Method for synthesizing high-viscosity and salt-resistant sodium polyacrylate thickener and preparation of three-in-one thickener

Abstract

The invention belongs to the field of polymer materials and specifically discloses a new method for synthesizing a high-viscosity and salt-resistant sodium polyacrylate thickener and a preparation method of the three-in-one thickener. The method comprises the following steps: weighing a certain amount of acrylic acid from which an inhibitor has been removed, adding a certain amount of pure water, neutralizing the solution with a certain concentration of NaOH solution, slowly adding the solution dropwise thereto while maintaining the temperature below 40°C to prepare a sodium acrylate neutralized solution with a neutralization degree of 80% and a solid content of 20% to 45%, and then using sodium sulfite (Na2SO3) and UV light curing technology to polymerize the solution under ultraviolet light irradiation to obtain the high-viscosity and salt-resistant sodium polyacrylate thickener. On this basis, the invention further prepares a three-in-one thickener with high viscosity, salt resistance and moisturizing functions, thereby expanding the application range of the sodium polyacrylate thickener.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials. Specifically, a sodium polyacrylate thickener with high viscosity and strong salt resistance is synthesized by a novel and simple method. On this basis, a three-in-one thickener with high viscosity, salt resistance and moisturizing functions is further prepared. Background Art

[0002] Thickeners come in a wide variety of types and are widely used. Synthetic polymer thickeners are the most widely used and have the largest sales volume. Among these synthetic polymer thickeners, polyacrylic acid thickeners are the most widely used. Because they are anionic polyelectrolytes, they are particularly sensitive to electrolyte salts. Once exposed to salts, their thickening ability is significantly reduced, and in severe cases, they can even become ineffective. Therefore, research on salt-tolerant sodium polyacrylate thickeners has become a hot topic. In summary, there are several ways to improve the salt resistance of thickeners. The first method is to introduce additives with certain salt resistance into the thickener formula as active monomers, so that it can be copolymerized with sodium acrylate to improve its salt resistance. For example, non-ionic monomers (acrylamide, N-vinyl pyrrolidone, etc.) are introduced. Since they are insensitive to electrolyte salts, their addition can improve the salt resistance of sodium polyacrylate thickeners. Another additive is a sulfonate monomer with strong salt resistance, such as 2-acrylamide-2-methylpropane sulfonic acid (AMPS). Because it contains a large molecular sulfonic acid group and an active double bond, it can be copolymerized with sodium acrylate, bringing the large molecular sulfonic acid group that is insensitive to salt into the sodium polyacrylate molecule, thereby improving its salt resistance. The second method is to introduce a small amount of hydrophobic groups into the hydrophilic sodium polyacrylate molecule to form a hydrophobic associating thickener. When dissolved in water, the hydrophobic groups are repelled by water molecules, causing them to aggregate. This aggregation can occur within the molecules (intramolecular association) or between molecules (when sufficient numbers are present) (intermolecular association). Once intermolecular association occurs, the entire system forms a dynamic physical cross-linked network, significantly increasing viscosity. The addition of electrolytes increases the polarity of the aqueous solution, strengthening the intermolecular associations and the number of cross-linked networks. This increases the viscosity and may even exceed that without electrolytes. The authors introduced tetradecyl methacrylate and hexadecyl methacrylate into a sodium acrylate solution and used a micellar copolymerization method, initiating them with ultraviolet light, to form a hydrophobically associating sodium polyacrylate thickener. These results were published in the following two papers: "Synthesis and Properties of a Hydrophobically Associating Sodium Acrylate Thickener" and "Synthesis and Properties of a Hydrophobically Associating Sodium Acrylate Thickener with Tetradecyl Methacrylate." The third method is to increase the hydrophilicity of the thickener. The hydrophobic monomer introduced above is fatty alcohol methacrylate. Because of its poor water solubility, a highly hydrophilic polyoxyethylene ether group - (CH2-CH2-O) can be introduced into it. nSynthesized fatty alcohol polyoxyethylene ether (meth) acrylate additives RO-(CH2-CH2-O) n -CO-CH=CH2, so that the long carbon chain hydrophobic group R can be introduced, and the hydrophilic group -(CH2-CH2-O) can also be introduced at the same time n Increasing the degree of polymerization increases its hydrophilicity. Furthermore, its double-chain structure makes it easily copolymerizable with sodium acrylate. The authors used a fatty alcohol (with a carbon chain length of 16-18) polyoxyethylene ether (degree of polymerization n=25) methacrylate to copolymerize with sodium acrylate under UV light, resulting in a sodium polyacrylate thickener with high viscosity and salt tolerance. This is described in detail in the paper "Study on the Hydrophobic Association of Fatty Alcohol Polyoxyethylene Ether Methacrylate with Sodium Acrylate Thickener." A fourth approach involves synthesizing amphoteric polymers, which include neutral amphoteric polymers and polymers containing both positive and negative charges within their molecular chains. In pure water, the electrostatic attraction between the positive and negative charges within these polymers cancels out, causing the molecules to shrink into clusters, reducing water volume and viscosity. However, upon addition of electrolyte salts, these ions dissociate in water, releasing positive and negative ions that adsorb onto the negatively and positively charged chains within the amphoteric polymer, shielding them and enhancing their interaction with water molecules. This stretches the molecular chains and increases viscosity, exhibiting distinct "anti-polyelectrolyte" behavior.

