Fast curing two-component polyurethane compositions with long pot life

Abstract

This invention relates to a polyurethane composition comprising a first component A and a second component B, wherein the first component A comprises at least one polyol Al having an average OH functionality greater than 2 and a number-average molecular weight M of 250 to 15,000 g / mol. n The composition comprises at least one compound T having at least one thiol group; and a second component B comprising at least one polyisocyanate I; wherein one of the two components further comprises at least one metal catalyst K for the reaction of the hydroxyl and isocyanate groups, which is capable of forming a thiocomplex; and the molar ratio of all thiol groups in at least one compound T to all metal atoms in at least one metal catalyst K is from 1:1 to 250:1; characterized in that compound T comprises or consists of a compound having only one thiol group; and polyisocyanate I comprises a polyurethane polymer PU containing isocyanate groups; and component B exhibits a total isocyanate content of 100 to 400 mmol NCO per kilogram of component B. Such a composition cures very rapidly to form a mechanically excellent block suitable for use as a structural adhesive or semi-structural elastic adhesive, but at the same time exhibits a sufficiently long pot life to allow for comfortable handling and can be formulated with very low isocyanate content, especially very low content of monomeric diisocyanate.

Description

Technical Field

[0001] This invention relates to the field of two-component polyurethane compositions and their uses, particularly as adhesives for industrial assembly and direct assembly, as well as methods for bonding a first substrate to a second substrate using the two-component composition and bonded articles obtained by such methods. Background Technology

[0002] Two-component polyurethane compositions based on polyols and polyisocyanates have been used for a long time. Two-component polyurethane compositions, cured by the reaction of isocyanate (NCO) groups with the hydroxyl groups of the polyol, offer advantages over one-component compositions: they cure rapidly after mixing and therefore can absorb and transfer higher forces in a very short time. For use as structural adhesives or semi-structural elastic adhesives, such compositions must meet high requirements regarding strength and adhesion, as these adhesives are load-bearing structural elements. Specifically, such compositions need to possess good mechanical properties upon curing, such as high tensile shear strength, but must not be brittle. Furthermore, for example in industrial manufacturing, it is desirable for such compositions to cure as quickly as possible, which reduces throughput or production cycle time.

[0003] To achieve the desired mechanical properties and, most importantly, exceptionally rapid curing, it is generally advantageous for such compositions to contain a high proportion of isocyanates present in one of the two components, either free or polymerically bonded, and for these isocyanates to cure upon mixing with the other component, which contains a polyol, to form a polymer network. However, the high isocyanate content causes problems. In particular, with the use of crosslinking catalysts, which are essential for selective, optimal crosslinking and curing, such two-component systems become almost uncontrollably fast and have too short a pot life for applications such as structural adhesives.

[0004] For the use of two-component polyurethane compositions, it is generally desirable to combine a sufficiently long pot life with subsequent very rapid curing and extremely rapid strength development. However, this is rarely achieved with common two-component compositions. Either the pot life is very short in the case of compositions with rapid curing and strength development, or curing and strength development are slow when dealing with compositions with long pot lives.

[0005] Therefore, two-component polyurethane compositions with long pot lifespans, which can even be adjusted within certain limits, have been developed, allowing for the processing of larger components or production components, while also exhibiting very rapid curing and strength (in the sense of structural bonding) within a very short time after application, such as less than one hour to a maximum of several days. WO2019 / 002538 A1 discloses such a two-component polyurethane composition. This publication teaches a special catalyst system comprising a metal catalyst and a compound containing a thiol group, which allows for an adjustable long pot life and then enables the composition to cure very rapidly.

[0006] US 5,587,448 A discloses similar two-component polyurethane compositions comprising such a catalyst system. The two-component polyurethane compositions taught therein are largely based on various polypropylene glycol-based polyether polyols and are particularly suitable as coatings.

[0007] Another example of a two-component polyurethane composition using this curing catalyst is disclosed in WO 2021 / 191045 A1. In this composition, the polyurethane composition is partly based on a hydrophobic polyol such as polybutadiene, which requires careful adjustment of the polyol mixture used.

[0008] However, known compositions employing this catalytic method, which results in long pot life and rapid curing, typically require high NCO content to achieve these effects. This is usually achieved by using a large amount of diisocyanate monomers (e.g., 4,4'-diphenylmethane diisocyanate (4,4'-MDI)) as the isocyanate component. Due to EHS concerns, the use of such monomeric diisocyanates has recently become more restricted, and legislation requires increasingly stringent safety measures. For example, the EU introduced REACH restrictions on diisocyanates (e.g., MDI) under Regulation 1907 / 2206, requiring special labeling and treatment precautions for chemical products (e.g., adhesives) containing ≥0.1% monomeric diisocyanates.

[0009] Two-component polyurethane compositions can be formulated with very low or even virtually no monomeric diisocyanate content. In this method, the isocyanate (curing agent) component may contain a polyurethane polymer with isocyanate groups instead of the monomeric diisocyanate and optionally an oligomeric polyisocyanate such as a polyisocyanate, biuret, or urethane. However, such two-component compositions based on NCO-functionalized polyurethane polymers as the curing agent component cannot be readily formulated to achieve the combination of long pot life and rapid curing properties as taught in WO 2019 / 002538 A1.

[0010] For certain applications, such as industrial or automotive assembly operations, like direct assembly processes in automobile manufacturing, it is essential that the two-component adhesive used has a long pot life for suitable treatment, such as 4 to 7 minutes, but cures so quickly after application that the assembled parts or objects can be moved within a short time (e.g., 10 to 20 minutes for treatment and 30 to 60 minutes for assembly) without the risk of misalignment of bonded parts or even bond failure. To date, this has only been achieved through two-component polyurethane compositions with a high NCO group content, using the monomer diisocyanate as a curing agent.

[0011] Therefore, it is desirable to obtain a two-component polyurethane composition based on a polymer having an isocyanate group as a curing agent, preferably having a low content of monomeric diisocyanate, and containing a catalyst system capable of achieving a long pot life, for example 4 to 7 minutes, and subsequently, extremely rapid curing, expressed, for example, by tensile shear strength of at least 0.1 MPa after 10 to 20 minutes of curing and at least 2.0 MPa after 30 to 60 minutes of curing, as measured according to DIN EN 1465. Summary of the Invention

[0012] Therefore, the object of the present invention is to provide a two-component polyurethane composition based on isocyanate functional polymers as curing agents, which cures very rapidly to form mechanically excellent blocks suitable for use as structural adhesives or semi-structural elastic adhesives, but at the same time exhibits a sufficiently long pot life to make it easy to handle and can be formulated with very low isocyanate content, especially very low content of monomeric diisocyanate.

[0013] Surprisingly, this objective is achieved by the polyurethane composition of the invention claimed in claim 1. It comprises, in a first component, at least one polyol having an average OH functionality greater than 2 and a compound having at least one thiol group, and in a second component, a polyisocyanate, wherein the compound having at least one thiol group must comprise or consist of a compound having only one thiol group, and wherein the polyisocyanate must comprise a polyurethane polymer having an isocyanate group, and wherein the curing agent component must exhibit a total isocyanate content of 100 to 400 mmol NCO per kilogram of the curing agent component.

[0014] To cure the composition, it also contains a metal catalyst capable of forming thiocomplexes, and the ratio of thiol groups to metal atoms in the composition is fixed. The composition exhibits very high tensile shear strength upon curing, which builds up very rapidly. After mixing the components and a sufficiently long pot life, it cures very quickly and achieves very good mechanical properties in just a short time.

[0015] Other aspects of the invention are the subject of the additional independent claims. Particularly preferred embodiments of the invention are the subject of the dependent claims. Detailed Implementation

[0016] The present invention relates, in a first aspect, to a polyurethane composition comprising a first component and a second component; wherein

[0017] —The first component A contains

[0018] - At least one polyol A1 having an average OH functionality greater than 2, preferably in the range of 3 to 6, and a number-average molecular weight M of 250 to 15,000 g / mol. n ;and

[0019] - At least one compound T having at least one thiol group; and

[0020] —Component B contains

[0021] - At least one polyisocyanate I;

[0022] One of the two components further comprises at least one metal catalyst K for the reaction of the hydroxyl and isocyanate groups, which is capable of forming a thiocomplex; and

[0023] The molar ratio of all thiol groups in at least one compound T to all metal atoms in at least one metal catalyst K is from 1:1 to 250:1;

[0024] Features are

[0025] Compound T comprises or consists of compounds having only one thiol group; and

[0026] Polyisocyanate I comprises a polyurethane polymer (PU) containing isocyanate groups; and

[0027] Component B shows the total isocyanate content of 100 to 400 mmol NCO per kilogram of component B.

