Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Aqueous coating agents, ~or example for lacquering
furniture, have hi-therto generally contained syn-thetic resins,
such as acrylic polymers or cellulose esters, as -the film-
forming agents. Methods for preparing aqueous emulsions of
suitable cellulose derivatives are known and are described,
~or example9 in German Auslegeschrift (German Published Specific.)
1,286,672 and U,S. Patent Specification 3,615,792, Emul-
sions of cellulose esters, for example of nitrocellulose, cannot
be used as the sole binders for coating agents9because they
only produce brittle and fragile ~ilms. They must be com-
bined with ketone resins or vinyl acetate copolymers in order
to achieve glossy coatings with good mechanical properties.
Cellulose esters, for example nitrocellulose, mostly
combined with alkyd resins, are used for lacquering wood or
similar materials. This combination leads to coatings o~
high gloss 7 adequate hardness, good elasticity and excellent
pore ~low, but it is not possible -to work with aqueous emul-
sions; instead, these combinations have hitherto had to be
processed from organic solutions~ All attempts hitherto to
emulsify alkyd resins and cellulose e$ters lead either to
emulsions of inadequate stability or to emulsions with particles
which are too coarse and which do not permit levelling to give
~3C~ glossy ooatirigs O~r cope~ding~Application (Specification
Serial No. P'~7 03 075~i~) relates to
aquçous dispersions o~ coating agents, consisting o~ 5 - 50
parts by weight of cellulose ester, 5 - 30 parts by weight of
plasticisert 5 - 50 parts by weight of alkyd resin, 30 - 80
parts by weight of water and 0~5 - 10 parts by weight o~
:
emulsifier~ which contain a vinyl alcohol hom~polymer or
copolymer clS the emulsi~ier and a short-oil alkyd resin9
containing 5 - 50% by weight of oil, as the al~yd resin.
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These dispersion~ are stable and give coating~ of
acceptable gloss.
The a~ore-mentioned copending applica-tion furth~r rela-tes
to a process for -the prep2ration of such dispersions of soatin~
agents, in which a cellulose ester, an alkyd resin and a plastic-
iser are dissolved in an organic solven-t, this solution is dispers-
ed into a solution consisting of emulsi~ier and water and th~
organic solvent ls removecl k~y distillation. According to the
present inventionS there is provide(l an aqueous coating agent
consisting of 5 to 50 parts by weight o~ cellulose ester, 5 -to 30
parts by weight of plastiGiser, 5 to 50 parts by weight of alkyd
resin, 30 to 80 parts by ~ieight of water, 0.1 to 10 parts by
weight of emulsifier, wherein the emulsi~ier is a vinyl alcohol
homopolymer or copolymer and the alkyd resin is a short-oil alkyd
resin having 5 to 50 % by weight o~ oil, and 4 to 40 parts by
weight of a urea resin and/or melamine resin (as hereinbefore
defined).
The size of the dispersed particles is particularly
important for -the stability o~ the dispersion and also ~or its
behaviaur in film formation According to -the in~ention it
is preferably O.l to 0.5 ~ and it does not change substantially
even on prolonged storage at 5 - 50C,
Cellulose esters which can be used according to the
invention are9 in particular, cellulose acetate, cellulose
acetobutyrate, cellulose acetate-benzoate and cellulose sorbate
acetate and mixtures of these esters, Nitrocellulose, ~or
example the customary collodion cotton grades, that is ~o
say cellulose nitric acid esters having a nitrogen content o~
10.2 to l2.4% by wel~ht, is very particularly suitable.
Plasticisers in the sense o~ the invention are, in
particular, esters, such as dlbutyl phthalate, dioctyl
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phthalate, dicyclohexyl phthalate, dibutyl adipate, benzyl butyl adipate,
dioctyl adipate, phosphoric acid esters, such as tricresyl phosphate, tri-
phenyl phosphate or trioctyl phosphate, and also benzenesulphonic acid N-
methylamide.
