JP2019177488A - Package for food container - Google Patents

Abstract

To provide, in a formed body for food, a container that has a heat-resistant property and a heat insulation property to withstand high-temperature content during use, and biodegrades after disposal.SOLUTION: The package for food container is characterized to be constructed of a laminate comprising: a substrate layer mainly composed of a paper; an outermost layer disposed on one side of the substrate layer and comprising a resin composition containing an aliphatic aromatic copolymerization polyester-based resin that foams by heating; and an innermost layer laminated on the other surface of the substrate layer and comprising a resin composition containing an aliphatic aromatic copolymerization polyester-based resin that is different from the resin composition used for the outermost layer.SELECTED DRAWING: None

Description

  The present invention requires heat resistance and heat insulation, for example, hot beverage containers (coffee, tea, soup), low-temperature foods (ice cream, chocolate bar, cereal bar, yogurt) instant noodle containers (ramen, udon, yakisoba) The present invention also relates to a food container package having biodegradability that can be used for a container for a microwave oven, a container for a boil. More specifically, the present invention relates to a molded article made of a thermoplastic biodegradable resin sheet having a heat insulating property obtained by steam-foaming a biodegradable resin layer and having excellent surface design properties, heat insulating properties, rigidity, and productivity.

  Conventionally, many plastics are used for various industrial containers such as food, agriculture and industrial use. Among these, examples of disposable containers include food packaging materials. The amount of general plastic containers used is increasing year by year, and the amount discarded is also increasing. In order to reduce the amount of waste, there is an active movement to reuse. However, reuse of the reuse method is costly to remove dirt such as adhesion of contents, and the reuse of the material recycling method is very difficult to separate for each used material. By mixing resins having different molecular weights and different additives, there are cases where it is unavoidable to use products different from those before recycling.

  Examples of the plastic constituting the plastic film include polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate. However, since these plastic films are produced from petroleum-derived raw materials, they have the problem of depletion of fossil resources and the problem of global warming due to carbon dioxide generated during incineration. Also, most plastics are durable in the environment, so that their shape is maintained when discarded, and waste problems such as environmental pollution and lack of landfill are becoming serious.

  For these reasons, containers have problems to be solved at the stage of disposal, and various biodegradable containers have been studied, such as embedding in the soil with the contents and promoting decomposition under favorable conditions. Yes.

  As a foamed paper cup that does not have simple biodegradability, a heat-insulating foamed paper layer such as a heat-insulated foamed paper cup manufactured by foaming low-density polyethylene by heat treatment, and a foamed heat-insulating layer with printing ink at the time of foaming There is a method of manufacturing a paper container having partially different thicknesses. (Patent Document 1)

  In recent years, plant-derived raw materials, resins produced from plants, and biodegradable resins have been used. Many researches have been made on plant-derived resin raw materials. Typical examples of plant-derived resin raw materials include paper, polylactic acid, polybutylene succinate, polybutylene succinate adipate, polycaprolactone, polybutylene terephthalate adipate, polybutylene. Aliphatic polyesters or araliphatic polyesters such as terephthalate succinate can be mentioned, and there is a technique of a composite container having a heat insulating air layer for imparting biodegradability and heat insulation (Patent Document 2).

  On the other hand, the double container has a problem that the material is duplicated and the manufacturing process is complicated. In addition, food containers such as instant noodles need to be cooked and the contents must be easy to handle (universal design), rigid, oil resistant, heat resistant, and heat insulating.

Japanese Patent Laid-Open No. 7-232774 JP 2003-40242 A

  This invention has a foaming layer using the biodegradable resin which has heat resistance and heat insulation with respect to the said subject seen in a prior art. That is, it is to provide a technology that ensures a practical performance including heat resistance during use and provides a technique for solving the problem by biodegradation after use.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a graft copolymer mainly composed of polybutylene adipic acid terephthalate, which contains a polyester-based biodegradable resin as a constituent component and is rich in adhesiveness and moldability, or the like. By using blended resin, it is possible to ensure a practical performance that can withstand the use of instant noodles and to obtain a container that can be decomposed into water and inorganic compounds by the action of microorganisms and hydrolysis under natural environment. The headline and the present invention were completed.

