Primerless one-component polyurethane adhesive, and preparation method and application thereof

Abstract

The application provides a kind of free primer single-component polyurethane bonding glue, and its preparation method and application.The preparation raw materials of the free primer single-component polyurethane bonding glue include 100 parts of polymer polyol, 25-60 parts of polyisocyanate, 2-10 parts of multiple hydrogen bond chain extender, 0.5-5.0 parts of isocyanate silane coupling agent, 0.05-0.50 parts of catalyst, 30-50 parts of filler, 10-40 parts of plasticizer and 0.1-6.0 parts of functional additive.The preparation raw materials of the free primer single-component polyurethane bonding glue of the application further use multiple hydrogen bond chain extender and isocyanate silane coupling agent on the basis of polymer polyol, polyisocyanate, catalyst, filler, plasticizer and functional additive.The synergy of multiple hydrogen bond chain extender and isocyanate silane coupling agent realizes the unity of low-temperature curing, fast cohesion and strong interface, and avoids the problem that the existing polyurethane bonding glue gives up one to get the other in cohesion and interface at low temperature.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and more particularly to a polyurethane adhesive, and even more particularly to a polyurethane adhesive for automotive windshield installation that can rapidly establish cohesive strength in a low-temperature environment (0℃~10℃) and achieve high-strength bonding to glass substrates without the use of any primer, as well as its preparation method. Background Technology

[0002] The bonding and installation of automotive windshields is a critical process in vehicle production, and the industry currently widely uses single-component moisture-curing polyurethane adhesives. This adhesive must simultaneously achieve stable bonding to both the glass and the painted steel body panels, while possessing excellent structural strength and toughness, making it a core auxiliary material for ensuring vehicle driving and collision safety. To simplify production processes, improve vehicle assembly efficiency, and reduce labor and material costs, primerless polyurethane windshield adhesives have become the mainstream research and application direction in the industry.

[0003] However, existing commercially available primerless polyurethane windshield adhesives have significant technical defects in low-temperature conditions of 0~10℃, which restricts their mass production and application at low temperatures.

[0004] On the one hand, the product's low-temperature curing kinetics are severely delayed. The low-temperature environment significantly inhibits the diffusion rate of moisture in the air, slows down the cross-linking and curing reaction of isocyanate and water in the polyurethane system, resulting in extremely slow growth of the cohesive strength of the adhesive layer. It usually takes more than 7 days to reach the qualified cohesive failure standard, which greatly prolongs the vehicle production cycle and reduces the overall vehicle production efficiency.

[0005] On the other hand, existing primerless products generally sacrifice the crosslinking density and the content of interfacial active groups in order to adapt to the flowability of the application. At low temperatures, the molecular chain mobility of the adhesive layer is weakened, the wettability of the substrate is greatly reduced, and the glass bonding interface is very prone to debonding. Its low-temperature tensile bond strength is generally lower than 8MPa, which poses a great driving safety hazard.

[0006] In existing technologies, multiple hydrogen bond modification methods can only improve the low-temperature toughness of polyurethane materials and alleviate the problem of low-temperature brittle fracture of the adhesive layer, but cannot solve the core problems of slow low-temperature curing rate and insufficient interfacial bonding strength. At present, there is no technical solution that can simultaneously overcome the two major technical bottlenecks of low-temperature curing lag and interfacial debonding of primerless polyurethane windshield adhesive. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a primer-free, one-component polyurethane adhesive, its preparation method, and its applications. This primer-free, one-component polyurethane adhesive successfully solves the dual technical challenges of slow cohesive development and weak interfacial adhesion in one-component polyurethane adhesives at low temperatures, and possesses extremely high industrial application value.

[0008] To achieve the above objectives, the first aspect of the present invention provides a primer-free, one-component polyurethane adhesive, the raw materials of which include 100 parts of polymeric polyol, 25-60 parts of polyisocyanate, 2-10 parts of multi-hydrogen bond chain extender, 0.5-5.0 parts of isocyanate silane coupling agent, 0.05-0.50 parts of catalyst, 30-50 parts of filler, 10-40 parts of plasticizer, and 0.1-6.0 parts of functional additives.

