A polyurethane adhesive, its preparation method and application

Abstract

The present invention provides a polyurethane adhesive, a preparation method and an application thereof. Calculated by weight parts, the raw materials for preparing the polyurethane adhesive include 65 to 94 parts of a high molecular polyol and 5 to 23 parts of a diisocyanate; the high molecular polyol includes a polyester polyol; the raw materials for preparing the polyester polyol include a dibasic acid and a diol; the diol includes a combination of a linear aliphatic diol and an alicyclic diol. In the present invention, by selecting a polyester polyol with a special structure as the raw material for preparing the polyurethane adhesive, the polyurethane adhesive has excellent hydrolysis resistance, high bonding strength, long open time, and a low activation temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer material preparation, and particularly relates to a polyurethane adhesive and its preparation method and application. Background Art

[0002] The polyurethane adhesive is composed of a high molecular polyol, a chain extender and a diisocyanate. Due to the existence of ester bonds in the polyester polyol in the high molecular polyol, the adhesive has good bonding strength, but also due to the existence of ester bonds, its hydrolysis resistance is poor, which limits its application in humid environments or on water.

[0003] In order to obtain better initial adhesion and final adhesion strength, the adhesive generally selects raw materials with a stronger crystallization rate. However, a fast crystallization rate will also lead to a shorter viscosity maintenance time. At present, many patents have explored how to obtain a hydrolysis-resistant thermoplastic polyurethane adhesive.

[0004] For example, CN110205077A discloses a hydrolysis-resistant solvent-based polyurethane adhesive synthesized from an organic solvent, methyl methacrylate, diisopropylbenzene peroxide, fluorine-modified microcrystalline wax, polyneopentyl glycol adipate polyol, 1,6-hexamethylene diisocyanate, a small molecule chain extender and a crosslinking agent. The added microcrystalline wax has good surface lubrication performance, which can improve the gloss of leather, reduce the crease rate, and has good hydrophobic properties, which can effectively improve the hydrolysis resistance of the finished product. However, the polyneopentyl glycol adipate polyol used in the adhesive results in poor crystallinity, and thus poor bonding strength.

[0005] CN114426805A discloses a preparation method of a hydrolysis-resistant polyurethane hot melt adhesive. By optimizing the matrix formula and adding modified inorganic fillers, etc., a polyurethane hot melt adhesive with excellent hydrolysis resistance is prepared. The inorganic filler is graft-modified, and liquefied MDI-100HL is grafted onto the surface of the inorganic filler with a silane coupling agent, so that the inorganic filler can be evenly dispersed in the polyurethane matrix. The inorganic filler reinforces the matrix, and at the same time, the carbodiimide group in MDI-100HL can improve the water resistance of the polyurethane through reaction. However, there is still a risk of uneven mixing by adding modified silica, and its bonding strength needs to be further improved.

[0006] So far, there are few reports at home and abroad on thermoplastic polyurethane adhesives that have both hydrolysis resistance, high bonding strength and long open time.

[0007] Therefore, developing a polyurethane adhesive that can have excellent hydrolysis resistance, high bonding strength, long tack time and low activation temperature is an urgent technical problem to be solved in this field. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a polyurethane adhesive and its preparation method and application. By selecting polyester polyols with special structures as the raw materials for preparing the polyurethane adhesive, the polyurethane adhesive has excellent hydrolysis resistance, high bonding strength, long open time, and low activation temperature.

[0009] To achieve this purpose, the present invention adopts the following technical solutions:

[0010] In the first aspect, the present invention provides a polyurethane adhesive. By weight, the raw materials for preparing the polyurethane adhesive include 65-94 parts of a high molecular polyol and 5-23 parts of a diisocyanate; the high molecular polyol includes a polyester polyol; the raw materials for preparing the polyester polyol include a dibasic acid and a diol; the diol is a combination of a linear aliphatic diol and an alicyclic diol.

[0011] In the present invention, the use of an alicyclic diol with a specific structure as the raw material of the polyester polyol can bring hydrolysis resistance while, to a certain extent, destroying the crystallinity of the adhesive, resulting in a longer open time; through the mutual cooperation of a linear aliphatic diol and an alicyclic diol with specific structures, the polyurethane adhesive has excellent hydrolysis resistance, high bonding strength, long open time, and low activation temperature.

[0012] Preferably, by weight, the raw materials for preparing the polyurethane adhesive include 65-94 parts of a high molecular polyol, such as 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, 92 parts, etc.

[0013] Preferably, by weight, the raw materials for preparing the polyurethane adhesive include 5-23 parts of a diisocyanate, such as 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, etc.

