Acid-modified polyester-based resin, biodegradable adhesive and laminate

Abstract

To provide an acid-modified polyester-based resin which, when used as an adhesive layer between a PVA resin layer and a biodegradable resin layer in a laminate comprising both layers, reduces orange peel in the laminate, provides excellent image clarity and improves the appearance of the laminate.SOLUTION: There is provided an acid-modified polyester-based resin in which an α,β-unsaturated carboxylic acid and / or its anhydride (X) is grafted to an aliphatic-aromatic polyester-based resin containing an aliphatic diol unit, an aliphatic dicarboxylic acid unit and an aromatic dicarboxylic acid unit, wherein the acid-modified polyester-based resin has a melt flow rate (210°C, load 2160 g) of 1.4 to 15 g / 10 min, the content of the α,β-unsaturated carboxylic acid and / or its anhydride (X) is 0.0001 to 0.8 pt.mass based 100 pts.mass of the aliphatic-aromatic polyester-based resin and the moisture content is 10 to 1000 ppm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an acid-modified polyester resin, a biodegradable adhesive, and a laminate. [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 are biodegradable or hydrolyzed 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. As such a conventional technique, for example, an acid-modified polyester resin in which the melt flow rate (MFR) and the amount of anhydride charged are specified has been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-145418 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the biodegradable polyester resin proposed in Patent Document 1 can have poor melt moldability when forming a multilayer film, and the control of resin fluidity in the adhesive layer is insufficient, so even if there are no wave-patterned flow marks, the appearance of the laminate tends to be poor, such as an orange peel pattern (uneven pattern) caused by unevenness at the layer interface.

[0006] Furthermore, for example, in a laminate containing a polyvinyl alcohol-based resin layer and a biodegradable resin layer, when an acid-modified polyester-based resin is used as an adhesive layer for both layers, existing technologies have been insufficient to achieve an acid-modified polyester-based resin that can produce a laminate with excellent appearance.

[0007] Therefore, under these circumstances, the present invention aims to provide an acid-modified polyester resin that can reduce flow marks and orange peel in a laminate, and also improve the laminate's thickness uniformity in the TD direction and image clarity, thereby improving the laminate's appearance. [Means for solving the problem]

[0008] However, in view of these circumstances, the present inventors have conducted extensive research and have discovered that by setting the MFR and anhydride content of the acid-modified polyester resin within specific ranges and by reducing the water content compared to conventional acid-modified polyester resins, it is possible to reduce flow marks and orange peel in the laminate, improve the thickness uniformity in the TD direction of the laminate, and improve the appearance of the laminate, thereby completing the present invention.

[0009] That is, the present invention has the following aspects. [1] An acid-modified polyester resin in which an α,β-unsaturated carboxylic acid and / or its anhydride (X) is grafted onto an aliphatic-aromatic polyester resin containing an aliphatic diol unit, an aliphatic dicarboxylic acid unit, and an aromatic dicarboxylic acid unit, the acid-modified polyester resin has a melt flow rate (210°C, load 2160g) of 1.4 to 15g / 10min; the content of the α,β-unsaturated carboxylic acid and / or anhydride thereof (X) is 0.0001 to 0.8 parts by mass relative to 100 parts by mass of the aliphatic-aromatic polyester resin; Acid-modified polyester resin with a water content of 10 to 1000 ppm. [2] The acid-modified polyester resin according to [1], which is a biodegradable polyester resin. [3] The acid-modified polyester resin according to [1] or [2], wherein the α,β-unsaturated carboxylic acid and / or anhydride thereof (X) is maleic anhydride. [4] A biodegradable adhesive containing the acid-modified polyester resin according to any one of [1] to [3]. [5] A laminate having at least one layer containing the acid-modified polyester resin according to any one of [1] to [3]. [6] A laminate having an adhesive layer between a polyvinyl alcohol-based resin (B) layer and a biodegradable resin (C) layer, The adhesive layer comprises the acid-modified polyester resin according to any one of [1] to [3]. [Effects of the Invention]

[0010] When the acid-modified polyester resin of the present invention is used as an adhesive layer for both layers in a laminate containing, for example, a polyvinyl alcohol-based resin layer and a biodegradable resin layer, the acid-modified polyester resin of the present invention can reduce flow marks and orange peel in the laminate, and can also improve the thickness uniformity and image clarity in the TD direction of the laminate, thereby improving the appearance of the laminate. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0012] In this specification, "x and / or y (x and y are optional configurations)" means at least one of x and y, and can mean three possibilities: x only, y only, or x and y. In this specification, when the expression "X to Y" (X and Y are any numbers) is used, unless otherwise specified, it means "X or more and Y or less," as well as "preferably larger than X" or "preferably smaller than Y." In this specification, when it is expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means that "it is preferably greater than X" or "it is preferably less than Y." In the present specification, when numerical ranges are described in stages, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In addition, in the numerical ranges described in this specification, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples. In this specification, the term "main component" means a component that has a significant effect on the properties of the target object, and the content of the component is usually 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, and may be 100% by mass.

[0013] In this specification, parts and percentages based on mass have the same meaning as parts and percentages based on weight.

[0014] In addition, in this specification, "biodegradable" means meeting the conditions specified in JIS K 6953-1:2011 (ISO 14855-1:2005).

[0015] [Acid-modified polyester resin (A)] An acid-modified polyester resin (A) according to one embodiment of the present invention (hereinafter sometimes referred to as "the present acid-modified polyester resin") is an acid-modified polyester resin obtained by grafting an α,β-unsaturated carboxylic acid and / or anhydride thereof (X) onto an aliphatic-aromatic polyester resin containing an aliphatic diol unit, an aliphatic dicarboxylic acid unit, and an aromatic dicarboxylic acid unit, wherein the acid-modified polyester resin has a melt flow rate (210°C, 2160 g load) of 1.4 to 15 g / 10 min, a content of the α,β-unsaturated carboxylic acid and / or anhydride thereof (X) of 0.0001 to 0.8 parts by mass relative to 100 parts by mass of the aliphatic-aromatic polyester resin, and a water content of 10 to 1000 ppm.

