Liquid Defoamer and Defoaming Process

This invention relates to a defoamer, and more particularly to a defoamer which has particular effectiveness in the paper making industry.

Canadian Pat. No. 534,604 discloses a solid foam combating composition which is particularly useful in the paper making industry. Such defoaming composition is comprised of a solid alcohol, a solid fatty acid and a solid fatty acid soap, and in order to use such defoamer, the solid has to be dispersed in hot, softened water at the site of application.

In many cases, it would be preferable to have a defoamer which is in free flowing liquid form in order to permit pumping of the defoamer directly from storage to the place of application. In attempting to disperse the prior art defoamer in water at a solids content which is economical for preparation and shipping, it was found that a thick gel or paste was formed which would prevent pumping of the defoamer from a storage tank to the place of desired application. For example, when the solids content exceeds about 3% to 4% a gel mass is formed which prevents pumping of the defoamer.

In accordance with the present invention, there is provided a free flowing aqueous defoaming composition which is comprised of (a) water; (b) at least one solid alcohol; (c) at least one solid fatty acid; (d) a soap of at least one solid fatty acid, with components (b), (c) and (d) being present in the water in an effective defoaming amount and to provide a dispersed solids content in the water of at least 5%; and (e) a surfactant which is comprised of at least one of non-ionic surfactants and anionic surfactants which prevents formation of a gelled mass of the solids and provides a free flowing dispersion of the solids in the water, said composition having been treated to provide the dispersed solids with hydrophobic surfaces. Thus, in accordance with the present invention, there is provided an effective liquid defoamer, having particular applicability to the paper making industry, which can be prepared in liquid form with a suitable solids content, and which is free flowing whereby the defoaming composition can be easily stored and pumped as required for defoaming in an aqueous system and which is effective over a wide pH range.

In accordance with the present invention, the composition is treated to provide the dispersed solids (which are gel-like particles dispersed in the water) with hydrophobic surfaces to thereby maintain the effectiveness of the defoaming composition over a wide pH range; in particular, defoaming efficiency is maintained in systems operated at higher pH values. In accordance with a particularly preferred embodiment, the composition is treated with at least one water soluble salt of a metal, which has a valence greater than one to provide the solids with hydrophobic surfaces. The water soluble salt may be a salt of iron (ferrous and/or ferric), calcium, magnesium, barium or aluminum, or mixtures thereof, preferably an aluminum salt, and as representative examples of such salts there may be mentioned: alum (Al.sub.2 (SO.sub.4).sub.3.18H.sub.2 O), calcium chloride, ferric chloride, barium chloride, magnesium chloride, etc. The treatment may be conveniently accomplished by formulating the composition, and subsequently adding the metal salt with the presence of such metal salt in the composition providing the dispersed solids with hydrophobic surfaces. Although applicant does not intend to limit the invention by any theoretical reasoning, it is believed that the added metal salt interacts at the particle surface, with the fatty acid and/or fatty acid soap to form on the surface the corresponding metal salt of the fatty acid to thereby provide hydrophobic particle surfaces.

The solid alcohol (solid at room temperature) component of the defoamer is a higher aliphatic alcohol, which generally has from 14 to 28 carbon atoms, and preferably from 16 to 18 carbon atoms. The solid alcohol component may be comprised of one or more of such alcohols. The alcohol component may contain one or more hydroxyl groups, and may contain groups in addition to such hydroxyl groups. Thus, for example, the alcohol component may be a partial ester of glycerin; e.g., glycerin monostearate or; for example, a partial ester of a glycol. The preferred compounds are hydrocarbon alcohols, and as hereinabove indicated, preferably those having from 16 to 18 carbon atoms.

The solid fatty acid (solid at room temperature) component of the defoamer is a higher aliphatic acid, which generally has from 14 to 28 carbon atoms, with fatty acids having from 16 to 18 carbon atoms, being preferred. The fatty acid may contain other functional groups; however, hydrocarbon fatty acids are preferred, particularly those having from 16 to 18 carbon atoms.

