Aqueous polyolefin resin dispersion and method for producing the same

Abstract

To provide a polyolefin resin aqueous dispersoid that has an increased solid content but has reduced viscosity to resist gelation, and offers good handleability and storage stability, and a method for producing the same.SOLUTION: A polyolefin resin aqueous dispersoid contains a polyolefin resin and an aqueous medium and has a solid content of 35 mass% or more and a viscosity of 180 mPa s or less at 25°C. Preferably the polyolefin resin aqueous dispersoid is substantially free of a nonvolatile hydrophilizing aid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous dispersion of a polyolefin resin that has a high solids concentration but can maintain a low viscosity even when a powder is added, and a method for producing the same. [Background technology]

[0002] Aqueous dispersions of polyolefin resins are used in a wide range of applications because they can produce coating films with excellent adhesion to various substrates. From the perspective of adoption in a wide range of applications and cost reduction, efforts have been made to increase the solids concentration of aqueous dispersions (e.g., Patent Document 1). Increasing the solids concentration of an aqueous dispersion increases viscosity, resulting in problems such as poor coatability. Therefore, efforts have been made to obtain aqueous dispersions with high solids concentration and low viscosity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-70092 Summary of the Invention [Problem to be solved by the invention]

[0004] The viscosity of the aqueous dispersion of polyolefin resin obtained by the technology disclosed in Patent Document 1 can be reduced to approximately 200 mPa·s at a solids concentration of 35% by mass. However, there is a problem in that the viscosity increases when the dispersion is stored for a long period of time in a high-temperature environment or when powders such as titanium oxide or talc used as pigments, dyes, fillers, etc. are added, resulting in reduced handleability and storage stability. [Means for solving the problem]

[0005] As a result of extensive research to solve the above problems, the present inventors have found that an aqueous dispersion capable of solving the above problems can be obtained, and have arrived at the present invention.

[0006] That is, the gist of the present invention is as follows. (1) Contains unsaturated carboxylic acid components Contains a polyolefin resin and an aqueous medium, The polyolefin resin The solid content is 35% by mass or more, and the viscosity at 25°C is 180 mPa·s or less. and is substantially free of non-volatile water-reforming aids. 1. An aqueous polyolefin resin dispersion comprising: ( 2 ) containing one or more hydrophobic amines and one or more hydrophilic amines, (1) Aqueous dispersion of polyolefin resin. ( 3 ) the total content of hydrophobic amines is 0.01 to 3 mass% and the total content of hydrophilic amines is 0.1 to 10 mass%, ( 2 ) Aqueous dispersion of polyolefin resin. ( 4 )(1)~ (3) a method for producing an aqueous polyolefin resin dispersion according to any one of the above, characterized in that a polyolefin resin and an aqueous medium containing an organic solvent are stirred at a temperature equal to or higher than the melting point of the polyolefin resin, and then the organic solvent is distilled off and water is added while maintaining the temperature at or above the melting point. ( 5 ) A polyolefin resin, an aqueous medium containing an organic solvent, and a first basic compound are stirred at a temperature equal to or higher than the melting point of the polyolefin resin, and then a basic compound different from the first basic compound is added; 4 ) A method for producing a polyolefin resin dispersion. [Effects of the Invention]

[0007] The aqueous polyolefin resin dispersion of the present invention has a further reduced viscosity at room temperature, even though it has an elevated solids concentration. Furthermore, it can maintain a low viscosity even when stored for a long period of time in a high-temperature environment or when it contains powder, and can inhibit gelation, thereby providing excellent handleability and storage stability. DETAILED DESCRIPTION OF THE INVENTION

[0008] The polyolefin resin aqueous dispersion of the present invention (hereinafter may be simply referred to as "aqueous dispersion") contains polyolefin resin particles and an aqueous medium. The polyolefin resin particles are dispersed or dissolved in an aqueous medium. In the present invention, the aqueous medium is a liquid containing water as a main component, and may contain an organic solvent, which will be described later.

[0009] The olefin component, which is the main component of the polyolefin resin, is not particularly limited, and examples thereof include alkenes such as ethylene, propylene, isobutylene, 2-butene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene, and norbornenes, and dienes such as butadiene and isoprene. Among these, alkenes having 2 to 6 carbon atoms are preferred, and ethylene and propylene are particularly preferred. A mixture of these may also be used. Furthermore, a copolymer of two or more types of olefin components may also be used. The content of the olefin component is preferably 50% by mass or more, and more preferably 70% by mass or more, from the viewpoint of fully exhibiting the properties derived from the olefin.

[0010] From the viewpoint of dispersibility in an aqueous medium, the polyolefin resin preferably contains an unsaturated carboxylic acid component. Examples of the unsaturated carboxylic acid component include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, etc., as well as half esters and half amides of unsaturated dicarboxylic acids. Among them, from the viewpoint of even better adhesiveness, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferred, acrylic acid and maleic anhydride are more preferred, and maleic anhydride is particularly preferred because it can suppress an increase in viscosity during long-term storage in a high-temperature environment or when a powder is contained.

[0011] The unsaturated carboxylic acid component in the polyolefin resin is contained by random copolymerization, block copolymerization, graft copolymerization (graft modification), or the like.

[0012] The content of the unsaturated carboxylic acid component in the polyolefin resin is preferably 0.1% by mass or more, more preferably 1 to 10% by mass, and even more preferably 2 to 5% by mass. If the content is less than 0.1% by mass, dispersion in an aqueous medium may be difficult. If the content exceeds 10% by mass, mixing stability may be poor.

