WO2002040264A2

WO2002040264A2 - Method for producing composite elements

Info

Publication number: WO2002040264A2
Application number: PCT/EP2001/013021
Authority: WO
Inventors: Matthias Hefner; Heinz Forster; Gerhard Bernard; Georg Riess; Georg Knoblauch
Original assignee: Basf Aktiengesellschaft
Priority date: 2000-11-14
Filing date: 2001-11-10
Publication date: 2002-05-23
Also published as: AU2002218293A1; DE10056377A1; WO2002040264A3

Abstract

The invention relates to composite elements having a structure comprising the following layers: (i) between 2 and 20 mm of metal, (ii) between 10 and 300 mm of polyisocyanate polyaddition products which can be obtained by reacting (a) isocyanates with (b) polymer polyols, as compounds which react with ioscyanates, and (iii) between 2 and 20 mm of metal. The invention is characterised in that the metallic layers (i) and (iii) are fixed in such a way that area (R) is formed between the same for layer (ii), (R) is sealed, with the exception of at least one opening for filling (R) and at least one other opening, and the sealing of (R) is checked by measuring the pressure difference on the opening(s), before filling (R) with the starting components for producing (ii).

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,

(ii) 10 mm to 300 mm, preferably 10 mm to 100 mm plastic, preferably polyisocyanate polyaddition products obtainable by reacting (a) isocyanates with (b) compounds reactive toward isocyanates, (iii) 2 mm to 20 mm, preferably 2 mm up to 10 mm, particularly preferably 5 mm to 10 mm metal.

The length specifications for the layers (i), (ii) and (iii) relate to the thickness of the respective layer.

For the construction of ships, for example ship 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, hulls of tankers usually consist of an inner and an outer hull, with each hull being constructed from 15 mm thick steel plates which are connected to one another 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 is the considerable amount of steel that is required, as well as the time-consuming and labor-intensive production. In addition, such structural 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 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 have to 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 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 this way that the starting materials for the production of the polyisocyanate polyadducts are poured or sprayed between the metal plates in a single step.

The object of the present invention was to develop an improved method for producing the composite elements shown at the beginning. This manufacturing process should in particular significantly reduce the proportion of defective elements.

This object was achieved in that the metal layers (i) and (iii) were fixed in such a way that the space (R) for the layer (ii) was formed between them, (R) with the exception of at least one opening for filling Seals (R) and at least one other opening and, before filling (R) with the starting components for the production of (ii), the sealing of (R) is checked by measuring the pressure difference at the openings.

During the development of suitable manufacturing processes, it was found that an uncontrolled running out of liquid starting components for the production of (ii) must be avoided in order to avoid faulty composite elements. It has proven to be particularly advantageous to fill the space between (i) and (iii) with one shot, ie to be carried out in a single, continuous operation. Due to the limited amount of (a) and (b) per filling process, an uncontrolled loss of starting material for the production of (ii) leads to incomplete filling of the space between (i) and (iii), which leads to a reduced adhesive area of ( ii) leads to (i) and (iii), as a result of which the functionality of the composite elements is severely impaired or even canceled. Such composite elements may have to be discarded.

In order to prevent loss of starting components, it has therefore proven to be crucial to check the cavity to be filled very carefully for its seal. Layers (i) and (iii) are usually fixed in a suitable arrangement, for example parallel to one another. The distance is usually like this chosen so that the space between (i) and (iii) has a thickness of 10 to 300 mm. (I) and (iii) can be fixed, for example, by spacers, for example in a form or in a 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 starting components for the production of (ii), but prevents these starting components from flowing out. Sealing can be done with conventional plastic, paper or metal foils and / or plates, which are glued, welded or pressed, for example, and which can also serve as spacers, if necessary. Usually at least one, preferably an opening for filling with the starting components is provided for the production of (ii). In addition, at least one further opening is provided, from which air can escape during the filling process and, after the space between (i) and (iii) has been completely filled with the starting components, can be used to produce (ii) excess starting components. This vent or overflow opening is preferably placed at the highest point of the composite element. The openings can be in (i) and / or (iii) as well as on the edges between (i) and (iii). The openings are preferably bores with a diameter of 0.5 to 5.0 cm, preferably 0.5 to 4.0 cm in (i) and / or (iii).

