A super-stable water-based foam containing nanocellulose, its preparation method and application

Abstract

The present invention belongs to the field of chemical engineering, and discloses a super-stable water-based foam containing nanocellulose, its preparation method and application. Calculated by mass fraction, it includes the following components: based on 100 parts of the total mass of the compounded water-based foam, 0.1-2.0 parts of nanocellulose hydrogel, 0.5-5.0 parts of sodium dodecyl sulfate, 1.0-5.0 parts of tetradecanol, 0.1-3.0 parts of polyvinyl alcohol, and the balance is water; the above components are foamed by high-speed stirring to obtain the super-stable water-based foam containing nanocellulose. By adding nanocellulose, tetradecanol and polyvinyl alcohol, the super-stable foam ground film of the present invention can effectively slow down the processes of drainage, coalescence and disproportionation, so that this foam has an extremely long lifespan and can be stable for more than 20 days. This water-based foam has good environmental adaptability and renewability. The multi-layer foam system of the present invention is more stable than the foam of a single-layer film. When used as a foam ground film, it has better water retention, humidity increase and heat preservation effects.

Description

Technical Field

[0001] The present invention belongs to the field of chemical engineering, and particularly relates to a super-stable water-based foam containing nanocellulose, a preparation method thereof, and an application thereof. Background Art

[0002] Foam systems have been widely used in many fields such as daily chemicals, fire protection, mineral flotation, petrochemical industry, oil exploitation (such as foam flooding in oil reservoirs), etc. However, foams are usually unstable systems because film drainage, coalescence and disproportionation of bubbles will surely occur, thereby reducing the free energy of the whole system. In order to achieve better foam stability, surfactants, polymers, proteins, or surface-active solid particles are usually added to the foam system. However, although surfactants can easily and quickly move to the gas-liquid interface, the high viscosity of the foam film when adding proteins and polymers, or the elastic layer formed by the aggregation of surface-active solid particles, these additives cannot effectively prevent the decay of bubbles; the space occupied by the foam liquid film will spontaneously decrease to reduce the overall surface free energy of the system and maintain its own stability. In the long run, the bursting of the foam is irreversible. The instability of the foam system has always been the key factor restricting its application. Currently, foam stabilizers mainly include high molecular polymers and solid-phase nanomaterials, but there are still problems such as poor material performance, high cost, and limited sources.

[0003] In modern agricultural production, the plastic film mulching technology is widely used to increase soil temperature, maintain soil moisture, inhibit weed growth, and improve the crop growth environment. Traditional plastic film materials mainly include plastic films such as polyethylene and polyvinyl chloride. While these materials play their roles, they also bring a series of environmental and ecological problems. Plastic mulch films are not easily degraded and will remain in the soil for a long time, causing soil structure damage and microplastic pollution, which have a negative impact on crops and the ecological environment.

[0004] To solve this problem, degradable mulch films have received wide attention. By an emulsification method, a liquid foam mulch film with soil improvement function can be prepared, which can be used as a sprayable green substitute for petroleum-based plastic mulch films and a soil repair agent for degraded soils. Currently, there is no report on using water-based foams as foam mulch films. Summary of the Invention

[0005] To solve the disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a super-stable water-based foam mulch film containing nanocellulose and a preparation method thereof. The water-based foam mulch film prepared by the present invention has high foaming property, strong stability, and a simple preparation process, which is easy for large-scale production.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] A super-stable water-based foam containing nanocellulose, calculated by mass fraction, includes the following components: based on 100 parts of the total mass of the compounded water-based foam, 0.1 - 2.0 parts of nanocellulose hydrogel, 0.5 - 5.0 parts of sodium dodecyl sulfate (SDS), 1.0 - 5.0 parts of tetradecyl alcohol (TDA), 0.1 - 3.0 parts of polyvinyl alcohol (PVA), and the balance is water; the above components are foamed by high-speed stirring to obtain the super-stable water-based foam.

[0008] Preferably, the length of the nanocellulose contained in the nanocellulose hydrogel is 500 - 1000 nm, and the diameter is 3 - 5 nm.

[0009] Preferably, the degree of alcoholysis of the polyvinyl alcohol is 88% - 100%.

