FR2784994A1 - Aqueous alkaline composition for stripping acrylic coatings comprises glycol ether, hydrotropic surfactant and alkaline phosphate, orthophosphate or polyphosphate - Google Patents

Abstract

An aqueous composition for stripping acrylic alkaline coatings, preferably of pH 7-12, comprises 7-99 wt.% of at least a glycol ether, 0.01-50 wt.% hydrotropic surfactant, and 0.01-30 wt.% alkaline phosphate, orthophosphate or polyphosphate. An aqueous composition for stripping acrylic coatings with alkaline pH, preferably = 7-12, comprises: 7-99, preferably 15-80 wt.% of (a) at least a glycol ether of formula R1-O-(R2-O)n-R3; R1 and R3 = alkyl, alcohol, aldehyde, ketone, ester or oxyethylene or oxypropylene group; R2 = less than 5C alkylene; and n = 1, 2 or 3, and (b) 0.01-50, preferably 3-10 wt.% at least a hydrotropic surfactant selected from the group comprising glucosides, alkylglucosides, natural or synthetic carboxylic acids and (alkyl, aryl or alkylaryl) sulfonic acids and their alkaline, alkaline earth or ammonium salts; and 0.01-30, preferably 2-10 wt.% at least an amine, alkanolamine or ammonium phosphate, orthophosphate or polyphosphate. An Independent claim is also included for a method for stripping acrylic coatings using claimed composition.

Description

COMPOSITION AND METHOD OF STRIPPING
ACRYLIC COATINGS
The subject of the invention is an aqueous composition for stripping acrylic coatings.

 It also relates to a process for the implementation of the composition in question.

 It is known to protect steel-based substrates with coatings based on aqueous acrylic resins.

 The expression "aqueous acrylic coating" denotes any dry film, obtained after drying and / or polymerization of a composition, containing this type of binder; such a composition, generally alkaline, may contain, moreover, inorganic or organic pigments, dispersant additives, antifoam, surfactants, colorants, coloring or non-coloring inorganic fillers or mixtures of these additives.

 Thus, patent FR-A-2,734,275 describes an aqueous phase anticorrosion coating composition, of basic pH, essentially comprising a film-forming binder in the form of an aqueous dispersion of an acrylic polymer and leading, after drying and / or or polymerization, forming a hydrophobic film.

 The patent in question describes a selection of film-forming binders that may be suitable for the preparation of anticorrosive coating compositions.

 In practice, it is often necessary to clean or etch a surface covered with an aqueous acrylic coating; thus, in the case of temporary corrosion protection, it is necessary to remove the coating to be able to perform subsequent treatments, such as the application of a paint; likewise, in the case of an unwanted accidental spraying, it is advisable to clean the surface; furthermore, after a holiday period, spraying equipment such as nozzles, pump, hoses and application equipment may need to be cleaned in general; finally, after its manufacture, such a composition can dry on the tank and pipes and it is then necessary to clean the entire installation.

 Aqueous cleaning formulations have already been developed to remove acrylic coatings.

 Thus, US-A-5,609,693 discloses a cleaning composition for cleaning the equipment necessary for the manufacture of acrylic coatings used in the medical field. The acrylic coatings mentioned in this patent are soluble in a neutral or alkaline medium and insoluble in an acid medium. The proposed cleaning formulation contains mainly a carboxylic acid and an ethoxylated organic component. It does not allow the etching of an aqueous acrylic coating as described above since the vast majority of formulations which, after drying, give rise to an aqueous acrylic coating are insoluble in alkaline medium.

Furthermore, US-A-5,733,380 describes a pickling composition containing mainly glycol ethers; this composition is used hot at about 90 ° C to remove organic coatings; such a composition has the disadvantages of the use of hot products, including a risk of burns for operators but also the formation of vapors that can reduce visibility; glycol ethers also tend to generate hot unpleasant odors that must be combated; Finally, they generate hot
Volatile Organic Compounds (VOCs), which need to be reduced because of their supposed greenhouse effect.

 The invention therefore aims, above all, to provide a <composition and a method for pickling, at room temperature of about 25 C, aqueous acrylic coatings, insoluble especially in alkaline medium; this composition will advantageously have anticorrosion performance.