[0028] The prefix "poly" in the names of substances in this document, such as "polyol", "polyisocyanate", "polyether" or "polyamine", indicates that the substance contains more than one functional group per molecule that appears in its name.

[0029] The term "polymer" in this document primarily refers to a collection of chemically homogeneous but different macromolecules in terms of degree of polymerization, molar mass, and chain length, produced by a "poly" reaction (polymerization, addition polymerization, condensation polymerization). Secondly, the term also encompasses derivatives of such a collection of macromolecules resulting from a "poly" reaction, i.e., compounds obtained by reactions (e.g., addition or substitution) on functional groups of a defined macromolecule, and these compounds can be chemically homogeneous or chemically heterogeneous. The term also encompasses so-called prepolymers, i.e., reactive oligomer initiation adducts whose functional groups participate in the formation of macromolecules.

[0030] The term "polyurethane polymer" encompasses all polymers produced according to the so-called diisocyanate addition polymerization process. This also includes polymers that contain little or no urethane groups. Examples of polyurethane polymers are polyether polyurethanes, polyester polyurethanes, polyether polyurea, polyurea, polyester polyurea, polyisocyanurate, and polycarbodiimide.

[0031] In this document, "molecular weight" is understood to mean the molar mass (in grams per mole) of a molecule or molecular residue. "Average molecular weight" refers to the number-average Maverage of a polydisperse mixture of oligomer or polymer molecules or molecular residues. n It is usually determined by gel permeation chromatography (GPC) relative to polystyrene as a standard.

[0032] Weight percentage values, abbreviated as % by weight, refer to the proportion of an ingredient in the composition by mass, based on the whole composition, unless otherwise stated. The terms "mass" and "weight" are used synonymously in this document.

[0033] "Primary hydroxyl group" refers to an OH group attached to a carbon atom with two hydrogen atoms.

[0034] In this document, “suitable period” refers to the time during which the polyurethane composition can be processed after the two components are mixed, before the viscosity produced by the crosslinking reaction becomes too high for further processing.

[0035] In this document, "room temperature" refers to a temperature of 20°C.

[0036] A substance or composition is described as “storage stable” or “storable” if it can be stored in a suitable container at room temperature for a relatively long period of time, typically at least 3 to 6 months or longer, without causing any change in its application or use properties, particularly viscosity and crosslinking rate, to the extent relevant to its use.

[0037] All industry standards and specifications mentioned in this document refer to the versions that were in effect on the date of initial submission.

[0038] "Average OH functionality" is the number of OH groups per polyol molecule, averaged over all polyol molecules. For example, if 50% of all polymer molecules contain two hydroxyl groups and the remaining 50% contain three hydroxyl groups, the result is an average OH functionality of 2.5. Specifically, average OH functionality can be determined by the hydroxyl group value and the molecular weight M as measured via GPC. n It is determined by calculation.

[0039] The polyurethane composition of the present invention consists of a first component A and a second component B, which are mixed only when the polyurethane composition is applied and are stored in separate packages prior to application.

[0040] Component A contains:

[0041] - At least one polyol A1 having an average OH functionality greater than 2, preferably in the range of 3 to 6, and a number-average molecular weight M in the range of 250 to 15,000 g / mol. n ;and

[0042] - At least one compound T, which has at least one thiol group.

[0043] Polyol A1

[0044] The first component A comprises at least one polyol A1 having an average OH functionality greater than 2, preferably in the range of 3 to 6, and a number-average molecular weight M in the range of 250 to 15,000 g / mol, preferably in the range of 250 to 10,000 g / mol, particularly in the range of 250 to 2,500 g / mol. n .

[0045] Preferably, component A contains 30% to 90% by weight, more preferably 50% to 85% by weight, and particularly 60% to 80% by weight of polyol A1, based on component A.

[0046] Polyol A1 can be, and preferably is, a mixture of different polyols. Therefore, the average OH functionality and average molecular weight M... n It can refer to the overall OH functionality and overall molecular weight M of a mixture of different polyols. n The mixture must meet these requirements.

[0047] In principle, suitable polyol A1 is all polyols currently used in the production of polyurethane polymers. Particularly suitable are polyether polyols, polyester polyols, poly(meth)acrylate polyols, polybutadiene polyols, polycarbonate polyols, and mixtures of these polyols.

[0048] Suitable polyether polyols, also known as polyoxyalkylene polyols or oligoetherols, particularly those that are polymers of ethylene oxide, 1,2-epoxypropane, 1,2- or 2,3-epoxybutane, oxetane, tetrahydrofuran, or mixtures thereof, optionally polymerized with the aid of an initiator molecule having two or more active hydrogen atoms, such as water, ammonia, or compounds having multiple OH or NH groups. Examples include 1,2-ethylene glycol, 1,2- and 1,3-propanediol, neopentyl glycol, diethylene glycol, triethylene glycol, isomeric dipropylene glycol and tripropylene glycol, isomeric butylene glycol, pentylene glycol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, 1,3- and 1,4-cyclohexanediol, bisphenol A, hydrogenated bisphenol A, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, glycerol, aniline, and mixtures of the compounds described herein. Applicable polyoxyalkylene polyols include those with low unsaturation (measured according to ASTM D-2849-69 and expressed as milliequivalent unsaturation per gram of polyol (mEq / g)), such as those produced using so-called bimetallic cyanide complex catalysts (DMC catalysts), and those with relatively high unsaturation, such as those produced using anionic catalysts such as NaOH, KOH, CsOH, or alkali metal alkoxides.

[0049] Particularly suitable are polyoxyethylene polyols and polyoxypropylene polyols, especially polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethylene triol and polyoxypropylene triol.

[0050] Particularly suitable are polyoxyalkylene glycols or polyoxyalkylene triols, which have an unsaturation degree of less than 0.02 mEq / g and a molecular weight M in the range of 1,000 to 15,000 g / mol. n Examples include polyoxyethylene glycol, polyoxyethylene triol, polyoxypropylene glycol, and polyoxypropylene triol, which have molecular weights ranging from 400 to 15,000 g / mol.

[0051] Also particularly suitable and preferred are so-called ethylene oxide-terminated (EO-terminated / ethylene oxide-terminated) polyoxypropylene polyols. The latter are specific polyoxypropylene polyoxyethylene polyols, which are obtained, for example, when pure polyoxypropylene polyols (especially polyoxypropylene glycols and triols) are further alkoxylated with ethylene oxide after the completion of the polypropoxylation reaction and thus acquire primary hydroxyl groups. In this case, polyoxypropylene polyoxyethylene glycols and polyoxypropylene polyoxyethylene triols are preferred.

[0052] Also suitable are hydroxyl-terminated polybutylene polyols, such as those produced by polymerization of 1,3-butadiene and allyl alcohol or by oxidation of polybutadiene and their hydrogenated products.

[0053] Also suitable are styrene-acrylonitrile grafted polyether polyols, such as those marketed under the trade name Lupronol. ® Those were purchased from Elastogran GmbH, a German company.

[0054] Suitable polyester polyols particularly include polyesters having at least two hydroxyl groups and produced by known methods, particularly the condensation polymerization of hydroxycarboxylic acids or the condensation polymerization of aliphatic and / or aromatic polycarboxylic acids with di or polyols.

[0055] More suitable are polyester polyols produced from di- to tri-ols such as 1,2-ethylene glycol, diethylene glycol, 1,2-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentanediol, glycerol, 1,1,1-trimethylolpropane, or mixtures of the above alcohols, and organic dicarboxylic acids or their anhydrides or esters, such as succinic acid, glutaric acid, adipic acid, trimethyl adipic acid, corkic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, dimer fatty acids, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, dimethyl terephthalic acid, hexahydrophthalic acid, trimellitic acid, and trimellitic anhydride, or mixtures of the above acids, for example, polyester polyols formed from lactones such as ε-caprolactone.

