A waterproof polyurethane coating and a method for preparing the same

Abstract

The application belongs to the technical field of surface treatment agent production, and discloses a waterproof polyurethane coating, which comprises polyurethane emulsion and inorganic fillers filled in the polyurethane emulsion, wherein the inorganic fillers are inorganic fillers modified by silane coupling agents; the inorganic fillers are at least one selected from calcium carbonate, kaolin, barium sulfate, magnesium oxide, calcium oxide, wollastonite, talcum powder and mica powder; the silane coupling agents are at least one selected from KH540, KH550, KH560 and KH570; the mass ratio of the inorganic fillers modified by the silane coupling agents to the polyurethane emulsion is 1:8-10; by adding the inorganic fillers, the application fills the micropores and defects in the polyurethane, thereby reducing the channels for water penetration and improving the compactness of the material; and since part of the inorganic fillers have good shielding effect, the water molecules can be blocked from penetrating into the polyurethane, thereby enhancing the waterproof performance; in addition, the application also discloses a preparation method of the waterproof polyurethane coating.

Description

Technical Field

[0001] This application relates to the field of surface treatment agent production technology, and in particular to a waterproof polyurethane coating and its preparation method. Background Technology

[0002] Pure natural leather products, based on proteins, possess strong hydrophilicity and breathability. However, processed leather often incorporates many hydrophilic groups such as hydroxyl, carboxyl, amino, and amide groups during manufacturing, resulting in poor water resistance and significantly impacting its usability. As consumer demand has increased, improving leather's water resistance has been a constant pursuit. As early as the 20th century, people improved leather's water resistance by adding waterproof substances like paraffin and animal fats during processing. This evolved into adding finishing touches to the leather surface, forming a uniform protective film and giving the leather vibrant colors, enhancing its decorative appeal and increasing its added value, thus gaining wider popularity. Therefore, waterproof coatings, as leather finishing agents, have become a crucial element in the leather processing industry, and the widespread application of waterproof leather has further promoted the development of waterproof coatings.

[0003] With advancements in production and daily life, people have increasingly higher demands for leather products in terms of both quality and performance. Leather products not only need to meet people's basic production and living needs, but also need to continuously meet the public's needs in terms of fashion and usability. Therefore, people expect leather to exhibit "three-proof" properties that leather itself does not possess, such as waterproofing, oil resistance, and stain resistance. Fluorinated leather waterproofing agents have emerged in response to people's needs and the needs of production development, and have gradually entered the public eye. In order to maintain the excellent waterproof and oil-resistant properties of leather, leather waterproofing agents are usually applied to the surface of the leather to form a uniform waterproof coating.

[0004] Fluorinated compounds, due to the presence of fluorine (CF), allow fluorine atoms to be tightly connected to the carbon backbone, resulting in superior properties unmatched by other materials. Therefore, they are widely used in chemical, industrial construction, and aerospace fields. Their unique and excellent properties have also led to their application in the preparation of leather waterproofing agents. Fluorinated waterproofing coatings are used in the leather industry. Leather treated with these agents not only retains its original softness and good breathability but also possesses "three-proof" properties, giving leather, cotton, polyester, nylon, and other materials highly durable waterproofing effects and excellent water resistance and aging resistance.

[0005] Chinese patent application 201910940003.6 discloses a fluorinated polyurethane material with waterproof, oil-proof, and stain-resistant properties. The preparation method is to first synthesize a dihydroxy fluorocarbon chain monomer through a mercapto-vinyl Michael addition reaction, then introduce it into the polyurethane through an addition polymerization reaction with a diisocyanate-terminated polyurethane prepolymer, and then obtain a fluorinated waterborne polyurethane material with waterproof, oil-proof, and stain-resistant properties through chain extension reaction and neutralization reaction respectively.

[0006] The fluorinated small-molecule organic compounds in this solution possess properties such as water resistance, oil resistance, stain resistance, and heat resistance. However, they readily bind to proteins in the blood, accumulating in the human body and potentially impacting health. Fluoropolymers, on the other hand, largely retain the properties of fluorinated small-molecule organic compounds and exhibit good biocompatibility. Furthermore, due to their low chemical and biological activity, they do not affect human health. Introducing fluorinated small-molecule organic compounds into polyurethane materials can significantly improve the water resistance and biocompatibility of polyurethane while also substantially reducing the toxicity of the fluorinated small-molecule organic compounds.

