CHLORINATED XYLENE DERIVATIVES FOR FLAME-RETARDANT RIGID POLYURETHANE FOAMS F R A N K B . S L E Z A K , ' J O H N
P. S T A L L I N G S , A N D I R V I N G ROSEN
T . R. Eoans Research Center, Diamond Alkali Co., Painesville, Ohio
Tetrachloroxylylene dichlorides may b e used for the preparation of chlorine-containing polyhydroxy compounds suitable for conversion into rigid polyurethane foams with built-in flame retardancy. Polyols such as glycerol, trimethylolpropane, 1,2,6-hexanetriol, or mixtures thereof react with tetrachloroxylylene dichlorides to form a mixture of chlorine-containing polyether polyols. The by-product hydrogen chloride initially formed in this reaction reacts with the polyether polyol, retaining in the reaction product essentially all of the chlorine originally present in the tetrachloroxylylene dichloride. The chlorine-containing polyether polyol may be converted into nonburning or self-extinguishing fluorocarbon-blown rigid polyurethane foams in one-shot reaction with crude tolylene diisocyanate, crude diphenylmethane diisocyanate, or polymethylene polyphenylisocyanate. The chlorine-containing polyether polyol may be diluted with substantial amounts of conventional polyols to yield foams with excellent physical properties, which still retain a high degree of flame retardancy.
URING
the past several years we have been interested in
D several aspects of the chemistry of chlorinated xylenes. One area of considerable interest has been the use of such intermediates in the preparation of polymers with built-in flame retardancy. Chlorinated xylylene dichlorides such as 3,4,5.6-tetrachloro-o-xylylene dichloride. 2,4:5:6-tetrachlorodichlom-xyl)-lene dichloride, 2.3,5,6-tetrachloro-p6-xylylene ride. or mixtures thereof proved to be of particular value in the preparation of reactive intermediates for such polymers. This paper deals with the use of such tetrachloroxylylene dichlorides for the preparation of mixtures of chlorine-containing polyhydroxy compounds suitable for the preparation of flame-retardant rigid polyurethane foams. Some of the formulations examined and the properties of the resulting foams are also presented. Xylylene dihalides will react with a n alcohol to form the corresponding a,a '-dialkoxyxylenes. The reaction is usually carried out in the presence of an acid acceptor ( I ? 2). I n some. as yet unreported, work prior to the present study we found that a xylylene dihalide, such as p-xy1)-!ene dichloride, will react with a polyol, such as glycerol, in the presence of a n acid acceptor to form a polyether poly01 isomer mixture which may be represented by Ia-c.
OH
OH' 6 O C H z C HI C H z O H
G O C H Z C HI C H z O H
CH20CH2YHCH20H OH Ia
CHzOH CHIOC~ CHzOH
, ,CHzOH
Ib
60CH \CH~OH
, , CHzOH
CH2OCH
'CH~OH IC 1 Present address, Research and Development Division, Union Bag-Camp Paper Corp., Princeton, N.J .
292
I&EC PRODUCT RESEARCH A N D DEVELOPMENT
I n the present study we found that xylylene dihalides, such as the tetrachloroxylylene dichlorides, can react with polyols such as glycerol. trimethylolpropane, 1.2,6-hexanetriol: and mixtures thereof, in the absence of a n acid acceptor, to form a useful mixture of polyether polyol isomers. From the standpoint of economics and properties of the resulting products, the use of glycerol \vas preferred. T h e remainder of this paper deals Lvith the products of the glycerol-tetrachloroxylylene dichloride reaction. Heating a mixture of about 3.25 moles of glycerol per mole of tetrachloroxylylene dichloride, a t a pot temperature of about 170' C. until about 3.1 moles of water per mole of tetrachloroxylylene dichloride is evolved, yields a chlorine-containing polyol mixture useful in the preparation of flame-retardant rigid polyurethane foams. T h e reaction was generally carried out in the presence of a small amount of a solvent such as n-octane, toluene, or xylene to facilitate the removal of the water formed during the reaction. The 3,4,5,6-tetrachloro-o-xylylene dichloride (m.p. 81-86' dichloride (m.p. 137-39' C . ) , 2,4,5,6-tetrachloro-rn-xylylene dichloride (m.p. 179C . ) , and 2,3,5,6-tetrachloro-p-xylylene 180' C . ) used in this study were Diamond .4lkali Co. development chemicals. Experimental Procedures
