Polyester containers

Abstract

The present invention provides a polyester container to which, when a polyester container with an adhesive label attached, comprising a resin base material and adhesive made of the same material as the polyester container is recycled, the yellowness and haze of the recycled product can be reduced to a predetermined value or less. [Solution] The polyester container is a polyester container to which an adhesive label is attached, the adhesive label having a polyester resin base material and a polyester adhesive layer, and the mass of the adhesive label is less than 5% of the mass of the polyester container minus the mass of the adhesive label.

Description

[Technical Field]

[0001] This invention relates to polyester containers. [Background technology]

[0002] In recent years, due to environmental pollution and the depletion of petroleum resources, there has been a strong demand for the recycling of polyester-based containers. Among polyester-based containers, the recycling of polyethylene terephthalate (PET) bottles is particularly desired.

[0003] In the material recycling of polyester containers, the containers are typically crushed into flakes, then heated and melted to homogenize the entire material, and the resulting recycled resin is used as the material for new polyester containers.

[0004] Typically, polyester containers such as PET bottles have adhesive labels (also called labels) attached to their surface, on which various information is recorded. When material recycling such polyester containers, including PET bottles with labels, if the resin base material of the label and the resin that makes up the polyester container are not compatible, the resin base material and adhesive of the label act as foreign matter, resulting in a problem where the mechanical properties of the recycled resin deteriorate. Therefore, in such cases, it is necessary to remove the label attached to the polyester container, crush it into pellets, and then heat melt it. However, the operation of removing labels from polyester containers is extremely complicated and time-consuming, and the recycling processing costs are high, resulting in problems that are disadvantageous both operationally and economically.

[0005] In this regard, for example, Patent Document 1 discloses an adhesive label comprising a polyester resin substrate compatible with a polyester container to be adhered to, and a polyester adhesive disposed on one side of the polyester resin substrate. With a label configured in this way, by using a resin substrate and adhesive made of the same material as the polyester container, recycling becomes possible without peeling the label off the polyester container. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2000-10489 [Overview of the project] [Problems that the invention aims to solve]

[0007] On the other hand, even polyester containers with adhesive labels made of the same resin base material and adhesive as the polyester container may have their yellowness or haze (turbidity) exceed specified values ​​when recycled, making them unusable as products. "Yellowness" is also called the "yellow index" and is defined by JIS K7373:2006. "Haze" is defined by JIS K7136:2000.

[0008] In view of the above problems, the inventors of the present invention have conducted diligent studies and have come to invent a polyester container to which an adhesive label comprising a resin base material and adhesive made of the same material as the polyester container is attached can reduce the yellowness and haze of the recycled product to a predetermined value or less when the polyester container is recycled.

[0009] The present invention aims to provide a polyester container to which, when a polyester container with an adhesive label made of the same material as the container and an adhesive is attached is recycled, the yellowness and haze of the recycled product can be reduced to a predetermined value or less. [Means for solving the problem]

[0010] The above objectives of the present invention are achieved by the following means.

[0011] (1) A polyester container formed by attaching an adhesive label, The aforementioned adhesive label is Polyester resin substrate, It has a polyester adhesive layer, A polyester container wherein the mass of the adhesive label is less than 5% of the mass obtained by subtracting the adhesive label from the mass of the polyester container.

[0012] (2) The polyester container according to (1), wherein the total light transmittance of the adhesive label is 70% or more.

[0013] (3) The aforementioned adhesive label is The polyester container according to (1) or (2), further comprising a desorption coating layer containing a polyester resin, provided on the side of the polyester resin substrate opposite to the side on which the polyester adhesive is provided.

[0014] (4) The aforementioned adhesive label is The polyester container according to (3), further comprising an alkali-insoluble coating layer provided on the side of the detachable coating layer opposite to the side on which the polyester resin substrate is provided.

[0015] (5) The aforementioned alkali-insoluble coating layer is a urethane-modified polyester resin, as described in (4), for the polyester container.

[0016] (6) The polyester container according to (4) or (5), wherein the resin contained in the alkali-insoluble coating layer is a crosslinked material. [Effects of the Invention]

[0017] According to the polyester container of the present invention, when the polyester container is recycled, the yellowness and haze of the recycled product can be made not more than a predetermined value.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic cross-sectional view showing an adhesive label according to an embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view showing an adhesive label according to another embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted. Also, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may be different from the actual ratios.

[0020] In this specification, "X~Y" indicating a range means "not less than X and not more than Y". Also, unless otherwise specified, operations, physical properties, etc. are measured under the conditions of room temperature (20~25°C) / relative humidity 45~55%RH.

[0021] The adhesive label is attached to a polyester container such as a polyethylene terephthalate (PET) bottle. Hereinafter, the PET bottle will be taken as an example to describe the adherend to which the adhesive label is attached. The shape of the adhesive label is not particularly limited, but is generally rectangular when viewed from the lamination direction. Note that the shape of the adhesive label may be triangular or circular. Also, the polyester-based adhesive layer is disposed, for example, on the entire surface of the polyester-based resin substrate.

[0022] The mass of the adhesive label 10 according to this embodiment is 0.05% or more and less than 5% of the mass obtained by subtracting the adhesive label from the polyester container, preferably less than 3%, and more preferably 1.5% or less. By reducing the amount of adhesive label in this way, the yellowness and haze of the recycled product can be kept below a predetermined value when the polyester container is recycled. Since the purpose of the adhesive label is to provide information, it has a certain size or larger. In order to ensure that the polyester container is recycled well while maintaining a certain size or larger, we conducted thorough research and found that, as can be understood by referring to the examples and comparative examples described later, the yellowness and haze decrease significantly when the mass of the adhesive label is 5% or less. The yellowness and haze are measured as described in the examples described later.

