DE102012023180A1 - Producing two-layer foam sheets by bonding of two thinner sheets of foam to at least two-layer foam sheet, comprises applying hot-melt adhesive comprising polymer e.g. polyolefins, polyesters, polyamides, on surface of thinner foam sheet - Google Patents

Abstract

Producing at least two-layer foam sheets by bonding of at least two thinner sheets of foam to at least two-layer foam sheet, comprises applying at least one hot-melt adhesive on at least one surface of at least a thinner foam sheet. The hot melt adhesive comprises at least one polymer comprising polyolefins, polyesters, polyamides, polyacrylates, styrene-isoprene copolymers, styrene-butadiene copolymers, ethylene-vinyl acetate copolymers or polyvinyl acetate.

Description

The present invention relates to a process for the production of at least two-layer foam sheets by bonding at least two thinner foam sheets, wherein at least one surface of at least one thinner foam sheet at least one hot melt adhesive is applied. The hot melt adhesive comprises at least one polymer (P1) such as polyvinyl acetate (PVA) or ethylene-vinyl acetate copolymers. Furthermore, the present invention relates to the foam sheets as such, which are at least two-ply. The number of layers of the foam sheet as such results from the number of thinner foam sheets which are glued together. For example, when three thinner foam sheets are bonded together, a three-layer foam sheet is obtained as such, in the case of four thinner foam sheets, therefore, a four-layer foam sheet as such is obtained.

EP-A 1 318 164 relates to a process for producing thick extruded polystyrene foam boards (XPS boards) by joining two or more thin boards. The thick plates are obtained by uniformly wetting the thin plates at the surfaces where they are to be joined with an organic solvent for polystyrene. As a result, the foam surface is dissolved and the plates can then be pressed together. Suitable solvents are, for example, hydrocarbons, alcohols or ethers which have a boiling point between 50 and 250 ° C. Furthermore, in the method according to EP-A 1318 164 the foaming skins are peeled on the major surfaces of the plates to be joined together before they are wetted with the solvent.

EP-A 1 213 119 discloses a method for joining at least two thermoplastic resin foam starting sheets to a new sheet, wherein the starting sheets are extrusion skinless at the mating surfaces, and the source sheets are bonded by fusion welding. For solvent welding organic solvents are used which have a boiling point <150 ° C, for example acetone or mixtures of organic solvents with water.

EP-A 1 566 400 discloses foam panels having a coating on at least one panel surface, the coating including a polymeric film having a glass transition temperature in the range of -60 to + 40 ° C. The foam sheets may be, for example, a particle foam of polystyrene or polyolefin. The polymer film is formed on the foam sheets by applying a corresponding polymer dispersion to the foam sheets, which is then allowed to dry. The polymer dispersion or the polymer film resulting therefrom as a coating usually contains an amorphous, thermoplastic polymer, preferably a styrene-containing polymers such as styrene-acrylates and styrene-butadiene copolymers are used. The polymer dispersion may also contain numerous other substances such as fillers, flame retardants or infrared (IR) absorbing solids. These foam boards are suitable for the adhesion of mortar, concrete and plaster systems, in particular, they are used as a thermal insulation material in construction. EP-A 1 566 400 however, does not disclose that a plurality of individual such foam sheets can be assembled into a multi-ply thicker foam sheet. Nor is it disclosed therein that the polymer dispersions used are hot melt adhesives.

Extruded plastic foam sheets of great thickness are used in DE-A 101 063 341 disclosed. With the method described for connecting at least two plastic foam output plates to a new plate, it is possible to produce plates with a minimum thickness of 70 mm. Preferably, these are fuorchlorkohlenwasserstofffreie polystyrene foam sheets. In the process, the starting plates, which are non-extrusion-free at the contact surface, are bonded together using a diffusion-open adhesive or mechanical fasteners. Alternatively, the method can also be carried out in such a way that a non-diffusible adhesive or only a slightly diffusible adhesive is used in the case of part-area connection and spot welding or partial bonding. As polystyrene foam boards are particularly suitable XPS boards. In DE-A 101 063 341 However, there is no information as to which specific chemical composition the adhesives used, which may also comprise reaction adhesives and / or hot-melt adhesives, or whether the adhesives may contain further components such as flame retardants or absorbers.

Another method for joining at least two plastic foam board starting sheets to a new sheet, which is preferably a polystyrene foam sheet having a minimum thickness of 70 mm, is disclosed in U.S. Pat EP-A 1 471 125 disclosed. In this process, starting plates are also used, which are extrusion skinless at least at the contact surface, and the starting plates are connected to a diffusion-open adhesive using a hot-melt adhesive and / or reaction adhesive. The adhesive consists of isocyanate and at least one other reaction group, which is a resin that in molten state is sticky and gives the adhesive bond an early strength.

