DE102016212100B3 - Composite film with silane-functional top coat and its use as surface protection film - Google Patents

Abstract

A composite foil comprising as layers at least one lacquer layer, a polymer foil layer and an adhesive layer, wherein the lacquer layer is bonded to a major surface of the polymer foil layer and the adhesive layer is bonded to the opposite major surface of the polymer foil layer such that the polymer foil layer is embedded between the lacquer layer and the adhesive layer in which the lacquer layer is a silane lacquer layer which comprises at least one at least partially crosslinked silane-functional resin, requires less hazardous starting materials, such as crosslinkers or solvents, and avoids the use of actinic radiation and has good gloss properties, Abrasion and scratch resistance.

Description

The invention relates to a composite film, in particular a surface protection film comprising at least one lacquer layer, a polymer film layer and an adhesive layer, wherein the lacquer layer is bonded to a major surface of the polymer film layer and the adhesive layer is bonded to the opposite major surface of the polymer film layer such that the polymer film layer between the lacquer layer and the adhesive layer is embedded, as well as the use of this composite film.

Surface protection films are often built up in multiple layers, in particular in the automotive sector, in order, for example, to give the surface a higher gloss or improved abrasion resistance.

Particularly known are multilayer surface protection films with a carrier film of a polyurethane and a cover layer of another polyurethane. For example, in the EP 1 874 541 B1 describes the preparation of the cover layer of an aqueous or solvent-based polyurethane. This polyurethane is crosslinked with crosslinkers such as aziridine or isocyanate. It is problematic that aziridine and isocyanate are harmful substances.

Also known in the prior art are surface protection films having a carrier film and a cover layer of a radiation-crosslinkable paint, in particular a radiation-crosslinkable paint based on polyfunctional (meth) acrylates, for example urethane acrylates.

Such surface protection films are for example the subject of DE 10 2006 002 595 A1 and the DE 10 2006 002 596 A1 ,

Radiation-curable coating formulations which are used for coating plastic films are also described in a number of other publications. Typically, these formulations have in common that at least one kind of polyfunctional (meth) acrylate is present in the formulation. By the action of suitable radiation, initiated in the case of UV curing by photoinitiators, these (meth) acrylated monomers, oligomers or polymers are excited to polymerize, resulting in a close-meshed network. The formulations may contain various other types of ingredients. In particular, inorganic particles have been described as being advantageously used with regard to higher paint hardnesses. Examples of radiation-curable coating formulations are in US 4,557,980 A Martin Processing Inc., in US 4,319,811 A the GAF Corp., in EP 0 050 996 B1 the Mitsui Petrochemical, in US 4,310,600 A the American Hoechst Corp., in JP 01 266 155 A the Sunstar and in US 5,104,929 to find the 3M.

One advantage of radiation-curable coating formulations lies in the fact that solvents can be dispensed with completely. The disadvantage, however, is that is irradiated with high-energy radiation, so that extensive occupational safety measures must be taken.

The object was to provide an improved surface protection film which avoids the disadvantages of the prior art. In particular, the production of the film should require less hazardous starting materials, such as crosslinkers or solvents, and avoid the use of actinic radiation. At the same time, however, the surface protection film should meet the requirements for gloss, abrasion and scratch resistance.

From different writing like the DE 60 2004 002 551 T2 or the US 2006/0173140 A1 are protective coatings based on silane-terminated polymers, are known. These are preferably used as scratch-resistant protective coatings, for example for floor panels, but also as a clearcoat for automobiles on rigid surfaces. Further connections can be found in the EP 2 905 296 A1 , Although such protective coatings have good scratch resistance, this is associated with the fact that the protective coatings are very hard and brittle, so that application to a film has not previously been considered.

The above object is achieved according to the invention with a composite film of the type mentioned, in which the lacquer layer comprises at least one at least partially crosslinked silane-functional resin. This lacquer layer comprising an at least partially crosslinked silane-functional resin according to the invention is referred to below as a silane lacquer layer. The composite film thus comprises a surface protection varnish, which is composed of silane-functional resins. These coating formulations are isocyanate-free, cure on contact with atmospheric moisture by silane crosslinking and can be adjusted to the necessary for surface protection films balanced property profile in terms of elasticity and hardness. In addition, they have good weathering stability.

The silane-functional resin is an oligomer or polymer comprising at least one, preferably at least two alkoxysilane groups. In the following, the term polymer also includes the oligomer.

