Poly alpha-hydroxy acrylic acid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of papermaking, and discloses poly alpha-hydroxy acrylic acid which comprises an alpha-hydroxy acrylic acid unit and an anionic polymerizable surfactant unit with a sulfonic acid group, the molar ratio of the alpha-hydroxy acrylic acid unit to the polymerizable surfactant unit is 1: (0.05-0.15). The polymer not only has an alpha-hydroxy acrylic acid unit, but also has a sulfonic acid group, the variety of chelating groups of the polymer is enriched by introducing the sulfonic acid group, and the sulfonic acid group is copolymerized into a chain segment, so that compared with hydroxyl or carboxyl of the polymer, the polymer has a more obvious steric hindrance effect; and molecular lactonization in the bleaching operation process can be inhibited, and the performance reduction of the polymer is effectively delayed, so that the polymer continuously keeps relatively excellent hydrogen peroxide stability. The invention also aims to provide a preparation method and application of the poly-alpha-hydroxy acrylic acid.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, and in particular to poly-α-hydroxy acrylic acid, a preparation method thereof and application thereof. Background Art

[0002] Pulp bleaching technology has undergone a transformation from traditional chlorine-containing bleaching (such as elemental chlorine and hypochlorite) to environmentally friendly chlorine-free bleaching (ECF and TCF). The core challenge lies in balancing bleaching efficiency, fiber damage and environmental protection requirements: although the early chlorine bleaching process was highly efficient, it produced highly toxic dioxins and was gradually replaced by chlorine dioxide, ozone and hydrogen peroxide.

[0003] Among them, hydrogen peroxide is the key oxidant for chlorine-free bleaching of pulp and is widely used in multi-stage bleaching processes such as oxygen delignification and alkaline extraction. Its core advantages are outstanding environmental protection, little fiber damage and stable bleaching effect. It is also suitable for multiple raw material systems such as wood pulp and bamboo pulp. However, it requires an alkaline high temperature environment (pH 10-12, 80-95℃) and silicate stabilizers to control decomposition, which has the disadvantages of high energy consumption and metal ion sensitivity (Fe 3+ / Mn 2+ Concentration > 0.5ppm accelerates decomposition) and wastewater pH neutralization problems.

[0004] Prior Art 1: Japanese patent application JP2001289541 discloses a hydrogen peroxide stabilizer for bleaching, scouring, and soaping fibers. The stabilizer exhibits excellent alkali resistance and hydrogen peroxide stabilization, maintaining hydrogen peroxide bleaching performance even in the presence of high alkali concentrations. The stabilizer is also capable of improving fiber whiteness. The stabilizer comprises: (a) a hydrogen peroxide stabilizer obtained by free radical polymerization of poly-α-hydroxyacrylic acid and / or its salts with at least one monomer selected from acrylic acid, methacrylic acid, maleic acid, and their salts; and (b) a water-soluble magnesium compound, wherein the weight ratio of the polymer to magnesium is 1:1 to 45:1.

[0005] Prior art 1 uses poly-α-hydroxy acrylic acid and / or its salts to polymerize at least one monomer selected from acrylic acid, methacrylic acid, maleic acid and their salts to achieve the effect of stabilizing hydrogen peroxide.

[0006] Poly-α-hydroxy acrylic acid exhibits significant advantages in paper bleaching, including stabilizing the activity of bleaching agents by chelating metal ions, synergistically degrading chromophores to improve decolorization efficiency, adsorbing and dispersing impurities to improve bleaching uniformity, and protecting fibers to reduce oxidative damage. It also has both biodegradability and synergy in wastewater treatment, meeting the needs of green papermaking. However, its application requires precise control of pH, temperature and molecular structure to adapt to different bleaching systems, and there are still optimization challenges for its stability in high-concentration metal ion environments. Summary of the Invention

[0007] One of the objectives of the present invention is to provide a poly-α-hydroxy acrylic acid. In addition to having α-hydroxy acrylic acid units, the polymer also has sulfonic acid groups. By introducing sulfonic acid groups, the types of its chelating groups are enriched. Moreover, the sulfonic acid groups copolymerized into the chain segments have a more significant steric hindrance than the hydroxyl or carboxyl groups possessed by the polymer itself, which can inhibit intramolecular esterification during the bleaching process, effectively delay the degradation of polymer performance, and enable the polymer to continuously maintain relatively excellent hydrogen peroxide stability.

[0008] Another object of the present invention is to provide a preparation method and use of poly-α-hydroxy acrylic acid.

[0009] To achieve the above objectives, the present invention provides a poly-α-hydroxy acrylic acid, comprising an α-hydroxy acrylic acid unit and an anionic polymerizable surfactant unit having a sulfonic acid group; the molar ratio of the α-hydroxy acrylic acid unit to the polymerizable surfactant unit is 1:0.05 to 0.15.

