WO2000024577A1 - Multilayer structures - Google Patents

Abstract

A multilayer structure is disclosed which comprises (A) a lignocellulose-based layer and (B) a layer including a substantially random interpolymer comprising in polymerized form i) one or more α-olefin monomers and ii) one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s); layer (B) being free from a substantial amount of tackifier. Floor, wall or ceiling coverings, furniture and decorative or protective overlays can be made from the multilayer structure. THe multilayer structure can be made by heat-laminating one or more layers (B) and optionally one or more adhesive layers (C) to one or more lignocellulose-based layers (A).

Description

MULTILAYER STRUCTURES

BACKGROUND OF THE INVENTION

This invention concerns multilayer structures comprising a lignocellulose- based layer and a polymer-containing layer and methods of preparing them. The invention further concerns articles that are at least partially made from such multilayer structures, such as floor, wall and ceiling coverings, decorative and protective overlays, doors and furniture. Multilayer structures that comprise a lignocellulose-based layer, preferably a wood-based layer, are widely used in many different applications. The wood-based layer can form a decorative or protective cover layer, a substrate layer or both. Examples of multilayer structures, which include a wood-based decorative or protective layer as well as a wood-based substrate layer, are parquet floorings and furniture. Usually they include a wood veneer layer and a particleboard or a fiberboard as a substrate layer. The wood veneer layer and the substrate layer are usually combined by means of an adhesive layer. Such parquet floorings and furniture are sold in large quantities because of their high esthetic and functional qualities. Flexible multilayer structures, which include a wood-based decorative or protective layer as well as a wood-based substrate layer, are also known. They are used as decorative overlays, for example, for furniture or the interior of automobiles.

Other multilayer structures include a wood-based substrate layer, such as a particleboard or a fiberboard, and a decorative or protective layer of a material which is not based on wood. Examples of such multilayer structures are laminated floor, wall or ceiling coverings and furniture. They are also sold in very large quantities. A wide variety of materials have been used in combination with wood-based substrate layers. Well known examples of decorative or protective layers are papers which are typically impregnated with a resin, such as a melamine resin, a polyester resin or urea formaldehyde resin. Other well- known examples of decorative or protective layers are polymeric layers, such as a coating made of a melamine resin or a polyvinyl chloride film. Polyvinyl chloride films are widely used due to their excellent physical properties, however there is an increasing pressure to find more environmentally friendly films. The 3^rd International Symposium "3D-lamination of wood-based panels" held in Bielefeld, Germany on May 18-20, 1998 illustrates the difficulty of finding suitable decorative or protective layers and suitable adhesives for lamination to three-dimensional wood-based substrates. Several symposium participants explain the problems when polyvinyl chloride films are replaced with polyolefins films, namely a small processing window, the need for a high processing temperature, and high recoil forces which require a strong adhesive to bond the polyolefin film to the three-dimensional wood-based substrate.

Other multilayer structures include a wood-based decorative or protective layer and a substrate layer, which is not based on wood. Examples of such well-known structures are wall coverings, floorings, entertainment systems, such as loudspeakers, or composite parts or panels for automotive applications, such as those described in U.S. Patent No. 5,766,395.

The desired and required properties of such multilayer structures including a wood-based layer vary a lot from one end-use to the other. In some applications flexibility is desired. For example, in the case of furniture with a three-dimensional surface the decorative or protective layer needs to adapt well to the profile of the furniture surface, such as edges, indentations or protruding structures. In the other applications, such as floor coverings, scratch resistance or abrasion resistance is of major concern, yet in other applications esthetic properties are important. In view of the large variety of end-uses, evidently no single material can entirely fulfill the wide range of required and desired properties of such multilayer structures.

Another problem associated with multilayer structures, which include a wood- based layer and a polymeric layer, is its production which is generally very time consuming, especially when the wood-based layer is three-dimensional. For various reasons, such as poor adhesion of the polymeric layer to wood and high recoil forces of the polymeric layer experienced with polymers that are commonly used for coating wood, such as polyvinyl chloride, a strong two-component adhesive system is recommended by the industry. According to a standard process used in the industry, a primer coat is first applied to the polymeric layer, usually as part of the polymer film manufacturing process. In the subsequent wood panel laminating process the 2-part adhesive is prepared by mixing a polyisocyanate crosslinker component with a polyurethane adhesive dispersion. The mixture is then sprayed onto the contoured wood panels and allowed to dry. The polymeric layer is then bonded to the wood panel during thermoforming by reaction of the two components of the adhesive system. However, this process is time-consuming, labor-intensive, and requires precise control of mixing time, open time, spray application, and drying time in order to achieve adequate adhesion between the polymer and wood.

In several applications multilayer structures comprising a wood-based layer and a polymer-containing layer should have a good heat resistance, that is, they should not tend to delaminate to a substantial degree from the wood-based layer at increased temperatures. Heat resistance is important because transportation temperatures in shipping containers can reach up to 70°C. Heat resistance is particularly important in kitchen furniture applications where temperatures near a stove can reach up to 100°C. In a presentation "PVC foils for the thermoforming technology" held at the above-mentioned 3^rd International Symposium "3D-lamination of wood based panels" H. Altmann explains that heat resistance is a main topic. He teaches that a foil pressed on a three-dimensional substrate is substantially stretched over the edges of the substrate. The pressed foil can show up to 50 percent shrinkage on a finished product. H. Altmann and many other skilled artisans teach that this shrinkage at elevated temperatures, also called memory effect, is only overcome by the use of very strong adhesives, specifically by the use of adhesives with a hardener. Two- component polyurethane based spray adhesives with a cross-linking agent are such well- known adhesives. T. Hippold, teaches in his paper "Polyurethane dispersions for 3D foil- lamination", presented at same International Symposium that heat resistance can only be achieved by means of a strong cross-linked adhesive, namely a polyurethane based adhesive.

To increase the variety of materials which are available to the industry for the manufacture of floor, wall and ceiling coverings, furniture, decorative and protective overlays, other wood-based articles, or other lignocellulose-based articles, it is an object of the present invention to provide new multilayer structures which include a cellulose-based layer and a polymer-containing layer.

A preferred object of the present invention is to provide new multilayer structures which include a lignocellulose-based layer and a polymer-containing layer and which can be produced without the need of multiple spraying steps for applying adhesive systems to the lignocellulose-based layer.

Another preferred object of the present invention is to provide new multilayer structures which include a lignocellulose-based layer and a polymer-containing layer and which have a good heat resistance.

SUMMARY OF THE INVENTION

One aspect of the present invention is a multilayer structure, which comprises

(A) a lignocellulose-based layer and (B) a layer including a substantially random interpolymer comprising in polymerized form i) one or more α-olefin monomers and ii) one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s), layer (B) being free from a substantial amount of a tackifier.

Another aspect of the present invention is an article, preferably a floor, wall or ceiling covering, a decorative or protective overlay, a door or furniture, which is at least partially made from the above-mentioned multilayer structure.

Yet another aspect of the present invention is a method of producing the above-mentioned multilayer structure by fixing one or more layers (B) and optionally one or more adhesive layers (C) to one or more lignocellulose-based layers (A).

DETAILED DESCRIPTION OF THE INVENTION

The multilayer structure comprises a lignocellulose-based layer (A) and a layer (B) including a substantially random interpolymer described further below.

The term "comprising" as used herein means "including". The term

"multilayer" as used herein means two or more layers.

The term "lignocellulose" encompasses materials, such as plant particles, which contain cellulose, hemicelluloses and lignin as the main solid chemical components. Examples of lignocelluloses are wood and annual plants, such as flax, hemp, bagasse, bamboo, esparto, reeds, ramie, corn stalks, cereal, or various types of straw, for example rice straw or wheat straw.

By the term "lignocellulose-based layer" is meant a layer which is entirely made of a lignocellulose, which is substantially made of a lignocellulose, which includes a lignocellulose in addition to other components or which is derived from a lignocellulose and is modified by a chemical or physical process, for example pulp or paper.

By the term "wood-based layer" is meant a layer which is entirely made of wood, which is substantially made of wood, which includes wood in addition to other components or which is derived from wood and is modified by a chemical or mechanical process, for example pulp or paper. . The terms "lignocellulose-based layer" or "wood-based layer" does not only include lignocellulose-based or wood-based monolayers but also lignocellulose-based or wood-based multilayers wherein the layers are fixed to each other. The term "lignocellulose- based layer" or "wood-based layer" as used herein means any lignocellulose-based two- dimensional or three-dimensional structure or any wood-based two-dimensional or three- dimensional structure respectively.

A wood-based layer is preferably solid wood, a wood laminate, a panel manufactured from wood flour, wood fibers and/or other wood particles, or a layer derived from wood, such as pulp or paper. The wood-based layer can have the two-dimensional or three-dimensional surface. Layer (A) can be based on a wide variety of wood types, such as spruce, pine, larch, Douglas fir, poplar, birch, walnut, beech, oak or ash. Layer (A) can be a decorative or protective layer or a substrate layer or a combination thereof. The thickness of layer (A) can substantially vary, depending on the desired end-use of the multilayer structure of the present invention. The thickness of layer (A) is preferably from 0.05 to 50 mm, more preferably from 0.1 to 30 mm. If layer (A) is a decorative or protective layer, its thickness preferably is from 0.05 to 2 mm, more preferably from 0.1 to 1 mm, most preferably from 0.1 to 0.5 mm. If layer (A) is a substrate layer, its thickness preferably is from 1 .5 to 50 mm, more preferably from 5 to 30 mm.

Exemplary of layer (A) made of solid wood is a wood veneer or a solid wood panel. The wood veneer may be backed with a paper or fleece to provide stability and strength and to minimize splintering and cracking. However the wood veneer is preferably used plain, that is, without such backing, in the multilayer structure of the present invention.

Exemplary of wood laminates is lamellar boards or plywood, such as veneer plywood, core plywood or composite plywood. In the composite plywood the core typically is made of a material of low density, such as an extruded particleboard, paper honeycomb or a foam, such as a polyurethane foam, that is planked on both sides with veneer. The individual layers in the wood laminate are usually fixed by means of a synthetic adhesive, such as urea-formaldehyde resins, melamine-formaldehyde resins, phenol-formaldehyde resins, melamine-urea-formaldehyde resins, or poly(vinyl acetate) adhesives.

