Reduction of volatile organic compound emission. I. Synthesis and characterization of alkoxy‐modified silsesquioxane

Abstract

ABSTRACT:The preparation and characterization of a class of alkoxy-modified silsesquioxane (AMS) compounds containing less than 5 wt % of latent alcohol is described. The AMS derived from octyl triethoxysilane (OTES) behaves as a shielding agent in silica-filled rubbers while significantly reducing the volatile organic compounds that are released during the manufacture of rubber articles. Analysis of AMS by high pressure liquid chromatography and 29 Si NMR shows that it has a plethora of structures present that can best be described as a highly condensed opened oligomeric, branched arrangement of silsesquioxanes units. This structure is moisture stable, hydrocarbon soluble, and reactive with silica at compounding temperatures. The AMS has been prepared by acid-or base-catalyzed hydrolysis and condensation in alcohol solution to form a product that often separates from the lower density reaction mixture. The kinetics of the AMS formation was examined and showed two separate rate processes occurring. The co-AMS prepared from OTES and 3-mercaptopropyl trimethoxysilane yielded an effective shielding agent and coupling agent when used in silica-filled vulcanizates.

Reduction of volatile organic compound emission. II. Use of alkoxy‐modified silsesquioxane for compounding silica‐filled rubbers

“…The preparation of the AMSs and co ‐AMSs has been described previously 1. The silanes used to prepare the AMSs and co ‐AMSs are listed in Table I.…”

“…1 The silanes used to prepare the AMSs and co-AMSs are listed in Table I. The AMS shown in Table II derived from silane 1 or 2 of Table I are designated as AMS 1.…”

“…Note that the POSS has the perfect closed structure 10 of silicon-oxygen bond when compared with those of AMS. 1 The amount of MPTMS in Ciptane V R 255LD used for stocks 4 and 5 is about 0.3 phr, a relatively small dosage used when compared with those using the TESPD. The formulation and ingredients used to prepare stocks 4, 5, and 6 are listed in Tables III and V. The processibility of these stocks is assessed by examining the ML 4 , t 5 , as well as the curing characteristics shown in Table VIII.…”

“…The first paper described the preparation of AMS and the elimination of about 95% of the alkoxy silane groups as a possible source of volatile organic compound (VOC) in subsequent uses. 1 Here, a comparison of the use of AMS to traditional alkoxysilyl containing reagents for the preparation of a silica-filled elastomeric composition will be made. Such coupling agents include bis-(triethoxysilyl propyl) polysulfides (e.g., tetrasulfide (TESPT) and disulfide (TESPD)), [2][3][4][5][6] combinations of octyltriethoxysilane (OTES) and 3-mercaptopropyl trialkoxy silanes 7 or thiooctanoyl propyl triethoxysilane 8 which have been employed to improve silica dispersion and processing as well to reinforcing the rubbers.…”

“…This is the second of the two papers on using various alkoxy‐modified silsesquioxane (AMS) for reinforcing silica‐filled rubbers. The first paper described the preparation of AMS and the elimination of about 95% of the alkoxy silane groups as a possible source of volatile organic compound (VOC) in subsequent uses 1. Here, a comparison of the use of AMS to traditional alkoxysilyl containing reagents for the preparation of a silica‐filled elastomeric composition will be made.…”