Preparation method and application of waterproof and oilproof auxiliary agent

Abstract

The invention discloses a preparation method and application of a waterproof and oilproof auxiliary agent. Belongs to the field of waterproof and oil-proof paper, and overcomes the defects that paper coated with a bio-based waterproof and oil-proof agent is poor in hydrophobicity and difficult to stably use for a long time due to the fact that most bio-based waterproof and oil-proof agent has a large number of strong hydrophilic hydroxyl groups in the chemical structure of the bio-based waterproof and oil-proof agent. The preparation of the acrylate copolymer is realized through a bio-based starch particle stable Pickering emulsion polymerization method, and finally the starch-based Pickering particle stable waterproof and oil-proof functional emulsion is obtained. According to the auxiliary agent disclosed by the invention, the use of toxic and harmful small-molecular surfactants is avoided, and higher stability can be provided. The auxiliary agent is used as a film-forming auxiliary agent to assist the acrylate copolymer in forming a more compact polymer film, so that the paper is endowed with more excellent waterproof and oil-proof performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of waterproof and oil-proof paper, and particularly relates to a preparation method and application of a waterproof and oil-proof additive. BACKGROUND

[0002] Plastics, as the most important packaging material, have brought great convenience to human life, but also caused disastrous "white pollution". Paper-based materials are a kind of materials prepared from plant fibers as the main raw material, which have a three-dimensional network structure, and have the advantages of being renewable, degradable, and low in price, and are excellent substitutes for plastic products. However, the porous structure and high surface energy of paper-based materials make it difficult to prevent liquids such as oil from penetrating into the paper through capillary action, thereby limiting the application of paper-based materials in the high-end packaging field.

[0003] Adding waterproof and oil-proof agents is the most common method to improve the waterproof and oil-proof performance of paper. According to whether the waterproof and oil-proof agent contains fluorine, the existing waterproof and oil-proof agents can be divided into fluorine-containing waterproof and oil-proof agents and fluorine-free waterproof and oil-proof agents. Fluorine-containing waterproof and oil-proof agents can produce perfluorooctanoic acid / perfluorooctane sulfonate (PFOA / PFOS) which is harmful to human body and environment during preparation and use. At present, the paper oil-proof agent used in industry is mainly C8 and C6 fluorine-containing waterproof and oil-proof agent (polymer containing 8 and 6 fluorinated carbon atom side chains, respectively), among which, the C8 fluorine-containing waterproof and oil-proof agent is difficult to degrade, has high PFOA / PFOS content, and is harmful to human body and environment, and the short-chain C6 fluorine-containing waterproof and oil-proof agent has a certain biodegradability, but still produces trace amounts of PFOA / PFOS during use, which poses a safety hazard. Therefore, it is urgent to develop a non-toxic, harmless, green and environmentally friendly industrial fluorine-free waterproof and oil-proof agent.

[0004] The fluorine-free waterproof and oil-proof agent can be further divided into petroleum-based acrylate copolymer waterproof and oil-proof agent and bio-based waterproof and oil-proof agent (chitosan, starch, sodium alginate, nanocellulose, soy protein isolate, etc.) according to the source of raw materials. Among them, the bio-based waterproof and oil-proof agent has attracted widespread attention in the early development of waterproof and oil-proof agents due to its non-toxicity, renewability, biodegradability, excellent film-forming property and other advantages. However, most bio-based waterproof and oil-proof agents have a large number of strong hydrophilic hydroxyl groups in their chemical structure, resulting in poor hydrophobicity of paper coated with bio-based waterproof and oil-proof agent, and it is difficult to achieve the purpose of long-term stable use. SUMMARY

[0005] The present application provides a preparation method of a paper waterproof and oil-proof additive, which can be used as a coating liquid to prepare paper with high waterproof and oil-proof performance.

[0006] In order to achieve the above technical problems, the present application adopts the following technical solutions: The application aims to provide a preparation method of a waterproof and oil-proof additive, characterized by comprising the following steps: Step 1, dissolving modified starch in N, N-dimethylformamide (DMF), then adding drop by drop into deionized water under stirring conditions, removing all DMF, and obtaining a starch-based Pickering particle water dispersion.

