High-loading molecular sieve / paper pulp fiber composite material as well as preparation method and application thereof

Abstract

The invention discloses a high-loading molecular sieve / paper pulp fiber composite material as well as a preparation method and application thereof. Comprising the following steps: (1) carrying out selective oxidation treatment on paper pulp fibers, and converting-OH into-COOH; an agent for selective oxidation treatment comprises an oxidizing chlorine-containing compound, and the effective chlorine dosage of the oxidizing chlorine-containing compound is 0.6-3.0 mmol / g absolute dry fiber; and (2) dipping the treated paper pulp fiber in an aqueous solution of an aluminum source and alkali, adding a silicon source solution, stirring, and carrying out aging and crystallization treatment to prepare the high-loading molecular sieve / paper pulp fiber composite material. The composite material can be applied to water-sensitive test paper, and the prepared water-sensitive test paper has higher sensitivity, is superior to commercially available test paper, and can be applied to the aspects of experiment teaching, moisture indication in dry food packaging, rapid judgment of moisture content in environment and the like.

Description

Technical Field

[0001] The present invention discloses a molecular sieve / pulp fiber composite material with a high loading amount, a preparation method thereof, and an application thereof, belonging to the field of plant fiber composite materials. Background Art

[0002] Molecular sieves are porous crystalline aluminosilicates with a regular framework structure formed by the alternation of silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons. They have characteristics such as a large specific surface area and uniformly distributed pore sizes, and are widely used in fields such as petrochemical industry and gas separation. Due to the micro-nano size of molecular sieves, their practical applications are subject to certain limitations. In order to fully utilize the specific surface area and surface properties of molecular sieves, they are usually loaded on the surfaces of fibers, membranes, and paper sheets to obtain composite materials. The loading situation of molecular sieves directly affects the performance of the materials.

[0003] Among many molecular sieve carriers, plant fibers, as natural fiber materials, have advantages such as biodegradability, wide sources, and low cost. They are a very promising molecular sieve carrier and can be used in hemostatic materials, adsorption materials, etc. Pulp fibers are fiber materials obtained from plant raw materials through processes such as cooking and screening. After loading molecular sieves, they can be formed into paper by wet forming to further expand the application of molecular sieve / plant fiber composite materials. According to existing research, the active -OH on the surface of pulp fibers is the binding site for molecular sieve loading. However, the effect of increasing the molecular sieve loading amount by increasing the content of active -OH is limited. In order to further increase the molecular sieve loading amount, it is necessary to further search for a method for preparing a molecular sieve / pulp fiber composite material with a high loading amount.

[0004] At the same time, the molecular sieves on the molecular sieve / pulp fibers can be modified to endow them with properties such as water sensitivity, antibacterial property, catalysis, and adsorption. Cobalt chloride, as a commonly used inorganic salt water-sensitive indicator, can change from blue anhydrous cobalt chloride to red cobalt hexahydrate after absorbing water. Impregnating molecular sieves with cobalt chloride solution can load cobalt chloride on them. Researchers prepared test papers using cobalt chloride-modified zeolites as fillers, which can make a color response to air humidity. However, a large amount of molecular sieve fillers have a low retention rate during the papermaking process, and there is a lack of binding between the fillers and the fibers, resulting in weak stability. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems in the prior art such as low loading amount and poor uniformity of molecular sieves on pulp fibers, and to provide a molecular sieve / pulp fiber composite material with a high loading amount, a preparation method thereof, and an application thereof.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A preparation method of a molecular sieve / pulp fiber composite material with a high loading amount, comprising the following steps:

[0008] (1) Selectively oxidize the pulp fibers to convert -OH to -COOH; the agent for the selective oxidation treatment includes an oxidizing chlorine-containing compound, and the effective chlorine dosage is 0.6 - 3.0 mmol / g of absolute dry fiber;

[0009] (2) Immerse the treated pulp fibers in an aqueous solution of an aluminum source and an alkali, then add a silicon source solution thereto, stir, and then carry out aging and crystallization treatments to obtain a molecular sieve / pulp fiber composite material with a high loading amount.

[0010] Preferably, the effective chlorine dosage of the oxidizing chlorine-containing compound is 1.2 - 2.4 mmol / g of absolute dry fiber; the oxidizing chlorine-containing compound is selected from at least one of hypochlorite, chloroisocyanuric acid, and chlorine dioxide.

[0011] Preferably, the agent for the selective oxidation treatment in step (1) is: the dosage of Tempo is 0.004 - 0.02 g / g of absolute dry fiber, the dosage of NaBr is 0.05 - 0.15 g / g of absolute dry fiber, and the effective chlorine dosage of the oxidizing chlorine-containing compound is 1.5 - 2.0 mmol / g of absolute dry fiber.

[0012] Preferably, the aging conditions in step (2) are: temperature 25 - 40 °C, time 15 - 120 min; the crystallization conditions are: temperature 60 - 120 °C, time 2 - 6 h.

[0013] Preferably, the molecular sieve in step (2) is a type A molecular sieve, which can be synthesized in one step by the hydrothermal method. The ratio of silicon, aluminum, alkali, and water used follows the formula of the type A molecular sieve, and the molar ratio of the aluminum source, silicon source, alkali, and water is: wNa2O.xSiO2.yAl2O3.zH2O (molar ratio), where x / y is 1.6 - 2, z / w is 30 - 70, and w / y is 1 - 4.

[0014] Preferably, the aluminum source is at least one of NaAlO2 and Na2Al2O4, and the alkali is NaOH; the silicon source is at least one of Na2SiO3·5H2O, Na2SiO3·9H2O, Na2SiO3, silica sol, and aqueous silica gel solution.

[0015] Preferably, the impregnation conditions in step (2) are: the impregnation pulp concentration is 1% - 20%, the stirring speed during impregnation is 0 - 2000 rpm, and the impregnation time is 15 - 120 min; the stirring speed after adding the silicate solution is 200 - 2000 rpm, and the stirring time is 15 - 120 min.

[0016] Preferably, in step (1), the pulp consistency of the pulp fibers is 0.1% to 5%, the stirring speed is 200 to 2000 rpm, and the reaction time is 0.5 to 6 h; the pulp fibers include at least one of cotton pulp fibers, hemp pulp fibers, bast pulp fibers, straw pulp fibers, wood pulp fibers, and bamboo pulp fibers.

[0017] Preferably, the oxidizing chlorine-containing compound is selected from at least one of NaClO, Ca(ClO)₂, and HClO.

[0018] Application of the prepared molecular sieve / pulp fiber composite material with a high loading amount in a water-sensitive test paper.

[0019] Preferably, the molecular sieve / pulp fiber composite material is impregnated in a cobalt chloride solution, and after washing, it is wet-formed and co-papered to obtain a water-sensitive test paper. The wet forming can be prepared by methods such as the Kayser automatic papermaking system, the KRK sheet-making method, and suction filtration.

[0020] Preferably, the impregnation conditions are as follows: the concentration of the cobalt chloride solution is 1% to 50%, the impregnation pulp consistency is 0.1% to 20%, the stirring speed is 0 to 2000 rpm, and the impregnation time is 20 to 120 min; the basis weight of the test paper is 20 to 180 g / m 2 , and the pulp used for co-papering is at least one of cotton pulp, hemp pulp, bast pulp, straw pulp, wood pulp, and bamboo pulp, and the co-papering ratio is 10% to 40%.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] (1) By selectively oxidizing the pulp fibers, this method can significantly increase the molecular sieve loading amount, and the loading amount is controllable.

[0023] (2) Utilizing the water absorption characteristics of the molecular sieve, the prepared water-sensitive test paper has high sensitivity and fast color change upon water absorption, which is superior to the existing commercially available test papers.

[0024] (3) The present invention can be applied to disposable medical packaging humidity indicator cards, experimental teaching, moisture indication in dry food packaging, rapid determination of moisture content in the environment, etc. Description of the Drawings

[0025] Figure 1 It is the SEM surface morphology diagram of the molecular sieve / pulp fiber composite material.

[0026] Figure 2 It is the XRD analysis result of the molecular sieve, pulp fiber, and molecular sieve / pulp fiber composite material.

[0027] Figure 3 It is the content of the molecular sieve in the molecular sieve / pulp fiber composite material under different available chlorine dosages in Example 3.

[0028] Figure 4 For the pore size distribution of the molecular sieve / pulp fiber composite material (NaA / BF) and the specific surface areas of the molecular sieve (NaA), pulp fiber (BF), and molecular sieve / pulp fiber composite material (NaA / BF).

[0029] Figure 5 For the true color development pictures (0 s to 20 s) of the water-sensitive test paper of Example 3 and the commercially available test paper in an environment with 50% humidity.

[0030] Figure 6 For the chromaticity change diagram of the water-sensitive test paper of Example 3; (a) Changes in the L* value and a* value of the test paper at different times; (b) Changes in the b* value of the test paper at different times. Detailed implementation manners

[0031] The technical solution of the present invention is further elaborated through specific examples below, but the protection scope of the present invention is not limited thereto.

[0032] Example 1

[0033] (1) Selective oxidation reaction of softwood pulp fibers: Take 15 g of bamboo pulp fibers (on an absolutely dry basis) and make a pulp with a concentration of 0.3%. Stir well to disperse the fibers, add 0.23 g of Tempo and 2 g of NaBr in sequence to dissolve them, then add a sodium hypochlorite solution with 52.5 mmol of available chlorine to start the oxidation reaction and keep the pH value of the system at 10. After 5 h, terminate the reaction and rinse with deionized water until the pH is neutral to obtain oxidized bamboo pulp fibers.

[0034] (2) Preparation method of the molecular sieve / bamboo pulp fiber composite material: Dissolve 8 g of NaAlO2 and 1 g of NaOH in 50 ml of deionized water, add 2 g (on an absolutely dry basis) of oxidized bamboo pulp fibers, and magnetically stir at 500 rpm for 60 min. Dissolve 32 g of Na2SiO3·5H2O and 0.5 g of NaOH in 50 ml of deionized water, and add it to the above-impregnated bamboo pulp fibers under magnetic stirring at 1000 rpm, and stir at room temperature for 60 min. Transfer it to a hydrothermal reaction kettle, place it in a constant-temperature oven and age at 25°C for 0.5 h. After aging, raise the oven temperature to 100°C and keep it warm for 4 h to complete the crystallization reaction. After the reaction, filter and wash with a 60-mesh filter screen and no product remains.

[0035] In this example, the dosage of available chlorine is too large, resulting in too high an oxidation degree of the fibers, and the molecular sieve / cotton pulp fiber composite material cannot be successfully prepared.

[0036] Example 2

[0037] (1) Selective oxidation reaction of cotton pulp fibers: Take 10 g of cotton fibers (on dry basis) and make a pulp with a concentration of 1%. Stir well to disperse the fibers, add 0.15 g of Tempo and 1.0 g of NaBr in sequence to dissolve them, then add a sodium hypochlorite solution with 12 mmol available chlorine to start the oxidation reaction and maintain the pH value of the system at 9.5. After 2 h, terminate the reaction and rinse with deionized water until the pH is neutral to obtain oxidized cotton fibers.

[0038] (2) Preparation method of molecular sieve / cotton fiber composite: Dissolve 24.6 g of NaAl2O3 and 2.9 g of NaOH in 149.7 ml of deionized water, add 6 g (on dry basis) of oxidized cotton pulp fibers, and stir magnetically at 300 rpm for 30 min. Dissolve 82.09 g of Na2SiO3·9H2O in 149.7 ml of deionized water, and add it to the above-impregnated cotton pulp fibers under magnetic stirring at 1000 rpm, and stir at room temperature for 30 min. Transfer it to a hydrothermal reaction kettle, place it in a constant-temperature oven and age at 40 °C for 1 h. After aging, raise the oven temperature to 90 °C and keep it warm for 4 h to complete the crystallization reaction, and wash with deionized water to obtain the molecular sieve / cotton pulp fiber composite. Ash the composite to obtain a molecular sieve loading of 51.32%, and the XRD results show that the molecular sieve is type A molecular sieve.

[0039] (3) Preparation of water-sensitive test paper: Immerse 2 g of molecular sieve / cotton pulp fibers in a 5 wt% cobalt chloride aqueous solution, stir at 500 rpm at room temperature for 1 h, and wash to obtain a modified molecular sieve / cotton pulp fiber composite. Make a water-sensitive test paper with a basis weight of 80 g / m² by filtering and forming a system with 60% of the composite and 40% of bleached softwood pulp. The test paper has an obvious color response within 30 s in a humidity environment of 32%. 2 The test paper has an obvious color response within 30 s in a humidity environment of 32%.

[0040] Example 3

[0041] (1) Selective oxidation reaction of bamboo pulp fibers: Take 20 g of bamboo pulp fibers (on dry basis) and make a pulp with a concentration of 2%. Stir well to disperse the fibers, add 0.32 g of Tempo and 2.0 g of NaBr in sequence to dissolve them, then add a sodium hypochlorite solution with 36 mmol available chlorine to start the oxidation reaction and maintain the pH value of the system at 10.5. After 3 h, terminate the reaction and rinse with deionized water until the pH is neutral to obtain oxidized bamboo pulp fibers.

[0042] (2) Preparation method of molecular sieve / bamboo pulp fiber composite material: Dissolve 23.43 g of NaAlO2 and 2.73 g of NaOH in 202.5 ml of deionized water, add 9.1 g (dry basis) of oxidized bamboo pulp fiber, and magnetically stir at 800 rpm for 20 min. Dissolve 58.38 g of Na2SiO3·9H2O in 101.1 ml of deionized water, and add it to the above-impregnated bamboo pulp fiber under magnetic stirring at 1200 rpm, and stir at room temperature for 20 min. Transfer it to a hydrothermal reaction kettle and age it in a constant-temperature oven at 25 °C for 1 h. After aging, raise the oven temperature to 100 °C and keep it warm for 4 h to complete the crystallization reaction, and wash it with deionized water to obtain the molecular sieve / bamboo pulp fiber composite material. Ash the composite material to obtain a molecular sieve loading of 63.9%, and the XRD results show that the molecular sieve is A-type molecular sieve.

[0043] (3) Preparation of water-sensitive test paper: Immerse 4 g of molecular sieve / bamboo pulp fiber in 30 wt% cobalt chloride aqueous solution, stir at 1000 rpm at room temperature for 1 h, and wash to obtain a modified molecular sieve / sisal pulp fiber composite material. Use 80% of the composite material and 20% of bamboo pulp (60°SR) to make a water-sensitive test paper with a basis weight of 60 g / m 2 The test paper has an obvious color response within 3 s in a 50% humidity environment.

[0044] By adjusting the addition amount of available chlorine, molecular sieve / pulp fiber composite materials with different molecular sieve contents are obtained. For details, see Figure 3 .

[0045] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a molecular sieve / pulp fiber composite material with a high loading amount, characterized in that, It includes the following steps: (1) Perform selective oxidation treatment on pulp fibers to convert -OH to -COOH; the agent for the selective oxidation treatment includes an oxidizing chlorine-containing compound, and the effective chlorine dosage is 0.6 - 3.0 mmol / g of absolute dry fiber; (2) Immerse the treated pulp fibers in an aqueous solution of an aluminum source and an alkali, then add a silicon source solution thereto, stir, and perform aging and crystallization treatments to obtain a high-loading molecular sieve / pulp fiber composite material.

2. The preparation method according to claim 1, characterized in that, The effective chlorine dosage of the oxidizing chlorine-containing compound is 1.2 - 2.4 mmol / g of absolute dry fiber; the oxidizing chlorine-containing compound is selected from at least one of hypochlorite, chloroisocyanuric acid, and chlorine dioxide.

3. The preparation method according to claim 2, wherein The agent for the selective oxidation treatment in step (1) is: the dosage of Tempo is 0.004 - 0.02 g / g of absolute dry fiber, the dosage of NaBr is 0.05 - 0.15 g / g of absolute dry fiber, and the effective chlorine dosage of the oxidizing chlorine-containing compound is 1.5 - 2.0 mmol / g of absolute dry fiber.

4. The preparation method according to claim 3, characterized in that, The aging conditions in step (2) are: temperature 25 - 40 °C, time 15 - 120 min; the crystallization conditions are: temperature 60 - 120 °C, time 2 - 6 h.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The molecular sieve in step (2) is type A molecular sieve; the aluminum source is at least one of NaAlO2 and Na2Al2O4, the alkali is NaOH; the silicon source is at least one of Na2SiO3·5H2O, Na2SiO3·9H2O, Na2SiO3, silica sol, and silica gel aqueous solution; the molar ratio of the aluminum source, silicon source, alkali, and water is: wNa2O.xSiO2.yAl2O3.zH2O, where x / y is 1.6 - 2, z / w is 30 - 70, and w / y is 1 - 4.

6. The preparation method according to claim 4, characterized in that, The impregnation conditions in step (2) are: the impregnation pulp concentration is 1% - 20%, the stirring speed during impregnation is 0 - 2000 rpm, and the impregnation time is 15 - 120 min; the stirring speed after adding the silicate solution is 200 - 2000 rpm, and the stirring time is 15 - 120 min; In step (1), the pulp concentration of the pulp fibers is 0.1% - 5%, the stirring speed is 200 - 2000 rpm, and the reaction time is 0.5 - 6 h; the pulp fibers include at least one of cotton pulp fibers, hemp pulp fibers, bast pulp fibers, straw pulp fibers, wood pulp fibers, and bamboo pulp fibers; the oxidizing chlorine-containing compound is selected from at least one of NaClO, Ca(ClO)2, and HClO.

7. A high-loading molecular sieve / pulp fiber composite material prepared by the method according to any one of claims 1 - 6.

8. Application of the high-loading molecular sieve / pulp fiber composite material according to claim 9 in a water-sensitive test paper.

9. The application according to claim 8, wherein Immerse the molecular sieve / pulp fiber composite material in a cobalt chloride solution, wash it, and wet-form and co-paper it to obtain a water-sensitive test paper.

10. The application according to claim 9, wherein, The impregnation conditions are as follows: the concentration of cobalt chloride solution is 1% - 50%, the pulp concentration for impregnation is 0.1% - 20%, the stirring speed is 0 - 2000 rpm, and the impregnation time is 20 - 120 min; the basis weight of the test paper is 20 - 180 g / m 2 , and the pulp used for blending is at least one of cotton pulp, hemp pulp, bast pulp, straw pulp, wood pulp, and bamboo pulp, and the blending ratio is 10% - 40%.

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