KR102439756B1 - Process for preparing aqueous acrylic adhesive composition - Google Patents

Abstract

The present invention relates to a method for producing an aqueous acrylic pressure-sensitive adhesive composition. More specifically, according to the present invention, an acrylic emulsion resin is prepared by emulsion polymerization by minimizing the content of hydrolyzable monomers, neutralized with an alkaline material, and then subjected to an aging process at high temperature for a predetermined time. Also provided is a method for producing an aqueous acrylic pressure-sensitive adhesive composition in which changes over time in adhesion properties such as initial adhesion, peeling force, and holding force are minimized.

Description

Method for producing an aqueous acrylic pressure-sensitive adhesive composition {PROCESS FOR PREPARING AQUEOUS ACRYLIC ADHESIVE COMPOSITION}

The present invention relates to a method for preparing an aqueous acrylic pressure-sensitive adhesive composition with minimal change over time.

Recently, the use of sticker-type surface finishing materials such as interior/exterior materials, interior materials, and advertisement materials for buildings to which Pressure-Sensitive Adhesive (PSA) is applied is increasing significantly. As the above adhesive, the existing oil-based adhesives cause headaches, irritation of eyes, nose, and throat, cough, itchiness, dizziness, fatigue, loss of concentration, etc. It causes symptoms, and when exposed for a long period of time, it causes the problem of sick house syndrome, which causes respiratory diseases, heart disease, and cancer.

For this reason, interest in water-based emulsion pressure-sensitive adhesives that are environmentally friendly and do not emit substances harmful to the human body by using water as a dispersion medium are concentrated and rapidly replaced. Aqueous emulsion adhesives are independent of the viscosity of the adhesive and the molecular weight of the dispersion polymer, so a polymer having a higher molecular weight can be used compared to solvent-based polymers, a wide range of solids concentration can be obtained, and good compatibility with other polymers has a

However, since water is used as a solvent, the drying rate is slow, the hydrophobic adhesive surface, the adhesiveness to the non-porous adherend is low, the selection range of the curing agent is narrow, and the initial adhesive strength is poor, as well as the emulsification. And since it contains a dispersing agent, it has problems such as low water resistance and does not reach the same physical properties as oil-based adhesives.

In addition, conventional water-based adhesives, which are generally prepared through emulsion polymerization, are processed and used in the form of labels, tapes, protective films, and the like. There is a problem that occurs. In particular, according to the long-term storage of latex, changes in pH, viscosity, peeling force, initial adhesive force, holding force, etc. occur, and a problem in which adhesive properties are deteriorated occurs.

An object of the present invention is to provide a method for preparing an aqueous acrylic pressure-sensitive adhesive composition having changes in adhesive properties by stabilizing changes in pH over time.

In addition, the present invention is to provide a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed using the aqueous acrylic pressure-sensitive adhesive composition prepared by the above manufacturing method.

According to one embodiment of the present invention,

i) together with a (meth)acrylic acid ester monomer having a C1-C18 alkyl group,

ii) unsaturated acetate, unsaturated nitrile, or mixtures thereof, iii) unsaturated carbonic acid, an unsaturated monomer containing a hydroxyl group or a mixture thereof, and iv) at least one comonomer selected from the group consisting of a styrenic monomer having a vinyl group preparing an acrylic emulsion resin by emulsion polymerization using a monomer mixture; and

After neutralizing the acrylic emulsion resin with an alkaline material, aging at 60 to 95° C. for 1 to 24 hours;

Based on 100 parts by weight of the i) (meth)acrylic acid ester monomer, the ii) unsaturated acetate, unsaturated nitrile, or a mixture thereof is included in an amount of 17 parts by weight or less,

A method for producing an aqueous acrylic pressure-sensitive adhesive composition is provided.

In addition, according to another embodiment of the present invention, there is provided a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer formed using the aqueous acrylic pressure-sensitive adhesive composition prepared by the method as described above.

Hereinafter, the present invention will be described in more detail. The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

Also, the meaning of "comprising" as used in the context of the present invention embodies a particular characteristic, region, integer, step, operation, element and/or component, and other characteristic, region, integer, step, operation, element and/or It does not exclude the presence or addition of ingredients.

Hereinafter, a method for producing a preferred aqueous acrylic pressure-sensitive adhesive composition of the present invention will be described in more detail.

According to one embodiment of the invention, i) together with a (meth)acrylic acid ester monomer having a C1-C18 alkyl group,

ii) unsaturated acetates, unsaturated nitriles or mixtures thereof, iii) unsaturated carbonic acids, unsaturated monomers containing hydroxyl groups or mixtures thereof, and iv) at least one comonomer selected from the group consisting of styrenic monomers having a vinyl group preparing an acrylic emulsion resin by emulsion polymerization using a monomer mixture; and

After neutralizing the acrylic emulsion resin with an alkaline material, aging at 60 to 95° C. for 1 hour to 24 hours;

Based on 100 parts by weight of the i) (meth)acrylic acid ester monomer, the ii) unsaturated acetate, unsaturated nitrile, or a mixture thereof is included in an amount of 17 parts by weight or less,

Provided is a method for preparing an aqueous acrylic pressure-sensitive adhesive composition.