[0056] Polyester glycols are particularly suitable, especially those produced from adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, dimer fatty acids, 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 diols, and 1,4-cyclohexanediethanol as diols.

[0057] Suitable polycarbonate polyols particularly include those that can be obtained by reacting, for example, the alcohols used to construct polyester polyols, with dialkyl carbonates such as dimethyl carbonate, diaryl carbonates such as diphenyl carbonate, or phosgene. Also suitable are polycarbonates that can be obtained by copolymerizing CO2 with epoxides such as ethylene oxide and propylene oxide. Polycarbonate diols, especially amorphous polycarbonate diols, are particularly suitable.

[0058] Another suitable polyol is poly(meth)acrylate polyol.

[0059] Also suitable are polyhydroxy functionalized fats and oils, such as natural fats and oils, particularly castor oil, or so-called oleochemical polyols obtained through chemical modification of natural fats and oils, such as epoxy polyesters or epoxy polyethers obtained by, for example, epoxidation of unsaturated oils and subsequent ring-opening with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils. Also suitable are polyols obtained from natural fats and oils through degradation processes (e.g., alcoholysis or ozone decomposition) and subsequent chemical linkages (e.g., transesterification or dimerization of the resulting degradation products or their derivatives). Suitable degradation products of natural fats and oils are, in particular, fatty acids and fatty alcohols, as well as fatty acid esters, especially methyl esters (FAME), which can be derived into hydroxy fatty acid esters, for example, through hydroformylation and hydrogenation.

[0060] Also suitable are polyhydric polyols, also known as oligohydric polyols, such as polyhydroxy functional ethylene-propylene, ethylene-butene, or ethylene-propylene-diene copolymers, such as those manufactured by Kraton Polymers, USA, or polyhydroxy functional copolymers of dienes such as 1,3-butadiene or mixtures of dienes with vinyl monomers such as styrene, acrylonitrile, or isobutene, or polyhydroxy functional polybutadiene polyols, such as those produced by copolymerization of 1,3-butadiene and allyl alcohol, which may also be hydrogenated.

[0061] Also suitable are polyhydroxy functionalized acrylonitrile / butadiene copolymers, such as those produced from epoxide or amino alcohol and carboxyl-terminated acrylonitrile / butadiene copolymers, which may be marketed under the trade name Hypro. ® (the old Hycar) ® CTBN was obtained commercially from Emerald Performance Materials, LLC, USA.

[0062] All the polyols described preferably have an average molecular weight M of 250 to 15,000 g / mol, more preferably 250 to 10,000 g / mol, and even more preferably 250 to 2,500 g / mol. n The average OH functionality is preferably in the range of 2 to 6, more preferably 3 to 6. However, it is entirely possible for the composition to also contain a certain proportion of a monohydric alcohol (a polymer having only one hydroxyl group), provided that the overall properties of the polyol A1 meet the defined range.

[0063] Particularly suitable polyols A1 are polyester polyols and polyether polyols, especially polyoxyethylene polyols, polyoxypropylene polyols and polyoxypropylene polyoxyethylene polyols, preferably polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethylene triol, polyoxypropylene triol, polyoxypropylene polyoxyethylene glycol and polyoxypropylene polyoxyethylene triol.

[0064] In addition, ethoxylated, meaning ethylene oxide-terminated (EO-terminated / ethylene oxide-terminated) small molecule polyols are particularly suitable and preferred, such as ethoxylated pentaerythritol, ethoxylated trimethylolpropane and ethoxylated dipentaerythritol.

[0065] Therefore, in a preferred embodiment, polyol A1 comprises at least one polyether polyol, particularly at least one ethylene glycol-terminated polyether polyol.

[0066] In the same or other preferred embodiments, the polyol A1 is a mixture of a first polyol A1a having an average OH functionality of 2 to 3 and a second polyol A1b having an average OH functionality of greater than 3, wherein the weight ratio of polyol A1a to polyol A1b is in the range of 10:1 to 2:1, preferably 9:1 to 3:1.

[0067] Preferably, the polyol Ala has a number-average molecular weight M in the range of 2,500 to 10,000 g / mol. n Furthermore, the polyol A1b has a number-average molecular weight M in the range of 250 to 1,000 g / mol. n .

[0068] In addition to the polyols A1 described above, small amounts of other low molecular weight binary or polyols may be included, such as diethylene glycol, triethylene glycol, isomeric dipropylene glycol and tripropylene glycol, isomeric decanediol and undecanediol, hydrogenated bisphenol A, dimer fatty 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 polyols, low molecular weight alkoxylated products of the above binary and polyols, and mixtures of the above alcohols. Furthermore, polyols containing other heteroatoms may also be present, such as methyldiethanolamine or thiodiglycol.

[0069] Furthermore, it is advantageous to add a small amount of water to component A, for example, 0.5% to 2.5% by weight, preferably 1% to 2% by weight, based on component A. The water provides the advantage that the content of active hydrogen in polyol component A can be easily adjusted to any given NCO content in component B, thereby avoiding excessive NCO during and after curing without completely reformulating the polyol composition.

[0070] Compound T having at least one thiol group

[0071] The first component A further comprises at least one compound T having at least one thiol group, provided that compound T comprises or consists of a compound having only one thiol group. Suitable are all compounds having at least one thiol group or mercapto group that can be formulated into the compositions of the present invention. Here, a thiol group is understood to mean a -SH group attached to an organic group, such as an aliphatic, alicyclic, or aromatic carbon group.

[0072] Compounds having 1 to 6, particularly 1 to 4, and most preferably 1 or 2 thiol groups are preferred; however, they must at least partially contain compounds having only 1 thiol group. Surprisingly, compound T must at least partially contain a monothiol compound, i.e., a compound having only one thiol group. Therefore, compound T may consist of at least one monothiol compound, which is preferred, or it may contain at least one monothiol compound and at least one other polythiol compound, i.e., a compound having more than one thiol group.

[0073] In a preferred embodiment, compound T consists of a compound having only one thiol group. In other preferred embodiments, compound T comprises at least 50% by weight, particularly at least 75% by weight, of a compound having only one thiol group based on the total compound T in component A.

[0074] Examples of suitable compounds having a thiol group are 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropane-1,2-diol, 2-mercaptomethylbenzylazole or 2-mercaptobenzothiazole, aliphatic monothiols, especially 1-decathiol and 1-dodecathiol, as well as alkyl esters of 3-mercaptopropionate and alkyl esters of mercaptoacetate, especially 2-ethylhexyl mercaptoacetate, 2-ethylhexyl-3-mercaptopropionate and isooctyl mercaptoacetate.

[0075] Examples of suitable compounds having more than one thiol group are ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, pentaerythritol hexa(3-mercaptopropionate), 2,3-dimercapto-1,3,4-thiadiazole, or pentaerythritol tetra(3-mercaptopropionate).

[0076] Compound T is preferably selected from ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate), and 3-mercaptopropyltrimethoxysilane.

[0077] In a preferred embodiment, at least one compound T is selected from alkyl monothiols and / or monothiols having carboxylic acid ester groups, and is preferably composed of such compounds. Such compounds allow for a particularly long pot life and particularly fast curing.

[0078] In the same or other preferred embodiments, at least one compound T contains neither an ether group nor a silane group. This adds an unexpected advantage, namely, much better storage stability of the composition without significant loss of curing properties after long-term storage of the components. In these embodiments, compound T is preferably selected from alkyl and carboxylic acid esters having only one thiol group.

[0079] Therefore, in a particularly preferred embodiment, at least one compound T comprises or consists of one or more compounds selected from or formed therefrom: aliphatic monothiols, particularly 1-decylthiol and 1-dodecylthiol, and alkyl esters of 3-mercaptopropionate and alkyl esters of mercaptoacetate, particularly 2-ethylhexyl mercaptoacetate, 2-ethylhexyl-3-mercaptopropionate and isooctyl mercaptoacetate.

