A highly elastic hand-scrapeable waterproof polyurethane coating based on modified MDI prepolymer and its preparation method

Abstract

The present invention belongs to the technical field of coatings, and provides a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer and a preparation method thereof. The modified MDI prepolymer is used as a core cross-linking component, and when reacting with a modified polyether polyol and a modified polyester polyol, a high-density polyurethane network structure can be uniformly formed. The aromatic ring structure of the MDI prepolymer significantly enhances the chemical stability and weather resistance of the system. The modified polyether polyol and the modified polyester polyol are used as copolymerization components, and the flexibility of the molecular structure is regulated by introducing acrylic groups, siloxane bonds and flexible ester bonds respectively; in addition, through the synergistic effect of the modified polyether polyol and the polyester polyol, siloxane bonds and acrylic groups are introduced respectively, thereby enhancing the weather resistance of the coating. The polyurethane coating prepared by the present invention has high elasticity, waterproofness and weather resistance, and meets the needs of long-term use in complex environments.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings and relates to a high-elasticity hand-scrapeable waterproof polyurethane coating based on modified MDI prepolymer and a preparation method thereof. Background Art

[0002] Polyurethane coatings are widely used in fields such as construction, automotive, and electronics due to their excellent physical and chemical properties. Traditional polyurethane coatings are typically prepared by reacting MDI (diphenylmethane diisocyanate) with polyols. As coating performance requirements increase, single MDI coatings are no longer able to meet the demands for high elasticity and durability. Therefore, the development of coatings based on modified MDI prepolymers has become an important research direction. By introducing various modifiers into modified MDI prepolymers, the elasticity and water resistance of the coating can be effectively improved, allowing it to maintain good performance even in extreme environments. In addition, hand-scrape coatings are particularly suitable for coating complex structures and irregular surfaces due to their ease of application and wide applicability. Chinese patent application publication number CN107286309A prepares a low-VOC, high-performance, two-component hand-scrape polyurea waterproof coating. Its preparation method contains carbon black and fumed silica. These fillers easily aggregate during high-speed stirring and are difficult to fully disperse. Although these ingredients can improve the strength and wear resistance of the coating, they may reduce the coating's flexibility. Therefore, it is necessary to develop a highly elastic hand-scrapeable waterproof polyurethane coating based on modified MDI prepolymer. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a highly elastic hand-scrapeable waterproof polyurethane coating based on modified MDI prepolymer and a preparation method thereof. The aromatic ring structure of the MDI prepolymer significantly enhances the chemical stability and weather resistance of the system. Modified polyether polyol and modified polyester polyol are used as copolymer components. By introducing acrylic groups, silanol bonds and flexible ester bonds respectively, the flexibility of the molecular structure is regulated to meet the needs of actual production.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer, the preparation method comprising:

[0006] Step S1, heating diphenylmethane diisocyanate to a first temperature, then adding dicyclohexylmethane diisocyanate, adjusting the temperature to a second temperature for sufficient reaction, then adding m-xylylene diisocyanate to continue the reaction, continuing to add vinyltriethoxysilane, raising the temperature to a third temperature to continue the reaction, then adding hydroxyethyl acrylate and a catalyst, maintaining the third temperature to continue the reaction, then adding maleic anhydride and an initiator, maintaining the third temperature to continue the reaction, then adding glycidyl methacrylate, maintaining the third temperature to continue the reaction, adding polycaprolactone diol, continuing the reaction at the third temperature to obtain modified diphenylmethane diisocyanate, mixing the modified diphenylmethane diisocyanate with polytetrahydrofuran, and continuing the reaction at the third temperature to obtain a diphenylmethane diisocyanate prepolymer;

[0007] Step S2, heating the polyether polyol to a third temperature, adding an initiator and glycidyl methacrylate, raising the temperature to a fourth temperature for sufficient reaction, then adding isobornyl acrylate to continue the reaction, adjusting the temperature to the second temperature, adding γ-methacryloxypropyltrimethoxysilane and stannous acetate, and raising the temperature to a third temperature for sufficient reaction to obtain a modified polyether polyol;

[0008] Step S3, heating the polyester polyol to the third temperature, adding dimethyl propylene glycol and a catalyst, raising the temperature to the fifth temperature under nitrogen protection for full reaction, cooling to 100° C., adding dicyclohexylmethane-4,4′-diisocyanate, raising the temperature to the fifth temperature for further reaction, and then adding caprolactone for full reaction to obtain a modified polyester polyol;

[0009] Step S4: Add diphenylmethane diisocyanate prepolymer, modified polyether polyol, modified polyester polyol, filler, dibutyltin dioctoate, additives, antioxidant and ultraviolet absorber in sequence and mix them, stir and mix at the sixth temperature and the first stirring speed, and obtain a high-elasticity hand-scrapeable waterproof polyurethane coating based on the modified MDI prepolymer after vacuum degassing.