The fatty acid soap component of the defoamer is a soap of a fatty acid of the type hereinabove described. The soap may be formed from a fatty acid identical to the fatty acid employed as the fatty acid component of the defoamer. Such soaps are generally formed as an alkali metal or amine soap of the fatty acid, preferably an amine soap. A preferred amine is triethanolamine. The soap is preferably formed, in situ, by adding a soap forming component, such as an amine, to the mixture of alcohol and fatty acid. The formation of a fatty acid soap is well known in the art, and no further details in this respect are needed for a complete understanding of the invention.

As hereinabove indicated, the three components of the defoaming composition are dispersed in water in an effective defoaming amount, and to provide a solids content dispersed in the water of at least 5%, preferably at least 20%, all by weight. In general, the solids content is no greater than 30%, by weight, with the solids content most generally being in the order of from 20% to 25%, all by weight.

In the composition, the weight ratio of fatty acid component to alcohol component does not exceed 0.5:1, with the fatty acid generally being present in an amount of at least 0.2:1 of the solid alcohol, all by weight. In most cases, the weight ratio of solid fatty acid to solid alcohol is in the order of from 0.2:1 to 0.4:1.

The fatty acid soap is present in the composition in an amount which provides a fatty acid soap to solid alcohol ratio of no greater than 0.5:1, with the soap generally being present in an amount to provide a fatty acid soap to alcohol ratio of at least 0.1:1, all by weight. In most cases, the ratio of fatty acid soap to alcohol is in the order of from 0.1:1 to 0.3:1, all by weight.

The selection of suitable amounts of the three components of the defoaming composition to provide effective defoaming amounts thereof for a particular purpose is deemed to be well within the scope of those skilled in the art from the teachings herein, and as a result, those skilled in the art can readily select optimum proportions from the present teachings.

The defoamer composition of the present invention further includes a surfactant comprised of at least one of a non-ionic surfactant or an anionic surfactant which prevents formation of a gelled mass of the solids to provide a free flowing dispersion of the solids in the water. Thus, in accordance with the present invention, by employing such a surfactant, it is possible to disperse the three components in the water in usable concentrations (at least 5%, preferably at least 20%, by weight), without formation of a gelled mass of the solids to thereby provide a free flowing aqueous defoaming composition which is capable of being pumped from storage.

The surfactant employed in the present invention, as hereinabove described, is a non-ionic and/or anionic surfactant which prevents formation of a gelled mass of the solids. Applicant has tested several cationic surfactants, and has found that such cationic surfactants are generally not suitable for the purposes of the present invention; i.e., such cationic surfactants do not prevent formation of a gelled mass of solids.

The non-ionic surfactants which have been found to be particularly suitable for the purposes of the present invention are ethylene oxide condensation products (polyoxyethylene) containing more than two, and preferably at least five ethylene oxide groups, with at least one end group thereof being terminated by condensation with either an alcohol; alkyl phenol, preferably nonyl phenol; or a long chain fatty acid; for example, mono oleate terminated ethylene oxide condensation product.

The anionic surfactants which have been found to be particularly suitable for the purposes of the present invention are alcohol sulfates, alkaryl sulfonates, ethoxylated alcohol sulfates, sulfates and sulfonates of ethoxylated alkyl phenols, sulfates of fatty esters, sulfates and sulfonates of alkyl phenols, sulfonates of condensed naphthalenes, sulfonates of naphthalene, sodium derivatives of sulfo-succinates, such as the disodium ethoxylated nonyl phenol half ester of sulfosuccinic acid, the disodium ethoxylated alcohol (C.sub.10 -C.sub.11), half-ester of sulfo-succinic acids; etc. alkali salts of petroleum sulfonates such as sodium petroleum sulfonate (Acto 632); alkali phosphate esters, such as a potassium salt of phosphate ester (Triton H66); sulfonated alkyl esters for example (Triton GR 7); sodium polymeric carboxylic acid (Tamol 731) and the like.