A polymer is a chemical compound consisting of chain or branched molecules (macromolecule) consisting of equal, similar or different units (the so-called monomers). In the simplest case, the macromolecule consists of only one type of monomer. Copolymers are made up of various monomers which can be distributed randomly in the macromolecule, distributed regularly or in blocks. Polymers contain at least three identical monomer units. A monomer unit within the meaning of this definition is the bonded form of a monomer in a polymer.

The polymer may be of linear, branched, star or grafted structure, to give but a few examples, and be constructed as a homopolymer, a random copolymer, an alternating or a block copolymer. The term "random copolymer" for the purposes of this invention includes not only those copolymers in which the comonomers used in the polymerization are purely randomly incorporated, but also those in which occur gradients in the comonomer composition and / or local enrichment of individual Comonomersorten in the polymer chains , Individual polymer blocks may be constructed as a copolymer block (random or alternating).

Polymers with few monomer units are often called oligomers. Preference is given to polymers having more than 5 monomer units, since the silane coating layer is then more flexible.

Preference is given to polymers having a weight-average molecular weight of more than 1000 g / mol, since the silane coating layer is then more flexible.

The alkoxysilane groups are preferably selected from unbranched or branched C ₁ -C ₁₀ -alkoxy groups, more preferably from the group methoxysilane and ethoxysilane, since the crosslinking is then particularly fast.

The silane is preferably formed as gamma or alpha silane. In the case of gamma-substituted silanes, the organic functionality is separated from the silicon atom by three carbon atoms, and by a carbon atom in the case of alpha-substituted silanes.

The silane functionality may be terminal on the polymer chain or as a side group. In particular, the silane functionalities are particularly preferably terminally arranged on both sides of the polymer chain, since this gives more flexible coatings.

It is known that in particular terminal silane-functional groups can have a multiplicity of silane functionalities due to the structure of dendritic structures. For example, the resin Genosil XB (Wacker AG) suggests a functionality of 18. The number of silane-functional groups in the resin is preferably between 1 and 6 at terminal functionalities, in particular between 4 and 6. With such a number, a higher hardness of the silane coating layer can be achieved. In the arrangement of the silane-functional groups in the side chain, the number of silane-functional groups may also be higher.

Preference is given to a mixture of resins with terminal functionalities and those with functionalities which are arranged in side chains, since in this way a particularly balanced ratio between hardness and elasticity can be achieved.

Such silane-functional resins are known, for example, by the term STP, which stands for silane-terminated polymer. They are offered, for example, by Kaneka (MS Polymer, Xmap, Gemlac), Wacker (Genosil STP, Genosil WP, Genosil XT, Genosil XB), Evonik (Vestanat EP-M, Polymer ST, Tegopac), Bayer (Desmoseal S, Desmodur XP2714), Momentive (SPUR), Risun (STP Polymer Resin), Gelest (Sibrid, SSP).

Silane-functional resins according to the invention may, in addition to the silane functionality, also carry one or more further functional groups. These may be, for example, cyclic ethers, hydroxyl groups, carboxyl, carbonyl groups, amines, vinyl or allyl groups, isocyanate, acrylate or methacrylate groups. Preferably, the number of silane functionalities exceeds that of the other functionalities. However, the silane-functional resins are particularly preferably substantially free of other functionalities.

Furthermore, it is preferred that the at least one resin above a temperature of 20 ° C is liquid or pasty. In particular, it has a dynamic viscosity of less than 10 Pas, more preferably less than 1 Pas, measured according to DIN 53019-1 with a cylinder rotation viscometer with a standard geometry at a measurement temperature of 23 ° C and a shear rate of 1 s ^-1 .

A dynamic viscosity of more than 50 mPas is advantageous.

The resins used in the invention are advantageously used as a crosslinking component for scratch-resistant and flexible coatings, from which the silane coating layer is constructed. They can be mixed to optimize the paint mechanics with polymeric binders that can also carry crosslinkable functional groups. Preferably, the at least one silane-functional resin is mixed with further resins from this group, for example, resins of different viscosity, with different molecular weight, different numbers of functionalities or with different alkoxysilane groups are mixed to set a balanced for the surface protection and paint application property profile. Also preferred is the use of modified or unmodified alkoxysilanes with further functional groups as a component of the paint mixture.

The proportion of silane resins according to the invention as a component in a lacquer is preferably 50 to 100 wt .-%, particularly preferably 70 to 90 wt .-%, based on the paint.

