KR20210041996A - Aqueous dispersion of ethylene-carboxylic acid copolymer and method of preparing the same - Google Patents

Abstract

A method for preparing an aqueous dispersion of an ethylene-carboxylic acid copolymer according to embodiments of the present invention comprises a step of mixing 30 wt% or more of an ethylene-(meth)acrylic acid copolymer, a basic compound, and water to form a mixed solution, and a step of adding an inorganic salt compound to the mixed solution. The ethylene-carboxylic acid copolymer can be effectively dispersed.

Description

Aqueous dispersion of ethylene-carboxylic acid copolymer and its manufacturing method TECHNICAL FIELD {AQUEOUS DISPERSION OF ETHYLENE-CARBOXYLIC ACID COPOLYMER AND METHOD OF PREPARING THE SAME}

The present invention relates to an aqueous dispersion of an ethylene-carboxylic acid copolymer and a method for producing the same. More specifically, it relates to an aqueous dispersion containing an ethylene-carboxylic acid copolymer and an inorganic additive, and a method for producing the same.

Ethylene-carboxylic acid copolymers, such as ethylene-carboxylic acid copolymers, are used in various applications such as coating materials, sealing materials, adhesives, packing materials, and optical films. The ethylene-carboxylic acid copolymer may be prepared by polymerizing ethylene and acrylic acid or methacrylic acid as a comonomer through a continuous reactor.

The ethylene-carboxylic acid copolymer can be dispersed in water and used as a coating agent, a sealing agent, an adhesive, or the like. Coating, sealing, adhesion, etc. can be performed by drying the water after applying the dispersion to the target material.

When the dispersion is dried, the smaller the content of water (the higher the concentration of the ethylene-carboxylic acid copolymer is), the less water is evaporated, so that coating, sealing, and bonding can be efficiently performed.

Further, for the same amount of the ethylene-carboxylic acid copolymer, the smaller the content of water in the dispersion is, the more advantageous it is in terms of transportation cost.

However, as the concentration of the ethylene-carboxylic acid copolymer increases, the viscosity of the dispersion increases, and gelation may occur. In this case, the coating property of the dispersion is remarkably deteriorated, and it cannot be applied as a coating agent, a sealing agent, an adhesive, or the like.

For example, U.S. Patent No. 6,852,792 discloses an aqueous dispersion for sealing containing an ethylene-carboxylic acid copolymer, but gelation is still suppressed and the viscosity is low, but the ethylene-carboxylic acid copolymer is contained in a high content. Development of an aqueous dispersion containing as is required.

US Patent Publication No. 6,852,792

An object of the present invention is to provide an aqueous dispersion of an ethylene-carboxylic acid copolymer having excellent dispersibility.

One object of the present invention is to provide a method for producing an aqueous dispersion of an ethylene-carboxylic acid copolymer having excellent dispersibility.

The method for preparing an aqueous dispersion of an ethylene-carboxylic acid copolymer according to exemplary embodiments of the present invention comprises forming a mixed solution by mixing 30% by weight or more of an ethylene-(meth)acrylic acid copolymer, a basic compound, and water. ; And adding an inorganic salt compound to the mixed solution.

In example embodiments, forming the mixed solution may include stirring at a temperature of 80°C or higher.

In exemplary embodiments, adding the inorganic salt compound may include adding an aqueous solution of the inorganic salt compound.

In exemplary embodiments, the inorganic salt compound may be added in an amount of 0.01 to 0.3% by weight, based on the total weight of the aqueous dispersion.

In exemplary embodiments, the inorganic salt compound is sodium chloride (NaCl), calcium chloride (CaCl ₂ ), sodium sulfite (Na ₂ SO ₃ ), sodium sulfate (Na ₂ So ₄ ), sodium carbonate (Na ₂ CO ₃ ), potassium chloride (KCl), trisodium phosphate (Na ₃ PO ₄ ), and ammonium chloride (NH ₄ Cl).

In exemplary embodiments, the ethylene-(meth)acrylic acid copolymer may include 70 to 85% by weight of ethylene-derived units and 15 to 30% by weight of (meth)acrylic acid-derived units.

