WO2024068274A1 - Adhésif durcissable par voie cationique avec indication de force de maintien - Google Patents

Adhésif durcissable par voie cationique avec indication de force de maintien Download PDF

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Publication number
WO2024068274A1
WO2024068274A1 PCT/EP2023/075108 EP2023075108W WO2024068274A1 WO 2024068274 A1 WO2024068274 A1 WO 2024068274A1 EP 2023075108 W EP2023075108 W EP 2023075108W WO 2024068274 A1 WO2024068274 A1 WO 2024068274A1
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WO
WIPO (PCT)
Prior art keywords
curable adhesive
adhesive
curable
curing
cationic
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PCT/EP2023/075108
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German (de)
English (en)
Inventor
Christian Schuh
Sven HEIDSIECK
Oleg Brinster
Marten Papenbroock
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Tesa Se
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Publication of WO2024068274A1 publication Critical patent/WO2024068274A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J9/00—Adhesives characterised by their physical nature or the effects produced, e.g. glue sticks
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J163/00—Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/10—Adhesives in the form of films or foils without carriers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/0041—Optical brightening agents, organic pigments
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/30—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
    • C09J2301/302—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier the adhesive being pressure-sensitive, i.e. tacky at temperatures inferior to 30°C
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
    • C09J2301/408—Additional features of adhesives in the form of films or foils characterized by the presence of essential components additives as essential feature of the adhesive layer
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2463/00—Presence of epoxy resin

Definitions

  • the invention relates to a curable adhesive and a reactive adhesive tape comprising a corresponding curable adhesive and an efficient method for connecting two or more components before carrying out further processing steps. Also disclosed are the use of corresponding curable adhesives and reactive adhesive tapes for bonding two or more components, as well as a method for producing corresponding curable adhesives.
  • Joining separate elements is one of the central processes in manufacturing technology.
  • bonding i.e. joining using an adhesive
  • pressure-sensitive adhesive tapes in particular are known, in which a pressure-sensitive adhesive ensures the adhesive effect, which is permanently sticky and adhesive under normal environmental conditions.
  • Corresponding pressure-sensitive adhesive tapes can be applied to a substrate by pressure and remain stuck there, but can later be removed more or less without leaving any residue.
  • Curable adhesives are known in the art and can have very different compositions from a chemical point of view. What these curable adhesives have in common is that the crosslinking reaction can be triggered by external influencing factors, for example by supplying energy, in particular by temperature, plasma or radiation curing, and / or contact with a substance that promotes polymerization, as is the case, for example, with moisture-curing ones Adhesives are the case. Examples of adhesives are, for example, DE 102015222028 A1, EP 3091059 A1, EP 3126402 B1, EP 2768919 B1, DE 102018203894 A1, WO 2017174303 A1, JP 461 1463 B2 and US 466154 2 A revealed.
  • curable adhesives Despite the known advantages of curable adhesives, they also have properties during processing that are perceived as disadvantageous. Since curable adhesives usually only achieve the necessary bonding strength during the curing process, when using curable adhesives to bond components it is often necessary to wait until the curable adhesive has cured sufficiently before further processing of the component composites created in this way can take place. This is particularly true in cases where the component composite created is exposed to strong mechanical stresses during further processing, which can lead to bond failure if the curing is inadequate.
  • the bonding of components with a curable adhesive can often become a time-limiting step in corresponding manufacturing processes, which adversely affects time and cost efficiency.
  • WO 20201 19898 A1 discloses curable adhesives to which a dye, in particular azo dyes or Sudan blue, is added, and which consequently not only show a color change after the adhesive is activated, but also show a renewed color change after the final bonding strength has been reached, in the case of WO 20201 19898 A1 after 24 hours. This makes it possible to reduce the time buffer described above to ensure complete curing despite the variance in the curing speed, since the achievement of the final bonding strength can be visually recognized by the workers employed.
  • a dye in particular azo dyes or Sudan blue
  • the primary object of the present invention was to eliminate or at least reduce the disadvantages of the prior art described above.
  • the curable adhesive should enable reliable bonding of the components and a high level of process reliability during use, especially when using untrained workers.
  • the curable adhesive mass to be specified should have the greatest possible flexibility in terms of chemical composition and thus in terms of the physico-chemical properties that can be achieved during curing, in particular in terms of the adhesive strength that can be achieved.
  • the curable adhesive mass to be specified should also be able to be produced predominantly from components that are used for conventional curable adhesive masses.
  • the curable adhesive mass should desirably be able to be implemented both as a liquid and as a solid, pressure-sensitive adhesive mass.
  • the inventors of the present invention have now found that the tasks described above can surprisingly be achieved if a color indicator is used in epoxy-based curable adhesives which cure via a cationic initiator, the selection of which is tailored to the other composition of the curable adhesive is that the curable adhesive shows a color change when the bond strength is in the range of 20 to 80% of the maximum bond strength achievable by cationic curing, as defined in the claims.
  • the invention is based on the surprising finding that, in the opinion of the inventors, the solution found in WO 20201 19898 A1, which in the opinion of the inventors will certainly also have its fields of application, rather set the wrong priorities with regard to the application-technical framework conditions and needs of modern manufacturing processes, which ultimately prevents a particularly advantageous increase in the time and cost efficiency of the process control, as is possible within the scope of the present invention.
  • the concentration of the cationic initiator or the concentration of the curing-active species generated from it during activation for example the strong acids
  • the concentration of the curing-active species generated from it during activation for example the strong acids
  • the concentration of the curing-active species generated from it during activation for example the strong acids
  • the concentration of the curing-active species generated from it during activation for example the strong acids
  • the concentration of the curing-active species generated from it during activation for example the strong acids
  • the pH value for example the pH value
  • WO 20201 19898 A1 based on the previously known state of the art, wants to indicate the immediate start of activation, the color change of the dye used there must take place at a time when the curable adhesive mass still corresponds almost to the initial state and the relevant parameter, e.g. the pH value, differs only slightly. However, this means conversely that the reverse color change back to the original color inevitably takes place when the relevant parameter is again close to the initial value, which, however, can only be achieved when the maximum possible curing is reached at the earliest. This indication of complete curing, for example when using Sudan Blue after 24 hours, is deliberately intended in WO 20201 19898 A1.
