NO323691B1 - Combination element containing polyisocyanate polyaddition products, process for preparing the combination element and use thereof. - Google Patents

Abstract

In a composite element comprising layers of (i) polyisocyanate poly-addition product (PU), (ii) optionally at least one plastic, (iii) a gas permeation barrier and (iv) at least one thermoplastic, layers (iii) and (iv) are bonded together by melting a layer (iiia) between them. Independent claims are also included for: (a) sandwich elements with the following layers: (iv) 1-25 mm thermoplastic, (iii) 0.1-200 micro m metal foil coated on the opposite side from (i) and (ii) with 20-500 micro m thermoplastic (iiia) which is melted to bond (iii) with (iv), (ii) optionally 5-1000 micro m plastic, (i) 0.5-80 cm PU and then layers (ii), (iii) and (iv) as above; (b) tubes with the following layers: (iv) as above and/or metal as inner tube, (i), (ii), (iii) as above and (iv) (above) as an outer tube; (c) tubes with the following layers: (iv) plastic as above and/or metal as inner tube, (iii), (ii), (i), (ii), (iii) as above and (iv) plastic (above) as an outer tube; (d) the production of composite elements by reacting isocyanates with NCO-reactive compounds in the presence of blowing agents and optionally catalysts and other additives etc. in a reaction space bounded by layers (ii) (optional), (iii) gas barrier material, (iiia) 20-500 micro m thermoplastic and (iv) 1-25 mm thermoplastic(s), so that layer (iiia) is melted by the heat of reaction and binds layers (iii) and (iv) together after cooling; and (e) composite elements obtained by (d).

Description

The invention relates to a combination element which exhibits the following layer:

i) polyisocyanate polyaddition product,

ii) possibly at least one plastic substance,

iii) material which prevents gas penetration, and which is associated with .

at least one

(iv) thermoplastic plastic by melting a layer (iiia), which is arranged between (iii) and (iv) and can be obtained by the fact that in a reaction space which is limited by the following layer:

ii) possibly at least one plastic substance, and in connection with this

iii) a material that prevents gas permeation,

iiia) 20 to 500 um of at least one thermoplastic plastic substance, as well as

iv) 1 to 25 mm of at least one thermoplastic plastic material,

isocyanates are reacted with compounds that are reactive in relation to isocyanates in the presence of propellants and possibly catalysts, auxiliaries and/or additives, whereby iiia) melts with the aid of heat of reaction and after cooling connects (iii) and (iv) with each other.

Furthermore, the invention relates to a method for producing a combination element, which is characterized in that in a reaction space which is limited by the following layer:

ii) possibly at least one plastic substance, and in connection with this

iii) a material that prevents gas permeation,

iiia) 20 to 500 um of at least one thermoplastic plastic substance, as well as

iv) 1 to 25 mm of at least one thermoplastic plastic material,

isocyanates are reacted with compounds that are reactive in relation to isocyanates in the presence of propellants and possibly catalysts, auxiliaries and/or additives, whereby iiia) melts with the help of the heat of reaction and after cooling connects (iii) and (iv) with each other.

Furthermore, the invention relates to the use of the combination elements, as well as sandwich elements and pipes which exhibit corresponding layers (i) to (iv).

The continuous or discontinuous production of combinations of polyisocyanate polyaddition products, usually polyurethane (PUR) or polyuretrate/polyisocyanurate (PUR/PIR) foams and compact cover layers has long been known. Such combinations are used, for example, as sandwich elements in house construction. An important area of application is further thermal insulation of pipes used for the transport of heat using hot water under pressure. These insulated pipes usually have an inner pipe that transports the heating medium, which is usually made of steel surrounded by PUR or PUR/PIR rigid foam for thermal insulation. The hard foam material is sealed on the outside with a casing tube as a moisture barrier, whereby for constructive reasons there must be a mechanical connection between the inner tube and the casing tube through the polyurethane hard foam material. A thermoplastic type of plastic, for example a polyolefin, is often used as the casing pipe. This is primarily due to the low price, the good technical properties, e.g. the very good gliding effect which in soil has a very beneficial effect when compensating for thermal spinning, the easy workability and water impermeability of the thermoplastic plastic material, which serves as a protective outer skin when it is laid in the soil. The properties of these insulated pipes are laid down in the standard DIN EN 253.

The heating medium transported in the pipes, which in most cases is water under pressure, is heated according to the current state of the art to temperatures of up to 140°C. Due to the energy savings that thereby take place for thermodynamic reasons, the trend is towards even higher temperatures, e.g. 150°C and • over a short time -160°C. It is therefore desirable to have a lasting improvement in the insulating effect of the foam material, above all when it comes to higher temperatures, and the thermal conductivity should be continuously reduced. Thereby, it is particularly desirable that the insulated pipes exhibit a low thermal conductivity and good strength during their entire useful life of 30-50 years.

When used in practice, the pipes, which are sheathed with hard foam materials and a plastic skin, are dug into the soil and must permanently withstand the pressure of the earth, also under conditions of thermal expansion by pipe bends at an elevated temperature, without the mechanical connection between the internal and the outer tube is affected. A too strong permanent deformation of the hard foam material at elevated temperature affects the durability of the combination, above all in the case of temperature conditions that are forced to constantly change during an annual cycle. This deformation cannot simply be reduced by setting a higher compressive E-modulus for the foam, because the associated brittleness also leads to the influence of the combination by excessive stress and cracking due to the thermal expansion that is not to avoid.

Through the continuous thermal load on the hard foam in the combination at elevated temperature at a permanent temperature of up to 140°C to 160°C on the inner tube and significantly lower temperature on the mantle tube in the soil, the foam ages and acquires a lower firmness. This aging occurs in an undesirable manner to a particularly strong degree in the interior of combinations with thermoplastic plastics such as casing pipes. This thermal aging manifests itself in a chemical destruction of the foam, which begins on the very thin cell walls with a thickness of less than 1 µm. This ageing, in addition to the reduction in strength, e.g. the compressive strength, can therefore also be demonstrated by an increase in the degree of open cells.

