KR20080027594A - Preparation of cationic acrylic emulsion containing ionic comonomer - Google Patents

Abstract

A method for preparing a cationic acrylic emulsion is provided to produce the stabilized emulsion having excellent compatibility with other cationic or non-ionic emulsion in a relatively simple manner. A method for preparing a cationic acrylic emulsion includes the steps of: polymerizing methylmethacrylate, a monomer which has a long side-branched acrylic or vinyl functional group and imparts flexibility and adhesion after copolymerization, an ionomer as a comonomer, and a nonionic surfactant having 20 ethylene oxide groups as an auxiliary surfactant, followed by preparing a pre-emulsion by stirring the resultant and water at high speed to provide a solid content of 40%; and preparing a stabilized cationic emulsion(100-200 nm) by polymerizing the pre-emulsion using an azo group-containing cationic radical initiator. The ionomer is obtained by neutralizing an amine-containing monomer and a vinyl monomer having 9-11 carbon atoms capable of imparting heat resistance, alkali resistance, and UV stability with an organic acid.

Description

Preparation method of cationic emulsion containing ionic comonomers {Preparation of cationic acrylic emulsion containing ionic comonomer}

1: micelle formation of neutralized DMAEMA and cosurfactant

The present invention relates to the preparation of cationic emulsions, and more particularly, to emulsions capable of exhibiting complete compatibility with existing cationic emulsions and expressing desired physical properties as binder resins for inks printed on foamed wallpaper, especially foamed wallpaper using PVC. It is about manufacture.

Recently, a resin, aka ink binder, which is coated and printed on PVC foamed wall paper manufactured by the method disclosed in Korean Patent Laid-Open Publication No. 1998-76004 and Korean Patent Laid-Open Publication No. 2001-0087057 and has been used as an emulsion, has been widely used. Anionic emulsions, which are most commonly manufactured and used, are stabilized by a surfactant system consisting of cationic emulsions and polar ions opposite to each other, so that when mixed, they form large particles and break up dispersion, resulting in precipitation of resin components. It was not possible to use mixed.

US Pat. No. 4,476,286 introduces a method in which lauryl amine is neutralized with an acid as an external surfactant and DMAEMA is also neutralized with an acid and copolymerized. However, this is because by using two types of acid, since the pH is too low, such as 2-3 after the polymerization, it is necessary to go through the process of adjusting the pH by using a buffer, it is difficult to find an appropriate buffer. In addition, there is a problem that the production cost is high because lauryl amine is used.

Some cationic acrylic emulsions on the market have more than 90% of methyl methacrylate (MMA). As a result, when looking at the physical properties of the film, it is found that ink binder resin is too hard and has poor adhesion. .

The present invention solves the above problems and provides a new method for preparing a cationic emulsion that satisfies various conditions such as storage stability, pigment dispersion, adhesion, water resistance, alkali resistance.

It is an object of the present invention to provide a new method of preparing a cationic acrylic emulsion to achieve better physical properties without reducing the physical properties when used alone or in combination with existing cationic emulsions.

The present inventors copolymerize the monomer having an ionic functional group through various embodiments to introduce the ionic functional group between the polymer main chain in the micelle to prepare an emulsion of a more stable state than the emulsion prepared using a conventional cationic surfactant. I found out that I could.

      The present invention provides a method of finally preparing a cationic acrylic emulsion by emulsion polymerization of methyl methacrylate, which is an acrylic monomer, as a main monomer and a monomer having a cationic functional group.

The main monomer used in the present invention is methyl methacrylate, which is used to impart the gloss and toughness of the film. This methyl methacrylate can be used as it is or after purification to remove the polymerization inhibitor. The dosage is determined in an amount of 50 to 95% by weight of the total solids.

In the present invention, n-butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, propyl acrylate and la to give flexibility and adhesion to copolymerize monomers that can improve the physical properties of the final film. Uryl methacrylate and the like are used. The monomer to be copolymerized can improve the flexibility and adhesion by lowering the glass transition temperature of the copolymer. The copolymer is copolymerized at about 10 to 40% by weight, and the final glass transition temperature of the copolymer is adjusted to be about -10 to 70 ° C. good.

In addition, in the present invention, copolymerization is carried out by adding a vinyl monomer having 10 carbon atoms at the end of the acryl group side branch to improve the water resistance and alkali resistance of the film. This monomer, like other copolymerization monomers, copolymerizes to give the film flexibility and to impart water resistance, chemical resistance, UV stability and alkali resistance. It is added together with the main monomers, where the amount added is from 0.5 to 15% by weight and preferably from 1 to 5% by weight.