[0080] The molar ratio of all thiol groups in at least one compound T to all metal atoms in at least one metal catalyst K must be from 1:1 to 250:1. It is preferably from 2:1 to 150:1, particularly from 5:1 to 80:1. This quantitative ratio allows the pot life to be specifically adjusted within the inherent limitations of a particular composition by, for example, the catalyst content, the reactivity of the present isocyanate, and its amount. The lower limit of the pot life is the pot life obtained in a given composition when a limited amount of catalyst is used without the addition of compound T. In many cases suitable for use as structural adhesives and semi-structural elastic adhesives according to the invention, and as a result of the high reactivity of isocyanate groups with hydroxyl groups in the presence of a catalyst without the addition of compound T, no actual pot life is achieved, and the composition begins to cure almost immediately after mixing the two components.

[0081] The upper limit of the adjustable pot life is correspondingly the pot life that would be reached through the uncatalyzed isocyanate-hydroxyl reaction without a catalyst. Even without a catalyst, the reaction will begin at some point after the two components are mixed. However, the reaction without a catalyst proceeds much more slowly and develops poor mechanical properties in the cured material very slowly.

[0082] The key advantage of the two-component polyurethane composition of this invention is its exceptionally rapid curing and strength development, while simultaneously possessing a sufficiently long pot life to allow for user-friendly processing. This means, for example, structural bonding can be performed on relatively large substrates that can withstand mechanical stress very shortly after adhesive application. This results in a significant reduction in throughput time, for example, in industrial production. Another advantage of the polyurethane composition of this invention is the feasibility of adjusting the pot life within certain limitations as described above. This is particularly advantageous in automated applications and can, for example, allow for further optimization of throughput time in industrial production, as the pot life can be tailored to the desired application.

[0083] The amount of compound T in the first component A is preferably from 0.1% to 10% by weight, based on component A.

[0084] Polyisocyanate I

[0085] The second component B contains at least one polyisocyanate I.

[0086] In addition, component B shows a total isocyanate content of 100 to 400 mmol NCO per kilogram of component B, preferably 200 to 300 mmol per kilogram of component B.

[0087] The total NCO content can be quantitatively determined, for example, by adding a known excess of dibutylamine and back-titering the unreacted dibutylamine with an aqueous hydrochloric acid solution.

[0088] The second component B, polyisocyanate I, must contain a certain proportion of polyurethane polymer (PU) containing isocyanate groups, and may even be composed of such polymers.

[0089] Polyurethane polymers (PUs) containing isocyanate groups can be produced alone by mixing polyisocyanates with at least one polyol, particularly at least one polyether polyol (optionally in the presence of a suitable catalyst), or polyurethane polymers (PUs) containing isocyanate groups can be formed in situ, wherein the isocyanate groups are present in stoichiometric excess relative to the OH groups.

[0090] In a preferred embodiment, the polyurethane polymer PU has an average molecular weight M of 3,500 to 15,000 g / mol, more preferably 4,000 to 12,000 g / mol, and particularly 5,000 to 10,000 g / mol. n The NCO content of the polyurethane polymer PU is preferably from 0.6% to 3.5% by weight, more preferably from 0.7% to 3% by weight, and particularly from 0.8% to 2.5% by weight, based on the polymer. It is preferably obtained by reacting at least one polyol with at least one monomeric diisocyanate, said polyol having an average OH functionality of 1.9 to 3 and an OH number of 8 to 56 mg KOH / g, preferably 10 to 42 mg KOH / g, and preferably using an NCO / OH ratio of 1.5 / 1 to 10 / 1.

[0091] In the reaction, the OH groups of the polyol react with the isocyanate groups of the monomeric diisocyanate. This also leads to the so-called chain extension reaction, in which the OH groups and / or isocyanate groups of the reaction products between the polyol and the monomeric diisocyanate react. The higher the chosen NCO / OH ratio, the lower the level of chain extension reaction that occurs, and the lower the polydispersity and therefore viscosity of the resulting polymer. A measure of chain extension reaction is the average molecular weight of the polymer, or the peak width and distribution in GPC analysis. Another measure is the effective NCO content of the polymer, excluding the monomer, relative to the theoretical NCO content calculated from the reaction of each OH group with the monomeric diisocyanate.

[0092] Suitable monomeric diisocyanates for the production of polyurethane polymers (PU) are commercially available aromatic or aliphatic diisocyanates, particularly diphenylmethane 4,4'-diisocyanate, optionally with a portion of diphenylmethane 2,4'- and / or 2,2'-diisocyanate (MDI), toluene 2,4-diisocyanate or a mixture thereof with toluene 2,6-diisocyanate (TDI), benzene 1,4-diisocyanate (PDI), naphthalene 1,5-diisocyanate (NDI), hexane 1,6-diisocyanate (HDI), 2,2(4), 4-Trimethylhexamethylene 1,6-diisocyanate (TMDI), cyclohexane 1,3- or 1,4-diisocyanate, 1-isocyano-3,3,5-trimethyl-5-isocyanomethylcyclohexane (isophorone diisocyanate or IPDI), perhydrodiphenylmethane 2,4'- or 4,4'-diisocyanate (HMDI), 1,3- or 1,4-bis(isocyanomethyl)cyclohexane, m- or p-xylene diisocyanate (XDI), m-tetramethylxylene diisocyanate (TMXDI), or mixtures thereof.

[0093] A particularly preferred monomeric aromatic diisocyanate is diphenylmethane 4,4'-diisocyanate (4,4'-MDI). This 4,4'-MDI contains only a small fraction of diphenylmethane 2,4'- and / or 2,2'-diisocyanate and is solid at room temperature. This allows moisture-curing polyurethane compositions to exhibit particularly rapid curing, exceptionally high strength, and high ductility and elasticity.

[0094] The 4,4'-MDI is preferably distilled and has a purity of at least 95%, especially at least 97.5%.

[0095] Commercially available diphenylmethane 4,4'-diisocyanate of this quality is, for example, Desmodur. ® 44MC (from Covestro) or Lupronat ® MRSS oder ME (from BASF) or Suprasec ®1400 (from Huntsman) or Millionate ® MT (from Tosoh).

[0096] More preferably, the monomeric diisocyanate is a sterically unhindered diisocyanate, particularly MDI, PDI, HDI, or HMDI. Such diisocyanates provide moisture-curing polyurethane compositions with particularly high curing rates and strengths.

[0097] The most preferred monomer is diphenylmethane 4,4'-diisocyanate. In this way, moisture-curing polyurethane compositions with surprisingly good storage stability, particularly rapid curing, exceptionally high strength, and high elasticity are obtained.

[0098] Suitable polyols are commercially available polyols commonly used in the synthesis of polyurethane polymers, and are preferably liquid at room temperature. For example, the same polyol as polyol A1 can be used.

[0099] Preferably, the average molecular weight M is 800 to 15,000 g / mol, more preferably 1,000 to 12,000 g / mol, and particularly 2,000 to 8,500 g / mol. n Polyols.

[0100] The polyol preferably has an average OH functionality of 1.7 to 3.

[0101] The polyol is preferably a diol or triol having an OH number of 8 to 185 mg KOH / g, especially 10 to 120 mg KOH / g.

[0102] The polyol is preferably a polyether polyol, and the resulting isocyanate-containing polyurethane polymer (PU) is therefore an isocyanate-containing polyether polyurethane polymer. Such a polymer allows the moisture-curing polyurethane composition to possess high extensibility and elasticity.

[0103] The repeating units present are preferably 1,2-ethylidene oxygen, 1,2-propylidene oxygen, 1,3-propylidene oxygen, 1,2-butylidene oxygen, or 1,4-butylidene oxygen group.

[0104] More preferably, the repeating units present in the polyether polyol are primarily or solely 1,2-propylidene groups. More specifically, based on all repeating units, it has 80% to 100% by weight of 1,2-propylidene groups and 0% to 20% by weight of 1,2-ethylidene groups.

[0105] Polyoxyalkylene glycols and / or polyoxyalkylene triols are particularly suitable, especially polymerization products of ethylene oxide or 1,2-epoxypropane or 1,2- or 2,3-epoxybutane or oxetane or tetrahydrofuran or mixtures thereof, wherein these can be polymerized with the aid of initiator molecules having two or more active hydrogen atoms, particularly initiator molecules such as water, ammonia or compounds having multiple OH or NH groups, for example, ethane-1,2- Diol, propane-1,2- or -1,3-diol, neopentyl glycol, diethylene glycol, triethylene glycol, isomeric dipropylene glycol or tripropylene glycol, isomeric butanediol, pentylene glycol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, cyclohexane-1,3- or -1,4-diethanol, bisphenol A, hydrogenated bisphenol A, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, glycerol or aniline, or mixtures of the above compounds.

