Multifunctional hyperbranched polyester polyol, preparation method thereof and low-temperature cured polyurethane laminated adhesive

Abstract

The invention discloses multifunctional hyperbranched polyester polyol, a preparation method thereof and a low-temperature cured polyurethane laminated adhesive, and belongs to the field of high polymer materials and adhesives. The polyester polyol is prepared from trimethylolpropane, dihydric alcohol, dibasic acid, 2, 2-dimethylolpropionic acid, an antioxidant, a catalyst and ethyl acetate as raw materials, the polyester polyol is of a three-layer structure with trimethylolpropane as a core, the first layer is a primary framework formed by polycondensation of the dihydric alcohol and the dibasic acid, and the second layer is a secondary framework formed by polycondensation of the dihydric alcohol and the dibasic acid; the second layer and the third layer are respectively of a hyperbranched structure which is obtained by taking 2, 2-dimethylolpropionic acid as an AB2 type branch monomer through layer-by-layer grafting. The product provided by the invention has the advantages of high functionality, uniform end group distribution and strong reaction activity, and can quickly react with isocyanate at 30-35 DEG C. The polyurethane laminated adhesive prepared from the polyester polyol is high in composite film peeling strength, excellent in water boiling resistance and steaming and boiling resistance, and suitable for the fields of food, medicine, daily chemical packaging and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high molecular materials and adhesives, and particularly relates to a multi-functional hyperbranched polyester polyol, a preparation method thereof and a low-temperature curing polyurethane laminating adhesive. BACKGROUND

[0002] The polyurethane laminating adhesive has been widely used in the fields of food, medicine and daily chemical packaging due to its good flexibility, bonding strength and high temperature resistance. The laminating adhesive is usually required to have high peeling strength after curing and to maintain stable bonding performance under high temperature cooking and boiling conditions. Most of the existing commercial polyurethane laminating adhesive systems rely on high temperature (above 50 DEG C) and long time (not less than 3 days) curing process to ensure that the crosslinking reaction between polyurethane molecules is fully carried out, so as to obtain the expected mechanical properties and heat resistance.

[0003] However, the existing high temperature and long period curing process has many deficiencies: first, the high temperature curing process consumes a large amount of energy, which is not conducive to energy saving and green production; second, high temperature action can easily cause thermal shrinkage, wrinkling or performance degradation of the composite film substrate, affecting the appearance and use performance of the final packaging material; in addition, the long curing period also delays the production progress and reduces the industrial application efficiency.

[0004] In order to solve the above problems, researchers try to reduce the curing temperature and shorten the curing time by introducing tin catalysts, adjusting the type of isocyanate, modifying polyester polyols and other ways. However, the existing technical solutions still have deficiencies: although tin catalysts can promote the reaction rate, their toxicity and environmental risk do not meet the increasingly strict environmental regulations; and most of the commonly used polyester polyols are linear or lowly branched structures, which have limited molecular functionality, and it is difficult for them to form a three-dimensional network with high crosslinking density with isocyanate under low temperature conditions, resulting in insufficient crosslinking rate, poor high temperature resistance and other problems. Therefore, how to provide a polyester polyol with high functionality, strong reactivity, fast curing at low temperature and excellent resistance to cooking and boiling is the key to the upgrading of laminating adhesive technology.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The present application aims to provide a multi-functional hyperbranched polyester polyol, a preparation method thereof and a low-temperature curing polyurethane laminating adhesive. The hyperbranched polyester polyol has high functionality and rich reactive groups, and can rapidly react with isocyanate at a relatively low temperature to form a dense crosslinking network, thereby ensuring fast curing while giving the laminating adhesive excellent resistance to cooking and boiling, and thus solving the problem of long time curing at above 50 DEG C of the existing polyurethane laminating adhesive.

[0007] The objective of this invention is achieved through the following technical solution: A multifunctional hyperbranched polyester polyol is made from trimethylolpropane, diol, diacid, 2,2-dimethylolpropionic acid, antioxidant, catalyst and ethyl acetate. It is a three-layer structure polyester polyol with trimethylolpropane as the core. The first layer is a primary skeleton formed by the polycondensation of diol and diacid. The second and third layers are hyperbranched structures obtained by grafting 2,2-dimethylolpropionic acid as AB2-type branching monomers layer by layer.

[0008] Preferably, the average functionality of the polyester polyol is 10 to 14.

[0009] Preferably, in the above-mentioned polyester polyol, the average molecular weight Mn of the polyester polyol is 4000-6000, the hydroxyl value is 130-170 mgKOH / g, the acid value is less than 1.0 mgKOH / g, the solid content is 70%-80%, and the rotational viscosity at 25°C is 3000-5000 mPa·s.

