WO2003002324A1

WO2003002324A1 - Method for producing composite elements

Info

Publication number: WO2003002324A1
Application number: PCT/EP2002/006690
Authority: WO
Inventors: Thomas Sandbank; Peter Reinerth
Original assignee: Basf Aktiengesellschaft
Priority date: 2001-06-27
Filing date: 2002-06-18
Publication date: 2003-01-09
Also published as: DE10292821D2; DE10130649A1

Abstract

The invention relates to a method for producing composite elements having the following layer structure: (i) 2 to 20 mm metal, plastic or wood; (ii) 10 to 300 mm plastic, (iii) 2 to 20 mm metal, plastic or wood. According to said method, the starting materials used for forming layer (ii) are poured in a liquid state into the space between (i) and (iii) and negative pressure is meanwhile generated in said space.

Description

Process for the production of composite elements

description

The invention relates to methods for producing composite elements which have the following layer structure:

(i) 2 mm to 20 mm, preferably 2 mm to 10 mm, particularly preferably 5 mm to 10 mm metal, plastic or wood, preferably metal,

(ii) 10 mm to 300 mm, preferably 10 mm to 100 mm plastic, preferably polyisocyanate polyaddition products

(iii) 2 mm to 20 mm, preferably 2 mm to 10 mm, particularly preferably 5 mm to 10 mm metal, plastic or wood, preferably metal,

by filling the space between (i) and (iii) with liquid starting components for the production of (ii), preferably with a reaction mixture containing (a) isocyanates and (b) compounds reactive toward isocyanates for the production of (ii) polyisocyanate polyadducts , The length data for layers (i), (ii) and (iii) shown at the beginning relate to the thicknesses of the respective layers.

For the construction of ships, for example hulls and cargo space covers, bridges, roofs or high-rise buildings, construction parts must be used that can withstand considerable loads from external forces. Due to these requirements, such construction parts usually consist of metal plates or metal supports, which are reinforced by a corresponding geometry or suitable struts. Due to increased safety standards, the hulls of tankers usually consist of an inner and an outer hull, whereby each hull is made up of 15 mm thick steel plates, which are connected by approx. 2 m long steel struts. Since these steel plates are exposed to considerable forces, both the outer and the inner steel shell are stiffened by welded-on reinforcement elements. A disadvantage of these classic construction parts are both the considerable amounts of steel that are required and the time-consuming and labor-intensive production. In addition, such construction parts have a considerable weight, which results in a lower tonnage of the ships and an increased fuel requirement. In addition, such classic construction elements elements based on steel are very maintenance-intensive, since both the outer surface and the surfaces of the steel parts between the outer and inner shell must be regularly protected against corrosion.

As a replacement for the steel structures, SPS elements (sandwich plate system) are known which contain a composite of metal and plastic. The adhesion of the plastic to the two metal layers creates composite elements with extraordinary advantages over known steel constructions. Such PLC elements are known from the documents US 6 050 208, US 5 778 813, DE-A 198 25 083, DE-A 198 25 085, DE-A 198 25 084, DE-A 198 25 087 and DE-A 198 35 727. These composite elements are usually produced in such a way that the starting materials for the production of the polyisocyanate polyaddition products are poured or injected between the metal plates in a single step. Since the reactive starting components for the production of the plastics in the composite element already start to react when they are mixed and a complete filling of the space between the metal plates is a prerequisite for a flawless product, the process of injecting the starting components is a crucial and critical step in the production of the composite elements ,

The object of the present invention was to develop an improved method for producing the composite elements shown at the beginning. This process was intended to optimize the filling of the space between the plates (i) and (iii), in particular with reactive starting components for the production of plastics (ii) between the plates (i) and (iii). This manufacturing process should, in particular, significantly reduce the proportion of defective elements and enable liquid components to be safely introduced between the plates of the composite element. In particular, cavities between layers (i) and (iii) should be avoided, i.e. the space to be filled between (i) and (iii) should be filled as completely as possible with the starting components for the preparation of (ii).