[0016] The acid-modified polyester resin (A) is an acid-modified polyester resin obtained by graft-reacting an α,β-unsaturated carboxylic acid and / or its anhydride (hereinafter, the α,β-unsaturated carboxylic acid and / or its anhydride may be referred to as "α,β-unsaturated carboxylic acids") onto an aliphatic-aromatic polyester resin.

[0017] The aliphatic-aromatic polyester resin contains an aliphatic diol unit, an aliphatic dicarboxylic acid unit, and an aromatic dicarboxylic acid unit, and thereby the biodegradability of the acid-modified polyester resin (A) is improved.

[0018] The acid-modified polyester resin (A) is preferably a biodegradable polyester resin. Specifically, the total content of aliphatic diol units, aliphatic dicarboxylic acid units, and aromatic dicarboxylic acid units in the acid-modified polyester resin (A) is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 90 mol % or more.

[0019] In particular, the acid-modified polyester resin (A) preferably contains 50 mol % or more of aliphatic diol units and aliphatic dicarboxylic acid units. The acid-modified polyester resin (A) has improved biodegradability when it contains aliphatic diol units and aliphatic dicarboxylic acid units in a total amount of 50 mol % or more. The acid-modified polyester resin (A) more preferably contains aliphatic diol units and aliphatic dicarboxylic acid units in a total amount of 70 mol % or more, and even more preferably 90 mol % or more.

[0020] The aliphatic carboxylic acid unit is preferably an aliphatic carboxylic acid unit represented by the following general formula (1): Furthermore, the aliphatic diol unit is preferably an aliphatic diol unit represented by the following formula (2):

[0021] [ka]

[0022] [In formula (1), l is an integer of 2 to 8.]

[0023] [ka]

[0024] [In formula (2), m is an integer of 2 to 10.]

[0025] In the above formula (1), l is an integer of 2 to 8, and is preferably an integer of 3 to 5 from the viewpoint of moldability and flexibility. In the above formula (2), m is an integer of 2 to 10, and preferably an integer of 3 to 5 from the viewpoint of moldability and flexibility.

[0026] The acid-modified polyester resin (A) is composed of structural units represented by aliphatic diol units, aliphatic dicarboxylic acid units, and aromatic dicarboxylic acid units, but may contain other structural units for the purpose of controlling heat resistance, strength, biodegradability, etc.

[0027] The acid-modified polyester resin (A) having an aliphatic diol unit, an aliphatic dicarboxylic acid unit, and an aromatic dicarboxylic acid unit can be obtained by condensation polymerizing at least one component selected from the group consisting of an aliphatic dicarboxylic acid, an aliphatic diol compound, a cycloaliphatic diol compound, a cycloaliphatic dicarboxylic acid, an aromatic dicarboxylic acid, and other components by a known method, and then modifying the component with an acid.

[0028] Examples of aliphatic dicarboxylic acids include succinic acid, glutaric acid, adipic acid, 1,6-hexanedicarboxylic acid, azelaic acid, and sebacic acid, and adipic acid is particularly preferred from the viewpoints of moldability and flexibility. These may be used alone or in combination of two or more.

[0029] Examples of aliphatic diol compounds include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol, with 1,4-butanediol being particularly preferred from the standpoint of moldability and flexibility. These compounds may be used alone or in combination of two or more.

[0030] Examples of cycloaliphatic diol compounds include 1,3-cyclohexanediol and 1,4-cyclohexanediol, and 1,4-cyclohexanediol is particularly preferred from the viewpoints of moldability and flexibility. These compounds may be used alone or in combination of two or more.

[0031] Examples of cycloaliphatic dicarboxylic acids include 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid is particularly preferred from the viewpoints of moldability and flexibility. These can be used alone or in combination of two or more kinds.

[0032] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, and furandicarboxylic acid. Terephthalic acid is particularly preferred from the viewpoint of moldability. Derivatives of aromatic dicarboxylic acids may also be used. These may be used alone or in combination of two or more.

[0033] Specific examples of other components include hydroxy acids such as 4-hydroxybutyric acid, 5-hydroxyvaleric acid, and 6-hydroxyhexanoic acid; dicarboxylic acids and derivatives thereof having less than two alkylene chains such as oxalic acid and malonic acid; hydroxycarboxylic acids and derivatives thereof having less than two alkylene chains such as glycolic acid and lactic acid; and other components known as copolymerization components for polyester resins. These can be used alone or in combination of two or more.

[0034] The acid-modified polyester resin (A) is an acid-modified polyester resin (A) obtained by graft-reacting the above-mentioned aliphatic-aromatic polyester resin (hereinafter sometimes referred to as "raw polyester resin (A")") with an α,β-unsaturated carboxylic acid and / or its anhydride (hereinafter sometimes referred to as "α,β-unsaturated carboxylic acid") (X). Such an acid-modified polyester resin (A) has excellent adhesive properties.

[0035] Specific examples of the α,β-unsaturated carboxylic acids (X) 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. Preferably, an anhydride of an α,β-unsaturated dicarboxylic acid is used, and more preferably, maleic anhydride is used. These α,β-unsaturated carboxylic acids (X) may be used not only as a single type but also as a combination of two or more types.

[0036] The method for grafting an α,β-unsaturated carboxylic acid (X) onto a raw material polyester resin (A") to obtain an acid-modified polyester resin (A) grafted with an α,β-unsaturated carboxylic acid (X) is not particularly limited, and any known method can be used. A thermal reaction alone is also possible, but in order to increase the reactivity, it is preferable to use a radical initiator (Y). Further, examples of the reaction method include a solution reaction, a reaction as a suspension, and a reaction in a molten state without using a solvent or the like (melt method), and among these, the melt method is preferable.

[0037] An example of a commercially available product of the raw material polyester resin (A") is "Ecoflex" manufactured by BASF, which contains as its main component a condensation polymer of adipic acid / terephthalic acid / 1,4-butanediol.

