JP2023119572A - Polyolefin resin aqueous dispersion and method for producing the same - Google Patents

Abstract

To provide a polyolefin resin aqueous dispersion which can greatly improve adhesion without giving a large influence to other physical properties by being mixed with other aqueous dispersion, is difficult to generate an aggregate even when strong shear force is applied thereto, and accordingly can achieve improvement of coating productivity, suppression of coating film defects, improvement of a yield, and improvement of coating film quality.SOLUTION: A polyolefin resin aqueous dispersion contains polyolefin resin particles, and an aqueous medium. The polyolefin resin contains 0.1 mass% or more of an unsaturated carboxylic acid component, a volume average particle size measured by a dynamic light scattering method of the polyolefin resin particles is 0.3 μm or less, and in a distribution peak observed in particle size distribution measured by a small angle X-ray scattering method, an average particle size of a peak A of the smallest particle group is 20 nm or less, and a volume fraction of the peak A to the whole distribution peak is 50% or more.SELECTED DRAWING: None

Description

The present invention relates to aqueous dispersions of polyolefin resins.

BACKGROUND ART Aqueous dispersions of polyolefin resins are used in a wide range of applications because they provide coating films having excellent adhesion to various substrates. Among them, aqueous dispersions using acid-modified polyolefin resins containing (meth)acrylic acid esters as copolymer components have high versatility in substrates that can be used, and are widely used in coating agents, adhesives, etc. ( For example, Patent Document 1).

Japanese Patent No. 3699935

The aqueous dispersion is an aqueous dispersion containing a resin other than a polyolefin resin (for example, an aqueous dispersion containing particles of a urethane resin or an acrylic resin, and may be referred to herein as "other aqueous dispersions"). ) can improve the adhesion of other aqueous dispersions to substrates. However, in order to ensure sufficient adhesion, it is necessary to increase the mixing amount of the aqueous dispersion, which sometimes affects other physical properties. For example, mixing a highly hydrophobic polyolefin resin may affect physical properties other than adhesion, lowering the wettability of the dry coating film surface (increasing the water contact angle of the coating film), and further There were problems such as poor coating when topcoating with paint. Therefore, it has been desired to improve the adhesion to the base material without affecting other physical properties, even if the amount of mixture is reduced as much as possible.
In addition, when shear stress is applied to the aqueous dispersion as described above, aggregates are likely to occur, and as a result, filter clogging during filtration and appearance defects when formed into a coating film may occur. , is in need of improvement.

The inventors of the present invention have made intensive studies to solve the above problems, and found that a conventional general method for measuring the resin particle size in an aqueous dispersion of a polyolefin resin containing an unsaturated carboxylic acid component in a specific range. By increasing the ratio of fine particles, which could not be confirmed by the dynamic light scattering method, to a certain level or more, even if the amount of the polyolefin resin aqueous dispersion mixed is small, it is clear that a large effect of improving adhesion performance can be obtained. did.
Furthermore, the present inventors have found that when the proportion of fine particles is above a certain level, the occurrence of aggregation when shear stress is applied is reduced, and as a result, filter clogging and coating film defects can be suppressed.
That is, the present inventors have found that an aqueous dispersion containing polyolefin resin particles having a particle size distribution within a specific range as measured by a small-angle X-ray scattering method has extremely fine particles dispersed uniformly in an aqueous medium at a certain ratio or more. When mixed with an aqueous dispersion other than polyolefin resin, even if the amount of polyolefin resin aqueous dispersion mixed is small, a large adhesion performance improvement effect can be obtained, and the effect on other physical properties is minimized. In addition, the stability of the dispersion is extremely excellent and it is difficult to generate aggregates even when a strong shearing force is applied. did. That is, the gist of the present invention is as follows (1) to (9).
(1) A polyolefin resin aqueous dispersion containing polyolefin resin particles and an aqueous medium, wherein the polyolefin resin contains 0.1% by mass or more of an unsaturated carboxylic acid component, and the polyolefin resin particles are measured by a dynamic light scattering method. The volume average particle size measured by the small angle X-ray scattering method is 0.3 μm or less, and the average particle size of the peak A of the smallest particle group among the distribution peaks observed in the particle size distribution measured by the small angle X-ray scattering method is 20 nm or less. , A polyolefin resin aqueous dispersion, wherein the volume fraction of peak A to the entire distribution peak is 50% or more.
(2) The polyolefin resin aqueous dispersion of (1), wherein the polyolefin resin contains 1 to 20% by mass of a (meth)acrylic acid ester component.
(3) The polyolefin resin aqueous dispersion of (1) or (2) containing a resin other than polyolefin resin.
(4) A coating film comprising the polyolefin resin aqueous dispersion according to any one of (1) to (3).
(5) An adhesive containing the polyolefin resin aqueous dispersion of any one of (1) to (3).
(6) A paint containing the polyolefin resin aqueous dispersion of any one of (1) to (3).
(7) A method for producing a polyolefin resin aqueous dispersion according to any one of (1) to (3), wherein, after the stirring step of stirring the polyolefin resin and the aqueous medium at a temperature of 110°C or higher, 1°C/ A method for producing a polyolefin resin aqueous dispersion, comprising a cooling step of cooling to 100°C or less at a rate of 100°C or less.
(8) After the first cooling step in which the cooling step cools from the maximum temperature to a temperature of 100 ° C. or less and more than 40 ° C. at a cooling rate of 1 ° C./min or less, 40 ° C. or less at a cooling rate of 3 ° C./min or less (7) the method for producing a polyolefin resin aqueous dispersion, comprising a second cooling step of cooling to
(9) The method for producing a polyolefin resin aqueous dispersion according to (7) or (8), wherein the stirring step is carried out at a temperature of 110°C or higher and 20°C or higher than the melting point of the polyolefin resin.

