Sedimentation-stable a-component for a thermally conductive two-component (2C) PU adhesive

Abstract

The present invention is directed to an adhesive composition comprising a first component (A) and a second component (B) comprising at least one polyisocyanate, wherein component (A) comprises a first polyol (P1); a second polyol (P2); at least one thermally conductive filler (F1); and wherein component (A) has a melting point Tm in the range of from 20°C to 30°C, determined using DSC according to DIN EN ISO 11357-1. Furthermore, the present invention is directed to a cured adhesive composition obtainable by curing said adhesive composition and a process for preparing an article comprising at least two bonded substrates, the process comprising applying the adhesive composition of the present invention. The present invention is also directed to the use of an adhesive composition according to the present invention in pipes, preferably cooling coils; in electronic components, preferably light emitting devices, computer devices, mobile phones, tablets, touch screens, automotive technology, hifi systems, and audio systems; in joints between heat pipes and water tanks in solar heated heating; in fuel cell and wind turbines; in the manufacture of computer chips; in light devices; batteries; in housings; in coolers; heat exchanging devices; wires; cables; heating wires; household appliances such as refrigerators and dishwashers; air conditionings; accumulators; transformers; lasers; functional clothing; car seats; medical devices; fire protection; electric motors; cars; batteries for cars; emobility; electric vehicles; planes and trains.

Description

[0001] 240581W001

[0002] Sedimentation-stable A-component for a thermally conductive two-component (2c) PU adhesive

[0003] The present invention is directed to an adhesive composition comprising a first component (A) and a second component (B) comprising at least one polyisocyanate, wherein component (A) comprises a first polyol (P1); a second polyol (P2); at least one thermally conductive filler (F1); and wherein component (A) has a melting point Tm in the range of from 20°C to 30°C, determined using differential scanning calorimetry (DSC) according to DIN EN ISO 11357-1. Furthermore, the present invention is directed to a cured adhesive composition obtainable by curing said adhesive composition and a process for preparing an article comprising at least two bonded substrates, the process comprising applying the adhesive composition of the present invention. The present invention is also directed to the use of an adhesive composition according to the present invention in pipes, preferably cooling coils; in electronic components, preferably light emitting devices, computer devices, mobile phones, tablets, touch screens, automotive technology, hifi systems, and audio systems; in joints between heat pipes and water tanks in solar heated heating; in fuel cell and wind turbines; in the manufacture of computer chips; in light devices; batteries; in housings; in coolers; heat exchanging devices; wires; cables; heating wires; household appliances such as refrigerators and dishwashers; air conditionings; accumulators; transformers; lasers; functional clothing; car seats; medical devices; fire protection; electric motors; cars; batteries for cars; emobility; electric vehicles; planes and trains.

[0004] Polyurethanes (PU) with high content of fillers are known for different applications. These highly filled systems are very challenging because they tend to sediment due to the different densities of the components. The sedimentation stability of a highly filled A-component is an important factor in the production of two-component (2c) PU adhesives. If the A-component is unstable and sediments form, this can lead to an uneven distribution of fillers in the adhesive. This can, in turn, result in poorer (fluctuating) adhesive performance and reduced durability. Therefore, good sedimentation stability of the A-component is crucial for the quality of the 2c PU adhesive.

[0005] Anti-settling additives and rheology additives for filled systems are well-known in the field. Furthermore, thickeners are also commonly used additives. Examples of thickeners include associative thickeners like polyurethane thickeners, acrylic thickeners, cellulose ethers, chemically modified cellulose derivatives (such as hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl methylcellulose, methylcellulose, hydroxypropyl cellulose, ethylhydroxyethyl cellulose, and others), hydrophobic modified polyether, gums, saccharides, polysaccharides, and polyvinyl alcohol. It is important to note that while these variants increase the viscosity of pastes, they can also have negative effects on processing properties, pumpability, and equipment abrasion, such as at the nozzles of a pumping system. Furthermore, according to the state of the art, the aforementioned additives / fi Ilers do not serve any additional purpose and weaken the PU matrix by diluting it, resulting in mechanical and processing properties that are inferior to those of an unmodified system.

[0006] EP3670558 discloses a two-component urethane-based composition comprising an ester-based polyol resin-containing main composition part; a polyisocyanate-containing curing agent composition part; and a filler, wherein the ester-240581W001

[0007] -2 -based polyol is an amorphous polyol, of which a crystallization temperature (Tc) and a melting temperature (Tm) are not observed in a DSC (differential scanning calorimetry) analysis as measured according to the description, or the ester-based polyol is a sufficiently low crystalline polyol having a melting temperature (Tm) of less than 15°C as measured according to the description, and wherein the polyisocyanate is a non-aromatic polyisocyanate. Esterbased polyols that are amorphous or have a low melting temperature (Tm) below 15°C exhibit several disadvantages compared to polyether polyols. These ester-based polyols tend to become unstable at elevated temperatures, starting to lose their mechanical properties and undergo degradation at temperatures between 60°C and 90°C. Additionally, they are more susceptible to hydrolysis, particularly in humid environments (and especially in the climate change test), which can significantly reduce their lifespan. Furthermore, ester-based polyols are prone to oxidative degradation at high temperatures, leading to alterations in their chemical structure and mechanical performance. In contrast, polyether polyols generally possess better thermal stability, resisting significant property changes up to 100°C to 120°C.

[0008] It was an object of the present invention to provide adhesive compositions for the preparation of highly filled PU systems with stable components.

