JP6180308B2 - Coating composition and coating film obtained therefrom, multilayer structure and method for producing multilayer structure - Google Patents

Description

  The present invention relates to a coating composition containing metal oxide fine particles, a coating film obtained therefrom, a multilayer structure and a method for producing the multilayer structure, and more specifically, a coating film and multilayer structure excellent in heat resistance. The present invention relates to a coating composition that can be obtained, and to a method for producing the multilayer structure obtained therefrom.

  Since acrylic resins are excellent in weather resistance, transparency, moldability, etc., they have been widely used for surface protection coating agents such as various interior materials and exterior materials, displays and outdoor display panels. In recent years, there has been a demand for a coating agent capable of obtaining a surface protective coating film excellent in heat resistance that does not shrink or color due to heat as the average temperature rises.

  As a heat-resistant coating composition for forming such a coating film, a coating composition comprising metal compound fine particles having a specific particle size and an aqueous dispersion (emulsion) of a specific chemical structure polymer emulsion particle having a specific particle size is provided. It has been proposed (see Patent Document 1).

In this document, metal compound fine particles having a specific particle size interact with an aqueous dispersion (emulsion) of a specific chemical structure polymer emulsion particle having a specific particle size, and the metal compound acts as a curing agent for the emulsion. By doing so, it is described that the heat resistance composite obtained from the resulting coating composition is improved in transparency and weather resistance (see Patent Document 1 [0013]). In addition, this composition has this metal oxide in 80-350 weight part with respect to 100 weight part of solid content of this emulsion.
However, the evaluation of the heat resistance of the above technique was limited to the condition of 10 minutes at 150 ° C.

In addition, a heat-resistant coating composition having a synthetic resin binder is known (see Patent Document 2). Such a composition describes a synthetic resin binder comprising an acrylic resin emulsion and a PVA resin.
In this technique, polyvinyl alcohol and its derivative are contained at 2 to 20% by weight in the total amount of the synthetic resin binder in the coating composition. Furthermore, a coating composition containing calcium carbonate or aluminum as a filler is described.
The said filler is mix | blended in 18 weight part and 21 weight part with respect to 100 weight part of solid content of the emulsion which a coating composition contains (refer patent document 2 Examples 10-13). Moreover, in this Example, content with respect to PVA-type resin of the filler in a coating composition is 100 weight part or 500 weight part with respect to 100 weight part of PVA-type resin.
However, the heat resistance evaluation of this technique has been limited to a temperature of 80 ° C.

  At the heat resistance level according to these above technologies, for example, an instrument panel of a car, a building outer wall, an outdoor display panel, etc., a member that is exposed to direct sunlight during use, becomes hot, or generates heat, etc. Furthermore, it is difficult to apply to applications that require high heat resistance. Therefore, there is a need for a high-quality coating film having a higher level of heat resistance suitable for such applications and a coating composition capable of obtaining it.

JP 2010-235680 A JP 2013-18915 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems and provide a coating film having a high level of heat resistance and a coating composition capable of obtaining the same.

  The present invention has been intensively studied in view of the above circumstances, and as a result, a specific small amount of metal oxide with respect to an emulsion having a polyvinyl alcohol resin (hereinafter sometimes referred to as PVA resin) as a dispersant and an acrylic resin as a dispersoid. The present invention was completed by finding that a coating composition having a high level of heat resistance can be obtained by using a coating composition containing fine particles.

  That is, the gist of the present invention includes (A) a polyvinyl alcohol resin as a dispersant, an acrylic resin as a dispersoid, an emulsion having water as a dispersion medium, and (B) metal oxide fine particles, and (B) metal oxidation. Coating composition in which the amount of the fine particles is (A) 0.1 to 1.5 parts by weight with respect to 100 parts by weight of the resin solid content of the emulsion, and the coating film, multilayer structure and multilayer structure obtained therefrom It exists in the manufacturing method of a body.

  In the present invention, a coating composition having a high level of heat resistance can be obtained by using a coating composition containing a specific small amount of metal oxide fine particles for an emulsion having a PVA resin as a dispersant and an acrylic resin as a dispersoid. The excellent effect that a film is obtained is exhibited.

  Generally, it is recalled that the blending amount of the metal oxide fine particles is increased in order to further improve the heat resistance based on the prior art. However, if the blending amount of the metal oxide fine particles is simply increased, the transparency of the coating film is increased. There is a problem of lowering. On the other hand, when the blending amount of the metal oxide fine particles is simply lowered, there is a problem that the heat resistance is naturally lowered.

  However, in the present invention, even if the blending amount of the metal oxide fine particles in the coating composition is lowered, the obtained coating film exhibits a high level of heat resistance. That is, shrinkage is suppressed even when subjected to severe heat at 150 ° C. for 3 hours. Furthermore, it is difficult to color. This is a result inconsistent with the conventional knowledge and can be said to be a remarkable and unexpected effect.

It is the result of having performed viscoelasticity evaluation in the Example of this invention.

Hereinafter, although it demonstrates in detail about the structure of this invention, these show an example of a desirable embodiment.
In the present specification, acrylic and methacryl are collectively referred to as (meth) acryl when not particularly distinguished, and acrylate and methacrylate are collectively referred to as (meth) acrylate when not particularly distinguished.
In the present invention, solid content and resin solid content mean those obtained by subjecting an object to a drying loss method at 105 ° C. for 3 hours.

  The coating composition of the present invention comprises (A) a polyvinyl alcohol resin as a dispersant, an acrylic resin as a dispersoid, an emulsion having water as a dispersion medium, and (B) metal oxide fine particles, and (B) metal oxidation. It is a coating composition containing 0.1 to 1.5 parts by weight of compound fine particles with respect to 100 parts by weight of resin solid content of the emulsion (A).

<(A) Description of emulsion>
The coating composition of the present invention comprises a coating obtained when a specific amount of metal oxide fine particles is blended using an emulsion having a polyvinyl alcohol resin as a dispersant, an acrylic resin as a dispersoid, and water as a dispersion medium. The film exhibits a high level of heat resistance.

