Biodegradable acid-modified polyester resin and laminate

Abstract

To provide a biodegradable acid-modified polyester resin, from which a laminate comprising a polyvinyl alcohol resin layer and a biodegradable resin layer can be obtained that has little roughness at an adhesive layer interface between the two layers and is excellent in both appearance and adhesiveness.SOLUTION: A biodegradable acid-modified polyester resin has an acid value of 3.0-6.5 mg KOH / g, and comprises at least one structural unit selected from structural units represented by the general formula (1) in the figure, structural units represented by the general formula (2) in the figure, and structural units represented by the general formula (3), -[C(O)-(CH2)n-O]-, in a total amount of 50 mol% or more. In the formulas, l, m and n are integers from 2 to 6.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a biodegradable acid-modified polyester resin, more specifically to a biodegradable acid-modified polyester resin that is preferably used as an adhesive layer between a polyvinyl alcohol resin layer (hereinafter, polyvinyl alcohol will be referred to as "PVA") and a biodegradable resin layer such as polylactic acid. The present invention also relates to a laminate having a layer containing the biodegradable acid-modified polyester resin. [Background technology]

[0002] Plastics are widely used as packaging materials because of their excellent moldability, strength, water resistance, transparency, etc. Examples of plastics used in such packaging materials include polyolefin resins such as polyethylene and polypropylene, vinyl resins such as polystyrene and polyvinyl chloride, and aromatic polyester resins such as polyethylene terephthalate. However, these plastics are poorly biodegradable, and if discarded in the natural environment after use, they may remain for a long time, damaging the landscape and causing environmental destruction.

[0003] In response to this, biodegradable resins that biodegrade or hydrolyze in soil or water and are useful for preventing environmental pollution have recently attracted attention and are being put to practical use. Examples of such biodegradable resins include aliphatic polyester resins, cellulose acetate, and modified starch. As packaging materials, polylactic acid, condensation polymers of adipic acid / terephthalic acid / 1,4-butanediol, and condensation polymers of succinic acid / 1,4-butanediol / lactic acid are used because of their excellent transparency, heat resistance, and strength.

[0004] However, aliphatic polyester resins such as polylactic acid have insufficient oxygen gas barrier properties and therefore cannot be used alone as packaging materials for contents that may be subject to oxidative deterioration, such as food and medicines.

[0005] Therefore, a laminate has been proposed in which a coating layer made of PVA, which has excellent gas barrier properties and is biodegradable, is formed on at least one surface of a polylactic acid film (see, for example, Patent Document 1).

[0006] Furthermore, a biodegradable laminate has been proposed that uses a melt-moldable PVA resin, making it possible to perform co-extrusion lamination and even stretching treatment. The biodegradable laminate has a gas barrier layer, the main component of which is a PVA resin having a 1,2-diol structure in its side chain, sandwiched on both sides by aliphatic polyester layers whose melting point differs from that of the gas barrier layer by 20°C or less (see, for example, Patent Document 2).

[0007] However, since the surface properties of the polylactic acid resin layer and the PVA resin layer are significantly different, the two layers have poor adhesion, making it difficult to obtain practical interlayer adhesive strength by directly laminating the two layers. For example, Patent Document 1 proposes surface activation treatments for polylactic acid films, such as corona discharge treatment, flame treatment, and ozone treatment, as well as anchor coating treatment, but these are still not satisfactory and there is room for improvement.

[0008] In addition, in Patent Document 2, although the interlayer adhesion between the polylactic acid-based resin layer and the PVA-based resin layer is improved somewhat by co-extrusion lamination, it is still insufficient for practical use.

[0009] Therefore, to obtain good interlayer adhesion between the polylactic acid-based resin layer and the PVA-based resin layer, it is necessary to provide an adhesive layer between the two layers. Furthermore, to take advantage of the biodegradability of the polylactic acid-based resin and the PVA-based resin, the adhesive layer used in the laminate containing them must also be biodegradable.

[0010] In view of these circumstances, it has been proposed to use a polyester resin having polar groups, obtained by graft polymerizing an α,β-unsaturated carboxylic acid or its anhydride onto a biodegradable polyester resin, as an adhesive layer (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2000-177072 [Patent Document 2] Japanese Patent Publication No. 2009-196287 [Patent Document 3] Japanese Patent Application Publication No. 2013-212682 Summary of the Invention [Problem to be solved by the invention]

[0012] However, the technology of Patent Document 3 has a problem in that when a laminate is produced using a feedblock multilayer extruder, poor appearance occurs due to roughness of the adhesive layer interface.

[0013] Therefore, under such circumstances, an object of the present invention is to provide a biodegradable acid-modified polyester-based resin that, when used as an adhesive layer for both layers in a laminate containing, for example, a PVA-based resin layer and a biodegradable resin layer, can give a laminate having high transparency at the adhesive layer interface and excellent both in appearance and adhesiveness. [Means for solving the problem]

[0014] However, after extensive research, the inventors of the present invention have discovered that the above problems can be solved by using a biodegradable acid-modified polyester resin that has a lower acid value than conventional acid-modified polyester resins.

[0015] That is, the present invention provides the following: <1> ~ <6> Regarding. <1> A biodegradable acid-modified polyester resin with an acid value of 2.0 to 6.5 mg KOH / g. <2> Having at least one structural unit selected from structural units represented by the following general formulas (1) to (3): <1> 1. The biodegradable acid-modified polyester resin according to claim 1.

[0016] [ka]

[0017] [In formula (1), l is an integer of 2 to 6.]

[0018] [ka]

[0019] [In formula (2), m is an integer of 2 to 6.]

