Note: Descriptions are shown in the official language in which they were submitted.
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Oil-in-water emulsions
Description
The invention relates to oil-in-water emulsions based on fatty alcohols and to
the use
thereof as antifoams or deaerators for aqueous compositions.
In numerous industrial processes, it is necessary to handle aqueous solutions
and
suspensions which have a tendency toward foam formation on account of their
ingredients. This foam formation makes the process difficult to carry out and
therefore
has to be kept as low as possible or avoided altogether. Examples of foam-
forming
aqueous compositions are detergent-comprising compositions, saponin-comprising
compositions, wastewater in water treatment plants, protein-comprising
compositions
such as soybean extracts and in particular paper stock suspensions, e.g.
groundwood-
and/or cellulose-comprising suspensions, as are used in particular in the
paper industry
for producing paper, board or cardboard.
Besides the formation of foam, which is permanently after-formed from
coalescing air
bubbles, the air incorporated in these systems, which is in a finely
dispersed, stable
form, also proves to be problematical. The reduction in the air content of
these systems
is therefore likewise of particular importance.
For these reasons, so-called antifoams and/or deaerators are added to the film-
forming
aqueous compositions during their processing and sometimes even during their
production; these antifoams and/or deaerators, even at low use concentrations,
suppress the undesired formation of foam, reduce the content of incorporated
air or
destroy foam which has already been produced.
The antifoams known from the prior art are often aqueous compositions based on
oil-
in-water dispersions or emulsions, the oil phase of which comprises at least
one
hydrophobic substance, for example mineral oils, silicone oils, polyalkylene
oxides,
esters thereof with fatty acids and ethers thereof with long-chain alcohols,
native fats
and/or oils, waxes, ester waxes or long-chain alcohols. Occasionally, the use
of
distillation residues which are formed during the production of long-chain
alcohols in
accordance with the Ziegler process or during oxo synthesis has also been
reported
(see e.g. EP-A 149812).
US 4,950,420 discloses antifoams for the paper industry which comprise 10 to
90% by
weight of a surface-active polyether, such as polyalkoxylated glycerol or
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polyalkoxylated sorbitol, and 10 to 90% by weight of a fatty acid ester of
polyhydric
alcohols, such as mono- and diesters of polyethylene glycol or polypropylene
glycol.
EP-A 531713 and WO 94/08091 describe antifoams for the paper industry based on
oil-in-water emulsions, the oil phases of which comprise alcohols, fatty acid
esters,
distillation residues, hydrocarbons in combination with polyglycerol esters.
DE 2157033 describes antifoams based on aqueous emulsions which comprise
C12-C22-alkanols and/or C12-C22-fatty acid esters of di- to trihydric alcohols
and paraffin
oil or C12-C22-fatty acids.
Joshi et al. established in Colloids and Surfaces A: Physicochem. Eng. Aspects
263
(2005) 239-249 that the effectiveness of an antifoam based on fatty alcohol
depends
on its aggregate state. The effectiveness is highest if it is partly molten.
This gives rise
in the specialist field to the requirement to use mixtures of fatty acid
alcohols which,
being mixtures, have a broader melting range than pure substances.
In the prior art, the effectiveness of an antifoam is often measured by its
ability to
suppress foam formation at a liquid surface. Particularly in papermaking,
however, it is
also of importance to reduce the air content in the aqueous liquids produced
during
papermaking, particularly in the paper stock suspensions. Antifoams which are
likewise
able to act as deaerators are not often described in the prior art. The known
antifoams
often leave something to be desired with regard to the deaerating effect,
particularly at
temperatures below 50 C, e.g. in the range from 20 to <50 C.
The object of the present invention is to provide compositions which have high
effectiveness both as antifoam and also as deaerator for aqueous compositions,
in
particular for aqueous paper stock suspensions.
