74 Oligomeric Phosphorus Esters with Flame Retardant Utility Downloaded by UNIV OF MASSACHUSETTS AMHERST on May 24, 2018 | https://pubs.acs.org Publication Date: November 11, 1981 | doi: 10.1021/bk-1981-0171.ch074
E D W A R D D. WEIL, RALPH B. F E A R I N G , and F R E D J A F F E Stauffer Chemical Company, Eastern Research Center, Dobbs Ferry, N Y 10522
The term oligomer refers to a polymer-like material having only a few repeating units. The oligomeric phosphorus esters which are the subject of the present paper are generally viscous liquids having an average of two or more phosphate and/or phosphonate ester units per molecule. Pioneering work on phosphorus ester oligomers has been done by Monsanto in the U.S. (1), by Hoechst in Germany (2), and in the Soviet Union. These "studies involved synthesis and flame retardant applications. The polycondensation of 2-chloroethyl phosphates as a route to oligomeric phosphorus esters (Equa tion 1) was first reported by Korshak et al. (3). This Russian publication describes the polycondensation of tris(2-chloro ethyl) phosphate at 240-280° under non-catalytic conditions. An acidic dark product was obtained. Besides the desired transalky lation, side reactions yielding acetaldehyde, vinyl chloride, phosphorus acids, and pyrophosphates were described by other Soviet researchers (4). Such a multitude of concurrent re actions is undesirable if this process is to be controllable and useful for flame retardant manufacture. P o l y c o n d e n s a t i o n o f 2 - C h l o r o a l k y l Phosphates and Phosphonates Each s t e p o f t h e p o l y c o n d e n s a t i o n can be d e s c r i b e d b y t h e following general reaction: (1)
#
2RR'P(0)0CH CH C1—RR P(0)OCH CH OP(0)RR 2
2
2
#
2
+ ClCI^CÏ^Cl
Polycondensation r e a c t i o n s o f 2 - c h l o r o a l k y l phosphates o r phosphonates t o o b t a i n products having a c o n t r o l l a b l e degree o f c o n d e n s a t i o n a n d l o w a c i d o r l a t e n t a c i d c o n t e n t s w e r e accom p l i s h e d i n o u r l a b o r a t o r y u s i n g c a t a l y s t s such as quaternary ammonium s a l t s , a m i n e s , a m i d e s , s o d i u m c a r b o n a t e , o r l i t h i u m c h l o r i d e (5) . R e d u c t i o n o f t h e t e m p e r a t u r e d i m i n i s h e d t h e 0097-6156/81/0171-0355$05.00/0 © 1981 American Chemical Society Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
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PHOSPHORUS CHEMISTRY
u n d e s i r a b l e s i d e r e a c t i o n s . Further e f f o r t was necessary to e l i m i n a t e l a t e n t a c i d products i f the products were to be u s e f u l i n , f o r example, urethane foams. T r e a t i n g the crude product w i t h ethylene oxide a f f o r d e d a means f o r c o n v e r t i n g phosphorus a c i d groups to hydroxyethyl e s t e r s . Anhydride groups could a l s o be removed by r e a c t i o n with epoxides. P a r t i c u l a r l y p e r s i s t e n t , how ever, were five-membered c y c l i c phosphate e s t e r groups, which i n the case of the polycondensation product o f t r i s ( 2 - c h l o r o e t h y 1 ) phosphate can occur as chain ends or as small molecules. These five-membered phosphate s t r u c t u r e s show a l a r g e Ρ shift (17-18 ppm) downfield from the a c y c l i c phosphates. Five-membered of h y d r o l y s i s corresponding c y c l i c esters used as flame
c y c l i c phosphate and phosphonate e s t e r s have r a t e s orders of magnitude g r e a t e r than those of the a c y c l i c e s t e r s (6), t h e r e f o r e such five-membered are u n d e s i r a b l e components i f the oligomers are retardants.
The presence o f these c y c l i c e s t e r s i n the crude polycondensation r e a c t i o n product was found to be unavoidable ; indeed some e v i dence was developed that the polycondensation a t l e a s t i n p a r t proceeds v i a these c y c l i c e s t e r s . Considerable e f f o r t was ex pended to f i n d means f o r e l i m i n a t i n g these c y c l i c five-membered e s t e r s from our polycondensation products. The c y c l i c e s t e r s can be e l i m i n a t e d by e i t h e r inducing them to polymerize by use of Lewis a c i d c a t a l y s t s such as stannous octoate, o r by subjec t i n g them to r i n g opening by means of an a l c o h o l or water ( 7 ) . Copolycondensation A f u r t h e r v a r i a t i o n on the t rans a I k y l a t i on r e a c t i o n described above i s the cocondensation of d i f f e r e n t phosphorus e s t e r s ( 8 ) ; as shown i n the f o l l o w i n g equation: q RP(0CH CH C1) 2
2
2
q + CH P(OCH ) 3
3
2
2 C H
3
Γ ç ο ι >» |-0^-OCH CH -o|-OCH CH
C 1
2
2
2
2
One embodiment o f t h i s general r e a c t i o n l e d to a product which was commercially produced f o r s e v e r a l years by S t a u f f e r as F y r o l 76 (9), a copolycondensation product o f dimethyl methylphosphonate with b i s ( 2 - c h l o r o e t h y l ) vinylphosphonate. The features o f F y r o l 76 were high phosphorus content (20%), water s o l u b i l i t y , and a b i l i t y to be polymerized by means of a r a d i c a l i n i t i a t o r to a c r o s s l i n k e d polymer. A r e l a t e d polycondensation product was developed from t r i s ( 2 - c h l o r o e t h y l ) phosphate and d i methyl methylphosphonate. By c o n t r o l of the reagents and proce dure used f o r n e u t r a l i z a t i o n , these o l i g o m e r i c products were produced with primary a l c o h o l f u n c t i o n a l groups (7) .
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
74.
WEIL
ET AL.
Oligomeric
Phosphorus
Esters
357
Oligomers V i a Metaphosphate(Phosphonate) Intermediates The d i s s o l u t i o n of P^O^ i n a phosphate or phosphonate e s t e r b r i n g s about a r e o r g a n i z a t i o n r e a c t i o n i n which a metaphosphate or metaphosphonate/phosphate i s formed (10). In the r e a c t i o n of 4°10 y ! methylphosphonate, the i n i t i a l l y - f o r m e d pro duct mixture at 60-110° undergoes a s t r u c t u r a l r e o r g a n i z a t i o n when the mixture i s h e l d a t r e a c t i o n temperature. An i n c r e a s e i n 0,0-dimethylphosphoric anhydride end groups ( $ - 1 1 . 4 , -11.6, -11.9) and Ρ-methyl(meta)phosphonic "middle" groups ($14.2, center of unresolved t r i p l e t and/or doublet of doublets) takes p l a c e at the expense of a decrease i n 0,P-dimethylphosphonic anhydride end groups (doublet at £ 25.7) and 0-methyl (meta)phosphoric anhydride middle groups (incompletely resolved t r i p l e t and/or doublet of doublets centered at -27.1). Branched phos p h o r i c anhydride (é-43) disappears e a r l y i n the h e a t i n g process.
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P
w
i
t
n
d i m e t n
The intermediate metaphosphate/phosphonate can then be made to r e a c t with ethylene oxide to e f f e c t the i n s e r t i o n of ethyleneoxy u n i t s i n t o the P-O-P l i n k a g e s . I f a l i m i t e d amount of water or an a l c o h o l i s added to the meta intermediate, the r e s u l t a n t oligomer can be produced with a c o n t r o l l e d hydroxy1 f u n c t i o n a l i t y (11, 12). An example of a f u n c t i o n a l oligomer made t h i s way i s the f o l l o w i n g : H-fOCH CH OP« -h0CH CH 0P — r 0 C H C H 0 H *2~"2 2 2 CH. CH„0 3 JxL ""3 2
o
2
n
O
o
v
