Composite gel matrix of high-porosity material and preparation method of composite gel matrix

Abstract

The invention discloses a preparation method of a composite gel matrix of a high-porosity material. The composite gel matrix is prepared from water, a water-soluble alkali-resistant high-molecular polymer, sodium alginate, dicalcium silicate, tricalcium silicate, silica fume, soluble silicate, soluble organic acid calcium salt and polyvinyl alcohol fiber according to a specific proportion. The porous material with porosity of more than 70% and extremely low density is obtained by constructing'egg-box 'structure composite hydrogel of'high-molecular polymer-sodium alginate-organic acid calcium salt' and combining with a sol mixing process and drying and forming under a normal temperature or heating condition. When the gel matrix is used for preparing a high-porosity material, a freeze-drying technology is not needed, the process is simple, the cost is low, and the gel matrix is suitable for the fields of ultralight materials, heat preservation and insulation, catalyst carriers, biological scaffolds and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of micro-nano materials, and particularly relates to a composite gel matrix of a high-porosity material and a preparation method thereof. Background Art

[0002] The porosity of ultra-high porosity materials is > 70%, with an extremely high porosity and an extremely low density. Due to their unique structures and properties, ultra-high porosity materials have extensive applications and important roles in multiple fields such as heat insulation and thermal insulation, adsorption and separation, energy storage and conversion, biomedicine, environmental protection, acoustic and vibration control, electronics and optoelectronics, aerospace and national defense. With the continuous progress of technology and the in-depth application, ultra-high porosity materials will play an important role in more fields, promoting the development and progress of related industries.

[0003] The preparation of ultra-high porosity materials usually involves complex processes such as sol-gel method, supercritical drying, template method, etc. These processes have extremely high requirements for equipment, environment, and technology. Processes such as supercritical drying require high-temperature and high-pressure conditions, with high energy consumption, increasing production costs; industrial production requires special equipment, with high initial investment costs; the production processes at the laboratory scale are difficult to directly scale up to industrial production. Ultra-high porosity silicates are usually prepared by foaming agents or freeze-drying processes, with problems such as complex processes, high energy consumption, and high costs. In the prior art, although the hydrogel template method can increase the porosity, it relies on freeze-drying technology to remove moisture, restricting industrial applications. In addition, existing materials still have deficiencies in terms of mechanical strength, alkali resistance, and environmental friendliness. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite gel matrix of a high-porosity material. The material prepared from this gel matrix has a large porosity and a low density, and does not require freeze-drying, effectively solving the problem of complex preparation processes of traditional high-porosity materials.

[0005] To achieve the above purpose, the present invention provides a preparation method for a composite gel matrix of a high-porosity material, including the following steps: S1. After dissolving a water-soluble alkali-resistant polymer and sodium alginate in water, the solution is dropped into an aqueous solution of an easily soluble calcium organic acid salt for cross-linking to obtain a composite hydrogel; S2. The composite hydrogel obtained in S1 is ground into a granular sol; S3. The sol obtained in S2 is evenly divided into two parts. One part is mixed with dicalcium silicate and tricalcium silicate to cause the sol to cross-link twice to form a highly fluid gel, obtaining component A; at the same time, the other part is mixed with an easily soluble silicate, microsilica powder, and polymer fibers to obtain component B; S4. Mix the component A and component B in S3 to form a composite gel, pour or spray the composite gel to form the desired shape, and the composite gel matrix of the high-porosity material can be obtained after standing and solidifying.

[0006] Further, in the preparation method of the composite gel matrix of the high-porosity material, the mass ratio of water, water-soluble alkali-resistant polymer, sodium alginate, dicalcium silicate, tricalcium silicate, microsilica, soluble silicate, soluble calcium organic acid salt, and polyvinyl alcohol fiber is 0.6~0.85: 0.025~0.035: 0.005~0.015: 0.06~0.1: 0.03~0.05: 0.01~0.05: 0.03~0.05: 0.02~0.04: 0.01~0.03.

