Adhesive labels

Abstract

To provide an adhesive label with excellent punching processability in a low-temperature environment, and in a high-temperature, high-humidity environment even when an adhesive label with a polyester resin base material and a polyester adhesive placed on one side of the polyester resin base material is used for a material-recycling purpose.SOLUTION: An adhesive label has a polyester resin base material and a polyester adhesive layer formed of an adhesive composition. The adhesive composition includes a polyester adhesive, a xylylene diisocyanate compound, and a tolylene diisocyanate compound.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive label.

Background Art

[0002] In recent years, due to problems such as environmental pollution and depletion of oil resources, recycling of polyester containers has been strongly desired. Among polyester containers, in particular, recycling of polyethylene terephthalate (PET) bottles has been desired.

[0003] In the material recycling of polyester containers, usually, after crushing the containers into flakes, they are heated and melted to homogenize the whole, and the obtained recycled resin is used as the material for polyester containers.

[0004] Generally, on the surface of polyester containers such as PET bottles, there are adhesive labels (also referred to as labels) on which various information is recorded. When material recycling such polyester containers with labels, such as label-attached PET bottles, if the resin base material of the label and the resin constituting the polyester container are not compatible, the resin base material and the adhesive constituting the label act as foreign substances, and the mechanical properties of the recycled resin deteriorate. Therefore, in such a case, it is necessary to peel off the label attached to the polyester container, then crush it into flakes, and heat and melt it. However, the operation of peeling off the label from the polyester container is extremely complicated and time-consuming, and the recycling treatment cost becomes high, resulting in problems that are disadvantageous both in terms of work and economy.

[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 Initiative] [Problems that the invention aims to solve]

[0007] Since adhesive labels are typically manufactured by die-cutting them into label shapes from roll-shaped sheets, good die-cutting properties are required. Specifically, good die-cutting properties include minimizing the amount of adhesive label that peels off together with the label residue when peeling off the non-adhesive label portion from the roll-shaped sheet, and minimizing contamination of the die-cutting blade.

[0008] However, in the case of adhesive labels with a polyester adhesive layer, there was a problem in that the die-cutting characteristics deteriorated when produced in winter or summer compared to commonly used acrylic adhesives.

[0009] The inventors have found that when polyester adhesives are aged in low-temperature environments such as winter or high-temperature, high-humidity environments such as summer, the adhesive does not crosslink sufficiently, and that defects in die-cutting are caused by insufficient crosslinking.

[0010] Therefore, the present invention aims to eliminate the insufficient crosslinking of polyester adhesives in low-temperature and high-temperature, high-humidity environments, and to provide an adhesive label having a polyester resin substrate and a polyester adhesive disposed on one side of the polyester resin substrate, which exhibits excellent die-cutting processability after aging in low-temperature and high-temperature, high-humidity environments. [Means for solving the problem]

[0011] The adhesive label according to the present invention, which achieves the above objective, has the following configuration.

[0012] 1. An adhesive label comprising a polyester resin substrate and a polyester adhesive layer formed from an adhesive composition, wherein the adhesive composition comprises a polyester adhesive, a xylylene diisocyanate compound, and a tolylene diisocyanate compound.

[0013] 2. The adhesive label according to 1, wherein the mass ratio of the xylylene diisocyanate compound and the tolylene diisocyanate compound is xylylene diisocyanate compound: tolylene diisocyanate compound = 1:0.1~2.

[0014] 3. An adhesive label, as described in 1. or 2., which is affixed to a polyester container.

[0015] A polyester container having an adhesive label attached as described in any one of sections 4.1 to 4.3.

[0016] 5. A method for manufacturing an adhesive label according to any one of 1 to 3, comprising die-cutting a roll-shaped adhesive sheet having a polyester resin substrate, a polyester adhesive layer formed from an adhesive composition, and a release liner. [Effects of the Invention]

[0017] The adhesive label of the present invention has a polyester resin base material and a polyester adhesive layer, so that polyester containers can be recycled without peeling the adhesive label off the container. Furthermore, the adhesive label of the present invention exhibits excellent die-cutting processability even when stored in low-temperature or high-temperature and high-humidity environments. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic cross-sectional view showing an adhesive label according to an embodiment of the present invention. [Figure 2] Figure 2(A) is a schematic diagram of one embodiment of a roll-shaped adhesive sheet, viewed from an oblique upper direction. Figure 2(B) is a schematic cross-sectional view BB of the adhesive sheet in Figure 2(A). Figure 2(C) is a schematic cross-sectional view CC of the adhesive sheet in Figure 2(A). Figure 2(D) is a schematic cross-sectional view DD of the adhesive sheet in Figure 2(A). [Modes for carrying out the invention]

