint stripper based on dimethylsulfoxide (DMSO), is characterized by containing 20 to 90 % by weight of DMSO and 10 to 80 % by weight of an alkyl glycol ether or an alkyl diglycol ether containing 2 to 8 carbon atoms in the alkyl group and one hydroxyl group.

Description

A paint stripper

This invention relates to a paint stripper based on dimethylsulfoxide (DMSO) .

A dissolving paint stripper of this type is known. It is applied to the dried paint coating and, after a short or long contact time, facilitates its removal from the substrate.

CH-PS 670832 describes an organic desizing, dissol¬ ving and paint removing composition free from chlorinated hydrocarbons. According to Example 4, this composition consists of 20% DMSO, 10% butyl glycolether, 2.5% alkyl- hydroxyalkyl cellulose, 1.5% alkylbenzenesulfonate, 10% swelling agent (tetrahydrofuran and tetrahydrofurfuryl alcohol) , 50% resin solvent (acetates and butyrolactone) and 6% evaporation retarders (paraffins and tetralin) . Published Japanese patent application 59/155474 also describes a paint stripper based on dimethylsulfoxide. According to claim 6, it consists of 50 parts of dimeth¬ ylsulfoxide, 30 parts of glycerol and 20 parts of poly¬ vinyl alcohol. According to claim 2, the viscosity of the stripper is said to be adjusted by thickeners to a value of 100 to 10,000 cpoises/25°C and its thixotropy to a value of 1.1 to 10 (T.I. value) .

European patent application EP 0 490 726 describes a paint stripper essentially consisting of the following components: 1 to 20% by volume of DMSO and 80 to 99% by volume of at least one ether from the group consisting of methyl-t-butylether, diethyl ether, t-amyl methylether, tetrahydrofuran and dioxane.

European patent application EP 0 573 339 also describes a paint stripper containing a) 1 to 99% by volume of a polar aprotic solvent and b) 99 to 1% of a certain ether containing at least one methoxy group. Ethers specifically mentioned include 1, 2-dime hoxyben- zene, 1, 3-dimethoxybenzene, 1, 4-dimethoxybenzene, 1,2,3- trimethoxybenzene, 2-methoxy-1, 3-dioxolane, 2-methoxy- 3 , 4-dihydropyran, 2 , 5-dimethoxytetrahydrofuran, ethylene glycol dimethylether, diethylene glycol dimethylether and i-t-butoxy-2-methoxyethane.

These known paint strippers have the disadvantage that they are not sufficiently effective. In particular, they run down vertical paint surfaces before they have sufficiently softened them. The solution provided by the invention is defined in the claims . It is based in particular on the choice of the co-solvent alkyl glycol ether or alkyl diglycol ether containing at least one OH group, the alkyl group con¬ taining 2 to 8 carbon atoms and, more particularly, 3 to 6 carbon atoms. The stripper contains 20 to 90% by weight of DMSO and 10 to 80% by weight of ether. Other constituents of the stripper may be: 0 to 5% by weight and more particularly 0.1 to 3% by weight of at least one thixotropic agent, - 0 to 5% by weight and more particularly 0.5 to 3.0% by weight of at least one thickener, for example based on cellulose, clay, starch, gum or a swellable polymer, more particularly based on cellulose derivatives, such as ethoxyethyl cellulose, or hydroxy propyl methyl cellulose

0 to 2% by weight and more particularly 0.5 to 1% by weight of at least one surfactant,

0 to 0.1% by weight of at least one evaporation retarder, - 0 to 0.1% by weight of at least one dye, 0 to 0.5% by weight of at least one corrosion inhibitor and

0 to 3% by weight of at least one activating acid or base. Chlorinated hydrocarbons and N-Methyl-2-pyrrolidone (NMP) are specifically ruled out as co-solvents.

The function of the thixotropic agent is to cause the stripper to form a low sag structure as quickly as possible after stirring. Thixotropic agents are well known in the paint industry and include, in particular, bentonites, kaolins, alginic acid and, above all, silica, for example fumed silica.

The function of the thickener is generally to increase the viscosity of the solution. Suitable thick- eners are inorganic thickeners, for example polysilicic acids and clay minerals, such as zeolites and silicas. Suitable organic modified natural substances may include carboxymethyl cellulose, 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.

The function of the surfactants is to improve wetting and washability. They may be anionic, cationic or nonionic. Alkylbenzenesulfonates in which the alkyl group contains 8 to 36 and more particularly 12 to 24 carbon atoms are particularly preferred.

Waxes and vegetable ester derivatives in particular are used to retard evaporation. Organic acids and esters above all are used for activation. Examples include formic acid, acetic acid and methyl phosphoric ester.

The percentages by weight of the additives are based on the mixture of DMSO and co-solvent. The components of the paint stripper according to the invention may readily be mixed together. The paint stripper according to the invention has the following positive effects: low odor, complete solubility in water, - low evaporation rate and above all a long and favorable effect on virtually all paint systems and, finally, low health risk compared to dichloromethane based paint removers. By virtue of its miscibility with water, the paint stripper according to the invention may readily be removed with water or with soap-containing water.

The broad application spectrum of the paint stripper according to the invention despite its small number of solvents is surprising. In a preferred embodiment, the paint stripper according to the invention contains only two solvents. 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. The paint stripper according to the invention is particularly suitable for paints based on alkyd resin and acrylic resins. The invention is illustrated by the following Examples:

Three paint strippers according to the invention are prepared by mixing dimethylsulfoxide, butyl diglycol ether and a cellulose thickener at room temperature in the quantities shown in the Table. The paint strippers were applied to approximately 10-year-old alkyd resin paints. The stripping ratio was measured and recorded as detailed in Table 1. Table l

Composition and properties of paint strippers according to the invention

Example Composition Cellulose Properties¹¹

No. DMSO BDGE thickener Stripping

% by weight % by weight % by weight ratio

1 30 68.5 1.5 192 2 50 47.5 1.5 38 3 75 23.5 1.5 16

DMSO = dimethylsulfoxide BDGE = butyl diglycol ether

ιι Stripping ratio is determined as follows by spot testing.

Stripping ratio = Overall time taken for sample to blister paint

Overall average time for reference dichloromethane based paint remover to blister paint. The lower the stripping ratio, the faster the stripping action.

Claims

1. A paint stripper based on dimethylsulfoxide (DMSO), characterized in that it contains 20 to 90% by weight of DMSO and 10 to 80% by weight of an alkyl glycol ether or an alkyl diglycol ether containing 2 to 8 carbon atoms in the alkyl group and one hydroxyl group.

2. A paint stripper as claimed in claim 1, charac¬ terized by 55 to 85% by weight of DMSO and 15 to 50% by weight of alkyl diglycol ether containing 3 to 6 carbon atoms in the alkyl group.

3. A paint stripper as claimed in claim 1 or 3, charac¬ terized by the following additives:

0 to 5% by weight and more particularly 0.1 to 3% by weight of a thixotropicizing agent, - 0 to 5% by weight and more particularly 0.5 to 3.0% by weight of a thickener, more particularly of cel¬ lulose derivatives, such as ethoxyethyl cellulose, 0 to 2% by weight and more particularly 0.5 to 1% by weight of a surfactant, - 0 to 0.1% by weight of an evaporation retarder, 0 to 0.1% by weight of a dye,

0 to 0.5% by weight of a corrosion inhibitor and 0 to 3% by weight of a activating acid or base, the percentages by weight being based on the sum of DMSO and ether.

4. The use of the paint stripper claimed in at least one of claims 1 to 3 for removing paints containing alkyd resins as binder.