Patent RU-2635138-C1 (RU)
Inventor: Kantyukov Rafael Rafkatovich
IPC: B29C44/56
Filed: 2016-10-11
Granted: 2017-11-09
Abstract: FIELD: technological processes. 
     SUBSTANCE: process for production of polyethylene foam includes mixing thereof with a foaming chemical agent, extruding hot mix, forming a film and calendering thereof, cross-linking before polyethylene foaming, dicumyl peroxide is used as a cross-linking agent, azodicarbonamide is used as a foaming agent, before mixing with initial polymer the foaming and cross-linking agents are mixed with each other at a temperature below their melting point, the resulting mixture of agents is mixed with polyethylene granules in extruder with zonal temperature distribution from 105°C to 125°C, the distribution of temperatures along the zones of the extruder is carried out due to preheating of components and softening of polyethylene, the components are mixed in accordance with formula, wt %: polyethylene 84.5; cross-linking agent 0.5; foaming agent 15, the formed polyethylene matrix film of given thickness is sent for final cross-linking and subsequent foaming to the cross-linking and foaming line with preheating, cross-linking, and two zones of uniform expansion, at that, the preheating zone temperatures are 160-180°C, cross-links at 185-200°C, zones of uniform foaming at 210-230°C and 230-245°C, with the possibility for adjusting temperature in each zone, feeding the polyethylene matrix film after the extruder, moving thereof in the cross-linking and foaming line and after the line at each stage with adjustment of drawing rate; after foaming in the furnace last zone, the polyethylene foam is cooled on cooling rolls to a temperature of the cooling rolls. The foam polyethylene production line includes a mixer for components, an extruder, conveying and calendering devices, the mixer being provided with dispensers for mixing the cross-linking and foaming agents with a mixing temperature below their melting point, the extruder blending a mixture of crosslinking and foaming agents with polyethylene granules is installed after the mixing station and made by with two augers and zonal temperature distribution with three temperature zones: a charging hopper with partial softening and decomposition temperature of the components at 105°C, working area of augers with softening and melting temperature of components, distribution of components throughout the volume and mixing thereof at 105-110°C, the extruder head zone with mix viscosity decrease temperature, partial decomposition and melting of the cross-linking agent, and forming film at 125°C, after the extruder the line for cross-linking and foaming is installed and connected with the extruder outlet by the transportation and calendering device and made with four temperature zones: film preheating at 160-180°C, cross-links at 185-200°C, beginning of uniform foaming at 210-225°C, completion of foaming at 230-245°C, the cross-linking and foaming line is equipped with adjustable ventilation system, the output of the cross-linking and foaming line is equipped with film cooling rollers. 
     EFFECT: adjusting pore formation process, providing uniformity of pore formation, reducing pore size and dispersion of their geometric dimensions. 
     7 cl