[0019] The present invention relates to an adhesive label comprising a polyester resin substrate (hereinafter also simply referred to as a resin substrate) and a polyester adhesive layer formed from an adhesive composition, wherein the adhesive composition contains a polyester adhesive, a xylylene diisocyanate compound, and a tolylene diisocyanate compound.

[0020] In the study of using a polyester-based resin substrate for the purpose of material recycling and a polyester-based adhesive disposed on one side of the polyester-based resin substrate, it was found that in an adhesive label using a polyester-based adhesive, when punching is performed after aging in a low-temperature or high-temperature and high-humidity environment after production, problems such as co-lifting and contamination of the punching blade occur. Such punching processability is often improved by crosslinking the adhesive to increase its hardness. However, basically, a polyester-based adhesive can contain a functional group (hydroxyl group) only at the end of the polymer main chain, so it is difficult to advance crosslinking by a crosslinking agent. Also, a polyester-based adhesive has a lower molecular weight compared to a general-purpose adhesive such as an acrylic-based adhesive, and thus it is difficult to increase the cohesive force of the adhesive. Under such circumstances, the inventors of the present invention found that by using a combination of two specific isocyanate-based crosslinking agents, even when aging is performed in a low-temperature and high-temperature and high-humidity environment, the subsequent punching processability is high. This is considered to be because by combining two specific isocyanate-based crosslinking agents, crosslinking by the crosslinking agent proceeds appropriately even when the aging environment is a low-temperature environment or a high-temperature and high-humidity environment, and the punching process characteristics are significantly improved.

[0021] The shape of the adhesive label is not particularly limited, but it 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 resin substrate.

[0022] Considering the adhesiveness to an adherend such as a PET bottle, the adhesive force of the adhesive label is preferably at least 3.5 N / 25 mm, more preferably at least 5 N / 25 mm, and even more preferably at least 6.5 N / 25 mm. Also, the adhesive force of the adhesive label does not particularly need to have an upper limit value set, but it may be 30 N / 25 mm or less, or 20 N / 25 mm or less. Note that the adhesive force to the adherend is the value measured according to the method described in the examples below.

[0023] Hereinafter, referring to FIG. 1, the structure of the adhesive label will be described. 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.

[0024] FIG. 1 is a schematic cross-sectional view of the adhesive label 10 according to the present embodiment. As shown in FIG. 1, the adhesive label 10 according to the embodiment of the present invention has, in order from above, a resin base material 11, an adhesive layer 12, and a release liner 13. Note that the adhesive label 10 may have other functional layers on the resin base material 11 or between the layers. Examples of other functional layers include a printing layer and a primer layer.

[0025] The concept of "label" includes those referred to as films, sheets, tapes, etc.

[0026] Hereinafter, each component of the adhesive label will be described. In the following description, a PET bottle is taken as an example of the adherend, but the adherend is not limited to this. In this specification, "X~Y" indicating a range means "X or more and Y or less". Also, unless otherwise specified, operations, physical properties, etc. are measured under the conditions of room temperature (20~25°C) / relative humidity 45~55%RH.

[0027] <Resin base material> As the resin base material, it is necessary to use a polyester-based film that is the same material and has compatibility with the adherend PET bottle. That is, the resin base material is a polyester-based resin base material. From the viewpoint of the quality of the recycled resin such as mechanical properties, it is particularly advantageous to use a resin base material of a polyester-based film that is close to the composition of the resin used for the PET bottle. Examples of the resin base material used for this polyester-based film include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. From these, according to the type of resin used for the adherend PET bottle, one kind or two or more kinds may be appropriately selected and used so that a resin base material compatible with it can be obtained.

[0028] Here, compatibility means that the material melts at the temperature at which the PET bottle is heated and melted, and mixes well with the molten resin base material of the PET bottle, without degrading 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.

