WO2017090482A1 - Lid - Google Patents

Abstract

This lid has at least a substrate layer, an anchor coat layer, a stress relaxation layer, and a hot-melt adhesive layer, and has a structure obtained by layering said layers in this order. The hot-melt adhesive that constitutes the hot-melt adhesive layer contains 20-50 mass% of an ethylene-vinyl acetate copolymer as a component (A), and relative to 100 parts by mass of the ethylene-vinyl acetate copolymer constituting the component (A), also contains 8-80 parts by mass of an adhesiveness-imparting agent as a component (B), 85-230 parts by mass of a wax as a component (C), and 15-200 parts by mass of talc as a component (D).

Description

Lid material

The present invention is a hot plate heating of an opening of a plastic container containing liquid or liquid foods such as yogurt, lactic acid bacteria beverages, fruit beverages, powdered foods such as wheat flour, solid foods such as ham and cheese, various pharmaceuticals, etc. Or it is related with the lid | cover material for adhere | attaching and sealing by high frequency induction heating.

Generally, the opening of the container main body for storing food or the like is sealed with a cover material having thermal adhesiveness. In recent years, from the viewpoint of ensuring the safety of food, etc., such lid materials require that the amount of substances eluted in organic solvents (relative to organic solvents) is small when the lid material is immersed in an organic solvent. Has been. As a cover material that meets these requirements, a base layer such as aluminum foil, an anchor coat layer such as urethane resin, a stress relaxation layer such as polyethylene film, and a hot-melt adhesive layer based on ethylene-vinyl acetate resin. A cover material having a laminated structure has been proposed (Patent Document 1).

In this lid material, it has been proposed to select a material that has a relatively small amount of substance that elutes in an organic solvent as a constituent material of the hot melt adhesive layer that is in direct contact with the contents contained in the container body. Specifically, an ethylene-vinyl acetate copolymer having a vinyl acetate content of 24 to 35% by weight and a melt index of 30 to 400 g / 10 minutes, 25 to 55% by weight, a molecular weight of 700 to 3,500, and a melting point of 95 to A hot melt adhesive containing 30 to 65% by weight of polyethylene wax at 125 ° C. and 10 to 30% by weight of a polymeric tackifier having a molecular weight of 700 to 1,400 and a softening point of 100 to 125 ° C. A melt adhesive layer is formed.

Japanese Patent Laid-Open No. 10-156995

By the way, although the elution amount of the substance which elutes to the edible fat and ethanol of the lid | cover material proposed by patent document 1 is very small and does not become a problem at all by normal use, it is edible fat and oil with respect to hexane. In some cases, the amount of substance elution (relative to hexane) may increase compared to ethanol and ethanol. For this reason, it is conceivable to reduce the amount of elution with respect to hexane by changing each constituent material of the hot melt adhesive to a higher molecular weight material and relatively reducing the content of low molecular weight impurities.

However, if a material having a higher molecular weight is used as the material constituting the hot melt adhesive, the sealing property of the hot melt adhesive layer of the lid material is lowered, so there is a concern that the sealing strength may be lowered under the same sealing conditions as before. . In order to avoid this, it is conceivable to tighten the sealing conditions. However, it has been very difficult to find the optimum sealing conditions.

The object of the present invention is to solve the above-mentioned problems of the prior art, and for a cover material in which a base material layer / anchor coat layer / stress relaxation layer / hot melt adhesive layer are laminated in this order, Even when the amount of elution with respect to an organic solvent is suppressed by changing the material constituting the hot melt adhesive layer to a higher molecular weight material, a good seal can be realized under the same sealing conditions as before. For the purpose.

The inventors of the present invention used an ethylene-vinyl acetate copolymer as the hot melt adhesive layer of a cover material in which a base material layer / anchor coat layer / stress relaxation layer / hot melt adhesive layer are laminated in this order. When formed from a hot melt adhesive in which a specific amount of talc is blended with a mixture of tackifier and wax in a specific range amount, the hot melt adhesive is used to reduce the amount of elution of the lid to the organic solvent. Even when a higher molecular weight material is selected as the constituent material, it has been found that the sealing performance can be prevented from being lowered, and the present invention has been completed.

That is, the present invention has at least a base material layer, an anchor coat layer, a stress relaxation layer, and a hot melt adhesive layer, which are laminated in this order, and constitutes a hot melt adhesive layer The hot-melt adhesive contains 20 to 50% by mass of an ethylene-vinyl acetate copolymer as component (A), and further contains the following components (B) to (D) with respect to 100 parts by mass of component (A): The lid | cover material contained in the mass part of is provided.

(A) 100 parts by mass of an ethylene-vinyl acetate copolymer;
(B) Tackifier 8-80 parts by mass;
(C) Wax 85-230 parts by mass; and (D) Talc 15-200 parts by mass.

