Heat-resistant polyol and corresponding polyurethane adhesive

Abstract

The invention relates to a heat-resistant polyol, a corresponding polyurethane adhesive and a corresponding preparation method, epoxidized cardanol obtained by epoxidation on the basis of cardanol derived from cashew nut shell oil is selected, and the heat-resistant polyol is prepared through ring opening of the epoxidized cardanol and bisphenol A series compounds. And the polyisocyanates of the component B and the component A are mixed for use, so that the heat resistance of the polyurethane adhesive is improved, and the defect that the tensile strength and the elongation of the polyurethane adhesive are reduced after high-temperature cooking is overcome. Meanwhile, a biological source renewable raw material cashew nut shell oil is utilized, so that more sustainable raw materials are provided to replace petroleum-based raw materials on the basis of improving the heat resistance.

Description

Technical Field

[0001] The present invention belongs to the field of advanced functional materials, and particularly relates to a heat-resistant polyol and a corresponding polyurethane adhesive. Background Art

[0002] Currently, the quality of food flexible packaging has been increasingly emphasized by production enterprises. The performance of flexible packaging is closely related to the adhesives used. Solventless polyurethane (PU) adhesives have the advantages of no pollution, less coating amount, and lower processing costs compared to solvent-based polyurethanes. They are mainly used in high-performance food packaging composite films. Compared with vinyl acetate adhesives, polyurethane adhesives are more in line with the future development trend both in terms of performance and environmental protection, and play an important role in the field of flexible packaging materials.

[0003] For retort pouch flexible packaging, due to its harsh use conditions, high requirements are imposed on polyurethane adhesives. Polyurethane adhesives are prone to hydrolysis in high-temperature and high-humidity environments, thereby reducing the bonding strength of the adhesives. For the tensile strength, elongation, and peel strength of the adhesive film before and after high-temperature cooking in the field of food flexible packaging, such properties of solventless polyurethane adhesives significantly decrease after high-temperature cooking, which is too different from before high-temperature cooking and is not conducive to their application in food packaging composite films. Therefore, to broaden the application scope, the molecular structure of solventless polyurethane adhesives needs to be further improved to enhance the high-temperature resistance performance.

[0004] The present invention selects epoxidized cardanol obtained by epoxidizing cardanol derived from cashew nut shell oil. Its molecular structure combines a rigid phenol ring and a flexible long hydrocarbon chain, which is very suitable for application scenarios requiring a combination of rigidity, chemical resistance, and waterproof performance. A heat-resistant polyol is obtained by ring-opening of epoxidized cardanol with bisphenol A series compounds, and it is used in the B component of the polyurethane adhesive and mixed with the A component polyisocyanate, thereby improving the heat resistance of the polyurethane adhesive and solving the defect that the tensile strength and elongation of the polyurethane adhesive decrease after high-temperature cooking. At the same time, using the bio-based renewable raw material cashew nut shell oil can also provide more sustainable raw materials to replace petroleum-based raw materials while improving the heat resistance of the adhesive. Summary of the Invention

[0005] Aiming at the defects of the prior art, the technical problem to be solved by the present invention is to provide a heat-resistant polyol and a corresponding polyurethane adhesive.

[0006] In the first aspect, a heat-resistant polyol is obtained by reacting a bisphenol A analog with epoxidized cardanol. The hydroxyl value range of the heat-resistant polyol is 30 - 500, and preferably, the hydroxyl value is not less than 250;

[0007] Among them, the structural general formula of the bisphenol A analog is The X group is selected from any one of the following: sulfone group, straight-chain, branched-chain or cyclic aliphatic hydrocarbon with 1 to 20 carbon atoms, halogen-substituted aliphatic hydrocarbon, aromatic hydrocarbon with 3 to 20 carbon atoms or alkyl-substituted aromatic hydrocarbon; the R group is selected from a hydrogen atom or a methyl group;

[0008] Preferably, the bisphenol A analog is selected from any one of the following: bisphenol A (BPA, CAS No.: 080-05-7), bisphenol AF (BPAF, CAS No.: 1478-61-1), bisphenol AP (BPAP, CAS No.: 1571-75-1), bisphenol B (BPB, CAS No.: 77-40-7), bisphenol C (BPC, CAS No.: 79-97-0), bisphenol E (BPE, CAS No.: 02081-8-5), bisphenol F (BPF, CAS No.: 620-92-8), bisphenol P (BPP, CAS No.: 2167-51-3), bisphenol S (BPS, CAS No.: 080-09-1), bisphenol Z (BPZ, CAS No.: 843-55-0);

[0009] Among them, the epoxidized cashew phenol includes any one or a combination of two of cashew phenol glycidyl ether and cashew phenol-based diphenyl diglycidyl ether.

[0010] In a second aspect, the preparation method of the heat-resistant polyol described above includes: reacting a bisphenol A analog with epoxidized cashew phenol under alkali catalysis at 150 to 200 °C, where the alkali is preferably an aqueous solution of an inorganic base.

[0011] Preferably, the molar ratio range of the phenolic hydroxyl group in the bisphenol A analog to the epoxy group in the epoxidized cashew phenol is 1:0.6 to 1:20.

[0012] In a third aspect, the application of the heat-resistant polyol described above in the preparation of polyurethane adhesives.

[0013] In a fourth aspect, a polyurethane adhesive includes: component A and component B, where component A is selected from polyisocyanates, and each molecule of the polyisocyanate contains at least 2 isocyanate groups, and the polyisocyanate is selected from at least one or a combination of aliphatic polyisocyanates, cycloaliphatic polyisocyanates or aromatic polyisocyanates;

[0014] Preferably, the polyisocyanate of component A is a combination of a cycloaliphatic polyisocyanate and an aromatic polyisocyanate;

[0015] Preferably, the aliphatic polyisocyanate is selected from at least one or a combination of hexamethylene diisocyanate (HDI), HDI biuret, HDI trimer or trimethylhexane diisocyanate;

[0016] Preferably, the alicyclic polyisocyanate is selected from at least one or a combination of isophorone diisocyanate (IPDI), IPDI trimer, 1,3-bis(isocyanatomethyl)cyclohexane, hydrogenated diphenylmethane diisocyanate, or hydrogenated benzodimethylen diisocyanate;

[0017] Preferably, the aromatic polyisocyanate is selected from at least one or a combination of toluene diisocyanate (TDI), TDI trimer, diphenylmethane diisocyanate (MDI), polymeric MDI, liquefied MDI, tetramethylm-xylylene diisocyanate (TMXDI), p-phenylene diisocyanate (PPDI), triphenylmethane triisocyanate, or 1,5-naphthalene diisocyanate (NDI);

[0018] Among them, component B is selected from the following compounds:

[0019] Polyester polyol: 0 - 50 parts by mass

[0020] The heat-resistant polyol described above: 20 - 80 parts by mass

[0021] Polyether polyol: 10 - 30 parts by mass

[0022] Castor oil: 0 - 20 parts by mass;

[0023] Preferably, component B is selected from the following compounds:

[0024] Polyester polyol: 0 - 30 parts by mass

[0025] The heat-resistant polyol described above: 50 - 70 parts by mass

[0026] Polyether polyol: 10 - 30 parts by mass

[0027] Castor oil: 5 - 15 parts by mass;

[0028] Among them, the polyester polyol refers to a polyol obtained by reacting a dibasic acid or dibasic anhydride with a diol and having a molecular weight between 300 and 5000;

[0029] Preferably, the molecular weight range of the polyester polyol is 500 - 2000;

[0030] Among them, the dibasic acid or dibasic anhydride is selected from one or a combination of succinic acid, glutaric acid, adipic acid, terephthalic acid, m-phthalic acid, phthalic acid or phthalic anhydride; the diol is selected from one or a combination of ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, methylbutylene glycol.

[0031] Among them, the polyether polyol refers to a polyether polyol obtained by polymerizing ethylene oxide and / or propylene oxide using propylene glycol or glycerol as the initiator and potassium hydroxide as the catalyst, and the molecular weight range of the polyether polyol is 300-5000;

[0032] Preferably, the molecular weight range of the polyether polyol is 300-2000.

[0033] Among them, the mass ratio of component A to component B is 1:0.6 to 1:1.2; preferably, the mass ratio of component A to component B is 1:0.8 to 1:1.0.

[0034] Fifthly, the preparation method of the polyurethane adhesive described above includes: mixing various hydroxyl-containing compounds of component B, and then mixing with component A.

[0035] Sixthly, the application of the polyurethane adhesive described above in the field of composite film soft packaging.

[0036] The beneficial effects of the present invention are as follows:

[0037] Heat-resistant polyol is obtained by introducing cardanol modification into polyol. The molecular structure of cardanol combines a rigid phenol ring and a flexible long hydrocarbon chain, which is very suitable for application scenarios that require a combination of rigidity, chemical resistance, and waterproof performance. Heat-resistant polyol is obtained by ring-opening epoxidized cardanol and bisphenol A series compounds, and it is used in the mixture of component B of the polyurethane adhesive and polyisocyanate of component A, thereby improving the heat resistance of the polyurethane adhesive, and thus solving the defect that the tensile strength and elongation of the polyurethane adhesive decrease after high-temperature cooking. At the same time, using the bio-based renewable raw material cashew shell oil, more sustainable raw materials are provided to replace petroleum-based raw materials on the basis of improving heat resistance. Specific Embodiments

[0038] The following combines specific embodiments to further illustrate the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0039] It should be noted that the terms used here are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention. As used here, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0040] If the specific experimental conditions are not specified in the examples, they are generally in accordance with the conventional conditions in the art or the conditions recommended by the reagent company; the materials, reagents, etc. used in the examples can be obtained through commercial channels without special instructions.

[0041] The epoxidized cashew phenol used in the following examples includes: cashew phenol-based diphenyl diglycidyl ether (brand: NC-514), cashew phenol glycidyl ether (brand: LITE 2513HP), which are provided by Cardolite Corporation. The epoxidized cashew phenol used in the examples is not further processed and is used as received.

[0042] Example 1

[0043] Synthesis of heat-resistant polyol 1: Add 100 g of bisphenol A and 10 g of 50% KOH aqueous solution, heat to 160 °C, and dehydrate under a vacuum of 0.001 mpa for 1 hour. Start to dropwise add 100 g of cashew phenol glycidyl ether LITE 2513HP, maintain the reaction at 150 °C for 5 hours, then add water and phosphoric acid to the reaction system for neutralization, and filter the insoluble substances in the reaction system to obtain polyol 1 with a hydroxyl value of 250.

[0044] Example 2

[0045] Synthesis of heat-resistant polyol 2: Add 100 g of bisphenol F and 10 g of 50% KOH aqueous solution, heat to 180 °C, and dehydrate under a vacuum of 0.001 mpa for 1 hour. Start to dropwise add 100 g of cashew phenol glycidyl ether LITE 2513HP, maintain the reaction at 150 °C for 5 hours. Then add water and phosphoric acid to the reaction system for neutralization, and filter the insoluble substances in the reaction system to obtain polyol 1 with a hydroxyl value of 250.

[0046] Example 3

[0047] Synthesis of heat-resistant polyol 3: Add 100 g of bisphenol S and 50 g of propylene glycol, and 10 g of 50% KOH aqueous solution, heat to 180 °C, and dehydrate under a vacuum of 0.001 mpa for 1 hour. Start to dropwise add 200 g of cashew phenol glycidyl ether LITE 2513HP, maintain the reaction at 150 °C for 5 hours. Then add water and phosphoric acid to the reaction system for neutralization, and filter the insoluble substances in the reaction system to obtain polyol 3 with a hydroxyl value of 380.

[0048] Example 4

[0049] Synthesis of heat-resistant polyol 4: 110 g of bisphenol A was added with 10 g of 50% KOH aqueous solution, heated to 160 °C, and dehydrated under a vacuum of 0.001 mpa for 1 hour. Then, 90 g of cardanol glycidyl ether LITE 2513HP and 15 g of cardanol-based diphenyl diglycidyl ether NC-514 were added dropwise, and the reaction was maintained at 150 °C for 5 hours. Subsequently, water and phosphoric acid were added to the reaction system for neutralization, and the insoluble substances in the reaction system were filtered to obtain polyol 4 with a hydroxyl value of 290.

[0050] The component ratios of the glue AB components in Examples 5 - 13 and Comparative Example 1 are shown in Table 1, where MDI-50 is a mixture of 2,4-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate.

[0051] Table 1

[0052]

[0053] The curing conditions of the solvent-free polyurethane adhesive film are as follows: First, the B component was mixed according to the ratio in Table 1. MDI-50, IPDI, and HDI trimer were selected as the isocyanate A component. After further mixing the A component and the B component according to the ratio in Table 1, the AB mixture was obtained. Subsequently, it was thermally cured into a film. Specifically, the AB mixture was placed in an oven at 50 °C and cured for 72 hours to obtain a polyurethane adhesive film.

[0054] The heat resistance experiment is as follows: The polyurethane adhesive film was placed in an oven at 140 °C and baked for 7 days, and then the tensile strength and elongation of the adhesive film were tested. The results are listed in Table 2.

[0055] From the results in Table 2, it can be seen that the polyurethane solvent-free adhesives (Examples 5 - 13) prepared by mixing the heat-resistant polyols prepared in Examples 1 - 4 as the B component with different types of polyisocyanates as the A component have higher heat resistance. Through the design of the chemical structure of the heat-resistant polyol, bisphenol A series analogues with high thermal stability and epoxidized cardanol containing a benzene ring and a long side chain were selected as raw materials, and the heat-resistant polyol was prepared through a high-temperature ring-opening reaction. The heat-resistant polyol contains multiple benzene ring structures, thus achieving the heat resistance of the molecular structure. At the same time, the long side chain of cardanol takes into account the elasticity (elongation) of the cured polyurethane adhesive film. Among them, the polyurethane adhesives prepared with the A component of the combination of MDI and IPDI in Examples 9 - 11 have the best balance between the two properties of tensile strength and elongation, and the reduction in the tensile strength and elongation of the polyurethane adhesive film before and after baking at 140 °C is the smallest.

[0056] Table 2

[0057]

[0058] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of them. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. Although the specific implementation manners of the present invention have been described above, it does not limit the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A heat-resistant polyol, characterized in that: The heat-resistant polyol is obtained by reacting bisphenol A analogs with epoxidized cardanol, and the hydroxyl value ranges from 30 to 500. Among them, the general structural formula of bisphenol A analogues is The X group is selected from any one of a sulfone group, a straight-chain, branched or cyclic aliphatic hydrocarbon having 1 to 20 carbon atoms, a halogen-substituted aliphatic hydrocarbon, an aromatic hydrocarbon having 3 to 20 carbon atoms or an alkyl-substituted aromatic hydrocarbon; the R group is selected from a hydrogen atom or a methyl group; The epoxidized cardanol includes any one or a combination of two of cardanol glycidyl ether and cardanol-based diphenyl diepoxy resin.

2. The method for preparing a heat-resistant polyol according to claim 1, characterized in that: The preparation method comprises: reacting bisphenol A analogue and epoxidized cardanol at 150-200° C. by base catalysis.

3. Use of the heat-resistant polyol as claimed in claim 1 in the preparation of polyurethane adhesive.

4. A polyurethane adhesive, characterized in that: The polyurethane adhesive comprises: component A and component B, wherein component A is selected from polyisocyanate, each molecule of the polyisocyanate contains at least 2 isocyanate groups, and the polyisocyanate is selected from at least one or a combination of aliphatic polyisocyanate, alicyclic polyisocyanate or aromatic polyisocyanate; Wherein, component B is selected from the following compounds: Polyester polyol: 0-50 parts by mass The heat-resistant polyol according to claim 1: 20-80 parts by mass Polyether polyol: 10-30 parts by mass Castor oil: 0-20 parts by mass.

5. The polyurethane adhesive according to claim 4, characterized in that: The aliphatic polyisocyanate is selected from at least one of hexamethylene diisocyanate (HDI), HDI biuret, HDI trimer or trimethylhexamethylene diisocyanate or a combination of multiple thereof.

6. The polyurethane adhesive according to claim 4, characterized in that: The alicyclic polyisocyanate is selected from at least one or a combination of isophorone diisocyanate (IPDI), IPDI trimer, 1,3-di(isocyanatomethyl)cyclohexane, hydrogenated diphenylmethane diisocyanate or hydrogenated xylylene diisocyanate.

7. The polyurethane adhesive according to claim 4, characterized in that: The aromatic polyisocyanate is selected from at least one of toluene diisocyanate (TDI), TDI trimer, diphenylmethane diisocyanate (MDI), polymeric MDI, liquefied MDI, tetramethyl meta-xylylene diisocyanate (TMXDI), para-xylylene diisocyanate (PPDI), triphenylmethane triisocyanate or 1,5-naphthalene diisocyanate (NDI), or a combination of the two.

8. The polyurethane adhesive according to claim 4, characterized in that: The mass ratio of the component A to the component B is 1:0.6 to 1:1.

2.

9. The method for preparing the polyurethane adhesive according to any one of claims 4 to 8, characterized in that: The preparation method comprises: mixing a plurality of hydroxyl-containing compounds of the B component and then mixing the mixture with the A component.

10. Use of the polyurethane adhesive according to any one of claims 4 to 8 in the field of composite film flexible packaging.

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