Elastic polyurethane finish paint for corrosion prevention of outer surface of PCCP (prestressed concrete cylinder pipe) and preparation method of elastic polyurethane finish paint

Abstract

The invention provides elastic polyurethane finish paint for corrosion prevention of the outer surface of a PCCP (prestressed concrete cylinder pipe) and a preparation method of the elastic polyurethane finish paint. The elastic polyurethane finish paint comprises a component A and a component B, the component A comprises 100-102 parts of an isocyanate prepolymer, and the component B comprises 18-30 parts of an amine chain extender, 0-22 parts of low molecular weight polyether amine, 35-75 parts of high molecular weight polyether amine, 0-23.4 parts of polyether polyol resin, 0-6.6 parts of polyester polyol resin, 0-0.2 part of a catalyst and 0-2 parts of carbon black color paste. Through cooperation of the component A and the component B, the elastic polyurethane has good mechanical properties and also has high strength and flexibility. Compared with the prior art, the elastic polyurethane finishing paint has the advantages that by introducing the polyol component which is relatively slow in reaction, more components are caused to post-reaction and are favorable for forming relatively good adhesion with a base material, so that the adhesive force of the elastic polyurethane is improved, and meanwhile, the introduced polyol has high functionality and is favorable for forming a 3D network structure and improving the crosslinking density of the elastic polyurethane, so that the tearing strength of the finishing paint is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of special coatings, in particular, to an elastic polyurethane finish for the anticorrosion of the outer surface of a PCCP pipe and a preparation method thereof. BACKGROUND

[0002] Prestressed concrete cylinder pipe (PCCP) is widely used in large water diversion projects such as South-to-North Water Diversion and urban water supply trunk lines due to its high strength, high permeability and durability. However, the steel cylinder and concrete structure of PCCP pipe are prone to chemical corrosion, electrochemical corrosion and microbial corrosion under harsh working conditions such as complex water environment (e.g. containing chloride ions, sulfate and other corrosive media), soil stress and wet-dry alternation, resulting in decreased pipe strength and increased leakage risk. According to statistics, the steel cylinder of PCCP pipe without effective corrosion protection measures may appear local corrosion perforation within 5-10 years, which seriously threatens the safety of water diversion and the service life of the project. Therefore, developing high-performance anticorrosive coatings has become a key to ensuring the long-term stable operation of PCCP pipe.

[0003] In the past 20 years, the anticorrosive coatings for the outer surface of PCCP pipe mainly include epoxy-based coatings, asphalt-based coatings and polyethylene-based coatings. Traditional epoxy anticorrosive coatings have good initial adhesion and chemical resistance, but poor flexibility, which easily leads to cracking when the PCCP pipe is subjected to foundation settlement, temperature change or water pressure fluctuation, resulting in coating failure; asphalt-based anticorrosive materials have low cost, but poor weather resistance, which easily ages and embrittles under long-term exposure to ultraviolet light and high temperature environment, and have weak water resistance and poor resistance to microbial corrosion; polyethylene coatings have good physical protection, but have limited adhesion to the steel cylinder, which easily peels off in humid environment and cannot effectively block the penetration of corrosive media. In recent years, with the requirement of high-quality development proposed by the state, new environmentally friendly materials are increasingly used in national projects. Elastic polyurethane, due to its environmental protection, high construction efficiency, excellent physical and anticorrosive properties, has been gradually promoted in national water diversion projects and eventually replaced traditional coatings. However, since elastic polyurethane is still in the early stage of promotion, relevant technical standards have not yet been formed, and owners, pipe manufacturers and coating manufacturers are still working together to actively explore suitable technical solutions. Currently, the performance requirements of elastic polyurethane for the anticorrosion of the outer surface of PCCP pipe mainly focus on dry performance, mechanical properties and anticorrosive properties.