The isocyanate and the resin thereby react to polyurethane, whereby the adhesive effect is achieved with a final strength.

Thermal insulation materials made of XPS composite materials, which are three-layered, are incorporated in WO 2012/016991 described. The three-ply nature of the composite materials results from combining lower, central, and upper XPS panels into the XPS composite, with each outboard side of this XPS composite comprising an extrusion skin. While the contact faces of the central XPS panel also have an extrusion skin, it is removed at the corresponding contact faces of the upper and lower XPS panels. The individual XPS panels are joined to the XPS composite material by thermal welding to the contact surfaces. WO 2012/016991 contains no information as to whether, alternatively or in addition to welding, adhesives may optionally be used in conjunction with flame retardants.

WO 2009/047487 discloses multilayer composite materials comprising a first layer of a closed cell foam of a thermoplastic and a second layer of a fiber reinforced resin deposited on the surface of the first layer. The closed-cell foam has a mean cell size of less than 100 microns, preferably it is a mixture of polystyrene and polyphenylene oxide (PS / PPO). These layered composite materials are suitable for producing larger structures, for example for wind turbine rotor blades.

A fundamental problem in gluing is the flammability and the performance of fire tests. Even if one takes into account that the to be bonded thinner plates and / or the adhesive itself are not or only very difficult to burn, a statement does not automatically apply to the product obtained, so the two- or multi-layer plates with a (compared to the thinner Output plates) of greater thickness. This different fire behavior is due to the formation of the so-called adhesive seam (also referred to as adhesive skin or adhesive layer) during the gluing process. The adhesive seam forms at the points where the surfaces of the thinner plates used are glued together. Depending on the presence or the thickness of the adhesive seam, the fire test B2 (in accordance with FIG DIN 4102 respectively. DIN EN ISO 11925-2: 2011-02 ) or not. The larger or thicker the adhesive seam, the higher the flames burn. This negative burning behavior (compared to the thinner starting plates) of the two-layered or multi-layered plates due to the presence of an adhesive seam is also referred to as the "wicking effect" which occurs at the boundary layer of the adhesive used to the thinner starting plate used. If, on the other hand, there is no adhesive seam or only a very thin adhesive seam, the respective thinner plates are not connected firmly enough so that the corresponding product is not stable.

The object underlying the present invention is to provide new two- or multi-layer foam boards as such or a corresponding method for producing such at least two-layer foam boards.

Is solved for the task by a method for producing at least two-layer foam boards by gluing at least two thinner foam sheets to the at least two-layer foam board, characterized in that at least one surface of at least one thinner foam plate at least one hot melt adhesive is applied, wherein the hot melt at least a polymer (P1) selected from the group of polyolefins, polyesters, polyamides, polyacrylates, styrene-isoprene copolymers, styrene-butadiene copolymers, ethylene-vinyl acetate copolymers or polyvinyl acetate (PVA).

The at least two-ply foam sheets produced by the method according to the invention are characterized in that the corresponding number of thinner foam sheets can be glued or joined in a very stable manner to the at least two-ply foam sheets and that these in particular have improved flame behavior. The improvement of the flame behavior is not at the expense of the adhesive effect.

As such, the at least two-layer foam boards have a high tensile strength, preferably a tensile strength of> 0.15 N / mm ² , and / or they pass fire tests in accordance with ISO standards B2. Particularly preferably, a tensile strength of> 0.15 N / mm ^{2 is} obtained even at a temperature of 70 ° C. The improved flame behavior is due to the use of the special hot melt adhesives comprising at least one polymer (P1), whereby the wicking effect is completely prevented or at least greatly reduced.

The stable assembly of the individual thinner foam boards according to the invention by gluing using the special hot melt adhesives comprising at least one polymer (P1). It is therefore not necessary that the individual thinner foam sheets are joined or glued together with the aid of a solvent (solvent welding) or by thermal welding. In the context of the present invention, however, in addition to the use of the particular hot melt adhesives comprising at least one polymer (P1), a thermal bonding step (by irradiation with electromagnetic radiation and optionally with the additional use of a corresponding absorber of electromagnetic radiation) may also be carried out to obtain the Cohesion or the adhesive effect of the individual thinner foam panels to increase further.

If an absorber of electromagnetic radiation is applied to the thinner foam boards together with the special hot-melt adhesive comprising at least one polymer (P1), a faster drying of the adhesive is observed as a result of the presence of the absorber or, if appropriate, the thermal welding represents another advantage. Due to the presence of the absorber, the adhesive can absorb much faster energy, resulting in faster drying and possibly better adhesive behavior.

