Laminate

Abstract

To provide a laminate with each layer having sufficient adhesiveness while substantially all of materials constituting the laminate are biodegradable.SOLUTION: In a laminate in which a paper substrate, an anchor coat layer, and a biodegradable resin layer are laminated in order, the laminate is characterized by that the anchor coat layer includes polybutylene adipate terephthalate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a novel laminate. More specifically, the present invention relates to a laminate having biodegradability.

Background Art

[0002] In applications such as containers and packaging materials, laminates obtained by laminating paper and resin are widely used. In recent years, as environmental countermeasure products, laminates using biodegradable resins as resin components have been demanded.

[0003] For this reason, laminates containing biodegradable resins and paper, which is a kind of biodegradable material, have been developed. For example, it is composed of a box-forming piece with a biodegradable laminate material attached to paper, and this box-forming piece is provided with side surfaces connected in parallel to each other, and an adhesive piece integrally provided from one of the side surfaces and pasted to the back surface of the other side surface in the assembled state of the box-forming piece. A packaging cardboard box has been proposed, characterized in that a surface treatment for improving adhesiveness is applied to the surface of the biodegradable laminate material of the adhesive piece (Patent Document 1).

[0004] Also, for example, a laminate having a first coating layer (A) on at least one of paper substrates and further having a second coating layer (B) on the first coating layer, wherein the first coating layer (A) contains at least one kind of modified starch (a), and the second coating layer (B) contains at least one kind of water-insoluble resin (b), and the total coating amount of the first coating layer (A) and the second coating layer (B) is 0.5 to 10 g / m 2 and the air barrier property is 20 kPa or less has been disclosed (Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the technology of Patent Document 1, two-component curable adhesives such as acrylic resin (liquid A) and isocyanate resin (liquid B), and pastes (adhesives) such as vinyl chloride-vinyl acetate copolymer resin and modified acrylic-vinyl acetate copolymer resin are used, but all of them are non-biodegradable resins. Therefore, for example, when biodegradation proceeds by composting under aerobic conditions, the paper layer and the biodegradable resin layer are biodegraded and decomposed into carbon dioxide and water, but the non-biodegradable resin remains undecomposed in the compost and becomes microplastics, which may contaminate the soil.

[0007] Also, in the technology of Patent Document 2, although the paper substrate and the first layer of modified starch layer have biodegradability, the second layer is laminated with non-biodegradable resins such as acrylic resin, polyester resin, and urethane resin. Therefore, similar to Patent Document 1, there is a risk that the non-biodegradable resin remains undecomposed and becomes microplastics, causing environmental pollution.

[0008] Thus, in the conventional laminate, although a biodegradable resin layer is adopted, the adhesive for bonding it is non-biodegradable. Therefore, in the process of biodegrading the laminate, non-biodegradable resins remain, which may lead to environmental pollution by microplastics. It can be said that there is room for further improvement in this regard.

[0009] On the other hand, it is also conceivable to use a conventionally known biodegradable resin for bonding the paper and the biodegradable resin layer. However, in that case, there is a problem that sufficient adhesiveness cannot be obtained in each layer of the laminate.

[0010] Therefore, the main object of the present invention is to provide a laminate in which substantially all of the materials constituting the laminate are biodegradable and each layer has sufficient adhesiveness.

Means for Solving the Problems

[0011] As a result of intensive research in view of the problems of the prior art, the present inventor has found that a laminate having a specific layer structure can achieve the above object, and has completed the present invention.

[0012] That is, the present invention relates to the following laminate. 1. A laminate in which a paper base material, an anchor coat layer, and a biodegradable resin layer are laminated in this order, wherein the anchor coat layer contains polybutylene adipate terephthalate. 2. The laminate according to item 1 above, wherein the anchor coat layer further contains starch. 3. The laminate according to item 1 above, wherein the biodegradable resin layer contains at least one biodegradable resin selected from the group consisting of polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polybutylene succinate (PBS), polyglycolic acid (PGA), polycaprolactone (PCL), polyhydroxybutyric acid (PHB), polybutylene succinate adipate (PBSA), polyethylene terephthalate succinate (PETS), and poly(3-hydroxybutanoic acid-co-3-hydroxyhexanoic acid) (PHBH). 4. The laminate according to item 1 above, wherein the film thickness of the biodegradable resin layer is 5 to 80 μm. 5. The laminate according to item 1 above, wherein the basis weight of the paper base material is 20 to 500 g / m 2 2. 6. The laminate according to item 1 above, wherein the coating amount of the anchor coat layer is 0.2 to 15 g / m in terms of solid content weight. 2 2. 7. The laminate according to item 1 above, which is used as a packaging material or a container.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a laminate in which substantially all of the materials constituting the laminate are biodegradable and each layer has sufficient adhesiveness.

[0014] In conventional containers and the like using biodegradable resins, since the adhesiveness between the paper and the biodegradable resin layer is not sufficient, the biodegradable resin layer may be broken by the forming load during the forming process. Further, if there is a leak in the biodegradable resin layer reaching the anchor coat layer, when the state of storing with food filled continues, moisture or oil may penetrate into the paper base material layer, resulting in a decrease in container strength and contamination of the food at the contacting portion.

[0015] On the other hand, in the laminate of the present invention, in the laminate in which a paper base material, an anchor coat layer, and a biodegradable resin layer are laminated in this order, since polybutylene adipate terephthalate (hereinafter also referred to as "PBAT") is contained in the anchor coat layer, it has excellent biodegradability, and the paper base material and the biodegradable resin layer are adhered, and it is difficult for defects such as resin leakage reaching the anchor coat layer to occur in the biodegradable resin layer.

