Lignin-based acrylate prepolymer, composite prepolymer, UV (ultraviolet) adhesive as well as preparation methods and application of lignin-based acrylate prepolymer, composite prepolymer and UV adhesive

Abstract

The invention discloses a lignin-based acrylate prepolymer, a composite prepolymer, a UV adhesive and a preparation method and application thereof. The lignin-based acrylate prepolymer is prepared by uniformly mixing raw materials including methacrylic acid lignin and a gallic acid-based cross-linking agent in vacuum under the action of an initiator and a co-initiator and then heating for reaction. A composite prepolymer is formed by raw materials including urethane acrylate, a lignin-based acrylate prepolymer and a polymerization inhibitor. Raw materials including a monomer, a photoinitiator, a composite prepolymer, a coupling agent and an auxiliary agent are subjected to a dark reaction in vacuum, and the UV adhesive containing the lignin-based acrylate prepolymer is prepared. The prepared adhesive has excellent mechanical properties and weather resistance, the industrial cost is reduced, the product is easy to degrade after being discarded, the environment-friendly requirement is met, and certain industrial application potential is achieved.

Description

Technical Field

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

[0002] Ultraviolet light curing (i.e. UV curing) uses light energy as energy, does not produce greenhouse gases, and uses less solvent. It is an energy-saving and environmentally friendly industrial technology that emerged in the 1960s. Its principle is that the photoinitiator (photosensitizer) in the system forms excited molecules under ultraviolet light irradiation, which are further decomposed into free radicals or ions to cause the unsaturated organic matter in the system to undergo chemical reactions such as polymerization, grafting, and cross-linking to achieve the purpose of curing. UV-curing adhesives have the advantages of low VOC emissions, low energy consumption, room temperature curing, and fast curing speed. They are green and environmentally friendly adhesives and have been widely used in the fields of optoelectronic device preparation, building materials, and medical materials. Among them, the research on acrylic adhesives is particularly active.

[0003] In addition to acrylate functional monomers, acrylate adhesives usually also include low molecular weight polymers (prepolymers) containing unsaturated functional groups, and their properties basically determine the main properties of the cured material. Generally speaking, prepolymers have large molecular weights, small volume shrinkage during curing, and fast curing speed, but large molecular weights will cause the viscosity of the system to increase, requiring more monomers for dilution. Therefore, the selection of prepolymers is an important part of UV adhesive formulation design. The preparation of traditional composite prepolymers uses non-renewable petroleum resources as raw materials, and petroleum-based prepolymers are difficult to degrade, which has a greater impact on the environment. Exploring and developing environmentally friendly raw materials for adhesives is the key to promoting the green and sustainable development of the adhesive industry, and has become one of the research hotspots in the adhesive field.

[0004] Compared with fossil energy, biomass resources such as lignin, starch, cellulose, and protein are widely available, abundant, 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 sustainable development of mankind. Lignin is commonly found in plant cell walls and is the second largest green renewable resource in nature (after 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 demand. Summary of the invention

[0005] In order to solve the problems in the prior art, the present invention proposes a lignin-based acrylate prepolymer, a composite prepolymer, a UV adhesive, and a preparation method and application thereof. The present invention modifies sulfate lignin by methacrylate, and polymerizes it with a tetrafunctional acrylate crosslinker generated after modification with gallic acid to form a composite prepolymer, and applies it to the preparation of UV adhesives, thereby realizing the value-added utilization of lignin. The photocurable adhesive provided by the present invention introduces a lignin-based acrylate composite prepolymer, and controls the addition amount of each raw material, so that the prepared bio-based acrylate adhesive has excellent mechanical properties and weather resistance. In addition, the present invention introduces biomass lignin materials, which reduces industrial costs, and the product is easily degraded after being discarded, which meets environmentally friendly requirements and has certain industrial application potential.

