Lignin-based acrylate prepolymer, composite prepolymer, adhesive composition, preparation method, and use

Abstract

Disclosed in the present invention are a lignin-based acrylate prepolymer, a composite prepolymer containing the lignin-based acrylate prepolymer, an adhesive composition comprising the composite prepolymer containing the lignin-based acrylate prepolymer, a preparation method, and a use. The adhesive of the present invention has good adhesion firmness, small volume shrinkage, and good flexibility and chemical resistance, has the advantages of cheap and easily available raw materials, environmental protection and the like, and has industrial application potentials.

Description

Lignin-based acrylate prepolymer, composite prepolymer, adhesive composition, and preparation method and application thereof Technical Field

[0001] The present invention relates to the technical field of bio-based adhesives, and more particularly to a lignin-based acrylate prepolymer, a composite prepolymer, an adhesive composition, and a preparation method and application thereof. Background Art

[0002] Acrylic adhesives are widely used in optoelectronic devices, building materials, medical materials and other fields due to their excellent bonding and curing properties.

[0003] Acrylate adhesives typically consist of, in addition to acrylic (ester) functional monomers, oligomers (prepolymers) containing unsaturated functional groups. The properties of these oligomers determine the primary properties of the cured material. Generally speaking, prepolymers with high molecular weights exhibit minimal volume shrinkage during curing and rapid cure. However, these high molecular weights increase system viscosity, necessitating the use of more monomers for dilution. Therefore, prepolymer selection is a crucial component of adhesive formulation design.

[0004] Traditional acrylic adhesives and prepolymers primarily rely on non-renewable petrochemical resources. These raw materials generate harmful substances during production, and petrochemical-based prepolymers are difficult to degrade, significantly impacting the environment. Due to the limited availability of these resources, reliance on them for production is also inconsistent with sustainable development requirements. Therefore, the exploration and development of new adhesives and their environmentally friendly raw materials is key to promoting the green and sustainable development of the adhesives industry and has become a research hotspot in the adhesives field.

[0005] Compared with fossil energy, biomass resources such as lignin, starch, cellulose, and protein are widely available, abundant in reserves, and renewable. They are easily degraded and re-enter the natural circulation system, which can achieve zero emissions of greenhouse gases such as carbon dioxide. They meet the requirements of environmentally friendly materials and have great potential in replacing petrochemical resources such as oil, coal, and natural gas, and supporting the green and sustainable development of industry. Biomass as a raw material is a favorable measure to actively promote the realization of carbon peak and carbon neutrality goals. Lignin is widely present in plant cell walls and is the second largest green renewable resource in nature (second only to cellulose). The papermaking industry and bioethanol industry alone can produce tens of millions of tons of lignin each year. Lignin contains many highly polar active groups and is easy to modify according to needs.

[0006] While bio-based acrylic adhesives offer significant environmental advantages, their performance still needs to be further improved to meet the demands of practical applications. In particular, their performance in areas such as bond strength, volume shrinkage, and weather resistance must meet or even exceed the standards of traditional acrylic adhesives.

[0007] Therefore, there is a need in the art to develop a bio-based acrylate adhesive system with high bonding strength, low volume shrinkage and good weather resistance.

[0008] Summary of the Invention

[0009] To address the aforementioned problems existing in the prior art, the present invention provides lignin-based acrylate prepolymers, composite prepolymers, novel adhesive compositions, and their preparation methods and applications. The present invention involves modifying lignin with acrylic acid and polymerizing it with a multifunctional crosslinker generated by modification with gallic acid to form a lignin-based acrylate prepolymer. This lignin-based acrylate prepolymer is then mixed with a polyurethane acrylate prepolymer to form a composite prepolymer, which is then used in the preparation of the novel adhesive composition. This effectively achieves value-added utilization of lignin, resulting in a bio-based acrylate adhesive system with high bonding strength, low volume shrinkage, and excellent weather resistance.

[0010] More specifically, the present invention solves the above technical problems through the following aspects.

[0011] In a first aspect, the present invention provides a lignin-based acrylate prepolymer, comprising a cross-linked backbone comprising polymeric structural units derived from at least one acrylic acid-functionalized lignin and linking groups connecting the cross-linked backbone, wherein the cross-linked backbone comprises polymeric structural units derived from at least one acrylic acid-functionalized lignin, and the linking groups are derived from at least one multifunctional gallic acid ester having at least three terminal olefinic groups.

[0012] In a second aspect, the present invention provides a method for preparing a lignin-based acrylate prepolymer according to the first aspect, the method comprising the following steps: mixing raw materials including at least one acrylic acid-functionalized lignin, at least one multifunctional gallic acid ester having at least three terminal olefin groups, a first initiator and an optional co-initiator under vacuum and then heating the mixture to react to obtain a lignin-based acrylate prepolymer.

[0013] In a third aspect, the present invention provides a composite prepolymer comprising a polyurethane acrylate prepolymer, a lignin-based acrylate prepolymer and an optional polymerization inhibitor; wherein the lignin-based acrylate prepolymer is obtained according to the first aspect of the present invention or by the preparation method according to the second aspect of the present invention.

[0014] In a fourth aspect, the present invention provides an adhesive composition comprising a polymerizable monomer, a second initiator, the composite prepolymer according to the third aspect of the present invention, a coupling agent, and an optional auxiliary agent.

[0015] In a fifth aspect, the present invention provides a method for preparing the adhesive composition according to the fourth aspect of the present invention, the method comprising the following steps:

[0016] a) mixing a polyurethane acrylate prepolymer, a lignin-based acrylate prepolymer, and an optional polymerization inhibitor in the dark to obtain a composite prepolymer;

[0017] b) mixing the polymerizable monomer, the second initiator, the composite prepolymer, the coupling agent and the optional auxiliary agent under vacuum and in the dark to obtain the adhesive composition.

[0018] In a sixth aspect, the present invention provides use of the adhesive composition according to the fourth aspect of the present invention in bonding optoelectronic devices, building materials, and medical materials.

[0019] The adhesive composition provided by the present invention incorporates a composite prepolymer containing a lignin-based acrylate prepolymer, resulting in a bio-based acrylate adhesive with excellent bonding properties, shrinkage resistance, and weather resistance. Furthermore, the introduction of biomass lignin reduces industrial costs, and the product is easily degradable after disposal, meeting environmentally friendly requirements and possessing potential for industrial application.

[0020] Therefore, the present invention provides a lignin-based acrylate prepolymer and a composite prepolymer thereof, as well as a novel adhesive composition comprising the composite prepolymer containing the lignin-based acrylate prepolymer. The adhesive has high bonding strength, low volume shrinkage, good flexibility and chemical resistance, and has the advantages of cheap and readily available raw materials and being green and environmentally friendly.

[0021] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the present application but do not constitute a limitation of the present application. In the accompanying drawings:

[0023] Figure 1 shows the relationship between (A) kraft lignin and (B) methacrylated lignin. 1 H nuclear magnetic resonance (NMR) spectrum.

[0024] FIG2 shows Fourier transform infrared (FT-IR) spectra of (A) kraft lignin and (B) methacrylated lignin.

[0025] Figure 3 shows the reaction of (C) gallic acid and (D) allylated gallic acid triacrylate 1 H NMR spectrum.

[0026] FIG4 shows the FT-IR spectra of (C) gallic acid and (D) allylated gallic acid triacrylate.

