Thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and transesterification characteristics and preparation and application thereof

Abstract

The present application belongs to the technical field of hot melt adhesive, and discloses a thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics, and a preparation method and application thereof. The thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics is prepared from the following components by mass: chelate coordination thermoplastic carboxyl starch 40-80 parts, ethylene-vinyl acetate copolymer 10-30 parts, tackifier 10-30 parts, and antioxidant 0.2-0.4 parts. The thermoplastic carboxyl starch-based hot melt adhesive of the present application uses chelate coordination thermoplastic carboxyl starch as the matrix, and only needs to be combined with a small amount of EVA resin to prepare a thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics and excellent performance. The chelate coordination thermoplastic carboxyl starch combines with metal salt, so that the hot melt adhesive of the present application not only exhibits excellent intrinsic antibacterial property, but also can realize significantly improved two-phase interface high-efficiency penetration and fusion effect through ester exchange reaction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hot melt adhesives, and particularly relates to a hot melt adhesive based on thermoplastic carboxyl starch with intrinsic antibacterial and ester exchange characteristics, and a preparation method and application thereof. BACKGROUND

[0002] Starch has a long history as an adhesive material, but ordinary starch has strong intermolecular hydrogen bonding force, making it difficult to be used directly as an adhesive. After being plasticized and thermoplastically processed, the obtained thermoplastic starch has good fluidity and adhesion, and is widely used as a substitute for traditional hot melt adhesives such as polyolefin, polyurethane and polyester by being used with other natural materials such as rosin resin and other tackifiers to prepare TPS-based hot melt adhesives. However, due to the rigidity of high molecular weight raw starch, the permeability to the bonding interface is poor, resulting in less than ideal bonding strength.

[0003] CN104312482B discloses a preparation technology of a rosin / starch-based biodegradable hot melt adhesive, which is prepared by high-temperature mixing of thermoplastic starch particles, rosin, polyol, catalyst and antioxidant. The obtained hot melt adhesive meets the technical standard requirements of ordinary commercially available hot melt adhesives. CN114381218A controls the molecular weight and viscoelasticity of TPS by acidifying and degrading TPS with organic acid, and further blends the TPS hot melt adhesive with matrix resin, tackifier and filler to obtain a TPS-based hot melt adhesive with high metal bonding strength. On this basis, CN117165218A further adds an antibacterial filler to obtain an antibacterial TPS-based hot melt adhesive with high matrix strength, and the copper sheet lap bonding strength can reach 3.5 MPa.

[0004] However, the antibacterial property of hot melt adhesives is limited by the addition of fillers, which is usually limited by the dispersibility of the fillers in the matrix; in addition, the bonding performance of the single thermoplastic starch-based hot melt adhesive is poor, and it needs to be compounded with traditional hot melt adhesives such as EVA; the above problems limit the improvement of the performance of the hot melt adhesive. Therefore, the performance improvement of the existing thermoplastic starch-based hot melt adhesive needs to overcome the problem of interfacial compatibility with the matrix resin. SUMMARY

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a hot melt adhesive based on thermoplastic carboxyl starch with intrinsic antibacterial and ester exchange characteristics.

[0006] Another purpose of the present application is to provide a preparation method of the above-mentioned hot melt adhesive based on thermoplastic carboxyl starch.

[0007] Still another purpose of the present application is to provide the application of the above-mentioned hot melt adhesive based on thermoplastic carboxyl starch.

[0008] The purposes of the present application are achieved by the following solutions:

[0009] A thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics is prepared from the following components by mass: chelate coordination thermoplastic carboxyl starch 40-80 parts, ethylene-vinyl acetate copolymer 10-30 parts, tackifier 10-30 parts, and antioxidant 0.2-0.4 parts.

[0010] Further, the chelate coordination thermoplastic carboxyl starch is prepared from the following components by mass: carboxyl starch 60-75 parts, plasticizer 25-40 parts, and metal salt 0.05-10 parts.

[0011] Still further, the carboxyl starch includes at least one of modified Fenton reagent oxidized starch (oxidized starch), maleic anhydride esterified starch, TEMPO oxidized starch, maleic anhydride esterified starch, and the like, and is more preferably oxidized starch.

