A polyurethane adhesive and its usage method

Abstract

The present invention provides a polyurethane adhesive and a method for using the same. The polyurethane adhesive comprises a main agent and a curing agent. The raw materials for preparing the main agent include the following components in parts by weight: 110-40 parts by weight of polyester polyol 1, 30-60 parts by weight of polyester polyol 2, 1-10 parts by weight of a flexible chain extender, 1-10 parts by weight of a polyisocyanate, 0.02-0.06 parts by weight of a catalyst, and 20-30 parts by weight of a solvent. The polyester polyol 1 is a hydroxyl-terminated polyester polyol with a number-average molecular weight of 3000-8000, and the polyester polyol 2 has a number-average molecular weight of 500-2000. The polyurethane adhesive of the present invention has high adhesiveness and excellent water-boiling resistance and retort resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesives, and particularly relates to a polyurethane adhesive and a method for using the same. Background Art

[0002] With the prosperity of plastic composite flexible packaging in China, as one of the important components of composite flexible packaging, flexible packaging adhesives have also developed vigorously. Solvent-based polyurethane adhesives are still the mainstream adhesives in the packaging industry due to their excellent comprehensive performance and irreplaceability. The concentration of traditional mainstream dry composite adhesives is generally 30% - 35%, which has problems such as high solvent content, high preparation cost, large energy loss during drying, environmental pollution caused by solvent volatilization, and solvent residue in products. The solid content of high-solid low-viscosity adhesives reaches 45% or more, reducing the amount of solvent used, thereby reducing VOC emissions. They have low viscosity and can be applied to high-speed production of composite flexible packaging at 150 - 250 m / min, thus improving economic benefits. However, it is currently a difficult problem that the industry has not been able to completely solve to make polyurethane adhesives simultaneously have high solid content, low viscosity, and excellent adhesiveness.

[0003] CN 110951045 A discloses a composite adhesive for rolling-tooth pharmaceutical flexible packaging. The adhesive is composed of a main agent and a curing agent in a weight ratio of 20:3 - 20:5, wherein: the main agent is an ethyl acetate solution of toluene diisocyanate-modified hydroxyl-terminated polyurethane resin, and the rotational viscosity of the main agent at 25°C is 2000 - 4000 mPa·s, and the solid content is 64 - 68%; the curing agent is an ethyl acetate solution containing a silane-modified isocyanate prepolymer, and the rotational viscosity of the curing agent at 25°C is 100 - 300 mPa·s, and the solid content is 58 - 62%. This technical solution prepares an adhesive with a main agent solid content of 64 - 68% by using toluene diisocyanate-modified hydroxyl-terminated polyurethane resin, but in order to further reduce the amount of solvent used, the solid content still needs to be further improved.

[0004] CN 106520052 A discloses a high-solid content and low-viscosity aqueous polyurethane adhesive, which includes polyester polyol. The polyester polyol reacts with polyisocyanate under the action of a hydrophilic chain extender and a catalyst to form a polyester polyol - polyisocyanate prepolymer. After adding sodium aminosulfonate, deionized water, an auxiliary agent, and a small molecule chain extender, an aqueous polyurethane dispersion or emulsion is formed; its characteristic is that the polyester polyol is polymerized by using tert-carbonic acid glycidyl ester monomers, polyacids, dianhydrides, and epoxy monomers under the action of a catalyst, a polymerization inhibitor, and an antioxidant. This technical solution reduces the viscosity by adding tert-carbonic acid glycidyl ester groups with hydrophobic characteristics and highly branched structures, making the solid content of the product reach 70%, but its preparation process is complex.

[0005] Therefore, there is an urgent need to develop a polyurethane adhesive with high solid content, low viscosity and high adhesion. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a polyurethane adhesive and its use method. In the present invention, by designing the raw materials for the main agent and the curing agent in the polyurethane adhesive, the prepared polyurethane adhesive has high adhesion, excellent water boiling resistance and steam cooking resistance.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a polyurethane adhesive, and the polyurethane adhesive includes a main agent and a curing agent.

[0009] The raw materials for preparing the main agent include the following components by weight:

[0010]

[0011] The polyester polyol 1 is a hydroxyl-terminated polyester polyol with a molecular weight of 3000 - 8000 (such as 3000, 3500, 4000, 4500, 5000, 6000, 6500, 7000, 7500 or 8000, etc.), and the molecular weight of the polyester polyol 2 is 500 - 2000 (such as 500, 600, 800, 1000, 1200, 1400, 1600, 1800, 1900 or 2000, etc.).

[0012] The polyester polyol 1 can be 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight or 40 parts by weight, etc.

[0013] The polyester polyol 2 can be 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 55 parts by weight or 60 parts by weight, etc.

[0014] The flexible chain extender can be 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight or 9 parts by weight, etc.

[0015] The polyisocyanate can be 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight or 9 parts by weight, etc.

[0016] The catalyst can be 0.02 parts by weight, 0.03 parts by weight, 0.04 parts by weight, 0.05 parts by weight or 0.06 parts by weight, etc.

[0017] The solvent can be 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, etc.

[0018] The polyurethane adhesive provided by the present invention comprises a main agent and a curing agent. The main agent is a combination of polyester polyol 1, polyester polyol 2, a flexible chain extender, a polyisocyanate, a catalyst and a solvent within a specific proportion range. By selecting a hydroxyl-terminated polyester polyol with a molecular weight of 3000 - 8000 and polyester polyol 2 with a molecular weight of 500 - 2000 and a special structure to be mutually matched as the main components of the main agent, the properties of the polyester polyol are compounded, and then mixed with the curing agent to obtain a polyurethane adhesive with excellent boiling water resistance and retort resistance. The polyurethane adhesive can be used for bonding composite structures including aluminized films or aluminum foils. The bonding performance between layers is good, and at the same time, the solid content of the polyurethane adhesive during machine operation is high.

[0019] Preferably, the mass ratio of the main agent to the curing agent is 5 - 10:1, such as 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0020] Preferably, the viscosity of the main agent is 300 - 4000 mPa·s, such as 300 mPa·s, 500 mPa·s, 800 mPa·s, 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s or 4000 mPa·s, etc.

[0021] Preferably, the solid content of the main agent is 70 - 80%, such as 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79% or 80%, etc.

[0022] Preferably, the curing agent is a mixture of a polyisocyanate prepolymer and ethyl acetate.

[0023] As a preferred technical solution of the present invention, selecting the combination of a polyisocyanate prepolymer and ethyl acetate as the curing agent to be paired with the main agent can make the performance of the polyurethane adhesive more excellent.

