HK1024018A - Water-based alcohol hydroxycarboxylic peroxide compositions, preparation, and uses thereof - Google Patents

Description

Water-based alcohol-hydroxycarboxylic acid-peroxide compositions, process for their preparation and their use

Strong acid and halocarbon solvent-based compositions have been used for decades to strip various protective coatings from metal and other substrates. In recent years, government legislation agencies throughout the world have limited and/or prohibited the use of these materials due to increased concerns about the adverse health and environmental effects of these strippers.

In U.S. patent 5215675, Wilkins et al teach an aqueous paint stripping composition based on a water-soluble ester such as ethyl lactate and a peroxide such as hydrogen peroxide.

In us patent 5405548 and us patent 5542986 Distaso describes the use of benzyl methyl formate or benzyl formate and formic acid in water-based systems for stripping various protective coatings.

However, these prior art compositions suffer from several disadvantages, namely low solvency (low efficiency), high cost, corrosiveness, narrow stability range, and especially strong, unpleasant pungent odor.

The present invention relates to a novel stripping composition which is effective in removing various protective coatings, especially epoxy, crosslinked polyurethane, and alkyd paints, from metal surfaces, such as aluminum-based alloys.

The paint stripper comprises three essential components in deionized or distilled water, namely, a solvent system based on one or more high boiling, high flash, aromatic alcohols with or without aromatic ethers; a hydroxycarboxylic acid; and a peroxide generating agent.

In general, the finished formulation comprises 5 to 50 parts by weight, preferably 25 to 35 parts by weight, of the solvent system; 3 to 20 parts by weight, preferably 3.5 to 7 parts by weight, of a hydroxycarboxylic acid; and 3 to 30 parts by weight, preferably 5 to 10 parts by weight of a peroxide generator. The paint remover contains deionized water or distilled water in 15-60 weight portions, preferably 40-50 weight portions. Other additives such as solubilizers, surfactants, coupling agents, rheology modifiers, corrosion inhibitors, stabilizers, and evaporation inhibitors may be used depending on the particular application.

In the present invention, parts by weight and weight percentages refer to parts by weight and weight percentages of the active ingredient. For example, if 50% aqueous hydrogen peroxide is used and it is desirable to include 10 parts by weight of the hydrogen peroxide generator in the finished composition, then 20 parts by weight of the aqueous hydrogen peroxide should be used.

The present invention provides an effective paint stripping composition that is free of chlorinated solvents, environmentally friendly and mild to the user. It is non-corrosive or only slightly corrosive to the substrate, non-flammable, non-toxic, low-odor, and fully biodegradable. The present invention also provides materials, processes and techniques for preparing liquid or paste (viscous) type formulations for stripping non-horizontally coated substrates coated by spray or brush coating.

The stripping composition of the invention is preferably prepared by premixing: (1) a polar phase comprising a hydroxycarboxylic acid, a hydrogen peroxide generator, deionized or distilled water, and selected additives; and (2) a non-polar phase comprising an organic solvent system. To prepare the liquid stripper, the nonpolar phase is slowly added to the polar phase under continuous mixing conditions, so that a stable microemulsion is formed. If a paste-type paint stripper is desired, the polar phase is slowly dispersed in the non-polar phase.

The polar phase is prepared by adding 3-20 parts by weight of hydroxycarboxylic acid, 5-30 parts by weight of peroxide-generating agent and 15-60 parts by weight of deionized or distilled water under continuous mixing conditions.

Generally, the non-polar phase comprises from 5 to 50 parts by weight of the formulation, preferably from 25 to 35 parts by weight. Benzyl alcohol, mixtures of benzyl alcohol with benzyl ether, phenoxypropanol, and mixtures of phenoxyethanol with benzyl ether are suitable. The weight ratio of aromatic alcohol to ether is preferably 2.5: 1.

To form a liquid stripper, the non-polar phase is slowly added to the polar phase under continuous mixing conditions until a clear, stable microemulsion-type composition is formed.

To obtain a paste (viscous) type paint stripper, the polar phase is slowly added to the non-polar phase using a controlled dispersion operation.

