Polyacrylic acid inverse emulsion thickener and method for preparing the same

Abstract

The application provides a polyacrylic acid reverse emulsion thickener and a preparation method thereof, and the polyacrylic acid reverse emulsion thickener comprises the following components in mass fractions: modified attapulgite 1-10 parts, hyperbranched acrylate 0.1-5 parts, acrylic acid 30-60 parts, hydrophobic long-chain acrylate monomer 1-5 parts, solvent oil 5-20 parts, emulsifier 0.5-5 parts, initiator 0.01-1 part and phase transfer agent 0.5-2.5 parts. The application first introduces isocyanate segments and double bond active groups on the surface of acid-activated attapulgite, so that the dispersibility and reactivity are improved; then hyperbranched acrylate with a hyperbranched structure and multiple double bonds is constructed by taking trimethylolpropane as a core, and the polyacrylic acid reverse emulsion thickener is prepared by a reverse emulsion method. The application significantly improves the thickening performance, electrolyte resistance and long-term stability through the synergistic effect of the hyperbranched acrylate, the modified attapulgite and the hydrophobic long-chain monomer.

Description

Technical Field

[0001] The present invention relates to the technical field of thickeners, and in particular to a polyacrylic acid inverse emulsion thickener and a preparation method thereof. Background Art

[0002] Thickeners, a crucial rheological additive, have demonstrated extensive application value in numerous fields, including coatings, inks, daily chemical industries, and oilfield chemistry. They primarily achieve effective control over product processing performance and stability by precisely adjusting the viscosity and rheological properties of the system. Water-based thickeners play a crucial role in this regard. With the rapid development of various industries, the performance requirements for water-based thickeners are also increasing. Polyacrylic acid thickeners, due to their superior thickening properties, excellent rheological control capabilities, and favorable environmental friendliness, have become the focus of current research. These thickeners are generally prepared using inverse emulsion polymerization technology, which offers significant advantages and can achieve efficient thickening effects in high-solids, low-viscosity systems.

[0003] Currently, the preparation of polyacrylic acid inverse emulsion thickeners generally adopts the inverse emulsion polymerization process with an oil phase as the continuous phase and an aqueous phase as the dispersed phase. The core of this process is to achieve efficient dispersion and polymerization of acrylic monomers in a water-in-oil (W / O) system through the compounding effect of hydrophobic emulsifiers and hydrophilic emulsifiers. The typical synthesis route usually involves dissolving acrylic monomers and functional comonomers in the aqueous phase, mixing them with an organic solvent containing an emulsifier to form a stable emulsion, and then triggering a free radical polymerization reaction with an initiator. Finally, the inverse emulsion thickener is obtained through phase inversion. This technical route has been widely used in water-based coatings, construction adhesives and daily chemical industries due to its fast polymerization rate, controllable molecular weight distribution and special rheological behavior of the product such as "shear thinning".

[0004] Although the existing technology system is relatively mature, there are still many aspects that need improvement. First, the linear molecular structure of traditional polyacrylic acid thickeners makes it easy for the molecular chain to disentangle at high shear rates, causing irreversible viscosity decay, making it difficult to meet the needs of dynamic processing processes such as high-speed coating and mechanical stirring; secondly, the inherent oil-water density difference and interfacial tension problems of the inverse emulsion system cause the latex particles to gradually aggregate and settle during storage, especially in high-solid content systems. Stratification is prone to occur, affecting product homogeneity; in addition, the pH sensitivity of the carboxylic acid group and its lack of adaptability to hydrophobic environments make the product prone to excessive molecular chain extension or phase separation in the presence of electrolytes. At the same time, the interfacial film weakening caused by emulsifier migration leads to deterioration of rheological properties, making it difficult to meet the needs of complex application scenarios.

[0005] In summary, it is necessary to develop a new technical solution to solve the problems existing in the existing technology. Summary of the Invention