[0010] Preferably, in the above-mentioned polyester polyol, the molar ratio of trimethylolpropane to diol and diacid in the first layer of the polyester polyol is: trimethylolpropane: diol: diacid = 1: 6.0~9.0: 3.0~6.0.

[0011] Preferably, in the above-mentioned polyester polyol, the total amount of 2,2-dimethylolpropionic acid used in the second and third layers is 9.0 to 15.0 times the molar amount of trimethylolpropane, and the 2,2-dimethylolpropionic acid is added in at least two batches, with the second and third layers accounting for 30 to 40 wt% and 60 to 70 wt% of the total 2,2-dimethylolpropionic acid, respectively.

[0012] Preferably, in the above-mentioned polyester polyol, the diol is one or more of neopentyl glycol, diethylene glycol, 1,4-butanediol, and ethylene glycol; The dicarboxylic acid is one or more of adipic acid, terephthalic acid, isophthalic acid, and sebacic acid.

[0013] Preferably, in the above-mentioned polyester polyol, the antioxidant is triphenyl phosphite, and the antioxidant accounts for 150-250 ppm of the total monomer. The catalyst is tetrabutyl titanate, and the catalyst accounts for 150-250 ppm of the total monomer.

[0014] A method for preparing the multifunctional hyperbranched polyester polyol of the present invention, comprising the following steps: taking various raw materials according to the multifunctional hyperbranched polyester polyol of the present invention. Step 1, the synthesis of the first layer: Trimethylolpropane, diol, diacid and antioxidant from the raw materials are added to the reaction vessel; Esterification was carried out under nitrogen protection. The reaction temperature was raised to 150°C to begin dehydration. The temperature was then increased by 10°C every hour until the reaction temperature gradually rose to 230-245°C. The esterification and dehydration reaction was maintained within this temperature range for 8-12 hours until the acid value of the system dropped to ≤10mgKOH / g, thus completing the first layer of esterification. After the esterification and dehydration reaction is completed, a polycondensation reaction is carried out. Catalyst of 1 / 3 of the total catalyst dosage is added to the reactor. Then, the reaction system is evacuated and the temperature is controlled at 230-245℃. During the polycondensation stage, the vacuum degree is increased sequentially from -0.02MPa, -0.04MPa, -0.06MPa to -0.08MPa, and each stage is maintained for 0.5-1 hour. After that, a long-term vacuum operation is carried out, raising the vacuum degree to -0.10MPa and maintaining it for 8-10 hours until the hydroxyl value of the product drops to 15-18mgKOH / g and the acid value is ≤1.0mgKOH / g, completing the first layer of polycondensation reaction and obtaining the first layer of primary skeleton. Step 2, the synthesis of the second layer: After the esterification and polycondensation reaction of the first layer is completed, the system is cooled to 150°C, and a predetermined amount of 2,2-dimethylolpropionic acid is added to the reactor. Esterification was carried out under nitrogen protection. Dehydration began at 150°C, and the temperature was increased by 10°C every hour until the reaction temperature gradually rose to 230-245°C. The esterification and dehydration reaction was maintained within this temperature range for 8-12 hours until the acid value of the system dropped to ≤10mgKOH / g, thus completing the second layer of esterification. After the esterification and dehydration reaction is completed, a polycondensation reaction is carried out. Catalyst of 1 / 3 of the total catalyst dosage is added to the reactor, and then the reaction system is evacuated and the temperature is controlled at 230-245℃. During the polycondensation stage, the vacuum degree is increased sequentially from -0.02MPa, -0.04MPa, -0.06MPa to -0.08MPa, and each stage is maintained for 0.5-1 hour. Then, a long-term vacuum operation is carried out, and the vacuum degree is increased to -0.10MPa and maintained for 8-10 hours until the hydroxyl value of the product drops to 15-18mgKOH / g and the acid value is ≤1.0mgKOH / g, completing the polycondensation reaction of the second layer and obtaining the hyperbranched structure of the second layer. Step 3, the synthesis of the third layer: After the esterification and polycondensation reaction of the second layer is completed, the system is cooled to 150°C again, and the remaining 2,2-dimethylolpropionic acid is added. Esterification was carried out under nitrogen protection. Dehydration began at 150°C, and the temperature was increased by 10°C every hour until the reaction temperature gradually rose to 230-245°C. The esterification and dehydration reaction was maintained within this temperature range for 8-12 hours until the acid value of the system dropped to ≤10mgKOH / g, thus completing the esterification reaction of the third layer. After the esterification and dehydration reaction is completed, a polycondensation reaction is carried out. The remaining catalyst is added to the reactor, and then the reaction system is evacuated and the temperature is controlled at 230-245℃. During the polycondensation stage, the vacuum degree is increased sequentially from -0.02MPa, -0.04MPa, -0.06MPa to -0.08MPa, and each stage is maintained for 0.5-1 hour. Then, a long-term vacuum operation is carried out, raising the vacuum degree to -0.10MPa and maintaining it for 8-10 hours until the hydroxyl value of the product reaches 140-160mgKOH / g and the acid value is ≤1.0mgKOH / g, completing the polycondensation reaction of the third layer and obtaining hyperbranched polyester polyol. Step 4, Preparation of multifunctional hyperbranched polyester polyols: The reaction system obtained in step 3 is cooled to below 70°C, diluted with ethyl acetate, and adjusted to the target solid content to obtain a multifunctional hyperbranched polyester polyol.