[0023] Furthermore, the total light transmittance of the adhesive label 10 is 70% or more, preferably 80% or more, and more preferably 85% or more. By setting the total light transmittance within the above numerical range, the yellowness and haze of the recycled product can be kept below a predetermined value when the polyester container is recycled. Note that "total light transmittance" is a value specified by JIS K7361-1:1997. If the adhesive label has a release liner, the total light transmittance is measured after removing the release liner and exposing the adhesive layer.

[0024] The adhesive strength of the adhesive label is preferably 3.5 N / 25 mm or higher, more preferably 5 N / 25 mm or higher, and even more preferably 6.5 N / 25 mm or higher, considering its adhesion to PET bottles. Furthermore, while there is no particular upper limit for the adhesive strength of the adhesive label, it may be 30 N / 25 mm or lower, or 20 N / 25 mm or lower. The adhesive strength to the substrate is measured by attaching the polyester adhesive layer surface of the adhesive label to a polyethylene terephthalate board, and after 24 hours, using a tensile testing machine in the 180° direction at a test speed of 0.3 m / min, according to JIS Z0237:2009. More specifically, the adhesive strength to the substrate is the value measured by the following method: the adhesive label is left to stand for 24 hours in a standard environment (23°C, 50% RH), the release liner is peeled off, and the polyester adhesive layer surface is attached to a polyethylene terephthalate board. After standing in a standard environment for 24 hours, the adhesive strength is measured according to JIS Z0237:2009. Specifically, the adhesive label is peeled off in a 180° direction at a test speed of 0.3 m / min using a tensile testing machine, and the adhesive strength is measured. The value is converted to the peeling force per 25 mm of film width (N / 25 mm).

[0025] The surface area of ​​the adhesive label is 1 cm². 2 Preferably, the surface area of ​​the adhesive label is 1 cm². 2 As a result, the adhesive label can be labeled with the minimum necessary information that should be conveyed to consumers, such as product information and recycling information. Furthermore, the surface area of ​​the adhesive label varies depending on the size of the container, but for example, 100 cm² 2 Preferably, the surface area of ​​the adhesive label is 100 cm². 2 The following conditions can suppress the increase in yellowness and haze.

[0026] The configuration of the adhesive label 10 will be described below with reference to Figure 1.

[0027] Figure 1 is a schematic cross-sectional view of the adhesive label 10 according to this embodiment. As shown in Figure 1, the adhesive label 10 according to this embodiment of the present invention has, from top to bottom, a printed portion 13, a release coating layer 14, a polyester resin substrate (hereinafter also simply referred to as the resin substrate) 16, a polyester adhesive layer 15, and a release liner 30. The release liner 30 is made up of a release agent layer 12 and a release substrate 11 arranged in that order. The release coating layer 14 decomposes and dissolves when it comes into contact with alkaline water, causing the printed portion 13 to detach (peel off) from the adhesive label 10. As a result, the detached printed portion 13 floats on the surface, making it easy to recover. The adhesive label 10 may have other functional layers such as a primer layer between each layer or on the surface. Here, it is preferable that the polyester adhesive layer 15 is provided over the entire surface of the polyester resin substrate 16. By providing it over the entire surface in this way, the adhesive strength of the adhesive label to the polyester container is improved, and the adhesive label can be suitably attached to the polyester container until the completion of recycling.

[0028] Figure 2 is a schematic cross-sectional view of an adhesive label 20 according to another embodiment. The adhesive label 20 has an alkali-insoluble coating layer 17 between the printed portion 13 and the desolvable coating layer 14. That is, the alkali-insoluble coating layer 17 is located on the desolvable coating layer 14 opposite the polyester resin substrate 16. The alkali-insoluble coating layer 17 does not dissolve during alkali peeling and remains as resin, so it is detached as a film together with the printed portion 13 above it. In other words, the printed portion does not become finely divided but maintains a certain size, making it easy to recover. Here, "on the desolvable coating layer" does not only mean that the desolvable coating layer and the alkali-insoluble coating layer are adjacent to each other, but there may also be other layers between the desolvable coating layer and the alkali-insoluble coating layer. The preferred form is that the desolvable coating layer and the alkali-insoluble coating layer are adjacent to each other.

[0029] Furthermore, it is preferable that there is no desorption coating layer between the resin substrate 16 and the polyester adhesive layer 15. A preferred configuration is in which the resin substrate 16 and the polyester adhesive layer 15 are adjacent to each other. With no desorption coating layer between the resin substrate 16 and the polyester adhesive layer 15, and a desorption coating layer 14 between the resin substrate 16 and the printed portion 13, or between the resin substrate 16 and the alkali-insoluble coating layer 17, the resin substrate 16 does not peel off from the polyester container (adhesion object) when in contact with alkaline water, and the polyester adhesive layer 15 and the resin substrate 16 remain attached to the polyester container. Therefore, both the resin substrate 16 and the polyester adhesive layer 15 can be recycled.

[0030] The concept of "label" encompasses things like film, sheets, and tape.

[0031] The following describes each component.

[0032] <Print section 13> The printed portion is a layer for displaying information, and in this invention, it is any layer. The method of forming the printed portion is not particularly limited and can be, for example, flexographic printing, offset printing, letterpress printing, gravure printing, screen printing, etc.

[0033] The information displayed in the printed section may be, for example, letters, numbers, illustrations, photographs, graphs, etc., or a combination thereof.

[0034] <Alkali-insoluble coating layer 17> The alkali-insoluble coating layer is a layer placed beneath the printed area. During alkali delamination, it remains as resin without dissolving, allowing the printed area to detach as a film and be easily recovered. For this reason, it is preferable to place the alkali-insoluble coating layer on the printed surface. In this invention, the alkali-insoluble coating layer is any layer.

