Composite stabilizer for low-temperature storage of natural latex and preparation method of composite stabilizer

Abstract

The invention belongs to the technical field of natural rubber processing, and particularly relates to a compound stabilizer for low-temperature storage of natural latex and a preparation method of the compound stabilizer. The specific nonionic surfactant, the bio-based polysaccharide and the nanoparticles are selected as main components, and low-temperature stability is achieved through the ternary synergistic effect. The prepared stabilizer can reduce the layering rate of natural latex at low temperature, is significantly superior to that of a traditional ammonia water system, reduces viscosity fluctuation, does not contain harmful substances such as ammonia, and meets the requirements of environmental protection and processability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of natural rubber processing, and particularly relates to a composite stabilizer for low-temperature storage of natural latex and a preparation method thereof. BACKGROUND

[0002] The wet masterbatch is prepared by directly liquid-phase compounding natural latex and carbon black slurry. The rubber masterbatch obtained by this method has good dispersibility, more excellent performance and is beneficial to processing. However, during the preparation of the wet masterbatch, the low temperature in winter can cause the colloidal stability of the natural latex to decrease, and the natural latex is prone to delamination (whey is separated from the upper layer, and high-concentration colloidal particles are precipitated in the lower layer), which leads to uneven dispersion in the subsequent wet compounding process and deterioration of the performance of the masterbatch. The traditional stabilizers (such as ammonia and soaps) have limited effect at low temperatures, and excessive use can cause the pH of the latex to be too high or introduce impurities, thereby affecting the processing performance of the masterbatch.

[0003] Therefore, it is necessary to provide a composite low-temperature stabilizer for natural latex used in the preparation of a wet masterbatch, which can significantly reduce the delamination rate during storage at low temperatures, prolong the storage period, and does not affect or improve the subsequent processing performance of the latex, and is environmentally friendly. SUMMARY

[0004] The application aims to provide a composite stabilizer for low-temperature storage of natural latex, which can reduce the delamination rate of natural latex at low temperatures, is significantly better than the traditional ammonia system, and can reduce the viscosity fluctuation and does not contain harmful substances such as ammonia, thereby meeting the requirements of environmental protection and processing performance.

[0005] A composite stabilizer for low-temperature storage of natural latex, which is prepared from the following raw materials in parts by weight: 1-2.4 parts of a stabilizer composition, 9-15 parts of deionized water, and 0.03-0.06 parts of citric acid.

[0006] Preferably, the stabilizer composition comprises 0.6-1.4 parts of a non-ionic surfactant, 0.2-0.4 parts of a bio-based polysaccharide, and 0.2-0.6 parts of nanoparticles by weight.

[0007] Preferably, the mass ratio of the non-ionic surfactant, the bio-based polysaccharide and the nanoparticles is (3-5): 1: (1-2).

[0008] Preferably, the non-ionic surfactant comprises a polyoxyethylene ether non-ionic surfactant and a polyhydric alcohol ester non-ionic surfactant.

[0009] Preferably, the mass ratio of the polyoxyethylene ether non-ionic surfactant and the polyhydric alcohol ester non-ionic surfactant is 1: (1-3); and more preferably, 2:3.

[0010] Preferably, the polyoxyethylene ether nonionic surfactant includes a fatty alcohol polyoxyethylene ether.

[0011] Preferably, the fatty alcohol polyoxyethylene ether has a structural formula of R-O-(CH2-CH2-O)9-H, and the R group is an alkyl chain of a linear fatty alcohol, and the carbon chain length is C12-C18.

[0012] Preferably, the fatty alcohol polyoxyethylene ether has an HLB value of about 13.5, and the number of ethylene oxide additions n is 9.

[0013] The fatty alcohol polyoxyethylene ether is from Guangzhou Jiamao Chemical Co., Ltd., AEO-9.

[0014] Preferably, the polyol ester nonionic surfactant includes a polyoxyethylene sorbitan fatty acid ester.

[0015] Preferably, the polyoxyethylene sorbitan fatty acid ester has a hydroxyl value of 65-82 mgKOH / g, a saponification value of 43-55 mgKOH / g, and an HLB value of 15.

[0016] The polyoxyethylene sorbitan fatty acid ester is from Nantong Aches Chemical Co., Ltd., Tween-80.

