Aqueous dispersion and coating layer using the same

Abstract

The objective is to obtain an aqueous dispersion of EVOH that is highly stable and has excellent water resistance when dried into a film. [Solution] An aqueous dispersion containing a dispersed phase (A) and a dispersant (B) is obtained, wherein the dispersed phase (A) contains an ethylene-vinyl ester copolymer saponified product and the dispersant (B) contains polyethyleneimine.

Description

Technical Field

[0001] The present invention relates to an aqueous dispersion of a saponified ethylene-vinyl ester copolymer, and more particularly to an aqueous dispersion of a saponified ethylene-vinyl ester copolymer that has excellent stability and can provide a dry film with good water resistance.

Background Art

[0002] The saponified ethylene-vinyl ester copolymer (hereinafter abbreviated as "EVOH") (for example, a saponified ethylene-vinyl acetate copolymer can be mentioned) is excellent in transparency, gas barrier property, solvent resistance, oil resistance, mechanical strength, etc., and is useful as a packaging material or a protective film material. For example, films, sheets, and bottles of multilayer structures having EVOH in the inner layer or intermediate layer are widely used as packaging materials for foods, pharmaceuticals, etc. that require antioxidant and fragrance retention properties for the contents. Also, it is possible to form an EVOH layer on the surface of plastics, metals, paper, wood, etc. to prevent plasticizers, preservatives, etc. contained therein from bleeding out and contaminating the surface, and to protect the surface from oil, organic solvents, etc.

[0003] Generally, as methods for forming an EVOH layer, there are a method by melt molding and a method of applying and drying an EVOH solution or dispersion to a substrate. For the production of multilayer structures such as films, the melt molding method is preferably used. On the other hand, when forming a surface protection layer, the coating and drying method is suitable because a thin film can be easily obtained and it can also cope with the surface of a substrate having a complex shape.

[0004] While both EVOH solutions and EVOH dispersions can be used for this coating and drying method, the DMSO (dimethyl sulfoxide) solution or water / alcohol mixed solvent solution, which are currently widely used as EVOH solutions, both require high temperatures for drying and have the problem of organic solvents volatilizing during use, thus worsening the working environment. Furthermore, high-concentration EVOH solutions have high viscosity, which is problematic in terms of coating properties and workability, and they also have the problem of viscosity increasing or solidifying after storage.

[0005] On the other hand, EVOH dispersions, especially those using water as the dispersion medium, have the advantages of having a low environmental impact and exhibiting minimal viscosity increase even at high concentrations. As an aqueous dispersion of EVOH, one method involves introducing ionic functional groups into EVOH, dissolving it in an alcohol-water mixture, and then volatilizing the alcohol to obtain particles (Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-086240 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the EVOH aqueous dispersion described in Patent Document 1 contains a large amount of EVOH with a low ethylene ratio, resulting in poor stability and insufficient long-term stability and water resistance. Therefore, the present invention aims to provide an aqueous dispersion of EVOH that is highly stable and has excellent water resistance when dried into a film. [Means for solving the problem]

[0008] In view of the above circumstances, the inventors of the present invention conducted diligent studies and found that the problems of the present invention can be solved by an aqueous EVOH dispersion using a specific dispersant, and thus completed the present invention. In other words, the gist of the present invention lies in the following [1] to [9]. [1] An aqueous dispersion comprising a dispersed phase (A) and a dispersant (B), wherein the dispersed phase (A) comprises an ethylene-vinyl ester copolymer saponified product and the dispersant (B) comprises polyethyleneimine. [2] The aqueous dispersion according to [1], wherein the ethylene content of the ethylene-vinyl ester copolymer saponified is 20 mol% or more and 60 mol% or less. [3] The aqueous dispersion according to [1], wherein the degree of saponification of the ethylene-vinyl ester copolymer saponified is 90 mol% or more.