In exemplary embodiments, the basic compound may be mixed in an amount of 1 to 12% by weight of the total weight of the mixed solution.

In example embodiments, the viscosity of the mixed solution before the inorganic salt compound is added may be 6,000 cP or more, and the viscosity of the aqueous dispersion to which the inorganic salt compound is added may be 5,000 cP or less.

In example embodiments, the viscosity of the aqueous dispersion may be 60% or less of the viscosity of the mixed solution.

The aqueous dispersion of the ethylene-carboxylic acid copolymer according to exemplary embodiments of the present invention contains 30% by weight or more of the ethylene-(meth)acrylic acid copolymer, a basic compound, an inorganic salt compound, and the remaining amount of water.

In exemplary embodiments, when the content of the ethylene-(meth)acrylic acid copolymer is 35% by weight or more, the following relational expression 1 may be satisfied.

[Relationship 1]

In the relational formula 1, V may be the viscosity (cP) of the aqueous dispersion, and Ce may be the content (% by weight) of the copolymer.

In exemplary embodiments, the inorganic salt compound may be included in an amount of 0.01 to 0.3% by weight based on the total weight of the aqueous dispersion.

In exemplary embodiments, the inorganic salt compound is sodium chloride (NaCl), calcium chloride (CaCl ₂ ), sodium sulfite (Na ₂ SO ₃ ), sodium sulfate (Na ₂ So ₄ ), sodium carbonate (Na ₂ CO ₃ ), potassium chloride (KCl), trisodium phosphate (Na ₃ PO ₄ ), and ammonium chloride (NH ₄ Cl).

In exemplary embodiments, the ethylene-(meth)acrylic acid copolymer may include 70 to 85% by weight of ethylene-derived units and 15 to 30% by weight of (meth)acrylic acid-derived units.

In exemplary embodiments, the basic compound may be included in an amount of 1 to 12% by weight of the total weight of the aqueous dispersion.

The coating film according to exemplary embodiments of the present invention includes 30% by weight or more of an ethylene-(meth)acrylic acid copolymer, a basic compound and an inorganic salt compound.

The multilayer film according to exemplary embodiments of the present invention includes the coating film.

In example embodiments, the multilayer film may include the coating film, a polyolefin layer bonded to one side of the coating film, and an aluminum layer bonded to the other side of the coating film.

According to exemplary embodiments of the present invention, by adding an inorganic salt compound to the aqueous dispersion of the ethylene-(meth)acrylic acid copolymer, the ethylene-(meth)acrylic acid copolymer can be effectively dispersed in the aqueous dispersion. Accordingly, it is possible to easily adjust the viscosity of the aqueous dispersion to provide an aqueous dispersion of an ethylene-(meth)acrylic acid copolymer having a high concentration and a low viscosity.

Therefore, the coating property of the aqueous dispersion can be improved, and gelation can be suppressed.

1 is a schematic flowchart showing a method of preparing an aqueous dispersion of an ethylene-carboxylic acid copolymer according to exemplary embodiments of the present invention.
2 is a schematic cross-sectional view illustrating a coating film and a multilayer film including the same according to exemplary embodiments of the present invention.
3 is a graph showing a change in viscosity of an aqueous dispersion when an inorganic salt compound is added according to exemplary embodiments of the present invention.
4 is a graph showing a change in viscosity of an aqueous dispersion in a range of 35 to 41% by weight of a copolymer concentration according to the addition of an inorganic salt compound.
5 is a graph showing a relationship between the type and concentration of inorganic salt compounds and the viscosity of the aqueous dispersion in an aqueous dispersion according to exemplary embodiments.

Exemplary embodiments of the present invention are prepared by mixing 30% by weight or more of an ethylene-(meth)acrylic acid copolymer, a basic compound, and water to form a mixed solution. It provides a method for preparing an aqueous dispersion of an ethylene-carboxylic acid copolymer in which an inorganic salt compound is added. An aqueous dispersion of an ethylene-carboxylic acid copolymer having a high concentration and a low viscosity can be easily prepared.