Exemplary of panels manufactured from wood particles, such as wood chips, wood shavings, wood wool, wood strands, wood fibers or wood flour, are chip boards, oriented strand boards, particleboards, such as flat pressed particleboards, extruded particleboards or molded particleboards; or fiberboards, such as hardboards, mediumboards, softboards, medium-density fiberboards (MDF) or high density fiberboards (HDF). Synthetic adhesives or other binders, which are suitable for binding the wood particles, are known in the art. Exemplary thereof is urea-formaldehyde resins, melamine- formaldehyde resins, phenol-formaldehyde resins, melamine-urea-formaldehyde resin, or polyisocyanate resins, such as polymeric methylene diphenylene isocyanate. However, in the present invention substantially random interpolymers of i) one or more α-olefin monomers and ii) one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s) are generally not used as binders for the wood particles in the mentioned boards.

Exemplary of layer (A), which is a decorative or protective layer, is a wood veneer or veneer plywood. It has been found that layer (B) defined further below is useful as an excellent backing for the wood veneer or veneer plywood layer (A). It provides good strength and a high protection against splintering and cracking of layer (A). The thickness of the wood veneer or veneer plywood layer (A) and the composition of layer (B) can be varied, such that varying degrees of flexibility are achieved. Surprisingly, it has been found that multilayer structures with an excellent flexibility can be produced. For example, flat structures can be produced which can be bent 90 degrees without cracking or splintering layer (A) to a noticeable degree. Such multilayer structures are excellent decorative or protective overlays for furniture or the interior of automobiles.

Paper and pulp are well-known examples of layer (A) that are derived from wood and are modified by a chemical or mechanical process. Dried pulp can be used as such in the multilayer structure of the present invention or it can be processed to paper before it is combined with one or more layers (B) to produce the multilayer structures of the present invention. Pulp can be produced by well-known mechanical or chemomechanical processes from wood fibers which leave a substantial amount of lignin in the pulp. Paper produced from such pulps is referred to as "wood-containing paper" in the art. Alternatively, pulp can be produced by well-known chemical processes wherein lignin and hemicelluloses are largely dissolved out of the wood-fibers. Paper produced from such pulps is referred to as "wood-free paper" in the art. Paper and pulp are described in more detail in Ullmann's Encyclopedia of Industrial Chemistry, Fifth Edition, Volume 18, pages 547-667.The above- mentioned wood-based materials are described in more detail in Ullmann's Encyclopedia of Industrial Chemistry, Fifth Edition, Volume 28, pages 320-350.

A layer (A) based one or more more lignocelluloses other than wood is preferably a panel manufactured from lignocellulose flour, fibers and/or other particles, or a layer derived from wood, such as pulp or paper. Examples of lignocelluloses other than wood are annual plants, such as flax, hemp, bagasse, bamboo, esparto, reeds, ramie, corn stalks, cereal, or various types of straw, for example rice straw or wheat straw. The thickness of layer (A) based on such other lignocelluloses is within the ranges indicated above for wood-based layers.

Preferably, panels are produced from particulate annual plants. They can be the residual from other processing of the plant, such as straw or grain husks. The particulate material can be combined with a suitable binder, such as urea-formaldehyde resins, melamine-formaldehyde resins, phenol-formaldehyde resins, melamine-urea-formaldehyde resin, or preferably, polyisocyanate resins, such as polymeric methylene diphenylene isocyanate. The production of shaped articles, such as panels, from particulate annual plants is described in detail in U.S. Patent No. 5,554,330.

Paper and pulp produced from annual plants are also useful as layer (A) in the present invention.

Wood and one or more other lignocelluloses can be used in combination to produce layer (A). The lignocellulose-based layer (A) generally comprises from 20 to 100 percent , preferably from 30 to 100 percent , more preferably from 50 to 100 percent of a lignocellulose, such as wood, and optionally up to 80 percent, preferably up to 70 percent, more preferably up to 50 percent of another material, such as a binder, based on the total weight of the wood-based layer (A). The surface of the lignocellulose-based material can be substantially two-dimensional, for example when the multilayer structure is used as a floor, wall or ceiling covering. Alternatively, the surface of the lignocellulose-based material can be three-dimensional, for example when producing doors or furniture, such as kitchen furniture or bathroom furniture.

Layer (B) of the multilayer structure of the present invention includes one or more substantially random interpolymers comprising in polymerized form i) one or more α- olefin monomers and ii) one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s).

Layer (B) does not include a substantial amount of a tackifier as defined in the International Patent Application with the publication No. WO 98/10017. If layer (B) includes a tackifier at all, its amount is less than 5 percent, preferably less than 2 percent, more preferably less than 1 percent, based on the total amount of tackifier and substantially random interpolymer described below. If the multilayer structure comprises several layers that include an above-mentioned substantially random interpolymer, at least one of these layers does not include a substantial amount of a tackifier. The term "tackifier" as used herein means a resin useful to raise the glass transition temperature of the substantially random interpolymer by at least 5^aC and/or to impart tack to a hot-melt adhesive, which comprises the substantially random interpolymer. The term "tack" is used herein according to ASTM D-1878-61 T, which defines tack as "the property of a material that enables it to form a bond of measurable strength immediately on contact with another surface. Tackifiers are for example wood rosin, gum, tall oil, tall oil derivatives, cyclopentadiene derivatives, aliphatic C₅ resins, polyterpene resins, hydrogenated resins, rosin esters, natural and synthetic terpenes, terpene-phenolics and hydrogenated rosins. The tackifiers are described in WO 98/10017, from page 15, third paragraph, to page 16, third paragraph.

The term "interpolymer" is used herein to indicate a polymer wherein at least two different monomers are polymerized to make the interpolymer.

The term "substantially random" in the substantially random interpolymer resulting from polymerizing i) one or more α-olefin monomers and ii) one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s) as used herein generally means that the distribution of the monomers of said interpolymer can be described by the Bernoulli statistical model or by a first or second order Markovian statistical model, as described by J. C. Randall in POLYMER SEQUENCE DETERMINATION, Carbon-13 NMR Method. Academic Press New York, 1977, pp. 71-78. Preferably, the substantially random interpolymer resulting from polymerizing one or more α-olefin monomers and one or more vinyl or vinylidene aromatic monomers, and optionally other polymerizable ethylenically unsaturated monomer(s), does not include more than 15 percent of the total amount of vinyl or vinylidene aromatic monomer in blocks of vinyl or vinylidene aromatic monomer of more than 3 units. More preferably, the interpolymer is not characterized by a high degree of either isotacticity or syndiotacticity. This means that in the carbon^'13 NMR spectrum of the substantially random interpolymer the peak areas corresponding to the main chain methylene and methine carbons representing either meso diad sequences or racemic diad sequences should not exceed 75 percent of the total peak area of the main chain methylene and methine carbons. By the subsequently used term "substantially random interpolymer" is meant a substantially random interpolymer produced from the above-mentioned monomers.

Suitable α-olefin monomers which are useful for preparing the substantially random interpolymer include, for example, α-olefin monomers including from 2 to 20, preferably from 2 to 12, more preferably from 2 to about 8 carbon atoms. Particularly suitable are ethylene, propylene, butene-1 , 4-methyl-1-pentene, hexene-1 or octene-1 or ethylene in combination with one or more of propylene, butene-1 , 4-methyl-1-pentene, hexene-1 or octene-1. Most preferred are ethylene or a combination of ethylene with C_3.8-α- olefins. These α-olefins do not contain an aromatic moiety.

Other optional polymerizable ethylenically unsaturated monomer(s) include strained ring olefins such as norbornene and C,_.10 alkyl or C₆₁₀ aryl substituted norbornenes, with an exemplary interpolymer being ethylene/styrene/norbomene.

Suitable vinyl or vinylidene aromatic monomers that can be employed to prepare the substantially random interpolymer include, for example, those represented by the following Formula I

Ar I

(CH₂)_n

R¹ — C = C(R²)₂ ,_c . .,

(Formula I)

wherein R¹ is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl; each R² is independently selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl; Ar is a phenyl group or a phenyl group substituted with from 1 to 5 substituents selected from the group consisting of halo, C_{1 4}-alkyl, and C_{1 4}-haloalkyi; and n has a value from zero to 4, preferably from zero to 2, most preferably zero. Particularly suitable monomers include styrene and lower alkyl- or halogen-substituted derivatives thereof. Preferred monomers include styrene, α-methyl styrene, the lower alkyl-(C₁-C₄) or phenyl-ring substituted derivatives of styrene, such as for example, ortho-, meta-, and para-methylstyrene, t-butyl styrene, the ring halogenated styrenes, such as chlorostyrene, para-vinyl toluene or mixtures thereof. A more preferred aromatic monovinyl monomer is styrene.

By the term "sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers", it is meant addition polymerizable vinyl or vinylidene monomers corresponding to the formula:

A' R¹ — C = C(R2)₂

wherein A¹ is a sterically bulky, aliphatic or cycloaliphatic substituent of up to 20 carbons, R¹ is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl; each R² is independently selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl; or alternatively R and A¹ together form a ring system. By the term "sterically bulky" is meant that the monomer bearing this substituent is normally incapable of addition polymerization by standard Ziegler-Natta polymerization catalysts at a rate comparable with ethylene polymerizations. α-Olefin monomers containing from 2 to 20 carbon atoms and having a linear aliphatic structure such as propylene, butene- 1 , hexene-1 and octene-1 are not considered as sterically hindered aliphatic monomers. Preferred sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compounds are monomers in which one of the carbon atoms bearing ethylenic unsaturation is tertiary or quaternary substituted. Examples of such substituents include cyclic aliphatic groups such as cyclohexyl, cyclohexenyl, cyclooctenyl, or ring alkyl or aryl-substituted derivatives thereof, tert-butyl or norbomyl. Most preferred sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compounds are the various isomeric vinyl-ring substituted derivatives of cyclohexene and substituted cyclohexenes, and 5-ethylidene-2-norbomene. Especially suitable are 1-, 3-, and 4-vinylcyclohexene.