  • the inventors have found that the state of maximum achievable curing, as indicated in WO 20201 19898 A1, for example, by a color change from Sudan Blue II after 24 hours, is not the absolutely necessary state for most manufacturing processes with a view to optimizing time and cost efficiency, particularly in light of a non-linear increase in bonding strength in many cases. Rather, in most cases, reliable further processing is possible even when the curing adhesive is still significantly removed from the state of maximum achievable bonding strength. Surprisingly, this applies in many cases even when further processing is associated with noticeable mechanical stresses on the component composite.
  • the inventors propose that, in contrast to the teaching of WO 20201 19898 A1, the curable adhesive should be adjusted in such a way that a color change occurs at a time when the adhesive has a medium curing state, which can be expediently adapted by the person skilled in the art to the specific requirements of the subsequent processing steps, i.e., for example, the expected mechanical load on the component assembly.
  • This enables much faster timing in corresponding manufacturing processes, since the workers employed and/or sensors aimed at the color change receive the visual information at exactly the optimized time that the manufactured component assembly is ready for further processing.
  • the invention relates to a curable adhesive comprising: a) one or more (co)polymers, b) one or more polymerizable epoxy compounds, c) one or more cationic initiators, and d) one or more pH color indicators with at least one pH-dependent color change, wherein the mass ratio of the combined mass of the cationic initiators to the combined mass of the pH color indicators in the curable adhesive is 5:1 or more, and wherein the curable adhesive is composed such that a pH-dependent color change of one or the multiple pH color indicators during the cationic curing of the curable adhesive at a point in time at which the bond strength of the curing adhesive is in the range of 20 to 80% of the maximum bond strength achievable through cationic curing.
  • curable adhesives are widely known to the person skilled in the art from the prior art, with the individual components specified above also being known to the person skilled in the art in isolation and being commercially available in various variations from numerous different suppliers, with preferred and exemplary representatives for the individual components also being disclosed below.
  • the curable adhesive as a polymerizable epoxy compound can exclusively comprise epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, which would mean that the curable adhesive comprises a large number of the corresponding molecules.
  • the curable adhesive according to the invention is curable. Due to the possibility of curing, the curable adhesive can function as a structural adhesive after curing.
  • structural adhesives are demonstrably suitable for producing load-bearing structures in which the Adhesive connection can be stressed over long periods of time with a high percentage of the maximum breaking force without failure (according to ASTM definition: "bonding agents used for transferring required loads between adherends exposed to service environments typical for the structure involved"). They are therefore adhesives for chemical and physically highly resilient adhesives, which help to strengthen the adhesive tapes when hardened.
  • the curable adhesive is composed in such a way that a pH-dependent color change of the one or more pH color indicators occurs during the cationic curing of the curable adhesive at a point in time at which the bonding strength of the hardening adhesive in The range is from 20 to 80% of the maximum bond strength that can be achieved by cationic curing, which means that the curable adhesive is set up or designed accordingly.
  • the curable adhesive being composed in such a way that after activation with a radiation dose of 1000 mJ/cm 2 or more, preferably 2000 mJ/cm 2 or more, a pH-dependent color change of the one or more pH color indicators occurs during the cationic curing of the curable adhesive at a point in time at which the bond strength of the curing adhesive is in the range of 20 to 80% of the maximum bond strength achievable by the cationic curing .
  • the inventors assume that, in case of doubt, the fine-tuning will be carried out with a predetermined radiation dose that corresponds to the radiation dose specified by the corresponding manufacturer of the curable adhesive compositions for their later use. In view of the observed low dependence on the initiation conditions, in case of doubt, a typical radiation dose can simply be specified.
  • the curable adhesive being composed in such a way that after activation with a radiation dose of 3000 mJ/cm 2 a pH-dependent color change of the one or more pH color indicators during the cationic Curing of the curable adhesive takes place at a point in time at which the bond strength of the hardening adhesive is in the range of 20 to 80% of the maximum bond strength achievable by cationic curing.
  • curable adhesive which comprises the components described above, the curable adhesive being composed in such a way that a pH-dependent color change of the one or more pH color indicators during the cationic Curing of the curable adhesive takes place at a point in time at which the bond strength of the hardening adhesive is in the range of 20 to 80% of the maximum bond strength achievable by cationic curing.
  • curable adhesive which comprises the components described above, wherein the adhesive can be cured by cationic curing in such a way that the adhesive shows a pH-dependent color change of the one or more pH color indicators when the curing adhesive has a bonding strength that is in the range of 20 to 80% of the maximum bonding strength achievable through cationic curing.
  • curable adhesive which comprises the components described above, wherein the adhesive, during cationic curing, at the time of a pH-dependent color change of the one or more pH color indicators, has a bonding strength which is in the range of 20 to 80% of the maximum bonding strength achievable by cationic curing.
  • this is therefore a curable adhesive according to the invention, wherein the curable adhesive is composed in such a way that the pH-dependent color change of the one or more pH color indicators is caused by an increase in the pH value.
  • the initial value of the pH value in the non-activated curable adhesive but also the temporal development of the pH value depends significantly on the components used in the adhesive, for example the type and concentration of the cationic initiators, so that the selection of the pH color indicators, by which the setting of the curable adhesive will be carried out in practice, can only be generalized with difficulty.
  • the person skilled in the art can, for example, proceed by first preparing a curable starting adhesive comprising: aal ) one or more (co)polymers, bb1 ) one or more polymerizable epoxy compounds, and cc1 ) one or more cationic initiators, in which the pH color indicators are thus still missing, but which is optimized with regard to the physicochemical properties, in particular after curing, to the respective requirements facing the person skilled in the art.
  • the expert initially only registers the time after which the desired bond strength is achieved, with which, for example, further processing is possible without damage to the adhesive bond.
  • This advantageously means that no quantification of the absolute values of the desired bond strength or the maximum achievable bond strength is necessary at this point in time.
  • the person skilled in the art can now identify suitable pH color indicators that he needs to implement the invention in various ways.
