KR100348866B1 - Method of making emulsion for hydrophilic ink consisting of hydrophilic polymer and hydrophobic polymer - Google Patents

Abstract

The present invention relates to a method for preparing an emulsion for an aqueous ink consisting of a hydrophilic polymer and a hydrophobic polymer, and more specifically, to synthesize a hydrophilic polymer derived from a carboxyl group first, and then adjust the pH of the hydrophilic polymer, The present invention relates to a method for preparing an emulsion resin in which a hydrophilic polymer and a hydrophobic polymer are present at the same time by synthesizing a polymer having hydrophobicity as a reaction site. The method of the present invention can change the physical properties of the final polymer, such as the composition, acid value, glass transition temperature, etc., by changing the particle size without changing the ink properties, such as hiding power, without a separate control operation, after the emulsion synthesis separate pH Since no control and ripening process is required, the overall reaction time can be greatly shortened.

Description

Method of making emulsion for aqueous ink consisting of hydrophilic polymer and hydrophobic polymer {Method of making emulsion for hydrophilic ink consisting of hydrophilic polymer and hydrophobic polymer}

The present invention relates to a method for preparing an emulsion for an aqueous ink comprising a hydrophilic polymer and a hydrophobic polymer. More specifically, a hydrophilic polymer derived from a carboxyl group is first synthesized, and a hydrophobic polymer is used as a reaction site. The present invention relates to a method for preparing an emulsion resin in which a hydrophilic polymer and a hydrophobic polymer are present simultaneously.

The storage stability of the emulsion resin and the storage stability of the ink using the same are determined by the number of carboxyl groups present on the surface of the emulsion particles used, and the physical properties such as water resistance and alkali resistance depend on the number of carboxyl groups throughout the emulsion resin. Is determined by Therefore, if the carboxyl group used can be present only on the particle surface, the maximum effect can be obtained as the minimum carboxyl group.

As part of this effort, a method of first synthesizing a hydrophilic polymer, a hydrophobic polymer, and drawing a carboxyl group of the hydrophilic polymer to the surface of the emulsion particle has been proposed.

For example, EP 0348 565 proposes a method of synthesizing a hydrophilic polymer in the first step and a hydrophobic polymer in the second step. More specifically, the present invention is a semi-continuous polymerization of the monomers required for the first and second stage polymerization in the form of a pre-emulsion mixed with water and an emulsifier and polymerized. In order to synthesize an emulsion having a final solid content of 38 to 47%. However, in the above method, the polymerization is carried out by fixing the pH at the same level as 2.0 to 4.0 during the first step and the second step polymerization, and when the pH of the emulsion is adjusted to 8.0 or more after the reaction, ammonia water is added for 10 to 15 minutes. Requires a maturation period of 10 days.

As such, the emulsion resin used in the ink should have an alkali property of pH of 8.0 or more due to the nature of the ink formulation, so if the pH of the final synthesized emulsion resin is not in the alkaline region, a separate pH adjustment process must be performed. In the nature of the polymerization, the hydrophilic polymer synthesized in the first is relatively low in molecular weight, the hydrophobic polymer synthesized in the second step is large in molecular weight. Therefore, when the pH is adjusted in the final step, since the solid content and molecular weight of the latex is greatly increased, it is necessary to adjust the pH to 8.0 or more, which requires a lot of maturation period to draw the carboxyl group of the latex to the particle surface. have.

Accordingly, the present inventors have conducted extensive research to solve the above problems, and as a result, first synthesize a hydrophilic polymer having a molecular weight controlled, and then adjust its pH to 8.0 or more, and then synthesize a hydrophobic polymer as a reaction site. In turn, it has been found that the carboxyl groups used are thermodynamically high in probability of being present on the particle surface, thereby obtaining the maximum effect as a minimum of carboxyl groups, and the present invention has been completed based thereon.

Accordingly, it is an object of the present invention to provide a method for producing an emulsion resin for an aqueous ink which is excellent in storage stability.

In order to achieve the above object, a method of preparing an emulsion resin for an aqueous ink according to the present invention is a method for preparing an emulsion for an aqueous ink, wherein the first step is polymerized with a hydrophilic polymer, and the pH of the latex is adjusted to 8-9 with ammonia water. To a region and polymerize the hydrophobic polymer in the second step.

Hereinafter, the present invention will be described in more detail.

The manufacturing method of the emulsion resin for baking ink of this invention consists of the following three steps.

First, a hydrophilic polymer is synthesized in the first step. Since the hydrophilic polymer is composed of a hydrophilic part and a hydrophobic part in the chemical structure, similar to a water-soluble resin of a general emulsifier or a resin polypeptide emulsion, the hydrophilic polymer behaves like an emulsifier and a water-soluble resin in an aqueous phase. That is, the hydrophilic part is dissolved in alkaline water, but the hydrophobic part is restricted in its behavior in water, and this limited behavior results in the formation of micelles (micelles) in the water. These micelles are used as reaction sites due to the unique reaction mechanism of emulsion polymerization, and the resulting polymer has a rounded particle form. In addition, the prepared hydrophilic polymer imparts structural or electrostatic stability to the synthesized polymer particles. The behavior of the hydrophilic polymer in the water phase is changed by the chemical structure of the hydrophilic part and the hydrophobic part, the ratio and molecular weight thereof, and in the present invention, the chemical structure and the ratio of the hydrophilic part and the hydrophobic part are fixed, and the molecular weight of the chain transter agent By varying the amount of use, by controlling the molecular weight of the polymer, by controlling the size and viscosity of the final particles it was possible to expect a variety of applications in the ink production site.

That is, in the first step, 5-16% by weight of methacrylic acid, 5-16% by weight of acrylic acid, 61-85% by weight of ethyl acrylate, 1-3% by weight of acrylonitrile and anionic in the presence of water and buffer solution. A hydrophilic polymer having a molecular weight of 10,000 to 60,000 can be obtained by reacting and polymerizing 0.1 to 4.0 parts by weight of a molecular weight modifier at 60 to 90 ° C with respect to 100 parts by weight of a monomer mixture composed of 1 to 3% by weight of an emulsifier.

At this time, if the molecular weight of the hydrophilic polymer is less than 10,000, the viscosity of the final latex prepared is more than 20,000cps, the problem occurs in handling during ink production, if it exceeds 60,000, the final latex particle size is 200nm or more ink stability This deterioration problem may occur.

Molecular weight regulators used in the hydrophilic polymer polymerization include methyl mercaptan, butyl mercaptan or lauryl mercaptan, and preferably methyl mercaptan.

In the present invention, by adjusting the amount of the molecular weight modifier used in the range of 0.1 to 4.0 parts by weight, other physical properties such as polymer composition are fixed and the size of the final particles and the viscosity of the latex are freely adjusted. That is, by controlling the molecular weight of the hydrophilic polymer, the final particle size is freely changed in the range of 70 ~ 190nm, the viscosity of the latex 400 ~ 10,000cps, it is possible to apply to various applications when applying the final ink, hiding power Ink properties such as can be changed without additional control.

Next, after ripening the synthesized hydrophilic polymer, the pH of the latex is adjusted to 8-9 with ammonia water. In this case, when the pH of the latex is less than 8, the carboxyl groups present in the hydrophilic polymer may not be sufficiently dissociated, thereby preventing stability in the polymerization of the hydrophobic polymer. When the latex is higher than 9, the excess ions may be added to adjust the pH. Due to misinterpretation of the water phase behavior of the hydrophilic polymer may cause a problem that inhibits the stability of the final latex.

In the second step, the hydrophilic polymer is used as a reaction site, and in the presence of water and a polymerization initiator, 70 to 90% by weight of styrene, 6 to 29% by weight of methyl methacrylate and 1 to 4% by weight of a nonionic emulsifier are used at 60 to 90 ° C. Reaction at to prepare a hydrophobic polymer.

As described above, the present invention synthesizes a hydrophilic polymer having a controlled molecular weight, adjusts the pH, and then performs a hydrophobic polymer polymerization, so that the pH can be effectively controlled in a shorter time than the method of controlling the pH in a conventional final step. .

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

Example 1

1126 g of deionized water, 7.9 g of anionic emulsifier (sodium lauryl sulfate) and 2.2 g of sodium bicarbonate were added to the reactor at a time, and the temperature of the reactor was raised to 80 ° C. When the temperature of the reactor reaches 80 ° C, a solution of 3.4 g of ammonium persulfate dissolved in 13.8 g of deionized water is added to the reactor at a time and stirred for 10 minutes. After 10 minutes, the monomer mixture consisting of 30.5 g of methacrylic acid, 30.5 g of acrylic acid, 258.8 g of ethyl acrylate, 8.0 g of acrylonitrile, and 6.0 g of methyl mercaptan as a molecular weight regulator was reacted at a flow rate of 5.9 ml / min for 60 minutes. After the addition, it is aged for 40 minutes. 48.6 g of ammonia water (28% solution) and 88.3 g of deionized water were added to the reactor at once to adjust the pH of the reaction to 8.0. After 10 minutes, a solution in which 5.8 g of ammonium persulfate was dissolved in 132.4 g of deionized water was started to the reactor at 0.9 ml / min. After 10 minutes, a monomer mixture consisting of 875 g of styrene, 108 g of methyl methacrylate and 19.6 g of a nonionic emulsifier (Pluronic L10, BASF) is charged to the reactor at a flow rate of 7.3 ml / min. Allow 60 minutes after the feeding is finished. Since the pH of the final latex is 8.0, it can be applied to the ink formulation without a separate pH adjustment process.

Examples 2-4

The emulsion resin was synthesized in the same manner as in Example 1, except that the amount of methyl mercaptan was changed as shown in Table 1 below.

