CN102660041A - Method for cross-linking and curing acrylic ester hydrosol by using zinc-ammonium ions - Google Patents

Abstract

The invention provides a method for cross-linking and curing acrylic ester hydrosol by using zinc-ammonium ions. The method comprises the following steps of: 1) synthesizing acrylic ester quadripolymer hydrosol; 2) preparing a zinc-ammonium ion cross-linking agent; and 3) utilizing the zinc-ammonium ions to cross-link and cure the acrylic ester hydrosol, wherein zinc ions and carboxyl generate cross-linking reaction to generate a cross-linking complex, so as to reach the aim of curing the hydrosol. The acrylic ester hydrosol prepared by the invention is a middle-temperature and middle-temperature cured type aqueous coating and has the advantages of safety, convenience in use, low pollution and the like; and meanwhile, a heating step is not needed in a construction process, so that energy sources and resources are saved. Meanwhile, the acrylic ester hydrosol has large cross-linking density, good transparency and better solvent resistance and water resistance; and furthermore, the zinc-ammonium ions are the cross-linking agent, and the cross-linking agent is non-toxic and environment-friendly and reduces the pollution to the environment.

Description

Method for cross-linking and curing acrylate hydrosol by using zinc ammonium ion

technical field

The invention relates to a method for cross-linking and curing acrylate hydrosol by using zinc ammonium ions.

Background technique

As an environmentally friendly material with low price, acrylate hydrosol has developed rapidly in recent years. It has good application prospects in architectural coatings, fabric printing, cloth and paper coatings, inks, leather finishing, etc., but it is not resistant to low temperature. 1. The disadvantage of being viscous at high temperature and brittle at low temperature greatly limits its application in various aspects. At present, there are two main solutions. One is soap-free polymerization, that is, no emulsifier is added. It is difficult to implement at present, and there is no large-scale industrial production. The inter-crosslinks are transformed into bulk structures, thereby improving the water resistance of the polymer film. There are different classification methods for crosslinking, which can be divided into two categories according to the curing temperature: high temperature baking and medium and low temperature curing. High-temperature baking means that during the film-forming process, the temperature rises to about 160°C, so that the active groups on the linear molecules are cross-linked to form a body-shaped structure, so as to achieve the purpose of insolubility and infusibility, but this method does not meet the requirements of energy saving. Development trend, practical operation is more difficult, so how to cross-link cured acrylate hydrosol at medium and low temperature is an important research direction. The advantages of medium and low temperature crosslinking are obvious. There is no need to use large heating equipment during construction, which not only saves energy, but also greatly expands its application range. Medium and low temperature curing water-based coatings have the advantages of safety, convenient use, and less pollution. At the same time, no heating is required during the construction process, thereby saving energy and resources to the greatest extent. The country's research on medium and low temperature curing water-based coatings is in the ascendant.

The acrylate copolymer contains carboxyl groups, which can undergo cross-linking reactions with metal ions to obtain a three-dimensional network structure, and the presence of carboxyl monomers can also improve the adhesion of the coating film to the metal substrate, and make the water sol Viscosity control is easier.

Metal ion crosslinking is one of the important medium and low temperature crosslinking methods. It realizes coating film crosslinking by reacting metal ions with functional groups on the copolymer molecular chain. The most commonly used preparation method of metal ion cross-linked hydrosol is to introduce unsaturated carboxylic acid or monomer containing chelating group into the hydrosol copolymerization system to obtain polymer hydrosol containing carboxyl group or chelating group on the molecular chain, Then add the transition metal ion complex in a certain way. The transition metal ions in the carboxylic acid-type ion-crosslinked hydrosol can exist in the form of ammonia complex ions. In the process of hydrosol film formation, with the volatilization of ammonia, metal ions gradually dissociate from the complex, and interact with the carboxyl groups on the polymer chain to form insoluble salts or complexes, thereby realizing the crosslinking of the coating film. Metal ion cross-linked polymer materials are characterized by high cross-linking density, good transparency, solvent resistance and water resistance. The film crosslinked by the metal ion crosslinking agent not only has chemical resistance and high temperature resistance, but also has a very low film forming temperature, and some films can be formed at room temperature. In addition, the cross-linking agent is non-toxic and has great development prospects. With the further wide application of water-based acrylic hydrosol resin, the rapid development of this crosslinking agent will be promoted, and it has broad application prospects.