[0106] Polyoxypropylene glycol, polyoxypropylene triol, or ethylene oxide-terminated polyoxypropylene glycol or triol are particularly preferred. These are polyoxyethylene / polyoxypropylene copolyols, which are specifically obtained by further alkoxylating the polyoxypropylene glycol or triol with ethylene oxide at the end of the polypropoxylation reaction, resulting in them ultimately having primary hydroxyl groups.

[0107] Preferred polyether polyols have an unsaturation level of less than 0.02 meq / g, especially less than 0.01 meq / g.

[0108] In one embodiment, a trimethylolpropane- or, particularly, glycerol- or, optionally, ethylene oxide-terminated polyoxypropylene triol is preferred, having an average molecular weight M of 3,500 to 15,000 g / mol, preferably 4,000 to 12,000 g / mol, and especially 4,500 to 8,500 g / mol. n .

[0109] In some preferred embodiments, the NCO / OH ratio in the reaction between the monomeric diisocyanate and the polyol is preferably 3 / 1 to 10 / 1, more preferably 3 / 1 to 8 / 1, and especially 4 / 1 to 7 / 1. Such a high NCO / OH ratio results in lower polydispersity and more uniform chain length in the obtained polyurethane polymer (PU).

[0110] The reaction between the monomeric diisocyanate and the polyol is preferably carried out at a temperature of 20 to 160°C, particularly 40 to 140°C, under conditions of moisture removal, and optionally in the presence of a suitable catalyst.

[0111] Following the reaction, any remaining monomeric diisocyanate in the reaction mixture can be removed using a suitable separation method to reduce it to an acceptable residual content. This is particularly desirable when a high NCO / OH ratio is used during synthesis and / or when a particularly low final content of monomeric diisocyanate in the composition is required.

[0112] The preferred separation method is distillation, especially thin-film distillation or short-path distillation, preferably carried out under reduced pressure.

[0113] A multi-stage method is particularly preferred, in which monomeric aromatic diisocyanates are removed in a short-path evaporator with a jacket temperature of 120-200°C and a pressure of 0.001-0.5 mbar.

[0114] In the case of 4,4'-MDI (preferably as the monomer diisocyanate), distillation removal is particularly demanding. For example, it must be ensured that the condensate does not solidify and clog the system. It is preferred to operate at a jacket temperature of 160-200°C at 0.001-0.5 mbar, and preferably to condense the removed monomer at a temperature of 40-60°C.

[0115] Preferably, the monomeric diisocyanate is reacted with the polyether polyol and then most of the remaining monomeric diisocyanate in the reaction mixture is removed without the use of a solvent or entraining agent.

[0116] Preferably, the removed monomeric diisocyanate is reused after the reaction, i.e., by reusing it to prepare polyurethane polymers (PU) containing isocyanate groups.

[0117] Polymers containing isocyanate groups and having low monomeric diisocyanate content preferably have a viscosity at 20°C of no more than 50 Pa·s, particularly no more than 40 Pa·s, and more preferably no more than 30 Pa·s. Here, a cone-plate viscometer was used to measure the viscosity at 10 s⁻¹. -1 Viscosity was determined at a shear rate of 25 mm. The viscometer had a cone diameter of 25 mm, a cone angle of 1°, and a cone tip-plate distance of 0.05 mm. Solvents and / or plasticizers may be added during or after the synthesis of the PU polymer to facilitate its mixing and processing, if necessary.

[0118] In a particularly preferred embodiment of the polyurethane composition according to the invention, the isocyanate-containing polyurethane polymer PU in polyisocyanate I is obtained from the reaction of at least one polyether polyol and diphenylmethane 4,4'-, 2,4'- and / or 2,2'-diisocyanate (MDI).

[0119] In the same or other particularly preferred embodiments of the polyurethane composition according to the invention, the polyether polyol used to produce the polyurethane polymer PU containing isocyanate groups is a mixture of polyether diol and polyether triol.

[0120] In addition to the polyurethane polymer PU, polyisocyanate I may contain other isocyanate functional compounds, particularly polyisocyanates.

[0121] Suitable polyisocyanates, especially monomeric di- or triisocyanates and oligomers, polymers and derivatives of monomeric di- or triisocyanates, and any desired mixtures thereof.

[0122] Suitable aromatic monomers, di- or triisocyanates, especially toluene 2,4- and 2,6-diisocyanates and any desired mixtures of these isomers (TDI); diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanates and any desired mixtures of these isomers (MDI); mixtures of MDI and MDI homologues (polymeric MDI or PMDI); 1,3- and 1,4-phenyl diisocyanates; 2,3,5,6-tetramethyl-1,4-diisocyanophenyl; naphthalene 1,5-diisocyanate (NDI); 3,3'-dimethyl-4,4'-diisocyanobiphenyl (TODI); bianisidine diisocyanate (DADI); 1,3,5-tris(isocyanomethyl)benzene; tris(4-isocyanophenyl)methane; and tris(4-isocyanophenyl)thiophosphate.

[0123] Suitable aliphatic monomers, specifically di- or triisocyanates, particularly tetramethylene 1,4-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, hexamethylene 1,6-diisocyanate (HDI), pentamethylene-1,5-diisocyanate (PDI), 2,2,4- and 2,4,4-trimethylhexamethylene 1,6-diisocyanate (TMDI), decamethylene 1,10-diisocyanate, dodecamethylene 1,12-diisocyanate, and lysine diisocyanate. Lysine ester diisocyanate, cyclohexane 1,3- and 1,4-diisocyanate, 1-methyl-2,4-diisocyanocyclohexane and -2,6-diisocyanocyclohexane, and any desired mixtures of these isomers (HTDI or H6TDI), 1-isocyano-3,3,5-trimethyl-5-isocyanomethylcyclohexane (= isophorone diisocyanate or IPDI), perhydrodiphenylmethane 2,4'- and 4,4'-diisocyanate (HMDI or H 12MDI), 1,4-diisocyanate-2,2,6-trimethylcyclohexane (TMCDI), 1,3- and 1,4-bis(isocyanate-methyl)cyclohexane, m- and p-xylene diisocyanates (m- and p-XDI), m- and p-tetramethylxylene-1,3- and 1,4-diisocyanates (m- and p-TMXDI), bis(1-isocyanate-1-methylethyl)naphthalene, dimer and trimer fatty acid isocyanates such as 3,6-bis(9-isocyanate-nonyl)-4,5-di(1-heptenyl)cyclohexene (dimeryldiisocyanate), and α,α,α',α',α'',α''-hexamethyl-1,3,5-mesene triisocyanate.

[0124] Among these, MDI, TDI, HDI, and IPDI are preferred.

[0125] Suitable oligomers, polymers, and derivatives of the monomeric di- and triisocyanates are described, particularly those derived from MDI, TDI, HDI, PDI, and IPDI. Of particular suitability among these are commercially available grades, especially HDI biuret such as Desmodur. ® N100 and N3200 (from Covestro), Takenate ® D-165 (from Mitsui Chemicals), Tolonate ® HDB and HDB-LV (from Vencorex), and Duranate ® 24A-100 (from Asahi Kasei); PDI urea esters or isocyanurates such as STABiO ® D-376N (from Mitsui Chemicals); HDI isocyanurates such as Desmodur ® N3300, N3600, and N3790BA (all from Covestro), Tolonate ® HDT, HDT-LV, and HDT-LV2 (from Vencorex), Duranate ® TPA-100 and THA-100 (from Asahi Kasei) and Coronate ® HX (from Nippon Polyurethane); HDI (urea diketone, such as Desmodur) ® N3400 (from Covestro); HDI iminooxadiazine dione, such as Desmodur ® XP2410 (from Covestro); HDI urea esters such as Desmodur ®VP LS2102 (from Covestro); IPDI isocyanurate, for example in solution form as Desmodur ® Z4470 (from Covestro) or in solid form as Vestanet ® T1890 / 100 (from Evonik); TDI oligomers such as Desmodur ® IL (from Covestro); and TDI / HDI-based mixed isocyanurates, such as Desmodur ® HL (from Covestro). Also particularly suitable is the form of MDI that is liquid at room temperature (so-called "modified MDI"), which is a mixture of MDI and MDI derivatives, especially MDI carbodiimide, MDI urea-ketimide, or MDI carbamate, under trade names such as Desmodur. ® CD, Desmodur ® PF, Desmodur ® PC (all from Covestro) or Isonate ® M143 (from Dow) is known, and mixtures of MDI and MDI homologues (polymeric MDI or PMDI) can be marketed under trade names such as Desmodur. ® VL, Desmodur ® VL50, Desmodur ® VLR10, Desmodur ® VLR20, Desmodur ® VH20N and Desmodur ® VKS20F (both from Covestro), Isonate ® M309, Voranate ® M229 and Voranate ® M580 (all from Dow) or Lupronat ® M10R (obtained from BASF). The aforementioned oligomeric polyisocyanates are, in practice, typically mixtures of substances with different degrees of oligomerization and / or chemical structures. They preferably have an average NCO functionality of 2.1–4.0.

