Patent Publication Number: US-4923627-A

Title: Hard translucent high moisture soap bar

Description:
TECHNICAL FIELD 
     This invention relates to a method of producing hard, translucent, high moisture soap bars and product produced thereby. 
     BACKGROUND OF THE INVENTION 
     The usual difference between non-transparent soaps and transparent or translucent soap lies in the crystallization of the finished soap product. Non-transparent soaps will normally solidify from a hot fluid state to a crystal conglomerate, which contains more or less soap in a colloidal dispersed state. On the other hand, translucent soap is made by keeping the crystal size of the soap bar small or by inhibiting crystallization of the soap during solidification of these bars. 
     In the past, translucent soaps were prepared by incorporating clarifying agents such as lower alkanols (soap crystallization inhibitors) and the soaps were framed, not milled and plodded. Subsequently, it was discovered that milled and plodded translucent soaps could be made by a variety of methods including careful regulation of electrolyte content, utilizing resin soaps, employing potassium soap, controlling moisture content, and utilizing specialized soap formulas. Also, careful control of the working of particular formulas and energy added to them during the processing was found to be useful in some cases in making translucent soap tablets by a process which included plodding of the soap and pressing of lengths cut from an extruded plodder bar. 
     For example, in U.S. Pat. No. 2,005,160 a natural resin is used in the production of a translucent soap bar and the process required spreading the hot fluid kettle soap in a thin layer and cooling that layer to room temperature, ie. specifically, it is stated that the soap is chilled to about 20° C. 
     Although prior art shows that translucent and transparent soap bars could be made, the processes and the product were too often unsatisfactory. For example, crystallization inhibitors often made the soap malodorous or adversely affected the soap&#39;s tactile properties. The additives tended to evaporate in the process of making the translucent bar and therefore caused the product to lose its transparency. Some crystallization inhibitors caused the development of hard specks in the soaps, while others made the soap mushy or liable to slough excessively when it became wet, as when standing in a soap dish with water in contact with the cake bottom. When certain working conditions were required to produce a transparent soap via milling, plodding, and pressing, the processes employed would often take too long to be economical, or the process control would be too critical, so that excessive scrapping of off-specification product would result. 
     Today, it is generally accepted, that translucent soap can be made by keeping the crystal size of the finished soap bar small through either the use of new crystallization inhibitors or by use of high shear extrusion, that requires expensive and specialized equipment, to break down the crystal size. For example, in U.S. Pat. Nos. 3,793,214 and 3,864,272, glycerine and polyethylene glycol are added to the soap to promote translucency. Other well known additives include lanolin, sorbitol, and ethanol, to mention only a few. 
     Although translucency is difficult to achieve in a soap bar without additives or use of specialized equipment, high moisture translucent soap bars are rarely produced, since high moisture content in soap bars tends to make these bars soft. High moisture soaps are commercially available today. However, these soaps are either opaque or in the form of laundry soaps, which are often soft, nonmachinable, and not very translucent. 
     It is therefore, an object of the present invention to provide a process for the manufacture of translucent, high moisture soap bars. 
     It is a further object of the present invention to produce high moisture, bars translucent soap bars, without special additives or by using specialized equipment. 
     It is a still further object of the present invention to produce a translucent, hard soap bar at a moisture content between 18-279. 
     SUMMARY OF THE INVENTION 
     A hard, translucent, high moisture soap bar is prepared without special additives or use of specialized equipment through the process of heating a wet kettle soap then spray drying the soap under vacuum, extruding the soap into pellets, plodding said pellets and pressing into bars. 
     The present invention comprises the following steps: 
     a. preparing a wet kettle soap at 29-32% moisture and in a molten state of 160-190° F.; 
     b. heating and spray drying said wet kettle soap at a temperature of 190-230° F. under vacuum; 
     c. extruding said soap containing 18-27% moisture to make pellets which are at 90-100° F.; 
     d. processing said pellets through a vacuum plodder; and 
     e. pressing soap into bars at a temperature of 90-120° F. 
    
    
     DETAILED DESCRIPTION 
     The present invention concerns a process for manufacturing, hard, translucent, high moisture soap bars. 
     Any wet kettle soap may be utilized in the present invention, provided that the soap contains between 29-32% H 2  O content. 
     This invention relates to attempting to keep the crystal size of the soap small by varying the conditions of spray drying under vacuum such that translucent soap is formed without using chemical additives or specialized equipment. In order to accomplish this task, the molten kettle soap is first heated to a temperature of 190° F. but not more than 230° F. The soap is then dried by spraying in a vacuum flash chamber at a temperature between 190-225° F. The vacuum in the flash chamber is between about 20-30 inches of mercury, but preferably 30 inches of mercury. The resultant 18-27% H 2  O dry soap is then extruded via a double stage twin-screw extruder to make pellets which are at between 90-100° F. 
     These pellets may be then transferred, stored, and processed through a conventional refiner and vacuum plodder, or continuously plodded into bars. The bars are then pressed and are at a temperature of between 90-120° F. and have a Dietart Hardness of 90-92. 
     Analysis of the crystalline phase profile through differential scanning calorimetry shows high moisture-binding properties. X-ray differentiation methods indicate these soaps to be high in the Beta phase (up to 90%).