[0029] There are no particular restrictions on the thickness of the resin substrate, and it is selected appropriately depending on the application, but it is generally preferable to be in the range of 25 to 100 μm. By making the resin substrate thickness 25 μm or more, the peeling of the adhesive label from the release liner in the labeling process is excellent. On the other hand, by making the resin substrate thickness 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. This resin substrate 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.

[0030] In the present invention, the resin substrate can be surface-treated on one or both sides, if desired, in order to improve adhesion with a coating layer provided thereon or with a polyester adhesive layer provided on the opposite side. Examples of such surface treatment methods include surface roughening treatments such as sandblasting or solvent treatment, or surface oxidation treatments such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, and ozone / ultraviolet irradiation treatment.

[0031] In the present invention, a printable coating layer (print-receiving layer) may be provided on one side of the resin substrate. As a result, printability is imparted to one side of the resin substrate. This coating layer prevents the occurrence of print gaps during printing caused by protrusions (fish eyes) resulting from undissolved resin mixed in during the film formation of the resin substrate, and also has the effect of improving the adhesion of the printing ink.

[0032] <Polyester-based adhesive layer> Next, the polyester adhesive layer will be described. The polyester adhesive layer is formed from an adhesive composition containing a polyester adhesive (polyester resin).

[0033] The adhesive composition comprises a polyester adhesive, a xylylene diisocyanate compound, and a tolylene diisocyanate compound.

[0034] The polyester adhesive 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.

[0035] [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.

[0036] Among these, it is preferable to include aromatic dicarboxylic acids because they impart cohesive force.

[0037] The content of such aromatic dicarboxylic acid is preferably 50 mol% or less relative to the total polycarboxylic acid component (A1), particularly preferably 5 to 40 mol%, and even more preferably 10 to 30 mol%. If the content is too high, the glass transition temperature will rise, and sufficient adhesive performance will not be obtained.

[0038] 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.

[0039] The content of such aliphatic dicarboxylic acid is preferably 20 mol% or more, particularly preferably 60 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 adhesion component decreases, which tends to reduce the adhesive strength to polar substrates.

[0040] 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, particularly preferably aromatic dicarboxylic acid / aliphatic dicarboxylic acid = 5 / 95 to 40 / 60, and even more preferably aromatic dicarboxylic acid / aliphatic dicarboxylic acid = 10 / 90 to 30 / 70.

[0041] Furthermore, to increase the branching points in the polyester adhesive, polycarboxylic acids with a valency of three or higher can be used. Examples of such polycarboxylic acids with a valency of three or higher 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 polycarboxylic acids with a valency of three or higher 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 manufacture of the polyester adhesive.

[0042] [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.

[0043] 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.

[0044] Furthermore, trivalent or higher polyhydric alcohols can be used in polyester adhesives 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 adhesive.

[0045] 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.

[0046] The polyester adhesive 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.

[0047] The number-average molecular weight of the polyester adhesive used in the present invention is preferably 5,000 to 150,000, particularly preferably 10,000 to 100,000, and even more preferably 15,000 to 100,000, from the viewpoint of cohesive force, heat resistance, mechanical strength, and adhesiveness.

[0048] The number-average molecular weight mentioned above is the number-average molecular weight calculated on a standard polystyrene molecular weight basis, and is measured using high-performance liquid chromatography (Tosoh Corporation, "HLC-8320GPC") with one "TSK guard column super HH" column, two "TSK gel super HM-H" columns in series, and one "TSK gel super H2000" column.

[0049] The glass transition temperature of polyester adhesives is preferably -80 to 20°C, more preferably -75 to 10°C, even more preferably -70 to -20°C, even more preferably -65 to -30°C, and particularly preferably -55 to -40°C, from the viewpoint of adhesive properties. Having the glass transition temperature within this range ensures initial tackiness and gives the adhesive appropriate cohesive force. The glass transition temperature (Tg) is a value measured using a differential scanning calorimeter (DSC) in a measurement temperature range of -90 to 100°C with a temperature rise rate of 10°C / min.

[0050] The acid value of the polyether-based adhesive is preferably 10 mg KOH / g or less, more preferably 3 mg KOH / g or less, and even more preferably 1.5 mg KOH / g or less. Being within the above range suppresses hydrolysis and makes it easier to maintain cohesive strength.