[0017] By compounding the specific polyoxyethylene ether (AEO-9) and the polyol ester (Tween-80) nonionic surfactant, the cloud point characteristics of the surfactant at low temperature can be optimized, the low-temperature precipitation phenomenon can be avoided, the interface compatibility between the carbon black slurry and the latex can be improved, and the viscosity fluctuation can be reduced. This may be because, on the one hand, the HLB value of the two nonionic surfactants after compounding is close to the best stable interval of the natural latex particles, and it is easier to form a dense adsorption layer on the particle surface. On the other hand, the fatty alcohol chain (C12-C14) of AEO-9 and the fatty acid ester chain (C18) of Tween-80 are intertwined through hydrophobic interaction to form an “integrated rigid and flexible” interface film. At low temperature, the fatty alcohol chain remains in an orderly arrangement, and the unsaturated bond of the fatty acid ester chain maintains the flexibility of the film, preventing the film from being broken due to low-temperature hardening. In addition, the sorbitan ring of Tween-80 can form hydrogen bonds with the hydroxyl groups on the surface of the carbon black, and the polyoxyethylene chain of AEO-9 prevents carbon black agglomeration through steric hindrance, and the two synergistically improve the dispersity of carbon black in the latex. Moreover, the two surfactants are inexpensive, which can reduce costs.

[0018] Preferably, the bio-based polysaccharide includes one or more of xanthan gum, gellan gum, and konjac glucomannan.

[0019] Preferably, the konjac glucomannan has a glucomannan content of ≥80%.

[0020] The konjac glucomannan is from Wuhan Hezhong Biochemical Co., Ltd.

[0021] Preferably, the nanoparticles include modified nanosilica.

[0022] By selecting non-ionic surfactants, bio-based polysaccharides and nanoparticles as the stabilizer composition, the natural latex low-temperature stratification rate can be significantly reduced, the storage period can be prolonged, the viscosity fluctuation and the masterbatch dispersion uniformity can be reduced, and the natural latex is very suitable for application in the preparation of wet masterbatch. This may be because the non-ionic surfactant reduces the surface tension of the rubber particles, reduces the intermolecular van der Waals attraction, and inhibits the aggregation tendency at low temperature, and the polyoxyethylene chain forms a hydration layer in the aqueous phase to provide steric hindrance; the bio-based polysaccharide forms a three-dimensional network structure in the aqueous phase to inhibit the sedimentation of the rubber particles, and the network structure remains flexible at low temperature to avoid viscosity increase; the nanoparticles can enhance the mechanical strength of the colloidal network through steric hindrance and hydrogen bonding, and prevent low-temperature stratification. The synergistic effect of the three, the surfactant reduces the interfacial energy, the polysaccharide provides network support, and the nanoparticles strengthen the interface anchoring, so that the Brownian motion rate of the particles during the storage of the latex at low temperature is reduced, and the stratification is effectively inhibited. In addition, the prepared composite stabilizer can replace ammonia to avoid ammonia volatilization pollution and achieve environmental protection. However, silica is an inorganic particle, and the composite stabilizer prepared by the present application is a water-soluble substance, but natural latex is an organic substance. In actual application, the compatibility of inorganic nanoparticles in the system may be poor, which affects the stability effect.

[0023] Preferably, the preparation method of the modified nanosilica comprises the following steps: ultrasonic dispersion of nanosilica in an ethanol aqueous solution, addition of a silane mixture, heating to 68-72℃, stirring at 400-500 rpm for 2-4h, centrifugation, washing with anhydrous ethanol for 3 times, and vacuum drying.

[0024] Preferably, the particle size of the nanosilica is 9-15nm, and the specific surface area is 195-245 m 2 / g.

[0025] The nanosilica is from Hangzhou Jibin New Material Co., Ltd.

[0026] Preferably, in the ethanol aqueous solution, the mass fraction of ethanol is 70%-80%, and the pH is adjusted to 5-5.5 by glacial acetic acid.

[0027] Preferably, the solid-liquid ratio of the nanosilica and the ethanol aqueous solution is 1g: (4-6) mL.

[0028] Preferably, the specific conditions of ultrasonic dispersion are: power 250-350W, frequency 38-42kHz, and time 10-20min.

[0029] Preferably, the silane mixture comprises long-chain alkyl silane and amino silane.

[0030] Preferably, the mass ratio of the long-chain alkyl silane and the amino silane is (3-4):1.

[0031] Preferably, the number of carbon atoms in the alkyl group of the long-chain alkyl silane is 6-10.

[0032] Preferably, the long-chain alkyl silane comprises octyl triethoxysilane.

[0033] Preferably, the amino silane comprises γ-aminopropyl triethoxysilane.

[0034] By selecting long-chain alkyl silane and amino silane to modify nano-silica, the dispersion stability of nano-silica in latex can be improved, the bridging effect between latex particles at low temperature can be enhanced, and the flow layering can be inhibited. In addition, the hydrogen bond strength with polysaccharide can also be enhanced, and the network structure can be strengthened. This may be because by grafting long-chain alkyl and amino on the surface of nano-silica, an amphiphilic interface structure can be formed, the hydrophobic chain of long-chain alkyl silane is adsorbed on the surface of rubber particles, the hydrophilic amino group of amino silane extends to the water phase, forming a "hydrophobic anchoring-hydrophilic lubrication" structure, so that the nanoparticles interact with both the rubber phase and the water phase. Moreover, by controlling the number of carbon atoms in the long-chain alkyl group to regulate the low-temperature stability, the change in hydrophobic interaction at low temperature is gentle, avoiding excessive aggregation of long alkyl chains leading to particle bridging; by grafting amino as a hydrophilic group, the amino group can still form hydrogen bonds with water at low temperature, maintaining the water phase dispersibility of the nanoparticles. After modification, the modified nano-silica forms hydrogen bonds with the hydroxyl groups of polysaccharide through the amino groups, and the polyoxyethylene chains of surfactants are entangled through van der Waals force, forming a three-dimensional network between rubber particles, thereby reducing the sedimentation rate of particles at low temperature.

[0035] Preferably, the addition amount of the silane mixture is 10%-20% of the mass of nano-silica.

[0036] Preferably, the specific conditions of vacuum drying are: vacuum degree of 3-6 Pa, temperature of 48-52 ℃, and time of 4-6 h.

[0037] The preparation method of the composite stabilizer for natural latex low-temperature storage comprises the following steps: S1, mixing the non-ionic surfactant in a 40 ℃ water bath, stirring at a speed of 280-320 rpm until transparent to obtain a premixed surfactant; S2, polysaccharide dissolution: dissolving the bio-based polysaccharide in deionized water at 60 ℃ to obtain a bio-based polysaccharide solution; S3, nano-dispersion: adding nanoparticles into the premixed surfactant and ultrasonic treatment to obtain a nano-dispersion liquid; S4, composite addition: mix the bio-based polysaccharide solution and the nanodispersion, add citric acid, and stir at 50°C and 180-220 rpm for 0.5-1.5 h to obtain.

[0038] Preferably, the addition amount of the natural latex low-temperature storage composite stabilizer in the natural latex is 1.2-2.2 parts of the stabilizer composition per 100 parts of the dry latex mass.

[0039] Preferably, in the step S3, the specific conditions of the ultrasonic treatment are as follows: the power is 250-350 W, the frequency is 38-42 kHz, and the time is 25-35 min.

[0040] Preferably, the application steps of the natural latex low-temperature storage composite stabilizer are as follows: the composite stabilizer is added to the natural latex according to the addition amount of the composite stabilizer in the natural latex, and stirred at 25°C and 180-220 rpm for 30 min, and then the natural latex can be used for low-temperature storage.

[0041] Compared with the prior art, the application has the following advantages and beneficial effects: 1. The natural latex low-temperature storage composite stabilizer is prepared, non-ionic surfactants, bio-based polysaccharides and nanoparticles are selected as main components, and the three components synergistically realize low-temperature stability. The prepared stabilizer can reduce the delamination rate of natural latex at low temperature, is significantly better than the traditional ammonia system, reduces the viscosity fluctuation, does not contain harmful substances such as ammonia, and meets the requirements of environmental protection and processing performance.

