Modifier for fly ash as well as preparation method and application of modifier

Abstract

The invention discloses a modifier for fly ash as well as a preparation method and application thereof, and belongs to the technical field of fly ash modifiers. The invention provides a novel modifier for fly ash, which has a good modification effect. The invention also provides a use method of the modifier. Compared with a polyurethane composite material using unmodified fly ash, the modifier and the use method provided by the invention have the advantages that the mechanical property of the prepared polyurethane composite material can be remarkably improved, the tensile strength can be improved by 80-147%, the bonding strength can be improved by 66-122%, and the improvement effect equivalent to that of a polydopamine coating can be achieved; the performance limit of wet modification of traditional coupling agents such as KH550 and KH560 is exceeded; the provided modifier is low in preparation cost, under the same modification concentration, the cost of a modified coating provided by the invention is about 15% of that of a polydopamine modified coating, the modification cost of the modified coating is equivalent to that of traditional silane coupling agents KH550 and KH560, and the modified coating has excellent cost performance and is suitable for large-scale popularization and application.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic material modifiers, in particular to a modifier for fly ash and a preparation method and application thereof. Background Art

[0002] The treatment and recycling of large amounts of fly ash generated during coal mining and combustion has become an important issue in the field of environmental protection and the development and utilization of renewable resources. How to increase the utilization rate of fly ash and develop other application methods for fly ash, especially high value-added applications, has become a key issue that urgently needs to be broken through.

[0003] Polyurethane materials are widely used in coatings, adhesives, building materials, paving materials, and other applications due to their diverse formulations, adjustable properties, non-toxicity, and durability. Adding inorganic powdered fillers to polyurethane systems not only effectively reduces production costs but also improves and / or enhances certain material properties. Fly ash, which exhibits stable mechanical properties after high-temperature combustion and significantly improves its compatibility with polymers through surface modification, can be used as an inorganic powdered filler in polyurethane materials.

[0004] Currently, fly ash modification methods include acid modification, alkaline modification, and coupling agent modification. Among them, coupling agent modification is a commonly used modification method to improve the compatibility of fly ash with polymer matrices. However, after high-temperature calcination, the amount of surface active groups remaining in fly ash is extremely small, and the number of silane coupling agents that can be grafted by chemical bonding is very limited, which limits the degree of fly ash interface enhancement. For example, Chinese invention patent CN103012738B discloses a modified fly ash reinforced rigid polyurethane foam material and its preparation method. The fly ash is modified with a composite silane coupling agent (two or more of titanate, aluminate, phosphate, and borate). Compared with the composite material prepared from unmodified fly ash, the compressive strength of the composite material prepared from the modified fly ash is only increased by 16% to 33%.

[0005] Inspired by the high-strength adhesion mechanism of marine mussels, polydopamine coating has become an effective modification strategy to improve the interfacial compatibility between fillers and substrates due to its rich surface active functional groups and physical anchoring effect. However, the high price of dopamine limits its industrial application. Summary of the Invention

[0006] The purpose of the present invention is to provide a modifier for fly ash, a preparation method and application thereof, so as to solve the problem that the amount of surface active groups remaining in fly ash after high-temperature calcination is extremely small, resulting in a small number of modifiers that can be used and relatively poor modification effects. A new, low-cost modifier is provided, and at the same time, an effective utilization direction for increasing the added value of fly ash is provided.

[0007] To achieve the above object, the present invention provides a modifier for fly ash, wherein the modifier is a dopamine-like solution, and the solution is an aqueous solution of dopamine-like solution with a working concentration of 10 to 20 mmol·L -1 .

[0008] A method for preparing the above-mentioned modifier for fly ash comprises the following steps:

[0009] Add catechol, amino compound and tris(hydroxymethyl)aminomethane hydrochloride to water in sequence, stir evenly, adjust the pH of the solution to 8.5, and then make up the volume, and stir while continuously introducing gas.

[0010] Preferably, the amino compound is triethylenetetramine or tetraethylenepentamine.

[0011] Preferably, the reaction concentration of the catechol solution is 10 to 20 mmol·L -1 The reaction concentration of the amino compound solution is 3.3 to 6.7 mmol·L -1 The reaction concentration of tris(hydroxymethyl)aminomethane hydrochloride buffer solution was 10 mmol·L -1 .

[0012] Preferably, hydrochloric acid solution is used to adjust the pH; the gas continuously introduced is air; and the stirring conditions are 200 rpm, 60° C., and stirring for 0.5 to 4 hours.

[0013] A method for using the above-mentioned modifier for fly ash comprises:

[0014] The fly ash to be modified is added to the modifier and stirred, the supernatant is removed by centrifugation, and the obtained precipitate is washed and dried.