[0007] Further, in the step S1, the water-soluble alkali-resistant polymer is one or more of polyvinyl alcohol, polyacrylamide, and polyethylene glycol, and the addition amount of the water-soluble alkali-resistant polymer is 2~3 times the mass of sodium alginate.

[0008] Further, the soluble calcium organic acid salt is one or more of calcium acetate, calcium citrate, calcium formate, calcium gluconate, and calcium lactate, and the concentration of the aqueous solution of the calcium organic acid salt is 5%~20% w / w.

[0009] Further, the particle size of the sol in S2 is not greater than 100 nm.

[0010] Further, the soluble silicate is one or more of sodium silicate, potassium silicate, lithium silicate, or ammonium silicate.

[0011] Further, the polymer fiber does not react with the soluble silicate, including polyvinyl alcohol fiber.

[0012] Further, the addition amount of the polymer fiber in S3 is 30~60% of the mass of the silicate, and the addition amount of tricalcium silicate is 50% of the mass of dicalcium silicate.

[0013] A composite gel matrix of a high-porosity material, the gel matrix is prepared by the preparation method of the composite gel matrix of the high-porosity material, the gel contains sol microparticles, polymer fibers, and calcium silicate hydrate crystals, the calcium silicate hydrate crystals form a three-dimensional network-like space framework between the sol microparticles and the polymer fibers, the sol microparticles are an interpenetrating network structure formed by calcium alginate and a water-soluble alkali-resistant polymer, the water content of the composite gel matrix is not less than 60%, and the compressive strength ranges from 0.1~10 MPa.

[0014] The composite gel is applicable to the fields of building thermal insulation materials, industrial equipment heat insulation coatings, solid water and heat storage, or agricultural water retention materials.

[0015] Beneficial effects: After being air-dried or dried in the air at normal pressure, the composite gel matrix prepared by the present invention has a porosity greater than 70% and a density as low as 0.1-0.5 g / cm³. The preparation process does not require freeze-drying, the energy consumption is reduced by more than 50%, the process is simple, no toxic or harmful chemical agents are used during the preparation, and it has excellent biocompatibility and can be effectively applied to fields such as ultra-light structures, thermal insulation, catalyst carriers, and biological scaffolds. Description of the drawings

[0016] Figure 1 It is the SEM micrograph of the composite gel; Figure 2 It is the graph of the sol microparticles observed under an optical microscope. Detailed implementation manners

[0017] The present invention will be further described below in conjunction with examples, but the protection scope is not limited thereto.

[0018] The present invention forms a "egg-box" structure composite hydrogel by a water-soluble alkali-resistant polymer and sodium alginate, and constructs a composite gel matrix of a super-high porosity material by combining the hydration reaction of calcium silicate and fiber reinforcement.

[0019] A preparation method of a composite gel matrix of a high-porosity material includes the following steps: S1. After dissolving a water-soluble alkali-resistant polymer and sodium alginate in water, dropping the solution into an aqueous solution of an easily soluble calcium organic acid salt for cross-linking to obtain a hydrogel with an "egg-box" type feature; The water-soluble alkali-resistant polymer is polyvinyl alcohol (PVA), polyacrylamide (PAM), or polyethylene glycol (PEG), and the easily soluble calcium organic acid salt is one or more of calcium acetate, calcium citrate, calcium formate, calcium gluconate, and calcium lactate. The concentration of the aqueous solution of the calcium organic acid salt is 5%-20% w / w.

[0020] S2. Grinding the hydrogel obtained in S1 into small-particle-size gels with a particle size less than 100 nm.

[0021] S3. Dividing the small-particle-size gels obtained in S2 into two equal parts. Mix one part with dicalcium silicate and tricalcium silicate to make the sol cross-link again to form a highly fluid gel, and obtain component A; at the same time, mix the other part with an easily soluble silicate, microsilica powder, and polyvinyl alcohol fibers to obtain component B; The easily soluble silicate is one or more of sodium silicate, potassium silicate, lithium silicate, and ammonium silicate; S4. Mix the component A and component B in S3 to form a composite gel, pour or spray the gel to form the desired shape, and after standing and solidifying to meet the design requirements, the composite gel matrix of the high-porosity material is obtained. After the component A and component B are mixed to form a composite gel, a sample is taken and observed with an optical microscope as Figure 2 shown.

