Hydrogen peroxide stabilizer

Abstract

The invention belongs to the technical field of papermaking bleaching, and discloses a hydrogen peroxide stabilizer which comprises the following components in parts by weight: 80-90 parts of poly-alpha-hydroxy acrylic acid; and 10-20 parts of polyvinyl alcohol. According to the stabilizer, poly-alpha-hydroxy acrylic acid and polyvinyl alcohol are combined for use, so that a gel phenomenon formed by lactonization of the poly-alpha-hydroxy acrylic acid due to an over-alkaline environment is relieved.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking bleaching, and in particular to a hydrogen peroxide stabilizer. Background Art

[0002] Hydrogen peroxide (H2O2) is widely used in the pulp bleaching process due to its strong oxidizing properties and environmentally friendly properties. However, trace metal ions (such as iron, copper, and manganese) remaining in the pulp can catalyze the rapid decomposition of hydrogen peroxide, leading to loss of active ingredients, reduced bleaching efficiency, and even affecting the whiteness and strength of the finished paper.

[0003] Therefore, the role of hydrogen peroxide stabilizer in paper bleaching is mainly reflected in controlling the decomposition rate of hydrogen peroxide and preventing it from decomposing prematurely, thereby ensuring the stability and effectiveness of the bleaching process. Among them, poly-α-hydroxy acrylic acid is used as a hydrogen peroxide stabilizer because of its outstanding stabilizing effect and is a more popular choice.

[0004] For example, prior art 1: JP4878710B2 discloses a hydrogen peroxide stabilizer for fiber bleaching, scouring, and soaping. It exhibits excellent alkali resistance and hydrogen peroxide stabilization, maintaining hydrogen peroxide bleaching performance even in the presence of high alkali concentrations. It is also a hydrogen peroxide stabilizer capable of improving fiber whiteness. The solution 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 discloses that poly-α-hydroxy acrylic acid is freely polymerized with at least one monomer of acrylic acid, methacrylic acid, maleic acid and salts thereof and then compounded with a water-soluble magnesium compound, which can more effectively stabilize hydrogen peroxide in the presence of a higher concentration of base.

[0006] However, in actual papermaking, caustic soda is added throughout the bleaching process. To save time, production workers often pour large amounts of caustic soda directly into the bleaching process. This causes the local alkalinity to become too high within a short period of time, leading to gelation of the poly-α-hydroxyacrylic acid, which affects its ability to stabilize hydrogen peroxide. Poly-α-hydroxyacrylic acid gels in strong alkaline environments, limiting its use in certain alkaline hydrogen peroxide formulations.

[0007] Therefore, it is necessary to find a method to avoid the poly-α-hydroxy acrylic acid gelation phenomenon caused by excessively high alkalinity in the local environment during actual production, avoid the reduction of bleaching efficiency, and at the same time improve the alkali resistance of poly-α-hydroxy acrylic acid, increase its stability in coexistence with alkali, and expand the application scenarios. Summary of the Invention

[0008] One of the purposes of the present invention is to provide a hydrogen peroxide stabilizer, which is a combination of poly-α-hydroxy acrylic acid and polyvinyl alcohol to alleviate the gelation phenomenon caused by lactonization of poly-α-hydroxy acrylic acid in an overly alkaline environment.

[0009] At the same time, the present invention also provides a hydrogen peroxide stabilizer, comprising the following components in parts by weight:

[0010] 80-90 parts of poly-α-hydroxy acrylic acid;

[0011] 10-20 parts of polyvinyl alcohol.

[0012] During the production process, a sudden local increase in the alkalinity of the water environment will cause poly-α-hydroxy acrylic acid to undergo lactonization, and its hydroxyl and carboxyl groups will be esterified to form a gel; the present invention uses water-soluble polyvinyl alcohol, which can be used to esterify with some of the carboxyl groups of poly-α-hydroxy acrylic acid, thereby reducing the esterification effect within and between poly-α-hydroxy acrylic acid molecules, effectively alleviating the gel phenomenon when the alkalinity suddenly increases. Testing revealed that, under the same alkaline conditions, the gelation phenomenon was extremely mild or even absent when using polyvinyl alcohol. The fundamental reason for this is that poly-α-hydroxyacrylic acid (PAA) exhibits dense esterification between and within its molecules. Adjacent carboxyl and hydroxyl groups, as well as adjacent carboxyl and hydroxyl groups within the same or other segments, undergo esterification, resulting in a high esterification density. Consequently, when the alkalinity of the system is diluted, its hydrolysis time is relatively long, and gelation takes a long time to disappear. While esterification also occurs when using PVA, this esterification between PVA and PVA is discontinuous, resulting in fewer esterification sites and increased steric hindrance on the PAA, making it difficult to form a sufficient cross-linked network and, consequently, gelation. Furthermore, due to the discontinuous esterification, the esterification density is low. Once the alkali in the water is diluted, the esterification sites rapidly hydrolyze, allowing the PAA to regain its hydrogen peroxide-stabilizing effect.

