JP7503929B2 - Biodegradable laminated paper and packaging materials - Google Patents

Description

The present invention relates to biodegradable laminated paper that is made by laminating paper and a biodegradable resin layer.

In recent years, attention has been focused on problems such as marine pollution caused by plastic waste. Since most plastic materials were developed with the aim of high functionality and long-term stability, they do not easily decompose in the natural environment. The increase in plastic waste has become a major social issue, and the development of environmentally friendly products is accelerating. As a measure to address the plastic waste problem, for example, "plastic-free" efforts are being made to reduce the amount of plastic materials used and the amount of plastic waste by switching to materials that have a lower environmental impact. Known examples of materials with a lower environmental impact include materials made from processed natural materials such as paper, biodegradable resins in which the plastic material itself is hydrolyzed and decomposed into harmless components such as carbon dioxide and water by microorganisms after disposal, and biomass plastics derived from living organisms that do not use petroleum. Among these, paper products have attracted attention because the raw materials can be recycled and can be decomposed after disposal.

In packaging materials such as containers for packaging various products including food, among other paper products, laminated paper made by bonding thermoplastic resin and paper is used with the aim of imparting performance according to the application, such as moisture resistance, oil resistance, heat sealability (also called thermal adhesion), etc. Known thermoplastic resins used in this laminated paper include polyolefin resins such as polyethylene and polypropylene, and polyester resins such as polyethylene terephthalate (PET). There are many applications for packaging materials that require heat sealability, and for example, Patent Document 1 discloses a packaging laminate that uses a thermoplastic resin with heat sealability as a surface layer.

On the other hand, laminated paper using biodegradable resin as thermoplastic resin is known. Examples of biodegradable resin include synthetic compounds such as polylactic acid (PLA), aliphatic polyester resin, aliphatic aromatic polyester resin, polyvinyl alcohol, etc., modified natural products such as chitosan, cellulose, starch, cellulose acetate, starch, etc., polyesters accumulated in the bodies of microorganisms such as bacteria, mold, and algae during the metabolic process, etc.
However, when biodegradable resins such as polylactic acid are used as packaging materials, they have heat sealability, but have poor oxygen barrier properties (i.e., poor oxygen permeability) compared to polyolefins such as polyethylene and polyesters, and are not suitable for packaging products that deteriorate in the presence of oxygen, limiting their applications. Thus, there has been a demand for a packaging material that is biodegradable and has both oxygen barrier properties and heat sealability.

As an example of a laminated paper with oxygen barrier properties, Patent Document 2 proposes a laminated food packaging material in which an oxygen barrier layer made of polyvinyl alcohol and fine layered silicate and a thermoplastic resin layer are laminated on a paper core layer.

The laminated food packaging material disclosed in Patent Document 2 has an oxygen barrier layer and is a packaging material with excellent biodegradability and oxygen barrier properties. However, polyvinyl alcohol is used for the oxygen barrier layer, but since it has a high degree of saponification and cannot be melt-molded, the oxygen barrier layer is formed directly on the paper core layer, and a thermoplastic resin is melt-extruded thereto to bond the thermoplastic resin layer and the oxygen barrier layer without using an adhesive. When the thermoplastic resin is polylactic acid, it has poor adhesion to polyvinyl alcohol, so the thermoplastic resin layer and the oxygen barrier layer peel off during use, and sufficient properties are not obtained as a packaging material. In addition, polyvinyl alcohol forming the oxygen barrier layer is a relatively hard resin, and combined with the fact that the hard oxygen barrier layer is laminated so as to be in contact with the paper, there is a risk that cracks will occur in the oxygen barrier layer during processing into a packaging material or when bending during use, resulting in a decrease in oxygen barrier properties.

Until now, no study has been done on preventing the deterioration of oxygen barrier properties during processing into packaging materials or folding operations during use, and there is still room for improvement to create a laminated paper that is biodegradable while also having oxygen barrier properties and heat sealability, making it suitable for packaging materials.

Furthermore, as a packaging material, it is necessary for the surface to have slipperiness, so that when two sheets of the resin are stacked so that they face each other, pressed down with a finger from above and moved horizontally from side to side, they can move easily. Some types of biodegradable resins have poor surface slipperiness, and when molded into a bag, for example, the opening of the bag can become blocked, making it difficult to open, making it difficult to use as a packaging material.

Japanese Patent Application Laid-Open No. 11-198289 JP 2008-105709 A

The present invention aims to provide a biodegradable laminated paper and packaging material that is suitable for use as packaging materials, which is a biodegradable laminate having a paper base material and a biodegradable resin layer, and which combines oxygen barrier properties and heat sealability, and in which the deterioration of oxygen barrier properties caused by folding operations during processing into packaging materials or during use is suppressed, and which also has a slippery surface.