After the fluorohydrocarbons (FCKW Fluorkohlenwaserstoffe) used as propellants for hard foam could no longer be used for ecological reasons, for example trichlorofluoromethane (R11), there has been a need to find alternative propellants. A frequently used option is the use of carbon dioxide from the reaction between isocyanate and water. With this variant, the ozone damage potential (ODP) is indeed reduced to zero and the global greenhouse potential (GWP) significantly reduced compared to R11, but at the same time the thermal insulation effect of the foam material is reduced, i.e. the heat conductivity is increased. When combining water with hydrocarbons, most often cyclopentane, as propellants, the ODP and GWP are reduced in much the same way as with pure carbon dioxide; the thermal conductivity of the foam is lower than when using pure carbon dioxide, but higher than when R11 is used as propellant.

The use of, for example, cyclopentane and water or water alone as a propellant necessarily leads to higher thermal conductivity than was previously the case with the propellant R11.1 In addition, foam materials in the insulated pipes with, for example, an outer skin of polyolefin, after a longer period of time show a higher thermal conductivity than at the beginning of their period of application. This unwanted increase was small when using R11, but is after switching to water and hydrocarbons, e.g. cyclopentane, as propellant undesirably high, and when water alone is used significantly higher.

One could assume that the production of metal-combination pipes, e.g. combinations of outer tubes of metal/PUR or PUR/PIR foam/inner tubes of metal could solve our task because e.g. in sandwich elements with thick cover layers of metal around or above 500 um only slightly change the thermal conductivity

for foams over time. However, for reasons of flexibility and due to the high forces involved in thermal expansion, only very short pipe lengths can be used with this combination. Longer pipes are quickly destroyed in use due to the possibility of constant changes in temperatures, because they do not have the stress-reducing properties that the pipe elements with an outer skin of thermoplastic plastic have. Otherwise, work must be done with an insulating material of e.g. minerals or fibres. In this way, however, no connection is provided between the medium-carrying inner pipe and the casing pipe, and the thermal insulation effect becomes even worse.

According to DE-A 29 615 423, heat-insulated pipes are manufactured for reasons of flexibility from corrugated metal pipes which do not exhibit these disadvantages. However, this production method is very complicated and therefore rather expensive.

EP-A 84 088 describes the manufacture of durable heat-insulating pipes which have good bending capacity, for house connections, i.e. secondary connections. For the durability of

the combination therefore only makes small demands. The optionally applicable aluminum foil with a copolymer layer is itself welded through the extrusion process, but it is attached by such a method both to the polyolefin protective jacket and to the insulating foam only to an insufficient extent. The strength required for a rigid connection does not thereby occur. This also applies correspondingly to DE-A 3 307 865, where likewise only the copolymer layer is described. Due to the corrugated inner tube, the problem of tensions arising is reduced, and the requirements for the combination are not so high.

DE-A 3 237105 describes a flexible combination of aluminum and polyolefin where the whole combination is unsuitable for absorbing forces.

In BE-A 636 337 only a flexible combination foil of aluminium, paper and por/ethylene is described, but no polyolefin/polyurethane combination which removes all the mentioned disadvantages of previous solutions.

As far as the mentioned documents describe a welding of the casing pipe, this takes place by extrusion. This heat treatment, which must be carried out after the production of the insulating foam, can likewise affect the foam in an unsatisfactory manner, and is also complicated.

From the state of the art, there is thus no known technical teaching which makes a solution to the task that lies at the basis of this invention imminent,

namely to make available a combination structure which exhibits a PUR or PUR/PIR foam and a thermoplastic layer and which entails the following pro-

parts:

• simple technical production, so that a firm connection can be achieved between the layers without extrusion of the mantle layer and which would be associated with an unwanted heat load on the insulating foam; • no diffusion of propellants from the air into the foam material; • permanent, fixed connection between the foam material and the thermoplastic plastic material;

• high stability and low thermal conductivity for the combination, also in case of

severe temperature stress over very long periods of time.

This task could be solved using the initially described combination element.

The combination elements according to the invention in particular exhibit a durable, fixed connection between the foam, the material which prevents a gas penetration and the thermoplastic plastic material. Precisely the connection between the material that prevents gas penetration, i.e. for example a diffusion of propellants from the foam material, and the thermoplastic plastic material, has so far not

could be achieved satisfactorily. This inconvenience could be cleared out of the way

by connecting (iv) to (tii). This melting is achieved by a layer of thermoplastic plastic material (iiia) which is arranged between (iii) and (iv), and which due to the reaction heat melts during the production of (i). After cooling, the previously molten layer connects layers (iii) and (iv). The layer (iiia) preferably has a thickness of from 20 to 500 µm. This small thickness ensures that the layer, due to the heat of reaction, preferably melts completely during the production of the foam material. A direct melting of (iv) onto (iii) is usually not possible because, due to the usually large thickness of (iv), this layer does not melt sufficiently and thus does not ensure that a satisfactory connection is produced between (iii) and ( iv). The melting of (iii) on (iv) by means of the heat of reaction that occurs in the preparation of (i) has the decisive advantage that a further complicated and too foamy harmful heat load is avoided in a fusion of (iii)

and (iv).

The combination elements according to the invention can thus be produced in such a way that in a reaction space which is limited by the following layer: ii) possibly at least one plastic material,

iii) a material that prevents gas permeation,

iiia) 20 to 500 um of at least one thermoplastic plastic substance, as well as

iv) 1 to 25 mm of at least one thermoplastic plastic material,

isocyanates are reacted with compounds that are reactive in relation to isocyanates in the presence of propellants and possibly catalysts, auxiliaries and/or additives, whereby iiia) pains due to the heat of reaction and, after cooling, connects (iii) and (iv) with each other.

