JP2024144312A - Acid-modified polyester resin composition and laminate - Google Patents

Abstract

To provide a resin composition which is preferably used to bond a PVA-based resin layer and a biodegradable resin layer such as a polylactic acid, and is also excellent in workability and appearance of a laminate.SOLUTION: An acid-modified polyester-based resin composition contains an acid-modified polyester-based resin as a main component, and a resin having a melting peak (ΔH) of 10 J/g or less and aliphatic ester.SELECTED DRAWING: None

Description

The present invention relates to an acid-modified polyester resin composition and a laminate, and more specifically to an acid-modified polyester resin composition that is preferably used for bonding a polyvinyl alcohol resin layer (hereinafter, polyvinyl alcohol is referred to as "PVA") to a biodegradable resin layer such as polylactic acid, and a laminate having a layer containing the acid-modified polyester resin composition.

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 dumped in the natural environment after use, they may remain for a long time, marring the scenery and causing environmental destruction.

In response to this, biodegradable resins that are biodegraded or hydrolyzed in soil or water and are useful for preventing environmental pollution have attracted attention in recent years, and efforts are being made to put them 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.

However, aliphatic polyester resins such as polylactic acid have insufficient oxygen gas barrier properties and cannot be used alone as packaging materials for foods, medicines, and other contents that may be subject to oxidative deterioration. For this reason, aliphatic polyester resins such as polylactic acid are laminated with PVA resins to form laminates.

However, because the surface characteristics of an aliphatic polyester resin layer such as polylactic acid and a PVA resin layer are significantly different, the two layers have poor adhesion, making it difficult to obtain a practical interlayer adhesive strength by directly laminating the two layers.

Therefore, an adhesive layer is provided to bond these resin layers together, and in order to take advantage of the biodegradability of aliphatic polyester resins such as polylactic acid and PVA resins, the adhesive layer must also be biodegradable.

For example, Patent Document 1 proposes a biodegradable adhesive resin in which an α,β-unsaturated carboxylic acid or its anhydride is graft-polymerized onto a biodegradable polyester resin to produce a biodegradable acid-modified polyester resin with an acid value of 2.0 to 6.5 mg KOH/g.

International Publication No. 2019/049798

However, the biodegradable acid-modified polyester resin described in Patent Document 1 was not necessarily satisfactory in terms of achieving both resin processability and the appearance of the laminate when used as an adhesive resin for the laminate.

Therefore, the present invention aims to provide a resin composition that is preferably used for bonding a PVA-based resin layer and a biodegradable resin layer, and that also has excellent processability and appearance of the laminate.

As a result of intensive research, the inventors discovered that the above problems could be solved by a resin composition that contains an acid-modified polyester resin as a main component, and further contains a resin with a melting peak (ΔH) of 10 J/g or less and a fatty acid ester, and thus completed the present invention.

Aspect 1 of the present invention is an acid-modified polyester resin composition that contains an acid-modified polyester resin as a main component and also contains a resin having a melting peak (ΔH) of 10 J/g or less and a fatty acid ester.

Aspect 2 of the present invention is an acid-modified polyester resin composition according to aspect 1, in which the resin having a melting peak (ΔH) of 10 J/g or less has a polar group.

Aspect 3 of the present invention is an acid-modified polyester resin composition according to aspect 1 or 2, in which the content of the resin having a melting peak (ΔH) of 10 J/g or less is 0.01 to 30 mass %.

Aspect 4 of the present invention is an acid-modified polyester resin composition according to any one of aspects 1 to 3, in which the fatty acid ester is a fatty acid ester composed of a polyhydric alcohol and a fatty acid having 1 to 18 carbon atoms.

Aspect 5 of the present invention is an acid-modified polyester resin composition according to any one of aspects 1 to 4, in which the content of the fatty acid ester is 0.01 to 20 mass%.

Aspect 6 of the present invention is an acid-modified polyester resin composition according to any one of aspects 1 to 5, in which the acid-modified polyester resin is biodegradable.

Aspect 7 of the present invention is an adhesive containing any one of the acid-modified polyester resin compositions of aspects 1 to 6.

Aspect 8 of the present invention is a laminate having at least one layer containing an acid-modified polyester resin composition according to any one of aspects 1 to 6.

Aspect 9 of the present invention is a laminate having an adhesive layer between a first layer and a second layer, at least one of the first layer and the second layer being a polyvinyl alcohol-based resin layer, and the adhesive layer containing any one of the acid-modified polyester-based resin compositions of aspects 1 to 6.

The acid-modified polyester resin composition of the present invention contains an acid-modified polyester resin as a main component, and also contains a resin and a fatty acid ester having a melting peak (ΔH) of 10 J/g or less, thereby suppressing the generation of excess radicals during acid modification, thereby increasing the MFR of the acid-modified polyester resin (reducing the viscosity), and therefore has excellent processability and is easy to handle. In addition, since the acid-modified polyester resin composition of the present invention has a reduced viscosity and is softened, for example, when used as an adhesive layer for both layers in a laminate containing a PVA resin layer and a biodegradable resin layer, the generation of flow marks caused by the high viscosity adhesive resin is suppressed, and a biodegradable laminate with excellent appearance is obtained.

The configuration of the present invention is described in detail below, but these are examples of preferred embodiments.

In addition, in this specification, "biodegradable" means meeting the conditions specified in JIS K 6953-1:2011 (ISO 14855-12005).

[Acid-modified polyester resin composition]
The acid-modified polyester resin composition of the present invention contains an acid-modified polyester resin as a main component, and also contains a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester.
Here, the main component of the acid-modified polyester resin composition refers to a component that accounts for 50% by mass or more of the entire composition.

(Acid-modified polyester resin)
The acid-modified polyester resin is a polyester resin obtained by graft polymerizing an α,β-unsaturated carboxylic acid or an anhydride thereof (hereinafter, the α,β-unsaturated carboxylic acid or anhydride thereof may be referred to as "α,β-unsaturated carboxylic acids") onto various polyester resins, and serves as the base resin of the acid-modified polyester resin composition of the present invention. By including the acid-modified polyester resin in the resin composition, the adhesive strength between the polyester resin such as polylactic acid and the PVA resin is improved.

The acid-modified polyester resin is preferably biodegradable. By using a biodegradable acid-modified polyester resin, the laminate obtained by laminating a PVA resin layer and a biodegradable resin layer using an adhesive layer containing the acid-modified polyester resin will be biodegradable as a whole.

Examples of polyester resins include aliphatic-aromatic copolymer polyester resins, aliphatic polyester resins, and aromatic polyester resins.

The aliphatic-aromatic copolymer polyester resin used in the present invention is an aromatic aliphatic copolymer polyester resin containing aliphatic diol units, aliphatic dicarboxylic acid units, and aromatic dicarboxylic acid units as main structural units. Specifically, for example, it is preferable that the main structural units are aliphatic diol units represented by the following formula (1), aliphatic dicarboxylic acid units represented by the following formula (2), and aromatic dicarboxylic acid units represented by the following formula (3), and that it is biodegradable.

