Two-component polyurethane compositions with adjustable pot life for spray applications

Abstract

The present invention relates to a polyurethane composition consisting of a first component and a second component, the first component A comprising at least one polyol A1 having an OH functionality in the range of 1.5 to 4 and an average molecular weight in the range of 250 to 15,000 g / mol, at least one diol A2 having two hydroxyl groups linked via a C2 to C9 carbon chain, and at least one compound T having at least one thiol group, the second component B comprising at least one polyisocyanate I, one of the two components additionally comprising at least one metal catalyst K for the reaction of hydroxyl groups with isocyanate groups, capable of forming thio complexes, the first component A comprising at least one acrylic acid, and a second component B comprising an isocyanate group-containing prepolymer P1 selected from polymers P1-1 based on at least one polyisocyanate, at least one polyether polyol, and at least one hydroxy-terminated polybutadiene polymer, or polymers P1-2 based on at least one polyisocyanate and at least one polyether polyol, and the use thereof, in particular as an adhesive for bonding components of consumer electrical devices in a spray process.

Description

[Technical Field]

[0001] The present invention relates to a two-component polyurethane composition and its uses, in particular as an adhesive for joining components of consumer electrical devices in a spray process. [Background technology]

[0002] In the field of electronic product assembly, particularly consumer electronics, hot melt adhesives are commonly used to bond components of electronic products, such as the frames of mobile phones and tablet computers, etc. However, due to the chemical and physical properties of hot melt adhesives, such bonding is often time consuming, expensive, and requires relatively harsh working conditions.

[0003] Additionally, the use of hot melt adhesives does not allow for the joining of electronic product components by a simpler and more material-saving spray process.

[0004] Two-component polyurethane compositions based on polyols and polyisocyanates have been in use for some time. They have the advantage that they cure quickly after mixing and are therefore able to absorb and transmit large forces after a very short time. However, they are usually used as structural adhesives or as matrices (binders) in composite materials.

[0005] It is desirable to have adhesive compositions that are suitable for spray application in very small amounts, especially when used to bond components of electrical devices, while having excellent mechanical and adhesive properties and rapid curing behavior. It would also be desirable if the pot life of such compositions could be tailored to the desired application. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention therefore aims to provide a two-component polyurethane composition that cures very quickly to form a mechanically excellent and chemically resistant material, especially when sprayed in very small amounts to bond components of electrical devices, and at the same time has a pot life that can be adjusted within certain limits, allowing for problem-free processing. [Means for solving the problem]

[0007] Surprisingly, this object is achieved by the polyurethane composition according to the present invention, as claimed in claim 1. The composition comprises a polyol, a short-chain diol, and a compound having at least one thiol group in a first component, and a sufficient amount of polyisocyanate in a second component. To cure the composition, the composition further contains a metal catalyst capable of forming a thiocomplex, and the ratio of thiol groups to metal atoms in the composition is fixed. It is important that the composition contains a certain amount of acrylonitrile and styrene-grafted polyether polyol H in the first component, and an isocyanate-containing prepolymer P1 selected from polymers P1-1 based on at least one polyisocyanate, at least one polyether polyol, and at least one hydroxy-terminated polybutadiene polymer, or polymers P1-2 based on at least one polyisocyanate and at least one polyether polyol.

[0008] It has also been found that the polyurethane compositions of the present invention, when cured, can cause adhesive failure at the substrate when peeled from the substrate to which they have been applied. In electronic devices, adhesive failure at the substrate can be desirable, particularly for repair of some electronic devices, because the adhesive can be removed without causing damage, such as cracking, to the substrate.

[0009] Further aspects of the invention are the subject of further independent claims. Particularly preferred embodiments of the invention are the subject of the dependent claims. DETAILED DESCRIPTION OF THE INVENTION

[0010] In a first aspect, the present invention provides a polyurethane composition comprising a first component and a second component, The first component A is - at least one polyol A1 having an OH functionality ranging from 1.5 to 4 and an average molecular weight ranging from 250 to 15,000 g / mol, at least one diol A2 having two hydroxyl groups linked via a C2-C9 carbon chain, - at least one compound T having at least one thiol group; Including, - the second component B, - at least one polyisocyanate I Includes; one of the two components additionally contains at least one metal catalyst K for the reaction of hydroxyl groups with isocyanate groups, which is capable of forming thio complexes, The first component A comprises acrylonitrile and styrene-grafted polyether polyol H in an amount of 7.5 to 25 wt. %; The second component B comprises an isocyanate group-containing prepolymer P1 selected from polymers P1-1 based on at least one polyisocyanate, at least one polyether polyol and at least one hydroxy-terminated polybutadiene polymer, or polymers P1-2 based on at least one polyisocyanate and at least one polyether polyol, The present invention relates to a polyurethane composition.

[0011] In a second aspect, the present invention provides a method for joining substrates, particularly components of an electrical device, comprising the steps of: mixing both components of the polyurethane composition of the present invention; and spraying the mixed composition onto the parts to be joined; The present invention relates to a method, comprising:

[0012] In this document, the prefix "poly" in the names of substances such as "polyols," "polyisocyanates," "polyethers," or "polyamines" indicates that the respective substance formally contains, per molecule, two or more of the functional groups appearing in the name.

[0013] In this document, the term "polymer" includes, firstly, a group of chemically uniform macromolecules resulting from "poly" reactions (polymerization, polyaddition, polycondensation) but differing in degree of polymerization, molar mass and chain length. Secondly, the term also includes derivatives of such a group of macromolecules resulting from polyreactions, i.e. compounds obtained by reactions, for example addition or substitution, of functional groups on a defined macromolecule, and which may be chemically uniform or chemically heterogeneous. The term also includes so-called prepolymers, i.e. reactive initial oligomeric adducts whose functional groups participate in the construction of the macromolecule.

