Patent GB-1440345-A (GB)
Title: Preparation of moulding compositions
IPC: C08K5/098
Filed: 1973-05-30
Abstract: 1440345 Unsaturated polyester resin moulding compounds BP CHEMICALS INTERNATIONAL Ltd 16 May 1974 [30 May 1973] 25626/73 Heading C3P A process for the preparation of an unsaturated polyester resin based sheet or rovings moulding compound comprises reacting a liquid unsaturated polyester resin system comprising an unsaturated polyester, a copolymerizable monomer, a polymerization initiator and a gelling agent for the said unsaturated polyester resin system to an elevated temperature below that at which crosslinking of the system occurs, impregnating a fibrous reinforcement with the said hot liquid unsaturated polyester resin system and subsequently cooling the resultant moulding compound to a temperatue below 30 C. at which temperature the liquid unsaturated polyester resin system forms a gel. The gelling agent is defined as an agent which is soluble in the unsaturated polyester/copolymerizable monomer mixture at an elevated temperature and which when the solution is cooled to ambient temperatures, i.e. below 30 C., results in formation of a high viscosity gel, e.g. sodium stearate and potassium stearate, which are soluble in the unsaturated polyester/ copolymerizable monomer mixture at 50-70 C. Preferred unsaturated polyesters are polypropylene glycol maleate or fumarate, such unsaturated polyesters with a minor proportion of the maleic or fumaric residues replaced by isophthalic acid or carbic acid (endomethylenetetrahydrophthalic acid) residues, unsaturated polyesters containing more than 50 molar per cent of maleic acid and fumaric acid residues and alcohol residues derived from the Bisphenol A, or those in which a proportion of the maleic or fumaric acid residues are replaced by tetrachlorophthalic or chlorendic acid residues. The copolymerizable monomer is preferably styrene, vinyl toluene or diallyl phthalate. The liquid unsaturated polyester resin stystem may contain 0À5-3% by weight of a polar material, e.g. hydroxy ethyl acrylate stearamide and polyethylene glycols. The fibrous reinforcement suitably of glass may be in the form of a continuous mat or as random fibres. The process may be used to produce (a) rovings moulding compounds (RMC) where all the components except the fibrous reinforcement are placed in a bath and the continuous filaments of the fibrous material are passed through the bath, (b) sheet moulding compounds (SMC) in which the fibrous reiforcement is deposited on a supporting carrier and then impregnated with the unsaturated polyester resin, or (c) conventional bulk moulding compounds where the reinforcement is in the form of fibres and all the constituents are mixed in a batch mixer. Further ingedients that may be present are fillers and modifier systems which control shrinkage on moulding, e.g. thermoplastic polymers. The specific Example (1) describes the production of a sheet moulding compound by applying a paste comprising polyethylene maleate (styrene, polypropylene adipate as shrink control agent, polyethylene glycol, a perester catalyst, butylated hydroxy toluene inhibitor, inorganic filler, stearamide and stearic acid heated to 70 C. to layers of glass strand mat to form a sheet moulding compound. The sodium salts of palmitic acid, beheric and hydroxystearic acids are shown to be suitable gelling agents in Example 2.