[0003] In summary, the first three methods for improving the salt tolerance of thickeners all involve modifying the base thickener by adding modifying additives, while the fourth method involves modifying the thickener's monomers to synthesize an amphoteric polymer with a unique structure. However, these methods are relatively complex and require tedious preparation, making them difficult to promote. Summary of the Invention

[0004] In response to the above problems, the present invention discloses a new method for synthesizing a high-viscosity and salt-resistant sodium polyacrylate thickener and its three-in-one thickener preparation method. Without changing the basic formula of the sodium polyacrylate thickener and without synthesizing another monomer with a special structure, UV light curing technology is used, but instead of adding a commonly used UV photoinitiator, a small amount of reducing agent sodium sulfite (Na2SO3) is added to prepare a sodium polyacrylate thickener with good salt resistance and high viscosity. This is a simple and easy new method.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] A new method for synthesizing a high-viscosity and salt-resistant sodium polyacrylate thickener comprises the following steps: weighing a certain amount of acrylic acid from which the polymerization inhibitor has been removed, adding a certain amount of pure water, then neutralizing it with a certain concentration of NaOH solution, slowly adding it dropwise while maintaining the temperature below 40°C to prepare a sodium acrylate neutralized solution with a neutralization degree of 80% and a solid content of 20% to 45%, then adding sodium sulfite (Na2SO3), and using UV light initiation technology to carry out a polymerization reaction under ultraviolet light irradiation, thereby obtaining a high-viscosity and salt-resistant sodium polyacrylate thickener.

[0007] The invention discloses a high-viscosity and salt-resistant sodium polyacrylate thickener, which is prepared by the above method.

[0008] On this basis, in order to increase the multifunctionality of the thickener, a moisturizer is further introduced. The present invention discloses a preparation method of a three-in-one thickener with high viscosity, high salt resistance and moisturizing ability, comprising the following steps:

[0009] S1. The neutralization degree of the above-prepared product is 80%, the solid content is 20% to 45%, and an alkaline neutralization solution containing Na2SO3 is used as the basis; xanthan gum, pregelatinized potato starch, one of hydroxyethyl cellulose or trehalose is then added, and a three-in-one sodium acrylate neutralization solution is configured;

[0010] S2. When the alkaline sodium acrylate neutralized solution begins to turn turbid from transparent, take it out and place it directly under a high-pressure mercury lamp. Adjust the distance between the mercury lamp and the sample from far to near until the reaction is completed after 2 hours. A transparent gel-like three-in-one product is obtained. Chop it into a 0.2wt% aqueous solution or further granulate it, dry it at 85°C to constant weight, and then crush it. Sieve it through a 100 mesh or larger sieve to obtain a white product, which is the three-in-one thickener.

[0011] Furthermore, the amount of Na2SO3 added (calculated on a monomer basis) is 0.1-8.0 wt%, preferably 0.5-5.0 wt%.

[0012] Furthermore, the added amount of the xanthan gum, pregelatinized potato starch, hydroxyethyl cellulose or trehalose (calculated on a monomer basis) is 0.2-5.0 wt%, preferably 0.5%-3.0 wt%.

[0013] The present invention also discloses a three-in-one thickener, which is prepared by any of the methods described above.