[0009] This object has been achieved by an adhesive composition comprising a first component (A) and a second component (B) comprising at least one polyisocyanate, wherein component (A) comprises a first polyol (P 1 ); a second polyol (P2); at least one thermally conductive filler (F1); and wherein component (A) has a melting point Tm in the range of from 20°C to 30°C, determined using DSC according to DIN EN ISO 11357-1.

[0010] It has surprisingly been found that the choice of polyol (P 1 ) and (P2) according to the present invention allows to prepare an A-component for the production of 2c PU adhesives which solidify at room temperature and become liquid and pumpable again at the processing temperature. Thus, the sedimentation of fillers in the A-component can be effectively prevented. In addition, the solidified blends can be stored for a significantly longer time without separating. This leads to higher product quality and durability of the 2c PU adhesive.

[0011] According to the present invention, component (A) comprises a first polyol (P1); a second polyol (P2); at least one thermally conductive filler (F1); and has a melting point Tm in the range of from 20°C to 30°C, determined using DSC according to DIN EN ISO 11357-1.

[0012] The melting point Tm of the component (A) is in the range of from 20°C to 30°C, determined using DSC according to DIN EN ISO 11357-1. Preferably, the melting point Tm of the component (A) is in the range of from 20°C to 25°C, determined using DSC according to DIN EN ISO 11357-1. According to the present invention, the polyols used and the amounts of polyols, in particular polyol (P1) and polyol (P2), are adjusted to adjust the melting point of the component (A).240581W001

[0013] - 3 - Polyols which are suitable as polyol (P1) and (P2) are in principle known. It is possible to use, as polyols (P1) an (P2), any of the known compounds having at least two hydrogen atoms reactive toward isocyanates, for example those with functionality from 2 to 8. Polyols preferably comprise polymeric compounds with at least two hydrogen atoms reactive towards isocyanate. Polymeric compounds with at least two hydrogen atoms reactive towards isocyanate usually have a functionality from 2 to 8 and number-average molar mass from 200 to 15000 g / mol. By way of example, it is possible to use compounds selected from the group of the polyether polyols, fatty acid based polyols, polybutadiene based polyols, polyester polyols, and mixtures thereof as polyol (P1) and (P2).

[0014] Polyether polyols are by way of example produced from epoxides; for example, propylene oxide and / or ethylene oxide, or from tetrahydrofuran, with starter compounds exhibiting hydrogen-activity containing 1 to 8, preferably 2 to 6 and more preferably 2 to 4 reactive hydrogen atoms bound, or a starter molecule mixture which contains 1.5 to 8, preferably 1.8 to 6 and more preferably 1.9 to 3.5 reactive hydrogen atoms bound in the presence of catalysts. As starter molecules for example aliphatic alcohols, phenols, amines, carboxylic acids, water, or compounds based on natural substances, for example sucrose, sorbitol or mannitol can be applied. Preferred starter molecules are aliphatic alcohols having 2 to 6, preferably 2 to 4 alcohol groups, aliphatic amines and water. In a preferred embodiment polyetherols comprise molecules produced from starter molecules selected from the group, consisting of aliphatic alcohols having 2 to 6, preferably 2 to 4 alcohol groups, aliphatic amines and water, more preferred from the group consisting of aliphatic alcohols having 2 to 4 alcohol groups and water. In a preferred embodiment, polyetherols consist of molecules produced from starter molecules selected from the group, consisting of aliphatic alcohols having 2 to 6, preferably 2 to 4 alcohol groups, aliphatic amines and water. According to the present invention aliphatic alcohols are not only compounds where the alcohol group is bound to an aliphatic carbon atom but a compound free of aromatic structures. If mixtures of starter molecules with different functionalities are used, fractional functionalities can be obtained. Influences on the functionality, for example through side reactions, are not considered in the nominal functionality. Examples for suitable catalysts are basic catalysts and double-metal cyanide catalysts, as described by way of example in PCT / EP2005 / 010124, EP 90444, or WO 05 / 090440.

[0015] Polyesterpolyols are by way of example produced from aliphatic or aromatic dicarboxylic acids and polyhydric alcohols, polythioether polyols, polyesteramides, hydroxylated polyacetals, and / or hydroxylated aliphatic polycarbonates, preferably in the presence of an esterification catalyst. Other possible polyols are mentioned by way of example in "Polyurethane Handbook, 2ndedition 1993, editor Guether Oertel, Carl HanserVerlag Munich, Chapter chapter 3.1.

[0016] In a particularly preferred embodiment of the present invention, polyol (P1) and (P2) may be selected from the group consisting of polyetherols. According to a further embodiment, the present invention is also directed to the adhesive as disclosed above, wherein (P1) and (P2) are selected from the group consisting of polyetherols.

[0017] In a preferred embodiment, polyol (P1) or polyol (P2) is at least one polyether polyol obtainable by reacting at least one starter molecule, selected from the group consisting of aliphatic alcohols having 2 to 6, preferably 2 to 4 and more preferred 2 to 3 alcohol groups, aliphatic amines, water and mixtures comprising a combination of at least two240581W001

[0018] -4-thereof, with alkylene oxides. In one preferred embodiment the polyetherpolyol is a polyetherpolyol obtainable by reacting at least one starter molecule having a functionality of 2, selected from aliphatic alcohols, water and a combination of at least one aliphatic alcohol and water, with alkylene oxide wherein the alkylene oxides. Suitable polyether polyols include, for example, polyoxyethylene, polyoxypropylene, polyoxybutylene, and polytetramethylene ether diols and triols.

[0019] Suitable are for example mixtures of polyether polyols having different molecular weights. For example, a mixture comprising a polyether polyol with a molecular weight in the range of from 500 to 1499 g / mol and a second polyether polyol with a molecular weight in the range of from 1500 to 2500 g / mol.