The most preferred substantially random interpolymers are interpolymers of ethylene and styrene and interpolymers of ethylene, styrene and at least one α-olefin containing from 3 to 8 carbon atoms. The substantially random interpolymers usually comprise in polymerized form i) from 0.5 to 65, preferably from 5 to 55, more preferably from 15 to 50, most preferably from 25 to 40 mole percent of at least one vinyl or vinylidene aromatic monomer and/or sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer and ii) from 35 to 99.5, preferably from 45 to 95, more preferably from 50 to 85, most preferably from 60 to 75 mole percent of at least one aliphatic α-olefin having from 2 to 20 carbon atoms.

The melt index l₂ according to ASTM D 1238 Procedure A, condition E, generally is from 0.01 to 50 g/10 minutes, preferably from 0.01 to 10 g/10 minutes, more preferably from 0.1 to 5 g/10 minutes, and most preferably from 0.1 to 3 g/10 minutes. The glass transition temperature (T_g) of the substantially random interpolymers is preferably from -40°C to +35°C, preferably from 0°C to +30°C, most preferably from +15°C to +30°C, measured according to dynamic mechanical spectrometry (DMS). Layer (B) may include two or more substantially random interpolymers which have different glass transition temperatures (T_g). Usually this facilitates the production of layer (B) and/or lamination of layer (B) to layer (A).

The density of the substantially random interpolymer is generally 0.930 g/cm³ or more, preferably from 0.930 to 1.045 g/cm³, more preferably from 0.930 to 1.040 g/cm³, most preferably from 0.930 to 1.030 g/cm³. The molecular weight distribution, M,/M_n, is generally from 1.5 to 20, preferably from 1.8 to 10, more preferably from 2 to 5.

While preparing the substantially random interpolymer, an amount of atactic vinyl or vinylidene aromatic homopolymer may be formed due to homopolymerization of the vinyl or vinylidene aromatic monomer at elevated temperatures. The presence of vinyl or vinylidene aromatic homopolymer is in general not detrimental for the purposes of the present invention and can be tolerated. The vinyl or vinylidene aromatic homopolymer may be separated from the substantially random interpolymer, if desired, by extraction techniques such as selective precipitation from solution with a nonsolvent for either the substantially random interpolymer or the vinyl or vinylidene aromatic homopolymer. For the purpose of the present invention it is preferred that no more than 30 weight percent, preferably less than 20 weight percent, based on the total weight of the interpolymers of atactic vinyl or vinylidene aromatic homopolymer is present.

The substantially random interpolymers may be modified by typical grafting, hydrogenation, functionalizing, or other reactions well known to those skilled in the art. The polymers may be readily sulfonated or chlorinated to provide functionalized derivatives according to established techniques. The substantially random interpolymers may also be modified by various chain-extending or cross-linking processes including, but not limited to peroxide-, silane-, sulfur-, radiation-, or azide-based cure systems. A full description of the various cross-linking technologies is described in U.S. Patent No. 5,869,591 and EP-A- 778,852, the entire contents of both of which are herein incorporated by reference. Dual cure systems, which use a combination of heat, moisture cure, and radiation steps, may be effectively employed. For instance, it may be desirable to employ peroxide crosslinking agents in conjunction with silane crosslinking agents, peroxide crosslinking agents in conjunction with radiation, or sulfur-containing crosslinking agents in conjunction with silane crosslinking agents. The substantially random interpolymers may also be modified by various crosslinking processes including, but not limited to the incorporation of a diene component as a termonomer in its preparation and subsequent crosslinking by the aforementioned methods and further methods including vulcanization via the vinyl group using sulfur for example as the crosslinking agent.

The above-mentioned substantially random interpolymer suitable in layer (B) of the multilayer structure of the present invention is preferably thermoplastic, which means it may be molded or otherwise shaped and reprocessed at temperatures above its melting or softening point.

One method of preparation of the substantially random interpolymers includes polymerizing a mixture of polymerizable monomers in the presence of one or more metallocene or constrained geometry catalysts in combination with various cocatalysts, as described in EP-A-416,815 by James C. Stevens et al., and U.S. Patent No. 5,703,187 by Francis J. Timmers, both of which are incorporated herein by reference in their entirety. Preferred operating conditions for such polymerization reactions are pressures from atmospheric up to 3000 atmospheres and temperatures from -30°C to 200°C. Polymerizations and unreacted monomer removal at temperatures above the autopolymerization temperature of the respective monomers may result in the formation of some amounts of homopolymer polymerization products resulting from free radical polymerization.

Examples of suitable catalysts and methods for preparing the substantially random interpolymers are disclosed in EP-A-514,828; as well as U.S. Patents: 5,055,438; 5,057,475; 5,096,867; 5,064,802; 5,132,380; 5,189,192; 5,321 ,106; 5,347,024; 5,350,723; 5,374,696; 5,399,635; 5,470,993; 5,703,187; and 5,721 ,185 all of which patents and applications are incorporated herein by reference.

The substantially random α-olefin/vinyl(idene) aromatic interpolymers can also be prepared by the methods described in JP 07/278230 employing compounds shown by the general formula

Cp l _{R l}

Cp2 ^/ R2

where Cp¹ and Cp² are cyclopentadienyl groups, indenyl groups, fluorenyl groups, or substituents of these, independently of each other; R and R² are hydrogen atoms, halogen atoms, hydrocarbon groups with carbon numbers of 1 to 12, alkoxyl groups, or aryloxyl groups, independently of each other; M is a group IV metal, preferably Zr or Hf, most preferably Zr; and R³ is an alkylene group or silanediyl group used to cross-link Cp¹ and Cp²).

The substantially random α-olefin/vinyl(idene) aromatic interpolymers can also be prepared by the methods described by John G. Bradfute et al., (W.R. Grace & Co.) in WO 95/32095; by R.B. Pannell (Exxon Chemical Patents, Inc.) in WO 94/00500; and in Plastics Technology, page 25 (September 1992).

Also suitable are the substantially random interpolymers which comprise at least one α-olefin/vinyl aromatic/vinyl aromatic/α-olefin tetrad disclosed in WO-98/09999-A by Francis J. Timmers et al. These interpolymers can be prepared by conducting the polymerization at temperatures of from -30°C to 250°C in the presence of a catalyst as those described in WO-98/09999-A. Particularly preferred catalysts include, for example, racemic-(dimethy1silanediyl)-bis-(2-methyl-4-phenylindenyl)zirconium dichloride, racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl)zirconium 1 ,4-diphenyl-1 ,3- butadiene, racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl)zirconium di-C,_.4-alkyl, racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl)zirconium di-C^-alkoxide, or any combination thereof. It is also possible to use the following titanium-based constrained geometry catalysts, [N-(1 ,1 -dimethylethyl)-1 ,1 -dimethyl-1 -[(1 ,2,3,4,5-h)-1 ,5,6,7-tetrahydro-s- indacen-1 -yl]silanaminato(2-)-N]titanium dimethyl; (1 -indenyl)(tert-butylamido)dimethylsilane titanium dimethyl; ((3-tert-butyl)(1 ,2,3,4,5-h)-1-indenyl)(tert-butylamido) dimethylsilane titanium dimethyl; and ((3-iso-propyl)(1 ,2,3,4,5-h)-1-indenyl)(tert-butyl amido)dimethylsilane titanium dimethyl, or any combination thereof.

Further preparative methods for the substantially random interpolymers used in the present invention have been described in the literature. Longo and Grassi (Makromol. Chem.. volume 191 , pages 2387 to 2396 [1990]) and D'Anniello et al. (Journal of Applied Polymer Science, volume 58, pages 1701 to 1706 [1995]) reported the use of a catalytic system based on methylalumoxane (MAO) and cyclopentadienyltitanium trichloride (CpTiCI₃) to prepare an ethylene-styrene copolymer. Xu and Lin (Polymer Preprints. Am. Chem. Soc. Div. Polvm. Chem.. volume 35, pages 686, 687 [1994]) have reported copolymerization using a MgCI TiCI₄/NdCIJAI(iBu)₃ catalyst to give random copolymers of styrene and propylene. Lu et al. (Journal of Applied Polymer Science, volume 53, pages 1453 to 1460 [1994]) have described the copolymerization of ethylene and styrene using a TiCI₄/NdCL/ MgCI₂ /AI(Et)₃ catalyst. Sernetz and Mulhaupt, (Macromol. Chem. Phvs.. volume 197, pages 1071 to 1083 [1997]) have described the influence of polymerization conditions on the copolymerization of styrene with ethylene using Me₂Si(Me₄Cp)(N-tert- butyl)TiCI-/methylaluminoxane Ziegler-Natta catalysts. Copolymers of ethylene and styrene produced by bridged metallocene catalysts have been described by Arai, Toshiaki and Suzuki (Polymer Preprints, Am. Chem. Soc. Div. Polvm. Chem. volume 38, pages 349, 350 [1997]) and in U.S. Patent 5,652,315, issued to Mitsui Toatsu Chemicals, Inc. The manufacture of α-olefin/vinyl aromatic monomer interpolymers such as propylene/styrene and butene/styrene are described in U.S. Patent 5,244,996, issued to Mitsui Petrochemical Industries Ltd. or U.S. Patent 5,652,315 also issued to Mitsui Petrochemical Industries Ltd. or as disclosed in DE 197 11 339 A1 to Denki Kagaku Kogyo KK. All the above methods disclosed for preparing the substantially random interpolymer are incorporated herein by reference.

Layer (B) of the multilayer structure of the present invention may optionally include up to about 80 weight percent, preferably up to about 70 weight percent, more preferably up to about 50 weight percent, most preferably up to about 30 weight percent, of one or more further polymeric components, such as those described further below, based on the total polymer weight in layer (B). The polymeric components described below are not encompassed by the term "tackifier" as defined further above. The amount of the above- described substantially random interpolymer(s) generally is at least about 20 percent, preferably at least about 30 percent, more preferably at least about 50 percent, most preferably at least about 70 percent, based on the total polymer weight in layer (B). Preferred additional, optional polymers are monovinyl or monovinylidene aromatic polymers, styrenic block copolymers or homopolymers or interpolymers of aliphatic α-olefins having from 2 to 20 carbon atoms or α-olefins having from 2 to 20 carbon atoms and containing polar groups. Preferred additional, optional polymers have a glass transition temperature Tg or a melting point that is higher than that of the above-described substantially random interpolymers, such as monovinyl or monovinylidene aromatic polymers, styrene/acrylonitrile copoymers, polypropylenes or high density polyethylene (HDPE).

