CA1143244A

CA1143244A - Defoaming composition

Info

Publication number: CA1143244A
Application number: CA000362585A
Authority: CA
Inventors: Robert E. Gansser; Gilbert S. Gomes
Original assignee: DIVERSEY Corp (THE)
Current assignee: DIVERSEY Corp (THE)
Priority date: 1979-10-22
Filing date: 1980-10-16
Publication date: 1983-03-22

Abstract

DEFOAMING COMPOSITION
Abstract of the Disclosure A defoaming composition for controlling and suppres-sing foam and dispersed air in aqueous systems. The composi-tion of this invention is particularly useful in pulp and paper mill operations and comprises:
a) a polyoxyethylene adduct of a polyoxypropylene hydrophobic base, said hydrophobic base having a molecular weight of about 3500 to 4500 and an oxyethylene content of about 2 to 20 percent by weight of the total molecule, b) a water insoluble solvent, c) a normally solid fatty acid amide, and d) a fatty alcohol mixture which may also include other hydrocarbons.
In addition to the above, the composition may include hydro-phobic silica particles.

Description

`~ ~1432~4 ~- DEFOAMING COMPOSITION
Background of the Invention 1. Field of the Invention The present invention relates generally to defoaming compositions for controlling and suppressing foam and dispersed air in aqueous systems. The composition of this invention is -~ particularly useful in pulp and paper mill operations~

- 2. Description of the Prior Art There are many industrial processes in which aqueous solutions or suspensions are processed. Frequently, due to the nature of the components in the aqueous system, foam and dispersed air present a serious problem which must be prevented or mitigated to prevent interference by the foam and dispersed air with the efficient conduct of the process.
Illustrative of types of aqueous systems in which such problems occur are cellulosic suspensions of the type used in the manufacture of various types of paper, sewage disposal systems, detergent-containing systems, saponin-containing systems, protein-containing systems, and the like.
In the paper industry, these problems are encountered in black liquor which is the spent cooking liquor obtained after cooking of wood pulp in accordance with the sulfate or Kraft process, particularly during the evaporation of black liquor prior to the recovery of the chemicals in the black liquor.
- Foam and dispersed air are also problems in the handling and utilization of Kraft paper slurries, sulfide pulp slurries, and ground wood pulp slurries, and paper-making machines, 11~324~

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including machines used prior to formation of the fibrous matter, such as beaters, refiners, mixers, and flow boxes.
Similarly, many protein-containing systems such as solutions of soybean protein extract, present these problems.
Statement of Relevant Patents Patent No. Inventor Assignee Date 4,032,473 Berg et al Assoc. Chem. Inc. 6/28/77

3,959,176 Mahn et al Drew Chem. Corp. 5/25/76 3,935,121 Lieberman et al Betz Labs. 1/27/76 3,923,683 Michalski et al Nalco Chem. Co. 12/2/75

4,032,473 discloses a water-based defoamer composi-tion in the form of aqueous emulsions containing a water-insoluble liquid hydrocarbon such as mineral oils; normally solid fatty acid diamides such as, for example, N,N'-ethylene bis-distearamide; hydrophobic silica particles and a nonionic emulsifier including various alkylene oxide compositions.
3,959,176 discloses a solid non-foaming dispersing composition comprising a block copolymer of polyoxyethylene and polyoxypropylene having an average molecular weight of from about 1000 to about 25,000, preferably from about 1500 to 15,000, with polyethylene being present in the block copolymer in an amount from about 5 percent to about 80 percent, prefer-ably 20 percent to 80 percent. Both the disclosure and claims of this patent are strictly limited to such block copolymers where the chain is terminated at both ends by polyoxypropylene.
The composition comprises such block copolymer in combination "