<(A) Description of PVA resin as dispersant>
The emulsion contained in the coating composition of the present invention has a PVA resin as a dispersant. As the PVA resin used in the present invention, a known PVA resin can be applied.

  The degree of saponification (measured in accordance with JIS K6726) of the PVA resin as a dispersant is usually 85 to 100 mol%, preferably 90 to 100 mol%, particularly preferably 95 to 100 mol%. If the degree of saponification is too low, a deacetic acid reaction or the like occurs and a conjugated structure tends to occur in the polyvinyl alcohol molecular main chain, and the resulting coating film tends to be colored.

  The average degree of polymerization (measured according to JIS K6726) is usually 50 to 2500, preferably 100 to 1700, more preferably 100 to 1000, and particularly preferably 200 to 500. If the average degree of polymerization is too low, the strength of the resulting coating film tends to be low. On the other hand, if the average degree of polymerization is too high, it is difficult to control the domain size of the dispersoids, and the standing stability of the emulsion is reduced. Tend.

  In the present invention, a known modified PVA resin may be used as the PVA resin as a dispersant. When a modified PVA-based resin is used, if the amount of modification (content of modified vinyl alcohol structural unit) is too large, the viscosity of the emulsion tends to increase, and is usually 15 mol% or less, preferably 10 mol% or less. A modified PVA resin having a modified amount of is used.

Examples of the modified monomer for the PVA resin include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, 3-buten-1-ol, 4-penten-1-ol, 5- Derivatives such as hydroxy group-containing α-olefins such as hexen-1-ol and acylated products thereof, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, undecylenic acid, Examples thereof include salts, monoesters or dialkyl esters, amides such as diacetone acrylamide, acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid, and salts thereof.
The modification method using these modified monomers for the PVA-based resin is copolymerization, and other known post-modifications such as graft modification can be used.

As the modified PVA-based resin, it is preferable to use a derivative-modified PVA-based resin such as a hydroxy group-containing α-olefin and an acylated product thereof, and further a PVA-based resin containing a structural unit represented by the following general formula (1) It is preferable to use a resin (hereinafter, referred to as “side chain 1,2-diol structural unit-containing PVA resin”).
(Wherein R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represents a hydrogen atom. Or an organic group.)

  The PVA-based resin used as a dispersant for the emulsion has such a structural unit, so that the emulsion easily interacts with the metal oxide fine particles, and the modified PVA when the coating composition containing such an emulsion becomes a coating film. Even if the coating film obtained from the coating agent containing such an emulsion is exposed to high temperature conditions, the system resin becomes a continuous phase, and low crystallization can be achieved while reducing the free volume of the amorphous part of the PVA resin. The shrinkage | contraction etc. accompanying crystallization of the PVA-type resin of a continuous layer can be suppressed, and it is preferable at the point from which high level heat resistance is obtained.

In the general formula (1), R ^{1 to} R ⁶ each independently represent a hydrogen atom or an organic group. R ^{1 to} R ⁶ are preferably all hydrogen atoms, but may be organic groups as long as the resin properties are not significantly impaired. Although it does not specifically limit as this organic group, For example, C1-C4 alkyl groups, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, are preferable, You may have substituents, such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, and a sulfonic acid group, as needed.

In the general formula (1), X is a single bond or a bonded chain, and is preferably a single bond from the viewpoint of improving crystallinity and reducing free volume (intermolecular void) in an amorphous part. The bonding chain is not particularly limited, but other hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene, naphthylene (these hydrocarbons may be substituted with halogen such as fluorine, chlorine, bromine, etc.) _{, -O -, - (CH 2} O) m -, - (OCH 2) m -, - (CH 2 O) mCH 2 -, - CO -, - COCO -, - CO (CH 2) mCO -, - _{CO (C 6 H 4) CO} -, - S -, - CS -, - SO -, - SO 2 -, - NR -, - CONR -, - NRCO -, - CSNR -, - NRCS -, - NRNR- _{, -HPO 4 -, - Si (} OR) 2 -, - OSi (OR) 2 -, - OSi (OR) 2 O -, - Ti (OR) 2 -, - OTi (OR) 2 -, - OTi ( _{OR) 2 O -, - Al} (OR) -, - OAl (OR) -, - OAl (O ) O-, and the like. R is each independently an arbitrary substituent, preferably a hydrogen atom or an alkyl group, and m is a natural number. Of these, alkylene having 6 or less carbon atoms, particularly methylene, or —CH ₂ OCH ₂ — is preferable from the viewpoints of viscosity stability and heat resistance during production.

In the most preferable structure of the 1,2-diol structural unit represented by the general formula (1), R ^{1 to} R ⁶ are all hydrogen atoms, and X is a single bond. That is, the structural unit represented by the following structural formula (1a) is most preferable.

  Such a side chain 1,2-diol structural unit containing PVA-type resin can be manufactured with a well-known manufacturing method. For example, it can be produced by the methods described in JP 2002-284818 A, JP 2004-285143 A, JP 2006-95825 A, and the like.

  When the PVA resin as a dispersant is a PVA resin containing a side chain 1,2-diol structural unit, the modification amount may be in a range different from the above range. The content of the side chain 1,2-diol structural unit is usually 0.5 to 15 mol%, preferably 1 to 10 mol%, more preferably 3 to 9 mol%. When the PVA-based resin contains a side chain 1,2-diol structural unit in such a range, a high level of heat resistance tends to be obtained more effectively. In addition, the graft ratio of the PVA resin to the acrylic resin that is a dispersoid increases, and the mechanical stability and storage stability of the emulsion tend to be improved.

In addition, the content of the side chain 1,2-diol structural unit in the PVA resin is ¹ H-NMR spectrum of the PVA resin having a saponification degree of 100% (solvent: DMSO-d6, internal standard: tetramethylsilane). Can be obtained from Specifically, it may be calculated from the peak area derived from the hydroxyl proton, methine proton, and methylene proton in the 1,2-diol structural unit, the main chain methylene proton, the hydroxyl proton linked to the main chain, and the like.

