JP2023183619A - Polyester-based container - Google Patents

Abstract

To provide a polyester-based container allowing yellowness and haze of the recycled products to be reduced to a specified value or less when the polyester-based container to which an adhesive label comprising an adhesive and resin base material made of the same as that of the polyester-based container is attached is recycled.SOLUTION: In a polyester-based container having an adhesive label stuck thereon, the adhesive label is made of a polyester-based resin base material and has a polyester-based adhesive layer. The mass of the adhesive label is less than 5% of the mass obtained by subtracting the mass of the adhesive label from the mass of the polyester-based container.SELECTED DRAWING: Figure 1

Description

The present invention relates to polyester containers.

In recent years, there has been a strong desire to recycle polyester containers due to problems such as environmental pollution and depletion of petroleum resources. Among polyester containers, recycling of polyethylene terephthalate (PET) bottles is particularly desired.

In material recycling of polyester containers, the container is usually crushed into flakes, then heated and melted to homogenize the whole, and the resulting recycled resin is used as the material for the polyester container.

Typically, a polyester container such as a PET bottle has an adhesive label (also referred to as a label) affixed to its surface on which various information is recorded. When recycling polyester containers such as labeled PET bottles, if the resin base material of the label and the resin constituting the polyester container are not compatible, the resin base material constituting the label may be A problem arises in that the material and the adhesive act as foreign substances, degrading the mechanical properties of the recycled resin. Therefore, in such a case, it is necessary to peel off the label affixed to the polyester container, then crush the polyester container into pellets, and heat and melt the container. However, the operation of peeling a label from a polyester container is extremely complicated and time-consuming, and the recycling process costs are high, resulting in problems in terms of both operational and economical points of view.

In this regard, for example, Patent Document 1 below describes a polyester resin base material that is compatible with a polyester container as an adherend, and a polyester resin base material disposed on one side of the polyester resin base material. An adhesive label having an adhesive is disclosed. According to the label configured in this way, by using the resin base material and adhesive made of the same material as the polyester container, recycling becomes possible without peeling off the label from the polyester container.

Japanese Patent Application Publication No. 2000-10489

On the other hand, even if a polyester container is affixed with an adhesive label containing a resin base material and adhesive made of the same material as the polyester container, when it is recycled, the yellowness and haze (turbidity) of the recycled product will reach a specified value. In some cases, the price may be higher than that of the actual product, and it may not be possible to use it as a product. "Yellowness" is also called "yellow index" and is defined by JIS K7373:2006. "Haze" is defined by JIS K7136:2000.

In view of the above-mentioned problems, the inventors of the present invention have conducted intensive studies and found that when recycling polyester containers to which adhesive labels comprising a resin base material and adhesive made of the same material as polyester containers are affixed, recycled products We have now invented a polyester container whose yellowness and haze can be kept below predetermined values.

The present invention makes it possible to reduce the yellowness and haze of the recycled product to below a predetermined value when recycling 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 affixed. The purpose of the present invention is to provide a polyester container that can be used.

The above object of the present invention is achieved by the following means.

(1)
A polyester container configured with an adhesive label attached,
The adhesive label is
A polyester resin base material,
It has a polyester adhesive layer,
A polyester container, wherein the weight of the pressure-sensitive adhesive label is less than 5% of the weight of the polyester container minus the pressure-sensitive adhesive label.

(2)
The polyester container according to (1), wherein the adhesive label has a total light transmittance of 70% or more.

(3)
The adhesive label is
The polyester container according to (1) or (2), further comprising a release coat layer containing a polyester resin and provided on a side of the polyester resin base material opposite to the side on which the polyester adhesive is provided. .

(4)
The adhesive label is
The polyester container according to (3), further comprising an alkali-insoluble coat layer provided on a side of the release coat layer opposite to the side on which the polyester resin base material is provided.

(5)
The polyester container according to (4), wherein the alkali-insoluble coat layer is a urethane-modified polyester resin.

(6)
The polyester container according to (4) or (5), wherein the resin contained in the alkali-insoluble coat layer is a crosslinked product.

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 kept below a predetermined value.

FIG. 1 is a schematic cross-sectional view showing an adhesive label according to an embodiment of the present invention. It is a cross-sectional schematic diagram which shows the adhesive label based on other embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in the description of the drawings, the same elements are given the same reference numerals, and redundant description will be omitted. Furthermore, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

In this specification, the range "X to Y" means "more than or equal to X and less than or equal to Y." Further, unless otherwise specified, operations, physical properties, etc. are measured under conditions of room temperature (20 to 25°C)/relative humidity of 45 to 55% RH.

Adhesive labels are applied to polyester containers such as polyethylene terephthalate (PET) bottles. Hereinafter, a PET bottle will be described as an example of an adherend to which an adhesive label is attached. The shape of the adhesive label is not particularly limited, but it is generally rectangular when viewed from the stacking direction. Note that the shape of the adhesive label may be triangular or circular. Further, the polyester adhesive layer is arranged, for example, on the entire surface of the polyester resin base material.

