CA1297755C

CA1297755C - Antifoam based on oil-in-water emulsions

Info

Publication number: CA1297755C
Application number: CA000527491A
Authority: CA
Inventors: Jaroslav Melzer; Wolfram Bergold
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1986-01-23
Filing date: 1987-01-16
Publication date: 1992-03-24
Anticipated expiration: 2009-03-24
Also published as: JPS62171715A; EP0230977A2; EP0230977A3; DE3601929A1

Abstract

Abstract of the Disclosure: In antifoams based on oil-in-water emulsions, the oil phase of the emulsion contains (a) C12-C26-alcohols, distillation residues which are obtained in the preparation of alcohols by the oxo synthesis or by the Ziegler method and/or (b) fatty acid esters of a C12-C22-carboxylic acid with a monohydric, dihydric or trihydric C1-C18-alcohol and, if required, (c) a hydrocarbon having a boiling point above 200°C
or a fatty acid of 12 to 22 carbon atoms, accounts for from 15 to 50% by weight of the emulsion, has a mean particle size of < 25 µm and furthermore contains finely divided, virtually water-insoluble, inert solids which have a particle diameter of <20 µm and which have not been rendered hydrophobic.

Description

- 1 - O.Z. 0050/38227 Antifoam based on oil-in-water emulsions German Patent 2,157,033 discloses a process for defoaming aqueous systems by means of emulsions which con-tain C12-C22-alkanols and/or C12-C22-fatty acid esters of dihydric or trihydric alcohols, as well as liquid paraf-fin and/or C12-C22-fatty acids as antifoams and conven-tional surfactants as emulsifiers. The emulsified water-insoluble substances have a mean particle size of from 4 to 9 ~m. The known antifoam emulsions have the disadvan-tage that they cream during storage and in some cases eventhicken to such an extent that such mixtures can then no longer be pumped.
U.S. Patent 3,408,306 discloses a process for de-foaming aqueous systems, in which the antifoam mixture used cons;sts of from 80 to 97X by weight of a water-soluble hydrophobic organic liquid (eg. a mineral oil, long-chain alcohol, ester or amine) and from 3 to 20~ by weight of finely divided solids (eg. silica, bentonite, talc or titanium dioxide), which have been rendered hydro-phobic. The antifoam mixture can, if required, containup to 5~ by weight of surfactant. An essential feature of these antifoam mixtures is that the finely divided solids are rendered hydrophobic with substances (eg. di-methylpolysiloxane oils) which are usually used as anti-foams. The preparation of finely divided solids which havebeen rendered hydrophob;c is technically complicated.
European Patent Appl;cat;on 149,812 discloses that antifoams which are based on oil-in-water emulsions in which the oil phase of the emulsion contains (a) a C12-C26-alcohol, distillation residues which are obtained in the preparation of higher alcohols by the oxo synthesis or by the Ziegler method and which may or may not be oxyalkylated, and/or (b) a fatty acid ester of a C12-C22-carboxylic acid with a monohydric, dihydric or trihydric C1-C18-alcohol and, if required, (c) a hydrocarbon having a boiling point above 200C

.~ ~

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- 2 - O.Z. 0050/38227 or a fatty acid of 12 to 22 carbon atoms, accounts for from 15 to 60% by weight of the emulsion and has a mean particle size of from 0.5 to 15 ~0 can be stabi-lized to prevent an increase in viscosity and creaming during storage by adding from 0.05 to 0.5% by weight of a high molecular weight, water-soluble homopolymer or copoly-mer of acrylic acid, methacrylic acid, acrylamide or meth-acrylamide.
It is an object of the present invention to make the known antifoams more environmentally compatible, ie.
to reduce the chemical oxygen demand in wastewaters, while substantially or completely maintaining the efficiency.
~ e have found that this object is achieved, accor-ding to the invention, by antifoams based on oil-in-water emulsions in which the oil phase of the emulsions contains (a) a C1z-Cz6-alcohol, dist;llation residues which are obta;nable in the preparation of higher alcohols by the oxo synthesis or by the Ziegler method and which may or may not be oxyalkylated, and/or (b) a fatty acid ester of a C12-Cz2-carboxylic acid with a monohydric, dihydric or trihydric C1-C18-alcohol and, if required~
(c) a hydrocarbon having a boiling point above 200C
or a fatty acid of 12 to 22 carbon atoms, accounts for from 5 to 50% by weight of the emulsion and has a mean particle size of < 25 ~m, if the oil-in-water emulsions contain finely divided, virtually water-insoluble, inert solids whose surface has not been rendered hydro-phobic.
Component (a) of the oil-in-water emulsions con-sists in particular of natural or synthetic alcohols of 1Z to 26 carbon atoms or mixtures of alcohols. Examples are myristyl alcohol, cetyl alcohol and stearyl alcohol.
The synthetic alcohols, which are obtainable, for examPle, by the Ziegler method by oxidation of aluminum alkyls, are saturated, straight-chain, unbranched alcohols. Synthetic alcohols are also obtained by the oxo synthesis, this method 12~