Hydroxycarboxylic acids can be described by the general formula:

HOOC-(CH₂)_n-(CH₂)_m-OH formula I

Wherein n and m are integers from 0 to 3 and the sum of n and m is at least 1; the sum of n and m is preferably equal to 1. The preferred hydroxycarboxylic acid is glycolic acid (glycolic acid), but other hydroxycarboxylic acids described by the above formula, such as hydroxypropionic acid, can also be used. Glycolic acid is generally used in an amount of 3 to 20 parts by weight, preferably 3.5 to 7 parts by weight.

The peroxide generator is preferably hydrogen peroxide. On the surface of most metals, including aluminum and its alloys, hydrogen peroxide undergoes a decomposition reaction to form a primary oxygen intermediate that is immediately capable of generating oxygen and water. Oxygen can accelerate the stripping step by first lifting the softened protective coating and then allowing a substantial amount of the stripping composition to penetrate the metal-coating interface. Although hydrogen peroxide is commercially available in concentrations of up to 70% by weight, it is preferred to use concentrations of 30-35%. This can be achieved by diluting the higher concentration of hydrogen peroxide with deionized water.

The inclusion of deionized water in the polar phase can enhance the overall stripping effect of the final stripping formulation. If the protective coating is polar, such as polyurethane, then a high dielectric constant solvent, such as water (e.g., 80.2 at 20℃.) can have a positive effect on the separation of the charged regions, thus facilitating softening of the film by other solvents in the formulation.

Deionized water most advantageously contains no more than about 1% by weight, preferably less than about 200ppm, dissolved inorganic salts. Distilled or deionized water having a conductivity of less than about 400mho/cm is particularly preferred. Failure to meet the above water parameters will result in decomposition of the peroxide and thus inhibition of the stripping effect.

Other additives may be added to the final composition, such as: coupling agents (alkylene glycols, DMSO); stabilizers (acetanilide); chelating agents (phosphonic acid, citric acid, EDTA); corrosion inhibitors (benzotriazole, borate); and rheology modifiers (hydroxypropyl cellulose, hydroxyethyl cellulose, various gums, fumed silica or precipitated silica). Such additives are well known in the art. In general, they are used in amounts of from 0.1 to 5.0% by weight, preferably from 0.2 to 3.0% by weight.

Evaporation inhibitors such as silicone fluids (polysiloxanes), water-based wax emulsions, or paraffin oils may also be used. In the finished composition, generally 0.1 to 3.0 parts by weight, preferably 0.2 to 2.5 parts by weight, are used. Solubilizing-emulsifying agents, such as polyethoxylated sorbitan esters, in particular polyethoxylated sorbitan monolaurate, monopalmitate, monostearate, tristearate, monooleate, or trioleate polysorbate, may also be added. Usually 0.5 to 5.0 parts by weight are used. About 0.4 to 1.0 parts by weight of a rheology modifier based on the finished composition is used.

The non-polar phase comprises one or more alcohols of formulae II and III, optionally one ether of formula IV:R₁-CH₂-O-CH₂-R₂

formula II formula III formula IV

Wherein X, Y and Z are both hydrogen atoms, or two hydrogen atoms and a methyl group. R may be ethyl, propyl or isopropyl; and R is₁And R₂Is a hydrogen atom and a benzyl group, orAre both benzyl groups.

To more fully describe the invention, attention may be directed to the following examples:

stainless steel cans and industrial dispersers capable of operating at speeds up to 2000rpm are commonly used in manufacturing processes. First, all the metal internal surfaces were treated (passivated) by contact with nitric acid (40% concentration) for 2-3 hours, and then the non-polar mixture consisting of alcohol or alcohol mixture was pumped into a stainless steel tank.

The silicone liquid as an evaporation inhibitor was slowly dispersed in the non-polar phase by mixing at 300-400rpm for 30-45 minutes. To the resulting mixture, the solubilizer-emulsifier, rheology modifier, and corrosion inhibitor are then added. The solubilizer-emulsifier is polyethoxylated sorbitan monooleate. The rheology modifier is hydroxypropyl cellulose. The corrosion inhibitor is benzotriazole.

