KR101725895B1 - Acrylic Emulsion Adhesive Comprising Aqueous Dispersion Type Cross-linking Agent and Method of Producing the Same - Google Patents

Abstract

(I) a (meth) acrylic acid ester monomer having an alkyl group of 1 to 18 carbon atoms, (ii) an allyl ester, a vinyl (meth) acrylate ester, At least one monomer selected from the group consisting of an unsaturated carboxylic acid, an ester, an unsaturated acetate, and an unsaturated nitrile, and iii) at least one monomer selected from the group consisting of an unsaturated carboxylic acid and a hydroxyl group-containing unsaturated monomer, Emulsion resins; And (b) a water-dispersible polymeric carbodiimide external crosslinking agent. The present invention also relates to a process for producing the acrylic emulsion pressure-sensitive adhesive.

Description

Technical Field [0001] The present invention relates to an acrylic emulsion pressure-sensitive adhesive containing a water-dispersible crosslinking agent and a method for producing the same. [0002]

The present invention relates to an acrylic emulsion pressure-sensitive adhesive comprising a water-dispersible crosslinking agent improved in water resistance, retention force and stability with time of an emulsion resin, and a method for producing the same.

Pressure-Sensitive Adhesive (PSA) is a semi-solid material with a property of adhering to adherend with a small pressure. It is a viscoelastic material different from adhesive and has basic properties of initial adhesion, cohesion and cohesion. Trademark, advertisement, as well as printing, chemicals, pharmaceuticals, household appliances, automobiles, and stationery.

The pressure-sensitive adhesive may be classified into an acrylic type, a rubber type, a silicone type, an EVA type, and the like depending on the monomers used in the production, and may be classified into a solvent type, an emulsion type and a hot-

In the past, most of the pressure sensitive adhesives used in adhesive tapes and adhesive labels were solvent type oil-based pressure sensitive adhesives. However, since the residual solvent is discharged into the air for a long time after the construction, the residents in the building suffer headache, irritation of the eyes, Dizziness, fatigue, loss of concentration, etc., and when exposed for a long time, there is a problem of generating Sick House Syndrome which causes respiratory diseases, heart disease, cancer and the like.

For this reason, attention has been focused on water-based emulsion pressure-sensitive adhesives as a solvent-free pressure-sensitive adhesive which is environmentally friendly and does not emit harmful substances to the human body by using water as a dispersion medium. The water-based emulsion pressure-sensitive adhesive has an advantage that a polymer having a higher molecular weight than the solvent-based polymer can be used because the viscosity of the pressure-sensitive adhesive is independent of the molecular weight of the dispersion polymer, and the concentration range of the solid content can be widely obtained.

However, since water is used as a solvent, the drying speed is low, and the coating property to a hydrophobic adhesive surface, for example, a polyolefin such as polyethylene or polypropylene having a low surface tension is low, It has a problem that it is narrow and does not have an initial adhesive strength, and since it contains an emulsifying and dispersing agent, its water resistance is low and its physical properties are not as high as oil-based pressure-sensitive adhesives.

Another problem when using water as a dispersion medium is the aging of the emulsion pressure-sensitive adhesive. A specific example of the aging change referred to in the present invention is a change in the adhesive force of the pressure sensitive adhesive, and more specifically, the initial adhesive force, the peeling force, and the holding force value vary with the storage time of the pressure sensitive adhesive. In the present invention, such a change with time is minimized so as to maintain a constant adhesive property.

The main cause of such aging changes occurs in the self-adhesive itself, but the external crosslinking agent added may also occasionally lose its activity over time. In general, there are aziridine and isocyanate as external crosslinking agents to be added for holding strength reinforcement. However, when the water is in contact with the water, the crosslinking functional groups lose their activity due to the hydrolysis, and the remaining crosslinking agent after crosslinking is toxic There is a limitation in use because it expresses. The unstable crosslinking agent activity has a disadvantage in that mixing time of the crosslinking agent and the emulsion adhesive resin must be minimized since time-dependent restrictions are imposed on the use of the emulsion pressure-sensitive adhesive. This time constraint increases the costs of the end-user coating process by adding a process that requires mixing of the cross-linking agent in the coating process.

Accordingly, there is a high need for a technique of a pressure-sensitive adhesive which is excellent in long-term stability and does not exhibit toxicity, while maintaining physical properties of the acrylic emulsion resin and maintaining the crosslinking performance even when mixed with the emulsion resin for a long time.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted extensive research and various experiments and have found that when an acrylic emulsion pressure-sensitive adhesive is prepared by mixing an acrylic emulsion resin with an aqueous dispersion type of polymeric carbodiimide, the properties of the acrylic emulsion resin The present inventors have found that carbodiimide does not remain so that no toxic substances are discharged and that even when mixed with the emulsion resin for a long time, the crosslinking performance can be maintained and excellent long-term stability can be achieved.