[0016] Here, there are several factors for obtaining adhesiveness between the anchor coat layer containing PBAT as a main component and the biodegradable resin layer. In this configuration, it is considered that the three factors of mechanical bonding, chemical interaction, and physical interaction, which are generally regarded as the principles of adhesion, can be effectively utilized.

[0017] Mechanical bonding is a phenomenon called the anchor effect, which is a principle of joining where a liquid material penetrates and solidifies in the uneven shape of the base material. In this configuration, the anchor coat penetrates the three-dimensional structure of the paper fibers, and the solvent volatilizes and solidifies there, so it is considered that the paper fibers and the anchor coat are joined and adhesiveness is obtained. To more effectively exhibit the anchor effect, it is better to use a formulation in which PBAT is dissolved in a solvent. By doing so, the anchor coat agent can easily penetrate into the paper substrate with high water resistance, and at that time, the resin is effectively drawn into the three-dimensional structure of the paper fibers, strengthening the adhesion. Also, in this configuration, the anchor coat does not completely eliminate the three-dimensional structure of the paper fibers of the paper substrate, and the biodegradable resin layer is also impregnated to some extent in the three-dimensional structure of the paper fibers. As a result, it is considered that a strong bond is realized by the anchor effect also in the three-dimensional structure of the upper biodegradable resin and paper.

[0018] Chemical interaction is the concept that bonding occurs by a chemical reaction between the base material and the coating resin, and adhesion is achieved. PBAT is considered to adhere not only by the anchor effect with the paper substrate. The reason for this is that although the anchor effect cannot be expected especially in the part where the fibers exist on the surface in the three-dimensional structure of the paper fibers, the paper fibers and PBAT adhere to the whole paper fibers. This factor is considered to be because a chemical bond by dehydration condensation occurs between the hydroxyl group of cellulose and the polyester structure of PBAT.

[0019] Physical interaction is bonding by intermolecular forces between the base material and the coating resin, and is a principle that the force of attraction becomes stronger when the affinity of the mutual materials is high. The affinity between the biodegradable resin layer and PBAT can also be inferred from, for example, the solubility parameter SP value. It is possible to infer that the closer the SP values are, the higher the affinity. There are various methods for estimating the SP value, but using Fedors' calculation formula, the SP value (cal / cm 3 ) 1 / 2When calculating, as an example, the SP value of PBAT is 11.57 and the SP value of PBS resin is 11.24. It can be confirmed that they have high affinity for each other, and it can be inferred that they are also joined by intermolecular forces. The inference of intermolecular forces based on the SP value can also be reconfirmed, for example, from the adhesion when PHBH resin is coated on PVA resin, polyethylene resin, and acrylic resin. When calculating the respective SP values, the SP value of PVA resin is 16.6, the SP value of polyethylene resin is 8.56, the SP value of acrylic resin is 9.48, which is far from the SP value of PBAT resin 11.57, and it has been confirmed that the results of the implementation also show non-adhesion.

[0020] As described above, the laminate of the present invention exhibits excellent adhesion (interlayer adhesiveness) during use to perform a predetermined function (especially the function as a packaging material or container), and can contribute to environmental protection due to its excellent biodegradability after use.

Brief Description of the Drawings

[0021]

Figure 1

Embodiments for Carrying Out the Invention

[0022] 1. Laminate The laminate of the present invention is a laminate in which a paper substrate, an anchor coat layer, and a biodegradable resin layer are laminated in this order, and the anchor coat layer contains polybutylene adipate terephthalate.

[0023] An example of the layer structure of the laminate of the present invention is shown in FIG. 1. The laminate 10 shown in FIG. 1 includes a paper substrate 11 as the lowermost layer, and an anchor coat layer 12 is laminated on the surface of the paper substrate 11. In the anchor coat layer 12, a biodegradable resin layer 13 is formed on the surface that does not contact the paper substrate 11. It is preferable that these layers are laminated so as to be in direct contact with each other. Thereby, each layer can be joined more firmly.

[0024] Further, the anchor coat layer 12 may be formed on the entire surface or a part of the surface of the paper base material, but it is preferably formed on the entire surface. Similarly, the biodegradable resin layer 13 may be formed on the entire surface or a part of the surface of the anchor coat layer, but it is preferably formed on the entire surface.

[0025] In the laminate 10 shown in FIG. 1, the paper base material 11 and the biodegradable resin layer 13 are arranged as the outermost layers. However, within a range that does not prevent the effects of the present invention, another layer may be further formed on the paper base material 11 or the biodegradable resin layer 13. For example, a printing layer, an antifouling layer, a heat seal layer, a gas barrier layer, a water vapor barrier layer, a reinforcing layer, a heat resistant layer, etc. can be mentioned.

[0026] From the viewpoint of the biodegradability of the laminate itself, it is desirable that the laminate of the present invention does not include a layer made of a non-biodegradable component. For the same reason, it is desirable that none of the paper base material, the anchor coat layer, and the biodegradable resin layer contain non-biodegradable components. In this regard, the content of the non-biodegradable component in the total mass of the laminate of the present invention is usually preferably 10% by mass or less, more preferably 5% by mass or less, and most preferably 1% by mass or less. Therefore, for example, the content of the non-biodegradable component in the total mass of the laminate of the present invention can be set to 0% by mass. Hereinafter, each component will be described in detail.

[0027] (1) Paper base material In the laminate of the present invention, the paper base material mainly serves as a base material for supporting the biodegradable resin layer, and at the same time has a role of ensuring the rigidity (or moldability) when the laminate of the present invention is used as a container.

