Adhesive sheet

Abstract

To provide an adhesive sheet which has excellent durability while maintaining moldability.SOLUTION: The adhesive sheet includes: a substrate formed of a resin composition which contains a polybutylene succinate resin and a carbodiimide compound; and an adhesive layer formed of an adhesive composition which contains a carbodiimide compound, at least one crosslinking agent selected from the group consisting of isocyanate compounds and metal chelate compounds, and an adhesive having a functional group capable of reacting with the crosslinking agent.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] [[ID=J12]]An adhesive sheet generally has a structure in which a base material for exhibiting aesthetic and decorative properties or presenting various information and an adhesive layer for adhering the base material to an adherent surface are laminated. As the base material, a resin base material such as polyethylene terephthalate is often used. Such an adhesive sheet may be used by being attached to a plastic container such as a shampoo bottle.

[0003] In recent years, due to the increasing environmental awareness, biodegradable plastic containers that can be composted after disposal have attracted attention, and an adhesive sheet to be attached to such a container is also required to have biodegradability so that it can be composted without peeling off. As a biodegradable adhesive sheet, for example, an adhesive sheet using a biodegradable base material such as polylactic acid has been proposed (for example, Patent Document 1, etc.).

[0004] On the other hand, it is known to use a carbodiimide-based compound to improve the hydrolysis resistance of a biodegradable film (for example, Patent Document 2, etc.).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Adhesive sheets, such as those used for shampoo bottle labels, often require water resistance during normal use. However, when attempting to improve durability, including water resistance, by incorporating a relatively large amount of carbodiimide compounds into the base material, a problem arises: the moldability decreases.

[0007] Therefore, the present invention aims to provide an adhesive sheet that maintains moldability, is highly durable, and is also biodegradable. [Means for solving the problem]

[0008] The present invention relates to a substrate formed from a resin composition containing a polybutylene succinate resin and a carbodiimide compound, and An adhesive layer formed from an adhesive composition comprising a carbodiimide compound, at least one crosslinking agent selected from the group consisting of aromatic isocyanate compounds and metal chelate compounds, and an adhesive having a functional group capable of reacting with the crosslinking agent. It is an adhesive sheet containing [something]. [Effects of the Invention]

[0009] The adhesive sheet of the present invention provides an adhesive sheet with excellent durability. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the adhesive sheet of the present invention. [Modes for carrying out the invention]

[0011] The present invention relates to an adhesive sheet comprising a substrate formed from a resin composition containing a polybutylene succinate resin and a carbodiimide compound, and an adhesive layer formed from an adhesive composition containing a carbodiimide compound, at least one crosslinking agent selected from the group consisting of aromatic isocyanate compounds and metal chelate compounds, and an adhesive having a functional group that can react with the crosslinking agent.

[0012] In this invention, the hydrolysis resistance of the substrate is improved by the migration of the carbodiimide compound contained in the adhesive layer to the substrate containing the polybutylene succinate resin. If the substrate does not contain the polybutylene succinate resin, no improvement in hydrolysis resistance is observed (see Comparative Example 2 below). Therefore, the migration of the carbodiimide compound to the substrate requires the substrate to contain the polybutylene succinate resin. Furthermore, by including the carbodiimide compound in the adhesive layer, the amount of the carbodiimide compound to be contained in the substrate can be reduced, and thus the moldability of the substrate can be maintained.

[0013] The concept of a sheet encompasses items such as tapes, labels, and films.

[0014] Figure 1 is a schematic cross-sectional view showing one embodiment of the adhesive sheet of the present invention. Note that the drawing is exaggerated for illustrative purposes, and the dimensional ratios of each component in the drawing may differ from those in reality. In Figure 1, the adhesive sheet 10 consists of a base material 11, an adhesive layer 12, and a release liner 13. The release liner 13 is formed to prevent dirt and other contaminants from adhering to the adhesive layer 12 until the adhesive sheet 10 is attached to the adherend. Therefore, the release liner 13 is peeled off when the sheet is attached to the adherend.

[0015] Furthermore, functional layers such as a printing layer, a print receiving layer, and a primer layer may be present between each layer or on the substrate. However, considering the migration of carbodiimide compounds to the substrate, it is preferable that the substrate 11 and the adhesive layer 12 are arranged adjacent to each other.

