Film-forming aid and aqueous emulsion composition containing the same

Abstract

To provide a film-forming aid that can sufficiently lower the lowest film-forming temperature of an aqueous emulsion composition even with a small amount of addition of the film-forming aid.SOLUTION: A film-forming aid comprises a compound represented by formula (1): R1-O-(CH2-CH(R3)-O)n-R2, where R1 and R2 each denote a C1-8 linear or branched alkyl group, where at least one of R1 and R2 is a C3-8 branched alkyl group, with the total number of carbon atoms of R1 and R2 being 6 or more, R3 is hydrogen, a methyl group or an ethyl group, and n denotes an average added mol number of -(CH2-CH(R3)-O)-, which is a number from 2 to 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film-forming aid and an aqueous emulsion composition containing the same. [Background technology]

[0002] Traditionally, in the field of paints, so-called organic solvent-based paints, which are used by evaporating organic solvents such as toluene and xylene to form a film, have been the mainstream. However, from the standpoint of occupational safety and reduction of environmental pollution, there is a strong desire to shift to water-based paints. A representative example of water-based paints is a paint using an aqueous emulsion composition (hereinafter referred to as "aqueous emulsion composition" or "aqueous emulsion paint"), in which resin particles are dispersed in an aqueous medium. Regarding the film formation mechanism of aqueous emulsion paints that use an aqueous medium as a solvent, in organic solvent-based paints, a continuous film is formed by the evaporation of the organic solvent, whereas in aqueous emulsion paints, a continuous film is not formed by the evaporation of water alone. After the evaporation of water, the resin particles come into contact with each other, deform and fuse together, and a smooth film without gaps is formed. At this time, additives called film-forming aids are generally used to promote the fusion of resin particles. Film-forming aids also have the effect of lowering the minimum film-forming temperature (MFT) of the paint and improving film-forming properties.

[0003] Currently, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol (registered trademark, the same hereinafter)) is widely used as a film-forming aid. Patent Document 1 also discloses that an alkylene glycol dialkyl ether having a boiling point of 150 to 220 °C is added to an acrylic resin dispersion to prepare an aqueous acrylic resin dispersion (corresponding to a paint). As the alkylene glycol dialkyl ether having a boiling point of 150 to 220 °C, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether are disclosed. On the other hand, this document also discloses a comparative example in which diethylene glycol di-n-butyl ether having a boiling point of 255 °C is used as a film-forming aid as an alkylene glycol dialkyl ether having a boiling point other than 150 to 220 °C.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol) or the alkylene glycol dialkyl ether described in Patent Document 1 is used as a film-forming aid, there is still room for improvement in reducing the minimum film-forming temperature of the aqueous emulsion paint. That is, in this case, in order to sufficiently lower the minimum film-forming temperature of the aqueous emulsion paint, a relatively large amount of the film-forming aid must be added, which causes a problem of adversely affecting the hardness and smoothness of the formed paint film.

[0006] Therefore, an object of the present invention is to provide a film-forming aid that can sufficiently lower the minimum film-forming temperature of an aqueous emulsion composition even with a small addition amount. [Means for solving the problem]

[0007] As a result of diligent research, the inventors of this invention have found the following formula (1):

[0008] [ka]

[0009] In the above equation (1), R 1 and R 2 R is a linear or branched alkyl group having 1 to 8 carbon atoms, and in this case, 1 and R 2 At least one of them is a branched alkyl group having 3 to 8 carbon atoms, and R 1 and R 2 The total number of carbon atoms is 6 or more. R 3 is hydrogen, a methyl group or an ethyl group, n is -(CH2-CH(R 3 This represents the average number of moles added (-O)-, and is a number between 2 and 4. We have discovered that the above problems can be solved by a film-forming aid containing the compound represented by [the formula shown], and have completed the present invention. [Effects of the Invention]

[0010] When the film-forming aid of the present invention is applied to an aqueous emulsion composition, the minimum film-forming temperature of the aqueous emulsion composition can be sufficiently lowered even when the amount of film-forming aid added is small. [Brief explanation of the drawing]

[0011] [Figure 1] This graph plots the relationship between the amount of each film-forming aid added to the aqueous emulsion composition of acrylic resin, as evaluated in the Examples section, and the minimum film-forming temperature. [Figure 2]A graph plotting the relationship between the addition amount of each film-forming aid to the aqueous emulsion composition of the acrylic styrene resin and the minimum film-forming temperature, evaluated in the Examples section. [Figure 3] A photographed image taken by a digital camera of a coating film formed from an aqueous emulsion composition of an acrylic resin, evaluated in the Examples section.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited only to the following embodiments. In this specification, “(meth)acrylate” is a general term for acrylate and methacrylate. Similarly, compounds containing “(meth)” such as (meth)acrylic, etc. are also general terms for compounds having “meth” in their names and compounds not having “meth”. Further, unless otherwise specified, “%” and “parts” mean “mass %” and “parts by mass” respectively, and “boiling point” means the boiling point at normal pressure. Also, in the following examples, unless otherwise specified, the operations were carried out under the conditions of room temperature (25 ° C.) / relative humidity 40 - 50% RH.