 And the Applicant Company has had the merit of having found, after extensive research, that this goal was achieved using an aqueous alkaline pH composition having particular proportions of at least one glycol ether at least one hydrotropic surfactant and at least one alkaline phosphate, orthophosphate or polyphosphate.

Therefore, the composition according to the invention is water-based, preferably demineralized and is characterized in that it is of alkaline pH, preferably 7 to 12 and it comprises, expressed as a percentage by weight /weight
from 7 to 99%, preferably from 15 to 80%, of at least one glycol ether of the formula R 1 -O- (R 2 -O) n -R 3 in which R 1 and R 3 represent an alkyl group, an alcohol, a an aldehyde, a ketone, an ester or an oxyethylenated or oxypropylene group, and wherein R2 represents an alkylene group having a carbon chain having less than 5 carbon atoms, n being an integer equal to 1, 2 or 3,
from 0.01 to 50%, preferably from 3 to 10%, of at least one hydrotrope surfactant preferably chosen from the group comprising glucosides, alkylglucosides, carboxylic acids of natural or synthetic origin, sulfonic, alkylsulphonic, arylsulphonic, alkylarylsulphonic acids and their alkali, alkaline earth or ammonium salts,
from 0.01 to 30%, preferably from 2 to 10%, of at least one alkaline phosphate, orthophosphate or polyphosphate of amine, alkanolamine or ammonium, as well as one or more additives selected from group comprising:
sequestering agents selected from the group comprising EDTA, NTA, phosphonates, gluconates and glucoheptanoates of alkali metals or alkanolamine, in an amount of 0.05 to 3%,
anticorrosion agents selected from the group consisting of alkali metal salts or alkanolamines of sulfonic or nitrogenous acids, carboxylic acids, alkylsarcosinic acids and alkylarylsulfoamidocarboxylic acids in an amount of 0.5 to 15% ,
preservatives chosen from the group comprising formalin, triazine derivatives, orthophenylphenol or its sodium salt, sodium omadine derivatives, isothiazolone derivatives and iodocarbamate derivatives, in an amount of 0.01 to 2%,
surfactants whose action can be wetting, foaming or dispersing in an amount of 0.01 to 6%, chosen either from the group comprising the anionic derivatives and in particular, on the one hand, the salts formed between a alkali metal hydroxide, an amine or an alkanolamine and a fatty acid of natural or synthetic origin having a carbon chain of C10 to C22 and, on the other hand, the salts of an alkaline hydroxide, an amine or a alkanolamine of a sulphonated or sulphated fatty substance, of sulphated fatty alcohols, of sulphated fatty amides, of amine oxides, of sulphonated hydrocarbons, of sulphonated alkylaryls, or of the group comprising nonionic derivatives, and in particular fluorinated polymers, polyethylene glycol esters, oxyethylenated and oxypropylenated derivatives of high molecular weight alcohols, amides, substituted amides, fatty acids, esters or amines,
dyes such as fluorescein,
perfumes such as pine oil,
thickening agents making it possible to modify the rheology of the product, chosen from the group comprising polysaccharides and cellulose derivatives, especially xanthan gum, carboxymethylcellulose and hydroxymethylcellulose, in an amount of 0.05 to 5%.

 It should be noted that among the glycol ethers, some such as methylglycol (CH3-O-CH2-CH2-OH), ethylglycol (CH3-CH2-O-CH2-CH2-OH), methylglycol (CH3-O-CH2-CH2-O- (C = O) -CH3) and ethylglycol acetate (CH3-CH2-O-CH2-CH2-O- (C = O) -CH3) are preferably discarded as they are suspected of being toxic to human reproduction.

The method according to the invention for implementing the aforementioned composition is characterized by the fact that
D depositing said composition on a steel substrate having an aqueous acrylic coating, with a brush or by spraying at a pressure of at least 1.5 bar, preferably at room temperature, in the form of a layer with a thickness of at least 0.5 mm,
that it is allowed to act for 1 to 30 minutes, preferably for 5 minutes, possibly brushing occasionally or possibly adding product if the thickness of the aqueous acrylic coating requires it,
) which is then rinsed with water with a cloth soaked with water or with water spray at a pressure of not less than 1.5 bar, and
drying at room temperature or by circulating a stream of hot air on the cleaned parts.

