Application method for pressure sensitive adhesives

Abstract

The invention is directed to a method application of a pressure sensitive adhesive by extrusion means, wherein the pressure sensitive adhesive is dispensed under pressure through a nozzle into a bead or dot and wherein the temperature of the pressure sensitive adhesive in the nozzle is at or below 65 °C, preferably at or below 50 °C. The invention also relates to the use of the method in a display bonding, panel bonding, honeycomb parts bonding, automotive assembly, door and / or window assembly, battery assembly, or in a battery box assembly process.

Description

[0001] APPLICATION METHOD FOR PRESSURE SENSITIVE ADHESIVES

[0002] Technical field

[0003] The invention relates to a method for application of pressure sensitive adhesives and use of the method for bonding of substrates. Particularly, the invention relates to application of pressure sensitive adhesives that are not applied as a melt.

[0004] Background of the invention

[0005] Pressure sensitive adhesives (PSA) are viscoelastic materials, which adhere immediately to almost any kind of substrates by application of light pressure and which are permanently tacky. Commonly used pressure sensitive adhesives include adhesives based on acrylic polymers, styrene block copolymers, amorphous polyolefins (APO), amorphous poly- alpha-olefins (APAO), vinyl ether polymers, bitumen, and rubbers.

[0006] Pressure sensitive adhesives can be provided as a water-based or solvent-based solution, hot-melt adhesive, or as an adhesive syrup. Water- and solvent based adhesives are applied on a surface as a wet film, which is then dried by allowing the volatile components (water, organic solvent) to evaporate. Hot-melt adhesives must be heated above their melting point to obtain a melt, which is then applied on a surface and allowed to cool and solidify. Pressure sensitive adhesives can further be provided in form of liquid monomer mixtures (syrups), which are applied as a film and cured by polymerization of the monomers. The polymers contained in the cured adhesive film can further be crosslinked to improve the mechanical properties of the adhesive. The monomer mixture and / or the adhesive film can be chemically cured / crosslinked, for example, by using a thermally activated free radical initiator, such as a peroxide, or cured by radiation, such as actinic radiation or UV or visible light using a photoinitiator.

[0007] Pressure sensitive adhesives are used in various applications in the construction, automotive, and home appliance industries. Due to the permanent tackiness, pressure sensitive adhesive can be used for bonding of almost all types of materials, for example, glass, wood, metals, polymers, and ceramics. In the construction industry, sheet-like elements such as waterproofing, roofing, and flashing membranes, can be provided as self-adhering elements having a layer of pressure sensitive adhesive coated on a surface of the membrane. In the automotive industry, pressure sensitive adhesives are commonly used in assembly and laminating processes, where the adhesive is applied as a thin film to a surface of a substrate using known lamination techniques, such as slot die coating, roller coating, extrusion coating, calander coating, or spray coating means. In some cases, the adhesive is first coated to a transfer sheet, which is used for transferring the adhesive layer to a surface of another substrate, such as a carrier layer of an adhesive tape or selfadhering membrane. Transfer sheets are especially used for application of radiation curable adhesive compositions, where the curing reaction is inhibited in the presence of oxygen.

[0008] Commonly used coating techniques are suitable for applying the adhesives in form of films. The coating techniques are thus suitable for producing adhesive articles having relatively large surface areas, such as self-adhering waterproofing and roofing membranes or adhesive tapes that are provided in form of rolls. However, these techniques are not suitable for application of small amounts of adhesives, particularly in form of beads or dots. On the other hand, adhesive beads are commonly used for bonding of substrates, where the adhesive does not have to be applied to cover the whole surface of the substrate to obtain sufficient bond strength. Bead application of adhesives enables significant savings in material costs and also increases application speed compared to film coating applications. Pressure sensitive hot-melt adhesives can easily be applied by bead application (continuous), intermittent application, and dot application due the high viscosity of the adhesive composition. However, other types of pressure sensitive adhesives typically have a very low viscosity, which prevents their application by conventional extrusion means. Paste-like two-component adhesives can also be applied by extrusion, but they are typically chemically curable compositions that require a relatively long curing time to develop sufficient bonding properties.

[0009] There thus remains a need for a novel application method for pressure sensitive adhesives, which enables providing self-adhesive articles and bonding of substrates to each other without having to apply an adhesive composition to cover substantially the whole surface area of the substrate. Summary of the invention

[0010] The objective of the present invention is to provide an improved method for application of pressure sensitive adhesives, which method enables providing self-adhesive articles and bonding of substrates to each other without having to apply an adhesive composition to cover substantially the whole surface area of the substrate.

[0011] Surprisingly it has been found out that the objects can be achieved with the features of claim 1 .

[0012] Specifically, according to the invention, a method for application of a pressure sensitive by extrusion means is provided, wherein the pressure sensitive adhesive is dispensed, particularly extruded, under pressure through a nozzle into a bead or dot and wherein the temperature of the pressure sensitive in the nozzle is at or below 65 °C, particularly at or below 50 °C.

[0013] Since the temperature of the applied adhesive is relatively ow, the proposed method enables application of pressure sensitive adhesives to substrates composed of thermally sensitive materials. Furthermore, the applied adhesive can be immediately contacted with a surface of another substrate without having to wait for the adhesive to cool, which enables significant cost savings in an industrial application process.

[0014] Other aspects of the present invention are presented in other independent claims. Preferred aspects of the invention are presented in the dependent claims.

[0015] Detailed description of the invention

[0016] The subject of the present invention is a method for application of a pressure sensitive adhesive by extrusion means, wherein the pressure sensitive adhesive is dispensed, particularly extruded, under pressure through a nozzle into a bead or dot and wherein the temperature of the pressure sensitive in the nozzle is at or below 65 °C, preferably at or below 50 °C. The prefix “poly” in substance designations such as “polyol” or “polyisocyanate” refers to substances which in formal terms contain two or more per molecule of the functional group that occurs in their designation. A polyol, for example, is a compound having two or more hydroxyl groups, and a polyisocyanate is a compound having two or more isocyanate groups.

[0017] The term “polymer” refers to a collective of chemically uniform macromolecules produced by a polyreaction (polymerization, polyaddition, polycondensation) where the macromolecules differ with respect to their degree of polymerization, molecular weight, and chain length. The term also comprises derivatives of said collective of macromolecules resulting from polyreactions, that is, compounds which are obtained by reactions such as, for example, additions or substitutions, of functional groups in predetermined macromolecules and which may be chemically uniform or chemically non- uniform.

[0018] The term “copolymer” refers in the present disclosure to a polymer derived from more than one species of monomer (“structural unit”). The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained by copolymerization of two monomer species are known as bipolymers and those obtained from three and four monomer species are called terpolymers and quaterpolymers, respectively.

[0019] The term “oligomer” designates a compound built up through the linkage of a few monomers, for example dimers, trimers, tetramers and other polymeric materials. Term “polyisocyanate oligomer” can designate an individual oligomer or a mixture of oligomers of diisocyanates, wherein these oligomers can be built up of like or different diisocyanates.

[0020] An amine or an isocyanate is called “aliphatic” when its amine group or its isocyanate group, respectively, is directly bound to an aliphatic, cycloaliphatic, or arylaliphatic moiety. The corresponding functional group is therefore called an aliphatic amine or an aliphatic isocyanate group, respectively.

[0021] An amine or an isocyanate is called “aromatic” when its amine group or its isocyanate group, respectively, is directly bound to an aromatic moiety. The corresponding functional group is therefore called an aromatic amine or an aromatic isocyanate group, respectively. The term “molecular weight” refers to the molar mass (g / mol) of a molecule or a part of a molecule, also referred to as “moiety”. The term “average molecular weight” can refer to weight or number average molecular weight (Mn, Mw) of an oligomeric or polymeric mixture of molecules or moieties. The molecular weight can be determined by conventional methods, preferably by gel permeation-chromatography (GPC) using polystyrene as standard, preferably using styrene-divinylbenzene gel with porosity of 100 Angstrom, 1000 Angstrom and 10000 Angstrom as columns, and, depending on the molecule, tetrahydrofurane as a solvent, at 35 °C, or 1 ,2,4-trichlorobenzene as a solvent, at 160 °C.

[0022] The term “melting temperature” refers to a temperature at which a material undergoes transition from the solid to the liquid state. The melting temperature (Tm) is preferably determined by differential scanning calorimetry (DSC) according to ISO 11357-3 standard using a heating rate of 2 °C / min. The measurements can be performed with a Mettler Toledo DSC 3+ device and the Tm values can be determined from the measured DSC- curve with the help of the DSC-software. In case the measured DSC-curve shows several peak temperatures, the first peak temperature coming from the lower temperature side in the thermogram is taken as the melting temperature (Tm).

[0023] The term “glass transition temperature” (Tg) refers to the temperature above which temperature a polymer component becomes soft and pliable, and below which it becomes hard and glassy. The glass transition temperature is preferably determined by dynamical mechanical analysis (DMA) as the peak of the measured loss modulus (G”) curve using an applied frequency of 1 Hz and a strain level of 0.1 %.

[0024] The “amount or content of at least one component X” in a composition, for example “the amount of the at least one acrylic compound A” refers to the sum of the individual amounts of all acrylic compounds A contained in the composition. Furthermore, in case the composition comprises 20 wt.-% of at least one acrylic compound A, the sum of the amounts of all acrylic compounds A contained in the composition equals 20 wt.-%.

[0025] The term “pressure sensitive adhesive” refers in the present disclosure to viscoelastic materials, which adhere immediately to almost any kind of substrates by application of light pressure and which are permanently tacky. The tackiness of an adhesive layer can be measured, for example, as a loop tack. Preferably, the pressure sensitive adhesive has a loop tack adhesion to a glass plate measured at a temperature of 23 °C of at least 2.5 N / 25 mm, preferably at least 5 N / 25 mm, more preferably at least 10 N / 25 mm. The loop tack adhesion can be measured using a "FINAT test method no. 9” (FTM 9) as defined in FINAT Technical Handbook, 9th edition, published in 2014.

[0026] In the method, the pressure sensitive adhesive is dispensed, particularly extruded, under pressure through a nozzle into a bead or dot, preferably to a surface of a substrate.

