Field of the Invention

This invention relates to defoaming compositions and methods especially suitable in pulp and paper industry, as well as in any other processing industry where foaming is an issue.

Background of the Invention

Defoamers are widely used in many industries including pulp and paper industry. Knockdown and longevity of activity of defoamers provide important information about the performance of defoamers. Upon formation of foam in a solution, e.g. aqueous liquid, the density of the solution decreases. Addition of a defoamer breaks the foam and the density of the solution increases again. The rate of the increase of the density due to the addition of a defoamer indicates how fast the defoamer acts; this is called knockdown. The quicker the knockdown, the more efficient the defoamer is. However, the defoaming effect is temporary and with time the defoamer begins to lose its efficacy and the density starts dropping again as the foam starts to regenerate. The longevity of activity or persistence of a defoamer indicates how long the defoamer works. The longer the longevity of activity or persistence of a defoamer, the more efficient the defoamer is. An ideal defoamer would have fast knockdown and longer longevity of activity or will persist over longer time i.e. foam would disappear quickly upon addition of the defoamer and it would take longer time for the foam to regenerate, Fig 2.

Although commercially available defoamers generally have relatively fast knockdown, they have poor longevity of activity or persistence. Currently available defoamers quickly lose their efficacy and density starts to drop rapidly, which is seen as reappearance of the foam.

In pulp industry specifically, silicone based defoamers (Si defoamers) are preferred over other defoamers due to lower dosage requirement and cost-effective performance. Moreover, there are limitations to possible defoamers in paper and pulp industry due to FDA guidelines for indirect food contact. Si defoamers fulfill these regulations, which also makes them preferable defoamers in paper and pulp industry. However, in order to increase the longevity of Si defoamers one would need to use larger amounts of these defoamers in the process. This would result in additional problems due to presence of higher amounts of hydrophobic components, such as silicone compounds in the process. Hydrophobic components have a tendency to stick on the fiber, and excess amount of hydrophobic components would necessitate additional washing steps later in the process. Therefore, amount of hydrophobic components in the end fiber needs to be limited and excess amount of Si defoamers cannot be a solution to limited longevity of the defoamers.

Improved operations and paper quality has been often times addressed by use of processing aids, such as flocculants and drainage aids. As an example, polyacrylamides are known in the paper and pulp industry as drainage aids and they are usually added later in the process. Polyacrylamides are water-soluble, and they affect the rheology of the solutions for which reason they have been used as viscosity modifiers. Even if polyacrylamides have certain uses in paper and pulp industry, they do not have characteristics that would make them appealing for defoaming process.

There is a clear need for improved and cost effective defoaming compositions with longer longevity of activity along with fast knockdown. This disclosure provides surprising solutions to the current state of the art.

Summary of the Invention

One objective of the present invention is to provide solutions to or alleviate the problems encountered in the prior art.

An objective of the present invention is to provide a method and composition, which control, prevent or reduce foam formation in an aqueous liquid.

Another objective of the present invention is to provide a method and composition, which increase longevity of activity and/or boost performance of a defoamer.

Another objective of the present invention is to provide a method and composition, which revive efficacy of a defoamer in an aqueous liquid. These objects are attained with an invention having the characteristics presented below in the characterizing parts of the independent claims. Some of the preferred embodiments of the invention are presented in the independent claims.

A typical method according to present invention of controlling, or preventing or reducing foam in a foam containing aqueous liquid or in an aqueous liquid which is susceptible to foaming, the method comprises the steps of:

- adding a defoamer to the aqueous liquid; and

- adding a polyacrylamide, having a weight average molecular weight at least 500 000 Da, to the aqueous liquid. A typical composition of components according to the present invention for controlling or preventing or reducing foam in a foam containing aqueous liquid or in an aqueous liquid susceptible to foaming comprising:

(i) a defoamer, i.e. a defoamer component, and

(ii) a polyacrylamide, i.e. a polyacrylamide component, which has a weight average molecular weight at least 500 000 Da.

