Resin dispersion composition

Abstract

The present invention provides an aqueous dispersion composition containing a copolymer containing α,β-unsaturated carboxylic acid or its ester in a structural unit in a stably dispersed manner, the aqueous dispersion composition is a composition having the characteristics of a high content of the copolymer and a low viscosity, and provides a method for manufacturing the same. The method for manufacturing the aqueous dispersion composition of a copolymer containing α,β-unsaturated carboxylic acid or its ester in a structural unit comprises the following steps: (1) a copolymer containing α,β-unsaturated carboxylic acid or its ester in a structural unit, an alkaline substance and water are mixed so that the concentration of the copolymer is 40 to 62% by mass, and the copolymer is neutralized to a neutralization degree of 10 to 35%; (2) the obtained mixture is pressurized at 0.1 to 2MPa; and (3) as required, water is further added after pressurization to adjust the copolymer concentration to 30 to 60% by mass.

Description

Technical Field

[0001] The present invention relates to a resin dispersion composition, etc. It should be noted that the contents of all the documents described in this specification are incorporated into this specification by reference. Background Art

[0002] Specific resins (such as ethylene / α,β-unsaturated carboxylic acid copolymers) can form films with good thermal adhesiveness and are therefore used in a wide range of applications, including coating agents, heat sealants, delayed tack agents, in-mold labels, topical coating agents, fiber treatment agents, and various adhesives.

[0003] Such resins used for various purposes exist in the case of being used in a solid state and in the case of being used in a state dissolved or dispersed in a solvent or water. In the case of the former, it is difficult to form a thin film as a laminating coating agent, and the global demand for reducing plastics as much as possible has been popularized in recent years, so the situation of using the latter state is increasing. In addition, among the resins in the latter state, it is particularly desirable to use water-based resins that do not require the use of solvents, particularly resins dispersed in water, from the viewpoint of saving resources, safety and environmental issues.

[0004] As the resin aqueous dispersion, for example, an aqueous dispersion obtained by neutralizing an ethylene / acrylic acid copolymer resin with an alkaline substance (ammonia, amine, or alkali metal hydroxide) is known (for example, Patent Documents 1 to 3).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 50-135141

[0008] Patent Document 2: Japanese Patent No. 6426751

[0009] Patent Document 3: Japanese Patent No. 4364983 Summary of the invention

[0010] Problems to be solved by the invention

[0011] For example, the following method is known: using a pressure-resistant homomixer or a pressure-resistant colloid mill, a resin having a carboxyl group (such as an ethylene / α,β-unsaturated carboxylic acid copolymer) is dispersed at a temperature above the melting point on the high temperature side while neutralizing the carboxyl group with an alkaline substance.

[0012] When an alkali metal salt is used as the alkaline substance, ammonia is usually used in combination, and in order to maintain the stability of the obtained water-dispersible composition, the resin (copolymer) content of the water dispersion is also reduced to, for example, 20% by mass or more and less than 30% by mass. In addition, when ammonia is used alone as the alkaline substance, the amount used becomes larger than when an amine or an alkali metal salt is used for neutralization, so there is a tendency that the viscosity of the obtained water-dispersible composition becomes very high or the stability becomes poor.

[0013] Therefore, the present inventors have conducted studies to develop an aqueous dispersion composition containing a resin having a carboxyl group in a stably dispersed state and having characteristics of a high content of the copolymer and a low viscosity.

[0014] Methods used to solve problems

[0015] The present inventors have studied using ethylene / α,β-unsaturated carboxylic acid copolymer as an example of a resin having a carboxyl group. It was then discovered that an aqueous dispersion composition in which a resin having a carboxyl group is dispersed generally has the following tendency: if the particle size of the resin is small, the viscosity becomes high. Therefore, in order to obtain an aqueous dispersion composition of the resin with a low viscosity, an attempt was made to prepare the resin with a large particle size.

[0016] In this attempt, the inventors found the following tendency: if the amount of the neutralizing agent (alkaline substance) used in preparing the aqueous dispersion composition of the resin having a carboxyl group is reduced, the particle size of the obtained resin becomes larger. Therefore, the inventors tried to reduce the amount of the neutralizing agent (alkaline substance) used in preparing the aqueous dispersion composition of the resin having a carboxyl group as much as possible, and found that if the amount of the neutralizing agent used is reduced, the obtained resin is difficult to be stably dispersed in an aqueous medium.

[0017] That is, it was found that, in order to obtain a low-viscosity aqueous dispersion composition of a resin having a carboxyl group, when an aqueous dispersion composition of the resin having a large particle size is prepared and the amount of the neutralizer used is reduced, the dispersion stability is deteriorated.

[0018] Further research was conducted to break this dead end, and it was found that by raising the internal pressure of a sealed pressure-resistant container for neutralizing a carboxyl-containing resin (particularly a copolymer containing an α,β-unsaturated carboxylic acid or its ester in a structural unit) in advance, and appropriately adjusting the concentration of the copolymer in a composition containing the copolymer to be neutralized, an aqueous dispersion composition containing the copolymer in a stable dispersion and having the characteristics of a high content of the copolymer and a low viscosity can be prepared. Further improvements were made based on this finding.