[0126] The polyisocyanate is preferably selected from MDI, TDI, HDI and IPDI, as well as oligomers, polymers and derivatives of the isocyanates described herein, and mixtures thereof.

[0127] Polyisocyanate I preferably comprises a compound having an isocyanurate, iminooxadiazine dione, urea dione, biuret, urethane, carbodiimide, urea ketimide, or oxadiazine trione group.

[0128] In the second component B of the composition of the present invention, polyisocyanate I is preferably present in an amount of 25% to 100% by weight, particularly 30% to 80% by weight, more preferably 40% to 60% by weight, based on the second component B.

[0129] catalyst K

[0130] Component A and / or component B further comprise at least one metal catalyst K for the reaction of hydroxyl and isocyanate groups, which is capable of forming a thiocomplex. Suitable metal catalyst K is therefore any metal catalyst that can be used as a crosslinking catalyst in polyurethane chemistry and can simultaneously form a thiocomplex with a thiol in its presence.

[0131] The metal catalyst K is preferably present only in the first component A. This has the advantage of achieving better storage stability.

[0132] The amount of metal catalyst K in the first component A is preferably from 0.05% to 10% by weight, more preferably from 0.1% to 5.0% by weight, particularly from 0.2% to 1.5% by weight, and more preferably from 0.25% to 1.0% by weight, based on the first component A.

[0133] When the catalyst is present in the second component B, the same preferred amount range as described above applies, but based on component B.

[0134] Examples of suitable metal catalysts are compounds of bismuth, zinc, tin, or zirconium, including complexes and salts of these metals.

[0135] In a preferred embodiment of the polyurethane composition according to the invention, the metal catalyst K comprises a bismuth (III) or tin (IV) compound.

[0136] The metal catalyst K preferably contains a bismuth compound, especially a bismuth(III) compound. In addition to the desired property of being able to form thiocomplexes as a catalyst, bismuth compounds also have the advantage of low acute toxicity.

[0137] 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 bromides, chlorides, or iodides; bismuth sulfides; basic bismuth carboxylatees, such as bismuth neodecanoate, basic bismuth gallate, or basic bismuth salicylate; and mixtures thereof.

[0138] 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. Preferably, it is bismuth(III) carboxylate containing 1 molar equivalent of an 8-hydroxyquinoline ligand.

[0139] In another preferred embodiment, the metal catalyst K is a bismuth(III) complex containing at least one ligand based on a 1,3-ketoamide. Such complexes are described in EP 2791153. Preferably, it is bismuth(III) carboxylate containing 1 to 3 molar equivalents of a 1,3-ketoamide ligand.

[0140] Other additives

[0141] In addition to the components already mentioned, the polyurethane composition may contain other components as known to those skilled in the art from two-component polyurethane chemistry. These may be present in only one component or in both components.

[0142] Preferred additional components are inorganic or organic fillers F, such as, in particular, natural, ground or precipitated calcium carbonate, optionally coated with fatty acids, especially stearic acid, barite (heavy spar), talc, quartz powder, quartz sand, dolomite, wollastonite, kaolin, calcined kaolin, mica (potassium aluminum silicate), molecular sieves, alumina, aluminum hydroxide, magnesium hydroxide, silica (including finely dispersed silica from pyrolysis processes), industrially produced carbon black, graphite, metal powders such as aluminum, copper, iron, silver or steel, PVC powder or hollow spheres, and flame-retardant fillers such as hydroxides or hydrates, especially aluminum hydroxide or aluminum hydrate, preferably aluminum hydroxide.

[0143] Preferably, the composition of the present invention contains at least one filler F in the first component A, the second component B, or both components.

[0144] Adding filler F is advantageous because it increases the strength of the cured polyurethane composition.

[0145] The polyurethane composition preferably contains at least one filler F, selected from calcium carbonate, carbon black, kaolin, barite, talc, quartz powder, dolomite, wollastonite, kaolin, calcined kaolin, and mica. Particularly preferred filler F is ground calcium carbonate, calcined kaolin, or carbon black.

[0146] Using a mixture of different fillers may be advantageous. The most preferred combination is calcium carbonate or calcined kaolin with carbon black.

[0147] The content of filler F in the composition is preferably in the range of 5% to 50% by weight, particularly 10% to 40% by weight, more preferably 15% to 35% by weight, based on the total composition.

[0148] The content of filler F in the first component A is preferably from 10% to 60% by weight, more preferably from 15% to 50% by weight, and particularly from 20% to 45% by weight, based on component A.

[0149] The content of filler F in the second component B is preferably from 0 wt% to 60 wt%, more preferably from 10 wt% to 50 wt%, and particularly from 10 wt% to 45 wt%, based on the second component B.

[0150] Additional components may be present, especially solvents, plasticizers and / or extenders, pigments, rheology modifiers such as, in particular, amorphous silica, desiccants such as, in particular, zeolites, adhesion promoters such as, in particular, organofunctionalized trialkoxysilanes, antioxidant, heat-resistant, light-resistant and UV-resistant stabilizers, flame retardants, and also surfactants, especially wetting agents and defoamers.

[0151] The polyurethane composition preferably contains less than 0.5% by weight, and especially less than 0.1% by weight, of carboxylic acid, based on the total composition. Any carboxylic acid ligands introduced by a metal catalyst are not included in the carboxylic acid.

[0152] The polyurethane composition preferably contains less than 1% by weight, especially less than 0.5% by weight, especially less than 0.1% by weight of the monomeric diisocyanate, based on the total composition.

[0153] The preferred polyurethane composition comprises a first component A, which, based on component A, contains

[0154] -30% to 80% by weight, preferably 40% to 75% by weight, especially 50% to 70% by weight of polyol A1, particularly a mixture of polyol A1a and polyol A1b as otherwise defined above;

[0155] -0.1% to 15% by weight, preferably 0.5% to 10% by weight, especially 1% to 7.5% by weight of at least one compound T having at least one, preferably only one, thiol group.

[0156] -0.05 wt% to 2.5 wt%, preferably 0.1 wt% to 2.0 wt%, especially 0.2 wt% to 1.5 wt%, more preferably 0.25 wt% to 1.0 wt% of the metal catalyst K, and

[0157] -10% to 60% by weight, preferably 15% to 50% by weight, especially 20% to 45% by weight of filler F,

[0158] And optional additional ingredients.

[0159] The same or other preferred polyurethane compositions comprise a second component B, which, based on component B, contains

[0160] -25% to 100% by weight, preferably 30% to 75% by weight, especially 40% to 60% by weight of polyisocyanate I.

[0161] -0% to 60% by weight, preferably 10% to 50% by weight, especially 10% to 45% by weight of filler F,

[0162] And optional additional ingredients.

[0163] Advantageously, when the first component A and the second component B are formulated such that their mixing ratio, in parts by volume or by weight, is 15:1 to 1:15, preferably 1:1 to 1:15, especially 1:8 to 1:13.

[0164] In the mixed polyurethane composition, prior to curing, the molar ratio between the number of isocyanate groups in component B and the number of isocyanate-reactive hydrogen-containing groups in component A is preferably 3 to 1, more preferably 2.5 to 2. However, the ratio of isocyanate groups to isocyanate-reactive groups can also be substoichiometric, although this is generally not preferred.