Due to the presence of the absorber for electromagnetic radiation, the thermal welding to be carried out (in addition to bonding) also causes only the surface of the corresponding thinner foam sheet provided with the absorber to be selectively heated. Consequently, no holes are burned in the plate body during bonding / welding or this takes place only to an extremely small extent. This has the consequence that the corresponding thinner foam boards are not distorted during bonding in conjunction with the thermal welding, so that a precise adhesion of the individual thinner thermoplastic foam panels is observed, which in turn has a positive effect on the strength of the at least two-layer foam boards.

A particularly firm adhesion of the thinner foam sheets to be bonded together is then determined within the scope of the method according to the invention if at least one of the surfaces to be bonded of the thinner foam sheets is foam-free (also referred to as foam-free). In particular, this is to be determined if the surface to be bonded of the two thinner foam boards is foam-free for each pair of boards to be bonded. By removing the foam skin, a plate surface is produced which can better absorb the special hot-melt adhesive which comprises at least one polymer (P1) and consequently also has better adhesion compared to foam plates in which the foam skin (extrusion skin) has not been removed , Foam boards with foam skin have a much smoother surface, which, however, is usually not plane-parallel with the surface of the second plate to be bonded. As a result, warping of the panels during the bonding process is often observed, possibly resulting in reduced cohesion / reduced strength of the at least two-ply foam panels after bonding.

Furthermore, a particularly firm adhesion - in conjunction with an improved flame behavior - of the thinner foam sheets to be bonded together in the process of the invention is then determined, provided that the order of the special hot melt adhesive comprising at least one polymer (P1) under "bias", especially when applied to foam-free surfaces. An application under bias in the context of the present invention means that the corresponding hot-melt adhesive is applied uniformly in one direction (for example the x-direction) of the respective plate surface of the thinner foam sheets to be bonded. As a result, first a pre-orientation / pre-orientation of the macromolecules is achieved both by the hotmelt adhesive and by the foam board.

The at least two-layer foam boards according to the invention as such and the production method according to the invention of these foam boards by gluing with hot melt adhesives are defined in more detail below.

The foam sheet according to the invention is at least two layers, so it can have exactly two layers or be three-ply, four-ply, five-ply or even higher ply. As already stated above, the number of layers of the foam sheet as such results from the number of thinner foam sheets which are glued together. In the case of a two-ply foam board as such, therefore, two thinner foam boards are glued together. In a slurry or four-ply foam board as such, three or four thinner foam boards are thus glued together. If even higher-layer foam boards are to be produced as such, for example a ten-ply foam board, the number of layers corresponding number of thinner foam boards, for example, ten thinner foam boards must be glued together accordingly. Preferably, the foam sheet according to the invention two-ply, three-ply or four-ply, in particular, the foam sheet according to the invention is two-ply.

With regard to their chemical composition, the thinner foam boards used for bonding correspond to the at least two-layered foam boards produced as part of the process according to the invention (without taking into account the hot melt adhesives applied to the surfaces during the bonding process and any optionally applied components such as flame retardants, binders, absorbers of electromagnetic radiation Etc.). The thinner foam sheets to be bonded together preferably have the same dimensions and / or the same chemical composition. Optionally, but also foam plates with different dimensions and / or different chemical composition can be glued together. For example, if three thinner foam sheets are glued together, all of which have the same sizing and are (for example) an extruded polystyrene foam (XPS foam), a three-ply extruded polystyrene foam (XPS) is thereby obtained.

The dimensioning of the thinner foam sheets to be bonded together is arbitrary. With regard to their length and width, they can measure in the centimeter range up to several meters. With regard to the third dimension (thickness), theoretically any dimensions are also conceivable; in practice, the thinner foam sheets have a thickness of 10 to 150 mm. The thickness of the at least two-layer foam boards produced in the process according to the invention thus results from the total thickness of the thinner foam boards used overall. In particular, if a pressing step is carried out in the context of the production method, the thickness of the at least two-layer foam sheets as such is less than the sum of the respective thicknesses of the thinner foam sheets used.

The thinner foam boards used for bonding as such are known in principle to the person skilled in the art. Suitable foam boards are for example in EP-A 1 566 490 or in the form of blends in WO 2009/047487 disclosed.

Preferably, the thinner foam sheets are a particle foam or an extrusion foam. Furthermore, it is preferred that the thinner foam sheets have a density <200 g / l. Furthermore, it is preferred that the thinner foam sheets are thinner thermoplastic foam sheets. This applies in particular to the case described below in that, in addition to bonding, thermal welding is carried out and / or the dried, thinner foam panels are activated by electromagnetic radiation.

