Polyacrylate sodium phosphate dispersing agent and preparation method thereof
Technical Field
The invention relates to a modified polyacrylate dispersant, in particular to a polyacrylate sodium phosphate dispersant and a preparation method thereof, belonging to the technical field of polymer dispersants.
Background
In the production of paint and ink, pigment dispersion is a crucial link, a proper dispersant is selected to easily obtain a paint with uniform pigment dispersion and stable storage, although the traditional dispersant shows an effective dispersion stabilizing effect in an aqueous dispersion medium, the traditional dispersant is not firmly adsorbed on the surface of pigment particles and is easily desorbed from the surface of the particles to cause re-aggregation or precipitation of the dispersed particles, the long-term stability of the system is poor, and the properties of paint film appearance, hardness, aging resistance and the like are also adversely affected, especially the characteristic of strong pertinence of the dispersant is that the same dispersant cannot be widely applied to the dispersion of different organic pigments, so that the production cost of a user is increased.
The dispersant is a surfactant which has two opposite properties of lipophilicity and hydrophilcity in a molecule, can uniformly disperse solid particles of inorganic and organic pigments which are difficult to dissolve in liquid, and simultaneously prevents the solid particles from settling and agglomerating. With the improvement of the requirements of people on health and environmental protection, the water-based environment-friendly paint becomes a new favorite in the field of architectural decoration, in the paint manufacturing process, the pigment is uniformly dispersed in the paint material in the form of tiny particles under the grinding and shearing force, and as the polarity of the surface of the pigment particles is low, but the surface tension of water is much greater than that of an organic solvent, some auxiliary agents are required to be added to reduce the surface tension of water and enhance the wetting effect on the pigment particles, so that the problem of dispersion stability is difficult to solve when preparing the water-based paint ink, and the application range of the water-based paint ink is narrowed; therefore, the surface of the pigment must be modified to cover the surface of the pigment particles with a dispersant, thereby improving the application properties of the pigment.
Chinese patent CN105295500A discloses a coating dispersant, which is prepared from the following components; acrylic acid, methyl methacrylate, ethylene glycol, an organic solvent, modified diatomite, an initiator, sodium sulfite and a neutralizer; the surface tension of the water-based paint can be reduced, the wetting effect on pigment particles is enhanced, the pigment particles are stably dispersed in a liquid phase and can be rapidly and firmly combined with surface groups of the paint, so that the pigment particles are stably suspended in a water solvent, the pigment is well dispersed, and the optimal dispersion effect is achieved; but the pressure is increased to 6-10Mpa in the reaction process, the reaction temperature is higher and exceeds 100 ℃, the reaction time is long, and a large amount of organic solvent is required to be added in the reaction process.
Chinese patent CN106009935A discloses a water-based dispersant, a preparation method and application thereof; it is prepared by the reaction of metal organic matter, polyisocyanate and polyethylene glycol; the effect of reducing the surface tension of water and pigment is remarkable, the color paste obtained after dispersion has the characteristics of low viscosity, high concentration, bright color, high stability and good ultraviolet resistance, and the water-based paint system can not generate flocculation and thickening phenomena in the storage process. However, polyisocyanate is used as a raw material, the reaction is difficult to complete, and when the isocyanate is used as an aqueous dispersant, unreacted isocyanate reacts with water, so that the dispersant and the material performance of the dispersant are influenced. The dispersant of the invention has no effect on the base material, and the water resistance of a paint film can be influenced by adding the dispersant.
Aiming at the problems of the existing dispersing agent, the dispersing agent has organic solvent volatilization in the production process or the using process and has no effect on the film forming process, the dispersing agent is comprehensively considered to have excellent dispersing performance and low production cost, and the inventor designs an efficient water-based paint dispersing agent through the research on the dispersing mechanism of the dispersing agent, wherein the efficient water-based paint dispersing agent can effectively disperse pigments and fillers, does not contain organic solvent and has a promoting effect on the adhesive force in the film forming process.
Disclosure of Invention
The polyacrylate macromolecular dispersant achieves the purpose of dispersion through the combined action of electrostatic repulsion and steric hindrance, and polyacrylic acid is easy to adsorb on the surface of polar powder (inorganic pigment) and generates stronger electrostatic repulsion, while molecular chains of acrylate can diffuse into a dispersion medium to generate steric hindrance between particles, and can form anchoring connection with the surfaces of organic pigment particles with similar structures, so that the co-dispersion performance is improved.
In order to solve the dispersion and stability of polyacrylate macromolecular dispersant in aqueous system, the invention introduces phosphate ester functional monomer into the end of polyacrylate, and after phosphate ester is neutralized, hydrophilic sodium salt is formed, thus improving the compatibility and dispersion stability with aqueous system. In addition, the strong polarity of the phosphate group and the base material generate strong chemical bonding effect, so that the metal base material is phosphorized, the adhesive force and the crosslinking density with the base material are improved, a compact protective film is formed, and the water resistance and the salt spray resistance are improved.
