Polyacrylic inverse emulsion thickener and preparation method thereof

Abstract

The invention provides a polyacrylic acid inverse emulsion thickener and a preparation method thereof. The polyacrylic inverse emulsion thickener is prepared from the following components in parts by mass: 1 to 10 parts of modified attapulgite, 0.1 to 5 parts of hyperbranched acrylate, 30 to 60 parts of acrylic acid, 1 to 5 parts of a hydrophobic long-chain acrylate monomer, 5 to 20 parts of solvent oil, 0.5 to 5 parts of an emulsifier, 0.01 to 1 part of an initiator and 0.5 to 2.5 parts of a phase inversion agent. The preparation method comprises the following steps: firstly, introducing an isocyanate chain segment and a double-bond active group to the surface of acid-activated attapulgite to improve dispersity and reaction activity; then trimethylolpropane is used as a core, hyperbranched acrylate with multiple double bonds and a hyperbranched structure is constructed, and then the polyacrylic acid inverse emulsion thickener is prepared through an inverse emulsion method. Through the synergistic effect of the hyperbranched acrylate, the modified attapulgite and the hydrophobic long-chain monomer, the thickening performance, the electrolyte resistance and the long-term stability are remarkably improved.

Description

Technical Field

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

[0002] As a crucial class of rheological aids, thickeners exhibit extensive application value in numerous fields such as coatings, inks, the daily chemical industry, and oilfield chemistry. They mainly achieve effective control of the processing performance and stability of products by precisely adjusting the viscosity and rheological properties of the system. Among them, water-based system thickeners play a particularly important role. With the rapid development of various industries, the performance requirements for water-based system thickeners are also increasing day by day. Polyacrylic acid thickeners have become the focus of current research due to their excellent thickening performance, outstanding rheological adjustment ability, and good environmental friendliness. Such thickeners are generally prepared by inverse emulsion polymerization technology, which has significant advantages and can achieve high-efficiency thickening effects in high-solid-content and low-viscosity systems.

[0003] Currently, the preparation of polyacrylic acid inverse emulsion thickeners generally adopts an inverse emulsion polymerization process with the oil phase as the continuous phase and the water phase as the dispersed phase. The core lies in the combined action of hydrophobic emulsifiers and hydrophilic emulsifiers to achieve efficient dispersion and polymerization of acrylic monomers in a water-in-oil (W / O) system. A typical synthesis route usually involves dissolving acrylic monomers and functional comonomers in the water phase, mixing them with an organic solvent containing emulsifiers to form a stable emulsion, triggering a free radical polymerization reaction through an initiator, and finally obtaining an inverse emulsion thickener through phase inversion. This technical route has been applied on a large scale in water-based coatings, construction adhesives, and the daily chemical industry due to its fast polymerization rate, controllable molecular weight distribution, and special rheological behaviors such as "shear thinning" of the product.

[0004] Although the existing technology system is relatively mature, there are still many aspects that need to be improved. First, the linear molecular structure of traditional polyacrylic acid thickeners causes the molecular chains to easily become entangled under high shear rates, leading to irreversible viscosity decay and making it difficult to meet the requirements of dynamic processing processes such as high-speed coating and mechanical stirring. Second, the inherent problems of the oil-water density difference and interfacial tension in the inverse emulsion system result in the gradual aggregation and sedimentation of latex particles during storage, especially in high-solid-content systems, where layering is likely to occur, affecting the homogeneity of the product. In addition, the pH sensitivity of carboxylic acid groups and the insufficient adaptability to the hydrophobic environment cause the molecular chains to overstretch or phase separate easily in the presence of electrolytes, and at the same time, the weakening of the interfacial film caused by the migration of emulsifiers leads to the deterioration of rheological properties, making it difficult to meet the requirements of complex application scenarios.