[0007] As can be seen, the above scheme improves the waterproof performance of polyurethane by incorporating fluorine into leather finishing agents to obtain polyurethane chains containing fluorine-containing small molecule organic compounds.

[0008] Chinese patent application 201610249143.5 discloses a high-strength polyurethane waterproof coating, the raw materials of which, by weight, include: 50-55 parts of high-strength hydrophobic polyurethane, 26-29 parts of short-oil alkyd resin, 7-10 parts of potassium tripolyphosphate, 3-5 parts of zinc stearate, 0.5-0.8 parts of calcium lignosulfonate, 5-8 parts of bentonite, 3-6 parts of light calcium carbonate, 2-5 parts of talc, 4-6 parts of butyl acetate, 1-3 parts of cyclohexanone, 0.1-0.4 parts of defoamer, 0.2-0.5 parts of leveling agent, and 0.3-0.6 parts of dispersant;

[0009] Further observation of this scheme reveals that in the high-strength hydrophobic polyurethane, adding castor oil during the phenolic resin preparation process introduces the unsaturated bonds in the castor oil into the molecular structure of the phenolic resin, crosslinking them into a three-dimensional network structure. This significantly improves the strength and brushability of the solution, while also increasing the density of the polyurethane, thereby enhancing its hydrophobic properties and achieving a waterproof effect. Furthermore, the castor oil-modified phenolic resin and diphenylmethane diisocyanate trimer can rapidly crosslink under the action of the small molecule chain extender dipropylene glycol, the crosslinking agent trimethylolethane, and the catalyst dibutyltin dilaurate to form a high-strength hydrophobic polyurethane with high strength, good toughness, and excellent waterproof performance. During the preparation process, high-strength hydrophobic... Polyurethane and short-oil alkyd resin, as film-forming substances, can fully crosslink and complement each other to form a coating film with excellent hydrophobic properties, thereby greatly improving the waterproof performance of polyurethane. The added potassium tripolyphosphate and zinc stearate can be dispersed in the network structure of the present invention, enhancing the fire resistance and strength of polyurethane. Calcium lignosulfonate has good wetting and dispersibility, which can improve the workability of the waterproof coating and improve the flexibility of the coating film. The addition of bentonite, light calcium carbonate, and talc powder significantly improves the consistency and anti-thixotropic properties of the present invention. They are evenly distributed in polyurethane, extending the service life and shelf life of polyurethane, giving polyurethane high strength, high toughness, and excellent waterproof performance after curing.

[0010] It is evident that the above scheme further enhances the waterproof performance of polyurethane by adding various additives, including fillers, and utilizing the interactions between these additives. However, it is clear that this scheme does not modify the inorganic fillers to improve their dispersibility in the polyurethane.

[0011] The problem this solution aims to solve is: how to develop a waterproof polyurethane coating that differs from existing technologies and has excellent waterproofing capabilities. Summary of the Invention

[0012] The purpose of this application is to provide a polyurethane coating with good waterproof performance. This coating improves the waterproof ability of the polyurethane emulsion after curing by adjusting the mass ratio of inorganic fillers, coupling agents and polyurethane emulsion, thereby reducing the problems of easy water absorption or instability in humid environments caused by the strong hydrophilicity of polyurethane during use.

[0013] To achieve the above objectives, this application discloses a waterproof polyurethane coating, comprising a polyurethane emulsion and an inorganic filler filled in the polyurethane emulsion, wherein the inorganic filler is an inorganic filler modified with a silane coupling agent.

[0014] The inorganic filler is selected from at least one of calcium carbonate, kaolin, barium sulfate, magnesium oxide, calcium oxide, wollastonite, talc, and mica powder.

[0015] The silane coupling agent is selected from at least one of KH540, KH550, KH560, and KH570;

[0016] The mass ratio of the inorganic filler modified with silane coupling agent to the polyurethane emulsion is 1:8 to 10.

[0017] Preferably, the silane coupling agent is a mixture of KH540 and KH550, and the mass ratio of KH540 to KH550 is 2 to 3:1.

