Laundry Detergents by Eduard Smulders

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Laundry Detergents
By Eduard Smulders
Laundry Detergents

Contents
1. Historical Review 1
2. Physical Chemistry of the Washing Process 7
2.1. Influence of the Water 7
2.2. Types of Soil 8
2.3. The Soil Removal Process 11
2.3.1. Oily/Greasy Soil 13
2.3.2. Particulate Soil 21
2.3.3. Calcium-Containing Soil 29
2.3.4. Influence of Textile Fiber Type 33
2.4. Subsequent Processes 34
2.4.1. Dispersion and Solubilization Processes 34
2.4.2. Adsorption 35
2.4.3. Soil Antiredeposition and Soil Repellent Effects 35
2.5. Concluding Remarks 38
3. Detergent Ingredients 38
3.1. Surfactants 39
3.1.1. Anionic Surfactants 45
3.1.2. Nonionic Surfactants 52
3.1.2.1. Alcohol Ethoxylates (AE) 52
3.1.2.2. Alkylphenol Ethoxylates (APE) 55
3.1.2.3. Fatty Acid Alkanolamides (FAA) 55
3.1.2.4. Alkylamine Oxides 56
3.1.2.5. N-Methylglucamides (NMG) 56
3.1.2.6. Alkylpolyglycosides (APG) 56
3.1.3. Cationic Surfactants 57
3.1.4. Amphoteric Surfactants 61
3.2. Builders 61
3.2.1. Alkalies 62
3.2.2. Complexing Agents 63
3.2.3. Ion Exchangers 68
3.2.4. Builder Combinations 74
3.3. Bleaches 74
3.3.1. Bleach-Active Compounds 75
3.3.2. Bleach Activators 80
3.3.3. Bleach Catalysts 83
3.3.4. Bleach Stabilizers 83
3.4. Further Detergent Ingredients 84
3.4.1. Enzymes 84
3.4.2. Soil Antiredeposition Agents, Soil Repellent/Soil Release Agents 88
3.4.3. Foam Regulators 90
3.4.4. Corrosion Inhibitors 92
3.4.5. Fluorescent Whitening Agents 92
3.4.6. Dye Transfer Inhibitors 96
3.4.7. Fragrances 96
3.4.8. Dyes 97
3.4.9. Fillers and Formulation Aids 98
4. Household Laundry Products 98
4.1. Heavy-Duty Detergents 99
4.1.1. Conventional Powder Heavy-Duty Detergents 100
4.1.2. Compact and Supercompact Heavy-Duty Detergents 103
4.1.3. Extruded Heavy-Duty Detergents 106
4.1.4. Heavy-Duty Detergent Tablets 106
4.1.5. Color Heavy-Duty Detergents 107
4.1.6. Liquid Heavy-Duty Detergents 108
4.2. Specialty Detergents 110
4.2.1. Powder Specialty Detergents 111
4.2.2. Liquid Specialty Detergents 111
4.3. Laundry Aids 112
4.3.1. Pretreatment Aids 113
4.3.2. Boosters 114
4.3.3. Aftertreatment Aids 115
4.3.3.1. Fabric Softeners 116
4.3.3.2. Stiffeners 117
4.3.3.3. Laundry Dryer Aids 119
4.3.4. Other Laundry Aids 119
4.3.4.1. Refreshing Products for Dryer Application 119
4.3.4.2. Odor Removers for Washer Application 120
5. Industrial and Institutional Detergents 120
6. Production of Powder Detergents 122
6.1. Technology Overview 123
6.2. Manufacturing Processes 125
6.2.1. Traditional Spray-Drying Process 125
6.2.2. Superheated Steam Drying 127
6.2.3. Nontower Agglomeration Process 127
6.2.4. Nontower Compound Technology 129
6.3. Densification Processes 129
6.3.1. Dry Densification in a Mixer 130
6.3.2. Dry Densification in a Spheronizer 130
6.3.3. Dry Densification in a Roller Press 131
6.3.4. Wet Granulation 131
6.3.5. Spaghetti Extrusion 132
6.3.6. Postaddition Process 135
6.3.7. Dry Densification in a Tablet Press 135
6.4. Raw Materials 138
6.4.1. Anionic Surfactants 138
6.4.2. Nonionic Surfactants 139
6.4.3. Builders 141
6.4.4. Peroxygen Bleaches 142
6.4.5. Enzymes 143
7. Analysis of the Composition 145
7.1. Detergent Ingredients 146
7.2. Purposes of Detergent Analysis 147
7.3. Sample Preparation 147
7.4. Analytical Methods 147
