Paper-plastic composite reactive polyurethane hot melt adhesive for low-temperature coating

Abstract

The invention discloses a paper-plastic composite reactive polyurethane hot melt adhesive for low-temperature coating, and belongs to the technical field of polyurethane adhesives, the paper-plastic composite reactive polyurethane hot melt adhesive for low-temperature coating comprises the following components by weight: 50-70 parts of modified polyester polyol, 30-50 parts of modified polyether polyol, 15-24 parts of diisocyanate, and 5-30 parts of tackifying resin, 0.1-1 part of a catalyst, 5-35 parts of a filler, 0.05-2 parts of a polymerization inhibitor and 0.1-0.5 part of an antioxidant; the modified polyester polyol is modified poly (butylene succinate); the modified polyether polyol is modified polypropylene glycol; the polyurethane hot melt adhesive prepared by modifying 5-norbornene-2-methylamine with a strong polar bond-NH and 3, 7-dimethyl octyl-6-ene-1-alcohol containing an insect-proof and mildew-proof functional component with polyhydric alcohol has relatively low melting temperature and viscosity, has initial viscous force of more than 1N and final viscous force of more than 5N at the same time, and has the characteristics of high temperature resistance, high temperature resistance, high temperature resistance and the like. The method can be well applied to paper-plastic compounding for low-temperature coating.

Description

Technical Field

[0001] This invention relates to the field of polyurethane adhesive technology, specifically to a low-temperature coating paper-plastic composite reactive polyurethane hot melt adhesive. Background Technology

[0002] Traditional paper-plastic composites use solvent-based polyurethane adhesives as raw materials in their production process. However, with increasing environmental regulations and consumer demand for environmentally friendly products, the development of solvent-free polyurethane hot melt adhesives has become urgent. While there is considerable research on polyurethane hot melt adhesives, there is relatively little research specifically on reactive polyurethane hot melt adhesives for low-temperature coating of paper-plastic composites. These adhesives have specific requirements compared to general polyurethane hot melt adhesives, demanding low coating viscosity and controllable peel strength. Currently, most polyurethane hot melt adhesives use structurally regular polyols such as polyhexyl adipate, polybutylene succinate, and polypropylene glycol as raw materials, polymerized with rigid 4,4'-methylenebis(phenyl isocyanate). The high crystallinity of these polyols leads to the formation of more microcrystals, which promotes molecular entanglement, thereby improving adhesion and imparting strong peel strength and heat and weather resistance to the material. However, due to the strong interchain interactions, not only does the viscosity increase, but the melting temperature is also high, typically above 150°C, making them unsuitable for paper-plastic composites requiring low-temperature operations, as this would damage the substrate. Summary of the Invention

[0003] To overcome the shortcomings of the existing technology, this invention provides a low-temperature coating paper-plastic composite reactive polyurethane hot melt adhesive. The polyurethane hot melt adhesive is a polymer made from modified polyol, diisocyanate, tackifying resin, catalyst, filler, polymerization inhibitor, and antioxidant. By modifying the polyol, branched 5-norbornene-2-methylamine is introduced onto polybutylene succinate, and branched 3,7-dimethyloctyl-6-en-1-ol is introduced onto polypropylene glycol. The sterically hindered long branches can disrupt the original crystallinity of the polyol, reducing the chain segment packing density and lowering the melting temperature. Simultaneously, the free movement of the chain segments results in a lower viscosity, and 3,7-dimethyloctyl-6-en-1-ol possesses certain insect-repellent and mildew-resistant properties. The introduction of -NH groups into 5-norbornene-2-methylamine enhances the bonding ability with the substrate, ensuring that the peel strength is within the target range.

[0004] The purpose of this invention is to provide a paper-plastic composite reactive polyurethane hot melt adhesive for low-temperature coating.

[0005] This invention is achieved through the following technical solution: A low-temperature coating paper-plastic composite reactive polyurethane hot melt adhesive, comprising, by weight, the following components: 50-70 parts modified polyester polyol, 30-50 parts modified polyether polyol, 15-24 parts diisocyanate, 5-30 parts tackifying resin, 0.1-1 part catalyst, 5-35 parts filler, 0.05-2 parts polymerization inhibitor, and 0.1-0.5 parts antioxidant; wherein the modified polyester polyol is modified polybutylene succinate; the modified polyether polyol is modified polypropylene glycol; and the molecular formulas of the modified polybutylene succinate and modified polypropylene glycol are shown in Formula 1 and Formula 2, respectively. Formula 1 Formula 2.