[0020] [ka]

[0021] (In formula (3), n is an integer of 2 to 6.) <3> A biodegradable polyester resin obtained by graft polymerizing an α,β-unsaturated carboxylic acid or an anhydride thereof. <1> or <2> 1. The biodegradable acid-modified polyester resin according to claim 1. <4> The composition contains at least one structural unit selected from the structural units represented by the general formulas (1) to (3) in a total amount of 50 mol % or more. <2> 1. The biodegradable acid-modified polyester resin according to claim 1. <5> <1> ~ <4> 1. A laminate having at least one layer containing the biodegradable acid-modified polyester resin according to any one of 1 to 8. <6> A laminate having an adhesive layer provided between a polyvinyl alcohol-based resin (B) layer and a biodegradable resin (C) layer, wherein the adhesive layer is <1> ~ <4> 1. A laminate comprising the biodegradable acid-modified polyester resin according to any one of 1 to 8. [Effects of the Invention]

[0022] When the biodegradable acid-modified polyester resin of the present invention is used, for example, as an adhesive layer for both a PVA-based resin layer and a biodegradable resin layer in a laminate containing both layers, a laminate having high transparency at the adhesive layer interface and excellent appearance and adhesiveness can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0023] The configuration of the present invention will be described in detail below, but these are merely examples of preferred embodiments. In this specification, "mass" is synonymous with "weight."

[0024] In addition, in this specification, "biodegradable" means meeting the conditions specified in JIS K 6950:2000 (ISO 14851:1999).

[0025] [Biodegradable acid-modified polyester resin (A)] The biodegradable acid-modified polyester resin (A) of the present invention is characterized by having an acid value of 2.0 to 6.5 mg·KOH / g.

[0026] If the acid value of the biodegradable acid-modified polyester resin (A) of the present invention is less than 2.0 mg KOH / g, the amount of polar groups contained in the polyester resin (A) will be reduced, which will weaken the attractive force between the polyester resin (A) and other resins, and the adhesiveness between the polyester resin (A) and other resins will tend to decrease.

[0027] If the acid value of the biodegradable acid-modified polyester resin (A) of the present invention is greater than 6.5 mg·KOH / g, the decomposition of the polyester resin by the acid component tends to proceed more easily.

[0028] When the biodegradable acid-modified polyester resin (A) of the present invention decomposes, viscosity unevenness occurs due to the decomposition, making it difficult to obtain a uniform layer, and as a result, the appearance of the laminate having a layer containing the polyester resin (A) is poor. Therefore, it is presumed that the effects of the present invention can be achieved by suppressing the decomposition of the polyester resin (A) by adjusting the acid value.

[0029] From the viewpoint of the appearance and adhesiveness of the laminate, the acid value is preferably 2.5 to 6.0 mg·KOH / g, more preferably 3.0 to 5.5 mg·KOH / g, and particularly preferably 3.5 to 5.0 mg·KOH / g.

[0030] The method for measuring the acid value is described in detail below. First, the biodegradable acid-modified polyester resin (A) to be measured is thoroughly washed with a solvent. Such washing is performed to wash away impurities in the biodegradable acid-modified polyester resin (A), mainly unreacted α,β-unsaturated carboxylic acid or its anhydride.

[0031] As such a solvent, it is necessary to use a solvent in which the biodegradable acid-modified polyester resin (A) does not dissolve, and examples thereof include water, acetone, methanol, ethanol, and isopropanol.

[0032] Next, 100 ml of tetrahydrofuran is placed in a test bottle as a solvent, and 5 g of biodegradable acid-modified polyester resin (A) is added while stirring with a hot stirrer (set temperature 75°C, stirrer rotation speed 750 rpm). Stir for 5 to 6 hours until the biodegradable acid-modified polyester resin (A) is dissolved. After dissolution, 4 ml of ultrapure water is added and stirred for an additional 10 minutes to prepare the test solution. This test solution is titrated with an aqueous potassium hydroxide solution (N / 10) using the automatic titrator described below, and the acid value is calculated using the following formula.

[0033]

number

[0034] A = Amount (ml) of potassium hydroxide aqueous solution (N / 10) required to neutralize biodegradable acid-modified polyester resin (A) B = Amount of potassium hydroxide solution (N / 10) required for blank test (ml) f = Potassium hydroxide solution (N / 10) S = Amount (g) of biodegradable acid-modified polyester resin (A) collected

[0035] Titrator Titration measuring device: Automatic potentiometric titration device AT-610 manufactured by Kyoto Electronics Industry Co., Ltd. Reference electrode: Composite glass electrode C-171 Titrant: Kishida Chemical potassium hydroxide aqueous solution (N / 10)

[0036] In order to set the acid value within the above specific range, for example, the following method can be mentioned. (i) A method of adjusting the amount of a radical initiator when graft polymerizing an α,β-unsaturated carboxylic acid or an anhydride thereof onto the biodegradable acid-modified polyester resin (A). (ii) A method in which the biodegradable acid-modified polyester resin (A) is dried to reduce the water absorption rate. Among these, method (i) is preferred because of the ease of controlling the acid value.

[0037] The biodegradable acid-modified polyester resin (A) of the present invention preferably has at least one structural unit selected from the structural units represented by the following general formulas (1) to (3).

[0038] [ka]

[0039] [In formula (1), l is an integer of 2 to 6, preferably an integer of 3 to 5.]

[0040] [ka]

[0041] [In formula (2), m is an integer of 2 to 6, and preferably an integer of 3 to 5.]

[0042] [ka]

[0043] [In formula (3), n is an integer of 2 to 6, and preferably an integer of 3 to 5.]

[0044] From the viewpoint of ease of biodegradability, the biodegradable acid-modified polyester resin (A) of the present invention is preferably composed of at least one structural unit selected from the structural units represented by the above general formulas (1) to (3), but may contain other structural units for the purpose of controlling heat resistance, strength, biodegradability, etc.

[0045] The total content of at least one structural unit selected from the structural units represented by the general formulae (1) to (3) is usually 50 mol % or more, preferably 70 mol % or more, and more preferably 90 mol % or more.

[0046] When the biodegradable acid-modified polyester resin (A) of the present invention has at least one structural unit selected from the structural units represented by the above general formulas (1) to (3), it can be obtained by condensation polymerization of at least one selected from the group consisting of aliphatic dicarboxylic acids, aliphatic diol compounds, and other components by a known method, and further acid-modifying the polymer.

