Flame Retardants ROBERT
he styrene family of plastics encompasses a wide T v a r i e ty of materials ranging from the simple polystyrene molding resins a n d foams t h r o u g h styrene-. acrylonitrile copolymers, to the varied types and grades of the acrylonitrile-butadiene-styrene polymers. While each part of this large family of plastics finds its own individual utility, in a large number of these end uses the necessity of providing a flame-retardant grade of plastic has become increasingly important. T h e value of flame retardants for styrene is also apparent from the large amount of research which has been directed toward that goal during the past 15 or more years. Indeed, this paper, not a critical review, uses over 200 references, the great bulk of which are directly concerned w i t h t h e discovery of f l a m e r e t a r d a n t s for polystyrene-based plastics. It can also be predicted, in view of the tendency toward more specific legislation related to building codes, automobile safety, and such, that increased pressure for the development of newer and better flame-retardant plastics will be felt by the plastics industry. This review, therefore, attempts to assemble the major portion of the pertinent literature and thereby to classify the areas of most intense investigation. I n general, an attempt has not been made to separate the retardant chemicals on the basis of the type of styrene polymer or copolymer, nor are the various types of retardants classified as to usefulness. T h e nature of fire or flame has been the subject of many investigations. A recent review containing 111 references ( 4 ) gives an excellent base for understanding the chemistry of flame propagation. The three elements necessary for flame are fuel, oxidizer, and heat. T h e search for a flame retardant will, therefore, be a n attempt to eliminate one or more of these elements. A number of authors h a \ e attacked the problem by investigating the mechanism of various flame retardants (80,188,197). Other authors have concerned themselves with specific problems peculiar to plastics containing flame-retardant additives such as ultraviolet stability (156), thermal stability as related to etching of extrusion dies (105),special mold releases for flame-retardant plastics (198), and even toxicity of the combustion products (120,165). Also, several review papers concerned with 70
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the over-all problem of plastics flame retardancy have been published (18,91,116,154). These problems will most probably be of concern for a long time. T h e major area of investigation of flame retardant for polystyrene has been in the use of additives. These additives have built into them a certain type of instability. This instability, which results in usefulness as flame retardants, also results in the aforementioned problems, or general degradation of the plastic system from both physical and chemical forces.
T E S T I N G O F F L A M E RETARDANTS One of the peripheral but major problems encountered in the development of a flame-retardant plastic is the means of determining or analyzing progress-that is, a method of testing that is both meaningful and reproducible. T h e tests now in common use range from small laboratory tests such as ASTM D635-63 ( 3 ) to large-scale tests such as the “tunnel” test ASTM E84-60T (2). While these tests have value, correlation in scale-up from one laboratory to another and, indeed, from one time to another is particularly difficult with thermoplastics. Recently, attempts have been made to develop tests which will more critically define the flammability of a plastic and give the investigator a more refincd method for analyzing the results of additives in a given system. Hopefully, this would then lead to a greater possibility for correlating structure and activity. One recent method described uses a muffle furnace set at progressively higher temperatures, a fresh sample being used for each step, until the temperature necessary to bring about flame is determined (119). Another method, which is gaining in popularity and is of particular interest in the early investigation of a compound because of the small sample required, is commonly called the “candle test” (70). I n this test, the < L oxygen index” is defined as n where n=-
[ 0 2
I
+ [SZI in the mixture of oxygen and nitrogen having an oxygen 1 0 2 1
content just capable of sustaining a burning sample. Therefore, the smaller the n, the more flammable the
Suitable additives can make a usually combustible plastic nonflammable
for Polystryene specimen, the larger the n, the more retardant the specimen. As an example, the limiting oxygen index for polystyrene 0.1 cm thick is 0.181 (71). Because the oxygen index for air is 0.21, a flame retardant must raise the oxygen index from 0.18 1 to >0.2 1 for this polystyrene to be self-extinguishing. By using this means of testing, it is possible to compare readily the effectiveness of two flame retardants even though they both give a self-extinguishing rating by tests such as ASTM D635-63. A diagram of this apparatus is shown in Figure 1.