[0006] In one specific embodiment, the diisocyanate is one of 4,4'-methylenebis(phenyl isocyanate), methylcyclohexyl diisocyanate, and isoflurane diisocyanate; the R value of the diisocyanate is 1-2.1.

[0007] In one specific embodiment, the tackifying resin is one of rosin resin, terpene resin, and acrylic resin.

[0008] In one specific embodiment, the catalyst is dibutyltin dilaurate.

[0009] In one specific embodiment, the filler is one or more combinations of calcium carbonate, carbon black, and silicon dioxide.

[0010] In one specific embodiment, the polymerization inhibitor is one of phosphoric acid and p-toluenesulfonic acid.

[0011] In one specific embodiment, the antioxidant is antioxidant 1010.

[0012] In one specific embodiment, the preparation of the modified polypropylene glycol includes the following steps: S1. Modified propylene oxide Under ammonia protection, 3,7-dimethyloct-6-en-1-ol, inorganic base, and phase transfer agent were added to anhydrous THF and stirred to dissolve. Epichlorohydrin was slowly added dropwise, and the temperature was raised to 35-50 °C. The reaction was completed after 12-24 hours. The mixture was cooled, filtered, and extracted to obtain the organic phase, which was then purified by column chromatography to obtain the product modified propylene oxide. S2. Epoxy ring-opening polymerization: Ethylene glycol and an alkaline catalyst were dehydrated under vacuum at 100-120 °C for 1-3 hours. After cooling, nitrogen gas was introduced and anhydrous THF was added in an ice bath. Dehydrated modified propylene oxide was slowly added dropwise, and the temperature was raised to 60-80 °C for 8-14 hours to complete the reaction. After cooling, the pH was adjusted to neutral, filtered, concentrated, and cold methanol was added dropwise to precipitate the polymer. After filtration and drying, modified polypropylene glycol with a hydroxyl value of approximately 32-74.8 mgKOH / g was obtained.

[0013] In a specific embodiment, in step S1, the amount of 3,7-dimethyloct-6-en-1-ol used is 1.01-1.5 equivalents of propylene oxide; the inorganic base is one of potassium carbonate, cesium carbonate, and potassium phosphate, and the amount used is 3-5 equivalents of propylene oxide; the phase transfer agent is one of tetrabutylammonium bromide or methyltrioctylammonium chloride, and the amount used is 0.5-1 wt%.

[0014] In a specific embodiment, in step S2, the amount of modified propylene oxide is 9.1-9.15 equivalents of ethylene glycol; the alkaline catalyst is one of KOH and NaOH, and the amount is 0.11-0.55 wt% of ethylene glycol; the number average molecular weight of the modified polypropylene glycol is 1500-3500.

[0015] In one specific embodiment, the modified polybutylene succinate is prepared in-house, and the preparation steps are as follows: S1. Modified succinic acid Dissolve bromosuccinic acid in ethanol, add concentrated sulfuric acid, heat to 60-70 ℃ and react for 10-12 hours; cool, extract with NaHCO3 and ethyl acetate, concentrate the extract and dry to obtain diethyl bromosuccinate. Under a nitrogen atmosphere, diethyl brominated succinate, 5-norbornene-2-methylamine, a base, and the ligand Ruphos were dissolved in toluene; catalyst Pd2(dba)3 was added and the temperature was raised to 100-110 °C, and the reaction was stirred for 18-24 hours; the filtrate was cooled and concentrated, NaOH solution was added, and the temperature was raised to 75-80 °C for 12-16 hours for salting; after the reaction was completed, the mixture was cooled, and 0.1M HCl was added dropwise until a precipitate formed. The precipitate was filtered and dried to obtain the product N-norbornene-N-2-succinate diethyl ester. Diethyl N-norbornene-N-2-butanoic acid was dissolved in THF solution, NaOH was added, and the reaction was stirred at 40-50 °C for 5-7 hours until the reaction was complete. The pH was acidified to 2, and the mixture was extracted, concentrated, and dried to obtain modified succinic acid. S2. Esterification and Polycondensation Modified succinic acid and 1,4-butanediol were added to a reactor, purged with nitrogen three times, and heated to 150-160 °C, stirring until the solid dissolved. The temperature was then raised to 180-200 °C, and esterification was carried out for 2-3 hours. Tetrabutyl titanate was added as a catalyst, and the temperature was raised to 220-240 °C. The vacuum was slowly reduced to <100 Pa, and the reaction was carried out for 2-4 hours for polycondensation. When the hydroxyl value reached about 28-56.1 mg KOH / g, the nitrogen gas was turned off, the pressure was reduced, and the material was discharged after cooling to obtain modified polybutylene succinate.