  According to the present invention, a container having excellent biodegradability and practical performance as an instant noodle container can be obtained.

  Hereinafter, preferred embodiments for carrying out the present invention will be described. The container according to the present embodiment has a base layer mainly composed of paper, a foam layer made of a resin composition containing an aliphatic aromatic copolymer polyester resin that foams by heating on at least one side of the base layer, Is provided. Here, the resin part of the container is composed of a biodegradable resin foam heat insulating layer containing 50% by weight or more of a graft copolymer made of polybutylene adipate terephthalate or a blend thereof. A decomposable container will be described as an example.

[Aliphatic aromatic copolyester resin]
The resin composition used in the present embodiment includes an aliphatic aromatic copolymer polyester resin mainly composed of an aliphatic diol and an aromatic dicarboxylic acid. In this case, the content of the aliphatic diol unit is 90 mol% or more, preferably 95 mol based on the total amount of the aromatic dicarboxylic acid unit and the aliphatic oxycarboxylic acid unit (100 mol%). % Or more, more preferably 98 mol% or more.

  Specific examples of the aliphatic oxycarboxylic acid used as a raw material for the aliphatic polyester resin include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, and 2-hydroxy-3. , 3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid and the like, or lower alkyl esters or intramolecular esters thereof. When optical isomers are present in these, any of D-form, L-form and racemic form may be used, and the form may be any of solid, liquid or aqueous solution. Among these, lactic acid or glycolic acid is particularly preferable.

  As specific examples of the aliphatic diol, an aliphatic diol component having 2 to 10 carbon atoms is preferable, and an aliphatic diol component having 4 to 6 carbon atoms is particularly preferable. Specific examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,4-butanediol is particularly preferable.

  Specific examples of the aromatic dicarboxylic acid are not particularly limited, and examples thereof include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and the like. Among them, terephthalic acid and isophthalic acid are preferable, and terephthalic acid is particularly preferable. Further, aromatic dicarboxylic acids in which a part of the aromatic ring is substituted with a sulfonate are also included.

  Two or more kinds of the aliphatic dicarboxylic acid component, the aliphatic diol component, and the aromatic dicarboxylic acid component can be used. Further, a small amount of an aliphatic oxycarboxylic acid unit may be contained within a range not impairing its properties.

  The content of the aliphatic aromatic copolymer polyester resin in the resin composition of the present invention is usually 30% or more, preferably 40% or more, in mass ratio, based on the whole resin composition (100%). Preferably it is 50% or more, and the upper limit of the content is usually 99% or less, preferably 90% or less, more preferably 85% or less. If the content of the aliphatic aromatic copolyester resin is too large, mechanical properties such as tensile elongation decrease and the biodegradation rate becomes slow, which is not preferable for use as various packaging materials. On the other hand, if the content of the aliphatic aromatic copolymer polyester resin is too small, the moldability deteriorates and the mechanical property strength becomes insufficient, which is not preferable.

  The synthesis of the described polyesters takes place in a two-stage reaction cascade. First, the dicarboxylic acid derivative is converted to a prepolyester in the presence of the diol and a transesterification catalyst. The prepolyester generally has a viscosity number (VZ) of 50 to 100 mL / g, preferably 60 to 80 mL / g. As catalysts, zinc catalysts, aluminum catalysts and in particular titanium catalysts are usually used. Titanium catalysts such as tetra (isopropyl) orthotitanate and especially tetrabutylorthotitanate (TBOT) are tin catalysts, antimony catalysts, cobalt catalysts and lead catalysts often used in the literature, such as tin dioctanoate. In comparison, the remaining amount of catalyst or catalyst by-product remaining in the product has the advantage that it is less toxic. This situation is particularly important in the case of biodegradable polyesters, since these polyesters can reach the environment directly through composting.