Preparation of Chlorine-Containing Polyol Mixture, A 12-liter round-bottomed flask was equipped with a nitrogen inlet tube, a thermometer which reached into the lower half of the flask, a mechanical stirrer, and a high-capacity Barretttype water trap surmounted by a n efficient water-cooled condenser. T h e flask was flushed with nitrogen and charged with tetrachloroxylylene dichloride (5008 grams, 16 moles) glycerol (4784 grams, 52 moles), a n d about 200 ml. of toluene. The stirred mixture was heated slowly by means of a n electric heating mantle until the reaction started (at about 155' C.) and then the temperature was allowed to rise to about 170' C. a t which point the reaction was usually brisk. A low initial heat input is desirable: since, on occasion, the reaction can be vigorous in its early stages. T h e heating rate was then controlled so as to maintain a rapid reflux of toluene and consequent rapid azeotropic removal of the required 893 ml. of water. T h e toluene was recycled to the reaction flask until about 700 ml. of water had separated and then the toluene and water were taken off together. As a result, essentially all
of the toluene was removed by the time the required amount of water had been collected. T h e reaction was usually finished in 6 hours. Preparation of Polyurethane Foams. Appropriate amounts of polyol or polyols, catalyst, surfactant, and trichlorofluoromethane were weighed into a suitable container (such P S a 1pint or 0.5-gallon paint can) and stirred to form a homogeneous mixture. Stirring was carried out with a variable transformercontrolled. 2/s-hp., ‘/r-inch electric drill motor with a speed in the range of 1600 to 2000 r.p.m. A 2-inch Conn (Conn and Co., Warren, Pa.) impeller was used to stir small amounts ( u p to about 0.5 pound) of composition while a 3-inch mediumlift impeller ( M . F. Fawcett Co.) was used to mix larger amounts of composition. T h e required amount of polyisocyanate was then added, the mixture was stirred about 20 to 30 seconds, and the homogeneous mixture was poured into a 1-cu. foot box, where the foam was allowed to rise. Some specific details of the amounts of components used and the properties of the resulting rigid polyurethane foams are presented in Table I V .
At least two other reactions require consideration in order to account for all the water formed during the course of the reaction. The first is the direct polyetherification of glycerol with a product such as IV to form a material which might be represented by V. A second possible reaction would be one in which the glycerol would react with a ring halogen to form a phenoxy ether and the by-product hydrogen chloride would react as before to form water eventually. We favor the direct
?H
FH20CHiCHCH20CH2CHCH20H
‘ 1 4 4 OH CH20CHzCHCHzCl
V etherification view but have no evidence to eliminate the second suggestion. The chlorine-containing polyol we have described may be used in a two-part, premixed, one-shot system to form fluorocarbon-blown rigid polyurethane foams using crude tolylene diisocyanate (.4llied Chemical Co. Nacconate-4040). crude diphenylmethane diisocyanate (Mobay Chemical Co. ,MondurM R ) , or polymethylene polyphenylisocyanate (Carwin Co. PAPI) as the polyisocyanate component. Pure tolylene diisocyanate may be used in such a one-shot system for very
Results and Discussion
T h e initial reaction of tetrachloroxylylene dichloride with glycerol may be considered as leading to a mixture of isomers represented by IIa-c and some dimers and trimers which may be represented by 111. Hydrogen chloride is also formed as a by-product of this initial reaction. T h e by-product hydrogen chloride is not lost from the reaction system but