The present invention also includes a food container having an opening in which a flange is formed, a liquid or solid food contained therein, and a lid material bonded to the flange formed in the opening of the food container. The container is a food in a container, wherein the lid is the above-mentioned lid, and the lid is bonded to the flange portion of the opening from the hot melt adhesive layer side Provide food containing.

In the lid material of the present invention in which the base material layer, the anchor coat layer, the stress relaxation layer, and the hot melt adhesive layer are laminated in this order, the hot melt adhesive is considered in consideration of the sealing property and the elution amount with respect to the organic solvent. As a hot melt adhesive for forming a layer, a hot melt adhesive in which a specific amount of talc is mixed with a mixture of ethylene-vinyl acetate copolymer, tackifier and wax in a specific range is used. is doing. For this reason, even when a higher molecular weight material is selected as the material constituting the hot melt adhesive in order to reduce the elution amount of the lid material with respect to the organic solvent, the sealing performance can be prevented from being lowered.

FIG. 1 is a schematic cross-sectional view of the lid member of the present invention. FIG. 2 is a characteristic diagram of seal strength by hot plate heating when attention is paid to the type of filler. FIG. 3 is a seal strength characteristic diagram by high-frequency induction heating when attention is paid to the type of filler. FIG. 4 is a characteristic diagram of seal strength by hot plate heating when attention is focused on the blending amount of talc. FIG. 5 is a characteristic diagram of seal strength by high-frequency induction heating when attention is paid to the blending amount of talc. FIG. 6 is a characteristic diagram of seal strength by hot plate heating when focusing on the average particle diameter of talc. FIG. 7 is a characteristic diagram of seal strength by high-frequency induction heating when attention is paid to the average particle diameter of talc.

Hereinafter, the lid of the present invention will be described with reference to the drawings.

<Cover material>
As shown in FIG. 1, the lid member 10 of the present invention has a structure in which a base material layer 1, an anchor coat layer 2, a stress relaxation layer 3, and a hot melt adhesive layer 4 are laminated in this order. The lid member 10 is a material for sealing the opening of the container body with a seal. Examples of the material constituting the container body include plastics such as polystyrene, polypropylene, polyethylene, polyvinyl chloride, polycarbonate, and polyacrylonitrile, composite laminates lined with these plastics, metals, polyethylene laminated paper, and glass. .

"Base material layer 1"
The base material layer 1 is a main layer that imparts initial mechanical strength to the lid material, and can have the same configuration as the base material layer of the conventional lid material. For example, thin films of metals or alloys such as iron, stainless steel, copper, aluminum and gold, thin films of ceramics such as silicon nitride, resin films such as polyethylene terephthalate, polyurethane, polystyrene, polyamide, polyimide, papermaking paper, and laminating them The composite material can be selected according to the purpose of use. In particular, in order to impart high frequency induction heating characteristics to the lid member 10, it is preferable to use a metal thin film that generates heat due to induction of eddy currents in itself when a high frequency is applied as the base material layer 1. Among these, aluminum foil can be preferably mentioned from the viewpoints of formability, high-frequency heating suitability, and economical efficiency.

The thickness of the base material layer 1 is usually 5 to 300 μm in consideration of mechanical strength and the material to be used. For example, when using a metal thin film such as an aluminum foil, the high frequency induction heating characteristics are taken into consideration. The thickness is preferably 5 to 50 μm, more preferably 20 to 40 μm.

The base material layer 1 can be formed by a known method according to the type and thickness of the material. In the case of a metal or alloy thin film, it can be formed using a cold rolling method, a vacuum deposition method, an electroless plating method, an electrolytic plating method, or the like. In the case of a resin thin film, it can be formed using a melt extrusion molding method, a solution casting method, a calendar method, or the like. The resin thin film may be stretched.

In addition, as the conditions for the high-frequency induction heating, the conditions of 140 W and 1.4 seconds can be exemplified, but can be appropriately changed depending on the layer configuration and the material used.

"Anchor coat layer 2"
The anchor coat layer 2 is a layer that causes the base material layer 1 and the stress relaxation layer 3 to adhere to each other, and can be selected according to their materials.

As the anchor coat layer 2, a layer formed from a modified polyolefin anchor coat agent modified with chlorine or acid, a polyester anchor coat agent, or a polyurethane anchor coat agent can be applied. The anchor coat layer 2 may contain additives such as various fillers as long as the adhesion between the base material layer 1 and the stress relaxation layer 3 is not impaired.

Such a layer thickness of the anchor coat layer 2 causes a decrease in seal strength if the layer thickness is too thin, and if it is too thick, the seal strength tends to decrease due to cohesive failure inside the anchor coat layer 2. The thickness is preferably 0.1 to 6.0 μm, more preferably 0.2 to 4.5 μm.

