JP5680444B2 - Heat seal container for packaging - Google Patents

Description

  The present invention relates to a heat seal container mainly applied to containers for packaging foods, and more specifically to a cup-shaped heat seal container for packaging yogurt, jelly, pudding, jam and the like.

  This type of heat-sealed container generally has an intermediate resin layer on the aluminum foil surface side of a base material layer comprising a base material film and an aluminum foil, with respect to a cup-shaped container body made of a polyethylene / paper / polyethylene laminate material. A cover material provided with a heat seal layer, that is, a heat seal layer is used, and the cover material is placed on the upper surface opening of the container body filled with an object to be packaged such as yogurt, and the peripheral portion is the upper edge of the container body. A sealed package is formed by heat-sealing on the flange portion.

  And in such a heat-sealing container, good heat-sealing property, sealing property and appropriate easy peelability for opening are required for the lid material to be used, and at the same time, the non-adhesiveness of the contents, that is, the container It is desired that the contents can be prevented from adhering to the back surface of the inner lid. If the contents adhere to the back of the lid, fingers, clothes, or the surrounding area may be soiled when opened, resulting in waste due to the loss of the contents, or time and effort to peel off the contents, and an unclean feeling. This is to cause a disadvantage such as hosting.

  In view of this, various proposals have been made on lid materials having contents adhesion prevention performance. Especially, the prior proposal technique shown in the following Patent Document 1 forms a porous layer having a three-dimensional network structure of very fine oxide particles such as hydrophobic silica as an adhesion preventing layer on the outer surface of the heat sealing layer. However, it has been attracting attention recently because of its excellent effect in preventing the adhesion of contents.

  However, the above-mentioned prior proposed technique has a heat sealing property because the adhesion preventing layer composed of a fine hydrophobic inorganic fine particle layer becomes a contaminant interposed between the container main body and the heat sealing layer of the lid material in the heat sealing part. There is a risk of damage. In this respect, in the description of the above-mentioned prior art document 1, the hydrophobic inorganic fine particles enter the heat sealing layer that is melted and softened at the time of heat sealing and are buried, so that the heat sealing property is not hindered. The distribution density of the hydrophobic inorganic fine particles in the adhesion preventing layer inevitably tends to vary considerably in the coating process of the fine particle dispersion. For this reason, the sealing strength and the opening strength are greatly different between the portion where the amount of the hydrophobic inorganic fine particles applied is large and the portion where the amount is small, and a new practical problem that the strength distribution is not stable has been derived.

  On the other hand, in order to eliminate or reduce such problems, when the heat sealing temperature is set high, the hydrophobic inorganic fine particles are completely taken into the heat sealing layer. There is a risk that the slightly severe heat effect from the hot plate will increase and the content adhesion prevention effect may be impaired, especially in the vicinity of the heat seal part, that is, in the vicinity of the flange part of the container, Compared to this, there is a concern that it will be significantly lowered. For this reason, the process management at the time of manufacture of a lid | cover material and heat sealing is a little troublesome, and there also existed a difficulty that handling was difficult.

  The inventors of the present invention have conducted extensive experiments and research on the solution to the above problems, and the effects of the composition and the structure of the adhesion preventing layer and the heat sealing layer on the base layer side are also affected. However, the heat seal part on the container body side, that is, the influence of the heat seal layer coated on the upper surface of the upper edge flange part was found to be large, and the present invention was completed based on such knowledge. .

Japanese Patent No. 4348401

  In view of the above problems in the prior art, the present invention is intended to improve them. Specifically, in a scene where a cover material having an adhesion preventing layer made of hydrophobic inorganic fine particles is applied, Improves low-temperature heat-sealability, exhibits stable and good heat-sealing performance, sealing strength, and easy-openability, prevents performance deterioration due to the heat effect of the anti-adhesion layer, and prevents good content adhesion even after heat sealing It aims at providing the heat seal container for packaging which can hold | maintain an effect.

The present invention presents the means of items [1] to [6] as means for achieving the above object.

[1] In a packaging container comprising a combination of a container body and a heat seal lid material,
The heat seal lid is a lid provided with a content adhesion preventing layer mainly composed of hydrophobic inorganic fine particles on the lower surface of the heat sealing layer,
The heat sealing layer is composed of an ethylene-unsaturated ester copolymer, a wax having a melting point of 80 to 130 ° C., and a resin composition having a softening point of 90 ° C. or higher, which contains a tackifier as essential components,
The container body has ethylene-vinyl acetate whose innermost layer of the barrel member has a vinyl acetate content of 1.0 to 10% by weight , a melt flow rate at 190 ° C. of 10 g / 10 min or more, and a melting point of 85 to 115 ° C. A heat seal container for packaging, comprising a copolymer.

[2] The packaging heat-sealing container according to [1], wherein the ethylene-vinyl acetate copolymer has a melt flow rate at 190 ° C. of 15 g / 10 min or more.

[3] The packaging heat-sealing container according to [1], wherein the ethylene-vinyl acetate copolymer has a melting point of 90 to 105 ° C.

[4] The heat-sealing container for packaging according to any one of [1] to [3] , wherein the hydrophobic inorganic fine particles in the content adhesion preventing layer are hydrophobic silica .

[5] The packaging heat seal container according to [4] , wherein the hydrophobic inorganic particles are hydrophobic silica having an average particle diameter of 1 to 5,000 nm .

[6] The packaging heat-sealing container according to any one of [1] to [5] , wherein the content adhesion preventing layer is composed of a mixed composition of hydrophobic inorganic fine particles and thermoplastic resin fine particles .

  In the configuration of the above item [1], the present invention is such that a content adhesion preventing layer made of hydrophobic inorganic fine particles such as hydrophobic silica is formed on the outer surface of the heat sealing layer. It has a unique excellent content adhesion prevention performance as described in the above.

On the other hand, the lid material uses a resin composition having a softening point of 90 ° C. or higher, which contains an ethylene-unsaturated ester copolymer, a wax having a melting point of 80 to 130 ° C., and a tackifier as essential components for the heat sealing layer. In the relative relationship with this, the innermost layer of the body member on the container body side where the lid member is heat sealed, that is, the upper surface layer of the flange part or the lip part of the peripheral edge of the opening part of the container body to be heat sealed, A relatively high fluidity ethylene-vinyl acetate copolymer having a vinyl acetate content of 1.0 to 10% by weight , a melt flow rate at 190 ° C. (MFR: compliant with JIS K7210) of 10 g / 10 min or more, and a melting point of 85 to 115 ° C. By being comprised with a polymer, the stable favorable heat seal performance can be expressed. In other words, even if there is some variation in the density distribution of hydrophobic inorganic fine particles in the adhesion prevention layer due to coating unevenness, a sealed state in which the sealing strength, sealing strength, and opening strength are stable over the entire circumference of the heat seal portion is realized. it can. Such stable heat-sealing performance is expressed by the low-temperature heat-sealing property on the container body side and the fluidity of the resin compared to this type of heat-sealing container that has been generally adopted in the past. The hydrophobic inorganic fine particles of the anti-adhesion layer intervening between the main body and the heat-sealing layer of the lid material can be sufficiently taken into the innermost molten resin layer on the container main body side during heat sealing. As a result, it is considered that the heat sealing performance by the heat sealing layer is not greatly impaired.

  In addition, the low temperature heat sealability of the innermost layer for heat sealing on the container body side can be improved, so that the low temperature heat sealability of the heat sealing layer on the lid material side can be relatively compensated, resulting in prevention of adhesion. The heat resistance of the layer can be improved, the thermal stability of the adhesion preventing performance can be improved, and the above excellent content adhesion preventing effect can be maintained well even after use of sealing on the container body. That is, by improving the low temperature heat sealability, it is not necessary to apply an excessively high heat load to the lid during heat sealing. In addition, a heat sealing layer on the lid side, for example, a wax having a relatively high melting point is contained in the component. By using it, it becomes possible to increase the softening point and to suppress or prevent the heat sealing layer from being melted early and excessively and exhibiting high fluidity during heat sealing. That is, melting of the heat sealing layer can be somewhat delayed during heat sealing, and can be suppressed. As a result, the hydrophobic inorganic fine particles of the anti-adhesion layer unintentionally sink into the heat sealing layer, or the molten component of the heat sealing layer enters the gaps between the fine particles by capillary action and fills the gaps. Can be prevented. Therefore, an extreme decrease in the exposed area of the hydrophobic surface of the fine particles can be prevented, and a good content adhesion preventing effect can be maintained even after receiving a severe heat history due to heat sealing.

Moreover, as described in the above item [2] , the above effect can be achieved even better by using an ethylene-vinyl acetate copolymer having a melt flow rate at 190 ° C. of 15 g / 10 min or more. .

Further, by adopting a low melting point ethylene-vinyl acetate copolymer having a melting point of 90 to 105 ° C. as described in the above item [3] , the effect of the invention in the above item [1] is more reliably and satisfactorily improved. Can be achieved.

In addition, as described in the above item [4] , when hydrophobic silica is selectively used for the hydrophobic inorganic fine particles, an excellent content adhesion preventing effect is achieved with a relatively inexpensive material that is easily available from the market. be able to.

In addition, by using hydrophobic silica having an average particle size as described in the above item [5] , the above-described content adhesion preventing effect can be obtained by using a relatively inexpensive material that is easily available from the market. This can be realized more reliably.

Furthermore, as described in the above item [6] , the adhesion preventing layer is made of a mixed composition of hydrophobic inorganic fine particles, which are main components, and thermoplastic resin fine particles. Compensates the bonding force between hydrophobic inorganic fine particles and improves adhesion to the heat sealing layer, and prevents the unintentional particles from falling off and the anti-adhesion layer from peeling off. Preventive effect can be maintained. In addition, the inclusion of the above-mentioned thermoplastic resin fine particles in the anti-adhesion layer acts to supplement the heat sealability of the heat seal layer, and it is good and stable against the container body of the lid regardless of the presence of hydrophobic inorganic fine particle groups. Therefore, it is possible to ensure a suitable heat sealing property, that is, a suitable sealing property in which easy opening and sealing properties are harmonized.

FIG. 1 is a cross-sectional view showing an outline of a laminated structure of a content adhesion preventing lid material according to the present invention. FIG. 2 is a cross-sectional view showing components of the heat seal container according to the present invention.

  The heat-sealed container according to the present invention is used for hermetic packaging of mainly viscous fluid foods such as yogurt, jam, jelly, and the like, and a cup-shaped container body (B) and a sheet for sealing the same It consists of a combination with a cover material (A).

  First, for convenience of explanation, the configuration of the lid member (A) will be described first.

(Contents adhesion prevention lid material)
As shown in FIG. 1, the lid material (A) used in the present invention comprises a base material layer (1) comprising a base film layer (2) and a metal foil layer (3), and the base material layer (1). A heat sealing layer (5) is provided via an intermediate resin layer (4) on the outer surface of the metal foil (3) side of 1), that is, the surface facing the inside of the container body when the lid is used. The above laminated structure is the same as that of the conventional lid, and the laminated body including the base material layer (1) and the heat sealing layer (5) will be referred to as a “lid body” here.

  The content adhesion preventing lid material according to the present invention further has an adhesion preventing layer (6) on the outer surface of the heat sealing layer (5) of the lid body.

  The base film layer (2) is disposed on the front side of the packaging container, and the material thereof is a single layer or composite film such as polyester, polyethylene, polypropylene, polyamide, polycarbonate, polyvinyl chloride, cellulose acetate, cellophane, etc. Or what laminated these films on paper etc. can be illustrated. The base film layer (2) is usually appropriately printed (7) to impart design properties.

  The metal foil layer (3) imparts gas barrier properties, light shielding properties, etc., and aluminum foil is often used. In particular, in the case of a lid for a yogurt container, an aluminum foil having a thickness of about 5 to 50 μm is preferably used in order to satisfy light shielding properties and light weight. Moreover, a general adhesive agent is used for lamination | stacking adhesion | attachment with a base film layer (2).

  In addition, as a base material layer (1), it is also possible to use the metal vapor deposition film which vapor-deposited metals, such as a silica and an alumina, to the base film layer (2), without using a metal foil layer (3). .

  The intermediate resin layer (4) is interposed between the base material layer (1) and the heat sealing layer (5), and imparts a predetermined rigidity and cushioning property at the time of heat sealing to the lid material. Provided as needed. Generally, olefin resin such as polyethylene, polypropylene, ethylene (meth) acrylic acid copolymer, ethylene (meth) acrylic acid ester copolymer, polyamide, polyester, polycarbonate, polyvinyl chloride, etc. having a thickness of 5 to 40 μm Used.

  The heat sealing layer (5) must have good adhesion to the intermediate resin layer (4) and the container side. In a preferred embodiment of the present invention, the heat-sealing layer contains an ethylene-unsaturated ester copolymer, a wax, and a tackifier as essential components, and further contains an anti-blocking agent, an antioxidant or the like as necessary. It consists of a resin composition containing an agent as an optional component.

  Conventionally, the resin composition that has been generally used generally has a relatively low melting point as the essential component wax. For example, paraffin wax having a melting point of about 65 ° C. is most commonly used, and a polyethylene wax having a relatively high melting point of at most about 75 ° C. has been used.

  Further, the resin composition generally has a softening point of about 65 ° C to 90 ° C.

  Under such a technical background, in a preferred practice of the present invention, as a wax that is one of the essential components of the resin composition, a melting point of 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. Using the above, it is desirable that the softening point of the resin composition is 90 ° C. or higher, preferably 100 ° C. or higher. By using such a resin composition containing a relatively high melting point wax and having a high softening point for the heat sealing layer, the hydrophobic inorganic material additionally formed on the outer surface side of the heat sealing layer as described above. It is possible to further improve the water repellency of the anti-adhesion layer by the fine particles, and thus the thermal stability of the anti-adhesion property.

  However, use of a wax having a melting point that is too high may increase the viscosity of the resin composition and reduce processability, and may impair stable and good heat sealability of the heat sealing layer. The one below ℃ should be used. It is preferable to use a material having a melting point of 120 ° C. or lower, more preferably 110 ° C. or lower.

  Furthermore, the softening point of the resin composition can be raised by using a component having a high melting point or softening point as the other component other than the wax, but the melting point of the wax is as described above. As described above, by setting the softening point of the resin composition to 90 ° C. or higher, the desired effect can be realized most simply and reliably.

  Even if the softening point of the resin composition is increased by increasing the melting point of the resin, the low-melting wax having high fluidity is easily dissolved and enters between the hydrophobic fine particles of the anti-adhesion layer to reduce the anti-adhesion effect. It is difficult to expect a sufficient improvement effect on the thermal stability of the adhesion prevention effect.

  Moreover, since the use of a resin composition having an excessively high softening point may impair the workability of the heat sealing layer and the stable good heat sealability, a resin composition having a softening point of 160 ° C. or lower should be used. . The softening point is preferably 140 ° C. or lower, more preferably 120 ° C. or lower.

  The ethylene-unsaturated ester copolymer, which is the main component of the heat-sealing layer, includes unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, and methyl methacrylate, vinyl acetate as the unsaturated ester monomer. Vinyl esters and the like can be used, and among them, vinyl acetate and methyl methacrylate are particularly preferable.

  The ethylene-unsaturated ester copolymer preferably has a melting point in the range of 70 to 100 ° C. When the temperature is less than 70 ° C., the heat stability of the adhesion preventing effect of the adhesion preventing layer may be lowered because the sealing temperature of the heat sealing layer is too low. On the contrary, when the temperature exceeds 100 ° C., the low-temperature heat sealing property is hindered, the sealing speed becomes slow, and the working efficiency at the time of actual content filling sealing is lowered. Most preferably, the melting point is in the range of 75 to 95 ° C.

  Examples of the wax that is the other main component in the resin composition include paraffin wax, microcrystalline wax, montan wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, carnauba wax, and modified wax. Is a polyethylene wax.

  Further, tackifiers include rosin, rosin derivatives (hydrogenated rosin, disproportionated rosin, rosin ester), alicyclic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, or their water attachments. And terpene resins (α-pinene, β-pinene), etc., but it is preferable to use an aromatic petroleum resin with water attached.

  In addition, the composition ratio of each component of the resin composition needs to be set in consideration of the softening point, melt viscosity, low temperature heat sealability, heat seal strength, open strength, etc. The saturated ester copolymer is set to 30 to 50 wt%, preferably 35 to 45 wt%, the wax is set to 30 to 50 wt%, preferably 35 to 45 wt%, and the tackifier is set to 5 to 25 wt%, preferably 15 to 25 wt%. As a result, it is possible to achieve good heat sealing properties, sealing properties, suitable easy peelability for opening, and improved thermal stability of content adhesion preventing effect. That is, sufficient sealing strength cannot be obtained with a resin composition in which the blending amount of the ethylene-unsaturated ester copolymer is less than 30 wt%. On the other hand, if it exceeds 50 wt%, the sealing strength becomes too high and the easy-openability of the sealing lid is impaired. On the other hand, when the blending amount of the wax is less than 30 wt%, the coating suitability (processing suitability) of the hot melt resin composition is impaired and the easy-openability is impaired. On the other hand, if it exceeds 50 wt%, sufficient seal strength cannot be obtained. Moreover, if the compounding amount is less than 5 wt%, it is difficult to obtain a sufficient seal strength. Conversely, if it exceeds 25 wt%, the adhesion preventing effect of the adhesion preventing layer may be reduced. There is.

  The thickness of the heat-sealing layer is not particularly limited, but is generally about 3 to 100 μm in thickness from the viewpoint of cost, sealing performance, productivity, etc., and preferably 10 to 50 μm. It is good to be in the range.

  The adhesion preventing layer (6) is composed of hydrophobic inorganic fine particles or a mixed composition of thermoplastic resin fine particles and hydrophobic inorganic fine particles.

  The hydrophobic inorganic fine particles play a dominant role in the content adhesion prevention performance of the lid material, and the material is not particularly limited as long as it is made of a hydrophobic substance having a surface energy of 20 mN / m or more. Specific examples include hydrophobic inorganic fine particles such as hydrophobic silica, alumina, calcium oxide, calcium carbonate, calcium sulfate, and calcium silicate. Of these, the use of hydrophobic silica or alumina is preferred from the viewpoint of hydrophobic performance, cost, availability of ultrafine particle materials from the market, and the like. As the hydrophobic silica, any of dry process silica and wet process silica can be suitably used. The average particle diameter of the hydrophobic inorganic fine particles should be in the range of 1 to 5,000 nm. Ultrafine particles having an average particle size of less than 1 nm are difficult to obtain from the market and are disadvantageous in terms of cost. On the other hand, if the average particle size exceeds 5,000 nm, the heat sealability may be impaired, and the adhesion preventing effect may be reduced, which is not suitable. A preferred average particle size is in the range of 3 to 1000 nm, particularly preferably 3 to 500 nm.

  The material of the thermoplastic resin fine particles is not particularly limited, but the thermoplastic resin has good compatibility with the heat sealing layer (5) and the hydrophobic inorganic fine particles, and has a good adhesion to the surface layer of the container body. It is desirable to select and use those containing at least the thermoplastic resin as a main component. Examples of such thermoplastic resins include homopolymers such as vinyl acetate resins, polyolefin resins, polyester resins, acrylic resins, styrene resins, or two or more types of copolymers. Since it is a thermoplastic resin, the use of waxes having a low molecular weight, which has been conventionally used as an anti-adhesion agent for lids, is excluded. As a particularly preferable type of thermoplastic resin, the most preferable result can be obtained by using a thermoplastic resin containing at least one or more olefinic resins as a main component.

  More specifically, specific examples of the olefin resin include polyethylene, polypropylene, and an ethylene-unsaturated ester copolymer. Examples of the ethylene-unsaturated ester copolymer include an ethylene-vinyl acetate copolymer, a vinyl acetate-vinyl chloride copolymer, and a vinyl acetate-vinyl chloride-maleic acid copolymer.

  The thermoplastic resin is used in a state where it is pulverized into fine particles or dissolved in a solvent and then precipitated as fine particles. The average particle diameter of the thermoplastic resin fine particles is preferably 1 nm to 5000 nm. If the thickness is larger than 5000 nm, it tends to fall off from the heat sealing layer, which is not preferable. If it is smaller than 1 nm, there arises a problem that it is difficult to obtain industrially. A preferable average particle diameter is 50 nm to 1000 nm, and more preferably 100 nm to 500 nm.

  The thermoplastic resin fine particles can be pulverized by a general plastic pulverizer, but it is preferable to use a pulverizer equipped with a cooling means capable of maintaining a low temperature so as not to soften and melt the resin during pulverization.

  Next, a preferable blending ratio of the thermoplastic resin fine particles and the hydrophobic fine particles is 0 to 50% by weight: 100 to 50% by weight in a weight ratio of the thermoplastic resin fine particles (solid content): the hydrophobic inorganic fine particles. If the blending amount of the hydrophobic inorganic fine particles is preferably 50% by weight or more, relatively good adhesion preventing performance can be obtained. The blending of the thermoplastic resin fine particles is preferable in that the sealing property with the container and the heat sealing property are improved.

  In the production of the anti-adhesion lid material used in the present invention, the method for forming the anti-adhesion layer (6) also has a significant influence on the content adhesion prevention performance of the lid material.

  The anti-adhesion layer (6) is formed by preparing a coating liquid by uniformly dispersing a predetermined amount of hydrophobic inorganic fine particles or thermoplastic resin fine particles and hydrophobic inorganic fine particles in a liquid dispersion medium. It is performed by applying to the outer surface of the heat sealing layer and drying.

  The coating liquid is prepared by dispersing thermoplastic resin fine particles and hydrophobic inorganic fine particles using water or an organic liquid dispersion medium to obtain a colloidal solution having a predetermined concentration. It is preferable to use a dispersion medium. Of these, the use of alcohols is preferred, and the use of methanol or ethanol is particularly preferred from the standpoints of cost, safety, water repellency, and the like. It has been found that when a solvent having no polar group, such as toluene, is used, the anti-adhesion performance is impaired. Although the mechanism is still unclear, it is presumed that the wax in the heat-sealing layer is partially dissolved by toluene and the adhesiveness with the hydrophobic silica particles becomes too high.

  Any known method can be employed for coating the coating liquid. For example, a gravure coating method, spraying, a bar coating method, etc. can be arbitrarily adopted.

The coating amount of the coating solution may be set according to the thickness of the adhesion preventing layer, but is preferably about 0.1 to 5.0 g / m ^{2 by} weight after drying, and preferably 0.2 to 1.2 g / m. ² is more preferable, and it is optimal to set it in the range of 0.4 to 0.8 g / m ² . If it is less than 0.1 g / m ² , the content adhesion preventing effect may be insufficient. On the other hand, if it exceeds 5.0 g / m ² , the cost is increased and there is a risk that the fine particles may fall off.

  The drying process after application is also an important factor. Naturally, it may be naturally dried, but in order to improve productivity and adhesion to the heat sealing layer, it should be dried by heating. In this case, the drying conditions are a temperature of 80 to 140 ° C., a time of 5 to 30 seconds. Should be set in the range. If the temperature is lower than the lower limit of 80 ° C., the drying process takes time, and if the time is less than 5 seconds, the drying becomes insufficient, and the adhesion preventing layer is likely to be partially peeled off or dropped during subsequent handling. On the other hand, when the drying temperature is set to a high temperature exceeding 140 ° C., or the time is set to a time exceeding 30 seconds, especially when hydrophobic dry silica is used for the hydrophobic inorganic fine particles, the hydrophobicity of the hydrophobic inorganic fine particles. The water repellency tends to be impaired.

(Container body)
As shown in FIG. 2, the container body (B) includes a body member (10) and a bottom member (10) made of a laminated material in which a paperboard is used as a base material (12) and a thermoplastic resin layer (13) (14) is coated on both surfaces thereof. 11) and formed into a bottomed cup shape. A trunk | drum member (10) has a flange part (10a) by which a surrounding wall is formed in a taper shape and a cover material (B) is heat-sealed in an upper end opening edge. The resin layer (13) on the inner side of the body member (10) forms the innermost layer (13A) of the body member (10), and therefore covers the upper surface of the flange portion (10a) and covers it. It serves as a heat seal layer for the material (A).

  The resin layers (13) and (14) have a thickness of about 40 μm for the inner resin layer (13) forming the innermost layer (13A) and about 20 μm, which is about half of the outer resin layer (14). It is normal to be formed.

  By the way, in this invention, the content adhesion prevention lid | cover material (A) of the specific structure which has the adhesion prevention layer (6) which has the above hydrophobic fine particles as a main component as a sealing lid | cover material (A) is used. In particular, the material of the innermost resin layer (13) of the body member (10) on the container body (A) side is specially improved.