[0007] Step 2, mixing methyl methacrylate (MMA), butyl acrylate (BA) and functional monomer A to obtain an oil phase; Step 3, mixing the oil phase with the starch-based Pickering particle water dispersion, emulsifying, and obtaining an oil-in-water emulsion; Step 4, adding an initiator and a reducing agent under nitrogen protection, continuously reacting under stirring at a certain reaction temperature, and obtaining the additive; The functional monomer A is one or more of methacrylic acid (MAA), acrylic acid (AA), vinyl acetate (VA) and vinyl pyrrolidone (NVP). The modified starch is obtained by adding butyl glycidyl ether for continuous reaction after acidolysis and alkali activation of corn starch.

[0008] Further limitation, the concentration of the starch-based Pickering particle water dispersion is 1 wt%-5 wt%.

[0009] Further limitation, the mass ratio of MMA to BA is 3:1-1:3; and the amount of the functional monomer A accounts for 3%-30% of the mass of the oil phase.

[0010] Further limitation, the mass ratio of the oil phase to the water dispersion is 1:3.

[0011] Further limitation, the initiator is ammonium persulfate (APS); and the reducing agent is NaHSO3.

[0012] Further limitation, the mass ratio of the initiator to the reducing agent is 1:1, and the amount of the initiator accounts for 0.1%-1% of the mass of the oil phase.

[0013] Further limitation, the reaction temperature is 35℃-45℃.

[0014] Further limitation, the modified starch is prepared by the following steps: adding corn starch into an ethanol-water mixed solution, acidolysis by dropwise adding concentrated hydrochloric acid under stirring and heating, then cooling, neutralizing by dropwise adding sodium bicarbonate solution under stirring, obtaining acidolysis starch through reduced pressure filtration, washing and drying; alkali activation by dispersing the acidolysis starch into water, adding sodium hydroxide, stirring and heating, adding butyl glycidyl ether for continuous reaction, adjusting the pH value of the product to 7.0 after cooling, collecting the precipitate through repeated reduced pressure filtration of the reaction liquid with acetone, and finally drying to obtain the modified starch.

[0015] Compared with the prior art, the present application has the following beneficial effects: The present application realizes the preparation of acrylate copolymer through the Pickering emulsion polymerization method of biobased starch particles, and finally obtains a starch-based Pickering particle stabilized water and oil repellent functional emulsion. First, the starch-based Pickering particles act as stabilizers in the functional emulsion to replace traditional small molecule surfactants to realize the stabilization of the emulsion, which not only avoids the use of toxic and harmful small molecule surfactants, but also provides higher stability. Secondly, the starch-based Pickering particles can also play the role of auxiliary film forming, and act as film forming aids to assist the acrylate copolymer to form a more compact polymer film during coating, thereby imparting the paper with more excellent water and oil repellency.

[0016] For a further understanding of the features and technical contents of the present application, please refer to the detailed description and the accompanying drawings. It should be noted that the accompanying drawings are provided for illustrative purposes only, and are not intended to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the oil repellency 9 level test picture of the A4 paper coated in Example 1; Figure 2 is the oil repellency 9 level test picture of the A4 paper coated in Comparative Example 1; Figure 3 is the oil repellency 7 level test picture of the A4 paper coated in Example 1; Figure 4 is the oil repellency test picture of the uncoated A4 paper. DETAILED DESCRIPTION

[0018] The present application will be described in detail below in combination with specific examples. These examples are helpful for those skilled in the art to further understand the present application, but should not be regarded as limiting the present application. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application.

[0019] Example 1. The modified starch was dissolved in N,N-dimethylformamide (DMF), then dropped into deionized water under stirring conditions, and all the DMF was removed to obtain a starch-based Pickering particle aqueous dispersion.

[0020] The modified starch is prepared according to the following steps: 80 g of waxy corn starch is weighed into a 500 mL three-necked flask, 300 mL of 90% ethanol is added, and the temperature is raised to 70°C under stirring, then 14 mL of concentrated hydrochloric acid is added dropwise, and the acid hydrolysis is continuously carried out for 1 h at a rotation speed of 250 rpm; then it is poured into a beaker and cooled in an ice water bath, and 1 mol / L sodium bicarbonate solution is added dropwise under stirring for neutralization, and the obtained product is filtered under reduced pressure, washed with deionized water for 3 times, and then washed with anhydrous ethanol for 1 time; finally, it is dried in a 90°C oven to obtain acid hydrolysis starch; 8.10 g of acid hydrolysis starch is weighed, dispersed in 60 mL of water in a 250 mL three-necked flask, 1.50 g of sodium hydroxide is added and stirred uniformly, and the temperature is raised to 75°C for alkaline activation for 1 h; then 6.50 g of butyl glycidyl ether is added, and the reaction is continuously stirred for 5 h in a 75°C oil bath, and the product is cooled in an ice water bath; 1M hydrochloric acid is added to adjust the pH value to 7.0, and the obtained reaction solution is added dropwise into acetone, and the precipitate is collected by filtration under reduced pressure, and then the obtained precipitate is dissolved in a proper amount of deionized water, and precipitated with acetone; the above process is repeated for three times, and then it is dried in a 50°C oven to obtain the modified starch.