[0024] Preferably, the viscosity of the curing agent is 1000 - 3000 mPa·s, such as 1000 mPa·s, 1500 mPa·s, 1800 mPa·s, 2000 mPa·s, 2500 mPa·s, 2800 mPa·s or 3000 mPa·s, etc.

[0025] Preferably, the solid content of the curing agent is 65 - 75%.

[0026] Preferably, the raw materials for preparing the polyester polyol 1 include the following components by weight:

[0027]

[0028] The adipic acid can be 16 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 24 parts by weight, 26 parts by weight, 28 parts by weight, etc.

[0029] The isophthalic acid can be 22 parts by weight, 24 parts by weight, 26 parts by weight, 28 parts by weight, 30 parts by weight, 32 parts by weight, 34 parts by weight, 36 parts by weight, 38 parts by weight, 40 parts by weight, etc.

[0030] The diethylene glycol can be 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, etc.

[0031] The neopentyl glycol can be 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, etc.

[0032] The ethylene glycol can be 1 part by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, 5 parts by weight, etc.

[0033] The catalyst can be 0.006 parts by weight, 0.008 parts by weight, 0.010 parts by weight, 0.015 parts by weight, 0.020 parts by weight, 0.025 parts by weight, 0.030 parts by weight, etc.

[0034] Preferably, the raw materials for preparing the polyester polyol 1 further include methylpentanediol and / or terephthalic acid.

[0035] Preferably, the content of methylpentanediol in the raw materials for preparing the polyester polyol 1 is 0 to 15 parts by weight and not equal to 0, such as 1 part by weight, 3 parts by weight, 5 parts by weight, 7 parts by weight, 10 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, etc.

[0036] Preferably, the content of terephthalic acid in the raw materials for preparing the polyester polyol 1 is 0 to 15 parts by weight and not equal to 0, such as 1 part by weight, 3 parts by weight, 5 parts by weight, 7 parts by weight, 10 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, etc.

[0037] Preferably, the hydroxyl value of the polyester polyol 1 is 14 to 37 mgKOH / g, such as 15 mgKOH / g, 17 mgKOH / g, 20 mgKOH / g, 25 mgKOH / g, 27 mgKOH / g, 30 mgKOH / g, 32 mgKOH / g, 35 mgKOH / g, or 37 mgKOH / g, etc.

[0038] Preferably, the acid value of the polyester polyol 1 is ≤1.5 mgKOH / g, such as 0.2 mgKOH / g, 0.5 mgKOH / g, 0.7 mgKOH / g, 1.0 mgKOH / g, 1.2 mgKOH / g, or 1.5 mgKOH / g, etc.

[0039] Preferably, the catalyst in the raw materials for preparing the polyester polyol 1 is any one or a combination of at least two of stannous octoate, antimony trioxide, dibutyltin dilaurate, antimony acetate, tetrabutyl titanate, or tetraisopropyl titanate.

[0040] Preferably, the polyester polyol 1 is prepared by the following method, and the method includes the following steps:

[0041] (A1) Mix adipic acid, diethylene glycol, and neopentyl glycol, and react to obtain a primary esterification product.

[0042] (A2) Mix the primary esterification product obtained in step (A1), isophthalic acid, ethylene glycol, a catalyst, optionally methylpentanediol, and optionally terephthalic acid, conduct an initial reaction, and then react again to obtain the polyester polyol 1.

[0043] Preferably, the temperature of the mixing in step (A1) is 130 to 150 °C, such as 130 °C, 132 °C, 135 °C, 138 °C, 140 °C, 142 °C, 145 °C, 148 °C, 150 °C, or 155 °C, etc.

[0044] Preferably, the temperature of the reaction in step (A1) is 200 to 240 °C, such as 200 °C, 205 °C, 210 °C, 215 °C, 220 °C, 225 °C, 230 °C, 235 °C, or 240 °C, etc.

[0045] Preferably, the reaction time in step (A1) is 2 to 4 h, such as 2 h, 2.5 h, 2.8 h, 3 h, 3.5 h, 3.8 h, or 4 h, etc.

[0046] Preferably, the temperature of the mixing in step (A2) is 110 to 130 °C, such as 111 °C, 112 °C, 114 °C, 116 °C, 118 °C, 120 °C, 124 °C, 126 °C, 128 °C, or 130 °C, etc.

[0047] Preferably, the temperature of the initial reaction in step (A2) is 220 to 240 °C, such as 220 °C, 222 °C, 225 °C, 228 °C, 230 °C, 234 °C, 236 °C, 238 °C or 240 °C, etc.

[0048] Preferably, the time of the initial reaction in step (A2) is 3 to 6 h, such as 3 h, 3.5 h, 3.8 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, etc.

[0049] Preferably, the acid value of the product of the initial reaction in step (A2) is ≤ 12 mg KOH / g, such as 2 mg KOH / g, 4 mg KOH / g, 6 mg KOH / g, 8 mg KOH / g, 10 mg KOH / g or 12 mg KOH / g, etc.

[0050] Preferably, the temperature of the re-reaction in step (A2) is 230 to 245 °C, such as 230 °C, 232 °C, 235 °C, 238 °C, 240 °C, 242 °C, 243 °C, 244 °C or 245 °C, etc.

[0051] Preferably, the re-reaction in step (A2) is carried out under reduced pressure.

[0052] Preferably, the pressure reduction operation specifically includes: evacuating the system to -10 to -20 kPa for the first time (such as -11 kPa, -12 kPa, -13 kPa, -14 kPa, -15 kPa, -16 kPa, -17 kPa, -18 kPa, -19 kPa or -20 kPa, etc.), maintaining the pressure for 30 to 60 minutes (such as 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, etc.), evacuating the system to -25 to -35 kPa for the second time (such as -26 kPa, -27 kPa, -28 kPa, -29 kPa, -30 kPa, -31 kPa, -32 kPa, -33 kPa, -34 kPa or -35 kPa, etc.), maintaining the pressure for 30 to 60 minutes (such as 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, etc.), evacuating the system to -55 to -65 kPa for the third time (such as -56 kPa, -57 kPa, -58 kPa, -59 kPa, -60 kPa, -61 kPa, -62 kPa, -63 kPa, -64 kPa or -65 kPa, etc.), maintaining the pressure for 30 to 60 minutes (such as 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, etc.), evacuating the system to -95 to -105 kPa for the fourth time (such as -96 kPa, -97 kPa, -98 kPa, -99 kPa, -100 kPa, -101 kPa, -102 kPa, -103 kPa, -104 kPa or -105 kPa, etc.), and maintaining the pressure for 180 to 360 minutes (such as 180 minutes, 200 minutes, 220 minutes, 240 minutes, 260 minutes, 280 minutes, 300 minutes, 320 minutes, 340 minutes or 360 minutes, etc.) to complete the pressure reduction operation.