[0013] The polyolefin resin may be further copolymerized with components other than the above-mentioned olefin component or unsaturated carboxylic acid component for the purpose of adjusting the melting point or melt flow rate (MFR) or improving dispersibility. Examples of other components include (meth)acrylic acid ester components such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate; maleic acid diester components such as dimethyl maleate, diethyl maleate, and dibutyl maleate; alkyl vinyl ether components such as methyl vinyl ether and ethyl vinyl ether; vinyl ester components such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl versatate; vinyl alcohol obtained by saponifying a vinyl ester component with a basic compound; and (meth)acrylic acid amide components, or mixtures thereof. Among these, (meth)acrylic acid ester components and vinyl ester components are preferred due to their excellent dispersibility, and (meth)acrylic acid ester components are more preferred due to their ability to suppress viscosity increases during long-term storage in high-temperature environments and when powders are contained. Note that "(meth)acrylic acid" means "acrylic acid or methacrylic acid."

[0014] The content of these other components in the polyolefin resin is preferably 1 to 45% by mass, more preferably 2 to 35% by mass, even more preferably 3 to 25% by mass, and particularly preferably 4 to 18% by mass. If the content is too high outside the above range, it may be difficult to reduce the viscosity when the solid content is increased, and if the content is too low, dispersibility and filterability may be impaired.

[0015] Specific examples of polyolefin resins include ethylene-(meth)acrylic acid copolymer, ethylene-maleic anhydride copolymer, propylene-maleic anhydride copolymer, ethylene-propylene-maleic anhydride copolymer, ethylene-butene-maleic anhydride copolymer, propylene-butene-maleic anhydride copolymer, ethylene-propylene-butene-maleic anhydride copolymer, ethylene-ethyl(meth)acrylate-maleic anhydride copolymer, etc. Among them, from the viewpoints of being able to suppress an increase in viscosity when stored for a long period of time in a high-temperature environment or when containing powder, and having excellent dispersibility, propylene-maleic anhydride copolymer, propylene-butene-maleic anhydride copolymer, ethylene-propylene-butene-maleic anhydride copolymer, and ethylene-ethyl(meth)acrylate-maleic anhydride copolymer are preferred, and ethylene-ethyl(meth)acrylate-maleic anhydride copolymer is most preferred.

[0016] The polyolefin resin may be chlorinated in the range of 5 to 40% by mass.

[0017] The polyolefin resin may contain an N-substituted imide unit such as an N,N-dimethylaminoethyl group, an N,N-dimethylaminopropyl group, an N,N-dimethylaminobutyl group, an N,N-diethylaminoethyl group, an N,N-diethylaminopropyl group, or an N,N-diethylaminobutyl group.

[0018] The melt flow rate (MFR) value (190°C, 21.2N load according to ISO 1133) of the polyolefin resin is preferably 300g / 10min or less, more preferably 100g / 10min or less, and even more preferably 0.001 to 70g / 10min.

[0019] The aqueous dispersion of the present invention has a solids concentration of 35% by mass or more and a viscosity at 25° C. of 180 mPa·s or less, preferably 100 mPa·s or less, more preferably 50 mPa·s or less, and even more preferably 30 mPa·s or less. Although the aqueous dispersion of the present invention has a high solids concentration of 35% by mass or more, the viscosity is kept low, gelation is inhibited, and the dispersion has excellent handleability and storage stability.

[0020] The aqueous dispersion of the present invention can maintain a low viscosity even when stored for a long period of time in a high-temperature environment. As an indicator of this, the increase in viscosity (viscosity change) after three months of storage of the aqueous dispersion of the present invention in an incubator at 50°C is preferably 200 mPa·s or less, more preferably 100 mPa·s or less, even more preferably 50 mPa·s or less, and particularly preferably 20 mPa·s or less, from the viscosity at 25°C. Furthermore, it is preferable that the viscosity after three months of storage in an incubator at 50°C is no more than twice the viscosity at 25°C.

[0021] Furthermore, the aqueous dispersion of the present invention can maintain a low increase in viscosity even when powder is contained therein. As an indicator of this, when 10 parts by mass of titanium oxide particles as powder are mixed with 100 parts by mass of the aqueous dispersion of the present invention having a solid content concentration of 35% by mass, the viscosity increase rate is preferably 650% or less, more preferably 500% or less, even more preferably 400% or less, and particularly preferably 300% or less.

[0022] Although the aqueous dispersion of the present invention does not exclude the use of a nonvolatile hydrophilic aid, it is preferable that the aqueous dispersion does not substantially contain a nonvolatile hydrophilic aid.In order to improve the stability of the aqueous dispersion and suppress the increase in viscosity, it is common to add a nonvolatile hydrophilic aid.However, in the present invention, even without substantially containing a nonvolatile hydrophilic aid, it is possible to produce an aqueous dispersion that has excellent dispersion stability of polyolefin resin particles and further suppresses the increase in viscosity while increasing the solid content concentration.

[0023] Here, "aqueous dispersion aid" refers to a chemical or compound added in the production of an aqueous dispersion for the purpose of promoting aqueous dispersion or stabilizing the aqueous dispersion, and "non-volatile" refers to a substance that has no boiling point at normal pressure or a high boiling point (e.g., 300°C or higher) at normal pressure.

[0024] "Substantially free of non-volatile water-reforming aids" means that such aids are not used during production (when dispersing the polyolefin resin in water), and the resulting aqueous dispersion consequently does not contain such aids. The amount of non-volatile water-reforming aid is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably less than 0.5% by mass, and most preferably 0% by mass, based on the polyolefin resin component.

