DE1245008B - Stoving enamels - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C09d

German class: 22 h-3

Number: I 245 008

File number: B 72469 IV c / 22 h

Filing date: June 28, 1963

Opened on: July 20, 1967

Stoving enamels

Baked enamels are known from the German Auslegeschrift I 102 410 which

I. organic solvents and

II. Copolymers from

A) esters of acrylic or methacrylic acid with alkanols,

B) Ethers of N-methylolacrylic or methacrylic acid amide with alkanols or phenylalkanols,

C) monoesters of acrylic or methacrylic acid with polyvalent hydroxyl compounds and, if necessary, additionally, ₅

D) other compounds containing an ethylenically unsaturated, copolymerizable group, such as acrylonitrile, acrylic and methacrylic acid, higher esters of ethylene carboxylic acids, Styrene and vinyl acetate

contain. Such stoving enamels are characterized by a number of valuable properties.

It has been found that stoving enamels of the type specified are improved in their properties can if a special quantitative as well as in particular a special qualitative selection the components of the copolymers is taken. The subject of the invention are accordingly Stoving enamels made as copolymers

a) 30 to 87.5 percent by weight, in particular 46 to percent by weight, of a mixture

a0 10 to 90 percent by weight, in particular 30 to 70 percent by weight, of an ester of acrylic or methacrylic acid with a 1 to 10, in particular 5 to 8 carbon atoms, alkanol or a mixture such ester and

a ₂ ) 10 to 90 percent by weight, in particular 30 to 70 percent by weight, of styrene or an alkyl styrene whose alkyl groups have 1 to 3 carbon atoms or a mixture of such hydrocarbons,

b) 10 to 45 percent by weight, in particular 15 to percent by weight, of an ether of N-methylolacryl- or methacrylic acid amide with 1 to 8, in particular 1 to 4, carbon atoms in the alkane radical containing alkanol, oxaalkanol or phenylalkanol or a mixture of these Ether,

Applicant:

Aniline & Soda Factory in Baden

Corporation,

Ludwigshafen / Rhine

Named as inventor:

Dr. Hans Wilhelm, Ludwigshafen / Rhine;

Dr. Gerhard Faulhaber,

Dr. Achilles Vlachos, Mannheim;

Dr. Matthias Marx, Bad Dürkheim

c) 2 to 15 percent by weight, in particular 3 to 10 percent by weight, of a monoester of the acrylic or methacrylic acid with 4 to 6, in particular 4, carbon atoms and exclusively terminal hydroxyl groups containing unbranched alkane or 3-oxaalkane diol or a mixture of such esters,

d) 0.5 to 10 percent by weight, in particular 1 to 4 percent by weight, acrylic or methacrylic acid or a mixture of these acids and optionally additionally

e) not more than 20 percent by weight, in particular not more than 10 percent by weight, one with the compounds designated under a) to d) which are not identical, one ethylenically unsaturated, copolymerizable Group-containing compound or a mixture of such compounds

The sum of the percentages under ai) and a ₂ ) as well as under a) to e) is 100 in each case.

The quantitative as well as special qualitative selection of the components of the copolymers The improvements achieved in the stoving enamels were surprising and unforeseeable. In the German Auslegeschrift 1102 410 it was assumed that copolymers of firstly esters of acrylic or methacrylic acid and secondly Methylol or methylol ether compounds of acrylic or methacrylamide are not sufficiently solvent-resistant are (column 1, lines 1 to 14). It has therefore been taught that this disadvantage is eliminated can be if, in addition, thirdly polymerizable ether or ester compounds are included in the copolymers are polymerized, which are still min-

709 617/549

have at least one free alcoholic hydroxyl group. According to the teaching, the structure is not the Methylol or methylol ether compounds are critical, as long as these compounds are only given the broad range Definition follow. In this context, there are already so many possible combinations that an actual experimental "trial and error" in the search for advantageous systems is no longer necessary can be considered. In order to come to the subject of the invention, the frame had to but to be put further. Besides the esters of acrylic acid and methacrylic acid, the special ones Methylol or methylol ether compounds and special ether or ester compounds had to be further two indispensable special components can be selected, with all five components being appropriate Have to work together in a wise way. Examples 4, 5 and 6 show how critical and complex the selection is and the comparative experiments. Although only one component in the copolymer is insignificant is changed, the properties of the end products, such as their elasticity, bending behavior, gloss value and swelling index. The beneficial properties the stoving enamels constructed according to the invention are therefore very surprising.

The stoving enamels according to the invention are distinguished in particular by the fact that they are improved Have pigment-binding capacity and the coatings produced from them already at relatively low Stoving temperatures fully or practically fully develop their valuable properties. Furthermore are off such stoving enamels to obtain coatings with improved adhesion and impact resistance, as well as coatings with particularly pronounced elasticity, weather resistance, hardness and saponification resistance. If desired, coatings can also be obtained which also have other properties, such as Resistance to light, flexural strength, solvent resistance and temperature resistance in particular Own dimensions.

Suitable solvents (1) for the stoving enamels according to the invention are the usual, for example alkylbenzenes, such as toluene and xylene, alcohols such as n- and i-butanols, monoethers of diols such as ethanediol monomethyl ether, Esters of alkanols, such as ethyl acetate, and monoether monoesters of diols, such as ethanediol monomethyl ether - monoacetic acid ester, as well as mixtures of such substances with one another or with petrol hydrocarbons.

In general, particularly suitable copolymers (2) are those which have a K value (according to H. Fikentscher, Cellulose-Chemie, 13 [1932], p. 58 ff.) From about 15 to 30, in particular about from 18 to 22.

The following can be stated in detail with regard to the structural components of the copolymers (2):

In general, particularly suitable components for aj) are esters of acrylic acid with 5 to 8 carbon atoms having alkanols, preferably those which are branched in the 2-position, such as 2-ethylhexanol, 2-ethylbutanol and 2,2-dimethylpentanol; Above all, these esters give the coatings a high degree of elasticity and weather resistance. By using or co-using esters of methacrylic acid with methanol, ethanol, butanol and i-butanol, the light resistance of the coatings can be favorably influenced, while the flexural strength of the coatings can be favorably influenced by using or co-using esters of acrylic acid with the same alkanols.

In general, particularly suitable components for a ₂ ) are styrene, followed by <x-, o-, m- and p-methylstyrene; Above all, these hydrocarbons give the coatings a high degree of hardness and resistance to saponification.

ίο As components of b) can in general with particular success the methyl, ethyl, propyl, i-propyl, butyl, 3-oxabutyl, 3-oxapentyl and Benzyl ether of N-methylolacrylic or methacrylic acid amide use; these ethers give the coatings mainly solvent resistance and temperature resistance, but affect - if they are used in too large quantities - Elasticity and weather resistance in a negative way.

As components for c), the monoesters of acrylic and methacrylic acid with butanediol (1,4) generally prove to be the best, followed by the corresponding monoesters of pentanediol (1,5), hexanediol (1,6) and 3 -Oxapentanediol- (l, 5). These monoesters are to a decisive extent responsible for the fact that the stoving lacquers are particularly compatible with pigments and that the lacquers produced from them can develop their valuable properties fully or practically fully even at relatively low stoving temperatures. Furthermore, these monoesters are able to give the coatings a particularly high level of adhesion and impact resistance; Special attention must therefore be paid to their type and quantity when setting up recipes for stoving enamels. The most reliable statements can be obtained from trial runs. Acrylic acid is generally preferred as component for d); Among other things, it acts as an internal hardening accelerator during stoving.
Acrylonitrile is particularly suitable as component for e); it generally leads to coatings which are particularly resistant to solvents of the hydrocarbon series. Esters of acrylic and methacrylic acid with more than 10 up to about 20 carbon atoms having alkanols are also suitable; they can serve for internal plasticization. For stoving enamels with special properties, for example, unsaturated dicarboxylic acids, such as maleic and fumaric acid, also vinyl esters, ethers and halides, such as vinyl acetate, vinyl butyrate, vinyl isobutyl ether, vinyl chloride and vinylidene chloride, and also acrylic and methacrylic acid amide and the N- Methylol derivatives of these amides and finally N-vinyl lactams and C- and N-vinylamines.

The production of the copolymers (2), for which no protection is claimed at this point, can carried out in the usual manner, generally expediently by solution polymerization in such Solvents that should also be part of the finished stoving enamels. The polymerization can expediently through the customary initiators or initiator systems composed of initiators and activators be initiated. Azo compounds, peroxy compounds and, for example, may be mentioned as such Systems of peroxy compounds and sulfinic acids and / or heavy metal compounds. By using the usual regulators, such as mercaptans and aldehydes, the degree of polymerization and thus

5 6

the K value of the copolymers on the desired 4-hydroxybutyl acrylate (c) in butanediol (1,4)

Measure can be adjusted. and 6 parts of acrylic acid (d) are in 212 parts of a

The stoving enamels according to the invention can, if a solvent mixture of equal parts of toluene

desired, the usual additives and butanol dissolved in baking enamels, with 4 parts of tert-dodecyl substances, such as pigments, soluble dyes, optical 5 mercaptan added and with constant stirring

Brighteners, as well as agents to promote the flow, heated to approx. 85 ° C within 45 minutes. at

and shine included. In particular, a solution of 8 parts can be added to this temperature

the stoving enamels in addition to the copolymers azo-di- (isobutyronitrile) in 30 parts of acetic acid

th (2) customary other paint binders, such as alkyd ethyl ester, continuously for 5 to 6 hours. resins, amino resins, phenolic resins, epoxy ίο A clear mixed polymer solution is obtained with

resins, rosins, drying and not a K value of 20.
drying oils, cellulose derivatives and polymers,

which are not identical to the copolymers (2) Example 1
are contained, dissolved and / or dispersed. The 30 parts of this copolymer solution are diluted with the weight ratio of the copolymers (2) to the 15-45 parts of toluene and with 7.5 parts of additional titanium paint binders should be generally more than 1, especially homogenized, in the dioxide pigment (rutile) for 24 hours on a wheelchair .

especially larger than 2. It has also generally been found that the stoving enamel obtained in this way is applied to a deep-drawing

have been found to be expedient if the weight plate is applied, briefly flashed off and the ratio of solvents (1) to the total 20 is ^{heated to 150 °} C. for 30 minutes. A glossy, white color is obtained

Binder content in the stoving enamels, for example from paintwork; it is adhesive and shockproof and has one

0.4 to 3, in particular approximately from 0.6 to 1.5. Erichsen value of 7.8 mm. After a heat treatment

For the manufacture of coatings of the lung can not be (24 hours at 150 ⁰ C), the elasticity practical baking varnishes using normal methodological table according to (Erichsenwert: 7.0 mm). The paintwork is applied to the objects to be painted 25 tion behaves with sharp bending before and after, z. B. by spraying on, brushing on, on the heat treatment flawlessly; it is after pouring, rolling, flooding, dipping or soaking. hours of boiling in 10% sodium hydroxide solution is practical.
mean expediently at temperatures about

from 120 to 18O ⁰ C, in particular about 130-30 preparation of Mischpolymerisatlösung

150 C and, depending on the temperature. for example 2
over a period of about 5 to 120 minutes,

in particular take about 20 to 40 minutes. 69 parts of 2-ethylhexyl acrylate (ai), 114 parts

Since the valuable properties of the coatings styrene (a ₂ ), 84 parts of N- (butoxymethyl) -methacryl-

in particular metals such as iron, aluminum, amide 35 (b), 40 parts of a 45 ° / ₀ solution of the acrylic

Magnesium, and alloys of these metals to gel acid 4-hydroxybutyl ester (c) in butanediol (1,4),

In particular, 6 parts of acrylic acid (d) and 9 parts of acrylonitrile (e) are suitable for the stoving enamels.

for painting objects made of sheet metal, e.g. B. in 212 parts of a solvent mixture

Parts of car bodies, ships, washing machines dissolved in equal parts toluene and butanol, with 4 parts

and freezers, also from cans, jugs, 40 tert-dodecyl mercaptan and under constant

Vats and appliances for industry and household. Stir to approximately within 45 to 60 minutes

The stoving enamels can also be heated to 85 ° C. At this temperature one gives in

for the production of base and top layers, it takes one hour each, four times two parts each

turn around; Because of their adhesive strength, they are suitable for azo-di- (isobutyronitrile) in solid form

also very good for the production of single-layer lacquer- 45 then lasts for about 6 hours

on metals, the high surface gloss being the same temperature. So you get a colorless,

generally makes repolishing unnecessary. clear solution of the copolymer; she has in DIN

If the paintwork is done with a cup that is as low as possible with nozzle no. 6, a flow time of approx

Temperatures should be burned in and / or 60 seconds.

Stoving enamels are used that are 50 B '' I 2

polymer (2) relatively little acrylic or methacrylic ^e ^ ' ^e

contain polymerized acid, it can expediently be divided into 18 parts of this copolymer solution

be the stoving enamels in the presence of curing a commercially available, suitable for stoving enamels

to burn in agents. As such, those for epoxy resin made from 2,2-bis (p-hydroxyphenyl) propane are suitable

Curing of polymers with N-2-Oxaalkylcarbonamid- 55 and l-chloro-2,3-epoxypropane stirred in, whereupon with

groups customary, such as acids or acid, splitting off 30 parts of toluene is diluted. After adding

Fabrics. The amount of hardening agent should be in 5 parts of titanium dioxide pigment (rutile) for 24 hours

generally expediently about 0.01 to 5, ins- homogenized on the wheelchair,

particular about 0.1 to 2 percent by weight of the mixed- The stoving enamel obtained in this way is used without a primer

polymers (2). 60 tion is applied to a deep-drawn sheet and, after

The parts and percentages mentioned in the examples are dried in the air for several hours, 30 minutes

relate to weight. heated to 150 ^{° C.} A glossy, white color is obtained

.,,. , ....,. ... paint with good surface hardness; she is liable

Production of the M.schpolymensatlosung _{and shockproof} ^ _{is made by slow boiling in}

for example 1 6 ₅ loo ^ jge, - sodium hydroxide solution not changed; it becomes further

84 parts of 2-ethylhexyl acrylate (aj), 132 parts by acids and the customary organic

Styrene (a ₂ ), 60 parts of N- (butoxymethyl)) - meihacryl- solvent at room temperature in 24 hours

acid amide (b), 40 parts of a 45 ° / _o solution of not attacked.

Preparation of the mixed polymer solution
for example 3

_{92 parts of ethyl acrylate (aj), 11.5 parts of styrene (a 2} ), 85.5 parts of N- (butoxymethyl) methacrylic acid amide (b) are placed in a vessel equipped with a stirrer, reflux condenser and a feed device for the polymerization initiator , 40 parts of a 45 ° / _o solution of the acrylic acid-4-hydroxybutylesters (c) in butanediol- (1,4) and 5 parts of acrylic acid (d) dissolved in 374 parts of a solvent mixture of equal parts of toluene and butanol, and with 4 parts of tert-Dodecyl mercaptan and 4 parts of cumene hydroperoxide are added. The contents of the vessel are then ^{heated to 105 °} C. over the course of one hour, with constant stirring, and kept at this temperature. After each hour a further 1.25 parts of cumene hydroperoxide are added; a total of five times. The polymerization has ended after 10 hours. The light-colored mixed polymer solution obtained has a K value of 20.

Example 3

20 parts of this Mischpolymerisatlösung with 10 parts of a 55 ° / _o solution of a handeisüblichen, suitable for baking enamels melamine formaldehyde condensation resin is mixed, then this mixture was diluted with 45 parts of toluene, and 7.5 parts Titandioxydpigment (rutile) 24 hours on the Wheelchair is homogenized.

The baking varnish thus obtained is applied without primer to a deep-drawn sheet metal and, after a brief flash-off, baked for 30 minutes at 150 ⁰ C. The result is a white, smooth finish that is resistant to diluted acids and alkalis at 20 ° C; ,. it is not changed substantially by lstündiges boiling in 10 ° / ₀ sodium hydroxide solution; its Erichsen value is 4.2 mm, its pendulum hardness 170 seconds; it is adhesive and shockproof.

Preparation of the mixed polymer solution
for example 4

300 parts of a mixture

a) 77 ° / o of a mixture

aj) 23% of the ester of acrylic acid with n-butanol and

as) 77% styrene,

b) 16 ° / ₀ of the ether of N-Methylolacrylsäureamids with n-butanol,

c) 5% of the monoester of acrylic acid with 1,4-butanediol and

d) 2% acrylic acid,

40

45 dissolved in a mixture of 115 parts of xylene and 115 parts 3 parts are added to n-butanol, 15 parts of methyl glycol acetate and 15 parts of 1,4-butanediol tert-dodecyl mercaptan and 1 part azodiisobutyronitrile.

In a vessel with stirrer and Rückfiußkühler this mass is heated to 90 ⁰ C and maintained during the further reaction at this temperature. After 2 hours, 1 part of azodiisobutyronitrile is added; the same procedure is repeated four times after each additional hour. After the final addition for 5 hours is maintained at 90 ⁰ C, then is cooled and (DIN 53182 after) / ₀ is set, the polymer with a mixture of equal parts of xylene and n-butanol at a solids content of 50 °.

Example 4

In each case 30 parts of this polymer solution and 35 parts of xylene are each with different Quantities (parts see below) titanium dioxide pigment (rutile) are added and the mixture is homogenized in the ball mill for 24 hours. In this way, stoving enamels with different pigment content (here based on the Binder) produced, namely

A) Lacquer with 50 ° / ₀ pigment
(7.5 parts pigment);

B) varnish with 100 ° / ₀ pigment
(15 parts pigment).

The stoving enamels obtained in this way are sprayed onto degreased deep-drawn metal sheets using a spray gun, flashed off for 30 minutes and ^{baked at 140 °} C. for 30 minutes. The Erichsen elasticity (in millimeters according to DIN 53156) and the behavior when the sheet metal is sharply bent (bending behavior) are determined on the paintwork obtained in this way; Further, the Erichsen elasticity of the coatings is determined after 24 hours of storage at 18O ⁰ C. The data obtained are given in the table.

Comparative experiment

In a comparative experiment, the same procedure is used as stated above, with the exception that when Prepare the polymer in place of the monoester of acrylic acid with 1,4-butanediol in the same amount of the monoester of acrylic acid is used with ethanediol. The paintwork obtained in this way The data obtained are also shown in Table 1.

Table I.

Paintwork data

according to the example
from lacquer AI from lacquer B

according to comparison test
made of lacquer A | made of lacquer B

Erichsen elasticity

Bending behavior

Erichsen elasticity after 24 hours at 180 ⁰ C.

8.1

6.8

5.5

Painting
bursts
not off

3.6

1.8

0.9

Painting
flakes off

ίο

Preparation of the mixed polymer solution
for example 5

300 parts of a mixture

a) 72 ° / ₀ of a mixture of

^ l) 39 ° / ₀ of the ester of acrylic acid with 2-ethylhexanol and

a ₂ ) 61 ° / ₀ styrene,

b) 20% of the ether of N-methylol methacrylic acid amide with n-butanol,

c) 6% of the monoester of acrylic acid with 1,4-butanediol and

d) 2% acrylic acid,

dissolved in a mixture of 115 parts of xylene, 115 parts of n-butanol, 18 parts of methyl glycol acetate and 18 parts of 1,4-butanediol are mixed with 3 parts tert-dodecyl mercaptan and 1 part azodiisobutyronitrile.

Example 5

This mass is given in exactly the same way as in Example 4, for stoving enamels with different pigment content further processed, namely

A) Lacquer with 50 ° / ₀ pigment
(7.5 parts pigment);

C) varnish with 200 ° / “pigment
(30 parts pigment).

The baking finishes thus obtained are sprayed with a spray gun onto degreased thermoforming sheets, flashed 30 minutes and baked for 30 minutes at 13O ⁰ C. The Erichsen elasticity and the gloss value (in%; black glass = 50%) are determined on the coatings obtained in this way; Further, the gloss value of the coatings after 24 hours of storage at 150 ⁰ C. is determined The data obtained are given in Table II.

Comparative experiment

In a comparative experiment, the same procedure is used as stated above, with the exception that when Prepare the polymer in place of the monoester of acrylic acid with 1,4-butanediol in the same amount of the monoester of acrylic acid is used with ethanediol. The paintwork obtained in this way The data obtained are also shown in Table II.

Table II

Paintwork data

according to example | according to comparison test

from lacquer A from lacquer C j from lacquer A I from lacquer C

Erichsen elasticity

Gloss value

Gloss value after 24 hours at 150 ⁰ C.

5.5
39
35

39
15th

Example 6

A 50% butanolic-xylene solution of a mixture of 80 parts of a copolymer from 28% 2-ethylhexyl acrylate, 44% styrene, 20% des Ether of N-methylol methacrylamide with n-butanol,

6% of the monoester of acrylic acid with 1,4-butanediol

and 2% acrylic acid and 20 parts of a commercially available melamine-formaldehyde condensate, such as 50 swelling index specified, applied as a varnish and baked for 30 minutes at various temperatures. In well-known The swelling index and the gel content of the stoved lacquers were then determined. the The results are shown in Table III.

run and the baked-on varnish always has an approximately 10% higher soluble portion.

Table III

Stoving temperature

Gel content 135 '
140 '
135 ^C
140 <

Example 6

6.7
3.8

76%
100%

Comparative experiment

7.7
5

65%
87%

55

Comparative experiment

The paint had the same composition as specified in Example 6, which contained the copolymer however, instead of 6% of the monoester of acrylic acid with 1,4-butanediol, the same amount of the monoester polymerized in acrylic acid with 1,2-ethanediol. As indicated in Example 6, the paints were baked and tested. As shown in Table III Results show that the varnish has a different curing rate from the varnish of Example 6

Claims (4)

Claim: Stoving enamels based on organic solvents and copolymers 1. Esters of acrylic or methacrylic acid with alkanols, 2. ethers of N-methylolacrylic or methacrylic acid amide, 3. Monoesters of acrylic or methacrylic acid with polyvalent hydroxyl compounds, as well as possibly additionally 4. other ethylenically unsaturated copolymerizable compounds, 709 617/549 characterized in that these stoving enamels consist of copolymers a) 30 to 87.5 percent by weight of a mixture a _x ) 10 to 90 percent by weight of an ester of acrylic or methacrylic acid with an alkanol having 1 to 10 carbon atoms or a mixture of such esters and a ₂ ) 10 to 90 percent by weight of styrene or an alkyl styrene whose alkyl groups have 1 to 3 carbon atoms or a mixture of such hydrocarbons, b) 10 to 45 percent by weight of an ether of N-methylolacrylic or methacrylic acid amide with an alkanol having 1 to 8 carbon atoms in the alkane radical, oxaalkanol ao or phenylalkanol or a mixture of such ethers, c) 2 to 15 percent by weight of a monoester of acrylic or methacrylic acid with a 4 to 6 carbon atoms and exclusively terminal hydroxyl groups unbranched alkane or 3-oxaalkane diol or a mixture of such esters, d) 0.5 to 10 percent by weight of acrylic or methacrylic acid or a mixture of these acids as well as possibly additionally e) not more than 20 percent by weight of a compound identified under a) to d) non-identical compound having an ethylenically unsaturated, copolymerizable group or a mixture of such compounds, contain, the sum of the percentages under Z ₁ ) to a ₂ ) and under a) to e) each being 100. Considered publications:
German interpretative document No. 1 102 410.