~ 1143244 with hydrophobic silica and an organic spreading liquid such as mineral oil.
3,923,683 discloses an antifoam composition com-prising a liquid hydrocarbon oil such as mineral oil, a bis-amide, and finely-divided hydrophobic silica.
3,935,121 discloses a foam control composition which comprises an organic emulsifier which may be cationic, anionic or nonionic, or mixtures thereof; a liquid hydrocarbon carrier such as mineral oil; and an amide which may be ethylene bis-stearamide.
Summary of the Invention The instant invention is directed to a defoaming composition particularly useful in the pulp and paper industry.
This composition comprises:
; a) a block copolymer polyoxyethylene adduct of a polyoxypropylene hydrophobic base. The hydro-phobic base has a molecular weight of about 3500 to 4500. The oxyethylene content is about 2 percent to 20 percent by weight of the total molecule and both ends of the block copolymer chain are polyoxyethylene;
b) water-insoluble solvent;
c) normally solid fatty acid amide, and d) a fatty alcohol mixture.
In addition, the composition may contain hydro-phobic silica particles.

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Description of the Preferred Embodiments It is preferred that the composition contain by weight about 1 to 10 percent, and most preferably about 2 to 5 percent, of the polyoxyethylene-polyoxypropylene copolymer (a). Such a compound is preferably a cogeneric ~ mixture of conjugated polyoxyalkylene compounds containing in ; its structure hydrophobic chain of units selected from the group consisting of oxypropylene and oxypropylene-oxyethylene units in which the oxygen/carbon atom ratio does not exceed 0.40 and at least one hydrophilic chain of units selected from the group consisting of oxyethylene and oxyethylene-oxy-propylene units in which the oxygen/carbon atom ratio is ,; greater than 0.40. This compound is usually represented by the generalized formula Ho(c2H4o)m(c3H6o)n(c2H4o)nH

wherein n has a value such that the molecular weight of the C3H6O groups ranges from about 3500 to 4500 and m has a value such that the C2H4O groups represent 10 percent of the total molecular weight.
The composition contains about 50 to 95 percent by weight, and preferably 80 to 90 percent by weight, of the water-insoluble solvent (b). The preferred solvents are those having a viscosity of~ about 30 SUS to 400 SUS at 100F and a boiling point of at least 150F. The boiling point of the solvent should be at least equal to the melting point of the fatty acid amide component. For example, with ethylene .

~143Z44 distearamide, a solvent having a boiling point greater than about 280F should be used. Suitable solvents include mineral hydrocarbons such as mineral oil, seal oil, and similar petroleum fractions, kerosene, naphtha, benzene, heptane, octane, etc., liquid halo hydrocarbons, long-chain alchols - such as oxoalcohols (C10 and higher), nonyl or octyl : alcohols, etc.; long-chain amines such as 2-ethyl-1-amino-heptane; long-chain esters such as diglycol laurate; fatty acids such as vegetable oils, etc. If desired, mixtures of any two or more of these or other similar solvents may be employed.
It is preferred to employ by weight about 0.5 to 10 percent, and more preferably about 1 to 5 percent, of the fatty amide (c). Useful amides include those obtained by reaction of a polyamine containing at least one alkylene group having from 2 to 6 carbon atoms and a fatty acid having from 6 to 25 carbon atoms, for example, the amide obtained by the reaction of a polyamine and a fatty acid or mixture of fatty acids such as hexanoic, decanoic, capric, myristic, arachidic, behenic, lauroleic, linoleic, linolenic, lauric, palmitic, oleic and stearic acids; hydroxy acids such as ricinoleic acid or naphthenic acids such as are obtained as by-products from the refining of petroleum. Natural mixtures of fatty acids such as tall oil acids, tallow fatty acids, ar.d the like, can also be used.
Diamides useful in the compositions of the invention are those obtained by reacting a polymethylene diamine con-taining from 2 to 6 methylene groups with a fatty acid, i.e., ~1~43Z44 long-chain aliphatic carboxylic acid having about 10 to 20 ; carbon atoms in the chain. Diamides based on fatty acids having 16 to 18 carbon atoms are preferred. A particularly preferred fatty acid diamide is the diamide formed from stearic acid and ethylene diamine, i.e., N,N'-ethylene distearamide.
The fatty alcohol mixture (d) is preferably employed in an amount by weight of about 2 to 20 percent and more preferably, 4 to 12 percent. Preferably, this is a mixture of fatty alcohols having about 10 to 40 carbon atoms.
This mixture may also include other hydrocarbons having about 20 to 50 carbon atoms. However, in the interest of simplicity of description, this mixture is referred to in the specification and claims as "fatty alcohol mixture" even though it may include such other hydrocarbons.
In addition to the above, the composition may include hydrophobic silica particles in an amount by weight of about 0.1 to 10 percent, and preferably 0.5 to 5 percent. For example, silica aerogel, fume silica, and precipitated silica, which have been treated in some manner to render them ` hydrophobic, may be employed. Any suitable method can be used to impart the required hydrophobic characteristic such as treatment with organo-chlorosilane vapors or long-chain amines, heating with~silicone oil, etc. The hydrophobic silica particles desirably should have an average particle size of less than one micron. A commercially available hydrophobic silica obtained by reacting precipitated silica . , .

