Polyurethane toughening agent and adhesive composition prepared from polyurethane toughening agent

Abstract

Relates to a polyurethane flexibilizer and an adhesive composition prepared from the polyurethane flexibilizer. Disclosed is a polyurethane polymer having the following structure: (I) wherein m is 10-100, 2lt; n; y is selected from a linear or branched alkyl group, a linear or branched alkenyl group, a linear or branched alkynyl group, an aryl group and any combination thereof; r1 and R2 are the same or different and are independently selected from a linear chain or branched chain alkyl group, a linear chain or branched chain alkenyl group, a linear chain or branched chain alkynyl group, an aryl group, a polyester structure, a polyether structure, a polyolefin structure and any combination thereof. The invention also discloses a preparation method of the polyurethane polymer, which comprises the following steps: (1) reacting polyol with excessive polyisocyanate compound to obtain a polymer with an isocyanate-terminated group; (2) enabling the polymer with the isocyanate-terminated group to react with a multifunctional reactive hydrogen-containing compound to obtain a branched structure; and (3) reacting the branched structure with a phenol end-capping reagent to obtain an end-capped polyurethane polymer. Further, an adhesive composition comprising the polyurethane polymer, and a substrate coated with the adhesive composition are disclosed. Also, a use of the polyurethane polymer is disclosed.

Description

Technical Field

[0001] This invention relates to the field of adhesives, and more particularly to polyurethane toughening agents suitable for adhesives and adhesive compositions prepared therefrom. Background Technology

[0002] The mechanical strength of an adhesive includes shear strength, peel strength, and impact peel strength on various substrates (including cold-rolled steel sheets, aluminum alloy sheets, galvanized sheets, etc.). Besides achieving a certain level of mechanical strength, the failure mode is generally required to be cohesive failure, meaning that adhesive residue should remain on the surface of the bonding substrates at the time of adhesive failure. However, in practice, in most cases, the failure behavior is better on one specific substrate but worse on another. Because different substrates have different surface properties and surface energies, it is difficult to achieve cohesive failure on multiple substrates with a single formulation. Therefore, it is necessary to introduce other components to adjust the surface energy, and toughening agents can achieve this effect.

[0003] Currently, widely used toughening agents in industry include core-shell toughening agents and modified nitrile rubber toughening agents. Core-shell toughening agents, with their uniformly dispersed core-shell rubber within the resin structure, exhibit good toughening effects. However, due to their spherical structure and surface energy similar to that of resins (such as epoxy resins), they cannot effectively improve the surface energy of adhesives. Modified nitrile rubber toughening agents can improve the surface energy of adhesives, but they become brittle at low temperatures; therefore, their dosage in adhesive compositions cannot be too high, limiting their adjustable range. In view of the above, providing a toughening agent suitable for different substrates and capable of improving various mechanical strengths and failure modes of adhesives has practical significance and excellent development prospects. Summary of the Invention

[0004] The inventors have conducted extensive research and developed a polyurethane (PU) toughening agent suitable for a variety of substrates and providing adhesive compositions with excellent mechanical properties, including shear strength and peel strength, while satisfying the cohesive failure mode. In particular, this polyurethane toughening agent enables the regulation (specifically, quantitative regulation) of the peel strength of the adhesive composition.

[0005] This invention discloses a polyurethane polymer having the following structure:

[0006]

[0007] (I)

[0008] in,

[0009] m is 10-100, 2 <n,

[0010] Y is selected from straight-chain or branched alkyl, straight-chain or branched alkenyl, straight-chain or branched alkynyl, aryl, and any combination thereof.

[0011] R 1 and R 2 They may be the same or different, each independently selected from straight-chain or branched alkyl, straight-chain or branched alkenyl, straight-chain or branched alkynyl, aromatic, polyester structure, polyether structure, polyolefin structure and any combination thereof.

[0012] This invention also discloses a method for preparing a polyurethane polymer, comprising:

[0013] (1) React a polyol with an excess of a polyisocyanate compound to obtain a polymer with terminal isocyanate groups;

[0014] (2) Reaction of polymers with terminal isocyanate groups with multifunctional compounds containing active hydrogen yields a branched structure; and

[0015] (3) React the branched structure with a phenolic end-capping agent to obtain a end-capped polyurethane polymer.

[0016] The present invention also discloses an adhesive composition comprising the polyurethane polymer described above or a polyurethane polymer obtained by the preparation method described above.

[0017] The present invention further discloses a coated substrate, comprising a substrate and the above-described adhesive composition coated on at least a portion of the substrate.

[0018] The present invention further discloses the use of the above-described polyurethane polymer or the polyurethane polymer obtained by the above-described preparation method for providing shear strength and / or T-peel strength in adhesive compositions.

[0019] The present invention further discloses the use of the above-described polyurethane polymer or the polyurethane polymer obtained by the above-described preparation method for adjusting the T-peel strength of the adhesive film formed by the adhesive composition in an adhesive composition.

[0020] The features and advantages of the present invention will be specifically presented in the following detailed description of the embodiments. Attached Figure Description

[0021] Figure 1 The graphs showing the T-peel strength of Examples 1-6 relative to the content of polyurethane polymer are presented;

[0022] Figure 2 The graphs showing the T-peel strength of Examples 7-12 relative to the content of polyurethane polymer are presented;

[0023] Figure 3 The graphs showing the T-peel strength of Examples 13-18 relative to the content of polyurethane polymer are illustrated; and

[0024] Figure 4 The graphs show the T-peel strength of Comparative Examples 1-6 relative to the toughening agent content. Detailed Implementation

[0025] In this application, unless otherwise expressly stated, the use of the singular includes the plural and the plural includes the singular. For example, although “one” polymer is referred to herein, one or more of the same substance may be used.

