Food packaging adhesive containing bio-based polyester polyol and preparation method and application thereof

Abstract

The present application relates to the technical field of adhesive, in particular to a food packaging adhesive containing bio-based polyester polyol and its preparation method and application. The adhesive comprises component A and component B; the component A comprises bio-based polyester polyol 40-55 parts, chain extender 1-3 parts, modified inorganic nano-oxide 6-7 parts, and catalyst 0.01-0.05 parts by weight; the component B comprises isocyanate curing agent. The adhesive has excellent peel strength and cooking resistance, and also has certain oxygen resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, in particular to a food packaging adhesive containing a bio-based polyester polyol and a preparation method and application thereof. BACKGROUND

[0002] Food soft packaging refers to the shape variable packaging without fillers, such as aluminum foil, plastic film or its composite. Adhesives are used for the compounding of packaging films in soft packaging. The selection of appropriate adhesives has a key influence on the quality of soft packaging. At present, the commonly used soft packaging adhesive is polyurethane adhesive, but this kind of adhesive has excessive fossil raw materials.

[0003] The peel strength of the adhesive is an important factor for evaluating the quality of the adhesive. With the increasing demand for soft packaging and the wider application range, the peel strength of the adhesive is also required to be higher and higher. At present, many researchers focus on increasing the peel strength of the adhesive, but they do not pay attention to the oxygen barrier of the adhesive, especially the oxygen barrier in the food packaging adhesive. SUMMARY

[0004] The present application provides a food packaging adhesive containing a bio-based polyester polyol. The adhesive comprises A component and B component. The A component comprises bio-based polyester polyol 40-55 parts by weight, chain extender 1-3 parts, modified inorganic nano-oxide 6-7 parts, and catalyst 0.01-0.05 parts. The B component comprises isocyanate curing agent. The preparation method of the bio-based polyester polyol comprises the following steps: esterification of polyol and polyacid under nitrogen protection and in the presence of strong acid cation exchange resin at 150-170℃, removal of product water by distillation during the reaction, addition of titanium acid tetraisopropylate after the reaction reaches an acid value of 35-40mgKOH / g, reduction of pressure to 10-15torr, increase of temperature to 210-230℃, removal of product water by distillation during the reaction, determination of the hydroxyl value of the mixture in the reaction vessel, cooling of the reaction vessel to reduce the temperature to room temperature, and termination of the reaction to obtain bio-based polyester polyol. At least one of the polyol and the polyacid is a bio-based raw material. The modified inorganic nano-oxide comprises acryloyl-modified inorganic nano-oxide and coupling agent-modified inorganic nano-oxide. The mass ratio of the coupling agent-modified inorganic nano-oxide to the acryloyl-modified inorganic nano-oxide is (0.8-1.2):1. The acryloyl-modified inorganic nano-oxide is obtained by in-situ polymerization of acryloyl monomer providing acrylamide structural units on inorganic nano-oxide.

[0005] Preparation of bio-based polyester polyol

[0006] In the present application, the pressure can be gradually reduced to 10-15 torr according to actual needs by those skilled in the art.

[0007] In the present application, the use of bio-based raw materials can ensure that the adhesive has a certain bio-based component.

[0008] As a preferred technical solution of the present application, the polyacid is selected from bio-based polyacids, and optionally petroleum-based polyacids.

[0009] In the present application, the optional petroleum-based polyacid means that it can contain petroleum-based polyacids or not.

[0010] As a preferred technical solution of the present application, the bio-based polyacid is selected from at least one of bio-based succinic acid, bio-based sebacic acid, bio-based undecanedioic acid, and bio-based dodecanedioic acid, preferably bio-based sebacic acid and / or bio-based dodecanedioic acid.

[0011] In the present application, succinic acid is also known as succinic acid, which is naturally derived from the resin of Pinus plants buried in the ground for a long time to form amber; sebacic acid is naturally present in castor oil; undecanedioic acid is mainly produced by biological fermentation.