These and other objects are achieved by oil-in-water emulsions, the oil phase
of which
consists to at least 95% by weight of the following constituents:
a) 50 to 80% by weight, in particular 55 to 75% by weight and
specifically 60 to 70%
by weight, based on the total weight of the oil phase, of at least one alkanol
having at least 16 carbon atoms, in particular having 16 to 20 carbon atoms,
where the fraction of alkanols having 16 to 18 carbon atoms constitutes at
least
80% by weight, in particular at least 90% by weight, specifically at least 95%
by
weight or at least 99%, based on the total amount of component A,
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b) 1 to 10% by weight, in particular 2 to 8% by weight, specifically 3 to
6% by
weight, based on the total weight of the oil phase, of at least one further
component B, which is selected from esters of C12-C36-alkanecarboxylic acids
with polyglycerol and esters of C12-C36-alkanecarboxylic acids with C12-C36-
alkanols, and mixtures thereof,
c) 10 to 49% by weight, in particular 20 to 40% by weight, specifically 25
to 35% by
weight, based on the total weight of the oil phase, of at least one further
component C, which is selected from organic substances which are liquid at 50
C
and 1013 mbar, at atmospheric pressure have a boiling point above 200 C, and
at 25 C and 1013 mbar have a solubility in water of less than 0.1 g/I.
Component A consists in particular of essentially unbranched alkanols having
at least
16, in particular 16 to 20, carbon atoms, i.e. saturated alcohols having at
least 16, in
particular 16 to 20, carbon atoms, in which the fraction of alcohols having 16
to
18 carbon atoms constitutes at least 80% by weight, in particular at least 90%
by
weight, specifically at least 95% by weight or at least 99%, based on the
total amount
of component A, and which are linear to at least 80%, in particular at least
90% and
specifically at least 95%. Such linear alkanols can be described by the
following
formula:
H-(CH2)-OH
in which n is an integer of at least 16 and in particular is in the range from
16 to 20. The
fraction of alkanols, in particular linear alkanols having 16 to 18 carbon
atoms, in
particular having 16 or 18 carbon atoms, is according to the invention at
least 80% by
weight, in particular at least 90% by weight, specifically at least 95% by
weight or at
least 99% by weight, based on the total weight of component A. Examples of
alcohols
suitable as component A are palmityl alcohol (cetyl alcohol), 1-heptadecanol,
stearyl
alcohol, arachyl alcohol (n-eicosanol), behenyl alcohol and mixtures thereof.
Preferably, component A consists to at least 80%, in particular at least 90%
and
specifically at least 95%, of palmityl alcohol, stearyl alcohol or mixtures
thereof.
According to the invention, component A comprises less than 20% by weight,
based on
component A, of alcohols having more than 18 carbon atoms. Preferably,
component A
comprises less than 10% by weight, in particular less than 5% by weight,
specifically
less than 1% by weight or less than 0.5% by weight, based on component A, of
alcohols having more than 18 carbon atoms.
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In a likewise preferred embodiment, palmityl alcohol or stearyl alcohol or a
mixture of
these alcohols is used as component A whereas component A is free (less than
0.5%
by weight, based on component A) from alcohols having more than 18 carbon
atoms.
According to the invention, the fraction of component A in the oil phase is 50
to 80% by
weight, preferably 55 to 75% by weight, in particular 60 to 70% by weight,
based on the
total weight of the oil phase.
Component B is selected from esters of alkanecarboxylic acids with
polyglycerol,
esters of alkanecarboxylic acids with alkanols and mixtures thereof.
Esters of alkanecarboxylic acids with polyglycerol are understood as meaning a
polyglycerol esterified with at least one fatty acid which has 12 to 36, in
particular 16 to
30, specifically 18 to 24, carbon atoms. The fatty acids contemplated for the
esterification of the polyglycerol may either be saturated fatty acids or
unsaturated fatty
acids and mixtures thereof. Fatty acids suitable for the esterification of the
polyglycerol
mixtures are preferably selected from saturated fatty acids having 12 to 36,
in particular
16 to 30, specifically 18 to 24, carbon atoms. Examples of suitable saturated
fatty acids
are lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid,
behenic acid and
montan wax acid. Examples of suitable unsaturated fatty acids are oleic acid,
hexadecanoic acids, elaidic acid, eicosenoic acids and docosenoic acids such
as
erucic acid or brassidic acid, and also polyunsaturated acids, such as
octadecenedienoic acids and octatrienoic acids, such as linoleic acid and
linolenic acid,
and mixtures of the specified saturated and unsaturated carboxylic acids.
Preferably,
the polyglycerol is esterified with saturated carboxylic acids having 18 to 24
carbon
atoms, which are selected in particular from palnnitic acid, stearic acid and
behenic acid
and mixtures thereof. In a specific embodiment, the polyglycerol ester is a
polyglycerol
esterified with behenic acid.