The anchor coat layer 2 can be formed using a solution coating method.

"Stress relaxation layer 3"
The stress relaxation layer 3 reinforces the mechanical strength of the lid material, relieves stress during high-frequency heating, suppresses excessive heat from being applied to the hot melt adhesive layer 4, and It also functions as a layer for firmly bonding the agent layer 4 to the back surface of the lid. As such a stress relaxation layer 3, a resin layer formed from a polyolefin-based thermoplastic resin such as polyethylene or polypropylene, or a resin layer formed from a polyester-based thermoplastic resin such as polyethylene terephthalate can be applied. Considering the stability of the high frequency seal strength and the like, a polyethylene layer, particularly an unstretched polyethylene layer can be preferably applied.

The layer thickness of the stress relaxation layer 3 is preferably 6 to 60 μm, more preferably 9 to 50 μm. Within this range, sufficient stress relaxation and thermal relaxation can be realized, and a sufficient amount of heat can be conducted from the base material layer 1 to the hot melt adhesive layer 4.

When the stress relaxation layer 3 is a polyethylene layer, the layer thickness is preferably 10 to 50 μm, more preferably 15 to 40 μm, considering high frequency sealing characteristics and moldability.

As a method of providing the stress relaxation layer 3 on the anchor coat layer 2, a known method can be employed. For example, the material constituting the stress relaxation layer 3 may be directly melt-extruded laminated to the anchor coat layer 2, or a film made of the material constituting the stress relaxation layer 3 may be dry laminated.

"Hot melt adhesive layer 4"
The hot melt adhesive layer 4 is a layer that adheres to the opening of the container body by the heat conducted from the base material layer 1 and is a layer that contacts the contents contained in the container body.

The adhesion amount of the hot melt adhesive layer 4 is preferably 3 to 40 g / m ² , more preferably 5 to 30 g / m ² . Within this range, sufficient high frequency sealing characteristics (especially seal strength) can be obtained by high frequency heating, the lid material can be peeled off stably, and the amount of elution with organic solvents can be further reduced.

The hot melt adhesive layer 4 can be formed by a known method such as a gravure coating method.

Since the hot melt adhesive layer 4 is a layer that comes into contact with the contents contained in the container body, the hot melt adhesive layer 4 is made of an adhesive material that can be adhered to the container body to be applied and that does not easily dissolve into the contents. Is required. In the present invention, it is formed from a hot melt adhesive containing the following components (A) to (D).

(A) Ethylene-vinyl acetate copolymer (B) Tackifier (C) Wax (D) Talc

<Component (A)>
The component (A) ethylene-vinyl acetate copolymer functions as a main component of the hot-melt adhesive, and the reason for using it is that it can be easily adhered to metal, resin, glass, etc. This is because they are easily compatible with wax and the like.

The content of the component (A) ethylene-vinyl acetate copolymer in the hot melt adhesive is 20 to 50% by mass, preferably 25 to 45% by mass. If it is this range, heat seal intensity | strength will not be reduced and the amount of organic solvent elution can be suppressed.

In the present invention, it is preferable to use an ethylene-vinyl acetate copolymer having the following characteristics (a1) to (a3).

(Characteristic (a1): Vinyl acetate content)
The vinyl acetate content of the ethylene-vinyl acetate copolymer is preferably 14 to 41% by mass, more preferably 19 to 33% by mass. If it is this range, a sealing strength will not be reduced and the amount of elution with respect to an organic solvent can be suppressed. The vinyl acetate content can be measured according to JIS K6924-2.

(Characteristic (a2): MFR value)
The MFR value (JIS K7210) of the ethylene-vinyl acetate copolymer is preferably 5 to 400 g / 10 minutes, more preferably 5 to 150 g / 10 minutes. If it is this range, the applicability | paintability of a hot-melt-adhesive agent will not be impaired, and the amount of organic solvent elution can be suppressed. The MFR value can be measured according to JIS K7210.

(Characteristic (a3): Vicat softening point)
The Vicat softening point of the ethylene-vinyl acetate copolymer is preferably 25 to 75 ° C, more preferably 30 to 65 ° C. If it is this range, the elution amount with respect to an organic solvent can be suppressed, and the fall of seal strength can be suppressed. The Vicat softening point can be measured according to JIS K7206.

Specific examples of the ethylene-vinyl acetate copolymer having the characteristics (a1) to (a3) described above include “Evaflex (registered trademark) EV420 and EV220” manufactured by Mitsui DuPont Polychemical Co., Ltd. “Ultrasen (registered trademark) 750” manufactured by Kogyo Co., Ltd. can be preferably mentioned. For example, the characteristics (a1) to (a3) of “Evaflex EV420” are as follows.