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

[0006] The present invention provides a polyacrylic acid inverse emulsion thickener and a preparation method thereof. First, isocyanate segments and double-bond active groups are introduced onto the surface of acid-activated attapulgite to improve its 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 the inverse emulsion method. Through the synergistic effect of hyperbranched acrylate, modified attapulgite, and hydrophobic long-chain monomers, the thickening performance, electrolyte tolerance, and long-term stability of the present invention are significantly improved. First, the three-dimensional network structure of hyperbranched acrylate acts as a crosslinking agent during polymerization, enhancing the entanglement between molecular chains. This not only improves the thickening efficiency but also endows the system with excellent shear recovery and anti-settling stability, while maintaining the long-term stability of the system. Second, the surface of isocyanate acrylate-modified attapulgite is grafted with active groups, improving its dispersibility and reactivity. Its layered structure forms an interpenetrating network with polyacrylic acid molecules through physical crosslinking, further enhancing the thixotropy and mechanical strength, and forming a synergistic effect with the thickening effect of the acrylic acid main chain. In addition, the introduction of hydrophobic long-chain acrylate monomers forms dynamic physical crosslinking points through hydrophobic association, reducing water sensitivity and enhancing electrolyte tolerance, so that the thickener maintains stable rheological properties in complex environments. Through the synergistic effect of the above components, the present invention comprehensively improves the thickening performance, electrolyte tolerance, and long-term stability, and has good application prospects.

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

[0008]

[0009] Wherein,

[0010] The modified attapulgite is obtained by the reaction of isocyanate acrylate and acid-activated attapulgite clay;

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

[0012] Further, 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, docosyl acrylate, docosyl methacrylate, acrylic docosyl ester or methacrylic docosyl ester.

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

[0014] Further, the emulsifier is Span 80.

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

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

[0017] Another object of the present invention is to provide a preparation method of the above polyacrylic acid reverse emulsion thickener, comprising the following steps:

[0018] S1. Immerse attapulgite clay in an acid solution, heat and ultrasonicate to obtain acid-activated attapulgite clay;

[0019] S2. Blend the acid-activated attapulgite clay, isocyanate acrylate and inhibitor, add a catalyst, and heat and react to obtain modified attapulgite;

[0020] S3. Heat and react acrylate and diethanolamine under the protection of an inert gas to obtain product 1; blend product 1 and trimethylolpropane, add p-toluenesulfonic acid, heat and react to obtain product 2, cool down, add isocyanate acrylate, inhibitor and catalyst, and heat and react to obtain hyperbranched acrylate;

[0021] S4. Blend the modified attapulgite, acrylic acid and hydrophobic long-chain acrylate monomer, add the hyperbranched acrylate as a crosslinking agent, adjust the pH, add solvent naphtha and emulsifier, emulsify by high-speed stirring, then prepare an aqueous solution of the initiator and add it, heat and react, cool down after the reaction is completed, add the phase inversion agent, and stir evenly to obtain the polyacrylic acid reverse emulsion thickener.

[0022] Further, 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; the heating temperature is 60-80 °C.

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

[0024] Further, 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 product 1 to trimethylolpropane is (3 - 8):1, and the heating temperature is 100 - 120°C. The dosage of the catalyst p-toluenesulfonic acid is 0.1 - 1 wt%; the molar ratio of product 2 to isocyanate acrylate is 1:(5 - 10); the inhibitor is p-methoxyphenol, and the addition amount is 0.01 - 1 wt% of the reactants; the catalyst is dibutyltin dilaurate, and the addition amount is 0.1 - 1 wt% of the reactants; the heating temperature is 40 - 60°C.

