A polyester polyol for adhesive and its preparation method and application

Abstract

The present invention belongs to the field of polymer compounds, and provides a polyester polyol for adhesives, and a preparation method and application thereof. The present invention first chemically modifies aliphatic dibasic acids by maleic anhydride, produces ester bonds with strong polarity, and introduces more reaction sites into the structure, thereby increasing the crosslinking density so that it can maintain stable adhesion under high temperature environments. Citric acid and epoxidized soybean oil are added to the formula. The introduction of citric acid as a polyacid enhances the crosslinking reaction ability of the material, forms a denser polymer network, and improves the heat resistance and chemical stability of the adhesive; the addition of epoxidized soybean oil gives the material better flexibility, and at the same time, the epoxy group can react with other components to form additional chemical crosslinks, further enhancing the strength and durability of the material, and forming a synergistic effect with the aliphatic dibasic acid modified by maleic anhydride, so that the material can still maintain its excellent performance under high temperature environments.

Description

Technical Field

[0001] The invention belongs to the field of polymer compounds and relates to polyester polyol for adhesive and a preparation method and application thereof. Background Art

[0002] Food packaging plays a vital role in daily life, especially as the pace of life accelerates, more and more food enters consumers' homes, supermarkets and catering industries in pre-packaged form. Food packaging not only needs to protect the quality and safety of food, but also meet the needs of storage, transportation and convenience. In order to ensure the sealing and stability of packaging, the role of adhesives is indispensable. Food adhesives are used in the composite structure of flexible packaging films and are an important link in maintaining the close connection between different layers of materials in packaging. Although food adhesives have been widely used in the packaging industry, existing adhesive products still have some limitations: some adhesives have a decrease in viscosity during high-temperature sterilization or cooking, resulting in stratification of composite materials, affecting the sealing of the packaging and the safety of the product, and causing packaging seal failure.

[0003] In the face of the above problems, the food packaging industry urgently needs an adhesive that can maintain strong viscosity under high-temperature cooking conditions. This type of adhesive must not only have excellent high-temperature resistance, good bonding strength and peel strength, but also meet food safety standards to ensure that it is non-toxic and harmless to food. In summary, the development of an adhesive that is highly viscous, resistant to high-temperature cooking, and meets food safety standards will significantly improve the stability and safety of packaging materials and meet the food industry's increasing requirements for packaging technology. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a polyester polyol for adhesive and a preparation method and application thereof, so as to solve the problem that the existing food packaging adhesive has insufficient viscosity under high-temperature cooking conditions. By introducing modified aliphatic dibasic acids, citric acid and epoxidized soybean oil, the high-temperature stability, bonding strength and water resistance of the adhesive are enhanced. By optimizing the ratio of aromatic and modified aliphatic dibasic acids, the application performance of the adhesive in food packaging is improved, thereby meeting the needs of actual production.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a polyester polyol for an adhesive, the preparation method comprising:

[0007] Step S1, adding an aliphatic dibasic acid, maleic anhydride and an organic tin catalyst to a reaction kettle A in sequence, heating the temperature to a first temperature, stirring at a first stirring speed, and after sufficient reaction, cooling the temperature to a second temperature, and adding triethylenetetramine to the reaction kettle A, heating the temperature to a third temperature, and sufficient reaction at the first stirring speed to obtain a modified aliphatic dibasic acid;

[0008] Step S2, adding an aromatic dibasic acid, a pendant-containing diol, sebacic acid and a styrene-ethylene-butylene-styrene block copolymer into a reaction kettle B in sequence, heating the reaction kettle B to a third temperature, stirring continuously at a first stirring speed to perform an esterification reaction, and reacting under the protection of an inert gas until the acid value of the reaction system drops to a first theoretical design value;

[0009] Step S3, after the esterification is completed, the reactor B is cooled to the fourth temperature, the modified aliphatic dibasic acid and the linear diol are sequentially added to the reactor B according to the ratio, and the temperature is raised to the third temperature to carry out the second stage of esterification reaction, and the heating and vacuuming are continued to promote the removal of water and accelerate the reaction, and the reaction is continued until the acid value of the reaction system drops to the second theoretical design value;

[0010] Step S4, when the acid value of the reaction system drops to the second theoretical design value, the reaction system is cooled to the fifth temperature, citric acid is added as a cross-linking agent, a cross-linking reaction is carried out, the temperature is maintained at the fifth temperature, and the stirring is carried out at the second stirring speed to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0011] Step S5, after the cross-linking reaction is completed, continue to cool to the second temperature, add epoxidized soybean oil to the reaction system, continue stirring at a third stirring speed to ensure that the epoxidized soybean oil is evenly dispersed in the system, and obtain a polyester polyol for adhesive after cooling;

[0012] The polyester polyol for adhesive includes the following components in percentage by mass:

[0013] Aromatic dibasic acid: 25-30%;

[0014] Modified aliphatic dibasic acid: 10-20%;

[0015] Sebacic acid: 10-15%;

[0016] Straight chain diol: 10-20%;

[0017] Containing pendant diol: 10-20%;

[0018] Styrene-ethylene-butylene-styrene block copolymer: 5-10%;

[0019] Citric acid: 1-2%;

[0020] Epoxidized soybean oil: 1-3%.

[0021] As a preferred technical solution of the present invention, in step S1, the feeding amount of the aliphatic dibasic acid is 20-30g, for example, it can be 20g, 21g, 22g, 23g, 24g, 25g, 26g, 27g, 28g, 29g or 30g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] In some optional examples, the amount of maleic anhydride added is 2-6 g, for example, 2.0 g, 2.4 g, 2.6 g, 2.8 g, 3.2 g, 3.6 g, 4.0 g, 4.4 g, 4.8 g, 5.2 g, 5.6 g or 6.0 g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] In some optional examples, the dosage of the organotin catalyst is 0.02-0.15g, for example, it can be 0.02g, 0.03g, 0.04g, 0.05g, 0.06g, 0.07g, 0.08g, 0.09g, 0.10g, 0.11g, 0.12g, 0.13g, 0.14g or 0.15g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] In some optional instances, the first temperature is 120-140°C, for example, 120°C, 122°C, 124°C, 126°C, 128°C, 130°C, 132°C, 134°C, 136°C, 138°C or 140°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In some optional examples, the first stirring speed is 300-400rpm, for example, it can be 300rpm, 310rpm, 320rpm, 330rpm, 340rpm, 350rpm, 360rpm, 370rpm, 380rpm, 390rpm or 400rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In some optional examples, the reaction time at the first temperature is 3-5h, for example, 3.0h, 3.2h, 3.4h, 3.6h, 3.8h, 4.0h, 4.2h, 4.4h, 4.6h, 4.8h or 5.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In some optional instances, the second temperature is 80-90°C, for example, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In some optional examples, the feeding amount of triethylenetetramine is 1-3g, for example, it can be 1.0g, 1.2g, 1.4g, 1.6g, 1.8g, 2.0g, 2.2g, 2.4g, 2.6g, 2.8g or 3.0g, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In some optional instances, the third temperature is 180-200°C, for example, it can be 180°C, 182°C, 184°C, 186°C, 188°C, 190°C, 192°C, 194°C, 196°C, 198°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] In some optional examples, the reaction time at the third temperature is 2-3h, for example, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, in step S2, the third temperature is 180-200°C, for example, it can be 180°C, 182°C, 184°C, 186°C, 188°C, 190°C, 192°C, 194°C, 196°C, 198°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In some optional examples, the first stirring speed is 300-400rpm, for example, it can be 300rpm, 310rpm, 320rpm, 330rpm, 340rpm, 350rpm, 360rpm, 370rpm, 380rpm, 390rpm or 400rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In some optional examples, the stirring time is 3-4h, for example, it can be 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] In some optional instances, the gas flow rate is 4-6 mL / min, for example, it can be 4.0 mL / min, 4.2 mL / min, 4.4 mL / min, 4.6 mL / min, 4.8 mL / min, 5.0 mL / min, 5.2 mL / min, 5.4 mL / min, 5.6 mL / min or 6.0 mL / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In some optional examples, the first theoretical design value is 20-30 mg KOH / g, for example, it can be 20 mg KOH / g, 21 mg KOH / g, 22 mg KOH / g, 23 mg KOH / g, 24 mg KOH / g, 25 mg KOH / g, 26 mg KOH / g, 27 mg KOH / g, 28 mg KOH / g, 29 mg KOH / g or 30 mg KOH / g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] As a preferred technical solution of the present invention, in step S3, the fourth temperature is 110-120°C, for example, it can be 110°C, 111°C, 112°C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C, 119°C or 120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In some optional instances, the third temperature is 180-200°C, for example, it can be 180°C, 182°C, 184°C, 186°C, 188°C, 190°C, 192°C, 194°C, 196°C, 198°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In some optional examples, the vacuum degree of the vacuum is 0.09-0.095 MPa, for example, it can be 0.09 MPa, 0.091 MPa, 0.092 MPa, 0.093 MPa, 0.094 MPa or 0.095 MPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In some optional examples, the reaction time at the third temperature is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In some optional examples, the second theoretical design value is 10-20 mg KOH / g, for example, it can be 10 mg KOH / g, 11 mg KOH / g, 12 mg KOH / g, 13 mg KOH / g, 14 mg KOH / g, 15 mg KOH / g, 16 mg KOH / g, 17 mg KOH / g, 18 mg KOH / g, 19 mg KOH / g or 20 mg KOH / g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] As a preferred technical solution of the present invention, in step S4, the second theoretical design value is 10-20 mgKOH / g, for example, it can be 10 mg KOH / g, 11 mg KOH / g, 12 mg KOH / g, 13 mg KOH / g, 14 mg KOH / g, 15 mgKOH / g, 16 mg KOH / g, 17 mg KOH / g, 18 mg KOH / g, 19 mg KOH / g or 20 mg KOH / g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0042] The fifth temperature is 100-110°C, for example, it can be 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C or 110°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In some optional examples, the second stirring speed is 200-300 rpm, for example, it can be 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm or 300 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In some optional examples, the stirring time is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] As a preferred technical solution of the present invention, in step S5, the second temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In some optional examples, the third stirring speed is 250-350rpm, for example, it can be 250rpm, 260rpm, 270rpm, 280rpm, 290rpm, 300rpm, 310rpm, 320rpm, 330rpm, 340rpm or 350rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] In some optional examples, the stirring time is 30-60 min, for example, it can be 30 min, 33 min, 36 min, 39 min, 42 min, 45 min, 48 min, 51 min, 54 min, 57 min or 60 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] As a preferred technical solution of the present invention, the polyester polyol for adhesive comprises the following components in percentage by mass:

[0049] The proportion of aromatic dibasic acid is 25-30%, the proportion of modified aliphatic dibasic acid is 10-20%, the proportion of sebacic acid is 10-15%, the proportion of straight-chain diol is 10-20%, the proportion of side-group-containing diol is 10-20%, the proportion of styrene-ethylene-butylene-styrene block polymer is 5-10%, the proportion of citric acid is 1-2%, and the proportion of epoxidized soybean oil is 1-3%. The proportion of aromatic dibasic acid can be 25.0%, 25.5%, 26.0%, 26.5%, 27.0%, 27.5%, 28.0%, 28.5%, 29.0%, 29.5% or 30.0%, the proportion of modified aliphatic dibasic acid can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, the proportion of sebacic acid can be 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5% or 15.0%, the proportion of straight-chain diol can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, and the proportion of diol containing side group can be 10%. , 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, the proportion of styrene-ethylene-butylene-styrene block polymer can be 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5% or 10.0%, the proportion of citric acid can be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%, and the proportion of epoxidized soybean oil can be 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8% or 3.0%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] The benzene ring in the aromatic dibasic acid has high rigidity and stability, and can form strong intermolecular interactions. In the polycondensation reaction, the benzene ring structure increases the thermal decomposition temperature of the polyester material and enhances its ability to resist thermal oxidation. This rigid skeleton not only provides heat resistance, but also improves the creep resistance of the material, especially in high temperature environments, it can reduce material deformation. In addition, the conjugated structure of the benzene ring has strong UV resistance, which can prevent the material from photodegradation under long-term light. The addition of this benzene ring further increases the material's resistance to chemical corrosion, especially in extreme environments such as acids and alkalis. The high rigidity structure of the aromatic dibasic acid combined with the flexible diol or modified aliphatic dibasic acid helps to build a molecular skeleton inside the material. The combination of rigid and flexible segments allows the material to maintain structural stability under high temperature conditions while having a certain toughness, thereby avoiding embrittlement in a hot environment.

[0051] The CC bond in the modified aliphatic dibasic acid is relatively flexible and can introduce flexibility into the polyester chain segment, making the material show good ductility and elongation at break. At the molecular level, the long chain structure of the modified aliphatic dibasic acid can effectively disperse stress, thereby improving the toughness of the material and reducing brittle fracture. In addition, the hydrophobicity of the modified aliphatic dibasic acid can reduce the entry of water molecules into the material, thereby enhancing the material's resistance to hydrolysis, which is particularly suitable for the humid environment in food soft packaging. The flexibility of the modified aliphatic dibasic acid complements the rigidity of the aromatic dibasic acid. Through this combination, the material has sufficient mechanical strength and heat resistance, while retaining good flexibility and tensile properties, ensuring stable performance in high-temperature cooking applications of food packaging adhesives.

[0052] The alcohol group in the straight-chain diol can undergo an esterification reaction with the dibasic acid to form an ester bond. In the polycondensation reaction, the long-chain structure of these straight-chain diols makes the polyester molecular chain softer, improves the elongation at break of the material, and gives the material higher flexibility. For example, 1,4-butanediol has a long carbon chain, which enables the material to effectively absorb energy when it is stressed and exhibits excellent impact resistance. At the same time, ethylene glycol and diethylene glycol are usually used to adjust the molecular weight of the material due to their shorter chain length, thereby optimizing the hardness and viscosity of the material. The reaction of straight-chain diols with dibasic acids forms flexible polyester segments, which are combined with other rigid materials to further optimize the comprehensive mechanical properties of the material. By adjusting the type and proportion of diols, the viscosity and hardness of the material can be customized to ensure that the material has both good operability and high performance.

[0053] The diols containing side groups have a large degree of freedom in the molecular chains of the materials through their branched structures, which reduces the mutual entanglement between the molecular chains and improves the flexibility and toughness of the materials. For example, the symmetry and branched structure of neopentyl glycol can prevent the excessive crystallization of the polyester molecular chains, thereby improving the heat resistance and thermal stability of the materials. In addition, alcohols containing branches can reduce the degradation rate of the materials under ultraviolet irradiation through the steric hindrance effect and extend the service life of the materials. The combination of diols containing side groups and modified aliphatic dibasic acids and aromatic dibasic acids can effectively improve the mechanical properties and weather resistance of the materials, while ensuring that the materials remain stable under long-term light and temperature changes.

[0054] Styrene-ethylene-butylene-styrene block copolymer is a thermoplastic elastomer with rubber-like flexibility. The styrene hard segment of styrene-ethylene-butylene-styrene block copolymer provides excellent mechanical strength, while the ethylene-butylene soft segment gives the material a high degree of flexibility and elasticity. In the polyester system, styrene-ethylene-butylene-styrene block copolymer can form a physical entanglement with the polyester matrix, thereby improving the flexibility and impact resistance of the material. At the same time, the rubber properties of styrene-ethylene-butylene-styrene block copolymer can improve the oil resistance of the material and prevent the material from losing adhesion when it comes into contact with food ingredients such as oils and fats. The combination of styrene-ethylene-butylene-styrene block copolymer with linear diols and modified aliphatic dibasic acids can form a material with high elasticity and flexibility, further optimizing the material's fatigue resistance. In a high-temperature cooking environment, the rubber elasticity of styrene-ethylene-butylene-styrene block copolymer can ensure that the material maintains stable structural properties after long-term use.

[0055] Sebacic acid is a long-chain aliphatic dibasic acid containing 10 carbon atoms. Due to its long carbon chain, the introduction of sebacic acid into the polyester system can increase the flexibility of molecules. This long-chain structure can provide a large molecular degree of freedom, so that polyester can better absorb energy under external stress and reduce the risk of fracture. The flexible chain segment also gives the material good impact resistance and ductility. Especially in the environment of high-temperature cooking, this long chain can prevent polyester from losing mechanical properties prematurely under thermal stress. In addition, the long carbon chain structure of sebacic acid has excellent hydrophobicity, which can effectively reduce the diffusion of water in the polyester chain and reduce the occurrence of hydrolysis reactions. Through this hydrophobic effect, sebacic acid can help improve the water resistance of the material and extend its service life. And the rigid combination of sebacic acid and aromatic dibasic acid makes the material have high strength while not easily causing brittle fracture due to excessive rigidity. The hydrophobicity of sebacic acid combined with epoxidized soybean oil can further improve the moisture resistance of the polyester system, reduce moisture absorption and hydrolysis. This synergistic effect is particularly important in applications such as food packaging that require water-resistant and heat-resistant environments.

[0056] As a tricarboxylic acid, citric acid can provide more crosslinking points in the polyester system. Its tricarboxyl structure undergoes esterification reaction with linear diols or modified aliphatic dibasic acids to form crosslinking points. Such crosslinking points can form a tight three-dimensional network structure between polyester chains, increase the crosslinking density of the material, and thus improve the mechanical strength, water resistance and chemical corrosion resistance of the material. This high crosslinking structure can also reduce the free volume of the material and reduce the permeability of water or gas, which means better hydrolysis resistance and aging resistance for food packaging materials. Under cooking conditions, this dense crosslinking structure also helps to improve the high temperature resistance of the material, allowing it to maintain structural stability under high temperature environments. Citric acid reacts with the epoxy groups of epoxidized soybean oil, further enhancing the compactness of the crosslinking network. The epoxy groups of epoxidized soybean oil can react with the carboxyl groups of citric acid through ring opening to form more crosslinking points. This synergistic effect not only increases the crosslinking density, but also reduces the unreacted free carboxyl groups, thereby reducing hydrolysis sensitivity and further improving high temperature and moisture resistance. The polycarboxyl structure of citric acid can also work synergistically with the long-chain flexible segment of sebacic acid, ensuring the strength of the material while maintaining flexibility, thereby balancing the requirements of heat resistance and flexibility.

[0057] Epoxidized soybean oil is an active epoxide containing multiple epoxy groups. The epoxy groups can undergo a ring-opening reaction with carboxyl groups in the polyester system to form a cross-linked structure to improve the flexibility of the material. It can also increase the strength of the polyester system by increasing the cross-linking points. Epoxidized soybean oil can reduce the interaction between polymer chains through its plasticizing effect, and enhance the ductility and flexibility of the material. Epoxidized soybean oil also exhibits excellent anti-aging and antioxidant properties under cooking conditions. Epoxy groups can capture free radicals in the system, reduce the occurrence of polymer degradation reactions, and delay the aging process of the material. At the same time, epoxidized soybean oil is a renewable resource with good environmental protection, which meets the environmental protection requirements of food packaging materials.

[0058] As a long-chain aliphatic dibasic acid, sebacic acid provides the material with flexibility and ductility, while citric acid provides cross-linking points through its multi-carboxyl structure, enhancing the stability of the material's network structure. The addition of epoxidized soybean oil further improves the material's viscosity and heat resistance, and forms additional cross-linking points with other components through its epoxy groups, further enhancing the overall performance of the material. In the high-temperature cooking-resistant adhesive, the synergistic effect of epoxidized soybean oil, citric acid and sebacic acid enables the material to maintain its viscosity and structural integrity under high temperature conditions. The long-chain structure of sebacic acid enhances the material's flexibility, making it less likely to break when subjected to external forces; the multi-point cross-linking structure of citric acid provides the material with water resistance and thermal stability; epoxidized soybean oil further improves the material's heat resistance and antioxidant capacity through cross-linking reactions, ensuring its stability and long-term effectiveness under high temperature conditions.

[0059] In a second aspect, the present invention provides a polyester polyol for adhesive obtained by the preparation method described in the first aspect.

[0060] In a third aspect, the present invention provides a polyester polyol for adhesives used in food packaging.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] (1) By using materials such as aromatic dibasic acids and epoxidized soybean oil, this scheme effectively enhances the heat resistance of the adhesive. Aromatic dibasic acids provide excellent heat resistance, allowing the material to remain stable under continuous high temperature environments. Aromatic dibasic acids contain a benzene ring structure, which has high thermal stability, making the polyester molecular chain more stable at high temperatures. Under high-temperature cooking conditions, the adhesive can maintain its bonding strength and prevent structural failure. At the same time, the conjugated system of the benzene ring can effectively disperse heat energy and avoid molecular chain breakage, giving polyester a higher thermal decomposition temperature, allowing the adhesive to maintain its bonding strength under cooking conditions;

[0063] (2) This formula significantly improves the bonding strength between the adhesive and the substrate through the modification of pendant diols and epoxidized soybean oil. The epoxy groups in the epoxidized soybean oil can undergo a cross-linking reaction with the polyester chain, thereby improving the viscosity of the adhesive. At the same time, the pendant diols increase the support of the molecular chain and improve the strength of the bonding interface. The epoxy groups in the epoxidized soybean oil can undergo a cross-linking reaction with the carboxyl groups in the polyester system to form a strong chemical bond. This cross-linking structure improves the internal adhesion of the adhesive, thereby enhancing the bonding strength between the adhesive and the substrate. The introduction of pendant diols increases the molecular support of the polyester chain and prevents shear damage at the bonding interface.

[0064] (3) The long chain structure of modified aliphatic dibasic acid and sebacic acid is hydrophobic, which reduces the absorption of water by the polyester system. The flexible long chain structure of sebacic acid can improve the flexibility of the material, thereby reducing the erosion of water on the molecular chain and reducing the probability of hydrolysis. The long carbon chain in the aliphatic structure can effectively shield water molecules and hinder their reaction with the polyester chain, thereby improving the hydrolysis resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 A flow chart of a method for preparing a polyester polyol for an adhesive provided in Examples 1-8 of the present invention;

[0066] Figure 2 This is the infrared spectrum of the modified aliphatic dibasic acid in Example 1 of the present invention. DETAILED DESCRIPTION

[0067] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments recorded herein.

[0068] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products, and their brands, specifications and manufacturer information are as follows:

[0069] Maleic anhydride, purity ≥99%, Shandong Jinhe Chemical Co., Ltd.;

[0070] Dibutyltin dilaurate, purity ≥98%, Nantong Haotai Chemical Products Co., Ltd.;

[0071] Triethylenetetramine, purity ≥98%, Jinan Liyang Chemical Co., Ltd.;

[0072] Phthalic acid, purity ≥99%, Shanghai Jiader Chemical Technology Co., Ltd.;

[0073] Isophthalic acid, purity ≥99%, Chengdu Yuanda Chemical Co., Ltd.;

[0074] Terephthalic acid, purity ≥99%, Tianjin Xiensi Biochemical Technology Co., Ltd.;

[0075] Adipic acid, purity ≥99%, Tianjin Xiensi Biochemical Technology Co., Ltd.;

[0076] Succinic acid, purity ≥99%, Nanjing Chemical Reagent Co., Ltd.;

[0077] Ricinoleic acid, purity ≥98%, Jinjinle (Hunan) Chemical Co., Ltd.;

[0078] 1,4-Butanediol, purity ≥99%, Shandong Xinheng Chemical Co., Ltd.;

[0079] Ethylene glycol, purity ≥99%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0080] Diethylene glycol, purity ≥99%, Shandong Zhengxing New Materials Co., Ltd.;

[0081] Neopentyl glycol, purity ≥99%, Jiangsu Bosite Chemical Technology Co., Ltd.;

[0082] 2-Methyl-1,3-propanediol, purity ≥99%, Tianjin Xiensi Biochemical Technology Co., Ltd.;

[0083] 3-Methyl-1,5-pentanediol, purity ≥99%, Kangdisi Chemical (Hubei) Co., Ltd.;

[0084] Dipropylene glycol, purity ≥99%, Guangzhou Nalong Chemical Co., Ltd.;

[0085] Sebacic acid, purity ≥99%, Jinan Huifengda Chemical Co., Ltd.;

[0086] Styrene-ethylene-butylene-styrene block copolymer, purity ≥99%, Shanghai Bevanta Biotechnology Co., Ltd.;

[0087] Citric acid, purity ≥99%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0088] Epoxidized soybean oil, purity ≥99%, Wuxi Mingri Chemical Technology Co., Ltd.;

[0089] Other raw materials can be purchased from the market.

[0090] Example 1

[0091] This embodiment provides a method for preparing a polyester polyol for an adhesive, wherein the polyester polyol material for an adhesive comprises the following components in percentage by mass:

[0092] Phthalic acid: 27%;

[0093] Modified aliphatic dibasic acid: 17%;

[0094] Sebacic acid: 13%;

[0095] 1,4-Butanediol: 17%;

[0096] 2-Methyl-1,3-propanediol: 16%;

[0097] Styrene-ethylene-butylene-styrene block copolymer: 6.5%;

[0098] Citric acid: 1.7%;

[0099] Epoxidized soybean oil: 1.8%.

[0100] like Figure 1 As shown, the preparation method specifically comprises the following steps:

[0101] Step S1, 22g of adipic acid, 3g of maleic anhydride and 0.04g of dibutyltin dilaurate are added to a reaction kettle A in sequence, the temperature is raised to 122°C, stirring is maintained at a speed of 330rpm, and the mixture is fully reacted for 3.4h, the temperature is lowered to 84°C, and 1.3g of triethylenetetramine is added to the reaction kettle A, the temperature is raised to 190°C, and the mixture is fully reacted at a speed of 330rpm for 2.1h to obtain a modified aliphatic dibasic acid;

[0102] Step S2, 27% phthalic acid, 16% 2-methyl-1,3-propanediol, 13% sebacic acid and 6.5% styrene-ethylene-butylene-styrene block copolymer were added to the reactor B in sequence, the reactor B was heated to 187° C., and the esterification reaction was carried out at 350 rpm and stirred for 3.6 h, and the reaction was carried out under N2 protection at a flow rate of 4.3 mL / min until the acid value of the reaction system dropped to 20 mg KOH / g;

[0103] Step S3, after the esterification is completed, the reactor B is cooled to 112°C, 17% modified aliphatic dibasic acid and 17% 1,4-butanediol are added to the reactor B in order according to the ratio, and the temperature is raised to 190°C to carry out the second stage of esterification reaction, and the heating is continued and the vacuum is evacuated to 0.091 MPa to promote water removal and accelerate the reaction, and the reaction is continued for 2.4 hours until the acid value of the reaction system drops to 12 mgKOH / g;

[0104] Step S4, when the acid value of the reaction system drops to 12 mg KOH / g, the reaction system is cooled to 105° C., 1.7% citric acid is added as a cross-linking agent, and a cross-linking reaction is performed. The temperature is maintained at 105° C. and stirred at 220 rpm for 1.3 h to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0105] Step S5, after the cross-linking reaction is completed, the temperature is further lowered to 84° C., 1.8% epoxidized soybean oil is added to the reaction system, and stirring is continued at 280 rpm for 41 minutes to ensure that the epoxidized soybean oil is evenly dispersed in the system. After cooling, a polyester polyol for adhesive is obtained.

[0106] Figure 2 The infrared spectrum of the modified aliphatic dibasic acid in this example is shown in Figure 1. The aliphatic dibasic acid reacts with maleic anhydride to form an ester group, which is shown at 1730 cm -1 A stronger carbonyl stretching vibration absorption appears at the cation, indicating the formation of an ester bond.

[0107] Example 2

[0108] This embodiment provides a method for preparing a polyester polyol for an adhesive, wherein the polyester polyol material for an adhesive comprises the following components in percentage by mass:

[0109] Isophthalic acid: 25%;

[0110] Modified aliphatic dibasic acid: 17%;

[0111] Sebacic acid: 12%;

[0112] Ethylene glycol: 18%;

[0113] Neopentyl glycol: 16%;

[0114] Styrene-ethylene-butylene-styrene block copolymer: 8.3%;

[0115] Citric acid: 1.5%;

[0116] Epoxidized soybean oil: 2.2%.

[0117] like Figure 1 As shown, the preparation method specifically comprises the following steps:

[0118] Step S1, 26 g of adipic acid, 4.4 g of maleic anhydride and 0.08 g of dibutyltin dilaurate are added to a reaction kettle A in sequence, the temperature is raised to 132° C., stirring is maintained at a speed of 350 rpm, and the mixture is fully reacted for 4.1 h, the temperature is lowered to 81° C., 2.2 g of triethylenetetramine is added to the reaction kettle A, the temperature is raised to 185° C., and the mixture is fully reacted at a speed of 350 rpm for 2.7 h to obtain a modified aliphatic dibasic acid;

[0119] Step S2, 25% isophthalic acid, 16% neopentyl glycol, 12% sebacic acid and 8.3% styrene-ethylene-butylene-styrene block copolymer were added to the reactor B in sequence, the reactor B was heated to 194° C., and the esterification reaction was carried out at 370 rpm and stirred for 3.2 h, and the reaction was carried out under N2 protection at a flow rate of 4.7 mL / min until the acid value of the reaction system dropped to 22 mgKOH / g;

[0120] Step S3, after the esterification is completed, the reactor B is cooled to 114°C, 17% of modified aliphatic dibasic acid and 18% of ethylene glycol are added to the reactor B in order according to the ratio, and the temperature is raised to 182°C to carry out the second stage of esterification reaction, and the heating is continued and the vacuum is evacuated to 0.094 MPa to promote water removal and accelerate the reaction, and the reaction is continued for 2.1 hours until the acid value of the reaction system drops to 10 mg KOH / g;

[0121] Step S4, when the acid value of the reaction system drops to 10 mg KOH / g, the reaction system is cooled to 103° C., 1.5% citric acid is added as a cross-linking agent, and a cross-linking reaction is performed. The temperature is maintained at 103° C. and stirred at 260 rpm for 1.6 h to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0122] Step S5, after the cross-linking reaction is completed, the temperature is further lowered to 87° C., 2.2% epoxidized soybean oil is added to the reaction system, and stirring is continued at 270 rpm for 39 minutes to ensure that the epoxidized soybean oil is evenly dispersed in the system. After cooling, a polyester polyol for adhesive is obtained.

[0123] Example 3

[0124] This embodiment provides a method for preparing a polyester polyol for an adhesive, wherein the polyester polyol material for an adhesive comprises the following components in percentage by mass:

[0125] Terephthalic acid: 27.5%;

[0126] Modified aliphatic dibasic acid: 16.2%;

[0127] Sebacic acid: 13.9%;

[0128] Diethylene glycol: 14.5%;

[0129] 3-Methyl-1,5-pentanediol: 17.7%;

[0130] Styrene-ethylene-butylene-styrene block copolymer: 6.4%;

[0131] Citric acid: 1.2%;

[0132] Epoxidized soybean oil: 2.6%.

[0133] like Figure 1 As shown, the preparation method specifically comprises the following steps:

[0134] Step S1, 21 g of ricinoleic acid, 3.5 g of maleic anhydride and 0.06 g of dibutyltin dilaurate are added to a reaction kettle A in sequence, the temperature is raised to 124° C., stirring is maintained at a speed of 310 rpm, and the mixture is fully reacted for 4.6 h, the temperature is lowered to 87° C., 1.7 g of triethylenetetramine is added to the reaction kettle A, the temperature is raised to 196° C., and the mixture is fully reacted at a speed of 310 rpm for 2.2 h to obtain a modified aliphatic dibasic acid;

[0135] Step S2, 27.5% isophthalic acid, 17.7% 3-methyl-1,5-pentanediol, 13.9% sebacic acid and 6.4% styrene-ethylene-butylene-styrene block copolymer were added to the reactor B in sequence, the reactor B was heated to 190° C., and the esterification reaction was carried out at 320 rpm and stirred for 3.8 h, and the reaction was carried out under N2 protection at a flow rate of 5.2 mL / min until the acid value of the reaction system dropped to 21 mg KOH / g;

[0136] Step S3, after the esterification is completed, the reactor B is cooled to 111°C, 16.2% of modified aliphatic dibasic acid and 14.5% of diethylene glycol are added to the reactor B in order according to the ratio, and the temperature is raised to 188°C to carry out the second stage of esterification reaction, and the heating is continued and the vacuum is evacuated to 0.092MPa to promote water removal and accelerate the reaction, and the reaction is continued for 2.5h until the acid value of the reaction system drops to 11mg KOH / g;

[0137] Step S4, when the acid value of the reaction system drops to 11 mg KOH / g, the reaction system is cooled to 108° C., 1.2% citric acid is added as a cross-linking agent, and a cross-linking reaction is performed. The temperature is maintained at 108° C. and stirred at 230 rpm for 1.2 h to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0138] Step S5, after the cross-linking reaction is completed, the temperature is further lowered to 83° C., 2.6% epoxidized soybean oil is added to the reaction system, and stirring is continued at 250 rpm for 44 minutes to ensure that the epoxidized soybean oil is evenly dispersed in the system. After cooling, a polyester polyol for adhesive is obtained.

[0139] Example 4

[0140] This embodiment provides a method for preparing a polyester polyol for an adhesive, wherein the polyester polyol material for an adhesive comprises the following components in percentage by mass:

[0141] Phthalic acid: 28.4%;

[0142] Modified aliphatic dibasic acid: 14.7%;

[0143] Sebacic acid: 12.9%;

[0144] 1,4-Butanediol: 18.1%;

[0145] Dipropylene glycol: 13.4%;

[0146] Styrene-ethylene-butylene-styrene block copolymer: 8.3%;

[0147] Citric acid: 1.8%;

[0148] Epoxidized soybean oil: 2.4%.

[0149] like Figure 1 As shown, the preparation method specifically comprises the following steps:

[0150] Step S1, 24 g succinic acid, 3.1 g maleic anhydride and 0.07 g dibutyltin dilaurate are added to the reaction kettle A in sequence, the temperature is raised to 136° C., stirring is maintained at 360 rpm, the reaction is fully reacted for 4.8 h, the temperature is lowered to 83° C., 1.6 g triethylenetetramine is added to the reaction kettle A, the temperature is raised to 187° C., and the reaction is fully reacted at 360 rpm for 2.8 h to obtain a modified aliphatic dibasic acid;

[0151] Step S2, 28.4% phthalic acid, 13.4% dipropylene glycol, 12.9% sebacic acid and 8.3% styrene-ethylene-butylene-styrene block copolymer were added to the reactor B in sequence, the reactor B was heated to 193° C., and the esterification reaction was carried out at 350 rpm and stirred for 3.3 h, and the reaction was carried out under N2 protection at a flow rate of 4.9 mL / min until the acid value of the reaction system dropped to 22 mg KOH / g;

[0152] Step S3, after the esterification is completed, the reactor B is cooled to 110°C, 14.7% of modified aliphatic dibasic acid and 18.1% of 1,4-butanediol are added to the reactor B in order according to the ratio, and the temperature is raised to 186°C to carry out the second stage of esterification reaction, and the heating is continued and the vacuum is evacuated to 0.091MPa to promote water removal and accelerate the reaction, and the reaction is continued for 2.6h until the acid value of the reaction system drops to 12mgKOH / g;

[0153] Step S4, when the acid value of the reaction system drops to 12 mg KOH / g, the reaction system is cooled to 102° C., 1.8% citric acid is added as a cross-linking agent, and a cross-linking reaction is performed. The temperature is maintained at 102° C. and stirred at 270 rpm for 1.4 h to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0154] Step S5, after the cross-linking reaction is completed, the temperature is further lowered to 86° C., 2.4% epoxidized soybean oil is added to the reaction system, and stirring is continued at 330 rpm for 49 minutes to ensure that the epoxidized soybean oil is evenly dispersed in the system. After cooling, a polyester polyol for adhesive is obtained.

[0155] Example 5

[0156] This embodiment provides a method for preparing a polyester polyol for an adhesive, wherein the polyester polyol material for an adhesive comprises the following components in percentage by mass:

[0157] Phthalic acid: 27.2%;

[0158] Modified aliphatic dibasic acid: 13.7%;

[0159] Sebacic acid: 13.6%;

[0160] Ethylene glycol: 18.4%;

[0161] Neopentyl glycol: 16.6%;

[0162] Styrene-ethylene-butylene-styrene block copolymer: 6.6%;

[0163] Citric acid: 1.4%;

[0164] Epoxidized soybean oil: 2.5%.

[0165] like Figure 1 As shown, the preparation method specifically comprises the following steps:

[0166] Step S1, 30 g succinic acid, 4.2 g maleic anhydride and 0.07 g dibutyltin dilaurate are added to the reaction kettle A in sequence, the temperature is raised to 127° C., stirring is maintained at 330 rpm, and the mixture is fully reacted for 3.7 h, the temperature is lowered to 80° C., 2.4 g triethylenetetramine is added to the reaction kettle A, the temperature is raised to 193° C., and the mixture is fully reacted at 330 rpm for 2.4 h to obtain a modified aliphatic dibasic acid;

[0167] Step S2, 27.2% phthalic acid, 16.6% neopentyl glycol, 13.6% sebacic acid and 6.6% styrene-ethylene-butylene-styrene block copolymer were added to the reactor B in sequence, the reactor B was heated to 186° C., and the esterification reaction was carried out at 370 rpm and stirred for 3.1 h, and the reaction was carried out under N2 protection at a flow rate of 5.0 mL / min until the acid value of the reaction system dropped to 20 mg KOH / g;

[0168] Step S3, after the esterification is completed, the reactor B is cooled to 113°C, 13.7% of modified aliphatic dibasic acid and 18.4% of ethylene glycol are added to the reactor B in order according to the ratio, and the temperature is raised to 194°C to carry out the second stage of esterification reaction, and the heating is continued and the vacuum is evacuated to 0.094MPa to promote water removal and accelerate the reaction, and the reaction is continued for 2.4h until the acid value of the reaction system drops to 11mg KOH / g;

[0169] Step S4, when the acid value of the reaction system drops to 11 mg KOH / g, the reaction system is cooled to 104° C., 1.4% citric acid is added as a cross-linking agent, and a cross-linking reaction is performed. The temperature is maintained at 104° C. and stirred at 300 rpm for 1.2 h to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0170] Step S5, after the cross-linking reaction is completed, the temperature is further lowered to 83° C., 2.5% epoxidized soybean oil is added to the reaction system, and stirring is continued at 310 rpm for 38 minutes to ensure that the epoxidized soybean oil is evenly dispersed in the system. After cooling, a polyester polyol for adhesive is obtained.

[0171] Example 6

[0172] This embodiment provides a method for preparing a polyester polyol for an adhesive, wherein the polyester polyol material for an adhesive comprises the following components in percentage by mass:

[0173] Terephthalic acid: 28.6%;

[0174] Modified aliphatic dibasic acid: 15.2%;

[0175] Sebacic acid: 13.7%;

[0176] Diethylene glycol: 18.9%;

[0177] 2-Methyl-1,3-propanediol: 15.1%;

[0178] Styrene-ethylene-butylene-styrene block copolymer: 5.3%;

[0179] Citric acid: 1.1%;

[0180] Epoxidized soybean oil: 2.1%.

[0181] like Figure 1 As shown, the preparation method specifically comprises the following steps:

[0182] Step S1, 27g of adipic acid, 3.9g of maleic anhydride and 0.09g of dibutyltin dilaurate are added to a reaction kettle A in sequence, the temperature is raised to 131°C, stirring is maintained at a speed of 370rpm, and the mixture is fully reacted for 3.4h, the temperature is lowered to 83°C, and 2.3g of triethylenetetramine is added to the reaction kettle A, the temperature is raised to 197°C, and the mixture is fully reacted at a speed of 370rpm for 2.1h to obtain a modified aliphatic dibasic acid;

[0183] Step S2, 28.6% terephthalic acid, 15.1% 2-methyl-1,3-propanediol, 13.7% sebacic acid and 5.3% styrene-ethylene-butylene-styrene block copolymer were added to the reactor B in sequence, the reactor B was heated to 188° C., and the esterification reaction was carried out at 360 rpm and continuously stirred for 3.3 h, and the reaction was carried out under N2 protection at a flow rate of 5.5 mL / min until the acid value of the reaction system dropped to 22 mg KOH / g;

[0184] Step S3, after the esterification is completed, the reactor B is cooled to 115°C, 15.2% of modified aliphatic dibasic acid and 18.9% of diethylene glycol are added to the reactor B in order according to the ratio, and the temperature is raised to 188°C to carry out the second stage of esterification reaction, and the heating is continued and the vacuum is evacuated to 0.095MPa to promote water removal and accelerate the reaction, and the reaction is continued for 2.2h until the acid value of the reaction system drops to 10mg KOH / g;

[0185] Step S4, when the acid value of the reaction system drops to 10 mg KOH / g, the reaction system is cooled to 102° C., 1.1% citric acid is added as a cross-linking agent, and a cross-linking reaction is performed. The temperature is maintained at 102° C. and stirred at 300 rpm for 1.9 h to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0186] Step S5, after the cross-linking reaction is completed, the temperature is further lowered to 88° C., 2.1% epoxidized soybean oil is added to the reaction system, and stirring is continued at 300 rpm for 54 minutes to ensure that the epoxidized soybean oil is evenly dispersed in the system. After cooling, a polyester polyol for adhesive is obtained.

[0187] Example 7

[0188] This embodiment provides a method for preparing a polyester polyol for an adhesive, wherein the polyester polyol material for an adhesive comprises the following components in percentage by mass:

[0189] Isophthalic acid: 26.4%;

[0190] Modified aliphatic dibasic acid: 16.5%;

[0191] Sebacic acid: 14.4%;

[0192] Ethylene glycol: 16.1%;

[0193] Neopentyl glycol: 15.2%;

[0194] Styrene-ethylene-butylene-styrene block copolymer: 7.7%;

[0195] Citric acid: 1.5%;

[0196] Epoxidized soybean oil: 2.2%.

[0197] like Figure 1 As shown, the preparation method specifically comprises the following steps:

[0198] Step S1, 23 g of ricinoleic acid, 3.3 g of maleic anhydride and 0.08 g of dibutyltin dilaurate are added to a reaction kettle A in sequence, the temperature is raised to 136° C., stirring is maintained at a speed of 340 rpm, and the mixture is fully reacted for 4.6 h, the temperature is lowered to 88° C., 2.0 g of triethylenetetramine is added to the reaction kettle A, the temperature is raised to 191° C., and the mixture is fully reacted at a speed of 340 rpm for 2.6 h to obtain a modified aliphatic dibasic acid;

[0199] Step S2, 26.4% isophthalic acid, 15.2% neopentyl glycol, 14.4% sebacic acid and 7.7% styrene-ethylene-butylene-styrene block copolymer were added to the reactor B in sequence, the reactor B was heated to 194° C., and the esterification reaction was carried out at 320 rpm and stirred for 3.7 hours, and the reaction was carried out under N2 protection at a flow rate of 5.1 mL / min until the acid value of the reaction system dropped to 20 mg KOH / g;

[0200] Step S3, after the esterification is completed, the reactor B is cooled to 114°C, 16.5% of modified aliphatic dibasic acid and 16.1% of ethylene glycol are added to the reactor B in order according to the ratio, and the temperature is raised to 193°C to carry out the second stage of esterification reaction, and the heating is continued and the vacuum is evacuated to 0.092MPa to promote water removal and accelerate the reaction, and the reaction is continued for 2.6h until the acid value of the reaction system drops to 12mg KOH / g;

[0201] Step S4, when the acid value of the reaction system drops to 12 mg KOH / g, the reaction system is cooled to 104° C., 1.5% citric acid is added as a cross-linking agent, and a cross-linking reaction is performed. The temperature is maintained at 104° C. and stirred at 240 rpm for 1.6 h to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0202] Step S5, after the cross-linking reaction is completed, the temperature is further lowered to 83° C., 2.2% epoxidized soybean oil is added to the reaction system, and stirring is continued at 320 rpm for 54 min to ensure that the epoxidized soybean oil is evenly dispersed in the system. After cooling, a polyester polyol for adhesive is obtained.

[0203] Example 8

[0204] This embodiment provides a method for preparing a polyester polyol for an adhesive, wherein the polyester polyol material for an adhesive comprises the following components in percentage by mass:

[0205] Terephthalic acid: 27.1%;

[0206] Modified aliphatic dibasic acid: 17.5%;

[0207] Sebacic acid: 12.4%;

[0208] Diethylene glycol: 18.4%;

[0209] Dipropylene glycol: 15.1%;

[0210] Styrene-ethylene-butylene-styrene block copolymer: 6.7%;

[0211] Citric acid: 1.3%;

[0212] Epoxidized soybean oil: 1.5%.

[0213] like Figure 1 As shown, the preparation method specifically comprises the following steps:

[0214] Step S1, 25 g succinic acid, 2.8 g maleic anhydride and 0.1 g dibutyltin dilaurate are added to a reaction kettle A in sequence, the temperature is raised to 133° C., stirring is maintained at 360 rpm, the reaction is fully reacted for 4.0 h, the temperature is lowered to 84° C., 1.9 g triethylenetetramine is added to the reaction kettle A, the temperature is raised to 188° C., and the reaction is fully reacted at 360 rpm for 2.7 h to obtain a modified aliphatic dibasic acid;

[0215] Step S2, 27.1% terephthalic acid, 15.1% dipropylene glycol, 12.4% sebacic acid and 6.7% styrene-ethylene-butylene-styrene block copolymer were added to the reactor B in sequence, the reactor B was heated to 184° C., and the esterification reaction was carried out at 330 rpm and stirred for 3.2 h, and the reaction was carried out under N2 protection at a flow rate of 5.7 mL / min until the acid value of the reaction system dropped to 21 mg KOH / g;

[0216] Step S3, after the esterification is completed, the reactor B is cooled to 112°C, 17.5% of modified aliphatic dibasic acid and 18.4% of diethylene glycol are added to the reactor B in order according to the ratio, and the temperature is raised to 190°C to carry out the second stage of esterification reaction, and the heating is continued and the vacuum is evacuated to 0.093MPa to promote water removal and accelerate the reaction, and the reaction is continued for 2.2h until the acid value of the reaction system drops to 11mg KOH / g;

[0217] Step S4, when the acid value of the reaction system drops to 11 mg KOH / g, the reaction system is cooled to 105° C., 1.3% citric acid is added as a cross-linking agent, and a cross-linking reaction is performed. The temperature is maintained at 105° C. and stirred at 240 rpm for 1.8 h to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network;

[0218] Step S5, after the cross-linking reaction is completed, the temperature is further lowered to 87° C., 1.5% epoxidized soybean oil is added to the reaction system, and stirring is continued at 350 rpm for 47 minutes to ensure that the epoxidized soybean oil is evenly dispersed in the system. After cooling, a polyester polyol for adhesive is obtained.

[0219] Comparative Example 1

[0220] This embodiment provides a polyester polyol for adhesives, which differs from Embodiment 1 in that the mass proportion of phthalic acid is adjusted to 32%. Compared with Embodiment 1, the mass proportion of phthalic acid in this embodiment is increased by 5%, and the increased proportion is deducted from the modified aliphatic dibasic acid, sebacic acid, 1,4-butanediol, 2-methyl-1,3-propanediol, styrene-ethylene-butylene-styrene block copolymer, citric acid and epoxidized soybean oil, so that the proportions of other components except phthalic acid remain unchanged. The mass percentages of each component of the polyester polyol for adhesives after adjustment are as follows:

[0221] Phthalic acid: 32%;

[0222] Modified aliphatic dibasic acid: 15.8%;

[0223] Sebacic acid: 13.0%;

[0224] 1,4-Butanediol: 15.8%;

[0225] 2-Methyl-1,3-propanediol: 14%;

[0226] Styrene-ethylene-butylene-styrene block copolymer: 6.1%;

[0227] Citric acid: 1.6%;

[0228] Epoxidized soybean oil: 1.7%

[0229] Other process parameters and operating conditions are exactly the same as those in Example 1.

[0230] Comparative Example 2

[0231] This embodiment provides a polyester polyol for adhesives, which differs from Embodiment 1 in that the mass proportion of phthalic acid is adjusted to 22%. Compared with Embodiment 1, the mass proportion of phthalic acid in this embodiment is reduced by 5%, and the reduced proportion is added to the modified aliphatic dibasic acid, sebacic acid, 1,4-butanediol, 2-methyl-1,3-propanediol, styrene-ethylene-butylene-styrene block copolymer, citric acid and epoxidized soybean oil in equal proportion, so that the proportions of other components except phthalic acid remain unchanged. The mass percentages of the components of the polyester polyol for adhesives after adjustment are as follows:

[0232] Phthalic acid: 22%;

[0233] Modified aliphatic dibasic acid: 18.2%;

[0234] Sebacic acid: 15%;

[0235] 1,4-Butanediol: 18.2%;

[0236] 2-Methyl-1,3-propanediol: 16%;

[0237] Styrene-ethylene-butylene-styrene block copolymer: 6.9%;

[0238] Citric acid: 1.8%;

[0239] Epoxidized soybean oil: 1.9%

[0240] Other process parameters and operating conditions are exactly the same as those in Example 1.

[0241] Comparative Example 3

[0242] This embodiment provides a polyester polyol for adhesives, which differs from Example 1 in that the mass proportion of 1,4-butanediol is adjusted to 22%. Compared with Example 1, the mass proportion of 1,4-butanediol in this embodiment is increased by 5%, and the increased proportion is deducted from phthalic acid, modified aliphatic dibasic acid, sebacic acid, 2-methyl-1,3-propanediol, styrene-ethylene-butylene-styrene block copolymer, citric acid and epoxidized soybean oil, so that the proportions of other components except 1,4-butanediol remain unchanged. The mass percentages of each component of the polyester polyol for adhesives after adjustment are as follows:

[0243] Phthalic acid: 25.4%;

[0244] Modified aliphatic dibasic acid: 16%;

[0245] Sebacic acid: 12.2%;

[0246] 1,4-Butanediol: 22%;

[0247] 2-Methyl-1,3-propanediol: 15%;

[0248] Styrene-ethylene-butylene-styrene block copolymer: 6.1%;

[0249] Citric acid: 1.6%;

[0250] Epoxidized soybean oil: 1.7%.

[0251] Other process parameters and operating conditions are exactly the same as those in Example 1.

[0252] Comparative Example 4

[0253] This embodiment provides a polyester polyol for adhesives, which differs from embodiment 1 in that the mass proportion of 1,4-butanediol is adjusted to 9%. Compared with embodiment 1, the mass proportion of phthalic acid in this embodiment is reduced by 8%, and the reduced proportion is added to phthalic acid, modified aliphatic dibasic acid, sebacic acid, 2-methyl-1,3-propanediol, styrene-ethylene-butylene-styrene block copolymer, citric acid and epoxidized soybean oil in equal proportion, so that the proportions between the other components except 1,4-butanediol remain unchanged. The mass percentages of the components of the polyester polyol for adhesives after adjustment are as follows:

[0254] Phthalic acid: 29.6%;

[0255] Modified aliphatic dibasic acid: 18.6%;

[0256] Sebacic acid: 14.3%;

[0257] 1,4-Butanediol: 9%;

[0258] 2-Methyl-1,3-propanediol: 17.5%;

[0259] Styrene-ethylene-butylene-styrene block copolymer: 7.1%;

[0260] Citric acid: 1.9%;

[0261] Epoxidized soybean oil: 2.0%.

[0262] Other process parameters and operating conditions are exactly the same as those in Example 1.

[0263] The determination of the hydroxyl value in the present invention refers to ASTM D4274, the determination of the moisture content refers to ASTM D4672, the peel strength test standard is GB / T2791-1995, and the boiling resistance test standard is to place the samples obtained in the embodiments and comparative examples at 120° C. for 50 minutes, and calculate the decrease rate of the peel strength. The decrease rate δ≤10% is qualified, and the decrease rate δ>10% is unqualified. The test results are shown in Table 1.

[0264] Table 1 Test results of polyester polyol for adhesive prepared in Examples 1-8 and Comparative Examples 1-4

[0265]

[0266] It can be seen from the test data of Example 1, Comparative Example 1 and Comparative Example 2 that the peel strength of Comparative Example 1 is lower than that of Example 1, and the boiling resistance is qualified; the peel strength of Comparative Example 2 is higher than that of Example 1, and the boiling resistance is unqualified. This is because the excessive aromatic dibasic acid in Comparative Example 1 will increase the rigidity of the polyester, causing the material to become brittle and the flexibility to decrease, and the peel strength will decrease accordingly, but the rigid structure of the aromatic dibasic acid can improve the heat resistance of the material and resist high-temperature boiling; the aromatic dibasic acid content in Comparative Example 2 is low, and the material will become softer and have better toughness, but the thermal stability at high temperature will be reduced. It can be seen from the test data of Example 1, Comparative Example 3 and Comparative Example 4 that the peel strength in Comparative Example 3 is higher than that in Example 1, and the boiling resistance is unqualified; the peel strength in Comparative Example 4 decreases, and the boiling resistance is qualified. This is because the excessive content of linear diols in Comparative Example 3 will increase the molecular weight of the polyester, increase the viscosity of the material, increase the peel strength but decrease the boiling resistance; in Comparative Example 4, too little linear diol content will reduce the molecular weight of the polyester, reduce the viscosity, reduce the peel strength, and improve the boiling resistance.

[0267] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing polyester polyol for adhesive, characterized in that: The preparation method is: Step S1, adding an aliphatic dibasic acid, 2-6 g of maleic anhydride and 0.02-0.15 g of an organic tin catalyst to a reaction kettle A in sequence, heating the temperature to a first temperature, stirring at a first stirring speed, and after sufficient reaction, cooling the temperature to a second temperature, adding 1-3 g of triethylenetetramine to the reaction kettle A, heating the temperature to a third temperature, and sufficient reaction at the first stirring speed to obtain a modified aliphatic dibasic acid; Step S2, adding an aromatic dibasic acid, a pendant-containing diol, sebacic acid and a styrene-ethylene-butylene-styrene block copolymer into a reaction kettle B in sequence, heating the reaction kettle B to a third temperature, stirring continuously at a first stirring speed to perform an esterification reaction, and reacting under the protection of an inert gas until the acid value of the reaction system drops to a first theoretical design value; Step S3, after the esterification is completed, the reactor B is cooled to the fourth temperature, the modified aliphatic dibasic acid and the linear diol are sequentially added to the reactor B according to the ratio, and the temperature is raised to the third temperature to carry out the second stage of esterification reaction, and the heating and vacuuming are continued to promote the removal of water and accelerate the reaction, and the reaction is continued until the acid value of the reaction system drops to the second theoretical design value; Step S4, when the acid value of the reaction system drops to the second theoretical design value, the reaction system is cooled to the fifth temperature, citric acid is added as a cross-linking agent, a cross-linking reaction is carried out, the temperature is maintained at the fifth temperature, and the stirring is carried out at the second stirring speed to ensure that the citric acid is evenly dispersed and fully reacted to form a cross-linked network; Step S5, after the cross-linking reaction is completed, continue to cool to the second temperature, add epoxidized soybean oil to the reaction system, continue stirring at a third stirring speed to ensure that the epoxidized soybean oil is evenly dispersed in the system, and obtain a polyester polyol for adhesive after cooling; The polyester polyol for adhesive includes the following components in percentage by mass: Aromatic dibasic acid: 25-30%; Modified aliphatic dibasic acid: 10-20%; Sebacic acid: 10-15%; Straight chain diol: 10-20%; Containing pendant diol: 10-20%; Styrene-ethylene-butylene-styrene block copolymer: 5-10%; Citric acid: 1-2%; Epoxidized soybean oil: 1-3%; The aliphatic dibasic acid is one or more of adipic acid, succinic acid and ricinoleic acid.

2. The method for preparing a polyester polyol for adhesive according to claim 1, characterized in that: The aromatic dibasic acid is one or more of phthalic acid, isophthalic acid and terephthalic acid.

3. The method for preparing a polyester polyol for adhesive according to claim 1, characterized in that: The linear diol is one or more of 1,4-butanediol, ethylene glycol, and diethylene glycol; The side group-containing diol is one or more of neopentyl glycol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol and dipropylene glycol.

4. The method for preparing a polyester polyol for adhesive according to claim 1, characterized in that: In the step S1, The feeding amount of the aliphatic dibasic acid is 20-30g; The organotin catalyst is dibutyltin dilaurate; The first temperature is 120-140° C.; The second temperature is 80-90°C; The third temperature is 180-200°C.

5. The method for preparing a polyester polyol for adhesive according to claim 1, characterized in that: In the step S2, The inert gas is N2, and the gas flow rate is 4-6 mL / min; The first theoretical design value is 20-30 mg KOH / g.

6. The method for preparing a polyester polyol for adhesive according to claim 1, characterized in that: In the step S3, The fourth temperature is 110-120°C; The vacuum degree of the vacuum is 0.09-0.095Mpa; The reaction time of the third temperature is 2-3h; The second theoretical design value is 10-20 mg KOH / g.

7. The method for preparing a polyester polyol for adhesive according to claim 1, characterized in that: In the step S4, The second stirring speed is 200-300 rpm; The stirring time is 1-2h.

8. The method for preparing a polyester polyol for adhesive according to claim 1, characterized in that: In the step S5, The third stirring speed is 250-350rpm; The stirring time is 30-60 min.

9. A polyester polyol for adhesive prepared according to the method for preparing a polyester polyol for adhesive according to any one of claims 1 to 8.

10. Use of the polyester polyol for adhesive according to claim 9 in food packaging.

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