[0042] 2. The non-ionic surfactants, bio-based polysaccharides and nanoparticles are selected as the stabilizer composition, which can significantly reduce the low-temperature delamination rate of natural latex, prolong the storage period, and is very suitable for preparing natural latex for wet-process masterbatch.

[0043] 3. The specific polyoxyethylene ether and polyol ester non-ionic surfactants are compounded, which can optimize the cloud point characteristics of the surfactants at low temperature, avoid low-temperature precipitation, improve the interfacial compatibility of the carbon black slurry and the latex, and reduce the viscosity fluctuation.

[0044] 4. The long-chain alkyl silane and amino silane are compounded to modify the amphiphilic property of the nanosilica, which can improve the dispersion stability of the nanosilica in the latex, enhance the bridging effect between the latex particles at low temperature, inhibit the flow delamination, and also can enhance the hydrogen bond strength with the polysaccharides and strengthen the network structure. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced.

[0046] Figure 1 The natural latex low-temperature storage composite stabilizer prepared according to the application example 1 is applied to prepare a wet-process master batch, and the SEM images of the wet-process master batch before (left) and after (right) the composite stabilizer is added. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0048] The raw materials used in the application are commercially available, and specifically: The fatty alcohol polyoxyethylene ether has an HLB value of about 13.5, and the number n of ethylene oxide addition is 9, and is from Guangzhou Jiamao Chemical Co., Ltd., AEO-9.

[0049] The polyoxyethylene sorbitan fatty acid ester has a hydroxyl value of 65-82 mgKOH / g, a saponification value of 43-55 mgKOH / g, and an HLB value of 15, and is from Nantong Aches Chemical Co., Ltd., Tween-80.

[0050] The konjac glucomannan has a glucomannan content of greater than or equal to 80%, and is from Wuhan Hezhongshenghua Manufacturing.

[0051] The nano-silicon dioxide has a particle size of 9-15 nm and a specific surface area of 195-245 m 2 / g, and is from Jiangxi Black Cat Carbon Black Co., Ltd.

[0052] Embodiment 1 The embodiment provides a natural latex low-temperature storage composite stabilizer, and raw materials for preparing the natural latex low-temperature storage composite stabilizer include, by weight, 1.7 parts of a stabilizer composition, 12 parts of deionized water, and 0.05 parts of citric acid.

[0053] The stabilizer composition includes, by weight, 1 part of a non-ionic surfactant, 0.3 parts of a bio-based polysaccharide, and 0.4 parts of a nano-particle.

[0054] The non-ionic surfactant is a polyoxyethylene ether non-ionic surfactant and a polyol ester non-ionic surfactant, and the mass ratio is 2:3.

[0055] The polyoxyethylene ether non-ionic surfactant is a fatty alcohol polyoxyethylene ether.

[0056] The polyol ester non-ionic surfactant is a polyoxyethylene sorbitan fatty acid ester.

[0057] The bio-based polysaccharide is konjac glucomannan.

[0058] The nanoparticle is modified nanosilica.

[0059] The preparation method of the modified nanosilica comprises the following steps: after nanosilica is ultrasonically dispersed in an ethanol aqueous solution, a silane mixture is added, the temperature is increased to 70 DEG C, stirring is performed at 450 rpm for 3 hours, centrifugation is performed, the nanosilica is washed with anhydrous ethanol for 3 times, and vacuum drying is performed.

[0060] In the ethanol aqueous solution, the mass fraction of ethanol is 75%, and the pH is adjusted to 5 by glacial acetic acid.

[0061] The solid-liquid ratio of the nanosilica and the ethanol aqueous solution is 1g:5mL.

[0062] The specific conditions of the ultrasonic dispersion are as follows: the power is 300W, the frequency is 40kHz, and the time is 15min.

[0063] The silane mixture is long-chain alkyl silane and amino silane, and the mass ratio is 3:1.

[0064] The long-chain alkyl silane is octyl triethoxysilane.

[0065] The amino silane is gamma-aminopropyl triethoxysilane.

[0066] The addition amount of the silane mixture is 15% of the mass of the nanosilica.

[0067] The specific conditions of the vacuum drying are as follows: the vacuum degree is 4Pa, the temperature is 50 DEG C, and the time is 5h.

[0068] The preparation method of the composite stabilizer for natural latex low-temperature storage comprises the following steps: S1, mixing a non-ionic surfactant in a 40 DEG C water bath, stirring at a speed of 300 rpm until transparent, to obtain a premixed surfactant; S2, polysaccharide dissolution: dissolving bio-based polysaccharide in 60 DEG C deionized water to obtain a bio-based polysaccharide solution; S3, nanodispersion: adding nanoparticles into the premixed surfactant and ultrasonically treating to obtain a nanodispersion; S4, composite addition: mixing the bio-based polysaccharide solution and the nanodispersion, adding citric acid, and stirring at 50 DEG C and a speed of 200 rpm for 1h.

[0069] In the step S3, the specific conditions of the ultrasonic treatment are as follows: the power is 300W, the frequency is 40kHz, and the time is 30min.

[0070] Example 2 The difference between this embodiment and embodiment 1 is that the non-ionic surfactant is a polyoxyethylene ether non-ionic surfactant and a polyol ester non-ionic surfactant, and the mass ratio is 3:7.

[0071] Comparative Example 1 The difference between this comparative example and embodiment 1 is that the non-ionic surfactant is a polyoxyethylene ether non-ionic surfactant and a polyol ester non-ionic surfactant, and the mass ratio is 3:2.

[0072] Comparative Example 2 The difference between this comparative example and embodiment 1 is that the stabilizer composition comprises, by weight parts, 1.0 parts of non-ionic surfactant, 0.2 parts of bio-based polysaccharide, and 0.4 parts of nanoparticles; the non-ionic surfactant is a polyoxyethylene ether non-ionic surfactant and a polyol ester non-ionic surfactant, and the mass ratio is 5:6.

[0073] Comparative Example 3 The difference between this comparative example and embodiment 1 is that the stabilizer composition comprises, by weight parts, 1.0 parts of non-ionic surfactant, 0.2 parts of bio-based polysaccharide, and 0.4 parts of nanoparticles.

[0074] Comparative Example 4 The difference between this comparative example and embodiment 1 is that the non-ionic surfactant is a polyol ester non-ionic surfactant.

[0075] Comparative Example 5 The difference between this comparative example and embodiment 1 is that the silane mixture is a long-chain alkyl silane and an amino silane, and the mass ratio is 1:1.

[0076] Comparative Example 6 The difference between this comparative example and embodiment 1 is that the long-chain alkyl silane is octadecyl trimethoxysilane (C18).

[0077] Performance test The prepared natural latex low-temperature storage composite stabilizer was added to natural latex with a solid content of 60%, and the latex was obtained after stirring at 25°C and 200 rpm for 30 min; the addition amount of the natural latex low-temperature storage composite stabilizer was 1.7 parts of stabilizer composition per 100 parts of dry latex mass.

[0078] Layering rate test: according to ISO 35 “Natural rubber latex concentrate. Determination of mechanical stability”, 300 mL of the latex to be tested was injected into a separatory funnel, the initial total mass m0 was recorded, the separatory funnel was moved into a 5°C constant-temperature storage tank, and was left to stand for 30 days; the valve of the separatory funnel was slowly opened, and the upper whey phase (clear liquid) was separated into a beaker and weighed m1. The layering rate = (m1 / m0) x 100%.

[0079] Viscosity fluctuation test: refer to ISO 2555, use a rotational viscometer to test the viscosity of the latex to be tested, the test conditions are: shear rate is 50 s -1 , temperature is 25℃. Viscosity fluctuation = |(η t -η0) / η0|*100% (η0= initial viscosity, η t = viscosity after storage).

[0080] Table 1 test results

[0081] According to statistics, the composite stabilizer prepared in Examples 1-2 of the application has low delamination rate at low temperature, and low viscosity fluctuation, and is suitable for preparing natural latex for wet-process masterbatch. In Comparative Example 1, AEO-9 is excessive; in Comparative Example 2, the content of bio-based polysaccharide is low, and the polysaccharide network support force decreases; in Comparative Example 3, the content of nanoparticles is low, resulting in insufficient steric hindrance; in Comparative Example 4, polyoxyethylene ether nonionic surfactant AEO-9 is not added; in Comparative Example 5, the amino silane is excessive, and in Comparative Example 6, the chain length of long-chain alkyl silane is too long, resulting in a composite stabilizer with high delamination rate and viscosity fluctuation.

