A method is provided for producing a di-acetal of sorbitol and an aromatic aldehyde wherein an aqueous solution containing a catalytic amount of a mineral acid and sorbitol is formed. Thereafter, an effective amount of an aromatic aldehyde such as benzaldehyde is incrementally admixed into the homogeneous aqueous admixture containing the sorbitol at a rate sufficient to allow a substantially spontaneous reaction to occur between the D-sorbitol and aromatic aldehyde; thus, forming an aqueous slurry containing crude di-acetal, e.g., dibenzylidene sorbitol. The amount of aromatic aldehyde employed is that amount sufficient to provide a molar ratio of D-sorbitol to aromatic aldehyde of from about 1:0.75 to about 1:1.75. Thereafter, the aqueous slurry is neutralized, and crude di-acetal is removed from the liquid phase and washed with water to remove mono-acetal impurities, e.g., monobenzylidene sorbitol. The washed di-acetal may then be dried to provide dried di-acetal, and the dried di-acetal may be further purified by washing with a relatively non-polar solvent.
The invention is concerned with diacetals resulting of the dehyrocondensation of an alditol comprising 5 or 6 carbon atoms and a benzoic aldehyde such as in particular DBS, BEBS, BMBS or DBX, featuring a purity of at least 95% and being free of organic solvent traces, and a process for preparing the same in aqueous medium, in the presence of an acid catalyst, according to which acetalization is carried out by mixing the reactants under stirring, the reaction mixture is then neutralized by a base, then the solid phase is separated from the liquid phase and washed with warm water, wherein: the initial molar ratio of the benzoic aldehyde to the alditol is lower than 2/1, the acid catalyst is an arylsulfonic acid, the initial molar ratio of the arylsulfonic acid to the benzoic aldehyde is higher than 0.6, and the reaction temperature is lower than about 45.degree. C. Application specially to the clarification and stabilization of polyolefins.
This invention provides hexagonal crystals of a diacetal represented by the formula (1) ##STR1## wherein R.sup.1 and R.sup.2 each represents an alkyl group having 1 to 4 carbon, atoms or a halogen atom, each of m and n is an integer of 0 to 2 and p is 0 or 1, a nucleating agent comprising the diacetal of the formula (1), wherein part or the whole of the diacetal is in the form of hexagonal crystals, a polyolefin resin composition and a molded product each comprising a polyolefin resin and the nucleating agent, and a method for molding the polyolefin resin composition. According to the invention, the occurrence of fish eyes and coloration in a molded product can be prevented, the optical, mechanical and thermal properties of the molded product are superior and the molding cycle is shortened.
The present invention relates to improved alditol acetal compositions, in particular 1,3-2,4-di(benzylidene) sorbitol (DBS) or one of its alkylated derivatives. The improvement in these compositions is expressed in particular in terms of flow behavior and/or thermal stability. It is obtained by combining the alditol acetal with an additive selected from tocopherols, polyols and certain of their respective derivatives. These additives may act as binding or densifying agents and/or stabilizing agents or odor maskers. The alditol acetal and additive are advantageously combined by cold mixing, followed by granulation or compaction, also cold. The compositions of the invention, for example based on DBS or the methylated derivatives of DBS, are in the form of densified or compacted powders, granules, pellets, pastilles or extrudates. They are used in particular for preparing plastic or jellified materials or additives for these types of materials.
A method of making acetals is provided by condensing an aromatic aldehyde and a polyhydric alcohol having five or more hydroxyl groups in the presence of an acid catalyst, a hydrophobic organic liquid medium and a processing agent selected from dihydric, trihydric and tetrahydric alcohols.
Disclosed is a process for preparing a diacetal compound such as a dibenzylidene sorbitol, comprising the steps of (i) condensing an aldehyde compound and a polyhydric alcohol in the presence of an acid catalyst and when required a lower alcohol in a hydrophobic organic solvent to give a reaction mixture containing a diacetal compound, (ii) neutralizing the reaction mixture, (iii) washing the mixture with water, (iv) removing the solvent from the mixture thus washed, and (v) drying the residual mass; the process being characterized in that an amine such as, for example, di(C.sub.10 -C.sub.26 alkyl or alkenyl)amine substituted on the nitrogen atom with a C.sub.1 -C.sub.4 alkyl group or with a group of the formula --C.sub.2 H.sub.4 O).sub.q H wherein q is an integer of 1 to 4, or a (C.sub.14 -C.sub.22 alkyl or alkenyl)amine sustituted on the nitrogen atom with one or two groups of the formula --C.sub.2 H.sub.4 O).sub.q H wherein q is 1 to 4, is added during the period from the formation of the reaction mixture to the completion of the drying step.
