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

Abstract

The invention relates to a polyurethane composition. The polyurethane composition consists of a first component and a second component, wherein-the first component A comprises-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 15000 g / mol, and-at least one diol A2 having two hydroxyl groups connected via a C2 to C9 carbon chain, and-at least one compound T having at least one thiol group; and-the second component B comprises-at least one polyisocyanate I; wherein one of the two components additionally comprises at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups, the reaction being capable of forming thiocomplexes; the first component A comprises an acrylonitrile and styrene grafted polyether polyol H in the range of 7.5% to 25% by weight, and the second component B comprises a prepolymer P1 comprising isocyanate groups, the prepolymer P1 is selected from the group consisting of polymers P1-1 based on at least one polyisocyanate, at least one polyether polyol and at least one hydroxyl-terminated polybutadiene polymer, or from the group consisting of polymers P1-2 based on at least one polyisocyanate and at least one polyether polyol; the invention also relates to the use thereof, in particular as an adhesive for bonding parts of consumer electronics in a spray coating process.

Description

TECHNICAL FIELD

[0001] The present invention relates to a two-component polyurethane composition and its use, in particular as an adhesive for bonding parts of consumer electronic devices in a spraying process. PRIOR ART

[0002] In the field of assembly of electronic products, especially consumer electronic products, hot melt adhesives are usually used to bond parts of electronic products, such as the frames of mobile phones and tablet computers. However, due to the chemical and physical properties of hot melt adhesives, such bonding is usually time-consuming and expensive, and requires relatively demanding operating conditions.

[0003] In addition, the use of hot melt adhesives also makes it impossible to achieve the bonding of electronic product components by a more convenient and material-saving spraying process.

[0004] Two-component polyurethane compositions based on polyols and polyisocyanates have been used for some time. The advantage of two-component polyurethane compositions is that they cure rapidly after mixing and can thus absorb and transfer higher forces after only a short time. However, two-component polyurethane compositions are generally used as structural adhesives or as matrices (binders) in composite materials.

[0005] There is a desire for an adhesive composition that is suitable for application in very small amounts of spraying, especially when bonding parts of electronic devices, and that has excellent mechanical properties and adhesion characteristics as well as a rapid curing behavior. During this period, it would be even more desirable if the pot life of such a composition could be customized for the desired use. SUMMARY OF THE INVENTION

[0007] Accordingly, the object of the present invention is to provide a two-component polyurethane composition that cures very rapidly to form a mechanically excellent and chemically resistant mass, especially when sprayed in very small amounts onto parts of electronic devices to bond them together. At the same time, it has a pot life that can be adjusted within certain limits, allowing it to be processed without problems.

[0008] This object is unexpectedly achieved with the polyurethane composition according to the invention as claimed in claim 1. The composition comprises a polyol, a short-chain diol, and also a compound having at least one thiol group in a first component and a sufficient amount of polyisocyanate in a second component. For the composition to cure, the composition further contains a metal catalyst capable of forming a thio complex, wherein the ratio of thiol groups to metal atoms in the composition is fixed. Importantly, the composition comprises a certain amount of acrylonitrile and styrene-grafted polyether polyol H in the first component, and a prepolymer P1 containing isocyanate groups, which prepolymer P1 is selected from polymer P1-1 based on at least one polyisocyanate, at least one polyether polyol, and at least one hydroxyl-terminated polybutadiene polymer, or is selected from polymer P1-2 based on at least one polyisocyanate and at least one polyether polyol.

[0009] Furthermore, it has also been found that when cured, the polyurethane composition of the invention may cause adhesion failure on the substrate from which it is applied. In electronic devices, especially for repairing some electronic components, adhesion failure on the substrate may be desirable because the adhesive can be removed without any damage, such as cracks, on the substrate.

[0010] A further aspect of the invention is the subject of the further independent claims. Particularly preferred embodiments of the invention are the subject of the dependent claims. Detailed Description

[0011] In a first aspect, the invention relates to a polyurethane composition, which consists of a first component and a second component; wherein

[0012] - The first component A comprises

[0013] - 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, and

[0014] - at least one diol A2 having two hydroxyl groups connected via a C2 to C9 carbon chain, and

[0015] - at least one compound T having at least one thiol group; and

[0016] - The second component B comprises

[0017] - at least one polyisocyanate I;

[0018] wherein one of the two components additionally comprises at least one metal catalyst K for the reaction of hydroxyl and isocyanate groups, which reaction can form a thio complex;

[0019] The first component A comprises a polyether polyol H grafted with acrylonitrile and styrene in an amount of 7.5% to 25% by weight, and

[0020] The second component B comprises a prepolymer P1 containing isocyanate groups, and the prepolymer P1 is selected from a polymer P1-1 based on at least one polyisocyanate, at least one polyether polyol, and at least one hydroxyl-terminated polybutadiene polymer, or a polymer P1-2 based on at least one polyisocyanate and at least one polyether polyol.

[0021] In a second aspect, the present invention relates to a method for bonding substrates, especially parts of electronic devices, which comprises:

[0022] mixing the two components of the polyurethane composition of the present invention; and

[0023] spraying the mixed composition onto the parts to be bonded.

[0024] In this document, the prefix "poly" in substance names such as "polyol", "polyisocyanate", "polyether", or "polyamine" indicates that the respective substance formally contains more than one functional group / molecule that appears in its name.