[0082] The latex to be tested prepared by using the natural latex low-temperature storage composite stabilizer prepared in Example 1 is applied to prepare a wet-process masterbatch, and the SEM images of the wet-process masterbatch before (left) and after (right) adding the natural latex low-temperature storage composite stabilizer are shown in Figure 1 . As can be seen from Figure 1 , the carbon black agglomeration is obvious without adding the stabilizer, and the carbon black is uniformly dispersed after adding the stabilizer of Example 1, the dispersion of carbon black in the system is improved, and the agglomeration is reduced.

[0083] Therefore, the natural latex low-temperature storage composite stabilizer prepared by using the raw materials and method described in the application can reduce the delamination rate of natural latex at low temperature, and reduce the viscosity fluctuation, and does not contain harmful substances such as ammonia, and meets the environmental protection and processing performance requirements.

[0084] The above is a preferred embodiment of the application, it should be noted that for those skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A composite stabilizer for low temperature storage of natural latex, characterized by, The preparation raw material, by weight parts, includes stabilizer composition 1-2.4 parts, deionized water 9-15 parts, citric acid 0.03-0.06 parts; The stabilizer composition, by weight parts, includes non-ionic surfactant 0.6-1.4 parts, bio-based polysaccharide 0.2-0.4 parts, nanoparticles 0.2-0.6 parts; The mass ratio of the non-ionic surfactant, bio-based polysaccharide, and nanoparticles is (3-5):1:(1-2).

2. The composite stabilizer for natural latex low temperature storage according to claim 1, characterized in that, The non-ionic surfactant includes polyoxyethylene ether non-ionic surfactant and polyhydric alcohol ester non-ionic surfactant.

3. The composite stabilizer for natural latex low temperature storage according to claim 2, characterized in that, The mass ratio of the polyoxyethylene ether non-ionic surfactant and the polyhydric alcohol ester non-ionic surfactant is 1:(1-3).

4. The composite stabilizer for natural latex low temperature storage according to claim 3, characterized in that, The polyoxyethylene ether non-ionic surfactant includes fatty alcohol polyoxyethylene ether.

5. The composite stabilizer for natural latex low temperature storage according to claim 3, characterized in that, The polyhydric alcohol ester non-ionic surfactant includes polyoxyethylene sorbitan fatty acid ester.

6. The complex stabilizer for natural latex low temperature storage according to claim 1, characterized in that, The preparation method of the modified nano-silicon dioxide includes the following steps: after ultrasonic dispersion of nano-silicon dioxide in an ethanol aqueous solution, a silane mixture is added, the temperature is raised to 68-72℃, stirring is performed at 400-500 rpm for 2-4h, centrifugation is performed, 3 times of washing with anhydrous ethanol are performed, and vacuum drying is performed, and then the modified nano-silicon dioxide is obtained.

7. The composite stabilizer for natural latex low temperature storage according to claim 6, characterized in that, The silane mixture includes long-chain alkyl silane and amino silane.

8. The composite stabilizer for natural latex low temperature storage according to claim 7, characterized in that, The mass ratio of the long-chain alkyl silane and the amino silane is (3-4):

1.

9. The composite stabilizer for natural latex low temperature storage according to claim 8, characterized in that, The number of carbon atoms in the alkyl group of the long-chain alkyl silane is 6-10.

10. A method for preparing the composite stabilizer for low temperature storage of natural latex according to any one of claims 1 to 9, characterized by, The method includes the following steps: S1, mixing the non-ionic surfactant in a 40℃ water bath, stirring at a speed of 280-320 rpm until transparent, and obtaining a premixed surfactant; S2, polysaccharide dissolution: dissolving the bio-based polysaccharide in 60℃ deionized water to obtain a bio-based polysaccharide solution; S3, nano-dispersion: adding the nanoparticles to the premixed surfactant, and ultrasonic treatment to obtain a nano-dispersion liquid; S4, composite addition: mixing the bio-based polysaccharide solution and the nano-dispersion liquid, adding citric acid, and stirring at 50℃ and a speed of 180-220 rpm for 0.5-1.5h, and then obtaining the product.

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