In addition, exemplary embodiments of the present invention provide an aqueous dispersion of an ethylene-carboxylic acid copolymer.

The term "(meth)acrylic acid" as used herein encompasses acrylic acid and methacrylic acid.

1 is a schematic flowchart showing a method of preparing an aqueous dispersion of an ethylene-carboxylic acid copolymer according to exemplary embodiments of the present invention.

According to exemplary embodiments, a mixed solution may be prepared by mixing an ethylene-(meth)acrylic acid copolymer, a basic compound, and water (for example, step S10).

The ethylene-(meth)acrylic acid copolymer may be mixed in an amount of 30% by weight or more based on the total weight of the mixed solution. Accordingly, the aqueous dispersion prepared according to exemplary embodiments of the present invention may contain the ethylene-(meth)acrylic acid copolymer at a high concentration. Preferably, the ethylene-(meth)acrylic acid copolymer may be mixed in an amount of 40% by weight or more, more preferably 42% by weight or 45% by weight or more.

In exemplary embodiments, the ethylene-(meth)acrylic acid copolymer may be mixed in an amount of 49% by weight or less based on the total weight of the mixed solution. When the amount is exceeded, gelation of the ethylene-(meth)acrylic acid copolymer is accelerated, and it may be practically difficult to adjust the viscosity of the aqueous dispersion of the ethylene-carboxylic acid copolymer to a range suitable for use as a coating agent.

In exemplary embodiments, the weight average molecular weight (Mw) of the ethylene-(meth)acrylic acid copolymer may be 10,000 to 60,000. Preferably, the weight average molecular weight may be 10,000 to 40,000, more preferably 20,000 to 40,000.

For example, the weight average molecular weight of the ethylene-(meth)acrylic acid copolymer may be 15,000 to 25,000 (first copolymer). By adding the inorganic salt compound to the aqueous dispersion of the first copolymer, the viscosity of the aqueous dispersion can be effectively reduced.

In addition, the ethylene-(meth)acrylic acid copolymer may have a weight average molecular weight of 25,000 to 35,000 (second copolymer). In the case of the second copolymer, the degree of increase in viscosity may be greater even at the same copolymer concentration. Therefore, in general, when the concentration of the second copolymer exceeds 30% of the aqueous dispersion, the concentration may increase excessively. However, as described later, the viscosity of the aqueous dispersion of the high molecular weight copolymer can be effectively controlled by adding an inorganic salt compound.

In some embodiments, the polydispersity index of the ethylene-(meth)acrylic acid copolymer may be 2 to 5, preferably 2.5 to 4.

In exemplary embodiments, the ethylene-(meth)acrylic acid copolymer may include 70 to 85% by weight of ethylene-derived units and 15 to 30% by weight of (meth)acrylic acid-derived units. When the (meth)acrylic acid-derived unit is less than 15% by weight, the ethylene (meth)acrylic acid copolymer may not be dispersed in an aqueous solution. Preferably, the ethylene-derived unit may be included in 75 to 80% by weight, and the (meth)acrylic acid-derived unit may be included in 20 to 25% by weight.

In some embodiments, the melting point (Tm) of the ethylene-(meth)acrylic acid copolymer may be 50 to 100°C. Therefore, the aqueous dispersion can be applied as a coating agent, a sealing agent, an adhesive, or the like at a low temperature. Preferably, the melting point may be 60 to 95 ℃, more preferably, it may be 70 to 80 ℃.

The ethylene-(meth)acrylic acid copolymer may have acidity due to a carboxyl group of a unit derived from (meth)acrylic acid. The basic compound can neutralize the carboxyl group of the (meth)acrylic acid-derived unit.

In exemplary embodiments, the basic compound is a group consisting of ammonium hydroxide (NH ₄ OH), lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), cesium hydroxide (CsOH), and organic amine compounds. It may include at least one selected from.

