A curable composition, a method for joining, molding and coating a substrate, and the use of the composition.

Abstract

The present invention relates to a one-pack curable composition comprising (A) at least one at least bifunctional solid isocyanate having a passivation surface; (B) at least one first liquid isocyanate reactive component selected from the group consisting of alcohols, amines, thiols and mixtures thereof; and (C) at least one second solid isocyanate reactive component having a melting point of at least 50°C. Furthermore, methods for bonding, molding, and / or coating substrates, as well as the use of the composition, are provided.

Description

Technical Field

[0001] (Field of the Invention) The present invention relates to a heat-curable isocyanate-based one-pack composition.

[0002] Furthermore, the present invention relates to a method of bonding, coating or molding a substrate, particularly an electronic component (or element or component), using this composition.

Background Art

[0003] (Technical Background) The use of polyisocyanates associated with polyamines or polyols in curable compositions is basically known. Due to their high reactivity, such compositions have a limited processing time and the components have to be mixed within a narrow time frame for use. Compositions that are stable during storage can be obtained by using blocked polyisocyanates that decompose the blocking agent at elevated temperatures. Alternatively, surface-passivated polyisocyanates are employed. For this purpose, solid, finely dispersed polyisocyanates are reacted with isocyanate-reactive compounds and thus modified with a passivating surface shell. By applying heat, a rapid polyaddition reaction to the isocyanate, and thus curing of the composition, can be achieved in such compositions. Suitable adhesives can be particularly suitable as an alternative to silicones having excellent flow properties and high flexibility at low temperatures of the cured composition.

[0004] So-called reflow soldering is preferred for electrically fixing surface-mount components on printed circuit boards. An advantage of this method is that components are initially bonded by solder paste during assembly, and final soldering occurs only afterward, for example, in a reflow soldering oven. Adhesives can be used to additionally fix, shape, and seal components. A disadvantage of this method is that the adhesive composition may be exposed to temperature peaks above 240°C for periods exceeding one minute, which can lead to a rapid decrease in the level of adhesion. Prior art does not describe solutions that would enable the broad application of polyisocyanate-based formulations for such applications.

[0005] EP 0 100 508 B1 describes a thermosetting composition based on polyisocyanates. Polyisocyanates, present in particle sizes from 0.1 μm to 150 μm, are first deactivated by an isocyanate-reactive compound, and 0.1 to 20 equivalent percent of isocyanate groups react. The composition thus obtained has a shelf life of at least 3 months.

[0006] EP 0 103 323 B1 describes a method for producing solid surface-passivated (or surface-inactivated) polyisocyanates and their use in storage-stable, heat-curable compositions. High molecular weight polyols and / or polyamine compounds and low molecular weight chain extenders are described as curing agents. Further components from the aforementioned group may be added as desired. Targeted use of high-melting-point amines to increase temperature stability and adhesion is not disclosed.

[0007] EP 0 153 579 B1 describes the use of polyisocyanate compositions as adhesives. Polyamines, hydrazines, amidines, and / or guanidines are employed to passivate (or passivate) finely dispersed polyisocyanates. This reaction occurs in a liquid component that also acts as a curing agent. Here again, higher molecular weight polyols and / or polyamines are used. Furthermore, polyols and / or polyamines with a molecular weight of less than 400 g / mol may be used.

[0008] EP 0 671 423 B1 describes a one-pack thermosetting polyurethane composition with increased resistance to temperature and moisture. Polyisocyanates having a diphenylurea backbone are used as preferred starting materials for temperature-stable formulations. Other polyisocyanates tend to soften, decompose, and foam. The addition of target high-melting-point amines is not disclosed. Structural limitations of the polyisocyanates limit the available property profiles of the cured compositions.

[0009] EP 3 749 700 A1 discloses a one-pack storage-stable composition based on a surface-passivated polyisocyanate. The addition of a radical radiation-curable component and a photopolymerization initiator makes the composition double-curable. The curing agent can be selected from the group of alcohols, amines, thiols, and mixtures thereof. The composition is further photofixable to prevent flow during curing. The addition of high-melting-point amines to increase temperature stability and adhesion is not described.

[0010] Therefore, there remains a need for a one-pack composition that can be introduced at room temperature, particularly for bonding, coating, or molding electronic components, that exhibits high flexibility, high temperature stability, especially high resistance to temperature peaks such as those that occur in reflow soldering processes, and improved adhesion. [Overview of the project]

[0011] (Summary of the invention) The object of the present invention is to provide a thermosetting one-pack composition that avoids the disadvantages of compositions known from the prior art and is distinguished in particular by its temperature stability and adhesion in the cured state.

[0012] This objective is achieved by the one-pack curable composition described in claim 1, in accordance with the present invention. Advantageous embodiments are shown in the dependent claims, which can be combined with each other as desired.