[0009] [4] The aqueous dispersion according to [1], wherein the hydrodynamic radius of the polyethyleneimine, calculated by the number average method of dynamic light scattering, is 0.1 nm or more and 50 nm or less. [5] The aqueous dispersion according to [1], wherein the mass ratio (A):(B) of the dispersed phase (A) to the dispersant (B) is 99.9:0.01 to 20:80. [6] The aqueous dispersion according to [1], wherein the total amount of the dispersed phase (A) and the dispersant (B) is 0.1% by mass or more and 60% by mass or less of the solid content in the aqueous dispersion. A coating agent composition containing an aqueous dispersion described in any of [7][1] to [6]. A coating layer obtained by drying an aqueous dispersion described in any of [8][1] to [6]. A heat sealant obtained by drying an aqueous dispersion described in any of [9][1] to [6]. [Effects of the Invention]

[0010] The aqueous dispersion of the present invention makes it possible to provide an aqueous dispersion of EVOH that yields a dry film with excellent water resistance, and enables its use in coating applications. Furthermore, by using polyethyleneimine as a dispersion stabilizer, the aqueous dispersion of the present invention makes it possible to create an EVOH aqueous dispersion with a high ethylene ratio. When the ethylene ratio of EVOH is increased, stability is particularly improved, and water resistance is further enhanced. [Modes for carrying out the invention]

[0011] The following description of the constituent elements is an example (representative example) of an embodiment of the present invention and is not limited to these contents. The following explains each point in order. The aqueous dispersion of the present invention is a dispersion containing a dispersed phase (A) and a dispersant (B), wherein the dispersed phase (A) contains an ethylene-vinyl ester copolymer saponified product (A1) and the dispersant (B) contains polyethyleneimine (B1).

[0012] [Ethylene-vinyl ester copolymer saponified (EVOH) (A1)] First, let's describe the ethylene-vinyl ester copolymer saponified product (EVOH)(A1) used in this invention. The EVOH(A1) used in this invention has vinyl alcohol structural units obtained by saponifying structural units derived from ethylene and vinyl ester. It is typically obtained by copolymerizing and saponifying ethylene and vinyl ester monomers.

[0013] The EVOH(A1) used in this invention has a content of ethylene-derived structural units (ethylene content) that is preferably 20 to 60 mol%, and particularly preferably 22 to 44 mol%. It is preferable that the ethylene content is within the above range because, due to the relationship with specific gravity, creaming is less likely to occur, and the dispersion becomes more stable.

[0014] Examples of the vinyl ester monomers used include aliphatic vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and vinyl versatate, as well as aromatic vinyl esters such as vinyl benzoate. These can be used individually or in combination. Vinyl acetate is preferred due to its availability from the market, economic efficiency, and good removal efficiency of by-products generated during the manufacturing process.

[0015] In addition to the above-mentioned monomers, unsaturated acids such as itaconic acid, maleic acid, acrylic acid or their salts or mono- or dialkyl esters; nitriles such as acrylonitrile, amides such as methacrylamide and diacetoneacrylamide, etc. may be copolymerized as long as they do not significantly affect the resin physical properties.

[0016] Such ethylene-vinyl ester copolymers can be produced by any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization, etc. Usually, solution polymerization under pressure of ethylene is preferably used. The pressure of ethylene may be appropriately controlled according to the desired ethylene content, but usually it is selected from the range of 25 to 100 kg / cm 2 is selected. In addition, as the solvent used in such solution polymerization, an alcohol-based solvent is suitable, and particularly methanol is preferably used.

[0017] Furthermore, saponification of the ethylene-vinyl ester copolymer can be carried out by adopting any of the known methods of acid saponification and alkali saponification. Usually, alkali saponification using an alkali metal hydroxide, preferably sodium hydroxide as a saponification catalyst, is carried out.

[0018] The ethylene content of the EVOH used in the present invention is, as described above, 20 to 60 mol%, particularly 20 to 50 mol%, and more preferably 22 to 44 mol%. If such ethylene content is too large, the gas barrier property of the EVOH layer obtained from the aqueous dispersion obtained therefrom tends to be insufficient. On the contrary, if it is too small, the affinity with water becomes strong, and the stability of the aqueous dispersion tends to be insufficient. Such ethylene content can be measured based on ISO14663.

[0019] Furthermore, the degree of saponification of such EVOH is usually 90 mol% or higher, particularly 98 mol% or higher, and even more preferably 99 mol% or higher. The higher the degree of saponification, the better the stability and heat-sealability of the dispersion and the EVOH layer can be obtained. If it is too low, the heat-sealability will be insufficient, and the stability of the aqueous dispersion will tend to be insufficient due to hydrophobic interactions. The degree of saponification can be measured according to JIS K6726 (wherein EVOH is used as a solution uniformly dissolved in water / methanol solvent).

[0020] (α-hydroxyalkyl group) The EVOH of the present invention may also be a modified EVOH containing an α-hydroxyalkyl group as a side chain. In this case, the α-hydroxyalkyl group usually has 2 to 10 carbon atoms, with 2 to 6 carbon atoms being particularly preferred, and even more preferably 2 to 4 carbon atoms. If the number of carbon atoms is too high, it can reduce the crystallinity of the EVOH due to steric hindrance, and the gas barrier properties tend to be insufficient. Furthermore, among α-hydroxyalkyl groups, 1,2-dihydroxyalkyl groups represented by the following general formula (1) are particularly preferred in terms of forming a hydration layer on the surface of dispersed particles.

[0021] [ka]

[0022] The content of the α-hydroxyalkyl group is usually 0.5 to 10 mol%, particularly 1 to 5 mol%, and more preferably 2 to 4 mol%, relative to the modified EVOH used in the present invention. If the content of such α-hydroxyalkyl groups is too low, the stability of the aqueous dispersion tends to be insufficient, and conversely, if it is too high, the water resistance in hot water tends to be insufficient.

[0023] Such α-hydroxyalkyl groups are preferably directly bonded to the EVOH main chain from the viewpoint of gas barrier properties and thermal stability, but they may also be bonded to the EVOH main chain via various bonding chains, as long as they do not hinder the effects of the present invention. Examples of such bonding chains include hydrocarbon chains such as alkylene, alkenylene, alkylene, phenylene, naphthylene, -O-, -(CH2O) m -, -CO-, -CO(CH2) - ether bond-containing chains, etc. m Examples include bond chains containing carbonyl groups such as CO-, bond chains containing sulfur atoms such as -S-, -SO-, -SO2-, bond chains containing nitrogen atoms such as -NR-, -CONR-, and bond chains containing metal atoms such as silicon, titanium, and aluminum. Since long bonding chains tend to reduce gas barrier properties due to steric hindrance, shorter chains are preferable, and it is desirable that the number of atoms be three or less.

[0024] The α-hydroxyalkyl group can be introduced to EVOH by either copolymerization or a post-reaction method. For example, one post-reaction method involves adding a glycidyl compound to the hydroxyl group of EVOH. However, in this method, the α-hydroxyalkyl group is bonded to the main chain via an ether linkage, which may be undesirable for applications requiring thermal stability. Furthermore, in the copolymerization method, when copolymerizing ethylene and vinyl ester monomers to form an ethylene-vinyl ester copolymer, an olefin compound having a hydroxyl group at the terminal end can be used as the copolymerization monomer. Examples of such olefin compounds include monohydroxyolefin compounds such as 4-hydroxy-1-butene, 5-hydroxy-1-pentene, and 6-hydroxy-1-hexene, and dihydroxyolefin compounds such as 3,4-dihydroxy-1-butene, 4,5-dihydroxy-1-pentene, and 5,6-dihydroxy-1-hexene. Furthermore, olefin compounds having hydroxyl groups in which the hydroxyl groups are protected by functional groups that can be deprotected in a saponification process are also preferred in terms of copolymerizability with vinyl esters, etc. Examples include derivatives such as acylated products of these compounds, and in particular, acetylated products that share common by-products in the saponification process with vinyl acetate, which is widely used as a vinyl ester monomer, are preferably used.

[0025] In the present invention, the most preferred embodiment is a method for obtaining a modified EVOH in which a 1,2-dihydroxy group represented by general formula (1) is directly bonded to the EVOH main chain, and includes methods such as (i) using 3,4-dihydroxy-1-butene or a derivative thereof such as an acylated product as the copolymer monomer, copolymerizing it with a vinyl ester monomer and ethylene, and then saponifying the resulting copolymer; (ii) using vinyl ethylene carbonate as the copolymer monomer, and saponifying and decarboxylating the resulting copolymer; and (iii) using 2,2-dialkyl-4-vinyl-1,3-dioxolane as the copolymer monomer, and saponifying and deacetalizing the resulting copolymer. Among these, method (i) is preferred because it exhibits excellent copolymerization reactivity, facilitates the uniform introduction of the modifying group into EVOH, and offers excellent industrial handling advantages. In particular, the use of acetylated 3,4-dihydroxy-1-butene is preferred because it exhibits excellent copolymerization with vinyl ester monomers, and because it shares common by-products during saponification with vinyl acetate, which is a widely used vinyl ester monomer, allowing for simultaneous separation and recovery of these by-products.