[0016] The following describes the composition of each layer that makes up the adhesive sheet. In this specification, "X~Y" indicating a range means "X or more and Y or less". Unless otherwise specified, operations and measurements of physical properties are performed under room temperature (20~25°C) / relative humidity 45~55%RH conditions.

[0017] <Base material> The base material is formed from a resin composition containing a polybutylene succinate resin and a carbodiimide compound.

[0018] Specifically, as the polybutylene succinate resin, a biodegradable polyester made of an aliphatic polyester resin formed by directly dehydrating and polycondensing 1,4-butanediol and succinic acid using them as main components can be used. As the polybutylene succinate resin, in addition to polybutylene succinate, a copolymer of polybutylene succinate and other hydroxycarboxylic acids, diols, and dicarboxylic acids may also be used. Specifically, examples of the polybutylene succinate resin include polybutylene succinate, polybutylene succinate / adipate copolymer, polycaprolactone / butylene succinate copolymer, and the like. Among them, the polybutylene succinate resin is preferably polybutylene succinate.

[0019] The polybutylene succinate resin preferably has a weight average molecular weight of 30,000 to 500,000, and more preferably 100,000 to 500,000. When the weight average molecular weight is at least the above lower limit, practical physical properties such as mechanical properties and heat resistance are good, and when it is 500,000 or less, the melt viscosity is low, so the molding processability is good. The weight average molecular weight can be measured using gel permeation chromatography (GPC).

[0020] In the resin composition, the content of the polybutylene succinate resin is preferably 30% by mass or more, and more preferably 40% by mass or more. Also, the content of the polybutylene succinate resin may be 98% by mass or less, 90% by mass or less, or 80% by mass or less.

[0021] The resin contained in the resin composition may include a resin other than the polybutylene succinate resin. A form in which the resin composition further contains a polylactic acid resin is suitable in terms of the strength of the base material.

[0022] The polylactic acid resin is obtained by polymerizing lactic acid monomers as the main component. Here, "using lactic acid monomers as the main component" means that among all the monomers constituting the resin, the lactic acid monomer content exceeds 50 mol% (the upper limit is 100 mol%), preferably 75 mol% or more, and more preferably 85 mol% or more. The polylactic acid resin may be polylactic acid or a copolymer of lactic acid monomers and other hydroxycarboxylic acid monomers, and may also contain a small amount of chain extender residues. As the lactic acid monomer, there are L-lactic acid and D-lactic acid.

[0023] As the polylactic acid, for example, it can be a polymer mainly composed of poly-L-lactic acid with a structural unit of L-lactic acid, poly-D-lactic acid with a structural unit of D-lactic acid, poly-DL-lactic acid with structural units of L-lactic acid and D-lactic acid, and mixtures thereof. As the composition of the polylactic acid, in terms of molar ratio, it is preferably D-lactic acid:L-lactic acid = 0:100 to 10:90. It is also possible to blend other polylactic acids with different composition ratios of D-lactic acid and L-lactic acid.

[0024] Other hydroxycarboxylic acid monomers that can copolymerize with polylactic acid may be copolymers with this unit and may also contain a small amount of chain extender residues. Examples of other hydroxycarboxylic acid monomers include bifunctional aliphatic hydroxycarboxylic acids such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxybutyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone. These may be used alone or in combination of two or more. Such other hydroxycarboxylic acid monomers are preferably 10 mol% or less in all the monomers constituting the polylactic acid.

[0025] The polylactic acid resin preferably has a weight-average molecular weight of 50,000 to 1,000,000, and more preferably 50,000 to 500,000. If the molecular weight is 50,000 or higher, practical properties such as mechanical properties and heat resistance are good, and if it is below the above upper limit, the melt viscosity is low, resulting in good moldability. The weight-average molecular weight can be measured using gel permeation chromatography (GPC).