[0012] Still further, the plasticizer can be any conventional plasticizer used in the art, and can include at least one of glycerol, ethylene glycol, pentaerythritol, and the like, and is more preferably glycerol.

[0013] Further, the metal salt can include at least one of soluble zinc salt, soluble calcium salt, soluble magnesium salt, and the like.

[0014] Still further, the soluble zinc salt can include at least one of zinc acetate, zinc chloride, zinc citrate, zinc tartrate, and the like.

[0015] Still further, the soluble calcium salt can include at least one of calcium tartrate, calcium chloride, calcium acetate, and the like.

[0016] Still further, the soluble magnesium salt can include magnesium chloride and the like.

[0017] In the thermoplastic carboxyl starch-based hot melt adhesive of the present application, the chelate coordination thermoplastic carboxyl starch is prepared by the following method: uniformly mixing carboxyl starch, plasticizer, and metal salt in a proportion, and reacting and extruding in an extruder to form a shape, and then cooling and granulating to obtain the chelate coordination thermoplastic carboxyl starch.

[0018] Further, the material can be left to stand after being uniformly mixed and then extruded and granulated. The standing time can be 8-48 hours.

[0019] Further, the extruder used can be a co-rotating parallel twin-screw extruder, the temperature from the extruder feeding port to the head can be 80-140°C, and the screw rotation speed can be 50-300 r / min, and is more preferably 120-150 r / min.

[0020] In the thermoplastic carboxyl starch-based hot melt adhesive of the present application, the viscosity of the tackifier is preferably 700-1800 cp (150°C).

[0021] Further, the tackifier can include at least one of rosin resin, hydrogenated rosin resin, etc., and more preferably includes rosin resin.

[0022] Further, the antioxidant can be any conventional antioxidant, such as antioxidant 168, antioxidant 1010, antioxidant 1076, etc., and more preferably includes antioxidant 1010.

[0023] Further, the EVA resin is preferably EVA 28400.

[0024] The present application also provides a preparation method of the thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics.

[0025] Further, the temperature of the internal mixer can be 120-170℃, the rotor speed can be 5-120r / min, and the mixing time can be 5-60min.

[0026] Further, the temperature of the internal mixer can be 140-150℃, the rotor speed can be 80-120r / min, and the mixing time can be 10-40min.

[0027] The present application also provides the application of the thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics. The thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics has excellent bonding effect on paper, non-woven fabric, metal and other materials, has high bonding strength, and can be applied in the fields of furniture, food, packaging, papermaking, sanitary products, etc.

[0028] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0029] (1) In the hot melt adhesive of the present application, the chelate coordination thermoplastic carboxyl starch is used as the matrix, and only a small amount of EVA resin is combined to prepare the thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics.

[0030] (2) In the hot melt adhesive of the present application, the carboxyl starch has the characteristics of containing rich carboxyl groups, which can change the ionization equilibrium of bacterial cells, destroy the bacterial expression and physiological activity of bacteria and inhibit the growth and reproduction of bacteria, thereby showing excellent intrinsic antibacterial property. The carboxyl starch as the matrix of the hot melt adhesive can widen the use scene of the thermoplastic starch-based hot melt adhesive and prolong its service life.

[0031] (3) The hot melt adhesive of the present application can greatly improve the affinity with metal through the chelation coordination of carboxyl and metal bonding interface, thereby further improving the bonding performance of the thermoplastic carboxyl starch-based hot melt adhesive to the metal substrate. In addition, the molecular weight of the carboxyl starch can be controlled during the preparation process, so as to realize the controllable reduction of the molecular weight and the increase of the dispersibility index, which is beneficial to improve the effective penetration and bonding of the thermoplastic carboxyl starch-based hot melt adhesive to the bonding interface.

[0032] (4) In the hot melt adhesive of the present application, the carboxyl starch can further react with polyester such as EVA under the catalysis of metal salt to promote the ester exchange reaction of carboxyl and ester group, so as to significantly reduce the defect points of the bonding substrate and realize the uniformity of the bonding interface and the stability of the interface layer.