[0165] Components A and B are produced separately, and preferably in the absence of moisture. The two components are typically stored separately in individual containers. Additional non-essential additives to the polyurethane composition as defined above may be present as components of either the first or second component; additional additives reactive to isocyanate groups are preferably components of the first component, A. Suitable containers for storing the respective components are, in particular, barrels, hoobocks, bags, cans, boxes, or tubes. At least in the preferred embodiment, both components are storage-stable, meaning they can be stored for months to a year or longer before use without any change in their respective properties to the extent relevant to their use.

[0166] Before mixing the composition, the two components A and B are stored separately and mixed only when or immediately before use. They are advantageously contained in a package consisting of two separate compartments.

[0167] In another aspect, the present invention comprises a package consisting of a package having two separate compartments, each containing a first component A and a second component B of the composition.

[0168] Mixing is typically carried out via a static mixer or with the aid of a dynamic mixer. During mixing, care must be taken to ensure that the two components A and B are mixed as uniformly as possible. If the two components are not mixed completely, local deviations from the favorable mixing ratio will occur, which may lead to the deterioration of mechanical properties.

[0169] When component A comes into contact with component B, curing begins through a chemical reaction. This involves the reaction of hydroxyl groups and any other substances present that are reactive with isocyanate groups. Excess isocyanate groups react primarily with moisture. Due to these reactions, the polyurethane composition cures to produce a solid material. This process is also known as crosslinking.

[0170] Therefore, the present invention also provides a cured polyurethane composition obtained by curing the polyurethane composition described herein.

[0171] The two-component polyurethane composition is advantageously used as a matrix in structural adhesives or semi-structural elastic adhesives, potting compounds or composite materials, and particularly as an assembly adhesive or direct assembly adhesive.

[0172] Therefore, the present invention also relates to a method for bonding a first substrate to a second substrate, the method comprising the following steps:

[0173] - Mix the first component A and the second component B described above.

[0174] - Apply the mixed polyurethane composition to at least one of the substrate surfaces to be bonded.

[0175] - Join the substrates to be bonded within the applicable period.

[0176] - To cure the polyurethane composition.

[0177] These two substrates can be made of the same material or different materials.

[0178] Therefore, the present invention also relates to a method for filling the joint and gap between two substrates, the method comprising the following steps:

[0179] - Mix the first and second components described above.

[0180] - Apply the mixed polyurethane composition to the joints or gaps.

[0181] - To cure the polyurethane composition.

[0182] In these methods used for bonding or for filling joints and gaps, a suitable substrate is particularly important.

[0183] - Glass, glass ceramics, glass mineral fiber mat;

[0184] - Metals and alloys, such as aluminum, iron, steel and non-ferrous metals, as well as surface-finished metals and alloys, such as zinc-plated or chromium-plated metals;

[0185] - Substrates for coating and painting, such as powder-coated metals or alloys and painted steel sheets;

[0186] - Plastics, such as polyvinyl chloride (rigid PVC and flexible PVC), acrylonitrile-butadiene-styrene copolymer (ABS), polycarbonate (PC), polyamide (PA), poly(methyl methacrylate) (PMMA), polyester, epoxy resin, especially epoxy resin-based thermosetting materials, polyurethane (PUR), polyoxymethylene (POM), polyolefin (PO), polyethylene (PE) or polypropylene (PP), especially talc-filled polypropylene, ethylene / propylene copolymer (EPM) and ethylene / propylene / diene terpolymer (EPDM), wherein the plastics may preferably have been surface-treated by means of plasma, corona or flame;

[0187] - Fiber-reinforced plastics, such as carbon fiber reinforced plastics (CFRP), glass fiber reinforced plastics (GFRP), such as glass fiber reinforced polypropylene, and sheet molding compounds (SMC);

[0188] - Wood, wood-based materials bonded with resins such as phenolic resins, melamine or epoxy resins, resin-textile composites, and other so-called polymer composites; and

[0189] - Concrete, mortar, brick, plaster and natural stone, such as granite, limestone, sandstone or marble.

[0190] In these methods, one or two substrates are preferably optionally coated metal or glass ceramic or glass or talc-filled polypropylene or glass fiber reinforced plastic or carbon fiber reinforced plastic or epoxy resin-based thermosetting material.

[0191] If necessary, the substrate may be pretreated before the composition is applied. Such pretreatment includes, in particular, physical and / or chemical cleaning processes and the application of adhesion promoters, adhesion promoter solutions or primers, or dry processing such as plasma treatment or flame treatment.

[0192] The bonding method described above produces an article in which the composition bonds two substrates together.

[0193] The articles, in particular lightweight structures, building structures (e.g., bridges), industrial products or consumer goods, especially windows, rotor blades of wind turbines or modes of transportation, especially vehicles, preferably automobiles, buses, trucks, railway vehicles or ships, or sandwich elements of aircraft or helicopters, or installable components of such articles.

[0194] The polyurethane composition is characterized by high strength and elasticity, which remain highly constant over a wide temperature range of -35°C to 85°C. It also exhibits good, largely temperature-independent adhesion to metallic substrates. Due to these properties, it is particularly well-suited as a structural adhesive or semi-structural elastic adhesive for stress-bearing bonding, especially outdoors at ambient temperatures.

[0195] Therefore, the present invention also provides the use of the polyurethane composition as a structural adhesive or semi-structural elastic adhesive to bond two substrates, particularly as an assembly adhesive or direct assembly adhesive.

[0196] The polyurethane composition is also advantageously used as a potting compound, especially for filling gaps and joints, for repair purposes as a ballast compensation compound, or for protecting electronic components.

[0197] Polyurethane compositions are also preferably used as potting compounds, especially electro-potting compounds. In another aspect, the invention therefore includes the use of two-component polyurethane compositions as potting compounds, particularly as electro-potting compounds.

[0198] In another aspect, the present invention therefore includes a method for filling joints and gaps in a substrate, the method comprising the following steps

[0199] a) Mix the first and second components of the two-component polyurethane composition as described above.

[0200] b) Apply the mixed polyurethane composition to the joint between two substrates or to the gap to be filled on the surface of the substrate.

[0201] c) Curing the polyurethane composition at the joints or gaps.

[0202] In another respect, the present invention therefore also includes a filled article that has been filled according to the above method.

[0203] Polyurethane compositions are also preferably used as a matrix in composite materials. Here, the polyurethane composition acts as an adhesive for embedding fibers or other reinforcing structures therein. In another aspect, the invention therefore includes the use of two-component polyurethane compositions as a matrix in composite materials.

[0204] Example

[0205] The substances used:

[0206]

[0207]

[0208] Table 1: Substances used.

[0209] Preparation of polyurethane compositions

[0210] To demonstrate the effects of the present invention, a series of two-component polyurethane compositions were prepared by first preparing individual components A and B. This is described below.

[0211] Component A

[0212] A series of exemplary components A (A-1 to A-20) were prepared to investigate the effects of different compounds with thiol groups and different polyols. The composition of component A is shown in Tables 2 to 5. The numerical values ​​of the components in each experiment represent the parts by weight added to their respective compositions.

[0213]

[0214] Table 2: Components A (A-1 to A-5). Values ​​are in parts by weight. Not based on the present invention.

[0215]

[0216] Table 3: Components A (A-6 to A-10 and A-21). Values ​​are in parts by weight.

[0217]

[0218] Table 4: Components A (A-11 to A-15). Values ​​are in parts by weight. Not based on the present invention.

[0219]

[0220] Table 5: Components A (A-16 to A-20). Values ​​are in parts by weight. Not based on the present invention.

[0221] Component B

[0222] An exemplary component B (B-1) is prepared and mixed with the exemplary component A defined above. The compositional details of component B-1 are shown in Table 6.

[0223]

[0224] Table 6: Component B (B-1) used in the experiment. Values ​​are in parts by weight.

