Coating composition and coating film protective coating material

Abstract

Provided is a coating composition which is not susceptible to sagging and is capable of efficiently forming a high-quality coating film protective coating material. Provided is a coating composition for forming a coating film protective coating material, the coating composition containing, as a base polymer, a polymer (A) that is a polymer containing a monomer component of an acrylic monomer, the polymer (A) being in the form of an aqueous emulsion dispersed in an aqueous solvent. The coating composition further contains a polyvinyl alcohol polymer (B) having a degree of saponification of 80 mol% or more and a degree of polymerization of 1200 or less. The content of the polymer (B) is from 0.3 parts by weight to 5.0 parts by weight (inclusive) per 100 parts by weight of the polymer (A). The coating composition has a viscosity of 25 Pa.s or more as measured by a BH-type viscometer under conditions of 30 DEG C and 2 rpm.

Description

TECHNICAL FIELD

[0001] The present application relates to a coated film protective coating material and a coating composition for forming a coated film protective coating material.

[0002] This application claims priority based on Japanese Patent Application No. 2023-061575 filed on April 5, 2023, the entire contents of which are incorporated herein by reference. BACKGROUND

[0003] For the purpose of preventing damage to a coated film, such as during transfer, storage, maintenance, construction, and the like, of an article having a coated film, such as a painted automobile, a component thereof, or a metal sheet such as a painted steel sheet, a molded product thereof, and the like, a technique is known in which a protective sheet is attached to the coated film to protect it. A coated film protective sheet for this purpose is generally configured as follows: a single-sided adhesive sheet with a backing substrate having an adhesive layer (also referred to as a pressure-sensitive adhesive. The same applies hereafter) on one side of a sheet-shaped backing substrate is attached to an adherend (object to be protected) via the adhesive, thereby achieving the purpose of protection. The coated film protective sheet that has fulfilled its protective function is then removed (re-stripped) from the adherend. As a technical document related to coated film protective sheets, Patent Literature 1 can be cited.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2011-111552

[0007] Patent Literature 2: Japanese Patent Application Publication No. 2004-224874 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, for a non-planar object to be protected, particularly an object to be protected having a complex three-dimensional shape such as an outer panel of an automobile, it is difficult to efficiently perform the work of properly attaching a coated film protective sheet to the object to be protected. In the case where a coated film protective sheet is not properly attached to an object to be protected, for example, when it is attached in a state where wrinkles are formed in the coated film protective sheet, the aforementioned wrinkles are blown into during storage or transfer of the object to be protected after attachment, and as a result, the coated film protective sheet peels off, and it can not be possible to achieve the original protective purpose.

[0010] On the other hand, there is also proposed a method of forming a protective film by directly applying a liquid composition for forming a protective film to a coated film of a protective object, and drying the liquid composition on the coated film to form a protective film. As a document relating to this technology, Patent Document 2 can be cited. In Patent Document 2, a coating material for a pressure-feed type roll coating in which the coating material is pressure-fed to the inside of a roll for coating to perform coating is proposed. However, in general, in pressure-feed roll coating, it is difficult to control the coating amount (further, the thickness of the protective film formed after drying), and it is difficult to efficiently form a high-quality protective film. In addition, the coating material designed to be suitable for pressure-feed roll coating has a tendency to easily cause sagging when applied to a non-horizontal surface (particularly, a vertical surface), and this tendency becomes more significant when the coating amount is increased.

[0011] In view of the above, an object of the present application is to provide a coating composition for forming a coated film protective coating material, which is less likely to cause sagging, and can efficiently form a high-quality coated film protective coating material. Another object related thereto is to provide a coated film protective coating material obtained from such a coating composition.

[0012] Solution to the problem

[0013] According to the present specification, a coating composition for forming a coated film protective coating material is provided. The above coating composition contains a polymer (A) as a base polymer, which is a polymer containing a monomer component of an acrylic monomer. In the above coating composition, the polymer (A) is in the form of an aqueous emulsion dispersed in an aqueous solvent. The above coating composition further contains a polyvinyl alcohol-based polymer (B). The saponification degree of the above polyvinyl alcohol-based polymer (B) is 80 mol% or more. The polymerization degree of the above polyvinyl alcohol-based polymer (B) is 1200 or less. The content of the above polyvinyl alcohol-based polymer (B) is 0.3 parts by weight or more and 5.0 parts by weight or less with respect to 100 parts by weight of the above polymer (A). The viscosity of the above coating composition, as measured by a BH-type viscometer under the conditions of 30°C and 2 rpm, is 25 Pa-s or more. According to a coating composition containing the above polyvinyl alcohol-based polymer (B) in an appropriate amount with respect to the above polymer (A), and having a BH viscosity of 25 Pa-s or more, sagging of the composition is less likely to occur, and a high-quality protective film can be efficiently formed. Note that, in the following, the viscosity measured by a BH-type viscometer is sometimes simply referred to as "BH viscosity".

[0014] In some aspects of the technology disclosed herein (including a coating composition, a method for producing a coating composition, a coated film protection method, a coated film protective coating material, and the like. The same applies hereinafter), the above coating composition further contains a tackifier. By using a tackifier, a coating composition satisfying the above BH viscosity can be preferably achieved.

[0015] In the coating composition of some preferred embodiments, the monomer component constituting the above-described polymer (A) contains a carboxyl group-containing monomer. That is, the above-described polymer (A) is preferably a polymer of the monomer component containing a carboxyl group-containing monomer. The technology disclosed herein can be preferably implemented in a scheme in which the polymer (A) composed of the monomer component of this composition is used as a base polymer.

[0016] In the coating composition of some preferred embodiments, the monomer component constituting the above-described polymer (A) contains a nitrogen atom-containing monomer. That is, the above-described polymer (A) is preferably a polymer of the monomer component containing a nitrogen atom-containing monomer. The technology disclosed herein can be preferably implemented in a scheme in which the polymer (A) composed of the monomer component of this composition is used as a base polymer. The above-described monomer component can also be a composition containing a carboxyl group-containing monomer and a nitrogen atom-containing monomer.

[0017] Further, according to the present specification, a method of manufacturing any of the coating compositions disclosed herein is provided. The manufacturing method includes: preparing a polymer emulsion containing an aqueous solvent, the above-described polymer (A), the above-described polyvinyl alcohol-based polymer (B) in an amount of 0.3 parts by weight or more and 5.0 parts by weight or less per 100 parts by weight of the above-described polymer (A), and a viscosity of 1.0 Pa-s or more and 4.5 Pa-s or less at a solid content of 47% by weight, measured at 30°C and 2 rpm by a BH-type viscometer; and adjusting the viscosity of the above-described polymer emulsion so that the viscosity measured at 30°C and 2 rpm by a BH-type viscometer is 25 Pa-s or more. The coating composition disclosed herein can be more preferably manufactured by such a manufacturing method. Note that the "viscosity at a solid content of 47% by weight" of the polymer emulsion refers to the viscosity of the above-described polymer emulsion as it is in the case where the solid content of the polymer emulsion is within the range of 47% by weight ± 1% by weight, and in the case of a polymer emulsion having a solid content outside the above-described range, it refers to the viscosity in the case where the solid content is adjusted to be within the range of 47% by weight ± 1% by weight.

[0018] According to the present specification, a coating film protective coating material (hereinafter, sometimes simply referred to as "coating material") formed from any of the coating compositions disclosed herein is provided. The above-described coating material can be formed by, for example, applying the above-described coating composition to a coating film of a protection target and drying it. The above-described coating material can be a dried film of any of the coating compositions disclosed herein.

[0019] Further, according to the present specification, a coating film protection method is provided, which includes: preparing any of the coating compositions disclosed herein; applying the coating composition on the coating film of a protection target object having a coating film; and drying the coating composition to form a coating film protection coating material that temporarily protects the coating film. The coating composition is less likely to cause sagging and drooping, and can efficiently form a high-quality coating material on the coating film of the protection target object. According to the coating film protection method using the coating composition, the coating film can be appropriately protected by the coating material. The application of the coating composition can be preferably performed using a slit die.

[0020] Note that a scheme obtained by appropriately combining each element described in the present specification can also be included in the scope of the invention for which patent protection is sought by the present application. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a cross-sectional view schematically showing one example of a protection target object protected by the coating film protection coating material of the present application.

[0022] Figure 2 is a block diagram showing one embodiment of the coating film protection method of the present application. DETAILED DESCRIPTION

[0023] Hereinafter, a preferred embodiment of the present application will be described. Matters necessary for practicing the present application other than matters specifically mentioned in the present specification can be understood by those skilled in the art based on the teachings described in the present specification regarding the practice of the invention and common technical knowledge at the time of filing. The present application can be practiced based on the content disclosed in the present specification and the common technical knowledge in the field.

[0024] Note that in the following drawings, sometimes the same reference numerals are assigned to members / positions that play the same role, and sometimes repeated description is omitted or simplified. Further, the embodiments described in the drawings are schematized for the purpose of clearly describing the present application, and do not necessarily accurately represent the dimensions, scales of actually provided products.

[0025] In the present specification, "acrylic monomer" refers to the concept including a monomer having at least one (meth)acryloyl group in one molecule (hereinafter, also referred to as "monomer containing (meth)acryloyl group") and (meth)acrylonitrile. Further, in the present specification, "(meth)acryloyl" refers to including acryloyl and methacryloyl. Likewise, "(meth)acrylate" refers to including acrylate and methacrylate, "(meth)acrylic acid" refers to including acrylic acid and methacrylic acid, and "(meth)acrylonitrile" refers to including acrylonitrile and methacrylonitrile.

[0026] In this specification, "polyvinyl alcohol polymers" (hereinafter, sometimes referred to as PVA) refers to polymers containing vinyl alcohol units (-CH2CH(OH)-) as their repeating units, and includes both unmodified and modified PVA. Unmodified PVA refers to PVA whose repeating units are essentially composed of vinyl alcohol units (-CH2CH(OH)-) and vinyl ester units (-CH2CH(OC(=O)R)-). A )-,here R A The PVA is composed of an alkyl group, such as an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, typically a methyl group. Examples of modified PVA include PVA having repeating units other than vinyl ester units (typically vinyl acetate units) (e.g., repeating units having anionic groups), and PVA with a structure in which at least a portion of the vinyl alcohol units has been modified by acetalization.

[0027] In this specification, "aqueous solvent" refers to water or a mixed solvent in which water is the main component (in a content of more than 50% by weight). The solvents constituting this mixed solvent, excluding water, can be one or more selected from various organic solvents (such as lower alcohols) that are homogeneous with water. Typically, in the aqueous solvents described in this specification, the proportion of water is 90% by weight or more, preferably 95% to 100% by weight.

[0028] <Polymer (A)>

[0029] The coating composition provided in this specification contains polymer (A) as a base polymer. Here, "base polymer" refers to a component comprising more than 50% by weight (typically 70% by weight or more, for example, 90% by weight or more, or possibly 95% by weight or more, or possibly 100% by weight) of the polymer contained in the coating composition. The base polymer in the protective coating material disclosed herein also has the same meaning. The aforementioned polymer (A) is a polymer containing monomeric components derived from acrylic monomers. Therefore, the aforementioned polymer (A) is a polymer containing monomeric units derived from acrylic monomers.

[0030] In the above polymer (A), the glass transition temperature calculated based on the composition of the monomer components used to synthesize the polymer (A) (calculated Tg) can be, for example, -50°C or higher and 10°C or lower. In some embodiments, the calculated Tg of the polymer (A) is preferably 0°C or lower. A calculated Tg of the polymer (A) of 0°C or lower is advantageous from the viewpoint of preventing the adhesion of marks to the coating material containing the polymer (A), and is also preferred from the viewpoint of easily achieving a coating material in which the elongation at break is moderately large as described later. From the viewpoint of easily obtaining a better mark-preventing adhesion, in some embodiments, the calculated Tg of the polymer (A) can be, for example, -5°C or lower, -9°C or lower (for example, -10°C or lower), or -15°C or lower. Reducing the calculated Tg of the polymer (A) is also advantageous from the viewpoint of improving the peeling workability when peeling the coating material from the coated film in a low-temperature environment such as outdoors in winter, for example, suppressing peeling failure caused by defects or breakage of the coating material, and suppressing the occurrence of cracks in the coating material due to differences in linear expansion coefficients of the protected object provided with the coating material and the like when the protected object is exposed to temperature changes. On the other hand, from the viewpoint of peeling properties and peeling workability in high-temperature regions, the calculated Tg of the polymer (A) is suitably -40°C or higher, advantageously -35°C or higher, preferably -30°C or higher, and can be -25°C or higher or -20°C or higher. The technology disclosed herein can be preferably implemented using a polymer (A) having a calculated Tg of, for example, -25°C or higher and -10°C or lower.

[0031] Herein, in the present specification, the calculated Tg of a polymer refers to the Tg calculated according to the Fox equation based on the composition of the monomer components used to synthesize the polymer. The Fox equation, which is a relationship between the Tg of a copolymer and the glass transition temperatures Tgi of homopolymers of the respective monomers that make up the copolymer, is shown below.