[0033] (5) In the hot melt adhesive of the present application, the coordination of carboxyl starch and metal salt can endow the thermoplastic carboxyl starch-based hot melt adhesive with temperature-sensitive reversible characteristics. Through the chelation coordination high-temperature dissociation and room temperature recombination characteristics, the adhesive can realize good flowability at high temperature and high substrate strength at room temperature. In addition, the chelation coordination structure can also effectively reduce the penetration of moisture to the substrate, thereby greatly prolonging the service period of the thermoplastic carboxyl starch-based hot melt adhesive. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0035] Figure 1 SEM image of the chelation coordination thermoplastic carboxyl starch-based hot melt adhesive of the present application.

[0036] Figures 2-3 SEM images of the hot melt adhesives prepared by Comparative Example 1 and Comparative Example 2, respectively. DETAILED DESCRIPTION

[0037] The present application will be further described in detail below with reference to the examples, but the embodiments of the present application are not limited thereto. The materials involved in the following examples can be obtained from commercial channels if no special instructions are given. For the process parameters not specifically mentioned, the conventional techniques can be referred to. The amount of each component is in mass volume parts, g, mL.

[0038] The EVA resin (brand: EVA28400) in the examples and comparative examples was purchased from Shanghai Haiyuan Chemical Co., Ltd.; the rosin resin was purchased from Jinan Fugang Chemical Co., Ltd., with a viscosity of 700-1800 cp (150℃) and a softening point of 110-120℃.

[0039] Example 1

[0040] 70 parts by mass of carboxyl starch, 30 parts by mass of glycerol, and 3 parts by mass of zinc acetate were mixed in a blender, and after standing for 24 h, the mixture was added to a co-rotating twin-screw extruder for reaction extrusion. The temperature of the extruder from the feeding port to the die head was set to 90-140°C (the temperature of each temperature control zone from the feeding port to the die head was set to 90°C, 110°C, 130°C, 135°C, 140°C, 140°C, 135°C, and 130°C, respectively), and the screw rotation speed was 150 r / min. After cooling and granulation, chelate coordination thermoplastic carboxyl starch particles were obtained.

[0041] After 50 parts by mass of chelate coordination thermoplastic carboxyl starch, 25 parts by mass of EVA resin, 25 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, the mixture was added to an internal mixer for melt blending. The temperature of the internal mixer was 150°C, the rotor rotation speed was 80 r / min, and after mixing for 10 min, the mixture was discharged, cooled, and granulated to obtain a thermoplastic carboxyl starch-based hot melt adhesive.

[0042] Example 2

[0043] 70 parts by mass of carboxyl starch, 30 parts by mass of glycerol, and 3 parts by mass of zinc acetate were mixed in a blender, and after standing for 24 h, the mixture was added to a co-rotating twin-screw extruder for reaction extrusion. The temperature of the extruder from the feeding port to the die head was set to 90-140°C (the temperature of each temperature control zone from the feeding port to the die head was set to 90°C, 110°C, 130°C, 135°C, 140°C, 140°C, 135°C, and 130°C, respectively), and the screw rotation speed was 150 r / min. After cooling and granulation, chelate coordination thermoplastic carboxyl starch particles were obtained.

[0044] After 60 parts by mass of chelate coordination thermoplastic carboxyl starch, 20 parts by mass of EVA resin, 20 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, the mixture was added to an internal mixer for melt blending. The temperature of the internal mixer was 150°C, the rotor rotation speed was 90 r / min, and after mixing for 20 min, the mixture was discharged, cooled, and granulated to obtain a thermoplastic carboxyl starch-based hot melt adhesive.

[0045] Example 3

[0046] 70 parts by mass of carboxyl starch, 30 parts by mass of glycerol, 3 parts by mass of zinc acetate were added into a blender and mixed uniformly, and after standing for 24 h, it was added into a co-rotating twin-screw extruder for reaction extrusion, the temperature from the feeding port to the die head of the extruder was set to 90-140°C (the temperature of each temperature control zone from the feeding port to the die head of the extruder was set to 90°C, 110°C, 130°C, 135°C, 140°C, 140°C, 135°C, 130°C), the screw rotation speed was 150 r / min, and after cooling and granulation, chelated coordination thermoplastic carboxyl starch particles were obtained.

[0047] After 70 parts by mass of chelated coordination thermoplastic carboxyl starch, 15 parts by mass of EVA resin, 15 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, they were added into an internal mixer for melt blending, the temperature of the internal mixer was 150°C, the rotor rotation speed was 100 r / min, and after mixing for 30 min, the material was discharged, cooled, and granulated to obtain a thermoplastic carboxyl starch-based hot melt adhesive sample.