PH
?H
/CHzOH CHiOCH CHZOH
‘
‘144
/ CHIOH
c144@
/CH,OH CHzOCH
CH~O~H
CH20CHzyHCHzOH
\
OH IIa
‘CH~OH
CHzOH
IIC
IIb
CI4
L
OH CI4
--
-In
I11 instead reacts, presumably with the hydroxyl-containing molecules, to form alkyl halide linkages and result in the evolution of by-product water. Approximately 95 to 98y0 of the by-product hydrogen chloride is utilized in this manner. A suggested representation of the resulting product is illustrated by IV. This allows the retention of a high chlorine
7’
CHzOCH2CHCHzOH
+
Hz0
- \
CHzOCHiCHCH2Cl IV
I
OH
content in the system, which in turn contributes to an improved flame-retardant efficiency. I n addition to the reaction shown, some of the hydrogen chloride reacts with glycerol to form. primarily, l-chlbro-2,3-dihydroxypropane.Gas-liquid chromatography shows the latter compound to be present to the extent of 12 to 14%, while less than 5% of the original tetrachloroxylylene dichloride remains unreacted. About 2 to 4% of the glycerol originally present undergoes an acid-catalyzed dehydration to acrolein, which is swept out of the reaction system. Table I summarizes some properties of a representative chlorine-containing polyol, made by the procedures described. dichloride. from glycerol and 2,4,5,6-tetrachloro-m-xylylene
small volumes (not exceeding 4 to 5 liters of finished foam) but, as might be expected from the reactivity of pure tolylene diisocyanate, considerable internal scorching and weakening of the cell structure result when pours as large as 1 cu. foot of foam are made. A representative formulation using the chlorinecontaining pol>-oldescribed in Table I along kvith Mondur-MR as the polyisocyanate component is presented in Table 11: with some physical properties of the resultant foam. Similar chlorine-containing polyols were prepared by the reaction of glycerol with 3.4,5~6-tetrachloro-o-xylylene didichloride. chloride and with 2,3,5,6-tetrachloro-p-xylylene The hydroxyl numbers of two such polyols are sho\z.n in Table I11 along with some physical properties of a fluorocarbon-
Table 1. Physical Properties of a Representative Glycerol2,4,5,6-Tetrachloro-m-xylylene Dichloride Polyol
Hydroxvl number, mg KOH/gram Acid number mg KOHIgram 11 ater content 5 ActiL e hvdrogpn equi\ dent weight qrams Color Vlscositb (Brookfield) at 25’ cps Chlorine content r;C
391 4 2 0 33 135
Dark brown 113 000
Theoreticalo Found For 700‘1, reutzlztatzon fo, znztrol by-product HCI
VOL. 3
NO. 4
DECEMBER
38 3 37 5
1964
293
Table 11. Representative Formulation and Foam Properties Using Chlorine-Containing Polyol from Table I and MondurMR
Polyol, grams 675 L-5310,” grams 48 D-22,* grams 13 Trichlorofluoromethane, grams 166 Mondur-MR,C grams 712 Density, Ib./cu. foot 2.1 Compressive strength, p.s.i. Before humid aging 36 After humid agrngz 32 Volume change on humid aging, yo +2 1 Nonburning Burning rate, ASTM D 1692-59T K factor. 0.12 a Union Carbide, silicone surfactant. Union Carbide, dibutyl tin M o b a y Chemical Co., crude diphenylmethane diisodilaurate catalyst. cyanate. d Humid aged 7 days at 758’ F., 700% relative humidity. e ( B . t . u . ) ( i n c h e s ) / ( h r . ) (sq. f t . ) ( O F . ) .
Teble 111. Properties of Tetrachloroxylylene DichlorideGlycerol Polyols and of Rigid Polyurethane Foams Made from Them and Mondur-MRa
Hydroxyl Number, Mg. KOHIG.
Polyurethane Foam Properties CompresDensity, siue strength, Burning Klb./cu. ft. p.s.i. rateb factorC
Starting Xylylene Dichloride 3,4,5,6-Tetrachloro-o430 1.9 28 NB 0.15 2,4,5,6-Tetrachloro-m422 1.8 26 NB 0.15 2,3,5,6-Tetrachloro-p480 2.0 33 NB 0.13 M o b a y Chemical Co., crude diphenylmethane diisocyanate. ASTM D 7692-59T; N B = nonburning. (B.t.u.) ( i n c h e s ) / ( h r . ) ( s q . f t . ) (OF.).
Formulations and Physical Properties of Rigid Polyurethane Foams from Chlorine-Containing Polyol of Table I with and without 40% Added Conventional Polyol Using Three Different Polyisocyanates 7 4 2 5 6 7 Formulation 3 8 9 70 77 12
Table IV.