[0035] The alkali-insoluble coating layer is mainly composed of resin. Here, "main component" means that it is present in the alkali-insoluble coating layer at a concentration of 60% by mass or more (upper limit 100% by mass). The resin is alkali-insoluble. Here, alkali-insoluble means, for example, that its solubility in a 1.5% by mass aqueous solution of sodium hydroxide (pH 13.6) at 70°C is 20% by mass or less (lower limit 0% by mass), preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 1% by mass or less.

[0036] Examples of resins that form the alkali-insoluble coating layer include urethane-modified polyester resins, acrylic ester (co)polymers, epoxy resins, and polyamide resins. Among these, urethane-modified polyester resin is preferred as the resin that forms the alkali-insoluble coating layer because it provides high print adhesion. Furthermore, since the resin that forms the alkali-insoluble coating layer has reduced solubility in alkaline water, it is preferable that its acid value be 3KOH mg / g or less, and more preferably 2KOH mg / g or less.

[0037] Specific examples of urethane-modified polyester resins include polymers (polyester urethanes) obtained by reacting various polyisocyanate compounds with a polyester polyol having a hydroxyl group at the end of a polymer obtained by condensation polymerization of a polyol and a carboxylic acid component.

[0038] Examples of polyisocyanate compounds include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate.

[0039] The number-average molecular weight (Mn) of the urethane-modified polyester resin is preferably 2,000 to 100,000, and more preferably 5,000 to 50,000. Here, the number-average molecular weight (Mn) is the number-average molecular weight on a polystyrene basis, measured by gel permeation chromatography (GPC).

[0040] The glass transition temperature of the urethane-modified polyester resin is preferably 100°C or lower, and more preferably -40 to 100°C.

[0041] In this invention, the number-average molecular weight (Mn) is a value obtained by gel permeation chromatography (GPC) on a standard polystyrene basis, and specifically, it is a value obtained by the method described below. (1) Number average molecular weight (Mn) The measurements were taken using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8320") under the following conditions, and the values ​​measured in terms of standard polystyrene equivalent were used. • Columns: "TSK guard column super HH", "TSK gel super HM-H (x2)", "TSK gel super H2000" (all manufactured by Tosoh Corporation) Column temperature: 40°C • Developing solvent: tetrahydrofuran ·Flow rate: 1.0mL / min (2) Glass transition temperature (Tg) Measurements are taken in accordance with JIS K 7121:2012, using a differential scanning calorimeter (manufactured by T.A. Instruments Japan, product name "DSC Q2000") at a heating rate of 20°C / min.

[0042] Commercially available urethane-modified polyester resins may be used. Examples of commercially available products include the Byron series (product name): manufactured by Toyobo Co., Ltd., such as Byron UR-2300 (number average molecular weight 32,000, Tg 18℃, acid value less than 1KOH mg / g), Byron UR-3200 (number average molecular weight 40,000, Tg -3℃, acid value less than 1KOH mg / g), Byron UR-3210 (number average molecular weight 40,000, Tg -3℃, acid value less than 1KOH mg / g), Ilon UR-6100 (number average molecular weight 25,000, Tg -30℃, acid value less than 1KOH mg / g), Byron UR-8200 (number average molecular weight 25,000, Tg 73℃, acid value less than 1KOH mg / g), Byron UR-8300 (number average molecular weight 30,000, Tg 23℃, acid value less than 1KOH mg / g), Byron UR-8700 (number average molecular weight 32,000, Tg -22℃, acid value less than 1KOH mg / g), etc., can be preferably used.

[0043] In the alkali-insoluble coating layer, the resin content is preferably 80 to 100% by mass, and more preferably 90 to 99% by mass.

[0044] The resin contained in the alkali-insoluble coating layer is preferably a crosslinked resin. This is preferable because the solubility in alkaline water is further reduced when the resin is crosslinked. To make the resin a crosslinked resin, a crosslinking agent can be included in the alkali-insoluble coating layer forming composition, which will be described later. In this case, a crosslinking agent that reacts with the crosslinkable reactive groups in the resin is appropriately selected. In particular, selecting a crosslinking agent that reacts with the carboxyl group, which is a crosslinkable reactive group, is preferable because it allows the carboxyl groups remaining in the resin to be crosslinked, further reducing the solubility in alkaline water.

[0045] Crosslinking agents that can react with carboxyl groups include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and metal chelate-based crosslinking agents.

[0046] In particular, it is preferable that the crosslinking agent be an isocyanate-based crosslinking agent because it provides high print adhesion in the coated layer after crosslinking. Examples of isocyanate-based crosslinking agents include the polyisocyanate compounds mentioned above.

[0047] The above crosslinking agents may be used individually or in combination of two or more.

[0048] The amount of crosslinking agent added is set appropriately considering the amount of crosslinkable reactive groups in the resin, but it is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of resin.

[0049] The thickness of the alkali-insoluble coating layer is preferably 0.05 to 1 μm, and more preferably 0.05 to 0.5 μm, considering the ease of recovery of the printed area and its thin film properties.

[0050] The alkali-insoluble coating layer may contain additives such as catalysts, UV absorbers, pigments, and fillers.

[0051] <Detachable coating layer 14> The desorbed coating layer is a layer formed from a coating layer-forming composition containing an aqueous polyester resin having an acid value of 10KOH mg / g or more. In the present invention, the desorbed coating layer is any layer.

[0052] From the viewpoint of deinking properties (removability of printing ink) when immersed in alkali, the thickness of the deleacing coating layer is preferably 0.01 to 3 μm, more preferably 0.03 to 1 μm, and even more preferably 0.05 to 0.5 μm.