[0013] <Film-Forming Aid> The film-forming aid of the present invention contains a compound represented by the following formula (1).

[0014]

Chemical Formula

[0015] In the above formula (1), R 1 and R 2 are linear or branched alkyl groups having 1 to 8 carbon atoms. At this time, at least one of R 1 and R 2 is a branched alkyl group having 3 to 8 carbon atoms, and the total number of carbon atoms of R 1 and R 2 is 6 or more, R 3 is hydrogen, a methyl group or an ethyl group, n is -(CH2-CH(R 3 This represents the average number of moles added (-O)-, and is a number between 2 and 4.

[0016] Furthermore, in one embodiment, the film-forming aid of the present invention includes a compound represented by formula (1) above that has a boiling point exceeding 220°C.

[0017] When this film-forming aid is applied to an aqueous emulsion composition, the minimum film-forming temperature of the aqueous emulsion composition can be sufficiently lowered even when the amount of the film-forming aid added is small. The mechanism by which this effect is achieved is unknown, but it is presumed to be as follows.

[0018] In aqueous emulsion compositions, a continuous film is not formed by the evaporation of water alone. After the evaporation of water, the resin particles come into contact with each other and fuse together, forming a smooth film without gaps. In this process, film-forming aids are used to promote the fusion of resin particles. However, when using currently commonly used film-forming aids, such as 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol) or alkylene glycol dialkyl ether described in Patent Document 1, a relatively large amount of the film-forming aid must be added to lower the minimum film-forming temperature of the aqueous emulsion composition. When an aqueous emulsion composition contains a large amount of film-forming aid, there is a problem that it adversely affects the hardness and smoothness of the formed coating film. This is thought to be because the coating film becomes plasticized due to the large amount of film-forming aid remaining in the coating film.

[0019] Therefore, the present inventors diligently studied the design of film-forming aids and found that the above problem can be solved by using a compound having at least one branched alkyl group with 3 to 8 carbon atoms at its terminal end, as represented by formula (1) above, as a film-forming aid. Generally, it is considered advantageous to use a hydrophobic film-forming aid because it penetrates the resin particles, swells the surface of the resin particles, promotes the fusion of resin particles after coating, and lowers the minimum film-forming temperature. However, when a hydrophobic film-forming aid is incorporated into an aqueous emulsion composition (paint), the resin particles dispersed in the aqueous medium become unstable and aggregate, which can make it difficult to coat the composition itself. In contrast, the compound represented by formula (1) above has an appropriate balance of an oxyalkylene group that imparts hydrophilicity and at least one branched alkyl group with 3 to 8 carbon atoms that imparts hydrophobicity. In particular, because the compound represented by formula (1) has a branched alkyl group with 3 to 8 carbon atoms at its terminal end, the film-forming aid containing the compound represented by formula (1) can efficiently reduce the surface tension of water in the aqueous emulsion composition. As a result, even with the addition of a small amount, the film-forming aid of the present invention can efficiently penetrate the resin particles, suppress the aggregation of the resin particles, and swell the surface of the resin particles. Furthermore, because the film-forming aid efficiently reduces the surface tension of water in the aqueous emulsion composition, the wettability of the aqueous emulsion composition to the object to be coated is improved. Therefore, the aqueous emulsion composition containing the film-forming aid of the present invention has good coatability on the object to be coated.

[0020] In other words, when an aqueous emulsion composition containing the film-forming aid of the present invention is applied to a substrate, the presence of the film-forming aid in the coating film allows it to penetrate the resin, and the resin particles, whose surfaces have swollen due to the action of the film-forming aid, easily fuse together in the coating film. At this time, the compound represented by formula (1) efficiently lowers the surface tension of water, allowing the film-forming aid to efficiently penetrate the resin particles and efficiently promote the swelling and fusion of the resin particles. As a result, even with the addition of only a small amount, the film-forming aid of the present invention can sufficiently lower the minimum film-forming temperature of the aqueous emulsion composition. Furthermore, since only a small amount of the film-forming aid of the present invention is needed to be added to the aqueous emulsion composition, the amount of film-forming aid remaining in the formed coating film is also small, which suppresses plasticization of the coating film. Therefore, the film-forming aid of the present invention minimizes adverse effects on the hardness and smoothness of the formed coating film. For this reason, for example, when the aqueous emulsion composition is used as a paint, the effect on the inherent properties of the paint (e.g., hardness, smoothness, etc.) can be minimized.

[0021] Furthermore, the present invention is not limited in any way to the mechanism described above.

[0022] As described above, the film-forming aid of the present invention contains a compound represented by the following formula (1). The film-forming aid may contain only one compound represented by the following formula (1), or two or more compounds. Hereinafter, the compound represented by the following formula (1) will also be referred to as "compound (1)".