[0027] Figure 5 is the FT-IR spectrum of lignin-based acrylate prepolymer. DETAILED DESCRIPTION

[0028] The specific implementation methods of the present application are described in detail below. However, it should be noted that the scope of protection of the present application is not limited by these specific implementation methods, but is determined by the claims in the appendix.

[0029] Except for the Examples section, any specific numerical value disclosed herein (including the endpoints of a numerical range) is not limited to the exact value of the numerical value, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within the range of ±5% of the exact value. Moreover, for the disclosed numerical range, any combination of the endpoints of the range, the endpoints and the specific point values ​​within the range, and the specific point values ​​can be combined to form one or more new numerical ranges, and these new numerical ranges should also be considered to be specifically disclosed herein.

[0030] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0031] In this application, except for the contents explicitly stated, any matters or issues not mentioned are directly applicable to aspects known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of this application, and should not be regarded as new content not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0032] The expressions "comprising" or "including" in this application should be interpreted as including all the specifically mentioned features as well as optional, additional, and unspecified features. As used herein, the use of the term "comprising" also discloses solutions in which other features than the specifically mentioned features are not present, for example, the expressions "consisting essentially of" and "consisting of.

[0033] All patent and non-patent literature, including but not limited to textbooks and journal articles, mentioned herein are incorporated by reference in their entirety.

[0034] In a first aspect, the present invention provides a lignin-based acrylate prepolymer comprising a cross-linked backbone and linking groups connecting the cross-linked backbone, wherein the cross-linked backbone comprises polymeric structural units derived from at least one acrylic acid-functionalized lignin, and the linking groups are derived from at least one multifunctional gallic acid ester having at least three terminal olefinic groups;

[0035] The acrylic acid functionalized lignin contains the following structural fragments:

[0036] where R 1 and R 2 Each independently represents H or C1-2 alkyl; R 3 and R 4 Each independently represents H, -OCH3 or a linker connected to other structural segments of the acrylic acid functionalized lignin.

[0037] According to some embodiments of the present invention, the acrylic acid functionalized lignin is selected from at least one of acrylic acid lignin, methacrylated lignin, and ethacrylated lignin. According to a preferred embodiment of the present invention, the acrylic acid functionalized lignin is methacrylated lignin, which contains the following structural fragment:

[0038] The structure of the lignin used in this invention is relatively complex. The above structure only shows the main reaction fragment; the unmarked bond breaks are the remaining structures of lignin, such as kraft lignin. The lignin structure is an amorphous polymer containing p-coumaryl alcohol monomers, coniferyl alcohol monomers, and sinapyl alcohol monomers. The structures of the three alcohol monomers are as follows:

[0039] According to some embodiments of the present invention, the lignin is selected from at least one of alkali lignin, lignin sulfonate, sulfate lignin, sulfonated alkali lignin, and ammonium alkali lignin.

[0040] According to some embodiments of the present invention, the lignin has a weight average molecular weight M of about 800-10000 g / mol, preferably about 1000-8000 g / mol, more preferably about 2000-5000 g / mol. w For example, in some embodiments, the lignin can have a weight average molecular weight M of about 800 g / mol, about 1000 g / mol, about 1500 g / mol, about 2000 g / mol, about 2500 g / mol, about 3000 g / mol, about 3500 g / mol, about 4000 g / mol, about 4500 g / mol, about 5000 g / mol, about 6000 g / mol, about 6500 g / mol, about 7000 g / mol, about 7500 g / mol, about 8000 g / mol, about 8500 g / mol, about 9000 g / mol, about 9500 g / mol, about 10000 g / mol, or in a range consisting of any two of the foregoing values. w .

[0041] According to some embodiments of the invention, 30% or more, preferably 50% or more, more preferably 70% or more, and 100% or less, preferably 90% or less, more preferably 80% or less of the hydroxyl groups of the lignin are functionalized with acrylic acid, preferably with methacrylic acid.

[0042] According to some embodiments of the present invention, the multifunctional gallic acid ester is at least one selected from gallic acid triacrylate, gallic acid trimethacrylate, allylated gallic acid triacrylate, and allylated gallic acid trimethacrylate.

[0043] According to a preferred embodiment of the present invention, the multifunctional gallic acid ester is a tetrafunctional gallic acid ester, preferably having the following structure:

[0044] According to some embodiments of the present invention, based on the total weight of the lignin-based acrylate prepolymer as 100 wt%, the content of the polymerized structural units derived from the acrylic acid functionalized lignin is 72 wt% to 93 wt%, preferably 80 wt% to 91 wt%, and the content of the groups derived from the multifunctional gallic acid ester is 5 wt% to 20 wt%, preferably 5 wt% to 16 wt%. For example, in some embodiments, based on the total weight of the lignin-based acrylate prepolymer as 100 wt%, the content of polymerized structural units derived from the acrylic acid functionalized lignin can be 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, or within a range consisting of any two of the above values. In some embodiments, based on the total weight of the lignin-based acrylate prepolymer as 100 wt%, the content of the groups derived from the multifunctional gallic acid ester can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, or within a range consisting of any two of the foregoing values.

[0045] According to some embodiments of the present invention, the viscosity of the lignin-based acrylate prepolymer ranges from 5000 to 50000 mPa·s, preferably from 10000 to 45000 mPa·s. For example, in some embodiments, the viscosity of the lignin-based acrylate prepolymer can be 5000 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 15000 mPa·s, 20000 mPa·s, 25000 mPa·s, 30000 mPa·s, 35000 mPa·s, 40000 mPa·s, 45000 mPa·s, 50000 mPa·s, or within a range consisting of any two of the above values.

[0046] According to some embodiments of the present invention, the weight average molecular weight of the lignin-based acrylate prepolymer ranges from 40,000 to 250,000 g / mol. For example, in some embodiments, the weight average molecular weight M of the lignin-based acrylate prepolymer ranges from 40,000 to 250,000 g / mol. w g / mol, 180,000 g / mol, 190,000 g / mol, 200,000 g / mol, 210,000 g / mol, 220,000 g / mol, 230,000 g / mol, 240,000 g / mol, or 250,000 g / mol, or within a range consisting of any two of the above values.

[0047] According to some embodiments of the present invention, the lignin-based acrylate prepolymer is obtained by mixing raw materials including at least one acrylic acid functionalized lignin, at least one multifunctional gallic acid ester having at least three terminal olefin groups, a first initiator and an optional co-initiator under vacuum and then heating the mixture for reaction.

[0048] In a second aspect, the present invention provides a method for preparing a lignin-based acrylate prepolymer, preferably the method for preparing a lignin-based acrylate prepolymer according to the first aspect of the present invention, the method comprising the following steps:

[0049] At least one acrylic acid functionalized lignin, at least one multifunctional gallic acid ester having at least three terminal olefin groups, a first initiator and an optional co-initiator are mixed under vacuum and then heated to react to obtain a lignin-based acrylate prepolymer.

[0050] According to some embodiments of the present invention, the first initiator is a thermal initiator, and the thermal initiator is preferably selected from at least one of peroxide compounds and / or azo compounds, more preferably selected from at least one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azoisobutylcyanamide, azobiscyclohexylcarbonitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl benzoyl peroxide, dicumyl peroxide, dodecyl peroxide, diisopropyl peroxydicarbonate, tert-butyl peroxy-2-ethylhexanoate, and methyl ethyl ketone peroxide, and most preferably selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl benzoyl peroxide, and methyl ethyl ketone peroxide.

[0051] According to some embodiments of the present invention, the co-initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine, and triethanolamine.