In the polyolefin resin aqueous dispersion of the present invention, very fine polyolefin resin particles are uniformly dispersed in an aqueous medium. Adhesion can be greatly improved. Furthermore, even when a strong shearing force is applied, it is difficult to generate agglomerates and has excellent stability, so filter clogging during coating is suppressed and coating productivity is improved. In addition, since defects in the appearance of the coating film are suppressed, the yield can be improved, and the quality of the coating film is excellent.

The polyolefin resin aqueous dispersion of the present invention (hereinafter sometimes simply referred to as "aqueous dispersion") contains polyolefin resin particles and an aqueous medium.
The polyolefin resin particles have a particle diameter measured by a dynamic light scattering method and a particle size distribution measured by a small-angle X-ray scattering method that both satisfy specific ranges.

From the viewpoint of being finely and stably dispersed, the polyolefin resin particles contained in the aqueous dispersion of the present invention have a volume average particle diameter of 0.3 μm or less and 0.25 μm or less as measured by a dynamic light scattering method. It is preferably 0.2 μm or less, more preferably 0.15 μm or less.
The volume-average particle size can be controlled, for example, by selecting the type of basic compound and organic solvent to be added and adjusting the amount of these added in the manufacturing method described below.

Furthermore, in the polyolefin resin particles contained in the aqueous dispersion of the present invention, among the distribution peaks observed in the particle size distribution measured by the small-angle X-ray scattering method, the average particle size of peak A of the smallest particle group is 20 nm. or less, preferably 15 nm or less, more preferably 10 nm or less. Also, the volume fraction of peak A to the entire peak observed by the same method is 50% or more, preferably 60% or more, more preferably 70% or more.

A dynamic light scattering method is generally used as a method for measuring the diameter of resin particles contained in an aqueous dispersion. This is because the measurable range of particle size based on the principle of the dynamic light scattering method is about 1 nm to several μm, which substantially covers the range necessary for performance evaluation of aqueous dispersions. However, when particles with a large particle size are present, it may be difficult to detect particles with a small particle size due to the influence of the particles with a large particle size. On the other hand, the small-angle X-ray scattering method has a measurable range of about 1 nm to 100 nm, and is particularly specialized in evaluating fine particle structures. can be evaluated.
As a result of paying attention to the particle size measurement results of a polyolefin resin aqueous dispersion by a dynamic light scattering method and the particle size measurement results of a small angle X-ray scattering method, the present inventors found that the presence of large particle size particles by the dynamic light scattering method In , information on a group of fine particles, which is difficult to analyze, can be obtained by the small-angle X-ray scattering method, and when the existing fine particles have a specific distribution, we have obtained the knowledge that characteristic performance is exhibited.
Then, the volume average particle diameter measured by dynamic light scattering method is 0.3 μm or less, and the peak A of the smallest particle group among the distribution peaks observed in the particle size distribution measured by small angle X-ray scattering method It has been found that fine particles are uniformly dispersed when the average particle size is 20 nm or less and the volume fraction of peak A to the entire distribution peak is 50% or more. By mixing such an aqueous dispersion with an aqueous dispersion containing resin particles other than polyolefin resin (other aqueous dispersions), adhesion is greatly improved even with a small amount of mixture without significantly affecting other physical properties. In particular, it has been found that adhesion to difficult-to-adhere substrates is improved. In addition, this aqueous dispersion does not easily generate aggregates even when a strong shear force is applied, and has excellent stability, so filter clogging during coating is suppressed, improving coating productivity and suppressing defects in the coating film. Therefore, it is possible to improve the yield and the quality of the coating film is also excellent.

As a method for making the average particle size and volume fraction of the peak A measured by the small-angle X-ray scattering method as a specific range for the resin particle size, a polyolefin resin is used in the method for producing an aqueous dispersion of the present invention, which will be described later. It is preferable to set the cooling rate at the time of dispersion within a specific range, or to select the type of basic compound or organic solvent to be added, or to adjust the amount of these added.

The olefin component that is the main component of the polyolefin resin is not particularly limited, but ethylene, propylene, isobutylene, 2-butene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, Examples include alkenes such as 3-methyl-1-pentene and norbornenes, and dienes such as butadiene and isoprene. A mixture of these may also be used. A copolymer obtained by copolymerizing two or more olefin components may also be used.

A polyolefin resin contains an unsaturated carboxylic acid component. Examples of unsaturated carboxylic acid components 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. is mentioned. Among them, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferable, and acrylic acid and maleic anhydride are particularly preferable, from the viewpoint of further excellent adhesiveness.

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

The content of the unsaturated carboxylic acid component in the polyolefin resin is 0.1% by mass or more, preferably 0.1 to 10% by mass, more preferably 1 to 8% by mass, and 2 to 5% by mass. % is more preferred. If the content is less than 0.1% by mass, the particle size of the polyolefin resin particles measured by the dynamic light scattering method and the particle size distribution measured by the small angle X-ray scattering method are within a specific range. or it becomes difficult to disperse the resin in water. Further, when the amount is 10% by mass or less, the adhesion is further improved when mixed with other aqueous dispersions.

The content of the (meth)acrylate component in the polyolefin resin is preferably 1 to 20% by mass, more preferably 2 to 19% by mass, even more preferably 4 to 18% by mass.
When the content of the (meth)acrylic acid ester component is within the above range, the adhesion to the substrate is further improved when mixed with other aqueous dispersions.
Examples of (meth)acrylic acid ester components include (meth)acrylic acid ester components such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate, dimethyl maleate, diethyl maleate, Maleic acid diester components such as dibutyl maleate; alkyl vinyl ether components such as methyl vinyl ether and ethyl vinyl ether; Examples thereof include vinyl alcohol obtained by saponification with a compound, a (meth)acrylic acid amide component, and the like, and a mixture thereof may also be used. Among them, a (meth)acrylic acid ester component and a vinyl ester component are preferred, and a (meth)acrylic acid ester component is more preferred. The term "(meth)acrylic acid" means "acrylic acid or methacrylic acid".