[0021] 18.75 g of MMA, 18.75 g of BA, and 4.5 g of VA are mixed as the oil phase solution, 120 g of 2 wt% starch-based Pickering particle aqueous dispersion is weighed as the water phase, and the two are mixed and emulsified for 180 s at 20,000 rotations per minute by using an IKA Ultra Turrax T18 homogenizer to prepare a starch-based Pickering particle stabilized oil-in-water emulsion. The obtained Pickering emulsion is transferred into a three-necked flask, nitrogen is kept flowing, and condensed water is connected, when the temperature of the water bath is raised to 35°C, 1050 μL of 20% APS aqueous solution is added as the initiator and 0.21 g of NaHSO3 is added as the reducing agent, and the reaction is continuously carried out for 6 h at a stirring speed of 250 rpm. A starch-based Pickering particle stabilized water and oil repellent functional emulsion is obtained.

[0022] Example 2. 19.5 g of MMA, 19.5 g of BA, and 3 g of VA are mixed as the oil phase solution, and the other steps are the same as in Example 1.

[0023] Example 3. 18 g of MMA, 18 g of BA, and 6 g of VA are mixed as the oil phase solution, and the other steps are the same as in Example 1.

[0024] Example 4. 16.5 g of MMA, 16.5 g of BA, and 9 g of VA are mixed as the oil phase solution, and the other steps are the same as in Example 1.

[0025] Example 5. Take 120 g of 1 wt% starch-based Pickering particle water dispersion as the water phase, and the others are the same as Example 1.

[0026] Example 6. Take 120 g of 3 wt% starch-based Pickering particle water dispersion as the water phase, and the others are the same as Example 1.

[0027] Example 7. Take 120 g of 4 wt% starch-based Pickering particle water dispersion as the water phase, and the others are the same as Example 1.

[0028] Example 8. Take 120 g of 5 wt% starch-based Pickering particle water dispersion as the water phase, and the others are the same as Example 1.

[0029] Example 9. Add 210 μL of 20% APS aqueous solution as initiator and 0.042 g of NaHSO3 as reducing agent, and the others are the same as Example 1.

[0030] Example 10. Add 2100 μL of 20% APS aqueous solution as initiator and 0.42 g of NaHSO3 as reducing agent, and the others are the same as Example 1.

[0031] Firstly, the intrinsic viscosity of Examples 1-10 was tested by using an Ubbelohde viscometer. The specific method is as follows: a small amount of emulsion product is precipitated with anhydrous ethanol, and the lower white precipitate is dried after centrifugation, then dissolved with ethyl acetate and tested for its intrinsic viscosity. The results are shown in Table 1. From the intrinsic viscosity results of Examples 1-4, it can be seen that the intrinsic viscosity of the emulsion product first decreases and then increases with the increase of the amount of VA. From the results of Examples 1 and 5-8, it can be seen that the intrinsic viscosity of the emulsion product increases with the increase of the amount of starch-based Pickering particles. From the results of Examples 1 and 9-10, it can be seen that the intrinsic viscosity of the emulsion product decreases with the increase of the amount of initiator.

[0032] Then, the particle size of Examples 1-10 was tested by using dynamic light scattering technology. The specific method is as follows: a small amount of emulsion product is diluted to 0.1 wt% with deionized water to test its particle size. The results are shown in Table 1. From the particle size results of Examples 1-4, it can be seen that the particle size of the emulsion product first decreases and then increases with the increase of the amount of VA. From the results of Examples 1 and 5-8, it can be seen that the particle size of the emulsion product decreases with the increase of the amount of starch-based Pickering particles. From the results of Examples 1 and 9-10, it can be seen that the particle size of the emulsion product decreases with the increase of the amount of initiator.

[0033] Table 1: Intrinsic viscosity and particle size results of Examples 1-10

[0034] A4 paper was selected as the original paper material, and the above starch-based Pickering particle stabilized water and oil repellent functional emulsion was used as the coating liquid to coat the surface of the A4 paper, and the coating thickness was 10 μm. After coating, the paper was placed in a 105°C oven for drying for 10 min, and then the oil repellency and water repellency of the paper were tested.

[0035] The oil repellency test method is as follows: different grades of fat solution are prepared according to GB / T22805.2-2008 "Determination of resistance to grease of paper and paperboard Part 2: surface repellency method", and the oil repellency grade of the coated paper is determined. As shown in Table 2: the starch-based Pickering particle stabilized water and oil repellent functional emulsion prepared in the above examples was used as the coating liquid for coating, and the oil repellency grade of the A4 paper after coating could reach level 9.

[0036] The water repellency test method is as follows: the water repellency of the coated paper was tested by using a Cobb water absorption tester, and the Cobb value was calculated according to the weight change before and after the paper absorbed water. As shown in Table 2: From the Cobb value results of Examples 1-4, the Cobb value of the coated paper showed a trend of first decreasing and then increasing with the increase of the amount of VA. This is related to the properties of the functional monomer VA. When the amount of VA increases, the film-forming property of the polymer is improved, which enables it to form a dense barrier layer on the surface of the paper, thereby improving the water and oil repellency of the material. However, when VA is a hydrophilic monomer, when its amount is too high, the hydrophilicity of the polymer film is enhanced, thereby leading to poor water repellency and increasing the Cobb value. From the Cobb value results of Examples 1 and 5-8, the Cobb value of the coated paper showed a trend of first decreasing and then increasing with the increase of the amount of starch-based Pickering particles. This is because the starch-based Pickering particles also function as auxiliary film-forming agents. When the amount of starch-based Pickering particles increases, the film-forming property of the polymer is improved, which enables it to form a dense barrier layer on the surface of the paper, thereby improving the water and oil repellency of the material. However, the starch-based Pickering particles also have strong hydrophilicity, and when their amount is too high, the hydrophilicity of the polymer film is enhanced, thereby leading to poor water repellency and increasing the Cobb value. From the Cobb value results of Examples 1 and 9-10, the Cobb value of the coated paper decreased with the increase of the amount of initiator. This may be related to the particle size of the water and oil repellent agent. The smaller the particle size, the more closely connected the particles are, and the more easily a dense polymer film is formed, thereby preventing the penetration of oil droplets and water droplets and improving the water and oil repellency of the material.

[0037] Table 2: Coating amount, oil repellency grade and Cobb value results of A4 paper coated with the coating liquid of Examples 1-10

[0038] Some of the following comparative examples will further describe the present application, but it does not constitute a limitation on the right of the present application.

[0039] Comparative Example 1. Take 18.75 g of MMA, 18.75 g of BA, 4.5 g of VA and mix them as the oil phase solution, take 120 g of 2wt% sodium dodecyl sulfate (SDS) aqueous solution as the water phase, mix the two and emulsify with IKA Ultra Turrax T18 homogenizer at 20000 rpm for 180 s to prepare SDS-stabilized oil-in-water emulsion. The obtained emulsion was transferred to a three-necked flask, nitrogen was kept flowing and connected with condensed water, when the temperature of the water bath was raised to 35℃, 1050 μL of 20% APS aqueous solution was added as initiator and 0.21 g of NaHSO3 as reducing agent, and the reaction was continued at a stirring rate of 250 rpm for 6 h. SDS-stabilized water and oil repellent functional emulsion was obtained. Table III shows the intrinsic viscosity and particle size of Example 1 and Comparative Example 1. As can be seen from Table III, the intrinsic viscosity of the starch-based Pickering particle-stabilized water and oil repellent functional emulsion (Example 1) is larger, because the starch-based Pickering particle is a macromolecule, which will affect the intrinsic viscosity of the polymer to some extent. Secondly, because SDS is a small molecule emulsifier, it is easier to form smaller micelles during emulsification, so the particle size of the SDS-stabilized water and oil repellent functional emulsion (Comparative Example 1) is smaller.

