3,235,519 United States Patent Office Patented Feb. 15, 1966 2 3,235,519 I have discovered that organic sulfonyl semicarbazides, SULFONY SEMICARBAZDES AS BELOWING like the parent sulfonyl hydrazides, decompose smoothly AGENTS FOR POLYMEREC MATERALS Byron A. Hunter, Woodbridge, Conn., assignor to United and controllably to produce nitrogen gas at elevated tem States Rubber Company, New York, N.Y., a corpora peratures. Further, I have discovered that my sulfonyl tion of New Jersey 5 Semicarbazide compounds produce more gas per unit No Drawing. Original application Dec. 31, 1959, Ser. weight than the sulfonyl hydrazides from which they are No. 863,129, now Patent No. 3,152,176, dated Oct. 6, derived. This is surprising in that the quantity of gas 1964. Divided and this application Oct. 31, 1963, Ser. produced by the new compounds exceeds the amount nor No. 320,523 mally to be expected as available nitrogen. I have dis 2 Claims. (CI. 260-2.5) 10 covered that carbon dioxide is produced in the decom This invention relates to the production of gas-expanded position of my semicarbazides as well as nitrogen gas. products with a new class of chemical blowing agents I have also observed that my sulfonyl semicarbazide denoted organic sulfonyl semicarbazides, and to certain compounds possess greater heat stability than the parent of them as new chemicals. sulfonyl hydrazides and can be heated to higher tempera The use of certain heat sensitive organic hydrazine 5 tures without danger of premature decomposition. For compounds as blowing agents is known. U.S. Patent No. tunately, the decomposition temperature of my preferred 2,626,933, dated January 27, 1953, to Friedrich Lober, sulfonyl semicarbazides lie in a range which permit their Max Bogemann, and Richard Wegler, discloses the use application as practical blowing agents in so-called "high of hydrazides of organic sulfonic acids for this purpose. density' polyethylene and other plastics which are nor Many of these are effective blowing agents but exhibit 20 mally processed at relatively high temperatures. Addi objectionable characteristics in certain applications. For tionally, preferred sulfonyl semicarbazides exhibit other example, benzene sulfonyl hydrazide decomposes smooth advantages over the parent sulfonyl hydrazides. For ly in a polyvinyl chloride plastisol composition to pro example, the reaction of certain odor-forming sulfonyl duce a white, cellular product having a fine, uniform cell hydrazides with cyanic acid produces blowing agents structure. Unfortunately, the expanded product exhibits 25 with greatly reduced odor characteristics. a disagreeable thiophenolic odor which greatly restricts Certain liquid type sulfonyl hydrazides are converted the utility of the product. pp'-Oxy bis-(benzene sul to nicely crystalline solids with unique properties when fonyl hydrazide), on the other hand, produces a similarly reacted with cyanic acid to form the sulfonyl semicar expanded vinyl composition which does not exhibit an bazides. objectionable odor. This latter substance (U.S. Patent 30 I have discovered that either aromatic or aliphatic sul No. 2,552,065, dated May 8, 1951, to Dwight L. Schoene) fonyl semicarbazides are useful as blowing agents for has gained wide commercial use as a blowing agent in rubbers or plastics. The sulfonyl group is directly linked rubber and plastics. A limiting factor in the use of the to the aromatic or aliphatic radicals, which are prefer material lies in the decomposition temperature (circa ably hydrocarbon, including aralkyl, groups. One type 150° C.) which is too low for many applications. In the 35 of aromatic sulfonyl semicarbazide is represented by the case of so-called "high density polyethylenes,' for exam formula ple, mixing temperatures may reach the decomposition R(SONH-NH CO. NH) temperature of the blowing agent. Under these circum where R is an unsubstituted or alkyl-substituted aromatic stances premature decomposition of the blowing agent hydrocarbon radical, and n is 2 or 3. Another desirable may occur during the incorporation step and part of the 40 type of aromatic sulfonyl semicarbazide is represented blowing gas will be lost with attendant impairment of by the formula blowing efficiency. The solution to the difficulty lies in the discovery of blowing agents which remain in the unde X (CHASONH NH- CO NH) 2 composed state at incorporation temperatures but de where X is an oxygen, sulfur, sulfonyl, or methylene compose smoothly with the production of gas at higher radical. expansion temperatures. An object of the present invention is to produce heat Examples of aromatic sulfonyl semicarbazides which sensitive nitrogen compounds which are stable at tem can be used for the purpose of this invention include: peratures below 