Applications of Wet-End Paper Chemistry (eBook)

Ian Thorn (Regional Sales and Marketing Manager) PhD and Che On Au (Application Engineer) PhD Eka Chemicals, Bridge House, Congresbury, Bristol, BS49 5JA Both co-edited the 1st Edition of "Applications of Wet-End Paper Chemistry" Thorn has also co-edited "Surface Application of Surface Chemicals", "Handbook of Toxicology and Ecotoxicology for the Pulp and Paper Industry" and "Toxicology and Ecotoxicology in Chemical Safety Assessment" Che On Au has also written a chapter entitled "Practical Applications of Paper of Paper Chemistry" in the book titled "Paper Chemistry" edited by John Roberts.

Applications of Wet-End Paper Chemistry 2
Chapter 1 11
Introduction 11
Background 11
Process Chemicals 12
Deposit Control 12
Retention, Drainage and Formation 13
Foam 13
Performance Chemicals 13
Sizing 13
Fillers 14
Dry Strength Resins 14
Wet Strength Resins 15
Wet-End Starch 15
Dyeing 16
Online Measurement and Control 16
Chapter 2 17
Improving Productivity and Quality by Controlling Organic, Inorganic and Microbiological Deposits 17
2.1 Introduction the Significance of Appropriate Surface Quality
2.2 Types of Deposits 19
2.2.1 Microbiological Deposits 20
2.2.1.1 Micro-organisms 21
2.2.1.2 The Five Stages of Biofilm Formation 24
Stage One: Formation of the Base Layer for Biofilm Growth 24
Stage Two: Colonialisation of the Surface 24
Stage Three: Biofilm Formation 24
Stage Four: Biofilm Maturation 25
Stage Five: Dislodging of Biofilm into the Process Flow 26
2.2.1.3 Measuring Microbiological Activity 26
Physical Methods 26
Analytical Methods 26
Biological Methods 27
2.2.1.4 Methods to Control Biofilm Formation 28
Minimising System Contamination 28
Using Microbicides 29
Oxidising Compounds 30
Biodispersants and Biofilm Inhibitors 30
2.2.2 Organic Deposits 31
2.2.2.1 Analysis of Organic Deposits 33
2.2.2.2 Physical Form of Organic Depositable Material 34
2.2.2.3 Mechanisms of Deposition 34
2.2.2.4 Methods to Control Deposition 35
Minimising the Content of Organic Material 36
Ageing of Wood 37
Removal by Washing 37
Retention of Colloidal Material 38
Minimising the Depositability 38
Maximising the Colloidal Stability 39
Minimising the Surface Affinity 40
2.2.3 Inorganic Deposits 41
2.2.3.1 Inorganic Scale Deposits 42
Calcium Carbonate 42
Calcium Oxalate 43
Barium Sulphate 43
Calcium Sulphate 43
Silicate Scale 44
Aluminium Hydroxide 44
2.2.3.2 Methods to Control Deposition 44
2.2.3.3 Inorganic Filler Accumulated in Felts 46
2.2.3.4 Incorporation of Filler in an Organic or Microbiological Deposit 46
2.2.4 Deposits of Water-Soluble Components 46
Chapter 3 48
Retention and Drainage 48
3.1 Introduction 48
3.2 Review of Chemistry 50
3.3 Basis of Selection 52
3.4 Methods of Evaluation 53
3.5 Limiting Factors and Detrimental Substances 57
3.5.1 Stock Approach Flow 57
3.5.2 Wet-End – The Biggest Problem Is Variability 57
3.5.3 Paper Machine 60
3.5.4 The Sheet 60
3.6 Troubleshooting Experiences 60
Chapter 4 62
Foam and Entrained Air Management: A Practical Perspective 62
4.1 Introduction 62
4.1.1 Examples of Problems 64
4.2 Foam Creation and Stabilisation 66
4.3 Foam Destruction 68
4.4 Product Type 72
4.5 Foam and Entrained Air Monitoring in a Mill 74
4.6 Application Strategies and Troubleshooting 76