[0014] The term "polyurethane polymer" includes all polymers produced according to the so-called diisocyanate polyaddition process. It also includes polymers that are substantially or completely free of urethane groups. Examples of polyurethane polymers are polyether polyurethanes, polyester polyurethanes, polyether polyureas, polyureas, polyester polyureas, polyisocyanurates, and polycarbodiimides.

[0015] In this document, "molecular weight" is understood to mean the molar mass (grams / mole) of a molecule or molecular residue. "Average molecular weight" is the number-average M of a polydisperse mixture of oligomeric or polymeric molecules or molecular residues, typically determined by gel permeation ion chromatography (GPC) using polystyrene as a standard. n In this document, "room temperature" refers to a temperature of 23°C. Weight percentage (abbreviated as wt.%) refers to the mass percentage of a component in a composition based on the total weight of the composition, unless otherwise specified. The terms "mass" and "weight" are used synonymously in this document.

[0016] "Primary hydroxyl group" refers to an OH group bonded to a carbon atom having two hydrogens.

[0017] In this document, "pot life" refers to the time that the polyurethane composition can be processed after mixing the two components before the viscosity due to the progression of the crosslinking reaction becomes too high for further processing.

[0018] In this document, the term "strength" refers to the strength of the cured composition, and strength means in particular the tensile strength and modulus of elasticity, especially in the elongation range of 0.05% to 0.25%.

[0019] In this document, "room temperature" refers to a temperature of 23°C.

[0020] A substance or composition is described as "storage-stable" or "storable" if it can be stored in a suitable container at room temperature for an extended period, typically at least 3 to 6 months or more, and this storage does not result in any change in its application or use properties, particularly viscosity and crosslinking rate, to an extent relevant to its use.

[0021] All industry standards and codes mentioned in this document relate to the editions in effect on the date of original filing.

[0022] The first component A firstly comprises at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and an average molecular weight in the range from 250 to 15000 g / mol.

[0023] Suitable polyols A1 are in principle all polyols currently used in the production of polyurethane polymers, with polyether polyols, polyester polyols, poly(meth)acrylate polyols, polybutadiene polyols, polycarbonate polyols and mixtures of these polyols being particularly suitable.

[0024] Suitable polyether polyols, also known as polyoxyalkylene polyols or oligoetherols, are in particular those which are the polymerization products of ethylene oxide, 1,2-propylene oxide, 1,2- or 2,3-butylene oxide, oxetane, tetrahydrofuran or mixtures thereof, optionally in the presence of water, ammonia or compounds containing multiple OH or NH groups, such as 1,2-ethanediol, 1,2- and 1,3-propanediol, neopentyl glycol, diethylene glycol, triethylene glycol, isomeric diols, Polymerized using initiator molecules with two or more active hydrogen atoms, such as propylene glycol and tripropylene glycol, isomeric butanediols, pentanediols, hexanediols, heptanediols, octanediols, nonanediols, decanediols, undecanediols, 1,3- and 1,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, glycerol, aniline, and mixtures of the listed compounds. For example, both polyoxyalkylene polyols with low unsaturation (measured in milliequivalents of unsaturation per gram of polyol (mEq / g) in accordance with ASTM D-2849-69) produced using so-called double metal cyanide complex catalysts (DMC catalysts) and polyoxyalkylene polyols with relatively high unsaturation produced using anionic catalysts such as NaOH, KOH, CsOH, or alkali metal alkoxides can be used.

[0025] Polyoxyethylene polyols and polyoxypropylene polyols, especially polyoxyethylene diols, polyoxypropylene diols, polyoxyethylene triols, and polyoxypropylene triols, are particularly preferred.

[0026] Particularly preferred are polyoxyalkylene diols or polyoxyalkylene triols having a degree of unsaturation of less than 0.02 mEq / g and a molecular weight in the range of 1,000 to 15,000 g / mol, and polyoxyethylene diols, polyoxyethylene triols, polyoxypropylene diols and polyoxypropylene triols having a molecular weight of 400 to 15,000 g / mol.

[0027] Likewise, so-called ethylene oxide-terminated (EO end-capped / ethylene oxide end-capped) polyoxypropylene polyols are particularly suitable. The latter are special polyoxypropylene polyoxyethylene polyols, which can be obtained, for example, when, after the polypropoxylation reaction is completed, pure polyoxypropylene polyols, especially polyoxypropylene diols and triols, are further alkoxylated with ethylene oxide and thus contain primary hydroxyl groups. In this case, polyoxypropylene polyoxyethylene diols and polyoxypropylene polyoxyethylene triols are preferred.

[0028] Also suitable are hydroxyl-terminated polybutadiene polyols produced, for example, by polymerization of 1,3-butadiene and allyl alcohol or by oxidation of polybutadiene, and hydrogenated products thereof.

[0029] Also suitable are styrene-acrylonitrile grafted polyether polyols such as those commercially available under the trade name Lupranol® from Elastogran GmbH, Germany.

[0030] Suitable polyester polyols include in particular polyesters having at least two hydroxyl groups and produced by known processes, in particular by polycondensation of hydroxycarboxylic acids or of aliphatic and / or aromatic polycarboxylic acids with dihydric or polyhydric alcohols.