[0004] The PCCP pipe surface has a large number of defects such as holes, and the stress at the hole is unbalanced, and the coating is prone to cracking, therefore, the elastic polyurethane needs to have excellent elasticity and strength, so that the coating is not easy to fail at the hole under external force; in addition, the outer surface of the PCCP pipe is a concrete material, and the surface continuously releases alkaline ions, the PCCP pipe laying path is long, and the geological environment of laying is complex, and may experience extreme corrosion environments such as saline-alkali land, therefore, the elastic polyurethane for the outer surface corrosion prevention of the PCCP pipe needs to have excellent corrosion resistance, such as acid resistance, alkali resistance, salt water resistance, etc.; at the same time, the PCCP pipe is exposed to the sun for a long time when it is exposed to the sun for a long time, and the northwest has long sunshine time and strong ultraviolet rays, therefore, the elastic polyurethane for the outer surface corrosion prevention of the PCCP pipe needs to have certain ultraviolet aging resistance.

[0005] CN108329883A fast-drying solvent-free polyurethane adhesive and its preparation method, the fast-drying solvent-free polyurethane adhesive, including A component terminal isocyanate prepolymer and B component hydroxyl compound;The terminal isocyanate prepolymer is generated by the reaction of polyol and polyisocyanate, and the B component hydroxyl compound comprises polyol, chain extender, crosslinking agent, wetting agent, leveling agent and adhesion promoter.The present application has the advantages of low viscosity, fast curing speed, two hours slitting, high peel strength and resistance to 121 DEG C high temperature cooking.But the corrosion resistance and mechanical properties are poor, not suitable for PCCP pipe.

[0006] CN101942265A an epoxy coal tar anticorrosive coating and manufacturing method, A component is composed of E-42 type bisphenol A type epoxy resin, dimethylbenzene, butanol, butanone, coal tar resin liquid, toughening resin, precipitated barium sulfate, sericite powder, talc powder, hybrid rheological control additive, isopropyl tri (dioctyl pyrophosphoric acid acyl oxygen) phthalate, fluorocarbon polymer compound, silicone defoamer;B component is composed of cashew phenolic amine, 2, 4, 6-tri (dimethyl aminomethyl) phenol, ethanol and hydroxyphenyl benzotriazole ultraviolet light absorber, both according to weight ratio A∶B=10∶1, after mixing evenly, use;It is a kind of epoxy coal tar anticorrosive coating with toughness, the coating is used for PCCP outer wall anticorrosion and has excellent adhesion, good resistance to biological corrosion, long construction and use period, and has certain light aging resistance.The coating of the present application can also be used for PCCP pipe, but the mechanical properties are limited, the strength and flexibility are not good, and the adhesion is also poor. SUMMARY

[0007] Therefore, the present application aims to provide a PCCP pipe outer surface corrosion prevention elastic polyurethane finish and a preparation method thereof, to solve the problems of poor mechanical properties and low adhesion of the finish for the outer surface of the PCCP pipe in the prior art.

[0008] To achieve the above-mentioned object, the technical scheme of the present application is as follows:

[0009] In one aspect, the present application provides an elastic polyurethane finish for PCCP pipe outer surface corrosion prevention, comprising component A and component B, wherein component A comprises 100-102 parts of isocyanate prepolymer, component B comprises 18-30 parts of amine chain extender, 0-22 parts of low molecular weight polyether amine, 35-75 parts of high molecular weight polyether amine, 0-23.4 parts of polyether polyol resin, 0-6.6 parts of polyester polyol resin, 0-0.2 parts of catalyst and 0-2 parts of carbon black paste.

[0010] Further, the polyether polyol resin and / or the polyester polyol resin is >0 parts, and the catalyst is >0 parts.

[0011] Further, the isocyanate prepolymer has a solid content of 100% and an NCO content of 15.4-18.2%.

[0012] Further, the amine chain extender is at least one of E100 and E300.

[0013] Further, the low molecular weight polyether amine is at least one of D230 and D400.

[0014] Further, the high molecular weight polyether amine is at least one of D2000 and T5000.

[0015] Further, the polyether polyol resin is a multifunctional polyol, has a solid content of 100%, a viscosity of 1000-2000 cps at (23±2) °C, and a hydroxyl content of 3.5-5.5%.