-O-R ¹ -O- ...(1)
In formula (1), R ¹ represents a divalent aliphatic hydrocarbon group.
-OC-R ² -CO-...(2)
In formula (2), R ² represents a single bond or a divalent aliphatic hydrocarbon group.
-OC-R ³ -CO- ...(3)
In formula (3), ^R3 represents a divalent aromatic hydrocarbon group.

The aliphatic diol that gives the aliphatic diol unit of formula (1) is not particularly limited, but from the perspective of the balance between cost and mechanical strength, one having 2 to 10 carbon atoms is preferred. Examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Among these, aliphatic diols having 2 to 4 carbon atoms are preferred, with ethylene glycol and 1,4-butanediol being more preferred, and 1,4-butanediol being particularly preferred. Note that two or more of the above aliphatic diols can also be used.

The aliphatic dicarboxylic acid component that gives the aliphatic dicarboxylic acid unit of formula (2) is not particularly limited, but is preferably one having 2 to 12 carbon atoms in terms of the balance between cost and biodegradability. Examples include succinic acid, adipic acid, suberic acid, sebacic acid, azelaic acid, dodecanedioic acid, and derivatives thereof such as alkyl esters. Among these, sebacic acid, adipic acid, azelaic acid, and derivatives thereof such as alkyl esters are preferred. Two or more types of the above aliphatic dicarboxylic acid components may also be used.

Examples of aromatic dicarboxylic acid components that give the aromatic dicarboxylic acid unit of formula (3) include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, furandicarboxylic acid, and the like, and derivatives thereof such as alkyl esters. Among them, from the viewpoint of biodegradability, R ³ is preferably a phenylene group, and specific examples of aromatic dicarboxylic acid components that give the aromatic dicarboxylic acid unit of formula (3) include terephthalic acid, isophthalic acid, and derivatives thereof such as alkyl esters, and terephthalic acid and derivatives thereof such as alkyl esters are particularly preferred. In addition, the aromatic dicarboxylic acid may be an aromatic dicarboxylic acid in which a part of the aromatic ring is substituted with a sulfonate. It is to be noted that two or more kinds of the aromatic dicarboxylic acid components can be used.

The content of aromatic dicarboxylic acid units in the aliphatic-aromatic copolymer polyester resin is preferably 5 mol% or more, more preferably 35 mol% or more, particularly preferably 40 mol% or more, and preferably 95 mol% or less, more preferably 65 mol% or less, particularly preferably 60 mol% or less, based on 100 mol% of the total dicarboxylic acid units, which are the aliphatic dicarboxylic acid units and the aromatic dicarboxylic acid units, from the viewpoints of melting point and biodegradability. In other words, the content of aromatic dicarboxylic acid units is preferably 5 mol% or more and 95 mol% or less, based on 100 mol% of the total dicarboxylic acid units, which are the aliphatic dicarboxylic acid units and the aromatic dicarboxylic acid units.

When two or more aromatic dicarboxylic acids are used, the aliphatic-aromatic copolymer polyester resin preferably has a ratio of terephthalic acid units in all aromatic dicarboxylic acid units of 40 mol% or more and 60 mol% or less. If this ratio is less than 40 mol%, heat resistance is insufficient, and if it exceeds 60 mol%, biodegradability tends to deteriorate. From this viewpoint, the ratio of terephthalic acid units in all aromatic dicarboxylic acid units in the aliphatic-aromatic copolymer polyester resin is more preferably 42 mol% or more and 58 mol% or less, and even more preferably 45 mol% or more and 55 mol% or less.

The aliphatic-aromatic copolymer polyester resin may have an aliphatic oxycarboxylic acid unit. Specific examples of the aliphatic oxycarboxylic acid component that gives the aliphatic oxycarboxylic acid unit include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, or a mixture thereof. Furthermore, the compound may be a derivative such as a lower alkyl ester or an intramolecular ester of these. When optical isomers exist, they may be in the D-form, L-form, or racemic form, and may be in the form of a solid, liquid, or aqueous solution. Among these, lactic acid or glycolic acid or a derivative thereof is preferred. These aliphatic oxycarboxylic acid components may be used alone or as a mixture of two or more types.

When the aliphatic-aromatic copolymer polyester resin contains these aliphatic oxycarboxylic acid units, the content is preferably 20 mol % or less, more preferably 10 mol % or less, assuming that the total constituent units constituting the aliphatic-aromatic copolymer polyester resin are 100 mol %.

Aliphatic polyester resins are aliphatic polyester resins that contain aliphatic diol units and aliphatic dicarboxylic acid units as the main constituent units. Aliphatic polyester resins are distinguished from the aliphatic-aromatic copolymer polyester resins described above in that they do not contain aromatic dicarboxylic acid units.

More specifically, the aliphatic polyester resin is a polyester resin containing an aliphatic diol unit represented by the following formula (4) and an aliphatic dicarboxylic acid unit represented by the following formula (5).
-O-R ⁴ -O- ...(4)
In formula (4), ^R4 represents a divalent aliphatic hydrocarbon group.
-OC-R ⁵ -CO-...(5)
In formula (5), R ⁵ represents a single bond or a divalent aliphatic hydrocarbon group.

The aliphatic diol unit represented by the above formula (4) and the aliphatic dicarboxylic acid unit represented by the above formula (5) may be derived from a compound derived from petroleum or from a compound derived from a plant raw material, but it is preferable that they are derived from a compound derived from a plant raw material.

When the aliphatic polyester resin is a copolymer, the aliphatic polyester resin may contain two or more aliphatic diol units represented by formula (4), and the aliphatic polyester resin may contain two or more aliphatic dicarboxylic acid units represented by formula (5).

The aliphatic diol that gives the aliphatic diol unit represented by formula (4) is not particularly limited, but from the viewpoint of moldability and mechanical strength, an aliphatic diol having 2 to 10 carbon atoms is preferred, and an aliphatic diol having 4 to 6 carbon atoms is particularly preferred. Examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol, and of these, 1,4-butanediol is particularly preferred. Note that two or more of the above aliphatic diols can also be used.

The aliphatic dicarboxylic acid component that gives the aliphatic dicarboxylic acid unit represented by formula (5) is not particularly limited, but is preferably an aliphatic dicarboxylic acid having 2 to 40 carbon atoms or a derivative such as an alkyl ester thereof, and particularly preferably an aliphatic dicarboxylic acid having 4 to 10 carbon atoms or a derivative such as an alkyl ester thereof. Examples of aliphatic dicarboxylic acids and derivatives such as alkyl esters thereof include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, etc., and derivatives such as alkyl esters thereof. Among these, succinic acid, adipic acid, and sebacic acid are preferred, and succinic acid and adipic acid are particularly preferred. It is also possible to use two or more types of the above aliphatic dicarboxylic acid components.