[0032] 1 / Tg = ∑(Wi / Tgi)

[0033] Note that in the above Fox equation, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0034] As the glass transition temperatures of the homopolymers used to calculate the calculated Tg, values described in publicly known documents are used. For example, with respect to the monomers listed below, the values described below are used as the glass transition temperatures of the homopolymers of the monomers.

[0035] n-Butyl acrylate: -55°C.

[0036] Acrylonitrile: 97°C.

[0037] Vinyl acetate: 32°C.

[0038] Methyl methacrylate: 105°C.

[0039] Acrylic acid: 106°C.

[0040] The glass transition temperature of the homopolymer of the monomer other than those exemplified above was used as the value described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). In the case where the Tg of the homopolymer is not described in the known literature, the value obtained by the following measurement method was used. Specifically, 100 parts by weight of the monomer, 0.2 parts by weight of azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent were charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and stirred for 1 hour while passing nitrogen. After thus removing oxygen in the polymerization system, it was warmed to 63°C and allowed to react for 10 hours. Next, it was cooled to room temperature to obtain a homopolymer solution having a nonvolatile content of 33% by weight. Next, the homopolymer solution was cast onto a release liner and dried to produce a test sample (a sheet-shaped homopolymer) having a thickness of about 2 mm. The test sample was punched into a disc having a diameter of 7.9 mm, and clamped with a parallel plate, and the viscoelasticity was measured by a shear mode at a temperature range of -70 to 150°C at a temperature elevation rate of 5°C / min while applying a shear strain at a frequency of 1 Hz using a viscoelasticity tester (manufactured by TA Instruments Japan, Inc., model name "ARES"), and the peak top temperature of tan δ was set as the Tg of the homopolymer.

[0041] In some embodiments, the SP value of the polymer (A) is suitably more than 9.5 (unit [(cal / cm 3 ) 1 / 2] The SP value of the polymer (A) is preferably 10.0 or more. The polymer (A) having the above-mentioned SP value can have an SP value largely different from (typically, on the higher side) the SP value of the coating film to be protected. The coating film can be, for example, a urethane-based coating film formed by the reaction of a polyol (e.g., an acrylic polyol) with a polyisocyanate, a coating film formed of an acid epoxy crosslinking type acrylic coating, or the like. By making the SP value of the polymer (A) largely different from the SP value of the coating film, there is a tendency that the interaction between the coating material containing the polymer (A) and the coating film decreases. This is advantageous from the viewpoint of suppressing the occurrence of peeling failure caused by the peeling strength of the coating material from the coating film becoming excessively high, the increase in the burden of peeling work; suppressing the deformation (trace adhesion) of the coating film caused by the movement of substances between the coating film and the coating material, and the like. In some cases, the SP value of the polymer (A) can be more than 10.0, can be 10.5 or more, can be 10.8 or more, can be 11.2 or more, or can be 11.5 or more. The upper limit of the SP value of the polymer (A) is not particularly limited. From the viewpoint of easily forming a coating material having a good balance of properties, in some cases, the SP value of the polymer (A) is appropriately about 14.0 or less, can be 13.5 or less, can be 13.0 or less, can be less than 12.5, can be 12.0 or less, can be less than 12.0, or can be 11.5 or less.

[0042] Herein, in the present specification, the SP value refers to the value of the solubility parameter calculated from the basic structure of the compound by the method proposed by Fedors. The SP value of the polymer (A) can be adjusted by selecting the composition of the monomer components constituting the polymer (A), specifically by selecting the kind, amount ratio, and the like of the monomers contained in the above-mentioned monomer components.

[0043] In some cases, the SP value of the polymer (A) is appropriately 0.2 or more, preferably 0.5 or more, more preferably 0.7 or more, and further preferably 1.0 or more, higher than the SP value of the coating film to be protected. According to the combination of the polymer (A) having such a difference in the SP value and the coating film to be protected, it is easy to preferably achieve good peeling properties and good trace adhesion resistance of the coating material containing the polymer (A).

[0044] The polymer (A) in the technology disclosed herein is a polymer containing a monomer component of one or more or more acrylic monomers. The proportion of the acrylic monomer in the monomer component can be, for example, 5 mol% or more, suitably 10 mol% or more, preferably 15 mol% or more, also 25 mol% or more, also 35 mol% or more, also 45 mol% or more, more than 50 mol%, also more than 70 mol%. In some preferred embodiments, the proportion of the acrylic monomer in the monomer component can be 85 mol% or more, 90 mol% or more, 95 mol% or more, or 100 mol%. Further, in some embodiments, the proportion of the acrylic monomer in the monomer component can be 50 mol% or less, also 40 mol% or less, also 30 mol% or less.

[0045] In some embodiments, the monomer component constituting the polymer (A) contains at least a (meth)acryl group-containing monomer as the acrylic monomer. The (meth)acryl group-containing monomer can be used alone or in combination with two or more. The proportion of the (meth)acryl group-containing monomer in the monomer component can be, for example, 5 mol% or more, suitably 10 mol% or more, preferably 15 mol% or more, more preferably 20 mol% or more, also 30 mol% or more, also 40 mol% or more, also 45 mol% or more, also 50 mol% or more, also 55 mol% or more, also 60 mol% or more. The entire monomer component (i.e., 100 mol%) can also be the (meth)acryl group-containing monomer. From the viewpoint of facilitating the balance between the calculation of the Tg defined below and the easy formation of a coating material having a good property balance, in some embodiments, the proportion of the (meth)acryl group-containing monomer in the monomer component is preferably 95 mol% or less, more preferably 90 mol% or less, also 85 mol% or less, also 80 mol% or less, also 75 mol% or less, also 70 mol% or less. The technology disclosed herein can also be implemented in embodiments in which the proportion of the (meth)acryl group-containing monomer in the monomer component is 65 mol% or less, 55 mol% or less, 45 mol% or less, or 35 mol% or less.

[0046] The monomer component constituting the polymer (A) preferably contains at least an alkyl (meth)acrylate as the (meth)acryl group-containing monomer. The alkyl (meth)acrylate contributes to the adjustment of the storage modulus, the adjustment of the tensile properties, the adjustment of the SP value described later, and the like by selecting the kind thereof and the amount thereof to be used. The alkyl (meth)acrylate can be used alone or in combination with two or more.

[0047] As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used.

[0048] CH2=C(R 1 COOR 2 (1)

[0049] Here, R in equation (1) above 1 R is a hydrogen atom or a methyl group. In formula (1) above, R... 2 It is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, this range of carbon atoms is sometimes expressed as "C". 1－20 The aforementioned chain alkyl groups can be straight-chain or branched.

[0050] As R 2 C 1－20 Alkyl (meth)acrylates ((meth)acrylate C 1－ Specific examples of 20-alkyl esters are not particularly limited, but can include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecanyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, etc.

[0051] Among these, it is preferred to use at least (meth)acrylic acid C. 4－20 Alkyl ester (preferably (meth)acrylic acid C) 4－14 Alkyl esters), preferably using at least acrylic acid C, from the perspective of helping to reduce the calculated Tg of polymer (A). 4－9 Alkyl esters. For example, the monomeric components described above preferably include one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA), more preferably at least BA.

[0052] The monomer component (meth)acrylic acid C in polymer (A) 1－20The proportion of the alkyl ester may be, for example, 5 mol% or more, suitably 10 mol% or more, preferably 15 mol% or more, also 25 mol% or more, also 35 mol% or more, also 45 mol% or more, also 55 mol% or more, and also 60 mol% or more. Further, from the viewpoint of easily achieving a suitable film property, the proportion of the alkyl ester in the monomer component (meth)acrylic acid C 1－20 The proportion of the alkyl ester is suitably 95 mol% or less, preferably 90 mol% or less, can be 85 mol% or less, also 80 mol% or less, also 75 mol% or less, also 70 mol% or less, and also 65 mol% or less. The technology disclosed herein can also be implemented in a scheme in which the proportion of the alkyl ester in the monomer component (meth)acrylic acid C 1－20 The proportion of the alkyl ester is 60 mol% or less, 50 mol% or less, 40 mol% or less, or 30 mol% or less.

[0053] The monomer component constituting the polymer (A) can contain (meth)acrylic acid C 4－9 The proportion of the alkyl ester in the monomer component (meth)acrylic acid C 4－9 The proportion of the alkyl ester may be, for example, 5 mol% or more, suitably 10 mol% or more, preferably 15 mol% or more from the viewpoint of easily obtaining a lower calculated Tg, can be 25 mol% or more, also 35 mol% or more, also 40 mol% or more, and also 45 mol% or more. On the other hand, from the viewpoint of easily obtaining a polymer (A) having a SP value of a prescribed value or more, the proportion of the alkyl ester in the monomer component (meth)acrylic acid C 4－9 The proportion of the alkyl ester is suitably 80 mol% or less, preferably 70 mol% or less, can be 65 mol% or less, also 60 mol% or less, and also 55 mol% or less. The technology disclosed herein can also be implemented in a scheme in which the proportion of the alkyl ester in the monomer component (meth)acrylic acid C 4－9 The proportion of the alkyl ester is 50 mol% or less, 40 mol% or less, 30 mol% or less, 25 mol% or less, or 20 mol% or less.

[0054] The monomer component constituting the polymer (A) can also combine an alkyl ester of (meth)acrylic acid and a monomer other than the alkyl ester of (meth)acrylic acid. As some examples of the monomer other than the alkyl ester of (meth)acrylic acid, mention can be made of a carboxyl group-containing monomer, a hydroxyl group (OH group)-containing monomer, a cyano group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, a monomer having a ring containing a nitrogen atom, an isocyanate group-containing monomer, an acid anhydride group-containing monomer, an epoxy group-containing monomer, a ketone group-containing monomer, an alkoxysilane group-containing monomer, and the like functional group-containing monomers. By suitably using a functional group-containing monomer, the cohesiveness of the polymer (A) can be improved. The functional group-containing monomer can also contribute to adjustment of the storage modulus, adjustment of the tensile properties, adjustment of the SP value described later, and the like.

[0055] As the monomer containing a carboxyl group, for example, acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid can be exemplified. Among them, AA and MAA are preferred.

[0056] As examples of the monomer containing a hydroxyl group, (meth) acrylate esters such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and polypropylene glycol mono(meth) acrylate, etc. can be exemplified. As the monomer containing a hydroxyl group, which is preferred, a straight-chain (meth) acrylate ester having an alkyl group with 2 to 4 carbon atoms can be exemplified.

[0057] As the monomer containing a cyano group, for example, acrylonitrile, methacrylonitrile, 2-cyanoethyl (meth) acrylate can be exemplified. Among them, acrylonitrile and methacrylonitrile are preferred, and acrylonitrile is particularly preferred.

[0058] As the monomer containing an amide group, for example, (meth) acrylamide, N,N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone (meth) acrylamide can be exemplified.

[0059] As the monomer containing an amino group, for example, aminoethyl (meth) acrylate, N,N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate can be exemplified.

[0060] As the monomer having a ring containing a nitrogen atom, for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylimidazole, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyl oxazole, N-vinyl morpholine, N-vinyl caprolactam, N-(meth) acryloylmorpholine, etc. can be exemplified, which are monomers having a structure in which a polymerizable functional group is bonded to a ring containing a nitrogen atom. As other examples, monomers containing a maleimide ring such as N-isopropylmaleimide, N-cyclohexylmaleimide can be exemplified.

[0061] As an example of the monomer containing an isocyanate group, 2-(meth) acryloyloxyethyl isocyanate can be exemplified.

[0062] As an example of the monomer containing an acid anhydride group, maleic anhydride, itaconic anhydride, etc. can be exemplified.

[0063] As the monomer containing a ketone group, for example, there can be mentioned: diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.

[0064] As the monomer having an epoxy group, for example, there can be mentioned: glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.

[0065] As the monomer containing an alkoxysilyl group, for example, there can be mentioned: 3- (meth)acryloyloxypropyl trimethoxysilane, 3- (meth)acryloyloxypropyl triethoxysilane, 3- (meth)acryloyloxypropyl methyl dimethoxysilane, 3- (meth)acryloyloxypropyl methyl diethoxysilane.

[0066] As the other copolymerizable component, for example, there can be mentioned: vinyl acetate (VAc), vinyl propionate, vinyl laurate, and other vinyl ester monomers; styrene, substituted styrenes (α-methylstyrene, etc.), vinyltoluene, and other aromatic vinyl compounds; cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, isobornyl (meth)acrylate, and other (meth)acrylic acid cycloalkyl esters; (meth)acrylic acid aryl esters (e.g., (meth)acrylic acid phenyl ester), (meth)acrylic acid aryloxyalkyl esters (e.g., (meth)acrylic acid phenoxyethyl ester), (meth)acrylic acid arylalkyl esters (e.g., (meth)acrylic acid benzyl ester), and other (meth)acrylic acid esters having an aromatic ring; olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine atom-containing monomers such as vinyl chloride and vinylidene chloride; methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, ethylcarbitol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, and other alkoxyl group-containing monomers; methyl vinyl ether, ethyl vinyl ether, and other vinyl ether monomers; 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and other multifunctional monomers having two or more (e.g., three or more) polymerizable functional groups (e.g., (meth)acryloyl groups) in one molecule; and the like.