This object was achieved in that the starting materials for the production of (ii) in the liquid state are filled into the space between (i) and (iii) and during this filling operation a negative pressure in the space to be filled between (i) and (iii ) generated. This has the advantage that the liquid is "sucked" into the room and even small cavities are filled with the liquid. The negative pressure in the space to be filled is preferably 0.2 bar to 0.8 bar, ie the pressure in the form to be filled is 0.8 to 0.2 bar lower than ambient air pressure. The negative pressure which can be generated, for example, by generally known vacuum pumps is preferably achieved in that (i) and / or (iii) in addition to the or the openings (iv) in (i) and / or (iii), via the the starting materials for the production of (ii) are entered, have at least one further opening (v) through which the negative pressure is applied. A hose is preferably interposed between a vacuum pump which generates the negative pressure and the opening (v) in (i). This hose can, for example, be pressed or glued to (i). The amounts of starting materials for the production of (ii) are difficult to measure in such a way that the space (R) to be filled is filled, but overflow is prevented. Therefore, a larger amount of starting components for the production of (ii) in the space between (i) and (iii) is preferably added than it can accommodate. The resulting overflow is preferably discharged through openings (v). As soon as the space between (i) and (iii) is completely filled with the starting components for the production of (ii), the filling can be terminated by means of an increase in the liquid in the hose, which is preferably transparent, and the openings (iv) and (v) be closed. The openings can be closed, for example, with a plastic or metal plug, preferably with a screw cap, which is located either in the overflow vessel or preferably between the overflow vessel and (i) and / or (iii). The openings (iv) preferably remain closed by the fixed mixing head until the end of the curing process of the mixture (a) and (b). The space to be filled between (i) and (iii) preferably has only the openings (iv) and (v), the outflow end, preferably the mixing head, being located at (iv) and the negative pressure being applied to (v). Since according to this preferred embodiment no air can get into the space to be filled, it is possible to generate a vacuum.

Layers (i) and (iii) usually have no features that can be used to attach an outflow end to fill the space between (i) and (iii) with liquids. The expression "outflow end" can be conventional devices by means of which liquids are filled, for example tank sockets, hose ends, mixing heads, static mixers or the like. The outflow end is preferably a mixing head. Mixing heads of this type are generally known and are commercially available, for example, in connection with conventional metering devices for polyurethane systems. The outflow end, preferably the mixing head, can preferably be attached in such a way that the outflow end of the conveying device or a holder for the outflow end of the conveying device. device is screwed to the layer (i) at at least three locations, preferably three to six locations, particularly preferably four or five locations. The liquid is preferably filled into the space between (i) and (iii) through at least one opening (iv) in (i) and / or (iii). For fastening a mixing head, for example, bolts with a thread, which are used to fasten the mixing head or a holder for the mixing head, can preferably be shot into layer (i). These bolts can preferably taper to a point on the side facing away from the thread in order to be able to introduce them more easily into the layer (i). The bolts preferably have a diameter of 6 mm to 20 mm and a length of 8 mm to 42 mm. The thread which is directed outward after the fixing of the bolts, ie on the side of (i) which faces away from (iii), preferably has a length of 4 mm to 30 mm. The bolts are inserted, for example, by shooting with the aid of a bolt pushing tool which is commercially available, for example, from Hilti. Preferably, (i) thus has threads by means of which the outflow end is screwed to (i) at the opening (iv) through which the liquid is filled. To improve the seal between the outflow end and the layer (i) between the layer (i) and the mixing head, an O-ring made of an elastic material can preferably be fixed. Such O-rings are generally known and their dimensions can be matched to the diameter of the opening (iv) and the mixing head. The mixing head is therefore preferably fixed close to the opening (iv) in (i) or (iii) through which the starting materials are introduced.

It is particularly preferred not to fix the outflow end directly to the layer (i), but to fix the outflow end to a holder which is screwed to (i). This holder, which can consist of conventional materials, for example plastics, wood or, preferably, conventional metals, is preferably a construction which has bores through which the threads fixed on (i) are guided and fastened, for example, by means of appropriate nuts , In addition, the holder has fastening elements for the outflow end, for example plug connections, screw connections or edges, with which the outflow end can be clamped to the holder by means of elastic bands. The outflow end is particularly preferably fastened to the holder at at least three points in order to avoid tilting. It is therefore preferred to screw a holder to at least three threads which are attached to (i) and fix the mixing head to this holder. After completion of the composite elements, the bolts can be sawed off, for example, on the surface of (i). The filling of the space between (i) and (iii) can be carried out with conventional conveying devices, preferably continuously, for example with high and low pressure machines, preferably high pressure machines. Filling with a high-pressure machine preferably takes place via one or more, preferably a mixing head in which the starting components are mixed, in a single working step, preferably an injection process. In a single injecting process means that the filling of the space between (i) and (iii), for example with the starting materials for the production of (ii), is not interrupted before the filling is complete. The starting materials are thus preferably given in a single shot under pressure in the space between (i) and (iii). This is especially true if the liquid is a reactive mixture that hardens with the reaction. The starting materials are therefore preferably introduced by means of a high-pressure apparatus through one or more, preferably a mixing head. The space between (i) and (iii) can be filled both in the vertical orientation of (i) and (iii) and in the horizontal orientation of (i) and (iii).

The layers (i) and (iii) can preferably be used as conventional plastic, wood or preferably metal plates, for example iron, steel, copper and / or aluminum plates, with the thicknesses according to the invention.

Both (i) and (ii) can be coated, for example primed, primed, painted and / or coated with customary plastics, in the production of the composite elements according to the invention. (I) and (iii) are preferably used uncoated and particularly preferably cleaned, for example, by conventional sandblasting.