The polyacrylic acid sodium phosphate dispersing agent is prepared, and the polymer with narrower molecular weight distribution and uniform distribution can be obtained by adopting the azodiisobutyronitrile initiator than the peroxide initiator.
According to the invention, an emulsifier is not required to be added in the production process, and alkyl acrylate sodium phosphate is taken as a reactive emulsifier, so that alkyl with a moderate carbon chain is introduced when the alkyl acrylate sodium phosphate is prepared, and if the carbon chain is too long, the steric hindrance is large during free radical polymerization, and the performance of the alkyl acrylate sodium phosphate is influenced; the carbon chain is too short, the emulsifying capacity is weak, gel is easy to generate during synthesis, and the compatibility is poor12-15。
The invention aims to provide a polyacrylate sodium phosphate dispersing agent and a preparation method thereof.
The molecular structural formula of the polyacrylate sodium phosphate dispersing agent is as follows:
wherein R in the formula is C12-15Alkyl radical, R1、R2、R3Can be H, -CH3;n=3~And 5, controlling the polymerization degree and the molecular weight and distribution thereof by a chain transfer agent.
The polyacrylate sodium phosphate dispersing agent has the molecular weight of 3500-5000 and the particle size of 100-150 nm.
In order to solve the technical problems, the invention adopts the following technical scheme: the invention relates to a polyacrylate sodium phosphate dispersing agent which comprises the following components in percentage by weight: 42.0-56.0% of acrylic monomer, 18.0-28.0% of alkyl acrylate sodium phosphate, 0.4-0.8% of azodiisobutyronitrile, 0.5-5.0% of chain transfer agent and 20.0-35.0% of deionized water.
Wherein, the acrylic monomer is the combination of at least two of methyl acrylate, methyl methacrylate, butyl methacrylate, 2-propyl heptyl acrylate, methyl 2-propyl heptyl acrylate, lauryl methacrylate or lauryl acrylate.
The chain transfer agent is dodecyl mercaptan or 3-isooctyl mercaptoacrylate.
The alkyl acrylate sodium phosphate is synthesized according to the following reaction formula:
r in the formula is C12-15An alkyl group.
The alkyl acrylate phosphate comprises the following components in percentage by weight: 20.0-25.0% of hydroxyethyl acrylate, 36-46.0% of R-OH, 0.1-0.5% of hydroquinone, 6.5-10% of sodium hydroxide and 25.0-32.0% of phosphorus pentoxide.
R-OH is alkyl C12-15The mono-alcohol of (1).
The preparation method of the sodium alkyl acrylate phosphate comprises the following steps:
adding hydroxyethyl acrylate and hydroquinone into a reaction kettle according to the formula amount, uniformly stirring, controlling the temperature to be 5-10 ℃, slowly adding phosphorus pentoxide and monoalcohol in batches, quickly heating to 82 ℃ after adding, carrying out heat preservation reaction for 3-4 hours, measuring the acid value every 0.5 hour, cooling to 50-60 ℃ when the detected acid value reaches a theoretical design value, adding sodium hydroxide, carrying out stirring reaction for 1 hour, cooling to below 40 ℃, and discharging, namely the alkyl acrylate sodium phosphate.
The invention provides a preparation method of a polyacrylate sodium phosphate dispersing agent, which comprises the following preparation steps:
a) weighing acrylic monomers according to the formula ratio, and stirring for 30min at 50 ℃ to obtain monomer premix;
b) adding 1/3 parts by weight of monomer premix, part of alkyl acrylate sodium phosphate, part of initiator and deionized water into a reaction kettle with a thermometer, a reflux condenser tube and a stirrer, stirring, emulsifying and dispersing for 0.5h, heating to 80-84 ℃, and carrying out heat preservation reaction for 0.5h to obtain seed emulsion;
c) controlling the temperature to be 80-84 ℃, dropwise adding the remaining mixed liquid of the monomer premixed liquid and part of the initiator, and finishing dropwise adding within 2.0-2.5 hours; and then slowly dropwise adding the remaining mixed solution of the alkyl acrylate sodium phosphate and the remaining initiator, after dropwise adding is completed within 2.0-2.5 h, heating to 85-88 ℃, adding a chain transfer agent, carrying out heat preservation reaction for 1h, cooling, filtering and discharging to obtain the polyacrylate sodium phosphate dispersing agent.
Compared with the traditional polycarboxylate ammonium salt type dispersing agent, the polyacrylate sodium phosphate dispersing agent disclosed by the invention is synthesized by a self-emulsifying method without an additional emulsifier, and is favorable for improving the water resistance of a film formed by a dispersion system.
