High-strength water-resistant magnesium oxychloride cement composite material as well as preparation method and application thereof

Abstract

The invention discloses a high-strength water-resistant magnesium oxychloride cement composite material as well as a preparation method and application thereof. The high-strength water-resistant magnesium oxychloride cement composite material is prepared from the following raw materials in parts by weight: 800 to 1200 parts of light calcined magnesia, 600 to 900 parts of 22.5 wt% magnesium chloride aqueous solution, 0.5 to 10 parts of polyethyleneimine and 0.5 to 10 parts of tartaric acid. The preparation method of the high-strength water-resistant magnesium oxychloride cement composite material is characterized by comprising the following steps: weighing the raw material components according to the weight ratio, dissolving the polyethyleneimine and the tartaric acid in a magnesium chloride aqueous solution, then mixing with the light calcined magnesia, and uniformly stirring to obtain the magnesium oxychloride cement composite material. The high-strength water-resistant magnesium oxychloride cement composite material is applied to constructional engineering. The polyethyleneimine and the tartaric acid are introduced as synergistic modifiers, so that the strength and the water resistance of the composite material are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of building materials, and in particular to a high-strength, water-resistant magnesium oxychloride cement composite material, its preparation method, and its application. Background Technology

[0002] Magnesium oxychloride cement is a cementitious material produced by reacting lightly calcined magnesium oxide, magnesium chloride, and water as the main raw materials. This material exhibits significant advantages such as rapid setting and hardening, excellent fire resistance, and high bonding strength, leading to its widespread application in fireproof boards, building decorative components, and other fields. However, the poor water resistance commonly found in MOC-based composite materials results in a significant decrease in strength upon contact with water and a tendency for surface efflorescence and blooming, severely hindering the large-scale promotion and application of this material in practical engineering projects.

[0003] To improve the overall performance of magnesium oxychloride cement materials, particularly addressing issues of water resistance and strength, various technical solutions have been proposed. For example, Chinese patent CN109942335A discloses a method for improving the water resistance of magnesium oxychloride cement and magnesium oxychloride cement products, primarily by adding organic acids (such as citric acid and oxalic acid) and their salts as modifiers. This patent demonstrates that its method can effectively improve water resistance. However, such organic acid-based modification techniques often face the problem of a significant decrease in the compressive strength of the material in practical applications. Meanwhile, Chinese patent CN112194433A discloses a resin-modified magnesium oxychloride cement composite material and its preparation method, using epoxy resin or phenolic resin to impregnate and composite modify the magnesium oxychloride cement material, aiming to improve performance by utilizing the hydrophobicity and adhesiveness of the resin. However, this technology carries the risk of releasing volatile harmful substances during resin curing, posing environmental and health hazards and limiting its application in environments with high environmental requirements, such as interior decoration. In addition, other modification methods, such as adding inorganic additives like phosphates, can improve water resistance, but they often fail to meet the economic requirements for large-scale production due to high raw material costs or complex processes.

[0004] Therefore, a new magnesium oxychloride cement modification technology is needed to solve the problems of reduced strength after modification, high environmental risks, or excessive costs in existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength, water-resistant magnesium oxychloride cement composite material, its preparation method, and its application. This invention significantly improves the strength and water resistance of the composite material by introducing polyethyleneimine and tartaric acid as synergistic modifiers.

[0006] The technical solution of this invention: A high-strength, water-resistant magnesium oxychloride cement composite material, comprising the following raw materials in parts by weight: 800-1200 parts of lightly calcined magnesium oxide, 600-900 parts of 22.5wt% magnesium chloride aqueous solution, 0.5-10 parts of polyethyleneimine, and 0.5-10 parts of tartaric acid.

[0007] The above-mentioned high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 900-1100 parts of lightly calcined magnesium oxide, 700-800 parts of 22.5wt% magnesium chloride aqueous solution, 1.8-7.2 parts of polyethyleneimine, and 3.0-7.0 parts of tartaric acid.

[0008] The aforementioned high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 900 parts of lightly calcined magnesium oxide, 735 parts of 22.5 wt% magnesium chloride aqueous solution, 5.4 parts of polyethyleneimine, and 5.4 parts of tartaric acid.

[0009] The aforementioned high-strength, water-resistant magnesium oxychloride cement composite material contains lightly calcined magnesium oxide, which is produced by calcining magnesite at 850°C and has an activity of 60-70%.