[0012] As a preferred technical solution of the present application, the petroleum-based polyacid includes one or more of petroleum-based phthalic acid, petroleum-based isophthalic acid, petroleum-based terephthalic acid, petroleum-based adipic acid, and petroleum-based azelaic acid.

[0013] In the present application, the bio-based raw material content in the bio-based polyester polyol is greater than 0, and the bio-based content is at most 100%, and those skilled in the art can also select petroleum-based polyacids according to the bio-based content or property requirements. As a preferred technical solution of the present application, the polyol is selected from bio-based polyols, and optionally petroleum-based polyols.

[0014] In the present application, the optional petroleum-based polyol means that it can contain or not contain petroleum-based polyol.

[0015] As a preferred technical solution of the present application, the bio-based polyol is selected from bio-based 1,4-butanediol and / or bio-based 1,3-propanediol, preferably bio-based 1,4-butanediol.

[0016] In the present application, 1,4-butanediol and 1,3-propanediol can be produced in nature, for example, by some microbial fermentation synthesis.

[0017] In the present application, the person skilled in the art can select one or more of petroleum-based ethylene glycol, petroleum-based diethylene glycol, petroleum-based 1,6-hexanediol, petroleum-based neopentyl glycol, petroleum-based 2-methyl-1,3-propanediol and petroleum-based 3-methyl-1,5-pentanediol according to the bio-based content or property requirements.

[0018] As a preferred technical solution of the present application, the strong acid cation exchange resin is selected from at least one of Amberlyst-15, Amberlyst-35 and Amberlyst-70.

[0019] As a preferred technical solution of the present application, the molar ratio of the polyol to the polybasic acid is (1.1-1.3):1.

[0020] As a preferred technical solution of the present application, the mass ratio of the strong acid cation exchange resin to the polyol is 0.01-0.1:1, preferably 0.04-0.05:1.

[0021] As a preferred technical solution of the present application, the mass of the titanium isopropylate is 0.1-0.5wt% of the mass of the polyol.

[0022] Acryl-modified inorganic nano-oxide

[0023] As a preferred technical solution of the present application, the preparation method of the acryl-modified inorganic nano-oxide comprises:

[0024] (1) mixing a solvent, an initiator and an acryl monomer to obtain a premix;

[0025] (2) mixing the premix with inorganic nano-oxide and then performing in-situ polymerization to obtain a polymer material;

[0026] (3) filtering the polymer material and then vacuum drying the filter cake to obtain the acryl-modified inorganic nano-oxide.

[0027] As a preferred technical solution of the present application, in the preparation of the acryl-modified inorganic nano-oxide, the mass ratio of the solvent, the initiator and the acryl monomer is (600-740):(0.2-0.3):100.

[0028] As a preferred technical solution of the present application, the acryl monomer is selected from 3-methyl acrylamido dopamine and / or 3-acrylamido dopamine, preferably 3-methyl acrylamido dopamine.

[0029] The adhesive in the present application has excellent comprehensive performance, and one of the possible reasons is that the special structure of dopamine and other components of the system can better synergize to provide higher peel strength and other properties.

[0030] The kind of initiator in the present application is not particularly limited, and preferably is an azo initiator, such as azobisisobutyronitrile or azobisisoheptyl nitrile.

[0031] As a preferred technical solution of the present application, the solvent is DMF.

[0032] As a preferred technical solution of the present application, the mass ratio of the premix to the inorganic nano-oxide is 100:(15-30), preferably 100:(15-18).

[0033] As a preferred technical solution of the present application, the in-situ polymerization conditions include: reacting at 80-85°C for 6-10h.

[0034] In the present application, the conditions for vacuum drying are not particularly limited, as long as the solvent can be removed, and the present application does not make too much elaboration on this.

[0035] Coupling agent modified inorganic nano-oxide

[0036] As a preferred technical solution of the present application, the preparation method of the coupling agent modified inorganic nano-oxide includes: mixing the coupling agent and the inorganic nano-oxide in pure water, then refluxing at 105-115°C for 2.5-4h, then centrifuging the reaction suspension to remove the supernatant, filtering the lower suspension and washing several times (such as 2-3 times) with water, and drying the solid phase to obtain the coupling agent modified inorganic nano-oxide.