[0010] Preferably, the mass ratio of sodium dodecyl sulfate, tetradecyl alcohol, polyvinyl alcohol to nanocellulose hydrogel is (2.5 - 5.0) : 2.0 : (0.5 - 2.0) : (0.5 - 1.5).

[0011] The preparation method of the super-stable water-based foam includes the following steps:

[0012] (1) Mix sodium dodecyl sulfate and tetradecyl alcohol in water and heat to make all solutes uniformly dispersed. After cooling, stir at high speed to obtain the SDS / TDA foam system;

[0013] (2) Add polyvinyl alcohol to the above foam system and stir at high speed after it is completely dissolved;

[0014] (3) Add the nanocellulose hydrogel to the foam system in step (2), mix evenly, and stir at high speed to obtain the super-stable water-based foam containing nanocellulose.

[0015] Preferably, the conditions of high-speed stirring in steps (1) to (3) are all mechanical stirring, with a rotation speed of 1000 - 1500 rpm and a time of 5 - 10 min.

[0016] Preferably, the heating condition in step (1) is heating at 60 ± 10 °C for 20 ± 10 min.

[0017] The application of the super-stable water-based foam containing nanocellulose in foam mulch film.

[0018] Preferably, the super-stable water-based foam can be sprayed onto the soil or water surface by high-pressure spraying to form a foam mulch film.

[0019] The super-stable water-based foam containing nanocellulose is formed by multi-layer foams. In the present invention, nanocellulose is uniformly dispersed in the water-based foam system, significantly improving problems such as poor foam stability and low foaming rate. This is because nanocellulose has a very high specific surface area, which can provide a large number of adsorption sites, promote the effective adsorption of surfactant molecules, thereby reducing the surface tension of the liquid and facilitating the formation and stability of foams. In addition, when nanocellulose is dispersed in a liquid medium, they can intertwine with each other to form a three-dimensional network structure. This structure provides additional mechanical strength for the foam, preventing the foam from easily breaking when subjected to external forces. The hydroxyl groups on the surface of nanocellulose give it good affinity with water molecules, which can enhance the strength of the liquid film in the foam, reduce the drainage rate of the liquid, and thus extend the lifespan of the foam. The multi-layer foam system of the present invention is more stable than the foam with a single-layer film because multi-layer foams can generally withstand a higher air pressure fluctuation threshold. And even if one layer of the film breaks, other layers can become stable without changing the foam structure, thus forming a super-stable system.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) By adding nanocellulose (NCF), tetradecanol (TDA) and polyvinyl alcohol (PVA) to the super-stable foam ground film of the present invention, the processes of drainage, coalescence and disproportionation can be effectively slowed down, making this foam have an extremely long lifespan and can be stable for more than 20 days.

[0022] (2) Nanocellulose is rich in sources and can be completely biodegradable. A small amount of addition can improve the foam stability and foaming rate, while reducing the dosage of chemical emulsifiers, which is beneficial to ecological environment protection.

[0023] (3) The water-based foam of the present invention has good environmental adaptability and renewability. Gas, such as CO 2 gas fertilizer, can be added to the foam film later, and it can also float in paddy fields. The multi-layer foam system of the present invention is more stable than the foam with a single-layer film. When used as a foam ground film, the composition ratio can be adjusted according to the plant growth cycle to control the degradation cycle of the foam ground film, and it has better water retention, humidity increase and heat preservation effects. Description of the Drawings

[0024] Figure 1 Macrophotographs of the foams prepared in Examples 1-3 after standing for 2 hours.

[0025] Figure 2 Macrophotographs of the foams prepared in Examples 4-6 after standing for 2 hours.

[0026] Figure 3 Macrophotographs of the foam prepared in Comparative Example 1 after standing for 2 hours.

[0027] Figure 4 Macrophotographs of the foams prepared in Example 4 after standing for 0 h (a), 24 h (b), 158 h (c), and 501 h (d), respectively.

[0028] Figure 5 shows macrophotographs of the foams prepared in Example 5 after standing for 0 h (a), 141 h (b), 309 h (c), 497 h (d), and 640 h (e), respectively; among them, the left figure is the overall state diagram, and the right figure is the enlarged surface layer diagram.

[0029] Figure 6 Macrophotographs of the foams prepared in Comparative Example 1 after standing for 0 h (left) and one week (right), respectively. Detailed implementation manners

[0030] The present invention will be further described in detail below with reference to examples and drawings, but the implementation manners of the present invention are not limited thereto.

[0031] For those not specified in the examples and comparative examples of the present invention, they are carried out according to conventional conditions or conditions recommended by the manufacturer.

[0032] Raw materials, reagents, etc. not specified by the manufacturer used are all conventional products that can be obtained through commercial purchase. In the examples, the nanocellulose hydrogel was purchased from Henan Kegao Radiation Chemical Industry Technology Co., Ltd., specifically the nanocellulose fiber hydrogel (concentration: 2 wt%), and tetradecanol (TDA, purity > 99%), sodium dodecyl sulfate (SDS, purity > 99%), and polyvinyl alcohol (PVA-1799, polymerization degree: 1700, alcoholysis degree: 99.8 - 100%) were all purchased from Aladdin.

[0033] Example 1

[0034] (1) Weigh 0.5 parts of SDS and 2.0 parts of TDA in deionized water, and heat at 60 °C for 20 min to ensure that all solutes are evenly dispersed; after cooling, rapidly stir the solution at 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam, obtaining the SDS / TDA foam system.

[0035] (2) Add 0.5 parts of PVA to the SDS / TDA foam system. After the PVA is completely dissolved, rapidly stir the solution at 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam.

[0036] (3) Accurately weigh 0.5 parts of nanocellulose hydrogel and add it to the above mixture. Rapidly stir the solution at 1500 rpm at 25 °C for 10 min by mechanical stirring to prepare a nanocellulose-containing super-stable water-based foam.

[0037] After experimental measurement, the foaming rate of the water-based foam prepared in Example 1 was ~84%.

[0038] Example 2

[0039] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA into deionized water, and heat at 60 °C for 20 min to ensure that all solutes are evenly dispersed; after cooling, rapidly stir the solution at 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam, obtaining the SDS / TDA foam system.

[0040] (2) Add 0.5 part of PVA to the SDS / TDA foam system. After the PVA is completely dissolved, rapidly stir the solution at 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam.

[0041] (3) Accurately weigh 0.5 part of nanocellulose hydrogel and add it to the above mixture. Rapidly stir the solution at 1500 rpm at 25 °C for 10 min by mechanical stirring to obtain the super-stable water-based foam containing nanocellulose.

[0042] After experimental measurement, the foaming rate of the water-based foam prepared in Example 1 was ~89%.

[0043] Example 3

[0044] (1) Weigh 5.0 parts of SDS and 2.0 parts of TDA into deionized water, and heat at 60 °C for 20 min to ensure that all solutes are evenly dispersed; after cooling, rapidly stir the solution at 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam, obtaining the SDS / TDA foam system.

[0045] (2) Add 0.5 part of PVA to the SDS / TDA foam system. After the PVA is completely dissolved, rapidly stir the solution at 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam.

[0046] (3) Accurately weigh 0.5 part of nanocellulose hydrogel and add it to the above mixture. Rapidly stir the solution at 1500 rpm at 25 °C for 10 min by mechanical stirring to obtain the super-stable water-based foam containing nanocellulose.

[0047] After experimental measurement, the foaming rate of the water-based foam prepared in Example 1 was ~92%.

[0048] Example 4

[0049] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA into deionized water, and heat at 60 °C for 20 min to ensure that all solutes are evenly dispersed; after cooling, quickly stir the solution at a speed of 1200 rpm for 5 min at 25 °C by mechanical stirring to generate foam, obtaining the SDS / TDA foam system.

[0050] (2) Add 0.5 part of PVA to the SDS / TDA foam system. After the PVA is completely dissolved, quickly stir the solution at a speed of 1200 rpm for 5 min at 25 °C by mechanical stirring to generate foam.

[0051] (3) Accurately weigh 1.0 part of nanocellulose hydrogel and add it to the above mixture. Quickly stir the solution at a speed of 1500 rpm for 10 min at 25 °C by mechanical stirring to obtain a super-stable water-based foam containing nanocellulose.

[0052] As determined by experiments, the foaming rate of the water-based foam prepared in Example 1 is ~90%.

[0053] Example 5

[0054] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA into deionized water, and heat at 60 °C for 20 min to ensure that all solutes are evenly dispersed; after cooling, quickly stir the solution at a speed of 1200 rpm for 5 min at 25 °C by mechanical stirring to generate foam, obtaining the SDS / TDA foam system.