[0019] The present invention includes, for example, the subject matters described in the following items.

[0020] Item 1.

[0021] A composition is an aqueous dispersion composition of a copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, wherein:

[0022] Containing 30 to 60% by mass of the polymer,

[0023] The viscosity of the composition at 25° C. is 5000 mPa·s or less.

[0024] Item 2.

[0025] The composition according to item 1, wherein

[0026] The α,β-unsaturated carboxylic acid is at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid,

[0027] The ester of α,β-unsaturated carboxylic acid is an alkyl ester of α,β-unsaturated carboxylic acid having 1 to 10 carbon atoms.

[0028] Item 3.

[0029] The composition according to item 1 or 2, wherein the copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof as a structural unit is a copolymer further containing at least one of ethylene, propylene, butylene, isobutylene, butadiene, isoprene and styrene as a structural unit.

[0030] Item 4.

[0031] The composition according to any one of items 1 to 3, wherein the degree of neutralization of the copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit is 10 to 35%.

[0032] Item 5.

[0033] The composition according to any one of items 1 to 4, wherein the copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof as a structural unit has a median particle size of 1 to 10 μm.

[0034] Item 6.

[0035] The composition according to any one of items 1 to 5, wherein the copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof as a structural unit is an ethylene / α,β-unsaturated carboxylic acid copolymer.

[0036] Item 7.

[0037] The composition according to item 6, wherein the ethylene / α,β-unsaturated carboxylic acid copolymer is an ethylene / (meth)acrylic acid copolymer.

[0038] Item 8.

[0039] A laminate comprising a paper substrate and a film on the paper substrate, wherein the film is formed using the composition according to any one of items 1 to 7.

[0040] Item 9.

[0041] A method for producing an aqueous dispersion composition of a copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, comprising the following steps:

[0042] (1) mixing a copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, a basic substance, and water so that the concentration of the copolymer is 40 to 62% by mass and the copolymer is neutralized to a degree of neutralization of 10 to 35%; and

[0043] (2) The obtained mixture is pressurized at 0.1 to 2 MPa.

[0044] Item 10.

[0045] A method for producing an aqueous dispersion composition of a copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, comprising the following steps:

[0046] (1a) mixing a copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, ammonia and water so that the concentration of the copolymer is 40 to 62% by mass and the amount of ammonia is 0.1 to 2 mol per 1 mol of carboxyl groups contained in the copolymer; and

[0047] (2) The obtained mixture is pressurized at 0.1 to 2 MPa.

[0048] Item 11.

[0049] A method for preparing an aqueous dispersion composition of an ethylene / (meth)acrylic acid copolymer comprises the following steps:

[0050] (1b) mixing an ethylene / (meth)acrylic acid copolymer, ammonia and water so that the concentration of the copolymer is 40 to 62% by mass and the concentration of ammonia is 1 to 2% by mass; and

[0051] (2) The obtained mixture is pressurized at 0.1 to 2 MPa.

[0052] Item 12.

[0053] The method for producing an aqueous dispersion composition according to any one of items 9 to 11, further comprising the following steps:

[0054] (3) After the pressurization, water is further added to adjust the copolymer concentration to 30 to 60% by mass.

[0055] Item 13.

[0056] The production method according to any one of items 9 to 12, wherein the aqueous dispersion composition has a viscosity of 5000 mPa·s or less at 25°C.

[0057] Effects of the Invention

[0058] An aqueous dispersion composition containing a copolymer containing an α,β-unsaturated carboxylic acid or its ester in a structural unit in a stably dispersed state can be provided, wherein the aqueous dispersion composition has the characteristics of a high content of the copolymer and a low viscosity. In addition, a method for producing the aqueous dispersion composition can be provided.

[0059] It should be noted that the aqueous dispersion composition has a feature that the amount of neutralizer (alkaline substance) remaining in the aqueous dispersion composition is also small because a small amount of neutralizer (alkaline substance) is used in the preparation. The aqueous dispersion composition can be used as a coating agent, for example. As a result, when the alkaline substance contained is small, the water resistance of the dried film of the aqueous dispersion composition is improved. Therefore, when used as a coating agent, it is particularly preferably used as a paper coating agent for the surface of wallpapers, etc., or as a food packaging coating agent.

[0060] In addition, the aqueous dispersion composition has a high concentration of a copolymer containing an α,β-unsaturated carboxylic acid or its ester in the structural units contained therein, so it has excellent film-forming properties. Furthermore, depending on the material of paper or the like on which the aqueous dispersion composition is applied, the penetration of the copolymer particles and the film thickness can be reduced, so that defects such as spots and holes after application can also be reduced.