Accordingly, the acrylic emulsion pressure-sensitive adhesive according to the present invention is a pressure-sensitive adhesive composition comprising: (a) (i) a (meth) acrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms, ii) an allyl ester, a vinyl ester, an unsaturated acetate and an unsaturated nitrile One or more monomers, and iii) at least one monomer selected from the group consisting of an unsaturated carboxylic acid and a hydroxyl group-containing unsaturated monomer; And

(b) an aqueous crosslinking polymeric carbodiimide external crosslinking agent;

And a control unit.

In the present specification, the term " mixed monomer " used herein is not particularly limited as long as an acrylic emulsion resin is prepared based on the above monomers. For example, the monomers may be prepared by being mixed together, And monomers can be manufactured by sequentially injecting them.

In one specific example, the aqueous dispersion type polycarbodiimide external crosslinking agent may be a polycarbodiimide in which a hydrophilic monomer is bonded.

The inventors of the present application have confirmed that when the aqueous dispersion type polycarbodiimide external crosslinking agent is mixed with the acrylic emulsion resin, the stability over time is guaranteed to be at least 3 months, and even when stored for 6 months or longer, there is no change in the adhesive property .

Thus, the hydrophilic monomer is disposed at the outermost periphery of the granulated polycarbodiimide, so that the carbodiimide group is not brought into contact with water, and a stable water-dispersed polycarbodiimide And the aqueous dispersed polycarbodiimide is dispersed in water by the hydrophilic monomer, so that the opportunity to make contact with the carboxylic acid group of the acrylic emulsion resin is also deprived. Since the hydrolysis and crosslinking reaction are difficult to occur when the carbodiimide group is difficult to contact with the water or the carbonic acid group, it is possible to maintain the activity of the carbodiimide for a long period of time by adding sufficient neutralizing agent to maintain the pH have.

On the other hand, the crosslinking reaction of the polycarbodiimide with the carboxylic acid group of the acrylic emulsion resin is carried out by a process of coating and drying the sheet or film with a mixture of the aqueous polycarbodiimide-based external crosslinking agent and the acrylic emulsion resin Specifically, as the water content of the coated pressure-sensitive adhesive is evaporated, the cross-linking points of the carboxylic acid group and the carbodiimide group are brought into contact with each other. For this cross-linking reaction to take place sufficiently, aging is required at room temperature for 3 to 7 days.

The cross-linking reaction between carbodiimide and carboxylic acid is as follows.

The crosslinking between the carboxylic acid group and the carbodiimide group can enhance the water resistance of the pressure-sensitive adhesive by reacting with the hydrophilic carboxylic acid group, because the carboxylic acid group remaining on the sheet or film without reacting can weaken the water resistance.

Of course, aziridine, melamine, isocyanate and the like, which are generally used as external crosslinking agents, can also undergo a crosslinking reaction with the carbonic acid group, so that the holding power and water resistance of the pressure-sensitive adhesive can be improved. However, these crosslinking agents react with the carbonic acid group contained in the acrylic emulsion resin And remains after being coated on a sheet or film thereafter, which may cause toxicity. On the other hand, the water-dispersible polycarbodiimide external crosslinking agent according to the present invention has a large number of functional groups in the resin, so that the crosslinking reaction easily takes place, and the remaining crosslinking agent is not present and toxicity is not expressed.

Specific examples of such water-dispersed polycarbodiimide type external crosslinking agents include products manufactured by Nissinbo Chemical Inc. as carbodilite E-02 and carbodilite E-03A Carbodilite E-03A, or a mixture of carbodilite E-02 and carbodilite E-03A selected from the group consisting of:

E-03A of the water-dispersed polycarbodiimide-based external crosslinking agent, as confirmed by applicants of the present invention, has a higher proportion of carbodiimide groups per unit mass that can react with the carboxylic acid group, It is more preferable that only E-03A is used, or when E-02 and E-03A are used together, better effect on the holding force than when E-02 is used alone.

Another type of polycarbodiimide is water-soluble polycarbodiimide such as carbodilite V-02, V-02-L2 and SV-02 which can also be used as an external crosslinking agent, Since the water-soluble polycarbodiimide is dissolved in water or dispersed in the form of small particles such as micelles and thus is not sufficiently protected by the hydrophilic segment of the polycarbodiimide, when mixed with the acrylic emulsion resin, The stability over time is deteriorated, which is contrary to the object of the present invention.

In one specific example, the specific content of the water-dispersible polycarbodiimide-based external crosslinking agent may be 0.1 to 10 parts by weight based on 100 parts by weight of the solid content of the acrylic emulsion resin.

If it is contained in an amount of less than 0.1 part by weight, it is not possible to obtain a desired holding power because it is insufficient as an external crosslinking agent. If the amount exceeds 10 parts by weight, the pressure-sensitive adhesive becomes firm, not.