586 404 480 829 584 404 Poly01 from Table I, grams 675 475 810 506 404 475 383 ... , . . ... ... LK-380,a grams 383 ... ... . . . 338 .. . . ... , . . ... ... 262 LS-490,b grams 262 ... , . . ... . . . 262 ... , . . , . . ... . . . 320 , , . , . . Voranol-450,c grams 267 ... 317 48 20 48 16.5 29 24 1 6 . 5 1 9 . 2 1 6 . 8 1 7 . 4 13.9 L-5310,d grams 16 8 16 22 5f 13 15 1 0 . 2 12 23 19 9 T-9,e grams 10 9 302 235 225 195 166 325 21 1 250 205 181 145 CC13F, grams 243 952 828 749 ... 712 ... ... ... ... Mondur-MR,Qgrams ... ... ... ,.. 893 1002 720 , . . 873 PAPI,h grams ... ... ... ... ... , . . , . . ... ... ... ... 698 699 576 697 Nacconate-4040,%grams 2.1 1.9 2.1 2.2 1.8 2.0 2.0 1.9 1.9 2.2 2.2 Density, Ib./cu. ft. 1.8 Compressive strength, p.s.i. 34 33 39 41 38 41 45 28 24 42 43 Before humid aging7 25 31 32 42 33 40 35 40 20 13 35 38 16 After humid aging 9.8 6.6 1. o 5.9 1 0 7.9 6 . 9 1 3 . 6 1 7 . 2 11.9 22.9 Volume swell upon humid aging, 7 0 9.2 NB SE NB NE NB NB NB SE SE Burning rate, inches/minuteb SE 3.36 7.74 Union Carbide oxypropylated sorbitol. C D o w oxypropylated sucrose. a Union Carbide aromatic-based polyol. Union Carbide silicone copolymer surfactant. e Metal and Thermit stannous octoate catalyst. Union Carbide N,N,N’,Nt-tetramethy1butane-1,3-diamine. Mobay crude diphenylAllied crude tolylene diisocyanate. i Humid aged 7 days at 758a F. and 700y0 methane diisocyanate. h Carwin polymethylene polyphenylisocyanate. relative humidity. k ASTM D 7692-59T, h’B = nonburning; SE = self-extinguishing. There w a s no signiJicant change in burning rate after humid aginx 7 days at 758’ F . and 700% relative humidity. . . I
Q
blown polyurethane foam made from the polyols. Another example of a 2,4,5,6-tetrachloro-rn-xylylene dichloride-glycerol-based polyol, taken from a different lot of polyol, is also included for comparison. Mondur-MR was used as the polyisocyanate component in all three cases shown in Table I11 a t a n isocyanate-to-active hydrogen ratio of 1.lo. T h e chlorine-containing polyols described may be diluted with substantial amounts of conventional polyols, which have no flame-retardant properties to speak of, a n d still result in polyurethane foams having a significant degree of flame retardancy. T h e ability to use the lower cost conventional polyols in this way helps to reduce the over-all cost of the flameretardant polyurethane foam system. T h e polyisocyanate used as a coreactant in such systems has a marked effect on the fire retardancy observed. Polyisocyanates such as MondurMR and PAP1 are essentially equal in this respect a n d superior to Xacconate-4040. Table IT’ shows a number of such formulations, a n d some physical properties of the resulting polyurethane foams, taken from a series of experiments in which the chlorine-containing poly01 was used in formulations u i t h three types of conventional polyols and coreacted with the three polyisocyanates. Where used (Table IV), the conventional polyol was present to the extent of approximately 40y0 of the poly01 content. Conclusions
Tetrachloroxylylene dihalides may react with polyols, such as glycerol, to yield a new type of chlorine-containing polyol 294
I&EC PRODUCT RESEARCH A N D DEVELOPMENT
suitable for the preparation of flame-retardant polyurethane foams. Essentially no chlorine is lost from the reacting system; thus both the fire-retardancy contribution of the polyol a n d the over-all economics of the product are improved. T h e chlorine-containing polyol may be converted into rigid polyurethane foams using two-part premixed one-shot systems based on several different polyisocyanates. Furthermore, it may be diluted with substantial amounts of lower cost conventional polyols and still yield polyurethane foams with desirable physical properties, including flame retardancy.
Acknowledgment
T h e authors thank the Process Research Section for the preparation of numerous large-scale lots of the polyol used in the formulation studies and the Applications Research Section for the extensive physical testing program on the polyurethane foams. They especially thank Joseph S. Mutko and Donald H. Wagner for help in this program.
Literature Cited
(1) Quelet, R., Bull. Soc. C h i n . 53, 222-34 (1933). (2) Ross, S. D., Markarian, M. (to Sprague Electric Co.), U. S . Patent 2,564,214 (Aug. 14, 1951). RECEIVED for review August 12, 1964 ACCEPTED October 13. 1964
