Abstract Process Economics Program Report 194A SUPERABSORBENT POLYMERS (April 2002) Superabsorbent polymers (SAPs) represent a class of organic chemicals defined primarily by the their functional capability rather than their chemical structure. SAPs are polymers that are capable of absorbing and retaining large quantities of water and other aqueous mixtures. They find attractive commercial applications in baby diapers, feminine hygiene products, and adult incontinence products. Other emerging applications include medical wound dressings, soil/water stabilization layers in farming and civil engineering structures, food packaging, fiber and metallic cable sealing, lubricants and sealants, and cosmetics. Global production of SAP is approximately 1 million metric tons annually. The vast majority of the capacity to produce SAP is in the hands of 4 companies: BASF, Nippon Shokubai, Stockhausen and Dow. As the demand in industrialized countries for SAP in personal hygiene products slows to levels approaching GDP rates, attention by SAP producers has been focused on better market penetration in developing countries, and expanding the application of SAP into new end-uses. Commercial superabsorbent polymers are made primarily via homopolymerization of glacial acrylic acid or acrylamide, copolymerization of acrylic acid with acrylamide, or vinyl alcohol, and graft copolymerization of polyacrylic acid with starch. Grafting of starch to polyacrylic acid is done to enhance biodegradability. SAPs are fabricated primarily in the form of dry, white powders, but there are emerging applications of SAP in fiber and laminate form. Nearly all commercial polymerization to make SAP is conducted in batch reactors where aqueous polymerization forms a viscous gel that is subsequently cut, dried and milled to desired end property specifications. A small proportion of SAP is produced via inverse emulsion polymerization, and a small proportion of production is manufactured via continuous reaction in moving belts and possibly in plug flow reactors. This report updates the 1990 original PEP190 report on superabsorbent polymers. We provide historical and forecast market data on supply and demand segmented geographically and by end use application, describe the competitor environment among producers, and describe and commercial technology utilized to make SAPs. We provide in this report preliminary process designs and the corresponding economics for making improved commercial specification SAP using batch, aqueous solution polymerization using processes and procedures documented by Dow Chemical. We also provide a design and the corresponding economics for a novel continuous polymerization reaction using a plug flow reactor design based upon patents by BASF. PEP 01 AP
CONTENTS GLOSSARY... xvii 1 INTRODUCTION... 1-1 PREVIOUS SRI CONSULTING REPORTS... 1-3 2 SUMMARY... 2-1 3 INDUSTRY STATUS... 3-1 WATER SOLUBLE POLYMERS... 3-1 HISTORICAL BACKGROUND... 3-6 Partially Neutralized, Lightly Cross-Linked Poly Acrylic Acid... 3-6 Non-lonic SAPs... 3-7 Polyacrylate SAP... 3-7 Starch Grafted Acrylonitrile SAP... 3-7 Poly Vinyl Alcohol Based SAP... 3-8 Isobutylene-Maleic Anhydride SAP... 3-8 COMMERCIALIZATION OF SAP INTO DISPOSABLE BABY DIAPERS... 3-8 CHEMICAL STRUCTURE OF SAPS... 3-9 SAP COMPOSITES... 3-10 ABSORBENCY LIMITATIONS... 3-11 COMPETING MATERIALS... 3-12 PHYSICAL FORMS OF SAPS... 3-12 INTEGRATED PRODUCT CHAIN FOR SAP... 3-13 PHYSICAL CHARACTERISTICS OF SAPS... 3-14 IMPACT OF MOLECULAR WEIGHT ON COMMERCIAL APPLICATIONS... 3-15 COMMERCIAL USES AND PERFORMANCE REQUIREMENTS... 3-15 SAP USE IN BABY DIAPERS... 3-17 SAP USE IN FEMININE TAMPON PRODUCTS... 3-27 iii
