Abstract: In a process for hardening phenol-formaldehyde resol resins, comprising conducting the hardening of the resins with an acidic solution of water and/or an organic solvent having dissolved therein an aromatic sulphonic acid and/or concentrated sulphuric acid, the improvement comprising the hardening in the presence of aniline added to the phenolic resin beforehand in a quantity of between about 0.5 and 2% relative to the weight of the phenolic resin whereby the pot life is extended and the cure time is satisfactory, the resultant products being especially useful as prepegs.

Abstract: A process for manufacturing a cellular plaster with plaster obtained by calcining phosphogypsum, comprising mixing dry plaster with a previously prepared aqueous foam and with about 0.1-5% by weight, relative to the dry plaster, of slaked lime.

Abstract: A process for polymerizing ethylene in the presence of a catalyst system comprising at least two halogen compounds of transition metals, one of which has the formula (TiCl.sub.3,Y3 AlCl.sub.3)(MY.sub.3).sub.x (MgYZ).sub.y, where M is a transition metal of Group VB or V1B, X is a halogen and 0.3.ltoreq.x.ltoreq.3, 0.ltoreq.y.ltoreq.20, and a Group I to III hydryde or organometallic activator and the mean residence time of the catalyst system in the polymerization reactor is between 2 and 100 seconds.

Abstract: A two stage process for interrogating a detector of the concentration of combustible gas in an atmosphere. In a first stage, the detector is supplied with a low voltage and the supply is cut and an optional alarm is sounded if a positive signal has been detected. In a second stage, if the signal detected in the first stage is negative or zero, then the detector is supplied with a second, higher voltage. The signal is compared to a predetermined range and, if not within that range, an optional alarm is sounded. A device to apply the process comprising a detector, an amplifier of the signal issued by the detector, a voltage reducing circuit, and a switch that controls the voltage reducing circuit slaved by a discriminator to the sign and/or to the maximum amplitude of the signal output by the amplifier. Application of the process and device to the detection of the concentration of methane.

Abstract: An anti-shrink additive for unsaturated polyester resins of the formula: ##STR1## wherein, R is the remainder of a triol or tetrol,x is 3 or 4,z is .gtoreq.1,R' is the remainder of the radical of the product carrying the acid function, andn and n' being such that the molecular weight of the non-acidified propoxylated compound is preferably between 1,000 and 3,000.The invention also comprises the method of making such additive and unsaturated polyester resins containing such additive.

Abstract: In a process for the manufacture of cyanuric acid by heating urea at a temperature above its melting point, an aqueous solution of urea is sprayed onto granules of crude cyanuric acid, recycled externally, and heated at a temperature of 220.degree.-280.degree. C. in a heat exchange zone heated by the walls thereof. A rotor in the device comprising a tubular shaft on which hollow discs are mounted, and in which a heat-transfer fluid circulates, is also employed to heat the material to the manufacture cyanuric acid in high yields.