Aqueous polyurea-cement-based composite material and method for its preparation and use

Abstract

This invention discloses a waterborne polyurea-cement-based composite material and its preparation and application methods. The method involves reacting polyetheramine and diisocyanate to obtain a polyurea prepolymer; then, a chain extender, neutralizing agent, and coupling agent are added to the polyurea prepolymer to react and obtain a polyurea. Finally, water is added to the polyurea with continuous stirring during the dropwise addition to obtain the waterborne polyurea. The waterborne polyurea is applied in cement paste and mortar mixing. The waterborne polyurea molecular chain of this invention contains abundant carboxyl sites, which can bind to the surface of cement particles through adsorption, effectively improving the cohesiveness, water retention, and workability of cement mortar. It can be uniformly dispersed and fully reacted in cement-based systems, thereby enhancing the mechanical strength of cement mortar.

Description

Technical Field

[0001] This invention relates to a waterborne polyurea-cement-based composite material and its preparation and application methods, belonging to the field of concrete admixtures in building materials. Background Technology

[0002] Cement mortar, as the most widely used cementitious material in construction engineering, has advantages such as high compressive strength, wide availability, and low cost. However, traditional cement mortar generally suffers from inherent defects such as high brittleness, low tensile strength, poor bonding performance, easy cracking, and insufficient impermeability and corrosion resistance. In engineering applications, especially in scenarios requiring high flexibility, bonding strength, and durability, such as external wall insulation systems, waterproofing projects, tile bonding, structural repair, and self-leveling mortars, traditional cement mortar cannot fully meet the requirements for construction and long-term service performance. To improve the performance of cement mortar, polymer modification is often used in existing technologies. By incorporating redispersible latex powder, polymer emulsions (such as acrylate emulsions, vinyl acetate-ethylene copolymer emulsions, etc.), or waterborne epoxy resins into cement mortar, an interpenetrating network structure can be formed between the cement hydration products and the polymer film, thereby significantly improving the mortar's bonding strength, flexibility, flexural strength, impermeability, and freeze-thaw cycle resistance.

[0003] Currently, different types of waterborne polymers exhibit varying effects on the hydration process, workability, and microstructure of cement paste. Effectively addressing the compatibility issues between waterborne polymers and the cement matrix, while fully leveraging the advantages of polyurethane materials' high flexibility and strong elastic recovery to achieve synergistic effects in mechanical properties and durability, remains a key technical challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a waterborne polyurea-cement-based composite material and its preparation and application methods. It effectively improves the cohesiveness, water retention, and workability of cement mortar, and can be uniformly dispersed and fully reacted in a cement-based system, thereby enhancing the mechanical strength of the cement mortar.

[0005] The technical solution of the present invention: a method for preparing a waterborne polyurea-cement-based composite material, the method comprising the following steps:

[0006] (1) The dehydrated polyetheramine and diisocyanate were continuously stirred and reacted in an anhydrous environment at 38-42°C to obtain a polyurea prepolymer;

[0007] (2) Add the chain extender to the polyurea prepolymer and stir continuously in an anhydrous environment at 85-95°C to obtain polyurea;

[0008] (3) Add water to the polyurea, add it slowly and stir continuously to obtain a transparent waterborne polyurea.

[0009] In the aforementioned method for preparing a waterborne polyurea-cement-based composite material, in step (1), the polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol; and the diisocyanate is isophorone diisocyanate.

[0010] In the aforementioned method for preparing a waterborne polyurea-cement-based composite material, in step (2), the chain extender is dimethylolpropionic acid, which contains two hydroxyl groups and one carboxyl group.

[0011] In the aforementioned method for preparing a waterborne polyurea-cement-based composite material, the mass ratio of diisocyanate: polyetheramine: chain extender is 50-60: 90-110: 8-12; and the mass ratio of polyurea to water is 35-45: 90-110.

[0012] In the aforementioned method for preparing a waterborne polyurea-cement-based composite material, the mass ratio of diisocyanate:polyetheramine:chain extender is 55.57:100:10.43; and the mass ratio of polyurea to water is 40:100.

[0013] In the aforementioned method for preparing a waterborne polyurea-cement-based composite material, in steps (1) and (2), the waterless environment is an oxygen-free environment, which is achieved by protection with nitrogen or an inert gas, with argon being the inert gas.

[0014] In the aforementioned method for preparing a waterborne polyurea-cement-based composite material, in step (1), the reaction time is 1 hour; in step (2), the reaction time is 2-3 hours; and in step (3), the mixture is continuously stirred for 30 minutes.

[0015] The aqueous polyurea prepared by the aforementioned method has a visible light transmittance of ≥90% and the polyurea forms small micelles of less than 100 nm in water.

[0016] An application of the aforementioned waterborne polyurea in the mixing of cement slurry and mortar involves adding the waterborne polyurea together with gelling materials, aggregates, admixtures, and water, wherein the mass ratio of waterborne polyurea, gelling materials, aggregates, admixtures, and water is 17–88:650–700:1300–1400:3–3.4:249–304.

[0017] In the aforementioned applications, the gelling material is at least one of cement, silica fume, or fly ash; the aggregate is sand; and the admixture is at least one of water-reducing agent, waterproofing agent, retarder, and existing early-strength agent.

[0018] The mass of the solute polyurea in waterborne polyurea accounts for 1%-5% of the mass of the gel material.

[0019] The beneficial effects of the present invention: Compared with the prior art, the present invention has the following advantages:

[0020] (1) The waterborne polyurea molecular structure of the present invention is rich in carboxyl groups and polyurea groups, which has excellent dispersion performance in water, high solubility, stable product, and is not easy to gel and aggregate in the highly alkaline cement slurry environment, making it easy to use in cement slurry, mortar and concrete mixing.

[0021] (2) The polyurea of ​​the present invention is rich in carboxyl groups, so it has a large number of carboxyl sites that can be adsorbed on the surface of cement particles, preventing cement from agglomerating, improving the cohesiveness, water retention and workability of cement mortar, and can be evenly dispersed and fully reacted in concrete, thereby improving the mechanical properties of cement mortar. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the compressive strength of mortar with different polyurea contents in the application of this invention;

[0023] Figure 2 This is a schematic diagram showing the flexural strength of mortar with different polyurea contents in the application of this invention;

[0024] Figure 3 This is a schematic diagram of the flowability of mortar with different polyurea contents in the application of this invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0026] Example 1 of the present invention: A method for preparing a waterborne polyurea-cement-based composite material, the method comprising the following steps:

[0027] (1) The dehydrated polyetheramine and diisocyanate were continuously stirred and reacted in an anhydrous environment at 40°C to obtain polyurea prepolymer. The water content of both polyetheramine and diisocyanate was less than 0.05 wt%. The required water content was achieved by a drying process, which included vacuum drying, barium chloride drying, or 4A molecular sieve drying.

[0028] The reactor is made of glass, enamel, or stainless steel.

[0029] The polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol. The diisocyanate is isophorone diisocyanate.

[0030] (2) A chain extender is added to the polyurea prepolymer, and the mixture is continuously stirred at 90°C in an anhydrous environment to obtain polyurea. The chain extender is dimethylolpropionic acid, which contains two hydroxyl groups and one carboxyl group. The polyurea consists of two parts: a hard segment and a soft segment. The hard segment contains diisocyanate and the chain extender, and the soft segment contains polyetheramine. The hard and soft segments are connected by urea bonds formed by the condensation of amino groups and isocyanates. The urea bonds are rich in hydrophilic groups such as carboxyl groups and urea bonds. To ensure good solubility of polyurea in water, the number average molecular weight of polyurea is 5000-10000 g / mol.

[0031] In steps (1) and (2), the anhydrous environment is an anhydrous and oxygen-free environment, which is achieved by nitrogen or an inert gas protection, with argon being used as the inert gas. In step (1), the reaction time is 1 hour, and in step (2), the reaction time is 2-3 hours.

[0032] (3) At room temperature, add water to the polyurea, add it slowly dropwise and stir continuously for 30 minutes, so that the polyurea is completely dissolved or highly stable and uniformly dispersed in the water, to obtain a transparent waterborne polyurea. The waterborne polyurea is an aqueous solution of polyurea with a small amount of coupling agent KH550 at the end.

[0033] In the above steps, the mass ratio of diisocyanate:polyetheramine:chain extender is 50:90:8; the mass ratio of polyurea and water is 35:90.

[0034] Example 2 of the present invention: A method for preparing a waterborne polyurea-cement-based composite material, the method comprising the following steps:

[0035] (1) The dehydrated polyetheramine and diisocyanate were continuously stirred and reacted in an anhydrous environment at 40°C to obtain polyurea prepolymer. The water content of both polyetheramine and diisocyanate was less than 0.05 wt%. The required water content was achieved by a drying process, which included vacuum drying, barium chloride drying, or 4A molecular sieve drying.

[0036] The reactor is made of glass, enamel, or stainless steel.

[0037] The polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol. The diisocyanate is isophorone diisocyanate.

[0038] (2) A chain extender is added to the polyurea prepolymer, and the mixture is continuously stirred at 90°C in an anhydrous environment to obtain polyurea. The chain extender is dimethylolpropionic acid, which contains two hydroxyl groups and one carboxyl group. The polyurea consists of two parts: a hard segment and a soft segment. The hard segment contains diisocyanate and the chain extender, and the soft segment contains polyetheramine. The hard and soft segments are connected by urea bonds formed by the condensation of amino groups and isocyanates. The urea bonds are rich in hydrophilic groups such as carboxyl groups and urea bonds. To ensure good solubility of polyurea in water, the number average molecular weight of polyurea is 5000-10000 g / mol.

[0039] In steps (1) and (2), the anhydrous environment is an anhydrous and oxygen-free environment, which is achieved by nitrogen or an inert gas protection, with argon being used as the inert gas. In step (1), the reaction time is 1 hour, and in step (2), the reaction time is 2-3 hours.

[0040] (3) At room temperature, add water to the polyurea, add it slowly dropwise and stir continuously for 30 minutes, so that the polyurea is completely dissolved or highly stable and uniformly dispersed in the water, to obtain a transparent waterborne polyurea. The waterborne polyurea is an aqueous solution of polyurea with a small amount of coupling agent KH550 at the end.

[0041] In the above steps, the mass ratio of diisocyanate:polyetheramine:chain extender is 60:110:12; the mass ratio of polyurea and water is 45:110.

[0042] Example 3 of the present invention: A method for preparing a waterborne polyurea-cement-based composite material, the method comprising the following steps:

[0043] (1) The dehydrated polyetheramine and diisocyanate were continuously stirred and reacted in an anhydrous environment at 40°C to obtain polyurea prepolymer. The water content of both polyetheramine and diisocyanate was less than 0.05 wt%. The required water content was achieved by a drying process, which included vacuum drying, barium chloride drying, or 4A molecular sieve drying.

[0044] The reactor is made of glass, enamel, or stainless steel.

[0045] The polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol. The diisocyanate is isophorone diisocyanate.

[0046] (2) A chain extender is added to the polyurea prepolymer, and the mixture is continuously stirred at 90°C in an anhydrous environment to obtain polyurea. The chain extender is dimethylolpropionic acid, which contains two hydroxyl groups and one carboxyl group. The polyurea consists of two parts: a hard segment and a soft segment. The hard segment contains diisocyanate and the chain extender, and the soft segment contains polyetheramine. The hard and soft segments are connected by urea bonds formed by the condensation of amino groups and isocyanates. The urea bonds are rich in hydrophilic groups such as carboxyl groups and urea bonds. To ensure good solubility of polyurea in water, the number average molecular weight of polyurea is 5000-10000 g / mol.

[0047] In steps (1) and (2), the anhydrous environment is an anhydrous and oxygen-free environment, which is achieved by nitrogen or an inert gas protection, with argon being used as the inert gas. In step (1), the reaction time is 1 hour, and in step (2), the reaction time is 2-3 hours.

[0048] (3) At room temperature, add water to the polyurea, add it slowly dropwise and stir continuously for 30 minutes, so that the polyurea is completely dissolved or highly stable and uniformly dispersed in the water, to obtain a transparent waterborne polyurea. The waterborne polyurea is an aqueous solution of polyurea with a small amount of coupling agent KH550 at the end.

[0049] In the above steps, the mass ratio of diisocyanate:polyetheramine:chain extender is 55.57:100:10.43; the mass ratio of polyurea and water is 40:100.

[0050] Example 4 of the present invention: The present invention also claims protection for the aqueous polyurea prepared by the preparation method of the above embodiments. The visible light transmittance of the aqueous polyurea is ≥90%, and the polyurea is a small micelle with a size of less than 100 nm in water.

[0051] Example 5 of the present invention: The present invention also provides an application of the above-mentioned waterborne polyurea in cement paste, mortar and concrete mixing. In the application process, the waterborne polyurea is added together with gelling material, aggregate, admixture and water. The mass ratio of waterborne polyurea, gelling material, aggregate, admixture and water is 17-88:650-700:1300-1400:3-3.4:249-304.

[0052] The gelling material is at least one of cement, silica fume, or fly ash; the aggregate is sand; and the admixture is at least one of water-reducing agent, waterproofing agent, retarder, and existing early-strength agent.