The basic compound may undergo an acid-base neutralization reaction with a carboxyl group of the (meth)acrylic acid-derived unit of the ethylene-(meth)acrylic acid copolymer. In this case, the dispersibility of the ethylene-(meth)acrylic acid copolymer in water may increase. In exemplary embodiments, the basic compound may be included in an amount of 1 to 12% by weight of the total weight of the mixed solution. When the content of the basic compound is less than 1% by weight, the neutralization reaction for the carboxyl group of the (meth)acrylic acid-derived unit may be insufficiently performed. Accordingly, the water dispersibility of the ethylene-(meth)acrylic acid copolymer may be reduced. When the content of the basic compound is more than 12% by weight, the ethylene-(meth)acrylic acid copolymer is excessively neutralized, so that the viscosity of the aqueous dispersion may increase. Preferably, the basic compound may be included in an amount of 2 to 6% by weight of the total weight of the mixed solution.

Water may be provided as a solvent and/or dispersion medium of the ethylene-(meth)acrylic acid copolymer and the basic compound. In some embodiments, the water may include pure or deionized water.

In exemplary embodiments, water may be included in a residual amount based on the total content of the ethylene-(meth)acrylic acid copolymer and the basic compound in the mixed solution. In one embodiment, the mixed solution may not contain components other than the ethylene-carboxylic acid copolymer, the basic compound, and the remaining amount of water.

In example embodiments, the step of forming the mixed solution (S10) may be performed by stirring at a temperature of 80°C or higher. In this case, the neutralization reaction between the ethylene-(meth)acrylic acid copolymer and the basic compound may be accelerated, and the at least partially neutralized ethylene-(meth)acrylic acid copolymer and the unreacted ethylene-(meth)acrylic acid copolymer are It can be effectively dissolved in water. Preferably, the mixing may be performed at a temperature of 90°C or higher.

In example embodiments, the viscosity of the mixed solution may be 6,000 cP or more. The viscosity may be a viscosity at room temperature (25°C). In this case, coating properties of the aqueous dispersion at room temperature may be insufficient.

In exemplary embodiments, an inorganic salt compound may be added to the mixed solution (eg, step S20).

The inorganic salt compound may be dissolved in the mixed solution to increase the ion concentration in the mixed solution. The ethylene-(meth)acrylic acid copolymer, at least partially ionized by the neutralization reaction, is effectively dispersed in the mixed solution by repulsive and repulsive forces between the ions, so that the viscosity of the aqueous dispersion can be effectively reduced.

For example, when preparing the mixed solution (for example, step S10), when mixing the inorganic salt compound with the ethylene-(meth)acrylic acid copolymer, the basic compound, and water, dissociated in water The inorganic salt compound may not affect the viscosity reducing effect of the aqueous dispersion.

In exemplary embodiments, the inorganic salt compound may be added in an amount of 0.01 to 0.3% by weight of the total weight of the aqueous dispersion. When the content of the inorganic salt compound is less than 0.01% by weight, the effect of reducing the viscosity of the aqueous dispersion of the ethylene-(meth)acrylic acid copolymer may be insufficient. When the content of the inorganic salt compound is more than 0.3% by weight, a precipitate may be formed in the aqueous dispersion of the ethylene-carboxylic acid copolymer of the inorganic salt compound. Preferably, the content of the inorganic salt compound may be 0.04, 0.07 or 0.1% by weight or more and 0.2% by weight or less.

In exemplary embodiments, the inorganic salt compound is sodium chloride (NaCl), calcium chloride (CaCl ₂ ), sodium sulfite (Na ₂ SO ₃ ), sodium sulfate (Na ₂ So ₄ ), sodium carbonate (Na ₂ CO ₃ ), potassium chloride (KCl), trisodium phosphate (Na ₃ PO ₄ ), and ammonium chloride (NH ₄ Cl). _{Preferably, sodium chloride (NaCl) and sodium sulfite (Na 2} SO ₃ ) may be used in terms of minimizing the impact of the packaging film formed of the aqueous dispersion of the copolymer on the object to be packaged.