[0020] Component (A) may also comprise further polyols.

[0021] Preferably, polyol (P1) and polyol (P2) are selected from polypropylene glycols and polyethylene glycols, in particular mixtures comprising one or more polyols selected from polypropylene glycols and polyethylene glycols with a molecular weight of more than 500 g / mol.

[0022] The mixture of the polyols preferably is adjusted to obtain a composition with a melting point above 20°C.

[0023] Preferably, the component (A) comprises polyol (P1) and polyol (P2) in a weight ratio in the range of from 2:1 to 1:2, more preferably in the range of from 1.8:1 to 1:1.8, in particular in the range of from 1.75:1 to 1: 1.75, for example in the range of rom 1.5:1 to 1:1.5, particularly preferable in the range of from 1.25:1 to 1:1.25, more preferable in the ange of from 1.1:1 to 1:1.1.

[0024] Preferably, the sum of the weight of polyol (P1 ) and polyol (P2) represents 8 to 50 wt.-% of component (A), preferably 10 to 40 wt.-% of component (A), more preferable 12 to 30 wt.-% of component (A), in particular 15 to 25 wt.-% of component (A).

[0025] Preferably, polyol (P1 ) is present in component (A) in an amount of at least 5 wt.-%, preferably 7.5 to 15 wt.-%, based in the total weight of component (A). Preferably, polyol (P2) is present in component (A) in an amount of at least 5 wt.-%, preferably 7.5 to 15 wt.-%, based in the total weight of component (A).

[0026] Unless otherwise noted, Gel Permeation Chromatography (GPC) measurements were performed in accordance with DIN EN ISO 13885-1, to determine the molecular weight of the polyols. This methodology is specifically designed to accurately determine the molecular weight distribution of polymers, with a particular emphasis on the calibration process. The calibration is conducted using homologous standards that correspond to the nature of the polyols being analyzed. For this purpose, a range of calibration standards is available, including poly(tetrahydrofuran) (PTHF), polyethylene glycol (PEG), polypropylene glycol (PPG), poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly (butylene adipate). This selection of standards ensures a robust and reliable framework for the measurement of molecular weight, allowing for accurate comparisons and assessments of the polymer samples. The GPC technique provides insights into the molecular weight averages, including number-average molecular weight (Mn) and weight-240581W001

[0027] - 5-average molecular weight (Mw), which are crucial for understanding the material properties and performance of the polymers in various applications.

[0028] Besides polymeric compounds having at least two hydrogen atoms reactive towards isocyanate, the component (A) preferably comprises chain extenders and / or crosslinking agents.

[0029] According to a further embodiment, the present invention is also directed to the adhesive as disclosed above, wherein component (A) comprises a chain extender (CE) having a molecular weight Mn in the range of from of 60 to 500 g / mol.

[0030] Chain extenders used here preferably are compounds of molar mass less than 200 g / mol, preferably less than 150 g / mol and more preferred 62 to 150 g / mol, which have two groups reactive toward isocyanates as for example -SH or NH2-groups and preferably OH-groups. According to the present invention, if chain extenders are used, they are preferably used in an amount of 0.1 to 20 wt.-%, more preferred 1 to 10 wt.-% and especially preferred 1 to 5 wt.-%, each based on the total weight of components. As chain extenders, use may be made of the chain extenders known in the production of polyurethanes. These are preferably low-molecular-weight compounds having two functional groups reactive toward isocyanates, for example monoethylene glycol, diethylene glycol, 1,2-propane diol, 1,3-propane diol, 1,4-butane diol, 1,3-butane diol, 1,5-pentane diol, 1,6-hexane diol, neopentyl glycol, tetraethylene glycol, dipropylene glycol, cyclohexane diol and aliphatic or aromatic amine based chain extenders as aliphatic or aromatic diamines like ethylene diamine, triethylene diamine and / or diethyl toluene diamine. In a preferred embodiment the chain extender is selected from the group, consisting of monoethylene glycol, diethylene glycol, dipropylene glycol, 1,2-propane diol, 1,3 propane diol, 1,4 butane diol, 1,6 hexane diol or mixtures thereof. Other possible low-molecular-weight chain extenders are mentioned by way of example in "Polyurethane Handbook”, Carl HanserVerlag, 2ndedition 1994, chapter 3.2 and 3.3.2.

[0031] In addition to chain extenders or instead of chain extenders, crosslinking agents may be added to the mixture. As crosslinking agents used in the invention preferably are compounds of molar mass less than 200 g / mol preferably less than 150 g / mol which have at least three groups reactive toward isocyanates. Examples for crosslinking agents are glycerine, trimethylolpropane, pentaerythritol and triethanolamine, in a preferred embodiment glycerine is used as crosslinking agent. Other possible low-molecular-weight crosslinking agents are mentioned by way of example in "Polyurethane Handbook”, Carl Hanser Verlag, 2ndedition 1994, chapter 3.2 and 3.3.2. According to the present invention, if chain extenders and / or crosslinking agents are used, they are used in an amount of 0.1 to 10 wt.-%, preferably 0.5-10 and especially preferred ably 1 to 5 wt.-%, each based on the total weight of components.

[0032] Component (A) further comprises a thermally conductive filler (F1). In the context of the present invention, the amount of the filler and also the chemical nature of the filler may vary in broad ranges.240581W001

[0033] - 6 - Suitable fillers may be selected from metals, metal oxides, metal nitrides, or metal hydroxides. Suitable fillers may for example be fillers with a thermal conductivity of greater than 2 W / mK, preferably greater than 14 W / mK, determined according to ASTM D5470 or ISO 22007.

