TW201734174A - Lid material - Google Patents

Abstract

To achieve favorable sealing with a sealing condition similar to the conventional condition even when restraining the elution amount of an organic solvent by changing the material composing a hot melt adhesive layer to a higher molecular-weight material in a lid material comprising laminating a substrate layer/anchor coat layer/stress relaxation layer/hot melt adhesive layer in this order. A lid material includes at least a substrate layer, anchor coat layer, stress relaxation layer and hot melt adhesive layer and has a structure in which those layers are laminated in this order. The hot melt adhesive composing the hot melt adhesive layer contains 20-50 mass% of ethylene-vinyl acetate copolymer as a component (A), and further contains 8-80 pts.mass of a tackifier (component (B)), 85-230 pts.mass of a wax (component (C)) and 15-200 pts.mass of a talc (component (D)) based on 100 pts.mass of the ethylene-vinyl acetate copolymer of the component (A).

Description

Cover material

The present invention relates to an opening for a plastic container for accommodating liquid foods such as acid condensate, lactic acid bacteria beverage, fruit juice beverage, powdered food such as wheat flour, solid food such as ham or cheese, and various pharmaceuticals. A cover material that is then sealed by heating plate heating or high frequency induction heating.

The opening of the container body for accommodating food or the like is generally sealed by a lid member having thermal adhesion. In recent years, in order to ensure the safety of foods and the like, it is required that the amount of the substance eluted in the organic solvent (the amount of elution in the organic solvent) is small when the cover material is immersed in the organic solvent. As a cover material for such a request, a stress relaxation layer such as a tackifier coating layer/polyethylene film such as a base material layer such as an aluminum foil/urethane resin or a vinyl-vinyl acetate resin-based hot melt adhesive is proposed. A cover material composed of a laminate of layers (Patent Document 1).

In the cover material, a material having a relatively small amount of a substance selected to be eluted in an organic solvent has been proposed as a constituent material of the hot-melt adhesive layer which is in direct contact with the contents of the container body. Specifically, the 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 min is 25 to 55 wt%, the molecular weight is 700 to 3,500, and the melting point is 95 to 125 ° C. Polyethylene wax 30~65% by weight, and molecular weight 700~1,400 Further, the polymer-based adhesion imparting agent having a softening point of 100 to 125 ° C is 10 to 30% by weight of a hot-melt adhesive to form a hot-melt adhesive layer.

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 10-156995

Here, although the amount of elution of the material eluted from the edible oil or the ethanol proposed in Patent Document 1 is very small, it is generally not a problem in use, but for hexane, it exists in the presence of edible fat or ethanol. The ratio of the amount of eluted material (dissolved in hexane) is increased. Therefore, in consideration of changing the constituent materials of the hot-melt adhesive to a higher molecular weight, the content of the low-molecular-weight impurities is relatively reduced, thereby reducing the amount of elution in hexane.

However, when a material having a higher molecular weight is used as a material constituting the hot-melt adhesive, the sealing property of the hot-melt adhesive layer of the lid member is lowered, so that the sealing strength is lowered if the sealing condition is the same as in the related art. . In order to avoid this, it is considered that the sealing condition is made strict, but in a state where it is strict, it is extremely difficult to find the optimum sealing condition.

An object of the present invention is to solve the above problems of the prior art, and an object of the present invention is to provide a cover material in which a base material layer, a tackifying coating layer, a stress relieving layer, and a hot-melt adhesive layer are laminated in this order. The material of the hot-melt adhesive layer is changed to a higher molecular weight, and the amount of elution in the organic solvent is suppressed. Even in this case, a good sealing can be achieved under the same sealing conditions as in the related art.

The present inventors have found that if the "ethylene-vinyl acetate copolymer, adhesion" The heat-adhesive agent of the talc blended with a specific amount of the wax and the wax is mixed in a specific range to form a "base material layer / tackifying coating layer / stress relieving layer / hot-melt adhesive layer The hot-melt adhesive layer of the cover material which is sequentially laminated, even when a material having a higher molecular weight is selected as a material constituting the hot-melt adhesive, in order to reduce the elution amount of the cover material in the organic solvent The present invention can be completed without lowering the sealing property.

That is, the present invention provides a cover material having at least a base material layer, a tackifying coating layer, a stress relieving layer, and a hot-melt adhesive layer, which are laminated in this order to constitute a hot-melt adhesive layer. The hot-melt adhesive contains 20 to 50% by mass of the ethylene-vinyl acetate copolymer as the component (A), and further contains the following components (B) to (D) in the following parts by mass based on 100 parts by mass of the component (A). ).

(A) Ethylene-vinyl acetate copolymer 100 parts by mass; (B) Adhesive imparting agent 8 to 80 parts by mass; (C) wax 85 to 230 parts by mass; and (D) talc 15 to 200 parts by mass.

