DE1669209C2 - Aqueous coating agent for electrophoretic deposition - Google Patents

Description

The invention relates to coating compositions which can be deposited electrophoretically in an aqueous medium dispersed resinous binders which are dilutable with water.

The electrophoretic deposition of resinous coating compositions from an aqueous medium is known. Many different resin binders have become known for their manufacture.

For example, the following types of coating compositions result.

1. Coating compounds using binders in aqueous dispersions or solutions, those by partial esterification of epoxy resin with drying or non-drying oil fatty acids and subsequent further esterification of the remaining hydroxyl group in the esterified one Mass can be obtained with polybasic acid or its anhydride.

2. Coating compounds using binders in aqueous dispersions or solutions by adding polybasic acid or These known binders undergo hydrolysis in the state of alkaline aqueous solutions and lead easy to change the state of electrodeposited electrodeposition coatings, and the dilutability of the binder components with water is poor, and moreover, it is impossible to obtain good coating films.

It has now been found that electrophoresis dipping paints, which do not have the disadvantages mentioned, if one of binders proceeds, which are based on certain derivatives of butadiene polymers.

The invention relates to a coating composition for electrophoretic deposition on the basis a binder dissolved or dispersed in an aqueous medium from the salt of a carb-

oxyl group-containing reaction product of unsaturated Monocarboxylic acids with unsaturated film formers, which is characterized in that it is as Binder contains 30 to 60 percent by weight of a derivative of a butadiene polymer, which by Implementation of an optionally modified one containing at least 70 percent by weight of butadiene units Butadiene polymers with an average molecular weight of 200 to 5000 with a Λ, / 3-ethylenic unsaturated monocarboxylic acid and neutralization of the adduct obtained with a base and has a pH of 7.0 to 8.5.

The electrophoretic coating compositions according to the invention, which contain the above special derivatives of butadiene polymers as binders, meet practically all of the properties required for electrophoretic deposition.
The butadiene polymers used in the present invention include homopolymers of butadiene, copolymers of butadiene, and derivatives thereof. The homopolymers of butadiene are 1,2-addition butadiene homopolymers, 1,4-addition butadiene homopolymers, and any 1,2- and 1,4-addition homopolymers. The copolymers of butadiene contain at least 70 percent by weight butadiene and at most 30 percent by weight other monomers; such as isoprene, chloroprene, styrene, methyl methacrylate or acrylonitrile. The modified butadiene homopolymers or copolymers are polybutadiene dicarboxylic acid, polybutadiene glycol, partially oxidized polybutadiene, partially hydrogenated polybutadiene or partially halogenated pulybutadiene. Of these butadiene polymers, butadiene homopolymers are most desirable because they provide excellent applied film upon electrodeposition. The butadiene polymers using 7U have a

LX

average molecular weight in the range from 200 to 5000, in particular from 800 to 4000 on. The smaller the distribution of the molecular weight, the better the result that can be achieved with the electrical deposition, the more uniform coatings results even after repeated use.

The butadiene polymers are known and are prepared by conventional methods such as free radical Polymerisation and ionic polymerisation. The most convenient method of polymerization is that active polymerization, since the polymer obtained by such a process has a narrow range of molecular weight distribution.

The active polymerization method of butadiene is known and has been disclosed in Japanese Patent Publications Published 7051/1965 and 17485/1967.

For example, the active polymerization of butadiene is usually carried out by adding butadiene or a mixture of butadiene with a diluent to form a mixture of a Lewis base, such as tetrahydrofuran and alkali metal, e.g. B. lithium or sodium, polymerizing the butadiene to the desired molecular weight and then adding a terminator to terminate the polymerization carried out. Naphtha-Hn, 1,2-diphenylbenzene and the like aromatic hydrocarbon activators can, if desired, be added to the polymerization system. If water, aliphatic alcohol, Lewis acid and the like is used as a terminator, 1,2-addition-butadiene homopolymer becomes When carbon dioxide is used as such an agent, one obtains 1.2 - Additionsbutadiene homopolymer dicarboxylic acid that has a Has carboxyl group, and if alkylene oxide is used, 1,2-addition butadiene homopolymer glycol is obtained, which has a hydroxyl group at both ends of the main polymer chain. In the production of copolymers of butadiene is a mixture of butadiene and one or more other monomers as the starting monomer used, and depending on the type of the above terminating agent can butadiene copolymer, butadiene copolymer dicarboxylic acid or butadiene copolymer glycol can be obtained.

The butadiene polymer are then reacted with \, beta ethylenically unsaturated monocarboxylic acids, to give the adducts of the two compounds. Any ethylenically unsaturated monocarboxylic acid can be used. Typical examples are acrylic acid, methacrylic acid, crotonic acid, 2-chloroacrylic acid and 2-bromoacrylic acid. The ratio of the acid to the butadiene polymers varies over a wide range, but the acid is used in the range from 5 to 50 parts by weight, in particular in the range from 7 to 30 parts by weight, based on 100 parts by weight of the butadiene polymer.

The addition reaction is carried out either in the molten state or in the presence of organic solvents. The preferred reaction temperature is usually in the range from 60 to 180 ^° C., preferably between 80 to 110 ^° C. In order to avoid undesirable side reactions, it is desirable to carry out the reaction in an inert gas atmosphere, for example nitrogen gas and the like. The organic solvents used if necessary have the ability to dissolve the starting butadiene polymers and acids and the reaction product, and various kinds of solvents can be used, but those having a hydrophilic property are preferred. Examples thereof are alkoxyalkanols, such as methoxyethanol, ethoxyethanol and butoxyethanol; Glycol ethers such as diethylene glycol methyl ether, diethylene glycol ethyl ether and 1-butoxyethoxy-2-propanol; Alcohols such as butyl alcohol, tetrahydrofurfuryl alcohol and tetrahydropyran-2-methanol; Glycols such as ethylene glycol, diethylene glycol, propylene glycol and hexylene glycol, and ethers such as tetrahydrofuran and dioxane. The solvents are preferably used in 30 to 100 parts by weight based on 100 parts by weight of the butadiene polymers.

In order to accelerate the reaction, 0.5 to 5.0 parts by weight of the catalyst are usually added to the reaction system, preferably 1.0 to 3.8 parts by weight, based on 100 parts by weight of i, / i-ethylenically unsaturated monocarboxylic acid. When Catalyst, radical initiators are used, such as benzoyl peroxide, tert-butyl peroxide, Cumene hydroperoxide and azobisisobutyronitrile, and redox catalysts such as Benzoyl peroxide dimethylaniline. Furthermore, in order to avoid the undesired gelatinization, mercaptans are used and like chain transfer agents or benzoquinone are added as a polymerization inhibitor.

The addition products of butadiene polymers and Ί, / '- ethylenically unsaturated monocarboxylic acids are thus obtained in the molten state or as a solution in an organic solvent.

The resulting adduct is then used to produce the desired water-dispersible salt neutralized with a base. It is not necessary to use the organic solvent before the neutralization reaction separate from the adduct solution if that solvent is hydrophilic, unless the presence such a solvent adversely affects the properties of the final composition regarding electrophoretic deposition. The neutralization reaction is usually around Carried out at room temperature. Sodium hydroxide, potassium hydroxide, ammonium hydroxide, Ammonium carbonate, sodium carbonate and similar inorganic bases and ethanolamine, diethanolamine, Triethanolamine, dimethylaminoethanol, diethylaminoethanol, trimethylamine, triethylamine, N-ethylmorpholine, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol, tris (hydroxymethyl) aminomethane and the like aliphatic amines are used. The base is in the form of an aqueous Solution and used at least in the amount necessary to dissolve the addition product in water to disperse. Preferably, 0.5 to 1.2 of the equivalent amount of base is used, calculated on the carboxyl group of the adduct.

The aqueous dispersion obtained contains the salts of the addition products of butadiene polymers and α, / 5-ethylenically unsaturated monocarboxylic acids in a concentration of 30 to 60 percent by weight and has a pH of 7.0 to 8.5. The aqueous dispersion is stable and can be used for electrodeposition after it has been pigmented with dye. The pigments used are z. B. talc, calcium carbonate, Iron oxide, titanium dioxide, lead chromate, strontium chromate

mat and soot. The weight ratio of dyes to binders is preferably in the range of 1: 1 to 1: 5. If necessary, dye dispersants, drying agents and customary auxiliaries can be used can be added. The aqueous dispersion or paint is diluted with water to the desired level, to obtain an electrodeposition bath composition The solids content in the Bath composition is usually in the range of 5 to 30 weight percent, preferably at 10 to 20 percent by weight

The composition of the invention is conventionally used by an electrical Current flows through the dispersion to the FUm on a submerged object, which is the anode of the electrical system represents to be deposited.

For a better understanding dtj invention will be given in the following examples, in which all parts and percentages are parts by weight, unless otherwise specified.

example 1 A. Preparation of the binder solution as

In a reaction vessel equipped with a thermometer, stirrer, dropping funnel, reflux condenser and gas injector, 100 parts of 1,2-addition butadiene homopolymer with an average a molecular weight of 1,000 made by active polymerization and 30 parts Brought butoxyethanol and heated to 100 ° C with stirring, nitrogen gas was introduced. When the temperature of the contents became constant, a mixture of 15 parts of acrylic acid, 15 parts of butoxyethanol and 0.3 parts of α, α'-Αζο-bisisobutyronitrile within 2 hours by the Dropping funnel added dropwise. At this time the contents were kept at 100 ° C. After Cooling was added to 138 parts of the obtained mixture containing 100 parts of resin with stirring 0.40 part of cobalt naphthenate and 0.35 part of lead naphthenate were added, followed by 112 parts of 12.5% aqueous solution of diethanolamine were slowly added. The stirring was followed by formation a homogeneous aqueous composition containing about 40 vol of water soluble resin.

The aqueous composition was very stable and no precipitate was observed after storage for 60 days at room temperature.

B. Manufacture of a pigmented varnish

From the aqueous composition prepared in the same manner as in Example 1A (hereinafter referred to as "aqueous composition according to Example 1A") was carried out in the following manner prepared a bath composition for electrophoretic deposition:

Aqueous composition according to Example IA 515 parts Titanium dioxide 280 parts

Carbon black 10 parts

Water 30 parts

The above ingredients were mixed in a ball mill for 20 hours to obtain the dye to disperse thoroughly. 1620 parts of the aqueous composition according to the example were added to the mixture IA and 80 parts of water were added and mixed for a further 2 hours, followed by the mixture was diluted with water. to make a bath composition for the electrophoretic deposition of gray color containing 10 · / · solids. The electrodeposition coating obtained therefrom was at room temperature or curable at elevated temperature and gave one water-insoluble film with excellent properties.

Example 2

A stable aqueous composition was prepared in the same manner as in Example IA except that 1,4-addition butadiene homopolymer having an average molecular weight of 1,000 was used in place of 1,2-addition butadiene homopolymer. From this aqueous composition became a bath composition in the same manner as in Example 1B produced, their deposited coating at room temperature or at elevated temperature was hardenable.

Example 3 A. Preparation of the binder dispersion

In the same reaction vessel as in Example IA, 100 parts of 1 ^ -addition butadiene homopolymer dicarboxylic acid prepared by active polymerization, which had a carboxyl group at both ends of the main polymer chain and had an average molecular weight of 1,500, were added. 30 parts of butoxyethanol and 0.2 parts of tert-butylated hydroxytoluene and stirred up 100 ° C heated, with nitrogen gas blown in and the system was kept at this temperature, whereupon a mixture of 15 parts of acrylic acid, 15 parts of butoxyethanol and 0.3 part of benzoyl peroxide were added dropwise in 2 hours. After the addition, the system was further stirred at 100 ° C. for 1.5 hours and then cooled to room temperature. After cooling, 138 parts of the resulting mixture were added to the Contained 100 parts resin, 0.40 part cobalt naphthenate and 0.35 part lead naphthenate added, followed by furthermore 112 parts of a 12.5 V aqueous diethanolamine solution were slowly added with stirring became. Thus a stable aqueous composition containing about 40 x / x resin was obtained.

B. Manufacture of a pigmented varnish

From the above aqueous composition, a bath composition was prepared in the same manner as in Example IB, the deposited Coating was curable at room temperature or elevated temperature.

ρ, - · ι, mertemperature or curable at elevated temperature

Example ^ _was

A. Preparation of the binder dispersion To clarify the properties of the invented

coating agents according to the invention were conventional binders

In the same reaction vessel as in Example IA 5 means A and B for electrophoretic deposition, 100 parts of 1,2-addition-butadiene homopoly coatings were produced in the following manner:
meres with an average molecular weight binder A is using linseed oil weight of 4000, which had been prepared by active polymerization instead of 1,2-addition butadiene homopolymer, 100 parts of butoxyethanol and according to Example 1 and by adding 1 part of cobalt tert. -Butylhydroxytoluene added and the ge io naphthenate and lead naphthenate in to cobalt or mixed heated to 80 ° C, nitrogen gas was blown in lead equivalent amounts of 0.06 and 0.25, after which a mixture of 18 parts by weight, based on the solid proportion of resin methacrylic acid, 18 parts of butoxyethanol and 5 parts of the mass, prepared dropwise to aqueous masses according to the same len lert.-butyl peroxide over a 3-hour process according to Example 1,
which was admitted. During this operation, the binder 15 B is by the usual method, the reaction temperature was maintained at 8O ⁰ C. the neutralization and dispersion of the alkyd After the above dropwise addition, 2 hour resins with an acid number of 50 and a viscosity of 5.5 Stokes in 50% ethylene glycol monobutyl and then cooled at 80 ° C. to terminate the reaction . After cooling, ethereal solutions were made.