[0010] The present invention introduces a monomer having a sulfonic acid group into the poly-α-hydroxy acrylic acid chain segment by copolymerization. The purpose of introducing the sulfonic acid group is twofold:

[0011] 1. The sulfonic acid group has a significant chelating ability for metal ions; it has a strong chelating property for divalent or higher valent metal ions, such as Ca 2+ Mg 2+ 、Cu 2+ and Mn 2+ ;

[0012] Second, the steric hindrance effect of the sulfonic acid group is significantly stronger than that of the carboxyl and hydroxyl groups in poly-α-hydroxy acrylic acid. It is interspersed in the chain segments and can inhibit the esterification phenomenon within and between chains, delaying the decrease in the polymer's stabilization efficiency for hydrogen peroxide during the papermaking process.

[0013] In the above-mentioned poly-α-hydroxy acrylic acid, the polymerizable surfactant unit is sodium methallyl sulfonate and / or sodium allyl sulfonate.

[0014] In the above-mentioned poly-α-hydroxy acrylic acid, the poly-α-hydroxy acrylic acid is obtained by soap-free emulsion polymerization.

[0015] At the same time, the present invention also discloses a method for preparing the poly-α-hydroxy acrylic acid as described above, comprising the following steps:

[0016] Step 1: Add water, a polymerizable surfactant, and α-chloroacrylic acid to a reaction vessel under an inert atmosphere, stir evenly to form a uniform emulsion, and heat the reaction system to a constant temperature of 70-85° C.;

[0017] Step 2: Add the initiator solution to the reaction system of step 1 for a reaction time of 3 to 6 hours;

[0018] Step 3: After the reaction is completed, filter and collect the polymer solid;

[0019] Step 4: Add the polymer solid into an alkaline aqueous solution for hydrolysis to obtain poly-α-hydroxy acrylic acid.

[0020] In the above-mentioned method for preparing poly-α-hydroxy acrylic acid, the initiator is a peroxidation initiator; the amount of the initiator used is 0.5 to 2 wt% of the total weight of the polymerizable surfactant and α-chloroacrylic acid.

[0021] In the above-mentioned method for preparing poly-α-hydroxy acrylic acid, the initiator is sodium persulfate, potassium persulfate or ammonium persulfate.

[0022] In the above-mentioned method for preparing poly-α-hydroxy acrylic acid, the weight ratio of the total weight of the polymerizable surfactant and α-chloroacrylic acid to water is 100:300-500.

[0023] In the above-mentioned method for preparing poly-α-hydroxy acrylic acid, the hydrolysis temperature in step 4 is 75-85° C., and the hydrolysis time is not less than 2 hours.

[0024] Finally, the present invention also discloses the use of any of the above-mentioned poly-α-hydroxy acrylic acid to prepare a hydrogen peroxide stabilizer.

[0025] Beneficial effects

[0026] Compared with the prior art, the present invention has at least the following advantages:

[0027] The present invention enriches the types of chelating groups by introducing sulfonic acid groups, and the sulfonic acid groups are copolymerized into the chain segments. Compared with the hydroxyl or carboxyl groups possessed by the polymer itself, the sulfonic acid groups have a more obvious steric hindrance effect, which can inhibit intramolecular esterification during the bleaching operation, effectively delay the degradation of polymer performance, and enable the polymer to continuously maintain relatively excellent hydrogen peroxide stability. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the embodiments, but this does not constitute any limitation to the present invention. Any limited modifications made within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0029] In order to explain the technical content of the present invention in detail, further description will be given below in conjunction with the embodiments.

[0030] Example 1

[0031] The preparation method of poly-α-hydroxy acrylic acid comprises the following steps:

[0032] Step 1: Add 341 g of water, 7.2 g of sodium allyl sulfonate (0.05 mol), and 106.5 g of α-chloroacrylic acid (1 mol) to a reaction vessel under an inert atmosphere, stir evenly to form a uniform emulsion, and heat the reaction system to 80° C. and maintain the temperature.

[0033] Step 2: Add 0.57 g of sodium persulfate solution to the reaction system of step 1 for 3 hours;

[0034] Step 3: After the reaction is completed, filter and collect the polymer solid;

[0035] Step 4: Add the polymer solid to a 1.5 mol / L sodium hydroxide aqueous solution for hydrolysis at a hydrolysis temperature of 80° C. for 3 h to obtain poly-α-hydroxy acrylic acid.