Moreover, the present invention provides a container-packed food product comprising a food container having an opening portion in which a flange portion is formed, a liquid or solid food contained therein, and a flange portion formed in an opening portion of the food container The lid member is characterized in that the lid member is a lid member as described above, and the lid member is attached to the flange portion of the opening portion from the side of the hot-melt adhesive layer.

In the cover material of the present invention in which the base material layer, the adhesion-promoting coating layer, the stress relaxation layer, and the hot-melt adhesive layer are sequentially laminated, the sealing property and the amount of elution in the organic solvent are considered, and A hot melt adhesive in which a specific amount of talc is blended in an ethylene-vinyl acetate copolymer, an adhesion imparting agent, and a wax in a specific range" as a hot-melt adhesive for forming a hot-melt adhesive layer . Therefore, even when a material having a higher molecular weight is selected as a material constituting the hot-melt adhesive in order to lower the elution amount of the cover material in the organic solvent, the sealing property may not be lowered.

1‧‧‧ substrate layer

2‧‧‧Adhesive coating layer

3‧‧‧stress relaxation layer

4‧‧‧Hot melt adhesive layer

10‧‧‧Cleaning

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic cross-sectional view of a cover material of the present invention.

Fig. 2 is a graph showing the sealing strength characteristics when heated by a heating plate in the case of the type of the filler.

Fig. 3 is a graph showing the sealing strength characteristics when high-frequency induction heating is used in the case of the type of the filler.

Fig. 4 is a graph showing the sealing strength characteristics when heated by a hot plate in the case where the amount of talc is blended.

Fig. 5 is a graph showing the sealing strength characteristics when high-frequency induction heating is used in the case where the amount of talc is blended.

Fig. 6 is a graph showing the sealing strength characteristics when heated by a hot plate in the case of the average particle diameter of talc.

Fig. 7 is a graph showing the sealing strength characteristics when high-frequency induction heating is used in the case of the average particle diameter of talc.

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

<Cover material>

As shown in FIG. 1, the cover material 10 of the present invention has a structure in which a base material layer 1, a tackifying coating layer 2, a stress relieving layer 3, and a hot-melt adhesive layer 4 are sequentially laminated. The cover member 10 is a material for sealing the opening of the container body by sealing. Examples of the constituent material of the container body include a plastic such as polystyrene, polypropylene, polyethylene, polyvinyl chloride, polycarbonate, or polyacrylonitrile, a composite laminate lined with the plastic, and a metal. Polyethylene laminated paper, glass, and the like.

"Substrate layer 1"

The base material layer 1 is a main layer that imparts initial mechanical strength to the lid member, and can be formed in the same configuration as the base material layer of the conventional lid member. For example, according to the purpose of use, a film of a metal or alloy such as iron, stainless steel, copper, aluminum or gold, a ceramic film such as tantalum nitride, polyethylene terephthalate, polyurethane, polystyrene, polyamine, A film of a resin such as polyimine, a papermaking paper, a composite material obtained by laminating the film, and the like are selected. In particular, in order to impart high-frequency induction heating characteristics to the lid member 10, a metal thin film which generates heat by inducing an eddy current itself when a high frequency is applied is preferably used as the base material layer 1. Among them, an aluminum foil is preferably used in terms of moldability, high-frequency heating suitability, and economy.

The layer thickness of the base material layer 1 is usually 5 to 300 μm in consideration of mechanical strength or a material to be used. For example, when a metal film such as aluminum foil is used, high-frequency induction heating characteristics and the like are considered, and it is preferably 5~. 50 μm thick, more preferably 20 to 40 μm thick.

The base material layer 1 can be formed by a known method depending on the kind or thickness of the material. In the case of a film of a metal or an alloy, it can be formed by a cold rolling method, a vacuum deposition method, an electroless plating method, a plating method, or the like. In the case of a resin film, a melt extrusion method can be utilized, Formed by a flow casting method, a calendering method, or the like. Further, the film of the resin may be subjected to an elongation treatment.

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

"Tackifying coating layer 2"

The adhesion-promoting coating layer 2 is a layer in which the base material layer 1 and the stress relaxation layer 3 are in close contact with each other, and can be selected according to the material of the material.

As the tackifier coating layer 2, a layer formed of a modified polyolefin-based tackifier coating agent modified with chlorine or acid, a polyester-based tackifier coating agent, or a polyurethane-based tackifier coating agent can be applied. . Further, an additive such as various fillers may be contained in the adhesion-promoting coating layer 2 within a range that does not inhibit the adhesion between the base material layer 1 and the stress relieving layer 3.