[0025] In this document, the term "polymer" first encompasses a group of macromolecules that are chemically homogeneous but have different degrees of polymerization, molar masses, and chain lengths, and this group is prepared by a "poly" reaction (polymerization, addition polymerization, condensation polymerization). The term secondly also encompasses derivatives of such a group of macromolecules obtained by polymerization reactions, that is, compounds obtained by reactions of functional groups on the defined macromolecules (such as addition or substitution) and that may be chemically homogeneous or chemically inhomogeneous. The term also further encompasses so-called prepolymers, that is, reactive initial oligomer adducts whose functional groups participate in the construction of macromolecules.

[0026] The term "polyurethane polymer" encompasses all polymers prepared according to the so-called diisocyanate addition polymerization method. This also includes polymers that contain little or almost no urethane groups. Examples of polyurethane polymers are polyether polyurethanes, polyester polyurethanes, polyether polyureas, polyureas, polyester polyureas, polyisocyanurates, and polycarbodiimides.

[0027] In this document, "molecular weight" is understood to mean the molar mass of a molecule or molecular residue (in grams per mole). "Average molecular weight" refers to the number-average M of a polydisperse mixture of oligomer or polymer molecules or molecular residues n, which is typically determined by gel permeation chromatography (GPC) using polystyrene as a standard. In this document, "room temperature" refers to a temperature of 23 °C. Unless otherwise stated, weight percentage values (abbreviated as wt.-%) refer to the mass ratio of the component in the composition based on the total composition. In this document, the terms "mass" and "weight" are used synonymously.

[0028] "Primary hydroxyl group" refers to an OH group attached to a carbon atom having two hydrogens.

[0029] In this document, "pot life" refers to the time during which the polyurethane composition can be processed after mixing the two components before the viscosity due to the progress of the crosslinking reaction becomes too high to allow further processing.

[0030] In this document, the term "strength" refers to the strength of the cured composition, where strength particularly means tensile strength and modulus of elasticity, particularly within the elongation range of 0.05% to 0.25%.

[0031] In this document, "room temperature" refers to a temperature of 23 °C.

[0032] A substance or composition is described as "storage stable" or "storable" if it can be stored at room temperature in a suitable container for an extended period of time, typically at least 3 months up to 6 months or longer, without this storage causing any change in its application or use properties, particularly viscosity and crosslinking rate, to an extent relevant to its use.

[0033] All industry standards and specifications mentioned in this document refer to the effective version as of the date of first submission.

[0034] The first component A first contains 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 15000 g / mol.

[0035] Suitable polyols A1 are in principle all polyols currently used in the preparation of polyurethane polymers. Particularly suitable are polyether polyols, polyester polyols, poly(meth)acrylate polyols, polybutadiene polyols, polycarbonate polyols, and also mixtures of these polyols.

[0036] Suitable polyether polyols, also known as polyoxyalkylene polyols or oligoether alcohols, are in particular those which are the polymerization products of ethylene oxide, 1,2-epoxypropane, 1,2- or 2,3-epoxybutane, oxetane, tetrahydrofuran or mixtures thereof optionally polymerized with starting molecule having two or more active hydrogen atoms such as water, ammonia, or compounds having multiple OH or NH groups, for example 1,2-ethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, diethylene glycol, triethylene glycol, isomeric dipropylene glycol and tripropylene glycol, isomeric butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, 1,3- and 1,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, 1,1,1-trimethylol ethane, 1,1,1-trimethylol propane, glycerol, aniline, and mixtures of the listed compounds.

[0037] Polyoxyalkylene polyols with low unsaturation (measured according to ASTM D-2849-69 and expressed in milliequivalents of unsaturation per gram of polyol (mEq / g)), for example those prepared using so-called double metal cyanide complex catalysts (DMC catalysts), and polyoxyalkylene polyols with relatively high unsaturation (for example those prepared using anionic catalysts such as NaOH, KOH, CsOH or alkali metal alcoholates) can both be employed.

[0038] Particularly suitable are polyoxyethylene polyols and polyoxypropylene polyols, especially polyoxyethylene diols, polyoxypropylene diols, polyoxyethylene triols and polyoxypropylene triols.

[0039] Particularly suitable are polyoxyalkylene diols or polyoxyalkylene triols having an unsaturation below 0.02 mEq / g and having a molecular weight in the range of 1000 to 15 000 g / mol, and also polyoxyethylene diols, polyoxyethylene triols, polyoxypropylene diols and polyoxypropylene triols having a molecular weight of 400 to 15 000 g / mol.

[0040] Also particularly suitable are so-called ethylene oxide-capped (EO-capped / ethylene oxide-capped) polyoxypropylene polyols. The latter are special polyoxypropylene polyoxyethylene polyols which are obtained, for example, when pure polyoxypropylene polyols, especially polyoxypropylene diols and triols, are further alkoxylated with ethylene oxide after the polypropoxylation reaction is completed, and thus have primary hydroxyl groups. In this case, polyoxypropylene polyoxyethylene diols and polyoxypropylene polyoxyethylene triols are preferred.

[0041] Also suitable are hydroxyl-terminated polybutadiene polyols, for example those prepared by the polymerization of 1,3-butadiene and allyl alcohol or by the oxidation of polybutadiene, and also their hydrogenation products.

[0042] Also suitable are styrene-acrylonitrile graft polyether polyols, such as those commercially available from Elastogran GmbH, Germany.