[0053] The delaminating coating layer forming composition, which is a material for forming the delaminating coating layer, contains an aqueous polyester resin (hereinafter also simply referred to as "aqueous polyester resin") having an acid value of 10KOH mg / g or more.

[0054] "Water-based polyester resin" refers to a polyester resin that can dissolve in an aqueous solvent to form an aqueous solution, or a polyester resin that can be dispersed as an emulsion in an aqueous solvent to form an aqueous dispersion. By using such a "water-based" polyester resin, it is possible to reduce the amount of volatile organic compounds emitted during coating. Here, the aqueous solvent refers to one that contains 60% by mass or more (up to 100% by mass) of water, preferably 70% by mass or more, more preferably 85% by mass or more, and most preferably 95% by mass or more of the aqueous solvent.

[0055] Components other than water contained in an aqueous solvent include organic solvents that dissolve in water. Examples of organic solvents that dissolve in water include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, dimethylformamide, methyl cellulose, tetrahydrofuran, and ethylene glycol mono-t-butyl ether.

[0056] In one embodiment of the present invention, in order to obtain an aqueous dispersion in which an aqueous polyester resin emulsion is dispersed in water, a small amount of emulsifier, surfactant, etc., may be used, to the extent that it does not impair the effects of the present invention.

[0057] However, low molecular weight components such as emulsifiers and surfactants may localize in the desorbed coating layer, leading to reduced adhesion and a decrease in interlayer adhesion. From the viewpoint of suppressing this phenomenon, in one embodiment of the present invention, the aqueous polyester resin is preferably a self-emulsifying aqueous polyester resin.

[0058] Self-emulsifying aqueous polyester resins can form emulsions without using low molecular weight components such as emulsifiers and surfactants, which can reduce interlayer adhesion, thus improving the interlayer adhesion of the resulting adhesive sheet. "Self-emulsifying" means that some hydrophilic group is chemically introduced into the resin skeleton, eliminating the need for emulsifiers or surfactants, and the resin itself possesses emulsifying ability.

[0059] The acid value of the aqueous polyester resin is 10 KOH mg / g or higher, preferably 15 KOH mg / g or higher, more preferably 20 KOH mg / g or higher, even more preferably 30 KOH mg / g or higher, even more preferably 40 KOH mg / g or higher, and particularly preferably 50 KOH mg / g or higher. In this specification, the acid value of the aqueous polyester resin is the value measured in accordance with JIS K 0070:1992.

[0060] The glass transition temperature (Tg) of the aqueous polyester resin used in one aspect of the present invention is preferably 30 to 55°C, more preferably 33 to 50°C, and even more preferably 36 to 48°C, from the viewpoint of improving interlayer adhesion with the resin substrate.

[0061] The number-average molecular weight (Mn) of the aqueous polyester resin is preferably 1,000 to 15,000, more preferably 1,500 to 10,000, and even more preferably 2,000 to 5,000, from the viewpoint of good solubility or dispersibility in water and improving interlayer adhesion between the formed primer layer and the substrate and / or adhesive layer. A Mn value within this range, where the aqueous polyester resin has a relatively low molecular weight, is preferable because it provides sufficiently high solubility and dispersibility in water, allowing the coating solution to be stored stably for a long period of time.

[0062] Examples of aqueous polyester resins used in one aspect of the present invention include copolymers obtained by polycondensation of an alcohol component and a carboxylic acid component, and modified products of said copolymers.

[0063] Examples of modified products of the copolymer include polyurethane-modified polyester resins obtained by the reaction of a hydroxyl group at the end of a copolymer obtained by polycondensation of an alcohol component and a carboxylic acid component with a polyisocyanate compound. In the present invention, such modified products of aqueous polyester resins are also included in "aqueous polyester resins".

[0064] As the alcohol component, a polyhydric alcohol having two or more hydroxyl groups in one molecule can be used.

[0065] Specific alcohol components include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, and hydroxypivalic acid neopentyl glycol ester. Examples include: polylactone diols obtained by adding lactones such as ε-caprolactone to these glycols; polyester diols such as bis(hydroxyethyl) terephthalate; divalent cyclic alcohols such as 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, spiroglycol, and dihydroxymethyltricyclodecane; ethylene oxide and propylene oxide adducts of bisphenol A; and trivalent or higher polyhydric alcohols such as glycerin, trimethylolpropane, trimethylolethane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, sorbitol, and mannitol. These alcohol components may be used individually or in combination of two or more.

[0066] As the carboxylic acid component, a polybasic acid having two or more carboxyl groups in one molecule can be used.

[0067] Specific carboxylic acid components include, for example, phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, hetic acid, maleic acid, fumaric acid, itaconic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, methylhexahydrophthalic acid, and other dicarboxylic acids. Examples include carboxylic acids and their anhydrides; tricarboxylic acids such as trimellitic acid, pyromellitic acid, trimesic acid, methylcyclohexentricarboxylic acid, hexahydrotrimellitic acid, and tetrachlorohexentricarboxylic acid, and their anhydrides; and tetracarboxylic acids such as 1,2,4,5-cyclohexanetetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, and pyromellitic acid, and their anhydrides. These carboxylic acid components may be used individually or in combination of two or more.

[0068] In one aspect of the present invention, the aqueous polyester resin used preferably has constituent units derived from a polybasic acid having three or more carboxyl groups in one molecule, and more preferably has constituent units derived from a tricarboxylic acid or a tricarboxylic acid anhydride, from the viewpoint of adjusting the acid value to the above range.

[0069] Furthermore, the aqueous polyester resin used in one aspect of the present invention is preferably an aqueous polyester resin containing a carboxyl group, from the same viewpoint as described above.

[0070] (particle) The desorbing coating layer formation composition may contain particles for purposes such as improving blocking resistance.