When the layer thickness of the thickening coating layer 2 is too thin, the sealing strength tends to be lowered, and if it is too thick, the aggregation of the coating layer 2 may be weakened. The tendency of the seal strength to decrease is preferably from 0.1 to 6.0 μm, more preferably from 0.2 to 4.5 μm.

The adhesion-promoting coating layer 2 can be formed by a solution coating method.

"stress relaxation layer 3"

The stress relieving layer 3 also serves as "the mechanical strength of the reinforcing cover material to alleviate the stress during high-frequency heating, and the excessive heat is suppressed from being added to the hot-melt adhesive layer 4, so that the hot-melt adhesive layer 4 is firmly adhered to the cover material. It functions as a layer on the back. As the stress relieving layer 3, a resin layer formed of a polyolefin-based thermoplastic resin such as polyethylene or polypropylene or a resin layer formed of a polyester-based thermoplastic resin such as polyethylene terephthalate can be used. If the stability of the high-frequency sealing strength or the like is considered, a polyethylene layer can be preferably applied, and a non-extended polyethylene layer can be preferably applied.

The layer thickness of the stress relaxation layer 3 is preferably from 6 to 60 μm, more preferably from 9 to 50 μm. As long as it is in this range, sufficient stress relaxation and thermal relaxation can be achieved, and sufficient heat can be conducted from the substrate layer 1 to the hot-melt adhesive layer 4.

In the case where the stress relieving layer 3 is a polyethylene layer, the layer thickness is preferably 10 to 50 μm, more preferably 15 to 40 μm, in consideration of high-frequency sealing property and moldability.

As a method of providing the stress relieving layer 3 on the adhesion-promoting coating layer 2, a known method can be employed. For example, the material constituting the stress relieving layer 3 may be directly melt-extruded and laminated on the tackifying coating layer 2, or the film formed of the material constituting the stress relieving layer 3 may be dry-laminated.

"hot melt adhesive layer 4"

The hot-melt adhesive layer 4 is adhered to the opening of the container body by the heat conducted from the substrate layer 1 and is in contact with the contents of the container body.

The adhesion amount of the hot-melt adhesive layer 4 is preferably from 3 to 40 g/m ² , more preferably from 5 to 30 g/m ² . As long as it is within this range, sufficient high-frequency sealing characteristics (especially sealing strength) can be obtained by high-frequency heating, and the lid member can be stably peeled off, and further, the amount of elution in the organic solvent can be reduced. .

The formation of the hot-melt adhesive layer 4 can be carried out by a known method such as gravure coating.

Since the hot-melt adhesive layer 4 is a layer which is in contact with the contents accommodated in the container main body, it is required to be composed of an adhesive material which can be attached to the applied container body and which is not easily eluted to the contents. In the present invention, it is formed of a hot-melt adhesive containing the following components (A) to (D).

(A) ethylene-vinyl acetate copolymer

(B) Adhesive imparting agent

(C) wax

(D) Talc

<ingredient (A)>

The ethylene-vinyl acetate copolymer of the component (A) functions as a main component of a hot-melt adhesive, and is used because it is easily adhered to a metal, a resin, a glass, or the like, and is easily compatible with a wax or the like.

The content of the ethylene-vinyl acetate copolymer of the component (A) in the hot-melt adhesive is 20 to 50% by mass, preferably 25 to 45% by mass. If it is in this range, the heat-sealing strength can be prevented from being lowered, and the amount of elution in the organic solvent can be suppressed.

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

(characteristic (a1): vinyl acetate content)

The vinyl acetate content of the ethylene-vinyl acetate copolymer is preferably from 14 to 41% by mass, more preferably from 19 to 33% by mass. When it is this range, it is possible to suppress the amount of elution in the organic solvent without lowering the sealing strength. The measurement of the vinyl acetate content can be carried out in accordance with JIS K6924-2.

(characteristic (a2): MFR value)

The MFR value (JIS K7210) of the ethylene-vinyl acetate copolymer is preferably from 5 to 400 g/10 min, more preferably from 5 to 150 g/10 min. If it is in this range, the coating property of the hot-melt adhesive is not impaired, and the amount of elution in the organic solvent can be suppressed. The MFR value can be measured according to JIS K7210 And proceed.

(Characteristic (a3): Fica softening point)

The thicarb softening point of the ethylene-vinyl acetate copolymer is preferably from 25 to 75 ° C, more preferably from 30 to 65 ° C. When it is in this range, the amount of elution in the organic solvent can be suppressed, and the decrease in the sealing strength can be suppressed. The measurement of the Fica softening point can be carried out in accordance with JIS K7206.