[0018] Preferably, the inorganic filler is a mixture of kaolin, barium sulfate and calcium oxide, and the mass ratio of kaolin, barium sulfate and calcium oxide is 2-3:1:0.5-1.

[0019] Preferably, the modified inorganic filler is prepared by mixing the inorganic filler and the silane coupling agent at a mass ratio of 1:1.5 to 2 and reacting them in an ethanol solvent at 100 to 115°C for 1 to 3 hours, followed by drying to obtain the inorganic filler modified with the silane coupling agent.

[0020] Preferably, the polyurethane emulsion comprises the following components by weight:

[0021]

[0022] The isocyanate is a mixture of diisocyanate and long-chain isocyanate, wherein the long-chain alkyl group in the long-chain isocyanate has not less than 12 carbon atoms.

[0023] Furthermore, the mass ratio of the diisocyanate to the long-chain isocyanate is 10 to 12:1.

[0024] Preferably, the diisocyanate is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, isoflurone diisocyanate, and phenylmethylene diisocyanate;

[0025] The long-chain isocyanate is selected from at least one of dodecylbenzene-2,4-diisocyanate, 1,12-diisocyanate tridecane, dodecyl isocyanate, tetradecyl isocyanate, and octadecyl isocyanate.

[0026] Preferably, the polyester polyol is selected from at least one of polyethylene adipate diol, polybutylene adipate diol, and polycaprolactone diol.

[0027] Preferably, the diol is selected from at least one of propylene glycol, butanediol, pentanediol, and hexanediol;

[0028] The solvent is selected from either toluene or acetone.

[0029] In addition, this application also discloses a method for preparing the above-mentioned waterproof polyurethane coating, comprising the following steps:

[0030] Step 1: Mix the inorganic filler and silane coupling agent at a mass ratio of 1:1.5-2 and place them in ethanol solvent. React at 100-115℃ for 1-3 hours, and then dry to obtain the inorganic filler modified with silane coupling agent.

[0031] Step 2: Mix polyester polyol, isocyanate and solvent and react at 70-90°C for 2-5 hours to obtain intermediate one;

[0032] Step 3: Dissolve 2,2-dimethylolpropionic acid in a solvent, and then react the solvent containing 2,2-dimethylolpropionic acid with intermediate one to generate intermediate two;

[0033] In step 2, the mass of the solvent is 70-85% of the total mass of the solvent, and in step 3, the mass of the solvent is 15-30% of the total mass of the solvent.

[0034] Step 4: Mix the diol with intermediate II and react at 70-80°C for 1.5-3 hours. Then add triethylamine for neutralization reaction for 30-50 minutes. Finally, add deionized water for emulsification to obtain a polyurethane emulsion.

[0035] Step 5: Disperse the inorganic filler modified with silane coupling agent into the polyurethane emulsion to obtain a waterproof polyurethane coating.

[0036] The beneficial effects of this application are:

[0037] The waterproof polyurethane coating disclosed in this application fills the micropores and defects in the polyurethane with the addition of inorganic fillers, thereby reducing the channels for water penetration and improving the density of the material. Furthermore, since some inorganic fillers have a good shielding effect, they can prevent water molecules from penetrating into the interior of the polyurethane, thus enhancing the waterproof performance. At the same time, the interfacial interaction between the inorganic fillers and the polyurethane matrix can improve the mechanical properties and water resistance of the material. The fillers that have undergone surface modification can form a better interfacial bond with the polyurethane matrix, thereby further enhancing the waterproof performance of the polyurethane. Detailed Implementation

[0038] The present invention will now be clearly and completely described in conjunction with embodiments thereof. It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0039] Before demonstrating the embodiments, the following necessary explanations are provided regarding the raw materials and preparation methods involved in the embodiments:

[0040] Information on the raw materials for each example is shown in Table 1:

[0041] Table 1

[0042]

[0043] The preparation method of the polyurethane coating agent in the examples and comparative examples is as follows:

[0044] Step 1: Mix the inorganic filler and silane coupling agent at a mass ratio of 1:1.5 and place them in ethanol solvent to react at 108±2℃ for 2h. Then dry to obtain the silane coupling agent modified inorganic filler.