[0051] The hydroxyl value of the polyether-based adhesive is preferably 1 to 50 mgKOH / g, more preferably 1 to 30 mgKOH / g, even more preferably 1 to 20 mgKOH / g, and particularly preferably 2 to 15 mgKOH / g. Having a hydroxyl value within this range makes it easier to obtain the effects of the present invention.

[0052] The acid value and hydroxyl value of polyester adhesives are determined by neutralization titration in accordance with JIS K 0070:1992.

[0053] From the viewpoint of adhesiveness, the polyester-based adhesive content is preferably 80% by mass or more, and more preferably 90% by mass or more, in the adhesive composition. Furthermore, the polyester-based adhesive content can be appropriately adjusted by the amount of crosslinking agent added, but for example, it is 99% by mass or less in the adhesive composition.

[0054] Xylylene diisocyanate compounds are xylylene diisocyanate and its modified forms. Examples of xylylene diisocyanates include xylylene-1,4-diisocyanate and xylylene-1,3-diisocyanate. Examples of modified forms of xylylene diisocyanate include adduct compounds of xylylene diisocyanate and polyol compounds such as trimethylolpropane. Xylylene diisocyanate compounds may be used individually or in combination of two or more types.

[0055] The content of xylylene diisocyanate compounds in the adhesive composition is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of polyester adhesive, considering the processing characteristics in low-temperature environments. Furthermore, the amount of xylylene diisocyanate compounds blended in the adhesive composition is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of polyester adhesive.

[0056] Tolylene isocyanate compounds are tolylene isocyanate and its modified forms. Examples of tolylene isocyanate include 2,4-tlylene isocyanate (2,4-TDI) and 2,6-tlylene isocyanate (2,6-TDI). Examples of modified forms of tolylene isocyanate include adducts of tolylene isocyanate and polyol compounds such as trimethylolpropane, and isocyanurates of tolylene isocyanate. Tolylene isocyanate compounds may be used individually or in combination of two or more.

[0057] The content of the tolylene diisocyanate compound in the adhesive composition is preferably 0.3 parts by mass or more per 100 parts by mass of adhesive, considering the processing characteristics under high temperature and high humidity conditions. Furthermore, the content of the tolylene diisocyanate compound in the adhesive composition is preferably 4 parts by mass or less, and more preferably 2 parts by mass or less per 100 parts by mass of adhesive.

[0058] From the viewpoint of the effects of the present invention, the mass ratio of xylylene diisocyanate compound and tolylene diisocyanate compound in the adhesive composition is preferably xylylene diisocyanate compound:tolylene diisocyanate compound = 1:0.1 to 2, and more preferably 1:0.3 to 1.5.

[0059] The amount of xylylene diisocyanate compounds and tolylene diisocyanate compounds can be appropriately set depending on the molecular weight and intended use of the polyester adhesive, but it is preferably 0.5 to 5 parts by mass, more preferably 0.8 to 5 parts by mass, even more preferably 1 to 3 parts by mass, and particularly preferably 1.5 to 3 parts by mass per 100 parts by mass of polyester adhesive. Furthermore, considering the effects of the present invention, the content of xylylene diisocyanate compounds in the adhesive composition may be 0.8 parts by mass or more per 100 parts by mass of polyester adhesive, and the total of xylylene diisocyanate compounds and tolylene diisocyanate compounds may be 1.5 parts by mass or more per 100 parts by mass of polyester adhesive, or the content of xylylene diisocyanate compounds in the adhesive composition may be 1 part by mass or more per 100 parts by mass of polyester adhesive, and the total of xylylene diisocyanate compounds and tolylene diisocyanate compounds may be 1.5 parts by mass or more.

[0060] The 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.

[0061] The method for forming the polyester adhesive layer is not particularly limited, but the polyester adhesive layer may be formed by directly coating the adhesive composition onto a resin substrate, or the polyester adhesive layer may be formed on a release liner and then laminated to the resin substrate. Specifically, one method is to apply and dry the adhesive composition on a release liner and then transfer the polyester adhesive layer made of the adhesive composition onto the resin substrate.

[0062] The method of applying the adhesive composition to the substrate or release liner is not particularly limited, and it can be applied using known coating devices such as roll coaters, knife coaters, air knife coaters, bar coaters, blade coaters, slot die coaters, lip coaters, and gravure coaters. The drying conditions are not particularly limited, and are usually carried out at 60 to 150°C for 10 to 90 seconds.

