CN103059216B - A kind of dispersion agent, its preparation method and the application in anionic polyacrylamide water-dispersible emulsion polymerization thereof - Google Patents

Abstract

The invention provides a comb-type graft copolymer dispersant, a preparation method of the dispersant; and an application method of the dispersant in anionic polyacrylamide emulsion polymerization. The comb-shaped graft copolymer is prepared by radical addition copolymerization of three monomers. The dispersant provided by the present invention has small molecular weight, low negative charge density, and strong side chain steric hindrance; small viscosity, fast dissolution, low salt sensitivity, rapid diffusion and adsorption, and high stability efficiency; adjustable molecular structure, can effectively The viscosity of the emulsion polymerization system is reduced, and the solid content of the product and the stability of the water-dispersed emulsion are increased.

Description

A dispersant, its preparation method, and its application in anionic polyacrylamide water-dispersed emulsion polymerization

technical field

The invention belongs to the technical field of water-soluble polymer synthesis, and in particular relates to a dispersant, a preparation method thereof, and a polymerization method of an anionic polyacrylamide water-dispersed emulsion.

Background technique

The structural characteristics and complete varieties of polyacrylamide make it widely used in various fields of the national economy, and enjoys the title of "auxiliary for all industries". In my country, the application of polyacrylamide in the three major fields of petroleum, water treatment and papermaking is particularly important.

The methods of synthesizing polyacrylamide include solution polymerization, inverse suspension polymerization and inverse emulsion polymerization. In the late stage of solution polymerization, the viscosity is very high, stirring and heat dissipation are very difficult, and special equipment is required to dry and make powder. The complicated process often leads to a series of side reactions such as cross-linking or degradation of polyacrylamide chains, which leads to a series of side reactions when the product is used. Dissolution is difficult and requires a long time and special dissolution equipment. Emulsion-type (water-in-oil) polyacrylamide has good solubility, but this method needs to use a large amount of hydrocarbon organic solvents and surfactants, which is easy to cause secondary pollution to the environment.

Aqueous dispersion polymerization (also known as water-in-water polymerization or aqueous two-phase polymerization) has become the research focus of various countries due to its high production efficiency, environmentally friendly process, and excellent product dissolution and flocculation performance. At present, some progress has been made in the synthesis of cationic polyacrylamide water-dispersed emulsions. European patents EP0183466 and EP0657478, and U.S. patents US4929655 and US5006590 all describe the combination of acrylamide and acrylic acid in an aqueous solution containing polyvalent anion salts and polymer stabilizers. Copolymerization of acyloxyethyltrimethylammonium chloride and acryloyloxyethyldimethylbenzylammonium chloride to obtain a water-in-water emulsion.

Compared with cationic polyacrylamide, the synthesis of anionic polyacrylamide in saline medium is much more difficult because it is difficult to select monomers of acrylamide derivatives with hydrophobic groups for copolymerization, and related researches are relatively rare. CN101649024A promotes precipitation and phase separation by adding acrylate hydrophobic monomers, and at the same time adds functional monomers with surface activity to improve the early stabilization efficiency, but the introduction of such hydrophobic monomers often reduces the molecular weight of the product, while the solubility is greatly improved become worse; CN1519259A improves the stabilizing effect by adopting a composite stabilizer of non-ionic polymer and polyol compound, but polyol compound has a chain transfer effect on free radical polymerization, which is unfavorable for obtaining high molecular weight products.