Specific examples of polyolefin resins include ethylene-maleic anhydride copolymer, ethylene-methyl acrylate-maleic anhydride copolymer, ethylene-methyl methacrylate-maleic anhydride copolymer, ethylene-ethyl acrylate- Maleic Anhydride Copolymer, Ethylene-Ethyl Methacrylate-Maleic Anhydride Copolymer, Ethylene-Butyl Acrylate-Maleic Anhydride Copolymer, Ethylene-Butyl Methacrylate-Maleic Anhydride Copolymer, Propylene- Maleic anhydride copolymer, propylene-1-butene-maleic anhydride copolymer, propylene-ethyl acrylate-maleic anhydride copolymer, propylene-1-butene-ethyl acrylate-maleic anhydride copolymer, etc. is mentioned.

The polyolefin resin may be chlorinated in the range of 40% by mass or less.

The maleic anhydride component constituting the polyolefin resin may be imidized, and its N position is an N,N-dimethylaminoethyl group, an N,N-dimethylaminopropyl group, or an N,N-dimethylaminobutyl group. , N,N-diethylaminoethyl group, N,N-diethylaminopropyl group, N,N-diethylaminobutyl group and the like.

In the aqueous dispersion of the present invention, polyolefin resin particles are dispersed in an aqueous medium. In the present invention, the aqueous medium is a liquid containing water as a main component, and may contain organic solvents and basic compounds, which will be described later.

By mixing the aqueous dispersion of the present invention with other aqueous dispersions, the adhesion of the other aqueous dispersions to difficult-to-adhere substrates such as olefin substrates is greatly improved without significantly affecting other physical properties. can be improved. Adhesion can be evaluated by a cross-cut peeling test (JIS K5400) or the like. In the case of the cross-cut peeling test, the number of sections of the remaining coating film after cross-cutting and tape peeling is most preferably 100, preferably 99-95.

The mixing ratio of the aqueous dispersion of the present invention and other aqueous dispersions is not particularly limited, but even a small amount of mixing can significantly improve adhesion. The mixing ratio of the aqueous dispersion of the present invention improves adhesion without impairing performance other than adhesion, so that the total solid content concentration in the aqueous dispersion after mixing is 20% by mass or less. is preferred, 10% by mass or less is more preferred, and 5% by mass or less is more preferred.

Other resins contained in the aqueous dispersion include, for example, polyurethane resins, acrylic resins (including styrene copolymers), styrene-butadiene resins, polyvinyl chloride resins, ethylene-vinyl acetate copolymers, polyester resins, and the like. Naru is mentioned.

Other properties affected by mixing the aqueous dispersion of the present invention with other aqueous dispersions include wettability (surface tension) and viscosity as liquid properties. The physical properties of the coating film include wettability (surface tension, contact angle), mechanical strength, hardness, heat resistance, blocking property, abrasion resistance, and the like. Since fine particles are uniformly dispersed in the aqueous dispersion of the present invention, the influence on other physical properties when mixed with other aqueous dispersions can be reduced.

In addition, in the aqueous dispersion of the present invention, the polyolefin resin particles have a small particle size and are stably and uniformly dispersed in the aqueous medium without containing coarse resin particles. It is less likely to generate particles, suppresses filter clogging during coating, and improves coating productivity. Furthermore, defects in the appearance of the coating film are suppressed, so that the yield can be improved and the quality of the coating film is also excellent.

The aqueous dispersions of the present invention are preferably substantially free of nonvolatile water rendering aids, although the use of nonvolatile water rendering aids is not excluded. In the present invention, it is possible to produce an aqueous dispersion in which polyolefin resin particles are excellent in dispersion stability and coarse resin particles are not present, even if substantially no non-volatile water-improving aid is contained.

Here, the term "aqueous agent" refers to a drug or compound added for the purpose of promoting aqueous dispersion or stabilizing the aqueous dispersion in the production of the aqueous dispersion. , means that it has no boiling point at normal pressure or has a high boiling point (for example, 300° C. or higher) at normal pressure.

The phrase "substantially free of non-volatile water-improving aids" means that such aids are not used during production (during aqueous dispersion of the polyolefin resin), and the resulting aqueous dispersion contains this aid as a result. means not. The content of the non-volatile water-improving aid is preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably less than 0.5% by mass, and 0% by mass with respect to the polyolefin resin component. is most preferred.

Examples of the non-volatile water-improving aid in the present invention include emulsifiers, compounds having a protective colloid action, modified waxes, acid-modified compounds with a high acid value, and water-soluble polymers.

Examples of emulsifiers include cationic emulsifiers, anionic emulsifiers, nonionic emulsifiers and amphoteric emulsifiers, and include surfactants in addition to those generally used for emulsion polymerization. For example, anionic emulsifiers include higher alcohol sulfates, higher alkylsulfonates, higher carboxylates, alkylbenzenesulfonates, polyoxyethylene alkylsulfates, polyoxyethylene alkylphenyl ether sulfates, vinyl sulfosuccinates, Nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, ethylene oxide propylene oxide block copolymers, polyoxyethylene fatty acid amides, ethylene oxide-propylene oxide. Examples include compounds having a polyoxyethylene structure such as copolymers, sorbitan derivatives such as polyoxyethylene sorbitan fatty acid esters, and the like. Amphoteric emulsifiers include lauryl betaine, lauryl dimethylamine oxide, and the like.

