Synthesis process of low-molecular-weight phosphono carboxylic acid

Abstract

The invention relates to a synthesis process of low-molecular-weight phosphono carboxylic acid, and belongs to the field of water treatment. The synthesis process comprises the following steps: selecting one or more unsaturated carboxylic acid monomers as polymerization monomers, dissolving phosphorous acid or a salt thereof in water, adding an alkaline neutralizer, adding the polymerization monomers and an initiator under the condition of 100-105 DEG C, carrying out heat preservation reflux for 1 hour, and cooling after the reaction is completed to obtain a faint yellow phosphono carboxylic acid solution. The synthesis process of the low-molecular-weight phosphono carboxylic acid provided by the invention is relatively simple in process, relatively high in safety coefficient, relatively short in production period and beneficial to batch production; the phosphorous acid utilization rate is high, and the molecular weight of the POCA can be effectively reduced, so that a POCA product with lower molecular weight is obtained and has excellent scale and corrosion inhibition performance.

Description

Technical Field

[0001] The invention belongs to the field of water treatment, and in particular relates to a synthesis process of low molecular weight phosphonocarboxylic acid (POCA). Background Art

[0002] Phosphonocarboxylic acid (POCA) is a polyacrylic acid homopolymer or copolymer generally obtained by polymerization reaction of phosphorous acid or phosphorous acid derivatives with AA, HPA, AMPS, SAA and other olefin monomers using peroxide or persulfate as initiator. The molecule contains phosphono groups (-PO3H2), carboxylic acid groups (-COOH), and may also contain hydroxyl groups (OH), ester groups (COOR) or sulfonic acid groups (-SO3H). Its general formula can be recorded as: M2PO3-{[COOM]CR'-CH2}-{R} m H, where m is an integer of 1 to 100, M = H, alkaline earth metal, alkali metal or NH4, where R' = H, -CH3, -CH2CH3, R = olefin monomer containing carboxylic acid group, ester group or sulfonic acid group. This type of polymer has a low phosphine content (PO4 <5%), has strong antioxidant properties, and almost does not react with chlorine-containing and bromine-containing oxidizing biocides. It has a high calcium tolerance and has an excellent effect on inhibiting the deposition of calcium phosphate, calcium sulfate, calcium carbonate, zinc salts, and dispersing iron oxide. It also has a corrosion inhibition function and is a truly multifunctional environmentally friendly agent.

[0003] As a scale inhibitor and corrosion inhibitor, choosing the right molecular weight plays a decisive role in its performance. Generally speaking, the lower the molecular weight, the better the corrosion inhibition performance, and the scale inhibition performance is not much different in the low molecular weight range.

[0004] Correspondingly, more molecular weight regulators are needed during synthesis. Phosphorous acid is used as a molecular weight regulator during the synthesis of POCA. However, phosphorous acid is relatively expensive and has a low utilization rate, which means that some of it does not participate in the reaction or is ineffective, resulting in a large amount of phosphite or its oxidation byproducts in the reaction product. These salts have no effect on the performance, but weaken the effective components of the polymer, and also have a certain impact on the stability of the polymer, such as turbid precipitation, etc. Therefore, it is particularly important to effectively use phosphorous acid as a chain transfer agent to play its role in regulating molecular weight. Summary of the invention

[0005] The purpose of the present invention is to provide a synthesis process of low molecular weight phosphonocarboxylic acid (POCA), especially to efficiently use phosphorous acid as a molecular weight regulator to synthesize low molecular weight phosphonocarboxylic acid (POCA) during the synthesis process.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A synthesis process of low molecular weight phosphonocarboxylic acid, the synthesis process comprises: selecting one or more unsaturated carboxylic acid monomers as polymerization monomers, dissolving phosphorous acid or its salt in water, adding an alkaline neutralizer, adding polymerization monomers and an initiator under the condition of 100-105°C, keeping the temperature under reflux for 1 hour, cooling after the reaction is completed to obtain a light yellow phosphonocarboxylic acid solution.

[0008] Furthermore, the polymerizable monomer is one or more of acrylic acid, methacrylic acid, maleic acid, and itaconic acid, but is not limited thereto.

[0009] Furthermore, the initiator is persulfate or other water-soluble peroxides.

[0010] Further, the synthesis process of the low molecular weight phosphonocarboxylic acid is as follows: 120 parts by weight of phosphorous acid and 150 parts by weight of water are added to a reaction kettle, and then 58.5 parts by weight of sodium hydroxide are added, the temperature is raised to 100-105° C., and 400 parts by weight of acrylic acid solution and 40 parts by weight of ammonium persulfate aqueous solution are added dropwise at a uniform speed in proportion, the addition time is 4 hours, the mixture is kept at 100-105° C. and refluxed for 1 hour, and a light yellow POCA solution is obtained after cooling.

[0011] Furthermore, the mass fraction of the acrylic acid solution in the synthesis process is 70-100%.