[0015] Preferably, the mass volume ratio of fly ash to be modified: modifier is 20 g:500 mL; the stirring conditions are 60° C., 200 rpm, and stirring for 10 to 28 hours; and deionized water is used for washing.

[0016] A use of the above-mentioned modifier for fly ash in fly ash modification.

[0017] A use of the above-mentioned modifier for fly ash in the preparation of polyurethane composite materials.

[0018] A method for using the above-mentioned modifier for fly ash is used in fly ash modification.

[0019] Therefore, the present invention provides a modifier for fly ash, a preparation method thereof, and an application thereof, and its specific technical effects are as follows:

[0020] (1) The present invention provides a novel modifier for fly ash with good modification effect; and also provides a method for using the modifier;

[0021] (2) Compared with polyurethane composites using unmodified fly ash, the modifier and method of use provided by the present invention can significantly improve the mechanical properties of the prepared polyurethane composites, with tensile strength increased by 80% to 147% and bonding strength increased by 66% to 122%, achieving an improvement effect comparable to that of polydopamine coatings and surpassing the performance limits of wet-method modification of traditional coupling agents such as KH550 and KH560;

[0022] (3) The preparation cost of the modifier provided by the present invention is low. At the same modification concentration, the cost of the modified coating provided by the present invention is about 15% of that of the polydopamine modified coating, which has excellent cost performance and is suitable for large-scale promotion and application.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 2 is a comparison chart of the tensile strength of Example 2 of the present invention and different comparative examples;

[0026] Figure 2 It is a comparison chart of the interfacial energy calculation results of Example 2 of the present invention and different comparative examples. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0028] In order to make the purpose, technical solutions and advantages of the present application clearer, more thorough and more complete, the technical solutions of the present invention are clearly and completely described below through the accompanying drawings and Examples. The following detailed description is an explanation of the embodiments and is intended to provide further details of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the application belongs.

[0029] The instruments, equipment, reagents and materials used in the examples were obtained from commercial sources; the methods and steps not described in detail in the examples are conventional techniques in the art.

[0030] Example 1

[0031] A dopamine-modified fly ash / polyurethane composite material is prepared, and the specific steps are as follows:

[0032] (1) Preparation of dopamine-like aqueous solution: Add 0.825g of catechol and 0.365g of triethylenetetramine to 450mL of water, then add 0.605g of tris(hydroxymethyl)aminomethane hydrochloride. After stirring evenly, add 1M hydrochloric acid dropwise and continuously test with pH test paper until the pH of the solution is adjusted to 8.5. Add water to a volumetric flask to make the volume up to 500mL, so that the concentrations of catechol, triethylenetetramine and tris(hydroxymethyl)aminomethane hydrochloride are 15mmol / L, 5mmol / L and 10mmol / L respectively. Continuously introduce air into the solution and stir at 60℃ and 200rpm for 2h to complete the oxidation process, thus obtaining 500mL of dopamine-like aqueous solution.

[0033] (2) Surface modification of fly ash: 20 g of fly ash was added to the dopamine-like aqueous solution obtained in step (1), and the mixture was stirred at 60° C. and 200 rpm for 12 h. The mixture was then centrifuged at 6000 rpm for 15 min, and the supernatant was removed to obtain modified fly ash. The modified fly ash was washed with deionized water, centrifuged three times, and then dried. The dopamine-like modified fly ash was obtained by ball milling at 400 rpm for 1 h.

[0034] (3) Preparation of polyurethane component: 45g of polyether diol PPG2000, 74g of polyether triol RT305 and 10g of modified fly ash obtained in step (2) were mixed to obtain component A. 0.15g of catalyst stannous octoate was added to 71g of toluene diisocyanate and mixed to obtain component B.

[0035] (4) Preparation of composite material: 64 g of component A prepared in step (3) and 36 g of component B were accurately weighed and stirred until uniform, and then allowed to stand for 3 h to solidify to obtain a modified fly ash / polyurethane composite material.

[0036] Example 2

[0037] A dopamine-modified fly ash / polyurethane composite material is prepared, and the specific steps are as follows:

[0038] (1) Preparation of dopamine-like aqueous solution: Add 0.825g of catechol and 0.365g of triethylenetetramine to 450mL of water, then add 0.605g of tris(hydroxymethyl)aminomethane hydrochloride. After stirring evenly, add 1M hydrochloric acid dropwise and continuously test with pH test paper until the pH of the solution is adjusted to 8.5. Add water to a volumetric flask to make the volume up to 500mL, so that the concentrations of catechol, triethylenetetramine and tris(hydroxymethyl)aminomethane hydrochloride are 15mmol / L, 5mmol / L and 10mmol / L respectively. Continuously introduce air into the solution and stir at 60℃ and 200rpm for 1h to complete the oxidation process, thus obtaining 500mL of dopamine-like aqueous solution.