Preferred monovinyl or monovinylidene aromatic polymers include homopolymers or interpolymers of one or more monovinyl or monovinylidene aromatic monomers or interpolymers of one or more monovinyl or monovinylidene aromatic monomers and one or more monomers interpolymerizable therewith other than an aliphatic α-olefin. Suitable monovinyl or monovinylidene aromatic monomers are represented by the following formula:

Ar I R¹ — C = CH₇

wherein R¹ and Ar have the meanings stated in Formula I further above. Exemplary monovinyl or monovinylidene aromatic monomers are those listed previously under formula I, particularly styrene. Examples of suitable interpolymerizable comonomers other than monovinyl or monovinylidene aromatic monomers include, for example, C₄-C₆ conjugated dienes, especially butadiene or isoprene. In some cases it is also desirable to copolymerize a cross-linking monomer such as a divinyl benzene into the monovinyl or monovinylidene aromatic polymer.

The polymers of monovinyl or monovinylidene aromatic monomers with other interpolymerizable comonomers preferably contain, polymerized therein, at least 50 percent by weight and, preferably, at least 90 percent by weight of one or more monovinyl or monovinylidene aromatic monomers.

Highly preferred additional, optional polymers are polystyrene or polymerized α-methyl styrene. These polymers preferably have a melt index of from 0.1 to 20, more preferably of from 0.5 to 6, measured according to ASTM 1238, condition G at 200°C. Other preferred additional, optional polymers are homopolymers or interpolymers of aliphatic α-olefins having from 2 to 20, preferably 3 to 18, more preferably 3 to 12, carbon atoms or α-olefins having from 2 to 20, preferably 3 to 18, more preferably 3 to 12, carbon atoms and containing polar groups. Suitable aliphatic α-olefin monomers which introduce polar groups into the polymer include, for example, ethylenically unsaturated nitrites such as acrylonitrile, methacrylonitrile, or ethacrylonitrile; ethylenically unsaturated anhydrides such as maleic anhydride; ethylenically unsaturated amides such as acrylamide or methacrylamide; ethylenically unsaturated carboxyiic acids (both mono- and difunctional) such as acrylic acid and methacrylic acid; esters (especially lower, for example, C,-C₆, alkyl esters) of ethylenically unsaturated carboxyiic acids, such as methyl methacrylate, ethyl acrylate, hydroxyethylacrylate, n-butyl acrylate or methacrylate, 2-ethyl-hexylacrylate; glycidyl acrylate or glycidyl methacrylate ethylenically unsaturated dicarboxylic acid imides, such as N-alkyl or N-aryl maleimides, such as N-phenyl maleimide, or vinyl esters, such as vinyl acetate.

Preferably, such monomers containing polar groups are acrylic acid, methacrylic acid, an ionomer thereof, a C₁-C₆-alkyl ester of acrylic acid or methacrylic acid, a vinyl ester, such as vinyl acetate, or maleic anhydride or acrylonitrile.

Halogen groups which can be included in the polymers from aliphatic α-olefin monomers include fluorine, chlorine and bromine; preferably such polymers are chlorinated polyethylenes (CPEs) or polyvinyl chloride.

Highly preferred additional, optional polymers are copolymers of ethylene or propylene and at least one of acrylic acid, vinyl acetate, maleic anhydride or acrylonitrile; preferably ethylene-vinyl acetate copolymers, or ethylene-acrylic acid copolymers. Preferred olefinic polymers are propylene homopolymers or interpolymers of propylene and one or more other α-olefins having from 4 to 8 carbon atoms.

Other preferred olefinic polymers are linear high density polyethylene polymers (HDPE) made using Ziegler polymerization processes (for example, U.S. Patent No. 4,076,698 (Anderson et al.), sometimes called heterogeneous polymers. HDPE consists mainly of long linear polyethylene chains. The HDPE usually has a density of at least 0.94 grams per cubic centimeter (g/cc) as determined by ASTM Test Method D 1505, and a melt index (ASTM-1238, condition 190°C/2.16 kg) in the range of from 0.01 to 100, and preferably from 0.1 to 50 grams per 10 minutes. Layer (B) may include a filler. If present, its amount generally is up to about 70 percent, preferably up to about 60 percent, more preferably up to about 40 percent, based on the total weight of layer (B). Useful fillers include organic and inorganic fillers, such as saw dust, wood fillers, such as wood flour or wood fibers, paper fibers, corn husks, straw, cotton, carbon black or graphite, talc, calcium carbonate, flyash, alumina trihydrate, glass fibers, marble dust, cement dust, clay, feldspar, silica or glass, fumed silica, alumina, magnesium oxide, zinc oxide, barium sulfate, aluminum silicate, calcium silicate, titanium dioxide, titanates, glass microspheres or chalk. Of these fillers, barium sulfate, talc, calcium carbonate, barium sulfate, silica/glass, glass fibers, alumina and titanium dioxide, and mixtures thereof are preferred. The term "a filler" as used herein includes a mixture of different fillers.

Layer (B) may include one or more additives, for example antioxidants, such as hindered phenols or phosphites; light stabilizers, such as hindered amines; plasticizers, such as dioctylphthalate or epoxidized soybean oil; waxes, such as polyethylene waxes; processing aids, such as stearic acid or a metal salt thereof; or crosslinking agents, such as peroxides or silanes; pigments or colorants, or antiblock additives; such as silica or talc. If the additives are comprised in layer (B), they are employed in functionally equivalent amounts known to those skilled in the art, generally in amounts of up to 30, preferably from 0.01 to 5, more preferably from 0.02 to 1 percent by weight, based upon the weight of layer (B).

Layer (B) preferably has a thickness of from 0.03 mm to 2 mm, more preferably from 0.1 mm to 1 mm, most preferably from to 0.2 mm to 0.5 mm.

The above-described substantially random interpolymer(s) can be combined with optional additives and processed to layer (B) by any suitable means known in the art such as, but not limited to, Banbury mixing, extrusion compounding, roll milling, calendering, compression molding, injection molding and/or sheet extrusion. Useful temperatures for processing the substantially random interpolymer(s) in combination with optional additives to layer (B) generally are from 100²C to 300²C, preferably from 140^eC to 270²C, more preferably from 180²C to 250²C. The produced layer (B) can be subjected to a finishing treatment, such as a corona treatment, a flame treatment or to embossing.

According to one preferred embodiment of the multilayer structure of the invention layer (B) is fixed to layer (A) without an intermediate layer. It has been surprisingly found that layer (B) has a good adhesion strength to the lignocellulose-based layer (A), when layer (B) is heat laminated to the lignocellulose-based layer (A) at a high pressure and temperature as described further below. The good adhesion strength to lignocellulose, preferably wood, facilitates the production process and/or enhances the quality of the multilayer structure.

According to another preferred embodiment of the invention the multilayer structure comprises one or more adhesive layers (C) between layer (B) and layer (A). The adhesive layer (C) preferably has a thickness of from 0.002 mm to 0.25 mm, more preferably from 0.01 mm to 0.15 mm, most preferably from 0.01 mm to 0.09 mm.

Various adhesives are useful in the adhesive layer (C), such as thermosetting adhesives, hot-melt adhesives or, preferably, thermoplastic adhesives. The multilayer structure may contain several adhesive layers which can be the same or different.

A preferred hot-melt or thermoplastic adhesive is a blend of from 5 to 95 percent, preferably from 25 to 95 percent, more preferably from 30 to 90 percent, of an above-described substantially random interpolymer and from 5 to 95, preferably from 5 to 75 percent, more preferably from 10 to 70 percent of a tackifier, based on the total weight of substantially random interpolymer and tackifier. Useful tackifiers are those that are mentioned further above and that are described in more detail in the International Patent Application with the publication No. WO 98/10017.

A preferred thermoplastic adhesive comprises an interpolymer of ethylene or propylene and an α-olefin having from 2 to 20, preferably 3 to 18, more preferably 3 to 12, carbon atoms and containing polar groups. Suitable aliphatic α-olefin monomers which introduce polar groups into the polymer include, for example, ethylenically unsaturated nitriles such as acrylonitrile, methacrylonitrile, or ethacrylonitrile; ethylenically unsaturated anhydrides such as maleic anhydride; ethylenically unsaturated amides such as acrylamide or methacrylamide; ethylenically unsaturated carboxyiic acids (both mono- and difunctional) such as acrylic acid and methacrylic acid, ionomers of such ethylenically unsaturated carboxyiic acids; esters (especially lower, for example, C,-C₆, alkyl esters) of ethylenically unsaturated carboxyiic acids, such as methyl methacrylate, ethyl acrylate, hydroxyethylacrylate, n-butyl acrylate or methacrylate, 2-ethyl-hexylacrylate, glycidyl acrylate or glycidyl methacylate; ethylenically unsaturated dicarboxylic acid imides, such as N-alkyl or N-aryl maleimides, such as N-phenyl maleimide. Preferably such monomers containing polar groups are acrylic acid, methacrylic acid, an ionomer thereof, a C^C.-alkyl ester of acrylic acid or methacrylic acid, a vinyl ester, such as vinyl acetate, or maleic anhydride or acrylonitrile. The more preferred thermoplastic adhesives comprise an interpolymer of i) ethylene and ii) acrylic acid, methacrylic acid, an acrylic ester, a vinyl ester, or an ionomer thereof.

A highly preferred adhesive layer (C) comprises an ethylene/acrylic acid copolymer as a main component. Another highly preferred adhesive layer (C) comprises from 10 to 90 percent, preferably from 50 to 90 percent, of an above-described substantially random interpolymer, from 0 to 25 percent of polystyrene or polymerized α-methyl styrene, from 5 to 50 percent, preferably from 10 to 25 percent, of an ethylene/acrylic acid copolymer and from 0 to 50 percent, preferably 10 to 25 percent, of an ethylene/vinyl acetate copolymer, based on the total weight of polymers, and optionally a colorant.