- 3 - O.Z. 0050/38227 generally giving mixtures of alcohols. Distillation resi-dues which are obtained in the preparation of the above alcohols by the oxo synthesis or by the Ziegler method may also be used as component (a) of the oil phase of the anti-foam emulsions. Other suitable components ta) of the saidoil phase are oxyalkylated distillation residues which can be obtained by the above process for the preparation of higher alcohols by oxo synthesis or by the Ziegler method.
The oxyalkylated distillation residues are obtained by reacting the above distillation residues with ethylene oxide or propyLene oxide or with a mixture of these. U~
to S ethylene oxide or propylene oxide groups undergo addition per OH group of the alcohol in the distillation residue. Preferably, 1 or 2 ethylene oxide groups are added per OH group of the sa;d alcohol.
Fatty acid esters of C12-C22-carboxylic acids w;th a monohydric, dihydric or trihydric C1-C1g-alcohol are used as component (b) of the oil phase of the anti-foam emulsion. The fatty acids on which the esters are based are~ for example, lauric acid, myr;stic acid, palmi-tic acid, stearic ac;d, arachic acid and behenic acid.
Palm;tates and stearates are preferably used. The stated carboxylic ac;ds can be esterified using monohydric C1-C1~-alcohols, eg. methanol, ethanol, propanol, butanol, hexa-nol, decanol or stearyl alcohol, as well as dihydric alco-hols, such as ethylene glycol, or trihydric alcohols, such as glycerol. The ~olyhydric alcohols may be completely or partially ester;f;ed. The oil phase of the antifoam emulsions contains a compound of component (a) or (b) or a mixture of components (a) and (b).
The components (a) and (b) can be used in any ratio for the preparation of the antifoams. In practice, for example, mixtures of (a) and (b) which contain from 40 to 60% by weight of (a) and from 60 to 40~ by weight of (b) have proven useful.
The oil phase of the emulsion may additionaLly con-tain a further class of water-insoluble compounds, which ~2~
- ~ - O.Z. 0050/382Z7 is referred to below as component (c). The compounds of component (c) can account for up to 50~ by weight, based on components (a) and (b), of the oil phase of the antifoam emulsion. They may be added either to a mixture of com-ponents (a) and (b) or to each of the compounds statedunder (a) or (b). Suitable components (c) are hydrocarbons having a boiling point of more than 200C under 1013 mbar and a pour point of less than 0C, and fatty acids of 12 to 22 carbon atoms. Preferred hydrocarbons are liquld paraffins, such as the commercial paraffin mixtures, which are also referred to as white oil.
The above compounds (a) and/or (b) and, if required, (c) form the oil phase of the oil-in-water emulsions.
This phase accounts for from S to 50% by weight of the oil-in-water emulsion, wh;le the aqueous phase accounts for from 95 to 50~ by weight of the said emulsion, the percen-tages in each case summing to 100. The mean particle size of the oiL phase of the said emulsion is less than 25 ~m, preferably from 0.5 to 15 ~m.
The essential feature of the present invention is that the oil phase of the oil-in-water emulsions contains finely divided, virtually water-insoluble inert solids whose surface has not been rendered hydrophobic. The par-ticle diameter of the said solids is less than 20 ~m, pre-ferably from 0.1 to 10 um. The novel antifoams can also be prepared by a method in which the finely d;vided, inert solids are emuls;f;ed in a conventional oil-in-water anti-foam, for example ;n an emuls;on of compounds (a) and/or (b) and, ;f required, (c) in water. For the novel anti-foams, it ;s poss;ble to use any ;nert solids which do notreact w;th the components of the antifoam mixture and fur-thermore are virtually insoluble ;n water. Preferably used inert solids are kaolin, chalk, calc;um sulfate, barium sulfate, talc, microcrystalline cellulose and/or crosslinked starch. Regarding the suitability of solids, there are no restrictions apart from the fact that the solids should be inert and should not have been rendered ~;~97~iS