The present invention has been made to solve the above problems, and the means for achieving this include:
A laminated paper comprising a paper base material and a biodegradable resin layer laminated on one or both sides of the paper base material,
the biodegradable resin layer has a biodegradable heat seal layer, a biodegradable adhesive layer, and a biodegradable oxygen barrier layer, and the biodegradable heat seal layers are laminated on both sides of the biodegradable oxygen barrier layer via the biodegradable adhesive layers;
the biodegradable heat seal layer contains polylactic acid and an aliphatic polyester-based resin and/or an aliphatic-aromatic polyester-based resin,
The biodegradable oxygen barrier layer is characterized by containing a butenediol-vinyl alcohol copolymer.

The biodegradable heat seal layer of the present invention preferably contains polylactic acid and aliphatic polyester resin in a mass ratio of 50/50 to 10/90.

The biodegradable heat seal layer of the present invention preferably contains polylactic acid and aliphatic aromatic polyester resin in a mass ratio of 80/20 to 10/90.

The biodegradable laminated paper of the present invention is suitable for use as a packaging material.

The present invention provides a biodegradable laminated paper that is suitable for use as a packaging material, and has a slippery surface, and is a biodegradable laminate that combines oxygen barrier properties and heat sealability, and is less susceptible to deterioration in oxygen barrier properties due to folding operations during processing into packaging materials or use.

FIG. 1 is a diagram illustrating an embodiment of the present invention. FIG. 13 is a diagram illustrating another embodiment of the present invention.

The embodiments of the present invention will be explained using the drawings. Note that the present invention is not limited to those shown in the drawings.

As shown in FIG. 1, the present invention is a biodegradable laminated paper 1 that is composed of a paper base material 2 and a biodegradable resin layer 3 laminated on one or both sides of the paper base material 2.

First, the biodegradable resin layer 3 of the present invention will be described.
The biodegradable resin layer 3 of the present invention comprises a biodegradable heat seal layer 3a, a biodegradable adhesive layer 3b, and a biodegradable oxygen barrier layer 3c, and all of these resin layers are biodegradable.
The total thickness of the biodegradable resin layer 3 may be appropriately set depending on the application. For example, when used as a packaging material, it is preferably 50 μm or less, and more preferably 30 μm or less. If the thickness is too thin, the strength and rigidity are reduced and film formation becomes difficult, so it needs to be 15 μm or more.

The biodegradable heat seal layer 3a (sometimes simply referred to as the heat seal layer) of the present invention contains polylactic acid and an aliphatic polyester resin and/or an aliphatic aromatic polyester resin.

As polylactic acid (PLA), a polymer containing lactic acid structural units as the main component and made from L-lactic acid, D-lactic acid, or their cyclic dimers L-lactide, D-lactide, and DL-lactide as raw materials can be used. Although homopolymers of these lactic acids are preferable, they may also contain copolymerization components other than lactic acids. Examples of such copolymerization components include aliphatic hydroxycarboxylic acids, aliphatic dicarboxylic acids, and aliphatic diols. The term "main component" as used herein refers to a polymer containing 90 mol % or more of lactic acid structural units.
In addition, polylactic acid usually contains both L- and D-isomers, but polylactic acid with an adjusted content ratio is commercially available. In the present invention, it is preferable to use polylactic acid with a D-isomer content of 1% by mass or more relative to 100% by mass of polylactic acid. The higher the D-isomer content, the lower the melting point of polylactic acid. Therefore, when the biodegradable resin layer 3 of the present invention is formed on the paper base material 2 by melt extrusion and the paper base material 2 and the biodegradable resin layer 3 are bonded together as described below, the interlayer adhesion between the paper base material 2 and the heat seal layer 3a containing polylactic acid is excellent. In addition, when used as a packaging material, the heat seal temperature can be set low, making heat sealing easy.

The aliphatic polyester resin of the present invention may be one containing, as a main component, a polymerized condensation product of an aliphatic dicarboxylic acid and an aliphatic diol.
Examples of aliphatic dicarboxylic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, cyclopentanedicarboxylic acid, cyclohexanedicarboxylic acid, etc., and those having 4 to 12 carbon atoms are usually used, and those having 4 to 8 carbon atoms are particularly preferred in terms of biodegradability. These can be used alone, but multiple compounds can also be used in combination to obtain desired properties.
Examples of the aliphatic diol include ethylene glycol, triethylene glycol, 1,4-butanediol, pentamethylene glycol, 1,8-octylene glycol, nanomethylene glycol, and decamethylene glycol, and generally, those having 2 to 10 carbon atoms are used, and in particular, those having 2 to 6 carbon atoms are preferably used in terms of biodegradability. In the case of the aliphatic diol, as in the case of the aliphatic dicarboxylic acid, these exemplified ones may be used alone or in combination.
Also usable are copolymers of aliphatic dicarboxylic acids and aliphatic diols with other structural units such as lactic acid. The term "main component" as used herein refers to a polymer containing 90 mol % or more of aliphatic polyester structural units.
As the aliphatic polyester resin of the present invention, it is preferable to use polybutylene succinate (PBS) because of its excellent adhesion to paper.