[0053] Preferably, the polyester polyol 2 is any one or a combination of at least two of polyester polyol PE-1020, polyester polyol PE-3010, polyester polyol HF-8056, polyester polyol HF-8211 or polyester polyol HF-8212.

[0054] Preferably, the structure of the flexible chain extender is as follows:

[0055]

[0056] Wherein, a = 1 to 3 (such as 1, 2 or 3, etc.), b = 10 to 16 (such as 10, 11, 12, 13, 14, 15 or 16, etc.), c = 1 to 3 (such as 1, 2 or 3, etc.), and a, b, c are all integers.

[0057] Preferably, the content of the flexible chain extender in the raw materials for preparing the main agent is 1 to 6 parts by weight, such as 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight or 6 parts by weight, etc.

[0058] Preferably, the polyisocyanate is any one or a combination of at least two of 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, toluene diisocyanate and its isomers, 1,5-naphthalene diisocyanate, hydrogenated MDI, isophorone diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate or methylcyclohexyl diisocyanate.

[0059] Preferably, the catalyst in the raw materials for preparing the main agent is any one or a combination of at least two of aliphatic amine catalysts, alicyclic amine catalysts, aromatic amine catalysts, alkanolamine and its ammonium salt catalysts, and metal carboxylate catalysts, and more preferably any one or a combination of at least two of dibutyltin dilaurate, stannous octoate or bismuth isooctoate.

[0060] Preferably, the solvent is ethyl acetate.

[0061] Preferably, the raw materials for preparing the main agent further include a coupling agent.

[0062] Preferably, the content of the coupling agent is 0.5 to 2.5 parts by weight, such as 0.6 parts by weight, 0.8 parts by weight, 1.0 parts by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2.0 parts by weight, 2.2 parts by weight or 2.4 parts by weight, etc.

[0063] Preferably, the main agent is prepared by the following method, which includes: first reacting polyester polyol 1, polyester polyol 2, flexible chain extender, polyisocyanate, catalyst and part of the solvent, and then adding the remaining part of the solvent and optionally a coupling agent for a second reaction to obtain the main agent.

[0064] Preferably, the first reaction is carried out at 40 to 60 °C (such as 42 °C, 44 °C, 46 °C, 48 °C, 50 °C, 52 °C, 54 °C, 56 °C, 58 °C or 60 °C, etc.) for 0.5 to 1 h (such as 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h or 1 h, etc.), and then the temperature is raised to 70 to 85 °C (such as 72 °C, 74 °C, 76 °C, 78 °C, 80 °C, 81 °C, 82 °C, 83 °C, 84 °C or 85 °C, etc.) and reacted for 8 to 12 h (such as 8 h, 9 h, 10 h, 11 h or 12 h, etc.).

[0065] Preferably, the temperature of the re - reaction is 40 - 60 °C (such as 42 °C, 44 °C, 46 °C, 48 °C, 50 °C, 52 °C, 54 °C, 56 °C, 58 °C or 60 °C, etc.).

[0066] Preferably, the time of the re - reaction is 1 - 2 h (such as 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h or 1.9 h, etc.).

[0067] In a second aspect, the present invention provides a method for using the polyurethane adhesive as described in the first aspect. The method for using includes: mixing the main agent and the curing agent, and coating the mixture on the surface of the object to be bonded.

[0068] When in use, the polyurethane adhesive provided by the present invention can be directly used in the composite of materials after mixing the main agent and the curing agent in a certain proportion.

[0069] In a third aspect, the present invention provides a multi - layer composite structure, which includes at least two substrates bonded together by the polyurethane adhesive as described in the first aspect.

[0070] Preferably, the substrate includes any one or a combination of at least two of aluminized film (VMPET), aluminum foil (Al) or cast polypropylene film (RCPP).

[0071] The multi - layer composite structure provided by the present invention is obtained by bonding at least two substrates together with the polyurethane adhesive provided in the first aspect of the present invention; exemplarily, the multi - layer composite structure can be a composite structure such as BOPP / VMPET / PE, PET / VMPET / PE or PET / Al / PE bonded together with the polyurethane adhesive provided in the first aspect of the present invention, which has excellent boiling water resistance; the multi - layer composite structure can also be a composite structure such as PA / RCPP bonded together with the polyurethane adhesive provided in the first aspect of the present invention, which has excellent 125 °C high - temperature cooking resistance; the multi - layer composite structure can also be a composite structure such as PET / Al / RCPP bonded together with the polyurethane adhesive provided in the first aspect of the present invention, which has excellent boiling water resistance and 125 °C high - temperature cooking resistance.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] In the present invention, a hydroxyl-terminated polyester polyol with a number-average molecular weight of 3000 to 8000 is selected and combined with a polyester polyol 2 with a number-average molecular weight of 500 to 2000, and other components such as a flexible chain extender are combined to prepare a main agent, and further combined with a curing agent to obtain a polyurethane adhesive. The polyurethane adhesive has a high solid content, low viscosity, good adhesion, and can withstand high-temperature cooking at 125 °C and boiling water. Mixing the main agent and the curing agent can be directly used for the bonding of multi-layer composite structures, and the solid content during its operation can reach more than 45%, and the starting speed for preparing the multi-layer composite structure can reach more than 200 m / min. Detailed Embodiments

[0074] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0075] The raw materials used in the embodiments and comparative examples of the present invention and their preparations are as follows:

[0076] Polyester polyol 1a is prepared by the following method:

[0077] (1) Add 30 parts by weight of adipic acid, 20 parts by weight of diethylene glycol, and 10 parts by weight of neopentyl glycol to a polyester synthesis kettle and mix at 140 °C. After mixing evenly, raise the temperature to 220 °C and react for 4 h. After the temperature of the fractionating column is lower than 60 °C, a primary esterification product is obtained.