[0071] The particles can be either inorganic or organic, as long as they are water-dispersible. Examples of inorganic particles include zirconia, silica, titanium dioxide, kaolin, alumina, titania, zeolite, calcium carbonate, barium sulfate, magnesium hydroxide, calcium phosphate, glass, mica, and talc. Examples of organic particles include acrylic resin particles such as polymethyl methacrylate, polystyrene particles, styrene-acrylic resin particles, and polycarbonate particles. Among these, silica is preferred.

[0072] The particle content in the desorbing coating layer forming composition is set appropriately to achieve the desired objective (e.g., improved blocking resistance), but is, for example, 0.1 to 10 parts by mass per 100 parts by mass of aqueous polyester resin.

[0073] The average particle diameter is set appropriately considering the desired purpose, but for example, if the purpose is to improve blocking resistance, it is preferably 0.1 to 1 μm, and more preferably 0.3 to 0.6 μm. In this specification, unless otherwise specified, the average particle diameter refers to the average particle diameter on a volume basis, and can be determined, for example, by measuring the particle dispersion using a Coulter counter particle size distribution analyzer (Beckman Coulter TA-II type) with a 50 μm aperture.

[0074] (General-purpose additives, other resin components) The desorbing coating layer-forming composition used in one aspect of the present invention may contain general-purpose additives such as antioxidants in addition to the above-mentioned aqueous polyester resins and particles, as long as the effects of the present invention are not impaired.

[0075] <Resin substrate 16> As the resin substrate, it is necessary to use a polyester film made of the same material as the PET bottle to be adhered, which has compatibility with it. In other words, the resin substrate is a polyester resin substrate. From the standpoint of quality, such as the mechanical properties of recycled resin, it is particularly advantageous to use a polyester film resin substrate with a composition close to that of the resin used in the PET bottle. Examples of polyester resins that can be used as resin substrates for this polyester film include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. From these, one or more types can be appropriately selected and used so as to obtain a resin substrate that is compatible with the type of resin used in the PET bottle to be adhered.

[0076] Here, compatibility means that the material melts at the temperature at which the PET bottle is heated and melted, mixes well with the molten resin base material of the PET bottle, and does not degrade the properties of the recycled product. Furthermore, if the resin base material constituting the PET bottle is a mixture of two or more compatible resins, one of the resins from the resin mixture constituting the PET bottle can be used as the resin of the resin base material 16.

[0077] There are no particular restrictions on the thickness of the resin substrate 16, and it can be appropriately selected depending on the application, but it is generally preferable that it be in the range of 25 to 100 μm. When attaching adhesive labels to containers, a labeling process may be provided in which an adhesive label is attached to the container using a labeling device, from the viewpoint of production efficiency. By making the thickness of the resin substrate 16 25 μm or more, the peeling of the adhesive label from the release liner 30 in the labeling process is excellent. Also, by making the thickness of the resin substrate 16 100 μm or less, the winding length of the roll installed in the labeling device can be made sufficiently long, which reduces the frequency of roll replacement and improves work efficiency. The resin substrate 16 may be obtained by any of the conventionally known film-forming methods, such as the extrusion method, calendering method, solution coating method, or casting method.

[0078] In the present invention, the resin substrate 16 may be surface-treated on one or both sides, if desired, in order to improve adhesion with the coating layer provided thereon and the polyester adhesive layer 15 provided on the opposite side. Examples of surface treatment methods include surface roughening treatment by sandblasting or solvent treatment, or surface oxidation treatment such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, or ozone / ultraviolet irradiation treatment. The resin substrate 16 may also contain colorants such as pigments.

[0079] <Polyester adhesive layer 15> Next, the polyester adhesive layer 15 will be described. The polyester adhesive layer 15 is formed from a polyester adhesive composition mainly composed of polyester resin (A).

[0080] The polyester resin (A) used in the present invention is obtained by copolymerizing a copolymer component containing a polycarboxylic acid component (A1) and a polyol component (A2) as constituent raw materials.

[0081] [Polyhydric carboxylic acid component (A1)] Examples of the polycarboxylic acid component (A1) used in the present invention include: Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, benzylmalonic acid, diphenic acid, 4,4'-oxydibenzoic acid, and naphthalenedicarboxylic acid; Aliphatic dicarboxylic acids such as malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, thiodipropionic acid, and diglycolic acid; Alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and adamantanedicarboxylic acid; Examples of divalent carboxylic acids include the following. These can be used individually or in combination of two or more.

[0082] Among these, it is preferable to include aromatic dicarboxylic acids because they impart cohesive force.

[0083] The content of such aromatic dicarboxylic acid is preferably 50 mol% or less, more preferably 5 to 40 mol%, and particularly preferably 10 to 30 mol%, relative to the total polycarboxylic acid component (A1). If the content is too high, the glass transition temperature tends to rise, and sufficient adhesive performance cannot be obtained.

[0084] Furthermore, in terms of imparting a tacky feel, it is preferable to include aliphatic dicarboxylic acids, and in particular, it is preferable to include aliphatic dicarboxylic acids having 4 to 12 carbon atoms.

[0085] The content of such aliphatic dicarboxylic acid is preferably 20 mol% or more, more preferably 50 mol% to 95 mol%, and even more preferably 70 to 90 mol%, relative to the total polycarboxylic acid component (A1). If the content is too low, the glass transition temperature tends to rise and sufficient adhesive strength cannot be obtained, and if the content is too high, the amount of adhesive component decreases and the adhesive strength to polar substrates tends to decrease.