[0037] As a preferred technical solution of the present application, the coupling agent is selected from L-O-phosphoserine and / or N-acetyl-D-serine, and preferably is L-O-phosphoserine.

[0038] As a preferred technical solution of the present application, the mass ratio of the coupling agent to the inorganic nano-oxide is (5-7):1.

[0039] As a preferred technical solution of the present application, the mass ratio of the inorganic nano-oxide to pure water is 1:(2-3).

[0040] In the present application, the conditions for the above centrifugation are not particularly limited, and preferably are centrifuging at 12000-14000rpm for 10-15min.

[0041] As a preferred technical solution of the present application, the inorganic nano-oxide in the coupling agent modified inorganic nano-oxide and the acryloyl modified inorganic nano-oxide is independently selected from at least one of nano-oxidized graphene, nano-silicon dioxide, nano-titanium dioxide and nano-zirconium dioxide, and preferably is nano-oxidized graphene, and preferably the mesh number of the nano-oxidized graphene is 180-250 thousand mesh.

[0042] chain extender

[0043] As a preferred technical solution of the present application, the specific type of the chain extender in the present application is not particularly limited, which can be a multifunctional small molecule alcohol or amine chain extender conventional in the art. As a preferred technical solution of the present application, the chain extender is selected from at least one of ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, trimethylolpropane, sorbitol, triethanolamine, diethylaminoethanol, diethyltoluene diamine and dimethylthio toluene diamine.

[0044] catalyst

[0045] In the present application, the type of the catalyst can be a metal catalyst conventional in the art, such as metal catalysts of organotin, organobismuth, organolead and organozinc, specifically, bismuth laurate catalyst, but the present application is not limited thereto.

[0046] isocyanate curing agent

[0047] As a preferred technical solution of the present application, the isocyanate curing agent is selected from diisocyanate and triphenylmethane triisocyanate.

[0048] As a more preferred technical solution of the present application, the weight ratio of the diisocyanate to triphenylmethane triisocyanate is 1:(0.1-1), preferably 1:(0.4-0.6).

[0049] As a preferred technical solution of the present application, the mass ratio of the A component to the B component is (1.8-2.5):1, for example, 1.8:1, 1.9:1, 2:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1.

[0050] The second aspect of the present application provides a preparation method of an adhesive, which comprises:

[0051] (1) dehydrating the bio-based polyester polyol at a temperature of 110-120℃ and a vacuum degree of -0.06 to -0.1 MPa for 40-60 min;

[0052] (2) mixing the dehydrated bio-based polyester polyol with modified inorganic nano-oxide, and then adding a chain extender and a catalyst to obtain an A component;

[0053] (3) mixing an isocyanate curing agent to obtain a B component.

[0054] The third aspect of the present application provides the application of the adhesive in the present application in food soft packaging bonding.

[0055] The soft packaging material in the present application comprises one or a combination of at least two of PET (polyethylene terephthalate film), PA (polyamide film), NY (nylon film), aluminum foil, CPP (cast polypropylene film), RCPP (high-temperature-resistant cooking polypropylene film), PE (polyethylene film) and PVDC (polyvinylidene chloride film).

[0056] In the present application, the components of aluminum foil and RCPP are non-limiting.

[0057] In the present application, the adhesive is used by mixing component A and component B and then coating, and the coating amount can be selected as required, and generally the dry coating amount is 1-2 g / m 2 After coating, the room temperature (20-30 DEG C) curing time is 1.5-2 h, and then the curing time at a temperature of 45-50 DEG C is 10-15 h.

[0058] Compared with the prior art, the present application has at least the following beneficial effects:

[0059] In the present application, the inventors have found through a series of experiments and in combination with experimental results that the adhesive in the present application has excellent peel strength and cooking resistance, and also has certain oxygen resistance, but when 3-methyl acrylamide dopamine modified inorganic nano-oxide is used alone, the cooking resistance of the adhesive is reduced, and the addition of L-O-serine phosphate modified inorganic nano-oxide not only solves the defect of reduced cooking resistance caused by the acryl structural unit, but also further increases the peel capacity and oxygen resistance of the adhesive.