Certain embodiments of the invention are related to a composition of components comprising a defoamer and a polyacrylamide. Certain embodiments of the invention are related to a method of controlling, preventing or reducing foam in foam containing aqueous liquid or in an aqueous liquid which is susceptible to foaming. The method comprises the steps of adding a defoamer to the liquid; and simultaneously or subsequently adding a polyacrylamide to the liquid. Certain embodiments are related to a method of increasing longevity of activity and/or boosting performance of a defoamer. The method comprises the steps of adding a polyacrylamide to a liquid containing the defoamer or to a liquid to which the defoamer would be added. Certain embodiments are related to methods of reviving efficacy of a defoamer in a liquid, where the method comprises a step of adding a polyacrylamide to the defoamer containing liquid. All the embodiments of the invention described herein relate to both to the composition and the various methods, whenever applicable, even if it is not always explicitly stated so. Furthermore, the different embodiments described can be combined which each other, whenever applicable.

In certain embodiments the defoamer is a Si defoamer. In certain embodiments the defoamer is an oil based defoamer. In certain embodiments the defoamer is an emulsion defoamer.

In certain embodiments the polyacrylamide is a cationic polyacrylamide. In certain embodiments the polyacrylamide is an anionic polyacrylamide. In certain embodiments the polyacrylamide is a nonionic polyacrylamide.

In certain embodiments weight ratio of the polyacrylamide and the defoamer in the solution is in range of 2: 1 to 1:8, preferably in range of 1: 1 to 1:2.

In certain embodiments for reviving efficacy of a defoamer in a liquid the polyacrylamide is added to the liquid more than once.

Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Brief Description of the Drawings

The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these schematical, exemplary, non-limiting drawings in combination with the detailed description of the specification embodiments presented herein.

Figure 1. Experimental set up for Foam and Entrained Air Tests (FEAT).

Figure 2. FEAT curve, knock down and longevity of defoamers. Figure 3 A. FEAT curve, density vs time profile for example 1, and

Figure 3B FEAT curve, density vs time profile for example 2.

Figure 4. FEAT curve, density vs time profile for example 3.

Figure 5. FEAT curve, density vs time profile for example 4.

Figure 6. FEAT curve, density vs time profile for example 5.

Figure 7. FEAT curve, density vs time profile for example 6.

Detailed Description of the Invention

Foaming is a common problem in many industrial processes, particularly in pulp, paper or board making operations where foam can prevent proper formation of the finished paper or board and possibly disrupt manufacturing operations.

Commercially available defoamers, although generally having fast knockdown, have limited longevity of activity or persistence. Once the defoamer loses its efficacy, the density of the liquid medium decreases and foam starts to regenerate. Adding more defoamer is not a solution to increase the defoaming effect, because excess amount of hydrophobic particles would lead to carryover on the final fiber and require additional washing steps. Increasing the amount of used defoamer also increases the costs, and reduces the overall economy of the process

Although polyacrylamides may be used as viscosity modifiers in the paper and pulp industry, they alone show very slow knockdown, and thus they are not efficient defoamers. This is exemplified in Fig 6. It was surprisingly found that the longevity of the activity of a defoamer significantly increases in presence of polyacrylamide. Especially, this was found in case of Si defoamers.

Moreover, it was surprisingly found that the efficacy of a defoamer is revived and the density of the aqueous liquid containing the defoamer increases again, if a polyacrylamide is added to the aqueous liquid. Especially this was found with the Si defoamers. The polyacrylamide may be cationic, anionic or non-ionic polyacrylamide. In some embodiments anionic polyacrylamides are preferable as the polyacrylamide component of the composition. Possibility to use cationic, anionic or non-ionic polyacrylamides makes the method and composition suitable for wide variety of different processes.

According to one embodiment of the invention the polyacrylamide component of the composition is emulsion polyacrylamide.