According to the polyacrylate sodium phosphate dispersing agent, the phosphate groups can generate a compact passivation film with a base material, so that the adhesion, water resistance and salt spray resistance of a film formed by a dispersing system are improved.
The polyacrylate sodium phosphate dispersing agent disclosed by the invention contains a plurality of branched chain structures, the static repulsion of acrylic acid and the steric hindrance of the branched chains form multi-anchor-point connection on the surface of pigment particles, the dispersing capacity is stronger, and the branched chains extend into a dispersing medium to generate bridging net distribution, so that the pigment particles are more uniformly distributed and more stable to store. The hydrophilic alkyl sodium phosphate can effectively extend into an aqueous system at the chain end, improves the compatibility of pigment particles and the aqueous system, and does not flocculate or float.
The polyacrylate sodium phosphate dispersing agent prepared by the invention is suitable for dispersing or co-grinding carbon black, phthalocyanine pigments, inorganic pigments and fillers, and improves the water resistance and salt fog resistance of the pigment dispersoid. Is suitable for various aqueous acrylic acid, aqueous alkyd, aqueous polyurethane, aqueous epoxy systems and the like, in particular for the dispersion or the co-grinding of the aqueous industrial anticorrosive and antirust primer.
Detailed Description
The invention is further described with reference to the following examples for the preparation of polyacrylate sodium phosphate dispersants. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention.
Example 1
The sodium phosphate A of alkyl acrylate is prepared by the following steps:
adding 21.8 parts of hydroxyethyl acrylate and 0.3 part of hydroquinone into a reaction kettle, uniformly stirring, controlling the temperature to be 5-10 ℃, slowly adding 27.0 parts of phosphorus pentoxide and 43.3 parts of dodecanol in batches, quickly heating to 82 ℃ after the addition, carrying out heat preservation reaction for 3-4 hours, measuring the acid value every 0.5 hour, cooling to 50-60 ℃ when the detected acid value reaches a theoretical design value, adding 7.6 parts of sodium hydroxide, carrying out stirring reaction for 1 hour, cooling to below 40 ℃, and discharging to obtain the alkyl acrylate sodium phosphate A.
Example 2
The sodium phosphate B of alkyl acrylate is prepared by the following steps:
24.0 parts of hydroxyethyl acrylate and 0.5 part of hydroquinone are added into a reaction kettle, the mixture is uniformly stirred, the temperature is controlled to be 5-10 ℃, 29.3 parts of phosphorus pentoxide and 37.9 parts of isotridecanol are slowly added in batches, the temperature is quickly raised to 82 ℃ after the addition, the heat preservation reaction is carried out for 3-4 hours, the acid value is measured every 0.5 hour, when the detected acid value reaches the theoretical design value, the temperature is reduced to 50-60 ℃, 8.3 parts of sodium hydroxide are added, the stirring reaction is carried out for 1 hour, the temperature is reduced to below 40 ℃, and the material is discharged, thus obtaining the alkyl acrylate sodium phosphate B.
Example 3
The sodium phosphate C of alkyl acrylate is prepared by the following steps:
adding 23.2 parts of hydroxyethyl acrylate and 0.4 part of hydroquinone into a reaction kettle, uniformly stirring, controlling the temperature to be 5-10 ℃, slowly adding 28.4 parts of phosphorus pentoxide and 40.0 parts of isotridecanol in batches, quickly heating to 82 ℃ after the addition, carrying out heat preservation reaction for 3-4 h, measuring the acid value every 0.5h, cooling to 50-60 ℃ when the detected acid value reaches a theoretical design value, adding 8.0 parts of sodium hydroxide, carrying out stirring reaction for 1h, cooling to below 40 ℃, and discharging to obtain the alkyl acrylate sodium phosphate C.