According to the invention, the tightness of (R) is checked by measuring the pressure difference. The expression pressure difference measurement means that one tries to build up a pressure difference between the space (R) and the external environment, 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 the openings that are provided for filling (R) with the starting components or as ventilation openings for air or 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 vacuum generated should preferably 0.1 to 0.8, preferably 0.3 bar to 0.5 bar, particularly preferably 0.4 bar, the overpressure 0.1 to 0.8, preferably 0.4 bar to 0.6 cash, especially before trains 0, 5 bar. The vacuum or overpressure generated in this way should not change over a period of 1 to 3 minutes, preferably over 2 minutes. The pressure difference can be recorded or evaluated using standard pressure measuring devices.

The composite elements preferably have the following layer structure:

(i) 2 to 20 mm metal, (ii) 10 to 300 mm, preferably 10 to 100 mm polyisocyanate polyadducts with a density of 350 to 1200 kg / m ³ obtainable by reacting (a) isocyanates with (b) against isocyanates reactive compounds in the presence of (f) blowing agents and / or 1 to 50% by volume, based on the volume of the polyisocyanate polyaddition products, at least one gas (c) and, if appropriate, (d) catalysts and / or (e) auxiliaries and / or additives, (iii) 2 to 20 mm metal.

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) on .

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, optionally in the presence of blowing agents (f) and preferably 1 to 50% by volume, based on the volume of the polyisocyanate polyadducts, of at least one gas (c) and particularly preferably (d) catalysts and / or (e ) Produces auxiliaries and / or additives which adhere to (i) and (iii).

The reaction is preferably carried out in a closed form, ie (i) and (iii), when filled with the starting components for the production of (ii), are in a form which, after complete entry of the starting components, is will close. After the starting components have been converted to produce (ii), the composite element can be removed from the mold.

The surfaces of (i) and (iii) are preferably blasted with sand or steel balls, preferably with corundum or iron gravel, before the production of the composite elements for cleaning and increasing the surface roughness.

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 sandblasting 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) is to adhere are preferably free of inorganic and / or organic substances which reduce adhesion, for example dust, dirt, oils and greases or are generally known as mold release agents substances.

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 space between (i) and (iii) can be filled with (a) and (b) and, if appropriate, the further starting materials, using conventional conveying devices, preferably continuously, for example high and low pressure machines, preferably high pressure machines.

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 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. Conventional metals can be used as layers (i) and (iii), usually plates, for example iron, conventional steel, all types of refined steel, aluminum and / or copper.

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

The preparation of the polyisocyanate polyadducts (ii), usually polyurethane and optionally polyisocyanurate products, in particular polyurethane elastomers, by reacting (a) isocyanates with (b) compounds reactive toward isocyanates, optionally in the presence of (f) blowing agents, (d) catalysts (e) Aids and / or additives and / or (c) gases have been described many times.

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. In particular, 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 called isocyanates. In addition, di- and / or polyisocyanates containing ester, urea, allophanate, carbodiimide, uretdione and / or urethane groups can be used in the process according to the invention. Preference is given to 2,4 ^λ -, 2,2'- and / or 4,4'-MDI ^λ and / or polyphenylpolymethylene polyisocyanates einge- sets, particularly preferably mixtures containing polyphenylpolymethylene polyisocyanates and at least one of the MDI isomers.

Compounds which are reactive towards isocyanates can be used, for example, compounds which have hydroxyl, thiol and / or primary and / or secondary amino groups as isocyanate-reactive groups and usually have a molar mass of 60 to 10,000 g / mol, eg 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, neopentylglycol, sugar, for example sucrose, pentaerythritol, sorbitol, ethylenediamine, propanediamine, neopentanediamine, hexamethylenediamine, isophoronediamine, 4, 4'-diaminodicyclohexylmethane, 2- (ethylamino) ethylentryamine, 3- (methylamino, 3- (methylamino Dipropylenetriamine and / or N, N ^X- 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.

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 become. 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 the production of (ii) containing the polyether polyalcohol enables the space between (i) and (iii) to be filled more quickly and easily with the reaction mixture for the production of the composite elements. Due to the considerable dimensions, particularly of structural parts in shipbuilding, low-viscosity liquids are of considerable advantage.