COMPOUNDS AND METHODS T h e chemical compositions and methods of incorporation that have been investigated for the purpose of producing a flame-retardant polystyrene article are many and varied. T h e method of classification of these chemical compositions chosen for this review is as follows:
A. Reactive (1) Monomeric ( 2 ) Reaction with polystyrene system
B. Additive ( I ) Inorganic ( 2 ) Organic, alone or in combination C. Synergistic Reactive Flame Retardants
T h e literature contains relatively few examples of building a flarnemretardant system by use of an intermediate polymerized into the styrene system. T h e use of substituted styrene as a copolymer with styrene has been investigated. Examples of substituted styrenes used included halogenated styrene (141,143) and m-(2,2-dibromocyclopropyl) styrene or m-(2,2-dichlorocyclopropyl) styrene (186). More complex systems involve the use of comonomers such as bromoethylacrylate (126), p-(methacrylox1oxy)ethyl diphenyl thiophosphinate (go), pentachloroethyl allyl urethane (144,dibromopropylmethacrylate (192), and unsaturated phosphonates (72). One specific system involves the treatment of an epoxidized styrene-butadiene copolymer with phosphorus oxychloride with subsequent treatment involving butadiene dioxide (26).
Fzgure 7.
F1ammabilzty-rating testing
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TABLE I. HA LOG ENATED COMPOUNDS
TABLE I I . P H OSPH 0 R US COMPOUNDS
(Other than Chlorinated Paraffin) A. PHOSPHATES Bis(2-bromoethyl)-Z-chloroethyl phosphate (22) Bis(dibromopheny1)alkyl phosphate (68, 69) Pentaerythritol dibromide, bis(bromoethylchloroethy1)diphosphate ( 5 ) Polychloroalkyl phosphates (75, 37, 33) Tris(2,3-dibromopropyl) phosphate (703, 727, 722, 738, 757, 779, 787) Tris(dichloropropy1) phosphate (747) Tris[2,2,2-tris(chloromethyI)ethyl]phosphate (28) Trithiophosphates (775) Tritolyl phosphate (57, 766)
A. ALIPHATIC Decachloroburane (767) Dibromotetrachloroethane (794) Hexabromododecane (779) Hexachloroethane (63,94-96,775, 767, 768, 769) Octabromohexadecane (737, 782) Pentabromoethane (706) Tetrabromobutane (740) Tetrabromoethane (77, 49, 53: 59, 62, 725)
B. OTHER PHOSPHORUS COMPOUNDS
B. ALICYCLIC Dibromoethyldibromocyclopentane (29) Dibromoethyldibromocyclohexane (35) Hexabromocyclododecane ( 7 7 , 72, 97, 737, 793, 799, 204) Hexachlorocyclopentadiene (94-96, 775, 767) Pentabromochlorocyclohexane (48, 65) Tetrabromocyclododecane (37)
C. AROMATIC Bromotrichlorobenzene (79) Chlorinated hexamethyl benzene (749) 1-(2,2-Dibromo-l-methyl cyclopropyl)-3-isopropenyl benzene (788) Hexachlorobenzene (767) Stvrene dibromide (65, 752)
A recent example claims that the important physical properties of ABS polymers (acrylonitrile, butadiene, styrene terpolymers) may be retained while achieving flame retardancy by copolymerization of a fourth monomer, bis(2,3-dibromopropyl) fumarate (42). Another approach which has received some attention is to effect a chain transfer onto the styrene polymer by irradiation of a mixture of polystyrene and a halogenated organic compound. Specific examples of halo-organics used include chloropolyfluoro compounds (43-#5),tetrabroinomethane (112,113), and tetrabromoethane (52). Early attention was given to the possibility of direct halogenation of polystyrene, one of the techniques used involying halogenation of an aqueous suspension of the polymer (6). Most of the halogenation work was directed toward bromination of polystyrene (75,127,159,180,189), presumably because of the lower halogen