[0025] Examples of the non-volatile water-imparting aids referred to in the present invention include emulsifiers, compounds having protective colloidal properties, modified waxes, acid-modified compounds with a high acid value, and water-soluble polymers.

[0026] Examples of emulsifiers include cationic emulsifiers, anionic emulsifiers, nonionic emulsifiers, and amphoteric emulsifiers, and include those generally used in emulsion polymerization as well as surfactants.For example, examples of anionic emulsifiers include sulfate salts of higher alcohols, higher alkyl sulfonates, higher carboxylates, alkylbenzene sulfonates, polyoxyethylene alkyl sulfate salts, polyoxyethylene alkylphenyl ether sulfate salts, and vinyl sulfosuccinate.Examples of nonionic emulsifiers include compounds having a polyoxyethylene structure such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, ethylene oxide-propylene oxide block copolymers, polyoxyethylene fatty acid amides, and ethylene oxide-propylene oxide copolymers, and sorbitan derivatives such as polyoxyethylene sorbitan fatty acid esters.Examples of amphoteric emulsifiers include lauryl betaine and lauryl dimethylamine oxide.

[0027] Examples of compounds having protective colloidal properties, modified waxes, acid-modified compounds with a high acid value, and water-soluble polymers include polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, modified starch, polyvinylpyrrolidone, polyacrylic acid and its salts, acid-modified polyolefin waxes and salts thereof having a number average molecular weight of typically 5,000 or less, such as carboxyl group-containing polyethylene wax, carboxyl group-containing polypropylene wax, and carboxyl group-containing polyethylene-propylene wax, carboxyl group-containing polymers and salts thereof having an unsaturated carboxylic acid content of 10% by mass or more, such as acrylic acid-maleic anhydride copolymers and salts thereof, styrene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid copolymers, isobutylene-maleic anhydride alternating copolymers, and (meth)acrylic acid-(meth)acrylic acid ester copolymers, polyitaconic acid and its salts, water-soluble acrylic copolymers having amino groups, gelatin, gum arabic, and casein, as well as compounds generally used as dispersion stabilizers for fine particles.

[0028] The aqueous dispersion of the present invention may contain other polymers, tackifiers, inorganic particles, crosslinking agents, pigments, dyes, etc. in order to further improve the performance depending on the purpose. The aqueous dispersion of the present invention can maintain a low viscosity even when it contains a powder. The powder is a powder or an aggregate of powders, and examples thereof include inorganic particles such as those described below, titanium oxide, zinc white, and carbon black.

[0029] The other polymers and tackifiers are not particularly limited, and examples thereof include polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester-maleic anhydride copolymer, styrene-maleic acid resin, styrene-butadiene resin, butadiene resin, acrylonitrile-butadiene resin, polyurethane resin, poly(meth)acrylonitrile resin, (meth)acrylamide resin, chlorinated polyethylene resin, chlorinated polypropylene resin, polyester resin, modified nylon resin, rosin, phenol resin, silicone resin, epoxy resin, etc., or tackifiers containing these, and a mixture of two or more of them may be used as needed.

[0030] These polymers may be used in the solid state, but in terms of maintaining the stability of the aqueous dispersion, it is preferable to use the polymers after processing them into an aqueous dispersion.

[0031] Examples of inorganic particles include inorganic particles such as metal oxides such as magnesium oxide, zinc oxide, and tin oxide, calcium carbonate, and silica, and layered inorganic compounds such as vermiculite, montmorillonite, hectorite, hydrotalcite, and synthetic mica. From the viewpoint of the transparency of the coating film, the average particle size of these inorganic particles is preferably 0.005 to 10 μm. Note that a mixture of multiple inorganic particles may be used.

[0032] Examples of the crosslinking agent that can be used include a crosslinking agent having self-crosslinking properties, a compound having a plurality of functional groups in the molecule that react with the unsaturated carboxylic acid component, and a metal having a polyvalent coordination site. Specific examples include oxazoline group-containing compounds, carbodiimide group-containing compounds, isocyanate group-containing compounds, epoxy group-containing compounds, melamine compounds, urea compounds, zirconium salt compounds, silane coupling agents, etc., and a mixture of two or more of these may be used as needed. Among these, from the viewpoint of ease of handling, oxazoline group-containing compounds, carbodiimide group-containing compounds, isocyanate group-containing compounds, and epoxy group-containing compounds are preferred.

[0033] Examples of pigments and dyes include titanium oxide, zinc oxide, and carbon black, and any of disperse dyes, acid dyes, cationic dyes, reactive dyes, and the like can be used. The aqueous dispersion of the present invention may further contain various chemicals such as a leveling agent, an antifoaming agent, an anti-popping agent, a pigment dispersant, an ultraviolet absorber, a thickener, a weathering agent, and a flame retardant, if necessary.

[0034] The aqueous dispersion of the present invention can be suitably used as an adhesive, a coating agent, a primer, a paint, an ink, etc. The aqueous dispersion of the present invention can maintain a low viscosity even when powders such as pigments, dyes, and fillers are added, and therefore is particularly suitable for applications containing such powders. The aqueous dispersion of the present invention is particularly suitable for use in metal products, electronic devices, packaging materials, automobile parts, and the like.

[0035] Specific examples of the above-mentioned uses include anchor coating agents for PP extrusion lamination, coating agents for secondary battery separators, primers for UV-curable coating agents, primers for shoes, primers for automobile bumpers, primers for clear boxes, paints for PP substrates, adhesives for packaging materials, adhesives for paper containers, adhesives for lid materials, adhesives for in-mold transfer foils, adhesives for PP steel plates, adhesives for solar cell modules, adhesives for flocking, adhesives for binders for secondary battery electrodes, adhesives for secondary battery exteriors, adhesives for automobile belt moldings, adhesives for automobile components, adhesives for dissimilar substrates, and fiber converging agents.