[0014] Compared with the existing technology, the present invention has the following advantages and beneficial effects:

[0015] This study employed an unconventional approach to synthesize a sodium polyacrylate thickener with high viscosity and salt tolerance. While employing photocuring technology, it eschewed the commonly used UV curing agents and thermal curing agents. Instead, it employed the lesser-known sodium sulfite (Na2SO3), which lacks UV absorption. Sodium sulfite is typically used as a reducing agent in redox initiator systems, reacting with peroxides to release reactive groups, enabling polymerization of sodium acrylate at lower temperatures. Alternatively, it can serve as a chain transfer agent, allowing for a more gradual polymerization reaction. Following extensive screening, we selected it as the sole initiator, enabling the polymerization of sodium acrylate under UV light to form a slightly cross-linked thickener. This structure exhibits a distinct "rod climbing" phenomenon when stirred in aqueous solution: the central liquid level climbs upward along the stirring rod, while the peripheral liquid level descends, a characteristic of viscoelastic fluids. This lightly cross-linked thickener forms a soft network in its aqueous solution, which not only increases the viscosity of the solution, but also protects the negatively charged carboxyl groups of sodium acrylate from or reduces the Na + The strength of the network structure depends on the strength of the crosslinks, which is affected by the amount of Na2SO3 added. If too little is added, the crosslinks fail to form, resulting in stickiness but no elasticity, and no salt resistance. Too much, and the crosslinked network becomes too strong and elastic, reducing solubility in solution and causing swelling. Therefore, finding the right amount of Na2SO3, along with the intensity and duration of UV light exposure, is crucial.

[0016] In addition, on the basis of high viscosity salt-tolerant sodium polyacrylate thickener, introduce the additive with good moisture retention property and make it to become three-in-one thickener.It should be understood that not all additives with moisture retention property can be used, because the addition of some additives can affect the carrying out of polymerization reaction, and some can make the product viscosity decline, or make its salt resistance decline or even disappear.Therefore, some suitable good moisture retention additives will be screened out and their optimal addition amount will be found out, because the addition amount is too much and the viscosity and anti-inflammatory property of the product will decline, and too little and can not play moisturizing effect, so an intermediate equilibrium value will be found.The present invention adopts a kind of simple and easy novel method to synthesize high viscosity, salt-tolerant sodium polyacrylate thickener, introduces wetting agent on this basis, prepares high viscosity salt-tolerant moisturizing three-in-one sodium polyacrylate thickener, thereby widens its range of application. DETAILED DESCRIPTION

[0017] The technical solution of the present invention:

[0018] The first step was to synthesize a highly viscous and salt-resistant sodium polyacrylate thickener. A base glue was selected as a sodium acrylate neutralizer with an 80% neutralization degree and a solids content of 20% to 45%. Four samples were then added with Na2SO3 at 0% (sample 0), 0.6% (sample a), 2.6% (sample b), and 5.2% (sample c). The percentage of Na2SO3 added was based on the monomer content. The 0% addition was the control sample. Instead of adding Na2SO3, a UV photoinitiator at 2.6 parts per million (monomer-based) was added. Polymerization was conducted at a distance from a high-pressure pump lamp, resulting in a transparent gel-like product. This solution was then prepared into an aqueous solution with a solids content of 0.2%. Its viscosity, η, was measured using an NPJ-1 rotary viscometer at 6 rpm, as well as its salt resistance (expressed as the viscosity retention, μ%, based on the neutralizer solution at 0.15% NaCl). The data obtained are as follows:

[0019] Table 1 Effect of Na2SO3 addition on the viscosity of 0.2% thickener aqueous solution

[0020]

[0021] Table 2 Effect of Na2SO3 addition on viscosity retention μ% of 0.2% thickener aqueous solution (NaCl addition 0.15% - based on neutralization solution)

[0022]

[0023] The data in the table shows that products obtained by UV photopolymerization with the addition of Na2SO3 exhibit high viscosity and salt resistance, particularly superior to commercially available sodium polyacrylate thickeners. The optimal Na2SO3 addition level is 0.6%. Above this level, both η and μ% values show a slow decline, due to the excess Na2SO3 acting as a chain transfer agent.

[0024] In the second step, based on the high-viscosity and salt-resistant thickener, additives with good moisturizing properties were introduced, and their water retention rate was used as a measure of moisturizing performance. Four additives with better performance were screened out through measurement: xanthan gum, pregelatinized potato starch, hydroxyethyl cellulose and trehalose, and their appropriate addition amount of 0.5%-3.0% was found to synthesize a three-in-one sodium polyacrylate thickener with high viscosity, salt tolerance and moisturizing properties.