[0036] Example 2

[0037] The preparation method of poly-α-hydroxy acrylic acid comprises the following steps:

[0038] Step 1: Add 483 g of water, 14.4 g of sodium allyl sulfonate (0.1 mol), and 106.5 g of α-chloroacrylic acid (1 mol) to a reaction vessel under an inert atmosphere, stir evenly to form a uniform emulsion, and heat the reaction system to and maintain the temperature at 80°C.

[0039] Step 2: Add 1.21 g of sodium persulfate solution to the reaction system of step 1 for 4 hours;

[0040] Step 3: After the reaction is completed, filter and collect the polymer solid;

[0041] Step 4: Add the polymer solid to a 1.5 mol / L sodium hydroxide aqueous solution for hydrolysis at a hydrolysis temperature of 85° C. for 4 h to obtain poly-α-hydroxy acrylic acid.

[0042] Example 3

[0043] The preparation method of poly-α-hydroxy acrylic acid comprises the following steps:

[0044] Step 1: Add 640 g of water, 21.6 g of sodium allyl sulfonate (0.15 mol), and 106.5 g of α-chloroacrylic acid (1 mol) to a reaction vessel under an inert atmosphere, stir evenly to form a uniform emulsion, and heat the reaction system to and maintain the temperature at 80°C.

[0045] Step 2: Add 2.56 g of sodium persulfate solution to the reaction system of step 1 for 5 hours;

[0046] Step 3: After the reaction is completed, filter and collect the polymer solid;

[0047] Step 4: Add the polymer solid to a 1.5 mol / L sodium hydroxide aqueous solution for hydrolysis at a hydrolysis temperature of 75° C. for 6 h to obtain poly-α-hydroxy acrylic acid.

[0048] Example 4

[0049] The preparation method of poly-α-hydroxy acrylic acid comprises the following steps:

[0050] Step 1: Add 640 g of water, 15.8 g of sodium methyl propylene sulfonate (0.1 mol), and 106.5 g of α-chloroacrylic acid (1 mol) to a reaction vessel under an inert atmosphere, stir evenly to form a uniform emulsion, and heat the reaction system to and maintain the temperature at 85°C.

[0051] Step 2: Add 1.21 g of sodium persulfate solution to the reaction system of step 1 for 4 hours;

[0052] Step 3: After the reaction is completed, filter and collect the polymer solid;

[0053] Step 4: Add the polymer solid to a 1 mol / L sodium hydroxide aqueous solution for hydrolysis at a hydrolysis temperature of 75° C. for 6 h to obtain poly-α-hydroxy acrylic acid.

[0054] Example 5

[0055] The preparation method of poly-α-hydroxy acrylic acid comprises the following steps:

[0056] Step 1: Add 640 g of water, 23.7 g of sodium methyl propylene sulfonate (0.15 mol), and 106.5 g of α-chloroacrylic acid (1 mol) to a reaction vessel under an inert atmosphere, stir evenly to form a uniform emulsion, and heat the reaction system to and maintain the temperature at 70°C.

[0057] Step 2: Add 1.95 g of sodium persulfate solution to the reaction system of step 1 for 5 hours;

[0058] Step 3: After the reaction is completed, filter and collect the polymer solid;

[0059] Step 4: Add the polymer solid to a 2 mol / L sodium hydroxide aqueous solution for hydrolysis at a hydrolysis temperature of 85° C. for 4 h to obtain poly-α-hydroxyacrylic acid.

[0060] Comparative Example 1

[0061] The preparation method of poly-α-hydroxy acrylic acid comprises the following steps:

[0062] Step 1: Add 426 g of water and 106.5 g of α-chloroacrylic acid (1 mol) to a reaction vessel under an inert atmosphere, stir evenly, and heat the reaction system to and maintain the temperature at 80°C;

[0063] Step 2: Add 1.07 g of sodium persulfate solution to the reaction system of step 1 for 4 hours;

[0064] Step 3: After the reaction is completed, filter and collect the polymer solid;

[0065] Step 4: Add the polymer solid to a 1.5 mol / L sodium hydroxide aqueous solution for hydrolysis at a hydrolysis temperature of 85° C. for 4 h to obtain poly-α-hydroxy acrylic acid.

[0066] Performance testing

[0067] 1. Pulp bleaching performance test

[0068] Take the pulp from the medium-concentration bleaching of a chemical pulp plant, and the pulp parameters of the high-concentration bleaching operation condition are as follows Table 1;

[0069] Table 1 Pulp parameters of a chemical pulp plant under high-consistency bleaching operation conditions

[0070]

[0071] The following experimental steps were used to test the bleaching performance of stabilized hydrogen peroxide:

[0072] (1) Weigh a certain amount of pulp into a polyethylene ziplock bag, add a certain amount of dilution water, add the required bleaching reagent according to the amount of reagent required for bleaching, knead for 5 minutes and then put it into a water bath at 95℃ and heat for 90 minutes.