The aliphatic polyester resin may have a repeating unit (aliphatic oxycarboxylic acid unit) derived from an aliphatic oxycarboxylic acid. Specific examples of the aliphatic oxycarboxylic acid component that gives the aliphatic oxycarboxylic acid unit include, for example, lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, and the like, or derivatives thereof such as lower alkyl esters or intramolecular esters. When optical isomers exist in these, they may be in any of the D-form, L-form, or racemic form, and may be in any of the forms of solid, liquid, or aqueous solution. Among these, lactic acid or glycolic acid or derivatives thereof are particularly preferred. These aliphatic oxycarboxylic acids may be used alone or as a mixture of two or more.

When the aliphatic polyester resin contains these aliphatic oxycarboxylic acid units, from the viewpoint of moldability, the content is preferably 20 mol% or less, more preferably 10 mol% or less, even more preferably 5 mol% or less, and most preferably 3 mol% or less, assuming that all the constituent units constituting the aliphatic polyester resin are 100 mol%.

The polyester resin may be obtained by synthesis or may be commercially available. When synthesizing, a known method for producing polyester may be used. In addition, the polyester resin is not limited to one type, and two or more types of polyester resins having different types of constituent units, ratios of constituent units, production methods, physical properties, etc. may be blended and used.

Examples of polyester resins include polybutylene adipate terephthalate (hereinafter sometimes referred to as "PBAT"), polybutylene succinate terephthalate (hereinafter sometimes referred to as "PBST"), polybutylene succinate adipate (hereinafter sometimes referred to as "PBSA"), polybutylene succinate (hereinafter sometimes referred to as "PBS"), polybutylene sebacate terephthalate (hereinafter sometimes referred to as "PBSeT"), polybutylene succinate adipate terephthalate (hereinafter sometimes referred to as "PBSAT"), polycaprolactone (hereinafter sometimes referred to as "PCL"), etc.

Examples of commercially available polyester resins include "Ecoflex" manufactured by BASF, which is mainly composed of a condensation polymer of adipic acid/terephthalic acid/1,4-butanediol, and "BioPBS" manufactured by Mitsubishi Chemical, which is mainly composed of a condensation polymer of succinic acid/1,4-butanediol.

As mentioned above, acid-modified polyester resins are obtained by modifying the raw polyester resin by graft polymerization with α,β-unsaturated carboxylic acids.

Specific examples of the 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. Of these, anhydrides of α,β-unsaturated dicarboxylic acids are preferably used.
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.

The method for graft polymerizing the α,β-unsaturated carboxylic acids onto the raw material polyester resin is not particularly limited, and any known method can be used. Although a thermal reaction alone is also possible, it is preferable to use a radical initiator to increase reactivity. In addition, examples of the reaction method include a solution reaction, a reaction in suspension, and a reaction in a molten state without using a solvent (melt method), among which the melt method is preferable.

The melting method will now be described in detail.
As the melting method, a method in which the raw material polyester resin, α,β-unsaturated carboxylic acid, and radical initiator are mixed in advance and then melt-kneaded in a kneader to react, or a method in which the α,β-unsaturated carboxylic acid and radical initiator are blended with the polyester resin in a molten state in a kneader, can be used.

As a mixer used to premix the raw materials, for example, a Henschel mixer or a ribbon blender can be used, and as a kneader used for melt kneading, for example, a single-screw or twin-screw extruder, a roll, a Banbury mixer, a kneader, a Brabender mixer, etc. can be used.

The temperature during melt kneading should be set appropriately within a temperature range that is equal to or higher than the melting point of the raw polyester resin and does not cause thermal degradation. Melt kneading is preferably performed at 100 to 250°C, more preferably 160 to 230°C.

The amount of α,β-unsaturated carboxylic acids is preferably 0.0001 to 5 parts by mass, particularly 0.001 to 2 parts by mass, and especially 0.02 to 1 part by mass, per 100 parts by mass of the raw polyester resin. If the amount is too small, a sufficient amount of polar groups will not be introduced into the polyester resin, and interlayer adhesion, particularly adhesion to the PVA resin layer, tends to be insufficient. If the amount is too large, α,β-unsaturated carboxylic acids that have not been graft-polymerized may remain in the resin, which tends to result in poor appearance, etc.

The radical initiator is not particularly limited, and known radical initiators can be used. For example, 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(isobutylamide)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 kinds.

The amount of radical initiator used is preferably 0.00001 to 5.0 parts by mass per 100 parts by mass of the raw polyester resin, and more preferably 0.0001 to 1.0 part by mass, and even more preferably 0.002 to 0.5 part by mass.

If the amount of the radical initiator is too small, the graft polymerization may not occur sufficiently and the effects of the present invention may not be obtained. If the amount of the radical initiator is too large, the polyester resin may decompose to a low molecular weight, and the adhesive strength may be insufficient due to insufficient cohesive force.

In the present invention, the acid-modified polyester resin is preferably an acid-modified aliphatic-aromatic copolymer polyester resin or an acid-modified aliphatic polyester resin, and more preferably an acid-modified aliphatic-aromatic copolymer polyester resin.

The weight average molecular weight of the acid-modified polyester resin is preferably 50,000 to 400,000, more preferably 100,000 to 200,000, and particularly preferably 140,000 to 180,000. If the weight average molecular weight is too large, the melt viscosity tends to be high and melt molding tends to be difficult, whereas if it is too small, the molded product tends to be brittle.
The weight average molecular weight of the acid-modified polyester resin is measured by gel permeation chromatography (GPC).

The acid-modified polyester resin preferably has an acid value of 1.0 to 6.5 mg·KOH/g, more preferably 1.1 to 6.0 mg·KOH/g, and further preferably 1.2 to 5.0 mg·KOH/g.
If the acid value is too high, the appearance will be poor, whereas if it is too low, the adhesiveness to other resins will tend to decrease. If the acid value is too high or too low, the effect of the present invention will not be obtained.

The method for measuring the acid value will be described in detail below.
First, the acid-modified polyester resin to be measured is thoroughly washed with a solvent. Such washing is for washing away impurities in the acid-modified polyester resin, mainly unreacted α,β-unsaturated carboxylic acid or its anhydride. As such a solvent, it is necessary to use a solvent in which the acid-modified polyester resin does not dissolve, and examples of such a solvent include water, acetone, methanol, ethanol, and isopropanol.
Next, after drying the washed acid-modified polyester, 100 ml of tetrahydrofuran is placed in a test bottle as a solvent, and 5 g of acid-modified polyester resin is added while stirring with a hot stirrer (set temperature 75°C, stirrer rotation speed 400 rpm). Stir for 5 to 6 hours until the acid-modified polyester resin is dissolved. After dissolution, 4 ml of ultrapure water is added and stirred for an additional 10 minutes to prepare a test solution. The test solution is titrated with an aqueous potassium hydroxide solution (N/10) using an automatic titrator, and the acid value is calculated using the following formula.

