Methanol silicone rubber

Another application of methanol is the production of methyl chloride, which is used in making silicone rubber, including the caulking and sealing compounds that will set at room temperature (the kind you buy in a tube at the hardware store.)... 

Membranes with improved separation factors would be useful for hydrophilic VOCs such as ethanol, methanol and phenol, for which the separation factor of silicone rubber is in the range 5-10. As yet, no good replacement for silicone rubber has been developed. The most promising results to date have... 

Silicone rubber methanol > ethanol> aldehydes> ketones water paraffins > olehns. 

Water can be removed from methanol by a membrane of polyvinyl alcohol cross-linked with polyacrylic acid, with a separation factor of 465.204 A polymeric hydrazone of 2,6-pyridinedialdehyde has been used to dehydrate azeotropes of water with n- and /-propyl alcohol, s- and tort butyl alcohol, and tetrahydrofuran.205 The Clostridium acetobutylicum which is used to produce 1-butanol, is inhibited by it. Pervaporation through a poly(dimethyl-siloxane) membrane filled with cyclodextrins, zeolites, or oleyl alcohol kept the concentration in the broth lower than 1% and removed the inhibition.206 Acetic acid can be dehydrated with separation factors of 807 for poly(4-methyl-l-pentene) grafted with 4-vinylpyridine,207 150 for polyvinyl alcohol cross-linked with glutaraldehyde,208 more than 1300 for a doped polyaniline film (4.1 g/m2h),209 125 for a nylon-polyacrylic acid membrane (5400 g/m2h), and 72 for a polysulfone.210 Pyridine can be dehydrated with a membrane of a copolymer of acrylonitrile and 4-styrenesulfonic acid to give more than 99% pyridine.211 A hydrophobic silicone rubber membrane removes acetone selectively from water. A hydrophilic cross-linked polyvinyl alcohol membrane removes water selectively from acetone. Both are more selective than distillation.212... 

C in 3.0 mL methanol under H2 in a thermostated reaction flask connected to a thermostated gas burette and equipped with a magnetic stirrer and a silicone rubber cap. This catalyst solution was prehydrogenated for 30 minutes. Following this the substrate (2.5 mmol) was added with a syringe and the reaction was followed by measuring hydrogen consumption. The reaction product was analyzed by GLC. 

To approximately 1 mg of the sample, contained in a serew top vial, add 1 ml of 2 M methanolic hydrochloric acid. Place in boiling water for 30 min with the screw top tightly closed. Use a silicone rubber seal. 

Properties Lt. yel. liq. sol. in benzene, toluene, petroleum ether, aromatic soivs. insol. in water, methanol m.w. 405.11 dens. 1.25 flash pt. > 230 F ref. index 1.4930 Toxicology TLV 0.1 mg(Sn)/m of air toxic irritant Uses Polymerization catalyst for mfg. of PU foam, coatings, adhesives, sealants, elastomers lubricant addition agent stabilizer for transfonner oils curing agent for RTV silicone rubber catalyst for PU resins in food-pkg. adhesives Regulatory FDA 21CFR 175.105... 

Differences in results can occur between tests in a liquid and a gaseous medium. This is often because different times are required to reach equilibrium temperature, and if crystallisation is occurring, for example, the stiffness will be dependent on time of conditioning. It is also essential that if a liquid medium is used the liquid does not affect the rubber by swelling it or removing extractables, as either process can have a considerable effect on low temperature behaviour. Ethanol is most widely used but acetone, methanol, butanol, silicone fluid and n-hexane are all suggested in ISO 2921. Not all of these will be suitable for all rubbers and the suitability of any proposed liquid must be checked by preliminary swelling tests. 

Biphenyl Fraction. The low molecular weight compounds, soluble in isooctane and hot methanol, were primarily biphenyl and o-, m-, and p-terphenyl. These products were identified by gas-liquid chromatography using a silicone gum rubber column (Figure 4) and a Carbowax 20M column with appropriate standards. The components were trapped and analyzed by infrared and NMR spectroscopy for confirmation. Biphenyl was present in sufficient quantity to be readily detected in the initial infrared spectrum and was isolated by sublimation. Quantitative data, obtained using the silicone column with appropriate calibration curves are presented in Table III. With the possible exception of biphenyl, the yields are very low considering the overall conversion noted. The o-, m-, and p-terphenyl ratio (1/0.4/1) indicates a preference for the para position beyond that expected for random attack. 

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