Specific examples of the ethylene-vinyl acetate copolymer having the characteristics (a1) to (a3) described above are preferably EVAFLEX (registered trademark) EV420 manufactured by DU PONT-MITSUI POLYCHEMICALS (share). EV220", "Ultrathene (registered trademark) 750" manufactured by Tosoh Co., Ltd., etc. For example, the characteristics (a1) to (a3) of "EVAFLEX EV420" are as follows.

Characteristic (a1): vinyl acetate content of 19% by mass

Characteristic (a2): MFR value 150g/10min

Characteristic (a3): Ficam softening point 42 ° C

<ingredient (B)>

The adhesiveness imparting agent of the component (B) is a component which imparts adhesiveness to the hot melt adhesive.

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

As the adhesiveness-imparting agent, a known adhesiveness-imparting agent can be used, and examples thereof include an alicyclic saturated hydrocarbon resin, an aliphatic aromatic copolymer resin, a terpene resin, and a rosin-based resin. Among them, a rosin-based resin can be preferably used from the viewpoint of improving the force.

In the present invention, the adhesiveness imparting agent represented by such a rosin-based resin has the following characteristics (b1).

(characteristic (b1): softening point)

The softening point of the tackifier as a representative of the rosin-based resin is preferably from 80 to 150 ° C, more preferably from 85 to 130 ° C. When it is in this range, the increase in the amount of elution in the organic solvent can be suppressed, and the decrease in the sealing strength can be suppressed. The measurement of the softening point can be carried out by the ring and ball method.

Specific examples of the adhesiveness-imparting agent having the above-described characteristics (b1) include "Arkon (registered trademark) P-125" (softening point 125 ° C) manufactured by Arakawa Chemical Industries Co., Ltd., and Japanese Ryan "Quintone (registered trademark) D100" (softening point 99 °C) manufactured by the company, "SUPER ESTER A-115" (softening point 108 ° C) manufactured by Arakawa Chemical Industry Co., Ltd., and "Arakawa Chemical Industry Co., Ltd." PENSEL (registered trademark) AZ" (softening point 95 ° C), "HARITACK ER95" (softening point 85 ° C) manufactured by Halima Chemicals Co., Ltd., etc.

<ingredient (C) wax>

The wax of the component (C) is a component which lowers the viscosity of the hot melt adhesive and imparts wettability.

The content of the wax of the component (C) in the hot-melt adhesive is from 85 to 230 parts by mass, preferably from 110 to 200 parts by mass, per 100 parts by mass of the ethylene-vinyl acetate copolymer of the component (A). When it is in this range, it is possible to suppress a decrease in coating processability due to high viscosity of the adhesive material, and also to suppress a decrease in coating processability due to low viscosity, and also to suppress the seal strength. Reduced.

As the wax, a known wax can be used. For example, a natural wax such as refined beeswax, refined kanabah wax, refined montan wax, paraffin wax, or microcrystalline wax; polyethylene wax, polypropylene wax, Synthetic waxes such as Fischer-Tropsch wax. Among them, in terms of the stability of the melting point or the molecular weight distribution, etc., a synthetic wax is preferred, and a Fisher-Bush Bus wax is more preferred.

As such a wax, it is preferred to have the following characteristics (c1).

(characteristic (c1): melting point)

The melting point of the wax represented by polyethylene wax or the like is preferably 80 to 130 ° C, more preferably 85 to 120 ° C. When it is in this range, the amount of elution in the organic solvent can be suppressed, and the decrease in the sealing property at a low temperature can be suppressed. The measurement of the melting point can be carried out by the DSC method.

Specific examples of the wax having the above-described characteristics (c1) include "Neo Wax L" (melting point 110 ± 10 ° C) manufactured by Yasuhara Chemical Co., Ltd., and "HI-WAX" manufactured by Mitsui Chemicals Co., Ltd. NL900" (melting point: 103 °C), "FT105" (melting point: 102 °C) manufactured by Japan Fine Wax Co., Ltd., etc.

<ingredient (D) talc>

The hot-melt adhesive used in the present invention contains talc as the component (D). The talc is excellent in dispersibility in other resin components, and can improve the cohesive force of the hot-melt adhesive, and further, is used to prevent excessive diffusion of heat from the base material layer 1 to the hot-melt adhesive layer 4. Pass the ingredients of heat.

The content of the talc of the component (D) in the hot-melt adhesive is 15 to 200 parts by mass, preferably 60 to 170 parts by mass, per 100 parts by mass of the ethylene-vinyl acetate copolymer of the component (A). When it is in this range, the decrease in the sealing property at a low temperature can be suppressed, and the amount of elution in the organic solvent can be suppressed, and the decrease in compatibility with other blends such as a resin can be suppressed, and the fluidity can be suppressed. Reduce the resulting decrease in coatability.