The mass of the adhesive label 10 according to this embodiment is 0.05% or more and less than 5% of the mass of the polyester container minus the adhesive label, preferably less than 3%, and more preferably 1.0%. It is less than 5%. By reducing the amount of adhesive labels in this manner, when a polyester container is recycled, the yellowness and haze of the recycled product can be kept below a predetermined value. Adhesive labels have a size larger than a certain size because their purpose is to provide information. In order to recycle polyester containers well while ensuring the size of the label is above a certain level, as a result of intensive study, we have developed adhesive labels that It was discovered that the degree of yellowness and haze decrease significantly when the mass of 5% is reached. Yellowness and haze are measured as described in Examples below.

Further, 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 in this way, when the polyester container is recycled, the yellowness and haze of the recycled product can be kept below a predetermined value. Note that "total light transmittance" is a value defined by JIS K7361-1:1997. In addition, when the adhesive label has a release liner, after removing the release liner, the total light transmittance is measured with the adhesive layer exposed.

The adhesive force of the adhesive label is preferably 3.5 N/25 mm or more, more preferably 5 N/25 mm or more, and preferably 6.5 N/25 mm or more, considering the adhesiveness to PET bottles. Even more preferred. Further, the adhesive strength of the adhesive label does not need to be set with a particular upper limit, but may be 30 N/25 mm or less, or 20 N/25 mm or less. The adhesive strength to the adherend was determined by pasting the polyester adhesive layer side of the adhesive label on a polyethylene terephthalate plate, and after 24 hours, using a tensile tester in accordance with JIS Z0237:2009, at a test speed of 0.3 m in a 180° direction. Measured in /min. More specifically, the adhesive strength to the adherend is a value measured by the following method; the adhesive label is left in a standard environment (23°C, 50% RH) for 24 hours, and the release liner is peeled off. Attach the polyester adhesive layer to the 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 tester, and the adhesive strength is measured. The numerical value is converted into peeling force per 25 mm of film width (N/25 mm).

The surface area of the adhesive label is preferably 1 cm ² or more. By having a surface area of the adhesive label of 1 cm ² or more, it is possible to provide the adhesive label with the minimum necessary information to be conveyed to consumers, such as product information and recycling information. Further, the surface area of the adhesive label varies depending on the size of the container, but is preferably 100 cm ² or less, for example. When the surface area of the adhesive label is 100 cm ² or less, increase in yellowness and haze can be suppressed.

The configuration of the adhesive label 10 will be described below with reference to FIG. 1.

FIG. 1 is a schematic cross-sectional view of an adhesive label 10 according to this embodiment. As shown in FIG. 1, the adhesive label 10 according to the embodiment of the present invention includes, in order from the top, a printing part 13, a release coat layer 14, a polyester resin base material (hereinafter also simply referred to as a resin base material) 16, It has a polyester adhesive layer 15 and a release liner 30. The release liner 30 includes a release agent layer 12 and a release base material 11 arranged in this order. When the release coat layer 14 comes into contact with alkaline water, it decomposes and dissolves, causing the printed portion 13 to release (peel off) from the adhesive label 10 . As a result, the detached printed portion 13 floats on the surface and can be easily recovered. Note that the adhesive label 10 may have other functional layers such as a primer layer between each layer or on the surface. Here, the polyester adhesive layer 15 is preferably provided on the entire surface of the polyester resin base material 16. By being provided on 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 recycling is completed.

FIG. 2 is a schematic cross-sectional view of an adhesive label 20 according to another embodiment. The adhesive label 20 has an alkali-insoluble coat layer 17 between the printing part 13 and the release coat layer 14. That is, the alkali-insoluble coat layer 17 is provided on the release coat layer 14 facing the polyester resin base material 16 . Since the alkali-insoluble coating layer 17 remains as a resin without being dissolved during alkali peeling, it is peeled off together with the upper printed portion 13 in the form of a film. In other words, since the printed portion is not small but has a size larger than a certain level, it is easy to collect the printed portion. Here, "on the release coat layer" refers not only to the state in which the release coat layer and the alkali-insoluble coat layer are adjacent to each other, but also to the state where the release coat layer and the alkali-insoluble coat layer are located between the release coat layer and the alkali-insoluble coat layer. Other layers may be present. A preferred form is one in which the release coat layer and the alkali-insoluble coat layer are adjacent to each other.

Further, it is preferable that there is no release coat layer between the resin base material 16 and the polyester adhesive layer 15. In one preferred form, the resin base material 16 and the polyester adhesive layer 15 are adjacent to each other. There is no release coat layer between the resin base material 16 and the polyester adhesive layer 15, and there is no release coat layer between the resin base material 16 and the printed portion 13 or between the resin base material 16 and the alkali-insoluble coat layer 17. Due to the presence of the coating layer 14, the resin base material 16 did not peel off from the polyester container (adherent) when it came into contact with alkaline water, and the polyester adhesive layer 15 and resin base material 16 were stuck to the polyester container. remain in the state. Therefore, both the resin base material 16 and the polyester adhesive layer 15 can be recycled.

The concept of "label" includes what is called a film, sheet, tape, etc.

Each component will be explained below.