[0055] (2) Add 0.5 part of PVA to the SDS / TDA foam system. After the PVA is completely dissolved, quickly stir the solution at a speed of 1200 rpm for 5 min at 25 °C by mechanical stirring to generate foam.

[0056] (3) Accurately weigh 1.5 parts of nanocellulose hydrogel and add it to the above mixture. Quickly stir the solution at a speed of 1500 rpm for 10 min at 25 °C by mechanical stirring to obtain a super-stable water-based foam containing nanocellulose.

[0057] As determined by experiments, the foaming rate of the water-based foam prepared in Example 1 is ~95%.

[0058] Example 6

[0059] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA into deionized water, and heat at 60 °C for 20 min to ensure that all solutes are evenly dispersed; after cooling, quickly stir the solution at a speed of 1200 rpm for 5 min at 25 °C by mechanical stirring to generate foam, obtaining the SDS / TDA foam system.

[0060] (2) Add 2.0 parts of PVA to the SDS / TDA foam system. After the PVA is completely dissolved, stir the solution rapidly at a speed of 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam.

[0061] (3) Accurately weigh 1.5 parts of nanocellulose hydrogel and add it to the above mixture. Stir the solution rapidly at a speed of 1500 rpm at 25 °C for 10 min by mechanical stirring to obtain a super-stable water-based foam containing nanocellulose.

[0062] As determined by experiments, the foaming rate of the water-based foam prepared in Example 1 is ~88%.

[0063] Comparative Example 1

[0064] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA in deionized water and heat at 60 °C for 20 min to ensure that all solutes are evenly dispersed; after cooling, stir the solution rapidly at a speed of 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam, obtaining the SDS / TDA foam system.

[0065] (2) Add 0.5 parts of PVA to the SDS / TDA foam system. After the PVA is completely dissolved, stir the solution rapidly at a speed of 1200 rpm at 25 °C for 5 min by mechanical stirring to generate foam. That is, a water-based foam without nanocellulose is obtained.

[0066] As determined by experiments, the foaming rate of the water-based foam prepared in Comparative Example 1 is ~65%.

[0067] The water-based foams prepared in Examples 1-6 and Comparative Example 1 were analyzed and measured by the following methods: (1) Measurement of the foaming rate of the foam: The foaming rate is calculated by the following equation

[0068] Foaming rate (overrun) = (V f - V s ) / V s

[0069] where V f and V s represent the volume of the foam after stirring and the initial volume, respectively.

[0070] Short-term drainage rate: The short-term drainage rate refers to the percentage of the volume of the drained liquid within 2 h after the foam is generated in the initial volume after foaming.

[0071] Short-term drainage rate ε = V / V 1 * 100, where V is the volume of the drained liquid and V 1 is the volume of the foam.

[0072] The stability of the foam is determined by the short-term drainage rate of the foam. A drainage rate lower than 8% (volume ratio) indicates "very good" stability, a drainage rate of 8%-10% (volume ratio) indicates "very good" stability, a drainage rate of 10%-12% (volume ratio) indicates "good" stability, and a drainage rate greater than 15% (volume ratio) indicates "poor" stability.

[0073] Table 1

[0074]

[0075] According to the data in Table 1, it can be seen from Examples 3-5 (in combination with Figure 1 and Figure 2 ) that as the NCF addition amount increases, the foaming rate of the foam continuously increases. This is because nanocellulose has a high specific surface area, which can provide a large number of adsorption sites, promote the effective adsorption of surfactant molecules, reduce the surface tension of the liquid, and is conducive to the formation and stability of the foam. According to Examples 4-5 ( Figure 2 ) and Comparative Example 1 ( Figure 3 ), the results show that the addition of nanocellulose is beneficial to improving the stability and density of the foam. This is because nanocellulose can reduce the surface tension of the liquid, promote the formation and stability of bubbles, and its adsorption at the gas-liquid interface helps to stabilize the bubbles and prevent the bubbles from merging or bursting too quickly. In addition, a large number of hydroxyl groups are contained on the surface of nanocellulose, which is easy to combine with water, can increase the foam viscosity, and make the formed foam dense. According to Examples 3 and 4 ( Figure 1 and Figure 2 ), the results show that the addition of nanocellulose can reduce the usage amount of emulsifier SDS without affecting the stability of the foam.