Characteristic (a1): Vinyl acetate content 19% by mass
Characteristic (a2): MFR value 150 g / 10 minutes Characteristic (a3): Vicat softening point 42 ° C.

<Component (B)>
The tackifier of component (B) is a component that imparts tackiness to the hot melt adhesive.

The content of the tackifier of the component (B) in the hot melt adhesive is 8 to 80 parts by mass, preferably 14 to 60 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer of the component (A). Part. If it is this range, the fall of seal strength can be suppressed and the amount of elution with respect to an organic solvent can be suppressed.

As the tackifier, known tackifiers can be used, and examples thereof include alicyclic saturated hydrocarbon resins, aliphatic aromatic copolymer resins, terpene resins, and rosin resins. Among these, a rosin resin can be preferably used from the viewpoint of improving adhesive strength.

In the present invention, such a rosin resin and other tackifiers have the following characteristics (b1).

(Characteristic (b1): softening point)
The softening point of the tackifier such as rosin resin is preferably 80 to 150 ° C, more preferably 85 to 130 ° C. If it is this range, the increase in the elution amount with respect to an organic solvent can be suppressed, and the fall of seal strength can be suppressed. The softening point can be measured by a ring and ball method.

Specific examples of the tackifier having the characteristic (b1) described above include “Arcon (registered trademark) P-125” (softening point 125 ° C.) manufactured by Arakawa Chemical Industries, Ltd., manufactured by Nippon Zeon Co., Ltd. “Quinton (registered trademark) D100” (softening point 99 ° C.), “Superester A-115” (softening point 108 ° C.) manufactured by Arakawa Chemical Industries, Ltd., “Pencel (registered trademark)” of Arakawa Chemical Industries, Ltd. AZ ”(softening point 95 ° C.),“ Haritack ER95 ”(softening point 85 ° C.) manufactured by Harima Kasei Co., Ltd., and the like.

<Ingredient (C) Wax>
The component (C) wax is a component that lowers the viscosity of the hot melt adhesive and imparts wettability.

The content of the component (C) wax in the hot melt adhesive is 85 to 230 parts by weight, preferably 110 to 200 parts by weight, based on 100 parts by weight of the ethylene-vinyl acetate copolymer of component (A). . If it is this range, the fall of the coating processability by high viscosity of an adhesive material can be suppressed, the fall of the coating processability by low viscosity can also be suppressed, and the fall of seal strength can also be suppressed. .

As the wax, a known wax can be used. Examples thereof include natural waxes such as purified beeswax, purified carnauba wax, purified montan wax, paraffin wax, and microcrystalline wax; and synthetic waxes such as polyethylene wax, polypropylene wax, and Fischer-Tropsch wax. Among these, synthetic waxes are preferable from the viewpoint of melting point and stability of molecular weight distribution, and Fischer-Tropsch wax is more preferable.

Such a wax preferably has the following characteristics (c1).

(Characteristic (c1): Melting point)
The melting point of waxes such as polyethylene wax is preferably 80 to 130 ° C, more preferably 85 to 120 ° C. If it is this range, the elution amount with respect to an organic solvent can be suppressed, and the fall of the sealing performance in low temperature can be suppressed. The melting point can be measured by a DSC method.

Specific examples of the wax having the characteristic (c1) described above include “Neowax L” (melting point 110 ± 10 ° C.) manufactured by Yashara Chemical Co., Ltd., and “High Wax NL900” (melting point 103) manufactured by Mitsui Chemicals, Inc. ° C), “FT105” (melting point: 102 ° C.) manufactured by Nippon Seiwa Co., Ltd., and the like.

<Ingredient (D) Talc>
The hot melt adhesive used in the present invention contains talc as the component (D). Talc is excellent in dispersibility in other resin components, can increase the cohesive strength of the hot melt adhesive, and further diffuses heat transfer from the base material layer 1 to the hot melt adhesive layer 4 excessively. It is a component for transmitting without.

The content of talc of component (D) in the hot melt adhesive is 15 to 200 parts by mass, preferably 60 to 170 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer of component (A). . If it is in this range, it suppresses the decrease in the sealing property at low temperature and suppresses the amount of elution with respect to the organic solvent, and also suppresses the decrease in the compatibility with other compounds such as resins and the coating due to the decrease in fluidity. Deterioration can be suppressed.

In the present invention, it is preferable to use talc having the following characteristics (d1) to (d3).

(Characteristic (d1): Particle size (D50))
The particle diameter (D50) (median diameter) of talc is preferably 0.1 to 50 μm, more preferably 0.5 to 25 μm. If it is this range, the increase in the volume of particle | grains can be suppressed, paint preparation can be made easy, and the fall of heat conductivity can be suppressed by suppressing the fall of heat conductivity. The particle diameter (D50) can be measured by a laser diffraction method.