[0016] In one specific embodiment, in step S1, the amount of ethanol used is 10-20 equivalents of bromosuccinic acid; the amount of concentrated sulfuric acid used is 5-10% equivalents of bromosuccinic acid. In a specific embodiment, in step S1, the amount of 5-norbornene-2-methylamine is 1.1-1.5 equivalents of diethyl brominated succinate; the base is one of potassium phosphate and cesium carbonate, and the amount is 3-5 equivalents of diethyl brominated succinate; the ligand is Ruphos, and the amount is 0.1-0.3 wt%; the amount of sodium hydroxide is 2-3 equivalents of brominated succinate.

[0017] In one specific embodiment, in step S1, the amount of NaOH used is 1-3 equivalents of diethyl N-norbornene-N-2-butanoate.

[0018] In one specific embodiment, in step S2, the amount of 1,4-butanediol used is 1.02-1.5 equivalents of modified succinic acid; the amount of tetrabutyl titanate used is 0.1-0.5 wt%; and the number average molecular weight of the modified polybutylene succinate is 2000-4000.

[0019] This invention also discloses a method for preparing a low-temperature coating paper-plastic composite reactive polyurethane hot melt adhesive, comprising the following steps: 1) Melt the diisocyanate into a clear liquid in an oven at 50-65 ℃ beforehand, and store it at the same temperature; 2) Add modified polyester polyol, modified polyether polyol, tackifying resin, polymerization inhibitor, and filler to a reactor, heat to 150-175 ℃ and mix, vacuum and dehydrate; cool to 90-115 ℃, add liquid isocyanate and polymerize for 1-3 hours, degas; add antioxidant, mix, discharge into a can and protect with nitrogen to obtain polyurethane hot melt adhesive.

[0020] Beneficial effects

[0021] This invention provides a low-temperature coating paper-plastic composite reactive polyurethane hot melt adhesive, which is obtained by co-polymerization of modified polyester polyol, modified polyether polyol, diisocyanate, tackifying resin, catalyst, filler, polymerization inhibitor, and antioxidant. By modifying the polyol, branched 5-norbornene-2-methylamine is introduced onto polybutylene succinate, and branched 3,7-dimethyloctyl-6-en-1-ol is introduced onto polypropylene glycol. The sterically hindered long branches can disrupt the original crystallinity of the polyol, reducing the chain segment packing density and imparting a melting temperature below 100 °C. Simultaneously, the free movement of the chain segments results in a lower viscosity, and 3,7-dimethyloctyl-6-en-1-ol possesses certain insect-repellent and mildew-resistant properties. The introduction of -NH groups into 5-norbornene-2-methylamine enhances the bonding ability with the substrate, ensuring its peel strength is within the target range. Attached Figure Description