[0010] The aromatic ring structure of MDI (diphenylmethane diisocyanate) provides a rigid molecular backbone. Its symmetry and high reactivity make it easy to react with hydroxyl groups to form polyurethane bonds. The aromatic ring provides strong mechanical strength and chemical resistance within the molecular structure. Dicyclohexylmethane diisocyanate is an alicyclic isocyanate, providing high flexibility and resistance to UV aging. The alicyclic structure is not as rigid as the aromatic ring, which can increase the proportion of flexible segments, thereby improving the toughness of the coating. The aromatic ring of m-xylylenediisocyanate contains two isocyanate groups. The symmetry of the meta-substitution helps form a uniform cross-linked network, providing rigidity. However, the meta-position structure allows for a certain degree of rotatability in the molecular chain, increasing its flexibility. The triethoxysilane group of vinyltriethoxysilane gradually hydrolyzes to form silanols during the reaction, which then undergoes a condensation reaction to form silanol bonds. Silanol bonds are extremely stable chemical structures that impart weathering and chemical resistance to the coating. The introduction of silanol bonds also forms a dense inorganic barrier, preventing the penetration of external moisture, oxygen, and corrosive chemicals. The hydroxyl group on the hydroxyethyl acrylate molecule is a nucleophilic reagent that can undergo a nucleophilic addition reaction with the diphenylmethane diisocyanate group to generate a new polyurethane chain segment. In the diphenylmethane diisocyanate group, the carbon atom exhibits strong electrophilicity due to its connection to highly electronegative nitrogen and oxygen. This makes it easily attacked by nucleophiles (such as the oxygen atom in the hydroxyl group). The oxygen atom in the hydroxyl group carries a lone pair of electrons and attacks the electrophilic carbon atom in the diphenylmethane diisocyanate group, forming a negatively charged intermediate. The intermediate then undergoes proton transfer to generate the final urethane structure, i.e., the polyurethane chain segment, which provides a dynamically adjustable molecular network and enhances the flexibility and elasticity of the material.

[0011] The maleic anhydride molecule contains a five-membered cyclic anhydride group (anhydrous diacid structure), a highly reactive chemical group capable of undergoing ring-opening reactions with hydroxyl or amine groups in the system to form ester or amide bonds, respectively. The anhydride group is a strongly electrophilic center, consisting of two carbonyl groups and a carboxyl oxygen atom. The carboxyl oxygen atoms readily attract electrons, making the two carbonyl carbon atoms in the anhydride ring highly electrophilic. The lone electron pair on the hydroxyl oxygen atom attacks the carbonyl carbon atom of the anhydride group, causing the anhydride ring to open, forming a carboxylic acid and an ester bond. The nitrogen atom in the amine group is an even stronger nucleophile, capable of attacking the carbonyl carbon atom of the anhydride group. This ring-opening reaction forms a carboxylic acid and an amide bond. Ester and amide bonds are highly stable chemical bonds that increase crosslinking of the molecular chains, enhancing the chemical strength and durability of the molecular network. At the same time, the maleic anhydride molecule also contains a carbon-carbon double bond, which is an unsaturated conjugated structure and can participate in free radical polymerization. The double bond electron cloud density in the maleic anhydride molecule is higher, and it is easily attacked by free radicals. Electron transfer is produced and a new free radical is produced in the double bond simultaneously. The new free radical generated can continue to attack other molecules containing double bonds and cause chain growth reaction. Because the double bond of maleic anhydride can be cross-linked with other double-bond molecules, a highly cross-linked three-dimensional network is finally formed. The free radical polymerization of the double bond of maleic anhydride provides additional crosslinking points for the system, significantly improving the compactness of the molecular network. Dicumyl peroxide also promotes the free radical polymerization of the double bond in the system. Under the conditions of heating, the peroxide bond of dicumyl peroxide undergoes homolysis, generating two isopropyl radicals. The free radical generated has unpaired electrons and shows strong reactivity. In particular, the double bond in the system (such as the double bond of an acrylic acid group or the double bond of maleic anhydride) is added, initiating free radical polymerization, further initiating chain growth and crosslinking reaction. Maleic anhydride reacts with hydroxyl or amine groups to form ester bonds or amide bonds, thereby improving the strength and stability of the chemical network. Carbon-carbon double bonds increase cross-linking points through free radical polymerization to construct a three-dimensional cross-linked network. Dicumyl peroxide acts as a free radical initiator to initiate the polymerization of acrylic acid groups and maleic anhydride double bonds in the system, significantly increasing the cross-linking density and thus giving the coating better weather resistance.

[0012] Polypropylene glycol is a typical polyether polyol with multiple hydroxyl groups in its molecule. Dicumyl peroxide undergoes homolytic cleavage of the peroxide bonds upon heating, generating two isopropyl radicals, which act as initiators to promote free radical polymerization of acrylic groups. Glycidyl methacrylate contains both reactive epoxy groups and methacrylic double bonds. The epoxy groups have high ring tension and are easily attacked by nucleophiles (such as the hydroxyl groups in polypropylene glycol), resulting in nucleophilic ring-opening reactions and ether bonds. Isobornyl acrylate contains a cage-like isobornyl structure and an acrylic group. The acrylic group participates in polymerization under free radical initiation, further increasing the crosslink density of the system. The polymerization of the double bonds further enhances the mechanical strength and weather resistance of the coating. γ-Methacryloxypropyltrimethoxysilane contains three methoxysilane groups and one methacryloyloxy group. The methoxysilane group hydrolyzes to form silanols, which form silane-oxygen bonds through condensation. The methacryloyloxy groups crosslink with other acrylic groups through free radical polymerization, further enhancing the crosslink density of the molecular network. Dimethylpropylene glycol is a low molecular weight diol that can introduce flexible chain segments, adjust the molecular structure of polyester and enhance flexibility. Dicyclohexylmethane-4,4'-diisocyanate has good flexibility and aging resistance. Its isocyanate group reacts with the hydroxyl group in polycarbonate diol to form a polyurethane bond. At the same time, caprolactone is an open-ring cyclic ester that generates flexible chain segments through esterification reaction with the hydroxyl group in the system, thereby enhancing the flexibility of the polyester chain.

[0013] As a preferred technical solution of the present invention, in step S1, the mass ratio of diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, meta-xylylenediisocyanate, and vinyltriethoxysilane is (100-120): (2-3.6): (1-2.4): (3-6).

