JP2021037619A - Polyester resin laminated sheet and polyester resin container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester-based resin laminated sheet and a polyester-based resin container having excellent water resistance, oxygen barrier property, and transparency. SOLUTION: In the polyester resin laminated sheet of the present invention, a polyester base sheet layer, an anchoring agent layer, a barrier layer and a waterproof protective layer are laminated in this order on at least one surface of the polyester base sheet layer. It is a laminated sheet, and the waterproof protective layer is a layer formed by a top agent in which a main agent containing a polyol and a curing agent containing a polyisocyanate are mixed. The polyester-based resin container of the present invention is a container formed by thermoforming the polyester-based resin laminated sheet of the present invention. [Selection diagram] None

Description

The present invention relates to a polyester resin laminated sheet and a polyester resin container having excellent water resistance, oxygen barrier properties, and transparency.

Polyester resins typified by polyethylene terephthalate (hereinafter referred to as "PET") are excellent in chemical and physical properties. Further, polyester resin is widely used for packaging containers such as beverage bottles, films, sheets and the like because it has excellent mechanical strength and transparency.

In packaging containers, especially food and beverage packaging containers, the contents to be stored (beverages, foods, etc.) are not adversely affected by gases such as oxygen or water vapor in the air, or are stored for a long period of time. Gas barrier properties may be required to prevent the loss of water. As a laminated film having a gas barrier property, Patent Document 1 discloses a laminated film for packaging in which an anchor coating agent whose main agent is a water-dispersible polyester urethane resin and a gas barrier resin are laminated on a base film. .. Further, high barrier PET (HB-PET) is also known, in which the gas barrier property is enhanced by laminating an ethylene-vinyl alcohol copolymer (EVAL) and a non-stretched polypropylene film (CPP).

In recent years, the consumption of polyester resin has been increasing. Therefore, the reuse of polyester resin is being promoted from the viewpoint of cost reduction and reduction of environmental load. However, since HB-PET gels by thermal decomposition when extruded under the same conditions as PET, it cannot be crushed and recycled like ordinary PET, and must be disposed of.

In order to solve such a recycling problem, a gas barrier film that does not use a barrier film made of a different material has been developed. As such a gas barrier film, for example, gas barrier PET whose layer structure is a waterproof protective layer / barrier layer / anchor coating agent layer / polyester film base material is known (see, for example, Patent Document 2).

Japanese Patent No. 4281294 JP-A-2019-48409

In the generally known gas barrier PET of waterproof protective layer / barrier layer / anchor coating agent layer / polyester film base material, when water droplets adhere to the waterproof protective layer due to dew condensation or the like, the moisture thereof. It was found that the film penetrates into the barrier layer and the adhesive layer, causing a problem that the barrier layer and the adhesive layer are peeled off from the film substrate. The polyester-based resin molded product described in Patent Document 2 has practical water resistance, but further improvement in water resistance is required for use as a packaging container, particularly a packaging container for food and drink. Has been done.

An object of the present invention is to provide a polyester resin laminated sheet and a polyester resin container having excellent water resistance, oxygen barrier properties, and transparency.

The polyester-based resin laminated sheet of the present invention is a laminated sheet in which a polyester-based base sheet layer and an anchoring agent layer, a barrier layer, and a waterproof protective layer are laminated in this order on at least one surface of the polyester-based base sheet layer. The waterproof protective layer is characterized by being a layer formed by a top agent in which a main agent containing a polyol and a curing agent containing a polyisocyanate are mixed.

The polyester-based resin container of the present invention is characterized by being a container formed by thermoforming the laminated sheet of the present invention.

The polyester-based resin laminated sheet and the polyester-based resin container of the present invention have excellent gas barrier properties and transparency, and have further improved water resistance. Therefore, the laminated sheet of the present invention can be suitably used for applications that require water resistance in addition to transparency, for example, packaging containers for foods and drinks.

Embodiments of the present invention will be described below. The present embodiment is an example of carrying out the present invention, and the present invention is not limited to the present embodiment.

(1) Polyester-based resin laminated sheet The polyester-based resin laminated sheet according to the present embodiment (hereinafter, referred to as "the present laminated sheet") is formed on at least one surface of the polyester-based base sheet layer and the polyester-based base sheet layer. A laminated sheet in which an anchoring agent layer, a barrier layer, and a waterproof protective layer are laminated in this order, and the waterproof protective layer is a mixture of a main agent containing a polyol and a curing agent containing a polyisocyanate. It is characterized by being a layer formed by a top agent. By having the waterproof protective layer, the laminated sheet has improved water resistance and can suppress peeling of the barrier layer and / or the anchoring agent layer due to moisture adhering to the sheet.