CONTENTS (Continued) PACKAGING APPLICATIONS FOR SAPS... 3-27 SAP USE AS A WATER CONSERVATION AGENT IN AGRICULTURE... 3-28 BIOLOGICAL APPLICATIONS FOR SAP... 3-29 BIODEGRADABLE SAP... 3-29 FOOD CONTACT APPROVAL FOR SAP... 3-31 BUSINESS ENVIROMENT FOR SAP IN 2001... 3-32 CONSUMPTION OF SAPS... 3-32 FORECAST SAP GROWTH RATE... 3-34 SAP PRODUCTION AND PRODUCERS... 3-37 SAP PRODUCERS IN THE US... 3-40 SAP PRODUCERS IN EUROPE... 3-41 SAP PRODUCERS IN JAPAN... 3-43 SAP PRODUCERS IN OTHER REGIONS... 3-43 SAP PRODUCERS PROFILES... 3-45 BASF... 3-45 Dow Chemical... 3-47 Elf Atochem... 3-49 Sanyo Chemical Industries... 3-51 Nippon Shokubai... 3-52 Stockhausen/Degussa... 3-53 Rohm & Haas... 3-58 COMMERCIAL PRICES FOR SAP... 3-58 4 PROCESS TECHNOLOGY TO MANUFACTURE SAP'S... 4-1 THERMODYNAMICS OF SAP CHEMISTRY... 4-2 POLYMERIZATION CHEMISTRY... 4-3 iv
CONTENTS (Continued) POLYACRYLIC ACID AND ITS SODIUM SALT... 4-7 SOLUTION CO-POLYMERIZATION OF ACRYLIC ACID... 4-8 INVERSE EMULSION POLYMERIZATION OF ACRYLIC ACID... 4-10 SUSPENSION POLYMERIZATION... 4-11 PRECIPITATION POLYMERIZATION... 4-11 GRAFT COPOLYMERIZATION... 4-11 CROSS-LINKING METHODS OF POLYMERIZATION... 4-12 CROSS-LINKING CHEMISTRY... 4-13 FUNCTIONALITY REACTIONS... 4-13 PRODUCT CHARACTERISTICS... 4-14 MORPHOLOGY OF SAP... 4-14 COMMERCIAL SAP MANUFACTURING SEQUENCE... 4-14 GEL BLOCKING... 4-25 SURFACE CROSS-LINKING... 4-25 POST POLYMERIZATION CROSS-LINKING... 4-26 CROSS-LINKING DEFICIENCIES... 4-26 RECYCLING OF FINES... 4-26 VENT GAS PURIFICATION... 4-27 CAPITAL COSTS TO BUILD SAP PLANTS... 4-27 5 RECENT TECHNOLOGY DEVELOPMENTS... 5-1 DRIVERS FOR CHANGE IN THE BABY DIAPER BUSINESS... 5-2 Expanding the Business Concept of Diapers... 5-4 RECENT COMMERCIAL DEVELOPMENTS IN BABY DIAPERS... 5-5 NONWOVEN AIRLAIDS & PREFORMED CORES... 5-6 ENVIROMENTALLY FRIENDLY SUPERABSORBENTS... 5-7 v
CONTENTS (Continued) USE OF NATURAL FEEDSTOCKS... 5-8 ASPARTIC ACID BASED SAPS... 5-8 BIODEGRADABLE FEMININE HYGIENE PRODUCTS... 5-9 SUPERABSORBENT FIBERS... 5-9 ENCAPSULATING AGENT FOR ORAL DRUG DELIVERY... 5-11 INTRAOCULAR LENS... 5-12 OTHER BIOLOGICAL APPLICATIONS FOR SAPS... 5-12 COLD WEATHER APPAREL... 5-13 POWDERED TABLETS... 5-13 EMERGING APPLICATIONS... 5-13 Self-Foaming spray for Covering Materials... 5-13 Geology and Archaeology Research... 5-13 Optical Nanoparticle Sensors... 5-14 Desiccant Applications... 5-14 Water Conservation Agent in Agriculture... 5-15 Optical Cable Protector... 5-15 Water Reducing Agents for Ready-Mix Concrete... 5-18 Other emerging applications... 5-18 IMPROVED SURFACE CROSS-LINKING... 5-18 6 DESIGN BASIS FOR PRODUCING SUPERABSORBENT POLYMERS... 6-1 DESIGN CONDITIONS... 6-1 SITE LOCATION... 6-1 FACILITY SITE BASIS... 6-1 COST BASIS... 6-2 Capital Investment... 6-2 CONSTRUCTION CAPITAL COST INDEX... 6-3 vi