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

(characteristic (d1): particle size (D50))

The particle diameter (D50) (median diameter) of the talc is preferably from 0.1 to 50 μm, more preferably from 0.5 to 25 μm. When it is in this range, it is possible to suppress the increase in the volume of the particles, thereby facilitating the preparation of the coating material, and suppressing the decrease in the thermal conductivity and suppressing the decrease in the heat-sealing property. The measurement of the particle size (D50) can be carried out by a laser diffraction method.

(characteristic (d2): apparent density)

The apparent density of talc is preferably from 0.05 to 0.7 g/mL, more preferably from 0.08 to 0.6 g/mL. When it is in this range, it is possible to suppress the increase in the volume of the particles, thereby facilitating the preparation of the coating material, and suppressing the decrease in the thermal conductivity and suppressing the decrease in the heat-sealing property. The measurement of the apparent density can be performed in accordance with JIS K5101.

(characteristic (d3): specific surface area)

The specific surface area of the talc is preferably from 1.5 to 100 m ² /g, more preferably from 2.5 to 40 m ² /g. When it is in this range, the decrease in thermal conductivity can be suppressed, and the decrease in sealing strength can be suppressed, and the preparation of the coating can be facilitated. The measurement of the specific surface area can be carried out by the BET method.

As a specific example of the talc having the characteristics (d1) to (d3) described above, "MICRO ACE (registered trademark) K-1" (particle diameter (D50)) manufactured by Nippon Talc Co., Ltd. is preferably exemplified. 8.0 μm, apparent density 0.25 g/mL, specific surface area 7.0 m ² /g), Nippon Talc (MS) manufactured by "MS-K" (particle size (D50) 16 μm, apparent density 0.40 g/mL, specific surface area 4.0 m ² / 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., and the like.

The hot-melt adhesive layer 4 described above can be heated by a known coating method such as a gravure coater, a comma coater, a die coater or the like. The flux is applied to the stress relieving layer 3 and formed by cooling. 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"

For the cover material of the present invention, a printed layer which can be formed by a known method can be provided on the outer surface of the base material layer 1. Further, a transparent protective layer may also be provided. Further, the outer surface of the base material layer 1 side of the lid member may be embossed as needed. It is also possible to provide a printing layer on the surface of the hot-melt adhesive layer, or to provide a printing layer on the substrate layer.

"sealing characteristics"

Since the lid member of the present invention has the above-described configuration, it exhibits good sealing properties (strength) when it is subjected to a sealing treatment by heating with a hot plate, high-frequency induction heating, ultrasonic heating or the like. For example, when heating with a hot plate, 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. In the case of using high-frequency induction heating, 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.

(dissolution amount in organic solvent)

The cover material of the present invention is formed from the contents of the container by "a hot-melt adhesive in which a specific amount of talc is blended in an ethylene-vinyl acetate copolymer, an adhesive imparting agent and a wax in a specific range". The hot melt adhesive layer 4 is in contact with the object. Therefore, even when a material having a higher molecular weight is selected as a material constituting the hot-melt adhesive in order to prevent a decrease in the sealing property, the elution amount of the lid member in the organic solvent can be lowered. In particular, the cover material of the present invention can be based on the specification of the Food Sanitation Law (No. 370 of the Ministry of Health and Welfare No. 370 of 1959) and the evaporation residue test method specified in the specification test of the appliance and container packaging (the eluate is n-heptane) Oily food dissolution test, and will The residue (the amount of elution in heptane) was set to 30 μg/mL or less.

Further, the lid material of the present invention can be made into a residue (the amount of elution in hexane) obtained by the test method described below as 30 mg/L or less.

(Dissolution test evaporation residue obtained with n-hexane)

According to the National Standard of the People's Republic of China, “Analytical Method for Sanitary Standards for Molded Polyethylene, Polystyrene and Polypropylene for Food Packaging” (GB/T5009.60-2003), the sample shall be cut to a size of 10 cm square. The test solution was prepared by immersing in 200 mL of n-hexane over the entire surface at 25 ° C for 2 hours. The test solution was transferred to an eggplant type flask, and concentrated under reduced pressure until the residual amount became several mL. To the obtained concentrate, a washing liquid obtained by separately washing the inner wall of the flask for concentration under reduced pressure with 5 mL of n-hexane was added, and the dried liquid was dried at 105 ° C in advance. Know the evaporating dish, let it evaporate and dry. Then, after drying at 105 ° C for 2 hours, it was allowed to cool in a desiccator. After cooling, the amount of the evaporating dish before and after the test was determined by weighing, and the amount (mg) of the evaporation residue per 1 L of the test solution was calculated.

"Manufacturing method of cover material"

As described above, the cover material of the present invention can be formed by forming the adhesion-promoting coating layer 2 on the base material layer 1 by a known method, further providing the stress relaxation layer 3, and further providing the hot-melt adhesive layer 4. .

