HISTORY OF SOAPS
Soaps have been valued for generations for their ability to clean clothing and household products as well as for bathing. Soap making is a craft that is often neglected in history whether it is the discussion of skills of 19th century or of the colonial period. Soap is manufactured when very basic ingredients, such as oils (or fats), water and lye (sodium hydroxide) undergoes a chemical process known as saponification.
the history of soap manufacturing dates back to almost 2800 B.C. The first such finding was done by the archaeologists when they discovered a clay cylinder, which was covered by a material similar to soap. The cylinders were found out from the remains of the Mesopotamian civilization and the archaeologists were astonished on their finding when they decoded the message that was on the excavated cylinders. In reality, it was the technique of soap making that described it as a boiling of fats along with ashes. But another matter that was left half way was soap like material, which was seen covering the cylinder. As the message given on cylinders did not indicate the use of this material the archeologists were left helpless.
Apart from the remains of Mesopotamian civilization, the archeologists also gained more information on soap history from the excavations of different civilizations. One such information was found from the Mesopotamian civilization from the artifacts of Pharaoh that suggests the various ways of soap making. Information on History of soap making has also been found from different books, like the medical text that was written by Papyrus. History of soap making also explains the various ways of soap manufacturing and one such way is to combine animal as well as vegetable fat along with alkaline salts. The substance, which is finally received, could be used for bathing or it can even be used to treat skin problems.
Soap Making In Bible:
The method of soap making was also introduced in holy books like Bible, in which it was conveyed that the Israelites use vegetable oils and ashes to make a substance like hair gel. Later in the second century A.D, noted physician Alexandria coined out the commercial uses of soaps by advocating soap to be used as a topical treatment for patients in order to keep them clean.
How Does Soap Get Its Name:
The soap got its name (according to an ancient Roman legend) from Mount Sapo, where animals were sacrificed. Rain washed a mixture of wood ashes and melted animal fat, or tallow, down into the clay soil along the river Tiber. Women found this clay mixture to be highly helpful in making the cleaning easy and effective. The ancient Gaul’s and Germans are also credited with the discovery of a substance called soap, made of tallow and ashes, which they used to tint their hair, red.
As the Roman civilization advanced, so did the bathing. The first of the famous Roman baths, supplied with water from their aqueducts, was designed around 312 B.C. These baths were highly luxurious that makes bathing very popular. By the second century A.D., the Greek physician, Galen advocated soap for both cleansing as well as medicinal purposes.
After the fall of Roman Empire in 467 A.D., bathing habits declined and as a result of which, much of the Europe felt the impact of filth upon public health. The lack of cleanliness and unsanitary living conditions led heavily to the plagues of the middle Ages and especially to the Black Death of 14th century. The poor cleanliness and bathing habits remain same till the 17th century in much of the Europe. However there were still some areas in the medieval world where personal cleanliness remained essential. Daily bathing was a normal custom in Japan during the middle Ages and in Iceland; pools warmed with water from Hot Springs were highly popular among people at gathering places on Saturday evenings.
Manufacturing of soap became an established craft in Europe by the 7th century. Soap manufacturers guilds guarded and protected their trade secrets closely. The soap makers use vegetable and animal oils with ashes of plants along with fragrances to offer a variety of soaps for bathing, shampooing, shaving as well as laundering.
Advent of Commercial Soapmaking:
Italy, Spain and France were emerged, as the early centers of soap manufacturing with their ready supply of raw materials, like oil from olive trees. The English started soap production during the 12th century. Around the year 1622, soap business was in great demand, which prompted King James I’ to grant monopoly to a soap maker for $100,000 a year. For several years during the 19th century, soap was heavily taxed as a luxury item in various countries. When the tax was lowered, it became available to ordinary people and as a result the cleanliness standards improved.
Commercial soap making started in the American colonies in 1608, which was the time when several soap makers, arrived on the second ship from England to reach Jamestown, VA. However, for several years, soap making remains primarily a household activity. Finally, professional soap makers started regularly collecting waste fats from households in exchange for soaps.
An important step towards large-scale soap manufacturing occurred in 1791 when a French chemist, Nicholas Leblanc, patented a technique for producing soda ash, or sodium carbonate, from common salt. Soda ash is an alkali, which is obtained from ashes by combining it with fat to produce soap. The Leblanc technique produces inexpensive soda ash in good quantities.
Discoveries and Inventions:
The science of modern soap making commenced with the discovery of another French chemist, Michel Eugene Chevreul, who described the chemical nature and the relationship of fats, glycerin and fatty acids. The study demonstrated the basis for both fat and soap chemistry.