level that is needed when bromine is used, one patent claiming a final bromine content of 0.5 to 1.O% (127). Another technique first coats the polymer beads with a butadiene-styrene latex and then proceeds with bromination (89),while still another impregnates the beads with petroleum ether before bromination (189). T h e use of chlorine, however, has also been recorded. One procedure involves the impregnation of beads with antimony or copper chloride, followed by exposure to chlorine withsubsequent neutralization (194), while others simply react polystyrene with chlorine in a suitable solvent such as methylene chloride (200,201). 72
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Bis(bromoalky1)bromoalkyl phosphonates (54, 770, 7 7 7) Bis(P-chloroisopropy1)isopropenyl phosphonate (774) Carbamoyl phosphoranes (778) Dicyclohexyl phosphenic acid (76) 6-Dimethoxy phospheno-3,4,5-trichloro-2H-2-pyranone (86, 87) Dimethyl(P,P,P-trichIoro-cr-hydroxyethyl) phosphonate (750) p,p'-EthyIene his(dipheny1 phosphine) copper iodide (84, 85) Ethylene bis[tris(Z-cyanoethy1)phosphoniumbromide1 (77, 79) High molecular weight phosphonates (27) Organophosphine oxides (40, 99, 100) Phosphonitrilic chloride derivatives (776) Phosphonium ethyl amine derivatives (87) Phosphonium salts (78, 82, 83) Phosphorus-polyamine product (66) Tritalyl phosphite (7) Vinyl phosphonic acids (763)
Most of the procedures used result in very low halogen content in the final product. I t is presumed that in most cases the halogen reacts with the small amount of styrene monomer retained in the polymer (159). Additive Flame Retardants
Inorganic chemicals. T h e use of inorganic chemicals as flame-retarding additives has received only limited attention. I n general, inorganic compounds will exhibit less compatibility with the polymer system than organic materials; thus, they are likely to affect physical properties in the same manner as ordinary fillers. T h e most commonly investigated material is ammonium bromide, a well-known flame retardant for many systems (50,128, 131, 145). Some work has been specifically directed at using ammonium bromide in films (93, 127). Ammonium perchlorate (16),ammonium hexachlorophosphate (133), and other ammonium salts (118, 132) have also been investigated. Another approach said to decrease burning rate is to simply fill the plastic with glass fiber (88), a technique which should reduce the fuel available at the flame front, thereby decreasing the speed of flame propagation and at the same time decreasing dripping.
Robert F. Lindemann is a Research Associate with the Michigan Chemical Corp. in St. Louis, Mich. 48880.
AUTHOR
TABLE 1 1 1 . ETHERS Bis(2,3-dibromopropoxy)octachIorodiphenyl(777) 1,Z-Bis(pentach1orophenoxy)ethane (748) Bis(pentach1orophenoxy ethyl) ether (148) Bis-tribromopropyl ether of tetrabromobisphenol-A (65) Brominated aromatic aliphatic ethers (770, 772, 773) Brominated diaromatic ethers (34, 36, 770)
TABLE IV. ACIDS AND DERIVATIVES Bis(pentabromopheny1)tetrachlorosuccinate (67) Brominated diallyltartrate (783) Brominated fumarate esters (25) Brominated maleate esters (736) Chlorinated fatty acids (729) 2,3-Dihaloalkyl succinic anhydride (202) Esters of dibromopropanol (7, 74, 739, 203) Esters of tetrabromobutane diol (8) Metal salts of acids (760, 784, 799) Tribromoallyl formate (55, 787) Tri- or pcntahromophenyl methacrylate (788)
TABLE V. POLY M E R l C COMPOUNDS Brominated butadiene or isoprene polymers (9) Brominated rubber (723, 734) Chlorosulfonatcd polyethylene (92) Polyvinyl bromide (30, 32) Polyvinyl chloride (27, 46, 57, 58, 77, 785, 797) Polyvinylidene chloride (27, 46, 735, 782, 797)