<Use of cover material>

The lid member of the present invention can be preferably used as a "food container having an opening portion in which a flange portion is formed, a liquid or solid food contained therein, and a flange portion formed in an opening portion of the food container. The lid material is used for the lid material of the food container. In this case, the cover material is applied to the flange portion of the opening from the adhesive layer side and is thermally heated by high frequency induction heating. The "container-packed food" thus obtained is also an aspect of the present invention. As the food container, a known food container made of polystyrene or the like can be mentioned.

"Liquid or solid" in a liquid or solid food means that if the container is tilted, the shape of the food as a content is deformed (flow, flow, etc.), or the shape of the food as a content does not occur. The state of deformation (solid). Examples of such liquid or solid foods include, but are not limited to, dairy products such as sourdough and lactic acid beverages, jam products, soups, curry sauces, stews, and rice-filled foods.

[Examples]

Hereinafter, the present invention will be more specifically described by way of examples and comparative examples.

Example 1

(A1 foil / tackifying coating layer / LDPE / hot melt adhesive layer)

A two-layer hardening type extrusion-adhesive thickening coating agent (isocyanate type) is applied by a gravure coater on one side of an aluminum foil having a thickness of 30 μm (alloy number: 1N30 specified in JIS H4160). Drying to form a 0.35 μm thick tackifying coating layer, and on the tackifying coating layer, a low density polyethylene (MFR=7) having a thickness of 30 μm was extruded and laminated, and further, using a gravure coater The hot-melt adhesive of the following formulation was applied in a dot shape so that the coating amount became 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 the talc was added to the hot-melt adhesive and the amount of the hot-melt adhesive applied was 12.1 g/m ² , and a cover material was further prepared.

Comparative example 2

Heat was prepared in the same manner as in Example 1 except that calcium carbonate (light calcium carbonate, average particle diameter: 2.0 × 0.4 μm) was used instead of talc, and the amount of the hot-melt adhesive applied was 14.4 g/m ² . The adhesive is further melted to further prepare a cover material.

Comparative example 3

The rutile type titanium dioxide (having an average particle diameter of 0.25 μm, a specific gravity of 4.1, and an oil absorption of 19 g/100 g) was used instead of the talc, and the coating amount of the hot-melt adhesive was set to 14.6 g/m ² , and Example 1 was used. A hot melt adhesive was prepared in the same manner to further prepare a cover material.

Comparative example 4

In the same manner as in Example 1, except that anatase type titanium dioxide (average particle diameter: 0.25 μm, oil absorption amount: 25 g/100 g) was used instead of talc, and the amount of the hot-melt adhesive applied was set to 14.0 g/m ² . A hot melt adhesive is prepared to further prepare a cover material.

Comparative Example 5

A hot-melt joint was prepared in the same manner as in Example 1 except that the talc was used in place of the talc (average particle diameter: 0.4 μm, oil absorption: 43 g/100 g), and the amount of the hot-melt adhesive was 12.2 g/m ² . The agent is further used to make a cover material.

Comparative Example 6

10 parts by mass of cerium oxide (average particle diameter of 3.5 to 4.3 μm, oil absorption of 300 to 350 mL/100 g (linseed oil)) was used instead of talc, and the coating amount of the hot melt adhesive was set to 11.8 g/m ² . A hot-melt adhesive was prepared in the same manner as in Example 1 except that the cover material was further prepared.

(evaluation test)

"The sealing strength obtained by heating with a hot plate"

The cover materials obtained in Example 1 and Comparative Examples 1 to 6 were each cut into short strips having a length of 10 cm and a width of 15 mm to prepare test pieces. The end portion of the test piece was sealed to 20 mm at a sealing temperature of Table 2, a sealing time of 1 second, and a sealing pressure of 0.2 MPa. The other end of the test piece in which the end portion was sealed to the polystyrene plate was placed in a tensile tester (Autograph (registered trademark) AGS-500NJ, Shimadzu Corporation (stock)), and the peeling speed was 300 mm/min, respectively, 5 times. 180° peel test. The average values of the seal strengths of the five tests obtained are shown in Table 2 and Figure 2. Under the sealing conditions of this test, in practical terms, the sealing strength is preferably 10 N/15 mm or more when the sealing temperature is 140 °C. Further, it is more preferably 5 N/15 mm or more when the sealing temperature is 100 °C.