4.6.1 Application Strategies 78
4.6.2 Troubleshooting 79
4.7 Summary 79
References 80
Chapter 5 82
Sizing in Acid, Neutral and Alkaline Conditions 82
5.1 Introduction 82
5.2 Product Type 83
5.2.1 Rosin Sizes 83
5.2.2 Alkyl Ketene Dimer Sizes (AKD) 85
5.2.3 Alkyl Succinic Anhydride (ASA) 87
5.2.4 Other Sizes 88
5.3 Application 89
5.3.1 Application of Rosin Size 92
5.3.2 Application of AKD Size 93
5.3.3 Application of ASA Size 93
5.3.4 Other Considerations 95
5.4 Troubleshooting Sizing Problems at the Wet-End 95
5.4.1 Lack of Sizing 96
5.4.1.1 Size Level 96
5.4.1.2 Lack of Sizing - Rosin Size 97
pH 97
Alkalinity 99
Anionic trash (and soluble anionic trash) 100
Stock temperature 101
Drying temperature 102
5.4.1.3 Synthetic Sizing 104
pH 104
Alkalinity 106
System charge 107
Anionic trash (and soluble anionic trash) 110
Stock temperature 111
Drying temperature 112
5.4.2 Slow Cure 114
5.4.2.1 Rosin Size 114
5.4.2.2 Synthetic Size 114
5.4.3 Loss of Sizing, or Fugitivity 115
5.4.3.1 Rosin Sizing 115
5.4.3.2 Synthetic Sizing 115
High moisture 117
5.4.4 Deposits 118
5.4.4.1 Rosin Size 118
5.4.4.2 Synthetic Sizes 118
5.4.5 Other Problems 119
5.4.5.1 Two Sidedness 119
5.4.5.2 Size Migration 120
5.4.5.3 Slip 120
5.4.5.4 Foam 120
5.4.5.5 Defoamers 121
5.4.5.6 Shelf Life 121
5.4.5.7 Size Storage 121
Chapter 6 122
Fillers 122
6.1 Introduction 122
6.2 Types of Fillers 123
6.2.1 Kaolin Clays 123
6.2.1.1 Hydrous Kaolin 123
6.2.1.2 Anhydrous or Calcined Kaolin 125
6.2.2 Calcium Carbonates 126
6.2.2.1 Chalk 126
6.2.2.2 Ground Calcium Carbonate (GCC) 127
6.2.2.3 Precipitated Calcium Carbonate (PCC) 127
6.2.3 Titanium Dioxide 129
6.2.4 Talc 130
6.2.5 Amorphous Silicates 131
6.3 Fundamental Filler Characteristics 132
6.3.1 Pigment Brightness 133
6.3.2 Refractive Index 134
6.3.3 Particle Morphology 135
6.3.3.1 Discrete Particles 136
6.3.3.2 Aggregated Fillers 137
6.3.4 Particle Size and Size Distribution 138
6.3.5 Specific Surface Area 141
6.4 Practical Considerations When Using Filler 141
6.4.1 Filler Interactions with Light 141
6.4.2 Retention 142
6.4.3 Drainage and Drying 143
6.4.4 Point of Addition 143
6.4.5 Potential Interactions with Other Papermaking Components 144
References 144
Chapter 7 146
The Improvement of Dry Strength by Synthetic Polymers 146
7.1 Introduction 146
7.2 Benefits of Dry Strength Resins 147
7.3 Strength Additives Versus Refining 147
7.4 Types of Synthetic Resin 148
7.5 Methods of Use 151
7.5.1 Addition Points 151
7.5.2 Dosages 152
7.5.3 Surface Addition 153
7.6 Troubleshooting 153
7.6.1 Loss of Strength on Addition of Resin 153
7.6.2 Poorer Sheet Formation 154
7.6.3 Loss of Charge Balance 154
7.7 Summary 155
References 155
Chapter 8 156
Wet-Strengthening of Paper in Neutral pH Papermaking Conditions 156
8.1 Introduction 156
8.1.1 Definition of Wet Strength 156
8.1.2 History of Wet Strength Resins 157
8.2 Polyaminopolyamide-Epichlorohydrin (PAE) Wet Strength Resins 158
8.2.1 Basic Chemistry and Classification of PAE Wet Strength Resins 158
8.2.2 General Mechanisms of Wet Strength Development 160
8.2.3 Application Guidelines for PAE Wet Strength Resins 162
8.2.3.1 Handling of PAE Resins 162
8.2.3.2 Factors Affecting the Retention of PAE Resins 162
8.2.3.3 Factors Affecting the Reaction of PAE Resins 165
8.2.3.4 Effect of Water Quality 165
