Hydroquinones INDEX

Purified monomer is usually inhibited before shipment by such materials as copper resinate, diphenylamine or hydroquinone, which are generally removed before polymerisation. The monomer is a sweet-smelling liquid partially miscible with water and with the following properties boiling point at 760mmHg, 72.5°C specific gravity at 20°C, 0.934 refractive index 1.395 vapour... 

Henderson and Sutherland have prepared a hydrocarbon synthetically which is possibly a modification of terpinene. They reduced thymo-hydroquinone, thus obtaining menthane-2-5-diol, which was heated for half an hour with twice its weight of sulphate of potash under a reflux condenser, and so yielded a terpene boiling at 179°, of specific gravity about 0 840 and refractive index 1-4779. 

Administration of hydroquinone (0.5% in the diet) for 20 weeks did not induce hyperplasia or papillomatous lesions in the forestomach in Syrian golden hamsters (Hirose etal., 1986). In male Fischer 344 rats, oral administration of hydroquinone for eight weeks (0.8% in the diet) did not induce hyperplasia or DNA synthesis, as measured by BrdU-labelling index in the forestomach epithelium. No cell proliferation, increased DNA synthesis or increase in pepsinogen-isoenzyme-1-altered neoplastic foci was observed in the pyloric mucosa (Shibata et al., 1990). 

Extract the aqueous phase with six 250-m portions of methylene chloride wash the solid cake with three of the portions prior to their use on the solution. Dry the combined extracts over 40 g of anhydrous magnesium sulfate and inhibit with 0.5 g of hydroquinone. Remove the drying agent by filtration and strip the methylene chloride by distillation at atmospheric pressure remove final traces of this solvent by stripping at 20 mm pressure and room temperature. Then separate the mixture of crude vinyl isomers by distillation at reduced pressure. By heating to a pot temperature of 90°C, the 2-methyl-5-vinyltetrazole is conveniently and almost completely removed at 1.0 mm pressure. A well cooled condenser and a receiver chilled in an ice-water bath are needed to prevent loss of the condensate. The weight of once distilled 2-isomer is 89.9 g the index of refraction at 25°C is 1.4814, corresponding to a purity of 97.2 percent. The corrected yield amounts to... 

The submitter observed a somewhat higher boiling point (41-42°/15 mm.) and did not report the refractive index of the product. Both the submitter and checkers used a column 20 cm. in length, 12 mm. in diameter, packed with glass helices, and equipped with a partial take-off head. If the fractionation is carefully conducted, the product is sufficiently pure for most polymerization work. The compound should be stabilized with hydroquinone and stored in a cold chest if it is not to be used immediately. 

In a rabbit study, hydroquinone at 150 mg kg day produced minimal developmental alterations in the presence of maternal toxicity. The no-observed-effect level for developmental toxicity was 75mgkg day In rat studies, maternal toxic effects from exposure to hydroquinone included changes in the ovaries, fallopian tubes, and menstrual cycle. Postimplantation mortality was also observed in rat studies. Observed paternal toxic effects from exposure to hydroquinone included changes in the testes, epididymis, sperm duct, prostate, seminal vesicle, Cowper s gland, accessory glands, and male fertility index. Further, exposure to hydroquinone produced skeletal malformations in chickens and ocular and skeletal malformations in rabbits. Hydroquinone can induce renal tubule adenomas, bladder carcinomas, hepatocellular neoplasms, and mononuclear cell leukemia in experimental animals. 

Properties Liquid. Bp 120C, d 0.879 (25C), refr index 1.4080 (25C), flash p 66F (18.8C) (TOC). Commercial grade contains 100 ppm hydroquinone monomethyl ether as stabilizer. 

Properties Colorless liquid stabilized with either hydroquinone or diphenylamine inhibitors. The hy-droquinone stabilized material can be polymerized without redistillation. The DPA-stabilized material must be distilled before polymerization. D 0.9345 (20/20C), fp -100.2C, bp 73C, refr index 1.3941, bulk d 7.79 lb/gal, flash p 30F (-1.1C) (TOC), aut-oign temp 800F (426.6C). Soluble in most organic... 

A similar effect on hardness development can be obtained by mixing two polymers made with different chain extenders. Table 6 shows that a polymer made with 1,4-butanediol as chain extender and another with the bis(hydroxyethylether) of hydroquinone as chain extender each have hardness build-up index values higher than does a 50/50 blend of the two. It is suggested that the poor spatial fit of the mixed hard segments results in slow domain formation on cooling. There is an important practical consequence of this observation as it relates to the mixing of TPU elastomers from different suppliers in an industrial molding operation. 

The product of this polymerization is applied in specialty areas, such as the manufacture of recording tapes and toners for photocopiers. When styrene (St) and butylmethacrylate (BMA) are mixed in the molar ratio 1 1, the polymer formed is transparent and has a glass transition temperature of about 30°C. Figure 8.3 shows the two monomers. The conversion in this case is measured gravimetrically. The product was dissolved in THF, and a small amount of hydroquinone was added to inhibit further reaetion. The molecular weight distribution was determined by gel permeation ehromato-graphy (GPC) with two mixed columns of polymer laboratories. The detection method used was by reactive index. 

A variety of methods are available for determining the purity of monomers by the measiu-ement of their saponification equivalent and bromine number, specific gravity, refractive index, and color (68-70). Minor components are determined by iodimetry or colorimetry for hydroquinone or MEHQ, Karl-Fisher method for water content, and tiu-bidimetry for measiuing trace levels of polymer. Gas-liquid chromatography is useful in both the general measurement of monomer purity as well as the identification of minor species within a monomer solution. 

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