[0078] (2) Mix the primary esterification product obtained in step (1), 15 parts by weight of isophthalic acid, 10 parts by weight of terephthalic acid, 2 parts by weight of ethylene glycol, 6 parts by weight of methylpentanediol, and 0.02 parts by weight of tetrabutyl titanate at 130 °C, and raise the temperature to 220 °C for an initial reaction of 4 h to obtain an initial product with an acid value of 12.6 mgKOH / g; then raise the temperature to 230 °C, and first evacuate the system to -15 kPa, hold the pressure for 30 min, evacuate the system to -30 kPa for the second time, hold the pressure for 30 min, evacuate the system to -60 kPa for the third time, hold the pressure for 30 min, and evacuate the system to -100 kPa for the fourth time, hold the pressure for 300 min to obtain the polyester polyol 1a.

[0079] According to the standard "HG / T 2709-1995 Determination of Hydroxyl Value in Polyester Polyols", the prepared polyester polyol 1a was tested by the method of hydrochloric acid titration. The hydroxyl value was measured to be 20.3 mgKOH / g, and the acid value was measured to be 1.24 mgKOH / g according to the standard "HG / T 2708-1995 Determination of Acid Value in Polyester Polyols". The number-average molecular weight was calculated to be 5258.

[0080] Polyester polyol 1b was prepared by the following method:

[0081] (1) 30 parts by weight of adipic acid, 15 parts by weight of diethylene glycol, and 10 parts by weight of neopentyl glycol were added to a polyester synthesis kettle and mixed at 150 °C. After mixing evenly, the temperature was raised to 210 °C and reacted for 2 h. After the temperature of the fractionating column was lower than 60 °C, a primary esterification product was obtained.

[0082] (2) The primary esterification product obtained in step (1), 20 parts by weight of isophthalic acid, 7 parts by weight of terephthalic acid, 5 parts by weight of ethylene glycol, 8 parts by weight of methylpentanediol, and 0.02 parts by weight of tetrabutyl titanate were mixed at 120 °C and the temperature was raised to 210 °C for an initial reaction of 5 h to obtain an initial product with an acid value of 13.5 mg KOH / g; the temperature was raised to 240 °C, and the system was evacuated to -15 kPa for the first time and held under pressure for 30 min, evacuated to -30 kPa for the second time and held under pressure for 30 min, evacuated to -60 kPa for the third time and held under pressure for 30 min, evacuated to -100 kPa for the fourth time and held under pressure for 300 min to obtain the polyester polyol 1b.

[0083] According to the standard "HG / T 2709-1995 Determination of hydroxyl value in polyester polyols", the prepared polyester polyol 1b was tested by the method of hydrochloric acid titration. The hydroxyl value was measured to be 18.5 mg KOH / g. According to the standard "HG / T 2708-1995 Determination of acid value in polyester polyols", the acid value was determined to be 1.02 mg KOH / g, and the number average molecular weight was calculated to be 5748.

[0084] Polyester polyol 1c was prepared by the following method:

[0085] (1) 30 parts by weight of adipic acid, 20 parts by weight of diethylene glycol, and 16 parts by weight of neopentyl glycol were added to a polyester synthesis kettle and mixed at 150 °C. After mixing evenly, the temperature was raised to 240 °C and reacted for 4 h. After the temperature of the fractionating column was lower than 60 °C, a primary esterification product was obtained.

[0086] (2) Mix the primary esterification product obtained in step (1), 35 parts by weight of isophthalic acid, 1 part by weight of ethylene glycol, 8 parts by weight of methylpentanediol, and 0.03 part by weight of stannous octoate at 110 °C, heat up to 240 °C for an initial reaction of 6 h to obtain an initial product with an acid value of 13.7 mg KOH / g; then heat up to 230 °C, and evacuate the system to -15 kPa for the first time, hold the pressure for 30 min, evacuate the system to -30 kPa for the second time, hold the pressure for 30 min, evacuate the system to -60 kPa for the third time, hold the pressure for 30 min, evacuate the system to -100 kPa for the fourth time, and hold the pressure for 300 min to obtain the polyester polyol 1c.

[0087] According to the standard "HG / T 2709-1995 Determination of Hydroxyl Value in Polyester Polyols", the prepared polyester polyol 1c was tested by the method of hydrochloric acid titration. The hydroxyl value was measured to be 14.0 mg KOH / g. According to the standard "HG / T 2708-1995 Determination of Acid Value in Polyester Polyols", the acid value was determined to be 1.12 mg KOH / g, and the number average molecular weight was calculated to be 8000.

[0088] The polyester polyol 1d was prepared by the following method:

[0089] (1) Add 20 parts by weight of adipic acid, 10 parts by weight of diethylene glycol, and 15 parts by weight of neopentyl glycol to a polyester synthesis kettle and mix at 140 °C. After mixing evenly, heat up to 230 °C and react for 3 h. After the temperature of the fractionating column is lower than 60 °C, a primary esterification product is obtained.

[0090] (2) Mix the primary esterification product obtained in step (1), 20 parts by weight of isophthalic acid, 3 parts by weight of ethylene glycol, 10 parts by weight of terephthalic acid, and 0.01 part by weight of antimony trioxide at 110 °C, heat up to 240 °C for an initial reaction of 6 h to obtain an initial product with an acid value of 14.5 mg KOH / g; then heat up to 230 °C, and evacuate the system to -15 kPa for the first time, hold the pressure for 30 min, evacuate the system to -30 kPa for the second time, hold the pressure for 30 min, evacuate the system to -60 kPa for the third time, hold the pressure for 30 min, evacuate the system to -100 kPa for the fourth time, and hold the pressure for 300 min to obtain the polyester polyol 1d.

[0091] According to the standard "HG / T 2709-1995 Determination of Hydroxyl Value in Polyester Polyol", the prepared polyester polyol 1d was tested by the method of hydrochloric acid titration. The hydroxyl value was measured to be 37.4 mg KOH / g. According to the standard "HG / T 2708-1995 Determination of Acid Value in Polyester Polyol", the acid value was measured to be 0.89 mg KOH / g, and the number-average molecular weight was calculated to be 3000.

[0092] Polyester polyol 1e was prepared by the following method:

[0093] (1) Add 15 parts by weight of adipic acid, 10 parts by weight of diethylene glycol, and 16 parts by weight of neopentyl glycol into a polyester synthesis kettle and mix at 140 °C. After mixing evenly, raise the temperature to 230 °C and react for 3 h. After the temperature of the fractionating column is lower than 60 °C, the primary esterification product is obtained.