It can be seen that the choice of dispersant has an important impact on the reaction. The current patents and literatures use linear anionic polymers or non-ionic polymers as dispersants, and stabilize the latex particles by utilizing the steric hindrance generated by the polymer adsorption on the particle surface. , which requires the dispersant to have a certain molecular weight (up to 500,000 to 1.5 million), which brings a series of problems: first, the reaction is carried out in a high-salt medium, and the dispersant with too high molecular weight is difficult to dissolve quickly. , its molecular conformation is in a curled state affected by the salt concentration, which greatly reduces its adsorption rate and stabilization effect; secondly, the high molecular weight of the dispersant causes a relatively high viscosity in the initial stage of the reaction, coupled with the entanglement between polymer chains, and The polymer chain is difficult to diffuse and move, and the adsorption rate of the dispersant is very slow at the initial stage of the reaction. Often, the viscosity of the system increases sharply due to the inability to stabilize the precipitated latex particles in time, leading to polymerization failure. Thirdly, the charge density of the linear anionic polymer is relatively high, and it has strong charge repulsion with latex ions, which easily causes the desorption of dispersant molecules on the surface of latex particles, which is not conducive to the long-term storage stability of water-dispersed emulsions.

Contents of the invention

The present invention provides a dispersant, which overcomes the above disadvantages and deficiencies; the present invention also provides a preparation method of the dispersant; and an application method of the dispersant of the present invention in anionic polyacrylamide emulsion polymerization.

Dispersant of the present invention is comb type graft copolymer, and its structure meets general formula (1),

In general formula (1), R ₁ , R ₂ , and R ₃ each independently represent H or CH ₃ ;

X represents O, _CH2O , _CH2CH2O or COO _;

Y represents H or CH ₂ CH ₂ N ⁺ (CH ₃ ) ₃ Cl ^- ;

a:b:c=(2.5-7.5):(2.5-5):1; the value of n is 5-25, and the molecular weight of the comb-shaped graft copolymer is 10,000-100,000.

The dispersant of the present invention has a smaller molecular weight, introduces a sulfonic acid group or a cationic group in the structure, and is less sensitive to salt, so it can maintain a more extended chain conformation in a high-salt system, and the diffusion rate and The adsorption rate is significantly improved; when applied to emulsion polymerization, it can quickly stabilize the latex particles generated at the initial stage of polymerization; at the same time, due to the grafted side chain with a large steric hindrance, its dispersion and stabilization effect is relatively conventional. The linear polymer is further improved, which is beneficial to the stability of the system in the later stage of the polymerization reaction, and also improves the long-term storage stability of the emulsion; in addition, the cationic groups on the chain links of the dispersant can strengthen the interaction between the dispersant and the negatively charged latex particles and reduce the stability. The desorption of the reagent has a significant effect on improving the conversion rate, product solid content and charge degree in the later stage of the reaction.

As an improvement, the value of n in the general formula (1) is 10-20.

When the n value is 5-10, the adsorption rate of the dispersant is faster, which is beneficial to the rapid stabilization of the latex particles formed in the early stage, so that the viscosity in the early stage is lower, but due to the shorter side chain, the viscosity of the final dispersion is slightly higher; When the n value is 20-25, the side chain of the dispersant is longer, the early dispersion effect is slightly worse, and the particle size of the latex particles formed is slightly larger, which has some influence on the solubility.

The preparation method of the dispersant of the present invention: the comb-shaped graft copolymer is obtained by free radical addition copolymerization of three monomers, the three monomers are: 2-acrylamide-2-methanol Propanesulfonic acid (formula 2), and general formula 3, the monomer shown in general formula 4;

The mass sum of comonomer accounts for 15～40% of the mass sum of the reactant of described radical addition copolymerization reaction, general formula (2), and general formula (3), the monomer shown in general formula (4) The molar ratio is a:b:c, and the a, b, and c are a, b, and c in the general formula (1).

The initiator used in the radical addition copolymerization reaction is selected from any one of ammonium persulfate, potassium persulfate, sodium persulfate and hydrogen peroxide. The initiator accounts for 0.5-5% of the total mass of the added monomers. In the free radical addition copolymerization reaction, the molecular weight of the dispersant is adjusted by adding the amount of the initiator.

The monomer mixed solution and the initiator solution are added dropwise into the reaction vessel separately, the time for adding the monomer mixed solution and the initiator solution is 1.5 to 5.0 hours, the solvent of the initiator solution is water, and the initiator accounts for 2% of the total mass of the solution. 0.5% to 5%.