  • the person skilled in the art can introduce various pH color indicators available to him into the starting adhesive and test experimentally which of these pH color indicators show a color change near the time estimated by the person skilled in the art, or ideally shortly after the estimated time.
  • the person skilled in the art can also determine the pH value of the material he considers to be optimally cured. curing adhesive and select a suitable pH color indicator based on tabulated values that tabulate the respective transition points for pH color indicators.
  • the expert can then fine-tune the system, whereby the expert can optimize the concentrations of the individual components of the curable adhesive in the usual way in routine experiments.
  • the expert will, for example, in an iterative optimization process, primarily compensate for or take into account the addition of the pH color indicator, which can at least potentially change the properties of the starting adhesive, at least if it is to be used in larger quantities, whereby in particular some basic pH color indicators can also influence the pH value and influence the cationic activation, so that the adhesive system can be gradually adjusted in a professional manner until its properties are sufficient for the intended application.
  • the person skilled in the art can then determine the bond strength at the time of the color change and compare this with the maximum bond strength achievable through cationic curing in order to verify that it lies within the interval to be set according to the invention.
  • the maximum achievable bonding strength can easily be determined as the bonding strength, which arises as the resulting limit value within the scope of the measurement inaccuracy of the determination method after the initiation of the cationic hardening. Since the bond strength generally reaches a plateau value in accordance with the expert understanding and the expert will usually be able, based on his experience, to meaningfully estimate when the curing is essentially complete, in practice it is usually possible to rely on time-dependent measurements of the Adhesion strength can be dispensed with.
  • the measurement of bond strength to be determined in the context of the present invention is an established quantity for those skilled in the art of bonding technology. In principle, this quantity can be measured in different experimental setups and under different conditions. Since in the context of the present invention a relative bond strength is defined based on a final value, the person skilled in the art can in principle use any method for determining the bond strength, as long as he determines both values using the same method, which, however, for the person skilled in the art will be self-evident.
  • the bond strength is determined in a dynamic tensile shear test in accordance with DIN EN 1465:2009-07 at 23 ° C and 50% relative humidity in a manner customary in the industry a test speed of 1 mm/min was determined.
  • the color change should not occur too early, since below 20% of the maximum achievable bond strength it is unlikely that the component composites that can be produced with this will have sufficient strength in subsequent processing steps.
  • the color change only occurs at more than 80% of the maximum achievable bonding strength, the inventors believe that the achievable advantages in the improved timing are too small.
  • the inventors suggest that this conflict of objectives is solved advantageously, especially with medium relative bond strengths.
  • a curable adhesive according to the invention is preferred, the curable adhesive being composed in such a way that a pH-dependent color change of the one or more pH color indicators occurs during the cationic curing of the curable adhesive at a point in time at which the bond strength of the curing adhesive in the range from 25 to 75%, preferably in the range from 30 to 70%, particularly preferably in the range from 35 to 65%, of the maximum bond strength that can be achieved by cationic curing.
  • a curable adhesive according to the invention is preferred for most practical applications, the curable adhesive being composed in such a way that a pH-dependent color change of the one or more pH color indicators during the cationic curing of the curable adhesive becomes one
  • the time at which the bonding strength of the hardening adhesive is in the range from 1.5 to 4.5 MPa, preferably in the range from 2.0 to 4.0 MPa, particularly preferably in the range from 2.5 to 3.5 MPa , measured according to DIN EN 1465:2009-07 at 23 °C and 50% relative humidity for a test speed of 1 mm/min.
  • curable adhesive composition comprising: a) one or more (co)polymers, b) one or more polymerizable epoxy compounds, c) one or more cationic initiators, and d) one or more pH color indicators with at least one pH-dependent color change, wherein the mass ratio of the combined mass of the cationic initiators to the combined mass of the pH color indicators in the curable adhesive composition is 5:1 or more, and wherein the curable adhesive composition is composed such that a pH-dependent color change of the one or more pH color indicators occurs during the cationic curing of the curable adhesive composition at a time when the bonding strength of the curing adhesive composition is in the range of 1.5 to 4.5 MPa, preferably in the range of 2.0 to 4.0 MPa, particularly preferably in the range of 2.5 to 3.5 MPa, measured according to DIN
  • the curable adhesive composition disclosed will in the majority of cases be a curable adhesive according to the invention.
  • the curable adhesive composition is also extremely advantageous in itself, whereby the above statements on the advantages and production as well as the following statements on preferred curable adhesives according to the invention each apply accordingly, whereby the curable adhesive compositions disclosed can also be used in particular in corresponding adhesive tapes, processes and uses.
  • the curable adhesives according to the invention can in principle also be provided as liquid systems in an advantageous manner. For later use in the end application, however, it is advantageous for the handling properties if the curable adhesive has an intrinsic pressure-sensitive adhesive and can thus be classified as a pressure-sensitive adhesive.
  • the pressure-sensitive adhesive allows reliable and safe application of the reactive adhesive tapes to the substrate before the curable adhesives have cured. Accordingly, a curable adhesive according to the invention is preferred, the curable adhesive being a pressure-sensitive adhesive.
  • the inventors believe it is expedient to set the combined mass fraction of the (co)polymers in the curable adhesive to 25% or more, preferably 30% or more, particularly preferably 35% or more.
  • a pressure-sensitive adhesive is an adhesive that has pressure-sensitive adhesive properties, ie the property of forming a permanent bond to an adhesive base even under relatively weak pressure.
  • Corresponding pressure-sensitive adhesive tapes can usually be removed from the adhesive base after use essentially without leaving any residue and are usually permanently self-adhesive even at room temperature, which means that they have a certain viscosity and stickiness to the touch, so that they can adhere to the surface of a substrate even at low temperatures Wet pressure.
  • the adhesiveness of a pressure-sensitive adhesive tape results from the fact that a pressure-sensitive adhesive is used as the adhesive.
  • a pressure-sensitive adhesive can be viewed as an extremely high-viscosity liquid with an elastic component, which therefore has characteristic viscoelastic properties that lead to the permanent inherent tack and pressure-sensitive adhesive ability described above. It is assumed that with corresponding pressure sensitive adhesives, mechanical deformation leads to both viscous flow processes and the build-up of elastic restoring forces. The proportionate viscous flow serves to achieve adhesion, while the proportionate elastic restoring forces are necessary in particular to achieve cohesion.
  • the connections between rheology and pressure sensitive tack are known in the art and are described, for example, in “Satas, Handbook of Pressure Sensitive Adhesives Technology”, Third Edition, (1999), pages 153 to 203.
  • an adhesive is preferably understood to be pressure-sensitively tacky and thus a pressure-sensitive adhesive if, at a temperature of 23 ° C in the deformation frequency range of 10 ° to 10 1 rad / sec, G 'and G "are each at least partially in the range of 10 3 to 10 7 Pa.
  • the mass proportions are stated as combined mass proportions of the one or more components, which expresses that the mass proportion of the correspondingly designed components taken together meets the corresponding criteria, whereby, in the absence of other information, the mass of the curable adhesive is the reference system.
  • the (co)polymers usually play the role of film former, which is particularly important when, for example, pressure-sensitive adhesives are to be obtained.
  • this is a curable adhesive, with the one or more (co)polymers being selected from the group consisting of film-forming (co)polymers.
  • a curable adhesive composition preference is given to a curable adhesive composition according to the invention, the one or more (co-)polymers being selected from the group consisting of poly(meth)acrylates, polyurethanes, polyvinyl acetals, such as polyvinyl butyral, polysiloxanes, synthetic rubbers, polyesters, phenoxy polymers , polyvinyl alcohols, polyvinyl alcohol copolymers, and alkene-vinyl acetate copolymers, are preferably selected from the group consisting of Poly(meth)acrylates, phenoxy polymers, polyvinyl alcohols, polyvinyl alcohol copolymers, polyvinyl acetals, such as polyvinyl butyral, and ethylene-vinyl acetate copolymers (EVA or EVAC, poly(ethylene-co-vinyl acetate)), in particular selected from the group consisting of poly(meth )acrylates, phenoxy polymers and ethylene-vinyl
  • block copolymers for example (meth)acrylate block copolymers
  • (co)polymers can also be used as (co)polymers.
  • block copolymers for example (meth)acrylate block copolymers
  • (co)polymers can also be used as (co)polymers.
  • block copolymers for example, in the documents US 201 1003947 A1, US 20080200589 A1, US 2007078236 A1, US 2007078236 A1, US 2012196952 A1, US 2016032157 A1, US 2008146747 A1 and US 2 016230054 A1 disclosed.
  • the number-average molar masses M n of the (co)polymers are preferably in a range from 50,000 to 10,000,000 g/mol, particularly preferably in a range from 100,000 to 5,000,000 g/mol, and most particularly preferably in a range from 150,000 to 2,000,000 g/mol.
  • the information on the number-average molar mass M n refers to the determination by gel permeation chromatography (GPC). The determination is carried out on 100 ⁇ l of a clear-filtered sample (sample concentration 4 g/l). Tetrahydrofuran with 0.1 vol.% trifluoroacetic acid is used as the eluent. The measurement is carried out at 25 °C.
  • a combination of columns of type PSS-SDV, 5 pm, 10 3 ⁇ as well as 10 5 ⁇ and 10 6 ⁇ , each with 8.0 mm * 300 mm is used (columns from Polymer Standards Service; detection using a Shodex RI71 differential refractometer). The flow rate is 1.0 ml per minute. Calibration is carried out for polyacrylates against PMMA standards (polymethyl methacrylate calibration) and otherwise (resins, elastomers) against PS standards (polystyrene calibration).
  • the combined mass fraction of the (co)polymers in the curable adhesive being in the range from 1 to 70%, preferably in the range from 2 to 60%, especially preferably in the range from 5 to 50%, very particularly preferably in the range from 10 to 40%, based on the mass of the curable adhesive.
  • the curable adhesive according to the invention also includes at least one polymerizable epoxy compound and optionally further polymerizable compounds. These compounds together form the part of the curable adhesive which is often referred to by those skilled in the art as reactive resin.
  • polymerizable here refers, in accordance with the understanding of those skilled in the art, to the ability of these compounds to undergo a polymerization reaction, if necessary after suitable activation.
  • polymerizable epoxy compounds polymerizability is made possible, for example, by the epoxy groups.
  • epoxy compounds are those compounds that carry at least one oxirane group. They can be aromatic or aliphatic, in particular cycloaliphatic, in nature.
  • Polymerizable epoxy compounds can include both monomeric and oligomeric or polymeric epoxy compounds. Polymerizable epoxy compounds often have on average at least two epoxy groups per molecule, preferably more than two epoxy groups per molecule. In this respect, preference is given to a curable adhesive according to the invention, wherein the one or more polymerizable epoxy compounds are selected from the group consisting of epoxy compounds with two or more epoxy groups, preferably two epoxy groups.
  • the oligomeric or polymeric epoxy compounds mostly include linear polymers with terminal epoxy groups (e.g. a diglycidyl ether of a polyoxyalkylene glycol), polymers with framework oxirane units (e.g. polybutadiene polyepoxide) and polymers with epoxy side groups (e.g. a glycidyl methacrylate polymer or copolymer) .
  • the molecular weight of such epoxide compounds can vary from 58 to about 100,000 g/mol or more, with the molecular weight being an important control variable for adjusting the dynamic viscosity.
  • Exemplary polymerizable epoxy compounds include epoxycyclohexanecarboxylates such as 4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate and bis(3,4-epoxy-6- methylcyclohexylmethyl) adipate. Further examples of polymerizable epoxy compounds are disclosed, for example, in US 3,117,099 A. Other polymerizable epoxy compounds that are particularly useful in the practice of this invention include glycidyl ether monomers such as those disclosed in US 3,018,262.
  • Examples are the glycidyl ethers of polyhydric phenols, which are obtained by reacting a polyhydric phenol with an excess of chlorohydrin, such as epichlorohydrin (e.g. the diglycidyl ether of 2,2-bis-(2,3-epoxypropoxyphenol)propane).
  • chlorohydrin e.g. the diglycidyl ether of 2,2-bis-(2,3-epoxypropoxyphenol)propane.