[0023] [ka]

[0024] In the above equation (1), R 1 and R 2 R is a linear or branched alkyl group having 1 to 8 carbon atoms, and in this case, 1 and R 2 At least one of them is a branched alkyl group having 3 to 8 carbon atoms, and R 1 and R 2 The total number of carbon atoms is 6 or more.

[0025] Examples of linear or branched alkyl groups having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, tert-pentyl group, neopentyl group, 1,2-dimethylpropyl group, n-hexyl group, isohexyl group, 1,3-dimethylbutyl group, 1-isopropylpropyl group, 1,2-dimethylbutyl group, n-heptyl group, 1,4-dimethylpentyl group, 3-ethylpentyl group, 2-methyl-1-isopropylpropyl group, 1-ethyl-3-methylbutyl group, n-octyl group, 2-ethylhexyl group, 3-methyl-1-isopropylbutyl group, 2-methyl-1-isopropyl group, 1-t-butyl-2-methylpropyl group, and 3,5,5-trimethylpentyl group. The linear or branched alkyl group having 1 to 8 carbon atoms is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 5 carbon atoms.

[0026] In the present invention, R 1 and R 2 At least one of them is a branched alkyl group having 3 to 8 carbon atoms. 1 and R 2As the branched alkyl group having 3 to 8 carbon atoms that at least one of the above-mentioned alkyl groups may be used. Of these, from the viewpoint of further lowering the minimum film-forming temperature of the aqueous emulsion composition, isopropyl group, isobutyl group, tert-butyl group, 2-ethylhexyl group, tert-pentyl group, 1,2-dimethylpropyl group, 1,3-dimethylbutyl group, 1,2-dimethylbutyl group, 1,4-dimethylpentyl group, 3-ethylpentyl group, 2-methyl-1-isopropylpropyl group, and 1-ethyl-3-methylbutyl group are preferred as branched alkyl groups having 3 to 8 carbon atoms. More preferably isopropyl group, isobutyl group, and tert-butyl group. As the branched alkyl group having 3 to 8 carbon atoms, it is more preferable that it be a branched alkyl group having 3 to 5 carbon atoms. 1 and R 2 Either one of them may have a branched alkyl group having 3 to 8 carbon atoms, or both may have a branched alkyl group having 3 to 8 carbon atoms. 1 and R 2 If both have branched alkyl groups with 3 to 8 carbon atoms, R 1 and R 2 The group is preferably an isopropyl group, an isobutyl group, a tert-butyl group, or a 2-ethylhexyl group, and more preferably an isopropyl group, an isobutyl group, or a tert-butyl group. 1 and R 2 If one of them has a branched alkyl group with 3 to 8 carbon atoms, R 1 and R 2 The other is preferably a linear alkyl group having 1 to 6 carbon atoms, and more preferably a linear alkyl group having 1 to 5 carbon atoms. In one embodiment, from the viewpoint of further improving the effects of the present invention, R 1 and R 2 R is a linear or branched alkyl group having 1 to 5 carbon atoms, and in this case, 1 and R 2 At least one of them is a branched alkyl group having 3 to 5 carbon atoms.

[0027] In the present invention, R 1 and R 2 The total number of carbon atoms is 6 or more. R1 and R 2 The total number of carbon atoms is preferably 7 or more, and more preferably 8 or more, from the viewpoint of further lowering the minimum film-forming temperature of the aqueous emulsion composition. R1 and R 2 There is no particular upper limit to the total number of carbon atoms, and theoretically it is 16, but from the viewpoint of practical application, it is preferably 15 or less, more preferably 12 or less, and even more preferably 10 or less.

[0028] In the above equation (1), R 3 is hydrogen, a methyl group, or an ethyl group. Here, in formula (1), "-(CH2-CH(R 3 )-O)-" represents an oxyalkylene group, and "-(CH2-CH(R 3 )-O)-」 is, for example, R 3 When it is hydrogen, it represents an oxyethylene group (-(CH2CH2-O)-); R 3 If it is a methyl group, it represents an oxypropylene group (-(CH2-CH(CH3)-O)-); R 3 When is an ethyl group, it represents an oxybutylene group (-(CH2-CH(CH2CH3)-O)-). In one embodiment, from the viewpoint of further improving the effects of the present invention, R 3 It is either a hydrogen atom or a methyl group.

[0029] In the above equation (1), "-(CH2-CH(R 3 )-O) n The hyphen "-" represents a polyoxyalkylene chain. n is -(CH2-CH(R 3 n represents the average number of moles added (-O)-, and is a number between 2 and 4. From the viewpoint of further lowering the minimum film-forming temperature of the aqueous emulsion composition, n is preferably a number between 3 and 4.

[0030] In the above equation (1), -(CH2-CH(R 3 )-O) n-When -(CH2-CH(R 3 )-O) n If - has two or more oxyalkylene groups, the sequence may be random or blocky.