The aliphatic aromatic polyester resin of the present invention may be one containing as a main component a polymerized condensation product of an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, and an aliphatic diol.
The aliphatic dicarboxylic acid and the aliphatic diol used may be the same as those exemplified above for the aliphatic polyester resin.
As the aromatic dicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, etc. are used.
In addition, the content of the aromatic dicarboxylic acid unit in the aliphatic aromatic polyester resin is preferably 10 mol % or more and 80 mol % or less relative to 100 mol % in total of the aliphatic dicarboxylic acid unit and the aromatic dicarboxylic acid unit.
In addition, copolymers of aliphatic dicarboxylic acids and aromatic dicarboxylic acids, aliphatic diols and other structural units such as lactic acid can also be used. The term "main component" as used herein refers to a polymer containing 90 mol % or more of aliphatic aromatic polyester structural units.
As the aliphatic aromatic polyester resin of the present invention, it is preferable to use polybutylene adipate terephthalate (PBAT) in view of its excellent flexibility and heat sealability.

In the present invention, aliphatic polyester resins and aliphatic aromatic polyester resins may be used in combination.

The biodegradable heat seal layer 3a of the present invention contains polylactic acid and an aliphatic polyester resin.
In the case of using an aliphatic polyester resin alone without containing polylactic acid, it is difficult to obtain the heat sealability of the present invention described below unless the heat sealing temperature is increased.
Therefore, it is preferable that the polylactic acid and the aliphatic polyester resin are contained in a mass ratio of 50/50 to 10/90.
Furthermore, when the polylactic acid and aliphatic polyester resin are contained in a mass ratio of 100/0 to 60/40, the resin is hard, so that there is a risk that cracks will develop in the biodegradable oxygen barrier layer 3c due to processing into a packaging material or bending operations during use, resulting in a deterioration of the oxygen barrier properties.

The biodegradable heat seal layer 3a of the present invention contains polylactic acid and an aliphatic aromatic polyester resin.
In the case of using only aliphatic aromatic polyester resin without polylactic acid, the surface has poor slip properties.
In the present invention, the surface slipperiness is evaluated by whether the obtained laminated paper 1 moves easily when two sheets are stacked with the biodegradable resin layers 3 facing each other, pressed from above with a finger, and moved horizontally from side to side. If it does not move easily, that is, if the surface slipperiness is poor, when it is formed into a bag, blocking occurs at the mouth of the bag, making it difficult to open, and so-called mouth opening properties are not obtained, making it difficult to use as a packaging material. Therefore, in order to use the biodegradable laminated paper of the present invention as a packaging material, it is necessary for the paper to have a surface slipperiness.
Therefore, it is preferable that the polylactic acid and the aliphatic aromatic polyester resin are contained in a mass ratio of 80/20 to 10/90.
Furthermore, when the polylactic acid and the aliphatic aromatic polyester resin are contained in a mass ratio of 100/0 to 90/10, the resin is hard, so that there is a risk that cracks will occur in the biodegradable oxygen barrier layer 3c when processed into a packaging material or when the layer is folded during use, resulting in a decrease in the oxygen barrier property.

An inorganic filler may be added to the biodegradable heat seal layer 3a of the present invention. By adding an inorganic filler, the water vapor barrier property, biodegradability, and the like can be improved.
Examples of inorganic fillers include anhydrous silica, mica, talc, mica, clay, titanium oxide, calcium carbonate, diatomaceous earth, allophane, bentonite, potassium titanate, zeolite, sepiolite, smectite, kaolin, kaolinite, glass, limestone, carbon, wollastonite, calcined perlite, silicates such as calcium silicate and sodium silicate, hydroxides such as aluminum oxide, magnesium carbonate and calcium hydroxide, salts such as ferric carbonate, zinc oxide, iron oxide, aluminum phosphate and barium sulfate, and the like, and preferably talc, mica, clay, calcium carbonate, and zeolite. Furthermore, the inorganic filler may be used alone or in combination of two or more.

The shape of the inorganic filler can be fibrous, granular, plate-like, or needle-like, with plate-like fillers being preferred. Examples of plate-like fillers include talc, kaolin, mica, clay, sericite, glass flakes, synthetic hydrotalcite, various metal foils, graphite, molybdenum disulfide, tungsten disulfide, boron nitride, plate-like iron oxide, plate-like calcium carbonate, and plate-like aluminum hydroxide.

The content of the inorganic filler in the biodegradable heat seal layer 3a of the present invention is not particularly limited, but should be at a level that does not impair the interlayer adhesion and heat sealability between the paper base material 2 and the biodegradable heat seal layer 3a. The content of the inorganic filler in the biodegradable heat seal layer 3a is preferably 15% by mass or more and 50% by mass or less.

The biodegradable heat seal layer 3 a of the present invention may contain other additives as long as they do not impair the heat sealability and adhesion to the paper base material 2 .
Examples of the additives include compatibilizers, antistatic agents, crystal nucleating agents, heat stabilizers, antioxidants, ultraviolet absorbers, flame retardants, plasticizers, lubricants, and fillers.