The polyacrylamide component is a polyacrylamide which has a weight average molecular weight at least 500 000 Da, preferably at least 1 000 000 Da, more preferably at least 5 000 000 Da, even more preferably at least 10 000 000 Da. According to one embodiment the polyacrylamide may have a weight average molecular weight MW in the range of the 100 000 - 100 000 000 Da, preferably 500 000 - 100 000 000 Da, more preferably 1 000 000 - 50 000 000 Da, even more preferably 10 000 000 - 30 000 000 Da.

Polyacrylamides can be added to the aqueous liquid continuously and/or at certain predetermined intervals. Amounts or dosage(s) of polyacrylamide added, time interval, and/or time duration of addition depend on factors including but not limited to the defoamer being used, amount of liquid to be treated, properties and components of the liquid, amount of foam, foaming susceptibility of the liquid, and the process itself. The polyacrylamide can be added in multiple batches to the liquid.

The polyacrylamide component may be added to the aqueous liquid before and/or after the addition of the defoamer component. It has been observed that this increases the longevity of activity and/or boost the performance of the defoamer component. In general, the present invention provides flexible regimes for addition of the different components, which makes it possible to adjust the addition of the polyacrylamide to the prevailing process conditions. In certain embodiments the polyacrylamide is added before the defoamer. In certain embodiments the polyacrylamide is added after the defoamer. In certain embodiments the polyacrylamide and the defoamer are added at the same time. In certain embodiments the polyacrylamide is added both before and after the defoamer. In certain embodiments the polyacrylamide is added before and at the same time as of the defoamer. In certain embodiments the polyacrylamide is added at the same time and after the defoamer. In certain embodiments the polyacrylamide is added before, after and at the same time as of the defoamer.

According to one preferable embodiment the defoamer component of the composition is selected from a group consisting of Si defoamers, emulsion defoamers and oil based defoamers. Si defoamers may be preferred. Si defoamers generally contain polysiloxanes and/or modified polysiloxanes. Oil based defoamers can be further classified into mineral oil based defoamers, native oil based defoamers and white oil based defoamers. Ethylene bis stearamide, certain alcohols, stearates and glycols also work as defoamers in some embodiments of the present invention. The present invention thus provides possibility to enhance, for example the longevity of activity and/or boosting performance of various different defoamer classes or defoamers.

Defoamer component of the composition can be added to the aqueous liquid continuously and/or at certain intervals. Amounts of the defoamer added, time interval, and time duration of addition depend on, factors including but not limited to, amount of the liquid to be treated, properties and components of the liquid, amount of foam, foaming susceptibility of the liquid and on the process itself. According to one embodiment weight ratio of the polyacrylamide and the defoamer in the solution may be in range of 2: 1 to 1:8, preferably in range of 1: 1 to 1:2.

In certain embodiments the liquid is an industrial process liquid. The methods of the present invention can be practiced in any industrial process in which foaming is a concern, including process streams commonly encountered when processing or manufacturing wood pulp, paper, textiles, cement or paint, in addition to processes for treating industrial wastewater, food processing, and oil drilling. The methods can be used practically with any industrial water system where foaming is a problem, but are particularly well-adapted to recirculating water systems as found in papermaking systems, cooling water systems (including cooling towers, open and closed loop cooling units), industrial raw water systems, drinking water distribution systems, sanitizing drinking water system, oil production or recovery systems (oil field water system, drilling fluids), fuel storage system, metal working systems, heat exchangers, reactors, equipment used for storing and handling liquids, boilers and related steam generating units, radiators, flash evaporating units, refrigeration units, reverse osmosis equipment, gas scrubbing units, blast furnaces, sugar evaporating units, steam power plants, geothermal units, nuclear cooling units, water treatment units, pool recirculating units, mining circuits, closed loop heating units, machining fluids used in operations such as for example drilling, boring, milling, reaming, drawing, broaching, turning, cutting, sewing, grinding, thread cutting, shaping, spinning and rolling, hydraulic fluids, cooling fluids, and the like. In some embodiments, the industrial process stream is an industrial process stream in a cement-making process or a paint- making process.