  The polyesters according to the invention typically have a number average molecular weight (Mn) in the range of 5000-100000 g / mol, in particular in the range of 10000-75000 g / mol, preferably in the range of 15000-38000 g / mol, 30000-300000 g / mol. Preferably having a mass average molecular weight (Mw) of 60000-200000 g / mol and a Mw / Mn ratio of 1-6, preferably 2-4. The viscosity number is 50 to 450 g / mL, preferably 80 to 250 g / mL (measured in o-dichloro-benzene / phenol (mass ratio 50/50)). The melting point is in the range of 85 to 150 ° C, preferably in the range of 95 to 140 ° C.

  The melt flow rate (MFR) of the aliphatic aromatic copolymer polyester resin used in the resin composition of the present invention is usually 0.5 g / in when measured at 190 ° C. and a load of 2.16 kg in accordance with JIS K7210. It is 10 minutes or more, preferably 1.0 g / 10 minutes or more, and more preferably 2.0 g / 10 minutes or more. Moreover, the upper limit of MFR is 50 g / 10min or less normally, Preferably it is 20 g / 10min or less, More preferably, it is 6.0 g / 10min or less. If the MFR is less than 2.0 g / 10 min, the fluidity during molding is poor, which is not preferable. On the other hand, if the MFR is larger than 6.0 g / 10 min, the mechanical properties of the film or the molded product are lowered.

  1,4-butanediol Polybutylene terephthalate consisting of terephthalic acid and adipic acid, based on the total mass of polybutylene terephthalate adipate, polyfunctional isocyanates, isocyanurates, oxazolines, carboxylic anhydrides such as maleic anhydride, epoxides (especially epoxides) Chain extender and / or crosslinker selected from the group consisting of (poly (meth) acrylates) and / or at least trifunctional alcohols or at least trifunctional carboxylic acids, preferably 0 to 10% by weight, preferably Contains 0.01 to 5 mass%.

  As a method for synthesizing an aliphatic aromatic copolymer polyester resin, a method in which aliphatic polyester and aromatic aliphatic polyester are bonded to each other with diisocyanate, polyfunctional carbodiimide, or the like, or transesterification is appropriately performed by transesterification. And a method for producing a multi-block copolymer by the above method. Examples of the reaction include solution reaction, melting reaction, and a method of reacting at the time of kneading.

  Typically, multifunctional isocyanates, isocyanurates, oxazolines, epoxides, carboxylic anhydrides, at least trifunctional alcohols or at least trifunctional to impart (graft) side chains from the polymer backbone The crosslinking agent and / or chain extender selected from the group consisting of carboxylic acids is 0.01-2% by mass, preferably 0.2%, based on the total mass of the aliphatic aromatic copolyester resin. -1.5% by weight and particularly preferably 0.35-1% by weight. As chain extenders, multifunctional and in particular bifunctional isocyanates, isocyanurates, oxazolines, carboxylic anhydrides or epoxides are worth considering.

  Chain extenders as well as alcohol or carboxylic acid derivatives having at least three functional groups can also be understood as crosslinkers. Particularly preferred compounds have 3 to 6 functional groups. Illustrative examples include: tartaric acid, citric acid, malic acid; trimethylolpropane, trimethylolethane; pentaerythritol; polyethertriol and glycerin, trimesic acid, trimellitic acid, trimellitic anhydride, pyromellitic. Acid and pyromellitic dianhydride. Preference is given to polyols such as trimethylolpropane, pentaerythritol and in particular glycerol. Using these, a biodegradable polyester having a structural viscosity composed of a grafted molecular structure such as low-density polyethylene can be synthesized. The rheological behavior of these melts is improved and the viscosity under load is lower.