The biodegradable adhesive layer 3b of the present invention is a layer for bonding the biodegradable heat seal layer 3a of the present invention to the biodegradable barrier layer 3c described below, and contains a modified polyester resin.
The modified polyester resin is a biodegradable resin obtained by graft-modifying a polyester resin, which is a polymerized condensation product containing at least one structural unit selected from an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, and an aliphatic diol constituting the above-mentioned aliphatic polyester resin or an aliphatic-aromatic polyester resin, and a hydroxycarboxylic acid, with an α,β-unsaturated carboxylic acid and/or an anhydride thereof.
The content of the modified polyester resin in the biodegradable adhesive layer 3b is 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

Here, examples of hydroxycarboxylic acids 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, and the like, or derivatives thereof such as lower alkyl esters or intramolecular esters. Among these, lactic acid or glycolic acid or derivatives thereof are particularly preferred. These hydroxycarboxylic acids can be used alone or as a mixture of two or more kinds.

In the present invention, examples of the α,β-unsaturated carboxylic acid or anhydride thereof include α,β-unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; and α,β- or unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citrus acid, tetrahydrophthalic acid, crotonic acid, and isocrotonic acid. Of these, α,β-unsaturated dicarboxylic acids are preferred.
These α,β-unsaturated carboxylic acid compounds may be used not only as a single compound but also as a combination of two or more compounds.

Among these, the modified polyester-based resin is preferably composed of a modified aliphatic polyester-based resin and/or aliphatic-aromatic polyester-based resin alone (referred to as a modified aliphatic polyester-based resin or a modified aliphatic-aromatic polyester-based resin) from the viewpoints of high biodegradability and processability and adhesion when used as an adhesive layer.
Furthermore, when the modified polyester resin contains both a modified aliphatic polyester resin and a modified aliphatic aromatic polyester resin, the biodegradable resin layer 3 of the present invention can be easily formed by melt extrusion, which will be described later, and is therefore more preferable.
In this case, the ratio of the modified aliphatic polyester resin to the modified aliphatic aromatic polyester resin is preferably 15 to 50 mass% of the modified aliphatic polyester resin and 50 to 85 mass% of the modified aliphatic aromatic polyester resin, based on a total of 100 mass% of the modified aliphatic polyester resin and the modified aliphatic aromatic polyester resin, from the viewpoints of biodegradability and processability.

The biodegradable adhesive layer 3b of the present invention may contain resins other than modified polyester resins as long as the adhesiveness is not impaired. Examples include aliphatic polyester resins such as polyhydroxyalkanoate, polycaprolactone, polyvinyl alcohol, cellulose ester, polylactic acid, polybutylene succinate (PBS), and polybutylene succinate adipate (PBSA), and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate (PBAT).

The thickness of the biodegradable adhesive layer 3b of the present invention is preferably 3 μm or more in order to obtain the desired adhesiveness.
The adhesion referred to in the present invention is an adhesive strength of 5 N/15 mm or more between the biodegradable heat seal layer 3a and the biodegradable adhesive layer 3b, measured using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon RTA-1T") under conditions of a tensile speed of 300 mm/min and 180° peeling.

The biodegradable oxygen barrier layer 3c of the present invention is a layer for suppressing oxygen permeation, and contains butenediol-vinyl alcohol copolymer (BVOH).
This BVOH can be formed into the biodegradable resin layer 3 of the present invention by melt extrusion, which will be described later.

The butenediol-vinyl alcohol copolymer (BVOH) of the present invention is a modified polyvinyl alcohol (PVA) resin obtained by saponifying a polyvinyl ester resin obtained by copolymerizing a vinyl ester monomer, and by introducing a functional group into the PVA resin mainly composed of vinyl alcohol structural units through a post-reaction, and has a 1,2-diol structure in the side chain.
The content of the functional group introduced by the post-reaction in such a modified PVA resin is usually 1 to 20 mol %, and a range of 2 to 10 mol % is particularly preferably used.
As the BVOH, for example, commercially available product "G-Polymer BVE8049P" manufactured by Mitsubishi Chemical Corporation can be used.

Here, polyvinyl alcohol (PVA) resins generally have a tendency to have poor oxygen barrier properties if their degree of saponification is too low. On the other hand, PVA resins with a high degree of saponification, specifically, those with a value of 80 to 100 mol% measured in accordance with JIS K6726, are used for packaging materials. Such PVA resins have no stretchability, and cracks are likely to occur in the oxygen barrier layer when processed into packaging materials or when folded during use. In addition, PVA resins with a high degree of saponification cannot be melt molded, so they are formed directly on the substrate by coating or the like, and it is difficult to use them for the biodegradable barrier layer 3c to be made into a laminate by melt extrusion.
Furthermore, ethylene-vinyl alcohol copolymer (EVOH), which is a copolymer of vinyl alcohol structural units and ethylene structural units and is well known as having vinyl alcohol structural units, has oxygen barrier properties but is not biodegradable and cannot be used for the biodegradable barrier layer 3c of the present invention.

The content of BVOH in the biodegradable oxygen barrier layer 3c is 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. If the content is too low, the performance of suppressing oxygen permeation, i.e., the oxygen barrier properties, tend to be insufficient.