Silane-functional resins are typically cured or crosslinked in a two-step sequence that requires first a reaction of water with an alkoxysilane group to form a silanol group, followed by a reaction of the silanol group with either another silanol group or an alkoxysilane. In one-component silane formulations, catalysts are typically added to increase the rate of reaction. In many cases, the absorption of water is a limiting step in the curing or crosslinking process. It is therefore preferred to add water directly to the paint.

However, the reactivity of the resins of the present invention may not be sufficient for a sufficient curing rate at ambient temperature. To increase the rate of crosslinking, it is therefore preferable to add catalysts and / or cure at temperatures above ambient. For this purpose, metal or transition metal chelates, salts or particles are suitable, for example based on titanium, aluminum, tin or zirconium complexes, sulfonic acids, phosphoric acid or phosphorous acids and derivatives thereof, carboxylic acids having melting points above 60 ° C., quaternary ammonium carboxylates , Amines, in particular aminosilanes, organotin compounds or combinations of said compounds.

According to the invention, the lacquer layer formed as a silane coating layer comprises an at least partially crosslinked silane-functional resin. The resin is at least partially cross-linked via its silane functionality. At least partially crosslinked means that at least some of the silane-functional components contained in the paint formulation are connected to one another via the curing of the silane functionality. An obvious indication of the at least partial crosslinking is the transition of the paint from the liquid to the solid phase.

The partial crosslinking can be determined quantitatively by determining the gel content in the cured paint formulation. According to the invention, the gel fraction is more than 20% by weight, based on the proportion of silane-functional components in the coating formulation, preferably more than 50% by weight. In the present case, the ratio of the proportion of the crosslinked lacquer which is not soluble in toluene at room temperature to the total mass of the silane-functional components in the lacquer formulation is defined here as the gel fraction.

The lacquers containing the at least one resin for the production of the first layer may be solvent-free or solvent-containing. Most preferably, the paints to be used are non-aqueous. Non-aqueous in the sense of the present invention means a content of water in the paint of not more than 1.0 wt .-%, preferably not more than 0.5 wt .-% based on the paint. In particular, in the case of two-component formulations, the previously mentioned small amount of water can be used to accelerate the curing. In particular, the paint system used is preferably free from water (maximum 500 ppm water).

The silane coating layers obtained on the basis of the silane-functional resins mentioned above are characterized by a high resistance to mechanical stress, in particular they have a high scratch resistance. It is surprising that the resulting coatings at the same time have a particularly flexibility, so that they are particularly suitable for the coating of a flexible polymer film.

The thickness of the at least one at least partially crosslinked silane-functional resin-containing silane coating layer is within the familiar to the skilled painter layer thicknesses, ie from about 0.05 to 100 microns. For very flexible surface protection films, preference is given to thin coating layer thicknesses in the range from 0.05 to 10 μm, in particular from 1 to 5 μm, since these have increased flexibility. For rigid surface protection films, paint layer thicknesses of 20 .mu.m to 100 .mu.m are preferred, since thus the paint layer can contribute to rigidity.

It has been found that a multilayer composite film according to the present invention provides at least equally good results in terms of mechanical resistance, in particular scratch resistance, as a film which has a polyurethane-based layer established in the market, but the health risks associated with the Production due to the required isocyanate crosslinking are avoided.

The polymer film can be selected from the polymer films known to the person skilled in the art. By way of example, but not by way of limitation, mention may be made of plastic films of: polyolefins such as polyethylene (PE) or polypropylene (PP), cyclic olefin copolymers (COC), polyvinyl chloride (PVC), polyesters - in particular polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polymethylpentene (PMP ), Ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), fluoropolymers such as polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycarbonate (PC), polyamide (PA), polyethersulfone (PES), polyetherimide (PEI), polyarylate (PAR), cellulose triacetate (TAC), polymethacrylate (PMMA) or polyimide (PI).

Preferably, the polymer film is selected from the group of PVC, PE and its copolymers such as EVA (ethylene-vinyl acetate), EAA (ethylane acrylate), EMA (ethylene methacrylate), fluoropolymers and polyurethane, since these films are particularly weather-resistant and elastic ,

Particularly preferred is a polyurethane film comprising an aliphatic polyurethane. Most preferably, the polymer film comprises a thermoplastic polycaprolactone-based polyurethane.

The thickness of the polymer film is in the range of the thicknesses of protective films known to those skilled in the art, that is to say in the range from 10 μm to 1000 μm.

The adhesive layer is preferably a hot melt adhesive layer or a pressure-sensitive adhesive layer. It particularly preferably comprises at least one pressure-sensitive adhesive and thus has pressure-sensitive adhesive properties at a temperature above 20 ° C.