(Characteristic (d2): Apparent density)
The apparent density of talc is preferably 0.05 to 0.7 g / mL, more preferably 0.08 to 0.6 g / mL. If it is this range, the increase in the volume of particle | grains can be suppressed, paint preparation can be made easy, and the fall of heat conductivity can be suppressed by suppressing the fall of heat conductivity. The apparent density can be measured according to JIS K5101.

(Characteristic (d3): Specific surface area)
The specific surface area of the talc is preferably 1.5 ~ 100m ² / g, more preferably 2.5 ~ ^40m 2 / g. If it is this range, the fall of heat conductivity can be suppressed, the fall of seal strength can be suppressed, and paint preparation can be facilitated. The specific surface area can be measured by the BET method.

Specific examples of talc having the characteristics (d1) to (d3) described above include “Microace (registered trademark) K-1” (particle diameter (D50) 8.0 μm, apparent density) manufactured by Nippon Talc Co., Ltd. 0.25 g / mL, specific surface area 7.0 m ² / g), “MS-K” (particle diameter (D50) 16 μm, apparent density 0.40 g / mL, specific surface area 4.0 m ² ) manufactured by Nippon Talc Co., Ltd. / G), “MS-KY” (particle diameter (D50) 25 μm, apparent density 0.55 g / mL, specific surface area 2.5 m ² / g) manufactured by Nippon Talc Co., Ltd. can be preferably mentioned.

The hot melt adhesive layer 4 described above can be formed by applying a hot melt adhesive to the stress relaxation layer 3 and cooling using a known coating method such as a gravure coater, comma coater, die coater or the like. it can. In this case, it may be a flat film shape, an embossed film shape, a dot shape, or a line shape.

"Printing layer, protective layer"
The lid material of the present invention can be provided with a print layer that can be formed by a known method on the outer surface of the base material layer 1. Furthermore, a transparent protective layer can be provided. Moreover, the embossing can also be given to the outer surface of the base material layer 1 side of the lid as necessary. A printing layer can be provided on the surface on which the hot melt adhesive layer is processed as required, and a printing layer can be provided on the base material layer.

"Seal characteristics"
Since the lid material of the present invention has the configuration as described above, it exhibits good sealing characteristics (strength) when sealed by hot plate heating, high frequency induction heating, ultrasonic heating, or the like. For example, when hot plate heating is employed, the sealing conditions include a sealing temperature of 80 to 240 ° C., a sealing time of 0.5 to 3 seconds, and a sealing pressure of 0.1 to 0.5 Mpa. When high frequency induction heating is employed, the sealing conditions include a power of 110 to 170 W, a sealing time of 0.5 to 1.5 seconds, and a sealing pressure of 0.1 to 0.3 Mpa.

(Vs. organic solvent elution)
The lid material of the present invention comprises a hot melt adhesive layer 4 that is in contact with the contents of a container, in which a specific amount of talc is mixed with a mixture of ethylene-vinyl acetate copolymer, tackifier, and wax in a specific range. It is formed from a hot melt adhesive blended with For this reason, since sealing performance can be prevented from being lowered, even when a material having a higher molecular weight is selected as the material constituting the hot melt adhesive, the elution amount of the lid to the organic solvent can be reduced. . In particular, the lid material of the present invention is based on the evaporation residue test method (eluent n-heptane) specified in the standard test of equipment and containers and packaging of the standard of the Food Sanitation Law (Ministry of Health and Welfare Notification No. 370 of 1959). Based on the oily food elution test, the residue (relative to heptane elution amount) can be 30 μg / mL or less.

Furthermore, the lid material of the present invention can have a residue (relative to hexane elution amount) of 30 mg / L or less obtained by the test method described below.

(Evaporation residue of elution test with n-hexane)
A sample cut to a size of 10 cm square was prepared according to the national standard of the People's Republic of China “Analytical method for hygienic standards of polyethylene, polystyrene and polypropylene molded products for food packaging” (GB / T5009.60-2003). Prepare the test solution by immersing the whole surface in hexane at 25 ° C. for 2 hours. This test solution is transferred to an eggplant-shaped flask and concentrated under reduced pressure until the residual amount reaches several mL. To the obtained concentrated solution, a washing solution obtained by washing the inner wall of the flask used for concentration under reduced pressure twice with 5 mL each of n-hexane was added and taken in an evaporating dish of known weight previously dried at 105 ° C., Evaporate to dryness. Next, after drying at 105 ° C. for 2 hours, it is allowed to cool in a desiccator. After standing to cool, the sample is weighed to determine the mass difference between before and after the evaporating dish test, and the amount (mg) of evaporation residue per liter of the test solution is calculated.

