A low-temperature-resistant and highly flexible bio-based hot melt adhesive and its preparation method

Abstract

The present invention belongs to the field of hot melt adhesive technology and specifically relates to a low-temperature-resistant, highly flexible bio-based hot melt adhesive and its preparation method. The bio-based hot melt adhesive comprises the following components by weight: 50-60 parts dimer acid; 2-4 parts dibasic acid; 25-30 parts polyetheramine; 5-6 parts diamine; 6-8 parts bio-based flame retardant; 0.5-1 part antioxidant; 0.05-0.08 parts catalyst; and 0.2-0.4 parts stearic acid. The present invention modifies the bio-based hot melt adhesive by adding a bio-based flame retardant to the bio-based hot melt adhesive components. The resulting bio-based hot melt adhesive has excellent bonding, mechanical, flame retardant, and antibacterial properties, particularly low-temperature resistance, flexibility, and environmental performance.

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 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 adhesion, temperature resistance, chemical corrosion resistance, mechanical properties and other advantages; traditional polyamide hot melt adhesive often faces the problem of a sharp drop in flexibility and easy brittle cracking in low temperature environments, which seriously affects the reliability and stability of electronic components in cold areas or low-temperature working environments. 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 renewability and degradability.

[0003] Chinese patent 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 condense 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 copolyamide hot melt adhesive obtained are insufficient; Chinese patent 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 a diamine, 20-40 parts of a dimer acid, 2-8 parts of a dibasic acid, 10-20 parts of a modifier, and 0.05-0.1 parts of a phosphoric acid catalyst. 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 requirements of high flexibility. Therefore, it is necessary to develop a bio-based electronic packaging hot melt adhesive that is both low-temperature resistant, 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 existing technology 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 good low-temperature resistance, flexibility and environmental protection performance.

[0005] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0006] A low-temperature-resistant and highly flexible bio-based hot melt adhesive comprises the following components in parts by weight: 50-60 parts of dimer acid; 2-4 parts of dibasic acid; 25-30 parts of polyetheramine; 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.

[0007] Furthermore, the dibasic acid is any one of sebacic acid, azelaic acid, and dodecanedioic acid, or a mixture of several of them.

[0008] Furthermore, the diamine is any one of ethylenediamine, pentamethylenediamine, and hexamethylenediamine, or a mixture of several of them.

[0009] Furthermore, the antioxidant is antioxidant 1010 or antioxidant 1076.

[0010] Furthermore, the catalyst is propionic acid or phosphorous acid.

[0011] In the technical solution of the present invention, the preparation method of the bio-based flame retardant is as follows: carboxymethyl chitosan is added to a reaction vessel containing a solvent, stirred evenly, flame retardant dimethyl hydantoin and triethylamine are added, and stirred and reacted at a temperature of 70-75°C for 5-6 hours to obtain the bio-based flame retardant.

[0012] Furthermore, the mass ratio of the carboxymethyl chitosan, the flame retardant dimethyl hydantoin, and triethylamine is 1:0.4-0.5:0.1-0.15; and the solvent is a 50-60wt% ethanol solution.

[0013] 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:

[0014] 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;

[0015] S2. Add dimethylhydantoin-aniline to a reaction vessel containing chloroform, stir evenly, slowly add epichlorohydrin dropwise, and after completion of the addition, react at a temperature of 35-40° C. for 4-5 hours, then add 3-bromopropanol and triethylamine, and continue the reaction at a temperature of 50-60° C. for 5-6 hours to obtain hydroxylated dimethylhydantoin;

[0016] S3. Add hydroxylated dimethyl hydantoin and triethylamine to a reaction vessel containing anhydrous chloroform, stir evenly, place in an ice bath, and slowly dropwise add diethylphosphite chloride. After the addition is complete, continue the reaction for 4-5 hours. After TLC detection, the reaction is complete. Naturally warm to room temperature, add sodium hypochlorite, and stir the reaction for 1-2 hours to obtain flame-retardant dimethyl hydantoin.

[0017] 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.

[0018] 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.

[0019] Furthermore, in step S3, the molar ratio of hydroxylated dimethylhydantoin, diethylphosphite chloride, triethylamine, and sodium hypochlorite is 1:2.1-2.2:1.5-1.8:1.3-1.5.