Adhesive adhesives are adhesives which, even under relatively weak pressure, permit a permanent bond with the primer and, after use, can be removed again from the primer without leaving any residue. Pressure-sensitive adhesives are permanently tacky at room temperature and therefore have a sufficiently low viscosity and high tack, so that they wet the surface of the respective adhesive base even at low pressure. The adhesiveness of the adhesives is based on their adhesive properties and the removability on their cohesive properties. As a basis for PSAs, various compounds come into question.

As pressure-sensitive adhesive it is possible to use all PSAs known to the person skilled in the art, for example those based on acrylates and / or methacrylates, polyurethanes, natural rubbers, synthetic rubbers, styrene block copolymer compositions with an elastomeric block of unsaturated or hydrogenated polydiene blocks (polybutadiene, polyisoprene, copolymers of both and others) elastomer blocks familiar to the person skilled in the art), polyolefins, fluoropolymers and / or silicones. This also includes other compositions which have pressure-sensitive adhesive properties according to the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (Satas & Associates, Warwick 1999).

If acrylate-based PSAs are mentioned in this document, PSAs based on methacrylates and based on acrylates and methacrylates are also included herein without explicit mention, unless expressly stated otherwise. Also within the meaning of the invention are combinations and blends of several base polymers and adhesives, fillers, anti-aging agents and crosslinkers additivierte adhesives, the list of additives is to be understood as illustrative and not restrictive.

The thickness of the adhesive layer is within the range of the thicknesses of adhesive layers known to those skilled in the art, that is to say in the range from 1 μm to 500 μm.

The production of composite films according to the invention takes place in processes known to the person skilled in the art, for example in US Pat DE 20 2006 021 212 U1 described in detail:
Thus, the silane resin layer can be formed in a conventional manner, for example by applying the mixture of dispersion or solution in a solvent, but preferably without the use of solvents or dispersants,

For the purposes of this invention, in principle any of the processes known to the person skilled in the art can be selected for coating the coating mixtures according to the invention on polymer films. Without wishing to be limiting, examples include doctor blade methods, roll methods, in particular anilox roller methods, dipping methods, spraying methods, knife methods, brush methods, casting methods and printing methods, in particular offset or flexographic printing methods. Combinations of various methods are also conceivable, such as the Mayer-Bar process, a coating process which combines rolls and doctor blades with one another, or rolling / casting systems in which rolls and doctor blades are combined with one another and which additionally incorporate the casting coating principle. Some methods which can be used according to the invention can be found, for example, in Scharenberg [R. T. Scharenberg in Encyclopedia of Polymer Science and Engineering, H.F. Mark, N.M. Bikales, C.G. Overberger, G. Menges (ed.), 3rd volume, 2nd ed., 1985, Wiley, New York].

After the coating of the paint mixture has been applied to the polymer film, it is particularly preferred to wet-coat a protective film and then cure it. The coated polymer film then forms a first composite film and can then be further processed together with the protective film, for example, be coated with the adhesive layer, rolled up into bales or directly cutting or punching processes are supplied. The protective film is uncovered at any time after mounting. for example, only after the application of the composite film according to the invention in its application. In a further variant, the protective film can also first be coated with the lacquer and then the polymeric film can be laminated. Any solvent or dispersant present in the paint mixture is essentially dried before the composite is produced. But also the absorption of the solvent by one of the films is a common procedure.

As film materials for protective films which can be used according to the invention, it is possible in principle to use all those which can be delaminated again after crosslinking of the liquid silane coating layer without damaging the then at least partially crosslinked silane coating layer, preference being given to polymer films. It is therefore important that the film surface does not chemically react with the thermosetting silane paint layer. For this purpose, the protective film can also be provided with a special layer, such as a release layer such as a siliconization or a release layer based on polyolefins, in particular polyethylene, or based on partially or perfluorinated hydrocarbons in particular of polymeric type. In the inventive sense, for example, polyolefin or polyester films or others which satisfy this requirement.

The protective film is preferably highly permeable to water vapor, so that the paint can cure faster. The film preferably has a water vapor permeability of more than 50 g / m ² d, such as, for example, polymethyl methacrylate. The WVTR is measured at 38 ° C and 90% relative humidity according to ASTM F-1249. In each case a double determination is carried out and the mean value is formed. The specified value is related to the respective thickness of the measured test object.

