Low-temperature-resistant high-flexibility bio-based hot melt adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of hot melt adhesives, and particularly relates to a low-temperature-resistant high-flexibility bio-based hot melt adhesive and a preparation method thereof. The bio-based hot melt adhesive comprises the following components in parts by weight: 50-60 parts of dimer acid; 2-4 parts of binary acid; 25 to 30 parts of polyether amine; 5 to 6 parts of diamine; 6-8 parts of a bio-based flame retardant; 0.5 to 1 part of an antioxidant; 0.05 to 0.08 part of a catalyst; 0.2 to 0.4 part of stearic acid; the bio-based hot melt adhesive is modified by adding the bio-based flame retardant into the components of the bio-based hot melt adhesive, and the prepared bio-based hot melt adhesive has good adhesive property, mechanical property, flame retardant property and antibacterial property, and particularly has good low temperature resistance, flexibility and environmental protection property.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot melt adhesives, and in particular relates to a low-temperature resistant and highly flexible bio-based hot melt adhesive and a preparation method thereof. Background Art

[0002] Electronic packaging materials play a vital role in electronic equipment. They are used to carry electronic components and their interconnections, protect electronic components, and ensure the performance and reliability of electronic products. Common organic polymer electronic packaging materials mainly include epoxy resin, polyamide, polyphenylene sulfide, polyurethane, etc. Among them, polyamide hot melt adhesive has been widely used in the field of electronic packaging due to its good viscosity, temperature resistance, chemical corrosion resistance, mechanical properties and other advantages; traditional polyamide hot melt adhesive often faces the problem of sharp decline in flexibility and easy brittle cracking in low temperature environment, which seriously affects the reliability and stability of electronic components in cold areas or low temperature working environment. Moreover, the raw materials for the preparation of traditional polyamide hot melt adhesive are mostly petroleum-based materials, which have certain defects in environmental protection. Bio-based materials are gradually replacing petroleum-based materials and becoming a new research hotspot due to their environmentally friendly properties such as renewable and degradable.

[0003] Chinese patent application with application number CN202410620085.7 discloses a copolyamide hot melt adhesive and a preparation method thereof. The main steps are to use a condensation polymerization reaction to polycondense a dibasic acid and a diamine to form a polyamide resin, add an amino acid, a tackifying resin and an antioxidant to the polyamide resin, and obtain the copolyamide hot melt adhesive after heating and stirring. The preparation method can accurately control the molecular structure and properties of the polyamide resin. By adding isocyanate during the preparation process, the mechanical strength and adhesion of the copolyamide hot melt adhesive are improved, but the flexibility and environmental performance of the obtained copolyamide hot melt adhesive are insufficient; Chinese patent application with application number CN202410912884.1 discloses a A high-performance bio-based polyamide hot melt adhesive is prepared by reacting the following parts by weight: 2-5 parts of diamine, 20-40 parts of dimer acid, 2-8 parts of dibasic acid, 10-20 parts of modifier, and 0.05-0.1 parts of phosphoric acid catalyst, wherein the modifier is prepared by reacting 2-[allyl(2-hydroxyethyl)amino]-1-ethanol, tripropylene glycol ether, and diethylene glycol adipate. The bio-based raw material dimer acid can improve the environmental friendliness of the bio-based polyamide hot melt adhesive, but the obtained bio-based polyamide hot melt adhesive still has the problem of insufficient flexibility and cannot meet the requirement of high flexibility. Therefore, it is necessary to develop a bio-based electronic packaging hot melt adhesive that is resistant to low temperatures, highly flexible, and environmentally friendly to meet market demand. Summary of the invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and provide a low-temperature resistant and highly flexible bio-based hot melt adhesive and a preparation method thereof. By adding a bio-based flame retardant to the bio-based hot melt adhesive component, the bio-based hot melt adhesive is modified. The prepared bio-based hot melt adhesive has good bonding properties, mechanical properties, flame retardant properties and antibacterial properties, especially low-temperature resistance, flexibility and environmental protection performance.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: A low-temperature-resistant and highly flexible bio-based hot melt adhesive, the bio-based hot melt adhesive comprising the following components in parts by weight: 50-60 parts of dimer acid; 2-4 parts of dibasic acid; 25-30 parts of polyether amine; 5-6 parts of diamine; 6-8 parts of bio-based flame retardant; 0.5-1 part of antioxidant; 0.05-0.08 part of catalyst; and 0.2-0.4 part of stearic acid.