[0034] Suitable fillers also include talcs, clays, silicas, calcium carbonates, graphites, glass, carbon black, plastic powders such as ABS; glass fibers or other ceramics, or polymers or polymer powders such as ABS, polyamide, propylene, polyurethane foams or recycled polyurethane foam.

[0035] Suitable fillers may also be inorganic fillers selected from silicon compounds such as silica, silicates and precipitated and fumed silica; metal oxides such as titanium dioxide, iron oxide, alumina, zinc oxide and magnesium oxide; metal carbonates such as calcium carbonate or dolomite; metal sulfates such as calcium sulfate (gypsum) and barium sulfate; metal hydroxides such as aluminum hydroxide, nitrides or carbides, clay minerals such as kaolin, fly ash, cement, glass and ceramic materials. For example, ceramic particles such as alumina, AIN (aluminum nitride), BN (boron nitride), silicon nitride, SiC or BeO may be used. The shape or ratio of the filler is not particularly limited. It is possible to use a spherical filler, but a filler in a form such as needle-like morphology or flattened morphology may also be used.

[0036] According to a further embodiment, the present invention is also directed to the adhesive as disclosed above, wherein the thermally conductive filler (F1) is selected from the group consisting of metal oxides, metal hydroxides, metal silicates, metal sulfides and combinations thereof.

[0037] The fillers used according to the invention may be of any particle size, for example from 0.1 pm to 300 pm, in particular between 1 pm and 200 pm. The filler may have a monomodal, bimodal, trimodal or multimodal size distribution, preferably a bimodal or trimodal size distribution

[0038] According to the present invention, also mixtures of different fillers or fillers having different particle size distribution may be used.

[0039] It is also possible that further fillers are added such as for example a flame retardant. Suitable fillers may for example be selected from melamine, phosphorous containing flame retardants, or metal hydroxides such as aluminum hydroxide and magnesium hydroxide.

[0040] The filler may be added in suitable amounts depending on the nature of the filler and the application. Suitable amounts may for example be in the range of from 10 to 95wt.-%, preferably in the range of from 20 to 90wt.-%, in particular in the range of from 30 to 80wt.-%, based on the weight of the polyurethane composition.240581W001

[0041] - 7 - According to a further embodiment, the present invention is also directed to the adhesive as disclosed above, wherein the filler (F1) is present in an amount of at least 10 wt.-%, preferably 30 to 80 wt.-%, based in the total weight of component (A).

[0042] According to the present invention, the ratio of the components (A) and (B) may vary depending on the composition of the respective components. Usually, the components (A) and (B) are used in a ratio by volume in the range of from 10:1 to 1:5, preferably 5:1 to 1:1, more preferable 2:1 to 1:1.

[0043] According to a further embodiment, the present invention is also directed to the adhesive as disclosed above, wherein the ratio by volume of components (A) and (B) is in the range of from 10: 1 to 1 :5.

[0044] The isocyanate component (B) comprises at least one polyisocyanate (IC). Suitable polyisocyanates are known to the person skilled in the art.

[0045] According to the invention, the polyisocyanate composition may also comprise two or more polyisocyanates. These may be unmodified or modified, wherein by a modification, the reaction of these isocyanates to isocyanate-termi-nated polyisocyanate prepolymer and I or the reaction to biuret, allophanat, uretdione, and I or isocyanurate-contain-ing isocyanates, preferably allophanate and I or isocyanurate containing isocyanates as well as their prepolymers is understood. These isocyanates can be used individually or in mixtures.

[0046] According to a further embodiment, the present invention is also directed to the adhesive as disclosed above, wherein component (B) comprises at least one polyisocyanate selected from the group consisting of aromatic (poly)isocyanates and aromatic (poly)isocyanate prepolymers.

[0047] Isocyanates used with preference are aliphatic, cycloaliphatic, araliphatic and / or aromatic isocyanates, more preferably tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methylpentamethylene 1 ,5-diisocyanate, 2-ethylbutylene 1 ,4-diisocyanate, pentamethylene 1,5-diisocyanate, butylene 1,4-diisocyanate, 1-isocyanato-3,3,5-tri-methyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1,4-bis(isocyanatomethyl)cyclohexane and / or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), paraphenylene 2,4-diisocyanate (PPDI), tetramethylenexylene 2,4-diisocyanate (TMXDI), dicyclohexylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate (H12 MDI), hexamethylene 1,6-diisocyanate (HDI), cyclohexane 1,4-diisocyanate, 1 -methylcyclohexane 2,4- and / or 2, 6-diisocyanate, diphenylmethane 2,2'-, 2,4'- and / or 4,4'-diisocyanate (MDI), naphthylene 1,5-diisocyanate (NDI), tolylene 2,4- and / or 2,6-diisocy-anate (TDI), diphenylmethane diisocyanate, 3,3,‘-dimethyl-4,4‘-diisocyanato-diphenyl (TODI), dimethyldiphenyl 3,3'-diisocyanate, diphenylethane 1 ,2-diisocyanate and / or phenylene diisocyanate or prepolymers of these isocyanates and polyols or isocyanates and isocyanate-reactive components.240581W001

[0048] - 8 - Particular preference is given to diphenylmethane 4,4'-diisocyanate (MDI), paraphenylene 2,4-diisocyanate (PPDI), naphthylene 1 ,5-diisocyanate (NDI), 3,3,‘-dimethyl-4,4‘-diisocyanato-diphenyl (TODI) , and linear aliphatic diisocyanates such as for example pentamethylene-1,5-diisocyanate, hexamethylene 1 ,6-diisocyanate.