[0026] [Dispersant containing polyethyleneimine (B1) (B)] Next, the dispersant (B) containing polyethyleneimine (B1) used in the present invention will be described. The polyethyleneimine (B1) used in the present invention is a component that disperses the dispersed phase (A) in the aqueous dispersion according to this invention, and linear or branched polyethyleneimine is preferably used.

[0027] The molecular weight of the polyethyleneimine (B1), particularly the linear or branched polyethyleneimine, is typically 200 to 70,000, and is preferably in the range of 5,000 to 30,000, as measured by the boiling point elevation method or the viscosity method. Furthermore, the hydrodynamic radius of polyethyleneimine (B1), calculated by number-average calculation using dynamic light scattering, is typically 0.1 nm to 50 nm. A range of 2.0 to 40 nm, and more preferably 4 to 30 nm, is used. If the molecular weight or hydrodynamic radius of polyethyleneimine is too small or too large, particle formation is not possible.

[0028] The ratio of polyethyleneimine (B1) to EVOH (A1) is preferably EVOH:polyethyleneimine = 99.9:0.01 to 20:80 by mass, with particularly suitable ranges of 99:1 to 50:50, and even more preferably 98:2 to 60:40. If the polyethyleneimine content is too low, it will not form particles, and conversely, if it is too high, the water resistance tends to be insufficient.

[0029] The dispersant (B) may consist solely of polyethyleneimine (B1), or it may also consist of a modified polyethyleneimine or a dispersant such as butene-divinyl alcohol or other divinyl alcohols. When using a dispersant other than polyethyleneimine, the amount of this other component should preferably be 0.01% by mass or more, and more preferably 0.1% by mass or more, relative to polyethyleneimine. Furthermore, 90% by mass or less is preferred, and more preferably 75% by mass or less. By keeping the amount within this range, the addition of polyethyleneimine (B1) allows for the formation of a particulate composition, enabling the stable acquisition of an emulsion.

[0030] [Production of aqueous dispersion according to the present invention] Methods for obtaining the aqueous dispersion according to the present invention include: dissolving EVOH in a good solvent and then adding it to a poor solvent to precipitate it; dissolving EVOH in a mixed solvent of a poor solvent and a good solvent, then removing only the good solvent by heating or reducing the pressure to precipitate EVOH and obtain a dispersion; melting and kneading EVOH at a high temperature and then adding an aqueous polyethyleneimine solution while it is flowing to emulsify it; and adding EVOH pellets and an aqueous polyethyleneimine solution to a predetermined pressure-resistant container, then applying pressure and heat to melt the EVOH pellets and emulsify them. In particular, a method is preferred in which EVOH is dissolved in a mixed solvent of a poor solvent and a good solvent, and then only the good solvent is removed by heating or reducing the pressure to precipitate the EVOH and obtain the dispersion, as this reduces the particle size in the resulting EVOH dispersion.

[0031] The conditions for dissolving EVOH in the present invention are not particularly limited as long as any solvent that dissolves it can be used, but a water-alcohol mixed solvent is preferred, and as the alcohol, a water-alcohol mixed solvent using an alcohol having the following volatilization temperature (boiling point) is preferred, and in particular, mixed solvents of water and lower alcohols having 1 to 4 carbon atoms such as water-methyl alcohol, water-ethyl alcohol, water-propyl alcohol, and water-butyl alcohol are preferred, and among these, a mixed solvent of water and lower alcohols having 1 to 4 carbon atoms is preferred in terms of economic efficiency and environmental impact in terms of purification and distillation of the solution after the reaction. Furthermore, it is preferable that the ratio of alcohol to water in this mixed solvent is 9:1 to 1:9 by mass ratio.

[0032] The volatilization temperature (boiling point) of the alcohol is preferably within 50 to 98°C, which is the temperature at which the alcohol volatilizes from the EVOH mixed solvent. A temperature of 70 to 95°C is particularly preferred, as temperatures that are too low tend to result in larger particle sizes or the formation of irregularly shaped particles. Depending on the boiling point of the alcohol, the rate of alcohol removal may be altered by reducing the pressure in the system or by blowing air.

