Introduction to Soap And Detergent, Soap Making And Recovery of Glycerine (Part - 1) | Chemical Technology - Chemical Engineering PDF Download

Introduction to Soap and Detergent, Soap Making and Recovery Of Glycerine

Introduction
 

Soap is one of the oldest chemical produced over two thousand years ago by saponification animal fats with the ashes from plants. Although soap are mainly used as surfactant for washing, bathing cleaning, but they are also being used in textile spinning and as important constituent of lubricating grease. Now soap and detergent have become integral part of our society. There has been continuous development Soap making technology starting with batch kettle making process in cottage industry and to present continuous modern soap making process using either fat saponification or by fatty acid neutralization utilizing a wide variety of natural and synthetic feed stock [Zhu et al., 2004]. Soaps are also key components of most lubricating grease which are usually emulsion of, calcium, sodium, lithium soaps and mineral oil.

Synthetic detergent is an effective substitute of washing soap have become now very popular replacing the soap. All soaps and detergents contain a surfactant as their active ingredient. However detergent has better cleaning properties than soap because good detergency and has increasingly popular. Environmental issues during initial stages because of non biodegradable nature of the detergent caused major concern. With the production of linear alkyl benzene there has been continuous increase in detergent production because of the biodegradable nature of the detergent.

During 40’s and 50’s the detergent market was primarily captured by the dodecyl benzene (DDB), a product formed by alkylation of benzene with propylene tetramer in a hard detergent alkylation unit. However, that the branched structure of the alkyl group was responsible for the poor biodegradability of the detergent, and the linear alkyl Benzene (LAB) was introduced in the early 60’s have substantially replaced its counter parts.

India is one of the largest producer of soap in the world. However, per capita consumption of toilet bathing soap in India is 0.8 kg against 6.5 kg in USA, 4.0 kg in china, 1.1 kg in Brazil and 2.5 kg in Indonesia. Soaps are the largest portion of the fast moving consumer Goods (FMG) markets with bathing soap and toilet soaps contributing about 30% of the soap market. In india soaps are available in five million retail stores out of which 3.75 million are in the rural area. The major player in the personal wash soap market are HUL, Nirma and P & G. In soap industry, the popular sector has witnessed growth with toilet soaps.

Soap and Detergent differ in their action with hard water. Soap form insoluble compounds with hard water containing calcium and magnesium ions which precipitates and reduce  foming and cleaning  while detergent may react with the ions responsible for hardeness but the resulting product is either soluble or colloidally dispersed in water [ Austin 1984].  

Soap 

Soap is the alkali salt of fatty acid. Some of the important fatty acids used in soap manufacture are lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, reicinolenic acid. Fatty acids  have varying chain length and may be saturated or unsaturated. Fatty acid content of the oils vary. Unsaturated fatty acids give softer soap  with lower melting point and are less stable while soap from saturated fatty acids are firm, slowly soluble, milder and have good detergency [Dixit,2011]. Total fatty acid is considered beneficial ingredient of toilet soap. Property of soap depends on the chain length of fatty acids in blend, amount of saturation and unsaturation, formulation and soap structure. A judicious blend of oils and fats are necessary to obtain soaps of ideal properties. 

Catogrisation of Soap 

Soaps has been graded in terms of total fatty matter. Soap may be catogorised astoilet soaps or bathing soap  or specialty soap like baby( comparatively  of high purity), transparent( soap with high glycerine content), herbal and antibacterial soap. Bureau of Indian standards (BIS) has catogrised on the basis of  total fatty matter(TFM): Grade I ( Minimum 76%), Grade II(minimum 70%), Grade III(minimum 60%), bathing bar (minimum TFM 40%). Soft soap are made by using potassium hydroxide instead of sodium hydroxide. Bathing bars may be made from partial soap and partial detergent or wholly synthetic detergent 

Raw Material  

Soaps are commonly made from fats and oil and sodium hydroxide. Oils and fats can be classified either lauric or nonlauric oils /fats. In soap making palm oil, coconut oil, caster oil,neem oil, kernel oil, ground nut oil, ricebran oil and animal fat especially tallow are used. Fatty acid present in tallow are mysteric acid, palmitic acid, stearic acid, oleic acid, linoleic acid whereas the coconut oil contains lauric acid, mysteric acid, palmitic acid, stearic acid. Different oils produce soaps of varying hardness, odour and lathering properties. Normally 75-85% tallow and 15-25 % coconut oil is used in soap making. C12 and C14 soaps lather quickly but they produce an unstable, coarse bubble foam while C16 and C18 lather slowly but lead to stable, fine bubble foamed. For saponification caustic lye (50% caustic soda) is used. Some of the other ingredient in soap are talc as filler which also act as carrier for perfume, fragrance. sodium silicate to give firmness to the soap, sodium carbonate, dyes to impart colour 

Soap Making Process 

The soap making process consists of reaction of animal fats along with coconut oil with sodium or potassium hydroxide. The traditional process consists of direct saponification of oil and fats in batch process. The commercial process consist saponification in a kettle pan boiling batch process or a continuous process The production of soap comprises saponification(soap making), removal of glycerol, soap purification, finishing which consist of mixing and homogenisation of the soap base with additive such as perfumes , coloring matter, skin grooming substances and final extrusion, cutting shaping and packaging. 

Basic Steps in Soap Manufacture are saponification, glycerine removal, soap purification, finishing [Table M-IV 1.1]. Figure M-IV 1.1illustrate the process diagram for soap manufacturing. Process for toilet soap bar making is shown in Figure M-IV 1.2

Table M-IV 1.1: Basic Steps in Soap Manufacture