[0043] Suitable polyester polyols particularly include polyesters carrying at least two hydroxyl groups and prepared by known methods, in particular by polycondensation of hydroxycarboxylic acids with diols or polyols or of aliphatic and / or aromatic polycarboxylic acids with diols or polyols.

[0044] More suitable are polyester polyols prepared from diols to triols (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) with organic dicarboxylic acids or their acid anhydrides or esters (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), and also polyester polyols formed from lactones such as ε-caprolactone.

[0045] Particularly suitable are polyester diols, especially those prepared from adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, dimer fatty acid, phthalic acid, isophthalic acid and terephthalic acid as dicarboxylic acids or from lactones such as ε-caprolactone and from ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, dimer fatty acid diol and 1,4-cyclohexanedimethanol as diols.

[0046] Suitable polycarbonate polyols particularly include those obtainable by reaction of, for example, the abovementioned alcohols used for constructing polyester polyols with dialkyl carbonates such as dimethyl carbonate, diaryl carbonates such as diphenyl carbonate, or phosgene. Also suitable are polycarbonates obtainable by copolymerization of CO2 with epoxides such as ethylene oxide and propylene oxide. Polycarbonate diols, especially amorphous polycarbonate diols, are particularly suitable.

[0047] Further suitable polyols are poly(meth)acrylate polyols.

[0048] Also suitable are polyhydroxy-functional fats and oils, such as natural fats and oils, in particular 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 by chemically linking natural fats and oils by degradation processes such as alcoholysis or ozonolysis and subsequent transesterification or dimerization, for example, of the degradation products or their derivatives thus obtained. Suitable degradation products of natural fats and oils are in particular fatty acids and fatty alcohols as well as fatty acid esters, in particular methyl esters (FAME), which can be derivatized to hydroxy fatty acid esters, for example, by hydroformylation and hydrogenation.

[0049] Furthermore, equally suitable are polyhydrocarbon polyols, also known as oligomeric hydrocarbon alcohols, such as polyhydroxy-functional ethylene-propylene, ethylene-butene or ethylene-propylene-diene copolymers, such as those prepared by Kraton Polymers, USA, or polyhydroxy-functional copolymers of dienes (such as 1,3-butadiene) or mixtures of dienes and vinyl monomers (such as styrene, acrylonitrile or isobutene), or polyhydroxy-functional polybutadiene polyols, such as those prepared by copolymerization of 1,3-butadiene and allyl alcohol and which can also be hydrogenated.

[0050] Also suitable are polyhydroxy-functional acrylonitrile / butadiene copolymers (such as those which can be prepared from epoxides or amino alcohols) and carboxyl-terminated acrylonitrile / butadiene copolymers, which are commercially available under the name (formerly known as ) CTBN from Emerald Performance Materials, LLC, USA.

[0051] All of the listed polyols have an average molecular weight in the range from 250 to 15,000 g / mol, preferably from 400 to 10,000 g / mol, more preferably from 1,000 to 8,000 g / mol and an average OH functionality in the range from 1.5 to 4, preferably from 1.7 to 3. However, it is entirely possible for the composition to also include a certain proportion of monoalcohols (polymers having only one hydroxyl group).

[0052] 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.

[0053] The first component A further comprises at least one diol A2 having two hydroxyl groups linked via a C2 to C9 carbon chain.

[0054] Suitable as diol A2 are straight-chain or branched alkylene diols having two primary or secondary hydroxyl groups, alkylene diols having one primary hydroxyl group and one secondary hydroxyl group, and alicyclic diols.

[0055] Diol A2 is preferably a straight-chain aliphatic diol having two primary hydroxyl groups linked via a C4 to C9 carbon chain.

[0056] In particular, diol A2 is selected from the group consisting of 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.

[0057] 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.

[0058] Diol A2 is most preferably selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,9-nonanediol. These diols are readily commercially available and provide polyurethanes having a particularly high modulus of elasticity at low elongation upon curing.

[0059] The first component A preferably contains 5% to 25% by weight of diol A2.

[0060] One of the key points of the present invention is that the first component A contains a polyether polyol H grafted with acrylonitrile and styrene, which is important for achieving the desired spray application and improving the adhesion properties of the substrate to be bonded. Necessarily, the amount of polyether polyol H is in the range of 7.5% - 25% by weight, preferably 12.0% - 20.0% by weight, based on the total polyurethane composition. It has been found that if polyether polyol H is used in an amount exceeding 25% by weight, the spray application may become difficult. In some cases, exceeding 25% by weight may also deteriorate mechanical properties such as elongation at break.

[0061] This acrylonitrile- and styrene-grafted polyether polyol is a polyether based on a polyether polyol grafted with acrylonitrile and styrene monomers, and can be obtained by free radical graft polymerization at a specific temperature under nitrogen protection and with the aid of an initiator. The polyether polyols suitable as starting materials for grafting can be those listed above as preferred polyether polyols.

[0062] The acrylonitrile- and styrene-grafted polyether polyol H can be commercially available under trademarks such as CHP-H45 from Changhua Chemical.