Another important discovery that led to the advancement of soap technology was that of a Belgian chemist - Ernest Solvay, who in mid-1800s described an ammonia process by which common table salt, or sodium chloride can also be used to make soda ash. Solvay's procedure helped in reducing the cost of obtaining this alkali, and increased both the quality as well as quantity of the soda ash available for producing soap.
Together with the development of power to operate factories, the discoveries and inventions in the field of soap making made the soap manufacturing one of the fastest-growing industries in developed countries. The broad availability of soap changed its condition from a luxury item to an everyday necessity and its widespread use lead to the development of milder soaps for bathing. Special soaps were developed for uses in the washing machines that were available to consumers by the turn of the century.
chemistry of SOAPS
Water, the liquid, which is primarily used for cleaning, has a characteristic known as surface tension. Under the surface of water, each water molecule is surrounded and attracted by other molecules. At the surface, however, these molecules are surrounded by only those water molecules that are on the water side. As the water molecules at the surface are pulled inside the body of water, a tension is created. This tension makes the water to bead up on surfaces (fabric, glass), as a result of which the wetting of surface and hence the cleaning process slows down.
For effective cleaning, the surface tension should be reduced in order to make water spread and wet surfaces. Chemicals that can do this effectively are known as surfactants or surface-active agents.
Surfactants also execute some other important cleaning functions, such as loosening, emulsifying (dispersing in water) and holding the soil in suspension till the time it can be rinsed away. These chemicals also provide alkalinity that has found to be effective in removing acidic soils.
Also known as surface-active agents, surfactants can also be classified on the basis of their ionic (electrical charge), anionic (negative charge), nonionic (no charge), cationic (positive charge) and amphoteric (either positive or negative charge) properties in water.
Soap is an anionic surfactant while main ingredients in today’s' detergents are other anionic as well as nonionic surfactants. Now let’s have a look at the chemistry of surfactants -
Soaps are water-soluble potassium or sodium salts of fatty acids, which are made by the chemical treatment of fats (or oils), or their fatty acids with a strong alkali. Now let us first examine the composition of fats, oils and alkalis.
Fats and Oils :
Fats and oils that are used in the manufacturing of soaps come from plant or animal sources. Each fat or oil molecule is made up of a typical mixture of different triglycerides.
In a triglyceride molecule, one glycerin molecule is attached to three molecules of a fatty acid. There are several types of fatty acids, with each having a particular combination of fatty acids. Components of fats and oils, which are used in soap making, fatty acids are weak acids that are composed of two parts.
A carboxylic acid group consists of two oxygen (O) atoms, one carbon (C) and one hydrogen (H) atom with a hydrocarbon chain attached to the carboxylic acid group. Typically, a fatty acid is made up of a long straight chain of carbon (C) atoms in which each carbon atom carries two hydrogen atoms.
An alkali is a soluble salt of an alkali metal, such as potassium or sodium. Earlier, the alkalis that were used in soap manufacturing were obtained from the ashes of plants but now they are commercially manufactured. Now days, the term alkali described a substance, which is a base (chemically) and that reacts with and neutralizes an acid.
Usually the alkalis that are used in soap making are potassium hydroxide (KOH), also known as potash (KOH) and sodium hydroxide (NaOH), also known as caustic soda.
Surfactants in Detergents:
A detergent is a better cleansing product as it contains one or more surfactants. Due to their chemical makeup, the surfactants that are used in detergents can be engineered to function well under different conditions. Such types of surfactants are less sensitive to hardness minerals in water than soap and most of them do not form a film.
Detergent surfactants were developed during World War I in response to a shortage of animal and vegetable fats and oils. The discovery of surfactant was also driven by the need of a cleaning product resistant to hard water to make the cleaning more effective. At that time, petroleum was found to be a readily available source for the manufacture of detergent surfactants. Today, detergent surfactants can be produced with a variety oleo chemicals (derived from fats and oils) and/or petrochemicals (derived from petroleum). Now let us first examine the composition of petrochemicals, oleo chemicals and alkalis prior to the review of how surfactant detergents work.
Petrochemicals and Oleo chemicals:
Like the fatty acids that are used in soap manufacturing, both the petroleum and fats and oils contain hydrocarbon chains, which are repelled by water but attracted to grease and oils in soils. The hydrocarbon chain sources are used to form the water-repelling end of the surfactant molecule.
Other chemicals include chemicals, like sulfur trioxide, sulfuric acid and ethylene oxide that can be used to produce the water-attracting end of the surfactant molecule.
As like soap making, an alkali is used to form detergent surfactants. Potassium and sodium hydroxide are the most commonly used alkalis.
BAR SOAPS MANUFACTURING PROCESS
The manufacturing of soaps consist of a comprehensive range of processing and packaging activities. The complexity and of these activities may vary from small plants that employ a few people to those with many hundred workers. Products may range from all purposes and uses to those that for used for a specific application or requirement.