[0026] Polylactic acid resins can be polymerized using known methods such as condensation polymerization and ring-opening polymerization. For example, in condensation polymerization, L-lactic acid or D-lactic acid, or mixtures thereof, can be directly dehydrated and condensed to obtain polylactic acid resins with any desired composition and crystallinity. In ring-opening polymerization (lactide method), lactide, a cyclic dimer of lactic acid, can be used to obtain polylactic acid resins using a suitable catalyst and polymerization regulators as needed. Lactide includes L-lactide (a dimer of L-lactic acid), D-lactide (a dimer of D-lactic acid), and DL-lactide (a dimer of D-lactic acid and L-lactic acid). By mixing and polymerizing these as needed, polylactic acid resins with any desired composition and crystallinity can be obtained.

[0027] In the resin composition, considering the effects and mechanical properties of the present invention, the content of polylactic acid resin is preferably polybutylene succinate resin:polylactic acid resin = 20:1 to 1:5 (mass ratio), more preferably 10:1 to 1:2 (mass ratio), and even more preferably 5:1 to 1:2 (mass ratio).

[0028] The resin composition contains a carbodiimide compound. In this invention, the carbodiimide compound is included in advance to a degree that does not affect the moldability, in terms of the hydrolysis resistance of the substrate. The carbodiimide compound improves the hydrolysis resistance of the substrate by encapsulating the carboxyl group ends of the polybutylene succinate resin (or other resin, e.g., polylactic acid) in the resin composition.

[0029] Carbodiimide compounds only need to have at least one carbodiimide group (-N=C=N-), and may have two or more carbodiimide groups. That is, carbodiimide compounds may be monocarbodiimide compounds (compounds having one carbodiimide group) or polycarbodiimide compounds (compounds having two or more carbodiimide groups). Furthermore, in carbodiimide compounds, the carbodiimide group may be bonded to a hydrocarbon group or a hydrocarbon skeleton. Carbodiimide compounds may be used individually or in combination of two or more.

[0030] Examples of preferred monocarbodiimide compounds include aliphatic monocarbodiimide compounds, alicyclic monocarbodiimide compounds, and aromatic monocarbodiimide compounds.

[0031] Examples of aliphatic monocarbodiimide compounds include 1,3-dimethylcarbodiimide, 1,3-diisopropylcarbodiimide, 1-isopropyl-3-t-butylcarbodiimide, 1,3-dihexylcarbodiimide, 1,3-dioctylcarbodiimide, 1-isopropyl-3-dodecylcarbodiimide, 1,3-dioctyldecylcarbodiimide, and dialkylcarbodiimide compounds such as 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

[0032] Examples of alicyclic monocarbodiimide compounds include dicycloalkylcarbodiimide compounds such as 1,3-dicyclohexylcarbodiimide.

[0033] Examples of aromatic monocarbodiimide compounds include diarylcarbodiimide compounds, arylcycloalkylcarbodiimide compounds, and alkylaralkylcarbodiimide compounds. Examples of diarylcarbodiimide compounds include N,N'-diphenylcarbodiimide (1,3-diphenylcarbodiimide), N,N'-di-o-tolylcarbodiimide, N,N'-bis(2,6-dimethylphenyl)carbodiimide, N,N'-bis(2,4,6-trimethylphenyl)carbodiimide, N,N'-bis(2,6-diethylphenyl)carbodiimide, N,N'-bis(2-ethyl-6-isopropylphenyl)carbodiimide, and N,N'-bis(2,6-diisopropylphenyl)carbodiimide. Examples include imides, N,N'-bis(2,4,6-triisopropylphenyl)carbodiimide, N,N'-bis(2-isobutyl-6-isopropylphenyl)carbodiimide, N,N'-bis(2,6-di-t-butylphenyl)carbodiimide, N-phenyl-N'-tolylcarbodiimide, N,N'-di-β-naphthylcarbodiimide, N,N'-di(p-nitrophenyl)carbodiimide, N,N'-di(p-aminophenyl)carbodiimide, and N,N'-di(p-hydroxyphenyl)carbodiimide. Examples of arylcycloalkylcarbodiimide compounds include N-tolyl-N'-cyclohexylcarbodiimide. Examples of alkylaralkylcarbodiimide compounds include benzylisopropylcarbodiimide.

