Note: Descriptions are shown in the official language in which they were submitted.
PATENT
Docket D 7 6 61
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THE USE OF ETHOXYLATED FATTY ALCOHOLS AS A SURFACTANT
ADDITIVE FOR GYPSUM-CONTAINING COMPOSITIONS
BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention relates to the use of ethoxylated C12-
C22 fatty alcoholæ having an HLB value of from 4.5 to 11 as
a surfactant additive for compositions containing methyl
cellulose or hydroxyalkylated derivatives thereof and
gypsum.
2. Statement of Related Art:
Gypsum compositions used as plasters, screeding
compounds and the liXe must be mixed with water before use.
Hard or soft lumps (nodules) are often formed during the
mixing process. However, the exact cause of this
undesirable phenomenon, which is particularly serious in
the case of very fine or readily disintegrating gypsum, is
unknown. One possible cause might be the presence of
impurities or the calcining process used for the gypsum
and, of course, also the specific surface of the gypsum and
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the methyl cellulose present and wetting problems.
Nodule formation i8 promoted by the additives, e.g.,
methyl cellulos~s and hydroxyalkylated derivatives thereof,
for subsequent processing. It is often recommended to add
anionic surfactantæ to the gypsum to suppress nodule
formation by improving wettability. These wetting agents,
which often also act as air-entraining agents, are dry-
mixed with the gypsum and reduce its surface tension during
mixing with water. It has also been recommended to use
thickeners such as polyacrylamides or starch ethers ~hich
are said to thicken the plaster during mixing so that the
nodules are broken down.
However, the measures mentioned above are rarely
successful because, despite the anionic surfactants, the
nodules are not sufficiently wetted by the water and the
shear forces normally occurring during mixing are not
s~fficient to destroy the nodules.
DESC~IPTION OF THE INVENTION
Other than in the operating examples, or where
otherwise indicated, all numbers expressing quantities of
ingredients or reaction conditions used herein are to be
understood as modified in all instances by the term
"about".
The present invention is based on the discovery that
nodule formation during mixing with water can be
effectively suppressed by the addition of ethoxylated Cl2-
C22 fatty alcohols having an HLB value of 4.5 to 11 to a
composition containing gypsum and methyl cellulose or
hydroxyalkylated derivatives thereof.
By HLB value is meant the parameter calculable by the
so-called HLB system (hydrophilic/lipophilic balance
system), cf. J. Falbe, Surfactants in Consumer Products,
Springer-Verlag Heidelberg 1987, pages 149 to 153, with
further literature references.
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The ethoxylated C12-C22 fatty alcohols to be used in
accordance with the invention are commercially available
products which may be obtained by ethoxylation of the
corresponding fatty alcohols, particularly lauryl alcohol,
myristyl alcohol, cetyl alcohol, stearyl alcohol, arachidyl
alcohol, behenyl alcohol, oleyl alcohol, elaidyl alcohol,
gadoleyl alcohol, arachidonic alcohol, erucic alcohol,
brassidylic alcohol, the HLB value being ad~ustable through
the degree of ethoxylation. Since the fatty alcohols are
normally produced from fatty acids of natural, more
especially vegetable, and animal or~gin and even synthetic
origin by hydrogenation of, in particular, the methyl
esters thereof, the commercial products mentioned are all
mixtures of various ethoxylated fatty alcohols.
Ethoxylated fatty alcohols containing 16 to 18 carbon
atoms in the fatty alcohol portion, which are also
commercially available and represent technical grade
mixtures of various ethoxylated fatty alcohols, are
preferably used for the purposes of the invention. A
typical example is a technical grade mixture of oleyl and
cetyl alcohol reacted with 5 mol of ethylene oxide per mol
of fatty alcohol mixture.
The ethoxylated fatty alcohols are preferably used in
a quantity of from 0.06 to 0.5% by weight and more
especially in a quantity of from 0.1 to 0.3% by weight,
based on the dry weight of the gypsum composition.
The gypsum compositions obtained using C1z~C22 fatty
alcohols in accordance with the invention contain as usual
methyl cellulose or hydroxyalkylated derivatives thereof,
for example methyl hydroxyethyl and/or methyl hydroxypropyl
cellulose. The gypsum compositions may also contain
standard additives, for example anionic surfactants which
often act as air-entraining agents, calcium carbonate,
calciu~ hydroxide, starch ethers, lightweight aggregates,
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pigments and the li~e.
Other nonionic surfactants obtainable by ethoxylation
and/or propoxylation of compounds colltaining reactive
hydrogen atoms, more especially polyglycol ethers of alkyl
phenols containing 8 to 12 carbon atoms in the alkyl
substituent, which should preferably also have an HLB
value in the above-mentioned range of 4.5 to 11, may also
be added to the gypsum compositions together with the
ethoxylated Cl2-Cz2 fatty alcohols having an HLB value of 4.5
lo to 11. Derivatives such as these are familiar to the
expert, cf. J. Falbe, loc. cit., pa~es 86 to 105, and N.
Schonfeldt, Grenzflachenaktive Ethylenoxid-Addukte,
Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart 1976,
pages 209 to 218, more especially pages 210/211, Table 42.
Accordingly, the ethoxylated C12-C22 ~atty alcohols to be
used in accordance with the invention may be partially
replace~ by other ethoxylated, nonionic surfactants, more
especially C8-C12 alkyl phenols.
The invention is illustrated by the following Examples
and Comparison Examples.
EXAMPLE 1
1,28 g of methyl hydroxyethyl cellulose (viscosity
30,000 mPa.s, 2% solution), 0.8 g of tartaric acid and 0.8
g of an oleyl-cetyl alcohol mixture alkoxylated with 5 mol
of ethylene oxide and having an HLB value of 9.0 were added
to 800 g of mechanical plaster gypsum containing approx.