[0016] Further, the polyester polyol resin is a multifunctional polyol, has a solid content of 100%, a viscosity of 1000-2000 cps at (23±2) °C, and a hydroxyl content of 3.5-5.5%.

[0017] Further, the catalyst is dibutyltin dilaurate.

[0018] In another aspect, the present application also provides a preparation method of the above-mentioned elastic polyurethane finish, comprising the following steps: accurately weighing each component in the formula, taking the isocyanate prepolymer as component A, adding the formula amount of amine chain extender, low molecular weight polyether amine, high molecular weight polyether amine, polyether polyol resin, polyester polyol resin, catalyst and carbon black paste into a stainless steel tank, and dispersing for 5-10 min at 500-800 r / min to obtain component B; spraying and mixing component A and component B at a ratio of 1:1 to obtain the elastic polyurethane finish.

[0019] Compared with the prior art, the elastic polyurethane finish for PCCP pipe outer surface corrosion prevention and the preparation method thereof have the following advantages:

[0020] (1) By matching the A component and the B component, the elastic polyurethane has good mechanical properties, high strength and flexibility;

[0021] (2) By introducing the polyol component with slow reaction, more components are caused to react later, which is beneficial to forming good adhesion with the base material, thereby improving the adhesion of the elastic polyurethane, meanwhile, the introduced polyol has high functionality, which is helpful to forming 3D network structure and improving the crosslinking density of the elastic polyurethane, thereby improving the tear strength of the topcoat.

[0022] (3) By adjusting the content of the chain extender, the topcoat has fast drying rate;

[0023] (4) The elastic polyurethane topcoat of the present application has good mechanical properties, adhesion, anticorrosion performance and ultraviolet aging resistance, fast drying rate and excellent comprehensive performance, which meets the requirements of PCCP pipe surface construction and corrosion prevention. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The present application is not limited in scope by the detailed description of the illustrative embodiments complementing the accompanying drawings. In the drawings:

[0025] Figure 1 The infrared spectrum of the isocyanate prepolymer 1-4 of the present application;

[0026] Figure 2 The viscosity curve of the A component and the B component of Example 3 of the present application;

[0027] Figure 3 The effect of the topcoat prepared in Example 3 of the present application is shown. DETAILED DESCRIPTION

[0028] The present application will be further described in conjunction with the specific embodiments. It should be first noted that the data in the following experimental examples are obtained by the inventors through a large number of experiments, and only a part of them are shown in the specification due to the limited space, and the ordinary skilled in the art can understand and implement the present application based on the data. These examples are only used to illustrate the present application and not to limit the scope of the present application. In addition, it should be understood that after reading the content of the present application, those skilled in the art can make various modifications or modifications to the present application, and these modifications or modifications also fall within the scope of the present application.

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0030] The present application will be further described in conjunction with the specific embodiments. It should be first noted that the data in the following experimental examples are obtained by the inventors through a large number of experiments, and only a part of them are shown in the specification due to the limited space, and the ordinary skilled in the art can understand and implement the present application based on the data. These examples are only used to illustrate the present application and not to limit the scope of the present application. In addition, it should be understood that after reading the content of the present application, those skilled in the art can make various modifications or modifications to the present application, and these modifications or modifications also fall within the scope of the present application.

[0031] The elastic polyurethane finish for the outer surface of the PCCP pipe of the present application comprises component A and component B, wherein the component A comprises isocyanate prepolymer 100-102 parts, the component B comprises amine chain extender 18-30 parts, low molecular weight polyether amine 0-22 parts, high molecular weight polyether amine 35-75 parts, polyether polyol resin 0-23.4 parts, polyester polyol resin 0-6.6 parts, catalyst 0-0.2 parts and carbon black paste 0-2 parts.

[0032] The component A is a prepolymer obtained by the reaction of isocyanate and polyol. Since the isocyanate prepolymer obtained by the reaction of the two is the prior art, it will not be described here. The solid content of the isocyanate prepolymer is 100%, and the NCO content is 15.4-18.2%.

[0033] As a specific example of the present application, the amine chain extender is at least one of E100, E300.