[0052] According to some embodiments of the invention, the reaction is carried out under one or more of the following conditions:

[0053] The reaction temperature is 40 to 70°C, for example, the reaction temperature can be 40°C, 50°C, 60°C, 70°C, or within a range consisting of any two of the above values;

[0054] The reaction time is 0.5 h to 3 h, for example, the reaction time can be 0.5 h, 1 h, 2 h, 3 h, or within a range consisting of any two of the above values;

[0055] The vacuum degree is -0.1 MPa to -0.005 MPa, for example, the vacuum degree may be -0.1 MPa, -0.05 MPa, -0.02 MPa, -0.01 MPa, -0.005 MPa, or within a range consisting of any two of the above values.

[0056] According to some embodiments of the present invention, based on the total weight of the raw materials as 100 wt%,

[0057] The amount of the acrylic acid functionalized lignin is 72 wt% to 93 wt%, preferably 80 wt% to 91 wt%, for example, the amount of the acrylic acid functionalized lignin can be 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, or within a range consisting of any two of the above values;

[0058] The amount of the multifunctional gallic acid ester is 5 wt% to 20 wt%, preferably 5 wt% to 16 wt%, for example, the amount of the multifunctional gallic acid ester can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, or within a range consisting of any two of the above values;

[0059] The amount of the first initiator is 1 wt% to 5 wt%, preferably 2 wt% to 4 wt%;

[0060] The amount of the co-initiator is 0.5 wt% to 3 wt%, preferably 1 wt% to 2 wt%.

[0061] In a third aspect, the present invention provides a composite prepolymer comprising a polyurethane acrylate prepolymer, a lignin-based acrylate prepolymer and an optional polymerization inhibitor; wherein the lignin-based acrylate prepolymer is obtained according to the first aspect of the present invention or by the preparation method according to the second aspect of the present invention.

[0062] According to some embodiments of the present invention, the polyurethane acrylate prepolymer is a di- to hexa-functional aliphatic polyurethane acrylate or an aromatic polyurethane acrylate, preferably a difunctional aliphatic polyurethane acrylate.

[0063] According to some embodiments of the present invention, the viscosity of the polyurethane acrylate prepolymer is in the range of 5000 to 40000 mPa·s, preferably 10000 to 30000 mPa·s, for example, 5000 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 15000 mPa·s, 20000 mPa·s, 25000 mPa·s, 30000 mPa·s, 35000 mPa·s, 40000 mPa·s, or in a range consisting of any two of the above values. In some embodiments, the polyurethane acrylate prepolymer used in the present invention is commercially available, for example, at least one of Changxing 6164L and Changxing 615-100 commercially available from Changxing Materials Industry Co., Ltd.

[0064] According to some embodiments of the present invention, the polymerization inhibitor is selected from at least one of hydroquinone, tert-butylcatechol, p-hydroxyanisole, and benzoquinone.

[0065] According to some embodiments of the present invention, based on the total weight of the composite prepolymer as 100 wt%,

[0066] The content of the lignin-based acrylate prepolymer is 20 wt% to 77 wt%, preferably 33 wt% to 66 wt%; for example, the content of the lignin-based acrylate prepolymer can be 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 77 wt%, or within a range consisting of any two of the above values;

[0067] The content of the polyurethane acrylate prepolymer is 20wt% to 77wt%, preferably 33wt% to 66wt%; for example, the content of the polyurethane acrylate prepolymer can be 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 77wt%, or within a range consisting of any two of the above values;

[0068] The content of the polymerization inhibitor is 0wt% to 3wt%, preferably 1wt% to 2wt%;

[0069] The weight ratio of the lignin-based acrylate prepolymer to the polyurethane acrylate prepolymer is 3.85:1 to 1:3.85, preferably 2:1 to 1:2. In some embodiments, the weight ratio of the lignin-based acrylate prepolymer to the polyurethane acrylate prepolymer may be 3.85:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:3.85, or within a range consisting of any two of the foregoing values.

[0070] In a fourth aspect, the present invention provides an adhesive composition comprising a polymerizable monomer, a second initiator, the composite prepolymer according to the third aspect of the present invention, a coupling agent, and an optional auxiliary agent.

[0071] According to some embodiments of the present invention, the content of the components in the adhesive composition is, in parts by weight:

[0072] According to some embodiments of the present invention, the polymerizable monomer comprises at least one of an acrylic monomer and an acrylate monomer.

[0073] The acrylic monomer is selected from at least one of acrylic acid and methacrylic acid; and / or,

[0074] The acrylic acid ester monomer is selected from at least one of methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, butyl acrylate, isooctyl acrylate, hydroxypropyl acrylate, glycidyl acrylate, tripropylene glycol diacrylate, trifluoroethyl methacrylate, methyl cyanoacrylate, ethyl cyanoacrylate, hydroxyethyl cyanoacrylate, and hydroxypropyl cyanoacrylate.

[0075] According to some embodiments of the present invention, the second initiator is a photoinitiator; preferably, the photoinitiator is selected from at least one of benzoin methyl ether, benzoin ethyl ether, benzoin butyl ether, diphenylethanedione, diethylaminodiphenylethanedione, diphenylacetophenone sulfonate, dialkoxyacetophenone (such as dimethoxyacetophenone), α-hydroxyalkyl phenone (such as 2-hydroxy-2-methyl-1-phenyl-1-propanone) and α-amino ketone compounds, benzophenone, and thioxanthone; preferably, the α-amino ketone compound is selected from at least one of 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone.

[0076] According to some embodiments of the present invention, the coupling agent is selected from silane coupling agents; preferably, the silane coupling agent is selected from trialkoxysilane coupling agents; more preferably, the silane coupling agent is selected from at least one of phenyltrimethoxysilane, phenyltriethoxysilane, γ-mercaptopropyltriethoxysilane, methyltriethoxysilane, and γ-aminopropyltriethoxysilane.

[0077] According to some embodiments of the present invention, the auxiliary agent is selected from at least one of a co-initiator, a stabilizer, and an inhibitor.

[0078] According to some embodiments of the present invention, the co-initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine, and triethanolamine.

[0079] According to some embodiments of the present invention, the stabilizer is selected from at least one of borate esters and organic acids; preferably, the stabilizer is selected from at least one of trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-o-cresyl borate, tri-m-benzyl borate, barbituric acid, salicylic acid, lauric acid, fumaric acid, and benzoic acid.

[0080] According to some embodiments of the present invention, the polymerization inhibitor is selected from at least one of hydroquinone, tert-butylcatechol, p-hydroxyanisole, and benzoquinone.

[0081] In a fifth aspect, the present invention provides a method for preparing an adhesive composition, preferably a method for preparing an adhesive composition according to the fourth aspect of the present invention, the method comprising the following steps:

[0082] a) mixing a polyurethane acrylate prepolymer, a lignin-based acrylate prepolymer, and an optional polymerization inhibitor in the dark to obtain a composite prepolymer;

[0083] b) mixing the polymerizable monomer, the second initiator, the composite prepolymer, the coupling agent and the optional auxiliary agent under vacuum and in the dark to obtain the adhesive composition.

[0084] According to the present invention, "light-proof" refers to conditions that avoid strong light, particularly ultraviolet light (UV light), to prevent premature initiation of the reaction and the impact on the performance of the adhesive composition. The light-proof method is not particularly limited and can be any conventional method in the art, as long as it can achieve the purpose of the present invention. For example, light-proof containers can be used, and operations can be performed in a dark room.