The first step in the manufacturing of bar soaps is the selection of raw materials. Raw materials are selected on the basis of several factors, which may include human and environmental safety, cost, compatibility with other ingredients, and the appearance and performance characteristics of the final product. While the actual production process may vary from manufacturer to manufacturer and company to company, there are some steps that are common to all bar soaps.
The traditional bar soaps are made from oils, fats or their fatty acids that are reacted with inorganic water soluble bases. The prime sources of fats are beef and mutton tallow, while coconut, palm and palm kernel oils are the main oils that are used in soap manufacturing. The raw materials of a bar soap can be pretreated to remove impurities and to achieve the desired color, odor and performance characteristics desired in the finished bar.
Bar soap can be manufactured by either using batch or continuous process. Soap was manufactured by using batch kettle boiling method, until shortly after World War II, when continuous processes were developed. Now days, continuous process of soap making are preferred because of their speed, flexibility and cost economy.
Both the batch as well as continuous soaps making processes produce the soap in liquid form (known as neat soap), and a valuable by-product, glycerin.
The glycerin is recovered from the soap mixture using the chemical treatment, which is followed by evaporation and refining. Refined glycerin is a valuable and expensive industrial material that is used in various products including cosmetics, foods, drugs, and many more.
The next steps after the saponification or neutralization process are drying. Vacuum spray drying is a technique, which is used to convert the neat soap into pellets of dry soap. The moisture content of the soap pellets may vary depending on the desired characteristics and properties of the soap bar.
In the final stage of processing, the dry soap pellets pass through a bar soap finishing line. The first unit in the line is a mixer (known as amalgamator), in which the soap pellets are blended together with colorants, fragrances, and many other ingredients as per the desired characteristics and properties in the final product. The mixture is then homogenized and refined using refining plodders and rolling mills to achieve thorough blending and a standard texture. In the end, the mixture is continuously extruded from the plodder, cut into bars of desired sizes and stamped into its final shape in a soap press.
Some of bar soaps available today are known as "combo bars" as they get their cleaning action from a combination of synthetic surfactants and soaps. Another bar soap bars, known as "syndet bars," feature surfactants as their prime cleansing ingredients. The processing technique for producing the synthetic base materials for these bars is very different from that, which is used in traditional soap making. However, with some minor modifications and adjustments, the finishing line equipment are same for both.
Industrial Soap Making:
The industrial soap making involves four basis steps -
• Glycerin Removal
• Soap Purification
These different steps involve various processing steps and operations in their own. A brief description of these different steps is given below -
The saponification process involves the mixing of tallow (animal fat) and coconut oil with sodium hydroxide and the application of heat. The process results in formation of soap, which is a salt of long chain carboxylic acid.
Glycerin is more valuable than soap, and hence most of it is removed for its uses in more expensive cosmetic projects. Some of the glycerin is left in the soap to make it soft and smooth. Soap is generally not very soluble in salt water, while glycerin is, hence the salt is added to the wet soap thereby causing it to separate out into glycerin and soap in salty water.
In the soap purification stage, any remaining sodium hydroxide is neutralized with a weak acid, like citric acid and two thirds of the remaining water is removed to obtain pure soap.
The final stage of industrial soap manufacturing process, finishing stage involves mixing of additives, such as colors, preservatives, and perfume into soap, which is then shaped into bars for sale.
Toilet Soap Manufacturing:
Toilet soap generally has less water and more fatty material than laundry soap and because of this, the base soap intended for manufacturing toilet soap usually has extra fatty acids that are blended with preservatives before it is vacuum dried. These measures ensure that there are no unreacted caustic remains in the soap by the time it reaches the consumer, and also make the soap softer. Additives, such as perfume, dye and opacifier are then mixed to the dried soap and the mixture is milled to ensure even mixing. It is then plodded and extruded out as a continuous bar, which is cut into billets and stamped ready for packaging and sale.
Detergents Manufacturing Process:
Detergents are manufactured using a synthetic surfactant in place of the metal fatty acid salts that are used in soaps. Made in powder detergents, these detergents are sold as laundry powders, hard surface cleansers, dishwashing detergents, fabric conditioners etc. Most of the powder detergents have soap in their mixture of ingredients, however it generally functions more as a foam depressant than as a surfactant.
Powder detergents are manufactured using various processes, such as spray drying, agglomeration, dry mixing or a combination of these. A brief description of these different processes is given below -
Spray Drying Process:
The different stages / operations performed in a spray drying process, are -
• Dry and liquid ingredients are first combined into a slurry, or thick suspension, in a tank known as crutcher.
• The slurry is heated and then pumped to the top of a tower where it is sprayed through nozzles (under high pressure) to create small droplets. The droplets fall through a current of hot air, thereby forming hollow granules as they dry.