[0047] Examples of the aliphatic dicarboxylic acid include succinic acid, glutaric acid, adipic acid, 1,5-pentanedicarboxylic acid, and 1,6-hexanedicarboxylic acid, with adipic acid being particularly preferred from the standpoint of moldability and flexibility.

[0048] Examples of the aliphatic diol compound include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol, with 1,4-butanediol being particularly preferred from the standpoint of moldability and flexibility.

[0049] Specific examples of other components include hydroxy acids such as 4-hydroxybutyric acid, 5-hydroxyvaleric acid, and 6-hydroxyhexanoic acid; those derived from aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid; those derived from dicarboxylic acids having less than two alkylene chains such as oxalic acid and malonic acid; those derived from hydroxycarboxylic acids having less than two alkylene chains such as glycolic acid and lactic acid; and other components known as copolymerization components for polyester resins.

[0050] The weight-average molecular weight of the biodegradable acid-modified polyester resin (A) of the present invention is usually 5,000 to 50,000, preferably 5,500 to 40,000, and particularly preferably 6,000 to 30,000. If the weight-average molecular weight is too large, the melt viscosity tends to increase, making melt molding difficult, while if the weight-average molecular weight is too small, the molded product tends to be brittle.

[0051] The weight-average molecular weight is the weight-average molecular weight converted into the molecular weight of standard polystyrene, and is measured using a high-performance liquid chromatograph (manufactured by Tosoh Corporation, "HLC-8320GPC") with two columns: TSKgel SuperMultipore HZ-M (exclusion limit molecular weight: 2 × 106, number of theoretical plates: 16,000 plates / column, packing material: styrene-divinylbenzene copolymer, packing particle size: 4 μm) connected in series.

[0052] The biodegradable acid-modified polyester resin (A) of the present invention is obtained by graft polymerizing an α,β-unsaturated carboxylic acid or its anhydride (hereinafter, the α,β-unsaturated carboxylic acid or its anhydride may be referred to as "α,β-unsaturated carboxylic acids") onto the raw material biodegradable polyester resin (A'), and the biodegradable acid-modified polyester resin (A) has good adhesive properties.

[0053] Specific examples of α,β-unsaturated carboxylic acids include α,β-unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; and α,β-unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citrus acid, tetrahydrophthalic acid, crotonic acid, and isocrotonic acid, or anhydrides thereof, and preferably, anhydrides of α,β-unsaturated dicarboxylic acids are used.

[0054] These α,β-unsaturated carboxylic acids may be used not only as a single type but also as a combination of two or more types.

[0055] The method for graft polymerizing the α,β-unsaturated carboxylic acid to the raw material biodegradable polyester resin (A') is not particularly limited, and known methods can be used. Although thermal reaction alone is also possible, it is preferable to use a radical initiator to enhance reactivity. Furthermore, reaction methods include solution reaction, reaction as a suspension, and reaction in a molten state without using a solvent (melt method), among which the melt method is preferred.

[0056] Commercially available biodegradable polyester resin (A') as a raw material includes, for example, "Ecoflex" manufactured by BASF, which is mainly composed of a condensation polymer of adipic acid / terephthalic acid / 1,4-butanediol, and "GS-PLA" manufactured by Mitsubishi Chemical Corporation, which is mainly composed of a condensation polymer of succinic acid / 1,4-butanediol / lactic acid.

[0057] The melting method will be described in detail below. As the melting method, a method in which the raw material biodegradable polyester resin (A'), α,β-unsaturated carboxylic acids, and radical initiator are mixed in advance and then melt-kneaded in a kneader to cause a reaction, or a method in which the α,β-unsaturated carboxylic acids and radical initiator are added to the biodegradable polyester resin (A') in a molten state in a kneader can be used.

[0058] Examples of mixers that can be used when premixing the raw materials include a Henschel mixer and a ribbon blender. Examples of kneaders that can be used for melt kneading include a single-screw or twin-screw extruder, a roll, a Banbury mixer, a kneader, and a Brabender mixer.

[0059] The temperature during melt-kneading may be set appropriately within a temperature range that is equal to or higher than the melting point of the raw material biodegradable polyester resin (A') and does not cause thermal degradation, preferably 100 to 250°C, more preferably 160 to 220°C.

[0060] The amount of α,β-unsaturated carboxylic acid is usually 0.0001 to 5 parts by weight, preferably 0.001 to 1 part by weight, and especially 0.02 to 0.45 parts by weight, per 100 parts by weight of the raw material biodegradable polyester resin (A'). If the amount is too small, a sufficient number of polar groups will not be introduced into the biodegradable polyester resin (A'), and interlayer adhesion, particularly adhesion to the PVA resin layer, tends to be insufficient. On the other hand, if the amount is too large, ungrafted α,β-unsaturated carboxylic acid may remain in the resin, which tends to result in poor appearance and the like.

[0061] The radical initiator is not particularly limited, and known radical initiators can be used. Examples thereof include organic or inorganic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-bis(t-butyloxy)hexane, 3,5,5-trimethylhexanoyl peroxide, t-butyl peroxybenzoate, benzoyl peroxide, m-toluoyl peroxide, dicumyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, dibutyl peroxide, methyl ethyl ketone peroxide, potassium peroxide, and hydrogen peroxide; azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis(isobutylamido)dihalide, 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and azodi-t-butane; and carbon radical generators such as dicumyl. These may be used alone or in combination of two or more.

[0062] The amount of the radical initiator to be added is usually 0.00001 to 0.5 parts by weight, particularly 0.0001 to 0.1 parts by weight, and especially 0.002 to 0.05 parts by weight, per 100 parts by weight of the raw material biodegradable polyester resin (A').

[0063] If the amount of such radical initiator is too small, graft polymerization may not occur sufficiently, and the effects of the present invention may not be obtained. If the amount of such radical initiator is too large, the biodegradable polyester resin may be decomposed to lower its molecular weight, and the adhesive strength may tend to be insufficient due to insufficient cohesive force.

[0064] [PVA resin (B) layer] The PVA-based resin (B) layer is preferably used as a gas barrier layer of the laminate of the present invention, which will be described later, and particularly preferably contributes to the gas barrier properties of the laminate of the present invention. The PVA-based resin (B) layer is preferably laminated to the biodegradable resin (C) layer described later on at least one side thereof via a layer (adhesive layer) containing the biodegradable acid-modified polyester-based resin (A) described above.