TABLE V I . M ISCELLAN EOUS C O M POUNDS Benzotriazole (56) Brominated diphenyl amine (777) Diene sulfones (755) Polybrominated peroxides (23) Tribromoaniline (727)
TABLE V I I . FREE RADICAL SYNERGISTS Azo compounds (97) N-chloro-N-nitroso compounds (702, 704) Dibutyl tin maleate (752) Dicumyl peroxide (59, 60, 62) Dimethylbis(tert-buty1peroxy)silane (730) 2,3-Dimethyl-2,3-diphenylbutane(77, 72) Disulfides (67) Hydrazine (67) Indigotin (77, 53) Nitroso secondary amines (706) Pentaphenyl phosphine (724) Peroxides (87) Tetraethyllead (97) 2,2,3,3-Tetramethyl butane (73) Tetraphenyl hydrazine (753) Xylyl disulfide (64)
i
Because a large amount of polystyrene is marketed in the form of foam castings, some effort has been directed toward the treatment of the finished foam. Examples include coatings of glass fiber and plaster (196), as well as of glass fiber and alkali silicate (73, 74),and salts such as calcium chloride and magnesium chloride or sulfate (190). Organic chemicals. T h e amount of research directed toward the use of organic flame-retardant chemicals both alone and in combinations including synergists is predictably large and contains examples of many classes of compounds. T h e great majority of those compounds claimed to have utility contain phosphorus, bromine, or chlorine alone or in combination. Nitrogen has become a more frequently used element. One review article concerns itself totally with the effect of halogen and nitrogen compounds on the flammability of cellular materials (162). Among the earliest materials investigated were the chlorinated paraffins. Perhaps because of their availability, usefulness in other areas, or price structure, a large amount of effort has been directed toward their use, particularly in combination with other organics or synergists such as antimony oxide. Chlorinated paraffins have been used alone to coat foam articles (107), in combination with other organics such as amines (142), and in combination with synergists (20,101,108,114). T h e use of the chlorinated paraffins and antimony oxide with polystyrene beads has received much attention (24, 41, 47, 117, 160). A coating of asbestos using a chlorinated paraffin as binder is also mentioned. Other additives used in combination with chlorinated paraffins include metal chelates such as Cu(I1) ethyl acetate ( 1 0 ) ; organic acid salts of tin, lead, copper, etc., the oxalate as an example (199);brominated esters (38); phosphorus-containing compounds such as phosphoric acid anilides (39) and tritolyl phosphate (146, 164); and metal complexes such as ferrocene (157). T h e value of using stabilizers (146) and the use of other synergists such as the oxides of sulfides of bismuth, arsenic, and antimony (19, 164) are known. A large number of other organic compounds have been investigated. Tables I through V I list references concerning a number of general classifications, as well as some specific compounds. T h e majority of those additives listed contain either halogen or phosphorus and, in many examples, both elements (190). Synergists
Synergists have been used with flame retardants for many years. These synergists take various forms but, in general, can be classified into two groups: heavy metal oxides and sulfides, and free radical initiators. T h e oldest group of synergists to find common use includes the oxides and sulfides of antimony, arsenic, and VOL.
