CN116376036B - Comb-type polycarboxylate dispersant, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a comb-type polycarboxylate dispersant, a preparation method and application thereof, wherein the molecular structure of the comb-type polycarboxylate dispersant is as follows: styrene-acrylic acid-maleic anhydride terpolymer is used as a main chain, and polyethylene glycol or polyethylene glycol derivatives are used as side chains. When the comb-type polycarboxylate dispersant is applied to the preparation of organic pigment color paste, the dispersibility and stability of the pigment color paste can be greatly improved, the pigment content in the color paste is improved, the color performance of the pigment is better reserved, the coating performance of the pigment is obviously improved, and the application of the comb-type polycarboxylate dispersant has the advantages of small usage amount, high efficiency, strong viscosity reduction effect, small influence on pigment functions and the like; in addition, the preparation method adopted by the invention has the advantages of low raw material cost, mild reaction condition, simple synthesis process and the like.

Description

A comb-type polycarboxylate dispersant and its preparation method and application

Technical Field

The invention relates to the technical field of organic synthesis and dispersants, and in particular to a comb-type polycarboxylate dispersant and a preparation method and application thereof.

Background Art

Anionic water-based polymer dispersants mainly include polycarboxylates, phosphates, sulfonates and other types. Polycarboxylate dispersants and their derivatives contain more carboxyl groups, which can be adsorbed on certain solid particles as anchoring groups, or provide electrostatic repulsion through hydrolysis and ionization, so they have a strong dispersing effect on solid particles in the dispersed system. In addition, polycarboxylate dispersants have the advantages of excellent water solubility, little influence by temperature changes, and small usage, and are outstanding representatives of water-based polymer dispersants.

Pigments have the advantages of good light fastness, rich colors, wide color spectrum, no discoloration after long-term storage, etc., and are also versatile, washable, and sunlight-resistant. Organic pigments generally exist as aggregate powders, are insoluble in water and general organic solvents, and are difficult to be wetted in water. They are often formulated into suspended dispersions for use. Therefore, the surface of the pigment particles can be covered with a certain dispersant to improve its dispersion stability. The structure of organic pigments contains a large number of highly hydrophobic benzene rings and groups with elements such as N and O that are easy to form hydrogen bonds, which provide anchor points for the dispersant.

Although pigments with small molecules and simple structures can also give bright colors, in order to improve the solvent resistance, heat stability and migration resistance of organic pigments, it is necessary to increase the molecular weight while introducing specific polar groups. C.I. Pigment Yellow 180, an important yellow pigment of benzimidazolone type launched on the market in recent years, has an increased molecular weight and excellent heat stability and migration resistance. It is the only disazo pigment in the benzimidazolone yellow series and is mainly used in the fields of coloring plastics, coatings, and paints.

Summary of the invention

Purpose of the invention: In order to solve the technical problems existing in the prior art, the present invention aims to provide a comb-type polycarboxylate dispersant that can efficiently disperse and stabilize organic pigment paste, and the present invention also provides a preparation method and application of the comb-type polycarboxylate dispersant.

Technical solution: The comb-type polycarboxylate dispersant described in the present invention is characterized in that the molecular structure of the comb-type polycarboxylate dispersant is: a styrene-acrylic acid-maleic anhydride terpolymer as a main chain and polyethylene glycol or a polyethylene glycol derivative as a side chain.

Furthermore, the molar ratio of styrene, acrylic acid and maleic anhydride is 3:1:3-3:3:3, preferably 3:2:3; the average molecular weight of the polyethylene glycol or polyethylene glycol derivative is 400-800, preferably 600, and the polyethylene glycol derivative is polyethylene glycol monomethyl ether.

Furthermore, the molar ratio of the acid anhydride to the polyethylene glycol or polyethylene glycol derivative in the terpolymer is 1:1-1:3, preferably 1:2.

