Preparation method of recyclable bio-based thermosetting polyurethane hot melt adhesive

Abstract

The present invention discloses a recyclable bio-based thermosetting polyurethane hot melt adhesive and its preparation method, which includes vegetable oil polyol, poly(propylene carbonate) diol, polyester polyol, macromolecular thermoplastic tackifying resin, isocyanate, furan compound containing active hydrogen, and bifunctional bismaleimide. First, the present invention reacts vegetable oil polyol, poly(propylene carbonate) diol, polyester polyol, and macromolecular thermoplastic tackifying resin with diisocyanate to generate a polyurethane prepolymer. Subsequently, the furan compound containing active hydrogen is reacted with the above prepolymer. Finally, bifunctional bismaleimide is added to form a dynamic covalent polymer therewith. The prepared bio-based thermosetting polyurethane hot melt adhesive has a low melt viscosity, a high ultimate peel strength, and recyclable characteristics. Some raw materials of the present invention are derived from biomass and renewable materials, which improves the green sustainability of the product's entire life cycle.

Description

Technical Field

[0001] The present invention belongs to the field of moisture-curing polyurethane hot melt adhesives, and particularly relates to a preparation method of a recyclable bio-based thermosetting polyurethane hot melt adhesive. Background Art

[0002] Moisture-curing polyurethane hot melt adhesives, abbreviated as HMPUR or PUR, are based on terminal -NCO group prepolymers, and are formulated with thermoplastic resins, tackifying resins, antioxidants, catalysts, fillers and other additives that do not react with isocyanate groups. When applying moisture-curing polyurethane hot melt adhesives, the adhesive is usually heated and melted into a fluid, coated on the surface of the substrate and then adhered. Since its terminal group is -NCO group, it can react with moisture in the air and active hydrogen on the surface of the substrate to generate a large number of cross-linked network structures, forming a thermosetting adhesive layer, making it have many advantages such as high bonding strength, heat resistance, and hydrolysis resistance, and has a wide range of applications in the fields of textiles, woodworking, automobiles, household appliances, etc. However, because moisture-curing polyurethane hot melt adhesives are thermosetting materials with a stable cross-linked structure, they cannot be recycled by melting after curing. At the same time, most of them are synthesized from petrochemical raw materials, which does not conform to the current development direction of "green chemistry".

[0003] In recent years, the usage amount of moisture-curing polyurethane hot melt adhesives has shown a large annual growth trend and occupies a place in polyurethane adhesives. The scale growth has also led to the backlog of scraps, waste or returned products that do not meet the standards generated during the production and downstream use of moisture-curing polyurethane hot melt adhesives, which not only causes profit losses to manufacturers, but also brings great pressure to the environment.

[0004] In order to make thermosetting polyurethane hot melt adhesives recyclable, the present invention introduces dynamic covalent bonds (D-A bonds) into the polyurethane chain segments, and uses the dynamic covalent bonds at the fracture surface to exchange and reconnect polyurethane molecular chains under high-temperature melting conditions, so that the moisture-curing polyurethane hot melt adhesive no longer exhibits traditional thermosetting properties, but has a certain degree of creep and stress relaxation behavior, thereby achieving the purpose of recyclable and reusable thermosetting polyurethane hot melt adhesives. In addition, controlling the terminal NCO content of the product in a lower range and adding some macromolecular thermoplastic tackifying resins will both contribute to the product of the present invention having both the high initial adhesion strength and high peel strength of thermosetting materials and the toughness and melt recyclability of thermoplastic materials; dynamic covalent bonds include disulfide bonds, imine bonds, ester bonds, diselenide bonds, Diels-Alder bonds, etc.

[0005] In order to implement the deep environmental protection policy, the present invention uses vegetable oil polyol and poly(propylene carbonate) diol synthesized by the carbon dioxide method as the soft segment of the polyurethane hot melt adhesive, not only enabling the recycling of polyurethane hot melt adhesive waste, but also starting from the source of synthetic materials to help reduce carbon dioxide emissions in the entire life cycle of the moisture-curing polyurethane hot melt adhesive upstream and downstream, achieving low-carbon, circular, and sustainable development. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a preparation method of a recyclable bio-based thermosetting polyurethane hot melt adhesive.

