7 High Solids Thermally Cured Systems Now, Forthcoming, and Future
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ROBERT W. JAMES, PAUL F. WESTFALL, K. L. PIERCE, and H. J. WRIGHT Cook Paint and Varnish Co., P. O. Box 389, Kansas City, MO 64141
This delivery will concentrate on 80% volume or higher solids, thermally cured systems and the position such coatings possess at the present, and will possess in the future, relative to the three "E" 's-environment, energy, and economics. High solids coatings are not novel--only the application of such systems to the container industry is relatively new. State and Federal environmental protection agencies thrust high solid systems to application reality faster than expected; however, regardless of regulations, economics would have forced the change. Conventional 30-60% solid coatings, in addition to being inefficient in the use of raw materials, are rapidly becoming too costly, due to the spiraling price of solvent. ENVIRONMENT : At the present point in time, billions of three-piece sanitary food cans have been commercially produced, beginning in August 1973, utilizing high solids coatings. High solids materials have been used as both interior and exterior protective coatings. The coating material, similar to an oleo resinous system, has a minimum 80% volume solids at a bake temperature of 10 minutes at 400°F. The coating contains approximately 15% by weight volatile exempt solvent. The system fulfills Ringleman II opacity requirements and, obviously, meet F.D.A. needs. Application problems associated with the above and similar high solid systems have been primarily substrate wetting. Plate wetting problems may be decreased or eliminated by the use of special flow agents, firm appli0-8412-0446-2/78/47-078-048$05.00/0 © 1978 American Chemical Society Strand; Modern Container Coatings ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
JAMES ET AL.
High
Solids Thermally
Cured
Systems
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c a t i o n r o l l s , and h e a t i n g t h e c o a t i n g d u r i n g rollcoat a p p l i c a t i o n . The u s e o f 45-55 d u r o m e t e r a p p l i c a t i o n r o l l s permits the c o a t e r o p e r a t o r to apply p r e s s u r e t o t h e s u b s t r a t e s h e e t w i t h o u t undue d i s t o r t i o n of p l a t e margins. C o n t r o l l e d h e a t i n g of the c o a t i n g t o 1 0 0 - 1 2 0 ° F . r e g u l a t e s v i s c o s i t y as w e l l as p r o m o t i n g s u b s t r a t e w e t t i n g and m i n i m i z e s f i l m weight v a r i a t i o n . High s o l i d s systems vary w i d e l y i n v i s c o s i t y response to h e a t i n g . The f o l l o w i n g c h a r t demons t r a t e s the v i s c o s i t y response of a t y p i c a l high s o l i d s oleo r e s i n o u s system to heat.
30 40 50 60 70 80 VIS.
90
#4 FORD CUP
Development problems p e r t a i n i n g to high s o l i d s c o a t i n g s have been d i s c o v e r i n g c u r e compositions which e x h i b i t reasonable three to four per cent fuming f a c t o r s a t d e s i g n e d bake s c h e d u l e s . T h i s has been p a r t i c u l a r l y t r u e o f melamine of u r e a c u r i n g a g e n t s , and t e n d s t o be a p r o b l e m w i t h any c o n d e n s a t i o n r e a c t i o n which emit a by-product other than carbon d i o x i d e or water. F u m i n g f a c t o r s may be g o v e r n e d t o an e x t e n t by c o n t r o l l e d m o l e c u l a r weight d i s t r i b u t i o n , s t a g e b a k i n g and r e d u c e d b a k i n g temperatures . Fuming f a c t o r s a r e not always o b j e c t i o n a b l e or unwanted. V o l a t i l a t i o n o f u n r e a c t e d monomer o r low m o l e c u l a r w e i g h t p o l y m e r s i s d e s i r a b l e and essential to e l i m i n a t e the p o s s i b i l i t y o f t h e s e p r o d u c t s being e x t r a c t e d i n t o the food. E x t r a c t i o n i n t o the food p r o d u c t c o u l d j e o p a r d i z e F.D.A. s t a t u s and p o s s i b l y cause " o f f f l a v o r " to the pack media. Volatilization o f t h e s e u n d e s i r a b l e s i s one a d v a n t a g e t h e r m a l l y cured c o a t i n g s d i s p l a y over " c o l d cure" u l t r a violet l i g h t , e l e c t r o n beam, e t c . , c u r i n g s y s t e m s t h a t u t i l i z e r e a c t i v e s o l v e n t s o r low m o l e c u l a r weight
Strand; Modern Container Coatings ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
MODERN CONTAINER
COATINGS
polymers. The o b j e c t i v e o f h i g h s o l i d s a p p l i c a t i o n reduce s o l v e n t emission. The f o l l o w i n g c h a r t s t r a t e s t h e r e l a t i o n s h i p between volume s o l i d s s u r f a c e c o a t e d p e r pound o f s o l v e n t r e l e a s e d . enamel i n t h e c h a r t i s f o r m u l a t e d w i t h a 1 t o weight pigment-binder r a t i o .
i s to demonand The 1 by
HIGH
SOLIDS
COATINGS
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SQUARE F E E T OF SURFACE COATED PER POUND OF SOLVENT RELEASED
VOLUME SOLIDS
% WT . GAL.