According to one preferable embodiment the composition and methods are especially suitable for use in manufacture of pulp, paper or board, especially in manufacture of pulp. The aqueous liquid in manufacture of pulp, paper and board may contain lignocellulosic fibers and/or dissolved organic/inorganic matter as well as organic/inorganic particles.

In certain embodiments a polyacrylamide is added to a defoamer containing liquid after foam starts forming in the liquid. In certain embodiments a polyacrylamide is added to a defoamer containing liquid before foam starts forming in the liquid and the polyacrylamide prevents and/or delays the foam from forming and/or reduces the amount of foam would have been formed without the polyacrylamide.

In certain embodiments the polyacrylamide is an emulsion polyacrylamide. Preferably the polyacrylamide is water-in-oil emulsion polyacrylamide. The polyacrylamides may have an average molecular weight of 500 000 - 100 000 000 Da, preferably 1 000 000 - 50 000 000 Da, more preferably 10 000 000 - 30 000 000 Da.

Components of the defoaming compositions of the current invention shows synergistic behavior, thus the defoaming efficiency of the composition is much higher than that of the individual components.

According to one embodiment the polyacrylamide component may be added into the aqueous liquid at a selected point before and/or after a foam starts regenerate in the liquid in order to revive the efficacy of the defoamer in the liquid. Suitable points for addition are locations near various pumps, mixing devices or locations where two or more flows are unified. The addition step of polyacrylamide into the liquid may be repeated at one or more selected points before and/or after the foam starts to regenerate. Definitions

The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one." Throughout this document, the term "about" is used to indicate that a value includes the standard deviation of error for the device or method being employed to determine the value.

The use of the term "or" in the claims is used to mean "and/or" unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and/or."

As used in this disclosure, the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

For the purpose of the current application, defoamers are chemicals that break foam after it has been formed and/or which prevent foam formation, also otherwise known as anti-foam agents, and/or remove air bubbles from a liquid and help them to rise to the surface, also otherwise known as air release agents. Commonly used defoamers are Si defoamers, emulsion defoamers, oil based defoamers and powder defoamers. Defoaming composition of components of the present invention prevent, control and/or reduce foaming. Prevention of foaming means not letting the foam being formed, control of foaming means limiting amount of foam to certain extent or amount depending on the process, reduction of foaming means decrease of amount of foam. Defoaming composition of components of the current invention are to be used to treat aqueous liquids susceptible to foaming and/or foam containing aqueous liquids. Treating the liquids with the defoamers is achieved by adding the defoamer to the liquids or vice versa. Terms "defoamer" and "defoamer component" are synonymous with each other in the present context and fully interchangeable. Terms "polyacrylamide" and "polyacrylamide component" are also synonymous with each other in the present context and fully interchangeable. Examples

The following examples as well as the figures are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples or figures represent techniques discovered by the inventors to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention. Foam and Entrained Air Tests (FEAT) were performed to test defoaming efficiency of compositions. The experimental set up contains a water bath, temperature control, a foam column, a micro pump, a density meter, a computer, and acquisition software, as schematically shown Fig. 1. For each of the examples, black liquor from softwood mill was used as the medium. 400 ml of black liquor was heated to 85 ^° C and circulated. As the medium was circulated, the density of the medium dropped due to formation of foams.

Example 1 : Si defoamer alone (reference)

50 Si defoamer was added to the liquid medium when the medium density reached a desired minimum point. The density increased rapidly to a maximum density approximately 1.02 g/cm ³ within 50 seconds. The density then dropped to 0.95 g/cm ³ within 160 seconds.

Example 2: Polyacrylamide increases longevity of Si defoamer 50 Si defoamer (same as in example 1) and 50 anionic polyacrylamide were added to the liquid medium simultaneously when the medium density reached a desired minimum point. The density of the medium increased rapidly to 1.02 g/cm ³ . It was surprisingly found that, it took more than three times as compared to example 1, i.e. 650 seconds, for the density to drop to 0.95 g/cm ³ . This indicates longevity of activity of defoamers significantly increases in presence of polyacrylamide.