[0006] The present invention provides a polyacrylic acid inverse emulsion thickener and a preparation method thereof. The present invention first introduces isocyanate segments and double-bond reactive groups onto the surface of acid-activated attapulgite to improve dispersibility and reactivity. Then, using trimethylolpropane as a core, a hyperbranched acrylate with multiple double bonds and a hyperbranched structure is constructed. The polyacrylic acid inverse emulsion thickener is then prepared using an inverse emulsion method. Through the synergistic effects of the hyperbranched acrylate, modified attapulgite, and hydrophobic long-chain monomers, the present invention significantly improves thickening performance, electrolyte resistance, and long-term stability. First, the three-dimensional network structure of the hyperbranched acrylate acts as a crosslinker during the polymerization process, enhancing the entanglement between molecular chains. This not only improves thickening efficiency but also imparts excellent shear recovery and anti-settling stability to the system, while maintaining long-term stability. Second, reactive groups are grafted onto the surface of the isocyanate acrylate-modified attapulgite, improving its dispersibility and reactivity. Its layered structure forms an interpenetrating network with polyacrylic acid molecules through physical crosslinking, further enhancing thixotropy and mechanical strength, creating a synergistic effect with the thickening effect of the acrylic acid backbone. Furthermore, the introduction of hydrophobic long-chain acrylate monomers creates dynamic physical crosslinking points through hydrophobic association, reducing water sensitivity while enhancing electrolyte tolerance, enabling the thickener to maintain stable rheological properties in complex environments. Through the synergistic effect of these components, the present invention achieves comprehensive improvements in thickening performance, electrolyte resistance, and long-term stability, demonstrating promising application prospects.

[0007] An object of the present invention is to provide a polyacrylic acid inverse emulsion thickener, wherein the polyacrylic acid inverse emulsion thickener comprises the following components in parts by weight:

[0008]

[0009] in,

[0010] The modified attapulgite is obtained by reacting isocyanate acrylate with acid-activated attapulgite clay;

[0011] The hyperbranched acrylate is obtained by grafting diethanolamine onto acrylate, which is then reacted with trimethylolpropane and then with isocyanate acrylate.

[0012] Furthermore, the hydrophobic long-chain acrylate monomer is selected from one or more of hexadecyl acrylate, hexadecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, eicosyl acrylate, eicosyl methacrylate, behenyl acrylate, behenyl methacrylate, behenyl acrylate or behenyl methacrylate.

[0013] Furthermore, the solvent oil is selected from one or more of kerosene, 3# white oil, 5# white oil, D80 solvent oil or D100 solvent oil.

[0014] Furthermore, the emulsifier is Span 80.

[0015] Furthermore, the initiator is selected from one or more of persulfate initiators and azo initiators.

[0016] Furthermore, the phase inversion agent is selected from one or more of Tween 80, isomeric tridecanol polyoxyethylene ether or fatty alcohol polyoxyethylene ether.

[0017] Another object of the present invention is to provide a method for preparing the above-mentioned polyacrylic acid inverse emulsion thickener, comprising the following steps:

[0018] S1, immersing attapulgite clay in an acid solution, heating and ultrasonicating, to obtain acid-activated attapulgite clay;

[0019] S2, blending the acid-activated attapulgite clay, isocyanate acrylate and polymerization inhibitor, adding a catalyst, and heating to react to obtain modified attapulgite;

[0020] S3, heating acrylate and diethanolamine under inert gas protection to react to obtain product 1; blending the product 1 with trimethylolpropane, adding p-toluenesulfonic acid, heating to react, to obtain product 2, cooling, adding isocyanate acrylate, an inhibitor and a catalyst, heating to react, to obtain hyperbranched acrylate;

[0021] S4. Blending the modified attapulgite, acrylic acid, and hydrophobic long-chain acrylate monomer, adding the hyperbranched acrylate as a cross-linking agent, adjusting the pH, adding solvent oil and an emulsifier, and emulsifying with high-speed stirring, then adding an initiator prepared into an aqueous solution, heating for reaction, cooling after completion of the reaction, adding a phase inversion agent, and stirring evenly to obtain a polyacrylic acid inverse emulsion thickener.

[0022] Furthermore, in step S1, the acid solution is selected from one or more of hydrochloric acid solution, nitric acid solution or sulfuric acid solution; the concentration of the acid solution is 1-5 mol / L; and the heating temperature is 60-80°C.

[0023] Furthermore, in step S2, the mass ratio of the acid-activated attapulgite clay to the isocyanate acrylate is 1:(1-10); the polymerization inhibitor is p-hydroxyanisole, and the addition amount is 0.01-1wt% of the reactant; the catalyst is dibutyltin dilaurate, and the addition amount is 0.1-1wt% of the reactant; and the heating temperature is 40-60°C.

[0024] Furthermore, in step S3, the molar ratio of the acrylate to diethanolamine is (1.1-1.5):1, and the heating temperature is 40-60°C; the molar ratio of the product 1 to trimethylolpropane is (3-8):1, the heating temperature is 100-120°C, and the amount of the catalyst p-toluenesulfonic acid is 0.1-1wt%; the molar ratio of the product 2 to isocyanate acrylate is 1:(5-10); the polymerization inhibitor is p-hydroxyanisole, and the added amount is 0.01-1wt% of the reactants; the catalyst is dibutyltin dilaurate, and the added amount is 0.1-1wt% of the reactants; and the heating temperature is 40-60°C.