[0025] Further, in step S4, the pH is 6 - 7; the heating temperature is 60 - 80°C; 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 active groups on the surface of acid-activated attapulgite to improve the dispersibility and reactivity; then uses trimethylolpropane as the core to construct a hyperbranched acrylate with multiple double bonds and a hyperbranched structure, and then prepares a polyacrylic acid inverse emulsion thickener by the inverse emulsion method. Through the synergistic effect of hyperbranched acrylate, modified attapulgite and hydrophobic long-chain monomers, the thickening performance, electrolyte tolerance and long-term stability of the present invention are significantly improved. First, the three-dimensional network structure of hyperbranched acrylate acts as a crosslinking agent during the polymerization process, enhancing the entanglement between molecular chains, not only improving the thickening efficiency, but also endowing the system with excellent shear recovery and anti-settling stability, while maintaining the long-term stability of the system. Second, the surface of the isocyanate acrylate-modified attapulgite is grafted with active groups, improving its dispersibility and reactivity. Its layered structure forms an interpenetrating network with polyacrylic acid molecules through physical crosslinking, further enhancing the thixotropy and mechanical strength, and forming a synergistic effect with the thickening effect of the acrylic acid main chain. In addition, the introduction of hydrophobic long-chain acrylate monomers forms dynamic physical crosslinking points through hydrophobic association, reducing water sensitivity and enhancing electrolyte tolerance, so that the thickener maintains stable rheological properties in a complex environment. Through the synergistic effect of the above components, the present invention realizes the comprehensive improvement of thickening performance, electrolyte tolerance and long-term stability, and has good application prospects. Specific Embodiments

[0028] In order to more clearly illustrate the technical solutions of the present invention, the following examples are listed. The raw materials, reactions and post-treatment means appearing in the examples are all common raw materials on the market and technical means well-known to those skilled in the art, unless otherwise specified.

[0029] The terms "preferred", "preferably", "more preferred", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain cases. However, in the same cases or other cases, other embodiments may also be preferred. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of the present invention.

[0030] It should be understood that, except in any operating instance or otherwise indicated, all numbers expressing quantities of ingredients or the like 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 attached claims are approximations that vary depending upon the desired properties sought to be obtained by the present invention.

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

[0032] Hydrophobic long-chain acrylate monomer: octadecyl methacrylate.

[0033] Solvent oil: No. 5 white oil, purchased from Shanghai Beit 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] All water in the present invention is deionized water.

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

[0040] Example 1

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

[0042]

[0043] Among them,

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

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

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

[0047] S1. Immerse attapulgite clay in 3 mol / L nitric acid solution, ultrasonicate for 30 min at 80 °C, wash with water until neutral, centrifuge, dry, and grind through a 400-mesh sieve to obtain acid-activated attapulgite clay;

[0048] S2. Using N,N-dimethylformamide as a solvent, blend the acid-activated attapulgite clay, isocyanate ethyl acrylate, and p-hydroxyanisole, add dibutyltin dilaurate (acid-activated attapulgite clay:isocyanate ethyl acrylate = 1:5, m / m; p-hydroxyanisole is 0.5 wt% of the reactants, and dibutyltin dilaurate is 0.1 wt% of the reactants), react at 50 °C, monitor the NCO content using the dibutylamine method, stop the reaction when the NCO content reaches the theoretical value, wash, dry, and grind through a 400-mesh sieve to obtain modified attapulgite;

[0049] S3. Using methanol as a solvent, blend methyl acrylate and diethanolamine (methyl acrylate:diethanolamine = 1.2:1, n / n), react under nitrogen protection at 50 °C for 5 h, rotary evaporate to remove the solvent and unreacted methyl acrylate to obtain Product 1; using N,N-dimethylformamide as a solvent, blend Product 1 and trimethylolpropane (Product 1:trimethylolpropane = 3.5:1, n / n), add p-toluenesulfonic acid (0.6 wt% of the reactants), react at 110 °C for 4 h to obtain Product 2, cool to 50 °C, add isocyanate ethyl acrylate, p-hydroxyanisole, and dibutyltin dilaurate (Product 2:isocyanate ethyl acrylate = 1:6, n / n, p-hydroxyanisole is 0.5 wt% of the reactants, and dibutyltin dilaurate is 0.1 wt% of the reactants), react at 50 °C, monitor the NCO content using the dibutylamine method, stop the reaction when the NCO content reaches the theoretical value, and remove the solvent by vacuum distillation to obtain hyperbranched acrylate;

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

[0051] Example 2

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

[0053]