[0006] One of the objects of the present invention is to provide a lignin-based acrylate prepolymer, wherein the lignin-based acrylate prepolymer is prepared from raw materials including methacrylated lignin and a gallic acid-based crosslinking agent;

[0007] The lignin-based acrylate prepolymer of the present invention comprises a mixture of a methacrylated lignin acid-based crosslinking agent copolymer obtained by reacting methacrylated lignin and a gallic acid-based crosslinking agent, and a homopolymer formed by polymerizing methacrylated lignin and a gallic acid-based crosslinking agent respectively; the viscosity thereof is 5000 to 50000 mPa.s;

[0008] The methacrylated lignin contains the following structural fragments:

[0009]

[0010] In the present invention, the structure of kraft lignin is relatively complex, and only the main reaction fragments are shown above; the remaining structure of kraft lignin is not indicated at the above bond breaking position. The kraft lignin structure is an amorphous polymer composed of the following three alcohol monomers, and the structures of the three alcohol monomers are as follows:

[0011]

[0012] The gallic acid-based crosslinking agent has the following structure:

[0013]

[0014] In the present invention, methacrylated lignin is an existing substance, and the gallic acid-based cross-linking agent can be purchased directly or prepared according to an existing method.

[0015] The second object of the present invention is to provide a method for preparing a lignin-based acrylate prepolymer, wherein 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;

[0016] It is preferred to prepare the lignin-based acrylate prepolymer as described in one of the objects of the invention.

[0017] In the method for preparing the lignin-based acrylate prepolymer of the present invention, preferably, in the present invention, the prepolymer is thermally initiated polymerization, using a thermal initiator, and the initiator is preferably selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl benzoyl peroxide, and methyl ethyl ketone peroxide; and / or,

[0018] The co-initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine and triethanolamine; and / or,

[0019] The temperature of the vacuum heating reaction is 40 to 70°C; and / or,

[0020] The vacuum heating reaction time is 0.5h to 3h; and / or,

[0021] The vacuum degree of the vacuum heating reaction is -0.1MPa to -0.01MPa; and / or,

[0022] Taking the total weight of raw materials as 100%,

[0023] The amount of methacrylated lignin added is 72 wt% to 93 wt%;

[0024] The gallic acid-based cross-linking agent is added in an amount of 5wt% to 20wt%;

[0025] The amount of initiator added is 1wt% to 5wt%;

[0026] The amount of the co-initiator added is 0.5wt% to 3wt%;

[0027] Preferably,

[0028] The amount of methacrylated lignin added is 80 wt% to 91 wt%;

[0029] The gallic acid-based cross-linking agent is added in an amount of 5wt% to 16wt%;

[0030] The amount of initiator added is 2wt% to 4wt%;

[0031] The amount of the co-initiator added is 1 wt% to 2 wt%.

[0032] The third object of the present invention is to provide a composite prepolymer, which is a mixture formed by raw materials including polyurethane acrylate, lignin-based acrylate prepolymer, and inhibitor; the lignin-based acrylate prepolymer prepared by the preparation method described in the first object of the present invention or the second object of the present invention.

[0033] In the composite prepolymer of the present invention, preferably,

[0034] The viscosity of the polyurethane acrylate is in the range of 5000 to 30000 cps; preferably, the polyurethane acrylate in the present invention can be an existing polyurethane acrylate, preferably at least one of commercial polyurethane acrylates such as Changxing 6164L and Changxing 615-100; and / or,

[0035] The polymerization inhibitor is selected from at least one of hydroquinone, tert-butyl catechol, p-hydroxyanisole and benzoquinone; and / or,

[0036] Taking the total weight of raw materials as 100%,

[0037] The amount of lignin-based acrylate added is 20wt% to 77wt%;

[0038] The amount of polyurethane acrylate added is 20wt% to 77wt%;

[0039] The amount of the inhibitor added is 1wt% to 3wt%;

[0040] Preferably,

[0041] The amount of lignin-based acrylate added is 33 wt% to 66 wt%;

[0042] The amount of polyurethane acrylate added is 33wt% to 66wt%;

[0043] The amount of the polymerization inhibitor added is 1 wt% to 2 wt%.