In the present specification, the aqueous acrylic adhesive is an acrylic emulsion adhesive using water as a dispersion medium, and includes an acrylic emulsion resin having water resistance and adhesiveness with a polyolefin-based film.

In addition, as used herein, the term "monomer mixture" refers to a state in which one or more monomers described below are mixed together based on acrylic monomers, and the one or more monomers may be added together and prepared, Since it may be sequentially introduced and manufactured, the manufacturing method thereof is not limited. In addition, the monomer mixture is not particularly limited as long as the acrylic emulsion resin is polymerized, and one or more various monomers well known in the art may be used.

The present inventors have conducted continuous experiments to solve the problem that the existing water-based adhesive is stored for a long time in a latex (water-dispersed polymer) state until it is processed into a product such as a label, tape, or protective film, and the According to the experimental results, when the amount of specific hydrolyzable monomer is minimized and the pH-controlled resin is aged at high temperature, pH 6 or higher is maintained even during long-term storage of latex, there is little change in viscosity, and initial adhesion and peeling force , it was confirmed that the change over time of holding force can be minimized, and the present invention was completed.

In the method according to an embodiment of the present invention, an acrylic emulsion resin is prepared by emulsion polymerization using a monomer mixture including a meth)acrylic acid ester monomer, and the acrylic emulsion resin is neutralized with an alkaline material to neutralize the pH. After adjusting as described above, high-temperature aging is performed to prepare an aqueous acrylic pressure-sensitive adhesive composition.

Specifically, each step of the method of the present invention will be described.

The step of preparing the acrylic emulsion resin is i) with a (meth)acrylic acid ester monomer having a C1-C18 alkyl group, ii) unsaturated acetate, unsaturated nitrile, or a mixture thereof, iii) unsaturated carbonic acid, an unsaturated monomer containing a hydroxyl group, or these and iv) emulsion polymerization using a monomer mixture containing one or more comonomers selected from the group consisting of styrenic monomers having a vinyl group.

Here, the i) (meth)acrylic acid ester monomer is a (meth)acrylic acid ester monomer having a C1-C18 alkyl group, that is, an alkyl group having 1 to 18 carbon atoms, and is not limited as long as it is a material known in the art. For example, the (meth) acrylic acid ester monomer is methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, t- It may be at least one selected from the group consisting of butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, and may be used in combination of two or more. have. Specifically, one or two or more selected from methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate may be preferably used.

The (meth)acrylic acid ester monomer is about 50% by weight or more, or about 50 to 98% by weight, or about 55% by weight or more, or about 55 to 95% by weight, or about 60% by weight or more, or about 60% by weight or more in the total content of the monomer mixture It may be included in an amount of 60 to 90% by weight.

In a more preferred embodiment of the present invention, the (meth)acrylic acid ester monomer is 50 to 95 wt% of 2-ethylhexyl acrylate, 5 to 30 wt% of methyl methacrylate, 0 to 20 wt% of methyl acrylate, or It may be 60 to 93 wt% of 2-ethylhexyl acrylate, 8 to 25 wt% of methyl methacrylate, and 0 to 15 wt% of methyl acrylate. In particular, since the adhesive properties are a result of the glass transition temperature (Tg) of the resin, the content ratio of the monomer and the comonomer is important. It is preferable to adjust the ratio of the remaining monomers to obtain suitable adhesive properties.

The monomer mixture comprises i) a (meth)acrylic acid ester monomer having a C1-C18 alkyl group, ii) an unsaturated acetate, an unsaturated nitrile or a mixture thereof, iii) an unsaturated carbonic acid, an unsaturated monomer containing a hydroxyl group or a mixture thereof, iv) It further includes at least one comonomer selected from the group consisting of styrenic monomers having a vinyl group.

The comonomer is about 40 parts by weight or less, or about 0 to 40 parts by weight, or about 25 parts by weight or less, or about 1 to 25 parts by weight, or about 20 parts by weight or less, based on 100 parts by weight of the (meth)acrylic acid ester monomer It may be added in an amount of about 3 to 20 parts by weight. When the content of the comonomer is included in excess of 40 parts by weight, it is not preferable because it is excessively hardened and may cause a decrease in adhesive strength. However, since the pressure-sensitive adhesive becomes too flexible and transfer may occur due to excessive adhesive properties, it is preferable to include the comonomer in an amount greater than or equal to the minimum content.

As an example of one of the comonomers, the ii) unsaturated acetate, unsaturated nitrile or mixtures thereof is vinyl acetate, vinyl butanoate, vinyl propionate, vinyl laurylate, vinyl pyrrolidone, acrylonitrile, and methacrylonitrile It may be one or more selected from the group consisting of, and may be used in combination of two or more. Specifically, vinyl acetate or the like can be preferably used.