The system was then slowly dispersed for 15-30 minutes. A polar phase comprising hydroxycarboxylic acid, peroxide-generating agent, and distilled or deionized water is separately prepared and then slowly added to the dispersion tank. The hydroxycarboxylic acid is glycolic acid. The peroxide generating agent is hydrogen peroxide. A significant increase in the viscosity of the composition occurs. In the next stage, the speed of the disperser was increased to 1000-1200rpm, at which time all the solid material was emulsified uniformly and then stabilized to produce a paste-type composition as will be described in more detail in Table A.

If a liquid composition is prepared, the non-polar phase is slowly added to the polar phase under continuous mixing conditions. The composition of the polar phase and the non-polar phase is as described above. Propylene glycol (coupling agent) and benzotriazole (corrosion inhibitor) were then added. A series of paste compositions are given in table a.

TABLE A

Composition (I)	(parts by weight)
		Benzyl alcohol benzyl ether 1-phenoxy-2-propanol glycolic acid hydrogen peroxide (50% by weight) Polysorbate Hydroxypropylcellulose 2-mercaptobenzotriazole siloxane liquid propylene glycol N-acetanilide deionized Water	P-1 P-2 P-3 P-4 P-5 P-6 P-7 P-835.0 20.0 ---- ---- 35.0 ---- 35.00 -------- 15.0 ---- 15.0 --- ---- ---- -------- ---- 35.0 20.0 ---- 35.0 ---- 35.010.0 10.0 10.0 10.0 10.0 10.0 ---- ----9.0 9.0 9.0 9.0 --- ---- 9.0 9.01.4 1.4 1.4 1.4 1.4 1.4 1.4 1.40.4 0.4 0.4 0.4 0.4 0.4 0.4 0.40.2 0.2 0.2 0.2 0.2 0.2 0.2 0.20.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3---- ---- ---- ---- ---- ---- ---- ----0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.0343.67 43.67 43.67 43.67 52.67 52.67 53.67 53.67

A series of liquid-type compositions are given in table B.

TABLE B

Composition (I)	(parts by weight)
		Benzyl alcohol benzyl ether 1-phenoxy-2-propanol glycolic acid hydrogen peroxide (50% by weight) Polysorbate Hydroxypropylcellulose 2-mercaptobenzotriazole siloxane liquid propylene glycol N-acetanilide deionized Water	L-1 L-2 L-3 L-4 L-5 L-6 L-7 L-835.0 20.0 ---- ---- 35.0 ---- 35.0 -------- 15.0 ---- 15.0 ---- ---- ---- -------- ---- 35.0 20.0 ---- 35.0 ---- 35.010.0 10.0 10.0 10.0 10.0 10.0 ---- ----9.0 9.0 9.0 9.0 ---- ---- 9.0 9.0---- ---- ---- ---- ---- ---- ---- -------- ---- ---- ---- ---- ---- ---- ----0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2---- ---- ---- ---- ---- ---- ---- ----4.0 15.0 4.0 15.0 4.0 4.0 4.0 4.00.03 0.03 0.03 0.03 0.03 0.03 0.03 0.0341.77 30.77 41.77 30.77 50.77 50.77 51.77 51.77

Sixteen identical aluminum alloy panels (5.5 x 8.5 inches) coated with a yellow epoxy-based primer and a gray linear polyurethane topcoat were tested for commercial and recreational aircraft. Eight out of sixteen panels were coated with a film of a paste-type composition at room temperature (20 c), and the remaining eight were immersed in the liquid composition. The effectiveness of these compositions was evaluated as a percentage of paint-release coating as a function of time, and the results are then set forth in Table C:

watch C

Percentage time (minute) observation of paint-stripped coating of the composition
	P-110045P-210060P-310055P-410080P-58090 has no H2O2P-680240 No H2O2P-795120 No glycolic acid P-890270 No glycolic acid
L-110025L-210030L-310035L-410030L-590120 is free of H2O2L-690130 is H-free2O2L-79045 glycolic acid free L-89060 glycolic acid free

The above data clearly show that both the paste formulations and the liquid formulations of the present invention (compositions P-1 to P-4, and L-1 to L-4) perform well in terms of paint removal rate and paint removal integrity compared to the comparative examples (P-5 to P-8, and L-5 to L-8) without glycolic acid and hydrogen peroxide.

