Multilayer adhesive films, methods of making and uses thereof

Abstract

The provided multilayer adhesive film exhibits excellent impact resistance, good adhesive strength, and excellent reprocessing ability after curing at low temperatures (e.g., no more than 90 DEG C).

Description

TECHNICAL FIELD

[0001] The present invention relates to a multilayer adhesive film, a process for its preparation and use. In particular, disclosed herein is a multilayer adhesive film which exhibits excellent impact resistance, good adhesive strength, and outstanding reworkability after curing at low temperature, such as not more than 90°C. BACKGROUND

[0002] Heat-activated adhesive films have been widely used in the manufacture of electronic devices to assemble substrates. The term "heat-activated" (or "thermally activatable") refers to a composition having latent adhesive properties which are activated only after being heated above a given temperature. Such compositions have other advantages, such as ease and speed of use, self-supporting, etc. During the manufacturing process, the heat-activated adhesive film is placed between the surfaces of the substrates to be assembled and kept in contact with them. At the same time, the assembly is heated to activate the adhesive composition. The heating time can vary with the thickness of the substrates, but it must not be too long to avoid thermal distortion of the substrates. Sometimes, a pre-lamination can partially cure the adhesive film at lower temperature, and the final lamination can cure the adhesive film and completely bond the substrates. After cooling, an adhesive film with a specific adhesive strength is obtained to assemble the substrates.

[0003] The existing heat-activated adhesive films disclosed in the prior art or existing on the market are based on thermoplastic polymers, polyols, and NCO-terminated isocyanates. It has been observed that such adhesive films exhibit insufficient impact resistance and adhesive strength after curing at low temperature, such as not more than 90°C, or exhibit unsatisfactory reworkability, resulting in damage or leaving residues on the substrates, which cannot meet the requirements of electronic device manufacturing.

[0004] In view of the above, there is a need for a multilayer adhesive film which exhibits excellent impact resistance, adhesive strength, and outstanding reworkability after curing at low temperature, such as not more than 90°C. SUMMARY

[0005] According to a first aspect of the present invention, disclosed herein is a multilayer adhesive film comprising: a first layer having a first major surface and a second major surface opposite to the first major surface, and a second layer disposed on the first major surface of the heat-activated adhesive film; wherein the first layer is a heat-activated adhesive film prepared by drying a solvent- borne heat-activated adhesive composition (A) until the solvent content does not exceed 5 wt.% of the total solvent-borne heat-activated adhesive composition, and the solvent-borne heat-activated adhesive composition (A) comprises at least one thermoplastic polymer (A1), at least one polyol (A2), at least one polyisocyanate having at least two isocyanate groups and at least one uretdione group in one molecule (A3), and an organic solvent (A4); wherein the second layer is obtained from a dispersion composition (B) comprising at least one water-based polyurethane dispersion (B1), and optionally a latent curing agent (B2).

[0006] A second aspect of the present application is a process for preparing a multilayer adhesive film according to the present application.

[0007] A third aspect of the present application is an article comprising a first substrate, a second substrate, and a multilayer adhesive film according to the present application disposed between the first substrate and the second substrate.

[0008] A fourth aspect of the present application is the use of a multilayer adhesive film according to the present application or an article comprising the same in the manufacture of automotive parts, truck bed covers, textile laminates, assembled goods, and electronic devices.

[0009] Other features and aspects of the subject matter will be set forth in greater detail DETAILED DESCRIPTION

[0010] A person of ordinary skill in the art will understand that the present application is a description of exemplary embodiments only and is not intended to limit the broader aspects of the present application. Unless explicitly stated otherwise, each aspect described thus far can be combined with any other aspect or aspects. In particular, any feature indicated as preferred or advantageous can be combined with any other feature or features indicated as preferred or advantageous.

[0011] In the context of the present application, the terms used will be interpreted according to the following definitions, unless otherwise specified.

[0012] The terms "a" and "an" and "the" as used herein include both singular and plural referents unless otherwise specified.

[0013] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, unrecited members, elements, or method steps.

[0014] The terms "at least one" or "one or more" as used herein to define a component refers to the type of component, not the absolute number of molecules. For example, "one or more polyols" means one type of polyol or a mixture of different polyols.

[0015] The term "heat-activated" is to be understood as meaning that the adhesive film has latent adhesive properties which are activated only after the film has been heated above a given temperature ("activation temperature"). During this heat-activation phase, the film exhibits its adhesive properties.

[0016] The term "adhesive film" means an adhesive in the form of a film.

[0017] The term "self-supporting adhesive film" means an adhesive film which is able to maintain its integrity without any substrate.

[0018] In the context of the present invention, a "liner" or "removable liner" is not considered to be a substrate.

[0019] The term "polyurethane" means polyurethane, and also polyurethanes containing urea groups in the main chain of the polyurethane.

[0020] The term "room temperature" as used herein refers to a temperature of about 20 °C to about 25 °C, preferably about 25 °C.

[0021] Unless otherwise stated, the inclusion of a range of values is meant to include all numbers and fractions of numbers within the range, as well as the recited endpoints.

[0022] All references cited in the present specification are hereby incorporated by reference in their entirety.

[0023] Unless otherwise defined, the molecular weight is the number average molecular weight (Mn). Unless otherwise defined, all molecular weight data refer to values obtained by gel permeation chromatography (GPC) according to DIN 55672, for example.

[0024] The softening point mentioned herein is determined according to DIN ISO 4625 by using the ring and ball method.

[0025] Unless otherwise defined, all terms (including technical and scientific terms) used in the present application have the meaning commonly understood by one of ordinary skill in the art to which this application belongs.

[0026] In one aspect, the present disclosure is a multilayer adhesive film comprising: a first layer having a first major surface, and a second major surface opposite to the first major surface, and a second layer disposed on the first major surface of the heat-activated adhesive film; wherein the first layer is a heat-activated adhesive film prepared by drying a solvent-based heat-activated adhesive composition (A) until the solvent content is not more than 5% by weight of the total solvent-based heat-activated adhesive composition, and the solvent-based heat-activated adhesive composition (A) comprises at least one thermoplastic polymer (A1), at least one polyol (A2), at least one polyisocyanate having at least two isocyanate groups and at least one uretdione group in one molecule (A3), and an organic solvent (A4); wherein the second layer is derived from a dispersion composition (B) comprising at least one water-based polyurethane dispersion (B1), and optionally a latent curing agent (B2).

[0027] (A) solvent-based heat-activated adhesive composition According to the present invention, the solvent-based heat-activated adhesive composition (A) comprises at least one thermoplastic polymer (A1), at least one polyol (A2), at least one polyisocyanate having at least two isocyanate groups and at least one uretdione group in one molecule (A3), and an organic solvent (A4).

[0028] (A1) Thermoplastic polymer The thermoplastic polymer (A1) provides a skeleton for the heat-activated adhesive film. Without the thermoplastic polymer, the multilayer adhesive film cannot achieve a self-supporting adhesive film.

[0029] The thermoplastic polymer is different from a thermoset polymer, which hardens via crosslinking or curing when heated, while the thermoplastic polymer is flexible at elevated temperatures and hardens upon cooling.

[0030] In some embodiments, the thermoplastic polyurethane polymer (A1) can have a weight-molecular weight (Mw) of not less than 10000 g / mol, preferably 10000 to 200000 g / mol, preferably 10000 to 150000 g / mol, more preferably 20000 to 100000 g / mol.