[0031] The boiling point of the compound represented by formula (1) contained in the film-forming aid of the present invention is not particularly limited, but it is desirable that it exceeds 220°C. A boiling point exceeding 220°C allows the film-forming aid to remain in the coating film even if water evaporates when a coating film is formed by the aqueous emulsion composition, enabling efficient swelling and fusion of resin particles. This allows the minimum film-forming temperature of the aqueous emulsion composition to be sufficiently lowered. The boiling point of the compound represented by formula (1) is preferably 225°C or higher, more preferably 230°C or higher, even more preferably 240°C or higher, particularly preferably 245°C or higher, and most preferably 250°C or higher. The intended effects of the present invention are further enhanced when the boiling point of the compound represented by formula (1) falls within the above range. Furthermore, the boiling point of the compound represented by formula (1) is preferably 400°C or lower, more preferably 380°C or lower, even more preferably 350°C or lower, and particularly preferably 330°C or lower. Because the boiling point of the compound represented by formula (1) is within the above range, the film-forming aid volatilizes after the fusion of resin particles is complete, minimizing its influence on the inherent properties of the paint (e.g., hardness, smoothness, etc.).

[0032] Examples of compounds represented by the above formula (1) include ethylene glycol dialkyl ethers such as ethylene glycol diisopropyl ether, ethylene glycol ethyl ether monotert-butyl ether, ethylene glycol mono-n-propyl ether monotert-butyl ether, ethylene glycol monoisopropyl ether monotert-butyl ether, and ethylene glycol ditert-butyl ether; diethylene glycol dialkyl ethers such as diethylene glycol diisopropyl ether, diethylene glycol ethyl ether monotert-butyl ether, diethylene glycol mono-n-propyl ether monotert-butyl ether, diethylene glycol monoisopropyl ether monotert-butyl ether, and diethylene glycol ditert-butyl ether; triethylene glycol diisopropyl ether, triethylene glycol monomethyl monotert-butyl ether, triethylene glycol monoethyl ether monotert-butyl ether, and triethylene glycol mono-n-propyl ether. Examples include triethylene glycol dialkyl ethers such as monotert-butyl ether, triethylene glycol monoisopropyl ether monotert-butyl ether, and triethylene glycol ditert-butyl ether; propylene glycol dialkyl ethers such as propylene glycol diisopropyl ether, propylene glycol ethyl ether monotert-butyl ether, propylene glycol monon-propyl ether monotert-butyl ether, propylene glycol monoisopropyl ether monotert-butyl ether, and propylene glycol ditert-butyl ether; and dipropylene glycol dialkyl ethers such as dipropylene glycol diisopropyl ether, dipropylene glycol ethyl ether monotert-butyl ether, dipropylene glycol monon-propyl ether monotert-butyl ether, dipropylene glycol monoisopropyl ether monotert-butyl ether, and dipropylene glycol ditert-butyl ether. These may be used individually or in combination of two or more.

[0033] The method for producing the compound represented by formula (1) above is not particularly limited. For example, R 1 -OH(R 1 R is in equation (1) above. 1 Alkylene oxide is added to an alcohol represented by (synonymous with), R 1 -(CH2-CH(R 3 )-O) n -H(R 1 and R 3 These are the R values ​​in equation (1) above. 1 and R 3 After obtaining an alkylene glycol monoalkyl ether represented by (synonymous with), an alkyl group is introduced to the terminal of the alkylene glycol monoalkyl ether, R 1 -(CH2-CH(R 3 )-O) n -R 2 (R 1 ~R 3 These are the R values ​​in equation (1) above. 1 ~R 3 One method for obtaining alkylene glycol dialkyl ethers (synonymous with) is mentioned.

[0034] Specifically, an alkylene oxide is added to an alcohol in the presence of a catalyst. By using alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide, an alkylene glycol monoalkyl ether in which an oxyalkylene group is introduced to the alcohol can be obtained. For example, by using ethylene oxide in addition to propylene oxide as the alkylene oxide to be added, R 1 Multiple oxyalkylene groups can be introduced to the -OH group. When adding two or more alkylene oxides, either random addition or block addition may be used. In the above method, the crude product after the reaction may be purified using purification means such as distillation.

[0035] Next, an alkylene glycol dialkyl ether can be obtained using the alkylene glycol monoalkyl ether and alkene obtained by the above method by a known method (for example, the method described in Chinese Patent Application Publication No. 106928032).

[0036] <Aqueous emulsion composition> The present invention also provides an aqueous emulsion composition comprising the above-mentioned film-forming aid, a resin, and an aqueous medium. This aqueous emulsion composition can form a coating film with a sufficiently low minimum film-forming temperature and good hardness and smoothness.

[0037] In the aqueous emulsion composition of the present invention, the content of the film-forming aid is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and particularly preferably 0.2 parts by mass or more, per 100 parts by mass of resin. If it is above the lower limit, the minimum film-forming temperature can be sufficiently lowered, and a desirable film-forming improvement effect can be obtained. Furthermore, in the aqueous emulsion composition of the present invention, the content of the film-forming aid is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, particularly preferably 7 parts by mass or less, and most preferably 5 parts by mass or less, per 100 parts by mass of resin. If it is below the upper limit, the minimum film-forming temperature of the aqueous emulsion composition can be sufficiently lowered, and adverse effects on the hardness and smoothness of the formed coating film can be kept to a minimum.

