DE1704811A1 - Products foamed from plastics and process for their manufacture - Google Patents

Description

Products foamed from plastics and process for their manufacture.

It is known (Belgian patent 622 887), composite cell bodies produce in such a way that one is capable of foaming material, for. B. introduces polystyrene foam granules into a liquid foamable reaction mixture. In this way, cell bodies with modified properties can be produced, in particular with an increased specific load capacity for the same volume weight. In the case of the use of foamable Pdystyrene granules, for example the exothermic reaction of a liquid two-component polyurethane mixture at the same time a softening and foaming of the introduced polystyrene material as a result of the Expansion of volatile hydrocarbons contained therein, e.g. pentane.

In the case of rigid polyurethane foams, preferably for cold insulation as well as for the production of composite elements are used, it is now in many ways usually by adding propellants which are gaseous under normal conditions, for example Haloalkanes to prepare a reaction mixture, which is in pre-expanded, creamy Condition is particularly easy to process.

Propellants such as fluorotrichloromethane are preferred in this two-component systems used, as a rule, before processing the polyol component added, Considerable losses of these propellants are indeesen with such a procedure unavoidable.

According to the invention, this additional gas loading takes place for generation low density partially or entirely in the form of foamable, a the gas-containing capsules of the microencapsulation type, adding at least one part the propellants to be used, gaseous at normal temperatures, in capsules encased, added, the envelope being made of a high polymer material, for example on the basis of foamable polystyrene or so-called microballoons from phenolic resin, or from such membrane envelopes such as gelatin, which in any way, Able to release their gas load through pressure and / or heat of reaction are. In this way, for example, in the case of using thermoplastic Wrapping material, both the escaping gas for the purpose of the desirable liquefaction of the reaction mixture as well as to achieve the lowest density, moreover the wrapping material made usable for additional cell wall formation.

For carrying out the procedure described according to the invention The one-step process is preferred in conjunction with diphenylmethane-4,4 Dilaocyanat in question, without, however, being restricted to it. Mixing the Reactants, in particular a polyol or polyol mixture, with the diisocyanate and the propellant encased according to the invention, accelerating in the presence of the usual acting additives causes a rapidly going on in a manner known per se Foam reaction. It can also be used in a two-stage process in the manner which is also known per se Way to be proceeded via a semi-prepolymer, the process in the sense of a Prereaction of the diisocyanate initiated with part of the required polyol If and to that extent, a slow reaction is particularly mentioned ist0 One can also, similar to the well-known frothing system, with two at different Temperature boiling propellants work, one of which, for example the higher-boiling ones, or both are encapsulated, in the former case about such that a liquid prosthesis produced in a manner known per se by primary expansion Bit a volume weight ton for example 150 kg / i3 one into a PVC polymer contains encapsulated higher boiling propellant, whereupon after its introduction into the cavity to be foamed the final foaming due to the still given Reactivity and the exothermic reaction caused thereby.

It is also known by mixing appropriate polyols Way in the hand, the viscosity of which to adapt to the conditions caused by the Mixing the foamable or already foamed material are given.

As already indicated, the timing of the reaction steer.

This can also be achieved through the appropriate choice and dimensioning of the activators, Emulsifiers and foam stabilizers that enable the foaming process to proceed and regulate the structure of the solidifying foam while passing through the Addition of the encapsulated additional propellant, the density is adjusted.

For carrying out the method described according to the invention the known process systems can thus be used, be it the procedure according to the one-step process or either according to the pre-adduct process, the pre-adduct either in the form of a prepolymer with free NCO groups or a semi-prepolymer represents in which either only part of the polyester or polyether component, or conversely, only part of the total diisocyanate is processed into a pre-adduct is, or according to the quasi-Prepolyser process, which in a known manner therein consists that the two main reactants before the supply to the actual Mixing head in the premixer or, if necessary, in a storage container with one another be mixed up.

Mixing with the encapsulated propellant is preferably carried out by machine. It is recommended, for example, that the capsule material premixing with the polyol portion and then reacting by mixing it in the to introduce the remaining components, or they do not or only partially prefoamed capsules in the cavity to be filled and injected the urethane reaction mixture at one or more suitable places, simultaneously or one after the other.

Of course, when it comes to construction sites, for example, you can are based on delivered two-component systems and, insofar as the one to be filled in Cavity is not presented the wrapping material, the latter in the one component, preferably introduce the polyol mixture.

Finally, you also have the option of using the encapsulated propellant mixture to be introduced into the cavity to be filled at the same time as the polyurethane foam components, for example by adding pneumatically. The encapsulated Propellant metered directly into the mixing chamber, for example in so-called open mixing systems, by introducing the microcapsules directly into the mixing zone, e.g. in such a way that that the propellant capsules over a vibrating chute a funnel and from there the mixing vessel continuously running in, which takes place simultaneously with the two in the polyurethane reaction participating components is fed.

The hardening of the double foam system is carried out if necessary Reheating causes or accelerates.

One can also work according to the overhaul procedure, for example in such a way that that each presented, relatively thin layers of propellant capsules be poured over with the Pclyurethan reaction mixture, whereupon following a reasonable waiting time for the next coating with capsules and with the foam mixture he follows.

For the simultaneous introduction of the polyurethane reaction mixture and the propellant capsules, the spray method with or without additional air is suitable such that simultaneously with the reaction mixture from a separate nozzle the capsule material is blown in. This also applies to the treatment of surfaces z. 3 vertical walls or of rotationally symmetrical shapes, for example for insulating casing of pipes.

For example, 100 parts by weight of a polyol, preferably one for the production of polyol mixtures suitable for rigid polyurethane foam are discussed in Combination with accelerating additives, activators and stabilizers, mixed with 240 parts of foamable polystyrene or microballoons in which up to lo % of a non-dissolving propellant or an inert gas are encased. This one 140 parts of diphenylmethane-4,4-diisocyanate are added to the mixture. Because of the heat tint the polyurethane reaction and / or mechanical friction is the gas in the capsules brought to evaporation, in the case of the polystyrene capsules at the same time Expansion and an increase in volume beyond the polyurethane foam he follows.

Claims (2)

Claims 1. Products and processes foamed from plastics for their production, characterized in that one in the production of rigid polyurethane foams customary additional gas loading in the form of including the additional propellant Capsules. 2. Products foamed from plastics and processes for their production Production according to claim 1, characterized in that the include the propellant Capsules made from a high polymer, preferably thermoplastic or curable material bostehen, which either expands under the reaction conditions or in Reaction mixture is partially or completely dissolved or mechanically shattered and releases the trapped gas.