[0038] The content of the α,β-unsaturated carboxylic acids (X) relative to 100 parts by mass of the raw material polyester resin (A") is usually 0.0001 to 0.8 parts by mass, preferably 0.001 to 0.6 parts by mass, and more preferably 0.02 to 0.45 parts by mass. When the content of the α,β-unsaturated carboxylic acid (X) relative to 100 parts by mass of the raw material polyester resin (A") is at least the above lower limit, a sufficient amount of polar groups is introduced into the aliphatic-aromatic polyester resin, and sufficient interlayer adhesion, particularly adhesion to the polyvinyl alcohol resin layer, is obtained. Furthermore, when the content of the α,β-unsaturated carboxylic acid (X) relative to 100 parts by mass of the raw material polyester resin (A") is at most the above upper limit, ungrafted α,β-unsaturated carboxylic acid (X) is less likely to remain in the resin, and poor appearance and the like resulting from this can be suppressed.

[0039] In order to prevent the occurrence of fisheyes, the content of the α,β-unsaturated carboxylic acids (X) relative to 100 parts by mass of the raw material polyester resin (A") is preferably 0.33 parts by mass or less, more preferably 0.30 parts by mass or less, and even more preferably 0.25 parts by mass or less.

[0040] In this embodiment, from the viewpoint of increasing the efficiency of the grafting reaction, it is preferable to incorporate a radical initiator (Y) during grafting. That is, the acid-modified polyester resin (A) incorporates a radical initiator (Y) during grafting.

[0041] The radical initiator (Y) is not particularly limited, and known radical initiators can be used, 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, and dicumyl peroxide. Examples of suitable peroxides include organic or inorganic peroxides 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.

[0042] The content of the radical initiator (Y) relative to 100 parts by mass of the raw material polyester resin (A") is preferably 0.00001 to 5.0 parts by mass, more preferably 0.0001 to 1.0 part by mass, and even more preferably 0.002 to 0.5 parts by mass. When the content of the radical initiator (Y) relative to 100 parts by mass of the raw material polyester resin (A") is at least the above lower limit, the graft reaction proceeds sufficiently, and the effects of the present invention are easily obtained. Furthermore, when the content of the radical initiator (Y) is at most the above upper limit, the polyester resin is less likely to be decomposed to reduce its molecular weight, and a lack of adhesive strength due to a lack of cohesive force can be suppressed.

[0043] The content ratio (Y' / X) of the radical (Y') obtained from the radical initiator (Y) to the α,β-unsaturated carboxylic acids (X) is preferably 0.5 to 5, more preferably 0.6 to 4, even more preferably 0.7 to 3, and particularly preferably 0.8 to 2. When Y' / X is within the above range, the α,β-unsaturated carboxylic acids (X) that have not undergone the graft reaction are less likely to remain in the resin, and poor appearance and the like caused thereby can be suppressed. The amount of radicals (Y') obtained from the radical initiator (Y) is the theoretical value of radicals that can be generated from the radical initiator (Y).

[0044] The melting method, which is a preferred method for preparing the acid-modified polyester resin (A), will be described in detail below. As the melting method, a method in which the raw material polyester resin (A"), α,β-unsaturated carboxylic acid (X), and radical initiator (Y) are mixed in advance and then melt-kneaded in a kneader to cause a reaction, or a method in which the raw material polyester resin (A") in a molten state in a kneader is blended with the α,β-unsaturated carboxylic acid (X) and radical initiator (Y), etc., can be used.

[0045] 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.

[0046] 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 polyester resin (A") and does not cause thermal degradation, but melt-kneading is preferably carried out at 100 to 250°C, more preferably 160 to 220°C.

[0047] When the grafting reaction is carried out using a kneader, the screw rotation speed of the kneader is preferably 150 to 800 rpm, more preferably 180 to 700 rpm, and even more preferably 190 to 680 rpm. When the screw rotation speed is within the above range, the MFR can be adjusted to a preferred range.

[0048] Furthermore, when the graft reaction is carried out using a kneader, the screw diameter (D) of the kneader is preferably 3 to 500 mm, more preferably 5 to 300 mm, even more preferably 10 to 200 mm, and particularly preferably 15 to 100 mm. When the screw diameter (D) is within the above range, the production amount can be improved while suppressing thermal degradation of the resin. The screw diameter (D) generally refers to the outer diameter of the screw.

[0049] The ratio (L / D) of the screw diameter (D) to the screw length (L) is preferably in the range of 10 to 200, more preferably 20 to 150, and even more preferably 25 to 100. When L / D is in the above range, the production volume can be improved while suppressing thermal degradation of the resin.

[0050] When the graft reaction is carried out using a kneader, the kneader may be provided with only one kneading section for carrying out kneading, or may be provided with a plurality of kneading sections.

[0051] The acid-modified polyester resin (A') obtained by the melt-kneading is dried by heating to obtain the acid-modified polyester resin (A) having a reduced water content. The heating time is not particularly limited as long as the heating is performed to achieve the desired moisture content, but is usually 60 to 420 minutes. The heating temperature is preferably 20 to 120° C., more preferably 30 to 100° C., and even more preferably 50 to 90° C. Examples of heat drying include drying with dehumidified air, drying under a nitrogen atmosphere, and vacuum heat drying, but vacuum heat drying is preferred from the viewpoint of reducing orange peel, etc.

[0052] The MFR of the acid-modified polyester resin (A) is 1.4 to 15 g / 10 min, preferably 2 to 10 g / 10 min, and more preferably 3 to 7 g / 10 min. If the MFR of the acid-modified polyester resin (A) is less than the above lower limit, the fluidity decreases, and the appearance of the multilayer film tends to deteriorate due to flow marks, etc. Furthermore, if the MFR of the acid-modified polyester resin (A) is equal to or less than the above upper limit, the viscosity difference with other resins during multilayer film formation is prevented from becoming large, and the appearance of the multilayer film can be improved.

[0053] The smaller the molecular weight of the acid-modified polyester resin (A), the larger the MFR and the higher the flowability. In this embodiment, it is presumed that the effect of the present invention is achieved by controlling the screw rotation speed during the graft reaction of the acid-modified polyester resin (A) to control shear in the extruder and reduce the molecular weight, thereby improving the flowability of the acid-modified polyester resin (A).