[0007] In the first aspect, a recyclable bio-based thermosetting polyurethane hot melt adhesive provided by the present invention adopts the following technical solution:

[0008] A recyclable bio-based thermosetting polyurethane hot melt adhesive, comprising the following components by mass:

[0009] Vegetable oil polyol: 10 - 35 parts;

[0010] Poly(propylene carbonate) diol: 25 - 55 parts;

[0011] Polyester polyol: 10 - 30 parts;

[0012] Macromolecular thermoplastic tackifying resin: 5 - 15 parts;

[0013] Isocyanate: 10 - 20 parts;

[0014] Active hydrogen-containing furan compound: 0 - 10 parts;

[0015] Bifunctional bismaleimide: 0 - 5 parts;

[0016] The present invention further sets the technical solution as that the vegetable oil polyol is castor oil-derived polyol or soybean oil polyol, and the hydroxyl value of the vegetable oil polyol is 20 - 200 mgKOH / g.

[0017] The present invention further sets the technical solution as that the hydroxyl value of the poly(propylene carbonate) diol is 30 - 120 mgKOH / g.

[0018] The present invention further sets the technical solution as that the hydroxyl value of the polyester diol is 20 - 100 mgKOH / g, and the polyester diol is one or more of poly(hexamethylene adipate) diol, poly(butylene adipate) diol, and poly(caprolactone) diol;

[0019] The present invention further sets the technical solution as that the macromolecular thermoplastic tackifying resin is thermoplastic polyurethane elastomer, solid acrylic resin, or ethylene vinyl acetate resin.

[0020] A further technical solution of the present invention is that the isocyanate is diphenylmethane diisocyanate.

[0021] A further technical solution of the present invention is that the active hydrogen-containing furan compound is furfurylamine or furfuryl glycidyl ether-2-furfurylamine.

[0022] A further technical solution of the present invention is that the bifunctional bismaleimide is diphenylmethane bismaleimide or 1,8-bismaleimide.

[0023] A further technical solution of the present invention is that the vegetable oil polyol is Oil D-2000: 25 parts;

[0024] The poly(propylene carbonate) diol is PPCD-531: 39 parts;

[0025] The polyester polyol is HDPOL-338: 18 parts;

[0026] The macromolecular tackifying resin is BR-106: 5 parts;

[0027] The isocyanate is MDI-100: 13 parts;

[0028] The active hydrogen-containing furan compound is FGE-FA: 2.7 parts;

[0029] The bifunctional bismaleimide is 1,8-BMI: 2.1 parts.

[0030] In a second aspect, the present invention discloses a preparation method of a recyclable bio-based thermosetting polyurethane hot melt, adopting the following technical solutions:

[0031] A preparation method of a recyclable bio-based thermosetting polyurethane hot melt adhesive, comprising a recyclable bio-based thermosetting polyurethane hot melt adhesive as described in any one of the above, and the preparation method adopts the following steps:

[0032] S1. Weigh the corresponding weight parts of vegetable oil polyol, poly(propylene carbonate) diol, polyester polyol, and macromolecular thermoplastic tackifying resin under a vacuum condition of -0.1 MPa, heat up to 140 °C, heat and stir for 1-2 h, and then cool down to 90-100 °C to obtain mixture A;

[0033] S2. Under the protection of an inert gas, add the isocyanate to mixture A, and react for 1-2 h under a vacuum condition of 110 °C to obtain mixture B;

[0034] S3. Under the protection of an inert gas, add the active hydrogen-containing furan compound to mixture B, and react for 1-2 h under a vacuum condition of 110 °C to obtain mixture C;

[0035] S4. Under the protection of inert gas, add bifunctional bismaleimide to mixture C, and react for 1 - 2 h under vacuum conditions at 110 °C to obtain mixture D;

[0036] S5. Debubble the mixture inside the reaction kettle for 5 minutes and then quickly seal and package it with an aluminum foil bag to prepare the recyclable bio - based thermosetting polyurethane hot - melt adhesive.

[0037] By adopting the above - mentioned technical solution, the preparation method provided by the present invention is simple and easy to control, requires relatively mild reaction conditions, and is suitable for large - scale industrial production.

[0038] To sum up, the present invention includes the following beneficial technical effects:

[0039] 1. In order to make the thermosetting polyurethane hot - melt adhesive recyclable, the present invention introduces dynamic covalent bonds (D - A bonds) into the polyurethane chain segments. The dynamic covalent bonds at the fracture surface exchange and reconnect the polyurethane molecular chains under high - temperature melting conditions, making the wet - curing polyurethane hot - melt adhesive no longer exhibit traditional thermosetting properties, but have a certain degree of creep and stress relaxation behavior, so as to achieve the purpose of recyclable and reusable thermosetting polyurethane hot - melt adhesive;

[0040] 2. By controlling the terminal NCO content of the product within a relatively low range (NCO content is 1.2 - 2 wt%) and adding some macromolecular thermoplastic tackifying resins, it is beneficial for the product of the present invention to have both the high initial adhesion strength and high peel strength of thermosetting materials and the toughness and melt recyclability of thermoplastic materials;

[0041] 3. In order to implement the deep environmental protection policy, the present invention uses vegetable oil polyol and poly(propylene carbonate) diol synthesized by the carbon dioxide method as the soft segment of the polyurethane hot - melt adhesive. This not only enables the recycling and reuse of polyurethane hot - melt adhesive waste, but also starts from the source of synthetic materials, helping to reduce carbon dioxide emissions in the entire life cycle of the upstream and downstream of polyurethane hot - melt adhesive, and achieving low - carbon, circular, and sustainable development. Specific Embodiments

[0042] The following further elaborates on the present invention with reference to embodiments. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments.

[0043] The present invention provides a recyclable thermosetting polyurethane hot - melt adhesive.

[0044] The recyclable thermosetting polyurethane hot - melt adhesive includes the following components (expressed in parts by weight):

[0045] Vegetable oil polyol: 10 - 35 parts;

[0046] Poly(propylene carbonate) diol: 25 - 55 parts;

[0047] Polyester polyol: 10 - 30 parts;

[0048] Macromolecular tackifying resin: 5 - 15 parts;

[0049] Isocyanate: 10 - 20 parts;

[0050] Active hydrogen-containing furan compound: 0 - 10 parts;

[0051] Bifunctional bismaleimide: 0 - 5 parts.

[0052] Among them, the vegetable oil polyol is a castor oil-derived polyol or a soybean oil polyol, and the hydroxyl value of the vegetable oil polyol is 20 - 220 mgKOH / g; such as: Vertellus Oil D-1000, D-2000; Helima HM10100, HM-10200, etc.

[0053] Poly(propylene carbonate) diol is Dazhi PPCD-531, PPCD-232, and the hydroxyl value is 37 ± 2 mgKOH / g.

[0054] The hydroxyl value of the polyester polyol is 20 - 100 mgKOH / g, and one or more of poly(hexamethylene adipate) diol, poly(butylene adipate) diol, and polycaprolactone diol are used. Such as: HDPOL-6640, HDPOL-338.

[0055] The macromolecular thermoplastic tackifying resin is TPU5906, BR-106, BR-113, EVA-40W.

[0056] The isocyanate used is diphenylmethane diisocyanate (MDI-100).

[0057] The active hydrogen-containing furan compound is furfurylamine (FA) or furfuryl glycidyl ether-2-furfurylamine (FGE-FA).

[0058] The bifunctional bismaleimide is diphenylmethane bismaleimide (BMI) or 1,8-bismaleimide (1,8-BMI).

[0059] A preparation method of a recyclable bio-based thermosetting polyurethane hot melt adhesive adopts the following steps:

[0060] S1. Weigh the corresponding weight parts of vegetable oil polyol, poly(propylene carbonate) diol, polyester polyol, and macromolecular thermoplastic tackifying resin under a vacuum condition of -0.1 MPa, heat up to 140 °C, heat and stir for 1 - 2 h, and then cool down to 90 - 100 °C to obtain mixture A;

[0061] S2. Under the protection of inert gas, add isocyanate to mixture A, and react for 1 - 2 h under vacuum condition at 110 °C to obtain mixture B;

[0062] S3. Under the protection of inert gas, add the active hydrogen-containing furan compound to mixture B, and react for 1 - 2 h under vacuum condition at 110 °C to obtain mixture C;

[0063] S4. Under the protection of inert gas, add bifunctional bismaleimide to mixture C, and react for 1 - 2 h under vacuum condition at 110 °C to obtain mixture D;

[0064] S5. Debubble the mixture inside the reaction kettle for 5 minutes and then quickly seal and package it with an aluminum foil bag to obtain the recyclable bio-based thermosetting polyurethane hot melt adhesive.

[0065] Example 1:

[0066] A recyclable thermosetting polyurethane hot melt adhesive comprises the following components (expressed in parts by weight):

[0067] The vegetable oil polyol is Oil D - 1000: 20 parts;

[0068] The poly(propylene carbonate) diol is PPCD - 531: 34 parts;

[0069] The polyester polyol is HDPOL - 6640: 26 parts;

[0070] The macromolecular tackifying resin is TPU - 5906: 5 parts;

[0071] The isocyanate is MDI - 100: 15 parts;

[0072] The active hydrogen-containing furan compound is FA: 2.7 parts;

[0073] The bifunctional bismaleimide is BMI: 2.1 parts.

[0074] A preparation method of a recyclable thermosetting polyurethane hot melt adhesive comprises the following steps:

[0075] S1. Weigh Oil D - 1000: 20 parts; PPCD - 531: 34 parts; HDPOL - 6640: 26 parts; TPU - 5906: 5 parts; Under the vacuum condition of -0.1 MPa, heat up to 120 - 140 °C, heat and stir for 1 - 2 h, and then cool down to 90 - 100 °C to obtain mixture A;

[0076] S2. Under the protection of inert gas, add 15 parts of MDI-100 to mixture A, and react for 1-2 h under vacuum conditions at 110 °C to obtain mixture B;

[0077] S3. Under the protection of inert gas, add 2.7 parts of FA to mixture B, and react for 1-2 h under vacuum conditions at 110 °C to obtain mixture C;

[0078] S4. Under the protection of inert gas, add 2.1 parts of BMI to mixture C, and react for 1-2 h under vacuum conditions at 110 °C to obtain mixture D;

[0079] S5. Debubble the mixture inside the reaction kettle for 5 minutes, sample and detect that the NCO value is 1.6%, and then seal and package it with an aluminum foil bag to obtain the recyclable bio-based thermosetting polyurethane hot melt adhesive.

[0080] Example 2:

[0081] A recyclable thermosetting polyurethane hot melt adhesive, comprising the following components (expressed in parts by weight):

[0082] Vegetable oil polyol is HM10100: 20 parts;

[0083] Poly(propylene carbonate) diol is PPCD-232: 29 parts;

[0084] Polyester polyol is HDPOL-6640: 31 parts;

[0085] Macromolecular tackifying resin is BR-113: 5 parts;

[0086] Isocyanate is MDI-100: 13 parts;

[0087] Active hydrogen-containing furan compound is FA: 0.6 part;

[0088] Bifunctional bismaleimide is BMI: 0.4 part.

[0089] A preparation method of a recyclable bio-based thermosetting polyurethane hot melt adhesive, comprising the following steps:

[0090] S1. Weigh HM10100: 20 parts; PPCD-232: 29 parts; HDPOL-6640: 31 parts; BR-113: 5 parts; under a vacuum condition of -0.1 MPa, heat up to 120-140 °C, heat and stir for 1-2 h, and then cool down to 90-100 °C to obtain mixture A;

[0091] S2. Under the protection of inert gas, add 13 parts of MDI-100 to mixture A, and react for 1-2 h under vacuum conditions at 110 °C to obtain mixture B;

[0092] S3. Under the protection of inert gas, add 0.6 parts of FA to mixture B, and react for 1 - 2 h under vacuum conditions at 110 °C to obtain mixture C;

[0093] S4. Under the protection of inert gas, add 0.4 parts of BMI to mixture C, and react for 1 - 2 h under vacuum conditions at 110 °C to obtain mixture D;

[0094] S5. Debubble the mixture inside the reaction kettle for 5 minutes, sample and detect that the NCO value is 1.6%, and then seal and package it with an aluminum foil bag to obtain the recyclable bio - based thermosetting polyurethane hot melt adhesive.

[0095] Example 3:

[0096] A recyclable thermosetting polyurethane hot melt adhesive, comprising the following components (expressed in parts by weight):

[0097] The vegetable oil polyol is Oil D - 2000: 25 parts;

[0098] The poly(propylene carbonate) diol is PPCD - 531: 39 parts;

[0099] The polyester polyol is HDPOL - 338: 18 parts;

[0100] The macromolecular tackifying resin is BR - 106: 5 parts;

[0101] The isocyanate is MDI - 100: 13 parts;

[0102] The active hydrogen - containing furan compound is FGE - FA: 2.7 parts;

[0103] The bifunctional bismaleimide is 1,8 - BMI: 2.1 parts.

[0104] A preparation method of a recyclable bio - based thermosetting polyurethane hot melt adhesive, comprising the following steps:

[0105] S1. Weigh Oil D - 2000: 25 parts; PPCD - 531: 39 parts; HDPOL - 338: 18 parts; BR - 106: 5 parts; Under vacuum conditions of - 0.1 MPa, heat up to 120 - 140 °C, heat and stir for 1 - 2 h, and then cool down to 90 - 100 °C to obtain mixture A;

[0106] S2. Under the protection of inert gas, add 13 parts of MDI - 100 to mixture A, and react for 1 - 2 h under vacuum conditions at 110 °C to obtain mixture B;

[0107] S3. Under the protection of inert gas, add 2.7 parts of FGE-FA to mixture B, and react at 110 °C under vacuum for 1 - 2 h to obtain mixture C;

[0108] S4. Under the protection of inert gas, add 2.1 parts of 1,8-BMI to mixture C, and react at 110 °C under vacuum for 1 - 2 h to obtain mixture D;

[0109] S5. Debubble the mixture inside the reaction kettle for 5 minutes, take a sample to detect that the NCO value is 1.6%, and then seal and package it with an aluminum foil bag to obtain the recyclable bio-based thermosetting polyurethane hot melt adhesive.

[0110] Example 4:

[0111] A recyclable thermosetting polyurethane hot melt adhesive, comprising the following components (expressed in parts by weight):

[0112] Vegetable oil polyol is HM-10200: 26 parts;

[0113] Poly(propylene carbonate) diol is PPCD-232: 35 parts;

[0114] Polyester polyol is HDPOL-6640: 21 parts;

[0115] Macromolecular tackifying resin is EVA-40W: 5 parts;

[0116] Isocyanate is MDI-100: 13 parts;

[0117] Active hydrogen-containing furan compound is FGE-FA: 2.7 parts.

[0118] A preparation method of a recyclable bio-based thermosetting polyurethane hot melt adhesive, comprising the following steps:

[0119] S1. Weigh HM-10200: 26 parts; PPCD-232: 35 parts; HDPOL-6640: 21 parts; EVA-40W: 5 parts; under a vacuum condition of -0.1 MPa, heat up to 120 - 140 °C, heat and stir for 1 - 2 h, and then cool down to 90 - 100 °C to obtain mixture A;

[0120] S2. Under the protection of inert gas, add 13 parts of MDI-100 to mixture A, and react at 110 °C under vacuum for 1 - 2 h to obtain mixture B;

[0121] S3. Under the protection of inert gas, add 2.7 parts of FGE-FA to mixture B, and react at 110 °C under vacuum for 1 - 2 h to obtain mixture C;

[0122] S4. Debubble the mixture inside the reaction kettle for 5 minutes, take a sample for testing, and the NCO value is 1.8%. Then seal and package it with an aluminum foil bag to obtain the recyclable bio-based thermosetting polyurethane hot melt adhesive.

[0123] Comparative Example 1:

[0124] A recyclable thermosetting polyurethane hot melt adhesive, comprising the following components (expressed in parts by weight):

[0125] The vegetable oil polyol is Oil D-1000: 20 parts;

[0126] The poly(propylene carbonate) diol is PPCD-531: 34 parts;

[0127] The polyester polyol is HDPOL-6640: 26 parts;

[0128] The macromolecular tackifying resin is TPU-5906: 5 parts;

[0129] The isocyanate is MDI-100: 15 parts.

[0130] Compared with Example 1, the introduction of the D-A bond was cancelled in Comparative Example 1;

[0131] A preparation method of a recyclable bio-based thermosetting polyurethane hot melt adhesive, comprising the following steps:

[0132] S1. Weigh Oil D-1000: 20 parts; PPCD-531: 34 parts; HDPOL-6640: 26 parts; TPU-5906: 5 parts; Under a vacuum condition of -0.1 MPa, heat up to 120 - 140 °C, heat and stir for 1 - 2 h, and then cool down to 90 - 100 °C to obtain mixture A;

[0133] S2. Under the protection of an inert gas, add 15 parts of MDI-100 to mixture A, and react under a vacuum condition of 110 °C for 1 - 2 h to obtain mixture B;

[0134] S3. Debubble the mixture inside the reaction kettle for 5 minutes and then quickly seal and package it with an aluminum foil bag to obtain the recyclable bio-based thermosetting polyurethane hot melt adhesive.

[0135] Comparative Example 2:

[0136] Oil D-1000: 24 parts;

[0137] PPCD-531: 34 parts;

[0138] HDPOL-6640: 26 parts;

[0139] MDI-100: 16 parts;

[0140] FA: 2.7 parts

[0141] BMI: 2.1 parts

[0142] Compared with Example 1, in Comparative Example 2, the introduction of the macromolecular tackifying resin was cancelled;

[0143] A preparation method of a recyclable thermosetting polyurethane hot melt adhesive, comprising the following steps:

[0144] S1, weigh Oil D-1000: 24 parts; PPCD-531: 34 parts; HDPOL-6640: 26 parts; under a vacuum condition of -0.1 MPa, heat up to 120 - 140 °C, heat and stir for 1 - 2 h, then cool down to 90 - 100 °C to obtain mixture A;

[0145] S2, under the protection of an inert gas, add 16 parts of MDI-100 to mixture A, react under a vacuum condition of 110 °C for 1 - 2 h to obtain mixture B;

[0146] S3, under the protection of an inert gas, add 2.7 parts of FA to mixture B, react under a vacuum condition of 110 °C for 1 - 2 h to obtain mixture C;

[0147] S4, under the protection of an inert gas, add 2.1 parts of BMI to mixture C, react under a vacuum condition of 110 °C for 1 - 2 h to obtain mixture D;

[0148] S5, carry out degassing treatment on the mixture inside the reaction kettle for 5 minutes, sample and detect that the NCO value is 1.6%, and then seal and package with an aluminum foil bag to obtain the recyclable bio-based thermosetting polyurethane hot melt adhesive.

[0149] Comparative Example 3:

[0150] Oil D-2000: 23 parts;

[0151] PPCD-531: 38 parts;

[0152] HDPOL-338: 16 parts;

[0153] BR-106: 5 parts;

[0154] MDI-100: 18 parts;

[0155] FGE-FA: 2.7 parts

[0156] 1,8-BMI: 2.1 parts

[0157] Compared with Example 3, in Comparative Example 3, the NCO content for wet curing was increased;

[0158] A preparation method of a recyclable bio-based thermosetting polyurethane hot melt adhesive, comprising the following steps:

[0159] S1, weigh Oil D-2000: 23 parts; PPCD-531: 38 parts; HDPOL-338: 16 parts; BR-106: 5 parts;

[0160] Under a vacuum condition of -0.1 MPa, heat up to 120 - 140 °C, heat and stir for 1 - 2 h, and then cool down to 90 - 100 °C to obtain mixture A;

[0161] S2, under the protection of an inert gas, add 18 parts of MDI-100 to mixture A, and react under a vacuum condition of 110 °C for 1 - 2 h to obtain mixture B;

[0162] S3, under the protection of an inert gas, add 2.7 parts of FGE-FA to mixture B, and react under a vacuum condition of 110 °C for 1 - 2 h to obtain mixture C;

[0163] S4, under the protection of an inert gas, add 2.1 parts of 1,8-BMI to mixture C, and react under a vacuum condition of 110 °C for 1 - 2 h to obtain mixture D;

[0164] S5, defoam the mixture inside the reaction kettle for 5 minutes, sample and detect the NCO value of 3.6%, and then seal and package with an aluminum foil bag to obtain the recyclable bio-based thermosetting polyurethane hot melt adhesive.

[0165] Performance test:

[0166] Respectively conduct physical property tests on the polyurethane hot melt adhesives prepared in Examples 1 - 4 and Comparative Examples 1 - 3, and record the test results in Table 1 below.

[0167] Among them, the melt viscosity test is carried out in accordance with HG / T3660-1999;

[0168] The peel strength test is carried out in accordance with FZ / T01085-2018;

[0169] Test substrate: polyester cloth (cloth pasted on cloth);

[0170] Recyclability test method: Place the polyurethane hot melt adhesives in Examples 1-4 and Comparative Example 1 in an incubator at 25°C and 50% humidity for two weeks. After taking them out and melting, observe the degree of surface skinning and evaluate it on a scale of 1-5 points (5 points indicating the lowest degree of skinning). In addition, after melting them, mix them with the cloth-to-cloth product NEL-1016 synthesized conventionally by our company, observe the uniformity of the glue and the particle condition, and the mixable ratio is measured with 100 parts of NEL-1016;

[0171] Table 1 Performance test results:

[0172]

[0173] From the data in the table, it can be seen that a recyclable bio-based thermosetting polyurethane hot melt adhesive prepared by the present invention can obtain a lower melt viscosity and a higher peel strength by introducing new raw materials and synthesis methods. In the present invention, dynamic covalent bonds (D-A bonds) are introduced into the polyurethane chain segments during the synthesis of the thermosetting polyurethane hot melt adhesive. The dynamic covalent bonds at the fracture surface exchange and reconnect the polyurethane molecular chains under high-temperature melting conditions, so that the wet-curing polyurethane hot melt adhesive no longer exhibits traditional thermosetting properties, but has a certain degree of creep and stress relaxation behavior, thereby achieving the purpose of recyclable reuse of the thermosetting polyurethane hot melt adhesive. In addition, controlling the terminal NCO content of the product in a lower range and adding some macromolecular thermoplastic tackifying resins will be beneficial for the product of the present invention to have both the high initial adhesion strength and high peel strength of thermosetting materials and the toughness and melt recyclability of thermoplastic materials; Using vegetable oil polyol and poly(propylene carbonate) diol synthesized by the carbon dioxide method as the soft segment of the polyurethane hot melt adhesive not only enables the recycling and reuse of polyurethane hot melt adhesive waste, but also helps to reduce carbon dioxide emissions in the entire life cycle of the upstream and downstream of the polyurethane hot melt adhesive from the source of synthetic materials, achieving low-carbon, circular, and sustainable development.

[0174] The following is the equation for synthesizing the recyclable bio-based thermosetting polyurethane hot melt adhesive of the present invention with FA and BMI.

[0175]

[0176] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details.

Claims

1. A recyclable bio-based thermosetting polyurethane hot melt adhesive, characterized in that, It is composed of the following substances in parts by mass: The vegetable oil polyol is Oil D-2000: 25 parts; The poly(propylene carbonate) diol is PPCD-531: 39 parts; The polyester polyol is HDPOL-338: 18 parts; The macromolecular tackifying resin is BR-106: 5 parts; The isocyanate is MDI-100: 13 parts; The active hydrogen-containing furan compound is FGE-FA: 2.7 parts; The bifunctional bismaleimide is 1,8-BMI: 2.1 parts; The preparation method adopts the following steps: S1. Weigh the corresponding parts by weight of the vegetable oil polyol, poly(propylene carbonate) diol, polyester polyol, and macromolecular thermoplastic tackifying resin, and under the vacuum condition of -0.1 MPa, heat up to 140 °C, heat and stir for 1 - 2 h, and then cool down to 90 - 100 °C to obtain mixture A; S2. Under the protection of an inert gas, add the isocyanate to mixture A, and react under the vacuum condition of 110 °C for 1 - 2 h to obtain mixture B; S3. Under the protection of an inert gas, add the active hydrogen-containing furan compound to mixture B, and react under the vacuum condition of 110 °C for 1 - 2 h to obtain mixture C; S4. Under the protection of an inert gas, add the bifunctional bismaleimide to mixture C, and react under the vacuum condition of 110 °C for 1 - 2 h to obtain mixture D; S5. Debubble the mixture inside the reaction kettle for 5 minutes and then quickly seal and package it with an aluminum foil bag to obtain the recyclable bio-based thermosetting polyurethane hot melt adhesive.

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