FLAME-RESISTANT URETHANE FOAMS FROM ADDUCTS OF HEXACHLOROCYCLOPENTADIENE AND CASTOR 01L C.
K.
LYON AND
GLENN
FULLER
Western Regional Research Laboratory, Agricultural Research Seruice, U. S . Department o f Agriculture, Albany, Calif. 94710 Diels-Alder type adducts containing 25 to 36% chlorine were readily obtained by heating mixtures of castor oil and hexachlorocyclopentadiene a t 150' C. Reixtion times were determined for desired extents of reaction. These adducts have very low acid contents and good storage stability. One-shot, rigid urethane foams were prepared using, as the polyol component, mixtures of these adducts with triisopropanolamine. These foams have excellent flame resistance, high strength, and little tendency to shrink after foaming.
RIGID urethane foams are widely used for thermal insulation and structural support. Their largest potential markets are in construction, where low cost and flame resistance are required. Fllame resistance has generally been achieved by the use of a large variety of phosphorusor halogen-containing polyols or additives, including halogenated castor oil derivatives (Dahm, 1965; Lyon and Applewhite, 1967) This paper describes the formation of adducts of castor oil with hexachlorocyclopentadiene and the preparation of flame-resistant urethane foams from these adducts.
Table I. Hexachlorocyclopentadiene-Castor Oil Adducts
React ion Conditio IZS Moles diene per equiv. castor oil Hours 1
2
O C .
7 24
140-145
25.7 31.4
107 98
1.0 1.0
26 17
10 24
150 140-145
34.3 36.3
91 86
0.4 0.7
10 7.7
150
Table II. Reaction Time vs. Chlorine Content of Adducts
Moles Diene per Equiu. Castor Oil in Reaction
Adduct Preparation
The reaction of hex,achlorocyclopentadiene with olefins is a Diels-Alder type condensation (Bloch, 1956; Fields, 1954) and in the case of castor oil reaction takes place
Product Analysis OH Acid Iodine % Cl No. No. value
1
Hours at 140-45" C. 4 7 16 24 24
2
5% Cl in Adductn 10.8 22.4 28.5 31.1 31.4'
20.9 26.3 33.5 35.6 36.3b
Calculated from UV determination o f unreacted diene. ' Chlorine analysis of isolated adduct.
a t the 9, 10 double bonds of the ricinoleic acid glycerides. Adducts were prepared by mixing castor oil (one equivalent, based on unsaturation) with 1 or 2 moles of hexachlorocyclopentadiene (C-56, Hooker Chemical Corp., or PCL, Velsicol Chemical Corp.) and heating the mixture under nitrogen for 7 to 24 hours a t 140" to 150" C. Any excess hexachlorocyclopentadiene was then distilled off under vacuum a t 100" to 150°C. a t 1 mm. of Hg. Properties of the addlucts obtained are listed in Table I. An adduct in which the double bonds of castor oil had reacted completely would contain 37.570 C1. For comparison, the chlorine content of fully chlorinated castor oil is 19%. Acid numbers of the adducts are very low, and they remain much lower on aging than those of chlorinated castor oil. These adducts are dark-colored, viscous liquids in which the viscosity increases with increasing chlorine content. Somewhat lighter colored products could be obtained by the addition of 2 to lo'% epoxidized soybean oil to reaction mixtures-for example, the color of adducts containing 29% C1 was reduced from Gardner 18 to Gard-
ner 14 when 10% epoxidized soybean oil was added during preparation. During the two 24-hour preparations, the extent of reaction was determined a t intervals by measurement of the ultraviolet absorption of unreacted diene a t its maximum of 322 mk (Lyon et al., 1967). From these measurements the chlorine contents of the adducts were calculated (Table 11). The reaction time for an adduct of any desired chlorine content can be estimated from this table. A second-order rate constant a t 150°C. of 1.8 x lo-' liter per mole second and an activation energy of 19.5 kcal. per mole have been reported for this reaction (Lyon et al., 1967). Urethane Foam Preparation and Evaluation
Rigid urethane foams were prepared from two of the castor oil-hexachlorocyclopentadiene adducts (25.7 and 34.3% C1) using the one-shot formulations given in Table VOL. 8 NO. 1 M A R C H 1 9 6 9
63
Table Ill. Formulations for 100 Grams of Polymer
Table IV. Polyol Mixtures for 100 Grams of Polymer"
Polyol Eguiualent Weight Component Polyol", g. PAPIb, g. L-530 silicone', g. Dibutyltin dilaurate', g. CCLF, g.
e
Polyol Awrage Equiualent Weight
120
130
140
Component
45.8 54.2 1.0 0.1 15.5
47.8 52.2 1.0 0.1 15.5
49.6 50.4 1.0 0.1 15.5
Adduct 25.7% C1, g. 34.3% c1, g. Castor oil, g. Triisopropanolamine, g. Sb203b, g.