Composition and Properties of Emulsion Resin for Water-based Inks Example 1 Example 2 Example 3 Example 4 Deionized water 1360.5 1360.5 1360.5 1360.5 Anionic emulsifiers ¹ 7.9 7.9 7.9 7.9 SB ² 2.2 2.2 2.2 2.2 APS ³ 9.2 9.2 9.2 9.2 MAA ⁴ 30.5 30.5 30.5 30.5 AA ⁵ 30.5 30.5 30.5 30.5 EA ⁶ 258.8 258.8 258.8 258.8 AN ⁷ 8.0 8.0 8.0 8.0 Molecular Weight Regulators ⁸ 6.0 8.0 9.5 10.5 ammonia 48.6 48.6 48.6 48.6 ST ⁹ 875.0 875.0 875.0 875.0 MAA ¹⁰ 108.0 108.0 108.0 108.0 Nonionic Emulsifiers ¹¹ 19.6 19.6 19.6 19.6 Solid content (%) 50.0 50.0 50.0 50.0 Molecular Weight (Mn) 61,000 43,000 30,000 27,000 Viscosity (cps) 400 1,200 5,000 10,000 Final pH 8.0 8.0 8.0 8.0 Particle size (nm) 190 115 80 70 Glass transition temperature (℃) 90 90 90 90 Acid value 33 34 31 34

1: Sodium Lauryl Sulfate, 2: Sodium Bicarbonate, 3: Ammonium Perselate, 4: Methacrylic acid, 5: Acrylic acid, 6: Ethyl acrylate, 7: Acrylonitrile, 8: Methyl mercaptan, 9 : Styrene, 10: methyl methacrylate, 11: Pluronic L 10 (BASF).

As shown in Table 1, by controlling the molecular weight of the hydrophilic polymer, it was possible to produce particles of various sizes having the same value as the glass transition temperature and acid value.

Comparative Example 1

40 minutes after the hydrophilic polymer was synthesized, and the ammonia solution was temporarily added to the reactor to adjust the pH of the reactant to 8.0. 2 is shown.

Composition and Properties of Emulsion Resin for Water-based Inks Example 2 Comparative Example 1 Deionized water 1360.5 1360.5 Anionic emulsifiers ¹ 7.9 7.9 SB ² 2.2 2.2 APS ³ 9.2 9.2 MAA ⁴ 30.5 30.5 AA ⁵ 30.5 30.5 EA ⁶ 258.8 258.8 AN ⁷ 8.0 8.0 Molecular Weight Regulators ⁸ 8.0 8.0 ammonia 48.6 0.0 ST ⁹ 875.0 875.0 MMA ¹⁰ 108.0 108.0 Nonionic Emulsifiers ¹¹ 19.6 19.6 Solid content (%) 50.0 50.0 Molecular Weight (Mn) 43,000 42,000 Viscosity (cps) 1,200 100 Final pH 8.0 4.0 Particle Size (nm) 115 Difficult to measure Glass transition temperature (℃) 90 90 Acid value 34 33

1-11 are shown in the said Table 1.

As shown in the comparative example, after the aging, when synthesized without adjusting the pH in advance, the stability of the latex is poor, a large amount of coagulum occurs, it was impossible to measure the exact particle size, the application to the ink prescription It was difficult.

As described above, the method for preparing an emulsion for aqueous ink of the present invention may first control the particle size and viscosity of the final latex produced by controlling the amount of the molecular weight regulator used in the hydrophilic polymer polymerization, and the method By using it, the physical properties such as composition, acid value, glass transition temperature, and the like of the final polymer can be freely changed within the range of 70 to 190 nm, and ink properties such as hiding power can be changed without additional control. In addition, since the pH is adjusted to 8.0 to 9.0 during the polymerization, no separate pH control and aging fixation are required, so that the overall reaction time can be greatly shortened, and thus it can be very usefully used industrially.

Claims (5)

In the method for preparing an emulsion for an aqueous ink, the first step is polymerized with a hydrophilic polymer, the pH of the latex is changed to an alkaline region of 8 to 9 with ammonia water, and the second step is polymerized with a hydrophobic polymer to produce particles of the final emulsion polymer. A method for producing an emulsion for plastic ink, characterized in that the hydrophilic polymer and the hydrophobic polymer are present at the same time. The method of claim 1, wherein the hydrophilic polymer is 5-16% by weight of methacrylic acid, 5-16% by weight of acrylic acid, 61-85% by weight of ethyl acrylate, 1-3 acrylonitrile in the presence of water and a buffer solution. And 0.1 to 4.0 parts by weight of the molecular weight modifier is reacted at 60 to 90 ° C to polymerize with respect to 100 parts by weight of the monomer mixture consisting of% by weight and 1 to 3% by weight of anionic emulsifier, wherein the molecular weight is 10,000 to 60,000. The method of claim 1, wherein the hydrophobic polymer is reacted with 70 to 90% by weight of styrene, 6 to 29% by weight of methyl methacrylate and 1 to 4% by weight of nonionic emulsifier at 60 to 90 ℃ in the presence of water and a polymerization initiator. To polymerize. The method of claim 1 wherein the final emulsion has a viscosity of 400-10,000 and a particle size of 70-190 nm. The method of claim 2, wherein the molecular weight modifier is methyl mercaptan, butyl mercaptan or lauryl mercaptan.