[0094] (2) Mix the primary esterification product obtained in step (1), 20 parts by weight of isophthalic acid, 3 parts by weight of ethylene glycol, 10 parts by weight of terephthalic acid, and 0.01 part by weight of antimony trioxide at 110 °C, and raise the temperature to 240 °C for an initial reaction of 6 h to obtain an initial product with an acid value of 16.5 mg KOH / g; then raise the temperature to 230 °C, and evacuate the system to -15 kPa for the first time, keep the pressure for 30 min, evacuate the system to -30 kPa for the second time, keep the pressure for 30 min, evacuate the system to -60 kPa for the third time, keep the pressure for 30 min, evacuate the system to -100 kPa for the fourth time, and keep the pressure for 300 min to obtain the polyester polyol 1d.

[0095] According to the standard "HG / T 2709-1995 Determination of Hydroxyl Value in Polyester Polyol", the prepared polyester polyol 1e was tested by the method of hydrochloric acid titration. The hydroxyl value was measured to be 12.1 mg KOH / g. According to the standard "HG / T 2708-1995 Determination of Acid Value in Polyester Polyol", the acid value was measured to be 1.05 mg KOH / g, and the number-average molecular weight was calculated to be 9272.

[0096] Example 1

[0097] This example provides a polyurethane adhesive, which is prepared by mixing a main agent and a curing agent in a mass ratio of 5:1.

[0098] The raw materials for preparing the main agent include the following components by weight:

[0099]

[0100] The preparation method of the main agent includes the following steps:

[0101] (1) 10 parts by weight of polyester polyol 1a, 50 parts by weight of polyester polyol 2 (HF-7737), flexible chain extender a, 15 parts by weight of ethyl acetate, and 0.02 parts by weight of catalyst (dibutyltin dilaurate) were added to a reactor. After heating to 60°C and mixing evenly, 6 parts by weight of toluene diisocyanate was added and reacted for 0.75 h. Then, the temperature was raised to 80°C and the reaction continued for 10 h to obtain an initial product.

[0102] (2) After cooling to 50°C, 1.5 parts by weight of coupling agent (KH560) and 13 parts by weight of ethyl acetate were added to the initial product obtained in step (1) and reacted for 1 h to obtain the main agent, with a solid content of 72.0% and a viscosity of 880 mPas.

[0103] The curing agent is a mixture of polyisocyanate prepolymer and ethyl acetate, JF-SAY-2750B, purchased from Zhejiang Huafeng Synthetic Resin Co., Ltd.

[0104] The structural formula of the flexible chain extender a is:

[0105]

[0106] Example 2

[0107] This example provides a polyurethane adhesive, which is obtained by mixing the main agent and the curing agent in a mass ratio of 5:1.

[0108] The raw materials for preparing the main agent include the following components in parts by weight:

[0109]

[0110] The preparation method of the main agent includes the following steps:

[0111] (1) 10 parts by weight of polyester polyol 1b, 45 parts by weight of polyester polyol 2 (HF-8211), flexible chain extender, 15 parts by weight of ethyl acetate, and 0.02 parts by weight of catalyst (dibutyltin dilaurate) were added to a reactor. After heating to 60°C and mixing evenly, 7 parts by weight of toluene diisocyanate was added and reacted for 0.5 h. Then, the temperature was raised to 70°C and the reaction continued for 12 h to obtain an initial product.

[0112] (2) After cooling to 50°C, 1.5 parts by weight of coupling agent (KH560) and 15 parts by weight of ethyl acetate were added to the initial product obtained in step (1) and reacted for 1 h to obtain the main agent, with a solid content of 70.7% and a viscosity of 1350 mPas.

[0113] The curing agent is a mixture of polyisocyanate prepolymer and ethyl acetate, JF-SAY-2750B, purchased from Zhejiang Huafeng Synthetic Resin Co., Ltd.

[0114] The structural formula of the flexible chain extender b is as follows:

[0115]

[0116] Example 3

[0117] This example provides a polyurethane adhesive, which is obtained by mixing a main agent and a curing agent in a mass ratio of 5:1.

[0118] The raw materials for preparing the main agent include the following components by weight:

[0119]

[0120]

[0121] The preparation method of the main agent includes the following steps:

[0122] (1) Add 15 parts by weight of polyester polyol 1c, 40 parts by weight of polyester polyol 2 (HF-8212), 4.5 parts by weight of the flexible chain extender, 15 parts by weight of ethyl acetate, and 0.02 parts by weight of a catalyst (dibutyltin dilaurate) into a reactor. After heating to 60 °C and mixing evenly, add 10 parts by weight of toluene diisocyanate and react for 0.5 h. Then heat to 70 °C and continue to react for 12 h to obtain an initial product.

[0123] (2) After cooling to 50 °C, add 2 parts by weight of coupling agent KH560, 0.5 parts by weight of coupling agent KH550, and 15 parts by weight of ethyl acetate to the initial product obtained in step (1) and react for 1 h to obtain the main agent, with a solid content of 70.7% and a viscosity of 980 mPas.

[0124] The curing agent is a mixture of a polyisocyanate prepolymer and ethyl acetate, JF-SAY-2750B, purchased from Zhejiang Huafeng Synthetic Resin Co., Ltd.

[0125] The structural formula of the flexible chain extender c is as follows:

[0126]

[0127] Example 4

[0128] This example provides a polyurethane adhesive, which is obtained by mixing a main agent and a curing agent in a mass ratio of 5:1.

[0129] The raw materials for preparing the main agent include the following components by weight:

[0130]

[0131]

[0132] The preparation method of the main agent comprises the following steps:

[0133] (1) 15 parts by weight of polyester polyol 1d, 40 parts by weight of polyester polyol 2 (HF-8212), a flexible chain extender, 15 parts by weight of ethyl acetate and 0.05 parts by weight of a catalyst (dibutyltin dilaurate) were added to a reactor, heated to 60°C and mixed uniformly, and then 10 parts by weight of toluene diisocyanate was added and reacted for 0.75h. The temperature was raised to 75°C and the reaction was continued for 12h to obtain an initial product.

[0134] (2) After cooling to 40° C., 2.5 parts by weight of a coupling agent (KH560) and 10 parts by weight of ethyl acetate were added to the initial product obtained in step (1) and reacted for 1 hour to obtain the main agent with a solid content of 75.6% and a viscosity of 2260 mPas.

[0135] The curing agent is a mixture of polyisocyanate prepolymer and ethyl acetate, JF-SAY-2750B, purchased from Zhejiang Huafeng Synthetic Resin Co., Ltd.

[0136] The structural formula of the flexible chain extender d is:

[0137]

[0138] Example 5

[0139] This embodiment provides a polyurethane adhesive, which is obtained by mixing a main agent and a curing agent in a mass ratio of 10:1.

[0140] The raw materials for preparing the main agent include the following components in parts by weight:

[0141]

[0142]

[0143] The preparation method of the main agent comprises the following steps:

[0144] (1) 20 parts by weight of polyester polyol 1a, 40 parts by weight of polyester polyol 2 (HF-8212), a flexible chain extender, 15 parts by weight of ethyl acetate and 0.03 parts by weight of a catalyst (dibutyltin dilaurate) were added to a reactor, heated to 60°C and mixed evenly, and then 6 parts by weight of toluene diisocyanate were added and reacted for 0.5h. The temperature was raised to 70°C and the reaction was continued for 12h to obtain an initial product.

[0145] (2) After cooling to 60 °C, 0.5 parts by weight of coupling agent KH560 and 15 parts by weight of ethyl acetate were added to the initial product obtained in step (1) and reacted for 1 h to obtain the main agent, with a solid content of 76.1% and a viscosity of 2550 mPas.

[0146] The curing agent is a mixture of polyisocyanate prepolymer and ethyl acetate, JF-SAY-2750B, purchased from Zhejiang Huafeng Synthetic Resin Co., Ltd.

[0147] The structural formula of the flexible chain extender a is:

[0148]

[0149] Example 6

[0150] This example provides a polyurethane adhesive, which is prepared by mixing a main agent and a curing agent in a mass ratio of 7:1.

[0151] The raw materials for preparing the main agent include the following components in parts by weight:

[0152]

[0153]

[0154] The preparation method of the main agent includes the following steps:

[0155] (1) 30 parts by weight of polyester polyol 1a, 60 parts by weight of polyester polyol 2 (HF-8056), 6 parts by weight of flexible chain extender, 15 parts by weight of ethyl acetate and 0.04 parts by weight of catalyst (dibutyltin dilaurate) were added to a reactor, heated to 60 °C and mixed evenly, then 6 parts by weight of 2,4'-diphenylmethane diisocyanate was added and reacted for 0.75 h, then heated to 80 °C and continued to react for 10 h to obtain an initial product.

[0156] (2) After cooling to 50 °C, 1.2 parts by weight of coupling agent (KH560) and 5 parts by weight of ethyl acetate were added to the initial product obtained in step (1) and reacted for 1 h to obtain the main agent, with a solid content of 78.0% and a viscosity of 3500 mPas.

[0157] The curing agent is a mixture of polyisocyanate prepolymer and ethyl acetate, JF-SAY-2750B, purchased from Zhejiang Huafeng Synthetic Resin Co., Ltd.

[0158] The structural formula of the flexible chain extender a is:

[0159]

[0160] Example 7

[0161] This embodiment provides a polyurethane adhesive, which is prepared by mixing a main agent and a curing agent in a mass ratio of 8:1.

[0162] The raw materials for preparing the main agent include the following components in parts by weight:

[0163]

[0164]

[0165] The preparation method of the main agent includes the following steps:

[0166] (1) Add 40 parts by weight of polyester polyol 1a, 30 parts by weight of polyester polyol 2 (PE-3010), 1 part by weight of flexible chain extender, 10 parts by weight of ethyl acetate, and 0.03 part by weight of catalyst (bismuth isooctanoate) to a reactor. After heating to 60 °C and mixing evenly, add 8 parts by weight of hexamethylene diisocyanate and react for 0.75 h. Then heat to 80 °C and continue to react for 10 h to obtain an initial product.

[0167] (2) After cooling to 50 °C, add 13 parts by weight of ethyl acetate to the initial product obtained in step (1) and react for 1 h to obtain the main agent with a solid content of 78.0% and a viscosity of 1000 mPa·s.

[0168] The curing agent is a mixture of polyisocyanate prepolymer and ethyl acetate, JF-SAY-2750B, purchased from Zhejiang Huafeng Synthetic Resin Co., Ltd.

[0169] The structural formula of the flexible chain extender a is:

[0170]

[0171] Comparative Example 1

[0172] This comparative example provides a polyurethane adhesive. The difference between this polyurethane adhesive and that in Example 1 is that polyester polyol 1a is not added to the raw materials for preparing the main agent, and the addition amount of polyester polyol 2 is 60 parts by weight. Other components, dosages, and preparation methods are the same as those in Example 1.

[0173] Comparative Example 2

[0174] This comparative example provides a polyurethane adhesive. The difference between this polyurethane adhesive and that in Example 1 is that polyester polyol 2 is not added to the raw materials for preparing the main agent, and the addition amount of polyester polyol 1a is 60 parts by weight. Other components, dosages, and preparation methods are the same as those in Example 1.

[0175] Comparative Example 3

[0176] This comparative example provides a polyurethane adhesive. The difference between this polyurethane adhesive and that of Example 1 is that no flexible chain extender is added to the raw materials for preparing the main agent, and the other components, dosages, and preparation methods are the same as those of Example 1.

[0177] Comparative Example 4

[0178] This comparative example provides a polyurethane adhesive. The difference between this polyurethane adhesive and that of Example 1 is that polyester polyol 1a in the raw materials for preparing the main agent is replaced with the same mass of polyester polyol 1e, and the other components, dosages, and preparation methods are the same as those of Example 1.

[0179] Comparative Example 5

[0180] This comparative example provides a polyurethane adhesive. The difference between this polyurethane adhesive and that of Example 1 is that the addition amount of polyester polyol 1a in the raw materials for preparing the main agent is 45 parts by weight, and the addition amount of polyester polyol 2 is 15 parts by weight, and the other components, dosages, and preparation methods are the same as those of Example 1.

[0181] Application Examples 1 - 7

[0182] This application example provides a PET / VMPET / PE composite structure, which is prepared by sequentially bonding a PET layer, a VMPET layer, and a PE layer with the polyurethane adhesives obtained from Examples 1 - 7 respectively.

[0183] Application Examples 8 - 14

[0184] This application example provides an Al / PE composite structure, which is prepared by sequentially bonding an Al layer and a PE layer with the polyurethane adhesives obtained from Examples 1 - 7 respectively.

[0185] Application Examples 15 - 21

[0186] This application example provides an Al / RCPP composite structure, which is prepared by bonding an Al layer and an RCPP layer with the polyurethane adhesives obtained from Examples 1 - 7 respectively.

[0187] Comparative Application Examples 1 - 5

[0188] This application example provides a PET / VMPET / PE composite structure, which is prepared by sequentially bonding a PET layer, a VMPET layer, and a PE layer with the polyurethane adhesives obtained from Comparative Examples 1 - 5 respectively.

[0189] Comparative Application Example 6

[0190] This application example provides a PET / VMPET / PE composite structure, which is prepared by sequentially bonding a PET layer, a VMPET layer, and a PE layer using a high-solid and low-viscosity polyurethane adhesive from Zhejiang Huafeng Synthetic Resin Co., Ltd. (the main agent is JF-SAY-6809A, the curing agent is JF-SAY-2750B, and the main agent and the curing agent are mixed at a mass ratio of 5:1).

[0191] Comparative application examples 7 to 11

[0192] This application example provides an Al / PE composite structure, which is prepared by sequentially bonding an Al layer and a PE layer using the polyurethane adhesives obtained from Comparative Examples 1 to 5 respectively.

[0193] Comparative application example 12

[0194] This application example provides an Al / PE composite structure, which is prepared by sequentially bonding a PET layer, an Al layer, and a PE layer using a high-solid and low-viscosity polyurethane adhesive from Zhejiang Huafeng Synthetic Resin Co., Ltd. (the main agent is JF-SAY-6809A, the curing agent is JF-SAY-2750B, and the main agent and the curing agent are mixed at a mass ratio of 5:1).

[0195] Comparative application examples 13 to 17

[0196] This application example provides an Al / RCPP composite structure, which is prepared by bonding an Al layer and an RCPP layer using the polyurethane adhesives obtained from Comparative Examples 1 to 5 respectively.

[0197] Comparative application example 18

[0198] This application example provides an Al / RCPP composite structure, which is prepared by sequentially bonding an Al layer and an RCPP layer using a high-solid and low-viscosity polyurethane adhesive from Zhejiang Huafeng Synthetic Resin Co., Ltd. (the main agent is JF-SAY-6809A, the curing agent is JF-SAY-2750B, and the main agent and the curing agent are mixed at a mass ratio of 5:1).

[0199] The composite structures of Application Examples 1 to 21 and Comparative Application Examples 1 to 18 were subjected to peel performance tests as follows:

[0200] The composite structures prepared in the application examples and comparative application examples were cured for 48 h in an environment with a temperature of 50 °C and a humidity of 40 - 60%, and then cut into standard specimens of 200 mm × 15 mm, and the peel strength was tested on a universal electronic experimental tensile machine according to the test method in GB / T 2791-1995:

[0201] (1) Initial adhesion: At the initial stage of composite gluing, 5 minutes after the multi-layer composite structure is bonded, cut it immediately to test the peel strength.

[0202] (2) Peel strength at room temperature: The peel strength was tested after aging for 48 hours at a temperature of 50°C and a humidity of 40-60%.

[0203] (3) Peel strength after boiling at 100°C: The matured sample was placed in a cooking pot and boiled at 100°C for 40 min. The sample was taken out and cooled to room temperature, and the peel strength was tested.

[0204] (4) 125℃ steaming peel strength: The matured sample was placed in a steamer and steamed at 125℃ for 40 min. After cooling to room temperature, the peel strength was tested.

[0205] The initial adhesion and room temperature peel strength test results of the PET / VMPET / PE composite structures obtained in Application Examples 1 to 7 and Comparative Application Examples 1 to 6 are shown in Table 1:

[0206] Table 1

[0207]

[0208]

[0209]

[0210] According to the data in Table 1, the PET / VMPET / PE composite structures provided by Application Examples 1 to 7 have an initial adhesion of the PET / VMPET layer of 2.01 to 3.01 N / 15 mm and a peel strength of 1.98 to 2.38 N / 15 mm at room temperature. By comparing the application examples and the comparative application examples, it can be found that the initial adhesion and room-temperature peel strength of the PET / VMPET layer and the VMPET / PE layer of the PET / VMPET / PE composite structures provided by the application examples are both high.

[0211] The test results of the initial adhesion, room temperature peel strength and 100°C boiling peel strength of the Al / PE composite structures obtained in Application Examples 8 to 14 and Comparative Application Examples 7 to 12 are shown in Table 2:

[0212] Table 2

[0213]

[0214]

[0215] It can be seen from the data in Table 2 that for the Al / PE composite structures provided in Application Examples 8-14, the initial adhesion of the Al / PE layer is 2.23-3.22 N / 15 mm, the peel strength at room temperature is 11.58-13.56 N / 15 mm, and the peel strength after boiling at 100 °C is 8.56-10.02 N / 15 mm; by comparing the application examples and the comparative application examples, it can be found that the peel strength of the Al / PE composite structure provided by the comparative application example decreases more after boiling at 100 °C.

[0216] The test results of the initial adhesion, peel strength at room temperature, and peel strength after cooking at 125 °C of the Al / RCPP composite structures obtained from Application Examples 15-21 and Comparative Application Examples 13-18 are shown in Table 3:

[0217] Table 3

[0218]

[0219]

[0220] It can be seen from the data in Table 3 that for the Al / RCPP composite structures provided in Application Examples 15-21, the initial adhesion of the Al / RCPP layer is 2.77-3.11 N / 15 mm, the peel strength at room temperature is 12.06-14.85 N / 15 mm, and the peel strength after cooking at 125 °C is 9.25-12.65 N / 15 mm; by comparing the application examples and the comparative application examples, it can be found that the peel strength of the Al / RCPP composite structure provided by the comparative application example decreases more after boiling at 125 °C.

[0221] In summary, the composite structure prepared by bonding with the polyurethane adhesive of the present invention has very excellent peel strength. The polyurethane adhesive has excellent resistance to boiling at 100 °C and cooking at 125 °C, and the peel strength after boiling and cooking does not decrease significantly. The polyurethane adhesive is suitable for bonding substrates such as aluminized films, aluminum foils, and RCPP films, and has a wide range of applications.

[0222] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate a polyurethane adhesive and its use method of the present invention, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polyurethane adhesive, characterized in that, The polyurethane adhesive includes a main agent and a curing agent; The preparation raw materials of the main agent include the following components by weight: The polyester polyol 1 is a hydroxyl-terminated polyester polyol with a number average molecular weight of 3000 - 8000, and the number average molecular weight of the polyester polyol 2 is 500 - 2000; The preparation raw materials of the polyester polyol 1 include the following components by weight: The hydroxyl value of the polyester polyol 1 is 14 - 37 mgKOH / g; The polyester polyol 2 is any one or a combination of at least two of polyester polyol PE-1020, polyester polyol PE-3010, polyester polyol HF-7737, polyester polyol HF-8056, polyester polyol HF-8211, or polyester polyol HF-8212; The structure of the flexible chain extender is as follows: Wherein, a = 1 - 3, b = 10 - 16, c = 1 - 3, and a, b, and c are all integers.

2. The polyurethane adhesive according to claim 1, characterized in that, The mass ratio of the main agent to the curing agent is 5 - 10:

1.

3. The polyurethane adhesive according to claim 1, characterized in that, The viscosity of the main agent is 300 - 4000 mPa·s.

4. The polyurethane adhesive according to claim 1, characterized in that, The solid content of the main agent is 70 - 80%.

5. The polyurethane adhesive according to claim 1, wherein The curing agent is a mixture of a polyisocyanate prepolymer and ethyl acetate.

6. The polyurethane adhesive according to claim 1, wherein The viscosity of the curing agent is 1000 - 3000 mPa·s.

7. The polyurethane adhesive according to claim 1, characterized in that, The solid content of the curing agent is 65 - 75%.

8. The polyurethane adhesive according to claim 1, wherein The preparation raw materials of the polyester polyol 1 further include methylpentanediol and / or terephthalic acid.

9. The polyurethane adhesive according to claim 8, wherein, The content of methylpentanediol in the preparation raw materials of the polyester polyol 1 is 0 - 15 parts by weight and not equal to 0.

10. The polyurethane adhesive according to claim 8, characterized in that, The content of terephthalic acid in the preparation raw materials of the polyester polyol 1 is 0 - 15 parts by weight and not equal to 0.

11. The polyurethane adhesive according to claim 1, wherein The acid value of the polyester polyol 1 ≤ 1.5 mgKOH / g.

12. The polyurethane adhesive according to claim 1, wherein, The catalyst in the preparation raw materials of the polyester polyol 1 is any one or a combination of at least two of stannous octoate, antimony trioxide, dibutyltin dilaurate, antimony acetate, tetrabutyl titanate, or tetraisopropyl titanate.

13. The polyurethane adhesive according to claim 1, wherein The polyester polyol 1 is prepared by the following method, and the method includes the following steps: (A1) Mix adipic acid, diethylene glycol, and neopentyl glycol, and react to obtain a primary esterification product; (A2) Mix the primary esterification product obtained in step (A1), isophthalic acid, ethylene glycol, a catalyst, optionally methylpentanediol, and optionally terephthalic acid, conduct an initial reaction, and react again to obtain the polyester polyol 1.

14. The polyurethane adhesive according to claim 13, characterized in that, The temperature of the mixing in step (A1) is 130 - 150 °C.

15. The polyurethane adhesive according to claim 13, wherein The temperature of the reaction in step (A1) is 200 - 240 °C.

16. The polyurethane adhesive according to claim 13, characterized in that, The time of the reaction in step (A1) is 2 - 4 h.

17. The polyurethane adhesive according to claim 13, characterized in that, The temperature of the mixing in step (A2) is 110 - 130 °C.

18. The polyurethane adhesive according to claim 13, wherein The temperature of the initial reaction in step (A2) is 220 - 240 °C.

19. The polyurethane adhesive according to claim 13, wherein The time of the initial reaction in step (A2) is 3 - 6 h.

20. The polyurethane adhesive according to claim 13, characterized in that, The acid value of the product of the initial reaction in step (A2) ≤ 12 mgKOH / g.

21. The polyurethane adhesive according to claim 13, characterized in that, The temperature of the re - reaction in step (A2) is 230 - 245 °C.

22. The polyurethane adhesive according to claim 13, wherein The re - reaction in step (A2) is carried out under reduced pressure.

23. The polyurethane adhesive according to claim 22, characterized in that, The specific steps of the pressure reduction operation are as follows: evacuate the system to -10 to -20 kPa for the first time, hold the pressure for 30 to 60 minutes, evacuate the system to -25 to -35 kPa for the second time, hold the pressure for 30 to 60 minutes, evacuate the system to -55 to -65 kPa for the third time, hold the pressure for 30 to 60 minutes, evacuate the system to -95 to -105 kPa for the fourth time, and hold the pressure for 180 to 360 minutes to complete the pressure reduction operation.

24. The polyurethane adhesive according to claim 1, characterized in that, The content of the flexible chain extender in the raw materials for preparing the main agent is 1 to 6 parts by weight.

25. The polyurethane adhesive according to claim 1, characterized in that, The polyisocyanate is any one or a combination of at least two of 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, toluene diisocyanate and its isomers, 1,5-naphthalene diisocyanate, hydrogenated MDI, isophorone diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate or methylcyclohexyl diisocyanate.

26. The polyurethane adhesive according to claim 1, wherein The catalyst in the raw materials for preparing the main agent is any one or a combination of at least two of aliphatic amine catalysts, alicyclic amine catalysts, aromatic amine catalysts, alkanolamine and its ammonium salt catalysts, and metal carboxylate catalysts.

27. The polyurethane adhesive according to claim 26, characterized in that, The catalyst in the raw materials for preparing the main agent is any one or a combination of at least two of dibutyltin dilaurate, stannous octoate or bismuth isooctanoate.

28. The polyurethane adhesive according to claim 1, characterized in that, The solvent is ethyl acetate.

29. The polyurethane adhesive according to claim 1, wherein The raw materials for preparing the main agent further include a coupling agent.

30. The polyurethane adhesive according to claim 29, wherein The content of the coupling agent is 0.5 to 2.5 parts by weight.

31. The polyurethane adhesive according to claim 1, wherein, The main agent is prepared by the following method, which includes: first reacting polyester polyol 1, polyester polyol 2, flexible chain extender, polyisocyanate, catalyst and part of the solvent, and then adding the remaining part of the solvent and optionally the coupling agent for a second reaction to obtain the main agent.

32. The polyurethane adhesive according to claim 31, characterized in that, The first reaction is carried out at 40 to 60 °C for 0.5 to 1 hour, and then the temperature is raised to 70 to 85 °C and reacted for 8 to 12 hours.

33. The polyurethane adhesive according to claim 31, wherein, The temperature of the second reaction is 40 to 60 °C.

34. The polyurethane adhesive according to claim 31, wherein, The time of the second reaction is 1 to 2 hours.

35. A method for using the polyurethane adhesive according to any one of claims 1 to 34, characterized in that, The using method includes: mixing the main agent and the curing agent and coating on the surface of the object to be bonded.

36. A multi-layer composite structure, characterized in that, The multi-layer composite structure includes at least two substrates bonded together by the polyurethane adhesive as described in any one of claims 1 to 34.

37. The multi-layer composite structure according to claim 36, wherein, The substrate includes any one or a combination of at least two of aluminized film, aluminum foil or cast polypropylene film.

Images