Method for producing aqueous resin dispersion composition

Abstract

Provided is a method for producing an aqueous resin dispersion composition from which a film having excellent blocking resistance can be formed. More specifically, a production method as mentioned below is provided. A method for producing an aqueous dispersion composition comprising two or more polymers each containing a constituent unit derived from acrylic acid and a neutralizer, wherein the two or more polymers are different from each other with respect to the amount of the constituent unit derived from acrylic acid. The method comprises: a step for mixing the two or more polymers together to obtain a mixed polymer composition; and a step for mixing the mixed polymer composition, the neutralizer, and water together to obtain an aqueous dispersion composition. When a blocking resistance temperature of a coated paper sheet prepared by applying the aqueous dispersion composition is measured under the conditions mentioned below, the blocking resistance temperature is 70°C or higher. [Measurement conditions] An aqueous dispersion composition to be measured is applied on uncoated woodfree paper sheets each having a basis weight of 52 g / m2 so as to achieve a dry coating amount of 5.0 g / m2, thereby obtaining coated paper sheets. The coated surfaces of the coated paper sheets are put together, and are then bonded under a sealing pressure of 5 kg / cm2, for a sealing time of 2 hours at sealing temperature of 60-80°C, thereby obtaining a bonded paper sheet (a test specimen). The bonded paper sheet is subjected to a T-type peeling test (tensile speed: 300 mm / min) in accordance with JIS Z 0238 (1998). A maximum temperature at which the bonded paper sheet is not broken and causes interfacial peeling is defined as the blocking resistance temperature.

Description

Method for manufacturing resin aqueous dispersion composition

[0001] The present disclosure relates to a method for producing an aqueous dispersion composition containing a polymer. Specifically, the present disclosure relates to a method for producing an aqueous dispersion composition containing a polymer including structural units derived from acrylic acid and a neutralizing agent.

[0002] Certain resins are capable of forming films with good thermal adhesion, and are therefore used in a wide range of applications, such as coating agents, heat sealing agents, dilatation tack agents, in-mold labels, percoat agents, fiber treatment agents, and various binders.

[0003] Resins used in these various applications may be used in a solid state or in a dissolved or dispersed state in a solvent or water. The former is difficult to form a thin film with, and therefore difficult to meet the recent global demand for a reduction in the amount of plastic used. Therefore, when forming a film, the latter state has become more common. Among the latter state resins, there has been a growing demand for aqueous resins, particularly those dispersed in water, that do not require the use of organic solvents, particularly from the viewpoints of resource conservation, safety, and environmental issues.

[0004] JP-A-50-135141 Patent No. 6426751 Patent No. 4364983

[0005] In view of the above circumstances, there is an increasing demand for aqueous resin dispersion compositions with excellent performance. In particular, depending on the type and application of the substrate, there is a demand for improved blocking resistance of the coating obtained from the aqueous resin dispersion composition.

[0006] The present disclosure includes, for example, the subject matter described in the following sections. Item 1. A method for producing an aqueous dispersion composition comprising two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers differing in the content of structural units derived from acrylic acid, the production method comprising: a step of melt-kneading the two or more polymers to obtain a mixed polymer composition; and a step of mixing the mixed polymer composition, the neutralizing agent, and water after the melt-kneading step. Item 2. A method for producing an aqueous dispersion composition comprising two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers differing in the content of structural units derived from acrylic acid, the production method comprising: a step of melt-kneading the two or more polymers in a twin-screw extruder to obtain a mixed polymer composition, and a step of mixing the mixed polymer composition, the neutralizing agent, and water. Item 3. A method for producing an aqueous dispersion composition containing two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers differing in the content of structural units derived from acrylic acid, the method comprising: a step of mixing the two or more polymers to obtain a mixed polymer composition; and a step of mixing the mixed polymer composition, the neutralizing agent, and water to obtain an aqueous dispersion composition, wherein the aqueous dispersion composition is an aqueous dispersion composition in which the blocking resistance temperature of coated paper coated with the aqueous dispersion composition is 70°C or higher when measured under the following conditions. [Measurement Conditions] The aqueous dispersion composition to be measured was coated with a paper having a basis weight of 52 g / m. ２ Dry coating amount 5.0 g / m on high-quality paper ２ The coated surfaces of the resulting coated papers were placed together and sealed at a seal pressure of 5 kg / cm. ２Item 4. A method for producing an aqueous dispersion composition comprising two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, the two or more polymers being different in content of structural units derived from acrylic acid, and the method comprising the step of mixing a composition in which the two or more polymers are melt-kneaded, the neutralizing agent, and water. Item 5. A method for producing an aqueous dispersion composition containing two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers differing in the content of structural units derived from acrylic acid, and the method comprises a step of mixing a composition containing the two or more polymers, the neutralizing agent, and water to obtain an aqueous dispersion composition, wherein the aqueous dispersion composition is an aqueous dispersion composition in which the blocking resistance temperature of coated paper coated with the aqueous dispersion composition is 70°C or higher when measured under the following conditions. [Measurement conditions] The aqueous dispersion composition to be measured was mixed with a paper having a basis weight of 52 g / m ２ Dry coating amount 5.0 g / m on high-quality paper ２ The coated surfaces of the resulting coated papers were placed together and a sealing pressure of 5 kg / cm was applied. ２ The adhesive paper (test piece) is subjected to a T-peel test (tensile speed: 300 mm / min) in accordance with JIS Z 0238 (1998), and the highest temperature at which interfacial peeling occurs without tearing of the paper is defined as the blocking resistance temperature. Item 6. The method according to any one of Items 1 to 5, wherein, in two or more polymers having different contents of structural units derived from acrylic acid, the content of structural units derived from acrylic acid in the copolymer (copolymer A) having the largest content of structural units derived from acrylic acid is defined as α% by mass, and the content of structural units derived from acrylic acid in the copolymer (copolymer B) having the smallest content of structural units derived from acrylic acid is defined as β% by mass, and the value of (α-β) is 0.5 to 50.