The degree of esterification of the polyglycerol esters is generally 20 to
100%,
preferably 60 to 100%, based on the number of hydroxyl functions in the
polyglycerol.
Preferred polyglycerol esters are in particular those which are obtainable by
esterifying
polyglycerol mixtures which comprise 15 to 40% by weight of diglycerol, 30 to
55% by
weight of triglycerol and 10 to 25% by weight of tetraglycerol, in each case
based on
the total amount of the polyglycerol, where the total amount of di-, tri- and
tetraglycerol
constitutes at least 60% by weight, in particular at least 80% by weight. In
particular,
mixtures with the following composition are used for the esterification:
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0 to 10% by weight of glycerol,
to 40% by weight of diglycerol,
30 to 55% by weight of triglycerol,
10 to 25% by weight of tetraglycerol,
5 0 to 15% by weight of pentaglycerol,
0 to 10% by weight of hexaglycerol and
0 to 5% by weight of more highly condensed polyglycerols.
In particular, the polyglycerol esters are those which are obtainable by
esterifying one
10 of the polyglycerol mixtures described above with at least one saturated
carboxylic acid
having 18 to 24 carbon atoms, the carboxylic acid being selected in particular
from
palmitic acid, stearic acid and behenic acid and mixtures thereof.
In the compositions according to the invention, particular preference is given
to those
15 polyglycerol esters which are obtainable by esterifying behenic acid
with a polyglycerol
mixture which consists of 0 to 10% by weight of glycerol, 15 to 40% by weight
of
diglycerol, 30 to 55% by weight of triglycerol, 10 to 25% by weight of
tetraglycerol, 0 to
15% by weight of pentaglycerol, 0 to 10% by weight of hexaglycerol and 0 to 5%
by
weight of more highly condensed polyglycerols.
The polyglycerol mixtures used for the esterification are accessible for
example by
alkaline catalyzed condensation of glycerol at elevated temperatures (cf. e.g.
Fette,
Seifen, Anstrichmittel, 88th volume, No. 3, pages 101 to 106 (1986)) or as in
DE-A 3842692 by reaction of glycerol with epichlorohydrin in the presence of
acidic
catalysts at elevated temperatures. However, the mixtures are also obtainable
by
mixing together the pure polyglycerol components, e.g. diglycerol, triglycerol
and
tetraglycerol.
The polyglycerols esterified with alkanecarboxylic acids are known, e.g. from
EP 531713 and WO 94/08091. They are typically prepared by esterification of
polyglycerol, in particular by esterification of the polyglycerol mixtures
described above,
with the desired fatty acid or mixture of fatty acids or ester-forming
derivatives thereof,
e.g. C1-C4-alkyl esters thereof, by methods known per se. As a rule, the
procedure is
carried out in the presence of an acidic esterification catalyst such as
sulfuric acid,
p-toluenesulfonic acid, citric acid, phosphorous acid, phosphoric acid,
hypophosphorous acid or basic catalysts, such as sodium methylate or potassium
tert-
butylate.
Further suitable as component B are esters of C12-C36-alkanecarboxylic acids
with
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C12-C36-alkanols. They are understood to include substances which are
obtainable by
esterification of at least one, preferably saturated, mono- to dibasic,
preferably
monobasic, alkanecarboxylic acid having 12 to 36, in particular 16 to 30,
specifically 18
to 24, carbon atoms with a C12-C36-alkanol. The alkanols suitable for the
esterification
are preferably saturated, linear and mono- to dihydric, in particular
monohydric. They
have 12 to 36, in particular 16 to 30, specifically 18 to 24, carbon atoms. It
is also
possible to use mixtures of alkyl esters of alkanoic acids. Suitable examples
of alkyl
esters of alkanoic acids are palmityl palmitate, stearyl stearate, arachyl
arachate,
behenyl behenate and lignoceryl lignocerate. Preferred esters of C12-C36-
alkanecarboxylic acids with C12-C36-alkanols are behenyl behenate and stearyl
stearate
and mixtures thereof.
