Computer Methods for Finding Solvent Blend Replacements and for

26

Downloaded by UNIV LAVAL on October 29, 2015 | http://pubs.acs.org Publication Date: September 24, 1982 | doi: 10.1021/bk-1982-0197.ch026

Computer Methods for Finding Solvent Blend Replacements and for Predicting Water/Cosolvent Evaporation at Any Humidity ALBERT L. ROCKLIN Shell Development Company, Westholow Research Center, Houston, TX 77001 Reformulation of coatings to cut solvents costs, accommodate shortages, and comply with regulations can be improved by computer simulation. Efficient optimization requiring the balancing of a large number of variables is easily handled by computer whereas it may be impossible by hand methods. The chemist does not have to be a computer expert to use a simulation program. Computer programs can be designed by programming experts for anyone who can use a typewriter. Two examples are given of previously described solvents programs that are convenient to operate and that have proved to be very useful. Of interest in water reducible systems is a program for predicting evaporation rate and solvent balance during evaporation of blends of water with any number of dissolved cosolvents at any humidity. For conventional solvent blends there is a program which finds lowest cost replacements having properties specified by the chemist. Rising p r i c e s , solvent shortages, and environmental r e s t r i c t i o n s on s o l v e n t e m i s s i o n s a r e p u t t i n g a n i n c r e a s i n g s t r a i n on t h e c o a t i n g s i n d u s t r y . Formulations employing t r a d i t i o n a l s o l v e n t b l e n d s w h i c h h a d been d e v e l o p e d a f t e r y e a r s o f t r i a l and e r r o r may now be found t o be t o o e x p e n s i v e o r b a s e d on u n a v a i l a b l e or discontinued solvents or i n v i o l a t i o n o f p o l l u t i o n c o n t r o l reg u l a t i o n s . To s t a y i n b u s i n e s s , m a n u f a c t u r e r s have t o r e f o r m u l a t e o r embrace new t e c h n o l o g y s u c h a s w a t e r - b o r n e , h i g h s o l i d s , o r powder. Whichever route i s chosen, o p t i m i z a t i o n i s d i f f i c u l t b e c a u s e o f t h e l a r g e number o f v a r i a b l e s t h a t must be t a k e n i n t o account. The t r a d i t i o n a l method o f l a b o r i o u s l y m e a s u r i n g t h e e f f e c t o f e a c h v a r i a b l e one a t a t i m e o v e r a s i g n i f i c a n t r a n g e i s cumbersome, e x p e n s i v e , and i m p r a c t i c a l . T h i s i s where c o m p u t e r s can h e l p . Computer s i m u l a t i o n s o f v a r i o u s a s p e c t s o f c o a t i n g s

0097-6156/82/0197-0427$06.00/0 © 1982 American Chemical Society In Computer Applications in Applied Polymer Science; Provder, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.


428

COMPUTER APPLICATIONS IN APPLIED POLYMER SCIENCE

b e h a v i o r p e r m i t a r a p i d s u r v e y o f t h e e f f e c t s o f c h a n g i n g one o r more v a r i a b l e s . S i n c e l e n g t h y c a l c u l a t i o n s a r e no l o n g e r a n o b s t a c l e , c o m b i n a t i o n s o f v a r i a b l e s c a n be e x p l o r e d e f f i c i e n t l y f o r optimum e f f e c t s . Though o p t i m i z a t i o n must be a r r i v e d a t t h r o u g h a c t u a l t e s t i n g and m e a s u r i n g , t h e c o m p u t e r s i m u l a t i o n c a n show t h e c o a t i n g s t e c h n o l o g i s t where a n a p p r o p r i a t e p l a c e i s t o s t a r t the experiments. I t can a l s o r e v e a l important trends that m i g h t be o v e r l o o k e d i n a c o n v e n t i o n a l e x p e r i m e n t a l p r o g r a m . The c o m p u t e r i s no s u b s t i t u t e f o r s k i l l , e x p e r t i s e , e x p e r i e n c e , o r judgment. I t i s a t o o l t h a t , i f used p r o p e r l y , c a n g r e a t l y increase the e f f e c t i v e n e s s o f a t e c h n o l o g i s t . Yet there a r e two o b s t a c l e s t h a t s t a n d i n t h e way o f e f f e c t i v e c o m p u t e r u t i l i z a t i o n - f e a r o f computers and d o m i n a t i o n by non-chemist computer e x p e r t s . C h e m i s t s u n f a m i l i a r w i t h c o m p u t e r s t e n d t o be a f r a i d o f them b e c a u s e t h e y t h i n k t h a t e f f e c t i v e u s e r e q u i r e s a n a d v a n c e d k n o w l e d g e o f c o m p u t e r l a n g u a g e s . T h i s i s n o t s o . The f a c t i s t h a t j u s t a s a p e r s o n n e e d n o t be a n e x p e r t , m e c h a n i c o r a u t o m o t i v e e n g i n e e r t o be a b l e t o d r i v e a c a r s k i l l f u l l y , s o d o e s t h e c h e m i s t n o t have t o be a programming o r c o m p u t e r l a n g u a g e e x p e r t t o use a computer t o advantage. Very l i t t l e s k i l l i s r e q u i r e d t o o p e r a t e a p r o g r a m . Those d e s c r i b e d i n t h i s p a p e r c a n be r u n w i t h ease a f t e r j u s t a few m i n u t e s o f i n s t r u c t i o n . Nor i s c o m p u t e r s k i l l r e q u i r e d i n d e s i g n i n g a p r o g r a m t o do a c e r t a i n j o b . I f t h e c h e m i s t knows what t h e j o b i s , f o r e x a m p l e c a l c u l a t i o n o f vapor p r e s s u r e s , a l l t h a t i s needed i s t o g i v e t h e a p p r o p r i a t e e q u a t i o n s t o a s k i l l e d programmer, a l o n g w i t h i n s t r u c t i o n s a s t o how t h e c h e m i s t p r e f e r s t o e n t e r d a t a and have r e s u l t s p r i n t e d o u t . The p r o g r a m c a n t h e n be w r i t t e n t o t h e c h e m i s t s t a s t e . B u t t h i s i s where t h e s e c o n d p r o b l e m c a n a r i s e . Frequently, visionary computer e x p e r t s w i l l i n i t i a t e programs a f t e r o n l y b r i e f c o n t a c t with chemists. Those p r o g r a m s a r e w r i t t e n f r o m t h e c o m p u t e r e x p e r t ' s p o i n t o f v i e w , n o t t h e c h e m i s t ' s , and so may be u n p o p u l a r b e c a u s e t h e y have t h e wrong f l a v o r . Worse s t i l l , i n many o r g a n i z a t i o n s c o m p u t e r d e p a r t m e n t s go f a r t h e r t h a n m e r e l y h e l p i n g t h e c h e m i s t s w i t h t h e i r c o m p u t e r p r o b l e m s . They e x e r c i s e c o m p l e t e c o n t r o l o v e r a c c e s s t o and u s e o f t h e company c o m p u t e r f a c i l i t i e s . A l l c o m p u t e r o p e r a t i o n must be f u n n e l l e d t h r o u g h a d e s i g n a t e d person. This s t i f l i n g procedure d i s c o u r a g e s p r o d u c t i v e and i m a g i n a t i v e u s e o f t h e c o m p u t e r b y t h o s e v e r y p e r s o n s f o r whom t h e p r o g r a m s were w r i t t e n . I t s h u t s them o f f f r o m t h o s e f e a t u r e s t h a t make i n t e r a c t i v e c o m p u t e r o p e r a t i o n s o a t t r a c t i v e - i m m e d i a c y and f l e x i b i l i t y . I t i s a s i f c h e m i s t s were n o t a l l o w e d t o d o t h e i r own w e i g h i n g s , t h e s e b e i n g p e r f o r m e d on r e q u e s t b y t h e k e e p e r o f t h e balances! In t h i s p a p e r , I d i s c u s s two e x a m p l e s o f c o m p u t e r p r o g r a m s t h a t p e r f o r m c a l c u l a t i o n s t h a t a r e i m p o s s i b l e b y hand m e t h o d s . B o t h have been p u b l i s h e d p r e v i o u s l y b u t a r e p r e s e n t e d h e r e t o i l l u s t r a t e t h e power o f t h e c o m p u t e r i n s o l v i n g p r a c t i c a l p r o b l e m s . Both perform c a l c u l a t i o n s u s i n g d a t a from a computerized d a t a f i l e o f i n d i v i d u a l s o l v e n t p r o p e r t i e s . The f i r s t p r e d i c t s e v a p o r a t i o n

In Computer Applications in Applied Polymer Science; Provder, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

26.

Solvent Blends and

ROCKLIN

429

Evaporation

b e h a v i o r o f aqueous s o l v e n t b l e n d s c o n t a i n i n g a n y number o f d i s s o l v e d c o s o l v e n t s a t any h u m i d i t y . I t s v a l u e c a n be a p p r e c i a t e d when i t i s r e a l i z e d t h a t h u m i d i t y has a s t r o n g e f f e c t o n t h e d r y i n g t i m e and s o l v e n t b a l a n c e o f a w a t e r r e d u c i b l e c o a t i n g , w i t h c o n s e q u e n t e f f e c t s on t h e q u a l i t y o f t h e f i l m p r o d u c e d . The s e c o n d c o m p u t e r method s e l e c t s minimum c o s t s o l v e n t b l e n d r e placements t h a t w i l l comply w i t h chosen s p e c i f i c a t i o n s . This can h e l p l o w e r c o s t , c i r c u m v e n t s h o r t a g e s , and c o m p l y w i t h p o l l u t i o n control regulations.


Evaporation

Program

The e v a p o r a t i o n p r o g r a m (I) u s e s a r e p e t i t i v e p r o c e d u r e f o r p r e d i c t i n g s o l v e n t e v a p o r a t i o n i n t h e S h e l l Evaporometer as i t w o u l d be measured by ASTM D 3 5 3 9 . The f i r s t s t e p c a l c u l a t e s t h e t i m e to evaporate a s m a l l p o r t i o n o f t h e blend a t a constant r a t e determined by t h e i n i t i a l c o m p o s i t i o n . F o l l o w i n g t h i s , a new c o m p o s i t i o n i s computed and t h e p r o c e s s r e p e a t e d u s i n g t h e new c o m p o s i t i o n t o c a l c u l a t e a new r a t e . A t e a c h s t e p , t h e e v a p o r a t i o n r a t e i s c a l c u l a t e d b y a d d i n g up t h e r a t e s o f t h e i n d i v i d u a l components a t t h e i r c o n c e n t r a t i o n s i n t h e b l e n d . The method t a k e s i n t o c o n s i d e r a t i o n t h e e f f e c t o f e v a p o r a t i v e c o o l i n g on evap o r a t i o n r a t e and a d j u s t s t h e r a t e s o f t h e i n d i v i d u a l components a c c o r d i n g t o the a c t u a l temperature o f the b l e n d as i s e v a p o r a t e s . A c t i v i t y c o e f f i c i e n t s a r e c a l c u l a t e d a t t h a t temperature by t h e UNIFAC ( 2 - 4 ) g r o u p method. H u m i d i t y i s accommodated by a p p l y i n g a l i n e a r c o r r e c t i o n f a c t o r t o the water e v a p o r a t i o n r a t e . These c o n c e p t s a r e i n c o r p o r a t e d i n t h e f o l l o w i n g e q u a t i o n w h i c h computes t h e t o t a l mass r a t e o f e v a p o r a t i o n a t e a c h s t e p a s t h e sum o f t h e e v a p o r a t i o n c o n t r i b u t i o n s o f e a c h component: r(t)

where

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(1)

r ( t ) = t o t a l r a t e o f e v a p o r a t i o n from s o l u t i o n a t time t , i n g r a m s / s e c o f t h e n components. x^(t) = mole f r a c t i o n o f component i i n t h e b l e n d a t t ime t . T ;L) = a c t i v i t y c o e f f i c i e n t o f component i a t t i m e t a t the a c t u a l temperature o f t h e b l e n d d u r i n g evaporation. T s o l = a c t u a l temperature o f the e v a p o r a t i n g blend. S O

r°

= r a t e o f e v a p o r a t i o n (g/s) o f pure i , a t i t s a c t u a l e v a p o r a t i o n temperature ( T i ) as m e a s u r e d b y ASTM D 3 5 3 9 a t 2 5 C . m

n

1/2 o The t e r m ( T i / T £ ) i s a t e m p e r a t u r e c o r r e c t i o n (_5) t o r i to account f o r the f a c t that each s o l v e n t i s evaporating a t s o l u t i o n temperature ( T ^ ) r a t h e r than a t t h e temperature a t w h i c h i t e v a p o r a t e s as a pure s o l v e n t ( T £ ) . s o

m

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430

F o r t h e w a t e r component o f t h e b l e n d , t h e e v a p o r a t i o n r a t e t e r m i n E q u a t i o n 1 i s m u l t i p l i e d by t h e l i n e a r h u m i d i t y c o r r e c t i o n f a c t o r (l-RH/100) as f o l l o w s : r

H 0 2

=

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H

2

(

)

Y

H

2

0

(t, T

s o l

) r

^ (T

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)

1 / 2

(2)

where RH i s r e l a t i v e h u m i d i t y o f t h e a m b i e n t a i r s u r r o u n d i n g t h e e v a p o r a t i n g b l e n d and r i s t^he e v a p o r a t i o n r a t e o f w a t e r f r o m the b l e n d . The p r o g r a m i s e a s y t o use . No computer programming t r a i n i n g i s r e q u i r e d . Using a simple t e r m i n a l w i t h a telephone connection to t h e c e n t r a l computer, t h e chemist e n t e r s t h e c o m p o s i t i o n o f t h e b l e n d and t h e r e l a t i v e h u m i d i t y i n r e s p o n s e t o s e q u e n t i a l q u e s t i o n s as they appear a t t h e t e r m i n a l . Figure 1 i l l u s t r a t e s a t y p i c a l d a t a e n t r y s e q u e n c e . The computer a s k s t h e q u e s t i o n s one a t a t i m e and t h e c h e m i s t e n t e r s t h e a p p r o p r i a t e r e s p o n s e a f t e r t h e = : prompt. The f i r s t g r o u p a s k s g e n e r a l q u e s t i o n s . Which c a l c u l a t i o n s a r e t o be done, and i n what f o r m w i l l t h e d a t a be entered? The s e c o n d g r o u p a s k s s p e c i f i c q u e s t i o n s . What i s t h e c o m p o s i t i o n o f t h e b l e n d , and a t what r e l a t i v e h u m i d i t y w i l l i t be evaporating? The q u e s t i o n sequence and a l l o p e r a t i o n a l and readout f e a t u r e s i n v o l v i n g c h e m i s t / c o m p u t e r i n t e r a c t i o n were d e s i g n e d by t h e chemist f o r t h e convenience o f t h e c h e m i s t , i n c o o p e r a t i o n w i t h a c o m p u t e r programmer who t h e n w r o t e t h e p r o g r a m . F i g u r e 2 shows t h e p r i n t o u t s o f t h e p r e d i c t e d e v a p o r a t i o n c u r v e s for an aqueous b l e n d e v a p o r a t i n g a t 15% and a t 7 5 % RH. The c o m p u t e r shows t h a t t h e b l e n d w i l l t a k e t h r e e t i m e s as l o n g t o evaporate a t the higher humidity. The f a t e o f c o s o l v e n t s c a n be p r e d i c t e d q u i t e c l o s e l y . F i g u r e 3 shows t h e change i n c o m p o s i t i o n o f a f o u r component b l e n d as i t e v a p o r a t e s , f i r s t a t 4 0 % RH, t h e n a t 6 5 % RH. The c a l c u l a t e d v a l u e s come v e r y c l o s e t o v a l u e s o b t a i n e d by GC a n a l y s i s o f t h e blend during evaporation. The above e x a m p l e s show how a computer p r o g r a m c a n p r e d i c t t h e p r o p e r t i e s o f a s o l v e n t b l e n d . T h i s c a n be a v a l u a b l e t o o l f o r a c o a t i n g s t e c h n o l o g i s t who i s d e s i g n i n g a c o a t i n g and w o u l d l i k e t o know ahead o f t i m e what w i l l be t h e p r o p e r t i e s o f a s o l v e n t b l e n d t h a t i s under c o n s i d e r a t i o n .


2

S o l v e n t B l e n d Replacement Program The s o l v e n t b l e n d r e p l a c e m e n t p r o g r a m (6) does a d i f f e r e n t job. I t c a l c u l a t e s t h e composition o f t h e cheapest organic s o l v e n t b l e n d t h a t w i l l have p r o p e r t i e s s p e c i f i e d b y t h e c h e m i s t . Solvent blend replacement i s b a s e d on t h e g e n e r a l l y a p p l i c a b l e p r i n c i p l e that i f the solvent p o r t i o n o f a conventional f o r m u l a t i o n i s r e p l a c e d by a new b l e n d o f d i f f e r e n t c o m p o s i t i o n b u t h a v i n g t h e same s o l v e n t p r o p e r t i e s as t h e o l d b l e n d , t h e new c o a t i n g w i l l p e r f o r m t h e same as t h e o l d . To u s e t h e p r o g r a m t o


In Computer Applications in Applied Polymer Science; Provder, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982. :l

IT WILL RPPERR RS THE FIRST SOLV

= :4

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£ IF UNLISTED SOLVENTS* 3 IF WRONG DRTR

TYPE 1 TO PROCEED* Figure 1.

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RELATIVE HUMIDITY

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Figure 3. Comparison of calculated solvent balance (lines) with observed concentrations (points) on evaporation of 4-component blend at two humidities. (Reproduced, with permission, from Ref. 1. Copyright 1980, Federation of Societies for Coatings Technology) a )

4-methoxy-4-methyl-2-pentanone; PENToXONE is a registered trademark of Shell Chemical Company.



26.

ROCKLIN

Solvent Blends and

Evaporation

435

a d v a n t a g e , t h e c h e m i s t must know w h i c h s o l v e n t p r o p e r t i e s a r e i m p o r t a n t t o c o a t i n g s p e r f o r m a n c e and u n d e r s t a n d t h e i r e f f e c t . The f i r s t s t e p i s t o c a l c u l a t e t h e p r o p e r t i e s o f t h e o r i g i n a l b l e n d . T h i s i s done b y t h e p r e v i o u s l y d e s c r i b e d c o m p u t e r p r o g r a m . F o r an o r g a n i c s o l v e n t b l e n d , t h a t p r o g r a m n o t o n l y c a l c u l a t e s evaporation c h a r a c t e r i s t i c s but also calculates solution pa rameters. S o l u b i l i t y parameter, p o l a r i t y , and hydrogen b o n d i n g a f f e c t t h e c a p a c i t y o f the b l e n d t o d i s s o l v e a r e s i n ; e v a p o r a t i o n r a t e a f f e c t s t h e d r y i n g r a t e o f t h e c o a t i n g whereas s o l v e n t b a l a n c e d u r i n g d r y i n g w i l l a f f e c t f i l m q u a l i t y . Not a l l t h e p r o p e r t i e s o f t h e o r i g i n a l must be r e p e a t e d i n t h e s u b s t i t u t e . The c h e m i s t d e c i d e s w h i c h p a r a m e t e r s t o s e l e c t and w h i c h v a l u e s t o s p e c i f y , t h e n c h o o s e s a g r o u p o f up t o f i f t e e n s o l v e n t s f r o m w h i c h t h e r e p l a c e m e n t m i g h t be made. The c o m p u t e r w i l l c a l l o n o n l y t h o s e s o l v e n t s t h a t a r e needed t o s a t i s f y t h e p a r a m e t e r v a l u e s a t t h e l o w e s t p r i c e . Computer f l e x i b i l i t y o f c h o i c e can be i n c r e a s e d by d e s i g n a t i n g t h e s p e c i f i e d v a l u e o f e a c h p a r a m e t e r as e i t h e r a minimum o r a maximum i n s t e a d o f one t o be met e x a c t l y . F o r e x a m p l e , a b l e n d c a n be c o n s t r a i n e d t o have a v i s c o s i t y no g r e a t e r t h a n 0.6 c p s and a s o l u b i l i t y p a r a m e t e r no l e s s t h a n 8 . 3 . Since e a c h p a r a m e t e r o r c o n s t r a i n t i s r e p r e s e n t e d i n t h e p r o g r a m by a l i n e a r e q u a t i o n , t h e c o m p u t e r s e l e c t i o n o f an optimum s o l v e n t b l e n d i s n o t h i n g more t h a n t h e s o l u t i o n t o a s e t o f s i m u l t a n e o u s e q u a t i o n s i n a s many v a r i a b l e s a s t h e r e a r e c o n s t r a i n t s . The j o b w o u l d be i m p o s s i b l e by hand b u t i s e a s y f o r t h e c o m p u t e r . T a b l e I shows a t y p i c a l r e p l a c e m e n t b l e n d . As e x p e c t e d , t h e R u l e 66 b l e n d i s more e x p e n s i v e t h a n t h e non-exempt o r i g i n a l , b u t i t s p r o p e r t i e s a r e a t l e a s t a s g o o d , and i n some r e s p e c t s b e t t e r . In p a r t i c u l a r , t h e r e p l a c e m e n t g i v e s a l o w e r v i s c o s i t y a t h i g h e r solids. To some e x t e n t , t h i s o f f s e t s t h e h i g h e r s o l v e n t s p r i c e b e c a u s e l e s s s o l v e n t i s needed t o o b t a i n a p p l i c a t i o n v i s c o s i t y . In t h i s e x a m p l e , t h e s u b s t i t u t e i s n o t an e x a c t m a t c h f o r t h e o r i g i n a l . I t r a r e l y has t o be. I f t h e computer c a l c u l a t e d b l e n d seems i n a p p r o p r i a t e , t h e c h e m i s t c a n t i n k e r w i t h t h e p a r a m e t e r s p e c i f i c a t i o n s , impose more o r d e l e t e some c o n s t r a i n t s , o r change the p a n e l o f s o l v e n t s c a n d i d a t e s u n t i l t h e c a l c u l a t e d blend a p p e a r s r e a s o n a b l e . A l a r g e number o f o p t i o n s c a n be e x p l o r e d i n a very short time. Conclusion These two computer programs i l l u s t r a t e t h e v a l u e o f a p p l y i n g c o m p u t e r m e t h o d s . The c h e m i s t need n o t s h y away f r o m c o m p l i c a t e d calculations. By s u r v e y i n g l o g i c a l p r o p o s a l s v i a computer s i m u l a t i o n , t h e c h e m i s t c a n be f a r more e f f i c i e n t and s e l e c t i v e i n d e s i g n i n g an e x p e r i m e n t a l o p t i m i z a t i o n p r o g r a m . I n t h e s e e x a m p l e s t h e p r e d i c t i o n s a r e b a s e d on r e a d i l y a v a i l a b l e t e c h n o l o g y and t h e c a l c u l a t i o n s a r e s t r a i g h t f o r w a r d , b u t t h e y a r e so l e n g t h y t h a t i t i s i m p o s s i b l e t o do them by hand. Without t h e computer t h e c a l c u l a t i o n s w o u l d n o t be done a t a l l , and t h e c h e m i s t w o u l d have


436


Table I. PROPERTIES OF NON-EXEMPT NITROCELLULOSE LACQUER SOLVENT BLEND AND ITS RULE 66 EXEMPT REPLACEMENT.


S o l i d s C o m p o s i t i o n , pbw RS 1/4 Second N i t r o c e l l u l o s e Non-Drying Coconut A l k y d Dioctyl Phthlalate

(Dry)

10 10 4

S o l v e n t C o m p o s i t i o n , %v n-Propyl Acetate Isobutyl Acetate n-Butyl Acetate M e t h y l I s o b u t y l Ketone Amyl A c e t a t e n-Butyl Alcohol Ethyl Alcohol Xylene Toluene VM&P N a p h t h a EC Solvent Properties Cost, Cents/Gallon S p e c i f i c G r a v i t y , 25/25C E s t i m a t e d E v a p o r a t i o n Time, s e c ) , S o l u b i l i t y Parameter Fractional Polarity Hydrogen Bonding Index ( S h e l l ) E s t i m a t e d V i s c o s i t y , c p s , 25C D e t e r m i n e d V i s c o s i t y , c p s , 25C a

25C

Non-Exempt Blend 14.0 26.0 4.8 27.6 27.6 ^_ 100.0

Exempt Replacement

206 0.864 348 8.83 0.048 4.99 0.65 0.62

231 0.814 322 8.92 0.102 2.45 0.69 0.66

25 7 14 15 6 2

9

100

Lacquer Properties 42 V i s c o s i t y a t A p p l i c a t i o n S o l i d s , c p s , 25C 55 20.4 17.8 A p p l i c a t i o n S o l i d s , %w Blush Resistance, % Relative 82 84 H u m i d i t y a t 80F ( 2 7 C ) 5-6 2 Flow on Glass (10 = B e s t ) 1.5 1.4 Film Thickness, Mils Tukon H a r d n e s s , KHN25 3.2 2.4 4 Hours A i r Dry 5.0 5.2 24 Hours A i r D r y P r i n t R e s i s t a n c e , 18 Hours 3.0 3.0 F i l m Thickness on Maple ( M i l s ) No P r i n t No P r i n t 1psi 2 psi Very, Very S l i g h t P r i n t 5 psi Very S l i g h t P r i n t a ) On S h e l l T h i n F i l m E v a p o r o m e t e r by ASTM D3539. (Reprinted with permission, from Ref. 6. Copyright 1970, Federation of Societies for Coatings Technology.)


26.

ROCKLIN

Solvent Blends and

Evaporation

437

t o f a l l b a c k on s l o w e r , and much l e s s a d e q u a t e , a p p r o x i m a t i o n s . The computer i s a w o n d e r f u l t o o l b u t i t has no o p i n i o n s , imagination, or intelligence. A l l i t c a n do i s c a l c u l a t e a c c u r a t e l y and r a p i d l y . I t knows n o t h i n g a b o u t c h e m i s t r y b u t i t can be an enormous h e l p t o a r e s o u r c e f u l c h e m i s t b y o p e n i n g up t h e p o s s i b i l i t y o f p e r f o r m i n g complex c a l c u l a t i o n s t h a t would never have been c o n s i d e r e d s e r i o u s l y .

Literature Cited


1. 2. 3. 4. 5. 6.

Rocklin, A. L.; Bonner, D. C. Journal of Coatings Technology, 52, No. 670, 27-36 (1980). Fredenslund, A.; Jones, R. L.; Prausnitz, J. M. AICHEJ., 21, 1086(1975). Fredenslund, A.; Gmehling, J.; Rasmussen, P. "Vapor-Liquid Equilibria Using UNIFAC," Elsevier, Amsterdam, 1977. Skjold-Jorgenssen, S.; Kolbe, B.; Gmehling, J.; Rasmussen, P. Ind. Eng. Chem. Proc. Des. Dev., 18, 714 (1979). Gardner, G. S. Ind. Eng. Chem., 32, 226 (1940). Walsham, J. G.; Edwards, G. D. Journal of Paint Technology, 43, No. 554, 64 (1971).

RECEIVED May 4, 1982.


Computer Methods for Finding Solvent Blend Replacements and for

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