JP7458545B1 - Release coating agents for polyester base materials, release sheets and laminates - Google Patents

Abstract

[Problem] To provide a release coating agent for polyester substrates that has excellent adhesion to polyester substrates and has heat-resistant peelability. [Solution] The release coating agent for polyester substrates according to the embodiment contains an aqueous dispersion in which a polyurethane resin is dispersed in an aqueous dispersion medium. The aqueous dispersion contains a (meth)acrylic polymer that contains, as constituent components, a monofunctional alkyl (meth)acrylate having an alkyl group with 4 to 22 carbon atoms and a poly(meth)acrylate with 2 to 6 functional groups. [Selected Figure] None

Description

Embodiments of the present invention relate to a release coating agent used by coating on a polyester base material, and a release sheet and laminate obtained using the release coating agent.

Release sheets (also called peeling sheets) are known that have a release layer formed by applying a release coating agent to a polyester substrate such as a polyester film. For example, Patent Document 1 discloses a release agent composition containing a silicone resin, an alkoxy group-containing silane-modified polyurethane resin, and a solvent as a release coating agent that is applied to the surface of a release base substrate to form a release layer. In addition to silicone-based release coating agents, such release coating agents also include non-silicone-based release coating agents that make it possible to avoid silicone migration.

Japanese Patent Application Publication No. 2011-099095

The release coating agent applied to the polyester base material is required to have adhesion to the polyester base material, as well as the adhesive film to be protected as a release sheet and the resin film formed on the release sheet. It is required to be easy to peel from the resin layer, that is, to have peelability to the resin layer. At that time, since the laminate of the release sheet and the resin layer may be placed in a heated atmosphere, it is desired that the laminate be able to be peeled off even after heat treatment, that is, have heat-resistant peelability.

An object of the embodiments of the present invention is to provide a release coating agent for polyester substrates that has excellent adhesiveness to polyester substrates and has heat-resistant peeling properties.

The present invention includes the embodiments shown below.
[1] A release coating agent for polyester substrates, comprising an aqueous dispersion in which a polyurethane resin is dispersed in an aqueous dispersion medium, the aqueous dispersion comprising a monomer having an alkyl group having 4 to 22 carbon atoms. A release coating agent for polyester substrates, comprising a (meth)acrylic polymer containing a functional alkyl (meth)acrylate and a poly(meth)acrylate having 2 to 6 functional groups as constituent components.
[2] The release coating agent for a polyester substrate according to [1], wherein the (meth)acrylic polymer is contained together with the polyurethane resin in each resin particle as a dispersoid.
[3] According to [1] or [2], the (meth)acrylic polymer contains 0.3 to 50 parts by mass of the poly(meth)acrylate based on 100 parts by mass of the alkyl (meth)acrylate. Release coating agent for polyester base materials.
[4] The release coating agent for polyester substrates according to any one of [1] to [3], wherein the alkyl group of the alkyl (meth)acrylate is a linear alkyl group.
[5] The release coating agent for polyester substrates according to any one of [1] to [4], wherein the poly(meth)acrylate has an acrylic equivalent, which is a molecular weight per functional group, of 80 to 150. .
[6] The release coat for a polyester base material according to any one of [1] to [5], wherein the amount of the alkyl (meth)acrylate is 40 to 350 parts by mass based on 100 parts by mass of the polyurethane resin. agent.
[7] According to any one of [1] to [6], the polyurethane resin contains a polyol including a polyester polyol as a constituent component, and contains the polyester polyol in an amount of 30% by mass or more based on 100% by mass of the polyol. The mold release coating agent for polyester base materials described above.

[8] A release sheet comprising a polyester substrate and a release layer formed on the polyester substrate, the release layer comprising the release coating agent according to any one of [1] to [7].
[9] A laminate comprising the release sheet according to [8] and a resin layer releasably provided on the release layer of the release sheet.

[10] Mixing a polyurethane resin having a hydrophilic group, a monofunctional alkyl (meth)acrylate having an alkyl group having 4 to 22 carbon atoms, and a poly(meth)acrylate having 2 to 6 functional groups, A release coating agent for a polyester substrate, comprising an aqueous dispersion obtained by dispersing a mixture in an aqueous dispersion medium and polymerizing the alkyl (meth)acrylate and the poly(meth)acrylate contained in the mixture.

[11] An aqueous dispersion in which a polyurethane resin is dispersed in an aqueous dispersion medium, comprising a monofunctional alkyl (meth)acrylate having an alkyl group having 4 to 22 carbon atoms and a polyurethane resin having a functional group having 2 to 6 carbon atoms. Use of an aqueous dispersion containing a (meth)acrylic polymer containing (meth)acrylate as a constituent component as a release coating agent for a polyester base material.

According to an embodiment of the present invention, it is possible to provide a release coating agent for a polyester base material that has excellent adhesiveness to a polyester base material and has heat-resistant releasability.

The mold release coating agent for polyester substrates according to the present embodiment (hereinafter also simply referred to as mold release coating agent) is a mold release coating agent containing an aqueous dispersion of a polyurethane resin, and the aqueous dispersion has a specific It contains a (meth)acrylic polymer. Therefore, the release coating agent includes an aqueous dispersion medium, a polyurethane resin, and a (meth)acrylic polymer.

In this specification, "(meth)acrylic polymer" means an acrylic polymer and/or a methacrylic polymer. Similarly, "alkyl (meth)acrylate" means alkyl acrylate and/or alkyl methacrylate, and "poly(meth)acrylate" means polyacrylate and/or polymethacrylate. The same applies to other "(meth)acrylics" and "(meth)acrylates".

[Aqueous dispersion medium]
The aqueous dispersion medium is a dispersion medium containing water, and includes water or a mixed medium of water and a hydrophilic organic solvent. From the viewpoint of dispersion stability of the aqueous dispersion, the aqueous dispersion medium is preferably water, and an organic solvent may be included, but preferably in a small amount. In one embodiment, the aqueous dispersion medium preferably contains water in an amount of 70% by mass or more, more preferably contains water in an amount of 80% by mass or more, and even more preferably contains water in an amount of 90% by mass or more. It may be 100% by mass. That is, in the aqueous dispersion medium, the mass ratio of water/hydrophilic organic solvent is preferably 70/30 to 100/0, more preferably 80/20 to 100/0, and still more preferably 90/3. It is 10 to 100/0.

As the hydrophilic organic solvent, various organic solvents that dissolve in water are used, such as lower monohydric alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and glycerin, N-methylpyrrolidone, dimethyl sulfoxide, Examples include aprotic polar solvents such as dimethylformamide and acetonitrile.

[Polyurethane resin]
Polyurethane resin is obtained by reacting polyol and polyisocyanate, and is a polymer having urethane bonds in the molecule. That is, the polyurethane resin contains a polyol and a polyisocyanate as its constituent components. Here, regarding the polyurethane resin, "containing it as a constituent component" means that it is used as a raw material (monomer) for synthesizing the polyurethane resin, and the polyurethane resin has a structure derived from this.

Examples of the polyurethane resin include those having hydrophilic groups; for example, various water-based polyurethane resins such as anionic polyurethane resins, cationic polyurethane resins, and nonionic polyurethane resins can be used. Examples of hydrophilic groups include anionic groups, cationic groups, and hydrophilic segments.

Anionic polyurethane resin is a water-based polyurethane resin having anionic groups. Examples of the anionic group include at least one selected from the group consisting of carboxy groups, sulfonic acid groups, phosphoric acid groups, and salts thereof. Examples of the salts include alkali metal salts such as lithium salts, sodium salts, and potassium salts, ammonium salts, and amine salts such as primary amines, secondary amines, and tertiary amines.

A cationic polyurethane resin is a water-based polyurethane resin having a cationic group. Examples of the cationic group include a quaternary ammonium group.