The preparation method of the comb-type polycarboxylate dispersant of the present invention comprises the following steps:

(1) Preparing a styrene-acrylic acid-maleic anhydride terpolymer: first dissolving maleic anhydride in an organic solvent to obtain a mixed solution 1, then dissolving styrene, acrylic acid and an initiator in an organic solvent to obtain a mixed solution 2, adding the mixed solution 2 dropwise to the mixed solution 1, stirring for reaction, washing with an organic solvent and filtering with suction after completion, and drying to obtain the styrene-acrylic acid-maleic anhydride terpolymer;

(2) Preparation of comb-type polycarboxylate dispersant: Styrene-acrylic acid-maleic anhydride terpolymer, polyethylene glycol and its derivatives and a catalyst are added to a solvent and mixed evenly, and refluxed to obtain a comb-type polycarboxylate dispersant.

Furthermore, in step (1), the organic solvent is toluene, the initiator is benzoyl peroxide, and the amount is 2-4wt% of the total mass; the speed of adding the second drop of the mixed solution to the first mixed solution is one drop every 1-2 seconds; the stirring reaction conditions are: temperature 80-90°C, time 3-5h;

Furthermore, in step (2), the solvent is acetone, the catalyst is p-toluenesulfonic acid, and the amount used is 0.2-0.3wt% of the total mass; the reflux temperature is 60-65°C, and the reflux time is 8-12h.

The invention discloses an application of the comb-shaped polycarboxylate dispersant in the preparation of organic pigment paste.

Furthermore, the organic pigment paste is a water-based organic pigment paste.

Furthermore, the organic pigment is an organic pigment containing a benzene ring structure, preferably C.I. Pigment Yellow 180.

Furthermore, the amount of organic pigment added to the organic pigment paste is 5-20wt%, preferably 10wt%; the amount of comb-type polycarboxylate dispersant added to the organic pigment paste is 0.5-3.5wt%, preferably 2wt%.

Principle of the invention: The action mechanism of the comb-type polycarboxylate dispersant for dispersing and stabilizing organic pigments is as follows: the benzene ring and hydroxyl group in the comb-type polycarboxylate dispersant can respectively undergo molecular interactions with the molecules of the organic pigment containing the benzene ring structure mainly based on π-π stacking and hydrogen bonding, so that the comb-type polycarboxylate dispersant is anchored on the pigment molecules to form a polymer coating layer on the surface of the pigment; in addition, the hydrolyzed carboxyl groups and polyether chains in the comb-type polycarboxylate dispersant extend into the water as hydrophilic groups and solvated chains respectively, preventing aggregation between particles through electrostatic repulsion or steric repulsion, thereby improving the stability of the dispersion.

Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

(1) The comb-shaped polycarboxylate dispersant of the present invention is a high molecular weight dispersant with cheap raw materials, stable performance and easy synthesis;

(2) When the comb-shaped polycarboxylate dispersant of the present invention is used for the dispersion stabilization of organic pigments, it can effectively reduce the viscosity of the product, improve the stability and the slurry color, and has broad application prospects in the field of coatings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an infrared spectrum of the comb-shaped polycarboxylate dispersant prepared in Example 1 of the present invention;

FIG2 is a ¹ HNMR spectrum of the comb-shaped polycarboxylate dispersant prepared in Example 1 of the present invention;

FIG. 3 is a schematic diagram showing the adsorption of the comb-shaped polycarboxylate dispersant of the present invention and the organic pigment.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with specific embodiments and drawings.

Example 1: The molecular structure of the comb-type polycarboxylate dispersant described in the present invention has a styrene-acrylic acid-maleic anhydride terpolymer as the main chain and polyethylene glycol as the side chain, wherein the molar ratio of styrene, acrylic acid and maleic anhydride is 3:1:3; the average molecular weight of the polyethylene glycol is 600.

The preparation method of the above-mentioned comb-type polycarboxylate dispersant comprises the following steps:

(1) Preparing a styrene-acrylic acid-maleic anhydride terpolymer: first dissolving maleic anhydride in an organic solvent, then dissolving styrene, acrylic acid and an initiator in an organic solvent, adding two drops of the mixed solution to a first mixed solution, stirring the mixture for reaction, washing with an organic solvent and filtering with suction after the reaction is completed, and drying to obtain a styrene-acrylic acid-maleic anhydride terpolymer;

First, maleic anhydride (14.709 g, 0.15 mol) was dissolved in 60 ml of toluene and transferred into a 250 ml three-necked flask to obtain a mixed solution 1; then, styrene (15.623 g, 0.15 mol), acrylic acid (3.603 g, 0.05 mol), and benzoyl peroxide (1.126 g, 3 wt.%) were dissolved in a total of 60 ml of toluene, and the three were mixed and then transferred into a constant pressure dropping funnel to obtain a mixed solution 2; then, the three-necked flask was placed in a water bath and connected to A mechanical stirring paddle and a condenser are used, and the stirring device and condensing water are turned on. The water bath temperature is set to 85°C. The solution temperature is measured with a mercury thermometer until it is constant. Then a dropping funnel is installed and dripping is started at a rate of 1 drop/2 seconds. After the dripping is completed, the reaction is continued for 4 hours. After the reaction is completed, the reaction product is filtered and washed three times with toluene to remove unreacted monomers and initiators. After being drained, it is transferred to a culture dish and dried in a vacuum at 50°C for 6 hours to obtain a white powder, which is styrene-acrylic acid-maleic anhydride terpolymer (SAM).

(2) Preparation of comb-type polycarboxylate dispersant: SAM (2.522 g), p-toluenesulfonic acid (0.25 g) and 20 mmol of polyethylene glycol (PEG) were dissolved in a total of 100 ml of acetone, and the two were mixed and transferred into a 250 ml three-necked flask. Then, the three-necked flask was placed in a water bath, connected to a condenser, and the magnetic stirring device and condensed water were turned on. The water bath temperature was set to 65°C, and the acetone was refluxed for 10 h under boiling conditions. The product was placed in a fume hood to evaporate the solvent until the total mass no longer decreased, and a comb-type polycarboxylate dispersant (denoted as SAM-PEG600 ₂ , where 600 is the average molecular weight of polyethylene glycol and 2 is the molar ratio of PEG to the anhydride in SAM) was obtained.

The comb-type polycarboxylate dispersant SAM-PEG600 ₂ prepared in Example 1 was subjected to structural characterization test, and the results are shown in Figures 1 and 2.

As shown in Figure 1, the stretching vibration of _-CH2- in _PEG6002 appears at around 2900cm ^-1 . The peak at 1709cm ^-1 corresponds to the stretching vibration of the carbonyl group in the carboxyl group and the ester group. The characteristic peaks in the range of 1650-1450cm ^-1 are attributed to the vibration of the benzene ring skeleton. The stretching vibration of the ester group C-O-C is located in the range of 1300-1050cm ^-1 . Through the test results of infrared spectroscopy, it can be preliminarily inferred that SAM and SAM- _PEG6002 were successfully synthesized.

As shown in Figure 2, the proton signals in the benzene ring are mainly concentrated in the low field region, i.e., around 7-8ppm. The chemical shifts of the protons adjacent to C=O are mainly concentrated in 2-3ppm, while the chemical shifts of the protons directly connected to the oxygen atom (mainly -CH2 _- O-) are between 3-4ppm, and the other methylene and methine signals are mainly between 1-2ppm. This further proves the successful synthesis of SAM-PEG600 ₂ .

Example 2: The difference from Example 1 is that the molar ratio of styrene, acrylic acid and maleic anhydride is 3:2:3; in step (1), the amount of acrylic acid is (7.206 g, 0.10 mol).

Example 3: The difference from Example 1 is that the molar ratio of styrene, acrylic acid and maleic anhydride is 3:3:3; in step (1), the amount of acrylic acid is (9.809 g, 0.15 mol).

Comparative Example 1: The difference from Example 1 is that no acrylic acid is added.

Example 4: The difference from Example 2 is that the average molecular weight of polyvinyl alcohol is 400, and a comb-shaped polycarboxylate dispersant (denoted as SAM-PEG400 ₂ ) is prepared.