The concentration of the initiator aqueous solution is not very demanding, as long as it is controlled to be dripped within a given time: if the concentration is high, the dripping will be slower, if the concentration is low, the dripping will be faster, if the concentration is too high, the solution volume will be less, and the dripping speed is difficult to control, so control Between 0.5% and 5%. In principle, there is no special requirement for the mass concentration, as long as the adding time can be controlled

The monomer mixture and the initiator solution are added separately and dropwise to control the uniformity of chain segment distribution of the dispersant and the stability of the polymerization reaction.

The free radical addition copolymerization reaction is carried out at 60-90° C. for 5-10 hours; the reaction temperature is determined by the decomposition temperature of the aforementioned initiator.

The preparation method of applying the dispersant of the present invention to the anionic polyacrylamide water-dispersed emulsion comprises the following steps:

a) Add nonionic monomer A, anionic monomer B, inorganic salt C, and dispersant D into the reactor according to the following proportions, add water to dissolve to obtain a reaction solution, and adjust the pH value of the system to 6-7;

Monomer 15-30%,

Inorganic salt C 15-25%,

Dispersant 1-3%,

water balance;

The monomer is composed of nonionic monomer A and anionic monomer B, and the nonionic monomer A is selected from acrylamide or methacrylamide; the nonionic monomer accounts for 20-80% of the total mass of the entire monomer system ; Anionic monomer B is one or more of acrylic acid, methacrylic acid, allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid and its sodium salt;

Inorganic salt C is sodium, ammonium, lithium ion salt, selected from one or any combination of two or more of ammonium sulfate, sodium sulfate, lithium sulfate, sodium chloride, ammonium chloride, sodium citrate, and sodium tartrate;

b) heating the reaction solution obtained in step (a) to 30-50° C., passing nitrogen gas to remove oxygen, adding initiator I, and the amount of initiator added accounts for 0.01-0.1% of the monomer mass;

c) After the reaction solution in step (b) is kept warm for 5 to 10 hours, it is cooled to room temperature and discharged to obtain an anionic polyacrylamide water-dispersed emulsion product.

The nonionic monomer A is acrylamide. With acrylamide, it is easier to obtain high molecular weight products, and at the same time, it has better water solubility.

The anionic monomer B is acrylic acid and/or 2-acrylamido-2-methylpropanesulfonic acid. When these two anionic monomers are used, the obtained polyacrylamide has higher molecular weight and better water solubility.

The inorganic salt C is selected from one or any combination of two or more of ammonium sulfate, lithium sulfate, and sodium chloride. When the above-mentioned inorganic salts are used, the obtained anionic polyacrylamide water-dispersed emulsion has a lower viscosity and dissolves more rapidly at the same time.

The initiator I is an azo initiator and/or a redox initiator; when the initiator adopts an azo initiator and a redox initiator, there is no special requirement on the amount of the two, as long as the total amount meets the requirements .

The azo initiator is selected from azobisisobutylamidine hydrochloride (V-50) or azobisisobutylimidazoline hydrochloride (VA-044)

The redox initiator is selected from hydrogen peroxide/ascorbic acid, potassium persulfate/sodium sulfite, potassium persulfate/sodium bisulfite, ammonium persulfate/sodium sulfite, ammonium persulfate/sodium bisulfite, ammonium persulfate/triethanolamine One of them, the mass ratio of the oxidizing agent to the reducing agent in the redox initiator is 2:1-1:2.

The molecular weight of the dispersant provided by the present invention is small, and the negative charge density is low. In addition, the dispersant of the present invention is a comb-type graft copolymer, and its side chain steric hindrance is strong; the viscosity is small, the dissolution is fast, and the salt sensitivity is low. Rapid diffusion adsorption and high stability efficiency; the molecular structure can be adjusted by adjusting the molar ratio of a:b:c. When applied to the emulsion polymerization system, different structures can be designed for different emulsion polymerization systems, which is highly targeted and effective The viscosity of the emulsion polymerization system is reduced, and the solid content of the product and the stability of the water-dispersed emulsion are increased.

