Oil acid resistant reactive polyurethane hot melt adhesive and preparation method thereof

Abstract

The application discloses an oil acid-resistant reactive polyurethane hot melt adhesive and a preparation method thereof. The formula of the adhesive comprises polyester polyol, polyether polyol, polycarbonate polyol, self-made polyfluorosilicone polyol, polyisocyanate, catalyst and additive. The self-made polyfluorosilicone polyol is added in the adhesive, and the polyester polyol, the polyether polyol and the polycarbonate polyol are combined to react with the polyisocyanate to prepare a polyurethane prepolymer. On the basis of retaining high bonding strength of the polyurethane adhesive, the oil acid-resistant performance of the polyurethane hot melt adhesive is greatly improved due to the introduction of the fluorine-containing group with great electron-withdrawing effect. The oil acid-resistant performance is realized by introducing the polyfluorosilicone chain segment instead of unilaterally improving the crosslinking density, so that the hot melt adhesive has good low-temperature flexibility and stable impact resistance after curing. The application can be widely applied to structural bonding and protection of wearable devices including smart watches, and has wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to an oleic acid-resistant moisture-curing reactive polyurethane hot melt adhesive and its preparation method. Background Technology

[0002] Adhesives are widely used in the consumer electronics industry, such as wearable devices, smartphones, tablets and other digital products.

[0003] Taking wearable devices as an example, with technological advancements and improved living standards, more and more people rely on smartwatches to monitor health indicators and process information. Smartwatches have precise components and complex structures, requiring them to maintain reliability when exposed to shocks, pressure, vibrations, extreme temperatures, and water or moisture. In this demand for compact yet powerful devices, the advantages of adhesives are obvious.

[0004] In current structural bonding solutions, the bonding of smartwatch screens to frames and the sealing of sensors are mostly accomplished using polyurethane hot melt adhesives in conjunction with various automated dispensing equipment. Polyurethane adhesives have good adhesion, fast curing speed, low-temperature resistance, moisture resistance, aging resistance, low VOC content, and are easy to apply, thus leading to their rapid development in the field of structural bonding.

[0005] However, as wearable devices that are used for extended periods and in continuous contact with the human body, smartwatches come into contact with sweat, sebum, oleic acid, and other substances secreted by the skin. With prolonged contact, these substances gradually seep into the smartwatch, causing corrosion and reducing the adhesive strength, eventually leading to bond failure and cohesive or adhesive breakdown, macroscopically manifested as delamination. Research indicates that the presence of oleic acid is the primary cause of delamination in polyurethane adhesives; therefore, developing a polyurethane adhesive product that effectively resists oleic acid corrosion is of paramount importance.

[0006] To date, there are no polyurethane adhesive products on the market that can effectively resist oleic acid corrosion. The development of polyurethane adhesives is still largely limited to meeting conventional market demands by controlling the hard and soft segments.

[0007] Patent CN112795350B discloses an oleic acid-resistant reactive polyurethane hot melt adhesive. Its polyols utilize polycarbonate diols, polyester diols, and polyether diols with special short-chain structures, resisting oleic acid erosion by increasing the system's polarity and crosslinking density. However, excessively increasing the crosslinking density, while achieving high adhesive strength and oleic acid resistance, negatively impacts the toughness of the cured product, significantly reducing the adhesive's resistance to mechanical vibration and drop tests. This polyurethane hot melt adhesive cannot meet the structural bonding requirements of wearable devices, including smartwatches. Summary of the Invention

[0008] To address the aforementioned problems in the prior art, this invention aims to provide a reactive polyurethane hot melt adhesive that not only meets the high bonding strength requirements of wearable device adhesives but also possesses good resistance to oleic acid aging, as well as good toughness and impact resistance.