7.4.1. Qualitative Analysis 147
7.4.2. Sample Preparation 148
7.4.3. Quantitative Analysis 149
7.4.4. Separation Methods 151
7.4.5. Structure Determination 152
7.4.6. Determination of Characteristic Values 153
7.4.7. Analysis Automation 153
7.5. Sources of Information 153
8. Test Methods for Laundry Detergents 154
8.1. Laboratory Methods 155
8.2. Practical Evaluation 156
8.3. Consumer Tests 157
9. Economic Aspects 157
9.1. Detergent Components 158
9.1.1. Surfactants 158
9.1.2. Builders 160
9.2. Laundry Detergents 161
9.3. Fabric Softeners 164
9.4. Other Laundry Aids 165
10. Ecology 165
10.1. Laundry, Wastewater, and the Environment 165
10.2. Contribution of Laundry to the Sewage Load 166
10.3. Detergent Laws 167
10.3.1. Development of the European Detergent Legislation 168
10.3.2. Regulatory Limitations on Anionic and Nonionic Surfactants 169
10.3.3. Primary Biodegradation Test Procedures 170
10.3.4. Regulation of Maximum Phosphate Content in Detergents 172
10.4. General Criteria for the Ecological Evaluation of Detergent
Chemicals 173
10.4.1. Concept 174
10.4.2. Environmental Exposure Assessment 174
10.4.2.1. Biodegradation 175
10.4.2.2. Biodegradability Standard Test Methods 176
10.4.2.3. Supplementary Biodegradation Test Methods 178
10.4.2.4. Exposure Analysis 179
10.4.3. Assessment of Environmental Effects 181
10.4.3.1. Basic Ecotoxicity Tests 182
10.4.3.2. Subchronic and Chronic Ecotoxicity Tests 184
10.4.3.3. Biocenotic Ecotoxicity Tests 184
10.4.3.4. Bioaccumulation 184
10.4.4. Process of Environmental Risk Assessment 185
10.5. Ecological Characterization of Main Detergent Ingredients 186
10.5.1. Surfactants 186
10.5.1.1. Anionic Surfactants 186
10.5.1.2. Nonionic Surfactants 190
10.5.1.3. Cationic Surfactants 192
10.5.2. Builders 193
10.5.2.1. Zeolites 193
10.5.2.2. Polycarboxylates 194
10.5.2.3. Citrates 195
10.5.2.4. Sodium Carbonate (Soda Ash) 195
10.5.2.5. Nitrilotriacetate (NTA) 196
10.5.3. Bleaching Agents 196
10.5.3.1. Sodium Perborate 196
10.5.3.2. Sodium Percarbonate 197
10.5.3.3. Tetraacetylethylenediamine (TAED) 197
10.5.4. Auxiliary Agents 198
10.5.4.1. Phosphonates 198
10.5.4.2. EDTA 199
10.5.4.3. Enzymes 200
10.5.4.4. Optical Brighteners 200
10.5.4.5. Carboxymethyl Cellulose 201
10.5.4.6. Dye Transfer Inhibitors 201
10.5.4.7. Fragrances 201
10.5.4.8. Foam Regulators 202
10.5.4.9. Soil Repellents 202
10.5.4.10. Dyes 202
10.5.4.11. Sodium Sulfate 203
11. Toxicology 203
11.1. Detergent Ingredients 204
11.1.1. Surfactants 204
11.1.2. Builders 206
11.1.3. Bleach-Active Compounds 206
11.1.4. Auxiliary Agents 207
11.2. Finished Detergents 208
11.3. Conclusions 208
12. Textiles 209
13. Washing Machines and Wash Programs (Cycles) 220
13.1. Household Washing Machines 220
13.1.1. Classification 220
13.1.2. Operational Parameters 224
13.1.3. Wash Programs 227
13.1.3.1. Japanese Washing Machines and Washing Conditions 227
13.1.3.2. North American Washing Machines and Washing Conditions 227
13.1.3.3. European Washing Machines and Washing Conditions 228
13.1.4. Energy and Water Consumption 230
13.1.5. Construction Materials Used in Washing Machines 230
13.1.6. The Market for Washing Machines 232
13.2. Laundry Dryers 234
13.3. Washing Machines for Institutional Use 236
13.3.1. Batch-Type Machines 236
13.3.2. Continuous Batch Washers 237
14. References 238
Index 261