[0033] The conditions under which the EVOH of the present invention is dispersed are preferably stirred regardless of the reaction temperature. There are no particular restrictions on the stirring conditions, but it is preferable to stir by rotating the container itself, such as a rotary evaporator, or by stirring the liquid inside the container with an anchor blade, paddle blade, or three-blade retractable blade.

[0034] From the viewpoint of dispersion stability, the EVOH dispersion of the present invention preferably has a total solid content of EVOH and polyethyleneimine of 0.1% by mass or more and 60% by mass or less in the aqueous dispersion. Furthermore, it is preferable that it be 20% by mass to 40% by mass. The aqueous dispersion of the present invention is characterized by its excellent stability even at high concentrations, but if the solid content concentration is too high, the drying rate is fast and a resin film may form at the gas-liquid interface.

[0035] The aqueous dispersion of the present invention may contain additives commonly used in aqueous dispersions, to the extent that they do not hinder the objectives of the present invention, such as electrolytes such as alkali (earth) metal salts as viscosity reducers, inorganic fillers such as layered inorganic compounds and inorganic oxides, dispersants such as film-forming aids and surfactants, antioxidants, various stabilizers, pigments, lubricants, fungicides, and preservatives. The aqueous dispersion of the present invention can be suitably used as a coating agent composition for forming a protective layer on the surface of plastics, metals, paper, wood, etc., or as a heat sealant for substrates, and can form a coating layer on plastics, metals, paper, wood, etc.

[0036] Furthermore, by using polyethyleneimine as a dispersion stabilizer, the aqueous dispersion of the present invention makes it possible to create an EVOH aqueous dispersion with a high ethylene ratio. It is presumed that as the ethylene ratio of EVOH increases, the low-temperature stability and water resistance are improved. [Examples]

[0037] The present invention will be described below with reference to examples, but the present invention is not limited to the descriptions in the examples unless it exceeds the essence of the invention. In the examples, "parts" and "%" refer to weight-based units unless otherwise specified.

[0038] <Evaluation Method> [Confirmation of emulsification feasibility and particle shape] For each example and comparative example, the mixture (dispersion or solid-liquid mixture) obtained was observed visually to determine whether an emulsion could be formed and whether it was a dispersion. It was then evaluated according to the following criteria, and the particle shape of the emulsified dispersion was evaluated by microscopic observation. ○: Forms an emulsion and disperses stably in water (and redisperses after settling if stirred). ×: No emulsion is obtained, and the polymer precipitates as a single mass.

[0039] [Hydrodynamic radius (R) calculated by number-averaged calculation using dynamic light scattering method] H )] After preparing a 1% by mass aqueous solution of polyethyleneimine, measurements were performed using an Otsuka Electronics ELSZNeoSE with a detection angle of 165° and 100 cumulative measurements. Subsequently, the cumulant diameter, calculated by number averaging, was halved to determine the final diameter.

[0040] [Particle size of dispersed particles] The aqueous dispersions obtained in the examples and comparative examples were diluted 10-fold and then stirred for 10 minutes. A cotton swab was soaked in the diluted solution, applied to a glass plate, and dried at room temperature. The dried particles were then measured using a KEYENCE VHX-1000. The number-average particle size was calculated using a sample size of 50 particles.

[0041] [water resistance] The aqueous dispersions obtained in the examples and comparative examples were diluted with deionized water to a solid content of 10%, and then coated onto glass plates to a thickness of 1 μm using an applicator and dried at room temperature. The dried coatings were immersed in a 23°C water bath and water resistance was evaluated according to the following criteria. ◎: The paint film does not peel off. ○: Some of the paint film has peeled off. ×: The entire paint film peels off.

