Polyacrylic emulsion and preparation method thereof

Abstract

The preparation method comprises the following steps: mixing a polymeric monomer with a double-bond structure with water to prepare a polymeric monomer solution, and adding an emulsifier and a reducing agent into the polymeric monomer solution to prepare a first pre-emulsion; dropwise adding the first pre-emulsion into an oxidant solution, and stirring and reacting at normal temperature to obtain a second pre-emulsion; adding a thickening agent into the second pre-emulsion to obtain a polyacrylic acid emulsion; the polymeric monomer comprises at least one or a mixture of more than two of acrylic acid, methyl methacrylate, styrene, acrylamide, vinyl trimethoxy silane and vinyl triacetoxysilane. The preparation method has the advantages that hydroxyl radicals are efficiently generated through Fenton reaction to initiate polymerization instead of traditional thermal polymerization, the emulsion is prepared at normal temperature, the components of the emulsion are simple, and the preparation method is simple and high in efficiency. Various types of acrylate emulsions such as styrene-acrylic emulsions, silicone-acrylic emulsions and pure acrylic emulsions can be rapidly prepared and synthesized at the room temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer material production, and particularly relates to a polyacrylic acid emulsion and a preparation method thereof. BACKGROUND

[0002] Acrylic acid occupies an important position in the chemical industry and is a key basic organic chemical raw material. Acrylic acid monomer is colorless and transparent at room temperature and normal pressure and has a pungent odor. After being prepared into polyacrylic acid or polyacrylic acid emulsion, the pungent odor is greatly reduced or even disappears due to the polymerization reaction, and the chemical properties are greatly expanded. Polyacrylic acid has good thickening, flocculation and chelation properties. For example, in building coatings, if acrylic acid is directly used, the pungent odor may be difficult to dissipate for a long time, and the use of polyacrylic acid emulsion as a film-forming material can not only avoid the harm of pungent odor to construction personnel and residents, but also make the coating more suitable for indoor decoration and other scenes with high odor requirements. In the pharmaceutical field, polyacrylic acid can be used as a drug carrier to combine with drug molecules to achieve drug sustained release and controlled release, and improve the efficacy and stability of the drug.

[0003] In the traditional method for preparing polyacrylic acid, acrylic acid monomer is usually dispersed in water, an initiator is added, and the monomer is polymerized under the condition of heating or ultraviolet light. The initiator usually needs to be slowly added by dripping, and the free radicals generated by the decomposition of the initiator initiate the chain growth reaction of the acrylic acid monomer to form polyacrylic acid. The reaction usually takes 3-10 hours to obtain the polyacrylic acid product, and the reaction rate is slow and the production efficiency is low. In addition, other double bond monomers need to be added for emulsion copolymerization, and toxic organic solvents are used.

[0004] In the prior art, for the preparation of hydroxyl polyacrylate emulsion, multi-component double bond monomers such as styrene, methyl methacrylate, etc. are used for emulsion thermal copolymerization with oligomers containing hydroxyl groups such as polyaldehyde resins, and are prepared at a reaction temperature above 80℃ for about 5 hours. The emulsion has high hardness and high gloss after being cured into a film at room temperature. For the preparation of water-based polyurethane acrylate copolymer emulsion, isocyanate, polyol, chain extender, hydroxyl acrylate and blocking agent are used as raw materials, and a phosphorus-containing water-based polyurethane emulsion containing carbon-carbon double bonds is prepared by chemical grafting method, and then emulsion thermal polymerization is carried out to prepare. The obtained water-based polyurethane acrylate copolymer emulsion has high solid content, short drying time, and the dried product has good flame retardant performance and heat decomposition resistance. The disadvantages are that the raw material components are complex, the raw materials need high temperature vacuum drying and other conditions, and the cost is high. For the preparation of water-based polyurethane / dopamine modified graphene nanocomposite emulsion, the introduction of dopamine modified graphene effectively improves the mechanical properties, antistatic property, electrical conductivity, electromagnetic shielding, thermal conductivity, chemical resistance and corrosion resistance of the water-based polyurethane film and coating. The disadvantage is that the graphene nanomaterial has high specific surface area and reactivity, and can easily cause the emulsion particles to attract and aggregate in the emulsion, causing precipitation and unstable storage.