[0020] The present 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, polyetheramine, bio-based flame retardant, antioxidant, and catalyst into a reactor in proportion by weight, stirring evenly, slowly dropping diamine at a temperature of 100° C., heating to 130-140° C. after the dropwise addition 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.

[0021] The present invention has the following beneficial effects:

[0022] 1. The present invention utilizes the amino group in carboxymethyl chitosan to react with the chlorinated hydrocarbon group in flame-retardant dimethyl hydantoin to graft the flame-retardant dimethyl hydantoin onto the carboxymethyl chitosan to prepare a bio-based flame retardant. The bio-based flame retardant prepared by the present invention is a carboxymethyl chitosan with flame-retardant bisphosphite groups, antibacterial chlorinated dimethyl hydantoin groups, and benzene ring groups grafted on the surface. 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 chlorinated dimethyl hydantoin group and the carboxymethyl chitosan molecule with 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.

[0023] 2. The present invention uses 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.

[0024] 3. The present invention achieves the modification of bio-based hot melt adhesive by adding bio-based flame retardants to the bio-based hot melt adhesive components. The obtained 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

[0025] 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 below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of 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.

[0026] In the technical solution 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. 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, and ethanol CAS No. 64-17-5.

[0027] Example 1

[0028] This embodiment provides a method for preparing flame-retardant dimethyl hydantoin. 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 as follows:

[0029] 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, and react at 75° C. for 8 h. The reaction is completed by TLC detection. Acetonitrile is removed, and ethyl acetate is added for extraction. The organic phase is concentrated 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:

[0030] ;

[0031] 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).

[0032] S2, 25.0g dimethyl hydantoin-aniline is joined in the reaction vessel containing 600mL chloroform, stir, 11.1g epichlorohydrin is slowly added dropwise, after completion of the dropwise addition, at a temperature of 40 ℃, the reaction is carried out for 4h, then 17.4g 3-bromopropanol and 15.0g triethylamine are added, at a temperature of 60 ℃, the reaction is continued for 5h, TLC detection reaction is complete, chloroform is removed, water and ethyl acetate are added for extraction, and the organic phase is concentrated under reduced pressure to obtain hydroxylated dimethyl hydantoin; wherein the mol ratio of dimethyl hydantoin-aniline, epichlorohydrin, 3-bromopropanol and triethylamine is 1:1.05:1.1:1.3; The reaction process is:

[0033] ;

[0034] 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).

[0035] S3, 29.0g hydroxylated dimethyl hydantoin and 11.9g triethylamine were added to a reaction vessel containing 400mL of anhydrous chloroform, stirred evenly, placed in an ice bath, and 25.8g of diethylphosphite chloride was slowly added dropwise. After the addition was complete, the reaction was continued for 5h. The reaction was completed by TLC detection. The temperature was naturally raised to room temperature, and 7.6g of sodium hypochlorite was added. The reaction was stirred for 1h, chloroform was removed, water and ethyl acetate were added for extraction, and the organic phase was concentrated under reduced pressure to obtain 41.5g of flame-retardant dimethyl hydantoin; wherein the molar ratio of hydroxylated dimethyl hydantoin, diethylphosphite chloride, triethylamine and sodium hypochlorite was 1:2.1:1.5:1.3; the reaction process was:

[0036] ;

[0037] Flame retardant dimethyl hydantoin: ESI (m / z): 645.5 [M+H] + ,1 H-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).

[0038] Example 2

[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 polyetheramine; 6 parts of diamine; 8 parts of bio-based flame retardant; 1 part of antioxidant; 0.08 parts of catalyst; and 0.4 parts of stearic acid. The dibasic acid is sebacic acid; the diamine is ethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is propionic acid.

[0040] The preparation method of the bio-based flame retardant is as follows: carboxymethyl chitosan is added to a reaction vessel containing a solvent, stirred evenly, flame-retardant dimethyl hydantoin and triethylamine are added, and the mixture is stirred and reacted at a temperature of 75°C for 5 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, the pH is adjusted to neutral, and the mixture is dropwise added 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 the flame-retardant dimethyl hydantoin is determined to be 13.4% by elemental analysis; the mass ratio of the 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.

[0041] 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, polyetheramine, bio-based flame retardant, antioxidant, and catalyst into a reactor in proportion by weight, stirring evenly, slowly adding diamine dropwise at a temperature of 100° C., heating to 140° C. after the addition is complete, 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 -0.092 MPa, continuing to stir and react for 0.5 hour, and cooling to obtain the bio-based hot melt adhesive.

