Soap IndustrySoap Industry

Dr. Noaman Ul-Haq

DefinitionDefinition

• The term "soap" refers to a particular typeThe term soap refers to a particular type of detergent in which the water-solubilized group is carboxylate and the positive ion is g p y pusually sodium or potassium. The largest soap market is bar soap used for personal b thibathing.

• Maybe defined as chemical compound or i t f d lti f thmixture of compounds resulting from the

interaction of fatty oils and fats with alkali.

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Raw MaterialsRaw Materials• Tallow

i th i i l f tt t i l– is the principal fatty material– the quantity used represent about three-fourths of total oils and fats– contains the mixed glycerides obtained from soild fat of cattle by steam

rendering• Greases

– Obtained from hogs and smaller domestic animals and are an important source of glycerides of fatty acids.

– Refined by steam rendering or by solvent extraction and are seldomRefined by steam rendering or by solvent extraction and are seldom used with out being blended with other fats.

• Coconut oil– the soap from here is firm and lathers well

t i l ti f th d i bl l id f l i d– contains large proportions of the very desirable glycerides of lauric and myristic acids

• Builders– these are inorganic chemicals added to the soap to make it soft, firm

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and hard

PropertiesProperties1. Surface active agents (Surfactants)g ( )

• soaps reduce surface tension when dissolved in water or organic solvents and in particular they tend to produce emulsions or colloidal suspensions

2. Cleansing action• the cleansing power of soap is different from

detergentdetergent• soap does not produce a good lather for proper

cleaning3 The properties and application of a particular3. The properties and application of a particular

soap depends upon the particular carboxylic acid and base that make up the soap molecule

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The Soap MakingThe Soap Making

• SaponificationSaponification– process of treating fats with base or alkali

a method involves heating fats and oils and– a method involves heating fats and oils and reacting them with a liquid alkali to produce soap and water (neat soap) and glycerinsoap and water (neat soap) and glycerin

3NaOH + (C17H35COO)3C3H5 3C17H35COONa + C3H5(OH)3

ti l l di l icaustic glyceryl sodium glycerinsoda stearate stearate

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Manufacturing processesManufacturing processes

1 Boiling Process1. Boiling Process– the objective of this is to produce neat soap

in purified condition free from glycerinin purified condition free from glycerin– Neat soap – also called kettle soap which

constitutes the starting material for makingconstitutes the starting material for making bars, flakes, beads, powders

– Soap kettle – the equipment where the raw p q pmaterials are mixed

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• Steps in Boiling processa) Introduction of melted materials into kettle.b) Separation of glycerin from soap

• 2 layers formed:1. the upper layer composed of a curdy mass of impure

soapp2. the lower layer is an aqeuous salt containing the

glycerin dissolved in it

c) Addition of strong caustic solution andc) Addition of strong caustic solution and boiling for several hours.

d) Pitching and Settlingd) Pitching and Settling• transformation of soap into neat form and the

final removal of dirt and coloring matter

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g

2. Hydrolyzer Process– in this process, the fat is split into fatty acids

and glycerin by means of water splitting at a high temperature and pressure in thehigh temperature and pressure in the presence of catalysts (zinc soap)

• e.g.e.g.Splitting reaction:(RCOO)3C3H5 + 3H2O 3RCOOH + C3H5(OH)3

fat water fatty acid glycerinfat water fatty acid glycerin

– considered as more economical than boiling process because it takes lesser time lessprocess, because it takes lesser time, less factory space, improved quality and better control of product characteristics

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p

3. Semi boiling Processh th d t b ll i t– has the advantage by allowing water adjustment, the direct production of either neat soap middle soap or in some nigreneat soap, middle soap, or in some nigre (liquid soap)

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Principal Sequences in Soap M kiMaking

• Principal Sequences in Soap MakingPrincipal Sequences in Soap Making using Water Splitting and Neutralization

1. Transportation of fats and oils2 T t ti d f t f ti2. Transportation and manufacture of caustic

soda3 Bl di f th t l t i id ith3. Blending of the catalyst, zinc oxide with

melted fat and heating with stream takes place in the blend tank

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place in the blend tank

4. Hot melted fats and catalysts are introduced into the bottom of the hydrolyzerinto the bottom of the hydrolyzer

5. Splitting of fat takes place counter currently in the hydrolyzer at 250°C and 4 1 MPain the hydrolyzer at 250 C and 4.1 MPa, continuously, the fat globules rising against a descending aqueous phaseg q p

6. The aqueous phase, having dissolved the split glycerin (about 12%), falls and p g y ( )separated

7. The glycerin water phase is evaporated and purified

8. The fatty acid phase at the top of the

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hydrolyzer is dried by flashing off the water and further heated

9. In a high vacuum, still the fatty acids are di till d f th b tt d tifi ddistilled from the bottoms and rectified

10.The soap is formed by continuous neutralization with 50% caustic soda in aneutralization with 50% caustic soda in a high speed mixer neutralizer.• at this point the neat soap analyzes:• at this point the neat soap analyzes:

a) 0.02 to 0.10% NaOHb) 0.3 to 0.6% NaClc) approx. 30% water

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11.Finishing Operations) Th th t t 3 5 MPa) The pressure on the neat soap rose to 3.5 MPa,

and the soap is heated to about 200°C in a high pressure steam exchanger

b) This heated soap is released to a flashed tank at atmospheric pressure, where partial drying (to about 20%) takes place because the soap solution is well above its boiling point at atmospheric pressure

c) This viscous and pasty soap is mixed with thec) This viscous and pasty soap is mixed with the desired amount of air in a mechanical-scraped wall heat-exchanger, where the soap is also cooled brine circulation in the outer shell fromcooled brine circulation in the outer shell from 105°C to about 65°C

d) To complete the process, cooling, stamping, and wrapping of the product follows

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wrapping of the product follows

Chemistry in SoapChemistry in Soap

• The most important carboxylic acids usedThe most important carboxylic acids used in soap making are the naturally occurring fatty acids that contain 12 14 16 18fatty acids that contain 12, 14, 16, 18 carbon atoms.