[0005] In summary, the resin emulsion reported at present is basically prepared by thermal polymerization in a reaction kettle, and some resins need to be protected by nitrogen gas during polymerization to isolate oxygen. The reaction temperature is high and the reaction time is long because the oxygen in the air hinders the polymerization of the resin. Therefore, it is necessary to develop a method for efficiently synthesizing polyacrylic acid emulsion at room temperature.

[0006] Therefore, the prior art still needs to be improved. SUMMARY

[0007] To solve the above technical problems, the embodiments of the present application propose a polyacrylic acid emulsion and a preparation method thereof to solve the technical problems of high reaction temperature and long reaction time in the preparation of acrylic acid emulsion in the prior art.

[0008] To solve the above technical problems, on the one hand, some embodiments of the present application disclose a preparation method of a polyacrylic acid emulsion, comprising: After mixing the polymerization monomer with a double bond structure with water to prepare a polymerization monomer solution, an emulsifier and a reducing agent are added to the polymerization monomer solution, and stirred uniformly at room temperature to prepare a first pre-emulsion; The first pre-emulsion is added dropwise to an oxidizing agent solution, and stirred at room temperature to obtain a second pre-emulsion; A thickening agent is added to the second pre-emulsion, and stirred uniformly at room temperature to obtain a polyacrylic acid emulsion; The polymerization monomer comprises at least one of acrylic acid, methyl methacrylate, styrene, acrylamide, vinyl trimethoxysilane and vinyl triacetoxysilane, or a mixture of two or more thereof.

[0009] In some embodiments, the content of acrylic acid in the polymerization monomer is more than 90% of the total mass of the polymerization monomer.

[0010] In some embodiments, the emulsifier is a non-ionic O / W emulsifier or an anionic surfactant. Alternatively, the oxidizing agent is a hydrogen peroxide solution, and the mass concentration of the polymerization monomer with a double bond structure in the polymerization monomer solution is not more than 10%.

[0011] In some embodiments, the emulsifier is one of OP-4, OP-7, OP-10, OP-50, Tween 20, Tween 40, Tween 60 and Tween 80, or a mixture of two or more thereof. Alternatively, the emulsifier is sodium dodecyl benzene sulfonate or sodium dodecyl sulfate.

[0012] In some embodiments, the reducing agent is a reducing agent with a divalent metal ion or a small-molecule organic compound with a catechol structure.

[0013] In some embodiments, the reducing agent is ferrous nitrate.

[0014] In some embodiments, the first pre-emulsion is added dropwise to the oxidizing agent solution, and when the reaction is stirred at room temperature, the pH is controlled to be 4-6, and the stirring rate is 5000-10000 rpm.

[0015] In some embodiments, the pH is controlled by adding an acid regulator. The acid regulator is sulfuric acid, nitric acid, phosphoric acid, sodium dihydrogen phosphate, acid salt zinc dihydrogen phosphate, copper sulfate or zinc nitrate.

[0016] In some embodiments, the thickening agent is polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP).

[0017] In another aspect, the present application also discloses a polyacrylic acid emulsion prepared by the above-mentioned method for preparing a polyacrylic acid emulsion; in an infrared spectrum, there is a stretching vibration peak of O-H of a carboxyl group at 2500-3300 cm -1 There is a stretching vibration peak of a carbonyl group at 1710-1730 cm -1 There is a stretching vibration peak of a carbonyl group at 1710-1730 cm -1 There is a stretching vibration peak of a carbonyl group at 1710-1730 cm

[0018] By using the above technical solutions, the present application has at least the following beneficial effects: The application provides an acrylic emulsion and a preparation method thereof, and the hydroxyl radical is efficiently generated by Fenton reaction to initiate polymerization instead of traditional thermal polymerization, so that the emulsion is prepared at room temperature, the emulsion composition is simple, the preparation method is simple, and the efficiency is high. The polymerization-emulsification method is adopted, and a protective colloid is finally added for preservation. The acrylic emulsion, such as styrene-acrylate emulsion, silicone-acrylate emulsion and pure acrylic emulsion, can be rapidly prepared and synthesized at room temperature. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0020] Figure 1 An image of a polyacrylic emulsion disclosed by an embodiment of the present application; Figure 2 An image of viscous polyacrylic acid disclosed by an embodiment of the present application; Figure 3 An image of diluted polyacrylic emulsion drops on a glass slide under an optical microscope disclosed by an embodiment of the present application; Figure 4 An infrared spectrum of a pure polyacrylic emulsion prepared at room temperature and after film formation disclosed by an embodiment of the present application. DETAILED DESCRIPTION

[0021] The embodiments of the present disclosure will be further described in detail below in combination with the drawings and examples. The detailed description of the following examples and the drawings are used to exemplarily illustrate the principles of the present disclosure, but cannot be used to limit the scope of the present disclosure, and the present disclosure can be implemented in many different forms, and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0022] The present disclosure provides these embodiments in order to make the present disclosure thorough and complete, and fully express the scope of the present disclosure to those skilled in the art. It should be noted that: unless otherwise specified, the relative arrangement of components and steps, the composition of materials, numerical expressions and numerical values set forth in these embodiments should be interpreted as merely exemplary, and not as a limitation.

[0023] It should be noted that in the description of the present disclosure, unless otherwise specified and limited, the meaning of "a plurality of" is greater than or equal to two; The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like is only for the convenience of describing the present disclosure and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present disclosure. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0024] In addition, "first", "second", and similar words used in the present disclosure do not indicate any order, number or importance, but are only used to distinguish different parts. "Vertical" is not strictly vertical, but within the allowable error range. "Parallel" is not strictly parallel, but within the allowable error range. "Include" or "contain" and similar words mean that the elements before the word cover the elements listed after the word, and do not exclude the possibility of also covering other elements.

[0025] It should also be noted that in the description of the present disclosure, unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; It can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present disclosure can be understood according to the specific circumstances. When it is described that a specific device is located between a first device and a second device, there can be an intermediate device between the specific device and the first device or the second device, or there can be no intermediate device.

[0026] All terms used in the present disclosure have the same meaning as understood by those skilled in the art to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted to have meanings consistent with their meanings in the context of the relevant art, and should not be interpreted in an idealized or extremely formalized sense, unless specifically defined here.

[0027] Techniques, methods and devices known to those skilled in the relevant art can not be discussed in detail, but in appropriate cases, the techniques, methods and devices should be considered as part of the specification.

[0028] Some embodiments of the present application disclose a preparation method of polyacrylic acid emulsion, comprising: mixing polymerized monomers with double bond structure and water to prepare a polymerized monomer solution, adding emulsifier and reducing agent to the polymerized monomer solution, stirring uniformly at room temperature to prepare a first pre-emulsion. Dropping the first pre-emulsion into an oxidizing agent solution, stirring and reacting at room temperature to obtain a second pre-emulsion; adding thickening agent to the second pre-emulsion, stirring uniformly at room temperature to obtain the polyacrylic acid emulsion as shown in formula (I). Figure 1 The polymerized monomers can include at least one of acrylic acid, methyl methacrylate, styrene, acrylamide, vinyl trimethoxysilane, and vinyl triacetoxysilane, or a mixture of two or more thereof.

[0029] The above reactions in the embodiments are all carried out at room temperature, and hydroxyl radicals are efficiently generated by Fenton reaction to initiate polymerization instead of traditional thermal polymerization, so that the emulsion is prepared at room temperature, the emulsion composition is simple, the preparation method is simple, and the efficiency is high. Figure 2 As shown in formula (II), the Fenton reaction between ferrous ions and hydrogen peroxide makes the polyacrylic acid yellow. The polymerization-emulsification method is adopted, and protective colloid is finally added for preservation. The polyacrylic acid emulsion, the silicon-acrylic emulsion, the pure-acrylic emulsion and various types of acrylic emulsion can be rapidly prepared at room temperature.

[0030] In the above embodiments, the silica sol protective colloid (thickening agent) is polyvinyl alcohol PVA, such as PVA1788, PVA1799, PVA2488, PVA0588, PVA0388, or polyvinylpyrrolidone PVP, such as PVP K30, PVP K25, PVPC15, PVP C 30. Preferably, PVA0388 and PVP K30. These polymers have excellent water solubility and can provide certain viscosity to thicken and disperse the latex colloid to avoid precipitation and aggregation.