[0054] The method for measuring the above MFR is described in detail below. A melt indexer conforming to JIS K 7210-1:2014 is used. 5 g of sample is placed into a cylinder set to 210°C and charged within 30 seconds. 4 minutes and 30 seconds after sample addition, a 2160 g weight is placed on the cylinder. Five minutes after sample addition, the extruded strand is cut and discarded. Subsequently, the strand is cut 6 minutes, 7 minutes, and 8 minutes after sample addition, and a total of three strands are collected. The masses of the three collected strands are measured and averaged. The MFR is calculated from the average mass calculated using the following formula. MFR(g / 10min)=W×10 W: Average mass of three strands (g) 10: Factor for converting grams per minute to grams per 10 minutes

[0055] In order to set the MFR within a specific range, for example, the following methods can be mentioned. (i) A method of adjusting the screw rotation speed of the extruder during the graft reaction of the acid-modified polyester resin (A). (ii) A method of adjusting the amount of the radical initiator (Y) used during the graft reaction of the acid-modified polyester resin (A). Among these, method (i) is preferred in terms of the efficiency of the grafting reaction.

[0056] The viscosity change of the acid-modified polyester resin (A) (MFR MIN / MFR MAX ) is preferably 0.3 or more, more preferably 0.5 or more, and even more preferably 0.6 or more. The larger this value, the more excellent the viscosity stability and the less likely appearance defects such as flow marks will occur during film formation.

[0057] The above MFR viscosity change (MFR MIN / MFR MAX ) is measured after storing in an atmosphere of 23°C for 21 days and after storing in an atmosphere of 60°C for 21 days, and the larger of the two values ​​is taken as the MFR MAX , the smaller value is MFR MIN As, MFR MIN / MFR MAX can be calculated.

[0058] The water content in the acid-modified polyester resin (A) is 1000 ppm or less, preferably 950 ppm or less, more preferably 900 ppm or less, and even more preferably 880 ppm or less. The lower limit is usually 10 ppm or more, preferably 50 ppm or more, more preferably 100 ppm or more, and even more preferably 150 ppm or more. If the water content in the acid-modified polyester resin composition is too high, excessive hydrolysis of the polyester occurs in the adhesive layer during multilayer film formation, causing unstable resin fluidity and disrupting the interface between adjacent layers, resulting in poor appearance of the laminate, such as orange peel. When a trace amount of water is contained in the acid-modified polyester resin composition, the plasticizing effect results in good resin fluidity, which tends to reduce flow marks and orange peel.

[0059] The moisture content is measured using a water-selective moisture meter (Brabender's "Aquatrac-V"), which uses a chemical reaction with calcium hydride as its measurement principle in accordance with DIN EN ISO 15512:2019.

[0060] The weight-average molecular weight of the acid-modified polyester resin (A) is preferably 5,000 to 500,000, more preferably 50,000 to 400,000, even more preferably 100,000 to 200,000, and particularly preferably 140,000 to 180,000. When the weight-average molecular weight is equal to or less than the upper limit, an increase in melt viscosity is suppressed, facilitating melt molding. When the weight-average molecular weight is equal to or greater than the lower limit, brittleness of molded products is suppressed.

[0061] The weight-average molecular weights mentioned above are those calculated in terms of standard polystyrene molecular weights. High performance liquid chromatography (Tosoh Corporation, "HLC-8320GPC") was performed using a column: TSKgel SuperMultipore HZ-M (exclusion limit molecular weight: 2 × 10 6 The measurement is performed using two columns in series (theoretical plate number: 16,000 plates / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 4 μm).

[0062] The present acid-modified polyester resin (A) can be suitably used as a biodegradable adhesive. That is, the biodegradable adhesive according to this embodiment contains the present acid-modified polyester resin (A).

[0063] The acid-modified polyester resin (A) used in this embodiment may also contain, in addition to the 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, a lubricant, or a crystal nucleating agent, provided that the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

[0064] This acid-modified polyester resin (A) has a fisheye count of 1,000 / 100cm when forming a single layer film.2 It is preferable that the number of particles is less than 600 / 100cm. 2 Less than 500 pieces / 100cm, more preferably 2 Less than 450 pieces / 100cm is particularly preferable. 2 The smaller this value, the better the molded appearance. The number of fisheyes when the acid-modified polyester resin (A) is formed into a single layer film can be measured by the method described in the examples below.

[0065] The acid-modified polyester resin (A) can be particularly suitably used as an adhesive composition for laminates, for example, as an adhesive layer when laminating a polyvinyl alcohol (hereinafter sometimes referred to as "PVA") resin (B) layer and a biodegradable resin (C) layer, which have different surface properties. The PVA resin (B) layer and the biodegradable resin (C) layer that constitute the laminate will be described below.

[0066] [PVA resin (B) layer] The PVA-based resin (B) layer is preferably used as a gas barrier layer in the laminate according to one embodiment of the present invention described below, and particularly preferably provides the gas barrier properties of the laminate according to one embodiment of the present invention. The PVA resin (B) layer is preferably laminated on at least one surface of the biodegradable resin (C) layer described below via a layer (adhesive layer) containing the acid-modified polyester resin (A) described above.

[0067] The PVA resin (B) layer used in this embodiment is a layer containing the PVA resin (B) as a main component, and the content of the PVA resin (B) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The upper limit is 100% by mass. When the content is equal to or greater than the above lower limit, sufficient gas barrier properties are obtained.

[0068] The PVA resin (B) used in the present embodiment 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.

[0069] 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. These may be used alone or in combination of two or more.

[0070] The average degree of polymerization (measured in accordance with JIS K6726-1994) of the PVA resin (B) used in this embodiment is preferably 200 to 1,800, more preferably 300 to 1,500, and even more preferably 300 to 1,000.

[0071] If the average degree of polymerization is equal to or greater than the lower limit, the PVA resin (B) layer has sufficient mechanical strength. If the average degree of polymerization is equal to or less than the upper limit, the PVA resin (B) layer can be formed by hot melt molding without reducing fluidity, improving moldability. Furthermore, abnormal shear heat generation during molding can be suppressed, making the PVA resin (B) less susceptible to thermal decomposition.