Compounds having a protective colloid action, modified waxes, acid-modified compounds with high acid values, and water-soluble polymers include polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, modified starch, and polyvinylpyrrolidone. , polyacrylic acid and its salts, carboxyl group-containing polyethylene wax, carboxyl group-containing polypropylene wax, carboxyl group-containing polyethylene-propylene wax and other acid-modified polyolefin waxes having a number average molecular weight of usually 5000 or less and salts thereof, acrylic acid-anhydride Maleic acid copolymer and its salt, styrene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid copolymer, isobutylene-maleic anhydride alternating copolymer, (meth)acrylic acid-(meth) Carboxyl group-containing polymers with an unsaturated carboxylic acid content of 10% by mass or more such as acrylic acid ester copolymers and salts thereof, polyitaconic acid and salts thereof, water-soluble acrylic copolymers having amino groups, gelatin, gum arabic and casein, which are generally used as dispersion stabilizers for fine particles.

The aqueous dispersion of the present invention may contain other polymers, tackifiers, inorganic particles, cross-linking agents, pigments, dyes and the like in order to further improve performance according to the purpose.
Other polymers and tackifiers are not particularly limited. For example, polyvinyl acetate, polyvinylidene chloride, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester-maleic anhydride copolymer, styrene-maleic acid resin, butadiene resin, acrylonitrile-butadiene resin , poly (meth) acrylonitrile resin, (meth) acrylamide resin, chlorinated polyethylene resin, chlorinated polypropylene resin, modified nylon resin, rosin, phenol resin, silicone resin, epoxy resin, etc., or tackifiers containing these. , may be mixed and used as required.
These polymers may be used as they are in a solid state, but from the viewpoint of maintaining the stability of the aqueous dispersion, it is preferable to use those processed into an aqueous dispersion.

Examples of inorganic particles include metal oxides such as magnesium oxide, zinc oxide, and tin oxide, inorganic particles such as calcium carbonate and silica, and layered inorganic compounds such as vermiculite, montmorillonite, hectorite, hydrotalcite, and synthetic mica. be done. The average particle size of these inorganic particles is preferably 0.005 to 10 μm from the viewpoint of the transparency of the coating film. A plurality of inorganic particles may be mixed and used.

As the cross-linking agent, a cross-linking agent having self-crosslinking properties, a compound having a plurality of functional groups that react with the unsaturated carboxylic acid component in the molecule, a metal having a polyvalent coordination site, or the like can be used.
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, and the like. You can use a mixture of things. Among them, oxazoline group-containing compounds, carbodiimide group-containing compounds, isocyanate group-containing compounds, and epoxy group-containing compounds are preferable from the viewpoint of ease of handling.

Examples of pigments and dyes include titanium oxide, zinc oxide, carbon black, and the like, and any of disperse dyes, acid dyes, cationic dyes, reactive dyes, and the like can be used.
The aqueous dispersion of the present invention further contains various agents such as leveling agents, antifoaming agents, anti-popping agents, pigment dispersants, ultraviolet absorbers, thickeners, weathering agents and flame retardants. good too.

The method of using the aqueous dispersion of the present invention is not limited to mixing with other aqueous dispersions. It can be suitably used as an adhesive, coating agent, primer, paint, ink, or the like.
Since the aqueous dispersion of the present invention has even better adhesion to difficult-to-adhere substrates such as olefin substrates, it is particularly suitably used for packaging materials, automobile parts, electronic devices, and the like.
Specific examples of these 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, and PP substrates. Paints, 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, secondary battery electrodes adhesives for binders, secondary battery exterior adhesives, automobile belt molding adhesives, automobile member adhesives, different base material adhesives, fiber sizing agents, and the like.

The aqueous dispersion of the present invention is excellent in film-forming ability. In order to form a coating film from the aqueous dispersion of the present invention, for example, the aqueous dispersion of the present invention is uniformly applied to the surface of various substrates, set at around room temperature as necessary, and then dried or dried. and heat treatment for baking. Thereby, a uniform coating film can be adhered to various substrate surfaces.

Application of the aqueous dispersion to the substrate can be performed by known methods such as gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, brush coating, and the like. can be adopted.

The amount of the aqueous dispersion to be applied to the base material is not particularly limited, and may be appropriately selected depending on the application ^. It is more preferably 1 to 50 g/m ² and even more preferably 0.2 to 30 g/m ² .

In addition, in order to adjust the coating amount, in addition to appropriately selecting the equipment used for coating and its usage conditions, it is necessary to use an aqueous dispersion whose concentration is adjusted according to the desired thickness of the coating film. is preferred. The concentration of the aqueous dispersion can be adjusted by adjusting the charge composition at the time of preparation, and the once prepared aqueous dispersion may be adjusted by appropriately diluting or concentrating.

As a heating device for the heat treatment after coating, an ordinary hot air circulation oven, an infrared heater, or the like can be used.
The heating temperature and heating time are appropriately selected depending on the properties of the base material or the amount of various components that can be arbitrarily added to the aqueous dispersion, but the heating temperature is low from the viewpoint of energy cost and damage to the base material. From the viewpoint of productivity, a shorter heating time is preferred. The heating temperature is preferably 20 to 130°C, more preferably 30 to 120°C, even more preferably 40 to 100°C. The heating time is preferably 1 second to 20 minutes, more preferably 5 seconds to 15 minutes, even more preferably 5 seconds to 10 minutes.
When the aqueous dispersion of the present invention contains a cross-linking agent, the heating temperature and time should be appropriately selected according to the type of the cross-linking agent in order to allow the reaction between the carboxyl groups in the polyolefin resin and the cross-linking agent to proceed sufficiently. is desirable.

The production method for obtaining the aqueous dispersion of the present invention is not particularly limited. , a basic compound, etc. are heated and stirred in a sealable container to disperse the resin.

As the container, a device used as a solid/liquid stirring device or an emulsifier can be used, and for example, it is preferable to use a device capable of applying a pressure of 0.1 MPa or more. The method of stirring and the rotational speed of stirring are not particularly limited. Therefore, high-speed stirring (for example, 1000 rpm or higher) is not essential, and an aqueous dispersion can be produced even with a simple apparatus.

Above all, as a method for producing an aqueous dispersion, it is preferable to mix raw materials such as a polyolefin resin and an aqueous medium, stir the mixture, and then cool the mixture from the stirring temperature to the lowest temperature at a cooling rate of 1° C./min or less.

Although the detailed mechanism is not known, as a result of various investigations by the present inventors, by cooling relatively slowly at a cooling rate of 1 ° C./min or less, the particle size distribution measured by the small angle X-ray scattering method is the above. It has been found that a specific range can be set.
The cooling rate is more preferably slow, more preferably 0.9° C./min or less, and particularly preferably 0.7° C./min or less.

The stirring temperature can be appropriately set from the viewpoint of pressure resistance, heating performance, energy cost, etc. of the apparatus, but it is preferably high from the viewpoint of keeping the particle size of the resin within the above range and from the viewpoint of dispersion stability. It is preferably 110° C. or higher, more preferably 120° C. or higher, and even more preferably 140° C. or higher.

Although the lowest temperature after cooling is not particularly limited, it is, for example, 100° C. or lower, more preferably 40° C. or lower.

The cooling may be performed in one stage at a cooling rate of 1° C./min or less, or may be performed in a plurality of stages in two or more stages with different cooling rates.
For example, after cooling from the stirring temperature to a temperature of 100 ° C. or less and over 40 ° C. at a cooling rate of 1 ° C./min or less, cooling to 40 ° C. or less at a cooling rate of 3 ° C./min or less. cooling may be employed. In this case, the cooling rate in the second stage is preferably 3° C./min or less, more preferably 2° C./min or less, and even more preferably 1° C./min or less.

The method for adjusting the cooling temperature is not particularly limited. For example, when adjusting the temperature of the heater or using a container with a jacket, the temperature of the steam, heat medium, water, etc. in the jacket can be adjusted.

Basic compounds include ammonia, triethylamine, N,N-dimethylethanolamine, isopropylamine, aminoethanol, dimethylaminoethanol, diethylaminoethanol, ethylamine, diethylamine, isobutylamine, dipropylamine, 3-ethoxypropylamine, 3- Diethylaminopropylamine, sec-butylamine, propylamine, n-butylamine, 2-methoxyethylamine, 3-methoxypropylamine, 2,2-dimethoxyethylamine, monoethanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine, pyrrole , pyridine and the like. Among them, ammonia, triethylamine, and N,N-dimethylethanolamine are preferable from the viewpoint of accelerating the dispersion of the resin.

The amount of the basic compound to be added is preferably 0.5 to 10 equivalents, more preferably 0.8 to 8 equivalents, and 1.0 to 5 equivalents relative to the carboxyl groups in the polyolefin resin. Equivalent weights are particularly preferred. If the amount is less than 0.5 equivalents, dispersion becomes insufficient, and it may be difficult to obtain an aqueous dispersion having the resin particle size and resin particle size distribution specified in the present invention. If the amount exceeds 10 equivalents, the drying time during coating film formation may become long, or the stability of the resulting aqueous dispersion may decrease.

In order to accelerate the dispersion of the polyolefin resin particles, reduce the dispersed particle size, and satisfy the particle size and particle size distribution specified in the present invention, it is preferable to add a hydrophilic organic solvent during aqueous dispersion. 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, with respect to the entire aqueous medium. ∼35% by mass is particularly preferred. If the content of the hydrophilic organic solvent exceeds 50% by mass, it cannot be regarded as a substantially aqueous medium. Depending on the amount, the stability of the aqueous dispersion may decrease.

The hydrophilic organic solvent preferably has a solubility in water at 20° C. of 10 g/L or more, more preferably 20 g/L or more, from the viewpoint of obtaining an aqueous dispersion with good dispersion stability. /L or more is more preferable.

The hydrophilic organic solvent preferably has a boiling point of 100° C. or less from the viewpoint of efficient drying and removal in the process of forming a coating film. Hydrophilic organic solvents with a boiling point exceeding 100°C tend to be difficult to disperse from the coating film by drying, and in particular, the water resistance of the coating film and adhesion to the substrate during low-temperature drying are reduced. There is

Preferred hydrophilic organic solvents include, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert- Alcohols such as 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, tetrahydrofuran, dioxane, etc. ethers, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, 3-methoxybutyl acetate, methyl propionate, ethyl propionate, diethyl carbonate, carbonic acid Esters such as dimethyl, glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol ethyl ether acetate, and 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-dimethyl glycerin, trimethylglycerin and the like.

Among them, when 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 used, polyolefin resin particles are obtained. Isopropanol is particularly preferred because it is more effective in promoting dispersion.

In the present invention, a plurality of these hydrophilic organic solvents may be mixed and used. In addition, a hydrophobic organic solvent may be further added in order to further promote aqueous dispersion of the polyolefin resin.