[0007] Provided is an aqueous resin dispersion composition capable of forming a film having excellent blocking resistance.

[0008] Each embodiment included in the present disclosure will be described in more detail below. The present disclosure preferably includes, but is not limited to, a method for producing a resin aqueous dispersion composition by mixing two or more "polymers containing structural units derived from acrylic acid" that differ in the content of structural units derived from acrylic acid, and then adding a neutralizing agent and water to the mixture. The present disclosure encompasses all methods disclosed herein and recognizable by those skilled in the art. The method for producing the resin aqueous dispersion composition may also be referred to as the manufacturing method of the present disclosure. The manufacturing method of the present disclosure includes a method comprising: (A) a step of mixing two or more "polymers containing structural units derived from acrylic acid" that differ in the content of structural units derived from acrylic acid to obtain a mixed polymer composition; and (B) a step of mixing the mixed polymer composition, the neutralizing agent, and water. These steps may be referred to as step (A) and step (B). The mixing in step (B) can produce an aqueous dispersion composition. The manufacturing method of the present disclosure also preferably includes a method comprising a step of mixing the mixed polymer composition containing the two or more "polymers containing structural units derived from acrylic acid" with a neutralizing agent and water to obtain an aqueous dispersion composition. The mixed polymer composition can be obtained by the step (A).

[0009] The polymer containing structural units derived from acrylic acid is an acrylic acid polymer (polyacrylic acid) or a copolymer containing structural units derived from acrylic acid and structural units derived from monomers other than acrylic acid (other monomer components). Examples of other monomer components include α,β-unsaturated carboxylic acids such as methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, as well as ethylene, propylene, butene, isobutene, butadiene, isoprene, and styrene. These other monomer components can be used alone or in combination of two or more. Among other monomer components, ethylene is more preferred. That is, copolymers containing structural units derived from acrylic acid and structural units derived from ethylene are particularly preferred. Copolymers containing structural units derived from acrylic acid and structural units derived from ethylene may also contain structural units derived from one or more other monomer components. For convenience, an acrylic acid polymer (polyacrylic acid) is considered to be an acrylic acid copolymer containing 0% by mass of structural units derived from other monomer components, and a polymer containing structural units derived from acrylic acid used in the production method of the present disclosure may be referred to as the acrylic acid copolymer of the present disclosure. In other words, the "acrylic acid copolymer of the present disclosure" encompasses acrylic acid polymers (polyacrylic acids). The acrylic acid copolymer of the present disclosure preferably contains 1 to 100 mass% of structural units derived from acrylic acid. The upper and lower limits of this range are 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, The range may be, for example, 2 to 80% by mass, or 3 to 50% by mass.The content (mass%) of structural units derived from acrylic acid in the acrylic acid copolymer of the present disclosure can be calculated from the amount of acrylic acid relative to the total amount of monomers contributing to the constitution of the copolymer.

[0010] Among the acrylic acid copolymers of the present disclosure, copolymers containing structural units derived from acrylic acid and structural units derived from ethylene (in other words, copolymers containing at least ethylene and acrylic acid as monomers) are particularly preferred. As described above, the copolymer may contain structural units other than structural units derived from ethylene and structural units derived from acrylic acid. Examples of such structural units include structural units derived from α,β-unsaturated carboxylic acids such as methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, as well as structural units derived from propylene, butene, isobutene, butadiene, isoprene, and styrene. When these are used, they may be used alone or in combination of two or more. Although not particularly limited, of all structural units of a copolymer containing structural units derived from acrylic acid and structural units derived from ethylene, the total proportion of structural units derived from acrylic acid and structural units derived from ethylene is preferably 80 mol% or more, and more preferably 85, 90, 95, 96, 97, 98, or 99 mol% or more of structural units derived from acrylic acid and structural units derived from ethylene. The total of the structural units derived from acrylic acid and the structural units derived from ethylene may be 100 mol % or more (that is, ethylene / acrylic acid copolymer: EAA).