In particular, among the comonomers, ii) hydrolyzable monomers such as unsaturated acetates, unsaturated nitriles, or mixtures thereof generate acids upon hydrolysis to lower pH, so it is preferable to minimize the amount of such hydrolyzable monomers. In this aspect, the hydrolyzable monomer is included in an amount of about 17 parts by weight or less, or about 0 to 17 parts by weight, or about 14 parts by weight or less, or about 0 to 12 parts by weight based on 100 parts by weight of the i) (meth)acrylic acid ester monomer. can When the content of the hydrolyzable monomer exceeds about 17 parts by weight, the pH is severely lowered, and the rate of change over time, such as viscosity and peeling force of the pressure-sensitive adhesive, and initial adhesive force, is not preferred.

iii) unsaturated carbonic acid, hydroxyl group-containing unsaturated monomer or mixtures thereof are acrylic acid, itaconic acid, maleic anhydride, fumaric acid, methacrylic acid crotonic acid, ethyl methacrylic acid, hydroxymethyl (meth) acrylate, hydroxyethyl ( Meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxylauryl (meth) acrylate , and may be one or more selected from the group consisting of hydroxypropylene glycol (meth) acrylate, and may be used in combination of two or more. Specifically, one or two or more selected from acrylic acid, hydroxy ethyl methacrylate and hydroxy ethyl acrylate may be preferably used.

Here, the iii) unsaturated carboxylic acid, the hydroxyl group-containing unsaturated monomer or a mixture thereof is about 10 parts by weight or less, or about 0 to 10 parts by weight, or about 5 parts by weight based on 100 parts by weight of the (meth)acrylic acid ester monomer. It may be included in less than or about 0.5 to 5 parts by weight. The content of the iii) unsaturated carbonic acid, the hydroxyl group-containing unsaturated monomer, or a mixture thereof is preferably 10 parts by weight or less or 5 parts by weight or less from the viewpoint of polymerization stability. However, iii) unsaturated carboxylic acid, hydroxyl group-containing unsaturated monomer, or a mixture thereof may be used in an amount of 0.5 parts by weight or more in terms of latex stability.

The iv) styrene-based monomer having a vinyl group may be at least one selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, and p-(t-butyl)styrene, and may be used in combination of two or more.

Here, the iv) styrenic monomer having a vinyl group is about 20 parts by weight or less, or about 0 to 20 parts by weight, or about 10 parts by weight or less, or about 1 to 10 parts by weight based on 100 parts by weight of the (meth)acrylic acid ester monomer. may be included as a part. The v) content of the styrenic monomer having a vinyl group is preferably 20 parts by weight or less or 10 parts by weight or less in terms of preventing a decrease in adhesive strength. However, v) the styrene-based monomer having a vinyl group may be used in an amount of 1 part by weight or more in terms of increasing adhesive strength.

In a preferred embodiment, the monomer mixture comprises: i) based on 100 parts by weight of the (meth)acrylic acid ester monomer having a C1-C18 alkyl group, ii) about 17 parts by weight or less of an unsaturated acetate, an unsaturated nitrile, or a mixture thereof, or about 0 to 17 parts by weight, iii) about 10 parts by weight or less or about 0 to 10 parts by weight of an unsaturated carbonic acid, an unsaturated monomer containing a hydroxyl group, or a mixture thereof, and iv) about 20 parts by weight or less of a styrenic monomer having a vinyl group or about 0 to 20 parts by weight; or i) based on 100 parts by weight of the (meth)acrylic acid ester monomer having a C1-C18 alkyl group, ii) about 12 parts by weight or less or about 0 to 12 parts by weight of an unsaturated acetate, unsaturated nitrile, or mixture thereof, iii) unsaturated carbon It may contain about 5 parts by weight or less or about 0.5 to 5 parts by weight of an acid, an unsaturated monomer containing a hydroxyl group, or a mixture thereof, and iv) about 10 parts by weight or less or about 1 to 10 parts by weight of a styrenic monomer having a vinyl group.

On the other hand, in the first polymerization reaction in the present invention, the monomer mixture is selected from the group consisting of molecular weight modifiers, crosslinking agents, initiators, emulsifiers, defoamers, thickeners, dispersants, UV stabilizers, antioxidants, antiseptics, surfactants, buffers, and fillers. One or more additives may be further included.

The molecular weight modifier serves as a chain transfer agent (CTA) during the polymerization reaction of the resin, and specifically, it attaches to the end of the molecule and transfers the radical to another place and makes a termination reaction. The molecular weight modifier is, for example, alcohol, ether, thioether, dithiocarbonate, natroxide, mercaptan, tempo (TEMPO), lauryl mercaptan, n-dodecyl mercaptan, t-dodecyl mer consisting of captan, n-octyl mercaptan, glycidyl mercaptan, mercapto acetic acid, 2-mercapto ethanol, thioglycolic acid, thioglycolic acid 2-ethylhexyl, and 2,3-dimercapto-1-propanol It may be at least one selected from the group.