(formula)
Acid value AV (mg KOH/g) = ((A-B) x f x 5.61) / S
A = Amount (ml) of potassium hydroxide aqueous solution N/10 required for acid-modified polyester resin B = Amount (ml) of potassium hydroxide aqueous solution N/10 required for blank test
f = Titer of N/10 potassium hydroxide aqueous solution S = Amount of acid-modified aliphatic polyester resin (B) collected (g)

As a titration device, for example, the following can be used:
Titration measuring device: Kyoto Electronics Manufacturing Co., Ltd. automatic potentiometric titrator AT-610
Reference electrode: Composite glass electrode C-171
Titration solution: Fujifilm Wako Pure Chemical Industries, Ltd. Potassium hydroxide aqueous solution (N/10)

The acid value can be controlled, for example, by the following methods.
(i) A method of adjusting the amount of a radical initiator when graft polymerizing an α,β-unsaturated carboxylic acid or anhydride thereof onto a polyester resin.
(ii) A method in which the acid-modified polyester resin is dried to reduce the water absorption rate.
Among these, the method (i) is preferred because of ease of controlling the acid value.

The melt flow rate (MFR) of the acid-modified polyester resin, measured at 210°C and 2.16 kg, is preferably 1.0 to 20.0 g/10 min, more preferably 1.5 to 10.0 g/10 min, and particularly preferably 2.0 to 8.0 g/10 min. The MFR of the acid-modified polyester resin can be adjusted by the molecular weight.

The melting point of the acid-modified polyester resin is preferably 65 to 260°C, more preferably 70 to 200°C, and even more preferably 75 to 140°C.

In the present invention, the acid-modified polyester resin is not limited to one type, and a blend of two or more types of acid-modified polyester resins having different types of constituent units, ratios of constituent units, manufacturing methods, physical properties, etc. can be used.

(Resin with melting peak (ΔH) of 10 J/g or less)
The acid-modified polyester resin composition of the present invention contains a resin having a melting peak (ΔH) of 10 J/g or less. It is presumed that the inclusion of a resin having a melting peak (ΔH) of 10 J/g or less scavenges excess active radicals and acid used in the graft polymerization reaction of the acid-modified polyester resin, thereby suppressing the increase in viscosity of the acid-modified polyester resin composition.

The melting peak (ΔH) of the resin is measured by a differential scanning calorimeter according to the following 1) to 3).
1) The resin is heated from -60°C to 220°C at a heating rate of 10°C/min, and then held at that temperature for 1 minute.
2) Cool to -60°C at a rate of 10°C/min.
3) The temperature is raised from -60°C to 220°C at a rate of 10°C/min, and the ΔH of the melting peak is measured by a differential scanning calorimeter.

The resin having a melting peak (ΔH) of 10 J/g or less is preferably a resin having a polar group, and examples of the polar group include an acid anhydride group, a carboxylic acid group, a hydroxyl group, an ester group, etc., and the same is true for preferred polar groups.

In addition, it is preferable that the resin having a melting peak (ΔH) of 10 J/g or less has at least one selected from the group consisting of a double bond, an aromatic ring, and a heteroatom. It is presumed that by having at least one selected from the group consisting of a double bond, an aromatic ring, and a heteroatom, excess active radicals and acid are captured, thereby suppressing the increase in viscosity in the acid-modified polyester resin composition, and therefore the effects of the present invention are easily obtained. Examples of heteroatoms include nitrogen (N) atoms, oxygen (O) atoms, and sulfur (S) atoms, and among these, it is preferable to have an oxygen (O) atom as the heteroatom.

From the viewpoint of improving processability, the melting peak (ΔH) is preferably 10 J/g or less, and although there is no particular lower limit, it is preferably 0 J/g or more, and more preferably 0.1 J/g or more.

Specific examples of resins with a melting peak (ΔH) of 10 J/g or less include hydrogenated petroleum resins, rosin esters, rosin diols, acid-modified rosins, and terpene phenols.

(Fatty acid ester)
The acid-modified polyester resin composition of the present invention contains a fatty acid ester as an additive. It is presumed that the inclusion of a fatty acid ester softens the acid-modified polyester, suppresses the occurrence of flow marks when the acid-modified polyester is laminated, and improves the appearance of the laminate.

From the viewpoint of compatibility, the fatty acid ester is preferably a fatty acid ester composed of a polyhydric alcohol and a fatty acid having 1 to 18 carbon atoms. Here, the number of carbon atoms of the fatty acid constituting the fatty acid ester is preferably 1 to 18, more preferably 1 to 12, and even more preferably 1 to 6. Suitable specific examples of fatty acid esters include glycerin fatty acid esters, sugar esters, polyglycerin fatty acid esters, etc.

(Acid-modified polyester resin composition)
As described above, the polyester resin composition of the present invention contains an acid-modified polyester resin as a base resin, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester.

The acid-modified polyester resin is preferably present in an amount of 50 to 99.98% by mass, more preferably 80 to 99.70% by mass, and even more preferably 90 to 99.50% by mass in the acid-modified polyester resin composition. If the content of the acid-modified polyester resin is 50% by mass or more, sufficient adhesive strength can be exerted, and if it is 99.98% by mass or less, processability is improved.

Resins having a melting peak (ΔH) of 10 J/g or less are preferably contained in the acid-modified polyester resin composition in the range of 0.01 to 30% by mass. When the content of resins having a melting peak (ΔH) of 10 J/g or less in the acid-modified polyester resin composition is 0.01% by mass or more, the desired effect of the present invention can be obtained. If the content of resins having a melting peak (ΔH) of 10 J/g or less is too high, the pellets may become tacky and difficult to handle, so it is preferable to contain them in an amount of 30% by mass or less. The content of resins having a melting peak (ΔH) of 10 J/g or less in the acid-modified polyester resin composition is more preferably 0.30% by mass or more, more preferably 0.50% by mass or more, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

The fatty acid ester is preferably contained in the acid-modified polyester resin composition in the range of 0.01 to 20% by mass. If the fatty acid ester content in the acid-modified polyester resin composition is 0.01% by mass or more, the desired effect of the present invention can be obtained, and if the fatty acid ester content is too high, venting due to the evaporation of the fatty acid ester during extrusion processing tends to occur, so it is preferable to contain it at 20% by mass or less. The fatty acid ester content in the acid-modified polyester resin composition is more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and more preferably 7% by mass or less, and even more preferably 5% by mass or less.

The acid-modified polyester resin composition of the present invention may contain other components within the scope of the present invention, so long as the effects of the present invention are not impaired. Examples of other components include reinforcing agents, fillers, plasticizers, pigments, dyes, lubricants, antioxidants, antistatic agents, UV absorbers, heat stabilizers, light stabilizers, surfactants, antibacterial agents, antistatic agents, drying agents, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, and crystal nucleating agents.