[0025] Furthermore, in step S4, the pH is 6-7; the heating temperature is 60-80° C.; and the mass concentration of the initiator aqueous solution is 1-10 wt %.

[0026] The present invention has the following beneficial effects:

[0027] The present invention first introduces isocyanate segments and double-bond reactive groups on the surface of acid-activated attapulgite to improve dispersibility and reactivity; then, using trimethylolpropane as the core, a hyperbranched acrylate with multiple double bonds and a hyperbranched structure is constructed, and then a polyacrylic acid inverse emulsion thickener is prepared by an inverse emulsion method. The present invention significantly improves thickening performance, electrolyte resistance, and long-term stability through the synergistic effect of hyperbranched acrylate, modified attapulgite, and hydrophobic long-chain monomers. First, the three-dimensional network structure of the hyperbranched acrylate acts as a cross-linking agent during the polymerization process, enhancing the entanglement between molecular chains, not only improving the thickening efficiency, but also giving the system excellent shear recovery and anti-settling stability, while maintaining the long-term stability of the system. Secondly, the surface of the isocyanate acrylate-modified attapulgite is grafted with reactive groups, improving its dispersibility and reactivity. Its layered structure forms an interpenetrating network with polyacrylic acid molecules through physical cross-linking, further improving thixotropy and mechanical strength, and forming a synergistic effect with the thickening effect of the acrylic acid backbone. Furthermore, the introduction of hydrophobic long-chain acrylate monomers creates dynamic physical crosslinking points through hydrophobic association, reducing water sensitivity while enhancing electrolyte tolerance, enabling the thickener to maintain stable rheological properties in complex environments. Through the synergistic effect of these components, the present invention achieves comprehensive improvements in thickening performance, electrolyte resistance, and long-term stability, demonstrating promising application prospects. DETAILED DESCRIPTION

[0028] In order to more clearly illustrate the technical solutions of the present invention, the following examples are given. Unless otherwise stated, the raw materials, reactions and post-processing methods mentioned in the examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0029] The terms "preferred," "preferably," "more preferred," and the like, used herein, refer to embodiments of the invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

[0030] It should be understood that, except in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties to be obtained by the present invention.

[0031] The present invention uses the following raw materials:

[0032] Contains hydrophobic long chain acrylate monomer: octadecyl methacrylate.

[0033] Solvent oil: 5# white oil, purchased from Shanghai Better Chemical Co., Ltd.

[0034] Emulsifier: Span 80.

[0035] Initiator: sodium persulfate.

[0036] Phase inversion agent: Tween 80, purchased from Hubei Yongkuo Technology Co., Ltd.

[0037] Attapulgite clay: purchased from Mingguang Hengding Attapulgite Co., Ltd.

[0038] The water in the present invention is all deionized water.

[0039] The "parts" in the present invention refer to parts by mass.

[0040] Example 1

[0041] A polyacrylic acid inverse emulsion thickener, comprising the following components in parts by mass:

[0042]

[0043] in,

[0044] The modified attapulgite is obtained by reacting ethyl isocyanate acrylate with acid-activated attapulgite clay;

[0045] The hyperbranched acrylate is obtained by grafting diethanolamine onto methyl acrylate, reacting with trimethylolpropane, and then reacting with ethyl isocyanate acrylate.

[0046] The preparation method of the polyacrylic acid inverse emulsion thickener comprises the following steps:

[0047] S1. Immersing attapulgite clay in a 3 mol / L nitric acid solution, ultrasonically treating at 80° C. for 30 min, washing with water until neutral, centrifuging, drying, and grinding through a 400-mesh sieve to obtain acid-activated attapulgite clay;

[0048] S2. Using N,N-dimethylformamide as a solvent, the acid-activated attapulgite, ethyl isocyanate acrylate and p-hydroxyanisole are blended, and dibutyltin dilaurate is added (acid-activated attapulgite:ethyl isocyanate acrylate=1:5, m / m; p-hydroxyanisole is a reactant 0.5wt%, and dibutyltin dilaurate is a reactant 0.1wt%), and the mixture is reacted at 50° C. The NCO content is monitored by a di-n-butylamine method. The reaction is stopped when the NCO content reaches the theoretical value, and the mixture is washed, dried, and ground through a 400-mesh sieve to obtain a modified attapulgite.