[0053] Due to the varying concentrations of waterborne polyurea, the mass of the solute polyurea in waterborne polyurea can account for 1-5% of the mass of the gel material, thereby improving the cohesiveness, water retention, and workability of the slurry and enhancing its mechanical properties.

[0054] In mortar mixing, waterborne polyurea is added together with cement, sand, and admixtures; the mass of polyurea accounts for 1-5% of the mass of the gel material. Waterborne polyurea has broad application prospects in building reinforcement and rapid road repair in mortar mixing.

[0055] In cement mortar mixing, waterborne polyurea is added together with cement, sand, and admixtures; the mass of polyurea accounts for 1-5% of the mass of the gel material. In concrete mixing, waterborne polyurea has broad application prospects in bridges, tunnels, and prefabricated components for prefabricated buildings.

[0056] To verify the effectiveness of the waterborne polyurea-cement-based composite material of the present invention, the following experiment was conducted.

[0057] Preparation of waterborne polyurea:

[0058] (1) 27.785 g of pre-dehydrated isophorone diisocyanate and 50 g of polyetheramine (number average molecular weight of 2000 g / mol) were added to a 500 ml glass reactor equipped with mechanical stirrer. Under nitrogen protection, the mixture was stirred and reacted at 40 °C for 1 h to obtain polyurea prepolymer.

[0059] (2) 5.216 g of dimethylolpropionic acid was added to the polyurea prepolymer as a chain extender and stirred at 90 °C for 2-3 h under nitrogen protection to obtain polyurea.

[0060] (3) At room temperature, 130g of deionized water was added dropwise to the polyurea while stirring continuously to obtain a transparent waterborne polyurea (visible light transmittance of 92%).

[0061] To evaluate the basic mechanical properties of waterborne polyurea in cement mortar mixing, 675g of cement, 1350g of sand, 3.37g of water-reducing agent, 88.8g of waterborne polyurea (as described in the implementation case), and 249g of water were added to a cement mortar mixing vessel. Following the relevant methods in DL / T5126-2001 "Test Procedure for Polymer-Modified Cement Mortar," the mixture was stirred until homogeneous, yielding cement products. After curing for 3, 7, and 28 days, the compressive strength, flexural strength, and flowability of the cement mortar specimens were measured.

[0062] For water-based polyurea modified mortar, the specific testing and inspection of various indicators shall be carried out as follows.

[0063] (1) Flowability test: The flowability of mortar is tested according to Chinese standard GB / T 2419-2005. During the test, the cement mortar is poured into the mold in two layers, and each layer needs to be compacted according to the specified standard. From the start of adding water to the mortar to the end of the measurement, the test should be completed within five minutes to reduce the impact of water loss on the results.

[0064] (2) Compressive and flexural strength tests: Mortar specimens for compressive and flexural strength were prism-shaped specimens measuring 40 mm × 40 mm × 160 mm. The loading rate for the compressive test was set to 2.4 kN / s, and the loading rate for the flexural test was set to 50 N / s. The test methods followed standards GB / T 17671-1999 and DLT 5126-2001. Mortar blocks with curing times of 3 days, 7 days, and 28 days were used to test the flexural and compressive strength.

[0065] Regarding the influence of waterborne polyurea on the fluidity of cement mortar, only repair mortar with good fluidity can fill the cracks and achieve the best repair effect. The mortar fluidity results for different polyurea contents are as follows: Figure 3As shown, waterborne polyurea has a strong effect on improving the fluidity of cement mortar. The fluidity of cement mortar initially increases and then decreases with increasing waterborne polyurea dosage, reaching an inflection point near the 2% dosage. When the dosage is 1%-2%, polyurea coats the surface of cement particles and disperses between them, exerting a "microbead effect," thereby improving the fluidity of the cement mortar. When the dosage exceeds 2%, due to the hydrophilic nature of polyurea, the higher the dosage, the more free water is adsorbed from the mortar, causing the mortar to become more viscous and its fluidity to decrease.

[0066] Regarding the influence of waterborne polyurea on the compressive strength of cement mortar, such as... Figure 1 As shown, using 42.5 grade ordinary Portland cement, the compressive strength of the control group at 3d, 7d, and 28d were 27.8 MPa, 35.6 MPa, and 46.3 MPa, respectively. With increasing polyurea content, the compressive strength of the cement mortar initially increased and then gradually decreased. At 28d, when the P / C ratio was 1%, the compressive strength was 51.2 MPa, an increase of 10.6% compared to the control group; however, when the P / C ratio was 5%, the compressive strength was 38.4 MPa, a decrease of 17.2% compared to the control group. The main reasons for the decrease are: during hydration, polyurea adsorbs onto the surface of cement particles, slowing down the hydration reaction and reducing mortar strength. Another reason is that polyurea has an air-entraining effect on the mortar, generating some air bubbles during mixing, resulting in a loose structure and reduced compressive strength after the mortar hardens.