Suitable alkyd resins are preferably oil-modified or fatty acid-
modified alkyd resins. Alkyd resins are understood as polyesters which are
prepared from alcohols and carboxylic acids by polycondensation according to
known processes and such as are defined, for example, in Ullmanns Enzyklo-
padie der Technischen Chemie (Ullmann's Encyclopaedia o~ Tndustrial Chemistry)
10 or are described in D.ll. Solomon, The Chemistry Oe Organic Filmformers, page75-101. In general, the alcohols employed contain 1 to 15, preferably 2 to
6, C atoms and the acids used, or their ester-forming derivatives, contain 2
to 14, preferably 4 to 12, C atoms. These alkyd resins can optionally be
mixed with other polyesters, for example also with oil-free polyesters.
Examples of suitable alcohols are pentaerythritol, glycerol, tri-
methylolpropane, trimethylolethane, 1,2,4-butane-triol, 1,2,6-hexanetriol,
ethylene glycol, propane-1,2-dioI, propane-1,3-diol, butane-1,2-diol, butane-
1,3-diol and butane-1,4-diol, neopentyl glycol, diethylene glycol, trithylene
glycol, dipropylene glycol, hexane-1,6-diol, 1,2-bis-~hydroxy-methyl)-cyclo-
20 hexane and 1,4-bis-~hydroxymethyl)-cyclohexane, 2-ethylpropane-1,3-diol, 2-
ethylhexane-1,3-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol and adipic
acid bis-~ethylene glycol~ ester; benzyl alcohol, cyclohexanol and other mono-
alcohols with 1 to 6 C atoms. Preferred alcohols are glycerol, trimethylol-
propane, neopentyl glycol and pentaerythritol.
The follolaing carboxylic acids, or their ester-forming derivatives,
ma~ be mentioned as examples of suitable acid
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componen-ts: ph-thalic acid, isophthalic acid, terephthalic acid,
-te-trahydrophthalic acid c~d hexahydroph-thalic acid, endo-
methylenete-trahydrophthalic acid, succinic acid, adipic acid,
sebacic acid, trimellitic acid, benzoic acid and -their
derivatives 9 such as, for example, p~tert.-butylbenzoic acid
and hexahydrobenzoic acid. Phthalic acid is the most
customary.
In the alkyd resins which are employed for the coating
emulsions according to the i~vention, the proportion o~ oil
can be 5 to 50% by weight, calculated as triglyceride and
relative to the alkyd resin. The drying or non-drying fat-ty
acids, which generally contain 6 to 24 C atoms, can be employed
either as such or in the form of their glycerol es-ters (tri-
glycerides). Animal and vegetable oils, fats or fatty
acids, such as, ~or example 9 coconut oil, groundnu-t oil, castor
oil, olive oil, soya bean oil ? linseed oil, cottonseed oil~
sa~floweroil orthe correspondingfatty acid~ dehydrated castor
oil or castor oil ~atty acid, mono-unsaturated fatty acids,
lard 7 tallow and train oils, tall oil fatty acid and synthetic
fatty acids, may be mentioned as being suitable.
Suitable emulsifiers are homopolymers and copolymers of
vinyl alcoholl for example polyvinyl alcohols which are formed
by hydrolysis of polyvinyl acetate and which are available
i commercially, for example under the designation Polyviol W
25/240 and W 25/140~ Hydrolysed copolymers of vinyl-
pyrrolidone and vinyl acetate are also suitable.
The dispersions of coating agents of the invention
preferably contain alkyd resins with an oil content of 20 to
45% by weight.
The coating agents according to the invention can be
prepared by dissolving the alkyd resin, the cellulose ester and
the plasticiser in a polar solvent which ls not soluble in water,
and which can be removed by distillation from the emulsion to
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be formed, combining the solution with an aqueous solution of
the emulsifier and thus forming an oil-in-water emulsion by
means of high shearing forces. The organic solvent is then
removed, on its own or in the form o~ an aqueous azeotrope, by
distillation. Solven-ts which are particularly suitable are
alkyl acetate and alkyl propionate. The aqueous emulsion
which remains can be dilu-ted with more water or a suitable
coalescing agent can be added to it. In the following tex-t
this will be designated a secondary emulsion.
