EP1345762A1

EP1345762A1 - Composite element containing polyisocyanate polyaddition products

Info

Publication number: EP1345762A1
Application number: EP01996458A
Authority: EP
Inventors: Edmund Stadler; Jürgen Mertes; Heinz Forster; Matthias Hefner; Peter Reinerth; Thomas Sandbank
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2000-11-14
Filing date: 2001-11-10
Publication date: 2003-09-24
Also published as: DE10056378A1; AU2002217017A1; WO2002040265A1; US20040038042A1

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.

Description

Composite elements containing polyisocyanate polyaddition products

description

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

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

(ii) 10 to 300 mm, preferably 10 to 100 mm, polyisocyanate

Polyaddition products obtainable by reacting (a) isocyanates with (b) polymer polyols as compounds reactive towards isocyanates,

(iii) 2 to 20 mm, preferably 2 to 10 mm, particularly preferably 5 mm to 10 mm metal.

Furthermore, the invention relates to methods for producing these composite elements and their use. The lengths of layers (i), (ii) and (iii) shown at the beginning 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, the hulls of tankers usually consist of an inner and an outer hull, whereby each hull is made 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 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 must be regularly protected against corrosion.

As a replacement for the steel constructions, 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 improvement potential with regard to the production of these composite elements consists in particular in controlling the heat of reaction in the production of the plastic between the metal layers and in particular the associated expansion of the system and the subsequent shrinkage during and after cooling. Neither the adhesion of the plastic to the metal layers nor the material properties should deteriorate noticeably.

The present invention was therefore based on the idea of new ones

To develop composite elements that have excellent adhesion of (ii) to (i) and (iii) both during the production of the plastic and in particular after cooling and the associated shrinkage of (ii). The composite elements produced should be able to withstand large loads from external forces and be used, for example, in ship, bridge or high-rise construction. The structural parts to be developed, also called composite elements, are intended to serve as a replacement for known steel structures and, in particular, have advantages in terms of weight, manufacturing process and maintenance intensity.

This object was achieved according to the invention by the composite elements described at the beginning.

The use of polymer polyols in particular can significantly reduce the shrinkage of 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.

Composite elements which have the following layer structure are preferred:

(i) 2 to 20 mm, preferably 5 to 10 mm metal, (ii) 10 to 300 mm, preferably 10 to 100 mm, polyisocyanate polyadducts with a density of 350 to 1100 kg / m ³ obtainable by reacting (a) isocyanates with (b) polymer polyols as compounds reactive toward 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 optionally (d) catalysts and / or (e) auxiliaries and / or additives,

(iii) 2 to 20 mm, preferably 5 to 10 mm metal.

Compounds known from polyurethane chemistry can generally be used as polymer polyols.

The polymer polyols are also generally known in the literature as polymer polyetherols, graft or graft polyetherols, which contain organic vinyl polymers as fillers. Graft polyetherols are stable dispersions of usually solid vinyl polymers, for example styrene-acrylonitrile copolymers, their homopolymers or other vinyl monomers such as e.g. Vinyl acetate, vinyl chloride or acrylic acid ester, in a conventional carrier polyetherol, e.g. the polyether polyols described later. The graft polyetherols are generally prepared by known processes, for example by in-situ polymerization of the vinyl monomer (s) in the carrier polyol, so that a graft polyetherol in addition to the unmodified carrier polyol and the vinyl polymers and graft copoly erisate, ie Carrier polyol modified with vinyl polymer. The graft copolymer serves as an emulsifier to stabilize the carrier polyol / vinyl polymer dispersion.

The viscosity of the graft polyether polyols increases relatively rapidly with the vinyl polymer content. The maximum proportion of vinyl polymer in the carrier polyol is therefore preferably about 60% by weight, but typically between 10 and 50% by weight and preferably between 30-45% by weight, in each case based on the total weight.

Bifunctional, trifunctional and also higher functional polyoxypropylene-polyetherols or polyoxypropylene-polyoxyethylene-polyetherols with a molar mass between 1000 and 10000 g / mol, preferably with a molar mass between 2000 and 8000 g / mol, can be used as carrier polyols. The following are typically used as carrier polyols: glycerol (Gly) and / or trimethylolpropane (TMP) propylene oxide (PO) or Gly (or TMP) PO / ethylene oxide (EO) or Gly (or TMP) -PO-EO or Gly (or TMP) -PO / EO-EO or Gly (or TMP) -PO / EO-PO.