[0022] Figure 1 This describes the synthesis pathway of polyurethane hot melt adhesive; Figure 2 The 1H NMR spectra of modified propylene oxide and modified succinic acid; Figure 3 The 1H NMR spectrum of modified succinic acid; Figure 4 Infrared spectra of modified polybutylene succinate, modified polypropylene glycol, and polyurethane hot melt adhesive; Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0025] The raw materials used in the examples and comparative examples are described below: Epichlorohydrin: 98%, product number E808995, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. 3,7-Dimethyloct-6-en-1-ol: 97%, catalog number A040585, purchased from Shanghai Anaiji Chemical Co., Ltd.; Phase transfer agent: Tetrabutylammonium bromide (TBAB), 99%, product number T818796, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Ethylene glycol: 99.7%, product number M0147827, purchased from Shanghai Anaiji Chemical Co., Ltd.; Bromosuccinic acid: 96%, product number B802431, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; 5-Norbornene-2-methylamine: 98%, product number N834686, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Catalyst 1: Tris(dibenzylacetone)dipalladium(0) (Pd2(dba)3), 98%, catalog number BD21135, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.; Ligand: 2-Dicyclohexylphosphine-2',6'-diisopropoxy-1,1'-biphenyl (Ruphos), 97%, catalog number BD74362, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.; 1,4-Butanediol: 98%, product number B802727, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Tackifying resin 1: Rosin resin; product number C832364, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Tackifying resin 2: Terpene resin; Product number BD01434229, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd. Catalyst 2: Dibutyltin dilaurate (DBTDL), 95%, product number D806313, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Isocyanate: 4,4'-methylenebis(phenyl isocyanate) (MDI), 98%, product number M813280, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Antioxidant 1010: 98%, product number P750268, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Polyether polyol: Polypropylene glycol, Mn2000, Shandong Lanxing Dongda Chemical Co., Ltd.; Polyester polyol: Polybutylene succinate, prepared in-house, the preparation steps are as follows: Succinic acid (1 equivalent) and 1,4-butanediol (1.3 equivalent) were added to a reactor, purged with nitrogen three times, heated to 155°C, and stirred until the solid dissolved. The temperature was then raised to 192°C and esterified for 3 hours. 0.3 wt% tetrabutyl titanate catalyst was added, the temperature was raised to 225°C, and a vacuum was slowly applied to <100 Pa. Polycondensation was carried out for 4 hours. When the hydroxyl value reached approximately 44.9 mg KOH / g, the nitrogen was turned off, the pressure was reduced, and the product was cooled and discharged to obtain polybutylene succinate with a number average molecular weight of 2500. Modified polypropylene glycol: prepared in-house, the preparation steps are as follows: S1. Modified propylene oxide Under ammonia protection, 3,7-dimethyloct-6-en-1-ol (1.2 equivalents), potassium carbonate (5 equivalents), and phase transfer agent tetrabutylammonium bromide (0.5 wt%) were added to anhydrous THF and stirred to dissolve. Epichlorohydrin (1 equivalent) was slowly added dropwise, and the mixture was heated to 45 °C. The reaction was completed after 18 hours. The mixture was cooled, filtered, and extracted to obtain the organic phase, which was then purified by column chromatography (12:1 petroleum ether: dichloromethane (v / v)) to obtain the modified epichlorohydrin product. The use of a weak base and low-temperature reaction conditions can reduce the generation of ring-opening side reactions in epichlorohydrin. S2. Epoxy ring-opening polymerization: Modified propylene oxide (9.1 equivalents) was dehydrated by passing it through an alkaline alumina column under nitrogen protection. Ethylene glycol (1 equivalent) and alkaline catalyst KOH (0.22 wt%) were vacuum dehydrated at 110 °C for 1 hour. After cooling, nitrogen was introduced, and anhydrous THF was added to dissolve the propylene oxide. The mixture was then cooled to 0 °C in an ice bath. The dehydrated modified propylene oxide was slowly added to the THF solution, and the mixture was heated to 75 °C and reacted for 12 hours until the reaction was complete. After cooling, 0.1 M HCl was added dropwise until neutral. The mixture was filtered to remove inorganic salts, concentrated, and then precipitated with cold methanol. After filtration and drying, modified polypropylene glycol with a hydroxyl value of approximately 56.1 mg KOH / g and a number average molecular weight of 2000 was obtained.

[0026] Modified polybutylene succinate: prepared in-house, the preparation steps are as follows: S1. Modified succinic acid Bromosuccinic acid (1 equivalent) was dissolved in ethanol (15 equivalents), concentrated sulfuric acid (6 equivalents) was added, and the mixture was heated to 60 °C and reacted for 10 hours. After cooling, NaHCO3 and ethyl acetate were added for extraction, the extract was concentrated and dried to obtain diethyl bromosuccinate. Under a nitrogen atmosphere, diethyl brominated succinate (1 equivalent), 5-norbornene-2-methylamine (1.3 equivalent), potassium phosphate (5 equivalent), and ligand Ruphos (0.1 wt%) were dissolved in toluene and bubbled for 30 minutes. Catalyst Pd₂(dba)₃ was added, and the mixture was bubbled for another 10 minutes. The temperature was raised to 100 °C, and the reaction was stirred for 24 hours until the reaction was complete. The reaction mixture was cooled to room temperature, the filtrate was concentrated, and NaOH solution (2 equivalents) was added. The mixture was heated to 80 °C and reacted for 12 hours for salting. After the reaction was complete, the mixture was cooled to a higher temperature, and 0.1 M HCl was added dropwise until a precipitate formed. The precipitate was filtered, washed with dilute hydrochloric acid, and dried to obtain the product, diethyl N-norbornene-N-2-succinate. Diethyl N-norbornene-N-2-succinate (1 equivalent) was dissolved in THF solution, and NaOH (3 equivalents) was added. The mixture was stirred at 50 °C for 5 hours until the reaction was complete. The pH was acidified to 2 with 1M HCl, and the mixture was extracted with ethyl acetate. The extract was concentrated and dried to obtain modified succinic acid. S2. Esterification and Polycondensation Modified succinic acid (1 equivalent) and 1,4-butanediol (1.3 equivalent) were added to a reactor, purged with nitrogen three times, heated to 155 °C, and stirred until the solid dissolved. The temperature was then raised to 192 °C and esterified for 3 hours. 0.3 wt% tetrabutyl titanate catalyst was added, the temperature was raised to 225 °C, and a vacuum was slowly applied to <100 Pa. Polycondensation was carried out for 4 hours. When the hydroxyl value reached approximately 44.9 mg KOH / g, the nitrogen was turned off, the pressure was reduced, and the product was cooled and discharged to obtain modified polybutylene succinate with a number average molecular weight of 2500.

[0027] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0028] Examples and Comparative Examples A low-temperature coating paper-plastic composite reactive polyurethane hot melt adhesive, the weight parts of which are shown in Table 1, is prepared as follows: 3) Melt the isocyanate into a clear liquid in a 50°C oven beforehand, and store it at the same temperature; 4) Add modified polyester polyol, modified polyether polyol, tackifying resin, polymerization inhibitor, and filler to a reactor, heat to 150-175 ℃ and mix, vacuum and dehydrate; cool to 90-115 ℃, add liquid isocyanate and polymerize for 1-3 hours, degas; add antioxidant, mix, discharge into a can and protect with nitrogen to obtain polyurethane hot melt adhesive.

[0029] Table 1. Paper-Plastic Composite Reactive Polyurethane Hot Melt Adhesive for Low-Temperature Coating (parts by weight)

[0030] The following performance tests were conducted on a low-temperature coating paper-plastic composite reactive polyurethane hot melt adhesive prepared in the examples and comparative examples. The results are shown in the attached figures and Table 2, respectively.

[0031] 1. Proton NMR spectroscopy: The synthesized modified propylene oxide and modified succinic acid samples were dissolved in deuterated DMSO to prepare a 1.0 wt% solution. The NMR spectrum of the samples was measured using a proton NMR spectrometer at 400 MHz. The results are as follows: Figure 2 and 3 As shown.

[0032] 2. Infrared Spectroscopy: Modified polypropylene glycol, modified polybutylene succinate, and polyurethane hot melt adhesive were mixed with potassium bromide at a ratio of 1:50 to prepare a tablet. An Avatar 380 spectrometer was used for this test. Before testing, a blank background was scanned, followed by the placement of the tablet sample for measurement. The scanning range was 500-4000 cm⁻¹. -1 The result is as follows Figure 4 As shown.

[0033] 3. Viscosity: The test was conducted according to GB / T 2794-1995 standard. The temperature was set to 90 ℃. After heating the hot melt adhesive to a flowing state, it was poured into the measuring cup that came with the viscometer. The lid was closed and kept warm for 20 minutes to ensure that the internal temperature of the hot melt adhesive was uniform before measurement.

[0034] 4. Initial and final tack strength: Tested according to GB / T528-1998 standard. Take two pieces of kraft paper and PET film with a width of 2.5 cm, apply adhesive with a thickness of 0.1 mm, heat in an oven at 60 ℃ for 10 min, and after bonding, apply pressure with a 3 kg weight for a certain period of time. After releasing the pressure and letting it stand for 10 min, measure the initial tack strength (N / mm) using a universal tensile testing machine. After 24 h, measure the final tack strength (N / mm) according to GB / T528-1998. The tensile testing machine is a WDW-T type manufactured by Jinan Nair Testing Machine Co., Ltd.

[0035] Table 2 Performance test results of polyurethane hot melt adhesive

[0036] From the appendix Figure 2 and 3 The 1H NMR spectrum shows that the integral number is consistent with the number of hydrogen atoms in the molecule, and the shifts of each hydrogen atom in the spectrum are consistent with their chemical environment, indicating that the target compounds modified propylene oxide and modified succinic acid were successfully synthesized.

[0037] From the appendix Figure 4 It can be seen that the peak occurs at 3520-3400 cm. -1 The stretching vibrations, attributed to the -OH group of polyols, peak at 2980–2850 cm⁻¹. -1 The stretching vibrations attributed to CH peak at 1112 cm⁻¹. -1 The nearby structures are attributed to the stretching vibrations of the polyol COC. In the modified polypropylene glycol (PPG) spectrum, at 1644 cm⁻¹... -1 The presence of a C=C vibration at this point indicates successful insertion of the citronellol side chain. In the spectrum of modified polybutylene succinate (PBS), the 1750-1700 cm⁻¹... -1 This is the characteristic absorption signal of the -C=O group in ester carbonyl groups -C=O and -NHCOO, with the peak appearing at 3300 cm⁻¹. -1 This is classified as CN stretching vibration, with peak values ​​occurring at 1650-1500 cm⁻¹. -1 The stretching vibration is attributed to the secondary amine NH, and a signal belonging to C=C can also be observed at 1644 cm⁻¹. -1This indicates that the norbornene structure was successfully incorporated into the PBS side chain. In the polyurethane hot melt adhesive spectrum, at 2270-2250 cm⁻¹... -1 The peak is the asymmetric vibration peak of -NCO in isocyanate MDI, and the absorption peak of -OH disappears, while the peak at 3400-3300 cm⁻¹ appears. -1 A new signal appeared at the point, which is the stretching vibration peak of NH in -NHCOO. It also contains characteristic signals of two other polyols, indicating that the two modified polyols and MDI reacted to prepare polyurethane hot melt adhesive.

[0038] As shown in Table 2, compared to the comparative examples which used polybutylene succinate and polypropylene glycol with higher crystallinity, the polyurethane hot melt adhesive with side chain modification has lower viscosity and an activation temperature of 80-105 °C. Furthermore, its initial tack is above 1 N, and its final adhesion is between 5 N and 15 N, indicating its suitability for low-temperature coated paper-plastic composites. Comparative Examples 1 and 2, using unmodified polybutylene succinate and polypropylene glycol respectively, exhibited excessively high viscosity and strong adhesion, making them unsuitable for paper-plastic products. Table 2 also shows that adjusting the raw material input amount adjusts the polymer's crosslinking degree, thereby adjusting a series of properties such as viscosity, adhesion, and activation temperature.

[0039] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-temperature coating paper-plastic composite reactive polyurethane hot melt adhesive, characterized in that, The polyurethane hot melt adhesive comprises, by weight, the following components: 50-70 parts modified polyester polyol, 30-50 parts modified polyether polyol, 15-24 parts diisocyanate, 5-30 parts tackifying resin, 0.1-1 part catalyst, 5-35 parts filler, 0.05-2 parts polymerization inhibitor, and 0.1-0.5 parts antioxidant; the modified polyester polyol is modified polybutylene succinate; the modified polyether polyol is modified polypropylene glycol; the molecular formulas of the modified polybutylene succinate and the modified polypropylene glycol are shown in Formula 1 and Formula 2, respectively. Formula 1 Equation 2.

2. The polyurethane hot melt adhesive as described in claim 1, characterized in that, The diisocyanate is one of 4,4'-methylenebis(phenyl isocyanate), methylcyclohexyl diisocyanate, and isoflurane diisocyanate; the R value of the diisocyanate is 1-2.

1.

3. The polyurethane hot melt adhesive as described in claim 1, characterized in that, The tackifying resin is one of rosin resin, terpene resin, and acrylic resin; the catalyst is dibutyltin dilaurate; the filler is one or more of calcium carbonate, carbon black, and silicon dioxide; the polymerization inhibitor is one of phosphoric acid and p-toluenesulfonic acid; and the antioxidant is antioxidant 1010.

4. The polyurethane hot melt adhesive as described in claim 1, characterized in that, The preparation of the modified polypropylene glycol includes the following steps: S1. Modified propylene oxide Under ammonia protection, 3,7-dimethyloct-6-en-1-ol, inorganic base, and phase transfer agent were added to anhydrous THF and stirred to dissolve. Epichlorohydrin was slowly added dropwise, and the temperature was raised to 35-50 °C. The reaction was completed after 12-24 hours. The mixture was cooled, filtered, and extracted to obtain the organic phase, which was then purified by column chromatography to obtain the product modified propylene oxide. S2. Epoxy ring-opening polymerization: Ethylene glycol and an alkaline catalyst were dehydrated under vacuum at 100-120 °C for 1-3 hours. After cooling, nitrogen gas was introduced and anhydrous THF was added in an ice bath. Dehydrated modified propylene oxide was slowly added dropwise, and the temperature was raised to 60-80 °C for 8-14 hours to complete the reaction. After cooling, the pH was adjusted to neutral, filtered, concentrated, and cold methanol was added dropwise to precipitate the polymer. After filtration and drying, modified polypropylene glycol with a hydroxyl value of approximately 32-74.8 mgKOH / g was obtained.

5. The polyurethane hot melt adhesive as described in claim 4, characterized in that, In step S1, the amount of 3,7-dimethyloct-6-en-1-ol used is 1.01-1.5 equivalents of epichlorohydrin; the inorganic base is one of potassium carbonate, cesium carbonate, and potassium phosphate, and the amount used is 3-5 equivalents of epichlorohydrin; the phase transfer agent is one of tetrabutylammonium bromide or methyltrioctylammonium chloride, and the amount used is 0.5-1 wt%.

6. The polyurethane hot melt adhesive as described in claim 4, characterized in that, In step S2, the amount of modified propylene oxide is 9.1-9.15 equivalents of ethylene glycol; the alkaline catalyst is one of KOH and NaOH, and the amount is 0.11-0.55 wt% of ethylene glycol; the number average molecular weight of the modified polypropylene glycol is 1500-3500.

7. The polyurethane hot melt adhesive as described in claim 1, characterized in that, The modified polybutylene succinate was prepared in-house, and the preparation steps are as follows: S1. Modified succinic acid Dissolve bromosuccinic acid in ethanol, add concentrated sulfuric acid, heat to 60-70 ℃ and react for 10-12 hours; cool, extract with NaHCO3 and ethyl acetate, concentrate the extract and dry to obtain diethyl bromosuccinate. Under a nitrogen atmosphere, diethyl bromide, 5-norbornene-2-methylamine, base and ligand Ruphos were dissolved in toluene; catalyst Pd2(dba)3 was added and the temperature was raised to 100-110 °C, and the reaction was stirred for 18-24 hours. Cool and concentrate the filtrate, add NaOH solution, heat to 75-80 ℃ and react for 12-16 hours for salting; after the reaction is completed, cool and add 0.1M HCl dropwise until a precipitate is formed, filter and dry to obtain the product N-norbornene-N-2-butanoic acid diethyl ester; Diethyl N-norbornene-N-2-butanoic acid was dissolved in THF solution, NaOH was added, and the reaction was stirred at 40-50 °C for 5-7 hours until the reaction was complete. The pH was acidified to 2, and the mixture was extracted, concentrated, and dried to obtain modified succinic acid. S2. Esterification and Polycondensation Modified succinic acid and 1,4-butanediol were added to a reactor, purged with nitrogen three times, and heated to 150-160 °C, stirring until the solid dissolved. The temperature was then raised to 180-200 °C, and esterification was carried out for 2-3 hours. Tetrabutyl titanate was added as a catalyst, and the temperature was raised to 220-240 °C. The vacuum was slowly reduced to <100 Pa, and the reaction was carried out for 2-4 hours for polycondensation. When the hydroxyl value reached about 28-56.1 mg KOH / g, the nitrogen gas was turned off, the pressure was reduced, and the material was discharged after cooling to obtain modified polybutylene succinate.

8. The polyurethane hot melt adhesive as described in claim 7, characterized in that, In step S1, the amount of ethanol used is 10-20 equivalents of bromosuccinic acid; the amount of concentrated sulfuric acid used is 5-10% equivalents of bromosuccinic acid; the amount of 5-norbornene-2-methylamine used is 1.1-1.5 equivalents of diethyl bromosuccinate; the base is one of potassium phosphate and cesium carbonate, and the amount used is 3-5 equivalents of diethyl bromosuccinate; the ligand is Ruphos, and the amount used is 0.1-0.3 wt%; the amount of sodium hydroxide used is 2-3 equivalents of bromosuccinic acid; and the amount of NaOH used is 1-3 equivalents of diethyl N-norbornene-N-2-succinate.

9. The polyurethane hot melt adhesive as described in claim 7, characterized in that, In step S2, the amount of 1,4-butanediol used is 1.02-1.5 equivalents of modified succinic acid; the amount of tetrabutyl titanate used is 0.1-0.5 wt%; and the number average molecular weight of modified polybutylene succinate is 2000-4000.

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