The preferred surfactant for the purposes of the present invention is one or more of the oxyethylene polymers containing more than two, and preferably at least five ethylene oxide groups, which have one end terminated by condensation with a compound, as hereinabove described, with particularly good results being obtained with nonyl phenol terminated polyoxyethylene products.

The anionic and/or non-ionic surfactant is employed in the composition as hereinabove described in an amount effective to prevent formation of a gelled mass of the solids and to provide a free flowing aqueous defoamer. In general, the surfactant is employed in an amount to provide at least 0.1 parts of surfactant per one part of the total of alcohol, fatty acid and soap, by weight. In general, the surfactant is not employed in an amount greater than 0.4 part per 1 part of the total of the alcohol, fatty acid and soap component in that no added beneficial effect is obtained by the use of greater amounts.

In employing a metal salt, as hereinabove described, to provide hydrophobic particle surfaces, such metal salt is added in an amount which is effective to provide such hydrophobic particle surfaces. In general, the salt is added in an amount sufficient to react with from 15% to 25% of the total fatty acid present in the composition, with such amounts providing hydrophobic surfaces while retaining defoaming efficiency.

The defoamer of the present invention may be conveniently formulated by emulsifying the solid fatty acid and solid alcohol with the surfactant at a temperature above the melting point of the solids, followed by cooling to room temperature. The mixture is then highly agitated and a soap forming component, such as triethanolamine is added. High agitation at a temperature above the melting point of the solids should be avoided, after soap formation, in that such high agitation may adversely affect defoaming efficiency. A metal salt, as hereinabove described, is then added to the defoamer to provide the dispersed solids with hydrophobic surfaces. The salt is added subsequent to formulating the dispersed solids defoaming composition in order to provide hydrophobic particle surfaces.

As an alternative method for producing the defoamer of the present invention, soap may be formed above the melting point of the solids by the use of very low agitation, such as that produced by a dough blender.

The defoamer of the present invention is suitable for providing defoaming in a wide variety of aqueous system; however, it has been found that such a defoamer has particular applicability to the paper industry, and is used particularly for defoaming in a paper machine stock. The defoaming composition of the present invention is added to the aqueous system in an effective defoaming amount, with such defoamer generally being added in an amount to provide at least 1 ppm of the total composition in the aqueous system. In general, no added beneficial affect is obtained by the use of amounts greater than 50 ppm. of the total composition (water, alcohol, acid, soap and surfactant). It is to be understood that the specific amount to be employed will vary with each system, and the selection of an optimum amount is deemed to be within the scope of those skilled in the art from the present teachings.

The invention will be further described with respect to the following examples, however, the scope of the invention is not to be limited thereby.

The defoamer composition has the following formulation:

The composition was prepared by emulsifying the solid alcohol, solid acid surfactant in water with agitation at 65.degree. C., followed by cooling to 30.degree. C. with high agitation and addition of the triethanolamine with high agitation, until homogeneous, at 30.degree. C. The alum was then added to provide hydrophobic surfaces.

The composition was employed in screen room stock (paper making operation) which was foaming under agitation at a level of 10 ppm. The foam was destroyed.

The present invention is particularly advantageous in that it is possible to provide an effective defoamer formed from a solid alcohol and a solid acid which contains a usable concentration of solids, and which is free flowing. This permits storage of the defoamer in a ready to use form; i.e., there is no necessity to effect dispersion thereof in a hot water solution, whereby the defoamer may be pumped from a suitable storage facility directly to the place of application. Moreover, by treating the defoamer to provide hydrophobic particle surfaces, defoaming effectiveness is maintained over a wide pH range; e.g., a pH range of from 4-11. In the absence of such treatment, defoaming efficiency is reduced in systems operated at higher pH values.

These and other advantages should be apparent to those skilled in the art from the teachings herein.

Numerous modifications and variations of the present invention are possible in light of the above teachings and, therefore, within the scope of the appended claims, the invention may be practised otherwise than as particularly described.