Abstract:
A method for inhibiting the formation of foam in a papermaking system by adding a foam control composition consisting of a) either a polyoxyethylene-polyoxypropylene fatty alcohol or polyoxyethylene-polyoxypropylene difatty acid and b) oleic diethanolamide.

Description:
This application is a continuation-in-part of Ser. No. 08/125,998, filed Sep. 23, 1993, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to foam control compositions, their preparation and use in aqueous systems. These foam control compositions are particularly effective in pulp and paper processing and in the treatment of effluent water. 
     BACKGROUND OF THE INVENTION 
     The persistence of foam in various aqueous industrial operations can cause process inefficiency and, in some cases, an inferior final product. The pulp and paper industry experiences some of the most troublesome foam problems. Common incessant foaming occurs in pulp washing and screening and papermaking processes. Stable foam also often surfaces during effluent wastewater treatment. Entrained air tends to be a more serious type foam. The spherical entrained air bubbles are finely dispersed in the bulk solution. Small bubble volumes tend to lack a sufficient buoyant force and thus often become attached to non-wettable fiber parts. These fibers and fines can flocculate to the surface and form dense stable foam. As a result, the stabilized bubbles can inhibit the drainage of washing liquor through the fiber mat which in turn slows down production. Entrained air is also known to impair paper formation and tensile strength. 
     Surface foam, on the other hand, is a more visible problem which can be evident in wire pits, stock chests and effluent ponds. The existence of surface foam surely indicates an entrained air problem. On the paper machine, collapsed surface foam can be carried back through the headbox and into the sheet where holes can be formed. On the deckers, mat filtration can be reduced when surface foam is picked up by the mat. Wastewater foaming can be hazardous to both the environment and man. In extreme cases, severe static foam can be blown across roads, thus creating traffic hazards and an unattractive mess. 
     Foam can be controlled by a variety of chemical methods. An effective antifoam should be slightly insoluble, yet dispersible, in the foaming medium. The antifoam should be able to control both entrained air and surface foam over a prolonged period of time. This present antifoam invention was developed to prevent or control the above described foaming problems while avoiding creating any undesirable side effects in the system or on the paper machines. 
     GENERAL DESCRIPTION OF THE INVENTION 
     The present invention provides an antifoam/defoamer composition comprising a combination of a) polyoxyethylene (EO)--polyoxypropylene (PO) fatty alcohol and/or polyoxyethylene (EO)--polyoxypropylene (PO) di-fatty acid having a melting point lower than 20° C. and b) oleic diethanolamide. This composition can be formulated at room temperature with no heating and cooling required. This defoaming mixture proves more effective in reducing and controlling both surface foam and entrained air than individual components or other conventional defoamers. The beneficial defoaming effects are more evident at lower temperatures, especially systems operating in the 20° C.-55° C. range such as deinked recycled tissue effluent treatment and acid/alkaline fine paper system. 
     DESCRIPTION OF RELATED ART 
     Many conventional foam control compositions embody fatty acid or fatty alcohol-based particulate emulsions to achieve a degree of water insolubility and hence defoaming effects. Some examples are set forth in U.S. Pat. No. 4,009,119 (Poschman et al.), U.S. Pat. No. 4,340,500 (Boylan), U.S. Pat. No. 4,221,600 (Alexander), U.S. Pat. No. 4,451,390 (Flannigan), and U.S. Pat. No. 4,477,370 (Kavchok et al.). Compositions as such comprise a hydrophobic dispersion of, for example, solid fatty alcohol of 14-28 carbon atoms, requiring the process steps of heating the material to at least 60° C., followed by cooling to ambient temperatures. The result is an efficacious product which contains defoaming particulates which are prone to undesirable deposition throughout the papermaking process. Furthermore, the shelf-life stability of these products is very poor. Due to the relatively low percent actives of these compositions the costs of transportation, storage and use tend to be uneconomical. 
     Another class of particulate defoamer agents encompasses the use of hydrocarbon oils, silicone oils, high melting point amides, paraffinic waxes, and hydrophobic silicas. Examples of various combinations of such are U.S. Pat. No. 3,705,860 (Duvall), U.S. Pat. No. 3,723,342 (Shane et al.), U.S. Pat. No. 3,935,121 (Lieberman et al.), U.S. Pat. No. 3,959,175 (Smith, ,Jr. et al.), U.S. Pat. No. 4,983,316 (Starch), and U.S. Pat. No. 5,045,232 (Dahanayake). Again, it is noted that the presence of such high melt point surfactants and silica particulates is critical for the primary functionality of said products. Defoaming effects can be achieved at the expense of impacting paper sheet properties and causing felt and machine deposition. The Dahanayake patent necessitates the use of a hydrophobic silica and propoxylated and ethoxylated C 6  to C 10  and C 12  to C 14  alkanols to provide static foam collapse. 
     Lappi et al. describes a defoaming agent which comprises EO/PO fatty alcohols and EO/PO nonylphenols for use in paper manufacturing (U.S. Pat. No. 4,445,971). Svarz (U.S. Pat. No. 4,950,420) describes an antifoam composition comprising a polyether surfactant and a polyhydric alcohol fatty acid ester for use in papermaking processes. These defoamers have several drawbacks. Firstly, they have limited water solubility and dispersability so that large amounts of these antifoams must be fed and even then, the defoaming is relatively low. Secondly, the spreading coefficients of these compounds are small which requires large amounts of antifoam to control the foam. Lastly these compounds are not water dilutable, and hence overfeeding is inevitable. Not only can overfeeding lead to excessive chemical costs but it also can cause adverse effects such as sizing, deposition. 