[0049] S3, using methanol as solvent, methyl acrylate and diethanolamine were mixed (methyl acrylate: diethanolamine = 1.2:1, n / n), and the mixture was reacted under nitrogen protection at 50 ° C for 5 h, and the solvent and unreacted methyl acrylate were removed by rotary evaporation to obtain product 1; using N, N-dimethylformamide as solvent, the product 1 and trimethylolpropane were mixed (product 1: trimethylolpropane = 3.5:1, n / n), p-toluenesulfonic acid (0.6 wt% of the reactant) was added, and the mixture was stirred at 110 ° C for 5 h. The mixture was reacted for 4 h to obtain product 2, and the temperature was lowered to 50° C., and ethyl isocyanate acrylate, p-hydroxyanisole, and dibutyltin dilaurate were added (product 2: ethyl isocyanate acrylate = 1:6, n / n, p-hydroxyanisole as the reactant 0.5wt%, dibutyltin dilaurate as the reactant 0.1wt%), and the reaction was carried out at 50° C. The NCO content was monitored by the di-n-butylamine method. The reaction was stopped when the NCO content reached the theoretical value, and the solvent was removed by distillation under reduced pressure to obtain a hyperbranched acrylate;

[0050] S4. Blend the modified attapulgite, acrylic acid, and hydrophobic long-chain acrylate monomer according to the above-mentioned mass fractions, add the hyperbranched acrylate as a cross-linking agent, adjust the pH to 6.5 with aqueous ammonia, add solvent oil and emulsifier, stir and emulsify at 1200 rpm for 2 hours, then add the initiator prepared into a 5 wt % aqueous solution, react at 70° C. for 12 hours, cool to room temperature after the reaction is completed, add a phase inversion agent, and stir evenly to obtain a polyacrylic acid inverse emulsion thickener.

[0051] Example 2

[0052] A polyacrylic acid inverse emulsion thickener, comprising the following components in parts by mass:

[0053]

[0054] in,

[0055] The modified attapulgite is obtained by reacting ethyl isocyanate acrylate with acid-activated attapulgite clay;

[0056] The hyperbranched acrylate is obtained by grafting diethanolamine onto methyl acrylate, reacting with trimethylolpropane, and then reacting with ethyl isocyanate acrylate.

[0057] The preparation method of the polyacrylic acid inverse emulsion thickener is the same as that in Example 1.

[0058] Example 3

[0059] A polyacrylic acid inverse emulsion thickener, comprising the following components in parts by mass:

[0060]

[0061] in,

[0062] The modified attapulgite is obtained by reacting ethyl isocyanate acrylate with acid-activated attapulgite clay;

[0063] The hyperbranched acrylate is obtained by grafting diethanolamine onto methyl acrylate, reacting with trimethylolpropane, and then reacting with ethyl isocyanate acrylate.

[0064] The preparation method of the polyacrylic acid inverse emulsion thickener is the same as that in Example 1.

[0065] Comparative Example 1

[0066] A polyacrylic acid inverse emulsion thickener. The difference between this comparative example and Example 1 is that step S2 is modified as follows:

[0067] The acid-activated attapulgite clay and the silane coupling agent KH570 were mixed in N,N-dimethylformamide as a solvent (acid-activated attapulgite clay: silane coupling agent KH570 = 1:5, m / m), reacted at 80° C. for 4 h, filtered, washed, dried, and ground through a 400-mesh sieve to obtain a modified attapulgite;

[0068] The amounts of other ingredients and the preparation method are the same as those in Example 1.

[0069] Comparative Example 2

[0070] A polyacrylic acid inverse emulsion thickener. The difference between this comparative example and Example 1 is that step S3 is modified as follows:

[0071] In N,N-dimethylformamide as a solvent, trimethylolpropane, ethyl isocyanate acrylate, p-hydroxyanisole and dibutyltin dilaurate (trimethylolpropane:ethyl isocyanate acrylate=1:3, n / n, p-hydroxyanisole as a reactant 0.5wt%, dibutyltin dilaurate as a reactant 0.1wt%) are reacted at 50° C., and the NCO content is monitored by a di-n-butylamine method. When the NCO content reaches a theoretical value, the reaction is stopped, and the solvent is removed by distillation under reduced pressure to obtain a branched acrylate.

[0072] The mass fraction of the hyperbranched acrylate was replaced by branched acrylate, and the amounts of other components and the preparation method were the same as those in Example 1.

[0073] Test Case

[0074] Performance tests were performed on Examples 1-3 and Comparative Examples 1-2.

[0075] Test method:

[0076] White slurry viscosity: Add water to the polyacrylic acid inverse emulsion thickener and stir thoroughly to prepare a white slurry with a mass fraction of 2%. Use an SNB-2 rotational viscometer to test the viscosity at a speed of 6 r / min.