[0010] In the aforementioned high-strength, water-resistant magnesium oxychloride cement composite material, the polyethyleneimine is a 50% aqueous solution with a molecular weight of 70,000.

[0011] The aforementioned method for preparing high-strength, water-resistant magnesium oxychloride cement composite material involves weighing each raw material component according to the weight ratio, dissolving polyethyleneimine and tartaric acid in an aqueous solution of magnesium chloride, and then mixing them with lightly calcined magnesium oxide and stirring evenly to obtain the magnesium oxychloride composite material.

[0012] The aforementioned high-strength, water-resistant magnesium oxychloride cement composite material is used in building engineering.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs a composite system of polyethyleneimine and tartaric acid for synergistic modification. Polyethyleneimine, as a high-molecular-weight organic template, effectively chelates Mg with its abundant amino groups. 2+ This provides a template for the directional growth of the main strength phase (5-phase crystal) in magnesium oxychloride cement, significantly improving the matrix strength. Tartaric acid, as a small-molecule organic acid, chelates Mg with its carboxyl group. 2+ This invention effectively induces needle-like five-phase crystals to transform into a gel-like morphology on the template surface, forming a unique "gel-needle crystal" interpenetrating network structure in the magnesium oxychloride hydration system. This structure creates a water-blocking barrier, significantly improving the water resistance of the matrix. Therefore, this invention solves the core contradiction in traditional modification techniques where strength and water resistance are difficult to balance.

[0014] 2. The modifier used in this invention is environmentally friendly, releasing no volatile harmful substances, making it suitable for scenarios with high environmental protection requirements, such as indoor decoration. The preparation method of this invention is simple, requires no complex equipment, and has controllable raw material costs, meeting the economic requirements for large-scale production.

[0015] 3. The composite material of the present invention has both high compressive strength and excellent water resistance, and retains the original advantages of magnesium oxychloride cement such as fast setting and good fire resistance. It effectively expands its application range in building decoration components, fireproof boards and other fields, and is especially suitable for engineering scenarios in humid environments. It has significant practical value and market prospects. Attached Figure Description

[0016] Figure 1 The compressive strength of each specimen in the test example after 28 days.

[0017] Figure 2 The diagram shows the softening coefficient of each sample in the test examples.

[0018] Figure 3 This is a schematic diagram showing the chelation of polyethyleneimine and tartaric acid with magnesium ions in the magnesium oxychloride system. Detailed Implementation

[0019] The following embodiments further illustrate the present invention, but are not intended to limit the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Furthermore, all component raw materials used in the embodiments are known commercially available products.

[0020] Unless otherwise specified, the percentage sign "%" used in this invention refers to the mass percentage; however, the percentage of a solution, unless otherwise specified, refers to the number of grams of solute contained in 100 ml of the solution; the percentage between liquids refers to the volume ratio at 20°C.

[0021] In the following examples, the lightly calcined magnesium oxide is obtained by calcining magnesite at 850°C. It is a white powder purchased from Tianjin Kemeio Company and has an activity of 60-70%.

[0022] The magnesium chloride aqueous solution was made from magnesium chloride with a purity >98% and was purchased from Wuxi Yatai United Chemical Co., Ltd.

[0023] Polyethyleneimine (MW70000, 50% aqueous solution) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0024] Tartaric acid (TA, 95%) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0025] The method for preparing magnesium chloride aqueous solution is as follows: add MgCl2•6H2O and water to a beaker and adjust the concentration to 22.5 wt%.

[0026] Example 1: A high-strength water-resistant magnesium oxychloride cement composite material and its preparation method The high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 900 kg of lightly calcined magnesium oxide, 735 kg of 22.5 wt% magnesium chloride aqueous solution, 1.8 kg of polyethyleneimine, and 5.4 kg of tartaric acid.

[0027] The preparation method of the high-strength, water-resistant magnesium oxychloride cement composite material is as follows: Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

[0028] Example 2: A high-strength, water-resistant magnesium oxychloride cement composite material and its preparation method The high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 900 kg of lightly calcined magnesium oxide, 735 kg of 22.5 wt% magnesium chloride aqueous solution, 3.6 kg of polyethyleneimine, and 5.4 kg of tartaric acid.

[0029] The preparation method of the high-strength, water-resistant magnesium oxychloride cement composite material is as follows: Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

[0030] Example 3: A high-strength water-resistant magnesium oxychloride cement composite material and its preparation method The high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 900 kg of lightly calcined magnesium oxide, 735 kg of 22.5 wt% magnesium chloride aqueous solution, 5.4 kg of polyethyleneimine, and 5.4 kg of tartaric acid.