• Collected from the bottom of the spray tower, the dried granules are screened to obtain a relatively standard size.
• After the granules have been cooled, heat sensitive ingredients, which are not compatible with the spray drying temperatures (like bleach, enzymes and fragrance) are added.
Traditional spray drying process produces relatively low-density detergent powders. Advancements in technology have enabled the soap and detergent manufacturers to reduce the air inside the granules during spray drying to obtain higher densities. The high-density detergent powders can be packed in much smaller packages than those needed previously.
Agglomeration is detergent powder manufacturing chemical technique that results in high-density powders. The process involves blending of dry raw materials with liquid ingredients. The technique involves machines, such as a liquid binder, rolling or shear mixing that causes the ingredients to collide and adhere to each other, producing larger particles.
Dry mixing is a detergent powder manufacturing technique, which is used to blend dry raw materials. The technique may also involve the addition of small quantities of a liquid.
Mentioned in the table below are the ingredients of a detergent base powder -
Sodium tripolyphsophate(STP) Water softener, pH buffers (to reduce alkalinity).
Sodium sulphate Bulking and free-flowing agent.
Soap noodles Causes rapid foam collapse during rinsing.
Zeolite Water softener (absorbs Ca 2+ and Mg 2+) in countries where STP is not used; granulating agent for concentrated detergents.
Sodium carboxymethyl cellulose Increases the negative charge on cellulosic fibers, like cotton and rayon, causing them to repel dirt particles (which are positively charged).
Linear alkylbenzene sulphonic acid (LAS) Surfactant - the main active ingredient
Caustic soda solution Neutralizes the LAS.
Coconut diethanolamide or a fatty alcohol ethoxylate Nonionic detergent and foam former.
Fluorescer Absorbs UV light and emits blue light, causing aging cotton to appear white rather than yellow.
Water Dissolves the various ingredients, causing them to mix better.
Detergent powder manufacturing has some specific environmental issues that are not associated with any other industry. These issues include dust control and volatile organic emissions. Dust present during the process of delivery and transfer of bulk powdered detergent is a potential problem. In order to filter out most of the dust, dry and wet cyclones are used, and all the emissions are monitored.
If the dust level in these does exceeds the acceptable limits, appropriate remedial action must be taken. The permissible dust levels in emissions are under below 50-mg m -3. The spray-drying tower also releases volatile organics, which can be minimized by having tight specifications specifying what can be added as a primary detergent active material. Spot checks must be made on the total hydrocarbon content of the exhaust gases using a flame ionization detector.
LIQUID DETERGENTS AND MANUFACTURING PROCESS
The liquid detergent manufacturing consists of a wide range processing and packaging operations and the size and complexities of these operations may vary depending on factors, such as the size of plant and the manufacturing process undertaken. Products may range from an all-purpose laundry cleaner to specialty cleaner such as glass cleaner.
The first step in the manufacturing of liquid detergents is the selection of raw materials. Raw materials are selected on the basis of several factors, such as human and environmental safety, cost, compatibility with other ingredients and the form and he specific properties desired in the final product. While the actual production processes may vary from manufacturer to manufacturer, some processes and techniques are common for all.
For manufacturing liquid detergent, both the batch as well as continuous blending processes is used. Both batch and continuous blending processes are used to manufacture liquid and gel cleaning products. Stabilizers may be added during manufacturing to ensure the uniformity and stability of the finished product.
In a typical continuous process, dry and liquid ingredients are added and blended to a uniform mixture using in-line or static mixers.
Recently, more concentrated liquid products have been introduced and a technique for developing these products is through the use of new high-energy mixing processes in combination with stabilizing agents.
To make liquid detergent, the dry powder is simply mixed back in with a solution consisting of chemicals and water, called as "solubilizers." These chemicals help the water and detergent to blend together more evenly. The amount of light reflected, in comparison to the amount reflected by a sample of the original fabric, is a measure of the degree of cleanliness. A reflection rate of 98 % is considered as quite good and shows that the detergent has cleaned properly.
Manufacture Process - Stages Involved -
The different stages involved in soap manufacturing include -
• Soap premix manufacture - Liquid detergents contain a combination of soap and synthetic surfactants. These are made first as a premix, after which other ingredients are blended into it. This stage simply consists of neutralizing fatty acids with either caustic soda (NaOH) or potassium hydroxide.
• Ingredient mixing - All ingredients except the enzymes are added and mixed at a high temperature. The ingredients used in the manufacturing of liquid detergents are usually sodium tripolyphosphate, caustic soda, sulphonic acid, perfume and water.
• Enzyme addition - In this stage, the mixture is cooled and milled, and the enzymes are added in powder form.