As the hydrophobic organic solvent, an organic solvent having a solubility in water at 20° C. of less than 10 g/L is preferable from the viewpoint of obtaining an aqueous dispersion with good dispersion stability. Moreover, in the process of forming a coating film, the organic solvent whose boiling point is 150 degreeC or less is preferable from a viewpoint of drying and removing efficiently. Examples of such hydrophobic organic solvents include olefinic solvents such as n-pentane, n-hexane, n-heptane, cycloheptane, cyclohexane and petroleum ether; aromatic solvents such as benzene, toluene and xylene; Halogen solvents such as carbon chloride, 1,2-dichloroethane, 1,1-dichloroethylene, trichlorethylene, 1,1,1-trichloroethane, chloroform, and the like can be mentioned. 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 relative to the aqueous dispersion. If the content of the hydrophobic organic solvent exceeds 15% by mass, gelation or the like may occur.

When the above organic solvent is used in the production of the aqueous dispersion, after the polyolefin resin is aqueously dispersed, part of it is distilled out of the system by a solvent removal treatment generally called "stripping" to obtain the organic solvent. The solvent content may be reduced. By stripping, the organic solvent content in the aqueous dispersion can be reduced to 10% by weight or less, more preferably 5% by weight or less, and more preferably 1% by weight or less from the environmental point of view. In the stripping process, it is possible to distill off substantially all of the organic solvent used in the aqueous dispersing process. , the lower limit of the organic solvent content is preferably about 0.01% by mass.

A stripping method includes heating the aqueous dispersion under normal pressure or reduced pressure while stirring to distill off the organic solvent. In addition, since the solid content concentration increases by distilling off the aqueous medium, for example, when the viscosity increases and the workability decreases, water is added to the aqueous dispersion in advance. good too.

The solid content concentration of the aqueous dispersion is not particularly limited and can be appropriately selected according to the application and the like. For example, it can be adjusted by a method of distilling off the aqueous medium or a method of diluting with water.

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not limited to these.
Various configurations and properties were measured or evaluated by the following methods.

(1) Composition of polyolefin resin
It was obtained from a ¹ H-NMR spectrometer (manufactured by JEOL Ltd., ECA500, 500 MHz). Measured at 120° C. using tetrachloroethane (d2) as a solvent.

(2) Melting point of polyolefin resin Measured by the DSC method using DSC7 manufactured by PerkinElmer. The sample is packed 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. was determined from the curve associated with the endotherm and exotherm of .

(3) Melt flow rate (MFR) of polyolefin resin
Measured at 190° C. under a load of 2160 g according to the method described in JIS K7210:1999.

(4) Solid Content Concentration of Aqueous Dispersion An appropriate amount of the aqueous dispersion was weighed and heated at 150° C. until the mass of the residue (solid content) reached a constant weight to determine the solid content concentration.

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

(6) Small-angle X-ray scattering method RINT-TTR III manufactured by Rigaku Co., Ltd. was used to measure small-angle scattering transmission. A sample was filled in a glass capillary with a diameter of 1 mm and measured under the conditions of X-ray Cu-Kα ray (1.54 Å), 50 kV, 300 mA, scanning range: 2θ = 0.06° to 4°. As a blank, a glass capillary with a diameter of 1 mm filled with pure water was used as a sample.
The obtained data were used to calculate the average particle size and volume fraction using the particle size/pore size analysis software NANO-Solver.
Blank data is removed using pure water glass capillary measurement data, the analysis range is set to 2θ = (0.1 to 2) ° region, and the dynamic light scattering method is used so that the calculated profile and the measured profile by the analysis software fit. Analysis was performed with two data, which is the particle diameter data of 1 and the additional particle group. Among the distribution peaks observed from the fitting results, the average particle size and volume fraction of peak A of the smallest particle group were evaluated.

(7) Viscosity of Aqueous Dispersion The rotational viscosity (mPa s) of the filtered aqueous dispersion at a temperature of 20° C. was measured using a B-type viscometer (manufactured by Tokimec, DVL-BII digital viscometer). .

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

(9) Shear stability (Marlon test)
After treatment with a Marlon tester under a load of 10 kg for 15 minutes, the product was filtered through a wire mesh with an opening of 200 μm. Calculated.
○: Residual aggregates are less than 0.1% by mass based on the solid content of the polyolefin resin aqueous dispersion. 5% by mass ×: Residual aggregates exceed 0.5% by mass based on the solid content of the polyolefin resin aqueous dispersion

(10) Effect of addition to polyurethane resin aqueous dispersion A polyurethane resin aqueous dispersion (Takelac W-6010, manufactured by Mitsui Chemicals, Inc.) was used as another aqueous dispersion. The polyurethane resin aqueous dispersion and the polyolefin resin aqueous dispersion obtained in Examples or Comparative Examples were mixed so that the polyolefin resin content was 5% by mass or 20% by mass in terms of the total solid content.
The coating film contact angle was evaluated for the polyurethane resin aqueous dispersion alone and the aqueous dispersion mixed with 5% by mass. Further, the adhesiveness was evaluated for an aqueous dispersion containing 5% by mass and an aqueous dispersion containing 20% by mass.