On the other hand, as described above, when such an aqueous dispersion type polycarbodiimide external crosslinking agent is used, the acidity (pH) should be appropriately controlled in order to maintain the performance of the carbodiimide group which is a crosslinking functional group. As the acidity (pH) is maintained, the reaction rate is slowed, and the stability of the aqueous dispersion type polycarbodiimide-based external crosslinking agent and acrylic emulsion resin mixture increases with time.

Thus, in one specific example, the pH of the acrylic emulsion resin for mixing the external crosslinking agent may range from 8 to 12.

If the pH of the acrylic emulsion resin is less than 8, the pH of the acrylic emulsion resin is less than 7 due to the change of pH over time, and the carbodiimide of the water dispersed polycarbodiimide external crosslinking agent is easily If the pH exceeds 12, the crosslinking functional group of the polycarbodiimide is hydrolyzed by contact with water to lose its activity, which is not preferable.

Hereinafter, the substances contained in the acrylic emulsion resin (a) according to the present invention will be described in detail.

In one specific example, the acrylic emulsion resin comprises, based on the total weight of the emulsion resin, i) 80 to 98% by weight of a (meth) acrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms, ii) allyl ester, vinyl ester, unsaturated acetate And 0.5 to 10% by weight of at least one monomer selected from the group consisting of unsaturated carboxylic acids and unsaturated nitriles, and iii) 0.5 to 10% by weight of at least one monomer selected from the group consisting of unsaturated carboxylic acids and hydroxyl group-containing unsaturated monomers. .

In addition, the acrylic emulsion resin may further include (vi) an internal crosslinking agent. The internal crosslinking agent may include 0.01 to 3% by weight based on the total weight of the acrylic emulsion resin.

In one specific example, the monomer of i) is selected from the group consisting of methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (Meth) acrylate, isodecyl acrylate, decyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl acrylate, isooctyl acrylate, octyl methacrylate, (Meth) acrylate, stearyl (meth) acrylate, and lauryl (meth) acrylate. More specifically, it may be at least one monomer selected from the group consisting of 5 to 90% by weight of 2-ethylhexyl acrylate, 5 to 90% by weight of butyl acrylate and 1 to 20% by weight of methyl methacrylate, .

If the amount of the monomer of i) is less than 80% by weight based on the total weight of the acrylic emulsion resin, the initial adhesion of the acrylic emulsion pressure-sensitive adhesive can not be ensured, The transfer of the pressure-sensitive adhesive to the adherend is largely undesirably caused at the time of removal after use.

The number of carbon atoms of the alkyl group in i) may be 1 to 18, more specifically, 2 to 14, and if it is less than 1, the cohesive force of the acrylic emulsion pressure- , The acrylic emulsion pressure-sensitive adhesive becomes too soft, resulting in deteriorated adhesive properties and a low proportion of monomers participating in the emulsion polymerization process.

In one specific example, the monomer of ii) is selected from the group consisting of vinyl acetate, vinyl butanoate, vinyl propionate, vinyl laurate, vinyl pyrrolidone, styrene, acrylonitrile and methacrylonitrile And more specifically vinyl acetate, styrene, vinyl butyrate or acrylonitrile.

The monomer of ii) may be contained in the range of from 2 to 10% by weight based on the total weight of the acrylic emulsion resin, and when it is contained in an amount of less than 0.5% by weight, sufficient amount of acrylic emulsion pressure- The adhesive property can not be ensured. When the content exceeds 10% by weight, the acrylic emulsion pressure-sensitive adhesive becomes excessively firm and the adhesive strength remarkably decreases, which is not preferable.

In one specific example, the monomer of iii) is selected from the group consisting of acrylic acid, itaconic acid, maleic anhydride, fumaric acid, crotonic acid methacrylic acid, ethylmethacrylic acid, hydroxymethyl (meth) acrylate, hydroxyethyl , Hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl Glycol (meth) acrylate, and the like.

The monomer of iii) may be contained within the above range based on the total weight of the acrylic emulsion resin. If the amount is less than 0.5% by weight, the acrylic emulsion pressure-sensitive adhesive becomes too soft, If it is contained in an amount of more than 10% by weight, the acrylic emulsion pressure-sensitive adhesive becomes excessively firm, resulting in a remarkable deterioration in the adhesive strength.

In one specific example, vi) the internal cross-linking agent is selected from the group consisting of polyethylene glycol diacrylate, polypropylene glycol diacrylate, allyl methacrylate, 1,6-hexanediol diacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate Hexanediol ethoxylate diacrylate, hexanediol propoxylate diacrylate, neopentyl glycol ethoxylate diacrylate, neopentyl glycol propoxylate diacrylate, pentaerythritol ethoxylate triacrylate , Pentaerythritol propoxylate triacrylate, vinyltrimethoxysilane, and divinylbenzene, and more specifically, polyethylene glycol diacrylate and polypropylene glycol diacrylate ≪ / RTI >

The above-mentioned vi) internal crosslinking agent may be included within the above range based on the total weight of the acrylic emulsion resin. When the acrylic emulsion pressure-sensitive adhesive has a sufficient cohesive strength within the above range, if it exceeds the above range, the cohesive force is excessively increased, .