[0048] Example 4

[0049] After 70 parts by mass of carboxyl starch, 30 parts by mass of glycerol, 3 parts by mass of zinc acetate were added into a blender and mixed uniformly, and after standing for 24 h, it was added into a co-rotating twin-screw extruder for reaction extrusion, the temperature from the feeding port to the die head of the extruder was set to 90-140°C (the temperature of each temperature control zone from the feeding port to the die head of the extruder was set to 90°C, 110°C, 130°C, 135°C, 140°C, 140°C, 135°C, 130°C), the screw rotation speed was 150 r / min, and after cooling and granulation, chelated coordination thermoplastic carboxyl starch particles were obtained.

[0050] After 80 parts by mass of chelated coordination thermoplastic carboxyl starch, 10 parts by mass of EVA resin, 10 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, they were added into an internal mixer for melt blending, the temperature of the internal mixer was 150°C, the rotor rotation speed was 110 r / min, and after mixing for 40 min, the material was discharged, cooled, and granulated to obtain a thermoplastic carboxyl starch-based hot melt adhesive.

[0051] Example 5

[0052] After 70 parts by mass of maleic anhydride esterified starch, 30 parts by mass of glycerol, and 3 parts by mass of zinc acetate were added into a blender and mixed uniformly, and after standing for 24 h, it was added into a co-rotating twin-screw extruder for reaction extrusion, the temperature from the feeding port to the die head of the extruder was set to 90-140°C (the temperature of each temperature control zone from the feeding port to the die head of the extruder was set to 90°C, 110°C, 130°C, 135°C, 140°C, 140°C, 135°C, 130°C), the screw rotation speed was 150 r / min, and after cooling and granulation, chelated coordination thermoplastic maleic anhydride esterified starch particles were obtained.

[0053] 80 parts by mass of the chelate coordination thermoplastic maleic anhydride esterified starch, 10 parts by mass of the EVA resin, 10 parts by mass of the rosin resin, and 0.4 parts by mass of the antioxidant 1010 are mechanically stirred and uniformly premixed, and then added into an internal mixer for melt blending. The temperature of the internal mixer is 140°C, the rotor speed is 120 r / min, and after 40 minutes of mixing, the material is discharged, cooled, and granulated to obtain the thermoplastic maleic anhydride esterified starch-based hot melt adhesive.

[0054] Example 6

[0055] 70 parts by mass of the chelate coordination thermoplastic maleic anhydride esterified starch, 30 parts by mass of glycerol, and 3 parts by mass of zinc acetate are uniformly mixed in a blender, and then allowed to stand for 24 hours. The mixture is then added into a co-rotating twin-screw extruder for reaction extrusion. The temperature of the extruder is set to 80-130°C (the temperature of each temperature control section from the feeding port to the die head is set to 80°C, 100°C, 120°C, 125°C, 130°C, 130°C, 125°C, and 120°C, respectively), the screw speed is 120 r / min, and after cooling and granulation, the chelate coordination thermoplastic maleic anhydride esterified starch particles are obtained.

[0056] 80 parts by mass of the chelate coordination thermoplastic maleic anhydride esterified starch, 10 parts by mass of the EVA resin, 10 parts by mass of the rosin resin, and 0.4 parts by mass of the antioxidant 1010 are mechanically stirred and uniformly premixed, and then added into an internal mixer for melt blending. The temperature of the internal mixer is 140°C, the rotor speed is 120 r / min, and after 40 minutes of mixing, the material is discharged, cooled, and granulated to obtain the thermoplastic maleic anhydride esterified starch-based hot melt adhesive.

[0057] Example 7

[0058] 60 parts by mass of the carboxyl starch, 40 parts by mass of glycerol, and 3 parts by mass of zinc acetate are uniformly mixed in a blender, and then allowed to stand for 24 hours. The mixture is then added into a co-rotating twin-screw extruder for reaction extrusion. The temperature of the extruder is set to 80-120°C (the temperature of each temperature control section from the feeding port to the die head is set to 80°C, 90°C, 110°C, 115°C, 120°C, 120°C, 115°C, and 110°C, respectively), the screw speed is 120 r / min, and after cooling and granulation, the chelate coordination thermoplastic carboxyl starch particles are obtained.