[0063] In addition to the polyols A1, A2, and H listed above, small amounts of other low molecular weight diols or polyols such as diethylene glycol, triethylene glycol, isomeric dipropylene glycol and tripropylene glycol, isomeric decanediol and undecanediol, hydrogenated bisphenol A, dimerized fatty alcohols, 1,1,1-trimethylol ethane, 1,1,1-trimethylol propane, glycerol, pentaerythritol, sugar alcohols such as xylitol, sorbitol or mannitol, sugars such as sucrose, other higher polyols, low molecular weight alkoxylated products of the above-mentioned diols and polyols, and mixtures of the above-mentioned alcohols can also be included. In addition, polyols containing other heteroatoms, such as methyldiethanolamine or thiodiglycol, can also be included.

[0064] 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 / thiol group and which can be formulated into the composition according to the invention. Here, the thiol group should be understood to mean the -SH group attached to an organic group (e.g., an aliphatic, alicyclic or aromatic carbon group).

[0065] Compounds having 1 to 6, more preferably 1 to 4, and most preferably 1 or 2 thiol groups are preferably considered. Compounds having a thiol group have the advantages that they do not form complexes with the metal catalyst K that tend to have poor solubility, and the pot life can be adjusted particularly precisely. Compounds having two thiol groups have the advantage that the mechanical properties of the composition are improved after curing.

[0066] Examples of suitable compounds T having a thiol group are 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercapto-1,2-propanediol, 2-mercaptotolylimidazole or 2-mercaptobenzothiazole.

[0067] Examples of suitable compounds T having more than one thiol group are ethylene glycol bis(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexakis(3-mercaptopropionate), 2,3-dimercapto-1,3,4-thiadiazole or pentaerythritol tetrakis(3-mercaptopropionate).

[0068] Compound T is preferably selected from the group consisting of ethylene glycol bis(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate), and 3-mercaptopropyltrimethoxysilane.

[0069] The molar ratio of all thiol groups in said at least one compound T to all metal atoms in said at least one metal catalyst K can be from 1:1 to 250:1. It is preferably from 2:1 to 150:1, more preferably from 5:1 to 100:1. This quantitative ratio allows for the specific adjustment of the pot life within the inherent limits of a particular composition, for example, by the content of the catalyst, the reactivity of the isocyanates present, and their amounts. The lower limit of the pot life is the pot life obtained in a given composition when using the defined amount of catalyst without adding compound T. The upper limit of the adjustable pot life is correspondingly the pot life that would be obtained if the isocyanate-hydroxy reaction were uncatalyzed. Even without using a catalyst, the reaction will start at some point after mixing the two components. However, the uncatalyzed reaction proceeds more slowly and is accompanied by the development of poorer mechanical properties in the cured material.

[0070] The key advantage obtained with the two-component polyurethane composition according to the invention is a system that cures and hardens at an extraordinary speed while having a pot life long enough to allow it to be processed 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 application and can, for example, allow for further optimization of production times in industrial production, since the pot life can be tailored to the desired use.

[0071] The second component B first comprises at least one polyisocyanate I.

[0072] The polyisocyanate I is present in a relatively high amount, which is very advantageous for the development of mechanical properties.

[0073] The second component can preferably contain enough polyisocyanate I such that it contains at least 5% by weight, preferably at least 6% by weight, more preferably at least 7.5% by weight of isocyanate groups based on the total polyurethane composition.

[0074] All commercially available polyisocyanates suitable for polyurethane preparation, especially diisocyanates, can be used as the polyisocyanate I for preparing the polyurethane polymer in the composition according to the invention.

[0075] Suitable polyisocyanates are in particular monomeric diisocyanates or triisocyanates as well as oligomers, polymers, and derivatives of monomeric diisocyanates or triisocyanates and any mixtures thereof.

[0076] Suitable aromatic monomeric diisocyanates or triisocyanates are in particular benzylidene 2,4- and 2,6-diisocyanates and any mixtures of these isomers (TDI), diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanates and any mixtures of these isomers (MDI), mixtures of MDI and MDI homologues (polymeric MDI or PMDI), 1,3- and 1,4-phenylene diisocyanates, 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene, naphthalene 1,5-diisocyanate (NDI), 3,3'-dimethyl-4,4'-diisocyanatobiphenyl (TODI), dimethoxyaniline diisocyanate (DADI), 1,3,5-tris(isocyanatomethyl)benzene, tris(4-isocyanatophenyl)methane and tris(4-isocyanatophenyl) thiophosphate.

[0077] Suitable aliphatic monomeric diisocyanates or triisocyanates are in particular tetramethylene 1,4-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, hexamethylene 1,6-diisocyanate (HDI), 2,2,4- and 2,4,4-trimethylhexamethylene 1,6-diisocyanate (TMDI), decamethylene 1,10-diisocyanate, dodecamethylene 1,12-diisocyanate, lysine diisocyanate and lysine ester diisocyanate, cyclohexane 1,3- and 1,4-diisocyanates, 1-methyl-2,4- and -2,6-diisocyanatocyclohexane and any mixtures 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 12 MDI), 1,4-diisocyanato-2,2,6-trimethylcyclohexane (TMCDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, meta- and para-xylylene diisocyanates (meta- and para-XDI), meta- and para-tetramethylxylylene 1,3- and 1,4-diisocyanates (meta- and para-TMXDI) and bis(1-isocyanato-1-methylethyl)naphthalene, dimer and trimer fatty acid isocyanates such as 3,6-bis(9-isocyanatononyl)-4,5-di-(1-heptenyl)cyclohexene (dimer diisocyanate) and α,α,α',α',α”,α”-hexamethyl-1,3,5-mesitylene triisocyanate.