[0072] The saponification degree (measured in accordance with JIS K6726-1994) of the PVA resin (B) used in this embodiment is preferably 80 to 100 mol %, more preferably 90 to 99.9 mol %, and even more preferably 98 to 99.9 mol %. When the degree of saponification is equal to or greater than the above lower limit, the gas barrier properties are improved.

[0073] In addition, in this embodiment, the PVA-based resin (B) may be a resin obtained by copolymerizing various monomers during the production of a polyvinyl ester-based resin and then saponifying the copolymer, or a variety of modified PVA-based resins obtained by introducing various functional groups into unmodified PVA by post-modification.

[0074] 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, and derivatives thereof such as acylated products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, 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, acrylamide, and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, or salts thereof, alkyl vinyl ethers, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, and vinyl compounds such as 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. These may be used alone or in combination of two or more.

[0075] 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.

[0076] 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 preferably in the range of 1 to 20 mol %, more preferably 2 to 10 mol %.

[0077] Among these various modified PVA-based resins, in this embodiment, a PVA-based 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 according to this embodiment, which will be described later.

[0078] [ka]

[0079] 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.

[0080] 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, and the alkyl group may have a functional group such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, a sulfonic acid group, etc. These may be used alone or in combination of two or more kinds.

[0081] 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 represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and t represents an integer of 1 to 5). These may be used alone or in combination of two or more. 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-.

[0082] X is most preferably a single bond in terms of thermal stability and stability at high temperatures and under acidic conditions.

[0083] 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.

[0084] [ka]

[0085] 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-A No. 2015-143356.

[0086] The content of the 1,2-diol structural units contained in such PVA resins having 1,2-diol structural units in their side chains is preferably 1 to 20 mol%, more preferably 2 to 10 mol%, and even more preferably 3 to 8 mol%. When this content is equal to or greater than the above lower limit, the effect of the 1,2-diol structure in the side chain can be fully obtained, and when this content is equal to or less than the above upper limit, deterioration of the gas barrier properties at high humidity can be suppressed.

[0087] 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.

[0088] The PVA-based resin (B) used in this embodiment may be one type or a mixture of two or more types. When the PVA-based 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-based resin having a structural unit represented by general formula (4); the PVA-based resins having a structural unit represented by general formula (4) with different degrees of saponification, polymerization, modification, etc.; the unmodified PVA; or the PVA-based resin having a structural unit represented by general formula (4) and another modified PVA-based resin.

[0089] The PVA resin (B) layer used in this embodiment 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, provided that the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

[0090] [Biodegradable resin (C) layer] Next, the biodegradable resin (C) layer preferably used as the outer layer of the laminate according to this embodiment will be described. The biodegradable resin (C) layer is a layer containing biodegradable resin (C) as the main component, and the content of biodegradable resin (C) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The upper limit is 100% by mass.

[0091] 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 alone or in combination of two or more.

[0092] Among these, 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.

[0093] 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.

[0094] The polylactic acid (C1) used in this embodiment 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.

[0095] 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. These may be used alone or in combination of two or more.

[0096] Furthermore, the content ratio of L-lactic acid component to D-lactic acid component in polylactic acid (C1) (mass of L-lactic acid component / mass of D-lactic acid component) is preferably 95 / 5 or more, more preferably 99 / 1 or more, and even more preferably 99.8 / 0.2 or more. 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 tendency for insufficient heat resistance.

[0097] 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.

[0098] The weight-average molecular weight of the polylactic acid (C1) used in this embodiment is preferably 20,000 to 1,000,000, more preferably 30,000 to 300,000, and even more preferably 40,000 to 200,000. When the weight-average molecular weight is equal to or less than the upper limit, the melt viscosity during hot melt molding can be prevented from becoming excessively high, and good film-forming properties can be obtained. When the weight-average molecular weight is equal to or greater than the lower limit, the mechanical strength of the resulting laminate can be sufficient.

[0099] Such weight average molecular weight can be determined by size exclusion chromatography (GPC, gel permeation chromatography) as polystyrene equivalent according to the ISO 16014-1:2012 and ISO 16014-3:2012 standards using tetrahydrofuran as eluent and a column (polystyrene gel) heated to 40°C.

[0100] 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.

[0101] Polybutylene adipate terephthalate (C2) is obtained by polycondensation of adipic acid, terephthalic acid, and 1,4-butanediol.

[0102] The content of adipic acid in the polybutylene adipate terephthalate (C2) is preferably 10 to 50 mol %, more preferably 15 to 40 mol %. The content of terephthalic acid in the polybutylene adipate terephthalate (C2) is preferably 5 to 45 mol %, more preferably 8 to 35 mol %. The content of 1,4-butanediol in the polybutylene adipate terephthalate (C2) is preferably 5 to 45 mol %, more preferably 10 to 30 mol %. When the content of each component is within the above range, workability and corrosion resistance are improved.

[0103] The weight-average molecular weight of the polybutylene adipate terephthalate (C2) is preferably 3,000 to 1,000,000, more preferably 20,000 to 600,000, and even more preferably 50,000 to 400,000. When the weight-average molecular weight is equal to or greater than the lower limit, production becomes easy, and when the weight-average molecular weight is equal to or less than the upper limit, melt viscosity decreases and moldability improves.

[0104] Such weight average molecular weight can be determined by size exclusion chromatography (GPC, gel permeation chromatography) as polystyrene equivalent according to the ISO 16014-1:2012 and ISO 16014-3:2012 standards using tetrahydrofuran as eluent and a column (polystyrene gel) heated to 40°C.

[0105] Polybutylene adipate terephthalate (C2) may contain other copolymerization components in addition to adipic acid, terephthalic acid, and 1,4-butanediol.

[0106] 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); hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-hydroxybenzoic acid oligomers and polymers. These can be used alone or in combination of two or more.

[0107] The content of such other copolymerization components is about 0.1 to 30 mol % of the entire polybutylene adipate terephthalate (C2).