     U.S. Pat. Nos. 4,151,101 and 4,391,722 and 4,540,511 reveal the use of fatty acid alkanolamide with an alcohol, monocarboxylic acid and/or dimethyl silicon fluid as an antifoam for use in non-aqueous systems such as phosphoric acid synthesis or hydraulic fluid. 
     U.S. Pat. No. 5,229,033 reveals the use of polybutene with nonionic surfactants such as oleic diethanolamide and PEG ester. This mixture is especially efficacious for fine paper systems where the temperature is moderately high (i.e., 110° F.-135° F.). The product becomes ineffective in tissue and effluent media where temperatures usually are from 78°-95° F. 
     The present invention achieves excellent defoaming effects while addressing the negative effects caused by the previously mentioned antifoams. The present defoamer is formulated as a water dilutable concentrate of ingredients and also can be blended at room temperature with no heating or cooling required. The composition will not deposit on felts or machines nor cause adverse effects on paper sheet properties as could occur with silicon oils, high melt point particulates, and silicas. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings which are incorporated in and form a part of the specification illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a bar chart illustrating the time in seconds foams of recycled deinked tissue medium processing waters containing antifoam compositions took to reach the top of a test container; 
     FIG. 2 is a bar chart illustrating the time in seconds foam of recycled deinked tissue medium processing waters containing antifoam compounds took to reach the top of a container; 
     FIG. 3 is a plot of foam height in centimeters versus time in seconds for a synthetic alkaline white water containing antifoam compounds; 
     FIG. 4 is a plot of foam height in centimeters versus time in seconds for a synthetic alkaline white water containing antifoam compounds; 
     FIG. 5 is a bar chart illustrating the time in seconds foams of synthetic tissue medium containing antifoam compounds took to reach the top of a container; and 
     FIG. 6 is a bar chart illustrating the time in seconds foams of recycled deinked tissue medium processing waters containing antifoam compounds took to reach the top of a container. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the present invention, the antifoam properties of EO/PO fatty alcohols and EO/PO difatty acid are considerably enhanced by combining them with an oleic diethanol amide. A water dilutable concentrate can be obtained by adding a small amount of PEG 400 DO, soybean oil and/or tridecyl alcohol. The resulting emulsion is stable for weeks. 
     The polyoxyethylene-polyoxypropylene fatty alcohols used in this invention have the structure: ##STR1## where R is a linear or branched alkyl having from 12 to 18 carbon atoms (preferably a C 14  -C 16  mixture); x=2 to 20; y=1 to 40. 
     The EO/PO fatty alcohols should have a cloud point of at least 16° C., preferably 20°-25° C., have a molecular weight of 1200 to 3000, and possess a melting point less than 20° C. 
     The polyoxyethylene-polyoxypropylene difatty acids should have a molecular weight of 1000 to 4000, a melting point below 20° C. and have the following structure: ##STR2## where R is a linear or branched unsaturated alkyl having from 12 to 18 carbon atoms (preferably C 18 ); x=1 to 10; y=1 to 35 moles. 
     The oleic diethanolamide used in this invention has the structure: ##STR3## 
     The foam control compositions of this invention are useful in controlling foam in aqueous systems, particularly fine paper, tissue and waste water systems where temperatures range from 75° F. to 130° F. 
     The weight ratio of a) oleic diethanol amide to b) EO/PO fatty alcohol and/or EO/PO difatty acid, a:b, is about 1:99 to about 15:85, preferably from about 5:95 to about 10:90. This mixture can be mixed with small amounts of PEG 400 DO (up to 15%), soybean oil or aliphatic hydrocarbon (up to 30%) and tridecyl alcohol 1:9 (up to 10%) to obtain a water dilutable concentrate. In some instances, as will be shown later, these additives also increase antifoam performance. Unlike other conventional antifoams, this composition can be made down with water and thus overfeeding can be prevented. The foam control compositions of this invention are added to aqueous systems in an amount effective to produce concentrations of the foam control compositions in an aqueous solution of from about 1 ppm to about 5000 ppm by weight. 
     A preferred foam control composition of this invention comprises 47% EO/PO C 14  C 16  fatty alcohol, 3% oleicdiethanolamide, 10% tridecyl alcohol, 30% soybean oil and 10% PEG 400 DO by weight. 
     The foam control compositions of this invention are especially formulated to inhibit the formation of foam over an extended period of time and to reduce existing foam within a short period of time. 
     The composition can be made simply by mixing the ingredients thoroughly at ambient (or room) temperature. 
     EXAMPLES 
     To illustrate the efficacy of the invention, a variety of pulp and paper processing waters (e.g., fine paper machine white water and tissue medium) are used as foaming media. 
     In evaluating the antifoam efficacy, the medium is circulated from a calibrated reservoir (0-295 cm) via a pump and is returned back to the reservoir. This action agitates the medium, which in turn causes foam. The medium temperature can be held approximately constant with a temperature controller and heat coil wrapped around the bottom cell reservoir. A known amount of the defoamer to be treated is introduced into the test cell before the pump is turned on. The foam levels are then recorded every 30 seconds until the foam reaches the maximum level (290 cm). At this point, the pump is turned off and the test time is recorded. The stability of the column of foam is also observed and is ranked on a scale of 1-5 (1=very unstable, 5=very stable). Ideally the more desirable efficacious antifoam should possess a higher time to top and a foam stability of 1. 
     