[0038] [resin] The resin used in the aqueous emulsion composition of the present invention is not particularly limited, and examples include acrylic resins, acrylic styrene resins, vinyl acetate resins, polyvinyl alcohol resins, vinyl acetate acrylic resins, vinyl acetate beova resins, ethylene vinyl acetate resins, synthetic rubber latex, urethane resins, epoxy resins, phenolic resins, alkyd resins, polyester resins, vinyl chloride resins, and vinylidene chloride resins. These may be used individually or in combination of two or more. As the resin, for example, acrylic resins or acrylic styrene resins are preferred.

[0039] Acrylic resin is a resin obtained by polymerizing (meth)acrylic monomers. Examples of (meth)acrylic monomers include (meth)acrylic acid; alkyl esters of (meth)acrylate such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; and 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxycyclohexyl (meth)acrylate. Examples include hydroxyalkyl esters of (meth)acrylates such as hydroxydecyl (meth)acrylate; polyoxyethylene (meth)acrylates such as ethylene glycol (meth)acrylate, diethylene glycol (meth)acrylate, propylene glycol (meth)acrylate, and dipropylene glycol (meth)acrylate; methacrylamides such as (meth)acrylamide, N-methylol(meth)acrylamide, N-butoxymethyl(meth)acrylamide, and diacetone acrylamide; epoxy group-containing (meth)acrylates such as glycidyl(meth)acrylate; and the like. These may be used individually or in combination of two or more.

[0040] Acrylic styrene resin is a resin obtained by polymerizing (meth)acrylic monomers and styrene monomers. Examples of (meth)acrylic monomers are as described above. Examples of styrene monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, and pn-dodecylstyrene. These can be used individually or in combination of two or more.

[0041] The glass transition temperature of the resin used in the aqueous emulsion composition of the present invention is not particularly limited, but is, for example, 10 to 35°C.

[0042] The resin content in the aqueous emulsion composition of the present invention is not particularly limited, but is, for example, 30 to 80% by mass. The resin may be incorporated into the aqueous emulsion composition, for example, as a resin emulsion.

[0043] [Aqueous medium] In this specification, an aqueous medium refers to a medium that contains water as its main component (preferably 50% by mass or more), and may further contain components other than water. Examples of components other than water include organic solvents that dissolve in water, such as methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. Preferably, only water is used as the aqueous medium.

[0044] [Optional ingredients] The aqueous emulsion composition of the present invention may further contain known additives in addition to the film-forming aid, resin, and aqueous medium, as long as they do not impair the effects of the present invention. Examples of additives include pigments, plasticizers, dispersants, thickeners, defoamers, preservatives, UV absorbers, and fragrances. The content is not particularly limited, but 0.1 to 30% by mass relative to the resin is preferred.

[0045] [Method for producing aqueous emulsion composition] The method for producing the aqueous emulsion composition of the present invention is not particularly limited. For example, one method involves preparing a resin emulsion by emulsion polymerization of monomer components constituting the resin in an aqueous medium in the presence of a polymerization initiator and an emulsifier, and then adding additives such as film-forming aids. Examples of emulsion polymerization include: (1) a method of polymerization in which monomer components are added dropwise to an emulsifier and an aqueous medium (monomer dropwise method); (2) a method of polymerization in which the entire amount of raw materials (monomer components, emulsifier, and aqueous medium) is mixed and polymerized all at once (monomer batch method); (3) a method of producing a seed emulsion by prepolymerization using a portion of the raw materials (one or more monomer components, emulsifier, aqueous medium, and polymerization initiator), and then adding the remaining raw materials to the seed emulsion to perform emulsion polymerization (seed emulsion method). Among these, method (3) above is preferred as a method for obtaining an emulsion from the viewpoint of obtaining an emulsion with good particle size control and polymerization stability. In the above method, known emulsifiers and polymerization initiators commonly used in emulsion polymerization can be used.

[0046] [Uses of aqueous emulsion compositions] The aqueous emulsion composition according to the present invention can form a coating film with a sufficiently low minimum film-forming temperature and good hardness and smoothness, making it suitable for use as a paint. Furthermore, the aqueous emulsion composition according to the present invention may also be used as an adhesive, tack, or the like. [Examples]

[0047] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples.

[0048] <Synthesis of film-forming aids> [Synthesis Example 1-1] Synthesis of triethylene glycol mono-n-butyl ether mono-tert-butyl ether (BTG-tBu) (1) Synthesis of triethylene glycol mono-n-butyl ether In an autoclave with a capacity of 3000 mL, equipped with a stirrer and temperature controller, 700 parts by mass of n-butanol (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.7 parts by mass of caustic potash (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (0.1% by mass relative to n-butanol) were charged. The container was then purged with nitrogen (0.1 MPa ⇔ 0.5 MPa) five times to remove air. Subsequently, 1247 parts by mass of ethylene oxide (manufactured by Nippon Shokubai Co., Ltd.) (3.0 mol relative to n-butanol) were intermittently introduced into the autoclave over 3 hours at 120-140°C, and the reaction was carried out at 140°C for 1 hour. After that, the reaction was carried out at a reaction temperature of 135-145°C for 2 hours. After the reaction was complete, the temperature was lowered to room temperature to obtain the crude product (triethylene glycol mono-n-butyl ether).