[0013] One-pack curable composition according to the present invention (A) At least one at least bifunctional solid isocyanate having a passivation surface and a melting point of at least 40°C; (B) at least one first liquid isocyanate-reactive component selected from the group consisting of alcohols, amines and thiols and mixtures thereof; and (C) At least one second solid isocyanate reactive component having a melting point of at least 50°C Includes.

[0014] This composition is liquid at room temperature and is distinguished by its high strength and temperature stability after curing. At temperatures above 180°C, the cured composition is considerably less likely to soften, decompose, or foam. The composition of the compound according to the present invention can be varied over a wide range, particularly with respect to the selection of resin components. This provides users with numerous options for tailoring the property profile of the cured composition to their requirements.

[0015] This invention is based on the remarkable discovery that the temperature stability and adhesion of a thermosetting one-pack composition based on a surface-passivated (or surface-inert) solid isocyanate can be significantly improved by mixing it with a solid isocyanate reactive component.

[0016] Therefore, the compositions according to the present invention are particularly suitable for reflow soldering, where such thermal stress may occur over longer periods. In addition, because the level of adhesion is significantly increased, especially on metal surfaces, these compositions are suitable for applications such as magnetic coupling or automotive sensors.

[0017] Furthermore, a method for joining, coating, or molding a substrate using the composition according to the present invention is proposed. [Modes for carrying out the invention]

[0018] (Detailed description of preferred embodiments) The present invention will be described in detail and illustratively below with reference to preferred embodiments, which should not be understood as limiting. The following definitions are used in this specification:

[0019] For the purposes of this invention, "one pack" or "one pack composition" means that the referred components are present together in a common formulation (or preparation or formula), i.e., they are not stored separately from one another.

[0020] A composition is considered "processable" if the viscosity of each readymix composition increases by less than 25% during storage at room temperature for at least 72 hours.

[0021] For the purposes of this invention, "liquid" means that, at room temperature, the loss modulus G'' determined by rheological measurement is greater than the storage modulus G' of the composition.

[0022] "At least bifunctional" means that each compound or mixture of substances has at least bifunctionality based on a specific functional group. Thus, at least bifunctional or polyfunctional isocyanates have at least two isocyanate groups (-NCO) in their molecule.

[0023] As long as the indefinite articles "a" or "an" are used, the plural form of "one or more" is also included unless explicitly excluded.

[0024] The weight percentages shown below refer to the total weight of the curable composition unless otherwise specified.

[0025] Component (A): At least a bifunctional solid isocyanate Basically, any at least bifunctional isocyanate having a melting point of 40°C or higher can be used as the solid at least bifunctional isocyanate (A). The at least bifunctional isocyanate preferably has a melting point of at least 60°C. Preferably, the melting point of the at least bifunctional isocyanate is at most 170°C.

[0026] Preferably, the isocyanate is an aliphatic, cycloaliphatic, heterocyclic or aromatic polyisocyanate. The polyisocyanate can exist at least partially, preferably completely, in the form of dimers. Examples of suitable polyisocyanates include dimeric (or dimer:dimeric) 2,4 - diisocyanatotoluene, dimeric 4,4’ - diisocyanatodiphenylmethane, 3,3’ - diisocyanato - 4,4’ - dimethyl - N,N’ - diphenylurea, the isocyanurate of isophorone diisocyanate, 1,4 - phenylene diisocyanate, naphthalene - 1,5 - diisocyanate, and addition products of diisocyanates with short - chain diols having 2 to 6 carbon atoms such as, for example, 1,4 - butanediol or 1,2 - ethanediol. Particularly preferred are dimeric 2,4 - diisocyanatotoluene, dimeric 4,4’ - diisocyanatodiphenylmethane, 3,3’ - diisocyanato - 4,4’ - dimethyl - N,N’ - diphenylurea, and / or the isocyanurate of isophorone diisocyanate.

[0027] To provide a storage-stable composition, the solid polyisocyanate is passivated (or inactivated) on its surface. For this purpose, to prevent the solid isocyanate from immediately reacting with the liquid isocyanate-reactive component (B) present in the one-pack composition, the solid polyisocyanate is reacted with a passivating agent (or inactivating agent) on its surface.

[0028] Preferably, the solid polyisocyanate is reacted with a passivating agent on its surface, for example, as described in EP 0 153 579 A2, EP 0 100 508 B1, or EP 3 749 700 A1.

[0029] The reaction between the solid polyisocyanate and the passivating agent creates a substantially inert shell on its surface, which prevents further reaction of the isocyanate groups located beneath it until heat is applied to break it down, causing the one-pack composition to harden.

[0030] Preferred passivating agents are compounds from the group consisting of polyamines, amidine and / or guanidine compounds, hydrazines, alkylhydrazines and / or hydrazide compounds, which react with isocyanate groups located on the surface of solid polyisocyanates to form urea groups.