[0061] Furthermore, if the viscosity of the composition is high, it becomes difficult to handle and the workability is deteriorated, but this is unlikely to occur because the aqueous dispersion composition has a low viscosity. DETAILED DESCRIPTION

[0062] Hereinafter, each embodiment included in the present invention is further described in detail. The present invention preferably includes an aqueous dispersion composition of a copolymer containing an α,β-unsaturated carboxylic acid or its ester in a structural unit and a method for producing the same, but is not limited thereto. The present invention includes all schemes disclosed in this specification and understandable to a person skilled in the art. It should be noted that a copolymer containing an α,β-unsaturated carboxylic acid or its ester in a structural unit is sometimes referred to as a copolymer (A).

[0063] The aqueous dispersion composition of the copolymer (A) included in the present invention contains 30% by mass or more (preferably 30 to 60% by mass) of the copolymer (A), and has a viscosity at 25° C. of 5000 mPa·s or less (more preferably 4500 mPa·s or less, 4000 mPa·s or less, 3500 mPa·s or less, 3000 mPa·s or less, 2500 mPa·s or less, 2000 mPa·s or less, 1500 mPa·s or less, 1000 mPa·s or less). Hereinafter, the aqueous dispersion composition included in the present invention may be referred to as "the composition of the present invention".

[0064] It should be noted that the viscosity of the composition of the present invention is measured using a BH type rotational viscometer. Specifically, the rotation speed of the spindle rotor is set to 60 revolutions per minute, and the viscosity value is read 1 minute after the rotor starts rotating at 25°C, thereby measuring. It should be noted that the rotor can be appropriately set according to the viscosity. As a standard, when it is less than 2000mPa·s, it is rotor No.3, when it is more than 2000mPa·s and less than 5000mPa·s, it is rotor No.4, when it is more than 5000mPa·s and less than 15000mPa·s, it is rotor No.5, when it is more than 15000mPa·s and less than 40000mPa·s, it is rotor No.6, and when it is more than 40000mPa·s, it is rotor No.7.

[0065] The copolymer (A) is a copolymer containing one or more α,β-unsaturated carboxylic acids in the structural unit, for example, it may be (i) a copolymer of one or more α,β-unsaturated carboxylic acids or their esters and one or more monomers other than α,β-unsaturated carboxylic acids or their esters, or (ii) a copolymer of two or more α,β-unsaturated carboxylic acids or their esters. It should be noted that "two or more α,β-unsaturated carboxylic acids or their esters" include: only two or more α,β-unsaturated carboxylic acids; only two or more α,β-unsaturated carboxylic acid esters; and one or more α,β-unsaturated carboxylic acids and one or more α,β-unsaturated carboxylic acid esters.

[0066] Examples of α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and the like. Among these, (meth)acrylic acid (i.e., methacrylic acid and / or acrylic acid) is more preferred. In addition, examples of esters of α,β-unsaturated carboxylic acids include alkyl esters having 1 to 10 carbon atoms (1, 2, 3, 4, 5, 6, 7, 8, 9, or 10). The alkyl portion of the alkyl ester may be linear or branched. More specifically, examples of esters of α,β-unsaturated carboxylic acids include methyl esters, ethyl esters, butyl (especially n-butyl) esters, and 2-ethylhexyl esters. In addition, examples of esters of α,β-unsaturated carboxylic acids include 2-methylaminoethyl esters, hydroxyethyl esters (especially 2-hydroxyethyl esters), and the like. Among these, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate are more preferred.

[0067] Examples of the monomer other than the α,β-unsaturated carboxylic acid or its ester include ethylene, propylene, butylene, isobutylene, butadiene, isoprene, and styrene.

[0068] As the copolymer (A), more specifically, preferably, for example, a copolymer of ethylene / α,β-unsaturated carboxylic acid or its ester, a copolymer of styrene / α,β-unsaturated carboxylic acid or its ester, etc. can be mentioned. Among these, ethylene / α,β-unsaturated carboxylic acid copolymers are more preferred. More specifically, ethylene / (meth)acrylic acid copolymers, styrene / (meth)acrylate copolymers, styrene / (meth)acrylic acid / (meth)acrylate copolymers, etc. can be further preferably mentioned. Ethylene / α,β-unsaturated carboxylic acid copolymers are particularly preferred.

[0069] The copolymer (A) can be prepared by a known method or a method that can be easily thought of by a known method. In addition, commercial products can also be purchased and used. For example, commercial products of ethylene / α,β-unsaturated carboxylic acid copolymers can also be purchased and used. As commercial products, for example, PRIMACOR 5980, PRIMACOR 5990 (made by Dow Chemical Japan Co., Ltd.), NUCREL AN4221C, NUCREL N5130H, NUCREL N2060, NUCREL N2050H, NUCREL N1560 (made by DuPont Mitsui Polychemical Co., Ltd.) and the like can be cited.

[0070] As the ethylene / α,β-unsaturated carboxylic acid copolymer, an ethylene / (meth)acrylic acid copolymer is particularly preferred.

[0071] The copolymer (A) is not particularly limited, but it is preferred that the carboxyl groups (derived from the α,β-unsaturated carboxylic acid) contained therein are appropriately neutralized.