170° C., but which decompose to produce Benzene sulfonyl semicarbazide nitrogen gas at temperatures between 170° C. and 250 50 p-Toluene sulfonyl semicarbazide C. A further objective is to produce organic nitrogen o-Toluene sulfonyl semicarbazide containing substances which can be successfully incor Benzene-1,3-bis-(sulfonyl semicarbazide) porated in rubber or plastic at normal mixing tempera Toluene bis-(sulfonyl semicarbazide) tures and which decompose controllably and smoothly Xylene sulfonyl semicarbazide at higher temperatures to release nitrogen as the princi 55 Xylene bis-(sulfonyl semicarbazide) pal gas and produce a cellular structure within the rubber Benzene tris-(sulfonyl semicarbazide) or plastic. Another objective is to provide blowing agents Biphenylene bis-(sulfonyl semicarbazide) which produce more gas per unit weight than presently Naphthalene sulfonyl semicarbazide available sulfonyl hydrazide compounds. A still further Naphthalene bis-(sulfonyl semicarbazide) objective is to provide new organic nitrogen compounds 60 Naphthalene tris-(sulfonyl semicarbazide) which exhibit unique physical and chemical properties p,p'-Oxy bis-(benzene sulfonyl semicarbazide) and which may find application in various fields of spe p,p'-Thiobis-(benzene sulfonyl semicarbazide) cialized interest. p,p'-Methylene bis-(benzene sulfonyl semicarbazide) I have discovered that organic sulfonyl hydrazides can p,p'-Sulfonyl bis-(benzene sulfonyl semicarbazide) be modified to produce a new class of blowing agents The above examples are merely illustrative of the aro by interaction with cyanic acid. The compounds that are matic sulfonyl semicarbazides which can be employed as produced by this reaction can be properly described as blowing agents. I prefer to use those aromatic sulfonyl organic sulfonyl semicarbazides. The reaction can be semicarbazides which are devoid of unnecessary substitu represented by the following equation: ents. I particularly prefer those compounds which are RSONHNH--HOCN->RSONHNHCONH devoid of substituents containing nitrogen attached di where R is aliphatic or aromatic. rectly to the aromatic ring, as, for example, nitro, nitroso, 3,235,519 3 4. amino, alkyl- and arylamino, acetamino. Such groups not uble imprities, reprecipitating the sulfonyl semicarbazide only add unnecessary bulk to the compound but are liable in purified form by the addition of acid. Although a to produce discoloration in the rubber or plastic into variety of acidulating agents may be used for the purpose which they are introduced. The effect of unnecessary I prefer to use mineral acids such as hydrochloric or sul bulk is to diminish the efficiency of the compound as a 5 furic acid. Acetic acid has also been found to be an effec blowing agent. In general, for optimum efficiency, the tive acidulating agent. blowing agents of this invention which contain a maximum The following examples are given to illustrate the of 10 carbon atoms per sulfonyl semicarbazide group are invention: preferred. (A) BENZENE SULFONYL SEMICARBAZIDE One type of aliphatic sulfonyl semicarbazide which can IO be used to produce a cellular structure in rubbers or plas (1) From benzene sulfonyl hydrazide and cyanic tics is represented by the formula acid-Benzene sulfonyl hydrazide (17.2 g.: 0.1 mole) was suspended in 100 cc. water and then treated with R' (SONH-NH CONH2)2 8.2 cc. (0.1 mole) of concentrated hydrochloric acid. where R' is a bivalent unsubstituted aliphatic hydrocarbon 15 The crystalline sulfonyl hydrazide passed into solution. radical. Illustrative of suitable aliphatic and aralkyl Sul The solution was filtered from a small quantity of sus fonyl semicarbazides are: pended matter and was then treated with a filtered solu tion prepared by adding 9.8 g. (0.15 mole) of sodium Methane sulfonyl semicarbazide cyanate in 100 cc. of water. A crystalline precipitate Ethane sulfonyl semicarbazide 20 formed immediately and a small amount of effervescence Propane sulfonyl semicarbazide was observed. Finally, another 8.2 cc. of concentrated Isopropyl sulfonyl semicarbazide hydrochloric acid was added to the mixture to destroy Butane sulfonyl semicarbazide excess sodium cyanate. The crystalline product was fil Isobutyl sulfonyl semicarbazide tered off and washed well with water and finally with a Pentane sulfonyl semicarbazide small quantity of alcohol. After drying, the product Hexane sulfonyl semicarbazide weighed 17.0 g. (79% yield). This melted with gas Octane sulfonyl semicarbazide evolution at 216 C. When recrystallized from acetic Dodecane sulfonyl semicarbazide acid the Substance decomposed at 218 C. The benzene Octadecane sulfonyl semicarbazide sulfonyl hydrazide used as the starting product melted Cyclohexane sulfonyl semicarbazide 30 with some decomposition