[0034] Polycarbodiimide compounds can be produced primarily by condensation reactions involving decarbonation of organic diisocyanates. Examples of organic diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diyl diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diyl diisocyanate, xylylene diisocyanate, hexamethylene-1,6-diisocyanate, lysine diisocyanate, hydrogenated methylenediphenyl diisocyanate, isophorone diisocyanate, and tetramethylxylylene diisocyanate. These may be used individually or in combination of two or more types.

[0035] Examples of polycarbodiimide compounds include aliphatic polycarbodiimide compounds, alicyclic polycarbodiimide compounds, and aromatic polycarbodiimide compounds. Examples of aliphatic polycarbodiimide compounds include polyalkylene carbodiimides such as polyhexamethylenecarbodiimide. Examples of alicyclic polycarbodiimide compounds include polydicycloalkylalkanecarbodiimides such as poly(4,4'-dicyclohexylmethanecarbodiimide). Examples of aromatic polycarbodiimide compounds include polyarylenecarbodiimide and polydiarylalkanecarbodiimide. Examples of polyarylenecarbodiimides include polym-phenylenecarbodiimide, polyp-phenylenecarbodiimide, polytylenecarbodiimide, poly(diisopropylphenylenecarbodiimide), and poly(methyldiisopropylphenylenecarbodiimide). Examples of polydiarylalkanecarbodiimides include poly(4,4'-diphenylmethanecarbodiimide).

[0036] The number-average molecular weight (Mn) of the polycarbodiimide compound is preferably 200 or more, more preferably 500 or more, preferably 50,000 or less, and more preferably 10,000 or less. The number-average molecular weight (Mn) is a value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0037] The terminal groups of polycarbodiimide compounds are not particularly limited and may be groups derived from the raw materials, such as isocyanate groups, and may be groups in which part or all of the terminal is sequestered or protected. For example, the terminal isocyanate group may be a group that has been sequestered with a chelating agent such as an amine, alcohol, or monoisocyanate. Since polycarbodiimide compounds are mainly produced by a condensation reaction involving decarbonization of organic diisocyanates, the terminal groups may be isocyanate groups. When a polycarbodiimide compound has a terminal isocyanate group, the proportion of isocyanate groups to the total polycarbodiimide compound is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, particularly preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. Furthermore, the proportion of isocyanate groups is preferably 30% by mass or less, more preferably 20% by mass or less, particularly preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0038] The carbodiimide compound included in the resin composition is preferably a polycarbodiimide compound, and more preferably an alicyclic polycarbodiimide compound, in terms of its chain length-extending effect.

[0039] The content of the carbodiimide compound in the resin composition is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of resin, considering moldability. Furthermore, the content of the carbodiimide compound in the resin composition is preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more, considering durability such as water resistance.

[0040] The resin composition may contain additives such as pigments, UV absorbers, antioxidants, lubricants, antistatic agents, and heat stabilizers.

[0041] The melt mass flow rate of the resin composition, measured at 190°C and under a 10kg load in accordance with JIS K 7210-1:2014, is preferably 0.1 to 30 g / 10 min from the viewpoint of moldability.

[0042] While there are no particular restrictions on the thickness of the substrate, from the viewpoint of mechanical properties, it is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 40 μm or more. Furthermore, from the viewpoint of thin film formation, it is preferably 200 μm or less, and more preferably 150 μm or less.

[0043] <Adhesive layer> The adhesive layer is formed from an adhesive composition comprising a carbodiimide compound, at least one crosslinking agent selected from the group consisting of aromatic isocyanate compounds and metal chelate compounds, and an adhesive having a functional group that can react with the crosslinking agent.

[0044] The adhesive composition contains a carbodiimide compound. The carbodiimide compound can be one of those listed in the "Substrate" section above.

[0045] The content of the carbodiimide compound in the adhesive composition is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and more preferably more than 2 parts by mass, per 100 parts by mass of adhesive, considering the transferability to the substrate. Furthermore, the content of the carbodiimide in the adhesive composition is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of adhesive, considering the adhesive properties.

[0046] A preferred embodiment of the present invention is one in which the effects of the present invention are further enhanced, and the mass percentage of the carbodiimide compound contained in the adhesive composition is greater than the mass percentage of the carbodiimide compound contained in the resin composition. The mass percentage of the carbodiimide compound contained in the adhesive composition may be, for example, 1.2 times, 1.5 times, or 2 times or more than the mass percentage of the carbodiimide compound contained in the resin composition.