[0034] As a specific example of the present application, the low molecular weight polyether amine is at least one of D230, D400, and the high molecular weight polyether amine is at least one of D2000, T5000.

[0035] As a specific example of the present application, the polyether polyol resin is a multifunctional polyol, the solid content is 100%, the viscosity at (23±2) ℃ is 1000-2000 cps, and the hydroxyl content is 3.5-5.5%. Further, the polyether polyol resin is AC2259 resin.

[0036] As a specific example of the present application, the polyester polyol resin is a multifunctional polyol, the solid content is 100%, the viscosity at (23±2) ℃ is 1000-2000 cps, and the hydroxyl content is 3.5-5.5%. Further, the polyester polyol resin is 440 resin.

[0037] As a specific example of the present application, the catalyst is butyl tin dilaurate.

[0038] The preparation method of the elastic polyurethane finish of the present application comprises the following steps: accurately weighing each component in the formula, the isocyanate prepolymer as component A, adding the formula amount of amine chain extender, low molecular weight polyether amine, high molecular weight polyether amine, polyether polyol resin, polyester polyol resin, catalyst and carbon black paste into a stainless steel tank, and dispersing for 5-10 min at 500-800 r / min to obtain component B; spraying and mixing component A and component B at a ratio (molar ratio) of 1:1 to obtain the elastic polyurethane finish.

[0039] The selection and amount of each component in examples 1-4 of the present application are shown in Table 1.

[0040] Table 1

[0041]

[0042]

[0043] The NCO content of isocyanate prepolymer 1 is 17.5%, the NCO content of isocyanate prepolymer 2 is 16.0%, the NCO content of isocyanate prepolymer 3 is 15.4%, and the NCO content of isocyanate prepolymer 4 is 18.2%. The solid content of the isocyanate prepolymer is 100%, and the viscosity at (23±2) °C is 400-2000 cps. The infrared spectra of isocyanate prepolymers 1-4 are shown in Figure 1

[0044] The components of Examples 1-4 are taken according to the parts in Table 1, and the isocyanate prepolymer is used as the A component. The formula amount of amine chain extender, low molecular weight polyether amine, high molecular weight polyether amine, polyether polyol resin, polyester polyol resin, catalyst, and carbon black paste are added to a stainless steel tank and dispersed at 500 r / min for 10 min to obtain the B component.

[0045] Experimental Example 1

[0046] The component selection, amount, and preparation method of Experimental Example 1 and Example 1 are the same, and the only difference is that in Experimental Example 1, the amine chain extender E100 is 30 parts, the high molecular weight polyether amine D2000 is 70 parts, and the carbon black paste is 1.5 parts.

[0047] Experimental Example 2

[0048] The component selection, amount, and preparation method of Experimental Example 2 and Example 1 are the same, and the only difference is that in Experimental Example 2, the amine chain extender E100 is 25 parts, and the high molecular weight polyether amine D2000 is 75 parts.

[0049] Experimental Example 3

[0050] The component selection, amount, and preparation method of Experimental Example 3 and Example 2 are the same, and the only difference is that the A component of Experimental Example 3 is 101.5 parts of isocyanate prepolymer with an NCO content of 17.5%.

[0051] Experimental Example 4

[0052] The component selection, amount, and preparation method of Experimental Example 4 and Example 2 are the same, and the only difference is that the A component of Experimental Example 4 is 101.5 parts of isocyanate prepolymer with an NCO content of 15.4%.

[0053] Experimental Example 5

[0054] ​The component selection, amount and preparation method of experimental example 5 and example 2 are the same, the difference is that the A component of experimental example 5 is 101.5 parts of isocyanate prepolymer with NCO content of 18.2%.

[0055] Experimental example 6

[0056] The component selection, amount and preparation method of experimental example 6 and example 3 are the same, the difference is that in experimental example 6, the high molecular weight polyetheramine D2000 is 65 parts, the polyether polyol resin AC2259 is 7.8 parts, and the polyester polyol resin 440 is 2.2 parts.

[0057] Experimental example 7

[0058] The component selection, amount and preparation method of experimental example 7 and example 3 are the same, the difference is that in experimental example 7, the isocyanate prepolymer with NCO content of 17.5% is 101.5 parts, and the catalyst is 0 parts.