The width of the composite elements can usually be 0.5 m to 10 m, preferably 1 m to 5 m. The length of the composite elements can generally be 0.5 m to 10 m, preferably 1 m to 5 m. Layers (i) and (iii) are preferably arranged in parallel. The lateral edges of the space between (i) and (iii), which is filled in with (ii), are preferably sealed, preferably with plastic, paper or metal foils or plates, particularly preferably metal plates, which are glued, welded or pressed, for example , preferably welded, and which can optionally also serve as spacers.

The space to be filled can preferably be dried. This offers the advantage that in particular liquid components to be filled which are reactive towards water, for example isocyanates, do not react in an undesirable side reaction. Drying, which preferably takes place directly before filling, can be carried out, for example, using hot air or compressed air. Furthermore, the space to be filled between (i) and (iii) can be dried by heating (i) and / or (iii) to a temperature of 20 ° C. to 150 ° C. for a period of 10 minutes to 180 minutes , The space to be filled between (i) and (iii) can preferably be dried by a blower, the air through openings (iv) and (v) in (i) and / or (iii) through the space to be filled between (i) and (iii) conducts.

The openings (iv) and (v) are preferably bores in (i) and / or (iii) with a diameter of 0.5 cm to 5.0 cm in (i) and / or (iii).

The space that is filled between (i) and (iii) with the starting materials for the production of (ii) need not represent the entire space between (i) and (iii). Both (i) and (iii) may protrude beyond the edges of (ii), i.e. only in a partial area of (i) and (iii) does (i) bind via (ii) to (iii). For example, the space between (i) and (iii) can be sealed prior to filling with the starting materials such that the seal is located within the space enclosed by (i) and (iii) and edges of (i) and / or (iii ) survive.

The delivery rate can be varied depending on the volume to be filled. In order to ensure a homogeneous hardening of (ii), the conveying capacity and conveying device is preferably selected such that the space to be filled can be filled with the components for the production of (ii) within 0.5 to 20 minutes. It is preferably low-pressure or particularly preferably high-pressure machines, preferably with piston metering, particularly preferably axial piston metering, the storage tank preferably being designed with an agitator and preferably being temperature-controllable, and preferably having a circuit of storage tank mixing head storage tank, preferably the discharge capacity 0. Is 1 to 3.0 kg / sec.

During the development of suitable manufacturing processes, it was found that an uncontrolled running out of liquid starting components for the manufacture of (ii) can hardly be remedied as a defect. Due to the limited amount per shot, an uncontrolled loss of starting material for the production of (ii) leads to an incomplete filling of the space between (i) and (iii). Due to the quick reaction and the very good adhesion of (ii) to (i) and (iii), incomplete filling creates large areas in the composite element that are not (ii) contain and can no longer be filled with starting components. Such composite elements unfortunately have to be discarded.

In order to prevent loss of starting components, it has therefore proven to be advantageous to check the shape to be filled very precisely for its tightness. Layers (i) and (iii) are usually fixed in a suitable arrangement, for example parallel to one another. The distance is usually chosen so that the space (R) between (i) and (iii) has a thickness of 10 to 300 mm. The fixation of (i) and (iii) can, for example, by spacers e.g. done in a form or suitable holder. The edges of the intermediate space are usually sealed in such a way that the space between (i) and (iii) can be completely filled with the liquid or the starting components for the preparation of (ii), but prevents these starting components from flowing out before they are completely filled , Sealing can be carried out using conventional plastic, paper or metal foils and / or plates, which are glued, welded or pressed on, for example, and which can also serve as a spacer, if necessary. This preferred sealing does not relate to the preferred openings (iv) and (v) which were presented at the beginning.

The tightness of (R) before filling with the starting components is preferably checked by measuring the pressure difference. The expression pressure difference measurement is understood to mean that one tries to build up a pressure difference between the room (R) and the external environment over a certain period of time, for example by trying to create a negative or positive pressure in (R) in relation to the external environment to reach. This can be achieved by conventional vacuum pumps or well-known compressors that pump air or gas into the room (R). If a stable overpressure or underpressure can be generated in (R), this indicates that the cavity is sufficiently dense and compatible with the

Starting components for the production of (ii) can be filled. It should preferably be noted that openings (iv) and (v), which are used to fill (R) with the starting components or as ventilation openings or as overflow openings for the exit of excess starting components, are also temporarily sealed , If necessary, at least one of these openings can be used to connect the vacuum pump or compressor to (R).

The form to be filled preferably consists of the specified ones

Layers (i) and (iii), which are preferably arranged in parallel, and preferably from seals between the layers (i) and (iii) which prevent the liquid from running out when filling. Layer (ii) is thus preferably arranged in an adhesive manner between layers (i) and (iii).

The liquid for the preparation of (ii) preferably contains (a) isocyanates and (b) compounds which are reactive toward isocyanates. Layer (ii) thus preferably represents polyisocyanate polyaddition products. In this document, the terms “starting materials” or “starting components” are to be understood in particular as (a) isocyanates and (b) compounds reactive toward isocyanates, but if appropriate, if they are used, also (c) gases, (d) catalysts, (e) auxiliaries and / or (f) blowing agents.