The content of the molecular weight regulator may be, for example, 0.06 parts by weight to 0.17 parts by weight, or 0.07 parts by weight to 0.15 parts by weight based on 100 parts by weight of the acrylic emulsion resin.

In the present invention, the crosslinking agent is, for example, allyl methacrylate, 1,6-hexanediol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethylene glycol diacrylate Late, ethylene glycol dimethacrylate, hexanediol ethoxylate diacrylate, hexanediol propoxylate diacrylate, neopentyl glycol ethoxylate diacrylate, neopentyl glycol propoxylate diacrylate, trimethylpropane selected from the group consisting of thoxylate triacrylate, trimethylpropanepropoxylate triacrylate, pentaerythritol ethoxylate triacrylate, pentaerythritol propoxylate triacrylate, vinyltrimethoxysilane, and divinylbenzene. There may be more than one type.

The content of the crosslinking agent may be, for example, 0.06 parts by weight to 0.25 parts by weight, or 0.06 parts by weight to 0.20 parts by weight based on 100 parts by weight of the acrylic emulsion resin.

In addition, the polymerization initiator may be a water-soluble polymerization initiator such as ammonium or alkali metal persulfate, hydrogen peroxide, peroxide, and hydroperoxide, and may be used together with one or more reducing agents to carry out the emulsion polymerization reaction at a low temperature, However, the present invention is not limited thereto.

In this case, the content of the polymerization initiator may be used in an amount of 0.1 to 2 parts by weight based on 100 parts by weight of the acrylic emulsion resin. In addition, the polymerization initiator may be appropriately divided and used within the above-described range by dividing at least once during the polymerization step of the acrylic emulsion resin to be described later.

In addition, the surfactant may be used for initial particle generation during the polymerization reaction, size control of the generated particles, and stability of the particles. These surfactants are composed of a hydrophilic group and a lipophilic group, and are divided into anionic, cationic, and nonionic surfactants, and mainly anionic and nonionic surfactants are mainly used, and mixed with each other to supplement mechanical stability and chemical stability also do The surfactant is, for example, sodium polyoxyethylene alkyl ether sulfate (various types depending on the EO group), diphenyl oxide disulfonate, sodium lauryl sulfate , sodium alkyldiphenyloxide disulfonate, or sodium methylallyl sulfonate, but is not limited thereto. In addition, these may be used alone or in combination of two or more. For example, a surfactant having a phenyl group can attract non-polar monomers well, and a surfactant having a methyl allyl group can accommodate many monomers because the molecule is not large.

Here, the composition of each surfactant may be adjusted slightly, but the total amount is about 5 parts by weight or less, or about 0 to 5 parts by weight, or about 4 parts by weight or less, or about 0.3 to 4 parts by weight based on 100 parts by weight of the acrylic emulsion resin. , or about 3 parts by weight or less, or about 0.05 to 3 parts by weight. When the surfactant is included in excess of about 5 parts by weight, it is not preferable because adhesive properties may change. For example, the composition of the surfactant is about 0.2 to 0.8 parts by weight or about 0.3 to 0.7 parts by weight of sodium polyethylene alkyl ether sulfate, and about 0.1 to 0.5 parts by weight of diphenyl oxide disulfonate and sodium lauryl sulfate, respectively, or It may be about 0.2 to 0.4 parts by weight.

In addition, it may further include a buffer (buffer) to adjust the pH in the polymerization reaction and impart polymerization stability, for example, sodium bicarbonate, sodium carbonate, sodium phosphate, sodium sulfate, sodium chloride, etc. However, the present invention is not limited thereto. In addition, these may be used alone or in combination of two or more.

The buffer may be included in an amount of about 0.5 parts by weight or less, or about 0 to 0.5 parts by weight, or about 0.3 parts by weight or less, or about 0 to 0.3 parts by weight based on 100 parts by weight of the acrylic emulsion resin.

On the other hand, in the present invention, the emulsion polymerization reaction may be carried out under a temperature condition of about 60 to 100 ℃, preferably, it may be carried out under a temperature condition of about 70 to 90 ℃. The polymerization reaction temperature may be performed at a temperature of about 60° C. or higher in terms of reaction initiation activation, and may be performed at a temperature of about 100° C. or lower due to the nature of the aqueous reaction process. The emulsion polymerization reaction time may be arbitrarily selected and applied within the range commonly employed in the art to which the present invention pertains, for example, about 1.5 to 12 hours, preferably about 2 to 10 hours.

By carrying out the emulsion polymerization reaction as described above, it is possible to prepare an acrylic emulsion resin having a pH of 6 or higher and having little change in viscosity even during long-term storage of Latex.

The acrylic emulsion resin may have a glass transition temperature (Tg) of about -60°C to -20°C.