[0015] A low-temperature curing polyurethane coating adhesive, comprising the following components in parts by weight: The present invention comprises 25-35 parts of hyperbranched polyester polyol, 25-35 parts of curing agent, and 40-50 parts of ethyl acetate.

[0016] Preferably, in the above-mentioned coating adhesive, the curing agent is an isocyanate-type product obtained by the addition chain extension reaction of toluene diisocyanate and trimethylolpropane.

[0017] Compared with the prior art, the multifunctional hyperbranched polyester polyol and its preparation method, along with the low-temperature curing polyurethane coating adhesive provided by this invention, have the following beneficial effects: By employing a multifunctional hyperbranched structure design, the polyester polyol molecules contain a large number of active hydroxyl groups, enabling rapid reaction with isocyanates at low temperatures. This achieves a curing process of 30–35°C for 48–72 hours, significantly shortening the curing time and reducing energy consumption. The three-dimensional structure of the hyperbranched polyester polyol in this invention greatly increases the crosslinking point density, resulting in a denser polyurethane network. Consequently, the composite film maintains high peel strength and structural stability even after being boiled at 135°C for 40 minutes. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the specific content of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments, which do not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0019] First, the following explanations are provided for the terms that may be used in this article: The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0020] The terms "comprising," "including," "containing," "having," or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.) should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0021] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0022] The term "parts by mass" indicates the mass ratio between multiple components. For example, if component X is described as x parts by mass and component Y as y parts by mass, then the mass ratio of component X to component Y is x:y. One part by mass can represent any mass; for example, one part by mass can be expressed as 1 kg or 3.1415926 kg, etc. The sum of the parts by mass of all components is not necessarily 100 parts; it can be greater than 100 parts, less than 100 parts, or equal to 100 parts. Unless otherwise stated, parts, proportions, and percentages mentioned herein are all measured by mass.

[0023] When concentration, temperature, pressure, size, or other parameters are expressed as numerical ranges, such ranges should be understood to specifically disclose all ranges formed by any pairing of upper limits, lower limits, or preferred values ​​within that range, regardless of whether the range is explicitly stated; for example, if the numerical range "2 to 8" is stated, then that range should be interpreted to include ranges such as "2 to 7", "2 to 6", "5 to 7", "3 to 4 and 6 to 7", "3 to 5 and 7", "2 and 5 to 7", etc. Unless otherwise stated, the numerical ranges described herein include both their endpoints and all integers and fractions within that range.

[0024] The solution provided by this invention will be described in detail below. Contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of this invention whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0025] This invention provides a multifunctional hyperbranched polyester polyol for low-temperature curing polyurethane coating adhesives. This polyester polyol is made from trimethylolpropane (TMP), diol, diacid, 2,2-dimethylolpropionic acid (DMPA), antioxidant, catalyst, and ethyl acetate. It has a three-layered hyperbranched structure with TMP as the core. The first layer is a primary skeleton formed by the condensation polymerization of diol and diacid; the second and third layers are hyperbranched structures obtained by grafting DMPA as an AB2-type branched monomer. The average functionality of this hyperbranched polyester polyol is 10–14.

[0026] Preferably, in the above-mentioned hyperbranched polyester polyol, the molar ratio of TMP to diol and diacid in the first layer is: TMP:diol:diacid = 1:6.0~9.0:3.0~6.0.

[0027] Preferably, in the above-mentioned hyperbranched polyester polyol, the total amount of DMPA used in the second and third layers is 9.0 to 15.0 times the molar amount of TMP, and the DMPA is added in at least two batches, with the second and third layers accounting for 30 to 40 wt% and 60 to 70 wt% of the total DMPA, respectively.

[0028] Preferably, in the above-mentioned hyperbranched polyester polyol, the antioxidant is triphenyl phosphite, and the antioxidant accounts for 150-250 ppm of the total monomer. The catalyst is tetrabutyl titanate, and the catalyst accounts for 150-250 ppm of the total monomer.