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bismuth with antimony oxide being the most common (67). Antimony oxide is used in combination with halogenated compounds and effects a large reduction in the level of organic compound necessary (20,67,158,191). One specific example states that self-extinguishing properties may be obtained by using either 357, PVC additive (polyvinyl chloride) or 10% PVC with 5y0 antimony oxide (58). Antimony oxide when used alone or without a halogencontaining compound imparts little or no reduction in flammability of the plastic system. T h e mechanism by which antimony oxide works has not been established. I t most probably causes formation of a n antimony oxygen halogen intermediate compound which increases the presence of halogen radicals with resulting interference in the free radical mechanism of the flame propagation. Much has been written concerning the burning of polymers and the free radical mechanism by which the flame is propagated. Those synergists classified as free radical initiators include the thermally unstable organic c o m p o u n d s s u c h as p e r o x i d e s , n i t r o s o - a n d a z o compounds, and structurally hindered compounds. Table VI1 lists a number of such compounds showing the great variety of chemical types which exhibit some amount of synergism as free radical initiators. I t is postulated that the free radical initiators accelerate the polymer decomposition adjacent to the flame, resulting in an increase in halogen concentration as well as a more stable halogen species a t the point of flame, thus giving a more efficient use of the halogen-containing additive. O n e specific example states that four phr of acetylene tetrabromide used alone are needed for self-extinguishing properties, but can be replaced by a combination of 0.5 phr of acetylene tetrabromide and 0.5 phr of dicumyl peroxide (59). T h e economic value of the synergist is readily apparent. Additionally, as the uses of flame-retardant plastics become more demanding, especially with regard to the physical properties of the products, the need to use synergists to decrease the total additive level will force the discovery of better synergists, allowing flame-retardant formulations at much lower additive levels. REF E R ENCES (1) American Cyanamid Co., British Patent 1,028,159 (May 5, 1966). (2) A S T M Std., 14. 331 (1964). (3) Ibid, 27, 177 (1965). (4) Anderson, R. C., 3. Chem. Educ., 44 (5), 248-60 (1967). (5) Anderson, R. M . , and Birum, G. H. (to Monsanto Chemical Co.), French Patent 1.349.088 . . . (Tan - 10., 1964). . (6) Aust R. and Wagner R. (to VEB Chemische Werke Buna), German Patent 1.093:OSd (Nov 17. 19i0). (7) BAdihche Anilin u’Soda Fabrik A.-G., British Patent 825,611 (Dec 16, 1959). (8) Badische Anilin u Soda Fabrik A.-G., German Patent 1,258,080 (Jan 4, 1968). ( 9 ) Badische Anilin u Soda Fabrik A,-G., ibid, 1,258,081 (Jan 4, 1968). (10) Badische Anilin u Soda Fabrik A.-G., Netherlands Patent Appl. 6,400,412 (July 24, 1964). (11) Badische Anilin u Soda Fabrik A.-G., ibtd, 6,604,209(Oct 3, 1966). (12) Badische Anilin u Soda Fahrik A , - G . , ibid, 6,611,862 (Feb 27, 1967). (13) Badische Anilin u Soda Fabrik A.-G., ibid, 6,611,863(Feb 27, 1967). (14) Badische Anilin u Soda Fabrik A.-G., U.S. Patent 3,361,687(Jan 2, 1968). (15) Bahr, V., Andres, K., and Braun, G. (to Farbenfabriken Bayer A,-G.), ibid, 3,027,349(March 27, 1962). (16) Bakhman, N. N., Evodkemov, V. V., and Tsyganov, S. A , , Dokl. Akad. Nauk SSSR, 168 (5), 1121-2 (1966). (17) Ballast, D. E.,and Griffin,J. D. (to Dow Chemical Co.), U.S. Patent 3,188,295 (June 8, 1965).