[0054] Among them,

[0055] The modified attapulgite is obtained by the reaction of isocyanate ethyl acrylate and acid-activated attapulgite clay;

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

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

[0058] Example 3

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

[0060]

[0061] Among them,

[0062] The modified attapulgite is obtained by the reaction of isocyanate ethyl acrylate and acid-activated attapulgite clay;

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

[0064] The preparation method of the above 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 to:

[0067] Using N,N-dimethylformamide as a solvent, blending the acid-activated attapulgite clay and silane coupling agent KH570 (acid-activated attapulgite clay: silane coupling agent KH570 = 1:5, m / m), reacting at 80 °C for 4 h, filtering, washing, drying, and grinding through a 400-mesh sieve to obtain modified attapulgite;

[0068] The usage amounts of other components 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 to:

[0071] Using N,N-dimethylformamide as the solvent, trimethylolpropane, ethyl isocyanate acrylate, p-methoxyphenol, and dibutyltin dilaurate (trimethylolpropane:ethyl isocyanate acrylate = 1:3, n / n, p-methoxyphenol is 0.5 wt% of the reactants, and dibutyltin dilaurate is 0.1 wt% of the reactants) were reacted at 50 °C. The NCO content was monitored by the di-n-butylamine method. When the NCO content reached the theoretical value, the reaction was stopped, and the solvent was removed by vacuum distillation to obtain branched acrylate;

[0072] Replace the same mass fraction of the hyperbranched acrylate with branched acrylate, and the dosages of other components and the preparation method are the same as those in Example 1.

[0073] Test Example

[0074] Perform performance tests 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 well to prepare a white slurry with a mass fraction of 2%. Use an SNB-2 type rotational viscometer to measure the viscosity at a rotational speed of 6 r / min.

[0077] Viscosity retention rate: The electrolyte resistance performance is expressed by the viscosity retention rate. Measure the viscosity of the thickener before and after adding 0.05 wt% of NaCl (solid) to the above white slurry at a rotational speed of 6 r / min. The viscosity retention rate = η 加NaCl后 / η 加NaCl前 , and 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, test the white slurry viscosity and viscosity retention rate according to the above method.

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

[0080] Table 1 Performance test results

[0081]

[0082]

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

[0084] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

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

Claims

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

2. The polyacrylic acid reverse emulsion thickener according to claim 1, wherein 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, docosyl acrylate, docosyl methacrylate, docosyl acrylate or docosyl methacrylate.

3. The polyacrylic acid inverse emulsion thickener according to claim 1, wherein 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 reverse emulsion thickener according to claim 1, wherein, 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 or azo initiators.

6. The polyacrylic acid reverse emulsion thickener according to claim 1, wherein The phase transfer agent is selected from one or more of Tween 80, isomeric tridecyl alcohol polyoxyethylene ether or fatty alcohol polyoxyethylene ether.

7. The preparation method of the polyacrylic acid inverse emulsion thickener according to any one of claims 1-6, characterized in that It includes the following steps: S1. Immerse attapulgite clay in an acid solution, heat and ultrasonicate to obtain acid-activated attapulgite clay; S2. Blend the acid-activated attapulgite clay, isocyanate acrylate and inhibitor, add a catalyst, and heat and react to obtain modified attapulgite; S3. React acrylate and diethanolamine under the protection of an inert gas by heating to obtain product 1; blend product 1 and trimethylolpropane, add p-toluenesulfonic acid, heat and react to obtain product 2, cool down, add isocyanate acrylate, inhibitor and catalyst, and heat and react to obtain hyperbranched acrylate; S4. Blend the modified attapulgite, acrylic acid and hydrophobic long-chain acrylate monomer, add the hyperbranched acrylate as a crosslinking agent, adjust the pH, add solvent oil and emulsifier, emulsify by high-speed stirring, then prepare the initiator into an aqueous solution and add it, heat and react, cool down after the reaction is completed, add the phase transfer agent, and stir evenly to obtain the polyacrylic acid inverse emulsion thickener.

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

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

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