- 5 - O.Z. 0050/38227 hydrophobic. 30th inorganic and organic solids which have not been surface-treated can be used. Examples of suit-able solids apart from those mentioned above are sheet silicates, such as bentonite, montmorillonite, nontronite, hectorite, saponite, volkonskoite, sauconite, beidellite, allevardite, illite, halloysite, attapulgite and sepiolite, and titanium dioxide, alumina, s;l;ca, satin white, syn thetic aluminum silicates, crosslinked urea/formaldehyde, melamine/formaldehyde and melamine/isobutyraldehyde conden-sates and homopolymers and copolymers of styrene, whichare disclosed in, for example, ~ritish Patent 1,229,503.
Urea/formaldehyde condensates, which are also referred to as methyleneureas, were obtained by condensing preconden-sates of urea and formaldehyde in a molar ratio of 1 or less than 1 in the presence of a strongly acidic catalyst at a pH of less than 2 (cf. German Published Application DAS 2,110,309) or by the process of U.S. Patent 3,931,063.
The condensates obtainable as described in German Laid-Open Application DOS 2,547,966 are also suitable. Mixtures of the inert inorganic solids, of the inert organic solids or of the inert inorganic solids with the inert organic solids may be used. The finely divided inorganic and organic solids are used in a form which has not been ren-dered hydrophobic and the~refore do not require any prior coating or treatment with substances which impart hydro-phobic propert;es.
The solids are preferably used ;n an amount such that they replace from 5 to 30X of the oil phase of the oil-in-water emulsions.
The novel antifoams are preferably prepared by a method in which first the finely divided inert solids are homogenized with the compounds (a) and/or (b) and, if required, (c), and the resulting m;xture ;s thèn emulsi-fied in water. The antifoams according to the invention may also be prepared by emulsifying the finely divided inert solids in a known oil-in-water antifoam, for example in an emulsion of the compounds (a) and/or (b) and, if ~z~ s - 6 - O.Z. 0050/38227 required, (c) in water. If the organic compounds which form the oil phase are solid substances at room temperature, they are first melted. One or more finely d;vided inert solids are then introduced into the melt, thorough mixing of the components being ensured. Components ~a) to (c) can be m;xed with the inert solids at from 50 to 100C.
The result;ng mixture ;s then emulsified in water in order to prepare the oil-in-water emulsion. This is done using the conventional surfactants, which have an HLE value of more than 6. These surfactants are oil-in-water emulsi-fiers or typical wetting agents. Among the surfactants, anionic, cationic or nonionic compounds may be used.