More preferably, the polymer film and / or the protective film has a high water content, so that the crosslinking of the silane-functional groups can take place at least partially without diffusion of water vapor from the surrounding atmosphere. This is advantageous, for example, when the composite of polymer film and / or protective film and the coated paint is wound onto a roll, so that the access of water vapor is hindered. Preferably, the water content is greater than 1 wt .-%.

The water absorption is determined after storage of the test specimen for 24 hours at 23 ° C and 50% relative humidity according to DIN 53715 (Karl Fischer titration). The measurement is carried out on a Karl Fischer Coulometer 851 in conjunction with an ovensampler (oven temperature 140 ° C). With a weight of about 0.3 g, a triple determination is carried out in each case. The water content is the arithmetic mean of the measurements.

Since the amount of water available for crosslinking also depends on the thickness of the film (s), it is altogether advantageous if the water content of at least one of the films is more than 0.5 g / m ² .

After coating the paint formulation and the optional but particularly preferred construction of a layer composite of the polymer film, the coated paint and a protective film, the curing process of the liquid, preferably solvent- and dispersant-free silane coating layer takes place.

• – eine Harzschicht
• – eine Polymerfolienschicht und
• – eine Schutzfolienschicht,

wobei die Harzschicht mit einer Hauptfläche der Polymerfolienschicht verbunden ist und die Schutzfolienschicht mit der gegenüberliegenden Hauptfläche der Harzschicht derart verbunden ist, dass die Harzschicht zwischen der Polymerfolienschicht und der Schutzfolienschicht eingebettet ist, und die Harzschicht eine Silanharzschicht ist, die zumindest ein silanfunktionelles Harz umfasst,
umfassend die folgenden Schritte:

• – Bereitstellen des Schichtverbundes
• – Wickeln des Schichtverbundes auf eine Rolle
• – Härten der Silanharzschicht,

dadurch gekennzeichnet, dass die Polymerfolienschicht und/oder die Schutzfolienschicht einen Wassergehalt von zumindest 0,5 g/m² aufweist,
so dass die Silanharzschicht ohne äußere Wasserzufuhr in der gewickelten Rolle zumindest teilweise aushärtet.Accordingly, a process for producing a composite film comprising at least the following layers is also disclosed:

• - a resin layer
• A polymer film layer and
• A protective film layer,

wherein the resin layer is bonded to a major surface of the polymer film layer and the protective film layer is bonded to the opposite major surface of the resin layer such that the resin layer is sandwiched between the polymer film layer and the protective film layer, and the resin layer is a silane resin layer comprising at least a silane functional resin,
comprising the following steps:

• - Providing the layer composite
• - Winding the layer composite on a roll
• Hardening of the silane resin layer,

characterized in that the polymer film layer and / or the protective film layer has a water content of at least 0.5 g / m ² ,
so that the silane resin layer at least partially cures without external supply of water in the wound roll.

The adhesive layer may be applied before or after curing of the silane resin layer on a main surface of the polymer film, for example, before providing the layer composite according to the invention. The term "silane coating layer" as used herein refers to the cured silane resin layer. Forming the polymer film layer may be accomplished by forming the polymer at an elevated temperature via an extrusion die. Forming the polymer film layer may also be accomplished by molding the polymer into the desired shape by casting or other molding process (such as rolling).

Silane resin and polymer film layers may also be bonded together after curing of the silane resin layer, such as by laminating the layers at elevated temperature and pressure levels. In this case, the initial temperature in the case of both the silane coating layer and the polymer film layer is at about room temperature or at least at too low a temperature in order to allow a sufficient connection between the silane coating layer and the polymer film layer. Then, at least one major surface of the polymer film layer or the one major surface of each of the silane varnish layer and the polymer film layer is heated to an elevated temperature sufficiently above room temperature to facilitate sufficient bonding between the silane varnish layer and the polymer film layer at the laminating pressure. In the hot lamination process, the layers are heated before or during exposure to the lamination pressure. When a hot lamination process is used, a major surface of the polymer film layer is typically releasably laminated to an easily removable backing or liner (such as a polyester backing) immediately after extrusion of the polymeric film layer to additionally structurally support the freshly formed polymeric film layer with a backing. Among others, a temperature of at least about 100 ° C and a pressure of at least about 10 N / cm ^{2 have} proven to be acceptable minimum temperatures and pressures for bonding the layers after the hot lamination process.