The polymer polyols used are preferably styrene-acrylonitrile graft polyols, in particular reactive graft polyether polyols having a hydroxyl number of 15 to 50 mg KOH / g, preferably 20 to 30 mg KOH / g, in particular 25 mg KOH / g, preferably made from a glycerin started polyoxypropylene-polyoxyethylene-polyol as a carrier polyol, and a solids content of 25 to

10 35% by weight, preferably 30 to 33% by weight, consisting of a styrene / acrylonitrile copolymer (for example Lupranol® 4100 from BASF Aktiengesellschaft), or else reactive graft polyether polyols with a hydroxyl number of 15 to 25 mg KOH / g, preferably 17 to 21 mg KOH / g, preferably produced from a glycerol started

¹⁵ polyoxypropylene-polyoxyethylene-polyol as carrier polyol and a solids content of 40 to 50% by weight, preferably 45% by weight, consisting of a styrene / acrylonitrile copolymer (for example Lupranol® 4800 from BASF Aktiengesellschaft).

The polymer polyols shown can be used as the only compounds that are reactive toward isocyanates, or in a mixture with generally known compounds that are reactive toward isocyanates, which are presented later. The proportion of the polymer polyols is preferably 10 to 100% by weight,

²⁵ particularly preferably 30 to 80% by weight, in each case based on the weight of all compounds (b) reactive toward isocyanates.

The use of these polymer polyols has the following advantages over inorganic fillers:

30 easier preparation of the filler-containing formulation (stirring in the filler)

stable dispersion (no settling of the filler)

35 no strong increase in viscosity at high filler concentrations, i.e. the system is easier to process and has better fluidity

^ 0 - no strong increase in density of the elastomer

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 -40 to +90 ° C (according to ⁴⁵ DIN 53457), an adhesion to (i) and (iii) of> 4 MPa (according to DIN 53530), an elongation of> 30% in the temperature range from -40 to + 90 ° 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).

In addition to excellent mechanical properties, the composite elements according to the invention have the particular advantage that composite elements with very large dimensions are also accessible. Composite elements of this type, which are obtainable by producing a plastic (ii) between two metal plates (i) and (iii), have hitherto only been accessible to a limited extent due to the shrinkage of the plastic (ii) during and after its implementation. Due to the shrinkage of the plastic (ii), for example the polyisocyanate polyadducts, the plastic (ii) is partially detached from the metal plates (i) and / or (iii). However, the most complete and very good adhesion of the plastic (ii) to the metal plates (i) and / or (iii) is of particular importance for the mechanical properties of such a composite element.

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

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

The surfaces of (i) and / or (iii) to which (ii) adheres after the production of the composite elements can preferably be irradiated with sand or steel balls. This sandblasting can be carried out using conventional methods. For example, the surfaces can be irradiated with conventional sand under high pressure and thus cleaned and roughened, 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) should adhere, are preferably free of inorganic and / or organic substances which reduce adhesion, for example oils and fats or substances generally known as mold release agents.

After the preferred treatment of the surfaces of (i) and (iii), these layers are preferably fixed in a suitable arrangement, for example parallel to one another. The distance is usually chosen so that the space between (i) and (iii) has a thickness of 10 to 100 mm. (I) and (iii) can be fixed, for example, by spacers. The edges of the intermediate space can preferably be sealed in such a way that the space between (i) and (iii) does indeed have (a), (b) and (f) and optionally (d) and / or (e) and / or (c) can be filled, but outflow of these components is prevented. Sealing can be done with conventional plastic or metal foils and / or metal plates, which can also serve as spacers.

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 filling of the space between (i) and (iii) with (a) and (b) and optionally the further starting materials can be carried out using conventional conveying devices, preferably continuously, for example using 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, 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 cleaned, for example, by conventional sandblasting.

The preparation of the polyisocyanate polyaddition products (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), (d) catalysts and / or (e) auxiliaries and / or additives and / or (c) has 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 have been biuretized and / or isoeyanurated by 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-1, 4, 2-methylpentamethylene-1, 5, tetra-methylene diisocyanate, 1, 4, Lysine ester diisocyanates (LDI), hexamethylene diisocyanate-1, 6 (HDI), cyclohexane-1, 3- and / or 1,4-di-isoeyanate, 2,4- and 2,6-hexahydrotoluenediisocyanate and the corresponding isomer mixtures, 4, 4'-, 2,2'- and 2, 4'-dicyclohexyl ethane diisocyanate and the corresponding isomer mixtures, l-isocyanato-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 diisoeyanate (MDI), polyphenylpolymethylene polyisocyanates and / or mixtures containing at least two of the isocyanates mentioned. 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. 2,4'-, 2,2'- and / or 4,4'-MDI and / or polyphenylpolymethylene polyisocyanates are preferably used, particularly preferably mixtures containing polyphenylpolymethylene polyisocyanates and at least one of the MDI isomers.

As (b) compounds which are reactive toward isocyanates, the polymer polyols according to the invention can, if appropriate, additionally be used, for example, compounds which are as opposite Isocyanate-reactive groups have hydroxyl, thiol and / or primary and / or secondary amino groups and usually have a molecular weight of 60 to 10,000 g / mol, for example polyols selected from the group of polyether polyalcohols, polyester-polyalcohols, polythioether-polyols, hydroxyl-containing polyacetals and hydroxyl-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-pro pylene oxide 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, ethane diol, diethylene glycol, 1,2- or 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1, β-hexanediol, 1,7-heptanediol, glycerol, trimethylolpropane can be used as starter substances. Neopentyl glycol, sugar, for example sucrose, pentaerythritol, sorbitol, ethylenediamine, propanediamine, neopentanediamine, hexamethylenediamine, isophoronediamine, 4,4'-diaminodicyclohexylmethane, 2- (ethylenedio) ethylamine, 3- (methylamino) propylamine and dipylenetriamine, diethylenetriamine, diethylenetriamine, diethylenetriamine, diethylenetriamine, and diethylenetriamine N, N ^V -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. 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 use of polyether polyalcohols offers considerable advantages due to the improved stability of the polyisocyanate polyaddition products against hydrolytic cleavage and because of 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 polyalcohols 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.

As compounds which are reactive toward isocyanates, in addition to the compounds mentioned having a customary molecular weight of 400 to 8000, diols and / or triols with molecular weights of 60 to <400 can optionally be used as chain extenders and / or crosslinking agents in the process according to the invention. 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-decanediol, 10, o-, m-, p -Dihydroxycyclohexane, diethylene glycol, dipropylene glycol and preferably butanediol-1, 4, hexanediol-1, 6 and bis- (2-hydroxyethyl) -hydroquinone, triols, such as 1,2,4-, 1,3, 5-trihydroxy- cyclohexane, glycerol and trimethylolpropane, low molecular weight hydroxyl-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 from 0 to 30% by weight, preferably from 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).

With the use of amine-started polyether polyalcohols, the hardening behavior of the reaction mixture for the preparation of (ii) can also be improved. 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 evaporate during the reaction either 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, component (c) is preferably already gaseous in the present invention. ig used as an aerosol for example in the polyol component.

Well-known compounds which greatly accelerate the reaction of isocyanates with the compounds reactive toward isocyanates can be used as catalysts (d), preferably a total catalyst content of 0.001 to 15% by weight, in particular 0.02 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- (dimethylaminopropyl) urea, N-methyl- or N-ethylmorpholine, N-cyclohexylmorpholine, N, N, N ', N' -tetramethylethylenediamine, N, N, N ', N'-tetramethylbutanedia in, N,, N', '-tetramethylhexanediamine-1,6 , Pentamethyldiethylenetriamine, Dirnethylpiperazin, N-Dimethylaminoethylpiperidin, 1, 2-Dimethylimidazol, 1-Azabicyclo- (2,2,0) -octane, 1, 4-Diazabicyclo- (2, 2, 2) -octane (Dabco) and Fertilize alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyl-diethanolamine, dimethylaminoethanol, 2- (N, N-dimethylaminoethoxy) ethanol, N, N ', N ¹ ' -Tris- (dialkylaminoalkyl) hexahydrotri - Azines, for example N, N, N ' ^X -Tris- (dimethylaminopropyl) -s-hexahydrotriazine, iron (II) chloride, zinc chloride, lead octoate and preferably tin salts such as tin dioctoate, tin diethylhee xoat, dibutyltin dilaurate and / or dibutyldilauryltin mercaptide, 2, 3-dimethyl-3, 4, 5, 6-tetrahydropyrimidine, tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide, alkali metal hydroxides, such as sodium hydroxide, alkali metal alcoholate and potassium alkaliate, such as sodium / alkali metal alcoholate, such as sodium methylalate, such as sodium / alkali metal alcoholate, such as sodium methylalate, such as sodium methylalate 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.