[0011] Although not particularly limited, the acrylic acid copolymer of the present disclosure preferably has a melt index of about 10 to 500 g / 10 min. A melt index of 10 g / 10 min or more makes it easier to emulsify, and a melt index of 500 g / 10 min or less makes it less sticky and easier to handle. The upper or lower limit of the range may be, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, or 490 g / 10 min. The range may be, for example, 20 to 450 g / 10 min or 40 to 400 g / 10 min. In the present disclosure, the melt index is a value obtained by heating and pressurizing a resin placed in a cylindrical extrusion-type plastometer at a constant temperature (190°C) and measuring the amount of resin extruded from the opening at the bottom of the container in 10 minutes.

[0012] In step (A), two or more (preferably 2, 3, 4, or 5, more preferably 2 or 3, and even more preferably 2) polymers that correspond to the acrylic acid copolymer of the present disclosure and have different contents of structural units derived from acrylic acid are mixed. By mixing, a composition in which two or more acrylic acid copolymers of the present disclosure are mixed is obtained. This composition is sometimes referred to as a mixed polymer composition. The two or more acrylic acid copolymers of the present disclosure to be mixed are not particularly limited, but, with the exception of polyacrylic acid, are preferably copolymers in which at least one structural unit other than the structural unit derived from acrylic acid is common, and more preferably copolymers in which all structural units are common. That is, if one of the acrylic acid copolymers of the present disclosure to be mixed is, for example, a copolymer containing structural units derived from acrylic acid and structural units derived from ethylene, it is preferable that the remaining one or more acrylic acid copolymers of the present disclosure to be mixed are also copolymers containing structural units derived from acrylic acid and structural units derived from ethylene; and further, if one of the acrylic acid copolymers of the present disclosure to be mixed is, for example, an ethylene / acrylic acid copolymer, it is more preferable that the remaining one or more acrylic acid copolymers of the present disclosure to be mixed are also ethylene / acrylic acid copolymers.

[0013] The content of the acrylic acid-derived structural units in the mixed polymer composition is preferably, for example, about 1 to 50% by mass. The upper or lower limit of this range may be, for example, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, or 49% by mass. For example, this range may be 2 to 30% by mass, 3 to 25% by mass, or 5 to 20% by mass. The content of the acrylic acid-derived structural units in the mixed polymer composition can be calculated based on the content of the acrylic acid-derived structural units in each of the two or more acrylic acid copolymers of the present disclosure used in the blending. Furthermore, when the acrylic acid-derived structural unit content of the copolymer having the largest acrylic acid-derived structural unit content (referred to as copolymer A) of the two or more acrylic acid copolymers of the present disclosure to be mixed is α% by mass, and the acrylic acid-derived structural unit content of the copolymer having the smallest acrylic acid-derived structural unit content (referred to as copolymer B) is β% by mass, it is more preferable that the value of (α-β) is 0.5 to 50. The upper or lower limit of the range of the (α-β) value may be, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, or 49. The range may be, for example, about 1 to 30, more preferably about 2 to 20, and even more preferably about 3 to 10. For example, when equal amounts of copolymer A and copolymer B are mixed, the acrylic acid content (% by mass) of the resulting mixed polymer composition is calculated by α×½ + β×½. Furthermore, when copolymer A and copolymer B are mixed in a mass ratio of 1:2, the acrylic acid content (% by mass) of the resulting mixed polymer composition is calculated by α×½ + β×½.

[0014] In step (A), two or more types of acrylic acid copolymers of the present disclosure are preferably mixed, and other components may be further contained within a range that does not particularly impair the effects of the invention according to the present disclosure. However, since it is preferable that two or more types of acrylic acid copolymers of the present disclosure are mixed uniformly, even if other components are contained, it is preferable that the amount thereof is relatively small. Examples of such other components include a neutralizing agent, a surfactant, water, etc. When a neutralizing agent is used as the other component, it is preferable that the neutralizing agent is the same component as the neutralizing agent used in step (B). Furthermore, when a surfactant is used as the other component, it is preferable that the surfactant is the same component as the surfactant that can be used as necessary in step (B).