One or more adhesive layers (C) can be laminated or extrusion coated to or co-extruded with one or more layers (B) comprising an above-described substantially random interpolymer. The laminated, extrusion coated or co-extruded structure can be applied to the lignocellulose-based layer (A) as described further below. It is understood that the adhesive layer (C) and the layer (B) both can include a substantially random interpolymer. At least one of the layers comprises a substantially random interpolymer without a substantial amount of a tackifier. Preferably, from 2 to 5 layers are laminated, extrusion coated or co-extruded. Exemplary of preferred laminated, extrusion coated or co- extruded structures are (B)/(C) or (B)/(C')/(C), wherein (B), (C) and (C) have the following meanings. (B) comprises from 0 to 80, preferably from 0 to 70, more from 0 to 50 percent of polystyrene or polymerized α-methyl styrene and from 20 to 100, preferably from 30 to 100, more preferably from 50 to 100 percent of an above-described substantially random interpolymer, based on the total weight of the polymers. The laminated, extrusion coated or co-extruded structures may comprise two layers (B) of which the first layer generally is non- pigmented and does not contain a polystyrene or polymerized α-methyl styrene, whereas the second layer generally is pigmented and preferably contains a polystyrene or polymerized α- methyl styrene. (C) mainly contains an ethylene/vinyl acetate copolymer and (C) is a thermoplastic adhesive described above, preferably an ethylene/acrylic acid copolymer.

The laminated, extrusion coated or co-extruded structure can be produced in a known manner. Useful lamination or extrusion temperatures generally are from 50°C to 300²C, preferably from 70²C to 250²C. It has been surprisingly found that multilayer structures of the invention can be produced without the need of a primer on the polymer layer (B) and multiple spraying steps for applying two-component adhesive systems to a lignocellulose-based layer (A). The new multilayer structure can generally be produced by heat-laminating one or more layers (B) and optionally one or more adhesive layers (C) to one or more lignocellulose-based layers (A). When at least one adhesive layer (C) is included in the multilayer structure, such adhesive layer is preferably a thermoplastic adhesive as described further above. According to the most preferred embodiment of producing the multilayer structure of the present invention one or more polymeric layers (B) and one or more adhesive layers (C) are co- extruded and subsequently heat-laminated to the lignocellulose-based layer (A). This simplifies the production process and solves problems encountered with sprayed adhesives, such as solvent evaporation, and the need of special ventilation during spraying. The lignocellulose-based layer (A) may be subjected to a flame or heat treatment, however there is generally no primer applied to the lignocellulose-based layer (A) prior to laminating layer (B) and optionally layer (C) thereto.

The most preferred multilayer structure of the present invention comprising a structure (B)/(C')/(C)/(A),

wherein (B) is a polymeric layer including the substantially random interpolymer and up to about 80 weight percent of a homopolymer or interpolymer of one or more monovinyl or monovinylidene aromatic monomers, based on the total polymer content in layer (B), (C) is a layer comprising an ethylene/vinyl acetate interpolymer, (C) is a layer comprising an ethylene/acrylic acid interpolymer and (A) is a wood-based layer.

It has also been surprisingly found that layer (B), that is laminated to the lignocellulose-based layer (A), preferably by means of one or more of the above-described adhesive layers (C), has a surprisingly good heat resistance, that is, it does not tend to delaminate from the lignocellulose-based layer to a substantial degree at increased temperatures. Heat resistance is important because transportation temperatures in shipping containers can reach up to about 70°C. Heat resistance is particularly important in kitchen furniture applications where temperatures near a stove can reach up to about 100°C. This finding is contrary to the teaching in the paper written by T. Hippold, "Polyurethane dispersions for 3D foil-lamination", presented at the above-mentioned 3^rd International Symposium "3D-lamination of wood based panels". This paper teaches that heat resistance can only be achieved by means of a cross-linked adhesive, namely a polyurethane based adhesive.

Moreover, layer (B) has an excellent thermoformability and conformability to the lignocellulose-based layer (A). This favorable property becomes readily apparent when a layer (B) and optionally one or more adhesive layers (C) are heat-laminated to a three- dimensional lignocellulose-based layer, which means that the layer (B) is stretched over edges and corners of the three-dimensional lignocellulose-based layer. Contrary to the teaching of H. Altmann at the above-mentioned 3^rd International Symposium, layer (B) in the multilayer structure of the present invention exhibits a substantial resistance to shrinkage and to delamination when the multilayer structure is exposed to elevated temperatures. Accordingly, layer (B) can be fixed to the lignocellulose-based (A) by means of a thermoplastic adhesive layer (C) and does not require the use of strong two-component spray adhesives, such as a polyurethane spray adhesive and a cross-linking agent.

One method of producing the multilayer structure of the present invention comprises the step of heat laminating layer (B) to layer (A) without the use of a primer or an adhesive layer. In this case, generally a temperature from 130°C to 250²C, preferably from 150°C to 220²C, more preferably from 160°C to 190²C, and a pressure of from 2 to 200 bar, preferably from 10 to 40 bar, more preferably from 15 to 25 bar is applied. Pressure and heat are generally applied for a time period of 20 seconds to 20 minutes, preferably from 30 seconds to 5 minutes. It has been found that layer (B) has a surprisingly high adhesion strength to layer (A). Layer (B) generally has a higher adhesion strength to the lignocellulose-based layer (A) than a layer made of a polyethylene resin.

Another method of producing the multilayer structure of the present invention comprises the step of fixing a layer (B) to a lignocellulose-based layer (A) by means of one or more thermoplastic adhesive layers (C), preferably by heat lamination. More preferably, a laminated or co-extruded structure containing a least one layer (B) and at least one adhesive layer (C) is heat-laminated to layer (A). In this case, generally a temperature from 50°C to 120²C, preferably from 70 to 110²C, and a pressure of from 3 to 30 bar, preferably from 4 to 20 bar, is applied. Pressure and heat are generally applied for a time period of from 20 seconds to 5 minutes, preferably from 30 seconds to 3 minutes.

Heat-lamination can be carried out in a known device, such as a roll laminator, a hot-platen press, a hot-membrane press, a continuous band press or a compression molding press. For applying layer (B) and optionally layer (C) to a three- dimensional lignocellulose-based layer, membrane pressing, vacuum pressing or waterbed pressing is preferred.

It is understood by those skilled in the art that the above-described methods of fixing layer (B) to the lignocellulose-based layer (A) are preferred methods, but that other methods known in the art are also within the scope of the present invention. For example, a monolayer film (B) can be produced by calendering, followed by extrusion coating of one or more adhesive layers (C) on layer (B). According to another method, a monolayer film (B) can be produced by calendering and laminated to an extruded or blown adhesive layer (C). When using two adhesive layers, one can serve as a tie layer between layer (B) and the second adhesive layer.

Alternatively layer (B) can be fixed to the lignocellulose-based layer (A) by other means, for example by spraying a solvent-based or water-based adhesive, such as a urea formaldehyde system, ethylene/vinyl acetate copolymer dispersed in water or polyurethane dispersed in water on layer (B) and/or on the lignocellulose-based layer (A). However, the methods described above are more preferred.

The above-described layer (B) has good adhesion and excellent printability, thermoformability and conformability to the lignocellulose-based layer (A).

Another aspect of the present invention is a lignocellulose-based article that is at least partially made from the novel multilayer structure. According to one preferred aspect of the invention, the lignocellulose-based article is a floor, wall or ceiling covering. By the term "floor, wall or ceiling covering" as used herein is meant an article with a length and width which are substantially greater than its thickness, such as a sheet, tile or board, and which is useful to cover at least a portion of a floor, wall or ceiling and which adheres to the floor, wall or ceiling by means of static pressure or a fastening agent, such as an adhesive system. "Substantially greater" generally means at least 10 times greater, preferably at least 50 times greater, more preferably at least 100 times greater. According to another preferred aspect of the invention, the lignocellulose-based article is furniture, such as tables, desks, cabinets, such as kitchen tables or kitchen cabinets; or chairs. According to yet another preferred aspect of the invention, the lignocellulose-based article is a door. The lignocellulose-based article may be two-dimensional or three-dimensional. Yet another aspect of the present invention is a decorative or protective overlay which is at least partially made from the multilayer structure of the present invention. Decorative or protective overlays are preferably applied to furniture, the interior of automobiles, walls, flooring and other surfaces.

The multilayer structure of the present invention can comprise one or more additional layers (D), wherein the sequence of the layers preferably is (A)/(B)/(D) or (D)/(A)/(B) or (D)/(A)/(B)/(D). It is understood that one or more adhesive layers are optionally applied between the above-mentioned layers. If the multilayer structure contains two or more layers (D), the layers (D) can be the same as or different from each other. The nature of the additional layer(s) (D) mainly depends on the desired end-use of the multilayer structure. Exemplary thereof are adhesive layers for bonding the multilayer structure to a substrate, print layers, lacquer layers, thermoplastic polymer layers, finishing layers, or UV protection layers, chemical resistant layers, scratch or abrasion resistant layers.

Layer (B) can serve various purposes in the multilayer structure. For example, layer (B) can be applied on top of layer (A) to protect the lignocellulose-based layer (A). This arrangement of the layers is particularly useful in floor, wall or ceiling coverings and furniture. In these applications layer (B) provides excellent scratch and wear resistance to the multilayer structure. Preferred structures of wall or ceiling coverings and furniture are (A)/(B)/(D) wherein layer (D) is a print layer, a transparent lacquer layer, a finishing layer and/or a UV protection layer. Preferred structures for floor coverings are (D')/(A)/(B)/(D), wherein (D') is an impregnated paper layer, which is preferably impregnated with a melamine resin, or a polymeric film which provides moisture protection, such as an above-described substantially random interpolymer, and layer (D) is a transparent lacquer layer.

