Preparation method of beta-dicarbonyl compound modified polyaspartic acid
Technical Field
The invention belongs to the field of high-molecular water treatment functional materials, and particularly relates to a preparation method of beta-dicarbonyl compound modified polyaspartic acid.
Background
For decades, researchers have conducted extensive research efforts on Polyaspartic Acid (PASP). The current research shows that the scale inhibition, dispersion and corrosion inhibition performance of PASP as a water treatment functional material is still in a certain gap with the phosphorus-containing water treatment agent which is widely applied at present, and the price of the PASP is slightly higher than that of the common water treatment agent. Therefore, in order to improve the performance and expand the application range, the core idea of research is to design the material by a proper modification technology, introduce functional groups with different functions into PASP molecules, and realize the structural functionalization and the performance diversification of PASP. Patent CN107602858A dehydrates and condenses carboxymethyl sugar and diamine under the condition of phosphoric acid catalysis to obtain glycosyl-acetyldiamine, adds L-aspartic acid and phosphoric acid into a kneading reactor respectively, mixes, stirs, heats, polymerizes to obtain polysuccinimide, and reacts with glycosyl-acetyldiamine to obtain polysuccinimide derivatives. Phosphoric acid is selected as the two catalysts, so that the catalytic effect is general, and unnecessary economic waste can be caused; patent CN103724625A is prepared from L-aspartic acid monomer by high-temperature polycondensation, hydrolysis under alkaline condition, and neutralization under certain conditions. The process has the advantages of low yield, complex steps and poor scale inhibition effect compared with the traditional phosphorus scale inhibitor; patent CN104387585A discloses a method for synthesizing an intermediate by using aspartic acid and lysine as raw materials, adding a small amount of catalyst and a proper amount of organic solvent under the microwave conditions of 915 +/-50 MHz and 400-10000W, radiating for 1-30 min, recovering all the organic solvent in a gas form, leaching the intermediate by pure water, separating the catalyst, and then carrying out alkaline hydrolysis to obtain an aspartic acid-lysine copolymer. In a previous publication by the inventor, C was selected2H5ONa and absolute ethyl alcohol are used as a catalyst and a solvent of beta-dicarbonyl compound graft modified polyaspartic acid, and the scale inhibition performance is still to be improved from the final experimental result.
Due to the existence of inorganic salt, corrosive ions and microorganisms in industrial water, the cooling water is recycled in equipment for a long time, and the problems of corrosion and scaling are inevitably generated, so that the heat transfer capacity of the equipment is reduced, and the waste of energy is caused. However, the traditional medicament has high phosphorus content, which is not beneficial to the normal development of an ecological system, and the scale inhibition efficiency of emerging products such as polyaspartic acid is not as high as that of the traditional medicament.
Disclosure of Invention
Aiming at the defects of the existing polyaspartic acid product, the invention provides a preparation method of beta-dicarbonyl compound modified polyaspartic acid so as to obtain ecological modified polyaspartic acid with high scale inhibition efficiency.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a preparation method of beta-dicarbonyl compound modified polyaspartic acid comprises the following steps: taking water as a solvent, and reacting polysuccinimide with a beta-dicarbonyl compound under the catalysis of sodium hydroxide to obtain the beta-dicarbonyl compound modified polyaspartic acid.
Preferably, the β -dicarbonyl compound is ethyl formylacetate, ethyl acetoacetate, diethyl malonate or ethyl benzoylacetate.
Preferably, the molar ratio of the polysuccinimide monomer to the beta-dicarbonyl compound to the sodium hydroxide is 1: 0.5-1.2: 1-2.
Preferably, the reaction temperature is 30-40 ℃ and the reaction time is 18-24 h.
Preferably, the polysuccinimide is prepared by taking maleic anhydride as a monomer through the following steps:
(1) reacting maleic anhydride and ammonium salt in a water solvent at 60-90 ℃ for 1.5-2.5 h to obtain a precursor;
(2) and heating the obtained precursor to 160-180 ℃, and reacting for 1-1.5 h to obtain the polysuccinimide.