Contents of the invention

The object of the present invention is to provide a method for crosslinking and curing acrylate hydrosol by using zinc ammonia ions, which not only has the advantages of energy saving and environmental protection, but also has the advantages of high crosslinking density, good transparency and solvent resistance of the obtained acrylate hydrosol. and water resistance are better.

The present invention is achieved in this way, a method for cross-linking and curing acrylate hydrosol by using zinc ammonia ion, characterized in that: the method includes: 1) Synthesis of acrylate tetrapolymer hydrosol, using solution polymerization method , with azobisisobutyl cyanide as a mixed solvent of ethylene glycol butyl ether and isopropanol, the initiator is dissolved in the mixed monomer and then slowly added dropwise to synthesize methyl methacrylate/butyl acrylate/acrylic acid/benzene Ethylene tetrapolymer hydrosol; 2) Prepare zinc ammonia ion crosslinking agent, then directly add zinc ammonia ion crosslinking agent to tetrapolymer hydrosol to crosslink acrylate hydrosol to make crosslinked hydrosol, The cross-linked hydrosol is prepared at a temperature of 50°C to 70°C; 3) adding a zinc ammonia ion crosslinking agent with a solution mass percentage of 4% to 8% in the crosslinked hydrosol, and crosslinking at a temperature of 60°C to 90°C Joint curing.

The method for preparing the zinc ammonia ion cross-linking agent is as follows: weigh 10 g of zinc sulfate, add water until the zinc sulfate is completely dissolved to form a solution, gradually add ammonia to the solution with a dropper to produce a white precipitate, continue to add ammonia Stirring, the PH=9 measured with PH test paper, the white precipitate gradually disappeared, and a colorless and transparent zinc-ammonia solution was obtained.

The technical effect of the present invention is: the acrylate hydrosol prepared by the present invention is a medium and low temperature curable water-based coating, which has the advantages of safety, convenient use, and less pollution. At the same time, it does not need to be heated during the construction process, thereby saving energy and resources. , At the same time, it also has high crosslinking density, good transparency, good solvent resistance and water resistance; in addition, zinc ammonium ions are crosslinking agents, which are non-toxic and environmentally friendly, reducing environmental pollution. the

Description of drawings

Figure 1 is a graph showing the influence of the crosslinking hydrosol preparation temperature on the water resistance of the coating film when the crosslinking agent content of the present invention is 6%.

Fig. 2 is a graph showing the influence of curing temperature on the water resistance of the coating film when the crosslinking agent content of the present invention is 6%.

Fig. 3 is the curve diagram of the influence of crosslinking agent dosage of the present invention on coating film swelling degree.

Fig. 4 is the curve diagram of the influence of the amount of zinc ammonia ion crosslinking agent of the present invention on the coating film mechanical properties.

Figure 5 is a graph showing the relationship between thermal expansion and temperature of uncrosslinked and crosslinked acrylate hydrosols of the present invention.

Detailed ways

The present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments.