[0065] The PVA resin (B) layer used in the present invention is a layer containing the PVA resin (B) as the main component, and typically contains 70% by weight or more of the PVA resin (B), preferably 80% by weight or more, and more preferably 90% by weight or more. The upper limit is 100% by weight. If the content is too low, the gas barrier properties tend to be insufficient.

[0066] The PVA resin (B) used in the present invention is a resin mainly composed of vinyl alcohol structural units, which is obtained by saponifying a polyvinyl ester resin obtained by polymerizing a vinyl ester monomer, and is composed of vinyl alcohol structural units and vinyl ester structural units in amounts corresponding to the degree of saponification.

[0067] Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl versatate, with vinyl acetate being economically preferred.

[0068] The average degree of polymerization (measured in accordance with JIS K6726) of the PVA resin (B) used in the present invention is usually 200 to 1800, particularly 300 to 1500, and particularly preferably 300 to 1000.

[0069] If the average degree of polymerization is too low, the mechanical strength of the PVA resin (B) layer tends to be insufficient, whereas if the average degree of polymerization is too high, the flowability and moldability tend to decrease when the PVA resin (B) layer is formed by hot melt molding, and abnormal shear heat may occur during molding, making the PVA resin (B) susceptible to thermal decomposition.

[0070] The saponification degree (measured in accordance with JIS K6726) of the PVA resin (B) used in the present invention is usually 80 to 100 mol %, particularly 90 to 99.9 mol %, and particularly preferably 98 to 99.9 mol %. If the degree of saponification is too low, the gas barrier properties tend to decrease.

[0071] In addition, in the present invention, as the PVA-based resin (B), it is possible to use those obtained by copolymerizing various monomers during the production of a polyvinyl ester-based resin and then saponifying the copolymer, or various modified PVA-based resins obtained by introducing various functional groups into unmodified PVA by post-modification.

[0072] Examples of monomers used for copolymerization with vinyl ester monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, and 3,4-dihydroxy-1-butene, as well as derivatives thereof such as acylated products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, as well as salts thereof, monoesters thereof, and dialkyl esters thereof; nitriles such as acrylonitrile and methacrylonitrile; and diacetone acrylate. Examples of suitable vinyl acetates include amides such as olefin sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, and salts thereof; alkyl vinyl ethers, dimethyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, and 3,4-diacetoxy-1-butene; substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate; vinylidene chloride, 1,4-diacetoxy-2-butene, and vinylene carbonate.

[0073] In addition, examples of modified PVA-based resins into which functional groups have been introduced by post-modification include those having acetoacetyl groups through reaction with diketene, those having polyalkylene oxide groups through reaction with ethylene oxide, those having hydroxyalkyl groups through reaction with epoxy compounds, and those obtained by reacting PVA with aldehyde compounds having various functional groups.

[0074] The content of modified species in such modified PVA-based resins, i.e., structural units derived from various monomers in the copolymer or functional groups introduced by post-reaction, cannot be generalized because the properties vary greatly depending on the modified species, but is usually 1 to 20 mol %, and a range of 2 to 10 mol % is particularly preferred.

[0075] Among these various modified PVA resins, in the present invention, a PVA resin having a structural unit having a 1,2-diol structure in a side chain, as represented by the following general formula (4) (hereinafter, sometimes referred to as a "1,2-diol structural unit"), is preferably used because it facilitates melt molding in the method for producing the laminate of the present invention described below.

[0076] [ka]

[0077] In addition, R in the 1,2-diol structural unit represented by the general formula (4) 1 ~R 4 each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.

[0078] Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. The alkyl group may have a functional group such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group, as necessary.

[0079] Furthermore, X in the 1,2-diol structural unit represented by general formula (4) represents a single bond or a bonding chain. Examples of such a bonding chain include hydrocarbons such as linear or branched alkylene groups having 1 to 6 carbon atoms, linear or branched alkenylene groups having 1 to 6 carbon atoms, linear or branched alkynylene groups having 1 to 6 carbon atoms, phenylene groups, and naphthylene groups (these hydrocarbons may be substituted with halogens such as fluorine, chlorine, and bromine), as well as -O-, -(CHO) t -, -(OCH2) t -, -(CHO) t CH2-, -CO-, -COCO-, -CO(CH2) t Examples thereof include CO-, -CO(CH)CO-, -S-, -CS-, -SO-, -SO-, -NR-, -CONR-, -NRCO-, -CSNR-, -NRCS-, -NRNR-, -HPO-, -Si(OR)-, -OSi(OR)-, -OSi(OR)O-, -Ti(OR)-, -OTi(OR)-, -OTi(OR)O-, -Al(OR)-, -OAl(OR)-, -OAl(OR)O- and the like (each R independently represents an arbitrary substituent and is a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and t is an integer of 1 to 5). Among these, from the viewpoint of stability during production or use, the linking chain is preferably a linear or branched alkylene group having 1 to 6 carbon atoms, particularly a methylene group, or -CH2OCH2-.

[0080] X is most preferably a single bond in terms of thermal stability and stability at high temperatures and under acidic conditions.

[0081] Among the 1,2-diol structural units represented by general formula (4), R 1 ~R 4 A structural unit represented by the following general formula (4'), in which all of are hydrogen atoms and X is a single bond, is most preferred.

[0082] [ka]

[0083] Examples of a method for producing such a PVA resin having a 1,2-diol structural unit in the side chain include the method described in paragraphs

[0026] to

[0034] of JP 2015-143356 A.

[0084] The content of 1,2-diol structural units contained in such PVA-based resins having 1,2-diol structural units in the side chains is usually 1 to 20 mol %, preferably 2 to 10 mol %, and particularly preferably 3 to 8 mol %. If the content is too low, it is difficult to obtain the effects of the 1,2-diol structure in the side chains, and conversely, if the content is too high, there is a tendency for the gas barrier properties at high humidity to deteriorate significantly.