[0072] Generally, the hydrophilicity of the copolymer (A) is low when the carboxyl groups are in a free state, and becomes higher when the carboxyl groups are in a salt state. Therefore, by neutralizing with a base, the neutralized carboxyl groups in the copolymer function as an emulsifier, and the aqueous dispersion can be prepared relatively easily.

[0073] As the base used for the neutralization, for example, ammonia, an organic amine, or an alkali metal hydroxide is preferably used.

[0074] Examples of organic amines include methylamine, ethylamine, diethylamine, diethanolamine, triethanolamine, and the like. In addition, examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide, and the like. Furthermore, ammonia can also be used in the form of ammonia gas or an aqueous ammonia solution, for example. These bases can be used alone or in combination of two or more. Among them, ammonia is preferably used.

[0075] The copolymer (A) contained in the composition of the present invention preferably has 10 to 35% of the carboxyl groups contained therein neutralized. That is, the neutralization degree of the ethylene / α,β-unsaturated carboxylic acid copolymer is preferably 10 to 35%. It should be noted that the upper or lower limit of the range may be, for example, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33% or 34%. It may be, for example, 12 to 33%. It should be noted that the % is the molar % of the carboxyl unit.

[0076] Although not particularly limited, the copolymer (A) preferably has an α,β-unsaturated carboxylic acid content of, for example, 8% by mass or more, and more preferably has an α,β-unsaturated carboxylic acid content of 8 to 50% by mass. The upper limit or lower limit of the range may be, for example, 9 mass%, 10 mass%, 11 mass%, 12 mass%, 13 mass%, 14 mass%, 15 mass%, 16 mass%, 17 mass%, 18 mass%, 19 mass%, 20 mass%, 21 mass%, 22 mass%, 23 mass%, 24 mass%, 25 mass%, 26 mass%, 27 mass%, 28 mass%, 29 mass%, 30 mass%, 31 mass%, 32 mass%, 33 mass%, 34 mass%, 35 mass%, 36 mass%, 37 mass%, 38 mass%, 39 mass%, 40 mass%, 41 mass%, 42 mass%, 43 mass%, 44 mass%, 45 mass%, 46 mass%, 47 mass%, 48 mass%, or 49 mass%. For example, it may be 9 to 49 mass%. It should be noted that the α,β-unsaturated carboxylic acid content here refers to the content of units derived from the α,β-unsaturated carboxylic acid.

[0077] In particular, when the copolymer (A) is an ethylene / α,β-unsaturated carboxylic acid copolymer, in order to have a balanced combination of the non-polar properties derived from the ethylene unit and the polar properties derived from the α,β-unsaturated carboxylic acid, a copolymer (A) having an α,β-unsaturated carboxylic acid content of 8 to 24% by mass is preferred. The upper or lower limit of the range may be, for example, 9% by mass, 10% by mass, 11% by mass, 12% by mass, 13% by mass, 14% by mass, 15% by mass, 16% by mass, 17% by mass, 18% by mass, 19% by mass, 20% by mass, 21% by mass, 22% by mass or 23% by mass. The range may be, for example, 18 to 23% by mass. By making the content of the α,β-unsaturated carboxylic acid 8% or more, due to the non-polar properties derived from the ethylene unit, the dispersibility in the aqueous dispersion medium becomes better, and an excellent aqueous dispersion composition can be efficiently obtained. Furthermore, when the content of the α,β-unsaturated carboxylic acid is less than 24% by mass, the resulting coating (coating film) produced when the aqueous dispersion composition is used as a coating agent has further excellent blocking resistance.

[0078] The median particle size of the copolymer (A) in the composition of the present invention is preferably 1 to 10 μm. The upper or lower limit of the range may be, for example, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm or 9.5 μm. For example, the range may be 1.5 to 9.5 μm. By making the median particle size 1 μm or more, the viscosity of the aqueous dispersion composition may become more preferred (not excessively high). In addition, by making the median particle size 10 μm or less, the stability of the aqueous dispersion composition may be further improved (i.e., the state in which the copolymer (A) is dispersed may be maintained more stably).

[0079] It should be noted that the median particle size is the median diameter, which is a value measured by a laser diffraction particle size distribution measuring method. That is, it is a value obtained when the aqueous dispersion composition of the copolymer (A) is measured by a laser diffraction particle size distribution measuring device. As the measuring device, for example, SALD2300 manufactured by SHIMADZU can be cited. More specifically, 20 ml of water is mixed with 0.1 g of anionic surfactant (polyoxyethylene lauryl ammonium sulfate, polyoxyalkylene alkyl ether sodium sulfate, etc.), 0.1 g of the aqueous dispersion composition of the copolymer (A) as the object of measurement is added thereto, ultrasonic waves are applied for 3 minutes while stirring, and the particles to be measured are measured by a laser diffraction particle size distribution measuring device. It should be noted that the measured particles showing the same diffraction / scattered light pattern as a ball with a diameter of X μm are calculated with a particle size of X μm regardless of their shape.