200 parts of the product obtained (the 100 parts »o There are bath compositions for electro-resin contained), 50 parts of a 35.8% aqueous phoretic deposit using the Trimethylamine solution slowly beige with stirring- binders A and B according to the given in example 1, whereby an aqueous composition is produced.

which contained about 40% resin. When using Binder, Hexaas bismethoxymethylmelamine to the mass at the time

B. Production of a pigmented varnish Ρ "" ¹ "added to ^the electrophoretic deposition

ben. The alkyd resin was after esterification

From the above composition, in the same way as in Example IB, from 30 parts by weight of soy, a bath composition of bean oil fatty acid, 30 parts by weight of phthalic acid composition, was obtained from 30 parts by weight of soy produced, the deposited anhydride, 7 parts by weight of trimellitic anhydride stratification made at room temperature or with increased and 32 parts by weight of trimethylolpropane. Temperature was curable. To 90 parts by weight of this resin became 30 parts by weight Ethylene glycol monobutyl ether, 13 parts by weight of triethylamine and 108 parts by weight of deft ·· 1 5 35 still water were added. The resulting mixture P was further dispersed to produce the composition of A. Production of the binder dispersion Binder B was further dispersed.

Using the methods described in Examples 1 to 5

In the same reaction vessel as in Example 1 A and the comparative binders A and B prepared 100 parts were prepared by active polymerization. Bath compositions were made under the following made 1,2-addition-butadiene homopolymer glycol, conditions an electrophoretic deposition the one carried out at both ends of the polymer backbone, and the electrodeposition hydroxyl group Contained and an average properties of the composition and that of it Molecular weight of 1,500 and 30 parts of deposited film are in the following tables Brought butoxyethanol and heated to 100 ° C, 45 reproduced.

nitrogen gas was blown in and then the electrophoretic deposition was carried out

ßend a mixture of 20 parts of acrylic acid, 20 parts by adding a steel plate of 5-10 cm, the len butoxyethanol and 0.5 part of α, α'-azobisisobu with zinc phosphate, as the anode of werentyronitrile added dropwise over 2 hours would. was det. During this process, the anode and cathode plates were placed 10 cm apart, held at 100 ° C for one groove, and immersed in the drop bath composition that had 10% solids added a solution of 0.1 part was also contained, and a constant constant current was added dropwise to the in 15 minutes, where the contents were fed to the bath at 25 ° C, wäh-α, α-azobisisobutyronitrile in 15 parts of butoxyethanol rend 2 minutes for electrodeposition. After the switch-off of the 100 ° C kept current for a further hour, the anode plate was to react with the electroplating earth. After cooling, 154 th coating were taken out and, after rinsing, parts of the product obtained (resin content 100% with water were baked at 140 ° C. for 30 minutes.
Parts) 96 parts of a 11, 5% aqueous sodium hydroxide solution slowly added with stirring,
whereby an aqueous composition obtained 60 '- distributability

which contained about 40% resin.

Spreadability means the ability of the color to Coating areas of the anode which weld

B. Manufacture of the pigmented paint are accessible. Two steel plates were in one

65 spacing of 2 mm used as the anode, and the

From the above composition, the amount of paint deposited and the areas dei in the same way as in Example 1B, a bath composite coated surface on the inner and outer layers produced, the coating of which on the surface of the anode plates was carried out according to ii

609632/32

"Deutsche Farben-Zeitschrift", September 1965, p. 361 to 370, examined the method described, and the amount of deposited amount on the

10

inner area as well as the extent of the area of the coating on the inner area was determined by the following equations are determined.

Extent of the deposited amount on _ deposited amount on the inner surface of the anode "the inner surface of the anode (%>) total deposited amount on the inner and outer

Area of the anode

Extent of the coating area on the inner surface of the anode (° / o)

Area of deposited film on the inner surface of the anode

Area of the deposited film on the outer surface of the anode

Table I.

Example Example Example Example Example Conversion

3 4 5 equal equal

binding agent

AWAY

Extent of the deposited amount on the inner surface of the anode (Vo) Extent of the coated area on the inner surface of the anode (%)

24 23 29 22nd 28 14th 20th 82 82 87 80 87 62 82

2. Relationship between the thickness of the film and the tension

The thickness of the deposited film on the plate at different voltage was measured, and that The relationship between the thickness and the tension is shown in Table II below.