[0049] Isocyanate reactive component (A) and isocyanate component (B) are preferably mixed at temperatures of 20 to 60°C, more preferred 25 to 50°C and especially preferred 30 to 35°C at an isocyanate index in the range of 60 to 150, preferably 70 to 130, more preferably 80 to 120, more preferred 95 to 115 and especially preferred 100 to 110 to form a reaction mixture and the reaction mixture is allowed to cure to form the thermal conductive polyurethane adhesive.

[0050] According to a further aspect, the present invention is also directed to a cured adhesive composition obtainable by curing an adhesive composition as disclosed above. With respect to preferred embodiments, reference is made to the disclosure above.

[0051] The cured adhesive composition according to the present invention may be a compact material or a foam.

[0052] The cured adhesive composition preferably exhibits a thermal conductivity in the range of from 1 to 4 W / mK, determined according to ISO 22007, preferably in the range of from 1 to 2.5 W / mK, determined according to ISO 22007, in particular in the range of from 1.5 to 2 W / mK, determined according to ISO 22007. According to a further embodiment, the present invention is also directed to the cured adhesive as disclosed above, wherein the composition exhibits a thermal conductivity in the range of from 1 to 2.5 W / mK, determined according to ISO 22007.

[0053] According to a further aspect, the present invention is also directed to a process for preparing an article comprising at least two bonded substrates, the process comprising:

[0054] (i) applying the adhesive composition as disclosed above onto the surface of a first substrate; and (ii) bringing the surface of the first substrate comprising the adhesive composition into contact with a second substrate.

[0055] According to the present invention, the adhesive composition is applied to the surface of a fist substrate according to step (i).

[0056] The adhesive composition can be applied manually or automatically by e.g., cartridges or process well known to a skilled person. Suitable methods for the application of a composition include for example dots and beads application, spray, web coating, brush and trowel, curtain coating, film application, or cartridge based hand gun. Suitable apparatuses include for example adhesive dispensing machines with direct material supply out of drums / hobbocks by using follower plates and various dosing pump types.240581W001

[0057] -9 - According to the present invention, the composition is applied in an amount and a way that allows bonding of the substrates to form an article. Typically, the composition has a density in the range of from 1.5 to 2.5 g / mL. The layer of the composition applied typically has a thickness in the range of from 0.2 to 2 mm, in particular 0.5 to 1.5 mm.

[0058] According to the present invention, at least two substrates are bonded but the article may comprise further parts. The parts may comprise different materials and may also vary in shape and size. According to the present invention, it is also possible that the at least two substrates comprise the same material. At least two substrates are bonded to form an article. According to the present invention, the article may also comprise further parts or components.

[0059] The first substrate may comprise a polymer, a metal, an alloy, leather, wood, a ceramic material, a textile material, glass, rubber, cement, minerals, for example a crepe rubber, a natural leather, a synthetic leather, a polyurethane (for example a polyurethane foam and / or a thermoplastic polyurethane TPU), a thermoplastic rubber, a styrene butadiene rubber, a polyvinyl acetate, a polyamide (PA), a polyvinyl chloride, a polystyrene, an acrylonitrile butadiene styrene, a polyethylene terephthalate (PET), a polybutylene terephthalate, a textile, a fabric, a thermo-plastic polyurethane knit fiber and a combination thereof.

[0060] The second substrate or component may comprise the same or a different material.

[0061] According to the present invention, it is also possible that one or more surfaces of the first substrate and / or second substrate are at least partially covered with the adhesive composition.

[0062] The process of the present invention may also comprise further steps, such as for example treatment steps of a surface. Surface treatment may for example include a surface treatment such as a physical treatment, a chemical treatment, a solvent treatment, or any combination thereof. Physical treatments can include treating a surface with an abrasive to increase a surface roughness. Chemical treatments can include etching a surface with acid. Solvent treatments can include contacting a surface with a solvent to remove contaminants from the surface. The treating step may also include a primer treatment (i.e. coating with a primer solution before application of the adhesive).

[0063] According to a further aspect, the present invention is also directed to an article obtainable according to the process as disclosed above.

[0064] The adhesive composition or cured adhesive composition is suitable for different applications depending on the chemical nature of the polyurethane and also the filler used, in particular in electronic components. According to a further aspect, the present invention is also directed to the use of an adhesive composition as disclosed above or a cured adhesive as disclosed above in pipes, preferably cooling coils; in electronic components, preferably light emitting devices, computer devices, mobile phones, tablets, touch screens, automotive technology, hifi systems, and audio systems; in joints between heat pipes and water tanks in solar heated heating; in fuel cell and wind turbines; in the manufacture of computer chips; in light devices; batteries; in housings; in coolers; heat exchanging devices;240581W001

[0065] - 10-wires; cables; heating wires; household appliances such as refrigerators and dishwashers; air conditionings; accumulators; transformers; lasers; functional clothing; car seats; medical devices; fire protection; electric motors; cars; batteries for cars; emobility; electric vehicles; planes and trains.

[0066] The composition according to the present invention preferably has improved (a reduced) squeeze flow (SQF) characteristics. As described by Frauenhofer et al. (Frauenhofer, M., Gormanns, M., Simon, M., Rutters, M., & Fricke, H. Optimized heat dissipation of energy storage systems, adhesion ADHESIVES+ SEALANTS, 17, 12-17 (2020)), for the assembly of the battery, the thermally conductive adhesive typically is applied on the cooling plate. Afterwards, the battery cells I modules are inserted into the adhesive. During this movement, the adhesive is effectively pressed against the surface to be wetted, and great care must be taken not to damage the pressure-sensitive battery cells. Therefore, the flow properties and the resulting pressing forces of the adhesive have to be adjusted to prevent any damage to the battery and the cooling plate. This is even more challenging since the adhesives have a high filler load. It is aimed to formulate adhesives which can be easily compressed also to ensure a good wetting, pumpability, and put less strain on the application equipment. In this regard, the squeeze flow (SQF) is a well-known topic in bonding technology, which occurs when joining substrates. The pressure in the adhesive can increase unexpectedly when squeezing small gap heights. Thus, low SQF pressure forces are desired. The SQF is well accepted to simulate the forces when battery cells I modules are pressed into the adhesive on the cooling plate.