[0036] The aqueous dispersion of the present invention has a high solids concentration but a low viscosity, and can maintain its low viscosity even when stored for a long period of time in a high-temperature environment or when powder is contained, thereby exhibiting excellent coatability and film-forming ability. To form a coating film from the aqueous dispersion of the present invention, for example, the aqueous dispersion of the present invention can be uniformly applied to the surface of various substrates, and if necessary, allowed to set at around room temperature, followed by a heat treatment for drying or drying and baking. This allows a uniform coating film to adhere to the surface of various substrates.

[0037] The aqueous dispersion can be applied to a substrate by any known method, such as gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, or brush coating.

[0038] The amount of the aqueous dispersion to be applied to the substrate is not particularly limited and is appropriately selected depending on the application. However, the amount of the aqueous dispersion to be applied after drying is preferably 0.01 to 100 g / m 2 It is preferable that the density is 0.1 to 50 g / m 2 More preferably, it is 0.2 to 30 g / m 2 It is more preferable that:

[0039] In order to adjust the coating amount, it is preferable to use an aqueous dispersion whose concentration has been adjusted according to the desired coating thickness, in addition to appropriately selecting the coating device and its operating conditions. The concentration of the aqueous dispersion can be adjusted by the charging composition during preparation, or it may be adjusted by appropriately diluting or concentrating the aqueous dispersion once prepared.

[0040] As a heating device for the heat treatment after coating, a normal hot air circulation type oven, an infrared heater, or the like can be used. The heating temperature and heating time are appropriately selected depending on the characteristics of the substrate or the amounts of various components that can be optionally incorporated into the aqueous dispersion. However, a lower heating temperature is preferable from the viewpoint of energy cost and damage to the substrate, and a shorter heating time is preferable from the viewpoint of productivity. The heating temperature is preferably 20 to 130°C, more preferably 30 to 120°C, and even more preferably 40 to 100°C. The heating time is preferably 1 second to 20 minutes, more preferably 5 seconds to 15 minutes, and even more preferably 5 seconds to 10 minutes. When a crosslinking agent is contained in the aqueous dispersion of the present invention, it is desirable to appropriately select the heating temperature and time depending on the type of crosslinking agent in order to sufficiently promote the reaction between the carboxyl groups in the polyolefin resin and the crosslinking agent.

[0041] As a manufacturing method for obtaining the aqueous dispersion of the present invention, a method can be adopted in which the various components described above, i.e., the polyolefin resin, the aqueous medium, and, if necessary, an organic solvent, a basic compound, any of various optional additives, etc. are stirred to disperse the resin.

[0042] Examples of the stirring method include a method of physically mixing using a blade or a propeller, or a method of blowing air or steam, and the mixture may be mixed in a sealable container. The vessel can be a device used as a solid / liquid mixer or emulsifier, and it is preferable to use a device capable of applying a pressure of 0.1 MPa or more. The stirring method and rotation speed are not particularly limited, but stirring at a low speed sufficient to make the polyolefin resin uniform in the aqueous medium is sufficient. Therefore, high-speed stirring (e.g., 1000 rpm or more) is not essential, and aqueous dispersions can be produced using simple equipment.

[0043] In particular, a method for producing an aqueous dispersion involves stirring a polyolefin resin and an aqueous medium containing an organic solvent at a temperature equal to or higher than the melting point of the resin, and then distilling off the organic solvent and adding water while maintaining the temperature at or above the melting point.

[0044] In the present invention, an aqueous medium containing an organic solvent is used in the production of an aqueous dispersion. After the polyolefin resin and the aqueous medium are stirred to form an aqueous dispersion, the organic solvent content is reduced by distilling off a portion of the organic solvent and adding water.

[0045] The organic solvent may be distilled off while stirring the aqueous dispersion. The distillation of the organic solvent and the addition of water may be performed alternately or simultaneously. By distilling off the organic solvent and adding water, the organic solvent content in the aqueous dispersion can be reduced to 10% by mass or less, more preferably 5% by mass or less, and more preferably 1% by mass or less from an environmental perspective. In the step of distilling off the organic solvent, it is possible to distill off substantially all of the organic solvent used in the aqueous dispersion, but this requires increasing the degree of vacuum in the apparatus and extending the operating time. Therefore, taking these productivity considerations into account, the lower limit of the organic solvent content is preferably about 0.01% by mass.

[0046] The organic solvent may be removed by distillation under normal pressure, reduced pressure, or increased pressure, but is preferably removed by distillation under increased pressure. By removing the organic solvent by distillation under increased pressure, an aqueous dispersion can be obtained in which an increase in viscosity is suppressed.

[0047] In conventional methods for producing aqueous dispersions, the various components are generally stirred at a temperature equal to or higher than the melting point of the resin, cooled, water is added, and the organic solvent is then distilled off. In contrast, in the present invention, the organic solvent is distilled off and water is added while the temperature is maintained at or higher than the melting point of the resin. By distilling off the organic solvent and adding water while maintaining the temperature above the melting point of the resin, the resin particles can be stably dispersed, and the viscosity can be kept below 180 mPa·s even at high solids concentrations of 35% by mass or higher.Furthermore, even when stored for long periods in a high-temperature environment or when powder is contained, the low viscosity can be maintained, resulting in an aqueous dispersion with excellent storage stability. The temperature at which the organic solvent is distilled off and water is added is preferably maintained at (melting point of resin + 5)°C or higher, more preferably (melting point of resin + 15)°C or higher, in order to prevent an increase in viscosity. The stirring temperature can be set appropriately from the viewpoint of the pressure resistance, heating performance, energy costs, etc. of the apparatus, even if it is a temperature above the melting point of the polyolefin resin, but is preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher.