The mixed monomer for the production of the acrylic emulsion resin may further contain an epoxy group-containing unsaturated monomer.

The acrylic emulsion pressure-sensitive adhesive according to the present invention may further comprise (c) 1 to 60 parts by weight of an aqueous dispersion tackifier, based on 100 parts by weight of the solid content of the acrylic emulsion resin. 5 to 50 parts by weight of (c) an aqueous dispersion tackifier.

When the content of the water-dispersed tackifier is less than 1 part by weight, the initial adhesive force and peel strength of the acrylic emulsion pressure-sensitive adhesive deteriorate. When the content of the water-dispersed and tackifier is less than 1 part by weight, The cohesive force of the pressure-sensitive adhesive may be lowered and the holding force may be decreased.

The softening temperature Ts of the water-dispersed tackifier has a higher value than the glass transition temperature (Tg) of the acrylic emulsion resin, so that if the water-dispersed tackifier is compatible with the acrylic emulsion resin, The Tg of the pressure-sensitive adhesive composition can be increased. It is very important to add a tackifier having an appropriate Ts in an appropriate amount as described above because the increase in Tg of the pressure-sensitive adhesive composition reduces the adhesive force at low temperatures.

 Accordingly, in the present invention, Ts may be in the range of 0 to 170 degrees Celsius, more specifically in the range of 50 to 160 degrees Celsius, so that the water dispersion tackifier may exhibit the adhesive strength to the desired degree of the present invention. More specifically, 70 degrees to 120 degrees.

Out of the above range, the tackifier having Ts of less than 0 deg. C does not contribute to increase the initial tackiness of the acrylic emulsion tackifier, and even if only a small amount thereof is used, the retention force of the tackifier is effectively reduced.

Such an aqueous dispersion tackifier may be at least one selected from the group consisting of rosin, terpene, xylene, petroleum, and polybutene, and may be, for example, a rosin- May be at least one selected from the group consisting of rosin, hydrogenated rosin and hydrogenated rosin esters.

As described above, the acrylic emulsion pressure-sensitive adhesive of the present invention can further improve the reaction stability and the initial pressure-sensitive adhesive force of the acrylic emulsion pressure-sensitive adhesive by further including an aqueous dispersion tackifier.

The present invention also discloses a process for producing the above acrylic emulsion pressure-sensitive adhesive.

The method for producing an acrylic emulsion pressure-

(I) 80 to 98% by weight of a (meth) acrylic acid ester monomer having an alkyl group of 1 to 18 carbon atoms, (ii) from the group consisting of allyl esters, vinyl esters, unsaturated acetates and unsaturated nitriles, based on the total weight of the acrylic emulsion resin 0.5 to 10% by weight of at least one selected monomer, and iii) 0.5 to 10% by weight of at least one monomer selected from the group consisting of an unsaturated carboxylic acid and a hydroxyl group-containing unsaturated monomer are mixed to polymerize the acrylic monomer mixture to obtain an acrylic emulsion resin ;

(B) adjusting the acidity (pH) of the acrylic emulsion resin of the step (A) to 8 to 12; And

(C) adding an aqueous dispersion type polymeric carbodiimide external crosslinking agent to the acrylic emulsion resin and stirring the mixture.

Further, in the preparation of the acrylic emulsion resin in the process (A), the acrylic monomer mixture may be further polymerized by further adding an internal cross-linking agent.

Here, the kind and content of the aqueous dispersion type polycarbodiimide external crosslinking agent are the same as those described above.

In one specific example, the polymerization reaction of the monomer mixture or the monomer mixture and the cross-linking agent is not particularly limited, but may be an emulsion polymerization in which the reaction heat can be easily controlled, and in particular, the emulsion polymerization includes water, A first step of adding a surfactant to a reactor and raising the temperature to 80 DEG C to remove oxygen and dissolving the initiator to prepare a solution; A second step of preparing an emulsion by adding water, an electrolyte and a surfactant to the monomer mixture or the mixture of the monomer mixture and the crosslinking agent to prepare an emulsion resin; A third step of continuously introducing the emulsion and the initiator of the second process into the solution of the first process, cooling the solution at a temperature of 80 ° C and then cooling it at room temperature to produce an acrylic emulsion resin; And a fourth step of adjusting the pH of the acrylic emulsion resin to 8 to 12.