[0028] The type of the paper base material is not particularly limited, and various paper base materials used in known or commercially available paper containers and the like can be appropriately adopted according to the desired use and the like. For example, pure white roll paper, kraft paper, parchment paper, ivory paper, manila paper, card paper, cup paper, etc. can be used. Also, recycled paper can be used as the paper.

[0029] The basis weight of the paper substrate is not limited, but is usually in the range of 20 to 500 g / m 2 and can be appropriately set according to the use, form, etc. of the laminate.

[0030] In particular, when the laminate of the present invention is used as a container formed into a three-dimensional shape using adhesives, high-frequency sealing, ultrasonic sealing, etc. in addition to paper plates and paper cups, it is 150 to 500 g / m 2 which is preferable. When the laminate of the present invention is used as a container, if the basis weight of the paper substrate used is less than 150 g / m 2 , when filled with food ingredients, the rigidity is inferior, so the strength as an eating container is insufficient. If the basis weight exceeds 500 g / m 2 , the formability is significantly reduced, resulting not only in high costs but also in over-specification as an eating container or the like. That is, there is a risk of wasting resources.

[0031] (2) Anchor coat layer The anchor coat layer is mainly a layer located between the paper substrate and the biodegradable resin layer. The anchor coat layer imparts adhesion to the paper substrate and the biodegradable resin layer and has biodegradability. In particular, when the biodegradable resin layer is not formed as a uniform film or coating such as coating with an aqueous dispersion of a biodegradable resin or a solution obtained by dissolving a biodegradable resin in a solvent, it also has a function of providing a sufficient blocking effect (a role of filling the gaps between the fibers of the paper substrate).

[0032] The anchor coat layer contains PBAT. By using PBAT as a component constituting the anchor coat layer, excellent adhesion (interlayer adhesiveness) can be obtained, and good biodegradability can also be obtained. PBAT itself is a known substance (copolymer), and commercially available products can also be used.

[0033] The content of PBAT in the anchor coat layer preferably usually contains 50 to 100% by mass, and more preferably 50 to 98% by mass. Thereby, in addition to the above-mentioned adhesiveness and biodegradability, high hydrolysis resistance can be exhibited, and it is also possible to improve heat resistance and biodegradability when starch is used in combination as described later.

[0034] In addition, since PBAT is flexible among biodegradable resins, an excellent effect on mechanical suitability during secondary processing can be obtained. Furthermore, many biodegradable materials have poor hydrolysis resistance, but high hydrolysis resistance can also be obtained by containing PBAT. In this regard, the laminate of the present invention can be suitably used for food packaging materials and the like that require hydrolysis resistance.

[0035] The laminated amount of the anchor coat layer is not limited, but from the viewpoints of biodegradability and adhesiveness, it is preferably 0.2 to 15 g / m in terms of solid content weight 2 and particularly preferably 0.5 to 12 g / m 2 By doing so, the paper substrate and the biodegradable resin layer can be adhered more closely. When the coating amount of the anchor coat layer is less than 0.2 g / m in terms of solid content weight 2 the anchor coat resin excessively penetrates into the three-dimensional structure of the paper fiber, and a sufficient amount of the anchor coat resin cannot be ensured on the contact surface between the paper and the biodegradable resin, making it difficult to obtain adhesiveness. When the coating amount of the anchor coat layer exceeds 15 g / m in terms of solid content weight 2 it becomes an excessive amount, and no cost merit appears, resulting in a waste of resources. Alternatively, in the manufacturing process, since it takes time to sufficiently dry the solvent of the anchor coat agent, it becomes necessary to reduce the manufacturing speed. Then, in addition to being a factor in cost increase, there is a risk of leading to defects in the secondary process due to embrittlement of the paper caused by excessive heat drying of the paper substrate.

[0036] When a blocking effect is required to reduce the three-dimensional structure of the paper fibers constituting the paper substrate, the anchor coat layer is 2 to 15 g / m in terms of solid content weight 2Preferably, it is set to 5 to 12 g / m 2 More preferably, it is set to this value. By doing so, the biodegradable resin coated on the upper layer is less likely to penetrate into the three-dimensional structure of the paper, and defects such as pinholes in the biodegradable resin layer reaching the anchor coat layer can be improved. When the solid content weight of the anchor coat layer is less than 2 g / m 2 In the case of less than this value, it may not be possible to sufficiently seal large gaps in the three-dimensional structure of the paper, and there is a risk of defects occurring in the biodegradable resin layer reaching the anchor coat layer of the paper.

[0037] Thus, when expecting both the adhesion of each layer by the anchor coat layer and the blocking effect, the anchor coat layer preferably has a solid content weight of 2.0 to 15 g / m 2 Preferably, it is set to 5 to 12 g / m 2 More preferably, it is this value.

[0038] In addition, in the present invention, in addition to PBAT, starch can be preferably used in combination in the anchor coat layer as described above. By using starch, the heat resistance of the anchor coat layer can be increased. Therefore, especially when filling and storing food, it can be expected to be utilized in applications such as filling food at a temporary eating temperature during barbecue or the like.

[0039] The type of starch is not particularly limited, and for example, at least one modified starch such as acetylated adipic acid cross-linked starch, acetylated phosphate cross-linked starch, acetylated oxidized starch, sodium octenyl succinate starch, acetic acid starch, oxidized starch, hydroxypropyl starch, hydroxypropyl phosphate cross-linked starch, phosphoric acid monoesterified phosphate cross-linked starch, phosphorylated starch, phosphate cross-linked starch, sodium starch glycolate can be preferably used. These can be known or commercially available products. Also, as a commercial product, for example, there is a resin composition containing starch and PBAT, and such a commercial product can also be used as a source of starch and PBAT of the present invention.