[0022] The moisture content of the composite gel matrix is not less than 60%, the porosity after air drying or drying at normal pressure is greater than 70%, and the density is 0.1 g / cm³ - 0.5 g / cm³.

[0023] Example 1 Prepare materials according to the following mass percentages: 72% water, 3% polyvinyl alcohol, 1% sodium alginate, 8% dicalcium silicate, 4% tricalcium silicate, 3% microsilica, 4% potassium silicate, 3% calcium citrate, 2% polyvinyl alcohol fiber.

[0024] A preparation method of a composite gel matrix of a high-porosity material includes the following steps: (1) Mix and dissolve water, polyvinyl alcohol, and sodium alginate, and drop into a 5% calcium citrate solution to obtain a hydrogel with a "egg-box" type feature; (2) After draining the excess calcium citrate solution, crush the obtained hydrogel into a sol with a particle size of 80 nm using a colloid mill; (3) Divide the fine particle sol obtained in step (2) into two equal parts. Component A: Mix 50% sol with dicalcium silicate and tricalcium silicate; Component B: Mix 50% sol with potassium silicate, microsilica, and polyvinyl alcohol fiber; (4) After mixing the component A and component B, pour them into a cube shape in a mold and demold after standing for 2 days. After the gel matrix obtained in this example is naturally air-dried for 20 days, the porosity of the material is 78%, the density is 0.15 g / cm³, and the compressive strength is 0.8 MPa.

[0025] Only the Na in the G unit of sodium alginate + can perform ion exchange with soluble calcium ions in an aqueous solution, so that multiple G units are cross-linked with calcium ions to form an "egg box" model, which can form a cross-linked sodium alginate calcium layer on the outer layer of sodium alginate, and the inside is a non-cross-linked sodium alginate area. However, "Time dependent gelling properties of cuboidal alginate gels made by external gelation method: Effects of alginate-CaCl 2The research results published in "solution ratios and pH" show that when sodium alginate is mixed with soluble calcium ions, a gel is temporarily formed. The gel shrinks as the gel time increases. In an alkaline medium, the carboxyl groups of the alginate gel dissociate, and the negatively charged carboxylate ions repel each other, absorbing water to fill the space in the calcium alginate network. Under strong alkaline conditions, sodium or potassium ions will displace the calcium ions in the gel, weakening the gel strength. Polyvinyl alcohol with strong alkali resistance is added in step (1). PVA can be incorporated into the alginate gel as a matrix. On the one hand, PVA has good miscibility with sodium alginate. Introducing sodium alginate into PVA helps to form a tight three-dimensional network interpenetrating structure, thus improving the mechanical properties and anti-shrinkage ability of the gel. On the other hand, PVA has good hydrophilicity and water retention ability, which can absorb and retain water, thus reducing the shrinkage of the gel during drying. On the third hand, hydrogen bonds can be formed between the hydroxyl groups (-OH) on the PVA molecular chain and the carboxyl groups on the sodium alginate molecular chain. This hydrogen bond interaction can stabilize the carboxyl groups and reduce their dissociation. On the fourth hand, the hydrophilicity of PVA can regulate the internal water environment of the gel, maintaining a relatively stable pH value, thus reducing the dissociation of carboxyl groups. After the formed sodium alginate-PVA composite gel is mixed with component A, the sodium alginate-PVA composite gel can maintain good stability and be relatively hard after being mixed with calcium silicate. After the sodium alginate-PVA composite gel is mixed with the dicalcium silicate tricalcium-sodium (potassium) silicate system, as Figure 1 shown, a three-dimensional network-like spatial framework (hydrated calcium silicate crystals) can be generated in the voids between the sol microparticles, improving the strength of the spatial framework, and the gel can also not shrink during drying without the need for the freezing method.