[0015] The mixing method is not particularly limited, but a method in which two or more types of acrylic acid copolymers of the present disclosure are mixed uniformly is preferred. Examples of mixing methods include a method in which two or more types of acrylic acid copolymers of the present disclosure are dissolved in a solvent and then the solvent is removed, and a method in which the copolymers are kneaded together (mixed while kneading). Among the kneading methods, melt kneading (preferably, kneading while melting the copolymers at a temperature equal to or higher than the melting points of all the copolymers to be mixed) is preferred. Specific kneading means include a single-screw or multiple-screw extruder, a kneader, and the like. As a multiple-screw extruder, a twin-screw or four-screw extruder is preferred, and a twin-screw extruder is more preferred. In particular, when melt kneading is performed, for example, a single-screw or multiple-screw extruder (particularly a twin-screw extruder) is preferred. Furthermore, the temperature when melt kneading is preferably a temperature equal to or higher than the melting point of the acrylic acid copolymer of the present disclosure having the highest melting point among the two or more acrylic acid copolymers of the present disclosure used. Specific temperatures vary depending on the melting points of the two or more acrylic acid copolymers of the present disclosure used, but may be, for example, about 100 to 250°C. The upper or lower limit of this range (100 to 250°C) may be, for example, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, or 245°C. For example, this range is preferably about 110 to 220°C or about 120 to 180°C. The mixing (preferably melt-kneading) time is not particularly limited as long as it is within a range that does not impair the effects of the invention according to the present disclosure, and can be set appropriately. Depending on the mixing means used, for example, about 1 to 60 minutes is an example.

[0016] In step (B), the mixed polymer composition, neutralizing agent, and water are mixed. The mixing means is not particularly limited as long as it is capable of mixing these components to produce an aqueous dispersion, and known means can be used. Examples include a single-screw or multiple-screw (e.g., twin-screw or four-screw) extruder, an autoclave equipped with a stirring means (e.g., a stirring blade), a kneader, and the like. Among these, a twin-screw extruder is particularly preferred. The mixing in step (B) produces an aqueous dispersion composition containing a polymer containing structural units derived from acrylic acid and a neutralizing agent. This aqueous dispersion composition is sometimes referred to as the aqueous dispersion composition of the present disclosure. Examples of preferred neutralizing agents include ammonia, organic amines, and alkali metal salts. Examples of preferred organic amines include diisopropanolamine, 2-amino-2-methyl-1-propanol, and triethanolamine. Examples of preferred alkali metal salts include sodium hydroxide and potassium hydroxide. Among neutralizing agents, ammonia is particularly preferred. Neutralizing agents can be used alone or in combination. The amount of neutralizing agent used can be set, for example, so that the degree of neutralization of the acrylic acid copolymer of the present disclosure in the mixed polymer composition (the mole percent of the acrylic acid moieties in the polymer that are neutralized) is about 25 to 65%. The upper or lower limit of this range may be, for example, 30, 35, 40, 45, 50, 55, or 60%. For example, the range may be about 30 to 60%.

[0017] The amount of water used is not particularly limited, but is set to, for example, 10 to 1,000 parts by mass, and preferably 10 to 250 parts by mass, per 100 parts by mass of the mixed polymer composition. By using an aqueous medium in such a range, an aqueous dispersion composition with good dispersion stability can be obtained. Furthermore, an aqueous dispersion composition with excellent productivity and practicality can be obtained.

[0018] In step (B), the resulting aqueous dispersion composition may further contain other components as long as the effects of the present invention are not particularly impaired. Examples of such other components include surfactants, defoamers, viscosity modifiers, pH adjusters, antifungal agents, antioxidants, blocking improvers such as fatty acid amides, waxes, and silicone oils, and alcohols. The mixing means in step (A) and the mixing means in step (B) may be the same or different. An example of using different mixing means is to perform the mixing in step (A) using a multi-screw extruder (particularly a twin-screw extruder), transfer the resulting mixed polymer composition to an autoclave equipped with a stirring means, and then perform the mixing in step (B) using the autoclave equipped with a stirring means. An example of using the same mixing means is to perform the mixing in step (A) using a multi-screw extruder (particularly a twin-screw extruder), and then mix the resulting mixed polymer composition directly with a neutralizing agent and water downstream of the multi-screw extruder, thereby performing the mixing in step (B). More specifically, for example, when a twin-screw extruder is used as the mixing means in step (A), two or more types of the acrylic acid copolymer of the present disclosure (and other components as needed) are fed from the upstream side (e.g., a first feed port) and melt-kneaded, and then a neutralizing agent and water (and other components as needed) are fed from the downstream side (e.g., a second feed port) and mixed, thereby producing an aqueous dispersion composition.

[0019] As described above, the aqueous dispersion composition of the present disclosure can form a film that exhibits excellent blocking resistance. More specifically, the aqueous dispersion composition of the present disclosure has a basis weight of 52 g / m ２ Dry coating amount 5.0 g / m on high-quality paper ２ When the coated surfaces of the resulting coated papers were placed together, a sealing pressure of 5 kg / cm was applied. ２The adhesive paper (test piece) is subjected to a T-peel test (tensile speed: 300 mm / min) in accordance with JIS Z 0238 (1998), and the maximum temperature at which interfacial peeling occurs without tearing the paper is preferably 70°C or higher, more preferably 70 to 90°C, even more preferably 70 to 85°C, and particularly preferably 70 to 80°C.