[0027] The term “extrusion” or “extruding” means that the adhesive material is dispensed from a container through a nozzle by applying pressure. This may include, for example, a cartridge containing the adhesive material with a moveable piston that effects this pressure, or a barrel with a pump, for example a piston pump. It may also include other means of conveying the adhesive material through the nozzle.

[0028] In embodiments, the adhesive bead has width of not more than 50 mm, preferably not more than 40 mm, more preferably not more than 30 mm and / or a thickness of at least 5 mm, preferably at least 10 mm, more preferably at least 15 mm.

[0029] In the same or other embodiments, the adhesive bead has width of not more than 50 mm, preferably not more than 30 mm and / or a thickness of at least 0.05 mm, preferably at least 0.1 mm.

[0030] In this context, the term “width” refers to the dimension of the adhesive bead, which is measured along a plane that is coplanar with the surface of the substrate and in direction that is perpendicular to the longitudinal direction of the adhesive bead. Furthermore, the term “thickness” refers to the dimension of the adhesive bead measured in a direction that is perpendicular to the longitudinal direction of the adhesive bead and perpendicular to the width of the adhesive bead.

[0031] In other embodiments, the adhesive bead is applied by spraying in the form of small droplets, meaning the applied adhesive beads have widths of less than 2.5 mm, preferably less than 1 mm, in particular less than 0.5 mm and / or a thickness of at least 0.05 mm, preferably at least 0.1 mm.

[0032] The pressure sensitive adhesive may be dispensed under pressure through a nozzle from any type of container, such as a tube, cartridge, or a bulk container. The size of the container depends on the further details of the application, particular on the dimensions of substrate.

[0033] The pressure sensitive adhesive applied with the method is preferably not a hot-melt adhesive. The term “hot-melt adhesive” refers in the present disclosure to adhesives that are applied on a surface of a substrate as a melt and allowed to cool and solidify.

[0034] In exemplary embodiments, the pressure sensitive adhesive is liquid at 23 °C. It may further be preferred that the pressure sensitive adhesive has a melting temperature (Tm) determined by differential scanning calorimetry (DSC) according to ISO 11357-3:2018 standard using a heating rate of 2 °C / min of at or below 25 °C, preferably at or below 15 °C and / or a pour point determined according to ISO 3016:2019 standard of at or below 25 °C, preferably at or below 15 °C.

[0035] Furthermore, the pressure sensitive adhesive may be a thixotropic fluid at a temperature of 23 °C. The term “thixotropic fluid” refers in the present disclosure to a fluid which takes a finite time to attain equilibrium viscosity when introduced to a steep change in shear rate. Furthermore, the term "thixotropic" as used herein is also meant to cover pseudoplastic.

[0036] In examples, the pressure sensitive adhesive has a thixotropy index defined as ratio of viscosities measured at shear rates of 10 s-1and 1000 s-1at a temperature of 25 °C of 2 - 75, preferably 2 - 50, more preferably 2.5 - 45, even more preferably 2.5 - 40. The viscosities of the pressure sensitive adhesive at share rates of 10 s_1and 1000 s_1at 25 °C can be measured, for example, by using a MCR-302 rheometer (from Anton Paar).

[0037] Particularly, the pressure sensitive adhesive can be cured without application of thermal energy.

[0038] In preferred embodiments, the pressure sensitive adhesive is a syrup pressure sensitive adhesive, preferably an acrylic syrup pressure sensitive adhesive.

[0039] The term “adhesive syrup” refers in the present disclosure to adhesive compositions that are not provided as a dispersion and that have a viscosity at normal room temperature that allows their direct application to a substrate at standard conditions without heating of the adhesive. Syrup adhesives typically comprise a relatively large amount of a monomer mixture (monomer syrup), which is applied to a substrate followed by chemical curing of the monomers. The cured adhesive contains polymers derived from the monomers and the properties of the adhesive can further be improved by crosslinking.

[0040] In exemplary embodiments, the pressure sensitive adhesive is a radiation curable syrup pressure sensitive adhesive, especially an UV- or visible light- curable syrup pressure sensitive adhesive.

[0041] In further exemplary embodiments, the pressure sensitive adhesive is a radiation curable acrylic syrup pressure sensitive adhesive, especially an UV- or visible light- curable acrylic syrup pressure sensitive adhesive.

[0042] In other exemplary embodiments, the pressure sensitive adhesive is a radical curable syrup pressure sensitive adhesive, especially a radical- curable acrylic syrup pressure sensitive adhesive.

[0043] The term “acrylic adhesive” is understood to mean an adhesive comprising at least one acrylic compound.

[0044] The term “acrylic compound” refers in the present disclosure to compounds having at least one (meth)acryloyl group in the molecule. The term “(meth)acryloyl” designates methacryloyl or acryloyl. Accordingly, “(meth)acrylic” designates methacrylic or acrylic. A (meth)acryloyl group is also known as (meth)acryl group.

[0045] In exemplary embodiments, the pressure sensitive adhesive comprises: a) At least one acrylic compound A, b) A reaction product RP obtained by polyaddition reaction of at least one compound P and at least one hardener H, and c) At least one free radical initiator I.

[0046] Examples of suitable acrylic compounds A include acrylic monomers, such as (meth)acrylates, alkyl(meth)acrylates, di(meth)acrylates, and derivatives thereof, for example, amides and nitriles of (meth)acrylates. The term “monomer” refers in the present disclosure to single, discreet molecule which is capable of combining to form polymers. Further suitable acrylic compounds A include (meth)acryl-functional polymers, such as (meth)acrylate, polyurethane, polyether / polyoxyalkylene, and polyester polymers containing one or more (meth)acryl groups. The (meth)acryl groups of an (meth)acryl- functional polymer may be in pendant positions in the polymer chain or in terminal positions.

[0047] It may be preferred that the pressure sensitive adhesive comprises at least 35 wt.-%, more preferably at least 45 wt.-%, even more preferably at least 55 wt.-%, still more preferably at least 60 wt.-%, especially at least 65 wt.-% of the at least one acrylic compound A.

[0048] In exemplary embodiments, the pressure sensitive adhesive comprises 35 - 95 wt.-%, preferably 45 - 90 wt.-%, more preferably 50 -85 wt.-%, even more preferably 65 - 85 wt.- % of the at least one acrylic compound A.

[0049] In exemplary embodiments, the at least one acrylic compound A contains exactly one acryl group.

[0050] The at least one acrylic compound A may have a weight average molecular weight (Mw) of not more than 25000 g / mol, more preferably not more than 15000 g / mol, even more preferably not more than 10000 g / mol.

[0051] The at least one acrylic compound A may have a weight average molecular weight (Mw) in the range of 100 - 15000 g / mol, preferably 125 - 10000 g / mol, more preferably 125 - 7500 g / mol, even more preferably 125 - 5000 g / mol and / or a viscosity at 20 °C determined according to ISO 3219:1994 standard in the range of 5 - 25000 mPa s, preferably 50 - 20000 mPa s, more preferably 100- 15000 mPa s, even more preferably 250 - 15000 mPa s.

[0052] The at least one acrylic compound A can be a monofunctional compound or a polyfunctional compound containing other functional groups than (meth)acryl groups, such as hydroxyl groups, isocyanate groups, or amine groups. It may be, however, preferred that the polyaddition reaction of the at least one compound P with the at least one hardener H is conducted or at least initiated in the absence of acrylic compounds containing isocyanate groups or isocyanate-reactive groups. In exemplary embodiments, the at least one acrylic compound A comprises at least one first acrylic compound A1 that does not contain any other functional groups than (meth)acryl group(s). Generally, the expression “the at least one component X comprises at least one component XN”, such as “the at least one compound A comprises at least one first acrylic compound A1” is understood to mean in the context of the present disclosure that the adhesive comprises one or more acrylic compounds A1 that do not contain any other functional groups than (meth)acryl group(s) as representatives of the at least one acrylic compound A.

[0053] In alternatives, the at least one first acrylic compound A1 comprises at least 35 wt.-%, more preferably at least 50 wt.-%, even more preferably at least 65 wt.-%, still more preferably at least 75 wt.-%, of the total weight of the at least one acrylic compound A.

[0054] In exemplary embodiments, the at least one first acrylic compound A1 is an acrylic monomer of formula (I): where

[0055] Ri is hydrogen or a hydrocarbyl moiety; and

[0056] R2 is a hydrocarbyl moiety, optionally containing one or more heteroatoms.

[0057] In alternatives, Ri is hydrogen or methyl and R2 is a hydrocarbyl moiety selected from the group consisting of alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl, substituted aryl, aralkyl, alkaryl, allyl, and alkynyl groups, optionally containing one or more heteroatoms, particularly selected from the group consisting of nitrogen, oxygen, boron, silicon, sulfur, and phosphorus atoms.

[0058] Examples of suitable acrylic monomers of formula (I) include, for example, alkyl (meth)acrylates, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate, and their branched isomers, for example, isobutyl acrylate, 2-ethylhexyl acrylate, 2 -ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, and 3,5-dimethyladamantyl acrylate, glycol(meth)acrylate, 2-(2-ethoxyethoxy) ethyl acrylate, 2[2-(2- ethoxyhexyloxy)ethoxy] ethyl acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, alkoxylated lauryl acrylate, alkoxylated phenol acrylate, polyethylene glycol (PEG) (meth)acrylates, polypropylene glycol (PPG) (meth)acrylates, methoxy polyethylene glycol (MPEG) (meth)acrylates, and polyethylene glycol polypropylene glycol (PEG / PPG) copolymer or block copolymer (meth)acrylates.

[0059] Acrylic monomers that are known to polymerize to homopolymers having a low Tg, such as of below 0 °C, particularly below -10 °C, are particularly suitable for use in acrylic pressure sensitive adhesives. However, acrylic monomers that are known to yield homopolymers having a high Tgcan also be used in small amounts as comonomers, for example, to enhance certain adhesive properties, for example to reduce cold creep and increase shear resistance of the pressure sensitive adhesive. Acrylic monomers of formula (I) that are suitable for use as comonomers in relatively small amounts include, for example, isobornyl acrylate, isobornyl methacrylate, and 4-acryloylmorpholine.