[0014] In some optional examples, the first temperature is 60-70°C, for example, it can be 60.0°C, 61.0°C, 62.0°C, 63.0°C, 64.0°C, 65.0°C, 66.0°C, 67.0°C, 68.0°C, 69.0°C or 70.0°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0015] In some optional examples, the second temperature is 70-80°C, for example, it can be 70.0°C, 71.0°C, 72.0°C, 73.0°C, 74.0°C, 75.0°C, 76.0°C, 77.0°C, 78.0°C, 79.0°C or 80.0°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0016] In some optional examples, the reaction time of adding dicyclohexylmethane diisocyanate is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0017] In some optional examples, the reaction time of adding meta-xylylenediisocyanate is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0018] In some optional examples, the third temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0019] In some optional examples, the reaction time of adding vinyltriethoxysilane is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0020] In some optional examples, the catalyst is stannous octoate.

[0021] In some optional examples, the reaction time for adding the catalyst is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0022] In some optional examples, the initiator is dicumyl peroxide.

[0023] In some optional examples, the reaction time for adding the initiator is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0024] In some optional examples, the reaction time for adding glycidyl methacrylate is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0025] In some optional examples, the reaction time for adding polycaprolactone diol is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0026] In some optional examples, the mass ratio of the polytetrahydrofuran to diphenylmethane diisocyanate is (3-4):1, for example, it can be 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1 or 4:1, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0027] In some optional examples, the reaction time of adding polytetrahydrofuran is 3-4h, for example, it can be 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0028] As a preferred technical solution of the present invention, in step S2, the polyether polyol is polypropylene glycol, and the mass ratio of the polyether polyol, initiator, glycidyl methacrylate, isobornyl acrylate, γ-methacryloyloxypropyltrimethoxysilane, and stannous acetate is (100-120): (1-2.4): (10-18): (2-3.6): (3-6): (0.1-0.6).

[0029] In some optional examples, the initiator is dicumyl peroxide.

[0030] In some optional examples, the fourth temperature is 90-95°C, for example, it can be 90.0°C, 90.5°C, 91.0°C, 91.5°C, 92.0°C, 92.5°C, 93.0°C, 93.5°C, 94.0°C, 94.5°C or 95.0°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0031] In some optional examples, the reaction time at the fourth temperature is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0032] In some optional examples, the reaction time for adding isobornyl acrylate is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0033] In some optional examples, the reaction time of adding stannous acetate is 3-4h, for example, it can be 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0034] As a preferred technical solution of the present invention, in step S3, the mass ratio of the polyester polyol, dimethyl propylene glycol, and catalyst is (100-120): (5-8.4): (0.1-0.6).

[0035] In some optional examples, the catalyst is tetrabutyl titanate.

[0036] In some optional instances, the fifth temperature is 120-130°C, for example, it can be 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C or 130°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0037] In some optional examples, the reaction time at the fifth temperature is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0038] In some optional examples, the reaction time of adding dicyclohexylmethane-4,4'-diisocyanate is 3-4h, for example, it can be 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0039] In some optional examples, the reaction time for adding caprolactone is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0040] As a preferred technical solution of the present invention, in step S4, the mass ratio of the diphenylmethane diisocyanate prepolymer, modified polyether polyol, modified polyester polyol, filler, and dibutyltin dioctoate is (100-120): (40-50): (30-40): (30-40): (0.5-1).

[0041] In some optional examples, the filler is one or more of talc, titanium dioxide, silicon dioxide, mica powder, and kaolin.

[0042] In some optional examples, the mass ratio of the diphenylmethane diisocyanate prepolymer, the auxiliary agent, the antioxidant, and the ultraviolet absorber is (100-120): (2-3): (0.1-0.5): (1-2).

[0043] In some optional examples, the antioxidant is antioxidant 1010.

[0044] In some optional examples, the ultraviolet absorber is UV-326.

[0045] In some optional examples, the sixth temperature is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0046] In some optional examples, the first stirring speed is 1500-2000 rpm, for example, it can be 1500 rpm, 1550 rpm, 1600 rpm, 1650 rpm, 1700 rpm, 1750 rpm, 1800 rpm, 1850 rpm, 1900 rpm, 1950 rpm or 2000 rpm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0047] In some optional examples, the stirring time is 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0048] In a second aspect, the present invention provides a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer obtained by the preparation method described in the first aspect.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) the hydroxyl group of hydroxyethyl acrylate provides an active site for reacting with the isocyanate group, so that the system can form a chemically cross-linked polyurethane network. The cross-linked structure can effectively improve the stability of the material, reduce the chain breakage caused by ultraviolet radiation or thermal oxidation degradation, enhance the UV resistance of the coating, improve the light aging resistance, and maintain good appearance and mechanical properties under long-term exposure to outdoor environments; (2) the isoborneol ring structure significantly improves the hardness of the coating by providing a rigid skeleton of the polymer chain. At the same time, the acrylic acid group can participate in free radical polymerization, further increase the cross-linking density, and give the coating excellent mechanical properties; (3) the triethoxysilane group of vinyltriethoxysilane gradually hydrolyzes to form silanol during the reaction, and then forms a silanol bond through a condensation reaction. The introduction of the silanol bond also forms a dense inorganic barrier, improves the hydrophobicity of the material, and prevents the penetration of external moisture, oxygen and corrosive chemicals. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A flow chart of a method for preparing a highly elastic, hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer provided in Examples 1-6 of the present invention;

[0051] Figure 2 This is a SEM image of the highly elastic hand-scrapeable waterproof polyurethane coating based on the modified MDI prepolymer prepared in Example 1 of the present invention;

[0052] Figure 3The contact angle of the highly elastic hand-scrapeable waterproof polyurethane coating based on the modified MDI prepolymer prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0053] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0054] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products.