  • diglycidyl ethers of bisphenols such as bisphenol-A (4,4'-(propane-2,2-diyl)diphenol) and bisphenol-F (bis(4-hydroxyphenyl)methane).
  • bisphenols such as bisphenol-A (4,4'-(propane-2,2-diyl)diphenol) and bisphenol-F (bis(4-hydroxyphenyl)methane).
  • Such reaction products are commercially available in different molecular weights and physical states (for
  • Typical examples of liquid bisphenol A diglycidyl ethers are Epikote 828, DER331 and Epon 828.
  • Typical solid BADGE resins are Araldite GT6071, GT7072, Epon 1001 and DER 662.
  • Other reaction products of phenols with epichlorohydrin are the phenol and cresol novolak resins such as Epiclon types or Araldite EPN and ECN types (e.g. ECN1273).
  • the one or more polymerizable epoxy compounds being selected from the group consisting of bisphenol A diglycidyl ethers and bisphenol F diglycidyl ethers, preferably bisphenol A diglycidyl ethers.
  • curable adhesives can be obtained if two or more different polymerizable epoxy compounds are used, especially if they differ in their physical state at room temperature.
  • a curable adhesive composition according to the invention is preferred, wherein the curable adhesive composition comprises one or more polymerizable epoxy compounds which are selected from the group of epoxy compounds which are solids at 25 ° C or highly viscous substances with a dynamic viscosity of 50 Pa s or more , preferably 100 Pa s or more, particularly preferably 150 Pa s or more, and / or wherein the curable adhesive comprises one or more polymerizable epoxy compounds selected from the group of epoxy compounds which are at 25 ° C a liquid with a dynamic viscosity of 40 Pa s or less, preferably 20 Pa s or less, most preferably 10 Pa s or less.
  • the dynamic viscosity is determined in accordance with DIN 53019-1 from 2008; at 25 °C, with a shear rate of 1 s -1 .
  • the combined mass fraction of the polymerizable epoxy compounds in the curable adhesive being in the range from 35 to 95%, preferably in the range from 40 to 90%, particularly preferably in Range from 45 to 85%, very particularly preferably in the range from 50 to 80%, based on the mass of the curable adhesive.
  • the curable adhesives according to the invention comprise at least one cationic initiator.
  • Corresponding cationic initiators are known to those skilled in the art based on their general specialist knowledge and are often used, particularly in the field of epoxy-based reactive adhesives. The person skilled in the art essentially adapts the catalyst system used for curing to the application requirements and the polymerizable epoxy compounds used.
  • a curable adhesive composition according to the invention is preferred, with the one or more cationic initiators being selected from the group consisting of radiation-activated initiators and thermally activated initiators, preferably selected from the group consisting of radiation-activated initiators, or wherein the curable adhesive is a radiation-curing and/or thermally curing, preferably radiation-curing, adhesive.
  • TAG thermally activated cationic initiators
  • thermal acid generator thermally activated cationic initiators
  • Suitable TAGs are known to those skilled in the art and are commercially available from numerous providers.
  • Preferred are TAG that comprise a cation selected from the group consisting of 4-substituted benzylanilinium, 4-substituted benzylpyridinium, 4-substituted benzylphosphonium, S-substituted diphenylsulfonium and substituted aryl-benzylsulfonium, preferably selected from the group consisting of 4-substituted benzylanilinium.
  • the TAG can in principle contain any anion, with weakly coordinating anions such as tetrafluoroborate (BF4), hexafluorophosphate (PFej, hexafluoroantimonate (SbFej, tetrakis(pentafluorophenyl)borate (B(CeFs)4j) and trifluoromethyl sulfonate (F3CSO3) being preferred.
  • weakly coordinating anions such as tetrafluoroborate (BF4), hexafluorophosphate (PFej, hexafluoroantimonate (SbFej, tetrakis(pentafluorophenyl)borate (B(CeFs)4j) and trifluoromethyl sulfonate (F3CSO3) being preferred.
  • BF4 tetrafluoroborate
  • PFej hexafluorophosphate
  • SBFej he
  • Combinations of a TAG made of cation and anion in which the resulting initiator has an activation temperature in the range from 50 ° C to 150 ° C are advantageous, with the person skilled in the art preferably adjusting the activation energy to the respective application requirements, in particular a range of 80 ° C up to 120 ° C is preferred in many cases in order to be able to carry out the polymerization at a comparatively moderate activation temperature and still enable a clearly defined initiation.
  • the activation temperature of reactive or chemically activated adhesives in general or of the TAG used is determined calorimetrically using Differential Scanning Calorimetry (DSC) according to DIN EN ISO 1 1357-3:2013-04.
  • anions that serve as counterions for the above-mentioned cations are tetrafluoroborate, tetraphenylborate, hexafluorophosphate, perchlorate, tetrachloroferrate, hexafluoroarsenate, hexafluoroantimonate, pentafluorohydroxyantimonate, hexachloroantimonate, tetrakispentafluorophenyl- borate, tetrakis-(pentafluoromethylphenyl)-borate, bi-(trifluoromethylsulfonyl)-amides and tris-(trifluoromethylsulfonyl)-methides.
  • chloride, bromide or iodide are also conceivable as anions, particularly for iodonium-based initiators, although initiators that are essentially free of chlorine and bromine are preferred.
  • iodonium-based initiators particularly for iodonium-based initiators, although initiators that are essentially free of chlorine and bromine are preferred.
  • a powerful example of such a system is triphenylsulfonium hexafluoroantimonate.
  • Other suitable initiators are, for example, in US 3,729,313 A, US 3,741,769 A, US 4,250,053 A, US 4,394,403 A, US 4,231,951 A, US 4,256,828 A, US 4,058,401 A, US 4,138,255 A and US 2010/06 3221 A1 disclosed.