[0060] In exemplary embodiments, acrylic monomers of formula (I) that polymerize to homopolymers having a Tgof at or above 0 °C, particularly at or above -10 °C make up not more than 50 wt.-%, preferably not more than 35 wt.-%, more preferably not more than 25 wt.-%, even more preferably not more than 15 wt.-%, of the total weight of the at least one first acrylic compound A1.

[0061] Particularly, the at least one acrylic monomer of formula (I) may be selected from the group consisting of ethylhexyl acrylate, butyl acrylate, and ethoxyethoxy ethyl acrylate, isooctyl acrylate, and propylheptyl acrylate.

[0062] In exemplary embodiments, the at least one acrylic compound A further comprises at least one second acrylic compound A2 containing other functional groups than (meth)acryl groups. In exemplary embodiments, the at least one second acrylic compound A2 is a difunctional compound containing one (meth)acryl group and one other functional group, preferably selected from the group consisting of hydroxyl, isocyanate, amine, silane, thiol, and carboxyl groups.

[0063] Suitable acrylic compounds for use as the second acrylic compound A2 include, for example, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, tert-butylaminoethyl (meth)methacrylate, HEMA phosphate (2-hydroxyethylmethacrylate acid phosphate), and (meth)acryl-functional silanes, such as 3-Trimethoxysilylpropyl-methacrylate.

[0064] In exemplary embodiments, the at least one second acrylic compound A2 makes up not more than 45 wt.-%, preferably not more than 35 wt.-%, more preferably not more than 25 wt.-%, such as 0.1 - 20 wt.-%, particularly 1 - 15 wt.-%, of the total weight of the at least one acrylic compound A.

[0065] The pressure sensitive adhesive further comprises as a second essential component a reaction product RP obtained by polyaddition reaction of at least one compound P and at least one hardener H. As used herein, the term “polyaddition reaction” refers to a reaction in which new bonds are formed by undergoing an addition reaction among functional groups of the compound having a functional group and the aforesaid reaction is successively repeated to form a polymer. Consequently, the at least one compound P contains first type of functional group(s) that react with second type of functional group(s) contained in the at least one hardener H in the polyaddition reaction.

[0066] Suitable first type of functional groups include, for example, isocyanate groups, epoxy groups, (meth)acryl groups, acid anhydride groups, and Michael acceptors. Suitable second type of functional groups include, for example, amine groups, hydroxyl groups, thiol groups, and Michael donors.

[0067] The reaction product RP comprises all reaction products that are produced in the reactions between the at least one compound P and the at least one hardener H, including any unconverted reactants. Particularly, if the polyaddition reaction is conducted in the presence of further compounds that are not reacted in the polyaddition reaction, these are not considered to form a part of the reaction product RP. It may be preferred that polyaddition reaction is conducted in a reaction mixture that contains at least a portion of the at least one acrylic compound A, particularly at least a portion of the at least one first acrylic compound A1, i.e. that the polyaddition reaction of the at least one compound P with the at least one hardener H is conducted in the presence of the at least one acrylic compound A, particularly in the presence of the at least one first acrylic compound A1. In this case the at least one compound P and / or the at least one hardener H are preferably first dissolved in at least a portion of the total amount of the at least one acrylic compound A, particularly in at least a portion of the total amount of the at least one first acrylic compound A1, which is then present in the reaction mixture as a solvent.

[0068] The polyaddition is preferably conducted such that the first type of functional groups of the at least one compound P in the reaction mixture are not in high stoichiometric excess over the second type of functional groups of the at least one hardener H, or vice versa. In case of a substantial stoichiometric excess of the first type of functional groups of the at least one compound P or the second type of functional groups of the at least one hardener H, the reaction product RP would contain unreacted compounds with first type of functional groups or unreacted compounds with second type of functional groups, respectively. Reaction products RP containing substantial amount of unreacted reactants are generally not preferred since they tend to decrease the viscosity of the pressure sensitive adhesive.

[0069] In exemplary embodiments, the polyaddition reaction between the at least one compound P and the at least one hardener H is conducted at a molar ratio of the first type of functional groups to the second type of functional groups of 0.5 - 1 .5, preferably 0.7 - 1 .2, more preferably 0.9 - 1 .1 , even more preferably 0.95 - 1 .05.

[0070] The polyaddition reaction between the at least one compound P and at least one hardener H can be conducted at a temperature in the range of 10 - 80 °C, preferably 15 - 70 °C, optionally in the presence of a catalyst.

[0071] In exemplary embodiments, the reaction product RP has:

[0072] - a weight average molecular weight (Mw) of at least 10000 g / mol, preferably at least 15000 g / mol, more preferably at least 25000 g / mol and / or

[0073] - a number average molecular weight (Mn) of at least 1000 g / mol, preferably at least 1500 g / mol, more preferably at least 2500 g / mol and / or

[0074] - a polydispersity index D of not more than 150, preferably not more than 125. The average molecular weights Mwand Mnof the reaction product RP are preferably determined by gel permeation-chromatography (GPC) using polystyrene as standard, preferably using styrene-divinylbenzene gel with porosity of 100 Angstrom, 1000 Angstrom and 10000 Angstrom as columns having dimensions of 0.8 x 30 cm, 5 pm, and tetrahydrofurane as a solvent using a flow of 1 mL / min at a temperature of 35 °C.

[0075] Preferably, pressure sensitive adhesive comprises not more than 75 wt.-%, more preferably not more than 65 wt.-%, even more preferably not more than 55 wt.-%, still more preferably not more than 50 wt.-% of the reaction product RP.

[0076] In exemplary embodiments, the pressure sensitive adhesive comprises 2.5 - 55 wt.-%, preferably 5 - 45 wt.-%, more preferably 5 - 40 wt.-%, even more preferably 5 - 35 wt.-%, still more preferably 7.5 - 35 wt.-%, particularly preferably 7.5 - 30 wt.-%, most preferably 10 - 30 wt.-% of the reaction product RP.

[0077] Particularly, the reaction product RP may have an isocyanate (NCO) content determined according to ISO 11909:2007 standard of not more than 5 wt.-%, preferably not more than 2.5 wt.-%, more preferably not more than 1 .5 wt.-%, even more preferably not more than 1 wt.-%, still more preferably not more than 0.5 wt.-%, especially not more than 0.15 wt.-%. The term “isocyanate content” as used herein is understood to mean the weight percentage of isocyanate groups to the total weight of the reaction product RP.

[0078] In exemplary embodiments, the reaction product RP is essentially free of isocyanate groups, i.e., the isocyanate content of the reaction product RP determined according to ISO 11909:2007 standard is less than 0.1 wt.-%, preferably less than 0.05 wt.-%, more preferably less than 0.01 wt.-%.

[0079] The at least one compound P may have a weight average molecular weight (Mw) of not more than 30000 g / mol, preferably not more than 25000 g / mol, more preferably not more than 15000 g / mol, even more preferably not more than 13500 g / mol.

[0080] Particularly, the at least one compound P may have: - a weight average molecular weight (Mw) in the range of 100 - 30000, preferably 100 - 25000 g / mol, more preferably 100 - 15000 g / mol, even more preferably 150 - 15000 g / mol, still more preferably 200 - 15000 g / mol, most more preferably 200 - 13500 g / mol and / or

[0081] - a viscosity at 20 °C determined according to ISO 3219:1994 standard in the range of 250

[0082] - 25000 mPa s, preferably 500 - 20000 mPa s, more preferably 1000 - 15000 mPa s, even more preferably 1500 - 15000 mPa s.

[0083] In exemplary embodiments, the at least one compound P contains isocyanate groups, i.e. the first type of functional groups of the at least one compound P are isocyanate groups and the at least one hardener contains isocyanate-reactive groups, i.e. the second type of functional groups of the at least one hardener H are isocyanate-reactive groups.

[0084] In exemplary embodiments, the polyaddition reaction between the at least one compound P and the at least one hardener H is conducted at a molar ratio of the isocyanate groups to the isocyanate-reactive groups of 0.5 - 1 .5, preferably 0.7 - 1 .2, more preferably 0.9 - 1 .1 , even more preferably 0.95 - 1 .05.

[0085] Suitable compounds containing isocyanate groups for use as the at least one compound P include, for example, polymers containing isocyanate groups (pre-polymers) and polyisocyanates, such as monomeric diisocyanates and oligomers, polymers, and derivatives of monomeric diisocyanates and mixtures thereof.

[0086] In exemplary embodiments, the at least one compound P has:

[0087] - an average isocyanate-functionality determined according to ISO 14896-2009 standard method A in the range of 0.1 - 2.7, preferably 0.2 - 2.2, more preferably 0.3 - 2.0, even more preferably 0.3 - 2.0 and / or

[0088] - an isocyanate content determined according to ISO 11909:2007 standard in the range of 0.3 - 35 wt.-%, preferably 1 .0 - 30 wt.-%, more preferably 1 .5 - 25 wt.-%, even more preferably 2.5 - 20 wt.-%.

[0089] In exemplary embodiments, the at least one compound P comprises at least one organic polymer P1 containing isocyanate groups and / or at least one polyisocyanate P2. The term “organic polymer” encompasses in the present disclosure a collective of macromolecules that are chemically homogeneous but differ in relation to degree of polymerization, molar mass, and chain length, which have a majority of carbon atoms in the polymer backbone, and reaction products of such a collective of macromolecules. The isocyanate groups of the organic polymer P1 may be in pendant positions in the polymer chain or in terminal positions and are bonded to the organic polymer via a carbon atom. Polymers having a polyorganosiloxane backbone (commonly referred to as “silicones”) are not organic polymers in the context of the present disclosure.

[0090] Examples of suitable organic polymers P1 include, for example, polyurethane, polyolefin, polyether, polyester, polycarbonate, polyamide, poly(meth)acrylate, polyurea, polyesterpolyurea, polyisocyanurate, and polycarbodiimide polymers containing isocyanate groups.

[0091] In exemplary embodiments, the at least one at least one organic polymer P1 has:

[0092] - a weight average molecular weight (Mw) in the range of 300 - 30000 g / mol, preferably 300 - 20000 g / mol, preferably 350 - 15000 g / mol, more preferably 450 - 15000 g / mol, even more preferably 500 - 13500 g / mol and / or

[0093] - a viscosity at 20 °C determined according to ISO 3219:1994 standard in the range of 250

[0094] - 25000 mPa s, preferably 500 - 20000 mPa s, more preferably 1000 - 15000 mPa s, even more preferably 1500 - 15000 mPa s.