The type of the polyol is not particularly limited as long as it has two or more hydroxyl groups and can react with the polyisocyanate contained in the curing agent to form a waterproof protective layer. The polyol may be used alone or in combination of two or more. Generally, alkylene glycol can be used as the polyol. The alkylene glycol may be linear or branched. The alkylene glycol usually has 2 to 10 carbon atoms. Specific examples of the alkylene glycol include ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, neopentyl glycol, heptanediol, and octanediol. Can be mentioned.

The type of the polyisocyanate is not particularly limited as long as it has two or more isocyanate groups and can form a waterproof protective layer. As the polyisocyanate, diisocyanate is usually used. Specific examples of the polyisocyanate include aliphatic (hexamethylene diisocyanate and the like), alicyclic (cyclohexane diisocyanate and the like), and aromatic isocyanate (diphenylmethane diisocyanate and the like). The polyisocyanate may be used alone or in combination of two or more.

The blending ratio (mass basis) of the polyol and the polyisocyanate can be appropriately set as needed. The blending ratio is usually 1: 0.1 or more, preferably 1: 0.2 or more. When the compounding ratio is 1: 0.2 or more, the water resistance can be further improved, which is preferable. The upper limit of the polyisocyanate in the compounding ratio is not particularly limited as long as the waterproof protective layer can be formed. The upper limit of the blending ratio can be, for example, 1: 0.6, 1: 0.5, or 1: 0.4.

The form of the top agent is not particularly limited. The top agent is usually prepared by dissolving the main agent and the curing agent in a solvent. The type of the solvent is not particularly limited as long as it can dissolve the main agent and the curing agent. Specific examples of the solvent include esters (ethyl acetate and the like) and ketones (methyl ethyl ketone and the like). The solvent may be only one kind or a mixed solvent of two or more kinds. Further, as long as the waterproof protective layer can be formed, the top agent may contain other components other than the main agent and the curing agent.

The waterproof protective layer can usually be formed by applying the top agent to the surface of the barrier layer and then drying it. The coating and drying methods and conditions are not particularly limited, and known methods can be used. Specific examples of the coating method include a normal wet coating method such as gravure coating. Specific examples of the drying method include hot air drying and infrared irradiation.

The polyester resin constituting the polyester-based base sheet (hereinafter, simply referred to as “base sheet”) layer is a polycondensate of a polyvalent carboxylic acid or a derivative thereof (ester, anhydride, etc.) and a polyalcohol. As long as, there is no limitation on the specific structure and type. A dicarboxylic acid is usually used as the polyvalent carboxylic acid, and a diol is usually used as the polyalcohol. As the polyvalent carboxylic acid, for example, an aromatic polyvalent carboxylic acid can be used. The polyester resin may be a polycondensate of the polyvalent carboxylic acid or a derivative thereof and the polyalcohol, and may be copolymerized with another monomer, for example, a monomer having a vinyl group such as styrene. It may be a polymer. Further, the polyester resin may be a polyester resin modified with another resin (for example, an epoxy resin).

Specifically, as the polyester resin, for example, polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene-1,2-bis (phenoxy) ethane-4,4'-. Examples thereof include dicarboxylate and polycyclohexylene methylene terephthalate. The polyester resin is preferably PET.

The polyester resin may be in either a crystalline state or an amorphous state. The polyester resin is preferably an amorphous polyester resin, and more preferably an amorphous PET. The "amorphous PET" includes a non-crystallized PET such as A-PET and a completely non-crystallized PET such as PET-G. The "amorphous PET" is preferably a non-crystallized PET such as A-PET.

The anchoring agent (hereinafter referred to as “AC agent”) layer is a layer formed on at least one surface of the base material sheet layer by the AC agent and adheres the base material sheet layer and the barrier layer. The type of the AC agent is not particularly limited as long as the base sheet layer and the barrier layer can be adhered to each other. It is preferable to use a water-soluble polyester-based AC agent as the AC agent because whitening (decrease in transparency) after container molding can be suppressed.

The specific configuration of the water-soluble polyester-based AC agent is not particularly limited as long as the polyester resin is dissolved or dispersed in the water-based medium and the base material sheet layer and the barrier layer can be adhered to each other. Absent. As described above, the water-soluble polyester-based AC agent includes not only the case where the polyester resin is dissolved in the water-based medium but also the case where the polyester resin is dispersed in the water-based medium as an emulsion or the like. The aqueous medium is water or a mixed medium of water and alcohol (eg, C1-C4 alcohol).