<Printing section 13>
The printing section is a layer for displaying information, and is an arbitrary layer in the present invention. There is no particular limitation on how the printing section is formed, and for example, it may be formed by flexographic printing, offset printing, letterpress printing, gravure printing, screen printing, or the like.

The information displayed on the print section may be, for example, letters, numbers, illustrations, photographs, graphs, etc., or a combination thereof.

<Alkali non-dissolving coat layer 17>
The alkali-insoluble coating layer is a layer placed below the printed area, and when removed with alkali, it does not dissolve and remains as a resin, so the printed area is detached in the form of a film, making it difficult to recover the printed area. Easy to do. For this reason, it is preferable that the alkali-insoluble coating layer be disposed on the printing surface. The alkali-insoluble coat layer is an optional layer in the present invention.

The alkali-insoluble coating layer has resin as its main component. Here, the main component refers to the content of 60% by mass or more (upper limit: 100% by mass) in the alkali-insoluble coating layer. The resin is alkali-insoluble. Here, alkali insolubility means, for example, that the amount dissolved in a 1.5% by mass sodium hydroxide aqueous solution (pH 13.6) at 70°C is 20% by mass or less (lower limit 0% by mass), preferably 10% by mass. Hereinafter, it is more preferably 5% by mass or less, particularly preferably 1% by mass or less.

Examples of the resin that forms the alkali-insoluble coating layer include urethane-modified polyester resins, acrylic ester (co)polymers, epoxy resins, and polyamide resins. Among them, it is preferable that the resin forming the alkali-insoluble coating layer is a urethane-modified polyester resin, since high print adhesion can be obtained. Further, the resin forming the alkali-insoluble coating layer preferably has an acid value of 3 KOHmg/g or less, more preferably 2KOHmg/g or less, since it reduces the solubility in alkaline water.

Specific examples of urethane-modified polyester resins include polymers obtained by reacting various polyisocyanate compounds with polyester polyols having hydroxyl groups at the ends of polymers obtained by condensation polymerization of polyols and carboxylic acid components. Coalescing (polyester urethane), etc. can be mentioned.

Examples of the polyisocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate.

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

The glass transition temperature of the urethane-modified polyester resin is, for example, preferably 100°C or lower, more preferably -40 to 100°C.

In the present invention, the value of number average molecular weight (Mn) is a standard polystyrene equivalent value measured by gel permeation chromatography (GPC) method, and specifically, it is measured based on the method described below. (1) Number average molecular weight (Mn), which is the value
Measurement was performed using a gel permeation chromatography device (manufactured by Tosoh Corporation, product name "HLC-8320") under the following conditions, and the values measured in terms of standard polystyrene were used.
・Column: "TSK guard column super HH""TSK gel super HM-H (x2)""TSK gel super H2000" (all manufactured by Tosoh Corporation)
・Column temperature: 40℃
・Developing solvent: Tetrahydrofuran ・Flow rate: 1.0 mL/min
(2) Glass transition temperature (Tg)
Measurement is performed in accordance with JIS K 7121:2012 using a differential scanning calorimeter (manufactured by TA Instruments Japan, product name "DSC Q2000") at a heating rate of 20° C./min.

As the urethane-modified polyester resin, commercially available products may be used. Examples of commercially available products include Vylon series (trade name) manufactured by Toyobo Co., Ltd., Vylon UR-2300 (number average molecular weight 32,000, Tg 18°C, acid value (less than 1KOHmg/g), Byron UR-3200 (number average molecular weight 40,000, Tg -3℃, acid value less than 1KOHmg/g), Byron UR-3210 (number average molecular weight 40,000, Tg -3℃, acid value (less than 1KOHmg/g), Byron UR-6100 (number average molecular weight 25,000, Tg -30℃, acid value less than 1KOHmg/g), Byron UR-8200 (number average molecular weight 25,000, Tg 73℃, acid value 1KOHmg/g) g), Vylon UR-8300 (number average molecular weight 30,000, Tg 23℃, acid value less than 1KOHmg/g), Vylon UR-8700 (number average molecular weight 32,000, Tg -22℃, acid value less than 1KOHmg/g) ) etc. can be preferably used.

The resin content in the alkali-insoluble coating layer is preferably 80 to 100% by mass, more preferably 90 to 99% by mass.

The resin contained in the alkali-insoluble coating layer is preferably a crosslinked resin. It is preferable for the resin to be a crosslinked product because the solubility in alkaline water is further reduced. In order to make the resin into a crosslinked body, a crosslinking agent may be included in the composition for forming an alkali-insoluble coat layer, which will be described later. At this time, a crosslinking agent that reacts with a crosslinkable reactive group in the resin is appropriately selected. In particular, it is preferable to select a crosslinking agent that reacts with carboxyl groups, which are crosslinkable reactive groups, because the carboxyl groups remaining in the resin can be crosslinked, further reducing the solubility in alkaline water.

Examples of crosslinking agents that can react with carboxyl groups include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, and metal chelate crosslinking agents.