Also suitable as compounds reactive toward isocyanates are substances which have a hydrocarbon skeleton with 10 to 40 carbon atoms and 2 to 4 groups reactive toward isocyanates. The term hydrocarbon skeleton is to be understood as an uninterrupted sequence of carbon atoms which is not interrupted, for example in the case of ethers, with oxygen atoms. Such substances, also referred to below as (b3), can be used, for example, castor oil and its derivatives.

In addition to the compounds mentioned with a customary molecular weight of 400 to 8000, diols and / or triols with molecular weights of 60 to <400 can also be used as chain extenders and / or crosslinking agents in the process according to the invention as compounds which are reactive toward isocyanates. 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, wise 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-di-hydroxycyclohexane, 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, these 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 used Compounds (b) reactive towards isocyanates are used.

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).

With the use of amine-started polyether polyalcohols, the hardening behavior of the reaction mixture for the preparation of (ii) can also be improved. The 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.

The preferred use of polymer polyols, especially styrene

Acrylonitrile graft polyols, can shrink the polyisocyanate

Polyaddition product, for example, significantly reduce the polyurethane and thus to an improved adhesion of (ii)

(i) and (iii) lead. If necessary, blowing agents (f) and / or gases (c) can preferably be used as a further measure to reduce the shrinkage. 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, preferably a total catalyst content of 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-propyl) -urea, N-methyl- or N-ethylmorpholine, N-cyclohexyl-morpholine, N, N, N ', N '-Tetramethylethylenediamine, N, N, N', N'-Tetramethylbutandiamin, N, N, N ', N'-Tetramethylhexdiamin-1, 6, Pentamethyldiethylenetriamine, Dirnethylpiperazin, N-Dimethylaminoethylpiperidin, 1, 2-dimethylimidazole, l-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-dimethylaminoethoxy) ethanol, N, N *, N '* -Tris- (dialkylaminoalkyl) hexahydrotriazine, e.g. N, NN ^{λ λ} -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, 6-tetrahydropyrimidine, tetraalkylammonium hydroxides such as tetramethylamm onium hydroxide, alkali hydroxides, such as sodium hydroxide, alkali alcoholates, such as sodium methylate and potassium isopropyl lat, and / or alkali metal 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 (ii) in the presence of (d) in order to accelerate the reaction.

Optionally, (e) auxiliaries and / or additives can be incorporated into the reaction mixture for producing the polyisocyanate polyaddition products (ii). Examples include fillers, surface-active substances, dyes, pigments, flame retardants, hydrolysis protection agents, fungistatic, bacteriostatic substances and foam stabilizers.

As surface-active substances there are e.g. 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 or of fatty acids and salts of fatty acids with amines, e.g. oleic acid diethylamine, stearic acid diethanolamine, ricinoleic acid diethanola in, salts of sulfonic acids, e.g. Alkali or ammonium salts of dodecylbenzene or dinaphthylmethane disulfonic acid and ricinoleic acid. The surface-active substances are usually used 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, ris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate, tetrakis ( 2-chloroethyl) ethylenediphosphate, dimethyl methane phosphonate, diethanolaminomethylphosphonic acid diethyl ester and commercially available halogen-containing bottle protection polyols. In addition to the halogen-substituted phosphates already mentioned, 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 melamine, or mixtures of at least two flame retardants, such as ammonium polyphosphates and melamine and melamine optionally corn starch or ammonium polyphosphate, melamine and expandable graphite and / or optionally aromatic polyesters can be used to flame retard the polyisocyanate polyaddition products. In general, it has proven to be advantageous to add 5 to 50% by weight, preferably 5 to 25% by weight, of the flame retardants mentioned, 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 sheet 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. Preferably used are kaolin (china clay), aluminum silicate and coprecipitates made from barium sulfate and aluminum silicate, and natural and synthetic fibrous minerals such as wollastonite, metal and glass fibers of short length. Examples of suitable organic fillers are: carbon, melamine, colophony, cyclopentadienyl resins and graft polymers, and 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.