[0085] The content of 1,2-diol structural units in PVA resin is the same as that of a completely saponified PVA resin. 1 The content can be determined from H-NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane). Specifically, the content can be calculated from the peak areas derived from hydroxyl group protons, methine protons, and methylene protons in the 1,2-diol structural unit, methylene protons in the main chain, and protons of hydroxyl groups linked to the main chain.

[0086] The PVA resin (B) used in the present invention may be a single type or a mixture of two or more types. When the PVA resin (B) is a mixture of two or more types, the following combinations may be used: the unmodified PVAs described above; the unmodified PVA and a PVA resin having a structural unit represented by general formula (4); the PVA resins having structural units represented by general formula (4) with different degrees of saponification, polymerization, modification, etc.; the unmodified PVA; or the PVA resin having a structural unit represented by general formula (4) and another modified PVA resin.

[0087] The PVA resin (B) layer used in the present invention may contain, in addition to the PVA resin (B), a heat stabilizer, an antioxidant, an ultraviolet absorber, a crystal nucleating agent, an antistatic agent, a flame retardant, a plasticizer, a lubricant, a filler, a lubricant, or a crystal nucleating agent.

[0088] [Biodegradable resin (C) layer] Next, the biodegradable resin (C) layer preferably used as the outer layer of the laminate of the present invention will be described below. The biodegradable resin (C) layer is a layer containing biodegradable resin (C) as the main component, and usually contains 70% by weight or more of biodegradable resin (C), preferably 80% by weight or more, and more preferably 90% by weight or more. The upper limit is 100% by weight.

[0089] Examples of biodegradable resins (C) include aliphatic polyesters such as polylactic acid (C1), condensation polymers of adipic acid / terephthalic acid / 1,4-butanediol (polybutylene adipate terephthalate (C2)), condensation polymers of succinic acid / 1,4-butanediol / lactic acid, and polyglycolic acid; modified starch; casein plastic; and cellulose, which may be used singly or in combination.

[0090] Among them, polylactic acid (C1) and polybutylene adipate terephthalate (C2) are preferred in terms of strength, and a mixture (C3) of polylactic acid (C1) and polybutylene adipate terephthalate (C2) is more preferred in terms of adhesiveness and strength.

[0091] Polylactic acid (C1) is an aliphatic polyester resin whose main component is a lactic acid structural unit, and is a polymer made from L-lactic acid, D-lactic acid, or its cyclic dimers, L-lactide, D-lactide, and DL-lactide.

[0092] The polylactic acid (C1) used in the present invention is preferably a homopolymer of these lactic acids, but may contain copolymer components other than lactic acids in an amount that does not impair the properties, for example, 10 mol % or less.

[0093] Examples of such copolymerization components include aliphatic hydroxycarboxylic acids such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid; lactones such as caprolactone; aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, and 1,4-butanediol; and aliphatic dibasic acids such as succinic acid, oxalic acid, malonic acid, glutaric acid, and adipic acid.

[0094] The ratio of L-lactic acid to D-lactic acid in polylactic acid (C1) (weight of L-lactic acid / weight of D-lactic acid) is usually 95 / 5 or more, particularly 99 / 1 or more, and particularly 99.8 / 0.2 is preferably used. The larger this value, the higher the melting point and the improved heat resistance. Conversely, the smaller this value, the lower the melting point and the less heat resistance there is.

[0095] Specifically, in the case of a homopolymer of polylactic acid (C1), the melting point of one with the above content ratio of 95 / 5 is 152°C, the melting point of one with the content ratio of 99 / 1 is 171°C, and the melting point of one with the content ratio of 99.8 / 0.2 is 175°C or higher.

[0096] The weight-average molecular weight of the polylactic acid (C1) used in the present invention is usually 20,000 to 1,000,000, preferably 30,000 to 300,000, and especially preferably 40,000 to 200,000. If the weight-average molecular weight is too large, the melt viscosity during hot melt molding tends to be too high, making it difficult to form a good film. Conversely, if the weight-average molecular weight is too small, the mechanical strength of the resulting laminate tends to be insufficient.

[0097] Such weight average molecular weight can be measured by size exclusion chromatography (GPC, gel permeation chromatography) as polystyrene equivalents according to ISO 16014-1 and ISO 16014-3 standards using tetrahydrofuran as eluent and a column (polystyrene gel) heated to 40°C.

[0098] Examples of commercially available polylactic acid (C1) include "Ingeo" manufactured by NatureWorks, "Lacea" manufactured by Mitsui Chemicals, Inc., "REVODE" manufactured by Zhejiang Haizheng Biomaterials Co., Ltd., and "Vyloecol" manufactured by Toyobo Co., Ltd.

[0099] Polybutylene adipate terephthalate (C2) is obtained by polycondensation of adipic acid, terephthalic acid, and 1,4-butanediol.

[0100] The content of adipic acid in the polybutylene adipate terephthalate (C2) is usually 10 to 50 mol %, preferably 15 to 40 mol %. The content of terephthalic acid in the polybutylene adipate terephthalate (C2) is usually 5 to 45 mol %, preferably 8 to 35 mol %. The content of 1,4-butanediol in the polybutylene adipate terephthalate (C2) is usually 5 to 45 mol %, preferably 10 to 30 mol %. If the content of each component is too high or too low, the workability and corrosion resistance tend to decrease.

[0101] The weight average molecular weight of the polybutylene adipate terephthalate (C2) is 3,000 to 1,000,000, preferably 20,000 to 600,000, and more preferably 50,000 to 400,000.

[0102] Such weight average molecular weight can be measured by size exclusion chromatography (GPC, gel permeation chromatography) as polystyrene equivalents according to ISO 16014-1 and ISO 16014-3 standards using tetrahydrofuran as eluent and a column (polystyrene gel) heated to 40°C.

[0103] If the weight average molecular weight is too small, production becomes difficult, whereas if the weight average molecular weight is too large, the melt viscosity increases and moldability tends to decrease.

[0104] Polybutylene adipate terephthalate (C2) may contain other copolymerization components in addition to adipic acid, terephthalic acid, and 1,4-butanediol.