[0073] (2) After the bleaching time is up, weigh 11g of slurry in sequence, take two from each bag, add 300g of purified water to each, and stir and disperse with a blender.

[0074] (3) Stir for 5 minutes and then filter.

[0075] (4) After filtration, press the tablets for 3 minutes and then dry them naturally under constant temperature and humidity conditions, and then test the whiteness.

[0076] (5) After weighing each bag of pulp, squeeze out the filtrate and measure the residual hydrogen peroxide.

[0077] The test results are shown in Table 2 below;

[0078] Table 2 Bleaching performance test of hydrogen peroxide stabilizer

[0079]

[0080] From the above data, it can be seen that compared with Comparative Example 1, Examples 1-5 introduce sulfonic acid groups into the molecular chain of poly-α-hydroxyacrylic acid through copolymerization, and the bleaching performance of hydrogen peroxide under stable alkaline conditions is improved. Comparative Examples 1-3 show that when the sulfonic acid groups are introduced within a certain range, the bleaching performance increases with the increase of the sulfonic acid groups in the molecular chain. Further increasing the number of introduced sulfonic acid groups no longer improves the bleaching performance but rather decreases. Therefore, it can be concluded that the amount of introduced sulfonic acid groups should be within a certain range.

[0081] 2. Determination of Metal Ion Chelation Ability

[0082] The metal ion chelating agent performance of the products of Examples 1-5 and Comparative Example 1 was tested according to the method of GB / T 21884-2008 for determination of chelating ability of textile printing and dyeing auxiliaries. The test results are shown in Table 3 below.

[0083] Table 3 Metal ion chelation performance

[0084] Calcium chelation value mg / L Iron chelation value mg / L Example 1 72 56 Example 2 78 63 Example 3 73 59 Example 4 76 62 Example 5 70 58 Comparative Example 1 65 44

[0085] From the above data, it can be seen that the metal ion chelating performance of Examples 1-5 is significantly improved compared with Comparative Example 1, and the trend of the metal ion chelating performance is the same as the trend of the stable alkaline hydrogen peroxide bleaching performance, indicating that the solution provided by the present invention can effectively improve the practical application effect of poly-α-hydroxy acrylic acid.

[0086] The embodiments presented herein are merely embodiments selected from a combination of all possible embodiments. The appended claims should not be limited by the embodiments describing the present invention. Some numerical ranges used in the claims include subranges therein, and variations in these ranges should also be covered by the appended claims.

Claims

1. A poly-α-hydroxy acrylic acid, characterized in that The invention comprises an α-hydroxy acrylic acid unit and an anionic polymerizable surfactant unit having a sulfonic acid group; the molar ratio of the α-hydroxy acrylic acid unit to the polymerizable surfactant unit is 1:0.05-0.

15.

2. The poly-α-hydroxy acrylic acid according to claim 1, characterized in that The polymerizable surfactant unit is sodium methyl allyl sulfonate and / or sodium allyl sulfonate.

3. The poly-α-hydroxy acrylic acid according to claim 1, characterized in that The poly-α-hydroxy acrylic acid is obtained by soap-free emulsion polymerization.

4. A method for preparing poly-α-hydroxy acrylic acid according to any one of claims 1 to 3, characterized in that: The steps include: Step 1: Add water, a polymerizable surfactant, and α-chloroacrylic acid to a reaction vessel under an inert atmosphere, stir evenly to form a uniform emulsion, and heat the reaction system to a constant temperature of 70-85° C.; Step 2: Add the initiator solution to the reaction system of step 1 for a reaction time of 3 to 6 hours; Step 3: After the reaction is completed, filter and collect the polymer solid; Step 4: Add the polymer solid into an alkaline aqueous solution for hydrolysis to obtain poly-α-hydroxy acrylic acid.

5. The method for preparing poly-α-hydroxy acrylic acid according to claim 4, wherein The initiator is a peroxidation initiator; the amount of the initiator used is 0.5 to 2 wt% of the total weight of the polymerizable surfactant and α-chloroacrylic acid.

6. The method for preparing poly-α-hydroxy acrylic acid according to claim 5, wherein The initiator is sodium persulfate, potassium persulfate or ammonium persulfate.

7. The method for preparing poly-α-hydroxy acrylic acid according to claim 4, wherein The weight ratio of the total weight of the polymerizable surfactant and α-chloroacrylic acid to water is 100:300-500.

8. The method for preparing poly-α-hydroxy acrylic acid according to claim 4, wherein The hydrolysis temperature in step 4 is 75-85° C., and the hydrolysis time is not less than 2 hours.

9. Use of the poly-α-hydroxy acrylic acid according to any one of claims 1 to 3 in preparing a hydrogen peroxide stabilizer.

Images