[0031] The room-temperature-synthesized polyacrylic acid emulsion in the above embodiments adopts hydroxyl radical to initiate polymerization, and the oxidizing agent can be hydrogen peroxide. The room-temperature-synthesized polyacrylic acid emulsion catalyzes hydrogen peroxide to generate hydroxyl radicals (reducing agent), and the metal ion is Fe 2+ , Co 2+ , Mn 2+ , Cr 2+ , Ni 2+ . These metal ions have certain reducing properties, or small-molecule organic compounds with catechol structure can be used, such as 5,6-dihydroxyindole, levodopa, dopamine, etc. The hydroxyl groups of catechol in these organic compounds have reducing properties. Generally, Fe 2+ is preferred based on cost and environmental protection considerations.

[0032] In the above examples, the pH value has a significant effect on the Fenton reaction or Fenton-like reaction. In acidic conditions, divalent metal ions can exist in the form of ions in the solution, which is conducive to the reaction. When the pH value is too high, the divalent metal ions and hydrolysis reaction occurs to generate hydroxide precipitate, affecting the generation of hydroxyl radicals; when the pH value is too low, the concentration of hydrogen ions in the solution is too high, which will inhibit the decomposition, and is not conducive to the generation of hydroxyl radicals, and the pH is preferably 4-6. The acid regulator is preferably one of sulfuric acid, nitric acid, phosphoric acid, sodium dihydrogen phosphate, or acid salt zinc dihydrogen phosphate, copper sulfate, zinc nitrate, etc.

[0033] In the above examples, the emulsifier can be selected from non-ionic O / W emulsifiers such as alkyl phenol polyoxyethylene ether such as OP-4, OP-7, OP-10, OP-50 or Tween 20, Tween 40, Tween 60, Tween 80, etc. One of them, or an anionic surfactant such as sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), etc. Preferably, OP series emulsifiers with high HLB are selected.

[0034] In the above examples, the defoaming agent can be selected from silicone defoaming agent, polyether defoaming agent or silane coupling agent KH550. Silicone defoaming agent such as polydimethylsiloxane (PDMS) emulsion, suitable for water-based system and high viscosity system. Polyether defoaming agent such as GPE type polyether defoaming agent, suitable for high temperature and strong acid and alkali environment. The demand for low-cost defoaming can also use silane coupling agent KH550 instead.

[0035] Due to the fast polymerization reaction, it is easy to occur that the degree of polymerization is too high and the reaction is not controlled, so the upper limit mass concentration of the polymerization monomer solution with double bond structure needs to be controlled to 10%. This embodiment adopts the method of polymerization and emulsification at the same time, which needs high-speed stirring. The stirring equipment can be selected from high-pressure homogenizer or high-shear emulsifier. The polymer is emulsified by high-speed stirring and shear force, and the stirring speed is 5000-10000 rpm.

[0036] Example 1 Room temperature rapid synthesis of pure acrylic emulsion: first, 7ml acrylic acid is added to deionized water and diluted to 20ml, 0.1ml OP-10 emulsifier and 0.02g ferrous sulfate are added and stirred uniformly to prepare pre-emulsion A. Then 50ml hydrogen peroxide solution B with a concentration of 0.1% is prepared by adding hydrogen peroxide to deionized water. While stirring the hydrogen peroxide solution B at high speed, slowly drop the pre-emulsion A into the solution B, the solution gradually becomes turbid, and after 5 minutes of droping, continue to stir for 5 minutes and then stand still. The preparation of pure acrylic emulsion with a mass concentration of about 10% is completed. Finally, 1g PVP K30 is added and stirred uniformly for standby. The obtained polyacrylic acid emulsion is shown in Figure 1 The performance parameters are shown in Table 1. AsFigure 3 The obtained polyacrylic acid emulsion was diluted and dropped on a glass slide, and the imaging under an optical microscope showed that the colloidal particle size was less than 1 micron and was uniformly distributed.