[0048] To promote dispersion of polyolefin resin particles, it is preferable to add a hydrophilic organic solvent among organic solvents. The content of the hydrophilic organic solvent is preferably 50% by mass or less, more preferably 1 to 45% by mass, even more preferably 10 to 40% by mass, and particularly preferably 25 to 35% by mass, based on the total weight of the aqueous medium. If the content of the hydrophilic organic solvent exceeds 50% by mass, the medium will not be considered an aqueous medium, which not only deviates from one of the objectives of the present invention (environmental protection), but also may reduce the stability of the aqueous dispersion depending on the hydrophilic organic solvent used.

[0049] As the hydrophilic organic solvent, from the viewpoint of obtaining an aqueous dispersion having good dispersion stability, one having a solubility in water at 20°C of 10 g / L or more is preferred, one having a solubility of 20 g / L or more is more preferred, and one having a solubility of 50 g / L or more is even more preferred.

[0050] The hydrophilic organic solvent preferably has a boiling point of 100° C. or less, from the viewpoint of efficient drying and removal during the process of forming the coating film.

[0051] Preferred hydrophilic organic solvents include, for example, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, and cyclohexanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, ethyl butyl ketone, and cyclohexanone; ethers such as tetrahydrofuran and dioxane; ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, and 3-methyl acetate; Examples of the solvent include esters such as butyl ether, methyl propionate, ethyl propionate, diethyl carbonate, and dimethyl carbonate; glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and ethylene glycol ethyl ether acetate; and further examples include 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 3-methoxy-3-methyl-1-butanol, methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetoacetate, 1,2-dimethylglycerin, 1,3-dimethylglycerin, and trimethylglycerin.

[0052] Among these, ethanol, n-propanol, isopropanol, n-butanol, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and diethylene glycol monomethyl ether are preferably used because they are more effective in promoting the dispersion of polyolefin resin particles, and isopropanol is particularly preferred.

[0053] In the present invention, a mixture of these hydrophilic organic solvents may be used, and a hydrophobic organic solvent may be further added to further promote aqueous dispersion of the polyolefin resin.

[0054] As the hydrophobic organic solvent, an organic solvent having a solubility in water at 20°C of less than 10 g / L is preferred in order to obtain an aqueous dispersion with good dispersion stability. Furthermore, an organic solvent having a boiling point of 150°C or less is preferred in order to enable efficient drying and removal during the process of forming a coating film.

[0055] Examples of such hydrophobic organic solvents include olefin-based solvents such as n-pentane, n-hexane, n-heptane, cycloheptane, cyclohexane, and petroleum ether; aromatic solvents such as benzene, toluene, and xylene; and halogen-based solvents such as carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, trichloroethylene, 1,1,1-trichloroethane, and chloroform. The content of these hydrophobic organic solvents is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the aqueous dispersion. If the content of the hydrophobic organic solvent exceeds 15% by mass, gelation or the like may occur.

[0056] The aqueous dispersion of the present invention may contain a basic compound. When a basic compound is contained, for example, the basic compound and other raw materials are stirred at a temperature equal to or higher than the melting point of the polyolefin resin. The basic compound may be added all at once when stirring at a temperature equal to or higher than the melting point of the polyolefin resin, or may be added in several portions. It may also be added before and after the temperature is raised to equal to or higher than the melting point of the polyolefin resin. In this case, the basic compound added later is preferably a different type of basic compound from the first basic compound added first. In this case, it is preferable to add a hydrophobic amine before raising the temperature to equal to or higher than the melting point of the polyolefin resin, in order to improve dispersibility and further suppress an increase in viscosity. It is also preferable to add a hydrophilic amine after raising the temperature to equal to or higher than the melting point of the polyolefin resin, since this has a high boiling point and makes it easy to adjust the content of the basic compound after distillation.

[0057] Examples of basic compounds include ammonia, triethylamine, tripropylamine, tributylamine, dicyclohexyldiamine, isopropylamine, aminoethanol, dimethylaminoethanol, diethylaminoethanol, ethylamine, diethylamine, isobutylamine, dipropylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, sec-butylamine, propylamine, n-butylamine, 2-methoxyethylamine, 3-methoxypropylamine, 2,2-dimethoxyethylamine, morpholine, N-methylmorpholine, N-ethylmorpholine, pyrrole, and pyridine. Among these, triethylamine and N,N-dimethylethanolamine are preferred from the viewpoint of promoting dispersion of the resin. In particular, it is more preferred to add one or more hydrophobic amines and one or more hydrophilic amines, as these improve dispersibility and further help to suppress an increase in viscosity after distillation of the organic solvent.

[0058] The hydrophobic amine in the present invention refers to an amine that dissolves in an amount of less than 10 g in 100 g of water at 25° C., and examples thereof include triethylamine, tripropylamine, tributylamine, and dicyclohexyldiamine. Of these, triethyleneamine is preferred from the viewpoints of economy and workability. The hydrophilic amine refers to an amine that dissolves 10 g or more in 100 g of water at 25° C. Examples of hydrophilic amines include aminoethanol, dimethylaminoethanol, diethylaminoethanol, diethanolamine, and triethanolamine. Of these, dimethylaminoethanol is preferred from the viewpoint of dispersion stability.