[0067] In some embodiments, the monomer component constituting the polymer (A) contains a nitrogen atom-containing monomer. As examples of the nitrogen atom-containing monomer, there can be mentioned: a monomer corresponding to at least one of the above-described cyano group-containing monomer, amide group-containing monomer, amino group-containing monomer, and monomer having a ring containing a nitrogen atom. The nitrogen atom-containing monomer can be used alone or in combination of two or more. The above-described monomer component preferably contains, in combination, an alkyl (meth)acrylate and a nitrogen atom-containing monomer, and more preferably contains, in combination, acrylic acid C 4－9alkyl ester and a monomer having a nitrogen atom. The monomer having a nitrogen atom has a tendency to show a higher SP value (for example, a higher SP value than that of an alkyl (meth)acrylate) by virtue of containing a nitrogen-containing moiety. By appropriately using a monomer having a nitrogen atom, a polymer (A) having a SP value of the above-described specification or more and a calculated Tg of the above-described specification or less is easily obtained. Furthermore, a monomer having a nitrogen atom has a tendency to have a high Tg of a homopolymer in general, and if a monomer having a nitrogen atom is used as a monomer component constituting the polymer (A), the calculated Tg of the polymer (A) easily increases, and in this case, by appropriately combining the use of the monomer having a nitrogen atom and a C 4－9 alkyl ester, a polymer (A) that can preferably achieve both a SP value of the above-described specification or more and a calculated Tg of the above-described specification or less.

[0068] In the case where the monomer component constituting the polymer (A) contains a monomer having a nitrogen atom, the proportion of the monomer having a nitrogen atom in the monomer component can be set to obtain a desired use effect. In some embodiments, the proportion of the monomer having a nitrogen atom in the monomer component can be, for example, 1 mol% or more, suitably 5 mol% or more, preferably 10 mol% or more, more preferably 15 mol% or more, also 20 mol% or more, also 25 mol% or more, also 30 mol% or more, also 35 mol% or more. On the other hand, from the viewpoint of easily making the calculated Tg of the polymer (A) be the above-described specification or less, the proportion of the monomer having a nitrogen atom in the monomer component is suitably 70 mol% or less, preferably 65 mol% or less, also 60 mol% or less, also 55 mol% or less, also 50 mol% or less, also 45 mol% or less, also 40 mol% or less.

[0069] In some preferred embodiments, the monomer component constituting the polymer (A) contains at least acrylonitrile as the above-described monomer having a nitrogen atom. By causing the monomer component to contain acrylonitrile, a coating material that balances good release properties and good anti-fingerprint adhesion properties in a good manner and a coating composition capable of forming the coating material are easily achieved. The proportion of acrylonitrile in the monomer having a nitrogen atom contained in the monomer component can be, for example, 25 mol% or more, also 50 mol% or more, also 70 mol% or more, also 85 mol% or more, also 95 mol% or more, also 100 mol%.

[0070] In the case where the monomer component constituting the polymer (A) contains acrylonitrile, the proportion of acrylonitrile in the monomer component may, for example, be 1 mol% or more, suitably 5 mol% or more, preferably 10 mol% or more, more preferably 15 mol% or more, also 20 mol% or more, also 25 mol% or more, also 30 mol% or more, also 35 mol% or more. On the other hand, from the viewpoint of easily making the calculated Tg of the polymer (A) fall within the prescribed range, the proportion of acrylonitrile in the monomer component is suitably 70 mol% or less, preferably 65 mol% or less, also 60 mol% or less, also 55 mol% or less, also 50 mol% or less, also 45 mol% or less, also 40 mol% or less.

[0071] The acid value of the polymer (A) is not particularly limited, and may, for example, be 60 mgKOH / g or less. In some cases, from the viewpoint of suppressing the peeling strength from the coated film, the acid value of the polymer (A) is advantageously 20.0 mgKOH / g or less, preferably 15.0 mgKOH / g or less, more preferably 12.0 mgKOH / g or less, also 11.0 mgKOH / g or less, also 10.0 mgKOH / g or less. The technology disclosed herein can also be implemented in a case where the acid value of the polymer (A) is 8.0 mgKOH / g or less, 6.0 mgKOH / g or less, 3.0 mgKOH / g or less, or 1.0 mgKOH / g or less. The acid value of the polymer (A) can be 0 mgKOH / g or higher. In some cases, from the viewpoint of improving the strength (e.g., the breaking strength) of the coating material and the like, the acid value of the polymer (A) may, for example, be 1.0 mgKOH / g or more, also 2.0 mgKOH / g or more, also 4.0 mgKOH / g or more, also 7.0 mgKOH / g or more. Improving the strength of the coating material is advantageous from the viewpoint of improving the peeling workability (e.g., preventing breakage and defects at the time of peeling).

[0072] The acid value of the polymer (A) is measured based on the potentiometric titration method prescribed in JIS K0070: 1992. As a sample for acid value measurement, for the polymer (A) contained in the coating material, the mixture obtained by adding the coating material to chloroform is left standing for 12 hours, after which the mixture is filtered with a filter, and a substance having a weight average molecular weight of 10,000 or more (measured by GPC) is used as the sample. In the case of the acid value of the polymer (A) contained in the coating composition, after the coating composition is dried at 80°C for 3 minutes to form a film (coating material) having a thickness of about 100 μm, the obtained substance is used as the sample in the same manner as the sample for acid value measurement of the polymer (A) contained in the coating material. The acid value of the polymer (A) contained in the aqueous emulsion of the polymer (A) described later is measured using the substance obtained in the same manner as the sample for acid value measurement of the polymer (A) contained in the coating composition as the sample. More specifically, for example, a sample taken by precise weighing is added to 50 mL of a solvent obtained by mixing diethyl ether and ethanol at a volume ratio of 4:1, and the sample is completely dissolved, and further, a phenothalin solution is added as an indicator, and a measurement solution is prepared. The measurement solution is subjected to potentiometric titration with a 0.1 mol / L potassium hydroxide ethanol solution, and the inflection point of the titration curve obtained is taken as the end point. The acid value is calculated according to the following formula. In the examples described later, the acid value of the polymer (A) is measured by this method.

[0073] Acid value (mgKOH / g) = (B x F x 5.611) / S

[0074] B: Amount of addition (mL) of the 0.1 mol / L potassium hydroxide ethanol solution at the end point.

[0075] F: 0.1 mol / L potassium hydroxide ethanol solution (1.0).

[0076] S: Sample taking amount (g).

[0077] In some aspects of the technology disclosed herein, the monomer component constituting the above-described polymer (A) contains a monomer (m T ) having a Tg of 90°C or higher as a homopolymer and a monomer (m L ) having a Tg of -30°C or lower as a homopolymer. In this case, the above-described monomer (m T ) can contain a monomer having a nitrogen atom having a Tg of 90°C or higher as a homopolymer. As one example of a monomer having a nitrogen atom having a Tg of 90°C or higher as a homopolymer, acrylonitrile (Tg of homopolymer: 97°C) can be given. The polymer (A) in this aspect can be a polymer containing the monomer (m L ) and a monomer (m T), and optionally further comprises a monomer component of other monomers. Note that the Tg of the homopolymer of each monomer is the value described in the publicly known literature, and in the case where the Tg of the homopolymer is not described in the publicly known literature, the inflection point temperature of the loss modulus G" obtained by the above-described measurement method is used.

[0078] monomer (m L ) can contribute to moderately lowering the calculated Tg of the polymer (A) and improving the stain adhesion resistance of the coating material containing the polymer (A). Lowering the calculated Tg of the polymer (A) can also be advantageous from the viewpoint of improving the low-temperature properties of the coating material (for example, suppressing the generation of cracks at low temperatures, suppressing the breaking, chipping, and the like at the time of peeling from the coating film at low temperatures, and the like). As the monomer (m L ), a monomer of which the Tg of the homopolymer is -30°C or lower can be used, and for example, can be selected from the above-described various monomers, but is not limited to these. The monomer (m L ) can be used alone or in combination with two or more kinds. The monomer (m L ) can be used alone or in combination with two or more kinds. Non-limiting specific examples of the monomer that can be used as the monomer (m

[0079] The lower limit of the Tg of the homopolymer of each monomer used as the monomer (m L ) is not particularly limited, and for example, can be -100°C or higher, -90°C or higher, or -80°C or higher. In some aspects, it can be preferable to use a monomer of which the Tg of the homopolymer is in the range of -60°C or higher and -40°C or lower as the monomer (m L ). In the monomer (m L ), the proportion of the monomer of which the Tg of the homopolymer is in the range of -60°C or higher and -40°C or lower can be, for example, 50 mol% or more, 75 mol% or more, 85 mol% or more, 95 mol% or more, or 100 mol%.

[0080] The monomer (m T ) can contribute to improving the cohesiveness of the coating material, the high-temperature properties (for example, suppressing the decrease in the storage modulus in the high-temperature region, the peeling properties at high temperatures, and the like). The monomer (m T ) can be used alone or in combination with two or more kinds. The monomer (m T) can include only one kind of monomer containing a nitrogen atom, or two or more kinds of monomers containing a nitrogen atom, or one or two or more kinds of monomers containing a nitrogen atom and other monomers (i.e., monomers other than monomers containing a nitrogen atom. Hereinafter, also referred to as "monomers not containing a nitrogen atom") having a Tg of 90°C or higher as a homopolymer. As the monomers (m T ), acrylonitrile can be used alone, or acrylonitrile and monomers not containing a nitrogen atom having a Tg of 90°C or higher as a homopolymer can be used in combination, or acrylonitrile, monomers not containing a nitrogen atom having a Tg of 90°C or higher as a homopolymer, and monomers containing a nitrogen atom (excluding acrylonitrile) having a Tg of 90°C or higher as a homopolymer can be used in combination. The monomers not containing a nitrogen atom having a Tg of 90°C or higher as a homopolymer can be appropriately selected from the above-described various monomers, but are not limited thereto. The above-described monomers not containing a nitrogen atom can be used alone or in combination with two or more kinds of monomers containing a nitrogen atom (e.g., acrylonitrile) having a Tg of 90°C or higher as a homopolymer. As the monomers (m T ), the upper limit of the Tg of the homopolymer of each monomer used is not particularly limited, and can be, for example, 250°C or lower, 200°C or lower, or 150°C or lower.

[0081] The monomers not containing a nitrogen atom that can be used as the monomers (m T ) include, for example, acrylic acid, methacrylic acid, methyl methacrylate, isobornyl acrylate, isobornyl methacrylate, dicyclopentyl acrylate, dicyclopentyl methacrylate, adamantyl acrylate, t-butyl methacrylate, and the like, and as preferred examples, acrylic acid (AA) and methyl methacrylate (MMA) can be given. The monomers containing a nitrogen atom that can be used as the monomers (m T ) include, for example, acrylonitrile, methacrylonitrile, acryloyl morpholine, acrylamide, and the like, and as a preferred example, acrylonitrile can be given.

[0082] The content of the monomers containing a nitrogen atom in the monomers (m T ) can be, for example, 35 mol% or more, and from the viewpoint of easily achieving appropriate film properties, is preferably 50 mol% or more, and more preferably 60 mol% or more. In some embodiments, the content of the monomers containing a nitrogen atom in the monomers (m T ) can exceed 70 mol%, can exceed 80 mol%, can exceed 90 mol%, can exceed 93 mol%, or can be 100 mol%. Furthermore, in some embodiments, the content of the monomers containing a nitrogen atom in the monomers (m T ) can be 85 mol% or less, can be 75 mol% or less, can be 70 mol% or less, or can be 65 mol% or less.

[0083] In some embodiments, the content of the monomers not containing a nitrogen atom in the monomers (m T) contains at least acrylonitrile. In this aspect, the monomer (m T ) The proportion of acrylonitrile in the monomer (m

[0084] In the aspect where the monomer (m T ) contains acrylonitrile, the content of acrylonitrile in the monomer (m T ) may, for example, be 35 mol% or more, and from the viewpoint of easily achieving a suitable film property, is suitably 50 mol% or more, and preferably 60 mol% or more. In some aspects, the content of acrylonitrile in the monomer (m T ) may exceed 70 mol%, or may exceed 80 mol%, or may exceed 90 mol%, or may exceed 93 mol%, or may be 100 mol%. Furthermore, in some aspects, the content of acrylonitrile in the monomer (m T ) may be 85 mol% or less, or may be 75 mol% or less, or may be 70 mol% or less, or may be 65 mol% or less.

[0085] In the aspect where the monomer component constituting the polymer (A) contains the monomer (m T ) and the monomer (m L ), the proportion of the monomer containing a nitrogen atom having a Tg of 90°C or more of the homopolymer in the entire monomer component described above may, for example, be 20 mol% or more, and from the viewpoint of easily achieving a suitable film property, is suitably 25 mol% or more (for example, 28 mol% or more), and preferably 30 mol% or more, and may be 35 mol% or more, or may be 40 mol% or more. The technology disclosed herein can be preferably implemented in an aspect where the proportion of the monomer containing a nitrogen atom having a Tg of 90°C or more of the homopolymer in the entire monomer component constituting the polymer (A) is more than 50 mol%. Furthermore, from the viewpoint of the softness of the coating material, the proportion of the monomer containing a nitrogen atom having a Tg of 90°C or more of the homopolymer described above is suitably 60 mol% or less, and preferably less than 60 mol%. In some aspects, the proportion of the monomer containing a nitrogen atom having a Tg of 90°C or more of the homopolymer described above may be 57 mol% or less, or may be 56 mol% or less. The technology disclosed herein can also be implemented in an aspect where the proportion of the monomer containing a nitrogen atom having a Tg of 90°C or more of the homopolymer described above is 53 mol% or less, 50 mol% or less, and further 40 mol% or less.

[0086] In the aspect where the monomer component constituting the polymer (A) contains the monomer (m T ) and the monomer (m LIn the proposed scheme, the acrylonitrile content in the total monomer component can be, for example, 20 mol% or more. From the viewpoint of easily achieving appropriate film properties, it is suitable to be 25 mol% or more (e.g., 28 mol% or more), preferably 30 mol% or more, or 35 mol% or more, or 40 mol% or more. The disclosed technology is preferably implemented with an acrylonitrile content in the total monomer component constituting polymer (A) of more than 50 mol%. Furthermore, from the viewpoint of the flexibility of the coating material, the acrylonitrile content is suitable to be 60 mol% or less, preferably less than 60 mol%. In some schemes, the acrylonitrile content can be 57 mol% or less, or 56 mol% or less. The disclosed technology can also be implemented with an acrylonitrile content of 53 mol% or less, 50 mol% or less, or even 40 mol% or less.

[0087] The monomer (m) in the above monomer components T ) and the above monomers (m L molar ratio (m) T / m L There are no specific limitations; for example, it can be around 0.05 to 3.00, or around 0.10 to 2.00. (m) T / m L For example, a value between 0.60 and 1.50 readily yields coating materials with storage moduli within the aforementioned range at various temperatures. In some embodiments, the aforementioned ratio (m) T / m L Preferably less than 1.5, more preferably less than 1.4, and can be less than 1.35, less than 1.30, less than 1.30 (e.g., less than 1.29), less than 1.28, or less than 1.25. Furthermore, in some embodiments, the above ratio (m) T / m L The value is preferably 0.70 or higher, more preferably 0.75 or higher, and can be 0.90 or higher, 1.0 or higher, or even greater than 1.0. This allows for a coating material that achieves a better balance between good peelability and good peelability at a higher level. The above ratio (m) T / m L The value can be 1.1 or higher, or 1.15 or higher, or 1.20 or higher, or 1.22 or higher, or 1.25 or higher.

[0088] The monomer components constituting polymer (A) may also include monomers other than (m) T ) and monomers (m L Monomers other than those in the homopolymer, i.e., monomers with a glass transition temperature higher than -30°C and lower than 90°C (and may also include monomers (m) I). As the monomer (m I ), for example, a monomer whose glass transition temperature of a homopolymer is in the above range can be selected from the above various monomers, but is not limited to these. The monomer (m I ) can be used singly or in combination of two or more. Non-limiting specific examples of the monomer which can be used as the monomer (m I ) include ethyl acrylate (EA), ethyl methacrylate, methyl acrylate (MA), n-butyl methacrylate, isobutyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, vinyl acetate, N-vinyl-2-pyrrolidone, and the like.

[0089] The amount of use of the monomer (m I ) can be appropriately set in the range of 0 or more and less than 100 mole% of the total amount of the monomer components, from which the amount (mole%) of the monomer (m T ) and the monomer (m L ) is removed. In some cases, the amount of use of the monomer (m I ) is appropriately 80 mole% or less (for example, 40 mole% or less) of the total amount of the monomer components, advantageously 30 mole% or less, preferably 20 mole% or less, and more preferably 15 mole% or less. The technology disclosed herein can be preferably implemented in a case where the amount of use of the monomer (m I ) is 0 mole% or more and less than 10 mole% of all the monomer components, for example, 0 mole% or more and less than 5 mole%. Here, the amount of use of the monomer (m I ) of 0 mole% of the total amount of the monomer components means that the monomer (m I ) is not intentionally used at least.

[0090] < Synthesis of Polymer (A) >

[0091] The method for obtaining the polymer (A) from the monomer components as described above is not particularly limited. For example, a publicly known polymerization method such as emulsion polymerization, solution polymerization, bulk polymerization, suspension polymerization, etc. can be appropriately employed. Alternatively, active energy ray irradiation polymerization such as light polymerization (typically, in the presence of a photopolymerization initiator) by irradiation of UV or the like, radiation polymerization by irradiation of β-rays, γ-rays or the like, etc. can be employed. From the viewpoint of easily preparing a coating composition in the form of an aqueous emulsion in which the polymer (A) is dispersed in an aqueous solvent, in some preferable embodiments, the polymer (A) is obtained by emulsion polymerization of the monomer components of the composition as described above. As the monomer feeding mode in the emulsion polymerization, a one-shot feeding mode in which all the monomer raw materials are fed at once, a continuous feeding (dropping) mode, a batch feeding (dropping) mode, etc. can be appropriately employed. A part or all of the monomer components can be emulsified by mixing with water and an emulsifying agent in advance, and the emulsion can be fed to a polymerization vessel.

[0092] The polymerization temperature can be appropriately selected depending on the kind of monomers and solvents used, the kind of polymerization initiator, etc. The polymerization temperature is appropriately set to be about 20°C or higher, preferably about 40°C or higher, more preferably about 50°C or higher, can be set to be about 60°C or higher, and can be set to be about 65°C or higher, further to be about 70°C or higher. In addition, the polymerization temperature is appropriately set to be about 170°C or lower (typically, about 140°C or lower), preferably about 95°C or lower (for example, about 85°C or lower). In emulsion polymerization, the polymerization temperature is preferably set to be about 95°C or lower (for example, about 85°C or lower).

[0093] In the polymerization, a publicly known or conventional thermal polymerization initiator, photopolymerization initiator, etc. can be used depending on the polymerization method, polymerization scheme, etc. The polymerization initiator can be used alone or in combination of two or more as appropriate.

[0094] As the thermal polymerization initiator, there is no particular limitation, and for example, an azo-based polymerization initiator, a peroxide-based initiator, a redox-based initiator based on a combination of a peroxide and a reducing agent, a substituted ethane-based initiator, etc. can be used.

[0095] As examples of the azo-based initiator, 2,2'-azobisisobutyronitrile, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(N,N'-dimethylisobutyramidine) dihydrochloride, etc. can be listed.

[0096] As examples of the peroxide-based initiator, there can be mentioned: persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, dilauryl peroxide, di-n-octyl peroxide, di(4-methylbenzoyl) peroxide, t-butyl peroxybenzoate, t-butyl peroxyisobutyrate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, di(2-ethylhexyl) peroxydicarbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl peroxyneodecanote, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, 1,1-bis(t-hexylperoxy)cyclohexane, hydrogen peroxide, and the like.

[0097] As examples of the redox-based initiator, there can be mentioned: a combination of a peroxide and ascorbic acid (a combination of hydrogen peroxide water and ascorbic acid, etc.), a combination of a peroxide and an iron (II) salt (a combination of hydrogen peroxide water and an iron (II) salt, etc.), a combination of a persulfate and a pyrosulfite (a combination of ammonium persulfate and sodium pyrosulfite, etc.), a combination of a persulfate and a bisulfite (e.g., sodium bisulfite), and the like.

[0098] As the photopolymerization initiator, there is no particular limitation, and it is possible to use, for example, a ketal-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, a benzoin ether-based photopolymerization initiator, an acyloxyphosphine-based photopolymerization initiator, an α-keto alcohol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzil-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, and the like.

[0099] The amount of the polymerization initiator used can be set to a usual amount corresponding to the polymerization method, the polymerization scheme, and the like, and there is no particular limitation. For example, it is possible to use about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example, about 0.01 to 1 part by weight) of the polymerization initiator with respect to 100 parts by weight of the monomer that is the object of polymerization.

[0100] At the time of polymerization, various chain transfer agents (which can also be understood as molecular weight regulators or polymerization degree regulators) conventionally known can be used as needed. The chain transfer agent can be used singly or in combination of two or more. As the chain transfer agent, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, mercaptoacetic acid, or the like can be used. Alternatively, a chain transfer agent not containing a sulfur atom (non-sulfur chain transfer agent) can also be used. As specific examples of the non-sulfur chain transfer agent, anilines such as N,N-dimethylaniline, N,N-diethylaniline, terpenoids such as α-pinene, terpinolene, styrenes such as α-methylstyrene, α-methylstyrene dimer, compounds having a benzylidene group such as dibenzylidene acetone, cinnamic alcohol, cinnamaldehyde, hydroquinones such as hydroquinone, naphthohydroquinone, quinones such as benzoquinone, naphthoquinone, olefins such as 2,3-dimethyl-2-butene, 1,5-cyclooctadiene, alcohols such as phenol, benzyl alcohol, allyl alcohol, benzyl hydrides such as diphenylbenzene, triphenylbenzene, and the like can be listed.

[0101] In the case of using the chain transfer agent, the amount of use thereof can be set to about 0.01 to 1 parts by weight or thereabout with respect to 100 parts by weight of the monomer component, for example. The technology disclosed herein can also be preferably implemented in a scheme in which no chain transfer agent is used.

[0102] The emulsion polymerization is usually performed in the presence of an emulsifier. As the emulsifier for the emulsion polymerization, there is no particular limitation, and a publicly known anionic emulsifier, nonionic emulsifier, or the like can be used. The emulsifier can be used singly or in combination of two or more.

[0103] As non-limiting examples of the anionic emulsifier, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkylsulfosuccinate, and the like can be listed. As non-limiting examples of the nonionic emulsifier, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer, and the like can be listed. An emulsifier having a reactive functional group (reactive emulsifier) can also be used. As examples of the reactive emulsifier, a radical polymerizable emulsifier having a structure in which a radical polymerizable functional group such as an acryl group or an allyl ether group is introduced into the above-described anionic emulsifier or nonionic emulsifier can be listed.

[0104] The emulsifier used in the emulsion polymerization can be used in an amount of, for example, 0.2 parts by weight or more, 0.5 parts by weight or more, 1.0 parts by weight or more, or 1.5 parts by weight or more, based on 100 parts by weight of the monomer component. In some embodiments, the emulsifier is used in an amount of, for example, 10 parts by weight or less, preferably 5 parts by weight or less, or 3 parts by weight or less, based on 100 parts by weight of the monomer component.

[0105] In some embodiments, the emulsion polymerization described above can be performed in the presence of a protective colloid. As the protective colloid, for example, polyvinyl alcohol-based polymers (PVA), cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose salts, natural polysaccharides such as guar gum, and the like can be exemplified. The protective colloid can be used alone or in combination with two or more kinds.

[0106] The protective colloid can be used in an amount of, for example, 0.1 parts by weight or more, advantageously 0.3 parts by weight or more, preferably 0.5 parts by weight or more (for example, 0.7 parts by weight or more), 1.0 parts by weight or more, 1.5 parts by weight or more, 2.0 parts by weight or more, or 2.5 parts by weight or more, based on 100 parts by weight of the monomer component. In addition, the protective colloid can be used in an amount of, for example, 10 parts by weight or less, 5.0 parts by weight or less, 4.0 parts by weight or less, 3.5 parts by weight or less, 3.0 parts by weight or less, or 2.5 parts by weight or less, based on 100 parts by weight of the monomer component.

[0107] In some embodiments, the emulsion polymerization is performed in the presence of PVA. The aqueous emulsion of the polymer (A) obtained by this emulsion polymerization tends to easily exhibit the tackifying effect brought about by the addition of a tackifier. By using such an aqueous emulsion of the polymer (A), a coating composition that exhibits excellent sag resistance can be preferably produced. From the viewpoint of easily obtaining a coating composition that exhibits excellent slit die coating suitability, it can also be advantageous to perform the emulsion polymerization in the presence of PVA. As the PVA, a substance corresponding to the polymer (B) described later can be preferably used, but is not limited thereto, and a PVA that does not correspond to the polymer (B) can also be used, or a PVA corresponding to the polymer (B) and a PVA that does not correspond to the polymer (B) can be used in combination. In some embodiments, the emulsion polymerization for obtaining the polymer (A) is performed in the presence of PVA, and 50% by weight or more (preferably 70% by weight, more preferably 90% by weight or more, or 100% by weight) of the PVA corresponds to the polymer (B). In this case, the polymer (B) used at the time of the emulsion polymerization is preferably one or two or more selected from the group consisting of unmodified PVA and anionic PVA (for example, carboxyl-modified PVA).