In exemplary embodiments, the inorganic salt compound may be added to the mixed solution in an aqueous solution state. For example, after dissolving the inorganic salt compound in water to prepare an aqueous solution of the inorganic salt compound, the aqueous solution of the inorganic salt compound is added to the mixed solution to prepare an aqueous dispersion of the ethylene-carboxylic acid copolymer. I can. In this case, the amount of the inorganic salt compound may be adjusted based on the total weight of the aqueous dispersion of the ethylene-carboxylic acid copolymer.

In exemplary embodiments, the step of adding the inorganic salt compound may be performed at a temperature of 60 to 80°C. For example, the aqueous solution of the inorganic salt compound may be added to the mixed solution and stirred at a temperature of 60 to 80°C. When the inorganic salt compound is added at a temperature of less than 60°C, uniform stirring of the aqueous solution and the mixed solution of the inorganic salt compound becomes difficult due to the increase in the viscosity of the mixed solution due to the decrease in temperature, thereby reducing the viscosity of the inorganic salt compound. Can be reduced. When the inorganic salt compound is added at a temperature of more than 80° C., the evaporation amount of water in the aqueous dispersion increases during the addition, so that the concentration of the ethylene-(meth)acrylic acid copolymer may increase excessively. Therefore, it may be difficult to adjust the viscosity of the aqueous dispersion to a desired range.

In exemplary embodiments, the viscosity of the aqueous dispersion of the ethylene-carboxylic acid copolymer to which the inorganic salt compound is added may be 6,000 cP or less. Therefore, the aqueous dispersion can be uniformly coated even under room temperature conditions. Preferably, the viscosity may be 5,000 cP or less or 3,000 cP or less, and more preferably, 1,000 cP or less.

In example embodiments, the viscosity of the aqueous dispersion may be 60% or less with respect to the viscosity of the mixed solution. For example, the viscosity of the aqueous dispersion may be reduced to 60% or less by the addition of the inorganic salt compound. Therefore, even if the mixed solution contains an ethylene-(meth)acrylic acid copolymer at a high concentration and has a high viscosity, the viscosity can be effectively controlled by using the inorganic salt compound. Preferably, the viscosity of the aqueous dispersion may be 20% or less, 15% or less, or 10% or less with respect to the viscosity of the mixed solution.

The ethylene-carboxylic acid copolymer aqueous dispersion includes an ethylene-(meth)acrylic acid copolymer aqueous dispersion, a basic compound, an inorganic salt compound, and a balance of water.

The ethylene-(meth)acrylic acid copolymer is included in an amount of 30% by weight or more of the total weight of the aqueous dispersion. Preferably, the ethylene-(meth)acrylic acid copolymer may be included in an amount of 40% by weight or more, and more preferably, in an amount of 41% by weight or 45% by weight or more of the total weight of the aqueous dispersion.

In exemplary embodiments, the basic compound is a group consisting of ammonium hydroxide (NH ₄ OH), lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), cesium hydroxide (CsOH), and organic amine compounds. It may include at least one selected from.

The basic compound may react with an acid-base neutralization reaction with a carboxyl group of the (meth)acrylic acid-derived unit of the ethylene-(meth)acrylic acid copolymer. In this case, the dispersibility of the ethylene-(meth)acrylic acid copolymer in water may be increased and gelation may be prevented.

In exemplary embodiments, the basic compound may be included in an amount of 1 to 12% by weight of the total weight of the aqueous dispersion of the ethylene-carboxylic acid copolymer. When the content of the basic compound is less than 1% by weight, the neutralization reaction for the carboxyl group of the (meth)acrylic acid-derived unit may be insufficiently performed. Accordingly, the water dispersibility of the ethylene-(meth)acrylic acid copolymer may be reduced. When the content of the basic compound is more than 12% by weight, the ethylene-(meth)acrylic acid copolymer is excessively neutralized, so that the viscosity of the aqueous dispersion may increase. Preferably, the basic compound may be included in an amount of 2 to 6% by weight of the total weight of the aqueous dispersion of the ethylene-carboxylic acid copolymer.

In the present specification, that the aqueous dispersion of the ethylene-carboxylic acid copolymer includes the inorganic salt compound may encompass that the aqueous dispersion contains ions from which the inorganic salt compound is dissociated.