[0042] Example 3

[0043] 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 polyetheramine; 5.5 parts of diamine; 7 parts of bio-based flame retardant; 0.8 parts of antioxidant; 0.07 parts of catalyst; and 0.3 parts of stearic acid. The dibasic acid is dodecanedioic acid; the diamine is pentamethylenediamine; the antioxidant is antioxidant 1076; and the catalyst is phosphorous acid.

[0044] The preparation method of the bio-based flame retardant is as follows: carboxymethyl chitosan is added to a reaction vessel containing a solvent, stirred evenly, flame-retardant dimethyl hydantoin and triethylamine are added, and the mixture is stirred and reacted at a temperature of 70°C for 6 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, the pH is adjusted to neutral, and the mixture is dropwise added 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 the flame-retardant dimethyl hydantoin is determined to be 12.8% by elemental analysis; the mass ratio of the 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.

[0045] 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, polyetheramine, bio-based flame retardant, antioxidant, and catalyst into a reactor in proportion by weight, stirring evenly, slowly adding diamine dropwise at a temperature of 100° C., heating to 135° C. after the addition is complete, stirring and reacting for 1.5 hours, continuously heating to 230° C., stirring and reacting for 1 hour, adding stearic acid, evacuating to a vacuum degree of -0.092 MPa, continuing to stir and react for 1 hour, and cooling to obtain the bio-based hot melt adhesive.

[0046] Example 4

[0047] 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 polyetheramine; 5 parts of diamine; 6 parts of bio-based flame retardant; 0.5 parts of antioxidant; 0.05 parts of catalyst; and 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.

[0048] The preparation method of the bio-based flame retardant is as follows: carboxymethyl chitosan is added to a reaction vessel containing a solvent, stirred evenly, flame-retardant dimethyl hydantoin and triethylamine are added, and the mixture is stirred and reacted at a temperature of 73°C for 5.5 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, the pH is adjusted to neutral, and the mixture is dropwise added 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 the flame-retardant dimethyl hydantoin is determined to be 12.1% by elemental analysis; the mass ratio of the 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.

[0049] 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, polyetheramine, bio-based flame retardant, antioxidant, and catalyst into a reactor in proportion by weight, stirring evenly, slowly adding diamine dropwise at a temperature of 100° C., heating to 130° C. after the addition is complete, stirring and reacting for 2 hours, further heating to 220° C., stirring and reacting for 1.2 hours, adding stearic acid, evacuating to a vacuum degree of -0.092 MPa, continuing to stir and react for 0.8 hours, and cooling to obtain the bio-based hot melt adhesive.

[0050] Comparative Example 1

[0051] Compared with Example 2, the bio-based flame retardant in this comparative example consists of carboxymethyl chitosan and flame retardant dimethyl hydantoin.

[0052] 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 polyetheramine; 6 parts of diamine; 8 parts of bio-based flame retardant; 1 part of antioxidant; 0.08 parts of catalyst; and 0.4 parts of stearic acid. The dibasic acid is sebacic acid; the diamine is ethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is propionic acid.

[0053] The bio-based flame retardant consists 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.

[0054] The preparation method of a low-temperature-resistant and highly flexible bio-based hot melt adhesive is the same as that of Example 2.

[0055] Comparative Example 2

[0056] Compared with Example 2, in this comparative example, the bio-based flame retardant in the bio-based hot melt adhesive component is carboxymethyl chitosan.

[0057] 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 polyetheramine; 6 parts of diamine; 8 parts of bio-based flame retardant; 1 part of antioxidant; 0.08 parts of catalyst; and 0.4 parts of stearic acid. The dibasic acid is sebacic acid; the diamine is ethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is propionic acid.

[0058] The bio-based flame retardant is carboxymethyl chitosan.

[0059] The preparation method of a low-temperature-resistant and highly flexible bio-based hot melt adhesive is the same as that of Example 2.

[0060] Comparative Example 3

[0061] Compared with Example 2, the bio-based hot melt adhesive component in this comparative example does not contain a bio-based flame retardant.

[0062] 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 polyetheramine; 6 parts of diamine; 1 part of antioxidant; 0.08 parts of catalyst; and 0.4 parts of stearic acid. The dibasic acid is sebacic acid; the diamine is ethylenediamine; the antioxidant is antioxidant 1010; and the catalyst is propionic acid.

[0063] The preparation method of a low-temperature-resistant and highly flexible bio-based hot melt adhesive is the same as that of Example 2.

[0064] Performance Testing

[0065] The bio-based hot melt adhesives prepared in Examples 2 to 4 and Comparative Examples 1 to 3 were subjected to performance tests. The viscosity test was conducted using a rotational viscometer in accordance with GB / T 2794-1995. The tensile strength test was conducted using GB / T 7124-2008. The elongation at break was conducted using GB / T 1040.3-2006. In the shear strength test, the bio-based hot melt adhesive was first formed into a 12.5 mm × 25 mm thin film with a thickness of 2 mm. The film was placed between aluminum substrates and placed in an oven at 120°C for 30 minutes. The film was then cooled to room temperature and the shear force of the sample was tested at 20°C and -20°C using a UTM2502 electronic universal testing machine. The limiting oxygen index test was conducted using GB / T 2406-2009. In the antibacterial test, the bio-based hot melt adhesive was first formed into a 5 mm diameter, 1 mm thick adhesive disc using the inhibition zone method. 200 μL of activated bacterial solution (the same amount of concentration was 10 μg / cm2) was evenly coated on the culture medium. 6 cfu / mL of Staphylococcus aureus suspension and Escherichia coli suspension), the gelatin disc was placed in the center of the culture dish, and cultured in a cell culture incubator at 37°C for 24 hours. The diameter of the inhibition zone was measured; the test results are shown in Table 1 below.

[0066] Table 1 Performance test results

[0067]

[0068] 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 adhesives 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 discloses a bio-based hot melt adhesive having a strong bonding effect in the adhesive, thereby helping 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. When added to the bio-based hot melt adhesive component, the flame retardant and antibacterial properties of the bio-based hot melt adhesive are effectively improved. The benzene ring has good low-temperature stability, 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.

[0069] It should be noted that, in this document, 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 that are inherent to such process, method, article or apparatus.

[0070] While 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 these embodiments without departing from the principles and spirit of the invention, and that the scope of the 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 polyetheramine; 5-6 parts of diamine; 6-8 parts of bio-based flame retardant; 0.5-1 part of antioxidant; 0.05-0.08 parts of catalyst; and 0.2-0.4 parts of stearic acid. The preparation method of the bio-based flame retardant comprises: adding carboxymethyl chitosan to a reaction vessel containing a solvent, stirring evenly, adding flame-retardant dimethyl hydantoin and triethylamine, and stirring and reacting at a temperature of 70-75° C. for 5-6 hours to obtain 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; 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. Add dimethylhydantoin-aniline to a reaction vessel containing chloroform, stir evenly, slowly add epichlorohydrin dropwise, and after completion of the addition, react at a temperature of 35-40° C. for 4-5 hours, then add 3-bromopropanol and triethylamine, and continue the reaction at a temperature of 50-60° C. for 5-6 hours to obtain hydroxylated dimethylhydantoin; S3, adding hydroxylated dimethyl hydantoin and triethylamine to a reaction vessel containing anhydrous chloroform, stirring evenly, placing in an ice bath, slowly adding diethylphosphite chloride dropwise, after the addition is complete, continuing the reaction for 4-5 hours, TLC detection of the reaction completion, naturally warming to room temperature, then adding sodium hypochlorite, stirring and reacting for 1-2 hours to obtain flame-retardant dimethyl hydantoin; The molar ratio of p-chloroaniline, 5,5-dimethylhydantoin, and potassium hydroxide in step S1 is 1:1-1.1:1.2-1.3; 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; and the molar ratio of hydroxylated dimethylhydantoin, diethylphosphite chloride, triethylamine, and sodium hypochlorite in step S3 is 1:2.1-2.2:1.5-1.8:1.3-1.

5.

2. 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.

3. 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.

4. 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, pentamethylenediamine and hexamethylenediamine, or a mixture of several of them.

5. 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.

6. A method for preparing a low-temperature-resistant and highly flexible bio-based hot melt adhesive according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: adding dimer acid, dibasic acid, polyetheramine, bio-based flame retardant, antioxidant and catalyst into a reactor in proportion by weight, 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 obtaining a bio-based hot melt adhesive after cooling.

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