The acrylic emulsion resin may have a pH of about 6 or more, or about 6 to 9, or a pH of about 6.5 or more, or about 6.5 to 8.5. In addition, the resin has a pH of about 5 or more, or about 5 to 8, or a pH of about 6 or more or about 6 to 7, measured after being left at room temperature for 30 days from the time of emulsion polymerization, maintaining a pH of about 5 or more characterized in that

The acrylic emulsion resin may have a viscosity of about 10 cps or more, or about 10 to 10000 cps, or about 20 cps or more, or about 20 to 9000 cps. In addition, the viscosity measured after leaving the resin at room temperature for 30 days from the time of emulsion polymerization is also about 200 cps or more, or about 200 to 8000 cps, or about 10 cps or more, or about 10 to 7000 cps, at the time of emulsion polymerization It is characterized by maintaining a high level of 75% or more, or 80% or more.

On the other hand, in the method according to an embodiment of the present invention, an acrylic emulsion resin is prepared through the emulsion polymerization reaction as described above, and the pH is adjusted to neutral or higher by neutralizing treatment with an alkaline material, and then high temperature aging is performed. including the process of

The acrylic emulsion resin may have a pH of about 6 or more, or about 6 to 9.5, or a pH of about 6.5 or more, or about 6.5 to 8.5 after being neutralized with an alkaline material. The pH of the resin after neutralization with an alkaline substance is preferably about 6 or more in terms of latex stability, and preferably about 9.5 or less in terms of odor suppression.

The alkali neutralizing agent may be, for example, at least one selected from the group consisting of hydroxides, chlorides, carbonates, aqueous ammonia, and organic amines of divalent metals, and specifically, aqueous ammonia and organic amines. In particular, in the present invention, ammonia water may be used for latex stability, and an aqueous ammonia solution of about 5% to 35% may be preferably used. The alkali neutralizing agent may be added in an amount such that the pH of the resin is in the range as described above, for example, in an amount of about 0.5 to 1.5 parts by weight based on 100 parts by weight of the acrylic emulsion resin, 25% to 30% aqueous ammonia solution can be put in

In the present invention, as described above, the pH-adjusted acrylic emulsion resin is characterized in that the aging stability is improved through aging at a high temperature.

The process of aging the pH-adjusted acrylic emulsion resin may be performed under a temperature condition of about 60 to 95 °C, preferably about 65 to 93 °C or about 70 to 90 °C It may be carried out under a temperature condition. This aging temperature should be carried out at a temperature of about 60 ° C. or higher in terms of accelerated stabilization over time, and should be carried out at a temperature of about 95 ° C. or less in terms of latex stability.

In addition, the aging process time may be performed for about 1 to 24 hours, preferably about 1.5 to 15 hours, or about 2 to 10 hours. In particular, this aging temperature should be carried out for about 1 hour or more in terms of completing the time-stabilized sample, and should be carried out for about 24 hours or less in terms of productivity improvement.

The method for preparing the pressure-sensitive adhesive composition may further include a step commonly employed in the art to which the present invention pertains in addition to the steps described above.

And, for coating properties, a wetting agent serving as an emulsifier to lower the surface tension may be additionally used, and the content thereof may be used within a range well known in the art.

On the other hand, according to another embodiment of the present invention, there is provided a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer formed using the aqueous acrylic pressure-sensitive adhesive composition prepared by the method as described above.

The adhesive sheet may be processed in the form of an adhesive label, an adhesive tape, an adhesive protective film, or the like. The adhesive sheet, for example, adhesive labels, etc. can be maintained to an excellent degree in all of the adhesive properties of peel force, loop tack and shear value even when stored for a long time in a latex (Latex, water-dispersible polymer) state.

In particular, the pressure-sensitive adhesive sheet, by using the aqueous acrylic pressure-sensitive adhesive composition prepared as described above, and left for 30 days from the time of emulsion polymerization of the acrylic emulsion resin contained in the pressure-sensitive adhesive composition, among the physical properties measured after the initial adhesive strength (Loop) Tack) is about 118% or less of the value measured at the point of emulsion polymerization, the peel force (90˚ peel) is less than 115% of the value measured at the point of emulsion polymerization, and the shear is about 118% or less of the value measured at the point of emulsion polymerization. 63% or more of the value, pH may have a difference of within 1.1 from the value measured at the point of emulsion polymerization, or viscosity may be about 83% or more of the value measured at the point of emulsion polymerization.

In the present invention, after preparing an acrylic emulsion resin by emulsion polymerization by minimizing the hydrolyzable monomer content, after neutralizing with an alkaline material, the aging process is performed at high temperature for a predetermined time. There is an effect of providing a water-based acrylic pressure-sensitive adhesive that minimizes changes in adhesive properties over time.

Hereinafter, the operation and effect of the invention will be described in more detail through specific examples of the invention. However, this is presented as an example of the invention and the scope of the invention is not limited in any sense by this.

< Example >

Example One

acrylic emulsion Preparation of resin

About 210 g of ion-exchanged water was put into a 2 L glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, and sodium polyoxyethylene lauryl ether sulfate (sodium polyoxyethylene lauryl) at a concentration of 26 wt% was added. About 1.0 g of ether sulfate) was added, the inside of the reactor was substituted with nitrogen while stirring, and then the temperature was raised to about 80° C. under a nitrogen atmosphere and maintained for about 60 minutes.