[0060] 1. The specific modified structure of the acryl monomer in-situ formed in the inorganic nano-oxide can better increase the peel capacity of the adhesive, possibly because the interaction of the acryl structural unit, L-O-serine phosphate and other components in the system of the present application can form a better viscoelastic network structure.

[0061] 2. The chain extender and other raw material components in the present application not only can act as a chain extender, but also can randomly insert into the specific system containing 3-methyl acrylamide dopamine modified inorganic nano-oxide, together with the structure of the L-O-serine phosphate modified inorganic nano-oxide coupling agent, especially the amino acid coupling agent, and when the coupling agent is L-O-serine phosphate, the L-O-serine phosphate modified inorganic nano-oxide can interact with other components in the system to play a better role, so that the interaction of each raw material component in the system forms a stable network space, greatly improves the compactness of the microstructure of the adhesive, and significantly improves the oxygen resistance.

[0062] 3. The specific structure of the L-O-phosphoserine modified inorganic nano-oxide can interact with other components in the adhesive to make the system have strong cohesive force and flexible segments, thereby better increasing its cooking resistance;

[0063] 4. The L-O-phosphoserine modified inorganic nano-oxide and the 3-methyl acrylamido dopamine modified inorganic nano-oxide used in the application can interact synergistically to avoid the "bubble" problem. This may be because the short-chain insertion of the methyl group of 3-methyl acrylamide in the system in the presence of the specific coupling agent L-O-phosphoserine can make the adhesive have better leveling property and can more uniformly bond to the substrate. DETAILED DESCRIPTION

[0064] The application will be described in detail below by examples. The following examples are only exemplary descriptions of specific technical solutions of the application and do not limit the scope of the application, that is, it should be understood that non-essential simple corrections, adjustments and combinations made by those skilled in the art according to the inventive concept of the application are within the scope of the application claimed.

[0065] In the following examples, all raw materials can be obtained by market purchase unless otherwise specified.

[0066] Example 1

[0067] Preparation of bio-based polyester polyol: bio-based 1,4-butanediol and bio-based sebacic acid with a molar ratio of 1.1:1 were esterified at 160℃ under nitrogen protection and in the presence of Amberlyst-15 (5wt% of bio-based 1,4-butanediol), and the product water was removed by distillation during the reaction. After the reaction was carried out to an acid value of 35mgKOH / g, titanium acid tetraisopropyl ester (0.3wt% of 1,4-butanediol) was added, the pressure was gradually reduced to 12torr, and the temperature was increased to 220℃ for reaction. The product water was removed by distillation during the reaction. The hydroxyl value of the mixture in the reaction vessel was determined. When the hydroxyl value reached 85mgKOH / g, the reaction vessel was cooled to reduce the temperature to room temperature, and the reaction was terminated to obtain bio-based polyester polyol.

[0068] Preparation of coupling agent modified inorganic nano-oxide: L-O-phosphoserine and nano-oxidized graphene (20 million mesh, purchased from Lingshou Jianshi Mineral Powder Factory) were mixed in pure water (mass ratio of 2.5:1) at a mass ratio of 5:1, and then refluxed at 115℃ for 2.5 hours. The supernatant was removed by centrifugation at 14000rpm for 10 minutes, and the lower suspension was filtered and washed with water twice to obtain the coupling agent modified inorganic nano-oxide.

[0069] Preparation of acryl-modified inorganic nano-oxide:

[0070] (1) A premix was prepared by mixing DMF, azobisisobutyronitrile and 3-methylacrylamidodopamine in a mass ratio of 600:0.25:100;

[0071] (2) The premix and nano-graphene oxide (20 million mesh, purchased from Jing Shou County Jian Shi Mineral Powder Factory) in a mass ratio of 100:15 were mixed and then subjected to in-situ polymerization at 80°C for 10 hours to obtain a polymer material;

[0072] (3) The polymer material was filtered, and the filter cake was vacuum dried to obtain the acryl-modified inorganic nano-oxide.