The reaction of (a) with (b) to (ii) is preferably carried out in the presence of 1 to 50% by volume of gases (c). Polymer polyols are preferably used as (b). The reaction of (a) with (b) is preferably carried out in the presence of (f) blowing agents.

The starting components for the preparation of the polyisocyanate polyadducts are usually mixed at a temperature from 0 to 100 ° C., preferably from 20 to 60 ° C., and introduced into the space between (i) and (iii) as already described. The mixing can be carried out mechanically by means of a stirrer or a stirring screw, but preferably by the countercurrent principle customary in high-pressure machines, in which the A and B component jets meet and mix in the mixing head under high pressure, the jet of each component also being divided can be. The reaction temperature, i.e. The temperature at which the reaction takes place is usually> 20 ° C., preferably 50 to 150 ° C., depending on the material thickness.

The polyisocyanate polyaddition products (ii) of the composite elements produced according to the invention preferably have an elastic modulus of> 275 MPa in the temperature range from -45 to + 50 ° C. (according to DIN 53457), an adhesion to (i) and (iii) of> 4 MPa (according to DIN 53530), an elongation of> 30% in the temperature range from -45 to + 50 ° C (according to DIN 53504), a tensile strength of> 20 MPa (according to DIN 53504) and a compressive strength of> 20 MPa (according to DIN 53421).

The composite elements according to the invention can be prepared in such a way that between (i) and (iii) polyisocyanate polyadducts (ii), usually polyurethanes, which may have urea and / or isocyanurate structures, by reacting (a) isocyanates with ( b) Compounds which are reactive toward isocyanates, if appropriate in the presence of blowing agents (f), 1 to 50% by volume, based on the volume of the polyisocyanate polyadducts, at least one gas (c), (d) catalysts and / or (e) auxiliaries, preferably (ii) adhering to (i) and (iii). The production of such polyisocyanate polyadducts (ii) has been described many times.

The surfaces of (i) and (iii) can preferably be blasted with corundum or iron gravel before the production of the composite elements for cleaning and increasing the surface roughness with sand or steel balls. This blasting can be carried out according to the usual methods, in which the blasting material strikes the surfaces under high pressure, for example. Suitable equipment for such treatment is commercially available.

This treatment of the surfaces of (i) and (iii) which are in contact with (ii) after the reaction of (a) with (b) leads to a significantly improved adhesion of (ii) to (i) and ( iii). The blasting is preferably carried out directly before the introduction of the components for the production of (ii) into the space between (i) and (iii). The surfaces of (i) and (iii) to which

(ii) should adhere, are preferably free of inorganic and / or organic substances which reduce adhesion, for example dust, dirt, oils and fats or substances generally known as mold release agents.

The starting materials (a), (b), (c), (d), (e) and (f) in the process according to the invention are described below by way of example:

Suitable isocyanates (a) are the aliphatic, cycloaliphatic, araliphatic and / or aromatic isocyanates known per se, preferably diisocyanates, which may or may not have been biuretized and / or iscyanurated using generally known methods. The following may be mentioned as examples: alkylene diisocyanates with 4 to 12 carbon atoms in the alkylene radical, such as 1, 12-dodecane diisocyanate, 2-ethyl-tetramethylene diisocyanate-1,4, 2-methylpentamethylene diisocyanate-1,5, tetramethylene diisocyanate- 1,4, lysine ester diisocyanates (LDI), hexamethylene diisocyanate-1, 6 (HDI), cyclohexane-1,3- and / or 1,4-diisocyanate, 2,4- and 2,6-hexahydrotoluenediisocyanate and the corresponding isomer mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane diisocyanate and the corresponding isomer mixtures, 1-isocyanate-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), 2,4- and / or 2,6-tolylene diisocyanate (TDI), 4,4'-, 2,4'- and / or 2,2'-diphenylmethane diisocyanate (MDI), polyphenylpolymethylene polyisocyanates and / or mixtures containing at least two of the above isocyanates. In addition, ester, urea, allo- di- and / or polyisocyanates containing phanate, carbodiid, uretdione and / or urethane groups can be used in the process according to the invention. 2,4'-, 2,2'- and / or 4,4'-MDI and / or polyphenylpolymethylene polyisocyanates are preferably used, particularly preferably mixtures comprising polyphenylpolymethylene polyisocyanates and at least one of the MDI isomers.

Compounds which are reactive towards isocyanates can be used, for example, as compounds which have hydroxyl, thiol and / or primary and / or secondary amino groups as isocyanate-reactive groups and usually have a molecular weight of 60 to 10,000 g / mol, e.g. Polyols selected from the group of polymer polyols, polyether polyalcohols, polyester polyalcohols, polythioether polyols, hydroxyl group-containing polyacetals and hydroxyl group-containing aliphatic polycarbonates or mixtures of at least two of the polyols mentioned. These compounds usually have a functionality towards isocyanates of 2 to 6 and a molecular weight of 400 to 8000 and are generally known to the person skilled in the art.