[0031] More preferred are polyester polyols produced from dihydric to trihydric alcohols such as 1,2-ethanediol, diethylene glycol, 1,2-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, glycerol, 1,1,1-trimethylolpropane, or mixtures of the above alcohols, and organic dicarboxylic acids or anhydrides or esters thereof, such as succinic acid, glutaric acid, adipic acid, trimethyladipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, dimer fatty acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, dimethyl terephthalate, hexahydrophthalic acid, trimellitic acid and trimellitic anhydride, or mixtures of the above acids, as well as polyester polyols formed from lactones such as ε-caprolactone.

[0032] Particularly preferred are polyester diols produced from dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, dimer fatty acids, phthalic acid, isophthalic acid and terephthalic acid, or from lactones such as ε-caprolactone, and from dihydric alcohols such as ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, dimer fatty acid diols and 1,4-cyclohexanedimethanol.

[0033] Suitable polycarbonate polyols include those obtained by reacting the above-mentioned alcohols used in the construction of polyester polyols with dialkyl carbonates such as dimethyl carbonate, diaryl carbonates such as diphenyl carbonate, or phosgene. Similarly suitable are polycarbonates obtained by copolymerization of CO2 with epoxides such as ethylene oxide and propylene oxide. Polycarbonate diols, especially amorphous polycarbonate diols, are particularly suitable.

[0034] Further suitable polyols are poly(meth)acrylate polyols.

[0035] Also suitable are polyhydroxy-functional fats and oils, such as natural fats and oils, especially castor oil, or so-called oleochemical polyols obtained by chemical modification of natural fats and oils, such as epoxy polyesters or epoxy polyethers obtained by epoxidation of unsaturated oils and subsequent ring-opening with carboxylic acids or alcohols, respectively, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils. Also suitable are polyols obtained from natural fats and oils by decomposition processes such as alcoholysis or ozonolysis and subsequent chemical coupling of the decomposition products or their derivatives obtained in this way, for example by transesterification or dimerization. Suitable decomposition products of natural fats and oils are, in particular, fatty acids and fatty alcohols and fatty acid esters, especially methyl esters (FAME), which can be derivatized, for example, by hydroformylation and hydrogenation, to give hydroxy fatty acid esters.

[0036] Also suitable are polyhydrocarbon polyols, also called oligohydrocarbonols, such as polyhydroxy-functional ethylene-propylene, ethylene-butylene or ethylene-propylene-diene copolymers (e.g., those manufactured by Kraton Polymers, USA), or polyhydroxy-functional copolymers of dienes, such as 1,3-butandien or diene mixtures, and vinyl monomers, such as styrene, acrylonitrile or isobutylene, or polyhydroxy-functional polybutadiene polyols (e.g., those obtained by copolymerization of 1,3-butadiene and allyl alcohol, which may be hydrogenated).

[0037] Also suitable are polyhydroxy-functional acrylonitrile / butadiene copolymers such as those that can be produced from epoxides or aminoalcohols, and carboxyl-terminated acrylonitrile / butadiene copolymers commercially available from Emerald Performance Materials, LLC, USA under the trade name Hypro® (formerly Hycar®) CTBN.

[0038] All of the polyols mentioned have an average molecular weight of 250 to 15,000 g / mol, preferably 400 to 10,000 g / mol, more preferably 1,000 to 8,000 g / mol, and an average OH functionality in the range of 1.5 to 4, preferably 1.7 to 3. However, it is entirely possible for the composition to also contain a certain proportion of monools (polymers with only one hydroxyl group).

[0039] Particularly suitable polyols are polyester polyols and polyether polyols, in particular polyoxyethylene polyols, polyoxypropylene polyols and polyoxypropylene polyoxyethylene polyols, preferably polyoxyethylene diols, polyoxypropylene diols, polyoxyethylene triols, polyoxypropylene triols, polyoxypropylene polyoxyethylene diols and polyoxypropylene polyoxyethylene triols.

[0040] The first component A further comprises at least one diol A2 having two hydroxyl groups linked via a C2-C9 carbon chain.

[0041] Suitable diols A2 include linear or branched alkylene diols having two primary or secondary hydroxyl groups, alkylene diols having one primary and one secondary hydroxyl group, and alicyclic diols.

[0042] Diol A2 is preferably a straight-chain aliphatic diol having two primary hydroxyl groups linked via a C4-C9 carbon chain.

[0043] In particular, diols A2 are ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,3-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,2-pentanediol, 2,4-pentanediol, 2-methyl-1,4-butanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,2-hexanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,2-octanediol, 3,6-octanediol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,7-dimethyl-3,6-octanediol, 1,4-cyclohexanediol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

[0044] Diol A2 is more preferably selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol and 1,9-nonanediol.

[0045] Diol A2 is most preferably selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,9-nonanediol, which are readily commercially available and which upon curing give polyurethanes with particularly high modulus and low elongation.

[0046] The first component A preferably contains 5 to 25% by weight of diol A2.

[0047] One of the essential features of the present invention is that the first component A contains an acrylonitrile- and styrene-grafted polyether polyol H, which is important for achieving the desired spray application and improving the adhesive properties of the substrate to be bonded. The amount of polyether polyol H is necessarily in the range of 7.5 to 25% by weight, preferably 12.0 to 20.0% by weight, based on the total weight of the polyurethane composition. It has been found that spray application can be difficult when polyether polyol H is used in an amount exceeding 25% by weight. In some cases, an amount exceeding 25% by weight may deteriorate mechanical properties such as elongation at break.

[0048] Such acrylonitrile and styrene grafted polyether polyols are polyethers based on polyether polyols grafted with acrylonitrile and styrene monomers, and can be obtained by free radical graft polymerization with the aid of an initiator at a specific temperature and under nitrogen protection. The polyether polyols suitable as initiators to be grafted may be those listed above as preferred polyether polyols.