[0078] Among these, MDI, TDI, HDI and IPDI are preferably considered.

[0079] Suitable oligomers, polymers and derivatives of the monomeric diisocyanates and triisocyanates listed are in particular those derived from MDI, TDI, HDI and IPDI. Particularly suitable among these are the commercially available types, in particular HDI biurets such as N100 and N 3200 (from Covestro), HDB and HDB-LV (from Vencorex) and 24A-100 (from Asahi Kasei); HDI isocyanurates such as N 3300, N 3600 and N 3790BA (all from Covestro), HDT, HDT-LV and HDT-LV2 (from Vencorex), TPA-100 and THA-100 (from AsahiKasei) and HX (from Nippon Polyurethane); HDI uretdiones such as N 3400 (from Covestro); HDI iminooxadiazinediones such as XP 2410 (from Covestro); HDI urethanes such as VP LS2102 (from Covestro); IPDI isocyanurates, for example in solution form such as Z 4470 (from Covestro) or in solid form such as T1890 / 100 (from Evonik); TDI oligomers such as IL (from Covestro); and also mixed isocyanurates based on TDI / HDI, for example, such as HL (from Covestro). Also particularly suitable are MDI forms that are liquid at room temperature (so-called "modified MDI"), which are mixtures of MDI and MDI derivatives, such as, in particular, MDI carbodiimide or MDI uretonimine or MDI ethyl carbamate, under trade names such as CD, PF, PC (all from Covestro) or M 143 (from Dow), and mixtures of MDI and MDI homologues (polymeric MDI or PMDI), under trade names such as VL,

[0080] VL50, VL R10, VL R20,

[0081] VH 20N, and VKS20F (all from Covestro), M309, M 229, and M 580 (all from Dow), or M 10R (from BASF). The above oligomeric polyisocyanates are actually typically mixtures of substances having different degrees of oligomerization and / or chemical structures. They preferably have an average NCO functionality of 2.1 to 4.0.

[0082] The polyisocyanates are preferably selected from the group consisting of MDI, TDI, HDI, and IPDI, and oligomers, polymers, and derivatives of the listed isocyanates, and mixtures thereof.

[0083] The polyisocyanates preferably contain isocyanurate, iminooxadiazinedione, uretdione, biuret, urethane, carbodiimide, uretonimine, or oxadiazinetrione groups.

[0084] Particularly preferred polyisocyanates are the MDI forms that are liquid at room temperature. These are in particular so-called polymeric MDI and also MDI containing a certain proportion of its oligomers or 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 wt% to 95 wt%, more preferably 60 wt% to 90 wt%.

[0085] Even more particularly preferred as the polyisocyanate is polymeric MDI and MDI forms that are liquid at room temperature and contain a certain proportion of MDI carbodiimide or its adducts.

[0086] In the case of these polyisocyanates, particularly good processing properties and particularly high strength are obtained.

[0087] The polyisocyanate of the second component may contain a certain proportion of polyurethane polymers having isocyanate groups. The second component may comprise a separately prepared polyurethane polymer having isocyanate groups, or the polyisocyanate has been mixed with at least one polyol, in particular a polyether polyol, in which the isocyanate groups are present in a stoichiometric excess relative to the OH groups.

[0088] As pointed out above, it is important in the present application to include in the second component B or in the polyisocyanate I a prepolymer P1 containing isocyanate groups, which prepolymer P1 is selected from polymer P1-1 based on at least one polyisocyanate, at least one polyether polyol and at least one hydroxyl-terminated polybutadiene polymer, or from polymer P1-2 based on at least one polyisocyanate and at least one polyether polyol.

[0089] The polyisocyanates and polyether polyols as specified above and their preferred forms are also suitable for those used in the preparation of the prepolymer P1 containing isocyanate groups.

[0090] In an advantageous embodiment, the polyisocyanates for prepolymers P1-1 and P1-2 can include aromatic monomeric diisocyanates or triisocyanates, especially benzylidene 2,4- and 2,6-diisocyanates and any mixture of these isomers (TDI), diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanates and any mixture of these isomers (MDI), mixtures of MDI and MDI homologues (polymeric MDI or PMDI), 1,3- and 1,4-phenylene diisocyanates, 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene, naphthalene 1,5-diisocyanate (NDI), 3,3'-dimethyl-4,4'-diisocyanatobiphenyl (TODI), dimethoxyaniline diisocyanate (DADI), 1,3,5-tris(isocyanatomethyl)benzene, tris(4-isocyanatophenyl)methane and tris(4-isocyanatophenyl) thiophosphate.

[0091] Suitable polyisocyanates for prepolymer P1 can also preferably be selected from aromatic diisocyanates or triisocyanates such as MDI or TDI, especially MDI, and oligomers, polymers and derivatives of the listed isocyanates, and mixtures thereof.

[0092] The polyisocyanate for prepolymer P1 can preferably contain isocyanurate, iminooxadiazinedione, uretdione, biuret, urethane, carbodiimide, uretonimine or oxadiazinetrione groups.

[0093] In an advantageous embodiment, based on the overall composition, the amount of the prepolymer P1 containing isocyanate groups is in the range of 10 wt% to 40 wt%, preferably 18 wt% to 36 wt%.