[0085] According to some embodiments of the present invention, in step b), the polymerizable monomer, composite prepolymer, coupling agent and optional auxiliary agent are first added and mixed uniformly, and then the second initiator is added and mixed under vacuum stirring conditions in the dark.

[0086] According to some embodiments of the invention, the method is performed under one or more of the following conditions:

[0087] The vacuum degree is -0.1 MPa to -0.005 MPa, for example, the vacuum degree can be -0.1 MPa, -0.05 MPa, -0.02 MPa, -0.01 MPa, -0.005 MPa, or within a range consisting of any two of the above values;

[0088] The mixing time is 1 to 2 hours, for example, the mixing time can be 1 hour, 1.5 hours, 2 hours, or within a range consisting of any two of the above values;

[0089] The stirring speed of the mixing is 300-600 rpm, for example, the stirring speed can be 300 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, or within a range consisting of any two of the above values.

[0090] In a sixth aspect, the present invention provides use of the adhesive composition according to the fourth aspect of the present invention in bonding optoelectronic devices, building materials, and medical materials.

[0091] In a seventh aspect, the present invention provides a method for bonding using the adhesive composition according to the fourth aspect of the present invention, comprising curing the adhesive composition under ultraviolet light. The curing is preferably performed under conditions of 365 nm, 100 mW / cm2 LED light source for 15-20 seconds.

[0092] Compared with the prior art, the present invention has at least the following advantages:

[0093] This invention leverages the ease of use, strong bonding, and excellent chemical resistance of a single-component acrylate-based curing adhesive system. It further incorporates a biomass-based lignin-based acrylate prepolymer into the system. This lignin-based prepolymer exhibits an interpenetrating network structure, enhancing the adhesive's wetting and chemical bonding. After curing, the adhesive exhibits high bond strength, minimal volume shrinkage, and excellent weather resistance. This approach effectively utilizes lignin, reduces production costs, and adheres to environmentally friendly principles, promising promising industrial applications.

[0094] The strength and bonding performance of the adhesive system obtained by the present invention meet the requirements for bonding optoelectronic devices, building materials, and medical materials. In addition, the addition of a degradable and biocompatible lignin-based acrylate prepolymer makes it particularly suitable for use in bonding medical materials.

[0095] This application also provides the following implementation scheme:

[0096] 1. A lignin-based acrylate prepolymer, characterized in that:

[0097] The lignin-based acrylate prepolymer is prepared from raw materials including methacrylated lignin and a gallic acid-based cross-linking agent;

[0098] The methacrylated lignin contains the following structural fragments:

[0099] The gallic acid-based cross-linking agent has the following structure:

[0100] 2. A method for preparing a lignin-based acrylate prepolymer, characterized in that:

[0101] The lignin-based acrylate prepolymer is prepared by mixing raw materials including methacrylated lignin and a gallic acid-based crosslinking agent under the action of an initiator and a co-initiator under vacuum and then heating for reaction;

[0102] The lignin-based acrylate prepolymer described in Scheme 1 is preferably prepared.

[0103] 3. The method for preparing the lignin-based acrylate prepolymer according to Scheme 2, characterized in that:

[0104] The initiator is selected from thermal initiators, preferably at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl benzoyl peroxide, and methyl ethyl ketone peroxide; and / or,

[0105] The co-initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine, and triethanolamine; and / or,

[0106] The temperature of the vacuum heating reaction is 40-70°C; and / or,

[0107] The vacuum heating reaction time is 0.5h to 3h; and / or,

[0108] The vacuum degree of the vacuum heating reaction is -0.1MPa to -0.01MPa; and / or,

[0109] Taking the total weight of raw materials as 100%,

[0110] The amount of methacrylated lignin added is 72 wt% to 93 wt%;

[0111] The amount of gallic acid-based cross-linking agent added is 5wt% to 20wt%;

[0112] The amount of initiator added is 1 wt% to 5 wt%;

[0113] The amount of the co-initiator added is 0.5wt% to 3wt%;

[0114] Preferably,

[0115] The amount of methacrylated lignin added is 80 wt% to 91 wt%;

[0116] The amount of gallic acid-based cross-linking agent added is 5wt% to 16wt%;

[0117] The amount of initiator added is 2 wt% to 4 wt%;

[0118] The amount of the co-initiator added is 1 wt% to 2 wt%.

[0119] 4. A composite prepolymer, characterized in that it is a mixture of raw materials including polyurethane acrylate, lignin-based acrylate prepolymer, and an inhibitor; the lignin-based acrylate prepolymer is obtained as described in claim 1 or as described in scheme 2 or 3.

[0120] 5. The composite prepolymer according to claim 4, characterized in that:

[0121] The viscosity of the polyurethane acrylate is in the range of 5000 to 30000 cps; and / or,

[0122] The polymerization inhibitor is selected from at least one of hydroquinone, tert-butylcatechol, p-hydroxyanisole, and benzoquinone; and / or

[0123] Taking the total weight of raw materials as 100%,

[0124] The amount of lignin-based acrylate added is 20 wt% to 77 wt%;

[0125] The amount of polyurethane acrylate added is 20wt% to 77wt%;

[0126] The amount of polymerization inhibitor added is 1 wt% to 3 wt%;

[0127] Preferably,

[0128] The amount of lignin-based acrylate added is 33 wt% to 66 wt%;

[0129] The amount of polyurethane acrylate added is 33wt% to 66wt%;

[0130] The addition amount of the polymerization inhibitor is 1 wt% to 2 wt%.

[0131] 6. A method for preparing the composite prepolymer described in any one of options 4-5 is characterized in that the composite prepolymer is prepared by uniformly mixing the raw materials including the polyurethane acrylate, lignin-based acrylate prepolymer, and inhibitor in the dark.

[0132] 7. A UV adhesive containing a lignin-based acrylate prepolymer, characterized in that:

[0133] The UV adhesive containing the lignin-based acrylate prepolymer comprises a monomer, a photoinitiator, the composite prepolymer described in any one of Schemes 4-5, a coupling agent, and an auxiliary agent;

[0134] The monomer is selected from at least one of acrylic monomers and acrylate monomers.

[0135] 8. The UV adhesive containing lignin-based acrylate prepolymer according to claim 7, characterized in that:

[0136] In the UV adhesive, in parts by weight:

[0137] 9. The UV adhesive containing lignin-based acrylate prepolymer according to claim 7, characterized in that:

[0138] The acrylic monomer is selected from at least one of acrylic acid and methacrylic acid; and / or,

[0139] The acrylic acid ester monomer is selected from at least one of methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, butyl acrylate, isooctyl acrylate, hydroxypropyl acrylate, glycidyl acrylate, tripropylene glycol diacrylate, trifluoroethyl methacrylate, methyl cyanoacrylate, ethyl cyanoacrylate, hydroxyethyl cyanoacrylate, and hydroxypropyl cyanoacrylate.

[0140] 10. The UV adhesive containing lignin-based acrylate prepolymer according to claim 7, characterized in that:

[0141] The photoinitiator is selected from at least one of benzoin methyl ether, benzoin ethyl ether, benzoin butyl ether, diphenylethanedione, diethylaminodiphenylethanedione, diphenylacetophenone sulfonate, dialkoxyacetophenone, α-hydroxyalkyl phenone, α-amino ketone compounds, benzophenone, and thioxanthone; preferably, the α-amino ketone compound is selected from at least one of 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone; and / or,

[0142] The coupling agent is selected from silane coupling agents; preferably, the coupling agent is selected from trialkoxysilane coupling agents; further preferably, the coupling agent is selected from at least one of phenyltrimethoxysilane, phenyltriethoxysilane, γ-mercaptopropyltriethoxysilane, methyltriethoxysilane, and γ-aminopropyltriethoxysilane.