[0049] Acrylonitrile and styrene grafted polyether polyol H may be commercially available from Changhua Chemical under trade names such as CHP-H45.

[0050] In addition to the polyols A1, A2, and H mentioned above, minor amounts of other low molecular weight dihydric or polyhydric alcohols such as diethylene glycol, triethylene glycol, isomeric dipropylene glycols and tripropylene glycols, isomeric decanediols and undecanediols, hydrogenated bisphenol A, dimeric aliphatic alcohols, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, glycerol, pentaerythritol, sugar alcohols such as xylitol, sorbitol, or mannitol, sugars such as sucrose, other higher polyhydric alcohols, low molecular weight alkoxylation products of the above dihydric and polyhydric alcohols, and mixtures of the above alcohols may also be included. In addition, other heteroatom-containing polyols, such as methyldiethanolamine or thiodiglycol, may also be included.

[0051] The first component A further comprises at least one compound T having at least one thiol group. Suitable are all compounds having at least one thiol / mercapto group and which can be incorporated into the composition according to the invention. Here, a thiol group is understood to mean an —SH group attached to an organic group, for example an aliphatic, alicyclic or aromatic carbon group.

[0052] Compounds having 1 to 6, more preferably 1 to 4, and most preferably 1 or 2 thiol groups are preferred. Compounds having thiol groups have the advantage that they do not form complexes with the metal catalyst K, which tend to have poor solubility, and that the pot life can be adjusted particularly precisely. Compounds having two thiol groups have the advantage that the mechanical properties of the composition after curing are improved.

[0053] Examples of suitable compounds T having a thiol group are 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercapto-1,2-propanediol, 2-mercaptotoluimidazole or 2-mercaptobenzothiazole.

[0054] Examples of suitable compounds T having two or more thiol groups are ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate), 2,3-dimercapto-1,3,4-thiadiazole or pentaerythritol tetrakis(3-mercaptopropionate).

[0055] Preferably, compound T is selected from the group consisting of ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate) and 3-mercaptopropyltrimethoxysilane.

[0056] The molar ratio of all thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K can be 1:1 to 250:1. It is preferably 2:1 to 150:1, and more preferably 5:1 to 100:1. This quantitative ratio allows for adjustment of the pot life within the inherent limits of a particular composition, particularly depending on, for example, the catalyst content and the reactivity and amount of isocyanate present. The lower limit of the pot life is the pot life obtained for a given composition without the addition of compound T and with a specified amount of catalyst. Thus, the upper limit of the adjustable pot life is the pot life that would be achieved in the uncatalyzed isocyanate-hydroxyl reaction if no catalyst were used. Even without a catalyst, the reaction will begin at some point after mixing the two components. However, the uncatalyzed reaction proceeds more slowly and manifests itself as poorer mechanical properties in the cured material.

[0057] An important advantage achieved by the two-component polyurethane composition according to the invention is a system that cures and hardens very quickly while at the same time having a reasonably long pot life that allows processing in a user-friendly manner.A further advantage of the polyurethane composition according to the invention is the possibility of adjusting the pot life as described above.This is particularly advantageous in automated applications, for example, as it allows the pot life to be tailored to the desired application, thereby allowing further optimization of throughput times in industrial production.

[0058] The second component B firstly comprises at least one polyisocyanate I.

[0059] The polyisocyanate I is present in relatively large amounts, which is highly advantageous for the development of the mechanical properties.

[0060] The second component preferably contains sufficient polyisocyanate I to contain at least 5% by weight, preferably at least 6% by weight, and more preferably at least 7.5% by weight, of isocyanate groups, based on the total polyurethane composition.

[0061] All commercially available polyisocyanates, in particular diisocyanates, suitable for the preparation of polyurethanes can be used as polyisocyanates I for the preparation of the polyurethane polymer in the composition according to the invention.

[0062] Suitable polyisocyanates are, in particular, di- or triisocyanate monomers and oligomers, polymers, and derivatives of di- or triisocyanate monomers, and mixtures of any of these.

[0063] Suitable di- or triisocyanate aromatic monomers are, in particular, tolylene 2,4- and 2,6-diisocyanate and mixtures of any of these isomers (TDI); diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate and mixtures of any of these isomers (MDI); mixtures of MDI and MDI homologues (polymeric MDI or PMDI); 1,3- and 1,4-phenylene diisocyanate, 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene, naphthalene 1,5-diisocyanate (NDI), 3,3'-dimethyl-4,4'-diisocyanatodiphenyl (TODI), dianisidine diisocyanate (DADI), 1,3,5-tris(isocyanatomethyl)benzene, tris(4-isocyanatophenyl)methane and tris(4-isocyanatophenyl)thiophosphate.

[0064] Suitable di- or triisocyanate aliphatic monomers are, in particular, tetramethylene 1,4-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, hexamethylene 1,6-diisocyanate (HDI), 2,2,4- and 2,4,4-trimethylhexamethylenemethylene 1,6-diisocyanate (TMDI), decamethylene 1,10-diisocyanate, dodecamethylene 1,12-diisocyanate, lysine diisocyanate and lysine ester. terdiisocyanate, cyclohexane 1,3- and 1,4-diisocyanate, 1-methyl-2,4- and -2,6-diisocyanatocyclohexane, and any mixture of these isomers (HTDI or H6TDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (=isophorone diisocyanate or IPDI), perhydrodiphenylmethane 2,4'- and 4,4'-diisocyanate (HMDI or H 12Dimeric and trimeric fatty acid isocyanates such as bis(1-isocyanato-1-methylethyl)naphthalene, 3,6-bis(9-isocyanatononyl)-4,5-di-(1-heptenyl)cyclohexene (dimethyl diisocyanate), α,α,α',α',α",α"-hexamethyl-1,3,5-mesitylene triisocyanate, and bis(1-isocyanato-1-methylethyl)naphthalene.