[0040] Table 3: Intrinsic viscosity and particle size results of Example 1 and Comparative Example 1

[0041] A4 paper was selected as the original paper material, and Example 1 and Comparative Example 1 were used as the coating liquid to coat the surface of the A4 paper with a coating thickness of 10 μm. After coating, the paper was placed in a 105℃ oven for drying for 10 min, and then the oil and water repellency of the paper was tested. The results are shown in Table 4. As can be seen from Table III, the A4 paper coated with the starch-based Pickering particle-stabilized water and oil repellent functional emulsion (Example 1) shows higher oil repellency grade and smaller Cobb value, because the starch-based Pickering particle plays a role in auxiliary film formation, allowing the polymer to form a dense barrier layer on the surface of the paper, thereby improving the water and oil repellency of the material.

[0042] Figure 1 is the oil repellency test picture of the A4 paper coated with Example 1, Comparative Example 1 and uncoated A4 paper. As can be seen from the figure, the A4 paper coated with Example 1 can reach an oil repellency grade of 9, and when the 9th test oil droplet is added to the surface of the paper, the oil droplet will not penetrate downward Figure 1 ); while the A4 paper coated with Comparative Example 1 can only reach an oil repellency grade of 6 Figure 2), when 7th grade test oil drops are added on the surface of the paper, the oil drops will quickly penetrate downwards ( Figure 3 ). The uncoated A4 paper does not have oil-proof performance ( Figure 4 ).

[0043] Table 4: Coating amount, oil-proof grade and Cobb value results statistics of A4 paper coating with the coating liquid of Example 1 and Comparative Example 1

[0044] The specific embodiments of the present application are described in detail above. It should be noted that the present application is not limited to the specific embodiments described above. Those skilled in the art can make various modifications or changes without departing from the protection scope defined by the claims, and these modifications or changes all belong to the technical scheme of the present application.

Claims

1. A process for the preparation of a water- and oil-repellent assistant, characterized in that The method comprises the following steps: Step 1, dissolving the modified starch in N, N-dimethylformamide (DMF), then adding drop by drop into deionized water under stirring conditions, removing all DMF, and obtaining a starch-based Pickering particle water dispersion; Step 2, mixing methyl methacrylate (MMA), butyl acrylate (BA) and functional monomer A to obtain an oil phase; Step 3, mixing the oil phase with the starch-based Pickering particle water dispersion, emulsifying, and obtaining an oil-in-water emulsion; Step 4, under nitrogen protection, adding an initiator and a reducing agent, continuously reacting under a certain reaction temperature under stirring, and obtaining the agent; The functional monomer A is one or more of methacrylic acid (MAA), acrylic acid (AA), vinyl acetate (VA) and vinyl pyrrolidone (NVP). The modified starch is obtained by first acidizing corn starch, then alkali-activating, adding butyl glycidyl ether and continuing to react.

2. The method of claim 1, wherein, The concentration of the starch-based Pickering particle water dispersion is 1 wt%-5 wt%.

3. The method of claim 1, wherein, The mass ratio of MMA to BA is 3:1-1:3; the amount of the functional monomer A accounts for 3%-30% of the mass of the oil phase.

4. The method of claim 1, wherein, The mass ratio of the oil phase to the water dispersion is 1:

3.

5. The method of claim 1, wherein, The initiator is ammonium persulfate (APS); the reducing agent is NaHSO3.

6. The method of claim 1, wherein, The mass ratio of the initiator to the reducing agent is 1:1, and the amount of the initiator accounts for 0.1%-1% of the mass of the oil phase.

7. The method of claim 1 wherein, The reaction temperature is 35℃-45℃.

8. The method of claim 1, wherein, The modified starch is prepared according to the following steps: adding corn starch into an ethanol-water mixed solution, acidizing under stirring after heating, then cooling, adding drop by drop a sodium bicarbonate solution under stirring for neutralization, filtering, washing and drying under reduced pressure to obtain acidized starch; dispersing the acidized starch into water, adding sodium hydroxide, stirring and heating for alkali-activation, adding butyl glycidyl ether for continuous reaction, cooling the product, adjusting the pH value to 7.0, repeatedly filtering the reaction liquid under reduced pressure to collect the precipitate with acetone, and finally drying to obtain the modified starch.

9. A waterproof and oil-proof agent prepared by the method of any one of claims 1-8.

10. The waterproof and oil-proof agent prepared by the method of any one of claims 1-8 as a coating liquid for preparing waterproof and oil-proof paper.

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