Patent GB-1436797-A (GB)
Title: Process and apparatus for continuously producing shaped products of an expanded polymer material
IPC: B29C44/20
Filed: 1973-08-17
Abstract: 1436797 Moulding cellular articles; laminates POLYMER PROCESSING RESEARCH INSTITUTE Ltd 17 Aug 1973 [18 Aug 1972] 38935/73 Headings B5A and B5N In a continuous process for producing an elongate article e.g. a rod, sheet or packaging material, or a sequence of individual articles, e.g. containers, pre-expanded polymer beads are supplied to a mould cavity or a sequence of mould cavities defined by or carried by one or more steam permeable endless belts and are fed thereby in succession through a pressure steam zone in which further particle expansion and adhesion occurs, a cooling zone and a delivery zone, the belt or belts passing through pressure sealing zones upstream and downstream of the pressure steam zone. The product may be cut or wound on a reel. In the first embodiment Fig. 1a, pre-expanded beads 1 are pneumatically fed from a source 2 to a mould cavity defined by two endless cloth belts 5, 6 which progress between pinch rollers 8, 8<SP>1</SP>, perforated plates 11, 12 in pressure steam chamber 10, perforated plates in pressure cooling chamber 23, before being separated at rollers 27, 28. Pressure sealing devices through which the belts pass are located upstream of the pressure steam chamber, between the pressure steam chamber and the cooling chamber and at the exit of the cooling chamber. The position of the upper pressure plate 11 in the steam chamber is adjustable and the plates converge towards the outlet of the steam chamber to reduce the volume of the product. The pressure in the cooling chamber counteracts the friction between the belts and the perforated walls the upper one of which converges towards the bottom one. A non- woven fabric, e.g. of glass fibres, may be supplied with the beads so that a reinforced product suitable as a building material is obtained. One or both belts may have projections so that the product is correspondingly patterned. In another example, Fig. 2a, the lower belt has teeth 42 into the gaps between which a row or rows of pre-expanded beads 46 is or are supplied from a silo 44. The belt can be vibrated to ensure uniform filling. The upper belt is of steam permeable cloth and both belts together with parallel fibre reinforcing material 51 pass between pinch rollers 49, 49<SP>1</SP>, through a pressure sealing device 53 into a steam chamber 54 from which they exit through a pressure sealing device 55 to pass between pinch rollers 57, 57<SP>1</SP> and cooling plates 58, 581. The belts are then separated and the moulded products 61 are removed attached to the parallel yarns. The parallel yarns may pass through slits in the teeth of the lower belt. If the product is to serve as a filter a non-woven fabric is used instead of parallel fibres. If liner material is fixed below and on top of the products corrugated board substitute is produced. In another example, Fig. 2b, the lower cloth belt carries or comprises a sequence of moulds 72, 73 which receive the pre-expanded beads from silo 75. The moulds pass through pinch rollers 80, 80<SP>1</SP>, pressure steam chamber 82 and cooling chamber 84, pressure sealing devices 81, 83, 86 being provided. The articles, e.g. containers or container covers, are removed by scraper 89 and fall on to receiver 90. Fibre reinforcement can be attached to the article during moulding. The sealing devices may comprise a tubular sleeve 94, Fig. 3a fixed at one end to a pipe 105 and extending within a pipe 97 between pinch plates 99, 102 the upper one of which is adjustable. Edge packing elements 103, 104, Fig. 3b are provided. The sealing unit may be constructed in the form of a gate valve.