[0006] Furthermore, the dibasic acid is any one of sebacic acid, azelaic acid, and dodecanedioic acid, or a mixture of several of them.

[0007] Furthermore, the diamine is any one of ethylenediamine, pentanediamine and hexamethylenediamine, or a mixture of several of them.

[0008] Furthermore, the antioxidant is antioxidant 1010 or antioxidant 1076.

[0009] Furthermore, the catalyst is propionic acid or phosphorous acid.

[0010] In the technical solution of the present invention, the preparation method of the bio-based flame retardant is: add carboxymethyl chitosan to a reaction container containing a solvent, stir evenly, add flame retardant dimethyl hydantoin and triethylamine, stir and react for 5-6 hours at a temperature of 70-75°C to obtain the bio-based flame retardant.

[0011] Furthermore, the mass ratio of the carboxymethyl chitosan, the flame retardant dimethyl hydantoin and the triethylamine is 1:0.4-0.5:0.1-0.15; and the solvent is a 50-60wt% ethanol solution.

[0012] In the technical solution of the present invention, the flame retardant dimethyl hydantoin is prepared by reacting p-chloroaniline as a raw material with 5,5-dimethyl hydantoin, epichlorohydrin, 3-bromopropanol, diethylphosphite chloride and sodium hypochlorite in sequence; the preparation method is: S1. Add 5,5-dimethylhydantoin and potassium hydroxide to a reaction vessel containing water and acetonitrile, stir for 5-10 minutes, then add p-chloroaniline, and react at a temperature of 75-80° C. for 7-8 hours to obtain dimethylhydantoin-aniline; S2, adding dimethyl hydantoin-aniline to a reaction vessel containing chloroform, stirring evenly, slowly dropping epichlorohydrin, after the dropping is complete, reacting at a temperature of 35-40°C for 4-5h, then adding 3-bromopropanol and triethylamine, and continuing the reaction at a temperature of 50-60°C for 5-6h to obtain hydroxylated dimethyl hydantoin; S3. Add hydroxylated dimethylhydantoin and triethylamine to a reaction vessel containing anhydrous chloroform, stir evenly, place in an ice bath, slowly drop diethylphosphite chloride, continue to react for 4-5 hours after the addition is complete, and detect the completion of the reaction by TLC. Naturally warm to room temperature, add sodium hypochlorite, and stir the reaction for 1-2 hours to obtain flame retardant dimethylhydantoin.

[0013] Furthermore, in step S1, the molar ratio of p-chloroaniline, 5,5-dimethylhydantoin and potassium hydroxide is 1:1-1.1:1.2-1.3.

[0014] Furthermore, in step S2, the molar ratio of dimethylhydantoin-aniline, epichlorohydrin, 3-bromopropanol and triethylamine is 1:1-1.1:1.1-1.2:1.3-1.5.

[0015] Furthermore, in step S3, the molar ratio of hydroxylated dimethyl hydantoin, diethylphosphite chloride, triethylamine and sodium hypochlorite is 1:2.1-2.2:1.5-1.8:1.3-1.5.

[0016] The invention provides a preparation method of a low-temperature resistant and highly flexible bio-based hot melt adhesive, comprising the following steps: adding dimer acid, dibasic acid, polyether amine, bio-based flame retardant, antioxidant and catalyst into a reaction kettle according to weight proportion, stirring evenly, slowly dropping diamine at a temperature of 100° C., heating to 130-140° C. after the dropping is completed, stirring and reacting for 1-2 hours, continuing to heat to 220-230° C., stirring and reacting for 1-1.5 hours, adding stearic acid, evacuating to a vacuum degree of -0.092 MPa, continuing to stir and react for 0.5-1 hour, and cooling to obtain the bio-based hot melt adhesive.