[0073] Preparation of component A: 55 parts of the above-mentioned bio-based polyester polyol were dehydrated at a temperature of 120°C and a vacuum degree of -0.1 MPa for 60 minutes, and then mixed uniformly with 3 parts of the acryl-modified inorganic nano-oxide and 3 parts of the coupling agent-modified inorganic nano-oxide, followed by the addition of 3 parts of trimethylolpropane and 0.03 parts of bismuth laurate catalyst to obtain component A.

[0074] Preparation of component B: 1 part of diisocyanate and 0.42 parts of triphenylmethane triisocyanate were mixed uniformly to obtain component B.

[0075] Example 2

[0076] Preparation of bio-based polyester polyol: bio-based 1,4-butanediol and bio-based dodecanedioic acid in a molar ratio of 1.3:1 were subjected to esterification reaction in the presence of Amberlyst-35 (3 wt% of bio-based 1,4-butanediol) at 170°C under nitrogen protection, and the generated water was removed by distillation during the reaction. After the acid value reached 35 mgKOH / g, titanium tetraisopropylate (0.2 wt% of 1,4-butanediol) was added, the pressure was gradually reduced to 15 torr, and the temperature was increased to 210°C for reaction. The generated water was removed by distillation during the reaction. The hydroxyl value of the mixture in the reaction vessel was determined. When the hydroxyl value reached 126 mgKOH / g, the reaction vessel was cooled to room temperature to terminate the reaction, thereby obtaining the bio-based polyester polyol.

[0077] Preparation of coupling agent-modified inorganic nano-oxide: L-O-phosphoserine and nano-graphene oxide (20 million mesh, purchased from Jing Shou County Jian Shi Mineral Powder Factory) in a mass ratio of 7:1 were mixed in pure water (2:1 of the mass ratio of nano-graphene oxide), and then subjected to reflux reaction at 110°C for 3 hours. The supernatant was removed by centrifugation at 12000 rpm for 12 minutes, and the lower suspension was filtered and washed with water twice to obtain the coupling agent-modified inorganic nano-oxide.

[0078] Preparation of acryl-modified inorganic nano-oxide:

[0079] (1) A premix was prepared by mixing DMF, azobisisobutyronitrile and 3-methylacrylamidodopamine in a mass ratio of 740:0.3:100;

[0080] (2) The premix and nano-graphene oxide (20 million mesh, purchased from Jing Shou Jian Shi Mineral Powder Factory) in a mass ratio of 100:18 were mixed and then subjected to in-situ polymerization at 80°C for 10 hours to obtain a polymer material;

[0081] (3) The polymer material was filtered, and the filter cake was vacuum dried to obtain acryl-modified inorganic nano-oxide.

[0082] Preparation of component A: 45 parts of the above-mentioned bio-based polyester polyol were dehydrated at a temperature of 110°C and a vacuum degree of -0.1 MPa for 60 minutes, and then mixed uniformly with 3 parts of the above-mentioned acryl-modified inorganic nano-oxide and 3 parts of the coupling agent-modified inorganic nano-oxide, followed by the addition of 1 part of trimethylolpropane and 0.04 parts of bismuth laurate catalyst to obtain component A.

[0083] Preparation of component B: 1 part of diisocyanate and 0.4 parts of triphenylmethane triisocyanate were mixed uniformly to obtain component B.

[0084] Example 3

[0085] Preparation of bio-based polyester polyol: bio-based 1,4-butanediol and bio-based dodecanedioic acid in a molar ratio of 1.2:1 were subjected to esterification reaction under nitrogen protection and in the presence of Amberlyst-70 (4 wt% of bio-based 1,4-butanediol), and the generated water was removed by distillation during the reaction. After the acid value reached 40 mgKOH / g, titanium tetraisopropoxide (0.3 wt% of 1,4-butanediol) was added, the pressure was gradually reduced to 10 torr, and the temperature was increased to 230°C for reaction. The generated water was removed by distillation during the reaction. The hydroxyl value of the mixture in the reaction vessel was measured, and when the hydroxyl value reached 45 mgKOH / g, the reaction vessel was cooled to reduce the temperature to room temperature, and the reaction was terminated to obtain bio-based polyester polyol.