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with an organic silicon compound and having an ultimate particle size of 15 millimicrons, a surface area of about 120 square meters per grams and a pH of about 11.5 has been used with good results. Such a product is manufactured by Philadelphia Quartz Company, Philadelphia, Pennsylvania, and marketed as QUSO WR-82.
The defoamer composition of this invention is generally prepared by first preparing a master batch of all four components or five components where the hydrophobic silica is employed. Such master batch is prepared by charging the solvent to a container in which it is heated and mixed.
The polyoxyethylene-polyoxypropylene copolymer, fatty alcohol mixture, and fatty acid amide are then added and the tempera-ture raised a sufficient amount to melt the amide. This is then mixed until a clear, air and foam-free liquid melt is achieved. The mixer is then stopped for a few minutes to allow all air to escape and then the mixing is continued at slow speed.
Additional solvent is charged to another con-tainer and mixed in a fast mixing operation. The master batch is then slowly added with rapid mixing but the temperature should not exceed 120F. The batch is then cooled to 75 to 85DF by any suitable conventional means and mixer speed is reduced to minimize air pickup.
The novel defoamer composition is utilized by adding a small amount to the aqueous system in which control of foaming is desired. The exact quantity required to control .,:

1~3Z~4 foam will vary widely, depending upon the nature of the liquid being treated, the individual defoamer composition, and upon the amount of foam and air dispersion which can be tolerated in the process. Typically, an amount ranging from about 1 ppm to about 1.0 percent by weight based upon the weight of the solids present in the system will be used. Although treatment levels above 1 percent are successful in controlling foam, the use of excesses above this level are not recommended due to cost considerations.
The present invention is further illustrated by the examples set forth below.
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In these examples, defoaming evaluations were carried out with a dynamic defoamer demonstration kit con-; sisting of three basic sections:
~- 1. A pump for recirculating the liquid under con-sideration and providing kinetic energy.
2. A foam producing section consisting of an air ; aspirator and impingement chamber.
3. A column to serve as a foam collectlng chamber and measuring device for both liquid and foam.
The column is filled with 500 mls. of the liquid under con-sideration and the pump started. As the liquid impinges into the impingement chamber, foam is created which overflows and settles upon the surface of liquid in the foam collecting chamber. Foam is permitted to rise to a height of 15 inches.
A drop of defoamer to be tested is added by means of a dropper.
At the instant the defoamer is added, a stopwatch is started.
If effective, the defoamer will cause the foam level to fall.
The time in seconds needed for the foam to reach its lowest point is noted ("quick kill time") along with the foam height at that point ("minimum foam height").
Pump operation and timing is continued and foam height gradually begins to climb. Eventually it will build to a height of 15 inches. A time reading is recorded as the - "persistence" of the`defoamer.
The motor and stopwatch are stopped and the test is . .
now complete. Some defoamers will suppress the foam for periods greater than ten minutes. It is generally recommended '' , -, ~1~3;~4~