"See Table I V . ' Polymethylene polyphenylisocyanate, Upjohn Co Union Carbide Corp.
120
120
140
25.2
25.2
31.4
20.6
20.6 2.0
18.2
120
140
24.7
30.8
21.1
18.8
120
130
27.1
30.7
18.7
17.1
'See Table I I I . ' Thermoguard L ( M & T Chemicals, Inc.).
Table V. Foam Properties
Humid Aging "/c C1 in Adduct 0 (castor oil) 26.1 25.1 + 2 pph Sb203 25.7 34.3 34.3
Polyol Equiu. W t .
Flammability"
120 130 120 120 140 120 140
Burns 4.9 in./min. Burns 4.8 in./min. SE, 2.1 in., 45 sec. SE, 0.6 in., 30 sec. SE, 2.4 in., 50 sec. SE, 0.9 in., 29 sec. SE, 1.2 in., 33 sec.
C o w . Strength, P.S.1.' Parallel Perp . 38 21 53 44 44 53 47
17 14 22 18 21 21 19
j14 D a y s i 7 p
c,I,
8 Severe shrink. 9 9 8 9 14
' A S T M method D 1692-67T, SE-self extinguishing. 'Normalized to compressive strength at deilsity of 2.00 1b:cu. 1961).
111, which are based on formulations that were shown previously (Lyon and Applewhite, 1967) to yield good foams. The poly01 portions were composed of mixtures of an adduct or castor oil with triisopropanolamine having average equivalent weights of 120 to 140 (Table IV). Triisopropanolamine was added to increase the crosslink density sufficiently to yield rigid foams. Other low molecular weight polyols such as Quadrol (Wyandotte Chemical Corp.) have also been used for this purpose. Foam components (about 70 grams) were mixed with an electric stirrer and poured into 7 % x 3 x 5 inch high cardboard boxes. Foaming was complete in 2 to 3 minutes. All tests, except that for flammability which was determined by ASTM method D 1692-67T, were run on 1 inch high x 1.5 inch diameter pellets as described previously (Lyon and Applewhite, 1967). Compressive strengths, measured a t 10% deflection, were normalized, by means of the empirical relationship
Strength,,=, =
(2idobsd)1.G
reported previously (Lyon et al., 1961), to those of foams with a density of 2.00 pounds per cu. foot. Actual densities were 1.9 to 2.2 pounds per cu. foot. Properties of these foams are listed in Table V. The unmodified castor oil-based foams burned readily, but foams prepared from the adducts had excellent flame resistance. The high chlorine content of foams from the 34.3% C1 adduct made these foams the least flammable. However, comparable extents of burning could be obtained with foams from the 25.7Y0 C1 adduct by the addition of 2 parts per hundred antimony oxide. Use of antimony oxide permitted a significant reduction in the chlorine content, but caused the reduction in compressive strength that is sometimes encountered when using solid additives. 64
I & E C PRODUCT RESEARCH A N D DEVELOPMENT
Closed Cells, %
% Vol. Incr.
90
... 88 91 90 88 90 ft.
(Lyon et al.,
I n addition to excellent flame resistance, these foams had good physical properties. Compared to the unmodified castor oil-based foams, the adduct-based foams had higher compressive strengths and less tendency to shrink after foaming. Foam buns (about 7 % x 3 x 5 inches) prepared from unmodified castor oil shrank excessively when poly01 equivalent weights over 120 were used. However, there was no apparent shrinkage of the adduct-based foams when poly01 equivalent weights up to 140 were used. The better properties of the adduct-based foams permit the use of formulations with higher equivalent weight polyols which require less of the costly isocyanate component. Literature Cited
Bloch, H. S. (to Universal Oil Products Co.), U. S. Patent 2,771,479 (Nov. 26, 1956). Dahrn, M. (to Farbenfabriken Bayer A. G.), U. S. Patent 3,206,416 (Sept. 14, 1965). Fields, E. K., J . A m . Chem. SOC.76, 2709 (1954). Lyon, C. K., Applewhite, T. H., J . Cellular Plastics 3, 91 (1967). Lyon, C. K., Fuller, G., Applewhite, T. H., J . A m . Oil. Chemists' SOC.44, 740 (1967). Lyon, C. K., Garrett, V. H., Goldblatt, L. A., J . A m . Oil Chemists' SOC.38, 262 (1961).
RECEIVED for review March 21, 1968 ACCEPTED November 21, 1968 Division of Organic Coatings and Plastics Chemistry, 154th Meeting, ACS, Chicago, Ill., September 1967. Reference to a company or product name does not imply approval or recommendation of the product by the U. S. Department of Agriculture t o the exclusion of others that may be suitable.