[0039] (2) Surface modification of fly ash: 20 g of fly ash was added to the dopamine-like aqueous solution obtained in step (1), and the mixture was stirred at 60° C. and 200 rpm for 12 h. The mixture was then centrifuged at 6000 rpm for 15 min, and the supernatant was removed to obtain modified fly ash. The modified fly ash was washed with deionized water, centrifuged three times, and then dried. The dopamine-like modified fly ash was obtained by ball milling at 400 rpm for 1 h.

[0040] (3) Preparation of polyurethane component: 43g of polyether diol PPG2000, 70g of polyether triol RT305 and 20g of modified fly ash obtained in step (2) were mixed to obtain component A. 0.15g of catalyst stannous octoate was added to 67g of toluene diisocyanate and mixed to obtain component B.

[0041] (4) Preparation of composite material: 66 g of component A prepared in step (3) and 34 g of component B were accurately weighed and stirred until uniform, and then allowed to stand for 3 h to solidify to obtain a modified fly ash / polyurethane composite material.

[0042] Example 3

[0043] A dopamine-modified fly ash / polyurethane composite material is prepared, and the specific steps are as follows:

[0044] (1) Preparation of dopamine-like aqueous solution: Add 0.825g of catechol and 0.365g of tetraethylenepentamine to 450mL of water, then add 0.605g of tris(hydroxymethyl)aminomethane hydrochloride. After stirring evenly, add 1M hydrochloric acid dropwise and continuously test with pH test paper until the pH of the solution is adjusted to 8.5. Add water to a volumetric flask to make the volume up to 500mL, so that the concentrations of catechol, tetraethylenepentamine and tris(hydroxymethyl)aminomethane hydrochloride are 15mmol / L, 5mmol / L and 10mmol / L, respectively. Continuously introduce air into the solution and stir at 60℃ and 200rpm for 1h to complete the oxidation process, thus obtaining 500mL of dopamine-like aqueous solution.

[0045] (2) Surface modification of fly ash: 20 g of fly ash was added to the dopamine-like aqueous solution obtained in step (1), and the mixture was stirred at 60° C. and 200 rpm for 12 h. The mixture was then centrifuged at 6000 rpm for 15 min, and the supernatant was removed to obtain modified fly ash. The modified fly ash was washed with deionized water, centrifuged three times, dried, and ball-milled at 400 rpm for 1 h to obtain dopamine-like modified fly ash.

[0046] (3) Preparation of polyurethane component: 40 g of polyether diol PPG2000, 66 g of polyether triol RT305 and 30 g of modified fly ash prepared in step (2) were mixed uniformly to obtain component A; 0.15 g of catalyst stannous octoate was added to 64 g of toluene diisocyanate and mixed uniformly to obtain component B.

[0047] (4) Preparation of composite material: 68 g of component A obtained in step (3) and 32 g of component B were accurately weighed and stirred until uniform, and then allowed to stand for 3 h to solidify to obtain a modified fly ash / polyurethane composite material.

[0048] Example 4

[0049] A dopamine-modified fly ash / polyurethane composite material is prepared, and the specific steps are as follows:

[0050] (1) Preparation of dopamine-like aqueous solution: Add 0.550g of catechol and 0.241g of triethylenetetramine to 450mL of water, then add 0.605g of tris(hydroxymethyl)aminomethane hydrochloride. After stirring evenly, add 1M hydrochloric acid dropwise and continuously test with pH test paper until the pH of the solution is adjusted to 8.5. Add water to a volumetric flask to make the volume up to 500mL, so that the concentrations of catechol, triethylenetetramine and tris(hydroxymethyl)aminomethane hydrochloride are 10mmol / L, 3.3mmol / L and 10mmol / L respectively. Continuously introduce air into the solution and stir at 60℃ and 200rpm for 1h to complete the oxidation process, thus obtaining 500mL of dopamine-like aqueous solution.

[0051] (2) The surface modification of fly ash, the preparation of polyurethane components and the preparation of composite materials are the same as in Example 2.