[0094] During the reaction for preparing prepolymer P1, the molar ratio of NCO groups to OH groups can generally be in the range of 2.1:1 to 3:1. In an advantageous embodiment, the content of NCO groups contained in prepolymer P1 can be in the range of 8 wt% to 12 wt%.

[0095] In the composition according to the invention, the polyisocyanate I is preferably present in an amount of from 10% to 40% by weight, more preferably from 15% to 35% by weight, particularly preferably from 20% to 30% by weight, based on component B.

[0096] The first component A and / or the second component B further comprises at least one metal catalyst K for the reaction of hydroxyl and isocyanate groups, which reaction is capable of forming a thio complex. Suitable metal catalysts K are all metal catalysts that can be used as crosslinking catalysts in polyurethane chemistry and that can simultaneously form a thio complex with them in the presence of thiols.

[0097] The metal catalyst K is preferably present only in the first component A. This has the advantage of obtaining better storage stability.

[0098] Examples of suitable metal catalysts are bismuth, zinc, tin or zirconium compounds, including complexes and salts of these metals.

[0099] The metal catalyst K preferably comprises a bismuth compound, in particular a bismuth(III) compound. In addition to the desired properties as a catalyst capable of forming a thio complex, bismuth compounds also have the advantage of low acute toxicity.

[0100] A variety of conventional bismuth catalysts can be used as bismuth compounds. Examples are bismuth carboxylates, such as bismuth acetate, bismuth oleate, bismuth octanoate or bismuth neodecanoate; bismuth nitrate; bismuth halides, such as bismuth bromide, bismuth chloride or bismuth iodide; bismuth sulfide; basic bismuth carboxylates, such as bismuth neodecanoate, bismuth subgallate or bismuth subsalicylate; and mixtures thereof.

[0101] In a preferred embodiment, the metal catalyst K is a bismuth(III) complex containing at least one ligand based on 8-hydroxyquinoline. Such complexes are described in EP 1551895. This is preferably bismuth(III) carboxylate containing one molar equivalent of 8-hydroxyquinoline ligand.

[0102] 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. This is preferably bismuth(III) carboxylate containing 1 to 3 molar equivalents of 1,3-ketoamide ligand.

[0103] In addition to the components already mentioned, the polyurethane composition may also contain further components known to the person skilled in the art from two-component polyurethane chemistry. These can be present in only one component or in both components.

[0104] Preferred additional components are inorganic or organic fillers such as, in particular, natural, ground or precipitated calcium carbonate, baryte / heavyspar, talc, quartz powder, quartz sand, dolomite, wollastonite, kaolin, calcined kaolin, mica (potassium aluminosilicate), molecular sieves, alumina, aluminum hydroxide, magnesium hydroxide, silica (including finely divided silica from a pyrolysis process), industrially produced carbon black, graphite, metal powders such as aluminum, copper, iron, silver or steel, PVC powder or hollow spheres, and also flame retardant fillers such as hydroxides or hydrates, in particular aluminum hydroxide or hydrate, preferably aluminum hydroxide.

[0105] The advantage of adding fillers is that they increase the strength of the cured polyurethane composition.

[0106] The polyurethane composition preferably contains at least one filler selected from the group consisting of calcium carbonate, carbon black, kaolin, baryte, talc, quartz powder, dolomite, wollastonite, kaolin, calcined kaolin and mica. Particularly preferred as fillers are ground calcium carbonate, calcined kaolin or carbon black.

[0107] It can be advantageous to use a mixture of different fillers. Most preferred is a combination of ground calcium carbonate or calcined kaolin and carbon black.

[0108] Based on the total composition, the content of filler F in the composition is preferably in the range of 5% to 50% by weight, more preferably 10% to 40% by weight, particularly preferably 15% to 30% by weight.

[0109] There can additionally be present further components, in particular solvents, plasticizers and / or extenders, pigments, rheological modifiers (such as, in particular, amorphous silica), desiccants (such as, in particular, zeolites), adhesion promoters (such as, in particular, organofunctional trialkoxysilanes), stabilizers against oxidation, heat, light and UV radiation, flame retardant substances, and also surface-active substances, in particular wetting agents and defoamers.

[0110] Based on the total composition, the polyurethane composition preferably contains less than 0.5% by weight, in particular less than 0.1% by weight, of carboxylic acid. Any carboxylate ligands introduced by the metal catalyst are not included in the carboxylic acids described herein.

[0111] The preferred polyurethane composition comprises a first component A which, based on the total weight of component A, comprises

[0112] - 10% to 60% by weight of polyol A1,

[0113] - 5% to 25% by weight of diol A2,

[0114] - 10 wt% to 45 wt% of polyether polyol H,

[0115] - 1 wt% to 5 wt% of a compound T having at least one thiol group,

[0116] - 0.05 wt% to 0.5 wt% of a metal catalyst K, and

[0117] - 10 wt% to 50 wt% of a filler,

[0118] and optionally additional ingredients.

[0119] A preferred polyurethane composition comprises a second component B which comprises 10 wt% to 40 wt%, in particular 15 wt% to 30 wt%, of a polyisocyanate I, wherein based on the total weight of component B, the amount of the prepolymer P1 containing isocyanate groups is in the range of 25 wt% to 75 wt%, preferably 35 wt% to 70 wt%. In the present application, the polyisocyanate I is a polyisocyanate compound as specified above but different from the prepolymer P1 containing isocyanate groups.

[0120] Advantageously, the first component and the second component are formulated such that their weight part mixing ratio 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.

[0121] In the mixed polyurethane composition, the ratio between the number of isocyanate groups and the number of groups reactive towards isocyanate before curing is preferably in the range of about 1.2 to 1, more preferably 1.15 to 1.05. However, although not usually preferred, the proportion of isocyanate groups can also be sub-stoichiometric with respect to the groups reactive towards isocyanate.

[0122] The preparation of these two components is carried out separately and preferably under exclusion of moisture. These two components are typically stored in separate containers. The additional ingredients of the polyurethane composition can be present as ingredients of the first component or the second component, wherein the additional ingredients reactive towards isocyanate groups are preferably ingredients of the first component A. Suitable containers for the storage of each component are in particular drums, sealed metal hobbocks, bags, buckets, cans, cartridges or tubes. Both components are storage-stable, meaning that they can be stored for several months up to one year or longer before use, with their respective properties related to their use remaining to a certain extent unchanged.

[0123] Before the mixed composition, the two components are stored separately and are only mixed with each other when in use or immediately before use. Advantageously, they are present in a packaging consisting of two separate chambers.

[0124] In a further aspect, the present invention comprises a packaging which consists of a packaging having two separate chambers which respectively contain the first component and the second component of the composition.

[0125] Mixing is typically achieved via 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 evenly as possible. If the two components are not mixed completely, local deviations from the favorable mixing ratio will occur, which may lead to deterioration of the mechanical properties.

[0126] When the first component comes into contact with the second component, curing starts by a chemical reaction. This involves the reaction of hydroxyl groups and any other substances present that are reactive towards isocyanate groups with the isocyanate groups. The excess isocyanate groups mainly react with moisture. Due to these reactions, the polyurethane composition cures to obtain a solid material. This operation is also called crosslinking.

[0127] Therefore, the present invention further provides a cured polyurethane composition obtained by curing a polyurethane composition as described in this document.

[0128] The described two-component polyurethane composition is advantageously usable as an adhesive that can be applied in a spraying process.

[0129] Therefore, the present invention also relates to a method for bonding substrates, especially parts of electronic devices, which comprises the following steps:

[0130] - Mixing the first component and the second component of the polyurethane composition as described above,

[0131] - Spraying the mixed composition onto at least one of the surfaces of the substrates to be bonded,

[0132] - Joining the substrates to be bonded within the pot life, and

[0133] - Curing the polyurethane composition.

[0134] The two substrates can be made of the same material or different materials and are especially parts of electronic devices (such as audio and video devices, information technology equipment, telecommunication terminal equipment, portable electronic devices such as laptop computers, mobile phones, tablets, tablet computers, etc.).

[0135] One or both substrates are preferably made of metal, or glass ceramic, or glass, or glass fiber reinforced plastic, or carbon fiber reinforced plastic or an epoxy-based thermosetting material.

[0136] If desired, the substrate can be pretreated before applying the composition. Such pretreatment particularly includes physical and / or chemical cleaning processes and the application of an adhesion promoter, an adhesion promoter solution, or a primer.

[0137] The present invention is further illustrated by the following examples, which are not intended to limit the invention in any way.

[0138] Examples

[0139] Substances used:

[0140]

[0141]

[0142] Preparation of Polymer-7, Polymer-10 and Polymer-18

[0143] Polymer - 7 (Polymer P1 - 2):

[0144] React 250 g of polyoxypropylene triol (ZSN - 330, GPRO group; OH value 56.5 mg KOH / g), 2500 g of polyoxypropylene polyoxyethylene glycol (DP - 1000, GRPO group / Kukdo Chemical Company; OH value 112.0 mg KOH / g), 750 g of polyoxypropylene polyoxyethylene glycol (VORANOL EP - 1900), 1000 g of polymeric MDI 4,4'-methylenediphenyl diisocyanate ( 2496, Huntsman) and 1250 g of modified MDI ( 2020, Huntsman Shanghai) at 80 °C by a known method to obtain an NCO - terminated polyurethane polymer having an isocyanate group content of 9.2 wt%.

[0145] Polymer - 10 (Polymer P1 - 1):

[0146] React 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 mgKOH / g), 1000 g of polymeric MDI (4,4'-methylenediphenyl diisocyanate) ( 2496, Huntsman) and 1250 g of modified MDI ( In 2020, NCO-terminated polyurethane polymers with an isocyanate group content of 11 wt% were obtained by reacting (Huntsman Shanghai) at 80 °C by a known method.

[0147] Polymer - 18 (Polymer P1 - 1):

[0148] 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) ( 2496, Huntsman) and 1250 g of modified MDI ( In 2020, NCO-terminated polyurethane polymers with an isocyanate group content of 9.4 wt% were obtained by reacting (Huntsman Shanghai) at 80 °C by a known method.

[0149] Preparation of polyurethane composition

[0150] For each composition, the components of the first component A specified in the table were processed into a homogeneous paste in the absence of moisture by means of a vacuum dissolver in the specified amounts (in parts by weight or wt.-%) and stored. The components of the second component B specified in the table were processed and stored in a similar manner. Then, these two components were processed for 30 seconds at a mixing ratio of 1:1 by means of a spraying machine ZST - 2K - Jet300 to form a homogeneous paste, which was immediately tested as follows:

[0151] To determine the mechanical properties, the adhesive was made into dumbbell-shaped specimens, type 3, according to ISO 37 and cured / stored at 23 °C and 50% RH (relative humidity) for the time specified in the table (7 days at 23 °C). After conditioning for a period of 24 h at 23 °C and 50% RH, the tensile strength of the test specimens thus prepared was measured at 23 °C and 50% RH and a test speed of 10 mm / min on a Zwick Z020 tensile testing machine according to ISO 37.