[0026] In this application, the terms "comprising," "including," and "containing" are not intended to limit the invention and exclude any variations or additions. Furthermore, although the present invention has used terms such as "comprising" to describe adhesive compositions, preparation methods, etc., the adhesive compositions, preparation methods, etc., detailed herein may also be described as "consisting substantially of" or "consisting of". In this case, "consisting substantially of" means that any additional ingredients will not have a substantial impact on the properties of the adhesive layer formed by the adhesive composition.

[0027] In this application, unless otherwise expressly stated, “or” is used to mean “and / or”, even if “and / or” may be explicitly used in certain circumstances. Furthermore, it should be understood that any numerical range listed herein is intended to include all subranges contained therein. For example, the range “1 to 10” is intended to include all subranges between the listed minimum value 1 and the listed maximum value 10 (inclusive), that is, all subranges having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0028] Except as explicitly stated in the embodiments or otherwise, it should be considered that the numerical values ​​of all representative components, etc., used in the specification and claims are all subject to variation in all cases according to the term "about". Therefore, unless stated to the contrary, the numerical parameters listed in the following specification and claims are approximate values ​​and may vary according to the performance desired by the invention. This is not intended to limit the application of the doctrine of equivalence to the scope of the claims. Each numerical parameter should be interpreted in significant figures and subject to ordinary rounding.

[0029] Although the numerical ranges and parameters described in this invention are approximate, the numerical values ​​listed in the specific embodiments are recorded as accurately as possible. However, any numerical value inherently possesses a certain degree of error, which is a necessary consequence of the standard deviation derived from the corresponding measurement method.

[0030] As described above, the present invention relates to a polyurethane polymer having the following structure:

[0031]

[0032] (I)

[0033] Among them,

[0034] m is from 10 to 100, 2 < n,

[0035] Y is selected from linear or branched alkyl groups, linear or branched alkenyl groups, linear or branched alkynyl groups, aromatic groups, and any combination thereof, and

[0036] R 1 and R 2 are the same or different and are each independently selected from linear or branched alkyl groups, linear or branched alkenyl groups, linear or branched alkynyl groups, aromatic groups, polyester structures, polyether structures, polyolefin structures, and any combination thereof.

[0037] In this article, the "polymer" can also be referred to as a "prepolymer" or a "copolymer". The "polyurethane polymer" refers to a polymer whose repeating units contain urethane groups (-NH-CO-).

[0038] In formula (I), m and n can be integers or non-integers. Specifically, n being greater than 2 means that more than two polymer segments are connected to Y, forming a branched structure. This branched structure can form an interpenetrating network structure with the components (such as resins) in the adhesive during the curing process, thereby improving the toughening effect of the polyurethane-based toughening agent and also making it easier to control the mechanical properties of the cured adhesive.

[0039] Preferably, 2 < n < 5 in formula (I). That is, n can be an integer or a non-integer greater than 2 and less than 5.

[0040] In formula (I), Y can be n-valent. In formula (I), Y can be a linear or branched alkyl group. In this article, the "alkyl group" includes saturated alkyl groups. Preferably, the alkyl group can be a linear or branched C1-C20 alkyl group, that is, an alkyl group containing one to twenty carbon atoms. Preferably, the alkyl group can be substituted and / or unsubstituted. For example, the alkyl group can be substituted by an aromatic group to obtain an alkylaryl group. For example, the alkylaryl group can be a C7-C12 alkylaryl group.

[0041] In formula (I), Y can be a linear or branched alkenyl group. Preferably, the alkenyl group can be a linear or branched C2-C20 alkenyl group, that is, an alkenyl group containing two to twenty carbon atoms. Preferably, the alkenyl group can be substituted and / or unsubstituted.

[0042] In formula (I), Y can be a linear or branched alkynyl group. Preferably, the alkynyl group can be a linear or branched C2-C20 alkynyl group, that is, an alkynyl group containing two to twenty carbon atoms. Preferably, the alkynyl group can be substituted and / or unsubstituted.

[0043] In formula (I), Y can be an aromatic group. In this document, "aromatic group" includes monophenyl and / or biphenyl groups. Suitably, the aromatic group can be a C6-C12 aromatic group. Suitably, the aromatic group can be substituted and / or unsubstituted. For example, the aromatic group can be substituted with an alkyl group to obtain an aralkyl group. For example, the aralkyl group can be a C7-C12 aralkyl group.

[0044] In equation (I), R 1 and / or R 2 It can be divalent. In equation (I), R 1 and R 2 They can be connected to each other, or at the ends. In equation (I), R 1 and / or R 2 It can be a straight-chain or branched alkyl group. Suitablely, R... 1 and / or R 2 It can be a straight-chain or branched alkyl group of C1-C20.

[0045] In equation (I), R 1 and / or R 2 It can be a straight-chain or branched alkenyl group. Suitablely, R... 1 and / or R 2 It can be a straight-chain or branched alkenyl group of C2-C20.

[0046] In equation (I), R 1 and / or R 2 It can be a straight-chain or branched alkynyl group. Suitablely, R... 1 and / or R 2 It can be a straight-chain or branched alkynyl group of C2-C20.

[0047] In equation (I), R 1 and / or R 2 It can be an aromatic group. Suitablely, R 1 and / or R 2 It can be an aromatic group of C6-C12.

[0048] In equation (I), R 1 and / or R 2 It can be an alkylaryl group. Suitablely, R 1 and / or R 2 It can be a C7-C12 alkylaryl group.

[0049] In equation (I), R 1 and / or R 2 It can be an aralkyl group. Suitablely, R 1 and / or R 2 It can be an aralkyl group of C7-C12.

[0050] In equation (I), R1 and / or R 2 It can be a polyester structure. The polyester structure can be as follows:

[0051]

[0052] (II)

[0053] in,

[0054] R 3 U can be any one of the following groups:

[0055] a) H;

[0056] b) C1-C6 straight-chain or branched alkyl, C2-C6 straight-chain or branched alkenyl or C2-C6 straight-chain or branched alkynyl;

[0057] o is 1-12, p is 10-100, where o and p can be integers or non-integers.