For example, suitable surface-active substances are compounds 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 wise emulsifiers, such as the sodium salts of castor oil sulfates or of fatty acids and salts of fatty acids with a in, for example oleic acid diethylamine, stearic acid diethanolamine, ricinoleic acid diethanolamine, salts of sulfonic acids, for example alkali metal or ammonium salts of dodecylbenzene methane or dinaphonic acid or dinaphthonic 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 compounds (b) reactive toward isocyanates used in total.

Suitable flame retardants are, for example, tricresyl phosphate, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate, Tetrakis (2-chloroethyl) ethylene diphosphate, Dirnethylmethanphosphonat, Diethanola inomethylphosphonsäure- diethylester and commercially available halogen-containing flame retardant 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, expanded graphite or cyanuric acid derivatives, such as e.g. Melamine, or mixtures of at least two flame retardants, 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 proven expedient to use 5 to 50% by weight, preferably 5 to 25% by weight, of the flame retardants mentioned, based on the weight of the compounds used which are reactive toward isocyanates.

Fillers, in particular reinforcing fillers, are to be understood as the conventional organic and inorganic fillers known per se, reinforcing agents, weighting agents, agents for improving the abrasion behavior in paints, coating agents, etc. The following may be mentioned as examples: inorganic fillers such as silicate minerals, for example layered silicates such as antigorite, serpentine, hornblende, amphiboles, 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 and others. 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 are preferably used. Examples of suitable organic fillers are: coal, melamine, rosin, cyclo- Pentadienyl resins and graft polymers as well as cellulose fibers, polyamide, polyacrylonitrile, polyurethane, polyester fibers based on aromatic and / or aliphatic dicarboxylic acid esters and especially 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.

For the preparation of (ii), conventional 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, e.g. Tegostab 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).

Blowing agents (f) known from polyurethane chemistry can be used as blowing agents, for example physical and / or chemical blowing agents. Physical blowing agents of this type generally have a boiling point at a pressure of 1 bar of greater than (ie at temperatures higher than) -50 ° C. Examples of physical blowing agents are, for example, CFCs, HFC W, 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 (boiling point -9.2 ° C), dichlorotrifluoroethane (boiling point 27.1 ° C), tetrafluoroethane (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).

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, carbamates, for example those described in EP-A 1000955, in particular 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 sufficient to obtain the preferred density of (ii). 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 preferably used in an amount of 0.05 to 10% by weight, in particular 0.1 to 5% by weight, in each case based on the total weight of the polyisocyanate polyadducts.

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

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) 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) 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 compressed by generally known loading devices, for example air loading devices, preferably under pressure, for example from a pressure vessel or by a compressor, e.g. are supplied through a nozzle to the corresponding component. 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. 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, ie the temperature at which the reaction takes place, is usually> 20 ° C., preferably 50 to 150 ° C.

The composite elements according to the invention which can be produced by the method according to the invention have the following advantages over known constructions:

The use of the polymer polyols causes less shrinkage when the system cools down after the reaction compared to polyurethanes. This results in better adhesion to (i) and (iii), since detachment during cooling is avoided.

Due to the preferred use of (c) and / or (f), a shrinkage of (ii) and thus an impairment of the adhesion of (ii) to (i) and (iii) can also be avoided.

Accordingly, 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 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 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 named fields 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. e Width and the length of the composite elements can usually be 5 to 10 m, preferably 1 to 5 m.

Claims

claims

1. Composite elements, the following layer structure on iron:

(i) 2 to 20 mm metal,

(ii) 10 to 300 mm polyisocyanate polyadducts obtainable by reacting (a) isocyanates with (b) polymer plastics as isocyanate-reactive

Links,

(iii) 2 to 20 mm metal.

2. Composite elements according to claim 1 containing as (b) styrene-acrylonitrile graft polyols.

3. Composite elements which 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) polymer polyols as compounds which are reactive toward isocyanates in

Presence of (f) blowing agents and / or 1 to 50% by volume, based on the volume of the polyisocyanate polyadducts, of at least one gas (c) and optionally (d) catalysts and / or (e) auxiliaries and / or additives,

(iii) 2 to 20 mm metal.

4. A method for producing composite elements according to one of claims 1 to 3, characterized in that between

(i) and (iii) polyisocyanate polyadducts (ii) by reacting (a) isocyanates with (b) isocyanate-reactive compounds which adhere to (i) and (iii).

Composite elements obtainable by a method according to claim 4.

6. Use of composite elements according to one of claims 1 to 3 or 5 as structural parts in shipbuilding or in buildings.

7. Ships or structures containing composite elements according to one of claims 1 to 3 or 5.