[0009] The primer-free, one-component polyurethane adhesive of this invention is prepared using polymeric polyols, polyisocyanates, catalysts, fillers, plasticizers, and functional additives, further enhanced with multi-hydrogen bond chain extenders and isocyanate silane coupling agents. It is a one-component adhesive with good thixotropy, excellent extrudability, and long storage stability, possessing extremely high industrial application value. It is fully compatible with robotic automatic dispensing or manual glue gun application for automotive windshield bonding and installation.

[0010] Conventional one-component polyurethane adhesives exhibit slow covalent cross-linking network formation at low temperatures, resulting in delayed cohesive strength development. This application utilizes a multi-hydrogen-bonding chain extender. Since the formation of multiple hydrogen bonds is a physical process, it is almost unaffected by temperature, allowing for the formation of a high-density physical cross-linking network within minutes of application, thus providing immediate cohesive strength. Furthermore, the strength of hydrogen bonding increases with decreasing temperature, which is the opposite of the characteristic of covalent bond reaction rates decreasing with decreasing temperature. Therefore, at low temperatures (e.g., 0°C), the enhanced hydrogen bonding can quickly establish sufficient cohesive strength to support glass positioning, resulting in rapid curing.

[0011] Isocyanate silane coupling agents contain isocyanate groups (-NCO) and hydrolyzable silane groups (-Si(OR)). The -NCO groups in these silane coupling agents exhibit mild reactivity and can be controlled to graft onto the main chain of prepolymers formed by the polymerization of polymeric polyols and polyisocyanates, thus without compromising the storage stability of the system. Furthermore, through the reaction of its -NCO groups with the terminal active groups of the prepolymer, the hydrolyzable silane groups are firmly grafted onto the ends of the main chain, with the alkyl groups exposed at the molecular chain ends, exhibiting extremely high interfacial activity. After sizing, even at a low temperature of 0°C, the silane groups hydrolyze into silanol groups under humid conditions, which can actively and rapidly migrate directionally to the glass interface, condensing with Si-OH on the glass surface to form Si-O-Si chemical bonds, quickly establishing interfacial chemical bonds and providing high-strength interfacial adhesion.

[0012] Therefore, multi-hydrogen bond chain extenders can rapidly cure to establish a physical cross-linking network within the adhesive layer, providing sufficient cohesive strength and preventing damage to the adhesive layer itself. Silane isocyanate coupling agents can rapidly establish high-strength interfacial adhesion. The synergistic effect of the multi-hydrogen bond chain extender and isocyanate silane coupling agent achieves a balance between rapid low-temperature curing, high cohesive strength, and strong interfacial adhesion, avoiding the problem of existing polyurethane adhesives sacrificing one for the other at low temperatures.

[0013] Furthermore, the polymer polyol is a trifunctional polyether polyol with a number average molecular weight of 3000-6000.

[0014] Furthermore, the polyisocyanate is selected from at least one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

[0015] Furthermore, the isocyanate silane coupling agent is selected from at least one of isocyanate-propyltriethoxysilane, isocyanate-propyltrimethoxysilane, and isocyanate-ethyltrimethoxysilane.

[0016] Furthermore, the catalyst is a mixture of dimorpholine diethyl ether and bismuth neodecanoate in equal mass ratios.

[0017] Furthermore, the filler is selected from at least one of carbon black, calcium carbonate, silica, talc, kaolin, and diatomaceous earth.

[0018] Furthermore, the plasticizer is selected from at least one of dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, dioctyl terephthalate, diisononyl terephthalate, tricresyl phosphate, and triphenyl phosphate.

[0019] Furthermore, the free NCO content of the primer-free one-component polyurethane adhesive is 1.0~3.5 wt.%.

[0020] Furthermore, the multiple hydrogen bond chain extender is a compound containing multiple hydrogen bond units with dihydroxyl groups.

[0021] Furthermore, the multiple hydrogen bond chain extender is selected from at least one of ureidopyrimidinone diol derivatives, diamide diols, and acylhydrazine diols.

[0022] Furthermore, the multiple hydrogen bond chain extender is selected from at least one of ureidopyrimidinone diol, N,N′-bis(2-hydroxyethyl)oxalamide, N,N′-bis(2-hydroxyethyl)hexamethylenediamide, aromatic bisamide diol derivatives, methoxy polyethylene glycol hydrazide, and furanyl hydrazide derivative diols.