[0031] At least bifunctional amines having a molecular weight of 60 to 600 g / mol are particularly preferred as passivating agents, most preferably polyetheramines commercially available under Jeffamine® D-400 or Jeffamine® T-403 from Huntsman Corporation. For passivation, 0.1 to 25 mol% of the total isocyanate groups present in the solid polyisocyanate can be reacted with the passivating agent, preferably 0.5 to 15 mol%, and particularly preferably 1 to 10 mol%. This reaction is preferably achieved by the formation of urea groups.

[0032] In a preferred embodiment, the solid polyisocyanate, existing in the form of fine particles, is reacted with a passivator in a liquid medium that is not itself a good solvent for the polyisocyanate, at a temperature below the melting point of the solid polyisocyanate. In particular, high molecular weight polyols or polyamines having a molecular weight of up to 20,000 g / mol can themselves be used as isocyanate-reactive components in the compositions according to the present invention and can function as liquid media.

[0033] According to a preferred embodiment, the surface-passivated solid polyisocyanate exists in the form of dispersed fine particles. This makes it possible to obtain a homogeneously cured composition when heat is applied.

[0034] Preferably, the solid polyisocyanate exists in the form of particles having a volume particle size d95 of up to 100 μm, preferably up to 40 μm, and particularly preferably up to 10 μm. By selecting different polyisocyanates and associated curing agent systems, compositions according to the present invention can be formulated to produce both rigid and very flexible systems that exhibit an elastic modulus profile that hardly changes over a wide temperature range.

[0035] According to a further aspect of the present invention, the composition comprises at least a bifunctional isocyanate in a proportion of 5 to 40% by weight, based on the total weight of the composition.

[0036] Component (B): First liquid isocyanate reactive component In addition to component (A), the composition according to the present invention contains, as component (B), at least one first liquid isocyanate-reactive component selected from the group consisting of alcohols, amines, thiols, and mixtures thereof.

[0037] In principle, the selection of component (B) from the group of alcohols, amines, thiols, and mixtures thereof is not limited, as long as at least one first isocyanate-reactive component (B) is liquid at room temperature.

[0038] When the composition is heated, component (B) reacts with polyisocyanate (A) to form a network, causing the composition to harden.

[0039] Component (B) is not further limited in terms of its chemical composition. Preferably, component (B) has an isocyanate-reactive group having an average number of functional groups greater than 1. Polyols, polyamines, and / or polythiols having at least two functional groups are particularly preferred as isocyanate-reactive compounds. Mixtures of different isocyanate-reactive compounds are also within the scope of the present invention.

[0040] The average functionality of component (B), and thus the crosslink density, can be adjusted almost arbitrarily by combinations of monofunctional, bifunctional, and more functional isocyanate-reactive compounds, insofar as a polymer network is formed by the addition reaction to at least a bifunctional isocyanate (A) when heat is supplied. Preferably, the average functionality is at least 1.4, particularly preferably at least 1.7, but preferably 5 or less, particularly 4 or less.

[0041] The cured composition can selectively form hard and soft segments. To form hard segments, an isocyanate-reactive component (B) having a molecular weight up to 400 g / mol is preferably employed as a so-called chain extender, which forms high-density linking groups such as (thio)urethane or urea groups with at least a bifunctional isocyanate, and then links together by a dense network of hydrogen bonds. To form soft segments, component (B) preferably comprises a long-chain isocyanate-reactive compound having a molecular weight of 400 g / mol to 20,000 g / mol.

[0042] Isocyanate-reactive compounds can be pre-extended with liquid, non-passivated isocyanates to form prepolymers.

[0043] Preferably, component (B) contains an amine. As the amine of component (B), a polyetheramine having a molecular weight of 600 g / mol or more, available as Jeffamine® D-2000 or Jeffamine® T-5000, may be used. More preferably, a high molecular weight aromatic amine having an average molecular weight of 400 g / mol to 12,000 g / mol, which can be obtained by alkaline hydrolysis of a compound having terminal isocyanate groups, particularly from isocyanate prepolymers by EP 0 071 834 A1. Suitable aromatic diamines are commercially available under Versalink® P-650 and Versalink® P-1000. In addition, aromatic diamines such as diethylenetoluenediamine, available as Ethacure 100, can be used as chain extenders.

[0044] Furthermore, a polyol can be used as component (B), and is particularly preferred to have an average molecular weight M of 400 g / mol to 20,000 g / mol. n Long-chain polyols having the following properties can be used. Examples of suitable long-chain polyols include polyether-based polyols commercially available as Acclaim® grades, polyesters and polycarbonates available as Kuraray® or Priplast® grades, and polybutadiene and hydrogenated polybutadiene-based polyols available as Krasol®, Polyvest® or Nisso-PB® grades.

