U R E T H A N E E L A S T O M E R S P R E P A R E D FROM D I P R O P Y L E N E GLYCOL-TOLYLENE D I ISOCYANATE A D D U C T S H A R O L D
R. B Y L S M A '
Technical Service and Development, T h e Dore Chemical Go., .Midland. M i c h
Urethane elastomers possessing superior physical properties, good chemical and solvent resistance, and easy handling can b e prepared b y reaction of mixtures of diol and iriol polypropylene glycols with a dipropylene glycol-tolylene diisocyanate adduct at room temperature. Poly(viny1 chloride) dispersion resins, carbon black, or mineral fillers can be advantageously incorporated into the lower property elastomers to reduce the cost and generally improve the physical properties. High property urethane elastomers-characterized b y tensile strengths greater than 4000 p.s.i. and split tear strengths greater than 200 p.1.i.-can b e prepared b y the use of polypropylene glycols of low molecular weight as chain extenders. Postcuring at elevated temperatures i s not required to obtain maximum physical properties. HE commercial development of castable urethane elastomers Tis proceeding along t\vo distinct routes. Very excellent elastomers are produced through the use of aromatic amines a n d high temperature cures. These materials are characterized by outstanding strength, resiliency, abrasion resistance, toughness. flexibility, a n d elongation. M a n y of the researchers (6. 9. 72) in this area have reported substituting polyethers and castor oil for polyesters. Through the use of select catalyst, "one-shot" methods (7-3) have also been developed bvhich reduce the processing temperatures and further reduce the cost; postcuring a t ele\,ated temperatures is required to obtain maximum mechanical properties. T h e second route is the de\relopment of two-component, room temperature-cured elastomers. These materials are characterized by their relatively low tensile and tear strengths, good compression properti;s, easy processing. good low temperature properties, good chemical resistance, and low cost. This paper deals with the preparation of urethane elastomers by the adduct method a t ambient temperatures. Through the use of dipropylene glycol as the adduct base, it is possible to obtain physical properties comparable to those of the lo\\ property elastomers, or intermediate between them a n d the properties cited for the one-shot polyether-toly-lene diisocyanate-aromatic amine, urethane-urea elastoplastics ( 4 ) .
Experimental
Raw Materials, POLYPROPYLENE GLYCOLS.Table I lists the polypropylene glycols used in this study. CATALYST.T h e 16% lead naphthenate and the 24Yc lead octoate \vere obtained from S u o d e x Product Division, Heyden Newport Chemical C o r p . , a n d the stannous octoate (T9) and the dibutyl tin dilaurate from hl & T Chemical Corp. TOLYLESE DIISOCY.ANATE ( T D I ) . H>-lene T M (E. I. d u Pont de Semours & Co., Inc.) \vas used to prepare the isocvanate adducts. I t is a n 80:20 mixture of 2.4:2.6-tolylene diisocyanate. Preparation of Tolylene Diisocyanate Adducts. T h e T D I was \veighed into a 1-liter flask equipped Lvith a stirrer. dropping funnuel, and nitrogen purge. \?i