CONTENTS (Continued) PROJECT CONSTRUCTION TIMING... 6-4 Production Costs... 6-4 FEEDSTOCK, PRODUCT AND ENERGY PRICING... 6-5 Effect of Operating Level on Production Costs... 6-5 SAP PROCESS TECHNOLOGY BASIS... 6-6 SUPERABSORBENT POLYMER PLANT CAPACITY... 6-6 PLANT CAPACITY UTILIZATION... 6-6 MATERIALS OF CONSTRUCTION... 6-6 SAP PRODUCT SPECIFICATIONS... 6-7 ACRYLIC ACID FEEDSTOCK REQUIRMENTS... 6-7 CAUSTIC SODA REQUIREMENTS... 6-8 AVAILABLE UTILITIES... 6-9 ROTATING EQUIPMENT DRIVERS... 6-9 CONTINUOUS VERSUS BATCH PROCESSING... 6-9 SAFETY CONSIDERATIONS... 6-9 PRESSURE VESSEL AND PIPING DESIGN CONSIDERATIONS... 6-10 7 SUPERABSORBENT POLYMER PRODUCTION BY CONTINUOUS REACTOR DESIGN PROCESS... 7-1 PATENT LITERATURE ON CONTINUOUS REACTOR PROCESSING... 7-1 DESIGN BASIS AND ASSUMPTIONS... 7-3 PRODUCTION CAPACITY... 7-5 SAP PRODUCT PROPERTIES AND PERFORMANCE... 7-5 BLOCK FLOW DIAGRAM... 7-5 PROCESS DESCRIPTION AND PROCESS FLOW DIAGRAM... 7-8 PROCESS WATER TREATMENT... 7-9 vii
CONTENTS (Continued) ACRYLIC ACID TREATMENT... 7-9 SODIUM HYDROXIDE SUPPLY... 7-9 DISSOLUTION AND NEUTRALIZATION... 7-9 SOLUTION MIXING... 7-10 CONTINUOUS POLYMERIZATION REACTION... 7-10 POLYMER CUTTING... 7-11 POLYMER DRYING... 7-11 SURFACE CROSS-LINKING... 7-11 DRY POLYMER MILLING... 7-12 SCREENING... 7-12 BAGGING AND PALLETIZING... 7-12 VENT GAS SCRUBBING... 7-13 CAPITAL COST ESTIMATE... 7-19 MANUFACTURING ECONOMICS... 7-19 ECONOMICS SENSITIVITIES... 7-23 8 SUPERABSORBENT POLYMER BY IMPROVED AQUEOUS SOLUTION POLYMERIZATION... 8-1 APPLICATION OF DOW CHEMICAL SAP PATENTS... 8-2 DESIGN BASIS... 8-2 DESIRED PRODUCT CHARACTERISTICS... 8-4 OVERVIEW OF PRODUCTION SEQUENCE... 8-4 Reaction Components... 8-4 Drying of the Polymer Gel... 8-5 Product Milling... 8-5 Post Treatment... 8-5 Bagging and Palletizing... 8-6 viii
CONTENTS (Continued) BLOCK FLOW DIAGRAM... 8-6 Processing Sequence... 8-8 MW/RF Radiation for Reducing Extractable Polymer Content... 8-9 Polymer Milling... 8-9 SURFACE CROSS-LINKING... 8-9 Surface Hardening... 8-10 Vent Gas Scrubbing... 8-11 PROCESS DESCRIPTION AND PROCESS FLOW DIAGRAM... 8-11 PROCESS WATER TREATMENT... 8-11 ACRYLIC ACID TREATMENT... 8-11 SODIUM HYDROXIDE SUPPLY... 8-12 DISSOLUTION AND NEUTRALIZATION... 8-12 BATCH POLYMERIZATION REACTION... 8-12 POLYMER HOT AIR DRYING... 8-14 Microwave Radiation Drying... 8-14 DRY POLYMER MILLING... 8-14 SCREENING... 8-14 SURFACE CROSS-LINKING... 8-14 Surface Hardening... 8-15 BAGGING AND PALLETIZING... 8-15 Vent Gas Scrubbing... 8-16 CAPITAL COST ESIMATE... 8-16 MANUFACTURING ECONOMICS... 8-24 ECONOMICS SENSITIVITIES... 8-27 APPENDIX A: PATENT SUMMARY TABLES... A-1 ix
CONTENTS (Concluded) APPENDIX B: CITED REFERENCES... B-1 APPENDIX C: PROCESS FLOW DIAGRAM... C-1 x
ILLUSTRATIONS 1.1 Chemical Structure of polyacrylic Acid... 1-2 1.2 Structure of Partially Neutralized Polyacrylic Acid with Cross-Linking Agents... 1-2 2.1 Distribution of End-Uses for Superabsorbent Polymers... 2-1 2.2 Regional Distribution of Superabsorbent Polymer Demand... 2-2 2.3 SAP Production Capacity of Major Producers... 2-2 2.4 Comparison of Continuous vs. Improved Aqueous Processes for Making SAP... 2-4 2.5 Comparison of Manufacturing Costs Between Continuous and Improved Aqueous SAP Processes... 2-5 3.1 Regional Demand of Water Soluble Polymers in 1997... 3-3 3.2 Forecast Annual Growth Demand Rate for Water Soluble Polymers Between 1997 and 2002 (%/year)... 3-4 3.3 Chemical Structure of Poly Acrylic Acid... 3-9 3.4 Chemical Structure of Poly Methyl Acrylate and Poly Methyl Methacrylate... 