JPH02305823A - Decoloration of aqueous alpha-hydroxyacryalte polymer solution - Google Patents

Abstract

PURPOSE:To decolorize an aqueous alpha-hydroxy acrylate polymer solution in good efficiency by bringing a specified oxidizing agent into contact with the solution in its production. CONSTITUTION:At least one oxidizing agent selected from among H2O2, H2O2- producing substance (e.g. sodium percabonate), a hypochlorite, a chlorite and O3 is brought into contact with an aqueous alpha-hydroxyacrylate polymer solution having a monomer unit of the formula [wherein R1-2 are each H or an (OH- or halogen-substitute) 1-3 C alkyl; and M is H, an alkali (alkaline earth) metal, ammonium or an amino] in its production.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an α-hydroxyacrylic acid based polymer F1.
, ~■ (referred to as AP) water-soluble) relates to a method for decolorizing.

Sodium poly-α-hydroxyacrylate (hereinafter referred to as PHA)
Poly-α-hydroxy acrylates (hereinafter referred to as PHA salts) represented by S are metal ion sequestering agents,
It is an important substance as a detergent builder and bleach stabilizer.

[Conventional technology]

Various methods have already been proposed for producing PHA salts.

For example, Tokko Akira! According to No. 57-39249, α, β
- Dihalogenopropionic acid is dehydrochlorinated in the gas phase in the presence of a catalyst such as alumina, and the resulting α-chloroacrylic acid is polymerized to form a lactone-type compound of poly-α-hydroxyacrylic acid (hereinafter referred to as PLAC). (call). According to Special Publication No. 54-5839, α, β-
We have proposed a method in which α-chloroacrylic acid is obtained by heating an aqueous solution of diglorpropion to a temperature of 100° C. or higher, and a Shinkin metal catalyst is applied to the aqueous solution to obtain PLAC.

Furthermore, in Japanese Patent Publication No. 57-27882, PLAC was produced by treating an aqueous solution of α-chloroacrylic acid with a polymerization catalyst having a radical-forming action and heating the resulting poly-α-chloroalkali acid without isolating it. We are proposing a method to obtain the .

The PHA salt can be obtained as an aqueous solution of PLAC obtained by these methods by reacting it with a desired alkaline substance.

Moreover, in Japanese Patent Publication No. 57-49561, α-chloroacrylic acid and acrylic acid are polymerized to obtain an α-hydroxyacrylic acid-acrylic acid copolymer.

Although it is possible to obtain a PHA salt aqueous solution by these methods, the aqueous solution has a yellow to reddish brown hue.

[Problem to be solved by the invention]

As mentioned above, PHA salts are used in a wide variety of fields, but depending on the application, they are often found to be colored. For example, when used as an ingredient in household detergents, the hue of the product is an extremely important factor, and therefore it is required to be as pale to colorless as possible.

However, until now, no method of decolorizing PHA salts has been known.

The present inventors have completed the present invention as a result of various studies on methods for decolorizing PHA salt aqueous solutions.

[Means to solve the problem]

That is, the present invention is based on the general formula (wherein R1 and R2 are hydrogen, or 1 to 3
represents an alkyl group having a skeleton of carbon atoms and which can be substituted with a hydroxyl group or a halogen, and M is hydrogen, an alkali metal, an alkaline earth metal, an ammonium group, or an amine group. ) When preparing α-hydroxyacrylic acid-based polymer (aqueous solution) containing one monomer unit represented by (a) hydrogen peroxide (b) a substance that generates hydrogen peroxide (c) hypochlorite The present invention relates to a method for decolorizing an aqueous solution of an α-hydroxyacrylic acid polymer, which comprises bringing into contact with at least one oxidizing agent selected from the group consisting of acid, (d) chlorite, and (e) ozone.

The hydrogen peroxide used in the present invention may be a commercially available industrial chemical or a reagent, and is generally used in the form of a 30-70% aqueous solution.

Substances that produce hydrogen peroxide are substances that can produce hydrogen peroxide in water, such as sodium percarbonate and sodium peroxide. is no different from hydrogen peroxide.

The hypochlorite includes sodium hypochlorite, potassium hypochlorite, etc., and thorium hypochlorite is generally used. It is usually used in the form of a 3-15% aqueous solution.

Chlorite is a substance represented by sodium chlorite, and is used in the form of solid or aqueous solution.

Ozone can be obtained using a general ozone generator, and is usually used at an air concentration of about 1 to 3%.

Although these oxidizing agents have an effect even when used alone, the method of using hypochlorite salt and hydrogen peroxide in combination has a synergistic effect, and it is possible to obtain extremely good results.

The amount of the oxidizing agent used in the present invention is not particularly limited, but is from 0.005 to 0 per 1 mole of unit formula jl of the polymer.
．． It is preferable to use 5 mol, more preferably 0.015 to
It is more preferable to use 0.15 mol.

If it is 0.005 times the mole or less, the decolorizing effect is small;
Practicality is low, 0. Even if it is added in an amount equal to or more than i5 times in mole, no further improvement in decolorization can be expected and it is uneconomical. Further, it is not preferable to use a large amount of an oxidizing agent because it may lead to deterioration of the polymer itself.

