Drying, latex

Another disadvantage is difficulty in drying latex mbber deposits that, with the usually accompanying shrinkage, rules out use of latex compounds in the production of soHd articles of thick section. 

The PVAc latex containing PVA as a protective colloid prepared in method [III] using the HPO (0.12%)-TA (0,10%) system as an initiator in Table 1 was cast to about 1.8 mm in thickness on a poly(ethylene) plate and dried at room temperature. The dried latex films were 0.7-0.9 mm in thickness and were semi-transparent. The porous film after acetone extraction changed to a white color without a change in the film size. 

There has been a conventional sense that the PVAc latexes prepared in the presence of PVA as a protective colloid contain the graft copolymer of PVA and PVAc, so that PVAc particles in the dried latex film are not extracted at a high ratio with solvents. In this Chapter, it has been defined without an influence by the usual sense that the porous PVA-PVAc composite can be prepared from the PVAc latex film with acetone extraction. The porous film consists of the spherical cells of PVA... 

Accordingly GPC analysis of dried latex samples were carried out. The carrier solvent was tetrahydrofuran and peaks were monitored by a Waters dual absorbance detector at wavelengths of 2 h and 3U0 nm. The latter detection was the closest to 350 nm available. 

The starting material for these 14-hydroxy compounds is the opium alkaloid thebaine (9). Although present in only small amounts in the alkaloid fraction from Papaver somniferum, it constitutes the major component (as much as 26% of the dried latex) from a... 

Morphine (10) and codeine (11), constituents of opium, are the most interesting alkaloids found in nature. Morphine is also the oldest alkaloid isolated, in 1805, by the German pharmacist Sertiimer from opium, the sun dried latex of Papaver somniferum. The structure of morphine with its so-called morphinan skeleton, once called the acrobat under the alkaloids, was finally elucidated in 1952 by the first total synthesis performed by Gates and Tschudi. Many syntheses would follow [26], but all morphine used today, whether legal or illicit, originates in the natural source P. somniferum or its extract, opium. The latex may contain up to 20% morphine. Most legal morphine is converted into the anticough medicine codeine (Table 5.1) by treatment with trimethylanilinium methoxide, whereas almost all illicit morphine is acetylated to the diacetate heroin. 

During the drying process, only water vaporizes.- With oil-based paints, naphtha or mineral spirits vaporize during drying. (Latex paints don t pollute the atmosphere.)... 

Morphine is the major alkaloid in opium, the dried latex obtained from the opium poppy, Papaver somniferum. About 25% of the mass of opium is composed of alkaloids, with morphine constituting about 12-15%. Morphine is a powerful analgesic, and remains one of the most valuable for relief of severe pain. However, most of the morphine extracted from opium is processed further to give a range of semi-synthetic drugs, with enhanced or improved properties. A means of extracting morphine from the other alkaloids in opium is thus desirable. 

Both morphine and codeine are valuable analgesics. Morphine is extracted from opium, the dried latex of the opium poppy, and codeine is usually obtained from morphine by semi-synthesis (see Box 6.2), since the amounts in opium are rather small. Thebaine is a valuable raw material for semi-synthesis of a wide range of morphine-like drugs. 

Codeine (12) and morphine (13), both major active constituents of opium resin, the dried latex from the immature fruits of Papaver som-niferum L., are pharmacologically important drugs as analgesic agents with considerable use today. Like other opiates, morphine and codeine... 

Figure 7.13 Atomic force microscope image of the surface of a drying latex film.

Opium alkaloids are nonpeptide agonists for the opioid peptide hormone receptors. The dried latex of Papaver somniferum (opium), or the seed capsule of the plant itself, are the sources of almost 25 alkaloids. Some simple isoquinolines from opium, like papaverine (5.86), are antispasmodics. The principal alkaloid ( 10% of the total) is morphine (3.11), which is also an isoquinoline (rings C and E) but can addihonally be considered a phenanthrene derivahve (rings A, B, and C). 

An average of eight measurements was taken as the contact angle. Water and methylene iodide were used as test liquids. Polarity of the dried latex films were estimated according to the method of Kaelble (10). 