More preferably, the thinner foam sheets are an extrusion foam, preferably a thermoplastic extrusion foam. The extrusion foam is preferably a polystyrene or styrene-made copolymer. Optionally, mixtures of such polymers can be used. More preferably, the extruded foam is extruded polystyrene (XPS), which is commercially available for example under the name styrodur ^® from BASF SE.

If the extrusion foam is based on (at least) one styrene copolymer (also referred to as styrene copolymers), this means that in addition to the monomer styrene at least one further monomer is required for the preparation of this copolymer. Preferably, this copolymer is prepared from styrene and another monomer. In principle, all styrene-polymerizable monomers are suitable as comonomers of styrene. Preferably, at least 50% by weight of styrene are copolymerized in this copolymer.

Preferably, a styrene-made copolymer as a comonomer to styrene has a monomer selected from α-methylstyrene, ring-halogenated styrenes, nuclear-alkylated styrenes, acrylonitrile, acrylic acid esters, methacrylic acid esters, N-vinyl compounds, maleic anhydride, butadiene, divinylbenzene or butanediol diacrylate. Acrylic acid esters and methacrylic acid esters are preferably obtainable from alcohols having 1 to 8 carbon atoms. A suitable N-vinyl compound is, for example, vinylcarbazole. Preferred copolymers prepared from styrene are styrene-acrylonitrile copolymers (SAN) or acrylonitrile-butadiene-styrene copolymers (ABS).

The hot melt adhesives usable as such in the process according to the invention are known to the person skilled in the art and are defined by the fact that the hot melt adhesive comprises at least one polymer (P1) selected from the group of polyolefins, polyesters, polyamides, polyacrylates, styrene-isoprene copolymers, styrene Butadiene copolymers, ethylene-vinyl acetate copolymers or polyvinyl acetate (PVA).

More preferably, the polymer (P1) is selected from polyvinyl acetate (PVA) or ethylene-vinyl acetate copolymers.

Preferred hot melt adhesives are further characterized in that the hot melt adhesive at temperatures of 80 ° C to 160 ° C, preferably from 85 ° C to 130 ° C, in particular from 90 ° C to 115 ° C, is applied.

Furthermore, it is preferred that the hot melt adhesive comprising at least one polymer (P1) is used as a mixture with a moisture-curing polyurethane hot melt adhesive. The last-mentioned hot-melt adhesive thus comprises at least one isocyanate-terminated polyurethane, it being possible for the isocyanate end groups to cure and / or crosslink preferably after joining the file with atmospheric moisture or with added water.

In the process according to the invention, at least one hot melt adhesive is applied to at least one surface of at least one thinner foam sheet, the hot melt adhesive comprising at least one polymer (P1) according to the above definitions.

Preferably, at least one hot-melt adhesive is applied to only one surface of the thinner foam boards to be bonded per board pair to be bonded. Methods for applying a hot melt adhesive are known in the art, for example, the hot melt adhesive can be applied over a large area on the corresponding surface of the thinner foam sheet. The application of the hot melt adhesive can be carried out by the usual methods, for example by brushing, spraying, rolling, knife coating or printing. The amount of adhesive applied is generally between 10 g / m ² to 400 g / m ² (solid), preferably 20 g / m ² to 200 g / m ² . The hot melt adhesive is particularly preferably applied in amounts of <100 g / m ² , preferably of <50 g / m ² (based on the surface of a plate to be bonded per plate pair). The minimum amounts are preferably 10 g / m ² , in particular 20 g / m ² . Preferably, the aforementioned amounts of adhesive are applied only to a surface to be bonded of the thinner foam sheets (per pair of plates), while on the second surface to be bonded no hot melt adhesive or other adhesive is applied. In the context of the present invention, no further adhesives are preferably used in addition to the hot-melt adhesives listed above.

Preferably, in the context of the method according to the invention, the hot-melt adhesive is applied in the molten state to the surface of the thinner foam boards to be bonded. The implementation of the melting of a hotmelt adhesive is known in the art.

In a preferred embodiment of the present invention, the hot-melt adhesive is applied, in the molten state, to at least one surface of at least one thinner foam sheet, wherein the application of the hot melt adhesive takes place uniformly in one direction of the respective sheet surface. This embodiment is also referred to as an application (of the hot-melt adhesive) under prestress.

In a further preferred embodiment of the present invention, the hot melt adhesive is structured, preferably dot-shaped, linear or latticed, in particular lattice-shaped, applied to at least one surface of at least one thinner foam board.

This embodiment of the present invention, which is also referred to as structured bonding, will be explained in more detail below. The structured bonding with the hot melt adhesive can be done by any structures or structural forms. Preferably, 20 to 80%, more preferably 40 to 80%, in particular 50 to 75%, of the respective plate surface are provided with hot melt adhesive on the surface of the thinner foam board, to which the hot melt adhesive is applied structured.