[0040] When starch is included in the anchor coat layer, the content of starch in the anchor coat layer is not particularly limited, but can be about 0.1 to 50% by mass. By including 0.1 to 50% by mass of starch in the anchor coat layer, the adhesion between the paper substrate of PBAT and the biodegradable resin layer is not impaired, and physical properties such as biodegradability and heat resistance can be improved. Therefore, for example, an anchor coat layer having a composition containing PBAT and 50 to 100% by mass (particularly 80 to 95% by mass) of the remainder being starch can also be employed.

[0041] Also, within a range that does not prevent the effects of the present invention, additives other than PBAT and starch may be included in the anchor coat layer. For example, thermoplastic resins, lubricants, inorganic fillers, plasticizers, antiblocking agents, odor absorbers, fragrances, antioxidants, antioxidants, weather resistance improvers, ultraviolet absorbers, crystal nucleating agents, mold release agents, water repellents, antibacterial agents, slidability improvers, colorants (pigments, dyes), etc. can be mentioned. In this case, it is desirable to use biodegradable components for these additives as much as possible. Therefore, examples of the above thermoplastic resins include at least one of polylactic acid, poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid), polybutylene succinate, polyglycolic acid, polycaprolactone, polyhydroxybutyric acid, polybutylene succinate adipate, cellulose acetate, polyvinyl alcohol, polyethylene terephthalate succinate, etc. The total content when these additives are included in the anchor coat layer can usually be 10% by mass or less, but is not limited thereto.

[0042] (3) Biodegradable resin layer The biodegradable resin layer is a layer adhered to the paper substrate via the anchor coat layer. In the laminate, the biodegradable resin layer mainly has roles such as water resistance, oil resistance, heat sealability, moldability, shape retention, etc.

[0043] The biodegradable resin layer contains a biodegradable resin. Examples of the biodegradable resin include, but are not limited to, polylactic acid (PLA), poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (copolyester composed of 3-hydroxybutyric acid and 3-hydroxyvaleric acid) (PHBV), polybutylene succinate (PBS), polyglycolic acid (PGA), polycaprolactone (PCL), polyhydroxybutyric acid (PHB), polybutylene succinate adipate (PBSA), polyethylene terephthalate succinate (PETS), poly(3-hydroxybutanoic acid-co-3-hydroxyhexanoic acid) (copolyester composed of 3-hydroxybutanoic acid and 3-hydroxyhexanoic acid) (PHBH). Among these, at least one of PLA and PHBH is preferable from the viewpoints of heat resistance, moldability, etc. These are all known substances, and commercially available products can also be used.

[0044] The film thickness of the biodegradable resin layer is not particularly limited, but it is usually preferably about 5 to 80 μm, and more preferably 10 to 50 μm. When the film thickness of the biodegradable resin layer is less than 5 μm, it is difficult to coat the biodegradable resin on the paper substrate without problems such as resin leakage. On the other hand, when the film thickness exceeds 80 μm, it becomes an excessive film thickness, and there is a possibility of occurrence of problems due to blocking of the resin layer or inability to use the conventionally used production equipment.

[0045] In the biodegradable resin layer, other additives may be contained as long as the effects of the present invention are not impaired. For example, a thermoplastic resin, a lubricant, an inorganic filler, a plasticizer, an antiblocking agent, an odor absorber, a fragrance, an antioxidant, an antioxidant, a weather resistance improver, an ultraviolet absorber, a crystal nucleating agent, a mold release agent, a water repellent, an antibacterial agent, a slidability improver, a colorant (pigment, dye), etc. may be blended. In this case, it is desirable to use biodegradable components for these additives as much as possible. Therefore, the thermoplastic resin is preferably a biodegradable resin. For example, at least one of polylactic acid, polybutylene adipate terephthalate, poly-3-hydroxybutyric acid-co-3-hydroxyvaleric acid, 3-hydroxybutyrate-co-3-hydroxyhexanoate polymer, polybutylene succinate, polyglycolic acid, polycaprolactone, polyhydroxybutyric acid, polybutylene succinate adipate, cellulose acetate, polyvinyl alcohol, polyethylene terephthalate succinate, etc. can be mentioned. The total content when these additives are contained in the anchor coat layer can usually be 5% by mass or less, but is not limited thereto.

[0046] 2. Method for manufacturing the laminate The manufacturing method of the laminate of the present invention is not limited as long as the above layer structure can be obtained. For example, it can be preferably manufactured by the following method. That is, it is a method for manufacturing a laminate in which a paper substrate, an anchor coat layer, and a biodegradable resin layer are laminated in this order. (1) A step of forming an anchor coat layer by applying a coating liquid containing polybutylene adipate terephthalate as an anchor coat component to a paper substrate and drying it (anchor coat layer forming step), (2) A manufacturing method including a step of forming a biodegradable resin layer containing a biodegradable resin on the anchor coat layer (biodegradable resin layer forming step) can preferably obtain the laminate of the present invention.

[0047] Anchor coat layer forming step In the anchor coat layer forming step, an anchor coat layer is formed by applying a coating liquid containing PBAT as an anchor coat component to a paper substrate and drying it.

[0048] The coating liquid can be prepared by dispersing or dissolving PBAT in a solvent. That is, it can be either a solution or a dispersion, but it is particularly desirable to use a solution in which PBAT is dissolved in an organic solvent as the coating liquid.