[0059] 80 parts by mass of the chelate coordination thermoplastic carboxyl starch, 10 parts by mass of the EVA resin, 10 parts by mass of the rosin resin, and 0.4 parts by mass of the antioxidant 1010 are mechanically stirred and uniformly premixed, and then added into an internal mixer for melt blending. The temperature of the internal mixer is 140°C, the rotor speed is 120 r / min, and after 40 minutes of mixing, the material is discharged, cooled, and granulated to obtain the thermoplastic carboxyl starch-based hot melt adhesive sample.

[0060] Example 8

[0061] 80 parts by mass of the chelate coordination thermoplastic carboxyl starch, 10 parts by mass of EVA resin, 10 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, and then were added into an internal mixer for melt blending. The temperature of the internal mixer was 150°C, and the rotor speed was 120 r / min. After mixing for 40 min, the material was discharged, cooled, and granulated to obtain a hot-melt adhesive sample based on the thermoplastic carboxyl starch.

[0062] 80 parts by mass of the chelate coordination thermoplastic carboxyl starch, 10 parts by mass of EVA resin, 10 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, and then were added into an internal mixer for melt blending. The temperature of the internal mixer was 150°C, and the rotor speed was 120 r / min. After mixing for 40 min, the material was discharged, cooled, and granulated to obtain a hot-melt adhesive sample based on the thermoplastic carboxyl starch.

[0063] Example 9

[0064] 80 parts by mass of the chelate coordination thermoplastic carboxyl starch, 10 parts by mass of EVA resin, 10 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, and then were added into an internal mixer for melt blending. The temperature of the internal mixer was 150°C, and the rotor speed was 120 r / min. After mixing for 40 min, the material was discharged, cooled, and granulated to obtain a hot-melt adhesive sample based on the thermoplastic carboxyl starch.

[0065] 80 parts by mass of the chelate coordination thermoplastic carboxyl starch, 10 parts by mass of EVA resin, 10 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, and then were added into an internal mixer for melt blending. The temperature of the internal mixer was 150°C, and the rotor speed was 120 r / min. After mixing for 40 min, the material was discharged, cooled, and granulated to obtain a hot-melt adhesive sample based on the thermoplastic carboxyl starch.

[0066] Comparative Example 1

[0067] 80 parts by mass of the chelate coordination thermoplastic carboxyl starch, 10 parts by mass of EVA resin, 10 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 were uniformly premixed by mechanical stirring, and then were added into an internal mixer for melt blending. The temperature of the internal mixer was 150°C, and the rotor speed was 120 r / min. After mixing for 40 min, the material was discharged, cooled, and granulated to obtain a hot-melt adhesive sample based on the thermoplastic carboxyl starch.

[0068] The 60 parts by mass of thermoplastic starch, 20 parts by mass of EVA resin, 20 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 are mechanically stirred and uniformly premixed, and then added into an internal mixer for melt blending. The temperature of the internal mixer is 150°C, and the rotor speed is 120 r / min. After 40 minutes of mixing, the material is discharged, cooled, and granulated to obtain the thermoplastic starch-based hot melt adhesive.

[0069] Comparative Example 2

[0070] The 70 parts by mass of carboxyl starch and 30 parts by mass of glycerol are uniformly mixed in a blender, and then left to stand for 24 hours. The mixture is then added into a co-rotating twin-screw extruder for reaction extrusion. The temperature of the extruder is set to 90-140°C (the temperature of each temperature control zone from the feeding port to the die head is set to 90°C, 110°C, 130°C, 135°C, 140°C, 140°C, 135°C, and 130°C, respectively), and the screw speed is 150 r / min. After cooling and granulation, the unchelated and coordinated thermoplastic carboxyl starch particles are obtained.

[0071] The 80 parts by mass of unchelated and coordinated thermoplastic carboxyl starch, 10 parts by mass of EVA resin, 10 parts by mass of rosin resin, and 0.4 parts by mass of antioxidant 1010 are mechanically stirred and uniformly premixed, and then added into an internal mixer for melt blending. The temperature of the internal mixer is 150°C, and the rotor speed is 110 r / min. After 40 minutes of mixing, the material is discharged, cooled, and granulated to obtain the unchelated and coordinated modified thermoplastic carboxyl starch-based hot melt adhesive.