Alternatively, the wood-based layer (A) can be applied on top of layer (B) and layer (B) can serve as an adhesive layer to fix layer (A) to a substrate, such as another wood-based layer, for example, for fixing a wood veneer layer to an MDF board. In these applications layer (B) exhibits excellent flexibility and conformability to uneven or contoured substrates, provided that layer (B) does not contain more than about 70 weight percent, preferably not more than about 40 weight percent of a filler. If the wood-based layer (A) undergoes lateral dimensional changes due to changes in temperature and/or moisture, the flexibility of layer (B) prevents its cracking. This arrangement of the layers is particularly useful in furniture but also in floor, wall or ceiling coverings. Preferred structures of wall, ceiling or, preferably, floor coverings are (A')/(B)/(A) or (D')/(B)/(A), wherein layer (A') is a lignocellulose-based layer, such as a particleboard or fiberboard; layer (D') is a melamine laminate, layer (B) is defined as described above and layer (A) is a wood-based layer, such as a wood veneer layer. Other preferred structures are (A')/(B)/(A)/(D) or (D')/(B)/(A)/(D), wherein layers (A'), (B) and (A) have the described meanings and layer (D) is a lacquer layer or a thermoplastic polymer layer, such as PVC, a polyolefin or an additional layer including an above-described substantially random interpolymer.

Furthermore, layer (B) can serve as a backing for the wood-based layer (A), such as a wood veneer layer. It provides good strength and a surprisingly high protection against splintering and cracking of layer (A). The wood-based layer (A), which contains a backing made of layer (B), is particularly useful as a decorative overlay for furniture or the interior of automobiles. In this application layer (B) preferably contains at least 70 percent, more preferably at least 90 percent of the substantially random interpolymer, based on the total weight of layer (B). Depending on the thickness of the wood-based layer (A), multilayer structures with a surprisingly high flexibility can be produced. Flexible structures are generally achieved if the wood-based layer has a thickness of from 0.1 to 1 mm.

The following examples are provided to illustrate the present invention. The examples are not intended to limit the scope of the present invention and they should not be so interpreted. Amounts are in weight parts or weight percentages unless otherwise indicated.

TESTING

The properties of the polymers and blends are determined by the following test procedures.

Melt Index (Ml) is determined by ASTM D-1238 (1979), Condition E (190°C;

2.16 kg).

The Flexural Modulus is measured according to ISO 178 using a Zwick Z010 measuring device, wherein the test specimen is a bar of 25 by 100 mm, the test speed is 1 mm/minute, the span distance is 16 mm and the cell load is 100N. The adhesion of the polymeric film to an MDF board is measured using a Zwick Z010 tensile machine at a tear rate of 100 mm/minute

The abrasion resistance is measured according to DIN 53516 at 10N.

Preparation of Ethylene/Styrene Interpolymers ESI-1. ESI-3. ESI-7. ESI-8 and ESI-9

The interpolymers are prepared in a continuously operating loop reactor (36.8 gal, 140 L). An Ingersoll-Dresser twin-screw pump provides the mixing. The reactor runs liquid full at 475 psig (3,275 kPa) with a residence time of approximately 25 minutes. Raw materials and catalyst/cocatalyst flows are fed into the suction of the twin-screw pump through injectors and Kenics static mixers. The twin-screw pump discharges into a 2" (5 cm) diameter line which supplies two Chemineer-Kenics 10-68 Type BEM Multi-Tube heat exchangers in series. The tubes of these exchangers contain twisted tapes to increase heat transfer. Upon exiting the last exchanger, loop flow returns through the injectors and static mixers to the suction of the pump. Heat transfer oil is circulated through the exchangers' jacket to control the loop temperature probe located just prior to the first exchanger. The exit stream of the loop reactor is taken off between the two exchangers. The flow and solution density of the exit stream is measured by a micromotion fiowmeter.

Solvent feed to the reactor is supplied by two different sources. A fresh stream of toluene from an 8480-S-E Pulsafeeder diaphragm pump with rates measured by a micromotion fiowmeter is used to provide flush flow for the reactor seals (20 Ib/hr (9.1 kg/hour). Recycle solvent is mixed with uninhibited styrene monomer on the suction side of five 8480-5-E Pulsafeeder diaphragm pumps in parallel. These five Pulsafeeder pumps supply solvent and styrene to the reactor at 650 psig (4,583 kPa). Fresh styrene flow is measured by a micromotion fiowmeter, and total recycle solvent/styrene flow is measured by a separate micromotion fiowmeter. Ethylene is supplied to the reactor at 687 psig (4,838 kPa). The ethylene stream is measured by a micromotion mass fiowmeter. A Brooks flowmeter/controller is used to deliver hydrogen into the ethylene stream at the outlet of the ethylene control valve. The ethylene/hydrogen mixture combines with the solvent/styrene stream at ambient temperature. The temperature of the entire feed stream as it enters the reactor loop is lowered to 2°C by an exchanger with -10°C glycol on the jacket. Preparation of the three catalyst components take place in three separate tanks: fresh solvent and concentrated catalyst/cocatalyst premix are added and mixed into their respective run tanks and fed into the reactor via variable speed 680-S-AEN7 Pulsafeeder diaphragm pumps. As previously explained, the three component catalyst system enters the reactor loop through an injector and static mixer into the suction side of the twin-screw pump. The raw material feed stream is also fed into the reactor loop through an injector and static mixer downstream of the catalyst injection point but upstream of the twin-screw pump suction.

Polymerization is stopped with the addition of catalyst kill (water mixed with solvent) into the reactor product line after the micromotion fiowmeter measuring the solution density. A static mixer in the line provides dispersion of the catalyst kill and additives in the reactor effluent stream. This stream next enters post reactor heaters that provides additional energy for the solvent removal flash. This flash occurs as the effluent exits the post reactor heater and the pressure is dropped from 475 psig (3,275 kPa) down to 450 mmHg (60 kPa) of absolute pressure at the reactor pressure control valve. This flashed polymer enters the first of two hot oil-jacketed devolatilizers. The volatiles flashing from the first devolatizer are condensed with a glycol jacketed exchanger, passed through the suction of a vacuum pump, and are discharged to the solvent and styrene/ethylene separation vessel. Solvent and styrene are removed from the bottom of this vessel as recycle solvent while ethylene exhausted from the top. The ethylene stream is measured with a micromotion mass fiowmeter. The measurement of vented ethylene plus a calculation of the dissolved gases in the solvent/styrene stream are used to calculate the ethylene conversion. The polymer and remaining solvent separated in the devolatilizer is pumped with a gear pump to a second devolatizer. The pressure in the second devolatizer is operated at 5 mmHg (0.7 kPa) absolute pressure to flash the remaining solvent. This solvent is condensed in a glycol heat exchanger, pumped through another vacuum pump, and exported to a waste tank for disposal. The dry polymer (< 1000 ppm total volatiles) is pumped with a gear pump to an underwater pelletizer with 6-hole die, pelletized, spin-dried, and collected in 1000 pound (454 kg) boxes.

Preparation of Ethylene/Styrene Interpolymers ESI-2. ESI-4. ESI-5 and ESI-6

Reactor Description

The single reactor used is a 6 gallon (22.7 L), oil-jacketed, autoclave continuously stirred tank reactor (CSTR). A magnetically coupled agitator with Lightning A- 320 impellers provides the mixing. The reactor runs liquid full at 475 psig (3,275 kPa). Process flow is in the bottom and out the top. A heat-transfer oil is circulated through the jacket of the reactor to remove some of the heat of reaction. After the exit from the reactor is a micromotion fiowmeter that measures flow and solution density. All lines on the exit of the reactor are traced with 50 psi (344.7 kPa) steam and insulated.

Procedure

Toluene solvent is supplied to the mini-plant at 30 psig (207 kPa). The feed to the reactor is measured by a micromotion mass fiowmeter. A variable speed diaphragm pump controls the feed rate. At the discharge of the solvent pump a side stream is taken to provide flush-flows for the catalyst injection line (1 lb/hour (0.45 kg/hour)) and the reactor agitator (0.75 lb/hour (0.34 kg/hour)). These flows are measured by differential pressure flowmeters and controlled by manual adjustment of micro-flow needle valves. Uninhibited styrene monomer is supplied to the mini-plant at 30 psig (207 kpa). The feed to the reactor is measured by a micromotion mass fiowmeter. A variable speed diaphragm pump controls the feed rate. The styrene stream is mixed with the remaining solvent stream. Ethylene is supplied to the mini-plant at 600 psig (4,137 kPa). The ethylene stream is measured by a micromotion mass fiowmeter just prior to the Research valve controlling flow. A Brooks flowmeter/controllers is used to deliver hydrogen into the ethylene stream at the outlet of the ethylene control valve. The ethylene/hydrogen mixture combines with the solvent/styrene stream at ambient temperature. The temperature of the solvent/monomer as it enters the reactor is dropped to about 5°C by an exchanger with -5°C glycol on the jacket. This stream enters the bottom of the reactor. The three component catalyst system and its solvent flush also enter the reactor at the bottom but through a different port than the monomer stream. Preparation of the catalyst components takes place in an inert atmosphere glove box. The diluted components are put in nitrogen-padded cylinders and charged to the catalyst run tanks in the process area. From these run tanks the catalyst is pressured up with piston pumps and the flow is measured with micromotion mass flowmeters. These streams combine with each other and the catalyst flush solvent just prior to entry through a single injection line into the reactor.

Polymerization is stopped with the addition of catalyst kill (water mixed with solvent) into the reactor product line after the micromotion fiowmeter measuring the solution density. Other polymer additives can be added with the catalyst kill. A static mixer in the line provides dispersion of the catalyst kill and additives in the reactor effluent stream. This stream next enters post reactor heaters that provide additional energy for the solvent removal flash. This flash occurs as the effluent exits the post reactor heater and the pressure is dropped from 475 psig (3,275 kPa) down to about 250mm of pressure absolute at the reactor pressure control valve. This flashed polymer enters a hot-oil jacketed devolatilizer. Approximately 85 percent of the volatiles are removed from the polymer in the devolatilizer. The volatiles exit the top of the devolatilizer. The stream is condensed and with a glycol jacketed exchanger, enters the suction of a vacuum pump and is discharged to a glycol jacket solvent and styrene/ethylene separation vessel. Solvent and styrene are removed from the bottom of the vessel and ethylene from the top. The ethylene stream is measured with a micromotion mass fiowmeter and analyzed for composition. The measurement of vented ethylene plus a calculation of the dissolved gasses in the solvent/styrene stream are used to calculate the ethylene conversion. The polymer separated in the devolatilizer is pumped out with a gear pump to a ZSK-30 devolatilizing vacuum extruder. The dry polymer exits the extruder as a single strand. This strand is cooled as it is pulled through a water bath. The excess water is blown from the strand with air and the strand is chopped into pellets with a strand chopper.