[0045] Long-chain polyols with an average molecular weight of 2000 g / mol to 20000 g / mol are particularly suitable for producing compositions that exhibit high flexibility and a low glass transition temperature at low temperatures after curing. As a chain extender, component (B) may include at least one low molecular weight polyol having a molecular weight up to 400 g / mol, such as glycol, glycerol, 1,4-butanediol, or 2-ethyl-1,3-hexanediol.

[0046] Suitable thiols for use in component (B) are ester-based thiols such as trimethylolpropane tris-(3-mercaptopropionate) or pentaerythritol tetrakis-(3-mercaptobutyrate). Furthermore, as isocyanate-reactive components, thiol-terminated polyethers, as well as thiol-supported polythioethers, or tris-(3-mercaptopropyl) isocyanurate may also be used.

[0047] The first liquid isocyanate-reactive component (B) is preferably present in the composition according to the present invention in a proportion of 5 to 90% by weight, more preferably 40 to 85% by weight, based on the total weight of the composition. The proportion varies widely depending on the functionality and molecular weight of the isocyanate-reactive component.

[0048] Mixtures of polyols, amines, and / or thiols can also be advantageously used in the curable composition.

[0049] Component (C): Second solid isocyanate reactive component In addition to the first liquid isocyanate reactive component (B), the composition contains at least one second solid isocyanate reactive component (C) having a melting point of at least 50°C. The second solid isocyanate reactive component (C) can be selected from the group consisting of alcohols, amines, thiols, and mixtures thereof. Preferably, component (C) is selected from the group consisting of alcohols and amines. Amines are particularly preferred, and at least bifunctional amines are particularly preferred.

[0050] As component (C), any solid isocyanate-reactive compound having a melting point of basically 50°C or higher, preferably 60°C or higher, particularly preferably 65°C or higher, and even more preferably 200°C or lower can be used.

[0051] Here, explicitly, component (C) does not contain any of the compounds of the first isocyanate-reactive component (B) described above. These compounds are liquids at room temperature and are therefore unsuitable as component (C).

[0052] The second solid isocyanate reactive component (C) is present in the curable composition, particularly in the form of fine particles, and does not dissolve in component (B).

[0053] Preferably, the second solid isocyanate-reactive component (C) exists in the form of particles having a volume particle size d95 up to 100 μm, particularly preferably up to 40 μm, and very particularly preferably up to 10 μm.

[0054] More preferably, based on the weight of component (C), at least 40% by weight, more preferably at least 50% by weight, and particularly preferably at least 60% by weight of component (C) consists of amines. Particularly preferably, component (C) is at least a bifunctional amine.

[0055] The structure of amines is not further limited and includes primary, secondary, and tertiary amines. Furthermore, amines may contain aliphatic, alicyclic, and / or aromatic groups, or exist cyclically bridged in the form of heterocyclic or aromatic amines. Different amine functionalities may exist in any desired combination within the compound.

[0056] The amine may be bifunctional or more polyfunctional and may contain any number of further isocyanate-reactive groups. In the case of mixed-functional amines, preferably, in addition to the amine functional group, a thiol functional group or a hydroxyl functional group is present. Particularly preferably, the amine functional group and the hydroxyl functional group are present in combination. An example of this is the epoxy-amine adduct, which contains at least one further hydroxyl group in addition to the amine functional group.

[0057] Preferably, a compound having a molecular weight of less than 5,000 g / mol, more preferably less than 2,000 g / mol, and particularly preferably less than 1,000 g / mol is used as the second solid isocyanate-reactive component (C).

[0058] Examples of the second solid isocyanate-reactive compound (C) include 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dichlorodiphenylmethane, 4,4'-oxydianiline, bis-(4-amino-3,5-diethylphenyl)methane, pentaerythritol, trimethylolpropane, or trimethylolethane.

[0059] Commercially available products include, for example, Huntsman's Aradur 9664-1 and Aradur 9719-1, and Perstorp's Charmor PM15.

[0060] Commercial epoxyamine adducts are available, for example, under ADEKA's EH-5011S, EH-5046S, EH-5015SS and EH-5057P, under Evonik's Ancamine 2014FG or Ancamine 2442, or under Sanho Chemical's Fujicure FXR-1020, Fujicure FXR-1030, Fujicure FXR-1081 or Fujicure FXR-1121.

[0061] The second solid isocyanate reactive component (C) is preferably present in the composition according to the present invention in an amount of 1 to 35% by weight, and more preferably 2 to 25% by weight.

[0062] Based on the weights of components (B) and (C), the proportion of the solid isocyanate-reactive component (C) is preferably in the range of 1 to 40% by weight, and more preferably in the range of 2 to 30% by weight.

[0063] Component (D): Additive In addition to components (A) to (C), the composition according to the present invention may contain further additives (D). Examples of additives (D) that may be used include catalysts, toughness modifiers such as core-shell particles or block copolymers, dyes, pigments, fluorescent agents, thixotropic agents, thickeners, heat stabilizers, stabilizers, antioxidants, plasticizers, fillers, flame retardants, corrosion inhibitors, water collectors, diluents, flow and wetting additives, adhesion promoters, and combinations thereof, which may be mentioned as additives (D), but are not exhaustive.