[0044] The fourth object of the present invention is to provide a method for preparing the composite prepolymer described in any one of the third objects of the present invention, characterized in that the composite prepolymer is prepared by mixing raw materials including polyurethane acrylate, the lignin-based acrylate prepolymer, and an inhibitor in a light-proof manner.

[0045] A fifth object of the present invention is to provide a UV adhesive containing a lignin-based acrylate prepolymer.

[0046] The UV adhesive containing lignin-based acrylate prepolymer comprises a monomer, a photoinitiator, a composite prepolymer as described in any one of the third objects of the present invention, a coupling agent and an auxiliary agent;

[0047] The monomer is selected from at least one of acrylic monomers and acrylate monomers.

[0048] The present invention utilizes the characteristics of the single-component acrylate UV curing adhesive system, which is easy to operate, has strong bonding and good chemical resistance, and introduces a biomass material, lignin-based acrylate prepolymer, into the system. The lignin-based acrylate prepolymer has an interpenetrating network structure, strengthens the wetting effect and chemical bond effect of the adhesive, has high bonding strength after curing, has small volume shrinkage and excellent weather resistance. The effective utilization of lignin is achieved, the production cost is reduced, it conforms to the concept of green environmental protection and environmental friendliness, and has a certain industrialization prospect.

[0049] In the UV adhesive containing lignin-based acrylate prepolymer of the present invention, preferably,

[0050] In the UV adhesive, by weight:

[0051]

[0052] In the UV adhesive containing lignin-based acrylate prepolymer of the present invention, preferably,

[0053] The acrylic monomer is selected from at least one of acrylic acid and methacrylic acid; and / or,

[0054] 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.

[0055] In the UV adhesive containing lignin-based acrylate prepolymer of the present invention, preferably,

[0056] 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,

[0057] The coupling agent is selected from silane coupling agents; preferably, the coupling agent is selected from trialkoxysilane coupling agents;

[0058] Further preferably, the coupling agent is selected from at least one of phenyltrimethoxysilane, phenyltriethoxysilane, γ-mercaptopropyltriethoxysilane, methyltriethoxysilane and γ-aminopropyltriethoxysilane.

[0059] In the UV adhesive containing lignin-based acrylate prepolymer of the present invention, preferably,

[0060] The auxiliary agent is selected from at least one of a self-initiator, a stabilizer, and an inhibitor; preferably,

[0061] The auxiliary initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine and triethanolamine; and / or,

[0062] The stabilizer is selected from at least one of boric acid ester and organic acid; and / or,

[0063] The polymerization inhibitor is selected from at least one of hydroquinone, tert-butylcatechol, p-hydroxyanisole and benzoquinone;

[0064] Further 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.

[0065] The sixth object of the present invention is to provide a method for preparing a UV adhesive containing a lignin-based acrylate prepolymer as described in any one of the fifth objects of the present invention, comprising the following steps:

[0066] 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.

[0067] In the method for preparing the UV adhesive containing lignin-based acrylate prepolymer of the present invention, preferably,

[0068] Firstly, raw materials including monomers, composite prepolymers, coupling agents and additives are added and mixed, and then a photoinitiator is added to react in a vacuum stirring condition in the dark;

[0069] Preferably,

[0070] The vacuum degree of the light-proof reaction is between -0.1MPa and -0.01MPa;

[0071] The reaction time in the dark is 1 to 2 hours;

[0072] The reaction temperature is 20-40℃.

[0073] The stirring speed is 400-600 rpm.

[0074] The seventh object of the present invention is to provide a UV adhesive containing lignin-based acrylate prepolymer as described in any one of the fifth objects of the present invention for use in bonding optoelectronic devices, building materials, and medical materials.

[0075] The strength and bonding performance of the bonding system obtained by the invention meet the use requirements of optoelectronic devices, building materials and medical material bonding scenarios. In addition, due to the addition of degradable and biocompatible lignin-based acrylate, it is particularly suitable for use in medical material bonding.