In one preferred embodiment, component B comprises at least one of the above-
described esters of alkanecarboxylic acids with polyglycerol (also referred to
below as
polyglycerol esters), in particular at least one of the polyglycerol esters
stated as being
preferred or particularly preferred. In one preferred embodiment, component B
comprises at least one of the above-described polyglycerol esters which is
obtainable
by esterification of the above-described polyglycerol with at least one
saturated
carboxylic acid having 18 to 24 carbon atoms, where the carboxylic acid is
selected in
particular from palmitic acid, stearic acid and behenic acid and mixtures
thereof. In one
particularly preferred embodiment, component B comprises at least one of the
above-
described polyglycerol esters which is obtainable by esterification of behenic
acid with
a polyglycerol mixture consisting of 0 to 10% by weight of glycerol, 15 to 40%
by weight
of diglycerol, 30 to 55% by weight of triglycerol, 10 to 25% by weight of
tetraglycerol, 0
to 15% by weight of pentaglycerol, 0 to 10% by weight of hexaglycerol and 0 to
5% by
weight of more highly condensed polyglycerols.
In one preferred embodiment, component B consists to at least 80% by weight,
in
particular to at least 90% by weight, specifically to at least 95% by weight,
based on the
total weight of component B, or exclusively of at least one of the above-
described
polyglycerol esters, in particular at least one of the polyglycerol esters
stated as being
preferred or particularly preferred. In one particularly preferred embodiment,
component B consists to at least 80% by weight, in particular to at least 90%
by weight,
specifically to at least 95% by weight, based on the total weight of component
B, or
exclusively of at least one of the above-described polyglycerol esters which
is
obtainable by esterification of the above-described polyglycerol with at least
one
saturated carboxylic acid having 18 to 24 carbon atoms, where the carboxylic
acid is
selected in particular from palmitic acid, stearic acid and behenic acid and
mixtures
thereof. In one particularly preferred embodiment, component B consists to at
least
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80% by weight, in particular to at least 90% by weight, specifically to at
least 95% by
weight, based on the total weight of component B, or exclusively of at least
one of the
above-described polyglycerol esters which is obtainable by esterification of
behenic
acid with a polyglycerol mixture consisting of 0 to 10% by weight of glycerol,
15 to 40%
by weight of diglycerol, 30 to 55% by weight of triglycerol, 10 to 25% by
weight of
tetraglycerol, 0 to 15% by weight of pentaglycerol, 0 to 10% by weight of
hexaglycerol
and 0 to 5% by weight of more highly condensed polyglycerols.
According to the invention, the fraction of component B in the oil phase is 1
to 10% by
weight, preferably 2 to 8% by weight, in particular 3 to 6% by weight, based
on the total
weight of the oil phase.
Component C present in the oil-in-water emulsions according to the invention
is one or
more organic substances which are liquid at 50 C and 1013 mbar, at atmospheric
pressure have a boiling point above 200 C, e.g. in the range from 200 to 400
C, in
particular of at least 250 C, and which at 25 C and 1013 mbar are essentially
insoluble
in water, i.e. have a solubility in water of less than 0.1 g/I. Suitable
substances are
hydrocarbons and triglycerides of fatty acids, in particular those having 12
to 22 carbon
atoms. Component C preferably consists to at least 80% by weight, in
particular 90%
by weight, specifically 95% by weight, based on the total weight of component
C, of
one or more hydrocarbons, which are in particular nonaromatic, i.e. aliphatic
or
cycloaliphatic, and have a boiling point of at least 200 C, preferably at
least 250 C, e.g.
in the range from 200 to 400 C 01 250 to 400 C at 1.013 bar, such as, for
example,
liquid paraffins, white oils, soft paraffins or other standard commercial
mineral oils.
According to the invention, the fraction of component C in the oil phase is 10
to 49% by
weight, preferably 20 to 40, in particular 25 to 35% by weight, based on the
total weight
of the oil phase.
To stabilize the oil phase in the aqueous emulsion, the emulsions according to
the
invention advantageously comprise at least one surface-active substance. The
emulsions according to the invention comprise the at least one surface-active
substance generally in an amount from 0.1 to 10% by weight, in particular in
an amount
from 0.5 to 5% by weight, based on the oil phase.
Suitable surface-active substances are, in principle, all substances known for
the
stabilization of hydrophobic particles or droplets in aqueous systems, e.g.
anionic,
cationic, amphoteric and/or nonionic emulsifiers, and also water-soluble ionic
and
nonionic polymers, preferably ionically amphiphilic copolymers which have
cationic or
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anionic groups and whose molecular weight, in contrast to the emulsifiers, is
usually
above 1000 daltons. Surface-active substances are sufficiently known to the
person
skilled in the art, e.g. from Ullmann's Encyclopedia of Industrial Chemistry,
5th ed.
vol. A9, pp. 297-339.
Examples of suitable anionic emulsifiers are:
salts, in particular sodium and ammonium salts, of higher fatty acids,
salts, in particular the sodium and ammonium salts, of sulfated ethoxylation
products of
C6-C22-alkylphenols, such as nonylphenol or octylphenol,
salts, in particular the sodium and ammonium salts, of C4-C22-
alkylarylsulfonates,
salts, in particular the sodium and ammonium salts, of sulfonates of
naphthalene,
salts, in particular the sodium and ammonium salts, of sulfonated C3-C22-
alkyldiphenyl
oxides, in particular of bis-sulfonated C8-C22-alkyldiphenyl oxides, such as
bis-
sulfonated dodecyldiphenyl oxide,
salts, in particular the sodium and ammonium salts, of naphthalenesulfonic
acid-
formaldehyde condensates or naphthalenesulfonic acid-formaldehyde-urea
condensates,
and also salts, in particular the sodium and ammonium salts, of di-C4-C20-
alkyl
sulfosuccinates.
Examples of suitable nonionic emulsifiers are:
alkoxylated C6-C22-alkylphenols with a degree of ethoxylation of preferably in
the range
from 5 to 50,
ethoxylated unsaturated oils such as reaction products of castor oil with 30
to 40 mol
equivalents of ethylene oxide, and
adduct formation products of ethylene oxide and/or propylene oxide with
aliphatic
alcohols having as a rule 12 to 20 carbon atoms, e.g. with fatty alcohols,
with
polyhydric alcohols, with amines, and also with carboxylic acids.
The emulsions according to the invention preferably comprise at least one
emulsifier, in
particular at least one anionic emulsifier in an amount of from 0.1 to 10% by
weight, in
particular in an amount of from 0.5 to 5% by weight, based on the oil phase.
In one
specific embodiment, the emulsions according to the invention comprise at
least one
anionic emulsifier selected from the salts, in particular the sodium and
ammonium
salts, of sulfated ethoxylation products of C6-C22-alkylphenols.
Examples of surface-active anionic polymers are homopolymers of acrylic acid,
homopolymers of methacrylic acid, copolymers of acrylic acid and methacrylic
acid in
any desired molar ratio, copolymers of acrylic acid and maleic acid in any
desired
molar ratio, copolymers of methacrylic acid and maleic acid, polyvinylsulfonic
acid,
polyacrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, copolymers
of
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acrylic acid and acrylamide or methacrylamide, copolymers of methacrylic acid
and
acrylamide or methacrylamide, or the alkali metal and ammonium salts of the
specified
polymers with molar masses of, for example, 1500 to 300 000.
Preferred anionic surface-active polymers are amphiphilic copolymers
comprising acid
groups and comprising, in copolymerized form,
(a) hydrophobic monoethylenically unsaturated monomers and
(b) monoethylenically unsaturated carboxylic acids, monoethylenically
unsaturated
sulfonic acids, monoethylenically unsaturated phosphonic acids or mixtures
thereof,
and optionally monomers (c) different therefrom, and also the salts, in
particular the
sodium and the ammonium salts, of such copolymers.
Examples of hydrophobic monoethylenically unsaturated monomers are: styrene,
methylstyrene, ethylstyrene, acrylonitrile, methacrylonitrile, C2- to C18-
olefins, esters of
monoethylenically unsaturated C3- to C5-carboxylic acids and monohydric
alcohols,
vinyl alkyl ethers, vinyl esters or mixtures thereof. From this group of
monomers,
preference is given to using isobutene, diisobutene, styrene and acrylic acid
esters
such as ethyl acrylate, isopropyl acrylate, n-butyl acrylate and sec-butyl
acrylate.
Examples of monomers (b) are: acrylic acid, methacrylic acid, maleic acid,
maleic
anhydride, fumaric acid, itaconic acid, vinylsulfonic acid, 2-
acrylamidomethylpropane-
sulfonic acid, acrylamidopropane-3-sulfonic acid, 3-sulfopropyl acrylate, 3-
sulfopropyl
methacrylate, styrenesulfonic acid, vinylphosphonic acid or mixtures thereof,
with
preference being given to acrylic acid, methacrylic acid and maleic acid and
also their
anhydride.