Separately, in a 2 L beaker, about 555 g of 2-ethylhexyl acrylate (2-EHA), about 70 g of methyl methacrylate (MMA), about 35 g of methyl acrylate (MA), and about 35 g of styrene (SM) , about 1 g of polyethyl glycol 400 diacrylate, and about 1 g of normal dodecyl mercaptan (n-DDM) were added, and then 697 g of a monomer mixture mixed for about 30 minutes was prepared. and, in the monomer mixture, about 7 g of a solution of sodium alkyldiphenyloxide disulfonate at a concentration of about 50% by weight, about 15 g of sodium polyoxyethylene alkyl ethersulfate at a concentration of about 26% by weight, about 2 g of sodium carbonate, and water An aqueous solution consisting of about 190 g was added, and the resulting aqueous solution was added and mixed with a stirrer to prepare a cloudy emulsion (pre-emulsion).

In the glass reactor, the emulsion of the cloudiness and about 80 g of the ammonium persulfate solution having a concentration of about 10% by weight are evenly and continuously added for about 4 hours, and when the ammonium persulfate solution and the emulsion are completed, the temperature is about 80 ° C. for about 1 hour. It was maintained for a while to prepare an acrylic emulsion resin.

acrylic emulsion neutralization of resin and aging (aging)

After raising the temperature to about 90 °C of the acrylic emulsion resin obtained as described above, an aqueous ammonia solution having a concentration of about 30 wt% was added to adjust the pH to about 8.0 to 9.5. And, while maintaining the temperature of the acrylic emulsion resin whose pH is adjusted at about 90 ° C., as a wetting agent that serves as an emulsifier to further lower the surface tension for coatability, about 65% sodium dodecyl sulfosuccinate About 10 g of nitrate was added and stirred for about 30 minutes. Thereafter, the acrylic emulsion resin [latex] was aged at about 90° C. for about 2 hours, and then cooled to room temperature to prepare an acrylic emulsion pressure-sensitive adhesive composition.

Example 2

As shown in Table 1 below, about 555 g of 2-ethylhexyl acrylate (2-EHA), about 105 g of methyl methacrylate (MMA), and about 35 g of vinyl acetate (Vac) were used as monomers. , An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Example 3

As shown in Table 1 below, as a monomer, about 555 g of 2-ethylhexyl acrylate (2-EHA), about 70 g of methyl methacrylate (MMA), about 35 g of methyl acrylate (MA), and about 35 g of vinyl acetate (Vac) ) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that about 35 g was used.

Example 4

As shown in Table 1 below, about 555 g of 2-ethylhexyl acrylate (2-EHA), about 70 g of methyl methacrylate (MMA), and about 70 g of vinyl acetate (Vac) were used as monomers. , An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

comparative example One

As shown in Table 1 below, about 485 g of 2-ethylhexyl acrylate (2-EHA), about 70 g of methyl methacrylate (MMA), and about 140 g of vinyl acetate (Vac) were used as monomers. , An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

comparative example 2

As shown in Table 1 below, 2-ethylhexyl acrylate (2-EHA) about 555 g, methyl methacrylate (MMA) about 70 g, methyl acrylate (MA) about 35 g, styrene (SM) as a monomer An acrylic emulsion adhesive was prepared in the same manner as in Example 1, except that an acrylic emulsion resin was prepared using about 35 g, the pH was adjusted with an aqueous ammonia solution, and a separate aging process was not performed after the wetting agent was treated. A composition was prepared.

comparative example 3

As shown in Table 1 below, about 555 g of 2-ethylhexyl acrylate (2-EHA), about 105 g of methyl methacrylate (MMA), and about 35 g of vinyl acetate (Vac) were used as monomers. , An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Comparative Example 2.

comparative example 4

As shown in Table 1 below, as a monomer, about 555 g of 2-ethylhexyl acrylate (2-EHA), about 70 g of methyl methacrylate (MMA), about 35 g of methyl acrylate (MA), and about 35 g of vinyl acetate (Vac) ) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Comparative Example 2, except that about 35 g was used.

comparative example 5

As shown in Table 1 below, about 555 g of 2-ethylhexyl acrylate (2-EHA), about 70 g of methyl methacrylate (MMA), and about 70 g of vinyl acetate (Vac) were used as monomers. , An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Comparative Example 2.

comparative example 6

As shown in Table 1 below, about 485 g of 2-ethylhexyl acrylate (2-EHA), about 70 g of methyl methacrylate (MMA), and about 140 g of vinyl acetate (Vac) were used as monomers. , An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Comparative Example 2.

comparative example 7

As described above, in performing the aging process after preparing the acrylic emulsion resin, adjusting the pH with an aqueous ammonia solution and treating the wetting agent, the aging process was performed at about 55° C. for about 2 hours Except for performing the aging process Then, an acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

comparative example 8

As described above, in performing the aging process after preparing the acrylic emulsion resin, adjusting the pH with an aqueous ammonia solution and treating the wetting agent, the aging process was performed at about 90 ° C. for about 0.5 hours Except for performing the aging process Then, an acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Specific monomer components and contents of the acrylic emulsion pressure-sensitive adhesive composition according to Examples and Comparative Examples are as shown in Table 1 below.