[0049] Next, the obtained crude product (triethylene glycol mono-n-butyl ether) was charged into a glass flask equipped with a packed column, thermometer, and condenser, and purified under the following distillation conditions. Specifically, the distillation temperature and pressure were set to 110-120°C and 170-200 mmHg to obtain the initial distillate. Next, the distillation temperature and pressure were set to 130-140°C and 20-40 mmHg to obtain a fraction containing triethylene glycol mono-n-butyl ether. The purity of the triethylene glycol mono-n-butyl ether obtained by distillation was confirmed (99% or higher) by gas chromatography (GC).

[0050] ≪GC conditions≫ The gas chromatography conditions are as follows: Equipment: Shimadzu GC-2025 gas chromatograph Detector: Hydrogen ionization detection method (FID) Sample introduction volume: Split injection method Column: ZB-1 (Length: 30m, Inner diameter: 0.32mm, Film thickness: 0.25μm) Injection volume: 0.2μl Linear speed: 30cm / sec Carrier gas: Helium Heating conditions: Heat from 100°C to 340°C at a rate of 20°C / min, then maintain at 340°C for 1 minute.

[0051] (2) Synthesis of BTG-tBu BTG-tBu was synthesized using triethylene glycol mono-n-butyl ether and isobutylene as raw materials by a known method (for example, the method described in Chinese Patent Application Publication No. 106928032). The obtained BTG-tBu was identified by gas chromatography (GC) and confirmed to have a purity of 95% or higher (GC conditions as described above). The boiling point of BTG-tBu was 270°C.

[0052] [Synthesis Example 1-2] Synthesis of Triethylene Glycol Monomethyl Ether Monotert-Butyl Ether (MTG-tBu) (1) Synthesis of triethylene glycol monomethyl ether Triethylene glycol monomethyl ether was synthesized in the same manner as in [Synthesis Example 1-1](1) above, except that n-butanol was replaced with methanol.

[0053] (2) Synthesis of MTG-tBu MTG-tBu was synthesized in the same manner as in [Synthesis Example 1-1](2) above, except that triethylene glycol mono-n-butyl ether was replaced with triethylene glycol monomethyl ether. The obtained MTG-tBu was confirmed to be a compound by gas chromatography (GC), and its purity was confirmed to be 95% or higher (GC conditions were as described above). The boiling point of MTG-tBu was 254°C.

[0054] <Synthesis of resin emulsions> [Synthesis Example 2-1] Synthesis of Acrylic Resin Emulsion (Resin Emulsion A) 49.5 parts by mass of butyl acrylate (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 49.5 parts by mass of methyl methacrylate (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 1 part by mass of acrylic acid (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were charged into a 300 ml Erlenmeyer flask and mixed. 43.4 parts by mass of deionized water and 6.6 parts by mass of Newcol 707-SF (polyoxyethylene polycyclic phenyl ether sulfate ammonium salt, 30% purity, manufactured by Nippon Emulsifier Co., Ltd.) were charged into another 500 ml Erlenmeyer flask and mixed with a stirring bar. The monomer mixture was then added to this flask in five separate additions. After thorough mixing, 5 parts by mass of 10% by mass aqueous solution of ammonium persulfate (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to prepare a pre-emulsion. A four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser, and dropping funnel was charged with 50 parts by mass of deionized water and 5.58 parts by mass of the prepared pre-emulsion (5% of the total volume), and the temperature was raised to 80°C. Initial polymerization was carried out by maintaining the temperature at 80°C for 30 minutes. After initial polymerization, the remaining pre-emulsion was added dropwise over 3 hours to carry out polymerization. After that, the mixture was aged at 80°C for 1 hour and then cooled to room temperature. The pH was adjusted to 8.0 with a 25% by mass aqueous ammonia solution to obtain resin emulsion A (butyl acrylate / methyl methacrylate / acrylic acid = 49.5 / 49.5 / 1 (mass ratio)) with a solid content of 49.4% by mass.

[0055] [Synthesis Example 2-2] Synthesis of Acrylic Styrene Resin Emulsion (Resin Emulsion B) In a 300 ml Erlenmeyer flask, 40 parts by mass of butyl acrylate (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 30 parts by mass of methyl methacrylate (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 30 parts by mass of styrene (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 2 parts by mass of acrylic acid (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were charged and mixed. In another 500 ml Erlenmeyer flask, 45.4 parts by mass of deionized water and 4.1 parts by mass of Newcol CMP-11-SN (polyoxyethylene cumylphenol ether sulfonate sodium salt, 50% purity, manufactured by Nippon Emulsifier Co., Ltd.) were charged and mixed with a stirring bar. The monomer mixture from earlier was added to this flask in five separate additions. After thorough mixing, 5.1 parts by mass of 10% by mass aqueous solution of ammonium persulfate (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to prepare a pre-emulsion. A four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser, and dropping funnel was charged with 50 parts by mass of deionized water and 7.83 parts by mass of the prepared pre-emulsion (5% of the total volume), and the temperature was raised to 80°C. Initial polymerization was carried out by maintaining the temperature at 80°C for 30 minutes. After initial polymerization, the remaining pre-emulsion was added dropwise over 3 hours to carry out polymerization. After that, the mixture was aged at 80°C for 1 hour and then cooled to room temperature. The pH was adjusted to 8.0 with a 25% by mass aqueous ammonia solution to obtain resin emulsion B (butyl acrylate / methyl methacrylate / styrene / acrylic acid = 40 / 30 / 30 / 2 (by mass ratio)) with a solid content of 50.7% by mass.

[0056] <Preparation of aqueous emulsion composition> [Aqueous emulsion composition of acrylic resin] To the resin emulsion A synthesized in Synthesis Example 2-1 above, the compound obtained in Synthesis Example 1-1 or 1-2 above, or the comparative compound described below, was added as a film-forming aid in an amount of 5, 10, or 20 parts by mass per 100 parts by mass of resin in the resin emulsion. The mixture was stirred at 25°C for 180 minutes, and then allowed to stand for 24 hours to prepare an aqueous emulsion composition.

[0057] [Aqueous emulsion composition of acrylic styrene resin] To the resin emulsion B synthesized in Synthesis Example 2-2 above, the compound obtained in Synthesis Example 1-1 or 1-2 above, or the comparative compound listed below, was added as a film-forming aid in an amount of 1, 2.5, 5, or 10 parts by mass per 100 parts by mass of resin in the resin emulsion. The mixture was stirred at 25°C for 180 minutes, and then allowed to stand for 24 hours to prepare an aqueous emulsion composition.

[0058] [Comparative Compounds] • DBDG (Diethylene glycol di-n-butyl ether, manufactured by Nippon Emulsifier Co., Ltd., boiling point 255°C) • TX-IB (2,2,4-trimethyl-1,3-pentanediol diisobutyrate, manufactured by Eastman Chemical Co., Ltd., boiling point 282°C) • Texanol (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, manufactured by Eastman Chemical Co., Ltd., boiling point 240°C).

[0059] <Evaluation of aqueous emulsion compositions> The film-forming properties and coating properties of aqueous emulsion compositions were evaluated. Table 1 shows the minimum film-forming temperature and hardness results for aqueous emulsion compositions using acrylic resin, and Table 2 shows the minimum film-forming temperature and hardness results for aqueous emulsion compositions using acrylic styrene resin. Table 3 shows the smoothness results for aqueous emulsion compositions using acrylic resin. In Tables 1 to 3, the "content (parts by mass)" of the film-forming agent represents the amount of film-forming agent added per 100 parts by mass of resin in the aqueous emulsion composition. In Tables 1 to 3, a "-" next to the film-forming agent means that the agent was not added, and a "-" next to the coating property means that its evaluation was not measured.

[0060] Furthermore, in the aqueous emulsion compositions, graphs plotting the relationship between the amount of each film-forming aid added and the minimum film-forming temperature are shown in Figures 1 and 2 (Figure 1: aqueous emulsion composition of acrylic resin, Figure 2: aqueous emulsion composition of acrylic styrene resin). For the evaluation of smoothness, the coating film surface used for the evaluation of gloss was photographed with a digital camera (1:1 magnification) and is shown in Figure 3 (Figure 3 (a) Example 1, (b) Example 4, (c) Comparative Example 4, (d) Comparative Example 10).

[0061] [Film forming property (minimum film forming temperature)] The aqueous emulsion composition prepared above was subjected to a minimum film formation temperature measuring instrument (MFG No. 67831, manufactured by Tester Sangyo Co., Ltd.), and the minimum film formation temperature (MFT) was measured under the conditions of a measurement temperature range of 0°C to 50°C, a coating film thickness of 0.2 mm, and a drying time of 1 hour.

[0062] [Coating film properties] The hardness and smoothness of the coating film of the aqueous emulsion composition prepared above were evaluated by the following method.

[0063] (hardness) The aqueous emulsion composition prepared above was applied to a glass plate using an applicator to achieve a wet film thickness of 75 μm, and then dried (110°C for 3 minutes → room temperature for 24 hours) to obtain a coating film. The obtained coating film was then measured using a pendulum hardness tester (SP0500, manufactured by Cortec Co., Ltd.), starting from a pendulum angle of 6° and measuring the number of oscillations until the angle became 3° or less. If the dried coating film does not reach the specified hardness, it is called insufficient hardness, which can cause problems such as the coating film surface being easily scratched.

[0064] (smoothness) Smoothness was evaluated by visual inspection and gloss of the coating film formed by the aqueous emulsion composition.