[0095] Suitable compounds for use as the at least one polyisocyanate P2 include, for example, monomeric diisocyanates. A monomeric diisocyanate contains no urethane groups and dimers, trimers, oligomers, and polymerization products or adducts of diisocyanate monomers are not monomeric diisocyanates. Monomeric diisocyanates having a number average molecular weight (Mn) of not more than 1000 g / mol, preferably not more than 500 g / mol, more preferably not more than 350 g / mol, are especially suitable for use as the at least one polyisocyanate P2.

[0096] Suitable monomeric diisocyanates include aromatic and aliphatic monomeric diisocyanates, such as 4,4'-diphenylmethane diisocyanate, optionally with proportions of 2,4'- and / or 2,2'-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate or mixtures with 2,6-tolylene diisocyanate (TDI), 1 ,4-phenylene diisocyanate (PDI), naphthalene-1 ,5-diisocyanate (NDI), 1 ,6-hexane diisocyanate (HDI), 2,2(4),4-trimethyl-1 ,6- hexamethylendiisocyanate (TMDI), cyclohexane-1 , 3- or -1 , 4-diisocyanate, 1 -isocyanato- 3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate or IPDI), perhydro-2,4'- or -4,4'-diphenylmethandiisocyanate (HMDI), 1 ,3- or 1 ,4-bis(isocyanato- methyl) cyclohexane, m- or p-xylylene diisocyanate (XDI), m-tetramethylxylylene diisocyanate (TMXDI ), or mixtures thereof.

[0097] Further suitable compounds for use as the at least one polyisocyanate P2 include oligomers, polymers, and derivatives of monomeric diisocyanates containing isocyanurate, iminooxadiazindione, biuret, allophanate, carbodiimide, uretonimine or oxadiazine-trione groups and having an average isocyanate-functionality determined according to ISO 14896-2009 standard method A in the range of 1 .2 - 2.7, preferably 1 .5 - 2.5, more preferably 1.7 - 2.2, even more preferably 1.9 - 2.1.

[0098] In embodiments, the at least one organic polymer P1 containing isocyanate groups makes up at least 50 wt.-%, preferably at least 65 wt.-%, more preferably at least 75 wt.-%, even more preferably at least 85 wt.-% of the total weight of the at least one compound P.

[0099] In exemplary embodiments, the at least one organic polymer P1 is an isocyanate- functional polyurethane polymer.

[0100] The term “polyurethane polymer” refers in the present disclosure to polymers prepared by so called diisocyanate polyaddition process. Examples of particularly suitable polyurethane polymers include polyether polyurethanes and polyester polyurethanes. The terms “isocyanate-functional polyurethane polymer” and “polyurethane pre-polymer” can be used interchangeably.

[0101] The isocyanate-functional polyurethane polymer is preferably obtained by reacting at least one polyol PO with at least one polyisocyanate PI, wherein the isocyanate groups (NCO) are used in significant stoichiometric excess to hydroxyl groups (OH). The reaction can be carried out via known methods, with exclusion of moisture at a temperature of 20 - 160 °C, preferably 40 - 140 °C, optionally in the presence of suitable catalysts, with metered addition of the polyisocyanate in such a way that the isocyanate groups thereof are present in the specified stoichiometric excess in relation to the hydroxyl groups of the polyol. Particularly suitable polyols to be used as the at least one polyol PO include polyether polyols, polyester polyols, polycarbonate polyols, poly(meth)acrylate polyols, and hydrocarbon polyols, such as polybutadiene polyols, polyhydroxy functional fats and oils, and polyhydroxy functional acrylonitrilie / butadiene copolymers. Preferred polyether polyols PO are polyoxypropylene polyols and polyoxypropylene polyoxyethylene polyols, particularly the diols.

[0102] Suitable polyisocyanates PI for use with the at least one polyol PO to obtain isocyanate- functional polyurethane polymers include monomeric di- and tri-functional isocyanates, as well as oligomers, polymers, and derivatives of monomeric di-functional isocyanates, and mixtures thereof.

[0103] Suitable aromatic di- and tri-functional isocyanates include 2,4- and 2,6- toluylendiisocyanate and mixtures of its isomers (TDI), 4,4'-, 2,4'- and 2,2'- diphenylmethandiisocyanate and mixture of its isomers (MDI), 1 ,3- and 1 ,4- phenylendiisocyanate, 2,3,5,6-tetramethyle-1 ,4-diisocyanatobenzol, naphthaline-1 ,5- diisocyanate (NDI), 3,3'-dimethyl-4,4'-diisocyanatodiphenyl (TODI), dianisidindiisocyanate (DADI), 1 ,3,5tTris-(isocyanatomethyl)benzol, tris-(4-isocyanatophenyl)methane and tris-(4- isocyanatophenyl)thiophosphat.

[0104] Suitable aliphatic di- and tri-functional isocyanates include 1 ,4-tetramethylendiisocyanat, 2- methylpentamethylene-1 ,5-diisocyanate, 1 ,6-hexamethylendiisocyanate (HDI), 2,2,4- and 2 ,4, 4-trim ethy 1-1 ,6-hexa-methylendiisocyanate (TMDI), 1 , 10-decamethylendiisocyanate, 1 ,12-dodecame-thylendiisocyanat, lysin- and lysinesterdiisocyanate, cyclohexane-1 ,3- and -1 ,4-diisocyanate, 1-methyl-2,4- and -2,6-diisocyanatocyclohexane and mixtures of its isomers (HTDI or H6TDI), 1-isocyanato-3,3,5-trimethyl-5-iso-cyanatomethyl-cyclohexane (=isophorondiisocyanate or IPDI), perhydro-2,4‘- and -4,4‘-diphenylmethandiisocyanate (HMDI or H12MDI), 1 ,4-diisocyanato-2,2,6-trimethylcyclohexane (TMCDI), 1 ,3- and 1 ,4- Bis-(isocyanatomethyl)cyclo-hexane, m- and p-xylylendiisocyanate (m- and p-XDI), m- and p-tetramethyle-1 ,3- and -1 ,4-xylylendiisocyanate (m- and p-TMXDI), bis-(1-isocyanato- 1-methyl-ethyl)naphthaline, dimer- and trimer fatty acid isocyanate such as 3,6-bis-(9- isocya-natononyl)-4,5-di-(1-heptenyl)cyclohexen (dimeryldiisocyanat) and a, a, a ', a ', a ", a "-hexamethyl-1 ,3,5-mesitylentriisocyanate. Especially suitable oligomers, polymers, and derivatives of monomeric polyisocyanates include those based on MDI, TDI, HDI, and IPDI. Commercially available versions of these include, for example, HDI-Biurete such as Desmodur® N 100 and N 3200 (from Covestro), Tolonate® HDB and HDB-LV (from Rhodia) and Duranate® 24A-100 (from Asahi Kasei); HDI-lsocyanurate, such as Desmodur® N 3300, ultra N 3300, N 3600, ultra N 3600 and N 3790 BA (all from Covestro), Tolonate® HDT, HDT-LV and HDT-LV2 (from Rhodia), Duranate® TPA-100 and THA-100 (from Asahi Kasei) and Coronate® HX (von Nippon Polyurethane); HDI-Uretdione such as Desmodur® N 3400 (von Covestro); HDI- Iminooxadiazindione such as Desmodur® XP 2410 (von Covestro); HDI-Allophanate such as Desmodur® VP LS 2102 (from Covestro); IPDI-lsocyanurate, for example as a solution such as Desmodur® Z 4470 (from Covestro) or in solid form such as Vestanat® T1890 / 100 (from Evonik Degussa); TDI-Oligomers such as Desmodur® IL (from Covestro); as well as mixtures of isocyanurates based on TDI / HDI, for example Desmodur® HL (von Covestro). Furthermore suitable are at standard room temperature liquid forms of MDI (“modified MDI“), which are mixtures of MDI with MDI derivatives, such as MDI- carbodiimides or MDI-uretonimines or MDI-urethanes that are commercially available under the trade names of Desmodur® CD, Desmodur® PF, Desmodur® PC (all from Covestro) or Isonate® M 143 (from Dow Chemicals), as well as mixtures of MDI and MDI- homologen (polymers of MDI or PMDI), which are commercially available unter the trade name of Desmodur® VL, Desmodur® VL50, Desmodur® VL R10, Desmodur® VL R20, Desmodur® VH 20 N and Desmodur® VKS 20F (all from Covestro), Isonate® M 309, Voranate® M 229 and Voranate® M 580 (all from Dow Chemicals) or Lupranat® M 10 R (from BASF). The oligomeric polyisocyanates discussed above are typically mixtures of substances having different degrees of oligomerization / polymerization and / or chemical structures and have an average isocyanate functionality in the range of 2.1 - 4.0.

[0105] In exemplary embodiments, the at least one organic polymer P1 comprises at least one isocyanate-functional aliphatic polyurethane polymer P11, preferably obtained by reacting the at least one polyol PO with at least one aliphatic monomeric polyisocyanate ALPI. Suitable aliphatic monomeric polyisocyanates include the aliphatic di- and tri-functional isocyanates as discussed above.

[0106] Aliphatic isocyanate-functional polyurethane polymers may be preferred over aromatic ones since the latter have in some cases been found out to form a gelled polymer structure in polyaddition reactions with the at least one hardener H, particularly with hardeners H containing amine groups. Pressure sensitive adhesives having a gelled polymer structure are heterogeneous mixtures, which cannot be coated on a surface to form a homogeneous adhesive film having a constant thickness. However, it has also been found out that the tendency of the aromatic isocyanate-functional polyurethane polymers to form a gelled polymer structure in reactions with the at least one hardener H may significantly be reduced by using them in mixtures with aliphatic isocyanate-functional polyurethane polymers.

[0107] In exemplary embodiments, the at least one isocyanate-functional aliphatic polyurethane polymer P11 makes up at least 25 wt.-%, preferably at least 50 wt.-%, more preferably at least 75 wt.-%, even more preferably at least 80 wt.-%, of the total weight of the at least one organic polymer P1.