The acid-modified polyester resin composition of the present invention is usually made into a molded product such as pellets or powder in order to be used as a molding material. Among them, the pellet shape is preferred from the viewpoints of ease of feeding into a molding machine, handling, and minimizing problems of fine powder generation.
While known methods can be used for forming the material into pellets, it is efficient to extrude the material in the form of a strand from an extruder, cool it, and then cut it to a predetermined length to form cylindrical pellets.
The size of such cylindrical pellets is preferably 1 to 4 mm in length, more preferably 2 to 3 mm, and is preferably 1 to 4 mm in diameter, more preferably 2 to 3 mm.

The method for producing the acid-modified polyester resin composition of the present invention is not particularly limited, and known methods can be used. Examples of the method include a method in which a resin having a melting peak (ΔH) of 10 J/g or less and a fatty acid ester are added and mixed when producing the acid-modified polyester resin, and a method in which a resin having a melting peak (ΔH) of 10 J/g or less and a fatty acid ester are added and mixed after producing the acid-modified polyester resin.
For example, the following (i) to (ix) can be mentioned.
(i) A method of mixing α,β-unsaturated carboxylic acids, a radical initiator, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester in advance with a polyester resin as a raw material, and then melt-kneading and reacting in a kneader. (ii) A method of mixing α,β-unsaturated carboxylic acids, a radical initiator, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester in a molten state in a kneader, melt-kneading and reacting. (iii) A method of mixing α,β-unsaturated carboxylic acids and a radical initiator in a molten state in a kneader, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester in a molten state in a kneader, melt-kneading and reacting. (iv) A method of mixing α,β-unsaturated carboxylic acids and a radical initiator in advance with a polyester resin as a raw material, and then melt-kneading and reacting in a kneader, while mixing and mixing a resin having a melting peak (ΔH) of 10 J/g or less and a fatty acid ester. (v) A method of dissolving α,β-unsaturated carboxylic acids, a radical initiator, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester in a solvent, mixing and reacting in a solution state with a polyester resin as a raw material; (vi) A method of dissolving α,β-unsaturated carboxylic acids, a radical initiator, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester in a solvent, mixing and reacting in a suspension state with a polyester resin as a raw material; (vii) A method of dry blending an acid-modified polyester resin, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester, melting and kneading the mixture; (viii) A method of dissolving an acid-modified polyester resin, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester in a solvent, mixing and mixing in a solution state; (ix) A method of pulverizing, melting and kneading a laminate containing an acid-modified polyester resin layer, a resin having a melting peak (ΔH) of 10 J/g or less, and a fatty acid ester layer. Although the methods (i) to (vi) can be carried out by thermal reaction alone, it is preferable to use a radical initiator in order to increase reactivity. As the reaction method, a solution reaction, a reaction in a suspension, a reaction in a molten state without using a solvent or the like (melting method), etc. can be mentioned, and among them, the melting method is preferable.
The method (ix) is mainly used for recycling the ends of a laminate.

As a mixer used to premix the raw materials, for example, a Henschel mixer or a ribbon blender can be used, and as a kneader used for melt kneading, for example, a single-screw or twin-screw extruder, a roll, a Banbury mixer, a kneader, a Brabender mixer, etc. can be used.

As a method of melt-kneading, in the production method (iv) above, for example, an acid-modified polyester resin, a resin having a melting peak (ΔH) of 10 J/g or less, an aliphatic ester and any optional components may be mixed using a mixer such as a Henschel mixer or a ribbon blender, and then melted and kneaded using a melt kneader such as a single-screw or twin-screw extruder, a roll, a Banbury mixer, a kneader or a Brabender mixer.
As for the manufacturing method of the above (ix), for example, there can be mentioned a method in which unnecessary parts such as both ends of a multilayer film having layers each containing an acid-modified polyester resin, a resin having a melting peak (ΔH) of 10 J/g or less, and an aliphatic ester are crushed, and an optional component is added as necessary, and the mixture is melted and kneaded in a melt kneader such as a single-screw or twin-screw extruder, a roll, a Banbury mixer, a kneader, or a Brabender mixer.

The temperature during melt kneading can be set appropriately within a temperature range that is equal to or higher than the melting points of the acid-modified polyester resin and the aliphatic ester and does not cause thermal degradation, but is preferably 100 to 300°C, more preferably 140 to 250°C, and particularly preferably 160 to 230°C.

The resin composition used in the present invention has excellent fluidity and is easy to handle, making it useful as a molding material. As a melt molding method, known molding methods such as extrusion molding, inflation molding, injection molding, blow molding, vacuum molding, compressed air molding, compression molding, and calendar molding can be used.

The molded products of the present invention can have a wide variety of shapes, including films, sheets, pipes, disks, rings, bags, bottles, and fibers.

[Laminate]
The acid-modified polyester resin composition of the present invention is used as an adhesive resin (adhesive) to bond two members together.
The laminate of the present invention has at least one layer containing the acid-modified polyester resin composition of the present invention.
Moreover, a laminate according to one aspect of the present invention includes an adhesive layer provided between a first layer and a second layer, at least one of the first layer and the second layer being a PVA-based resin layer, and the adhesive layer contains the acid-modified polyester-based resin composition of the present invention.
In particular, the laminate of the present invention is preferably one in which a PVA-based resin layer is used as the gas barrier layer and a biodegradable resin layer is used as the outer layer.

Hereinafter, the laminate including an adhesive (A) layer containing the acid-modified polyester resin composition of the present invention, a PVA-based resin (B) layer, and a biodegradable resin (C) layer will be mainly described, but the present invention is not limited thereto.

(Adhesive (A) Layer)
The adhesive (A) layer is an adhesive layer used when laminating a PVA-based resin (B) layer and a biodegradable resin (C) layer, and is formed from an adhesive resin containing the acid-modified polyester-based resin composition of the present invention described above.
The adhesive resin contains the acid-modified polyester resin composition of the present invention as a main component, and the content of the acid-modified polyester resin composition 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.

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

The PVA resin (B) used in the present invention is a resin mainly composed of vinyl alcohol structural units, 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 corresponding to the degree of saponification.

The vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, etc., with vinyl acetate being economically preferred.

The average degree of polymerization of the PVA-based resin (B) used in the present invention (measured according to JIS K6726) is preferably 200 to 1800, more preferably 300 to 1500, and even more preferably 300 to 1000.

If the average degree of polymerization is too small, the mechanical strength of the PVA-based resin (B) layer tends to be insufficient. Conversely, if the average degree of polymerization is too large, the flowability tends to decrease and moldability decreases when the PVA-based resin (B) layer is formed by hot melt molding, and abnormal shear heat may occur during molding, making the PVA-based resin (B) more susceptible to thermal decomposition.