[0049] The organic solvent is not particularly limited. For example, ethanol, methanol, isopropyl alcohol, cyclohexane, toluene, acetone, dioxolane, propylene glycol, hexylene glycol, butyl diglycol, pentamethylene glycol, normal pentane, normal hexane, hexyl alcohol, methyl ethyl ketone, methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, isopentyl acetate, normal-butyl acetate, normal-propyl acetate, normal-pentyl acetate, cyclohexane, isobutyl alcohol, isopropyl alcohol, isopentyl alcohol, ethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether, ethylene glycol monomethyl ether, ortho-dichlorobenzene, xylene, cresol, chlorobenzene, cyclohexanol, cyclohexanone, N,N-dimethylformamide, tetrahydrofuran, 1,1,1-trichloroethane, toluene, etc. can be mentioned. Among these, it is preferable to contain a heterocyclic compound having an acetal structure as a solvent, and it is more preferable to contain dioxolane (1,3-dioxolane) particularly because of the easy solubility and distillation of PBAT which is the main component of the anchor coat layer.

[0050] The solid content concentration of PBAT in the coating liquid is not particularly limited, but it is usually good to be about 5 to 35% by mass, and it is particularly preferable to be 8 to 30% by mass. If the solid content concentration is less than 5% by mass, the amount of solvent is large, and it is better to avoid it in view of the balance of drying time, production cost, productivity, etc. Also, when the solid content concentration exceeds 35% by mass, the viscosity is high and it may not dissolve sufficiently in the solvent.

[0051] The method of applying the coating liquid to the paper substrate is not particularly limited. For example, methods using a blade coater, a bar coater, an air knife coater, a curtain coater, a spray coater, a roll coater, a die coater, a reverse roll coater, etc. can be mentioned. The viscosity, solid content concentration, etc. of the coating liquid can be appropriately adjusted according to the coating apparatus, coating system, etc. used.

[0052] Regarding the biodegradation mechanism of the anchor coat layer, PBAT, which is the main component, is an enzyme-degradable biodegradable resin, and it is known that the decomposition proceeds mainly by the enzymes secreted by microorganisms in the soil cutting the polymer bonds. After PBAT is decomposed into oligomers by enzymes, it is decomposed into the components (1,4-butanediol, adipic acid, terephthalic acid) that make up the resin. Although it has good degradability in industrial composting, PBAT alone is difficult to decompose in home composting. Therefore, since biodegradability can be obtained by suitably using starch, as described above, it is preferable that the anchor coat layer also contains starch.

[0053] Biodegradable resin layer forming step In the biodegradable resin layer forming step, a biodegradable resin layer containing a biodegradable resin is formed on the anchor coat layer.

[0054] The method for forming the biodegradable resin layer is not particularly limited. For example, various methods such as (a) a method of applying an aqueous dispersion containing a biodegradable resin, heating and melting it to form a film, (b) a method of applying a solution in which a biodegradable resin is dissolved in an organic solvent and drying it, (c) a method of heating and melting a raw material containing a biodegradable resin and performing extrusion lamination, etc. can be adopted.

[0055] More specifically, the method (a) is a method including the steps of 1) applying an aqueous dispersion in which a biodegradable resin is dispersed on the anchor coat layer and 2) forming a film by heating and melting the obtained coating film.

[0056] The solid content concentration of the biodegradable resin in the aqueous dispersion may be, for example, about 30 to 60% by mass, but is not limited thereto. Also, such an aqueous dispersion can be a commercially available product. Examples of the type of the biodegradable resin include those described above.

[0057] The method of applying the aqueous dispersion is not limited, and examples thereof include methods using a blade coater, a bar coater, an air knife coater, a curtain coater, a spray coater, a roll coater, a die coater, a reverse roll coater, etc.

[0058] Next, the biodegradable resin is melted and formed into a film by heating the coating film obtained by applying the aqueous dispersion. The heating temperature may be a temperature exceeding the melting point of the biodegradable resin contained in the aqueous dispersion, but it is preferably set to a temperature and time sufficient for the biodegradable resin to melt and form a film. Thereby, the biodegradable resin particles dispersed in the aqueous dispersion can be melted and bonded to form an integral film.

[0059] Thereafter, the laminate of the present invention can be obtained by cooling. The cooling method is not particularly limited, and either natural cooling or forced cooling may be used.

[0060] More specifically, the method of (b) above is a method including 1) a step of applying a solution in which a biodegradable resin is dissolved onto the anchor coat layer and 2) a step of drying the obtained coating film.

[0061] The solid content concentration of the biodegradable resin in the solution may be, for example, about 10 to 40% by mass, but is not limited thereto. Examples of the type of the biodegradable resin include those described above.

[0062] In addition, the organic solvent used in the above solution may be any one that can dissolve the biodegradable resin to be used. For example, ethanol, methanol, isopropyl alcohol, cyclohexane, toluene, acetone, dioxolane, propylene glycol, hexylene glycol, butyl diglycol, pentamethylene glycol, normal pentane, normal hexane, hexyl alcohol, methyl ethyl ketone, methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, isopentyl acetate, normal-butyl acetate, normal-propyl acetate, normal-pentyl acetate, cyclohexane, isobutyl alcohol, isopropyl alcohol, isopentyl alcohol, ethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether, ethylene glycol monomethyl ether, ortho-dichlorobenzene, xylene, cresol, chlorobenzene, cyclohexanol, cyclohexanone, N,N-dimethylformamide, tetrahydrofuran, 1,1,1-trichloroethane, toluene, etc. At least one of these can be mentioned. Among these organic solvents, due to the solubility of PBAT which is the main component, the drying property due to the low boiling point, and the hygiene aspect in the point of using for food packaging, it is preferable to use dioxolane (1,3-dioxolane).

[0063] The method of applying the solution is not limited. For example, methods using a blade coater, a bar coater, an air knife coater, a curtain coater, a spray coater, a roll coater, a die coater, a reverse roll coater, etc. can be mentioned.