[0059] Experimental example 8

[0060] The component selection, amount and preparation method of experimental example 8 and example 3 are the same, the difference is that in experimental example 8, the high molecular weight polyetheramine D2000 is 45 parts, the polyether polyol resin AC2259 is 23.4 parts, and the polyester polyol resin 440 is 6.6 parts.

[0061] The coatings prepared in the above examples 1-4 and experimental examples 1-8 are sprayed on the polytetrafluoroethylene template by using a two-component spraying device, and the sample mold is formed at one time. The sample mold is cut according to the specifications in Tables 2 and 3, and the corresponding tests are carried out. In Table 2, the sample mold after cutting is 1.5 mm thick, and in Table 3, the sample mold after cutting is 600 μm thick.

[0062] Table 2 sample mold cutting specifications and quantity (1.5 mm thickness)

[0063]

[0064] Table 3 sample mold cutting specifications and quantity (600 μm thickness)

[0065] Item Sample size Number / each Resistance to ion penetration 150mm*150mm 3

[0066] The coatings prepared in the above examples 1-4 and experimental examples 1-8 are sprayed on the polytetrafluoroethylene template by using a two-component spraying device, and the sample mold is formed at one time. The sample mold is cut according to the specifications in Tables 2 and 3, and the corresponding tests are carried out. In Table 2, the sample mold after cutting is 1.5 mm thick, and in Table 3, the sample mold after cutting is 600 μm thick.

[0067] Table 4 test sample size specifications

[0068]

[0069] It should be noted that when the following tests are carried out to explore the influence of a functional component on the mechanical properties, the amount of the base component needs to be adjusted to ensure that the content of component A and component B is 1:1.

[0070] Influence of different chain extender contents on properties

[0071] In the present application, through the study of the influence of chain extender content, low molecular weight polyether amine, high molecular weight polyether amine content and polyol content on drying performance, it is found that the decisive factor affecting the drying rate is the chain extender content, and the content of other components has little effect on the drying rate.

[0072] The components A and B prepared in Example 1, Experimental Example 1 and Experimental Example 2 were mixed respectively, and after stirring uniformly, the paint was sprayed on a polytetrafluoroethylene sample plate using a two-component spraying device to prepare a test sample film, and the performance test was carried out using the cutting specifications in Tables 2 and 3, and the test results are shown in Table 5.

[0073] Table 5

[0074]

[0075]

[0076] As can be seen from Table 5, the drying time of the sample films of Experimental Example 1, Experimental Example 2 and Example 1 changes little, and all dry within 30s. With the decrease of the chain extender content from 30wt% to 25wt%, the tensile strength is first increased from 16.6MPa to 21.4MPa, and then decreased to 16.4MPa, the elongation at break is increased from 415.9% to 503.6%, the tear strength is first increased from 73.9 to 105.6N / mm, and then decreased to 76.4N / mm. This is mainly due to the small molecular weight and high reactivity of the chain extender, which consumes more isocyanate groups in the initial stage of the reaction, and the crosslinking density of the sample is high in the initial stage of the reaction. However, when the chain extender content is high, too many isocyanate groups are consumed by the small molecular chain extender, resulting in that part of the polyether amine structure is not fully linked into the crosslinked structure, forming defects or acting as a plasticizer, which leads to the decrease of the tensile strength and tear strength of the sample film. Therefore, when the chain extender content is 27.5%, the mechanical properties of the sample are the best, and at this time, the mechanical property decrease rate of the sample film after resistance to NaCl, H2SO4, HCl and NaOH is less than 20%, which meets the requirements.

[0077] Influence of different isocyanate prepolymer types on properties

[0078] The components A and B prepared in Example 2 and Experimental Examples 3-5 were mixed and stirred uniformly, and the paint was sprayed on a polytetrafluoroethylene sample plate using a spraying device to prepare a test sample film. The performance test was carried out using the cutting specifications in Tables 2 and 3, and the test results are shown in Table 6.