At this time, the pH of the acrylic emulsion resin can be controlled by an alkaline substance, and the alkaline substance may be an inorganic substance such as a hydroxide of a monovalent metal or a divalent metal, a chloride, a carbonate, an ammonia or an organic amine

The initiator in the polymerization reaction may be a water-soluble polymerization initiator such as persulfate of ammonium or alkali metal, hydrogen peroxide, peroxide, hydroperoxide and the like, and may be used together with one or more reducing agents for emulsion polymerization reaction at low temperature It is possible. The reducing agent may be sodium bisulfite, sodium metabisulfite, sodium hydrosulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate, ascorbic acid, and the like.

The polymerization reaction may be carried out at a temperature of from 0 to 100 ° C, more specifically from 40 to 90 ° C, in view of the physical properties of the resin. The polymerization may be carried out either singly or in combination with one kind of the initiator Or a mixture of two or more of them may be used.

The electrolyte to be used in the polymerization reaction is controlled to have an appropriate pH during polymerization and impart stability to the acrylic emulsion resin to be polymerized. Specific examples thereof include sodium bicarbonate, sodium carbonate, sodium phosphate, sodium sulfate and sodium chloride And may be sodium carbonate in detail, and may be 0.05 to 5 parts by weight, more specifically 0.1 to 3 parts by weight, based on 100 parts by weight of the mixture.

The surfactant is used for initial particle formation, size control of the generated particles and stability of particles in the polymerization reaction. The surfactant is composed of a hydrophilic group and a lipophilic group, and is divided into an anion, a cation and a nonionic surfactant. It mainly uses anionic and nonionic surfactants, and is mixed with other surfactants to compensate for mechanical stability and chemical stability.

The anionic surfactant may be sodium alkyldiphenyl oxide disulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene lauryl ether sulfate, sodium dialkyl sulfosuccinate, sodium lauryl sulfate, The ionic surfactants may be polyethylene oxide alkyl aryl ethers, polyethylene oxide alkyl amines, polyethylene oxide alkyl esters, etc. These may be used singly or in combination of two or more. Anionic surfactants and nonionic surfactants may be used in combination Can be more effective.

On the other hand, the acrylic emulsion pressure-sensitive adhesive may be prepared by further adding an aqueous dispersion tackifier to the acrylic emulsion resin in the step (C). The specific kind, characteristics and content of the tackifier are as described above.

In addition, the acrylic emulsion pressure-sensitive adhesive may further include a thickening agent and a wetting agent to prevent shrinkage of the acrylic emulsion, which is generated when coating the surface of the silicone release paper.

The thickening agent may be CMC (Carboxyl Methyl Cellulose), acrylic sol, polyvinyl alcohol, starch, alginate, dextrin and the like, and more specifically polyvinyl alcohol.

The wetting agent may be a surfactant mixture, and may further include a glycol or an alcohol. The hydrophilic adhesive may be hydrophobic to closely adhere the adhesive to the surface of the hydrophobic silicone release paper.

Since the acrylic emulsion pressure-sensitive adhesive contains a surfactant, foaming occurs during the mixing of the adherent (thickener, wetting agent, etc.), and this foam makes the coated surface of the pressure-sensitive adhesive uneven, so that it can be removed using a defoaming agent .

The antifoaming agent is classified into a silane coupling agent, a surfactant agent, a paraffin agent, a mineral oil agent and the like, preferably a silicone agent.

The present invention also provides an adhesive sheet for forming a pressure-sensitive adhesive layer by adding the above acrylic emulsion pressure-sensitive adhesive onto an ink film or sheet.

The pressure-sensitive adhesive sheet according to the present invention can have a sufficient adhesive force, and the pressure-sensitive adhesive sheet on which the pressure-sensitive adhesive layer is formed can be applied to various materials such as building interior and exterior materials, interior materials, The adhesive layer may have a thickness of 1 to 100 탆, more specifically 5 to 30 탆. The pressure-sensitive adhesive layer is laminated on the pressure-sensitive adhesive layer with a paper release paper whose surface is coated with silicone or polyamide or clay, in order to apply and protect the pressure-sensitive adhesive, increase storage stability of the product, and ensure smoothness.

Specifically, KRAFT or GLASSINE is suitable as the paper releasing paper, and the thickness of the releasing paper is preferably 50 to 200 mu m.

INDUSTRIAL APPLICABILITY As described above, the acrylic emulsion pressure-sensitive adhesive according to the present invention is prepared by mixing an acrylic emulsion resin and an aqueous dispersion type polycarbodiimide-based external crosslinking agent, thereby enhancing the physical properties such as the adhesive strength of the acrylic emulsion resin, There is no release of the toxic substance because it does not remain, and the crosslinking performance is maintained even in the state of mixing with the emulsion resin for a long time, and excellent long-term stability can be exhibited.

Further, since the external crosslinking agent reacts with the hydrophilic crosslinking functional group of the acrylic emulsion resin, the water resistance of the pressure-sensitive adhesive can be reinforced.

Hereinafter, the present invention will be described with reference to Examples. However, the following Examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

≪ Example 1 >

Preparation of acrylic emulsion resin

280 g of ion-exchanged water and 20 g of a sodium lauryl sulfate solution having a concentration of 30% by weight as a surfactant were placed in a 3 L glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introduction tube and a reflux condenser, Exchanged with nitrogen, then heated to 80 DEG C under a nitrogen atmosphere and kept for 60 minutes.

Separately, 500 g of butyl acrylate, 300 g of 2-ethylhexyl acrylate, 100 g of methyl methacrylate, 70 g of vinyl acetate, 25 g of acrylic acid and 5 g of polypropylene glycol diacrylate were added to a 3 L beaker, , A solution of 50 g of a sodium alkyldiphenyloxy disulfonate solution having a concentration of 30 wt% as an anionic surfactant, 5 g of sodium carbonate, and 645 g of water was added and mixed with a stirrer to prepare a white emulsion.

150 g of the emulsion and 10 g of the ammonium persulfate solution were continuously added to the glass reactor for 4 hours. When the ammonium persulfate solution and the emulsion were added, the glass reactor was heated to 80 ° C and the temperature was maintained for 2 hours And then cooled to room temperature to prepare an acrylic emulsion resin.

A 30% by weight aqueous ammonia solution was added to the acrylic emulsion resin to adjust the pH to 8.5

Preparation of acrylic emulsion pressure-sensitive adhesive

To the acrylic emulsion resin prepared above, 300 g of 50% rosin as a rosin-based water-dispersion tackifier was added and stirred for 10 minutes. Then, an aqueous dispersed polycarbodiimide crosslinking agent Carbodite E-02 (manufactured by Nissinbo Inc.) 30 g and stirred for 30 minutes to prepare an acrylic emulsion pressure-sensitive adhesive.

≪ Example 2 >

An acrylic emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that the content of E-02 was changed to 100 g in Example 1.

≪ Example 3 >

An acrylic emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 30 g of E-02 in Example 1 was changed to 30 g of E-03A (manufactured by Nissinbo Inc.).

<Example 4>

An acryl-based emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 30 g of E-02 in Example 1 was changed to 100 g of E-03A.

&Lt; Example 5 >

An acryl-based emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 30 g of E-02 in Example 1 was changed to 15 g of E-02 and 15 g of E-03A.

&Lt; Example 6 >

An acryl-based emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 70 g of the water-dispersed polycarbodiimide-based crosslinking agent Carbodite E-03A was further added.

&Lt; Comparative Example 1 &

An acryl-based emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 30 g of E-02 in Example 1 was changed to 30 g of V-02.

&Lt; Comparative Example 2 &

An acryl-based emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 30 g of E-02 in Example 1 was changed to 100 g of V-02.

&Lt; Comparative Example 3 &

An acryl-based emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that 30 g of E-02 in Example 1 was changed to 100 g of SV-02.

&Lt; Comparative Example 4 &

An acrylic emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that E-02 was not added in Example 1.

&Lt; Comparative Example 5 &

An acryl-based emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that the pH was adjusted to 7.0 in Example 1.

&Lt; Comparative Example 6 >

An acryl-based emulsion pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that the pH was adjusted to 4.0 in Example 1.

<Experimental Example 1>

Manufacture of Adhesive Coated Adhesive Specimen

The acrylic emulsion pressure-sensitive adhesive was applied onto an art paper or a 38 탆 PET film and dried in an oven at 110 캜 for 2 minutes so that the acrylic emulsion pressure-sensitive adhesive layer had a thickness of 20 탆. This was laminated with a release paper to form a pressure-sensitive adhesive sheet. The adhesive sheet was cut to a size of 25 mm x 200 mm to prepare an adhesive tape specimen.

The adhesive properties of the acrylic emulsion pressure-sensitive adhesives prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were tested by the following methods, and the results are shown in Tables 1 to 3 below.

* Adhesive strength at room temperature (90 degree peel force) Test : Adhesive tape specimens coated on art paper were placed on the adhered SUS so that the bubbles would not enter. 5 mm And then aged at room temperature for 30 minutes, and then measured with a TA Texture Analyzer at a rate of 5 mm / sec while peeling at 90 degrees.

* Initial Tack (Loop Tack) Test : The initial tack strength of the adhesive sample coated on art paper was measured according to the official testing standard FINAT TEST METHOD. This is followed by the FTM9- 'loop' tack measurement as a method of measuring the initial adhesive force by making the adhesive tape specimen into a loop.

* Retention force : Adhesive tape specimens coated on art paper were attached to the adhered SUS with an area of 25 mm * 25 mm, and the adhered adhesive tape specimen was reciprocated 5 times at a rate of 300 mm / min with 2 kg rolls. Lt; / RTI &gt; Thereafter, a weight of 1 kg was applied to the opposite portion of the adhesive tape specimen, and the time during which the adhesive specimen fell was measured.