[0065] Of these, MDI, TDI, HDI and IPDI are preferred.

[0066] Suitable oligomers, polymers and derivatives of the di- and triisocyanate monomers mentioned are in particular those derived from MDI, TDI, HDI and IPDI. Among these are commercially available types, in particular HDI biurets such as Desmodur® N 100 and N 3200 (manufactured by Covestro), Tolonate® HDB and HDB-LV (manufactured by Vencorex) and Duranate® 24A-100 (manufactured by Asahi Kasei Corporation); HDI isocyanurates such as Desmodur® N 3300, N 3600 and N 3790 BA (all manufactured by Covestro), Tolonate® HDT, HDT-LV and HDT-LV2 (manufactured by Vencorex), Duranate® TPA-100 and THA-100 (manufactured by Asahi Kasei Corporation) and Coronate® HX (manufactured by Nippon Polyurethane Industry Co., Ltd.); HDI uretdiones such as Desmodur® N 3400 (manufactured by Covestro); Desmodur® XP Particularly suitable are HDI iminooxadiazinediones such as 2410 (Covestro); HDI allophanates such as Desmodur® VP LS 2102 (Covestro); IPDI isocyanurates in solution, for example Desmodur® Z 4470 (Covestro) or in solid form, for example Vestanat® T1890 / 100 (Evonik); TDI oligomers, for example Desmodur® IL (Covestro); and mixed isocyanurates based on TDI / HDI, for example Desmodur® HL (Covestro).Also particularly suitable are MDI forms that are liquid at room temperature (so-called "modified MDI"), in particular mixtures of MDI and MDI derivatives, such as MDI carbodiimides or MDI uretonimines or MDI urethanes (known under trade names such as Desmodur® CD, Desmodur® PF, Desmodur® PC (all from Covestro) or Isonate® M 143 (from Dow)), as well as mixtures of MDI and MDI homologues (polymeric MDI or PMDI) (Desmodur® VL, Desmodur® VL 50, 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 manufactured by Dow) or Lupranat® M 10 R (manufactured by BASF). The above oligomeric polyisocyanates are in fact typically mixtures of substances with different degrees of oligomerization and / or chemical structures. They preferably have an average NCO functionality of 2.1 to 4.0.

[0067] The polyisocyanates are preferably selected from the group consisting of MDI, TDI, HDI and IPDI, as well as the oligomers, polymers and derivatives of the mentioned isocyanates, and mixtures thereof.

[0068] The polyisocyanates preferably contain isocyanurate, iminooxadiazinedione, uretdione, biuret, allophanate, carbodiimide, uretonimine or oxadiazinetrione groups.

[0069] Particularly preferred polyisocyanates are MDI forms that are liquid at room temperature. These are, in particular, so-called polymeric MDI and MDI containing a certain proportion of oligomers or their derivatives. The content of MDI (=diphenylmethane 4,4'-, 2,4'-, or 2,2'-diisocyanate, and any mixture of these isomers) in such liquid MDI forms is preferably 50 to 95% by weight, more preferably 60 to 90% by weight.

[0070] As polyisocyanates, polymeric MDI and forms of MDI which are liquid at room temperature and contain a certain proportion of MDI carbodiimide or an adduct thereof are more particularly preferred.

[0071] These polyisocyanates provide particularly good processing properties and particularly high strength.

[0072] The polyisocyanate of the second component may contain a polyurethane polymer having a proportion of isocyanate groups, which may be produced separately, or the polyisocyanate may be mixed with at least one polyol, particularly a polyether polyol, so that the isocyanate groups are present in a stoichiometric excess relative to the OH groups.

[0073] As pointed out above, in the present application it is important to include in the second component B or polyisocyanate I an isocyanate group-containing prepolymer P1 selected from polymers P1-1 based on at least one polyisocyanate, at least one polyether polyol and at least one hydroxy-terminated polybutadiene polymer, or from polymers P1-2 based on at least one polyisocyanate and at least one polyether polyol.

[0074] The above-mentioned polyisocyanates and polyether polyols and their preferred embodiments also apply to those used in the preparation of the isocyanate group-containing prepolymer P1.

[0075] In one advantageous embodiment, the polyisocyanates used in the prepolymers P1-1 and P1-2 are di- or triisocyanate aromatic monomers, in particular tolylene 2,4- and 2,6-diisocyanate and mixtures of any of these isomers (TDI); diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate and mixtures of any of these isomers (MDI); mixtures of MDI and MDI homologues (polymeric MDI or PMDI); 1,3 - and 1,4-phenylene diisocyanate, 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene, naphthalene 1,5-diisocyanate (NDI), 3,3'-dimethyl-4,4'-diisocyanatodiphenyl (TODI), dianisidine diisocyanate (DADI), 1,3,5-tris(isocyanatomethyl)benzene, tris(4-isocyanatophenyl)methane, and tris(4-isocyanatophenyl)thiophosphate.

[0076] Suitable polyisocyanates of the prepolymer P1 may also preferably be selected from aromatic diisocyanates or triisocyanates such as MDI or TDI, in particular MDI, as well as oligomers, polymers and derivatives of the isocyanates mentioned, and mixtures thereof.

[0077] The polyisocyanates for the prepolymer P1 may preferably contain isocyanurate, iminooxadiazinedione, uretdione, biuret, allophanate, carbodiimide, uretonimine or oxadiazinetrione groups.

[0078] In one advantageous embodiment, the amount of isocyanate group-containing prepolymer P1 is in the range of 10% to 40% by weight, preferably 18% to 36% by weight, based on the total weight of the composition.