0 10 20 30 40 50 60 70 80 90 100
0 15. 6 29. 4 42 . 7 52. 7 62 . 5 71. 5 79. 6 87 . 0 93. 8 100. 0
WT. GAL.
SQ. F T . COVERAGE . 2 MIL DRY F I L M
7. 52 8. 03 8. 53 9. 02 9. 53 10. 04 10. 54 11. 05 11. 55 12. 05 12 . 55
0 800 1600 2400 3200 4000 4800 5600 6400 7200 8000
1:1
LBS. OF SOLVENT PER GAL. OF PAINT
SURFACE COATED PER POUND SOLVENT RELEASED
7. 52 6. 76 6. 01 5. 26 4 .51 3. 76 3. 00 2 .25 1. 50 75 0
Wt./Pigment B i n d e r
0 110 235 455 710 1065 1600 2485 4265 9600 00
Ratio
C h a r t #3 d e m o n s t r a t e s a c o m m e r c i a l l y a v a i l a b l e c o m p l i a n c e h i g h s o l i d s c l e a r and a c o m p l i a n c e waterbased c o a t i n g . The w a t e r - b a s e d c o a t i n g c o n t a i n s 20% exempt s o l v e n t i n t h e v o l a t i l e . HIGH
H.S. Water
SOLIDS
V S . WATER
SQ. F T . COVERAGE PER .2 MIL F I L M
SURFACE COATED PER L B . OF SOLVENT RELEASED
VOL. SOLIDS
WT. GAL.
80 26.75 Clear
7.98 6400 8.46 2140 unpigmented process
4010 1686 coatings
Strand; Modern Container Coatings ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
7.
JAMES ET AL.
is of
High
Solids Thermally
Cured
51
Systems
A n o t h e r way o f c o m p a r i n g p o l l u t i o n e f f i c i e n c y pounds o f s o l i d s v s . pounds o f s o l v e n t p e r g a l l o n coating. POUNDS OF SOLIDS V S . POUNDS OF SOLVENT CONTAINED IN ONE GALLON OF COATING LBS.
High S o l i d s Water
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Water-based
OF SOLIDS
L B S . OF SOLVENT
6.72 2.49 contains
1.26 1.19 2 0 % exempt
solution
RATIO 5.34:1 2.09:1
volatile
New d e v e l o p m e n t s a r e now b e i n g i n t r o d u c e d t o the s a n i t a r y c o a t i n g market which e x h i b i t s lower fuming f a c t o r s , lower bake s c h e d u l e , and c o m p l i a n c e with Ringleman I o p a c i t y requirements. F u t u r e c o a t i n g s w i l l q u i t e p o s s i b l y be h i g h e r t h a n 80% volume s o l i d s w o r k i n g toward t h e g o a l o f 100% v o l u m e s o l i d s . P o s s i b l y two-package system with g r e a t l y reduced cure response which approach zero emission. ENERGY H i g h v o l u m e s o l i d s exempt s o l v e n t s y s t e m s a l l o w m a n u f a c t u r e r s t o c o m p l y w i t h E.P.A. r e g u l a t i o n s i n c e r t a i n georgraphical areas without i n c i n e r a t i o n . This f a c t leads to s u b s t a n t i a l energy savings over c o n v e n t i o n a l s o l v e n t s y s t e m w h i c h must be i n c i n e r ated . Two-component h i g h s o l i d s s y s t e m s , r e q u i r i n g s h o r t e r bake c y c l e a t low t e m p e r a t u r e w i l l r e d u c e energy consumption drastically. ECONOMICS In g e n e r a l , h i g h s o l i d s s y s t e m s o f c o m p a r a b l e types d i s p l a y equal t o lower a p p l i e d c o s t s than conv e n t i o n a l o r w a t e r - b a s e d c o a t i n g s due t o t h e f o l l o w ing factors : 1. L e s s m a n u f a c t u r i n g expense p e r pound o f solids. 2. Less warehouse expense. 3. Lower e n e r g y e x p e n s e . 4. No r e d u c t i o n s o l v e n t . 5. Lower s h i p p i n g c o s t s .
Strand; Modern Container Coatings ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
MODERN CONTAINER COATINGS
52
SUMMARY : High s o l i d s c o a t i n g s a r e b e i n g consumed i n l a r g e q u a n t i t i e s i n g e o g r a p h i c a l a r e a s r e q u i r e d t o meet E.P.A. r e g u l a t i o n s . H i g h s o l i d s s y s t e m s a r e economi c a l , e n e r g y s a v i n g , a n d c a n be a p p l i e d w i t h existing equipment. Future developments p o i n t e d toward h i g h e r t h a n 80% v o l u m e s o l i d s a n d l o w e r c u r e t e m p e r a t u r e s w i l l make h i g h s o l i d s e v e n more a t t r a c t i v e .
Downloaded by TUFTS UNIV on June 3, 2018 | https://pubs.acs.org Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0078.ch007
RECEIVED MAY 22, 1978.
Strand; Modern Container Coatings ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