[0143] 11. The UV adhesive containing lignin-based acrylate prepolymer according to claim 7, characterized in that:

[0144] The auxiliary agent is selected from at least one of an initiator, a stabilizer, and an inhibitor; preferably,

[0145] The co-initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine, and triethanolamine; and / or,

[0146] The stabilizer is selected from at least one of borate esters and organic acids; and / or,

[0147] The polymerization inhibitor is selected from at least one of hydroquinone, tert-butylcatechol, p-hydroxyanisole, and benzoquinone;

[0148] More preferably, the stabilizer is selected from at least one of trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-o-cresyl borate, tri-m-benzyl borate, barbituric acid, salicylic acid, lauric acid, fumaric acid, and benzoic acid.

[0149] 12. A method for preparing a UV adhesive containing a lignin-based acrylate prepolymer according to any one of claims 7 to 11, comprising the following steps:

[0150] Raw materials including monomers, photoinitiators, composite prepolymers, coupling agents and additives are reacted in a vacuum and in the dark to prepare a UV adhesive containing lignin-based acrylate prepolymers.

[0151] 13. The method for preparing a UV adhesive containing a lignin-based acrylate prepolymer according to claim 12, wherein:

[0152] First, raw materials including monomers, composite prepolymers, coupling agents, stabilizers, and polymerization inhibitors are added and mixed, and then photoinitiators and co-initiators are added and reacted in the dark under vacuum stirring conditions;

[0153] Preferably,

[0154] The vacuum degree of the light-proof reaction is -0.01MPa to -0.1MPa;

[0155] The reaction time in the dark is 1 to 2 hours;

[0156] The stirring speed is 400-600 rpm.

[0157] 14. Use of the UV adhesive containing lignin-based acrylate prepolymer described in any one of solutions 7 to 11 in bonding optoelectronic devices, building materials, and medical materials.

[0158] In order to facilitate the understanding of the present invention, the present invention provides the following embodiments, but the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0159] Example

[0160] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0161] The present invention is described in detail below through examples. Unless otherwise specified, all methods used are conventional methods. All reagents used are commercially available and analytically pure unless otherwise specified. Room temperature refers to approximately 25°C. All acrylate monomers and their synthesis reagents were purchased from Inotech. Kraft lignin was purchased from Aladdin.

[0162] The polyurethane acrylate prepolymers used were commercial polyurethane acrylates Changxing 6164L and Changxing 615-100, wherein Changxing 615-100 was purchased from Changxing Chemical Industry Co., Ltd. and had a viscosity of 10,000 to 20,000 mPa·s (25°C); Changxing 6164L was purchased from Changxing Chemical Industry Co., Ltd. and had a viscosity of 15,000 to 23,000 mPa·s (25°C).

[0163] Characterization methods:

[0164] Molecular weight: A Waters 1515 gel chromatography instrument (Waters, USA) was used at 60°C, with polymethyl methacrylate as the standard for calibration and N,N-dimethylformamide as the eluent.

[0165] Viscosity: measured using a Brookfield-RVT dial-type rotational viscometer at 25°C and 20 rpm.

[0166] Nuclear Magnetic Resonance ( 1 H NMR) test: The samples were tested using a Bruker Avance 500 MHz nuclear magnetic resonance spectrometer from Bruker, Germany, and the samples were dissolved in Acetone-d6 or DMSO-d6.

[0167] Infrared test: The sample was tested using the German Bruker INVENIO Fourier transform infrared spectrometer with a scanning range of 500 to 4000 cm -1 , resolution 4cm -1 , scan times 32 times.

[0168] Methacrylated lignin and its preparation method can be found in the paper "Ultraviolet Curable Coatings of Modified Lignin" by Soheil Hajirahimkhan, et al., ACS Sustainable Chem. Eng. 2018, 6, 14685-14694, the entire contents of which are hereby incorporated by reference into the present invention. Allylated gallic acid trimethacrylate and its preparation method can be found in the paper "Bio-based tetrafunctional crosslink agent from gallic acid and its enhanced soybean oil-based UV-cured coatings with high performance" by Songqi Ma, et al., RSC Adv. 2014, 4, 23036-23042, the entire contents of which are hereby incorporated by reference into the present invention.

[0169] In the embodiment of the present invention, the acrylic acid functionalized lignin used is prepared in the following manner:

[0170] Preparation of methacrylated lignin: Dry kraft lignin (2 g, M w ≈5000g / mol) was added to a round-bottom flask containing 20mL of tetrahydrofuran (THF) and stirred for 5 minutes (800rpm), followed by the addition of 0.2mg of 1-methylimidazole (1MIM) and 1.68g of methacrylic anhydride. The mixture was stirred at 60°C for 60 minutes under a nitrogen atmosphere. The obtained brown mixture was then added dropwise to n-hexane (150mL), stirred, precipitated and filtered to obtain a light brown powder. The obtained powder was then dissolved in dichloromethane (20mL) and washed three times with deionized water to remove the catalyst and unreacted raw materials. The organic phase was then precipitated in n-hexane (150mL), and the obtained powder was vacuum dried to obtain methacrylated lignin. The reaction formula is shown below:

[0171] Kraft lignin (A) and methacrylated lignin (B) 1 The H NMR spectrum is shown in Figure 1, and the FT-IR spectrum is shown in Figure 2.

[0172] In the embodiment of the present invention, the multifunctional gallic acid ester used is prepared in the following manner:

[0173] Preparation of allylated gallic acid trimethacrylate: 10.2 g of gallic acid, 14.52 g of allyl bromide, 200 g of acetone, and 36.48 g of potassium carbonate were added to a three-necked flask and vigorously stirred at room temperature (800 rpm) for 10 minutes. The mixture was then heated to 60°C and refluxed for 2 hours. After cooling to room temperature, 17.92 g of acryloyl chloride was added dropwise over 30 minutes. The mixture was heated to 40°C and reacted for 12 hours. The unreacted raw materials and acetone were then removed by rotary evaporation to obtain allylated gallic acid triacrylate. The reaction formula is shown below:

[0174] Gallic acid (C) and allylated gallic acid triacrylate (D) 1 The H NMR spectrum is shown in Figure 3, and the FT-IR spectrum is shown in Figure 4.

[0175] Preparation Example 1

[0176] Preparation of lignin-based acrylate prepolymer:

[0177] 90 parts of methacrylated lignin and 6 parts of allylated gallic acid triacrylate were added to a reactor and mixed, and then 3 parts of azobisisobutyronitrile and 1 part of triethanolamine were added. The mixture was stirred at a vacuum degree of -0.01 MPa at a speed of 500 rpm. After stirring for 1 hour until uniform, it was slowly heated to 60°C and stirred at a constant temperature for 2 hours to obtain a viscous liquid discharge.

[0178] The viscosity of the lignin-based acrylate prepolymer obtained in Preparation Example 1 is 42800 mPa·s, and the weight average molecular weight M w The FT-IR spectrum is shown in Figure 5.

[0179] Preparation of composite prepolymer 1:

[0180] 66 parts of the prepared lignin-based acrylate prepolymer and 33 parts of Changxing 6164L were uniformly mixed, 1 part of hydroquinone was added, and the mixture was stirred in the dark for 1 hour to obtain a composite prepolymer 1.