[0105] Other copolymerization components include, for example, dihydroxy compounds such as diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, and polytetrahydrofuran (poly-THF); glycolic acid, D-lactic acid, L-lactic acid, D,L-lactic acid, 6-hydroxyhexanoic acid, and cyclic derivatives thereof such as glycolide (1,4-dioxane-2,5-dione), D-dilactide, and L-dilactide (3,6-dimethyl-1,4-dioxane-2,5-dione); and hydroxycarboxylic acids such as p-hydroxybenzoic acid and oligomers and polymers of p-hydroxybenzoic acid.

[0106] The content of such other copolymerization components is about 0.1 to 30 mol % of the entire polybutylene adipate terephthalate (C2).

[0107] Alternatively, a mixture (C3) of polylactic acid (C1) and polybutylene adipate terephthalate (C2) can be used. The mixing ratio of polylactic acid / polybutylene adipate terephthalate (weight ratio) is 10 / 90 to 90 / 10, preferably 20 / 80 to 60 / 40.

[0108] In addition, the biodegradable resin (C) layer used in the present invention may contain, in addition to the biodegradable resin (C), a heat stabilizer, an antioxidant, an ultraviolet absorber, a crystal nucleating agent, an antistatic agent, a flame retardant, a plasticizer, a lubricant, a filler, a lubricant, a crystal nucleating agent, etc.

[0109] [Laminate] The laminate of the present invention has at least one layer containing the biodegradable acid-modified polyester resin (A) of the present invention (hereinafter, sometimes referred to as "biodegradable acid-modified polyester resin (A) layer").

[0110] The biodegradable acid-modified polyester resin (A) layer is a layer containing the biodegradable acid-modified polyester resin (A) as the main component, and typically contains 70% by weight or more of the biodegradable acid-modified polyester resin (A), preferably 80% by weight or more, and more preferably 90% by weight or more, with the upper limit being 100% by weight.

[0111] The biodegradable acid-modified polyester resin (A) layer used in the present invention may contain, in addition to the biodegradable acid-modified polyester resin (A), a heat stabilizer, an antioxidant, an ultraviolet absorber, a crystal nucleating agent, an antistatic agent, a flame retardant, a plasticizer, a lubricant, a filler lubricant, a crystal nucleating agent, etc.

[0112] The laminate of the present invention preferably has a biodegradable resin (C) layer as a layer other than the biodegradable acid-modified polyester resin (A) layer. In particular, the laminate of the present invention is preferably one in which a PVA resin (B) layer is used as the gas barrier layer and a biodegradable resin (C) layer is used as the outer layer.

[0113] The laminate of the present invention is a laminate having an adhesive layer between a PVA resin (B) layer and a biodegradable resin (C) layer, and the adhesive layer preferably contains the biodegradable acid-modified polyester resin (A) of the present invention, and has a layer structure of usually 3 to 15 layers, preferably 3 to 7 layers, and particularly preferably 5 to 7 layers.

[0114] The configuration of the laminate of the present invention is not particularly limited, but any combination is possible, such as c / a / b, c / a / b / a / c, or c / b / a / b / a / b / c, where c is the biodegradable resin (C) layer, b is the PVA-based resin (B) layer, and a is the biodegradable acid-modified polyester-based resin (A) layer (adhesive layer). When multiple biodegradable resin (C) layers are present in the laminate, the multiple biodegradable resin (C) layers may be the same or different. The same applies when multiple PVA-based resin (B) layers and multiple biodegradable acid-modified polyester-based resin (A) layers are present in the laminate.

[0115] In order to prevent deterioration of the gas barrier performance due to moisture absorption by the PVA-based resin (B) layer, it is usually preferable to provide a layer of biodegradable resin (C) in the part of the PVA-based resin (B) layer that comes into contact with the outside air or the contents containing moisture.

[0116] The thickness of the laminate of the present invention is usually 1 to 30,000 μm, and is preferably in the range of 3 to 13,000 μm, and particularly preferably 10 to 3,000 μm.

[0117] Furthermore, with regard to the thickness of each layer constituting the laminate, the thickness of the biodegradable resin (C) layer is usually 0.4 to 14,000 μm, preferably 1 to 6,000 μm, and particularly preferably 4 to 1,400 μm. If the thickness of the biodegradable resin (C) layer is too thick, the laminate tends to be too hard, and conversely, if the thickness of the biodegradable resin (C) layer is too thin, the laminate tends to be brittle.

[0118] The thickness of the PVA resin (B) layer is usually 0.1 to 1,000 μm, preferably 0.3 to 500 μm, and particularly preferably 1 to 100 μm. If the PVA resin (B) layer is too thick, the laminate tends to be hard and brittle, whereas if the PVA resin (B) layer is too thin, the gas barrier properties tend to be poor.

[0119] The thickness of the biodegradable acid-modified polyester resin (A) layer (adhesive layer) is usually 0.1 to 500 μm, preferably 0.15 to 250 μm, and particularly preferably 0.5 to 50 μm. If the thickness of the biodegradable acid-modified polyester resin (A) layer is too thick, the appearance may be poor, and conversely, if the thickness of the biodegradable acid-modified polyester resin (A) layer is too thin, the adhesive strength tends to be weak.

[0120] Furthermore, when there are multiple layers of each type, the ratio of the thickness of the biodegradable resin (C) layer to the thickness of the PVA-based resin (B) layer (thickness of biodegradable resin (C) layer / thickness of PVA-based resin (B) layer) is the ratio of the total thicknesses of those layers and is usually 1 to 100, preferably 2.5 to 50. If this ratio is too large, the barrier properties tend to be reduced, and if this ratio is too small, the laminate tends to be hard and brittle.

[0121] Furthermore, the thickness ratio of the laminate of the present invention to the biodegradable acid-modified polyester resin (A) layer (adhesive layer) (thickness of biodegradable acid-modified polyester resin (A) layer / thickness of the laminate of the present invention), which is the ratio of the total thickness of multiple biodegradable acid-modified polyester resin (A) layers (adhesive layers), is usually 0.005 to 0.5, and preferably 0.01 to 0.3. If this ratio is too large, the appearance tends to deteriorate, and if this ratio is too small, the adhesive strength tends to weaken.