[0026] In component B of step (3), potassium silicate, microsilica and polyvinyl alcohol fibers do not react. The polyvinyl alcohol fibers and 50% of the sol act as diluents for potassium silicate, evenly dispersing potassium silicate and microsilica, reducing their local concentration, and avoiding the rapid formation of hydrated calcium silicate crystals in the voids between the sol microparticles due to too high local concentration when potassium silicate and microsilica are directly added to component A, avoiding local caking, hindering stirring and hindering the dispersion of potassium silicate, and also preventing the uneven pore structure of the gel. Adding the polyvinyl alcohol fibers in component B to component A can also play a role in enhancing the gel strength and crack resistance.

[0027] In addition, component A is more viscous than component B, and it is difficult to stir the polyvinyl alcohol fibers in A, resulting in uneven dispersion. B is thinner and has good fluidity, so it is easier to disperse the fibers evenly when they are first placed in B.

[0028] Example 2 Formulation ratio (mass percentage): Water 65%, polyacrylamide 3.5%, sodium alginate 1.5%, dicalcium silicate 10%, tricalcium silicate 5%, microsilica 3%, sodium silicate 5%, calcium acetate 4%, polyvinyl alcohol fiber 3%.

[0029] The preparation method is the same as that of Example 1, and the main difference is only that polyacrylamide is used to replace polyvinyl alcohol. Polyacrylamide has the same function as polyvinyl alcohol. The preparation method includes: Mix and dissolve water, polyvinyl alcohol, and sodium alginate, and add 5% calcium acetate solution for solidification to obtain a composite hydrogel; Crush the hydrogel into a sol with a particle size of 50 nm; Prepare Component A: Mix 50% sol with dicalcium silicate and tricalcium silicate; Prepare Component B: Mix 50% sol with sodium silicate, microsilica, and polyvinyl alcohol fiber; Mix Component A and Component B and spray them on the metal surface, with a coating thickness of 5 mm.

[0030] After the gel matrix obtained in this example is naturally air-dried, the porosity of the material is 70%, the density is 0.21 g / cm³, the compressive strength is 0.91 MPa, and the thermal conductivity is 0.03 W / (m·K).

[0031] In this example, polyacrylamide and sodium alginate can form a double-network hydrogel. This hydrogel combines the advantages of the two polymers. When the carboxyl group in sodium alginate reacts with Ca² + to form a calcium alginate cross-linked network, polyacrylamide provides additional mechanical properties through its own polymerization network, making the composite gel have higher mechanical strength and stability.

[0032] Comparative Example 1 The difference from Example 1 is that the soluble silicate (potassium silicate) is replaced by calcium chloride, and polyvinyl alcohol fiber is not added.

[0033] Prepare the materials according to the following mass percentages: water 72%, polyvinyl alcohol 3%, sodium alginate 0.8%, dicalcium silicate 12%, tricalcium silicate 3.2%, microsilica 3%, calcium chloride 4%, calcium acetate 2%, polyvinyl alcohol fiber 0%.

[0034] A preparation method of a high-porosity composite gel includes the following steps: (1) Mix and dissolve water, polyvinyl alcohol, and sodium alginate, and drop into 5% calcium acetate solution to obtain a hydrogel with the characteristics of an "egg-box" type; (2) After draining the excess calcium acetate solution, crush the obtained hydrogel into a sol with a particle size of 80 nm using a colloid mill; (3)Divide the micro-particle sol obtained in S2 into two equal parts. Component A: Mix 50% of the sol with dicalcium silicate and tricalcium silicate. Component B: Mix 50% of the sol with calcium chloride and microsilica powder. (4)After mixing Components A and B, pour them into a mold to form a cubic block, and demold after standing for 2 days. The gel material obtained in this example has a porosity of 61.3%, a density of 0.32 g / cm³, and a compressive strength of 0.12 MPa after natural air drying for 20 days.