[0064] Components having radical-curable double bonds and radical generators may also be used as additives (D). This makes it possible to achieve photofixation of the composition in the sense of EP 3 749 700 A1.

[0065] The catalyst (D1) used is preferably a compound known to those skilled in the art that catalyzes the reaction between an isocyanate reactive group and a polyisocyanate. Examples of suitable catalysts include, in particular, metal catalysts based on tin, zinc, lead, mercury, or bismuth, or tertiary amines such as triethylenediamine or DBU.

[0066] In principle, inert organic solvents can also be used as diluents, as long as they do not dissolve the solid polyisocyanate. However, preferably, the composition does not contain inert organic solvents, because the use of such solvents is undesirable from an environmental standpoint. In principle, water can also be used as a dispersion medium. However, this requires a complex drying process in the processing of the composition, and the use of aqueous dispersions is also undesirable.

[0067] Fumed silica, if surface-modified as needed, preferably functions as a thixotropic agent.

[0068] The additive is present in the curable composition in a proportion of preferably 0 to 80% by weight, and particularly preferably 0 to 50% by weight, based on the total weight of the composition.

[0069] Formulation of the composition according to the present invention The composition according to the present invention preferably comprises or consists of the above-mentioned components (A) to (C). Advantageously, the composition may contain at least one of the above-mentioned additives (D).

[0070] According to a first preferred embodiment, the composition according to the present invention comprises the following components: (A) At least one solid at least bifunctional isocyanate having a melting point of at least 40°C, preferably at least 60°C, obtained by passivating its surface by reacting 0.5-15% isocyanate groups with a polyamine, amidine and / or guanidine compound, hydrazine, alkylhydrazine and / or hydrazide compound; (B) At least one first liquid isocyanate-reactive component having an average functionality of 1.7 to 4; and (C) At least one second solid isocyanate reactive component having a melting point of at least 50°C Includes.

[0071] In a further preferred embodiment, the isocyanate-reactive component (C) is at least a bifunctional amine having a melting point of at least 60°C, and particularly at least 65°C.

[0072] Based on the weights of components (B) and (C), the second solid isocyanate-reactive component is preferably present in a proportion of 1 to 40% by weight.

[0073] More preferably, the composition contains at least one thixotropic agent and / or catalyst as component (D).

[0074] Characteristics of the composition according to the present invention: The composition according to the present invention is liquid at room temperature and is formulated (or compounded) as a one-pack composition. By selecting components (A) to (C) and passivating the isocyanate-containing component (A), this composition can be processed for a certain period of time even at room temperature.

[0075] The compositions according to the present invention are distinguished by their high temperature stability and adhesion after heat curing. This means that, for example, for compositions cured at temperatures exceeding 180°C in 90 minutes or 240°C in 1 minute, particularly in reflow soldering processes, only a limited decrease in adhesive strength in compressive shear strength and / or tensile strength is observed. In the prior art, this could only be achieved by significantly limiting the formulation range, particularly with respect to the structural diversity of component (A). In the present invention, the addition of a further high-melting-point isocyanate reactive component (C) has enabled the achievement of heat resistance of the curable composition while maintaining or even improving its mechanical properties. Thus, compared to other isocyanate-based addition-crosslinkable compositions, the compositions according to the present invention allow for the use of various isocyanate-functionalized resin components. This results in a wide range of formulation options for favorably adjusting the mechanical properties of the cured composition. Furthermore, by appropriately selecting a second solid isocyanate reactive component (C), the linear elastic behavior can be varied over a wide range.

[0076] Processing method using the composition according to the present invention The compositions according to the present invention, comprising at least components (A) to (C), are distinguished in that they can be cured at low temperatures. The joints thus obtained consistently maintain a high level of adhesion even at high operating temperatures and temperature peaks exceeding 180°C.

[0077] A corresponding method for joining, molding, or coating a substrate using the composition according to the present invention involves the following steps: (a) A step of providing the composition according to the present invention; (b) The step of introducing (or adding or adding) the composition to the first substrate; (c) optionally, a step of supplying a second substrate to the composition to form a substrate composite; and (d) A step of thermally curing the composition on the substrate and / or in the substrate composite by heating to a temperature of at least 60°C. Includes.

[0078] Heat curing preferably occurs at a temperature at which the solid isocyanate dissolves or melts, breaking the urea or polyurethane shell. Preferably, the heat curing is carried out at a maximum temperature of about 160°C.

[0079] In preferred use, this composition is used in reflow soldering processes. This composition can be advantageously used, for example, for additional fixing or casting and sealing of components on printed circuit boards. In a suitable bonding process, steps (a) to (d) are carried out. After thermal curing, a further heating step is performed, in particular to achieve temperatures exceeding 240°C. The temperature and time of the further heating step are selected so that the substrate composite is sufficiently heated to achieve solder melting and adhesive bonding of the components.

[0080] Due to the properties of the compositions according to the present invention, the level of adhesion is maintained despite high thermal stresses such as those that occur during the reflow soldering process. In some cases, it is even possible to increase the level of adhesion of the cured composition.

[0081] In further embodiments, the composition may be further fixed with light prior to thermal curing. Formulation components necessary for photofixation are taught in EP 3 749 700 A1. In particular, radiation-curable components such as (meth)acrylates are used for photofixation, and photopolymerization initiators are used for radical polymerization; these are incorporated into the composition as further components. A corresponding method for molding, coating, or bonding a substrate using a composition according to the present invention with photofixation preferably involves the following steps: (a) A step of providing a curable composition; (b) A step of adding the composition to the first substrate; (c) A step of irradiating the composition with light radiation; (d) optionally supplying a second substrate to form a substrate composite and bringing the second substrate into contact with the irradiated composition; and (e) A step of thermal curing the irradiated composition on and / or in the substrate composite by heating to a temperature of at least 60°C. Includes.

[0082] If the joining method includes step (d), then steps (c) and (d) may also be carried out in reverse order. This process sequence offers the advantage that the components can be further fixed in place by irradiation with actinic (or light) radiation prior to the thermosetting process.

[0083] Using the composition according to the present invention and with the help of the described method, a high degree of positional accuracy of the bonded components can be achieved until final curing. Conventional fixing aids are either not practical for miniaturized components or involve an unreasonable amount of additional work, but thus they can be avoided.

[0084] Components joined and fixed by methods using the compositions of the present invention can be reliably positioned even when mounted at an angle. Even in the case of components in which radioactive material cannot be penetrated by actinic radiation, fillet welds can be fixed by actinic radiation using the methods described using the compositions of the present invention.

[0085] Measurement method and definition room temperature Room temperature is defined as 23°C ± 2°C.

[0086] hardening "Crosslinking" or "curing" is defined as a polymerization, addition, or condensation reaction that exceeds the gel point (or gelation point). The gel point is the point at which the storage modulus G' equals the loss modulus G''.

[0087] Thermal DSC measurement The melting point was determined as an endothermic peak using a differential scanning calorimeter (DSC) (Mettler Toledo DSC822e).

[0088] Furthermore, 6-10 mg of the sample was weighed into an aluminum crucible (40 μL), sealed with a perforated lid, and subjected to measurement at temperatures ranging from 30 to 220°C at a heating rate of 2 K / min. The process gas was nitrogen at a volumetric flow rate of 30 mL / min.

[0089] Particle size distribution The particle size distribution was measured using a Microtrac S3500 particle size analyzer by laser diffraction in accordance with ISO 13320. The distribution indicated by size d95 represents the volume particle diameter.

[0090] Tensile strength Tensile properties such as tensile strength and elongation at break were measured according to DIN EN ISO 527-2:2012-06. Type 5A specimens were used. Tests were performed at room temperature using a Zwick Roell Allround-Line 20 kN universal tester at a speed of 200 mm / min. Heat curing was carried out in a preheated convection oven at 120°C for 30 minutes. After the specimen mold cooled, the cured composition specimens were removed from the mold and conditioned (or conditioned) at room temperature for 24 hours.

[0091] Compressive shear strength Two clad aluminum specimens (dimensions 20mm x 20mm x 5mm) were bonded together with a 5mm overlap using their respective compositions. For this purpose, beads of the composition were applied to the first specimen. The second specimen was then bonded. The thickness of the 0.1mm adhesive layer and the overlap were adjusted using spacer wires and bonding devices. The bonded specimens were cured in a preheated 120°C convection oven for 30 minutes.

[0092] Preparation example To prepare the composition according to the present invention, first a first liquid isocyanate reactive component (B) was mixed with a passivating agent, and then a finely powdered solid isocyanate (A) was added. Next, a second solid isocyanate reactive component (C) and optionally further additives (D) were added.

[0093] Each component was mixed according to the weight percentages shown in the table. Thorough mixing was performed using a lab top with a sickle-shaped kneading arm (PC lab system). Subsequently, the composition was degassed and filled into cartridges.

[0094] Curing of the compositions according to the present invention and comparative compositions by application of heat begins with the dissolution or melting of the solid isocyanate at high temperature, decomposing the urea or polyurethane shell. Curing of the compositions according to the present invention and comparative examples was carried out by heating at 120°C for 30 minutes. Depending on the type and amount of passivation agent in the solid isocyanate, adjustment of the curing temperature may be necessary.

[0095] Energy input for thermosetting can be achieved, for example, by convection in a convection oven, by heat conduction through a heating plate or thermomode, or by electromagnetic radiation through an IR radiation source, laser, microwave, or induction.

[0096] The following list shows all the compounds and their abbreviations used to prepare the curable composition.

[0097] Component (A): Surface-passivated, at least bifunctional solid isocyanate A-1 Thanecure T9 SF AD-V - Micronized TDI urezion, melting point 155℃ (Safic-Alcan) A-2 Jeffamine D-400 - Liquid polyetheramine (as a passivator) (Huntsman Corporation)

[0098] Component (B): First liquid isocyanate reactive component B-1 Jeffamine T-5000 - Liquid Polyetheramine (Huntsman Corporation) B-2 Ethacure 100 - Diethyltoluenediamine (liquid) as a chain extender (Albemarle Corporation) B-3 Krasol HLBH-P3000 - Liquid Polyol (Cray Valley) B-4 2-ethyl-1,3-hexanediol - liquid polyol (Sigma Aldrich)

[0099] Component (C): Second solid isocyanate reactive component C-1 Dapsone-4,4'-diaminodiphenylsulfone, melting point 178℃ (Atul Ltd.) C-2 Adeka Hardener EH-5046S - Epoxy-amine adduct, melting point 110°C (Adeka Corporation) C-3 Ancamine 2014 FG-epoxyamine adduct, melting point 69°C (Evonik Industries) C-4 Ancamine 2442 - Epoxyamine adduct, melting point 71°C (Evonik Industries)

[0100] Component (D): Additive D-1 Cab-O-Sil TS-720 - Fumed Silica (Cabot Corporation) D-2 Bismuth neodecanoate catalyst (Sigma Aldrich)

[0101] Dispersion of the second solid isocyanate-reactive component (C) According to the present invention, the second solid isocyanate-reactive component (C) exists in a dispersed form within component (B). For testing, a similar formulation without the solid isocyanate component (A) was prepared, and the formation of dispersion was confirmed by microscopic observation. To detect the intermediate dissolution of the second solid isocyanate-reactive component (C) in the mixture of component (B), the mixture was stored at room temperature for 1 day and 7 days, and then microscopic observations were performed. The formulations and results are summarized in Table 1.

[0102] [Table 1]

[0103] Mechanical properties of the composition according to the present invention The compositions prepared and cured using the above method were tested for heat resistance and aging resistance (or durability). For this purpose, compressive shear strength was measured as an indicator of initial adhesion, and the tensile strength of test specimens to which the compositions were joined was measured after curing and after aging (or deterioration or change over time) at 180°C for 90 minutes.

[0104] The ratio of passivated isocyanate (A) to liquid isocyanate-reactive component (B) was kept constant in each composition compared. The type and proportion of an additional solid isocyanate-reactive component (C) were varied.

[0105] The compositions evaluated and the results obtained are shown in Table 2.

[0106] [Table 2]

[0107] The composition according to Example 7 does not contain any further solid isocyanate-reactive amines as component (C). Therefore, this composition is not in accordance with the present invention. After aging of the cured composition of Example 7, a sharp decrease in tensile strength after aging at 180°C can be observed. By adding solid isocyanate-reactive component (C), this decrease in tensile strength can be considerably reduced, as can be seen in Examples 8 to 11 according to the present invention. The cured composition of Example 8 even exhibits higher tensile strength after aging than the composition immediately after curing.

[0108] The initial adhesion of the joint, measured as the compressive shear strength of the intermetallic bond, does not deteriorate in Examples 8-11 of the present invention compared to Comparative Example 7, and is even partially improved. After aging, all values ​​stabilize sufficiently and are higher than the initial values.

[0109] Further compositions containing different solid isocyanate reactive components (C) and their mechanical properties are shown in Table 3 below.

[0110] [Table 3]

[0111] Compared to the compositions shown in Table 2, the formulations in Table 3 show an increased proportion of solid isocyanate component (A), and thus exhibit a higher level of strength. The composition according to Example 13 does not contain any further solid isocyanate-reactive amine as component (C), and is therefore not in accordance with the present invention. After aging of the cured composition of Example 13, a sharp decrease in tensile strength is observed after aging at 180°C. In contrast, Examples 14-17 according to the present invention show a significantly increased tensile strength compared to the initial value. Therefore, the aging resistance of the joint at 180°C is considerably improved by the use of solid isocyanate-reactive component (C).

[0112] Examples 14-17 of the present invention exhibit even higher initial compressive shear strength, which is an improvement in part compared to Comparative Example 13. However, while the compressive shear strength of the cured composition of Comparative Example 13 decreases significantly after aging at 180°C, the adhesion level of the compositions of Examples 14-17 of the present invention increases considerably after aging.

[0113] The effect of the proportion of the second solid isocyanate-reactive component (C) on the mechanical properties of the cured composition is shown in Table 4 below.