The interest in papain increased enormously after the publication by Kimmel and Smith D ] of a modification of the purification procedure of Balls and Lineweaver [5j. This modification permitted the isolation of pure papain from papaya dried latex and was used for many years as the standard method for the production of papain. The crystalline papain of Kimmel and Smith consists of three components active papain, reversibly oxidized papain, and irreversibly oxidized papain. Reversibly oxidized papain can be converted into active papain by reduction of the active-site thiol by low molecular weight thiols [10], sodium borohydride [11], or CN [12]. In active papain, the Cys-25, which is essential far catalytic activity, is present in a reduced form, while in reversibly oxidized papain the Cvs-25 forms a mixed disulfide with cysteine. Drenth et al. reported that in irreversibly oxidized papain the Cys-25 has been oxidized to the sulfuric acid... 

When this purification procedure was applied to spray-dried latex, the papain was often contaminated with chymopapain [14]. 

Varieties of Papaver somniferum with varying content of morphine alkaloids have been studied, and varieties having a genetically governed low alkaloid content have been identified.143 The dynamics of the variation of amount of morphine and codeine present in P. somniferum with time of harvesting of the capsule have been studied.144 The thebaine content of P. bracteatum in relationship to plant development has been studied, and strains have been isolated from which may be obtained a dried latex that contains >55% thebaine, corresponding theoretically to a yield of 58 kg ha-1 or approximately 50 kg ha-1 from harvested capsule.145... 

Opium is an alkaloid obtained from the dried latex of incised unripe flower pods of the poppy plant Papaver somniferum and is comprised of as many as 25 different alkaloids, including pharmacologically active morphine, codeine, and papaverine. Opium is cultivated in Southeast Asia, Turkey, Pakistan, Afghanistan, India, Iran, Nigeria, and Mexico. Heroin is produced by acetylation of morphine. 

Diamorphine is prepared by the isolation and acetylation of morphine. While morphine was first discovered in the dried latex of P. somniferum shortly after 1800, it is now known that of the approximately 110 species of Papaver, only two are known to prodnce morphine in significant quantities, namely P. somniferum L. and P. setigerum DC [1,2]. Of the two species, it is P. somniferum which is nsed to provide the dried latex for heroin production. 

Morphine is extracted from the dried latex (opium) from the seed capsule of the poppy. Incisions, abont 1 mm deep, are made in the seed capsnle approximately two weeks after the petals have fallen from the flower and the seed head is mature, and the latex exndes from the seed head, dries and oxidizes in the sun and is collected the following day. With successive harvestings, a pod may produce anywhere between 10 and 100 mg of opium. The latex contains 10-20 wt% alkaloids, with the remainder of the latex being sugars, proteins, lipids, gums and water. 

Heroin can be encountered in the form of powder samples and as residues on the paraphernalia used for its administration and on the equipment involved in its mixing, cutting and distribution. Heroin is the mixture of products formed when morphine is extracted from the dried latex of the field poppy, purified (often incompletely) and then subsequently acetylated to form diamorphine, the target drug. 

The presence of free surfactant is not preferred in some applications of polymer emulsions. It may, for instance, result in water sensitivity of dried latex coatings or... 

Papain. Papain was first isolated in crystalline form from fresh latex by Balls et al. 22), but it is more conveniently isolated from commercially available dried latex by the procedure of Kimmel and Smith 23). Papain prepared by this procedure, however, is not fully active see Activation and Inhibition below) and usually contains only 0.5 mole SH per mole of protein. Fully active papain containing I mole SH per mole of protein may be prepared by affinity chromatography on a column of an inhibitor, Gly-Gly-Tyr (Bzl)-Arg, covalently linked to agarose 24). Two other techniques which have been used to purify papain involve... 

Papaver somniferum (opium poppy) contains a variety of opioid and related alkaloids, including codeine, morphine, noscapine, papaverine, and thebaine. Crude opium is the air-dried latex obtained by incising the unripe capsules of P. somniferum. Paregoric is ammoniated tincture of opium (Scotch paregoric) or camphorated tincture of opium (English paregoric). The use of these formulations has largely been replaced by use of the purified compounds. 

In parallel, the dry latexes, obtained by the freeze drying procedure, and coated latexes were analyzed by solid-state Si NMR in order to determine the extent of condensation of silanols... 

The Tg of bulk ethylcellulose is in the range of 129-133 C, and therefore at ambient conditions films of ethylcellulose are substantially brittle. To be used in film coating applications, ethylcellulose requires the addition of pla.sticizer to improve film flexibility and toughness. The Tg of dried latex particles of Aquacoat ECD has been reported to be 89 C (7). The reduced Tg of ethylcellulose particles dried from a pseudolatex is the result of the temporary plasticizing effects of water. Although the Tg of ethylcellulose... 

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