[0045] Step 2: The polyester polyol, isocyanate and solvent are mixed and reacted at 80±5℃ for 3.5±0.5h to obtain intermediate one;

[0046] Step 3: Dissolve 2,2-dimethylolpropionic acid in a solvent, and then react the solvent containing 2,2-dimethylolpropionic acid with intermediate one to generate intermediate two;

[0047] In step 2, the mass of the solvent is 80% of the total mass of the solvent, and in step 3, the mass of the solvent is 20% of the total mass of the solvent.

[0048] Step 4: Mix the diol with intermediate II and react at 75±5℃ for 2.5±0.5h, then add triethylamine for neutralization reaction for 30-50min, then add deionized water for emulsification to obtain polyurethane emulsion;

[0049] Step 5: Disperse the inorganic filler modified with silane coupling agent into the polyurethane emulsion to obtain a waterproof polyurethane coating;

[0050] It should be further noted that the specific formulation of the polyurethane used in each embodiment and the specific selection of inorganic fillers and silane coupling agents are described in detail in each embodiment.

[0051] Examples 1-4

[0052] The formulations of the polyurethane emulsions are shown in Table 2:

[0053] Table 2

[0054]

[0055] It should be noted that in Examples 1-4, the polyester polyol is specifically polyethylene adipate diol;

[0056] In Examples 1-4, the diisocyanate is specifically a mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate, and in Example 1, the mass ratio of the mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate is 10:1;

[0057] In Example 2, the mass ratio of the mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate was 12:1;

[0058] In Example 3, the mass ratio of the mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate was 11:1;

[0059] In Example 3, the mass ratio of the mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate was 10:1;

[0060] The solvent used in Examples 1-4 is acetone;

[0061] Furthermore, the inorganic filler in Examples 1-4 is kaolin, and the silane coupling agent is KH540;

[0062] The mass ratio of the silane coupling agent-modified inorganic filler to the polyurethane emulsion is 1:9.

[0063] Example 5

[0064] It is basically the same as Example 1, except that the mass ratio of the silane coupling agent modified inorganic filler to the polyurethane emulsion is 1:8.

[0065] Example 6

[0066] It is basically the same as Example 1, except that the mass ratio of the silane coupling agent modified inorganic filler to the polyurethane emulsion is 1:10.

[0067] Example 7

[0068] It is basically the same as Example 1, except that the silane coupling agent is KH550.

[0069] Example 8

[0070] The method is basically the same as in Example 1, except that the silane coupling agent is a mixture of KH540 and KH550, and the mass ratio of KH540 to KH550 is 2:1.

[0071] Example 9

[0072] The method is basically the same as in Example 1, except that the silane coupling agent is a mixture of KH540 and KH550, and the mass ratio of KH540 to KH550 is 3:1.

[0073] Example 10

[0074] The method is basically the same as in Example 1, except that the silane coupling agent is a mixture of KH540 and KH550, and the mass ratio of KH540 to KH550 is 2.5:1.

[0075] Example 11

[0076] It is basically the same as Example 1, except that barium sulfate is used instead of kaolin.

[0077] Example 12

[0078] It is basically the same as Example 1, except that calcium oxide is used instead of kaolin.

[0079] Example 13

[0080] The method is basically the same as in Example 1, except that a mixture of kaolin, barium sulfate and calcium oxide is used to replace kaolin, and the mass ratio of kaolin, barium sulfate and calcium oxide is 3:1:1.

[0081] Example 14

[0082] It is basically the same as Example 1, except that a mixture of kaolin, barium sulfate and calcium carbonate is used to replace kaolin, and the mass ratio of kaolin, barium sulfate and calcium carbonate is 3:1:1.

[0083] Example 15

[0084] The mixture is essentially the same as in Example 1, except that the mass ratio of the toluene diisocyanate to the dodecylbenzene-2,4-diisocyanate mixture is 8:1.

[0085] Example 16

[0086] It is essentially the same as Example 1, except that toluene diisocyanate is used instead of the mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate.

[0087] Comparative Example 1

[0088] It is basically the same as Example 1, except that the mass ratio of the silane coupling agent modified inorganic filler to the polyurethane emulsion is 1:7.

[0089] Comparative Example 2

[0090] It is basically the same as Example 1, except that the mass ratio of the silane coupling agent modified inorganic filler to the polyurethane emulsion is 1:11.