[0114] [Table 4]

[0115] Examples 18-21 each contain different proportions of solid isocyanate reactive component C-2. Comparative Example 7 serves as a reference example in which the same ratio of passivated isocyanate (A) to liquid isocyanate reactive component (B) was used in the compositions of Examples 18-21. The cured composition of Comparative Example 7 shows a significant decrease in tensile strength after aging at 180°C for 90 minutes, while the corresponding values ​​of the compositions of Examples 18-21 are maintained at considerably high levels due to the addition of solid isocyanate reactive component (C).

[0116] A decrease in tensile strength after aging can be observed solely due to the proportion of the isocyanate-reactive component (C), which is approximately 30% by weight. Nevertheless, the initial adhesion is considerably improved compared to Comparative Example 7.

[0117] In the above examples, the compositions according to the present invention were formulated using a nitrogen-containing compound, particularly an amine, as the liquid isocyanate-reactive component (B). Alternatively or additionally, a polyol that is liquid at room temperature may be used as component (B). An example of such a composition is shown in Table 5 below.

[0118] [Table 5]

[0119] In the compositions of Comparative Example 22 and Example 23, a polyol was used as the liquid isocyanate reactive component (B). Furthermore, the composition according to the present invention in Example 23, which further contains a solid amine as component (C), exhibits high initial adhesion and further shows improvement in tensile strength after aging at 180°C.

[0120] Without the addition of the second solid isocyanate reactive component (C), the compressive shear strength decreases considerably after aging at 180°C, and the adhesive bond no longer exhibits sufficient adhesion. In addition, the tensile strength of the cured composition of Comparative Example 22, which does not contain the solid isocyanate reactive component (C), is no longer measurable after aging because the test specimen collapses.

Claims

1. A one-pack composition that is liquid at room temperature and curable by heat, (A) At least one at least bifunctional solid isocyanate having a passivation surface and a melting point of at least 40°C; (B) at least one first liquid isocyanate-reactive compound selected from the group consisting of alcohols, amines, thiols, and mixtures thereof; and (C) At least one second solid isocyanate-reactive compound having a melting point of at least 50°C A one-pack composition containing the above.

2. The composition according to claim 1, wherein at least a bifunctional solid isocyanate (A) reacts on its surface with a passivating agent selected from the group consisting of polyamines, amidine and / or guanidine compounds, hydrazines, alkylhydrazines and / or hydrazide compounds.

3. The composition according to claim 1 or 2, wherein at least a bifunctional solid isocyanate (A) is present at least partially in the form of a dimer.

4. - The composition according to any one of claims 1 to 3, wherein the molar ratio of free non-passivated isocyanate groups of component (A) to isocyanate-reactive groups of component (B) is 0.4 to 2.

5.

5. The composition according to any one of claims 1 to 4, wherein the second solid isocyanate reactive component (C) has a particle size of up to 100 μm, preferably up to 40 μm, and particularly preferably up to 10 μm.

6. The composition according to any one of claims 1 to 5, wherein at least 60% by weight of the second solid isocyanate reactive component (C) consists of an amine-functional compound.

7. The composition according to any one of claims 1 to 6, wherein the second solid isocyanate reactive component (C) is selected from the group consisting of epoxy-amine adducts, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dichlorodiphenylmethane, 4,4'-oxydianiline, bis-(4-amino-3,5-diethylphenyl)methane, pentaerythritol, trimethylolpropane, trimethylolethane, and combinations thereof.

8. The composition according to claim 6 or 7, wherein the second solid isocyanate reactive component (C) is an amine-functional compound.

9. The composition according to any one of claims 1 to 8, wherein the second solid isocyanate reactive component (C) is present in a proportion of 1 to 35% by weight, more preferably 2 to 25% by weight, based on the weights of components (B) and (C).

10. The composition consists of the following components: (A) At least one solid, at least bifunctional solid isocyanate having a melting point of at least 40°C, preferably at least 60°C, by passivating its surface by reacting 0.5 to 15% of the isocyanate groups with a polyamine, amidine and / or guanidine compound, hydrazine, alkylhydrazine and / or hydrazide compound; (B) At least one first liquid isocyanate-reactive component having an average functionality of 1.7 to 4; and (C) At least one second solid isocyanate reactive component having a melting point of at least 50°C A composition according to any one of claims 1 to 9, comprising:

11. A method for joining, molding and / or coating a substrate using a curable composition according to any one of claims 1 to 10, comprising the following steps: (a) A step of providing the curable composition according to any one of claims 1 to 10; (b) A step of adding the composition to the first substrate; (c) Optionally, a step of supplying a second substrate to the composition to form a substrate composite; (d) A step of thermally curing the composition on the substrate and / or in the substrate composite by heating to a temperature of at least 60°C. A method that includes this.

12. Use of the composition according to any one of claims 1 to 10 in a reflow soldering process for manufacturing electronic components and for joining magnets, speakers and automotive sensors.

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