A modified cellulose adhesive and a method for preparing the same

Abstract

The application belongs to the technical field of natural polymer material chemical modification, and particularly relates to a modified cellulose adhesive and a preparation method thereof. The modified cellulose adhesive comprises the following components in parts by weight: modified cellulose base emulsion 50-70 parts, VAE composite emulsion 10-20 parts, rosin water emulsion 5-8 parts, crosslinking agent 3-8 parts, and plasticizer 2-5 parts. The modified cellulose is obtained by grafting nano-cellulose solution with an epoxy group hypophosphorous acid ester compound and a fluorine-containing penta-phenyl alkyne dicarboxylic acid compound. The modified cellulose adhesive prepared by the application realizes targeted improvement of waterproofness, durability and bonding strength through molecular design.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical modification of natural high molecular materials, and particularly relates to a modified cellulose adhesive and a preparation method thereof. BACKGROUND

[0002] As a natural high molecular material, cellulose has the advantages of being renewable and biocompatible in the field of adhesives, but also has the following core problems due to structural limitations: 1. Insufficient interfacial adhesion: the intermolecular hydrogen bonding of natural cellulose is weak, resulting in low interfacial bonding strength; 2. Poor water resistance: a large number of hydrophilic hydroxyl groups swell in water, reducing the bonding strength; 3. Stability defects: easy to depolymerize in high temperature or high humidity environment.

[0003] Current conventional modification methods cannot fundamentally break through the performance bottleneck, such as physical blending method which only enhances the viscosity by blending thickening agent and cannot improve the interfacial bonding strength, and phase separation leads to delamination; simple etherification or esterification only modifies a single functional group, and the active sites of the molecular chain are not fully utilized; lack of thermal stability skeleton, and the interface is easy to fail at high temperature, etc. SUMMARY

[0004] In order to overcome the deficiencies of the prior art, the present application provides a modified cellulose adhesive and a preparation method thereof, which realizes performance targeted improvement through molecular design, including multi-active site synergistic design, construction of anti-hydrolysis barrier and dual toughening mechanism.

[0005] The technical scheme for achieving the object of the present application is as follows:

[0006] A modified cellulose adhesive is prepared by compounding a plurality of raw materials, and the adhesive comprises the following components in parts by weight: 50-70 parts of a modified cellulose-based emulsion, 10-20 parts of a VAE composite emulsion, 5-8 parts of a rosin water emulsion, 3-8 parts of a crosslinking agent, and 2-5 parts of a plasticizer, wherein the modified cellulose-based emulsion is obtained by mixing cellulose and modified cellulose in a certain proportion; the modified cellulose is obtained by grafting nano-cellulose solution with an epoxy-based hypophosphorous acid ester compound and a fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound; and the structure of the modified cellulose is shown in Formula 1.

[0007] Formula 1.

[0008] Preferably, the VAE composite emulsion is composed of two VAE emulsions with different glass transition temperatures, one of which has a glass transition temperature lower than 0℃, and the other has a glass transition temperature higher than or equal to 0℃; the mass ratio of the two emulsions is (0.45-0.55):(0.45-0.55); the crosslinking agent is trimethylolpropane triglycidyl ether; and the plasticizer is diphenic acid dimerized propylene glycol ester.

[0009] Preferably, the VAE emulsion with a glass transition temperature lower than 0℃ is VAE920 emulsion from Wacker, Germany, and the VAE emulsion with a glass transition temperature higher than or equal to 0℃ is DA102 VAE emulsion from Dalian Chemical, Taiwan, China; further preferably, the mass of the VAE920 emulsion is 45% of the total emulsion mass.

[0010] The gradient stirring is 80 rpm for 0~2 min, 120 rpm for 3~5 min, and 150 rpm for 6~10 min.

[0011] The preparation method of the modified cellulose comprises the following steps:

[0012] S1. Dissolve 2.5 eq of furan and 1 eq of 1-aminomethyl maleimide hydrochloride in toluene, and heat to 90℃ with a Dean-Stark device for 17~20 h. After the reaction is completed, remove the solvent under reduced pressure, and purify the crude product by silica gel column chromatography to obtain an amino Diels-Alder addition product, the structure of which is shown in the following formula:

[0013] ;

[0014] S2. Dissolve and mix 1.0 eq of the product of step S1 and 1.2 eq of an epoxy hypophosphite compound in tetrahydrofuran under a nitrogen atmosphere, heat to 60℃ and stir for 20~24 h. After the reaction is completed, remove the solvent by distillation under reduced pressure, and purify by silica gel column chromatography to obtain a hypophosphite-esterified amino Diels-Alder addition product, the structure of which is shown in the following formula:

[0015] ;