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(18) Bell, K . M . , Plust. Inst. Trans. 3., Conf. Suppi. No, 2, 27-31 (1967). (19) Benoit J. Hermant M . and Bryks, J. (to Etablissements Kuhlmann), Frcnch Patent 1,59&,394 ( A p h 3: 1965). ( 2 0 ) Bierly, L. A. (to Diamond Alkali Co.), U.S. Patent 2,669,521(Feb 16, 1954). (21) Birum, G. H . (to Monsanto Chemical Co.), ibzd, 3,058,941 (Oct 16, 1962). (22) Birum, G. H . Schwendeman J , L. and Anderson, R . M. (to Monsanto Chemical Co.), iiid, 3,344,112(Sept 22, 1967). (23) Bradford, R. A . (to Koppers Co., Inc.), ibid, 3,304,332(Feb 14, 1967). (24) Bramstang, T. E., and Erlandssen, E. L. (to WMB International A/B), British Patent 839,862 (June 29, 1960). (25) Brown J. P. and Whitby, F. J. (to Monsanto Chrmical, Ltd.), ibid, 1,094,723 (Dec 13, i967): (26) Canadian Industries, Ltd., tbid, 1,061,616 (hlarch 15, 1967). (27) Carlsohn, H . (to G. Carlsohn, D. Carlsohn, B. Carlsohn), German Patent 1,182,808 (Dec 3, 1964). (28) Carpenter, S., Witt, E. R . (to Celanese Corp.), U.S. Patent 3,324,205 (July 6, 1967). (29) Chemische Fabrik Kalk G.m.b.H., British Patent 1,093,165 (Nov 29, 1967). (30) Chemische Fahrik Kalk G.m.b.H., ibid, 1,093,805 (Dec 6 , 1967). (31) Chemische Fahrik Kalk G.m.b.H., French Patent 1,437,408(May 6, 1966). (32) Chemische Fabrik Kalk G.m.b.H., German Patent 1,250,632 (Sept 21, 1967). (33) Chemische Fabrik Kalk G.m.b.H., ibid, 1,252,413(Oct 19, 1967). (34) Chemische Fabrik Kalk G.m.b.H., zbid, 1,253,719 (Nov 9 , 1967). (35) Chemische Fabrik Kalk G.m.b.H., Netherlands Appl. 6,515,049 (May 23, 1966) (36) Chemische Werke Hulls A.-G., British Patent 874,006 (May 24, 1960). (37) Chemische Werke Hulls A,-G., ibid, 893,774 (April 11, 1962). (38) Chemische Werke Hulls A.-G., ibid, 1,093,101 (Nov 29, 1967). (39) Chemische Werke Hulls A.-G., German Patent 1,253,452(Nov 2, 1967). (40) Clampitt, R. B., Birum, G. H., and Anderson, R . H . (to Monsanto Chemical Co.), U.S. Patent 3,306,937 (Feb 28, 1967). (41) Croft, P. W., Lee, R . H., and Pogany, G. A. (to Shell Research, Ltd.), British Patent 929,652(June 26, 1963). (42) Cummings, W., and Stark, R. E., Div. Ind. Eng. Chem., Paper 15, ACS Meeting, San Francisco, 1968. (43) D’Alelio, G. F., French Patent 1,295,733(June 8, 1962). (44) D’Alelio, G. F., German Patent 1,213,117 (March 24, 1966). (45) D’Alelio, G. F. (to Dal Man Research Co.), U.S. Patent 3,104,214(Sept 17, 1963). (46) Daumiller, G . , Herrle, K., and Rauschenbach, R . D. (to Badische Anilin u Soda Fabrik A.-G.), Belgian Patent 629,640 (Oct 21, 1963). (47) Dereich, J. E. (to Diamond Alkali Co.), U.S. Patent 2,924,532(Feb 9 , 1960). (48) Dow Chemical Co., British Patent 867,468 (May 10, 1961). (49) Dow Chemical Co., ibid, 877,864 (July 20, 1760). (50) Dow Chemical Co., ibid, 890,426 (Feb 28, 1962). (51) Dow Chemical Co., i b d , 918,440 (Feb 13, 1963). (52) Dow Chemical Co., ibid, 927,118(May 29, 1963). (53) Dow Chemical Co., ibid, 950,292 (Feh 26, 1964). (54) Dow Chemical Co.. French Patent 1,332,588(July 19, 1963). ( 5 5 ) Dow Chemical Co., ibid, 1,477,270 (April 14, 1967). (56) Dow Chemical Co., German Patent 1,251,946 (Oct 12, 1967). (57) Dow Chemical Co., Netherlands Patent Appl. 6,411,316(April 5, 1965). (58) Dynamit-Nobel A.