United States Patent (19) [11] 3,945,974 Schwarcz et al. (45) Mar. 23, 1976 54 SMOKE SUPPRESSANTS FOR 2,855,266 l Of 1958 James .............................. 260/45.75 2,948,638 8/1960 Baird............................... 260/45.75 HALOGEN-CONTAINING PLASTIC 3,202,567 8/1965 Muri et al. ...................... 106/15 FP COMPOSITIONS 3,705,128 12/1972 Knowles........................... 260/45.75 75) Inventors: Joseph Schwarcz, Highland Park; 3,766, 57 10/1973 Parts................................ 260/45.75 Bernard Engelbart, Trenton; 3,770,577 1 1/1973 Humpbrey....................... 260/45.75 Edward L. White, Freehold, all of N.J. OTHER PUBLICATIONS 73 Assignee: NL Industries, Inc., New York, Journal of the American Chemical Society Vol. 61, N.Y. No. 12 pp. 3241 to 3244 Dec. 19, 1939. (22 Filed: Dec. 20, 1973 21) Appl. No.: 426,492 Primary Examiner-V. P. Hoke 52 U.S. C.260/31.8 R; 260/45.7 R; 260/45.75 W; 57 ABSTRACT 260/45.75 B (5) Int. Cl.............................................. C08J 3/20 Zinc is added to a halogen-containing plastic composi 58 Field of Search. 260/45.75 R, 45.7 R, 45.75 B, tion with or without a flame retardant additive to 260/45.75 W, 45.75 K, 29. R serve as a smoke suppressant during combustion of the plastic. (56) References Cited UNITED STATES PATENTS 16 Claims, No Drawings 2,772, 59 l/1956 Elliott............................. 260/45.75 3,945,974 2 tions and in particular plasticized polyvinyl chloride SMOKE SUPPRESSANTS FOR include zinc dust, zinc oxide, zinc carbonate, normal HALOGEN-CONTAINING PLASTC zinc trimellitate, acid zinc trimellitate, zinc borate, zinc COMPOSITIONS benzoate, zinc caprate, zinc fumarate, tribasic Zinc phosphite, tribasic zinc sulfate-silicate, pentabasic zinc BACKGROUND OF INVENTION sulfate, tribasic zinc phosphate, dibasic zinc phosphate, Plastic materials including plastic sheeting, synthetic pentadecabasic zinc sulfate, tetrabasic zinc sulfate-sili fibers and the like are generally considered to be haz cate, tribasic zinc trimellitate, heptabasic zinc trimeli ardous materials from the standpoint of flammability; tate and decabasic zinc trimellitate. and in many cases it is the practice to add various flame O The zinc dust and all of the foregoing zinc com retardants to the plastic materials to reduce flammabil pounds were tested for smoke suppression effect in ity during combustion. Recently, however, the propen halogen-containing polymer compositions, the Smoke sity of plastics to create large volumes of smoke, when suppression evaluation being made using the National combusted, has come to be regarded as at least as haz Bureau of Standards Smoke Test hereinafter described. ardous, if not more so, than its flammability. Increasing 5 The incorporation of the zinc or zinc compounds into concern with consumer safety and several tragic acci the halogen-containing plastic compositions is effected dents have contributed to the recognition of smoke by blending the zinc or zinc compounds with the com evolution as a significant hazard. In many instances of ponents used in formulating the plastic compositions. fire, the resulting fatalities have been due to smoke which has prevented safe evacuation of a building due 20 PREFERRED EMBODIMENT OF INVENTION to lack of visibility; or to the toxic gases generated The instant invention comprehends the addition of during combustion of the plastic. zinc or a zinc compound to a halogen-containing poly As mentioned above, extensive studies have been mer composition. While it has been discovered that made in the area of flame-retardant additives for halo zinc or any zinc compound is an effective smoke sup gen-containing plastic compositions examples of which 25 pressant in halogen containing polymer compositions are antimony trioxide; antimony pentaoxide, antimony the degree of smoke suppression is not always the silico oxide see U.S. Pat. No. 3,740,245 and other or same, some zinc materials being more effective than ganic and said antimony-silco oxide comprising amor others. In addition to the smoke suppresant effective phous materials prepared by reacting antimony trioxide ness of these zinc materials they may have other effects (SbO) with hydrous silica or hydrous alkali or alka 30 in polymer compositions which effects are known to line earth metal silicates in weight ratio range 1:4 to 1:1 the art as for example some zinc compounds may have attemperatures in the range 400-550°C in an oxygen an adverse effect on heat stability, some zinc com containing atmosphere; the specific gravity of the an pounds are hygroscopic, deliquescent, unstable or cor timony-silico compounds being in the range 2.4 - 3.6 rosive and some may have a beneficial effect on flame and having an index of refraction of from 1.5 to 1.7, 35 retardancy. Therefore, in selecting a preferred zinc inorganic compositions of antimony. Zinc borate has compound to be used in a specific polymer composi been used also as a flame retardant but so far as is tion besides the smoke suppressant efficiency of the known never as a smoke suppressant and always at zinc other considerations such as cost and those men relatively high levels as for example from 3 to 8 parts tioned above must be taken into account. In light of per 100 parts resin since lesser amounts are ineffective 40 these considerations the preferred zinc compound used as a flame retardant. Moreover, the concept of Sup in a specific polymer composition may not necessarily pressing smoke as well as retarding flammability is be the most effective smoke suppresant but one com disclosed in U.S. Pat. No. 3,723, 139 Larkin et all who bining smoke suppressancy with minimum degradation, disclose the addition of antimony oxide in combination maximum flame retardancy, minimum cost etc. As an with sodium antimonate to polyvinyl chloride plastics 45 example, those zinc compounds which exhibit optimum both to minimize flammability and to suppress smok smoke suppression in plasticized PVC are zinc oxide, ling. W Zinc benzoate, Zinc caprate, zinc metaborate and triba It is desirable, however, to provide a smoke suppres sic zinc phosphite. However, these have an adverse sant for halogen-containing polymer compositions effect on heat stability and hence require the addition which may be used alone and preferably in combina 50 of heat stabilizers which is an added expense in the tion with flame retardants and which are more effective total cost of the polymer composition. Examples of zinc than smoke suppressants heretofore known and used. additives which require little or no heat stabilizer addi tives and for this reason are preferred over the foresaid SUMMARY OF INVENTION zinc compounds, even though somewhat less effective The present invention is the discovery that zinc in 55 as smoke suppressants, are zinc carbonate, zinc dust, substantially any form which can generate zinc oxide acid Zinc trimellitate, normal zinc trimelitate, zinc during the combustion of the polymer, i.e. Zinc dust, fumarate, dibasic zinc fumarate, and zinc peroxide. and inorganic or organic compounds of zinc, and in It will be understood, however, that the zinc com amounts at extremely low levels as for example in the pounds listed above are not restrictive but that other range of about 0.5 to 1.00 parts per hundred parts 60 Zinc compounds, inorganic, organic or organo-metallic resin, as zinc oxide, is a superior smoke suppressant for which can generate zinc oxide during combustion in many halogen-containing polymer compositions in intimate mixture with halogen containing polymer cluding polyvinyl chloride, ABS and halogenated un compositions are contemplated within the scope of this saturated polyesters and the like; and that the zinc is invention. effective whether added alone or in combination with a 65 The instant invention is thus concerned with halogen flame retardant additive. The zinc additives which have containing polymer compositions containing zinc or a been found to be effective as smoke suppressants when compound of zinc as a smoke suppressant, and prefer incorporated in halogen-containing polymer composi ably with a flame retardant, the invention being di 3,945,974 3 4. rected particularly to plasticized polyvinyl chloride in TABLE I-continued the form of flexible sheeting, wire insulation, powders, ZINC COMPOUNDS AS SMOKE SUPPRESSANTS massive forms and the like which contain antimony IN FLEXBLE PVC INCLUDING ANTIMONY base flame retardant additives. TROXIDE FAME RETARDANT Concentration Preparation of these halogen-containing polymer Additive Zinccas ZnO) Dm compositions is effected by standard methods and stan Example Additive PHR PHR dard equipment in the art, the amount of zinc added, 8 Zn Benzo- 92 0.5 327 being in the range of from 0.5 to 1.0 parts per 100 parts ate resin expressed in ZnO. 9 Zn Caprate 255 378 A typical polyvinyl chloride formulation containing 10 O Zn Fuma- 1.13 0.5 432 zinc as a smoke suppressant is as follows: *Trimelitate PVC resin - Geon 102 EPF5 (B.F. Goodrich - 100 parts Co.) As shown in the data in Table I above, a polyvinyl Clarite NS-2 (modified dibutyltin maleate - 1.5 parts 15 stabilizer) chloride plastic material containing no zinc had a maxi Dioctyl phthalate - 50 parts mum specific smoke density Dm of 461. In contradis Antimony trioxide (flame retardant) - 3.0 parts tinction all of those tested specimens which contained Zinc Additive (expressed as ZnO) 0.5 - 1.0 parts zinc or zinc dust, or inorganic or organic zinc com pounds, had Dm values which were significantly lower 20 SMOKE TEST than the test specimen containing no zinc. The smoke suppressant capabilities of the zinc or EXAMPLES 1 1-31 zinc compounds used in test specimens of plasticized Additional test specimens were prepared using the halogen-containing polymer compositions was tested procedure described above in which the zinc additive using the National Bureau of Standards (NBS) Smoke 25 was, in all instances, at a concentration of 0.75 PHR (as Density Chamber a detailed description of which is ZnO).