[0009] The specific technical solution is as follows:

[0010] An oleic acid-resistant reactive polyurethane hot melt adhesive, characterized in that the polyurethane hot melt adhesive is a 100% solids content, single-component, solvent-free, moisture-curing reactive polyurethane hot melt adhesive, and its formulation comprises the following components by weight: 30-60 parts polyester polyol, 10-30 parts polyether polyol, 1-10 parts polycarbonate polyol, 0.1-5 parts self-made polyfluorosiloxane polyol, 10-30 parts polyisocyanate, and 0.1-0.5 parts catalyst.

[0011] The self-made polyfluorosiloxane polyol is a polyfluorosiloxane diol with the following structure (Formula I):

[0012]

[0013] (Formula I)

[0014] Where m = 5~50, n = 5~50.

[0015] Furthermore, the self-made polyfluorosiloxane polyol is prepared according to the following steps:

[0016] (1) Synthesis of fluorine-containing monomers

[0017] Equimolar amounts of 3-fluoropropene and methyldichlorosilane were introduced into an ultra-low temperature high-pressure reactor using platinum black as a catalyst. The reaction was stirred for 2–5 hours at 1.2 MPa and 0 °C until completion. The pressure was released and the mixture was allowed to return to room temperature, yielding a transparent, colorless liquid. This liquid was then added dropwise to a 1 mol·L⁻¹ solution with stirring. -1 A white solid was obtained by drying in potassium hydroxide solution under vacuum at room temperature for 24 hours, ultimately yielding a fluorine-containing monomer (referred to as A). The reaction formula is as follows:

[0018]

[0019] (2) Synthesis of hydroxyl-terminated polyfluorosiloxane polyols

[0020] The dried fluorinated monomer (referred to as A) prepared in the previous reaction was added to a three-necked flask in a molar ratio of 1:10 to 10:1 with commercially available octamethylcyclotetrasiloxane (referred to as B). Tetramethylammonium hydroxide (100-300 ppm relative to the total amount of A and B) was added as a catalyst. The mixture was slowly heated to 70-80°C and stirred at 300-500 rpm for 0.5-1 hour to obtain a colorless, transparent liquid. Then, 10,000-100,000 ppm of water was added as a capping agent, and the temperature was raised to 100-110°C, reacting for 0.5-1 hour. The temperature was further raised to 120-130°C, and low-boiling components were removed under vacuum until the volatile content was less than 0.5%, yielding the final product: a hydroxyl-capped polyfluorosiloxane polyol. The reaction formula is as follows:

[0021]

[0022] Regarding a further definition of the self-made polyfluorosiloxane polyol (Formula I) described in this invention, the self-made polyfluorosiloxane polyol is a hydroxyl-terminated polyfluorosiloxane polyol.

[0023] Furthermore, the self-made polyfluorosiloxane polyol is a polyfluorosiloxane polyol with a degree of polymerization of 10~100 (where m=5~50, n=5~50).

[0024] Furthermore, the molecular weight of the self-made polyfluorosiloxane polyol is 1,000 to 10,000.

[0025] Furthermore, the viscosity of the self-made polyfluorosiloxane polyol is 50~800cps (25℃).

[0026] Furthermore, as a preferred raw material, wherein:

[0027] The polyester polyol is selected from one or more of the following: hexanediol adipate, hexanediol terephthalate, polybutylene adipate-terephthalate, polycaprolactone diol, polyhexanediol-neopentyl glycol adipate diol, or poly-2-methyl-1,3-propanediol terephthalate diol.

[0028] The polyether polyol is selected from one or more of polyethylene glycol, polypropylene glycol, or polytetrahydrofuran glycol.

[0029] The polycarbonate polyol is selected from one or more of polycarbonate 1,6-hexanediol diol, polycarbonate-1,4-butanediol-1,6-hexanediol diol, polycaprolactone hexylene diol, or polycaprolactone hexylene diol.