[0108] In exemplary embodiments, the at least one organic polymer P1 comprises the at least one aliphatic isocyanate-functional polyurethane polymer P11 and at least one aromatic isocyanate-functional polyurethane polymer P12, preferably obtained by reacting the at least one polyol PO with at least one aromatic monomeric polyisocyanate ARPI. Suitable aromatic monomeric polyisocyanates include the aromatic di- and tri-functional isocyanates as discussed above. In exemplary embodiments, the ratio of total weight of the at least one aliphatic isocyanate-functional polyurethane polymer P11 and the at least one aromatic isocyanate-functional polyurethane polymer P12 is from 10:1 to 1 :2, preferably from 6:1 to 1 :1 , more preferably from 5:1 to 1 :1 , even more preferably from 5:1 to 2:1.

[0109] In further exemplary embodiments, the at least one organic polymer P1 is an isocyanate- functional polyether urethane polymer, preferably obtained by the reaction of at least one polyether polyol PO1 with the at least one polyisocyanate PI. The term “polyether urethane polymer” refers to a polymer that contains ether groups as repeating units and also contains urethane groups.

[0110] The at least one polyether polyol PO1 may have:

[0111] - a number average molecular weight (Mn) in the range of 400 - 25000 g / mol, preferably 1500 - 20000 g / mol, more preferably 2000 - 10000 g / mol and / or - hydroxyl number in the range of 5 - 112 mg KOH / g, preferably 8 - 75 mg KOH / g, more preferably 10 - 56 mg KOH / g.

[0112] Particularly suitable polyether polyols PO1 include polyoxyalkylene diols and / or polyoxyalkylene triols, especially the polymerization products of ethylene oxide or 1 ,2- propylene oxide or 1 ,2- or 2,3-butylene oxide or oxetane or tetrahydrofuran or mixtures thereof, which can be polymerized with using a starter molecule having two or three active hydrogen, in particular one, such as water, ammonia or a compound with several OH or NH groups, such as 1 ,2-ethanediol, 1 ,2- or 1 ,3-propanediol, neopentyl glycol, diethylene glycol, triethylene glycol, the isomeric dipropylene glycols or tripropylene glycols, the isomeric butanediols, pentanediols, hexanediols, heptanediols, octanediols, nonanediols, decanediols, undecanediols, 1 ,3- or 1 ,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, 1 ,1 ,1 -trimethylolethane, 1 ,1 ,1 - trimethylolpropane, glycerol or aniline, or mixtures of the aforementioned compounds.

[0113] Polyoxypropylene diols and ethylene oxide-term inated polyoxypropylene diols are particularly preferred. These are polyoxyethylene-polyoxypropylene mixed polyols, which are obtained, for example, by further alkoxylating polyoxypropylene diols with ethylene oxide after the polypropoxylation reaction has ended and as a result ultimately having primary hydroxyl groups.

[0114] In exemplary embodiments, the at least one compound P further comprises at least one isocyanate-functional acrylic ester resin P3, preferably an aliphatic isocyanate-functional acrylic ester resin. Bi-functional reactants such as the resin P3 may be used to add acrylate functionality to the reaction product RP, which enables covalent linking of the in- situ formed high molecular weight polymers to the polyacrylate network formed during the final curing reaction of the pressure sensitive adhesive. This may improve the cohesion, reduce the cold creep, and improve the heat resistance of the adhesive composition.

[0115] In exemplary embodiments, the at least one isocyanate-functional acrylic ester resin P3 has:

[0116] - an average isocyanate-functionality determined according to ISO 14896-2009 standard method A in the range of 1 .2 - 2.7, preferably 1 .5 - 2.5, more preferably 1 .7 - 2.2, even more preferably 1 .9 - 2.1 and / or - an isocyanate (NCO) content determined according to ISO 11909:2007 standard in the range of 5 - 25 %, preferably 10 - 20 %.

[0117] Suitable isocyanate-functional acrylic ester resins can be obtained, for example, by reacting monohydric alcohols containing one or more (meth)acryloyl group(s) with suitable polyisocyanates, preferably diisocyanates. Suitable isocyanate-functional acrylic ester resins are commercially available, for example, under the trade name of Laromer® (from BASF) and under the trade name of Ebecryl® (from Allnex).

[0118] The reaction mixture comprises, in addition to the at least one compound P, at least one hardener H.

[0119] The at least one hardener H may have a molecular weight of not more than 7500 g / mol, more preferably not more than 5000 g / mol, even more preferably not more than 3500 g / mol, still more preferably not more than 2500 g / mol, most preferably not more than 1500 g / mol.

[0120] In exemplary embodiments, the at least one hardener H contains exactly two second type of functional groups. Particularly, the at least one hardener H may be a di-functional compound containing exactly two second type of functional groups.

[0121] In exemplary embodiments, the at least one hardener H contains isocyanate-reactive groups, i.e. the second type of functional groups of the at least one hardener H are isocyanate-reactive groups.

[0122] Suitable isocyanate-reactive groups include amine groups, hydroxyl groups, and thiol groups. In exemplary embodiments, the at least one hardener H contains exactly two isocyanate-reactive groups. Particularly, the at least one hardener H may be a difunctional compound containing exactly two isocyanate-reactive groups.

[0123] In exemplary embodiments, the at least one hardener H comprises at least one diamine H1 and / or at least one diol H2.

[0124] The at least one diamine H1 may be an aliphatic diamine, preferably having molecular weight of not more than 7500 g / mol, especially not more than 5000 g / mol, particularly not more than 3500 g / mol, for example not more than 2500 g / mol, especially not more than 1500 g / mol.

[0125] Suitable aliphatic diamines for use as at least one diamine H1 include, for example, the following commercially available amines:

[0126] - aliphatic, cycloaliphatic or arylaliphatic primary diamines, such as ethylenediamine, 1 ,2- propanediamine, 1 ,3-propanediamine, 2-methyl-1 ,2-propanediamine, 2,2-dimethyl-1 ,3- propanediamine, 1 ,3-butanediamine, 1 ,4-butanediamine, 1 ,3-pentanediamine (DAMP),

[0127] 1 ,5-pentanediamine, 1 ,5-diamino-2-methylpentane (MPMD), 2-butyl-2-ethyl-1 ,5- pentanediamine (C11 -neodiamine), 1 ,6-hexanediamine, 2,5-dimethyl-1 ,6-hexanediamine, 2,2,4- and 2,4,4-trimethylhexamethylenediamine (TMD), 1 ,7-heptanediamine, 1 ,8- octanediamine, 1 ,9-nonanediamine, 1 ,10-decanediamine, 1 ,11 -undecanediamine, 1 ,12- dodecanediamine, 1 ,2-, 1 ,3- and 1 ,4-diaminocyclohexane, 1 ,4-diamino-2,2,6- trimethylcyclohexane (TMCDA), bis-(4-aminocyclohexyl)-methane (H12-MDA), bis-(4- amino-3-methylcyclohexyl)-methane, bis-(4-amino-3-ethylcyclohexyl)-methane, bis-(4- amino-3,5-dimethylcyclohexyl)-methane, bis-(4-amino-3-ethyl-5-methylcyclohexyl)- methane (M-MECA), 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (= isophoronediamine or IPDA), 2- and 4-methyl-1 ,3-diaminocyclohexane and mixtures thereof, 1 ,3- and 1 ,4-bis-(aminomethyl)cyclohexane, 2,5-bis-(aminomethyl)- bicyclo[2.2.1]heptane (NBDA), 3,8-bis-(aminomethyl)-tricyclo[5.2.1.02,6]decane, 1 ,8- menthanediamine and 1 ,3- and 1 ,4-bis-(aminomethyl)benzene;

[0128] - ether group-containing aliphatic primary diamines, such as in particular bis-(2- aminoethyl) ether, 3,6-dioxaoctane-1 ,8-diamine, 4,7-dioxadecane-1 ,10-diamine, 4,7- dioxadecane-2,9-diamine, 4,9-dioxadodecane-1 ,12-diamine, 5,8-dioxadodecane-3,10- diamine, 4,7,10-trioxatridecane-1 ,13-diamine and higher oligomers of these diamines, 3,9- bis-(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, bis-(3- aminopropyl)polytetrahydrofuran and other polytetrahydrofuran diamines, Jeffamine® RFD-270 (from Huntsman), as well as polyoxyalkylene diamines (“polyether-diamines"). The latter are products from the amination of polyoxyalkylene diols and are available, for example, under the name of Jeffamine® (from Huntsman), under the name of Polyetheramine (from BASF) or under the name of PC Amine® (from Nitroil). Especially suitable polyoxyalkylene diamines are Jeffamine® D-205, Jeffamine® D-230, Jeffamine® D-400, Polyetheramine D 230, Polyetheramine D 400, PC Amine® DA 250 and PC Amine® DA 400. The at least one diol H2 may have a molecular weight of not more than 7500 g / mol, particularly not more than 5000 g / mol, especially not more than 3500 g / mol, such as not more than 2500 g / mol, for example not more than 1500 g / mol.

[0129] Suitable diols for use as the at least one diol H2 include, for example, ethylene glycol, 1 ,2- and 1 ,3-propanediol, 2,2-dimethyl-1 ,3-propanediol, 1 ,4-butanediol, 1 ,6-hexanediol, 2,2,4- trimethyl-1 ,6-hexanediol, 2, 4, 4-trimethyl-1 ,6-hexanediol, 1 ,7-heptanediol, 1 ,12- dodecanediol, 9,10-octadecene-1 ,12-diol, thiodiglycol, 1 ,18-octadecanediol, 2,4-dimethyl- 2-propyl-1 ,3-heptanediol, 1 ,4-butanediol, 1 ,4-butanediol, diethylene glycol, triethylene glycol, and tetraethylene glycol.

[0130] Hardeners with amine groups are generally preferred for use in the polyaddition reaction over those with hydroxyl groups since reaction products RP containing urea linkages instead of urethane linkages have been found out to enable an especially strong thickening effect in the pressure sensitive adhesive. Without being bound to any theory, it is believed that the viscosity increasing effect results from the inter- and intramolecular interactions of the urea moieties formed in isocyanate-amine reactions. The effect would then be significantly less pronounced when hardeners with hydroxyl groups are used since the reaction product RP then contains urethane instead of urea moieties.

[0131] In exemplary embodiments, the at least one diamine H1 makes up at least 50 wt.-%, preferably at least 65 wt.-%, more preferably at least 75 wt.-%, even more preferably at least 85 wt.-%, still more preferably at least 90 wt.-%, of the total weight of the at least one hardener H.

[0132] The at least one diamine H1 may be an aliphatic polyoxyalkylene diamine, preferably having a molecular weight in the range of 100 - 3500 g / mol, more preferably 150 - 2500 g / mol, even more preferably 200 - 1500 g / mol.

[0133] The pressure sensitive adhesive further comprises at least one free radical initiator I.

[0134] In exemplary embodiments, the pressure sensitive adhesive comprises 0.1 - 7.5 wt.-%, preferably 0.2 -5 wt.-%, more preferably 0.35 - 3 wt.-%, even more preferably 0.5 - 2.5 wt.-% of the at least one free radical initiator I. In exemplary embodiments, the at least one free radical initiator I is a photoinitiator.

[0135] Photoinitiators are compounds that create reactive species (free radicals, cations or anions) when exposed to radiation in the wavelength range of UV or visible light. Adhesive compositions containing an UV-radiation activatable photoinitiator are typically characterized as “UV-curable adhesives”. The term “curing” refers here to chemical reactions comprising forming of bonds resulting, for example, in chain extension and / or crosslinking of polymer chains.

[0136] Preferred type of the photoinitiator depends on the wavelength of the UV-radiation used for curing of the adhesive composition. Furthermore, it has been found out that films of adhesives containing high amounts of acrylic monomers and having a thickness of more than 100 pm may preferably be cured by using UV-A radiation having a wavelength in the range of 315 - 420 nm, particularly with UVA-1 radiation having a wavelength in the range of 340 - 400 nm .

[0137] In exemplary embodiments, the at least one free radical initiator I is a photoinitiator that can be activated with UV-A radiation and / or UV-radiation, especially with UVA-1 radiation.

[0138] Especially suitable photoinitiators showing absorption maximum in the UVA-1 wavelength range include so called Norrish type I initiators, which are all phosphine oxides as well as some Norrish type II initiators.

[0139] Particularly suitable Norrish type I photoinitiators include phospine oxides (PO), such as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), ethyl phenyl(2,4,6- trimethylbenzoyl) phosphinate (TPO-L), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (BAPO-1 ), 2- benzyl-2-(dimethylamino)-4-morpholino-butyrophenone (BDMB), phenyl-bis-(2,4,6- trimethylbenzoyl) phosphine oxide (BAPO-2), benzophenone dimethyl ketal (BDK), and benzil dimethyl ketal. These are commercially available, for example, under the trade name of Lucirin TPO (from IGM Resins), Genocure (from Rahn AG), Speedcure (from Lambson (part of Arkema), Irgacure (from IGM Resins), Songcure (from Songwon), Omnirad® (from IGM resins, and from Bodo Moller Chemie. Especially suitable Norrish type II photoinitiators include thiozanthones (TX), for example, 2-lsopropylthioxanthone (ITX), thioxanthone-anthracene (TX-A), 2,4-diethylthioxanthone (DETX), 2-Chlorothioxanthone (CTX), 2,4-Dimethylthioxanthone (RTX), 2,4- diisopropylthioxanthone (DITX), 1 -Chloro-4-propoxythioxanthone (CPTX), polymeric TXs such as polymeric CPTX, polyTHF-di(thioxanthone-2-oxyacetate), and polymeric TX and dl-camphorquinine 2,3-bornanedione (CQ). These are commercially available, for example, under the trade names of Genocure® (from Rahn GmbH), Omnirad® (from IGM resins), and SpeedCure® (from Lambson).

[0140] In exemplary embodiments, the at least one free radical initiator I is a photoinitiator that can be activated with IIV-A radiation, especially with UVA-1 radiation.

[0141] In exemplary embodiments, the at least one free radical initiator I is selected from the group consisting of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), ethyl phenyl(2,4,6-trimethylbenzoyl) phosphinate (TPO-L), phenylbis(2,4,6- trimethylbenzoyl)phosphine oxide (BAPO), bis-(2,6-dimethoxybenzoyl)-2,4,4- trimethylpentylphosphine oxide (BAPO-1 ), 2-benzyl-2-(dimethylamino)-4-morpholino- butyrophenone (BDMB), benzophenone dimethyl ketal (BDK), and benzil dimethyl ketal.

[0142] Furthermore, the photoinitiators may be used in combination with synergists / activators that are well known to skilled person. Preferred type of the synergist depends on the type of the photoinitiator, for example, the radical formation with Norrish type II initiators is known to require a hydrogen donor as a synergist. Examples of suitable synergists for the Norrish II initiators include, for example, amino benzoates, acrylated amines, and thiol compounds.

[0143] In other embodiments, free radical initiator I is a thermally activatable free radical initiator, preferably a peroxide, a hydroperoxide or a perester, most preferably dibenzoyl peroxide (DBPO). In these embodiments, the adhesive composition is preferably a two-part composition consisting of two separate components that are stored separately and only mixed immediately before or during application. In these embodiments the first component contains the adhesive composition itself as described above, while the second component contains at least the free radical initiator I.

[0144] In these embodiments, preferably the second component contains 5 to 60 wt.-%, preferably 10 to 40 wt.-%, most preferably 10 to 30 wt.-%, based on the total weight of the second component, of the at least one free radical initiator I, in particular the a thermally activatable free radical initiator, preferably a peroxide, a hydroperoxide or a perester, most preferably dibenzoyl peroxide (DBPO).

[0145] Preferred thermally activatable free radical initiator I especially include those which are still sufficiently stable at room temperature but form radicals at even slightly elevated temperature. Such free radical initiators include in particular a peroxide, a perester or a hydroperoxide. Organic peroxides are preferred. Dibenzoyl peroxide is most preferred.

[0146] Such thermally activatable free radical formers are, for example, commercially available as DBPO (CAS-No. 94-36-0) as Peroxan BP-Paste from Pergan.

[0147] In a preferred embodiment of this two-part adhesive composition embodiment comprising a thermally activatable free radical initiator I, the composition in the first component additionally contains 0.1 to 2.5 wt.-%, preferably 0.5 to 2 wt.-%, based on the total weight of the first component, of at least one catalyst, which acts as an activator for free-radical curing using thermally activatable free radical initiators I.

[0148] Such a catalyst is in particular a tertiary amine, in particular an aromatic amine, a transition metal salt or a transition metal complex. Examples of such suitable tertiary amines are N,N-dimethylaniline, N, N-diethylaniline, N,N-dimethyl-p-toluidine, N, N-diethyl-p-toluidine, N-methyl-N-hydroxyethyl-p-toluidine, N,N-b / s(2-hydroxyethyl)-p-toluidine and alkoxylated N,N-b / s(hydroxyethyl)-p-toluidines, N-ethoxylated p-toluidine, N-alkylmorpholine and mixtures thereof. Transition metal salts and transition metal complexes are for example salts and complexes of cobalt, nickel, copper, manganese or vanadium. Mixtures of such substances may also be used as activator catalyst.

[0149] Examples of tertiary amines is especially para-toluidine ethoxylate (CAS-No. 3077-12-1 ) which is available from GEO specialty chemicals under the trade name Bisomer® PTE.

[0150] The adhesive composition may additionally contain an inhibitor for free-radical curing, especially in embodiments where a two-part composition containing a thermally activatable free radical initiator I is prepared. In such embodiments it is preferable that the first component contains the inhibitor. Such an inhibitor is selected from substances which slightly retard or moderate the free-radical mechanisms of curing or inhibit undesired curing reactions (for example UV light- or atmospheric oxygen-induced mechanisms), thus leading to improved storage stability and / or a more controlled, more uniform curing.

[0151] Particularly preferred inhibitors are alkylated phenols, such as 2,6-di-tert-butyl-p-cresol (sold as Pergaslow PK-100 from Pergan), heterocyclic compounds such as (4-hydroxy- 2,2,6,6-tetramethylpiperidin-1 -yl)oxyl, commonly known as 4-Hydroxy TEMPO.

[0152] It is preferred in such embodiments when the first component contains between 0.001 wt.- % to 0.5 wt.-%, more preferably 0.01 wt.-% to 0.2 wt.-%, based on the total weight of the first component, of at least one inhibitor for free-radical curing.

[0153] In exemplary embodiments, the adhesive pressure sensitive adhesive further comprises: d) At least one crosslinking agent CA.

[0154] Particularly, the at least one crosslinking agent CA is different from the at least one acrylic compound A.

[0155] The at least one crosslinking agent CA may be a polyfunctional acrylic compound containing at least two (meth)acryl groups, particularly having molecular weight of not more than 5000 g / mol, especially not more than 3500 g / mol, such as not more than 1500 g / mol.

[0156] Suitable polyfunctional acrylic compounds include, for example, butanediol dimethacrylate, ethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate, triethyleneglycol dimethacrylate, trimethylolpropane trimethacrylate, butanediol diacrylate, hexanediol diacrylate, trimethylolpropane triacrylate, and tripropyleneglycol diacrylate, trimethylolpropane ethoxy triacrylate, trimethylolpropane triacrylate, tripropylene glycol diacrylate, propylene glycol dimethacrylate, dipropylene glycol diacrylate, dipentaerythritol hydroxy pentaacrylate, neopentyl glycol propoxylate diacrylate, bisphenol A ethoxylate dimethacrylate, alkoxylated hexanediol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated neopentyl glycol diacrylate, propoxylated glyceryl triacrylate, polybutadiene diacrylate, polybutadiene dimethacrylate, polyethylene glycol (PEG) di(meth)acrylates, polypropylene glycol (PPG) di(meth)acrylates, methoxy polyethylene glycol (MPEG) di(meth)acrylates, and polyethylene glycol polypropylene glycol (PEG / PPG) copolymer or block copolymer di(meth)acrylates, and polyurethane di(meth)acrylates.

[0157] In exemplary embodiments, the at least one crosslinking agent CA is a difunctional acrylic compound containing exactly two (meth)acryl groups, preferably having a molecular weight of not more than 3500 g / mol, more preferably not more than 2500 g / mol, still more preferably not more than 1500 g / mol, even more preferably not more than 1000 g / mol.

[0158] The pressure sensitive composition may comprise 0.01 - 5 wt.-%, preferably 0.05 - 3.5 wt.-%, more preferably 0.1 - 2.5 wt.-% of the at least one crosslinking agent CA.

[0159] In further exemplary embodiments, the pressure sensitive adhesive further comprises: e) At least one vinyl compound VC and / or f) At least one tackifying resin TR.

[0160] Particularly, the at least one vinyl compound VC is different from the at least one acrylic compound A. Suitable vinyl compounds include, for example, ethylenically unsaturated hydrocarbons with functional groups, vinyl esters, vinyl halides, vinylidene halides, nitriles of ethylenically unsaturated hydrocarbons, phosphoric acid esters, and zinc salts of (meth)acrylic acid.

[0161] Examples of especially suitable vinyl compounds include the ones comprising at least one polar functional group, preferably at least one carboxyl group and / or hydroxyl group. Vinyl compounds containing polar functional groups, such as acrylic acid, may act as adhesion promoters and / or as physical (non-covalent, ionic) crosslinking agents when present in the pressure sensitive adhesive.

[0162] Suitable vinyl compounds with polar functional groups for use as the at least one vinyl compound VC include, for example, acrylic acid, beta-acryloyloxypropionic acid, vinylacetic acid, fumaric acid, crotonic acid, aconitic acid, trichloroacrylic acid, and itaconic acid and hydroxyl group containing acrylic monomers, such as 2- hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl butyl(meth)acrylate, 2- hydroxy-hexyl(meth)acrylate, 6-hydroxy hexyl(meth) acrylate, 8- hydroxyoctyl(meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12- hydroxylauryl(meth)acrylate, and adducts of hydroxyethyl acrylate with succinic acid anhydride. It may be preferred that the at least one vinyl compound VC is not present in the reaction mixture but added to the pressure sensitive adhesive after the formation of the reaction product RP.

[0163] The pressure sensitive adhesive may further contain at least one tackifying resin TR.

[0164] The term “tackifying resin” designates in the present disclosure resins that in general enhance the adhesion and / or tackiness of an adhesive composition. The term “tackiness” designates in the present disclosure the property of a substance of being sticky or adhesive by simple contact. The tackiness can be measured, for example, as a loop tack. Preferred tackifying resins are tackifying at standard room temperature.

[0165] Examples of suitable tackifying resins to be used in the pressure sensitive adhesive include natural resins, synthetic resins and chemically modified natural resins.

[0166] Examples of suitable natural resins and chemically modified natural resins include rosins, rosin esters, phenolic modified rosin esters, and terpene resins. The term “rosin” is to be understood to include gum rosin, wood rosin, tall oil rosin, distilled rosin, and modified rosins, for example dimerized, hydrogenated, maleated and / or polymerized versions of any of these rosins.

[0167] Suitable commercially available rosin ester resins include, for example, Sylvatac® RAZ 100S, Sylvatac® RE 85, Sylvatac® RE 95, Sylvatac® RE 98, Sylvatac® RE 101 RM, and Sylvatac® RE 103S (all from Kraton); and Sylvalite® RE 80HP, Sylvalite® RE 85GB, Sylvalite® RE 88F, Sylvalite® RE 100F, Sylvalite® RE 100L, Sylvalite® RE 100S, Sylvalite® RE 105L, Sylvalite® RE 105 XL, Sylvalite®, Sylvalite® RE 110L, and Sylvalite® RE 115, and Sylvares® 1115 (all from Kraton).

[0168] Suitable terpene resins include copolymers and terpolymers of natural terpenes, such as styrene / terpene and alpha methyl styrene / terpene resins; polyterpene resins generally resulting from the polymerization of terpene hydrocarbons, such as the bicyclic monoterpene known as pinene, in the presence of Friedel-Crafts catalysts at moderately low temperatures; hydrogenated polyterpene resins; and phenolic modified terpene resins including hydrogenated derivatives thereof. Suitable commercially available terpene resins include, for example, Sylvares® TP 96, Sylvares® TP 115P, Sylvares® TP 300, Sylvares® TP 2019, Sylvares® TP 2040, Sylvares® TP 2040HM, Sylvares® TR 7115, Sylvares® TR 7125, Sylvares® TR B115, Sylvares® TR M1115, and Sylvares® ZT 106LT (all from Kraton).

[0169] The term “synthetic resin” refers to compounds obtained from the controlled chemical reactions such as polyaddition or polycondensation between well-defined reactants that do not themselves have the characteristic of resins. Monomers that may be polymerized to synthesize the synthetic resins may include aliphatic monomer, cycloaliphatic monomer, aromatic monomer, or mixtures thereof. Aliphatic monomers can include C4, Cs, and Ce paraffins, olefins, and conjugated diolefins. Examples of aliphatic monomer or cycloaliphatic monomer include butadiene, isobutylene, 1 ,3-pentadiene, 1 ,4-pentadiene, cyclopentane, 1 -pentene, 2-pentene, 2- methyl-1 -pentene, 2-methyl-2-butene, 2-methyl-2- pentene, isoprene, cyclohexane, 1 ,3-hexadiene, 1 -4-hexadiene, cyclopentadiene, dicyclopentadiene, and terpenes. Aromatic monomer can include Cs, C9, and C10 aromatic monomer. Examples of aromatic monomer include styrene, indene, derivatives of styrene, derivatives of indene, coumarone and combinations thereof.

[0170] Suitable synthetic resins include synthetic hydrocarbon resins made by polymerizing mixtures of unsaturated monomers that are obtained as by-products of cracking of natural gas liquids, gas oil, or petroleum naphthas. Synthetic hydrocarbon resins obtained from petroleum -based feedstocks are referred in the present disclosure as “hydrocarbon resins” or “petroleum hydrocarbon resins”. These include also pure monomer aromatic resins, which are made by polymerizing aromatic monomer feedstocks that have been purified to eliminate color causing contaminants and to precisely control the composition of the product. Hydrocarbon resins typically have a relatively low average molecular weight (Mn), such in the range of 250 - 5000 g / mol and a glass transition temperature, determined by dynamical mechanical analysis (DMA) as the peak of the measured loss modulus (G”) curve using an applied frequency of 1 Hz and a strain level of 0.1 %, of above 0 °C, preferably equal to or higher than 15 °C, more preferably equal to or higher than 30 °C.

[0171] Examples of suitable hydrocarbon resins include C5 aliphatic hydrocarbon resins, mixed C5 / C9 aliphatic / aromatic hydrocarbon resins, aromatic modified C5 aliphatic hydrocarbon resins, cycloaliphatic hydrocarbon resins, mixed C5 aliphatic / cycloaliphatic hydrocarbon resins, mixed C9 aromatic / cycloaliphatic hydrocarbon resins, mixed C5 aliphatic / cycloaliphatic / C9 aromatic hydrocarbon resins, aromatic modified cycloaliphatic hydrocarbon resins, C9 aromatic hydrocarbon resins, polyterpene resins, and copolymers and terpolymers of natural terpenes as well hydrogenated versions of the aforementioned hydrocarbon resins. The notations "C5" and "C9" indicate that the monomers from which the resins are made are predominantly hydrocarbons having 4-6 and 8-10 carbon atoms, respectively. The term “hydrogenated” includes fully, substantially and at least partially hydrogenated resins. Partially hydrogenated resins may have a hydrogenation level, for example, of 50 %, 70 %, or 90 %.

[0172] Suitable hydrocarbon resins are commercially available, for example, under the trade name of Wingtack® series, Wingtack® Plus, Wingtack® Extra, and Wingtack® STS (all from Cray Valley); under the trade name of Escorez® 1000 series, Escorez® 2000 series, and Escorez® 5000 series (all from Exxon Mobile Chemical); under the trade name of Novares® T series, Novares® TT series, Novares® TD series, Novares® TL series, Novares® TN series, Novares® TK series, and Novares® TV series (all from Rain Carbon Inc); under the trade name of Kristalex®, Plastolyn®, Piccotex®, Piccolastic® and Endex® (all from Eastman Chemicals), and Regalrez® 1000, 3000, and 6000 series (from Synthomer).

[0173] In exemplary embodiments, the at least one tackifying resin TR is selected from the group consisting of rosins, rosin ester resins, phenolic modified rosin ester resins, and terpene resins.

[0174] The pressure sensitive adhesive may comprise at least 0.5 wt.-%, preferably at least 2.5 wt.-%, such as 0.5 - 35 wt.-%, preferably 1 .5 - 30 wt.%, more preferably 5 - 25 wt.-% of the at least one tackifying resin TR.

[0175] The pressure sensitive adhesive may further comprise one or more additional constituents including, for example, waxes and plasticizers as well as one or more additives such as, for example, flame retardants, wetting agents, optical brighteners, pigments, dyes, and desiccants. Preferably, the amount of such additional constituents and additives makes up not more than 20 wt.-%, more preferably not more than 15 wt.-%, even more preferably not more than 10 wt.-%, of the total weight of the adhesive. The pressure sensitive adhesive is preferably a one-part adhesive composition. The term “one-part adhesive composition” refers in the present disclosure to an adhesive composition, which is contained in a single container, preferably a moisture-tight container, and which composition has a certain storage stability. The term “storage stability” refers to the ability of a composition to be stored at room temperature in a suitable container under exclusion of moisture for a certain time interval, in particular several months, without undergoing significant changes in application or end-use properties.

[0176] The preferences given above for the acrylic compound A, compound P, hardener H, free radical initiator I, crosslinking agent CA, vinyl compound VC, and to the tackifying resin TR apply equally to all other aspects of the present invention unless specified otherwise.

[0177] The pressure sensitive adhesive may be prepared by using a method comprising steps of: i) Providing a mixture comprising:

[0178] - At least one first acrylic compound A1 ,

[0179] - At least one compound P, and

[0180] - At least one hardener H, and ii) Conducting polyaddition reaction between the at least one compound P and the at least one hardener H to obtain a mixture containing a reaction product RP.