[0067] Regarding the influence of waterborne polyurea on the toughening effect of cement mortar, such as... Figure 2 As shown, the flexural strength of waterborne polyurea-modified cement mortar first increases and then decreases with increasing polyurea content, reaching a peak at a polyurea content of 2%. After 7 days and 28 days of curing, the flexural strength of the mortar modified with 2% polyurea content was 18.8% and 10% higher than that of the control group, respectively, indicating that the toughness of the repair material was significantly improved.

[0068] Waterborne polyurea has excellent toughening effects, but excessive amounts of waterborne polyurea can actually reduce the compressive and flexural strength of the mortar. The high-strength, high-toughness cement mortar modified with a small amount of waterborne polyurea developed in this invention has the following characteristics:

[0069] (1) Waterborne polyurea affects the toughness of cement mortar. Appropriate addition can improve the compressive and flexural strength of cement mortar. When the addition amount is 2%, after curing for 28 days, the flexural strength of cement mortar modified with waterborne polyurea increases by 10%.

[0070] (2) The compressive strength of waterborne polyurea modified cement mortar first increases and then decreases with the addition of polyurea content.

[0071] (3) Waterborne polyurea will cause the mortar fluidity to rise first and then fall, with an inflection point at a 3% addition amount.

Claims

1. A method for preparing a waterborne polyurea-cement-based composite material, characterized in that: The method includes the following steps: (1) The dehydrated polyetheramine and diisocyanate were continuously stirred and reacted in an anhydrous environment at 38-42°C to obtain a polyurea prepolymer; (2) Add the chain extender to the polyurea prepolymer and stir continuously in an anhydrous environment at 85-95°C to obtain polyurea; (3) Add water to the polyurea, add it slowly and stir continuously to obtain a transparent waterborne polyurea.

2. The method for preparing a waterborne polyurea-cement-based composite material according to claim 1, characterized in that: In step (1), the polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol; the diisocyanate is isophorone diisocyanate.

3. The method for preparing a waterborne polyurea-cement-based composite material according to claim 1, characterized in that: In step (2), the chain extender is dimethylolpropionic acid, which contains two hydroxyl groups and one carboxyl group.

4. The method for preparing a waterborne polyurea-cement-based composite material according to claim 1, characterized in that: The mass ratio of diisocyanate: polyetheramine: chain extender is 50-60: 90-110: 8-12; the mass ratio of polyurea and water is 35-45: 90-110.

5. The method for preparing a waterborne polyurea-cement-based composite material according to claim 4, characterized in that: The mass ratio of diisocyanate:polyetheramine:chain extender is 55.57:100:10.43; the mass ratio of polyurea and water is 40:

100.

6. The method for preparing a waterborne polyurea-cement-based composite material according to claim 1, characterized in that, In steps (1) and (2), the waterless environment is an oxygen-free environment, which is achieved by protection with nitrogen or an inert gas, with argon being the inert gas.

7. The method for preparing a waterborne polyurea-cement-based composite material according to claim 1, characterized in that, In step (1), the reaction time is 1 hour; in step (2), the reaction time is 2-3 hours; in step (3), the stirring is continued for 30 minutes.

8. An aqueous polyurea prepared by the preparation method according to any one of claims 1-7, characterized in that, Waterborne polyurea has a visible light transmittance of ≥90%, and polyurea in water consists of small micelles smaller than 100 nm.

9. The application of the waterborne polyurea as described in any one of claims 1-7 in the mixing of cement slurry and mortar, characterized in that, The aqueous polyurea is added together with gel material, aggregate, additives and water, and the mass ratio of aqueous polyurea, gel material, aggregate, additives and water is 17-88:650-700:1300-1400:3-3.4:249-304.

10. The application according to claim 9, characterized in that, The gelling material is at least one of cement, silica fume, or fly ash; the aggregate is sand; and the admixture is at least one of water-reducing agent, waterproofing agent, retarder, and existing early-strength agent. The mass of the solute polyurea in waterborne polyurea accounts for 1%-5% of the mass of the gel material.

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