[0023] Furthermore, the functional additive is selected from at least one of p-toluenesulfonate isocyanate, molecular sieve, calcium oxide, and triethyl phosphate.

[0024] The second aspect of the present invention provides the use of the aforementioned primer-free one-component polyurethane adhesive in automotive windshield installation.

[0025] A third aspect of this invention provides a method for preparing a primer-free, one-component polyurethane adhesive, comprising the steps of: (I) Synthesis of prepolymer After dehydrating the polymer polyol and plasticizer to a moisture content of ≤0.03%, polyisocyanate was added and polymerization was carried out under an inert atmosphere to obtain the prepolymer. (II) Chain extension and grafting modification A multi-hydrogen bond chain extender is first added to the prepolymer to carry out a chain extension reaction, and then an isocyanate silane coupling agent is added for chemical grafting. (III) Hybridization and Packaging After adding catalysts, fillers, and functional additives, the mixture is dispersed and then sealed and filled.

[0026] In the preparation method of this invention, a plasticizer is added during the formation of the prepolymer from the polymeric polyol and polyisocyanate, which ensures that the plasticizer is uniformly dispersed in the adhesive matrix. Chain extension is performed using a multi-hydrogen-bonding chain extender, introducing multiple hydrogen bonds to provide immediate cohesive strength within minutes after application. Chemical grafting with an isocyanate silane coupling agent introduces hydrolyzable silane groups at the ends of the main chain, enabling rapid establishment of interfacial chemical bonds after application and providing high-strength interfacial adhesion. Furthermore, fillers and functional additives are added and dispersed uniformly, thereby expanding the application range of the one-component polyurethane adhesive.

[0027] Furthermore, the chemical grafting to obtain a free NCO content of 1.0~3.5 wt.% is further described.

[0028] Furthermore, the dehydration is carried out at 100~120℃ and under a vacuum of ≤-0.095MPa.

[0029] Furthermore, the polyisocyanate is added while the system temperature is controlled at 60~80°C.

[0030] Furthermore, the inert atmosphere is selected from nitrogen, helium, neon, or argon.

[0031] Furthermore, the polymerization reaction is carried out at a temperature of 75-90°C for 2-4 hours.

[0032] Furthermore, the chain extension reaction is carried out at a temperature of 50-70°C for 1-2 hours.

[0033] Furthermore, the chemical grafting temperature is 50~70℃ and the time is 0.5~1.0h.

[0034] Furthermore, the dispersion is carried out at a temperature below 50°C and at a vacuum of 300-1000 rpm for 1-2 hours. Detailed Implementation

[0035] The primerless, single-component polyurethane adhesive of this invention exhibits rapid cohesive development and strong interfacial adhesion at low temperatures. After curing, its tensile strength is >8MPa, and it can achieve ≥95% cohesive failure within 72 hours at 0~10℃. It has extremely high industrial application value, and is especially suitable for the bonding and installation of automotive windshields, which can meet the fast-paced requirements of automotive production lines.

[0036] The free NCO content of the primer-free one-component polyurethane adhesive of the present invention is 1.0~3.5 wt.%. The raw materials for preparing the primer-free one-component polyurethane adhesive, by weight, include 100 parts of polymeric polyol, 25~60 parts of polyisocyanate, 2~10 parts of multi-hydrogen bond chain extender, 0.5~5.0 parts of isocyanate silane coupling agent, 0.05~0.50 parts of catalyst, 30~50 parts of filler, 10~40 parts of plasticizer, and 0.1~6.0 parts of functional additives.

[0037] The polymer polyol is a trifunctional polyether polyol. Compared to difunctional polyether polyols, trifunctional polyether polyols offer higher crosslinking density and better low-temperature modulus build-up. The number-average molecular weight of the polymer polyol is 3000-6000. Preferably, the polymer polyol is a homopolymer ether mainly composed of propylene oxide units, formed by grafting propylene oxide (PO) monomers onto the hydroxyl ends of the initiator via ring-opening polymerization using glycerol or trimethylolpropane as the initiator.

[0038] The weight percentage of the polyisocyanate may be, but is not limited to, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, or 60 parts. The polyisocyanate is selected from at least one or more of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI). Preferably, the polyisocyanate is a mixture of MDI and IPDI, which makes it easier to control the reactivity of the system and improves low-temperature toughness.