In the context of the present invention, the structures may also be referred to as patterns or structuring patterns. A structure is made up of at least one structural form, which may also be referred to as a structural unit. In the context of the present invention, a structural unit (structural form) is understood to mean the smallest unit in a pattern (structure). Such a structural unit may, for example, be a check, a rhombus, a rectangle, a cross, a square or a line. Optionally, such structural units can alternate or be combined with one another. Thus, patterns are conceivable which are constructed from a plurality of different structural units, for example from a plurality of lines of different thickness (width) and / or depth, which alternate, for example, with diamonds or squares. Thus, also in a grid, different structural units may be included, for example, squares of different sizes, which are arranged alternately. Such structures are also called rasters. For example, a grid can also be formed from several crosses. Such a structure, in the context of the present invention, represents an embodiment of a grid.

The distances between the individual structural units on the respective surface of the thinner thermoplastic foam sheet produced by applying the hot-melt adhesive may take on any values (sizes). Preferably, the distance between the individual structural units of the structured applied hot melt adhesive is 5 to 50 mm (average over the entire pattern), in particular Distance 7.5 to 20 mm. The width of a structural unit (structure), for example, the diameter of a dot (in a dot-shaped structure) or the width of a line (in a line or lattice-shaped structure) may be arbitrary, preferably in the range of 1 to 100 mm, more preferably 5 to 50 mm, in particular 10 to 25 mm.

If, in this embodiment of the present invention, the hot melt adhesive per pair of plates is to be applied to both surfaces of the thinner foam sheets to be bonded to one another, it is preferred that the two surfaces to be bonded have identical or at least 80% matching patterning patterns (pattern or structure). The two surfaces to be bonded preferably have identical patterning patterns. Furthermore, it is preferred that the surfaces to be bonded are superimposed prior to bonding in such a way that as many as possible of the structures produced with the hot melt adhesive come to coincide with one another on both surfaces to be bonded. Particularly preferred in this embodiment of this embodiment, two surfaces are glued together with identical structuring pattern, wherein the surfaces to be bonded are superimposed prior to bonding so that the structures produced with the hot melt adhesive on both surfaces to be bonded completely coincide with each other.

As mentioned above, in addition to the special hot melt adhesives which comprise at least one polymer (P1), it is also possible to apply further substances with different use properties to the surface to be bonded of the corresponding thinner foam boards. Suitable further substances may be, for example, flame retardants, graphite, absorbers of electromagnetic radiation and / or binders and, if appropriate, solvents. Flame retardants, graphite, absorbers of electromagnetic radiation, binders and solvents as such are known to the person skilled in the art. The aforementioned optional components may be used alone or in any combination with the particular hot melt adhesives comprising at least one polymer (P1).

In one embodiment of the method according to the invention, the hot-melt adhesive is part of a mixture which additionally contains at least one flame retardant and / or graphite.

Flame retardants as such are known in the art. Suitable flame retardants are, for example, in Jürgen Troitzsch "Plastics Flammability Handbook" (3rd ed., Hanser Verlag) described. Preferred flame retardants in the context of the present invention are selected from a phosphate, a phosphite, a phosphonate, a polyphosphonate, melamine, a metal oxide hydrate, in particular an aluminum oxide hydrate, or a halogenated organic compound.

Preferred phosphates and phosphonates are selected from DMMP (dimethymethylphosphonate), DMPP (dimethylpropyl phosphonate), TCEP (tris (chloroethyl) phosphate), TCPP (tris (chloropropyl) phosphate), TDCPP (tris (dichloroisopropyl) phosphate), TPP (triphenyl phosphate), TEHP (Tris (2-ethylhexyl) phosphate), TKP (tricresyl phosphate) or TCEP (trichloropropyl phosphate).

A particularly preferred flame retardant is dimethylpropylphosphonate (DMPP), which is commercially available, for example, under the name Levagard DMPP from Lanxess.

Non-water-soluble flame retardant or graphite are preferably track levels as a fine powder, examples are expandable graphite, commercially available as Melapur MC ^® and Melapur MP ^® from BASF. Powdered flame retardants can also be surface-modified, so that a good distribution is possible.

• i) die Gesamtmenge an Flammschutzmittel ≥ 4 Gew.-% (bezogen auf die Gesamtmenge an Klebstoff) beträgt, oder
• ii) die Gesamtmenge an Flammschutzmittel ≥ 2,5 Gew.-% beträgt, sofern das Flammschutzmittel als Gemisch mit mindestens 2,5 Gew.-% Graphit eingesetzt wird (Mengenangaben jeweils bezogen auf die Gesamtmenge an Klebstoff).