[0091] Comparative Example 3

[0092] The process is basically the same as in Example 1, except that after obtaining the polyurethane emulsion in step 4, no inorganic filler modified with silane coupling agent is added to the polyurethane emulsion. The types and amounts of the remaining polyester polyol, diisocyanate, 2,2-dimethylolpropionic acid, diol, and solvent are the same as in Example 1.

[0093] The specific preparation method is as follows:

[0094] Step 1: The polyester polyol, isocyanate and solvent are mixed and reacted at 80±5℃ for 3.5±0.5h to obtain intermediate one;

[0095] Step 2: Dissolve 2,2-dimethylolpropionic acid in a solvent, and then react the solvent containing 2,2-dimethylolpropionic acid with intermediate one to generate intermediate two;

[0096] In step 2, the mass of the solvent is 80% of the total mass of the solvent, and in step 3, the mass of the solvent is 20% of the total mass of the solvent.

[0097] Step 3: Mix the diol with intermediate II and react at 75±5℃ for 2.5±0.5h. Then add triethylamine for neutralization reaction for 30-50min. Finally, add deionized water for emulsification to obtain a polyurethane emulsion.

[0098] Comparative Example 4

[0099] It is basically the same as Comparative Example 3, except that toluene diisocyanate is used instead of the mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate.

[0100] Performance testing:

[0101] Waterproof performance test:

[0102] The polyurethane coatings prepared in the above examples and comparative examples were used to form films, and their waterproof performance was tested according to JC / T 864-2023.

[0103] Emulsification difficulty test:

[0104] Since the preparation process of polyurethane coatings specifically involves neutralizing intermediate diethylamine with triethylamine in step 4 and then adding deionized water for emulsification, the presence of long-chain isocyanates in the isocyanate may affect the emulsification time of deionized water. Therefore, the emulsification time of deionized water in the preparation process of different embodiments and comparative examples is statistically analyzed to determine the ease or difficulty of emulsification in each embodiment.

[0105] The specific testing method is as follows: during the preparation of polyurethane coating, the rotation speed of each embodiment and comparative example during the emulsification process is controlled to be the same (the rotation speed is 1500 rpm). After emulsification, the emulsions all show an appearance without layering or clumping. The emulsification time is counted, and the difficulty of emulsification is judged from the length of the emulsification time. The longer the emulsification time, the more difficult the emulsification.

[0106] The specific results are shown in Table 3:

[0107] Table 3

[0108]

[0109]

[0110] Results analysis:

[0111] 1. As can be seen from Examples 1-4, when the amount of each raw material added to the polyurethane emulsion in the coating agent is adjusted slightly, the water absorption rate and emulsification time of Examples 1-4 fluctuate, but the overall fluctuation range is relatively small.

[0112] 2. As can be seen from Examples 1 and 5-6, when the mass ratio between the silane coupling agent modified inorganic filler and the polyurethane emulsion is slightly adjusted, the water absorption rate of the coating agent increases with the increase of the proportion of the silane coupling agent modified inorganic filler, but overall, the change in water absorption rate is relatively small.

[0113] 3. As can be seen from Examples 1 and 7-10, on the one hand, when silane coupling agent KH540 was replaced with silane coupling agent KH550, the water absorption rate of Example 7 did not show a significant fluctuation trend compared to Example 1. However, further observation of Examples 8-10 shows that when a mixture of silane coupling agents KH540 and KH550 was used to replace silane coupling agent KH540 in Examples 8-10, the water absorption rate of Examples 8-10 showed varying degrees of inhibition compared to Example 1. It is speculated that the reason for this phenomenon may be that, on the one hand, the mixed use of KH550 and KH540 resulted in a more uniform and stable interface layer between the inorganic filler and the polyurethane matrix during the mixing process of the inorganic filler and the polyurethane emulsion; this interface layer can effectively prevent water penetration, thereby improving the waterproof performance of the material.

[0114] On the other hand, the combined use of the two and the modification of the inorganic filler further enhance the bonding ability between the inorganic filler and the polyurethane emulsion, thereby improving the waterproofing ability of the coating.