3-9 3.5 Chemical Structure of Acrylamide and Poly Acrylamide... 3-10 3.6 Time Related Deterioration in SAP Absorbency Due to Cations in Solution... 3-11 3.7 SAP Absorbency as a Function of Salt... 3-12 3.8 Integrated Product Chain for SAP... 3-13 3.9 End Use Consumption of us Acrylic Acid Production in 2000... 3-13 3.10 Distribution of End Uses for SAP... 3-17 3.11 Impact of SAP Cross-Linking in Retention Capacity and Absorbency Under Load... 3-20 3.12 Composition Change of Baby Diapers Over Time (Courtesy StockHausen)... 3-22 3.13 Historical Trend of SAP in Diaper Free Absorbency Versus Absorbency Under Load Experienced by Sanyo Chemical Industries... 3-24 3.14 Historical Trend of SAP in Gel Stability Experienced by Sanyo Chemical Industries... 3-25 3.15 Historical Trend of SAP in Residual Acrylic Acid Monomer Content of SAP... 3-26 3.16 Historical Trend of SAP in Fine Particulates Content of SAP... 3-26 3.17 StockHausen Estimate of Regional Segmentation of Global SAP Demand in 1999... 3-33 xi
ILLUSTRATIONS (Continued) 3.18 Domestic and Export Consumption of Japanese SAP... 3-34 3.19 Historic Global Growth in SAP Demand... 3-35 3.20 Regional Growth in SAP Demand... 3-36 3.21 Historical and Forecast Growth Rate in SAP Demand... 3-37 3.22 SAP Producer Capacity in 2001... 3-38 3.23 Nameplate SAP Capacity by Region... 3-38 3.24 Regional Distribution of SAP Capacity... 3-39 3.25 Structure of Elf Atochem's Partially Neutralized SAP... 3-49 3.26 Water Absorption Rate of Stockosorb SAP Versus Competing Products for Soils Application... 3-55 4.1 Structure of the Major Commercial Acrylic-Based SAP Polymers... 4-1 4.2 Collapsed (dry) and Expanded (gel) State of Water Soluble Polymer Chains... 4-3 4.3 Free Radical Polymerization of Acrylic Acid Monomer... 4-4 4.4 Impact of PH on SAP Absorption Rate... 4-5 4.5 Block Flow Diagram for the Commercial Manufacture of Superabsorbent Polymer... 4-15 4.6 PAA Reaction Rate as a Function of PH... 4-19 5.1 Annual US Patents Granted for SAP's Since 1980... 5-1 5.2 Moisture Absorption of SAP and Silica Gel as a Function of Relative Humidity... 5-14 5.3 Cross Section of Generic Optical Cable... 5-17 5.4 Neptico's Determination of SAP Viscosity Necessary to Seal Fiber Optic Cable. 5-18 6.1 Historical PEP Construction Cost Index for the US Gulf Coast... 6-4 7.1 Block Flow Diagram for Continuous Reactor SAP Process... 7-6 7.2 Impact of Production Capacity on Manufacturing Economics... 7-23 7.3 Impact of Glacial Acrylic Acid Feedstock Price on SAP Production Cost... 7-24 8.1 Fluidized Bed Dryer for SAP Post Treatment... 8-6 8.2 Block Flow Diagram for the Producing Superabsorbent Polymer by improved, Aqueous Polymerization... 8-7 xii
ILLUSTRATIONS (Concluded) 8.3 Capital Cost Estimate for Improved Aqueous Polymerization SAP Plant at Various Annual Capcities... 8-24 8.4 Impact of Production Capacity on Manufacturing Economics... 8-27 8.5 Sensitivity of SAP Production Cost to Acrylic Acid Feedstock Cost... 8.28 C.1 Continuous Reactor SAP... C-3 C.2 Improved Aqueous Solution Process for Making SAP... C-11 xiii