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`' that the evaluation be terminated at ten minutes. If the foam has not reached 15 inches, the defoamer persistence reading should be recorded as greater than 10 minutes. Alternatively, a standard height of less than fifteen inches is selected depending upon the foaming tendency of the liquid under ; consideration. Persistence is then recorded as the time for the foam level to reach one or more standard heights.
The Kit is drained, flushed several times with water, cleaned as necessary and a second evaluation run on another defoamer, recording the "minimum foam heightn, "quick kill time" and "persistence".
An examination of the data sheets, when prepared for two or more defoamers under consideration, will give an ex-cellent comparative evaluation of their effectiveness on a basis of both initial foam suppressing capability as well as foam suppressing persistency.
This is an empirical test whereby comparing relative standings of the defoamers tested provides a guideline as to which defoamers may prove more effective. The kit is provided with a guartz heating element so that the temperature of the liquid can be maintained at that of the actual process liquid during the course of the trial. A thermometer is placed in the upper tube and the`desired temperature maintained by manually controlling~the heater control switch. Once the entire system (liquid and associated equipment parts) is warmed to the desired levels, very little additional heat will ~ be required to maintain temperature throughout the test.

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' ' 11~3Z44 Examples 1-8 Eight formulations employing all or part of the components of the instant invention, having the components in the proportions by weight set forth below in Table 1, were tested with a Dynamic Defoamer Demonstration Kit as described above at a temperature of 110F.

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The defoamer formulations were prepared by first preparing the master batch as described above. In Examples 1-7, the master batch was prepared at 270 to 280F whereby the ethylene distearamide was melted. In Example 8, the ethylene distearamide was not melted but was merely added with stirring to the other ingredients at room temperature. The master batch is then mixed with additional mineral oil at room temperature, all as described above.
Defoaming tests were conducted by adding one drop of defoamer from a dropping pipette to 500 milliliters of the foaming liquor in the foam collecting chamber of the demon-stration kit. The foaming liquor was a synthetic paper mill screen room process liquor which consisted of a solution of 12.5 parts per million of a polyoxyalkylene copolymer in tap water. The copolymer was a polyoxyethylene adduct of a polyoxypropylene hydrophobic base having a molecular weight of the hydrophobic base of about 1750 and an oxyethylene content s", of about 80 weight percent of the molecule. This was prepared by first preparing a stock solution of 0.25 grams of the nonionic in one liter of tap water. 25 milliliters of the stock solution was then added to 475 milliliters of tap water in the Dynamic Defoamer Demonstration Kit to prepare 500 milliliters of synthetic foaming liquor. One drop of the defoamer represents approximately 50 parts per million.
Immediately after the addition of one drop of defoamer to the foaming liquor, a stopwatch was started. The time required for the foam level to fall to its minimum value ("quick kill ',:

llA3244 time") as well as the level of foam ("minimum foam height") was recorded (these are set forth in Table 2 below as "Time to Min." and "Minimum"). After the foam reached the minimum level, the time required for the foam to build back up to the preselected levels indicated in Table 2 below was recorded (persistence).