[0058] In equation (I), R 1 and / or R 2 It can be a polyether structure. The polyether structure can be as follows:

[0059]

[0060] (III)

[0061] in,

[0062] R 4 R 5 V can be any one of the following groups:

[0063] c) H;

[0064] d) C1-C6 straight-chain or branched alkyl, C2-C6 straight-chain or branched alkenyl, or C2-C6 straight-chain or branched alkynyl;

[0065] q is 1-6 and t is 10-100, where q and t can be integers or non-integers.

[0066] In equation (I), R 1 and / or R 2 It can be a polyolefin structure. The polyolefin structure can be as shown in formula (IV) or (V):

[0067] ,

[0068] (IV) (V)

[0069] in,

[0070] R 6 R 7 R 8 R 9 W and X can be any one of the following groups:

[0071] e) H;

[0072] f) C1-C6 straight-chain or branched alkyl or C2-C6 straight-chain or branched alkenyl;

[0073] u and v are 10-100 respectively, where u and v can be integers or non-integers.

[0074] In the polyurethane polymer according to the invention, more than two polymer segments are connected to Y to form a branched structure. During curing, the branched structure forms an interpenetrating network with components in the adhesive (e.g., resin), preventing slippage during large deformations, thereby improving the toughening effect of the polyurethane-based toughening agent and making it easier to control the mechanical properties of the cured adhesive.

[0075] The branched structure can be obtained by reacting a first compound containing an isocyanate group with a second compound containing an active hydrogen atom. The active hydrogen atom can be derived from an amino group and / or a hydroxyl group. Suitably, the active hydrogen atom can be derived from a hydroxyl group.

[0076] The first compound containing an isocyanate group may be a polyisocyanate compound. In this document, "polyisocyanate compound" refers to a compound having at least two isocyanate groups. The polyisocyanate compound may include one or more of the following: isoflurane diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and dicyclohexylmethane diisocyanate (HMDI).

[0077] The second compound containing active hydrogen may be a multifunctional compound. In this document, "multifunctional compound" refers to a compound having two or more functions. Suitably, the multifunctional second compound containing active hydrogen may have at least three functions. For example, the second compound may have three or four functions. Suitably, the multifunctional second compound containing active hydrogen may include one or more selected from: trimethylolpropane, glycerol, and pentaerythritol.

[0078] Suitably, the molar ratio of the first compound to the second compound can be (40-20):1. For example, the molar ratio of the first compound to the second compound can be 35:1, 30:1, or 25:1. Suitably, the molar ratio of the first compound to the second compound can be 40:1 or lower, or 35:1 or lower, and / or 20:1 or higher, 25:1 or higher, or 30:1 or higher. Suitably, the molar ratio of the first compound to the second compound can be from 25:1 to 35:1, or any range from the endpoints of the above ratios.

[0079] The polyurethane polymer according to the invention may further include a portion obtained by reacting polyisocyanate groups with a polyol. Hereinafter, "polyol" refers to a compound comprising at least two hydroxyl groups. Suitably, the polyol may include one or more of the following: polycaprolactone polyol (PCL), polypropylene oxide polyol (PPG), polytetrahydrofuran polyol (PTMEG), hydroxyl-terminated polybutadiene polyol (HTPB), and hydrogenated hydroxyl-terminated polybutadiene.

[0080] The polyurethane polymers according to the present invention may not contain free isocyanate groups. Hereinafter, "free isocyanate groups" refers to isocyanate groups located at the ends and capable of further chemical reactions. Suitably, the polyurethane polymers according to the present invention may include phenol-terminated polyurethane polymers. The phenol (phenol-termining agent) may include one or more of the following: 2,2'-diallylbisphenol A, 4-vinylphenol, p-aminophenol, cashew phenol, p-acetaminophen, and p-acetylphenol. At the curing temperature, the phenol-terminated polyurethane polymer undergoes a deblocking reaction, thereby yielding free isocyanate functional groups for further reaction with components in the adhesive.

[0081] The polyurethane polymers according to the present invention can have a number-average molecular weight (Mn) of 2000-50000. The number-average molecular weight can be determined by gel permeation chromatography using appropriate standards such as polystyrene standards, and expressed in g / mol.

[0082] The polyurethane polymers according to the present invention can have a Mw / Mn ratio of 1 to 5. The “Mw” represents the weight-average molecular weight, which can be determined by gel permeation chromatography using appropriate standards such as polystyrene standards, and is expressed in g / mol.

[0083] The polyurethane polymer according to the present invention can have an n of 50,000 to 300,000 cPs. 60。 The η 60This represents the viscosity value at 60°C. In this paper, the viscosity is measured using a Brookfield RVT7 at 50 rpm.

[0084] This invention also relates to a method for preparing polyurethane polymers, comprising:

[0085] (1) React a polyol with an excess of a polyisocyanate compound to obtain a polymer with terminal isocyanate groups;

[0086] (2) Reaction of polymers with terminal isocyanate groups with multifunctional compounds containing active hydrogen yields a branched structure; and

[0087] (3) React the branched structure with a phenolic end-capping agent to obtain a end-capped polyurethane polymer.

[0088] The polyisocyanate compound, the multifunctional active hydrogen-containing compound, and / or the phenolic end-capping agent can constitute at least a portion of the hard segments of the polyurethane polymer. The polyol can constitute at least a portion of the soft segments of the polyurethane polymer. Suitably, the weight ratio of the hard segments to the soft segments can be 1:(3-7). For example, the weight ratio of the hard segments to the soft segments can be 1:4, 1:5, or 1:6. Suitably, the weight ratio of the hard segments to the soft segments can be 1:3 or lower, 1:4 or lower, or 1:5 or lower, and / or 1:7 or higher, or 1:6 or higher. Suitably, the weight ratio of the hard segments to the soft segments can be from 1:4 to 1:6, or any range from the endpoints of the above ratios. In the polyurethane polymer, the combination of hard segments and soft segments can enable the adhesive to have good wettability on a variety of substrate surfaces, easily improve its adhesion, and obtain a better mode of failure. Therefore, the polyurethane polymer according to the present invention can be used as a toughening agent in adhesive compositions.