[0030] The polyisocyanate is selected from one or more of 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), toluene diisocyanate (TDI), phenyl dimethyl diisocyanate (XDI), tetramethylphenyl dimethylene diisocyanate (TMXDI), 1,6-hexamethylene diisocyanate (HDI), or isophorone diisocyanate (IPDI).

[0031] The catalyst is selected from one or more of 2,2-dimorpholine diethyl ether, N-methylmorpholine, N-ethylmorpholine, N,N-dimethylbenzylamine, triethylenediamine, dibutyltin dilaurate, or dimethyltin dinedecanoate.

[0032] Furthermore, the oleic acid-resistant reactive polyurethane hot melt adhesive also includes 0-1 parts of additives. Substances and additives that can be used in the additives of the present invention include, optionally, one or more of plasticizers, stabilizers, antioxidants, silane coupling agents, resins, polymers, dyes or fillers.

[0033] This invention also discloses a method for preparing an oleic acid-resistant moisture-curing reactive polyurethane hot melt adhesive, comprising the following steps:

[0034] (1) Put 30-60 parts of polyester polyol, 10-30 parts of polyether polyol, 1-10 parts of polycarbonate polyol and 0.1-5 parts of self-made polyfluorosiloxane polyol into a three-necked flask, and vacuum dehydrate at 110-120°C for 1-2 hours at a speed of 300-500 r / min until the moisture content is below 250 ppm.

[0035] (2) Under nitrogen protection, the mixed polyol is cooled to 70~80℃, 10~30 parts of polyisocyanate are added, and the reaction is carried out at 100~110℃ for 1~2 hours.

[0036] (3) Under nitrogen protection, add 0.1 to 0.5 parts of catalyst and 0 to 1 part of additive at 100 to 110°C and stir for 0.5 to 1 hour.

[0037] (4) Under nitrogen protection, hot discharge into a hot melt adhesive tube, put into an aluminum foil bag containing desiccant, vacuum and store at room temperature.

[0038] The polyurethane adhesive prepared according to the present invention is a hot-melt adhesive, which is solid at 25°C but has a viscosity of 1,500~10,000 cps at 110°C. The polyurethane hot-melt adhesive exhibits high bond strength and good toughness after application and curing, and meets the requirements for resistance to oleic acid aging.

[0039] The beneficial effects of this invention are as follows:

[0040] (1) This invention produces a hydroxyl-terminated polyfluorosiloxane and uses it as a polyol, which is then combined with polyester polyol, polyether polyol, and polycarbonate polyol to react with polyisocyanate to prepare a polyurethane prepolymer. While retaining the high adhesive strength of polyurethane adhesives, the introduction of fluorinated groups with a large electron-withdrawing effect significantly improves the oleic acid resistance of polyurethane hot melt adhesives. The inventors further discovered that even when the self-made polyfluorosiloxane polyol is added at a ratio of less than 1% (based on the total weight of the hot melt adhesive), the oleic acid resistance of the hot melt adhesive can still be effectively improved.

[0041] (2) The polyfluorosiloxane side chain introduced in this invention is monofluoropropyl. Compared with perfluoroalkyl and polyfluoroalkyl (PFAS) organofluorine compounds, monofluoropropyl complies with the EU POPs regulations and REACH regulations and has no risk of persistent organic pollution.

[0042] (3) This invention achieves oleic acid resistance by introducing polyfluorosiloxane segments, rather than by unilaterally increasing the crosslinking density, giving the hot melt adhesive good low-temperature flexibility and significant impact resistance after curing. It can meet the structural bonding and protection requirements of adhesives for wearable devices, representing a significant and substantial improvement. Detailed Implementation

[0043] The principles and features of the present invention are described below with reference to embodiments and comparative examples. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Any product identical or similar to the present invention, derived by any person based on the teachings of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0044] The self-made polyfluorosiloxane polyol disclosed in this invention is prepared according to the following steps:

[0045] Preparation Example 1:

[0046] (1) Synthesis of fluorine-containing monomers

[0047] Equimolar amounts of 3-fluoropropylene and methyldichlorosilane were introduced into an ultra-low temperature high-pressure reactor using platinum black as a catalyst. The mixture was stirred for 3 hours at 1.2 MPa and 0°C until the reaction was complete. After depressurization and restoration to room temperature, a transparent, colorless liquid was obtained. This liquid was then added dropwise to a 1 mol·L⁻¹ potassium hydroxide solution with stirring to obtain a white solid. This solid was dried under vacuum at room temperature for 24 hours to finally obtain the fluorinated monomer.