[0016] S3. Dissolve 1.1~1.3 eq of a fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound in anhydrous dichloromethane, cool to 0℃ in an ice bath, and then add 1.2 eq of dicyclohexyl carbodiimide, stir for 10 min, add 0.1 eq of 4-dimethylaminopyridine, and finally add 1 eq of a hypophosphite-esterified amino Diels-Alder addition product in anhydrous dichloromethane solution with a molar concentration of 0.1 mol / L dropwise. Remove the ice bath, and stir at room temperature for 15~20 h. After the reaction is completed, filter, and then wash the filtrate with 5% citric acid aqueous solution, saturated sodium bicarbonate solution, and brine successively, dry with anhydrous sodium sulfate, and purify by silica gel column chromatography to obtain a hypophosphite ester monomer, the structure of which is shown in the following formula:

[0017] ;

[0018] S4. Synthesis of polyhypophosphite: under nitrogen atmosphere, 1 eq of hypophosphite monomer obtained in step S3 and 1 / 200~1 / 50 eq of catalyst were dissolved in toluene, ring-opening metathesis polymerization was carried out, after being heated to 50~90 ℃ for 3~5 h, vinyl ethyl ether was added to quench the reaction, the solvent was removed, and polyhypophosphite was obtained by recrystallization from acetone;

[0019] S5. Epoxidation of polyhypophosphite: under nitrogen atmosphere, polyphosphite obtained in step S4 was dissolved in toluene, m-chloroperbenzoic acid was added at 10~25 ℃, and the mixture was stirred for 2~5 h, then excess methanol was added to precipitate the epoxidized polyhypophosphite;

[0020] S6. Cellulose modification: the nanocellulose aqueous suspension was diluted to a solution with a solid content of 0.5% by weight, 1.2 eq of 0.5 mol / L MgCl2 aqueous solution was added relative to the nanocellulose, and the mixture was stirred at room temperature for 30 min; the epoxidized polyhypophosphite was added, the mass ratio of nanocellulose solid content to epoxidized polyhypophosphite was (3~9):1, the mixture was stirred at 600~800 rpm for 8~12 h at 25~40 ℃, and then ultrasonic dispersion was continued for 10~30 min; 20 min after the addition of disodium ethylenediaminetetraacetate solution and stirring, the mixture was left to stand at room temperature to remove air bubbles, and then was frozen in liquid nitrogen for 5~10 min; the frozen sample was placed in a freeze dryer at a temperature of -60~-50 ℃ and a pressure of 1~20 Pa for freeze drying for 60~72 h, to obtain a gel-like solid; the obtained gel was placed in a vacuum drying oven at a temperature of 110~120 ℃ for 5~10 min, to obtain hypophosphite-modified cellulose.

[0021] Ring-opening metathesis polymerization was used to obtain polyphosphite with different molecular weights by changing the ratio of phosphite monomer to catalyst, wherein the catalyst was one or more of Grubbs first-generation catalyst, Grubbs second-generation catalyst, and Grubbs third-generation catalyst, and the molar ratio of phosphite monomer to catalyst was (50~200):1.

[0022] Preferably, the catalyst was Grubbs second-generation catalyst.

[0023] The preparation method of the fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound comprises the following steps:

[0024] (1) 2.5 eq of 4-fluorobenzyl bromide, 1 eq of 2,5-diiodobenzene-1,4-diol and 0.25 eq of 18-crown-6 ether are mixed in anhydrous acetone, 5-6 eq of potassium carbonate is added, and the mixture is treated with nitrogen degassing, stirred to 60°C, and reacted for 18-20 h; after the reaction is completed, the hot mixture is filtered, recrystallized in acetone, and 2,5-diiodobis(4-fluorobenzyloxy)benzene is obtained, as shown in the following formula:

[0025] ;

[0026] (2) 1 eq of 2,5-diiodobis(4-fluorobenzyloxy)benzene, 4 eq of methyl 4-ethynylbenzoate, 0.3 eq of cuprous iodide, and 0.1 eq of bis(triphenylphosphine)palladium(II) dichloride are mixed, the mixture is degassed with nitrogen, anhydrous tetrahydrofuran and anhydrous triethylamine are added, and stirring is performed under a nitrogen atmosphere for 18-20 h in the dark; after the reaction is completed, it is cooled to room temperature and poured into water, and 2,5-bis(4-fluorobenzyloxy)-1,4-bis(4-methylphenylacetylenyl)benzene is obtained by silica gel column chromatography, as shown in the following formula:

[0027] ;

[0028] (3) 1 eq of 2,5-bis(4-fluorobenzyloxy)-1,4-bis(4-methylphenylacetylenyl)benzene is dissolved in 15 mL of tetrahydrofuran, 250 eq of potassium hydroxide is dissolved in 8 mL of methanol and added to the above mixture, and stirring is performed at room temperature for 20-22 h; the reaction mixture is acidified with 120 mL of a 2 mol / L trifluoroacetic acid tetrahydrofuran solution, stirring is performed at room temperature for 1 h, and then the mixture is poured into water; the precipitate is filtered, washed with water, treated with boiling water, and ultrasonically shaken to remove inorganic salt impurities; the solid is dried and recrystallized in chloroform to obtain a fluorine-containing pentaphenylacetylenyl dicarboxylic acid compound, as shown in formula 2:

[0029] , formula 2.

[0030] The preparation method of the epoxy hypophosphite compound comprises the following steps:

[0031] (1) 6 eq of sodium hypophosphite monohydrate, 1 eq of propargyl glycidyl ether, and 1 eq of triethylborane solution are mixed in a solution of methanol:dioxane at a volume ratio of 5:1 under an air atmosphere; the solution is stirred under an air atmosphere at room temperature for 4 h, and after the reaction is completed, the precipitate is filtered, washed with cold methanol three times, and dried in a vacuum through phosphorus pentoxide to obtain a sodium phosphate salt intermediate, as shown in the following formula:

[0032] ;

[0033] (2) Under the atmosphere of nitrogen, 1 eq sodium phosphate salt intermediate, 2.2-2.5 eq bromoalkane and 0.05-0.10 eq tetrabutylammonium bromide are mixed with anhydrous acetonitrile, heated to 80-90°C with stirring, and reacted for 24 h; after the reaction is completed, it is cooled to room temperature, the solvent is removed under reduced pressure, and the residue is extracted with ethyl acetate and saturated brine, the organic phases are combined, dried with anhydrous sodium sulfate solid, and purified by silica gel column chromatography to obtain an epoxy hypophosphite compound, the structure of which is shown in formula 3:

[0034] Formula 3.

[0035] Preferably, the bromoalkane includes one or more of 1-bromopentane, 1-bromohexane, 1-bromoheptane, 1-bromooctane, 1-bromononane, 1-bromodecane, 1-bromoundecane, 1-bromododecane, 1-bromotridecane, 1-bromotetradecane, 1-bromopentadecane, and 1-bromohexadecane.

[0036] The present application also protects the preparation method of the modified cellulose adhesive, which comprises the following steps:

[0037] (1) Preparation of modified cellulose-based emulsion: mix cellulose and modified cellulose in a mixed solvent at a mass ratio of (1-8): 1, heat to 60-65°C, and dissolve with ultrasonic auxiliary treatment at 1200-1500 rpm for 30-40 min;

[0038] (2) Preparation of rosin water emulsion: add solid rosin resin to boiling water, gradually add surfactant, stir at 800 rpm for 20 min, cool to 60°C to obtain rosin water emulsion, and remove undispersed particles through a 200-mesh sieve; the mass ratio of rosin to water is 1:(5-8); the mass ratio of rosin to surfactant is (10-15): 1; the surfactant is an anionic surfactant, preferably sodium dodecyl sulfate;

[0039] (3) Preparation of VAE composite emulsion: mix two VAE emulsions at 40°C, add 0.3% silicone defoaming agent by mass fraction, and stir at 200 rpm for 15 min to obtain a VAE composite emulsion;

[0040] (4) Crosslinking agent and plasticizer treatment: dilute the crosslinking agent with an equal volume of ethanol; preheat the plasticizer to 50°C;

[0041] (5) Preparation of modified cellulose adhesive: the reaction kettle is preheated to 45 DEG C in the dark environment, the modified cellulose base emulsion and VAE composite emulsion are added and gradient stirring is carried out for 10 min, then the rosin water emulsion is added and stirring is carried out for 5 min, the pretreated plasticizer is slowly added in 5 min, the diluted crosslinking agent is slowly added dropwise in 10 min, the temperature is maintained at 45 DEG C, stirring is carried out at 150 rpm for 10-15 min, vacuum degassing is carried out for 20 min, the pH is adjusted to 7 with ammonia water, and the modified cellulose adhesive is obtained after 0.5 mu m precision filtration.

[0042] The mixed solvent is a mixed solvent with a volume ratio of water to NMP of 7:3; the ultrasonic assistance parameters are set to 40 kHz and 600 W.

[0043] Beneficial effects

[0044] The present application comprises the following beneficial effects:

[0045] The present application provides a modified cellulose adhesive and a preparation method thereof, which realizes performance targeted improvement through molecular design of cellulose:

[0046] 1. Multi-active site synergistic design: a "rigid and flexible" chain structure is constructed, the rigid fluorine-containing aromatic ring inhibits high-temperature slippage of the molecular chain, long-chain alkyl ester groups are used to enhance the hydrophobic interface to form a hydrophobic barrier; the fluorine-containing alkyne conjugated system enhances the van der Waals force through electron cloud density and helps resist ultraviolet degradation, which helps to prolong the service life of the adhesive; the phosphate group forms multiple hydrogen bonds and metal chelation with the cellulose hydroxyl group, which synergistically improves the bonding strength and water resistance of the modified cellulose adhesive;

[0047] 2. Construction of anti-hydrolysis barrier: ether bond is beneficial to resist acid and alkali attack, and imide bond is more stable than ordinary amide bond, and the two synergistically form an anti-hydrolysis barrier;

[0048] 3. Dual toughening mechanism: ether bond and alkyl chain combination help to enhance the molecular elongation at break and impact resistance. In addition, through the cooperation with VAE composite emulsion, rosin water emulsion and other components, the initial viscosity is improved, the hydrophobic fluorine of modified cellulose and rosin synergistically reduce the alternating surface tension, so that the wetting speed of the adhesive is accelerated and the spreading uniformity is better; rosin resin fills the intermolecular pores of cellulose, so that the cohesive force of the adhesive is enhanced and the shear strength is improved; VAE composite emulsion wraps the cellulose chain, solving the problems of high brittleness and high shrinkage of cellulose; the fluorine atom of modified cellulose and VAE film barrier synergistically avoid water erosion, realizing long-term non-mildew and non-delamination of the modified cellulose adhesive. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The synthesis steps of the modified cellulose.

[0050] Figure 2 The nuclear magnetic resonance hydrogen spectrum of the hypophosphorous ester monomer synthesized in step S3 of Preparation Example 1 is shown below. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0052] In the embodiments, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0053] The raw materials and equipment used in the examples and comparative examples are described as follows:

[0054] Epoxy hypophosphite compound 1: self-made, and the preparation method is as follows:

[0055] (1) In an air atmosphere, 6 eq of sodium hypophosphite monohydrate, 1 eq of propargyl glycidyl ether and 1 eq of triethylborane solution were mixed in a solution with a volume ratio of methanol: dioxane of 5:1; the solution was stirred at room temperature for 4 h in an air atmosphere, and after the reaction was completed, the precipitate was washed with cold methanol three times, and the sodium phosphate salt intermediate was dried in vacuum through phosphorus pentoxide to obtain the sodium phosphate salt intermediate, and the structure is shown in the following formula:

[0056] ;

[0057] (2) Under a nitrogen atmosphere, 1 eq of the sodium phosphate salt intermediate, 2.2-2.5 eq of 1-bromohexadecane and 0.05-0.10 eq of tetrabutylammonium bromide were mixed with anhydrous acetonitrile, and stirred and heated to 80-90°C, and reacted for 24 h; after the reaction was completed, the temperature was cooled to room temperature, the solvent was removed under reduced pressure, and the residue was extracted with ethyl acetate and saturated brine, the organic phases were combined and dried with anhydrous sodium sulfate solid, and then purified by silica gel column chromatography to obtain epoxy hypophosphite compound 1, and the structure is shown in the following formula:

[0058] ;

[0059] Epoxy hypophosphite compound 2: self-made, and the preparation method is compared with that of epoxy hypophosphite compound 1, the difference is that 1-bromohexadecane in step (2) is replaced by 1-bromopentane, and other conditions are unchanged, to obtain epoxy hypophosphite compound 2, and the structure is shown in the following formula:

[0060] ;

[0061] Epoxy compound 3: n-butyl glycidyl ether, product number B829911, purchased from Shanghai Macklin Biochemical Technology Co., Ltd., structure as shown in the following formula:

[0062] ;

[0063] Fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound 1: self-made, preparation method as follows:

[0064] (1) 2.5 eq of 4-fluorobenzyl, 1 eq of 2,5-diiodobenzene-1,4-diol and 0.25 eq of 18-crown-6 were mixed in anhydrous acetone, 5-6 eq of potassium carbonate was added, and the mixture was treated with nitrogen degassing, stirred to 60°C, and reacted for 18-20 h; after the reaction was completed, the hot mixture was filtered, recrystallized in acetone, and 2,5-diiodobis(4-fluorobenzyloxy)benzene was obtained, structure as shown in the following formula:

[0065] ;

[0066] (2) 1 eq of 2,5-diiodobis(4-fluorobenzyloxy)benzene, 4 eq of methyl 4-ethynylbenzoate, 0.3 eq of cuprous iodide, and 0.1 eq of bis(triphenylphosphine)palladium(II) dichloride were mixed, the mixture was degassed with nitrogen, anhydrous tetrahydrofuran and anhydrous triethylamine were added, and stirred for 18-20 h in the dark under nitrogen atmosphere; after the reaction was completed, it was cooled to room temperature and poured into water, and purified by silica gel column chromatography to obtain 2,5-bis(4-fluorobenzyloxy)-1,4-bis(4-methylcarboxyphenyl ethynyl)benzene, structure as shown in the following formula:

[0067] ;

[0068] (3) 1 eq of 2,5-bis(4-fluorobenzyloxy)-1,4-bis(4-methylcarboxyphenyl ethynyl)benzene was dissolved in 15 mL of tetrahydrofuran, 250 eq of potassium hydroxide was dissolved in 8 mL of methanol and added to the above mixed solution, and stirred at room temperature for 20-22 h; the reaction mixture was acidified with 120 mL of 2 mol / L trifluoroacetic acid tetrahydrofuran solution, stirred at room temperature for 1 h, then poured into water, and the precipitate was filtered and washed with water, the crude product was treated with boiling water and ultrasonic vibration to remove inorganic salt impurities, and the solid was dried and recrystallized in chloroform to obtain fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound 1, structure as shown in the following formula:

[0069] ;

[0070] Fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound 2: self-made, the preparation method is compared with that of fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound 1, the difference is that 4-fluorobenzyl in step (1) is replaced by benzyl bromide, and other conditions are unchanged, and fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound 2 is obtained, the structure is as shown in the following formula:

[0071] ;

[0072] Dicarboxylic acid compound 3: heptanedioic acid, product number 1016832, purchased from Shanghai Haohong Biomedical Science and Technology Co., Ltd.;

[0073] Commercially available cellulose: nanocellulose aqueous suspension, mass fraction 1%, diameter: 15-25 nm, product number JLC12335, purchased from Jingkang Biotechnology Co., Ltd.

[0074] Crosslinking agent: trimethylolpropane triglycidyl ether, product number T856506, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.;

[0075] Plasticizer: dipropylene glycol dibenzoate, product number 1028018, purchased from Shanghai Haohong Biomedical Science and Technology Co., Ltd.;

[0076] Silicone defoamer: BYK-028, purchased from Guangzhou Qiangang Trading Co., Ltd.

[0077] Surfactant: sodium dodecyl sulfate, product number S850167, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.

[0078] Propargyl glycidyl ether: product number 1269676, purchased from Shanghai Haohong Biomedical Science and Technology Co., Ltd.

[0079] Sodium hypophosphite monohydrate: product number S822520, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.

[0080] Triethylborane solution: 1 mol / L in hexane, product number T466127, purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.

[0081] Phosphorus pentoxide: product number P431841, purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.

[0082] 1-bromopentane: product number B802255, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.

[0083] 1-bromohexadecane: product number 1017242, purchased from Shanghai Haohong Biomedical Science and Technology Co., Ltd.

[0084] 4-Fluorobenzyl bromide: product number SY001307, purchased from Shanghai Sower Biotech Co., Ltd.;

[0085] 2,5-Diiodobenzene-1,4-diol: product number 1181381, purchased from Shanghai Haohong Biological Medicine Science and Technology Co., Ltd.;

[0086] 18-Crown-6: product number 1023772, purchased from Shanghai Haohong Biological Medicine Science and Technology Co., Ltd.;

[0087] 4-Ethynylbenzoic acid methyl ester: product number 1028851, purchased from Shanghai Haohong Biological Medicine Science and Technology Co., Ltd.;

[0088] Cuprous iodide: product number C017283, purchased from Shanghai Genview Chemical Technology Co., Ltd.;

[0089] Bis(triphenylphosphine)palladium(II) dichloride: product number 1020950, purchased from Shanghai Haohong Biological Medicine Science and Technology Co., Ltd.;

[0090] 1-Aminomethylmaleimide hydrochloride: purchased from Nantong Weindai Pharmaceutical Technology Co., Ltd.;

[0091] Grubbs 2nd generation catalyst: product number G810692, purchased from Shanghai McLean Biochemical Technology Co., Ltd.;

[0092] M-chloroperbenzoic acid: content 85%, purchased from Shanghai Mayreer Biochemical Technology Co., Ltd.;

[0093] EDTA disodium solution: 50 g / L aqueous solution, product number E766637, purchased from Shanghai McLean Biochemical Technology Co., Ltd.;

[0094] Rosin resin: purchased from Chengdu Purei Pharmaceutical Research and Development Co., Ltd.;

[0095] VAE emulsion 1: glass transition temperature -20℃, VAE920 emulsion of Wacker, Germany;

[0096] VAE emulsion 2: glass transition temperature 0℃, DA102 VAE emulsion of Dalian Chemical, Taiwan, China.

[0097] Preparation Example

[0098] Preparation Example 1

[0099] Modified cellulose-based emulsion 1: self-made, the preparation method is as follows:

[0100] (1) Preparation of modified cellulose 1

[0101] S1. 2.5 eq of furan and 1 eq of 1-aminomethylmaleimide hydrochloride were dissolved in toluene, heated to 90°C with a Dean-Stark apparatus for 20 h, after the reaction was completed, the solvent was removed under reduced pressure, and the crude product was purified by silica gel column chromatography to obtain the amino Diels-Alder addition product, the structure of which is shown in the following formula:

[0102] ;

[0103] S2. 1.0 eq of the product of step S1 and 1.2 eq of the epoxy hypophosphite compound 1 were dissolved and mixed in tetrahydrofuran under a nitrogen atmosphere, heated to 60°C and stirred for 24 h, after the reaction was completed, the solvent was removed by distillation under reduced pressure, and the hypophosphite-esterified amino Diels-Alder addition product was purified by silica gel column chromatography, the structure of which is shown below:

[0104] ;

[0105] S3. 1.2 eq of the fluorine-containing pentaphenylalkynyl dicarboxylic acid compound 1 was dissolved in anhydrous dichloromethane, cooled to 0°C in an ice bath, 1.2 eq of dicyclohexyl carbodiimide was added, stirred for 10 min, 0.1 eq of 4-dimethylaminopyridine was added, and finally 1 eq of the hypophosphite-esterified amino Diels-Alder addition product was added dropwise in anhydrous dichloromethane solution with a molar concentration of 0.1 mol / L; remove the ice bath, stir at room temperature for 20 h, after the reaction is completed, filter, and then wash the filtrate with 5% citric acid aqueous solution, saturated sodium bicarbonate solution and brine successively, dry with anhydrous sodium sulfate, and purify by silica gel column chromatography to obtain the hypophosphite monomer, the structure of which is shown in the following formula:

[0106] ;

[0107] S4. Synthesis of polyhypophosphite: 1 eq of the hypophosphite monomer obtained in step S3 was dissolved in toluene with 1 / 50 eq of catalyst under a nitrogen atmosphere, and ring-opening metathesis polymerization was carried out, after heating to 70°C for 4 h, vinyl ether was added to quench the reaction, the solvent was removed, and polyhypophosphite was obtained by recrystallization from acetone;

[0108] S5. Epoxidation of polyhypophosphite: the polyhypophosphite obtained in step S4 was dissolved in toluene under a nitrogen atmosphere, and m-chloroperoxybenzoic acid was added at 20°C and stirred for 4 h, then excess methanol was added to precipitate the epoxidized polyhypophosphite;

[0109] S6. Cellulose modification: dilute the nanocellulose water suspension to a solution with a solid content of 0.5% by weight, add 1.2 eq of MgCl2 aqueous solution with a concentration of 0.5 mol / L relative to the nanocellulose, stir at room temperature for 30 min; add epoxidized polyhypophosphite, the mass ratio of nanocellulose solid content to epoxidized polyhypophosphite is 6:1, stir at 800 rpm for 12 h at 30°C, then continue ultrasonic dispersion for 30 min, add disodium ethylenediaminetetraacetate solution and stir for 20 min; after standing at room temperature to remove bubbles, freeze in liquid nitrogen for 10 min, place the frozen sample in a freeze dryer at a temperature of -50°C and a pressure of 20 Pa for freeze drying for 60 h, obtain a gel-like solid, place the obtained gel in a vacuum drying oven at a temperature of 110°C for 10 min, obtain modified cellulose 1.

[0110] (2) Modified cellulose-based emulsion 1: mix cellulose and modified cellulose 1 in a mixed solvent of water:NMP with a volume ratio of 7:3 at a mass ratio of 4.5:1, heat to 65°C, dissolve by stirring at 1200 rpm and ultrasonic assisted treatment for 30 min, to obtain modified cellulose-based emulsion 1;

[0111] Preparation Example 2

[0112] Modified cellulose-based emulsion 2: self-made, the preparation method is compared with modified cellulose-based emulsion 1, the difference is that in step (1) S6, the mass ratio of nanocellulose solid content to epoxidized polyhypophosphite is replaced by 3:1, and other conditions remain unchanged, to obtain modified cellulose-based emulsion 2.

[0113] Preparation Example 3

[0114] Modified cellulose-based emulsion 3: self-made, the preparation method is compared with modified cellulose-based emulsion 1, the difference is that in step (1) S6, the mass ratio of nanocellulose solid content to epoxidized polyhypophosphite is replaced by 9:1, and other conditions remain unchanged, to obtain modified cellulose-based emulsion 3.

[0115] Preparation Example 4

[0116] Modified cellulose-based emulsion 4: self-made, the preparation method is compared with modified cellulose-based emulsion 1, the difference is that in step (1) S2, epoxy hypophosphite compound 1 is replaced by epoxy hypophosphite compound 2, and other conditions remain unchanged, to obtain modified cellulose 4.

[0117] Preparation Example 5

[0118] Modified cellulose-based emulsion 5: self-made, the preparation method is compared with modified cellulose-based emulsion 1, the difference is that in step (1) S2, epoxy hypophosphite compound 1 is replaced by epoxy compound 3, and other conditions remain unchanged, to obtain modified cellulose-based emulsion 5.

[0119] Preparation Example 6

[0120] Modified cellulose-based emulsion 6: self-made, the preparation method is compared with that of modified cellulose-based emulsion 1, the difference lies in that the fluorine-containing pentaphenyl alkynyl dicarboxylic compound 1 in step (1) S3 is replaced by fluorine-containing pentaphenyl alkynyl dicarboxylic compound 2, and other conditions are unchanged, and modified cellulose-based emulsion 6 is obtained.

[0121] Preparation Example 7

[0122] Modified cellulose-based emulsion 7: self-made, the preparation method is compared with that of modified cellulose-based emulsion 1, the difference lies in that the fluorine-containing pentaphenyl alkynyl dicarboxylic compound 1 in step (1) S3 is replaced by dicarboxylic compound 3, and other conditions are unchanged, and modified cellulose-based emulsion 7 is obtained.

[0123] Preparation Example 8

[0124] Modified cellulose-based emulsion 8: self-made, the preparation method is compared with that of modified cellulose-based emulsion 1, the difference lies in that the ratio of cellulose to modified cellulose 1 in step (2) is replaced by 1:1, and other conditions are unchanged, and modified cellulose-based emulsion 8 is obtained.

[0125] Preparation Example 9

[0126] Modified cellulose-based emulsion 9: self-made, the preparation method is compared with that of modified cellulose-based emulsion 1, the difference lies in that the ratio of cellulose to modified cellulose 1 in step (2) is replaced by 9:1, and other conditions are unchanged, and modified cellulose-based emulsion 9 is obtained.

[0127] Preparation Example 10

[0128] Modified cellulose-based emulsion 10: self-made, the preparation method is compared with that of modified cellulose-based emulsion 1, the difference lies in that the modified cellulose 1 is replaced by commercially available cellulose, and other conditions are unchanged, and modified cellulose-based emulsion 10 is obtained.

[0129] Examples and comparative examples

[0130] Examples 1~11 and comparative examples

[0131] Modified cellulose adhesives 1~11: self-made, the preparation method is as follows:

[0132] (1) Preparation of rosin water emulsion: add solid rosin resin into boiling water, gradually add surfactant, stir at 800 rpm for 20 min, cool to 60°C to obtain rosin water emulsion, remove undispersed particles through a 200 mesh sieve; the mass ratio of rosin to water is 1:6; the mass ratio of rosin to surfactant is 13:1; the surfactant is an anionic surfactant, preferably sodium dodecyl sulfate;

[0133] (2) Preparation of VAE composite emulsion: mix two VAE emulsions at 40°C, add 0.3% mass fraction of silicone defoaming agent, stir at 200 rpm for 15 min, and obtain VAE composite emulsion;

[0134] (3) Crosslinking agent and plasticizer treatment: dilute the crosslinking agent with an equal volume of ethanol; preheat the plasticizer to 50°C;

[0135] (4) Preparation of modified cellulose adhesive: preheat the reaction kettle to 45°C in a light-proof environment, add modified cellulose-based emulsion 1-10 and VAE composite emulsion gradient stirring for 10 min, then add rosin water emulsion stirring for 5 min, slowly add the pretreated plasticizer within 5 min, slowly drop the diluted crosslinking agent within 10 min, maintain the temperature at 45°C, stir at 150 rpm for 10 min, vacuum degassing for 20 min, adjust the pH to 7 with ammonia water, pass through 0.5 μm precision filter, and obtain modified cellulose adhesive 1-11 and comparative examples.

[0136] Table 1 Formulation of modified cellulose adhesive of examples 1-11 and comparative examples (by weight)

[0137]

[0138] The following are the test methods of the performance parameters involved in the present application:

[0139] 1. Adhesion strength test: test according to JC / T438-2019 standard, and test instrument adopts WDT type electronic universal material testing machine;

[0140] 2. Water resistance test: after the adhesive is coated under the same conditions, immerse it in water at 25°C for 24 h, observe the swelling condition and record the water immersion strength retention rate / %;

[0141] Table 2 Performance test results of adhesive of examples 1-11 and comparative examples

[0142]

[0143] From the data in Table 2, in Examples 1-3, the proportion of modified cellulose in Example 2 is reduced, and the bonding strength is relatively reduced compared with Example 1; the proportion of modified cellulose in Example 3 is increased, and the bonding strength is increased due to high filler; in Example 4, the modified cellulose 2 has high polyphosphonate content and good water resistance, but the relative proportion of cellulose is reduced, and the strength is slightly lower than that of Example 1; in Example 5, the modified cellulose 3 has relatively reduced water resistance and strength due to high cellulose proportion; in Example 6, the modified cellulose 4 uses a short chain structure, and the bonding strength and water resistance are reduced; in Example 7, the modified cellulose 5 does not contain phosphorus, and the bonding strength and water resistance are reduced; in Example 8, the modified cellulose 6 does not contain fluorine groups, and the water resistance and bonding strength are relatively reduced compared with Example 1; in Example 9, heptanedioic acid flexible chain is used to replace the rigid structure of benzene ring and alkyne group, and the water resistance and bonding strength are reduced; and in the comparative example, commercially available cellulose is used without modification, and the performance is the worst.

[0144] In summary, the fluorine-containing alkyne conjugated system enhances the van der Waals force through the electron cloud, the long-chain alkane prevents water molecules from penetrating the interface through the hydrophobic barrier, and the phosphate group forms multiple hydrogen bonds with the hydroxyl group of cellulose, thereby enhancing the bonding strength and water resistance of the modified cellulose adhesive from multiple aspects. The performance is targetedly improved through molecular design.

[0145] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details, nor limit the application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the specification. The specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A modified cellulose binder, characterized by, By weight parts, including the following components: modified cellulose-based emulsion 50~70 parts, VAE composite emulsion 10~20 parts, rosin water emulsion 5~8 parts, crosslinking agent 3~8 parts, plasticizer 2~5 parts; the modified cellulose-based emulsion is obtained by mixing cellulose and modified cellulose in proportion; the modified cellulose is obtained by grafting nano-cellulose solution with epoxy hypophosphite compound and fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound; the structure of the modified cellulose is shown as formula 1: , formula 1.

2. The modified cellulose binder according to claim 1, wherein The preparation method of the modified cellulose comprises the following steps: S1. Furan and 1-aminomethyl maleimide hydrochloride are dissolved in toluene, and a Dean-Stark device is used for heating and refluxing to obtain an amino Diels-Alder addition product; S2. The product of step S1 and the epoxy hypophosphite compound are dissolved and mixed in tetrahydrofuran under a nitrogen atmosphere, and heated and stirred to obtain a hypophosphite-esterified amino Diels-Alder addition product; S3. The fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound is dissolved in anhydrous dichloromethane, cooled to 0℃ in an ice bath, and then dicyclohexyl carbodiimide, 4-dimethylamino pyridine are added in sequence, and the hypophosphite-esterified amino Diels-Alder addition product in anhydrous dichloromethane solution with a molar concentration of 0.1 mol / L is added dropwise; after the ice bath is removed and the reaction is completed at room temperature, a hypophosphite monomer is obtained; S4. Synthesis of polyhypophosphite: under a nitrogen atmosphere, the hypophosphite monomer obtained in step S3 and a catalyst are dissolved in toluene, ring-opening metathesis polymerization is carried out, after heating and reaction, vinyl ether is added to quench the reaction, and polyhypophosphite is obtained by recrystallization from acetone; S5. Epoxidation of polyhypophosphite: under a nitrogen atmosphere, the polyhypophosphite obtained in step S4 is dissolved in toluene, and meta-chloro peroxibenzoic acid is added and stirred to react, then excess methanol is added to precipitate the epoxidized polyhypophosphite; S6. Cellulose modification: the nano-cellulose aqueous suspension is diluted to a solution with a solid content of 0.4%~0.8% by weight, an aqueous MgCl2 solution is added, and stirred at room temperature; the epoxidized polyhypophosphite is added, stirred, and then ultrasonic dispersion is continued, and an ethylenediaminetetraacetic acid disodium salt solution is added and stirred; after standing at room temperature to remove bubbles, freeze-drying is performed to obtain a gel-like solid, and vacuum drying is performed to obtain hypophosphite-modified cellulose.

3. The modified cellulose binder according to claim 2, wherein The catalyst in step S4 is one or more of Grubbs first-generation catalyst, Grubbs second-generation catalyst, and Grubbs third-generation catalyst.

4. The modified cellulose binder according to claim 1, wherein The structure of the fluorine-containing pentaphenyl alkynyl dicarboxylic acid compound is shown as formula 2: , formula 2.

5. The modified cellulose binder of claim 1, wherein The structure of the epoxy hypophosphite compound is shown as formula 3: , formula 3.

6. The modified cellulose binder according to claim 1, wherein The VAE composite emulsion is composed of two VAE emulsions with different glass transition temperatures, one of which has a glass transition temperature lower than 0℃, and the other has a glass transition temperature higher than or equal to 0℃, and the mass ratio of the two emulsions is (0.45~0.55):(0.45~0.55); the crosslinking agent is trimethylolpropane triglycidyl ether; and the plasticizer is dipolypropylene glycol dibenzoate.

7. The modified cellulose binder according to claim 1, wherein The mass ratio of the cellulose to the modified cellulose is (1~8):

1.

8. The method of producing a modified cellulose binder according to any one of claims 1 to 7, characterized by, The preparation method comprises the following steps: (1) Preparation of modified cellulose-based emulsion: mix cellulose and modified cellulose in mixed solvent, heat and stir, ultrasonic-assisted dissolution; (2) Preparation of rosin water emulsion: add solid rosin resin to boiling water, gradually add surfactant, stir and cool to obtain rosin water emulsion; (3) Preparation of VAE composite emulsion: mix two kinds of VAE emulsion at 40℃, add silicone defoaming agent, stir to obtain VAE composite emulsion; (4) Crosslinking agent and plasticizer treatment: dilute crosslinking agent with equal volume of ethanol; preheat plasticizer to 50℃; (5) Preparation of modified cellulose adhesive: preheat the reaction kettle in a dark environment, add modified cellulose-based emulsion and VAE composite emulsion with gradient stirring, then add rosin water emulsion and stir, slowly add pretreated plasticizer, then slowly add diluted crosslinking agent, maintain temperature at 45℃, stir, vacuum degassing, adjust pH to 7, precision filtration, to obtain modified cellulose adhesive.

9. The method of producing a modified cellulose binder according to claim 8, wherein the cellulose derivative is a cellulose ether. The mixed solvent in step (1) is a mixed solvent with a volume ratio of water to NMP of 7:3; the ultrasonic-assisted parameters are set to 40 kHz and 600 W.

10. The method of producing a modified cellulose binder according to claim 8, wherein the cellulose derivative is a cellulose ether. The gradient stirring in step (5) is 80 rpm for 0-2 min, 120 rpm for 3-5 min, and 150 rpm for 6-10 min.

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