[0020] In addition, the aqueous dispersion composition of the present disclosure also has excellent dispersibility of the resin (i.e., the acrylic acid copolymer of the present disclosure). More specifically, when the aqueous dispersion composition of the present disclosure is filtered through an 80-mesh polyethylene screen and the residue is heat-dried at 60°C for 2 hours, the amount of the resulting dried residue is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass, based on the total amount of the acrylic acid copolymer of the present disclosure used in producing the aqueous dispersion composition.

[0021] In the aqueous dispersion composition of the present disclosure, the content of the acrylic acid copolymer of the present disclosure is preferably approximately 10 to 40% by mass, although there are no particular limitations as long as the effects of the present invention are not impaired. The upper or lower limit of this 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, 34, 35, 36, 37, 38, or 39% by mass. For example, this range may be 15 to 35% by mass or 20 to 30% by mass. The aqueous dispersion composition of the present disclosure may contain other components as long as the effects of the present invention are not impaired. For example, it may contain defoamers, viscosity modifiers, pH adjusters, surfactants, antifungal agents, etc., and, if necessary, antioxidants, blocking improvers such as fatty acid amides, waxes, and silicone oils, alcohols, etc. The aqueous dispersion composition of the present disclosure is useful, for example, as a binder or coating agent. The composition of the present disclosure can be applied to a substrate and dried to form a film. A preferred example of the substrate is paper, and more preferably food and beverage packaging paper. The film can prevent food and beverage from coming into direct contact with the paper (packaging paper). Furthermore, the film is preferable because it has little adverse effect on the food and beverage. The present disclosure also preferably includes, for example, a laminate including a substrate (preferably paper) and a film on the substrate, wherein the film is formed by coating the aqueous dispersion composition of the present disclosure on the substrate.

[0022] In this specification, the term "comprising" includes "consisting essentially of" and "consisting of." Furthermore, the present disclosure encompasses any and all combinations of the constituent elements described in this specification. Furthermore, the various characteristics (properties, structures, functions, etc.) described for each embodiment of the present disclosure above may be combined in any way to specify the subject matter encompassed by the present disclosure. In other words, the present disclosure encompasses all subject matter comprised of any and all combinations of the combinable characteristics described in this specification.

[0023] Hereinafter, the embodiments of the present disclosure will be described more specifically with reference to examples, but the embodiments of the present disclosure are not limited to the following examples.

[0024] Preparation of aqueous dispersion composition (Example 1) A hopper was installed at the upstream tip of a twin-screw extruder (model: MFU15 (manufactured by Technovel Co., Ltd.), shaft diameter: 15 mm, L / D: 90), and ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid 20.0% by mass, melt index 300 g / 10 min) was mixed and charged at 0.7 kg / hr, and ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid 15.0% by mass, melt index 60 g / 10 min) was mixed and charged at 0.3 kg / hr. After melt-kneading at a cylinder temperature of 140 ° C. and a rotation speed of 300 rpm, a 2% by mass aqueous ammonia solution at 25 ° C. was used as a neutralizing agent from a second supply port provided at a position 530 mm from the upstream tip of the twin-screw extruder using a plunger pump. Kneading and emulsification were carried out from the upstream tip of the twin-screw extruder to a third supply port located 1,175 mm away at a cylinder temperature of 90°C and a rotation speed of 300 rpm, and then pure water was supplied from the third supply port using a plunger pump at a rate of 2.0 kg / hr. Kneading was carried out from the third supply port to the outlet of the twin-screw extruder at a cylinder temperature of 90°C and a rotation speed of 300 rpm, and then the mixture was discharged from the twin-screw extruder, yielding an aqueous dispersion composition of ethylene / acrylic acid copolymer with an acrylic acid-derived structural unit content of 18.5% by mass.

[0025] (Example 2) A hopper was installed at the upstream tip of a twin-screw extruder (model: MFU15 (manufactured by Technovel Co., Ltd.), shaft diameter: 15 mm, L / D: 90), and ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 20.0% by mass, melt index: 300 g / 10 min) was mixed and charged at 0.5 kg / hr, and ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 15.0% by mass, melt index: 60 g / 10 min) was mixed and charged at 0.5 kg / hr. After melt-kneading at a cylinder temperature of 140 ° C. and a rotation speed of 300 rpm, a 2% by mass aqueous ammonia solution at 25 ° C. was used as a neutralizing agent and fed at 1.00 kg / hr using a plunger pump from a second feed port provided at a position 530 mm from the upstream tip of the twin-screw extruder. Kneading and emulsification were carried out from the upstream tip of the twin-screw extruder to a third supply port provided at a position 1,175 mm from the tip at the upstream side at conditions of a cylinder temperature of 90°C and a rotation speed of 300 rpm, and then pure water was supplied from the third supply port using a plunger pump at a rate of 2.0 kg / hr. Kneading was carried out from the third supply port to the outlet of the twin-screw extruder at conditions of a cylinder temperature of 90°C and a rotation speed of 300 rpm, and then the mixture was discharged from the twin-screw extruder, yielding an aqueous dispersion composition of ethylene / acrylic acid copolymer having an acrylic acid-derived structural unit content of 17.5% by mass.