[0029] Preferably, in the above-mentioned hyperbranched polyester polyol, the diol is one or more of neopentyl glycol (NPG), diethylene glycol (DEG), 1,4-butanediol (BDO), and ethylene glycol; and the diacid is one or more of adipic acid (ADA), terephthalic acid (PTA), isophthalic acid (IPA), or sebacic acid.

[0030] Preferably, in the above-mentioned hyperbranched polyester polyol, the average molecular weight Mn of the polyester polyol is 4000-6000; the hydroxyl value is 130-170 mgKOH / g; the acid value is less than 1.0 mgKOH / g; the solid content is 70%-80%; and the rotational viscosity at 25°C is 3000-5000 mPa·s.

[0031] The present invention also provides a method for preparing the above-mentioned multifunctional hyperbranched polyester polyol, comprising the following steps: Step 1, the synthesis of the first layer: Take the raw materials according to the above formula, and add the TMP, diol, diacid and antioxidant from the raw materials into the reaction vessel; Esterification was carried out under nitrogen protection. The reaction temperature was raised to 150°C to start dehydration. The temperature was then increased by about 10°C every hour until the reaction temperature gradually rose to 230-245°C. The esterification and dehydration reaction was maintained within this temperature range for 8-12 hours until the acid value of the system dropped to ≤10mgKOH / g, thus completing the first layer of esterification. After the esterification and dehydration reaction is completed, a reduction reaction is carried out. Catalyst of 1 / 3 of the total catalyst dosage is added to the reactor, and then the reaction system is evacuated and the temperature is controlled at 230-245℃. During the polycondensation stage, the vacuum degree is gradually increased sequentially from -0.02MPa, -0.04MPa, -0.06MPa to -0.08MPa, and each stage is maintained for 0.5-1h. Then, a long-term vacuum operation is carried out, raising the vacuum degree to -0.10MPa and maintaining it for 8-10h until the hydroxyl value of the product drops to 15-18mgKOH / g and the acid value is ≤1.0mgKOH / g, completing the first layer of polycondensation reaction and obtaining the first layer of primary skeleton. Step 2, the synthesis of the second layer: After the esterification and polycondensation reaction of the first layer is completed, the system is cooled to 150°C, a predetermined amount of DMPA and 1 / 3 of the total amount of catalyst are added to the second layer, and the esterification and polycondensation reaction is carried out in accordance with the esterification and polycondensation reaction method of step 1 above to obtain the hyperbranched structure of the second layer. Step 3, the synthesis of the third layer: After the esterification and polycondensation of the second layer are completed, the system is cooled to 150°C again, and the remaining DMPA and catalyst are added. The esterification and polycondensation reactions are repeated in the same manner as in step 2 to obtain hyperbranched polyester polyol. Step 4: The reaction system is then cooled to below 70°C, and ethyl acetate is added for dilution to adjust to the target solid content, thus obtaining a multifunctional hyperbranched polyester polyol.

[0032] The present invention also provides a low-temperature curing polyurethane coating adhesive, which is composed of the following components in parts by weight: 25-35 parts of the multifunctional hyperbranched polyester polyol prepared above, 25-35 parts of curing agent and 40-50 parts of ethyl acetate.

[0033] Preferably, in the above-mentioned coating adhesive, the curing agent is an isocyanate product obtained by addition chain extension reaction of toluene diisocyanate (TDI) and trimethylolpropane (TMP).

[0034] Preferably, the above-mentioned coating adhesive, after being coated on the film substrate and cured at 30-35°C for 48-72 hours, is boiled in water at 100°C for 30 minutes and steamed at 121°C and 135°C for 40 minutes, the composite film does not crack or delaminate, and has a peel strength ≥5.0N / 15mm.

[0035] In summary, the multifunctional hyperbranched polyester polyol of this invention, applied to low-temperature curing polyurethane coating adhesives, is widely applicable to various substrates such as PET, PA, CPP, PE, and aluminum foil used in food, pharmaceutical, and daily chemical packaging. This coating adhesive can complete low-temperature curing at 30–35°C, and the composite film maintains excellent peel strength and structural stability after being boiled in water at 100°C and then steamed at 135°C for 40 minutes, demonstrating superior resistance to boiling and steaming. This invention not only overcomes the limitations of traditional high-temperature, long-cycle curing processes, achieving energy saving, consumption reduction, and efficient production, but also meets the urgent domestic and international demand for high-performance, green coating adhesives. It has significant practical importance and broad market application value for replacing imported products and promoting the green and high-end development of the packaging industry.