[0079] Table 6

[0080]

[0081]

[0082] The type of isocyanate prepolymer has a great influence on the mechanical properties. In order to maintain good mechanical properties, the NCO content of the isocyanate prepolymer used in the present application is 15.4-18.2%. If the NCO content is too low, the strength of the topcoat is insufficient, and if the NCO content is too high, the flexibility of the topcoat is insufficient.

[0083] As shown in Table 6, the tensile strength is 16.3-21.2 MPa and the elongation at break is 228.9-653.4% when different types of isocyanate prepolymer (i.e. different NCO contents) are used. In Example 2, the NCO content of the isocyanate prepolymer is 16.0%, and the mechanical properties are optimal, with a tensile strength of 21.2 MPa, an elongation at break of 653.4%, a tear strength of 86.8 N / mm, and a Shore A hardness of 94. The mechanical properties of the sample film after resistance to NaCl, H2SO4, HCl and NaOH are all reduced by less than 20%, meeting the requirements.

[0084] Effect of polyol and catalyst on performance

[0085] The components A and B prepared in Example 3 and Experimental Examples 6-8 were mixed and stirred uniformly, and the paint was sprayed on a polytetrafluoroethylene sample plate using a spraying device to prepare a test sample film. The performance test was carried out using the cutting specifications in Tables 2 and 3, and the test results are shown in Table 7.

[0086] Table 7

[0087]

[0088] As shown in Table 7, in the presence of the catalyst, with the increase of the polyol content, the tensile strength of the sample film first increases from 17.8 MPa to 21.3 MPa, and then decreases to 13.7 MPa, the tear strength first increases from 75 N / mm to 86.9 N / mm, and then decreases to 78.4 N / mm, when the polyol content is 20 wt%, the tensile strength and the tear strength are the highest, and the elongation at break is higher than 200%, which meets the requirements. In addition, when the polyol content is 20 wt%, the mechanical property reduction rates of the sample film after NaCl, H2SO4, HCl and NaOH resistance are all lower than 20%, which meets the requirements.

[0089] According to the above results, compared with each experimental example, examples 1-4 have excellent drying performance, mechanical properties and NaCl, H2SO4, HCl and NaOH resistance. The comprehensive performance of examples 1-4 is tested by the specifications in Tables 2-4, and the results are shown in Table 8. The performance index is a preliminary index in the industry.

[0090] Table 8

[0091]

[0092]

[0093] As shown in Table 8, examples 1-4 all meet the performance index requirements. The elastic polyurethane topcoat prepared in examples 1-4 has a surface dryness of 10-20 s, a real dryness of 20-70 s, a tensile strength of 21.2-21.5 MPa, an elongation at break of 372.9-653.4%, a tear strength of 86.8-105.6, an abrasion resistance of 19-27 mg, an adhesion of 3.0-4.2 MPa, a shore A hardness of 94-96, an impact resistance of 1 kg*m, a low temperature bending of -35℃ without cracks, a water impermeability of 0.4 MPa for 120 min, and a chloride ion penetration resistance of 0.65-0.83 Mg / (cm 2 * d) without peeling and blistering under 10% NaCl (3000 h), 20% H2SO4 (30 d), 20% NaOH (30 d) and 10% HCl (30 d), without peeling and blistering under artificial weathering (1000 h), and a tensile strength retention rate of 82.4-87.3%. It can be seen that the PCCP pipe outer surface corrosion-resistant elastic polyurethane topcoat has excellent drying performance, adhesion, mechanical properties, corrosion resistance and ultraviolet aging performance.

[0094] Among them, example 1 has the fastest drying rate and the highest tear strength, but the cost also increases accordingly due to the high content of chain extender. Example 2 has the lowest cost, but the drying rate is slow. Examples 3-4 have a drying rate comparable to example 1, and can reduce the cost compared to example 1.

[0095] The viscosity curves of Examples 3-4 have the same trend, and for the sake of brevity, only Example 3 is taken as an example to illustrate the viscosity condition. The viscosity curves of the A component and the B component of Example 3 are shown in Figure 1. Figure 2 As shown in Figure 1, when the temperature is ≥ 60℃, the viscosity of the A component and the B component is closest, and it is easy to carry out proportional spraying. The effect of the topcoat prepared by using Example 3 for coating is shown in Figure 2. Figure 3 As shown in Figure 2, the paint surface is smooth and flat.

