GB344872A - Moulding compositions and moulded articles made therefrom - Google Patents

Abstract

In the manufacture of moulding compositions comprising fibrous materials and a mixed condensation product of urea and thiourea with formaldehyde, the condensation product is prepared by condensing a sum of 2 mols. of urea and thiourea jointly with less than 4 mols. of formaldehyde in a medium having a hydrion concentration greater than pH 5, preferably pH 3, and heating the reaction mixture until a hydrophobe product is obtained. The products form stable sols. in the heat, thereby by facilitating their incorporation with the fibrous materials; the latter may, however, be present ab initio. The urea and the thiourea may be condensed simultaneously with formaldehyde, or one component may be added after the other has been preliminarily condensed, but the desired products are not obtainable by condensing one of the components almost completely with formaldehyde and then adding the other, or by mixing together condensation products separately obtained. Opaque products are prepared by briefly heating urea (1 mol.) with aqueous formaldehyde (1,5 mols.) in an acid medium as stated above, and then adding thiourea (1 mol.) and formaldehyde (1,5 mols.) with continued heating. Transparent products are obtained by adding urea (1 mol.) to a hot acid solution of thiourea (1 mol.) in aqueous formaldehyde (3 mols.) with continued heating. The hot solutions, after mixing with the fibrous materials, are dried, first in the air and then by heat, e.g. at 90-100 DEG C. Drying may be effected on heated rolls or in a rotary drum, and at atmospheric or reduced pressure. The products may then be ground and finally heated until a sample loses about 5 per cent of its weight when heated at 100 DEG C. They are then ready for moulding, the small amount of residual water being necessary to ensure sufficient fluidity. Moulding is effected at 140-180 DEG C. at 150-300 kg. per sq. cm. pressure, and the moulded materials are preferably dried at 80-100 DEG C. for 12-20 hours in a current of air. To obtain mixed effects, the products may be jointly moulded with phenol-formaldehyde condensation products for which the stated conditions of moulding are suitable. Examples are given describing the manufacture of transparent and opaque products under the conditions set out above, the necessary acidity being obtained by means of oxalic acid or aluminium sulphate, and the fibrous material being cellulose. Other specified fibrous materials are asbestos, cotton, and artificial silk. Filling materials and organic or inorganic colouring materials may also be included, with or without small quantities of fats. Specification 294,253, [Class 2 (iii), Dyes &c.], is referred to.ALSO:Moulding compositions comprise fibrous materials and a mixed condensation product of urea and thiourea with formaldehyde, the condensation product being prepared by condensing a sum of 2 mols. of urea and thiourea jointly with less than 4 mols. of formaldehyde in a medium having a hydrion concentration greater than pH5, preferably pH3, and heating the reactio mixture until a hydrophobe product is obtained. The products form stable sols in the heat, thereby facilitating their incorporation with the fibrous materials; the latter may, however, be present ab initio. The hot solutions, after mixing with the fibrous materials, are dried, first in the air and then by heat, e.g. at 90-100 DEG C. Drying may be effected on heated rolls or in a rotary drum, and at atmospheric or reduced pressure. The products may then be ground and finally heated until a sample loses about 5 per cent of its weight when heated at 100 DEG C. They are then ready for moulding, the small amount of residual water being necessary to ensure sufficient fluidity. Moulding is effected at 140-180 DEG C. at 150-300 kg. per sq. cm. pressure, and the moulded materials are preferably dried at 80-100 DEG C. for 12-20 hours in a current of air. To obtain mixed effects, the products may be jointly moulded with phenol-formaldehyde condensation products for which the stated conditions of moulding are suitable. Specified fibrous materials are cellulose, asbestos, cotton, and artificial silk. Filling materials and organic or inorganic colouring materials may also be included, with or without small quantities of fats. Specification 294,253, [Class 2 (iii), Dyes &c.], is referred to.