1.1) Synthesis of acrylate tetrapolymer hydrosol, in a three-necked flask equipped with a stirrer, heating mantle, dropping funnel, reflux condenser and 1000mL, add 60mL of isopropanol and 140mL of ethylene glycol butyl ether Mix the solvent, set the temperature to about 110°C, start to heat up, start the stirrer; weigh 117mL methyl methacrylate, 117mL butyl acrylate, 30mL acrylic acid, 36mL styrene into the beaker, add the initiator azo Stir 3g of diisobutylcyanide evenly, slowly drop the mixed monomer into the three-necked flask from the dropping funnel to start solution polymerization, keep the reaction temperature at about 110°C, drop all the monomers in about 4 hours, and keep the temperature The stirring reaction was continued for 1 hour. Lower the temperature to about 70°C, add 30mL diethanolamine to neutralize to PH = 7-8, and continue stirring for 30 minutes to obtain a light yellow viscous acrylate tetrapolymer aqueous sol, which is stored in a jar ;2) Preparation of cross-linking agent zinc ammonia, weigh 10g of zinc sulfate, add a small amount of water to dissolve completely, gradually add ammonia water to the solution with a dropper, and produce white precipitate, continue to add ammonia water and stir, the white precipitate gradually disappears, Until it is colorless and transparent, the zinc ammonia solution is obtained, and the PH=9 measured with PH test paper is put into a jar for later use; 3) Use zinc ammonia ion to crosslink and cure the acrylate hydrosol, the reaction formula is:

It can be seen from the above formula that the cross-linking reaction between the zinc ion and the carboxyl group generates a cross-linking compound to achieve the purpose of hydrosol curing.

2. Preparation of cross-linked hydrosol and coating film

Stirring at different temperatures and adding the prepared zinc-ammonia complex into the hydrosol to form a cross-linked hydrosol. Apply the prepared hydrosol evenly on the prepared iron sheet, let it dry at room temperature for 30 minutes, then put it into an oven, and cure it at 80°C for different times to obtain the required polyacrylate hydrosol coating film.

3. Effect of preparation temperature of cross-linked hydrosol on water resistance

Adding Zn ²⁺ ammonia coordination compound to the hydrosol at room temperature will cause the coagulation and precipitation of the polymer. After raising the temperature to 40°C, a uniformly mixed slightly milky white hydrosol can be obtained. Adding 6% at different temperatures The water resistance of the cross-linked hydrosol coating film prepared by the Zn ²⁺ ammonia coordination compound is shown in Figure 1 of the specification. In Figure 1, S is the degree of swelling. As the temperature increases, the swelling degree of the coating film first decreases and then increases, and the swelling degree is the smallest at 60°C, indicating the best water resistance. Therefore, when preparing the cross-linked hydrosol, the temperature at which the Zn ²⁺ ammonia coordination compound cross-linking agent is added to the hydrosol is selected to be 60°C.

4. Selection of coating film curing temperature

The influence of the curing temperature of the coating film on the water resistance of the coating film is shown in Figure 2 of the specification. In Figure 2, S is the degree of swelling. It can be seen from Figure 2 that as the curing temperature increases, the swelling degree of the cross-linked hydrosol film becomes smaller and the water resistance improves, but when the temperature rises to 80°C, the curing temperature has almost no effect on the performance of the coating film. It shows that the reaction between Zn ²⁺ and -COO ^- is complete at 80℃, and on the whole, the curing temperature has little effect on the water resistance of the coating film, indicating that the crosslinking reaction is basically complete at low temperature.

5. The effect of the amount of crosslinking agent on the properties of the coating film

5.1. The effect of the amount of crosslinking agent on the water resistance of the coating film

The hydrosol coating films with different cross-linking agent contents were put into water and soaked for 24 hours, and the effect of the amount of zinc-ammonia cross-linking agent on the swelling degree of the coating film was obtained. It can be seen from Figure 3 of the description that the swelling degree of the coating film gradually decreases with the increase of the amount of the crosslinking agent zinc-ammonia coordination compound. The curve is divided into two stages. Before the amount of cross-linking agent is 4%, with the increase of the amount of cross-linking agent, the swelling degree is greatly reduced, and the water resistance of the film is greatly improved, but after 4%, with the With the increase of cross-linking agent dosage, the water resistance performance of the film basically has no change. It can be seen that when the amount of cross-linking agent is 4%, ^-COO- on the surface of the film reacts completely with Zn ²⁺ to form a coordination polymer. When the amount of cross-linking agent continues to increase, Zn ²⁺ and the interior The—COO ^— continues to react, but does not contribute to the water resistance of the coating film, but only increases the degree of crosslinking accordingly.

5.2, the effect of the amount of crosslinking agent on the mechanical properties of the coating film

The influence of different contents of zinc ammonium ion crosslinking agent on the tensile strength and elongation at break of the coating film is shown in Figure 4 of the specification. With the increase of Zn ²⁺ content, the tensile strength of the coating film increases continuously, and the elongation at break decreases continuously, because the polymer network structure is formed by cross-linking, and the cross-linking degree increases continuously. The tensile strength of the coating film first increases gradually and then decreases slightly, and reaches the maximum value when the content of crosslinking agent is 6%. Because the polymer contains butyl acrylate, which is a soft monomer, the toughness of the coating film is very good. With the increase of Zn ²⁺ content, the crosslinking degree of the coating film gradually increases, which makes the elongation at break of the coating film decrease. , poor toughness.

5.3, the effect of the amount of crosslinking agent on the heat resistance of the coating film

Take the prepared coating films with different crosslinking agent contents, heat them at different temperatures for 30 minutes, observe the temperature when they become sticky and deform and record them in Table 1. With the increase of Zn ²⁺ content, the heat resistance of the coating film is gradually enhanced. As the content of cross-linking agent increases, the cross-linking is further improved, and the movement between polymer chains is more difficult. Therefore, heat resistance improves.

Table 1 The effect of the amount of zinc ammonium ion crosslinking agent on the heat resistance of the coating film

Zn ²⁺ /% 0 1 2 3 4 5 6 T/℃ 30 40 52 65 70 80 90

, thermomechanical performance analysis

As the temperature rises, the polymer begins to soften and bends under the action of force. The point where the thermal expansion value in the thermomechanical analysis diagram drops the fastest can be considered as the glass transition temperature of the polymer. The thermomechanical performance analysis of acrylate tetrapolymer P (St-co-MMA-co-BA-co-AA) hydrosol and cross-linked acrylate hydrosol is shown in Figure 5 of the specification. It can be seen from the figure that The glass transition temperature of the tetrapolymer crosslinked with zinc and ammonia is higher than that of the acrylate tetrapolymer. This is because the hydrosol added with zinc ammonia crosslinking agent is equivalent to crosslinking on this basis to form a network structure, thereby further increasing the glass transition temperature of the hydrosol.

Claims (2)

1. utilize the method for the zinc ammonium ion crosslinking curing propenoate water-sol, it is characterized in that: said method is 1) the propenoate tetrapolymer water-sol synthetic, adopt solution polymerization process; With butyl glycol ether and Virahol is mixed solvent; With the azo-bis-isobutyl cyanide is slowly to drip the first synthesizing methylmethacrylate/Bing Xisuandingzhi/vinylformic acid/vinylbenzene tetrapolymer water-sol, 2 after initiator is dissolved in mix monomer) preparation zinc ammonium ion linking agent; Then zinc ammonium ion linking agent is directly joined in the tetrapolymer water-sol; The cross linked acrylic water-sol is processed the crosslinked water-sol, and said crosslinked water-sol preparation temperature is 50 ℃～70 ℃; 3) in the crosslinked water-sol, adding solution quality percentage ratio is 4%～8% zinc ammonium ion linking agent, crosslinking curing under 60 ℃～90 ℃ temperature.

2. the method for utilizing the zinc ammonium ion crosslinking curing propenoate water-sol as claimed in claim 1, it is special to be that the described method for preparing zinc ammonium ion linking agent is: the zinc sulfate of weighing 10g adds entry to zinc sulfate and dissolves fully; Form solution, add ammoniacal liquor gradually in this solution, produce white precipitate with dropper; Continuing to add ammoniacal liquor stirs; With the PH=9 that the PH test paper is surveyed, white precipitate fades away, and obtains water white transparency zinc ammonia solution.

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