[0067] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1, 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0068] 1. Adhesive composition comprising a first component (A) and a second component (B) comprising at least one polyisocyanate, wherein component (A) comprises a first polyol (P1 ); a second polyol (P2); at least one thermally conductive filler (F1); and

[0069] wherein component (A) has a melting point Tm in the range of from 20°C to 30°C, determined using differential scanning calorimetry (DSC) according to DIN EN ISO 11357-1 .

[0070] 2. The adhesive composition according to embodiment 1, wherein (P1) and (P2) are selected from the group consisting of polyetherols.240581W001

[0071] - 11 - 3. The adhesive composition according to any one of embodiments 1 or 2, wherein the thermally conductive filler (F1) is selected from the group consisting of metal oxides, metal hydroxides, metal silicates, metal sulfides and combinations thereof.

[0072] 4. The adhesive composition according to any one of embodiments 1 to 3, wherein the filler (F1) is present in an amount of at least 10 wt.-%, preferably 30 to 80 wt.-%, based in the total weight of component (A).

[0073] 5. The adhesive composition according to any one of embodiments 1 to 4, wherein the ratio by mass of components (A) and (B) is in the range of from 10:1 to 1 :5.

[0074] 6. The adhesive composition according to any one of embodiments 1 to 5, wherein component (B) comprises at least one polyisocyanate selected from the group consisting of aromatic (poly)isocyanates and aromatic (poly)isocyanate prepolymers.

[0075] 7. The adhesive composition according to any one of embodiments 1 to 6, wherein component (A) comprises a chain extender (CE) having a molecular weight Mn in the range of from of 60 to 500 g / mol.

[0076] 8. Cured adhesive composition obtainable by curing an adhesive composition according to any of embodiments 1 to 7.

[0077] 9. Cured adhesive composition obtainable by curing an adhesive composition comprising a first component (A) and a second component (B) comprising at least one polyisocyanate, wherein component (A) comprises a first polyol (P1); a second polyol (P2); at least one thermally conductive filler (F1); and

[0078] wherein component (A) has a melting point Tm in the range of from 20°C to 30°C, determined using differential scanning calorimetry (DSC) according to DIN EN ISO 11357-1 .

[0079] 10. The cured adhesive composition according to embodiment 9, wherein (P1) and (P2) are selected from the group consisting of polyetherols.

[0080] 11. The cured adhesive composition according to any one of embodiments 9 or 10, wherein the thermally conductive filler (F1) is selected from the group consisting of metal oxides, metal hydroxides, metal silicates, metal sulfides and combinations thereof.

[0081] 12. The cured adhesive composition according to any one of embodiments 9 to 11, wherein the filler (F1) is present in an amount of at least 10 wt.-%, preferably 30 to 80 wt.-%, based in the total weight of component (A).240581W001

[0082] - 12 - 13. The cured adhesive composition according to any one of embodiments 9 to 12, wherein the ratio by mass of components (A) and (B) is in the range of from 10:1 to 1 :5.

[0083] 14. The cured adhesive composition according to any one of embodiments 9 to 13, wherein component (B) comprises at least one polyisocyanate selected from the group consisting of aromatic (poly)isocyanates and aromatic (poly)isocyanate prepolymers.

[0084] 15. The cured adhesive composition according to any one of embodiments 9 to 14, wherein component (A) comprises a chain extender (CE) having a molecular weight Mn in the range of from of 60 to 500 g / mol.

[0085] 16. Cured adhesive composition according to embodiment 8, wherein the composition exhibits a thermal conductivity in the range of from 1 to 2.5 W / mK, determined according to ISO 22007.

[0086] 17. Cured adhesive composition according to any one of embodiments 9 to 14, wherein the composition exhibits a thermal conductivity in the range of from 1 to 2.5 W / mK, determined according to ISO 22007.

[0087] 18. Process for preparing an article comprising at least two bonded substrates, the process comprising:

[0088] (I) applying the adhesive composition according to any of embodiments 1 to 7 onto the surface of a first substrate; and

[0089] (ii) bringing the surface of the first substrate comprising the adhesive composition into contact with a second substrate.

[0090] 19. Process for preparing an article comprising at least two bonded substrates, the process comprising:

[0091] (i) applying an adhesive composition onto the surface of a first substrate; and

[0092] (ii) bringing the surface of the first substrate comprising the adhesive composition into contact with a second substrate;

[0093] wherein the adhesive composition comprises a first component (A) and a second component (B) comprising at least one polyisocyanate, wherein component (A) comprises a first polyol (P1); a second polyol (P2); at least one thermally conductive filler (F1); and

[0094] wherein component (A) has a melting point Tm in the range of from 20°C to 30°C, determined using differential scanning calorimetry (DSC) according to DIN EN ISO 11357-1 .

[0095] 20. The process according to embodiment 19, wherein (P1) and (P2) are selected from the group consisting of polyetherols.240581W001

[0096] - 13 - 21. The process according to any one of embodiments 19 or 20, wherein the thermally conductive filler (F1) is selected from the group consisting of metal oxides, metal hydroxides, metal silicates, metal sulfides and combinations thereof.