[0077] Viscosity retention rate: Electrolyte resistance is expressed as viscosity retention rate. The viscosity of the thickener before and after adding 0.05wt% NaCl (solid) to the above white slurry is measured at a speed of 6r / min. Viscosity retention rate = η 加NaCl后 / η 加NaCl前 , the higher the viscosity retention rate, the better the electrolyte resistance.

[0078] Long-term white slurry viscosity and long-term viscosity retention rate: After the polyacrylic acid inverse emulsion thickener is placed at room temperature for 6 months, the white slurry viscosity and viscosity retention rate are tested according to the above method.

[0079] The test results are shown in Table 1.

[0080] Table 1 Performance test results

[0081]

[0082]

[0083] The above test results show that the polyacrylic acid inverse emulsion thickener of the present invention has strong thickening ability, high viscosity retention, and excellent electrolyte resistance. It can also maintain high thickening ability and excellent electrolyte resistance after long-term storage. However, the performance of Comparative Examples 1-2 is reduced to varying degrees compared to that of the present invention due to incomplete modification.

[0084] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0085] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A polyacrylic acid inverse emulsion thickener, characterized in that: The polyacrylic acid inverse emulsion thickener comprises the following components in parts by mass: in, The modified attapulgite is obtained by reacting isocyanate acrylate with acid-activated attapulgite clay; The hyperbranched acrylate is obtained by grafting diethanolamine onto acrylate, which is then reacted with trimethylolpropane and then with isocyanate acrylate.

2. The polyacrylic acid inverse emulsion thickener according to claim 1, characterized in that The hydrophobic long-chain acrylate monomer is selected from one or more of hexadecyl acrylate, hexadecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, eicosyl acrylate, eicosyl methacrylate, behenyl acrylate or behenyl methacrylate.

3. The polyacrylic acid inverse emulsion thickener according to claim 1, characterized in that The solvent oil is selected from one or more of kerosene, 3# white oil, 5# white oil, D80 solvent oil or D100 solvent oil.

4. The polyacrylic acid inverse emulsion thickener according to claim 1, characterized in that The emulsifier is Span 80.

5. The polyacrylic acid inverse emulsion thickener according to claim 1, characterized in that The initiator is selected from one or more of persulfate initiators and azo initiators.

6. The polyacrylic acid inverse emulsion thickener according to claim 1, characterized in that The phase inversion agent is selected from one or more of Tween 80, isomeric tridecanol polyoxyethylene ether or fatty alcohol polyoxyethylene ether.

7. The method for preparing the polyacrylic acid inverse emulsion thickener according to any one of claims 1 to 6, characterized in that: The steps include: S1, immersing attapulgite clay in an acid solution, heating and ultrasonicating, to obtain acid-activated attapulgite clay; S2, blending the acid-activated attapulgite clay, isocyanate acrylate and polymerization inhibitor, adding a catalyst, and heating to react to obtain modified attapulgite; S3, heating acrylate and diethanolamine under inert gas protection to react to obtain product 1; blending the product 1 with trimethylolpropane, adding p-toluenesulfonic acid, heating to react, to obtain product 2, cooling, adding isocyanate acrylate, an inhibitor and a catalyst, heating to react, to obtain hyperbranched acrylate; S4. Blending the modified attapulgite, acrylic acid, and hydrophobic long-chain acrylate monomer, adding the hyperbranched acrylate as a cross-linking agent, adjusting the pH, adding solvent oil and an emulsifier, and emulsifying with high-speed stirring, then adding an initiator prepared into an aqueous solution, heating for reaction, cooling after completion of the reaction, adding a phase inversion agent, and stirring evenly to obtain a polyacrylic acid inverse emulsion thickener.

8. The method for preparing the polyacrylic acid inverse emulsion thickener according to claim 7, wherein: In step S1, the acid solution is selected from one or more of hydrochloric acid solution, nitric acid solution or sulfuric acid solution.

9. The method for preparing the polyacrylic acid inverse emulsion thickener according to claim 7, wherein: In step S2, the mass ratio of the acid-activated attapulgite clay to the isocyanate acrylate is 1:(1-10).

10. The method for preparing the polyacrylic acid inverse emulsion thickener according to claim 7, characterized in that: In step S3, the molar ratio of the acrylate to diethanolamine is (1.1-1.5):1; the molar ratio of the product 1 to trimethylolpropane is (3-8):1; and the molar ratio of the product 2 to isocyanate acrylate is 1:(5-10).

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