Claims (15)

1. An aqueous paint stripper formulation comprising:

(a)5 to 50 parts by weight of aromatic alcohols of formulae II and III, optionally containing aromatic ethers of formula IV, and mixtures thereof:R₁-CH₂-O-CH₂-R₂

formula II formula III formula IV

Wherein X, Y and Z are both hydrogen atoms, or two hydrogen atoms and oneMethyl, R may be ethyl, propyl or isopropyl, and R₁And R₂Is a hydrogen atom and a benzyl group, or both are benzyl groups;

(b)5-30 parts by weight of hydrogen peroxide;

(c)3-20 parts by weight of a hydroxycarboxylic acid of formula I:

HOOC-(CH₂)_n-(CH₂)_m-OH formula I

Wherein n and m are integers from 0 to 3 and the sum of n and m is equal to 1; and

(d)15-60 parts by weight of deionized water or distilled water.

2. The formulation according to claim 1, wherein the aromatic alcohol is benzyl alcohol or methylbenzyl alcohol.

3. The formulation according to claim 1, wherein said aromatic alcohol is 1-phenoxy-2-propanol.

4. The formulation according to claim 1, wherein the aromatic ether is benzyl ether.

5. The formulation of claim 1, wherein the peroxide generator is hydrogen peroxide.

6. The formulation according to claim 1, wherein said hydroxycarboxylic acid is glycolic acid.

7. A paint stripper formulation comprising a mixture of: (a)5-50 parts by weight of benzyl alcohol, (b)5-30 parts by weight of hydrogen peroxide, (c)3-20 parts by weight of glycolic acid, and (d)15-60 parts by weight of deionized or distilled water.

8. A paint stripper formulation of the composition of claim 7, comprising 0.5-5 parts by weight of polyethoxylated sorbitan esters or mixtures thereof as solubilizer-emulsifier.

9. The formulation of claim 1, further comprising 0.4 to 1 part by weight of a rheology modifier selected from the group consisting of hydroxypropyl cellulose, hydroxypropyl methylcellulose, precipitated silica, and mixtures thereof.

10. The formulation according to claim 1, wherein 0.1 to 3.0 parts by weight of a silicone liquid, a paraffin oil, or a water-based wax emulsion is contained as the evaporation inhibitor.

11. The formulation according to claim 1, further comprising 0.1 to 0.5 parts by weight of 2-mercaptobenzothiazole, tolyltriazole, benzotriazole, or 2(3H) -benzothiazole-ethanedione as corrosion inhibitors.

12. The formulation according to claim 1, further comprising 0.1 to 1.0 parts by weight of bis (hexamethylene) triamino-penta (methylene-phosphonic acid), citric acid, or EDTA as a chelating agent.

13. The formulation according to claim 1, further comprising 0.1 to 1.0 parts by weight of benzotriazole as a corrosion inhibitor and 0.1 to 1.0 parts by weight of bis (hexamethylene) triamino-penta (methylene-phosphonic acid) as a chelating agent.

14. A method for preparing a paste-type paint stripping composition comprising dispersing a first mixture comprising 5 to 50 parts by weight of benzyl alcohol in a second mixture comprising 5 to 30 parts by weight of hydrogen peroxide, 3 to 20 parts by weight of glycolic acid, and 15 to 60 parts by weight of deionized or distilled water, said dispersion further comprising 0.5 to 5.0 parts by weight of a polyethoxylated sorbitan ester, 0.4 to 1.0 parts by weight of a hydroxypropylcellulose, and 0.1 to 3.0 parts by weight of a silicone fluid, paraffin oil, or emulsifying wax (solid).

15. A process for preparing a paste stripper comprising: dispersing a polar phase comprising 3-20 parts by weight glycolic acid, 5-30 parts by weight hydrogen peroxide, and 15-60 parts by weight deionized or distilled water in a non-polar phase comprising 5-50 parts by weight benzyl alcohol to obtain a finished composition further comprising 0.5-5.0 parts by weight polyethoxylated sorbitan ester, 0.4-1.0 parts by weight hydroxypropyl cellulose, and 0.1-3.0 parts by weight of a silicone fluid, paraffin oil, or water-based wax emulsion.