[0076] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0077] Compared with the prior art, the present invention has at least the following advantages:

[0078] The present invention provides a lignin-based acrylate and a composite prepolymer thereof, and provides a light-curing acrylate type adhesive system with high bonding strength and good weather resistance. The adhesive has good adhesion firmness, small volume shrinkage, good flexibility and chemical resistance, and has the advantages of cheap and readily available raw materials, green and environmental protection, etc. DETAILED DESCRIPTION

[0079] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0080] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0081] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0082] In the present invention, conventional methods in the prior art can be used to confirm the structural units in the copolymer, such as infrared spectroscopy and the amount of monomers added during the polymerization process.

[0083] The present invention will be described in detail below through examples. All reagents used are commercially available. Room temperature refers to 25° C. All kinds of acrylate monomers and synthetic reagents are purchased from Inotech.

[0084] The composite prepolymer is prepared by mixing polyurethane acrylate and lignin-based acrylate in a certain proportion. The polyurethane acrylate in the present invention adopts existing commercial polyurethane acrylate Changxing 6164L and Changxing 615-100.

[0085] Changxing 615-100 is purchased from (Changxing Chemical Industry Co., Ltd.), and its viscosity is 10,000 to 20,000 cps;

[0086] Changxing 6164L is purchased from (Changxing Chemical Industry Co., Ltd.) and has a viscosity of 30,000 to 40,000 cps.

[0087] In the embodiment of the present invention, methacrylated lignin is an existing material and can be prepared in the following manner: Preparation of methacrylated lignin: Add dried kraft lignin KL (purchased from Aladdin) (2 g) to a round-bottom flask containing 20 mL of tetrahydrofuran THF, stir vigorously for 5 minutes (800 rpm), then add 0.2 mg of 1-methylimidazole, 1.68 g of methacrylic anhydride, stir for 60 minutes under a nitrogen atmosphere and heating (60 ° C), then drop the obtained brown mixture into n-hexane (150 mL), stir and precipitate to filter out a light brown powder. Then dissolve it in dichloromethane (20 mL) and wash it three times with deionized water to remove the catalyst and unreacted raw materials. Then precipitate it with n-hexane, and the obtained powder is vacuum dried to obtain methacrylated lignin. The specific synthesis method is as follows:

[0088]

[0089] In the embodiment of the present invention, the gallic acid-based cross-linking agent is an existing substance and can be prepared by the following method:

[0090] Preparation of gallic acid-based crosslinking agent: 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, stirred vigorously at room temperature for 10 minutes (800 rpm) until uniform, heated to 60°C and refluxed for 2 hours, cooled to room temperature, 17.92 g of acryloyl chloride was added dropwise over 30 minutes, heated to 40°C and reacted for 12 hours, and then the unreacted raw materials and acetone were removed by rotary evaporation to obtain a gallic acid-based crosslinking agent. The specific synthesis method is as follows:

[0091]

[0092] Preparation Example 1

[0093] Preparation of lignin-based acrylate prepolymer:

[0094] 90 parts of methacrylated lignin and 6 parts of gallic acid-based crosslinking agent were added into the reactor for mixing, and then 3 parts of initiator azobisisobutyronitrile and 1 part of co-initiator triethanolamine were added, and stirred at a vacuum degree of -0.01 MPa at a speed of 500 rpm. After stirring for 1 hour until uniform, the mixture was slowly heated to 60°C and stirred at a constant temperature for 2 hours to obtain a viscous liquid discharge.

[0095] Since the lignin-based acrylate prepolymer is composed of a mixture, it cannot be characterized and analyzed by nuclear magnetic resonance, and it exists in various forms, so the specific structural formula cannot be given.

[0096] Preparation of composite prepolymer:

[0097] 66 parts of the prepared lignin-based acrylate prepolymer and 33 parts of Changxing 6164L were uniformly mixed, 1 part of an inhibitor (hydroquinone) was added, and the mixture was stirred for 1 hour in a dark environment to obtain a composite prepolymer 1.

[0098] Preparation Example 2

[0099] Preparation of lignin-based acrylate prepolymer:

[0100] 90 parts of methacrylated lignin and 6 parts of gallic acid-based crosslinking agent were added into the reactor for mixing, and then 3 parts of initiator azobisisoheptanenitrile and 1 part of co-initiator triethanolamine were added, and stirred at a vacuum degree of -0.02 MPa at a speed of 400 rpm. After stirring for 2 hours until uniform, the mixture was slowly heated to 55°C and stirred at a constant temperature for 3 hours to obtain a viscous liquid discharge.

[0101] Preparation of composite prepolymer:

[0102] 49 parts of the prepared lignin-based acrylate prepolymer and 49 parts of Changxing 6164L were uniformly mixed, 2 parts of a polymerization inhibitor (tert-butyl catechol) were added, and the mixture was stirred for 2 hours in a dark environment to obtain a composite prepolymer 2.

[0103] Preparation Example 3

[0104] Preparation of lignin-based acrylate prepolymer:

[0105] 90 parts of methacrylated lignin and 6 parts of gallic acid-based crosslinking agent were added into the reactor for mixing, and then 2 parts of initiator benzoyl peroxide and 2 parts of co-initiator triethanolamine were added, and 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.

[0106] Preparation of composite prepolymer:

[0107] 39 parts of the prepared lignin-based acrylate prepolymer and 59 parts of Changxing 615-100 were uniformly mixed, 2 parts of a polymerization inhibitor (p-hydroxyanisole) were added, and the mixture was stirred for 1 hour in a dark environment to obtain a composite prepolymer 3.

[0108] Preparation Example 4

[0109] Preparation of lignin-based acrylate prepolymer:

[0110] 90 parts of methacrylated lignin and 6 parts of gallic acid-based crosslinking agent were added into the reactor for mixing, and then 2 parts of initiator methyl ethyl ketone peroxide and 2 parts of co-initiator triethanolamine were added, and stirred at a vacuum degree of -0.02 MPa at a speed of 400 rpm. After stirring for 2 hours until uniform, the mixture was slowly heated to 60°C and stirred at a constant temperature for 2 hours to obtain a viscous liquid discharge.

[0111] Preparation of composite prepolymer:

[0112] 33 parts of the prepared lignin-based acrylate prepolymer and 66 parts of Changxing 615-100 were uniformly mixed, 2 parts of polymerization inhibitor (benzoquinone) were added, and stirred for 2 hours in a dark environment to obtain a composite prepolymer 4.

[0113] Preparation Example 5

[0114] The formula of Preparation Example 1 was used, except that the amount of methacrylated lignin used in the formula was 80 parts, and the amount of gallic acid-based crosslinking agent used was 16 parts; the composite prepolymer 5 was obtained by the same preparation method.

[0115] Preparation Example 6

[0116] The formula of Preparation Example 1 was used, except that the amount of methacrylated lignin used in the formula was 86 parts, and the amount of gallic acid-based crosslinking agent used was 10 parts; the composite prepolymer 6 was obtained by the same preparation method.

[0117] Preparation Example 7

[0118] The formula of Preparation Example 1 was used, except that the amount of methacrylated lignin used in the formula was 91 parts, and the amount of gallic acid-based crosslinking agent used was 5 parts; the composite prepolymer 7 was obtained by the same preparation method.

[0119] Example 1

[0120] 100 parts of acrylate functional monomers (including 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 coupling agent phenyltrimethoxysilane, 2 parts of stabilizer trimethyl borate, and 2 parts of inhibitor tert-butyl catechol were added into a reactor, and mixed at a speed of 300 rpm for 30 minutes until uniform, and then 4 parts of photoinitiator benzoin methyl ether and 3 parts of co-initiator dimethylaminobenzoic acid isooctyl ester 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 until uniform, to obtain UV adhesive sample 1.