[0014] Preferably, the dibasic acid includes a C4-C12 dibasic acid, such as C4, C5, C6, C7, C8, C9, C10, C11 dibasic acids.

[0015] In the present invention, the polyester polyol prepared from a dibasic acid with a long carbon chain and a diol can further improve the comprehensive performance of the polyurethane adhesive.

[0016] Preferably, the dibasic acid includes at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, or sebacic acid.

[0017] Preferably, the mass ratio of the dibasic acid to the diol is 1:(0.8 - 1.6), and specific values within (0.8 - 1.6) can be, for example, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98, 1, 1.1, 1.2, 1.3, 1.4, 1.5, etc.

[0018] Preferably, the linear aliphatic diol includes C4 - C12 linear aliphatic diols, which can be, for example, C5, C6, C7, C8, C9, C10, C11 linear aliphatic diols, etc.

[0019] Preferably, the linear aliphatic diol includes at least one of butanediol, hexanediol, decanediol, or dodecanediol.

[0020] Preferably, the alicyclic diol includes C4 - C20 alicyclic diols, which can be, for example, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19 alicyclic diols, etc.

[0021] Preferably, the alicyclic diol includes at least one of cyclopentane - 1,3 - diol, 1,2 - cyclohexanediol, 1,4 - cyclohexanediol, 1,5 - cyclooctanediol, or 1,4 - cyclohexanedimethanol.

[0022] Preferably, the mass ratio of the linear aliphatic diol to the alicyclic diol is 1:(0.5 - 1), and specific values within (0.5 - 1) can be, for example, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98, etc.

[0023] Preferably, the acid value of the polyester polyol is less than 1 mgKOH / g, which can be, for example, 0.2 mgKOH / g, 0.4 mgKOH / g, 0.6 mgKOH / g, 0.8 mgKOH / g, etc.

[0024] Preferably, the hydroxyl value of the polyester polyol is 28 - 62 mgKOH / g, which can be, for example, 30 mgKOH / g, 35 mgKOH / g, 40 mgKOH / g, 45 mgKOH / g, 50 mgKOH / g, 55 mgKOH / g, 60 mgKOH / g, etc.

[0025] Preferably, the number-average molecular weight of the polymer polyol is 1,800 to 4,000 g / mol, for example, it can be 1,900 g / mol, 2,000 g / mol, 2,100 g / mol, 2,200 g / mol, 2,400 g / mol, 2,600 g / mol, 2,800 g / mol, 3,000 g / mol, 3,200 g / mol, 3,400 g / mol, 3,600 g / mol, 3,800 g / mol, etc., and more preferably 2,500 to 3,500 g / mol.

[0026] In the present invention, the preparation method of the polyester polyol includes: reacting a dicarboxylic acid with a diol to obtain the polyester polyol.

[0027] Preferably, the reaction includes reacting through a first stage, a second stage, and a third stage.

[0028] Preferably, the reaction temperature in the first stage is 130 to 140 °C, for example, it can be 132 °C, 134 °C, 136 °C, 138 °C, etc.; the reaction time is 1 to 2 h, for example, it can be 1 h, 1.5 h, 2 h, etc.

[0029] Preferably, the reaction temperature in the second stage is 160 to 170 °C, for example, it can be 162 °C, 164 °C, 166 °C, 168 °C, etc.; the reaction time is 1 to 2 h, for example, it can be 1 h, 1.5 h, 2 h, etc.

[0030] Preferably, the reaction temperature in the third stage is 200 to 210 °C, for example, it can be 202 °C, 204 °C, 206 °C, 208 °C, etc.; the reaction time is 3 to 4 h, for example, it can be 3 h, 3.5 h, 4 h, etc.

[0031] Preferably, the reaction is carried out under vacuum conditions.

[0032] Preferably, the polymer polyol further includes at least one of polycaprolactone polyol, polyether polyol, or polycarbonate polyol.

[0033] Preferably, the diisocyanate includes at least one of diphenylmethane diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, m-xylene diisocyanate, 1,5-naphthalene diisocyanate, and is preferably at least one of hexamethylene diisocyanate, diphenylmethane diisocyanate, or isophorone diisocyanate.

[0034] Preferably, based on parts by weight, the raw materials for preparing the polyurethane adhesive further include 0 to 18 parts of a chain extender, for example, it can be 0.5 part, 1 part, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, etc.

[0035] Preferably, the chain extender includes at least one of 1,2-ethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethylene glycol or cis-1,2-cyclohexanedimethanol, and more preferably at least one of neopentyl glycol, 1,4-butanediol, 1,6-hexanediol or cis-1,2-cyclohexanedimethanol.

[0036] As a preferred technical solution of the present invention, by weight, the raw materials for preparing the polyurethane adhesive include 70-92 parts of a high molecular polyol, 12-22 parts of a diisocyanate and 0.1-10 parts of a chain extender.

