HCl Acceptor Research Articles

Synthese de sequences polychlorure de vinyle α-ω difonctionnelles et extension en copolymeres multisequences

It is possible to synthesize α-ω diacid PVC sequences by direct ozonization of the polymer, but their thermal stability is low because peroxides are introduced simultaneously in the polymer backbone. Also they cannot be used to prepare block copolymers by polycondensation at temperature above 100°. They are reactive enough to be transformed to α-ω acid chlorides which can be condensed with diols, diamines and bisphenol A to give block copolymers. Triethylamine acts as catalyst but also as HCl acceptor and favours high molecular weight formation. The α-ω acid chlorides can be hydroxylated and polycondensed with diphenylmethane diisocyanate. The thermal stability of these block copolymers is satisfactory if the peroxides are previously reduced.

Synthesis of card polyesters prepared from dibenzoyl phthalic acid chlorides

Aromatic polyesters were synthesized by polycondensation of 2,4-dibenzoylisophthalic and 2.5-dibenzoylterephthalic acid dichlorides with various bisphenols. It was shown that carrying out the process in organic solvents without HCl acceptors mainly results in the formation of card polyesters under fairly mild conditions, compared with well known synthesis from aromatic dihalide compounds. Some properties of the polymers obtained were examined.

Use of Crosslinked Poly(4‐vinylpyridine) as HCl Acceptor

Use of Crosslinked Poly(4‐vinylpyridine) as HCl Acceptor

Photochemical degradation of polyvinylchloride

Fresh light has been thrown on some novel features of the photochemical degradation of PVC. Crosslinking of the macromolecules and the formation of chromophore groups in PVC as well as the total interaction of thermostabilizers with HCl, leading to a major change in the mechanical properties of the material, do not take place in the entire volume of the material, but only in thin (up to 0·005 cm) surface layers on the side exposed to irradiation. Highly effective stabilization of PVC towards the action of UV light is obtainable by increased protection of the surface of PVC materials by means of thermostabilizers that are HCl acceptors.

Antioxidative stabilization of poly(vinyl chloride)

AbstractHalogenated resins such as poly(vinyl)chloride undergo rapid degradation when exposed to heat. Such degradation is significantly increased by oxygen, and it is believed that the induction of the process of decomposition is caused by autoxidation of the polymer, followed by extensive dehydrohalogenation. Sulfur‐containing peroxide decomposers allow primary stabilization of PVC with organic compounds which are not HCl acceptors but prevent free radical cross‐linking of the polymer. This implies a discolored polymer melt (due to loss of HCl and formation of polyenes) which nonetheless exhibits good long term stability (no cross‐linking). The stabilization of labile chlorine atoms results from the oxidation of various chain irregularities, and thus the elimination of the early discoloration can be achieved by the use of small quantities of monohydrocarbyltin co‐stabilizers. The relative performance of various antioxidant systems are reported and possible stabilization mechanisms are discussed.

New silicon-containing heterocyclic rings derived from 1, 3-bis(methyldichlorosilyl)propane

Reaction of 1,3-bis(methyldichlorosilyl)propane with alcohols gives (methylalkoxychlorosilyl)propanes. Hydrolysis of the latter with the calculated amount of water in the presence of a HCl acceptor gives 2, 6-dimethyl-2,6-dialkoxy-1-oxa-2,6-disilacyclohexanes. Hydrolysis of 1,3-bis(methyl-dichlorosilyl)propane and 1,3-bis(methylalkoxy-chlorosilyl)propane gives a tricyclic carbocyclosiloxane. A study is made of the reactions of 2, 6-dimethyl-2, 6-dialkoxy-1-oxa-2, 6-disilacyclohexane with alcohols, triethylsilanol, triethylchlorosilane, and C6H5MgBr.

Aromatic polydiketopiperazines

AbstractAromatic polydiketopiperazines have been prepared from bis‐2‐chloroacetamides of aromatic diamines in the presence of an epoxide as HCl acceptor and a quaternary ammonium halide catalyst. The structures of the polymers were characterized by infrared and NMR spectra. These polymers were soluble in organic acids such as formic acid, dichloroacetic acid, and trifluoroacetic acid but insoluble in common organic solvents such as dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Thermogravimetric analysis indicated that these polymers decomposed at 300–340°C.

HCl acceptors in emulsion polyamidation with participation of aromatic reagents

HCl acceptors in emulsion polyamidation with participation of aromatic reagents

Siloxy methylene oxide compounds

AbstractSilicon containing chain and ring formals of the structures magnified image were synthesized from the reaction of a chlorosilane with formaldehyde or a formaldehyde donor in acid solution or in the presence of an HCl acceptor. Mono‐, di‐, tri‐, and tetrafunctional “silyl formals” were obtained; they are oily products of various degrees of polymerization and of relatively high refractive index and specific gravity. Silyl formals are stable at room temperature. They are useful intermediates in cases in which a siloxy group should be introduced into an organic molecule by reaction with an organic OH group or active hydrogen. Tri‐ and tetrafunctional silyl formals are effective crosslinkers in various systems.