• These are straight chain acids found in• These are straight-chain acids found in fats and oils as esters of glycerin, as glyceridesglycerides.

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Table 1. Important fatty Acids in SoapsTable 1. Important fatty Acids in Soaps

Name C atoms Structure

Lauric acidLinoleic acid

1218

SaturatedUnsaturated: 2 double bonds

Linoleic acidMyristic acid

1814

Unsaturated: 3 double bondsSaturated

Oleic acidPalmitic acid

Recinoleic acid

181618

Unsaturated: 1 double bondsSaturated

Unsaturated: 2 double bond d 1 h d l

Stearic acid 18

and 1 hydroxyl groupSaturated

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Table 2. Common Fats and Oils used in S kiSoap making

Name Fatty acid Constituents

Beef tallow

Coconut oil

Oleic, palmiti, stearic acids

Lauric myristic acidsCoconut oil

Castor oil

Lauric, myristic acids

Ricinolic acid

Lard

Palm oil

Linoleic, oleic, palmiti acids

Oleic palmitic acids

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Palm oil Oleic, palmitic acids

• Fatty acids– components of fats and oils that are weak acid which are p

composed of two parts:1) Carboxylic group2) Hydrocarbon chain

Chemical Reactions– The following is an example of chemical reactions in soap

having one of the fatty acids used in soap making:

(C17H35COO)C3H5 + 3H2O 3C17H35COOH + C3H3(OH)3glycerin stearic acid glycerinstearate

C17H35COOH + NaOH C17H35COONa + H2O17 35 17 35 2stearic acid caustic sodium

soda stearate

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Types of SoapsTypes of Soaps

1. Framed soaps1. Framed soaps – usually made by pumping molten neat soap into

molds or frames to cool2. Floating soaps

– the molten neat soap is either aerated and then idl hill d hill d t i lid diti drapidly chilled or chilled to a semisolid condition and

then chilled3 Milled soaps3. Milled soaps

– soap products that undergone milling process

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4. Granulated soaps, beads, powders t d h d t d i– to produce such products, spray drying method are applied

5 Medicated soaps5. Medicated soaps– soap itself has germicidal power against

some organisms and many of the cationicsome organisms and many of the cationic synthetic detergents are strongly germicidal

6. Textile soapsp– soaps used in textile or clothing industry

7. Shaving creamsg– usually mixtures of potash and soda soaps

of tallow and coconut oil

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Cleansing ActionCleansing Action• Soap solution owe their cleansing power to:p g p

1. The ease with which they wet dirty clothing, dishes, etc.2. The fact that they form emulsions and prevent its return to the

article being washed• Soapy water penetrates and spreads over the surface of

immersed articles much more readily than plain water; thus its wetting power is greater

• Pure water cannot dissolve greasePure water cannot dissolve grease

• How soap cleanses:– the surfactant molecules of soaps, especially detergents have

polar, or hydrophilic ends, which attract water molecules;– nonpolar or hydrophobic ends which lacks attraction to water

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• As these molecules lower the water’s surface tension they improve the water’s ability totension, they improve the water s ability to penetrate and loosen the grease or oil, present in the articles being washed.

• Surface tension– happens when the water molecule in the body of

water is surrounded and attracted by other waterwater is surrounded and attracted by other water molecules; however, at the surface, those molecules are surrounded by other water molecules only on the sideside

• Micelle– formed when surfactants aggregates helps in gg g p

loosening dirt attached to articles being washed, when loosened up, the dirt being washed or rinsed away by the water

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y y

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Some resolutionsSome resolutions1. A variety of emollient materials, such as shea y

or cocoa butters, are substantive to the skin.2. Poorly finished soaps contain alkali, NaOH

react mildly with skin and fabrics; commercialreact mildly with skin and fabrics; commercial products are finished to neutrality or to weak acid content to prevent this and be more compatible with the skin’s acidic pHcompatible with the skin s acidic pH.

3. Commercial products use chelating molecules, often EDTA derivatives to bind with any free Ca

M i d Th lor Mg ions and prevent soap scum. These also help reduce fragrance loss, discoloration and rancidity.

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y

Advantages and DisadvantagesAdvantages and Disadvantages• Very effective as a • When used in hard water, y

bactericide, • It will form gels, emulsify

oil and lower the surfaces

soap can produced a scum.

• Considerable rinsing isoil and lower the surfaces tension of water.

SAMPLE PRODUCT

Considerable rinsing is required to remove soap scum.

• Soap may produce aSAMPLE PRODUCT: IVORY

• Soap may produce a greasy build-up on the surface which can be slipperyslippery.

• More expensive than synthetic detergents.

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Further ReadingFurther Reading

• Chapter 29 Soap and Detergents;Chapter 29, Soap and Detergents; Shreve’s Chemical Process Industries.

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