Examples of suitable polyether polyalcohols are those which, according to known technology, are obtained by addition of alkylene oxides, for example tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide, styrene oxide and preferably ethylene oxide and / or 1,2-propylene lenoxid are available on usual starter substances. Known aliphatic, araliphatic, cycloaliphatic and / or aromatic compounds which contain at least one, preferably 2 to 4 hydroxyl groups and / or at least one, preferably 2 to 4 amino groups can be used as starter substances. For example, ethanediol, diethylene glycol, 1,2- or 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, glycerol, trimethyl thylolpropane, neopentyl glycol, sugar, for example sucrose, pentaerythritol, sorbitol, ethylenediamine, propanediamine, neopentanediamine, hexamethylenediamine, isophoronediamine, 4,4'-diaminodicyclohexylmethane, 2- (ethylamino) ethylamine, 3- (methylamino) propylamine , Dipropylenetriamine and / or N, N'-bis (3-aminopropyl) ethylenediamine can be used.

The alkylene oxides can be used individually, alternately in succession or as mixtures. Alkylene oxides which lead to primary hydroxyl groups in the polyol are preferably used. Particularly preferred polyols are those which have been alkoxylated with ethylene oxide at the end of the alkoxylation and thus have primary hydroxyl groups. Compounds known from polyurethane chemistry, preferably styrene-acrylonitrile graft polyols, can be used as polymer polyols, a special class of polyether polyols.

Especially the use of polymer polyols can shrink the

Significantly reduce the polyisocyanate polyaddition product, for example the polyurethane, and thus lead to improved adhesion of (ii) to (i) and (iii). If necessary, blowing agents (f) and / or gases (c) can preferably be used as further measures to reduce the shrinkage.

Suitable polyester polyols can be prepared, for example, from organic dicarboxylic acids with 2 to 12 carbon atoms, preferably aliphatic dicarboxylic acids with 4 to 6 carbon atoms, and polyhydric alcohols, preferably diols, with 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms. The polyester polyols preferably have a functionality of 2 to 4, in particular 2 to 3, and a molecular weight of 480 to 3000, preferably 600 to 2000 and in particular 600 to 1500.

The composite elements according to the invention are preferably produced using polyether polyalcohols as component (b) for the reaction with the isocyanates, advantageously those with an average functionality compared to isocyanates of 1.5 to 8, preferably 2 to 6, and a molecular weight of 400 to 8000.

The use of polyether polyalcohols offers considerable advantages due to the improved stability of the polyisocyanate polyaddition products against hydrolytic cleavage and due to the lower viscosity, in each case in comparison with polyester polyalcohols. The improved stability against hydrolysis is particularly advantageous when used in shipbuilding. The lower viscosity of the polyether polyalcohols and the reaction mixture for producing (ii) containing the polyether polyalcohols enables the space between (i) and (iii) to be filled more quickly and easily with the reaction mixture for producing the composite elements. Due to the considerable dimensions, particularly of structural parts in shipbuilding, low-viscosity liquids are of considerable advantage.

As isocyanate-reactive compounds, furthermore, in addition to the compounds mentioned with a customary molecular weight of 400 to 8000, optionally diols and / or triols with molecular weights of 60 to <400 as chain extenders and / or crosslinking agents in the inventive compound driving can be used. However, the addition of chain extenders, crosslinking agents or, if appropriate, mixtures thereof can prove to be advantageous for modifying the mechanical properties, for example the hardness. The chain extenders and / or crosslinking agents preferably have a molecular weight of 60 to 300. For example, aliphatic, cycloaliphatic and / or araliphatic diols with 2 to 14, preferably 4 to 10 carbon atoms, such as, for example, ethylene glycol, 1,3-propanediol, 1, 10-decanediol, 10-, o-, m-, p-dihydroxycyclohexane , Diethylene glycol, dipropylene glycol and preferably butanediol-1, 4, hexanediol-1, 6 and bis- (2-hydroxy-ethyl) -hydroquinone, triols, such as 1,2,4-, 1, 3, 5-trihydroxy- cyclohexane, glycerol and trimethylolpropane, low molecular weight hydroxyl group-containing polyalkylene oxides based on ethylene and / or 1,2-propylene oxide and the aforementioned diols and / or triols as starter molecules and / or diamines such as diethyltoluenediamine and / or 3,5 -Dimethylthio-2,4-toluenediamine.

If chain extenders, crosslinking agents or mixtures thereof are used to prepare the polyisocyanate polyaddition products, they are advantageously used in an amount of 0 to 30% by weight, preferably 1 to 30% by weight, based on the weight of the total isocyanates used reactive compounds (b).