[0025] If it is a commercial product, the gel-like three-in-one sodium polyacrylate thickener can be further processed by cutting it into small particles, then drying it in an oven at 85°C to constant weight, crushing it and sieving it to a size of 100 mesh or more to obtain a white powder, and packaging it.

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below through examples. However, it should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0028] Example 1

[0029] The first step is to prepare the basic neutralizing solution. Weigh a certain amount of acrylic acid from which the inhibitor has been removed, add a certain amount of pure water, and then neutralize it with a certain concentration of caustic soda (NaOH) solution. Slowly add it dropwise, keeping the temperature below 40°C, and prepare a sodium acrylate neutralizing solution with a neutralization degree of 80% and a solid content of 20%~45% as the basic liquid.

[0030] In the second step, weigh 100g of the above-mentioned basic neutralizing solution, add 1.2g of 20% concentration Na2SO3 aqueous solution, stir thoroughly, then add 5.0g of 10% concentration xanthan gum solution (prepare it overnight to allow it to fully dissolve), and stir thoroughly to prepare a three-in-one sodium acrylate neutralizing solution with a Na2SO3 content of 0.63% (monomer basis) and a xanthan gum content of 1.3% (monomer basis).

[0031] In the third step, when the neutralized solution begins to turn turbid from transparent, take it out and place it directly under a high-pressure mercury lamp. The distance between the mercury lamp and the sample is adjusted from far to near. After the reaction is completed, a transparent gel-like three-in-one product is obtained. The product is chopped into pieces and prepared into a 0.2% aqueous solution. The viscosity η, viscosity retention rate μ% and water retention rate P% are then measured. The obtained data are listed in Table 3.

[0032] Example 2

[0033] Weigh 100g of the above-mentioned basic neutralizing solution, add 1.9g of a 20% aqueous solution of NaSO, stir thoroughly, then add 5.0g of a 10% aqueous solution of pregelatinized potato starch (prepared overnight to allow for full swelling), and stir thoroughly again. This creates a three-in-one sodium acrylate neutralizing solution with a NaSO content of 1.00% and a pregelatinized starch content of 1.31%. UV curing polymerization was performed using the same steps as in Example 1 to produce a three-in-one thickener. Its η, μ%, and P% values were measured and are listed in Table 3.

[0034] Example 3

[0035] Weigh 100 g of the above-mentioned basic neutralizing solution, add 2.5 g of a 20% aqueous solution of Na2SO3, stir evenly, then add 2.0 g of a 10% aqueous solution of hydroxyethyl cellulose (prepared overnight to allow it to fully dissolve), and stir evenly to prepare an alkaline sodium acrylate neutralizing solution with a Na2SO3 content of 1.31% and a hydroxyethyl cellulose content of 0.52%. UV light curing polymerization is carried out according to the steps shown in Example 1 to prepare a three-in-one thickener, which is then prepared into a 0.2% aqueous solution. The η, μ% and P% values are measured, and the data are listed in Table 3.

[0036] Example 4

[0037] Weigh 100g of the above basic neutralization solution, add 3.0g of 20% concentration Na2SO3 aqueous solution, and stir evenly.

[0038] Then, 1.0 g of trehalose was added and stirred to dissolve to prepare a three-in-one sodium acrylate neutralized solution with a Na2SO3 content of 1.57% and a trehalose content of 2.64%. UV light curing polymerization was carried out in the same manner as in Example 1 to prepare a three-in-one thickener. The solution was then prepared into a 0.2% aqueous solution, and its η, μ% and P% were measured. The obtained data are listed in Table 3.

[0039] Example 5

[0040] This is a comparative sample. Only 1.57% Na2SO3 was added to the basic neutralizing solution. The process was exactly the same as the previous example. The obtained data are listed in Table 3.

[0041] Table 3 Performance of three-in-one thickener and commercially available sodium polyacrylate thickener (0.2% aqueous solution)

[0042]

[0043] From the data in Table 3, it can be seen that (1) the performance (viscosity, salt resistance, and moisturizing properties) of all sodium polyacrylate thickeners containing Na2SO3 systems are superior to those of commercially available sodium polyacrylate thickeners. (2) In the (sodium acrylate-Na2SO3) thickener system, the addition of a humectant has little effect on its original viscosity η. (3) The addition of a humectant will reduce the μ% value of the three-in-one thickener, that is, its salt resistance is reduced, but its moisturizing properties are significantly improved. Therefore, it is particularly important to find a balance between moisturizing properties and salt resistance, so that the three-in-one thickener has good moisturizing properties and salt resistance at the same time.