Applying the dispersant of the present invention to anionic polyacrylamide water-dispersed emulsion polymerization can produce anionic polyacrylamide water-dispersed emulsion with fast dissolution rate, high molecular weight, good fluidity and convenient use.

specific embodiment

The preparation process of the anionic polyacrylamide water-dispersed emulsion of the present invention is described in more detail below in conjunction with the examples, and these examples are provided in an illustrative manner, and its purpose is to allow those familiar with the art to understand the content of the present invention and according to the present invention To practice, but these examples in no way limit the scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

In the synthesis examples of the present invention, the molecular weight of the dispersant was measured using aqueous gel permeation chromatography (GPC). The experimental conditions are as follows:

Gel column: Shodex SB806+803 two chromatographic columns connected in series

Eluent: 0.1M NaNO ₃ solution

Mobile phase speed: 1.0ml/min

Injection: 20 μl of 0.5% aqueous solution

Detector: Shodex RI-71 differential refractive index detector

Standard: polyethylene glycol GPC standard (Sigma-Aldrich, molecular weight 1010000, 478000, 263000, 118000, 44700, 18600, 6690, 1960, 628, 232)

The raw materials and abbreviations used in the following synthesis examples and examples are shown in Table 1, and the synthesized anionic polyacrylamide water-dispersed emulsion is abbreviated as APD.

Raw materials used in table 1 synthesis example and embodiment

The synthesis example is the synthesis method of the dispersant D used in the present invention.

Synthesis Example 1 (Synthesis of Dispersant D-1)

In a glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, add 100 milliliters of deionized water, purging the reaction vessel with nitrogen while stirring, and raising the temperature to 75 ° C, and then 30 grams of (B-4) and 7 grams of (B-1) and 5 grams of (F-1) and 80 milliliters of water to make a mixed monomer aqueous solution, which is dropped into the reactor for 2 hours, and Simultaneously, 20 grams of 10% ammonium persulfate initiator solution was added dropwise for 5 hours. After the dropwise addition, the solution was incubated and reacted for 5 hours and cooled to room temperature to obtain dispersant D-1 with a molecular weight of 15,000.

Synthesis Example 2-4 (Synthesis of Dispersant D-2-D-4)

D-2-D-4 of the present invention was prepared according to the steps of Synthesis Example 1, and the ratios described in Table 2 were used for feeding.

The feeding ratio and molecular weight of table 2 dispersant preparation

The embodiment is the synthesis method of the anionic polyacrylamide water-dispersed emulsion of the present invention.

Embodiment 1 (synthesis of APD-1)

In a glass reactor equipped with a thermometer, stirrer, nitrogen inlet tube and reflux condenser, add 59.84 grams of (A-1), 15.16 grams of (B-1), 100 grams of (C-1) and 5 grams of (C -4), 5 grams of (D-1) and 315 grams of deionized water, adjust the pH of the system to be 6 to 7, purge the reaction vessel with nitrogen while stirring, and heat up to 35 ° C, then add 0.020 grams of (I- 1), heat preservation reaction for 10 hours and then cool to room temperature to obtain anionic polyacrylamide water-dispersed emulsion APD-1.

Embodiment 2-12 (synthesis of APD-2-APD-12)

Prepare APD-2-APD-12 of the present invention according to the steps of Example 1, and feed according to the ratio described in Table 3.

In the examples of the present invention, the molecular weights of all anionic polyacrylamide water-dispersible emulsions are measured by viscosity method according to GB17514-2008. Before the determination, the sample must be processed to remove the inorganic salt and unreacted monomer in the sample.