[0152] To measure the ultimate lap shear strength, various test specimens were prepared by applying adhesive beads on the first PC board in each case and then placing the second PC board on it under pressure to form an adhesive surface of 1 - 2 mm × 0.7 mm. After the test specimens were stored and cured at 23 °C for 7 days, the lap shear strength was determined at a speed of 10 mm / mins according to ISO 4587.

[0153] To measure chemical resistance, samples prepared as in the lap shear strength test were immersed in a 1:1 mixture of oleic acid and squalene for 3 days. Then, they were taken out and wiped clean. Their lap shear strength was tested again, and the test results were compared with the normal lap shear strength (without immersion) for percentage reduction. The smaller the percentage reduction, the better the chemical resistance.

[0154] To measure sprayability, the device ZST-2K-Jet300 was adjusted to a certain pressure (usually 0.2 MPa) to spray the adhesive through the nozzle onto the surface to be bonded after mixing components A and B in the mixing tube. The nozzle was 4 mm away from the substrate. The adhesive was applied in a straight line or in an arc form, and then the width and height of the applied bead size were measured. A size with a height-to-width ratio greater than 0.8 was rated as good, otherwise it was rated as poor. After stopping spraying, the sagging phenomenon of the spray nozzle was observed. If there was no sagging, it was rated as good. But if there was sagging or it was even difficult to spray at the same pressure, it was rated as poor.

[0155] During the final lap shear strength test, the failure mode of the samples on the substrate after removing the adhesive from the substrate was observed. Cohesive failure (CF) occurred when the fracture allowed the layer of the adhesive to remain on both surfaces. Adhesive failure (AF) refers to the state when the adhesive loses adhesion from one of the bonding surfaces. The occurrence probability of AF or CF in the test samples was recorded in %. For example, if AF occurred on five out of ten samples, it was recorded as 50%.

[0156] In the electronics market, especially for repairing some electronic components such as glass screens that may be expensive and do not allow any cracks, adhesive failure is particularly desirable.

[0157] Table 1: Compositions of each example

[0158]

[0159]

[0160] Table 2: Measured properties of each example

[0161]

Claims

1. A polyurethane composition, which consists of a first component and a second component; wherein - The first component A comprises - 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, and - at least one diol A2 having two hydroxyl groups connected via a C2 to C9 carbon chain, and - at least one compound T having at least one thiol group; and - The second component B comprises - at least one polyisocyanate I; wherein one of the two components additionally comprises at least one metal catalyst K for the reaction of hydroxyl and isocyanate groups, and the reaction can form a thio complex; The first component A comprises acrylonitrile and styrene-grafted polyether polyol H in the range of 7.5 wt% - 25 wt%, and The second component B comprises a prepolymer P1 containing isocyanate groups, and the prepolymer P1 is selected from polymer P1-1 based on at least one polyisocyanate, at least one polyether polyol and at least one hydroxyl-terminated polybutadiene polymer, or selected from polymer P1-2 based on at least one polyisocyanate and at least one polyether polyol.

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

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

4. The polyurethane composition according to any one of claims 1 to 3, characterized in that, The diol A2 is a straight-chain aliphatic diol having two primary hydroxyl groups connected via a C4 to C9 carbon chain, particularly selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 1,9-nonanediol.

5. The polyurethane composition according to any one of the preceding claims, characterized in that The at least one compound T comprises a polythiol compound having 2 to 6 thiol groups, or a mercapto silane.

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

7. The polyurethane composition according to any one of the preceding claims, characterized in that 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 1:1 to 250:1 and preferably 5:1 to 100:

1.

8. The polyurethane composition according to any one of the preceding claims, characterized in that, The metal catalyst K is present in the first component A.

9. The polyurethane composition according to any one of the preceding claims, characterized in that, The amount of the polyether polyol H is in the range of 12.0 wt% - 20.0 wt% based on the total polyurethane composition.

10. The polyurethane composition according to any one of the preceding claims, characterized in that, Based on the total composition, the amount of the prepolymer P1 containing isocyanate groups is in the range of 10 wt% to 40 wt%, preferably 18 wt% to 36 wt%.

11. A method for bonding substrates, especially parts of electronic devices, which comprises the following steps: - Mixing the first component and the second component of the polyurethane composition as described above, - Spraying the mixed composition onto at least one of the surfaces of the substrates to be bonded, - Joining the substrates to be bonded within the pot life, and - Curing the polyurethane composition.

12. The method according to claim 11, wherein, The substrate may be composed of the same or different materials made of metal, or glass-ceramics, or glass, or glass fiber reinforced plastic, or carbon fiber reinforced plastic, or epoxy-based thermosetting materials.

13. The method according to claim 11 or 12, wherein, The substrate is a part of electronic devices such as audio and video devices, information technology devices, telecommunication terminal devices, portable electronic devices such as laptops, mobile phones, tablets, tablet computers, etc.

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