[0181] Preparation Example 2

[0182] Preparation of lignin-based acrylate prepolymer:

[0183] 90 parts of methacrylated lignin and 6 parts of allylated gallic acid triacrylate were added to a reactor and mixed. Then, 3 parts of azobisisoheptanenitrile and 1 part of triethanolamine were added. The mixture was stirred at a speed of 400 rpm under a vacuum of -0.02 MPa for 2 hours until uniform. The mixture was then slowly heated to 55°C and stirred at a constant temperature for 3 hours to obtain a viscous liquid discharge.

[0184] The viscosity of the lignin-based acrylate prepolymer obtained in Preparation Example 2 is 40500 mPa·s, and the weight average molecular weight M w It is 204837g / mol.

[0185] Preparation of composite prepolymer 2:

[0186] 49 parts of the prepared lignin-based acrylate prepolymer and 49 parts of Changxing 6164L were uniformly mixed, 2 parts of tert-butyl catechol were added, and the mixture was stirred in the dark for 2 hours to obtain a composite prepolymer 2.

[0187] Preparation Example 3

[0188] Preparation of lignin-based acrylate prepolymer:

[0189] 90 parts of methacrylated lignin and 6 parts of allylated gallic acid triacrylate were added to a reactor and mixed, and then 2 parts of benzoyl peroxide and 2 parts of triethanolamine were added. The mixture was stirred at a vacuum degree of -0.01 MPa at a speed of 500 rpm. After stirring for 1 hour until uniform, it was slowly heated to 60°C and stirred at a constant temperature for 2 hours to obtain a viscous liquid discharge.

[0190] The viscosity of the lignin-based acrylate prepolymer obtained in Preparation Example 3 is 41500 mPa·s, and the weight average molecular weight M w It is 212347g / mol.

[0191] Preparation of composite prepolymer 3:

[0192] 39 parts of the prepared lignin-based acrylate prepolymer and 59 parts of Changxing 615-100 were uniformly mixed, 2 parts of p-hydroxyanisole were added, and the mixture was stirred in the dark for 1 hour to obtain a composite prepolymer 3.

[0193] Preparation Example 4

[0194] Preparation of lignin-based acrylate prepolymer:

[0195] 90 parts of methacrylated lignin and 6 parts of allylated gallic acid triacrylate were added to a reactor and mixed, and then 2 parts of methyl ethyl ketone peroxide and 2 parts of triethanolamine were added. The mixture was stirred at a speed of 400 rpm under a vacuum degree of -0.02 MPa for 2 hours until uniform, and then slowly heated to 60°C and stirred at a constant temperature for 2 hours to obtain a viscous liquid discharge.

[0196] The viscosity of the lignin-based acrylate prepolymer obtained in Preparation Example 4 is 41700 mPa·s, and the weight average molecular weight M w It is 216539g / mol.

[0197] Preparation of composite prepolymer 4:

[0198] 33 parts of the prepared lignin-based acrylate prepolymer and 66 parts of Changxing 615-100 were uniformly mixed, 2 parts of benzoquinone were added, and the mixture was stirred in the dark for 2 hours to obtain composite prepolymer 4.

[0199] Preparation Example 5

[0200] The formulation of Preparation Example 1 was used, except that the amount of methacrylated lignin used in the formulation was 80 parts, and the amount of allylated gallic acid triacrylate used in the formulation was 16 parts; a composite prepolymer 5 was obtained using the same preparation method.

[0201] Preparation Example 6

[0202] The formulation of Preparation Example 1 was used, except that the amount of methacrylated lignin used in the formulation was 86 parts, and the amount of allylated gallic acid triacrylate used in the formulation was 10 parts; a composite prepolymer 6 was obtained using the same preparation method.

[0203] Preparation Example 7

[0204] The formulation of Preparation Example 1 was used, except that the amount of methacrylated lignin used in the formulation was 91 parts and the amount of allylated gallic acid triacrylate used in the formulation was 5 parts; composite prepolymer 7 was obtained using the same preparation method.

[0205] Example 1

[0206] 100 parts of acrylic acid (ester) functional monomers (containing 50 parts of methyl methacrylate MMA, 10 parts of methacrylate MAA, 17 parts of butyl acrylate BA, 15 parts of hydroxyethyl methacrylate HEMA, and 8 parts of trifluoroethyl methacrylate TFEMA), 22 parts of composite prepolymer 1, 5 parts of phenyltrimethoxysilane, 2 parts of trimethyl borate, and 2 parts of tert-butylcatechol were added to a reactor and mixed at a speed of 300 rpm for 30 minutes. Then, 4 parts of benzoin methyl ether and 3 parts of isooctyl p-dimethylaminobenzoate were added. The vacuum degree was maintained at -0.02 MPa, the speed was 400 rpm, and mechanical stirring was carried out at room temperature in the dark for 1 hour to obtain the adhesive sample of Example 1.

[0207] Example 2

[0208] 100 parts of acrylic acid (ester) functional monomers (containing 50 parts of ethyl methacrylate EMA, 8 parts of acrylic acid AA, 17 parts of isooctyl acrylate 2-EHA, 15 parts of hydroxypropyl methacrylate HPMA, and 10 parts of methyl cyanoacrylate MCA), 24 parts of composite prepolymer 2, 1 part of propyltriethoxysilane, 3 parts of triethyl borate, and 2 parts of hydroquinone were mixed in a reactor at a speed of 300 rpm for 30 minutes, and then 4 parts of benzoin ethyl ether and 3 parts of diethanolamine were added. The vacuum degree was maintained at -0.03 MPa, the speed was 500 rpm, and mechanical stirring was carried out at room temperature in the dark for 1 hour to obtain the adhesive sample of Example 2.

[0209] Example 3

[0210] 100 parts of acrylic acid (ester) functional monomers (containing 54 parts of butyl methacrylate BMA, 8 parts of methacrylate MAA, 18 parts of glycidyl acrylate GA, 15 parts of hydroxypropyl acrylate HPA, and 5 parts of tripropylene glycol diacrylate TPGDA), 19 parts of composite prepolymer 3, 4 parts of γ-mercaptopropyltriethoxysilane, 2 parts of tri-n-propyl borate, and 2 parts of p-hydroxyanisole were mixed in a reactor at a speed of 300 rpm for 30 minutes, and then 4 parts of benzoin butyl ether and 3 parts of diethanolamine were added. The vacuum degree was maintained at -0.02 MPa, the speed was 600 rpm, and mechanical stirring was carried out at room temperature in the dark for 1 hour to obtain the adhesive sample of Example 3.

[0211] Example 4

[0212] 100 parts of acrylic acid (ester) functional monomers (including 47 parts of ethyl methacrylate EMA, 16 parts of acrylic acid AA, 18 parts of butyl acrylate BA, 10 parts of hydroxypropyl acrylate HPA, and 9 parts of tripropylene glycol diacrylate TPGDA), 25 parts of composite prepolymer 4, 3 parts of methyltriethoxysilane, 1 part of triisopropyl borate, and 2 parts of benzoquinone were mixed in a reactor at a speed of 300 rpm for 30 minutes, and then 4 parts of diphenylethanedione and 3 parts of triethanolamine were added. The vacuum degree was maintained at -0.02 MPa, the speed was 400 rpm, and mechanical stirring was carried out at room temperature in the dark for 2 hours to obtain the adhesive sample of Example 4.