The molar mass of the amphiphilic copolymers is generally 1000 to 100 000 and
is
preferably in the range from 1500 to 10 000. The acid numbers of the anionic
amphiphilic copolymers are generally 50 to 500, preferably 150 to 350 mg of
KOH/g of
polymer.
Suitable surface-active polymers for stabilizing the compositions according to
the
invention are also:
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= graft polymers of 5 to 40 parts by weight of N-vinylformamide per 100
parts by
weight of a polyalkylene glycol with a molar mass of from 500 to 10 000,
= zwitterionic polyalkylenepolyamines,
= zwitterionic polyethyleneimines,
5 = zwitterionic polyetherpolyamines or
= zwitterionic crosslinked polyalkylenepolyamines.
Graft polymers of N-vinylformamide on polyalkylene glycols are described, for
example,
in WO-A-96/34903. The grafted-on vinylformamide units may optionally be up to
10%
10 hydrolyzed. The fraction of grafted-on vinylformamide units is
preferably 20 to 40% by
weight, based on polyalkylene glycol. Preference is given to using
polyethylene glycols
with molar masses of from 2000 to 10000.
Zwitterionic polyalkylenepolyamines and zwitterionic polyethyleneimines are
known, for
example, from EP-B 112592. Such compounds are obtainable, for example, by
firstly
alkoxylating a polyalkylenepolyamine or polyethyleneimine, e.g. with ethylene
oxide,
propylene oxide, and/or butylene oxide, and then quaternizing the alkoxylation
products, e.g. with methyl bromide or dimethyl sulfate, and then sulfating the
quaternized alkoxylated products with chlorosulfonic acid or sulfur trioxide.
The molar
mass of the zwitterionic polyalkylenepolyamines is, for example, 1000 to 9000,
preferably 1500 to 7500. The zwitterionic polyethyleneimines preferably have
molar
masses in the range from 2000 to 1700 daltons.
The compositions according to the invention preferably comprise at least one
anionic
surface-active substance. This is preferably selected from the aforementioned
anionic
emulsifiers, the aforementioned acid-carrying, water-soluble polymers and
mixtures
thereof.
For the stability of the emulsions according to the invention, it has proven
advantageous if they comprise 0.05 to 8% by weight, in particular 0.1 to 5% by
weight,
based on the oil phase, of at least one acid-having water-soluble homo- or
copolymer,
preferably of a salt thereof and optionally at least one anionic emulsifier.
The
emulsifiers are preferably likewise used in an amount of from 0.05 to 5% by
weight,
based on the total weight of the oil phase. In particular, those emulsions
which
comprise at least one anionic emulsifier and at least one of the
aforementioned acid-
carrying water-soluble polymers are advantageous.
Besides the oil phase, the emulsions according to the invention can comprise,
as
further disperse constituent, finely divided, virtually water-insoluble, inert
solids with
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particle sizes (weight-average particle diameter) below 20 pm, preferably in
the range
from 0.1 to 10 pm. If desired, the emulsion according to the invention
comprises these
further inert solids in an amount of, for example, 0.1 to 50% by weight,
preferably 1 to
35% by weight, based on the weight of the oil phase of the oil-in-water
emulsions.
Suitable inert solids are in particular inorganic solids such as e.g. kaolin,
chalk,
bentonite, talc, barium sulfate, silicon dioxide, zeolites, but also organic
solids such as
urea-formaldehyde pigments, melamine-formaldehyde pigments and
microcrystalline
cellulose, where the inert inorganic solids may also be hydrophobized, e.g. by
treatment with trialkylsilyl halides. In contrast to the oil phase, these
inert solids are
solid at a temperature of 100 C. In one preferred embodiment of the invention,
the
emulsions comprise no finely divided, virtually water-insoluble, inert solids
different
from components A, B and C.
As a rule, the solids content of the oil-in-water emulsion according to the
invention is in
a range from 10 to 50% by weight, in particular 15 to 45% by weight,
specifically 20 to
40% by weight, based on the total weight of the oil-in-water emulsion.
The emulsions according to the invention frequently comprise one or more
thickeners
for setting the viscosity required for the respective application. In
principle, it is possible
to use all thickeners known for thickening oil-in-water systems. These include
natural
thickeners such as polysaccharides, carrageenates, Tragacanth, alginates,
starch,
caseinates, modified organic polymers such as carboxymethylcellulose,
synthetic
thickeners such as polyacrylic acids, polyvinyl alcohol, polyethylene glycols,
polyacrylamides, and, in particular, copolymers of acrylamide with
ethylenically
unsaturated carboxylic acids, in particular with acrylic acid, and optionally
with
comonomers. These thickeners are described in EP-A 149 812, the disclosure of
which
is hereby referred to. Further suitable thickeners are mentioned in the
overview article
by Warren. B. Shapiro, Oil-in Water-Emulsions, Cosmetics & Toiletries, vol.