[0017] The present invention has the following beneficial effects: 1. The present invention utilizes the amino group in carboxymethyl chitosan to react with the chlorinated hydrocarbon group in the flame-retardant dimethyl hydantoin, and grafts the flame-retardant dimethyl hydantoin onto the carboxymethyl chitosan to obtain a bio-based flame retardant. The bio-based flame retardant prepared by the present invention is a carboxymethyl chitosan with surface grafted flame-retardant bisphosphite groups, antibacterial chlorodimethyl hydantoin groups, and benzene ring groups. The present invention adds the bio-based flame retardant to the bio-based hot melt adhesive component, which has a strong binding effect in the bio-based hot melt adhesive. The flame-retardant bisphosphite group effectively improves the flame retardant properties of the bio-based hot melt adhesive. The antibacterial chlorodimethyl hydantoin group and the carboxymethyl chitosan molecule which has antibacterial effect itself synergistically enhance the antibacterial properties of the bio-based hot melt adhesive. The benzene ring group has good low-temperature stability, which also helps to improve the low-temperature resistance of the bio-based hot melt adhesive.

[0018] 2. The present invention adopts bio-based dimer acid as the main raw material of bio-based hot melt adhesive. Its long-chain structure gives the bio-based hot melt adhesive good flexibility and low-temperature resistance. The addition of long-chain dibasic acid can further improve the flexibility of the hot melt adhesive. Moreover, the bio-based dimer acid has good biodegradability, which gives the bio-based hot melt adhesive good environmental protection. The bio-based flame retardant of the present invention is based on carboxymethyl chitosan with good biocompatibility and degradability as the main structure, which further enhances the environmental protection performance of the bio-based hot melt adhesive.

[0019] 3. The present invention achieves the modification of bio-based hot melt adhesive by adding bio-based flame retardant to the bio-based hot melt adhesive component. The prepared bio-based hot melt adhesive has good bonding properties, mechanical properties, flame retardant properties and antibacterial properties, especially low temperature resistance, flexibility and environmental protection performance. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] In the technical scheme of the present invention, the chemical reagents used are all commercially available, including dimer acid CAS No. 61788-89-4, polyetheramine CAS No. 9046-10-0, sebacic acid CAS No. 111-20-6, azelaic acid CAS No. 123-99-9, dodecanedioic acid CAS No. 693-23-2, ethylenediamine CAS No. 107-15-3, pentamethylenediamine CAS No. 462-94-2, hexamethylenediamine CAS No. 124-09-4, antioxidant 1010 CAS No. 6683-19-8, antioxidant 1076 CAS No. 2082-79-3, propionic acid CAS No. 79-09-4, phosphorous acid CAS No. 10294-56-1, stearic acid CAS No. 57-11-4, carboxymethyl chitosan CAS No. 83512-85-0 (molecular weight 8.5kDa, deacetylation degree 90%, carboxymethylation degree 85%), p-aminobenzyl chloride CAS No. 65581-19-3, 5,5-dimethylhydantoin CAS No. 77-71-4, potassium hydroxide CAS No. 1310-58-3, epichlorohydrin CAS No. 106-89-8, 3-bromopropanol CAS No. 627-18-9, triethylamine CAS No. 121-44-8, diethylphosphite chloride CAS No. 589-57-1, sodium hypochlorite CAS No. 7681-52-9, acetonitrile CAS No. 75-05-8, chloroform CAS No. 67-66-3, ethyl acetate CAS No. 141-78-6, ethanol CAS No. 64-17-5.