"Manufacturing method of lid"
As already described, the lid material of the present invention is formed by forming the anchor coat layer 2 on the base material layer 1, further providing the stress relaxation layer 3, and further providing the hot melt adhesive layer 4 using a known method. Can be manufactured.

<Applications of lid materials>
The lid material of the present invention is a food container having an opening in which a flange portion is formed, a liquid or solid food contained therein, and a lid adhered to the flange portion formed in the opening of the food container. It can apply preferably as the said cover material of the foodstuffs in a container comprised from a material. In this case, the lid member is applied to the flange portion of the opening from the adhesive layer side and thermally bonded by high frequency induction heating. “Food in a container” thus obtained is also an embodiment of the present invention. Examples of food containers include known food containers made of polystyrene.

“Liquid or solid” in liquid or solid food means a state where the shape of the food as the contents is deformed (outflow, flow, etc.) when the container is tilted, or a state where the shape of the food as the contents is not deformed (solid ). Examples of such liquid or solid foods include, but are not limited to, dairy products such as yogurt and lactic acid beverages, jam products, soups, curry sauces, stews, and sprinkles.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1
(AL foil / anchor coat layer / LDPE / hot melt adhesive layer)
A two-component curable extrusion laminating anchor coating agent (isocyanate) is applied to one side of a 30 μm thick aluminum foil (alloy number: 1N30 as defined in JIS H4160) and dried to 0.35 μm. A thick anchor coat layer is formed, 30 μm-thick low density polyethylene (MFR = 7) is extruded and laminated on the anchor coat layer, and a hot melt adhesive having the following formulation is applied with a gravure coater. It was applied in the form of dots so that the amount was 12.7 g / m ² to obtain a lid material.

Comparative Example 1
A hot melt adhesive was prepared in the same manner as in Example 1 except that talc was not added to the hot melt adhesive and the amount of the hot melt adhesive applied was 12.1 g / m ^2. did.

Comparative Example 2
Example 1 except that calcium carbonate (light calcium carbonate, average particle size 2.0 × 0.4 μm) is used instead of talc and the amount of hot melt adhesive applied is 14.4 g / m ^2. Similarly, a hot melt adhesive was prepared, and a lid material was further produced.

Comparative Example 3
Other than using rutile titanium oxide (average particle size 0.25 μm, specific gravity 4.1, oil absorption 19 g / 100 g) instead of talc, and applying the hot melt adhesive to 14.6 g / m ² A hot melt adhesive was prepared in the same manner as in Example 1, and a lid was further produced.

Comparative Example 4
Example 1 except that anatase-type titanium oxide (average particle size 0.25 μm, oil absorption 25 g / 100 g) is used instead of talc and the amount of hot melt adhesive applied is 14.0 g / m ² Similarly, a hot melt adhesive was prepared, and a lid material was further produced.

Comparative Example 5
Example 1 except that kaolin clay (average particle size 0.4 μm, oil absorption 43 g / 100 g) is used instead of talc, and the amount of hot melt adhesive applied is 12.2 g / m ² A hot melt adhesive was prepared, and a lid was further produced.

Comparative Example 6
Instead of talc, 10 parts by mass of silica (average particle size 3.5 to 4.3 μm, oil absorption 300 to 350 mL / 100 g (linseed oil)) is used, and the application amount of hot melt adhesive is 11.8 g / m. ^A hot melt adhesive was prepared in the same manner as in Example 1 except that it was set to ^2, and a lid member was further produced.

(Evaluation test)
"Seal strength by hot plate heating"
The lid materials obtained in Example 1 and Comparative Examples 1 to 6 were cut into strips each having a length of 10 cm and a width of 15 mm to obtain test pieces. The end 20 mm of this test piece was sealed on a polystyrene plate at the sealing temperature shown in Table 2, the sealing time 1 second, and the sealing pressure 0.2 MPa. The other end of the test piece sealed at the end of a polystyrene plate is set in a tensile tester (Autograph (registered trademark) AGS-500NJ, Shimadzu Corporation), and a 180 ° peel test at a peel speed of 300 mm / min. Each was performed 5 times. The average of the five seal strengths obtained is shown in Table 2 and FIG. Under the present sealing conditions, it is preferable for practical use that the seal strength is 10 N / 15 mm width or more when the seal temperature is 140 ° C. Furthermore, when the seal temperature is 100 ° C., the width is more preferably 5 N / 15 mm width or more.