[0108] 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 (mass ratio) is preferably 10 / 90 to 90 / 10, and more preferably 20 / 80 to 60 / 40.

[0109] Furthermore, the biodegradable resin (C) layer used in this embodiment 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., within the range that does not impair the effects of the present invention. These may be used alone or in combination of two or more kinds.

[0110] [Laminate] A laminate according to one embodiment of the present invention (hereinafter sometimes referred to as "the laminate") has at least one layer containing the present acid-modified polyester resin (A) (hereinafter sometimes referred to as "acid-modified polyester resin (A) layer").

[0111] The acid-modified polyester resin (A) layer is a layer containing the acid-modified polyester resin (A) as a main component, and specifically, the content of the acid-modified polyester resin (A) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, with the upper limit being 100% by mass.

[0112] The acid-modified polyester resin (A) layer used in this embodiment may contain, in addition to the 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. These may be used alone or in combination of two or more kinds.

[0113] The present laminate preferably has a biodegradable resin (C) layer as a layer other than the acid-modified polyester resin (A) layer. In particular, it is preferable that the present laminate uses a PVA resin (B) layer as the gas barrier layer and a biodegradable resin (C) layer as the outer layer.

[0114] The present laminate is a laminate having an adhesive layer provided between the PVA resin (B) layer and the biodegradable resin (C) layer, and the adhesive layer preferably contains the present acid-modified polyester resin (A).The laminate preferably has a layer structure of 3 to 15 layers, more preferably 3 to 7 layers, and even more preferably 5 to 7 layers.

[0115] The configuration of the laminate 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 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 acid-modified polyester-based resin (A) layers are present in the laminate.

[0116] 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.

[0117] The thickness of the present laminate is preferably 1 to 30,000 μm, more preferably 3 to 13,000 μm, and even more preferably 10 to 3,000 μm.

[0118] Regarding the thickness of each layer constituting the laminate, the thickness of the acid-modified polyester resin (A) layer (adhesive layer) is preferably 0.1 to 500 μm, more preferably 0.15 to 250 μm, and even more preferably 0.5 to 50 μm. When the thickness of the acid-modified polyester resin (A) layer is equal to or less than the upper limit, the appearance is good. Furthermore, when the thickness of the acid-modified polyester resin (A) layer is equal to or more than the lower limit, a decrease in adhesive strength can be suppressed.

[0119] The thickness of the PVA-based resin (B) layer is preferably 0.1 to 1000 μm, more preferably 0.3 to 500 μm, and even more preferably 1 to 100 μm. If the thickness of the PVA-based resin (B) layer is equal to or less than the upper limit, the laminate can be prevented from becoming hard and brittle. On the other hand, if the thickness of the PVA-based resin (B) layer is equal to or more than the lower limit, the gas barrier properties are improved.

[0120] The thickness of the biodegradable resin (C) layer is preferably 0.4 to 14,000 μm, more preferably 1 to 6,000 μm, and even more preferably 4 to 1,400 μm. If the thickness of the biodegradable resin (C) layer is equal to or less than the upper limit, the laminate can be prevented from becoming too hard. On the other hand, if the thickness of the biodegradable resin (C) layer is equal to or more than the lower limit, the laminate can be prevented from becoming brittle.

[0121] When there are a plurality of each layer, 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), expressed as the ratio of the sum of the thicknesses thereof, is preferably 1 to 100, more preferably 2.5 to 50. When this ratio is equal to or less than the upper limit, the barrier properties are improved, and when this ratio is equal to or more than the lower limit, the laminate can be prevented from becoming hard and brittle.

[0122] The thickness ratio of the present laminate to the acid-modified polyester resin (A) layer (adhesive layer) (thickness of acid-modified polyester resin (A) layer / thickness of the present laminate), which is the ratio of the total thickness of the acid-modified polyester resin (A) layers (adhesive layers) when there are multiple acid-modified polyester resin (A) layers (adhesive layers), is preferably 0.005 to 0.5, more preferably 0.01 to 0.3. If this ratio is equal to or less than the upper limit, the appearance is improved, and if this ratio is equal to or more than the lower limit, the adhesive strength is improved.

[0123] The present laminate preferably has a uniform thickness in the TD direction. Specifically, the coefficient of variation of the thickness of the laminate is preferably 0.5 or less, more preferably less than 0.32, even more preferably 0.3 or less, particularly preferably 0.2 or less, and especially preferably 0.1 or less. By keeping the coefficient of variation of the thickness of the laminate below the upper limit, poor appearance after stretching can be suppressed. The coefficient of variation of the thickness of the laminate can be measured by the method described in the Examples below. Examples of a method for adjusting the coefficient of variation of the thickness of the laminate within the above range include a method for adjusting the fluidity of the resin of each layer and a method for adjusting the pressure at which the resins of each layer join together.

[0124] The present laminate preferably has an image clarity of 70% or more, more preferably 73% or more, and even more preferably 75% or more. The image clarity of the laminate can be measured by the method described in the Examples below. By having the image clarity of the laminate be equal to or greater than the above lower limit, good image clarity and a good appearance can be achieved.

[0125] The present laminate can be produced by a conventionally known molding method, specifically, a melt molding method or a molding method from a solution state.

[0126] Examples of melt molding methods include a method in which an acid-modified polyester resin (A) and a PVA-based resin (B) are melt-extruded sequentially or simultaneously onto a film or sheet of a biodegradable resin (C); a method in which an acid-modified polyester resin (A) and a biodegradable resin (C) are melt-extruded sequentially or simultaneously onto a film or sheet of a PVA-based resin (B); and a method in which the biodegradable resin (C), the acid-modified polyester resin (A), and the PVA-based resin (B) are co-extruded.

[0127] In addition, examples of molding methods from a solution state include a method in which a solution of the acid-modified polyester resin (A) dissolved in a good solvent is solution-coated onto a film or sheet of the biodegradable resin (C), and after drying, an aqueous solution of the PVA resin (B) is solution-coated.

[0128] Among these, the melt molding method is preferred, and the co-extrusion method is particularly preferred, because 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).