The polyester resin contained in the water-soluble polyester-based AC agent may be a saturated polyester resin or an unsaturated polyester resin. As the polyester resin, a polyester resin having a hydroxyl group or a carboxyl group at the molecular terminal is preferable. Specific examples of the polyester resin include polyacrylic acid esters and ethylene-acrylic acid ester copolymers. Examples of commercially available products of the water-soluble polyester-based anchoring agent include "GX-1143" manufactured by GOO CHEMICAL CO., LTD.

When forming the AC agent layer, the water-soluble polyester-based AC agent may be used alone or in combination of two or more. Further, only the water-soluble polyester-based AC agent may be used, or other anchoring agents may be used in combination as long as the effects of the present invention are not impaired.

The AC agent layer can usually be formed by applying an AC agent to the surface of the base material sheet layer and then drying it. The coating and drying methods and conditions are not particularly limited, and known methods can be used. Specific examples of the coating method include a normal wet coating method such as gravure coating. Specific examples of the drying method include hot air drying and infrared irradiation.

The barrier layer is laminated on the outside of the AC agent layer (the surface of the surface of the AC agent layer on the side not in contact with the base sheet layer), and as long as it has a gas barrier property, its specific configuration is defined. There is no particular limitation. Specific examples of the material constituting the barrier layer include resins, metal oxides (aluminum oxide, silicon oxide, magnesium oxide, etc.) or inorganic compounds (nitrides such as aluminum nitride and silicon nitride, carbides such as silicon carbide). ) Thin film. The barrier layer is preferably a barrier layer formed of a resin. The type of the resin is not particularly limited. Specific examples of the resin include polyvinylidene chloride resin, polyvinyl alcohol resin, and ethylene vinyl alcohol copolymer.

The barrier layer may contain other components. When the barrier layer is a barrier layer formed of a resin, specific examples of the other components include layered inorganic compounds. Specific examples of the layered inorganic compound include layered minerals and layered silicates. By containing the layered inorganic compound, the gas barrier property can be improved, which is preferable. Specifically, the layered silicates include, for example, hydrous silicates (phyllosilicate minerals, etc.), kaolinite group clay minerals (haloisite, kaolinite, enderite, dikite, nacrite, etc.), antigolite group clay minerals. (Antigolite, chrysotile, etc.), smectite clay minerals (montmorillonite, biderite, nontronite, saponite, hectrite, soconite, stibunsite, etc.), vermiculite clay minerals (vermiculite, etc.), mica or mica clay minerals (white clouds) Mother, mica such as gold mica, margarite, tetrasilic mica, teniolite, etc.) can be mentioned. These may be natural minerals or synthetics. The layered inorganic compound may be used alone or in combination of two or more. The layered inorganic compound is preferably a layered silicate, more preferably montmorillonite.

The method for forming the barrier layer is not particularly limited. The barrier layer can be appropriately formed by a known method depending on the type of material constituting the barrier layer. When the barrier layer is a barrier layer formed of a resin, a resin solution or a dispersion (if necessary, the layered inorganic compound may be contained in the medium) is applied to the surface of the AC agent layer. It can then be formed by drying. The coating and drying methods and conditions are not particularly limited, and known methods can be used. Specific examples of the coating method include a normal wet coating method such as gravure coating. Specific examples of the drying method include hot air drying and infrared irradiation.

The barrier layer may have a single-layer structure or a multi-layer structure, for example, a two-layer, three-layer, or four-layer structure. The barrier layer having a multi-layer structure can be formed, for example, by repeatedly applying and drying the resin solution or dispersion. When the barrier layer has a multi-layer structure, the structure of each layer may be the same or different. For example, all the layers constituting the barrier layer may contain the layered inorganic compound, or only a part of the layers may contain the layered inorganic compound.

The method for producing the laminated sheet is not particularly limited. In this laminated sheet, the AC agent layer is usually formed by applying and drying an AC agent on the surface of the polyester resin constituting the base material sheet layer, and then a barrier agent is applied to the outside of the AC agent layer and It can be produced by forming the barrier layer by drying, and then forming the waterproof protective layer by applying a top agent to the outside of the barrier layer and drying.

The thickness of the laminated sheet and each layer constituting the laminated sheet is not particularly limited. The thickness of these layers can be appropriately determined as needed. For example, the thickness of the waterproof protective layer can be 0.5 μm or more. It is preferable to use the two-component mixed type top agent because the thickness of the waterproof protective layer can be made thicker than that of the one-component type acrylic resin.