-G., ibid, 6,411,769(April 13, 1965). ( 5 9 ) Eichhorn, J., ACS Div. Org. Coatings and Plastics, Preprints, 23 ( I ) , 37-49 (1963). (60) Eichhorn, J., 3. Appl. Poly. Sci.,8 (6): 2497-524 (1964). (61) Eichhorn, J. (to Dow Chemical Co.), French Patent 1,391,298 (March 5, 1965). (62) Eichhorn, J. (io Dow Chemical Co.), U.S. Patent 3,058,928(Sept 28, 1959). (63) Eichhorn, J. (to Dow Chemical Co.), ibid, 3,124,557(March 10, 1964). (64) Eichhorn, J. ( t o Dow Chemical Co.), ibid, 3,284,544 (Nov 8, 1966). (65) Elder, M. E., Dickerson, R. T., and Tousignant, W. F. (to Dow Chemical Co.), tbid, 3,324,076 (June 6, 1967). (66) Epstein M. Buckler S. A. Sherr A . E. and Gillham, H . C. (to American Cyanamid’Co.j, ibid, 3,532,889(Julb 2 5 , 1667). (67) Farwerke Hoechst A,-G., Belgian Patent 633,433 (Dec 10, 1963). (68) Farwerke Hoechst A . - G . , zbid, 648,213 (Nov 23, 1964). (69) Farwerke Hoechst A,-G., Netherlands Patent Appl. 6,405,455(Nov 23, 1964). (70) Fenimore, C. P., and Martin, F. J., Combust. Flame, 10 (2), 135-9 (1966). (71) Fink, H. (to Vereinigte Korkindustrie A,-G.), German Patent 1,173,646 (July 9, 1964). (72) Friedman, L. (to Pure Chemicals, Ltd.), French Patent 1,375,860 (Oct 23, 1964). (73) Gaeth R. Schmitt B. and Brew R. (to Badische Anilin u Soda Fabrik A.-G.), U.S. Patdnt !3,259,5,345:392 (0,; 3, 1967). (86) Greenbaum, S. B. (to Hooker Chemical Co.), ibid, 3,200,131 (Jan 3, 1962). (87) Greenbaum, S. B. (to Hooker Chemical Co.), ibid, 3,243,406 (March 29, 1966). (88) Hallori, K., and Harris, D. (to Rexall Chemical Co.), Plast. Res. Proc., 7 (8), 28-30 (1967). (89) Hare, D. G . (to Monsanto Chemical Co.), British Patent 1,016,904 (Jan 12, 1966). (90) Hashimoto, S., and Furukawa, J,, Kobunshi Kugaku, 24 (262), 152-6 (1967). (91) Hauck, J. E., Matcr. Eng., 66 (3), 80-4 (1967). (92) Herbig, J. A,, and Salyer, I. 0. (to Monsanto Chemical Co.), U.S. Patent 3,158,665 (Nov 24, 1964). (93) Hill, R. L. (to Dow Chemical Co.), ibid, 3,132,045 (Oct 26, 1961). (94) Hooker Chemical Co., British Patent 1,013,786 (Dec 22, 1965). (95) Hooker Chemical Co., ibid, 1,090,814 (Nov 15, 1967). (96) Hooker Chemical Co., Netherlands Patent Appl. 6,415,331 (Feb 18, 1966). (97) Ilgemann R. and Rauschenbach R D. (to Badische Anilin u Soda Fabrik A.-G.), Fredch Patent 1,411,363 (dept‘17, 1965). (99) Ilgemann, R., Rauschenbach, R. D., and Foerster, G. (to Badische Anilin u Soda Fabrik A,&.) ibid, 1,410,556 (Sept IO, 1966). (100) I1 emann, R., Rauschenbach, R . D., and Foerster, G. (to Badische Anilin u Soda fiabrik A,-G.), ibid, 1,411,368 (Sept 17, 1965). (101) Illbruck, French Patent 1,461,192 (Dec 2, 1966). (102) Ingram, A. R., ACS Div. Org. 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VOL.
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MAY
1969
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