[0026] (Example 3) A hopper was installed at the upstream tip of a twin-screw extruder (model: MFU15 (manufactured by Technovel Co., Ltd.), shaft diameter: 15 mm, L / D: 90), and ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 20.0% by mass, melt index: 300 g / 10 min) was mixed and charged at 0.3 kg / hr, and ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 15.0% by mass, melt index: 60 g / 10 min) was mixed and charged at 0.7 kg / hr. After melt-kneading at a cylinder temperature of 140 ° C. and a rotation speed of 300 rpm, a 2% by mass aqueous ammonia solution at 25 ° C. was used as a neutralizing agent and fed at 1.00 kg / hr using a plunger pump from a second feed port provided at a position 530 mm from the upstream tip of the twin-screw extruder. Kneading and emulsification were carried out from the upstream tip of the twin-screw extruder to a third supply port provided at a position 1,175 mm from the tip at the upstream side at conditions of a cylinder temperature of 90°C and a rotation speed of 300 rpm, and then pure water was supplied from the third supply port using a plunger pump at a rate of 2.0 kg / hr. Kneading was carried out from the third supply port to the outlet of the twin-screw extruder at conditions of a cylinder temperature of 90°C and a rotation speed of 300 rpm, and then the mixture was discharged from the twin-screw extruder, yielding an aqueous dispersion composition of ethylene / acrylic acid copolymer with an acrylic acid-derived structural unit content of 16.5% by mass.

[0027] Example 4 A hopper was installed at the upstream tip of a twin-screw extruder (model: KZW15 (manufactured by Technovel Co., Ltd.), shaft diameter: 15 mm, L / D: 45), and an ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 20.0% by mass, melt index: 300 g / 10 min) was mixed and charged at 0.7 kg / hr and an ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 15.0% by mass, melt index: 60 g / 10 min) was mixed and charged at 0.3 kg / hr. After melt-kneading at a cylinder temperature of 120 ° C. and a rotation speed of 50 rpm, the resin discharged from the twin-screw extruder was cooled in a water bath at 25 ° C. and cut into pellets using a pelletizer to obtain an ethylene / acrylic acid copolymer having a structural unit content of 18.5% by mass derived from acrylic acid. A 1000 ml pressure vessel (autoclave) equipped with a stirrer was charged with 75 g of the obtained copolymer, 5.38 g of 28% by weight aqueous ammonia as a neutralizing agent, and 115.1 g of water, and sealed. Then, while stirring at 500 rpm, the temperature was raised from 25 ° C to 95 ° C, and the vessel was maintained at 95 ° C and stirred for 4 hours. The mixture was then cooled to 90 ° C at room temperature, and 104.5 g of pure water was added. The mixture was then cooled to 50 ° C at room temperature, and the contents were filtered through a polyethylene 80-mesh screen to obtain an aqueous dispersion composition of ethylene / acrylic acid copolymer with a content of 18.5% by weight of structural units derived from acrylic acid.

[0028] Example 5 A hopper was installed at the upstream tip of a twin-screw extruder (model: KZW15 (manufactured by Technovel Co., Ltd.), shaft diameter: 15 mm, L / D: 45), and an ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 20.0% by mass, melt index: 300 g / 10 min) was mixed and charged at 0.5 kg / hr, and an ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 15.0% by mass, melt index: 60 g / 10 min) was mixed and charged at 0.5 kg / hr. After melt-kneading at a cylinder temperature of 120 ° C. and a rotation speed of 50 rpm, the resin discharged from the twin-screw extruder was cooled in a water bath at 25 ° C., and the resin was cut into pellets using a pelletizer to obtain an ethylene / acrylic acid copolymer having a structural unit content of 17.5% by mass derived from acrylic acid. A 1000 ml pressure vessel (autoclave) equipped with a stirrer was charged with 75 g of the obtained copolymer, 5.36 g of 28% by weight aqueous ammonia as a neutralizing agent, and 114.8 g of water, and sealed. Then, while stirring at 500 rpm, the temperature was raised from 25 ° C to 95 ° C, and the vessel was maintained at 95 ° C and stirred for 4 hours. The mixture was then cooled to 90 ° C at room temperature, and 104.9 g of pure water was added. The mixture was then cooled to 50 ° C at room temperature, and the contents were filtered through a polyethylene 80-mesh screen to obtain an aqueous dispersion composition of ethylene / acrylic acid copolymer with a content of 17.5% by weight of structural units derived from acrylic acid.