Each layer constituting the laminated sheet may contain other components, if necessary, as long as the water resistance, oxygen barrier property, and transparency are not significantly impaired. For example, the base material sheet layer may contain a resin other than the polyester resin. Specifically, as the other components, for example, additives used in known resin sheets, such as flame retardants, ultraviolet absorbers, fluorescent whitening agents, antistatic agents, antifogging agents, lubricants, and antiblocking agents. Agents, fluidity improvers, plasticizers, dispersants, and antibacterial agents.

The polyester-based resin container (hereinafter, referred to as “the present container”) according to the present embodiment is obtained by thermoforming the present laminated sheet. This molding method is not particularly limited. As the molding method, a known molding method generally adopted for polyester resin, specifically, for example, a vacuum molding method (plug assist molding method, etc.), an injection molding method, an ultra-high speed injection molding method, an injection compression molding method. , Two-color molding method, hollow molding method such as gas assist, molding method using heat insulating mold, molding method using rapid heating mold, foam molding (including supercritical fluid), insert molding, IMC (in-molding) (Coating molding) molding method, extrusion molding method, sheet molding method, thermal molding method, rotary molding method, laminated molding method, press molding method, blow molding method can be mentioned. Further, the molding conditions are not particularly limited. Molding conditions can be appropriately determined as needed.

There are no particular restrictions on the shape, dimensions, and specific uses of this container. Examples of the use of this container include containers such as packaging containers, for example, food and beverage packaging containers. The "container" includes not only the entire container but also a part of the container. For example, the "container" includes not only the main body of the container but also the lid of the container.

Hereinafter, the present invention will be specifically described with reference to Examples. The present invention is not limited to the embodiments shown in the examples. The embodiments of the present invention can be variously modified within the scope of the present invention according to the purpose, use and the like.

1. 1. Manufacture of Laminated Sheets and Containers <Examples 1 to 3>
The following components were used as raw materials. The IV value (dl / g) of the following "(A) A-PET" was measured according to JIS K 7376-5. As a solvent, a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (weight ratio 3/1) was used.
(A) A-PET (base material); PET resin "YS-H01" manufactured by Hainan Isemori Petrochemical Co., Ltd. (IV value = 0.78 dl / g, thickness 0.85 mm)
(B) AC agent; "GX-1143" manufactured by Reciprocal Chemical Co., Ltd. (ingredient: water-soluble polyester). At the time of use, the AC agent was diluted with a diluent (isopropyl alcohol: water = 1: 2 on a mass basis).
(C) Barrier agent; "EXCEIER" manufactured by Sumitomo Chemical Co., Ltd. (containing montmorillonite)
(D) Top agent (waterproof protective layer); "FC4208"(component; polyol) as the main agent, "LG curing agent D"(component; isocyanate) as the curing agent, "PU-TS515" (component: ethyl acetate) as the solvent , Methyl ethyl ketone. Solid content concentration; 16 wt%) was used (both manufactured by Tokyo Ink Co., Ltd.). The main agent and the curing agent were dissolved in the solvent to prepare a top agent.

The A-PET is subjected to a corona discharge treatment, and then the AC agent, the barrier agent, and the top agent are applied in this order on the corona discharge treated surface of the A-PET using a gravure plate (6-zone printing machine). By drying (coating the barrier agent 4 times. Gravure plate used: 20 μm, 200 lines. Line speed: 30 m / min. Drying temperature: 80 ° C.), it has an AC agent layer, a barrier layer, and a waterproof protective layer. A laminated sheet was manufactured (see Table 1). Table 2 shows the ratios of the main agent, the curing agent, and the solvent (based on mass) of Examples 1 to 3 and the film thickness (measured value) of the waterproof protective layer.

A container (container size; diameter 101 mm, height 250 mm) was manufactured by thermoforming the laminated sheet obtained by the above method by a vacuum compressed air molding method. Specifically, by using a convex resin mold called a plug together and pressing a part of the resin sheet softened by heating with the plug, the resin sheet is given the inner shape of the container corresponding to the outer shape of the plug. After that, the bottom and side surfaces of the container are formed by evacuating the cavity mold. The upper heater temperature in vacuum compressed air molding is 375 ° C., and the lower heater temperature is 395 ° C.

<Comparative example 1>
Instead of the top agent of the example, "Stipuri" manufactured by Osaka Printing Ink Co., Ltd. was used, and "Stipuri" was diluted with a diluent (styrol) at the time of use ("Stipuri": diluent = 1: 1 on a mass basis). Laminated sheets and containers were produced by the same methods as in Examples 1 to 3 except for the above. Table 2 shows the film thickness (estimated value) of the waterproof protective layer of Comparative Example 1.