  The following compounds are suitable as difunctional chain extenders: Aromatic diisocyanates are, inter alia, toluylene-2,4-diisocyanate, toluylene-2,6-diisocyanate, 2,2 ′. -Diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthylene-1,5-diisocyanate or xylylene-diisocyanate. Among them, 2,2'-, 2,4'- and 4,4'-diphenylmethane diisocyanate are particularly preferred. In general, the latter diisocyanates are used as a mixture. In a secondary amount, for example up to 5% by weight, based on the total weight, the diisocyanate can also contain urethion groups, for example to cap the isocyanate groups.

  Examples of the aliphatic aromatic copolymer polyester resin in the present embodiment include polybutylene adipate terephthalate or a polybutylene adipate terephthalate graft polymer added with a crosslinking agent and / or a chain extender during synthesis, and biodegradable resins thereof. It is particularly preferred to use a blend with

[Organic additives]
You may add an organic additive to the resin composition of this invention in the mass ratio of 5% or less with respect to the whole resin composition as needed. Specific examples of organic additives include carbodiimide compounds, diisocyanate compounds, oxazoline compounds, epoxy compounds, acid anhydrides, starch, modified starch, pregelatinized starch, rice flour, pulp, chitin / chitosan, coconut shell powder, wood flour, Bamboo powder, bark powder, natural fiber, powders such as kenaf and persimmon etc. are mentioned. These may be used alone or in combination of two or more.

  The addition amount of the organic additive is usually 0.001% or more, preferably 0.01% or more, more preferably 0.05% or more, by mass ratio with respect to the entire resin composition. The upper limit of the addition amount is usually 5% or less, and the expected effect cannot be obtained if the addition amount is less than 0.001%. On the other hand, if the addition amount exceeds 5%, the moldability of the resin composition is deteriorated, and the mechanical properties and heat resistance of the resin composition molded article are also unfavorable.

[Other additives]
For the purpose of adjusting the antistatic effect, a high molecular weight antistatic agent, carbon black, a conductivity imparting agent, a higher alcohol, or the like may be added to the thermoplastic resin of the present invention. Furthermore, if necessary, compatibilizers, anti-smudge agents, colorants, dispersants, mold release agents, stabilizers (antioxidants, UV absorbers, heat stabilizers, etc.), flame retardants, lubricants, You may add an antiblocking agent, a filler, etc. The addition amount is generally 5% or less, preferably 3% or less, and more preferably 1% or less in terms of mass ratio to the extent that the biodegradability is not impaired, based on the entire resin composition (100%).

[Laminate]
The laminate according to the present embodiment includes a layer having biodegradability and water vapor foamability on at least one side. Typically, 2-7 layers and preferably 2-3 layers are used in the paper coat. Multi-layer coatings offer the possibility of individually optimizing the welding properties, barrier properties and adhesion of the coat to the cardboard for the layers by providing an intermediate layer.

The intermediate layer is usually also called a support layer or a barrier layer for increasing rigidity. In the coating of paper with a thin film, the intermediate layer can also be omitted completely.
The innermost layer is a contact layer to cardboard, and if it is a food container, it is a food contact layer. This inner layer typically must be soft and must adhere well to cardboard or paper. This preferably consists of a biodegradable resin such as polylactic acid.

The average basis weight of the paper is here typically 10 to 500 g / m ² and preferably 30 to 400 g / m ² , more preferably 50 to 350 g / m ² . Also, since water is used for foaming by water vapor in the subsequent process, the water content of the paper is usually 2 to 20 parts by weight, preferably 3 to 15 parts by weight, more preferably, to the paper base material. Is 5-9 parts by weight,

The film thickness of the biodegradable resin layer is usually 10 to 100 μm, preferably 15 to 80 μm, and more preferably 30 to 70 μm.
The total thickness of the biodegradable resin sheet is 0.1 to 3.0 mm, preferably 0.2 to 2.0 mm, and more preferably 0.3 to 1.2 mm.