[0013] In addition, polyvinyl alcohol is also a relatively good metal ion chelating agent. Like poly-α-hydroxy acrylic acid, it can also stabilize hydrogen peroxide by chelating metal ions.

[0014] Therefore, even if some polyvinyl alcohol is added, the overall hydrogen peroxide stabilization effect is not inferior to that of poly-α-hydroxy acrylic acid of the same weight.

[0015] In the above-mentioned hydrogen peroxide stabilizer, the viscosity of a 4 wt% polyvinyl alcohol aqueous solution at 20° C. is 3.0 to 300 mPa·s.

[0016] In the above-mentioned hydrogen peroxide stabilizer, the viscosity of a 4 wt% polyvinyl alcohol aqueous solution at 20° C. is 10 to 150 mPa.s.

[0017] In the above-mentioned hydrogen peroxide stabilizer, the polyvinyl alcohol is composed of a first polyvinyl alcohol and a second polyvinyl alcohol; a 4wt% aqueous solution of the first polyvinyl alcohol has a viscosity of 10 to 50 mPa.s at 20°C; a 4wt% aqueous solution of the second polyvinyl alcohol has a viscosity of 110 to 150 mPa.s at 20°C; and the weight ratio of the first polyvinyl alcohol to the second polyvinyl alcohol is 1 to 10:1 to 10.

[0018] As the more commonly used polyvinyl alcohol in this field, the fully hydrolyzed polyvinyl alcohol produced by Shin-Etsu Corporation can be selected. The specific brands are: JF-03, JF-04, JF-05, JF-10, JF-17, JF-17L, JF-20, JC-25, JC-33, JC-40, etc.

[0019] In the above hydrogen peroxide stabilizer, the weight ratio of the first polyvinyl alcohol to the second polyvinyl alcohol is 1-3:7-9.

[0020] In the above hydrogen peroxide stabilizer, the molecular weight of the poly-α-hydroxy acrylic acid is 20,000 to 400,000, and the molecular weight distribution is 1 to 10.

[0021] Beneficial effects

[0022] Compared with the prior art, the present invention adopts a combination of poly-α-hydroxy acrylic acid and polyvinyl alcohol. In a strong alkaline environment, the esterification between poly-α-hydroxy acrylic acid and polyvinyl alcohol partially replaces the intermolecular and intramolecular esterification of poly-α-hydroxy acrylic acid, so as to alleviate the gelation phenomenon caused by the lactonization of poly-α-hydroxy acrylic acid in an overly alkaline environment.

[0023] At the same time, the stabilizing effect of the stabilizer of the present invention is not inferior to that of poly-α-hydroxy acrylic acid of the same weight. DETAILED DESCRIPTION

[0024] 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.

[0025] In order to explain the technical content of the present invention in detail, further description will be given below in conjunction with the embodiments.

[0026] Part I Preparation of Poly-α-Hydroxyacrylic Acid

[0027] Example 1

[0028] A method for preparing poly-α-hydroxy acrylic acid comprises the following steps:

[0029] Step 1: Add 700 g of water, 100 g of α-chloroacrylic acid, and 0.4 g of sodium persulfate to a reaction vessel under an inert atmosphere, and react at a constant temperature of 80° C. for 3 h while stirring;

[0030] Step 2: Stop the reaction and filter to collect the polymer solid;

[0031] Step 3: The polymer solid was added to a 1.5 mol / L sodium hydroxide aqueous solution and fully hydrolyzed at 80° C. to obtain poly-α-hydroxy acrylic acid, which was named poly-α-hydroxy acrylic acid 1.