[0122] The laminate of the present invention can be produced by a conventionally known molding method, specifically, a melt molding method or a molding method from a solution state can be used.

[0123] Examples of melt molding methods include a method in which a biodegradable acid-modified polyester resin (A) and a PVA-based resin (B) are melt-extrusion laminated sequentially or simultaneously onto a film or sheet of biodegradable resin (C); a method in which a biodegradable acid-modified polyester resin (A) and a biodegradable resin (C) are melt-extrusion laminated sequentially or simultaneously onto a film or sheet of PVA-based resin (B); and a method in which the biodegradable resin (C), the biodegradable acid-modified polyester resin (A), and the PVA-based resin (B) are co-extruded.

[0124] In addition, examples of molding methods from a solution state include a method in which a solution of biodegradable acid-modified polyester resin (A) dissolved in a good solvent is solution-coated onto a film or sheet of biodegradable resin (C), and after drying, an aqueous solution of PVA resin (B) is solution-coated.

[0125] Among these, the melt molding method is preferred, and the co-extrusion method is particularly preferred, since it can be produced in one step and can give a laminate with excellent interlayer adhesion. When using such a melt molding method, it is preferable to use a PVA resin having a 1,2-diol structural unit in the side chain as the PVA resin (B).

[0126] Examples of the co-extrusion method include inflation, T-die, multi-manifold die, feed block, and multi-slot die. The die shape may be a T-die, a round die, or the like. The melt molding temperature during melt extrusion is usually 190 to 250°C, preferably in the range of 200 to 230°C.

[0127] The laminate of the present invention may be further subjected to a heat stretching treatment, and such a stretching treatment is expected to improve the strength and gas barrier properties.

[0128] In particular, in the laminate of the present invention, when a PVA resin having a 1,2-diol structural unit in the side chain is used as the PVA resin (B), good stretchability is obtained.

[0129] For the stretching treatment, known stretching methods can be used. Specific examples include uniaxial stretching and biaxial stretching, in which both edges of a multilayer structure sheet are gripped and expanded; mold forming methods such as deep drawing, vacuum forming, pressure forming, and vacuum pressure forming, in which a multilayer structure sheet is stretched using a mold; and methods in which a preformed multilayer structure such as a parison is processed using a tubular stretching method, stretch blow method, etc.

[0130] As such a stretching method, when a film or sheet-like molded product is intended, it is preferable to employ a uniaxial stretching method or a biaxial stretching method.

[0131] In addition, in the case of a mold forming method such as deep drawing, vacuum forming, pressure forming, or vacuum pressure forming, it is preferable to uniformly heat the laminate using a hot air oven, a heater oven, or a combination of both, and stretch it using a chuck, plug, vacuum force, compressed air force, or the like.

[0132] When the target product is a molded product such as a cup or a tray, in which the drawing ratio (depth of molded product (mm) / maximum diameter of molded product (mm)) is usually 0.1 to 3, it is preferable to employ a mold forming method in which a mold is used for stretching processing, such as deep drawing, vacuum forming, pressure forming, or vacuum pressure forming.

[0133] The laminate of the present invention thus obtained has strong adhesive strength between any of the layers, for example, between the biodegradable resin (C) layer and the biodegradable acid-modified polyester resin (A) layer, and between the PVA resin (B) layer and the biodegradable acid-modified polyester resin (A) layer.

[0134] Furthermore, the biodegradable acid-modified polyester resin (A), the biodegradable resin (C), and the PVA-based resin (B) are all biodegradable, and the laminate of the present invention having at least one layer of the biodegradable acid-modified polyester resin (A) also has excellent biodegradability.

[0135] The laminate of the present invention is biodegradable and can be disposed of directly in compost, and is therefore suitable for use in products such as coffee capsules (coffee bean containers for capsule-type coffee makers), shrink films, and other food and beverage containers.

[0136] Furthermore, when the laminate of the present invention has a PVA resin (B) layer, the PVA resin (B) layer can be removed by dissolving it in water, and only the remaining water-insoluble resin can be recycled. [Example]

[0137] The present invention will be described below with reference to examples, but the present invention is not limited to the description of the examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by weight.

[0138] [Example 1] [Preparation of biodegradable acid-modified polyester resin (A)] The raw material biodegradable polyester resin (A') was dry-blended with 100 parts of adipic acid / 1,4-butanediol condensation polymer (BASF's Ecoflex C1200), 0.35 parts of maleic anhydride, and 0.25 parts of 2,5-dimethyl-2,5-bis(t-butyloxy)hexane (NOF's Perhexa 25B) as a radical initiator. The mixture was then melt-kneaded in a twin-screw extruder under the following conditions, extruded into strands, cooled with water, and cut with a pelletizer to obtain cylindrical pellets of biodegradable acid-modified polyester resin (A).

[0139] Twin-screw extruder Diameter (D): 15mm, L / D:60 Screw rotation speed: 200 rpm Mesh: 90 / 90mesh Processing temperature: 210℃

[0140] [Measurement of Acid Value] The acid value of the biodegradable acid-modified polyester resin (A) obtained above was measured by the above-mentioned acid value measurement method. The results are shown in Table 1.

[0141] [Preparation of PVA-based resin (B)] A reactor equipped with a reflux condenser, dropping funnel, and stirrer was charged with 68.0 parts of vinyl acetate, 23.8 parts of methanol, and 8.2 parts of 3,4-diacetoxy-1-butene, and 0.3 mol% (relative to the vinyl acetate charged) of azobisisobutyronitrile was added. The temperature was raised under a nitrogen stream while stirring to initiate polymerization. When the vinyl acetate conversion reached 90%, m-dinitrobenzene was added to terminate the polymerization. Subsequently, unreacted vinyl acetate monomer was removed from the system by blowing in methanol vapor, yielding a methanol solution of the copolymer.