[0097] 22. The process according to any one of embodiments 19 to 21, wherein the filler (F1) is present in an amount of at least 10 wt.-%, preferably 30 to 80 wt.-%, based in the total weight of component (A).

[0098] 23. The process according to any one of embodiments 19 to 22, wherein the ratio by mass of components (A) and (B) is in the range of from 10:1 to 1 :5.

[0099] 24. The process according to any one of embodiments 19 to 23, wherein component (B) comprises at least one polyisocyanate selected from the group consisting of aromatic (poly)isocyanates and aromatic (poly)isocy a- nate prepolymers.

[0100] 25. The process according to any one of embodiments 19 to 24, wherein component (A) comprises a chain extender (CE) having a molecular weight Mn in the range of from of 60 to 500 g / mol.

[0101] 29. Article obtained or obtainable according to the process according to embodiment 18.

[0102] 30. Article obtained or obtainable according to the process according to any one of embodiments 19 to 25.

[0103] 31. Use of an adhesive composition according to any of embodiments 1 to 7 in pipes, preferably cooling coils; in electronic components, preferably light emitting devices, computer devices, mobile phones, tablets, touch screens, automotive technology, hifi systems, and audio systems; in joints between heat pipes and water tanks in solar heated heating; in fuel cell and wind turbines; in the manufacture of computer chips; in light devices; batteries; in housings; in coolers; heat exchanging devices; wires; cables; heating wires; household appliances such as refrigerators and dishwashers; air conditionings; accumulators; transformers; lasers; functional clothing; car seats; medical devices; fire protection; electric motors; cars; batteries for cars; emobility; electric vehicles; planes and trains.

[0104] The invention is further illustrated by the following examples.

[0105] Raw materials:240581W001

[0106] - 14- Polyol 1: Polypropylene glycol obtained by propoxylation of propylene oxide having an OH-Number of 104 mgKOH / g.

[0107] Polyol 2: Polypropylene glycol obtained by propoxylation of propylene oxide having an OH-Number of 55 mgKOH / g.

[0108] Polyol 3: Poly(tetrahydrofuran) homopolymer, having an OH-number of 112 mg KOH / g.

[0109] Polyol 4: Poly(tetrahydrofuran) homopolymer, having an OH-number of 56 mg KOH / g.

[0110] Additive 1: Silane-based adhesion promoter

[0111] Filler 1: AEROSIL® R 202 is a fumed silica after-treated with polydimethylsiloxane from Evonik.

[0112] TC filler 1: Alkyl-silane treated aluminium trihydroxide having a particle size D90 of about 100 m

[0113] TC filler 2: Alkyl-silane treated aluminium oxide filler having a particle size D100 of about 20 pm.

[0114] TC filler 3: Aluminium trihydroxide filler having a particle size D50 of about 90 pm.

[0115] Chain extender: 1 ,2-propylene glycol

[0116] Cross-linker: Glycerine (97.7%)

[0117] Drying agent 1: Alkali aluminosilicate

[0118] Dye:

[0119] Methods:

[0120] Testing the settling behavior:

[0121] The settling behavior of highly filled A-components for a thermally conductive (TC) two-component (2c) polyurethane adhesive was determined using a centrifuge (Labofuge Ae Heraeus Sepatech). The centrifugal forces accelerate the settling and sedimentation behavior, thus not requiring long periods of time (3-6 months) under normal conditions. For this purpose, the centrifuge tubes are filled with 50 g of the A-component, then centrifuged on the same day of preparation at a speed of 1500 rpm for 30 or 60 minutes and subsequently evaluated visually. This procedure was repeated with 7 days aged A-component. The evaluation is as follows:

[0122] Excellent: The entire A-component shows a homogeneous image after centrifugation. No fillers have settled, no phases are visible within the filled area, and no liquid film has formed on the surface. When testing the mechanical properties, there are no differences when material is taken from the upper, middle, or lower filled part of the centrifuge tube and then reacted with an isocyanate (B-component) component.

[0123] Good: The entire A-component shows a homogeneous image after centrifugation. No fillers have settled, no phases are visible within the filled area, and a minimal liquid film has formed only on the surface at the edge of the centrifuge tube. This liquid film does not wet the surface otherwise. When testing the mechanical properties, there are no differences when material is taken from the upper, middle, or lower filled part of the centrifuge tube and then reacted with an isocyanate (B-component) component.240581W001

[0124] - 15 - Satisfactory: The entire A-component shows a homogeneous image after centrifugation. No fillers have settled, no phases are visible within the filled area, and a minimal liquid film has formed on the surface that partially (<1 mm) the surface. When testing the mechanical properties, there are no differences when material is taken from the upper, middle, or lower filled part of the centrifuge tube and then reacted with an isocyanate (B-component) component.

[0125] Poor: The entire A-component shows an inhomogeneous image after centrifugation. Fillers have settled and / or phases are visible within the filled area and / or a liquid film >1 mm overhang is visible on the surface. When testing the mechanical properties, there are differences when material is taken from the upper, middle, or lower filled part of the centrifuge tube and then reacted with an isocyanate (B-compo- nent) component.

[0126] Squeeze flow:

[0127] To measure the SQF, a rotationally symmetrical cylinder with diameter D is mounted such to be axially movable. The gap between the underside of the cylinder and a plane surface is filled with the thermally conductive adhesive. In tests where the cylinder has been lowered at a linear speed v, the force F(h) occurring during the axial movement of the cylinder and the height of the gap h(t) are simultaneously measured. The movement of the cylinder causes a radial squeezing of the adhesive out of the gap. The maximum hydrostatic pressure in the adhesive occurs on the rotational axis (r=0). The exact parallelism of the cylinder and the plane surface are decisive for the measuring quality, as are the speed control and the very precise measurement of the gap height h(t).