The treatment temperature can be carried out in the range of -10 to 120 °C, but since treatment at a temperature of 80 °C or higher may lead to deterioration of the polymer itself, it is preferably carried out at 0 to 80 °C. Furthermore, it is more preferable to carry out at 5 to 50°C.

When hydrogen peroxide is used as an oxidizing agent, it is effective to use it together with ultraviolet irradiation. As a source of ultraviolet light,
General ultraviolet lamps such as high-pressure mercury lamps and low-pressure mercury lamps can be used, and in the method of the present invention, the wavelengths are as follows:
Although this objective can be achieved by contacting an aqueous PHA salt solution with an oxidizing agent, as mentioned above, PHA salts are generally obtained by reacting an alkaline substance with a precursor called PLAC. In this case, it is more effective to bring the PLAC into contact with the oxidizing agent in advance and then react with the alkaline substance. In order to bring the PLAC into contact with the oxidizing agent, the PLAC is usually dispersed in water and the oxidizing agent is added thereto, and the time required for this may be 3010 to 2 hr. Even if 2+tr or more is applied, no further effect is expected. The amount of oxidizing agent, treatment temperature, etc. are preferably the same as those described above.

[For production]

Since the structure of the coloring component in the PHA salt aqueous solution is unknown,
Although the mechanism of action of the present invention is not clear, there is probably a chromophore centered around the double bond site in the polymer structure, and the double bond undergoes reactions such as hydroxylization by the oxidizing agent. It is thought that the color will disappear as a result.

〔Effect of the invention〕

PHA salt aqueous solutions obtained by conventional methods have a yellow to reddish brown coloration, which poses a major problem depending on the application. According to the method of the present invention, it is possible to reduce the degree of coloration, and depending on the conditions, it is possible to obtain a colorless solution.

〔Example〕

Examples 1 to 1O Wet-1P obtained according to the examples of Japanese Patent Publication No. 54-5839
LAc (35% pure, 65% water) was used as a PHAS precursor.

Wet PLAC 790.4g (of which, pure content 276゜6g)
, equivalent to 3.64 molar formula weight as unit formula weight = 76)
, 1064g of water and 145.6g of NaOH are reacted,
2,000 g of 20% PHAS aqueous solution was obtained.

This solution was divided into portions, a predetermined amount of oxidizing agent was added to each portion at room temperature (approximately 25° C.), and after 1 hr, the pigment in the solution was measured using a color difference meter. The results are shown in Table 1. Color difference Δ in the table
E is the color difference with pure water (ΔE=[(ΔL)2+′(Δa)
``+(Δb)2]1'2, and the smaller this value is, the closer it becomes to colorless.

Example 11 To 790.4 g of the same wet PLAC as in Example 1, 724 g of water was added.
．． 3 g was added and stirred to form a slurry. Here, 6.
Add 14 g of 60% H2O2 (0.108 mol, equivalent to 2.98 mol% based on polymer unit) and stir at room temperature for lh.
r Stirred.

To this slurry, 485.3 g of 30% NaOH was added to prepare a PHAS solution.

When the chromaticity of this liquid was measured, L=98.37, a=-1
, 27, b=6.41, and ΔE=6.70.

Example 12 The solution of Example 1 (after addition of H202) was placed in a 20-volume cell made of quartz glass, and irradiated with light from a 150 W high-pressure mercury lamp at a distance of 20 ports for 30 minutes.

When the chromaticity of this liquid was measured, L=99.13, a=-1
, 12, b=3.22, and ΔE=3.48.

Example 13 Air containing 1% ozone generated from an ozone generator was added to 100 g of the untreated solution in Example 1.
Blowing was carried out for 120 minutes at a speed of 200 d/min.

When the chromaticity of this liquid was measured, L=99.34. a='-
1,17, b=3.15, ΔE: 3.39.

Claims (1)

[Claims] 1. General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, in the formula, R_1 and R_2 are hydrogen or 1 to
It represents an alkyl group having a skeleton of three carbon atoms and which can be substituted with a hydroxyl group or a halogen, and M is hydrogen, an alkali metal, an alkaline earth metal, an ammonium group, or an amine group. ) When preparing an α-hydroxyacrylic acid polymer aqueous solution containing monomer units represented by (a) hydrogen peroxide (b) a substance that generates hydrogen peroxide (c) hypochlorite (d A method for decolorizing an aqueous solution of an α-hydroxyacrylic acid polymer, which method comprises contacting with at least one oxidizing agent selected from the group consisting of chlorite (e) ozone. 2. The method according to claim 1, characterized in that hydrogen peroxide or a substance that generates hydrogen peroxide and hypochlorite are used as the oxidizing agent. 3. Claim 1, characterized in that hydrogen peroxide or a substance that generates hydrogen peroxide is brought into contact and ultraviolet rays are irradiated.
Method described. 4. The method according to claims 1 to 3, wherein the polylactone compound corresponding to the general formula according to claim 1 is brought into contact with an oxidizing agent in advance, and then reacted with an alkaline substance.