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

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

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-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 their salts, monoesters, and dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; and diacetone acrylate. Examples of suitable vinyl compounds include amides such as arylamide, acrylamide, and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or their salts, 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 3,4-diacetoxy-1-butene, as well as vinyl compounds such as isopropenyl acetate and 1-methoxyvinyl acetate, as well as substituted vinyl acetates, vinylidene chloride, 1,4-diacetoxy-2-butene, and vinylene carbonate.

Modified PVA resins into which functional groups have been introduced by post-modification include those that have acetoacetyl groups by reaction with diketene, those that have polyalkylene oxide groups by reaction with ethylene oxide, those that have hydroxyalkyl groups by reaction with epoxy compounds, and those obtained by reacting PVA with aldehyde compounds having various functional groups.

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 characteristics vary greatly depending on the modified species, but it is preferably 1 to 20 mol%, and especially preferably in the range of 2 to 10 mol%.

Among these various modified PVA-based resins, in the present invention, a PVA-based resin having a structural unit having a 1,2-diol structure in the side chain, as shown in the following general formula (6) (hereinafter, sometimes referred to as a "1,2-diol structural unit"), is preferably used because it facilitates melt molding in the manufacturing method of the laminate of the present invention described below.

In the 1,2-diol structural unit represented by the general formula (6), R ¹¹ to R ¹⁴ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.

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. If necessary, 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.

Furthermore, X in the 1,2-diol structural unit represented by the general formula (6) represents a single bond or a bonding chain.
Examples of such bonding chains 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 halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms), as well as -O-, -(CH ₂ O) _t -, -(OCH ₂ ) _t -, -(CH ₂ O) _t CH ₂ -, -CO-, -CO
Examples of such groups include CO-, -CO(CH2) _tCO- , -CO( _{C6H4 )} CO-, -S-, -CS-, -SO-, -SO2-, -NR- _, -CONR-, -NRCO-, -CSNR-, -NRCS-, -NRNR-, -HPO4-, _-Si (OR) _2- , -OSi(OR)2-, -OSi(OR) _2O- , -Ti(OR) _2- , -OTi(OR) _2- , -OTi(OR) _2O- , -Al(OR)-, -OAl(OR)-, -OAl(OR)O- and the like (each R is independently any 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).
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 _{--CH.sub.2OCH.sub.2--} .

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

Among the 1,2-diol structural units represented by general formula (6), a structural unit represented by the following general formula (6') in which R ¹¹ to R ¹⁴ are all hydrogen atoms and X is a single bond is most preferred.

Examples of a method for producing a PVA-based 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.

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 preferably 1 to 20 mol %, more preferably 2 to 10 mol %, and particularly preferably 3 to 8 mol %. If the content is too low, it is difficult to obtain the effect 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 decrease significantly.

The content of 1,2-diol structural units in a PVA-based resin can be determined from the ^1H -NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane) of a completely saponified PVA-based resin. 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 units, methylene protons in the main chain, and protons of hydroxyl groups linked to the main chain.

The PVA-based resin (B) used in the present invention 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 can be used: the above-mentioned unmodified PVAs, unmodified PVA and a PVA-based resin having a structural unit represented by general formula (6), PVA-based resins having structural units represented by general formula (6) with different degrees of saponification, polymerization, modification, etc., unmodified PVA, or a PVA-based resin having a structural unit represented by general formula (6) and another modified PVA-based resin, etc.

In addition, the PVA-based resin (B) layer used in the present invention may contain, in addition to the PVA-based 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, and a crystal nucleating agent.

(Biodegradable resin (C) layer)
The biodegradable resin (C) layer is a layer containing the biodegradable resin (C) as a main component, and preferably contains 70% by mass or more, more preferably 80% by mass or more, of the biodegradable resin (C). % by mass or more, more preferably 90% by mass or more, with the upper limit being 100% by mass.

Examples of biodegradable resins (C) include polylactic acid (PLA), condensation polymer of adipic acid/terephthalic acid/1,4-butanediol (polybutylene adipate terephthalate (PBAT)), condensation polymer of succinic acid/1,4-butanediol/lactic acid, polybutylene succinate terephthalate (PBST), polybutylene succinate adipate (PBSA), polybutylene succinate (PBS), polybutylene sebacate terephthalate (PBSeT), polybutylene succinate adipate terephthalate (PBSAT), polycaprolactone (PCL), aliphatic polyesters such as polyglycolic acid; modified starch; casein plastic; cellulose, etc., and these can be used alone or in combination of two or more.

Among these, polylactic acid and polybutylene adipate terephthalate are preferred in terms of strength. Furthermore, a mixture of polylactic acid and polybutylene adipate terephthalate is preferred in terms of adhesion and strength.

Polylactic acid is an aliphatic polyester resin whose main component is lactic acid structural units, and is a polymer made from L-lactic acid, D-lactic acid, or their cyclic dimers L-lactide, D-lactide, and DL-lactide.

The polylactic acid used in the biodegradable resin (C) layer 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.

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.

The content ratio of L-lactic acid and D-lactic acid in polylactic acid (mass of L-lactic acid/mass of D-lactic acid) is preferably 95/5 or more, particularly 99/1 or more, and especially 99.8/0.2 or more. The higher this value, the higher the melting point and the better the heat resistance, and conversely, the lower this value, the lower the melting point and the more likely the heat resistance is insufficient.

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

The weight-average molecular weight of polylactic acid is preferably 20,000 to 1,000,000, particularly 30,000 to 300,000, and especially 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, and conversely, if the weight-average molecular weight is too small, the mechanical strength of the resulting laminate tends to be insufficient.

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

Examples of commercially available polylactic acid 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.

Polybutylene adipate terephthalate is obtained by condensation polymerization of adipic acid, terephthalic acid, and 1,4-butanediol.

The content of adipic acid in polybutylene adipate terephthalate is preferably 10 to 50 mol %, more preferably 15 to 40 mol %.
The content of terephthalic acid in polybutylene adipate terephthalate is preferably from 5 to 45 mol %, more preferably from 8 to 35 mol %.
The content of 1,4-butanediol in polybutylene adipate terephthalate is preferably 5 to 45 mol %, more 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.

The weight average molecular weight of polybutylene adipate terephthalate is 3,000 to 1,000,000, preferably 20,000 to 600,000, and more preferably 50,000 to 400,000. If the weight average molecular weight is too small, production becomes difficult, and if the weight average molecular weight is too large, the melt viscosity tends to increase and moldability tends to decrease.

The weight average molecular weight can be measured by the method described above.

Polybutylene adipate terephthalate may contain other copolymer components in addition to adipic acid, terephthalic acid, and 1,4-butanediol.

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.

The content of such other copolymerization components is approximately 0.1 to 30 mol % of the total polybutylene adipate terephthalate.