Example 4
Polyacrylate sodium phosphate dispersant A1The preparation method comprises the following steps:
a) weighing 7.0 parts of methyl acrylate, 10.5 parts of butyl methacrylate, 17.5 parts of 2-propylheptyl acrylate and 18.5 parts of lauryl methacrylate, and stirring at 50 ℃ for 30min to obtain a monomer premix;
b) adding 16.0 parts of monomer premix, 7.0 parts of alkyl acrylate sodium phosphate A, 0.2 part of azobisisobutyronitrile and 20.3 parts of deionized water into a reaction kettle with a thermometer, a reflux condenser tube and a stirrer, stirring, emulsifying and dispersing for 0.5h, heating to 80-84 ℃, and carrying out heat preservation reaction for 0.5h to obtain seed emulsion;
c) controlling the temperature to be 80-84 ℃, dropwise adding a mixed solution of 37.5 parts of monomer premixed solution and 0.2 part of azodiisobutyronitrile, and finishing dropwise adding within 2.0-2.5 hours; then slowly dripping a mixed solution of 18.0 parts of alkyl acrylate sodium phosphate A and 0.2 part of azodiisobutyronitrile, after finishing dripping for 2.0-2.5 hours, heating to 85-88 ℃, adding 0.6 part of dodecyl mercaptan, carrying out heat preservation reaction for 1 hour, cooling, filtering and discharging to obtain the polyacrylate sodium phosphate dispersing agent A1。
Example 5
Polyacrylate sodium phosphate dispersant B1The preparation method comprises the following steps:
a) weighing 6.5 parts of methyl acrylate, 9.8 parts of butyl methacrylate, 17.5 parts of methyl 2-propyl heptyl acrylate and 16.8 parts of lauryl acrylate, and stirring at 50 ℃ for 30min to obtain a monomer premix;
b) adding 15.0 parts of monomer premix, 6.0 parts of alkyl acrylate sodium phosphate B, 0.2 part of azobisisobutyronitrile and 24.8 parts of deionized water into a reaction kettle with a thermometer, a reflux condenser tube and a stirrer, stirring, emulsifying and dispersing for 0.5h, heating to 80-84 ℃, and carrying out heat preservation reaction for 0.5h to obtain seed emulsion;
c) controlling the temperature to be 80-84 ℃, dropwise adding 35.6 parts of monomer premixed solution and 0.2 part of azodiisobutyronitrile mixed solution, and finishing dropwise adding within 2.0-2.5 hours; then slowly dripping a mixed solution of 17.0 parts of alkyl acrylate sodium phosphate B and 0.2 part of azodiisobutyronitrile, after finishing dripping for 2.0-2.5 hours, heating to 85-88 ℃, adding 1.0 part of dodecyl mercaptan, carrying out heat preservation reaction for 1 hour, cooling, filtering and discharging to obtain the polyacrylate sodium phosphate dispersing agent B1。
Example 6
Polyacrylate sodium phosphate dispersant C1The preparation process comprises the following steps:
a) weighing 7.2 parts of methyl methacrylate, 10.8 parts of butyl methacrylate, 17.2 parts of 2-propylheptyl acrylate and 18.6 parts of lauryl acrylate, and stirring at 50 ℃ for 30min to obtain a monomer premix;
b) adding 16.0 parts of monomer premix, 8.0 parts of alkyl acrylate sodium phosphate C, 0.2 part of azodiisobutyronitrile and 20.6 parts of deionized water into a reaction kettle with a thermometer, a reflux condenser tube and a stirrer, stirring, emulsifying and dispersing for 0.5h, heating to 80-84 ℃, and carrying out heat preservation reaction for 0.5h to obtain seed emulsion;
c) controlling the temperature to be 80-84 ℃, dropwise adding a mixed solution of 37.8 parts of monomer premixed solution and 0.2 part of azodiisobutyronitrile, and finishing dropwise adding within 2.0-2.5 hours; then slowly dropwise adding a mixed solution of 16.0 parts of alkyl acrylate sodium phosphate C and 0.2 part of azodiisobutyronitrile, after dropwise adding is finished for 2.0-2.5 h, heating to 85-88 ℃, adding 1.0 part of 3-isooctyl mercaptoacrylate, carrying out heat preservation reaction for 1h, cooling, filtering and discharging to obtain the polyacrylate sodium phosphate dispersing agent C1。
Example 7
Application example: a gray water-based alkyd rust-proof primer comprises the following components: 42.0 parts of water-based alkyd resin, 1.0 part of propylene glycol, 2.5 parts of dispersant, 2.0 parts of zinc dinitrobenzoate, 11.0 parts of zinc phosphate, 4.0 parts of zinc molybdate, 5.0 parts of aluminum zinc phosphate hydrate, 6.0 parts of mica powder, 10.0 parts of kaolin, 2.5 parts of titanium dioxide, 0.8 part of carbon black, 0.2 part of defoaming agent, 0.2 part of flatting agent, 0.1 part of pH regulator, 2.0 parts of dipropylene glycol methyl ether, 0.4 part of anti-settling agent and 10.3 parts of deionized water.
Wherein the dispersants are respectively: polyacrylate sodium phosphate dispersant A1Polyacrylate sodium phosphate dispersant B1Polyacrylate sodium phosphate dispersant C1And (BYK190W + Tego 750W).
The examples of the present invention and comparative examples (BYK190W + Tego750W) were applied to a water-borne alkyd rust inhibitive primer, and the performance indexes thereof measured according to the relevant standards are shown in Table 1.
Table 1: technical indexes of performance of water-based alkyd rust-inhibiting primer
Although the present invention has been described in detail and with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.