[0129] 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 preferably 190 to 250°C, more preferably 200 to 230°C.

[0130] The present laminate may be further subjected to a heat stretching treatment, and such a stretching treatment is expected to improve the strength and gas barrier properties.

[0131] In particular, when a PVA resin having a 1,2-diol structural unit in the side chain is used as the PVA resin (B) in the present laminate, good stretchability is obtained.

[0132] For the stretching treatment, known stretching methods can be used. Examples of such methods 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] The thus obtained laminate is free from flow marks and orange peel and has excellent thickness uniformity in the TD direction and image clarity.

[0137] Furthermore, the present laminate has strong adhesive strength between any of the layers, for example, between the biodegradable resin (C) layer and the acid-modified polyester resin (A) layer, and between the PVA resin (B) layer and the acid-modified polyester resin (A) layer.

[0138] The acid-modified polyester resin (A) has excellent biodegradability. Furthermore, both the biodegradable resin (C) and the PVA resin (B) are biodegradable, and the laminate having at least one layer of the acid-modified polyester resin (A) also has excellent biodegradability.

[0139] Because this laminate is biodegradable, it can be easily disposed of in the compost, and is therefore suitable for use in products such as coffee capsules (coffee bean containers for capsule coffee makers), shrink film, and other food and beverage containers.

[0140] Furthermore, when the present laminate 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]

[0141] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by mass.

[0142] <Preparation of Acid-Modified Polyester Resin> First, an acid-modified polyester resin was prepared as follows.

[0143] [Comparative Example 1] As the raw material polyester resin (A"), 100 parts of adipic acid / terephthalic acid / 1,4-butanediol condensation polymer (BASF's Ecoflex C1200), 0.35 parts of maleic anhydride (X-1), and 0.25 parts of 2,5-dimethyl-2,5-bis(t-butyloxy)hexane (NOF Corporation's Perhexa 25B) as a radical initiator (Y) were dry blended, and the mixture was melt-kneaded in a twin-screw extruder under the conditions described below, extruded into strands, water-cooled, and cut with a pelletizer to obtain cylindrical pellets of acid-modified polyester resin (A'-1). The content ratio (Y' / X) of the radical (Y') obtained from the radical initiator (Y) to the maleic anhydride (X-1) was 0.96 in terms of molar ratio.

[0144] (Twin-screw extruder conditions) Screw diameter (D): 15mm Mixing section: one location Screw length (L) / screw diameter (D): 60 Screw rotation speed: 650 rpm Mesh: 100 / 100 mesh Processing temperature: C1 / C2 / C3 / C4 / C5 / C6 / H=30 / 160 / 160 / 160 / 160 / 160 / 180℃ (C1~C6: each cylinder, H: head)

[0145] Comparative Example 2 An acid-modified polyester resin (A'-2) was obtained in the same manner as in Comparative Example 1, except that in the preparation of the acid-modified polyester resin (A'-1) of Comparative Example 1, the content of maleic anhydride (X-1) was changed as shown in Table 1. The content ratio (Y' / X) of the radical (Y') obtained from the radical initiator (Y) to the maleic anhydride (X-1) was 0.96 in molar ratio.

[0146] Comparative Example 3 An acid-modified polyester resin (A'-3) was obtained in the same manner as in Comparative Example 1, except that in the preparation of the acid-modified polyester resin (A'-1) of Comparative Example 1, the screw rotation speed of the extruder and the content of maleic anhydride (X-1) were changed as shown in Table 1. The content ratio (Y' / X) of the radical (Y') obtained from the radical initiator (Y) to the maleic anhydride (X-1) was 0.96 in molar ratio.

[0147] [Example 1] The acid-modified polyester resin (A'-1) obtained in Comparative Example 1 was vacuum dried at 70°C to obtain the acid-modified polyester resin (A-1) of Example 1.

[0148] [Example 2] to [Example 3] The acid-modified polyester resin (A'-2) obtained in Comparative Example 2 was vacuum-dried at 70°C to the moisture content shown in Table 1, thereby obtaining the acid-modified polyester resin (A-2) of Example 2 and the acid-modified polyester resin (A-3) of Example 3.

[0149] [Example 4] to [Example 5] The acid-modified polyester resin (A'-3) obtained in Comparative Example 3 was vacuum-dried at 70°C to the moisture content shown in Table 1, thereby obtaining the acid-modified polyester resin (A-4) of Example 4 and the acid-modified polyester resin (A-5) of Example 5.

[0150] [Initial MFR measurement] The initial MFR of the acid-modified polyester resin obtained above was measured by the above-mentioned MFR measurement method. The results are shown in Table 1.

[0151] [Measurement of moisture content] The water content of the acid-modified polyester resin obtained above was measured by the following procedure. The results are shown in Table 1. Measurement was performed using a water-selective moisture meter ("Aquatrac-V" manufactured by Brabender) under the following conditions. Sample size: 12.5g ·Temperature: 120℃ ·Specific gravity: 1.23g / cm 3

[0152] <Preparation of laminate> Prior to the production of the laminate, the following materials were prepared. Acid-modified polyester resin (A-1) Polylactic acid (C1) (NatureWorks "Ingeo4032D") PVA resin (B): Prepared as follows:

[0153] [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.

[0154] 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 prepare a PVA-based resin (B) having 1,2-diol structural units in its side chains, represented by general formula (4').

[0155] 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 %.

[0156] The average degree of polymerization of the PVA resin (B) was analyzed in accordance with JIS K 6726-1994 and was found to be 450. In addition, the content of 1,2-diol structural units 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 %.