[0086] Preparation of coupling agent modified inorganic nano-oxide: L-O-Phosphonoserine and nano-oxidized graphene (20 million mesh, purchased from JingShou County JianShi Mineral Powder Factory) were mixed in pure water (mass ratio of 3:1) and then refluxed at 105°C for 4 hours. The reaction suspension was centrifuged at 12000 rpm for 15 minutes to remove the supernatant, and the lower suspension was filtered and washed with water twice to obtain the coupling agent modified inorganic nano-oxide.

[0087] Preparation of acryl modified inorganic nano-oxide:

[0088] (1) DMF, azobisisobutyronitrile and 3-methyl acrylamido dopamine were mixed in a mass ratio of 740:0.3:100 to obtain a premix;

[0089] (2) The premix and nano-oxidized graphene (20 million mesh, purchased from JingShou County JianShi Mineral Powder Factory) were mixed in a mass ratio of 100:18 and then in-situ polymerized at 80°C for 10 hours to obtain a polymer material;

[0090] (3) The polymer material was filtered and the filter cake was vacuum dried to obtain the acryl modified inorganic nano-oxide.

[0091] Preparation of A component: The above-mentioned bio-based polyester polyol 40 parts was dehydrated at a temperature of 110°C and a vacuum degree of -0.1 MPa for 40 min, and then mixed uniformly with the acryl modified inorganic nano-oxide 3 parts and the coupling agent modified inorganic nano-oxide 3 parts, and then mixed uniformly with trimethylolpropane 2 parts and bismuth laurate catalyst 0.03 parts to obtain the A component.

[0092] Preparation of B component: Diisocyanate and triphenylmethane triisocyanate were mixed uniformly in a mass ratio of 1:0.6 to obtain the B component.

[0093] Comparative Example 1

[0094] According to the method of Example 1, except that,

[0095] Preparation of A component: The bio-based polyester polyol in Example 1, 55 parts, was dehydrated at a temperature of 120°C and a vacuum degree of -0.1 MPa for 60 min, and then mixed uniformly with the coupling agent modified inorganic nano-oxide in Example 1, 6 parts, and then mixed uniformly with trimethylolpropane 3 parts and bismuth laurate catalyst 0.03 parts to obtain the A component.

[0096] Comparative Example 2

[0097] According to the method of Example 1, except that,

[0098] In the preparation of the coupling agent modified inorganic nano-oxide and acryl modified inorganic nano-oxide, nano-silica (20 million mesh) is used to replace nano-graphene oxide.

[0099] Comparative Example 3

[0100] According to the method of Example 1, except that,

[0101] Preparation of coupling agent modified inorganic nano-oxide suspension: the pH value of pure water (mass ratio of 2.5:1 with nano-graphene oxide) is adjusted to 9 using ammonia water, and the coupling agent KH550 with a mass ratio of 5:1 is mixed with nano-graphene oxide (2000 mesh, purchased from Lingshou Jianshi Mineral Powder Factory), then refluxed at 115°C for 2.5 hours, then the reaction suspension is centrifuged at 14000 rpm for 10 minutes to remove the supernatant, the lower suspension is filtered and washed with water twice, then the solid phase is dried to obtain the coupling agent modified inorganic nano-oxide.

[0102] Comparative Example 4

[0103] According to the method of Example 1, except that,

[0104] Preparation of A component: according to the weight parts, 55 parts of bio-based polyester polyol in Example 1 is dehydrated at a temperature of 120°C and a vacuum degree of-0.1 MPa for 60 min, then mixed uniformly with 6 parts of acryl modified inorganic nano-oxide in Example 1, then 3 parts of trimethylolpropane and 0.03 parts of bismuth laurate catalyst are added and mixed uniformly to obtain A component.

[0105] Performance test

[0106] Components A and B in the examples and comparative examples are mixed according to the mass ratio of 2.5:1, and the coating dry weight is 2g / m 2 , and the room temperature curing time is 2h, and then the aging time at 45°C is 12h.

