DE1245102B - Process for the production of lightweight molded parts from hardenable plastic foams - Google Patents

Description

OUND REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

B29d

German KL: 39 a3 - 27/00

Number: 1245 102

File number: C 24982 X / 39 a3

Filing date: September 1, 1961

Opened on: July 20, 1967

The invention relates to a method for producing lightweight molded parts with densities from 0.2 to 0.9 made of curable plastic foams, in particular based on polyurethanes, in which the foamable mixture of the components is poured into a cooled preform and used for the purpose the reaction of the components causing the crosslinking is introduced into a finished mold, where the final deformation of the foam body is carried out using the exothermic heat of reaction will.

The processing of curable plastic foams is known to take place in such a way that the finished foamed and cooled plastic foam is subjected to hot pressing in a compression mold forming an outer skin of sintered plastic. However, this hot pressing is necessary on the other hand, a considerable compression of the foam, so that the specific weight of such Molded parts is naturally limited downwards. It has also been suggested that with a plastic foam, the deformable initial state within a relatively short time and without further measures changes to the stable final state due to hardening, switching on a post-compression, since the plastic foam is still easily deformable in the initial state and such changes in shape stay. In any case, a homogeneous structure of the foam is strived for on all sides is surrounded by a solid outer skin. In addition, the known method aims to reduce the number of pores of the foam at least approximately unchanged and a homogeneous structure during to maintain the redensification.

According to another known method, the reactive foam mass is poured into molds and then subcooled to such an extent that the inflation agent becomes ineffective and foaming cannot be done. These so frozen bodies that still have no reaction in the sense of a Foaming has taken place can be stored until under at a given time Supply of heat to be brought to thawing and reacting. In particular, after This known method gaps are filled with foam by making pieces this frozen mixture is poured into it. However, this two-step procedure has no influence on the structure of the foam body itself, which has a continuous homogeneous structure and does not have a closed, hard outer skin.

In the method of the invention, the method is for making lightweight molded parts made of curable plastic foams

Register

Collo Rheincollodium Cologne,

Company with limited liability,

Hersei plant,

Hersei near Bonn

Named as inventor:

Pvolf Moroni, Hersei near Bonn;

Peter Kisteneich, Spich near Troisdorf

The task is to produce lightweight molded molded parts from foamable plastics while saving shapes and working time with an inhomogeneous structure, in such a way that the density of the foam body gradually increases from the core to the edge zone and the body itself is enveloped in the edge area by a sintered skin of the plastic foam is. The solution to this problem is that the reaction mixture is introduced in the warm state into a preform cooled below room temperature and the preform thus formed, the density of which is preferably 10 to 20 % below the final density of the foam body, then in a cooled, but not yet fully reacted state is introduced into a finished mold consisting of a mutually movable die and male mold, in which the foam molding reacts exothermically and is finished-formed using the known application of pressure with simultaneous compression of the edge areas. The foam production and subsequent hot deformation thus take place in directly successive work cycles essentially in one heat, namely by utilizing the heat of reaction. It is essential, however, that at the beginning of the reaction the cooled mold causes a delay in foam formation in the edge areas of the foam body adjacent to the walls of the mold, so that the formation of a closed sintered skin in this area is promoted during the final molding. On the other hand, this skin prevents the gases from escaping from the inner cells of the foam body during the final molding process, so that the low density is preserved in this area

709 617/524

3 4

remain. The subsequent application of pressure then has the effect of short-term reshaping for surface

As a result, this density serve remuneration from the outside to the inside.

gradually decreases, so that an inhomogeneous body

is obtained with increasing from the inside out- mass penetrates and fills it, forming here

the density and firm skin of 5 sintered together form a kind of inner skeleton, which is later used for reinforcement

Cell walls. A special supply of heat is advantageous when the prefabricated parts are used. The interior armament

the method according to the invention is not required, tion can by itself and also in conjunction with the

because the exothermic previously described surface reinforcement arising in the reaction process is used

Heat inside the freshly produced foam.

The body is used for the subsequent pressing process using the method according to the present invention will. In addition, hard, semi-hard and soft preformed foam can only be found shortly before Foam blank through the immediate use of polystyrene, phenol-formaldehyde-based materials Further processing by and resin, urea formaldehyde resin, polyvinyl chloride, through is plastic, so that when directly attached, epoxy resin, polyester resin, polyurethane groups are decisive Finished molding an otherwise occurring 15 holding plastics, silicone resin, vulcanizable dangerous structural changes in the core and in the products or others due to polyaddition or poly area the edge zone, as processed by foam blanks obtained by hot molding from merization can occur, not to end. The pace of production is dreaded by the is. reversible reaction speed of the foam

Another advantage of the new process consists of 20 ganges and the foam blank during the pressing process

furthermore, that the required pressure depending on the remaining foam body reaction temperature

determined according to the desired thickness of the foam door produced.