         ______________________________________Synthetic Media Formulations______________________________________A. Synthetic Alkaline White Water18 liter       DI H.sub.2 O54.0 g         CaCO.sub.32.16 g         Al.sub.2 (SO.sub.4).sub.3 -12-14H.sub.2 O2.16 g         Rosin0.90 g         NaCl0.27 g         MgSO.sub.416.20 g        Na.sub.2 SO.sub.41.44 g         Na.sub.2 SiO.sub.3.5H.sub.2 O1.44 g         CaCl.sub.2.2H.sub.236.00 g        Microcrystalline Cellulose4.50 g         Formaldehyde (37%)1.08 g         AKD72.00 g        5% Starch SolutionB. Synthetic Recycle Deinked Tissue Medium18 liter       DI H.sub.2 O4.572 g        Na.sub.2 SiO.sub.3.5H.sub.2 O0.144          MgSO.sub.46.984 g        CaCl.sub.2.2H.sub.2 O4.680 g        CaCO.sub.39.162 g        Na.sub.2 SO.sub.4n  1           Surfonic N-95 (n = 150, 200) or          DI2000-82 Surfactant (EO/PO block          copolymer and EO fatty alcohol;          n = 350)20 g           KymeneC. Synthetic Alkaline Fine PaperDI H.sub.2 O   74.18%Tap H.sub.2 O  25.00%AKD            0.006%5% Starch      0.4%3% Alum        0.15%37% Formaldehyde          0.025%Cellulose      0.17%CaCO.sub.3     0.06%5% Rosin       0.25%______________________________________ 
    