[0042] <Ingredients> (Dispersed phase (A): Ethylene-vinyl ester copolymer saponified) Soanol DT2904RB... Manufactured by Mitsubishi Chemical Corporation, ethylene content: 29 mol%, MFR: 3.8 (210℃, 2160 gf), hereinafter abbreviated as "DT2904RB". Soanol AT4403B... Manufactured by Mitsubishi Chemical Corporation, ethylene content: 29 mol%, MFR: 3.5 (210℃, 2160 gf), hereinafter abbreviated as "AT4403B". EVAL L171B... Manufactured by Kuraray Co., Ltd., ethylene content: 27 mol%, MFR: 4.0 (190℃, 2160 gf), hereinafter abbreviated as "L171B". · EVAL H171B··· Manufactured by Kuraray Co., Ltd., ethylene content: 38 mol%, MFR: 1.7 (190℃, 2160 gf), hereinafter abbreviated as "H171B". EVAL F101B... Manufactured by Kuraray Co., Ltd., ethylene content: 32 mol%, MFR: 1.6 (190℃, 2160 gf), hereinafter abbreviated as "F101B". EVAL L104B... Manufactured by Kuraray Co., Ltd., ethylene content: 27 mol%, MFR: 8.0 (210℃, 2160 gf), hereinafter abbreviated as "L104B". EVAL G156B... Manufactured by Kuraray Co., Ltd., ethylene content: 48 mol%, MFR: 6.4 (190℃, 2160 gf), hereinafter abbreviated as "G156B".

[0043] (Dispersed phase (A): Modified ethylene-vinyl ester copolymer saponified) G-Soanol GH3304B is an α-hydroxyalkyl group-containing ethylene-vinyl alcohol copolymer, manufactured by Mitsubishi Chemical Corporation, with an ethylene content of 33 mol%, and an MFR of 4.0 (210℃, 2160 gf). Hereafter, it will be abbreviated as "GH3304B". G-Soanol GH3804B is an α-hydroxyalkyl group-containing ethylene-vinyl alcohol copolymer, manufactured by Mitsubishi Chemical Corporation, with an ethylene content of 38 mol%, and an MFR of 4.0 (210℃, 2160 gf). Hereafter, it will be abbreviated as "GH3804B".

[0044] (Dispersant (B): Branched polyethyleneimine (PEI)) • Epomin SP-200... Manufactured by Nippon Shokubai Co., Ltd., R H = 1.0 nm, 30 mass% solution, hereinafter abbreviated as "SP-200". • Epomin HM-2000... Manufactured by Nippon Shokubai Co., Ltd., R H =1.7 nm, 30 mass% solution, hereinafter abbreviated as "HM-2000". • Epomin P-1000... Manufactured by Nippon Shokubai Co., Ltd., R H =3.8 nm, 30 mass% solution, hereinafter abbreviated as "P-1000". • Epomin P-3000... Manufactured by Nippon Shokubai Co., Ltd., R H =4.0 nm, 30 mass% solution, hereinafter abbreviated as "P-3000".

[0045] (Dispersant (B): Other) G Polymer AZF8035W (butenediol vinyl alcohol) polymer, manufactured by Mitsubishi Chemical Corporation, 10% by mass solution, hereinafter abbreviated as "AZF8035W". • Exceval RS-2117: Special modified polyvinyl alcohol, manufactured by Kuraray Co., Ltd., 10% by mass solution, hereinafter abbreviated as "RS-2117". • Gosenor GL-05: Partially saponified polyvinyl alcohol, manufactured by Mitsubishi Chemical Corporation, degree of saponification: 86.5-89.0%, 10% by mass solution, hereinafter abbreviated as "GL-05". PVNA GE191-104: Poly-N-vinylacetamide, manufactured by Showa Denko K.K., 10% by mass solution, hereinafter abbreviated as "GE191-104". PEO...Polyethylene oxide, manufactured by Sigma-Aldrich, molecular weight: 2000, 10% by mass solution, hereinafter referred to as "PEO". CMC Daicel 1380...Carboxymethylcellulose, manufactured by Daicel Corporation, 1% by mass solution, hereinafter referred to as "CMC".

[0046] (solvent) Isopropyl alcohol... Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., hereinafter referred to as "IPA". Ethyl alcohol... Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., hereinafter referred to as "EtOH". n-propyl alcohol... Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., hereinafter referred to as "nPA".

[0047] (Example 1) (Preparation of aqueous dispersions) 10 g of DT2904RB, 4.5 g of a 30 wt% P-1000 solution, 54 g of IPA, and 32.85 g of deionized water were added to a cylindrical three-neck separable flask fitted with an anchor wing. After adding the raw materials, the temperature was raised to 85°C and stirred at 400 rpm for 4 hours to dissolve the pellet. Then, the rotation speed was reduced to 200 rpm, the rubber stopper of the cylindrical three-neck separable flask was removed to create an open system, and the temperature was raised to 95°C and stirred for 2 hours to remove the IPA. After cooling to room temperature, the evaluation described above was performed. The results are shown in Table 1.