Anionic or nonionic surfdctants or mixtures of the two are preferably employed. Examples of substances of the stated type ar~ sodium salts or ammonium salts of higher fatty acids, such as ammonium oleate or stearate, oxyalkylated alkylphenols, such as nonylphenol or isooctylphenol, which have been reacted with ethylene oxide in a molar ratio of from 1:2 to 1:50, oxyethylated unsaturated oils, for 20 example the reaction products of 1 mole of castor oil and from 30 to 40 moles of ethylene oxide, and the reaction products of 1 mole of sperm oil alcohol with from 60 to 80 moles of ethylene oxide. Other preferably used emulsi-f;ers are sulfonated oxyethylation products of nonylphenol 25 or octylphenol, wh;ch are ;n the form of the sodium or ammonium salt of the corresponding sulfuric acid half-ester. 100 parts by weight of the oil-in-water emulsions usually contain from 0.5 to S parts by weight of an emulsi-fiQr or an emulsifier mixture. A major part of the emulsi-fier is dissolved in the aqueous phase. In addition tothe emulsifiers stated above, it is also possible to use protective colloids, such as high molecular weight poly-saccharides and soaps or other conventional additives, such as stabilizers (reference may be made to European Patent Application 149,812.
~---- ~The oil phase (a mixture of components (a) to (c) and the inert solids) can be emuls;f;ed us;ng a 77~;S
.
- 7 - O.Z. 0050/38227 conventional apparatus, for example a disperser. If the oil phase is in the form of a solid material, it is first melted and then emulsified in water. Emulsification of the oil phase in water can be carried out at room temper3-ture or elevated temperatures, for example at from 50 to 95C ~
Directly after the preparation, the antifoam emul-sions have a viscosity of from 300 to 700 mPa.s. Surpris-ingly, the oil-in-water emulsions suffer virtually no loss of efficiency as antifoams as a result of adding the inert solids, which in themselves are not effective as antifoams.
The particle size of the inert, water-insoluble solids is always less than the particle size of the oil phase of the oil-in-water emulsion and is no higher than 95~ of the part;cle s;ze of the part;cular o;l-;n-water emwls;on used.
The novel o;l-in-water emulsions are used as anti-foams in foam-forming aqueous systems in an amount of about O.OZ-0.5, preferably 0.05-0.3, part by weight of the antifoam emulsion per 100 parts by weight of a foam-forming med;um. The ant;foam emulsions according to the invention are used in particular as antifoams in papermaking, and are employed both in sulfite pulp cooking and in paper-making, in the paper stock and in paper coating compounds.
The antifoams can also be used for controlling foam in the food industry, in the starch industry and ;n waste-water treatment plants.
In the Examples, parts and percentages are by weight. The mean particle size of the particles of the oil phase which are emulsified in water was determined with the aid of a Coulter counter, the particle diameter of the inert solids was from 0.5 to 15 ~m.
Determination of the foam value:
5 l of a foam-forming paper stock suspension are circulated for 5 minutes in a channel made of transparent plastic. The amount of foam formed on the surface of the stock suspension is then measured in units of area (cm2) ~297~$~
- 8 - O.Z. OOSO/38227 with the aid of a grid on the wall of the channel and is stated as the foam value for assessing the efficiency of an antifoam.
If the paper stock susPension is circulated in the absence of an antifoam, the foam value after S minutes is 1200 cm2. ~y adding, in each case, 2 mg/l of an effec-tive antifoam to the paper stock suspension, this value is substantially reduced, so that it constitutes a measure of the efficiency of an antifoam. However, if instehd of an antifoam 2 mg/l of an inert, finely divided (O.S-15 ~m) solid which has not been rendered hydrophobic is aJded, for example kaolin, CaS04, talc, chalk, barium sulfate, crosslinked starch, TiO2, bentonite, Al203 or SiO2, the foam value does not change.

20.5 parts of a mixture of glycerol triesters of C16-C1g-fatty acids, a C16-C20-fatty alcohol mixture and a mineral oil in a weight ratio of 14:10:6 are mixed with 10 parts of kaolin (mean particle diameter of more than 94% of the particles less than 1 ~m) at 70C in a stirred container. This mixture is then emulsified in a sol-ution of 2 parts of an emulsifier tadduct of 25 moles of ethylene oxide with 1 mole of isooctylphenol whlch has been reacted with sulfuric acid to give the sulfuric acid half ester) in 67.5 parts of water. Advantageously, the aqueous phase is initially taken in a dis~erser and the kaolin-containing oil phase is added. The resulting oil-in-water emulsion has a viscosity of 450 mPa.s at 20C
directly after the preparation and gives a foam value of 191 cm2 on testing the antifoam action. The mean par-ticle size of the oil phase is 3 ~m.

30.5 parts of an oil phase consisting of glycerol triesters of C16-C1g-fatty acids, a C16-C20-fatty alcohol mixture and a mineral oil in a weight ratio of 14:10:6 are emulsifled at 70C in a disperser in 69.5 parts of an aqueous phase comprising 67.5 parts of water and 2 parts 7'~$

- 9 - 0.Z. 0050/38227 of emulsifier (adduct of 25 moles of ethylene oxide ~ith 1 mole of isooctylphenol which has been reacted wieh sulf-uric acid to give the sulfuric acid half ester). The mean particle size of the oil phase is 3 ~m~ When the efficiency as an antifoam is tested, a foam value of 189 cm2 is determined.
As shown by this Comparative Example, the content of kaolin surprisingly produces virtually no reduction in the efficiency of the antifoam according to Example 1.
~XAMPLE 2 15.5 parts of a mixture of glycerol triesters of C16-Clg-fatty acids, a C16-Czo-fatty alcohol mixture and a mineral oil in a weight ratio of 14:10:6 are mixed with 15 parts of kaolin (mean particle size of 94X of the particles less than 1 ~m) at 70C and then emulsified directly in 69.5 parts of a solution of 2 parts of the emulsifier described in Example 1 in 67.5 parts of water.
The mean particle diameter of the oil phase of the oil-in-water antifoam emul,ion is 2.5 ~m. On testing the efficiency of the emulsion as an antifoam~ a foam value of 182 cm2 is determined.

25.5 parts of a mixture of glycerol triesters of C16-C1g-fatty acids, a C16-C20-fatty alcohol mixture and a mineral oil in a weight ratio of 14:10:6 are heated to 70C and mixed w;th S parts of a finely divided chalk (mean particle diameter of 96X of the particles less than 1 ~m). This Inixture is then emulsified in 69.5 parts of an aqueous solution which contains 2 parts of the emulsi~
fier described in Example 1 dissolved in 67.5 parts of water. The oil phase of the resulting oil-in-water emul-sion has a mean particle size of 3.5 ~m. On testing the efficiency as an antifoam, a foam value of 194 cm2 is determined by the method of measurement described above.

15.5 parts of a mixture of glycerol triesters of C16-C1g-fatty acids, a C16-C20-fatty alcohol mixture ~2g~7~
- 10 - O.Z. 0050/38227 and 3 mineral oil in a weight ratio of 14:10:6 are heated to 70C and mixed with 15 parts of chalk in which 96~ of the particles have a mean particle size of less than 1 ~m.
This mixture is then emulsified directly in 69.5 parts of S a solution of 2 parts of the emulsifier described in Example 1 in 67.5 parts of water. The mean particle size of the oil phase of the resulting oil-in-water emulsion is 3.5 ~m. On testing the efficiency of this emulsion as an antifoam by the method described above, a foam value of 187 cm2 is obtained.

15.5 parts of a mixture of glycerol triesters of C16-C1g-fatty acids, a C16-C20-fatty alcohol mi~ture and a mineral oil in a weight ratio of 14:10:6 are heated to 70C and mixed thoroughly with 15 ~arts of calcium sul-fate having a mean particle size of 0.2 ~m. This mixture is then emulsified in 69.5 parts of an aqueous solution of 2 parts of the emulsifier described in Example 1. An oil-in-water emulsion results whose oil phase has a mean particle size of 3 ~m and which gives a foam value of 196 cm2 when tested as an antifoam by the method stated above.

15.5 parts of a mixture of glycerol triesters of C16-C1g-fatty acids, a C16-C1g-alcohol mixture and a mineral oil in a weight ratio of 14:10:6 are heated to 80C and mixed thoroughly with 15 parts of talc having a mean particle size of 0.5 ~m. This mixture is then emul-sified in 69.5 parts of an aqueous solution of 2 parts of the emulsifier described in Example 1. An oil-in-water emulsion results whose oil phase has a mean particle size of 3 um and which gives a foam value of 186 cm2 when tested as an antifoam by the method stated above.

15.5 parts of a mixture of glycerol triesters of C16-C1g-fatty acids, a C16-C20-fatty alcohol mixture and a mineral oil in a weight ratio of 14:10:6 are heated ~ 7~.~5 ~ O.Z. OOSO/38Z27 to 70C and mixed thoroughly with 15 parts of a microcrys-talline cellulose having a mean particle size of less than 1 ~m. This mixture is then emulsified in 69.5 parts of an aqueous solution which contains 2 parts of the emulsifier S described in Example 1. An oil-in-water emulsion results whose oil phase has a particle size of 4 ~m and which gives a foam value of 200 cm2 on testing the efficiency as an antifoam by the method described above.

15.5 parts of a mixture of glycerot triesters of C16-C1g fatty acids, a C16-C20-fatty alcohol mixture and a mineral oil in a weight ratio of 14:1G:6 are heated to 80C
and homogenized with 15 parts of a commercial crosslinked starch whose mean particle size is less than 5 ~m. The m;xture thus obtained is then emulsified in 69.5 parts of an aqueous solution containing 2 parts by weight of the emulsifier described in Example 1. The oil phase of the resulting oil-in-water emulsion has a particle size of 8 ~m. On testing the efficiency as an antifoam, a foam 0 value of 179 cm2 is determined for this emulsion.

3 parts of kaolin (particle diameter of 94% of the particles < 1 ~m) are added, at 30C, to 100 parts of an emulsion of 30 parts of a mixture of glycerol triesters of C16-C1g-fatty acids, a C16-C20-fatty alcohol mixture and a mineral oil in a weight ratio of 14:10:6 in 70 parts of water which contains, in solution, 2 parts by weight of the emulsifier described in Example 1. The mixture is homo-genized in a disperser. The particle size of the oil phase of the resulting emulsion is 6 um. In the test described above, the emulsion g;ves a foam value of 184 cm2.

Example 9 is repeated, except that, instead of 3 parts, 12 parts of kaolin of the stated sPecification are added in this case. An antifoam emulsion is obtained whose oil phase has a particle size of 6 ~m and which gives a foam value of 186 cm2 when tested by the above method.

Claims

1. An antifoam based on an oil-in-water emulsion, in which the oil phase of the emulsion accounts for from 5 to 50% by weight of the emulsion, has a mean particle size of < 25 µm and contains (a) a C12-C26-alcohol, distillation residues which are obtainable in the preparation of higher alcohols by the oxo synthesis or by the Ziegler method and which may or may not be oxyalkylated, and/or (b) a fatty acid ester of a C12-C22-carboxylic acid with a monohydric, dihydric or trihydric C1-C18-alcohol and, if required, (c) a hydrocarbon having a boiling point above 200°C
or a fatty acid of 12 to 22 carbon atoms, wherein the oil-in-water emulsion contains finely divided, virtually water-insoluble, inert solids which have a particle diameter of <20 µm and whose surface has not been rendered hydrophobic.

2. An antifoam as claimed in claim 1, wherein the non-aqueous components of the oil-in-water emulsion consist of from 50 to 99.9% by weight of the oil phase and from 50 to 0.1% by weight of finely divided, virtually water-insoluble, inert solids which have a particle diameter of < 20 µm and whose surface has not been rendered hydrophobic.

3. An antifoam as claimed in claim 1 or 2, wherein kaolin, sheet silicates, chalk, calcium sulfate, barium sulfate, talc, titanium dioxide, alumina, silica, satin white, microcrystalline cellulose, urea/formaldehyde or melamine/formaldehyde condensates and/or crosslinked starch or mixtures of these are used as finely divided, virtually water-insoluble, inert solids whose surface has not been rendered hydrophobic.

4. A process for the preparation of an antifoam as claimed in claim 1, wherein the finely divided, inert solids whose surface has not been rendered hydrophobic are first homogenized with the compounds (a) and/or (b) and, if required, (c), and the mixture is then emulsified in water.

5. A process for the preparation of an antifoam as - 13 - O.Z. 0050/38227 claimed in claim 1, wherein the finely divided, inert solids whose surface has not been rendered hydrophobic are emulsified in an emulsion of the compounds (a) and/or (b) and, if required, (c) in water.