[0108] The protective colloid (e.g., PVA corresponding to the polymer (B)) can be used in combination with the emulsifier as described above, or can be used without the emulsifier. In some preferred embodiments, the emulsifier and the protective colloid are used in combination as described above. For example, the emulsion polymerization can be performed in such a manner that water and the protective colloid are added to a polymerization vessel, a part or all of the monomer ingredients are previously mixed and emulsified with the water and the emulsifier to obtain an emulsified liquid, and the emulsified liquid is supplied to the above polymerization vessel. Note that in the case where the protective colloid is anionic (e.g., anionically modified PVA) and the emulsifier are used in combination, from the viewpoint of polymerization stability and the like, as the emulsifier, it is preferable to use one or two or more selected from the group consisting of anionic emulsifiers and nonionic emulsifiers.

[0109] <Polyvinyl alcohol-based polymer (B)>

[0110] The coating composition provided by the present specification contains a polyvinyl alcohol-based polymer (B). As the polyvinyl alcohol-based polymer (B) (hereinafter, sometimes simply referred to as "polymer (B)") in the technology disclosed herein, one or two or more PVA satisfying the prescribed saponification degree and polymerization degree is used. By using the polymer (B), the film-forming properties (e.g., suppression of cracking) when forming a coating film protective coating material from a water-based emulsion form coating composition, the anti-sagging properties can be improved.

[0111] From the viewpoint of the drying properties when forming a coating film protective coating material from a water-based emulsion form coating composition, the saponification degree of the PVA used as the polymer (B) is appropriately 80 mol% or more, more preferably 82 mol% or more, can be 84 mol% or more, can be 85 mol% or more, can be 86 mol% or more or 87 mol% or more, can be 88 mol% or more, 90 mol% or more, or 93 mol% or more. In some embodiments, as the polymer (B), a PVA sometimes generally referred to as a fully saponified PVA, having a saponification degree of 95 mol% or more (e.g., 96 mol% or more, 98 mol% or more, or 99 mol% or more) can be used. Furthermore, in some embodiments, from the viewpoint of the film-forming properties and the like, the saponification degree of the PVA used as the polymer (B) can be less than 99 mol%, can be 98 mol% or less, can be 97 mol% or less, can be 90 mol% or less (e.g., less than 90 mol%), can be 89 mol% or less, or can be 88 mol% or less. A saponification degree that is not too high can also be advantageous from the viewpoint of the stability of the emulsion.

[0112] The polymerization degree of the PVA used as the polymer (B) is suitably 1200 or less, preferably 1000 or less, can be 900 or less, can be 800 or less, can be 700 or less, can be 600 or less, can be 500 or less, from the viewpoint of the drying property, stability of the emulsion, and the like. Further, the lower limit of the polymerization degree of the PVA is not particularly limited, and can be suitably selected in a manner that suitably exerts the effect of use. In some aspects, the polymerization degree of the PVA used as the polymer (B) is suitably 200 or more, preferably 300 or more, can be 400 or more, can be 500 or more.

[0113] Note that the saponification degree and the polymerization degree of the PVA are measured based on JIS K6726:1994. In the case where a nominal value is provided by the manufacturer, the distributor, or the like, the value can be adopted.

[0114] The PVA used as the polymer (B) can be a modified PVA, or can be an unmodified PVA. One or two or more modified PVAs and one or two or more unmodified PVAs can also be used in combination. As examples of the modified PVA, anionic modified PVAs in which anionic groups such as carboxyl groups, sulfonic acid groups, phosphoric acid groups, and the like are introduced; cationic modified PVAs in which cationic groups such as quaternary ammonium salts are introduced; nonionic modified PVAs in which oxyalkylene groups (for example, oxyethylene groups, oxypropylene groups, and the like) or polyoxyalkylene structures obtained by repeating the same are introduced in the side chain; and the like can be listed. The anionic modified PVA is obtained, for example, by saponifying a copolymer of a monomer having an anionic group and a vinyl ester (for example, vinyl acetate). As the anionic group in the anionic modified PVA, a carboxyl group, a sulfonic acid group is preferred. In some preferred aspects, as the polymer (B), one or two or more selected from the group consisting of unmodified PVAs and anionic modified PVAs (for example, carboxyl modified PVAs, sulfonic acid modified PVAs, and the like) are used.

[0115] The polymer (B) contained in the coating composition disclosed herein can be a substance used as a protective colloid when the polymer (A) is synthesized by emulsion polymerization. In addition, the polymer (B) contained in the coating composition disclosed herein can be a substance added after an aqueous emulsion of the polymer (A) obtained by emulsion polymerization in the absence of the polymer (B) is prepared, or a substance added during or after the preparation of an aqueous emulsion of a polymer (A) obtained by a method other than emulsion polymerization, such as a solution polymerization method, dispersed in an aqueous solvent. In some preferred embodiments, at least a portion of the polymer (B) contained in the coating composition is a substance used as a protective colloid during the above-described emulsion polymerization. The proportion of the polymer (B) used as the above-described protective colloid in the total amount of the polymer (B) contained in the coating composition is, for example, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, and can be 100% by weight.

[0116] In the coating composition disclosed herein, the content of the polymer (B) (in the case where two or more PVAs are used as the polymer (B), the total content thereof) is appropriately 0.3 parts by weight or more, advantageously 0.5 parts by weight or more (for example, 0.7 parts by weight or more), preferably 1.0 parts by weight or more, can be 1.5 parts by weight or more, can be 2.0 parts by weight or more, and can be 2.5 parts by weight or more, relative to 100 parts by weight of the polymer (A), from the viewpoint of easily appropriately exerting the use effect of the polymer (B). In addition, the content of the polymer (B) is appropriately 5.0 parts by weight or less, preferably 4.0 parts by weight or less, can be 3.5 parts by weight or less, can be 3.0 parts by weight or less, and can be 2.5 parts by weight or less, relative to 100 parts by weight of the polymer (A), from the viewpoint of the drying property and the like of the coating composition. The above-described content of the polymer (B) can also be applied to the amount of the polymer (B) present relative to 100 parts by weight of the monomer component in the case where the polymer (A) is obtained by emulsion polymerization in the presence of the polymer (B). The amount of the polymer (B) is not excessively large from the viewpoint of the polymerization stability when the polymer (A) is obtained by emulsion polymerization in the presence of the polymer (B), the stability of the obtained emulsion, and the like.

[0117] The coating composition disclosed herein can contain a PVA other than the polymer (B) in addition to the polymer (B). The content of the PVA other than the polymer (B) is appropriately less than 50% by weight, preferably less than 20% by weight, and more preferably less than 10% by weight (for example, less than 5% by weight) of the entire PVA (i.e., the total amount of the PVA corresponding to the polymer (B) and the PVA other than the polymer (B)) from the viewpoint of easily appropriately exerting the use effect of the polymer (B). The coating composition can also be substantially free of the PVA other than the polymer (B).

[0118] <Other components>

[0119] The coating composition disclosed herein can contain other arbitrary components as desired. As examples of such arbitrary components, additives such as well-known tackifiers, thixotropic agents, dispersants, defoaming agents, and inorganic powders can be cited. For example, various additives can be incorporated into the aqueous emulsion of the polymer (A) obtained by emulsion polymerization as described above (polymerization reaction liquid), thereby preparing a coating composition in the form of an aqueous emulsion containing the above-described additives. Further, for example, in the case where the aqueous emulsion of the polymer (A) is obtained by emulsion polymerization in the presence of the polymer (B), the aqueous emulsion can be used as it is or a substance obtained by pH adjustment (for example, adjustment of the pH to about 6 to 8 by the addition of ammonia water) and / or concentration adjustment (for example, adjustment of the solid content to about 40 to 60% by weight by the addition of water) of the aqueous emulsion can be used as the coating composition.

[0120] (Tackifier)

[0121] The tackifier can contribute to the adjustment of the viscosity characteristics of the coating composition. As the tackifier, for example, well-known tackifiers such as urethane-based tackifiers, cellulose-based tackifiers, polyether-based tackifiers, and acrylic-based tackifiers can be used. The tackifier can be used alone or in combination of two or more as appropriate.

[0122] As commercially available products of urethane-based tackifiers, for example, the following can be mentioned: "RHEOBYK-H 3300VF", "RHEOBYK-T 1010", "RHEOBYK-L 1400" manufactured by BYK Co., Ltd., "ADEKA NOL UH-450VF", "ADEKA NOL UH-420", "ADEKA NOL UH-462", "ADEKA NOL UH-472", "ADEKA NOL UH-540", "ADEKA NOL UH-756VF", "ADEKA NOL UH-814N" manufactured by ADEKA Co., Ltd., "SN THICKENER 612", "SN THICKENER 621N", "SN THICKENER 625N", "SN THICKENER 627N", "SN THICKENER 660T" manufactured by San Nopco Co., Ltd., and the like. In some embodiments, as the urethane-based tackifier, a urethane associative tackifier can be preferably used. As preferred examples of the urethane associative tackifier, the following can be mentioned: "RHEOBYK-H 3300VF", "RHEOBYK-T 1010", "RHEOBYK-L 1400" manufactured by BYK Co., Ltd., "ADEKA NOL UH-450VF", "ADEKA NOL UH-420" manufactured by ADEKA Co., Ltd., and the like.

[0123] As examples of the cellulose-based tackifier, the following can be mentioned: hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and the like. As commercially available products, for example, "SANHEC L" manufactured by San-Ei Chemical Industry Co., Ltd. can be mentioned.

[0124] As examples of the polyether-based tackifier, the following can be mentioned: polyethylene glycol, polyether dialkyl ester, polyether dialkyl ether, polyether epoxy modifier, and the like. As commercially available products, for example, "POLYOX WSR N-80" manufactured by Dow Chemical Co. can be mentioned.

[0125] As examples of the acrylic-based tackifier, the following can be mentioned: acrylic polymers such as sodium polyacrylate. As commercially available products, for example, "Primal ASE-60", "Primal TT-615", "Primal RM-5" manufactured by Rohm and Haas Co., "SN THICKENER 613", "SN THICKENER 618", "SN THICKENER 630", "SN THICKENER 634", "SN THICKENER 636" manufactured by San Nopco Co., Ltd., and the like can be mentioned.

[0126] The amount of use of the tackifier is not particularly limited and can be appropriately adjusted to obtain desired viscosity properties (e.g., BH viscosity measured at 30°C at 2 rpm). From the viewpoint of suppressing excessive influence on the properties of the film, in some aspects, the amount of use of the tackifier is appropriately set to 15 parts by weight or less, preferably 10 parts by weight or less, more preferably 5.0 parts by weight or less (e.g., 3.0 parts by weight or less) with respect to 100 parts by weight of the polymer (A), and can be 2.5 parts by weight or less, 2.0 parts by weight or less, or 1.5 parts by weight or less. The lower limit of the amount of use of the tackifier is not particularly limited and, for example, can be 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more with respect to 100 parts by weight of the polymer (A).

[0127] (Inorganic powder)

[0128] By containing the inorganic powder in the coating composition, a coating material containing the inorganic powder is formed. According to this coating material, light such as ultraviolet light can be shielded by the above inorganic powder, and light degradation of the coating material itself and the coating film protected by the coating material can be suppressed. As the inorganic powder, oxides such as titanium oxide, zinc oxide, magnesium oxide, aluminum oxide, and silicon dioxide; carbonates such as calcium carbonate; sulfates such as barium sulfate; and the like can be used. Preferably, the inorganic powder that can color the coating film protective coating material white. According to the white coating film protective coating material, for example, by suppressing the temperature rise caused by the irradiation of sunlight, the degradation of the coating material and the coating film can be more favorably suppressed.

[0129] The amount of use of the inorganic powder can be, for example, 0.5 parts by weight or more with respect to 100 parts by weight of the polymer (A), and is appropriately set to 1 part by weight or more, preferably 2 parts by weight or more, more preferably 3 parts by weight or more, and can be 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more from the viewpoint of the light shielding effect. In addition, the amount of use of the inorganic powder can be, for example, 100 parts by weight or less with respect to 100 parts by weight of the polymer (A), and is appropriately set to 80 parts by weight or less, advantageously 60 parts by weight or less, and preferably 50 parts by weight or less from the viewpoint of the strength and film formability of the coating material, and can be 40 parts by weight or less, 30 parts by weight or less, or 20 parts by weight or less.

[0130] In some preferred embodiments, the above inorganic powder contains at least titanium oxide (TiO2). Titanium oxide can be used in combination with another inorganic powder or two or more inorganic powders (e.g., calcium carbonate). The type of titanium oxide is not particularly limited, and any crystalline form of titanium oxide such as rutile, anatase, brookite, etc. can be used. Among them, rutile-type titanium oxide is preferred. Titanium oxide having a coating on the surface of the particles can also be used. The material of the coated titanium oxide particles is not particularly limited, and can be an inorganic oxide such as silica, alumina, zinc oxide, etc. As a preferred example, high-weatherability titanium oxide (typically, rutile-type titanium oxide) having a particle surface coated with Si-Al2O3, etc. can be mentioned.

[0131] The amount of titanium oxide used can be, for example, 0.1 parts by weight or more, and is appropriately 0.5 parts by weight or more, preferably 1 part by weight or more, more preferably 2 parts by weight or more, and can be 3 parts by weight or more, from the viewpoint of light shielding effect, with respect to 100 parts by weight of the polymer (A). In addition, the amount of titanium oxide used can be, for example, 30 parts by weight or less, and is appropriately 20 parts by weight or less, preferably 15 parts by weight or less, can be 10 parts by weight or less, and can be 8 parts by weight or less, with respect to 100 parts by weight of the polymer (A).