[0086] In the present invention, from the viewpoint of balancing adhesive properties, it is preferable to use aromatic dicarboxylic acid and aliphatic dicarboxylic acid in combination as the polycarboxylic acid component (A1), and the content ratio (molar ratio) is preferably aromatic dicarboxylic acid / aliphatic dicarboxylic acid = 1 / 99 to 90 / 10, more preferably aromatic dicarboxylic acid / aliphatic dicarboxylic acid = 5 / 95 to 49 / 51, and even more preferably aromatic dicarboxylic acid / aliphatic dicarboxylic acid = 10 / 90 to 30 / 70.

[0087] Furthermore, in order to increase the branching points in the polyester resin (A), trivalent or higher polycarboxylic acids can be used. Examples of such trivalent or higher polycarboxylic acids include trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, and trimesic acid. Among these, trimellitic acid is preferred because it is relatively less prone to gelation. The content of such trivalent or higher polycarboxylic acids is preferably 10 mol% or less, and particularly preferably 0.1 to 5 mol%, relative to the total polycarboxylic acid component (A1), in order to enhance the cohesive strength of the adhesive. If the content is too high, gelation tends to occur during the production of the polyester resin (A).

[0088] [Polyol component (A2)] Examples of polyol components (A2) used in the present invention include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,2 Examples of dihydric alcohols include aliphatic diols such as 4-trimethyl-1,6-hexanediol; alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecanedimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; and aromatic diols such as 4,4′-thiodiphenol, 4,4′-methylenediphenol, 4,4′-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and their ethylene oxide and propylene oxide adducts. These can be used alone or in combination of two or more.

[0089] Among these, aliphatic diols and alicyclic diols are preferred due to their excellent reactivity, and particularly preferred are ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol as aliphatic diols, and 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol as alicyclic diols.

[0090] Furthermore, trivalent or higher polyhydric alcohols can be used in the polyester resin (A) to increase the number of branching points. Examples of trivalent or higher polyhydric alcohols include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, and adamantanetriol. The content of such trivalent or higher polyhydric alcohols is preferably 10 mol% or less, and particularly preferably 0.1 to 5 mol%, relative to the total polyol component (A2). If the content is too high, it tends to become difficult to manufacture the polyester resin (A).

[0091] The preferred ratio of polycarboxylic acid component (A1) to polyol component (A2) is 1 to 2 equivalents of polyol component (A2) per equivalent of polycarboxylic acid component (A1), and particularly preferably 1.1 to 1.7 equivalents. If the content of polyol component (A2) is too low, the acid value tends to increase, making it difficult to increase the molecular weight, and if it is too high, the yield tends to decrease.

[0092] The polyester resin (A) used in the present invention is produced by arbitrarily selecting the above-mentioned polycarboxylic acid component (A1) and polyol component (A2) and carrying out a polycondensation reaction of these in the presence of a catalyst using a known method.

[0093] The number average molecular weight of the polyester resin (A) used in the present invention is preferably 5,000 to 100,000, more preferably 10,000 to 100,000, and even more preferably 15,000 to 80,000 from the viewpoints of cohesive force, heat resistance, mechanical strength, adhesiveness, etc.

[0094] Usually, the polyester resin (A) is crosslinked using a crosslinking agent to obtain excellent cohesive force and exhibit the performance as an adhesive. Examples of such crosslinking agents include compounds having functional groups that react with hydroxyl groups and / or carboxyl groups contained in the polyester resin (A), such as polyisocyanate compounds (isocyanate-based crosslinking agents) and polyepoxy compounds. Among these, a polyisocyanate compound is particularly preferred from the viewpoint of achieving a good balance between initial adhesiveness, mechanical strength, and heat resistance. As the polyisocyanate compound, those described in the description of the alkali-insoluble coating layer 17 can be used.

[0095] The blending amount of such a crosslinking agent can be appropriately selected according to the molecular weight of the polyester resin (A) and the purpose of use. Usually, considering adhesiveness and the like, it is preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the polyester resin (A).

[0096] Additives such as conventionally known hydrolysis inhibitors, softeners, ultraviolet absorbers, stabilizers, antistatic agents, and tackifiers can be blended in the polyester-based adhesive composition within a range that does not impair the effects of the present invention.

[0097] The storage elastic modulus of the polyester-based adhesive layer 15 is preferably 1×10 5 ~100×10 5 Pa, more preferably 5×10 5 ~50×10 5 Pa at 23°C and a frequency of 1 Hz. If the storage elastic modulus G' of the polyester-based adhesive layer 15 is 100×10 5 Pa or less, the adhesive force is easily ensured. On the other hand, when the storage elastic modulus G' of the adhesive layer is 1×10 5If the storage modulus G' is Pa or higher, cohesive force is more easily ensured. The storage modulus G' of the adhesive layer can be adjusted by appropriately changing the type, molecular weight, and blending ratio of monomers constituting the polymer (adhesive) contained in the adhesive layer, as well as the degree of polymerization of the polymer, and, if a crosslinking agent is included, the amount of crosslinking agent (crosslinking density of the polymer).

[0098] The storage modulus G' of the adhesive layer is determined using a dynamic viscoelasticity measuring instrument, ARES (manufactured by T.A. Instruments Japan). A laminate with an adhesive layer of 500 μm to 1 mm thickness (e.g., 800 μm) formed between two release liners is punched out into an 8 mm diameter disc, and the remaining material after removing the release liners is used as the adhesive layer sample. The storage modulus G'(Pa) at 23°C is recorded when measured in shear mode with a heating rate of 5°C / min and a frequency of 1 Hz in the temperature range of -50°C to 150°C.

[0099] The thickness of the adhesive layer is not particularly limited, but for example, it may be 5 to 100 μm, or 10 to 50 μm.

[0100] <Release Liner 30> As shown in Figure 1, the release liner 30 has a release substrate 11 and a release agent layer 12. In the present invention, the release liner is any layer.

[0101] Examples of release substrates include laminated paper, which is made by laminating a thermoplastic resin such as polyethylene onto a paper substrate, or polyester-based films.