The layers are arranged in such a way that during production, layer (ii) is in direct contact with the reaction system containing the isocyanates, the compounds that are reactive in relation to isocyanates, propellants and possibly catalysts, auxiliaries and/or additives, join the layer (iii) on layer (ii), on this follows layer (iiia) and finally layer (iv) is arranged.

The layer (iiia), which in the method according to the invention is arranged between (ii) and (iv), preferably fuses completely with (iv), so that this layer in the combination element, on the condition that (iiia) and (iv) consists of the same thermoplastic plastic material, is not detectable. Preferably, (iii) and (iiia) are already used as a combination foil, for example a metal foil which has already been coated with a thermoplastic plastic material. Such a combination foil which can preferably be used instead of layers (iii) and (iiia) usually has a thickness of 20.1 to 1100 µm, the metal layer usually having a thickness of 0.1 to 600 µm, preferably 0.1 to 200 µm, and the layer of the thermoplastic plastic usually has a thickness of from 20 to 500 µm. Such a combination foil is oriented by the method according to the invention and in the combination elements according to the invention in such a way that the thermoplastic plastic material in the coated foil adjoins the layer (iv), so that after melting due to the heat of reaction and the subsequent cooling to be connected with layer (iv). For example, multi-layer foils which are known from the packaging industry and which exhibit the aforementioned layer order can be used as combination foil, e.g. with the layer order polyethylene (iiia), aluminum (iii), polyethylene terephthalate (ii), the aluminum being incorporated as foil or can e.g. are splashed on.

As thermoplastic plastic material for layer (iiia), (iv) and/or the combination foil, it can e.g. common polyolefins are used, e.g. polyethylene, polypropylene, polypropylene/polyethylene polymers, the said polyolefins possibly being in modified form, commonly used, other thermoplastic plastics such as por/styrene, polyamides and/or polyethylene terephthalate, the said polyolefins being preferred.

The layers (iii), (iv) or the combination foil used for layer construction can contain the same or different thermoplastic plastics. Furthermore, ordinary metals or metal alloys can also be used as layer (iv), for example steel, aluminium, stainless steel alloys, copper, magnesium and/or ordinary alloys of these mentioned metals, especially if layer (iv) forms the inner tube of an insulated pipe according to the invention.

The layer (iv) can usually also be distinguished from this by a complete fusion with the layer (iiia) or the thermoplastic plastic layer in the combination foil, as a thermoplastic plastic substance is usually used as layer (iv) which is usually fired with carbon black, graphite, ground fibres, micro-glass spheres, zeolites, organic absorbers for infrared such as e.g. Paliogen<®->black from BASF Aktiengesellschaft, lignins, silicates, mica, glass fibers, chalk, titanium dioxide and/or other known fillers A difference between layer (iiia) or the thermoplastic plastic in the combination foil and layer (iv) would e.g. be possible to see using a light or electron microscope. In this case, the combination elements according to the invention, the sandwich elements and the tubes between the layers (iii) and (iv) demonstrably contain the layer (iiia), which usually exhibits the already indicated thickness.

Combination elements according to the invention are shown, for example, in fig. 1 and 2, as in fig. 2 shows a combination element where the layers (iiia) and (iv) can be distinguished from each other.

Layers (i), (ii), (iii) and (iv) preferably have the following thickness

(i) 0.5 to 80 cm, preferably 2 to 15 cm,

(ii) 5 to 1000 µm,

(iii) 0.1 to 600 µm, preferably 0.1 to 200 µm,

(iv) 1 to 25 mm, preferably 1.5 to 10 mm.

As a material that prevents gas penetration, a foil can be used, for example, which can consist of common metals, e.g. aluminium, steel, stainless steel alloys, copper, magnesium, tin, silver, gold, other precious metals and/or common alloys of the aforementioned metals.

Preferred according to the invention is a combination element which in cross-section shows the following layer:

i) 0.5 to 80 cm polyisocyanate polyaddition product,

ii) possibly 5 to 1000 um of at least one plastic material,

iii) 0.1 to 600 µm, preferably 0.1 to 200 µm, of a metal foil which on the side facing away from (i) and (ii) has a layer of 20 to 500 µm of at least one thermoplastic plastic material ( iiia), which by fusion connects (iii) and (iv) with each other,

iv) 1 to 25 mm of at least one thermoplastic plastic material.

The combination elements according to the invention are preferably used as insulated pipes, for example as so-called plastic jacket pipes, sandwich elements, thermal insulation elements for cooling or heating units, for example hot water containers, thermally insulated containers, e.g. in vehicle construction, or in similar areas of application.

A sandwich element according to the invention is e.g. shown in fig. 3, and exhibits the following layer in cross-section:

iv) 1 to 25 mm of at least one thermoplastic plastic material,

iii) 0.1 to 200 µm of a metal foil which on the side facing away from (i) and

(ii) has a layer of 20 to 500 µm of at least one thermoplastic plastic substance (iiia),

which, by fusion, connects (iii) and (iv) with each other,

ii) possibly Style 1000 um of at least one plastic material,

i) 0.5 to 80 cm polyisocyanate polyaddition product,

ii) possibly 5 to 1000 um of at least one plastic material,

iii) 0.1 to 200 µm of a metal foil, which on the side facing away from (i)

and (ii) has a layer of 20 to 500 µm of at least one thermoplastic plastic substance (iiia) which, when melted, connects (iii) and (iv) to each other,

iv) 1 to 25 mm of at least one thermoplastic plastic material.

A pipe according to the invention is shown, for example, in fig. 4, and exhibits the following layer in cross-section: iv) 1 to 25 mm of at least one thermoplastic plastic material and/or at least one metal

as inner tubes,

i) 0.5 to 80 cm polyisocyanate polyaddition product,

ii) possibly 5 to 1000 um of at least one plastic material,

iii) 0.1 to 200 µm of a metal foil, which on the side facing away from (i)

and (ii) has a layer of 20 to 500 µm of at least one thermoplastic plastic substance (iiia) which, when melted, connects (iii) and (iv) to each other,

iv) 1 to 25 mm of at least one thermoplastic plastic material as outer tube.