[0012] Furthermore, the mass fraction of the ammonium persulfate aqueous solution in the synthesis process is 10-40%.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The synthesis process of low molecular weight phosphonocarboxylic acid (POCA) provided by the present invention has relatively simple procedures, high safety factor, short production cycle, and is conducive to mass production; phosphorous acid utilization rate is high, and the molecular weight of POCA can be effectively reduced, thereby obtaining a POCA product with a lower molecular weight, and has excellent scale and corrosion inhibition performance. DETAILED DESCRIPTION

[0015] The technical solutions and effects of the present invention are further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0016] Comparative Example 1

[0017] 120g of phosphorous acid and 150g of water were added to the reactor, and then 117g of 50% sodium hydroxide solution was added, the temperature was raised to 100-105°C, and 500g of 80% acrylic acid solution and 140g of 28% ammonium persulfate aqueous solution were added dropwise at a uniform speed in proportion, the addition time was 4 hours, and the mixture was refluxed at 100-105°C for 1 hour. After cooling, a light yellow POCA solution was obtained with a molecular weight Mw of 988.

[0018] Example 1

[0019] 120g of phosphorous acid and 150g of water were added to the reactor, and then 117g of 50% sodium hydroxide solution was added, the temperature was raised to 100-105°C, and 500g of 80% acrylic acid solution and 140g of 28% ammonium persulfate aqueous solution were added dropwise at a uniform speed in proportion, the addition time was 4 hours, and the mixture was refluxed at 100-105°C for 1 hour. After cooling, a light yellow POCA solution was obtained with a molecular weight Mw of 988.

[0020] Example 2

[0021] 120g of phosphorous acid and 150g of water were added to the reactor, the temperature was raised to 100-105°C, and 500g of 80% acrylic acid solution and 140g of 28% ammonium persulfate aqueous solution were added dropwise at a uniform speed in proportion. The addition time was 4 hours, and the mixture was refluxed at 100-105°C for 1 hour. After cooling, a light yellow POCA solution was obtained with a molecular weight Mw of 3216.

[0022] Example 3

[0023] 120g of phosphorous acid and 150g of water were added to the reactor, the temperature was raised to 100-105°C, and 500g of 80% acrylic acid solution, 140g of 28% ammonium persulfate aqueous solution and 117g of 50% sodium hydroxide solution were added dropwise at a uniform speed in proportion. The addition time was 4 hours, and the mixture was refluxed at 100-105°C for 1 hour. After cooling, a light yellow POCA solution was obtained with a molecular weight Mw of 2880.

[0024] Example 4

[0025] 120g of phosphorous acid and 150g of water were added to the reactor, and then 234g of 50% sodium hydroxide solution was added, the temperature was raised to 100-105°C, and 500g of 80% acrylic acid solution and 140g of 28% ammonium persulfate aqueous solution were added dropwise at a uniform speed in proportion, the addition time was 4 hours, and the mixture was kept at 100-105°C and refluxed for 1 hour. After cooling, a light yellow POCA solution with a molecular weight Mw of 1050 was obtained.

[0026] It can be seen from the above examples that under the same phosphorous acid conditions, the molecular weight in Example 1 is the lowest, indicating that the regulating effect of phosphorous acid is the most obvious and the utilization rate is the highest. Comparing Examples 1 and 3, it can be seen that under the same neutralization amount, the utilization rate of neutralized phosphorous acid (converted into sodium hydrogen phosphite) is higher than that of neutralized monomer or system phosphorous acid. From the above 4 examples, it can be seen that in the POCA synthesis process, the regulating effect is more obvious after phosphorous acid is converted into sodium hydrogen phosphite or sodium phosphite, and the effective utilization rate of phosphorous acid is the highest.

[0027] Table 1 Performance comparison of POCA prepared in Examples 1-4

[0028]

[0029] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A synthesis process for low molecular weight phosphonocarboxylic acid, characterized in that: The synthesis process is as follows: one or more unsaturated carboxylic acid monomers are selected as polymerization monomers, phosphorous acid or its salt is dissolved in water, an alkaline neutralizer is added, the polymerization monomer and the initiator are added at 100-105° C., the mixture is refluxed for 1 hour, and after the reaction is completed, the mixture is cooled to obtain a light yellow phosphonocarboxylic acid solution.

2. The synthesis process of low molecular weight phosphonocarboxylic acid according to claim 1, characterized in that: The polymerizable monomer is one or more of acrylic acid, methacrylic acid, maleic acid, and itaconic acid, but is not limited thereto.

3. The synthesis process of low molecular weight phosphonocarboxylic acid according to claim 1, characterized in that: The initiator is persulfate or other water-soluble peroxides.

4. The synthesis process of low molecular weight phosphonocarboxylic acid according to claim 1, characterized in that: The synthesis process of the low molecular weight phosphonocarboxylic acid comprises the following steps: adding 120 parts by weight of phosphorous acid and 150 parts by weight of water into a reaction kettle, adding 58.5 parts by weight of sodium hydroxide, heating the reaction kettle to 100-105° C., and dripping 400 parts by weight of acrylic acid solution and 40 parts by weight of ammonium persulfate aqueous solution. The dripping is carried out at a uniform speed and in proportion for 4 hours. The reaction kettle is kept at 100-105° C. and refluxed for 1 hour. After cooling, a light yellow POCA solution is obtained.

5. The synthesis process of low molecular weight phosphonocarboxylic acid according to claim 1, characterized in that: The mass fraction of acrylic acid solution in the synthesis process is 70~100%.

6. The synthesis process of low molecular weight phosphonocarboxylic acid according to claim 1, characterized in that: The mass fraction of the ammonium persulfate aqueous solution in the synthesis process is 10~40%.

Images