 The invention will be better understood with the aid of non-limiting examples but relating to advantageous embodiments and comparative examples which follow.

 Examples 1 to 4 are comparative examples whereas Examples 5 to 10 relate to compositions in accordance with the invention.

 The compositions according to Examples 1 to 10 are used on an aqueous anticorrosive coating whose composition is described in Example 1 of Patent FR-A2 734 275 and which is applied to a degreased, dried and non-phosphated steel sheet.

 The thickness of the dry film after drying is 43 μm.

 The constituents of the compositions according to Examples 1 to 5 appear in Table I below and those of Examples 6 to 10 in Table II; the quantities are expressed as a weight / weight percentage.

TABLE I

<tb><SEP> Proportions <SEP> (%) <SEP>
<tb><SEP> Constituent
<tb><SEP> Ex. <SEP> 1 <SEP> Ex. <SEP> 2 <SEP> Ex. <SEP> 3 <SEP> Ex. <SEP> 4 <SEP> Ex. <SEP> 5 <SEP > Ex <SEP> 6 <SEP>
<tb> Demineralized water <SEP><SEP> 69.8 <SEP> 68.8 <SEP> 83.8 <SEP> 88.8 <SEP> 63.8 <SEP> 68
<tb> Ether <SEP> of <SEP> Glycol * <SEP> 25, <SEP> 0 <SEP> 25.0 <SEP> 5.0 <SEP> 0 <SEP> 25.0 <SEP> 20, <SEP> 0
<tb> Orthophosphate <SEP> of <SEP> dipotassium <SEP> 0 <SEP> 6.0 <SEP> 5.0 <SEP> 6.0 <SEP> 6.0 <SEP> 5.0
<tb> Alkylglucoside <SEP> 5.0 <SEP> 0 <SEP> 5.0 <SEP> 5.0 <SEP> 5.0 <SEP> 6.0
<tb> Phosphoric <SEP> acid <SEP> 0.2 <SEP> 0.2 <SEP> 0.2 <SEP> 0.2 <SEP> 0.2 <SEP> 0.2
<tb> Carboxymethylcellulose <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0, <SEP> 8 <SEP>
<tb> * the one known under the trademark DOWANOL PB40
TABLE II

<tb><SEP> Proportions <SEP> (%)
<tb><SEP> Constituent
<tb><SEP> Ex. <SEP> 7 <SEP> Ex. <SEP> 8 <SEP> Ex. <SEP> 9 <SEP> Ex. <SEP> 10 <SEP>
<tb> Demineralized <SEP> water <SEP> 63, <SEP> 8 <SEP> 63.8 <SEP> 63.8 <SEP> 63.8
<tb> Butyldiglycol <SEP> 25, <SEP> 0 <SEP> 25.0 <SEP> 0 <SEP> 0
<tb> Tripropylene Glycol Ether <SEP> 0 <SEP> 0 <SEP> 25, <SEP> 0 <SEP> 0 <SEP>
<tb> Acetate <SEP> of <SEP> butylglycol <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 25, <SEP> 0
<tb> Orthophosphate <SEP> of <SEP> dipotassium <SEP> 6, <SEP> 0 <SEP> 6.0 <SEP> 0 <SEP> 6, <SEP> 0
<tb> Pyrophosphate <SEP> of <SEP> Tetrapotassium <SEP> 0 <SEP> 0 <SEP> 6.0 <SEP> 0
<tb> Xylene <SEP> sulfonate <SEP> of <SEP> sodium <SEP> 5, <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0
<tb> Cumene <SEP> sulfonate <SEP> of <SEP> sodium <SEP> 0 <SEP> 5.0 <SEP> 0 <SEP> 0
<tb> Mixtures <SEP> acids <SEP> Ethercarboxylic <SEP> 0 <SEP> 0 <SEP> 5.0 <SEP> 0
<tb> Alkylglucoside <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 5, <SEP> 0
<tb> Phosphoric <SEP> acid <SEP> 0, <SEP> 2 <SEP> 0.2 <SEP> 0.2 <SEP> 0.2
<Tb>
The appearance of the compositions according to Examples 1 to 5 and 7 to 10 is that of a yellow liquid. The appearance of the composition of Example 6 is that of a straw-yellow transparent gel. All compositions have a pH of 8.0.