The composition of the three-component catalyst systems used in the described polymerization processes are listed in Table 1A below:

Table IA

The aluminum catalyst component is a commercially available modified methalumoxane Type 3A (MMAO-3A).

The boron cocatalyst type 1 is tris(pentafluorophenyl)borane.

The titanium catalyst type 2 is (t-butylamido)dimethyl(3-phenyl-s-indacen-1 - yl)silanetitanium(IV)dimethyl.

The titanium catalyst type 1 is (1 H-cyclopenta[l]phenanthrene-2-yl)dimethyl(t- butylamido)-silanetitanium 1 ,4-diphenylbutadiene). It is prepared as described below.

Preparation of Catalyst-Type 1 :(1 H-cyclopenta[l]phenanthrene-2-yl)dimethyl(t-butylamido)- silanetitanium 1 ,4-diphenylbutadiene)

1 ) Preparation of lithium 1 H-cvclopentamphenanthrene-2-yl

To a 250 mL round-bottom flask containing 1.42 g (0.00657 mole) of 1 H-cyclopenta[l]phenanthrene and 120 mL of benzene is added dropwise, 4.2 mL of a 1.60 M solution of n-Buϋ in mixed hexanes. The solution is allowed to stir overnight. The lithium salt is isolated by filtration, washing twice with 25 mL benzene and drying under vacuum. Isolated yield is 1.426 g (97.7 percent). 1 H NMR analysis indicated the predominant isomer is substituted at the 2-position.

2) Preparation of (1 H-cvclopenta[l]phenanthrene-2-yl)dimethylchlorosilane

To a 500 mL round-bottom flask containing 4.16 g (0.0322 mole) of dimethyldichlorosilane (Me₂SiCI₂ ) and 250 mL of tetrahydrofuran (THF) is added dropwise a solution of 1.45 g (0.0064 mole) of lithium 1 H-cyclopenta[l]phenanthrene-2-yl in THF. The solution is stirred for approximately 16 hours, after which the solvent is removed under reduced pressure, leaving an oily solid which is extracted with toluene, filtered through diatomaceous earth filter aid (Celite™), washed twice with toluene and dried under reduced pressure. Isolated yield is 1.98 g (99.5 percent). 3) Preparation of (1 H-cvclopentaN1phenanthrene-2-yl)dimethyl(t-butylamino, silane

To a 500 mL round-bottom flask containing 1.98 g (0.0064 mole) of (1 H- cyclopenta[l]phenanthrene-2-yl)dimethylchlorosilane and 250 mL of hexane is added 2.00 mL (0.0160 mole) of t-butylamine. The reaction mixture is allowed to stir for several days, then filtered using diatomaceous earth filter aid (Celite™), washed twice with hexane. The product is isolated by removing residual solvent under reduced pressure. The isolated yield is 1.98 g (88.9 percent).

4) Preparation of dilithio (1 H-cvclopentaN1phenanthrene-2-yl)dimethyl(t-butylamido)silane

To a 250 mL round-bottom flask containing 1.03 g (0.0030 mole) of (1 H- cyclopenta[l]phenanthrene-2-yl)dimethyl(t-butylamino)silane) and 120 mL of benzene is added dropwise 3.90 mL of a solution of 1.6 M n-BuLi in mixed hexanes. The reaction mixture is stirred for approximately 16 hours. The product is isolated by filtration, washed twice with benzene and dried under reduced pressure. Isolated yield is 1.08 g (100 percent).

5) Preparation of (1 H-cvclopenta[llphenanthrene-2-yl)dimethyl(t-butylamido)silanetitanium dichloride

To a 250 mL round-bottom flask containing 1.17 g (0.0030 mole) of ΗCI3 • 3THF and about 120 mL of THF is added at a fast drip rate, about 50 mL of a THF solution of 1.08 g of dilithio (1 H-cyclopenta[l]-phenanthrene-2-yl)dimethyl(t- butylamido)silane. The mixture is stirred at about 20°C for 1.5 hours at which time 0.55 gm (0.002 mole) of solid PbCl2 is added. After stirring for an additional 1.5 hours the THF is removed under vacuum and the residue is extracted with toluene, filtered and dried under reduced pressure to give an orange solid. Yield is 1 .31 g (93.5 percent).

6) Preparation of (1 H-cvclopentari1phenanthrene-2-yl)dimethyl(t-butylamido)silanetitanium 1 ,4-diphenylbutadiene

To a slurry of (1 H-cyclopenta[l]phenanthrene-2-yl)dimethyl(t-butylamido)- silanetitanium dichloride (3.48 g, 0.0075 mole) and 1.551 gm (0.0075 mole) of 1 ,4-diphenylbutadiene in about 80 mL of toluene at 70°C is add 9.9 mL of a 1.6 M solution of n-BuLi (0.0150 mole). The solution immediately darkened. The temperature is increased to bring the mixture to reflux and the mixture is maintained at that temperature for 2 hours. The mixture is cooled to about -20°C and the volatiles are removed under reduced pressure. The residue is slurried in 60 mL of mixed hexanes at about 20°C for approximately 16 hours. The mixture is cooled to about -25°C for about 1 hour. The solids are collected on a glass frit by vacuum filtration and dried under reduced pressure. The dried solid is placed in a glass fiber thimble and the solid extracted continuously with hexanes using a Soxhlet extractor. After 6 hours a crystalline solid is observed in the boiling pot. The mixture is cooled to about -20°C, isolated by filtration from the cold mixture and dried under reduced pressure to give 1.62 g of a dark crystalline solid. The filtrate is discarded. The solids in the extractor are stirred and the extraction continued with an additional quantity of mixed hexanes to give an additional 0.46 gm of the desired product as a dark crystalline solid.

The monomer amounts and polymerization conditions are provided in Table

1 B. The polymer properties are provided in Table 1C.

Table IB

Table IC

na = not analyzed

Example 1 and Comparative Example A

A wood veneer of 0.50 mm thickness was used. In Comparative Example A the flexural modulus and the bending stiffness of the non-modified wood veneer was tested.

In Example 1 a polymeric sheet of 0.40 mm thickness was cast from 85 percent ESI-1 , 10 percent of a polyethylene-based slip concentrate containing 2 percent erucamide in polyethylene and 5 percent of a polyethylene based antiblock additive containing 20 percent silica in polyethylene.

The produced polymeric sheet was heat-laminated to the wood veneer in a frameless Buerkle press at a pressure of 5 bar during 5 minutes, with the temperature of the top plate and bottom plate being 180°C. The heat-laminated sheet was cooled to 40°C.

The Flexural Modulus of the non-coated wood veneer of Comparative Example A and of the coated wood veneer of Example 1 are measured. The Flexural Modulus data listed in Table II below are an average of six samples each. "Machine direction" (MD) and "cross-direction" (CD) relate to the direction of the wood fibers.

Visual bending test: Samples of non-coated wood veneer of Comparative

Example A and of coated wood veneer of Example 1 are bent around metal cylinders of various diameters such that the wood fibers run parallel to the metal cylinder. It is visually inspected to determine whether the wood veneer breaks or not.

Table II

Table II illustrates that the multilayer structure of the present invention has a substantially lower flexural modulus, which means a substantially higher flexibility, than the wood veneer alone. This finding is confirmed in the visual bending test.

Examples 2 to 11 and Comparative Examples B and C

An MDF board of 1 cm thickness was used. Polymeric films of a thickness of 0.4 mm are prepared by pressing granular material between two steel plates at 180^aC.

The polymeric film of 0.4 mm thickness was pressed on the MDF board in a Buerkle press at a pressure at 3 bar during 4 minutes and then at 20 bar during 2 minutes, the temperature of the top plate being 180°C, the temperature of the bottom plate being 100°C. The heat-laminated sheet was cooled to 40°C.

The composition of the polymeric films, their adhesion to the MDF board and their abrasion resistance are listed in Table III.

The polyethylene used to prepare the Comparative Example B is commercially available from The Dow Chemical Company under the trademark AFFINITY POP DSH 1505. PRIMACOR 1410 copolymer used in Comparative Example C is the trademark for an ethylene/acrylic acid copolymer commercially available from The Dow Chemical Company.

STYRON 648 used in Example 11 is the trademark of The Dow Chemical Company for a polystyrene.

Table

na: not analyzed ^' film breakage

Table III illustrates that a polymeric film comprising an above-described substantially random interpolymer has generally a higher adhesion strength to an MDF board than a film made of a polyethylene resin. When the polymeric film comprises the most preferred substantially random interpolymer(s), as described further above, an equal or even higher adhesion strength can be achieved than with a film made of an ethylene/acrylic acid copolymer which is well known for its excellent adhesion strength to various substrates.

Moreover, Table III illustrates the excellent abrasion resistance of a polymeric film comprising an above-described substantially random interpolymer. For comparative purposes, the abrasion of the MDF board used in the present examples is 758 mm³. Examples 12 to 17

In Examples 12 to 17 the following materials are used:

ethylene/acrylic acid copolymers, which are commercially available from The Dow Chemical Company under the trademark PRIMACOR 1410, PRIMACOR 5980E and PRIMACOR 5980,

ethylene/vinyl acetate copolymers, which are commercially available from Dupont under the trademark ELVAX 3175, ELVAX 4050, and ELVAX 3190,

a polystyrene, which is commercially available from The Dow Chemical Company under the trademark STYRON 665,

a low density polyethylene, which is commercially available under the trademark PROXMELT E4050,

an MAH graft polymer containing maleic anhydride units, which is commercially available from Dupont under the trademark BYNEL 3861 ,

a white colorant, which is commercially available from Ampacet under the trademark Ampacet White 11560,

a slip additive, which is commercially available from Ampacet under the trademark Ampacet 10061.

Example 12 and 13

A three-layer film is made by hot roll laminating a stack of monolayer films of a size of about 20 cm by 30 cm, as listed in Table IV below.