"The sealing strength obtained by high frequency induction heating"

The lid member obtained in Example 1 and Comparative Examples 1 to 6 was cut into a circular shape having an outer diameter of 38 mm, and was attached to a container having an outer diameter of 24 mm in the opening and an inner diameter of 20 mm in the opening and having a bottle shape of 65 mL. The polystyrene container was sealed at a power of 110 to 170 W, a sealing pressure of 0.05 MPa, and a sealing time of 1.4 seconds. After the sealing, the end portion of the lid member was peeled off at a speed of 300 mm/min with respect to the surface of the container sealed with the lid member in a direction of 45 degrees, and the maximum value at the time of peeling was defined as the sealing strength. The peel test was carried out 5 times and the average value was used. In practical terms, it is preferred to maintain a sealing strength of 125 W and 7 N or more. The results obtained are shown in Table 3 and Figure 3.

Example 2~6

The amount of talc added was changed from 30 parts by mass 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. (Example 6), and the hot-melt agent is then coated amount of from 12.7g / m ^2, respectively, to ^{12.5g / m 2, 14.5g / m} 2, 14.0g / m 2, 14.2g / m 2 or 14.8 A hot-melt adhesive was prepared in the same manner as in Example 1 except that g/m ² was used, and a lid member was further prepared.

(evaluation test)

In the cover materials of Examples 2 to 6, the "sealing strength obtained by heating with a hot plate" and "sealing strength obtained by high-frequency induction heating" were tested in the same manner as in the first embodiment. The results obtained are shown together with the results of Example 1 and Comparative Example 1, and the former is shown in Table 4 and Figure 4, and the latter is shown in Table 5 and Figure 5.

Examples 7, 8

The talc having an average particle diameter (D50) of 16 μm (Example 1) was changed to talc having an average particle diameter (D50) of 8 μm (visual density: 0.25 g/mL, specific surface area: 7.0 m ² /g) (Example 7), or average Talc having a particle diameter (D50) of 25 μm (visual density: 0.55 g/mL, specific surface area: 2.5 m ² /g) (Example 8), and the coating amount of the hot-melt adhesive was set to 12.4 from 12.7 g/m ² , respectively. A hot-melt adhesive was prepared in the same manner as in Example 1 except that g/m ² or 12.8 g/m ² was used, and a cover material was further prepared.

(evaluation test)

In the cover materials of Examples 7 and 8, the "sealing strength obtained by heating with a hot plate" and "sealing strength obtained by high-frequency induction heating" were tested in the same manner as in the first embodiment. The results obtained are shown together with the results of Example 1, and the former is shown in Table 6 and Figure 6, and the latter is shown in Table 7 and Figure 7.

"Dissolution in 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) were each cut to a size of 10 cm square. A sample piece was prepared. According to the National Standard of the People's Republic of China, “Analytical Method for Sanitary Standards for Shaped Products of Polyethylene, Polystyrene and Polypropylene for Food Packaging” (GB/T5009.60-2003), the sample piece is applied at 25 ° C. The test solution was prepared by immersing in 200 mL of n-hexane for 2 hours. The obtained test solution was separately transferred to an eggplant type flask, and concentrated under reduced pressure until the residual amount became several mL. To the obtained concentrate, a washing liquid obtained by separately washing the inner wall of the flask for concentration under reduced pressure with 5 mL of n-hexane was added, and the dried liquid was dried at 105 ° C in advance. Know the evaporating dish, let it evaporate and dry. Then, after drying at 105 ° C for 2 hours, it was allowed to cool in a desiccator. After cooling, the amount of the evaporating dish before and after the test was determined by weighing, and the amount (mg) of the evaporation residue per 1 L of the test solution was calculated. The results obtained are shown in Table 8.

(examine)

From the results of Table 2 (Fig. 2) and Table 3 (Fig. 3), it is understood that among the various fillers, talc can improve the sealing strength obtained by heating with a hot plate or high frequency induction heating. It can be seen that, especially in the case of Example 1 using talc, a sealing strength of 15.2 N/15 mm width was obtained at 140 ° C in heating of the hot plate, and it was kept more than in the case of Comparative Examples 2 to 6 using other fillers. Excellent sealing strength. In high frequency induction heating, it also maintains superior sealing strength compared to other fillers.

From the results of Table 4 (Fig. 4) and Table 5 (Fig. 5), the following tendency was observed: when the content of talc was gradually increased from 5 parts by mass, the sealing strength was improved (Examples 1 to 6). When the talc is added in an amount of 5 parts by mass or more, the sealing strength at 140 ° C is preferably a sealing strength, that is, 10 N/15 mm or more, and when the talc is added in an amount of 20 parts by mass or more, the talc is added in an amount of 20 parts by mass or more. It is also kept at 5 N/15 mm or more at 100 ° C, and thus is more preferable. In the high-frequency induction heating, by adding 5 parts by mass or more of talc, even at a low power of 125 W, a sealing strength of 7.1 N is maintained, and processing can be performed in a region where power is low.