[0107] The substrate used is 20um AL, and 25um CPP, which are compounded together with an adhesive, and the adhesive used is the adhesive in the above examples to obtain an aluminum-plastic composite film.

[0108] 1. Peel strength test: according to GB / T 8808-1988, the Al layer and the CPP layer in the aluminum-plastic composite film are tested, the width is 20mm, the speed is 300mm / min,

[0109] 2. Cooking resistance test: after cooking at 135°C for 40min, the peel strength is tested according to the above method

[0110] 3. Oxygen transmission rate test: The oxygen transmission rate was measured according to the method of ASTM D 3985-95 on an oxygen transmission rate tester, and the test conditions were as follows: test temperature 23°C, flow rate 10 sccm.

[0111] 5. Appearance: The laboratory technician visually inspected the aluminum-plastic composite film for bubbles in the middle layer.

[0112] The test results are shown in Table 1.

[0113] Table 1

[0114]

[0115] As can be seen from the results in Table 1, the adhesive in Examples 1-3 including the technical solution of the present application has excellent peel strength, boiling resistance, and also excellent oxygen barrier property and appearance, specifically,

[0116] Compared with the adhesive containing only 3-methacrylamido dopamine modified inorganic nano-oxide (nano-oxidized graphene) or the adhesive containing only coupling agent (L-O-phosphoserine) modified inorganic nano-oxide (nano-oxidized graphene) in the component, the peel strength and oxygen barrier property of the adhesive containing both 3-methacrylamido dopamine modified inorganic nano-oxide (nano-oxidized graphene) and coupling agent (L-O-phosphoserine) modified inorganic nano-oxide (nano-oxidized graphene) are more excellent, and the problem of "bubbles" can be avoided. In particular, the addition of modified inorganic nano-oxide (nano-oxidized graphene) not only can synergistically increase the peel strength and oxygen barrier property of the adhesive with 3-methacrylamido dopamine modified inorganic nano-oxide (nano-oxidized graphene), but also can improve the poor boiling resistance of 3-methacrylamido dopamine modified inorganic nano-oxide (nano-oxidized graphene). Further, when the inorganic nano-oxide is nano-oxidized graphene, the boiling resistance is more excellent than when the inorganic nano-oxide is silicon oxide.

Claims

1. A food packaging adhesive comprising a bio-based polyester polyol, characterized in that, the adhesive comprises a component A and a component B; the component A comprises, in parts by weight, 40-55 parts of a bio-based polyester polyol, 1-3 parts of a chain extender, 6-7 parts of a modified inorganic nano-oxide, and 0.01-0.05 parts of a catalyst; the component B comprises, in parts by weight, an isocyanate-based curing agent; a preparation method of the bio-based polyester polyol comprises: esterification of a polyol and a polybasic acid at 150-170℃ in the presence of a strong acid cation exchange resin under nitrogen protection, removal of product water by distillation during the reaction, addition of tetraisopropyl titanate after the reaction until the acid value is 35-40mgKOH / g, reduction of the pressure to 10-15torr, increase of the temperature to 210-230℃ for reaction, removal of product water by distillation during the reaction, determination of the hydroxyl value of the mixture in the reaction vessel, cooling of the reaction vessel to reduce the temperature to room temperature to terminate the reaction to obtain the bio-based polyester polyol; wherein at least one of the polyol and the polybasic acid is a bio-based raw material; the modified inorganic nano-oxide comprises acryloyl-modified inorganic nano-oxide and coupling agent-modified inorganic nano-oxide, and the mass ratio of the coupling agent-modified inorganic nano-oxide to the acryloyl-modified inorganic nano-oxide is (0.8-1.2) : 1; the acryloyl-modified inorganic nano-oxide is obtained by in-situ polymerization of an acryloyl monomer providing an acrylamide structural unit on inorganic nano-oxide; the inorganic nano-oxide in the coupling agent-modified inorganic nano-oxide and the acryloyl-modified inorganic nano-oxide is nano-oxidized graphene; a preparation method of the coupling agent-modified inorganic nano-oxide comprises: mixing a coupling agent and inorganic nano-oxide in pure water, followed by refluxing at 105-115℃ for 2.5-4 hours, centrifuging the reaction suspension to remove the supernatant, filtering the lower suspension and washing with water for several times, and drying the solid phase to obtain the coupling agent-modified inorganic nano-oxide; the coupling agent is L-O-phosphoserine; the acryloyl monomer is 3-methyl acrylamido dopamine. 2.The adhesive according to claim 1, characterized in that, the polybasic acid is selected from bio-based polybasic acid and optionally petroleum-based polybasic acid; the bio-based polybasic acid is selected from at least one of bio-based succinic acid, bio-based sebacic acid, bio-based undecanedioic acid and bio-based dodecanedioic acid; and the petroleum-based polybasic acid comprises one or more of petroleum-based phthalic acid, petroleum-based isophthalic acid, petroleum-based terephthalic acid, petroleum-based adipic acid and petroleum-based azelaic acid. The polyol is selected from bio-based polyol, and optionally petroleum-based polyol; the bio-based polyol is selected from bio-based 1,4-butanediol and / or bio-based 1,3-propanediol; the petroleum-based polyol includes one or more of petroleum-based ethylene glycol, petroleum-based diethylene glycol, petroleum-based 1,6-hexanediol, petroleum-based neopentyl glycol, petroleum-based 2-methyl-1,3-propanediol and petroleum-based 3-methyl-1,5-pentanediol; the molar ratio of the polyol to the polybasic acid is (1.1-1.3):1; The strong acidic cation exchange resin is selected from at least one of Amberlyst-15, Amberlyst-35 and Amberlyst-70; The mass ratio of the strong acidic cation exchange resin to the polyol is 0.01-0.1:

1.

3. The adhesive according to claim 1 or 2, wherein, The preparation method of the acryl-modified inorganic nano-oxide includes: (1) mixing a solvent, an initiator and an acryl monomer to obtain a premix; (2) mixing the premix with inorganic nano-oxide and then performing in-situ polymerization to obtain a polymer material; (3) filtering the polymer material, vacuum drying the filter cake to obtain the acryl-modified inorganic nano-oxide.

4. The adhesive according to claim 3, wherein, The mass ratio of the solvent, the initiator and the acryl monomer is (600-740):(0.2-0.3):100; the solvent is DMF; the initiator is an azo initiator; the mass ratio of the premix to the inorganic nano-oxide is 100:(15-30); the in-situ polymerization is performed at 80-85°C for 6-10 hours.

5. The adhesive according to claim 1 or 2, wherein, The mass ratio of the coupling agent to the inorganic nano-oxide is (5-7):1; the mass ratio of the inorganic nano-oxide to pure water is 1:(2-3); the centrifugation is performed at 12000-14000 rpm for 10-15 minutes.

6. The adhesive according to claim 1, wherein, The mesh number of the nano-oxidized graphene is 180,000-250,000.

7. The adhesive according to claim 1 or 2, wherein, The chain extender is selected from at least one of ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, trimethylolpropane, sorbitol, triethanolamine, diethylaminoethanol, diethyltoluene diamine and dimethylthio toluene diamine; The catalyst is at least one of metal catalysts of organic tin, organic bismuth, organic lead and organic zinc; The isocyanate curing agent is diisocyanate and triphenylmethane triisocyanate; The weight ratio of the diisocyanate to the triphenylmethane triisocyanate is 1:(0.1-1); The mass ratio of the A component to the B component is (1.8-2.5):

1.

8. A preparation method of the adhesive according to any one of claims 1-7, wherein, The preparation method of the adhesive includes: (1) the bio-based polyester polyol is dehydrated at a temperature of 110-120℃ and a vacuum degree of-0.06 to-0.1 MPa for 40-60 min; (2) the dehydrated bio-based polyester polyol is mixed with modified inorganic nano-oxide, and then a chain extender and a catalyst are added to obtain component A; (3) isocyanate curing agents are mixed to obtain component B.

9. Use of the adhesive according to any one of claims 1-7 in food soft packaging bonding.

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