[0031] In some embodiments, the thermoplastic polymer (A1) exhibits an optimal activation temperature of no higher than 100°C, preferably lower than 85°C, preferably 30°C to lower than 80°C, very preferably 30°C to lower than 70°C, and even very preferably 30°C to lower than 60°C. Within the preferred range, the thermally activated adhesive film obtained from this solvent-based thermally activated adhesive composition (A) is self-supporting and exhibits a certain adhesive strength after curing at low temperatures (e.g., not exceeding 90°C).

[0032] The term "optimal activation temperature" as used herein refers to a temperature range (or point) within which agglomeration (physically) occurs within the thermoplastic polymer, resulting in satisfactory strength with a non-agglomerated proportion of less than 10%. The optimal activation temperature of the thermoplastic polymers described herein can be determined according to EN 12961:2001.

[0033] Typically, the thermoplastic polymer (A1) described herein is non-chemically reactive; when heated, it coalesces and results in a flexible state with certain adhesive properties. In some embodiments, the thermoplastic polymer (A1) may contain hydroxyl groups capable of reacting with component (A3).

[0034] A variety of known thermoplastic polymers can be used in this invention. Suitable thermoplastic polymers used in this invention can be selected from thermoplastic polyurethane polymers, polyester polymers, acrylic polymers, ethylene-vinyl acetate copolymers, styrene block copolymers, polyvinyl acetone alcohol, styrene-acrylonitrile, polyolefins, polyacrylonitrile, ethylene-vinyl acetate terpolymers, functionalized ethylene-vinyl acetate, ethylene-acrylate copolymers, ethylene-acrylate terpolymers, ethylene-butadiene copolymers, and block copolymers; preferably selected from thermoplastic polyurethane polymers, polyester polymers, acrylic polymers, styrene block copolymers, and combinations thereof.

[0035] In some embodiments, thermoplastic polyurethane polymers can be used as components (A1) in this invention. Suitable thermoplastic polyurethane polymers can be obtained by ring-opening polymerization of lactones (such as ε-caprolactone), or by reaction of polyester polyols and polyether polyols with diisocyanates, and can also optionally be obtained by further reaction of such components with chain extenders (such as low molecular weight polyols, preferably diols) or by further reaction with diamines to form urea bonds.

[0036] Examples of useful polyester polyols for preparing thermoplastic polyurethane polymers used as component (A1) include polyester polyols obtained, for example, from linear dicarboxylic acids, derivatives of dicarboxylic acids (e.g., acid anhydrides, esters, and acyl chlorides), aliphatic polyols, alicyclic polyols, linear polyols, branched polyols, and combinations thereof. Examples of useful dicarboxylic acids (from which the polyester polyol can be obtained) include adipic acid, succinic acid, sebacic acid, dodecanoic acid, phthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, dimer acids, and combinations thereof. Examples of useful aliphatic diols (from which the polyester polyol can be obtained) include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentanediol, diethylene glycol, methylpropanediol, 3-methyl-1,5-propanediol, and combinations thereof.

[0037] Examples of useful polyether polyols for preparing thermoplastic polyurethane polymers used as component (A1) can be obtained by polymerization of cyclic oxides (e.g., ethylene oxide, propylene oxide, butane oxide, and tetrahydrofuran); or by addition of one or more such oxides to a multifunctional initiator having at least two active hydrogens, such as water, polyols (e.g., ethylene glycol, propylene glycol, diethylene glycol, cyclohexanediol, glycerol, trimethylolpropane, pentaerythritol, and bisphenol A), ethylenediamine, propylenediamine, triethanolamine, and 1,2-propanedithiol.

[0038] Useful thermoplastic polyurethane polymers used as components (A1) typically consist of soft segments (e.g., polyether polyols or polyester polyols) and hard segments (typically obtained by reacting low molecular weight diols with diisocyanates). Commercially available thermoplastic polyurethane polymers used as components (A1) include, but are not limited to: the Pearlstick series from Lubrizol, such as 5707, 5703, 5701, 5714, 5713, 5715, 45-40, 45-50, 45-60, 45-80, 45-90, 48-60, 40-70, 46-10; the HF-4003LH, 3003EH series, HF-3H, 6H series from Huafeng Chemicals; and the WHT-61, 63, 64, 65, 67 series from Wanhua Chemicals.

[0039] Suitable polyester polymers for use as component (A1) can be obtained by polycondensation of at least one polyester glycol with at least one dicarboxylic acid or its ester or anhydride derivative, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol (1,4-butanediol; 1,2-butanediol; 1,3-butanediol), neopentyl glycol, 2-methyl-1,3-propanediol, hexanediol (hexamethylene glycol), propylene glycol (propane-1,2-diol, propane-1,3-... Diol, or propylene glycol), trimethylolpropane, cyclohexanediol, or combinations thereof; one of the at least one dicarboxylic acid or its ester or anhydride derivative, such as terephthalic acid, dimethyl terephthalate, isophthalic acid, adipic acid, azelaic acid, sebacic acid, cyclohexanedicarboxylic acid, dodecanoic acid (1,10-decanedicarboxylic acid), succinic acid, dimer acid, phthalic anhydride, maleic anhydride, and hydroxycarboxylic acids, such as diesters obtained from polycaprolactone or ε-caprolactone and diethylene glycol, or combinations thereof. Commercially available polyester polymers used as component (A1) include, but are not limited to: BX1001 manufactured by TOYOBO; CAPA from Perstorp. TM 6800, 6500, 6400; PLACEL H series manufactured by Daicel; and PCL65000 and PCL68000 from Hunan Juren Chemical.

[0040] Polymerizing ester monomers of acrylic acid and methacrylic acid can yield suitable acrylic polymers for use as component (A1). Exemplary and useful monomers for synthesizing component (A) include soft monomers (such as ethyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate) and hard monomers (such as methyl methacrylate, isobutyl acrylate). Exemplary acrylic polymers for use as component (A1) include polymethyl methacrylate, n-butyl acrylate-based block copolymers, n-butyl acrylate / 2-ethylhexyl acrylate-based block copolymers, and combinations thereof. Acrylic block polymers obtained from soft monomers and hard monomers are preferred. Commercially available acrylic polymers for use as component (A1) include, but are not limited to, Kuraray manufactured by SANYO. TM LA2140, n-butyl acrylate-methyl methacrylate copolymer, etc.

[0041] Suitable styrene block copolymers used as component (A1) include aromatic vinyl polymer blocks and saturated mesoblocks, preferably hydrogenated conjugated diene polymer blocks or unsaturated mesoblocks. The blocks can be arranged in various configurations (e.g., linear, branched, radial, star-shaped, and combinations thereof). Aromatic vinyl polymer blocks can be derived from various aromatic vinyl compounds, including, for example, styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, tert-butylstyrene-2,4,6-trimethylstyrene, monofluorostyrene, difluorostyrene, monochlorostyrene, dichlorostyrene, methoxystyrene, 1,3-vinylnaphthalene, vinylanthracene, indene, acenaphthene, and combinations thereof. Hydrogenated diene polymer blocks can be derived from various diene-containing compounds, including, for example, isoprene, butadiene, hexadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and combinations thereof. Useful styrene block copolymers with saturated mezzanine blocks as components (A1) include, for example, triblock copolymers, multi-arm copolymers, and radial copolymers, including, for example, styrene-ethylene / butene-styrene (SEBS), styrene-ethylene / propylene-styrene (SEPS), styrene-ethylene-ethylene / propylene-styrene (SEEPS), styrene / isobutylene / styrene (SIBS), and combinations thereof. Useful styrene block copolymers with unsaturated mezzanine blocks as components (A1) include styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-butadiene-isobutylene-styrene (SBBS), styrene-isoprene-butadiene-styrene (SIBS), and combinations thereof. Commercially available styrene block copolymers as components (A1) include, but are not limited to, HYBRAR from Kuraray. TM 125 and 7311.