[0102] The thickness of the thermoplastic resin laminate layer is, for example, 10 to 40 μm.

[0103] Examples of paper substrates used in laminated paper include glassine paper and high-quality paper.

[0104] Polyester-based films such as polyethylene terephthalate and polyethylene naphthalate can be used.

[0105] The thickness of the release liner 30 is preferably 25 to 100 μm. A thickness of 25 μm or more provides excellent suitability for die-cutting adhesive labels. A thickness of 100 μm or less provides excellent peelability of the release liner from the polyester adhesive layer during the labeling process.

[0106] Examples of release agents that make up the release agent include silicone-based release agents, long-chain alkyl-based release agents, fluorine-based release agents, and rubber-based release agents. Among these, silicone-based release agents are preferred. The thickness of the release agent layer is usually about 0.01 to 5 μm.

[0107] <Manufacturing method> The method for manufacturing the adhesive label of the present invention is not particularly limited, but includes a method in which an adhesive roll or sheet is prepared, and then, if necessary, printed, die-cut, and waste removed to produce the adhesive label. The method for manufacturing the adhesive roll or sheet includes (1) a method in which a polyester-based adhesive composition is applied to a release liner to form a polyester-based adhesive layer, and then this is bonded to a resin substrate, and (2) a method in which a polyester-based adhesive composition is directly applied to a resin substrate to form a polyester-based adhesive layer, and then a release liner is bonded to it.

[0108] The method for applying the adhesive composition to a resin substrate or release liner is not particularly limited, and can be applied using known coating devices such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, or gravure coater.

[0109] Furthermore, a coating layer and an alkali-insoluble coating layer can be pre-formed onto the resin substrate.

[0110] For each coating layer, a coating layer-forming composition (a desorbing coating layer-forming composition or an alkali-insoluble coating layer-forming composition, hereinafter collectively referred to simply as a coating layer-forming composition) is prepared by mixing a resin, additives as needed, and a solvent. The solvent is appropriately selected depending on the form of the resin. When the resin is a water-based polyester resin, the solvent is preferably water or alcohols (e.g., ethanol, isopropanol, etc.), and more preferably water. The solvent may be used alone or in combination of two or more. When the resin is a urethane-modified polyester resin, the solvent is, for example, toluene, methyl ethyl ketone, or ethyl acetate.

[0111] Subsequently, the coating layer-forming composition is applied to the resin substrate or coating layer to form a coating layer (a desorbable coating layer or an alkali-insoluble coating layer). There are no particular limitations on the application method, and conventionally known methods, such as applying the coating layer-forming composition onto the resin substrate and drying it to form each coating layer, can be employed. There are no particular limitations on the application method, but for example, various coating devices such as blade coaters, air knife coaters, rod blade coaters, bar blade coaters, gravure coaters, bar coaters, multi-stage roll coaters, roll coaters, reverse roll coaters, and curtain coaters can be appropriately selected and used for application.

[0112] After applying the coating layer-forming composition, a drying process may be performed. Drying conditions are set as appropriate, but for example, 80 to 160°C for 10 to 60 seconds.

[0113] <Polyester containers> The present invention also provides a polyester container to which the above-mentioned adhesive label is attached. A polyester container refers to a container made of a polyester resin. Examples of polyester resins include polyethylene terephthalate. The container can be manufactured by injection molding, vacuum forming, pressure forming, etc., of the polyester resin.

[0114] <Labeling Method> Next, the labeling method will be described. Labeling of the polyester container with the adhesive label 10 is performed using a labeling device such as the one disclosed in Japanese Patent No. 5956220.

[0115] During labeling, the adhesive label 10 attached to the release liner 30 is transported, and when the adhesive label is peeled off the release liner, the release liner is folded back. At this time, the adhesive layer is exposed, and the exposed adhesive layer is attached to the polyester container. However, if the thickness of the resin substrate 16 is too thin, or the thickness of the release liner 30 is too thick, even if the release liner 30 is folded back, the polyester adhesive layer 15 may not be easily exposed, and the adhesive label may not be able to be attached to the polyester container. The transport speed (labeling speed) of the adhesive label 10 of the labeling device is not particularly limited, but is 20 to 150 m / min. [Examples]

[0116] Next, we will describe the examples. In the examples, the units "parts" or "%" may be used, but unless otherwise specified, they represent "parts by mass" or "mass%". Also, unless otherwise specified, each operation is carried out at room temperature (25°C).

[0117] (Example 1) A polyester adhesive composition was prepared by adding and mixing 100 parts by mass (solids) of polyester resin (manufactured by Mitsubishi Chemical Corporation, product name "NP-110S50EO") with 2 parts by mass (solids) of crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L") and 40 parts by mass of ethyl acetate.

[0118] The obtained polyester adhesive composition was applied to a release liner (thickness: 88 μm) coated with a silicone-based release agent on polyethylene laminate glassine paper using a knife coater to achieve a film thickness of 15 μm after drying. The mixture was then dried at 90°C for 1 minute to form a polyester adhesive layer.

[0119] A self-emulsifying aqueous polyester resin solution (solids content 25% by mass, viscosity 10 mPa·s (20℃), aqueous solvent, polyester resin: acid value 50 mg KOH / g, carboxyl group contained, number average molecular weight 3,000, Tg 46℃) was mixed with 1 part by mass of silica (average particle size 0.45 μm) per 100 parts by mass of the aqueous polyester resin solids to obtain a composition for forming a detachable coating layer. The composition for forming a detachable coating layer was applied to a 50 μm thick polyethylene terephthalate film (polyester resin substrate) using a bar coater and dried to a dry film thickness of 0.06 μm. On the obtained desorbed coating layer, a urethane-modified polyester resin (Toyobo Co., Ltd., Byron UR-8200) and 3 parts by mass of a crosslinking agent (hexamethylene diisocyanate, Tosoh Corporation, trade name "Coronate HX") were mixed per 100 parts by mass of resin solids, and the resulting alkali-insoluble coating layer-forming composition, diluted with methyl ethyl ketone, was applied and dried using a bar coater to a dry film thickness of 0.08 μm to form an alkali-insoluble coating layer.