* Water resistance test : Adhesive tape specimen coated on PET film was attached to the glass plate, and the adhesive tape specimen attached was reciprocated five times at a rate of 300 mm / min with 2 kg rolls, and the sample was aged at room temperature for 60 minutes . This sample was immersed in ionized water for 24 hours to check whether whitening occurred.

* Change over time of latex: The change with time of latex is a measuring process to check whether the above-mentioned normal temperature cohesion, initial cohesion, retention force and the like are constantly changed without increasing the storage time. Measurements were made on adhesive properties and retentive strength according to 1 day, 7 days, 30 days, 60 days, 90 days and 180 days.

division Initial adhesion (g / in) 90 degree peel force (g / in) Holding force (min) Water resistance Example 1 1970 1010 1250 Transparency Example 2 1810 820 2200 Transparency Example 3 1920 890 3350 Transparency Example 4 1660 760 9280 Transparency Example 5 1850 910 2040 Transparency Example 6 1940 920 3670 Transparency Comparative Example 1 2120 1270 1080 Transparency Comparative Example 2 2050 980 3040 Transparency Comparative Example 3 1860 780 4030 Transparency Comparative Example 4 2210 1320 60 all sorts of flowers Comparative Example 5 2150 1070 520 all sorts of flowers Comparative Example 6 2090 1050 370 all sorts of flowers

90 deg. Peel strength Change over time (g / in) 1 day 7 days 30 days 60 days 90 days 180 days Example 1 1010 1050 1110 980 970 990 Example 2 820 800 790 830 820 810 Example 3 890 930 960 850 930 940 Example 4 760 750 770 770 760 750 Example 5 910 970 920 940 900 940 Example 6 920 930 890 920 940 940 Comparative Example 1 1270 1260 1320 1350 1340 1390 Comparative Example 2 980 1020 1200 1340 1300 1400 Comparative Example 3 780 1040 1260 1410 1390 1350 Comparative Example 4 1320 1430 1390 1360 1390 1410 Comparative Example 5 1070 1330 1410 1370 1360 1380 Comparative Example 6 1050 1420 1400 1390 1400 1380

Change in retention force with time (min) 1 day 7 days 30 days 60 days 90 days 180 days Example 1 1250 1400 1020 1800 1120 1010 Example 2 2200 2240 3000 1910 2120 2670 Example 3 3350 3270 3280 3440 3230 3350 Example 4 9280 8900 8740 8500 8510 8410 Example 5 2040 2090 2100 1980 2020 2030 Example 6 3670 3510 3410 3390 3420 3350 Comparative Example 1 1080 500 460 160 50 40 Comparative Example 2 3040 2080 1550 550 80 70 Comparative Example 3 4030 1580 1730 630 40 50 Comparative Example 4 60 70 130 100 70 50 Comparative Example 5 520 60 80 80 50 50 Comparative Example 6 370 70 80 90 70 70

Referring to Table 1, in the case of Examples 1 to 6 in which an aqueous polycarbodiimide-based external crosslinking agent was added, as compared with Comparative Example 6 in which no polycarbodiimide external crosslinking agent was added, initial adhesion and peeling force were slightly lower, , While the holding power is significantly increased.

With reference to Tables 2 and 3, it can be seen that the 90 degree peel force of Examples and Comparative Examples shows a change with time and a change with time of retention force. Examples 1 to 6 in which an aqueous dispersion type polycarbodiimide external crosslinking agent is added In the case of Comparative Examples 1 to 3 in which a water-soluble polycarbodiimide-based external crosslinking agent was added, the 90-degree peel strength was gradually increased, while the retention force The value is gradually decreased, but the rate of change of the holding force is considerably larger than the peeling force.

In addition, Comparative Examples 5 to 6 are experiments to confirm the phenomenon that occurs when the pH is lower than the reference use range. Concretely, in Comparative Examples 5 to 6, not only the retention force was significantly lowered but also the physical properties were changed more rapidly. Since the retention force and the 90-degree peel force with time were largely changed within 7 days, It is very important to use the external crosslinking agent of the mid-system.

On the other hand, it can be confirmed from Examples 1 to 6 and Comparative Examples 1 to 3 that addition of a carbodiimide external crosslinking agent to water resistance does not cause whitening. However, as can be seen from Comparative Examples 5 to 6, when the pH was lower than the reference use range, the activity of the carbodiimide-based external crosslinking agent disappeared, failing to play a role of reinforcing the water resistance.