Preferably, the polysuccinimide is purified as follows: dissolving polysuccinimide by using N, N-dimethylformamide, stirring for 4-6 hours at 40-50 ℃, and then carrying out suction filtration; and adding ethanol, precipitating for 20-40 min, and performing suction filtration to obtain a filter cake, namely the purified polysuccinimide.
Preferably, the ammonium salt is ammonium carbonate, ammonium bicarbonate, ammonium chloride, ammonium sulfate or ammonium nitrate.
Preferably, the molar ratio of the maleic anhydride to the ammonium salt is 1: 1.2-1.5, wherein the molar amount of the ammonium salt is calculated by ammonium ions.
The purification of Polysuccinimide (PSI) is an important guarantee for the normal proceeding of the ring-opening grafting reaction of beta-dicarbonyl compound and PSI.
If using C2H5ONa and absolute ethyl alcohol are used as a catalyst and a solvent, the viscosity average molecular weight of the PASP product obtained by reaction is too high, a water-soluble polymer chain is too long, the PASP product mainly plays a role in adsorption and bridging in a solution, flocculation precipitation of fine particles in the solution is accelerated, the dispersing capacity is obviously reduced, and the scale inhibition capacity is weakened. Compared with the prior art, the invention selects NaOH and water as the catalyst and solvent for the reaction of polysuccinimide and beta-dicarbonyl compound, and can overcome C2H5The defects of ONa and absolute ethyl alcohol enable the modified PASP product to have stable and proper viscosity average molecular weight, ensure that the modified PASP product has excellent scale inhibition performance, and the degradation modes of the beta-dicarbonyl compound are acid decomposition and ketoneThe products are nontoxic micromolecules. Provides a new idea for the design and development of green high-efficiency water treatment chemicals, and has very important significance for developing an industrial circulating cooling water technology, improving the industrial production utilization rate and relieving the water resource shortage.
Effect of different catalysts and solvents on the Properties of modified polyaspartic acid with beta-dicarbonyl Compounds
This section is a further detailed description of the catalysts and solvents (NaOH, water) selected in the invention, and a thorough analysis of the catalysts and solvents (C) selected by the inventors before2H5ONa, absolute ethanol). A large number of experimental studies show that: NaOH and water are selected as a catalyst and a solvent for Polyaspartic Acid (PASP) grafting reaction, so that the finally modified product has 100 percent of scale inhibition rate and higher corrosion inhibition performance, and C2H5ONa and absolute ethyl alcohol do not achieve such an effect. This will be explained in detail in the following in three points of view of the protonation effect, steric effect and solvation effect:
1 reaction mechanism of two groups of catalysts and solvents
The reaction mechanism of using NaOH and water as catalyst and solvent is shown in FIG. 1;
with C2H5The reaction mechanism of ONa and absolute ethyl alcohol as a catalyst and a solvent is shown in figure 2;
wherein n is1=n2=n3,α2<<α1<α3,β2<<β1<β3,α1+β1<n1,α2+β2<n2,α3+β3<n3The respective numerical relationships will be described in detail below.
2 analysis of reaction mechanism
2.1 solvation Effect
In the absolute ethanol solvent, ethanol can not be ionized, and hydrogen protons hardly exist in the solution, so that only sodium ions, alkoxy anions and beta anions (beta-dicarbonyl compound anions) form the charge balance of the solution, and therefore, the figure shows that2 is not an H proton but a sodium ion; in the same way, the ester group is not decomposed into carboxylic acid group in the final modified product, and an important precondition for the ester decomposition into carboxylic acid and alcohol is that the solution can provide water for the final modified product, so that the molecular weight of the monomer of an ethanol system is much larger than that of a water system, which is one of the reasons for the viscosity average molecular weight of the final modified product to be higher than the normal value (the scale inhibition performance of the product is obviously reduced due to the excessively high viscosity average molecular weight), and the opposite is true in the system of NaOH and water, and because of the existence of hydroxide ions, a small part of polysuccinimide is subjected to side reaction with the polysuccinimide to generate PASP, so that alpha exists2<<α1<α3,β2<<β1<β3Such a quantitative relationship.
2.2 protonation Effect
Since anhydrous ethanol does not contain hydrogen protons and hydroxide ions, when sodium ethoxide is used as a catalyst, the final modified product does not have effective end capping groups (X, Y may be alkoxy, sodium ions, and the ionic mobility in the anhydrous ethanol system is poor), i.e., alpha1+β1<α3+β3The viscosity average molecular weight is higher than the normal value, the water-soluble polymer chain is too long, and the water-soluble polymer chain mainly plays a role in adsorption and bridging in the solution, accelerates the flocculation precipitation of fine particles in the solution, obviously reduces the dispersion capacity, and weakens the scale inhibition capacity; NaOH and a water system have stronger end group closed groups (H-, -OH), and the cohesive molecular weight of the modified polymer is controlled to a certain extent, so that the modified polymer has excellent scale and corrosion inhibition properties. However, the pH should be controlled during the synthesis to avoid the occurrence of PASP (alpha) as a by-product due to excessive protonation2+β2<<α1+β1)。
2.3 space Effect
The space effect is established on the solvation effect and the protonation effect, and different solvents and catalyst systems influence the reaction process, so that the final product has different water-soluble long chains and different space structures. The detailed structure is shown in fig. 1 and 2.
The three effects complement each other, the first being the solvation effect, the second being the protonation effect and the steric effect.
3 details of the differences in the reaction mechanisms
First, the beta-dicarbonyl compound is reacted with NaOH (or C)2H5ONa), forming beta negative ions under the action of the ONa), wherein the beta negative ions attack carbon-oxygen double bonds in the PSI, so that original negative charges are transferred to oxygen atoms in newly formed carbon-oxygen single bonds, at the moment, beta-dicarbonyl compounds are connected to the PSI, meanwhile, the negative charges of the carbon-oxygen single bonds are moved back to force the original carbon-nitrogen bonds to be broken, and the negative charges are transferred to nitrogen atoms, so that the difference is reflected, because the content of hydrogen protons in an absolute ethyl alcohol system is very little, the nitrogen negative ions can only be connected with sodium ions with poor activity to form charge balance, and a water system is rich in hydrogen protons and is enough to be combined with the nitrogen negative ions;
the side reaction for generating PASP is also carried out in a water system at the same time, the reaction degree can be reduced to the minimum by operating technologies such as pH value adjustment and the like, namely, hydroxyl replaces beta negative ions to carry out nucleophilic reaction to form a byproduct;
another important difference is the end-capping effect, which is that the effective capping groups such as hydrogen group and hydroxyl group are rich in water system, and the chain length of repolymerization reaction is controlled to make the viscosity-average molecular weight at normal value (1.0X 10)4) Whereas the absolute ethanol system is different, the convergence of the polymerization degree is difficult, and an effective end-group blocking group is lacked, so that the result is alpha1+β1<α3+β3;
Along with the primary formation of a modified product, ester hydrolysis reaction can occur in a water system, so that a final product contains carboxyl, an ester group in an absolute ethyl alcohol system cannot be hydrolyzed, and the condition of ester hydrolysis reaction is lacked, so that the final ester group is retained;
the important reason for the poor scale and corrosion inhibition performance of the absolute ethyl alcohol system is that the viscosity-average molecular weight of the absolute ethyl alcohol system is higher than the normal value (1.0 multiplied by 10)4) The product has poor dispersion performance, and focuses on a flocculating agent, and the system needs to be further improved, so the method selects NaOH and water as a catalyst and a solvent for the grafting reaction.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a reaction mechanism of a beta-dicarbonyl compound and PSI with NaOH and water as catalysts and solvents;
FIG. 2 is a graph represented by C2H5ONa and absolute ethyl alcohol are used as a catalyst and a solvent, and a reaction mechanism of the beta-dicarbonyl compound and PSI is adopted.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
Example 1
Weighing 9.8g of maleic anhydride, dissolving in 20ml of distilled water at 60 ℃, adding 5.76g of ammonium carbonate into an ice water bath in portions, heating to 70 ℃ after dissolving, and carrying out amination hydrolysis for 2.5h to obtain white pasty substance maleimide. And then heating to 165 ℃, and carrying out high-temperature thermal polycondensation reaction for 1.5h to obtain unpurified orange-yellow brittle solid PSI.
Weighing the 15.0g of PSI, dissolving the PSI by using 60ml of N, N-Dimethylformamide (DMF), stirring for 4 hours in a constant-temperature water bath at 40 ℃, carrying out suction filtration on the PSI, removing residues, adding absolute ethyl alcohol, precipitating for 30min, carrying out suction filtration by using a Buchner funnel, wherein a filter cake is the purified PSI, and recovering filtrate.
10.4g of ethyl formylacetate (EHA) and 4.8g of NaOH were weighed out and added to 141ml of water, and after 30min of reaction, 9.7g of purified PSI was added and the reaction was continued at 40 ℃ for 18 hours to obtain a reddish brown solution. Adjusting pH of the system to 5.8 with 4mol/L hydrochloric acid, purifying with 5 times volume of anhydrous ethanol, stirring to obtain red brown viscous solid, drying to obtain brown modified polyaspartic acid (EHA-PASP), and recovering supernatant.
Example 2
Weighing 9.8g of maleic anhydride, dissolving in 20ml of distilled water at 60 ℃, adding 6.72g of ammonium carbonate into an ice water bath in portions, heating to 80 ℃ after dissolving, and carrying out amination hydrolysis for 2.0h to obtain white pasty substance maleimide. And then heating to 165 ℃, and carrying out high-temperature thermal polycondensation reaction for 1.5h to obtain unpurified orange-yellow brittle solid PSI.
Weighing the 15.0g of PSI, dissolving the PSI by using 60ml of N, N-Dimethylformamide (DMF), stirring for 4 hours in a constant-temperature water bath at 40 ℃, carrying out suction filtration on the PSI, removing residues, adding absolute ethyl alcohol, precipitating for 30min, carrying out suction filtration by using a Buchner funnel, wherein a filter cake is the purified PSI, and recovering filtrate.
11.7g of ethyl acetoacetate (EAA) and 6.0g of NaOH were weighed into 155ml of water, reacted for 35min, 9.7g of purified PSI were added, and the reaction was further carried out at 35 ℃ for 20 hours to obtain a reddish brown solution. Adjusting pH of the system to 5.8 with 4mol/L hydrochloric acid, purifying with 5 times volume of anhydrous ethanol, stirring to obtain reddish brown viscous solid, drying to obtain brown modified polyaspartic acid (EAA-PASP), and recovering supernatant.
Example 3
Weighing 9.8g of maleic anhydride, dissolving in 20ml of distilled water at 60 ℃, adding 6.72g of ammonium carbonate into an ice water bath in portions, heating to 85 ℃ after dissolving, and carrying out amination hydrolysis for 1.5h to obtain white pasty substance maleimide. And then heating to 170 ℃, and carrying out high-temperature thermal polycondensation reaction for 1.2h to obtain unpurified orange-yellow brittle solid PSI.
Weighing the 15.0g of PSI, dissolving the PSI by using 60ml of N, N-Dimethylformamide (DMF), stirring for 4 hours in a constant-temperature water bath at 40 ℃, carrying out suction filtration on the PSI, removing residues, adding absolute ethyl alcohol, precipitating for 30min, carrying out suction filtration by using a Buchner funnel, wherein a filter cake is the purified PSI, and recovering filtrate.
12.8g of diethyl malonate (DEM) and 6.4g of NaOH are weighed into 164ml of water, 9.7g of purified PSI is added after 40min of reaction, and the mixture is reacted for 20 hours at 34 ℃ to obtain a reddish brown solution. Adjusting pH value of the system to 6 with 4mol/L hydrochloric acid, purifying with 5 times volume of anhydrous ethanol, stirring to obtain reddish brown viscous solid, drying to obtain brown modified polyaspartic acid (DEM-PASP), and recovering supernatant.