[0072] Performance characterization

[0073] (1) The compatibility of the TPS-based hot melt adhesive prepared in the above examples and the EVA hot melt adhesive prepared in Comparative Example 1 is observed using SEM, and the results are shown in FIGS. Figure 1 、 Figure 2 、 Figure 3 Figure 1 FIG. 4 is an SEM image of the chelated and coordinated thermoplastic carboxyl starch-based hot melt adhesive of Example 4 of the present application. Figure 2 and Figure 3 are SEM images of the hot melt adhesives prepared in Comparative Example 1 and Comparative Example 2, respectively.

[0074] As can be seen from the figures, the phase domains of EVA / rosin resin in the chelated and coordinated thermoplastic carboxyl starch are smaller than those in the unchelated and coordinated thermoplastic starch / acrylamide grafted starch hot melt adhesive, and are basically less than 1 μm. This is because the ester exchange between carboxyl starch and EVA under the catalysis of metal salt promotes the dispersibility of the resin in the thermoplastic carboxyl starch matrix. This feature will help to improve the uniformity of the adhesive matrix and the stability of the adhesive interface, thereby greatly improving the strength of the matrix and the adhesive strength.

[0075] ​(2) The hot melt adhesive of the present application is subjected to antibacterial performance test, and the experimental operation is as follows: the antibacterial performance of the hot melt adhesive sample on Staphylococcus aureus (ATCC6538) and Escherichia coli (ATCC8739) is tested by using the inhibition zone method. The specific operation steps are as follows: 100 μL of activated bacteria liquid (OD=0.5) is uniformly coated on the agar culture medium, and the sample (cut into a small disc with a diameter of 8 mm and a thickness of 1 mm) is placed on the surface of the culture medium. After the sample is placed, the culture medium is placed in a 37℃ cell incubator for 24h. After the culture is completed, the diameter of the inhibition zone is measured by using the cross method. The blank is the comparative example 1, the relative growth rate of the inhibition zone is calculated, and the results are shown in Table 1.

[0076] Relative growth rate of inhibition zone % = (inhibition zone diameter of example - inhibition zone diameter of blank comparison) / inhibition zone diameter of blank comparison * 100%

[0077] Table 1

[0078]

[0079] As shown in the table, the hot melt adhesive of the present application has excellent antibacterial effect, and the diameter of the inhibition zone can reach 45 mm. In the hot melt adhesive of the present application, the carboxylated starch is used as the matrix, which can change the ionization equilibrium of the bacterial cells, destroy the bacterial expression and physiological activity of the bacteria, and inhibit the growth and reproduction of the bacteria, thereby showing excellent intrinsic antibacterial property.

[0080] (3) The hot melt adhesives prepared in the above examples 1-9 and comparative examples 1-2 are subjected to copper sheet lap joint bonding strength test (tested according to GB / T 7124-2008 standard, and the tensile rate is set to 5 mm / min), and aluminum strip peeling strength test (tested according to GB / T2791-1995 standard, and the tensile rate is 200 mm / min), and the test results are shown in Table 2.

[0081] Table 2

[0082]

[0083] From the table, compared with the comparative examples, the bonding strength of the carboxyl starch-based hot melt adhesive with transesterification characteristics of the application is significantly improved compared with ordinary thermoplastic starch-based hot melt adhesive and carboxyl starch-based hot melt adhesive without metal ions. The comparison results of comparative example 2 and comparative example 1 show that carboxyl starch is crucial to the bonding strength of hot melt adhesive. This is because the molecular weight of carboxyl starch decreases controllably during preparation, the molecular weight distribution becomes wider, and a large number of polar groups carboxyl are introduced. The rich polar groups and low molecular weight components can help the thermoplastic carboxyl starch-based hot melt adhesive to effectively penetrate the bonding interface and improve the interfacial bonding strength. At the same time, carboxyl can not only improve the affinity with the bonding interface through double hydrogen bonds, but also improve the cohesive energy density of the hot melt adhesive matrix to prevent cohesive failure of the adhesive layer.

[0084] In addition, through the catalysis of metal salt, carboxyl starch can undergo transesterification reaction with the ester bond of EVA, promoting efficient penetration and fusion of the two-phase interface, which will significantly reduce the defect points of the bonding matrix, realize the uniformity of the bonding interface and the stability of the interface layer. More importantly, the coordination of carboxyl starch and metal salt can endow the thermoplastic carboxyl starch-based hot melt adhesive with temperature-sensitive reversible properties. Through the chelation and coordination of high-temperature dissociation and room temperature recombination characteristics, the adhesive achieves good flowability at high temperature and high matrix strength at room temperature. In addition, the chelation and coordination structure can also effectively reduce the penetration of moisture into the matrix, greatly extending the service life of the thermoplastic carboxyl starch-based hot melt adhesive. In addition, carboxyl starch contains rich carboxyl groups, which can change the ionization balance of bacterial cells, destroy the bacterial expression and physiological activity of bacteria and inhibit their growth and reproduction, thereby showing excellent intrinsic antibacterial properties. Carboxyl starch as a hot melt adhesive matrix can widen the use scenarios of thermoplastic starch-based hot melt adhesive and prolong its service life.

[0085] The above embodiments are the preferred embodiments of the application, but the embodiments of the application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the application shall be equivalent replacement methods, which are all included in the protection scope of the application.

Claims

1. A thermoplastic carboxystarch-based hot-melt adhesive with intrinsic antibacterial and transesterification properties, characterized in that it comprises It is prepared from the following components by mass: chelate coordination thermoplastic carboxyl starch 40-80 parts, ethylene-vinyl acetate copolymer 10-30 parts, tackifier 10-30 parts, antioxidant 0.2-0.4 parts; The chelate coordination thermoplastic carboxyl starch is prepared from the following components by mass: carboxyl starch 60-75 parts, plasticizer 25-40 parts, metal salt 0.05-10 parts; the plasticizer includes at least one of glycerol, ethylene glycol, and pentaerythritol; the metal salt includes at least one of soluble zinc salt, soluble calcium salt, and soluble magnesium salt; The chelate coordination thermoplastic carboxyl starch is prepared by the following steps: uniformly mixing carboxyl starch, plasticizer, and metal salt in proportion, and reacting and extruding into shape in an extruder, and then cooling and granulating to obtain the chelate coordination thermoplastic carboxyl starch.

2. Thermoplastic carboxystarch-based hot-melt adhesive with intrinsic antibacterial and transesterification properties according to claim 1, characterized by the fact that: The carboxyl starch includes at least one of modified Fenton reagent oxidized starch, maleic anhydride esterified starch, and TEMPO oxidized starch.

3. The thermoplastic carboxystarch-based hot-melt adhesive with intrinsic antibacterial and transesterification characteristics according to claim 1, characterized by the fact that: The soluble zinc salt includes at least one of zinc acetate, zinc chloride, zinc citrate, and zinc tartrate; the soluble calcium salt includes at least one of calcium tartrate, calcium chloride, and calcium acetate; the soluble magnesium salt includes magnesium chloride.

4. The thermoplastic carboxyl starch-based hot-melt adhesive with intrinsic antibacterial and transesterification characteristics according to claim 1, characterized by the fact that: The temperature from the feeding port of the extruder to the die head is 80-140℃, and the screw rotation speed is 50-300r / min.

5. Thermoplastic carboxystarch-based hot-melt adhesive with intrinsic antibacterial and transesterification properties according to any one of claims 1-4, characterized by the fact that: The tackifier includes at least one of rosin resin and hydrogenated rosin resin; the antioxidant includes at least one of antioxidant 168, antioxidant 1010, and antioxidant 1076.

6. Process for the preparation of thermoplastic carboxystarch-based hot-melt adhesives with intrinsic antibacterial and transesterification properties according to any one of claims 1 to 5, characterized in that After mixing the components in proportion, melt blending is performed in an internal mixer, and then cooling and granulation are performed to obtain the product.

7. The method of preparing a thermoplastic carboxyl starch-based hot melt adhesive according to claim 6, characterized in that: The temperature of the internal mixer is 120-170℃, the rotor rotation speed is 5-120r / min, and the mixing time is 5-60min.

8. Use of the thermoplastic carboxyl starch-based hot melt adhesive with intrinsic antibacterial and ester exchange characteristics according to any one of claims 1-5 in the fields of furniture, food, packaging, papermaking, and sanitary products.

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