The inorganic salt compound may improve the water dispersibility of the ethylene-(meth)acrylic acid copolymer. For example, the inorganic salt compound may be dissolved in water to increase the ion concentration in the aqueous dispersion.

In exemplary embodiments, the inorganic salt compound may be included in an amount of 0.01 to 0.3% by weight of the total weight of the aqueous dispersion. When the content of the inorganic salt compound is less than 0.01% by weight, the viscosity of the aqueous dispersion of the ethylene-(meth)acrylic acid copolymer may not be sufficiently reduced. When the content of the inorganic salt compound is more than 0.3% by weight, some of the components of the aqueous dispersion of the ethylene-carboxylic acid copolymer may aggregate to form a precipitate in the dispersion.

In exemplary embodiments, the inorganic salt compound is sodium chloride (NaCl), calcium chloride (CaCl ₂ ), sodium sulfite (Na ₂ SO ₃ ), sodium sulfate (Na ₂ So ₄ ), sodium carbonate (Na ₂ CO ₃ ), potassium chloride (KCl), trisodium phosphate (Na ₃ PO ₄ ), and ammonium chloride (NH ₄ Cl). _{Preferably, sodium chloride (NaCl) and sodium sulfite (Na 2} SO ₃ ) may be used in terms of minimizing the impact of the packaging film formed of the aqueous dispersion of the copolymer on the object to be packaged.

Water may be provided as a solvent and/or dispersion medium of the ethylene-(meth)acrylic acid copolymer, the basic compound, and the inorganic salt compound. In some embodiments, the water may include pure or deionized water. For example, the basic compound and the inorganic salt compound may be dissolved in water to substantially exist in an ionic state.

In exemplary embodiments, water may be included in a residual amount with respect to the ethylene-carboxylic acid copolymer, the basic compound, and the inorganic salt compound. In one embodiment, the aqueous dispersion may not contain components other than the ethylene-carboxylic acid copolymer, the basic compound, the inorganic salt compound, and the remaining amount of water.

The aqueous dispersion of the ethylene-carboxylic acid copolymer may have a viscosity of about 6,000 cP or less when the concentration of the copolymer is about 41% by weight. In addition, when the concentration of the copolymer is about 35% by weight, the aqueous dispersion may have a viscosity of about 1,000 cP or less or about 500 cP or less. The viscosity may be a viscosity measured at room temperature (25° C.).

In exemplary embodiments, when the content of the ethylene-(meth)acrylic acid copolymer is 35% by weight or more, the aqueous dispersion may satisfy the following relationship.

[Relationship 1]

In the relational formula 1, V may be the viscosity (cP) of the aqueous dispersion, and Ce may be the content (% by weight) of the copolymer.

The aqueous dispersion that satisfies the above relational equation 1 may have a low viscosity even if it contains the copolymer at a high concentration. In this case, the concentration of the aqueous dispersion can be further increased while maintaining coatability.

In some embodiments, the aqueous dispersion may not contain an organic solvent. Therefore, it is possible to easily form a coating layer by evaporating moisture after applying the aqueous dispersion.

The aqueous dispersion of the ethylene-carboxylic acid copolymer according to exemplary embodiments may be used as a coating agent or a bonding agent. For example, the aqueous dispersion may coat the surface of the metal thin film.

2 is a schematic cross-sectional view illustrating a coating film and a multilayer film including the same according to exemplary embodiments of the present invention.

In example embodiments, the aqueous dispersion may be applied on a substrate and then dried to form the coating film 10.

The coating film 10 may form a multilayer film 100 by stacking another layer on at least one surface. For example, the upper layer 20 may be stacked on the top of the coating film 10 and the lower layer 30 may be stacked on the bottom to form the multilayer film 100. The other layer may include a polymer film layer and a metal thin film layer.

For example, a polyolefin layer is bonded to one side of the coating film 10 and an aluminum layer is bonded to the other side to form the multilayer film 100.

The multilayer film 100 may be provided, for example, as a food packaging material.