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li432~4 The mineral oil employed was basically a still bottom mineral oil from the fractional distillation of petro-leum to produce gasoline and other conventional products. It is composed of 29.4 percent alkyl-substituted aromatics, 70.0 percent saturates, and 0.6 percent polar compounds. It has a boiling point range of from 313C to over 382C with a flash point C.O.C. (ASTM Spec. No. 1848) of 174C. The average molecular weight is 325. The carbon atom analysis revealed an average of 4 aromatic carbon atoms, 53 naphthenic carbon atoms, and 43 paraffinic carbon atoms. Such product is sold under the name SHELLFLEX 212 by the Shell Oil Company.
The fatty alcohol mixture was a blend of linear and branched alcohols having from 20 to 32 carbon atoms and ", ; hydrocarbons having from 24 to 40 carbon atoms. The alcohols compose approximately 66 percent by weight of the blend and the minimum hydroxyl value is 90 milligrams KOH/g, and the minimum congealing point is 43C. This product is sold by Ethyl Corporation under the trademark EPAL 20+ alcohol.
;: The nonionic was a polyoxyethylene adduct of a - 20 polyoxypropylene hydrophobic base having a molecular weight of the hydrophobic base of about 4000 and an oxyethylene content of about 10 weight percent of the molecule. The molecule is terminated on both ends with oxyethylene groups.
The hydrophobic silica was the product described above which is sold by the Philadelphia Quartz Company under the trademark QUSO WR-B2.

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As can be seen from the above Table, Examples 1 and

5, which do not contain the ethylene distearamide, and Example 4, which does not contain the alcohol mixture, are, with the exception of Example 8 f generally inferior to the other examples which contain all four of the essential com-ponents of applicants' invention. Example 8 shows inferiority in defoaming performance to the examples of the instant invention due to the fact that the ethylene distearamide was not melted but rather was simply added in finely-divided form with stirring to the other ingredients at room temperature.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A defoaming composition particularly useful for controlling and suppressing foam and air dispersion in aqueous systems comprising:
a) a polyoxyethylene adduct of a polyoxypropylene hydrophobic base, said hydrophobic base having a molecular weight of about 3500 to 4500 and an oxyethylene content of about 2 to 20 percent by weight of the total molecule, b) a water insoluble solvent, c) a normally solid fatty acid diamide, and d) a fatty alcohol mixture.

2. A defoaming composition particularly useful for controlling and suppressing foam and air dispersion in aqueous systems comprising by weight:
a) 1-10% of a polyoxyethylene adduct of a polyoxy-propylene hydrophobic base, said hydrophobic base having a molecular weight of about 3500 to 4500 and an oxyethylene content of about 2 to 20 percent by weight of the total molecule, b) 50-95% of a water insoluble molecule, c) 0.5-10% of a normally solid fatty acid diamide, and d) 2-20% of a fatty alcohol mixture.

3. A process for suppressing foaming and air dispersion in an aqueous system comprising the addition to said aqueous system of about 1 ppm to about 1.0 percent of the foaming composition of claim 2 based on the weight of the solids in said aqueous system.

4. The composition of claim 2 wherein the alcohol in said fatty alcohol mixture has about 10 to 40 carbon atoms.

5. The composition of claim 4 including a hydro-phobic silica.

6. The composition of claim 4 wherein said fatty alcohol mixture also includes other hydrocarbons having about 20 to 40 carbon atoms.

7. The composition of claim 6 including a hydro-phobic silica.

8. The composition of claim 2 including from about 0.1 to 10 percent by weight of said hydrophobic silica.

9. The composition of claim 2 wherein said solvent is mineral oil, said fatty amide is ethylene distearamide and said fatty alcohol mixture is a blend of linear and branched alcohols containing about 20 to 32 carbon atoms and hydrocarbons containing about 25 to 40 carbon atoms, and wherein the alcohols compose about 66 percent by weight of the blend.

10. A process for suppressing foaming and air dispersion in an aqueous system comprising the addition to said aqueous system of about 1.0 ppm to about 1.0 percent of the composition of claim 9 based on the weight of the solids in said system.

11. The composition of claim 9 including about 0.1 to 10 percent by weight hydrophobic silica.

12. A process for suppressing foaming in an aqueous system comprising the addition to said system of about 1.0 ppm to about 1.0 percent of the composition of claim 11 based on the weight of the solids in said aqueous system.