[0039] The weight parts of the multiple hydrogen bond chain extender may be, but are not limited to, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts. The multiple hydrogen bond chain extender is a compound containing multiple hydrogen bond units with dihydroxyl groups. Preferably, the multiple hydrogen bond chain extender is selected from at least one of ureidopyrimidinone diol derivatives, bisamide diols, and acylhydrazide diols. More preferably, the multiple hydrogen bond chain extender is selected from at least one of ureidopyrimidinone diol, N,N′-bis(2-hydroxyethyl)oxalamide, N,N′-bis(2-hydroxyethyl)hexamethylenediamide, aromatic bisamide diol derivatives, methoxy polyethylene glycol acylhydrazides, and furanylhydrazide derivative diols. Further preferred, the multi-hydrogen bond chain extender is ureidopyrimidinone diol, which has a fourfold hydrogen bond self-complementary property. At low temperature, the ureidopyrimidinone (UPy) unit can quickly and reversibly form a high-density physical cross-linking network through the fourfold hydrogen bond self-complementary effect, providing instant cohesive strength to the colloid.

[0040] The weight parts of the isocyanate silane coupling agent may be, but are not limited to, 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.5 parts, 4.0 parts, 4.5 parts, and 5.0 parts. The isocyanate silane coupling agent is selected from at least one of isocyanate-propyltriethoxysilane, isocyanate-propyltrimethoxysilane, and isocyanate-ethyltrimethoxysilane. These isocyanate silane coupling agents are all small molecules, which are beneficial for direct grafting to the ends of the polyurethane prepolymer backbone through chemical reaction.

[0041] The catalyst can be, but is not limited to, 0.05 parts, 0.10 parts, 0.30 parts, 0.50 parts, 1.00 parts, 1.50 parts, 2.00 parts, 2.50 parts, 3.00 parts, 3.50 parts, 4.00 parts, 4.50 parts, and 5.00 parts by weight. The catalyst can regulate the reaction rate and can be a metal catalyst or an amine catalyst. The metal catalyst can be an organotin catalyst or an organobismuth catalyst. The organotin catalyst can be dibutyltin dilaurate (DBTDL), dioctyltin dilaurate (DOTL), dibutyltin oxide (DBTO), dimethyltin (DMDS), or tributyltin (TBT). The organobismuth catalyst can be bismuth neodecanoate (DY-20), bismuth laurate, or bismuth isooctanoate. Preferably, the catalyst is a compound of dimorpholine diethyl ether and bismuth neodecanoate in equal mass ratio. This compound has high efficiency in catalyzing moisture curing at low temperatures and has little impact on the storage period of the system.

[0042] The filler weight percentage can be, but is not limited to, 30 parts, 35 parts, 40 parts, 45 parts, or 50 parts. The filler is selected from at least one of carbon black, calcium carbonate, silica, talc, kaolin, and diatomaceous earth to improve the mechanical properties of polyurethane adhesives and adapt to the strength requirements of different scenarios.

[0043] The plasticizer can be present in parts by weight, but is not limited to, 10, 15, 20, 25, 30, 35, or 40 parts. The plasticizer is selected from at least one of dioctyl phthalate (DOP / DEHP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), dioctyl terephthalate (DOTP), diisononyl terephthalate (DINP-T), tricresyl phosphate (TCP), and triphenyl phosphate. The plasticizer can intercalate between the molecular chains of polyurethane, weakening intermolecular forces and allowing for freer chain movement, thereby directly improving the flexibility and low-temperature adaptability of polyurethane adhesives.

[0044] The functional additives may be, but are not limited to, 0.1 parts, 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.5 parts, 4.0 parts, 4.5 parts, and 6.0 parts. The functional additives are selected from at least one of p-toluenesulfonate isocyanate, molecular sieves, calcium oxide, and triethyl phosphate. These substances can remove small amounts of residual moisture to improve the storage stability of the adhesive.

[0045] The preparation method of the primer-free one-component polyurethane adhesive of the present invention includes the following steps: (I) Synthesis of prepolymer After dehydrating the polymer polyol and plasticizer to a moisture content of ≤0.03%, polyisocyanate was added and polymerization was carried out under an inert atmosphere to obtain the prepolymer. (II) Chain extension and grafting modification A multi-hydrogen bond chain extender is first added to the prepolymer to carry out a chain extension reaction, and then an isocyanate silane coupling agent is added for chemical grafting. (III) Hybridization and Packaging After adding catalysts, fillers, and functional additives, the mixture is dispersed and then sealed and filled.

[0046] The preparation method of the present invention introduces multiple hydrogen-bonded groups and silane groups on the polyurethane prepolymer, which can achieve a balance between cohesive strength and interfacial strength of polyurethane adhesives during low-temperature curing and fast curing, thus avoiding the problem of existing polyurethane adhesives sacrificing one aspect for the other in terms of cohesive strength and interfacial strength at low temperatures.

[0047] The dehydration process was carried out at 100–120°C and a vacuum of ≤-0.095 MPa to reduce the water content in the system. The polyisocyanate was added at a controlled temperature of 60–80°C. The inert atmosphere was selected from nitrogen, helium, neon, or argon. The polymerization reaction was carried out at 75–90°C for 2–4 hours, under which the polymer polyol and polyisocyanate formed a prepolymer. The chain extension reaction was carried out at 50–70°C for 1–2 hours. The chemical grafting reaction was carried out at 50–70°C for 0.5–1.0 hours, until the free NCO content was 1.0–3.5 wt.%. A catalyst was added to ensure complete reaction and to prevent excessively high reactivity in the chain extension reaction, which could lead to gel formation. Dispersion was carried out below 50°C and under a vacuum of 300–1000 rpm for 1–2 hours.

[0048] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0049] Example 1 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number-average molecular weight 5000, glycerol as initiator, and propylene oxide as monomer), 35 parts of MDI, 4 parts of ureidopyrimidinone diol, 2.0 parts of propyltriethoxysilane isocyanate, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0050] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0051] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.5 h. Then, propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0052] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0053] Example 2 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number-average molecular weight 5000, glycerol as the initiator, and propylene oxide as the monomer), 35 parts of MDI, 2 parts of ureidopyrimidinone diol, 2.0 parts of propyltriethoxysilane isocyanate, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0054] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0055] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.0 h. Then, propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0056] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0057] Example 3 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number-average molecular weight 5000, glycerol as initiator, and propylene oxide as monomer), 35 parts of MDI, 8 parts of ureidopyrimidinone diol, 2.0 parts of propyltriethoxysilane isocyanate, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0058] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0059] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 2.0 h. Then, propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0060] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0061] Example 4 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number-average molecular weight 5000, glycerol as initiator, and propylene oxide as monomer), 35 parts of MDI, 5 parts of N,N′-di(2-hydroxyethyl)oxalamide, 2.0 parts of propyltriethoxysilane isocyanate, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0062] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0063] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. N,N′-bis(2-hydroxyethyl)oxalamide was added to the prepolymer and reacted for 1.5 h. Then, propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0064] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0065] Example 5 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number-average molecular weight 5000, glycerol as initiator, and propylene oxide as monomer), 35 parts of MDI, 4 parts of ureidopyrimidinone diol, 0.5 parts of propyltriethoxysilane isocyanate, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0066] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0067] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.5 h. Then, propyltriethoxysilane isocyanate was added and reacted for 30 min until the free NCO content was 2.5 wt.%.

[0068] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0069] Example 6 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts trifunctional polyether polyol (number average molecular weight 5000, glycerol as initiator, propylene oxide as monomer), 35 parts MDI, 4 parts ureidopyrimidinone diol, 4.0 parts propyltriethoxysilane isocyanate, 0.1 parts dimorpholine diethyl ether, 0.1 parts bismuth neodecanoate, 25 parts carbon black, 15 parts nano-calcium carbonate, 25 parts DINP, and 3 parts p-toluenesulfonate isocyanate.

[0070] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0071] (II) Chain extension and grafting modification The temperature was lowered to 60°C and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.5 h. Then, propyltriethoxysilane isocyanate was added and reacted for 60 min until the free NCO content was 2.5 wt.%.

[0072] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0073] Example 7 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts trifunctional polyether polyol (number average molecular weight 5000, glycerol as initiator, propylene oxide as monomer), 25 parts MDI, 12 parts IPDI, 4 parts ureidopyrimidinone diol, 2.0 parts propyltriethoxysilane isocyanate, 0.1 parts dimorpholine diethyl ether, 0.1 parts bismuth neodecanoate, 25 parts carbon black, 15 parts nano-calcium carbonate, 25 parts DINP, and 3 parts p-toluenesulfonate isocyanate.

[0074] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI and IPDI were added, and the mixture was reacted at 85°C under a nitrogen atmosphere for 3.5h to obtain the prepolymer.

[0075] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.5 h. Then, propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0076] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0077] Example 8 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts trifunctional polyether polyol (number-average molecular weight 3500, glycerol as initiator, propylene oxide as monomer), 35 parts MDI, 4 parts ureidopyrimidinone diol, 2.0 parts propyltriethoxysilane isocyanate, 0.1 parts dimorpholine diethyl ether, 0.1 parts bismuth neodecanoate, 25 parts carbon black, 15 parts nano-calcium carbonate, 25 parts DINP, and 3 parts p-toluenesulfonate isocyanate.

[0078] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 100°C and vacuum degree ≤ -0.095MPa for 2.0h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant while MDI was added. The mixture was then reacted at 80°C under a nitrogen atmosphere for 3h to obtain the prepolymer.

[0079] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.5 h. Then, propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0080] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0081] Example 9 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number-average molecular weight 6000, initiator is trimethylolpropane, propylene oxide is the monomer), 35 parts of MDI, 4 parts of ureidopyrimidinone diol, 2.0 parts of propyltriethoxysilane isocyanate, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0082] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 115°C and vacuum degree ≤ -0.095MPa for 3.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0083] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.5 h. Then, propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0084] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0085] Example 10 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number-average molecular weight 5000, glycerol as initiator, and propylene oxide as monomer), 35 parts of MDI, 4 parts of ureidopyrimidinone diol, 2.0 parts of propyltriethoxysilane isocyanate, 0.15 parts of DBTDL, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0086] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0087] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.5 h. Then, propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0088] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, DBTDL, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0089] Example 11 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number average molecular weight 5000, glycerol as initiator, propylene oxide as monomer), 50 parts of MDI, 4 parts of ureidopyrimidinone diol, 2.0 parts of isocyanate-based ethyltrimethoxysilane, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 35 parts of carbon black, 30 parts of DINP, and 2.5 parts of molecular sieve.

[0090] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 80°C and kept constant. MDI was added and reacted at 75°C under a helium atmosphere for 4h to obtain the prepolymer.

[0091] (II) Chain extension and grafting modification The temperature was lowered to 65°C and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 2.0 h. Then isocyanate ethyltrimethoxysilane was added and reacted for 45 min until the free NCO content was 3.0 wt.%.

[0092] (III) Hybridization and Packaging The mixture was cooled to 40°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and molecular sieve were added. The mixture was then stirred at 800 rpm under vacuum for 1.0 h and sealed for filling.

[0093] Example 12 This embodiment describes a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number-average molecular weight 5000, glycerol as initiator, and propylene oxide as monomer), 45 parts of MDI, 4 parts of ureidopyrimidinone diol, 2.0 parts of isocyanate-propyltrimethoxysilane, 0.2 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 15 parts of talc, 30 parts of nano-calcium carbonate, 25 parts of DOTP, 3 parts of molecular sieve, and 0.2 parts of calcium oxide.

[0094] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DOTP were dehydrated at 110℃ and vacuum degree ≤ -0.095MPa for 2.0h until the moisture content was ≤0.03%. The temperature was then lowered to 70℃ and kept constant. MDI was added and reacted at 80℃ under nitrogen atmosphere for 2h to obtain the prepolymer.

[0095] (II) Chain extension and grafting modification The temperature was lowered to 65°C and kept constant. Ureidin pyrimidinone diol was added to the prepolymer and reacted for 1.0 h. Then isocyanate propyltrimethoxysilane was added and reacted for 25 min until the free NCO content was 3.5 wt.%.

[0096] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, molecular sieve, and calcium oxide were added. The mixture was then stirred at 650 rpm under vacuum for 1.5 hours and sealed for filling.

[0097] Comparative Example 1 This comparative example is a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number average molecular weight 5000, glycerol as initiator, propylene oxide as monomer), 35 parts of MDI, 1.8 parts of 1,4-butanediol, 2.0 parts of propyltriethoxysilane isocyanate, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0098] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0099] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. 1,4-Butanediol was added to the prepolymer and reacted for 1.5 h. Then propyltriethoxysilane isocyanate was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0100] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0101] Comparative Example 2 This comparative example is a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts of trifunctional polyether polyol (number average molecular weight 5000, glycerol as initiator, propylene oxide as monomer), 35 parts of MDI, 4 parts of ureidopyrimidinone diol, 2.0 parts of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1 parts of dimorpholine diethyl ether, 0.1 parts of bismuth neodecanoate, 25 parts of carbon black, 15 parts of nano-calcium carbonate, 25 parts of DINP, and 3 parts of p-toluenesulfonate isocyanate.

[0102] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0103] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. Ureidinidone diol was added to the prepolymer and reacted for 1.5 h. Then γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0104] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0105] Comparative Example 3 This comparative example is a primer-free, one-component polyurethane adhesive. By weight, its preparation materials include 100 parts trifunctional polyether polyol (number average molecular weight 5000, glycerol as initiator, propylene oxide as monomer), 35 parts MDI, 1.8 parts 1,4-butanediol, 2.0 parts γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1 parts dimorpholine diethyl ether, 0.1 parts bismuth neodecanoate, 25 parts carbon black, 15 parts nano-calcium carbonate, 25 parts DINP, and 3 parts p-toluenesulfonate isocyanate.

[0106] The preparation method of this primer-free, one-component polyurethane adhesive includes the following steps: (I) Synthesis of prepolymer Polyether polyol and DINP were dehydrated at 110°C and vacuum degree ≤ -0.095MPa for 2.5h until the moisture content was ≤0.03%. The temperature was then lowered to 70°C and kept constant. MDI was added and reacted at 80°C under nitrogen atmosphere for 3h to obtain the prepolymer.

[0107] (II) Chain extension and grafting modification The temperature was lowered to 60℃ and kept constant. 1,4-Butanediol was added to the prepolymer and reacted for 1.5 h. Then γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added and reacted for 45 min until the free NCO content was 2.5 wt.%.

[0108] (III) Hybridization and Packaging The mixture was cooled to 45°C and kept at a constant temperature. Then, dimorpholine diethyl ether, bismuth neodecanoate, carbon black, nano calcium carbonate, and p-toluenesulfonate isocyanate were added. The mixture was then stirred at 1000 rpm under vacuum for 1.5 hours and sealed for filling.

[0109] The one-component polyurethane adhesives of Examples 1-12 and Comparative Examples 1-3 were cured at 5°C and RH 50% for 72 hours, and the bonding condition, tensile strength, extrusion retention rate, surface drying time, curing speed and initial extrusion condition were obtained.

[0110] The bonding condition was tested according to standard GB / T 7124-2008, "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)". Tensile strength was tested according to standard GB / T 528-2009, "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber". Extrusion, surface drying time, and curing speed were tested according to standard GB / 13477.15-2017, "Test Methods for Building Sealing Materials".

[0111] Table 1 Performance test results of the one-component polyurethane adhesives of Examples 1-12 and Comparative Examples 1-3

[0112] As shown in Table 1, the raw materials used in the preparation of the primerless one-component polyurethane adhesives in Examples 1-12 are multiple hydrogen bond chain extenders and isocyanate silane coupling agents. These adhesives exhibit rapid surface drying and curing at low temperatures, high cohesive breakdown, and high tensile strength, indicating rapid cohesive development and high interfacial strength. Furthermore, the high extrusion retention rate and low initial extrudability indicate a long storage stability period. Therefore, they are fully adaptable to robotic automatic dispensing or manual glue gun application for automotive windshield bonding and installation.

[0113] Comparing Examples 1 and 4, it can be seen that the performance of ureidopyrimidinone diol as the multi-hydrogen bond chain extender is better, which may be due to its four-fold hydrogen bond self-complementary properties.

[0114] Comparing Example 1 and Example 10, it can be seen that the catalyst is a compound of dimorpholine diethyl ether and bismuth neodecanoate, which has better performance. This is because the compound has high efficiency in catalyzing moisture curing at low temperatures and has little impact on the storage period of the system.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A primer-free, one-component polyurethane adhesive, characterized in that, The raw materials for preparation, by weight, include 100 parts of polymer polyol, 25-60 parts of polyisocyanate, 2-10 parts of multi-hydrogen bond chain extender, 0.5-5.0 parts of isocyanate silane coupling agent, 0.05-0.50 parts of catalyst, 30-50 parts of filler, 10-30 parts of plasticizer and 0.1-6.0 parts of functional additives.

2. The primer-free, single-component polyurethane adhesive according to claim 1, characterized in that, Includes at least one of the following features (i) to (vii): (i) The polymer polyol is a trifunctional polyether polyol with a number average molecular weight of 3000 to 6000; (ii) The polyisocyanate is selected from at least one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate; (iii) The isocyanate silane coupling agent is selected from at least one of isocyanate-propyltriethoxysilane, isocyanate-propyltrimethoxysilane, and isocyanate-ethyltrimethoxysilane; (iv) The catalyst is a mixture of dimorpholine diethyl ether and bismuth neodecanoate in equal mass ratio; (v) The filler is selected from at least one of carbon black, calcium carbonate, silica, talc, kaolin and diatomaceous earth; (vi) The plasticizer is selected from at least one of dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, dioctyl terephthalate, diisononyl terephthalate, tricresyl phosphate and triphenyl phosphate; (vii) The free NCO content of the primer-free single-component polyurethane adhesive is 1.0~3.5 wt.%.

3. The primer-free, single-component polyurethane adhesive according to claim 1, characterized in that, The multiple hydrogen bond chain extender is a compound containing multiple hydrogen bond units with dihydroxyl groups.

4. The primer-free, single-component polyurethane adhesive according to claim 3, characterized in that, The multiple hydrogen bond chain extender is selected from at least one of ureidopyrimidinone diol derivatives, bisamide diols, and acylhydrazide diols.

5. The primer-free, single-component polyurethane adhesive according to claim 4, characterized in that, The multiple hydrogen bond chain extender is selected from at least one of ureidopyrimidinone diol, N,N′-bis(2-hydroxyethyl)oxalamide, N,N′-bis(2-hydroxyethyl)hexamethylenediamide, aromatic bisamide diol derivatives, methoxy polyethylene glycol hydrazide, and furanyl hydrazide derivative diols.

6. The primer-free, single-component polyurethane adhesive according to claim 1, characterized in that, The functional additive is selected from at least one of p-toluenesulfonate isocyanate, molecular sieve, calcium oxide, and triethyl phosphate.

7. The use of the primer-free single-component polyurethane adhesive according to any one of claims 1 to 6 in the installation of automotive windshields.

8. A method for preparing a primer-free, one-component polyurethane adhesive, characterized in that, Including the following steps: (I) Synthesis of prepolymer After dehydrating the polymer polyol and plasticizer to a moisture content of ≤0.03%, polyisocyanate was added and polymerization was carried out under an inert atmosphere to obtain the prepolymer. (II) Chain extension and grafting modification A multi-hydrogen bond chain extender is first added to the prepolymer to carry out a chain extension reaction, and then an isocyanate silane coupling agent is added for chemical grafting. (III) Hybridization and Packaging After adding catalysts, fillers, and functional additives, the mixture is dispersed and then sealed and filled.

9. The method for preparing the primerless single-component polyurethane adhesive according to claim 8, characterized in that, Includes at least one of the following features (1) to (8): (1) The content of free NCO obtained by chemical grafting is 1.0~3.5 wt.%; (2) The dehydration is carried out at 100~120℃ and vacuum degree ≤-0.095MPa; (3) The polyisocyanate is added at a controlled temperature of 60~80℃; (4) The inert atmosphere is selected from nitrogen, helium, neon or argon; (5) The polymerization reaction is carried out at a temperature of 75~90℃ for 2~4 hours; (6) The chain extension reaction is carried out at a temperature of 50~70℃ for 1~2h; (7) The temperature of the chemical grafting is 50~70℃ and the time is 0.5~1.0h; (8) The dispersion is carried out at a temperature below 50°C and at a vacuum of 300~1000 rpm for 1~2 hours.

Images