[0055] Example 1

[0056] This embodiment provides a method for preparing a highly elastic hand-scrape waterproof polyurethane coating based on a modified MDI prepolymer, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0057] Step S1, 105g of diphenylmethane diisocyanate (MDI) was heated to 63°C, 2.4g of dicyclohexylmethane diisocyanate was added, the temperature was adjusted to 72°C and the reaction was fully carried out for 1.2h, 1.4g of m-xylylenediisocyanate was added and the reaction was continued for 1.3h, 3.6g of vinyltriethoxysilane was added, the temperature was raised to 83°C and the reaction was continued for 2.1h, 1.9g of hydroxyethyl acrylate and 0.24g of stannous octoate were added, and the temperature was maintained at 83°C and the reaction was continued. The mixture was reacted for 1.3 h, followed by the addition of 2.4 g of maleic anhydride and 0.63 g of dicumyl peroxide, and the reaction was continued at 83° C. for 1.4 h. 1.6 g of glycidyl methacrylate was then added, and the reaction was continued at 83° C. for 2.2 h. 2.9 g of polycaprolactone diol was added, and the reaction was continued at 83° C. for 2.1 h to obtain modified MDI. 40 g of the modified MDI was mixed with 156 g of polytetrahydrofuran, and the reaction was continued at 83° C. for 3.3 h to obtain an MDI prepolymer.

[0058] Step S2: 109 g of polypropylene glycol was heated to 83° C., 1.3 g of dicumyl peroxide and 11 g of glycidyl methacrylate were added, the temperature was raised to 92° C. and the mixture was fully reacted for 2.5 h. 2.6 g of isobornyl acrylate was then added and the reaction was continued for 1.3 h. The temperature was adjusted to 73° C., 3.6 g of γ-methacryloyloxypropyltrimethoxysilane and 0.14 g of stannous acetate were added, the temperature was raised to 83° C. and the mixture was fully reacted for 3.3 h to obtain modified polypropylene glycol.

[0059] Step S3, heating 107 g of polycarbonate diol to 84° C., adding 3.9 g of dimethyl propylene glycol and 2.9 g of tetrabutyl titanate, raising the temperature to 122° C. under nitrogen protection and fully reacting for 2.2 h, cooling to 100° C., adding 4.2 g of dicyclohexylmethane-4,4'-diisocyanate, raising the temperature to 122° C. and continuing the reaction for 3.3 h, and then adding 2.8 g of caprolactone and fully reacting for 2.1 h to obtain modified polycarbonate diol;

[0060] Step S4: 109 g of MDI prepolymer, 43 g of modified polypropylene glycol, 34 g of modified polycarbonate diol, 33 g of filler, 0.59 g of dibutyltin dioctoate, 2.2 g of additive, 0.25 g of antioxidant 1010, and 1.3 g of UV-326 are added and mixed; the mixture is stirred at 54° C. and 1500 rpm for 23 minutes; and vacuum degassing is performed to obtain a highly elastic, hand-scrapeable, waterproof polyurethane coating based on the modified MDI prepolymer.

[0061] Figure 2 This is an SEM image of the highly elastic hand-scrapeable waterproof polyurethane coating based on the modified MDI prepolymer prepared in this example. It can be seen that the coating surface is smooth, dense, and has no obvious irregular shapes; Figure 3 The contact angle of the polyurethane coating prepared in this example with water is 136°, indicating that the coating has a good hydrophobic effect.

[0062] Example 2

[0063] This embodiment provides a method for preparing a highly elastic hand-scrape waterproof polyurethane coating based on a modified MDI prepolymer, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0064] Step S1, heat 112g of diphenylmethane diisocyanate (MDI) to 65°C, add 2.9g of dicyclohexylmethane diisocyanate, adjust the temperature to 73°C and fully react for 1.4h, then add 2.3g of m-xylylenediisocyanate and continue to react for 1.5h, then add 4.1g of vinyltriethoxysilane, raise the temperature to 85°C and continue to react for 2.4h, then add 1.2g of hydroxyethyl acrylate and 0.33g of stannous octoate, maintain 85°C and continue to The mixture was reacted for 1.5 h, followed by the addition of 2.3 g of maleic anhydride and 0.88 g of dicumyl peroxide, and the reaction was continued at 85° C. for 1.6 h. 1.3 g of glycidyl methacrylate was added, and the reaction was continued at 85° C. for 2.4 h. 2.1 g of polycaprolactone diol was added, and the reaction was continued at 85° C. for 2.3 h to obtain modified MDI. 40 g of the modified MDI was mixed with 133 g of polytetrahydrofuran, and the reaction was continued at 85° C. for 3.5 h to obtain an MDI prepolymer.

[0065] Step S2: 103 g of polypropylene glycol was heated to 84° C., 1.8 g of dicumyl peroxide and 16 g of glycidyl methacrylate were added, the temperature was raised to 91° C. and the mixture was fully reacted for 2.2 h. 2.2 g of isobornyl acrylate was then added and the reaction was continued for 1.5 h. The temperature was adjusted to 72° C., 3.1 g of γ-methacryloyloxypropyltrimethoxysilane and 0.19 g of stannous acetate were added, the temperature was raised to 84° C. and the mixture was fully reacted for 3.1 h to obtain modified polypropylene glycol.

