Field of the Invention This invention relates to a defoamer/antifoam composition comprising a diester of an ethylene oxide/propylene oxide block copolymer and a fatty acid containing from 2 to 30 carbon atoms which may be used individually or as a mixture with a diester of a polyethylene glycol and a fatty acid containing from 2 to 30 carbon atoms .

Foam is consistently a problem in the processing of pulp during the manufacture of paper products. Virtually all segments of the papermaking process generate entrained air and surface foam which are extremely undesirable due to their deleterious effect upon process efficiency and the finished product. Discussion of Related Art

A variety of antifoam/defoa er agents have been used with varying degrees of success . Many defoamers are stearic acid or fatty acid based emulsion products. Some

examples of emulsion products are set forth in the following patents: U.S. Pat, Nos. 3,705,860 (Duvall) , issued Dec. 12, 1972, 3,337,595, and U.S. Pat. No. 4,451,390 (Flannigan) , issued May 29, 1984. Antifoam products are usually sold in diluted form causing them to be bulky and costly to transport. These defoaming agents may also contain undesirable particulate additives which may deposit throughout the papermaking process resulting in undesirable deposits throughout the system. Particulate additives which may cause deposits and plugging of papermaking systems are typically stearic acids, fatty acids, silicones, hydrophobic silica, waxes or other organic particles .

Other defoamer agents contain particulate additives, such as silicone, hydrocarbons or other organic particles. The use of glycols or glycerols as foam-inhibiting agents is also known.

It would be desirable to provide a novel defoamer/antifoam composition which substantially reduces transportation costs and overcomes deposition problems associated with the aforementioned defoaming agents . In addition, it would be advantageous to avoid the problems associated with conventional antifoam products by forming a concentrate of active ingredients without any oil, amide, hydrophobic silica or silicone additives.

The present invention provides a concentrated, 100% active, product which has many cost saving advantages over conventional defoa ers . Containing only pure active

ingredient, the composition of the present invention has no base or carrier resulting in reduced transportation and container costs. Furthermore, the fact that it is not an oil-based defoamer assists in preventing the loss of paper sheet properties, such as brightness, sizing efficiency and strength. Having no oil, amide, e.g. ethylene bis- stearamide, hydrophobic silica or silicone additives prevents deposition and felt filling. It has also been discovered that the defoamer composition of the present invention is a much more effective agent for control of entrained air than conventional defoaming agents . Additional advantages of the present invention shall become apparent as described below.

SUMMARY OF THE INVENTION The present invention provides a defoamer/antifoam composition comprising a diester of an ethylene oxide/propylene oxide block copolymer and a fatty acid containing from 2 to 30 carbon atoms. In an alternative embodiment, the defoamer/antifoam composition may comprise a mixture of said diester with a diester of a polyethylene glycol and a fatty acid containing from 2 to 30 carbon atoms. It has been found that the ethylene oxide/propylene oxide diester used alone is more efficient in almost every paper machine water tested, for example where tissue, linerboard or writing paper is made, at most temperatures with respect to holdout and long term effects, while the ethylene oxide/propylene oxide diester and polyethylene glycol diester mixture has better foam

knockdown effects over the ethylene oxide/propylene oxide diester product used alone.

The mixture of ethylene oxide/propylene oxide block copolymer-diester of fatty acid and polyethylene glycol- diester of fatty acid may comprise a weight ratio of from about 10:90 to 90:10, preferably from about 25:75 to

75:25, and more preferably from about 25:75 to 50:50.

The ethylene oxide/propylene oxide block copolymer employed in preparing the diester may contain from about 1 to about 100 moles of ethylene oxide, preferably from about 10 to about 60 moles of ethylene oxide, and from about 1 to about 100 moles of propylene oxide, preferably from about 10 to about 50 moles of propylene oxide. In preparing the diester with a fatty acid, the fatty acid may contain from 2 to 30 carbon atoms, preferably from 16 to 24 carbon atoms. The mole ratio of fatty acid to ethylene oxide/propylene oxide block copolymer used in preparing the diester may be from about 1:5 to about 5:1, preferably from about 1:1 to about 1:3. In preparing the polyethylene glycol -diester of fatty acid, the fatty acid may contain from 2 to 30 carbon atoms, preferably from 16 to 24 carbon atoms, and the mole ratio of fatty acid to polyethylene glycol may be from about 3:1 to about 1:3, preferably from about 2.5:1 to about 1.5:1. An additional object of the present invention is a method for controlling foam in a papermaking process which includes the step of adding to a pulp slurry, papermaking furnish, and/or pulp suspension the antifoam/defoamer

composition of this invention. The antifoam/defoamer composition is added at a concentration in the range between about 0.01-10.0 lbs. /ton of paper produced, preferably in a range between about 0.10-3.0 lbs/ton of paper produced. The present invention may also include many additional features which shall be further described below.

Description of the Drawings Fig. 1 is a graph which plots foam height (in cm) versus time (in minutes) for two defoamer compositions. In Fig. 1, defoamer A represents a polyhydric alcohol fatty acid ester/polyether surfactant blend prepared in a weight ratio of 1 to 2. Defoamer X represents a 25%/wt blend of an ethoxylated/propoxylated tall oil fatty acid diester and 75%/wt of ethoxylated tall oil fatty acid diester. As shown in Fig. 1, defoamer A and defoamer X were evaluated at a concentration of 0.1%/wt at 100°F in the white water of mill y.