     The following ingredients, as the percentage by weight indicates, were mixed at room temperature unless otherwise stated. 
     Example 1 
     Oleic diethanolamide 
     Example 2 
     EO/PO dioleate 
     Example 3 
     A blend of polyether surfactant and polyhydric alcohol fatty acid ester (U.S. Pat. No. 4,950,420). 
     Example 4 
     Ethoxylated adol ether alcohol 
     Example 5 (U.S. Pat. No. 5,229,033) 
     Polybutene 
     PEG 600 DO 
     PEG 400 DO 
     Example 6 
     15% active water-based defoamer containing fatty alcohol as particles. 
     Example 7 
     PEG 600 DO 
     Example 8 
     10% Oleic Diethanolamide (Example 1) 
     90% EO/PO dioleate (Example 2) 
     Example 9 
     20% Oleic Diethanolamide (Example 1) 
     80% EO/PO dioleate (Example 2) 
     Example 10 (U.S. Pat. No. 4,445,971) 
     EO/PO C 16  C 18  alcohol 
     Example 11 (U.S. Pat. No. 4,445,971) 
     EO/PO C 14  C 16  alcohol 
     Example 12 
     5% oleic diethanolamide (Example 1) 
     25% aliphatic hydrocarbon 
     70% EO/PO C 14  C 16  fatty alcohol (Example 11) 
     Example 13 
     47% EO/PO C 14  C 16  fatty alcohol (Example 11) 
     3% oleic diethanolamide (Example 1) 
     10% tridecyl alcohol 
     30% soybean oil 
     10% PEG 400 DO 
     Example 14 
     10% tridecyl alcohol 
     3% oleic diethanolamide (Example 1) 
     30% soybean oil 
     57% EO/PO C 14  C 16  fatty alcohol (Example 11) 
     Example 15 
     3% oleic diethanolamide (Example 1) 
     10% PEG 400 DO 
     87% EO/PO C 14  C 16  fatty alcohol (Example 11) 
     Example 16 
     Oil-based defoamer containing PEG esters and C 14  C 16  saturated fatty alcohol. 
     Example 17 
     Mineral Oil 
     PEG ester 
     Example 18 
     Oil-based defoamer containing PEG esters and stearic acid. 
     Example 19 
     EBS Defoamer 
     Example 20 
     Silica Defoamer 
     Example 21 
     EO Dioleate 
     Example 22 (U.S. Pat. No. 4,445,971) 
     EO/PO alkyl phenol 
     Example 23 
     Water-based defoamer containing EO/PO block copolymer, glycol ester and propylene glycol. 
     Example 24 
     Water-based defoamer containing ethoxylated material, organic ester and water. 
     Example 25 
     PEG 400 DO 
     Example 26 
     Ethoxylated triglyceride 
     Example 27 
     Water-based defoamer containing organic esters, silicon oil and hydrocarbon wax. 
     Example 28 
     30% soybean oil 
     3% oleic diethanolamine 
     67% Example 11 
     Example 29 
     L-61 dioleate 
     Example 30 
     Adol ether alcohol, Pluronic block copolymer, PEG ester 
     Example 31 
     EO/PO Block Copolymer (i.e., Pluronic) 
     
                       TABLE I______________________________________Defoamer Efficacy Results Tested in SyntheticAlkaline Fine Paper(pH = 7.3, Temperature = 125° F.)               Time in Seconds to Overflow               i.e., Time Required for FoamComposition of        ppm    to Exceed 290 cm______________________________________Blank (Control)        --     15Example 1    1.5    20Example 2    1.5    178Example 3    1.5    164Example 4    1.5    37Example 5    1.5    171Example 6    1.5    126Example 7    1.5    133Example 25   1.5    35Example 26   1.5    35Example 21   1.5    28Example 9    1.5    56Example 8    1.5    180 + @225 cm______________________________________ 
    