  The laminate according to the present embodiment is composed of a base paper containing one foamed heat insulating layer and another layer of moisture in a multilayer. The laminated body concerning this embodiment can be prepared by methods, such as a co-extrusion method, heat lamination, and dry lamination, and does not necessarily require an adhesive agent. In addition, the resin layer that is not suitable for the food hygiene law should not touch food directly.

The method for producing the biodegradable laminate substrate of the present invention is not particularly limited, and the resin composition pellets are supplied to an ordinary extruder, melt-kneaded, and die (flat, T-shaped (T Die), cylindrical shape (circular die), etc.] can be extruded into a sheet shape, and the sheet structure at this time is preferably a single layer, two types, two layers, or two types, three layers. May contain a biodegradable resin, and other layers (for example, an intermediate layer) may be blended so as to contain a biodegradable resin, an inorganic additive, and a barrier layer.
The laminate substrate is usually an unstretched coating in which a draw (drawing) is applied in the extrusion direction. The coated surface is usually cooled with a cooling roll (chill roll) and can be wound up. The melting temperature is about 150 to 250 ° C, preferably about 200 to 240 ° C.

When the melting point of the body part outer surface foamed layer and the melting point of the body part inner surface layer are close to each other when cup molding is performed in a subsequent process, it is difficult to control the temperature when foaming. Therefore, the difference between the melting point of the barrel outer surface foaming and the melting point of the barrel inner surface layer is preferably 5 ° C. or higher, and more preferably 10 ° C. or higher.

The trunk portion outer surface foamed layer will be described in more detail. The thickness of the outer foam layer is preferably 25 to 80 μm. If it is this range, since the film thickness of a trunk | drum outer surface foaming layer (after foaming) will become 300 micrometers or more easily, sufficient heat insulation is realizable.
The thickness of the inner surface layer of the trunk portion is preferably 30 μm or more. When the thickness is 30 μm or more, the surface of the inner surface layer is merely melted, and the risk that a part of the paper is exposed can be reduced.
The bottom inner layer will be described in more detail. The film thickness of the bottom inner surface layer is usually 20 to 80 μm. Unlike the trunk, the bottom does not have a process of foaming the outer surface. Therefore, an adhesive resin can be used for the bottom inner surface layer.

  In addition, the laminate product may be printed to the extent that the biodegradability is not deteriorated by using an existing printing method such as flexo, offset, and gravure on the surface that does not come into contact with food.

[Secondary processed molded products]
The laminated body according to this embodiment can be subjected to secondary molding by die-cutting, conventional thermoforming such as bending, pressure forming, match mold forming, hot plate forming, or the like. Examples of secondary molded products include packaging materials, food containers, chemical containers, trays, embossed tapes, carrier tapes, and the like.
Further, the surface of the sheet or the secondary molded product may be subjected to surface treatment (for example, discharge treatment such as corona discharge or glow discharge, acid treatment, wrinkle treatment, etc.).
Furthermore, imparting chemical functions, electrical functions, magnetic functions, mechanical functions, friction / abrasion / lubricating functions, optical functions, thermal functions, biocompatibility and other surface functions to the resin composition molded body For the purpose, secondary processing can be appropriately performed. Examples of secondary processing include embossing, painting, adhesion, printing, metalizing (plating, etc.), machining, surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, Coating) and the like.
In this embodiment, after molding, the moisture present in the laminate is oven-heated and expanded as a water vapor to expand the resin having foaming characteristics, thereby forming a foam heat insulating layer. The foaming ratio at this time (foaming heat insulation layer after foaming / foaming heat insulation layer before foaming) varies depending on the thickness and type of the foamed resin layer, or the foaming temperature, but is usually 400 to 3000%. is there

  The molded body according to the present invention is excellent in heat resistance, rigidity, and impact properties, and is suitable for instant noodles, instant food containers and beverages, for example.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these. In addition, the evaluation method of each evaluation item in an Example, and the content of each used component are as follows.