[0047] The adhesive composition contains at least one crosslinking agent selected from the group consisting of aromatic isocyanate compounds and metal chelate compounds. These crosslinking agents have a fast crosslinking rate, which prevents the carbodiimide compound from being completely consumed in crosslinking the adhesive. In addition, in this invention, the adhesive is crosslinked with the crosslinking agent in order to impart cohesive force. From the viewpoint of adhesion to the substrate, a preferred embodiment is in which the adhesive composition contains an aromatic isocyanate compound.

[0048] Examples of aromatic isocyanate compounds include 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, 4,4'-toluidine diisocyanate, 1-methylbenzene-2,4,6-triyltriisocyanate, 1,3,5-benzenetriyltriisocyanate, dianisidine diisocyanate, diphenyl ether-4,4'-diisocyanate, triphenylmethane-4,4',4''-triyltriisocyanate, 1,4-tetramethylxylylenediisocyanate, and 1,3-tetramethylxylylenediisocyanate.

[0049] These aromatic isocyanate compounds may also be trimethylolpropane adduct type modified polyisocyanates, biuret type modified polyisocyanates reacted with water, or isocyanurate type modified polyisocyanates containing an isocyanurate ring.

[0050] Furthermore, the aromatic isocyanate compound may be a polymer polyisocyanate obtained by reacting the above-mentioned polyisocyanate with a polyol compound to obtain a polymer with two or more isocyanate groups per molecule. Alternatively, a polymer polyisocyanate obtained by polymerizing the above-mentioned polyisocyanate to obtain a polymer with two or more isocyanate groups per molecule may be used.

[0051] Aromatic isocyanate compounds may be used individually or in combination of two or more types.

[0052] The content of aromatic isocyanate compounds in the adhesive composition is appropriately set considering the degree of crosslinking of the adhesive and the residual amount of carbodiimide compounds, but is, for example, 0.5 to 5 parts by mass per 100 parts by mass of adhesive.

[0053] Examples of metal chelate compounds include coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, vanadium, magnesium, chromium, and zirconium with acetylacetone or ethyl acetoethyl acetate.

[0054] The content of the metal chelate compound in the adhesive composition is appropriately set considering the degree of crosslinking of the adhesive and the residual amount of the carbodiimide compound, but is, for example, 0.1 to 5 parts by mass per 100 parts by mass of adhesive.

[0055] The adhesive has functional groups that can react with the crosslinking agent. Examples of such adhesives include acrylic resins, urethane resins, and polyester resins.

[0056] In particular, urethane resins and polyester resins are preferred as adhesives because they are easier to impart biodegradability to. Urethane resins are more preferred.

[0057] Urethane resins can be produced by reacting polyester polyols and / or polyether polyols with polyfunctional isocyanate compounds.

[0058] Polyester polyols can be synthesized, for example, from an acid component such as a polycarboxylic acid and a glycol component or a polyol component. Examples of polyester polyols include those obtained by reacting an acid component such as terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, or trimellitic acid with a glycol component such as 3-methyl-1,5-pentanediol or propylene glycol, or a polyol component such as glycerin, trimethylolpropane, or pentaerythritol. Examples of polyester polyols include those obtained by ring-opening polymerization of lactones such as polycaprolactone, poly(β-methyl-γ-valerolactone), and polyvalerolactone. The molecular weight of the polyester polyol is preferably 1,000 to 6,000.

[0059] As polyether polyols, for example, polyalkylene glycol adducts of polyhydric alcohols are preferably used. As polyhydric alcohols, for example, aliphatic dihydric alcohols such as ethylene glycol, propylene glycol, 1,4-butylene glycol (tetramethylene glycol), neopentyl glycol, etc.; glycerin, trioxyisobutane, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-1,2,3-propanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-pentanetriol, 2,3,4-hexanetriol, 4-propyl-3,4,5-heptanetriol, 2,4-dimethyl Examples include trihydric alcohols such as 2,3,4-pentanetriol, pentamethylglycerin, pentaglycerin, 1,2,4-butanetriol, 1,2,4-pentanetriol, and trimethylolpropane; tetrahydric alcohols such as erythritol, pentaerythritol, 1,2,3,4-pentanetetraol, 2,3,4,5-hexanetetraol, 1,2,3,5-pentanetetraol, and 1,3,4,5-hexanetetraol; pentahydric alcohols such as adonitol, arabitol, and xylitol; and hexahydric alcohols such as sorbitol, mannitol, and isitol. The molecular weight of the polyether polyol is preferably 1,000 to 6,000.