As a polymerization initiator which can be used by this invention, a water-soluble radical initiator is used. Generally, water-soluble radical initiators are decomposed in the form of ions to have water solubility and can be divided into two types, anionic radical initiators and cationic radical initiators, depending on the form of the decomposed ionic radicals. In other words, if radical ions after decomposition are anionic, they are called cationic radical initiators when they form radical cations after decomposition with anionic initiators. Anionic radical initiators include potassium persulfate (KPS) and ammonium persulfate (APS) sodium persulfate.

(sodium persulfate) and the like, and cationic radical initiators can be used mainly azo compounds. 2,2'-azobis (N, N'-dimethyleneisobutylamidine) dihydrochloride, 2,2'-azobis (2-amidino-propane) dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutylamidine), 4,4'-azobis (4-cyanopentanoic acid), 2,2'-azobis {2-methyl-N- [1,1-bis ( Hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) ethyl] propionamide}, 2,2 ' -Azobis [2-methyl-N- (2hydroxyethyl) propionamide], 2,2'-azobis (isobutylamide) dihydrate and the like can be used. The structure of the cationic surfactant used in the present invention is that the counterion is an anion, but since KPS or APS is a metal ion such as K ⁺ or a cation such as NH ⁺ , it is present in water as a solvent when the cationic emulsion is prepared. It causes instability between particles, causing aggregation and degrading storage stability. Accordingly, cationic or anionic emulsion systems may in some cases require the selection of appropriate initiators.

In the present invention, the polymerization is initiated by using the above-listed cationic water-soluble radical initiators. These are well soluble in water and have been widely used as water-soluble radical initiators such as KPS. When the initiator absorbs a certain amount of energy, the diazo groups decompose into nitrogen molecules to form radicals. The most distinctive feature of the above-mentioned initiators is that they have little effect on the pH change of the polymerization system, so that the radical initiation efficiency is good, unlike KPS, even in an acidic or basic state. Therefore, for the polymerization system of the present invention that proceeds in an acidic state, it can be said to be an optimal polymerization initiator. Appropriate dose added during the polymerization is about 0.1 to 2% by weight of the total solids.

In addition, the present invention was used to neutralize the monomer that can produce the surfactant effect for the purpose of stabilizing the dispersion of the emulsion particles in the present invention is expressed as an internal surfactant. In addition, in the present invention, a monomer having an ionic functional group was copolymerized to help stabilize the dispersion of the emulsion and to exhibit the surfactant effect of the polymer particles themselves. Monomers having such functional groups are called ionomers and are called internal surfactants in the present invention to distinguish them from externally added surfactants. As the ionomer, that is, the internal surfactant, monomers are selected to be composed of lipophilic and hydrophilic parts similar to anionic, cationic, and nonionic surfactants. As the anion, monomers having ionic functional groups such as carboxylic acid, sulfate, nitrate, and phosphate in the side chain are usually used, and these functional groups are attached to the end of the side chain and attached to a long carbon chain having a relatively high carbon number. It is known that the surface active effect is excellent. In the case of nonionicity, it is a case where the monomer which has long chain of ethylene oxide, propylene oxide, and tetramethylene oxide in the side chain is used. That is not unusual. Ionomers used in the case of cationic are mainly monomers in the form of quaternary ammonium salts when treated with acid because they have secondary or tertiary amine or amide functional groups in the side chain. That _{^{is, -NR 4 + A - (R}} : H or a methyl group, an ethyl group, a propyl group, an acyl kilgi etc., A: sulfone group, a chlorine group, a bromine group, an iodine group, a phosphoric acid group, a carboxylic acid group, ethyl group, etc.) and By having the same ionic functional group, it exhibits a cationic surfactant effect that can be dissolved in water. The amine-containing acrylic monomers used as internal surfactants include dimethylaminomethylmethacrylate, diethylaminoethylmethacrylate, tert-butylaminoethylmethacrylate, N-methyldiallylamine, vinylbenzyldimethylamine and oxa. Zolidinyl ethyl methacrylate, aminoethyl methacrylate, N- (3-dimethylamino) propyl methacrylamide