[0036] To more clearly demonstrate the technical solution and its effects provided by the present invention, the following detailed description of the solution provided by the embodiments of the present invention is provided with reference to specific examples.

[0037] Example 1 This embodiment provides a multifunctional hyperbranched polyester polyol for low-temperature curing polyurethane coating adhesives, the preparation method of which includes: The following raw materials were taken in the following proportions by weight: trimethylolpropane, 1,4-butanediol, diethylene glycol, neopentyl glycol, adipic acid, terephthalic acid, isophthalic acid, triphenyl phosphite, tetrabutyl titanate, and 2,2-dimethylolpropionic acid, with the following proportions by weight: 10:22:18:26:8:20:10:0.02:0.02:90; (1) Synthesis of the first layer:

[0038] Trimethylolpropane, 1,4-butanediol, diethylene glycol, neopentyl glycol, adipic acid, terephthalic acid and isophthalic acid are added to a reaction vessel, along with triphenyl phosphite as an antioxidant and tetrabutyl titanate (catalyst) at 1 / 3 of the total amount of tetrabutyl titanate. Esterification reaction: Heat to 150℃ under nitrogen protection to begin dehydration, increase the temperature by about 10℃ every 1 hour until the temperature reaches 240℃; maintain the esterification reaction for 8-12 hours until the acid value of the system is ≤10mgKOH / g. Polycondensation reaction: After esterification, vacuum polycondensation is carried out at 240℃, with the vacuum degree gradually increased from −0.02MPa to −0.10MPa, and each stage is maintained for 0.5 to 1h. Finally, the vacuum is evacuated for a long time for 8 to 10h until the acid value is ≤1.0mgKOH / g, thus obtaining the primary skeleton of the first layer. (2) Synthesis of the second layer: The above product was cooled to 150°C, and 2,2-dimethylolpropionic acid (30 wt% of the total amount of 2,2-dimethylolpropionic acid) and tetrabutyl titanate (1 / 3 of the total amount of tetrabutyl titanate) were slowly added dropwise. Esterification and polycondensation were carried out under the same process conditions as the first layer until the acid value was ≤1.0 mgKOH / g, thus obtaining the hyperbranched structure of the second layer. (3) Synthesis of the third layer After the second layer reaction is completed, the temperature is lowered to 150℃ again, and the remaining 2,2-dimethylolpropionic acid and the remaining tetrabutyl titanate are slowly added dropwise. Esterification and polycondensation are carried out under the same process conditions as the second layer until the hydroxyl value of the product reaches 140 mgKOH / g and the acid value is ≤1.0 mgKOH / g, thus obtaining the hyperbranched polyester polyol. (4) Discharge and dilution

[0039] The product was cooled to below 70°C, and ethyl acetate was slowly added under stirring to dilute it, adjusting the solid content to 70 wt%, thus obtaining a multifunctional hyperbranched polyester polyol.

[0040] Example 2 This embodiment provides a multifunctional hyperbranched polyester polyol for low-temperature curing polyurethane coating adhesives, the preparation method of which includes: The following raw materials were prepared in the following proportions by weight: trimethylolpropane, ethylene glycol, diethylene glycol, neopentyl glycol, sebacic acid, terephthalic acid, isophthalic acid, triphenyl phosphite, tetrabutyl titanate, and 2,2-dimethylolpropionic acid, with proportions of 10:16:28:25:10:18:12:0.03:0.03:100. (1) Synthesis of the first layer: Trimethylolpropane, ethylene glycol, diethylene glycol, neopentyl glycol, sebacic acid, terephthalic acid and isophthalic acid are added to a reaction vessel, along with triphenyl phosphite as an antioxidant and tetrabutyl titanate (catalyst) at 1 / 3 of the total amount of tetrabutyl titanate. Esterification reaction: Heat to 150℃ under nitrogen protection to begin dehydration, increase the temperature by about 10℃ every 1 hour until the temperature reaches 240℃; maintain the esterification reaction for 8-12 hours until the acid value of the system is ≤10mgKOH / g. Polycondensation reaction: After esterification, vacuum polycondensation is carried out at 240℃, with the vacuum degree gradually increased from −0.02MPa to −0.10MPa, and each stage is maintained for 0.5 to 1h. Finally, the vacuum is evacuated for a long time for 8 to 10h until the acid value is ≤1.0mgKOH / g, thus obtaining the primary skeleton of the first layer.

[0041] (2) Synthesis of the second layer: The above product was cooled to 150°C, and 2,2-dimethylolpropionic acid (35 wt% of the total amount of 2,2-dimethylolpropionic acid) and tetrabutyl titanate (1 / 3 of the total amount of tetrabutyl titanate) were slowly added dropwise. Esterification and polycondensation were carried out under the same process conditions as the first layer until the acid value was ≤1.0 mgKOH / g, thus obtaining the hyperbranched structure of the second layer.