[0042] Suitable ethylene-vinyl acetate copolymers used as component (A1) are obtained from at least one ethylene monomer and at least one vinyl acetate monomer. From the perspective of the strength and flexibility of the heat-activated adhesive film, the vinyl acetate content of the ethylene-vinyl acetate copolymer used as component (A1) is preferably 18% by mass or greater. Commercially available ethylene-vinyl acetate copolymers used as component (A1) include, but are not limited to, Levamelt from ARLANXEO. TM 686 (68% vinyl acetate by weight), KBE-68 A and KBE-68 B manufactured by Kuraray Co., Ltd., etc.

[0043] Other useful thermoplastic polymers used as component (A1) include, but are not limited to, polyvinyl acetone alcohol, styrene-acrylonitrile, polyolefins, polyacrylonitrile, ethylene-vinyl acetate terpolymers, functionalized ethylene-vinyl acetate, ethylene-acrylate copolymers, ethylene-acrylate terpolymers, ethylene-butadiene copolymers and block copolymers, and combinations thereof.

[0044] The thermoplastic polymers mentioned above can be used alone or in combination of two or more.

[0045] Particularly preferably, based on the total weight of the solvent-based thermally activated adhesive composition (A), component (A1) may be present in amounts from 1% to 95% by weight, preferably from 10% to 40% by weight.

[0046] (A2) Polyols According to the present invention, the solvent-based heat-activated adhesive composition (A) comprises at least one polyol (A2), which can react with the following component (A3) when heated to form an effective adhesive.

[0047] The polyols (A2) useful in this invention include those that have at least two hydroxyl groups (e.g., three or four hydroxyl groups) in a molecule and have one or more aromatic groups in the molecule, preferably having a hydroxyl value of not less than 10 mg KOH / g, preferably greater than or equal to 15 mg KOH / g, very preferably in the range of 20 to 90 mg KOH / g, and even more preferably 30 to 60 mg KOH / g.

[0048] Preferably, component (A2) is a polyester polyol with a weight-average molecular weight (Mw) of less than 10,000 g / mol.

[0049] The component (A2) used in this invention is preferably a solid at ambient temperature (20°C). In some embodiments, from the perspective of solubility in organic solvents, component (A2) may be selected from amorphous polyester polyols, semi-crystalline polyester polyols, crystalline polyester polyols, and combinations thereof, preferably from amorphous polyester polyols, semi-crystalline polyester polyols, and combinations thereof.

[0050] As used herein, the term "amorphous polyester polyol" means a polyester polyol that, when measured using differential scanning calorimetry (DSC), exhibits no melt transition and has no crystalline form. It preferably has a crystallinity of less than 10%, more preferably less than 5%, advantageously less than 2%, and even more advantageously less than 1% (by weight).

[0051] The term "semi-crystalline polyester polyol" refers to a polyester polyol whose structure includes crystalline and amorphous regions. It preferably has a crystallinity of at least 20% to less than 80%, more preferably at least 30% to less than 80%, and even more preferably at least 40% and less than 80% (by weight).

[0052] As used herein, the term "crystalline polyester polyol" refers to a polyester polyol that, when measured using differential scanning calorimetry (DSC), exhibits a melt transition and has a crystalline form. It preferably has a crystallinity of at least 80%, and more preferably at least 90%, by weight.

[0053] Crystallinity (representing the proportion of a substance in a crystalline state) can be determined by: X-ray diffraction analysis at different incident angles; calorimetry, such as DSC (differential scanning calorimetry); or any other technique that can estimate the crystalline phase ratio of a semi-crystalline polyester polyol.

[0054] The amorphous polyester polyols useful as component (A2) in this invention comprise the reaction product of a polyacid component (e.g., polyacid, polyacid anhydride, polyacid ester, and polyacrylamide halide) and a stoichiometric excess of polyol. At least one polyacid component and the polyol contain an aromatic group. Suitable polyacids include, for example, diacids (e.g., dicarboxylic acids), tricarboxylic acids (e.g., tricarboxylic acids), and more advanced acids, examples of which include aromatic dicarboxylic acids, their anhydrides, and esters (e.g., terephthalic acid, isophthalic acid, dimethyl terephthalate, diethyl terephthalate, phthalic acid, phthalic anhydride, methylhexahydrophthalic acid, methylhexahydrophthalic anhydride, methyltetrahydrophthalic acid, methyltetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, and...). Tetrahydrophthalic acid), aliphatic dicarboxylic acids and their anhydrides (e.g., maleic acid, maleic anhydride, succinic acid, succinic anhydride, glutaric acid, glutaric anhydride, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, chlorobacteric acid, 1,2,4-butanetricarboxylic acid, decanedicarboxylic acid, octadecanedicarboxylic acid, dimer acids, dimer fatty acids, trimer fatty acids, and fumaric acid), and alicyclic dicarboxylic acids (e.g., 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid), and mixtures thereof. Examples of suitable polyols include aliphatic polyols such as ethylene glycol, propylene glycol (e.g., 1,2-propanediol and 1,3-propanediol), butanediol (e.g., 1,3-butanediol, 1,4-butanediol, and 1,2-butanediol), 1,3-butenediol, 1,4-butenediol, 1,4-butynediol, pentanediol (e.g., 1,5-pentanediol), pentenediol, pentynediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, neopentanediol, and dioxanediol. Ethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol (e.g., dipropylene glycol and tripropylene glycol), 1,4-cyclohexanediol, 1,4-cyclohexanediol, dimerized glycol, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, glycerol, tetramethylene glycol, polytetramethylene glycol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, trimethylolpropane, pentaerythritol, sorbitol, glucose, and combinations thereof.

[0055] Specific examples of useful amorphous polyester polyols include poly(hexanediol phthalate) polyol; poly(neopentylene glycol adipate) polyol; poly(neopentylene glycol phthalate) polyol; poly(neopentylene glycol hexanediol phthalate) polyol; poly(diethylene glycol phthalate) polyol; poly(ethylene glycol adipate terephthalate) polyol; polyethylene terephthalate polyol; random copolymer diols of ethylene glycol, hexanediol, neopentylene glycol, adipic acid and terephthalic acid; and combinations thereof.

[0056] When using solid amorphous polyester polyols, from the perspective of achieving good adhesive strength after complete curing and being easily soluble in solvent-based heat-activated adhesive compositions (A), it is preferable to have a softening point of not higher than 130°C, preferably not higher than 120°C, preferably not higher than 105°C, for example 60°C, 80°C, 100°C.