[Melt flow rate (MFR, unit: g / 10 min)]
Based on JIS K7210, it measured at 190 degreeC and the load 2.16kg using the melt indexer. The unit is g / 10 minutes.

[density]
The density was measured according to JIS K6922-1. Specifically, it was extruded with a standard melt indexer in accordance with JIS K7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg, and the extruded strand was cut out from the melt indexer and allowed to stand with air cooling. After inserting a strand into the sample tube and substituting with nitrogen, annealing is performed in an oil bath at 120 ° C. for 1 hour, and the sample tube is allowed to cool in a constant temperature laboratory atmosphere for 1 hour. The density of the test piece is a density gradient tube according to ISO 1183 The measurement was made within 24 hours by the method. The unit of density is kg / m3.

[Measurement method of elastic modulus and tensile elongation at break]
It measured by the tension test based on ISO527 using the tensilon universal testing machine (Orientec Co., Ltd. "UCT-10T").
The tensile elastic modulus is calculated by the following equation using the first linear portion of the load-deformation curve.
E = Δσ / Δε
E: Tensile modulus (MPa)
Δσ: Stress difference between two points on the straight line (MPa)
Δε: Difference in deformation between the same two points (%)

[Melting point]
The melting point was measured by a differential scanning calorimeter (manufactured by Seiko Co., Ltd., product name: DSC220).
) Was used. About 10 mg of sample is precisely weighed, heated and melted in a nitrogen stream at a flow rate of 40 mL / min, cooled at a rate of 10 ° C./min, and then the melting peak top when the temperature is continuously raised at a rate of 10 ° C./min The temperature was taken as the melting point.

[Biodegradability]
In the sense of the present invention, the characteristic “biodegradable” is for a substance or substance mixture if the substance or substance mixture has a percentage of biodegradability of at least 90% corresponding to ISO 14855-2. be satisfied. In general, biodegradability leads to the sample disintegrating within an adequate and detectable period. Said degradation can be carried out enzymatically, hydrolytically, oxidatively and / or by the action of electromagnetic radiation, for example ultraviolet radiation, and for the most part microorganisms such as bacteria, yeast, fungi and algae It can be caused by the action of Biodegradability can be quantified, for example, by mixing the sample with compost and storing for a specific time. For example, according to ISO 14855-2, CO ₂ free air is sent to the aged compost being composted and this compost is subjected to a defined temperature program. In this case, biodegradability is defined as the net CO ₂ release of the sample (after subtracting the CO ₂ release from compost without the sample) versus the maximum CO ₂ release of the sample (calculated from the carbon content of the sample). Is defined as the percentage of biodegradability. Biodegradable polyesters (mixtures) typically show obvious degradation phenomena such as fungal growth, crack formation and hole formation already several days after composting.
Other methods for measuring biodegradability are described, for example, in ASTM D 5338 or DIN EN 13432.

  Whether it was biodegradable or not was evaluated as follows. Each film having a thickness of 30 μm was produced from the biodegradable sample and the mixture produced for comparison by pressing at 190 ° C. These films were each cut into square pieces having an edge length of 2 × 5 cm. The masses of these film pieces were measured and defined as 100 parts by mass. Over a period of 4 weeks, the film pieces were heated to 58 ° C. in a plastic container filled with moist compost soil in a dryer. After the test, the remaining mass of the film piece was measured, and judged by the presence or absence of a decrease of 90% by mass.

[Cup molding evaluation]
11 g of instant coffee powder was dissolved in 3 liters of hot water, and about 80% of the content of the molded product was injected. After 15 minutes, leakage from the side seal part and the bottom seal part was confirmed.
○: No leakage ×: Leakage

[Foaming evaluation]
The sample cross section before and after foaming was shaved with a feather blade, the thickness of the laminar layer was confirmed with an AZ100M optical microscope manufactured by NIKON CORPORATION, and the foaming ratio was calculated from the thickness ratio before and after foaming.
○: 4 or more times foaming △: Partially foaming or 1 to 4 times foaming ×: No foaming

<Materials used and their properties>
[Low density polyethylene LDPE]
Product name: Petrocene (registered trademark) manufactured by Tosoh Corporation was used. The resin had MFR = 15.0 g / 10 min, a melting point of 103 ° C., and a density of 917 kg / m 3.