The biodegradable oxygen barrier layer 3c may contain resins other than BVOH as long as the barrier properties are not impaired. Examples include aliphatic polyester resins such as polyhydroxyalkanoate, polycaprolactone, polyvinyl alcohol, cellulose ester, polylactic acid, polybutylene succinate (PBS) and polybutylene succinate adipate (PBSA), and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate (PBAT).

The thickness of the biodegradable oxygen barrier layer 3c of the present invention is preferably 5 μm or more. If it is 5 μm or more, the oxygen barrier property is excellent.
Here, oxygen permeability is used as an index of oxygen barrier property. The oxygen permeability is a value measured using an oxygen permeability measuring device (manufactured by MOCON, product name "OX-TRAN2/22L") under conditions of 23°C x 50% RH in accordance with JIS K7126. In the present invention, a biodegradable resin layer 3 having an oxygen permeability of 5 cc/ ^m2 day atm or less is considered to have excellent oxygen barrier property, and more preferably 1 cc/ ^m2 day atm or less.

The biodegradable resin layer 3 of the present invention has a biodegradable heat seal layer 3a laminated on both sides of a biodegradable oxygen barrier layer 3c via a biodegradable adhesive layer 3b, that is, laminated in the order of biodegradable heat seal layer 3a/biodegradable adhesive layer 3b/biodegradable oxygen barrier layer 3c/biodegradable adhesive layer 3b/biodegradable heat seal layer 3a.
In this way, since the biodegradable oxygen barrier layer 3c is sandwiched between the biodegradable adhesive layer 3b and the biodegradable heat seal layer 3a, it is possible to prevent cracks from occurring in the biodegradable oxygen barrier layer 3c due to folding operations during processing into packaging materials or during use, and it is possible to maintain the oxygen barrier properties for a long period of time.
Furthermore, when the biodegradable laminated paper 1 of the present invention is used in the form of a bag with the paper base material 2 side as the outer surface, even if the paper base material 2 comes into contact with water or other substances, the presence of the biodegradable heat seal layer 3a and the biodegradable adhesive layer 3b between the paper base material 2 and the biodegradable oxygen barrier layer 3c prevents water and other substances from seeping into the bag from the paper base material 2 side, and the bag has excellent water resistance.

In the biodegradable resin layer 3 of the present invention, the thickness and layer ratio of each layer may be appropriately set depending on the application, but in order to obtain the desired oxygen barrier properties and interlayer adhesion, it is desirable for the barrier layer to be 5 μm or more and the adhesive layer to be 3 μm or more.

Next, the paper base material 2 of the present invention will be described.
The paper substrate 2 of the present invention is not particularly limited as long as it is a commonly used one, and examples thereof include kraft paper, fine paper, colored fine paper, form paper, pure white roll paper, paperboard, cardboard, etc. Coated paper such as art paper and coated paper and other special papers can also be used, but the use of synthetic paper made mainly from synthetic polymers will hinder the biodegradability of the entire laminate, which is the object of the present invention, and therefore selection is required.
The thickness of the paper base 2 is not particularly limited and may be appropriately set according to the intended use.

FIG. 1 shows an example in which a biodegradable resin layer 3 is laminated on one side of a paper base material 2, but as shown in FIG. 2, the biodegradable resin layer 3 may be laminated on both sides, or the biodegradable resin layer 3 of the present invention may be laminated on one side and a different biodegradable resin layer may be laminated on the other side.
The different biodegradable resin layer may be any layer that is biodegradable, and may be, for example, a resin layer containing one or more of the above-mentioned polylactic acid, aliphatic polyester resin, and aliphatic aromatic polyester resin, and may be formed in a single layer or in a multi-layer structure.

A method for producing the biodegradable laminated paper 1 of the present invention will be described.
Any method generally used for laminating a paper substrate and a resin may be used. For example, there is a method in which a three-type, five-layer laminate of the biodegradable resin layer 3 is formed in advance by melt extrusion, and then laminated to the paper substrate 2. In this case, the biodegradable resin layer 3 may be laminated to the paper substrate 2 when it is in a molten state without being completely cured, or the biodegradable resin layer 3 may be pressed between heated rolls after it has completely solidified.

The biodegradable laminated paper 1 of the present invention is a biodegradable laminate having a paper base material 2 and a biodegradable resin layer 3, and has both oxygen barrier properties and heat seal properties, and is a biodegradable laminated paper suitable for packaging materials that is prevented from decreasing in oxygen barrier properties due to folding operations during processing into packaging materials or during use, and also has a slippery surface. It is preferable that the biodegradable laminated paper has excellent adhesion between the biodegradable heat seal layer 3a and the biodegradable adhesive layer 3b, and between the paper base material 2 and the biodegradable resin layer 3.