Fig. 2 is a graph which plots foam height (in cm) versus time (in minutes) for two defoamer compositions in accordance with this invention. In Fig. 2, defoamer Y represents a 100% ethoxylated/propoxylated tall oil fatty acid diester. Defoamer X represents a 25%/wt blend of ethoxylated/ propoxylated tall oil fatty acid diester and 75%/wt of ethoxylated tall oil fatty acid diester. As shown in fig. 2, defoamer Y and defoamer X were evaluated at a concentration of 0.1%/wt at 100°F in the white water of mill z.

Fig. 3 is a graph which plots foam height (in cm) versus time (in minutes) for two defoamer compositions. In Fig. 3, defoamer F represents a polyhydric alcohol fatty acid ester/polyether surfactant blend prepared in a weight ratio of 2 to 1. Defoamer X represents a 25%/wt blend of ethoxylated/propoxylated tall oil fatty acid diester and 75%/wt ethoxylated tall oil fatty acid diester. As shown in Fig. 3, defoamer F and defoamer X were evaluated at a concentration of 0.1%/wt at 1G0 ^C F in the white water of mill c.

Fig. 4 is a graph which plots foam height (in cm) versus time (in seconds) for five defoamer compositions at a temperature of 45°C in paper machine water containing 0.1%/wt of paper size. DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an antifoam/defoamer concentrate having superior activity and cost/performance than conventional oil or water based defoamers. The composition is highly effective in reducing or eliminating entrained air and surface foam in many pulp and paper process streams. Furthermore, the defoamer composition of the present invention does not contain oil, amides, hydrophobic silica or silicone additives, thereby avoiding deposition and felt filling problems. Examples of some paper manufacturing applications in which this defoamer composition provides particularly good foam control and drainage enhancement are as follows: general wet-end foam control, groundwood/TMP systems.

secondary fiber systems, bleach plants/screen rooms, and effluent streams.

The defoamer/antifoam composition of the instant invention comprises a diester of an ethylene oxide/propylene oxide block copolymer and a fatty acid containing from 2 to 30 carbon atoms, preferably from 16 to 24 carbon atoms. Optimum results have been obtained with a diester of ethylene oxide/propylene oxide block copolymer and tall oil fatty acid having a weight average molecular weight of about 2,000.

In an alternative embodiment, the defoamer/antifoam composition of the instant invention comprises a mixture of a diester of an ethylene oxide/propylene oxide block copolymer and a fatty acid containing from 2 to 30 carbon atoms and a diester of a polyethylene glycol and a fatty acid containing from 2 to 30 carbon atoms.

Optimum results have been obtained with a diester of a polyethylene glycol and a tall oil fatty acid having a weight average molecular weight of from about 200 to about 800, preferably about 400.

The ethylene oxide/propylene oxide block copolymer - diester of fatty acid and the polyethylene glycol -diester of fatty acid may be mixed together in a weight ratio of from about 10:90 to 90:10, preferably from about 25:75 to 75:25, and more preferably from about 25:75 to 50:50.

The mixture of ethylene oxide/propylene oxide block copolymer -diester of fatty acid and the polyethylene glycol -diester of fatty acid can be prepared in a "one-

pot" reaction process.

Example 1 A laboratory evaluation of four defoamer/antifoam compositions was conducted using an antifoam recirculation tester. The compositions tested were as follows.

1. a 0.1%/wt solution of a polyhydric alcohol fatty acid ester/polyether surfactant blend in a weight ratio of 1 to 2 identified as defoamer A.

2. a 0.1%/wt solution of an ethoxylated/propoxylated tall oil fatty acid diester blend with ethoxylated tall oil fatty acid diester in a weight ratio of 25 to 75 identified as defoamer X.

3. a 0.1%/wt solution of a polyhydric alcohol fatty acid ester/polyether surfactant blend in a weight ratio of 2 to 1 identified as defoamer F.

4. a 0.1%/wt solution of 100%/wt ethoxylated/propoxylated tall oil fatty acid diester identified as defoamer Y. The antifoam and defoaming properties of the aforementioned compositions are illustrated in Fig. 1, Fig. 2 and Fig. 3. The data in the figures clearly show that the composition of defoamer X, i.e., a 25%/wt mixture of ethoxylated/propoxylated tall oil fatty acid diester and 75%/wt of ethoxylated tall oil fatty acid diester works more effectively as an antifoam/defoamer agent. In some instances, as shown in Fig. 4, defoamer Y is the most effective antifoam/defoamer agent.

Example 2 A laboratory evaluation of five (5) defoaming agents

O 97/14490 PC17US96/16127

9 was conducted using an antifoam recirculation tester. The compositions tested were:

1. Defoamer A - a polyether and polyhydric alcohol fatty acid ester.

2. Defoamer B - an oil-based defoamer containing a polyether surfactant and mineral oil.

3. Defoamer C - ethoxylated diester of oleic acid.

4. Defoamer X - 25%/wt of ethoxylated/propoxylated tall oil fatty acid diester and 75%/wt of ethoxylated tall oil fatty acid diester.

5. Defoamer Y - ethoxylated/propoxylated tall oil fatty acid diester.

The results of the aforementioned defoaming evaluations are set forth in Fig. 4 wherein foam height (in cm) was measured versus time (in seconds) at a temperature of 45°C after adding 25 ml of the defoaming composition to 600 ml of paper machine water containing 0.1%/wt of Stayfor* resin ( estvaco) size. It can be seen therefrom that defoamer Y was the most effective in controlling the amount of foam generated over time.