<Description of (A) Dispersoid Acrylic Resin>
The emulsion contained in the coating composition of the present invention has an acrylic resin as a dispersoid. As the acrylic resin used in the present invention, a known acrylic resin used for an acrylic emulsion can be applied.

  An acrylic resin is a polymer of an acrylic monomer. Examples of the acrylic monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and tert-butyl. Acrylate, n-pentyl (meth) acrylate, i-pentyl (meth) acrylate, hexyl (meth) acrylate, 2-hexyl (meth) acrylate, octyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, etc. (Meth) acrylic ester monomers: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 5-hydroxy B carboxymethyl pentyl methacrylate, hydroxyl group-containing (meth) acrylates such as 6-hydroxyhexyl methacrylate. These can be used alone for polymerization, but are preferably used in combination of two or more.

  Such an acrylic resin can be copolymerized with a monomer other than the acrylic monomer as long as the effects of the present application are not impaired. When other monomers other than the acrylic monomer are copolymerized, the content thereof is usually less than 20% by weight, preferably less than 10% by weight, based on the acrylic monomer. Examples of monomers other than acrylic monomers include vinyl ester monomers, diene monomers, olefin monomers, acrylamide monomers, acrylonitrile monomers, styrene monomers, vinyl ether monomers, and allyl monomers.

  The acrylic monomer constituting the acrylic resin is preferably a (meth) acrylic ester monomer, more preferably a (meth) acrylic ester monomer having 5 to 15 carbon atoms, and particularly preferably 5 to 10 carbon atoms. It is a (meth) acrylic ester monomer.

[Emulsion polymerization: Synthesis of emulsion]
In such an emulsion, particles containing a PVA resin as a dispersant and an acrylic resin as a dispersoid as described above are dispersed in an aqueous dispersion medium. This is obtained as a result of emulsion polymerization of the acrylic monomer (and optionally other monomers other than the acrylic monomer) in the presence of a dispersant.

  As a method for carrying out the emulsion polymerization, i) temporary or continuous acrylic monomer (and other monomers as required) as a dispersoid raw material in the presence of water, a PVA resin as a dispersant and a polymerization catalyst. A method of emulsion polymerization by mixing and heating and stirring; ii) preparing a dispersion in which an acrylic monomer (and optionally other monomers other than an acrylic monomer) is mixed and dispersed in an aqueous solution of a PVA resin And the method of carrying out emulsion polymerization by mixing this prepared dispersion liquid in the system in which water, PVA-type resin, and the polymerization catalyst were mix | blended temporarily or continuously, heating and stirring is mentioned. Such a method using a preliminarily prepared dispersion is particularly called a pre-emulsion method. This method is preferable because even if the monomer composition to be polymerized is complex, emulsion polymerization can be carried out without reducing productivity.

  The dispersion medium in the reaction solution used for the emulsion polymerization is usually water. If desired, an organic solvent that can be mixed with water (for example, a lower alcohol having 1 to 3 carbon atoms) can be used in combination with water. However, from the viewpoint of the dispersibility of the monomer subjected to emulsion polymerization, water alone is preferred.

  The blending amount of the PVA resin used as a dispersant during the emulsion polymerization varies somewhat depending on the type of PVA resin used, the concentration of the emulsion to be synthesized, etc., but is usually 0.1% relative to the whole emulsion polymerization reaction system. -30% by weight, more preferably 1-25% by weight, and particularly preferably 1-20% by weight. If the blending amount of the PVA resin is too small, the emulsion state of the acrylic monomer (and other monomers other than the acrylic monomer if desired) becomes unstable and the polymerization reactivity is lowered, or the emulsion obtained by polymerization The stability of the emulsified state of the particles tends to decrease. On the other hand, when there is too much content of PVA-type resin, the viscosity of a reaction liquid will increase too much, polymerization reaction may become slow, or the viscosity of the emulsion obtained tends to become too high.

  As the polymerization catalyst, a polymerization catalyst usually used in the field of emulsion polymerization can be used. For example, potassium persulfate, ammonium persulfate, potassium bromate, acidic sodium sulfite, hydrogen peroxide-tartaric acid, hydrogen peroxide-iron salt, hydrogen peroxide-ascorbic acid-iron salt, hydrogen peroxide-longarit, hydrogen peroxide- Examples thereof include water-soluble redox polymerization catalysts such as Rongalite-iron salt, and these can be used alone or in admixture of two or more. Specifically, a catalyst comprising an organic peroxide and a redox system such as “Kayabutyl B” manufactured by Kayaku Akzo Co., Ltd. or “Kayabutyl A-50C” manufactured by Kayaku Akzo may be used.

The amount of the polymerization catalyst used is usually 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the monomer used for the polymerization. Part. If the amount of the polymerization initiator used is too small, the polymerization rate tends to be slow, and conversely if too large, the polymerization stability tends to decrease.
In addition, there is no restriction | limiting in particular as a compounding method of a polymerization initiator, You may mix | blend in a reaction liquid collectively in the initial stage, and you may add continuously with progress of superposition | polymerization.

Emulsion polymerization may be performed in one step or may be performed in multiple steps of two or more steps. In particular, when performing in two stages, the glass transition point (Tg) of the inner layer formed in the first stage and the outer layer formed in the second stage is changed by changing the monomer charge amount (feed ratio) between the first stage and the second stage. It can also be changed.
Specifically, the following two-stage polymerization is exemplified.

(1) First-stage polymerization step A part of the monomer to be polymerized is charged into a reaction vessel containing a dispersion medium and a dispersant, and the first-stage emulsion polymerization is performed. The amount of the monomer added to the first stage is not particularly limited, but is usually about 1 to 50% by weight, preferably 5 to 30% by weight of the monomer used for polymerization. What is necessary is just to determine suitably the conditions of the emulsion polymerization process of the 1st step | paragraph by the kind of monomer to be used, a composition, the usage-amount of a polymerization initiator, etc.
The temperature of the emulsion polymerization reaction is usually 30 to 90 ° C, particularly preferably 40 to 80 ° C, and the polymerization time is preferably 1 to 4 hours. In the first stage emulsion polymerization step, the polymerization conversion rate is preferably 50% or more, and more preferably 60% or more.