The interlayer adhesion between the biodegradable heat seal layer 3a and the biodegradable adhesive layer 3b is evaluated by adhesive strength. The adhesive strength is measured using a test piece (width 15 mm) consisting of the three-kind, five-layer biodegradable resin layer 3 of the present invention, with a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon RTA-1T"), and is the strength when the biodegradable heat seal layer 3a and the other four layers (3b/3c/3b/3a) are each gripped with a clip and peeled at a tensile speed of 300 mm/min and 180 degrees. In the present invention, adhesive strength of 5 N/15 mm or more is considered to be excellent in adhesiveness.

The interlayer adhesion between the paper base material 2 and the biodegradable resin layer 3 is evaluated using a test piece (width 15 mm) made of the biodegradable laminated paper 1 of the present invention, a tension tester (manufactured by Orientec Co., Ltd., product name "Tensilon RTA-1T"), in which the paper base material 2 and the biodegradable resin layer 3 are each gripped with a clip and peeled at a tensile speed of 100 mm/min and 180 degrees. In the present invention, the paper base material 2 in a state in which it is entirely transferred to the biodegradable resin layer 3 is considered to have excellent adhesion.

The oxygen barrier property is evaluated by oxygen permeability as described above. The oxygen permeability can be measured in accordance with JIS K7126 under conditions of 23°C x 50% RH using an oxygen permeability measuring device (manufactured by MOCON, product name "OX-TRAN2/22L"). In the present invention, when the oxygen permeability of the biodegradable resin layer 3 is 5 cc/ ^m2 day atm or less, it is considered to have oxygen barrier property, and when it is 1 cc/ ^m2 day atm or less, it is considered to be excellent.

In addition, to evaluate the oxygen barrier properties caused by folding operations during processing into packaging materials or during use, the oxygen permeability after folding the test piece in four at right angles can be evaluated in the same manner as described above.

The heat sealability of the present invention is evaluated by the adhesive strength after heat sealing. Specifically, two sheets of the biodegradable laminated paper 1 of the present invention cut to a width of 10 cm are prepared, stacked so that the biodegradable resin layers 3 face each other, and set in a heat seal tester (manufactured by Tester Sangyo Co., Ltd., product name "TP-701-B"), and thermally bonded (heat sealed) under conditions of a constant temperature, a pressure of 0.1 MPa, and a heating time of 3 seconds. After heat sealing, the adhesive strength between the layers of the biodegradable laminated paper is measured in accordance with JIS Z0238. At this time, a test piece with a width of 15 mm is used, and a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon RTA-1T") is used to grip each biodegradable laminated paper 1 with a clip, and the strength (maximum point load) is measured when peeled off at a tensile speed of 300 mm/min and 180 degrees. In the present invention, a bonding strength of 6 N/15 mm or more is deemed to have heat sealability, and a bonding strength of 15 N/15 mm or more is deemed to be excellent.
In the present invention, a material that can provide an adhesive strength of 6 N/15 mm or more even at a heat sealing temperature as low as 90° C. or less is considered to have excellent heat sealability.

The biodegradable laminated paper of the present invention can be used for a variety of purposes, and is particularly suitable for use as a packaging material. This is because it combines heat sealability and oxygen barrier properties, and the deterioration of the oxygen barrier properties caused by folding operations during processing into packaging materials and use is suppressed, and it also has a slippery surface. Therefore, it can also be used for standing pouches that require folding processing.

The biodegradable laminated paper 1 of the present invention is made of biodegradable materials, so after disposal it is decomposed by hydrolysis and microorganisms into harmless components such as carbon dioxide and water. Disposal methods that can be used include composting and landfilling.

[Examples 1 to 3, 5 to 7, Reference Examples 4 and 8 ]
As shown in Table 1, a 50 μm-thick resin laminate consisting of three types of five layers, heat seal layer/adhesive layer/barrier layer/adhesive layer/heat seal layer, was formed by melt extrusion using a T-die extruder set at 220° C. Next, the obtained resin laminate was laminated to a paper substrate with a basis weight of 50 g/m2 while in a molten state and pressed between a metal roll and a rubber roll at 20° C. to obtain a laminated paper. At this time, the heat seal layer was 19 μm thick, the adhesive layer was 3 μm thick, and the barrier layer was 6 μm thick.
The numerical values shown for the layer structures in the table indicate parts by mass.

[ Reference Example 9]
Laminated papers were obtained in the same manner as in Examples 1 to 3, 5 to 7 and Reference Examples 4 and 8 , except that the thickness of the barrier layer was 3 μm and the thickness of the heat seal layer was 20.5 μm.

Example 10
Laminated papers were obtained in the same manner as in Examples 1 to 3, 5 to 7 and Reference Examples 4 and 8 , except that resin laminates having the same layer structure were laminated to both sides of the paper base material.

Comparative Examples 1 to 5
As shown in Table 2, a 50 μm thick resin laminate consisting of three types of five layers, heat seal layer/adhesive layer/barrier layer/adhesive layer/heat seal layer, was formed by melt extrusion using a T-die extruder set at 220° C. Next, the obtained resin laminate was attached to a paper substrate while in a molten state and pressed between a metal roll and a rubber roll at 20° C. to obtain a laminated paper. At this time, the heat seal layer was 19 μm thick, the adhesive layer was 3 μm thick, and the barrier layer was 6 μm thick.
In addition, only in Comparative Example 4, no adhesive layer or barrier layer was included, and only the heat seal layer having a thickness of 50 μm was bonded to the paper substrate.

Comparative Example 6
As shown in Table 2, a resin laminate consisting of three types of three layers, a heat seal layer, an adhesive layer, and a barrier layer, was formed by melt extrusion using a T-die extruder set at 220° C. Next, the obtained resin laminate was attached to a paper substrate while in a molten state so that the barrier layer and the paper substrate were in contact with each other, and the laminated paper was obtained by pressure bonding between a metal roll and a rubber roll at 20° C. At this time, the heat seal layer was 19 μm thick, the adhesive layer was 3 μm thick, and the barrier layer was 6 μm thick.

The materials used are shown below.
[Heat seal layer]
Polylactic acid A:
Zhejiang Haizheng Biomaterials Co., Ltd., product name "REVODE190", D-isomer 0.5% by mass
Polylactic acid B:
Zhejiang Haizheng Biomaterials Co., Ltd., product name "REVODE110", D-isomer 2.5% by mass
PBS (Polybutylene succinate):
Manufactured by Mitsubishi Chemical Corporation, product name "BiOPBSFZ91PB"
PBAT (Polybutylene adipate terephthalate):
BASF Japan, product name "Ecoflex C1200"
[Adhesive Layer]
Modified polyester resin A:
100 parts by mass of adipic acid/1,4-butanediol condensation polymer ("Ecoflex C1200" manufactured by BASF), 0.1 parts by mass of maleic anhydride, and 0.01 parts by mass of 2,5-dimethyl-2,5-bis(t-butyloxy)hexane ("Perhexa 25B" manufactured by NOF Corporation) as a radical initiator were dry-blended, and the mixture was melt-kneaded under the following conditions in a twin-screw extruder, extruded into a strand shape, cooled with water, and cut with a pelletizer to obtain a cylindrical pellet-shaped polyester resin having a polar group. Modified polyester resin B:
Mitsui Chemicals, Inc., product name "Admer SF600"
[Oxygen Barrier Layer]
BVOH (butenediol vinyl alcohol copolymer):
Mitsubishi Chemical Corporation, product name "G-Polymer BVE8049P"
EVOH (ethylene-vinyl alcohol copolymer):
Manufactured by Kuraray Co., Ltd., product name "Eval F101B"
[Paper base material]
Kraft paper: basis weight 50 g/ ^m2

The obtained resin laminates or laminated papers were evaluated for interlayer adhesion, adhesion to the paper substrate, heat sealability, oxygen permeability, surface slipperiness, and biodegradability as described below. The results are shown in Tables 1 and 2.
In Comparative Example 4, no adhesive layer or barrier layer was included, and the oxygen permeability before folding was rated as x, so that the interlayer adhesion and the oxygen permeability after folding were not evaluated. In Comparative Example 6, the adhesion between the paper and the resin laminate was not obtained, so that the heat sealability, oxygen permeability, surface slipperiness, and biodegradability could not be evaluated, and therefore the results were deemed unmeasurable.

[Interlayer adhesion]
A 15 mm wide rectangular test piece was cut out from the obtained resin laminate, and the interlayer adhesion between the heat seal layer and the other four layers (adhesive layer/barrier layer/adhesive layer/heat seal layer) was evaluated. For the measurement, a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon RTA-1T") was used, and the heat seal layer and the other four layers (adhesive layer/barrier layer/adhesive layer/heat seal layer) were each held with a clip, and the strength when peeled at a tensile speed of 300 mm/min and 180 degrees was measured, and the evaluation was based on the following criteria. In Comparative Example 6, the interlayer adhesion between the heat seal layer and the other two layers (adhesive layer/barrier layer) was evaluated.

○ 5N/15mm or more × Less than 5N/15mm

[Adhesion to paper]
A 15 mm wide rectangular test piece was cut out from the obtained laminated paper, and using a tension tester (manufactured by Orientec Co., Ltd., product name "Tensilon RTA-1T"), the paper base material and the resin laminate were each held with a clip, and the condition when peeled off at 180 degrees at a tensile speed of 100 mm/min was evaluated according to the following criteria.

○ The paper base material is completely transferred to the resin laminate. × The paper base material is not transferred to the resin laminate.

[Heat sealability]
Two test pieces with a width of 10 cm were cut out from the obtained laminated paper, and the resin laminates were stacked so that they faced each other and set in a heat seal tester (manufactured by Tester Sangyo Co., Ltd., product name "TP-701-B"), and thermal adhesion processing (heat sealing) was performed under conditions of a constant temperature in the range of 80 ° C. to 120 ° C., a pressure of 0.1 MPa, and a heating time of 3 seconds. After heat sealing, the adhesive strength between the layers of the laminated paper was measured in accordance with JIS Z0238. At this time, a test piece with a width of 15 mm was used, and a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon RTA-1T") was used to grip each of the laminated papers with a clip, and the strength (maximum point load) when peeled at a tensile speed of 300 mm / min and 180 degrees was measured, and evaluated according to the following criteria. Tables 1 and 2 show the heat sealing temperatures at which adhesive strengths of 6 N / 15 mm and 15 N / 15 mm were obtained.

○ The processing temperature at which an adhesive strength of 6N/15mm or more can be obtained is 90°C or less. △ The processing temperature at which an adhesive strength of 6N/15mm or more can be obtained is between 90°C and 100°C or less. × The processing temperature at which an adhesive strength of 6N/15mm or more can be obtained is over 100°C.

[Oxygen permeability]
A test piece having a width of 10.8 cm and a length of 10.8 cm was cut out from the obtained resin laminate, and the oxygen permeability was measured using an oxygen permeability measuring device (manufactured by MOCON, product name "OX-TRAN2/22L") under the conditions of 23 degrees and 50% RH in accordance with JIS K7126, and evaluated according to the following criteria. At this time, the oxygen permeability was measured before and after folding the test piece in four at right angles.

○ 1cc/ ^m2 -day-atm or less △ Over 1cc/ ^m2 -day-atm, 5cc/m2-day-atm or less × Over 5cc/ ^m2 -day-atm

[Surface slipperiness]
Two sheets of the obtained laminate paper were stacked so that the resin laminates faced each other, pressed down with a finger from above and moved horizontally from side to side. The state was evaluated according to the following criteria.

○ Easy to move × Two pieces move at the same time

[Biodegradability]
The obtained resin laminate was pulverized, and 30 g of the test material was mixed with compost as an inoculant source in a container, and a control material, cellulose and compost, was mixed in a container. The mixture was left at rest for 45 days under conditions maintained at a temperature of 58±2°C and a humidity of 50%, and the degree of biodegradation thereafter was determined in accordance with JIS K6953-1 and evaluated according to the following criteria.

○ Biodegradability 70% or more × Biodegradability less than 70%

As shown in Table 1, in Examples 1 to 3 and 5 to 7 , laminated papers were obtained that had both oxygen barrier properties and heat sealability, and further, were able to maintain their oxygen barrier properties even after bending, and also had a smooth surface.

On the other hand, as shown in Table 2, Comparative Example 1 used only polylactic acid as the biodegradable resin layer, and Comparative Example 2 used only aliphatic polyester, and both had poor oxygen barrier properties and heat sealability after bending.
In Comparative Example 3, an aliphatic aromatic polyester was used alone as the biodegradable resin layer, but the surface had poor slipperiness and was not suitable for use as a packaging material.
In Comparative Example 4, which did not have an adhesive layer or a barrier layer as a biodegradable resin layer, the heat sealability was good, but the oxygen barrier property was poor.
In Comparative Example 5, EVOH was used as the barrier layer, but biodegradability was not obtained.
In Comparative Example 6, the barrier layer and the paper base material were directly bonded to each other, and no adhesion between the barrier layer and the paper base material was obtained, making the product unsuitable for use as a packaging material.

In this way, the present invention provides a biodegradable laminated paper suitable for use as a packaging material, which is a biodegradable laminate having a paper base material and a biodegradable resin layer, and which has excellent adhesion between the layers, as well as oxygen barrier properties and heat sealability, and in which the deterioration of oxygen barrier properties due to folding operations during processing into packaging materials or use is suppressed.

Reference Signs List 1 Biodegradable laminated paper 2 Paper substrate 3 Biodegradable resin layer 3a Biodegradable heat seal layer 3b Biodegradable adhesive layer 3c Biodegradable oxygen barrier layer

Claims (3)

The present invention comprises a paper base material and a biodegradable resin layer laminated on one or both sides of the paper base material,
the biodegradable resin layer has a biodegradable heat seal layer, a biodegradable adhesive layer, and a biodegradable oxygen barrier layer, and the biodegradable heat seal layers are laminated on both sides of the biodegradable oxygen barrier layer via the biodegradable adhesive layers;
the biodegradable heat seal layer contains polylactic acid and an aliphatic aromatic polyester resin in a mass ratio of 80/20 to 10/90;
The biodegradable oxygen barrier layer has a thickness of 5 μm or more and contains a butenediol-vinyl alcohol copolymer. The present invention comprises a paper base material and a biodegradable resin layer laminated on one or both sides of the paper base material,
the biodegradable resin layer has a biodegradable heat seal layer, a biodegradable adhesive layer, and a biodegradable oxygen barrier layer, and the biodegradable heat seal layers are laminated on both sides of the biodegradable oxygen barrier layer via the biodegradable adhesive layers;
the biodegradable heat seal layer contains polylactic acid and an aliphatic polyester resin in a mass ratio of 50/50 to 10/90;
The biodegradable oxygen barrier layer has a thickness of 5 μm or more and contains a butenediol-vinyl alcohol copolymer. A packaging material comprising the biodegradable laminated paper according to claim 1 or 2 .