[0080] The copolymer (A) content in the composition of the present invention is preferably, for example, 30 to 60 mass%. The upper or lower limit of this range may be, for example, 31 mass%, 32 mass%, 33 mass%, 34 mass%, 35 mass%, 36 mass%, 37 mass%, 38 mass%, 39 mass%, 40 mass%, 41 mass%, 42 mass%, 43 mass%, 44 mass%, 45 mass%, 46 mass%, 47 mass%, 48 mass%, 49 mass%, 50 mass%, 51 mass%, 52 mass%, 53 mass%, 54 mass%, 55 mass%, 56 mass%, 57 mass%, 58 mass% or 59 mass%. For example, the range may be 35 to 55 mass%.

[0081] The copolymer (A) can be used alone or in combination of two or more.

[0082] As the aqueous medium of the composition of the present invention, water is preferred, and various waters such as tap water, industrial water, ion-exchanged water, deionized water, and pure water can be used. Deionized water or pure water is particularly preferred.

[0083] It should be noted that the composition of the present invention may contain other ingredients within the range that does not impair the effect. For example, it may contain a defoamer, a viscosity modifier, a pH modifier, a surfactant, a mildew preventer, etc., and may also contain an antioxidant, a fatty acid amide, wax, silicone oil and other adhesion improvers, alcohols, etc. as needed.

[0084] The composition of the present invention is useful as, for example, an adhesive or a coating agent. The composition of the present invention can be applied to a substrate and dried to form a film. As the substrate, preferably, for example, paper can be cited, and more preferably, food and beverage packaging paper can be cited. Utilizing the aforementioned film, it is possible to prevent food and beverage from directly contacting paper (wrapping paper). In addition, the film has few adverse effects on food and beverage, which is preferred.

[0085] The present invention also preferably includes, for example, a laminate comprising a paper substrate and a film on the paper substrate, wherein the film is formed using the composition of the present invention.

[0086] The composition of the present invention can be prepared, for example, by mixing the copolymer (A), an alkaline substance and water so that the copolymer has a specific concentration and is neutralized to a specific degree of neutralization, and pressurizing (if necessary, further heating). More preferably, after pressurizing, the copolymer is further diluted with water so that the copolymer has a specific concentration.

[0087] In the mixing of copolymer (A), alkaline substance and water, the concentration of copolymer (A) is preferably mixed in a manner of 40 to 62 mass %. The upper limit or lower limit of the concentration range can be, for example, 41 mass %, 42 mass %, 43 mass %, 44 mass %, 45 mass %, 46 mass %, 47 mass %, 48 mass %, 49 mass %, 50 mass %, 51 mass %, 52 mass %, 53 mass %, 54 mass %, 55 mass %, 56 mass %, 57 mass %, 58 mass %, 59 mass %, 60 mass % or 61 mass %. For example, the concentration range can be, for example, 40 to 55 mass % or 45 to 55 mass %.

[0088] As described above, the neutralization degree of the copolymer (A) contained in the composition of the present invention is preferably 10 to 35%. In the mixing herein, the alkaline substance is preferably mixed so that the copolymer (A) is neutralized to a neutralization degree of 10 to 35%.

[0089] More specifically, for example, when using ethylene / (meth)acrylic acid copolymer as copolymer (A) and ammonia as alkaline substance, it is preferred to mix ethylene / (meth)acrylic acid copolymer with water in a concentration of 40 to 62% by mass in the obtained mixture and ammonia in a neutralization degree of 10 to 35% in the copolymer. The amount of amine is not particularly limited if it is a range of amount that can achieve the neutralization degree, for example, the concentration of ammonia is preferably 1 to 2% by mass in the obtained mixture. In addition, the amount of ammonia used is preferably 0.1 to 2 moles, more preferably 0.4 to 1 mole, relative to 1 mole of carboxyl groups contained in the ethylene / α,β-unsaturated carboxylic acid copolymer. It should be noted that the mixing of ammonia is preferably carried out by mixing with aqueous ammonia.

[0090] The mixture obtained by mixing the copolymer (A), the alkaline substance and water is pressurized. The mixture is preferably pressurized while being mixed (e.g., stirred). The pressurization is preferably, for example, about 0.1 MPa to about 2 MPa. The upper or lower limit of the range may be, for example, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa or 1.9 MPa. For example, the range may be 0.2 to 1.5 MPa.

[0091] The pressurization can be carried out, for example, by placing the mixture in a closed and stirred pressure-resistant container and then introducing an inert gas into the container. Examples of the inert gas include nitrogen, etc. In addition, examples of the container include a pressure-resistant autoclave with a stirrer, etc.

[0092] In addition, during the pressurization, it is preferred to heat as needed. For example, it is preferred to heat to a temperature higher than the temperature at which the copolymer (A) softens in an aqueous medium. More specifically, for example, it is preferred to heat to about 90°C to about 150°C, and more preferably to about 95°C to about 140°C. When the copolymer (A) is an ethylene / (meth)acrylic acid copolymer, it is particularly desirable to heat to this temperature and ripen it.

