This invention relates to an improved and simplified process of built soap making. More particularly it relates to a method for preparing soap products containing sodium tripolyphosphate.
Soap is generally produced by either reacting glycerides (generally from oils and greases) or fatty acids with strong caustic. Oil and greases, used as raw materials for the manufacture of soap contain glycerides of the formula:
C3 H5 (OH)n(OCOR)3 --n Formula (1)
Wherein n is an integer from 0 to 2 and R in each case is a hydrocarbon radical containing from three to 26 carbon atoms selected from the group consisting of alkyl radicals and ethylenically unsaturated aliphatic hydrocarbon radicals. These glycerides react with caustic to form water soluble salts of aliphatic acids (soap) and glycerine. Fatty acids of the formula R--COOH, wherein R is a hydrocarbon radical as described in formula 1 are also neutralized with strong caustic to form a water soluble salt thereof (soap) and water. No glycerine is formed in this reaction.
In the preparation of soaps, regardless of whether fatty acids or oils and greases are used, a multistep process is generally used to maximize the yield of soap and to produce an acceptable product. For example, if an excess of caustic is used to achieve a relatively complete conversion of the other raw material, a low-quality soap is produced due to the presence of the excess caustic unless purification steps are added which result in increased production costs. If less than or only the theoretical amount of caustic is used, some of the fatty acid or glyceride is left unsaponified and an inferior quality soap is produced. Thus, regardless of the amount of caustic used in the initial reaction, extra steps are required to produce a high-quality soap. Furthermore, when additives such as the alkali metal polyphosphates are used to produce a built soap product, additional steps are required to incorporate these additives into a complete formulation and to produce a desirable dry, granular product. It is believed, therefore, that a process which produces a high-quality built soap product and which process has fewer processing steps than the processes heretofore used, is an advancement in the art.
In accordance with this invention, it has been discovered that a built soap product can be produced by saponifying a material selected from the group of glycerides and fatty acids previously mentioned with an excess of caustic and then adding to the resulting mixture containing soap, water and caustic, an amount of alkali metal trimetaphosphate sufficient to react with the excess caustic. The reaction of alkali metal trimetaphosphate and caustic produces alkali metal tripolyphosphate, which is used as a builder in soap and detergent products. The heat evolved in this reaction generally causes the reaction mixture to exceed the boiling point, and with the proper choice of conditions, as will be illustrated, the mixture containing soap, tripolyphosphate and other desirable materials, is converted to a damp mass which can be screened yielding granules of a desirable size. It has been found that by using the process of this invention, built soap products containing from about 1 percent by weight of soap to about 50 percent by weight of soap, or even more, such as 99 percent by weight, can be produced in an exceedingly simple process, which requires none of the complicated extraction, washing reboiling, settling and decantation steps which are typical of the traditional soap-making processes. Especially preferred are soap compositions containing from about 15 percent by weight to about 90 percent by weight of soap based upon the combined weight of soap and sodium tripolyphosphate on an anhydrous basis.
Saponification, as used herein, refers to the formation of a water-soluble salt of a fatty acid (soap) whether the raw material for the soap is glycerides or fatty acids. As heretofore mentioned, the glycerides, which are useful in the practice of this invention, are represented by the formula, C3 H5 (OH)n(OCOR)3 --n wherein n is an integer from 0 to 2 and R in each instance is a hydrocarbon radical containing from about three to about 26 carbon atoms selected from the group consisting of alkyl radicals and ethylenically unsaturated aliphatic hydrocarbon radicals. Although most natural occuring glycerides from fats and oils such as tallow, grease, coconut oil, palm oil, cottonseed oil and the like are mixtures of compounds having aliphatic group of varying chain lengths, an average length is generally used to specify a particular glyceride. For example, certain mixtures of oils and grease will generally contain mixtures of the triglycerides but are referred to as tripalmitin, tristearin, triolein, trilaurin and the like. Additionally, the R groups above can be the same or can have differing chain lengths and can be saturated or ethylenically unsaturated; for example, glyceryl oleopalmitostearate contains an unsaturated, C15 H31 group and two saturated, C17 H35 groups Additionally, glyceryl butyrollauropalmitate contains as R groups in the beforementioned formula one C3 H7 group, a C11 H23 group and a C15 H31 group. It is preferred to use glycerides wherein at least one R group contains from about 12 to about 18 carbon atoms. It is especially preferred to use triglycerides wherein each of the R groups contains from 12 to 18 carbon atoms. In most instances, when natural oils and greases are used, a major proportion of the soap will be a water soluble salt of palmitic, stearic and oleic acids.
Since a large volume of the fatty acids used in soap making are obtained from the hydrolysis of natural fats and oils, the R group in the formula, R--COOH, will vary from about three to about 26 carbon atoms with the preferred chain length being from about 12 to about 18 carbon atoms, such as stearic, oleic, palmitic acids and the like, other examples of fatty acids and glycerides which are suitable in the manufacture of soap and in the practice of this invention are to found in Bailey's Industrial Oil and Fat Products, second Ed. Interscience Publishers, New York (1951) which is incorporated herein by reference.