When using a mixture of polylactic acid and polybutylene adipate terephthalate, the mixing ratio (mass ratio) of polylactic acid/polybutylene adipate terephthalate is preferably 10/90 to 90/10, and more preferably 20/80 to 60/40.

The biodegradable resin (C) layer used in the present invention may also contain, in addition to the biodegradable resin (C), heat stabilizers, antioxidants, ultraviolet absorbers, crystal nucleating agents, antistatic agents, flame retardants, plasticizers, lubricants, fillers, lubricants, crystal nucleating agents, etc.

The laminate of the present invention preferably has a layer structure of 3 to 15 layers, more preferably 3 to 7 layers, and particularly preferably 5 to 7 layers.

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

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 configuration in which a biodegradable resin (C) layer is provided in the portion of the PVA-based resin (B) layer that comes into contact with the outside air or the contents containing moisture.

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

Furthermore, with regard to the thickness of each layer constituting the laminate, the thickness of the biodegradable resin (C) layer is preferably 0.4 to 14,000 μm, more 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.

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

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

When there are multiple layers of each, the ratio of the thickness of the biodegradable resin (C) layer to the thickness of the PVA-based resin (B) layer (thickness of the biodegradable resin (C) layer/thickness of the PVA-based resin (B) layer) is preferably 1 to 100, more preferably 2.5 to 50, in terms of the ratio of the total thicknesses. 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.

In addition, the thickness ratio of the laminate of the present invention and the adhesive (A) layer (adhesive layer) (thickness of adhesive (A) layer/thickness of the laminate of the present invention) is preferably 0.005 to 0.5, and more preferably 0.01 to 0.3, in terms of the ratio of the total thickness when there are multiple adhesive (A) layers. If this ratio is too large, the appearance tends to deteriorate, and if this ratio is too small, the adhesive strength tends to weaken.

The laminate of the present invention can be manufactured by a conventional molding method, specifically, a melt molding method or a molding method from a solution state.

For example, examples of melt molding methods include a method of melt extrusion laminating an adhesive (A) containing the acid-modified polyester resin of the present invention and a PVA-based resin (B) sequentially or simultaneously onto a film or sheet of a biodegradable resin (C); conversely, a method of melt extrusion laminating an adhesive (A) and a biodegradable resin (C) sequentially or simultaneously onto a film or sheet of a PVA-based resin (B); or a method of co-extruding a biodegradable resin (C), an adhesive (A), and a PVA-based resin (B).

As a molding method from a solution state, for example, a method can be used in which a solution of adhesive (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-based resin (B) is solution-coated.

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

Examples of the co-extrusion method include an inflation method, a T-die method, a multi-manifold die method, a feed block method, and a multi-slot die method. The shape of the die may be a T-die, a round die, or the like.
The melt molding temperature during melt extrusion is preferably in the range of 140 to 250°C, more preferably 160 to 230°C.

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

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

When the objective is to produce a film or sheet-like molded product, it is preferable to use uniaxial or biaxial stretching as such a stretching method.

In the case of die forming methods such as deep drawing, vacuum forming, pressure forming, and 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, pressure air force, etc.

When the object is to produce a molded product such as a cup or 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 use a mold forming method in which a mold is used for stretching, such as deep drawing, vacuum forming, pressure forming, or vacuum pressure forming.

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 adhesive (A) layer, and between the PVA-based resin (B) layer and the adhesive (A) layer.

At least, both the biodegradable resin (C) and the PVA-based resin (B) are biodegradable, and the laminate of the present invention also has excellent biodegradability. From this viewpoint, it is also preferable that the acid-modified polyester-based resin composition contained in the adhesive (A) is biodegradable.

The laminate of the present invention is biodegradable and can be easily disposed of in compost, for example, coffee capsules (coffee bean containers for capsule-type coffee makers), shrink films, and other food and beverage containers.

Furthermore, when the laminate of the present invention has a PVA-based resin (B) layer, the PVA-based resin (B) layer can be dissolved in water and removed, and only the remaining water-insoluble resin can be recycled.

The present invention will be described below with reference to examples. However, the present invention is not limited to the description of the examples as long as it does not depart from the gist of the present invention.
In the examples, "parts" and "%" are based on mass.

The raw material resins and additives used in each example are as follows:
<Raw material resin>
(A) Polybutylene adipate terephthalate (PBAT): "Ecoflex C1200" manufactured by BASF
(B) Polybutylene succinate terephthalate (PBST): polyester copolymer produced in Production Example 1 below <Additive>
(a) Rosin ester: "RE100L" manufactured by Kraton Corporation (melting peak (ΔH) 3.2 J/g, double bond/heteroatom included)
(b) Terpene phenol: "TP2040" manufactured by Kraton Corporation (melting peak (ΔH) 2.2 J/g, double bond/aromatic ring/heteroatom included)
(c) Glycerol fatty acid ester: "Triacetin" (number of carbon atoms of fatty acid: 2) manufactured by Tokyo Chemical Industry Co., Ltd.
(d) Glycerol fatty acid ester: "Tributyrin" (number of carbon atoms of fatty acid: 5) manufactured by Tokyo Chemical Industry Co., Ltd.

The melting peaks (ΔH) of the additives (a) and (b) were measured using a differential scanning calorimeter (TA Instruments' DSC Q2000) according to the following steps 1) to 3). 1) The additive was heated from -60°C to 220°C at a heating rate of 10°C/min, and then held at that temperature for 1 minute. 2) The additive was cooled to -60°C at a cooling rate of 10°C/min.
3) The ΔH of the melting peak when the temperature was raised from −60° C. to 220° C. at a heating rate of 10° C./min was measured by a differential scanning calorimeter.

(Production Example 1: Production of Polybutylene Succinate Terephthalate (PBST))
[Preparation of polycondensation catalyst]
343.5 parts of magnesium acetate tetrahydrate were placed in a reactor equipped with a stirrer, and 1434 parts of anhydrous ethanol (purity 99% or more) were added. 218.3 parts of ethyl acid phosphate (mixture mass ratio of monoester and diester is 45:55) were added and stirred at 23°C. After confirming that magnesium acetate was completely dissolved, 410.0 parts of tetra-n-butyl titanate were added. Stirring was continued for another 10 minutes to obtain a homogeneous mixed solution. This mixed solution was concentrated under reduced pressure while controlling the temperature at 60°C or less. Approximately half of the amount of ethanol added was distilled off, leaving a translucent viscous liquid. 1,108 parts of 1,4-butanediol were added thereto, and further concentration was performed under reduced pressure while controlling the temperature at 80°C or less to obtain a catalyst solution with a titanium atom content of 3.5%.