[0022] Embodiment 1 This embodiment provides a method for preparing flame-retardant dimethyl hydantoin. The flame-retardant dimethyl hydantoin is prepared by reacting p-chloroaniline as a raw material with 5,5-dimethyl hydantoin, epichlorohydrin, 3-bromopropanol, diethylphosphite chloride, and sodium hypochlorite in sequence. The preparation method is: S1. Add 19.9 g of 5,5-dimethylhydantoin and 10.3 g of potassium hydroxide to a reaction vessel containing 300 mL of water and 400 mL of acetonitrile, stir for 10 min, then add 20.0 g of p-chloroaniline, react at 75° C. for 8 h, TLC detection shows that the reaction is complete, remove acetonitrile, add ethyl acetate for extraction, and concentrate the organic phase under reduced pressure to obtain 25.6 g of dimethylhydantoin-aniline; wherein the molar ratio of p-chloroaniline, 5,5-dimethylhydantoin and potassium hydroxide is 1:1.05:1.3; the reaction process is: ; Dimethylhydantoin-aniline: ESI (m / z): 220.2 [M+H] + , 1H-NMR (600MHz, DMSO-d6, δppm): 10.86 (s, 1H), 7.12 (d, J=8.4Hz, 2H), 6.22 (d, J=8.4Hz, 2H), 4.52 (s, 2H), 1.48 (s, 6H).

[0023] S2, 25.0g of dimethyl hydantoin-aniline was added to a reaction vessel containing 600mL of chloroform, stirred evenly, 11.1g of epichlorohydrin was slowly added dropwise, and after completion of the addition, the reaction was carried out at a temperature of 40°C for 4h, and then 17.4g of 3-bromopropanol and 15.0g of triethylamine were added, and the reaction was continued for 5h at a temperature of 60°C. The reaction was completed by TLC detection, chloroform was removed, water and ethyl acetate were added for extraction, and the organic phase was concentrated under reduced pressure to obtain hydroxylated dimethyl hydantoin; wherein the molar ratio of dimethyl hydantoin-aniline, epichlorohydrin, 3-bromopropanol and triethylamine was 1:1.05:1.1:1.3; the reaction process was: ; Hydroxylated dimethylhydantoin: ESI (m / z): 370.9 [M+H] + , 1 H-NMR (600MHz, DMSO-d6, δppm): 10.84 (s, 1H), 7.09 (d, J=8.4Hz, 2H), 6.90 (d, J=8.4Hz, 2H), 5.37 (s, 1H) , 4.43 (s, 1H), 3.86-3.90 (m, 1H), 3.52-3.63 (m, 4H), 3.33-3.38 (m, 4H), 1.72-1.79 (m, 2H), 1.49 (s, 6H).

[0024] S3, add 29.0g hydroxylated dimethyl hydantoin and 11.9g triethylamine to a reaction vessel containing 400mL anhydrous chloroform, stir evenly, place in an ice bath, slowly drop 25.8g diethylphosphite chloride, after the dropwise addition is complete, continue to react for 5h, TLC detection reaction is complete, naturally warm to room temperature, add 7.6g sodium hypochlorite, stir to react for 1h, remove chloroform, add water and ethyl acetate for extraction, and concentrate the organic phase under reduced pressure to obtain 41.5g flame retardant dimethyl hydantoin; wherein the molar ratio of hydroxylated dimethyl hydantoin, diethylphosphite chloride, triethylamine, and sodium hypochlorite is 1:2.1:1.5:1.3; the reaction process is: ; Flame retardant dimethyl hydantoin: ESI (m / z): 645.5 [M+H] + , 1H-NMR (600MHz, DMSO-d6, δppm): 7.10 (d, J=8.4Hz, 2H), 6.91 (d, J=8.4Hz, 2H), 3.80-3.9 0 (m, 11H), 3.60-3.65 (m, 2H), 3.32-3.38 (m, 4H), 1.71-1.78 (m, 8H), 1.25-1.30 (m, 12H).

[0025] Embodiment 2 A low-temperature-resistant and highly flexible bio-based hot melt adhesive comprises the following components in parts by weight: 60 parts of dimer acid; 4 parts of dibasic acid; 28 parts of polyether amine; 6 parts of diamine; 8 parts of bio-based flame retardant; 1 part of antioxidant; 0.08 parts of catalyst; 0.4 parts of stearic acid; wherein the dibasic acid is sebacic acid; the diamine is ethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is propionic acid.

[0026] The preparation method of the bio-based flame retardant is as follows: carboxymethyl chitosan is added to a reaction container containing a solvent, stirred evenly, flame-retardant dimethyl hydantoin and triethylamine are added, and the reaction is stirred for 5 hours at a temperature of 75°C. After the reaction is completed, the temperature is naturally lowered to room temperature, the pH is adjusted to be neutral, and the mixture is added dropwise to acetone for precipitation, filtered, and the product is washed with acetone and dried to obtain the bio-based flame retardant; the degree of substitution of flame-retardant dimethyl hydantoin is determined to be 13.4% by elemental analysis; the mass ratio of carboxymethyl chitosan, flame-retardant dimethyl hydantoin and triethylamine is 1:0.5:0.15; the solvent is a 60wt% ethanol solution; and the amount of the solvent is 30 times the mass of the carboxymethyl chitosan.

[0027] A method for preparing a low-temperature resistant and highly flexible bio-based hot melt adhesive comprises the following steps: adding dimer acid, dibasic acid, polyether amine, bio-based flame retardant, antioxidant and catalyst into a reaction kettle according to weight proportion, stirring evenly, slowly dropping diamine at a temperature of 100°C, heating to 140°C after the dropping is completed, stirring and reacting for 1 hour, continuing to heat to 225°C, stirring and reacting for 1.5 hours, adding stearic acid, evacuating to a vacuum degree of -0.092MPa, continuing to stir and react for 0.5 hours, and obtaining the bio-based hot melt adhesive after cooling.

[0028] Embodiment 3 A low-temperature-resistant and highly flexible bio-based hot melt adhesive comprises the following components in parts by weight: 55 parts of dimer acid; 3 parts of dibasic acid; 30 parts of polyether amine; 5.5 parts of diamine; 7 parts of bio-based flame retardant; 0.8 parts of antioxidant; 0.07 parts of catalyst; 0.3 parts of stearic acid; wherein the dibasic acid is dodecanedioic acid; the diamine is pentamethylenediamine; the antioxidant is antioxidant 1076; and the catalyst is phosphorous acid.

[0029] The preparation method of the bio-based flame retardant is as follows: carboxymethyl chitosan is added to a reaction container containing a solvent, stirred evenly, flame-retardant dimethyl hydantoin and triethylamine are added, and the reaction is stirred for 6 hours at a temperature of 70°C. After the reaction is completed, the reaction is naturally cooled to room temperature, the pH is adjusted to be neutral, and the reaction is dropped into acetone for precipitation, filtered, and the product is washed with acetone and dried to obtain the bio-based flame retardant; the substitution degree of the flame-retardant dimethyl hydantoin is determined to be 12.8% by elemental analysis; the mass ratio of carboxymethyl chitosan, flame-retardant dimethyl hydantoin and triethylamine is 1:0.45:0.12; the solvent is a 50wt% ethanol solution; and the amount of the solvent is 30 times the mass of the carboxymethyl chitosan.

[0030] A method for preparing a low-temperature resistant and highly flexible bio-based hot melt adhesive comprises the following steps: adding dimer acid, dibasic acid, polyether amine, bio-based flame retardant, antioxidant and catalyst into a reaction kettle according to weight proportion, stirring evenly, slowly dropping diamine at a temperature of 100°C, heating to 135°C after the dropping is completed, stirring and reacting for 1.5 hours, continuing to heat to 230°C, stirring and reacting for 1 hour, adding stearic acid, evacuating to a vacuum degree of -0.092MPa, continuing to stir and react for 1 hour, and obtaining the bio-based hot melt adhesive after cooling.

[0031] Embodiment 4 A low-temperature-resistant and highly flexible bio-based hot melt adhesive comprises the following components in parts by weight: 50 parts of dimer acid; 2 parts of dibasic acid; 25 parts of polyether amine; 5 parts of diamine; 6 parts of bio-based flame retardant; 0.5 parts of antioxidant; 0.05 parts of catalyst; 0.2 parts of stearic acid; wherein the dibasic acid is azelaic acid; the diamine is hexamethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is phosphorous acid.

[0032] The preparation method of the bio-based flame retardant is as follows: carboxymethyl chitosan is added to a reaction container containing a solvent, stirred evenly, flame-retardant dimethyl hydantoin and triethylamine are added, and the reaction is stirred for 5.5 hours at a temperature of 73°C. After the reaction is completed, the temperature is naturally lowered to room temperature, the pH is adjusted to be neutral, and the mixture is added dropwise to acetone for precipitation, filtered, and the product is washed with acetone and dried to obtain the bio-based flame retardant; the degree of substitution of flame-retardant dimethyl hydantoin is determined to be 12.1% by elemental analysis; the mass ratio of carboxymethyl chitosan, flame-retardant dimethyl hydantoin and triethylamine is 1:0.4:0.1; the solvent is a 55wt% ethanol solution; and the amount of the solvent is 30 times the mass of the carboxymethyl chitosan.

[0033] A method for preparing a low-temperature resistant and highly flexible bio-based hot melt adhesive comprises the following steps: adding dimer acid, dibasic acid, polyether amine, bio-based flame retardant, antioxidant and catalyst into a reaction kettle according to weight proportion, stirring evenly, slowly dropping diamine at a temperature of 100°C, heating to 130°C after the dropping is completed, stirring and reacting for 2h, continuing to heat to 220°C, stirring and reacting for 1.2h, adding stearic acid, evacuating to a vacuum degree of -0.092MPa, continuing to stir and react for 0.8h, and obtaining the bio-based hot melt adhesive after cooling.

[0034] Comparative Example 1 Compared with Example 2, the bio-based flame retardant in this comparative example consists of carboxymethyl chitosan and flame-retardant dimethyl hydantoin.

[0035] A low-temperature-resistant and highly flexible bio-based hot melt adhesive comprises the following components in parts by weight: 60 parts of dimer acid; 4 parts of dibasic acid; 28 parts of polyether amine; 6 parts of diamine; 8 parts of bio-based flame retardant; 1 part of antioxidant; 0.08 parts of catalyst; 0.4 parts of stearic acid; wherein the dibasic acid is sebacic acid; the diamine is ethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is propionic acid.

[0036] The bio-based flame retardant is composed of carboxymethyl chitosan and flame retardant dimethyl hydantoin, wherein the amount of flame retardant dimethyl hydantoin is 13.4% of the total mass of the bio-based flame retardant.

[0037] The preparation method of a low-temperature resistant and highly flexible bio-based hot melt adhesive is the same as that of Example 2.

[0038] Comparative Example 2 Compared with Example 2, the bio-based flame retardant in the bio-based hot melt adhesive component in this comparative example is carboxymethyl chitosan.

[0039] A low-temperature-resistant and highly flexible bio-based hot melt adhesive comprises the following components in parts by weight: 60 parts of dimer acid; 4 parts of dibasic acid; 28 parts of polyether amine; 6 parts of diamine; 8 parts of bio-based flame retardant; 1 part of antioxidant; 0.08 parts of catalyst; 0.4 parts of stearic acid; wherein the dibasic acid is sebacic acid; the diamine is ethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is propionic acid.

[0040] The bio-based flame retardant is carboxymethyl chitosan.

[0041] The preparation method of a low-temperature resistant and highly flexible bio-based hot melt adhesive is the same as that of Example 2.

[0042] Comparative Example 3 Compared with Example 2, the bio-based hot melt adhesive component in this comparative example does not contain a bio-based flame retardant.

[0043] A low-temperature-resistant and highly flexible bio-based hot melt adhesive comprises the following components in parts by weight: 60 parts of dimer acid; 4 parts of dibasic acid; 28 parts of polyether amine; 6 parts of diamine; 1 part of antioxidant; 0.08 parts of catalyst; 0.4 parts of stearic acid; wherein the dibasic acid is sebacic acid; the diamine is ethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is propionic acid.

[0044] The preparation method of a low-temperature resistant and highly flexible bio-based hot melt adhesive is the same as that of Example 2.

[0045] Performance Testing The performance tests were conducted on the bio-based hot melt adhesives prepared in Examples 2 to 4 and Comparative Examples 1 to 3, wherein the viscosity test was conducted in accordance with GB / T 2794-1995 standard and measured by a rotational viscometer; the tensile strength test was conducted in accordance with GB / T 7124-2008 standard; the elongation at break test was conducted in accordance with GB / T 1040.3-2006 standard; the shear strength test was conducted by first making the bio-based hot melt adhesive into a 12.5 mm × 25 mm thin film with a thickness of 2 mm, placing it between aluminum sheet substrates, baking it in an oven at 120° C. for 30 min, cooling it to room temperature, and testing the shear force of the sample at 20° C. and -20° C. using a UTM2502 electronic universal testing machine; the limiting oxygen index test was conducted in accordance with GB / T 2406-2009 standard; the antibacterial property test was conducted by using the inhibition zone method, first making the bio-based hot melt adhesive into a 5 mm diameter, 1 mm thick adhesive layer disc, and evenly coating 200 μL of activated bacterial solution (the same amount of concentration was 10 6 cfu / mL of Staphylococcus aureus suspension and Escherichia coli suspension), the gelatin disc was placed in the center of the culture dish, cultured in a cell culture incubator at 37°C for 24 hours, and the diameter of the inhibition zone was measured; the test results are shown in Table 1 below.

[0046] Table 1 Performance test results From the results in Table 1, it can be seen that the viscosity, tensile strength, elongation at break, shear strength at 20°C and -20°C, limiting oxygen index and inhibition zone diameter of the bio-based hot melt adhesive prepared in Examples 2 to 4 are all greater than those in Comparative Examples 1 to 3, indicating that the bio-based hot melt adhesive prepared in the present invention has good bonding properties, mechanical properties, flame retardant properties and antibacterial properties, especially good low temperature resistance and flexibility; compared with Comparative Example 1, the bio-based flame retardant in Example 2 of the present invention is carboxymethyl chitosan grafted flame retardant dimethyl hydantoin, and the two are connected by chemical bonds in the bio-based hot melt The invention has a strong bonding effect in the adhesive, which helps to improve the comprehensive performance of the bio-based hot melt adhesive. Compared with comparative examples 2 to 3, the carboxymethyl chitosan in the bio-based flame retardant in Example 2 of the present invention is grafted with flame-retardant dimethyl hydantoin containing a flame-retardant bisphosphite group, an antibacterial chlorodimethyl hydantoin group, and a benzene ring group, and is added to the bio-based hot melt adhesive component, which effectively improves the flame retardant and antibacterial properties of the bio-based hot melt adhesive. The low-temperature stability of the benzene ring is good, which not only adjusts the mechanical properties of the bio-based hot melt adhesive, but also improves the low-temperature resistance of the bio-based hot melt adhesive.

[0047] It should be noted that, in this article, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0048] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low temperature resistant and highly flexible bio-based hot melt adhesive, characterized in that: The bio-based hot melt adhesive comprises the following components by weight: 50-60 parts of dimer acid; 2-4 parts of dibasic acid; 25-30 parts of polyether amine; 5-6 parts of diamine; 6-8 parts of bio-based flame retardant; 0.5-1 parts of antioxidant; 0.05-0.08 parts of catalyst; 0.2-0.4 parts of stearic acid; The preparation method of the bio-based flame retardant is as follows: adding carboxymethyl chitosan into a reaction container containing a solvent, stirring evenly, adding flame-retardant dimethyl hydantoin and triethylamine, stirring and reacting for 5-6 hours at a temperature of 70-75°C, and obtaining the bio-based flame retardant; the flame-retardant dimethyl hydantoin is prepared by reacting p-chloroaniline as a raw material with 5,5-dimethyl hydantoin, epichlorohydrin, 3-bromopropanol, diethylphosphite chloride, and sodium hypochlorite in sequence.

2. The low temperature resistant and highly flexible bio-based hot melt adhesive according to claim 1, characterized in that: The preparation method of the flame retardant dimethyl hydantoin is: S1. Add 5,5-dimethylhydantoin and potassium hydroxide to a reaction vessel containing water and acetonitrile, stir for 5-10 minutes, then add p-chloroaniline, and react at a temperature of 75-80° C. for 7-8 hours to obtain dimethylhydantoin-aniline; S2, adding dimethyl hydantoin-aniline to a reaction vessel containing chloroform, stirring evenly, slowly dropping epichlorohydrin, after the dropping is complete, reacting at a temperature of 35-40°C for 4-5h, then adding 3-bromopropanol and triethylamine, and continuing the reaction at a temperature of 50-60°C for 5-6h to obtain hydroxylated dimethyl hydantoin; S3. Add hydroxylated dimethylhydantoin and triethylamine to a reaction vessel containing anhydrous chloroform, stir evenly, place in an ice bath, slowly drop diethylphosphite chloride, continue to react for 4-5 hours after the addition is complete, and detect the completion of the reaction by TLC. Naturally warm to room temperature, add sodium hypochlorite, and stir the reaction for 1-2 hours to obtain flame retardant dimethylhydantoin.

3. The low temperature resistant and highly flexible bio-based hot melt adhesive according to claim 2, characterized in that: The molar ratio of p-chloroaniline, 5,5-dimethylhydantoin and potassium hydroxide in step S1 is 1:1-1.1:1.2-1.

3.

4. The low temperature resistant and highly flexible bio-based hot melt adhesive according to claim 2, characterized in that: The molar ratio of dimethylhydantoin-aniline, epichlorohydrin, 3-bromopropanol and triethylamine in step S2 is 1:1-1.1:1.1-1.2:1.3-1.

5.

5. The low temperature resistant and highly flexible bio-based hot melt adhesive according to claim 2, characterized in that: The molar ratio of hydroxylated dimethyl hydantoin, diethylphosphite chloride, triethylamine and sodium hypochlorite in step S3 is 1:2.1-2.2:1.5-1.8:1.3-1.

5.

6. The low temperature resistant and highly flexible bio-based hot melt adhesive according to claim 1, characterized in that: In the preparation method of the bio-based flame retardant, the mass ratio of the carboxymethyl chitosan, the flame retardant dimethyl hydantoin and the triethylamine is 1:0.4-0.5:0.1-0.15; and the solvent is a 50-60wt% ethanol solution.

7. The low temperature resistant and highly flexible bio-based hot melt adhesive according to claim 1, characterized in that: The dibasic acid is any one of sebacic acid, azelaic acid and dodecanedioic acid or a mixture of several of them.

8. The low temperature resistant and highly flexible bio-based hot melt adhesive according to claim 1, characterized in that: The diamine is any one of ethylenediamine, pentanediamine and hexamethylenediamine or a mixture of several of them.

9. The low temperature resistant and highly flexible bio-based hot melt adhesive according to claim 1, characterized in that: The antioxidant is antioxidant 1010 or antioxidant 1076; the catalyst is propionic acid or phosphorous acid.

10. A method for preparing a low temperature resistant and highly flexible bio-based hot melt adhesive according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: adding dimer acid, dibasic acid, polyetheramine, bio-based flame retardant, antioxidant and catalyst into a reaction kettle according to weight proportion, stirring evenly, slowly dropping diamine at a temperature of 100°C, heating to 130-140°C after the dropping is completed, stirring and reacting for 1-2h, continuously heating to 220-230°C, stirring and reacting for 1-1.5h, adding stearic acid, evacuating to a vacuum degree of -0.092MPa, continuously stirring and reacting for 0.5-1h, and obtaining a bio-based hot melt adhesive after cooling.

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