[0032] Example 2

[0033] A method for preparing poly-α-hydroxy acrylic acid comprises the following steps:

[0034] Step 1: Add 700 g of water, 100 g of α-chloroacrylic acid, and 0.8 g of sodium persulfate to a reaction vessel under an inert atmosphere, and react at a constant temperature of 75° C. for 4 h while stirring;

[0035] Step 2: Stop the reaction and filter to collect the polymer solid;

[0036] Step 3: The polymer solid was added into a 2 mol / L sodium hydroxide aqueous solution and fully hydrolyzed at 80° C. to obtain poly-α-hydroxy acrylic acid, which was named poly-α-hydroxy acrylic acid 2.

[0037] Example 3

[0038] A method for preparing poly-α-hydroxy acrylic acid comprises the following steps:

[0039] Step 1: Add 700 g of water, 100 g of α-chloroacrylic acid, and 2 g of sodium persulfate to a reaction vessel under an inert atmosphere, and react at a constant temperature of 85° C. for 1 h while stirring;

[0040] Step 2: Stop the reaction and filter to collect the polymer solid;

[0041] Step 3: The polymer solid was added to a 2.5 mol / L aqueous solution of sodium hydroxide and fully hydrolyzed at 80° C. to obtain poly-α-hydroxy acrylic acid, which was named poly-α-hydroxy acrylic acid 3.

[0042] The molecular weight and molecular weight distribution of the above-mentioned poly-α-hydroxy acrylic acid 1 to poly-α-hydroxy acrylic acid 3 can be seen in Table 1 below; the molecular weight is measured by dynamic light scattering method.

[0043] Table 1 Molecular weight of poly-α-hydroxy acrylic acid

[0044]

[0045] Part 2 Hydrogen Peroxide Stabilizer

[0046] The composition of hydrogen peroxide stabilizer can be referred to Table 2 below;

[0047] Table 2 Composition of hydrogen peroxide stabilizer

[0048]

[0049] Among them, the viscosity of a 4wt% aqueous solution of JF-03 at 20°C is 3.0-4.0mPa.s;

[0050] The viscosity of a 4 wt% aqueous solution of JF-17 at 20°C is 28.0-32.0 mPa.s;

[0051] The viscosity of a 4 wt% aqueous solution of JC-33 at 20°C is 110.0-150.0 mPa.s.

[0052] Part III Performance Test

[0053] 3.1 Alkali resistance test

[0054] Test method:

[0055] (1) Prepare 15% sodium hydroxide solution;

[0056] (2) Take 30g of the stabilizer to be tested in a 500ml beaker and slowly add 270g of the above sodium hydroxide solution;

[0057] (3) Observe the gel agglomeration phenomenon in the solution and record the amount of sodium hydroxide solution added when gel agglomeration occurs. After the sodium hydroxide solution is added, let it stand for observation and record the time when the gel agglomeration disappears. The test results are as follows:

[0058] Table 3 Alkali resistance test of hydrogen peroxide stabilizer

[0059]

[0060] The above experimental results show that:

[0061] 1. The larger the molecular weight of poly-α-hydroxyacrylic acid, the worse its alkali resistance. Adding a small amount of sodium hydroxide can cause it to gel and agglomerate, and it takes longer for the gel agglomeration to disappear. This may be because the longer the poly-α-hydroxyacrylic acid molecular chain, the more carboxyl and hydroxyl groups that can be lactone-converted are contained in each molecular weight, making it easier for gel agglomeration to occur. The spatial structure of the formed gel agglomeration is more complex, and it takes longer to re-extend into a chain structure in the solution.

[0062] 2. When poly-α-hydroxy acrylic acid is added with the first polyvinyl alcohol JF-03 or JF-33 alone or the second polyvinyl alcohol JF-17 alone, the alkali resistance is improved to a certain extent. At the same time, it can be seen that the alkali resistance improvement effect of poly-α-hydroxy acrylic acid is JF-33>JF-17>JF-03. This may be because the polyvinyl alcohol with a longer molecular chain is more tightly bonded to the carboxyl ester of poly-α-hydroxy acrylic acid, and the alkali resistance improvement effect is more significant.