[Polymerization of polybutylene succinate terephthalate (PBST)]
A reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer and pressure reducing port was charged with 33.6 parts of succinic acid, 38.6 parts of terephthalic acid, 69.7 parts of 1,4-butanediol, 0.138 parts of trimethylolpropane (0.200 mol% relative to 100 mol% of the total of succinic acid and terephthalic acid), 0.10 parts of polyethylene wax (Honeywell's "ACumistB6", melting point: 124 ° C.), and 0.0017 parts of sodium hydroxide (NaOH), and further added tetra-n-butyl titanate so that the titanium atom was 30 ppm per polyester resin obtained. Nitrogen gas was introduced into the vessel while stirring the contents of the vessel, and the system was placed under a nitrogen atmosphere by vacuum replacement. Next, the temperature was raised from 160 ° C. to 230 ° C. over 1 hour while stirring the system, and the reaction was carried out at this temperature for 3 hours. The terminal acid value of the resulting ester oligomer was measured and found to be 90 eq./ton.
The catalyst solution was added to this ester oligomer in an amount to give 70 ppm titanium atom per polyester obtained, and the temperature was raised to 250° C. over 45 minutes. At the same time, the pressure was reduced to 0.07×10 ³ Pa or less over 1 hour and 20 minutes. Polycondensation was continued while maintaining the heated and reduced pressure state. The polymerization was terminated when a predetermined viscosity was reached, and polybutylene succinate terephthalate (PBST) was obtained.
The obtained PBST had an MFR of 4.5 g/10 min. The MFR was measured at 190° C. and a load of 2.16 kg according to JIS K7210 (2014).

Example 1
[Preparation of Acid-Modified Polyester Resin Composition]
As the raw polyester resin, 100 parts of (A) PBAT, 0.1 parts of maleic anhydride, and 0.14 parts of 2,5-dimethyl-2,5-bis(t-butyloxy)hexane ("Trigonox 101-50D-PD" manufactured by Kayaku Nouryon Co., Ltd.) as a radical initiator were dry-blended. To this mixture, 0.5% of (a) rosin ester and 1% of (c) glycerin fatty acid ester were added, and the mixture was melt-kneaded under the following conditions in a twin-screw extruder, extruded into a strand shape, air-cooled, and cut with a pelletizer to obtain an acid-modified polyester resin composition in the form of cylindrical pellets.

Twin screw extruder diameter (D): 15 mm
L/D: 60
Screw rotation speed: 200 rpm
Mesh: 60/90/60 mesh
Processing temperature: 190°C
Discharge volume: 5kg

(Examples 2 to 18, Comparative Examples 1 to 13)
Except for changing the resin composition as shown in Table 1, the same procedure as in Example 1 was carried out to obtain an acid-modified polyester resin composition.

For Examples 1 to 18 and Comparative Examples 1 to 13, the MFR of the resin composition was measured, and the appearance of the laminate was evaluated.
The results are shown in Table 1.

[Measurement of MFR of resin]
The melt flow rate (MFR) of the resin composition was measured by Method A in accordance with JIS K 7210 (1999). The measurement temperature was 210° C. and the load was 2.16 kg.
<Evaluation criteria>
Criteria: 3.1 [g/10 min] or more indicates good processability.

[Preparation of Laminate]
Using polylactic acid (C) (Nature Works'"Ingeo4032D"), PVA-based resin (B) (Mitsubishi Chemical's "Nichigo G-Polymer"), and acid-modified polyester-based resin composition (A), a three-type, five-layer laminate of polylactic acid (C) layer/acid-modified polyester-based resin composition (A) layer/PVA-based resin (B) layer/acid-modified polyester-based resin composition (A) layer/polylactic acid (C) layer was produced using a three-type, five-layer multilayer cast molding machine. The thickness of the obtained laminate was 100 μm, and the thicknesses of the individual layers were 30 μm/10 μm/20 μm/10 μm/30 μm.

The set temperatures of each extruder and roll were as follows: (C1 to C4: cylinders, H: head, AD1 to AD3: adapters, FB1 to FB2: feed blocks, D1 to D6: dies).
Polylactic acid (C): C1/C2/C3/C4/H/AD1/AD2/AD3 = 180/200/210/210/210/200/200/200°C
PVA resin (B): C1/C2/C3/C4/H/AD1/AD2=190/200/210/210/210/210/210°C
Acid-modified polyester resin composition (A): C1/C2/C3/H/AD1/AD2/AD3=180/200/210/210/210/210/210°C
Feed block: FB1/FB2=200/200° C.
Dice: D1/D2/D3/D4/D5/D6 = 200/200/200/200/200/200℃
Roll temperature: 60°C
Take-up speed: 8m/min
Die width: 450 mm

[Appearance evaluation]
The appearance of the obtained laminate was evaluated based on the following criteria: With respect to the following evaluation criteria, "A" and "B" are acceptable, and "C" and "D" are unacceptable.
・Thickness: Measured with a contact type film thickness gauge ・Transparency: Visually check for appearance defects such as flow marks and orange peel <Evaluation criteria>
A: The laminate had no uneven thickness and had high transparency.
B: The laminate had no uneven thickness or had high transparency.
C: The thickness of the laminate was partially non-uniform and the laminate was partially cloudy.
D: The thickness of the laminate was uneven throughout the entire laminate, and the laminate was generally cloudy.

All of Examples 1 to 18, which used acid-modified polyester resin compositions containing a resin with a melting peak (ΔH) of 10 J/g or less and a fatty acid ester, were found to have a high MFR and excellent appearance when used in laminates. On the other hand, Comparative Examples 1 to 13, which did not contain a resin with a melting peak (ΔH) of 10 J/g or less or a fatty acid ester, or did not contain either, showed poor performance in either case and were unable to achieve both processability and appearance.

Claims (9)

An acid-modified polyester resin composition comprising an acid-modified polyester resin as a main component, and also comprising a resin having a melting peak (ΔH) of 10 J/g or less and a fatty acid ester. The acid-modified polyester resin composition according to claim 1, characterized in that the resin having a melting peak (ΔH) of 10 J/g or less has a polar group. The acid-modified polyester resin composition according to claim 1, characterized in that the content of the resin having a melting peak (ΔH) of 10 J/g or less is 0.01 to 30 mass %. The acid-modified polyester resin composition according to claim 1, characterized in that the fatty acid ester is a fatty acid ester composed of a polyhydric alcohol and a fatty acid having 1 to 18 carbon atoms. The acid-modified polyester resin composition according to claim 1, characterized in that the fatty acid ester content is 0.01 to 20% by mass. The acid-modified polyester resin composition according to claim 1, characterized in that the acid-modified polyester resin is biodegradable. An adhesive comprising the acid-modified polyester resin composition according to any one of claims 1 to 6. A laminate having at least one layer containing the acid-modified polyester resin composition according to any one of claims 1 to 6. A laminate having an adhesive layer between a first layer and a second layer,
At least one of the first layer and the second layer is a polyvinyl alcohol-based resin layer,
A laminate comprising the acid-modified polyester resin composition according to any one of claims 1 to 6, wherein the adhesive layer comprises: