Patent GB-582853-A (GB)
Title: Improvements in or relating to the manufacture of synthetic resins
IPC: C08G12/10
Filed: 1944-04-21
Abstract: Synthetic resins are prepared by dispersing one or more hydrocarbons which are liquid and not polymerizable under the conditions of the reaction and at least the bulk of which boils above 250 DEG  C., by agitation in an aqueous solution of formaldehyde and one or more of the following derivatives of cyanamide, viz: urea, thiourea, dicyandiamide, dicyandiamidine, and thiodicyandiamidine, at a temperature high enough to initiate an exothermic reaction with production of a homogeneous mixture, and stabilising by further heating (generally at 80-90 DEG  C.) and removal of excess water, the reaction product and/or a product obtained therefrom by standing and/or filtration.  Part of the formaldehyde may be substituted by paraformaldehyde.  If a filler is added it is generally mixed with reaction mixture immediately after it homogenises.  Wood flour is a suitable filler and is advantageously prepared from a wood containing resins which act as mould lubricants or may be coated with resins or with hydrocarbons which may or may not be the same as those used in the formation of the resins.  Suitable resins are natural resins, polystyrene or polymethylmethacrylate.  The paste consisting of dispersions and fillers may be dried in a preforming mould. Preferably reaction conditions are slightly acid, and a large proportion of the hydrocarbons are paraffinic, some of them branched chain, boiling between 250 and 400 DEG  C.  Excess formaldehyde may be used and recovered during drying.  When using certain hydrocarbons and stopping agitation after the first temperature rise, unused oil can be removed and the product recovered by evaporation or used in solution.  If agitation is continued without removing hydrocarbons a second rise of temperature occurs and the emulsion thickens. Excess water may separate and be removable by filtration.  In certain circumstances both temperature rises occur together as a single rise. During the intermediate stage before curing, resins may be extracted from the reaction product, e.g. with acetone. The products may be cured with heat and pressure.  Very vigorous reactions may need modifying, e.g. by use of cooling means, dilution, suitable substitution of other reactants, or dissolving the hydrocarbons in a solvent.  Small quantities of hydrocarbons boiling below 250 DEG  C. in the mixture increase fluidity and facilitate dispersion and small quantities of bituminous matter in the hydrocarbons produce patterns on the surface of the cured product.  Suitable hydrocarbon mixtures are obtainable from straight run or cracked petroleum residues, from asphalts, shale oil, bituminous sand coal tar, or liquefaction products of coal. In the examples: (1) Urea, thiourea, water, sulphonic acid, formalin, and a mixture containing 50 per cent of the hydrocarbon mixture known as Pool Diesoleum and 50 per cent of unbleached petroleum jelly, were mixed and agitated while heating to 40 DEG  C. During further agitation the temperature rose to 50 DEG C. and then started to fall.  At this stage oil separates if agitation ceases. Continued agitation and heating to 55 DEG  C. started a second reaction which raised the temperature to 63 DEG  C. and rendered the mixture homogeneous.  Wood flour was added to form a paste which was dried at 80 DEG  C. until the weight was reduced by 32 per cent. The product could be cured at 140 DEG  C. and 1.7 tons/sq. in. in 2 minutes.  (2) In this example the wood flour was impregnated with a petroleum ether solution of the hydrocarbon mixture used in the resin production and dried to remove ether and water before use. (3) Urea, paraffin wax (softening point about 60 DEG  C.) and water are heated to 62 DEG  C. and agitated to effect dispersion.  Acidified formalin heated to 60 DEG  C. was added or mixed in.  The temperature rose to 75 DEG  C. and then fell slightly. Agitation was stopped after about 10 minutes.  Asbestos powder was added and the mixture again agitated and filtered.  The solid was dried at 105 DEG  C. and then cured at 140 DEG  C.  The filtrate contained some resins or condensation products and if sprayed on to the drying solid it improved the properties of the cured material. (4) Urea, thiourea, a hydrocabon fraction boiling between 250 DEG  C. and 350 DEG  C. from a waxy crude, formaldehyde and sulphuric acid were mixed and agitated at 14 DEG  C.  The temperature rose slowly to 22 DEG  C. Agitation for 12 hours yielded a cream which did not separate. Mixed with wood flour it formed a paste which was dried at 105 DEG  C., and cured under pressure at 140 DEG  C.  (5) The hydrocarbons were a distillation residue of a waxy crude from which compounds boiling below 350 DEG  C. had been removed.  It was mixed with aromatic solvent naphtha and agitated with warm water.  Urea, sulphuric acid and formalin were added.  The temperature was 25 DEG C.  With agitation it rose to 40.5 DEG  C.  The final brownish, creamy homogeneous mixture was mixed with wood flour to a paste, dried at 110-120 DEG  C. and could be cured at 140 DEG  C. under pressure.  (6) The hydrocarbon consisted of a fraction mainly boiling between 250 DEG  and 385 DEG  C. obtained from cracking a residue from a crude containing very little paraffinic but some aromatic hydrocarbons. They were mixed with urea, thiourea, sulphuric acid and formalin at 8.5 DEG  C.  With agitation the temperature rose to 23.5 DEG  C. and the creamy mixture became very fluid.  It was mixed with wood flour, dried at 110-120 DEG  C. and cured at 140 DEG  C. under pressure. (7) Urea, thiourea, formalin, sulphuric acid and liquid paraffin were agitated and heated to a temperature of about 103 DEG C.  After standing to cool, excess oil was removed, leaving a glass-like, soft, thermosetting resin.  (8) Similar to (7) without the thiourea.  (9) Thiourea, liquid paraffin and formalin were agitated together and heated.  Excess oil was removed after stopping the agitation, and some more after standing and kneading of the jelly-like product.  (10) Example 9 was repeated with small additions of caustic soda or sulphuric acid, and with urea, or dicyandiamide in place of thiourea.  Similar jellies were obtained in varying yields. The acid thiourea jelly was mixed with asbestos powder dried and cured to form pellets.  (11) Instead of the liquid paraffin of example 9, a mixture of Pool Diesoleum, aromatic solvent naphtha and a fraction (B.P. 380-420 DEG  C.) from a cracked residuum was used. There was no excess oil.  The jelly product was mixed with asbestos powder and dried at 100 DEG  C. in an oven and under pressure at 110 DEG  C. in a mould.  (12) The thiodicyandiamidine containing residual liquor from the production of thiourea from calcium cyanamide and sulphur (see Specification 412,254) after removal of calcium is mixed with formalin, sulphuric acid and a mixture of Pool Diesoleum and petroleum jelly.  There was no excess oil.  The product was a light jelly.