97, 1982,
27-33. Particular preference is also given to so-called associative
thickeners, e.g.
hydrophobically modified polyurethanes, hydrophobically modified cellulose
ethers,
which build up high molecular weight network structures in accordance with the
principle of hydrophobic interaction in aqueous phase. Associative thickeners
are
known to the person skilled in the art, e.g. J. Bielemann, Additives for
Coatings, Wiley-
VCH Weinheim 2000 and are commercially available, e.g. under the names
RHOPLEX and PRIMAL TT 935 from Rohm & Haas, USA. In one preferred
embodiment of the invention, the emulsions comprise no thickener.
In addition, the emulsions according to the invention also frequently comprise
commercially available biocides for preservation, e.g. formaldehyde,
isothiazolinone
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compounds such as the products sold by Arch Chemicals under the name PROXEL
and the products sold by Thor Chemie GmbH under the name ACTICIDE .
To prepare the emulsion according to the invention, as a rule the oil phase is
emulsified
in the aqueous phase. For this, a melt of components A, B and C of the oil
phase will
usually be incorporated, i.e. emulsified, into an aqueous phase which
optionally
comprises one or more surface-active substances. The incorporation and/or
emulsification generally takes place at temperatures above the melting point
of the oil
phase, e.g. at temperatures in the range from 55 to 100 C. The incorporation
takes
place in a manner known per se for producing emulsions by using apparatuses
such as
e.g. dispersing devices, in which the components of the emulsion are subjected
to a
considerable shear gradient. In order to obtain particularly stable oil-in-
water
emulsions, the emulsification of the oil phase in the aqueous phase is
preferably
carried out in the presence of surface-active substances.
Emulsifying the oil phase in the aqueous phase gives oil-in-water emulsions.
Immediately after preparation, these generally have a viscosity in the range
from 300 to
3000 mPa.s (determined in accordance with Brookfield at 25 C, e.g. with
spindle 4 at
revolutions per minute).
The average particle size (weight average of the droplet diameter) of the oil-
in-water
emulsion is generally below 25 pm, preferably in the range from 0.1 to 15 pm,
in
particular 0.5 to 10 pm, determined by means of light scattering at 20 C.
The oil-in-water emulsions according to the invention can be used as antifoams
and/or
deaerators for controlling foam and/or deaeration of aqueous media, for
example in the
food industry, the starch industry, in waste treatment plants or in the paper
industry.
Preference is given to their use as borehole solution and in the paper
industry, in
particular during pulp cooking, pulp washing, the grinding of paper stock,
papermaking
and the dispersion of pigments for papermaking. Specifically, the oil-in-water
emulsions
according to the invention are used in the paper industry as deaerators of
paper stock
suspensions. Particular preference is given here to the use as deaerators of
the
headbox in papermaking.
As antifoams or deaerators, the oil-in-water emulsions are generally used in
amounts
of from 0.01 to 2 parts by weight per 100 parts by weight of the foam-forming
aqueous
liquid, preferably in amounts of from 0.02 to 1 part by weight per 100 parts
by weight of
the foam-forming liquid, in particular in amounts of from 0.05 to 0.5 parts by
weight per
100 parts by weight of the foam-forming liquid.
0000070862 CA 02821380 2013-06-12
13
The advantages of the emulsions according to the invention are evident
particularly at
temperatures in the range from 20 to 50 C.
The examples below are intended to illustrate the invention in more detail and
are not
to be understood as being limiting.
Physicochemical test methods
The average particle size (weight-average particle diameter d50) of the
particles of the
oil phase emulsified in water was determined with the help of a Coulter
counter from
Beckmann.
The viscosity was determined using a Brookfield rotary viscometer model RVT,
spindle 4 at 20 revolutions per minute at 25 C.
The solids content was determined by back-weighing the samples following
storage in
a drying cabinet at 110 C to constant weight.