Example 5: The difference from Example 2 is that the average molecular weight of polyvinyl alcohol is 800, and a comb-shaped polycarboxylate dispersant (denoted as SAM-PEG800 ₂ ) is prepared.

Example 6: The difference from Example 2 is that the side chain is polyethylene glycol monomethyl ether (mPEG) with an average molecular weight of 400, and a comb-shaped polycarboxylate dispersant (denoted as SAM-mPEG400 ₂ ) is prepared.

Example 7: The difference from Example 6 is that the average molecular weight of polyethylene glycol monomethyl ether is 600, and a comb-shaped polycarboxylate dispersant (denoted as SAM-mPEG600 ₂ ) is prepared.

Example 8: The difference from Example 6 is that the average molecular weight of polyethylene glycol monomethyl ether is 800, and a comb-shaped polycarboxylate dispersant (denoted as SAM-mPEG800 ₂ ) is prepared.

Example 9: The difference from Example 2 is that the molar ratio of PEG to the acid anhydride in SAM is 1:1, and a comb-shaped polycarboxylate dispersant (denoted as SAM-PEG600 ₁ ) is prepared.

Example 10: The difference from Example 2 is that the molar ratio of PEG to the acid anhydride in SAM is 3:1, and a comb-shaped polycarboxylate dispersant (denoted as SAM-PEG600 ₃ ) is prepared.

Comparative Example 2: The difference from Example 2 is that no side chain is included.

Example 11: The comb-type polycarboxylate dispersant prepared in Example 1-Example 10 and Comparative Example 1-Comparative Example 2 is used to prepare an organic pigment C.I. Pigment Yellow 180 color paste. The application method is: 2g of the comb-type polycarboxylate dispersant (added in an amount of 2wt%) is dissolved in 20g of a 1mol/L NaOH solution, and mixed with 10g of C.I. Pigment Yellow 180 (added in an amount of 10wt%), 200g of zirconium beads and 68g of deionized water. The resulting mixture is placed in a high-speed disperser with a speed of 1500r/min, and ground for 90min. The color paste after ultrafine grinding is sealed and stored for standby use.

The results of the effects of the comb-type polycarboxylate dispersants obtained from Examples 1 to 10 and Comparative Examples 1 to 2 on the dispersibility of the organic pigment C.I. Pigment Yellow 180 color paste are shown in Tables 1 to 3.

Table 1 Effect of different acrylic acid addition amounts on the dispersion properties of C.I. Pigment Yellow 180

Table 1 compares the effects of different amounts of acrylic acid added on the dispersant effect during the preparation of the comb-type polycarboxylate dispersant (taking SAM-PEG600 ₂ as an example). It can be seen that the dispersant synthesized by adding 7.206g of acrylic acid has the best effect. Due to the addition of the side chains, the number of carboxyl groups on the main chain is reduced, so the addition of acrylic acid supplements the number of carboxyl groups in the comb-type polycarboxylate dispersant to provide sufficient electrostatic repulsion. However, too much acrylic acid causes a corresponding reduction in the number of benzene rings and side chains contained in a certain mass of the comb-type polycarboxylate dispersant, resulting in a reduction in the anchoring effect of the comb-type polycarboxylate dispersant on the pigment particles and the wettability in water, which is not conducive to the dispersion of the pigment.

Table 2 Effect of different dispersants on the dispersibility of C.I. Pigment Yellow 180

As shown in Table 2, compared with SAM, the comb-type polycarboxylate dispersant with branches has significantly better performance. This is mainly because SAM only provides electrostatic repulsion through carboxyl groups, and there is no solvated branch to enhance hydrophilicity; at the same time, the grinding aid performance of the branch also significantly reduces the viscosity of the product. Further, SAM-PEG600 ₂ has the best dispersion effect compared with other SAM-(m)PEG Mn _2. This is mainly because the solvated branch is too short to provide sufficient hydrophilicity, and the wettability of the pigment particles in water is still low; and the overly long branches are prone to entanglement, which is not conducive to the dispersion and stability of the particles; compared with SAM-(m)PEG400 ₂ , SAM-(m)PEG600 ₂ and SAM-(m)PEG800 ₂ both have lower viscosity, which is attributed to the longer solvated polyether chain.

Table 3 Effect of PEG addition amount on dispersion effect during dispersant synthesis

name Average particle size (nm) PDI Example 9 SAM-PEG600 ₁ 295.8 0.126 Example 2 SAM-PEG600 ₂ 264.6 0.089 Example 10 SAM-PEG600 ₃ 260.0 0.190

As can be seen from Table 3, SAM-PEG600 ₂ has the best dispersion effect compared with other SAM-(m)PEG600 _x (x is 1, 2 or 3). As the proportion of PEG increases, the median particle size of the pigment particles gradually decreases, but the decrease rate decreases, which may be because when too much PEG is added, they are not all grafted onto the SAM main chain.

Example 12: The comb-type polycarboxylate dispersant prepared in Example 2 is used to prepare an organic pigment C.I. Pigment Yellow 180 color paste. The application method is as follows: 0.5 g of the comb-type polycarboxylate dispersant (added in an amount of 0.5 wt%) is dissolved in 20 g of a 1 mol/L NaOH solution, and mixed with 10 g of C.I. Pigment Yellow 180, 200 g of zirconium beads and 69.5 g of deionized water. The resulting mixture is placed in a high-speed disperser with a speed of 1500 r/min and ground for 90 min. The color paste after ultrafine grinding is sealed and stored for later use.

Example 13: The comb-type polycarboxylate dispersant prepared in Example 2 is used to prepare an organic pigment C.I. Pigment Yellow 180 color paste. The application method is as follows: 3.5 g of the comb-type polycarboxylate dispersant (added in an amount of 3.5 wt%) is dissolved in 20 g of 1 mol/L NaOH solution, mixed with 10 g of C.I. Pigment Yellow 180, 200 g of zirconium beads and 66.5 g of deionized water, and the resulting mixture is placed in a high-speed disperser with a speed of 1500 r/min. The mixture is ground for 90 min, and the color paste after ultrafine grinding is sealed and stored for later use.

Example 14: The comb-type polycarboxylate dispersant prepared in Example 2 is used to prepare an organic pigment C.I. Pigment Yellow 180 color paste. The application method is as follows: 2g of the comb-type polycarboxylate dispersant is dissolved in 20g of a 1mol/L NaOH solution, and mixed with 5g of C.I. Pigment Yellow 180 (added amount 5wt%), 200g of zirconium beads and 73g of deionized water. The resulting mixture is placed in a high-speed disperser with a speed of 1500r/min and ground for 90min. The color paste after ultrafine grinding is sealed and stored for later use.

Example 15: The comb-type polycarboxylate dispersant prepared in Example 2 is used to prepare an organic pigment C.I. Pigment Yellow 180 color paste. The application method is as follows: 2g of the comb-type polycarboxylate dispersant is dissolved in 20g of a 1mol/L NaOH solution, and mixed with 15g of C.I. Pigment Yellow 180 (added amount 15wt%), 200g of zirconium beads and 63g of deionized water. The resulting mixture is placed in a high-speed disperser with a speed of 1500r/min, and ground for 90min. The color paste after ultrafine grinding is sealed and stored for later use.

Example 16: The comb-type polycarboxylate dispersant prepared in Example 2 is used to prepare an organic pigment C.I. Pigment Yellow 180 color paste. The application method is as follows: 2g of the comb-type polycarboxylate dispersant is dissolved in 20g of a 1mol/L NaOH solution, and mixed with 20g of C.I. Pigment Yellow 180 (added amount 20wt%), 200g of zirconium beads and 58g of deionized water. The resulting mixture is placed in a high-speed disperser with a speed of 1500r/min, and ground for 90min. The color paste after ultrafine grinding is sealed and stored for later use.

The results of the effect of the comb-type polycarboxylate dispersant in Example 2, Example 12-Example 13 and Example 14-Example 16 in Example 11 on the dispersibility of the organic pigment C.I. Pigment Yellow 180 color paste are shown in Tables 4-5.

Table 4 Effect of dispersant addition on dispersion effect

Addition amount Average particle size (nm) PDI Example 12 0.5wt.％ 306.9 0.162 Example 11 - Example 2 2.0wt.％ 264.6 0.089 Example 13 3.5wt.％ 286.3 0.223

As can be seen from Table 4, when the amount of dispersant added is 2.0wt.%, the dispersant can show the best effect. This is because too little dispersant cannot fully cover the surface of the pigment particles and cannot obtain the best surface wettability; when the amount of dispersant added increases to 3.5wt.%, the most significant feature is the obvious increase in PDI, which is mainly because excessive dispersant introduces too many polyether chains, and the mutual entanglement between chains seriously hinders the smooth dispersion and grinding of particles.

It can be seen from Table 5 that the most suitable pigment content is 10 wt.%. This is because when grinding in a container of a certain volume, the more particles there are, the smaller the probability of them colliding with the limited zirconium beads, so the grinding effect becomes worse.

Table 5 Effect of pigment content on dispersion effect

content Average particle size (nm) PDI Embodiment 14 5wt.％ 261.7 0.114 Example 11 - Example 2 10wt.％ 264.6 0.089 Embodiment 15 15wt.％ 292.7 0.234 Example 16 20wt.％ 310.3 0.217

The schematic diagram of the adsorption of comb-type polycarboxylate dispersants and organic pigments is shown in Figure 3. The benzene rings and hydroxyl groups in the dispersant interact with the organic pigment molecules through molecular interactions mainly based on π-π stacking and hydrogen bonding, so that the dispersant is anchored on the pigment molecules and a polymer coating layer is formed on the surface of the pigment. In addition, the hydrolyzed carboxyl groups and polyether chains in the dispersant extend into the water as hydrophilic groups and solvated chains, respectively, preventing aggregation between particles through electrostatic repulsion or steric repulsion, thereby improving the stability of the dispersion.

Claims (3)

1. The application of the comb-type polycarboxylate dispersant in preparing the organic pigment color paste is characterized in that the molecular structure of the comb-type polycarboxylate dispersant is as follows: taking a styrene-acrylic acid-maleic anhydride terpolymer as a main chain, and taking polyethylene glycol or polyethylene glycol derivatives as side chains, wherein the molar ratio of the styrene to the acrylic acid to the maleic anhydride is 3:2:3, the average molecular weight of the polyethylene glycol or the polyethylene glycol derivatives is 600, the polyethylene glycol derivatives are polyethylene glycol monomethyl ether, and the molar ratio of the anhydride in the terpolymer to the polyethylene glycol or the polyethylene glycol derivatives is 1:1-1:3; the preparation method of the comb-type polycarboxylate dispersant comprises the following steps:

(1) Preparation of styrene-acrylic acid-maleic anhydride terpolymer: firstly, dissolving maleic anhydride in an organic solvent to obtain a first mixed solution, then dissolving styrene, acrylic acid and an initiator in the organic solvent to obtain a second mixed solution, dropwise adding the second mixed solution into the first mixed solution, stirring for reaction, washing with the organic solvent and carrying out suction filtration treatment after the reaction is finished, and drying to obtain the styrene-acrylic acid-maleic anhydride terpolymer;

(2) Preparing a comb-type polycarboxylate dispersant: adding a styrene-acrylic acid-maleic anhydride terpolymer, polyethylene glycol or a polyethylene glycol derivative and a catalyst into a solvent, uniformly mixing, and carrying out reflux reaction to obtain a comb-type polycarboxylate dispersant; the organic pigment is C.I. pigment yellow 180, and the addition amount of the comb-type polycarboxylate dispersant in the organic pigment color paste is 0.5-3.5wt%.

2. The use according to claim 1, wherein in step (1), the two drops of the mixture are added to the first mixture at a rate of one drop every 1-2 seconds; the conditions of the stirring reaction are as follows: the temperature is 80-90 ℃ and the time is 3-5h.

3. The use according to claim 1, wherein in step (2) the reflux temperature is 60-65 ℃ and the reflux time is 8-12h.