[0089] This invention also relates to an adhesive composition comprising the aforementioned polyurethane polymer or a polyurethane polymer obtained by the aforementioned preparation method. By varying the amount of polyurethane polymer in the adhesive composition, the surface energy of the adhesive can be adjusted, thereby achieving the purpose of adjusting the T-peel strength while ensuring basic mechanical strength, thus obtaining a T-peel strength that meets the requirements. Suitably, the adhesive composition may comprise 5 to 30 wt% of polyurethane polymer based on the total weight of the adhesive composition. For example, the adhesive composition may comprise 10 wt%, 15 wt%, 20 wt%, or 25 wt% of polyurethane polymer based on the total weight of the adhesive composition. Suitably, the adhesive composition may comprise 5 wt% or more, 10 wt% or more, or 15 wt% or more, and / or 30 wt% or less, 25 wt% or less, or 20 wt% or less of polyurethane polymer based on the total weight of the adhesive composition. Suitablely, the polyurethane polymer may be present in the adhesive composition in amounts of 5-20 wt%, 10-20 wt%, or any range extending beyond these values. Within this polyurethane polymer content range, the T-peel strength of the adhesive composition exhibits a linear relationship with the polyurethane polymer content; that is, the T-peel strength of the adhesive composition increases with increasing polyurethane polymer content. Therefore, this polyurethane polymer enables the adjustment (specifically, quantitative adjustment) of the peel strength of the adhesive composition. Herein, "quantitative adjustment" means that the desired peel strength value / range can be achieved through controllable adjustment.

[0090] The adhesive composition may further comprise an epoxy resin. The epoxy resin may comprise an epoxide containing a plurality of epoxy groups in its molecular structure, for example, an epoxide containing two epoxy groups. Suitable epoxy resins for use in this invention include, but are not limited to, saturated polyepoxides, unsaturated polyepoxides, aliphatic polyepoxides, alicyclic polyepoxides, aromatic polyepoxides, and / or heterocyclic polyepoxides. Suitably, the epoxy resin may be an epoxy resin prepared by bisphenol A and epichlorohydrin under alkaline catalysis, and / or an epoxy resin prepared by bisphenol F and epichlorohydrin under alkaline catalysis.

[0091] Suitably, the epoxy resin may include mixed epoxy resins. Suitably, the epoxy resin may include solid epoxy resins and liquid epoxy resins. In this document, "solid epoxy resin" and "liquid epoxy resin" refer to resins that are solid and liquid at room temperature and atmospheric pressure (e.g., 23°C and 101325 Pa), respectively. As used herein, the terms "solid" and "liquid," unless otherwise stated, refer to the state of matter at room temperature (e.g., 23°C).

[0092] Solid epoxy resins suitable for use in the adhesive compositions of the present invention may include bisphenol A diglycidyl ether. The epoxy equivalent of the solid epoxy resin may be 400-550 g / eq, such as 450-500 g / eq. The epoxy equivalent refers to the mass of epoxy resin containing 1 mol of epoxy groups and can be determined by titration.

[0093] The liquid epoxy resin suitable for use in the adhesive compositions of the present invention may comprise bisphenol A diglycidyl ether and / or bisphenol F diglycidyl ether. For example, the liquid epoxy resin may comprise bisphenol A diglycidyl ether and bisphenol F diglycidyl ether. Suitably, the epoxy equivalent of the bisphenol A diglycidyl ether may be 180-220 g / eq, such as 190-210 g / eq. The epoxy equivalent of the bisphenol F diglycidyl ether may be 150-190 g / eq, such as 160-180 g / eq.

[0094] The mass ratio of the liquid bisphenol A diglycidyl ether to the liquid bisphenol F diglycidyl ether can be 1 : (0.5~1). The weight ratio of the solid epoxy resin to the liquid epoxy resin can be (>0~0.5): 1, such as (0.01~0.5): 1.

[0095] During the curing process, the aforementioned polyurethane polymer can be advantageously grafted into the resin, forming an interpenetrating network structure, thereby preventing slippage and achieving improved toughening effect. It also makes it easier to control the mechanical properties of the cured adhesive. Suitablely, the weight ratio of the epoxy resin to the polyurethane polymer can be from 30:30 to 40:5.

[0096] The adhesive composition according to the invention may further include a core-shell rubber, which is a liquid rubber toughening agent having a core-shell structure. The liquid rubber toughening agent with a core-shell structure may include rubber particles uniformly and sufficiently dispersed in a liquid epoxy resin. The rubber particles include a core material and a shell material coating the core material.

[0097] The core material may be composed of an elastomeric polymer, such as a diene monomer homopolymer and / or a copolymer of a diene monomer and a monoolefin. Suitably, the monoolefin may include vinyl aromatic monomers, acrylonitrile monomers, and / or acrylic monomers. Suitably, the core material may have a glass transition temperature (Tg) less than -30°C. The glass transition temperature may be determined by differential scanning calorimetry using the following parameters: a temperature range of -90°C to 100°C, and a rate of 10°C / min.

[0098] The shell material may include polymers of acrylic monomers and vinyl aromatic monomers, and / or polymers of acrylic monomers and unsaturated halogenated olefin monomers. For example, the shell material may include epoxy-functionalized alkyl (meth)acrylate homopolymers, and / or copolymers of epoxy-functionalized alkyl (meth)acrylates and vinyl monomers. The shell material may have a glass transition temperature greater than 50°C.

[0099] The volume average particle size of the core-shell structured liquid rubber toughening agent is less than 300 nm, such as 100-200 nm. This particle size can be determined by dynamic light scattering. For example, the particle size can be determined using a DynaPro-TC-04 instrument set to a wavelength of 830 nm for particle size distribution analysis.