From the results of Table 6 (Fig. 6) and Table 7 (Fig. 7), it can be seen that if the particle size of the talc becomes small, the sealing strength is improved under relatively high sealing conditions (Examples 1, 7, and 8). ). It can be seen that in the range of the results of this experiment, excellent sealing strength is also obtained under the lower sealing conditions.

Further, as is clear from the results of Table 8, when the content of talc is increased, the amount of n-hexane eluted is decreased. Moreover, as a result of the evaporation residue test using the eluate n-heptane according to the specifications of the Food Sanitation Law, in Examples 1, 5, and 6, the residue in n-heptane was 20 μg/mL or less. The n-heptane dissolution based on the specifications of the Food Sanitation Law also maintains excellent quality.

[Industrial availability]

In the cover material of the present invention in which the substrate layer, the adhesion-promoting coating layer, the stress relaxation layer, and the hot-melt adhesive layer are sequentially laminated, the sealing property and the amount of elution in the organic solvent are considered, and "ethylene" is used. A vinyl acetate copolymer, an adhesion imparting agent, and a hot-melt adhesive in which a wax is blended in a specific amount by a specific amount of talc is used as a hot-melt adhesive for forming a hot-melt adhesive layer. Therefore, even when a material having a higher molecular weight is selected as a material constituting the hot-melt adhesive in order to lower the elution amount of the cover material in the organic solvent, the sealing property may not be lowered. Therefore, it is useful as a cover material for a food container or a pharmaceutical container.

1‧‧‧ substrate layer

2‧‧‧Adhesive coating layer

3‧‧‧stress relaxation layer

4‧‧‧Hot melt adhesive layer

10‧‧‧Cleaning

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 to form a heat of a hot melt adhesive layer The fluxing agent contains 20 to 50% by mass of the ethylene-vinyl acetate copolymer as the component (A), and further contains the following components (B) to (D) of the following parts by mass based on 100 parts by mass of the component (A): (A) 100 parts by mass of the ethylene-vinyl acetate copolymer; (B) 8 to 80 parts by mass of the adhesion imparting agent; (C) 85 to 230 parts by mass of the wax; and (D) 15 to 200 parts by mass of the talc. For example, the cover material of the first item of the patent scope, wherein the talc of the component (D) has the following characteristics (d1) to (d3): (d1) particle size (D50) 0.1 to 50 μm; (d2) apparent density 0.05~ 0.7 g/mL; and (d3) specific surface area of 1.5 to 100 m ² /g. The cover material of claim 1 or 2, wherein the ethylene-vinyl acetate copolymer of the component (A) has the following characteristics (a1) to (a3): (a1) vinyl acetate content of 14 to 41 mass %; (a2) MFR value 5~400g/10min; and (a3) Ficam softening point 25~75 °C. The cover material according to any one of claims 1 to 3, wherein the adhesive imparting agent of the component (B) has the following characteristics (b1): (b1) Softening point 80~150 °C. The cover material of the fourth aspect of the patent application, wherein the adhesive imparting agent of the component (B) is a rosin-based resin. The cover material according to any one of claims 1 to 5, wherein the wax of the component (C) has the following characteristics (c1): (c1) a melting point of 80 to 130 °C. The cover material according to any one of claims 1 to 6, wherein the wax of the component (C) is a synthetic wax. A cover material according to item 7 of the patent application, wherein the synthetic wax is a Fischer-Tropsch wax. The cover material according to any one of claims 1 to 8, wherein the substrate layer has a layer thickness of 5 to 300 μm, the adhesion-promoting layer has a layer thickness of 0.1 to 6.0 μm, and the stress relaxation layer has a layer thickness. It is 6 to 60 μm, and the adhesion amount of the hot-melt adhesive layer is 3 to 40 g/m ² . The cover material according to any one of claims 1 to 9, wherein the base material layer is a metal or alloy film or a resin film, and the adhesion-promoting coating layer is a modified polyolefin-based adhesion-promoting coating agent layer. The ester-based thickening coating agent layer or the polyurethane-based thickening coating agent layer, and the stress relieving layer is a polyolefin-based or polyester-based thermoplastic resin layer. The cover material of claim 9 or 10, wherein the base material layer is an aluminum foil having a thickness of 5 to 50 μm. The cover material of claim 9 or 10, wherein the stress relieving layer is a non-extended polyethylene layer of 10 to 50 μm thick. The cover material according to any one of claims 1 to 12, wherein a printed layer is formed on the outer surface of the substrate layer. A container-packed food comprising a food container having an opening formed with a flange portion, a liquid or solid food contained therein, and a lid member attached to a flange portion formed in an opening of the food container. The cover material is a cover material according to any one of claims 1 to 13, which is attached to the flange portion of the opening from the side of the hot melt adhesive layer.