TABLES 3.1 Chemical Types Used in Water Soluble Polymers... 3-2 3.2 Historic and Forecast Demands for Water Soluble Polymers in Industrial Regions (thousand metric tons/year)... 3--3 3.3 Categories of Water Soluble Polymers... 3-5 3.4 Historic and Forecast Demand for Water Soluble Polymers in the Industrial Regions by Polymer Type (thousand metric tons/year)... 3-6 3.5 Performance Comparison of Various SAP Formulations... 3-10 3.6 Percentage of 2000 Acrylic Acid Production (KT/Y) Devoted to SAP... 3-14 3.7 Physical Properties of Acrylic Acid and Acrylamide... 3-14 3.8 Commercial Applications for SAPs... 3-16 3.9 Distribution of Cost to Manufacture Baby Diapers... 3-18 3.10 Performance Parameter Comparison of First and Second Generation SAP in Diaper Applications... 3-20 3.11 Performance Parameter Comparison of Second and Third Generation SAP in Diaper Applications... 3-21 3.12 Edana Test Procedures for SAPs... 3-21 3.13 Starch Based Graft Copolymers with Enhanced Biodegradability... 3-31 3.14 Consumption of Superabsorbent Polymers by Region (thousand metric tons/year)... 3-33 3.15 Anticipated SAP Annual Demand Growth Rates Between 2000-2005... 3-35 3.16 Trade Names of Major SAP Producers... 3-39 3.17 Major SAP Producers in the US... 3-40 3.18 Major SAP Producers in Europe... 3-42 3.19 Major SAP Producers in Japan... 3-43 3.20 Other Major SAP Producers... 3-44 3.21 Recent SAP Capacity Announcements... 3-45 3.22 Recent US Patents Granted to BASF for SAP... 3-46 3.23 Recent US Patents Granted to Dow Chemical for SAP... 3-48 3.24 Characteristics of Elf Atomchem SAP Baby Diaper Grades... 3-50 xiv
TABLES (Continued) 3.25 Recent US Patents Granted to Elf Atomchem for SAP... 3-51 3.26 Recent US Patents Granted to Sanyo Chemical for SAP... 3-52 3.27 Recent US Patents Granted to Nippon Shokubai for SAP... 3-53 3.28 Physical Characteristics of StockHausen Favor SAP... 3-55 3.29 Physical Characteristics of Stockosorb SAP... 3-56 3.30 Recent US Patents Granted to Stockhausen for SAP... 3-57 3.31 Historical Prices for SAP in JAPAN... 3-59 4.1 Taylor Screen Size Versus Particle Size... 4-24 5.1 Emerging Applications for SAP's... 5-2 5.2 Estimated Cost of Disposable Diapers Versus Alternatives... 5-4 5.3 US Patents for SAP Fibers... 5-10 5.4 Testing Protocols for Water Resistant Fiber Optic Cable... 5-16 5.5 Source and Length of Water Intrusion for Failed Optical Fiber Cable... 5-17 6.1 Construction Cost Site Location Factors... 6-1 6.2 Commercial Inhibitors for Glacial Acrylic Acid... 6-8 6.3 Commercial Specifications for Acrylic Acid... 6-8 7.1 Producing Superabsorbent Polymer by Continuous Reactor Polymerization Design Bases... 7-4 7.2 Continuous Polymerization Reaction Process Stream Flows... 7-14 7.3 Continuous Process for Producing SAP Major Equipment... 7-17 7.4 Factored Capital Cost Estimate for Continuous Process SAP Plant (thousands of dollars)... 7-19 7.5 Continuous Process SAP Plant Total Capital Investment... 7-20 7.6 Continuous Reactor Process to Make SAP Production Costs... 7-21 8.1 Producing Superabsorbent Polymer by Improved Aqueous Solution Polymerization Design Bases... 8-3 xv
TABLES (Concluded) 8.2 Improved Aqueous Polymerization to Produce SAP Stream Flows... 8-17 8.3 Improved Aqueous Process to Manufacture SAP Major Equipment... 8-21 8.4 Improved Aqueous Polymerization SAP Plant Total Capital Investment... 8-23 8.5 Factored Capital Cost Estimate for Improved Aqueous Polymerization SAP Plant... 8-24 8.6 Improved Aqueous Plolymerization Process to Make SAP Production Costs... 8-25 xvi