[0100] The adhesive composition according to the invention may further comprise resin-modified nitrile rubber. The nitrile rubber may be liquid nitrile rubber. In the liquid nitrile rubber, the molecular backbone may comprise a copolymer of butadiene monomer, isobutadiene monomer, and acrylonitrile monomer. Suitably, the liquid nitrile rubber may comprise 15-30 wt% of acrylonitrile monomer based on the total weight of the rubber. Suitably, the liquid nitrile rubber may comprise a liquid nitrile rubber having terminal carboxyl groups, having a weight-average molecular weight (Mw) of 3000-10000. The weight-average molecular weight can be determined by gel permeation chromatography using suitable standards such as polystyrene standards. Suitably, the resin-modified nitrile rubber may comprise epoxy resin-modified nitrile rubber.

[0101] Suitable, the weight ratio of the liquid rubber toughening agent of the core-shell structure to the resin-modified nitrile rubber and the polyurethane polymer can be from 5:30 to 30:5.

[0102] The adhesive composition according to the invention may further include a reactive diluent. The reactive diluent is used to improve viscosity and rheological properties and participates in the curing reaction. The reactive diluent may include a bifunctional reactive diluent and / or a trifunctional reactive diluent. For example, the reactive diluent may include a bifunctional reactive diluent, such as a bifunctional epoxy diluent. Suitably, the bifunctional epoxy diluent comprises a diglycidyl ether of a saturated aliphatic diol, such as a diglycidyl ether of a saturated aliphatic C3-C5 diol.

[0103] The adhesive composition according to the present invention may further include a curing agent. The curing agent may include a thermally activated latent curing agent. The present invention may select a high-temperature epoxy curing agent, which is activated by heating, with a curing temperature above 140°C. The thermally activated latent curing agent is selected from one or more of guanidine and its derivatives, amines and their derivatives. For example, the curing agent may include a powdered dicyandiamide curing agent, wherein the particle size of the powder is ≤10 μm to improve dispersion and simultaneously improve the storage stability of the adhesive. The particle size can be determined by dynamic light scattering. For example, the particle size can be determined using a DynaPro-TC-04 instrument set to a wavelength of 830 nm for particle size distribution analysis.

[0104] The adhesive composition according to the invention may further include a curing accelerator. The curing accelerator may include catalytically active substituted ureas containing phenyl and dimethyl compounds, which, in addition to their catalytic activity, can significantly extend the product's shelf life. Suitably, the curing accelerator may include dimethylurea curing accelerators with lower catalytic activity, such as p-chlorophenyl-N,N-dimethylurea, 3-phenyl-1,1-dimethylurea, 3,4-dichlorophenyl-N,N-dimethylurea, 2,4-toluenebis(dimethylurea), phenyldimethylurea, 4,4'-methylenebis(phenyldimethylurea), and alicyclic diureas.

[0105] The adhesive composition according to the invention may further include a thixotropic agent. Suitably, the thixotropic agent may include hydrophobic fumed silica, which can significantly improve high-temperature thixotropy and prevent high-temperature sagging.

[0106] The adhesive composition according to the invention may further include fillers. The fillers may include inorganic fillers such as calcium oxide, calcium carbonate, talc, mica, quartz powder, bentonite, wollastonite, metal powder, mica iron oxide, carbon black, alumina, aluminum hydroxide, and / or glass microspheres.

[0107] The adhesive composition according to the invention has excellent shear strength and T-peel strength, and is suitable for a variety of substrates, maintaining cohesive failure mode on a variety of metal substrates such as cold-rolled steel, aluminum alloy, and / or galvanized sheet.

[0108] The adhesive composition according to the invention can be a one-component (1K) composition. As used herein, the term "one-component (1K)" means that all resins, fillers, and / or additives of the adhesive composition are packaged in one container, thus providing advantages such as ease of storage and use.

[0109] The adhesive composition according to the invention can be cured under heating conditions. The adhesive composition according to the invention can be cured within 20 to 40 minutes at 150 to 180°C. For example, the adhesive composition according to the invention can be cured within 30 minutes at 170°C. After curing, the adhesive composition according to the invention can have a film thickness of 0.2 mm.

[0110] The present invention also relates to a substrate coated with the above-described adhesive composition, comprising a substrate and an adhesive film formed by coating at least a portion of the substrate with the above-described adhesive composition. The substrate may include an untreated substrate or a pretreated substrate. The substrate may include an uncoated substrate or a pre-coated substrate. Suitably, the substrate may include cold-rolled steel, aluminum alloy, and / or galvanized sheet. Suitably, the substrate is part of a vehicle.

[0111] Furthermore, this invention relates to the use of the polyurethane polymer described above, or the polyurethane polymer obtained by the preparation method described above, in providing excellent shear strength and / or peel strength in adhesive compositions. The polyurethane polymer is present in an amount of 5 to 30 wt% of the total weight of the adhesive composition.

[0112] This invention also relates to the use of the polyurethane polymer described above, or the polyurethane polymer obtained by the preparation method described above, in an adhesive composition for quantitatively adjusting the peel strength of the adhesive film formed by the adhesive composition. The peel strength of the adhesive film is a linear function of the content of the polyurethane polymer. The content of the polyurethane polymer can be 5 to 30 wt% of the total weight of the adhesive composition.

[0113] Example

[0114] The following embodiments further illustrate the invention, but should not be construed as limiting the invention to the details described in the embodiments. Unless otherwise stated, all parts and percentages in the following embodiments are by weight.