[0093] After cooling, the mixture is returned to normal pressure, and water is preferably added to the obtained mixture as needed to adjust the mixture to contain 30 to 60% by mass of the copolymer (A). It should be noted that, when heating is performed during pressurization, it is preferred to first cool to below 90°C (e.g., 90 to 80°C), then release the pressure in the container and return to normal pressure, and further add water as needed. When adding water, the amount of water is preferably adjusted so that the content of the copolymer (A) in the mixture is 30 to 60% by mass. In addition, mixing (stirring) is preferably performed as needed.

[0094] By going through the above steps, it is possible to obtain an aqueous dispersion composition in which the copolymer (A) is stably dispersed and has a viscosity at 25°C of 5000 mPa·s or less (more preferably 4500 mPa·s or less, 4000 mPa·s or less, 3500 mPa·s or less, 3000 mPa·s or less, 2500 mPa·s or less, 2000 mPa·s or less, 1500 mPa·s or less, 1000 mPa·s or less).

[0095] It should be noted that, during the production process, a surfactant is used to particularly assist dispersion. However, according to the present invention, even without particularly using a surfactant, an aqueous dispersion composition can be provided that contains the copolymer (A) in a stably dispersed state and has the characteristics of a high content of the copolymer and a low viscosity.

[0096] It should be noted that, in the present specification, “comprising” also includes “consisting essentially of” and “consisting of.” In addition, the present invention includes all arbitrary combinations of the constituent elements described in the present specification.

[0097] In addition, when limiting the subject matter included in the present invention, the various characteristics (properties, structures, functions, etc.) described in the above-mentioned embodiments of the present invention can be combined arbitrarily. That is, the present invention includes all the subject matter consisting of all combinations of the combinable characteristics recorded in this specification.

[0098] Example

[0099] Although the embodiments of the present invention will be described in more detail below with reference to examples, the embodiments of the present invention are not limited to the following examples.

[0100] <Method for measuring median particle size>

[0101] The median particle size of the resin (copolymer containing α,β-unsaturated carboxylic acid or its ester in the structural unit) in the aqueous dispersion composition is measured as follows: 20 ml of water and 0.1 g of anionic surfactant (synthetic detergent containing polyoxyethylene ammonium lauryl sulfate and sodium polyoxyalkylene alkyl ether sulfate) are mixed in a 100 ml beaker, 0.1 g of the sample (aqueous dispersion composition) is added thereto, and ultrasonic waves are applied for 3 minutes while stirring with a spatula, and the particle size distribution is measured using a laser diffraction particle size distribution analyzer (SALD2300 manufactured by SHIMADZU).

[0102] <Viscosity measurement method>

[0103] The aqueous dispersion composition was immersed in a constant temperature water tank kept at 25° C., and the viscosity of the aqueous dispersion was measured at 25° C. In the viscosity measurement, Brookfield DV-II+ was used with rotor No. 3 and a predetermined rotation speed to measure the viscosity.

[0104] The rotation speeds in each example are shown in Table 1 below.

[0105] [Table 1]

[0106] example Speed ​​(rpm) Example 1 60 Example 2 60 Comparative Example 1 6 Comparative Example 2 1 Comparative Example 3 - Comparative Example 4 60 Comparative Example 5 6

[0107] <Solid content (mass %) measurement method>

[0108] 1 g of the aqueous dispersion composition was weighed and dried at 130° C. for 3 hours using a hot air dryer (DRE320DR manufactured by ADVANTEC) to obtain a dry solid. The solid content (mass %) was calculated by the following formula.

[0109]

[0110] <Residue (mass %) measurement method>

[0111] The content of the composition obtained after neutralization of the copolymer containing α,β-unsaturated carboxylic acid or its ester in the structural unit was filtered through a polyethylene 80-mesh mesh, and then the weight of the filtration residue remaining on the 80-mesh mesh was confirmed. The residue (mass %) was calculated by the following formula.

[0112]

[0113] In the following examples, an ethylene / α,β-unsaturated carboxylic acid copolymer was used as a copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit.

[0114] (Example 1)

[0115] 200 g of ethylene / α,β-unsaturated carboxylic acid copolymer (EAA (ethylene / acrylic acid copolymer); product name PRIMACOR 5980, acrylic acid content 20%, manufactured by LG Global) as a neutralizing agent, 8.4 g of 28% ammonia water and 191.6 g of water were added to a 1000 mL pressure-resistant container with a stirrer, and the container was sealed. Next, nitrogen gas was introduced and pressurized to 0.5 MPa as measured by the pressure gauge of the pressure-resistant container. Then, the temperature was raised to 130°C while stirring at 200 revolutions per minute, and the container was kept at 130°C and stirred for 4 hours. Then, after cooling to 90°C while stirring at 100 revolutions per minute, the remaining pressure in the kettle was released and restored to normal pressure, 100 g of water was added from the side pipe of the container to dilute, and then cooled to 50°C. The contents were filtered with a polyethylene 80-mesh net to obtain an aqueous dispersion. The obtained aqueous dispersion composition had a solid content of 39.8% by mass, a median particle size of 4 μm, a viscosity of 50 mPa·s, and a residue of 1.0% by mass or less.