(Paint film contact angle)
The polyurethane resin aqueous dispersion alone, or the polyurethane resin aqueous dispersion obtained by mixing 5% by mass of the aqueous dispersion obtained in Examples or Comparative Examples, was coated on a 50 μm polyester film (Emblet manufactured by Unitika Ltd.) to a dry film thickness of 3 μm. and dried at 100° C. for 3 minutes to obtain a dry film. The water contact angle of the resulting coating film was measured by the sessile drop method. That is, in an environment of 20 ° C. and 65% RH, using a contact angle meter CA-D manufactured by Kyowa Interface Science Co., Ltd., pure water was dropped so as to form a water droplet with a diameter of 2.0 mm, and the contact angle was measured after 10 seconds. did. The average value of 5 measurements was taken.
After that, the difference between the contact angle of the aqueous dispersion mixed with 5% by mass and the contact angle (65°) of the polyurethane resin aqueous dispersion alone was taken, and the contact angle increase value due to the addition of the polyolefin resin aqueous dispersion was calculated according to the following criteria. evaluated.
○: Increased value is 2° or less △: Increased value is 3 to 5°
×: Increase value is 6° or more

(Adhesion)
Each of the aqueous dispersion mixed with 5% by mass and the aqueous dispersion mixed with 20% by mass was bar-coated on a molded piece of cycloolefin resin (Zeonex 480R manufactured by Nippon Zeon Co., Ltd.) so that the dry film thickness was 3 μm, A dry coating film was obtained by drying at 100° C. for 3 minutes.
The coating film on the obtained molded piece was subjected to tape peeling (crosscut test) by the crosscut method described in JIS K5400. That is, the coating film was cut into 100 sections by cross-cutting, and the number of sections of the coating film remaining after the tape was peeled off was used to evaluate the adhesion by a cross-cut test according to the following criteria.
○: 100 sections remained.
△: 95 to 99 sections remained.
x: 94 sections or less remained.

Polyolefin resins (P-1) to (P-13) used in Examples and Comparative Examples are as follows. Table 1 shows the composition and physical properties of these polyolefin resins.

Polyolefin resin (P-1)
Ethylene-ethyl acrylate-maleic anhydride copolymer (Bondine HX-8290, manufactured by Arkema) was used.

Polyolefin resin (P-2)
Ethylene-ethyl acrylate-maleic anhydride copolymer (Bondine LX-4110, manufactured by Arkema) was used.

Polyolefin resins (P-3), (P-4), (P-7), (P-8), (P-12), (P-13)
Based on the method described in Example 1 of JP-A-61-60709, ethylene-ethyl acrylate-maleic anhydride copolymer (P-3) was prepared so as to have the composition shown in Table 1. Obtained.
Polyolefin resins (P-4), (P-7), (P-8), (P-12) and (P-13) were obtained in the same manner.

Polyolefin resin (P-5)
280 g of a propylene-butene copolymer (mass ratio: propylene/1-butene = 65/35) was heated and dissolved in 470 g of xylene in a four-necked flask under a nitrogen atmosphere, and then the system temperature was kept at 140°C. While stirring, 40.0 g of maleic anhydride, 60.0 g of ethyl acrylate, and 28.0 g of dicumyl peroxide were each added over 2 hours, and then reacted for 6 hours. After completion of the reaction, the obtained reactant was poured into a large amount of acetone to precipitate the resin, thereby obtaining a polyolefin resin (P-5).

Polyolefin resin (P-6)
Polypropylene obtained by subjecting a homopolypropylene resin having an isotactic structure (MFR = 0.1 g/10 min-170°C, 2160 g) to thermal degradation treatment at normal pressure at 360°C for 80 minutes under nitrogen gas flow. 1000 g of resin was placed in a jacketed reactor and purged with nitrogen. Then, after heating to 180° C. and melting, 125 g of maleic anhydride and 100 g of ethyl acrylate were added and uniformly mixed. 125 g of xylene in which 6.3 g of dicumyl peroxide was dissolved was added dropwise thereto, and the mixture was stirred at 180° C. for 30 minutes to react. After the completion of the reaction, the obtained reaction product is put into a large amount of acetone to precipitate the resin, and the polyolefin resin (
P-6) was obtained.

Polyolefin resin (P-9)
Polyolefin resin (P-9) was obtained in the same manner as in the production of polyolefin resin (P-5), except that ethyl acrylate was not added.

Polyolefin resin (P-10)
Polyolefin resin (P-10) was obtained in the same manner as in the production of polyolefin resin (P-6), except that ethyl acrylate was not added.

Polyolefin resin (P-11)
An ethylene-methacrylic acid copolymer (Nucrel AN42115C, manufactured by Mitsui-DuPont Chemical Co., Ltd.) was used.

Example 1
60.0 g of polyolefin resin (P-1), 60.0 g of isopropanol (hereinafter referred to as IPA) 3.9 g (maleic anhydride 1.2 times equivalent to the carboxyl group of) of N,N-dimethylethanolamine (hereinafter, DMEA) and 176.1 g of distilled water were charged in a glass container, and the stirring blade was stirred at a rotation speed of 300 rpm. , the heater was turned on and the temperature was raised to 140°C. Stirring was performed for 60 minutes while maintaining the temperature at 140°C. Thereafter, the heating was stopped while the stirring speed was maintained, and the mixture was cooled to 100°C over 60 minutes, then placed in a water bath and cooled to 40°C over 30 minutes. Pressure filtration (air pressure 0.2 MPa) was performed through a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave) to obtain a milky white uniform aqueous dispersion.

Example 2
The same operation as in Example 1 was performed except that the amount of DMEA was changed as shown in Table 2.

Example 3
The same operation as in Example 1 was performed except that the cooling rate from the stirring temperature (140° C.) to 100° C. was changed as shown in Table 2.

Example 4
The same operation as in Example 1 was performed except that the cooling rate from 100° C. to 40° C. was changed as shown in Table 2.

Example 5
The same operation as in Example 1 was performed except that the temperature during stirring was changed to 120°C.

Examples 6, 8-11
The same operation as in Example 1 was performed except that the polyolefin resin was changed to P-2 to P-6, respectively, as shown in Table 2.

Example 7
The same operation as in Example 6 was performed except that the temperature during stirring was changed to 120°C.

Example 12
The same operation as in Example 1 was performed except that cooling was not performed in two steps, but cooling was performed in one step from the stirring temperature (140° C.) to 40° C. over 100 minutes.