Example 4
Weighing 9.8g of maleic anhydride, dissolving in 20ml of distilled water at 60 ℃, adding 6.72g of ammonium carbonate into an ice water bath in portions, heating to 90 ℃ after dissolving, and carrying out amination hydrolysis for 1.5h to obtain white pasty substance maleimide. And then heating to 180 ℃, and carrying out high-temperature thermal polycondensation reaction for 1.0h to obtain unpurified orange-yellow brittle solid PSI.
Weighing the 15.0g of PSI, dissolving the PSI by using 60ml of N, N-Dimethylformamide (DMF), stirring for 4 hours in a constant-temperature water bath at 40 ℃, carrying out suction filtration on the PSI, removing residues, adding absolute ethyl alcohol, precipitating for 30min, carrying out suction filtration by using a Buchner funnel, wherein a filter cake is the purified PSI, and recovering filtrate.
15.2g of benzoylacetic acid ethyl Ester (EBA) and 8g of NaOH were weighed out and added to 186ml of water, and after 50min of reaction, 9.7g of purified PSI was added, and further reaction was carried out at 30 ℃ for 24 hours to obtain a reddish brown solution. Adjusting pH value of the system to 6 with 4mol/L hydrochloric acid, purifying with 5 times volume of anhydrous ethanol, stirring to obtain red brown viscous solid, drying to obtain brown modified polyaspartic acid (EBA-PASP), and recovering supernatant.
Example 5
Weighing 9.8g of maleic anhydride, dissolving in 20ml of distilled water at 60 ℃, adding 5.76g of ammonium carbonate into an ice-water bath in portions, heating to 80 ℃ after dissolving, and carrying out amination hydrolysis for 2.0h to obtain white pasty substance maleimide. And then heating to 165 ℃, and carrying out high-temperature thermal polycondensation reaction for 1.5h to obtain unpurified orange-yellow brittle solid PSI.
Weighing the 15.0g of PSI, dissolving the PSI by using 60ml of N, N-Dimethylformamide (DMF), stirring for 4 hours in a constant-temperature water bath at 40 ℃, carrying out suction filtration on the PSI, removing residues, adding absolute ethyl alcohol, precipitating for 30min, carrying out suction filtration by using a Buchner funnel, wherein a filter cake is the purified PSI, and recovering filtrate.
10.4g of EBA and 4.8g of NaOH are weighed out and added to 141ml of water, after a reaction time of 30min, 9.7g of purified PSI are added, and the reaction is continued for 18 hours, after which a reddish brown solution is obtained. Adjusting pH of the product to 5.8 with 4mol/L hydrochloric acid, purifying with 5 times volume of anhydrous ethanol, stirring to obtain red brown viscous solid, drying to obtain brown modified polyaspartic acid (EBA-PASP), and recovering supernatant.
Three kinds of modified polyaspartic acid (EHA-PASP, DEM-PASP and EBA-PASP) are subjected to different treatments by adopting a static scale inhibition method (refer to GB/T16632-2008' determination of scale inhibition performance of water treatment agent-calcium carbonate deposition method)Dosage, scale inhibition temperature, scale inhibition time and Ca2+Scale inhibition performance under the conditions of concentration and the like (mainly CaCO)3Scale) were studied and the results were as follows:
(1) the EHA-PASP has the concentration of 8mg/L, the scale inhibition time of 6-10 h and the scale inhibition temperature of 40-E
80℃,Ca2+The scale inhibition rate is 100% when the concentration is 50-250 mg/L;
(2) the EAA-PASP has the concentration of 8mg/L, the scale inhibition time of 6-10 h, the scale inhibition temperature of 40-80 ℃ and Ca2+The scale inhibition rate is 100% when the concentration is 50-250 mg/L;
(3) DEM-PASP has the concentration of 10mg/L, the scale inhibition time of 6-8 h, the scale inhibition temperature of 40-75 ℃ and Ca2+The scale inhibition rate is 100% when the concentration is 50-150 mg/L;
(4) EBA-PASP has the concentration of 8mg/L, the scale inhibition time of 6-10 h, the scale inhibition temperature of 40-80 ℃ and Ca2+The scale inhibition rate is 100% when the concentration is 50-250 mg/L.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.