Example 3: Polyacrylamide increases longevity of Si defoamer

50 Si defoamer (same as in example 1) and 25 anionic polyacrylamide were added to the liquid medium simultaneously when the medium density reached a desired minimum point. The density of the medium increased rapidly to 1.02 g/cm ³ . After 320 seconds, the density dropped to 0.97 g/cm ³ . In this experiment the volume ratio of Si-defoamer: anionic polyacrylamide was 2: 1, while in Example 2 the ratio was 1: 1. It is seen that increased longevity is obtained even at lower polyacrylamide dosage.

Example 4: Efficacy of Si defoamer can be revived by polyacrylamide

50 Si defoamer (same as in example 1) was added to the liquid medium when the medium density reached a desired minimum point. Density of the medium rapidly increased to 1.02 g/cm ³ . After 140 seconds the density of the medium rapidly dropped to 0.95 g/cm ³ . At this point, 50μί anionic polyacrylamide was added to the liquid medium. The density increased to 0.99 g/cm ³ in 65 seconds and after that the density slowly dropped to 0.98 g/cm ³ in 370 seconds. Again at this point, 50 μί anionic polyacrylamide was added. The density increased to 0.99 g/cm ³ in 100 seconds. The medium was kept under circulation for additional 340 seconds and the density slowly dropped only to 0.98 g/cm ³ during this time. The results from this example show that polyacrylamide considerably increase longevity of activity of Si defoamer. Especially it is seen that addition of polyacrylamide after the addition of defoamer can revive the defoaming efficacy of the defoamer. Example 5: Polyacrylamide alone is not efficient defoamer but increases longevity of activity of Si-defoamer 25 of anionic polyacrylamide was added to the liquid medium when the medium density reached a desired minimum point. No substantial increase in density was observed even after 130 seconds. This showed polyacrylamide by itself is not an efficient defoamer. After 130 seconds of addition of the anionic polyacrylamide, 50 Si defoamer (same as in example 1) was added to the medium. Density rapidly increased to 1.02 g/cm ³ within 75 seconds. Again, similar to example 2, it was surprisingly found that, it took more than three times as compared to example 1, i.e. 560 seconds, for the density to drop to 0.97 g/cm ³ . The results show that the polyacrylamide is effective for increasing the longevity also when it is added before the addition of the defoamer.

Example 6: Anionic polyacrylamide and cationic polyacrylamide are both effective in increasing longevity of activity of Si defoamers

100 Si defoamer (same as in example 1) was added to the liquid medium when the medium density reached a desired minimum point. The density increased rapidly to a maximum density approximately 1.02 g/cm ³ within 50 seconds. The density then dropped to 0.96 g/cm ³ in 160 seconds.

100 Si defoamer (same as in example 1) and 100 anionic polyacrylamide was added to the medium when the medium density reached a desired minimum point. The density increased rapidly to approximately 1.02 g/cm ³ . After that, even after 160 seconds density of the medium remained above 1.01 g/cm ³ .

100 Si defoamer (same as in example 1) and 100 μί cationic polyacrylamide was added to the medium when the medium density reached a desired minimum point. The density increased rapidly to a maximum density approximately 1.02 g/cm ³ . After that, even after 160 seconds density of the medium remained above 1.01 g/cm ³ .

Results of these experiments show both cationic polyacrylamide and anionic polyacrylamide significantly increases longevity of activity of defoamers.

Example 7: Polvacrylamides increase longevity of activity of polymeric defoamers 100 μΙ_, polymeric defoamer was added to the medium when the medium density reached a desired minimum point. The density increased to a maximum density approximately 1 g/cm ³ within around 65 seconds. The density then dropped to 0.98 g/cm ³ in 130 seconds. 100 polymeric defoamer and 100 anionic polyacrylamide was added to the medium when the medium density reached a desired minimum point. The density increased to approximately 1.02 g/cm ³ within around 65 seconds. After that, even after 130 seconds density of the medium only dropped to around 1.01 g/cm ³ . Results of these experiments show polyacrylamides significantly increases longevity of activity of polymeric defoamers.