Table IV

The stack of films is placed between two glass fiber reinforced sheets of tetrafluoroethylene fluorocarbon polymers and then run through a laboratory scale roll laminator. The laminator temperature control was set at 350°F (177°C) and the roll speed was 5 cm/minutes. In both Examples 12 and 13, the three films were bonded together after lamination and could not be pulled apart by hand.

The three-layer film was then placed on top of a wood particleboard with the dimensions of 20 cm by 20 cm by 0.6 cm (8 by 11 by 0.25 inches) and run through the roll laminator at a set-point temperature of 500°F (260°C) and speed of 5 cm/minute. After cooling to room temperature, the three-layer film was pulled from the wood substrate by hand to determine the type of bond failure. After pulling in both Examples 12 and 13, the bottom side of the three-layer film was covered with wood fibers from the particleboard, indicating cohesive failure in the particleboard.

The three-layer film of Example B is stiffer than the three-layer film of

Example A.

Examples 14 and 15

Three-layer films are fabricated on a KILLION three-layer cast coextrusion pilot line. Polymers were plasticated in a 25.5 mm diameter single-screw extruder. The mass flow rate from each extruder was adjusted such that the output rate provides material in the ratio listed in Table V below. The layers listed in Table V below are combined in a

KILLION feedblock and cast from a 25.4 cm wide coat-hanger style film die. The film was quenched onto a chill roll and wound onto a 38.1 mm diameter core. Table V

The films were laminated to contoured Medium Density Fiberboard (MDF) panels using a membrane press. The films had been cut to a size larger than the MDF board and were placed on top of the board, such that the bottom layer was in contact with the board surface. The boards were pressed in the membrane press using the following conditions:

Membrane Temperature: 177°C Glue-line temperature, top of board: 130°C Glue-line temperature, edge of board: 96°C Pressure: 4 bar Pressure dwell time: 50 seconds

After pressing, the boards were removed from the membrane press and allowed to cool to room temperature. Both films of Examples 14 and 15 showed excellent thermoformability into the contoured shape of the MDF panel. Adhesion was evaluated by pulling the three-layer film from the board and observing whether the film removed wood particles from the board, indicating cohesive failure in the board substrate. Both films showed excellent adhesion to the MDF, with cohesive failure in the board.

The boards were then tested for heat resistance according to NRRI Standard Testing Procedure NRRI 1-96. This test determines the temperature at which the film delaminates from the edge a distance of greater than 0.2mm. The film of Example 14 had an average failure temperature of 100°C, and the film of Example 15 had an average failure temperature of 97°C.

For comparative purposes the following commercially available films were also tested: a PVC film with a pre-applied hot-melt adhesive, commercially available from BEMIS, and PVC films from Renolit and Hoechst with polyurethane-(PU) based spray adhesives from Jowat, Daubert and Helmitin which had been applied to the MDF panel. The measured heat resistance and heat resistance data reported by T. Hippold, "Polyurethane dispersions for 3D foil-lamination", presented at the 3^rd International Symposium "3D- lamination of wood based panels" held in Bielefeld, Germany on May 18-20, 1998 are listed in Table VI below.

Table VI

" Measured values

^2> Values reported by T. Hippold, "Polyurethane dispersions for 3D foil-lamination", presented at the 3^rd International Symposium "3D-lamination of wood based panels" held in Bielefeld, Germany on May 18-20, 1998.

These results illustrate that the multilayer structures of the invention had a higher heat resistance than that of a PVC film on wood using a conventional water-based polyurethane dispersion with polyisocyanate crosslinker, and a much higher heat resistance than PVC on wood using either a conventional pre-applied hot-melt adhesive or a water- based polyurethane dispersion without crosslinker. The results also indicate that the multilayer structures of the invention have a higher heat resistance than PET or polypropylene on wood using water-based polyurethane dispersion without cross-linker.

PET and polypropylene films which were bonded to wood using a cross-linker had an equivalent or higher heat resistance, but must use the undesirable spray application process. In addition, polyolefin films, such as polypropylene films, were reported to require higher pressing temperature, tighter control of pressing temperature, longer preheating times, and heavier glue application than PVC, see Hilmar Sorgenfrei, "3D Pressing Technology Under Factory Operating Conditions," 3^rd International Symposium on 3D-Lamination of Wood Based Panels. May 18-20, 1998, Bielefeld, Germany.

Layer (B) in the multilayer structure of the invention can be pressed on the wood-based layer (A) at temperature and time conditions similar to PVC, but without the addition of a spray adhesive. In the multilayer structures of the invention the polymeric film has a higher resistance to delaminate from the wood-based layer, which is essential in applications such as kitchen furniture or during transportation at elevated temperatures.

Examples 16 and 17

Two- and three-layer films are produced as described for Examples 14 and 15 above.

Table VII

The films of Examples 16 and 17 are cut to 127mm x 152mm rectangles and placed on a flat MDF board of 305mm x 305mm with the bottom layer against the board. They are laminated to a flat MDF board using a hydraulic platen press under the following conditions: Platen Temperature: 77 °C Platen Pressure: 270 bar Cycle time: 30 seconds.

After pressing, the boards are allowed to cool to room temperature and then the films are pulled from the MDF board. The films show significant coverage with wood fibers, indicating cohesive failure within the wood substrate.

Examples 18 to 21

In Examples 18-21 the following materials are used:

A styrene-butadiene copolymer, which is commercially available from The Dow Chemical Company under the trademark STYRON 404,

an ethylene/vinyl acetate copolymer, which is commercially available from Dupont under the trademark ELVAX 3180,

modified ethylene polymers, which are commercially available from Dupont under the trademark BYNEL 3860 and BYNEL E418, and

a white colorant, which is commercially available from Ampacet under the trademark Ampacet white 110598.

Other materials used in these examples are described in more detail in Examples 12-17 above.

Two layer films are made by cast coextrusion as described in Examples 14 and 15 with the following process revisions:

Table VIII

The films are laminated to contoured Medium Density Fiberboard (MDF) panels using a membrane press. The films have been cut to a size larger than the MDF board and are placed on top of the board, such that the bottom layer is in contact with the board surface. The boards are pressed in the membrane press using the following conditions:

Membrane Temperature: 144°C Glue-line temperature, top of board: 77°C Glue-line temperature, edge of board: 77°C Pressure: 4 bar Pressure dwell time: 40 seconds

After pressing, the boards are removed from the membrane press and allowed to cool to room temperature. All films of Examples 18-21 show excellent thermoformability into the contoured shape of the MDF panel. Adhesion is evaluated by pulling the three-layer film from the board and observing whether the film removes wood particles from the board, indicating cohesive failure in the board substrate. All films show excellent adhesion to the MDF, with cohesive failure in the board.

Claims

CLAIMS:

1. A multilayer structure comprising

(A) a lignocellulose-based layer and

(B) a layer including a substantially random interpolymer comprising in polymerized form i) one or more α-olefin monomers and ii) one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s); layer (B) being free from a substantial amount of tackifier.

2. The multilayer structure of Claim 1 wherein the lignocellulose-based layer is a wood-based layer.

3. The multilayer structure of Claim 2 wherein the wood-based layer is made of solid wood, is a wood laminate, or is a panel manufactured from wood flour, wood fibers or other wood particles.

4. The multilayer structure of Claim 2 or 3 wherein the surface of the wood- based layer is three-dimensional.

5. The multilayer structure of any one of Claims 1 to 4 wherein said substantially random interpolymer includes interpolymerized.

(I) from 50 to 85 mole percent of one or more α-olefin monomers and

(II) from 50 to 15 mole percent of one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s).

6. The multilayer structure of any one of Claims 1 to 5 wherein said substantially random interpolymer is an interpolymer of ethylene and styrene.

7. The multilayer structure of any one of Claims 1 to 6 wherein layer (B) includes up to 80 percent of one or more additional polymers, based on the total polymer weight in layer (B).

8. The multilayer structure of Claim 7 wherein the additional polymer is a homopolymer or interpolymer of one or more monovinyl or monovinylidene aromatic monomers.

9. The multilayer structure of any one of Claims 1 to 8 wherein layer (B) is fixed to layer (A) without an intermediate layer.

10. The multilayer structure of any one of Claims 1 to 9 comprising one or more adhesive layers (C) between layer (B) and layer (A), wherein layer (C) comprises a thermoplastic adhesive.

11. The multilayer structure of Claim 10 wherein one or more adhesive layers (C) comprise a blend of from 5 to 95 percent of the substantially random interpolymer and from 5 to 95 percent of a tackifier, based on the total weight of substantially random interpolymer and tackifier.

12. The multilayer structure of Claim 10 wherein one or more adhesive layers (C) comprise an interpolymer of i) ethylene and ii) acrylic acid, methacrylic acid, an acrylic ester, a vinyl ester, or an ionomer thereof.

13. The multilayer structure of Claim 10 comprising a structure (B)/(C')/(C)/(A),

wherein (B) is a polymeric layer including the substantially random interpolymer and up to 80 weight percent of a homopolymer or interpolymer of one or more monovinyl or monovinylidene aromatic monomers, based on the total polymer content in layer (B),

(C) is a layer comprising an ethylene/vinyl acetate interpolymer,

(C) is a layer comprising an ethylene/acrylic acid interpolymer and

(A) is a wood-based layer.

14. The multilayer structure of any one of Claims 1 to 13 comprising one or more additional layers (D) selected from print layers, transparent lacquer layers, finishing layers, UV protection layers, chemical resistant layer, scratch and abrasion resistant layers.

15. An article being at least partially made from the multilayer structure of any one of Claims 1 to 14.

16. The article of Claim 15 being selected from floor, wall and ceiling coverings, decorative and protective overlays, doors and furniture.

17. A method of producing the multilayer structure of any one of Claims 1 to

14 which comprises the step of fixing one or more layers (B) and optionally one or more adhesive layers (C) to one or more lignocellulose-based layers (A).

18. The method of Claim 17 wherein a layer (B) is directly applied to a lignocellulose-based layer (A) at a temperature of from 130°C to 250²C and a pressure of from 10 to 40 bar.

19. The method of Claim 17 wherein a layer (B) is fixed to a lignocellulose- based layer (A) by means of one or more thermoplastic adhesive layers (C) at a temperature of from 50°C to 120^aC and a pressure of from 3 to 30 bar.