[0132] The average particle diameter of the inorganic powder is not particularly limited. For example, from the viewpoint of obtaining a good light shielding effect, the average particle diameter of the inorganic powder is preferably 150 nm or more, more preferably 180 nm or more, can be 220 nm or more, and can be 250 nm or more. On the other hand, from the viewpoint of dispersibility in the resin component, the average particle diameter of the inorganic powder is appropriately 2000 nm or less, preferably 1500 nm or less, more preferably 1000 nm or less (e.g., 800 nm or less), can be 500 nm or less, can be 400 nm or less, and can be 350 nm or less. For example, titanium oxide particles having an average particle diameter of about 250 to 350 nm can be preferably used.

[0133] (Thixotropic agent)

[0134] The thixotropic agent can contribute to the adjustment of the viscosity characteristics of the coating composition. As the thixotropic agent, for example, inorganic materials such as bentonite, modified bentonite, montmorillonite, hectorite, etc. can be used. The thixotropic agent can be used alone or in combination with two or more.

[0135] The amount of the thixotropic agent used is not particularly limited and can be appropriately adjusted to obtain the desired viscosity characteristics. From the viewpoint of suppressing excessive influence on the properties of the film, in some embodiments, the amount of the thixotropic agent used is appropriately set to 10 parts by weight or less, preferably 5.0 parts by weight or less, and can be 3.0 parts by weight or less, 2.5 parts by weight or less, or 2.0 parts by weight or less, with respect to 100 parts by weight of the polymer (A). The lower limit of the amount of the thixotropic agent used is not particularly limited and, for example, can be 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.1 parts by weight or more, with respect to 100 parts by weight of the polymer (A).

[0136] The thixotropic agent can also function as a tackifier. For the tackifier and the thixotropic agent as described above, they can be used in combination or only one of them can be used. In the case where the tackifier and the thixotropic agent are used in combination, the total amount of the tackifier and the thixotropic agent used can be set to, for example, 15 parts by weight or less, 10 parts by weight or less, 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.5 parts by weight or less, 2.0 parts by weight or less, or 1.5 parts by weight or less, with respect to 100 parts by weight of the polymer (A). In addition, the total amount of the tackifier and the thixotropic agent used can be set to, for example, 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more, and can be 0.7 parts by weight or more, 1.0 parts by weight or more, or 1.5 parts by weight or more, with respect to 100 parts by weight of the polymer (A).

[0137] <Properties of the coating composition>

[0138] (BH viscosity)

[0139] The viscosity (V B2 ) of the coating composition disclosed herein, which is measured by a BH-type viscometer under the conditions of 30°C and 2 rpm, is appropriately 25 Pa-s or more, desirably 30 Pa-s or more (for example, 32 Pa-s or more), preferably 40 Pa-s or more (for example, 45 Pa-s or more), and more preferably 50 Pa-s or more (for example, 55 Pa-s or more). As the viscosity measured under such low shear rate conditions becomes higher, there is a tendency that the sag resistance of the coating composition applied to a protection target (for example, the sag resistance when applied to a vertical surface) improves. On the other hand, from the viewpoints of the defoaming property and the leveling property of the coating composition, the viscosity (V B2 ) of the coating composition is appropriately 200 Pa-s or less, preferably 150 Pa-s or less, and more preferably 100 Pa-s or less (for example, 80 Pa-s or less).

[0140] In the coating composition disclosed herein, the viscosity (VB20 ) is not particularly limited, and for example, can be around 5 Pa-s to 50 Pa-s. When the viscosity (V B20 ) is in the above range, it is easy to obtain a coating composition in which the viscosity (V B2 ) is in the above range.

[0141] The viscosity (BH viscosity) of the coating composition obtained by a BH-type viscometer is measured at 30°C under conditions of 2 rpm and 20 rpm by a BH-type viscometer. The rotor used in the measurement is appropriately selected depending on the viscosity. For example, in the case where the measurement device is marked with a scale of 0 to 100, a rotor falling within the range of 10 to 90 of the scale can be selected for measurement.

[0142] (Rheometer viscosity)

[0143] In some embodiments, the viscosity (V －1 ) of the above coating composition measured by a cone-plate type rheometer at a shear rate of 100 sec R100 -1 is preferably 1.0 Pa-s or more, more preferably 1.3 Pa-s or more, can be 1.5 Pa-s or more, can be 2.0 Pa-s or more, and can be 2.3 Pa-s or more. By setting the viscosity (V R100 ) measured under the condition of high shear rate to the above, the coatability based on a slit die (die coatability) can be improved. The upper limit of the viscosity (V R100 ) is not particularly limited, and from the viewpoints of easiness in compatibility with defoaming property, easiness in liquid feeding, and the like, it is appropriately 15 Pa-s or less, preferably 10 Pa-s or less, can be 8.5 Pa-s or less, and can be 6.0 Pa-s or less. The above viscosity (rheometer viscosity) of the coating composition obtained by a rheometer can be measured by using a commercially available rheometer (for example, a rheometer viscometer "Rheo Stress 1" manufactured by HAAKE Co. or the like thereof), using a conical rotor (cone diameter: 35 mm, cone angle: 0.5 deg.), and according to the condition at 30°C, causing the shear rate to continuously change from 0.1 to 2000 sec －1 -1, and reading the viscosity at a shear rate of 100 sec －1 -1.

[0144] (pH)

[0145] The pH of the coating composition disclosed herein is preferably 5.5 or more (more preferably 6.5 or more, for example 7.0 or more) from the viewpoint of dispersion stability, storage stability of the composition. In addition, the pH of the coating composition disclosed herein is preferably 11.0 or less, more preferably 10.0 or less, and even more preferably 9.0 or less (for example 8.0 or less) from the viewpoint of operability of the composition, and corrosion inhibition of a coating machine.

[0146] (Solid content)

[0147] The solid content of the coating composition disclosed herein is preferably 25% by weight or more (for example 35% by weight or more) from the viewpoint of drying efficiency, coatability, and the like, and is more preferably 40% by weight or more, and even more preferably 44% by weight or more from the viewpoint of film formability. In addition, the solid content of the coating composition disclosed herein is preferably 70% by weight or less, and more preferably 60% by weight or less, and can be 55% by weight or less, or 50% by weight or less from the viewpoint of coatability, dispersion stability of the emulsion, and the like. The solid content of the coating composition can be adjusted by the amount of use of the aqueous solvent, and the like. For example, the amount of the aqueous solvent used in the emulsion polymerization, and the addition of water after the completion of the emulsion polymerization can be adjusted to thereby adjust the solid content of the coating composition.

[0148] <Manufacture of coating composition>

[0149] The coating composition disclosed herein can be manufactured, for example, by a method including at least the steps of: preparing a polymer emulsion containing an aqueous solvent, a polymer (A), and a polymer (B) having a viscosity of 15 Pa-s or less at a solid content of 47% by weight, measured at 30°C and 2 rpm by a BH-type viscometer; and adjusting the viscosity of the polymer emulsion so as to have a viscosity of 25 Pa-s or more, measured at 30°C and 2 rpm by a BH-type viscometer. The content of the polymer (B) contained in the polymer emulsion disclosed herein can be, for example, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or less, or 0.3 parts by weight or more, per 100 parts by weight of the polymer (A). In the case where the content of the polymer (B) contained in the polymer emulsion disclosed herein is less than 0.3 parts by weight per 100 parts by weight of the polymer (A), the content of the polymer (B) contained in the finally obtained coating composition can be set to any of the above ranges (for example 0.3 parts by weight or more and 5.0 parts by weight or less) per 100 parts by weight of the polymer (A) by adding the polymer (B) to the polymer emulsion.

[0150] The viscosity of the above-mentioned polymer emulsion, measured by a BH-type viscometer at 30°C at 2 rpm, is preferably 0.5 Pa-s or more at a solid content of 47% by weight, and from the viewpoint of tackiness, it is preferably 1.0 Pa-s or more, more preferably 1.2 Pa-s or more (e.g., 1.5 Pa-s or more). In addition, from the viewpoint of polymerization stability and the like in the case of synthesizing the polymer (A) by emulsion polymerization, the viscosity of the above-mentioned polymer emulsion, measured by a BH-type viscometer at 30°C at 2 rpm, is preferably 10 Pa-s or less at a solid content of 47% by weight, desirably 7.0 Pa-s or less, preferably 5.0 Pa-s or less, more preferably 4.5 Pa-s or less (e.g., 4.0 Pa-s or less).

[0151] The pH of the above-mentioned polymer emulsion is desirably in the range of 5.5 or more (preferably 6.5 or more, e.g., 7.0 or more) and 9.0 or less (preferably 8.0 or less) from the viewpoint of dispersion stability and storage stability of the emulsion. A polymer emulsion having the above-mentioned viscosity at this pH is preferred. For example, a polymer emulsion having the above-mentioned viscosity and a pH of about 7.0 to 8.0 (e.g., about 7.5) is preferred.

[0152] In some embodiments, the solid content of the above-mentioned polymer emulsion is desirably 25% by weight or more or 35% by weight or more, preferably 40% by weight or more, more preferably 44% by weight or more, and in addition, desirably 70% by weight or less, preferably 60% by weight or less, and can be 55% by weight or less or 50% by weight or less, from the viewpoint of easily setting the solid content of the coating composition obtained using the polymer emulsion to any of the above-mentioned ranges. The solid content of the polymer emulsion can be adjusted by the amount of use of the aqueous solvent and the like. For example, the amount of the aqueous solvent used in emulsion polymerization and the addition of water after the completion of emulsion polymerization can be adjusted to thereby adjust the solid content of the polymer emulsion.

[0153] <Coating Film Protective Coating Material>

[0154] According to the present specification, a coating film protective coating material (hereinafter, sometimes simply referred to as "coating material") formed from any of the coating compositions disclosed herein is provided. The coating material disclosed herein is, for example, obtained by applying (preferably, by slit die coating) the above-mentioned coating composition to a coating film of a protective object, and drying it. Thereby, for example, as shown in Figure 1 Fig. 1, a coating film protective coating material 10 formed from the above-mentioned coating composition can be provided on the coating film 22 of the protective object 20 having the coating film 22.

[0155] As a method of applying the coating composition on the coating film of the object to be protected, for example, application using a coater such as a die coater, a spray coater, roll coating, dip coating, and the like can be used. The above-mentioned application using a die coater can be performed by a coating system including a robot arm provided with a slit die. For example, by controlling the above-mentioned robot arm in such a manner that the above-mentioned coating composition is sprayed in a continuous liquid film shape (strip shape) and the above-mentioned slit die is moved along the shape of the object to be protected, even if the object to be protected is a non-planar shape (for example, a complicated three-dimensional shape like the outer panel of an automobile), the coating composition can be efficiently and accurately applied on the object to be protected.

[0156] From the viewpoint of efficiency, high precision, and the like in forming the coating material, drying of the applied coating composition is preferably performed under heating. The drying temperature can be set to, for example, about 40°C to 100°C, and is generally preferably set to about 60°C to 90°C.

[0157] The thickness of the coating film of the coating material is not particularly limited, and is appropriately 20 μm or more from the viewpoint of improving the protective effect, and is preferably 50 μm or more, more preferably 70 μm or more (for example, 85 μm or more), and can be 100 μm or more, or 120 μm or more from the viewpoint of strength, peeling workability, and the like. The thickness of the coating material can be adjusted by the application amount and the solid content of the coating composition. The thickness of the coating material is appropriately 300 μm or less, preferably 200 μm or less, and more preferably 180 μm or less (for example, 150 μm or less) from the viewpoint of drying property, and anti-sagging of the applied composition.

[0158] The storage modulus at 70°C (G'(70)) of the coating material disclosed herein can be, for example, 0.40 MPa or more, without particular limitation. A coating material having a G'(70) of the prescribed value or more is, for example, a coating material that does not become excessively soft at a temperature higher than ordinary temperature, such as when a protected object provided with the coating material is left outdoors in summer, and can be appropriately peeled from the coating film. From the viewpoint of improving peelability at high temperatures, in some embodiments, the G'(70) is advantageously 0.50 MPa or more, preferably 0.60 MPa or more, can be 0.70 MPa or more, can be 0.80 MPa or more, and can be 0.90 MPa or more. The technology disclosed herein can be implemented in an embodiment in which the G'(70) is 1.0 MPa or more, 1.1 MPa or more, or 1.2 MPa or more. Furthermore, a G'(70) of the coating material of the prescribed value or less is preferable from the viewpoint of easily preventing marks from adhering to the coating film. Furthermore, the G'(70) of the coating material disclosed herein can be, for example, 1.30 MPa or less, can be 1.20 MPa or less, can be 1.10 MPa or less, or can be 1.00 MPa or less. The technology disclosed herein can also be implemented in an embodiment in which the G'(70) of the coating material is 0.90 MPa or less or 0.80 MPa or less.