[0057] The crystalline polyester polyols suitable as component (A2) in this invention can be obtained by ring-opening polymerization of lactones (such as ε-caprolactone) or by diols and diacids. Exemplary diols for preparing preferred polyester polyols include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, and combinations thereof. Examples of diacids for preparing preferred polyester polyols include succinic acid, glutaric acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, and 1,12-dodecanoic acid, dimer acids, and combinations thereof. The diacid range includes various diacid derivatives, such as carboxylic acid esters (especially methyl and ethyl esters), acyl halides (such as acyl chlorides), acid anhydrides, and combinations thereof.

[0058] Specific examples of suitable crystalline polyester polyols include poly(hexanediol adipate) polyol, poly(butanediol adipate) polyol, poly(ε-caprolactone) polyol, poly(hexanediol dodecanoate) polyol, poly(hexanediol terephthalate adipate) polyol, and combinations thereof.

[0059] The polyester polyols mentioned above can be used alone or in combination of two or more of them.

[0060] Suitable commercially available polyols (A2) are sold by GUANGZHOU FTRT CHEMICAL CO., LTD as FZPE-A03130; by Evonik Industries AG as DYNACOLL 7110, 7130, 7140 and 7150; and by Xuchuan Chemical (Suzhou) Co., Ltd. as FLP PA-1000N, etc.

[0061] Particularly preferably, based on the total weight of the solvent-based thermally activated adhesive composition (A), component (A2) may be present in an amount of 0.01% to 80%, preferably 5% to 40%.

[0062] (A3) Polyisocyanates According to the present invention, the solvent-based thermally activated adhesive composition (A) comprises at least one polyisocyanate (A3) having at least two isocyanate groups and at least one ureidone group in one molecule.

[0063] One or more useful polyisocyanates (A3) that can be used according to the present invention correspond to the following formula (I):

[0064] in: - R is a divalent group containing 6 to 13 carbon atoms, and - n is an integer ranging from 0 to 10.

[0065] Preferably, R is a divalent aromatic or polyaromatic group, more preferably generated from an aromatic diisocyanate (such as toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI)).

[0066] Examples of one or more polyisocyanates (A3) that may be used according to the present invention correspond to one of the following formulas (I-1) or (I-2):

[0067] Preferably, relative to the weight of the polyisocyanate, one or more polyisocyanates (A3) used according to the present invention may exhibit an NCO content ranging from 15% to 40% by weight, more preferably from 20% to 35% by weight.

[0068] Preferably, the solvent-based thermally activated adhesive composition (A) has an NCO / OH molar ratio ranging from 0.1 to 8:1. According to the invention, the isocyanate groups are provided by component (A3) present in the solvent-based thermally activated adhesive composition (A) according to the invention, and the hydroxyl groups are provided by a small amount of hydroxyl groups (if present) in component (A1) and component (A2). Under the condition of satisfying the above molar ratio, the weight percentages of the polyol (A2) and the polyisocyanate (A3) are not particularly limited.

[0069] Suitable commercially available polyisocyanates (A3) are sold as follows: Grilbond sold by EMS-Griltech. TM A2bond (MDI urea diketone); Addolink sold by Rhein Chemie TM TT (TDI ureadione).

[0070] Particularly preferably, based on the total weight of the solvent-based thermally activated adhesive composition (A), component (A3) may be present in amounts from 0.05% to 20% by weight, preferably from 0.5% to 5% by weight.

[0071] (A4) Organic solvents According to the present invention, the solvent-based thermally activated adhesive composition (A) comprises at least one organic solvent (A4).

[0072] The organic solvent (A4) that can be used according to the invention preferably makes components (A1) and (A2) and other optional components or additives soluble in the organic solvent (A4) to form a mixture, and component (A3) can be uniformly dispersed in the mixture, thereby making the solvent-based thermally activated adhesive composition (A) easy to use on a substrate.

[0073] Preferably, the organic solvent (A4) has a concentration in the range of 6.9 to 10.0 (cal / cm³). 3 ) 1 / 2 The solubility parameter delta(δ) (also known as the Hildebrand solubility parameter, HSP) and the hydrogen bond index (HBI) gamma(γ) ranging from 5.0 to 7.7. These parameters are defined in a well-known manner in the literature, for example in sections 38 and 39 of patent application US 2004 / 0204524: - The solubility parameter delta is defined in Römpp Lexikon Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, “Solubility parameters,” pp 361 to 365; - The hydrogen bonding index describes the ability of solvent molecules to form hydrogen bonds. Donor solvents have a negative hydrogen bonding index, while acceptor solvents have a positive hydrogen bonding index. The hydrogen bonding index is determined based on the deviation of the infrared band relative to the RO-H stretching band (RCNelson, RW Hemwall and GD Edwards, Journal of Paint Technology, “Treatment of hydrogen bonding in predicting miscibility”, Vol. 42, No. 550, 1970, pp 636 to 643).

[0074] Preferably, the organic solvent (A4) is selected from ketones, more preferably from aliphatic ketones, and even more preferably from acetone, methyl ethyl ketone (MEK), 2-pentanone, 3-pentane, methyl isobutyl ketone, ethyl acetate, and combinations thereof.

[0075] Preferably, the boiling point of the organic solvent (A4) (e.g., below 100°C, more preferably below 80°C) is lower than the optimal activation temperature of the thermoplastic polymer (A1) to ensure that the organic solvent can be evaporated to form a heat-curable adhesive film without activating the thermoplastic polymer (A1).

[0076] The components mentioned above (A4) can be used alone or in combination of two or more.

[0077] In a specific embodiment, based on the total weight of the solvent-based thermally activated adhesive composition (A), an organic solvent (A4) is present in an amount greater than 36% to 95% by weight, preferably 50% to 85% by weight. After drying, based on the total weight of the thermally activated adhesive film, the thermally activated adhesive film has at least 2.0% by weight, preferably less than 0.5% by weight, and preferably less than 0.1% by weight of at least one organic solvent.

[0078] The solvent-based thermally activated adhesive composition (A) according to the invention may contain or not contain at least one optional component selected from silanes, pigments (e.g., carbon black), defoamers, leveling agents, stabilizers (antioxidants, UV stabilizers, heat stabilizers), catalysts, dyes, and mixtures thereof, provided that the advantageous properties of the solvent-based thermally activated adhesive composition (A) according to the invention are not altered.

[0079] According to the present invention, the solvent-based thermally activated adhesive composition (A) may further contain 1% to 10% by weight of at least one optional additive as defined above.

[0080] In a particularly preferred embodiment, the total weight of the thermally activated adhesive film comprises, based on the total weight of the thermally activated adhesive film: (A1) At least one thermoplastic polymer with a weight-average molecular weight (Mw) of not less than 10,000 g / mol, comprising 1% to 95% by weight, preferably 10% to 40% by weight. (A2) 0.01% to 80% by weight, preferably 5% to 40% by weight, of at least one polyol with a weight-average molecular weight (Mw) of less than 10,000 g / mol. (A3) 0.05% to 20% by weight, preferably 0.5% to 5% by weight, of at least one polyisocyanate, said polyisocyanate having at least two isocyanate groups and at least one ureidone group in one molecule, and (A4) At least one organic solvent in amounts less than 2.0% by weight, preferably less than 0.5% by weight, and preferably less than 0.1% by weight.

[0081] dispersion composition (B) According to the present invention, a multilayer adhesive film includes a second layer disposed on a first main surface of a first layer. The second layer is obtained from a dispersion composition (B) comprising at least one water-based polyurethane dispersion (B1) and optionally a latent curing agent (B2). When peeled from a substrate, a single-layer adhesive film obtained from a solvent-based composition (A) typically breaks repeatedly, resulting in ineffective reprocessing capability. Because the second layer obtained from the dispersion composition (B) has high resistance and can provide a reliable carrier for the first layer, the multilayer adhesive film, after curing at low temperatures (not exceeding 90°C), not only achieves excellent reprocessing capability but also enhances the impact resistance of the multilayer adhesive film.

[0082] In some embodiments, the second layer obtained from the dispersion composition (B) consists of at least one water-based polyurethane dispersion (B1), which makes component (B) a non-reactive polyurethane dispersion adhesive.

[0083] In some embodiments, the solids content of the water-based polyurethane dispersion (B1) used in this invention is less than 50%, preferably not more than 40%.

[0084] In some embodiments, the water-based polyurethane dispersion (B1) used in this invention has a polyurethane polymer with a weight-average molecular weight (Mw) of 50,000 g / mol to 80,000 g / mol.

[0085] Commercial products of water-based polyurethane dispersions (B1) include: Adwel 1665A, Adwel 1676, Adwel 1663, and Adwel 1630C, available from Wanhua Chemistry; ESACOTE PU 6419 and ESACOTEPU A32D, available from Lamberti; NH-102U, available from Sam Myung Bio Chem Co., Ltd; ESACOTEPU A32D, available from DSM; and DISPERCOLL U XP 2682, DISPERCOLL U XP 2612, DISPERCOLL U XP 2643, DISPERCOLL U XP 2849, DISPERCOLL U 53, and DISPERCOLL U 56, available from COVESTRO.

[0086] The aforementioned component (B2) can be used alone or preferably in combination of two or more.

[0087] In other embodiments, the second layer is obtained from a dispersion composition (B) comprising at least one water-based polyurethane dispersion (B1) and a latent curing agent (B2), which makes component (B) a latent reactive polyurethane dispersion adhesive under heat conditions.

[0088] Suitable latent curing agents (B2) include latent reactive solid isocyanates. Examples include aliphatic, alicyclic, heterocyclic, and aromatic polyisocyanates (e.g., methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI)), preferably TDI.

[0089] The latent curing agent (B2) preferably comprises a group selected from the following: ethylenediamine, 1,3-propanediamine, diethylenetriamine, triethylenetetramine, 2,5-dimethylpiperazine, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, methylnonane-diamine, isophorone diamine, 4,4'-diamino-dicyclohexylmethane, diaminopolypropylene ether and triaminopolypropylene ether, polyamide amines, and combinations thereof.

[0090] A suspension of latent reactive solid isocyanate is preferred. The preferred aqueous suspension of latent reactive solid isocyanate has a solids content of less than 50%. According to the test method of M105-ISO 11909, the desired aqueous suspension of latent reactive solid isocyanate has an NCO content of 5% to 15%.

[0091] Aqueous suspensions of useful latent reactive solid isocyanates can be activated at 60°C to 80°C.

[0092] Commercially available latent curing agents (B2) include CARMOT BL-1045 from OSIC and Thanecure from TSE. ® T9 SuperFine.

[0093] In a particularly preferred embodiment, the second layer is obtained from a dispersion composition (B) comprising 80% to 100% by weight of a water-based polyurethane dispersion (B1) and 0% to 20% by weight of a latent curing agent (B2).

[0094] Multilayer adhesive film According to the present invention, the multilayer adhesive film includes: a first layer having a first main surface and a second main surface opposite to the first main surface; and a second layer disposed on the first main surface of the thermally activated adhesive film.

[0095] In some embodiments, at least one removable liner is disposed on the second main surface of the first layer, and at least one removable liner is disposed on the open surface of the second layer.

[0096] In some embodiments, the multilayer adhesive film further includes a third layer in direct contact with the second primary surface of the thermally activated adhesive film, wherein the third layer may be the same as or different from the second layer, and the third layer comprises at least one water-based polyurethane dispersion and optionally a latent curing agent. Optionally, at least one removable liner is disposed on the exposed surface of the third layer, and at least one removable liner is disposed on the exposed surface of the second layer.

[0097] The total thickness of the multilayer adhesive film ranges from 150 μm to 400 μm, preferably from 200 μm to 300 μm.

[0098] According to the present invention, the multilayer adhesive film is characterized by a self-supporting adhesive film. It can be cured at low temperatures (e.g., below 90°C, preferably not exceeding 80°C) while exhibiting excellent push-out strength (e.g., at least 5 MPa according to the test method described herein) and excellent impact resistance (e.g., at least 0.5 J, preferably at least 0.8 J according to the test method described herein).

[0099] Preparation method According to a second aspect of the present invention, the present invention relates to a method for preparing a multilayer adhesive film, the method comprising the following steps: (1) Applying the solvent-based thermally activated adhesive composition (A) according to the invention to a removable liner and heating it to a temperature of 40°C to 100°C until the solvent content does not exceed 5% by weight of the total solvent-based thermally activated adhesive composition, and cooling it to room temperature, thereby forming the first layer of a multilayer adhesive film; and (2) The dispersion composition (B) according to the invention is applied to the first main surface of the thermally activated adhesive film and heated to a temperature of 40°C to 100°C to dry the dispersion composition, and cooled to room temperature to form the second layer of the multilayer adhesive film.

[0100] In some embodiments, the multilayer adhesive film based on the above method further includes the following steps: (3) Remove the removable liner from the second primary surface of the thermally activated adhesive film, apply the dispersion composition (B) according to the invention, and heat to a temperature of 40°C to 100°C to dry the dispersion composition, then cool to room temperature to form the third layer of the multilayer adhesive film; and (4) Optionally, a removable liner is applied to the exposed surfaces of the second layer and the third layer.

[0101] During step (1), the solvent-based thermally activated adhesive composition (A) can be obtained by mixing a thermoplastic polymer (A1), a polyol (A2), and optionally present components or additives dissolved in an organic solvent (A4) under rapid stirring, preferably under thermal conditions (e.g., at a temperature less than or equal to 75°C, preferably less than or equal to 65°C), before introducing the polyisocyanate (A3); then, the polyisocyanate (A3) can be added at room temperature to obtain a homogeneous mixture of the solvent-based thermally activated adhesive composition (A).

[0102] In step (2), the drying temperature is typically between 40°C and 100°C, preferably between 40°C and no more than 60°C. If the drying temperature is too high, it will affect the film formation of the dispersion composition (B); however, even at a drying temperature as high as 100°C, the actual temperature of the film will not be too high to affect film formation because the dispersion composition (B) contains sufficient water and the evaporation removes heat. The drying time depends on the film thickness, the length of the drying channel, and the manufacturing capability. In some embodiments, the second layer is dried at 80°C for 10 minutes to exhibit an acceptable film-forming state for further use.

[0103] In step (3), the dispersion component (B) may be the same as or different from the second layer, which comprises at least one water-based polyurethane dispersion according to the invention and optionally a latent curing agent.

[0104] In some embodiments, the removable liner used in the above steps has a non-sticky surface on which the composition is applied. For example, a solvent-based thermally activated adhesive composition (A) is applied in the form of a uniform layer to this non-sticky surface of the removable liner (such as a silicone-treated surface). Application can be performed using a film applicator or a doctor blade coater. After steps (1) and (2), a bilayer adhesive film is advantageously obtained. After steps (1) through (4), a trilayer adhesive film is advantageously obtained.

[0105] Optionally, the multilayer adhesive film according to the invention can be prepared by the following steps: (1) Apply the solvent-based thermally activated adhesive composition (A) according to the invention to a removable liner and heat it to a temperature of 40°C to 100°C until the solvent content does not exceed 5% by weight of the total solvent-based thermally activated adhesive composition, and cool it to room temperature to form the first layer of the multilayer adhesive film; (2) Applying the dispersion composition (B) according to the invention onto a removable liner and heating to a temperature of 40°C to 100°C to dry the dispersion composition, then cooling to room temperature, thereby forming a second layer of the multilayer adhesive film; and (3) At a temperature of 40°C to 80°C and a pressure of 1 to 5 bar, the second layer of the multilayer adhesive is laminated onto the first layer of the multilayer adhesive film.

[0106] In addition, the above preparation method may include the following steps: (4) Remove the removable liner of the first layer of the multilayer adhesive film, and apply the dispersion composition (B) according to the invention, heat to a temperature of 40°C to 100°C to dry the dispersion composition, and cool to room temperature to form the third layer of the multilayer adhesive film; and (5) Apply a removable liner to the exposed surface of the third layer.

[0107] During this method, the equipment used for mixing, stirring, dispersing, etc., is not particularly limited. Automated mortars, Henschel mixers, three-roll mills, ball mills, planetary mixers, bead mills, etc., equipped with stirrers and heaters can be used. In addition, appropriate combinations of these devices can be used. The method of preparing composition (A) or composition (B) is not particularly limited, as long as the above components are mixed uniformly.

[0108] During this method, composition (A) or composition (B) can be applied using any suitable application method, including, for example, automatic fine-line dispensing, jet dispensing, slot die coating, roll coating, gravure coating, transfer coating, pattern coating, screen printing, spraying, filament coating, by extrusion, air knife, air knife, drag knife, brushing, dip coating, doctor blade, offset gravure coating, rotary gravure coating, and combinations thereof. Composition (A) or composition (B) can be applied as a continuous or discontinuous coating in the form of a single layer or multiple layers and combinations thereof.

[0109] Article and use According to a third aspect, this document provides articles of manufacture comprising: First substrate, Second substrate, and The multilayer adhesive film according to the present invention is disposed between the first substrate and the second substrate.

[0110] In another embodiment, the article includes a first substrate, a second substrate, and a multilayer adhesive film of the present invention disposed between the two substrates and in direct contact with the two substrates.

[0111] The first substrate and / or the second substrate may be a single material and a single layer, or multiple layers of the same or different materials. The layers may be continuous or discontinuous.

[0112] The substrate of the article described herein may have a variety of properties, including rigidity (e.g., a rigid substrate, i.e., a substrate that cannot be bent by a person's hands, or a substrate that will break if an attempt is made to bend it by hands), flexibility (e.g., a flexible substrate, i.e., a substrate that can be bent with a force no greater than that of two hands), porosity, conductivity, lack of conductivity, and combinations thereof.

[0113] The substrate of the article can take many forms, including, for example, fibers, threads, yarns, woven fabrics, nonwoven fabrics, films (e.g., polymer films, metallized polymer films, continuous films, discontinuous films, and combinations thereof), foils (e.g., metal foils), sheets (e.g., metal sheets, polymer sheets, continuous sheets, discontinuous sheets, and combinations thereof), and combinations thereof.

[0114] In a preferred embodiment, at least one of the substrates may be selected from metals, such as anode aluminum, metal sintering slurry, tin, molybdenum, and silver; conductive metal oxides, such as indium tin oxide (ITO), fluorine-doped tin oxide, and aluminum-doped zinc oxide; glass, such as ink-coated glass and bare glass; and resins, such as polycarbonate, polybutylene terephthalate, and polyamide. Furthermore, suitable metals also include copper, gold, palladium, platinum, aluminum, indium, silver-plated copper, silver-plated aluminum, tin, and tin-plated copper. Preferably, both substrates are selected from one of the materials mentioned above.

[0115] According to an alternative form of this preferred embodiment, the article may be a multilayer article obtained by laminating multiple substrates using a multilayer adhesive film according to the invention.

[0116] In one embodiment, an article having a first substrate and a second substrate is prepared by: after removing a removable liner (if any), contacting the first substrate with a first primary surface of any of the multilayer adhesive films; after removing the removable liner (if any), contacting the second substrate with a second primary surface of the film, such that the second primary surface of the film is in direct contact with the second substrate to form the article; and applying heat at a temperature below 90°C (preferably 60°C to 80°C) and optionally a pressure of 0.5 to 6 bar to the article to cure the adhesive film, such that the two substrates are bonded together.

[0117] In another embodiment, an article having a first substrate and a second substrate is prepared by contacting the first substrate with a first primary surface of either of the multilayer adhesive films; applying heat to the adhesive film at a temperature of 40°C to 60°C before or after applying the adhesive film to the first substrate to form a pre-laminated compound, which can be stored and transported to different locations. During pre-lamination, partial coalescence occurs before the solvent-based thermally activated adhesive composition (A) has begun to cure or crosslink. Once ready, the pre-laminated compound is used to prepare the final article by contacting the second substrate with a second primary surface of the film, such that the second primary surface of the film is in direct contact with the second substrate to form the article; and applying heat at a temperature below 90°C (preferably 60°C to 80°C) and optionally present pressure (e.g., membrane pressure or airbag pressure, heated platen) to the article to fully cure the multilayer adhesive film, such that the two substrates are bonded together by the adhesive film.

[0118] As should be understood, the time and temperature curing characteristics of the multilayer adhesive films according to the present invention will vary, and different multilayer adhesive films can be designed to provide curing characteristics suitable for specific industrial manufacturing processes.

[0119] Use A fourth aspect of the invention is the use of the multilayer adhesive film or article according to the invention in the manufacture of automotive parts, truck body covers, textile laminates, assembled articles, and electronic devices.

[0120] Multilayer adhesive films can be used in a variety of applications, including, for example: temporary bonding of at least one substrate, permanent bonding of at least one or two substrates, protection of substrates, inhibition or prevention of movement of a first substrate relative to a second substrate, and combinations thereof. Multilayer adhesive films can also be used in a variety of processes, including: manufacturing processes (e.g., bonding two parts of an article together and maintaining a fixed relationship between the two parts during the manufacturing process), transportation processes, stacking techniques, and combinations thereof.

[0121] Multilayer adhesive films can be used to manufacture a variety of articles, including, for example, automotive parts, truck bed covers, textile laminates, various assembled articles, and electronic devices.

[0122] Suitable electronic devices include, but are not limited to, wearable electronic devices (e.g., wristwatches and glasses), handheld electronic devices (e.g., telephones (e.g., cellular phones and cellular smartphones), cameras, tablets, e-readers, monitors (e.g., monitors for use in hospitals and by healthcare workers, athletes, and individuals), watches, calculators, mice, touchpads, and joysticks), computers (e.g., desktop computers and laptops), computer monitors, televisions, media players, or other electronic components.

[0123] Examples The following examples are intended to help those skilled in the art better understand and practice the present invention. The scope of the invention is not limited by the examples, but is defined by the appended claims. Unless otherwise stated, all parts and percentages are based on weight.