[Polybutylene terephthalate PBT]
Toray Industries, product name: Toraycon (registered trademark) was used. The melting point was 235 ° C., and the density was 1210 kg / m 3.

[Aliphatic polyester polylactic acid PLA]
A product name: Ingeo (registered trademark) manufactured by Nature Works was used. The resin had MFR = 6.0 g / 10 min, a melting point of 156 ° C., and was composed of 98 mol% lactic acid. The density was 1240 kg / m3.

[Aliphatic Aromatic Copolyester Resin Polybutylene Adipic Acid Terephthalate PBAT-1 Ecoflex]
Product name: Ecoflex (registered trademark) manufactured by BASF Corporation was used. The resin had MFR = 4.5 g / 10 min, melting point 110 ° C., and as a result of 1H-NMR, the content of terephthalsan units was 22 mol%, the content of adipic acid units was 28 mol%, 1, 4 The content of butanediol units was 50 mol%.

[Aliphatic Aromatic Copolyester Resin Polybutylene Adipic Acid Terephthalate PBAT-2 Graft Polymerization]
Using PBAT, which is an aliphatic aromatic copolymer polyester resin, as a base resin, a crosslinker and / or chain extender is added during synthesis to perform graft polymerization, and a polyester having a network molecular structure is synthesized as follows. did.

  In a reaction vessel equipped with a stirrer, a nitrogen inlet, a heating device, a thermometer, and a pressure reducing port, PBAT containing 15 mol% terephthalic acid, 35 mol% adipic acid, and 50 mol% 1,4-butanediol was blended, 0.37 parts by weight of malic acid and 4.1 parts by weight of 1,6-hexamethylene diisocyanate are added to the total mass of PBAT, 0.01 parts by weight of titanium tetrabutyrate as a catalyst, and magnesium acetate tetrahydrate 0.074 parts by mass of the product was charged. Nitrogen gas was introduced into the container while stirring the contents of the container, and the system was placed in a nitrogen atmosphere by vacuum replacement.

Next, the temperature in the system was increased to 185 ° C. while stirring, and the reaction was carried out at this temperature for 45 minutes. Then, it heated up at 220 degreeC over 1 hour 30 minutes. Thereafter, the temperature was raised to 260 ° C. over 1 hour, and at the same time, the pressure was reduced for a long time, and the polymerization was continued while maintaining the heated and reduced pressure state. When the viscosity reached a predetermined level, the polymerization was terminated to obtain a copolymer. The resin had an MFR = 4.8 g / 10 min, a melting point of 102 ° C., and a density of 1120 kg / m ³ .

  The materials used and their properties are shown in Table 1.

<Evaluation of physical properties of single layer of foam layer>
The PBAT / PLA blend product was added to the above materials used for physical property evaluation.

[Aliphatic Aromatic Copolyester Resin / Polylactic Acid Blend Product Polybutylene Adipic Acid Terephthalate PBAT-1 / PLA Blend]
Product name: Ecoflex manufactured by BASF Corporation was used. The resin used was MFR = 4.5 g / 10 min, melting point 110 ° C., manufactured by Nature Works, product name: Ingeo. The resin was MFR = 6.0 g / 10 min, melting point 156 ° C., dry blended at a weight ratio of 70:30, kneaded with a twin screw extruder, and the kneaded pellets were dried at 70 ° C. under nitrogen for 10 hours. And sealed.

  Each material used was subjected to inflation molding to obtain a film having a thickness of 50 μm, and the mechanical properties were measured. The results are shown in Table 2.

<Manufacture of laminate base material>
A base paper of 300 g / m @ 2 (water content 7.9%) was used. In this base paper, the composition ratio and thickness of the sheet shown in Table 3 were used, and the extruder used was a tandem specification capable of foam layer coating and inner surface layer coating. The biodegradable foam layer was coated with a single layer T die using a twin screw extruder with a screw diameter of 65 mm and a screw length of 3400 mm. On the opposite layer side, aluminum vapor-deposited cellophane and PLA laminate were bonded by single-layer T-die coating using a twin screw extruder with a screw diameter of 50 mm and a screw length of 2650 mm. Both machines were melt-kneaded at an extruder cylinder temperature of 240 ° C., and then used a 1500 mm wide die, and the die pressure was controlled at a constant temperature with a gear pump at a die temperature of 230 ° C., and the coating was adjusted. The thickness flare in the TD direction was controlled by a heat bolt method and adjusted so as to be within ± 8% of the center thickness.
Aluminum vapor-deposited cellophane and PLA laminate are obtained by dry-lamination with a 30-μm PLA inflation film on a double-sided polyvinylidene chloride coating on cellophane 23 μm and single-sided aluminum vapor deposition on one side.

  Cooling was performed using an air knife method and cast on a 35 ° C. cooling roll to form a sheet while rapidly solidifying. The take-up speed was 60 m / min, and the take-up sheet total thickness was adjusted to 0.45 mm.

[Manufacture of molded products]
A blank for a container trunk member and a blank for a container bottom plate member were punched out from the laminated base paper. This blank was assembled into a container with a conventional cup molding machine. The container had a paper opening inner diameter of 96 mm, a bottom inner diameter of 68 mm, and a height of 107 mm. The thickness of the paper container body (total thickness of paper and laminate film) was 0.41 mm. The paper container was placed in a conveyor oven and heated at 120 ° C. for 360 seconds. A paper container having a foam heat insulating layer only on the outer peripheral surface of the container body was obtained. The evaluation results of each of the examples and comparative examples are shown in FIG.

As described above, according to the present invention, as proved in the above experimental example, a biodegradable resin and a paper laminate containing a certain amount of water are molded and heat-treated to thereby produce the biodegradable resin. Is softened, the attractive force between the paper and the biodegradable resin is weakened, and the moisture in the paper is volatilized, so that it is lifted from the biodegradable resin layer by pressure, and a heat insulating layer (or air pocket) is generated between them. When it is cooled, the biodegradable resin, which is a thermoplastic resin, is solidified and the voids are maintained. Therefore, the overall thickness is increased, and excellent heat insulation is obtained.
As a result, it was possible to obtain the same foamed state by bringing the elastic modulus and elongation close to those of low-density polyethylene by the synthesis method and blending of the biodegradable resin.
The present invention is not only capable of inexpensively manufacturing a paper container having excellent heat insulation properties by laminating a biodegradable resin on the entire surface where a user grips a cup and foaming with heated water vapor from paper field moisture. Since the container of the present invention is mostly paper, it can save petroleum resources and can be buried in the ground in terms of waste.

Claims (4)

A base material layer mainly composed of paper;
An outermost layer made of a resin composition containing an aliphatic aromatic copolymer polyester resin that is located on one side of the base material layer and foams by heating,
An innermost layer made of a resin composition that is laminated on the other surface of the base material layer and contains a biodegradable resin;
A package for food containers, comprising a laminate comprising:   The food device packaging body according to claim 1, further comprising a waterproof barrier layer between the base material layer and the innermost layer.   The package for food containers according to claim 1 or 2, wherein the resin composition used for the outermost layer is a graft copolymer made of polybutylene adipate terephthalate or a blend thereof. A base material layer mainly composed of paper;
A foam layer comprising a resin composition containing an aliphatic aromatic copolymer polyester resin that foams by heating on at least one surface of the base material layer;
A package for food containers, comprising a laminate comprising: