Eastman Polyester Resin Intermediates for Powder Coatings eastman
Powder Coatings continue to grow rapidly as more and more industrial finishers switch from liquid paint to powder. The reasons to make the switch are compelling: Improved coating performance Lower cost in most applications Elimination of VOC s (volatile organic compounds) HAP s (hazardous air pollutants) Hazardous waste generation/disposal problems. Over half of the worldwide production of powder coatings utilizes polyester resins as a significant portion of the binder system. The broad choices of polyester resins coupled with the various cross-linker options provide the powder coating formulator a wide range of coating properties to cost-effectively meet most end-use needs. There are two basic types of thermoset polyester resins for powders, hydroxyl and carboxyl terminated. Each type utilizes a different set of cross-linkers to make up the powder coating binder system. The resin and cross-linker combinations follow: Polyester Resin Type Hydroxyl Terminated Carboxyl Terminated Matching Cross-Linker Type Blocked Isocyanates Glycoluril (Powderlink 1174) Triglycidylisocyanurate (TGIC) ß-Hydroxylalkylamide (Primid XL552) Epoxy Resins The choice of monomers used in polyester resins has a significant effect on the appearance, physical properties, and storage stability of the resulting powder coatings. This publication describes Eastman Chemical Company s monomers as well as the properties they bring to polyester resins and to powder coatings. 1
NPG Glycol (Neopentyl Glycol) CH 3 HO CH 2 C CH 2 OH CH 3 IUPAC: 2,2-Dimethyl-1,3-Propanediol NPG glycol and purified terephthalic acid (PTA) are the primary components for most polyester resins for powder coatings. Resins based on NPG glycol and PTA can be made with a glass transition temperature (T g ) of 52 68 C (125.6 154.4 F) (2nd heating cycle, midpoint by DSC), the most popular range for powder coatings. Resins based on NPG glycol and PTA have low initial color and good color stability. Excellent weathering (UV resistance and nonyellowing) characteristics with cross-linkers such as TGIC, ß-Hydroxylalkylamide or blocked isocyanate. Good powder flow and fluidization characteristics. Good balance of hardness and flexibility. Good chemical and stain resistance. PIA (Purified Isophthalic Acid) O HO C C OH O IUPAC: 1,3-Benzenedicarboxylic Acid PIA is more soluble and therefore more reactive than PTA in molten glycols and in resins. For this reason, it is often the monomer of choice for converting hydroxyl resins to carboxyl resins during the second stage of the resin synthesis. PIA/NPG glycol-based resins have a T g approximately 7 C lower than their PTA/NPG glycol counterparts but the storage stability of the powders made from these resins is still adequate. PIA/NPG-based resins provide coatings with Superior weathering (UV resistance) characteristics. Less impact resistance and flexibility than other polyester powders but comparable to that of acrylic powders. 2
HPHP (Hydroxypivalyl Hydroxypivalate) CH 3 O CH 3 HO CH 2 C C O CH 2 C CH 2 OH CH 3 CH 3 IUPAC: 3-Hydroxy-2,2-Dimethylpropyl 3-Hydroxy-2,2-Dimethylpropanoate HPHP has structural features and reactivity similar to those of NPG glycol. Resin T g is reduced by approximately 0.2 C for every mole % replacement of NPG glycol in a TPA/NPG resin. HPHP is best suited for carboxyl resins intended for outdoor applications because carboxyl resins have higher initial T g than their hydroxyl equivalent and because of its excellent weathering characteristics. Improved smoothness and flexibility in TGIC and ß-Hydroxylalkylamide systems without sacrificing weathering (UV resistance) properties (NPG and HPHP have similar weathering properties). Good chemical and stain resistance. CHDM (1,4-Cyclohexanedimethanol) CH 2 OH CH 2 OH IUPAC: 1,4-Cyclohexanedimethanol CHDM has no effect on the T g as it replaces NPG glycol in PTA/NPG-based resins. CHDM raises the T g by approximately 0.2 C for every mole replacement of NPG glycol in PIA/NPG-based resins. CHDM s primary alcohol functionality provides good reactivity during resin synthesis and low resin color. CHDM-containing resins provide superior detergent resistance for appliance and other applications where this property is important. 1,4-CHDA (1,4-Cyclohexanedicarboxylic Acid) CO 2 H CO 2 H IUPAC: 1,4-Cyclohexanedicarboxylic Acid Reduced resin cook time is possible because CHDA is more soluble in NPG than PTA and therefore reacts faster. T g is reduced by approximately 0.4 C for every mole replacement of PTA with CHDA in PTA/NPG-based resins. CHDA-containing resins are particularly well suited for applications where excellent flexibility is required and where hardness is also important (i.e., blank and coil coatings, primer surfacers, appliance coatings, etc.). Better smoothness (less orange peel) is achieved as CHDA partially replaces TPA in resins because CHDA is more efficient at reducing melt viscosity. 3
Typical Properties a Physical Molecular Product Form Weight NPG Glycol Platelets 104.15 Molten NPG-90 Glycol Slurry 104.15 CHDM-D Solid 144.21 Molten CHDM-D90 Liquid 144.21 HPHP Solid 204.26 Nugget Molten 1,4-CHDA Powder 172.00 PIA Powder 166.14 a Properties reported here are typical of average lots. Eastman makes no representation that the material in any particular shipment will conform exactly to the values given. b Crystallizes below 31 C (88 F) 4
Specific Assay, Melting Boiling Gravity, Weight % Weight % Point, C Point, C 20 /20 C Solids Volatile Available Packaging 99.5 127 210 1.06 100 1,000-kg (2,205-lb) bulk bags 500-kg (1,100-lb) bulk bags 20-kg (44-lb) bags 22.7-kg (50-lb) bags Tank trucks 89 31 b 0.94 90 Water Tank trucks (60 C) Tank cars 99.5 50 284 288 1.023 100 Cast in 190-kg (419-lb) drums Tank trucks 90 30 0.948 90 Water 205-kg (452-lb) drums Tank trucks 98.1 46 50 293 1.01 100 Cast in 200-kg (441-lb) drums 20-kg (44-lb) bags Tank trucks 99.5 164 167 1.38 100 1,000-kg (2,205-lb) bulk bags 500-kg (1,100-lb) bulk bags 20-kg (44-lb) bags 99.8 345 348 1.507 100 22.7-kg (50-lb) kraft bags 25-kg (55-lb) kraft bags 500-kg (1,100-lb) bulk bags 1,000-kg (2,205-lb) bulk bags Bulk railcar Truckload 5
eastman Eastman Chemical Company Corporate Headquarters P.O. Box 431 Kingsport, TN 37662-5280 U.S.A. Telephone: U.S.A. and Canada 800-EASTMAN (800-327-8626) Other Locations (1) 423-229-2000 Fax: (1) 423-229-1673 http://www.eastman.com/cirbo Technical Service Centers Outside U.S.A. Liverpool, ENGLAND (44) 1-51-547-2002 Singapore, SINGAPORE (65) 275-6881 Material Safety Data Sheets providing safety precautions that should be observed in handling and storing Eastman products are available on request. You should obtain and review the available material safety information before handling any of these products. If any materials mentioned are not Eastman products, appropriate industrial hygiene and other safety precautions recommended by their manufacturers should be observed. Neither Eastman Chemical Company nor its marketing affiliates shall be responsible for the use of this information, or of any product, method, or apparatus mentioned, and you must make your own determination of its suitability and completeness for your own use, for the protection of the environment, and for the health and safety of your employees and purchasers of your products. No warranty is made of the merchantability or fitness of any product, and nothing herein waives any of the Seller s conditions of sale. Eastman and NPG are trademarks of Eastman Chemical Company. Eastman Chemical Company, 1998. ECP 9145 Publication N-352 December 1998 Printed in U.S.A.