[0124] Raw materials: WH6190A is a thermoplastic polyurethane polymer available from Wanhua Chemistry, having a weight-average molecular weight (Mw) of 50,000 g / mol and an optimal activation temperature of 55°C.

[0125] FZPE-A03130 is an amorphous polyester polyol with a weight-average molecular weight (Mw) of 3000 g / mol, available from GUANGZHOU FTRT CHEMICAL CO., LTD.

[0126] Silquest A-189 is a silane available from Momentive.

[0127] Carbon black is a pigment that can be obtained from Cabot.

[0128] BYK-141 is a defoamer available from BYK.

[0129] BYK-3550 is a leveling agent available from BYK.

[0130] Addolink TM TT is a toluene diisocyanate dimer available from Rhein Chemie.

[0131] MEK is a methyl ethyl ketone with a boiling point of 70°C to 80°C, available from Sinopharm.

[0132] Adwel 1665A is an aqueous polyurethane dispersion available from Wanhua Chemistry, the aqueous polyurethane dispersion having a solids content of 50% and having a weight-average molecular weight (Mw) of 50,000 g / mol to 80,000 g / mol of polyurethane polymer.

[0133] Adwel 1676 is an aqueous polyurethane dispersion available from Wanhua Chemistry, the aqueous polyurethane dispersion having a solids content of 50% and having a weight-average molecular weight (Mw) of 50,000 g / mol to 80,000 g / mol of polyurethane polymer.

[0134] CARMOT BL-1045 is a dispersion available from OSIC containing 40% TDI dimer and having an NCO content of 7% to 8%.

[0135] METOLAT 348 is a leveling agent available from MUNZING.

[0136] Carboset ® 527 is a thermoplastic acrylic resin available from Lubrizol.

[0137] AT501 is a thermoplastic epoxy elastomer available from Daicel Corporation.

[0138] Preparation of solvent-based heat-activated adhesive composition (A) and first layer of multilayer adhesive film The solvent-based thermally activated adhesive composition (A) according to the present invention is prepared according to the following steps: (1) At a temperature below 65°C, add 25g WH6190A (A1), 5g FZPE-A03130 (A2), 1g Silquest A-189, 1g carbon black, 1.5g BYK-141, and 1.5g BYK-3550 to 85g MEK (A4) while slowly stirring for about 10 hours until the polymer dissolves; and (2) After dissolution, allow the solution to cool to room temperature. Then add 1.2 g Addolink™ TT (A3), then transfer the mixture to a suitable container and stir rapidly twice for 1 minute each time at 2000 rpm (rev / min) using a high-speed mixer to obtain the solvent-based adhesive composition (A) (“F11”).

[0139] The solvent-based adhesive composition of F11 was applied to the removable liner using a 500 μm film applicator and dried at 40°C for 20 minutes to evaporate MEK (A4) until the MEK content did not exceed 5%, thereby obtaining the first layer of the multilayer adhesive film according to the invention.

[0140] Preparation of dispersion composition (B) and second / third layer of multilayer adhesive film According to the present invention, two dispersion compositions (B) F21 and F22 are prepared by mixing the components shown in Table 1 while stirring slowly at 400 to 800 rpm for about 2 hours at room temperature.

[0141] The contents shown in Table 1 are expressed in grams (g).

[0142] Table 1

[0143] The dispersion compositions F21 and F22 are applied to the removable liner or to the first main surface of the thermally activated adhesive film obtained above, respectively. The dispersion compositions are then dried in an oven at 45°C for 10 minutes and cooled to room temperature to form the second / third layer of the multilayer adhesive film.

[0144] Comparative examples 1-3 Comparative Example 1 is a single-layer F11 thermally activated adhesive film.

[0145] Comparative Examples 2 and 3 are bilayer adhesive films, wherein the bilayer adhesive film comprises a thermally activated adhesive film of F11 as the first layer, and the second layer is obtained from a composition of CF1 and CF2 prepared as follows.

[0146] A thermoplastic polymer different from that of the present invention, along with additives, is added to MEK as shown in Table 2, while the mixture is slowly stirred at a temperature below 65°C for about 10 hours until the polymer dissolves, to obtain dispersion compositions of “CF1” and “CF2”.

[0147] The contents shown in Table 1 are expressed in grams (g).

[0148] Table 2

[0149] In Comparative Examples 2 and 3, dispersion compositions of CF1 and CF2 were each applied to the first main surface of a thermally activated adhesive film F11, heated to a temperature of 40°C to 100°C to dry the dispersion compositions of CF1 and CF2, and cooled to room temperature to form a bilayer adhesive film.

[0150] Inventive examples 1-3 Each of the multilayer adhesive films of the present invention is prepared by: applying a dispersion of F21 / F22 to the first main surface of a thermally activated adhesive film F11 at room temperature, and placing the coated film in an oven at 45°C for 10 minutes to evaporate water, thereby forming a second layer. After drying, the double-layer adhesive film is stored at room temperature. A removable liner is then applied to the exposed surface of the second layer of the double-layer adhesive film.

[0151] In Example 3, the removable liner attached to the second main surface was removed, and the dispersion composition of F22 was applied to the second main surface and placed in an oven at 45°C for 10 minutes to evaporate water. After drying, the formed three-layer adhesive film was stored at room temperature for two days. The removable liner was then applied to the exposed surface of the third layer of the three-layer adhesive film.

[0152] Table 3 shows the composition, thickness ratio, and total thickness of the various layers of the multilayer adhesive film in the examples and comparative examples of the invention.

[0153] Test methods Push-out strength Sample pre-lamination: The multilayer adhesive films of the inventive examples and comparative examples were cut into pieces of 25 × 25 mm each, and then pre-laminated on a heated platform using test specimens. The test specimens consisted of an anodized aluminum block and a separate window-shaped component made of anodized aluminum. The adhesive film was uniformly applied to the surface of the ink-coated glass block on the platform at a temperature of 50°C. A 500 g weight was applied to press the adhesive film for 30 seconds. The backing was then removed from the adhesive film. The ink-coated glass block was then pressed onto the window-shaped component at a temperature of 60°C and a pressure of 2 kg for an additional 30 seconds (where the bonding area was 225 mm²). 2 This pre-lamination step helps activate the coalescence of the thermoplastic polymer, while also providing initial adhesion.

[0154] Final lamination / thermosetting process: The obtained samples were transferred to a heat compressor for final lamination / thermocurable processing at 80°C. The heat compressor had flat metal heating blocks at the top and bottom (both pre-set to 80°C). Final lamination was performed at approximately 2 bar pressure and 80°C for 10 minutes (typically 3 to 6 test samples were pressed at a time), during which the adhesive film crosslinked and cured. The samples were then transferred from the heat compressor to room temperature and then compressed for another 6 minutes with a 2 kg weight.

[0155] Sample testing Push-out strength tests were conducted using a universal testing machine with a punch at 23±2℃ and 50%±5% relative humidity. The punch applied pressure to the metal block of the test specimen at a pushing speed of 10 mm / min until the component could no longer withstand the load. The maximum load was recorded in Table 3, and the push-out strength was calculated by dividing the total load by the bonded area.

[0156] Adhesive films exhibiting a roll-out strength of at least 5 MPa are acceptable.