 A number of details are given below with respect to the constituents used in the examples and identified in Tables I and II.

 The glycol ether used is the propylene glycol ether known under the trademark DOWANOL PB 40 marketed by Dow Chemical; it is a mixture of methyl and n-butyl ethers of propylene glycol with 1 2 C3H6 R3 = H and R'1 = C4H9, R'2 = C3H6, R'3 = H with n = 1.

The butyldiglycol employed is butyl ether of diethylene glycol marketed by the Company.
Districhimie.

Tripropylene glycol ether is that sold under the trademark DOWANOL TPM by Dow Chemical; it is the methyl ether of tripropylene glycol with R1 = CH3, R2 =
C3H6, R3 = H, n = 3.

Butylglycol acetate, namely acetate of ethylene glycol monobutyl ether [R1 = (CH3-C = O), R2 =
C2H4, R3 = C4H9, n = 1], is that marketed by
Districhimie.

Dipotassium orthophosphate is that marketed under the trade name RHODIA-PHOS DKP by Rhône-Alpes.
Poulenc and tetrapotassium pyrophosphate is that marketed by Exter Catalonia.

  The alkylglucoside is the one sold under the trademark LUTENSOL GD 70 by BASF.

Sodium xylene sulphonate is that marketed under the trademark ELTESOL SX 93 by &
Wilson.

Sodium cumene sulphonate is that marketed under the trademark ELTESOL SC 40 by &
Wilson.

 The ether carboxylic acid mixture is that marketed under the trademark AKYPO LF 4 by Lambert-Rivière.

 The carboxymethylcellulose is that marketed under the trade name BLANOSE 7 HC by the company Aqualon.

COMPARATIVE EXAMPLE 1
A layer of the composition of Example 1 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is noted that there is no stripping of the coating and that, in places, appears corrosion of the sheet.

 This composition does not contain phosphate.

COMPARATIVE EXAMPLE 2
A layer of the composition of Example 2 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is noted that there is no stripping of the coating.

 The composition used does not comprise a hydrotrope surfactant.

COMPARATIVE EXAMPLE 3
A layer of the composition of Example 3 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is noted that there is no stripping of the coating.

 The composition used comprises 5% glycol ether.

COMPARATIVE EXAMPLE 4
A layer of the composition of Example 4 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is noted that there is no stripping of the coating.

 The composition used does not include glycol ether.

EXAMPLE 5 (in accordance with the invention)
A layer of the composition of Example 5 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is found that the coating is removed from the surface. The sheet does not show any corrosion. The composition of this example is therefore found to be well suited to the present practical case.

EXAMPLE 6 (in accordance with the invention)
A layer of the composition of Example 6 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. For reasons inherent in the process, the sheet is held vertically during the experiment. It is found that the coating is removed from the surface. The sheet does not show any corrosion. The composition of this example is therefore found to be well suited to the present practical case.

EXAMPLE 7 (in accordance with the invention)
A layer of the composition of Example 7 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is found that the coating is removed from the surface. The sheet does not show any corrosion. The composition of this example is therefore found to be well suited to the present practical case.

EXAMPLE 8 (in accordance with the invention)
A layer of the composition of Example 8 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is found that the coating is removed from the surface. The sheet does not show any corrosion. The composition of this example is therefore found to be well suited to the present practical case.

EXAMPLE 9 (in accordance with the invention)
A layer of the composition of Example 9 having a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is found that the coating is removed from the surface. The sheet does not show any corrosion. The composition of this example is therefore found to be well suited to the present practical case.

EXAMPLE 10 (in accordance with the invention)
A layer of the composition of Example 10 with a thickness of 2 millimeters on the aqueous acrylic coating is deposited with a brush at 25 ° C. Allowed to act for 5 minutes. Rinse with a cloth soaked in water. It is then dried while maintaining the steel sheet at 25 C. It is found that the coating is removed from the surface. The sheet does not show any corrosion. The composition of this example is therefore found to be well suited to the present practical case.

 An additional practical example, numbered 11, was made using the composition of Example 5.

EXAMPLE 11 (in accordance with the invention)
The composition of Example 5 is sputtered with a sprayer at 30 bar for 20 seconds at 50 cm at 25 ° C. on a 55 micron aqueous acrylic coating accidentally deposited on the paint of a wing. car.