[0181] The mixture provided in step i) may be obtained by mixing a first portion of the at least one first acrylic compound A1 with the at least one compound P and a second portion with the at least one hardener H followed by combining of the thus obtained pre-mixtures.

[0182] Alternatively, the at least one first acrylic compound A1, the at least one compound P, and the at least one hardener H may be mixed with each other in one step.

[0183] In exemplary embodiments, the at least one first acrylic compound A1 makes up at least 50 wt.-%, preferably at least 55 wt.-%, more preferably at least 60 wt.-%, even more preferably at least 65 wt.-%, still more preferably at least 70 wt.-% of the total weight of the mixture provided in step i). Particularly, the mixture provided in step i) may comprise 50 - 95 wt.-%, preferably 55 - 92.5 wt.-%, more preferably 60 - 90 wt.-%, even more preferably 65 - 90 wt.-%, still more preferably 70 - 90 wt.-% of the at least one first acrylic compound A1.

[0184] In exemplary embodiments, the viscosity of the mixture obtained from step ii) measured at 20 °C and determined according to ISO 3219:1994 standard by using a cone / plate rheometer using a shear rate of 1 / 100 s is at least 1 .5 times, preferably at least 2 times, more preferably at least 5 times, even more preferably at least 10 times, as high as the viscosity of the mixture provided in step i) measured at 20 °C and determined according to ISO 3219:1994 standard by using a cone / plate rheometer using a shear rate of 1 / 100 s.

[0185] Particularly, the mixture obtained from step ii) may be a thixotropic fluid at a temperature of 23 °C.

[0186] The at least one compound P preferably contains first type of functional groups that react with second type of functional groups contained in the at least one hardener H in the polyaddition reaction.

[0187] The molar ratio of the first type of functional groups to the second type of functional groups in the mixture provided in step i) may be in the range of 0.5 - 1 .5, preferably 0.7 - 1.2, more preferably 0.9 - 1 .1 , even more preferably 0.95 - 1 .05. The polyaddition reaction between the at least one compound P and at least one hardener H may be conducted at a temperature in the range of 10 - 80 °C, preferably 15 - 70 °C, optionally in the presence of a catalyst.

[0188] In exemplary embodiments, the at least one compound P contains isocyanate groups, i.e. the first type of functional groups of the at least one compound P are isocyanate groups and the at least one hardener contains isocyanate-reactive groups, i.e. the second type of functional groups of the at least one hardener H are isocyanate-reactive groups.

[0189] The molar ratio of the isocyanate groups to the isocyanate-reactive groups in the mixture provided in step i) may be in the range of 0.5 - 1 .5, preferably 0.7 - 1 .2, more preferably 0.9 - 1.1 , even more preferably 0.95 - 1.05. Alternatives and preferred embodiments of the at least one first acrylic compound A1, the at least one compound P, the at least one hardener H, and the reaction product RP have already been discussed above.

[0190] The method for preparing the pressure sensitive adhesive may comprise a further step of adding:

[0191] - At least one free radical initiator I and

[0192] - At least one second acrylic compound A2 and / or

[0193] - At least one crosslinking agent CA and / or

[0194] - At least one vinyl compound VC and / or

[0195] - At least one tackifying resin TR, to the mixture provided in step i) and / or to the mixture obtained from step ii).

[0196] Alternatives and preferred embodiments for the at least one free radical initiator I, the at least one second acrylic compound A2, the at least one crosslinking agent CA, the at least one vinyl compound VC, and the at least one tackifying resin TR, have already been discussed above.

[0197] In exemplary embodiments, the method for preparing the pressure sensitive adhesive comprises a step of adding the at least one free radical initiator I and the at least one crosslinking agent CA to the mixture provided in step i) and / or to the mixture obtained from step ii), preferably to the mixture obtained from step ii).

[0198] Furthermore, the at least one second acrylic compound A2, the at least one vinyl compound VC, and the at least one tackifying resin TR, if used, are preferably added to the mixture obtained from step ii).

[0199] Another aspect of the present invention is use of the method for application of a pressure sensitive adhesive in a display bonding, panel bonding, honeycomb parts bonding, automotive vehicle assembly, for example truck assembly and trailer and caravan assembly, door and / or window assembly, battery assembly, or in a battery box assembly process. In these uses the pressure sensitive adhesive may be applied on a surface of a first substrate followed by contacting the applied adhesive with a surface of the second substrate to form an adhesive bond between the first and second substrates.

[0200] The first and second substrates can be composed of any conventional material including polymeric material, metal, painted metal, glass, mineral material, for example silicate minerals such as mica (Muscovite), wood, wood derived materials such as natural fiber polypropylene (NFPP), and fiber materials. Suitable polymeric materials include, for example, polyethylene (PE), in particular high density polyethylene (HDPE), polypropylene (PP), glass-fiber reinforced polypropylene (GFPP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polycarbonate (PC), polymethylmethacrylate (PMMA), acrylonitrile butadiene styrene (ABS), polyamide (PA), polyurethane, and combinations thereof.

[0201] The choice of materials for the first and second substrates depends on the embodiment of the use.

[0202] For example, in case of a battery assembly or battery box assembly process, the first and / or second substrate may comprise stainless steel, electro-plated steel, aluminum, aluminum alloy, especially electro nickel-plated steel or aluminum 3003 alloy, or a mineral material, particularly a silicate mineral, such as mica. These types of materials are commonly used in car battery shells, which are designed to carry and protect battery modules, especially battery modules of electric vehicles.

[0203] Still another aspect of the present invention is a method for bonding of substrates, comprising steps of:

[0204] I) Providing a first substrate and using the method according to claims 1 -13 to apply a pressure sensitive adhesive to a surface of the first substrate,

[0205] II) Subjecting the applied adhesive to radiation, preferably UV- or visible light radiation thereby to effect at least partial curing of the adhesive and contacting the at least partially cured adhesive with a surface of a second substrate or

[0206] II’) Contacting applied adhesive with a surface of a second substrate and subjecting the applied adhesive to radiation, preferably UV- or visible light radiation thereby to effect at least partial curing of the adhesive. In exemplary embodiments, the method comprises a further step of applying sufficient pressure to the second substrate to effect adhesive bonding between the first and second substrates.

[0207] It may further be preferred that the step of subjecting the applied adhesive to radiation is conducted in an environment with reduced oxygen. For example, the radiation curing step may be conducted in nitrogen atmosphere or the adhesive layer, especially in step II), may be covered with a transparent film that prevents the diffusion of oxygen to the adhesive layer during the radiation curing step.

[0208] In exemplary embodiments, in step II) of the method, the applied adhesive is subjected to UV-radiation, preferably to IIV-A radiation characterized by a wavelength of 315 - 420 nm, more preferably to UVA-1 radiation characterized by a wavelength of 340 - 400 nm.

Claims

Claims1 . Method application of a pressure sensitive adhesive by extrusion means, wherein the pressure sensitive adhesive is dispensed under pressure through a nozzle into a bead or dot and wherein the temperature of the pressure sensitive adhesive in the nozzle is at or below 65 °C, preferably at or below 50 °C.

2. Method according to claim 1 , wherein the adhesive bead has width of not more than 50 mm, preferably not more than 30 mm and / or a thickness of at least 0.05 mm, preferably at least 0.1 mm.

3. Method according to claim 1 or 2, wherein the pressure sensitive adhesive is dispensed from a tube, cartridge, or a bulk container.

4. Method according to any one of previous claims, wherein the pressure sensitive adhesive is not a hot-melt-adhesive.

5. Method according to any one of previous claims, wherein the pressure sensitive adhesive is a thixotropic fluid at a temperature of 23 °C.

6. Method according to any one of previous claims, wherein the pressure sensitive adhesive has a thixotropy index defined as ratio of viscosities measured at shear rates of 10 s-1and 1000 s-1at a temperature of 25 °C of 2 - 75, preferably 2 - 50.

7. Method according to any one of previous claims, wherein the pressure sensitive adhesive can be cured without application of thermal energy.

8. Method according to any one of previous claims, wherein the pressure sensitive adhesive is a syrup pressure sensitive adhesive, preferably an acrylic syrup pressure sensitive adhesive.

9. Method according to any one of previous claims, wherein the pressure sensitive adhesive is a radiation curable acrylic syrup pressure sensitive adhesive, preferably an UV- or visible light- curable acrylic syrup pressure sensitive adhesive.

10. Method according to any one of previous claims, wherein the pressure sensitive adhesive comprises: a) At least one acrylic compound A, b) A reaction product RP obtained by polyaddition reaction of at least one compound P and at least one hardener H, and c) At least one free radical initiator I.11 . Method according to claim 10, wherein the at least one compound P contains first type of functional group(s) that react with second type of functional group(s) contained in the at least one hardener H in a polyaddition reaction and wherein the polyaddition reaction between the at least one compound P and the at least one hardener H is conducted at a molar ratio of the first type of functional group(s) to the second type of functional group(s) of 0.5 - 1 .5, preferably 0.7 - 1.2.

12. Method according to claim 10 or 11 , wherein the reaction product RP has a weight average molecular weight (Mw) determined by gel permeationchromatography using polystyrene as standard of at least 10000 g / mol, preferably at least 15000 g / mol.

13. Use of the method according to any one of previous claims in a display bonding, panel bonding, honeycomb parts bonding, automotive assembly, door and / or window assembly, battery assembly, or in a battery box assembly process.

14. Method for bonding of substrates, comprising steps of:I) Providing a first substrate and using the method according to claims 1 -12 to apply a pressure sensitive adhesive to a surface of the first substrate,II) Subjecting the applied adhesive to radiation, preferably UV- or visible light radiation thereby to effect at least partial curing of the adhesive and contacting the at least partially cured adhesive with a surface of a second substrate or II’) Contacting applied adhesive with a surface of a second substrate and subjecting the applied adhesive to radiation, preferably UV- or visible light radiation thereby to effect at least partial curing of the adhesive.

15. Method according to claim 14, wherein the applied adhesive is subjected to UV radiation, preferably to IIV-A radiation characterized by a wavelength of 315 - 420 nm.

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