[0048] (Examples 2-9) In Example 1, aqueous dispersions were prepared in the same manner as in Example 1, except that the dispersed phase (A) and dispersant (B) were the compounds listed in Table 1, and the above evaluation was performed. The results are shown in Table 1.

[0049] (Examples 10-12) An aqueous dispersion was prepared in the same manner as in Example 6, except that the dispersant (B) was changed to the compound listed in Table 1, and the above evaluation was performed. The results are shown in Table 1.

[0050] (Examples 13-14) An aqueous dispersion was prepared in the same manner as in Example 6, except that the solvent was changed to the compound shown in Table 2, and the evaluation described above was performed. The results are shown in Table 2.

[0051] (Example 15) In Example 6, as shown in Table 2, an aqueous dispersion was prepared in the same manner as in Example 6, except that P-3000 was used as the dispersant (B) in addition to P-1000, and the above evaluation was performed. The results are shown in Table 2.

[0052] (Example 16) In Example 6, as shown in Table 2, an aqueous dispersion was prepared in the same manner as in Example 6, except that AZF8035W was used as the dispersant (B) in addition to P-1000, and the amount of deionized water was changed. The evaluation described above was then performed. The results are shown in Table 2.

[0053] (Example 17) In Example 6, an aqueous dispersion was prepared in the same manner as in Example 6, except that the amounts of dispersant (B) and solvent were changed, as shown in Table 2, and the above evaluation was performed. The results are shown in Table 2.

[0054] (Examples 18, 20) In Example 6, an aqueous dispersion was prepared in the same manner as in Example 6, except that the amount of dispersant (B) was changed, as shown in Table 2, and the above evaluation was performed. The results are shown in Table 2.

[0055] (Example 19) In Example 17, an aqueous dispersion was prepared in the same manner as in Example 17, except that the amount of dispersant (B) was changed, as shown in Table 2, and the above evaluation was performed. The results are shown in Table 2.

[0056] [Table 1]

[0057] (Comparative Examples 1-7) In Example 6, an aqueous dispersion was prepared and evaluated in the same manner as in Example 6, except that the type and amount of dispersant (B) and the amount of solvent were changed as shown in Tables 2 and 3.

[0058] [Table 2]

[0059] [Table 3]

[0060] As is clear from these results, the aqueous dispersion of the present invention can produce a film with excellent water resistance when polyethyleneimine is used. On the other hand, when polyethyleneimine is not used, dispersed particles cannot be obtained. [Industrial applicability]

[0061] The aqueous dispersion of the present invention exhibits minimal aggregation, allows for long-term storage, and provides excellent stability during use. Furthermore, its dried film has superior water resistance and heat-sealing properties. Due to these characteristics, the aqueous dispersion of the present invention can be suitably used as a coating liquid for forming surface protective layers on plastics, metals, paper, wood, and other materials, as well as a heat-sealing agent for substrates.

Claims

1. An aqueous dispersion containing a dispersed phase (A) and a dispersant (B), An aqueous dispersion comprising an ethylene-vinyl ester copolymer saponified product and a polyethyleneimine dispersant (B).

2. The aqueous dispersion according to claim 1, wherein the ethylene content of the ethylene-vinyl ester copolymer saponified is 20 mol% or more and 60 mol% or less.

3. The aqueous dispersion according to claim 1, wherein the degree of saponification of the ethylene-vinyl ester copolymer saponified is 90 mol% or more.

4. The aqueous dispersion according to claim 1, wherein the hydrodynamic radius of the polyethyleneimine, calculated by the number-average method of dynamic light scattering, is 0.1 nm or more and 50 nm or less.

5. The aqueous dispersion according to claim 1, wherein the mass ratio (A):(B) of the dispersed phase (A) to the dispersant (B) is 99.9:0.01 to 20:

80.

6. The aqueous dispersion according to claim 1, wherein the total amount of the dispersed phase (A) and the dispersant (B) is 0.1% by mass or more and 60% by mass or less of the solid content in the aqueous dispersion.

7. A coating agent composition containing the aqueous dispersion according to any one of claims 1 to 6.

8. A coating layer obtained by drying the aqueous dispersion according to any one of claims 1 to 6.

9. A heat sealant obtained by drying an aqueous dispersion according to any one of claims 1 to 6.

Images