 The painting in question is the result of the full range cataphoresis, apprt, lacquer then varnish; the varnish is in the form of a 50 μm layer.

 Allowed to act for 12 minutes.

 Rinsed by spraying water with a sprayer at 10 bar.

 It is then dried by passing a stream of hot air with a fan on the wing of the car.

 It is noted that the coating is stripped and that the paint does not present any particular scratches or visual modifications such as craters or rings.

 From the examination of the examples, it appears that the presence of glycol ether, hydrotropic surfactant and phosphate in the proportions in accordance with the invention is necessary to obtain the desired etching.

Claims (3)

 from 0.01 to 30%, preferably from 2 to 10% of at least one alkaline phosphate, orthophosphate or polyphosphate of amine, alkanolamine or ammonium ,.  from 0.01 to 50%, preferably from 3 to 10%, of at least one hydrotropic surfactant preferably chosen from the group comprising glucosides, alkylglucosides, carboxylic acids of natural or synthetic origin, sulphonic, alkylsulphonic, arylsulphonic and alkylarylsulphonic acids and their alkaline, alkaline earth or ammonium salts,  from 7 to 99%, preferably from 15 to 80%, of at least one glycol ether of formula R 1 -O- (R 2 -O) n -R 3 in which R 1 and R 3 represent an alkyl group, an alcohol, an aldehyde, a ketone, an ester or an oxyethylenated or oxypropylene group, and wherein R2 represents an alkylene group having a carbon chain having less than 5 carbon atoms, n being an integer equal to 1, 2 or 3,  1. An aqueous composition for stripping acrylic coatings, characterized in that it is of alkaline pH, preferably from 7 to 12 and it comprises, expressed as a weight / weight percentage  2. Composition according to claim 1, characterized in that it comprises one or more additives chosen from the group comprising:  sequestering agents selected from the group comprising EDTA, NTA, phosphonates, gluconates and glucoheptanoates of alkali metals or alkanolamine, in an amount of 0.05 to 3%,  anticorrosion agents selected from the group consisting of alkali metal salts or alkanolamines of sulfonic or nitrogenous acids, carboxylic acids, alkylsarcosinic acids and alkylarylsulfoamidocarboxylic acids in an amount of 0.5 to 15% ,  preservatives chosen from the group comprising formalin, triazine derivatives, orthophenylphenol or its sodium salt, sodium omadine derivatives, isothiazolone derivatives and iodocarbamate derivatives, in an amount of 0.01 to 2%,  surfactants whose action can be wetting, foaming or dispersing in an amount of 0.01 to 6%, chosen either from the group comprising the anionic derivatives and in particular, on the one hand, the salts formed between a alkali metal hydroxide, an amine or an alkanolamine and a naturally occurring or synthetic fatty acid having a C0 to C22 carbon chain and, on the other hand, salts of an alkaline hydroxide, an amine or a alkanolamine of a sulphonated or sulphated fatty substance, of sulphated fatty alcohols, of sulphated fatty amides, of amine oxides, of sulphonated hydrocarbons, of sulphonated alkylaryls, or of the group comprising nonionic derivatives, and in particular fluorinated polymers, polyethylene glycol esters, oxyethylenated and oxypropylenated derivatives of high molecular weight alcohols, amides, substituted amides, fatty acids, esters or amines,  dyes such as fluorescein,  perfumes such as pine oil,  thickening agents making it possible to modify the rheology of the product, chosen from the group comprising polysaccharides and cellulose derivatives, especially xanthan gum, carboxymethylcellulose and hydroxymethylcellulose, in an amount of 0.05 to 5%.  3. Process for the implementation of the composition according to one of claims 1 and 2, characterized by the fact  said composition is deposited on a steel substrate having an aqueous acrylic coating, with a brush or by spraying at a pressure of at least 1.5 bar, preferably at room temperature, in the form of a layer with a thickness of at least 0.5 mm,  that it is allowed to act for 1 to 30 minutes, preferably for 5 minutes, possibly brushing occasionally or possibly adding product if the thickness of the aqueous acrylic coating requires it,  that is then rinsed with water with a cloth soaked in water or by spraying water under a pressure of at least 1.5 bar, and  3 "that it is dried at room temperature or by circulation of a current of hot air on the cleaned parts.