, N- (beta-dimethylamino) ethylacrylamide, 10-aminodecyl vinyl ether, 8-aminooxyl vinyl ether, diethylaminohexyl methacrylate, diethylaminoethyl vinyl ether, 5-aminopentyl vinyl Ether, dimethylaminoethyl vinyl ether, N- (3,5,5-trimethylhexyl) aminoethyl vinyl ether, N-cyclohexylaminoethyl vinyl ether, N-methylaminoethyl vinyl ether, vinyl beta- Dimethylaminopropionate, 3-dimethylamino-2,2-dimethylpropyl methacrylate, 1-dimenylamino-2-propylmethacrylate, 5-aminopentyl vinyl sulfide, beta-hydroxyethylaminoethyl vinyl , (N-beta-hydroxyethyl-N-methyl) aminoethyl vinylether, hydroxyethyldimethyl (vinyloxyethyl) ammonium hydroxide, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-methyl-5--vinylpyridine, 5-methyl-2-vinylpyridine, 4-methyl-2-vinylpyridine, 2-ethyl-5-vinylpi Lidine, 2,3,4-trimethyl-5-vinylpyridine, 3,4,5,6-tetramethyl-5-vinylpyridine, 3-ethyl-5-vinylpyridine, 2,6-diethyl-4-vinyl Pyridine, 2-isopropyl-4-nonyl-5-vinylpyridine, 2-methyl-5-undecyl-3-vinylpyridine, 3-dodecyl-4-vinylpyridine, 2,4-dimenyl-5,6 -Diphenyl-3-vinylpyridine, 2-decyl-5- (alpha-methylvinyl) -pyridine, 3- (4-pyridyl) propy methacrylate, 1- (4-pyridyl) ethyl methacrylate, 2- (4-pyridyl) ethyl acrylate and 3-methacryloxypyridine. In the present invention, the above monomers are referred to as "amine-containing monomers". These amine-containing monomers are used as primary, secondary or tertiary amines, all of which are neutralized with organic or inorganic acids. The acids that can be used are p-toluenesulfonic acid, hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, acetic acid, etc. . These monomers have the properties of a weak base, and when neutralized with an acid, they exhibit a cationic surfactant effect as a hydrophilic functional group of the 2,3,4 ammonium salt, that is, a cationic ionomer. As cationic ionomers, ammonium salts are most suitable, and in salt formation, a final emulsion having better dispersibility when neutralized with organic acid than inorganic acid such as hydrochloric acid or sulfuric acid is produced. At neutralization, the proper pH is in the range of 4-8, preferably in the range of 5-7. Looking at the final structure, the cationic functional group present in the amine-containing monomer, that is, the ions of the ammonium salt have a hydrophilic property, and the resulting polymer itself has a more stable water dispersion stability as the surface active agent of the emulsion developed in the present invention It is the biggest feature.

In addition, in the present invention, since the particles of the emulsion are not stabilized only by the neutralized amine-containing monomer, a nonionic surfactant was added as an auxiliary surfactant to stabilize the emulsion. As the auxiliary surfactant added here, a nonionic surfactant having a number of ethylene oxide groups of 20 was used, and the amount thereof was 2 to 10% by weight of the monomer.

In general, the polymerization of emulsions used as paint binders is often used in a semi-batch or continuous manner using a single reactor. Sometimes, all the reactants are put in a reactor and reacted at once or divided into two or more times and injected into the reactor. Is also used. Batch type has the advantage that the polymerization process is simple and the particle size distribution is narrow, but it is difficult to control the heat of polymerization generated during the polymerization. On the other hand, the semi-batch type or continuous type is easy to control the heat of polymerization, but has the disadvantage of widening the particle size distribution and increasing the overall particle size. For this reason, the present inventors determined that the three-part injection method is most suitable for heat dissipation because it is not easy to control the polymerization heat in equipment operation.

The emulsion production method in the present invention will be described by dividing into two processes as follows.

① pre-emulsion manufacturing process

A monomer which forms a polymer by being copolymerized with methyl methacrylate as an ionomer and neutralized with an amine-containing monomer with an organic acid, and a nonionic surfactant is mixed with water as an auxiliary surfactant for improving dispersion stability. Thereafter, methyl methacrylate and acryl monomer having 4 to 10 carbon atoms and side vinyl monomers having 9 to 11 carbon atoms are added as main monomers, and a pre-emulsion is prepared by stirring at a speed of 250 rpm or more.

② polymerization reaction process

Maintain the reactor temperature at 60 ~ 95 ℃ and the pre-emulsion prepared by the process of the above ① and the aqueous solution of the cationic radical initiator is divided into three times at intervals of about 30 ~ 90 minutes. From the time when the final tertiary initiator was added to maintain the reactor internal temperature at 60 ~ 90 ℃ and stirred for 2 to 5 hours or more to proceed with the polymerization.

EXAMPLE

In the following Examples the present invention has been described in more detail. However, the present invention is not limited to the following examples.