[0063] The thickness of the adhesive layer (film thickness after drying) is typically 5 to 100 μm, preferably 10 to 50 μm.

[0064] <Removable Liner> The release liner is a component that protects the polyester adhesive layer and prevents a decrease in adhesiveness. The release liner is peeled off from the adhesive sheet when it is applied to the substrate. Therefore, the adhesive sheet in this invention also includes those that do not have a release liner.

[0065] The release liner can be any type of paper, though not particularly limited, such as fine paper, glassine paper, clay-coated paper, polyethylene laminated paper; polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; or plastic films such as polyolefin films such as polypropylene and polyethylene.

[0066] The thickness of the release liner is typically around 10 to 400 μm. Furthermore, the surface of the release liner may be provided with a layer made of a release agent, such as silicone, to improve the release properties of the polyester adhesive layer. When such a layer is provided, its thickness is typically around 0.01 to 5 μm.

[0067] <Manufacturing method> The method for manufacturing adhesive labels is not particularly limited, but one method is to produce a roll of adhesive sheet, and then, if necessary, print, die-cut, and remove excess material to produce adhesive labels. Methods for manufacturing rolls of adhesive sheets include (1) a method of forming a polyester adhesive layer by coating a release liner with a polyester adhesive composition, and then laminating this to a resin substrate, and (2) a method of forming a polyester adhesive layer by directly coating a resin substrate with a polyester adhesive composition, and then laminating a release liner to it.

[0068] Figure 2(A) is a schematic diagram of one embodiment of a roll-shaped adhesive sheet, viewed from an oblique upper direction. Figure 2(A) shows how the roll-shaped adhesive sheet is fed out in direction A (longitudinal direction) by, for example, a conveyor roll. Figure 2(B) is a schematic cross-sectional view BB of the adhesive sheet in Figure 2(A). As shown in Figure 2(B), the adhesive sheet 20 is a laminate in which a release liner 23, a polyester adhesive layer 22, and a resin substrate 21 are laminated in this order. The fed-out adhesive sheet has cut lines 24 made along the lamination direction using, for example, a punching blade 25 (punching). Figure 2(C) is a schematic cross-sectional view CC of the adhesive sheet in Figure 2(A). In the adhesive sheet 30 of Figure 2(C), the cut lines 24 are made up to the interface between the polyester adhesive layer 22 and the release liner 23 in the lamination direction. In this way, the cut lines 24 provided along the lamination direction form the label portion and the unnecessary portion. Unnecessary parts are removed by scraping. Figure 2(D) is a schematic DD cross-sectional view of the adhesive sheet shown in Figure 2(A). Unnecessary parts are removed by scraping, and the label portion that is attached to the PET bottle is formed from a resin substrate 21', a polyester adhesive layer 22', and a release liner 23.

[0069] The adhesive labels of the present invention maintain high retention of the polyester adhesive layer even when aged in low temperature, high temperature, and high humidity environments. Therefore, even when die-cutting is performed as described above, there is little to no co-printing or contamination of the die-cutting blade.

[0070] <Polyester containers> Adhesive labels are preferably affixed to polyester containers such as polyethylene terephthalate (PET) bottles. The present invention also provides polyester containers to which the above-mentioned adhesive labels are affixed. A polyester container refers to a container made of a polyester resin. Examples of polyester resins include polyethylene terephthalate. Containers can be manufactured by injection molding, vacuum forming, pressure forming, etc., of the polyester resin. [Examples]

[0071] 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).

[0072] (Example 1) An 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", glass transition temperature -50℃), 0.8 parts by mass (solids) of xylylene diisocyanate compound (xylylene diisocyanate trimethylolpropane adduct, solids concentration 75% by mass), 0.6 parts by mass (solids) of tolylene diisocyanate compound (tolylene diisocyanate trimethylolpropane adduct: manufactured by Tosoh Corporation, product name "Coronate® L", solids concentration 75% by mass), and 35 parts by mass of ethyl acetate.

[0073] The obtained adhesive composition was applied to the release agent layer of the release liner using a knife coater so that the film thickness after drying was 15 μm, and then dried at 90°C for 1 minute to form an adhesive layer.

[0074] A 50 μm polyethylene terephthalate film was attached to the adhesive layer to obtain the adhesive label of Example 1.