"Seal strength by high frequency induction heating"
The lid material obtained in Example 1 and Comparative Examples 1 to 6 was cut into a circular shape having an outer diameter of 38 mm, and a 65 mL polystyrene container having a bottle shape with an outer diameter of 24 mm and an inner diameter of 20 mm. And sealed at a work rate of 110 to 170 W, a seal pressure of 0.05 MPa, and a seal time of 1.4 seconds. After sealing, the end of the lid was peeled off at 45 ° with respect to the container surface sealed with the lid at a speed of 300 mm / min, and the maximum value at the time of peeling was defined as the seal strength. The peel test was performed 5 times and the average value was used. Practically, it is preferable to maintain a seal strength of 7N or more at a power of 125W. The obtained results are shown in Table 3 and FIG.

Examples 2 to 6
The amount of talc added is 30 to 5 parts by mass (Example 2), 10 parts by mass (Example 3), 20 parts by mass (Example 4), 50 parts by mass (Example 5) or 70 parts by mass (implemented). example change in 6), and hot-melt, respectively the amount of the adhesive applied from ^{12.7g / m 2 12.5g / m 2} , 14.5g / m 2, 14.0g / m 2, 14.2g / m ^A hot melt adhesive was prepared in the same manner as in Example 1 except that it was set to ² or 14.8 g / m ^2, and a lid was further produced.

(Evaluation test)
The lid materials of Examples 2 to 6 were tested for “seal strength by hot plate heating” and “seal strength by high frequency induction heating” in the same manner as in Example 1. The obtained results together with the results of Example 1 and Comparative Example 1 are shown in Table 4 and FIG. 4 for the former and in Table 5 and FIG. 5 for the latter.

Examples 7 and 8
Talc with a mean particle size (D50) of 16 μm (Example 1), talc with a mean particle size (D50) of 8 μm (apparent density 0.25 g / mL, specific surface area 7.0 m ² / g) (Example 7), or The average particle diameter (D50) was changed to talc (apparent density 0.55 g / mL, specific surface area 2.5 m ² / g) of 25 μm (Example 8), and the application amount of the hot melt adhesive was 12.7 g / m. ^A hot melt adhesive was prepared in the same manner as in Example 1 except that the amount was changed from ² to 12.4 g / m ² or 12.8 g / m ² , respectively, and a lid member was further produced.

(Evaluation test)
The lid materials of Examples 7 and 8 were tested for “seal strength by hot plate heating” and “seal strength by high-frequency induction heating” in the same manner as in Example 1. The obtained results together with the results of Example 1 are shown in Table 6 and FIG. 6 for the former and in Table 7 and FIG. 7 for the latter.

"Amount of elution from n-hexane"
The cover materials of Comparative Example 1 (without talc), Example 1 (30 parts by mass of talc), Example 5 (50 parts by mass of talc), and Example 6 (70 parts by mass of talc) are cut into a size of 10 cm square. A sample piece was obtained. This sample piece was placed in 200 mL of n-hexane at 25 ° C. according to the national standard of the People's Republic of China “Analytical method for sanitary standards of polyethylene, polystyrene, and polypropylene molded products for food packaging” (GB / T5009.60-2003). A test solution was prepared by dipping the entire surface for 2 hours. Each of the obtained test solutions was transferred to an eggplant-shaped flask and concentrated under reduced pressure until the residual amount reached several mL. To the obtained concentrated solution, a washing solution obtained by washing the inner wall of the flask used for concentration under reduced pressure twice with 5 mL each of n-hexane was added and taken in an evaporating dish of known weight previously dried at 105 ° C., Evaporate to dryness. Subsequently, after drying at 105 degreeC for 2 hours, it stood to cool in a desiccator. After standing to cool, it weighed and calculated | required the mass difference before and behind the test of an evaporating dish, and computed the quantity (mg) of the evaporation residue per 1L of test solutions. Table 8 shows the obtained results.

(Discussion)
From the results of Table 2 (FIG. 2) and Table 3 (FIG. 3), it can be seen that talc among various fillers can improve the sealing strength by hot plate heating or high frequency induction heating. In particular, in the case of Example 1 using talc, the hot plate heating has obtained a sealing strength of 15.2 N / 15 mm width at 140 ° C., compared with Comparative Examples 2 to 6 using other fillers. It can be seen that excellent seal strength is maintained. Even in the high frequency induction heating, the sealing strength superior to that of other fillers is maintained.

From the results of Table 4 (FIG. 4) and Table 5 (FIG. 5), it can be seen that the seal strength tends to increase as the talc content is increased from 5 parts by mass (Examples 1 to 6). In the case of heating plate heating, when 5 parts by mass or more of talc is added, the seal strength at 140 ° C. is 10 N / 15 mm or more, which is a preferable seal strength, and even at 100 ° C., when the amount of talc added is 20 parts by mass or more, 5 N / 15 mm. Since the width or more is maintained, it can be seen that it is more preferable. Also in the high frequency induction heating, by adding 5 parts by mass or more of talc, the seal strength of 7.1 N is maintained even at 125 W where the work rate is low, and it can be understood that it can be processed even in the region where the work rate is low.

