Saponification poly

Poly(vinyl alcohol) [9002-89-5] was discovered through the addition of alkaU to a clear alcohoHc solution of poly(vinyl acetate), which resulted in the ivory-colored poly(vinyl alcohol) (4). The same discovery has been made by studying the reversible transformation between poly(vinyl alcohol) and poly(vinyl acetate) via esterification and saponification (5). The first scientific reports on poly(vinyl alcohol) were pubUshed in 1927 (6,7). 

Fig. 14. The belt saponification process as used in the production of poly(vinyl alcohol) (265).

In the screw conveyor process, solutions of poly(vinyl acetate) and catalyst are mixed in a high intensity mixer and continuously introduced to a screw-type saponification and conveyor system (270). Downstream details are similar to those found in the belt process. 

The PVA process is highly capital-iatensive, as separate faciUties are required for the production of poly(viayl acetate), its saponification to PVA, the recovery of unreacted monomer, and the production of acetic acid from the ester formed during alcoholysis. Capital costs are far in excess of those associated with the traditional production of other vinyl resins. 

Poly(ethylene-i (9-vinyl alcohol) is made by saponification of ethylene—vinyl acetate copolymers. The properties of these materials depend on the amount of vinyl alcohol present in the copolymer. High vinyl alcohol content results in more hydrophilic materials possessing higher densities, stiffness, and moduh. They are used commercially as barrier resins for packaging. Important producers include Du Pont and EVALCA (74) (see Barrier polymers). 

Poly(vinyl alcohol). Poly(vinyl alcohol) (see Vinyl polymers) is more easily prepared, in a form that can be filtered and washed in a practical way, by alcoholysis of poly(vinyl acetate), than by its saponification in an aqueous system ... 

As with poly(vinyl alcohol), poly(vinyl cinnamate) is prepared by chemical modification of another polymer rather than from monomer . One process is to treat poly(vinyl alcohol) with cinnamoyl chloride and pyridine but this is rather slow. Use of the Schotten Baumann reaction will, however, allow esterification to proceed at a reasonable rate. In one example poly(vinyl alcohol) of degree of polymerisation 1400 and degree of saponification of 95% was dissolved in water. To this was added a concentrated potassium hydroxide solution and then cinnamoyl chloride in methyl ethyl ketone. The product was, in effect a vinyl alcohol-vinyl cinnamate copolymer Figure 14.8)... 

Infrared spectra and the degree of specific rotation show typical features of the malic acid polyester (Table 3). Ultraviolet absorbance spectra of )3-poly(L-malate) from both P. polycephalum and Aureobasidium sp, A-91 are similar and are reminiscent of malate itself [4,5]. For a solution of 1.0 mg/ml polymer, absorbance increases from 0.40 units at 230 nm to 10 units at 190 nm wavelength. After saponification and pH-neutralization, the absorbance increased from 8.7 units at 230 nm to 100 units at 190 nm. 

The completely synthesized and covalently bridged chains where separated from poly(ethylene glycol) (PEG) by saponification with triethylamine in methanol. 

Polyamide and polyester fibres are generally scoured using an alkyl poly(oxyethylene) sulphate and sodium carbonate. Some polyester qualities are subjected to a causticisation treatment with sodium hydroxide in the presence of a cationic surfactant to give a lighter fabric with a silkier handle [154,156]. This treatment involves etching (localised saponification) of the polyester surface and is broadly analogous to the S-finish used on triacetate fibres. The process has attracted considerable interest in recent years but its... 

Poly(vinyl alcohol) has the structure 10.67. Poly(vinyl acetate) is the fully esterified derivative of polyfvinyl alcohol), in which the -OH groups are replaced by -OCOCH3 groups. As indicated in Table 10.5, commercial polyvinyl sizes are effectively copolymers of polyfvinyl acetate) and polyfvinyl alcohol) that vary in the degree of saponification of the ester groups. These products may comprise 100% of either polymer, or combinations of the two monomers in any proportions. Crotonic acid (2-butenoic acid), widely used in the preparation of resins, may also be a component. This compound exhibits cis-trans isomerism (Scheme 10.17). The solid trans form is produced readily by catalysed rearrangement of the liquid cis isomer. 

A Berger, E Katchalski. Poly-L-aspartic acid, (saponification). J Am Chem Soc 73, 4084, 1951. 

PVA Formation Reaction. Poly(vinyl alcohol) is itself a modified polymer being made by the alcoholysis of poly(vinyl acetate) under acid or base catalysis as shown in Equation 1 (6.7). This polymer cannot be made by a direct polymerization because the vinyl alcohol monomer only exists in the tautomeric form of acetaldehyde. This saponification reaction can also be run on vinyl acetate copolymers and this affords a means of making vinyl alcohol copolymers. The homopolymer is water soluble and softens with decomposition at about 200°C while the properties of the copolymers would vary widely. Poly(vinyl alcohol) has been widely utilized in polymer modification because ... 

Charge on a polymer molecule can also affect reactivity by altering the concentration of the small molecule reactant within the polymer domains. The reaction of a charged polymer with a charged reactant results in acceleration for oppositely charged species and retardation when the charges are the same. For example, the rate constant for the KOH saponification of poly(methyl methacrylate) decreases by about an order of magnitude as the reaction proceeds [Plate, 1976]. Partially reacted poly(methyl methacrylate) (IV) repells hydroxide ion, while... 

Poly(vinyl acetate) Saponification Poly(vinyl alcohol) 5-1 HW 2042 K 1504... 

In the above-mentioned example of the polymer-analogous saponification of poly(vinyl acetate) the reactant and the product differ in their properties, for example, in their solubility however, both compounds have the same average degree of polymerization. The poly(vinyl alcohol) obtained by saponification can, in principle, be esterified back to poly(vinyl acetate) with the original molecular weight the reacetylated polymer then has the same properties as the original material. The viscosity number may be used to check whether in fact any chain scission has occurred during the reaction sequence of saponification and reacetylation (see Example 5-1). 

The type of support chosen can have an impact on the facility with which nucleophilic cleavage takes place. Polystyrene, a very hydrophobic support, is difficult to perfuse with small ions such as hydroxide, and for this reason the saponification of poly-styrene-bound esters usually proceeds more slowly than the corresponding solution reaction. Tentagel, polyacrylamides, or other more hydrophilic supports are generally a better choice if saponifications or other reactions involving small ions are to be performed. 

First by mixing poly(vinyl alcohol) PVA (Kuraray 117H Mw 74800 saponification 99.6%), poly(acrylic acid) PAA (SP2 Mw 170000), and poly(allylamine) hydrochloride PAlAm.HCl (Nittobo Mw 60000) a homogeneous aqueous solution of PVA PAA PAlAm was obtained at concentrations of... 

The role of the conjugated polyimine intermediate in the observed crosslinking can be seen by comparing the saponification of a starch-g-PAN (No. 9, Table IV) with that of a starch-g-polyacrylamide prepared under the same conditions (No. 10). Although polyacrylamide is an intermediate in the conversion of PAN to poly(acrylic acid salt-co-acrylamide), the polyimine structure is of course not formed during its saponification. 

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