To facilitate or at least improve bonding between the polymeric film layer and the adhesive layer, it may be desirable to apply the corona treatment (such as air or N ₂ corona treatment) and / or thermal lamination to the major surface of the molded polymeric film layer to be bonded to the adhesive layer undergo. For this purpose, the main surface of the polymer film layer, which does not rest against the silane resin layer, is exposed and subsequently corona treated.

The composite films according to the invention are preferably used as surface protection films and decorative films.

The present inventive composite film is typically made transparent and possibly even translucent for paint protection applications. Also for the protection or the refinement of other surfaces, you can perform the present inventive composite film transparent, translucent or even opaque. For some applications, it may also be desirable to color the present composite film. For this purpose, the present film can additionally be provided, for example, in one or more of its layers with a pigment or another colorant.

If the present composite film is to serve, for example, as a paint protection film, it has been found to be desirable to size and shape it accordingly before application to the surface to be protected. Namely, preformatted pieces of the present composite film may be used in relation to the protection of the painted surface of various body parts of a vehicle such as a motor vehicle, aircraft, watercraft, etc., particularly parts of the vehicle body (such as the leading edge leading edge and other leading surfaces , Entrance panels, etc.) against stone chips and dirt from dust and bouncing insects and the like, quite as commercially prove desirable.

Examples:

Used measuring methods:

Trickle test with gloss measurement

The test determines the abrasion resistance under impact stress, as it is relevant for example for the stone impact protection effect of a surface protection film. The test is carried out at 23 ° C and 50% relative humidity.

Before the trickling test, a gloss measurement is made on the 10 × 10 cm ² black pattern bonded patterns using the Reflektometer REFO 3D from HACH LANGE, according to EN ISO 2813 at an angle of 20 °. Then, in accordance with DIN 52348, with approx. 2 kg of angular granular cast steel with a grain size of 0.2 to 0.7 mm and a hardness of 64 to 68 HRC (according to EN ISO 11124, Steelstra GH 50 from Stratec) from a mean drop height of 910 mm on the sample plate inclined at an angle of 45 °. After the trickle test, the gloss is measured again with the REFO 3D and the gloss loss in gloss units is calculated.

Sclerometertest

Here, in accordance with DIN EN ISO 1518-1, the surface of the paint is scratched. Using a hardness test rod (Hardness Test Pencil Model 318S from ERICHSEN), the engraving tip No. 1 (0.75 mm) and No. 2 (1 mm tip radius) are scratched with 5 N contact force over the paint surface of the pattern bonded to black sheet metal. The depth of the scratch and its restoring behavior are assessed qualitatively.

Marten hardness (surface hardness according to DIN-EN-ISO 14577-1)

The measurement of the surface hardness is carried out on a FischerScope HCU from HELMUT FISCHER GmbH & Co. KG at a temperature of 23 ° C. and a relative atmospheric humidity of 50%. The Martens hardness (HM) in N / mm ² at max. Test force. Marten hardness (universal hardness until 2003) is defined as the ratio of the maximum force to the corresponding contact surface. The test piece is a diamond Vickers pyramid. The shape correction for the indentor is not included in the default setting.

The measurement is continuously force-controlled with a gradient of 300 mN / 20 s up to a maximum test load of 300 mN. After a holding time of 5 s, the load is relieved with the same pitch (designation of the parameters according to ISO 14577-1: HM 0.300 / 20.0 / 5.0).

During the measurement, the force and the penetration depth are continuously recorded. The penetration depth is graphically displayed over the force.

bend test

The kink test is a bending test over a defined radius that can cause cracking or spalling of the coating on hard paints. This is a on the ground side with a 50 microns thick Silicone liner covered pattern with fingers folded / folded (180 °), then removed the cover and glued the pattern for optical inspection on a black sheet. The bending radius thus corresponds to the thickness of the polymer film layer plus the liner thickness. The resulting crease can be checked so well for cracks, breaks or flaking.

yellowing

For this purpose, samples of the surface protection film are glued to a white substrate (tile) and at room temperature from a distance of about 50 cm with a sunlight lamp (Osram 300 W ULTRA-VITALUX, 30 ° radiation angle, 13.6 W UV-A, 3 W UV -B) irradiated. The degree of yellowing b * and its change to the initial value Δb * (taken from the L * a * b * color space according to DIN 5033) are measured according to the spectral method with standard illuminant D65 at the observer angle of 10 ° with the BYK spectro-guide Gardner (ball d / 8 spin) after the specified storage time (one and two weeks).

layer thickness

The layer thickness is determined by scanning electron microscopy (SEM). The samples are cut under liquid nitrogen. From the cross-sections overview shots and detail shots are made. The thickness of the protective lacquer layer is measured on the polymer film layer.