The specific treatment process is as follows: dissolve the anionic polyacrylamide water-dispersible emulsion in water to form an aqueous solution with a mass concentration of 2%, and then pour it into an aqueous ethanol solution (the volume ratio of absolute ethanol to aqueous solution is 3:1) for precipitation The polymer was removed and washed with acetone. This process was repeated three times, and the precipitate was then vacuum-dried at 40 °C.

The viscosity of the anionic polyacrylamide water-dispersed emulsion was measured using a SNB AI intelligent Brookfield viscometer, and the No. 27 rotor was used to measure the Brookfield viscosity at 10RPM. The lower the viscosity of anionic polyacrylamide water-dispersed emulsion, the better its fluidity

Table 3 Ratio of reactants for preparation of anionic polyacrylamide water-dispersed emulsion, viscosity of prepared anionic polyacrylamide water-dispersed emulsion (abbreviated as dispersion in the table) and molecular weight of polyacrylamide

Comparative Synthesis Example 1 (synthesis of common dispersant D-5)

In a glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, add 250 ml of deionized water, 45 g of B-4, and 8.7 g of sodium hydroxide, and stir until all the solids are dissolved , raised the temperature to 50°C, purged nitrogen at the same time, added 0.01 g of I-7 after half an hour, reacted for 20 hours, raised the temperature to 80°C and reacted for 6 hours to obtain the dispersant D-5 (2-acrylamido-2-methyl Sodium propane sulfonate homopolymer-conventional linear polymer dispersant) is used to measure the intrinsic viscosity according to GB 17514-2008, and the molecular weight is calculated to be 750,000 by the MH equation of the literature (Macromolecules 10 (1977) 949-954).

Comparative Example 1:

Anionic polyacrylamide water-dispersed emulsion APD-13 with a composition similar to that of Example 1 was synthesized using common dispersant D-5, and the viscosity and molecular weight of the obtained anionic polyacrylamide water-dispersed emulsion were measured according to the detection method of the example. The obtained data can be found in The following table:

Table 4 Example 1 and Comparative Example 1 The feed ratio of each reactant, the viscosity of the obtained anionic polyacrylamide water-dispersed emulsion (abbreviated as dispersion liquid in the table) and the molecular weight of polyacrylamide

From the viscosity data listed in Table 4, it can be seen that the anionic polyacrylamide water-dispersed emulsion obtained by using a common dispersant has a relatively high viscosity, that is, its fluidity is not good.

Comparative example 2 (use common dispersant D-5 to synthesize the anionic polyacrylamide water dispersion emulsion of similar composition with embodiment 4)

The synthesis method and proportion follow APD-4, except that the dispersant D-2 is replaced by D-5. In the experiment, it was found that after adding the initiator and reacting for 10 hours, the viscosity of the system suddenly increased, forming a large number of milky white lumps, and the polymerization system lost Macroscopic stability, unable to obtain a stable water-dispersed emulsion. Stable water-dispersed emulsions cannot be obtained under the condition of high anionicity by using common dispersants.

Comparative example 3 (use common dispersant D-5 to synthesize the anionic polyacrylamide water dispersion emulsion of similar composition with embodiment 9)

The synthesis method and proportion follow APD-9, except that the dispersant D-2 is replaced by D-5. In the experiment, it was found that after adding the initiator for two hours, the viscosity of the system suddenly increased, forming a transparent gel, and severe rod climbing occurred at the same time. Phenomenon, unable to obtain stable water dispersion emulsion. A stable water-dispersed emulsion cannot be obtained under the condition of high monomer dosage and high salt concentration by using common dispersants.