If the inner tube of the tube contains thermoplastic plastic material, the tube according to the invention preferably has the following layer:

iv) 1 to 25 mm of at least one thermoplastic plastic material as the inner tube,

tii) 0.1 to 200 µm of a metal foil, which on the side facing away from (i)

and (ii) has a layer of 20 to 500 µm of at least one thermoplastic plastic material (iiia), which, when melted, connects (iii) and (iv) to each other,

ii) possibly 5 to 1000 fim of at least one plastic material,

i) 0.5 to 80 cm polyisocyanate polyaddition product,

ii) possibly 5 to 1000 glues of at least one plastic substance,

iii) 0.1 to 200 µm of a metal foil, which on the side facing away from (i)

and (ii) has a layer of 20 to 500 µm of at least one thermoplastic plastic material (iiia), which, when melted, connects (iii) and (iv) to each other,

iv) 1 to 25 mm of at least one thermoplastic plastic material as outer tube.

Figures 3 and 4 are, for example, as fig. 2 designed for the case that layers (iiia) and (iv) can be distinguished from each other. If the same materials are used for layers (iiia) and (iv), here too layer (iiia) goes up into this layer (iv) due to the strong fusion with layer (iv). A distinction between layers (iiia) and (iv) will then not be possible.

Preferred are combination elements according to the invention where the layers (iiia) and (iv) can be distinguished from each other, for example by the described addition of carbon black, graphite, ground fibres, micro-glass spheres, zeolites, organic infrared absorbers such as for example Paliogen <®->black from BASF Aktiengesellschaft, lignins, silicates, mica, glass fibers, chalk, titanium dioxide and/or

other known fillers for layer (iv) and absence of these substances in layer (iiia).

As layer (ii), ordinary materials can be used to which the polyisocyanate-polyaddition products sufficiently adhere after their preparation. The following materials are preferably used: Polyamide, plastics containing ester structures, e.g. polyethylene terephthalate, polystyrene, polyvinyl chloride and/or polyolefins, the surface of (ii) being particularly preferably corona-etched.

In the combinations according to the invention, layers (ii), (iii), (iiia) and (iv), especially layers (iii) and (iiia), can also be arranged one after the other several times, for example in a sequence (i), (ii), (iii), (iiia), (iii), (iiia), (iv).

The products according to the invention can be produced according to usual methods in a continuous or discontinuous manner, for example on a band plant or on analogous plants for the production of insulated pipes, the reaction space as described at the outset being limited for the production of the polyisocyanate-polyaddition products by already produced layer.

The reaction of isocyanates with compounds which are reactive in relation to isocyanates in the presence of propellants and possibly catalysts, auxiliaries and/or additives to (i) the polyisocyanate-polyaddition products is widely known and often described. Preferably, the polyisocyanate polyaddition products (i) constitute foamed polyisocyanate polyaddition products, particularly preferably polyurethane and/or polyisocyanurate rigid foams.

As isocyanates, preferably organic and/or modified organic polyisocyanates, the per se known aliphatic, cycloaliphatic, araliphatic and preferably aromatic multivalent isocyanates come into consideration, as they are for example listed in EP-A 0 421 269, (column 4 , line 49, to column 6, line 22) or in EP-A 0 719 807 (column 2, line 53, to column 4, line 21).

Drphenylmethane/diisocyanate isomeric mixtures or crude MDI with a diphenylmethane diisocyanate isomer content from 33 to 55 mass% and urethane group-containing polyisocyanate mixtures based on diphenylmethane diisocyanate with an NCO content from 15 to 33 mass% have proven to be very good.

As compounds which are reactive in relation to isocyanates, compounds with at least two hydrogen atoms which are reactive in relation to isocyanates can be used. For this, compounds bearing two or more reactive groups, selected from OH groups, SH groups, NH groups, NH2 groups and CH-acidic groups, in the molecule come into consideration.

Those with a functionality from 2 to 8, preferably 2 to 6, and an average molecular weight from 60 to 8000 are suitably used. Usable are e.g. polyether polyamines and/or preferably polyols selected from the group of polyether polyols, polyester polyols, polythioether polyols, polyesteramides, hydroxyl group-containing polyacetals and hydroxyl group-containing aliphatic polycarbonates or mixtures of at least two of the aforementioned polyols, which preferably have an average molecular weight from 301 to 4000. Polyester polyols and/or polyether polyols are preferably used. The hydroxyl number for the polyhydroxyl compounds is then usually 100 to 850 and preferably 200 to 600. Further details regarding the compounds that can be used are e.g. to be found in EP-A 0 421 269 (column 6, line 23, to column 10, line 5) or EP-A-0 719 807 (column 4, line 23, to column 7, line 55). The PUR hard foams can be produced without or with the combined use of chain extenders and/or cross-linking agents. For modification of the mechanical properties, e.g. hardness, it may however prove advantageous to add chain extenders, cross-linking agents or possibly also mixtures thereof. Diols and/or triols with molecular weights lower than 400, preferably from 60 to 300, can be used as chain extenders and/or cross-linking agents. Aliphatic, cycloaliphatic and/or araliphatic diols with 2 to 14, preferably 4 to 10, carbon atoms are preferably considered. Further details regarding these

and further other useful compounds can be found, for example, in EP-A-0 421 269 (column 10, lines 6 to 48).

If chain extenders, cross-linking agents or mixtures thereof are used for the production of the rigid foams, these are suitably used in an amount of from 0 to 20% by weight, preferably from 2 to 8% by weight, calculated on the weight of the isocyanate-reactive compounds with a molecular weight from 60 to 8000.