In the process of this invention, one or more of the foregoing useful soap-producing materials are mixed with water and an excess amount of caustic. It is preferred to use an amount of water which is about two times the weight, on an anhydrous basis, of the caustic to be added. However, the mount of water to be added in the process and whether all of the water is to be added to the soap-producing materials and caustic depends upon several factors including the proportion of soap to tripolyphosphate and the amount of free water desired in the final product and the handling of materials. If desired, only enough water can be added to enable relatively easy mixing of the soap-producing material with the excess caustic.
By excess caustic, it is meant that more than the equivalent amount of neutralizing agent which would be theoretically required to achieve saponification is used. In most instances, an alkali metal hydroxide, such as sodium or potassium hydroxide, is used; however, if desired, other alkali metal neutralizing agents such as the alkali metal carbonates or silicates can be used. Other alkaline neutralizing agents such as ammonium hydroxide and other materials containing the ammonium ion are also useful. The term "caustic" as used herein includes the materials which will react with the glycerides and fatty acids disclosed herein to yield a water soluble salt of the corresponding aliphatic acid which is soluble at least to the extent of 0.1 grams in 100 cc. of water at 25° C. For natural fats and greases the saponification number gives a reference to the amount of caustic theoretically required to saponify the raw material. When fatty acids are used, reference is made to the average molecular weight in determining the theoretical caustic required. Although an excess of caustic greater than about 200 percent, such as 330 percent, can be used and the benefits of this invention can be achieved, it is preferred in some cases to use from about 105 percent to about 120 percent of the theoretical amount to achieve preferred results.
The amount of excess caustic used in the saponification step does not necessarily determine the proportion of soap to tripolyphosphate in the final product because after some saponification has occurred, the caustic level can be increased to the level that is required for the reaction with trimetaphosphate to yield the amount of tripolyphosphate that is desired in the final product. Although sodium trimetaphosphate is the preferred alkali metal trimetaphosphate in the practice of this invention, for economic reasons the other alkali metal trimetaphosphates such as potassium trimetaphosphate, lithium trimetaphosphate and the like can be used if desired.
The rate of saponification is determined by the amount of excess caustic the efficiency of mixing, the amount of water in the saponification slurry, and the temperature of the aqueous mixture containing the saponifiable materials, caustic, and water.
A desirable saponification rate with most saponifiable materials, that is, fatty acids or glycerides, can be achieved at temperatures of from about 90° to about 130° C. or higher, with temperatures of from about 105° to about 120° C. being desired. The temperature of the medium will normally increase from about 3° to about 35° C. during the saponification, thus the temperature of the mixture containing water, soap, and excess caustic will generally increase in some cases to about 135° C. After at least some soap is formed, the trimetaphosphate and if desired, water, additional caustic, and other useful detergent materials such as colorants, fillers, water-conditioning agents, and perfumes are added to the mixture of soap, water and excess caustic. The slurry thus formed is hereinafter referred to as the reaction slurry or reaction mixture The reaction slurry may be prepared in any of several ways to produce a homogeneous mixture of the desired composition One of the preferred methods of preparing the reaction mixture is as follows:
1. Cool the saponified mixture (containing soap, water and excess caustic) to a temperature usually between about 30° and about 100° C. with about 50° to about 85° C. being preferred for most formulations.
2. Add the amount of water necessary to make a final reaction slurry water content of from about 15 percent to about 40 percent by weight, with about 20 percent to about 30 percent being preferred.
3. Add the amount of alkali metal trimetaphosphate and other detergent components for the desired formulation. Mix until a relatively homogeneous mixture results. Adjust the slurry temperature to the desired temperature which is usually between about 30° and about 85° C. with about 50° to about 75° C. being preferred for most formulations.
4. Add any additional caustic necessary to react with the alkali metal trimetaphosphate and continue mixing until the resulting reaction slurry is relatively homogeneous, and then discontinue the mixing.
Another preferred method of preparing the reaction mixture is as follows:
1. Add all of the caustic necessary for the completed reaction mixture at any time before the alkali metal trimetaphosphate is added (can be added simultaneously with the caustic used for saponification).
2. Cool the saponified mixture containing soap, excess caustic and water to the desired temperature which is between about 30° and about 100° C. with about 50° to about 75° C. being preferred for most formulations.
3. Add the amount of water necessary to have a reaction slurry water content of from about 15 percent to about 40 percent by weight with about 20 percent to about 30 percent being preferred.
4. Add the amount of other detergent components for the desired formulation. Adjust the slurry to the desired temperature which is usually between about 30° and about 85° C., with about 50° to about 75° C., being preferred for most formulations.
5. Add the amount of alkali metal trimetaphosphate for the desired formulation and stir until a relatively homogeneous slurry results, then stop the mixing.
The second method given above is usually preferred for formulations containing low weight levels of soap, such as below about 20 percent soap. When producing compositions of higher levels of soap, that is, up to 50 percent by weight or higher, the first method given above is usually more effective.
In most instances, it will be desired to have an alkali metal tripolyphosphate content of from about 10 percent to about 85 percent and a soap content from about 15 percent to about 90 percent by weight based upon the combined weight of the soap and alkali metal tripolyphosphate, the phosphate taken on an anhydrous basis; however, compositions containing as little as 1 percent soap or tripolyphosphate can be made if desired.
Products of desirable moisture content, granularity, and bulk density are obtained in this process with relatively small amounts of drying and particle size reduction. For example, in this process, removal of amounts of water such as from about 3 to 15 parts of water per 100 parts of product yields relatively dry product which can easily be screened to produce a free-flowing noncaking granular product having desirable particle size. Generally, after the product has been dried and conveyed to a screen, no more than from about 5 percent to about 15 percent of the product particles are larger than the openings in a U.S. Standard 4 mesh screen. These larger particles can be milled to reduce their size to normal granular built soap product sizing. If desired, instead of milling, these larger particles can be recycled; however, since the product mills relatively easy without excessive particle attrition, there is generally no need for recycle. If soap bars are desired, the product can be formed into the bars without screening.
The following nonlimiting detailed examples are presented, all parts, proportions and percentages are by weight unless otherwise indicated.
About 426 parts of lard having a saponification number of about 200 are heated to 115° C. in a vessel containing an agitator and a cooling jacket. About 126 parts of 50 percent sodium hydroxide solution at 100° C. are added to the melted lard and stirred for about 10 minutes. The saponification mixture temperature rises to about 125° C. About 145 parts of water are added, and cooling water is applied to the mixer jacket and the mixture is cooled to about 85° C. About 232 parts of finely divided sodium trimetaphosphate are added and mixing is continued until a relatively homogeneous slurry is produced as determined by visual observation. The slurry temperature is adjusted to about 74° C. A second charge of about 110 parts of 50 percent sodium hydroxide solution is added and the mixture is mixed for about 45 seconds. Agitation is stopped and in about 10 seconds, the temperature of the mixture is above the boiling point, steam is evolved and the slurry is converted to a mass of slightly damp granules. After air drying and shaking through a 8 mesh U.S. Standard sieve, the product characteristics are as shown in table I.
About 155 parts of fat having a saponification number of about 200 is heated to about 120° C. in a reaction vessel as described in example I. About 181 parts of 50 percent sodium hydroxide solution at about 100° C. are added to the melted fat and mixed for about 8 minutes. The temperature of the mixture rose to about 117.5° C. About 127 parts of water, 85 parts of 47 percent sodium silicate solution, and about 120 parts of sodium sulfate are added and the temperature of the mixture is adjusted to about 75° C. About 266 parts of finely divided sodium trimetaphosphate are added and the mixing is continued for about 30 seconds, then stopped. In about 30 seconds after the mixing is discontinued the mixture boils and the reaction mixture is converted to a mass of slightly damp granules. After air drying and shaking through a 8 mesh U.S. Standard sieve, the product characteristics are shown in table I.
About 310 parts of lard having a saponification number of about 200 are heated to about 120° C. in a reaction vessel as described in example I. About 92 parts of a 50 percent aqueous sodium hydroxide solution at a temperature of about 100° C. is added and mixed for about 15 minutes. The saponification mixture temperature rose to about 126° C. About 154 parts of water, about 85 parts of 47 percent sodium silicate solution, about 120 parts of sodium sulfate, and 200 parts of sodium trimetaphosphate are added and the mixing is continued until a relatively homogeneous slurry results. The slurry temperature is adjusted to about 74° C, and about 97 grams of 50 percent sodium hydroxide solution is added then the slurry is mixed for 30 seconds and then stopped. The slurry temperature rises above the boiling point almost immediately and converts to a mass of slightly damp granules. After air drying and shaking through a 8 mesh U.S. standard sieve, the product characteristics are as shown in table I. ---------------------------------------------------------------------------
example Example Example 1 2 3 __________________________________________________________________________ Calculated Formulation % phosphate as sodium tripolyphosphate 33 40 28 % soap 52 20 38 % glycerine 5 2 4 % sodium silicate 0 5 5 % sodium sulfate 0 15 15 % water, dried product 10 18 10 Reaction slurry water content 20.5 27.5 25 Reacted product water content before air drying 17.0 23.6 17.0 Product Characteristics pH, 1% solution 10.8 10.8 10.7 Density, grams/cc., loose bulk 0.32 0.32 0.32 Particle size distribution (before scalping 8 mesh) % +8 mesh, USS sieves 2 5 3 % CR40 mesh USS sieves 64 -- -- % CR60 mesh USS sieves 90 -- -- % CR100 mesh USS sieves 97 98 98 Actual water content 10.8% 16.8% 10.7% __________________________________________________________________________
Additionally, high-quality soap products are prepared having substantially similar characteristics when other fats, oils and greases having saponification numbers varying from about 180 to about 220 are substituted in substantially equal molar quantities for the lard and fat in the foregoing examples. Fatty acids can also be used in a similar manner with equally good results.