[0037] Second, the present invention provides a method for preparing the polyurethane adhesive according to the first aspect, and the preparation method includes:

[0038] Mix the high molecular polyol and the diisocyanate, and react to obtain the polyurethane adhesive.

[0039] Preferably, the raw materials for mixing further include a chain extender.

[0040] Preferably, the reaction is carried out in a twin-screw extruder.

[0041] Preferably, the temperature of the twin-screw extruder is 150-200 °C, for example, it can be 160 °C, 170 °C, 180 °C, 190 °C, etc.

[0042] In the present invention, the twin-screw extruder is divided into a first zone, a second zone, a third zone, a fourth zone, a fifth zone, a sixth zone, a seventh zone, an eighth zone, a ninth zone, and a tenth zone. The temperatures of the first zone and the second zone are each independently 150-170 °C; the temperatures of the third zone, the fourth zone, and the fifth zone are each independently 160-180 °C; the temperatures of the sixth zone, the seventh zone, and the eighth zone are each independently 170-190 °C; the temperatures of the ninth zone and the tenth zone are each independently 160-180 °C; the temperature of the die head of the twin-screw extruder is 160-180 °C.

[0043] Preferably, after the reaction, there is also a step of granulation.

[0044] In the present invention, the granulation is carried out in water.

[0045] In the present invention, when the polyurethane adhesive is used, the adhesive needs to be first dissolved in a solvent to form a solution, and additives can be added according to requirements during dissolution.

[0046] Preferably, the solvent includes at least one of methyl ethyl ketone, acetone, toluene, ethyl acetate, methyl acetate, dimethyl carbonate or tetrahydrofuran.

[0047] Preferably, the auxiliary agent includes at least one of a leveling agent, a thickening agent, a curing agent, a UV auxiliary agent or a hydrolysis resistance agent.

[0048] In a third aspect, the present invention provides an application of the polyurethane adhesive according to the first aspect in bonding PVC, fabric, leather or foam; preferably for bonding substrates in a humid environment, more preferably for bonding PVC, fabric, leather, foam with a long working time in a humid environment.

[0049] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the specific point values included in the described ranges are not exhaustively listed in the present invention.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] For the polyurethane adhesive provided by the present invention, by selecting diols and dibasic acids with specific structures as the raw materials for preparing the polyester polyol, the polyurethane adhesive has excellent hydrolysis resistance performance, bonding performance, a long open time and a low activation temperature; the peel strength can reach more than 2.1 N / mm at 25 °C and even cause substrate damage, the hydrolysis strength retention rate is ≥88% after being treated for 7 days under the conditions of 70 °C and 95% RH, and the pot life is ≥120 min, with excellent comprehensive performance. Detailed Embodiments

[0052] 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 on the present invention.

[0053] The raw materials and instruments used and their uses (all are chemically pure) are as follows:

[0054] Adipic acid (Huafeng)

[0055] Sebacic acid (Macklin)

[0056] Hexanediol (Macklin)

[0057] Decanediol (Macklin)

[0058] Dodecanediol (Macklin)

[0059] Cyclopentane-1,3-diol (Macklin)

[0060] 1,4-Cyclohexanediol (Macklin)

[0061] 1,5-Cyclooctanediol (Macklin)

[0062] 1,4-Cyclohexanedimethanol (Macklin)

[0063] 1,2 - Cyclohexanediol (Maclean)

[0064] Neopentyl glycol (Maclean)

[0065] Butanediol (Wanhua Chemical)

[0066] Hexamethylene diisocyanate (Wanhua Chemical)

[0067] Diphenylmethane diisocyanate (Wanhua Chemical)

[0068] Isophorone diisocyanate (Wanhua Chemical)

[0069] Chengyang glass burette: To test the acid value of polyester polyol;

[0070] Hydroxyl value analyzer (Thermo Fisher Antarisll): To determine the hydroxyl value of polyester polyol;

[0071] Extruder: Nanjing Ruia Extruder Manufacturing Co., Ltd. RXT (Diameter: 42mm, Length - diameter ratio: 46).

[0072] Preparation Example 1

[0073] A polyester polyol with a special structure, the raw materials for preparing the polyester polyol include dibasic acid and diol with a mass ratio of 1:0.942; the dibasic acid includes sebacic acid; the diol includes dodecanediol and 1,5 - cyclooctanediol with a mass ratio of 1:0.713.