[0128] For the patent experiments, the following measurement setup was used:

[0129] • Test speed: v = 1 mm / s

[0130] • Diameter D of the cylinder = 40 mm; diameter of the plane surface = 60 mm

[0131] • Initial gap of 5 mm was lowered to a final gap of 0.3 mm

[0132] • The SQF force was evaluated at a gap of 0.5 mm

[0133] • Apparatus: Table-top testing machine Zwicki Z2.5 (ZwickRoell) with PC and measurement and control software (testXpert III and testControl II).

[0134] According to the formulations as given in Table 1:

[0135] The composition composed of component A (polyol-component) is shown in T able 1. The polyol component was obtained as follows:

[0136] Polyol components: in a speed blender cup all liquid components and on top of them the fillers are added (in total 500 g). These ingredients are then stirred with a speed mixer for 1 min at 800 rpm and another minute at 1600 rpm. Then the mixing is continued for 10 minutes under vacuum at 800 rpm.240581W001

[0137] - 16 -

[0138]

[0139] Table 1: Composition of component A of the examples (Ex.) and reference examples (Ref. Ex.) and the resulting settling behavior.

[0140] All the A-component formulations shown here can be processed at 35°C under the conditions typically used for an adhesive dispensing machine system for adhesive application in the automotive industry. The SOF was measured after heating the A-component to 35°C, and the SGF for all formulations were below 400 N.

[0141] After solidification at room temperature for 7 days, all inventive formulations (Ex.1 and Ex. 2) exhibit excellent settling properties and show no visual changes after centrifugation for 30 or 60 minutes. This indicates that they are highly stable during storage. This applies to low polyether polyols with a low glass-transition temperature (Tg) with a melting temperature higher than room temperature.

[0142] Literature cited:

[0143] EP3670558

[0144] PCT / EP2005 / 010124

[0145] EP 90444

[0146] WO 05 / 090440

[0147] "Polyurethane Handbook, 2ndedition, editor Guether Oertel, Carl HanserVerlag Munich, Chapter chapter 3.1, 3.2 and 3.3.2

[0148] Frauenhofer, M., Gormanns, M., Simon, M., Rutters, M., & Fricke, H. Optimized heat dissipation of energy storage systems, adhesion ADHESIVES+ SEALANTS, 17, 12-17 (2020)

Claims

1. 240581W001- 17- Claims1. Adhesive composition comprising a first component (A) and a second component (B) comprising at least one polyisocyanate, wherein component (A) comprises a first polyol (P1); a second polyol (P2); at least one thermally conductive filler (F1); andwherein component (A) has a melting point Tm in the range of from 20°C to 30°C, determined using differential scanning calorimetry (DSC) according to DIN EN ISO 11357-1.

2. The adhesive composition according to claim 1, wherein (P1) and (P2) are selected from the group consisting of polyetherols.

3. The adhesive composition according to any one of claims 1 or 2, wherein the component (A) comprises polyol (P1) and polyol (P2) in a weight ratio in the range of from 2:1 to 1:2.

4. The adhesive composition according to any one of claims 1 to 3, wherein polyol (P1) is present in component (A) in an amount of at least 5 wt.-%, based in the total weight of component (A).

5. The adhesive composition according to any one of claims 1 to 4, wherein polyol (P1) is present in component (A) in an amount of at least 5 wt.-%, based in the total weight of component (A).

6. The adhesive composition according to any one of claims 1 to 5, wherein the thermally conductive filler (F1) is selected from the group consisting of metal oxides, metal hydroxides, metal silicates, metal sulfides and combinations thereof.

7. The adhesive composition according to any one of claims 1 to 6, wherein the filler (F1) is present in an amount of at least 10 wt.-%, preferably 30 to 80 wt.-%, based in the total weight of component (A).

8. The adhesive composition according to any one of claims 1 to 7, wherein the ratio by mass of components (A) and (B) is in the range of from 10:1 to 1:5.

9. The adhesive composition according to any one of claims 1 to 8, wherein component (B) comprises at least one polyisocyanate selected from the group consisting of aromatic (poly)isocyanates and aromatic (poly)iso- cyanate prepolymers.

10. The adhesive composition according to any one of claims 1 to 9, wherein component (A) comprises a chain extender (CE) having a molecular weight Mn in the range of from of 60 to 500 g / mol.240581W001- 18 -11. Cured adhesive composition obtainable by curing an adhesive composition according to any of claims 1 to 10.

12. Cured adhesive composition according to claim 11, wherein the composition exhibits a thermal conductivity in the range of from 1 to 2.5 W / mK, determined according to ISO 22007.

13. Process for preparing an article comprising at least two bonded substrates, the process comprising:(I) applying the adhesive composition according to any of claims 1 to 10 onto the surface of a first substrate; and(ii) bringing the surface of the first substrate comprising the adhesive composition into contact with a second substrate.

14. Article obtained or obtainable according to the process according to claim 13.

15. Use of an adhesive composition according to any of claims 1 to 10 in pipes, preferably cooling coils; in electronic components, preferably light emitting devices, computer devices, mobile phones, tablets, touch screens, automotive technology, hifi systems, and audio systems; in joints between heat pipes and water tanks in solar heated heating; in fuel cell and wind turbines; in the manufacture of computer chips; in light devices; batteries; in housings; in coolers; heat exchanging devices; wires; cables; heating wires; household appliances such as refrigerators and dishwashers; air conditionings; accumulators; transformers; lasers; functional clothing; car seats; medical devices; fire protection; electric motors; cars; batteries for cars; emobility; electric vehicles; planes and trains.

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