[0063] 3. When JF-33 and JF-07 are used together, they have a synergistic effect on improving the alkali resistance of poly-α-hydroxy acrylic acid. When the two are used in appropriate amounts, poly-α-hydroxy acrylic acid will not coagulate or agglomerate when mixed with alkali. This surprising effect may be due to the fact that poly-α-hydroxy acrylic acid contains units of different molecular chain lengths. JF-33 is esterified with the carboxyl group of poly-α-hydroxy acrylic acid with a longer molecular chain, and JF-07 is esterified with the carboxyl group of poly-α-hydroxy acrylic acid with a relatively short molecular chain, synergistically improving the alkali resistance of poly-α-hydroxy acrylic acid.

[0064] 3.2 Chelation performance test

[0065] According to the determination of chelating ability of textile printing and dyeing auxiliaries chelating agent GB / T 21884-2008, the chelating performance of hydrogen peroxide stabilizer is tested as shown in Table 4 below;

[0066] Table 4 Hydrogen peroxide stabilizer chelating performance test

[0067]

[0068] From the above data, it can be seen that when polyvinyl alcohol is partially used to replace poly-α-hydroxy acrylic acid for compounding, under the condition of the same total weight, the chelating performance is basically equivalent to the chelating performance of poly-α-hydroxy acrylic acid. This may be because polyvinyl alcohol has a certain chelating effect, and when a small amount replaces poly-α-hydroxy acrylic acid, it has little effect on its overall chelating performance.

[0069] 3.3 Bleaching performance test

[0070] 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 shown in Table 5 below;

[0071] Table 5 Pulp parameters of a chemical pulp plant under high-consistency bleaching operation conditions

[0072]

[0073] The following experimental steps were used to test the bleaching performance of stabilized hydrogen peroxide:

[0074] (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 90℃ and heat for 60 minutes.

[0075] (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.

[0076] (3) Stir for 5 minutes and then filter.

[0077] (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.

[0078] (5) After weighing each bag of pulp, squeeze out the filtrate and measure the residual hydrogen peroxide.

[0079] The test results are shown in Table 6 below;

[0080] Table 6 Stabilizer test hydrogen peroxide bleaching performance

[0081]

[0082] From the above data, it can be seen that when poly-α-hydroxy acrylic acid and alkali are added separately, they have good stabilization of hydrogen peroxide and bleaching effects. When poly-α-hydroxy acrylic acid is added in a mixed manner with alkali, the bleaching performance and hydrogen peroxide stabilization effect are significantly reduced. This may be due to the effect of gelation when it encounters alkali. When poly-α-hydroxy acrylic acid is compounded with polyvinyl alcohol, even if it is mixed with alkali and added, the bleaching performance and hydrogen peroxide stabilization effect of the stabilizer do not decrease. This shows that the method provided by the present invention effectively solves the problem of gelation of poly-α-hydroxy acrylic acid when it encounters alkali, which is of great significance for the actual production and use of poly-α-hydroxy acrylic acid.

[0083] 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 hydrogen peroxide stabilizer, characterized in that It comprises the following components in parts by weight: 80-90 parts of poly-α-hydroxy acrylic acid; 10-20 parts of polyvinyl alcohol.

2. The hydrogen peroxide stabilizer according to claim 1, characterized in that The viscosity of a 4 wt% polyvinyl alcohol aqueous solution at 20° C. is 3.0 to 300 mPa.s.

3. The hydrogen peroxide stabilizer according to claim 2, characterized in that The viscosity of a 4 wt% polyvinyl alcohol aqueous solution at 20° C. is 10 to 150 mPa.s.

4. The hydrogen peroxide stabilizer according to claim 3, characterized in that The polyvinyl alcohol is composed of a first polyvinyl alcohol and a second polyvinyl alcohol; the viscosity of a 4wt% aqueous solution of the first polyvinyl alcohol at 20°C is 10-50mPa.s; the viscosity of a 4wt% aqueous solution of the first polyvinyl alcohol at 20°C is 110-150mPa.s; the weight ratio of the first polyvinyl alcohol to the second polyvinyl alcohol is 1-10:1-10.

5. The hydrogen peroxide stabilizer according to claim 4, characterized in that The weight ratio of the first polyvinyl alcohol to the second polyvinyl alcohol is 1-3:7-9.

6. The hydrogen peroxide stabilizer according to claim 1, characterized in that The molecular weight of the poly-α-hydroxy acrylic acid is 20,000 to 400,000.

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