[0048] (2) Synthesis of hydroxyl-terminated polyfluorosiloxane diols

[0049] The dried fluorinated monomer prepared in the previous reaction was added to a three-necked flask at a molar ratio of 1:1 with commercially available octamethylcyclotetrasiloxane. 150 ppm of tetramethylammonium hydroxide was added as a catalyst, and the mixture was slowly heated to 70°C and stirred at 500 rpm for 45 min to obtain a colorless, transparent liquid. Then, 50,000 ppm of water was added as a capping agent, and the mixture was heated to 110°C and reacted for 45 min. The temperature was further increased to 125°C, and low-boiling compounds were removed under vacuum until the volatile content was less than 0.5%, yielding the final product, hydroxyl-capped polyfluorosiloxane diol.

[0050] The obtained polyfluorosiloxane diol has a molecular weight of approximately 2,000 and a viscosity of approximately 150 cps.

[0051] Preparation Example 2:

[0052] (1) Synthesis of fluorine-containing monomers

[0053] Same as preparation example 1.

[0054] (2) Synthesis of hydroxyl-terminated polyfluorosiloxane diols

[0055] The dried fluorinated monomer prepared in the previous reaction was added to a three-necked flask in a 1:1 molar ratio with commercially available octamethylcyclotetrasiloxane. 300 ppm of tetramethylammonium hydroxide was added as a catalyst, and the mixture was slowly heated to 80°C and stirred at 500 rpm for 1 hour to obtain a colorless, transparent liquid. Then, 10,000 ppm of water was added as a capping agent, and the mixture was heated to 110°C and reacted for 1 hour. The temperature was further increased to 125°C, and low-boiling compounds were removed under vacuum until the volatile content was less than 0.5%, yielding the final product, a hydroxyl-capped polyfluorosiloxane diol.

[0056] The obtained polyfluorosiloxane diol has a molecular weight of approximately 6,000 and a viscosity of approximately 550 cps.

[0057] The self-made polyfluorosiloxane diols used in Examples 1-5 below were all obtained through the above steps.

[0058] Example 1:

[0059] An oleic acid-resistant reactive polyurethane hot melt adhesive, comprising the following raw materials:

[0060]

[0061] In this embodiment, the preparation method is as follows:

[0062] (1) 26 parts of polyhexanediol adipate, 24 parts of polyhexanediol terephthalate, 19 parts of polypropylene glycol, 9 parts of poly(1,6-hexanediol carbonate) diol and 2.5 parts of self-made polyfluorosiloxane diol (Preparation Example 1) were put into a three-necked flask and dehydrated under vacuum at 115°C for 2 hours at a speed of 400 r / min until the moisture content was less than 250 ppm.

[0063] (2) Under nitrogen protection, the mixed polyol was cooled to 80°C, and 19 parts of 4,4'-diphenylmethane diisocyanate were added. The mixture was reacted at 110°C for 1 hour.

[0064] (3) Under nitrogen protection, add 0.5 parts of catalyst 2,2-dimorpholine diethyl ether at 110℃ and stir for 30 min.

[0065] (4) Under nitrogen protection, hot discharge into a hot melt adhesive tube, put into an aluminum foil bag containing desiccant, vacuum and store at room temperature.