[0059] The total amount of basic compounds added is preferably 0.5 to 10 times the equivalent of the carboxyl groups in the polyolefin resin, more preferably 0.6 to 7 times, and particularly preferably 0.7 to 5 times. If the amount is less than 0.5 times, dispersion may be insufficient. If the amount is more than 10 times, the drying time during coating film formation may be prolonged, or the stability of the resulting aqueous dispersion may be reduced.

[0060] The basic compound can be distilled off simultaneously with the organic solvent. The content of the basic compounds after distillation can be appropriately determined taking into consideration the stability and workability of the aqueous dispersion, and the like. From the viewpoint of suppressing an increase in viscosity and achieving excellent storage stability, the total content of hydrophobic amines is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less. From the viewpoint of suppressing an increase in viscosity and achieving excellent storage stability, the total content of hydrophilic amines is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0061] The lower limit of the total content of hydrophobic amines is preferably 0.01% by mass, more preferably 0.02% by mass, and even more preferably 0.03% by mass. The lower limit of the total content of hydrophilic amines is preferably 0.1% by mass, more preferably 0.2% by mass, and even more preferably 0.3% by mass. When the content is equal to or greater than the respective lower limits, the polyolefin resin tends to be less prone to precipitation and exhibit excellent storage stability. In addition, an increase in viscosity is easily suppressed.

[0062] After the organic solvent is distilled off and water is added, the mixture is preferably cooled. The temperature after cooling is not particularly limited, but is preferably 100°C or lower, and more preferably 40°C or lower.

[0063] In the production method of the present invention, the aqueous dispersion polyolefin resin can be dispersed with a volume average particle diameter of, for example, 150 nm or less, more preferably 140 nm or less, and even more preferably 130 nm or less. Generally, the larger the volume average particle diameter, the more the viscosity increase can be suppressed and the tendency is such that an aqueous dispersion with a low viscosity can be obtained. However, in the present invention, even if the volume average particle diameter is reduced by improving dispersibility, an aqueous dispersion with a low viscosity of 180 mPa s or less can be obtained at a solid content concentration of 35 mass% or more. [Example]

[0064] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples. Various configurations and properties were measured or evaluated by the following methods.

[0065] (1) Polyolefin resin composition 1 The measurements were performed using a H-NMR analyzer (manufactured by JEOL Ltd., ECA500, 500 MHz) at 120°C using tetrachloroethane (d2) as a solvent.

[0066] (2) Melting point of polyolefin resin Measurement was performed by DSC using a DSC7 manufactured by PerkinElmer Co. The sample was placed in an aluminum pan, heated to 200°C at 10°C / min, held for 5 minutes, cooled to -10°C at 10°C / min, and then heated to 200°C at 10°C / min. The heat transfer coefficient was calculated from the endothermic and exothermic curves.

[0067] (3) Melt flow rate (MFR) of polyolefin resin Measurement was carried out in accordance with the method described in JIS K7210:1999 at 190°C under a load of 2160g.

[0068] (4) Solids concentration of aqueous dispersion An appropriate amount of the aqueous dispersion was weighed and heated at 150°C until the mass of the remaining matter (solid content) reached a constant weight, and the solid content concentration was determined.

[0069] (5) Number-average particle size and volume-average particle size of polyolefin resin particles (dynamic light scattering method) The number average particle size (mn) and volume average particle size (mw) were measured using a Nanotrac Wave-UZ152 particle size distribution analyzer manufactured by Nikkiso Co., Ltd. The refractive index of the resin was set to 1.5.

[0070] (6) Viscosity of aqueous dispersion The rotational viscosity (mPa·s) of the filtered aqueous dispersion was measured at 25°C using a B-type viscometer (Tokimec Co., Ltd., DVL-BII type digital viscometer).

[0071] (7) Content of basic compound in aqueous dispersion 1 The values ​​were determined by H-NMR analysis (manufactured by JEOL Ltd., ECA500, 500 MHz) at room temperature using deuterated methanol (d4) as a solvent and 1,4-dioxane as an internal standard.

[0072] (8) Yield The yield of the aqueous dispersion was calculated using the following formula. Yield (%) = solid concentration × yield of aqueous dispersion ÷ amount of resin used for dispersion × 100

[0073] (9) Filterability The filterability of the aqueous dispersion was judged according to the following criteria. 5: Normal pressure filtration is possible with a 600 mesh stainless steel filter 4: By applying nitrogen pressure (0.1 MPa), filtration is possible through a 600 mesh stainless steel filter. 3: Filtration is possible with a 300 mesh stainless steel filter 2: By applying nitrogen pressure (0.1 MPa), it can be filtered through a 300 mesh stainless steel filter. 1:300 mesh stainless steel filter cannot be used for filtration

[0074] (10) Storage stability The aqueous dispersion was stored in an incubator at 50°C, and storage stability was evaluated based on the presence or absence of gel formation and viscosity change after 3 months. ○: The aqueous dispersion did not gel, and the viscosity did not change (increase) by 200 mPa·s or more than two times the viscosity before storage. △: The aqueous dispersion did not gel, but the viscosity changed (increased) by 200 mPa·s or more, or by two times or more, from before storage. ×: Gelation occurs in the aqueous dispersion.

[0075] (11) Viscosity increase rate when powder is added To 100 parts by mass of the polyolefin resin aqueous dispersion, 10 parts by mass of titanium oxide (manufactured by Ishihara Sangyo Kaisha, Ltd., "CR-50", average particle size: 0.25 μm, oil absorption: 18) was added, and the mixture was stirred at room temperature until uniformly dispersed. Thereafter, the viscosity was measured under the same conditions as for the aqueous dispersion in (6), and the viscosity increase rate was calculated using the following formula. Viscosity increase rate (%) = (viscosity after adding titanium oxide ÷ viscosity before adding titanium oxide - 1) × 100 This viscosity increase rate is preferably 650% or less, more preferably 500% or less, and even more preferably 300% or less.