[0213] Example 5

[0214] 100 parts of acrylic acid (ester) functional monomers (including 47 parts of methyl methacrylate MMA, 10 parts of methacrylate MAA, 19 parts of isooctyl acrylate 2-EHA, 14 parts of hydroxypropyl methacrylate HPMA, and 10 parts of ethyl cyanoacrylate ECA), 15 parts of composite prepolymer 1, 2 parts of γ-aminopropyltriethoxysilane, 2 parts of barbituric acid, and 1 part of tert-butylcatechol were mixed in a reactor at a speed of 300 rpm for 30 minutes, and then 3 parts of dimethoxyacetophenone and 2 parts of isooctyl p-dimethylaminobenzoate were added. The vacuum degree was maintained at -0.01 MPa, the speed was 500 rpm, and mechanical stirring was carried out at room temperature in the dark for 2 hours to obtain the adhesive sample of Example 5.

[0215] Example 6

[0216] 100 parts of acrylic acid (ester) functional monomers (containing 59 parts of butyl methacrylate BMA, 8 parts of acrylic acid AA, 15 parts of glycidyl acrylate GA, 8 parts of hydroxyethyl methacrylate HEMA, and 10 parts of trifluoroethyl methacrylate TFEMA), 40 parts of composite prepolymer 2, 3 parts of phenyltrimethoxysilane, 1 part of lauric acid, and 1 part of hydroquinone were mixed in a reactor at a speed of 300 rpm for 30 minutes, and then 3 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone and 2 parts of isooctyl p-dimethylaminobenzoate were added. The vacuum degree was maintained at -0.03 MPa, the speed was 600 rpm, and mechanical stirring was carried out at room temperature in the dark for 2 hours to obtain the adhesive sample of Example 6.

[0217] Example 7

[0218] A scheme substantially the same as that of Example 4 was adopted, except that composite prepolymer 5 was used in place of composite prepolymer 4 in the formulation, and the mixture was mixed uniformly in the same preparation manner to obtain the adhesive sample of Example 7.

[0219] Example 8

[0220] A scheme substantially the same as that of Example 4 was adopted, except that composite prepolymer 6 was used in place of composite prepolymer 4 in the formulation, and the same preparation method was used to mix until uniform, to obtain the adhesive sample of Example 8.

[0221] Example 9

[0222] A scheme substantially the same as that of Example 4 was adopted, except that composite prepolymer 7 was used in place of composite prepolymer 4 in the formulation, and the mixture was mixed uniformly in the same preparation manner to obtain the adhesive sample of Example 9.

[0223] Comparative Example 1

[0224] A scheme substantially the same as that of Example 1 was adopted, except that the prepolymers used in the formula were replaced with polyurethane acrylate prepolymers (Changxing 6164L), and the mixture was mixed uniformly in the same preparation manner to obtain the adhesive sample of Comparative Example 1.

[0225] Comparative Example 2

[0226] A scheme substantially the same as that of Example 1 was adopted, except that the prepolymers used in the formula were replaced with lignin-based acrylate prepolymers, and the mixture was mixed until uniform using the same preparation method to obtain the adhesive sample of Comparative Example 2.

[0227] Comparative Example 3

[0228] A scheme substantially the same as that of Example 1 was adopted, except that no coupling agent was added to the formula. The same preparation method was used and mixed until uniform, to obtain an adhesive sample of Comparative Example 3.

[0229] Comparative Example 4

[0230] A scheme basically the same as Example 1 was adopted, except that the crosslinking agent used in the preparation of the lignin-based acrylate prepolymer in the formula was tetra(ethylene glycol) diacrylate (TEGDA, structure as follows). The same preparation method was used to mix until uniform, to obtain the adhesive sample of Comparative Example 4.

[0231] Performance testing:

[0232] The adhesive samples of the embodiments and comparative examples were tested as follows:

[0233] (1) Viscosity: measured using a Brookfield-RVT dial-type rotational viscometer at 25°C and 20 rpm.

[0234] (2) Tensile bond strength: tested according to ASTM D1623.

[0235] (3) Linear curing shrinkage: The test is conducted according to the ISO 2577 method. The change in length of a fixed length of film before and after curing is measured. The shrinkage is obtained by dividing the reduced value by the original value.

[0236] (4) Adhesion: Tested according to the GB / T 9286-1998 method. The results are divided into 0-5 levels, with 0 being the best and 5 being the worst.

[0237] (5) Flexibility: Tested in accordance with GB / T 1731-1993 “Determination of paint film flexibility”.

[0238] (6) Chemical resistance: Prepare a film with a dry film thickness of 60 μm, place it in an oven at 100°C for 1 day, and then soak it in a 50% ethanol solution for 12 hours. Observe whether the film becomes white, soft, or sticky. If the film remains unchanged, it passes the chemical resistance test. If it becomes white, soft, or sticky, it fails the chemical resistance test.

[0239] The above tests were repeated three times and the average value was taken.

[0240] The performance parameter measurement results of each embodiment and comparative example are shown in Table 1 below.

[0241] Table 1

[0242] Comparing Comparative Example 1 with Example 1 reveals that the composite prepolymer containing the lignin-based acrylate prepolymer exhibits greater tensile bond strength and lower linear cure shrinkage. This is primarily due to the formation of a cross-linked interpenetrating network structure after the multifunctional methacrylated lignin reacts with the gallic acid-based crosslinker. This significantly increases the density of the bonding system and strengthens the molecular cohesion, resulting in higher bond strength, lower shrinkage, better stability, and enhanced adhesion.

[0243] Comparisons of Comparative Examples 1 and 2 with Example 1 show that the adhesive system prepared by mixing a polyurethane acrylate prepolymer and a lignin-based acrylate prepolymer in a certain proportion to obtain a composite prepolymer achieves a comprehensive performance balance of high bonding strength, low shrinkage, good adhesion, flexibility, and chemical resistance compared to adhesive systems prepared using either a single polyurethane acrylate prepolymer or a lignin-based acrylate prepolymer. Comparisons of Comparative Example 3 with Example 1 show that the addition of a coupling agent can further improve the bonding effect of the adhesive system. Comparisons of Comparative Example 4 with Example 1 show that when the prepolymer obtained using a multifunctional gallate crosslinker according to the present invention is used in an adhesive system, the performance in terms of bonding strength, cure shrinkage, and adhesion is improved relative to an adhesive system based on a prepolymer obtained using a TEGDA crosslinker. The adhesive system according to the present invention not only achieves efficient utilization of lignin, a biomass resource, and reduces costs, but also improves the performance of bio-based acrylate adhesive systems, promoting green, environmentally friendly, and sustainable development in the field of adhesive applications.

[0244] The preferred embodiments of the present application are described in detail above. However, the present application is not limited to the specific details of the above embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the scope of protection of the present application.

[0245] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this application will not further describe various possible combinations.

[0246] In addition, the various implementation methods of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A lignin-based acrylate prepolymer comprising a cross-linked backbone and a linking group connecting the cross-linked backbone, wherein the cross-linked backbone comprises a polymerized structural unit derived from at least one acrylic acid functionalized lignin, and the linking group is derived from at least one multifunctional gallic acid ester having at least three terminal olefinic groups; The acrylic acid functionalized lignin contains the following structural fragments: Where R 1 and R 2 Each independently represents H or C1-2 alkyl; R 3 and R 4 Each independently represents H, -OCH3 or a linker connected to other structural fragments of the acrylic acid functionalized lignin.

2. The lignin-based acrylate prepolymer according to claim 1, wherein the multifunctional gallic acid ester is selected from at least one of gallic acid triacrylate, gallic acid trimethacrylate, allylated gallic acid triacrylate, and allylated gallic acid trimethacrylate; preferably, the multifunctional gallic acid ester is a tetrafunctional gallic acid ester, preferably having the following structure: and / or The lignin is selected from at least one of alkali lignin, lignin sulfonate, sulfate lignin, sulfonated alkali lignin and ammonium alkali lignin.