[0064] Next, the coating film obtained by applying the solution is dried. The drying may be either natural drying or forced drying, but a method of drying under heating is particularly preferable. In this case, the heating temperature may be a temperature at which the organic solvent contained in the solution volatilizes sufficiently, and can be set to about 50 to 150 °C, for example. The heating time can be appropriately set according to the heating temperature and the like.

[0065] The method in (c) above specifically includes a step of forming a film from a raw material containing a biodegradable resin, and a step of laminating the obtained film on the anchor coat layer by thermocompression bonding either as it is or after stretching. This method is advantageous over other methods in that it does not require the use of solvents or the like.

[0066] The method of forming the film is not limited and may be any of, for example, the melt extrusion method (T-die method, inflation method, etc.), the solution casting method, the calendar molding method, etc. Further, when the film obtained by these methods is unstretched, a stretching step (uniaxial stretching or biaxial stretching) or the like may be carried out as necessary.

[0067] The film thus obtained (usually about 5 to 80 μm) is laminated on the anchor coat layer. The lamination method is not limited and can be laminated, for example, by thermocompression bonding (heat sealing), an adhesive, or the like. Also, when the melt extrusion method is adopted, a biodegradable resin layer can be laminated on the anchor coat layer of the laminate having a paper base material / anchor coat layer by coextrusion.

[0068] 3. Use of the laminate The laminate of the present invention can be used for various applications, including packaging materials and containers, and can be particularly preferably used as a packaging material.

[0069] When used as a packaging material or a container, the laminate of the present invention can be used as a packaging material as it is, can be processed into the form of a packaging bag, or can be formed into a container by a normal molding method. When used as a packaging material or a container, for example, the biodegradable resin layer can be formed or used so as to be the inner surface (the surface in contact with the contents), but the reverse configuration may be adopted as necessary. The form of the packaging bag (bag body) is also not limited and may be any of, for example, a two-side bag, a three-side bag, a clasp bag, a gusset bag, a stand bag, a side seal bag, a bottom seal bag, etc. Further, as necessary, it can also be used in a form in which another layer (preferably another biodegradable layer) is laminated on the paper base material or the biodegradable resin layer.

[0070] When used as a packaging material or a container, more specifically, it can be suitably used for various applications such as outdoor tableware, sample containers for tasting and drinking, garbage bags, lunch boxes, food trays, and fast food containers.

Examples

[0071] Examples and comparative examples are shown below to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to the examples. In the examples and comparative examples, “%” means “% by weight”.

[0072] [Example 1] An anchor coating agent was applied to a paper base material with a basis weight of 300 g / m 2 . The anchor coating agent was “Mater-bi EF03A0 (containing PBAT as the main component and modified starch in the balance)” manufactured by Novamont, which was heated and dissolved in 1,3-dioxolane at 60° C. and adjusted to a solid content concentration of 17.5%. This anchor coating agent was applied to the paper base material with a wire bar #24 and dried in a drying oven at 150° C. for 20 seconds to form an anchor coating layer with a solid content of 8.1 g / m 2 . As the upper biodegradable resin layer, a poly(lactic acid) resin (PLA) LX175 manufactured by Total Corbion was heated and dissolved in 1,3-dioxolane at 60° C. and adjusted to a coating solution with a solid content of 25%. This coating agent was applied to the anchor coating layer with a 4-mil (101.6 μm) applicator while being heated to 60° C. and dried in a drying oven at 150° C. for 20 seconds to form a poly(lactic acid) resin layer (PLA resin layer) with a film thickness of 25.4 μm. In this way, the laminate of the present invention (“paper / AC / TP” laminate) was produced. In addition, as a sample for evaluating the adhesion between the paper base material and the anchor coating layer, up to the application of the anchor coating layer in the above process was carried out, and a laminate (“paper / AC” laminate) was also produced. Furthermore, as a sample for evaluating the adhesion between the anchor coat layer and the PLA resin layer, a laminate ("PET / AC / TP" laminate) was also produced in the same manner as above, except that the anchor coat agent was applied to a 25-μm PET film.

[0073] [Example 2] Novamont's "Mater-bi EX52A0 (containing modified starch as the remainder with PBAT as the main component)" was heated and dissolved in 1,3-dioxolane at 60°C as the anchor coat agent, and adjusted to a solid content concentration of 12.5%. This anchor coat agent was applied to a paper substrate with a wire bar #28, and dried in a drying oven at 150°C for 20 seconds to form an anchor coat layer with a solid content of 6.6 g / m 2 . A sample of the laminate was obtained in the same manner as in Example 1. Also, in the same manner as in Example 1, "paper / AC" and "AC / TP" laminates were produced.

[0074] [Example 3] BASF's "Ecovio C1200 (made of PBAT)" was heated and dissolved in 1,3-dioxolane at 60°C as the anchor coat agent, and adjusted to a solid content concentration of 15.0%. This anchor coat agent was applied to a paper substrate with a wire bar #24, and dried in a drying oven at 150°C for 20 seconds to form an anchor coat layer with a solid content of 6.8 g / m 2 . A sample of the laminate was obtained in the same manner as in Example 1. Also, in the same manner as in Example 1, "paper / AC" and "PET / AC / TP" laminates were produced.

