DE2460470A1 - Aqueous coatings - Google Patents

Description

BASF Aktiengesellschaft

Our reference: 0.Z ₀ 31 053 Dd / lSo 67OO Ludwigshafen, December 18, 197 ^

Aqueous coating agents

The invention relates to coating compositions based on an aqueous Solution or dispersion of a thermosetting binder that carries basic nitrogen groups.

To protect the environment against harmful emissions, attempts are made to use conventional binders in low-solvent or low-solvent to produce solvent-free preparation. In this context, water-soluble or water-thinnable binders have gained great importance. Solubility of the binders can be, for. B. brought about by incorporation more hydrophilic cationic groups that are neutralized with acids. Most of these neutralizing agents escape when the solutions are dried or stoved. trouble result from the fact that the acids often cause corrosion damage in the drying or stoving systems.

The area of application also poses special problems electrocoating. Here organic or inorganic binders are used to neutralize and disperse the binders Acids such as hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, Acetic acid, maleic acid, formic acid or lactic acid are used. These acids or their decomposition products formed during stoving impair the properties of the coating and also make the Diving facility required. In addition, the addition of the Acids Dosing problems, as over-acidification must be avoided as far as possible.

The invention was based on the object of developing water-soluble or water-thinnable cationic binders for coatings, which do not have the disadvantages indicated.

This problem is solved by using nitrogenba-595 / 74.6-Q9827 / Q9.3Q. . ₂ _

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sic groups-bearing, water-insoluble organic compounds, which in an aqueous medium by carbonic acid protonated and thereby brought into solution or converted into a stable dispersion.

The binders used are low molecular weight, oligomeric or preferably polymeric organic compounds that stick carry off basic groups. In addition, those compounds are also suitable, the sulfonium or phosphonium groups form.

The following low molecular weight or oligomeric compounds are possible:

N, N ^! -Di (hydroxyne openty1) -pi perazine

_{3 r} ^

HO-CH ₀ -C -CHo-N N-CH ₀ -C-CH ₀ -OH

^d t ^ \ / d ! d

CH-. CH,

3 3

or condensation products of urea, aldehydes and ammonia or secondary amines (basic urea resins; cf.Houben-Weyl, Methods of Organic Chemistry, Vol. 14/2, pages 342 ff, Thieme-Verlag 1963)

or urea resins made from diureas with basic links about the structure

H ₀ NC-NH-CH ₀ -CH ₀ -N-CH ₀ -CH ₀ -NH-C-Nh ₀

d « dd t dd η d

0 CO 0

R.
(R = alkyl).

Resins that can be used as polymeric binders are those obtained by polymerization, Polycondensation or polyaddition were produced. Such binders can be produced, for example by copolymerization of unsaturated compounds that carry basic nitrogen groups, copolymerizable with others Monomers. The unsaturated basic nitrogen groups bearing compounds should preferably be in the copolymer Amounts between 3 and 30 percent by weight be incorporated. In

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For example, aminoalkyl esters are more polymerizable Acids, such as aminoalkyl esters or dialkylaminoalkyl esters of acrylic acid or methacrylic acid] unsaturated aminoalkylamides Acids such as 1-aminoalkylamides or 1- (N, N-dialkylamino) alkylamides acrylic acid or methacrylic acid] also vinylated nitrogen-based heterocycles, such as N-vinylimidazole or N-vinylmethylimidazoline, also C-vinylamines or vinylbenzylamines. The main comonomers are allyl esters or hydroxyalkyl esters acrylic acid or methacrylic acid in question, as well as styrene. In addition, the copolymers expediently contain 3 to 30 percent by weight of an amide, alkyl amide, Oxyalkylamides or oxaalkylamides of acrylic acid or methacrylic acid; 2-oxaalkylamides being particularly suitable. Such copolymers are z. Bo in the DT-AS 1 276 260, 1 546 840 and 1 546 848.

Polycondensation products are, for example, polyesters or polyester amides that carry amino end groups, basic nitrogen groups in the polymer chain or equivalent Page groups included.

Suitable polyadducts are those based on polyepoxy resins or groups of polyurethane, for example by reacting diepoxides or diisocyanates with 2 moles of acrylic acid or methacrylic acid to form epoxy acrylates or urethane acrylates and subsequent addition of secondary amines to the double bonds can be produced. Phenolic resins into which amino groups have been incorporated by polymer-analogous reactions are also very suitable. You can z. B, according to DT-OS 2 320 30I can be prepared by conversion of epoxy resins with Mannich bases from condensed phenols, e.g. B. bisphenol A, secondary amines, the hydroxy1-alkyl groups wear and formaldehyde ,,

Other suitable binders are described, _e B. DT-A 1 814th

The organic compounds bearing nitrogen-based groups

6Q9827 / Q93Q - ² ^ -

2A60470

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fertilize must meet an important criterion if they are for the aqueous coating agents according to the invention should be suitable: They must be water-insoluble per se, but in aqueous medium can be protonated by carbonic acid and thereby brought into solution or converted into a stable dispersion can be. A simple test can be used to determine whether this criterion is met:

1 g of the organic compound to be tested is placed in a test tube, either as a powder or as a solution in up to 2 g of an organic, water & scourable solvent, add 9 g Add water and 1 g dry ice and shake at room temperature. It can be stirred with a glass rod if necessary or a slight overpressure can be generated by closing the test tube with your thumb. If after the latest 5 minutes if a clear solution or a cloudy but stable dispersion has formed, the compound acts as a binder for suitable for the purpose of the invention. “Stable dispersion” is to be understood as meaning a dispersion which becomes clear after 10 minutes Standing without stirring must not have settled.

The content of basic nitrogen groups alone is not always sufficient to make the binding agent with the help of carbonic acid in water To make soluble or dispersible, in some cases, can the binder can be made water-soluble by incorporating components with greater hydrophilicity. This is due to the following Try explained:

Acrylic ester copolymers were produced in which monomer N-dimethylaminopropylacrylamide bearing nitrogen-based groups (I) was incorporated. An improvement in solubility can be achieved by

a) Use of hydrophilic acrylic esters:

10 parts 1/90 part BA insoluble

10pcs. I / 90 Tl. ÄA partially soluble 10 Tl. I / 90 parts of MA soluble

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b) addition of Hydroxyaerylatern

5 Tl. 1/10 Tl. ΗΡΑ / 85 Tl. BA insoluble

5 Tl. 1/10 Tl. ΗΡΑ / 85 Tl. ÄA cloudy soluble

5 parts 1/10 part HPA / 85 parts MA clearly soluble

c) Increasing the content of the basic nitrogen groups bearing monomers;

5 Tl, I / 10 Tl. HPA / 85 Tl. MA soluble

3 parts 1/10 part HPA / 87 parts MA insoluble

The abbreviations mean:

BA = n-butyl acrylate

M = ethyl acrylate

MA = methyl acrylate

ΗΡΑ = hydroxypropyl acrylate

In practice, the water-insoluble binder is used in powder form or, preferably, as a solution in a water-miscible organic solvent, e.g. B. isopropanol, butanol, methyl glycol, dimethyl glycol or dioxane, mixed with water. 0.5 to 15 parts of water can be used for 1 part of binder. The amount of the organic solvent should preferably be at most 20 percent by weight, based on the mixture. While stirring, carbonic acid is added either in gaseous form or as dry ice. The dispersion process can be obtained by increasing the temperature to 50 to 6O ⁰ C and / or be accelerated by slight overpressure.

The aqueous coating agent can of course contain the usual additives, such as pigments, dyes, leveling agents, Contain stabilizers, curing catalysts or antifoam agents. Also the presence of small amounts Acids other than carbon dioxide should not be excluded. The pH in the aqueous system is generally above 6, preferably between 6.5 and 9.5.

The coating agents according to the invention can in the form of their aqueous

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solutions or dispersions can be used for cationic electrocoating of metals. It is after usual procedures worked in the cited publications are described in detail »

The coating agents can also be applied by conventional application methods, such as painting or spraying on substrates such as metals, wood or plastic.

For binders or crosslinkers that are not in The binders according to the invention can be water-dispersible serve as dispersing aids or stabilizers.

In the case of continuous application processes, it can be advantageous to add dry ice to the solution or dispersion from time to time or add gaseous COg to reduce the concentration of carbonic acid keep constant.

The coatings are baked onto the substrate after they have been applied, where hardening occurs with crosslinking.

The parts and percentages given in the examples are based on weight.

example 1

10 parts of the 70 following solution in isopropanol of a copolymer of 10 parts of N-dimethylaminopropyl acrylamide, 20 parts of hydroxypropyl acrylate and 70 parts of methyl acrylate are dissolved in 20 parts of water by adding 1 part of dry ice (CO ₂ ). 4 parts of a hexamethoxymethylmelamine are added to this solution as a crosslinker. It is sprayed onto deep-drawn sheet metal using a spray gun and baked for 30 minutes at different temperatures. »High-gloss, hard coatings are obtained.

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Stoving conditions

Film pendulum hardness Erichsen value exposure strength DIN 53 157 DIN 53 I56 of xylene

30 min / i50 ° C 17
30 min./i70 ° C 15
30 min./19O ⁰ C 17

169 179 174

5.8

5.3 4.8

no attack no attack no attack

Example 2

13 parts of the 70 following solution in isopropanol of a copolymer of 70 parts of ethyl acrylate, 20 parts of hydroxypropyl acrylate and 10 parts of N-diethylaminopropyl acrylamide are dissolved in 110 parts of water by introducing COp. 1.3 parts of a hexamethylolmelamine etherified with methanol are added. In an electrodeposition system, films are deposited by applying a direct voltage of 150 volts to the cathode and baked in at various temperatures. The paintwork has the following properties

Stoving conditions

Film thickness (/ u)

Pendulum hardness DIN 53 157

Erichsen value DIN 53 156

30 min / i50 ° C 25
30 min./i70 ° C 20
30 min. / 190 ⁰ C 23

> 9

> 9

Example 3

(R)

30 parts of a polyaddition product made from Epikote 1001 (Condensation product from bisphenol A and epichlorohydrin) and bisphenol A are in 80 # butanolic solution with 4 parts of p-formaldehyde and 14 parts of diethanolamine implemented.

The reaction product is dispersed in 100 parts of water and brought into solution by introducing COg gas. A coated with zinc phosphate Bonder sheet is coated by immersion in the binder solution and then baked at 200 ⁰ C I5 minutes. It becomes a hard, elastic, good one

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Adhesive coating obtained after 500 hours of exposure in the salt spray test (ASTM B 117-64) one on both sides into the The paintwork of the dug-in cross-cut shows a maximum of 1 mm rusting underneath.

609827 / 093Q

Claims (1)

Line 31 053 Claims 1 "Coating agent containing an aqueous solution or dispersion of a thermosetting binder, the nitrogen" carries basic groups, characterized in that the Binder is a water-insoluble organic compound, which in an aqueous medium by carbonic acid protonated and thereby brought into solution or in a stable aqueous dispersion was transferred, 2, use of the coating agent according to claim 1 in the form its aqueous solution or "dispersion for the cationic electrodeposition of metals" 3 »Use of the coating agent according to claim 1 in the form its aqueous solution or "dispersion for coating substrates by spraying or brushing" BASF Aktiengesellschaft 609827/093 0.