[0076] (12) pH The pH at 20°C was measured using a portable pH meter D-74 manufactured by HORIBA.

[0077] The following polyolefin resins were used: The compositions of the polyolefin resins are shown in Table 1. HX8290: Arkema Bondine HX8290 (HX8290) 5980I: Primacol 5980I (5980I), manufactured by Dow 350S: Nippon Paper Industries, Auroren 350S (350S) [Table 1]

[0078] Example 1 Using a stirrer equipped with a sealable, pressure-resistant 1-liter glass container with a heater, 90.0 g of acid-modified polyolefin resin (Arkema's "Bondine HX8290," ethylene / ethyl acrylate / maleic anhydride = 80 / 18 / 2 (mass%), melting point 81°C, MFR 65 g / 10 min), 90.0 g of isopropanol, 3.0 g of triethylamine, and 117.0 g of distilled water were charged into the glass container, and the stirring blade rotation speed was set to 300 rpm. The heater was then turned on and the mixture was heated. The temperature inside the system was then maintained at 135°C and the mixture was stirred for an additional 30 minutes.

[0079] The glass vessel was then gradually opened while maintaining a rotation speed of 300 rpm and a system temperature of 130°C, and 46.0 g of a mixture of organic solvent and water was distilled off. Subsequently, while maintaining a rotation speed of 300 rpm and a system temperature of 130°C, 3.5 g of triethylamine and 74 g of water were added using a liquid transfer pump, and an additional 74 g of a mixture of organic solvent and water was distilled off. Thereafter, the dispersion was cooled to room temperature (about 25° C.) and then filtered at normal pressure using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a milky white, uniform aqueous dispersion of polyolefin resin.

[0080] Examples 2 and 3 Aqueous polyolefin resin dispersions were obtained in the same manner as in Example 1, except that the type of polyolefin resin used was changed to one shown in Table 2.

[0081] [Table 2] In Table 2, TEA represents triethylamine, and DMEA represents dimethylaminoethanol.

[0082] Example 4 An aqueous polyolefin resin dispersion was obtained in the same manner as in Example 1, except that the amount of water added using a liquid feed pump was changed to 42 g.

[0083] Examples 5 and 7 An aqueous polyolefin resin dispersion was obtained in the same manner as in Example 1, except that the type of basic compound added using a liquid delivery pump was changed to one shown in Table 2, and the amounts of basic compound and water added using a liquid delivery pump were changed so that the content of the basic compound and the solid concentration would be those shown in Table 2. Example 6 An aqueous polyolefin resin dispersion was obtained in the same manner as in Example 1, except that the amounts of the basic compound and water added using a liquid pump were changed so that the content of the basic compound and the solid concentration would be as shown in Table 2.

[0084] Example 8 Using a stirrer equipped with a sealable, pressure-resistant 1-liter glass container with a heater, 90.0 g of acid-modified polyolefin resin (Arkema's "Bondine HX8290," ethylene / ethyl acrylate / maleic anhydride = 80 / 18 / 2 (mass%), melting point 81°C, MFR 65 g / 10 min), 90.0 g of isopropanol, 0.3 g of triethylamine, and 119.7 g of distilled water were charged into the glass container, and the stirring blade rotation speed was set to 300 rpm. The heater was then turned on and the mixture was heated. The temperature inside the system was then maintained at 135°C and the mixture was stirred for an additional 30 minutes.

[0085] Thereafter, 3.5 g of triethylamine was added using a liquid pump, but 4.2 g of dimethylaminoethanol was added, and the amount of water added using a liquid pump was changed from 74 g to 73.3 g. An aqueous polyolefin resin dispersion was obtained in the same manner as in Example 1, except that different types of basic compounds were added in two stages.

[0086] Examples 9-10 An aqueous polyolefin resin dispersion was obtained in the same manner as in Example 8, except that the amounts of the basic compound and water added using a liquid pump were changed so that the contents and solid concentrations of the two types of basic compounds used would be as shown in Table 2.

[0087] Example 11 Using a stirrer equipped with a sealable, pressure-resistant 1-liter glass container with a heater, 90.0 g of acid-modified polyolefin resin (Arkema's "Bondine HX8290," ethylene / ethyl acrylate / maleic anhydride = 80 / 18 / 2 (mass%), melting point 81°C, MFR 65 g / 10 min), 90.0 g of isopropanol, 3.0 g of triethylamine, and 117.0 g of distilled water were charged into the glass container, and the stirring blade rotation speed was set to 300 rpm. The heater was then turned on and the mixture was heated. The temperature inside the system was then maintained at 135°C and the mixture was stirred for an additional 30 minutes.

[0088] The mixture was then cooled to 81°C while stirring at a rotation speed of 300 rpm. 4.5 g of dimethylaminoethanol and 72.7 g of water were added. The pressure was reduced while maintaining the system temperature at 81°C, and 43.0 g of the organic solvent and water mixture was distilled off. The dispersion was then cooled to room temperature (approximately 25°C). The mixture was then filtered under pressure (air pressure 0.2 MPa) using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a milky-white, uniform aqueous polyolefin resin dispersion.

[0089] Example 12 Using a stirrer equipped with a heater-equipped, sealable, pressure-resistant 1-liter glass container, 90.0 g of acid-modified polyolefin resin (Arkema's "Bondine HX8290," ethylene / ethyl acrylate / maleic anhydride = 80 / 18 / 2 (mass%), melting point 81°C, MFR 65 g / 10 min), 90.0 g of isopropanol, 3.0 g of triethylamine, 4.5 g of dimethylaminoethanol, and 112.5 g of distilled water were charged into the glass container. The stirring was performed at a rotation speed of the stirring blade at 300 rpm, and the heater was turned on to heat the mixture. The temperature in the system was then maintained at 135°C and the mixture was stirred for an additional 30 minutes. In other words, the two basic compounds were added all at once during the charging process and the mixture was stirred.

[0090] The glass vessel was then gradually opened while maintaining a rotation speed of 300 rpm and a system temperature of 130°C, and 43.0 g of the organic solvent and water mixture was distilled off. Subsequently, while maintaining a rotation speed of 300 rpm and a system temperature of 130°C, 74 g of water was added using a liquid transfer pump, and another 74 g of the organic solvent and water mixture was distilled off. The dispersion was then cooled to room temperature (approximately 25°C). It was then pressure-filtered (air pressure 0.2 MPa) using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a milky-white, uniform aqueous polyolefin resin dispersion.

[0091] Comparative Example 1 Using a stirrer equipped with a sealable, pressure-resistant 1-liter glass container with a heater, 90.0 g of acid-modified polyolefin resin (Arkema's "Bondine HX8290," ethylene / ethyl acrylate / maleic anhydride = 80 / 18 / 2 (mass%), melting point 81°C, MFR 65 g / 10 min), 90.0 g of isopropanol, 3.0 g of triethylamine, and 117.0 g of distilled water were charged into the glass container, and the stirring blade rotation speed was set to 300 rpm. The heater was then turned on and the mixture was heated. The temperature inside the system was then maintained at 135°C and the mixture was stirred for an additional 30 minutes.

[0092] The mixture was then cooled to room temperature (approximately 25°C) while stirring at a rotation speed of 300 rpm. After cooling, 4.5 g of dimethylaminoethanol and 74 g of water were added and heated until the temperature inside the system reached 40°C. The pressure was reduced while maintaining the temperature inside the system at 40°C, and 120 g of a mixture of organic solvent and water was distilled off. The mixture was then cooled to room temperature and further filtered under pressure (air pressure 0.2 MPa) using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a milky-white, uniform aqueous dispersion of polyolefin resin.

[0093] Comparative Example 2 Using a mixer equipped with a heater and a sealable, pressure-resistant 1-liter glass container, 105 g of acid-modified polyolefin resin (Arkema's "Bondine HX8290"), 60.0 g of isopropanol, 3.0 g of 28% ammonia water, and 132.0 g of distilled water were placed in the glass container. The container was stirred at a rotation speed of 300 rpm, and no resin particles were observed at the bottom of the container; the resin particles were confirmed to be floating. While maintaining this state, the heater was turned on after 10 minutes. The system temperature was then maintained at 140-145°C and stirred for an additional 30 minutes. After the specified time had elapsed, the mixture was cooled to 25°C while stirring at 300 rpm. It was then filtered under pressure (air pressure 0.2 MPa) through a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a milky-white, uniform aqueous dispersion.

[0094] The evaluation results of the aqueous dispersions obtained in Examples 1 to 12 and Comparative Examples 1 and 2 are summarized in Tables 2 and 3. [Table 3]

[0095] In Examples 1 to 12, even when the solid content was 35% by mass or more, the viscosity at 25°C was low, at 180 mPa·s or less, and the low viscosity was maintained even after storage for 3 months in a high-temperature environment or when powder was added, and aqueous dispersions with excellent handleability and storage stability were obtained. The aqueous dispersion obtained in Comparative Example 1 had a viscosity of 70,000 mPa·s at a solids concentration of 35% by mass, making it impossible to measure pH or particle size. Furthermore, gelation occurred after storage for 3 months in a high-temperature environment or when powder was added, making it impossible to measure. Furthermore, in order to reduce the viscosity of the aqueous dispersion of Comparative Example 1 to 180 Pa·s or less, the solids concentration had to be less than 35% by mass, making it impossible to obtain a high-concentration, low-viscosity aqueous dispersion. The aqueous dispersion obtained in Comparative Example 2 was obtained by using ammonia as the basic compound, cooling to room temperature, and distilling off the organic solvent. Compared to Example 1, the viscosity was higher and the storage stability was poor.

Claims

1. An aqueous polyolefin resin dispersion comprising a polyolefin resin containing an unsaturated carboxylic acid component and an aqueous medium, wherein the solids concentration of the polyolefin resin is 35 mass% or more and the viscosity at 25°C is 180 mPa·s or less, and the dispersion is substantially free of non-volatile water-soluble additives.

2. 2. The aqueous polyolefin resin dispersion according to claim 1, comprising at least one hydrophobic amine and at least one hydrophilic amine.

3. 3. The polyolefin resin aqueous dispersion according to claim 2, wherein the total content of hydrophobic amines is 0.01 to 3 mass % and the total content of hydrophilic amines is 0.1 to 10 mass %.

4. A method for producing the aqueous polyolefin resin dispersion according to any one of claims 1 to 3, comprising stirring the polyolefin resin and an aqueous medium containing an organic solvent at a temperature equal to or higher than the melting point of the polyolefin resin, and then distilling off the organic solvent and adding water while maintaining the temperature at or higher than the melting point of the polyolefin resin.

5. 5. The method for producing the polyolefin resin dispersion according to claim 4, characterized in that a polyolefin resin, an aqueous medium containing an organic solvent, and a first basic compound are stirred at a temperature equal to or higher than the melting point of the polyolefin resin, and then a basic compound different from the first basic compound is added.

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