In Comparative Example 4, it was confirmed that whitening occurred due to the absence of such an external crosslinking agent and water resistance was not reinforced, and the retention was relatively low.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (19)

(a) at least one monomer selected from the group consisting of i) a (meth) acrylic acid ester monomer having an alkyl group of 1 to 18 carbon atoms, ii) an allyl ester, a vinyl ester, an unsaturated acetate and an unsaturated nitrile, and iii) An acrylic emulsion resin produced by polymerization of a mixed monomer comprising at least one monomer selected from the group consisting of a hydroxyl group-containing unsaturated monomer; And
(b) an aqueous crosslinking polymeric carbodiimide external crosslinking agent;
Lt; / RTI &gt;
The pH of the acrylic emulsion resin is in the range of 8.5 to 12,
The aqueous dispersion type polycarbodiimide external crosslinking agent is at least one selected from the group consisting of carbodilite E-02 and carbodilite E-03A, and the solid content of the acrylic emulsion resin is 100 parts by weight 3 to 10 parts by weight based on 100 parts by weight of the acrylic emulsion. The acrylic emulsion resin according to claim 1, wherein the acrylic emulsion resin (a) comprises, based on the total weight of the emulsion resin, i) 80 to 98% by weight of a (meth) acrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms, ii) 0.5 to 10% by weight of at least one monomer selected from the group consisting of esters, unsaturated acetates and unsaturated nitriles, and iii) 0.5 to 10% by weight of at least one monomer selected from the group consisting of unsaturated carboxylic acids and hydroxyl group- Wherein the acrylic polymer emulsion is polymerized including the mixed monomer. The acrylic emulsion pressure-sensitive adhesive according to claim 1, wherein the acrylic emulsion resin is further polymerized by further comprising an internal cross-linking agent. The acrylic emulsion pressure-sensitive adhesive according to claim 3, wherein the internal crosslinking agent is contained in an amount of 0.01 to 3% by weight based on the total weight of the acrylic emulsion resin. delete delete The aqueous dispersion type polycarbodiimide external crosslinking agent according to claim 1, wherein the aqueous dispersion type carbodiimide external crosslinking agent is carbodilite E-03A or a mixture of carbodilite E-02 and carbodilite E-03A Wherein the pressure-sensitive adhesive is an acrylic emulsion pressure-sensitive adhesive. delete delete The acrylic emulsion pressure-sensitive adhesive according to claim 1, wherein the acrylic emulsion pressure-sensitive adhesive further comprises (c) an aqueous dispersion tackifier. The acrylic emulsion pressure-sensitive adhesive according to claim 10, wherein the water-based cohesive agent is contained in an amount of 1 to 60 parts by weight based on 100 parts by weight of the solid content of the acrylic emulsion resin. The acrylic emulsion pressure-sensitive adhesive according to claim 10, wherein the softening temperature (Ts) of the water-dispersed tackifier is from 0 to 170 degrees centigrade. The acrylic emulsion pressure-sensitive adhesive according to claim 10, wherein the water-dispersion tackifier is at least one selected from the group consisting of rosin, terpene, xylene, petroleum, and polybutene. 14. The acrylic emulsion pressure-sensitive adhesive according to claim 13, wherein the rosin-based tackifier is at least one selected from the group consisting of rosin, hydrogenated rosin and hydrogenated rosin esters. A process for producing an acrylic emulsion pressure-sensitive adhesive according to claim 1,
(I) 80 to 98% by weight of a (meth) acrylic acid ester monomer having an alkyl group of 1 to 18 carbon atoms, (ii) from the group consisting of allyl esters, vinyl esters, unsaturated acetates and unsaturated nitriles, based on the total weight of the acrylic emulsion resin 0.5 to 10% by weight of at least one selected monomer, and iii) 0.5 to 10% by weight of at least one monomer selected from the group consisting of an unsaturated carboxylic acid and a hydroxyl group-containing unsaturated monomer are mixed to polymerize the acrylic monomer mixture to obtain an acrylic emulsion resin ;
(B) adjusting the acidity (pH) of the acrylic emulsion resin of the step (A) to 8.5 to 12; And
(C) adding and dispersing an aqueous polymeric carbodiimide external crosslinking agent to the acrylic emulsion resin;
/ RTI &gt;
The aqueous dispersion type polycarbodiimide external crosslinking agent is at least one selected from the group consisting of carbodilite E-02 and carbodilite E-03A, and the solid content of the acrylic emulsion resin is 100 parts by weight 3 to 10 parts by weight based on 100 parts by weight of the acrylic emulsion. 16. The process for producing an acrylic emulsion pressure-sensitive adhesive according to claim 15, wherein, in the preparation of the acrylic emulsion resin in the step (A), an acrylic cross-linking agent is further added to the acrylic monomer mixture. delete 16. The process for producing an acrylic emulsion pressure-sensitive adhesive according to claim 15, wherein an aqueous dispersion tackifier is further added to the acrylic emulsion resin in the step (C). A pressure-sensitive adhesive sheet, wherein the acrylic emulsion pressure-sensitive adhesive according to any one of claims 1 to 4, 7 and 10 to 14 is added as a pressure-sensitive adhesive layer on a point-application film or sheet.