     Table I shows the defoaming results tested in synthetic alkaline white water and it is evident that the antifoam of the present invention (Example 8) exhibits improved foam control characteristics as compared to each individual component (Examples 1, 2) and also outperforms conventional prior art defoamers. It&#39;s noteworthy that too much oleic diethanolamine (Example 9) reduces the performance. 
     Table II reveals the antifoaming results. The medium was obtained from a recycle deinked tissue mill (Northeast). The data in Table II clearly demonstrate that the defoamer compositions of the present invention (Examples 12, 28, 14, 13) work effectively as antifoaming agents. Same medium was used but tested at a higher temperature as shown in FIG. 1. The defoamer of the present invention (Example 13) clearly demonstrates the persistence (i.e., highest top time) and unstable surface foam (foam stability=2) during the processing of recycle deinked tissue furnish. 
     
                       TABLE II______________________________________Defoamer Efficacy Results Tested inRecycle Deinked Tissue Mill (North East)(pH = 7.6, Temperature = 78°)               Time in Seconds to Overflow               i.e., Time Required for FoamComposition of        ppm    to Exceed 290 cm______________________________________Blank (Control)        --      8Example 10   7.5     26Example 12   7.5    538Example 11   7.5     26Example 28   7.5    522Example 22   7.5    144Example 14   7.5    375Example 5    7.5     7Example 1    7.5     8Example 13   7.5    420______________________________________ 
    
     Antifoam efficacy was also tested in 100% recycle deinked tissue medium received from a Southern tissue mill. The results are depicted in FIG. 2. As should be apparent from FIG. 2, the present invention (Example 13) shows an exceptional antifoaming performance (i.e., high top time, low foam stability) when compared to other conventional defoamers (e.g., silica, EBS, fatty alcohol, etc.). 
     The medium used for testing Examples 13 and 31 was obtained on-site from a virgin tissue mill located in a southern state and the results are shown in Table III. Again, it is evident that the defoaming composition of the present invention (Example 13) is superior to a conventional EO/PO block copolymer defoamer (Example 31 ). 
     
                       TABLE III______________________________________Defoamer Efficacy inVirgin Tissue Medium (Southern State)               Time in Seconds to Overflow               i.e., Time Required for FoamComposition of        ppm    to Exceed 290 cm______________________________________Example 13   7.5    631Example 31   7.5     19______________________________________ 
    
     Further testing was also done in synthetic tissue medium (FIG. 3) and in synthetic alkaline white water (FIG. 4). The results of these figures show the comparative substantivity properties of the composition of Example 13 as compared with the typical water-based defoamer containing fatty alcohol (Example 6) and polybutene-based product (Example 5). 
     As mentioned previously, U.S. Pat. Nos. 4,151,101, 4,391,722 and 4,540,511 disclose the use of dialkanolamide and/or monoalkanolamide with an alcohol, carboxylic acid, and dimethyl silicon fluid as an antifoaming agent for use in non-aqueous systems. The following defoaming compositions were formulated according to U.S. Pat. Nos. 4,151,101 and 4,540,511. 
     Example 32 (U.S. Pat. No. 4,151,101) 
     67% dimethyl siloxane 
     33% oleic diethanolamide 
     Example 33 (U.S. Pat. No. 4,540,511 ) 
     80% fatty acid 
     15% coconut monoethanolamide 
     5% C 13  alcohol 
     Example 34 (U.S. Pat. No. 4,540,511) 
     80% fatty acid 
     15% oleic diethanolamide 
     5% C 13  alcohol 
     These examples are then compared to the present invention (Example 13). The results are shown in FIGS. 5 and 6. It is evident that the composition according to the present invention (Example 13) exhibits improved foam control characteristics when compared to examples taken from the convention art (Examples 32, 33 and 34). Furthermore, unlike our novel composition (Example 13), defoaming composition taken from U.S. Pat. No. 4,151,101 separated shortly (i.e., 20 minutes) at ambient. It can also be seen from FIG. 5 that the defoaming composition disclosed in this invention demonstrates a synergistic effect (i.e., comparing Example 13 with Examples 25 and 20). 
     While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of the invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.