  • usable sulfonium salts are in particular triarylsulfonium salts, for example triphenylsulfonium hexafluoroarsenate, triphenylsulfonium hexafluoroborate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium tetrakis-(pentafluorobenzyl)borate,
  • Methyldiphenylsulfonium tetrafluoroborate methyldiphenylsulfonium tetrakis (pentafluorobenzyl) borate
  • iodonium salts are diphenyliodonium tetrafluoroborate, di-(4-methylphenyl)-iodonium tetrafluoroborate, phenyl-4-methylphenyliodonium tetrafluoroborate, di-(4-chlorophenyl)-iodonium hexafluorophosphate, dinaphthyliodonium tetrafluoroborate, di-(4-trifluoromethyl-phenyl)-iodonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, di-(4-methylphenyl)-iodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, di-(4-phenoxyphenyl)- iodonium tetrafluoroborate, phenyl-2-thienyliodonium
  • Diaryliodonium tetrakis-(pentafluorophenyl)-borate such as diphenyliodonium tetrakis-(pentafluorophenyl)-borate, [4-(2-hydroxy-n-tetradesiloxy)-phenyl]-phenyliodonium hexafluoroantimonate, [4-(2-hydroxy-n-tetradesiloxy)-phenyl]-phenyliodonium trifluorosulfonate, [4-(2-hydroxy-n-tetradesiloxy)-phenyl]-phenyl- iodonium hexafluorophosphate, [4-(2-hydroxy-n-tetradesiloxy)-phenyl]-phenyliodonium tetrakis-
  • Photoinitiators are typically used individually or as a combination of two or more photoinitiators. When using photoinitiators, combinations with so-called sensitizers are very helpful for adapting the activation wavelength of the photoinitiation system to the selected emission spectrum, for the literature known to those skilled in the art, such as “Industrial Photoinitiators: A technical guide” 2010 by A.W. Green, is referred.
  • the mass fraction of photoinitiators in the curable adhesive is typically not more than 4% but at least 0.1%, and is preferably in the range from 0.5 to 2%.
  • the mass fraction of sensitizers is usually not more than 3% and is preferably in the range from 0.5 to 2%.
  • a curable adhesive composition according to the invention largely independent of the selection of the specific cationic initiator, wherein the combined mass fraction of the cationic initiators in the curable adhesive composition is in the range from 0.1 to 7%, preferably in the range from 0.3 to 5%, particularly preferably in the range of 0.5 to 4%, based on the mass of the curable adhesive.
  • color change means that the absorption behavior of the pH color indicators for electromagnetic radiation of a wavelength in the visible light range, i.e. in the range from 380 to 780 nm, changes, so that an adhesive compound mixed with the pH color indicator results in a changed transmission or remission as a result of the color change.
  • a curable adhesive according to the invention is preferred, wherein the one or more pH color indicators have exactly one pH-dependent color change.
  • a curable adhesive according to the invention is particularly preferred, wherein the one or more pH color indicators have a pH-dependent color change, preferably in the case of several change points the highest color change in terms of pH value, at a pH Have a value of 4 or less, preferably 3 or less, particularly preferably 2.5 or less.
  • a curable adhesive composition wherein the one or more pH color indicators are selected from the group consisting of cresol red (CAS: 1733-12-6), methyl violet (CAS: 8004-87-3), crystal violet (CAS: 548-62-9), ethyl violet (CAS: 2390-59-2), malachite green (acetate - CAS: 1272-40-6; hydrochloride - CAS: 569-64-2; oxalate - CAS: 2437-29-8), methyl green (CAS: 71 14-03-6), ethyl green (CAS: 14855-76-6), 2-(p-dimethylaminophenylazo)pyridine (CAS: 13103-75-8), metanil yellow (CAS: 587-98-4), 4- Phenylazodiphenylamine (CAS: 101 -75-7), Thymol Blue (CAS: 62625-21 -2), Metacresol Purple (CAS: 2303- 01 -7
  • the inventors have found that, particularly with regard to the targeted adjustment of the color change to the desired relative bonding strength but also with regard to the areas of relative bonding strength accessible via the pH color indicator, it is advantageous not to use azo dyes as a pH color indicator and to use the curable ones Rather, the adhesive should be as free as possible from azo dyes or with at least only a small proportion of azo dye. Accordingly, preference is given to a curable adhesive composition according to the invention, the one or more pH color indicators being selected from the group consisting of azo bridge-free pH color indicators. Preferred is a curable adhesive according to the invention, the combined mass fraction of azo dyes in the curable adhesive being 0.005% or less, preferably 0.0001% or less, based on the mass of the curable adhesive.
  • the inventors have found that it is advantageous, particularly with regard to the targeted adjustment of the color change to the desired relative bond strength but also with regard to the areas of relative bond strength accessible via the pH color indicator, not to use Sudan Blue II, which is Anthraquinone dye from the group of Sudan dyes should be used and the curable adhesive should be made as free of Sudan blue as possible. Accordingly, preference is given to a curable adhesive according to the invention, the curable adhesive being essentially free of Sudan blue II, the mass fraction of Sudan blue II in the curable adhesive preferably being 0.0001% or less, based on the mass of the curable adhesive.
  • a curable adhesive according to the invention tends to be preferred, the combined mass fraction of Sudan dyes in the curable adhesive being 0.005% or less, preferably 0.0001% or less, based on the mass of the curable adhesive.
  • the combined mass fraction of anthraquinone dyes in the curable adhesive being 0.005% or less, preferably 0.0001% or less, based on the mass of the curable adhesive.
  • a curable adhesive according to the invention is preferred, largely independent of the selection of the specific pH color indicator, the combined mass fraction of the pH color indicators in the curable adhesive being in the range from 0.01 to 0.4%, preferably in the range from 0.015 to 0.3 %, is based on the mass of the curable adhesive. Additionally or alternatively, a curable adhesive according to the invention is also preferred, the combined mass fraction of the pH color indicators in the curable adhesive being 0.25% or less, preferably 0.2% or less, based on the mass of the curable adhesive, and/ or wherein the combined mass fraction of the pH color indicators in the curable adhesive is 0.1% or more, preferably 0.15% or more, based on the mass of the curable adhesive.
  • curable adhesives according to the invention by the fact that the mass ratio of the combined mass of the cationic initiators to the combined mass of the pH color indicators in the curable adhesive is 5:1 or more.
  • a curable adhesive according to the invention Preference is given to a curable adhesive according to the invention, the mass ratio of the combined mass of the cationic initiators to the combined mass of the pH color indicators in the curable adhesive being 6:1 or more, preferably 8:1 or more, particularly preferably 10:1 or more. amounts. Additionally or alternatively, a curable adhesive according to the invention is preferred, the mass ratio of the combined mass of the cationic initiators to the combined mass of the pH color indicators in the curable adhesive being in the range from 5:1 to 30:1, preferably in the range from 5:1 to 20:1.
  • curable adhesives according to the invention are very flexible with regard to the presence of further components, which advantageously makes it possible to adapt the physicochemical properties in a particularly targeted manner to the respective requirements of the applications.
  • a curable adhesive according to the invention is preferred, the curable adhesive comprising one or more polyols, preferably in a combined mass fraction in the range from 0.5 to 15%, particularly preferably in the range from 1 to 10%.
  • a curable adhesive composition according to the invention is also preferred, wherein the curable adhesive composition comprises one or more further additives, preferably in one combined mass fraction in the range from 0.1 to 50%, particularly preferably in the range from 0.2 to 40%, based on the mass of the curable adhesive, and / or wherein the one or more further additives are preferably selected from the group consisting from adhesive resins, anti-aging agents, light stabilizers, UV absorbers, rheological additives and additives to increase opacity.
  • an opacity (“haze”) may be desired for the curable adhesive according to the invention or the adhesive tape comprising the curable adhesive according to the invention.
  • Such special applications are, for example, adhesive tapes for the electrical insulation of an object, such as battery cells.
  • a certain opacity is desirable to conceal optical defects such as scratches.
  • the curable adhesive according to the invention which further comprises one or more additives to increase the opacity is preferred.
  • Combinations of a combined mass fraction of a maximum of 0.3% pH color indicator and a combined mass fraction of a maximum of 5% of one or more additives to increase the opacity, based on the mass of the curable adhesive have proven particularly advantageous in terms of the curability of the adhesive, color strength and opacity.
  • Combined mass fractions in the range from 0.1 to 0.25% pH color indicator and combined mass fractions in the range from 0.1 to 0.3% titanium dioxide are particularly preferred.
  • insoluble fillers that can be added to the curable adhesive in order to obtain a filled curable adhesive.
  • particulate fillers with an average particle diameter (D50) of 5 pm or more, preferably 10 pm or more, particularly preferably 20 pm or more, which are not soluble in the curable adhesive and are accordingly present in it as a dispersion, as well as macroscopic fillers such as fibers.
  • the insoluble fillers are preferably selected from the group consisting of particulate fillers.
  • the insoluble fillers are particularly preferably selected from the group consisting of expandable hollow polymer spheres, non-expandable hollow polymer spheres, solid polymer spheres, hollow glass spheres, solid glass spheres, hollow ceramic spheres, solid ceramic spheres and/or solid carbon spheres.
  • insoluble fillers can also be fibers, scrims, platelets and rods made of materials that are insoluble in the curable adhesive. Due to their partially macroscopic dimensions and lack of solubility, these essentially have no influence on the above-disclosed relationships of the composition chemistry of the curable adhesives, but rather are present in a heterogeneous mixture with the curable adhesive.
  • these insoluble fillers are not included in the curable adhesive in the context of the present invention and are not taken into account when calculating mass fractions relative to the mass of the curable adhesive. Rather, within the context of the present invention, it is defined that the addition of insoluble fillers to a curable adhesive according to the invention results in a filled curable adhesive, ie a filled curable adhesive comprising: i) a curable adhesive according to the invention, preferably as disclosed above as preferred, and ii) one or more insoluble fillers.
  • the combined mass fraction of the insoluble fillers is particularly preferably in the range from 1 to 50%, preferably in the range from 2 to 40%, particularly preferably in the range from 5 to 30%, based on the mass of the filled curable adhesive.
  • Curable adhesives according to the invention can, for example, be used directly as adhesives, and depending on the application method they can be provided in particular in the form of tapes.
  • the invention therefore also relates to an adhesive tape, in particular a reactive adhesive tape, comprising a curable adhesive composition according to the invention as an adhesive layer, the adhesive tape preferably comprising a carrier layer.
  • curable adhesive compositions according to the invention are used as the adhesive layer of a single- or double-sided adhesive tape, which also includes a carrier layer, or when the adhesive layer is arranged on a separating layer, for example a liner which the adhesive layer can be easily removed.
  • tape refers to all thin, flat structures, i.e. structures with a predominant extension in two dimensions, in particular films, film sections and labels, preferably tapes with an extended length and limited width as well as corresponding tape sections.
  • the carrier layer usually refers to the layer of such a multi-layer adhesive tape, which largely determines the mechanical and physical properties of the adhesive tape, such as tear strength, stretchability, insulation or resilience.
  • Common materials for the carrier layer are, for example, fabrics, scrims and plastic films, for example PET films and polyolefin films.
  • the carrier layer itself can also be adhesive.
  • the adhesive tape according to the invention can be a double-sided adhesive tape, the carrier layer of which is provided on both sides with a curable adhesive composition according to the invention.
  • the carrier layer can also have electrically insulating properties, so that the corresponding adhesive tape according to the invention has electrically insulating properties and can be used to electrically insulate an object.
  • insulating carrier films with a specific Contact resistance of >10 15 Dem, preferably >10 16 Dem, more preferably >10 17 Dem, determined according to DIN EN 62631 -3-1 (VDE 0307-3-1): 2017-01 used.
  • the adhesive tape according to the invention can therefore, in a preferred embodiment, be a double-sided adhesive tape, the insulating carrier film of which is provided on both sides with a curable adhesive according to the invention.
  • the adhesive tape according to the invention is a one-sided adhesive tape whose electrically insulating carrier film is provided on one side with a curable adhesive according to the invention.
  • Such single-sided adhesive tapes are ideal for covering battery cells in hybrid vehicles and purely electric vehicles.
  • the insulating carrier film comprises one or more materials selected from the group consisting of polyimide, polybenzimidazole, polyamideimide, polyetherimide, polyacetal, polyphenylene sulfide, polyetheretherketone, polytetrafluoroethylene, polyamide 6, ultra high molecular weight polyethylene, polypropylene, vinyl chloride resin, polystyrene, polyethylene terephthalate, acrylonitrile-butadiene-styrene, polycarbonate, polyvinyl chloride, ethylene-vinyl acetate copolymer and polyester, more preferably from the group consisting of polypropylene, polyethylene terephthalate, polycarbonate and polyvinyl chloride, more preferably from the group consisting of polypropylene and polyethylene terephthalate.
  • the carrier preferably has a thickness in the range from 20 pm to 100 pm, more preferably in the range from 30 pm to 90 pm, more preferably in the range from 40 pm to 75 pm.
  • the adhesive layers can be covered with a separating cover, a so-called release liner, in order to enable problem-free unwinding and to protect the PSA from contamination.
  • release liners usually consist of a plastic film siliconized on one or both sides (e.g. PET or PP) or a siliconized paper carrier.
  • the invention also relates to a method for connecting two or more components before further processing steps, with which advantageous timing and excellent time and cost efficiency can be achieved.
  • the method according to the invention comprises the method steps: w) producing or providing an adhesive tape according to the invention; x) connecting two or more components with the adhesive tape and initiating the cationic curing of the curable adhesive by activating the one or more cationic initiators to obtain a component composite, y) curing the curable adhesive until the color of the one or more pH color indicators changes to obtain a component composite ready for further processing with a still incompletely cured curable adhesive, and z) carrying out one or more further processing steps on the component composite ready for further processing.
  • the further processing steps can be all typical processing steps such as can occur, for example, in a typical production line, for example in automobile production, wherein the further processing steps are in particular further processing steps in which the connection of the components produced in the component assembly is subjected to mechanical stress, wherein the mechanical stress is expediently lower than the bonding strength at the time of the color change.
  • a pH-dependent color change of the one or more pH color indicators takes place during the cationic curing of the curable adhesive, thus preferably at a time at which the bonding strength of the curing adhesive reaches a predetermined value which is greater than the mechanical stress experienced in method step z) by the component assembly ready for further processing.
  • the use of a curable adhesive composition according to the invention or an adhesive tape according to the invention for bonding two or more components by curing the curable adhesive composition, preferably in a process according to the invention, is also disclosed.
  • curable adhesives were obtained by mixing the components in the usual way (as laboratory smears from a 40% butanone solution).
  • Triarylsulfonium hexafluorophosphate (50% in propylene carbonate; CAS: 109037-77-6; the weight information in Table 1 refers to the solution) was used as the cationic initiator.
  • the adhesive strengths were determined analogously to ISO 29862 (method 3) at 23 °C and 50% relative humidity at a peel speed of 300 mm/min and a peel angle of 180°.
  • the thickness of the adhesive layer was 100 pm in each case.
  • Steel plates in accordance with the standard were used as the substrate.
  • the uncured measuring strip was bonded using a 4 kg rolling machine at a temperature of 23 °C.
  • the adhesive tapes were removed immediately after application.
  • the measured value (in N/cm) was the average of three individual measurements and the failure pattern was documented as follows: adhesive failure (A) or cohesive failure (K).
  • suitable light Hönle 365 nm LED lamp with a UV-A dose of 3000 mJ/cm 2
  • the liquid curable adhesive E1 was applied as a formless adhesive with a layer thickness of 100 pm (as is usual when testing liquid adhesives, a few glass beads with a particle size of 100 pm were scattered into the adhesive joint as spacers).
  • the curable adhesive was irradiated with suitable light (Hönle 365 nm LED emitter with a UV-A dose of 3000 mJ/cm 2 ) before the test bars were joined together and the test specimens were joined together immediately afterwards.
  • suitable light Hönle 365 nm LED emitter with a UV-A dose of 3000 mJ/cm 2
  • the bond strength was measured after a color change was observed.
  • the maximum bond strength achievable by cationic curing was also determined after 7 days on fully cured samples. For E2, for example, this was 8.9 MPa.
  • A adhesive failure
  • K cohesive failure
  • samples E2 to E4 show advantageous cohesion and pressure-sensitive adhesive properties.
  • the liquid adhesive E1 shows cohesive failure before curing, so that no meaningful adhesive strength can be determined.
  • the observed color change is a color change that lies within the expected interval of the relative bond strength, whereby in most cases a further color change occurs immediately after irradiation, which advantageously indicates the successful irradiation, but in which the relative bond strengths will in any case still be outside the interval.
  • the tensile shear tests after curing show that the adhesives according to the invention cure and that bonding strengths of between 45% and 78% of the respective maximum achievable bonding strength can be achieved during the color change, so that the color change can reliably indicate that component assemblies bonded with corresponding curable adhesives can already be subjected to further processing without fear of bond failure.
  • the cycle rate and thus the production speed can be increased in an advantageous manner in a manufacturing process that includes corresponding bonding.
  • V1 when unsuitable dyes are used, the color change (V1) only occurs when the curing is almost complete. If the ratio of dye to initiator is too high, as shown in V2 as an example, i.e. too much dye is used, the adhesive will no longer harden properly.

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Abstract

L'invention concerne un adhésif durcissable comprenant : a) un ou plusieurs (co)polymères, b) un ou plusieurs composés époxydes polymérisables, c) un ou plusieurs initiateurs cationiques, et d) un ou plusieurs indicateurs de couleur de pH ayant au moins un changement de couleur dépendant du pH, le rapport en masse de la masse combinée des initiateurs cationiques à la masse combinée des indicateurs de couleur de pH dans l'adhésif durcissable étant de 5:1 ou plus, et la composition de l'adhésif durcissable étant telle qu'un changement de couleur dépendant du pH du ou des indicateurs de couleur de pH a lieu pendant le durcissement cationique de l'adhésif durcissable à un moment auquel la force de liaison de l'adhésif de durcissement se situe dans la plage de 20 % à 80 % de la force de liaison maximale pouvant être obtenue au moyen du durcissement cationique.
PCT/EP2023/075108 2022-09-28 2023-09-13 Adhésif durcissable par voie cationique avec indication de force de maintien WO2024068274A1 (fr)

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