United States Patent Office Patented Dec
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3,631,000 United States Patent Office Patented Dec. 28, 1971 2 SUMMARY OF THE INVENTION 3,631,000 SOCYANURATE-CONTAINING POLYSOCYA We have found that superior isocyanurate-containing NATES AND METHOD OF PREPARATION polyisocyanates are inexpensively prepared by the two Perry A. Argabright and Brian L. Philips, Littleton, Colo., step process of: (1) chloroalkylating a mono-substituted and Vernon J. Sinkey, South St. Paul, Minn., assignors benzene compound, and (2) reacting the polychloro to Marathon Oil Company, Findlay, Ohio alkylated benzene-substituted compounds with a metal No Drawing. Filed June 4, 1969, Ser. No. 830,541 cyanate in the conjoint presence of a bromide or iodide Int. C. C08g 22/18, 22/44 of an alkali metal or an alkaline earth metal, and in the U.S. C. 260-77.5 NC 1. Claims presence of an aprotic solvent, herein defined. The mole IO ratio of metal cyanate to the chloride in the polychloro alkylated benzene-substituted compound is from about ABSTRACT OF THE DESCLOSURE 0.8 to about 1.5 to produce the polyisocyanates. These Improved organic polyisocyanates are prepared by re polyisocyanate compositions are starting materials for acting chlorinated benzene-substituted compounds, espe Various polymeric systems, e.g. a rigid polyurethane foam cially chloromethylated aromatics, with metal cyanates in 5 produced by conventional polymerization or copolymeri the presence of a metal iodide or bromide and in the zation with an appropriate monomer (e.g. a polyester or presence of a dipolar aprotic solvent where the mole ratio polyether based polyol). Particularly preferred products of cyanate in the metal cyanate to chlorine in the chlo are polyurethane and polyurea foams, coatings, elasto rine-containing benzene-substituted compound is from mers and adhesives. about 0.8 to about 1.5. The polyisocyanate compositions 20 are useful as starting materials in the production of flame PREFERRED EMBODIMENTS OF THE retardant urethane polymers as coatings, films, foams, INVENTION adhesives, etc. The process and compositions of the present invention. represent a significant improvement over the processes CROSS REFERENCES TO RELATED 25 and compositions of the prior art and copending applica tion Ser. No. 611,588. The principal advantages are APPLICATIONS realized when the chlorinated organic starting materials U.S. application Ser. No. 611,588 now U.S. Pat. 3,458. are chloroalkylated benzene-substituted compounds, es 448, filed Jan. 25, 1967, and assigned to the assignee pecially polychloromethylated toluene. Further advan of the present invention, relates to the preparation of 30 tages are realized when mixtures of chloroalkylated polyisocyanate compositions similar to those of the pres benzene-substituted compounds are used as starting mate ent invention. rials. The products of the present invention are superior to those of the prior art, less expensive to produce, and BACKGROUND OF THE INVENTION because of their improved solubility properties, are easier Folyisocyanates, particularly tolylene diisocyanate 35 to handle, and may be charged in a continuous process (TDI), are widely used in the production of polyure for the preparation of polyurethanes. thane polymers as coatings, films, foams, adhesives, and Polyisocyanate product mixtures made in accordance elastomers, for example. Urethane polymers offer advan with the present invention have a higher functionality tages where superior resistance to abrasion, acid, alkali, 40 than the current commercial products and when reacted and weather is required. Polyurethane foams are particu with polyols produce urethanes of higher cross-link den larly suitable for thermal and sound insulation as well sity than urethanes heretofore prepared. Furthermore, as resilience. Significant disadvantages of presently avail preparation of the polyurethanes requires shorter cure able urethane compositions are their tendency to de times. Another advantage which the urethane products grade when exposed to sunlight, poor thermal stability, 45 possess is their higher thermal stability derived from the and flammable characteristics. presence of diary methane groups (from about 1 to 25 The present invention permits the production of new mole percent) provided in the polyisocyanate product 1)olyisocyanates in which the nitrogen of the isocyanate mixtures of the present invention. adical (-N=C=O) is not attached to an aromatic ring. Another advantage is realized, surprisingly, by the it has been discovered that polymers derived from iso 50 presence of a substituent, preferably a lower alkyl sub cyanates having this special molecular characteristic are stituent, e.g. -CH3, on the aromatic ring of the com 1 markedly more resistant to degradation and