Example 1

To prepare the pre-emulsion, 7.5% by weight of the amine-containing monomer / monomer was neutralized with an organic acid so that the pH was about 5 to 6.5, followed by 72.5% by weight of MMA / monomer, 15% by weight of n-butyacrylate / monomer and Veova-. 10 ^® (Resolution Performance Products) (R) and mix for 5 wt% / monomers. When this monomer is 100% converted after polymerization, NP-20 ^® (5% by weight) of a monomer is dissolved in water so that the solid content is 40% by weight, and then stirred at a speed of 250 rpm or more to prepare a pre-emulsion. It was. Maintain Thereafter the reactor temperature was 70 ℃ and initiator, ^{V-50 ® (Wako Pure chemical} industries, Ltd.) ( R) 0.3% by weight / by dissolving the monomer in a small amount of water and one of the pre-emulsion and the initiator solution / 3 was added and reacted twice to give a stable cationic emulsion.

Example 2

 Cationic acrylic emulsion was obtained by the operation method of all Example 1 except having changed the addition amount of cosurfactant in Example 1 to 3wt% / monomer.

Example 3

The cationic emulsion was prepared by changing the cosurfactant in Example 1 to dodecylammonium chloride (dodecylamine + HCl) (DAC) in an amount of 2wt% / monomer and in a one-shot process in which raw materials were added at a time. Was prepared. Since the cationic emulsions of Examples 1, 2, and 3 were all used with ionomers, it was confirmed that storage stability was improved.

TABLE 1

Example 1 Example 2 Example 3 Type of auxiliary surfactant NP-20 ^® NP-20 ^® DAC input 3wt% 5wt% 2wt% Average particle diameter 290.9 nm 180.8 nm 81.7 nm Viscosity 66.7cp 83.3cp 1876cp

Comparative Example 1

Cationic acrylic emulsion was obtained by the operation method of Example 3 except not adding an ionomer in Example 3.

Comparative Example 2

Except having changed the initiator into KPS in the comparative example 1, the cationic acrylic emulsion of the average particle size of 108 nm and the viscosity of 22.7 cps was obtained by the operation method of the comparative example 1.

TABLE 2

Freezing - Thaw test

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 test results stability stability stability Destruction Destruction

Stable: Keep the emulsion stable.

Destruction: The particles of the emulsion break up and clump together.

This confirmed that there was a problem of low temperature storage stability due to the aggregation of particles due to the breakdown of the emulsion during the freezing-thaw test. That is, it means that the cationic acrylic emulsion prepared by the method provided by the present invention is more stable.

The cationic emulsion prepared by the method of the present invention has strong alkali resistance, excellent water resistance and luster as it is crosslinked by introducing functional groups capable of crosslinking at the same time with the cationic groups in the chain, and is suitable as an ink binder for PVC wallpaper, and is suitable for plastic films. It is also suitable as a coating resin. Since it is an aqueous and cationic emulsion, it can be used in combination with other cationic emulsions and thus has economic advantages.

Claims (7)

Methyl methacrylate, monomer having long side branched acrylic or vinyl functionalities, resulting in low glass transition temperature after copolymerization, giving flexibility and adhesion, and carbon number giving water, alkali, chemical and UV stability Using an ionomer neutralized from 9 to 11 vinyl monomers and an amine-containing monomer with an organic acid as a comonomer, a nonionic surfactant having 20 ethylene oxide groups as a cosurfactant is added to water and 40% solids after polymerization. Pre-emulsion was prepared by high speed stirring, and a stable cationic emulsion of 100-200 nm was prepared using a cationic radical initiator containing azo groups. The method according to claim 1, wherein an ionomer obtained by neutralizing an 1,2 or tertiary amine-containing acrylic or vinyl monomer with an organic acid is used at the side of the branch. The method according to claim 2, wherein the pre-emulsion and the polymerization initiator aqueous solution are divided into three portions. The method according to claim 3, wherein the amount of cationic radical initiator containing a diazo group as the water-soluble polymerization initiator is 0.2 to 0.3 wt% of the total weight of the monomers. The method of claim 4, wherein the amount of the nonionic surfactant containing an ethylene oxide group as the auxiliary surfactant is 3 to 5 wt% based on the total weight of the monomers. The method according to claim 5, wherein 2 wt% of the total weight of the monomer is added by changing the cosurfactant to a neutral or inorganic acid having 1, 2 and 3 alkylamines having 5 to 20 carbon atoms. The method according to claim 1, wherein the polymerization initiator input temperature is 60 to 85 ° C.

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