53% gypsum, 40% ground calcium carbonate, 5% calcium
hydroxide and 2% lightweight aggregate. The batch was
mixed for lo minutes in a standard (Lodige) mixer and was
then mixed with 448 g of water in a standard (Hobart~ mixer
(10 seconds' scattering, 50 seconds' mixing, stage I).
To determine nodule formation, the plaster with a
slump factor of 200 to 220 mm was applied in a layer
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thickness of 5 mm to gypsum plaster~oards. No nodules were
observed.
EXAMPLE 2
The procedure was as in Example l except that the
nonionic surfactant used in Example 1 was replaced by
another commercial surfactant consisting of nonyl phenol
alkoxylated with 6.5 ethylene oxide units and technical
grade cetyl/oleyl alcohol alkoxylated with 5 ethylene oxide
units (HLB value 10.9 and 9.0, respectively). Only a few
small gypsum nodules were observed.
COMPARISON EXAMPLE 1
The procedure was as in Example 1 except that, on the
one hand, no surfactant was added and, on the other hand,
the nonionic surfactant used in Example 1 was replaced by
sodium lauryl sulfate (HLB value approx. 40). Numerous
large nodules were formed in each case.
EXAMPLE 3
The procedure was as in Example 1 using 0.05 and 0.2%
by weight, based on the dry weight of the gypsum
composition, of the nonionic surfactant used in Example 1.
Numerous large gypsum nodules were observed in the first
case and hardly any in the second case.
EXAMPLE 4
The procedure was as in Example 2 using 0.05 and 0.2%
by weight, based on the gypsum composition, of the nonionic
surfactant used in Example 2. Numerous large gypsum
nodules were observed in the first case, but only a few
small nodules in the second case.
EXAMPLE S
800 g of a hand plaster basic mix (composition as in
Example 1, but using molding plaster and relatively coarse
calcium carbonate) were mixed and stirred as in Example 1
with 1.36 g methyl hydroxypropyl cellulose (viscosity
approx. 12,000 mPa.s in 2% solution), 0.16 g sodium lauryl
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8ulfate as air entraining agent, 0.28 g of a hydroxypropyl
starch ether (commercial) as thickener, 1.6 g of the
nonionic surfactant of Example 1 and 700 g water. The test
according to Example 1 produced only a few small nodules.
COMPARISON ~XAMP~E 2
Repetition of Example 5 with no nonionic surfactant
added produced numerous large nodules.
EXAMPLE 6
30 kg of the hand plaster basic mix of Example 5 were
mixed and stirred as in Example 5 with 51 g methyl
hydroxypropyl cellulose, g g sodium lauryl sulfate, 30 and
60 g nonionic surfactant and 15 1 water, the nonionic
surfactant being diluted with 30 g ethanol and sprayed onto
the hand plaster basic mix by means of a spray bottle with
the mixer running.
Pilot-scale testing was carried out after the mass had
been allowed to drain for 5 minutes and then stirred for 5
minutes ("Motorquirl") by throwing the mass onto a gypsum
plasterboard wall and spreading it in a layer thickness of
1 cm. Where 30 g of the nonionic surfactant were used, a
few nodules were formed during throwing and some smaller
nodules after smoothing. When the quantity of nonionic
surfactant was increased to 60 g, only a very few nodules
were formed during throwing and hardly any after smoothing.
- 25 COMPARISON EXAMPLE 3
3 Repetition of Example 6 with no nonionic surfactant
added produced numerous large nodules both during throwing
and after smoothing.
EXAMPLE 7
`- 30 A premix was prepared from 2 g of the nonionic
surfactants according to Table 1 below and 10 g of a ready-
made plaster according to Example 1. The resulting mixture
was mixed with 990 g of the ready-made plaster according to
Example 1 for lo minutes in a L6dige mixer and then stirred
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with 750 g water for 30 seconds in a Hobart mixer. The
plaster obtained was applied to a gypsum plasterboard in a
layer thickness of 5 mm. After drying, nodule and crack
formation were evaluated.
S The nonionic fatty alcohol surfactants used (FA
surfactants) and the results obtained are shown in Table 1
below. In the left-hand column of the Table, "Cl6-Cl8-
saturated x 2 EO" for example means that a technical grade
mixture of saturated Cl6-Cl8 fatty alcohols reacted with 2
mol ethylene oxide was used. In the "nodule formation"
column, +++ = numerous large modules, ++ = some large
nodules, + = some medium-large nodules, --- = no nodules, -
- = hardly any nodules and - - some nodules. In the "crack
formation" column, - = no cracks, + = some cracks and ++ =
numerous cracks.
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TABLE 1
Nonionic HLB value Nodule Crack
FA surfactant formation
C1618-unsaturated 4.0 +++
X 0 E0
C16 18-saturated 4 . 7 --
x 2 EO
C12~l8-saturated 6 . 5 --
x 3 E0
C12~8-unsaturated 9.O --
x 5 EO
Cl6 18-unsaturated 12.7 + +
x 10 E0
Cl6~l8-saturatecl 13 . 5 + +
x 12 E0
C16 18-saturated 15.3 ++ ++
X 20 E0
C16 18-saturated 16.9 +++ ++
X 30 E0
none +++
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It can be seen from Table 1 that nodule formation is
effectively avoided only ln the HLB range from 4.5 to 11.
In addition, the gypsum compositions thus obtained show no
tendency to form cracks.
EXAMPLE 8
A gypsum composition was prepared as in Example 7
using 1 and 3 g of a saturated Cl2-C18 fatty alcohol reacted
with 2 mol ethylene oxide. Only a few small nodules ana
hardly any nodules, re~pectively, were observed, nor dld the
composition show any signs of cracking.