molecular weight

The molecular weight determinations of the number-average molecular weights M _n and the weight-average molecular weights M _{w were} carried out by means of gel permeation chromatography (GPC). The eluent used was THF (tetrahydrofuran) containing 0.1% by volume of trifluoroacetic acid. The measurement was carried out at 25 ° C. The precolumn used was PSS-SDV, 5 μ, 10 ³ Å, ID 8.0 mm × 50 mm. For separation, the columns PSS-SDV, 5 μ, 10 ³ and 10 ⁵ and 10 ⁶ , each with ID 8.0 mm × 300 mm were used. The sample concentration was 4 g / l, the flow rate 1.0 ml per minute. It was measured against polystyrene standards.

Viscosity:

A measure of the flowability of the resin is dynamic viscosity. The dynamic viscosity can be determined according to DIN 53019. As liquid or pasty, a viscosity of less than 10 ⁵ Pas is called. The viscosity is measured in a cylinder rotation viscometer with a standard geometry according to DIN 53019-1 at a measuring temperature of 23 ° C. and a shear rate of 1 s ^-1 .

gel content:

The gel fraction is defined as the ratio of the toluene-insoluble fraction of the crosslinked paint at room temperature to the total mass of the silane-functional components in the paint formulation.

The carefully dried, solvent-free paint samples are shrink-wrapped in a non-woven polyethylene (Tyvek fleece). From the difference of the sample weights before extraction and after a 72-hour extraction by toluene at 23 ° C, the not soluble in toluene weight fraction of the paint is determined. The extractant is renewed after 24 h and after 48 h. The sample mass remaining in the sachet gives, based on the mass of the silane-functional components in the varnish, the gel fraction, also called gel value. This is given as the mean of a triple determination in%.

Used ingredients:

For the preparation of the silane resin layer (top coat) for the surface protection film, the following silane-modified resins were tested: TABLE 1 Resins used Manufacturer Product name Chemical construction EVONIK VESTANAT EP-MF 201 Polyurethane with trimethoxysilane end groups having a viscosity of 250 mPas VESTANAT EP-M 222 Trimethoxysilane-terminated polyurethane having a viscosity of 4 Pas (85% by weight in butyl acetate)

Production of top coats:

For the preparation of the silane resin mixture, the polymers were added in the desired ratio at room temperature and mixed well.

Example 1 and 5-7: VESTANAT EP-MF 201
Example 2: VESTANAT EP-MF 201 / VESTANATE EP-M222 in butyl acetate (70:30)
Example 3: VESTANAT EP-MF 201 / VESTANATE EP-M222 in butyl acetate (50:50)
Example 4: VESTANAT EP-MF 201 / VESTANATE EP-M222 in butyl acetate (30:70)

After the components had mixed well, the varnish was spread on the Mayer-Bar spreading table on the non-pressure-sensitive coated side of KPMF's K82200 stone chip (Kay Premium Marking Films Ltd., Newport) at room temperature for about one day dried. The smears crosslinked slowly and were therefore dried at elevated temperature. This resulted in promising patterns that showed good results in the test.

After painting, some of the samples were coated with a 50 μm thick polyester film from DuPont (Melinex 401) without bubbles (water vapor permeability about 10 g / m ² d at 38 ° C./90% relative humidity).

The rockfall protection film K82200 comprises a polymer film of polycaprolactone-based polyurethane (thickness 200 μm) and a layer of an acrylate pressure-sensitive adhesive (thickness 60 μm).

As a comparative example with a polyurethane lacquer-based layer instead of a silane lacquer layer, the product K82205 from KPMF was used, likewise a polycaprolactone-based polymer film (thickness 200 μm) with a layer of an acrylate pressure-sensitive adhesive (thickness 60 μm). This product carries on the main surface opposite to the PSA of the polymer film, a polyurethane lacquer layer with a thickness of about 20 to 25 microns.

Table 2: Measurement results

In the sclerometer test, the patterns with more MF 201 matched the control, while those with higher levels of M 222 were slightly worse.

The gloss before the trickle test was in the range of the comparison sample, the abrasion resistance, however, was consistently on a much higher level, despite the reduced compared to the comparison pattern layer thickness, which was evident by the lower gloss loss. This confirmed the higher load capacity of the patterns with more EF 201 already indicated by the Sclerometer test.