Among these, it is preferable that the crosslinking agent is an isocyanate-based crosslinking agent because high print adhesion can be obtained in the coat layer after crosslinking. Examples of the isocyanate crosslinking agent include the above-mentioned polyisocyanate compounds.

The above crosslinking agents may be used alone or in combination of two or more.

The amount of the crosslinking agent added is appropriately set in consideration of the amount of crosslinkable reactive groups in the resin, etc., but it is preferably 0.01 to 10 parts by mass, and preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the resin. More preferably, it is 5 parts by mass.

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

The alkali-insoluble coating layer may contain additives such as catalysts, ultraviolet absorbers, pigments, and fillers.

<Release coat layer 14>
The release coat layer is a layer formed from a coat layer forming composition containing an aqueous polyester resin having an acid value of 10 KOHmg/g or more. The release coat layer is an optional layer in the present invention.

The thickness of the release coat layer is preferably 0.01 to 3 μm, more preferably 0.03 to 1 μm, from the viewpoint of deinking performance (removability of printing ink) when immersed in alkali. , even more preferably from 0.05 to 0.5 μm.

The composition for forming a release coat layer, which is a material for forming the release coat layer, contains an aqueous polyester resin (hereinafter also simply referred to as "aqueous polyester resin") having an acid value of 10 KOHmg/g or more.

"Aqueous polyester resin" means a polyester resin that can be dissolved in an aqueous solvent to take the form of an aqueous solution, or a polyester resin that can take the form of an aqueous dispersion dispersed as an emulsion in an aqueous solvent. 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 containing 60% by mass or more (upper limit: 100% by mass) of water, preferably 70% by mass or more, more preferably 85% by mass or more, and most preferably an aqueous solvent containing 95% by mass or more. % by mass or more.

Components other than water contained in the aqueous solvent include organic solvents that dissolve in water. Examples of organic solvents soluble in water include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, dimethyl formamide, methyl cellosolve, tetrahydrofuran, ethylene glycol mono-t-butyl ether, and the like.

In one embodiment of the present invention, in order to obtain an aqueous dispersion in which the aqueous polyester resin is dispersed as an emulsion in water, small amounts of emulsifiers, surfactants, etc. may be used as long as the effects of the present invention are not impaired. good.

However, low molecular weight components such as emulsifiers and surfactants may become localized in the release coat layer, resulting in decreased adhesion and 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.

Self-emulsifying water-based polyester resins can form emulsions without using low-molecular-weight components such as emulsifiers and surfactants that cause deterioration in interlayer adhesion. Interlayer adhesion can be further improved. In addition, "self-emulsifying type" means that some kind of hydrophilic group is chemically introduced into the resin skeleton, and the resin itself has emulsifying ability without requiring the addition of an emulsifier or surfactant.

The acid value of the aqueous polyester resin is 10KOHmg/g or more, preferably 15KOHmg/g or more, more preferably 20KOHmg/g or more, still more preferably 30KOHmg/g or more, even more preferably 40KOHmg/g or more, particularly preferably is 50KOHmg/g or more. In this specification, the acid value of the aqueous polyester resin is a value measured in accordance with JIS K 0070:1992.

The glass transition temperature (Tg) of the aqueous polyester resin used in one embodiment of the present invention is preferably 30 to 55°C, more preferably 33 to 50°C, from the viewpoint of improving interlayer adhesion with the resin base material. More preferably the temperature is 36 to 48°C.

The number average molecular weight (Mn) of the water-based polyester resin is determined from the viewpoint of improving solubility or dispersibility in water and improving interlayer adhesion between the formed primer layer and the base material and/or adhesive layer. , preferably 1,000 to 15,000, more preferably 1,500 to 10,000, and still more preferably 2,000 to 5,000. If the Mn of the aqueous polyester resin is in such a relatively low molecular range, the solubility and dispersibility in water will be sufficiently high, and the coating solution can be stored stably for a long period of time, which is preferable. .

Examples of the aqueous polyester resin used in one embodiment of the present invention include a copolymer obtained by polycondensing an alcohol component and a carboxylic acid component, a modified product of the copolymer, and the like.

The modified copolymer is a polyurethane-modified polyester resin obtained by reacting a hydroxyl group at the end of a copolymer obtained by polycondensing an alcohol component and a carboxylic acid component with a polyisocyanate compound. etc. In the present invention, modified products of such aqueous polyester resins are also included in the "aqueous polyester resin."

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

Specific alcohol components include, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, and 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, hydroxypivalic acid neopentyl glycol ester, and other glycols; polylactone diols obtained by adding lactones such as ε-caprolactone to these glycols; polyester diols such as bis(hydroxyethyl) terephthalate; 1, Dihydric cyclic alcohols such as 3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, spiroglycol, dihydroxymethyltricyclodecane; ethylene oxide of bisphenol A and propylene oxide adducts; trivalent or higher valences such as glycerin, trimethylolpropane, trimethylolethane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, dipentaerythritol, sorbitol, mannitol, etc. Examples include polyhydric alcohols. These alcohol components may be used alone or in combination of two or more.