<Comparative example 2>
A container was manufactured by the same method as in the example using the above-mentioned A-PET instead of the laminated sheet of the example.

<Comparative example 3>
HB-PET obtained by dry-laminating an A-PET sheet (thickness 0.85 mm) and an EVAL film "EF-E" (manufactured by Kuraray Co., Ltd., thickness 30 μm) instead of the laminated sheet of the example. Was used to produce a container in the same manner as in the examples.

2. Performance evaluation (I) Water resistance evaluation <Test 1; Water droplet water resistance test>
Pure water was dropped on the surface of the waterproof protective layer of the laminated sheets of Examples 1 to 3 and Comparative Example 1 with a dropper. After allowing to stand for 6 hours, the dropping portion was rubbed with a cotton swab, and the presence or absence of peeling of the barrier agent layer was visually confirmed.

<Test 2; Condensation water resistance test>
The containers of Examples 1 to 3 and Comparative Example 1 were allowed to stand in a refrigerator (4 ° C.) for 19 hours. Next, the container was allowed to stand in a humid environment (22 ° C., humidity 60% or more) for 5 hours to cause dew condensation. Then, the dew-condensed container was rubbed by hand, and the presence or absence of peeling of the barrier agent layer was visually confirmed. These steps were repeated for 2 months.

The results of tests 1 and 2 are shown in Table 3. The evaluation criteria in Table 3 are as follows.
"X"; The barrier agent layer was peeled off.
“Δ”; The barrier agent layer was partially peeled off.
"○"; The barrier agent layer was not peeled off at all.

From Table 3, in Comparative Example 1 (waterproof protective layer of acrylic resin), the barrier agent layer was peeled off in both Tests 1 and 2. On the other hand, in Example 1, it can be seen that the peeling of the barrier agent layer remains partially and the water resistance is superior to that of Comparative Example 1. Further, it can be seen that in Examples 2 and 3 in which the ratio of the curing agent (isocyanate) to the main agent (polyol) is high, the barrier agent layer does not peel off and the water resistance is further excellent as compared with Example 1.

(II) Oxygen permeability For the containers of Example 2 and Comparative Examples 2 and 3, the oxygen permeability was measured under the following conditions according to JIS K7126. The results are shown in Table 4.
Measuring instrument; Dansensor "CheckMate 3"
Test environment; 23 ° C
Filling gas; N ₂ 100%

(III) Miso browning test The containers of Example 2 and Comparative Examples 2 and 3 were filled with miso and stored under the temperature and humidity environment shown in the following conditions 1 or 2. The color of miso on the 7th, 14th, and 70th days after storage was measured with a color difference meter (“NR-11” manufactured by Nippon Denshoku Kogyo Co., Ltd.). The results are shown in Table 5. The values in Table 5 represent L values (white: L = 100, black: L = 0). The "difference" represents the difference between the initial reference value and the value on the 70th day.

From Table 4, in the examples, the average oxygen concentration is lower than that of A-PET and known HB-PET, and it is difficult for oxygen to pass through. The discoloration of miso is mainly due to oxygen and temperature. From Table 5, the discoloration of the examples is different from that of A-PET and known HB-PET under both condition 1 and condition 2 (high humidity condition). The degree of is low. These results indicate that the examples have excellent gas barrier properties as compared with A-PET and known HB-PET, and can suppress browning of miso in a normal temperature and high humidity environment.

(IV) Haze value The haze value of the sheets and containers of Example 2 and Comparative Examples 2 and 3 was measured according to JIS K 7136. The results are shown in Table 6.

From Table 6, both the sheet and the container of the example have a lower haze value and excellent transparency as compared with the known HB-PET.

Claims (4)

A laminated sheet in which a polyester-based base sheet layer and an anchoring agent layer, a barrier layer, and a waterproof protective layer are laminated in this order on at least one surface of the polyester-based base sheet layer.
A polyester-based resin laminated sheet, wherein the waterproof protective layer is a layer formed by a top agent in which a main agent containing a polyol and a curing agent containing a polyisocyanate are mixed. The polyester-based resin laminated sheet according to claim 1, wherein the barrier layer is a layer formed of a barrier agent containing a layered silicate. The polyester-based resin laminated sheet according to claim 1 or 2, wherein the blending ratio (mass standard) of the polyol and the polyisocyanate is 1: 0.2 or more. A polyester-based resin container, which is a container formed by thermoforming the laminated sheet according to any one of claims 1 to 3.