[0115] Preparation Example 1: Polyurethane polymer 1 according to the present invention

[0116] The polyurethane polymer 1 according to the present invention is prepared by the following method: 151 g of polycaprolactone diol (PCL, Mw~2000) is dehydrated under vacuum at 110°C for 2 h, and then cooled to 85°C; 34 g of isophorone diisocyanate (IPDI) is added, along with a trace amount of dioctyltin dilaurate (DOTDL) catalyst, and the mixture is stirred thoroughly for 2 h; then 0.8 g of dry trimethylolpropane (TMP) is added, and the mixture is stirred for another 2 h to obtain a colorless, transparent, viscous prepolymer; and 24 g of 4-vinylphenol is added, and the mixture is heated to 105°C for 1 h, then cooled to 85°C until the free isocyanate groups in the prepolymer are completely consumed.

[0117] Preparation Example 2: Polyurethane polymer 2 according to the present invention

[0118] The polyurethane polymer 2 according to the present invention is prepared by the following method: 181 g of polypropylene oxide diol (PPG, Mw~2000) is dehydrated under vacuum at 110°C for 2 h, and then cooled to 85°C; 41 g of isophorone diisocyanate (IPDI) is added, along with a trace amount of dioctyltin dilaurate (DOTDL) catalyst, and the mixture is stirred thoroughly for 2 h; then 1 g of dry trimethylolpropane (TMP) is added, and the mixture is stirred for another 2 h to obtain a colorless, transparent, viscous prepolymer; and 32 g of acetaminophen is added, and the mixture is heated to 105°C for 1 h, then cooled to 85°C until the free isocyanate groups in the prepolymer are completely consumed.

[0119] Preparation Example 3: Polyurethane polymer 3 according to the present invention

[0120] The polyurethane polymer 3 according to the present invention is prepared by the following method: 300 g of polytetrahydrofuran diol (PTMEG, Mw~2000) is dehydrated under vacuum at 110°C for 2 h, and then cooled to 85°C; 67 g of isophorone diisocyanate (IPDI) is added, along with a trace amount of dioctyltin dilaurate (DOTDL) catalyst, and the mixture is stirred thoroughly for 2 h; then 1.7 g of dry trimethylolpropane (TMP) is added, and the mixture is stirred for another 2 h to obtain a colorless, transparent, viscous prepolymer; and 120 g of 2,2'-diallylbisphenol A is added, and the mixture is heated to 105°C for 1 h, then cooled to 85°C until the free isocyanate groups in the prepolymer are completely consumed.

[0121] Preparation Example 4: Polyurethane polymer 4 according to the present invention

[0122] The polyurethane polymer 4 according to the present invention is prepared by the following method: 214 g of hydroxyl-terminated polybutadiene (HTPB, Mw~2000) is dehydrated under vacuum at 110°C for 2 h, and then cooled to 85°C; 48 g of isophorone diisocyanate (IPDI) is added, along with a trace amount of dioctyltin dilaurate (DOTDL) catalyst, and the mixture is stirred thoroughly for 2 h; then 1.1 g of dry trimethylolpropane (TMP) is added, and the mixture is stirred for another 2 h to obtain a colorless, transparent, viscous prepolymer; and 83 g of cardol phenol (CardoliteNX-2022) is added, heated to 105°C for 1 h, and cooled to 85°C until the free isocyanate groups in the prepolymer are completely consumed.

[0123] Preparation of Comparative Example 1: Comparative example polyurethane polymer 1

[0124] Comparative polyurethane polymer 1 The prepolymer was prepared as follows: 300 g of polytetrahydrofuran diol (PTMEG, Mw~2000) was dehydrated under vacuum at 110 °C for 2 h, and then cooled to 85 °C; 67 g of isophorone diisocyanate (IPDI) and a trace amount of dioctyltin dilaurate (DOTDL) catalyst were added, and the mixture was stirred thoroughly for 2 h; then 1.7 g of dry 1,4-butanediol (BDO) was added, and the mixture was stirred for another 2 h to obtain a colorless, transparent, viscous prepolymer; and then 120 g of 2,2'-diallylbisphenol A was added, and the mixture was heated to 105 °C for 1 h, then cooled to 85 °C until the free isocyanate groups in the prepolymer were completely consumed.

[0125] The polyurethane polymers of the above embodiments and the comparative examples were used respectively. An adhesive composition is prepared. The composition and content of the adhesive composition are shown in the table below, and the preparation steps include: mixing epoxy resin and heating to melt it to obtain a mixed epoxy resin; adding an active diluent, core-shell rubber, modified butyl rubber, and polyurethane polymer to the mixed epoxy resin and dispersing them evenly; then adding fillers, thixotropic agents, curing agents, curing accelerators, and other additives, mixing and stirring the mixture evenly; and then vacuum degassing the mixture to obtain the adhesive composition.

[0126] Adhesive Examples 1-6: Adhesive compositions comprising polyurethane polymer 3

[0127] Table 1. Adhesive compositions including polyurethane polymer 3

[0128]

[0129] Adhesive Examples 7-12: Adhesive compositions comprising polyurethane polymer 2

[0130] Table 2. Adhesive compositions including polyurethane polymer 2

[0131]

[0132] Adhesive Examples 13-18: Adhesive compositions comprising polyurethane polymer 2

[0133] Table 3. Adhesive compositions including polyurethane polymer 2

[0134]

[0135] Adhesives Comparative Examples 1-6: including the polyurethane polymers of the comparative examples 1 adhesive composition

[0136] Table 4. Polyurethane polymers including comparative examples 1 adhesive composition

[0137]

[0138] The adhesive compositions obtained above in Examples 1-18 and Comparative Examples 1-6 were applied to substrates using a doctor blade and cured at 170°C for 30 minutes to obtain adhesive films with a thickness of 0.2 mm. Tensile shear strength and T-peel strength tests were then performed on the cured adhesive films.

[0139] Tensile shear strength test:

[0140] Sample preparation and testing methods refer to standard GB / T 7124-2008; the testing rate is 10 mm / min.

[0141] T-peel strength test:

[0142] The peel strength test method refers to ISO 11339-2010 standard, using 0.7 mm galvanized steel sheet, with an adhesive surface of 150 mm x 25 mm, using 0.2 mm diameter metal wire to control the adhesive layer thickness, and the test rate is 100 mm / min.

[0143] The test results are summarized as follows:

[0144] Table 5. Test results of Examples 1-6

[0145]

[0146] By observing the adhesive layer bonding area with the naked eye, the types of damage are as follows: CF represents cohesive damage, which means that there is adhesive residue on both surfaces of the bonding area; AF represents interfacial damage, which means that at least one surface of the bonding area has exposed substrate; and film damage means that there is a film-like adhesive residue on at least one surface of the bonding area, with an effect between CF and AF.

[0147] Figure 1 A graph showing the T-peel strength of Examples 1-6 relative to the content of polyurethane polymer is presented.

[0148] Table 5 shows that the adhesive shear strength on CRS is above 30 MPa, and there is no significant change with the increase of polyurethane polymer content, indicating that the polyurethane toughening agent has little effect on the shear strength. On commonly used aluminum alloy 6016, the adhesive also exhibits good adhesive strength and cohesive failure mode. This is due to the synergistic effect between the hard and soft segments of the polyurethane polymer, which enables the adhesive to have good adhesive strength and adhesion on substrates with different surface energies.

[0149] For T-peel strength, by Figure 1 It can be seen that as the mass fraction of polyurethane polymer in the entire adhesive composition increases, the T-peel strength shows a linear increasing trend with a high degree of linearity. This indicates that polyurethane polymer significantly improves the toughening effect of adhesives in interpenetrating network resin systems, and this improvement can be quantitatively controlled.

[0150] Table 6. Test results of Examples 7-12

[0151]

[0152] By observing the adhesive layer bonding area with the naked eye, the types of damage are as follows: CF represents cohesive damage, which means that there is adhesive residue on both surfaces of the bonding area; AF represents interfacial damage, which means that at least one surface of the bonding area has exposed substrate; and film damage means that there is a film-like adhesive residue on at least one surface of the bonding area, with an effect between CF and AF.

[0153] Figure 2 A graph showing the T-peel strength of Examples 7-12 relative to the content of polyurethane polymer is presented.

[0154] Table 6 shows that the adhesive shear strength on CRS is above 30 MPa, and there is no significant change with the increase of polyurethane polymer content, indicating that the polyurethane-based polymer has little effect on the shear strength. On commonly used aluminum alloy 6016, the adhesive also exhibits good adhesive strength and cohesive failure mode. This is due to the synergistic effect of hard and soft segments in the polyurethane-based polymer, which enables the adhesive to have good adhesive strength and adhesion on substrates with different surface energies.

[0155] As for T-peel strength, it is determined by... Figure 2 It can be seen that as the mass fraction of polyurethane polymer in the entire adhesive composition increases, the T-peel strength exhibits a linear increasing trend with a high degree of linearity. This indicates that polyurethane-based polymers have a significant toughening effect on adhesives in interpenetrating network resin systems, and the improvement can be quantitatively controlled.

[0156] Table 7. Test results of Examples 13-18

[0157]

[0158] By observing the adhesive layer bonding area with the naked eye, the types of damage are as follows: CF represents cohesive damage, which means that there is adhesive residue on both surfaces of the bonding area; AF represents interfacial damage, which means that at least one surface of the bonding area has exposed substrate; and film damage means that there is a film-like adhesive residue on at least one surface of the bonding area, with an effect between CF and AF.

[0159] Figure 3 A graph showing the T-peel strength of Examples 13-18 relative to the content of polyurethane polymer is presented.

[0160] Table 7 shows that the adhesive shear strength on CRS is above 30 MPa, and there is no significant change with the increase of polyurethane polymer content, indicating that the polyurethane-based polymer has little effect on the shear strength. On commonly used aluminum alloy 6016, the adhesive also exhibits good adhesive strength and cohesive failure mode. This is due to the synergistic effect of hard and soft segments in the polyurethane-based polymer, which enables the adhesive to have good adhesive strength and adhesion on substrates with different surface energies.

[0161] As for T-peel strength, it is determined by... Figure 3 It can be seen that as the mass fraction of polyurethane polymer in the entire adhesive composition increases, the T-peel strength exhibits a linear increasing trend with a high degree of linearity. This indicates that polyurethane-based polymers have a significant toughening effect on adhesives in interpenetrating network resin systems, and the improvement can be quantitatively controlled.

[0162] Table 8. Test results of Comparative Examples 1-6

[0163]

[0164] By observing the adhesive layer bonding area with the naked eye, the types of damage are as follows: CF represents cohesive damage, which means that there is adhesive residue on both surfaces of the bonding area; AF represents interfacial damage, which means that at least one surface of the bonding area has exposed substrate; and film damage means that there is a film-like adhesive residue on at least one surface of the bonding area, with an effect between CF and AF.

[0165] Figure 4 The graphs show the T-peel strength of Comparative Examples 1-6 relative to the toughening agent content.

[0166] As shown in Table 8, the adhesive shear strength on CRS tends to decrease with increasing polyurethane polymer content. When the polyurethane polymer content exceeds 15 wt%, its shear strength drops below 30 MPa. The introduction of polyurethane polymer causes its linear molecular chains to slip within the resin's cross-linking network, leading to a decrease in shear strength even with high toughening agent content, and the interface failure mode is primarily surface-level damage.

[0167] For the peel strength of T, it is determined by... Figure 4 It can be seen that as the mass fraction of polyurethane polymer in the entire adhesive composition increases, the T-peel strength first increases and then decreases, and the overall T-peel strength is lower than that of the example. This is because at low polyurethane polymer content, the adhesive is brittle, lacks toughness, and has poor resistance to large deformations; as the polyurethane polymer content increases, the toughness of the adhesive gradually increases. Since linear polyurethane polymers cannot form a good interpenetrating structure with the resin crosslinking network, when the linear polyurethane polymer content exceeds a certain threshold, due to thermodynamic incompatibility, large-scale phase separation occurs between polyurethane molecules and epoxy molecular chains, which directly leads to a precipitous drop in the mechanical properties of the adhesive.