3. The lignin-based acrylate prepolymer according to claim 1 or 2, Wherein, taking the total weight of the lignin-based acrylate prepolymer as 100 wt%, The content of the structural units derived from the acrylic acid functionalized lignin is 72 wt% to 93 wt%, preferably 80 wt% to 91 wt%, The content of the groups derived from the multifunctional gallic acid ester is 5wt% to 20wt%, preferably 5wt% to 16wt%; and / or The viscosity of the lignin-based acrylate prepolymer is in the range of 5000 to 50000 mPa·s, preferably 10000 to 45000 mPa·s; and / or The weight average molecular weight of the lignin-based acrylate prepolymer is in the range of 40,000 to 250,000 g / mol.

4. A method for preparing a lignin-based acrylate prepolymer, preferably a method for preparing a lignin-based acrylate prepolymer according to any one of claims 1 to 3, comprising the following steps: The raw materials including at least one acrylic acid functionalized lignin, at least one multifunctional gallic acid ester having at least three terminal olefin groups, a first initiator and an optional co-initiator are mixed under vacuum and then heated to react to obtain the lignin-based acrylate prepolymer. The acrylic acid functionalized lignin contains the following structural fragments: Where R 1 and R 2 Each independently represents H or C1-2 alkyl; R 3 and R 4 Each independently represents H, -OCH3 or a linker connected to other structural fragments of the acrylic acid functionalized lignin.

5. The preparation method according to claim 4, characterized in that: The multifunctional gallic acid ester is selected from at least one of gallic acid triacrylate, gallic acid trimethacrylate, allylated gallic acid triacrylate, and allylated gallic acid trimethacrylate; preferably, the multifunctional gallic acid ester is a tetrafunctional gallic acid ester, preferably having the following structure: and / or The first initiator is a thermal initiator, which is preferably selected from at least one of peroxide compounds and / or azo compounds, and more preferably selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl benzoyl peroxide, and methyl ethyl ketone peroxide; and / or, The auxiliary initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine and triethanolamine; and / or, Taking the total weight of the raw materials as 100wt%, The amount of the acrylic acid functionalized lignin is 72wt% to 93wt%, preferably 80wt% to 91wt%; The amount of the multifunctional gallic acid ester is 5wt% to 20wt%, preferably 5wt% to 16wt%; The first initiator is used in an amount of 1 wt% to 5 wt%, preferably 2 wt% to 4 wt%; The amount of the co-initiator is 0.5 wt% to 3 wt%, preferably 1 wt% to 2 wt%, and / or The reaction is carried out under one or more of the following conditions: The reaction temperature is 40-70°C; The reaction time is 0.5h~3h; The vacuum degree is -0.1MPa~-0.005MPa.

6. A composite prepolymer, characterized in that The invention comprises a polyurethane acrylate prepolymer, a lignin-based acrylate prepolymer and an optional polymerization inhibitor; wherein the lignin-based acrylate prepolymer is obtained according to any one of claims 1 to 3 or by the preparation method according to claim 4 or 5.

7. The composite prepolymer according to claim 6, characterized in that The viscosity of the polyurethane acrylate prepolymer is in the range of 5000 to 40000 mPa·s, preferably 10000 to 30000 mPa·s, and the viscosity of the lignin-based acrylate prepolymer is in the range of 5000 to 50000 mPa·s, preferably 10000 to 45000 mPa·s; and / or, The inhibitor is selected from hydroquinone, tert-butyl catechol, p-hydroxyanisole, benzoquinone At least one of; and / or, Taking the total weight of the composite prepolymer as 100wt%, The content of the lignin-based acrylate prepolymer is 20wt% to 77wt%, preferably 33wt% to 66wt%; The content of the polyurethane acrylate prepolymer is 20wt% to 77wt%, preferably 33wt% to 66wt%; The content of the polymerization inhibitor is 0wt% to 3wt%, preferably 1wt% to 2wt%; and / or, The weight ratio of the lignin-based acrylate prepolymer to the polyurethane acrylate prepolymer is 3.85:1 to 1:3.85, preferably 2:1 to 1:

2.

8. An adhesive composition, characterized in that: The adhesive composition comprises a polymerizable monomer, a second initiator, the composite prepolymer according to any one of claims 6 to 7, a coupling agent and an optional auxiliary agent.

9. The adhesive composition according to claim 8, characterized in that: The content of components in the adhesive composition is, in parts by weight:

10. The adhesive composition according to claim 8 or 9, characterized in that: The polymerizable monomer comprises at least one of an acrylic monomer and an acrylic ester monomer; preferably, the acrylic monomer is selected from at least one of acrylic acid and methacrylic acid, and / or the acrylic ester monomer is selected from at least one of methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, butyl acrylate, isooctyl acrylate, hydroxypropyl acrylate, glycidyl acrylate, tripropylene glycol diacrylate, trifluoroethyl methacrylate, methyl cyanoacrylate, ethyl cyanoacrylate, hydroxyethyl cyanoacrylate and hydroxypropyl cyanoacrylate; and / or, The second initiator is a photoinitiator; preferably, the photoinitiator is selected from at least one of benzoin methyl ether, benzoin ethyl ether, benzoin butyl ether, diphenyl ethanedione, diethylamino diphenyl ethanedione, diphenyl acetophenone sulfonate, dialkoxy acetophenone, α-hydroxyalkyl phenone, α-amino ketone compounds, benzophenone, and thioxanthone; preferably, the α-amino ketone compounds The compound is selected from at least one of 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone; and / or, The coupling agent is selected from silane coupling agents; preferably, the silane coupling agent is selected from trialkoxysilane coupling agents; more preferably, the silane coupling agent is selected from at least one of phenyltrimethoxysilane, phenyltriethoxysilane, γ-mercaptopropyltriethoxysilane, methyltriethoxysilane, and γ-aminopropyltriethoxysilane.

11. The adhesive composition according to any one of claims 8 to 10, characterized in that: The auxiliary agent is selected from at least one of an initiator, a stabilizer, and an inhibitor; Preferably, The auxiliary initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine and triethanolamine; and / or, The stabilizer is selected from at least one of boric acid esters and organic acids, preferably selected from at least one of trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-o-cresyl borate, tri-m-benzyl borate, barbituric acid, salicylic acid, lauric acid, fumaric acid and benzoic acid; and / or, The polymerization inhibitor is selected from at least one of hydroquinone, tert-butylcatechol, p-hydroxyanisole and benzoquinone.

12. A method for preparing the adhesive composition according to any one of claims 8 to 11, characterized in that: The following steps are involved: a) mixing a polyurethane acrylate prepolymer, a lignin-based acrylate prepolymer, and an optional polymerization inhibitor under light protection to obtain a composite prepolymer; b) mixing the polymerizable monomer, the second initiator, the composite prepolymer, the coupling agent and the optional auxiliary agent under vacuum and in the dark to obtain the adhesive composition.

13. The preparation method according to claim 12, characterized in that: The method is carried out under one or more of the following conditions: Vacuum degree: -0.1MPa~-0.005MPa; The mixing time is 1 to 2 hours; The stirring speed of the mixing is 300 to 600 rpm.

14. Use of the adhesive composition according to any one of claims 8 to 11 in bonding optoelectronic devices, building materials, and medical materials.

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