In addition, aliphatic, araliphatic, cycloaliphatic and / or aromatic carboxylic acids can be used as (b) to optimize the curing process in the preparation of (ii). Examples of such carboxylic acids are formic acid, acetic acid, succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, citric acid, benzoic acid, salicylic acid, phenylacetic acid, phthalic acid, toluenesulfonic acid, derivatives of the acids mentioned, isomers of the acids mentioned and any mixtures of the acids mentioned. The proportion by weight of these acids can be 0 to 5% by weight, preferably 0.2 to 2% by weight, based on the total weight of (b).

The use of amine-started polyether polyalcohols can also improve the curing behavior of the reaction mixture for the preparation of (ii). Compounds (b), like the other components for the preparation of (ii), are preferably used with the lowest possible water content in order to avoid the formation of carbon dioxide by reaction of the water with isocyanate groups. As component (c) for the preparation of (ii), generally known compounds can be used which have a boiling point at a pressure of 1 bar of less (ie at temperatures lower than) -50 ° C., for example air, carbon dioxide, nitrogen, helium and / or neon. Air is preferably used. Component (c) is preferably inert towards component (a), particularly preferably towards components (a) and (b), ie a reactivity of the gas towards (a) and (b) is scarcely, preferably not detectable. The use of gas (c) differs fundamentally from the use of conventional blowing agents for the production of foamed polyurethanes. While conventional blowing agents (f) are used in liquid form or are soluble in the polyol component in the case of gaseous physical blowing agents) and during the reaction they either evaporate due to the development of heat or in the case of water due to the reaction with If the isocyanate groups develop gaseous carbon dioxide, in the present invention component (c) is preferably already used in gaseous form as an aerosol, for example in the polyol component.

Generally known compounds can be used as catalysts (d), which greatly accelerate the reaction of isocyanates with the compounds reactive towards isocyanates, a total catalyst content of preferably 0.001 to 15% by weight, in particular 0.05 to 6% by weight, based on the weight of the total isocyanate-reactive compounds used. For example, the following compounds can be used: triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine,

N, N, N ', N'-tetramethyl-diamino-diethyl ether, bis- (dimethylamino-propy1) urea, N-methyl- or N-ethylmorpho1in, N-cyc1ohexy1-morpholine, N, N, N', N 'Tetramethylethylenediamine, N, N, N', N'-tetramethylbutanediamine, N, N, N ', N'-tetramethylhexanediamine-1, 6, pentamethyldiethylenetriamine, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1, 2- Dimethylimidazole, 1-azabicyclo (2, 2.0) octane, 1,4-diazabicyclo- (2,2,2) octane (Dabco) and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl and N -Ethyl-diethanolamine, dimethylaminoethanol, 2- (N, N-dimethylaminoethethoxy) ethanol, N, N ', N "-Tris- (dialkylaminoalkyl) hexahydrotriazine, for example N, N', N" -Tris- (dimethylaminopropyl ) -s-hexahydrotriazine, iron (II) chloride, zinc chloride, lead octoate and preferably tin salts such as tin dioctoate, tin diethylhexoate, dibutyltin dilaurate and / or dibutyldilauryltin mercaptide, 2, 3-dimethyl-3, 4,5, β-teidinium tetrahydro pyrrole , such as tetramethylammonium hydroxide, alk alihydroxides, such as sodium hydroxide, alkali alcoholates, such as sodium methylate and potassium isopropylate, and / or Al- potash salts of long-chain fatty acids with 10 to 20 carbon atoms and optionally pendant OH groups.

It has proven very advantageous to carry out the preparation of 5 (ii) in the presence of (d) in order to accelerate the reaction.

The reaction mixture for the preparation of the polyisocyanate polyaddition products (ii) can optionally (e) be admixed with auxiliaries. Examples include fillers, surface-active substances, dyes, pigments, flame retardants, hydrolysis protection agents, fungistatic, bacteriostatic substances and foam stabilizers.

15 For example, surface-active substances include Compounds into consideration which serve to support the homogenization of the starting materials and, if appropriate, are also suitable for regulating the structure of the plastics. Examples include emulsifiers such as the sodium salts of castor oil sulfates

20 or of fatty acids and salts of fatty acids with amines, e.g. oleic acid diethylamine, stearic acid diethanolamine, ricinoleic acid diethanolamine, salts of sulfonic acids, e.g. Alkali or ammonium salts of dodecylbenzene or dinaphthylmethane disulfonic acid and ricinoleic acid. The surface-active substances are more common-

25, in amounts of from 0.01 to 5% by weight, based on 100% by weight of the total isocyanate-reactive compounds (b) used.