Examples 5 to 7 show that even at paint thicknesses below 1 μm (0.1 to 0.2 μm), it is possible to produce outstandingly suitable surface protection films which in particular have a high flow resistance.

The yellowing resistance under the SoLiLa is also improved compared to the comparative sample, which underlines the good stability of the crosslinking by the silane-functional resins.

Marten hardness can be brought into the usual range by formulation variation. The tests show how the paints harden with increasing E 222 content.

The paints cure relatively slowly, but also the usual polyurethane paints reach their final hardness only after about 7 days. At room temperature, it took more than 24 hours, so part of the tests tried to accelerate the curing by temperature.

An acceleration of the crosslinking without a deterioration of the coating properties seems to be well possible, with a drying temperature between 60 ° C and 100 ° C appears meaningful for a drying time between 1 and 3 minutes, and is therefore preferred. The 100 ° C pattern (Example No. 6) even shows a particularly high abrasion resistance.

It is known to improve the surface smoothness of a lacquer layer by covering with a very smooth protective film (see above DE 10 2006 002 595 A1 ). It could be shown that the covering is possible both before the start of the curing reaction and after the start of the curing reaction. In both cases, despite the low water vapor permeability, the moisture curing of the silane-functional groups surprisingly continues and results in abrasion-resistant surface protection films. Since the cure proceeds more slowly with a little water vapor-permeable protective film, the paint surface has more time to flow onto the surface of the protective film and mold it. This can also be used for the production of structured surfaces. Therefore, it is advantageous to use a polymeric protective film with a water vapor permeability of less than 50 g / m ² d, in particular less than 20 g / m ² d. However, the use of a more water vapor-permeable polymeric protective film, preferably having a water vapor permeability of more than 50 g / m ² d, is advantageous for rapid curing.

Claims (15)

Composite foil comprising at least the following layers: a lacquer layer a polymer film layer and an adhesive layer, wherein the lacquer layer is bonded to a major surface of the polymer film layer and the adhesive layer is bonded to the opposite major surface of the polymer film layer such that the polymer film layer is sandwiched between the lacquer layer and the adhesive layer, characterized in that the lacquer layer is a silane lacquer layer comprising at least one at least partially crosslinked silane-functional resin, wherein the silane-functionalized resin is a polymer comprising at least one alkoxysilane group. Composite film according to claim 2, characterized in that the silane-functionalized resin is a polymer comprising at least two alkoxysilane groups. Composite film according to claim 1 or 2, characterized in that the polymers have a weight-average molecular weight of more than 500 g / mol. Composite film according to at least one of claims 1 to 3, characterized in that the alkoxy groups of the alkoxysilane groups are at least one group selected from unbranched or branched C ₁ -C ₁₀ alkoxy groups, in particular methoxy or ethoxy groups. Composite film according to at least one of claims 1 to 4, characterized in that the number of silane-functional groups in the resin at terminal functionalities between 1 and 6, preferably between 4 and 6, is. Composite film according to at least one of claims 1 to 5, characterized in that the resin at a temperature of 20 ° C has a viscosity of less than 10 Pas, preferably less than 1 Pas. Composite film according to at least one of claims 1 to 6, characterized in that the proportion of the silane-functional resin to the silane coating layer is 50 to 100 wt .-%, in particular 70 to 90 wt .-%. Composite film according to at least one of claims 1 to 7, characterized in that the silane coating layer contains not more than 1 wt .-%, preferably not more than 0.5 wt .-%, in particular not more than 500 ppm, water. Composite foil according to at least one of Claims 1 to 8, characterized in that the silane coating layer has a thickness of 0.05 to 100 μm, preferably of 0.05 to 10 μm, in particular of 1 to 5 μm. Composite film according to at least one of claims 1 to 9, characterized in that the polymer film layer is a film of a compound selected from the group consisting of polyvinyl chloride, polyethylene, copolymers of polyethylene, preferably ethylene-vinyl acetate, ethylane-acrylate, ethylene-methacrylate, fluoropolymers and polyurethanes, is. Composite film according to at least one of claims 1 to 10, characterized in that the polymer film is a thermoplastic polycaprolactone-based polyurethane. Composite foil according to one of claims 1 to 11, characterized in that the adhesive layer is a pressure-sensitive adhesive layer comprising at least one pressure-sensitive adhesive. Composite film according to at least one of claims 1 to 12, characterized in that at least one of the layers contains a colorant. Use of a composite film according to at least one of claims 1 to 13 as surface protection film. Use of a composite film according to at least one of claims 1 to 13 as a decorative film.