[0042] (3) Synthesis of the third layer: After the second layer reaction is completed, the temperature is lowered to 150℃ again, and the remaining 2,2-dimethylolpropionic acid and the remaining tetrabutyl titanate are slowly added dropwise. Esterification and polycondensation are carried out under the same process conditions as the second layer until the hydroxyl value of the product reaches 160 mgKOH / g and the acid value is ≤0.8 mgKOH / g, thus obtaining the multifunctional hyperbranched polyester polyol.

[0043] (4) Discharge and dilution The product was cooled to below 70°C, and ethyl acetate was slowly added under stirring to dilute it, adjusting the solid content to 70 wt%, thus obtaining a multifunctional hyperbranched polyester polyol.

[0044] Example 3 This embodiment provides a multifunctional hyperbranched polyester polyol for low-temperature curing polyurethane coating adhesives, the preparation method of which includes: The following raw materials were prepared in the following proportions by weight: trimethylolpropane, 1,4-butanediol, ethylene glycol, diethylene glycol, neopentyl glycol, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, triphenyl phosphite, tetrabutyl titanate, and 2,2-dimethylolpropionic acid, with proportions of 10:22:12:18:26:8:14:15:10:0.02:0.02:110; (1) Synthesis of the first layer: Trimethylolpropane, 1,4-butanediol, ethylene glycol, diethylene glycol, neopentyl glycol, adipic acid, sebacic acid, terephthalic acid and isophthalic acid are added to a reaction vessel, along with triphenyl phosphite as an antioxidant and tetrabutyl titanate (catalyst) at 1 / 3 of the total amount of tetrabutyl titanate. Esterification reaction: Heat to 150℃ under nitrogen protection to begin dehydration, increase the temperature by about 10℃ every 1 hour until the temperature reaches 240℃; maintain the esterification reaction for 8-12 hours until the acid value of the system is ≤10mgKOH / g. Polycondensation reaction: After esterification, vacuum polycondensation is carried out at 240℃, with the vacuum degree gradually increased from −0.02MPa to −0.10MPa, and each stage is maintained for 0.5 to 1h. Finally, the vacuum is evacuated for a long time for 8 to 10h until the acid value is ≤1.0mgKOH / g, thus obtaining the primary skeleton of the first layer.

[0045] (2) Synthesis of the second layer: The above product was cooled to 150°C, and 2,2-dimethylolpropionic acid (37 wt% of the total amount of 2,2-dimethylolpropionic acid) and tetrabutyl titanate (1 / 3 of the total amount of tetrabutyl titanate) were slowly added dropwise. Esterification and polycondensation were carried out under the same process conditions as the first layer until the acid value was ≤1.0 mgKOH / g, thus obtaining the hyperbranched structure of the second layer.

[0046] (3) Synthesis of the third layer: After the second layer reaction is completed, the temperature is lowered to 150℃ again, and the remaining 2,2-dimethylolpropionic acid and the remaining tetrabutyl titanate are slowly added dropwise. Esterification and polycondensation are carried out under the same process conditions as the second layer until the hydroxyl value of the product reaches 153 mgKOH / g and the acid value is ≤0.6 mgKOH / g, thus obtaining the multifunctional hyperbranched polyester polyol.

[0047] (4) Discharge and dilution: The product was cooled to below 70°C, and ethyl acetate was slowly added under stirring to dilute it, adjusting the solid content to 70 wt%, thus obtaining the multifunctional hyperbranched polyester polyol.

[0048] Comparative Example This comparative example provides a linear polyester polyol, the preparation method of which is as follows: Raw material ratio (parts by weight): 20 parts 1,4-butanediol, 15 parts diethylene glycol, 25 parts neopentyl glycol, 10 parts adipic acid, 20 parts terephthalic acid, 10 parts isophthalic acid, 0.02 parts triphenyl phosphite, and 0.02 parts tetrabutyl titanate.

[0049] 1,4-Butanediol, diethylene glycol, neopentyl glycol, adipic acid, terephthalic acid, and isophthalic acid were added to a reactor, along with the antioxidants triphenyl phosphite and tetrabutyl titanate. Under nitrogen protection, the mixture was heated to 150°C to begin dehydration, with the temperature increased by approximately 10°C every hour until it reached 240°C. The esterification reaction was maintained for 8–12 hours until the acid value of the system was ≤10 mgKOH / g. After esterification, vacuum polycondensation was performed at 240°C, with the vacuum level gradually increased from −0.02 MPa to −0.10 MPa, maintained for 0.5–1 hour in each stage. Finally, a prolonged vacuum period of 8–10 hours was applied until the hydroxyl value was 15 mgKOH / g and the acid value was ≤1.0 mgKOH / g, yielding the linear polyester polyol.