[0079] The molar ratio of NCO groups to OH groups in the reaction for preparing the prepolymer P1 can generally be in the range of 2.1: 1 to 3: 1. In an advantageous embodiment, the content of NCO groups contained in the prepolymer P1 can be in the range of 8% to 12% by weight.

[0080] In the composition according to the invention, the polyisocyanate I is preferably present in an amount of 10% to 40% by weight, more preferably 15% to 35% by weight, particularly preferably 20% to 30% by weight, based on component B.

[0081] The first component A and / or the second component B further comprise at least one metal catalyst K for the reaction of hydroxyl groups with isocyanate groups, which is capable of forming thio complexes. Suitable metal catalysts K are therefore all metal catalysts which can be used as crosslinking catalysts in polyurethane chemistry and which are at the same time capable of forming thio complexes with thiols, if present.

[0082] The metal catalyst K is preferably present only in the first component A. This has the advantage that better storage stability is achieved.

[0083] Examples of suitable metal catalysts are bismuth, zinc, tin or zirconium compounds, including complexes and salts of these metals.

[0084] The metal catalyst K preferably comprises a bismuth compound, in particular a bismuth(III) compound. In addition to the desirable catalytic property of being able to form a thio complex, bismuth compounds have the advantage of low acute toxicity.

[0085] Many of the conventional bismuth catalysts can be used as the bismuth compound, examples being bismuth carboxylates such as bismuth acetate, bismuth oleate, bismuth octoate or bismuth neodecanoate, bismuth nitrate, bismuth halides such as bismuth bromide, bismuth chloride or bismuth iodide, bismuth sulfide, bismuth basic carboxylates such as bismuth neodecanoate, bismuth gallate or bismuth subsalicylate, and mixtures thereof.

[0086] In a preferred embodiment, the metal catalyst K is a bismuth(III) complex containing at least one ligand based on 8-hydroxyquinoline. Such a complex is described in EP 1 551 895. It is preferably a bismuth(III) carboxylate containing one molar equivalent of the 8-hydroxyquinoline ligand.

[0087] In a further preferred embodiment, the metal catalyst K is a bismuth(III) complex containing at least one ligand based on 1,3-ketoamide. Such complexes are described in EP 2791153. They are preferably bismuth(III) carboxylates containing 1 to 3 molar equivalents of 1,3-ketoamide ligands.

[0088] In addition to the components already mentioned, the polyurethane composition may contain further components known to those skilled in the art from two-component polyurethane chemistry, which may be present in only one component or in both components.

[0089] Preferred further constituents are in particular natural, ground or precipitated calcium carbonate, optionally coated with a fatty acid, in particular stearic acid, barite (baryte), talc, quartz flour, quartz sand, dolomite, wollastonite, kaolin, calcined kaolin, mica (potassium aluminum silicate), molecular sieves, aluminum oxide, aluminum hydroxide, magnesium hydroxide, silica, including finely divided silica derived from pyrolysis processes, industrially produced carbon black, graphite, metal powders such as aluminum, copper, iron, silver or steel, inorganic or organic fillers in PVC powder or hollow spheres, and flame-retardant fillers such as aluminum hydroxides or hydrates, in particular aluminum hydroxides or hydrates, preferably aluminum hydroxide.

[0090] The addition of fillers is advantageous in that it increases the strength of the cured polyurethane composition.

[0091] The polyurethane composition preferably contains at least one filler selected from the group consisting of calcium carbonate, carbon black, kaolin, barite, talc, quartz powder, dolomite, wollastonite, kaolin, calcined kaolin, and mica, with ground calcium carbonate, calcined kaolin, or carbon black being particularly preferred.

[0092] It may be advantageous to use a mixture of different fillers, with ground calcium carbonate or calcined kaolin in combination with carbon black being most preferred.

[0093] The content of filler F in the composition is preferably within the range of 5 to 50% by weight, more preferably 10 to 40% by weight, and particularly preferably 15 to 30% by weight, based on the total amount of the composition.

[0094] Further constituents may additionally be present, such as in particular solvents, plasticizers and / or extenders, pigments, rheology modifiers, such as in particular amorphous silica, drying agents, such as in particular zeolites, adhesion promoters, such as in particular organofunctional trialkoxysilanes, stabilizers against oxidation, heat, light and UV light, flame retardants, and surface-active substances, in particular wetting agents and defoamers.

[0095] The polyurethane composition preferably contains less than 0.5 wt. %, especially less than 0.1 wt. %, of a carboxylic acid, based on the total weight of the composition. Carboxylate ligands introduced via metal catalysts are not included in the carboxylic acids described herein.

[0096] A preferred polyurethane composition comprises a first component A, which comprises, based on the total weight of component A: 10 to 60% by weight of polyol A1, - 5 to 25% by weight of diol A2, 10 to 45% by weight of polyether polyol H, - 1 to 5% by weight of a compound T having at least one thiol group, 0.05 to 0.5% by weight of a metal catalyst K, and - 10 to 50% by weight of filler, a first component A comprising: and, optionally, further components Includes.

[0097] A preferred polyurethane composition comprises a second component B containing 10% to 40% by weight, in particular 15% to 30% by weight, of polyisocyanate I, wherein the amount of isocyanate group-containing prepolymer P1 is in the range of 25% to 75% by weight, preferably 35% to 70% by weight, based on the total weight of component B. In the present application, polyisocyanate I is the polyisocyanate compound specified above, but different from the isocyanate group-containing prepolymer P1.