[0044] (7) Supplementary explanation of performance test

[0045] 1. Viscosity test: using NDJ-1 rotary viscometer, the speed is 6 rpm (6 revolutions per minute), #2 rotor, the solution concentration is 0.2%;

[0046] 2. Salt resistance test, the viscosity retention rate is μ% to represent its salt resistance, which is defined as

[0047] μ%=n / ηx100%, where η is the viscosity of the aqueous solution when the concentration is 0.2% without adding electrolyte salt.

[0048] n is the viscosity measured after adding 0.15% NaCl salt, so the larger the μ% value, the less the viscosity of the solution decreases after adding salt, and the stronger the salt resistance.

[0049] 3 Moisturizing performance test. The specific determination method is to weigh 30g of double fly powder, add 10g of 0.2% glue solution, stir thoroughly, and then put it in a sealed jar in a dark place and let it age for 30 minutes to allow the double fly powder to fully absorb the glue. After that, put the wetted double fly powder micelle on a flat plate with a certain surface area, spread it evenly and press it lightly, weigh its weight m1, place it in a ventilated space with a certain humidity and temperature, and after 48 hours, weigh its weight m2 again. The water retention rate P% of the test sample can be calculated according to the following formula:

[0050] P%=(1-(m1-m2) / m0)x100%

[0051] Where m0 is the water content in the sample. It can be seen that the greater the water retention rate P%, the better the moisturizing performance. However, this is only a relative data, compared with the commercial sodium polyacrylate thickener and the sample without moisturizer. Because the water retention rate is related to the surface area of the flat plate and the humidity, temperature and ventilation conditions of the storage space, it is only a comparative value.

[0052] In summary: The present invention adopts a simple and easy new method to synthesize highly viscous and salt-resistant sodium polyacrylate

[0053] Thickener, on this basis, a humectant was introduced to prepare a high-viscosity, salt-resistant and moisturizing three-in-one sodium polyacrylate thickener, thereby broadening its application range.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or equivalent structural or equivalent process transformations made using the contents of the present invention's description and drawings, and direct or indirect application of the above technical solutions to other related technical fields, are all included in the scope of protection of the patent of the present invention.

Claims

1. A method for synthesizing a highly viscous and salt-resistant sodium polyacrylate thickener, characterized in that: The following steps are involved: Weigh a certain amount of acrylic acid from which the polymerization inhibitor has been removed, add a certain amount of pure water, and then neutralize it with a certain concentration of NaOH solution. Slowly add it dropwise while maintaining the temperature below 40°C to prepare a sodium acrylate neutralization solution with a neutralization degree of 80% and a solid content of 20%~45%. Then add sodium sulfite (Na2SO3) and polymerize under ultraviolet light to obtain a high-viscosity and salt-resistant sodium polyacrylate thickener.

2. A high-viscosity and salt-resistant sodium polyacrylate thickener, characterized in that: Prepared by the method of claim 1.

3. A method for preparing a three-in-one thickener, characterized in that: The following steps are involved: S1. The neutralization degree of 80% and solid content of 20% to 45% alkaline neutralization solution prepared in claim 1 is added with Na2SO3 and stirred thoroughly; xanthan gum, pregelatinized potato starch, hydroxyethyl cellulose or trehalose are then added to prepare a three-in-one sodium acrylate neutralization solution; S2. When the three-in-one sodium acrylate neutralized solution begins to turn turbid from transparent, take it out and place it directly under a high-pressure mercury lamp. Adjust the distance between the mercury lamp and the sample from far to near until the reaction is completed after 2 hours. A transparent gel-like three-in-one product is obtained. Chop it into a 0.2wt% aqueous solution or further granulate it, dry it at 85°C to constant weight, then crush it and sieve it through 100 mesh or above to obtain a white product, which is the three-in-one thickener.

4. The method for preparing a three-in-one thickener according to claim 3, characterized in that: The amount of Na2SO3 added is 0.1-8.0 wt% calculated on a monomer basis.

5. The method for preparing a three-in-one thickener according to claim 3, characterized in that: The added amount of the xanthan gum, pregelatinized potato starch, hydroxyethyl cellulose or trehalose is 0.2-5.0 wt % calculated on a monomer basis.

6. A three-in-one thickener, characterized in that: The method is prepared by any one of claims 3 to 5.

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