A nonionic polyurethane resin is an uncharged water-based polyurethane resin that does not have an anionic group or a cationic group. Examples of nonionic polyurethane resins include polyurethane resins having hydrophilic segments such as polyoxyethylene groups.

Examples of polyols constituting the polyurethane resin include polymer polyols such as polyester polyols (e.g., aliphatic polyester polyols, aromatic polyester polyols), polycarbonate polyols, polyether polyols (e.g., polytetramethylene glycol), and polybutadiene polyols. Any one of these may be used, or two or more may be used in combination.

The molecular weight of the polymer polyol is not particularly limited, and for example, the number average molecular weight (Mn) may be from 500 to 5,000, from 800 to 4,000, or from 1,000 to 3,000.

In this specification, the number average molecular weight (Mn) is a value measured by GPC method (gel permeation chromatography method) and calculated using a standard polystyrene calibration curve. Specifically, the GPC conditions were as follows: column: "TSKgel G4000HXL+TSKgel G3000HXL+TSKgel G2000HXL+TSKgel G1000HXL+TSKgel G1000HXL" manufactured by Tosoh Corporation, mobile phase: THF (tetrahydrofuran), mobile phase flow rate: 1.0 mL/m in, column temperature: 40°C, sample It can be measured with an injection volume of 50 μL and a sample concentration of 0.2% by mass.

Examples of polyols constituting the polyurethane resin include, together with or separately from the above polymer polyols, ethylene glycol, propylene glycol, propanediol, butanediol, pentanediol, 3-methyl-1,5-pentanediol, Low-molecular polyhydric compounds such as hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, bisphenol A, bisphenol F, bisphenol S, hydrogenated bisphenol A, trimethylolpropane, glycerin, pentaerythritol, etc. Alcohol (preferably dihydric alcohol or trihydric alcohol) may also be used. Any one type of these may be used, or two or more types may be used in combination.

In one embodiment, the polyol constituting the polyurethane resin preferably includes a polyester polyol in order to enhance the effect of improving adhesiveness to the polyester base material. That is, it is preferable that the polyurethane resin contains a polyol including a polyester polyol as a constituent component. The amount of polyester polyol in the polyol is, for example, preferably 30% by mass or more based on 100% by mass of the polyol, more preferably 60% by mass or more, still more preferably 70 to 99% by mass, and 80% by mass or more. It may be up to 95% by mass.

In this specification, when the polyol contains an anionic group described below, the amount of each component constituting the polyol is calculated based on 100% by mass of the polyol, assuming that the anionic group is in the acid form. The amount of anionic group-containing polyol is similarly calculated assuming that the anionic group is in the acid form. Furthermore, when the polyol contains a cationic group as described below, it is calculated using the amount of the polyol before the cationic group is neutralized with an acid or quaternized with a quaternizing agent.

In one embodiment, the polyol constituting the polyurethane resin preferably includes a polyol having three or more functional groups. As a result, a crosslinked structure is introduced into the polyurethane resin, and the water resistance of the release layer can be improved. Examples of polyols having three or more functional groups include polyhydric alcohols having three or more hydroxy groups such as trimethylolpropane, or the above-mentioned polymer polyols having three or more hydroxy groups in the molecule. Things can be mentioned.

The amount of the polyol having 3 or more functional groups in the polyol is not particularly limited, and may be, for example, 0.1 to 10% by mass, 0.5 to 8% by mass, 1 to 5% by mass, based on 100% by mass of the polyol. It may also be mass %.

Examples of the polyisocyanate constituting the polyurethane resin include aliphatic polyisocyanate, alicyclic polyisocyanate, and aromatic polyisocyanate. Any one type of these may be used, or two or more types may be used in combination.

Examples of aliphatic polyisocyanates include tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate.

Examples of the alicyclic polyisocyanate include isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1, Examples include 3-bis(isocyanatomethyl)cyclohexane.

Examples of the aromatic polyisocyanate include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric MDI, xylylene diisocyanate (XDI), and naphthalene diisocyanate.

Further, isocyanurate forms, adduct forms, bullet forms, allophenate forms, carbodiimide forms, etc. of these polyisocyanates may be used. Moreover, any one type of these polyisocyanates may be used or two or more types may be used in combination.

In one embodiment, as the polyurethane resin, an anionic polyurethane resin obtained by reacting a polyol containing an anionic group-free polyol and an anionic group-containing polyol with a polyisocyanate is preferably used. Examples of such anionic polyurethane resins include the following (A) and (B). Among these, the chain elongation type (A) is advantageous in improving the water resistance of the release layer.

(A) An anionic polyurethane resin obtained by synthesizing an isocyanate group-containing urethane prepolymer from an anionic group-free polyol, an anionic group-containing polyol, and polyisocyanate, and chain-extending the urethane prepolymer using a chain extender.

(B) A hydroxy group-containing anionic polyurethane resin obtained by reacting an anionic group-free polyol, an anionic group-containing polyol, and a polyisocyanate.

As the anionic group-free polyol used to synthesize the anionic polyurethane resin, polyols having no anionic group or cationic group among the various polyols listed above can be used. The anionic group-containing polyol is preferably a carboxyl group-containing polyol having a carboxyl group in the molecule, such as dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dioxymaleic acid, , 6-dioxybenzoic acid, 3,4-diaminobenzoic acid and other carboxylic acid-containing compounds, derivatives thereof, and salts thereof. Any one type of these may be used, or two or more types may be used in combination.

Here, the anionic group is not only an acid type (for a carboxy group: -COOH) but also a salt type (for a carboxy group: a carboxylic acid group represented by -COOX. However, X represents a carboxylic acid and a salt. The concept also includes cations (formed cations), and the acid type and salt type may coexist. By neutralizing the anionic group to form a salt, the final polyurethane resin can be made water-dispersible. Therefore, in the aqueous dispersion of polyurethane resin, the anionic group may exist in the form of a salt. On the other hand, in the state of the coating film obtained by drying the aqueous dispersion, when a nonvolatile base is used as a neutralizing agent, it exists as a salt form, and when a volatile base is used, it exists as an acid form. You may.

In the anionic polyurethane resin, the amount of the anionic group-free polyol in the polyol is not particularly limited, and may be, for example, 75 to 99% by mass, 80 to 97% by mass, 85 to 99% by mass, based on 100% by mass of the polyol. It may be up to 95% by mass. The amount of the anionic group-containing polyol in the polyol is not particularly limited, and may be, for example, 1 to 25% by weight, 3 to 20% by weight, or 5 to 15% by weight based on 100% by weight of the polyol.

In one embodiment, the polyurethane resin may be a cationic polyurethane resin obtained by reacting a polyol containing a cationic group-free polyol and a cationic group-containing polyol with a polyisocyanate. Examples of such cationic polyurethane resins include the following (C).

(C) A cationic polyurethane resin obtained by synthesizing an isocyanate group-containing urethane prepolymer from a cationic group-free polyol, a cationic group-containing polyol, and a polyisocyanate, and extending the chain of the urethane prepolymer using a chain extender.

As the cationic group-free polyol used to synthesize the cationic polyurethane resin, polyols having no anionic group or cationic group among the various polyols listed above can be used. Examples of the cationic group-containing polyol include alkyl dialkanolamines such as N-methyldiethanolamine and N-ethyldiethanolamine, and those obtained by quaternizing these with an acid or a quaternizing agent can also be used. Here, the cationic group includes, for example, a tertiary or quaternary ammonium group obtained by neutralizing a tertiary amino group with an acid or quaternizing it with a quaternizing agent. Further, the cationic group-containing polyol may be a tertiary amine group-containing compound capable of forming a tertiary or quaternary ammonium group.

In the cationic polyurethane resin, the amount of the cationic group-free polyol in the polyol is not particularly limited, and may be, for example, 75 to 97% by weight or 80 to 95% by weight based on 100% by weight of the polyol. The amount of the cationic group-containing polyol in the polyol is not particularly limited, and may be, for example, 3 to 25% by weight or 5 to 20% by weight based on 100% by weight of the polyol.