[0074] The preparation method of the polyester polyol includes:

[0075] Add sebacic acid, dodecanediol and 1,5 - cyclooctanediol into a reaction kettle equipped with a fractionating tower and a distillation receiver, react at 140 °C for 2h, at 170 °C for 2h, and at 210 °C for 4.0h in sequence. Meanwhile, turn on the vacuum to remove the reaction product water and excess alcohol monomer. When the acid value is less than 1mg KOH / g and the hydroxyl value reaches 38mg KOH / g, stop the reaction. At this time, the corresponding number - average molecular weight is 3000g / mol.

[0076] Preparation Example 2

[0077] A polyester polyol with a special structure, the raw materials for preparing the polyester polyol include dibasic acid and diol with a mass ratio of 1:0.866; the dibasic acid includes sebacic acid; the diol includes decanediol and 1,4 - cyclohexanedimethanol with a mass ratio of 1:0.828.

[0078] The preparation method of the polyester polyol includes:

[0079] Sebacic acid, decanediol and 1,4-cyclohexanedimethanol were added to a reaction kettle equipped with a fractionating column and a distillation receiver, and reacted at 140 °C for 1 h, at 170 °C for 1.5 h, and at 210 °C for 4.0 h in sequence. Meanwhile, vacuum was turned on to remove the reaction product water and excess alcohol monomers. When the acid value was less than 1 mg KOH / g and the hydroxyl value reached 38 mg KOH / g, the reaction was stopped. At this time, the corresponding number-average molecular weight was 3000 g / mol.

[0080] Preparation Example 3

[0081] A polyester polyol with a special structure, the preparation raw materials of the polyester polyol include a dibasic acid and a diol with a mass ratio of 1:0.866; the dibasic acid includes sebacic acid; the diol includes dodecanediol and 1,2-cyclohexanediol with a mass ratio of 1:0.574.

[0082] The preparation method of the polyester polyol includes:

[0083] Sebacic acid, dodecanediol and 1,2-cyclohexanediol were added to a reaction kettle equipped with a fractionating column and a distillation receiver, and reacted at 140 °C for 1.5 h, at 170 °C for 2 h, and at 210 °C for 3.5 h in sequence. Meanwhile, vacuum was turned on to remove the reaction product water and excess alcohol monomers. When the acid value was less than 1 mg KOH / g and the hydroxyl value reached 38 mg KOH / g, the reaction was stopped. At this time, the corresponding number-average molecular weight was 3000 g / mol.

[0084] Preparation Example 4

[0085] A polyester polyol with a special structure, the preparation raw materials of the polyester polyol include a dibasic acid and a diol with a mass ratio of 1:0.866; the dibasic acid includes sebacic acid; the diol includes dodecanediol and 1,5-cyclooctanediol with a mass ratio of 1:0.892.

[0086] The preparation method of the polyester polyol is the same as that of Preparation Example 1.

[0087] Preparation Example 5

[0088] A polyester polyol with a special structure, the preparation raw materials of the polyester polyol include a dibasic acid and a diol with a mass ratio of 1:0.882; the dibasic acid includes adipic acid; the diol includes hexanediol and 1,4-cyclohexanediol with a mass ratio of 1:0.983.

[0089] The preparation method of the polyester polyol includes:

[0090] Adipic acid, hexanediol, and 1,4 - cyclohexanediol were added to a reaction kettle equipped with a fractionating column and a distillation receiver, and the reaction was carried out at 140 °C for 1 h, at 170 °C for 2 h, and at 210 °C for 4.0 h in sequence. Meanwhile, vacuum was applied to remove the reaction product water and excess alcohol monomers. When the acid value was less than 1 mg KOH / g and the hydroxyl value reached 38 mg KOH / g, the reaction was stopped. At this time, the corresponding number - average molecular weight was 3000 g / mol.

[0091] Preparation Example 6

[0092] A polyester polyol with a special structure, the difference from Preparation Example 1 is only that the total mass of dodecanediol and 1,5 - cyclooctanediol remains unchanged, and the mass ratio is 1:0.25. Other raw materials, dosages, and preparation methods are the same as those in Preparation Example 1.

[0093] Preparation Example 7

[0094] A polyester polyol with a special structure, the difference from Preparation Example 1 is only that the total mass of dodecanediol and 1,5 - cyclooctanediol remains unchanged, and the mass ratio is 1:1.2. Other raw materials, dosages, and preparation methods are the same as those in Preparation Example 1.

[0095] Preparation Example 8

[0096] A polyester polyol with a special structure, the difference from Preparation Example 1 is only that dodecanediol is replaced by 1,6 - hexanediol; 1,5 - cyclooctanediol is replaced by 1,4 - cyclohexanedimethanol. Other raw materials, dosages, and preparation methods are the same as those in Preparation Example 1.

[0097] Comparative Preparation Example 1

[0098] A polyester polyol, the preparation raw materials of the polyester polyol include a dibasic acid and a diol with a mass ratio of 1:0.566; the dibasic acid includes sebacic acid; the diol includes butanediol and hexanediol with a mass ratio of 1:1.311.

[0099] The preparation method of the polyester polyol includes:

[0100] Sebacic acid, butanediol, and hexanediol were added to a reaction kettle equipped with a fractionating column and a distillation receiver, and the reaction was carried out at 130 °C for 1 h, at 160 °C for 1.5 h, and at 200 °C for 3 h in sequence. Meanwhile, vacuum was applied to remove the reaction product water and excess alcohol monomers. When the acid value was less than 1 mg KOH / g and the hydroxyl value reached 38 mg KOH / g, the reaction was stopped. At this time, the corresponding number - average molecular weight was 3000 g / mol.

[0101] Comparative Preparation Example 2

[0102] A polyester polyol, the raw materials for preparing the polyester polyol include a dibasic acid and a diol with a mass ratio of 1:0.594; the dibasic acid includes sebacic acid; the diol includes cyclopentane-1,3-diol and 1,2-cyclohexanediol with a mass ratio of 1:1.137.

[0103] The preparation method of the polyester polyol includes:

[0104] Add sebacic acid, cyclopentane-1,3-diol and 1,2-cyclohexanediol into a reaction kettle equipped with a fractionating column and a distillation receiver, react at 140 °C for 1 h, react at 170 °C for 1.5 h, and react at 210 °C for 4 h in sequence. At the same time, turn on the vacuum to remove the water of the reaction product and the excess alcohol monomer. When the acid value is less than 1 mg KOH / g and the hydroxyl value reaches 38 mg KOH / g, stop the reaction. At this time, the corresponding number average molecular weight is 3000 g / mol.

[0105] Comparative Preparation Example 3

[0106] This comparative example provides a polyester polyol, the difference from Preparation Example 1 is only that the 1,5-cyclooctanediol is replaced by dodecanediol, and other raw materials, dosages and preparation methods are the same as those in Preparation Example 1.

[0107] Comparative Preparation Example 4

[0108] This comparative example provides a polyester polyol, the difference from Preparation Example 1 is only that the dodecanediol is replaced by 1,5-cyclooctanediol, and other raw materials, dosages and preparation methods are the same as those in Preparation Example 1.

[0109] Comparative Preparation Example 5

[0110] This comparative example provides a polyester polyol, the difference from Preparation Example 1 is only that the dodecanediol is replaced by 2-methyl-2,5-decanediol, and other raw materials, dosages and preparation methods are the same as those in Preparation Example 1.

[0111] Example 1

[0112] This example provides a polyurethane adhesive. By weight, the raw materials for preparing the polyurethane adhesive include 81 parts of polyester polyol (Preparation Example 1), 15 parts of 4,4-diphenylmethane diisocyanate and 4 parts of cis-1,2-cyclohexanedimethanol.

[0113] This example provides a preparation method of a polyurethane adhesive, which specifically includes the following steps:

[0114] The polyester polyol, 4,4-diphenylmethane diisocyanate and cis-1,2-cyclohexanedimethanol were added into an extruder and mixed evenly, and then subjected to twin-screw reactive extrusion; the temperatures of the extruder were as follows: 160 °C for the first, second, third, fourth and fifth zones, 170 °C for the sixth, seventh and eighth zones, 160 °C for the ninth and tenth zones, and the die head temperature was 160 °C. Subsequently, underwater pelletization was carried out to obtain the polyurethane adhesive.

[0115] Example 2

[0116] This example provides a polyurethane adhesive. By weight, the raw materials for preparing the polyurethane adhesive include 84 parts of polyester polyol (Preparation Example 1), 12 parts of hexamethylene diisocyanate and 4 parts of 1,4-butanediol.

[0117] This example provides a method for preparing a polyurethane adhesive, which specifically includes the following steps:

[0118] The polyester polyol, hexamethylene diisocyanate and 1,4-butanediol were added into an extruder and mixed evenly, and then subjected to twin-screw reactive extrusion; the temperatures of the extruder were as follows: 160 °C for the first and second zones, 170 °C for the third, fourth and fifth zones, 180 °C for the sixth, seventh and eighth zones, 170 °C for the ninth and tenth zones, and the die head temperature was 170 °C. Subsequently, underwater pelletization was carried out to obtain the polyurethane adhesive.

[0119] Example 3

[0120] This example provides a polyurethane adhesive. By weight, the raw materials for preparing the polyurethane adhesive include 83 parts of polyester polyol (Preparation Example 2), 13.5 parts of isophorone diisocyanate and 3.5 parts of neopentyl glycol.

[0121] This example provides a method for preparing a polyurethane adhesive, which specifically includes the following steps:

[0122] The polyester polyol, isophorone diisocyanate and neopentyl glycol were added into an extruder and mixed evenly, and then subjected to twin-screw reactive extrusion; the temperatures of the extruder were as follows: 170 °C for the first and second zones, 180 °C for the third, fourth and fifth zones, 190 °C for the sixth, seventh and eighth zones, 180 °C for the ninth and tenth zones, and the die head temperature was 180 °C. Subsequently, underwater pelletization was carried out to obtain the polyurethane adhesive.

[0123] Example 4

[0124] This example provides a polyurethane adhesive. By weight, the raw materials for preparing the polyurethane adhesive include 81 parts of polyester polyol (Preparation Example 2), 13 parts of hexamethylene diisocyanate and 6 parts of 1,6-hexanediol.

[0125] This embodiment provides a method for preparing a polyurethane adhesive, specifically including the following steps:

[0126] Mix the polyester polyol, hexamethylene diisocyanate, and 1,6 - hexanediol evenly in an extruder, and carry out twin - screw reactive extrusion; the temperature of the extruder: the first zone and the second zone are both 170 °C, the third zone, the fourth zone, and the fifth zone are all 180 °C, the sixth zone, the seventh zone, and the eighth zone are all 190 °C, the ninth zone and the tenth zone are both 180 °C, and the die head temperature is 180 °C. Then, underwater pelletize to obtain the polyurethane adhesive.

[0127] Example 5

[0128] This embodiment provides a polyurethane adhesive. By weight, the raw materials for preparing the polyurethane adhesive include 90 parts of polyester polyol (Preparation Example 3), 9 parts of isophorone diisocyanate, and 1 part of 1,4 - butanediol.

[0129] This embodiment provides a method for preparing a polyurethane adhesive, specifically including the following steps:

[0130] Mix the polyester polyol, isophorone diisocyanate, and 1,4 - butanediol evenly in an extruder, and carry out twin - screw reactive extrusion; the temperature of the extruder: the first zone and the second zone are both 160 °C, the third zone, the fourth zone, and the fifth zone are all 170 °C, the sixth zone, the seventh zone, and the eighth zone are all 180 °C, the ninth zone and the tenth zone are both 170 °C, and the die head temperature is 170 °C. Then, underwater pelletize to obtain the polyurethane adhesive.

[0131] Example 6

[0132] This embodiment provides a polyurethane adhesive, which is only different from Example 1 in that the polyester polyol provided in Preparation Example 4 is selected, and other raw materials, dosages, and preparation methods are the same as those in Example 1.

[0133] Example 7

[0134] This embodiment provides a polyurethane adhesive. By weight, the raw materials for preparing the polyurethane adhesive include 83 parts of polyester polyol (Preparation Example 5), 13 parts of isophorone diisocyanate, and 4 parts of 1,6 - hexanediol.

[0135] This embodiment provides a method for preparing a polyurethane adhesive, specifically including the following steps:

[0136] Mix the polyester polyol, isophorone diisocyanate, and 1,6 - hexanediol evenly in an extruder, and carry out twin - screw reactive extrusion; the temperature of the extruder: the first zone and the second zone are both 150 °C, the third zone, the fourth zone, and the fifth zone are all 160 °C, the sixth zone, the seventh zone, and the eighth zone are all 170 °C, the ninth zone and the tenth zone are both 160 °C, and the die head temperature is 160 °C. Then, underwater pelletize to obtain the polyurethane adhesive.

[0137] Examples 8 - 10

[0138] The polyurethane adhesives provided in Examples 8 - 10 are different from those in Example 1 only in that the polyester polyols are respectively selected from the polyester polyols provided in Preparation Examples 6 - 8, and other raw materials, dosages and preparation methods are the same as those in Example 1.

[0139] Comparative Example 1

[0140] This comparative example provides a polyurethane adhesive. In terms of parts by weight, the raw materials for preparing the polyurethane adhesive include 85 parts of PCL - 3000, 11.5 parts of hexamethylene diisocyanate and 3.5 parts of 1,4 - butanediol.

[0141] This comparative example provides a preparation method of a polyurethane adhesive, which specifically includes the following steps:

[0142] Add PCL - 3000, hexamethylene diisocyanate and 1,4 - butanediol into an extruder and mix evenly, then carry out twin - screw reactive extrusion. The temperatures of the extruder are as follows: the first zone and the second zone are both 160 °C, the third zone, the fourth zone and the fifth zone are all 170 °C, the sixth zone, the seventh zone and the eighth zone are all 180 °C, the ninth zone and the tenth zone are both 170 °C, and the die head temperature is 170 °C. Then carry out underwater pelletizing to obtain the polyurethane adhesive.

[0143] Comparative Example 2

[0144] This comparative example provides a polyurethane adhesive. In terms of parts by weight, the raw materials for preparing the polyurethane adhesive include 84 parts of polyester polyol (Comparative Preparation Example 1), 12 parts of hexamethylene diisocyanate and 4 parts of 1,4 - butanediol.

[0145] This comparative example provides a preparation method of a polyurethane adhesive, which specifically includes the following steps:

[0146] Add the polyester polyol, hexamethylene diisocyanate and 1,4 - butanediol into an extruder and mix evenly, then carry out twin - screw reactive extrusion. The temperatures of the extruder are as follows: the first zone and the second zone are both 160 °C, the third zone, the fourth zone and the fifth zone are all 170 °C, the sixth zone, the seventh zone and the eighth zone are all 180 °C, the ninth zone and the tenth zone are both 170 °C, and the die head temperature is 170 °C. Then carry out underwater pelletizing to obtain the polyurethane adhesive.

[0147] Comparative Example 3

[0148] This comparative example provides a polyurethane adhesive. In terms of parts by weight, the raw materials for preparing the polyurethane adhesive include 84 parts of polyester polyol (Comparative Preparation Example 2), 12 parts of hexamethylene diisocyanate and 4 parts of 1,4 - butanediol.

[0149] This comparative example provides a method for preparing a polyurethane adhesive, which specifically includes the following steps:

[0150] Mix the polyester polyol, hexamethylene diisocyanate, and 1,4-butanediol evenly in an extruder, and perform twin-screw reactive extrusion. The temperatures of the extruder are as follows: the first and second zones are both 160 °C, the third, fourth, and fifth zones are all 170 °C, the sixth, seventh, and eighth zones are all 180 °C, the ninth and tenth zones are both 170 °C, and the die head temperature is 170 °C. Then, perform underwater pelletizing to obtain the polyurethane adhesive.

[0151] Comparative Examples 4 to 6

[0152] The polyurethane adhesives provided in Comparative Examples 4 to 6 are different from those in Example 1 only in that the polyester polyols are the polyester polyols provided in Comparative Preparation Examples 3 to 5, respectively, and the other raw materials, dosages, and preparation methods are the same as those in Example 1.

[0153] Performance testing

[0154] Hydrolysis resistance performance: The test substrate is PVC. After placing the pasted sample strip in a constant temperature and humidity chamber (70 °C / 95% humidity) for 14 days, compare the peel strength with the blank sample strip to test the strength retention rate after hydrolysis; Instrument: Damp heat aging chamber (Memmert CTCZ56);

[0155] Stickable time: Coat the adhesive solution on the substrate and test whether it has stickiness at room temperature at regular intervals. The duration of maintaining stickiness is the stickable time;

[0156] Peel strength: The substrate is PE, and the tensile testing machine is (SHIMADZU AGX-X); Test according to GB / T 528-2009.

[0157] Among them, "-" indicates that the peel strength is so high that the substrate is damaged and the specific value cannot be measured, indicating excellent bonding performance.

[0158] The specific test results are shown in Table 1:

[0159] Table 1

[0160]

[0161] As can be seen from the above table, for the polyurethane adhesive provided by the present invention, by selecting diols and dibasic acids with specific structures as the raw materials for preparing the polyester polyol, the polyurethane adhesive has both excellent hydrolysis resistance and bonding performance, and a long open time and a low activation temperature. As can be seen from Examples 1 to 7, for the polyurethane adhesive, the peel strength can reach more than 3.2 N / mm at 25°C and can even cause damage to the substrate. After hydrolysis treatment for 14 days under the conditions of 70°C and 95% RH, the strength retention rate is 88-99%, and the pot life is 260-330 min, with excellent comprehensive performance.

[0162] As can be seen from Example 1 and Examples 8 to 9, when the mass ratio of the linear aliphatic diol to the alicyclic diol is not within a specific range, the pot life is shortened or the peel strength is reduced.

[0163] As can be seen from Example 1 and Example 10, when the 1,6-hexanediol and 1,4-cyclohexanedimethanol selected for the linear aliphatic diol and the alicyclic diol, the pot life is shortened and the peel strength is reduced.

[0164] As can be seen from Example 1 and Comparative Example 1, when a common polycaprolactone polyol is used to replace the polyester polyol with a special structure in the present application, the hydrolysis resistance of the polyurethane adhesive decreases and the pot life is shortened.

[0165] As can be seen from Example 1 and Comparative Examples 2 and 3, when two different linear aliphatic diols or two different alicyclic diols are selected as the diol, the hydrolysis resistance of the polyurethane adhesive decreases, the pot life is shortened or the peel strength is reduced.

[0166] As can be seen from Example 1 and Comparative Examples 4 to 6, when there is no alicyclic diol or linear aliphatic diol in the diol, or the main chain of the aliphatic diol contains side groups, the pot life of the polyurethane adhesive is shortened or the peel strength is reduced, and the activation temperature is high.

[0167] In summary, for the polyurethane adhesive provided by the present invention, by using long linear chain diols and long linear chain dibasic acids with specific structures, the polyurethane has both excellent water resistance and excellent bonding performance, and a long open time and a low activation temperature. It is particularly suitable for bonding PVC, fabrics, leathers, and foams with long working hours in humid environments.

[0168] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A polyurethane adhesive, characterized in that, The raw materials for preparing the polyurethane adhesive include 65 to 94 parts by weight of a high molecular polyol and 5 to 23 parts by weight of a diisocyanate; The high molecular polyol includes a polyester polyol; The raw materials for preparing the polyester polyol include a dibasic acid and a diol; The diol is a combination of a straight-chain aliphatic diol and an alicyclic diol; the straight-chain aliphatic diol is a C9-C12 straight-chain aliphatic diol; The mass ratio of the straight-chain aliphatic diol to the alicyclic diol is 1:(0.5 to 1).

2. The polyurethane adhesive according to claim 1, wherein The dibasic acid includes a C4-C12 dibasic acid.

3. The polyurethane adhesive according to claim 2, wherein The dibasic acid includes at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid or sebacic acid.

4. The polyurethane adhesive according to claim 1, wherein The mass ratio of the dibasic acid to the diol is 1:(0.8 to 1.6).

5. The polyurethane adhesive according to claim 1, wherein The straight-chain aliphatic diol includes at least one of decanediol or dodecanediol.

6. The polyurethane adhesive according to claim 1, characterized in that, The alicyclic diol includes a C4-C20 alicyclic diol.

7. The polyurethane adhesive according to claim 6, wherein The alicyclic diol includes at least one of cyclopentane-1,3-diol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,5-cyclooctanediol or 1,4-cyclohexanedimethanol.

8. The polyurethane adhesive according to claim 1, characterized in that, The acid value of the polyester polyol is less than 1 mgKOH / g.

9. The polyurethane adhesive according to claim 1, characterized in that, The hydroxyl value of the polyester polyol is 28 to 62 mgKOH / g.

10. The polyurethane adhesive according to claim 1, wherein The number average molecular weight of the high molecular polyol is 1800 to 4000 g / mol.

11. The polyurethane adhesive according to claim 1, wherein The high molecular polyol further includes at least one of a polycaprolactone polyol, a polyether polyol or a polycarbonate polyol.

12. The polyurethane adhesive according to claim 1, wherein The diisocyanate includes at least one of diphenylmethane diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, m-xylene diisocyanate, 1,5-naphthalene diisocyanate.

13. The polyurethane adhesive according to claim 12, wherein The diisocyanate is at least one of hexamethylene diisocyanate, diphenylmethane diisocyanate or isophorone diisocyanate.

14. The polyurethane adhesive according to claim 1, wherein The raw materials for preparing the polyurethane adhesive further include 0 to 18 parts by weight of a chain extender.

15. The polyurethane adhesive according to claim 14, wherein, The chain extender includes at least one of 1,2-ethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethylene glycol or cis-1,2-cyclohexanedimethanol.

16. The polyurethane adhesive according to claim 15, wherein The chain extender is at least one of neopentyl glycol, 1,4-butanediol, 1,6-hexanediol or cis-1,2-cyclohexanedimethanol.

17. The polyurethane adhesive according to claim 1, wherein The raw materials for preparing the polyurethane adhesive include 70 to 92 parts by weight of a high molecular polyol, 12 to 22 parts by weight of a diisocyanate and 0.1 to 10 parts by weight of a chain extender.

18. A method for preparing the polyurethane adhesive according to any one of claims 1 to 17, characterized in that, The preparation method includes: Mixing the high molecular polyol and the diisocyanate, and reacting to obtain the polyurethane adhesive.

19. The preparation method according to claim 18, characterized in that, The raw materials for mixing further include a chain extender.

20. The preparation method according to claim 18, wherein, The reaction is carried out in a twin-screw extruder.

21. The preparation method according to claim 20, characterized in that, The temperature of the twin-screw extruder is 150 to 200 °C.

22. The preparation method according to claim 18, characterized in that, After the reaction, there is further a step of pelletizing.

23. Use of the polyurethane adhesive according to any one of claims 1 to 17 in bonding PVC, fabric, leather or foam.

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