[0116] (Example 2)

[0117] 200 g of ethylene / α,β-unsaturated carboxylic acid copolymer (EAA (ethylene / acrylic acid copolymer); product name PRIMACOR 5980 acrylic acid content 20% manufactured by LG Global) as a neutralizing agent, 8.8 g of 28% ammonia water and 191.2 g of water were added to a 1000 mL pressure-resistant container with a stirrer, and the container was sealed. Next, nitrogen gas was introduced and pressurized to 0.5 MPa as measured by the pressure gauge of the pressure-resistant container. Then, the temperature was raised to 130°C while stirring at 200 revolutions per minute, and the container was kept at 130°C and stirred for 4 hours. Then, after cooling to 90°C while stirring at 100 revolutions per minute, the remaining pressure in the kettle was released and restored to normal pressure, 50 g of water was added from the side tube of the container to dilute it, and then cooled to 50°C. The contents were filtered with an 80-mesh polyethylene net to obtain an aqueous dispersion. The obtained aqueous dispersion composition had a solid content of 44.9% by mass, a median particle size of 4 μm, a viscosity of 300 mPa·s, and a residue of 1.0% by mass or less.

[0118] (Comparative Example 1)

[0119] 240 g of ethylene / α,β-unsaturated carboxylic acid copolymer (EAA (ethylene / acrylic acid copolymer); product name PRIMACOR 5980 acrylic acid content 20% manufactured by LG Global) and 129.0 g of water as a neutralizing agent were added to a pressure-resistant container with a volume of 1000 mL and sealed. Next, nitrogen gas was introduced and pressurized to 0.5 MPa according to the pressure gauge provided in the pressure-resistant container. Then, the temperature was raised to 130°C while stirring at 200 revolutions per minute, and the container was kept at 130°C and stirred for 4 hours. Then, after cooling to 90°C while stirring at 100 revolutions per minute, the remaining pressure in the kettle was released and restored to normal pressure, and 250 g of water was added from the side pipe of the container to dilute it, and then cooled to 50°C. An attempt was made to filter the contents, but it was difficult to filter due to the high viscosity, so filtration was not performed and an aqueous dispersion was obtained. The obtained aqueous dispersion composition had a median particle size of 0.1 μm and a viscosity of 16,000 mPa·s.

[0120] (Comparative Example 2)

[0121] 200 g of ethylene / α,β-unsaturated carboxylic acid copolymer (EAA (ethylene / acrylic acid copolymer); product name PRIMACOR 5980 acrylic acid content 20% manufactured by LG Global) and 186.5 g of water as a neutralizing agent were added to a pressure-resistant container with a volume of 1000 mL and sealed. Next, nitrogen gas was introduced and pressurized to 0.5 MPa as measured by the pressure gauge of the pressure-resistant container. Then, the temperature was raised to 130°C while stirring at 200 revolutions per minute, and the container was kept at 130°C and stirred for 4 hours. Then, after cooling to 90°C while stirring at 100 revolutions per minute, the remaining pressure in the kettle was released and restored to normal pressure, 100 g of water was added from the side pipe of the container to dilute, and then cooled to 50°C. An attempt was made to filter the contents, but the viscosity was high and it was difficult to filter, so filtration was not performed and an aqueous dispersion was obtained. The obtained aqueous dispersion composition had a median particle size of 0.2 μm and a viscosity of 100,000 mPa·s.

[0122] (Comparative Example 3)

[0123] 200 g of ethylene / α,β-unsaturated carboxylic acid copolymer (EAA (ethylene / acrylic acid copolymer); product name PRIMACOR 5980 acrylic acid content 20% manufactured by LG Global) as a neutralizing agent, 6.7 g of 28% ammonia water and 193.3 g of water were added to a 1000 mL pressure-resistant container with a stirrer, and the container was sealed. Next, nitrogen gas was introduced and pressurized to 0.5 MPa as measured by the pressure gauge of the pressure-resistant container. Then, the temperature was raised to 130°C while stirring at 200 revolutions per minute, and the container was kept at 130°C and stirred for 4 hours. Then, after cooling to 90°C while stirring at 100 revolutions per minute, the remaining pressure in the kettle was released and restored to normal pressure, 100 g of water was added from the side tube of the container to dilute it, and then it was cooled to 50°C. When the contents were confirmed, the resin remained as it was, in an undispersed state.

[0124] (Comparative Example 4)

[0125] 200 g of ethylene / α,β-unsaturated carboxylic acid copolymer (EAA (ethylene / acrylic acid copolymer); product name PRIMACOR 5980 acrylic acid content 20% LG Global) was added to a pressure-resistant container with a stirrer of 1000 mL, 8.8 g of 28% ammonia water as a neutralizer, and 191.2 g of water were sealed. Then, the temperature was raised to 130°C while stirring at 200 revolutions per minute, and the container was kept at 130°C and stirred for 4 hours. Next, after cooling to 90°C while stirring at 100 revolutions per minute, the remaining pressure in the kettle was released and restored to normal pressure, 100 g of water was added from the side pipe of the container to dilute, and then cooled to 50°C. The contents were filtered with a polyethylene 80-mesh net to obtain an aqueous dispersion. The solid content of the obtained aqueous dispersion composition was 40% by mass, the median particle size was 3 μm, the liquid viscosity was 135 mPa·s, and the residue was less than 20% by mass.

[0126] (Comparative Example 5)

[0127] 160 g of ethylene / α,β-unsaturated carboxylic acid copolymer (EAA (ethylene / acrylic acid copolymer); product name PRIMACOR 5980 acrylic acid content 20%, manufactured by LG Global) and 10.5 g of 28% ammonia water as a neutralizing agent and 229.5 g of water were added to a 1000 mL pressure-resistant container with a stirrer, and the container was sealed. Next, nitrogen gas was introduced and pressurized to 0.5 MPa as measured by the pressure gauge attached to the pressure-resistant container. Then, the temperature was raised to 130°C while stirring at 200 revolutions per minute, and the container was kept at 130°C and stirred for 4 hours. Then, after cooling to 90°C while stirring at 100 revolutions per minute, the remaining pressure in the kettle was released to return to normal pressure and cooled to 50°C. An attempt was made to filter the contents, but the viscosity was high and difficult to carry out, so filtration was not carried out and an aqueous dispersion was obtained. The obtained aqueous dispersion composition had a median particle size of 9.5 μm and a liquid viscosity of 17,000 mPa·s.

[0128] The above results are summarized in Table 2. It should be noted that the resin in the table represents an ethylene / α,β-unsaturated carboxylic acid copolymer (specifically, an ethylene / acrylic acid copolymer). It should be noted that the concentration (mass %) of the solid content in these examples can be referred to as the concentration of the ethylene / α,β-unsaturated carboxylic acid copolymer in the aqueous dispersion composition.

[0129]

Claims

1. A composition, which is an aqueous dispersion composition containing a copolymer of an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, wherein: Containing 30 to 60% by mass of the copolymer, The median particle size of the copolymer is 1 to 10 μm. The copolymer is neutralized under a pressure of 0.1 to 2 MPa, and the degree of neutralization is 22 to 35%. The viscosity of the composition at 25° C. is 2000 mPa·s or less.

2. The composition according to claim 1, wherein The α,β-unsaturated carboxylic acid is at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid, The ester of α,β-unsaturated carboxylic acid is an alkyl ester of α,β-unsaturated carboxylic acid having 1 to 10 carbon atoms.

3. The composition according to claim 1, wherein The copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof as a structural unit is a copolymer further containing at least one of ethylene, propylene, butylene, isobutylene, butadiene, isoprene and styrene as a structural unit.

4. The composition according to claim 1, wherein The copolymer containing α,β-unsaturated carboxylic acid or its ester in the structural unit is an ethylene / α,β-unsaturated carboxylic acid copolymer.

5. The composition according to claim 4, wherein The ethylene / α,β-unsaturated carboxylic acid copolymer is an ethylene / (meth)acrylic acid copolymer.

6. The composition according to any one of claims 1 to 5, wherein The α,β-unsaturated carboxylic acid or its ester is neutralized with ammonia.

7. The composition according to any one of claims 1 to 5, wherein The median particle size of the copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit is 3.5 to 10 μm.

8. A laminate comprising a paper substrate and a film on the paper substrate, wherein: The film is formed using the composition according to any one of claims 1 to 7.

9. A method for producing an aqueous dispersion composition containing a copolymer of an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, comprising the following steps: (1) mixing a copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, a basic substance, and water so that the concentration of the copolymer is 40 to 62% by mass and the copolymer is neutralized to a degree of neutralization of 22 to 35%; and (2) The obtained mixture is pressurized at 0.1 to 2 MPa.

10. A method for producing an aqueous dispersion composition containing a copolymer of an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, comprising the following steps: (1a) mixing a copolymer containing an α,β-unsaturated carboxylic acid or an ester thereof in a structural unit, ammonia and water so that the concentration of the copolymer is 40 to 62% by mass, the amount of ammonia is 0.1 to 2 mol per 1 mol of carboxyl groups contained in the copolymer, and the copolymer is neutralized to a degree of neutralization of 22 to 35%; and (2) The obtained mixture is pressurized at 0.1 to 2 MPa.

11. A method for producing an aqueous dispersion composition of an ethylene / (meth)acrylic acid copolymer, comprising the following steps: (1b) mixing an ethylene / (meth)acrylic acid copolymer, ammonia and water so that the concentration of the copolymer is 40 to 62% by mass, the concentration of ammonia is 1 to 2% by mass, and the copolymer is neutralized to a degree of neutralization of 22 to 35%; and (2) The obtained mixture is pressurized at 0.1 to 2 MPa.

12. The method for producing an aqueous dispersion composition according to any one of claims 9 to 11, wherein The following steps are also included: (3) After the pressurization, water is further added to adjust the copolymer concentration to 30 to 60% by mass.

13. The production method according to any one of claims 9 to 11, wherein: The aqueous dispersion composition has a viscosity of 2000 mPa·s or less at 25° C.

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