[0159] The storage modulus at 23°C (G'(23)) of the coating material disclosed herein can be, for example, 250 MPa or more, can be 300 MPa or more, can be 350 MPa or more, can be 450 MPa or more, or can be 500 MPa or more, without particular limitation. A coating material having a G'(23) of the prescribed value or more tends not to be easily broken or excessively elongated when peeled from the coating film in the ordinary temperature range. This is advantageous from the viewpoint of improving peelability. On the other hand, a G'(23) that is not excessively high is advantageous from the viewpoint of suppressing marks from adhering to the coating film. Furthermore, it is easy to perform an operation that creates a peel opportunity (for example, an operation in which the end of the coating material is scraped with a fingernail or the like to cause it to float up from the coating film) when peeling the coating material from the coating film, and thus is also preferable from the viewpoint of peel workability. In some embodiments, the G'(23) of the coating material can be, for example, 800 MPa or less, can be 750 MPa or less, can be 700 MPa or less, can be 600 MPa or less, can be 500 MPa or less, or can be 400 MPa or less.

[0160] In some embodiments of the coating material disclosed herein, the storage modulus at -30°C (G'(-30)) of the coating material is, for example, suitably less than 2200 MPa from the viewpoint of preventing trace adhesion. From the viewpoint of easily achieving better trace adhesion, G'(-30) is preferably 2000 MPa or less, more preferably 1900 MPa or less, and can be 1800 MPa or less, 1700 MPa or less, or 1600 MPa or less. The lower limit of G'(-30) is not particularly limited. From the viewpoint of easily forming a coating material in which G'(70), G'(23) are in a moderate range, in some embodiments, G'(-30) is suitably 500 MPa or more, preferably 800 MPa or more, more preferably 1000 MPa or more, can be 1200 MPa or more, 1300 MPa or more, or 1400 MPa or more.

[0161] The storage modulus (G'(70), G'(23), G'(-30)) of the coating material is measured by the following method. That is, the coating material of the evaluation object is overlapped in multiple layers, integrated by pressing, thereby producing a laminated film having a thickness of about 1 mm. The laminated film is punched into a disc shape having a diameter of 7.9 mm using a parallel plate to prepare a measurement sample, and the viscoelasticity is measured by a shear mode at a temperature range of -70 to 150°C at a temperature increasing rate of 5°C / minute while applying a shear strain at a frequency of 1 Hz using a viscoelasticity tester, and the storage modulus G' at each temperature is calculated. The coating material described above is obtained by applying the coating composition to the coated surface of a coated steel sheet (on the coating film), drying it, and then peeling it from the coated steel sheet at room temperature. As the coated steel sheet, for example, a coated steel sheet coated with an acid epoxy crosslinking type acrylic paint (manufactured by KANSAI PAINT Co., Ltd., trade name "KINO 1210TW") is suitably used. As the viscoelasticity tester, "ARES G2" manufactured by TA Instruments Co., Ltd., or the equivalent thereof can be used.

[0162] The glass transition temperature (hereinafter, also referred to as "RSA-Tg") of the coating material of some embodiments, which is calculated in the form of the temperature corresponding to the inflection point of the loss modulus G" in the viscoelasticity measurement, is suitably 5°C or more, preferably 15°C or more, and more preferably 20°C or more. In addition, the RSA-Tg can be, for example, 40°C or less, 35°C or less, or 30°C or less (for example, 25°C or less). According to the coating material in which the RSA-Tg is in the above range, it is easy to obtain a coating material in which one or more of the above G'(70), G'(23), and G'(-30) are in a suitable range.

[0163] In some embodiments, the coating material disclosed herein has a breaking strength of, for example, 12 N / 25 mm or more, advantageously 15 N / 25 mm or more, preferably 20 N / 25 mm or more, and more preferably 25 N / 25 mm or more (e.g., 30 N / 25 mm or more). For example, it is preferable that the coating material have a breaking strength in the above range at a thickness of about 100 to 150 μm (e.g., at a thickness of about 100 μm).

[0164] In some embodiments, the coating material disclosed herein has an elongation at break of, for example, 100% or more, advantageously 150% or more, preferably 200% or more, and can be 220% or more, or 250% or more. Such a coating material can disperse stress by deforming moderately when peeled off from the coating film, and thus can inhibit damage to the coating material caused by local stress concentration. The upper limit of the elongation at break is not particularly limited, and for example, can be 500% or less, 450% or less, or 400% or less. An elongation at break that is not too large can be advantageous in terms of improving work efficiency when peeled. For example, it is preferable that the coating material have an elongation at break in the above range at a thickness of about 100 to 150 μm (e.g., at a thickness of about 100 μm).

[0165] The breaking strength and the elongation at break of the coating material are measured by the following method. That is, a measurement sample in the form of a strip having a width of 25 mm (e.g., a long strip shape having a width of 25 mm and a length of 100 mm) is prepared from the coating material to be evaluated. The measurement sample is set in a tensile tester under an environment of 23°C and 50% RH, and a tensile test is performed at a gauge length of 50 mm and a tensile speed of 0.3 m / min, whereby the breaking strength [N / 25 mm] and the elongation at break are measured. The measurement sample can be obtained, for example, by applying the coating composition to the coated surface of a coated steel sheet (to the coating film), drying it, peeling it from the coated steel sheet at room temperature, and cutting it to an appropriate size. As the coated steel sheet, for example, a coated steel sheet coated with an acid epoxy crosslinking type acrylic paint (KANSAI PAINT Co., Ltd., trade name "KINO 1210TW") is appropriately used. As the tensile tester, a device manufactured by Shimadzu Corporation, trade name "TENSILON" or the equivalent thereof can be used.

[0166] The coating material of some embodiments of the technology disclosed herein has a peel strength measured by the following method of, for example, 4.0 N / 25 mm or less, and preferably 2.5 N / 25 mm or less, from the viewpoint of obtaining good peelability from the coating film.

[0167] [Measurement of Peel Strength]

[0168] A coated steel sheet on which an acid epoxy crosslinking type acrylic paint (KANSAI PAINT Co., Ltd., trade name "KINO 1210TW") was applied was held horizontally with the coated surface facing upward. The coating composition was applied to the coated surface of the coated steel sheet in a manner such that the thickness of the coating composition, in terms of solid content, was 100 μm, and the coating was dried at 80°C for 3 minutes to form a film (coating film protective coating material). Subsequently, the coated steel sheet was moved into a constant temperature chamber at 70°C and held for 7 days. The coated steel sheet was removed from the constant temperature chamber and held in an environment at 23°C and 50% RH for 30 minutes or more, and then a film on the coating film was cut into two straight cuts (25 mm apart) and a cut orthogonal to the cuts, and the film was partially peeled from the cut orthogonal to the cuts, and the film was set in a tensile tester and peeled in the 180-degree direction at a tensile speed of 0.3 m / min, and the peeling strength of the film from the coated steel sheet [N / 25 mm] was measured. As the tensile tester, for example, a device manufactured by Shimadzu Corporation, trade name "TENSILON" or the like can be used.

[0169] In some embodiments, the peeling strength is more preferably 2.0 N / 25 mm or less, further preferably 1.5 N / 25 mm or less, can be 1.2 N / 25 mm or less, or 1.0 N / 25 mm or less. A low peeling strength is preferable from the viewpoint of reducing the work burden at the time of peeling, and is also advantageous from the viewpoint of suppressing the breaking and the like of the coating material at the time of peeling. In addition, from the viewpoint of obtaining a moderate adhesion to the coating film, the peeling strength is appropriately 0.1 N / 25 mm or more, preferably 0.2 N / 25 mm or more, can be 0.3 N / 25 mm or more, or 0.5 N / 25 mm or more, or 0.7 N / 25 mm or more. The peeling strength is not too low from the viewpoint of preventing the phenomenon in which the coating material is unintentionally peeled from the coating film during the protection period of the coating film.

[0170] In some embodiments, the breaking strength [N / 25 mm] is appropriately 5 times or more the peeling strength [N / 25 mm]. The ratio of the breaking strength to the peeling strength (i.e., the breaking strength / peeling strength ratio) is advantageously 8 or more, or preferably 10 or more. When the breaking strength / peeling strength ratio is large, there is a tendency that the breaking and the like at the time of peeling from the coating film to be protected do not easily occur. From this viewpoint, the breaking strength / peeling strength ratio can be 15 or more, or 20 or more, or 25 or more, or 30 or more, or 35 or more, or 40 or more. The upper limit of the breaking strength / peeling strength ratio is not particularly limited, and is appropriately 100 or less, or can be 80 or less, or 70 or less, or 60 or less, from the viewpoint of easily balancing a moderate peeling strength and good anti-trace adhesion.

[0171] <Coating film protection method>

[0172] According to the present specification, a coating film protection method is provided, which includes: preparing any of the coating compositions disclosed herein; applying the coating composition on the coating film of a protection target object having a coating film; and drying the coating composition to form a coating film protection coating material that temporarily protects the coating film.

[0173] Reference Figure 2 An embodiment of the coating film protection method is described. That is, any of the coating compositions disclosed herein is prepared (step S10). The coating composition is applied (for example, by slit die coating) on the coating film of a protection target object having a coating film (step S20). The applied coating composition is dried to form a coating film protection coating material that temporarily protects the coating film (step S30). By thus providing a coating material on the coating film, the coating film can be protected from damage and deterioration. Note that the coating material that has completed the protection function is peeled off (for example, peeled off by being torn) from the coating film at a desired timing (step S40).

[0174] The matters disclosed in the present specification include the following.

[0175] 〔1〕 A coating composition for forming a coating film protection coating material, the coating composition comprising a polymer (A) as a base polymer, the polymer (A) being a polymer of a monomer component including an acrylic monomer, the polymer (A) being in the form of an aqueous emulsion dispersed in an aqueous solvent, the coating composition further comprising a polyvinyl alcohol-based polymer (B), the polyvinyl alcohol-based polymer (B) having a saponification degree of 80 mol% or more, the polyvinyl alcohol-based polymer (B) having a polymerization degree of 1200 or less, the content of the polyvinyl alcohol-based polymer (B) being 0.3 parts by weight or more and 5.0 parts by weight or less with respect to 100 parts by weight of the polymer (A), the coating composition having a viscosity of 25 Pa・s or more as measured by a BH-type viscometer at 30℃ and 2 rpm.

[0176] 〔2〕 The coating composition according to the above item 〔1〕, wherein the coating composition further contains an adhesion promoter.

[0177] 〔3〕 The coating composition according to the above item 〔1〕 or 〔2〕, wherein the monomer component constituting the polymer (A) contains a carboxyl group-containing monomer.

[0178] 〔4〕 The coating composition according to any one of the above items 〔1〕 to 〔3〕, wherein the monomer component constituting the polymer (A) contains a nitrogen atom-containing monomer.

[0179] 〔5〕 A method for producing the coating composition according to any one of the above-mentioned items 1 to 4, the method comprising: preparing a polymer emulsion containing an aqueous solvent, the above-mentioned polymer (A), the above-mentioned polyvinyl alcohol-based polymer (B) in an amount of 0.3 parts by weight or more and 5.0 parts by weight or less per 100 parts by weight of the above-mentioned polymer (A), and having a viscosity of 1.0 Pa-s or more and 4.5 Pa-s or less at a solid content of 47% by weight, measured at 30°C and 2 rpm by a BH-type viscometer; and adjusting the viscosity of the above-mentioned polymer emulsion so as to have a viscosity of 25 Pa-s or more, measured at 30°C and 2 rpm by a BH-type viscometer.

[0180] 〔6〕 A coating film protection method, comprising: preparing the coating composition according to any one of the above-mentioned items 1 to 4; applying the coating composition to a coating film of an object to be protected having the coating film; and drying the coating composition to form a coating film protection coating material for temporarily protecting the coating film.

[0181] 〔7〕 The coating film protection method according to the above-mentioned item 6, wherein the coating of the coating composition is performed by a slit die.

[0182] 〔8〕 A coating film protection coating material formed from the coating composition according to any one of the above-mentioned items 1 to 4.

[0183] Examples

[0184] Hereinafter, some experimental examples relating to the present application will be described, but the present application is not intended to be limited to the contents shown in the specific examples. Note that in the following description, "parts" and "%" indicating the amount of use and content are weight-based unless otherwise specified. Further, the amount of use of each material is effective ingredient amount-based unless otherwise specified.

[0185] <Used Polyvinyl Alcohol-Based Polymer>

[0186] PVA-1: Partially saponified anion-modified polyvinyl alcohol (Mitsubishi Chemical Corporation, trade name "GOHSENX L-3266").

[0187] PVA-2: Partially saponified polyvinyl alcohol (KURARAY Co., Ltd., product number 3-80).

[0188] PVA-3: Partially saponified polyvinyl alcohol (KURARAY Co., Ltd., product number 3-88).

[0189] PVA-4: Partially saponified polyvinyl alcohol (Denka Co., Ltd., product number B-05).

[0190] PVA-5: Partially saponified polyvinyl alcohol (KURARAY Co., Ltd., product number 9-88).

[0191] PVA-6: Partially saponified polyvinyl alcohol (KURARAY Co., Ltd., product number 22-88).

