Low solvent, water-dilutable binders for air drying coating compositions

Water-dilutable binders for air drying coating compositions, the content of the auxiliary organic solvent being below 15% of the binder solids are described. The binders comprise the partial condensation products of PA0 (A) 30-70% by weight of a film forming fatty acid modified alkyd resin intermediate with an acid value of between 30 and 200 mg KOH/g, an intrinsic viscosity .zeta..sub.A of from 4.5 to 8 ml/g and an oil length of from 5 to 60%, with PA0 (B) 70-30% by weight of a film forming fatty acid modified alkyd resin intermediate with an acid value of below 5 mg KOH/g, a hydroxyl value of from 50 to 300 mg KOH/g, an intrinsic viscosity .zeta..sub.B of from 8 to 12 ml/g and an oil length of from 5 to 60%, the ratio between the intrinsic viscosities .zeta.B/.zeta.A lying between 1.4 and 2.7. Solutions of the binders ready for application are obtained which have a high solids content.

The invention is concerned with a water-dilutable binder for air drying 
coating compositions, the content of auxiliary organic solvent being below 
15% of binder solids. The coating compositions are based on fatty acid 
modified alkyd resins. 
"Water-dilutable binders," as the term is used herein, means polycarboxylic 
acid resins which can be rendered water soluble through at least partial 
salt formation with ammonia or amines. 
The acceptance of water-dilutable binders as a protective coating which are 
used in the formulation of air drying paints which can be used for 
professional and industrial use and for the do-it-yourself sector, is 
hindered by abnormal viscosity curve of the binders known in the art (E. 
Huttmann, Plaste und Kautschuk 17,202, 1970). This abnormal viscosity 
curve is the reason why only solutions having a low solids content on the 
further dilution down to application viscosity for spraying or dipping are 
possible. The obtained films are thin and thus require several coatings to 
obtain an adequate protective coating. Many suggestions have been made to 
overcome this deficiency including, on the one hand, the co-employment of 
very high levels of auxiliary organic solvents and, on the other hand, 
polyalkylene glycols are to be built into the resins (DT-AS No. 12 03 
407). The first measure is going away from the primary of water-soluble 
binders, and the second, in many cases, leads to films with unsatisfactory 
water resistance. 
AT-PS No. 328 587 discloses aqueous coating compositions for baking coating 
compositions which are obtained by blending or partially condensing a 
polycarboxylic acid resin, a polyhydroxy compound, and a hardening 
component, such as an amine resin. Through judicial choice of the reaction 
partners, products may be obtained which do not show the above-mentioned 
disadvantages with regard to viscosity decline. However, the process 
disclosed is not possible with products containing high levels of 
oxidizing oil fatty acids as is the case with air drying binders. Through 
the higher level of hydrophobic compounds further essential criteria are 
necessary in order to achieve satisfactory products. 
It is the primary objective of the present invention to provide 
water-dilutable binders which are air drying at ambient temperature, or 
which can be force-dried, on the basis of oil modified alkyd resins 
carrying carboxy groups and having an oil length of from 30 to 60%. "Oil 
length," as the term is used herein, is the content of oxidizing drying 
fatty acids or fatty acid radicals, expressed as percent by weight, in the 
intermediate or the final product. 
In general, the primary objective is realized through a specific choice of 
the essential specific figures for the intermediate and the final product. 
The present invention is concerned with low solvent containing binders for 
air drying coating compositions, water dilutable upon partial or total 
salt formation with ammonia or an amine on the basis of fatty acid 
modified alkyd resins with an oil length of from 30 to 60% and an 
intrinsic viscosity of between 10 and 15 ml/g (measured on a 2% solution 
in N,N-dimethylformamide, at 20.degree. C.), which are obtained through 
partial condensation at elevated temperature of 
(A) 30-70% by weight of a film forming fatty acid modified alkyd resin 
intermediate with an acid value of between 30 and 200 mg KOH/g, an 
intrinsic viscosity of .zeta..sub.A of from 4.5 to 8 ml/g and an oil 
length of from 5 to 60%, with 
(B) 70-30% by weight of a film forming fatty acid modified alkyd resin 
intermediate with an acid value of below 5 mg KOH/g, a hydroxyl value of 
from 50 to 300 mg KOH/g, an intrinsic viscosity .zeta..sub.B of from 8 to 
12 ml/g and an oil length of from 5 to 60%, the ratio between the 
intrinsic viscosities .zeta.B/.zeta.A lying between 1.4 to 2.7. 
The coatings prepared from the binders obtained according to the invention, 
upon customary addition of siccatives, show very fast drying at room 
temperature, radiant brilliance and excellent water resistance. Pigment 
compatibility is excellent, no flocculation could be observed. It could 
not be forseen that these characteristics would be obtained, because the 
components A and B themselves, although both film forming, do not have the 
aforesaid properties. 
Through the partial condensation it is possible to integrate the water 
insoluble component (B)into a water soluble resin compound. It is 
surprising that despite the high molecular weight--expressed as intrinsic 
viscosity of from 10 to 15 ml/g--and the low acid value of the total 
system of from 25 to 70 mg KOH/g, preferably 25 to 40 mg KOH/g, water 
dilutability is sufficiently good whereby paints can be formulated which 
combine a high solids content with a sufficiently low application 
viscosity. Thus, with the application of a single coat the dry film 
thickness is satisfactory. The auxiliary solvent, optionally added, 
primarily serves as a processing aid and should not exceed 15% by weight 
of the binder. Preferably, less than 10% by weight of auxiliary solvent is 
used. 
Components (A) and (B), in their composition as used herein, are known 
alkyd resins and are described, for example, in "Ullmann Encyklopadie der 
Technischen Chemie," 4th edition, Volume 15, chapter "Paints." The methods 
of preparation and appropriate raw materials are known to those skilled in 
the art. In place of the natural oils or their fatty acids, it is evident 
that synthetic drying oils such as carboxy groups containing polydiene 
oils may be used for the alkyd intermediates. Furthermore, the alkyd 
resins may be modified through methods known in the art, as for example 
with isocyanates or copolymerizable monomers. 
The essential characteristics for the binders of the invention are the 
ranges of the specific values as follows: 
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Component (A) 
Component (B) 
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Acid value (mg KOH/g) 
30-200 below 5 
Hydroxyl value (mg KOH/g) 
0-200 50-300 
Intrinsic viscosity (ml/g) 
4.5-8 8-12 
(2% in 
N,N--dimethylformamide) 
Oil length (%) 5-60 5-60 
Water dilutability 
infinitely insoluble 
(upon total neutralization 
(clear to 
with triethylamine) 
opaque 
solution) 
Film forming with driers 
yes yes 
______________________________________ 
"Infinite water dilutability" as used herein means that a solution 
neutralized with triethylamine and diluted down to 10% by weight with 
water does not form insoluble precipitates after 1 hour. 
The condensation between components (A) and (B) is carried out at between 
90.degree. to 145.degree. C. Care should be exercised that the reaction 
blend does not surpass the soluble state. The weight ratios between the 
components lie between 30 to 70% by weight for component (A) and between 
70 to 30% by weight for component (B). It is essential that the quotient 
of the intrinsic viscosity values of components (A) and (B) is 1 to 
1.4-2.7, that means that the intrinsic viscosity of component (B) if 1.4 
to 2.7 times higher than that of component (A) and that the intrinsic 
viscosity of the final product ranges between 10 and 15 ml/g. In this 
phase of condensation the solvents optionally contained in the 
intermediates are totally or partially removed from the reaction mass 
through distillation. In order to obtain the desired results it is of 
essential importance to keep within the given ranges for the intrinsic 
viscosity. The method for determining the intrinsic viscosity and the 
fundamental theory are given in " Ullmanns Encyklopadie der Technischen 
Chemie," 3rd edition, Volumn II/1, chapter "Viscosimetrie." 
The carboxy groups of the binders can be neutralized with ammonia, 
aliphatic tertiary alkyl and alkanolamines, preferably with triethylamine 
or N,N-dimethylethanolamine. The optionally pigmented paints are applied 
in normal manner, through brushing, spraying, dipping, flow coating or 
analogous application methods. Depending on the selection of the raw 
materials, with the aid of these binders, anticorrosive paint or finishes 
can be formulated. 
The coatings dry at ambient temperature, upon addition of appropriate 
driers. It is evident that they also may be force-dried at from 
60.degree.-80.degree. C.; when used in conjunction with amine or phenolic 
resins, they may be stoved at from 140.degree. to 180.degree. C. 
The following examples illustrate the invention. All figures given in parts 
or percentages refer to weight, unless otherwise stated. 
Preparation of Component (A) 
(A1) 540 parts of pentaerythritol, 480 parts of isophthalic acid, 1150 
parts of linoleic oil fatty acid and 178 parts of p-tert. butyl benzoic 
acid are esterified at 220.degree. C. to an acid value of below 5 mg KOH/g 
and are then reacted at 110.degree. C. with 471 parts of 
tetrahydrophthalic anhydride. As soon as the acid value has fallen to 
about 70 mg KOH/g, the batch is diluted to 95% solids with toluene and 
down to 85% solids with methylethylketone. The intrinsic viscosity of the 
product is 6.3 ml/g. After neutralization with triethylamine a sample 
becomes nearly clear. The oil length of the intermediate is 44%. 
(A2) 540 parts of pentaerythritol, 513 parts of tetrahydrophthalic acid, 
575 parts of linoleic oil fatty acid, 575 parts dehydrated castor oil 
fatty acid, 178 parts of p-tert, butyl benzoic acid and 21 parts of 
neopentylglycol are esterified at 220.degree. C. to an acid value of below 
5 mg KOH/g and thereafter reacted at 160.degree. C. with 595 parts of 
trimellitic anhydride. As soon as the acid value has fallen to 124 mg 
KOH/g, the batch is diluted at 90.degree. C. with toluene to a solids 
content of 95% and with methylethylketone down to 85%. The intrinsic 
viscosity is 6.7 ml/g. Upon neutralization with triethylamine a sample is 
nearly clear. The oil length of the intermediate is 41%. 
Preparation of Component (B) 
(B1) 540 parts of pentaerythritol, 480 parts of isophthalic acid, 530 parts 
of linoleic oil fatty acid, 530 parts of dehydrated castor oil fatty acid 
and 178 parts of p-tert. butyl benzoic acid are esterified at 230.degree. 
C. to an acid value of below 5 mg KOH/g and then condensed to an intrinsic 
viscosity of 10.6 ml/g. The efflux time, DIN 53 211/20.degree. C. of a 50% 
solution in monoethyleneglycol monobutylether is 93 s. The intermediate 
has a calculated hydroxyl value of 144 mg KOH/g. 
(B2) 32 parts of isomeric acid, 168 parts of dehydrated caster oil fatty 
acid, 136 parts of pentaerythritol and 120 parts of isophthalic acid are 
esterified at 230.degree. C. to an acid value of below 5 mg KOH/g and 
condensed further to an intrinsic viscosity of 9.5 ml/g. The efflux time, 
DIN 53 211/20.degree. C. of a 50% solution in monoethyleneglycol 
monobutylether is 85 s. The intermediate has a calculated hydroxyl value 
of 237 mg KOH/g. 
__________________________________________________________________________ 
Analogous to components A1 and B1 intermediates are prepared with the 
composition as listed below. 
Dehydrated p.tert. Tetrahydro- 
Penta- 
Isophthalic 
Linolic Oil 
Castor Oil 
Tall Oil* 
butylben- 
Neopen- 
phthalic 
Component 
erythritol 
Acid Fatty Acid 
Fatty Acid 
Fatty Acid 
zoic Acid 
tylglycol 
Acid 
__________________________________________________________________________ 
A 3 540 397 -- 855 855 -- -- 471 
A 4 540 513 881 -- -- 349 21 471 
A 5 540 349 855 -- 855 107 -- 471 
B 3 136 104 140 140 -- -- -- -- 
B 4 540 513 178 357 178 399 21 -- 
__________________________________________________________________________ 
rosin acid content ca. 2% 
The intermediates have the following characteristics: 
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Intermediates: A 3 A 4 A 5 B 3 B 4 
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Acid value mg KOH/g 
60 74 58 &lt;5 &lt;5 
Intrinsic viscosity 
5.8 6.5 4.7 10.8 10.7 
ml/g 
Oil length % 58 34 57 58 35 
Hydroxyl value -- -- -- 198 153 
mg KOH/g 
______________________________________

EXAMPLE 1 
60 parts of Component (B1) and 47 parts (40 parts resin solids) of 
Component (A1) are heated to 130.degree. C., with the solvent being 
distilled off, and condensed until the intrinsic viscosity is 12.5 ml/g. 
The acid value falls from 33 mg KOH/g to 28.2 mg KOH/g. The batch is 
cooled to 85.degree. C. and diluted with a blend of 11 parts of 
monoethyleneglycol monobutylether, 4.8 parts of triethylamine and 111.2 
parts of deionized water to a solids content of 44%. The pH-value of a 10% 
aqueous solution is approximately 9. The final product has an oil length 
of 48%; the ratio between the intrinsic viscosities of the intermediates 
is .zeta.B/.zeta.A=1.68. 
EXAMPLE 2 
50 parts of Component (B2) and 58.8 parts of Component (A2) (50 parts resin 
solids) are heated to 130.degree. C. under vacuum and with solvent 
distillation and condensed until the intrinsic viscosity has attained a 
value of 13.5 ml/g. The acid value of the condensation product is 58 mg 
KOH/g. The batch is cooled to 80.degree. C. and diluted with a blend of 
9.2 parts of triethylamine and 118 parts of deionized water to a solids 
content of 44%. The pH-value of a 10% aqueous solution is above 8.5. The 
final product has an oil length of 41%; the ratio between the intrinsic 
viscosities of the intermediates .zeta.B/.zeta.A is 1.41. 
EXAMPLES 3-5 
In Examples 3-5 components A and B are condensed according to the method 
set forth in Example 2 in the ratios listed below. As soon as the given 
intrinsic viscosity is attained they are neutralized with triethyl amine 
(degree of neutralization about 100%) and are diluted with deionized water 
to a solids content of 44%. 
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Example 3 4 5 
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Blending ratio 
A4 45/B4 55 
A3 50/B3 50 
A5 70/B4 30 
A/B (Parts) 
Acid value mg 
35 26 41 
KOH/g 
Intrinsic viscosity 
11.8 14.8 10.2 
ml/g 
Oil length percent 
35 58 50 
(%) 
##STR1## 1.65 1.86 2.23 
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Paint Performance Evaluation Of The Binders Of The Invention 
Two paints were prepared according to the listed formulations. The mill 
pastes listed in the first section were obtained through dispersion for 1 
hour in a pearl mill. The paint was finished by adding the rest of the 
listed ingredients in the given sequence and dispersing the whole blend 
with a high speed dispenser. 
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Formula 1 
Formula 2 
______________________________________ 
Titanium Dioxide 24 24 
Pigment (Kronos RN 59) 
Violet Pigment 3 3 
(Hostaperm Violett RL) 
Blue Pigment (Hostaperm 
13.5 13.5 
Blau AFL) 
Carbon Black (LTD) 1.5 1.5 
Binder of Example 1, 44% 
80 -- 
Binder of Example 3, 44% 
-- 80 
Deionized Water 20 20 
Pigment Paste 142 142 
Binder of Example 1, 44% 
586.7 -- 
Binder of Example 3, 44% 
-- 586.7 
Triethylamine 3.0 3.0 
Driers: 
Co (Octa-Soligen, 1% WS) 
14.9 14.9 
Pb (Octa-Soligen, 10% WS) 
14.9 14.9 
Ca (Octa-Soligen, 2% WS) 
14.9 14.9 
Paint Additives: 
Antiskinning Aid 7.7 7.7 
(Additol XL 297) 
Levelling Aid 1.5 1.5 
(Additol XL 121) 
Deionized Water 285.5 76.2 
Paint I 1071.1 -- 
Paint II 861.6 
Paint Solids % 31.9 39.7 
pH-Value 9.3 9.5 
Water Content of Paint, % 
58.7 48.7 
Organic Solvents and Amine 
9.4 11.6 
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Paints I and II, after having been allowed to stand for 24 hours, upon 
dilution with water to application viscosity, were applied by a spray gun 
to glass plates and to clean steel plates and allowed to dry at room 
temperature (20.degree. C./60% relative humidity). Evaluation of the films 
of about 30 .mu.m dry film thickness gave the following values: 
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Paint I 
Paint II 
______________________________________ 
Tack-free, Hours 31/2 11/2 
KONIG Pendulum Hardness 
DIN 53 157, Seconds 
(a) After 24 Hours 24 49 
(b) After 1 Week 42 75 
(c) After 3 Weeks 42 75 
(d) After 4 Weeks 45 82 
Gloss, 20.degree. Gonioreflectometer 
69% 86% 
Cross-hatch DIN 53 151 
(a)-(d) Gt 0 Gt 0 
Impact (Joule) 9.04 1.13 
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As will be apparent to one skilled in the art, various modifications can be 
made within the scope of the aforesaid description. Such modifications, 
being within the ability of one skilled in the art, form a part of the 
present invention and are embraced by the appended claims.