Process and apparatus for producing foam
AssigneePoliglas, S.A.
InventorsJesús Ladera Sainz, Laura Figueras Nadal
Life of this patent
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Abstract
CO2 is used as the blowing agent, and a first and second control agents are injected into the melt, the first control agent being designed to dissolve and cool the melt and consisting of ethanol, while the second control agent is only designed to cool the melt and consists of H2O2, the injected amount of ethanol being just sufficient for achieving the highest possible dissolution of CO2 in the melt and the injected amount of H2O2 being such that the foaming produced by ethanol is minimized. The apparatus includes arrangements for conditioning and feeding the blowing agent and control agents into the melt. The blocks and boards exhibit dimensional stability and good self-extinction features.
Claims13
Process for producing polystyrene foam, said process comprising:
- plastifying a mixture of polystyrene with nucleating agents, plasticisers and additives at a pressure and temperature respectively above atmospheric pressure and room temperature to form a melt,
- suddenly decompressing and cooling the melt to atmospheric pressure and room temperature, on being extruded through a final extrusion die,
- injecting a blowing agent designed to produce the desired foaming and only consisting of CO2 into the melt so that said blowing agent is dissolved in the melt, and
- also injecting a first and a second control agents into the melt, the first control agent being designed to dissolve and cool the melt and consisting of ethanol, while the second control agent is only designed to cool the melt and consists of H2O2, the injected amount of ethanol being such that it is just sufficient for achieving the highest possible dissolution of CO2 in the melt, and the injected amount of H2O2 being such that the foaming produced by ethanol is minimised.
Apparatus for for producing polystyrene foam, said apparatus comprising
- a kneader-extruder and a dynamic mixer arranged in series, the kneader-extruder comprises means for effecting initial plastifying of a mixture of polystyene, nucleating agents, plasticisers and additives into a melt and injection of CO2 and ethanol into the melt, and the dynamic mixer being provided with a cooling device for feeding the melt into an extrusion head carrying a final extrusion die, means for injection of H2O2 located between the kneader-extruder and the dynamic mixer, a first static mixer and a second static mixer inserted respectively immediately downstream of the kneader-extruder and immediately downstream of the dynamic mixer, and the means for the injection of H2O2 being arranged between the kneader-extruder and the first static mixer.
Process for producing polystyrene blocks or boards, said process comprising the steps of:
- a) plastifying into a melt a mixture of polystyrene with nucleating agents, plasticisers and additives in a kneader-extruder, the polystyrene having a molecular weight of less than about 150,000, a melt flow index of about 20 g/10 min (ISO 1133H) and a VICAT VST B 50 (according to ISO 306 B 50) softening temperature above
- b) injecting into the melt, in the kneader-extruder, CO2 and ethanol, at a pressure of about 20 MPa;
- c) transferring the melt from the kneader-extruder to a first static mixer and injecting H2O2 into the melt between the kneader-extruder and the first static mixer;
- d) homogenising the melt in the first static mixer;
- e) transferring the melt from the first static mixer to a dynamic mixer, in which homogenisation is accompanied by a decrease in the temperature and the pressure to which the melt is subjected;
- f) transferring the melt from the dynamic mixer to a second static mixer, in which the decrease in the temperature and the pressure to which the melt is subjected continues;
- g) transferring the melt from the second static mixer to a final extrusion head, in which the temperature and pressure are controlled so that they remain close to about 100° C. and 7.6 MPa, respectively, the CO2 always being maintained under supercritical conditions until the final extrusion;
- at the time of the final extrusion, the melt comprises 2.25-5% by weight of CO2, 0.3-3.0% by weight of ethanol and 0.2-1.7% by weight of H2O2, the remainder being polystyrene and nucleating agents, plasticisers and additives.
Dependencies are inferred from the claim text.