The production speed for foaming can be kept at less than 10 kg / cm ² , so that even for large and large moldings and the immediately subsequent pressing, a very economical construction of molds and 25 is increased by the fact that the presses, if necessary, are heated is guaranteed by a single pre-press mold made of heat-insulating material press mold already a large number of pieces per minute f _en , such as synthetic resins or solidified plastics can be achieved. According to the method of the foams made in accordance with, as by the heat invention may therefore moldings of all kinds of insulating effect, the reaction temperature in the foam-Leichtkunststofien be made in which the ₃₀ blank is increased and thus the plastic deformation specific gravity even under half of 1 , 4 is facilitated during the pressing process. In this context it is noteworthy that the deformation of the location of the blanks produced by known, expensive processes, the foaming process carried out immediately before the molded parts made of non-foamed art, still has a high material density of 1.4 to 1.8 can occur. ₃₅ own temperature, if necessary also

In a further embodiment of the method, it can be carried out without a heated post-press mold.
According to the invention, the foam blank is formed with a foam mold for a pre-soft, suitably supercooled to below 10 ° C., semi-hard and hard foams. This makes it possible to use the initial density of, for example, 0.6 to 0.01 g / cm ¹ _{surface strength of} the finished part except for the 40, namely not only compression described for molded parts and possibly all kinds of sintering, but also in the same way for a tion during repressing to improve the continuous production of z. B. webs or that in the preform foaming process of the Schaumstoffkör- profiles. For this purpose, according to the inventor, a specifically heavy skin with a density is proposed that, in a manner known per se, receives 1.0 g / cm *. This skin formed in the supercooled pre- _4S with continuous pre-foaming in a cold-foam mold encloses the web-shaped or profiled material body produced by the foamed molds as a sealing and solidifying shell. Foam blanks immediately afterwards between heated or unheated calender rollers, when the still hot foam bodies are pressed, this skin is still largely plastic, so that calibration is carried out until it has hardened,
50 Instead of this, it can also be used, in particular for the solidifying inserts or cover layers, production of molded parts of limited dimensions, e.g. B. wood veneers, foils, nonwovens, fabrics can be applied to the well-known press cushion process on angeder basis of metals, plastics, paper, cardboard, with undercut pressed parts or glass entering into an intimate connection. These fabrics are easy to shape in and out of. As a mold material, however, as is also known per se, 55 for elastic molds, depending on the type of temperature during the introduction of the reactive temperature of the press media and depending on the temperature, foam compound can be embedded in the mold or, in the case of the blanks, for example, polyethylene, silicone application of cover layers Rubber, Polytetrafiuoräthylen, Polyvinylchlorid be glued to the mass. The composite molded parts or natural or synthetic rubber produced in this way behave as a result of the embedding or cover layers. Furthermore, additional solidification and an expansion or, according to the invention, elastic materials can partially multiply the intended use for the method. Furthermore, or completely for the post-deformation, the surface of the blank can be used before the pressing process after the, if one uses partially or completely liquid or spraying or immersion processes using a gaseous pressing media. The layer of reactive compounds based on the press media are used, if appropriate, as temperature-controlled gases or condensation, polymerization, polyaddition, volcanic fluids.

nization or with emulsions of all kinds, e.g. B. Also It is also possible to reduce the deformation of the

be provided with bitumen mixtures, the wäh- foam body over a solid mold into the

Claims (7)

the foam body is inserted, to be carried out according to the rubber bag method. But you can also proceed in such a way that the foam body blank is completely enveloped by an elastic and dense molded film and a gas or liquid pressure is allowed to act evenly distributed over the entire surface of the foam blank (autoclave process). Here z. B. a large number of blanks are each wrapped with a dense molded film, which is removed after the Naclipreßvorgang, or immediately after the foaming process, the still hot foam blank with a liquid or gas-tight dip coating based on the repressing process in the autoclave Paint, plastics, bitumen or rubber are provided, which remain on the compacted prefabricated part in order to improve the surface. If necessary, it is possible in the autoclave process in the bag or wrapping process to wrap the foam or foam composite blanks together with a support shape corresponding to the final contour of the finished part, for example made of sheet metal, whereby a perfect, true-to-size reproduction of the finished part can be achieved. In this way, full or hollow prefabricated foam parts or corresponding foam composite bodies can be produced. Patent claims: 1. Process for the production of lightweight molded parts with densities of 0.2 to 0.9 from curable Plastic foams, in particular based on polyurethanes, in which the foamable Mixture of the components is poured into a cooled preform and for the purpose of the crosslinking reaction of the components is introduced into a finished form, where the final deformation of the foam body under Utilization of the exothermic heat of reaction is carried out, characterized in that that the reaction mixture in the warm state in a cooled below room temperature Preform is introduced and the preform thus formed, the density of which is preferably 10 to 20% below the final density, then in cooled, but not yet fully reacted State introduced into a finished form consisting of a matrix and a male mold that can be moved relative to one another is, in which the foam molding reacts exothermically and among known per se Application of pressure with simultaneous compaction of the peripheral areas is finished. 2. The method according to claim 1, characterized in that the preform is ^{cooled to below 1O 0} C and lined in a known manner with solidifying inserts or cover layers or that these deposits or cover layers during the introduction of the reactive foam mass into the mold Mass embedded or pressed onto the mass. 3. The method according to claim 1, characterized in that the final pressing in itself is carried out in a known manner in a form consisting of heat insulating materials. 4. The method according to claim 1, characterized in that in a known manner the Web-shaped or profiled shapes produced in continuous pre-expansion on cooled molds Foam blanks immediately afterwards between heated or unheated calender rolls be calibrated completely. 5. The method according to claim 1, characterized in that the preform is known per se Way is finished pressed by the press pad process. 6. The method according to claim 1, characterized in that the preform is known per se Way is finished-pressed by the rubber bag process. 7. The method according to claim 1, characterized in that the preform in itself in a known manner by the autoclave process is finished pressed. Considered publications:
German patent specifications No. 626 942, 940 787,
323; Austrian Patent No. 190 684;
Swiss Patent No. 329 734;
U.S. Patent No. 2706311.