As propellants, the usual physical propellants such as alkanes, alkenes, cycloalkanes, esters, ethers, ketones, acetals and/or fluoroalkanes, and chemically acting propellants, such as water, can be used. For example, the following must be mentioned in detail: Butane, n-pentane, iso-pentane, cyclopentane, cyclohexane, methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl ethyl ether, diethyl ether, acetone, formaldehyde dimethyl acetal, tetrafluoroethane, difluorochloromethane and/or 1,1,1-dtchlorofluoroethane. The physical propellants can of course also be used in the form of mixtures.

The use of a combination of physical propellants and water, i.e. carbon dioxide, which is formed by the reaction of water with isocyanate, is preferred. Particularly preferably, a propellant mixture containing water and cyclopentane is used, especially a propellant mixture containing water, cyclopentane and at least

one substance isopentane and/or n-pentane.

As catalysts for the production of the PUR and/or PUR/PIR rigid foams, compounds are used in particular which greatly accelerate the reaction of compounds in component (b) containing reactive hydrogen atoms, especially hydroxyl groups, with the organic, optionally modified polyisocyanates (a). The isocyanate group can be brought into reaction by means of suitable catalysts,

but can also be brought into reaction with each other, since in addition to the adducts between the isocyanate and the compounds with hydrogen-active groups, isocyanurate structures are preferably formed.

Substances that accelerate the reaction of the isocyanates, especially urethane, urea and isocyanurate formation, are therefore used as catalysts. Preferred for this are tertiary amines, tin and bismuth compounds, alkali and alkaline earth carboxylates, quaternary ammonium salts, s-hexahydrotriazines and tris-(dialkylaminomethyl)phenols.

Further details regarding applicable catalysts are e.g. to find

in EP-A-0 719 807 (column 9, lines 5 to 56).

The reaction mixture for the production of the PUR and/or PUR/PIR rigid foams can optionally be mixed with auxiliaries and/or additives. For example, surface-active substances, foam stabilizers, cell regulators, fire protection agents, fillers, dyes, pigments, hydrolysis protection agents, fungistatic and bacteriostatic substances should be mentioned. Further details regarding the applicable compounds are e.g. to be found in EP-A-0 421 269 (column 12, line 55, to column 14, line 16) or EP-A-0 719 807 (section 9, line 58, to column 13, line 17).

For the production of the PUR rigid foams, the organic and/or modified organic polyisocyanates and the compounds reactive in relation to isocyanates are brought into circulation in such quantities that the equivalence ratio of NCO groups in the polyisocyanates to the sum of the reactive hydrogen atoms is 0.85 to 1.75 :1, preferably 1.0 to 1.3:1 and especially 1.1 to 1.2:1. If the isocyanate-based hard foams at least partially contain isocyanurate groups in bound form, a ratio of NCO groups in the isocyanates to the sum of the reactive hydrogen atoms in the compounds that are reactive to isocyanates is usually used from 1.5 to 60:1, preferably 3 to 8: 1.

The hard foam materials are advantageously manufactured according to the one-shot method (one-shot-Verfahren), for example using high-pressure or low-pressure technology, in open or closed molding tools, for example metallic molding tools. It has proven to be particularly advantageous to work according to the two-component method and to combine the isocyanate-reactive compounds, propellants and possibly the catalysts, auxiliaries and/or additives in the component

(A), the so-called polyol component, and to use as component (B), the so-called isocyanate component, the isocyanates or mixtures of the isocyanates and optionally

propellants.

The production of sandwich elements, pipes or other objects according to the invention is generally known.

For example, the starting components are mixed at a temperature from 15 to 80°C, preferably from 20 to 30°C, and placed in an open or possibly under elevated pressure in a closed molding tool. The mold temperature is suitably 20 to 70°C, preferably 30 to 60°C, especially 40 to 50°C. Preferably, the walls of the mold tool can be thermally insulated, for example by inserting hard foam parts.

In the production of polyurethane or polyurethane/polyisocyanurate foams, temperatures preferably occur between 100 and 170°C. At these temperatures, layer (iiia) melts without destroying layer (iv).

Sandwich elements can, for example, be produced discontinuously by inserting the layer order according to the invention into a molding press and foaming the cavity in a known manner with hard foam substances on an isocyanate basis. If the layer order is placed over rollers in a double conveyor belt, the combinations according to the invention can be produced continuously in the form of sandwich elements also in a manner known per se, as layer (i) is added by continuous addition of the mixture which is capable of foaming.

In an analogous way, insulated pipes can be produced discontinuously, by fixing the medium pipe centrically in the casing pipe with the layer order according to the invention by means of spacers and foaming out the cavity between the pipes in a known manner. Due to the poor heat conduction in the casing tube, temperatures occur in the interior which lead to the welding of the layers (iii), (iiia) and (iv). A continuous production of the pipes according to the invention is also possible, for example, with the help of a known mold conveyor belt, as the foam system is first fed onto the medium pipe and directly in connection, the layers according to the invention are wrapped, for example. Also in this way, according to the invention, the welding of the layers takes place with the help of the heat of reaction that occurs.

The invention shall be explained in more detail on the basis of the following examples.

The starting components for the production of the polyisocyanate polyaddition products are shown in table 1.

The entries in table 1 are parts by weight.

Polyol 1: Polyol mixture based on sorbitol, pentaerythritol and sucrose; hydroc.

number of stitches: 458 (440-480), average functionality: 4.5 (4.4-4.6).

Polyol 2: Polyol mixture based on sorbitol and propylene glycol; hydroxyl number: 397

(380-420), average functionality: 4.2 (4.1 -4.3)..

Polyol 3: Polyol mixture based on sorbitol, pentaerythritol, sucrose and glycerol;

hydroxyl number: 492 (480-510), average functionality: 4.6 (4.5-4.7).