[0029] (Example 6) A hopper was installed at the upstream tip of a twin-screw extruder (model: KZW15 (manufactured by Technovel Co., Ltd.), shaft diameter: 15 mm, L / D: 45), and an ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 20.0% by mass, melt index: 300 g / 10 min) was mixed and charged at 0.3 kg / hr, and an ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid: 15.0% by mass, melt index: 60 g / 10 min) was mixed and charged at 0.7 kg / hr. After melt-kneading at a cylinder temperature of 120 ° C. and a rotation speed of 50 rpm, the resin discharged from the twin-screw extruder was cooled in a water bath at 25 ° C., and the resin was cut into pellets using a pelletizer to obtain an ethylene / acrylic acid copolymer having a content of structural units derived from acrylic acid of 16.5% by mass. A 1000 ml pressure vessel (autoclave) equipped with a stirrer was charged with 75 g of the obtained copolymer, 5.37 g of 28% by weight aqueous ammonia as a neutralizing agent, and 114.9 g of water, and sealed. Then, while stirring at 500 rpm, the temperature was raised from 25 ° C to 95 ° C, and the vessel was maintained at 95 ° C and stirred for 4 hours. The mixture was then cooled to 90 ° C at room temperature, and 104.7 g of pure water was added. The mixture was then cooled to 50 ° C at room temperature, and the contents were filtered through an 80-mesh polyethylene screen to obtain an aqueous dispersion composition of ethylene / acrylic acid copolymer with a content of 16.5% by weight of structural units derived from acrylic acid.

[0030] (Comparative Example 1) 52.5 g of ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid 20.0% by mass, melt index 300 g / 10 min), 22.5 g of ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid 15.0% by mass, melt index 60 g / 10 min), 5.38 g of 28 mass% ammonia water as a neutralizing agent, and 115.1 g of water were charged into a 1000 ml pressure-resistant vessel (autoclave) equipped with a stirrer, and the vessel was sealed. Then, while stirring at 500 revolutions per minute, the temperature was raised from 25 ° C. to 95 ° C., and the vessel was kept at 95 ° C. and stirred for 4 hours. Next, the mixture was allowed to cool at room temperature to 90 ° C., and 104.5 g of pure water was added. Thereafter, the contents were allowed to cool at room temperature to 50°C, and filtered through an 80-mesh polyethylene mesh to obtain an aqueous dispersion composition of ethylene / acrylic acid copolymer having a content of structural units derived from acrylic acid of 18.5% by mass.

[0031] (Comparative Example 2) 37.5 g of ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid 20.0% by mass, melt index 300 g / 10 min), 37.5 g of ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid 15.0% by mass, melt index 60 g / 10 min), 5.36 g of 28 mass% ammonia water as a neutralizing agent, and 114.8 g of water were charged into a 1000 ml pressure-resistant vessel (autoclave) equipped with a stirrer, and the vessel was sealed. Then, while stirring at 500 revolutions per minute, the temperature was raised from 25 ° C. to 95 ° C., and the vessel was kept at 95 ° C. and stirred for 4 hours. Next, the mixture was allowed to cool at room temperature to 90 ° C., and 104.9 g of pure water was added. Thereafter, the contents were allowed to cool at room temperature to 50°C, and the contents were filtered through an 80-mesh polyethylene mesh to obtain an aqueous dispersion composition of ethylene / acrylic acid copolymer having a content of structural units derived from acrylic acid of 17.5% by mass.

[0032] (Comparative Example 3) In a 1000 ml pressure vessel (autoclave) equipped with a stirrer, 22.5 g of ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid 20.0% by mass, melt index 300 g / 10 min), 52.5 g of ethylene / acrylic acid copolymer (content of structural units derived from acrylic acid 15.0% by mass, melt index 60 g / 10 min), 5.37 g of 28 mass% ammonia water as a neutralizing agent, and 114.9 g of water were charged and sealed. Then, while stirring at 500 revolutions per minute, the temperature was raised from 25 ° C to 95 ° C, and the inside of the vessel was kept at 95 ° C and stirred for 4 hours. Next, it was cooled to 90 ° C at room temperature, and 104.7 g of pure water was added. Thereafter, the contents were cooled to 50°C at room temperature and filtered through an 80-mesh polyethylene mesh to obtain an aqueous dispersion of an ethylene / acrylic acid copolymer having a content of structural units derived from acrylic acid of 16.5% by mass.

[0033] (1) The aqueous dispersion compositions prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were coated onto coated paper sheets with a basis weight of 52 g / m ２ Wet coating amount 10g / m on high-quality paper ２ , Dry coating amount 2.5g / m ２ (2) The coated paper obtained in (1) above was dried by heating at 125°C for 2 minutes using a heating dryer (DRE320DR manufactured by ADVANTEC). (3) The aqueous dispersion composition was again applied to the coated surface of the coated paper obtained in (2) above using the same procedure as in (1). (4) The coated paper obtained in (3) above was dried under the same drying conditions as in (2) above, to a final dry coating amount of 5.0 g / m. ２ Thus, a coated paper having the following properties was obtained.