[0142] Next, the methanol solution was further diluted with methanol to a concentration of 45%, and then charged into a kneader. While maintaining the solution temperature at 35°C, a 2% methanol solution of sodium hydroxide was added at a ratio of 10.5 mmol per mole of the total amount of vinyl acetate structural units and 3,4-diacetoxy-1-butene structural units in the copolymer, thereby carrying out saponification. As the saponification proceeded, the saponified product precipitated, and when it became particulate, it was filtered off, thoroughly washed with methanol, and dried in a hot air dryer to produce PVA-based resin (B) having 1,2-diol structural units in the side chains.

[0143] The degree of saponification of the resulting PVA resin (B) was analyzed based on the amount of alkali consumed for hydrolysis of the remaining vinyl acetate and 3,4-diacetoxy-1-butene, and was found to be 99.2 mol %.

[0144] The average degree of polymerization of the PVA resin (B) was analyzed in accordance with JIS K 6726 and was found to be 450. The content of the 1,2-diol structural unit represented by the general formula (4) is 1 Calculation from the integrated value measured by 1 H-NMR (300 MHz proton NMR, d6-DMSO solution, internal standard: tetramethylsilane, 50° C.) revealed that the content was 6 mol %.

[0145] [Preparation of Laminate] Using polylactic acid (C1) (NatureWorks "Ingeo4032D"), PVA resin (B), and biodegradable acid-modified polyester resin (A), a three-type, five-layer laminate was produced using a three-type, five-layer multilayer film-forming device equipped with three extruders: polylactic acid (C1) layer / biodegradable acid-modified polyester resin (A) layer / PVA resin (B) layer / biodegradable acid-modified polyester resin (A) layer / polylactic acid (C1) layer. The thickness of the resulting laminate was 120 μm, with the thicknesses of the individual layers being 50 μm / 5 μm / 10 μm / 5 μm / 50 μm. The set temperatures of each extruder and roll were as follows:

[0146] Set temperature (C1 to C4: Cylinders, H: Head, J: Joint, FD1, 2: Front Dies, D1 to 3: Dies.) Polylactic acid (C1): C1 / C2 / C3 / C4 / H / J=180 / 190 / 200 / 200 / 200 / 200℃ PVA resin (B): C1 / C2 / C3 / C4 / H / J=180 / 200 / 210 / 210 / 210 / 210℃ Biodegradable acid-modified polyester resin (A): C1 / C2 / H / J = 180 / 200 / 210 / 210°C Dies: FD1 / FD2 / D1 / D2 / D3=200 / 200 / 200 / 200 / 200℃ Roll: 60℃

[0147] [Evaluation of Appearance of Laminate] The laminate obtained above was visually observed and evaluated based on the following criteria. The results are shown in Table 1. ⊚: There were no uneven thicknesses of the layers inside or at the edges of the laminate, and the transparency was high. ◯: There were some areas inside the laminate and at the edges of the laminate where the thickness of each layer was uneven, and the laminate was partially cloudy. x: The thickness of each layer was uneven in the interior and at the edges of the laminate, and the laminate was cloudy overall.

[0148] [Adhesion Strength Evaluation] The laminate obtained above was cut into a strip having a width of 15 mm, and the adhesive strength at the interface between the layers was measured using a 50 N load cell of a tensile tester "AG-IS 5kN" (manufactured by Shimadzu Corporation). The test speed was set to 100 mm / min, and the average of five measurements was used as the adhesive strength value. The measurement was performed in an environment of 23°C / 50% RH. The results are shown in Table 1.

[0149] [Example 2] A laminate was produced in the same manner as in Example 1, except that the amount of maleic anhydride used in producing the biodegradable acid-modified polyester resin (A) in Example 1 was changed to 0.40 parts. The appearance and adhesiveness of the resulting laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0150] [Example 3] A laminate was prepared in the same manner as in Example 1, except that the polylactic acid (C1) was replaced with a mixture of polybutylene adipate terephthalate and polylactic acid (C3) ("ECOVIO" manufactured by BASF). The appearance and adhesiveness of the resulting laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0151] [Comparative Example 1] A laminate was produced in the same manner as in Example 1, except that the amount of maleic anhydride used in producing the biodegradable acid-modified polyester resin (A) in Example 1 was changed to 0.50 parts. The appearance and adhesiveness of the resulting laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0152] Comparative Example 2 A laminate was produced in the same manner as in Example 1, except that neither maleic anhydride nor a radical initiator was added in the preparation of the biodegradable acid-modified polyester resin (A) in Example 1. The appearance and adhesiveness of the resulting laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0153] [Table 1]

[0154] The laminates of Examples 1 to 3, which used the biodegradable acid-modified polyester resin (A) of the present invention, were excellent in both appearance and adhesiveness. On the other hand, the laminate of Comparative Example 1, which used a polyester resin with a high acid value, had low transparency and was inferior in appearance. Furthermore, the laminate of Comparative Example 2, which used a polyester resin with a low acid value, had poor adhesiveness.

[0155] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2017-172065) filed on September 7, 2017, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0156] The biodegradable acid-modified polyester resin (A) of the present invention can be suitably used as an adhesive layer between a PVA resin (B) layer and a biodegradable resin (C) layer. The resulting laminate is biodegradable and therefore suitable for compostable products, such as coffee capsules (coffee bean containers for capsule coffee makers), shrink films, and other food and beverage containers.

Claims

1. an acid value of 3.0 to 6.5 mg KOH / g; A biodegradable acid-modified polyester resin having a total of 70 mol % or more of at least one structural unit selected from structural units represented by the following general formulas (1) to (3): 【Chemistry 1】 [In formula (1), l is an integer of 2 to 6.] 【Chemistry 2】 [In formula (2), m is an integer of 2 to 6.] 【Transformation 3】 [In formula (3), n is an integer of 2 to 6.]

2. A laminate having at least one layer containing the biodegradable acid-modified polyester resin according to claim 1.

3. A laminate comprising a polyvinyl alcohol-based resin (B) layer and a biodegradable resin (C) layer and an adhesive layer therebetween, A laminate, wherein the adhesive layer contains the biodegradable acid-modified polyester resin according to claim 1.

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