(2) Second-stage polymerization step The second-stage emulsion polymerization is carried out by introducing the remaining monomers into the reaction vessel after the first-stage polymerization. The charging is preferably performed while dropping. Further, a polymerization catalyst may be added in the second stage polymerization. The second stage emulsion polymerization is carried out under conditions where the polymerization temperature is 40 to 80 ° C. and the polymerization time is 1 to 6 hours.
It is also possible to use a power feed polymerization method in which the dropping monomer composition ratio is continuously changed. Alternatively, polymerization may be performed while dropping a dispersion obtained by mixing and dispersing monomers in the presence of a PVA resin as a dispersant.
If necessary, it is also possible to carry out the polymerization for 1 to 6 hours after this step. A polymerization catalyst may be added during such polymerization.

  In the emulsion polymerization as described above, a molecular weight regulator may be included as necessary. Specific examples of molecular weight regulators include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan; dimethylxanthogen disulfide, diisopropylxanthogen Xanthogen compounds such as disulfide; thiuram compounds such as terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide; phenols such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol Compounds; allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, and carbon tetrabromide; α-benzyloxys Vinyl ethers such as len, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide; triphenylethane, pentaphenylethane, acrolein, methacrolein, acetaldehyde, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate, α-methylstyrene Dimer etc. are mentioned. In the emulsion polymerization step, these molecular weight regulators can be used alone or in combination of two or more.

  In addition, in the polymerization step, a surfactant such as a nonionic surfactant or an anionic surfactant is allowed to coexist in the system, as long as the dispersion stabilizing effect by the PVA resin is not inhibited. Also good. The amount of such a surfactant is usually 10% by weight or less, preferably 5% by weight or less, based on the total amount of the emulsion polymerization reaction system.

  Examples of the nonionic surfactant include polyoxyethylene-alkyl ether type, polyoxyethylene-alkylphenol type, polyoxyethylene-polyhydric alcohol ester type, ester of polyhydric alcohol and fatty acid, oxyethylene / oxypropylene block Examples thereof include polymers.

Examples of anionic surfactants include higher alcohol sulfates, higher fatty acid alkali salts, polyoxyethylene alkylphenol ether sulfates, alkylbenzene sulfonates, naphthalene sulfonate formalin condensates, alkyl diphenyl ether sulfonates, and dialkyl sulfosuccinates. Higher alcohol phosphate ester salts and the like.
Furthermore, plasticizers such as phthalate esters and phosphate esters, pH adjusters such as sodium carbonate, sodium acetate, and sodium phosphate may be used in combination.

<(A) About emulsion>
By performing emulsion polymerization as described above, an emulsion in which particles containing a synthesized acrylic resin (dispersoid) and a PVA resin as a dispersant are dispersed in an aqueous dispersion medium is obtained.

  The average particle diameter of the particles is usually 100 to 700 nm, preferably 200 to 500 nm. In addition, the value measured with the zeta potential measuring apparatus is employ | adopted for the average particle diameter of the said particle | grain.

  The resin solid content of the obtained (A) emulsion is usually 10 to 60% by weight, more preferably 20 to 58% by weight, still more preferably 30 to 55% by weight, and particularly preferably 35 to 53%. % By weight. In addition, the resin solid content of the (A) emulsion is the total amount of resin contained in the (A) emulsion, and is a value measured by a loss on drying method. Such resin solid content includes a synthesized acrylic resin (dispersoid) and a PVA resin as a dispersant.

  The viscosity of the obtained (A) emulsion is usually 100 to 20000 mPa · s, more preferably 300 to 10000 mPa · s, and particularly preferably 450 to 8000 mPa · s. In addition, the value measured with the B-type viscometer is employ | adopted for the viscosity of an emulsion.

<Description of (B) metal oxide fine particles>
Examples of the (B) fine metal oxide particles used in the coating composition in the present invention include alkaline earth metal oxides such as magnesium oxide and calcium oxide, Group 4 metal oxides such as titanium oxide and zirconium oxide, and aluminum oxide. (Hereinafter also referred to as alumina), Group 15 element metal oxides such as indium oxide, Group 14 element metal oxides such as silicon dioxide, tin oxide and lead oxide, and 15th group such as antimony oxide. Group element metal oxides can be used. These metal oxide chemical species may be used alone or in combination.
Among these, in terms of effectively obtaining a high level of heat resistance, the metal oxide fine particles of Group 13 to Group 15 elements are preferred, and the metal oxide fine particles of Group 13 elements are more preferred. Particularly preferred are aluminum oxide fine particles.

The average particle size of the metal oxide fine particles is measured by measuring the particle size from an electron micrograph, and the average value is usually 1 to 1000 nm, preferably 1 to 100 nm, particularly preferably 10 to 50 nm. When this value is too large, it tends to be difficult to disperse and become an aggregate, and when it is too small, bubbles tend to be mixed during stirring.
The aspect ratio of such fine particles is usually 1 or more and less than 10, preferably 1 to 8, particularly preferably 1 or more and less than 3. When the aspect ratio is in the above range, the metal oxide fine particles tend to be uniformly dispersed. The shape is preferably spherical.
The state of the metal oxide fine particles may be any state such as a solid powder, an aqueous dispersion thereof, an aqueous solution of sol, colloidal silica, or the like. From the viewpoint of affinity with the emulsion, an aqueous dispersion or an aqueous solution is preferred.

  Such (B) metal oxide fine particles are not included in the resin solid content in the coating composition of the present invention.