yellowing pound to be chloroalkylated. The presence of the sub than are the polymers produced from conventional iso stituent allows subsequent cyanation of the gross chloro cyanates in which the nitrogen of the isocyanate group alkylated product mixture to give superior polyisocyanate is attached to an aromatic ring. These polyisocyanate 55 products. In contrast, chloroalkylation of benzene gives product mixtures contain at least about 0.1 and prefer an undesirable mixture of products which must be sepa ably from 10 to about 75 mole percent (based on the rated before cyanation can suitably be commenced. The total moles of nitrogen in composition) of isocyanurate reason why the gross chloroalkylated product mixture groups which have been discovered to render additional of benzene is unsuitable for direct cyanation is not com thermal stability and resistance to degradation of finished 60 pletely understood, but is believed to be due to an adverse polymers. It has also been observed that the incorpora steric effect of certain isomers in the mixture. Further tion of isocyanurate ring into a polymeric structure in more, these polyisocyanate products demonstrate low creases the flame retarding properties of the structure. reactivity toward polyols and tend to function as chain The polyisocyanate products of the present invention stoppers in the reaction with polyols to form urethanes, preferably have at least 0.5 and more preferably at least 65 a preferred embodiment of this invention. 2.0 milliequivalents free isocyanate content per gran Another advantage in using alkyl benzene starting ma of product. terials lies in the ease of handling of crude chloroalkylated 3,631,000 3 4 product mixtures. These products are liquid at room cyanates may be used. The most preferred metal cyanates temperature. Chloralkylated benzene mixtures, however, are Sodium cyanate and potassium cyanate. Such as those containing p-xylylene dichloride, are solid The catalyst used for the cyanation reaction is a metal at room temperature. This distinguishing characteristic bromide or iodide, preferably an alkaline earth or alkali and its advantages become substantial when a continuous 5 metal bromide or iodide, exemplified by sodium bromide, process is desired where fluidity of charge stock is im potassium bromide, sodium iodide, and potassium iodide portant. Furthernlore, the economics of such a con which are all readily soluble in the aprotic solvent sys tinuous process are improved by using an alkyl-substituted tems, especially in preferred dimethylformamide (DMF). benzene compound, such as toluene, rather than the more The metal cation of the catalyst may be the same or dif expensive benzene as a starting material. Other improve O ferent from the metal cation of the metal cyanate. Using ments and advantages of the invention will become ap a catalyst Such as Sodium bromide is preferred because parent upon a reading of the specification. the by-product (sodium chloride) formed during the reac The organic polychloride reactant is preferably ob tion is insoluble in the solvent (e.g. DMF) and separa tained by chloroalkylating, preferably chloromethylating, tion from the product polyisocyanate is readily achieved a monosubstituted benzene compound. The only restric by decantation, filtration, or by other well-known liquid tion placed on the substituent is that it must not interfere Solid separation methods. With either the chloromethylation reaction or the subse By aprotic solvents is meant compositions which are quent reaction with cyanate ion. Thus, in some cases, liquid under the conditions of the reaction, which have petroleum fractions may be suitable as feeds. The most a high dielectric constant (greater than about 15 at 25 preferred compounds include toluene, ethyl benzene, 20 C.), which are dipolar, that is, one part of the molecule propyl benzene, and isopropyl benzene. Other monosub has a more positive electrical charge relative to the other stituted benzenes useful in the instant invention include parts of the molecule causing the molecule to act as a chlorobenzene, bromobenzene, biphenyl, bibenzyl, di dipole, are sufficiently inert not to enter into deleterious phenyl ether and diphenyl methane. side reactions to a significant degree under the reaction The chloroalkylation of aromatics is well known in the conditions and which do not possess hydrogen atoms art (see, for instance, Olah, Friedel-Crafts and Related capable of hydrogen bonding with or transferring to Reactions, vol. 2, part 2, Interscience Publishers, New anions in solution in the reaction mixture. The aprotic York, 1964, pp. 659-784) and involves basically the reac solvent can be composed of a mixture of liquids So long tion of an aromatic hydrocarbon with an aldehyde (e.g. as the overall liquid compositions meet the above