In one embodiment of the method according to the invention, on at least one surface of at least one thinner foam sheet, a mixture containing at least one hot melt adhesive comprising at least one polymer (P1) and at least one flame retardant is applied, wherein in the mixture

• i) the total amount of flame retardant ≥ 4 wt .-% (based on the total amount of adhesive) is, or
• ii) the total amount of flame retardant ≥ 2.5 wt .-%, if the flame retardant is used as a mixture with at least 2.5 wt .-% graphite (quantities in each case based on the total amount of adhesive).

In the mixture containing at least one hotmelt adhesive which comprises at least one polymer (P1) and at least one flame retardant is (according to the first variant of the present embodiment), the total amount of flame retardant ≥ 4 wt .-% (based on the total amount of hot melt adhesive), preferably the total amount of flame retardant 4.5 to 15 wt .-% (based on the total amount of hot melt adhesive), in particular, the total amount of flame retardant 5 to 10 wt. -% (based on the total amount of hot melt adhesive).

In this embodiment of the present invention, the total amount of flame retardant (second variant) may also be slightly less than ≥ 4 wt .-% (based on the total amount of hot melt adhesive), if the flame retardant is used as a mixture with graphite, preferably with expandable graphite. According to the second variant, the total amount of flame retardant ≥ 2.5 wt .-%, if the flame retardant is used as a mixture with at least 2.5 wt .-% graphite (quantities in each case based on the total amount of hot melt adhesive). According to the second variant, the total amount of flame retardant is preferably ≥ 3.5 wt .-% (based on the total amount of hot melt adhesive), more preferably, the total amount of flame retardant 4.5 to 15 wt .-% (based on the total amount of hot melt adhesive ), in particular, the total amount of flame retardant 5 to 10 wt .-% (based on the total amount of hot melt adhesive). The total amount of graphite, preferably of expandable graphite, is preferably ≥ 4% by weight (based on the total amount of hot melt adhesive), in particular the total amount of graphite is 5 to 10% by weight (based on the total amount of hot melt adhesive).

In one embodiment of the method according to the invention, the hot-melt adhesive is part of a mixture which comprises at least one absorber of electromagnetic radiation ("absorber"). Suitable absorbers are for example in WO 2009/071499 on pages 9 to 11. In the context of the present invention, an absorber of electromagnetic radiation is generally used when, in addition to bonding, preferably simultaneously or subsequently, a thermal welding step is carried out. If appropriate, at least one absorber of electromagnetic radiation can additionally be applied to at least one thinner foam board without a thermal welding step being carried out.

Preferably, in the context of the present invention, the absorber of electromagnetic radiation is selected as a function of the electromagnetic radiation used for thermal welding. For example, when thermal welding is performed using microwave rays, it is preferable to select an electromagnetic radiation absorber having a good absorption ability in the microwave wavelength region.

Suitable absorbers are, for example, organic IR absorbers, organic microwave absorbers, inorganic IR absorbers or inorganic microwave absorbers.

For the purposes of this application, IR absorber is understood as meaning a compound which, when applied in a layer thickness of 50 μm when irradiated with at least one wavelength from a wavelength range from 700 nm to 1, exhibits an absorption ≥90%. Preferably, the wavelength range of> 700 nm to 2000 nm, and the wavelengths 9.6 microns and 10.6 microns.

In the context of this application, microwave absorber is to be understood as meaning a compound which absorbs microwaves of the wavelength range of> 1 mm to 1 m. Particularly preferred are the technically relevant frequencies of 2.45 GHz, 433-444 MHz and 902-928 MHz.

Preferably, the absorber of electromagnetic radiation is an infrared (IR) absorber and / or microwave absorber, in particular graphite or carbon black. Furthermore, it is preferred that the electromagnetic radiation are IR rays and / or microwave rays.

The performance of the thermal welding as such is known to the person skilled in the art. The person skilled in the art also knows the equipment required for generating the suitable electromagnetic radiation. For example, a coated plate in the second to minute range can be irradiated in a microwave oven or with an IR radiator. According to the invention, thermal welding is carried out only if at least one thinner foam plate has been previously applied with at least one absorber of electromagnetic radiation. Preferably, the thermal welding is carried out after the joining of the thinner foam boards to the surfaces to be bonded or following a compression of the assembled thinner foam boards.

If in the context of the present invention, a thinner foam board, to which preferably at least one hot melt adhesive and optionally other components such as flame retardants have been applied, electromagnetic radiation is exposed without the absorber of electromagnetic radiation has been applied to the corresponding thinner foam board, is such an operation in the context of the present invention is not referred to as thermal welding, but as activation of said thinner foam sheet. In general, the activation takes place after the hotmelt adhesive has been applied to at least one surface of the thin foam sheets to be bonded, preferably following a drying step of the thin foam sheets provided with the above mixture. Optionally, the activation step can also after the joining of the thinner foam boards to the surfaces to be bonded or after pressing the assembled thinner foam boards done.