[0066] Example 2:

[0067] An oleic acid-resistant reactive polyurethane hot melt adhesive, comprising the following raw materials:

[0068]

[0069] The preparation method of this embodiment is the same as that of Example 1, except that the weight of the self-made polyfluorosiloxane diol (Preparation Example 1) in this embodiment is 0.25 parts.

[0070] Example 3:

[0071] An oleic acid-resistant reactive polyurethane hot melt adhesive, comprising the following raw materials:

[0072]

[0073] The preparation method of this embodiment is the same as that of Example 1, except that the self-made polyfluorosiloxane diol in this embodiment is prepared in Example 2 and the weight part is 0.25 parts.

[0074] Example 4:

[0075] An oleic acid-resistant reactive polyurethane hot melt adhesive, comprising the following raw materials:

[0076]

[0077] In this embodiment, the preparation method is as follows:

[0078] (1) 30 parts of polycaprolactone diol, 25 parts of polyethylene terephthalate, 17 parts of polyethylene glycol, 8 parts of poly(1,6-hexanediol carbonate) diol and 0.5 parts of self-made polyfluorosiloxane diol (Preparation Example 1) were put into a three-necked flask and dehydrated under vacuum at 110°C for 1.5 hours at a speed of 400 r / min until the moisture content was lower than 250 ppm.

[0079] (2) Under nitrogen protection, the mixed polyol was cooled to 70°C, and 19 parts of 4,4'-diphenylmethane diisocyanate were added. The mixture was reacted at 100°C for 1 hour.

[0080] (3) Under nitrogen protection, add 0.5 parts of catalyst 2,2-dimorpholine diethyl ether at 100℃ and stir for 30 min.

[0081] (4) Under nitrogen protection, hot discharge into a hot melt adhesive tube, put into an aluminum foil bag containing desiccant, vacuum and store at room temperature.

[0082] Example 5:

[0083] An oleic acid-resistant reactive polyurethane hot melt adhesive, comprising the following raw materials:

[0084]

[0085] In this embodiment, the preparation method is as follows:

[0086] (1) 35 parts of polycaprolactone diol, 21 parts of poly(adipate-butylene terephthalate), 10 parts of polyethylene glycol, 10 parts of polytetrahydrofuran diol, 4 parts of polycaprolactone hexylene diol, and 0.1 parts of self-made polyfluorosiloxane diol (Preparation Example 2) were put into a three-necked flask and dehydrated under vacuum at 110°C for 1.5 hours at a speed of 400 r / min until the moisture content was lower than 250 ppm.

[0087] (2) Under nitrogen protection, the mixed polyol was cooled to 70°C, and 19 parts of 4,4'-diphenylmethane diisocyanate were added. The mixture was reacted at 100°C for 1 hour.

[0088] (3) Under nitrogen protection, add 0.5 parts of catalyst 2,2-dimorpholine diethyl ether at 100℃ and stir for 30 min.

[0089] (4) Under nitrogen protection, hot discharge into a hot melt adhesive tube, put into an aluminum foil bag containing desiccant, vacuum and store at room temperature.

[0090] Comparative Example 1:

[0091] Comparative Example 1 includes the following raw materials:

[0092]

[0093] In this comparative example, the preparation method is as follows:

[0094] (1) 26 parts of polyhexanediol adipate, 24 parts of polyhexanediol terephthalate, 19 parts of polypropylene glycol, and 9 parts of poly(1,6-hexanediol carbonate) diol were put into a three-necked flask and dehydrated under vacuum at 115°C for 2 hours at 400 r / min until the moisture content was less than 250 ppm.

[0095] (2) Under nitrogen protection, the mixed polyol was cooled to 80°C, 19 parts of isocyanate were added, and the reaction was carried out at 110°C for 1 hour.

[0096] (3) Under nitrogen protection, add 0.5 parts of catalyst 2,2-dimorpholine diethyl ether at 110℃ and stir for 30 min.

[0097] (4) Under nitrogen protection, hot discharge into a hot melt adhesive tube, put into an aluminum foil bag containing desiccant, vacuum and store at room temperature.

[0098] Comparative Example 2:

[0099] Comparative Example 2 uses the method disclosed in Chinese invention patent document "An Oleic Acid Reactive Polyurethane Hot Melt Adhesive" (Patent No.: CN112795350B) (Example 1) to prepare the hot melt adhesive.

[0100] Comparative Example 2 includes the following raw materials:

[0101]

[0102] In this comparative example, the preparation method is as follows:

[0103] (1) Add 30 parts of polyethylene adipate diol, 10 parts of polypropylene glycol, 25 parts of polycarbonate cyclohexyldiethanol-1,6-hexanediol diol, 1 part of chain extender 1,4-cyclohexyldiol, and 0.6 parts of antioxidant 1010 into a three-necked flask, and dehydrate under vacuum at 120°C for 2 hours at a speed of 400 r / min until the moisture content is below 250 ppm.

[0104] (2) Under nitrogen protection, the mixed polyol was cooled to 80°C, and 35.55 parts of terephthalic diisocyanate were added. The mixture was reacted at 100°C for 15 min.

[0105] (3) Under nitrogen protection, 0.04 parts of catalyst bismuth neodecanoate were added at 100℃ and stirred for 45 min; 1 part of coupling agent γ-mercaptopropyltrimethoxysilane and 0.1 part of catalyst 2,2-dimorpholine diethyl ether were added and stirred for 45 min.

[0106] (4) Under nitrogen protection, hot discharge into a hot melt adhesive tube, put into an aluminum foil bag containing desiccant, vacuum and store at room temperature.

[0107] The hot melt adhesive samples prepared in Examples 1-5 were compared with the hot melt adhesive samples prepared in Comparative Examples 1-2. The test items included melt viscosity, open time, bond strength (10min positioning strength, 24h final bond strength), drop ball impact test and oleic acid resistance test.

[0108] I. Materials and Methods

[0109] 1.1 Experimental Location: Xintai Yonghe (Yantai) New Materials Co., Ltd.

[0110] 1.2 Experimental Testing:

[0111] (1) Melt viscosity: According to the test method of GB / T 21059-2007, the sealed polyurethane hot melt adhesive was placed in a syringe heater at 110℃ and kept for 10 minutes. At this time, the hot melt adhesive had become a molten fluid. It was then quickly poured into the sleeve of the Brookfield DV viscometer. The heater temperature was set at 110℃ and kept for 10 minutes to make the internal temperature of the hot melt adhesive uniform and defoamed. The viscosity at 10 rpm on a 27# rotor was tested at 110℃.

[0112] (2) Open time: Refer to the test method of HG / T3716-2003, apply a 0.15-0.2mm thick layer of adhesive to the release paper, press the paper strip into the melt at a specific time, and the open time is when the paper strip fibers are no longer torn.

[0113] (3) Adhesive strength (10-min positioning strength, 24-hour final adhesive strength): According to the test method of GB / T7124-2008, a standard polycarbonate (PC) sample was used. The 26# needle was heated to 130°C, the tube was heated to 100°C, the dispensing pressure was 0.4 MPa, and the dispensing time was 3 seconds. After dispensing, the test piece was naturally pressed together, and then pressed with a 200g cap for 10 minutes. The 10-min positioning shear strength was measured. Similarly, after pressing, it was naturally placed in an environment of 25°C and 50% RH for 24 hours to cure, and the 24-hour final shear strength was measured.

[0114] (4) Drop ball impact test: Using a dispensing machine, apply adhesive at 110℃ to form a 25mm×25mm rectangular adhesive frame on the PC substrate with a width of approximately 1mm. Then, attach another PC substrate to the PC substrate. After dispensing and bonding, cure the sample in an environment of 25℃ and 50%RH for 24 hours. Place the bonded sample horizontally and use a drop ball tester to repeatedly drop a 200g weight from a height of 200mm onto one of the PC substrates of the prepared sample until the prepared sample is separated by impact. Record the number of impacts displayed by the instrument. Each sample is tested 3 times, and the average value is taken.

[0115] (5) Oleic acid resistance test: Prepare the sample according to the method in (3), let it cure naturally in an environment of 25℃ and 50%RH for 24 hours, then immerse the sample in oleic acid at 60℃ for 168 hours, take it out and wipe the oleic acid off the sample surface, test the bonding strength and calculate the bonding strength retention rate.

[0116] The test data are shown in Table 1. The beneficial effects of the present invention will be further illustrated below with reference to the experimental data.

[0117] Table 1

[0118]

[0119] II. Results and Analysis

[0120] The test data comparison between Examples 1-5 and Comparative Examples 1-2 in Table 1 shows that Examples 1-5 introduced a self-made polyfluorosiloxane diol as one of the polyols, combined with polyester polyols, polyether polyols, and polycarbonate polyols, and reacted with polyisocyanates to prepare polyurethane prepolymers. While retaining the high adhesive strength of the polyurethane adhesive, the oleic acid resistance of the polyurethane hot melt adhesive was significantly improved compared to Comparative Examples 1-2. The test data comparison between Examples 2-3 and Example 1 shows that even when the self-made polyfluorosiloxane polyol is added at a proportion of less than 1%, the oleic acid resistance of the hot melt adhesive can be effectively improved. Compared with Example 1, Examples 4-5 show that the addition of the self-made polyfluorosiloxane polyol can effectively improve the oleic acid resistance of hot melt adhesives based on different compositions for various polyester polyols, polyether polyols, and polycarbonate polyols.

[0121] Furthermore, in the drop ball impact test, Examples 1-5 exhibited drop resistance comparable to Comparative Example 1, indicating that the introduction of polyfluorosiloxane diol still allows the hot melt adhesive to maintain good low-temperature flexibility and stable impact resistance after curing. Additionally, Comparative Example 2 shows that unilaterally increasing the crosslinking density to improve oleic acid resistance significantly reduces the low-temperature flexibility and impact resistance of the cured hot melt adhesive.

[0122] Therefore, the reactive polyurethane hot melt adhesive prepared by this invention has excellent oleic acid resistance, good low-temperature flexibility after curing, and significant impact resistance. It can be used as an adhesive for precision electronic components in wearable devices that are in long-term contact with human skin.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An oleic acid-resistant reactive polyurethane hot melt adhesive, characterized in that, The formulation comprises the following components in parts by weight: 30-60 parts of polyester polyol 10-30 parts of polyether polyol, 1-10 parts of polycarbonate polyol Prepare 0.1-5 parts of homemade polyfluorosiloxane polyol. 10-30 parts of polyisocyanate, Catalyst 0.1~0.5 parts; The self-made polyfluorosiloxane polyol is a polyfluorosiloxane diol with the following structure: Formula I. (Formula I) Where m = 5~50, n = 5~50; The self-made polyfluorosiloxane polyol is prepared according to the following steps: (1) Synthesis of the reaction products of fluorine-containing monomers Equimolar amounts of 3-fluoropropene and methyldichlorosilane were reacted with platinum black as a catalyst and stirred at 1.2 MPa and 0 °C for 2–5 hours until the reaction was complete. The pressure was then released and the mixture was allowed to return to room temperature to obtain a transparent, colorless liquid. This transparent, colorless liquid was then added dropwise to a 1 mol·L⁻¹ solution. -1 In potassium hydroxide solution, a white solid was obtained, which, after drying, yielded a fluorine-containing monomer; (2) Synthesis of hydroxyl-terminated polyfluorosiloxane polyols The fluorinated monomer reaction product prepared in the previous step was added to a three-necked flask in a molar ratio of 1:10 to 10:1 with octamethylcyclotetrasiloxane. 100-300 ppm of tetramethylammonium hydroxide (relative to the total amount of fluorinated monomer and octamethylcyclotetrasiloxane) was added as a catalyst. The mixture was slowly heated to 70-80°C and stirred at 300-500 rpm for 0.5-1 hour to obtain a colorless, transparent liquid. Then, 10,000-100,000 ppm of water was added as a capping agent, and the mixture was heated to 100-110°C and reacted for 0.5-1 hour. The temperature was further increased to 120-130°C, and low-boiling substances were removed under vacuum until the volatile content was less than 0.5%, yielding the final product, a hydroxyl-capped polyfluorosiloxane polyol.

2. The oleic acid-resistant reactive polyurethane hot melt adhesive according to claim 1, characterized in that: The self-made polyfluorosiloxane polyol is a polyfluorosiloxane polyol with a degree of polymerization of 10 to 100; the molecular weight of the self-made polyfluorosiloxane polyol is 1,000 to 10,000, and the viscosity at 25°C is 50 to 800 cps.

3. The oleic acid-resistant reactive polyurethane hot melt adhesive according to claim 1, characterized in that: The polyester polyol is selected from one or more of the following: hexanediol adipate, hexanediol terephthalate, polybutylene adipate-terephthalate, polycaprolactone diol, polyhexanediol-neopentyl glycol adipate diol, or poly-2-methyl-1,3-propanediol terephthalate diol.

4. The oleic acid-resistant reactive polyurethane hot melt adhesive according to claim 1, characterized in that: The polyether polyol is selected from one or more of polyethylene glycol, polypropylene glycol, or polytetrahydrofuran glycol.

5. The oleic acid-resistant reactive polyurethane hot melt adhesive according to claim 1, characterized in that: The polycarbonate polyol is selected from one or more of poly(1,6-hexanediol) carbonate diol, poly(1,4-butanediol) carbonate diol, poly(caprolactone hexanediol) diol, or poly(hexanediol) carbonate diol.

6. The oleic acid-resistant reactive polyurethane hot melt adhesive according to claim 1, characterized in that: The polyisocyanate is selected from one or more of 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, toluene diisocyanate, phenyl dimethyl diisocyanate, tetramethylphenyl dimethylene diisocyanate, 1,6-hexamethylene diisocyanate or isophorone diisocyanate.

7. The oleic acid-resistant reactive polyurethane hot melt adhesive according to claim 1, characterized in that: The catalyst is selected from one or more of 2,2-dimorpholine diethyl ether, N-methylmorpholine, N-ethylmorpholine, N,N-dimethylbenzylamine, triethylenediamine, dibutyltin dilaurate, or dimethyltin dinedecanoate.

8. The oleic acid-resistant reactive polyurethane hot melt adhesive according to claim 1, characterized in that: Its formulation also includes 0 to 1 part of additives, wherein the additives are selected from one or more of plasticizers, stabilizers, antioxidants, silane coupling agents, resins, polymers, dyes or fillers.

9. The method for preparing the oleic acid-resistant reactive polyurethane hot melt adhesive according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Put 30-60 parts of polyester polyol, 10-30 parts of polyether polyol, 1-10 parts of polycarbonate polyol and 0.1-5 parts of self-made polyfluorosiloxane polyol into a three-necked flask, and vacuum dehydrate at 110-120°C for 1-2 hours at a speed of 300-500 r / min until the moisture content is less than 250 ppm; (2) Under nitrogen protection, the mixed polyol is cooled to 70~80℃, 10~30 parts of polyisocyanate are added, and the reaction is carried out at 100~110℃ for 1~2 hours; (3) Under nitrogen protection, add 0.1 to 0.5 parts of catalyst and 0 to 1 part of additive at 100 to 110°C and stir for 0.5 to 1 hour; (4) Under nitrogen protection, hot discharge into a hot melt adhesive tube, put into an aluminum foil bag containing desiccant, vacuum and store at room temperature.

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