[0034] Measurement method [Blocking resistance] Two sheets of the prepared coated paper were stacked with their coated surfaces facing each other, and the blocking resistance was measured using a heat seal tester manufactured by Tester Sangyo Co., Ltd. at a sealing pressure of 5 kg / cm. ２The test pieces were bonded at a sealing time of 2 hours and sealing temperatures of 60, 65, 70, 75, and 80°C. A T-peel test was performed on each of the test pieces prepared according to JIS Z 0238 (1998). The highest temperature at which the paper was not torn and the interfacial peeling occurred was determined as the blocking resistance temperature for the test pieces prepared at sealing temperatures of 60, 65, 70, 75, and 80°C. The higher the blocking resistance temperature, the higher the blocking resistance. The T-peel test was performed using an autograph (AGS-X model manufactured by Shimadzu Corporation) with a tensile speed set to 300 mm / min.

[0035] [Residue Rate] The produced aqueous dispersion composition was filtered through an 80-mesh polyethylene mesh, and the residue was dried by heating at 60°C for 2 hours in a heating dryer (DRE320DR manufactured by ADVANTEC). The weight of the dried residue was measured, and the residue rate was calculated using the following formula: Residue rate (mass%) = dried residue mass / charged resin mass × 100

[0036] The results are summarized in Table 1.

[0037] According to the present disclosure, a method for producing an aqueous dispersion composition capable of forming a film exhibiting excellent blocking resistance can be provided. Such an aqueous dispersion composition can be said to be a material that meets the recent global demand for reducing the amount of plastic used and is environmentally friendly.

Claims

1. A method for producing an aqueous dispersion composition comprising two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers differing in the content of structural units derived from acrylic acid, the method comprising: a step of melt-kneading the two or more polymers to obtain a mixed polymer composition; and a step of mixing the mixed polymer composition, the neutralizing agent, and water after the melt-kneading step.

2. A method for producing an aqueous dispersion composition containing two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers with different contents of structural units derived from acrylic acid, the method comprising: a step of melt-kneading the two or more polymers in a twin-screw extruder to obtain a mixed polymer composition; and a step of mixing the mixed polymer composition, the neutralizing agent, and water.

3. A method for producing an aqueous dispersion composition containing two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers differing in the content of structural units derived from acrylic acid, the method comprising: a step of mixing the two or more polymers to obtain a mixed polymer composition; and a step of mixing the mixed polymer composition, the neutralizing agent, and water to obtain an aqueous dispersion composition, wherein the aqueous dispersion composition is an aqueous dispersion composition in which the blocking resistance temperature of coated paper coated with the aqueous dispersion composition is 70°C or higher when measured under the following conditions. [Measurement conditions] The aqueous dispersion composition to be measured is an aqueous dispersion composition having a basis weight of 52 g / m ２ Dry coating amount 5.0 g / m on high-quality paper ２ The coated surfaces of the resulting coated papers were placed together and a sealing pressure of 5 kg / cm was applied. ２ The adhesive paper (test piece) obtained is subjected to a T-peel test (tensile speed: 300 mm / min) in accordance with JIS Z 0238 (1998), and the highest temperature at which the paper undergoes interfacial peeling without tearing is taken as the blocking resistance temperature.

4. A method for producing an aqueous dispersion composition containing two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers differing in the content of structural units derived from acrylic acid, the method comprising the step of mixing a composition in which the two or more polymers are melt-kneaded, the neutralizing agent, and water.

5. A method for producing an aqueous dispersion composition containing two or more polymers containing structural units derived from acrylic acid and a neutralizing agent, wherein the two or more polymers are two or more polymers differing in the content of structural units derived from acrylic acid, and the method comprises a step of mixing a composition containing the two or more polymers, the neutralizing agent, and water to obtain an aqueous dispersion composition, wherein the aqueous dispersion composition is an aqueous dispersion composition in which the blocking resistance temperature of coated paper coated with the aqueous dispersion composition is 70°C or higher when measured under the following conditions: [Measurement conditions] The aqueous dispersion composition to be measured is mixed with a paper having a basis weight of 52 g / m ２ Dry coating amount 5.0 g / m on high-quality paper ２ The coated surfaces of the resulting coated papers were placed together and a sealing pressure of 5 kg / cm was applied. ２ The adhesive paper (test piece) obtained is subjected to a T-peel test (tensile speed: 300 mm / min) in accordance with JIS Z 0238 (1998), and the highest temperature at which the paper undergoes interfacial peeling without tearing is taken as the blocking resistance temperature.

6. The method according to any one of claims 1 to 5, wherein, in two or more polymers having different contents of structural units derived from acrylic acid, the value of (α - β) is 0.5 to 50, where α is the content of structural units derived from acrylic acid in the copolymer having the largest content of structural units derived from acrylic acid and β is the content of structural units derived from acrylic acid in the copolymer having the smallest content of structural units derived from acrylic acid.

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