Furthermore, in the mixture containing at least one hot melt adhesive and at least one flame retardant and / or graphite and binder may be present, preferably if it is additionally contained in the mixture at least one absorber of electromagnetic radiation.

Suitable binders in the context of the present invention are selected from polyacrylates and copolymers thereof, polystyrene and copolymers thereof, ethylene-acrylate copolymers, ethylene-vinyl acetate copolymers, polyurethanes and polyurethane-acrylate hybrids. Preferred copolymers of polystyrene are styrene-butadiene copolymers.

In a preferred embodiment of the present invention, the hot melt adhesive is applied to at least one surface of at least one thinner foam board, the surface being free of foaming skin. For completeness, it is pointed out that when using an extrusion foam, the corresponding surface is also referred to as extrusion skin-free instead of foam-skin-free.

In a further preferred embodiment of the present invention, the method is carried out so that each surface to be bonded of the thinner foam sheets is free of foaming skin.

In a further embodiment, it is preferred that the hot-melt adhesive is applied to only one surface of the thinner foam boards to be bonded to each pair of boards to be bonded

In one embodiment of the present invention, if a thermal welding step is additionally performed, at least one thinner foam sheet to which an absorber of electromagnetic radiation has additionally been applied is heated by the irradiation of electromagnetic radiation to temperatures above the glass transition temperature of the foam sheet.

Furthermore, it is preferred that in the process according to the invention, a compression of the thinner foam sheets joined together at the surfaces to be bonded is carried out. The compression is generally carried out in the minute range and / or at a compression pressure of 0.01 to 0.5 bar. The process according to the invention is preferably carried out with a pressure of from 0.01 to 0.1 bar and / or a pressing time of ≦ 1 second.

In a particularly preferred embodiment, the method according to the invention is carried out by the time between application of the hotmelt adhesive to at least one thinner foam board and the compression of the thinner foam boards joined together on the surfaces to be bonded being ≦ 3 seconds.

Furthermore, in the process according to the invention, a drying step can be carried out after the hotmelt adhesive, if appropriate in the form of a mixture with further components such as flame retardants, has been applied to the surface of the thinner thermoplastic foam boards. Drying normally takes place for a period of ten minutes to two hours and / or at a temperature in the range of 50 to 100 ° C. However, the drying step is usually not required in the process of the invention due to the use of hot melt adhesive.

• a) Bereitstellen von mindestens zwei dünneren Schaumstoffplatten, wobei jede zu verklebende Oberfläche der dünneren Schaumstoffplatten schäumhautfrei ist,
• b) Aufschmelzen von mindestens einem Schmelzkleber,
• c) Aufbringen von mindestens einem aufgeschmolzenem Schmelzkleber auf (pro zu verklebendem Plattenpaar) mindestens eine zu verklebende Oberfläche der dünneren Schaumstoffplatten,
• d) gegebenenfalls Aktivieren der getrockneten dünneren Schaumstoffplatten mit elektromagnetischer Strahlung,
• e) Zusammenfügen der dünneren Schaumstoffplatten an den zu verklebenden Oberflächen,
• f) Verpressen der zusammengefügten dünneren Schaumstoffplatten und gegebenenfalls anschließendes Aushärten unter Erhalt einer zumindest zweilagigen Schaumstoffplatte.

In a further preferred embodiment in the present invention, the method comprises the following steps:

• a) providing at least two thinner foam sheets, each surface of the thinner foam sheets to be bonded being free of foaming skin,
• b) melting at least one hot-melt adhesive,
• c) applying at least one molten hot melt adhesive to (per pair of plates to be bonded) at least one surface to be bonded to the thinner foam boards,
• d) optionally activating the dried thinner foam sheets with electromagnetic radiation,
• e) joining the thinner foam boards to the surfaces to be bonded,
• f) pressing the assembled thinner foam sheets and optionally subsequent curing to obtain an at least two-layer foam sheet.

The curing in step f) described above is preferably carried out if the hotmelt adhesive contains at least one polymer (P1) and at least one isocyanate-terminated polyurethane.

Another object of the present invention are the foam sheets as such, which are at least two layers and can be produced by the method described above.

The invention will be clarified below with reference to the examples.

Styrodur is a commercial product of BASF SE in the form of an extruded polystyrene foam (XPS). The plates used in the examples (100 x 100 mm ² ) all have a thickness of 48 mm.