[0075] (Examples 2-7, Comparative Examples 1 and 2) Adhesive labels were obtained in the same manner as in Example 1, except that the amounts of xylylene diisocyanate and tolylene diisocyanate compounds added were changed as shown in Table 1.

[0076] (Comparative Examples 3 and 4) Adhesive labels were obtained in the same manner as in Example 1, except that an adhesive composition containing only a xylylene diisocyanate compound (1 part by mass) without the addition of a tolylene diisocyanate compound (Comparative Example 3) and an adhesive composition containing only a tolylene diisocyanate compound (0.6 parts by mass) without the addition of a xylylene diisocyanate compound (Comparative Example 4) were used. The labels exhibited a retention force of 5,000 seconds or less after being left standing at 23°C for 7 days, and did not exhibit sufficient retention force even after aging at room temperature. For this reason, retention force tests after low-temperature and high-temperature aging were not performed for Comparative Examples 3 and 4.

[0077] (Measurement method 1: Adhesion immediately after measurement) Two types of adhesive labels were prepared: (1) those left standing for 7 days at 10°C (low temperature), and (2) those left standing for 7 days at 30°C and 80%RH (high temperature and high humidity). After peeling off the release liner from each adhesive label, the adhesive layer was attached to a polyethylene terephthalate board at 23°C and 50%RH (attachment conditions: 2kg rubber roller, one-way application). Immediately after attachment, the adhesive strength was measured according to JIS Z0237:2009. Specifically, the sheet was peeled off in a 180° direction at a test speed of 0.3m / min using a tensile testing machine, and the adhesive strength was measured. The values ​​are converted to peeling force per 25mm sheet width (N / 25mm). The results are shown in Table 1.

[0078] (Measurement method 2: Holding power test) The holding strength test was conducted in accordance with JIS Z0237:2009.

[0079] Two types of adhesive labels were prepared: (1) those left standing for 7 days at 10°C, and (2) those left standing for 7 days at 30°C and 80%RH. After peeling off the release liner from the adhesive label, the adhesive layer side was attached to a stainless steel plate (SUS) at 23°C and 50%RH (attachment conditions: 5 passes with a 2kg rubber roller). The test was conducted with a sample attachment area of ​​25mm x 25mm, a load of 9.8N, and a temperature of 40°C. The results are shown in Table 1.

[0080] Furthermore, the retention strength test can serve as an indicator of cutting and labeling properties.

[0081] [Table 1]

[0082] As shown above, the adhesive labels of the examples exhibit high retention even after aging in low-temperature and high-temperature, high-humidity environments. This reduces the occurrence of problems such as co-feeding during die-cutting and contamination of the die-cutting blade.

[0083] Furthermore, in all of the examples, the adhesive labels had an initial adhesive strength of 6.5 N / 25 mm or more, and the immediate adhesive strength was sufficiently guaranteed. [Explanation of Symbols]

[0084] 10, 20, 30 adhesive labels, 11, 21, 21' Resin base material, 12, 22, 22' Polyester adhesive layer, 13, 23 Release Liner, 24 cut lines, 25 punching blades.

Claims

1. It comprises a polyester resin substrate and a polyester adhesive layer formed from an adhesive composition, The adhesive composition comprises a polyester adhesive, a xylylene diisocyanate compound, and a tolylene diisocyanate compound. The xylylene diisocyanate compound is a trimethylolpropane adduct of xylylene diisocyanate, and the tolylene diisocyanate compound is a trimethylolpropane adduct of tolylene diisocyanate. An adhesive label in which the blending mass ratio of the xylylene diisocyanate compound and the tolylene diisocyanate compound is xylylene diisocyanate compound: tolylene diisocyanate compound = 1:0.1 to 2.

2. The adhesive label according to claim 1, wherein the total content of the xylylene diisocyanate compound and the tolylene diisocyanate compound is 0.5 to 5 parts by mass per 100 parts by mass of the polyester adhesive.

3. The adhesive label according to claim 1 or 2, which is an adhesive label to be affixed to a polyester container.

4. A polyester container to which the adhesive label described in claim 1 or 2 is attached.

5. A method for manufacturing an adhesive label according to claim 1 or 2, comprising the step of die-cutting a roll-shaped adhesive sheet having a polyester resin substrate, a polyester adhesive layer formed from an adhesive composition, and a release liner.

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