One or more coalescing or aggregating agents can also
be added to the dispersion in order to achieve a clear film of
high gloss. Coalescing agents which form an azeotrope with
the water are preferred here. It is then necessary to add
to the dispersion sufficient coalescing agent so that the
azeotrope is first distilled off and, in addition, to add
further coalescing agent which effects the aggregation of the
particles Possible coalescing agents are ethylene glycol
monomethyl ether, ethylene glyool monoethyl ether and ethylene
glycol monobutyl ether-acetate, diethylene glycol, diethylene
glycol monobutyl ether, diacetone alcoho~ methylglycol acetate,
methyl amyl ketone and diisobutyl ketone.
The primary emulsion consisting of cellulose ester,
alkyd resin, emulsifier, plasticiser, water and organic solvent
is produced in a commercially available device having an
adequately high peripheral speed of 5 to 50 m/second, pre~er-
ably 10 - 30 m/second.
Examples are: Ultra-Tu ~ type 45 of 10,000 re~olutions
per minute; Gaulin~Homogeniser? Dissolver and bead mills.
The emulsifying time in theUltra-Tu~ axshould not be
more than 2 minute$, since otherwise too great an evolution of~
heat takes place. This tlme is ade~uate to produce small,
spherical partlcles of 0.1 - 0.5 ~ from the constituents of
the ultimate emulsion.
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In the sense o~ -the invention, urea resins and mela-
mine resins are condensation produc-ts o~, respec-tively, urea or
melaminewith ~o~aldehydewhich havebeenpreparedin analkaline
medium. These productsare knownfrom theliterature, They are
generally water-soluble and are added in the form of aqueous
solutions to -the dispersions ofour a~ore-mentioned copending
application. They cause cro3slinking of the coatings prepared
from the dispersions and thus improve the stability and gloss v~
the coatings. Catalytic amounts of p-toluenesulphonic acid can
be added in order to accelera-te the crosslinking.
Example 1 (Comparison)
A lacquer of the following composition was prepared:
groundnut oil ~atty acid alkyd resin
having 41% of oil, 60% strength
solution in xylene152 parts by weight
collodion cotton (cellulose nitric acid
ester containing approximately 12% o~
nitrogen), Standard Specification type 24
E, DIN 53~1799 in the form of chips111 parts by weight
dibutyl phthalate 8 parts by weight
ethylene glycol monoethyl ether59 parts by weight
butyl acetate 190 parts by weight
ethyl acetate 140 parts by weight
xylene 300 parts by weight
ethylglycol acetate40 parts by weight
The resulting lacquer exhibited a viscosity correspond-
ing to a flow time of approximately 30 seconds~ measured in
accordance with DIN 5~211 (DIN cup No. 4~. The curing to
give ~ilms and the assessment are described in Table 1.
; 30 Example 2
A lacquer of the following composition was prepared:
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dispersion -From Example 1 oF Canadian application
Serial No. 295,556 as described on page 2 of
the present application, ~0% strength in water 580 parts by weight
ethylene glycol monoethyl ether3~ parts by weight
ethylglycol acetate 34 parts by weight
ethylene glycol monomethyl ether3~ parts by weight
methylglycol acetate 3~ parts by weight
~-me-thyl-~-hydroxy-pentan-2-one3~ parts by weight
Resimene 980X1 70 parts by weight
water 17~ parts by weight
levelling agent (alkylbenzenesulphonate) 6 parts by weight
1,000 parts by weight
para-toluenesulphonic acid, 25%
strength solution in water17 parts by weight
1) methylated, non-plasticised water-soluble urea resin from
Messrs. Monsanto. Trade mark.
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