[0192] PVA-7: Partially saponified polyvinyl alcohol (KURARAY Co., Ltd., product number L-8).

[0193] PVA-8: Fully saponified anion-modified polyvinyl alcohol (Mitsubishi Chemical Corporation, trade name "GOHSENX CKS-50").

[0194] PVA-9: Fully saponified polyvinyl alcohol (KURARAY Co., Ltd., product number 3-98).

[0195] PVA-10: Fully saponified polyvinyl alcohol (Denka Co., Ltd., product number K-05).

[0196] Example 1

[0197] (Polymer emulsion preparation)

[0198] Into a reaction vessel equipped with a condenser, a nitrogen introduction tube, a thermometer, and a stirring device, 75 parts of ion exchange water was added, and 2.0 parts of PVA-1 as a polyvinyl alcohol-based polymer was dissolved at room temperature while introducing nitrogen gas, and then the temperature was raised to 70°C and maintained.

[0199] Into another vessel, 25 parts of ion exchange water was added, and 2 parts of polyoxyalkylene alkylene ether (Kao Corporation, trade name "LATEMUL PD-420") and 0.5 parts of sodium dodecylbenzenesulfonate (Kao Corporation, trade name "NEOPELEX G-65") were dissolved in a surfactant solution, and 100 parts of a monomer component composed of n-butyl acrylate (BA) 44 mol%, acrylonitrile (AN) 55 mol%, and acrylic acid (AA) 1 mol% was added, and the mixture was stirred to prepare a monomer emulsion.

[0200] To the above reaction vessel, the system was maintained at around 70°C and over a period of 5 hours, the above monomer emulsion (containing monomer component 100 parts), aqueous sodium metabisulfite 0.3 parts (solid component basis), and aqueous ammonium persulfate 0.3 parts (solid component basis) were fed, and emulsion polymerization was performed. After the feeding was completed, the temperature was maintained for a further 3 hours to perform maturation. After the resulting reaction mixture was cooled to room temperature, the pH was adjusted to 7.5 by adding 10% aqueous ammonium, and a polymer emulsion El (solid component content 47%) was obtained in which the polymer (A) of the above monomer was dispersed in water. The calculated Tg of the above polymer (A) based on the composition of the monomer component was -18.8°C, and the SP value was 11.8. Further, the acid value of the above polymer (A) was measured by the above method, and the result was 4 mgKOH / g.

[0201] (Preparation of the coating composition)

[0202] To the resulting polymer emulsion El, 1.0 part of an adhesion promoter (ADEKA Co., Ltd., trade name "ADEKA NOU UH-420") was mixed with respect to 100 parts of the polymer (A) contained in the polymer emulsion El, and the coating composition Cl of the present example was obtained.

[0203] <Examples 2 to 12 and Comparative Examples 1 to 3>

[0204] The kind and the amount of use of the polyvinyl alcohol-based polymer were changed as shown in Table 1, and otherwise, the polymer emulsion corresponding to each example was obtained in the same manner as in the production of the polymer emulsion El of Example 1.

[0205] The coating composition corresponding to each example was obtained in the same manner as in the preparation of the coating composition Cl of Example 1, using the polymer emulsion corresponding to each example instead of the polymer emulsion El.

[0206] <Comparative Example 4>

[0207] The polymer emulsion of the present example was obtained in the same manner as in the production of the polymer emulsion El of Example 1, without using the polyvinyl alcohol-based polymer.

[0208] The coating composition of the present example was obtained in the same manner as in the preparation of the coating composition Cl of Example 1, using the polymer emulsion of the present example instead of the polymer emulsion El.

[0209] Note that the polymer emulsions of each of the above examples and comparative examples were each adjusted to a solid component content of 47% by appropriately adding ion exchange water.

[0210] <Measurement and Evaluation>

[0211] [Viscosity measurement by BH-type viscometer]

[0212] The BH viscosity of each of the polymer emulsions (viscosity before addition of tackifier) and the BH viscosity of each of the coating compositions (viscosity after addition of tackifier) were measured using a BH viscometer (manufactured by TOKIMEC Corporation) at 30°C at 2 rpm. As the rotor used in the measurement, No. 2 rotor was used in the polymer emulsion, and No. 4 rotor was used in the coating composition.

[0213] [Tackifying property]

[0214] Based on the results of the viscosity measurement described above, the viscosity increase amount was calculated according to the following equation.

[0215] Viscosity increase amount [Pa-s] = (viscosity before addition of tackifier [Pa-s]) - (viscosity after addition of tackifier [Pa-s])

[0216] Based on the value of the viscosity increase amount obtained, the tackifying property was evaluated in the following three grades.

[0217] G (Good): The viscosity increase amount was 30 Pa-s or more.

[0218] A (Acceptable): The viscosity increase amount was 20 Pa-s or more and less than 30 Pa-s.

[0219] P (Poor): The viscosity increase amount was less than 20 Pa-s.

[0220] [Polymerization stability]

[0221] The polymer emulsion obtained in each example was subjected to normal pressure filtration at room temperature using a 150-mesh nylon filter (bag type), and on this basis, the coating composition of each example was prepared. Based on the filterability when about 1 liter of the polymer emulsion was subjected to the normal pressure filtration described above, the polymerization stability was evaluated in the following three grades.

[0222] G (Good): No emulsion block was left on the filter, and the filtration speed was not reduced.

[0223] A (Acceptable): Emulsion blocks and accumulations were observed on the filter, but the filtration speed was not reduced.

[0224] P (Poor): Many emulsion blocks were left on the filter, and the filtration speed was reduced midway.

[0225] [Coating property]

[0226] A steel sheet on which an acid epoxy crosslinking type acrylic paint (manufactured by Kansai Paint Co., Ltd., trade name "KINO 1210TW") was applied was held horizontally with the applied surface facing upward. Each of the coating compositions of the examples was applied in a square shape of 100 mm in length and 100 mm in width on the applied surface (coating film) of the steel sheet using a coater manufactured by TP Techno Research Co., Ltd., and dried at 80°C for 5 minutes to form a film (coating film protective coating material). The application amount of the coating composition was set so that the thickness of the solid content became 120 μm.

[0227] The film thus formed on the applied surface was visually observed, and the film formation was evaluated in terms of the following three levels.

[0228] G (Good): No cracks were observed.

[0229] A (Acceptable): Slight cracks were observed, but did not penetrate the film.

[0230] P (Poor): Obvious cracks were observed, which penetrated the film.

[0231] [Drying property]

[0232] The film after drying at 80°C for 5 minutes in the above film formation evaluation was observed, and the drying property was evaluated in terms of the following three levels. Note that if the aqueous solvent remained, the film became hazy.

[0233] G (Good): No fogging (haze) of the film was observed.

[0234] A (Acceptable): Slight fogging of the film was observed, but it could be cleanly peeled off from the applied steel sheet.

[0235] P (Poor): Fogging of the film was observed, and it could not be cleanly peeled off from the applied steel sheet.

[0236] [Anti-sagging property]

[0237] An applied steel sheet on which an acid epoxy crosslinking type acrylic paint (manufactured by Kansai Paint Co., Ltd., trade name "KINO 1210TW") was applied was held horizontally with the applied surface facing upward. Each of the coating compositions of the examples was applied in a strip shape of 100 mm in width and a thickness of 400 μm in wet thickness on the applied surface of the above applied steel sheet using a coater manufactured by TP Techno Research Co., Ltd. in an environment at 23°C. Immediately after the application, the above applied steel sheet was vertically erected, and the state of the applied material (the composition applied to the applied steel sheet) after standing for 1 minute was visually observed. Based on the result, the anti-sagging property was evaluated in terms of the following three levels.

[0238] G (Good): No sagging and drooping were observed.

[0239] A (Acceptable): sagging was observed, but no dripping was generated.

[0240] P (Poor): dripping was generated.

[0241] [Table 1]

[0242]

[0243] As shown in Table 1, in the case of the coating compositions of Examples 1 to 12, the polymerization stability of the polymer (A) during synthesis was good, and the viscosity increase of the polymer emulsion, the drying property of the composition, the film forming property, and the dripping resistance were all good, and the compositions were suitable for efficiently forming a high performance protective film. On the other hand, the polymerization stability of Comparative Examples 1 and 3 was low, and the drying property of Comparative Examples 2 and 3 was low. Further, the viscosity increase, the film forming property, and the dripping resistance of Comparative Example 4, which did not use a polyvinyl alcohol-based polymer during polymerization, were insufficient.

[0244] Note that, 0.1 parts of an antifoaming agent (San Nopco Co., Ltd., NOPCO NXZ) was further added to 100 parts of the polymer (A) contained in the polymer emulsion El, and a coating composition was prepared in the same manner as Example 1, except for this, and as a result, the viscosity before viscosity increase of the composition was 1.9 Pa-s, and the viscosity after viscosity increase was 44 Pa-s. Further, the film forming property, the drying property, and the dripping resistance of the coating composition having a viscosity of 44 Pa-s were evaluated by the above method, and as a result, they were all good (evaluation G). On the other hand, 2.0 parts of PVA-3 was further added to 100 parts of the polymer contained in the polymer emulsion obtained in Comparative Example 4, and a coating composition was prepared in the same manner as Comparative Example 4, except for this, and as a result, the viscosity before viscosity increase was 0.8 Pa-s, and the viscosity after viscosity increase was 13 Pa-s. The film forming property, the viscosity increase, the drying property, and the dripping resistance of the coating composition having a viscosity of 13 Pa-s were evaluated by the above method, and as a result, although the drying property was good (evaluation G), the film forming property and the dripping resistance were insufficient (evaluation P).

[0245] The above detailed description of the specific examples of the present application is merely exemplary and does not limit the claims. The technology described in the claims includes various modifications and changes of the above described specific examples.

[0246] Industrial Applicability

[0247] The coating composition provided by the technology described in this specification is suitable as a coating composition for forming a coating film protective coating material used in such a manner that it is provided on a coating film of a protection target object having the coating film to play a role of protecting the coating film from damage, contamination, and the like, and is peeled off from the protection target object after the protection role is completed. The protection target object can be, for example, a coated metal sheet (for example, a coated steel sheet used in housing materials, construction materials, ships, railway vehicles, automobiles, and the like) having a coating film on the surface of a metal sheet (a steel sheet, a stainless steel sheet, an aluminum sheet, and the like), a synthetic resin sheet having a coating film, a molded product thereof, and the like. The coating film protective coating material formed from the coating composition can be preferably used, for example, for the purpose of protecting a coating film of a protection target article (an article having a coating film formed by coating treatment, for example, a metal sheet such as a steel sheet, a molded product thereof, and the like) on which coating treatment has been performed with a coating material of various compositions such as an acrylic coating material, a polyester coating material, an alkyd coating material, a melamine coating material, a urethane coating material, an acid epoxy crosslinking coating material, or a composite system thereof (for example, an acrylic melamine coating material, an alkyd melamine coating material), and the like, by being provided on the coating film of the protection target article to protect the coating film.

[0248] BRIEF DESCRIPTION OF DRAWINGS

[0249] 10: coating film protective coating material; 20: protection target object; 22: coating film.

Claims

1. A coating composition for forming a protective coating material, The coating composition comprises polymer A as a base polymer, wherein polymer A is a polymer containing acrylic monomers, and polymer A is in the form of an aqueous emulsion dispersed in an aqueous solvent. The coating composition further comprises polyvinyl alcohol polymer B. The degree of saponification of the polyvinyl alcohol polymer B is above 80 mol%. The degree of polymerization of the polyvinyl alcohol polymer B is below 1200. The content of the polyvinyl alcohol polymer B relative to 100 parts by weight of polymer A is 0.3 parts by weight or more and 5.0 parts by weight or less. The viscosity of the coating composition, as measured by a BH type viscometer at 30°C and 2 rpm, is greater than 25 Pa·s.

2. The coating composition according to claim 1, wherein, The coating composition also contains a tackifier.

3. The coating composition according to claim 1 or 2, wherein, The monomer components constituting polymer A include carboxyl-containing monomers.

4. The coating composition according to claim 1 or 2, wherein, The monomer components constituting polymer A include nitrogen-containing monomers.

5. A method for manufacturing a coating composition, comprising: Prepare a polymer emulsion comprising an aqueous solvent, polymer A, and a polyvinyl alcohol-based polymer B in an amount of 0.3 to 5.0 parts by weight relative to 100 parts by weight of polymer A, wherein the viscosity, measured by a BH viscometer at 30°C and 2 rpm, is 47% by weight and has a viscosity of 1.0 Pa·s or more and 4.5 Pa·s or less. The viscosity of the polymer emulsion is adjusted so that its viscosity, as measured by a BH type viscometer at 30°C and 2 rpm, is greater than 25 Pa·s.

6. A coating protection method, wherein, include: Prepare the coating composition as described in claim 1 or 2; The coating composition is applied onto the coating film of the protected object having the coating film. as well as The coating composition is dried to form a protective coating material that temporarily protects the coating film.

7. The coating protection method according to claim 6, wherein, The coating composition is applied using a slit die.

8. A protective coating material formed from the coating composition as described in claim 1 or 2.

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