There i s some evidence that the r e a c t i o n of ethylene oxide with the metaphosphonate/phosphate may a c t u a r y form some c y c l i c f i v e membered e s t e r s i n i t i a l l y , as shown by r s i g n a l s a t 18.4, 17.4 (phosphates) and 49 (phosphonate) which then are converted to a c y c l i c e s t e r s . In another example of t h i s route to o l i g o m e r i c phosphorus e s t e r s , P^O^Q i s reacted with t r i s ( 1 , 3 - d i c h l o r o i s o p r o p y l ) phosphate to prepare a metaphosphate which i s ethoxylated with ethylene oxide to produce a s u b s t a n t i a l l y hydroxy-free phosphate oligomer (12). A p p l i c a t i o n s as Flame Retardants S e v e r a l commercial products have r e s u l t e d from our phosphorus oligomer r e s e a r c h . F y r o l 99, a 2 - c h l o r o e t h y l ethylene phosphate oligomer, has been s u c c e s s f u l l y used as a flame r e t a r d a n t a d d i t i v e i n rebonded urethane foam, i n thermoset r e s i n s , i n intumescent c o a t i n g s , adhesives, paper a i r f i l t e r s (13), and r e l a t e d uses. T h i s product i s l e s s v o l a t i l e and has a h i g h e r flame r e tardant e f f i c a c y than the parent compound t r i s ( 2 - c h l o r o e t h y l ) phosphate. A r e l a t e d product was developed e s p e c i a l l y f o r use i n f l e x i b l e polyurethane foams. A vinylphosphonate/methylphospho-
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
PHOSPHORUS CHEMISTRY
358
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n a t e o l i g o m e r whose c h e m i s t r y was d e s c r i b e d above ( F y r o l 76) was found e f f e c t i v e f o r meeting t h e F e d e r a l f l a m m a b i l i t y standard f o r c h i l d r e n ' s c o t t o n sleepwear ( 1 4 ) . A r e l a t e d methylphosphate/phosphonate oligomer has primary a l c o h o l e n d g r o u p s , a n d c a n c o r e a c t w i t h amino r e s i n s t o f o r m a w a t e r - r e s i s t a n t f l a m e r e t a r d a n t r e s i n f i n i s h on p a p e r o r o n t e x t i l e s u b s t r a t e s . The a p p l i c a t i o n o f t h i s o l i g o m e r w i t h a c o r e a c t a n t me t h y l o l m e 1 a m i n e o n c o t t o n u p h o l s t e r y f a b r i c c a n e n a b l e f u r n i t u r e c o v e r e d w i t h t h i s f a b r i c t o p a s s t h e Consumer Product S a f e t y Commission's proposed c i g a r e t t e i g n i t i o n t e s t . LITERATURE CITED
1. Birum, G. H. (to Monsanto Co.), U.S. Pats. 3,014,956 (1961), 3,042,701 (1962). 2. Wortmann, J., Dany, F. J., and Kandler, J. (to Hoechst A.-G.), U.S. Pat. 3,850,859 (1974). 3. Korshak, V. V., Gribova, I. Α., and Shitikov, V. Κ., Proc. Acad. Sci. USSR, Div. Chem. Sci., 196-201 (1958). 4. Kafengauz, I. M., Samigulin, F. Κ., Kafengauz, A. P., Polyakova, Τ. A., Tsarfin, Ya. A., and Gefter, E. L . , Soviet Plastics, 73-75 (Apr. 1967). 5. Weil, Ε. D. (to Stauffer Chemical Co.), U.S. Pats. 3,896,187 (1975), 4,005,034 (1977), and 4,013,814 (1977). 6. Westheimer, F. H., Acc. Chem. Res. 1, 70-77 (1968). 7. Weil, E. D. (to Stauffer Chemical Co.), U.S. Pat. 3,891,727 (1975); Shim, K. S. and Walsh, Ε. Ν. (to Stauffer Chemical Co.), 3,959,414 (1976), 3,959,416 (1976); Walsh, Ε. N. (to Stauffer Chemical Co.), 4,012,463 (1977). 8. Weil, E. D. (to Stauffer Chemical Co.), U.S. Pats. 4,086,303 (1978), 4,152,371 (1979), 4,202,842 (1980), 4,225,522 (1980). 9. Weil, E. D. (to Stauffer Chemical Co.), U.S. Pats. 3,822,327 (1974), 3,855,359 (1974), 4,017,257 (1977), 4,067,927 (1978). 10. Schep, R. A., Coetzee, J. H. J., and Norval, S., J. S. Afr. Chem. Inst. 27, 63-69 (1974); Inorg. Chem. 12, 2711-13 (1973). 11. Fearing, R. B. (to Stauffer Chemical Co.), U.S. Pat. 4,199,534 (1980). 12. Hardy, T. A. and Jaffe, F. (to Stauffer Chemical Co.), S. Afr. Pat. 79/1120 (Mar. 26, 1980). 13. Weil, E. D., Leitner, G. J., and Kearnan, J. Ε., "Phosphorus Flame Retardants for Resin-Treated Paper", in Proc. TAPPI Paper Synthetics Conf., Orlando, FL, Sept. 27, 1978. 14. Eisenberg, B. J. and Weil, E. D., Textile Chemist and Colorist 6 (8), 180-2 (1974); Bruce, J., Am. Dyestuffs Rep. 62 (10), 68-70 (1973). RECEIVED
June 30,
1981.
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