[0120] An adhesive layer, with a release liner laminated on the opposite side of the delamination coating layer of a polyethylene terephthalate film, was attached and left to stand for 7 days under standard conditions (23°C, 50% RH) to obtain an adhesive label. At this time, the polyester adhesive layer was 15 g / m². 2 Furthermore, the total light transmittance of the adhesive label in Example 1 was 85%.

[0121] Next, a film was manufactured with container recycling in mind. First, the obtained adhesive labels were placed in a 1.5% by mass sodium hydroxide aqueous solution at 70°C and stirred to detach the detachable coating layer and the alkali-insoluble coating layer from the labels. Next, 100 parts by mass of polyethylene terephthalate resin and 0.1 parts by mass of the above adhesive labels were mixed, and compound pellets were produced using a small twin-screw compounding extruder. A film with a thickness of 65 μm was obtained using the produced pellets with a small T-die extruder. At this time, the proportion of the polyester adhesive layer in the film was 0.018% by mass.

[0122] (Example 2) A film was obtained in the same manner as in Example 1, except that the amount of adhesive label mixed with 100 parts by mass of polyethylene terephthalate resin was 1 part by mass. At this time, the proportion of the polyester adhesive layer in the film was 0.17% by mass.

[0123] (Example 3) A film was obtained in the same manner as in Example 1, except that the amount of adhesive label mixed with 100 parts by mass of polyethylene terephthalate resin was 1.5 parts by mass. At this time, the proportion of the polyester adhesive layer in the film was 0.26% by mass.

[0124] (Example 4) In Example 4, a film was obtained in the same manner as in Example 1, except that a white polyethylene terephthalate film (containing 15% by mass of titanium dioxide) was used instead of the polyethylene terephthalate film. The total light transmittance of the adhesive label in Example 4 was 10%.

[0125] (Example 5) In Example 1, a film was obtained in the same manner as in Example 1, except that a white pigment was added to the polyester adhesive (titanium dioxide content 23% by mass). The total light transmittance of the adhesive label in Example 5 was 30%.

[0126] (Comparative Example 1) A film was obtained in the same manner as in Example 1, except that the amount of adhesive label mixed with 100 parts by mass of polyethylene terephthalate resin was 5 parts by mass. At this time, the proportion of the polyester adhesive layer in the film was 0.84% ​​by mass.

[0127] (Comparative Example 2) In Comparative Example 1, a film was obtained in the same manner as in Comparative Example 1, except that the polyester-based adhesive was changed to an acrylic-based adhesive.

[0128] (Reference example 1) Compound pellets were produced using only 100 parts by mass of polyethylene terephthalate resin without mixing in adhesive labels, using a small twin-screw compounding extruder. A film with a thickness of 65 μm was then obtained using the produced pellets with a small T-die extruder.

[0129] [Measurement of yellowness] The yellowness of the films obtained in Examples 1 to 5, Comparative Examples 1 and 2, and Reference Example 1 was measured using the transmission measurement method specified in JIS K7373:2006. The results are shown in Table 1 below.

[0130] [Measurement of haze] The haze was measured for the films obtained in Examples 1 to 4 and Comparative Examples 1 and 2, according to JIS K7136:2000. The haze can be measured using a haze meter (for example, NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 1 below.

[0131] JPEG2026136379000002.jpg55166

[0132] As shown above, the film of the example was able to achieve a yellowness and haze level below a predetermined value.

[0133] Although the configuration of the adhesive label according to the present invention has been described above through embodiments and examples, the present invention is not limited to the embodiments and examples described above, and can be modified in various ways within the scope of the claims.

[0134] For example, in the embodiment described above, the adhesive label had a detachable coating layer and an alkali-insoluble coating layer, but it does not have to have a detachable coating layer or an alkali-insoluble coating layer. [Explanation of symbols]

[0135] 10 adhesive labels, 11 base material, 12 Release agent layer, 13 Printing Department, 14 Detached coating layer, 15 Polyester adhesive layer, 16 Resin substrate, 17. Alkali-insoluble coating layer, 30. Release liner.

Claims

1. A polyester container formed by attaching an adhesive label, The aforementioned adhesive label is Polyester resin substrate, Polyester adhesive layer, The polyester resin substrate has a desorption coating layer containing an aqueous polyester resin, provided on the side opposite to the side where the polyester adhesive is provided. The mass of the adhesive label is less than 5% of the mass obtained by subtracting the adhesive label from the mass of the polyester container. The aqueous polyester resin is self-emulsifying, The acid value of the aqueous polyester resin is 10 KOH mg / g or more. The number average molecular weight of the aqueous polyester resin is 1,000 to 15,000. The polyester container comprises a polyester resin whose polyester adhesive layer is crosslinked using a polyisocyanate compound.

2. The polyester container according to claim 1, wherein the total light transmittance of the adhesive label is 70% or more.

3. The aforementioned adhesive label is The polyester container according to claim 1 or 2, further comprising an alkali-insoluble coating layer provided on the side of the desorbing coating layer opposite to the side on which the polyester resin substrate is provided.

4. The polyester container according to claim 3, wherein the alkali-insoluble coating layer is a urethane-modified polyester resin.

5. The polyester container according to claim 3, wherein the resin contained in the alkali-insoluble coating layer is a crosslinked material.

Images