Table II

voltage Thickness of the film » Example 3 Example 4 Example 5 Comparison Comparison Example 1 Example 2 binder A binder B

12th
23
30th
38

12 23 30 38

10

17 22 28 32

13th

22nd
33
40

11 17 23 28 34

25 32 53

16 25 36 42

3. Stability of the bath composition with long-term electrodeposition

By adding paint to the bathroom every day to replace the entire amount of paint in a week (Turnover: per week), shadows under the eyes of the electrodeposition and the appearance of the

£ uv Γ ™ ^{in the 1115} P "" ¹ ^ ^{1011611 state and na} <* 4 months and the results are given in Table III below. °

Table ΙΠ

example 1

initial state

after

Months

Example 3

initial Status

after

Months

Example 5

initial state

after

4 months

Specific conductivity μΩ ^ - voltage

Initial Current (A)
Film thickness (μ)
Current efficiency (mg / A-sec)
Appearance of the cured film

2.21-

80

1.58

29

17.0

Well

2.25-103

1.65
31
16.8
Well

2.85

100

1.88

28

14.0

Well

10 »2.88 · ΙΟ«

1.96 29 13.6 good

2.63

100

1.70

28

16.0

Well

2.70-1O ³

1.82 27 15.7 good

Table III

Comparative binder A after 4 months Comparative binder B after initial initial 4 months Status 8.23 · 10 » Status 3.30-10 ³ Specific conductivity μΩ - 3.01 · ΙΟ » electrical 1.01 · 10 ' 100 voltage 60 more phoretic 60 1.92 Initial Current (A) 2.03 Deposition 2.51 18th Film thickness (μ) 32 coating 25th 14.3 Current efficiency (mg / A-sec) 2.31 impossible 21.4 bad Appearance of the cured film bad Well

4. Properties of the electrodeposited film

The results of measurement of the electrodeposited films using the bath composition of Example 1, 3 and 4 and the comparative binders A and B are shown in Table IV below illustrated.

Table IV example 1 Example 3 Example 4

Comparative comparative binder A binder B

Film thickness (μ)

Pencil hardness

Impact resistance

(Du Pont process 500 g, W)

rear

Erichsen test

Adhesion test (hatching)

Salt spray resistance (after 168 hours)

Immersion test (in 5% aqueous

NaOH solution at 25 ° C for 3 days)

25th 27 25th 28 30th H H 2H 3B 3H 50 cm 50 cm 50 cm 50 cm 10 centimeters 50 cm 50 cm 50 cm 50 cm bad 8 mm 8 mm 8 mm 8 mm 1 mm excellent excellent excellent Well bad under 3 mm under 3 mm under 3 mm under 6 mm unier 8 now no ver no ver no ver softened no ver modification modification modification modification

From the above electrodeposition properties and the properties measured above the electrodeposited films show the following:

1. The distributability is excellent.

2. When electrodeposing is performed consecutively for 4 months at a weekly turnover, the deposition properties show practically no difference in the initial state and after 4 months, and this also shows that the bath composition is stable over a long period of time and the electrodeposition selectivity is stable is extremely low and negligible.
The properties of the electrodeposited films are exceptionally good.

Claims (5)

Patent claims: 1. Coating agents for electrophoretic deposition based on an aqueous solution Medium dissolved or dispersed binder from the salt of a carboxyl group Reaction product of unsaturated monocarboxylic acids with unsaturated film formers, characterized in that it is 30 to 60 percent by weight of a binder Derivatives of a butadiene polymer contains, by conversion of at least 70 percent by weight Butadiene units containing, optionally modified, titadiene polymers with an average molecular weight of 200 to 5000 with a Λ, / ί-ethylenically unsaturated monocarboxylic acid in an amount of 5 to 50 parts by weight of acid, based on 100 parts by weight of butadiene polymers, and neutralization of the obtained adduct has been prepared with a base, and a pH of 7.0 to 8.5 having. 2. Coating agent according to claim 1, characterized in that it consists of a binder Has butadiene polymers of molecular weight 800 to 4000. 3. Coating agent according to claim 1 and 2, characterized in that it also contains a pigment having. 4. A bath composition containing a coating agent according to claim 3, characterized in that that it has a solids content in the range from 5 to 30 percent by weight. Anhydride to acrylic acid resin containing hydroxyl groups can be obtained. 3. Coating compositions using carriers in aqueous dispersions or solutions Aminoplasts and alkyl resins. 4. Coating compositions using binders in aqueous dispersions or solutions made of aminoplasts and acrylic acid resin. 5. Coating compounds using binders in aqueous dispersions or solutions, which are mainly composed of maleate oil.