DE2420212A1 - PROCESS FOR THE PRODUCTION OF SELF-CROSSLINKING PAINT - Google Patents

Description

PATENT LAWYERS

Dipl.-Ing. P. WIRTH ■ Dr. V. SCHMIED-KOWARZIK Dipl.-Ing. G. DANNENBERG Dr. P. WEINHOLD Dr. D. GUDEL

281134 6 FRANKFURT AM MAIN

TELEPHONE C06I1)

287014 ■ GB. ESCHENHEIMER STRASSE 39

L.P. 1118

LONZA AG
Gampel / Wallis
(Management: Basel)

Process for the production of self-crosslinking paints ,

509838/0938

The invention relates to a method for producing pigmented ones or non-pigmented, self-crosslinking lacquers based on an aqueous dispersion.

The previously common metal coatings based on a drying Oil, a quick-drying paint base with natural resins, a combination of natural and synthetic Resins or an alkyd resin modified with a urea, melamine or phenol-formaldehyde resin volatile organic solvents which are often flammable and which are harmful during the coating process Develop fumes. For these reasons, special measures for recovering the solvents are necessary.

Other proposed binders for coatings contain unsaturated ones Polymer systems such as butadiene-styrene latices, however, this type of polymer has its known disadvantages to become brittle and discolored as the oxidation progresses.

In contrast, there has long been a need for coating compositions, which can be applied from aqueous media and therefore not undesirable, flammable or toxic Develop vapors and are self-crosslinking through the action of heat alone.

Known aqueous systems are described in U.S. Patents 2,760,886, 2,918,391 and 3,033,811. These coating compounds are unsatisfactory as they tend to when

• 509838/0938

Application to dry prematurely or as a result of blistering, during the. Heat treatment ,, not a smooth film surface able to form. ... ........._

There are also thermosetting coating compositions in the form more watery. Latices known (DOS 2 21.1 169), which were customary after a. Manufactured emulsion polymerization and their binders are composed of two components, on the one hand from an addition copolymer consisting of an aromatic HonovinylHionomer, an ester of acrylic or methacrylic acid, at least one olefinically unsaturated monomer with a Amide or, hydroxyl group and an olefinically unsaturated monomer with a .Carboxyl group and on the other hand from one water-soluble urea-formaldehyde resin.

The disadvantage of these coating compositions is that. they are not Selbstverne.tzend and thus a large number of important properties. wd.e pigment compatibility and pigment distribution, Adhesion, gloss, water and solvent resistance, thermal and weather stability, impaired will.

The aim of the invention is to provide self-crosslinking paints based on to produce an aqueous dispersion with good thermal and weather stability and high chemical resistance and which give high-gloss coatings that are both hard and tough.

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According to the invention this is achieved in that the binder essentially from

a) 30-70 parts by weight of a monomer or a monomer mixture, the theoretical glass transition temperatures of the homopolymer being below 1O ⁰ G,

b) JO - 70 parts by weight of a monomer or a monomer mixture, the theoretical glass transition temperatures of the homopolymer being above 3O ⁰ C,

c) 0.5-5 parts by weight of a polymerized acid or their salt,.

el) 2-35 parts by weight of a reactive monomer and e) 0.5-5 parts by weight of an alkali or ammonium salt a polymerizable sulfonic acid bond

and the polymerization at temperatures of 15 - 30 ⁰ C with the help of an Eedox system, consisting of 0.005 - 0.5%, based on the monomers *, of an alkali or ammonium persulfate, 0.001 - O ^%, based on the monomers *, Ascorbic acid and 10-30 ppm of an iron (II) salt, based on the monomers *, is carried out at a starting pH of 3 - 4, with a maximum of 30 % of the monomers * initially introduced together with the main amount of the persulfate and the the remaining amount of the monomer is metered in in parallel with the iron (II) salt and the ascorbic acid in such a way that a preselected constant polymerization ^{temperature (+ 1 0} C) results.

* i.e. the total amount * of all monomers present

509838/0 9 38

_ 5 -

The appropriate temperature to be used is 20-23 ° C. The temperature control is expediently automatic, the metering in of the iron (II) salt and the ascorbic acid as well as the monomers and the external cooling being coordinated with one another, in order to maintain a preselected constant polymerization temperature, which should ^{only deviate by + 1 ° C. during the polymerization,} maintain.

Potassium persulfate is preferably used as the persulfate, although sodium and ammonium persulfate can also be used. The preferred amounts are 0.05-0.2 %. At least 50 % of this is initially charged and the remainder is metered in during or at the end of the reaction.

Ascorbic acid is preferably added in amounts of 0.01-0.2 % together with emulsifiers and the iron (II) salt. The iron (II) salt used is primarily iron (II) sulfate in. Amounts of 10-20 ppm are used. In addition, other iron compounds and complexes can also be used which, under the given conditions, are capable of releasing iron (II) ions. Such are iron (III) sulfate, iron (II) chloride, the iron salt of ethylenediaminetetraacetic acid or ferrocene.

The starting pH, which is between 3 "and 4, preferably 3? 5, if necessary with organic acids, preferably with polymerizable acids such as acrylic acid, methacrylic acid, Maleic acid, fumaric acid, etc. set. During the polymerization, the pH can change without the poly-

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iaerization is impaired.

For special purposes, for example around the stoving temperature to reduce, the dispersion after the polymerization can be 1-15 percent by weight, based on the dispersion, water-soluble Melamine or urea resin can be added.

Monomers whose homopolymers have a theoretical glass transition temperature of below 10 C include, for example, acrylic acid esters with 1-8 carbon atoms in the ester residue, such as methyl acrylate, ethyl acrylate, ethylhexyl acrylate, methacrylic acid esters with 6-18 carbon atoms in the ester residue, such as hexyl methyl acrylate, octyl methyl acrylate, n-decyl methacrylate, n-tetradecyl methacrylate, vinyl esters with 3-20 carbon atoms in the acid residue, preferably those with a branched carbon chain such as vinyl propionate, vinyl butyrate, vinyl valerate, vinyl caproate, vinyl stearate, vinyl asobutyrate and vinyl versatate ^ ⁷ , olefins such as ethylene, butylene , Propylene, butadiene, maleic acid and fumaric acid esters with more than up to 4-18 carbon atoms in the ester residue. Preferably 40 parts by weight of these monomers are used.

As monomers whose homopolymers have a theoretical glass transition temperature of about 3O ⁰ C, suitably 30-150 have ° C, such as methacrylic come with 1-4 carbon atoms in the Esterrest in question, such as methyl methacrylate, Aethylmethylacrylat, propyl methacrylate, butyl methacrylate, further! Acrylonitrile, vinyl chloride, vinyl acetate, vinyl chloroacetate, trifluoro

509838/0938

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vinyl acetate, vinyl benzoate, styrene, «* .- methylstyrene, Vinytoluene. Expediently, 40-60 parts by weight of these monomers are used.

The glass transition temperatures are a common criterion and are from Flöry in "! Principles of Polymer Chemistry", P. 56 and 57? (1953)? Cornell University Press. Although "you get the actual measurement of the glass transition temperature preferably, they can also be calculated as described by Fox in Bull. Am / Physics Soc. 1, 3, p. 125 (1956).

As polymerizable acids or their salts come e.g. Acrylic, methacrylic, itaconic and crctonic acids and unsaturated dicarboxylic acids, such as maleic and fumaric acid, their half-esters with 1 to 18 carbon atoms in the ester radical or their anhydrides in question. The preferred amount of these acids is 2-4 weight st rush ·.

The reactive monomers, -the preferred amounts of 10 parts by weight are used, for example, monomers with functional hydroxyl groups, such as glycol monoacrylate and monomethacrylate, Hydroxymaleic acid ester, butanediol-1,5-monoacrylate and -monomethacrylate, butanediol-1,4-mono acrylate and monomethacrylate, Monopolypropylene glycol acrylate and methacrylate, γ-chlorohydroxy esters of unsaturated acids, such as 3- (1-chloro-2-hydroxy) ~ propyl acrylate, 3- (1-chloro-2-hydroxypropyl) isopropyl methylate; Monomers with functional amide groups, such as Acrylamide, maleic acid monoureide, with methylolized amide

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groups like IT-Methy3.olmethacrylaBiid or their disguised Methylol derivatives such as n-butoxymethylene acrylamide; Monomers with functional allyl groups, such as allyl methacrylate, Diallyl maleate; Monomers with functional aziridinyl groups, like 2 (l-aziridinyl) ethyl methacrylate.

As alkali or ammonium salts of polymerizable sulfonic acid compounds are, for example, those of methallyl sulfonic acid, yinyl sulfonic acid, sulfonated allyl esters, e.g. sulfonated To understand maleic and! Fumaric acid esters and sulfobetaines. 1-3 parts by weight are preferably used.

The anionic wetting agents known per se can expediently be used as emulsifiers in amounts of 0.05-3 %, based on the monomers. Suitable anionic emulsifiers are alkyl sulfates, sulfates of alkyl and alkylaryl polyethoxyalkanols, alkyl _{sulfonates, alkylarylsulfonates 3} and esters of sulfosuccinic acid with alkanols.

The viscosity of these latices, which are used as binders for coatings, can be subsequently adjusted with various thickeners to adjust. Colloids such as polyvinyl alcohol and water-soluble modifications can be used for this purpose of that; water-soluble cellulose derivatives, such as hydroxyethyl, Hydropropyl, methyl, ethyl, carboxymethyl cellulose; water-soluble polysaccharides and derivatives thereof; Polyacrylic acid and water-soluble derivatives thereof.

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The dispersions obtained after the polymerization are adjusted to a pH of between 5 and 9 with a water-soluble tertiary amine such as, for example, triethylamine, dimethy1aminoethanol, triethanolamine, and then heated for about 10 minutes to improve pigment compatibility and storage stability Aged 50 - 60 ^{0 C.}

The products which can be prepared by the process of the invention can be used without the need for any further addition of dispersing aids be pigmented. If pigments are used, the ratio of pigments to solids of the excess in can be varied over a wide range, depending on the one used Pigment and the special application. So can that Ratio of pigment to solids of the "coating from 1:20 to 20: 1. The clear coats are particularly valuable as top coats that are used to make decorative undercoats to protect without impairing the decorative effect. Since the coatings according to the invention are completely clear and are clear and both hard and tough, high gloss, excellent solvent resistance and water and high adhesiveness to a variety of surfaces they are ideal as overprint finishes.

The self-crosslinking paints according to the invention can on

509838/0938

A variety of substrates can be applied, with the only restriction that the substrate undergoes the curing process able to withstand, which is essential for the production of the coatings. Metals are particularly suitable. So are iron, steel, chrome plated steel, tin plated Steel, aluminum, copper, bronze or brass in sheet metal or rolled-up form are excellent substrates for the • according to the invention Coating compositions. Ceramic surfaces and in some cases wood surfaces are used as substrates also suitable.

For the paints according to the invention, a variety of Pigments are used. Typical suitable pigments are titanium dioxide, iron oxide, chromium oxide, cadmium oxide, light spar, Calcium silicate, quartz flour, talc, soot, calcium carbonate,

(R)

Barytes and organic pigments, such as printasol paints

The coating compositions can be used with suitable devices be applied, e.g. with spray guns, brushes or rollers or by immersion and surprisingly by direct rolling, i.e. a single roller applies the coating to the substrate, in which case it is in a bath Coating composition rotates. The applied layer can in any case by direct exposure to heat to one smooth film to be hardened.

The resulting paints are characterized by high gloss, good chemical resistance, special toughness and hardness as well due to excellent pigment compatibility and pigment distribution

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the end. These good properties come about because very finely divided dispersions according to the process of the invention, so-called hydrosols, can be achieved.

General polymerization process

In a stirred autoclave with heating and cooling equipment as well Dosing options are initially a part of the aqueous Phase in which the emulsifiers and the persulfate are dissolved, submitted. After flushing with nitrogen, a certain amount of the monomer mixture, the desired amount, is pre-emulsified Temperature (20-23 ° C) set and the polymerization by metering in an aqueous solution of ascorbic acid and Iron (TI) salt started. A sudden increase in temperature of 1 - 2 ° C is observed, followed by the dosing speed the reducing agent is throttled. At the same time, the feed of the remaining monomers can be utilized the cooling capacity of the reaction vessel on the dosing speed of the reducing agent can be adjusted in such a way that the preselected constant polymerization temperature a door (+ 1 ° C) is maintained.

Polymerizable components that are not monomer-soluble, For example, certain acids, reactive monomers or emulsifiers, are in aqueous solution, parallel to the rest Monomergemi sch, metered in. Polymerizable acids can partially before addition with a water-soluble tertiary amine be neutralized.

Will introduce the reactive methylol group in situ

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carried out, the amount of formaldehyde required for this is placed in front of and dosed together with the aqueous phase eligible monomeric amide depending on use.

example 1

Following this general procedure, a 2-liter stirring

autoclave polymerizes the following approach:

1st template

deionized water 410 g Fenopon 00-436 ^ (50%) 5 g

Methallyl sulfonate (sodium salt) 1 g

Potassium Persulfate (KPS) 0.8 g

2. Dosage

2.1. aqueous phase

deionized water - 100 g

Acrylic acid (with triethyle.min to pH set)

N-methylolacrylamide methallyl sulfonate

2.2. monomeric phase

Ethyl acrylate)

_. , »Of which 20 g at the start

2.3. Activator solution deionized water ascorbic acid iron (II) sulfate (Fe SO4 · 7K ^ O) 0.05 M

aqueous solution 0.5 g

Fenopon CQ-436 ^w

Polymerization temperature 27 ° C

Reaction time (= feed time of the monomers) 4 hours. pH adjusted to 6 with triethylamine

According to Example 1), a number of further experiments were carried out, with the composition and reaction

509838/0938

8th G G 32 G 0 , 5 160 G 122 G G 50 G 0 , 3

I WILL FOLLOW

conditions according to Table IA vary.

In Table IB are the properties of the dispersion obtained listed. The conversion is in any case over 99.5%. The solids contents are between 35 and 40%. Table 2 shows the coating properties of the pigmented stoved films.

Example 2

This experiment was carried out in a 5 liter stirred autoclave and at the same time 5 times the amount of the batch in example 1a) polymerized. The amount of initiator used could be approx can be reduced by half.

Example 3

Compared to Example 1a), the ratio of styrene to Ethyl acrylate increased and an additional emulsifier is used in the template.

Example 4

The 'submitted formaldehyde was in situ in the acrylamide and Maleic acid monoureide incorporated. The dosed portion of methallyl sulfonate has been raised.

Example 5

The emulsifier mixture corresponded to Example 3). Opposite to Example 1a), polypropylene glycol monoacrylate was used as an additional crosslinking component and the formaldehyde addition 'Made on acrylamide as in Example 4). The proportion of methallyl sulfonate dosed corresponded to that in Example 4).

509838/0938

FOLLOW-UP IT

- 14- -

Table t (Examples 1 & - 5)

- 2.2. B. Example IMr. 1a 2 3 4th 5 A 1. template deionized tosser 127.5 120.5 123.9 107.7 106.3 Fenopon C0-43S (ö) 0.77 0.73 0.75 0.69 0.67 2.3. Tensopol A 0.75 0.67 Methallyl sulfonate 0.31 0.29 0.3 0.2B 0.27 KPS 0.25 0.15 0.24 0.22 0.22 Formaldehyde 100 % 4.14 5.19 2. dosage 2.1. aqueous phase deionized water 30.9 30.7 29.9 27.6 27.0 Acrylic acid (pH adjusted) 2.47 2.48 2.40 4.14 4.05 N-methylalacrylamide 9.89 9.46 9.73 Acrylamide 8.5 8.38 Shark Acid Monoureid 2.76 Methallyl sulfonate 0.15 0.15 0.15 0.55 0.54 monomeric phase Ethyl acrylate 49.5 49.7 40.5 47 44.6 Styrene 37.7 37.9 46.8 35.9 34.0 Polypropylene glycol monoacrylate 8.1 Activator solution deionized water 15.5 14.6 15.0 13.8 13.5 Ascorbic acid 0.09 0.04 0.09 0.08 0.08 Iron (II) sulfate (Fe 50, · 7H Π) "]
0.05 M aqueous solution J 0.15 0.08 0.15 0.15 0.15 Fenopon CO-436 ® 7th Polymerization ^{temperature (0} C) 0.03 0.03 0.03 0.03 0.03 Reaction time = feed time 27 27 27 21 21 of monomers (hours) A. A. O A. 2 1 /? Solid (55) H H 39.8 Monomer residue ζ% on disp.
related) 36.3 35.4 36.6 39.4 0.22 Viscosity Din-4 cup (sec.) 0.35 0.19 0.30 0.28 16.8 pH 28.6 21. 19.2 17th 6th 6th 6th 6th 6th

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NACHGERKI

- 15 -

The dispersions prepared according to Example 1a were 5 with titanium dioxide (rutile) in the ratio 1: 1, "based on the Peststoffgehalt the dispersion is ground in the ball mill.

The films of the pigmented stoving enamel produced were applied to chromated aluminum (0.6 mm thick) with an 80th ai spindle and were stoved at 180-260 ° C. for 2 minutes. Bubble-free, white, high-gloss coatings with excellent flow and very good coating properties were obtained.

509838/0938

A-
burning
temp.
⁰ C layer
thickness
μ Pendulum
hardness
after
King
Sec. shine
% Grid
cut T
Bend Solution medium resistance Glacial acetic acid
1 min. Example 1a 240 20-21 150 94 0 2 acetone
3 min. Well Example 2 260
240
200
180 21-23
20-21
20-22
20-23 160
149
135
128 88
89
88
90 0
1
1
1 6th
3
3
5 Well Well
Well
satisfactory
satisfactory Example 2
with 5%, re .
on dispersion
Melamine resin additive
sentence 180 20-21 151 90 0 3 Well
Well
satisfactory
satisfactory Well Example 3 240 21-23 165 97 0 2 Well Well Example 4 240 22-24 .142 97 1 2 Well good up
very good Example 5 240 22-24 148 97 0 3 good up
very good good up
so good good up
very good

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Claims (4)

Patent claims (1) Process for the production of pigmented or non-pigmented, by heat treatment of self-crosslinking paints based on an aqueous dispersion, characterized in that that the binder consists essentially of a) 30 - 70 parts by weight of a monomer or a monomer mixture, wherein the theoretical glass transition temperatures of the homopolymer less than 10 ⁰ C, b) 30 - 70 parts by weight of a monomer or monomer mixture wherein the theoretical glass transition temperatures of the homopolymer are above 30 ⁰ C, c) 0.5-5 parts by weight of a polymerizable acid or their salt, d) 2-35 parts by weight of a reactive monomer and e) 0.5-5 parts by weight of an alkali or ammonium salt of a polymerizable sulfonic acid compound consists andman the polymerization at temperatures of 15-30 ⁰ C with the help of a redox system, consisting of 0.005 0.5 % ■> based on the total monomers, an alkali or ammonium persulfate, 0.001-0.5 % ·> based on the total monomers, ascorbic acid and 10-30 ppm of an iron (II) salt, based on the total monomers, carried out at a starting pH of 3-4, with a maximum of 30 % of the monomers presented together with the main amount of the persulfate and the remaining amount of the Monomers, in parallel with the iron (II) salt and the ascorbic acid, are metered in such that a preselected constant polymerization ^{temperature (+ 1 0} C) results. 509838/0938 2) Method according to claim 1, characterized in that the rate of polymerization via the dosage the reducing initiator components is controlled so that a constant polymerization temperature (+ 1 ° C) is maintained. 3) Method according to claims 1-2, characterized in that the self-crosslinking paints are adjusted to a pH value in the range from 5 to 9 with a tertiary amine and then by brief aging at a higher temperature, in particular between 50 and 60 ^° C and are made storage-stable in each EaIl below the stoving temperature, 4) Method according to claims 1-3, characterized in that that 1-15 percent by weight, based on the polymerization on the dispersion, a water-soluble melamine or urea resin is added. 509838/0938