8.2.3.5 Using Additional Polymers to Enhance PAE Resin Performance 167
8.2.4 Effects of Other Chemical Additives 169
8.2.4.1 Dyes and Optical Brightening Agents 169
8.2.4.2 Softeners and De-bonders 169
8.2.4.3 Absorbency Aids 170
8.2.4.4 Sizing Agents 170
8.2.5 Choice of PAE Wet Strength Resins 170
8.3 Glyoxalated Polyacrylamide (GPAM) Wet Strength Resins 171
8.3.1 Basic Chemistry and Wet Strength Mechanisms 172
8.3.2 Relative Cure Rate of Wet Strength Functionality 173
8.3.3 Application Guidelines for GPAM Wet Strength Resins 175
8.3.3.1 Effect of pH 176
8.3.3.2 Effect of Alkalinity 176
8.3.3.3 Effect of Free Chlorine and Sulphite 177
8.3.3.4 Impact on Crêping 177
8.3.3.5 Impact on Absorbency 177
Chapter 9 179
Starch in the Wet-End 179
9.1 Introduction 179
9.2 Chemistry of Starch 179
9.2.1 Phosphorus Content 182
9.3 Preparation of Starch 182
9.3.1 Batch Cooking 182
9.3.2 Continuous Cooking 183
9.3.3 Batch Versus Jet Cooking 184
9.3.4 Overcooking 184
9.3.5 Starch Distribution 185
9.3.6 Retrogradation or Set-Back 185
9.4 Application of Starch 186
9.4.1 Native Starch in the Wet-End – Starch Spraying 186
9.4.2 Anionic Starch in the Wet-End 187
9.4.3 Cationic Starch in the Wet-End 187
9.4.4 Cationic Starch Production Process 188
9.4.5 Cationic Starch Adsorption 189
9.4.6 Effects of Salts 189
9.4.7 Effect of DS 190
9.4.8 Mixing Shear and Time Effects 191
9.4.9 Amphoteric Starches 191
9.4.10 Dual Starch Systems 193
9.5 Function of Starch 193
9.5.1 Effects of Starch in Paper 193
9.5.2 Strength Mechanisms 194
9.5.3 Strength and Flocculation 195
9.5.4 Filled Papers 195
9.5.5 Retention 196
9.5.6 Size Emulsification 196
9.5.7 Anionic Trash Catcher 197
9.6 Mill Experience with Starch 197
9.6.1 Wet-End Strategy and Starch Selection 197
9.6.2 Starch Hygiene 198
9.6.3 Returned Size Press Starch 199
9.7 Summary 200
References 201
Chapter 10 203
Paper Colouration 203
10.1 Introduction to Colour in Paper 203
10.1.1 Colour in Paper 203
10.1.2 Why Is Paper Coloured? 203
10.2 Chemistry 204
10.2.1 Chemistry of Colours 204
10.2.2 Types of Colourants Used Within the Paper Industry 205
10.3 Colour – How to Achieve It 208
10.3.1 Selection of Colourants 208
10.3.2 Application of Colour 209
10.4 Factors Affecting Colourant Choice and Performance 210
Pulp freeness 210
Furnish variations 210
Consistency 210
Water hardness 211
Filler 211
Broke 211
Fixing agents 211
Sheet moisture content 211
10.5 Colour Measurement – the CIE L*a*b*C*h System 212
Chapter 11 214
Online Monitoring and Control in the Wet-End 214
11.1 Introduction 214
11.2 Elements of a Pulp Suspension and Various Measuring Parameters 215
11.3 Charge Measuring Principles Based on Streaming Potential 216
11.3.1 Zeta Potential 216
11.3.2 Cationic Demand 216
11.4 Approach to Control Chemicals Based on a Wet-End Charge Survey 217
11.4.1 Wet-End Charge Surveys at a Paper Machine 217
11.5 Description of Various Control Strategies 219
11.5.1 Fixative Control 219
11.5.2 Retention Aid Control 220
11.5.3 Ash Control 221
11.5.4 Gas/Air Control 221
11.5.5 Combined Control Strategies 221
11.5.6 Multivariable Control (MVC) 221
11.6 Applications in Different Paper Grades 222
11.6.1 Fine Paper 222
11.6.2 Newsprint 224
11.6.3 Specialty Paper and Tissue 225
11.6.4 Board 226
11.7 Summary and Conclusions 227
References 227
Index 228