[0052] Example 5

[0053] (1) Preparation of dopamine-like aqueous solution: Add 1.1 g of catechol and 0.634 g of tetraethylenepentamine to 450 mL of water, then add 0.605 g of tris(hydroxymethyl)aminomethane hydrochloride. After stirring evenly, add 1 M hydrochloric acid dropwise and continuously test with pH test paper until the pH of the solution is adjusted to 8.5. Add water to a volumetric flask to make the volume up to 500 mL, so that the concentrations of catechol, tetraethylenepentamine, and tris(hydroxymethyl)aminomethane hydrochloride are 20 mmol / L, 6.7 mmol / L, and 10 mmol / L, respectively. Continuously introduce air into the solution and stir at 60°C and 200 rpm for 1 h to complete the oxidation process, thus obtaining 500 mL of dopamine-like aqueous solution.

[0054] (2) The surface modification of fly ash, the preparation of polyurethane components and the preparation of composite materials are the same as in Example 2.

[0055] Comparative Example 1

[0056] A fly ash / polyurethane composite material was prepared. The difference from Example 2 was that the dopamine-modified fly ash was replaced with an equal amount of unmodified fly ash. The remaining components, component amounts and preparation steps were the same as Example 2.

[0057] Comparative Example 2

[0058] A dopamine-modified fly ash / polyurethane composite was prepared. This composite differed from Example 2 in that the polyamine-modified fly ash was replaced with an equal amount of fly ash modified with the silane coupling agent 3-aminopropyltriethoxysilane (KH550). The silane coupling agent 3-aminopropyltriethoxysilane (KH550)-modified fly ash was prepared by adding 50 mL of deionized water to 450 mL of anhydrous ethanol and stirring thoroughly. 1.66 g of the silane coupling agent KH-550 was then added to a final concentration of 15 mmol / L. The mixture was stirred and hydrolyzed for 2 hours, followed by the addition of 20 g of fly ash and stirring for 2 hours. After the modification process, the supernatant was removed by centrifugation to obtain the modified fly ash. The ash was then washed with deionized water and centrifuged three times. After drying, the ash was ball-milled at 400 rpm for 1 hour to obtain the KH550-modified fly ash. The composite material was prepared using the same steps as in Example 2.

[0059] Comparative Example 3

[0060] A dopamine-modified fly ash / polyurethane composite was prepared. This composite differed from Example 2 in that the polyamine-modified fly ash was replaced with an equal amount of fly ash modified with the silane coupling agent 3-(2,3-epoxypropyloxy)propyltrimethoxysilane KH560. The preparation methods for the fly ash modified with the silane coupling agent 3-(2,3-epoxypropyloxy)propyltrimethoxysilane KH560 and the composite material were the same as those used in Comparative Example 2.

[0061] Comparative Example 4

[0062] A polydopamine-modified fly ash / polyurethane composite material was prepared. The difference from Example 2 was that catechol and triethylenetetramine were replaced with equal amounts of dopamine, with a final dopamine concentration of 15 mmol / L. The fly ash modification and composite material preparation process were the same as in Example 2.

[0063] The tensile strength and bonding strength of the polyurethane composite materials prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were tested according to standards GB / T 528-2009 and GB / T 7124-2008. The mechanical property test results are shown in Table 1.

[0064] Table 1 Material mechanical properties data

[0065]

[0066] As can be seen from Table 1, at the same modification concentration and fly ash content, the mechanical properties (tensile strength and bond strength) of the polydopamine-modified fly ash / polyurethane composite prepared in Example 2 are comparable to those of the polydopamine-modified fly ash / polyurethane composite in Comparative Example 4, demonstrating significant advantages in mechanical properties. The tensile strengths of Examples 1 to 5 range from 27 to 37 MPa, and the bond strengths range from 15 to 20 MPa. Comparative Example 1, on the other hand, has a tensile strength of only 15 MPa and a bond strength of 9 MPa, representing increases of 80% to 147% in tensile strength and 66% to 122% in bond strength over Comparative Example 1. At the same modification concentration, the tensile strength of the dopamine-modified fly ash / polyurethane composite material prepared in Example 2 was increased by 23% and 32% respectively, and the bonding strength was increased by 25% and 18% compared with the tensile strength of the KH550 modified fly ash / polyurethane composite material prepared in Comparative Example 2 and the KH560 modified fly ash / polyurethane composite material prepared in Comparative Example 3. This shows that the composite material prepared by dopamine-modified fly ash has a significant improvement in strength compared with the polyurethane composite material with unmodified fly ash added and the composite material with fly ash modified by a conventional silane coupling agent, further proving that the fly ash modification method provided by the present invention can effectively enhance the mechanical properties of polyurethane materials.

[0067] The contact angle test was performed on the modified fly ash prepared or used in Example 2 and Comparative Examples 1 to 4, and the interfacial energy data of the composite materials were calculated and shown in Table 2.