[0060] Examples of polyfunctional isocyanate compounds include hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and trimethylolpropane / tolylene diisocyanate trimer adducts.

[0061] Chain extenders may be used during the production of polyurethane resin to adjust the molecular weight of the polyurethane resin. Examples of chain extenders include polyamines such as ethylenediamine and 1,4-tetramethylenediamine; polyols such as ethylene glycol and propylene glycol; and polyalkylene glycols such as polyethylene glycol.

[0062] A catalyst may be used when manufacturing urethane resins. Examples of catalysts include tin-based compounds such as dioctyl tin dilaurate and dibutyl tin dilaurate, and tertiary amine compounds such as triethylamine and triethylenediamine.

[0063] Examples of solvents that can be used in the manufacture of urethane resins include toluene, ethyl acetate, and methyl ethyl ketone.

[0064] The adhesive composition may further contain other conventionally known additives. Examples of such additives include crosslinking agents, fillers, pigments, and ultraviolet absorbers other than those mentioned above. Examples of fillers include zinc oxide, silica, and calcium carbonate.

[0065] The method for forming the adhesive layer is not particularly limited, but the adhesive layer may be formed by directly coating the adhesive composition onto the substrate, or the adhesive layer may be formed on a release liner and then bonded to the substrate. Specifically, one method is to apply and dry the adhesive composition on a release liner and then transfer the adhesive layer made of the adhesive composition to the substrate.

[0066] 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.

[0067] The thickness of the adhesive layer (film thickness after drying) is typically 5 to 100 μm, preferably 10 to 50 μm.

[0068] <Removable Liner> A release liner is a component that protects the adhesive layer and prevents a decrease in tackiness. 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.

[0069] 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.

[0070] The thickness of the release liner is typically around 10 to 400 μm. Additionally, a layer made of a release agent, such as silicone, may be provided on the surface of the release liner to improve the release properties of the adhesive layer. When such a layer is provided, its thickness is typically around 0.01 to 5 μm.

[0071] The adhesive sheet of the present invention can be used as various decorative sheets, display sheets, protective sheets (films), etc. Furthermore, it is preferable to use biodegradable resins such as polylactic acid, polybutylene succinate, or polybutylene succinate adipate as the adherend so that the adherend can be composted together. However, non-biodegradable adherends such as metal, polyester, polyethylene, and polypropylene can also be used; in this case, the adhesive sheet is peeled off the adherend and only the adhesive sheet is composted.

[0072] <Manufacturing method> The method for molding the resin composition onto a substrate is not particularly limited. For example, a method may be used in which the resin composition is melted, or the components constituting the resin composition are melted and mixed, and then formed into a film using a known molding method. Apparatus for melt mixing may include a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader, various extrusion and injection molding machines, or a reactor equipped with a stirring device and a vacuum device. Preferably, this melt mixing is carried out under an inert gas atmosphere and / or under reduced pressure.

[0073] In the present invention, it is possible to reduce the amount of carbodiimide compounds in the resin composition, thereby suppressing the increase in viscosity of the resin composition. Therefore, extrusion molding can be easily performed.

[0074] Accordingly, a preferred embodiment of the present invention is a method for producing an adhesive sheet, comprising the steps of: obtaining a substrate by melt extrusion of a resin composition containing a polybutylene succinate resin and a carbodiimide compound; and forming an adhesive layer from an adhesive composition containing at least one crosslinking agent selected from the group consisting of a carbodiimide compound, an aromatic isocyanate compound, and a metal chelate compound, and an adhesive having a functional group that can react with the crosslinking agent. [Examples]

[0075] The effects of the present invention will be explained using the following examples and comparative examples. In the examples, the units "parts" or "%" may be used, but unless otherwise specified, they represent "parts by mass" or "mass%". Unless otherwise specified, each operation is performed at room temperature (25°C).