After neutralization of NH ₄ OH
High temperature aging Monomer (g) MA Vac MMA SM 2-EHA Example 1 O 35 70 35 555 Example 2 O 35 105 555 Example 3 O 35 35 70 555 Example 4 O 70 70 555 Comparative Example 1 O 140 70 485 Comparative Example 2 X 35 70 35 555 Comparative Example 3 X 35 105 555 Comparative Example 4 X 35 35 70 555 Comparative Example 5 X 70 70 555 Comparative Example 6 X 140 70 485 Comparative Example 7 O 70 70 555 Comparative Example 8 O 70 70 555

< Experimental example >

Manufacture of adhesive sheet coated with adhesive

The acrylic emulsion pressure-sensitive adhesive composition prepared in Examples and Comparative Examples was applied on a silicone-coated release paper, and dried in an oven at about 110° C. for about 2 minutes so that the pressure-sensitive adhesive layer had a thickness of about 20 μm. The adhesive resin applied on the silicone release paper was laminated with a polypropylene film to make an adhesive sheet. The adhesive sheet was cut to a size of about 25 mm x 200 mm to prepare an adhesive label specimen.

Physical property evaluation

The pH, viscosity, and adhesive properties of the acrylic emulsion adhesive of the acrylic emulsion resin (latex) prepared in Examples and Comparative Examples were measured at the time point (fresh) within 10 minutes after preparation and at the time point (30 days) after 30 days at room temperature. It was tested by the following method. The results are shown in Table 2 below.

acrylic emulsion pH of latex

After maintaining the acrylic emulsion resin (latex) at 23±1° C., the pH was measured.

acrylic emulsion Viscosity of latex (cps)

After maintaining the acrylic emulsion resin (latex) at 23 ± 1 °C, the viscosity was measured.

adhesive peel force (peel) test (N/inch)

Test method FINAT TEST METHOD NO. According to 2, the acrylic emulsion adhesive paper label specimen is reciprocated twice at a speed of about 300 mm/min with an about 2 kg roller, attached to a high-density polyethylene (HDPE) film, aged at room temperature for about 20 minutes, and then TA It was measured while peeling at 90 degrees (90 degrees) at a speed of about 300 mm/min using a Texture Analyzer device.

Loop tack test of adhesive (N/inch)

Specimen preparation for loop

- Sample size: 25mm X 150mm

- Adhesive: Glass (or HDPE)

- Measurement conditions: 23±2℃, 50±5%RH

- Measurement method: The specimen was made in a loop shape and fixed to the clamp, and the specimen was attached to glass (or high-density polyethylene/HDPE-high-density polyethylene film) at a constant speed. After about 5 seconds, the force corresponding to the highest value when separating in the opposite direction by applying a measuring speed of about 300 mm/min was measured as the loop tack peeling force.

adhesive retention (shear)

Holding Power test (Shear test) was performed in the following way.

- Sample size: 25mm X 70mm

- Adhesive: A bright stainless steel plate was prepared (Bright SUS: shiny and more slippery)

- Measurement conditions: 23±2℃, 50±5%RH

-Measuring method: After reciprocating the specimen with a roller of about 2 kg once and attaching it to the adherend in an area of 25 mm X 25 mm, the holding force was measured without dwell time (measuring speed 300 mm/min).

After a fixed load of about 1 kg was applied to the lower end of the sample, the time at which the pressure-sensitive adhesive sample fell was measured.

Acrylic emulsion resin (latex) adhesive sheet pH viscosity Loop tack (N/inch) 90° peel (N/inch) Shear(min) Fresh 30 days Fresh 30 days rate of change
(%) Fresh 30 days rate of change
(%) Fresh 30 days rate of change
(%) Fresh 30 days rate of change
(%) Example 1 8.5 8.2 1,600 1,500 94 9.7 10.7 110 7.5 7.9 105 15,200 14,200 93 Example 2 7.0 6.5 2,400 2,200 92 11.4 12.5 110 8.4 9.7 115 7,000 5,300 76 Example 3 6.9 6.6 1,800 15,00 83 12.1 14.3 118 8.8 9.4 107 12,100 8,600 71 Example 4 6.5 6.1 1,700 1400 82 13.2 16.3 123 8.6 10.3 120 17,800 12,200 68 Comparative Example 1 6.2 5.7 1,700 1200 71 14.1 19.7 140 9.2 13.7 149 27,500 5,400 20 Comparative Example 2 8.9 8.3 2,200 1,600 72 10.2 10.5 103 8.1 8.1 100 16,000 13,600 85 Comparative Example 3 8.7 7.0 3,300 2,000 60 12.3 15.1 125 8.4 10.4 124 6500 2200 34 Comparative Example 4 8.7 6.9 3,300 1.900 58 11.5 14.4 125 8.6 10.7 124 7300 3100 42 Comparative Example 5 8.8 6.7 4,000 1,800 45 10.6 16.1 152 7.7 14.1 183 12,500 2200 18 Comparative Example 6 8.7 5.9 4,200 1,600 38 11.8 18.9 160 7.9 17.6 223 16,300 1,500 9 Comparative Example 7 8.2 6.7 3900 1900 48 10.7 15.4 144 7.8 13.9 178 12700 3,200 25 Comparative Example 8 8.3 6.6 3800 1700 45 10.2 16.4 161 7.1 14.4 202 15,500 3,000 19