<Description of other components>
In the coating composition of the present invention, a compounding agent usually used for paints and molding resins used for coating films can be blended. For example, light stabilizer, ultraviolet absorber, thickener, leveling agent, thixotropic agent, antifoaming agent, freezing stabilizer, matting agent, crosslinking reaction catalyst, pigment, curing catalyst, crosslinking agent, anti-skinning agent, Dispersant, wetting agent, antioxidant, UV absorber, rheology control agent, film forming aid, rust inhibitor, dye, plasticizer, lubricant, reducing agent, preservative, antifungal agent, deodorant, yellow Examples thereof include an anti-change agent, an antistatic agent, and a charge control agent. They can be selected or combined according to their purpose. When a coating composition mix | blends these compounding agents, the organic content of the compounding agent to contain is contained in the resin solid content of a coating composition.
The amount of the compounding agent is usually less than 10 parts by weight, preferably less than 5 parts by weight, based on 100 parts by weight of the resin solid content of the emulsion (A) in the coating composition.

  In particular, in the coating composition of the present invention, a second PVA resin different from the PVA resin (first PVA resin) as a dispersant in the emulsion (A) contained in the coating composition is a second PVA resin. It is preferable to mix. This tends to increase the emulsion particle gap appropriately, or to further improve the heat resistance when a coating film is formed. In addition, when a coating composition contains 2nd PVA-type resin, the content is contained in the resin solid content in the coating composition of this invention.

As this 2nd PVA-type resin, it is possible to use well-known PVA-type resin similarly to the above-mentioned PVA-type resin which is a dispersing agent.
The degree of saponification (measured according to JIS K6726) of the second PVA resin is usually 80 to 100 mol%, preferably 85 to 100 mol%. If the degree of saponification is too low, a deacetic acid reaction or the like occurs and a conjugated structure tends to occur in the polyvinyl alcohol molecular main chain, and the resulting coating film tends to be colored.

  The average degree of polymerization (measured in accordance with JIS K6726) of the second PVA resin is usually 50 to 2500, preferably 100 to 2500, more preferably 300 to 2400, and particularly preferably 300 to 1000. is there. The degree of polymerization and the concentration of the second PVA resin to be added can be arbitrarily set according to the viscosity of the target coating composition. When the average degree of polymerization is too low, it tends to be difficult to adjust the viscosity of the coating composition and the resin content. Moreover, when the average degree of polymerization is too high, the resin component tends to be difficult to adjust, and the degree of freedom in controlling the thickness tends to be reduced.

  Also in the second PVA resin, a modified PVA resin can be used in the same manner as the PVA resin as the dispersant. However, the second PVA resin is preferably an unmodified polyvinyl alcohol resin having no modifying group.

When the second PVA-based resin is used, the first PVA-based resin and the second PVA-based resin, which are dispersants for the emulsion used in the present invention, are completely compatible with each other (sea-sea structure) and form a uniform phase. Or form a sea-island structure. From the viewpoint of the strength of the continuous layer in the film obtained from the coating composition of the present invention, when forming a sea-island structure, it is preferable to control the domain size to be small (usually a domain diameter of 1.5 μm or less). From this viewpoint, the saponification degree difference between the first PVA resin and the second PVA resin is usually 0 to 15 mol%, preferably 3 to 10 mol%.
Moreover, it is preferable that the saponification degree of the 1st PVA-type resin which is a dispersing agent of the emulsion used for this invention is higher than the saponification degree of 2nd PVA-type resin. In such a case, in the continuous phase of the coating film obtained from the coating composition, since the first PVA-based resin can form a stable matrix, it is considered that the strength of the continuous layer is maintained well.

When the second PVA resin is used, the blending amount thereof may be different from the above, and is usually 0.1 to 30% by weight of the coating composition, preferably 1 to 20% by weight, particularly preferably 3 to 10%. % By weight.
Moreover, it is 5-1000 weight part normally with respect to 100 weight part of resin solid content of (A) emulsion in a coating composition, Preferably it is 10-100 weight part, Especially preferably, it is 10-30 weight part.

The second PVA resin may be blended after mixing the component (A) and the component (B), or may be blended in advance for either or both of the component (A) and the component (B). Good.
In particular, it is preferable from the viewpoint of dispersion stability of the dispersoid of the emulsion (A) that it is preliminarily blended with the emulsion as the component (A) to prepare an emulsion composition.

<Description of coating composition>
The coating composition of the present invention comprises (A) a polyvinyl alcohol resin as a dispersant, an acrylic resin as a dispersoid, an emulsion having water as a dispersion medium and metal oxide fine particles, and (B) the metal oxide fine particles The blending amount is a coating composition containing 0.1 to 1.5 parts by weight with respect to 100 parts by weight of resin solid content of the emulsion (A).
A coating film obtained by blending metal oxide fine particles in a specific small amount with respect to the resin solid content of the emulsion (A) of the coating composition, even though the amount of metal oxide fine particles blended is very small. Has remarkable heat resistance. This effect is completely different from the conventional knowledge and is an unexpected effect.

The “resin solid content in the coating composition” of the present invention refers to (A) the resin solid content in the emulsion and, if desired, the sum of the above-mentioned compounding agent and the above-mentioned second PVA-based resin. Means component (B) is not included. Such resin solids can be measured by the loss on drying method after the component (B) is separated from the coating composition.
The resin solid content in the coating composition is usually 10 to 60% by weight, more preferably 20 to 58% by weight, still more preferably 30 to 55% by weight, and particularly preferably 35 to 50% by weight. is there. In addition, the value measured by the drying loss method is employ | adopted for this resin solid content.
The blending amount of the (A) emulsion in the coating composition is usually 5 to 60% by weight, preferably 10 to 55% by weight, particularly preferably 20 to 40% by weight, based on the resin solid content of the (A) emulsion. It is.
When the content is too large, the viscosity of the coating composition tends to increase, and the coating properties and leveling properties tend to decrease. When the content is too small, the storage stability of the coating composition tends to decrease. .

The blending amount of the (B) metal oxide fine particles in the coating composition is 0.1 to 1.5 parts by weight, preferably 0.1 to 1.2 parts per 100 parts by weight of the resin solid content of the coating composition. Part by weight, particularly preferably 0.3 to 1 part by weight.
Moreover, the compounding quantity with respect to 100 weight part of resin solid content of (A) emulsion of (B) metal oxide fine particle in a coating composition is 0.1-1.5 weight part normally, Preferably it is 0.1-1 .2 parts by weight, particularly preferably 0.3 to 1 part by weight.
When such a blending amount is within the above range, a high level of heat resistance of the resulting coating film can be obtained.