Suitable flame retardants are, for example, tricresylphosphate

30 phat, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1, 3-dichloropropyl) phosphate, tris (2, 3-dibromopropyl) phosphate, tetrakis (2-chloroethyl) Ethylene diphosphate, dimethyl methane phosphonate, diethanolaminomethylphosphonic acid diethyl ester and commercially available halogen-containing flame retardant polyols. In addition to the

Halogen-substituted phosphates already mentioned can also contain inorganic or organic flame retardants, such as red phosphorus, aluminum oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, expandable graphite or cyanuric acid derivatives, such as e.g. Melamine, or mixtures of at least two flame

40 protective agents, e.g. Ammonium polyphosphates and melamine and optionally corn starch or ammonium polyphosphate, melamine and expandable graphite and / or optionally aromatic polyesters are used to flame retard the polyisocyanate polyaddition products. In general, it has been found to be useful to 5 to

45 50% by weight, preferably 5 to 25% by weight, of the flame To use protective agents, based on the weight of the total isocyanate-reactive compounds used.

Fillers, in particular reinforcing fillers, are to be understood as the conventional organic and inorganic fillers, reinforcing agents, weighting agents, agents for improving the abrasion behavior in paints, coating agents, etc., which are known per se. The following may be mentioned as examples: inorganic fillers such as silicate minerals, for example layered silicates such as antigorite, serpentine, hornblende, amphibole, chrisotile and talc, metal oxides such as kaolin, aluminum oxides, titanium oxides and iron oxides, metal salts such as chalk, heavy spar and inorganic pigments, such as cadmium sulfide and zinc sulfide, and glass, etc. Kaolin (china clay), aluminum silicate and coprecipitates made from barium sulfate and aluminum silicate as well as natural and synthetic fibrous minerals such as wollastonite, metal and glass fibers of short length are preferably used. Examples of suitable organic fillers are: carbon, melamine, rosin, cyclopentadienyl resins and graft polymers as well as cellulose fibers, polyamide, polyacrylonitrile, polyurethane, polyester fibers based on aromatic and / or aliphatic dicarboxylic acid esters and in particular carbon fibers. The inorganic and organic fillers can be used individually or as mixtures.

10 to 70% by weight of fillers, based on the weight of (ii), are preferably used as (e) auxiliaries in the preparation of (ii). Talc, kaolin, calcium carbonate, heavy spar, glass fibers and / or microglass balls are preferably used as fillers. The size of the particles of the fillers should preferably be chosen so that the introduction of the components for the production of (ii) into the space between (i) and (iii) is not hindered. The fillers particularly preferably have particle sizes of <0.5 mm.

The fillers are preferably used in a mixture with the polyol component in the reaction for the production of the polyisocyanate polyaddition products.

The fillers can be used to reduce the thermal expansion coefficient of the polyisocyanate polyaddition products, which is greater than that of steel, for example, and thus to match that of the steel. This is particularly advantageous for a sustainable, firm bond between the layers (i), (ii) and (iii), since this results in lower stresses between the layers under thermal stress. For the preparation of (ii), customary foam stabilizers which are commercially available and are generally known to the person skilled in the art are preferably used as (e), for example generally known polysiloxane-polyoxyalkylene block copolymers, for example Tegostab 5 2219 from Goldschmidt. The proportion of these foam stabilizers in the preparation of (ii) is preferably 0.001 to 10% by weight, particularly preferably 0.01 to 10% by weight, in particular 0.01 to 2% by weight, based on the weight of the for the production of (ii) components (b), (e) and optionally 10 (d). The use of these foam stabilizers has the effect that component (c) in the reaction mixture is stabilized to produce (ii).

15 blowing agents known from polyurethane chemistry can be used as blowing agents (f), for example physical and / or chemical blowing agents. Such physical blowing agents generally have a boiling point at a pressure of 1 bar greater than (i.e. at temperatures higher than) -50 ° C. Examples of physical blowing agents are e.g. CFCs, 20 HCFCs, HFCs, aliphatic hydrocarbons, cycloaliphatic hydrocarbons, each with, for example, 4 to 6 carbon atoms or mixtures of these substances, for example trichlorofluoromethane (boiling point 24 ° C.), chlorodifluoromethane (boiling point -40.8 ° C.), dichlorofluoroethane (boiling point 32 ° C), chlorodifluoroethane 25 (boiling point -9.2 ° C), dichlorotrifluoroethane (boiling point 27.1 ° C), terafluoroethane (boiling point -26.5 ° C), hexafluorobutane (boiling point 24.6 ° C), iso-pentane (boiling point 28 ° C), n- Pentane (boiling point 36 ° C), cyclopentane (boiling point 49 ° C).

30 As chemical blowing agents, i.e. Blowing agents which form gaseous products due to a reaction, for example with isocyanate groups, come, for example, water, hydrate-containing compounds, carboxylic acids, tert.-alcohols, e.g. t-butanol, carbamates, for example those described in EP-A 1000955, in particular

35 further described on pages 2, lines 5 to 31 and page 3, lines 21 to 42 carbamates, carbonates, e.g. Ammonium carbonate and / or ammonium hydrogen carbonate and / or guanidine carbamate.

Water and / or carbamates are preferably used as blowing agents (f).