[0115] Furthermore, observation of Example 10 shows that when the mass ratio of KH540 to KH550 was adjusted to 2.5:1 in Example 10, the water absorption rate of Example 10 showed a further increasing trend. It can be seen that when the mass ratio of KH540 to KH550 is 2.5:1, the above-mentioned silane coupling agent has a more significant effect on improving the stability of the interface layer and the bonding ability between the inorganic filler and the polyurethane emulsion.

[0116] 4. As can be seen from Examples 1 and 11-12, when barium sulfate or calcium oxide was used to replace kaolin in Examples 11 and 12, the water absorption rate of Examples 11-12 increased to a certain extent compared with Example 1. However, when a mixture of kaolin, barium sulfate and calcium oxide was used to replace kaolin in Example 13, the water absorption rate of Example 13 showed a more obvious inhibitory effect compared with Example 1. It is speculated that the reason for this phenomenon may be that the combined use of kaolin, barium sulfate and calcium oxide may have made the filler form a more complex physical barrier in the coating agent, thereby increasing the path length of water penetration and thus improving the waterproof performance of the coating agent.

[0117] However, further observation of Example 14 reveals that although Example 14 also uses three inorganic fillers in combination and differs from Example 13 only in that calcium carbonate is used to replace calcium oxide, Example 14 did not achieve a water absorption rate similar to that of Example 13. This may be because calcium carbonate cannot form a complex physical barrier with kaolin and barium sulfate in the coating agent, or the density of the physical barrier formed is relatively low, which leads to a decline in the waterproof performance of the coating agent compared to Example 13.

[0118] 5. Further observation of Examples 1 and 15 shows that when the proportion of dodecylbenzene-2,4-diisocyanate in diisocyanate is increased in Example 15, the water absorption rate of Example 15 shows a certain downward trend compared with Example 1. However, the emulsification time shows that the emulsification process takes significantly longer.

[0119] 6. As can be seen from Example 1 and Comparative Example 1, when the proportion of inorganic filler in the coating agent is increased in Comparative Example 1, the final coating agent product cannot be obtained. Although the polyurethane emulsion exhibits a good appearance during the emulsification process, the addition of too much inorganic filler in the subsequent process causes the inorganic filler to agglomerate in the polyurethane emulsion and become undispersible.

[0120] Further observation of Comparative Example 2 shows that when the proportion of inorganic filler in the coating agent is reduced, the water absorption rate of the inorganic filler increases. This is because the proportion of inorganic filler in the coating agent is too small, which leads to a decrease in the shielding effect, allowing more water molecules to penetrate into the polyurethane and affecting the waterproof performance.

[0121] As can be seen from Comparative Example 3, when no inorganic filler is added to the polyurethane coating, the waterproof performance of Comparative Example 3 shows a significant downward trend. Although some long-chain isocyanates are used in the diisocyanate to provide hydrophobic groups to improve the waterproof performance of the material, its waterproof ability is improved but not as significantly as that of Example 1.

[0122] 7. Further, observing Examples 1 and 16, it can be seen that the difference between Examples 1 and 16 lies in the different composition of the diisocyanate. In Example 1, the diisocyanate is a mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate, and the mass ratio of the mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate is 10:1.

[0123] In Example 16, the diisocyanate contained only toluene diisocyanate;

[0124] Further observation of the water absorption rate between the two shows that the water absorption rate of Example 1 is reduced by approximately 4.6% compared to Example 16;

[0125] Meanwhile, observations of Comparative Examples 3 and 4 show that the difference between them also lies in the different composition of the diisocyanate. In Comparative Example 3, the diisocyanate is a mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate, and the mass ratio of the mixture of toluene diisocyanate and dodecylbenzene-2,4-diisocyanate is 10:1.

[0126] In Comparative Example 4, the diisocyanate contained only toluene diisocyanate;

[0127] Further observation of the water absorption rate between the two showed that the water absorption rate of Comparative Example 3 decreased by approximately 2.9% compared to Comparative Example 4.