In preparing such a coating composition, the above-mentioned emulsion (or emulsion composition) and a dispersion containing the compounding agent as required are usually 1000 to 3000 rpm, preferably 1500 to 2500 rpm, usually 0.1 to 60 minutes, The stirring is preferably performed for 0.1 to 30 minutes, particularly preferably for 0.1 to 15 minutes.
Such a stirring step can be performed in a plurality of stages.

  The viscosity of the resulting coating composition is usually 100 to 20000 mPa · s, more preferably 300 to 10000 mPa · s, and particularly preferably 450 to 8000 mPa · s. In addition, the value measured with the B-type viscometer is employ | adopted for the viscosity of a coating composition. In order to adjust the viscosity, it is also possible to blend water, alcohols having 1 to 4 carbon atoms and miscibility with water, and ketones.

<Manufacturing method of coating film>
The coating film of the present invention is obtained from the coating composition containing the above (A) emulsion and (B) metal oxide fine particles, and is a coating film having a dispersed phase and a continuous phase. Such a coating film has (A) a water-insoluble dispersed phase derived from an acrylic resin as a dispersoid of an emulsion as a main component, and (A) a water-soluble continuous phase derived from a PVA resin as a dispersing agent for an emulsion. It has a trace amount.
A coating film can be obtained by coating and heat-treating the coating composition of the present invention on a substrate.

  Such a substrate is not particularly limited, and examples of the material include synthetic resins such as thermoplastic resins and thermosetting resins, metal materials such as glass and aluminum foil, and natural materials such as paper and wood. Examples of the shape include a coating film, a sheet, a nonwoven fabric, and various molded products.

  Examples of the thermoplastic resin include low density polyethylene, ultra low density polyethylene, high density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, and ethylene-methyl methacrylate copolymer. Polyolefin resins such as polymers and ionomer resins; aromatic polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; aliphatic polyester resins such as polylactic acid, polybutylene succinate and polybutylene succinate adipate; Polyamide resins such as nylon-6, nylon 6,6, metaxylylenediamine-adipic acid condensation polymer; acrylic resins such as polymethacrylate and polymethylmethacrylate; polystyrene, styrene Styrenic resins such as acrylonitrile; cellulose resins such as cellulose triacetate and cellulose diacetate; halogen-containing resins such as polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride; polycarbonate resins, polysulfone resins, polyethersulfone resins, And engineering plastics such as polyetheretherketone resin, polyphenylene oxide resin, and liquid crystal polymer.

  It is also preferable to activate the substrate surface by plasma treatment, corona treatment, electron beam treatment or the like before applying the coating composition.

  As a method of applying the coating composition of the present invention to the above-mentioned substrate, a gravure method such as a direct gravure method or a reverse gravure method; a roll coating method such as a two-roll beat coat method or a bottom feed three-roll method; A known coating method such as doctor knife method; die coating method; dip coating method; bar coating method; spray method;

After the coating composition of the present invention is applied to a substrate, the film of the present invention is obtained by heat treatment. Such heat treatment should be appropriately adjusted according to the thickness of the coating layer. The heat treatment temperature is usually 40 to 200 ° C, preferably 50 to 150 ° C, particularly preferably 60 to 120 ° C.
Moreover, although the heat processing time is also suitably adjusted according to the above-mentioned heat processing temperature, it is 0.1 to 200 hours normally, Preferably it is 0.5 to 1 hour.
Such heat treatment can be performed in a plurality of stages. Also, when using polyolefin resins with a low melting point as the base material (porous coating, coating film, nonwoven fabric, etc.), use a wavelength control drying system (such as NGK) to suppress damage to the base material. In general, drying is preferably performed under conditions of 40 ° C to 90 ° C.

In such a coating film, the content of (B) metal oxide fine particles corresponds to the content in the coating composition. Further, the contained metal oxide fine particles are present in the PVA resin phase which is a substantially continuous phase. Therefore, a high level of heat resistance can be obtained despite the incorporation of only a small amount of metal oxide fine particles.
The content of the metal oxide fine particles in the continuous phase of the coating film is usually from 95 to 100 based on the total weight of the metal oxide fine particles present in the coating film (that is, (B) metal oxide fine particle content in the coating film). % By weight, preferably 99-100% by weight.
The content of the metal oxide fine particles in the dispersed phase of the coating film is usually 0 to the total weight of the metal oxide fine particles present in the coating film (that is, (B) metal oxide fine particle content in the coating film). 5% by weight, preferably 0 to 1% by weight.
The content of the metal oxide fine particles in the continuous phase and the dispersed phase is, for example, the shift value of the peak value (tan δ) of each resin phase in a graph obtained by subjecting the coating film to a viscoelasticity measuring device, or an electron micrograph of the film It is possible to measure more.

  The film thickness of the coating film obtained by the coating composition of the present invention thus obtained can be appropriately adjusted depending on the intended use. Usually 5 to 100 μm, in particular 5 to 50 μm, in particular 10 to 30 μm. If the film thickness is too thin, the strength of the coating film tends to decrease, whereas if the film thickness is too thick, the transparency tends to decrease.

  The obtained coating film is usually used as a multilayer structure with a substrate. In addition to the coating layer, the multilayer structure may contain a synthetic resin such as a thermoplastic resin or a thermosetting resin, a metal material such as glass or aluminum foil, or a natural material layer such as paper or wood. .

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In the examples, “parts” means weight basis unless otherwise specified.

<Evaluation method>
(1) Shrinkage evaluation A film 4 × 4 cm obtained by cutting out a coating film obtained from the coating composition was held at 150 ° C. for 3 hours.
The long side and short side length and thickness of the heat-treated coating film were measured, and the area and volume shrink rate (%) were calculated by the following formula.
The smaller the shrinkage ratio, the smaller the shrinkage change after heat treatment and the better the coating film.
Area shrink rate:
{1- (Vertical length after heat treatment [cm] / 4 [cm]} × (Horizontal length after heat treatment [cm] / 4 [cm]) × 100
Volume shrink rate:
Area shrink rate [%] x (thickness after heat treatment [cm] / thickness before heat treatment [cm])

(2) Colorability evaluation The transmission type YI value of the coating film after heat treatment obtained in (1) above was measured with a color difference meter SZ-Σ90 (manufactured by Nippon Denshoku Industries Co., Ltd.). The lower the value, the better the coating film without coloring.

(3) Viscoelasticity evaluation The coating film obtained from a coating composition was measured with the viscoelasticity measuring apparatus DVA-225 (made by IT measurement control company). The results are shown in FIG. Table 1 shows the peak value of the PVA resin phase, that is, tan δ.

[Example 1]
<Preparation of emulsion contained in coating composition>
Water as an emulsion dispersion medium, polyvinyl alcohol resin containing 1,2-diol structural unit represented by the above chemical formula (1a) in the side chain as a dispersant (degree of saponification; 98.5 mol%, average degree of polymerization 300,1, 2-diol structural unit content; 8 mol%), and a mixed monomer of butyl acrylate / methyl methacrylate = 55/45 (weight ratio) was used as an acrylic monomer to be a dispersoid acrylic resin.
Polyvinyl alcohol resin containing 1,2-diol structural unit represented by the above chemical formula (1a) in the side chain in 715 parts of water (degree of saponification; 98.5 mol%, average degree of polymerization 300,1,2-diol) An aqueous solution in which 46.2 parts of structural unit content (8 mol%) was dissolved was prepared. In addition, 700 parts of a mixed monomer of butyl acrylate / methyl methacrylate = 55/45 (weight ratio) as an acrylic monomer was prepared.

The aqueous solution was charged into a stainless steel reaction vessel equipped with a stirrer and a reflux condenser, and the temperature of the reaction vessel was kept at 80 ° C.
Here, 70 parts of the above mixed monomer [butyl acrylate / methyl methacrylate = 55/45 (weight ratio)] is blended as the first-stage emulsion polymerization monomer, and an aqueous ammonium persulfate solution (10 wt% concentration) is used as the polymerization initiator. 5.7 parts was blended to start the first polymerization reaction. Polymerization was carried out at a reaction temperature of 80 ° C. for 1 hour.
Next, 630 parts of the mixed monomer was used as the second stage emulsion polymerization monomer, and 11.3 parts of the ammonium persulfate aqueous solution was used as the polymerization initiator. The polymerization was continued while dripping them into the reaction vessel over 4 hours.
After the completion of the second stage emulsion polymerization (that is, after completion of the dropping), 1.9 parts of the ammonium persulfate aqueous solution was blended, and the chasing polymerization was continued at 80 ° C. for 1 hour.

Then, it cooled to room temperature and obtained (A) emulsion. The resin solid content of the emulsion was 50.7% by weight as measured by the loss on drying method at 105 ° C. for 3 hours.
An emulsion composition containing 356 parts by weight of an aqueous polyvinyl alcohol solution (concentration of 20% by weight) (polyvinyl alcohol saponification degree: 89 mol%, average polymerization degree: 500) and emulsion (A) is prepared in the emulsion (A). Obtained.
The resin solid content of the emulsion composition was 44.4% by weight as measured by the loss on drying method at 105 ° C. for 3 hours.

<Preparation of coating composition>
The above emulsion composition was used. Further, spherical metal oxide fine particles (AEROXIDE Alu C, manufactured by Nippon Aerosil Co., Ltd.) having an average particle diameter of 13 nm were used as the metal oxide fine particles.

  100 parts by weight of the emulsion composition and 0.34 parts by weight of aluminum oxide fine particles were blended, and the mixture was stirred at 2000 rpm for 10 minutes with a kneader (Thinky ARE-250 made by Thinky), and then stirred at 2200 rpm for 0.5 minutes. Thus, a coating composition of the present invention was obtained.

The resin solid content in such a coating composition is 44.2% by weight. The resin solid content of the emulsion (A) in such a coating composition is 40.4% by weight.
The blending amount of the (B) metal oxide fine particles with respect to 100 parts by weight of the resin solid content of the (A) emulsion in such a coating composition is 0.8 parts by weight.

  The resulting coating composition was cast on an 8 × 15 cm polytetrafluoroethylene (hereinafter sometimes referred to as PTFE) sheet using a 100 um applicator. This sample was kept at 23 ° C. for 48 hours, and then kept at 105 ° C. for 3 hours to prepare an 8 × 15 cm coating film. This coating film was peeled off from the PTFE sheet with a spatula and dried with a desiccator containing phosphorus pentoxide for one week.

  About the obtained coating film, said (1)-(3) evaluation was performed. The results of evaluation (1) and (2) are shown in Table 1. The result of evaluation (3) is shown in FIG.

[Comparative Example 1]
A coating composition and a coating film were prepared in the same manner as in Example 1 except that the blending amount of the aluminum oxide fine particles was changed to 0.71 part by weight in Example 1, and the same evaluation was performed.
The resin solid content in such a coating composition is 44.1% by weight. The resin solid content of the emulsion (A) in such a coating composition is 40.2% by weight.
The blending amount of the (B) metal oxide fine particles with respect to 100 parts by weight of the resin solid content of the (A) emulsion in such a coating composition is 1.8 parts by weight.
The results are shown in Table 1 and FIG.

[Comparative Example 2]
In Example 1, a coating composition and a coating film were prepared and evaluated in the same manner as in Example 1 except that the blending amount of the aluminum oxide fine particles was 1.6 parts by weight.
The resin solid content in such a coating composition is 43.7% by weight. The resin solid content of the emulsion (A) in such a coating composition is 39.9% by weight.
The blending amount of the (B) metal oxide fine particles with respect to 100 parts by weight of the resin solid content of the (A) emulsion in such a coating composition is 3.9 parts by weight.
The results are shown in Table 1 and FIG.

[Reference Example 1]
A coating composition and a coating film were prepared in the same manner as in Example 1 except that the metal oxide fine particles were not blended in Example 1, and the same evaluation was performed. The resin solid content in the coating composition was 44.4% by weight.
The results are shown in Table 1 and FIG.

[Table 1]

(B) Compared to Reference Example 1 containing no metal oxide fine particles, 3.9 parts by weight of (B) metal oxide fine particles per 100 parts by weight of resin solid content of (A) emulsion in the coating composition In Comparative Example 2 having, the area shrinkage ratio and the volume shrinkage ratio were low, and the YI value was low. That is, it can be seen that when a large amount of metal oxide fine particles is blended, an effect of improving heat resistance is obtained.
Furthermore, as shown in FIG. 1, the acrylic resin phase tan δ peak did not change from the viscoelasticity measurement results, but the PVA resin phase tan δ peak shifted to a high temperature.
From these effects, it can be seen that the metal oxide fine particles contained in the coating composition are present in a continuous phase which is a PVA resin phase when a coating film is formed.

(B) When the coating composition of Comparative Example 1 in which the content of metal oxide fine particles is about half that of Comparative Example 2, the area shrinkage ratio, the volume shrinkage ratio, and the YI value are naturally higher than those of Comparative Example 2. As shown in FIG. 1, the acrylic resin phase tan δ peak did not change, but the PVA resin phase tan δ peak shifted to a lower temperature than in Comparative Example 2.
The result of Comparative Example 1 is a result according to the conventional knowledge that the heat resistance effect cannot be sufficiently obtained because the metal oxide fine particle content is reduced.

However, in Example 1 using the coating composition of the present invention having 0.9 parts by weight of (B) metal oxide fine particles with respect to 100 parts by weight of resin solid content of (A) emulsion in the coating composition, Although the blending amount of the oxide fine particles was about half that of Comparative Example 1 and about one-fourth that of Comparative Example 2, a significantly better result was obtained than Comparative Examples 1 and 2.
In the shrinkage evaluation, the comparative example 2 showed a better value in the area shrinkage ratio, but it showed an excellent value of about one third of the comparative example 1. Further, the volume shrinkage ratio was about a half of the coating film of Comparative Example 2, and was about a quarter of the value for Comparative Example 1. In addition, the color evaluation was about half that of Comparative Example 2, and about one-fourth that of Comparative Example 1 was excellent.

Further, referring to the viscoelasticity measurement results of FIG. 1, when the results of Example 1, Comparative Example 1, Comparative Example 2, and Reference Example are compared, as described above, all of them show the peak of acrylic resin (7. 0 to 10.0 ° C.).
On the other hand, the peak of PVA-based resin (86.0 to 92.5 ° C.) compared to Reference Example 1 in which metal oxide fine particles were not blended, Example 1 and Comparative Examples 1 and 2 in which metal oxide fine particles were blended. In both cases, the peak shifts to a high temperature. From this, it is clear that the metal oxide fine particles are present in the continuous phase as the PVA-based resin and are not present in the dispersed phase.
That is, in Example 1 and Comparative Examples 1 and 2, the content of the metal oxide fine particles in the continuous phase of the coating film is 100% by weight with respect to the total weight of the coating film. Further, the content of the metal oxide fine particles in the dispersed phase of the coating film is 0% by weight with respect to the total weight of the coating film.

In Comparative Example 1, the peak temperature is 88.6 ° C., and its strength is the same as in Reference Example 1, and the heat resistance improvement effect is insufficient. On the other hand, in the case of Example 1, the peak was 92.5 ° C. and the temperature was remarkably shifted to a high temperature, and the strength was low. Therefore, it can be said that the heat resistance was significantly improved.
In Comparative Example 2, the peak temperature was 92.5 ° C., which was a high temperature comparable to Example 1, but as described above, the coloring evaluation was insufficient.

From the above results, the effect of the present invention was found because the metal oxide fine particles were present locally in the continuous phase in the coating film, and a specific small amount was found to be remarkably distributed in the continuous phase. It is thought that it is obtained. This effect of the present invention is an unexpected effect that is contrary to conventional knowledge as described above.
The coating film obtained from the coating composition of the present invention has a high level of heat resistance.

  Since the coating agent of the present invention and the coating film obtained from the coating agent have a high level of heat resistance, it may be exposed to direct sunlight during use, such as an instrument panel of an automobile, an outer wall of a building, or an outdoor installation display panel. It is useful as a coating composition for forming a coating film that protects members exposed to an environment where heat generation occurs, such as various secondary ion battery separators, and suppresses shrinkage, and a multilayer structure containing the same. is there.

1. 2 is a graph showing viscoelasticity measurement evaluation results in Example 1.
2. 5 is a graph showing a viscoelasticity measurement evaluation result in Comparative Example 1.
3. It is a graph of the viscoelasticity measurement evaluation result in the comparative example 2.
4). It is a graph of the viscoelasticity measurement evaluation result in a reference example.

Claims (8)

  (A) A polyvinyl alcohol-based resin as a dispersant, an acrylic resin as a dispersoid, an emulsion having water as a dispersion medium, and (B) metal oxide fine particles, A) Coating composition which is 0.1 to 1.5 parts by weight with respect to 100 parts by weight of resin solid content of emulsion.   The coating composition according to claim 1, wherein the metal oxide fine particles (B) are metal oxide fine particles of Group 13 to 15 elements of the periodic table. The coating composition according to claim 1 or 2, wherein the polyvinyl alcohol resin of the emulsion (A) is a polyvinyl alcohol resin having a structural unit represented by the following chemical formula (1).
(Wherein R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R ⁴ , R ⁵ and R ⁶ each independently represents a hydrogen atom. Or an organic group.)   The coating composition according to any one of claims 1 to 3, comprising a second polyvinyl alcohol resin.   The coating film obtained from the coating composition of Claims 1-4.   The coating film according to claim 5, wherein 95 to 100% by weight of (B) metal oxide fine particle content in the coating film is present in the continuous phase.   A multilayer structure having a coating layer according to claim 6 on a substrate.   The manufacturing method of the multilayer structure which apply | coats the coating composition of Claims 1-5 on a base material, and forms into a film, and obtains a multilayer structure.