Polyol 4: Polyol mixture based on sorbitol, pentaerythritol, sucrose and glycerol;

hydroxyl number: 489 (470-500), average functionality: 4.8 (4.7-4.9). Propellant: Physically acting propellant based on alkanes/cycloalkanes.

The rigid foam materials exhibit the reaction parameters indicated in Table 2.

Has each example been carried out with four systems? Please indicate which products were manufactured with which system.

Production of the polyurethane/hard foam combinations

A) Plate-shaped combinations

100 parts by weight of the A component were foamed corresponding to the mixing ratio indicated in the table under intensive stirring or with the aid of a high-pressure foaming machine. The mixture of the A component and the isocyanate as B component was immediately after mixing poured into a 45°C tempered mold tool with the dimensions 300 mm x 400 mm x 80 mm, the mold tool having been made narrower by inserting hard foam material parts to a thickness of 40 mm. Because of the foam inserts, temperatures occur in the combination to be produced during the foaming which allow a thermoplastic polyethylene/polyethylene connection. In this molding tool, which has been made narrower, in the comparison experiment, polyethylene sheets with a thickness of 3 mm are inserted and, when producing the combination according to the invention, in addition, combination foils for building up the combination layer order at the top and bottom, so that the cavity of 4080 cm<3> which is to be foamed with foam, is approx. 34 mm thick. 285.6 g of the foam system was fired into this cavity, so that the total thickness of the hard foam core in the combination was 70 kg/m<3>. After a shaping time of 30 minutes, the combination bodies were taken out. These were stored for 24 hours at room temperature (corresponding to a freshly prepared combination) and several months at 80°C (corresponding to an aged combi-

nation). During storage at 80°C, the sides of the combination plate with the dimensions 300 mm x 400 mm x 40 mm are sealed with a polyurethane molding compound, covered with a 200 µm aluminum layer, so that gas exchange processes only take place

above the combination layers. Immediately before the measurement, the test bodies 200 are separated

mm x 200 mm x 40 mm with a hard foam core with a thickness of 34 mm from the center of the plate.

The thermal conductivity at room temperature was measured with the apparatus ANACON, model 88, from the company Anacon, St. Peters Road, Maidenhead, Berkshire, England SL6 7QA, at a mean temperature of 23.9°C (gradient 37.7°C /10°C) and the thermal conductivity at elevated temperature with the device Rapid-k VT 400 from the company Holometrix Inc., Boston, USA.

The aging of the foam in the combination was investigated as follows

storage in a temperature gradient ("gradient storage"):

The combination according to the invention, e.g. The layer order steel/PUR foam (i)/plastic layer (ii)/barrier layer (iii)/polyolefin layer (itta)/polyolefin layer (iv) is heated on the steel side by means of a hot plate to a temperature of 180°C and on the outer polyolefin side (e) at 80°C (when placing the device in a ventilated cabinet with an internal temperature of 80°C).

The combination is stored for three months in this way.

For comparison, a combination that is not according to the invention is stored, e.g. the layer order steel/PUR foam (i)/polyolefin layer (iv) in the same way. Before and after storage, the nature of the foam material in the surroundings of the hot steel layer is assessed.

B) Tubular combinations

A steel pipe with a length of 6 m with an outer diameter of 60.3 mm fix-

res in a known manner concentrically in a polyethylene tube with an inner diameter of 125

mm with plastic spacers, and the front sides are sealed with steel washers. The space between the tubes of 56,51 is foamed out with rigid foam material, as the mechanically produced reaction mixture of A and B components is introduced through suitable openings in one of the steel discs. The overall density of the foam is chosen between 80 and

100 kg/m<3>.

Combinations according to the invention were by inserting the pas-

send layer-order produced in the form of pre-produced foils in the interior of

the polyethylene pipe. The foils were thereby pressed onto the polyethylene pipe inner wall before foaming by inflation.

The thermal conductivity of the foam material is measured with the ANACON device on 20 mm thick test pieces, which are taken out of the pipe and have dimensions of 7.5 cm x 20 cm.

Example 1

Plate-shaped combination according to (A) (comparison)

Layer order in the combination:

Layer (iv) polyethylene, 3 mm thickness, corona-etched on the inner side, i.e. against

rigid foam side,

layer (i) hard foam4,

layer (iy) polyethylene, corona-etched on the inside, 3 mm.

Adhesive strength in the combination, according to DIN 53292: > 0.1 N / mm<2>

Thermal conductivity at 23°C after 24 hours of storage at room temperature 22.9 mW/mK

Thermal conductivity at 23°C after 3 months of storage/80°C: 27 mW/mK

Corona etching is a known method for surface treatment with the aim of improving adhesion by means of electrical discharge, i.e. high voltage spark discharge. A suitable device is e.g. the type Arcojet<®> from the company Agrodyn Hoch-spannungs-GmbH, Steinhagen. Such a surface treatment is preferably carried out in the method according to the invention.

Example 2

Plate-shaped combination according to (A) (comparison)

Layer order in the combination:

Layer (iv) polyethylene, corona-etched on the inside, 3 mm,

layer (iii) aluminum, 30 um,

layer (i) hard foam4,

layer (iii) aluminum, 30 um,

layer (iv) polyethylene, corona-etched on the inside, 3 mm.

No adhesive combination could be produced.

Example 3

Plate-shaped combination according to (A) (according to the invention) Layer order in the combination:

Layer (iv) polyethylene, corona-etched on the inside, 3 mm,

layer (iiia) polyethylene, 50 um, laminated,

layer (iii) aluminum, 6 µm, laminated,

layer (ii) polyethylene terephthalate, 12 µm, and polyamide, 15 µm, where the nylon shows i

direction of the rigid foam material,

layer (i) rigid foam 4, thickness 33.9 mm,

layer (ii) polyethylene terephthalate, 12 µm, and polyamide, 15 µm, where the nylon points in the direction of the rigid foam,

layer (iii) aluminum, 6 um,

layer (iiia) polyethylene, 50 µm,

layer (iv) polyethylene, corona-etched on the inside, 3 mm.