Claims (10)

1. apply the method that comb-shaped graft copolymer dispersion agent prepares anionic polyacrylamide water-dispersion emulsion, it is characterized in that comprising the steps:

A) join in reactor by non-ionic monomer A, anionic monomer B, inorganic salt C, dispersion agent D by following mass ratio, be dissolved in water and obtain reaction solution, regulation system pH value is 6 ~ 7;

Described monomer is made up of non-ionic monomer A and anionic monomer B, and described non-ionic monomer A is selected from acrylamide or Methacrylamide; Non-ionic monomer accounts for the 20-80% of whole monomer system quality; Anionic monomer B is vinylformic acid, methacrylic acid, allyl sulphonic acid, 2-acrylamide-2-methylpro panesulfonic acid and sodium salt thereof one or several arbitrarily wherein;

Inorganic salt C is sodium, ammonium, lithium ion salt, is selected from one or more arbitrary combination in ammonium sulfate, sodium sulfate, Lithium Sulphate, sodium-chlor, ammonium chloride, Trisodium Citrate, sodium tartrate;

B) reaction solution through step a) gained is warming up to 30-50 DEG C, logical nitrogen deoxygenation, add initiator I, the add-on of initiator accounts for the 0.01-0.1% of monomer total mass;

C) through step b) reaction solution insulation reaction after 5 ~ 10 hours, cool to room temperature, discharging, obtained anionic polyacrylamide water-dispersion product emulsion;

Described dispersion agent is comb-grafted copolymer, and its structure meets general formula (1),

R in general formula (1) ₁, R ₂, R ₃represent H or CH independently of one another ₃;

X represents O, CH ₂o, CH ₂cH ₂o or COO;

Y represents H or CH ₂cH ₂n ⁺(CH ₃) ₃cl ^-;

A:b:c=(2.5 ~ 7.5): (2.5 ~ 5): 1; N value is 5 ~ 25, and the molecular weight of described comb-grafted copolymer is 10000 ~ 100000.

2. method according to claim 1, is characterized in that: the n value in described general formula (1) is 10 ~ 20.

3. method according to claim 1, it is characterized in that: obtain described comb-grafted copolymer by the copolyreaction of three kinds of monomer generation free radical additions, described three kinds of monomers are: 2-acrylamide-2-methylpro panesulfonic acid (formula 2), with general formula (3), monomer shown in general formula (4);

The quality summation of comonomer accounts for 15 ~ 40% of the quality summation of the reactant of described free radical addition copolyreaction, general formula (2), with general formula (3), shown in general formula (4), the molar ratio of monomer is a:b:c, described a, b, c are a in general formula (1), b, c.

4. method according to claim 3, it is characterized in that free radical addition copolymerization initiator used is selected from ammonium persulphate, Potassium Persulphate, Sodium Persulfate and hydrogen peroxide any one; Initiator accounts for 0.5 ~ 5% of added monomer total mass.

5. method according to claim 3, is characterized in that: monomer mixed solution and initiator solution are separately added dropwise in reaction vessel, and the time for adding of monomer mixed solution and initiator solution is 1.5 ~ 5.0 hours; The solvent of described initiator solution is water, and initiator accounts for 0.5% ~ 5% of solution total mass.

6. method according to claim 3, is characterized in that: free radical addition copolyreaction is reacted 5 ~ 10 hours at 60 ~ 90 DEG C.

7. method according to claim 1, is characterized in that: described non-ionic monomer A is acrylamide.

8. method according to claim 1, is characterized in that: described anionic monomer B is vinylformic acid and/or 2-acrylamide-2-methylpro panesulfonic acid.

9. method according to claim 1, is characterized in that: described inorganic salt C is selected from one or more arbitrary combination in ammonium sulfate, Lithium Sulphate, sodium-chlor.

10. method according to claim 1, is characterized in that: described initiator I is azo-initiator and/or redox initiator;

Described azo-initiator is selected from azo diisobutyl amidine hydrochloride or azo two isobutyl imidazoline hydrochloride; Described redox initiator be selected from hydrogen peroxide/xitix, Potassium Persulphate/S-WAT, Potassium Persulphate/sodium bisulfite, ammonium persulphate/S-WAT, ammonium persulphate/sodium bisulfite, ammonium persulphate/trolamine any one, in redox initiator, the mass ratio of oxygenant and reductive agent is 2:1 ~ 1:2.