From the results shown in Table 6 (FIG. 6) and Table 7 (FIG. 7), when the particle size of talc is small, the seal strength tends to increase under relatively high sealing conditions (Examples 1, 7, and 8). It can be seen that excellent sealing strength can be obtained even under low sealing conditions within the range of the experimental results.

From the results in Table 8, it can be seen that as the talc content increases, the n-hexane elution amount decreases. In addition, when an evaporation residue test was performed with the eluent n-heptane according to the standards of the Food Sanitation Law, the residue with respect to n-heptane in all of Examples 1, 5, and 6 was 20 μg / mL or less. The quality of the n-heptane elution based on the standard specification of was maintained.

In the lid material of the present invention in which the base material layer, the anchor coat layer, the stress relaxation layer, and the hot melt adhesive layer are laminated in this order, the hot melt adhesive is considered in consideration of the sealing property and the elution amount with respect to the organic solvent. As a hot melt adhesive for forming a layer, a hot melt adhesive in which a specific amount of talc is mixed with a mixture of ethylene-vinyl acetate copolymer, tackifier and wax in a specific range is used. is doing. For this reason, even when a higher molecular weight material is selected as the material constituting the hot melt adhesive in order to reduce the elution amount of the lid material with respect to the organic solvent, the sealing performance can be prevented from being lowered. Therefore, it is useful as a lid for food containers and pharmaceutical containers.

DESCRIPTION OF SYMBOLS 1 Base material layer 2 Anchor coat layer 3 Stress relaxation layer 4 Hot melt adhesive layer 10 Lid

Claims (14)

A cover material having at least a base material layer, an anchor coat layer, a stress relaxation layer, and a hot melt adhesive layer, which are laminated in this order, and a hot melt adhesive constituting the hot melt adhesive layer Further, the component (A) contains 20 to 50% by mass of an ethylene-vinyl acetate copolymer, and further contains the following components (B) to (D) in the following parts by mass with respect to 100 parts by mass of the component (A). Lid:
(A) 100 parts by mass of an ethylene-vinyl acetate copolymer;
(B) Tackifier 8-80 parts by mass;
(C) Wax 85-230 parts by mass; and (D) Talc 15-200 parts by mass. The talc of component (D) has the following characteristics (d1) to (d3):
(D1) Particle size (D50) 0.1-50 μm;
(D2) Apparent density 0.05 to 0.7 g / mL; and (d3) Specific surface area 1.5 to 100 m ² / g;
The lid material according to claim 1, comprising: The component (A) ethylene-vinyl acetate copolymer has the following characteristics (a1) to (a3):
(A1) Vinyl acetate content 14-41% by mass;
(A2) MFR value 5 to 400 g / 10 min; and (a3) Vicat softening point 25 to 75 ° C .;
The lid member according to claim 1 or 2, comprising: The tackifier of component (B) has the following characteristics (b1):
(B1) Softening point 80-150 ° C .;
The lid material according to any one of claims 1 to 3, wherein The lid material according to claim 4, wherein the tackifier of component (B) is a rosin resin. Component (C) wax has the following properties (c1):
(C1) Melting point 80-130 ° C;
The lid material according to any one of claims 1 to 5, wherein The lid material according to any one of claims 1 to 6, wherein the component (C) wax is a synthetic wax. The lid material according to claim 7, wherein the synthetic wax is Fischer-Tropsch wax. The thickness of the base material layer is 5 to 300 μm, the thickness of the anchor coat layer is 0.1 to 6.0 μm, the thickness of the stress relaxation layer is 6 to 60 μm, and the adhesion of the hot melt adhesive layer The lid material according to any one of claims 1 to 8, wherein the amount is 3 to 40 g / m ² . The base material layer is a metal or alloy thin film or a resin film,
The anchor coat layer is a modified polyolefin anchor coat agent layer, a polyester anchor coat agent layer or a polyurethane anchor coat agent layer,
The lid material according to any one of claims 1 to 9, wherein the stress relaxation layer is a polyolefin-based or polyester-based thermoplastic resin layer. The lid material according to claim 9 or 10, wherein the base material layer is an aluminum foil having a thickness of 5 to 50 µm. The lid material according to claim 9 or 10, wherein the stress relaxation layer is an unstretched polyethylene layer having a thickness of 10 to 50 µm. The lid material according to any one of claims 1 to 12, wherein a printing layer is formed on the outer surface of the base material layer. A container comprising a food container having an opening formed with a flange, a liquid or solid food contained therein, and a lid material bonded to the flange formed in the opening of the food container A food product, wherein the lid material is the lid material according to any one of claims 1 to 13, and the lid material is bonded to the flange portion of the opening from the hot melt adhesive layer side. Food in containers.

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