Hereinafter, experimental examples including specific examples and comparative examples are presented to aid in understanding of the present invention, but this is only illustrative of the present invention and does not limit the scope of the appended claims, and the scope and spirit of the present invention It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope, and it is natural that such modifications and modifications fall within the appended claims.

Example 1

Ethylene-carboxylic acid copolymer (weight ratio of ethylene:acrylic acid = 80:20, weight average molecular weight (Mw) = 30,000) about 35% by weight, _{about 3% by weight of NH 4} OH and the remaining amount of distilled water at about 90° C. for 1 hour Mixed to form a mixed solution.

NaCl was dissolved in 3 mL of water to prepare an aqueous NaCl solution.

The prepared aqueous NaCl solution was added to the mixed solution and stirred at about 70° C. to prepare an aqueous dispersion of the ethylene-carboxylic acid copolymer of Example.

At this time, the content of NaCl was adjusted to 0.1% by weight of the total weight of the aqueous dispersion of the ethylene-carboxylic acid copolymer.

Example 2

In Example 1, an aqueous dispersion was prepared in the same manner, except that the ethylene-carboxylic acid copolymer was mixed in an amount of 41% by weight when the mixed solution was formed.

Experimental Example 1

By measuring the viscosity of the aqueous dispersion of Examples 1 and 2 and the mixed solutions to which NaCl aqueous solution was not added in Examples 1 and 2 (the mixed solution of Example 1 and the mixed solution of Example 2) The graph of Table 2 was obtained.

Viscosity was measured using a Brookfield viscometer at room temperature (25 ℃), and a plate spindle was used.

Referring to FIG. 3, compared to the dispersion without adding the inorganic salt compound (NaCl) (0 wt%), the viscosity of the examples to which the inorganic salt compound was added was significantly reduced. The viscosity of the 35% by weight aqueous dispersion was measured to be about 6848 cP before the addition of the inorganic salt compound and about 463 cP after the addition of the inorganic salt compound. The viscosity of the aqueous dispersion at a concentration of 41% by weight was measured to be about 10,500 cP before the addition of the inorganic salt compound and about 5,715 cP after the addition of the inorganic salt compound.

The trend of changes in viscosity was calculated based on the viscosity at the concentration of 35% by weight and 41% by weight of the aqueous dispersion to which the inorganic salt compound was not added and the aqueous dispersion to which the inorganic salt compound was added, and is shown in the graph of FIG. 4.

4, it was confirmed that the viscosity (V) of the aqueous dispersion to which the inorganic salt compound was added satisfies the following relational formula 1 even when the content (Ce) of the ethylene-(meth)acrylic acid copolymer was 35% by weight or more. .

[Relationship 1]

V <33,193 ln(Ce)-11,5014

Example 3

Ethylene-carboxylic acid copolymer (weight ratio of ethylene:acrylic acid = 80:20, weight average molecular weight (Mw) = 30,000) about 35% by weight, _{about 3% by weight of NH 4} OH and the remaining amount of distilled water at about 90°C for 1 hour Mixed to form a mixed solution.

NaCl, CaCl ₂ and Na ₂ SO _{3 NaCl, CaCl 2} and Na ₂ SO ₃ aqueous solution each dissolved in 3 mL of water was prepared.

The NaCl, CaCl ₂ and Na ₂ SO ₃ aqueous solutions were added to the mixed solution, respectively, to prepare an aqueous dispersion of an ethylene-carboxylic acid copolymer. At this time, the _{concentrations of NaCl, CaCl 2} and Na ₂ SO _{3 in} the aqueous dispersion were adjusted to 0.04 and 0.07% by weight, respectively.

Experimental Example 2

The viscosity of the aqueous dispersions of Example 3 was measured and shown in FIG. 5.

Referring to FIG. 5, it was confirmed that the viscosity of the aqueous dispersion can be effectively reduced by controlling the type and concentration of the inorganic salt compound.