[0075] [Example 4] The anchor coat agent was applied to a paper substrate with a basis weight of 300 g / m 2 . The anchor coat agent was Novamont's "Mater-bi EF03A0", which was heated and dissolved in 1,3-dioxolane at 60°C and adjusted to a solid content concentration of 17.5%. This anchor coat agent was applied to the paper substrate with a wire bar #24, and dried in a drying oven at 150°C for 20 seconds to form an anchor coat layer with a solid content of 8.1 g / m 2 . As the upper biodegradable resin layer, an aqueous dispersion coating agent of polybutylene succinate adipate resin (PBSA) was prepared. This coating agent was applied to the substrate with a wire bar #24 and dried in a drying oven at 180 °C for 120 seconds to form a polybutylene succinate adipate resin layer with a film thickness of 23.1 μm. Also, in the same manner as in Example 1, "paper / AC" laminates and "PET / AC / TP" laminates were also produced.

[0076] [Example 5] An anchor coating agent was applied to a paper substrate with a basis weight of 300 g / m 2 . The anchor coating agent was "Mater-bi EF03A0" manufactured by Novamont, which was heated and dissolved in 1,3-dioxolane at 60 °C and adjusted to a solid content concentration of 17.5%. This anchor coating agent was applied to the paper substrate with a wire bar #24 and dried in a drying oven at 150 °C for 20 seconds to form an anchor coating layer with a solid content of 8.1 g / m 2 . As the upper biodegradable resin layer, "FORZEAS FT0019" manufactured by Mitsubishi Chemical was heated and dissolved in 1,3-dioxolane at 60 °C and adjusted to a solid content concentration of 12.0%. This coating agent was applied to the anchor coating layer with a 6 mil (152.4 μm) applicator while being heated to 60 °C and dried in a drying oven at 150 °C for 20 seconds to form a polybutylene succinate resin layer with a film thickness of 18.3 μm. Also, in the same manner as in Example 1, "paper / AC" laminates and "PET / AC / TP" laminates were also produced.

[0077] [Example 6] An anchor coating agent was applied to a paper substrate with a basis weight of 300 g / m 2 . The anchor coating agent was "Mater-bi EF03A0" manufactured by Novamont, which was heated and dissolved in 1,3-dioxolane at 60 °C and adjusted to a solid content concentration of 17.5%. This anchor coating agent was applied to the paper substrate with a wire bar #24 and dried in a drying oven at 150 °C for 20 seconds to form an anchor coating layer with a solid content of 8.1 g / m 2 . As the upper biodegradable resin layer, commercially available polycaprolactone was dissolved in xylene and adjusted to a solid content concentration of 25.0%. This coating agent was applied to the anchor coat layer with a 4-mil (101.2 μm) applicator and dried in a drying oven at 150 °C for 20 seconds to form a polycaprolactone resin layer with a film thickness of 25.4 μm. Also, in the same manner as in Example 1, "paper / AC" laminates and "PET / AC / TP" laminates were also produced.

[0078] [Example 7] The basis weight of the paper was 300 g / m 2 and an anchor coating agent was applied to the paper substrate. The anchor coating agent was "Mater-bi EF03A0" manufactured by Novamont, heated and dissolved in 1,3-dioxolane at 60 °C, and adjusted to a solid content concentration of 17.5%. This anchor coating agent was applied to the paper substrate with a wire bar #24 and dried in a drying oven at 150 °C for 20 seconds to form an anchor coat layer with a solid content of 8.1 g / m 2 . As the upper biodegradable resin layer, poly 3-hydroxybutanoic acid - co (copolymerized) - 3-hydroxyhexanoic acid (PHBH) was heated and dissolved in 1,3-dioxolane at 60 °C and adjusted to a solid content concentration of 25.0%. This coating agent was applied to the anchor coat layer with a 4-mil (101.2 μm) applicator and dried in a drying oven at 150 °C for 20 seconds to form a poly 3-hydroxybutanoic acid - co (copolymerized) - 3-hydroxyhexanoic acid (PHBH) resin layer with a film thickness of 25.4 μm. Also, in the same manner as in Example 1, "paper / AC" laminates and "AC / TP" laminates were also produced.

[0079] [Comparative Example 1] Commercially available polyvinyl alcohol was adjusted to a solid content of 12% with ion-exchanged water as the anchor coating agent. This anchor coating agent was applied to the paper substrate with a wire bar #32 and dried in a drying oven at 150 °C for 20 seconds to form an anchor coat layer with a solid content of 8.0 g / m 2 . Otherwise, laminate samples were obtained in the same manner as in Example 1. Also, in the same manner as in Example 1, "paper / AC" laminates and "PET / AC / TP" laminates were also produced.

[0080] [Comparative Example 2] As the anchor coating agent, "FORZEAS FT0019" manufactured by Mitsubishi Chemical was heated and dissolved in 1,3-dioxolane at 60°C, and adjusted to a solid content concentration of 12.0%. This anchor coating agent was applied to a paper substrate with a wire bar #28, and dried in a drying oven at 150°C for 20 seconds to form an anchor coating layer with a solid content of 6.7 g / m 2 . Other than this, a sample of the laminate was obtained in the same manner as in Example 1. Also, in the same manner as in Example 1, "paper / AC" and "PET / AC / TP" laminates were also produced.

[0081] [Comparative Example 3] As the anchor coating agent, PHB was heated and dissolved in 1,3-dioxolane at 60°C, and adjusted to a solid content concentration of 10.0%. While maintaining the heating state, this anchor coating agent was applied to a paper substrate with a wire bar #32, and dried in a drying oven at 150°C for 20 seconds to form an anchor coating layer with a solid content of 6.5 g / m 2 . Other than this, a sample of the laminate was obtained in the same manner as in Example 1. Also, in the same manner as in Example 1, "paper / AC" and "AC / TP" laminates were also produced.

[0082] [Comparative Example 4] As the anchor coating agent, a commercially available epoxy paint was applied to a paper substrate with a wire bar, and dried in a drying oven at 180°C for 60 seconds to form an anchor coating layer with a solid content of 8.2 g / m 2 . Other than this, a sample of the laminate was obtained in the same manner as in Example 1. Also, in the same manner as in Example 1, "paper / AC" and "PET / AC / TP" laminates were also produced.

[0083] [Comparative Example 5] A commercially available olefin paint was applied to a paper substrate as the anchor coating agent with a wire bar #28, and dried in a drying oven at 150°C for 20 seconds to form an anchor coating layer with a solid content of 8.0 g / m 2 . Other than this, a sample of the laminate was obtained in the same manner as in Example 1. Also, in the same manner as in Example 1, "paper / AC" and "PET / AC / TP" laminates were also produced.

[0084] [Comparative Example 6] A commercially available acrylic paint was applied to a paper substrate with a wire bar #20 as an anchor coating agent, dried in a drying oven at 150 °C for 20 seconds, and an anchor coating layer with a solid content of 6.6 g / m 2 was formed. A sample of the laminate was obtained in the same manner as in Example 1 except for this. Also, in the same manner as in Example 1, a "paper / AC" laminate and an "AC / TP" laminate were also produced.

[0085] [Comparative Example 7] A commercially available urethane paint was applied to a paper substrate with a wire bar #20 as an anchor coating agent, dried in a drying oven at 150 °C for 20 seconds, and an anchor coating layer with a solid content of 6.5 g / m 2 was formed. A sample of the laminate was obtained in the same manner as in Example 1 except for this. Also, in the same manner as in Example 1, a "paper / AC" laminate and a "PET / AC / TP" laminate were also produced.

[0086] [Test Example 1] Regarding the laminates produced in each Example and Comparative Example, evaluation of adhesion and biodegradability was carried out in the following manner. The results are shown in Table 1.

[0087] (1) Adhesion evaluation To evaluate the adhesion between the layers of the laminates prepared in each Example and Comparative Example, after holding for 1 day after laminate preparation, cuts were made with a blade in a cross shape on the paper substrate, and a 15 mm wide cellophane tape was pressed by hand on it. Then, it was quickly peeled off with a finger in a 45° direction with respect to any of the cuts, and the peeling form of the paper substrate was visually confirmed. In this case, regarding the "paper / AC" laminate and the "paper / AC / TP" laminate, a state of cohesive failure on the paper substrate was regarded as "〇" (qualified), and a state where only the resin layer adhered to the cellophane tape and the paper substrate was not broken was regarded as "×" (unqualified). Regarding the "PET / AC / TP" laminate, when the coated laminate did not adhere to the cellophane tape, it was rated as "〇" (qualified). On the other hand, when the film adhered to the cellophane tape, it was possible that the anchor coat was not sufficiently adhered to the PET film. Therefore, a new cellophane tape was attached to the film adhered to the cellophane tape and peeled off to evaluate whether it was adhered. When the film adhered to the cellophane tape could not be peeled off by that method, the adhesion was rated as "〇" (qualified), and when it was peeled off and the laminate was separated, the adhesion was rated as "×" (unqualified).

[0088] (2) Biodegradability evaluation The biodegradability of the laminates of each example and comparative example was evaluated. The compost used in the biodegradation of the laminate was prepared using a seed source manufactured by Yawata Bussan Co., Ltd., commercially available sea sand, and ion-exchanged water. The solid content of the seed source was measured with a heating and drying moisture meter. Also, the sea sand was a product with a particle size of 425 - 850 μm (20 - 35 mesh), washed with ion-exchanged water, and dried in a drying oven at 105 °C for 12 hours. An amount of sea sand that had been sufficiently dried relative to the solid content weight of the seed source was mixed in an amount 5 times as much, and adjusted with ion-exchanged water so that the total moisture content was 35%. The prepared compost was separately placed in a 1900 mL polypropylene container, and a 10 cm square laminate was buried and covered. The container was placed in an incubator set at 58 °C and held, and samples were taken out every week and observed visually. The compost was stirred and water was added every week, and the taken-out laminate was buried again. When no laminate could be visually confirmed after 4 weeks, the biodegradability was rated as "〇" (qualified), and when a laminate that could be visually confirmed remained, the biodegradability was rated as "×" (unqualified).

[0089]

Table 1

[0090] As is clear from the results in Table 1, the laminate of the present invention is a laminate containing a paper substrate and a resin through a specific anchor coat layer, and it can be seen that although all the resins are biodegradable, each layer has sufficient adhesiveness.

Claims

1. A laminate in which a paper substrate, an anchor coat layer, and a biodegradable resin layer are laminated in this order, wherein the anchor coat layer contains polybutylene adipate terephthalate.

2. The laminate according to claim 1, wherein the anchor coat layer further contains starch.

3. The laminate according to claim 1, wherein the biodegradable resin layer contains at least one biodegradable resin selected from the group consisting of polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polybutylene succinate (PBS), polyglycolic acid (PGA), polycaprolactone (PCL), polyhydroxybutyric acid (PHB), polybutylene succinate adipate (PBSA), polyethylene terephthalate succinate (PETS), and poly(3-hydroxybutyric acid-co-3-hydroxyhexanoic acid) (PHBH).

4. The laminate according to claim 1, wherein the film thickness of the biodegradable resin layer is 5 to 80 μm.

5. The basis weight of the paper base material is 20 to 500 g / m ２ The laminate according to claim 1, wherein the laminate is as described above.

6. The laminated amount of the anchor coat layer is 0.2 to 15 g / m in terms of solid content weight ２ The laminate according to claim 1, wherein the laminated amount is as defined above.

7. The laminate according to claim 1, which is used as a packaging material or a container.

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