The layers (iiia), (iii) and (ii) were used in the form of a pre-cased combination foil from the company ITOCHU STAHL, GmbH, Dusseldorf.

Thermal conductivity at 23°C after 24 hours of storage at room temperature: 23.0 mW/mK

Thermal conductivity at 23°C after 3 months of storage/80°C: 23.0 mW/mK

Adhesive strength: > 0.1 N/mm<2>

Example 4

Plate-shaped combination according to (A) (according to the invention) Layer order in the combination:

Layer (iv) polyethylene, corona-etched on the inside, 3 mm,

layer (iiia) polyethylene, 100 µm,

layer (iii) aluminum, 9 um,

layer (ii) polyamide, 15 µm,

layer (i) rigid foam 1,

layer (ii) polyamide, 15 fim,

layer (iii) aluminum,.9 fim,

layer (iiia) polyethylene, 100 µm,

layer (iv) polyethylene, corona-etched on the inside, 3 mm.

The layers (iiia), (iii) and (ii) were used in the form of a pre-cased combination foil of type OPA15/ALU9/PE from the company DANISCO, Lyngby, Denmark.

Thermal conductivity at 23°C after 24 hours of storage at room temperature: 22.8 mW/mK

Thermal conductivity at 23°C after 3 months of storage/80°C: 23.0 mW/mK Thermal conductivity at 60°C after 24 hours of storage at room temperature: 28 mW/mK Thermal conductivity at 60°C after 3 months of storage/80°C: 27.9 mW/mK

Adhesive strength: > 0.1 N/mm<2>

Example 5

Plate-shaped combination according to (A) (according to the invention) Layer order in the combination:

Layer (iv) polyethylene, corona-etched on the inside, 3 mm,

layer (iiia) polyethylene, 100 µm,

layer (iiia) polyethylene terephthalate, 100 µm,

layer (iii) aluminium, sputtered, 0.20 fim,

layer (iiia) polyethylene terephthalate, 100 µm,

layer (iii) aluminum, 30 fim,

layer (ii) polyethylene terephthalate, 100 µm,

layer (i) rigid foam 1,

layer (ii) polyethylene terephthalate, 100 µm,

layer (iii) aluminum, 30 um,

layer (iiia) polyethylene terephthalate, 100 µm,

layer (iii) aluminium, sputtered, 0.20 um,

layer (iiia) polyethylene terephthalate, 100 µm,

layer (iiia) polyethylene, 100 µm,

layer (iv) polyethylene, corona-etched on the inside, 3 mm.

The layers (iiia), (iii) and (ii) were in the specified order and the specified number applied to layers in the form of a pre-cased combination foil.

Thermal conductivity at 23°C after 24 hours of storage at room temperature: 23.2 mW/mK

Thermal conductivity at 23°C after 3 months of storage/80°C: 23.4 mW/mK

Adhesive strength: > 0.1 N/mm<2>

Example 6

Plate-shaped combination according to (A) (according to the invention) Layer order in the combination:

Layer (ii) polyethylene, corona-etched on the inside, 3 mm,

layer (iiia) polyethylene, 100 µm,

layer (iiia) polyethylene terephthalate, 100 µm,

layer (iii) aluminum, sputtered, 0.2 fim,

layer (iiia) polyethylene terephthalate, 100 µm,

layer (iii) aluminum, 30 um,

layer (ii) of polyethylene terephthalate, 100 µm,

layer (i) rigid foam 6,

layer (ii) polyethylene terephthalate, 100 µm,

layer (iii) aluminum, 30 f<i>m,

layer (iiia) of polyethylene terephthalate, 100 µm,

layer (iii) aluminium, sputtered, 20 um,

layer (iiia) polyethylene terephthalate, 100 µm,

layer (iiia) polyethylene, 100 µm,

layer (iv) polyethylene, corona-etched on the inside, 3 mm.

The layers (iii), (iiia) and (ii) were applied in the specified order and the specified number to layers in the form of a pre-cased combination foil.

Thermal conductivity at 23°C after 24 hours of storage at room temperature 29.0 mW/mK

Thermal conductivity at 23°C after 3 months of storage/80°C: 29.3 mW/mK

Example 7

Plate-shaped combination according to (A) (comparison)

Layer order in the combination:

Layer (iv) polyethylene, 3 mm, corona-etched on the inside,

layer (i) rigid foam 2,

layer (iv) polyethylene, corona-etched on the inside, 3 mm.

Thermal conductivity at 23°C after 24 hours of storage at room temperature 29.2 mW/mK

Thermal conductivity at 23°C after 3 months of storage/80°C: 38.3 mW/mK

Example 8

Tubular combination according to (B) (comparison) Layer order from inside to outside:

(iv) steel (inner), 2.9-3.0,

(i) rigid foam, respectively 40 mm or 32.5 mm,

(iv) polyethylene, 3 mm.

0.5 m long pipe pieces were stored at 80°C with a seal on the side using a polyurethane molding compound with 200 µm aluminum foil.

The thermal conductivity for removed test pieces is:

Before storage (24 hours after foaming): 23.5 mW/mK

After 3 months of storage: 28.0 mW/mK

Example 9

Tubular combination according to (B) (according to the invention) Layer order from inside to outside:

(iv) steel (inner),

(i) rigid foam 1,

(ii) polyamide, 15 µm,

(iii) aluminium, 9 µm,

(iiia) polyethylene, 100 µm,

(iv) polyethylene, 3 mm, corona-etched on the inside.

Layers (iii), (iiia) and (ii) were used in the form of a pre-cased combination foil of type OPA15/ALU9/PE from the company DANISCO, Lyngby, Denmark.

0.5 m long pipe pieces were stored at 80°C with a seal on the side as in example 8.