Claims (20)

Mixing 30% by weight or more of an ethylene-(meth)acrylic acid copolymer, a basic compound, and water to form a mixed solution; And
A method for producing an aqueous dispersion of an ethylene-carboxylic acid copolymer comprising the step of adding an inorganic salt compound to the mixed solution. The method of claim 1, wherein the forming of the mixed solution comprises stirring at a temperature of 80°C or higher. The method of claim 1, wherein the step of adding the inorganic salt compound comprises adding an aqueous solution of the inorganic salt compound. The method of claim 1, wherein the step of adding the inorganic salt compound comprises stirring at a temperature of 60 to 80°C. The method of claim 1, wherein the inorganic salt compound is added in an amount of 0.01 to 0.3% by weight based on the total weight of the aqueous dispersion. The method according to claim 1, wherein the inorganic salt compound is sodium chloride (NaCl), calcium chloride (CaCl ₂ ), sodium sulfite (Na ₂ SO ₃ ), sodium sulfate (Na ₂ So ₄ ), sodium carbonate (Na ₂ CO ₃ ), Potassium chloride (KCl), trisodium phosphate (Na ₃ PO ₄ ), and ammonium chloride (NH ₄ Cl), comprising at least one selected from the group consisting of, an ethylene-carboxylic acid copolymer aqueous dispersion. The method according to claim 1, wherein the ethylene-(meth)acrylic acid copolymer comprises 70 to 85% by weight of ethylene-derived units and 15 to 30% by weight of (meth)acrylic acid-derived units. Manufacturing method. The method of claim 1, wherein the ethylene-(meth)acrylic acid copolymer has a weight average molecular weight (Mw) of 10,000 to 60,000. The method of claim 1, wherein the basic compound is mixed in an amount of 1 to 12% by weight based on the total weight of the mixed solution. The number of ethylene-carboxylic acid copolymers according to claim 1, wherein the viscosity of the mixed solution before adding the inorganic salt compound is 6,000 cP or more, and the viscosity of the aqueous dispersion to which the inorganic salt compound is added is 5,000 cP or less. A method for preparing a dispersion. The method of claim 1, wherein the viscosity of the aqueous dispersion is 60% or less compared to the viscosity of the mixed solution. An aqueous dispersion of an ethylene-carboxylic acid copolymer comprising 30% by weight or more of an ethylene-(meth)acrylic acid copolymer, a basic compound, an inorganic salt compound, and a balance of water. The aqueous dispersion of an ethylene-carboxylic acid copolymer according to claim 12, which satisfies the following relational formula 1 when the content of the ethylene-(meth)acrylic acid copolymer is 35% by weight or more:
[Relationship 1]

(In the relational formula 1, V is the viscosity (cP) of the aqueous dispersion, and Ce is the content (% by weight) of the copolymer). The ethylene-carboxylic acid copolymer aqueous dispersion according to claim 12, wherein the inorganic salt compound is contained in an amount of 0.01 to 0.3% by weight based on the total weight of the aqueous dispersion. The method of claim 12, wherein the inorganic salt compound is sodium chloride (NaCl), calcium chloride (CaCl ₂ ), sodium sulfite (Na ₂ SO ₃ ), sodium sulfate (Na ₂ So ₄ ), sodium carbonate (Na ₂ CO ₃ ), Potassium chloride (KCl), trisodium phosphate (Na ₃ PO ₄ ) and ammonium chloride (NH ₄ Cl) containing at least one selected from the group consisting of, ethylene-carboxylic acid copolymer aqueous dispersion. The ethylene-carboxylic acid copolymer aqueous dispersion according to claim 12, wherein the ethylene-(meth)acrylic acid copolymer comprises 70 to 85% by weight of ethylene-derived units and 15 to 30% by weight of (meth)acrylic acid-derived units. The ethylene-carboxylic acid copolymer aqueous dispersion according to claim 12, wherein the basic compound is contained in an amount of 1 to 12% by weight of the total weight of the aqueous dispersion. Ethylene-(meth)acrylic acid copolymer 30% by weight or more, comprising a basic compound and an inorganic salt compound, a coating film. A multilayer film comprising the coating film of claim 18. The multilayer film of claim 19, comprising the coating film, a polyolefin layer bonded to one side of the coating film, and an aluminum layer bonded to the other side of the coating film.

Images