[0076] <Example 1> 1. Preparation of the base film A polyester resin composition was obtained by kneading 50 parts by mass of polylactic acid resin (weight-average molecular weight 180,000, D-lactic acid:L-lactic acid = 1.5:98.5 (molar ratio)), 50 parts by mass of polybutylene succinate resin (weight-average molecular weight 250,000), and 1 part by mass of poly(dicyclohexylmethanecarbodiimide) (number-average molecular weight 2,000) at 230°C. The obtained resin composition was extruded using a T-die film-making machine at a film-making temperature of 230°C to obtain a film A1 with a thickness of 100 μm.

[0077] 2. Preparation of adhesive composition In a reaction vessel equipped with a stirrer, thermometer, and fractionation tube, 130 parts by mass of 3-methyl-1,5-pentanediol, 215 parts by mass of sebaciic acid, and 0.05 parts by mass of dibutyltin dilaurate, a polymerization catalyst, were mixed and the mixture was heated to 200°C under atmospheric pressure and nitrogen, and then reacted for a further 4 hours. Next, the pressure was reduced to carry out the deglycolization reaction, and then the mixture was cooled to 180°C and returned to atmospheric pressure. Then, 0.05 parts by mass of phosphonic acid was added and stirred to obtain a polyester polyol, which is a raw material for polyurethane resin.

[0078] In a reaction vessel similar to the one described above, 100 parts by mass of the obtained polyester polyol and 100 parts by mass of toluene were added to dissolve the resin. The temperature was then raised to 110°C, and 3 parts by mass of hexamethylene diisocyanate were added to carry out the polyaddition reaction. After cooling, the mixture was further diluted with toluene to obtain a polyurethane resin solution.

[0079] To 100 parts by mass (solids) of the polyurethane resin obtained above, 2 parts by mass (solids) of tolylene diisocyanate and 2 parts by mass (solids) of 1,3-diphenylcarbodiimide were added, and then mixed with a diluent (toluene) to prepare adhesive composition B1 with a solids content of 30% by mass.

[0080] 3. Preparation of adhesive sheets The adhesive composition B1 obtained above was applied onto a release liner (glassine paper coated with silicone, 66 μm thick) so that its thickness after drying was 20 μm, and dried at 90°C for 1 minute to form an adhesive layer B1'. The adhesive layer B1' was laminated to film A1, and then left to stand for 7 days at 23°C and 50% RH to obtain adhesive sheet 1.

[0081] <Example 2> 1. Preparation of adhesive composition In the adhesive composition preparation process of Example 1, the amount of 1,3-diphenylcarbodiimide added was changed to 4 parts by mass (solid content) to obtain adhesive composition B2.

[0082] 2. Preparation of adhesive sheets Adhesive composition B2 was applied to a release liner so that its thickness after drying was 20 μm, and dried at 90°C for 1 minute to form adhesive layer B2'. Adhesive layer B2' was laminated to film A1 prepared in the same manner as in Example 1, and then left to stand for 7 days at 23°C and 50% RH to obtain adhesive sheet 2.

[0083] <Example 3> 1. Preparation of the base film A polyester resin composition was obtained by kneading 30 parts by mass of polylactic acid resin (weight-average molecular weight 180,000, D-lactic acid:L-lactic acid = 1.5:98.5 (molar ratio)), 70 parts by mass of polybutylene succinate resin, and 1 part by mass of poly(dicyclohexylmethanecarbodiimide) (number-average molecular weight 2,000) at 230°C. The obtained resin composition was extruded using a T-die film-making machine at a film-making temperature of 230°C to obtain a film A'1 with a thickness of 100 μm.

[0084] 2. Preparation of adhesive sheets An adhesive sheet 3 was obtained in the same manner as in Example 2, except that film A'1 was used.

[0085] <Example 4> 1. Preparation of adhesive composition In the adhesive composition preparation process of Example 1, 1,3-diphenylcarbodiimide was replaced with poly(1,3,5-triisopropylbenzene)polycarbodiimide (number average molecular weight 3,500), and the amount added was changed to 4 parts by mass (solid content) to obtain adhesive composition B3.

[0086] 2. Preparation of adhesive sheets Adhesive composition B3 was applied to a release liner so that its thickness after drying was 20 μm, and dried at 90°C for 1 minute to form adhesive layer B3'. Adhesive layer B3' was laminated to film A1 prepared in the same manner as in Example 1, and then left to stand for 7 days at 23°C and 50% RH to obtain adhesive sheet 4.

[0087] <Comparative Example 1> In the adhesive composition preparation process of Example 1, 1,3-diphenylcarbodiimide was not added to obtain adhesive composition B4. Adhesive composition B4 was applied to a release liner so that the thickness after drying was 20 μm, and dried at 90°C for 1 minute to form adhesive layer B4'. Adhesive layer B4' was laminated to film A1, and then left to stand for 7 days at 23°C and 50% RH to obtain adhesive sheet 5.

[0088] <Comparative Example 2> 100 parts by mass of polylactic acid resin (weight-average molecular weight 180,000, D-lactic acid:L-lactic acid = 1.5:98.5 (molar ratio)) and 1 part by mass of poly(dicyclohexylmethanecarbodiimide) (number-average molecular weight 2,000) were kneaded at 230°C to obtain a polyester resin composition. The obtained resin composition was extruded using a T-die film-making machine at a film-making temperature of 230°C to obtain a film A2 with a thickness of 100 μm.

[0089] The adhesive layer B1' obtained in the same manner as in Example 1 was laminated with film A2, and then left to stand for 7 days at 23°C and 50% RH to obtain adhesive sheet 6.

[0090] <Evaluation Method> • Evaluation of resistance to moisture and heat The adhesive sheets of the examples and comparative examples were attached to stainless steel plates and left to stand for 3 months at 40°C and 80% RH before their appearance was examined.

[0091] ○...No cracks in the film △...There are minor, acceptable cracks in the film. ×...Cracks in the film

[0092] [Table 1]

[0093] From the results above, it can be seen that the adhesive sheet of the example has higher durability than the adhesive sheet of the comparative example. [Explanation of Symbols]

[0094] 10 adhesive sheets, 11 base material, 12 Adhesive layer, 13. Release liner.

Claims

1. A substrate formed from a resin composition containing a polybutylene succinate resin, a polylactic acid resin, and a carbodiimide compound, and The adhesive layer comprises an adhesive composition comprising a carbodiimide compound, at least one crosslinking agent selected from the group consisting of aromatic isocyanate compounds and metal chelate compounds, and an adhesive having a functional group that can react with the crosslinking agent. An adhesive sheet in which the mass percentage of the carbodiimide compound contained in the adhesive composition is greater than the mass percentage of the carbodiimide compound contained in the resin composition.

2. The adhesive sheet according to claim 1, wherein the content of the carbodiimide compound in the adhesive composition is 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the adhesive.

3. The adhesive sheet according to claim 1 or 2, wherein the content of the polybutylene succinate resin and the polylactic acid resin is such that the ratio of the polybutylene succinate resin to the polylactic acid resin is 20:1 to 1:5 (by mass).

4. The adhesive sheet according to any one of claims 1 to 3, wherein the amount of the carbodiimide compound contained in the resin composition is 5 parts by mass or less per 100 parts by mass of the resin contained in the resin composition.

5. The adhesive sheet according to any one of claims 1 to 4, wherein the content of the polybutylene succinate resin in the resin composition is 30% by mass or more.

6. The adhesive sheet according to any one of claims 1 to 5, wherein the adhesive is a urethane resin.

7. A process to obtain a substrate by melt extrusion of a resin composition containing a polybutylene succinate resin, a polylactic acid resin, and a carbodiimide compound, A step of forming an adhesive layer from an adhesive composition comprising a carbodiimide compound, at least one crosslinking agent selected from the group consisting of aromatic isocyanate compounds and metal chelate compounds, and an adhesive having a functional group that can react with the crosslinking agent, It has, A method for producing an adhesive sheet, wherein the mass percentage of the carbodiimide compound contained in the adhesive composition is greater than the mass percentage of the carbodiimide compound contained in the resin composition.

Images