[0168] In contrast, the branched polyurethane polymer can form an interpenetrating network structure with the epoxy crosslinked network structure, avoiding the large-scale phase separation phenomenon caused by thermodynamics from a kinetic physical structure perspective. Therefore, its toughening effect can show a linear relationship with the increase of content.

[0169] Although specific aspects of the invention have been explained and described, it will be apparent to those skilled in the art that many other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the appended claims are intended to cover all such changes and modifications that fall within the scope of the invention.

Claims

1. A polyurethane polymer having the following structure: (I) in, m is 10-100, 2 <n, Y is selected from straight-chain or branched alkyl, straight-chain or branched alkenyl, straight-chain or branched alkynyl, aryl, and any combination thereof. R 1 and R 2 They may be the same or different, each independently selected from straight-chain or branched alkyl, straight-chain or branched alkenyl, straight-chain or branched alkynyl, aromatic, polyester structure, polyether structure, polyolefin structure and any combination thereof.

2. The polyurethane polymer of claim 1, wherein more than two polymer segments are connected to Y to form a branched structure.

3. The polyurethane polymer as claimed in claim 1 or 2, wherein 2 <n<5。 4. The polyurethane polymer of claim 2 or 3, wherein the branched structure is obtained by reacting a first compound containing an isocyanate group with a second compound containing active hydrogen.

5. The polyurethane polymer of claim 4, wherein the second compound is a multifunctional compound.

6. The polyurethane polymer of claim 5, wherein the multifunctional compound has at least 3 functions.

7. The polyurethane polymer of claim 5 or 6, wherein the multifunctional compound comprises one or more of the following: trimethylolpropane, glycerol, and pentaerythritol.

8. The polyurethane polymer according to any one of claims 4-7, wherein the first compound is a polyisocyanate compound, the polyisocyanate compound comprising one or more of the following: isoflurane diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and dicyclohexylmethane diisocyanate (HMDI).

9. The polyurethane polymer according to any one of claims 4-8, wherein the molar ratio of the first compound to the second compound is (40-20):

1.

10. The polyurethane polymer according to any one of claims 1-9, wherein the polyurethane polymer does not contain free isocyanate groups.

11. The polyurethane polymer according to any one of claims 1-10, wherein the polyurethane polymer comprises a phenol-terminated polyurethane polymer.

12. The polyurethane polymer of claim 11, wherein the phenol comprises one or more of the following: 2,2'-diallylbisphenol A, 4-vinylphenol, p-aminophenol, cashew phenol, p-acetaminophen, and p-acetylphenol.

13. The polyurethane polymer according to any one of claims 1-12, further comprising a portion prepared by reacting a polyisocyanate group with a polyol, said polyol comprising one or more of the following: polycaprolactone polyol (PCL), polypropylene oxide polyol (PPG), polytetrahydrofuran polyol (PTMEG), hydroxyl-terminated polybutadiene polyol (HTPB), and hydrogenated hydroxyl-terminated polybutadiene.

14. A method for preparing a polyurethane compound, comprising: (1) React a polyol with an excess of a polyisocyanate compound to obtain a polymer with terminal isocyanate groups; (2) Reaction of polymers with terminal isocyanate groups with multifunctional compounds containing active hydrogen yields a branched structure; and (3) React the branched structure with a phenolic end-capping agent to obtain a end-capped polyurethane polymer.

15. The preparation method of claim 14, wherein the polyisocyanate compound, the multifunctional active hydrogen-containing compound, and / or the phenolic end-capping agent constitute at least a portion of the hard segments of the polyurethane polymer.

16. The preparation method of claim 14 or 15, wherein the polyol constitutes at least a portion of the soft segments of the polyurethane polymer.

17. The preparation method according to claim 16, wherein the weight ratio of the hard segment to the soft segment is 1:(3-7).

18. An adhesive composition comprising a polyurethane polymer as claimed in any one of claims 1-13 or a polyurethane polymer obtained by the preparation method as claimed in any one of claims 14-17.

19. The adhesive composition of claim 18, comprising 5 to 30 wt% of a polyurethane polymer based on the total weight of the adhesive composition.

20. The adhesive composition of claim 18 or 19, further comprising an epoxy resin, wherein the weight ratio of the epoxy resin to the polyurethane polymer is 30:30 to 40:

5.

21. The adhesive composition of claim 20, wherein the epoxy resin comprises a solid epoxy resin and a liquid epoxy resin, and the weight ratio of the solid epoxy resin to the liquid epoxy resin is (>0~0.5):

1.

22. The adhesive composition of any one of claims 18-21, further comprising a core-shell liquid rubber toughening agent and / or resin-modified nitrile rubber, wherein the weight ratio of the sum of the core-shell liquid rubber toughening agent and the resin-modified nitrile rubber to the polyurethane polymer is 5:30 to 30:

5.

23. A coated substrate comprising a substrate and an adhesive film formed by the adhesive composition of any one of claims 18-22 coated on at least a portion of the substrate.

24. The coated substrate of claim 23, wherein the substrate comprises cold-rolled steel, aluminum alloy, and / or galvanized sheet.

25. Use of a polyurethane polymer as claimed in any one of claims 1-13 or a polyurethane polymer obtained by the preparation method as claimed in any one of claims 14-17 for providing shear strength and / or T-peel strength in an adhesive composition.

26. Use of a polyurethane polymer as claimed in any one of claims 1-13 or a polyurethane polymer obtained by the preparation method as claimed in any one of claims 14-17 for adjusting the T-peel strength of the adhesive film formed by the adhesive composition in an adhesive composition.

27. The use as described in claim 25 or 26, wherein the polyurethane polymer content is 5 to 30 wt% of the total weight of the adhesive composition.

28. The use as described in claim 26 or 27, wherein the T-peel strength of the adhesive film is a linear function of the polyurethane polymer content.

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