Sucrose and Modified Sucrose Polyols in Rigid Urethane Foam

18 Sucrose and Modified Sucrose Polyols in Rigid

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on October 6, 2015 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0041.ch018

Urethane Foam ALLAN R. MEATH and L. D. BOOTH Dow Chemical Co., Bldg. B-4810, Freeport, Tex. 77566

Sucrose i s used w i d e l y as an i n i t i a t o r f o r p o l y o l s t o make r i g i d u r e t h a n e f o a m . The p r i m a r y r e a s o n s f o r t h e u s e o f s u g a r a r e , (a) i t i s r e a d i l y a v a i l a b l e from a n u m b e r o f s o u r c e s , (b) l a b o r a t o r y e v a l u a t i o n s h a v e shown t h a t s u g a r d e r i v e d f r o m e i t h e r s u g a r b e e t s o r sugar cane i s a c c e p t a b l e , (c) c o n s i s t e n t q u a l i t y and p u r i t y o f s u g a r make i t a n i d e a l c h e m i c a l s t a r t i n g m a t e r i a l , (d) s u g a r w i t h e i g h t r e a c t i v e h y d r o x y l g r o u p s has t h e f u n c t i o n a l i t y n e c e s s a r y t o o b t a i n t h e h i g h d e gree o f c r o s s l i n k i n g needed t o produce a r i g i d urethane foam, a n d (e) p r i c e . A p o l y o l , u s e a b l e f o r r i g i d u r e t h a n e foam, i s prepared by t h e a d d i t i o n o f an a l k y l e n e o x i d e t o t h e sucrose molecule. A l k y l e n e oxides used a r e : Ethylene Oxide, Propylene Oxide, and Butylène O x i d e . One o r m o r e m o l e c u l e s o f a l k y l e n e o x i d e i s a d d e d t o each o f t h e e i g h t r e a c t i v e h y d r o x y l groups on t h e s u crose molecule. The r e s u l t i n g p r o d u c t i s a l i q u i d p o l y o l w i t h e i g h t r e a c t i v e h y d r o x y l groups. The c h o i c e o f w h i c h a l k y l e n e o x i d e i s u s e d h a s several effects. The c h o i c e o f o x i d e s e f f e c t s t h e reaction rate o f thealkylene oxide addition t o the sucrose molecule. I t a l s o h a s an e f f e c t on t h e p h y s i c a l c h a r a c t e r i s t i c s o f t h er e s u l t i n g p o l y o l and p l a y s a major r o l e on t h e p h y s i c a l p r o p e r t i e s o f t h e f i n a l r i g i d u r e t h a n e foam. T a b l e I shows t h e e f f e c t s o f using ethylene oxide, propylene o x i d e , and mixtures of t h e two o x i d e s . Butylène o x i d e o f f e r s a n a d v a n t a g e over t h e other oxides i nt h e area o f h y d r o l y t i c s t a b i l ity. H o w e v e r , butylène o x i d e i s n o t w i d e l y u s e d b e c a u s e i t commands a h i g h p r i c e a n d c a n n o t b e j u s t i 257

In Sucrochemistry; Hickson, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.


258

SUCROCHEMISTRY

f i e d on a p r i c e f o r performance b a s i s . As c a n be seen from Table I , e t h y l e n e oxide o f f e r s advantages i n t h e following areas: a faster reaction rate f o rthe oxide a d d i t i o n t o sucrose; a r e s u l t i n g p o l y o l w i t h a lower v i s c o s i t y ; and a p o l y o l c o n t a i n i n g p r i m a r y h y d r o x y l g r o u p s w h i c h i n c r e a s e t h e p o l y o l ' s r e a c t i v i t y w i t h an isocyanate. However, e t h y l e n e o x i d e has a major d i s advantage i n t h a t an e t h o x y l a t e d p o l y o l produces a r i g i d u r e t h a n e foam w i t h p o o r h y d r o l y t i c s t a b i l i t y . S i n c e t h e m a j o r a p p l i c a t i o n s f o r r i g i d u r e t h a n e foams r e q u i r e good h y d r o l y t i c s t a b i l i t y , p r o p y l e n e o x i d e i s the most w i d e l y used a l k y l e n e o x i d e . In the f i n a l a n a l y s i s , t h e type o r r a t i o o f a l k y l e n e oxide used i s dependent on t h e i n t e n d e d end u s e s . Table I . E f f e c t o f D i f f e r e n t Oxides on P o l y o l P r e p a r a t i o n and End P r o p e r t i e s Ethylene Oxide Faster oxide addition rates Lower p o l y o l v i s c o s i t y Primary h y d r o x y l groups F a s t e r urethane r e a c t i o n Poor humidity aging p r o p e r t i e s Propylene Oxide Secondary h y d r o x y l groups Slower urethane r e a c t i o n Better humidity aging s t a b i l i t y M i x t u r e o f E t h y l e n e and Propylene Oxide Faster oxide addition Primary and secondary h y d r o x y l s Lower p o l y o l v i s c o s i t y Good h u m i d i t y a g i n g p r o p e r t i e s

(£)

Also a f f e c t i n g the sucrose i n i t i a t e d p o l y o l i s the amount o f a l k y l e n e o x i d e a d d e d . T a b l e I I shows, g r a p h i c a l l y , t h a t , a s y o u i n c r e a s e t h e amount o f o x i d e added t o t h e s u c r o s e m o l e c u l e , t h e l o w e r w i l l be t h e r e s u l t i n g p o l y o l v i s c o s i t y and t h e l e s s r i g i d t h e foam. W i t h t h e a d d i t i o n o f o n l y one a l k y l e n e o x i d e p e r h y d r o x y l g r o u p o n t h e s u c r o s e m o l e c u l e , t h e r e a r e some a p p l i c a t i o n s where t h e r e s u l t i n g foam i s t o o r i g i d o r friable. The a l k y l a t i o n o f t h e s u c r o s e m o l e c u l e c a n b e a c c o m p l i s h e d u s i n g a h i g h p r e s s u r e and temperature reaction. I f a c o i n i t i a t o r i s used, the r e a c t i o n can be c a r r i e d o u t a t l o w p r e s s u r e . The c o i n i t i a t o r i s a l i q u i d m a t e r i a l h a v i n g " l a b i l e " h y d r o g e n s , (1) r e a c -


18.

MEATH

AND BOOTH

Rigid Urethane Foam

t i v e enough t o r e a c t w i t h p r o p y l e n e and i n w h i c h t h e s u g a r i s s o l u b l e .

259 o r ethylene

oxide

Table I I . Oxide Level vs Polyol Properties 300

400

Usable viscosity High viscosity Reduced polyol cost Foam very r i g i d i Useful f o r : i Foam useful f o r : i B i l l e t s (boardstock) i Spray , Pour-In-Place , Thin section High density Pour-In-Place


1

600

500

1

1

Number

1 1

i i Oxide/OH

2 PO/OH

1 PO/OH

T a b l e I I I shows t h e r a w m a t e r i a l c h a r g e a n d r e a c tion conditions f o ra high pressure, polyol preparation r e a c t i o n where s u c r o s e was u s e d a s t h e s o l e i n i t i a t o r . While t h e e n t i r e charge o f sucrose, a l k y l e n e o x i d e , a n d c a t a l y s t may b e m i x e d b e f o r e t h e r e a c t i o n i s i n i t i a t e d , t h i s may r e s u l t i n u n d e s i r a b l y v i g o r o u s r e a c t i o n a n d p o o r t e m p e r a t u r e c o n t r o l , e s p e c i a l l y when e t h y l e n e oxide i s being used. A p r e f e r r e d procedure comprises mixing t h e sucrose, t h e c a t a l y s t and a small p o r t i o n o f the a l k y l e n e o x i d e , h e a t i n g t h emixture t o r e a c t i o n t e m p e r a t u r e a n d t h e n , when t h e r e a c t i o n h a s b e g u n , feeding i n t h e remaining oxide a t about t h e r a t e a t which i t r e a c t s , thus p e r m i t t i n g a steady r a t e o f r e a c t i o n ande f f e c t i v e temperature c o n t r o l (2), Table

III.

Reactor Charge

Example o f High -

Pressure

P r e s s u r e P r o c e s s (2)

Autoclave

S u

crose Propylene Oxide Trialkylamine or Metal Hydroxide

2400g 3600g 21g

Reaction Conditions Temperature 105 - 110°C f o r 6 h r 110 - 115°C f o r 4 h r 105°C f o r2h r Pressure Maximum Final

107 30

psig psig


SUCROCHEMISTRY


260

M a t e r i a l s w i t h r e a c t i v e hydrogens which a r e used a s c o i n i t i a t o r s w i t h s u c r o s e t o make r i g i d p o l y o l include: Water, Trimethylolpropane, Glycerol, Ethylenediamine, Diethylenetriamine, P r o p y l e n e G l y c o l , and Dipropylene Glycol. An e x a m p l e o f a r a w m a t e r i a l c h a r g e a n d r e a c t i o n c o n d i t i o n s f o r a low pressure process p r e p a r a t i o n of a sucrose-glycerol, c o i n i t i a t e d p o l y o l i s given i n Table IV. The s u c r o s e , g l y c e r o l , a n d c a t a l y s t w e r e p r e m i x e d u n t i l t h e s u g a r was d i s s o l v e d a n d t h e n t h e m i x t u r e was p r e h e a t e d t o 130°C. The p r o p y l e n e o x i d e was a d d e d o v e r a 12 h r p e r i o d . During t h i s period, the p r e s s u r e m a i n t a i n e d b y t h e p r o p y l e n e o x i d e was f r o m 30-40 p s i g a n d t h e t e m p e r a t u r e m a i n t a i n e d a t 125 t o 135°C. Upon c o m p l e t i o n o f t h e p r o p y l e n e o x i d e a d d i t i o n , t h e r e a c t i o n m i x t u r e was d i g e s t e d f o r 2 h r a t 130°C ( 3 ) . Table

IV *

Reactor

E x a m p l e o f Low P r e s s u r e P r o c e s s -

(3)

Low P r e s s u r e V e s s e l

17.1 l b Charge 11.5 l b Sucrose . . . . 105 g Glycerine . . . 45 l b Trialkylamine . Propylene Oxide Reactor Conditions Temperature 125 - 135°C f o r d u r a t i o n o f t h e r e a c t i o n Pressure 30 - 40 p s i g The s u c r o s e , g l y c e r o l , a n d a m i n e c a t a l y s t w e r e p r e m i x e d u n t i l t h e s u g a r was d i s s o l v e d a s t h e m i x t u r e was p r e h e a t e d t o 130°C. T h e p r o p y l e n e was a d d e d over a 12-hr p e r i o d . Advantages o f u s i n g a c o i n i t i a t o r w i t h include: I n c r e a s e d speed

of alkylation

sucrose

reaction,



18.

MEATH

A N D BOOTH

Rigid Urethane Foam

261

Decreased p o l y o l f u n c t i o n a l i t y , Decreased p o l y o l v i s c o s i t y , Improved c o m p a t a b i l i t y w i t h p o l y m e r i c i s o c y a n a t e and f l u o r o c a r b o n b l o w i n g agent, A b i l i t y t o use l o wpressure p r o c e s s i n g , and E l i m i n a t i o n o f n e c e s s i t y o f h a n d l i n g and blending high v i s c o s i t y sucrose i n i t i a ted polyol. A c t u a l l y , there a r e s p e c i f i c advantages t o u s i n g e a c h t y p e o f c o i n i t i a t o r shown a b o v e . F o r example: H 0 2

Faster a l k y l a t i o n reaction, Diol to polyol introduction, Improved compatability, Decreased p o l y o l v i s c o s i t y , and No c h a n g e i n p o l y o l r e a c t i v i t y . Amines I n c r e a s e d speed o f a l k y l a t i o n p r o c e s s , Low p r e s s u r e p r o c e s s i n g , Decreased p o l y o l f u n c t i o n a l i t y , Decreased p o l y o l v i s c o s i t y , Improved compatability, Increased polyol r e a c t i v i t y , I n t e r n a l c a t a l y s t , and Increased raw m a t e r i a l cost. Glycerol

-

Increased Decreased Decreased No c h a n g e Increased

speed o f a l k y l a t i o n , polyol functionality, polyol viscosity, i n p o l y o l r e a c t i v i t y ,and p o l y o l raw m a t e r i a l cost.

P o l y o l s based on sucrose o r sucrose and a c o i n i t i a t o r a r e u s e d p r i m a r i l y t o make r i g i d u r e t h a n e f o a m s f o r a wide v a r i e t y o f end-uses. F o l l o w i n g a r e some a p p l i c a t i o n s l i s t e d by a p p l i c a t i o n method. S p r a y Foam Insulation Building (roofs) Reaction and storage

vessels


SUCROCHEMISTRY


262

tor.

Pour-In-Place Insulation Refrigeration Portable Coolers Pipe Coverings Sandwich Panels Buoyancy Boats Barge Repair Packaging F u r n i t u r e - Wood R e p l a c e m e n t Billets Insulation Pipes and V e s s e l s C o l d S t o r a g e Rooms Commercial B u i l d i n g s In c o n c l u s i o n , s u c r o s e i s a v e r y good c a n d i d a t e as t h e b a s e i n i t i a t o r f o r p r e p a r a t i o n o f r i g i d u r e t h a n e foam. I t s b i c y c l i c s t r u c t u r e and e i g h t r e a c t i v e s i t e s p r o v i d e t h e u r e t h a n e polymer w i t h good t h e r m a l and dimensional s t a b i l i t y . V a r i o u s a p p l i c a t i o n s have d i f f e r e n t p h y s i c a l p r o perty requirements. Sucrose w i t h i t s high f u n c t i o n a l i t y a l l o w s one t o b l e n d i t w i t h a v a r i e t y o f c o i n i t i a t o r s t o meet t h e v a r i o u s r e q u i r e m e n t s .

Abstract Sucrose-initiated polyols for use in rigid urethane foams can be made commercially by methods described as high pressure and low pressure processes. The advantages and disadvantages of these two processes are discussed. In the low pressure process it is necessary to dissolve or disperse the sugar in a coinitiaCommonly used are water, trimetholpropane, glycerol, ethylenediamine, and diethylenetriamine. The choice of coinitiator changes the resulting polyol and the final rigid urethane foam's properties. The choice of oxide and the amount of oxide added to the sucrose and coinitiator w i l l vary the average molecular weight and the ratio of primary and secondary hydroxyl groups. These changes affect the rate of reactivity of a polyol with an isocyanate and the foam end-use physical properties. Literature cited 1. United States 2. United States 3. United States 4. United States

Patent Patent Patent Patent

2,990,376 2,902,478 2,990,376 3,865,806


18. MEATH AND BOOTH

Rigid Urethane Foam

263

Biographic Notes Allan R. Meath, M.Sc., M.B. A., Group Leader in Alkylene Oxide Derivatives. Educated at North Dakota Univ. and Central Michigan Univ. Joined the Dow Chemical Co., in 1955 specializing in latexes, epoxy resins and urethane chemicals. Dow Chemical Co., Building B-4810, Freeport, Texas 77566 U.S.A. Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on October 6, 2015 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0041.ch018

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Sucrose and Modified Sucrose Polyols in Rigid Urethane Foam

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