[0031] The preparation method of the high-strength, water-resistant magnesium oxychloride cement composite material is as follows: Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

[0032] Example 4: A high-strength water-resistant magnesium oxychloride cement composite material and its preparation method The high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 900 kg of lightly calcined magnesium oxide, 735 kg of 22.5 wt% magnesium chloride aqueous solution, 7.2 kg of polyethyleneimine, and 5.4 kg of tartaric acid.

[0033] The preparation method of the high-strength, water-resistant magnesium oxychloride cement composite material is as follows: Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

[0034] Example 5: A high-strength water-resistant magnesium oxychloride cement composite material and its preparation method The high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 900 kg of lightly calcined magnesium oxide, 735 kg of 22.5 wt% magnesium chloride aqueous solution, 9 kg of polyethyleneimine, and 5.4 kg of tartaric acid.

[0035] The preparation method of the high-strength, water-resistant magnesium oxychloride cement composite material is as follows: Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

[0036] Example 6: A high-strength water-resistant magnesium oxychloride cement composite material and its preparation method The high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 800 kg of lightly calcined magnesium oxide, 900 kg of 22.5 wt% magnesium chloride aqueous solution, 0.5 kg of polyethyleneimine, and 10 kg of tartaric acid.

[0037] The preparation method of the high-strength, water-resistant magnesium oxychloride cement composite material is as follows: Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

[0038] Example 7: A high-strength water-resistant magnesium oxychloride cement composite material and its preparation method The high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 1200 kg of lightly calcined magnesium oxide, 600 kg of 22.5 wt% magnesium chloride aqueous solution, 10 kg of polyethyleneimine, and 0.5 kg of tartaric acid.

[0039] The preparation method of the high-strength, water-resistant magnesium oxychloride cement composite material is as follows: Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

[0040] Example 8: A high-strength water-resistant magnesium oxychloride cement composite material and its preparation method The high-strength, water-resistant magnesium oxychloride cement composite material comprises the following raw materials in parts by weight: 1000 kg of lightly calcined magnesium oxide, 750 kg of 22.5 wt% magnesium chloride aqueous solution, 5 kg of polyethyleneimine, and 5 kg of tartaric acid.

[0041] The preparation method of the high-strength, water-resistant magnesium oxychloride cement composite material is as follows: Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

[0042] Example 9: The high-strength water-resistant magnesium oxychloride cement composite material from Example 3 was applied to the preparation of finished exterior wall decorative panels: A standard mold of 1200mm×800mm×15mm was selected, and a release agent was applied to the inner wall. First, a layer of glass fiber mesh was laid, and half the volume of composite slurry was poured in. The slurry was leveled with a scraper, and then a second layer of glass fiber mesh was laid. The remaining slurry was poured in and leveled again to ensure that the fiber mesh was completely embedded in the slurry. The mold was placed in a constant temperature and humidity chamber (25℃ / 63% RH) for curing for 24 hours to obtain the finished exterior wall decorative panel.

[0043] Comparative Example 1: The raw material weight parts and preparation method of Example 3 are followed, but the difference is that only the lightly calcined magnesium oxide and magnesium chloride aqueous solution are uniformly mixed to obtain magnesium oxychloride cement.

[0044] Comparative Example 2: The raw material weight parts and preparation method are the same as in Example 3, but the difference is that only lightly calcined magnesium oxide, magnesium chloride aqueous solution and polyethyleneimine are uniformly mixed to obtain magnesium oxychloride cement.

[0045] Comparative Example 3: The raw materials and preparation method are the same as in Example 3, but the difference is that only lightly calcined magnesium oxide, magnesium chloride aqueous solution and tartaric acid are uniformly mixed to obtain magnesium oxychloride cement.

[0046] Test Example: The high-strength water-resistant magnesium oxychloride cement composite material of Examples 1-5 of the present invention and the magnesium oxychloride cement of Control Examples 1-3 were respectively injected into standard molds (30mm×30mm×30mm), placed in a constant temperature and humidity chamber (25℃ / 63%RH) for curing and molding, demolded after 24 hours, and then used for testing after curing in a constant temperature and humidity chamber for the specified number of days. The prepared samples were tested according to the following test methods.

[0047] Compressive strength: Measured according to (GB / T 5486−2008, China). Magnesium oxychloride cement samples were subjected to compression failure using a universal testing machine. The sample was placed on a bearing plate with the compression surface in contact with the plate. Loading was applied to the specimen at a rate of (10±1) mm / min until failure. The failure load P (N) was recorded, and the compressive strength σ = P / S (MPa) was calculated. The test results are shown in Table 1 and... Figure 1 . Figure 1 The compressive strength of each sample after 28 days.

[0048] Softening coefficient: Measured according to (GB / T 15231−2008, China). Magnesium oxychloride cement samples that had cured for 7 days were immersed in water for 7 days. The compressive strength and water absorption rate of the samples before and after immersion were tested. The softening coefficient Rf = σ1 / σ0 was calculated, where σ1 is the compressive strength after immersion for 7 days, and σ0 is the compressive strength before immersion. The test results are shown in Table 1 and... Figure 2 . Figure 2 The diagram shows the softening coefficient of each sample.

[0049] Table 1

[0050] From Table 1, Figure 2 and Figure 3 It can be seen that the 28-day compressive strength of the embodiments (except for Embodiment 5) is generally higher. The 28-day strength of Embodiment 3 reaches 41.9 MPa, which is much higher than that of the control group (maximum 33.7 MPa). The strength of each embodiment of the present invention gradually increases with curing time, and the strength development is more stable. As for the softening coefficient, the softening coefficient of Embodiment 3 is 0.73, the softening coefficient of Embodiment 4 reaches 0.84, while the highest in the control group is only 0.69 (the softening coefficients of control groups 1 and 2 are only 0.25 and 0.22, respectively, with extremely poor water resistance). This shows that the problem of strength decay of the modified material when exposed to water is greatly improved. Based on the above experimental data, the raw material ratio of Embodiment 3 can be regarded as the optimal example for obtaining a balance between compressive strength and softening coefficient.

[0051] The above experimental results show that the polyethyleneimine / tartaric acid synergistic modified magnesium oxychloride cement composite material provided by this invention exhibits significantly improved compressive strength and excellent water resistance. Polyethyleneimine and tartaric acid play a synergistic role in the system, with their amino and carboxyl groups similar to those of Mg... 2+ The chelation effect promotes the formation of organic-inorganic hybrid structures, effectively regulating the formation and microstructure of hydration products, and constructing a unique "gel-needle crystal" interpenetrating network. This structure is key to improving the overall performance of the material, and its formation mechanism is as follows: Figure 3 As shown. In summary, the inorganic magnesium oxychloride composite material prepared by this invention has high compressive strength, good water resistance, and the product obtained has high quality stability.

[0052] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A high-strength, water-resistant magnesium oxychloride cement composite material, characterized in that, It contains the following ingredients by weight: 800-1200 parts of lightly calcined magnesium oxide, 600-900 parts of 22.5wt% magnesium chloride aqueous solution, 0.5-10 parts of polyethyleneimine, and 0.5-10 parts of tartaric acid.

2. The high-strength, water-resistant magnesium oxychloride cement composite material according to claim 1, characterized in that, It contains the following ingredients by weight: 900-1100 parts of lightly calcined magnesium oxide, 700-800 parts of 22.5wt% magnesium chloride aqueous solution, 1.8-7.2 parts of polyethyleneimine, and 3.0-7.0 parts of tartaric acid.

3. The high-strength, water-resistant magnesium oxychloride cement composite material according to claim 2, characterized in that, It contains the following ingredients by weight: 900 parts of lightly calcined magnesium oxide, 735 parts of 22.5 wt% magnesium chloride aqueous solution, 5.4 parts of polyethyleneimine, and 5.4 parts of tartaric acid.

4. The high-strength, water-resistant magnesium oxychloride cement composite material according to any one of claims 1-3, characterized in that, The lightly calcined magnesium oxide is produced by calcining magnesite at 850°C, with an activity of 60-70%.

5. The high-strength, water-resistant magnesium oxychloride cement composite material according to any one of claims 1-3, characterized in that, The polyethyleneimine is a 50% aqueous solution with a molecular weight of 70,000.

6. The method for preparing the high-strength, water-resistant magnesium oxychloride cement composite material according to any one of claims 1-5, characterized in that, Weigh each raw material component according to the weight ratio, dissolve polyethyleneimine and tartaric acid in magnesium chloride aqueous solution, then mix with lightly calcined magnesium oxide and stir evenly to obtain magnesium oxychloride composite material.

7. The application of the high-strength water-resistant magnesium oxychloride cement composite material according to any one of claims 1-5 in building engineering.

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