[0128] It is evident that the difference between the two sets of cases lies in the different isocyanate compositions. Therefore, theoretically, the difference in water absorption rates between the two sets of cases should be similar. However, in reality, there is a difference in water absorption rates between the two sets of cases. The only difference between Examples 1 and 16 and Comparative Examples 3 and 4 is that Examples 1 and 16 added inorganic fillers, while Comparative Examples 3 and 4 did not add inorganic fillers. Therefore, it is speculated that the reason for the further decrease in water absorption rate of Example 1 compared to Example 16 may be due to the synergistic effect between the inorganic filler and the long-chain isocyanate. The principle may be that the part of the polyurethane chain involving the long-chain isocyanate may further react chemically with the inorganic filler, thereby improving the interfacial bonding force between the filler and the polyurethane matrix, thus further preventing water penetration.

Claims

1. A waterproof polyurethane coating, characterized in that, It includes a polyurethane emulsion and an inorganic filler filled in the polyurethane emulsion, wherein the inorganic filler is an inorganic filler modified with a silane coupling agent; The inorganic filler is selected from at least one of calcium carbonate, kaolin, barium sulfate, magnesium oxide, calcium oxide, wollastonite, talc, and mica powder. The silane coupling agent is a mixture of KH540 and KH550, and the mass ratio of KH540 to KH550 is 2.5:

1. The mass ratio of the inorganic filler modified with silane coupling agent to the polyurethane emulsion is 1:8 to 10.

2. The waterproof polyurethane coating according to claim 1, characterized in that, The inorganic filler is a mixture of kaolin, barium sulfate and calcium oxide, and the mass ratio of kaolin, barium sulfate and calcium oxide is 2-3:1:0.5-1.

3. The waterproof polyurethane coating according to claim 1, characterized in that, The modified inorganic filler is prepared by mixing the inorganic filler and silane coupling agent at a mass ratio of 1:1.5 to 2 and reacting them in ethanol solvent at 100 to 115°C for 1 to 3 hours, followed by drying to obtain the inorganic filler modified with silane coupling agent.

4. The waterproof polyurethane coating according to claim 1, characterized in that, The polyurethane emulsion comprises the following components by mass parts: 40-60 parts of polyester polyol; 15-30 parts isocyanate; 2-5 parts of diol; 1 to 5 parts of 2,2-dimethylolpropionic acid; Solvent 50-90 parts; The isocyanate is a mixture of diisocyanate and long-chain isocyanate, wherein the long-chain alkyl group in the long-chain isocyanate has not less than 12 carbon atoms. Furthermore, the mass ratio of the diisocyanate to the long-chain isocyanate is 10 to 12:

1.

5. The waterproof polyurethane coating according to claim 4, characterized in that, The diisocyanate is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, isoflurone diisocyanate, and phenylmethylene diisocyanate; The long-chain isocyanate is selected from at least one of dodecylbenzene-2,4-diisocyanate, 1,12-diisocyanate tridecane, dodecyl isocyanate, tetradecyl isocyanate, and octadecyl isocyanate.

6. The waterproof polyurethane coating according to claim 4, characterized in that, The polyester polyol is selected from at least one of polyethylene adipate diol, polybutylene adipate diol, and polycaprolactone diol.

7. The waterproof polyurethane coating according to claim 4, characterized in that, The diol is selected from at least one of propylene glycol, butanediol, pentanediol, and hexanediol; The solvent is selected from either toluene or acetone.

8. A method for preparing the waterproof polyurethane coating according to any one of claims 3-7, characterized in that, Includes the following steps: Step 1: Mix the inorganic filler and silane coupling agent at a mass ratio of 1:1.5-2 and place them in ethanol solvent. React at 100-115℃ for 1-3 hours, and then dry to obtain the inorganic filler modified with silane coupling agent. Step 2: Mix polyester polyol, isocyanate and solvent and react at 70-90°C for 2-5 hours to obtain intermediate one; Step 3: Dissolve 2,2-dimethylolpropionic acid in a solvent, and then react the solvent containing 2,2-dimethylolpropionic acid with intermediate one to generate intermediate two; In step 2, the mass of the solvent is 70-85% of the total mass of the solvent, and in step 3, the mass of the solvent is 15-30% of the total mass of the solvent. Step 4: Mix the diol with intermediate II and react at 70-80°C for 1.5-3 hours. Then add triethylamine for neutralization reaction for 30-50 minutes. Finally, add deionized water for emulsification to obtain a polyurethane emulsion. Step 5: Disperse the inorganic filler modified with silane coupling agent into the polyurethane emulsion to obtain a waterproof polyurethane coating.

Images