The hot melt adhesives are tested for their properties in adhesive and fire tests. The melted hotmelt adhesives are applied by means of a doctor blade to one of the plates (Styrodur 3035 CS, density 33 g / l) and the two previously removed on the surfaces to be bonded from the foam skin foam boards at a pressure of 0.1 bar after the specified "drying time / Cooling time "compressed. The plates are after tensile strength in plate plane after DIN EN 1607 and on fire behavior on B2 DIN EN ISO 11925-2: 2011-02 checked. In the fire test, the bonded contact point is directly flamed.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1318164 A [0002, 0002]
• EP 1213119A [0003]
• EP 1566400 A [0004, 0004]
• DE 101063341 A [0005, 0005]
• EP 1471125 A [0006]
• WO 2012/016991 [0008, 0008]
• WO 2009/047487 [0009, 0024]
• EP 1566490A [0024]
• WO 2009/071499 [0051]

Cited non-patent literature

• DIN 4102 [0010]
• DIN EN ISO 11925-2: 2011-02 [0010]
• Jürgen Troitzsch "Plastics Flammability Handbook" (3rd ed., Hanser Verlag) [0044]
• DIN EN 1607 [0073]
• DIN EN ISO 11925-2: 2011-02 [0073]

Claims (15)

Method for producing at least two-layered foam sheets by bonding at least two thinner foam sheets to the at least two-layer foam sheet, characterized in that at least one hot melt adhesive is applied to at least one surface of at least one thinner foam sheet, the hot melt adhesive comprising at least one polymer (P1), which is selected from the group of polyolefins, polyesters, polyamides, polyacrylates, styrene-isoprene copolymers, styrene-butadiene copolymers, ethylene-vinyl acetate copolymers or polyvinyl acetate (PVA). A method according to claim 1, characterized in that the hot melt adhesive at temperatures of 80 ° C to 160 ° C, preferably from 85 ° C to 130 ° C, in particular from 90 ° C to 115 ° C, is applied. A method according to claim 1 or 2, characterized in that the hot melt adhesive is used as a mixture with a moisture-curing polyurethane hot melt adhesive. Method according to one of claims 1 to 3, characterized in that the hot melt adhesive is part of a mixture which additionally contains at least one flame retardant and / or graphite. A method according to claim 4, characterized in that the flame retardant is selected from a phosphate, a phosphite, a phosphonate, a polyphosphate, melamine, a metal oxide hydrate or a halogenated organic compound. A method according to any one of claims 1 to 5, characterized in that the thinner foam sheet is a particle foam or an extrusion foam, preferably an extrusion foam of polystyrene or of a copolymer made of styrene. Method according to one of claims 1 to 6, characterized in that the hot melt adhesive is applied to at least one surface of at least one thinner foam sheet, wherein the surface is free of foam skin. A method according to any one of claims 1 to 7, characterized in that each surface to be bonded of the thinner foam sheet is free of foam and / or that is applied per adhesive pair of plates on only one surface to be bonded to the thinner foam sheets of hot melt adhesive. Method according to one of claims 1 to 8, characterized in that the hotmelt adhesive is structured, preferably dot-shaped, linear or latticed, in particular latticed, applied to at least one surface of at least one thinner foam board. Method according to one of claims 1 to 9, characterized in that the hotmelt adhesive in amounts of <100 g / m ² , preferably of <50 g / m ² (based on the surface to be bonded to a plate per plate pair), is applied. Method according to one of claims 1 to 10, characterized in that the joined together on the surfaces to be bonded thinner foam sheets are pressed, wherein preferably a pressing pressure of 0.01 to 0.1 bar and / or preferably a pressing time ≤ 1 second is performed. A method according to any one of claims 1 to 11, characterized in that the time between application of the hot melt adhesive to at least one thinner foam sheet and the compression of the joined together on the surfaces to be bonded thinner foam sheets ≤ 3 seconds. A method according to any one of claims 1 to 6, characterized in that the hot melt adhesive is applied in a molten state to at least one surface of at least one thinner foam sheet, wherein the application of the hot melt adhesive takes place uniformly in a direction of the respective plate surface. Method according to one of claims 1 to 13, comprising the following steps a) providing at least two thinner foam sheets, each surface of the thinner foam sheets to be bonded being free of foaming skin, b) melting at least one hot-melt adhesive, c) applying at least one molten hot melt adhesive to (per pair of plates to be bonded) at least one surface to be bonded to the thinner foam boards, d) optionally activating the dried thinner foam sheets with electromagnetic radiation, e) joining the thinner foam boards to the surfaces to be bonded, f) pressing the assembled thinner foam sheets and optionally subsequent curing to obtain an at least two-layer foam sheet. Foam board which is at least two layers, can be produced by a process according to one of claims 1 to 14.