Example 13
In Example 1, the same operation was performed except that the first stage cooling was performed from the stirring temperature to 80 ° C. over 90 minutes, and the second stage cooling was performed from 80 ° C. to 40 ° C. over 20 minutes. .

Example 14
The same operation as in Example 1 was performed except that the organic solvent was changed to tetrahydrofuran (THF).

Example 15
The same operation as in Example 1 was performed, except that the amount of IPA added was changed as shown in Table 2.

Examples 16-21
The same operation as in Example 1 was performed except that the polyolefin resin was changed to P-7 to P-11 and P-13, respectively, as shown in Table 2.

Comparative example 1
The same operation as in Example 1 was performed, except that the cooling rate from 140° C. to 100° C. was changed as shown in Table 2.

Comparative Examples 2-6
The same operation as in Comparative Example 1 was performed except that the polyolefin resin was changed to P-2, P-4, P-5, P-6 and P-7 as shown in Table 2.

Comparative example 7
The same operation as in Example 1 was performed, except that the amounts of IPA and DMEA added were changed as shown in Table 2.

Comparative example 8
The same operation as in Example 1 was performed except that the polyolefin resin was changed to P-12 as shown in Table 2.

Table 2 summarizes the production conditions of the aqueous dispersions in Examples and Comparative Examples.

Tables 3 and 4 show the compositions and evaluation results of the aqueous dispersions obtained in Examples 1 to 21 and Comparative Examples 1 to 8, and coating films made of them.

As in Examples 1 to 21, the aqueous dispersion of the present invention, when mixed with the polyurethane resin aqueous dispersion at a solid content of 5% by mass, has a solid content of 20% by mass without significantly affecting the coating film contact angle. % solid content, the adhesion to the substrate could be improved. In addition, excellent shear stability is obtained, which makes it possible to improve coating productivity, suppress coating film defects, improve yield, and improve coating film quality.

Further, even if the amount of the basic compound added during aqueous dispersion is reduced as in Example 2, or the amount of the organic solvent added is reduced as in Example 15, the aqueous dispersion of the present invention can be obtained. I was able to

Furthermore, the cooling rate during aqueous dispersion was increased as in Example 3 or 4, the stirring temperature during aqueous dispersion was decreased as in Example 5, and the temperature was reduced to 1 stage instead of 2 stages as in Example 12. The aqueous dispersion of the present invention could be obtained by cooling in stages or by changing the temperature in the first stage of cooling as in Example 13.
Furthermore, even if the type of polyolefin resin used is changed as in Examples 6 to 11 and 16 to 21, or the type of organic solvent to be added is changed as in Example 14, the aqueous dispersion of the present invention I was able to get a body

In Comparative Examples 1 to 6, since the cooling rate during cooling during aqueous dispersion was fast, in the obtained aqueous dispersion, among the distribution peaks observed in the particle size distribution measured by the small angle X-ray scattering method , the volume fraction of peak A of the smallest particle group was below 50%. Even if a small amount of this aqueous dispersion was added to other aqueous dispersions, the adhesion to the substrate was poor. Moreover, it was inferior also in shear stability.

In Comparative Example 7, since the amount of the organic solvent and the basic compound added during the aqueous dispersion was small, the volume average particle diameter measured by the dynamic light scattering method exceeded 0.3 μm, and the peak A of the smallest particle group was An aqueous dispersion was obtained with an average particle size greater than 20 nm. Adhesion to the substrate was not improved even when this aqueous dispersion was mixed with the polyurethane resin aqueous dispersion at 5% by mass. Moreover, it was inferior also in shear stability.

Comparative Example 8 uses a polyolefin resin having an unsaturated carboxylic acid content below the specified range of the present invention. The polyolefin resin only swelled with the solvent and did not disperse, and an aqueous dispersion could not be obtained.

Claims (9)

A polyolefin resin aqueous dispersion containing polyolefin resin particles and an aqueous medium, wherein the polyolefin resin contains 0.1% by mass or more of an unsaturated carboxylic acid component, and the volume average of the polyolefin resin particles measured by a dynamic light scattering method The particle size is 0.3 μm or less, and among the distribution peaks observed in the particle size distribution measured by the small-angle X-ray scattering method, the average particle size of peak A of the smallest particle group is 20 nm or less, and the distribution peak A polyolefin resin aqueous dispersion, wherein the volume fraction of peak A to the whole is 50% or more. 2. The polyolefin resin aqueous dispersion according to claim 1, wherein the polyolefin resin contains 1 to 20% by mass of (meth)acrylic acid ester component. 3. The polyolefin resin aqueous dispersion according to claim 1, which contains a resin other than polyolefin resin. A coating film comprising the polyolefin resin aqueous dispersion according to any one of claims 1 to 3. An adhesive comprising the polyolefin resin aqueous dispersion according to any one of claims 1 to 3. A paint comprising the polyolefin resin aqueous dispersion according to any one of claims 1 to 3. A method for producing the polyolefin resin aqueous dispersion according to any one of claims 1 to 3,
A method for producing a polyolefin resin aqueous dispersion, comprising a cooling step of cooling to 100° C. or less at a rate of 1° C./min or less after a stirring step of stirring a polyolefin resin and an aqueous medium at a temperature of 110° C. or higher. After a first cooling step in which the cooling step cools from the maximum temperature to a temperature of 100°C or less and above 40°C at a cooling rate of 1°C/min or less, cooling to 40°C or less at a cooling rate of 3°C/min or less. 8. The method for producing a polyolefin resin aqueous dispersion according to claim 7, comprising a second cooling step. 9. The method for producing an aqueous polyolefin resin dispersion according to claim 7 or 8, wherein in the stirring step, stirring is performed at a temperature of 110°C or higher and 20°C or higher than the melting point of the polyolefin resin.