[0065] The aqueous emulsion composition prepared above was applied to a glass plate using an applicator to achieve a wet film thickness of 75 μm, and then dried (0°C for 24 hours) to obtain a coating film. The gloss of the coating film (incident angle: 60°, 20°) was measured using a gloss meter (GROSS METER IG-331, Horiba, Ltd.). Gloss represents the degree of specular reflection of light hitting the surface and indicates the smoothness of the coating film surface. A higher gloss indicates a flatter coating film surface.

[0066] [Table 1]

[0067] [Table 2]

[0068] [Table 3]

[0069] [Film forming property] As shown in Table 1, in acrylic resin emulsion systems, the compositions of Examples 1 to 6, which contained the film-forming aid of the present invention, showed significantly lower MFTs compared to the compositions of Comparative Examples 1 to 9, which contained a film-forming aid (comparative compound) outside the scope of the present invention, and the composition of Comparative Example 10, which did not contain a film-forming aid.

[0070] Furthermore, as shown in Table 2, in the acrylic styrene resin emulsion system, the compositions of Examples 7 to 14, which contained the film-forming aid of the present invention, showed significantly lower MFTs compared to the compositions of Comparative Examples 11 to 14, which contained a film-forming aid (comparative compound) outside the scope of the present invention, and the composition of Comparative Example 15, which did not contain a film-forming aid.

[0071] These results show that even with the addition of only a small amount, the film-forming aid of the present invention can sufficiently lower the minimum film-forming temperature of an aqueous emulsion composition and improve film-forming properties.

[0072] [Coating film properties] For aqueous emulsion compositions containing a film-forming aid at the amount of additive that showed a reduction in the minimum film-forming temperature as described above in the [film-forming properties] section, the hardness and smoothness of the formed coating film were confirmed.

[0073] As shown in Tables 1 and 2, the coatings formed from the compositions containing the film-forming aid of the present invention in Examples 1 to 14 showed superior hardness when compared with coatings formed from compositions containing film-forming aids outside the scope of the present invention, for each amount of film-forming aid added.

[0074] As shown in Table 3, the coatings formed from the compositions containing the film-forming aid of the present invention in Example 1 and Example 4 showed higher gloss and superior smoothness compared to the coatings formed from the compositions of Comparative Example 1 and Comparative Example 10. Furthermore, as shown in Figure 3, the coatings formed from the compositions containing the film-forming aid of the present invention in Example 1 and Example 4 showed significantly fewer white thread-like spots and superior smoothness compared to the coatings formed from the compositions of Comparative Example 1 and Comparative Example 10.

[0075] As shown in Figures 1 and 2, the film-forming aid of the present invention is highly effective in lowering the minimum film-forming temperature even with small amounts of addition. Therefore, when comparing compositions containing the film-forming aid of the present invention with compositions containing film-forming aids outside the scope of the present invention for each amount of addition, it can be seen that compositions containing the film-forming aid of the present invention have a lower minimum film-forming temperature. In other words, when trying to achieve a certain minimum film-forming temperature, using the film-forming aid of the present invention allows for a significantly reduced amount of addition compared to using film-forming aids outside the scope of the present invention. Consequently, with the reduction in the amount of film-forming aid added, the impact of adding the film-forming aid on the coating film (e.g., hardness and smoothness) can also be reduced.

[0076] From the above results, it was confirmed that the film-forming aid of the present invention can sufficiently lower the minimum film-forming temperature while suppressing adverse effects on the hardness and smoothness of the formed coating film. Furthermore, since the film-forming aid of the present invention can sufficiently lower the minimum film-forming temperature even with the addition of a small amount, an aqueous emulsion composition is provided in which adverse effects on the hardness and smoothness of the formed coating film are suppressed.

Claims

1. The following formula (1): 【Chemistry 1】 In the above formula (1), R １ and R ２ R is a linear or branched alkyl group having 1 to 8 carbon atoms, and in this case, １ and R ２ At least one of them is a tert-butyl group, and R １ and R ２ The total number of carbon atoms is 6 or more. R ３ is hydrogen, a methyl group or an ethyl group, n represents the average number of moles added of -(CH ２ -CH(R ３ )-O)- and is a number from 2 to 4, A film-forming aid for aqueous emulsions, containing the compound represented by [the formula shown], for use as an additive to aqueous emulsions.

2. R ３ The film-forming aid according to claim 1, wherein is a hydrogen or methyl group.

3. R １ and R ２ R is a linear or branched alkyl group having 1 to 5 carbon atoms, and in this case, １ and R ２ The film-forming aid according to claim 1 or 2, wherein at least one of the members is a tert-butyl group.

4. An aqueous emulsion composition comprising a film-forming aid according to any one of claims 1 to 3, a resin, and an aqueous medium.

5. The aqueous emulsion composition according to claim 4, comprising 5 parts by mass or less of the film-forming aid per 100 parts by mass of the resin.

6. The aqueous emulsion composition according to claim 4 or 5, wherein the resin is an acrylic resin or an acrylic styrene resin.

7. A water-based emulsion composition according to any one of claims 4 to 6, which is used as a paint.

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