[0076] In order to test the long-term stability of the foam, Examples 4 and 5, and Comparative Example 1 were used as examples for experiments, and the experimental results are as follows:

[0077] Macroscopic photos of the foam after standing for 0 h (a), 24 h (b), 158 h (c), and 501 h (d) were taken with a Sony camera TX-10. See Figure 4 (Example 4). The freshly prepared foam is about 1400 ml of foam, with small and evenly distributed foam, in a milkshake-like state (a). After one day, a foam layer with larger pore sizes is observed on the surface, with a thickness of about 0.1 cm and no water leakage (b). After 158 h, the foam is still stable, with 100 ml of thin foam on the upper layer and the remaining foam being dense (c). After 501 h, 600 ml of thin foam remains (d). It can be seen that the foam prepared by the present invention can be stable for more than 20 days.

[0078] As can be seen from Figure 5 (Example 5), after storing for 0 hours, the foam is fine and yogurt-like, with a volume of 1250 ml (a). After 141 hours, storing for about six days, there is a slightly dry foam film on the upper layer, with a volume of 1250 ml (b). After 309 hours, storing for about thirteen days, the upper film is slightly concave, with a wider thickness, and a volume of 1250 ml (c). After 497 hours, about 20 days, the whole is relatively stable, and the upper film is somewhat broken (d). After 640 hours, about 26 days, only 600 ml of dense foam remains, the film is separated from the foam, and there is about 80 ml of dilute foam on the upper layer (e). The upper film is very firm, probably due to air-drying upon contact with air.

[0079] As can be seen from Figure 6 (Comparative Example 1) that the foam stability is poor. After standing for one week, the water output is relatively high, there is a film on the surface, and the foam is small and relatively dispersed.

[0080] In summary, in the SDS / DDA / PVA / NCF system, due to the addition of NCF / PVA, the hydrogen bond between water and solvent molecules is enhanced. Near the sulfur atom and sodium ion of the sulfonic acid group of SDS, the distribution intensity of bound water increases significantly. In addition, the addition of NCF can enhance the gas-liquid interface and improve the compactness of molecules in the network. This results in a decrease in the gas diffusion rate, making the foam system stable. At the same time, compared with the single-layer film foam structure formed by SDS emulsified foam, the multi-layer film structure is beneficial to the pressure balance between air layers in the system, has a higher fluctuation threshold compared with the single-layer film structure, and is conducive to the formation of super-stable foam.

[0081] The above embodiments are the 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 are all included in the protection scope of the present invention.

Claims

1. An ultra-stable water-based foam containing nanocellulose, characterized in that: The invention comprises the following components by mass fraction: based on 100 parts of the total mass of the composite water-based foam, 1.0-2.0 parts of nanocellulose hydrogel, 2.5-5.0 parts of sodium lauryl sulfate, 1.0-5.0 parts of tetradecanol, 0.1-3.0 parts of polyvinyl alcohol, and the balance is water; the nanocellulose contained in the nanocellulose hydrogel has a length of 500-1000 nm and a diameter of 3-5 nm; The method for preparing the ultra-stable water-based foam comprises the following steps: (1) Mix sodium dodecyl sulfate and tetradecanol in water and heat at 60±10°C for 20±10 min to evenly disperse all the solutes. After cooling, stir at high speed to obtain an SDS / TDA foam system. (2) Add polyvinyl alcohol to the above foam system, dissolve it completely, and stir at high speed; (3) Adding the nanocellulose hydrogel to the foam system of step (2), mixing evenly, and stirring at high speed to obtain an ultra-stable water-based foam containing nanocellulose.

2. The ultra-stable water-based foam according to claim 1, characterized in that The alcoholysis degree of the polyvinyl alcohol is 88%-100%.

3. The ultra-stable water-based foam according to claim 2, characterized in that The high-speed stirring conditions in steps (1) to (3) are all mechanical stirring, with a rotation speed of 1000-1500 rpm and a time of 5-10 min.

4. Use of the ultra-stable water-based foam containing nanocellulose according to any one of claims 1 to 3 in foam mulch.

5. The use according to claim 4, characterized in that: Ultra-stable water-based foam is sprayed onto the soil or water surface through high-pressure spray to form a foam film.

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