[0037] Figure 4 The infrared spectrum of the film formed by the pure polyacrylic acid emulsion prepared at room temperature is shown. Figure 4 It can be seen that there is a wide O-H stretching vibration peak of the carboxyl group (-COOH) at 2500-3300 cm-1, a stretching vibration peak of the carbonyl group (C=O) at about 1710-1730 cm-1, and a stretching vibration peak of C-O at 1200-1400 cm-1. It is proved that the polyacrylic acid emulsion is successfully formed into a film.

[0038] Example 2: Room temperature rapid synthesis of silicone-acrylate emulsion: first, 5 ml of acrylic acid, 2 ml of vinyl triacetoxy silane, 0.1 ml of OP-10, and 0.02 g of nickel sulfate were added to ionized water and diluted to 20 ml to prepare a pre-emulsion A. Then, 50 ml of a hydrogen peroxide solution B with a concentration of 0.1% was prepared by adding hydrogen peroxide to deionized water. While stirring the hydrogen peroxide solution B at high speed, the pre-emulsion A was slowly added dropwise into the solution B. The solution gradually became turbid, and after 5 minutes of dropwise addition, stirring was continued for 5 minutes and then the solution was left to stand. The preparation of a silicone-acrylate emulsion with a mass concentration of about 10% was completed. Finally, 1 g of PVA0388 was added and stirred uniformly to obtain a silicone-acrylate emulsion. The performance parameters of the obtained silicone-acrylate emulsion are shown in Table 1.

[0039] Example 3: Room temperature rapid synthesis of benzene-acrylate emulsion: first, 5 ml of acrylic acid, 0.1 ml of styrene, and 0.1 ml of methyl methacrylate were added to ionized water and diluted to 20 ml to prepare a pre-emulsion A. Then, 0.1 ml of OP-10 and 0.02 g of cobalt nitrate were added and stirred uniformly. 50 ml of a hydrogen peroxide solution B with a concentration of 0.1% was prepared by adding hydrogen peroxide to deionized water. While stirring the hydrogen peroxide solution B at high speed, the pre-emulsion A was slowly added dropwise into the solution B. The solution gradually became turbid, and after 5 minutes of dropwise addition, stirring was continued for 5 minutes and then the solution was left to stand. The preparation of a benzene-acrylate emulsion with a mass concentration of about 10% was completed. Finally, 1 g of PVA0388 was added and stirred uniformly to obtain a benzene-acrylate emulsion. The performance parameters of the obtained benzene-acrylate emulsion are shown in Table 1.

[0040] Example 4: Room temperature fast synthesis of styrene acrylamide emulsion: first, 5g acrylamide, 0.1ml styrene, 0.1ml methyl methacrylate were added to deionized water and diluted to 20ml, 0.05g sodium dodecyl sulfate, 0.02g ferrous sulfate were added and stirred uniformly to prepare pre-emulsion A. Then 50ml hydrogen peroxide solution B with a concentration of 0.1% was prepared by adding hydrogen peroxide to deionized water, 1wt% phosphoric acid was added dropwise to adjust the pH to 4-5, while stirring the hydrogen peroxide solution B at high speed, pre-emulsion A was slowly added dropwise into solution B, the solution gradually became turbid, 5 minutes after the dropwise addition was completed, stirring was continued for 5 minutes and then the mixture was left to stand, thus a styrene acrylamide emulsion with a mass concentration of about 10% was prepared, finally 1g PVA0388 was added and stirred uniformly before use. The performance parameters of the obtained acrylamide emulsion are shown in Table 1.

[0041] Example 5: Room temperature fast synthesis of pure acrylic emulsion: first, 7ml acrylic acid was added to deionized water and diluted to 20ml, 0.05g sodium dodecylbenzenesulfonate, 0.02g dopamine hydrochloride were added and stirred uniformly to prepare pre-emulsion A. Then 50ml hydrogen peroxide solution B with a concentration of 0.1% was prepared by adding hydrogen peroxide to deionized water, while stirring the hydrogen peroxide solution B at high speed, pre-emulsion A was slowly added dropwise into solution B, the solution gradually became turbid, 5 minutes after the dropwise addition was completed, stirring was continued for 5 minutes and then the mixture was left to stand, thus a pure acrylic emulsion with a mass concentration of about 10% was prepared, finally 1g PVP K30 was added and stirred uniformly before use. The performance parameters of the obtained pure acrylic emulsion are shown in Table 1.

[0042] Comparative Example 1: The difference from the example is that polymerization is carried out first and then emulsification is carried out, rather than simultaneous polymerization and emulsification: First, 7ml acrylic acid was added to deionized water and diluted to 20ml, 0.02g ferrous sulfate was added and stirred uniformly. Then 1ml hydrogen peroxide with a mass fraction of 3% was added dropwise and stirred at high speed until the solution gradually became viscous, after stirring for 5 minutes, the mixture was left to stand to obtain viscous polyacrylic acid. Then 0.1ml OP-10 was added to 50ml deionized water and stirred uniformly, the viscous polyacrylic acid was poured into the water containing the emulsifier and stirred at high speed until it became milky white, and then left to stand before use. As shown in Table 1, the disadvantage of this pure acrylic emulsion is that it is prone to precipitation and is not stable.

[0043] Comparative Example 2: The difference from the example is that the pre-emulsion monomers are added to the aqueous solution containing divalent iron with hydrogen peroxide dropwise: Firstly, 5ml of acrylic acid, 0.1ml of styrene, 0.1ml of methyl methacrylate were added to deionized water and diluted to 50ml, 0.05g of sodium dodecyl sulfate, 0.2ml of 10% hydrogen peroxide were stirred to prepare pre-emulsion A. Then 0.02g of ferrous nitrate was added to 20ml of deionized water to prepare a 0.1% iron nitrate solution B. While stirring the hydrogen peroxide solution B, the pre-emulsion A was slowly added to the solution B, the solution gradually became turbid, and after 5 minutes of dropwise addition, stirring was continued for 5 minutes and then left to stand, to complete the preparation of a mass concentration of about 10% of the styrene-acrylic emulsion. Finally, 1g of PVA0388 was added and stirred to prepare the emulsion. As shown in Table 1, the disadvantage of this dropwise addition sequence is that the excess of reducing agent leads to uneven polymerization of acrylic acid, and the molecular weight distribution is wide, and the emulsion is prone to precipitation.

[0044] Comparative Example 3: The difference from the example is that no PVP or PVA is added as a anti-settling and film-forming aid.

[0045] Firstly, 5ml of acrylic acid, 0.1ml of styrene, 0.1ml of methyl methacrylate were added to deionized water and diluted to 20ml, 0.05g of sodium dodecyl sulfate, 0.2ml of 10% hydrogen peroxide were stirred to prepare pre-emulsion A. Then 0.02g of ferrous nitrate was added to 50ml of deionized water to prepare a 0.1% iron nitrate solution B. While stirring the hydrogen peroxide solution B, the pre-emulsion A was slowly added to the solution B, the solution gradually became turbid, and after 5 minutes of dropwise addition, stirring was continued for 5 minutes and then left to stand, to complete the preparation of a mass concentration of about 10% of the styrene-acrylic emulsion. As shown in Table 1, the emulsion has slightly weak anti-settling performance and precipitates after a period of time.

[0046] Comparative Example 4: The difference from the example is that no high-speed stirring or homogenizer equipment is used.

[0047] Firstly, 7ml of acrylic acid was added to deionized water and diluted to 20ml, 0.05g of sodium dodecylbenzenesulfonate, 0.02g of ferrous nitrate were stirred to prepare pre-emulsion A. Then hydrogen peroxide was added to deionized water to prepare a 0.1% hydrogen peroxide solution B, and the pre-emulsion A was slowly added to the solution B, the solution gradually became turbid, and after 5 minutes of dropwise addition, stirring was continued for 5 minutes and then left to stand, to complete the preparation of a mass concentration of about 10% of the pure acrylic emulsion. Finally, 2g of PVP K30 anti-settling agent was added and stirred to prepare the emulsion. As shown in Table 1, the polymer has not been subjected to high-speed shearing, and precipitates after a period of time.