[0121] Example 2

[0122] 100 parts of acrylate functional monomers (including 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 coupling agent propyltriethoxysilane, 3 parts of stabilizer triethyl borate, and 2 parts of inhibitor hydroquinone are mixed in a reactor, and mixed at a speed of 300 rpm for 30 minutes until uniform, and then 4 parts of photoinitiator benzoin ethyl ether and 3 parts of co-initiator diethanolamine are added, the vacuum degree is maintained at -0.03 MPa, the speed is 500 rpm, and mechanical stirring is carried out at room temperature in the dark for 1 hour until uniform, to obtain UV adhesive sample 2.

[0123] Example 3

[0124] 100 parts of acrylate functional monomers (including 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 coupling agent γ-mercaptopropyl triethoxysilane, 2 parts of stabilizer tri-n-propyl borate, and 2 parts of inhibitor p-hydroxyanisole are mixed in a reactor, and mixed at a speed of 300 rpm for 30 minutes until uniform, and then 4 parts of photoinitiator benzoin butyl ether and 3 parts of co-initiator diethanolamine are added, the vacuum degree is maintained at -0.02 MPa, the speed is 600 rpm, and mechanical stirring is carried out at room temperature in the dark for 1 hour until uniform, to obtain UV adhesive sample 3.

[0125] Example 4

[0126] 100 parts of acrylate 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 coupling agent methyltriethoxysilane, 1 part of stabilizer triisopropyl borate, and 2 parts of inhibitor benzoquinone are mixed in a reactor, and mixed at a speed of 300 rpm for 30 minutes until uniform, and then 4 parts of photoinitiator diphenylethylenedione and 3 parts of co-initiator triethanolamine are added, the vacuum degree is maintained at -0.02 MPa, the speed is 400 rpm, and mechanical stirring is carried out at room temperature in the dark for 2 hours until uniform, to obtain UV adhesive sample 4.

[0127] Example 5

[0128] 100 parts of acrylate 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 coupling agent γ-aminopropyl triethoxysilane, 2 parts of stabilizer barbituric acid, and 1 part of inhibitor tert-butyl catechol are mixed in a reactor, and mixed at a speed of 300 rpm for 30 minutes until uniform, and then 3 parts of photoinitiator dialkoxyacetophenone and 2 parts of co-initiator dimethylaminobenzoic acid isooctyl ester are added, the vacuum degree is maintained at -0.01 MPa, the speed is 500 rpm, and mechanical stirring is carried out at room temperature in the dark for 2 hours until uniform, to obtain UV adhesive sample 5.

[0129] Example 6

[0130] 100 parts of acrylate functional monomers (including 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 coupling agent phenyltrimethoxysilane, 1 part of stabilizer lauric acid, and 1 part of inhibitor hydroquinone are mixed in a reactor, and mixed at a speed of 300 rpm for 30 minutes until uniform, and then 3 parts of photoinitiator α-hydroxyalkyl phenone and 2 parts of co-initiator dimethylaminobenzoic acid isooctyl ester are added, the vacuum degree is maintained at -0.03 MPa, the speed is 600 rpm, and mechanical stirring is carried out at room temperature in the dark for 2 hours until uniform, to obtain UV adhesive sample 6.

[0131] Example 7

[0132] The formula of Example 4 was used, except that composite prepolymer 5 was used instead of composite prepolymer 4 in the formula. The mixture was mixed and stirred in the same preparation manner until uniform, to obtain UV adhesive sample 7.

[0133] Example 8

[0134] The formula of Example 4 was used, except that composite prepolymer 6 was used instead of composite prepolymer 4 in the formula. The mixture was mixed and stirred in the same preparation manner until uniform, to obtain UV adhesive sample 8.

[0135] Example 9

[0136] The formula of Example 4 was used, except that composite prepolymer 7 was used instead of composite prepolymer 4 in the formula. The mixture was mixed and stirred in the same preparation manner until uniform, to obtain UV adhesive sample 9.

[0137] Comparative Example 1

[0138] The method is basically the same as that of Example 1, except that the prepolymers used in the formula are replaced with polyurethane acrylate (Changxing 6164L), and the mixture is mixed and stirred in the same preparation method until uniform.

[0139] Comparative Example 2

[0140] It adopts a scheme that is basically the same as that of Example 1, except that the prepolymers used in the formula are replaced with lignin-based acrylate prepolymers, and the mixture is mixed and stirred in the same preparation method until uniform.

[0141] Comparative Example 3

[0142] The method is basically the same as that of Example 1, except that no coupling agent is added to the formula, and the mixture is mixed and stirred in the same preparation method until uniform.

[0143] Performance test: The UV adhesive system described in the embodiment and the comparative example was tested as follows:

[0144] (1) Viscosity test method: Brookfield-RVT dial type rotational viscometer, test temperature 25°C, 20 rpm.

[0145] (2) Tensile bond strength test: refer to ASTM D1623 test method.

[0146] (3) Linear curing shrinkage test: Refer to the ISO 2577 test method to measure the change in length of a fixed length of film before and after curing. The shrinkage is obtained by dividing the reduced value by the original value.

[0147] (4) Adhesion: Refer to GB / T 9286-1998 test method, the results are divided into 0-5 levels, 0 is the best and 5 is the worst.

[0148] (5) Flexibility: Flexibility is tested according to the method described in the national standard GB / T 1731-1993 “Determination of paint film flexibility”.

[0149] (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, soak it in 50% ethanol solution for 12 h, and observe whether the film turns white, softens, or becomes sticky. If it turns white, softens, or becomes sticky, it is abnormal.

[0150] The above tests were repeated three times and the average value was taken.

[0151] The measurement results of some performance parameters of various embodiments and comparative examples are shown in Table 1 below.

[0152] Table 1

[0153]

[0154] As can be seen from the above table, the viscosity, tensile bonding strength, linear curing shrinkage, adhesion, flexibility and chemical resistance parameters of each embodiment are different, which is mainly related to the acrylate monomer formula, composite prepolymer type and content in each system. Comparative Example 1 Compared with Example 1, the embodiment after adding lignin-based acrylate to the composite prepolymer shows greater bonding strength and lower linear curing shrinkage. This is mainly because the multifunctional methacrylated lignin and gallic acid crosslinker form a cross-interpenetrating network structure after curing, which greatly increases the density of the bonding system and enhances the intramolecular force, thereby having higher strength, lower shrinkage, better stability and better adhesion effect.

[0155] By comparing Comparative Example 1 and Comparative Example 2 with Example 1, a composite prepolymer mixture is obtained by mixing commercial polyurethane acrylate with the prepared biomass lignin-based acrylate in a certain ratio. Compared with the UV adhesive system prepared by a single polyurethane acrylate or lignin-based acrylate prepolymer, the composite prepolymer of the present invention has better effects, higher adhesive strength, low shrinkage and other functional effects, which not only reduces the cost, but also realizes the efficient utilization of biomass resource lignin, and meets the green environmental protection requirements of the adhesive application field within a certain range. By comparing Comparative Example 3 with Example 1, it can be seen that the addition of a coupling agent in the bonding system can further improve the effect of the bonding system.

[0156] The present invention is described in detail above in conjunction with the exemplary embodiments of the specific embodiments, but these descriptions cannot be understood as limiting the present invention. It is understood by those skilled in the art that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The protection scope of the present invention shall be subject to the attached claims.

[0157] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0158] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0159] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A lignin-based acrylate prepolymer, Features: The lignin-based acrylate prepolymer is prepared from raw materials including methacrylated lignin and a gallic acid-based crosslinking agent; The methacrylated lignin contains the following structural fragments: The gallic acid-based crosslinking agent has the following structure:

2. A method for preparing a lignin-based acrylate prepolymer, Features: 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; Preferably, the lignin-based acrylate prepolymer according to claim 1 is prepared.

3. The method for preparing the lignin-based acrylate prepolymer according to claim 2, Features: 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, The co-initiator is selected from at least one of isooctyl p-dimethylaminobenzoate, diethanolamine and triethanolamine; and / or, The temperature of the vacuum heating reaction is 40 to 70°C; and / or, The vacuum heating reaction time is 0.5h to 3h; and / or, The vacuum degree of the vacuum heating reaction is -0.1MPa to -0.01MPa; and / or, Taking the total weight of raw materials as 100%, The amount of methacrylated lignin added is 72 wt% to 93 wt%; The gallic acid-based cross-linking agent is added in an amount of 5wt% to 20wt%; The amount of initiator added is 1wt% to 5wt%; The amount of the co-initiator added is 0.5wt% to 3wt%; Preferably, The amount of methacrylated lignin added is 80 wt% to 91 wt%; The gallic acid-based cross-linking agent is added in an amount of 5wt% to 16wt%; The amount of initiator added is 2wt% to 4wt%; The amount of the co-initiator added is 1 wt% to 2 wt%.

4. A composite prepolymer, It is characterized in that A mixture formed by raw materials including polyurethane acrylate, lignin-based acrylate prepolymer, and inhibitor; the lignin-based acrylate prepolymer is obtained as described in claim 1 or according to the preparation method described in claim 2 or 3.

5. The composite prepolymer according to claim 4, It is characterized in that The viscosity of the polyurethane acrylate is in the range of 5000 to 30000 cps; and / or, The polymerization inhibitor is selected from at least one of hydroquinone, tert-butyl catechol, p-hydroxyanisole and benzoquinone; and / or, Taking the total weight of raw materials as 100%, The amount of lignin-based acrylate added is 20wt% to 77wt%; The amount of polyurethane acrylate added is 20wt% to 77wt%; The amount of the inhibitor added is 1wt% to 3wt%; Preferably, The amount of lignin-based acrylate added is 33 wt% to 66 wt%; The amount of polyurethane acrylate added is 33wt% to 66wt%; The amount of the polymerization inhibitor added is 1 wt% to 2 wt%.

6. A method for preparing the composite prepolymer according to any one of claims 4 to 5, It is characterized in that The composite prepolymer is prepared by mixing raw materials including the polyurethane acrylate, lignin-based acrylate prepolymer and polymerization inhibitor uniformly under light protection.

7. A UV adhesive containing a lignin-based acrylate prepolymer, Features: The UV adhesive containing lignin-based acrylate prepolymer comprises a monomer, a photoinitiator, a composite prepolymer according to any one of claims 4 to 5, a coupling agent and an auxiliary agent; The monomer is selected from at least one of acrylic monomers and acrylate monomers.

8. The UV adhesive containing lignin-based acrylate prepolymer according to claim 7, Features: In the UV adhesive, by weight:

9. The UV adhesive containing lignin-based acrylate prepolymer according to claim 7, Features: The acrylic monomer is selected from at least one of acrylic acid and methacrylic acid; and / or, 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.

10. The UV adhesive containing lignin-based acrylate prepolymer according to claim 7, Features: 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, 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.

11. The UV adhesive containing lignin-based acrylate prepolymer according to claim 7, Features: The auxiliary agent is selected from at least one of a self-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 ester and organic acid; and / or, The polymerization inhibitor is selected from at least one of hydroquinone, tert-butylcatechol, p-hydroxyanisole and benzoquinone; Further 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.

12. A method for preparing a UV adhesive containing a lignin-based acrylate prepolymer according to any one of claims 7 to 11, It is characterized in that The following steps are involved: 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.

13. The method for preparing the UV adhesive containing lignin-based acrylate prepolymer according to claim 12, Features: Firstly, raw materials including monomer, composite prepolymer, coupling agent, stabilizer and polymerization inhibitor are added and mixed, and then photoinitiator and co-initiator are added to react in the dark under vacuum stirring conditions; Preferably, The vacuum degree of the light-proof reaction is between -0.01MPa and -0.1MPa; The reaction time in the dark is 1 to 2 hours; The stirring speed is 400-600 rpm.

14. Use of the UV adhesive containing lignin-based acrylate prepolymer according to any one of claims 7 to 11 in bonding optoelectronic devices, building materials, and medical materials.

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