[0157] [Preparation of Laminate] Using polylactic acid (C1) (NatureWorks "Ingeo 4032D"), PVA resin (B), and the acid-modified polyester resin (A-1) obtained in Example 1, a three-type, five-layer laminate was produced using a three-type, five-layer multilayer film-forming device equipped with three extruders and a 45 cm wide T-die: polylactic acid (C1) layer / acid-modified polyester resin (A-1) layer / PVA resin (B) layer / acid-modified polyester resin (A-1) layer / polylactic acid (C1) layer. The thickness of the resulting laminate was 100 μm, with the thicknesses of the individual layers being 30 μm / 10 μm / 20 μm / 10 μm / 30 μm, and the width of the resulting laminate was 37 to 40 cm. The set temperatures of each extruder and roll were as follows:

[0158] (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℃ Acid-modified polyester resin: C1 / C2 / H / J=180 / 200 / 210 / 210℃ Dies: FD1 / FD2 / D1 / D2 / D3 = 200 / 200 / 200 / 200 / 200℃ Roll: 60℃

[0159] [Flow mark evaluation] The laminate obtained above was visually observed and evaluated based on the following criteria. The results are shown in Table 1. 〇: No flow marks and good appearance ×: Flow marks occurred and the appearance was poor

[0160] [Orange peel evaluation] The laminate obtained above was visually observed and evaluated based on the following criteria. The results are shown in Table 1. 〇: No orange peel and good appearance ×: Orange peel occurred and the appearance was poor.

[0161] [Image clarity of laminate] The image clarity of the laminate obtained above was calculated according to the following procedure. The image clarity measurement device ICM-1 (manufactured by Suga Test Instruments Co., Ltd.) was used, and the measurement principle conformed to JIS K7374 "Plastics - Determination of image clarity." Test pieces were taken from the center of the laminate in the TD direction, measuring 5 cm x 5 cm. Evaluation was performed with n=3, and the average value was calculated for each optical comb width of 0.125 mm, 0.25 mm, 0.5 mm, 1.0 mm, and 2.0 mm. The values ​​for each optical comb were then averaged to calculate image clarity (%). 70% or more: The laminate has good image clarity and good appearance Less than 70%: Good image clarity of laminate, poor appearance

[0162] [Thickness uniformity in the TD direction of the laminate] The thickness uniformity in the TD direction of the laminate obtained above was calculated by the following procedure. A dot was placed in the center of the laminate in the TD direction, and 17 dots were placed at 1 cm intervals from that dot toward one edge of the laminate. Similarly, 17 dots were placed from the center dot toward the opposite edge, for a total of 35 dots on the laminate. The thickness of the laminate at each point was measured with a film thickness meter, and the average and standard deviation were calculated, followed by the coefficient of variation (= standard deviation / average). The results are shown in Table 1.

[0163] Laminates of Examples 2 to 5 and Comparative Examples 1 to 3 were produced in the same manner as in Example 1, except that the acid-modified polyester resin used in Example 1 was changed as shown in Table 1. The resulting laminates were evaluated for flow marks, orange peel appearance, image clarity, and thickness uniformity in the same manner as in Example 1. The results are shown in Table 1.

[0164] [Table 1]

[0165] The results in Table 1 above show that the laminates of Examples 1 to 5, which used acid-modified polyester resin (A) having a specific moisture content lower than conventional ones, had reduced orange peel in the laminate and excellent image clarity. On the other hand, the laminates of Comparative Examples 1 to 3, which used acid-modified polyester resins with relatively high water contents, showed orange peel and were poor in image clarity.

[0166] The acid-modified polyester resin obtained above was used to measure the change in MFR viscosity during storage and the number of fisheyes during single-layer film formation, according to the following procedures. The results are shown in Table 2.

[0167] [MFR viscosity change] The biodegradable acid-modified polyester resin obtained above was stored in an atmosphere of 23°C for 21 days, and the MFR was measured using the method described above. The biodegradable acid-modified polyester resin stored in an atmosphere of 60°C for 21 days was also measured using the same procedure. The larger of the obtained values ​​was taken as the MFR. MAX The smaller value is the MFR MIN As, MFR MIN / MFR MAX was calculated.

[0168] [Measurement of fisheye count] (single layer film formation) A single layer film of an acid-modified polyester resin was produced under the following conditions using a single layer film-forming device equipped with one extruder and a 15 cm wide T-die. The thickness of the obtained monolayer was 30 μm, and the width of the monolayer was 10 to 13 cm. (Set temperature) Acid-modified polyester resin: C1 / C2 / C3 / AD / H=180 / 210 / 220 / 210 / 200℃ (C1 to C3: Cylinders, AD: Adapter, H: Head, D: Die.) Die: 200℃ Roll: 3℃ (measurement) A 10 x 10 cm piece was cut out from the monolayer, enlarged to 50 cm x 50 cm using an overhead projector (OHP), and the number of fisheyes (FE) was visually confirmed.

[0169] [Table 2]

[0170] From the results in Table 2 above, the acid-modified polyester resins of Examples 2 to 5, which used acid-modified polyester resins with reduced maleic anhydride (X-1) content, showed smaller MFR viscosity changes during storage and smaller FE numbers during single-layer film formation than the corresponding comparative examples. This suggests that the acid-modified polyester resins of Examples 2 to 5 are less likely to cause flow marks and can provide better laminate appearance with lower FE. [Industrial Applicability]

[0171] The 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 use in 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-modified polyester resin in which an α,β-unsaturated carboxylic acid and / or an anhydride thereof (X) is grafted onto an aliphatic-aromatic polyester resin containing an aliphatic diol unit, an aliphatic dicarboxylic acid unit, and an aromatic dicarboxylic acid unit, the acid-modified polyester resin has a melt flow rate (210°C, load 2160g) of 1.4 to 15g / 10min; the content of the α,β-unsaturated carboxylic acid and / or anhydride thereof (X) is 0.0001 to 0.8 parts by mass relative to 100 parts by mass of the aliphatic-aromatic polyester resin; An acid-modified polyester resin having a water content of 10 to 1000 ppm.

2. The acid-modified polyester resin according to claim 1, which is a biodegradable polyester resin.

3. 2. The acid-modified polyester resin according to claim 1, wherein the α,β-unsaturated carboxylic acid and / or its anhydride (X) is maleic anhydride.

4. A biodegradable adhesive comprising the acid-modified polyester resin according to any one of claims 1 to 3.

5. A laminate having at least one layer containing the acid-modified polyester resin according to any one of claims 1 to 3.

6. 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 acid-modified polyester resin according to any one of claims 1 to 3.

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