The thermal conductivity of the removed samples was:

Before storage (24 hours after foaming): 23.5 mW/mK

After 3 months of storage: 24.0 mW/mK

Example 10

Plate-shaped combination according to (A) (comparison)

Layer order in combination:

(iv) steel, 2 mm,

(i) rigid foam, 35 mm,

(iv) polyethylene, 3 mm, corona-etched on the side facing the foam,

After gradient storage 180°C (steel side)/80°C (polyethylene side) for 3 months, the foam on the steel is charred and severely damaged.

Example 11

Plate-shaped combination according to (A) (according to the invention) Layer order in the combination:

(iv) steel, 2 mm,

(i) rigid foam 1,

(ii) polyamide, 15 fim,

(iii) aluminium, 9 fim,

(iiia) polyethylene, 100 fim,

(iv) polyethylene, 3 mm, corona-etched on the side facing the foam,

The layers (iiia), (iii) and (ii) were used in the form of a pre-cased combination foil of type OPA15/ALU9/PE from the company DANISCO, Lyngby, Denmark.

After gradient storage 180°C (steel side)/80°C (polyethylene side) for 3 months, the foam on the steel is still undamaged and only slightly discolored.

Claims (9)

1. Combination element characterized in that it exhibits the following layer: i) polyisocyanate-polyaddition product, ii) possibly at least one plastic material, iii) material that prevents gas penetration, and which is connected to at least one (iv) thermoplastic plastic material and can be achieved by the fact that in a reaction space which is limited by the following layer: ii) possibly at least one plastic material, and in addition to this iii) a material that prevents gas penetration, Hia) 20 to 500 pm of at least one thermoplastic plastic material, as well as iv) 1 to 25 mm of at least one thermoplastic plastic material, isocyanates are reacted with compounds that are reactive in relation to isocyanates in the presence of propellants and possibly catalysts, auxiliaries and/or additives, whereby iiia) melts with the help of the heat of reaction and after cooling connects (iii) and (iv) with each other. 2. Combination element according to claim 1, characterized in that it has a metal foil as (iii). 3. Combination element according to claim 1 or 2, characterized in that it exhibits the following layer in cross-section: i) 0.5 to 80 cm polyisocyanate-polyaddition product, ii) optionally 5 to 1000 µm of at least one plastic material, iii) 0.1 to 200 µm of a metal foil which on the side which is turned away from (i) and (ii) has a layer of 20 to 500 µm of at least one thermoplastic plastic substance (iiia) which, when melted, connects (iii) and (iv) to each other, iv) 1 to 25 mm of at least one thermoplastic plastic material. 4. Use of combination elements according to one of claims 1 to 3 as insulated pipes, sandwich elements, thermal insulation elements for cooling and heating units and/or thermally insulated containers. 5. Sandwich element which is a combination element according to claim 1, . characterized in that it exhibits the following layer in cross-section: iv) 1 to 25 mm of at least one thermoplastic plastic material. iii) 0.1 to 200 µm of a metal foil which, on the side facing away from (i) and (ii), has a layer of 20 to 500 µm of at least one thermoplastic plastic substance (iiia) which, when melted, connects (iii) and (iv) with each other, ii) optionally 5 to 1000 µm of at least one plastic material, i) 0.5 to 80 cm polyisocyanate-polyaddition product, ii) optionally 5 to 1000 µm of at least one plastic material, iii) 0.1 to 200 um of a metal foil which, on the side facing away from (i) and (ii), has a layer of 20 to 500 um of at least one thermoplastic plastic substance (iiia) which, when melted, connects (iii) and (iv) to each other, iv) 1 to 25 mm of at least one thermoplastic plastic material. 6. Pipe which is a combination element according to claim 1, characterized in that it exhibits the following layer in cross-section: iv) 1 to 25 mm of at least one thermoplastic plastic material and/or at least one metal as inner pipe, i) 0.5 to 80 cm polyisocyanate polyaddition product, ii) optionally 5 to 1000 µm of at least one plastic material, iii) 0.1 to 200 µm of a metal foil which, on the side facing away from (i) and (ii), has a layer of 20 to 500 um of at least one thermoplastic plastic material (iiia) which, when melted, connects (iii) and (iv) to each other, iv) 1 tii 25 mm of at least one thermoplastic plastic material as outer tube. 7. Pipe which is a combination element according to claim 1, characterized in that it exhibits the following layer in cross-section: iv) 1 to 25 mm of at least one thermoplastic plastic material and at least one metal as inner tube, iii) 0.1 to 200 µm of a metal foil which on the side facing away from ( i) and (ii) have a layer of 20 to 500 µm of at least one thermoplastic plastic material (iiia) which, when melted, connects (iii) and (iv) to each other, ii) optionally 5 to 1000 µm of at least one plastic material, i) 0.5 to 80 cm porisocyanate polyaddition product, ii) optionally 5 to 1000 µm of at least one plastic material, iii) 0.1 to 200 µm of a metal foil which, on the side facing away from (i) and (ii), has a layer of 20 to 500 µm of at least one thermoplastic plastic material (iiia) which, when melted, connects (iii) <p>g (iy) to each other, iv) 1 to 25 mm of at least one thermoplastic plastic material as outer tube. 8. Method for producing a combination element, characterized in that there is a reaction space which is limited by the following layer: ii) possibly at least one plastic material, and in addition to this iii) a material that prevents gas penetration, iiia) 20 to 500 um of at least one thermoplastic plastic material, and iv) 1 to 25 mm of at least one thermoplastic plastic material, isocyanates are reacted with compounds that are reactive in relation to isocyanates in the presence of propellants and possibly catalysts, auxiliaries and/or additives, whereby iiia) melts with the help of the heat of reaction and after cooling connects (iii) and (iv) with each other. 9. Method according to claim 8, characterized in that (iii) and (iiia) are used in the form of a layer of applied combination foil.