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

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

From the viewpoint of adjusting the acid value within the above range, the aqueous polyester resin used in one aspect of the present invention preferably has a structural unit derived from a polybasic acid having three or more carboxyl groups in one molecule, It is more preferable to have a structural unit derived from tricarboxylic acid or tricarboxylic acid anhydride.

Further, from the same viewpoint as above, the aqueous polyester resin used in one embodiment of the present invention is preferably an aqueous polyester resin containing a carboxyl group.

(particle)
The composition for forming a release coat layer may contain particles for the purpose of improving blocking resistance.

The particles may be either inorganic particles or organic particles 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 the organic particles include acrylic resin particles such as polymethyl methacrylate, polystyrene particles, styrene-acrylic resin particles, and polycarbonate particles. Among these, silica is preferred.

The content of particles in the composition for forming a release coat layer is appropriately set in order to achieve a desired purpose (for example, improving blocking resistance). , 0.1 to 10 parts by mass.

The average particle diameter of the particles is appropriately set in consideration of the desired purpose, but for example, if the purpose is to improve blocking resistance, it is preferably 0.1 to 1 μm, and 0.3 to 0.6 μm. It is more preferable that In this specification, the average particle size refers to the average particle size on a volume basis unless otherwise specified, and for example, the particle dispersion is measured using a Coulter counter method particle size distribution analyzer (Model TA-II manufactured by Beckman Coulter). It can be determined by measuring with an aperture of 50 μm.

(General purpose additives, other resin components)
The composition for forming a release coat layer used in one embodiment of the present invention may contain general-purpose additives such as antioxidants in addition to the water-based polyester resin and particles described above, to the extent that the effects of the present invention are not impaired. You can.

<Resin base material 16>
As the resin base material, it is necessary to use a polyester film, which is the same material and is compatible with the PET bottle as the adherend. That is, the resin base material is a polyester resin base material. From the viewpoint of quality such as mechanical properties of the recycled resin, it is particularly advantageous to use a resin base material for the polyester film that has a composition close to that of the resin used in PET bottles. Examples of the resin base material used for this polyester film include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Depending on the type of resin being used, one or more types may be appropriately selected and used so as to obtain a resin base material that is compatible with the resin.

Here, compatibility means that it melts at the temperature at which the PET bottle is heated and melted, mixes well with the resin base material of the melted PET bottle, and does not deteriorate the characteristics of the recycled product. In addition, when the resin base material constituting the PET bottle is a mixture of two or more compatible resins, one resin from the resin mixture constituting the PET bottle is used as the resin for the resin base material 16. be able to.

The thickness of the resin base material 16 is not particularly limited and is appropriately selected depending on the intended use, but is generally preferably in the range of 25 to 100 μm. When applying an adhesive label to a container, from the viewpoint of production efficiency, a labeling step is sometimes provided in which the adhesive label is applied to the container using a labeling device. By setting the thickness of the resin base material 16 to 25 μm or more, the peelability of the adhesive label from the release liner 30 in the labeling process is excellent. Further, by setting the thickness of the resin base material 16 to 100 μm or less, the winding length of the roll installed in the labeling device can be sufficiently increased, the frequency of replacing the roll can be reduced, and work efficiency can be increased. This resin base material 16 may be obtained by any conventional film forming method, such as an extrusion method, a calendar method, a solution coating method, or a casting method.

In the present invention, this resin base material 16 has one or both sides, as desired, for the purpose of improving adhesion with the coating layer provided thereon and the polyester adhesive layer 15 provided on the opposite surface. Surface treatment can be applied. Examples of surface treatment methods include surface roughening treatment such as sandblasting or solvent treatment, or surface oxidation treatment such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, and ozone/ultraviolet irradiation treatment. Can be mentioned. Further, the resin base material 16 may contain a coloring agent such as a pigment.

<Polyester adhesive layer 15>
Next, the polyester adhesive layer 15 will be explained. The polyester adhesive layer 15 is formed from a polyester adhesive composition containing polyester resin (A) as a main component.

The polyester resin (A) used in the present invention is obtained by copolymerizing copolymerization components containing a polyhydric carboxylic acid component (A1) and a polyol component (A2) as constituent raw materials.

[Polyhydric carboxylic acid component (A1)]
Examples of the polyhydric carboxylic 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, naphthalene dicarboxylic acid;
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 , aliphatic dicarboxylic acids such as diglycolic acid;
Alicyclic groups such as 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, adamantanedicarboxylic acid, etc. dicarboxylic acid;
Dihydric carboxylic acids such as These can be used alone or in combination of two or more.

Among these, it is preferable to include aromatic dicarboxylic acid from the viewpoint of imparting cohesive force.

The content of the aromatic dicarboxylic acid is preferably 50 mol% or less, more preferably 5 to 40 mol%, particularly preferably 10 to 30 mol%, based on the entire polyhydric carboxylic acid component (A1). %. If the content ratio is too high, the glass transition temperature becomes high, and there is a tendency that sufficient adhesive performance cannot be obtained.

Further, from the viewpoint of imparting a tackiness, it is preferable to contain an aliphatic dicarboxylic acid, and it is particularly preferable to contain an aliphatic dicarboxylic acid having 4 to 12 carbon atoms.