[0066] Step S3, heating 112 g of polycarbonate diol to 81° C., adding 3.2 g of dimethyl propylene glycol and 2.6 g of tetrabutyl titanate, raising the temperature to 124° C. under nitrogen protection and fully reacting for 2.4 h, cooling to 100° C., adding 3.2 g of dicyclohexylmethane-4,4'-diisocyanate, raising the temperature to 124° C. and continuing the reaction for 3.5 h, and then adding 2.4 g of caprolactone and fully reacting for 2.3 h to obtain modified polycarbonate diol;

[0067] Step S4: 105 g of MDI prepolymer, 41 g of modified polypropylene glycol, 31 g of modified polycarbonate diol, 31 g of filler, 0.66 g of dibutyltin dioctoate, 2.5 g of additive, 0.19 g of antioxidant 1010, and 1.5 g of UV-326 are added and mixed, and the mixture is stirred at 52° C. and 1600 rpm for 24 minutes. After vacuum degassing, a highly elastic hand-scrapeable waterproof polyurethane coating based on the modified MDI prepolymer is obtained.

[0068] Example 3

[0069] This embodiment provides a method for preparing a highly elastic hand-scrape waterproof polyurethane coating based on a modified MDI prepolymer, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0070] Step S1: Heat 110g of diphenylmethane diisocyanate (MDI) to 67°C, add 3.6g of dicyclohexylmethane diisocyanate, adjust the temperature to 75°C and fully react for 1.6h, then add 1.5g of m-xylylenediisocyanate and continue to react for 1.1h, then add 5.2g of vinyltriethoxysilane, raise the temperature to 87°C and continue to react for 2.1h, then add 1.7g of hydroxyethyl acrylate and 0.57g of stannous octoate, maintain 87°C and continue to The mixture was reacted for 1.3 h, followed by the addition of 3.0 g of maleic anhydride and 0.72 g of dicumyl peroxide, and the reaction was continued at 87° C. for 1.3 h. 2.3 g of glycidyl methacrylate was then added, and the reaction was continued at 87° C. for 2.5 h. 2.6 g of polycaprolactone diol was added, and the reaction was continued at 87° C. for 2.4 h to obtain modified MDI. 40 g of the modified MDI was mixed with 142 g of polytetrahydrofuran, and the reaction was continued at 87° C. for 3.2 h to obtain an MDI prepolymer.

[0071] Step S2: 110 g of polypropylene glycol was heated to 81° C., 1.5 g of dicumyl peroxide and 13 g of glycidyl methacrylate were added, the temperature was raised to 90° C. and the mixture was fully reacted for 2.5 h. 3.1 g of isobornyl acrylate was then added and the reaction was continued for 1.3 h. The temperature was adjusted to 75° C., 4.9 g of γ-methacryloyloxypropyltrimethoxysilane and 0.42 g of stannous acetate were added, the temperature was raised to 81° C. and the mixture was fully reacted for 3.1 h to obtain modified polypropylene glycol.

[0072] Step S3, heating 115 g of polycarbonate diol to 83° C., adding 5.7 g of dimethyl propylene glycol and 2.1 g of tetrabutyl titanate, raising the temperature to 126° C. under nitrogen protection and fully reacting for 2.6 hours, cooling to 100° C., adding 3.7 g of dicyclohexylmethane-4,4'-diisocyanate, raising the temperature to 126° C. and continuing the reaction for 3.6 hours, and then adding 2.1 g of caprolactone and fully reacting for 2.6 hours to obtain modified polycarbonate diol;

[0073] Step S4: 108 g of MDI prepolymer, 44 g of modified polypropylene glycol, 38 g of modified polycarbonate diol, 31 g of filler, 0.72 g of dibutyltin dioctoate, 2.2 g of additive, 0.24 g of antioxidant 1010, and 1.7 g of UV-326 are added and mixed; the mixture is stirred at 55° C. and 1700 rpm for 26 minutes; and vacuum degassing is performed to obtain a highly elastic, hand-scrapeable, waterproof polyurethane coating based on the modified MDI prepolymer.

[0074] Example 4

[0075] This embodiment provides a method for preparing a highly elastic hand-scrape waterproof polyurethane coating based on a modified MDI prepolymer, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0076] Step S1, 104g of diphenylmethane diisocyanate (MDI) was heated to 62°C, 3.1g of dicyclohexylmethane diisocyanate was added, the temperature was adjusted to 77°C and the reaction was fully carried out for 1.3h, 1.9g of m-xylylenediisocyanate was added and the reaction was continued for 1.3h, 5.8g of vinyltriethoxysilane was added, the temperature was raised to 82°C and the reaction was continued for 2.6h, 2.3g of hydroxyethyl acrylate and 0.17g of stannous octoate were added, and the temperature was maintained at 82°C. The reaction was continued for 1.7 hours, followed by the addition of 2.5 g of maleic anhydride and 1.1 g of dicumyl peroxide, the reaction was continued at 82° C. for 1.4 hours, the addition of 2.0 g of glycidyl methacrylate, the reaction was continued at 82° C. for 2.1 hours, the addition of 2.4 g of polycaprolactone diol, the reaction was continued at 82° C. for 2.5 hours to obtain modified MDI, and the mixture of 40 g of modified MDI and 127 g of polytetrahydrofuran was mixed and the reaction was continued at 82° C. for 3.5 hours to obtain an MDI prepolymer;

[0077] Step S2: 114 g of polypropylene glycol was heated to 83° C., 2.3 g of dicumyl peroxide and 12 g of glycidyl methacrylate were added, the temperature was raised to 95° C. and the mixture was fully reacted for 2.6 h. 3.5 g of isobornyl acrylate was then added and the reaction was continued for 1.5 h. The temperature was adjusted to 77° C., 3.5 g of γ-methacryloyloxypropyltrimethoxysilane and 0.38 g of stannous acetate were added, the temperature was raised to 85° C. and the mixture was fully reacted for 3.4 h to obtain modified polypropylene glycol.

[0078] Step S3, heating 104 g of polycarbonate diol to 87° C., adding 5.1 g of dimethyl propylene glycol and 3.5 g of tetrabutyl titanate, raising the temperature to 127° C. under nitrogen protection and fully reacting for 2.1 h, cooling to 100° C., adding 3.1 g of dicyclohexylmethane-4,4'-diisocyanate, raising the temperature to 127° C. and continuing the reaction for 3.2 h, and then adding 3.1 g of caprolactone and fully reacting for 2.1 h to obtain modified polycarbonate diol;

[0079] Step S4: 111 g of MDI prepolymer, 42 g of modified polypropylene glycol, 33 g of modified polycarbonate diol, 35 g of filler, 0.79 g of dibutyltin dioctoate, 2.3 g of additive, 0.36 g of antioxidant 1010, and 1.4 g of UV-326 are added and mixed; the mixture is stirred at 58° C. and 1800 rpm for 24 min; and vacuum degassing is performed to obtain a highly elastic, hand-scrapeable, waterproof polyurethane coating based on the modified MDI prepolymer.

[0080] Example 5

[0081] This embodiment provides a method for preparing a highly elastic hand-scrape waterproof polyurethane coating based on a modified MDI prepolymer, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0082] Step S1, 112g of diphenylmethane diisocyanate (MDI) was heated to 66°C, 2.5g of dicyclohexylmethane diisocyanate was added, the temperature was adjusted to 74°C and the reaction was fully carried out for 1.5h, 2.2g of m-xylylenediisocyanate was added and the reaction was continued for 1.4h, 4.5g of vinyltriethoxysilane was added, the temperature was raised to 88°C and the reaction was continued for 2.3h, 2.0g of hydroxyethyl acrylate and 0.39g of stannous octoate were added, and the temperature was maintained at 88°C. The reaction was continued for 1.3 hours, and then 3.5 g of maleic anhydride and 1.0 g of dicumyl peroxide were added, and the reaction was continued at 88°C for 1.1 hours. Then, 1.7 g of glycidyl methacrylate was added, and the reaction was continued at 88°C for 2.5 hours. 3.0 g of polycaprolactone diol was added, and the reaction was continued at 88°C for 2.7 hours to obtain modified MDI. 40 g of the modified MDI was mixed with 136 g of polytetrahydrofuran, and the reaction was continued at 88°C for 3.3 hours to obtain an MDI prepolymer.

[0083] Step S2: 103 g of polypropylene glycol was heated to 82° C., 2.0 g of dicumyl peroxide and 17 g of glycidyl methacrylate were added, the temperature was raised to 92° C. and the mixture was fully reacted for 2.4 h. 2.5 g of isobornyl acrylate was added and the reaction was continued for 1.3 h. The temperature was adjusted to 73° C., 5.6 g of γ-methacryloyloxypropyltrimethoxysilane and 0.26 g of stannous acetate were added, the temperature was raised to 82° C. and the mixture was fully reacted for 3.7 h to obtain modified polypropylene glycol.

[0084] Step S3, heating 116 g of polycarbonate diol to 89° C., adding 4.2 g of dimethyl propylene glycol and 3.2 g of tetrabutyl titanate, raising the temperature to 129° C. under nitrogen protection and fully reacting for 2.3 h, cooling to 100° C., adding 5.1 g of dicyclohexylmethane-4,4'-diisocyanate, raising the temperature to 125° C. and continuing the reaction for 3.6 h, then adding 3.5 g of caprolactone and fully reacting for 2.5 h to obtain modified polycarbonate diol;

[0085] Step S4: 114 g of MDI prepolymer, 46 g of modified polypropylene glycol, 37 g of modified polycarbonate diol, 32 g of filler, 0.88 g of dibutyltin dioctoate, 2.6 g of additive, 0.44 g of antioxidant 1010, and 1.9 g of UV-326 are added and mixed; the mixture is stirred at 60° C. and 1900 rpm for 23 minutes; and vacuum degassing is performed to obtain a highly elastic, hand-scrapeable, waterproof polyurethane coating based on the modified MDI prepolymer.

[0086] Example 6

[0087] This embodiment provides a method for preparing a highly elastic hand-scrape waterproof polyurethane coating based on a modified MDI prepolymer, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0088] Step S1, 107g of diphenylmethane diisocyanate (MDI) was heated to 62°C, 2.8g of dicyclohexylmethane diisocyanate was added, the temperature was adjusted to 77°C and the reaction was fully carried out for 1.9h, 2.0g of m-xylylenediisocyanate was added and the reaction was continued for 1.6h, 3.1g of vinyltriethoxysilane was added, the temperature was raised to 86°C and the reaction was continued for 2.2h, 2.1g of hydroxyethyl acrylate and 0.44g of stannous octoate were added, and the temperature was maintained at 86°C. The reaction was continued for 1.8 hours, followed by the addition of 2.9 g of maleic anhydride and 0.63 g of dicumyl peroxide, the reaction was continued at 86°C for 1.6 hours, the addition of 1.5 g of glycidyl methacrylate, the reaction was continued at 86°C for 2.3 hours, the addition of 2.7 g of polycaprolactone diol, the reaction was continued at 86°C for 2.4 hours to obtain modified MDI, the mixture of 40 g of modified MDI and 147 g of polytetrahydrofuran, the reaction was continued at 86°C for 3.3 hours to obtain an MDI prepolymer;

[0089] Step S2: 117 g of polypropylene glycol was heated to 86° C., 1.7 g of dicumyl peroxide and 18 g of glycidyl methacrylate were added, the temperature was raised to 94° C. and the mixture was fully reacted for 2.2 h. 2.1 g of isobornyl acrylate was then added and the reaction was continued for 1.4 h. The temperature was adjusted to 76° C., 5.9 g of γ-methacryloyloxypropyltrimethoxysilane and 0.51 g of stannous acetate were added, the temperature was raised to 85° C. and the mixture was fully reacted for 3.5 h to obtain modified polypropylene glycol.

[0090] Step S3, heating 110 g of polycarbonate diol to 86° C., adding 4.7 g of dimethyl propylene glycol and 2.4 g of tetrabutyl titanate, raising the temperature to 126° C. under nitrogen protection and fully reacting for 2.6 hours, cooling to 100° C., adding 5.7 g of dicyclohexylmethane-4,4'-diisocyanate, raising the temperature to 126° C. and continuing the reaction for 3.4 hours, and then adding 2.5 g of caprolactone and fully reacting for 2.7 hours to obtain modified polycarbonate diol;

[0091] Step S4: 119 g of MDI prepolymer, 44 g of modified polypropylene glycol, 39 g of modified polycarbonate diol, 36 g of filler, 0.96 g of dibutyltin dioctoate, 2.8 g of additive, 0.41 g of antioxidant 1010, and 2.0 g of UV-326 are added and mixed; the mixture is stirred at 57° C. and 2000 rpm for 26 minutes; and vacuum degassing is performed to obtain a highly elastic, hand-scrapeable, waterproof polyurethane coating based on the modified MDI prepolymer.

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer. The difference from Example 1 is that in step S1, the mass of hydroxyethyl acrylate is adjusted to 3.7 g. Compared with Example 1, the mass of hydroxyethyl acrylate is increased by 1.8 g. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer. The difference from Example 1 is that in step S1, the mass of hydroxyethyl acrylate is adjusted to 0.1 g. Compared with Example 1, the mass of hydroxyethyl acrylate is reduced by 1.8 g. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0096] Comparative Example 3

[0097] This comparative example provides a method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer. The difference from Example 1 is that in step S2, the mass of isobornyl acrylate is adjusted to 5.1 g. Compared with Example 1, the mass of isobornyl acrylate is increased by 2.5 g. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0098] Comparative Example 4

[0099] This comparative example provides a method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer. The difference from Example 1 is that in step S2, the mass of isobornyl acrylate is adjusted to 0.1 g. Compared with Example 1, the mass of isobornyl acrylate is reduced by 2.5 g. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0100] The polyurethane coating prepared in the present invention was tested for weather resistance according to GB / T 1865-2009; hardness according to GB / T 6739-2022; water resistance according to GB / T 1733-1993; and tensile strength and elongation at break according to JG-T 172-2014. The test results are shown in Table 1.

[0101] Table 1 Test results of high elasticity hand-scrape waterproof polyurethane coatings based on modified MDI prepolymers prepared in Examples 1-6 and Comparative Examples 1-4

[0102]

[0103] The data in the table show that the weather resistance, hardness, water resistance, and tensile strength of Comparative Example 1 are all lower than those of Example 1, while the strain at break is higher than that of Example 1; the weather resistance, hardness, water resistance, tensile strength, and strain at break of Comparative Example 2 are all lower than those of Example 1. This is because the excessive amount of hydroxyethyl acrylate in Comparative Example 1 introduces more acrylic groups, which are susceptible to photooxidative degradation under ultraviolet irradiation, resulting in accelerated aging of the coating; the excessive acrylic segments form flexible chains or low-molecular segments, thereby reducing the overall crosslink density and hardness; the hydroxyl groups in the hydroxyethyl acrylate molecules are hydrophilic groups, and the excessive amount of hydroxyethyl acrylate introduces more hydroxyl groups into the coating. These hydrophilic sites increase the affinity of the material surface for water, reducing water resistance; the excessive amount of hydroxyethyl acrylate leads to uneven crosslink density, which may form more low-molecular segments or flexible segments in the coating, reducing the overall strength of the network; the increased proportion of flexible segments reduces the overall rigidity of the system, while the low crosslink density regions of the acrylic segments increase the system's ductility to a certain extent. In Comparative Example 2, insufficient hydroxyethyl acrylate results in a decrease in the number of acrylic groups in the system, a decrease in cross-linking density, and a decrease in weather resistance; insufficient hydroxyethyl acrylate will lead to a decrease in cross-linking points and a decrease in the hardness of the coating; insufficient hydroxyethyl acrylate will reduce the amount of hydroxyl groups introduced, and the hydrophobicity of the material surface may be slightly improved. Due to insufficient cross-linking density, microstructural defects increase, making it easier for moisture to pass through the coating, resulting in reduced water resistance; insufficient hydroxyethyl acrylate leads to a decrease in the number of cross-linking points, an incomplete polyurethane network structure, insufficient physical and chemical bonding between molecular chains, and a decrease in tensile strength; the cross-linking density is reduced, the flexibility and ductility of the material are insufficient, brittle fracture is prone to occur in stress concentration areas, and the tensile strain rate decreases.

[0104] From the data in the table, it can be seen that the water resistance and tensile strength of Comparative Example 3 are lower than those of Example 1, while the weather resistance remains unchanged, and the hardness and fracture strain rate are higher than those of Example 1. The weather resistance, hardness, water resistance, and tensile strength of Comparative Example 4 are lower than those of Example 1, while the fracture strain rate is higher than that of Example 1. This is because in Comparative Example 3, the isobornyl structure in isobornyl acrylate contains an asymmetric saturated cyclic skeleton, which has high chemical stability to ultraviolet rays, and the weather resistance of the coating remains unchanged. The isobornyl ring structure is a chemical unit with high rigidity. Excessive use can lead to excessive crosslinking density or rigid segment ratio in the coating, thereby increasing the hardness of the coating. Excessive isobornyl acrylate can lead to uneven crosslinking density in the coating, excessively high ratio of local rigid segments, and may form microcracks or defects, resulting in decreased water resistance. The isobornyl ring structure makes the crosslinking structure of the coating more compact and rigid, increasing the tensile stress resistance of the coating. Excessive use can cause the coating to become too brittle, lose certain ductility and toughness, and thus increase tensile strength and decrease fracture strain rate. In Comparative Example 4, insufficient isobornyl structure leads to decreased UV resistance and aging resistance of the coating, and decreased weather resistance; the proportion of isobornyl acrylate in the coating structure is reduced, the cross-linking density is reduced, resulting in decreased hardness; low cross-linking density increases the water absorption rate and moisture permeability of the coating, and decreased water resistance; insufficient isobornyl acrylate leads to insufficient rigid chain segments, decreased cross-linking density and tensile strength within the molecule, and an excessively high proportion of flexible segments, thereby decreasing tensile strength and increasing the fracture strain rate.

[0105] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer, characterized in that: The preparation method is: Step S1, heating diphenylmethane diisocyanate and then adding dicyclohexylmethane diisocyanate, heating to react, then adding m-xylylenediisocyanate and vinyltriethoxysilane to react, then adding hydroxyethyl acrylate and a catalyst to continue the reaction, then adding maleic anhydride and an initiator to react, then adding glycidyl methacrylate to react, then adding polycaprolactone diol to react to obtain modified diphenylmethane diisocyanate, and then mixing the modified diphenylmethane diisocyanate with polytetrahydrofuran to react to obtain a diphenylmethane diisocyanate prepolymer; Step S2, heating the polyether polyol and adding an initiator and glycidyl methacrylate, heating the reaction, adding isobornyl acrylate, adjusting the temperature, adding γ-methacryloyloxypropyltrimethoxysilane and stannous acetate, and reacting to obtain a modified polyether polyol; Step S3, heating the polyester polyol and adding dimethyl propylene glycol and a catalyst, raising the temperature to react under nitrogen protection, cooling to 100° C., adding dicyclohexylmethane-4,4'-diisocyanate to react, and then adding caprolactone to react to obtain a modified polyester polyol; Step S4, adding diphenylmethane diisocyanate prepolymer, modified polyether polyol, modified polyester polyol, filler, dibutyltin dioctoate, additives, antioxidant and ultraviolet absorber in sequence and mixing, and vacuum degassing to obtain a highly elastic hand-scrapeable waterproof polyurethane coating based on the modified MDI prepolymer; The mass ratio of the diphenylmethane diisocyanate, hydroxyethyl acrylate, catalyst, maleic anhydride, and initiator is (100-120): (1-2.4): (0.1-0.6): (2-3.6): (0.5-1.2); the mass ratio of the polyether polyol, initiator, glycidyl methacrylate, isobornyl acrylate, γ-methacryloyloxypropyltrimethoxysilane, and stannous acetate is (100-120): (1-2.4): (10-18): (2-3.6): (3-6): (0.1-0.6).

2. The method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer according to claim 1, characterized in that: Step S1, The mass ratio of the diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, m-xylylenediisocyanate and vinyltriethoxysilane is (100-120): (2-3.6): (1-2.4): (3-6).

3. The method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer according to claim 1, characterized in that: Step S1, The catalyst is stannous octoate; The initiator is dicumyl peroxide.

4. The method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer according to claim 1, characterized in that: Step S1, The mass ratio of the diphenylmethane diisocyanate, glycidyl methacrylate, and polycaprolactone diol is (100-120): (1-2.4): (2-3.6); The mass ratio of the polytetrahydrofuran to diphenylmethane diisocyanate is (3-4):

1.

5. The method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer according to claim 1, characterized in that: Step S2, The initiator is dicumyl peroxide.

6. The method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer according to claim 1, characterized in that: Step S3, The mass ratio of the polyester polyol, dimethyl propylene glycol and catalyst is (100-120): (5-8.4): (0.1-0.6); The catalyst is tetrabutyl titanate.

7. The method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer according to claim 1, characterized in that: Step S3, The mass ratio of the polyester polyol, dicyclohexylmethane-4,4'-diisocyanate and caprolactone is (100-120): (3-6): (2-3.6).

8. The method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer according to claim 1, characterized in that: Step S4, The mass ratio of the diphenylmethane diisocyanate prepolymer, modified polyether polyol, modified polyester polyol, filler and dibutyltin dioctoate is (100-120): (40-50): (30-40): (30-40): (0.5-1); The filler is one or more of talc, titanium dioxide, silicon dioxide, mica powder and kaolin.

9. The method for preparing a highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer according to claim 1, characterized in that: Step S4, The mass ratio of the diphenylmethane diisocyanate prepolymer, the auxiliary agent, the antioxidant, and the ultraviolet absorber is (100-120): (2-3): (0.1-0.5): (1-2); The auxiliary agent is one or more of hydroxypropyl methylcellulose and polyvinyl alcohol; The antioxidant is antioxidant 1010; The ultraviolet absorber is UV-326.

10. A highly elastic hand-scrapeable waterproof polyurethane coating based on a modified MDI prepolymer obtained by the preparation method according to any one of claims 1 to 9.

Images