In one embodiment, as the polyurethane resin, a nonionic polyurethane resin obtained by reacting a polyol containing a hydrophilic segment-containing polyol and a hydrophilic segment-free polyol with a polyisocyanate may be used. Examples of such nonionic polyurethane resins include the following (D).

(D) A nonionic polyurethane resin obtained by synthesizing an isocyanate group-containing urethane prepolymer from a hydrophilic segment-containing polyol, a hydrophilic segment-free polyol, and a polyisocyanate, and chain-extending the urethane prepolymer using a chain extender.

Examples of polyols containing hydrophilic segments include polyols having nonionic hydrophilic segments such as polyoxyethylene groups. Examples of polyols not containing hydrophilic segments include polyols that do not have anionic groups, cationic groups, or hydrophilic segments, among the various polyols listed above.

In the nonionic polyurethane resin, the amount of the hydrophilic segment-containing polyol in the polyol is not particularly limited, and may be, for example, 5 to 60% by mass or 10 to 50% by mass based on 100% by mass of the polyol. The amount of the hydrophilic segment-free polyol is also not particularly limited, and may be, for example, 40 to 95% by weight or 50 to 90% by weight based on 100% by weight of the polyol.

The chain extender for extending the chain of the isocyanate group-containing urethane prepolymer is not particularly limited, and examples thereof include water, and aliphatic polyamine compounds (for example, ethylenediamine, trimethylenediamine, propylenediamine, diethylenetriamine, triethylene tetramine), aromatic polyamine compounds (e.g. metaxylene diamine, tolylene diamine, diaminodiphenylmethane), alicyclic polyamine compounds (e.g. piperazine, isophorone diamine), polyhydrazide compounds (e.g. hydrazine, adipic acid dihydrazide), etc. Examples include polyvalent amine compounds.

[(meth)acrylic polymer]
The (meth)acrylic polymer is composed of a monofunctional alkyl (meth)acrylate (X) having an alkyl group having 4 to 22 carbon atoms and a poly(meth)acrylate (Y) having 2 to 6 functional groups. Contains as a constituent. Here, regarding the (meth)acrylic polymer, "containing it as a constituent component" refers to using the polymer as a raw material (monomer) for synthesizing the polymer, and the (meth)acrylic polymer has a structure derived from this.

When the number of carbon atoms in the alkyl group of the alkyl (meth)acrylate (X) is 4 or more, the initial releasability can be improved, and when the number of carbon atoms in the alkyl group is 22 or less, it is possible to improve the peelability by heating. Deterioration of releasability can be suppressed. The alkyl preferably has 6 to 20 carbon atoms, more preferably 8 to 18 carbon atoms, and still more preferably 10 to 16 carbon atoms. The alkyl (meth)acrylate (X) may be a mixture of alkyl groups having different numbers of carbon atoms.

Although the alkyl group of the alkyl (meth)acrylate (X) may be branched, it is preferably a linear alkyl group from the viewpoints of peelability, heat-resistant peelability, and water resistance.

Specific examples of alkyl (meth)acrylate (X) include n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, n-icosyl (meth)acrylate, and n-docosyl (meth)acrylate. Any of these may be used alone or in combination of two or more.

Poly(meth)acrylate means an ester compound having two or more (meth)acryloyl groups. Therefore, poly(meth)acrylate (Y) having 2 to 6 functional groups is a (meth)acrylic acid ester having 2 to 6 (meth)acryloyl groups in one molecule. By using such poly(meth)acrylate (Y), it is possible to improve heat resistance to peeling.

In one embodiment, the poly(meth)acrylate (Y) preferably has an acrylic equivalent, which is the molecular weight per functional group, of 80 to 150, and more preferably has an acrylic equivalent of 90 to 150.

Specific examples of poly(meth)acrylate (Y) include (poly)alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate; Examples include pentaerythritol tetra(meth)acrylate and dipentaerythritol hexa(meth)acrylate. Any one type of these may be used, or two or more types may be used in combination.

Among these, (poly)alkylene glycol di(meth)acrylate is preferable as poly(meth)acrylate (Y). Here, "(poly)alkylene glycol" means monoalkylene glycol and/or polyalkylene glycol. The "poly" (number of repeating bonds) of the polyalkylene glycol is preferably 2 to 3, and the number of carbon atoms in the "alkylene" is preferably 2 to 4.

The (meth)acrylic polymer is a copolymer of alkyl (meth)acrylate (X) and poly(meth)acrylate (Y), and may be composed only of these (X) and (Y). , other monomers may be included as constituents within a range that does not impair the effects of this embodiment. The total amount of alkyl (meth)acrylate (X) and poly(meth)acrylate (Y) in 100% by mass of all constituent components of the (meth)acrylic polymer is preferably 80% by mass or more, more preferably 90% by mass. % by mass or more.

Although the ratio of alkyl (meth)acrylate (X) and poly(meth)acrylate (Y) in the (meth)acrylic polymer is not particularly limited, ) The amount of acrylate (Y) is preferably 0.3 to 50 parts by weight, more preferably 1 to 30 parts by weight, and still more preferably 5 to 20 parts by weight. When the amount of poly(meth)acrylate (Y) is 50 parts by mass or less, initial peelability can be improved, and when it is 0.3 parts by mass or more, the effect of improving heat-resistant peelability can be enhanced. .

Polymerization of a monomer containing an alkyl (meth)acrylate (X) and a poly(meth)acrylate (Y) may be carried out by adding a known polymerization initiator. Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-amidinopropane) dihydro Azo-based compounds such as chloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, and 2,2'-azobis(N,N'-dimethyleneisobutyramidine) Initiators, substituted ethane initiators such as phenyl-substituted ethane, etc. can be used. Alternatively, peroxide initiators such as persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, peroxides such as hydrogen peroxide, t-butyl hydroperoxide, and cumene hydroperoxide; Using redox initiators in combination with reducing agents such as sulfites, bisulfites such as sodium bisulfite, metal salts such as cuprous sulfate and ferrous sulfate, and organic reducing agents such as L-ascorbic acid. Good too.

The amount of the polymerization initiator is not particularly limited, and may be, for example, 0.005 to 1 part by mass based on 100 parts by mass of the total monomers containing the alkyl (meth)acrylate (X) and the poly(meth)acrylate (Y). good.

[Aqueous dispersion of polyurethane resin]
The aqueous dispersion of polyurethane resin is an aqueous dispersion in which a polyurethane resin is dispersed in an aqueous dispersion medium, and contains the above-mentioned (meth)acrylic polymer.

In the aqueous dispersion, the (meth)acrylic polymer is preferably contained in the particles of the polyurethane resin. That is, the (meth)acrylic polymer is preferably contained together with the polyurethane resin in each resin particle as a dispersoid. At that time, the (meth)acrylic polymer may exist inside the particles, may exist on the surfaces of the particles, or may exist inside and on the surfaces of the particles. While polyurethane resins have hydrophilic groups, (meth)acrylic polymers are hydrophobic and therefore tend to exist inside particles. Therefore, it is preferable that the (meth)acrylic polymer exists inside the particles, and that the polyurethane resin having hydrophilic groups exists on the particle surface so as to cover this, and thereby the effects of this embodiment can be enhanced.

The content of the polyurethane resin in the aqueous dispersion is not particularly limited, and may be, for example, 10 to 50% by mass, 15 to 45% by mass, or 20 to 40% by mass, based on the total mass of the aqueous dispersion. .