The average air content was determined by pumping in each case 10 I of a foam-
developing paper stock suspension 0.1% (groundwood) in a container made of a
transparent plastic for 5 minutes. The amount of air formed in the stock
suspension
was then ascertained using an air measuring device (e.g. based on impedance
methods as in the case of the Son ica device from Conrex or based on sonic
speed
measurements as in the case of Sonatrac from Cidra). To assess the
effectiveness of a
deaerator, the average air content was stated 5 minutes after adding the
deaerator.
If the paper suspension is pumped round in the absence of an antifoam for 5
minutes,
then an average air content of 4% by volume is obtained. By adding in each
case
5 mg/I of an effective deaerator to the paper stock suspension, this value is
significantly
reduced, meaning that it is a measure of the effectiveness of a deaerator.
After testing, the temperature of the paper stock suspension in each case was
30 or
C, the temperature being kept constant to +/- 1 C during the 5 minute test. In
this
35 terminology, the more effective the antifoam, the lower the average air
content in the
paper stock suspension.
The parts stated in the examples are parts by weight.
0000070862 CA 02821380 2013-06-12
14
The C16/18-fatty alcohol used below as component A consists to 32% by weight
of a
linear C16-alcohol, to 67% by weight of a linear C18-alcohol and to 1% by
weight of a
linear Caralcohol. The melting range of this mixture is 51 to 52 C.
The C20.-alcohol used in the comparative examples as component A consisted of
3%
by weight of a linear C18-alcohol, 45% by weight of a linear C20-alcohol, 25%
by weight
of a linear C22-alcohol, 15% by weight of a linear C24-alcohol and 12% by
weight of
higher alcohols. The melting range of this mixture was 45 C to 54 C.
The polyglycerol ester used as component B was prepared by esterifying a
polyglycerol
mixture consisting of 27% diglycerol, 44% triglycerol, 19% tetraglycerol and
10% more
highly condensed polyglycerols with behenic acid. The degree of esterification
was
60%.
The hydrocarbon (paraffin) used as component C has a melting point of 38 C.
The surface-active substances used were:
sodium salt of the sulfuric acid half-ester of isooctylphenol ethoxylated with
25 mol/mol
of ethylene oxide as anionic emulsifier;
anionic copolymer of 70% by weight of acrylamide and 30% by weight of acrylic
acid
with a K value of 270.
Example 1
The components of the oil phase were firstly heated to a temperature of 110 C
and
then incorporated into the aqueous phase heated to 80 C by means of a
dispersing
device.
The oil phase had the following composition, based on the total weight of the
emulsion:
= 20 parts of the Cm/18-fatty alcohol,
= 9 parts of paraffin and
= 1 part of polyglycerol ester.
The water phase consisted, based on the total weight of the emulsion, of:
= 68.3 parts of water,
= 1 part of the anionic emulsifier,
= 0.5 part of the anionic copolymer and
= 0.2 part of sodium hydroxide solution.
..
0000070862 CA 02821380 2013-06-12
.
,
The physical properties and the deaerating effect of this emulsion are given
in table 2.
The examples and comparative examples given in table 1 were prepared in an
analogous manner. The quantitative data are % by weight, based on the total
weight of
5 the emulsion. The composition of the water phase corresponded
in all examples to the
water phase of example 1. The physical properties and the deaerating effect of
this
emulsion are given in table 2.
Table 1:
Example 1 2 3 4 5 Cl C2 C3 C4
Component
Cm/la-fatty 20 20 20 20 17.5 20 20 10 10
alcohol
C20,-alcohol -- -- -- -- 2.5 -- -- 10
5
Polyglycerol 1 1 -- 1 -- -- 1 1
ester
Behenyl 3 3 -- -- -- -- -
-
behenate .
Paraffin 9 7 -- -- 9 -- 10 9 9
Palm oil -- -- 9 7 -- 10 -- -- -
-
Table 2: Physical properties and deaerating effect of the antifoams
Average particle Viscosity Solids content Air
content [%]
size [urn] [mPa.s] [ /0] 30 C 40 C
1 2.1 420 29.8 0.1 0.1
2 2.2 470 29.9 0.1 0.1
3 2.1 450 29.7 0.2 0.2
4 2.0 490 29.8 0.2 0.2
5 2.3 440 29.9 0.3 0.2
Cl 2.2 390 29.7 0.8 1.0
C2 2.2 420 29.8 1.0
1.2
C3 2.6 360 29.8 0.5
0.4
C4 2.3 390 29.9 0.4
0.4