[0098] Advantageously, the first and second components are combined so that their mixing ratio by parts by weight is in the range of 10:1 to 1:10, preferably 5:1 to 1:5, in particular 2:1 to 1:2 or about 1:1.

[0099] In the mixed polyurethane composition, before curing, the ratio between the number of isocyanate groups and the number of isocyanate-reactive groups is preferably in the range of approximately 1.2 to 1, more preferably 1.15 to 1.05. However, although not usually preferred, it is possible for the proportion of isocyanate groups to be substoichiometric relative to the isocyanate-reactive groups.

[0100] The two components are produced separately, preferably with the exclusion of moisture. The two components are typically stored in separate containers. The additional component of the polyurethane composition may be present as a component of the first or second component, with the additional component reactive with isocyanate groups preferably being a component of the first component. Suitable containers for storing each component are, in particular, drums, pails, bags, buckets, cans, cartridges, or tubes. Both components are storage-stable, meaning they can be stored for several months to a year or more before use without their respective properties changing to a degree relevant to their use.

[0101] The two components are kept separate prior to mixing of the composition and are mixed together only at or shortly before use, and are advantageously present in a package consisting of two separate chambers.

[0102] In a further embodiment, the invention includes a pack comprising a package having two separate chambers containing the first and second components of the composition, respectively.

[0103] The mixing is typically carried out by means of a static mixer or by means of a dynamic mixer. During mixing, care must be taken to ensure that the two components are mixed as homogeneously as possible. If the two components are not mixed completely, deviations from the favorable mixing ratio will occur locally, which can lead to deterioration of the mechanical properties.

[0104] When the first and second components come into contact, curing begins via a chemical reaction. This involves the reaction of the isocyanate groups with any other substances present that are reactive with hydroxyl and isocyanate groups. Excess isocyanate groups react primarily with moisture. As a result of these reactions, the polyurethane composition cures to form a solid material. This process is also known as crosslinking.

[0105] Therefore, the present invention also further provides a cured polyurethane composition obtainable by curing the polyurethane composition described herein.

[0106] The two-component polyurethane compositions described can be advantageously used as adhesives that can be applied by a spray process.

[0107] The present invention therefore also provides a method for joining substrates, in particular components of an electrical device, comprising: - mixing the first and second components of the polyurethane composition; - spraying the mixed composition onto at least one of the surfaces of the substrates to be joined; - joining the substrates to be joined during the pot life, and - curing the polyurethane composition The present invention relates to a method comprising:

[0108] These two substrates may consist of the same or different materials and may be parts of electrical devices, such as audio and video equipment, information technology equipment, communication terminal equipment, portable electronic devices such as laptops, mobile phones, pads, tablets, etc.

[0109] One or both of the substrates is preferably formed from metal, glass ceramic, glass, glass fiber, reinforced plastic, carbon fiber reinforced plastic, or epoxy-based thermosetting resin.

[0110] If necessary, the substrate can be pretreated before application of the composition, such pretreatment including, inter alia, physical and / or chemical cleaning processes and the application of adhesion promoters, adhesion promoter solutions or primers.

[0111] The present invention is further illustrated by the following examples, which are not intended to limit the invention in any way. [Example]

[0112] [Table 1]

[0113] Preparation of Polymers-7, -10 and -18 Polymer-7 (Polymer P1-2): 250 g of polyoxypropylene triol (ZSN-330, GPRO group; OH value 56.5 mg KOH / g), 2500 g of polyoxypropylene polyoxyethylene diol (DP-1000, GRPO group / Kukdo Chemical Company; OH value 112.0 mg KOH / g), 750 g of polyoxypropylene polyoxyethylene diol (VORANOL EP-1900), 1000 g of polymeric MDI 4,4'-methylenediphenyl diisocyanate (Suprasec® 2496, Huntsman), and 1250 g of modified MDI (Suprasec® 2020, Huntsman Shanghai) were reacted at 80°C by a known method to obtain an NCO-terminated polyurethane polymer with an isocyanate group content of 9.2 wt%.

[0114] Polymer-10 (Polymer P1-1): 750 g of polyoxypropylene triol (ZSN-330, GPRO group; OH value 56.5 mg KOH / g), 650 g of polybutadiene diol (POLYVEST HT, OH value 44-51 mg KOH / g), 1000 g of polymeric MDI (4,4'-methylenediphenyl diisocyanate) (Suprasec® 2496, Huntsman) and 1250 g of modified MDI (Suprasec® 2020, Huntsman Shanghai) were reacted at 80°C by a known method to obtain an NCO-terminated polyurethane polymer with an isocyanate group content of 11 wt%.

[0115] Polymer-18 (Polymer P1-1): 1200 g of polyoxypropylene polyoxyethylene diol (VORANOL EP-1900), 250 g of polybutadiene diol (POLYVEST HT, OH value 44-51 mg KOH / g), 1000 g of polymeric MDI (4,4'-methylenediphenyl diisocyanate) (Suprasec® 2496, Huntsman), and 1250 g of modified MDI (Suprasec® 2020, Huntsman Shanghai) were reacted at 80°C by a known method to obtain an NCO-terminated polyurethane polymer with an isocyanate group content of 9.4 wt%.

[0116] Preparation of Polyurethane Composition For each composition, the components of the first component A listed in the table were processed in the amounts listed (parts by weight or wt.%) into a homogeneous paste using a vacuum dissolver while excluding moisture, and then stored. The components of the second component B listed in the table were processed in the same way and stored. The two components were then processed for 30 seconds in a 1:1 mixing ratio using a ZST-2K-Jet300 jetting machine into a homogeneous paste, which was immediately tested as follows:

[0117] To measure the mechanical properties, the adhesives were molded into dumbbell shapes according to ISO 37, Type 3, and cured / stored at 23°C and 50% RH (relative humidity) for the times indicated in the table (7 days at 23°C). After a 24 hour conditioning period at 23°C and 50% RH, the tensile strength of the prepared specimens was measured according to ISO 37 on a Zwick Z020 tensile tester at 23°C, 50% RH, and a test speed of 10 mm / min.