From the results in Table 2 above, Examples 1 to 4 performed emulsion polymerization by minimizing the content of hydrolyzable monomers, and performing an aging process at a high temperature for a predetermined time after neutralization, an acrylic emulsion resin (latex) and an adhesive sheet using the same It was confirmed that there was little change in pH and viscosity. In particular, as in Example 1, the rate of change in the physical properties of the latex was very small in the sample without vinyl acetate, and it can be confirmed from Examples 2, 3, and 4 that the change over time is relatively small when high temperature aging is performed after neutralization even if vinyl acetate is included. have. In addition, it can be seen that, in addition to these latex physical properties, the range of physical property change in Examples 1 to 4 in which high temperature aging was performed after neutralization was relatively small.

On the other hand, Comparative Examples 1 to 6 did not perform high-temperature aging after neutralization, and it can be seen that the change in latex properties was large and the change in adhesion properties was also significantly increased compared to Examples 1 to 4. In addition, even if 7 and 8 are included in the comparison, it can be confirmed that it is difficult to achieve latex aging stabilization if the aging temperature is too low or the time is too short.

Claims (12)

i) together with a (meth)acrylic acid ester monomer having a C1-C18 alkyl group,
ii) unsaturated acetate, unsaturated nitrile, or mixtures thereof, iii) unsaturated carbonic acid, an unsaturated monomer containing a hydroxyl group or a mixture thereof, and iv) at least one comonomer selected from the group consisting of a styrenic monomer having a vinyl group preparing an acrylic emulsion resin by emulsion polymerization using a monomer mixture; and
After neutralizing the acrylic emulsion resin with an alkaline material, aging at 60 to 95° C. for 1 to 24 hours;
Based on 100 parts by weight of the i) (meth)acrylic acid ester monomer, the ii) unsaturated acetate, unsaturated nitrile, or a mixture thereof is included in an amount of 17 parts by weight or less,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
The method of claim 1,
The comonomer is included in an amount of 40 parts by weight or less based on 100 parts by weight of the (meth)acrylic acid ester monomer having a C1-C18 alkyl group.
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
According to claim 1,
The monomer mixture comprises: i) based on 100 parts by weight of the (meth)acrylic acid ester monomer having a C1-C18 alkyl group, ii) 17 parts by weight or less of an unsaturated acetate, an unsaturated nitrile, or a mixture thereof, iii) an unsaturated carbonic acid, containing a hydroxyl group 10 parts by weight or less of an unsaturated monomer or a mixture thereof, and iv) 20 parts by weight or less of a styrenic monomer having a vinyl group,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
According to claim 1,
The i) (meth)acrylic acid ester monomer having a C1-C18 alkyl group is methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylic rate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and at least one selected from the group consisting of lauryl (meth) acrylate,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
According to claim 1,
wherein i) the (meth)acrylic acid ester monomer having a C1-C18 alkyl group is 50 to 95 wt% of 2-ethylhexyl acrylate, 5 to 30 wt% of methyl methacrylate, and 0 to 20 wt% of methyl acrylate,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
According to claim 1,
ii) unsaturated acetate, unsaturated nitrile, or a mixture thereof is one selected from the group consisting of vinyl acetate, vinyl butanoate, vinyl propionate, vinyl laurate, vinyl pyrrolidone, acrylonitrile, and methacrylonitrile more than,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
The method of claim 1,
iii) unsaturated carbonic acid, hydroxyl group-containing unsaturated monomer or mixtures thereof are acrylic acid, itaconic acid, maleic anhydride, fumaric acid, methacrylic acid crotonic acid, ethyl methacrylic acid, hydroxymethyl (meth) acrylate, hydroxyethyl ( Meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxylauryl (meth) acrylate , And at least one selected from the group consisting of hydroxypropylene glycol (meth) acrylate,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
According to claim 1,
iv) the styrene-based monomer having a vinyl group is at least one selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, and p-(t-butyl)styrene,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
According to claim 1,
The emulsion polymerization reaction is carried out under a temperature condition of 60 to 100 ℃,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
The method of claim 1,
The pH after neutralization treatment with the alkaline substance is 6 or more,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
The method of claim 1,
The alkaline material is at least one selected from the group consisting of hydroxides, chlorides, carbonates, aqueous ammonia, and organic amines of divalent metals,
A method for producing an aqueous acrylic pressure-sensitive adhesive composition.
A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed using the aqueous acrylic pressure-sensitive adhesive composition prepared by any one of claims 1 to 11.