The blowing agents (f) are preferably used in an amount which is sufficient to obtain the preferred density of (ii) from 350 to 45 1200 kg / m ³ . This can be determined using simple routine experiments which are generally known to the person skilled in the art. The blowing agents (f) are particularly preferred in an amount of 0.05 to 10% by weight, in particular 0.1 to 5% by weight, based in each case on the total weight of the polyisocyanate polyaddition products.

The weight of (ii) by definition corresponds to the weight of the components (a), (b) and, if appropriate, (c), (d), (e) and / or (f) used to produce (ii).

To produce the polyisocyanate polyaddition products according to the invention, the isocyanates and the compounds which are reactive toward isocyanates are reacted in amounts such that the equivalence ratio of NCO groups of the isocyanates (a) to the sum of the reactive hydrogen atoms of the compounds which are reactive toward isocyanates (b) and optionally (f) 0.85 to 1.25: 1, preferably 0.95 to 1.15: 1 and in particular 1 to 1.05: 1. If (ii) at least partially contain isocyanurate groups, a ratio of NCO groups to the sum of the reactive hydrogen atoms of 1.5 to 60: 1, preferably 1.5 to 8: 1, is usually used.

The polyisocyanate polyaddition products are usually produced by the one-shot process or by the prepolymer process, for example with the aid of high-pressure or low-pressure technology.

It has proven to be particularly advantageous to work according to the two-component process and the compounds (b) reactive towards isocyanates, optionally the blowing agents (f) and optionally the catalysts (d) and / or auxiliaries (e) in the component (A) ( Polyol component) to combine and preferably to mix intimately and to use the isocyanates (a) as component (B).

Component (c) can be fed to the reaction mixture comprising (a), (b) and optionally (f), (d) and / or (e), and / or the individual components (a), (b) already described , (A) and / or (B). The component that is mixed with (c) is usually in liquid form. The components are preferably mixed into component (b).

The corresponding component can be mixed with (c) by generally known methods. For example, (c) can be supplied to the corresponding component by generally known loading devices, for example air loading devices, preferably under pressure, for example from a pressure vessel or by a compressor, for example through a nozzle. There is preferably extensive mixing of the speaking components with (c), so that gas bubbles of (c) in the usually liquid component preferably have a size of

0.0001 to 10, particularly preferably 0.0001 to 1 mm.

The content of (c) in the reaction mixture for the preparation of (ii) can be determined in the return line of the high-pressure machine using generally known measuring devices via the density of the reaction mixture. The content of (c) in the reaction mixture can preferably be regulated automatically on the basis of this density via a control unit. The component density can be determined and regulated online during the normal circulation of the material in the machine, even at a very low circulation speed.

The composite elements obtainable according to the invention are used above all in areas in which construction elements are required which can withstand great forces, for example as construction parts in shipbuilding, e.g. in ship hulls, for example ship's double hulls with an outer and an inner wall, and cargo space covers, cargo space partitions, loading flaps or in structures, for example bridges or as construction elements in house construction, in particular in high-rise buildings.

The composite elements according to the invention are not to be confused with classic sandwich elements, which contain a polyurethane and / or polyisocyanurate rigid foam as the core and are usually used for thermal insulation. Known sandwich elements of this type would not be suitable for the mentioned application areas due to their comparatively lower mechanical resilience.

Claims

claims

1. Process for producing composite elements which have the following layer structure:

(i) 2 to 20 mm metal, plastic or wood

(ii) 10 to 300 mm plastic,

(iii) 2 to 20 mm metal, plastic or wood

characterized in that the starting materials for the production of (ii) in liquid state are filled into the space between (i) and (iii) and during this filling process a negative pressure is created in the space to be filled between (i) and (iii).

2. The method according to claim 1, characterized in that the negative pressure in the space to be filled is 0.2 to 0.8 bar.

3. The method according to claim 1, characterized in that (i) and / or (iii) in addition to the or the openings (iv) in (i) and / or (iii), via which the starting materials for the preparation of (ii) be entered, have at least one further opening (v) through which the negative pressure is applied.

4. The method according to claim 1, characterized in that one enters the starting materials continuously without interruption in a single step in the space to be filled between (i) and (iii).

5. The method according to claim 1, characterized in that one enters the starting materials by means of a high pressure apparatus via one or more mixing heads.

6. The method according to claim 5, characterized in that the mixing head at the opening (iv) in (i) or (iii), through which the entry of the starting materials takes place, tightly fixed.

7. The method according to claim 5, characterized in that one screws the mixing head or a holder for the mixing head at least three locations with the layer (i).

8. The method according to claim 1, characterized in that (ii) represent polyisocyanate polyadducts obtainable by reaction of the starting materials (a) isocyanate and (b) compounds reactive toward isocyanates.

9. Composite elements obtainable by a method according to one of claims 1 to 8.

10. Ships or structures containing composite elements according to claim 9.