Food packaging adhesive containing bio-based polyester polyol as well as preparation method and application of food packaging adhesive

Abstract

The invention relates to the technical field of adhesives, in particular to a food packaging adhesive containing bio-based polyester polyol as well as a preparation method and application of the food packaging adhesive. The adhesive comprises a component A and a component B, the component A is prepared from the following components in parts by weight: 40 to 55 parts of bio-based polyester polyol, 1 to 3 parts of chain extender, 6 to 7 parts of modified inorganic nano oxide and 0.01 to 0.05 part of catalyst; and the component B comprises an isocyanate curing agent. The adhesive provided by the invention has excellent peel strength and boiling resistance, and also has certain oxygen barrier property.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to a food packaging adhesive comprising bio-based polyester polyols, and a preparation method and application thereof. Background Art

[0002] Food flexible packaging refers to packaging with changeable shapes without fillers, such as aluminum foil, plastic film or their composites. Adhesives are used to compound the packaging film in flexible packaging. The selection of suitable adhesives has a key impact on the quality of flexible packaging. Currently, the most commonly used flexible packaging adhesives are polyurethane adhesives, but these adhesives are made from excessive fossil raw materials.

[0003] The peel strength of adhesive is an important factor in evaluating the quality of adhesive. With the increasing demand for flexible packaging and the wider application range, the requirements for the peel strength of adhesive are getting higher and higher. At present, many researchers focus on increasing the peel strength of adhesives, but do not pay attention to the isolation of adhesives from oxygen, especially in food packaging adhesives, where isolation from oxygen is particularly important. Summary of the invention

[0004] The first aspect of the present invention provides a food packaging adhesive containing bio-based polyester polyol, the adhesive comprising component A and component B; in parts by weight, the component A comprises: 40-55 parts of bio-based polyester polyol, 1-3 parts of chain extender, 6-7 parts of modified inorganic nano oxide, and 0.01-0.05 parts of catalyst; the component B comprises: an isocyanate curing agent; the preparation method of the bio-based polyester polyol comprises: polyol and polyacid are subjected to esterification reaction at 150-170° C. under nitrogen protection and in the presence of a strongly acidic cation exchange resin, the product water is removed by distillation during the reaction, tetraisopropyl titanate is added after the reaction to an acid value of 35-40 mgKOH / g, the pressure is reduced to 10-15 torr, the temperature is increased to The method comprises the steps of: reacting at 210-230° C., removing product water by distillation during the reaction, measuring the hydroxyl value of the mixture in the reaction container, and cooling the reaction container when the hydroxyl value reaches 25-225 mgKOH / g to reduce the temperature to room temperature, terminating the reaction and obtaining a bio-based polyester polyol; wherein at least one of the polyol and the polyacid is a bio-based raw material; the modified inorganic nano-oxide comprises an acryl-modified inorganic nano-oxide and a coupling agent-modified inorganic nano-oxide, and the mass ratio of the coupling agent-modified inorganic nano-oxide to the acryl-modified inorganic nano-oxide is (0.8-1.2):1; the acryl-modified inorganic nano-oxide is obtained by in-situ polymerization of an acryl monomer providing an acrylamide structural unit on an inorganic nano-oxide.

[0005] Preparation of Bio-based Polyester Polyols

[0006] In the present invention, those skilled in the art can gradually reduce the pressure to 10-15 torr according to actual needs.

[0007] The use of bio-based raw materials in the present invention can ensure that the adhesive has a certain bio-based component.

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

[0009] In the present invention, the optional petroleum-based polybasic acid means that the petroleum-based polybasic acid may be contained or may not be contained.

[0010] As a preferred technical solution of the present invention, 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 invention, succinic acid is also called succinic acid, and its natural source is succinic acid formed by the resin of pine plants buried underground for a long time; sebacic acid exists naturally in castor oil; and undecanedioic acid is mainly produced by biological fermentation.

[0012] As a preferred technical solution of the present invention, 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 invention, the bio-based polyester polyol has a bio-based raw material content greater than 0, and the maximum bio-based content is 100%. Those skilled in the art can also select petroleum-based polyacids according to the bio-based content or characteristic requirements. As a preferred technical solution of the present invention, the polyol is selected from bio-based polyols and optionally petroleum-based polyols.

[0014] In the present invention, the optional petroleum-based polyol means that the petroleum-based polyol may be contained or may not be contained.

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

[0016] In the present invention, 1,4-butanediol and 1,3-propanediol can be produced in nature, for example, synthesized by fermentation of some microorganisms.

[0017] In the present invention, those skilled in the art can select petroleum-based polyols according to bio-based content or property requirements, including 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.

[0018] As a preferred technical solution of the present invention, the strongly acidic 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 invention, the molar ratio of the polyol to the polyacid is (1.1-1.3):1.

[0020] As a preferred technical solution of the present invention, the mass ratio of the strongly acidic 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 invention, the mass of the tetraisopropyl titanate is 0.1-0.5wt% of the mass of the polyol.

[0022] Acryloyl modified inorganic nano oxide

[0023] As a preferred technical solution of the present invention, 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 the inorganic nano-oxide and performing in-situ polymerization to obtain a polymer material;

[0026] (3) After filtering the polymer material, the filter cake is vacuum dried to obtain an acryl-modified inorganic nano-oxide.

[0027] As a preferred technical solution of the present invention, when preparing 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 invention, the acryl monomer is selected from 3-methacrylamide dopamine and / or 3-acrylamide dopamine, preferably 3-methacrylamide dopamine.

[0029] The adhesive of the present invention has excellent comprehensive properties, which may be partly due to the special structure of dopamine and other components of the system being able to better cooperate with each other to provide higher peel strength and other properties.

[0030] The type of initiator in the present invention is not particularly limited, and is preferably an azo initiator, such as azobisisobutyronitrile and azobisisoheptanenitrile.

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

[0032] As a preferred technical solution of the present invention, 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 invention, the conditions of the in-situ polymerization include: reacting at 80° C. to 85° C. for 6 to 10 hours.

[0034] In the present invention, there is no particular limitation on the conditions for vacuum drying, as long as the solvent can be removed, and the present invention will not elaborate on this in detail.

[0035] Coupling agent modified inorganic nano oxide

[0036] As a preferred technical solution of the present invention, 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 reflux reacting at 105-115°C for 2.5-4 hours, then centrifuging the reaction suspension to remove the supernatant, filtering the lower suspension and washing it with water several times (for example 2-3 times), and solid phase drying to obtain the coupling agent modified inorganic nano-oxide.

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

[0038] As a preferred technical solution of the present invention, 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 invention, the mass ratio of the inorganic nano-oxide to pure water is 1:(2-3).

[0040] In the present invention, the centrifugal conditions are not particularly limited, and preferably centrifugation is performed at 12000-14000 rpm for 10-15 minutes.

[0041] As a preferred technical solution of the present invention, the inorganic nano-oxides in the coupling agent-modified inorganic nano-oxide and the acryl-modified inorganic nano-oxide are independently selected from at least one of nano-graphene oxide, nano-silicon dioxide, nano-titanium dioxide and nano-zirconium dioxide, preferably nano-graphene oxide, and preferably the mesh number of the nano-graphene oxide is 180,000-250,000 mesh.

[0042] Chain Extender

[0043] As a preferred technical solution of the present invention, the specific type of the chain extender in the present invention is not particularly limited, and can be a conventional multifunctional small molecule alcohol or amine chain extender in the art. As a preferred technical solution of the present invention, 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, diethyltoluenediamine and dimethylthiotoluenediamine.

[0044] catalyst

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

[0046] Isocyanate curing agent

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

[0048] As a more preferred technical solution of the present invention, 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 invention, the mass ratio of component A to component B 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] A second aspect of the present invention provides a method for preparing an adhesive, the method comprising:

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

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

[0053] (3) Mix the isocyanate curing agent to obtain component B.

[0054] The third aspect of the present invention provides the use of the adhesive of the present invention in bonding food flexible packaging.

[0055] The material of the soft package in the present invention includes 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 cooking resistant polypropylene film), PE (polyethylene film) and PVDC (polyvinylidene chloride film).

[0056] In the present invention, the components of aluminum foil and RCPP are used as non-limiting illustrations.

[0057] When the adhesive of the present invention is used, component A and component B are mixed and then applied. The coating amount can be selected according to needs, and the coating dry amount is generally 1-2 g / m 2 After coating, it is cured at room temperature (20-30°C) for 1.5 to 2 hours, and then matured at 45 to 50°C for 10 to 15 hours.

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

[0059] In the present invention, the inventors have conducted a series of experiments and found that the adhesive of the present invention has excellent peel strength and boiling resistance, and also has certain oxygen barrier properties. However, when 3-methacrylamide dopamine-modified inorganic nano-oxide is used alone, the boiling resistance of the adhesive is reduced. The addition of LO-phosphoserine-modified inorganic nano-oxide can not only solve the defect of reduced boiling resistance caused by the acryl structural unit, but also further increase the peeling ability and oxygen barrier of the adhesive. It is speculated from the experimental data analysis that:

[0060] 1. The specific modified structure formed by the acryl monomer in situ in the inorganic nano-oxide interacts with other components in the system, especially the inorganic nano-oxide modified with LO-phosphoserine can better increase the peeling ability of the adhesive, which may be because in the system of the present invention, the acryl structural unit, LO-phosphoserine and other components in the system interact to form a better viscoelastic network structure;

[0061] 2. The raw material components such as the chain extender in the present application can not only act as a chain extender, but also the chain structure itself can be randomly interspersed in a specific system containing 3-methylacrylamide dopamine modified inorganic nano-oxides, and the coupling agent, especially the amino acid coupling agent LO-phosphoserine modified inorganic nano-oxide structure together, and when the coupling agent is LO-phosphoserine, the LO-phosphoserine modified inorganic nano-oxide can play a better role in the system with other components, so that the various raw material components in the system interact with each other to form a stable network space, which greatly improves the density of the microstructure of the adhesive and significantly improves the oxygen barrier capacity;

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

[0063] 4. The synergistic effect of the inorganic nano-oxide modified with LO-phosphoserine and the inorganic nano-oxide modified with 3-methylacrylamide dopamine in the present invention can avoid the "bubble" problem. This may be because in the presence of the specific coupling agent LO-phosphoserine, the short chain interlacing of the methyl group of 3-methylacrylamide in the system can increase the leveling property of the adhesive and enable more uniform bonding to the substrate. DETAILED DESCRIPTION

[0064] The present invention is described in detail below through examples. The following examples are only illustrative of the specific technical solutions of the present invention and do not limit the scope of the present invention. That is, it should be understood that non-essential simple corrections, adjustments and combinations made by those skilled in the art based on the inventive concept of the present invention are all within the scope of protection claimed by the present invention.

[0065] In the following examples, unless otherwise specified, all raw materials are commercially available.

[0066] Example 1

[0067] Preparation of bio-based polyester polyols: Bio-based 1,4-butanediol and bio-based sebacic acid with a molar ratio of 1.1:1 were subjected to esterification reaction at 160°C under nitrogen protection and in the presence of Amberlyst-15 (5wt% of bio-based 1,4-butanediol). During the reaction, the product water was removed by distillation. After the reaction reached an acid value of 35mgKOH / g, tetraisopropyl titanate (0.3wt% of 1,4-butanediol) was added, the pressure was gradually reduced to 12torr, and the temperature was increased to 220°C for reaction. During the reaction, the product water was removed by distillation, and the hydroxyl value of the mixture in the reaction vessel was measured. 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 polyols.

[0068] Preparation of coupling agent modified inorganic nano-oxide: LO-phosphoserine and nano-graphene oxide (mesh size of 200,000, purchased from Lingshou County Jianshi Mineral Powder Factory) were added in a mass ratio of 5:1 to pure water (with a mass ratio of 2.5:1 to nano-graphene oxide), and then refluxed at 115°C for 2.5 hours. The reaction suspension was then centrifuged at 14,000 rpm for 10 minutes to remove the supernatant. The lower suspension was filtered and washed twice with water and then solid-phase dried to obtain the coupling agent modified inorganic nano-oxide.

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

[0070] (1) DMF, azobisisobutyronitrile, and 3-methacrylamide dopamine are mixed in a mass ratio of 600:0.25:100 to obtain a premix;

[0071] (2) mixing the premix with a mass ratio of 100:15 with nano-graphene oxide (mesh size of 200,000, purchased from Jianshi Mineral Powder Factory, Lingshou County) and performing in-situ polymerization at 80° C. for 10 h to obtain a polymer material;

[0072] (3) After filtering the polymer material, the filter cake is vacuum dried to obtain an acryl-modified inorganic nano-oxide.

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

[0074] Preparation of component B: diisocyanate and triphenylmethane triisocyanate in a mass ratio of 1:0.42 were uniformly mixed to obtain component B.

[0075] Example 2

[0076] Preparation of bio-based polyester polyols: Bio-based 1,4-butanediol and bio-based dodecanedioic acid with a molar ratio of 1.3:1 were subjected to esterification reaction at 170°C under nitrogen protection and in the presence of Amberlyst-35 (3wt% of bio-based 1,4-butanediol). During the reaction, the product water was removed by distillation. After the reaction reached an acid value of 35 mgKOH / g, tetraisopropyl titanate (0.2wt% of 1,4-butanediol) was added, the pressure was gradually reduced to 15 torr, and the temperature was increased to 210°C for reaction. During the reaction, the product water was removed by distillation, and the hydroxyl value of the mixture in the reaction vessel was measured. When the hydroxyl value reached 126 mgKOH / g, the reaction vessel was cooled to reduce the temperature to room temperature, and the reaction was terminated to obtain bio-based polyester polyols.

[0077] Preparation of coupling agent modified inorganic nano-oxide: In pure water (with a mass ratio of 2:1 to nano-graphene oxide), LO-phosphoserine and nano-graphene oxide (mesh size of 200,000, purchased from Lingshou County Jianshi Mineral Powder Factory) with a mass ratio of 7:1 were mixed, and then refluxed at 110°C for 3 hours. The reaction suspension was then centrifuged at 12000rpm for 12 minutes to remove the supernatant. The lower suspension was filtered and washed twice with water and then solid-phase dried to obtain the coupling agent modified inorganic nano-oxide.

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

[0079] (1) DMF, azobisisobutyronitrile, and 3-methacrylamide dopamine are mixed in a mass ratio of 740:0.3:100 to obtain a premix;

[0080] (2) mixing the premix with a mass ratio of 100:18 with nano-graphene oxide (mesh size of 200,000, purchased from Jianshi Mineral Powder Factory, Lingshou County) and performing in-situ polymerization at 80° C. for 10 h to obtain a polymer material;

[0081] (3) After filtering the polymer material, the filter cake is vacuum dried to obtain an acryl-modified inorganic nano-oxide.

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

[0083] Preparation of component B: diisocyanate and triphenylmethane triisocyanate in a mass ratio of 1:0.4 were uniformly mixed to obtain component B.

[0084] Example 3

[0085] Preparation of bio-based polyester polyols: Bio-based 1,4-butanediol and bio-based dodecanedioic acid with a molar ratio of 1.2:1 were subjected to esterification reaction at 150°C under nitrogen protection and in the presence of Amberlyst-70 (4wt% of bio-based 1,4-butanediol). During the reaction, the product water was removed by distillation. After the reaction reached an acid value of 40mgKOH / g, tetraisopropyl titanate (0.3wt% of 1,4-butanediol) was added, the pressure was gradually reduced to 10torr, and the temperature was increased to 230°C for reaction. During the reaction, the product water was removed by distillation, and the hydroxyl value of the mixture in the reaction vessel was measured. When the hydroxyl value reached 45mgKOH / g, the reaction vessel was cooled to reduce the temperature to room temperature, and the reaction was terminated to obtain bio-based polyester polyols.

[0086] Preparation of coupling agent modified inorganic nano-oxide: In pure water (with a mass ratio of 3:1 to nano-graphene oxide), LO-phosphoserine and nano-graphene oxide (mesh size of 200,000, purchased from Lingshou County Jianshi Mineral Powder Factory) with a mass ratio of 6:1 were mixed, and then refluxed at 105°C for 4 hours. The reaction suspension was then centrifuged at 12000rpm for 15 minutes to remove the supernatant. The lower suspension was filtered and washed twice with water and solid-phase dried to obtain the coupling agent modified inorganic nano-oxide.

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

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

[0089] (2) mixing the premix with a mass ratio of 100:18 with nano-graphene oxide (mesh size of 200,000, purchased from Jianshi Mineral Powder Factory, Lingshou County) and performing in-situ polymerization at 80° C. for 10 h to obtain a polymer material;

[0090] (3) After filtering the polymer material, the filter cake is vacuum dried to obtain an acryl-modified inorganic nano-oxide.

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

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

[0093] Comparative Example 1

[0094] The method of Example 1 is as follows, except that

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

[0096] Comparative Example 2

[0097] The method of Example 1 is as follows, except that

[0098] When preparing coupling agent-modified inorganic nano-oxides and acryl-modified inorganic nano-oxides, nano-silicon oxide (mesh size of 200,000) is used to replace nano-graphene oxide.

[0099] Comparative Example 3

[0100] The method of Example 1 is as follows, except that

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

[0102] Comparative Example 4

[0103] The method of Example 1 is as follows, except that

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

[0105] Performance Testing

[0106] Component A and component B in the embodiment and comparative example were mixed at a mass ratio of 2.5:1, and the coating dry weight was 2 g / m 2 , curing at room temperature for 2 hours, and then aging at 45°C for 12 hours.

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

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

[0109] 2. Retort resistance test: After retorting at 135°C for 40 minutes, test the peel strength according to the above method.

[0110] 3. Oxygen permeability test: Oxygen permeability tester is used to test according to the method of ASTM D 3985-95. The test conditions are as follows: test temperature 23°C, flow rate 10 sccm.

[0111] 5. Appearance: Laboratory technicians visually inspect whether there are bubbles between the layers of the aluminum-plastic composite film.

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

[0113] Table 1

[0114]

[0115] From the results in Table 1, it can be seen that the adhesives in Examples 1-3 of the technical solution of the present invention have excellent peel strength and boiling resistance, as well as excellent oxygen barrier properties and appearance. Specifically,

[0116] Compared with the adhesive containing only 3-methacrylamide dopamine modified inorganic nano oxide (nano graphene oxide) or the adhesive containing only coupling agent (LO-phosphoserine) modified inorganic nano oxide (nano graphene oxide), the adhesive containing both 3-methacrylamide dopamine modified inorganic nano oxide (nano graphene oxide) and coupling agent (LO-phosphoserine) modified inorganic nano oxide (nano graphene oxide) has better peel strength and oxygen barrier properties, and can avoid " The problem of "bubbles" is solved, especially the addition of modified inorganic nano-oxide (nano-graphene oxide) can not only synergize with 3-methacrylamide dopamine modified inorganic nano-oxide (nano-graphene oxide) to further increase the peel strength and oxygen barrier of the adhesive, but also improve the defect of poor retortability of 3-methacrylamide dopamine modified inorganic nano-oxide (nano-graphene oxide); further, when the inorganic nano-oxide is nano-graphene oxide, the retort resistance is better than that 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 component A and component B; In parts by weight, the component A comprises: 40 to 55 parts of bio-based polyester polyol, 1 to 3 parts of chain extender, 6 to 7 parts of modified inorganic nano-oxide, and 0.01 to 0.05 parts of catalyst; In parts by weight, the component B includes: an isocyanate curing agent; The preparation method of the bio-based polyester polyol comprises: carrying out an esterification reaction of a polyol and a polyacid at 150-170° C. under nitrogen protection and in the presence of a strongly acidic cation exchange resin, removing product water by distillation during the reaction, adding tetraisopropyl titanate after the reaction reaches an acid value of 35-40 mgKOH / g, reducing the pressure to 10-15 torr, raising the temperature to 210-230° C. for reaction, removing product water by distillation during the reaction, measuring the hydroxyl value of the mixture in the reaction container, cooling the reaction container to reduce the temperature to room temperature when the hydroxyl value reaches 25-225 mgKOH / g, terminating the reaction to obtain the bio-based polyester polyol; wherein at least one of the polyol and the polyacid is a bio-based raw material; The modified inorganic nano-oxide includes an acryl-modified inorganic nano-oxide and a coupling agent-modified inorganic nano-oxide, and the mass ratio of the coupling agent-modified inorganic nano-oxide to the acryl-modified inorganic nano-oxide is (0.8-1.2):1; The acryl-modified inorganic nano-oxide is obtained by in-situ polymerization of an acryl monomer providing an acrylamide structural unit on an inorganic nano-oxide.

2. The adhesive according to claim 1, characterized in that: The polyacid is selected from bio-based polyacids and optionally petroleum-based polyacids; 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; 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; The polyol is selected from bio-based polyols and optionally petroleum-based polyols; the bio-based polyol is selected from bio-based 1,4-butanediol and / or bio-based 1,3-propylene glycol; the petroleum-based polyol is 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 polyacid is (1.1-1.3):1; The strongly acidic cation exchange resin is selected from at least one of Amberlyst-15, Amberlyst-35 and Amberlyst-70; The mass ratio of the strongly acidic cation exchange resin to the polyol is 0.01-0.1:

1.

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

4. The adhesive according to claim 3, characterized in that: The mass ratio of the solvent, the initiator and the acryl monomer is (600-740): (0.2-0.3): 100; the acryl monomer is selected from 3-methacrylamide dopamine and / or 3-acrylamide dopamine; 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 conditions of the in-situ polymerization include: reacting at 80° C. to 85° C. for 6 to 10 hours.

5. The adhesive according to claim 1 or 2, characterized in that: The preparation method of the coupling agent modified inorganic nano oxide comprises: mixing the coupling agent and the inorganic nano oxide in pure water, and then reflux reacting at 105-115° C. for 2.5-4 hours, and then centrifuging the reaction suspension to remove the supernatant, filtering the lower suspension, washing with water for several times, and solid phase drying to obtain the coupling agent modified inorganic nano oxide; The coupling agent is selected from LO-phosphoserine and / or N-acetyl-D-serine; 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 centrifugal conditions include: centrifugation at 12000-14000 rpm for 10-15 minutes.

6. The adhesive according to claim 1 or 2, characterized in that: The inorganic nano-oxides in the coupling agent-modified inorganic nano-oxide and the acryl-modified inorganic nano-oxide are independently selected from at least one of nano-graphene oxide, nano-silicon dioxide, nano-titanium dioxide and nano-zirconium dioxide.

7. The adhesive according to claim 6, characterized in that: The inorganic nano-oxides in the coupling agent-modified inorganic nano-oxide and the acryl-modified inorganic nano-oxide are each independently selected from nano-graphene oxide; The mesh number of the nano graphene oxide is 180,000-250,000 meshes.

8. The adhesive according to claim 1 or 2, characterized in that: 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, diethyltoluenediamine and dimethylthiotoluenediamine; The catalyst is at least one of the metal catalysts of organotin, organobismuth, organopion and organozinc; The isocyanate curing agent is selected from diisocyanate and triphenylmethane triisocyanate; The weight ratio of the diisocyanate to triphenylmethane triisocyanate is 1:(0.1-1); The mass ratio of component A to component B is (1.8-2.5):

1.

9. A method for preparing the adhesive according to any one of claims 1 to 8, characterized in that: The preparation method of the adhesive comprises: (1) dehydrating the bio-based polyester polyol at a temperature of 110-120° C. and a vacuum degree of -0.06 to -0.1 MPa for 40 to 60 minutes; (2) mixing the dehydrated bio-based polyester polyol with the modified inorganic nano-oxide, and then adding a chain extender and a catalyst to obtain component A; (3) Mix the isocyanate curing agent to obtain component B.

10. Use of the adhesive according to any one of claims 1 to 8 in bonding food flexible packaging.

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