The content of such aliphatic dicarboxylic acid is preferably 20 mol% or more, more preferably 50 mol% to 95 mol%, even more preferably 70 to 95 mol%, based on the entire polycarboxylic acid component (A1). It is 90 mol%. If this content ratio is too low, the glass transition temperature tends to be high and sufficient adhesive strength cannot be obtained, whereas if this content ratio is too high, the adhesion component decreases, resulting in a decrease in adhesive strength to polar adherends. There is a tendency to

In the present invention, from the viewpoint of the balance of adhesive physical properties, it is preferable to use aromatic dicarboxylic acid and aliphatic dicarboxylic acid together as the polyhydric carboxylic acid component (A1), and the content ratio (molar ratio) is Preferably, dicarboxylic acid/aliphatic dicarboxylic acid = 1/99 to 90/10, more preferably aromatic dicarboxylic acid/aliphatic dicarboxylic acid = 5/95 to 49/51, even more preferably aromatic dicarboxylic acid/ Aliphatic dicarboxylic acid = 10/90 to 30/70.

In addition, for the purpose of increasing branching points in the polyester resin (A), a trivalent or higher-valent polycarboxylic acid can also be used, and such trivalent or higher-valent carboxylic acids include, for example, trimellitic acid, pyromellitic acid, etc. , adamantanetricarboxylic acid, trimesic acid, etc. Among them, it is preferable to use trimellitic acid because it is relatively less likely to cause gelation. The content of the trivalent or higher polycarboxylic acid is preferably 10 mol% or less, particularly preferably 10 mol% or less, based on the entire polycarboxylic acid component (A1), since it can increase the cohesive force of the adhesive. is 0.1 to 5 mol%, and if the content is too large, gelation tends to occur during the production of the polyester resin (A).

[Polyol component (A2)]
Examples of the polyol component (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- Aliphatic diols such as pentanediol, 2,2,4-trimethyl-1,6-hexanediol; 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, Alicyclic diols such as tricyclodecane dimethanol, adamantane diol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 4,4'-thiodiphenol, 4,4'-methylene diphenol , 4,4'-dihydroxybiphenyl, o-, m- and p-dihydroxybenzene, 2,5-naphthalene diol, p-xylene diol and aromatic diols such as ethylene oxide and propylene oxide adducts thereof; Examples include alcohols. These can be used alone or in combination of two or more.

Among these, aliphatic diols and alicyclic diols are preferred in terms of their excellent reactivity, and particularly preferred aliphatic diols include ethylene glycol, 1,3-propanediol, and 2-methyl-1,3-propanediol. diol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and alicyclic diols include 1,2-cyclohexanedimethanol and 1,3-cyclohexanedimethanol. , 1,4-cyclohexanedimethanol.

Furthermore, a trivalent or higher polyhydric alcohol can also be used for the purpose of increasing branching points in the polyester resin (A). Examples of trivalent or higher polyhydric alcohols include pentaerythritol, dipentaerythritol, tripentaerythritol, and tripentaerythritol. Examples include erythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, adamantanetriol, and the like. The content ratio of the trihydric or higher polyhydric alcohol is preferably 10 mol% or less, particularly preferably 0.1 to 5 mol%, based on the entire polyol component (A2), and such a content ratio is too high. This tends to make it difficult to produce the polyester resin (A).

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

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 subjecting them to a polycondensation reaction in the presence of a catalyst by a known method. be done.

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

Usually, by crosslinking the polyester resin (A) using a crosslinking agent, it has excellent cohesive force and exhibits performance as an adhesive. Examples of such crosslinking agents include compounds having a functional group that reacts with the hydroxyl group and/or carboxyl group contained in the polyester resin (A), such as polyisocyanate compounds (isocyanate crosslinking agents) and polyepoxy compounds. Among these, polyisocyanate compounds are particularly preferred since they can achieve a good balance of initial tackiness, mechanical strength, and heat resistance. As the polyisocyanate compound, those described in the description of the alkali-insoluble coat layer 17 can be used.

The amount of the crosslinking agent to be added can be appropriately selected depending on the molecular weight of the polyester resin (A) and the purpose of use, but it is usually 0.00 parts by mass based on 100 parts by mass of the polyester resin (A), taking into consideration adhesiveness, etc. The amount is preferably 5 to 5 parts by mass.

The polyester pressure-sensitive adhesive composition may contain conventionally known additives such as hydrolysis inhibitors, softeners, ultraviolet absorbers, stabilizers, antistatic agents, and tackifiers, to the extent that they do not impair the effects of the present invention. Can be blended.

The storage modulus of the polyester adhesive layer 15 is preferably in the range of 1×10 ⁵ to 100×10 ⁵ Pa, more preferably in the range of 5×10 ⁵ to 50×10 ⁵ Pa at 23° C. and a frequency of 1 Hz. When the storage elastic modulus G' of the polyester adhesive layer 15 is 100×10 ⁵ Pa or less, the adhesive strength is easily ensured. On the other hand, if the storage modulus G' of the adhesive layer is 1×10 ⁵ Pa or more, cohesive force is likely to be ensured. The storage modulus G' of the adhesive layer depends on the type, molecular weight and blending ratio of monomers constituting the polymer (adhesive) contained in the adhesive layer, the degree of polymerization of the polymer, and if a crosslinking agent is included. It can be adjusted by appropriately changing the amount of crosslinking agent (crosslinking density of the polymer), etc.

The storage modulus G' of the adhesive layer is determined using a dynamic viscoelasticity measuring device ARES (manufactured by TA Instruments Japan). A laminate in which an adhesive layer with a thickness of 500 μm to 1 mm (for example, 800 μm) was formed between two release liners was punched out into a disc shape with a diameter of 8 mm, and the product after removing the release liner was called an adhesive layer sample. do. The storage modulus G' (Pa) at 23° C. is recorded when the measurement is performed in the temperature range of −50° C. to 150° C. at a heating rate of 5° C./min and in a shear mode with a frequency of 1 Hz.

The thickness of the adhesive layer is not particularly limited, but is, for example, 5 to 100 μm, and may be 10 to 50 μm.

<Release liner 30>
The release liner 30 has a release base material 11 and a release agent layer 12, as shown in FIG. In the present invention, the release liner is an optional layer.

Examples of the release base material include laminated paper obtained by laminating a thermoplastic resin such as polyethylene on a paper base material, or a polyester film.

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

Paper base materials for laminated paper include glassine paper, high-quality paper, and the like.

As the polyester film, polyethylene terephthalate, polyethylene naphthalate, etc. can be used.

The thickness of the release liner 30 is preferably 25 to 100 μm. By setting the thickness of the release liner 30 to 25 μm or more, the adhesive label has excellent suitability for punching. Further, by setting the thickness of the release liner 30 to 100 μm or less, the release liner has excellent releasability from the polyester adhesive layer in the labeling process.

Examples of the release agent constituting the release agent include a silicone release agent, a long-chain alkyl release agent, a fluorine release agent, and a rubber release agent. Among these, silicone release agents are preferred. The thickness of the release agent layer is usually about 0.01 to 5 μm.

<Manufacturing method>
The method of manufacturing the adhesive label of the present invention is not particularly limited, but examples include a method of manufacturing an adhesive label by manufacturing an adhesive roll or sheet, and then performing printing, half-cutting, and scraping as necessary. It will be done. The method for manufacturing the adhesive roll or sheet includes (1) coating a polyester adhesive composition on a release liner to form a polyester adhesive layer, and then bonding this to a resin base material; (2) Examples include a method in which a polyester adhesive composition is directly coated on a resin base material to form a polyester adhesive layer, and then a release liner is attached.

The method for applying the adhesive composition to the resin base material or release liner is not particularly limited, and for example, known methods such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, and gravure coater can be used. The coating can be applied using a coating device.

Moreover, a coating layer and an alkali-insoluble coating layer can be formed on the resin base material in advance.

Each coat layer is prepared by mixing a resin, additives if necessary, and a solvent to form a coat layer forming composition (release coat layer forming composition or alkali-insoluble coat layer forming composition, hereinafter collectively referred to as a composition for forming a release coat layer or a composition for forming an alkali-insoluble coat layer). (also simply referred to as a coating layer forming composition) is prepared. The solvent is appropriately selected depending on the form of the resin, and when the resin is a water-based polyester resin, the solvent is preferably, for example, water or alcohols (eg, ethanol, isopropanol, etc.), and more preferably water. One type of solvent may be used alone, or two or more types may be used in combination. Further, when the resin is a urethane-modified polyester resin, the solvent is, for example, toluene, methyl ethyl ketone, or ethyl acetate.

Thereafter, a coat layer forming composition is applied to the resin base material and the coat layer to form a coat layer (release coat layer or alkali-insoluble coat layer). The coating method is not particularly limited, and conventionally known methods such as a method of coating a coat layer forming composition on a resin base material and drying it to form each coat layer can be adopted. can. The coating method is not particularly limited, but examples include a blade coater, air knife coater, rod blade coater, bar blade coater, gravure coater, bar coater, multi-roll coater, roll coater, reverse roll coater, curtain coater, etc. It is possible to adopt a method of applying by appropriately selecting various coating devices.

After applying the coating layer forming composition, it may be subjected to a drying process. Drying conditions are appropriately set, and are, for example, 80 to 160° C. and 10 to 60 seconds.

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

<Labeling method>
Next, the labeling method will be explained. Labeling of polyester containers with the adhesive label 10 is performed using a labeling device as disclosed in, for example, Japanese Patent No. 5,956,220.

During labeling, the adhesive label 10 attached to the release liner 30 is transported, and when the adhesive label is peeled off from 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. Here, if the thickness of the resin base material 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 will not be easily exposed, and the adhesive label will be made of polyester. It may not be possible to attach it to system containers. Note that the conveying speed (labeling speed) of the adhesive label 10 of the labeling device is not particularly limited, but is 20 to 150 m/min.

Next, an example will be described. In the examples, "parts" or "%" may be used, but unless otherwise specified, "parts by mass" or "% by mass" is indicated. Furthermore, unless otherwise specified, each operation is performed at room temperature (25° C.).

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

The obtained polyester pressure-sensitive adhesive composition was applied using a knife coater onto a release liner (thickness: 88 μm) prepared by coating polyethylene laminated glassine paper with a silicone release agent so that the film thickness after drying was 15 μm. Thereafter, it was dried at 90° C. for 1 minute to form a polyester adhesive layer.

Self-emulsifying aqueous polyester resin solution (solid content 25% by mass, viscosity 10 mPa・s (20°C), water solvent, polyester resin: acid value 50 mgKOH/g, carboxyl group content, number average molecular weight 3,000, Tg 46°C ) and 1 part by mass of silica (average particle size: 0.45 μm) were mixed with 100 parts by mass of aqueous polyester resin solid content to obtain a composition for forming a release coat layer. The composition for forming a release coat layer was applied onto a polyethylene terephthalate film (polyester resin base material) having a thickness of 50 μm using a bar coater and dried to a dry film thickness of 0.06 μm. On the resulting release coat layer, a urethane-modified polyester resin (manufactured by Toyobo Co., Ltd., Vylon UR-8200) and a crosslinking agent (hexamethylene diisocyanate, manufactured by Tosoh Corporation, product name "Coronate HX") were added to 100 parts by mass of resin solid content. '') and diluted with methyl ethyl ketone to form an alkali-insoluble coating layer was applied and dried using a bar coater to a dry film thickness of 0.08 μm to form an alkali-insoluble coating layer. .

An adhesive layer laminated with a release liner was attached to the opposite side of the release coat layer of the polyethylene terephthalate film, and the adhesive layer was left to stand in a standard environment (23°C, 50% RH) for 7 days to obtain an adhesive label. . At this time, the weight of the polyester adhesive layer was 15 g/m ² . Further, the total light transmittance of the adhesive label of Example 1 was 85%.

We then produced a film with the idea that the container could be recycled. First, the obtained adhesive label was poured into a 1.5% by mass aqueous sodium hydroxide solution at 70° C. and stirred to remove the release coat layer and the alkali-insoluble coat layer from the label. Next, 100 parts by mass of polyethylene terephthalate resin and 0.1 part by mass of the above-mentioned adhesive label were mixed, and a compound pellet was produced using a small twin-screw kneading extruder. obtained the film. At this time, the proportion of the polyester adhesive layer in the film was 0.018% by mass.

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

(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 the 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.

(Example 4)
A film was obtained in the same manner as in Example 1 except that a white polyethylene terephthalate film (titanium oxide content: 15% by mass) was used instead of the polyethylene terephthalate film. Further, the total light transmittance of the adhesive label of Example 4 was 10%.

(Example 5)
A film was obtained in the same manner as in Example 1 except that a white pigment was added to the polyester adhesive (titanium oxide content: 23% by mass). Further, the total light transmittance of the adhesive label of Example 5 was 30%.

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

(Comparative example 2)
A film was obtained in the same manner as in Comparative Example 1, except that the polyester adhesive was changed to an acrylic adhesive.

(Reference example 1)
Compound pellets were produced using a small twin-screw kneading extruder using only 100 parts by mass of polyethylene terephthalate resin without mixing an adhesive label, and a film with a thickness of 65 μm was obtained using a small T-die extruder using the produced pellets. .

[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 by the transmission measurement method specified in JIS K7373:2006. The results are shown in Table 1 below.

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

As shown above, the films of Examples were able to have yellowness and haze below the predetermined values.

Although the structure of the adhesive label according to the present invention has been described above through the embodiments and examples, the present invention is not limited to the embodiments and examples described above, and various modifications can be made within the scope of the claims. can.

For example, in the embodiments described above, the adhesive label has a release coat layer and an alkali-insoluble coat layer, but it may not have a release coat layer or an alkali-insoluble coat layer.

10 adhesive label,
11 base material,
12 release agent layer,
13 Printing Department,
14 release coat layer,
15 polyester adhesive layer,
16 resin base material,
17 Alkali non-dissolving coat layer,
30 Release liner.

Claims (6)

A polyester container configured with an adhesive label attached,
The adhesive label is
A polyester resin base material,
It has a polyester adhesive layer,
A polyester container, wherein the weight of the pressure-sensitive adhesive label is less than 5% of the weight of the polyester container minus the pressure-sensitive adhesive label. The polyester container according to claim 1, wherein the adhesive label has a total light transmittance of 70% or more. The adhesive label is
The polyester container according to claim 1 or 2, further comprising a release coat layer containing a polyester resin and provided on a side of the polyester resin base material opposite to the side on which the polyester adhesive is provided. The adhesive label is
The polyester container according to claim 3, further comprising an alkali-insoluble coating layer provided on a side of the release coating layer opposite to the side on which the polyester resin base material is provided. The polyester container according to claim 4, wherein the alkali-insoluble coating layer is a urethane-modified polyester resin. The polyester container according to claim 4, wherein the resin contained in the alkali-insoluble coating layer is a crosslinked product.