[0096] In addition, the elastic polyurethane topcoat of the present application is a fast-drying system, and although fast drying can be achieved, fast drying will result in poor adhesion. The formula of the elastic polyurethane topcoat of Example 1 and Example 2 adds polyether amine, and due to the fast reaction of isocyanate and amino group, the improvement effect on adhesion is limited. In addition to adding polyether amine, Example 3 also adds polyether polyol and / or polyester polyol, and the hydroxyl group in the polyol will form a post-reaction with isocyanate, so that the whole system will not be cured immediately, which helps to form a better adhesion with the substrate, thereby improving the adhesion of the elastic polyurethane. At the same time, the introduced polyol has high functionality, which helps to form a 3D network structure and improve the crosslinking density of the elastic polyurethane, thereby improving the tear strength of the material.

[0097] However, the presence of polyol will result in poor mechanical properties, which is mainly because the reaction between NCO group and hydroxyl group is slow, and a side reaction between NCO group and water molecules will occur in this process. This side reaction produces gas, resulting in more defects in the material, thereby reducing the mechanical properties. Therefore, the addition of polyether polyol and / or polyester polyol must be accompanied by the simultaneous addition of a catalyst, which can inhibit the occurrence of side reactions.

[0098] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be limited by the scope defined in the claims.

Claims

1. An elastic polyurethane topcoat for anticorrosion of the outer surface of a PCCP pipe, characterized in that: The invention comprises component A and component B, wherein component A comprises 100 to 102 parts of isocyanate prepolymer, and component B comprises 18 to 30 parts of amine chain extender, 0 to 22 parts of low molecular weight polyether amine, 35 to 75 parts of high molecular weight polyether amine, 0 to 23.4 parts of polyether polyol resin, 0 to 6.6 parts of polyester polyol resin, 0 to 0.2 parts of catalyst and 0 to 2 parts of carbon black paste.

2. The elastic polyurethane topcoat according to claim 1, characterized in that The polyether polyol resin and / or polyester polyol resin is greater than 0 part, and the catalyst is greater than 0 part.

3. The elastic polyurethane topcoat according to claim 1, characterized in that The solid content of the isocyanate prepolymer is 100%, and the NCO content is 15.4-18.2%.

4. The elastic polyurethane topcoat according to claim 1, characterized in that The amine chain extender is at least one of E100 and E300.

5. The elastic polyurethane topcoat according to claim 1, characterized in that The low molecular weight polyetheramine is at least one of D230 and D400.

6. The elastic polyurethane topcoat according to claim 1, characterized in that The high molecular weight polyetheramine is at least one of D2000 and T5000.

7. The elastic polyurethane topcoat according to claim 1, characterized in that The polyether polyol resin is a multifunctional polyol with a solid content of 100%, a viscosity of 1000 to 2000 cps at (23±2)° C., and a hydroxyl content of 3.5 to 5.5%.

8. The elastic polyurethane topcoat according to claim 1, characterized in that The polyester polyol resin is a multifunctional polyol with a solid content of 100%, a viscosity of 1000 to 2000 cps at (23±2)° C., and a hydroxyl content of 3.5 to 5.5%.

9. The elastic polyurethane topcoat according to claim 1, characterized in that The catalyst is butyltin dilaurate.

10. A method for preparing the elastic polyurethane topcoat according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: accurately weighing each component in a formula, taking the isocyanate prepolymer as component A, adding a formulated amount of an amine chain extender, a low molecular weight polyether amine, a high molecular weight polyether amine, a polyether polyol resin, a polyester polyol resin, a catalyst and a carbon black slurry into a stainless steel tank, and dispersing the mixture at 500 to 800 r / min for 5 to 10 minutes to obtain component B; and spraying and mixing component A and component B in a ratio of 1:1 to obtain an elastic polyurethane topcoat.

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