[0068] Table 2 Contact angle measurement data of (modified) fly ash and interfacial energy data of composite materials

[0069]

[0070] It can be seen that after the fly ash is modified with coupling agent and polydopamine / dopamine-like, the interfacial energy between the fly ash and the polyurethane matrix is ​​reduced. The interfacial energy of the unmodified fly ash / polyurethane composite material in Comparative Example 1 is 28.7 mJ / m 2 In comparative example 2, the interfacial energy of the KH550 modified fly ash / polyurethane composite material was reduced to 16.7 mJ / m 2 (reduced by 42% compared with comparative example 1), the interfacial energy of the KH560 modified fly ash / polyurethane composite material in comparative example 3 is 16.1 mJ / m 2 (reduced by 44% compared with comparative example 1), the interfacial energy of the polydopamine modified fly ash / polyurethane composite material in comparative example 4 was 11.2 mJ / m 2 (reduced by 61% compared to comparative example 1), the interfacial energy of the dopamine-modified fly ash / polyurethane composite material in Example 2 is 10.2 mJ / m 2 (A decrease of ~64% compared to Comparative Example 1.) This indicates that the enhanced mechanical properties of the composite material are largely due to the reduction in interfacial energy, and the reduction in interfacial energy indicates an improvement in interfacial compatibility. That is, after the fly ash is modified using the method of Example 2, the interfacial compatibility between the fly ash and the polyurethane matrix is ​​greatly improved.

[0071] The possible reason is that the dopamine-like structure on the fly ash surface forms hydrogen bonds, π-π stacking effects, and chemical bonding with the polyurethane matrix, thereby significantly reducing the interfacial energy of the composite material and significantly improving the interfacial compatibility, thereby significantly improving the mechanical properties, surpassing the effect of conventional coupling agent modification on improving interfacial compatibility.

[0072] Therefore, the present invention provides a novel modifier for fly ash with good modification effect; a method for using the modifier is also provided; compared with a polyurethane composite material using unmodified fly ash, the mechanical properties of the prepared polyurethane composite material can be significantly improved by using the modifier and the method for using the present invention, with the tensile strength increased by 80% to 147%, and the bonding strength increased by 66% to 122%, achieving an improvement effect comparable to that of a polydopamine coating, and surpassing the performance limit of wet modification of traditional coupling agents such as KH550 and KH560; the preparation cost of the provided modifier is low, and at the same modification concentration, the cost of the modified coating provided by the present invention is approximately 15% of that of a polydopamine-modified coating, comparable to the modification cost of conventional silane coupling agents KH550 and KH560, having excellent cost-effectiveness and being suitable for large-scale promotion and application.

[0073] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between the various embodiments can be referred to in conjunction with each other. The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced with equivalents, and such modifications or replacements will not cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A modifier for fly ash, characterized in that: The modifier is a dopamine-like solution, and the solution is a dopamine-like aqueous solution with a working concentration of 10 to 20 mmol·L -1 .

2. A method for preparing a modifier for fly ash according to claim 1, characterized in that: include: Add catechol, amino compound and tris(hydroxymethyl)aminomethane hydrochloride to water in sequence, stir evenly, adjust the pH of the solution to 8.5, and then make up the volume, and stir while continuously introducing gas.

3. The method for preparing a modifier for fly ash according to claim 2, wherein: The amino compound is triethylenetetramine or tetraethylenepentamine.

4. The method for preparing a modifier for fly ash according to claim 2, wherein: The reaction concentration of catechol solution is 10~20mmol·L -1 The reaction concentration of the amino compound solution is 3.3 to 6.7 mmol·L -1 The reaction concentration of tris(hydroxymethyl)aminomethane hydrochloride buffer solution was 10 mmol·L -1 .

5. The method for preparing a modifier for fly ash according to claim 2, wherein: The pH was adjusted using hydrochloric acid solution; the gas continuously introduced was air; and the stirring conditions were 200 rpm, 60° C., and stirring for 0.5 to 4 h.

6. A method for using the modifier for fly ash according to claim 1, characterized in that: The steps include: The fly ash to be modified is added to the modifier and stirred, the supernatant is removed by centrifugation, and the obtained precipitate is washed and dried.

7. The method for using a modifier for fly ash according to claim 6, characterized in that: The mass volume ratio of fly ash to be modified: modifier is 20g:500mL; the stirring conditions are 60°C, 200rpm, and stirring for 10 to 28h; and deionized water is used for washing.

8. Use of the modifier for fly ash according to claim 1 in fly ash modification.

9. Use of the modifier for fly ash according to claim 1 in the preparation of polyurethane composite materials.

10. Use of the method for using the modifier for fly ash according to claim 6 or 7 in fly ash modification.

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