[0157] Impact resistance The impact resistance of the samples was evaluated using the DuPont impact energy by using an lap shear assembly.

[0158] The sample preparation, pre-lamination, and final curing conditions are the same as those for the above-mentioned push-out strength test.

[0159] Sample testing: A 50 g weight was dropped onto the specimen from a height of 1 m (the initial height) at a speed of 4.43 m / s. If the substrate did not peel off from the polycarbonate substrate after three drops, the weight was raised to a height 2 cm higher than the previous drop. The DuPont impact energy was calculated using the following formula: , Where E is the impact energy (J), m is the weight of the substrates when they are peeled off (g), h is the height of the released weight when the substrates are peeled off (m), and g is 9.8 m / s². 2 The test results are shown in Table 3. A DuPont impact energy value of at least 0.5 J, preferably at least 0.8 J, is acceptable for impact resistance.

[0160] Reprocessability test The reprocessing capability of the samples was evaluated using the following method.

[0161] Sample preparation The assembly structure having a first substrate with anodized aluminum and a second substrate with ink glass is prepared by: after removing a removable liner (if any), contacting the first substrate with the exposed surface of the second main surface or the third layer of the first layer of the multilayer adhesive film in the example of the invention or the single-layer adhesive film of the comparative example or the multilayer adhesive film; after removing the removable liner (if any), contacting the second substrate with the exposed surface of the second layer of the multilayer adhesive film, such that the second layer of the film is in direct contact with the second substrate to form the assembly structure; and applying heat at a temperature of 80°C and a pressure of 2 bar to cure the adhesive film, thereby bonding the two substrates together.

[0162] Sample testing First, the first substrate is detached from the component structure. Then, the adhesive film is peeled off from the second substrate using a scraper, and the film is further peeled off by hand at room temperature at a controlled angle of 30 to 45 degrees. The condition and reprocessing capability level of the adhesive film are evaluated and are shown in Table 3. A reprocessing capability level of 5 indicates an excellent reprocessing capability level.

[0163] Table 3

[0164] While some preferred embodiments have been described, many modifications and variations can be made to them based on the above teachings. Therefore, it should be understood that the invention can be practiced in ways different from those specifically described without departing from the scope of the appended claims.

Claims

1. Multilayer adhesive film comprising: a first layer having a first major surface and a second major surface opposite to the first major surface, and a second layer disposed on the first major surface of a heat-activated adhesive film; wherein the first layer is the heat-activated adhesive film prepared by drying a solvent-based heat-activated adhesive composition (A) until the solvent content is not more than 5 wt.% of the total solvent-based heat-activated adhesive composition, and the solvent-based heat-activated adhesive composition (A) comprises at least one thermoplastic polymer (Al), at least one polyol (A2), at least one polyisocyanate having at least two isocyanate groups and at least one uretdione group in one molecule (A3), and an organic solvent (A4); wherein the second layer is derived from a dispersion composition (B) comprising at least one water-based polyurethane dispersion (Bl), and optionally a latent curing agent (B2).

2. Multilayer adhesive film according to claim 1, wherein the thermoplastic polymer (Al) has an optimum activation temperature not higher than 100°C, preferably lower than 85°C, preferably 30°C to lower than 80°C, very preferably 30°C to lower than 70°C, even very preferably 30°C to lower than 60°C.

3. Multilayer adhesive film according to claim 1 or 2, wherein the thermoplastic polymer (Al) has a weight average molecular weight (Mw) not less than 10000 g / mol, preferably 10000 to 200000 g / mol, preferably 10000 to 150000 g / mol, more preferably 20000 to 100000 g / mol.

4. Multilayer adhesive film according to any one of the preceding claims, wherein the polyol (A2) is a polyester polyol having a weight average molecular weight (Mw) less than 10000 g / mol.

5. Multilayer adhesive film according to any one of the preceding claims, wherein the heat-activated adhesive composition (A) has a NCO / OH molar ratio ranging from 0.1 to 8:

1.

6. Multilayer adhesive film according to any one of the preceding claims, wherein the water-based polyurethane dispersion (Bl) has a solid content of at least 40% to 70%, preferably 45% to 60%.

7. Multilayer adhesive film according to claim 8, wherein the water-based polyurethane dispersion (Bl) has a weight average molecular weight (Mw) of 50000 g / mol to 80000 g / mol.

8. Multilayer adhesive film according to any one of the preceding claims, wherein the latent curing agent (B2) is a water suspension of a latent reactive solid isocyanate.

9. The multilayer adhesive film of any one of the preceding claims, wherein the multilayer adhesive film further comprises: a third layer in direct contact with the second major surface of the heat-activated adhesive film, wherein the third layer is the same or different from the second layer, the third layer comprising at least one water-based polyurethane dispersion and optionally a latent curing agent; optionally at least one removable liner disposed on an exposed surface of the third layer, and at least one removable liner disposed on an exposed surface of the second layer.

10. The multilayer adhesive film according to any one of the preceding claims, wherein the total thickness of the multilayer adhesive film ranges from 150 pm to 400 pm, preferably from 200 pm to 300 pm.

11. A process for making a multilayer adhesive film, the process comprising the steps of: (1) applying the solvent-based heat-activated adhesive composition (A) according to any one of claims 1-10 on a removable liner and heating to a temperature of 40°C to 100°C until the solvent content is no more than 5 wt% of the total solvent-based heat-activated adhesive composition, cooling to room temperature, thereby forming a first layer of the multilayer adhesive film; and (2) applying the dispersion composition (B) according to any one of claims 1-10 on the first major surface of the heat-activated adhesive film and heating to a temperature of 40°C to 100°C to dry the dispersion composition, cooling to room temperature, thereby forming a second layer of the multilayer adhesive film.

12. The process for making a multilayer adhesive film according to claim 12, further comprising the step of: (3) removing the removable liner from the second major surface of the heat-activated adhesive film and applying the dispersion composition (B) according to any one of claims 1-10 and heating to a temperature of 40°C to 100°C to dry the dispersion composition, cooling to room temperature, thereby forming a third layer of the multilayer adhesive film; and (4) optionally, applying removable liners on the exposed surfaces of the second and third layers.

13. A process for making a multilayer adhesive film, the process comprising the steps of: (1) applying the solvent-based heat-activated adhesive composition (A) according to any one of claims 1-10 on a removable liner and heating to a temperature of 40°C to 100°C until the solvent content is no more than 5 wt% of the total solvent-based heat-activated adhesive composition, cooling to room temperature, thereby forming a first layer of the multilayer adhesive film; (2) applying the dispersion composition (B) according to any one of claims 1-10 on a removable liner and heating to a temperature of 40°C to 100°C to dry the dispersion composition, cooling to room temperature, thereby forming a second layer of the multilayer adhesive film; and (3) laminating the second layer of the multilayer adhesive on the first layer of the multilayer adhesive film at a temperature of 40°C to 80°C and a pressure of 1 to 5 bar.

14. An article comprising: a first substrate, a second substrate, and a multilayer adhesive film according to any one of claims 1-13 disposed between the first and second substrates. The multilayer adhesive film of any one of claims 1-10 disposed between the first substrate and the second substrate.

15. Use of the multilayer adhesive film of any one of claims 1-10 or the article of claim 14 in the manufacture of automotive parts, truck bed covers, textile laminates, assembled articles, and electronic devices.

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