[0048] In the research process, it is found that the Fenton reaction is high in efficiency for preparing polyacrylic emulsion, especially for the monomer of acrylic acid, and the effect of room temperature polymerization on other double bond monomers such as styrene and methyl methacrylate is not obvious, so the monomer for room temperature emulsion synthesis is mainly acrylic acid monomer, therefore, in the polymerization monomer of the preferred embodiment, the content of acrylic acid is more than 90% of the total polymerization monomer mass. The compatibility with vinyl triacetoxy silane is very excellent, and it can be used for room temperature preparation of silicone-acrylate emulsion. In terms of emulsifying performance, the OP series emulsifiers have high HLB value, and the emulsifying performance is better than that of SDBS and SDS. In terms of generating hydroxyl radicals by oxidation and reduction, ferrous ions and dopamine as reducing agents can catalyze the generation of free radicals by H2O2 with high efficiency, and can initiate the rapid polymerization and gelation of acrylic acid monomer, and in combination with the cost consideration, the use of ferrous ions for preparing polyacrylic emulsion has the highest efficiency and the lowest cost.

[0049] Table 1: Formulation and final performance comparison of examples and comparative examples

[0050] So far, various embodiments of the present disclosure have been described in detail. In order to avoid obscuring the concept of the present disclosure, some details known in the art are not described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein according to the above description.

[0051] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, and are not intended to limit the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified or some technical features can be replaced equivalently without departing from the scope and spirit of the present disclosure. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way.

Claims

1. A method for preparing a polyacrylic acid emulsion, characterized in that: include: After mixing a polymerizable monomer having a double bond structure with water to prepare a polymerizable monomer solution, an emulsifier and a reducing agent are added to the polymerizable monomer solution, and the mixture is stirred uniformly at room temperature to prepare a first pre-emulsion; Adding the first pre-emulsion dropwise to the oxidant solution, stirring at room temperature for reaction, to obtain a second pre-emulsion; adding a thickener to the second pre-emulsion and stirring uniformly at room temperature to obtain a polyacrylic acid emulsion; The polymerizable monomers include at least one of acrylic acid, methyl methacrylate, styrene, acrylamide, vinyltrimethoxysilane, and vinyltriacetoxysilane, or a mixture of two or more thereof.

2. The method for preparing a polyacrylic acid emulsion according to claim 1, wherein In the polymerizable monomers, the content of acrylic acid accounts for more than 90% of the total mass of the polymerizable monomers.

3. The preparation method of polyacrylic acid emulsion according to claim 1, wherein The emulsifier is a nonionic O / W emulsifier or an anionic surfactant; Alternatively, the oxidant is a hydrogen peroxide solution, and the mass concentration of the polymerizable monomer having a double bond structure in the polymerizable monomer solution is not greater than 10%.

4. The method for preparing a polyacrylic acid emulsion according to claim 1, wherein The emulsifier is one or a mixture of two or more of OP-4, OP-7, OP-10, OP-50 or Tween 20, Tween 40, Tween 60, and Tween 80; Alternatively, the emulsifier is sodium dodecylbenzenesulfonate or sodium dodecyl sulfate.

5. The method for preparing a polyacrylic acid emulsion according to claim 1, wherein The reducing agent is a reducing agent having divalent metal ions or a small molecule organic compound having a catechol structure.

6. The method for preparing the polyacrylic acid emulsion according to claim 5, wherein The reducing agent is ferrous nitrate.

7. The method for preparing a polyacrylic acid emulsion according to claim 1, wherein The first pre-emulsion is added dropwise to the oxidant solution, and the reaction is carried out under stirring at room temperature, with the pH controlled at 4-6 and the stirring rate at 5000-10000 rpm.

8. The method for preparing the polyacrylic acid emulsion according to claim 7, wherein The pH is controlled by adding an acidic regulator; The acidic regulator is sulfuric acid, nitric acid, phosphoric acid, sodium dihydrogen phosphate, acid salt zinc dihydrogen phosphate, copper sulfate or zinc nitrate.

9. The method for preparing a polyacrylic acid emulsion according to claim 1, wherein The thickener is polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP).

10. A polyacrylic acid emulsion, characterized in that The polyacrylic acid emulsion is prepared by the preparation method of any one of claims 1 to 9; in the infrared spectrum, 2500 - 3300 cm -1 There is a stretching vibration peak of OH in the carboxyl group, 1710-1730 cm -1 There is a stretching vibration peak of carbonyl group at 1200-1400 cm -1 There is a stretching vibration peak of CO.

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