[0118] To measure the final lap shear strength, various test specimens were prepared in each case by applying a bead of adhesive to a first PC plate and then placing a second PC plate on top under pressure to form an adhesive surface of 1-2 mm x 0.7 mm. The specimens were stored at 23°C for 7 days to allow them to harden, after which the lap shear strength was measured at a speed of 10 mm / min according to ISO 4587.

[0119] To measure chemical resistance, specimens prepared for the lap shear strength test were immersed in a 1:1 mixture of oleic acid and squalene for three days. They were then removed and wiped clean. They were then tested again for lap shear strength, and the test results were compared to normal lap shear strength (without immersion) for percent reduction. A smaller percent reduction indicates better chemical resistance.

[0120] To measure sprayability, a ZST-2K-Jet300 device was adjusted to a certain pressure (typically 0.2 MPa), and after mixing the A and B components in the mixing tube, the adhesive was sprayed onto the surface to be joined through a nozzle. The nozzle was positioned 4 mm away from the substrate. The adhesive was applied in a straight or arc shape, and the size of the applied bead was then measured in terms of width and height. Sizes with a height-to-width ratio greater than 0.8 were ranked as good, otherwise they were ranked as poor. After spraying was stopped, the spray nozzle was observed for drooling. If there was no drooling, it was ranked as good. However, if there was drooling or if spraying was difficult under the same pressure, it was also ranked as poor.

[0121] During the final lap shear strength test, the specimens were observed for failure morphology on the substrate after the adhesive was removed from the substrate. Cohesive failure (CF) occurs when the adhesive layer remains on both surfaces after the rupture. Adhesive failure (AF) refers to a condition in which the adhesive loses adhesion to one of the mating surfaces. The probability of AF or CF occurring on the specimens was recorded. For example, if AF occurred in 5 out of 10 specimens, a score of 50% was recorded.

[0122] Adhesion failure is particularly desirable in the electronics market, especially for repairing some electronic components such as glass screens, which are expensive and any cracks cannot be tolerated.

[0123] [Table 2]

[0124] [Table 3]

Claims

1. A polyurethane composition comprising a first component and a second component, said first component A is at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and an average molecular weight in the range from 250 to 15,000 g / mol, at least one diol A2 having two hydroxyl groups linked via a C2-C9 carbon chain, at least one compound T having at least one thiol group; Including, said second component B is at least one polyisocyanate I Including, one of the two components additionally contains at least one metal catalyst K for the reaction of hydroxyl groups with isocyanate groups, which is capable of forming thio complexes, The first component A contains acrylonitrile and styrene-grafted polyether polyol H in the range of 7.5 to 25 wt. %; the second component B comprises an isocyanate group-containing prepolymer P1 selected from polymers P1-1 based on at least one polyisocyanate, at least one polyether polyol and at least one hydroxy-terminated polybutadiene polymer, or polymers P1-2 based on at least one polyisocyanate and at least one polyether polyol; Polyurethane composition.

2. 2. The polyurethane composition according to claim 1, characterized in that the metal catalyst K comprises a bismuth(III) compound, preferably a bismuth(III) carboxylate.

3. 3. The polyurethane composition according to claim 2, wherein the bismuth(III) compound additionally contains an 8-hydroxyquinoline ligand or a 1,3-ketoamide ligand.

4. 4. The polyurethane composition according to claim 1, wherein the diol A2 is a linear aliphatic diol having two primary hydroxyl groups linked via a C4-C9 carbon chain, and is in particular selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 1,9-nonanediol.

5. 4. The polyurethane composition according to claim 1, wherein the at least one compound T comprises a polythiol compound having 2 to 6 thiol groups or a mercaptosilane.

6. 6. The polyurethane composition according to claim 5, wherein said at least one compound T is selected from the group consisting of ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate) and 3-mercaptopropyltrimethoxysilane.

7. 4. The polyurethane composition according to claim 1, wherein the molar ratio of all the thiol groups in the at least one compound T to all the metal atoms in the at least one metal catalyst K is from 1:1 to 250:1, preferably from 5:1 to 100:

1.

8. 4. The polyurethane composition according to claim 1, wherein the metal catalyst K is present in the first component A.

9. The polyurethane composition according to any one of claims 1 to 3, wherein the amount of the polyether polyol H is in the range of 12.0 to 20.0 wt% based on the total amount of the polyurethane composition.

10. 4. The polyurethane composition according to claim 1, wherein the amount of the isocyanate group-containing prepolymer P1 is in the range of 10% to 40% by weight, preferably 18% to 36% by weight, based on the total amount of the composition.

11. 1. A method for joining substrates, particularly components of an electrical device, comprising: - mixing the first and second components of the polyurethane composition of claim 1; - spraying said mixed composition onto at least one of the surfaces of said substrates to be joined; - joining the substrates to be joined during the pot life, and - curing said polyurethane composition A method comprising:

12. 12. The method of claim 11, wherein the substrates may be made of the same or different materials, such as metal, glass ceramic, glass, glass fiber reinforced plastic, carbon fiber reinforced plastic, or epoxy-based thermosetting resin.

13. 13. The method according to claim 11 or 12, wherein the substrate is a part of an electrical device such as audio and video equipment, information technology equipment, communication terminal equipment, portable electronic devices such as laptops, mobile phones, pads, tablets, etc.

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