[0225] By making M with 5'000 g / mol n Polypropylene glycol (PPG) triol and M with 2,000 g / moln NCO-functionalized polyurethane polymer P-1 was prepared by reacting a 1:1 (w / w) mixture of polypropylene glycol (PPG) diol with 4,4'-diphenylmethane diisocyanate (4,4'-MDI) using a known method with an NCO / OH molar ratio of 1.67 and using 18 wt% diisononyl adipate as the reaction medium based on the total composition. The resulting polymer had an NCO content of 1.5 wt% and a residual MDI content of 2 wt%. The total NCO content of the polymer mixture was 143 mmol per kilogram of polymer mixture. In component B-1, this mixture was used as "NCO-functionalized polyurethane polymer P-1" without further purification.

[0226] The content of residual unreacted MDI in the prepared NCO functional polymer mixture was determined by HPLC (detection via photodiode array; 0.04M sodium acetate / acetonitrile as mobile phase) after prior derivatization with N-propyl-4-nitrobenzylamine.

[0227] Considering the aforementioned "NCO-functional polyurethane polymer P-1" and the additional NCO-functional additives (isocyanurate and urethane), the total NCO content of component B-1 is 293 mmol NCO per kilogram of component B-1.

[0228] The total NCO content was determined by adding an excess of dibutylamine and back-titering the unreacted dibutylamine with an aqueous hydrochloric acid solution.

[0229] Two-component composition

[0230] A series of exemplary two-component compositions were prepared, using compositions A-1 to A-21 as component A and composition B-1 as component B. In each experiment, the mixing ratio (weight / weight or volume / volume) of component A to component B was 1:10.

[0231] For each composition, the ingredients of component A, as specified in the table, are processed into a homogeneous paste using a vacuum dissolver while removing moisture, in the prescribed amounts (parts by weight) and stored. The ingredients of component B, as specified in the table, are processed and stored in the same manner. Then, using a SpeedMixer... ® (DAC 150FV, Hauschild) The two components were mixed together for 15 seconds to form a homogeneous paste, which was then immediately tested as follows:

[0232] The pot life is measured in a viscometer as the time from when the two components are mixed until the viscosity reaches 10,000 Pa·s. Specifically, the pot life is defined as the intercept of the slope of the viscosity (y-axis) against time (x-axis) when the viscosity reaches 10,000 Pa·s. This is done at a frequency of 10 s.-1 Viscosities were measured at 20°C using an MCR 302 parallel plate rheometer (Anton Paar) with a diameter of 25 mm and a plate spacing of 1 mm. This was achieved by first mixing the two components in a SpeedMixer (Hauschild) for 15 seconds and then immediately applying the mixture to the plates within an additional minute for measurement.

[0233] To measure tensile shear strength, various test specimens were produced. In each case, an adhesive was applied between two heptane-degreased cathodic electrophoretically coated steel plates in a 2 mm thick layer with an overlapping bonding area of ​​15 × 45 mm. The adhesive was applied 15 seconds after the mixing time was completed. The test specimens were individually stored / cured at 20°C for 10 minutes or 40 minutes, and then measured immediately. Tensile shear strength was determined according to DIN EN 1465.

[0234] The storage stability of some compositions was evaluated. For this purpose, individual components A and B of each composition were stored in sealed containers at 60°C for one week to simulate the aging process of the components. Subsequently, the individual components were stored at 23°C for one day to allow them to cool, and then mixed and tested using the same procedure as described above for freshly prepared compositions.

[0235] Details of the mixed compositions and the results of the test protocols are shown in Tables 7 to 10. “Molar ratio SH:Bi” indicates the molar ratio of all thiol groups in compound T to all bismuth atoms contained in catalyst K.

[0236] Compositions considered superior are those exhibiting a pot life of 4 to 7 minutes, a tensile shear strength of at least 0.1 mPa after curing for 10 to 20 minutes, and a tensile shear strength of at least 2.0 mPa after curing for 30 to 60 minutes. Such compositions combine a long pot life with rapid curing, making them suitable for industrial or automotive applications where sufficient operating time and very fast process cycles are required.

[0237]

[0238] Table 7: Experimental results of compositions C-1 to C-5. Not based on the present invention.

[0239]

[0240] Table 8: Experimental results for compositions C-6 to C-10 and C-21.

[0241]

[0242] Table 9: Experimental results of compositions C-11 to C-15. Not based on the present invention.

[0243]

[0244] Table 10: Experimental results for compositions C-16 to C-20. Not based on the present invention.

[0245] Tables 7 to 10 show that only the compositions according to the invention achieve a pot life of at least 4 minutes, while exhibiting a tensile shear strength of at least 0.1 mPa (as determined according to DIN EN 1465) after 10 minutes of curing and a tensile shear strength of at least 2 mPa (as determined according to DIN EN 1465) after 40 minutes of curing. In the preferred embodiment, these values ​​are achieved even after artificial aging of the components (by storing them at 60°C for 1 week), thus demonstrating excellent storage stability.

Claims

1. A polyurethane composition comprising a first component and a second component; in —The first component A contains - At least one polyol A1 having an average OH functionality greater than 2, preferably 3 to 6, and a number-average molecular weight M of 250 to 15,000 g / mol. n M n The determination was performed using gel permeation chromatography (GPC) relative to polystyrene as a standard; and - at least one compound T having at least one thiol group; and —The second component B contains - At least one polyisocyanate I; One of the two components further comprises at least one metal catalyst K for the reaction of the hydroxyl and isocyanate groups, which is capable of forming a thiocomplex; and 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 is from 1:1 to 250:1; Features are Compound T comprises or consists of compounds having only one thiol group; and Polyisocyanate I comprises a polyurethane polymer (PU) containing isocyanate groups; and Component B shows a total isocyanate content of 100 to 400 mmol NCO per kilogram of component B, wherein the total isocyanate content can be quantitatively determined by adding a known excess of dibutylamine and back titrating the unreacted dibutylamine with an aqueous hydrochloric acid solution.

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

3. The polyurethane composition according to any one of claims 1 or 2, characterized in that the polyol A1 comprises at least one polyether polyol, particularly at least one ethylene glycol-terminated polyether polyol.

4. The polyurethane composition according to any one of claims 1 to 3, characterized in that the at least one compound T is selected from alkyl monothiols and / or monothiols having a carboxylic acid ester group.

5. The polyurethane composition according to any one of claims 1 to 4, characterized in that the at least one compound T contains neither ether groups nor silane groups.

6. The polyurethane composition according to claim 4, characterized in that the at least one compound T comprises or consists of one or more compounds selected from or formed thereof: Aliphatic monothiols, particularly 1-decylthiol and 1-dodecylthiol, as well as alkyl esters of 3-mercaptopropionate and alkyl esters of mercaptoacetate, particularly 2-ethylhexyl mercaptoacetate, 2-ethylhexyl-3-mercaptopropionate and isooctyl mercaptoacetate.

7. The polyurethane composition according to any one of the preceding claims, characterized in that 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 is from 5:1 to 80:

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 polyol A1 is a mixture of a first polyol A1a having an average OH functionality of 2 to 3 and a second polyol A1b having an average OH functionality of greater than 3, wherein the weight ratio of polyol A1a to polyol A1b is 10:1 to 2:1, preferably 9:1 to 3:

1.

10. The polyurethane composition according to claim 9, characterized in that the polyol Ala has a number-average molecular weight M of 2,500 to 10,000 g / mol. n Furthermore, the polyol A1b has a number-average molecular weight M of 250 to 1,000 g / mol. n M n The determination was performed using gel permeation chromatography (GPC) relative to polystyrene as a standard.

11. The polyurethane composition according to any one of the preceding claims, characterized in that the isocyanate-containing polyurethane polymer PU in polyisocyanate I is obtained from the reaction of at least one polyether polyol and diphenylmethane 4,4'-, 2,4'- and / or 2,2'-diisocyanate (MDI).

12. The polyurethane composition according to claim 11, characterized in that the polyether polyol used to produce the polyurethane polymer PU containing isocyanate groups is a mixture of polyether diol and polyether triol.

13. A method for bonding a first substrate to a second substrate, comprising the following steps: - Mix the first and second components of the polyurethane composition according to any one of claims 1 to 12. - Apply the mixed polyurethane composition to at least one of the substrate surfaces to be bonded. - Join the substrates to be bonded during the open time. - To cure the polyurethane composition.

14. Use of the polyurethane composition according to any one of claims 1 to 12 as a structural adhesive for bonding two substrates, particularly as an assembly adhesive or direct assembly adhesive.

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