[0050] Performance testing The usage and performance testing methods of the multifunctional hyperbranched polyester polyols in Examples 1, 2, and 3 of this invention are as follows: Dry base sizing amount: 3-4 g / m 2 ; Composite structure; PETink / AL / RCPP; Curing conditions: 30-35℃ × 72h; Boiling test conditions: 100℃×30min; Steaming test conditions: 135℃×40min; Thermal creep test conditions: 100℃×5min; Using the multifunctional hyperbranched polyester polyols prepared in the above embodiments as the main agent, a curing agent and ethyl acetate were added to prepare a working solution. The solution was then coated and its application performance was tested. The test results were compared with the application performance of the linear polyester polyols prepared in the comparative example. The results are shown in Tables 1 and 2 below.

[0051] Table 1 shows the test results. .

[0052] Table 2 shows the test results. .

[0053] In summary, the multifunctional hyperbranched polyester polyol of this invention exhibits significant advantages in the application of low-temperature curing polyurethane coating adhesives. The prepared composite film demonstrates excellent peel strength, water resistance, boiling resistance, and good thermal creep stability. This performance advantage stems from the unique molecular structure of the hyperbranched polyester polyol, whose high functionality provides more reaction sites. Therefore, this system can achieve rapid curing at 30–35°C, significantly reducing energy consumption and shortening the production cycle. The coating adhesive can be widely used in composite material fields such as food, pharmaceutical, and daily chemical packaging, meeting the comprehensive performance requirements of high strength, high temperature resistance, and environmental friendliness, and possesses broad application prospects and market value.

[0054] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A multifunctional hyperbranched polyester polyol characterized in that, The polyester polyol is prepared from trimethylolpropane, dihydric alcohol, diacid, 2,2-dimethylol propionic acid, antioxidant, catalyst and ethyl acetate, and is a three-layer structure polyester polyol with trimethylolpropane as the core, wherein the first layer is a primary skeleton formed by polycondensation of dihydric alcohol and diacid; the second layer and the third layer are both hyperbranched structures obtained by layer-by-layer grafting using 2,2-dimethylol propionic acid as an AB2 type branching monomer.

2. The multifunctional hyperbranched polyester polyol according to claim 1, characterized in that, The average functionality of the polyester polyol is 10-14.

3. The multi-functionality hyperbranched polyester polyol according to claim 1, wherein, The average molecular weight Mn of the polyester polyol is 4000-6000, the hydroxyl value is 130-170 mgKOH / g, the acid value is less than 1.0 mgKOH / g, the solid content is 70%-80%, and the rotational viscosity at 25°C is 3000-5000 mPa·s.

4. The multi-functional hyperbranched polyester polyol according to any one of claims 1 to 3, characterized in that, In the polyester polyol, the molar ratio of trimethylolpropane to dihydric alcohol and diacid in the first layer is: trimethylolpropane: dihydric alcohol: diacid = 1: 6.0-9.0: 3.0-6.

0.

5. The multi-functional hyperbranched polyester polyol according to any one of claims 1 to 3, characterized in that, In the polyester polyol, the total amount of 2,2-dimethylol propionic acid used in the second layer and the third layer is 9.0-15.0 times the number of moles of trimethylolpropane, and the 2,2-dimethylol propionic acid is added in at least two batches, with the second layer and the third layer accounting for 30-40 wt% and 60-70 wt%, respectively, of the total amount of 2,2-dimethylol propionic acid.

6. The multi-functional hyperbranched polyester polyol according to any one of claims 1 to 3, characterized in that, The dihydric alcohol is one or more of neopentyl glycol, diethylene glycol, 1,4-butanediol, and ethylene glycol; The diacid is one or more of adipic acid, terephthalic acid, isophthalic acid, and sebacic acid.

7. The multi-functional hyperbranched polyester polyol according to any one of claims 1 to 3, characterized in that, In the polyester polyol, the antioxidant is triphenyl phosphite, and the amount of antioxidant is 150-250 ppm based on the total amount of monomers; The catalyst is tetrabutyl titanate, and the amount of catalyst is 150-250 ppm based on the total amount of monomers.