Historical Review
The symbol used by the ancient Egyptians to represent a launderer was a pair of legs immersed in water. This choice was logical, because at that time the standard way to wash clothes was to tread on them. The “fullones” of ancient Rome earned their bread, too, by washing clothes with their feet. The washing process then was very simple: laundry of every kind was subjected to purely mechanical treatment consisting of beating, treading, rubbing, and similar procedures. It has long been known, however, that the washing power of water can be increased in various ways. Rainwater, for example, was found to be more suitable for washing than well water. Hot water also was found to have more washing power than cold, and certain additives seemed to improve any water's effectiveness.

Even the ancient Egyptians used soda ash as a wash additive. This was later supplemented with sodium silicate to make the water softer. These two substances also formed the basis for the first commercial detergent brand to appear on the German market, Henkel's “Bleichsoda”, introduced in 1878. Its water-softening effect was a result of the precipitation of calcium and magnesium ions, and it simultaneously eliminated iron salts, which had a tendency to turn laundry yellow. Used along with soap, which had also been known since antiquity, this product prevented the formation of inactive material known as “lime soaps”, and the laundry no longer suffered from a buildup of insoluble soap residues.

Soap is the oldest of the surfactants. It was known to the Sumerians by ca. 2500 b.c., although the Gauls were long credited with its discovery. For more than 3000 years, soap was regarded strictly as a cosmetic—in particular a hair pomade—and as a remedy. Only in the last 1000 years has it come to be used as a general purpose washing and laundering agent. Soap remained a luxury until practical means were discovered for producing soda ash required for saponification of fats. With the beginning of the 20th century and the introduction in Germany of the first self-acting laundry detergent (Persil, 1907), soap took its place as one ingredient in multicomponent systems for the routine washing of textiles. In these, soap was combined with so-called builders, usually sodium carbonate, sodium silicate, and sodium perborate. The new detergents were capable of sparing people the weather-dependent drudgery of bleaching their clothes on the lawn, and the enhanced performance of these new agents substantially reduced the work entailed in doing laundry by hand.

The next important development was the transition brought about by technology from the highly labor-intensive manual way of doing laundry to machine washing. This change in turn led to a need for appropriate changes in the formulation of laundry detergents. Soap, notorious for its sensitivity to water hardness, was gradually replaced by so-called synthetic surfactants with their more favorable characteristics. The term “synthetic surfactants” is erroneous when used to distinguish from soap, which itself is made through synthesis as well. The first practical substitutes for soap were fatty alcohol sulfates, discovered in Germany by Bertsch and coworkers in 1928 [1]. The availability of synthetic alkyl sulfates based on natural fats and oils made possible the first neutral detergent for delicate fabrics: Fewa, introduced in Germany in 1932. This was followed in 1933 on the U.S. market by Dreft, a similarly conceived product. Fatty alcohol sulfates and their derivatives (alkyl ether sulfates, obtained by treating fatty alcohols with ethylene oxide and subsequent sulfation) still retain their importance in many applications, particularly in heavy-duty detergents, specialty detergents, dishwashing agents, cosmetics, and toiletries. The general acceptance worldwide of synthetic surfactants, with their reduced sensitivity to water hardness relative to soap, is a development of the 1940s. Procter & Gamble introduced the synthetic detergent Tide in the USA in 1946. By the 1950s the widespread availability of tetrapropylenebenzenesulfonate (TPS), a product of the petrochemical industry, had largely displaced soap as the key surfactant from the detergent market in the industrialized nations. The only remaining role of soap in the industrialized countries became that of a foam regulator. The favorable economics associated with TPS, along with its desirable properties, caused this branched-chain synthetic surfactant to capture ca. 65 % of the total synthetic surfactant demand in the Western world in the late 1950s.


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