[0035] Comparative Example 2 The difference from Example 1 is that the soluble silicate (potassium silicate) is replaced by magnesium phosphate, and the rest is the same. The gel material obtained in this example has a porosity of 60.2%, a density of 0.44 g / cm³, and a compressive strength of 0.06 MPa after natural air drying for 20 days.

[0036] Comparative Example 3 The difference from Example 1 is that the water-soluble alkali-resistant polymer is not added, and the rest is the same. After mixing Components A and B in this example, pour them into a mold to form a cubic block, and demold after standing for 2 days. The test block immediately crushes and has almost no compressive strength.

[0037] The above examples have described the present invention in detail, but they are only a part of the embodiments of the present invention, not all of them. Other embodiments can also be obtained based on these examples without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite gel matrix of a high-porosity material, characterized in that: The following steps are involved: S1. After dissolving a water-soluble alkali-resistant polymer and sodium alginate in water, the solution is dropped into a soluble organic acid calcium salt aqueous solution for cross-linking to obtain a composite hydrogel; S2. Grinding the composite hydrogel obtained in S1 into a granular sol; S3. The sol obtained in S2 is divided into two parts, one part is mixed with dicalcium silicate and tricalcium silicate, and the sol is secondary cross-linked to form a high fluidity gel to obtain component A; at the same time, the other part is mixed with a soluble silicate, microsilica powder, and a polymer fiber to obtain component B; S4. Component A and component B in S3 are mixed to form a composite gel, and the composite gel is cast or sprayed to form a desired shape, and the composite gel matrix of the high-porosity material is obtained after standing and solidifying.

2. The method for preparing a composite gel matrix of a high-porosity material according to claim 1, characterized in that: The mass ratio of water, water-soluble alkali-resistant high molecular polymer, sodium alginate, dicalcium silicate, tricalcium silicate, microsilica powder, soluble silicate, soluble organic acid calcium salt and polyvinyl alcohol fiber is 0.6~0.85: 0.025~0.035: 0.005~0.015: 0.06~0.1: 0.03~0.05: 0.01~0.05: 0.03~0.05: 0.02~0.04: 0.01~0.

03.

3. The method for preparing a composite gel matrix of a high-porosity material according to claim 1, characterized in that: In the step S1, the water-soluble alkali-resistant high molecular polymer is one or more of polyvinyl alcohol, polyacrylamide, and polyethylene glycol, and the added amount of the water-soluble alkali-resistant high molecular polymer is 2 to 3 times the mass of sodium alginate.

4. The method for preparing a composite gel matrix of a high-porosity material according to claim 1, characterized in that: The soluble organic acid calcium salt is one or more of calcium acetate, calcium citrate, calcium formate, calcium gluconate and calcium lactate, and the concentration of the organic acid calcium salt aqueous solution is 5% to 20% w / w.

5. The method for preparing a composite gel matrix of a high-porosity material according to claim 1, characterized in that: The particle size of the sol in S2 is not greater than 100 nm.

6. The method for preparing a composite gel matrix of a high-porosity material according to claim 1, characterized in that: The soluble silicate is one or more of sodium silicate, potassium silicate, lithium silicate or ammonium silicate.

7. The method for preparing a composite gel matrix of a high-porosity material according to claim 1, characterized in that: The high molecular polymer fiber does not react with easily soluble silicate, and includes polyvinyl alcohol fiber.

8. A composite gel matrix of a high porosity material, characterized in that: The composite gel is prepared by the method described in any one of claims 1 to 7, and contains sol microparticles, polymer fibers and hydrated calcium silicate crystals. The hydrated calcium silicate crystals form a three-dimensional network-like spatial skeleton between the sol microparticles and the polymer fibers. The sol microparticles are an interpenetrating network structure formed by calcium alginate and a water-soluble alkali-resistant polymer. The water content of the composite gel is not less than 60%, and the compressive strength ranges from 0.1 to 10 MPa.

9. The use of the composite gel matrix of high porosity material according to claim 8, characterized in that: The composite gel is suitable for the fields of building thermal insulation materials, industrial equipment thermal insulation coatings, solid water storage and heat storage or agricultural water retention materials.

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