8. A process for the preparation of the multifunctional hyperbranched polyester polyol according to any one of claims 1 to 7, characterized in that, The multifunctional hyperbranched polyester polyol according to any one of claims 1-7 is prepared from the raw materials, comprising the following steps: Step 1, synthesis of the first layer: The trimethylolpropane, dihydric alcohol, diacid, and antioxidant in the raw materials are added to a reaction kettle; The esterification reaction is carried out under nitrogen protection, the reaction is heated to 150°C to start dehydration, and then the temperature is increased by 10°C every 1 hour until the reaction temperature gradually reaches 230-245°C; the esterification and dehydration reaction is maintained at this temperature range for 8-12 hours until the acid value of the system is detected to be ≤10 mgKOH / g, and the esterification reaction of the first layer is completed; After the esterification and dehydration reaction is completed, the polycondensation reaction is carried out, 1 / 3 of the total catalyst is added into the reaction kettle, then the reaction system is vacuumized, and the temperature is controlled at 230-245 DEG C. In the polycondensation stage, the vacuum degree is increased in turn at -0.02 MPa, -0.04 MPa, -0.06 MPa to -0.08 MPa, each stage is maintained for 0.5-1 hour; then the long-time vacuum operation is carried out, the vacuum degree is increased to -0.10 MPa and maintained for 8-10 hours, until the product hydroxyl value is reduced to 15-18 mgKOH / g, and the acid value is less than or equal to 1.0 mgKOH / g, the first layer of the polycondensation reaction is completed, and the first layer of the primary skeleton is obtained; Step 2, synthesis of the second layer: After the esterification and polycondensation reaction of the first layer is completed, the system is cooled to 150 DEG C, and a predetermined amount of 2,2-dimethylol propionic acid is added into the reaction kettle; The esterification reaction is carried out under the protection of nitrogen, dehydration is started at 150 DEG C, then the temperature is increased by 10 DEG C every 1 hour, until the reaction temperature is gradually increased to 230-245 DEG C; the esterification and dehydration reaction is maintained at the temperature range for 8-12 hours, until the acid value of the system is reduced to less than or equal to 10 mgKOH / g, and the esterification reaction of the second layer is completed; The polycondensation reaction is carried out after the esterification and dehydration reaction is completed, 1 / 3 of the total catalyst is added into the reaction kettle, then the reaction system is vacuumized, and the temperature is controlled at 230-245 DEG C. In the polycondensation stage, the vacuum degree is increased in turn at -0.02 MPa, -0.04 MPa, -0.06 MPa to -0.08 MPa, each stage is maintained for 0.5-1 hour; then the long-time vacuum operation is carried out, the vacuum degree is increased to -0.10 MPa and maintained for 8-10 hours, until the product hydroxyl value is reduced to 15-18 mgKOH / g, and the acid value is less than or equal to 1.0 mgKOH / g, the second layer of the polycondensation reaction is completed, and the second layer of the hyperbranched structure is obtained; Step 3, synthesis of the third layer: After the esterification and polycondensation reaction of the second layer is completed, the system is cooled to 150 DEG C again, and the remaining 2,2-dimethylol propionic acid is continuously added; The esterification reaction is carried out under the protection of nitrogen, dehydration is started at 150 DEG C, then the temperature is increased by 10 DEG C every 1 hour, until the reaction temperature is gradually increased to 230-245 DEG C; the esterification and dehydration reaction is maintained at the temperature range for 8-12 hours, until the acid value of the system is reduced to less than or equal to 10 mgKOH / g, and the esterification reaction of the third layer is completed; After the esterification and dehydration reaction is completed, the residual catalyst is added into the reactor, and then the reaction system is vacuumized, and the temperature is controlled at 230-245℃. In the polycondensation stage, the vacuum degree is increased in turn at -0.02MPa, -0.04MPa, -0.06MPa to -0.08MPa, and each stage is maintained for 0.5-1 hour. Then, the long-time vacuum operation is performed, the vacuum degree is increased to -0.10MPa and maintained for 8-10 hours, until the product hydroxyl value reaches 140-160mgKOH / g, and the acid value is ≤1.0mgKOH / g, the third layer of polycondensation reaction is completed, and the hyperbranched polyester polyol is obtained. Step 4, preparation of the multifunctional hyperbranched polyester polyol: The reaction system obtained in step 3 is cooled to below 70℃, and diluted with ethyl acetate, and adjusted to the target solid content, to obtain the multifunctional hyperbranched polyester polyol.

9. A low temperature curable polyurethane coating adhesive characterized by, Composed of the following components by mass parts: The hyperbranched polyester polyol 25-35 parts, the curing agent 25-35 parts and the ethyl acetate 40-50 parts according to any one of claims 1-7. The curing agent is an isocyanate type product prepared by addition chain extension reaction of toluene diisocyanate and trimethylolpropane.

10. The low temperature cured polyurethane film adhesive of claim 9, wherein, ​