In the preparation of (ii), preference is given to using 10 to 70% by weight of fillers, based on the weight of (ii), as (e) auxiliaries and / or additives. Talc, kaolin, calcium carbonate, heavy spar, glass fibers and / or micro glass 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 impeded. 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 serve to reduce the coefficient of thermal expansion of the polyisocyanate polyaddition products, which is greater than that of steel, for example, and thus to adapt it to that of the steel. This is particularly advantageous for a permanently strong 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 (d). The use of these foam stabilizers has the effect that component (c) in the reaction mixture is stabilized to produce (ii).

5 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, 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 5 (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).

0 As a chemical blowing agent, 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, carba ate, for example that described in the document EP-A 1000955, in particular 5 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.

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

The blowing agents (f) are preferably used in an amount sufficient to obtain the preferred density of (ii). 5 This can be determined using simple routine experiments that 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 from 0.1 to 5% by weight, based in each case on the total weight of the polyisocyanate polyadducts.

No blowing agents are particularly preferably used.

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

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 towards 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) which are reactive toward isocyanates, if appropriate the blowing agents (f) and if appropriate the catalysts (d) and / or auxiliaries and / or additives (e) in the Combine component (A) (polyol component) and preferably mix them intimately and 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 container or by a compressor, for example through a nozzle. the. The corresponding components are preferably thoroughly mixed 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 production 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 sandwich element can be produced, for example, by sealing the space to be filled between (i) and (iii) with the starting components for the production of (ii) with the exception of a supply line and discharge line for the starting components, and the starting components (a), ( b) and optionally (c), (d), (f) and / or (e), preferably mixed via the feed line, preferably with a conventional high-pressure machine, into the space between (i) and (iii).

The starting components are usually mixed at a temperature of 0 to 100 ° C., preferably 20 to 60 ° C., and introduced into the space between (i) and (iii) as already described. Mixing can be carried out mechanically using a stirrer or a stirring screw, but preferably using 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 being used can also be divided. 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 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, for example 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, especially in high-rise buildings. The composite elements according to the invention should not be confused with classic sandwich elements which contain a polyurethane and / or polyisocyanurate hard foam as the core and are usually used for thermal insulation. Known sandwich elements of this type would not be suitable for the named areas of application due to their comparatively lower mechanical strength.

Compact polyisocyanate polyadducts, i.e. Products that are not part of a network of gas-filled

Cells exist that are connected to one another via webs and cell walls.

The width and the length of the composite elements can usually be 0.5 to 10 m, preferably 1 to 5 m.

Claims

claims

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

(i) 2 to 20 mm metal,

(ii) 10 to 300 mm plastics,

(iii) 2 to 20 mm metal,

characterized in that the metal layers (i) and (iii) are fixed in such a way that the space (R) for the layer (ii) is formed between them, (R) with the exception of at least one opening for filling (R) and seals at least one further opening and, before filling (R) with the starting components for the production of (ii), the sealing of (R) is checked by measuring the pressure difference at the opening or openings.

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

(i) 2 to 20 mm metal,

(ii) 10 to 300 mm polyisocyanate polyaddition products obtainable by reacting (a) isocyanates with (b) compounds reactive towards isocyanates, (iii) 2 to 20 mm metal,

3. The method according to claim 2, characterized in that one uses as (b) polymer polyols.

4. The method according to claim 2, characterized in that the composite elements have the following layer structure:

(i) 2 to 20 mm metal, (ii) 10 to 300 mm polyisocyanate polyadducts with a density of 350 to 1100 kg / m ³ obtainable by reacting (a) isocyanates with (b) compounds reactive towards isocyanates in the presence of ( f) blowing agents and / or 1 to 50% by volume, based on the volume of the polyisocyanate polyadducts, at least one gas (c) and, if appropriate, (d) catalysts and / or (e) auxiliaries and / or additives, (iii) 2 to 20 mm metal.

5. The method according to claim 2, characterized in that between (i) and (iii) polyisocyanate polyadducts (ii) by reacting (a) isocyanates with (b) isocyanate-reactive compounds in the presence of blowing agents (f) and / or 1 to 50% by volume, based on the volume of the polyisocyanate polyadducts, of at least one gas (c) and, if appropriate, (d) catalysts and / or (e) auxiliaries and / or additives which (i) and (iii ) be liable.