The content of the (meth)acrylic resin is preferably set as follows in terms of the content of the alkyl (meth)acrylate. That is, the amount of the alkyl (meth)acrylate is preferably 40 to 350 parts by mass, more preferably 45 to 300 parts by mass, even more preferably 60 to 200 parts by mass, and even more preferably 70 to 150 parts by mass, per 100 parts by mass of the polyurethane resin. By setting the content of the alkyl (meth)acrylate to 40 parts by mass or more, it is possible to improve the peelability and water resistance, and by setting it to 350 parts by mass or less, it is possible to improve the adhesion to the polyester substrate.

The size of the resin particles in the aqueous dispersion is not particularly limited, and may be, for example, an average particle size of 0.001 to 0.5 μm. Here, the average particle size is the 50% cumulative particle size (d50) measured using a Microtrac UPA-UZ152 manufactured by Nikkiso Co., Ltd.

The aqueous dispersion of polyurethane resin may contain other components as long as their effects are not impaired. For example, crosslinking agents for crosslinking polyurethane resins, surfactants for dispersing polyurethane resins, (meth)acrylic resins, or their monomers in aqueous dispersion media, polymerization initiators for polymerizing (meth)acrylic resins, etc. may be included.

As a crosslinking agent, a reactive group capable of reacting with at least one active hydrogen-containing group selected from the group consisting of a hydroxy group, a primary amino group, a secondary amino group, and a thiol group possessed by the polyurethane resin is used. Examples include compounds having two or more. Thereby, the water resistance of the release layer formed from the release coating agent can be improved. When the polyurethane resin has a carboxyl group, the crosslinking agent can also cause a crosslinking reaction with the carboxyl group.

Examples of the crosslinking agent include carbodiimide compounds, oxazoline compounds, blocked isocyanate compounds, and epoxy compounds, and any one type of these may be used or two or more types may be used in combination.

The amount of the crosslinking agent is not particularly limited, and may be, for example, 1.0 to 20 parts by weight based on 100 parts by weight of the polyurethane resin.

The surfactant is not particularly limited, and anionic surfactants and nonionic surfactants are preferably used. Examples of the anionic surfactant include polyoxyalkylene alkyl ether sulfate, polyoxyalkylene styrenated phenyl ether sulfate, polyoxyalkylene alkyl ether phosphate, and the like. Examples of the nonionic surfactant include polyoxyalkylene alkyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene phenyl ether, polyoxyethylene polyoxypropylene glycol, and the like.

The amount of the surfactant is not particularly limited, and may be, for example, 0.1 to 5.0 parts by weight based on 100 parts by weight of the total amount of the polyurethane resin and (meth)acrylic polymer.

[Method for producing aqueous dispersion]
The method for producing the aqueous dispersion of polyurethane resin is not particularly limited, and may be produced, for example, by a method including the following steps (1) to (4).

Step (1): Step of reacting polyol and polyisocyanate.
Step (2): A step of mixing the polyurethane resin having a hydrophilic group obtained in Step (1), alkyl (meth)acrylate (X), and poly(meth)acrylate (Y).
Step (3): A step of dispersing the mixture in an aqueous dispersion medium.
Step (4): A step of polymerizing the alkyl (meth)acrylate (X) and poly(meth)acrylate (Y) contained in the mixture dispersed in the aqueous dispersion medium.

In this way, it is believed that by mixing a polyurethane resin having a hydrophilic group with an alkyl (meth)acrylate (X) and a poly(meth)acrylate (Y) and dispersing it in an aqueous dispersion medium, and polymerizing the alkyl (meth)acrylate (X) and poly(meth)acrylate (Y) in the mixture in this dispersed state, the (meth)acrylic polymer can be efficiently incorporated into the polyurethane resin particles.

In the above step (1), the reaction between the polyol and the polyisocyanate may be carried out without an organic solvent or in an organic solvent having no active hydrogen group, such as methyl ethyl ketone or acetone. The concept of the polyurethane resin obtained by the reaction in step (1) also includes a urethane prepolymer before chain elongation or the like. Therefore, in step (2), the urethane prepolymer may be mixed with an acrylic monomer containing the above (X) and (Y).

In addition, if the polyurethane resin has an anionic group or a cationic group, the anionic group or cationic group can be removed using a neutralizing agent before or after mixing the polyurethane resin and the acrylic monomer in step (2). The cationic group may be neutralized, or the cationic group may be quaternized using a quaternizing agent.

Examples of bases that neutralize anionic groups include non-volatile bases such as sodium hydroxide and potassium hydroxide, tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine, and triethanolamine, and volatile bases such as ammonia.

Examples of acids that neutralize cationic groups include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, malic acid, and malonic acid. Examples of quaternizing agents that quaternize cationic groups include alkyl halides such as methyl chloride and methyl bromide, and dialkyl sulfates such as dimethyl sulfate and diethyl sulfate.

In step (3), the method of dispersing the mixture in the aqueous dispersion medium is not particularly limited, and examples thereof include (i) a method of adding the mixture or a resin solution thereof while stirring the aqueous dispersion medium with a homogenizer, homomixer, etc., and (ii) a method of adding the aqueous dispersion medium while stirring the mixture or a resin solution thereof with a homogenizer, homomixer, etc. Note that a surfactant may be added to facilitate emulsification and dispersion of the mixture containing the polyurethane resin and the acrylic monomer in the aqueous dispersion medium.

When the urethane prepolymer is synthesized in step (1), the chain may be extended using a chain extender after or during dispersion in step (3). The chain extension reaction may be performed simultaneously with the polymerization reaction of step (4), or may be performed before the polymerization reaction of step (4).

The polymerization in step (4) may be thermal polymerization, but it is preferable to add a polymerization initiator to carry out the polymerization reaction. The polymerization temperature is adjusted depending on the type of polymerization initiator, and may be, for example, 20°C to 100°C.

In addition, when the reaction between the polyol and the polyisocyanate is carried out in an organic solvent in step (1), the organic solvent is may be removed.

In one embodiment, when the anionic polyurethane resin of (A) above is used as the polyurethane resin, it may be produced by the following steps (a1) to (a6).
Step (a1): A step of reacting an anionic group-free polyol, an anionic group-containing polyol, and a polyisocyanate to synthesize an isocyanate group-containing urethane prepolymer.
Step (a2): A step of neutralizing the anionic groups of the isocyanate group-containing urethane prepolymer.
Step (a3): A step of mixing the isocyanate group-containing urethane prepolymer, alkyl (meth)acrylate (X), and poly(meth)acrylate (Y).
Step (a4): A step of dispersing the mixture in an aqueous dispersion medium.
Step (a5): A step of chain-extending the isocyanate group-containing urethane prepolymer in the mixture dispersed in the aqueous dispersion medium using a chain extender.
Step (a6): A step of polymerizing alkyl (meth)acrylate (X) and poly(meth)acrylate (Y) in a mixture dispersed in an aqueous dispersion medium.

Step (a1) corresponds to the above step (1), step (a3) corresponds to the above step (2), step (a4) corresponds to the above step (3), and step (a6) corresponds to the above step ( 4), and steps (a2) and (a5) are additional steps.

In step (a1), the polyisocyanate is used so that the amount of isocyanate groups is stoichiometrically in excess of the amount of hydroxyl groups contained in the polyol, for example, so that the equivalent ratio of hydroxyl groups to isocyanate groups (NCO/OH) is 1.05 to 1.70 (more preferably 1.10 to 1.60).

Note that the order of step (a2) and step (a3) does not matter. Furthermore, in step (a5), the chain extender may be added after or during the dispersion of the polyurethane prepolymer in the aqueous dispersion medium in step (a4). The chain extender is as described above, and water also serves as a chain extender. When water is used as a chain extender, the water as an aqueous dispersion medium also serves as the chain extender.

In one embodiment, when the anionic polyurethane resin of (B) above is used as the polyurethane resin, it may be produced by the following steps (b1) to (b5).
Step (b1): A step of reacting an anionic group-free polyol, an anionic group-containing polyol, and a polyisocyanate to synthesize a hydroxy group-containing polyurethane resin.
Step (b2): A step of neutralizing the anionic groups of the hydroxy group-containing polyurethane resin.
Step (b3): A step of mixing the hydroxy group-containing polyurethane resin, alkyl (meth)acrylate (X), and poly(meth)acrylate (Y).
Step (b4): A step of dispersing the mixture in an aqueous dispersion medium.
Step (b5): A step of polymerizing alkyl (meth)acrylate (X) and poly(meth)acrylate (Y) in a mixture dispersed in an aqueous dispersion medium.

Step (b1) corresponds to the above step (1), step (b3) corresponds to the above step (2), step (b4) corresponds to the above step (3), and step (b5) corresponds to the above step ( 4), and step (b2) is an additional step.

In step (b1), the polyol has a stoichiometric excess of hydroxyl groups than the amount of isocyanate groups contained in the polyisocyanate, for example, the equivalent ratio of hydroxyl groups to isocyanate groups (NCO/OH) is 0.70. ~0.95 (more preferably 0.75 to 0.90). Note that the order of steps (b2) and (b3) does not matter.

In one embodiment, when the above cationic polyurethane resin (C) is used as the polyurethane resin, it may be produced by the following steps (c1) to (c6).
Step (c1): A step of reacting a cationic group-free polyol, a cationic group-containing polyol, and a polyisocyanate to synthesize an isocyanate group-containing urethane prepolymer.
Step (c2): A step of neutralizing the cationic groups of the isocyanate group-containing urethane prepolymer with an acid or quaternizing with a quaternizing agent.
Step (c3): A step of mixing the isocyanate group-containing urethane prepolymer, alkyl (meth)acrylate (X), and poly(meth)acrylate (Y).
Step (c4): A step of dispersing the mixture in an aqueous dispersion medium.
Step (c5): A step of chain-extending the isocyanate group-containing urethane prepolymer in the mixture dispersed in the aqueous dispersion medium using a chain extender.
Step (c6): A step of polymerizing alkyl (meth)acrylate (X) and poly(meth)acrylate (Y) in a mixture dispersed in an aqueous dispersion medium.

Step (c1) corresponds to the above step (1), step (c3) corresponds to the above step (2), step (c4) corresponds to the above step (3), and step (c6) corresponds to the above step ( 4), and steps (c2) and (c5) are additional steps.

Note that the order of step (c2) and step (c3) does not matter. The equivalent ratio of hydroxy groups and isocyanate groups in step (c1), the timing of addition of the chain extender in step (c5), and the case where water is used as the chain extender are determined by the above steps (a1) and (a5). It's the same.

In one embodiment, when the above nonionic polyurethane resin (D) is used as the polyurethane resin, it may be produced by the following steps (d1) to (d5).
Step (d1): A step of reacting a hydrophilic segment-containing polyol, a hydrophilic segment-free polyol, and a polyisocyanate to synthesize an isocyanate group-containing urethane prepolymer.
Step (d2): A step of mixing the isocyanate group-containing urethane prepolymer, alkyl (meth)acrylate (X), and poly(meth)acrylate (Y).
Step (d3): A step of dispersing the mixture in an aqueous dispersion medium.
Step (d4): A step of chain-extending the isocyanate group-containing urethane prepolymer dispersed in the aqueous dispersion medium using a chain extender.
Step (d5): A step of polymerizing alkyl (meth)acrylate (X) and poly(meth)acrylate (Y) in a mixture dispersed in an aqueous dispersion medium.

Step (d1) corresponds to the above step (1), step (d2) corresponds to the above step (2), step (d3) corresponds to the above step (3), and step (d5) corresponds to the above step ( 4), and step (d4) is an additional step. The equivalent ratio of hydroxy groups and isocyanate groups in step (d1), the timing of addition of the chain extender in step (d4), and the case where water is used as the chain extender are determined by the above steps (a1) and (a5). It's the same.

[Release coating agent for polyester base material]
The release coating agent for polyester substrates according to the present embodiment contains the above-mentioned aqueous dispersion, and therefore contains an aqueous dispersion medium, a polyurethane resin, and a (meth)acrylic resin. The release coating agent may consist only of the above aqueous dispersion, and may contain various additives such as antioxidants, antistatic agents, surfactants, antifoaming agents, and surface conditioners together with the above aqueous dispersion. But that's fine.

The content of the polyurethane resin in the release coating agent is not particularly limited, and may be, for example, 10 to 50% by mass, 15 to 45% by mass, or 20 to 40% by mass, based on the total mass of the release coating agent. good.

[Release sheet]
The release sheet according to one embodiment includes a polyester substrate and a release layer provided on the polyester substrate, the release layer being formed from the release coating agent.

As the polyester base material, those formed from various polyesters containing dicarboxylic acid and diol as constituent components (monomers) can be used. Examples of polyester substrates include polyethylene terephthalate (PET) substrates, polyethylene naphthalate (PEN) substrates, polyethylene furanoate (PEF) substrates, polytrimethylene terephthalate (PTT) substrates, and polybutylene terephthalate (PBT) substrates. Examples include base materials, polybutylene naphthalate (PBN) base materials, and the like. Among these, polyester base materials formed from polyester containing aromatic dicarboxylic acid and ethylene glycol as constituent components, specifically PET base materials, PEN base materials, PEF base materials, etc., are more preferably used.

The polyester base material may be in the form of a film or a plate, and its thickness is not particularly limited. Further, the polyester base material may be one that has been subjected to surface treatment such as corona surface treatment.

The release layer is a resin layer laminated on at least one of the front and back surfaces of the polyester base material, and can be formed by applying a release coating agent to the polyester base material and drying it. In addition, when the mold release coating agent contains the said crosslinking agent, the polyurethane resin is crosslinked by performing heat treatment, such as drying, after applying the mold release coating agent.

The thickness (dry film thickness) of the release layer is not particularly limited, and may be, for example, 0.01 to 50 μm, or 0.05 to 10 μm.

The release sheet can be used, for example, as a process protection film, and is applied to an adhesive or non-adhesive object to protect the object. When the object to which the release sheet is attached is used, the release sheet is peeled off. The peeled off release sheet may be discarded.

[Laminated body]
A laminate according to one embodiment includes the above-mentioned release sheet and a resin layer releasably provided on the release layer. The release sheet is used, for example, as (1) a protective sheet for protecting an adhesive film, or (2) as a support sheet for forming a resin film.

In the case of the protective sheet in (1) above, the release sheet is used to protect the adhesive film on a product that has an adhesive film formed on the surface, and the release sheet is used to protect the adhesive film on the surface of the product. A release sheet is pasted on the adhesive surface. Therefore, the adhesive film corresponds to the resin layer, and the product and the release sheet attached to the adhesive surface constitute the laminate. The release sheet is peeled off from the adhesive surface when the product is used. Examples of the above-mentioned products include liquid crystal polarizing plates and the like.

In the case of the support sheet (2) above, a resin liquid is applied or poured onto the release layer of the release sheet and cured by drying or the like to form a resin film. Therefore, the resin film corresponds to the resin layer, and the release sheet provided with the resin film corresponds to the laminate. The release sheet is peeled off from the resin film when the resin film is used.

Hereinafter, the present invention will be explained in more detail based on Examples and Comparative Examples, but the present invention is not limited thereto.

Details of each component used in the examples are as follows.

[Polyol]
- Polyester polyol 1: aromatic polyester diol (number of functional groups: 2, number average molecular weight: 2000). The synthesis method is as follows.
54.72 parts by mass of isophthalic acid, 8.63 parts by mass of adipic acid, 23.89 parts by mass of neopentyl glycol, and ethylene were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank, and a nitrogen gas introduction pipe. 12.76 parts by mass of glycol was charged, and the temperature was raised to 250°C while stirring under a nitrogen stream. The reaction was carried out until the acid value became 5 mgKOH/g or less to obtain an aromatic polyester diol.

- Polyester polyol 2: aromatic polyester diol (number of functional groups: 2, number average molecular weight: 2000). The synthesis method is as follows.
52.41 parts by mass of terephthalic acid, 8.77 parts by mass of adipic acid, and 26.58 parts by mass of 1,6-hexanediol were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank, and a nitrogen gas introduction tube. , and 12.24 parts by mass of ethylene glycol were charged, and the temperature was raised to 250°C while stirring under a nitrogen stream. The reaction was carried out until the acid value became 5 mgKOH/g or less to obtain an aromatic polyester diol.

・Polycarbonate polyol: Polycarbonate diol (number of functional groups: 2, number average molecular weight: 2000), "UH-200" manufactured by UBE Co., Ltd.
・Bisphenol type polyol: EO adduct of bisphenol A (number of functional groups: 2, number average molecular weight: 325), "Newpol BPE-20NK" manufactured by Sanyo Chemical Industries, Ltd.
・Trifunctional polyol: trimethylolpropane (number of functional groups: 3), manufactured by Mitsui Gas Chemical Co., Ltd. ・POE-containing polyol: polyoxyethylene group-containing nonionic polyol (number of functional groups: 2, number average molecular weight: 600), Perstorp Manufactured by "Ymer N180"
- Cationic group-containing polyol: N-methyldiethanolamine, manufactured by Tokyo Chemical Industry Co., Ltd. - Dimethylolpropionic acid: "Bis-MPA (registered trademark)" manufactured by Perstorp (number of functional groups: 2)

[Polyisocyanate]
・IPDI: Isophorone diisocyanate (number of functional groups: 2, molecular weight: 222.3), "VESTANAT (registered trademark) IPDI" manufactured by Evonik
・Hydrogenated MDI: dicyclohexylmethane 4,4'-diisocyanate (number of functional groups: 2, molecular weight: 262), "VESTANAT (registered trademark) H12MDI" manufactured by Evonik
・HDI: Hexamethylene diisocyanate (number of functional groups: 2, molecular weight: 168.2), “Duranate (registered trademark) 50M-HDI” manufactured by Asahi Kasei Corporation

[(meth)acrylic acid ester]
・N-Butyl acrylate: “Butyl acrylate” manufactured by Mitsubishi Chemical Corporation
・N-Octyl acrylate: “NOAA” manufactured by Osaka Organic Chemical Industry Co., Ltd.
・N-Dodecyl acrylate: “LA” manufactured by Osaka Organic Chemical Industry Co., Ltd.
・Stearyl acrylate: “STA” manufactured by Osaka Organic Chemical Industry Co., Ltd.
・N-Dodecyl methacrylate: “Light Ester L” manufactured by Kyoeisha Chemical Co., Ltd.
・2-ethylhexyl acrylate: manufactured by Mitsubishi Chemical Corporation ・Ethyl acrylate: manufactured by Mitsubishi Chemical Corporation

[Poly(meth)acrylate]
・Dimethacrylate 1: Ethylene glycol dimethacrylate, “Light Ester EG” manufactured by Kyoeisha Chemical Co., Ltd.
・Dimethacrylate 2: Triethylene glycol dimethacrylate, “Light Ester 3EG” manufactured by Kyoeisha Chemical Co., Ltd.
・Hexaacrylate: Dipentaerythritol hexaacrylate (DPHA), “Light Acrylate DPE-6A” manufactured by Kyoeisha Chemical Co., Ltd.

[Other additives]
Surfactant: "Hitenol (registered trademark) LA-12" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
Crosslinking agent: "V02-L02" manufactured by Nisshinbo Chemical Co., Ltd. (non-volatile content 40%, NCN equivalent 385)
Polymerization initiator 1: tert-butyl hydroperoxide (70% aqueous solution) manufactured by Tokyo Chemical Industry Co., Ltd. Polymerization initiator 2: sodium sulfite manufactured by Nacalai Tesque, Inc.

The evaluation method for the release coating agent is as follows.

[Peelability 1A (initial peelability for acrylic adhesive)]
A corona discharge-treated PET base material ("Lumirror T-60", manufactured by Toray Industries, Inc.) was used as the PET base material. A release coating agent was applied to the PET base material using a bar coater to a dry film thickness of 1 μm, and dried at 160°C for 1 minute to form a test piece (coating film) on which a coating film of the release coating agent was formed. I got it. However, in Comparative Example 3, a PP base material ("Torefan BO", manufactured by Toray Industries, Inc.) was used instead of the PET base material. Acrylic adhesive tape "No. 31B" manufactured by Nitto Denko Corporation was applied to the coating film of the test piece using a 2 kg roller, and the peel strength (unit: mN/25 mm) after 3 hours was measured. The peel strength was measured using a 180° peel test (300 mm/min) in accordance with JIS Z0237:2009. The lower the peel strength, the better the peelability.

[Peelability 1B (Heat-resistant peelability for acrylic adhesive, 70°C x 20 hours)]
An acrylic adhesive tape "No. 31B" manufactured by Nitto Denko Co., Ltd. was applied to the coating film of a test piece prepared in the same manner as Peelability 1A using a 2 kg roller and heated at 70° C. for 20 hours. Thereafter, after cooling to room temperature, the peel strength (unit: mN/25 mm) was measured in the same manner as in peelability 1A. The lower the peel strength, the better the heat-resistant peelability. In the measurement of peel strength, the case where the entire coating film was peeled off was indicated as "F".

[1B/1A]
1B/1A is the ratio of the peel strength of peelability 1B to the peel strength of peelability 1A. The smaller this ratio is, the less deterioration in releasability due to heating occurs. In peelability 1B, those in which the entire coating film was peeled off were indicated as "F".

[Peelability 1C (Heat-resistant peelability for acrylic adhesive, 150°C x 5 minutes)]
An acrylic adhesive tape "No. 31B" manufactured by Nitto Denko Co., Ltd. was applied to the coating film of a test piece prepared in the same manner as in Peelability 1A using a 2 kg roller and heated at 150° C. for 5 minutes. Thereafter, after cooling to room temperature, the peel strength (unit: mN/25 mm) was measured in the same manner as in peelability 1A. In the measurement of peel strength, the case where the entire coating film was peeled off was indicated as "F".

[1C/1A]
1C/1A is the ratio of the peel strength of peelability 1C to the peel strength of peelability 1A. The smaller this ratio, the less the deterioration of the peelability due to heating. In peelability 1C, peeling together with the coating film was indicated as "F."

[Peelability 2A (initial peelability for silicone adhesive)]
A silicone adhesive tape "No. 336" manufactured by Nitto Denko Corporation was applied to the coating film of a test piece prepared in the same manner as in Peelability 1A using a 2 kg roller, and the peel strength after 3 hours (unit: mN/ 25 mm) was measured. The peel strength was measured using a 180° peel test (300 mm/min) in accordance with JIS Z0237:2009. The lower the peel strength, the better the peelability.

[Peelability 2B (Heat-resistant peelability against silicone adhesive, 70°C x 20 hours)]
A silicone adhesive tape "No. 336" manufactured by Nitto Denko Co., Ltd. was applied to the coating film of a test piece prepared in the same manner as in Peelability 1A using a 2 kg roller and heated at 70° C. for 20 hours. Thereafter, after cooling to room temperature, the peel strength (unit: mN/25 mm) was measured in the same manner as in peelability 2A. The lower the peel strength, the better the heat-resistant peelability. In the measurement of peel strength, the case where the entire coating film was peeled off was indicated as "F".

[2B/2A]
2B/2A is the ratio of the peel strength of peelability 2B to the peel strength of peelability 2A. The smaller this ratio is, the less deterioration in releasability due to heating occurs. Those in which the entire coating film was peeled off in peelability 2B were labeled as "F."

[Removability 2C (heat-resistant peelability against silicone-based adhesive, 150°C x 5 minutes)]
A silicone adhesive tape "No. 336" manufactured by Nitto Denko Corporation was applied to the coating film of the test piece prepared in the same manner as in Release 1A using a 2 kg roller, and heated at 150°C for 5 minutes. After cooling to room temperature, the peel strength (unit: mN/25 mm) was measured in the same manner as in Release 2A. In the measurement of the peel strength, the case where the coating film peeled off was indicated as "F".

[2C/2A]
2C/2A is the ratio of the peel strength of peelability 2C to the peel strength of peelability 2A. The smaller this ratio is, the less deterioration in releasability due to heating occurs. Those in which the entire coating film was peeled off in peelability 2C were designated as "F".

[Adhesiveness]
A test piece on which a coating film of a release coating agent was formed was obtained in the same manner as in Release 1A. The coating surface of the test piece was rubbed with a cotton swab moistened with isopropyl alcohol, and evaluated according to the following criteria. Here, rubbing was performed by pressing the flat side of a cotton swab lightly against the coating surface and moving it back and forth about 2 cm (one time for each round trip), and observed the state after the first and second rubbing. .
◎: No peeling after the second rubbing. ○: No peeling after the first rubbing, but peeling occurred after the second rubbing.
×: Peeled off during the first rubbing.

[water resistance]
A release coating agent was poured onto a fluororesin-coated frying pan so that the dry thickness was 500 μm, and then dried at 40° C. for 15 hours, at 80° C. for 6 hours, and then at 120° C. for 20 minutes to produce a film made of the release coating agent. The film was used as a test piece, and the test piece was immersed in warm water at 40° C. for 24 hours, and the mass of the film after immersion was measured. The increase rate (%) of the mass after immersion relative to the initial mass before immersion was calculated. The smaller the increase rate, the smaller the swelling due to water and the better the water resistance.

[Example 1]
A four-neck flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube was added with 54.2 parts by weight of polyester polyol 1, 2.6 parts by weight of trifunctional polyol, 8.8 parts by weight of dimethylolpropionic acid, and 100 parts by weight of methyl ethyl ketone, thoroughly stirred and dissolved, then 34.4 parts by weight of IPDI was added, and the content of free isocyanate groups relative to the solid content was reacted at 75 ° C. until 2.9% by weight, to obtain a methyl ethyl ketone solution of an isocyanate group-containing urethane prepolymer. This prepolymer solution was cooled to 45 ° C., neutralized by adding 6.64 parts by weight of triethylamine as a neutralizing agent, and then 100 parts by weight of n-dodecyl acrylate, 10 parts by weight of dimethacrylate 1, 2.2 parts by weight of a surfactant, and 200 parts by weight of methyl ethyl ketone were added and mixed with stirring. Subsequently, 600 parts by weight of distilled water was added as a dispersion medium while stirring with a homogenizer to emulsify and disperse, and the dispersion was stirred at 40 ° C. for 1 hour to complete the chain extension reaction with water. Thereafter, 0.16 parts by mass of polymerization initiator 1 and 0.15 parts by mass of polymerization initiator 2 were each diluted 10 times with distilled water and then added, and the mixture was reacted for 3 hours at 35° C. to 45° C. to polymerize a (meth)acrylic polymer. Thereafter, methyl ethyl ketone was distilled off under heating and reduced pressure, and water for adjusting the solid content was added to obtain a release coating agent consisting of an aqueous dispersion with a solid content of 30% by mass.

[Examples 2 to 18, 20 to 21, and 25, and Comparative Examples 1 to 4]
The types and amounts of polyol, polyisocyanate, and acrylic monomer, and the amounts of neutralizer and polymerization initiator 1 and 2 were changed as shown in Tables 1 and 2 below, and the rest was the same as in Example 1, to obtain release coating agents consisting of aqueous dispersions in Examples 2 to 18, 20 to 21, and 25, and Comparative Examples 1 to 4. However, the amount of free isocyanate groups at the end of the urethane reaction to obtain an isocyanate group-containing urethane prepolymer was 2.9% by mass in Examples 2 to 3, 5 to 18, and Comparative Examples 1 to 4, 3.92% by mass in Example 4, 5.35% by mass in Example 20, 1.8% by mass in Example 21, and 2.3% by mass in Example 25. The amount of distilled water added as a dispersion medium was adjusted so that the solids concentration of the aqueous dispersion was 30% by mass.

[Example 19]
1.87 parts by mass of ethylenediamine as a chain extender was added to the dispersion after emulsification and dispersion, and the chain extension reaction was completed by stirring at 40°C for 1 hour. A release coating agent consisting of an aqueous dispersion was obtained.

[Example 22]
Instead of 600 parts by mass of distilled water as a dispersion medium, 550 parts by mass of distilled water and 50 parts by mass of N-methylpyrrolidone (NMP) were added, and after the emulsion dispersion, chain extension reaction, polymerization reaction, and distillation of methyl ethyl ketone, water for adjusting the solid content was added to make the dispersion medium composition distilled water/NMP = 90/10 (mass ratio), and the rest was the same as in Example 1, to obtain a release coating agent consisting of the aqueous dispersion of Example 22.

[Example 23]
A mold release coating agent consisting of the aqueous dispersion of Example 23 was obtained in the same manner as in Example 1 except that no surfactant was added.

[Example 24]
After the (meth)acrylic polymer was polymerized and the methyl ethyl ketone was distilled off, 18.7 parts by mass of a crosslinking agent was added, and the rest of the procedure was the same as in Example 1, to obtain a release coating agent made of the aqueous dispersion of Example 24.

[Example 26]
In a four-neck flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 65.6 parts by mass of polyester polyol 1, 2.6 parts by mass of trifunctional polyol, and 8.8 parts by mass of dimethylolpropion were added. Acid and 100 parts by mass of methyl ethyl ketone were added and dissolved with sufficient stirring. Next, 23 parts by mass of IPDI was added and reacted at 75°C until the content of free isocyanate groups based on the solid content was 0.05% by mass or less. A methyl ethyl ketone solution of the group-containing polyurethane resin was obtained. This prepolymer solution was cooled to 45° C. and neutralized by adding 6.64 parts by mass of triethylamine as a neutralizing agent, followed by 100 parts by mass of n-dodecyl acrylate, 10 parts by mass of dimethacrylate 1, 2. 2 parts by mass of a surfactant and 200 parts by mass of methyl ethyl ketone were added and mixed with stirring. Subsequently, while stirring using a homogenizer, 600 parts by mass of distilled water was added as a dispersion medium to emulsify and disperse. Thereafter, 0.16 parts by mass of polymerization initiator 1 and 0.15 parts by mass of polymerization initiator 2 were diluted 10 times with distilled water and added, and reacted at 35 to 45°C for 3 hours (meth). The acrylic polymer was polymerized. Thereafter, methyl ethyl ketone was distilled off under heating and reduced pressure, and water for adjusting the solid content was added to obtain a release coating agent consisting of an aqueous dispersion with a solid content of 30% by mass.

[Example 27]
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 33.0 parts by mass of polyester polyol 1, 35.0 parts by mass of POE-containing polyol, and 2.6 parts by mass of trifunctional polyol were added. , and 100 parts by mass of methyl ethyl ketone were added and dissolved with sufficient stirring, then 29.4 parts by mass of IPDI was added, and the reaction was carried out at 75°C until the content of free isocyanate groups based on the solid content was 2.5% by mass to obtain isocyanate. A methyl ethyl ketone solution of the group-containing urethane prepolymer was obtained. After cooling this prepolymer solution to 45°C, 100 parts by mass of n-dodecyl acrylate, 10 parts by mass of dimethacrylate 1, 2.2 parts by mass of surfactant, and 200 parts by mass of methyl ethyl ketone were added and mixed with stirring. did. Subsequently, while stirring using a homogenizer, 600 parts by mass of distilled water was added as a dispersion medium to emulsify and disperse the dispersion, and the dispersion was stirred at 40° C. for 1 hour to complete the chain extension reaction by water. Thereafter, 0.16 parts by mass of polymerization initiator 1 and 0.15 parts by mass of polymerization initiator 2 were diluted 10 times with distilled water and added, and reacted at 35 to 45°C for 3 hours (meth). The acrylic polymer was polymerized. Thereafter, methyl ethyl ketone was distilled off under heating and reduced pressure, and water for adjusting the solid content was added to obtain a release coating agent consisting of an aqueous dispersion with a solid content of 30% by mass.

[Example 28]
In a four-neck flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 47.3 parts by mass of polyester polyol 1, 2.6 parts by mass of trifunctional polyol, and 10.5 parts by mass of cationic polyol were added. Add the group-containing polyol and 100 parts by mass of methyl ethyl ketone and dissolve with sufficient stirring, then add 39.6 parts by mass of IPDI and react at 75°C until the content of free isocyanate groups based on the solid content becomes 3.2% by mass. A methyl ethyl ketone solution of an isocyanate group-containing urethane prepolymer was obtained. This prepolymer solution was cooled to 45°C and quaternized by adding 11.11 parts by mass of dimethyl sulfuric acid as a quaternizing agent, followed by 100 parts by mass of n-dodecyl acrylate, 10 parts by mass of dimethacrylate 1, 2.2 parts by mass of a surfactant and 200 parts by mass of methyl ethyl ketone were added and mixed with stirring. Subsequently, while stirring using a homogenizer, 600 parts by mass of distilled water was added as a dispersion medium to emulsify and disperse the mixture, and the dispersion was stirred at 40° C. for 1 hour to complete the chain extension reaction by water. Thereafter, 0.16 parts by mass of polymerization initiator 1 and 0.15 parts by mass of polymerization initiator 2 were diluted 10 times with distilled water and added, and reacted at 35 to 45°C for 3 hours (meth). The acrylic polymer was polymerized. Thereafter, methyl ethyl ketone was distilled off under heating and reduced pressure, and water for adjusting the solid content was added to obtain a release coating agent consisting of an aqueous dispersion with a solid content of 30% by mass.

The release coating agents of Examples 1 to 28 and Comparative Examples 1 to 4 were evaluated for releasability 1A, 1B, 1C, releasability 2A, 2B, 2C, adhesion, and water resistance. The results are shown in Tables 1 and 2.

In Tables 1 and 2, "Water" in the "Chain extender: Ethylenediamine" column means that water was used as the chain extender, and "None" means that the chain was not extended. "Amount of polyurethane resin" is the amount of polyurethane resin in the final aqueous dispersion, expressed in parts by mass per 100 parts by mass of the total of the polyol and isocyanate used as raw materials. "Index: NCO/OH" is the equivalent ratio of the hydroxyl group to the isocyanate group in the urethane prepolymer. "Substrate" refers to the substrate used in the evaluation of peelability and adhesion, with "PET" meaning a PET substrate and "PP" meaning a PP substrate. The numerical value for the evaluation of peelability is peel strength (unit: mN/25 mm).

As shown in Tables 1 and 2, Comparative Example 1 did not contain alkyl (meth)acrylate (X), and therefore had poor initial peelability and heat resistance. Comparative Example 2 used ethyl acrylate, which has an alkyl group with two carbon atoms, as the alkyl (meth)acrylate, and therefore had poor initial peelability and heat resistance. Comparative Example 3 used a PP substrate, and therefore had poor adhesion between the release layer and the substrate. Comparative Example 4 did not contain poly(meth)acrylate (Y), and therefore had poor heat resistance.

On the other hand, Examples 1 to 28 had excellent adhesion to the PET base material, suppressed deterioration of peelability due to heating, and had heat-resistant peelability. From a comparison between Examples 1 and 2 and Examples 3 and 4, the initial peelability was improved by using polyester polyol. From a comparison between Examples 1 and 2 and Examples 5 and 6, from the viewpoint of adhesiveness, cycloaliphatic polyisocyanates are preferable to aliphatic polyisocyanates, and IPDI is more preferable. From a comparison between Examples 1 and 2 and Examples 7 and 8, it is found that as the number of carbon atoms in the alkyl group of the alkyl (meth)acrylate (X) increases, the initial peelability and water resistance tend to improve. It can be seen from Example 9 that when the number of carbon atoms is too large, the heat-resistant adhesiveness tends to decrease. Furthermore, from the results of Examples 10 and 11, as for the alkyl (meth)acrylate (X), alkyl acrylate has better initial peelability than alkyl methacrylate, and the alkyl group has a straight chain rather than a branched chain. It can be seen that the initial removability is better.

In Example 23, no surfactant was added compared to Example 1, and the releasability, adhesion and heat resistance were the same as in Example 1, but filtration residue was generated during preparation. In Example 24, a crosslinking agent was added to Example 1, and although the initial releasability tended to decrease slightly, the water resistance was improved.

Note that the upper and lower limits of the various numerical ranges described in the specification can be arbitrarily combined, and all combinations are described herein as preferred numerical ranges. Furthermore, the description of the numerical range "X to Y" means from X to Y, not more than Y.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their omissions, substitutions, modifications, etc. are included within the scope and gist of the invention as well as the invention and its equivalents as set forth in the claims.

Claims (8)

A release coating agent for a polyester base material, comprising an aqueous dispersion in which a polyurethane resin is dispersed in an aqueous dispersion medium,
The aqueous dispersion is a (meth)acrylic polymer containing as constituent components a monofunctional alkyl (meth)acrylate having an alkyl group having 4 to 22 carbon atoms and a poly(meth)acrylate having 2 to 6 functional groups. Including coalescence,
The (meth)acrylic polymer is contained in resin particles as a dispersoid together with the polyurethane resin,
The (meth)acrylic polymer contains 0.3 to 50 parts by mass of the poly(meth)acrylate based on 100 parts by mass of the alkyl (meth)acrylate.
Release coating agent for polyester base materials. The release coating agent for polyester substrates according to claim 1, wherein the alkyl group of the alkyl (meth)acrylate is a straight-chain alkyl group. The release coating agent for polyester substrates according to claim 1, wherein the poly(meth)acrylate has an acrylic equivalent, which is a molecular weight per functional group, of 80 to 150. The release coating agent for polyester substrates according to claim 1, wherein the amount of the alkyl (meth)acrylate is 40 to 350 parts by mass based on 100 parts by mass of the polyurethane resin. The release coating agent for a polyester base material according to claim 1, wherein the polyurethane resin contains a polyol including a polyester polyol as a constituent component, and the polyester polyol is contained in an amount of 30% by mass or more based on 100% by mass of the polyol. A release sheet comprising a polyester base material and a release layer comprising the release coating agent according to any one of claims 1 to 5 provided on the polyester base material. A laminate comprising the release sheet according to claim 6 and a resin layer releasably provided on the release layer of the release sheet. A polyurethane resin having a hydrophilic group, a monofunctional alkyl (meth)acrylate having an alkyl group having 4 to 22 carbon atoms, and a poly(meth)acrylate having 2 to 6 functional groups are mixed, and the mixture is made into an aqueous system. A release coating agent for a polyester base material, comprising an aqueous dispersion obtained by dispersing in a dispersion medium and polymerizing the alkyl (meth)acrylate and the poly(meth)acrylate contained in the mixture ,
The (meth)acrylic polymer obtained by polymerizing the alkyl (meth)acrylate and the poly(meth)acrylate is contained in the resin particles as a dispersoid together with the polyurethane resin,
The (meth)acrylic polymer contains 0.3 to 50 parts by mass of the poly(meth)acrylate based on 100 parts by mass of the alkyl (meth)acrylate, a release coating agent for polyester substrates.