That is, the innermost layer (13A) of the body member (10) is an ethylene-vinyl acetate copolymer having a vinyl acetate content of 1.0 to 10% by weight , and the melt flow rate at 190 ° C. is 10 g / 10 min or more. The resin layer (13) is made of an ethylene-vinyl acetate copolymer.

When the vinyl acetate content is less than 1.0% by weight , the low temperature heat sealability is poor, and a sufficient improvement effect of the heat seal performance as the main point of the present invention cannot be expected. On the other hand, if it exceeds 10% by weight , new problems such as stickiness and odor of the ethylene-vinyl acetate copolymer are derived, and it is disadvantageous in that it is difficult to adjust the sealing strength and the opening strength. The preferred vinyl acetate content is in the range of 3-8% by weight.

  On the other hand, the ethylene-vinyl acetate copolymer used for the innermost layer (13A) needs to have a relatively high fluidity. Specifically, the melt flow rate (MFR) at 190 ° C. needs to be at least 10 g / 10 min. When the MFR is less than 10 min, the hydrophobic inorganic fine particles of the adhesion preventing layer (6) cannot be sufficiently and quickly incorporated into the innermost resin layer (13) at the time of heat sealing, and the effect of improving the heat sealing performance is achieved. On the other hand, if the melt flow rate is too high, such as exceeding 50 g / 10 min, in addition to the decrease in molding processability during extrusion coating onto paperboard, the addition during heat sealing is not possible. This is not preferable because the resin flows too much under pressure and causes problems such as failure to obtain a good seal. A suitable lower limit of the melt flow rate is 15 g / 10 min or more, more preferably 20 g / 10 min or more.

On the other hand, it is desirable to use the ethylene-vinyl acetate copolymer having a melting point (DSC method: conforming to JIS K6863) of 85 to 115 ° C. For those below 85 ° C,
Since the vinyl acetate content is increased and stickiness, odor problems, and problems such as difficulty in adjusting the sealing strength and opening strength may occur in the same manner as described above, it is not suitable for use. On the other hand, when the melting point is higher than 115 ° C., the low temperature heat sealability is hindered, and it is necessary to increase the temperature at the time of heat sealing, and the adhesion preventing layer on the lid (A) side receives an unfavorable heat history. Therefore, the adhesion preventing performance of the lid material (A) is impaired particularly in the peripheral area of the flange portion (10a) of the container body (B). A preferable melting point range of the ethylene-vinyl acetate copolymer to be used is 90 to 105 ° C.

  In the above description, the case of using a paper cup in which resin layers are laminated on both the inner and outer surfaces of a cardboard base material has been described as the container body. However, a cup made of synthetic resin such as polystyrene, polypropylene, or polyethylene may be used. In that case, for example, when vacuum forming a container from a sheet, a resin layer similar to the resin layer (13) used for the innermost layer (13A) of the body member (10) described above is used as a heat seal layer on the container inner surface side. An example of the method for forming the coating is the uppermost layer of the body member (10) described above on the upper surface of the flange portion where the lid (A) is heat-sealed at the upper end of the synthetic resin container body. A resin layer similar to the used resin layer (13) may be formed as a heat seal layer.

(Sealed package)
In the heat seal container according to the present invention, the container body (13) is filled with contents such as yogurt and jam, and then the lid (A) is heat sealed to the flange (10a) at the periphery of the upper end opening. This constitutes a sealed package as a product.

  Next, in order to confirm the effect of the present invention, various examples will be shown in comparison with comparative examples.

(Preparation of lid material (A))
A polyethylene terephthalate film having a thickness of 12 μm was used as the substrate film (2), and an aluminum foil (3) having a thickness of 30 μm was bonded to one surface thereof with a polyurethane-based dry laminate adhesive to obtain a substrate layer (1).

  Next, an intermediate resin layer (4) is formed by laminating and bonding a 20 μm thick polyethylene film to the surface of the base material layer (1) on the aluminum foil (3) side using the same adhesive as described above. A heat sealing layer (5) was formed on the outside by a gravure coating method. The laminate of the base material layer (1) / intermediate resin layer (4) / heat sealing layer (5) obtained in this way was used as the lid body.

Here, as the heat sealing layer (5), a resin composition having the following material composition was applied and formed at a coating rate of 18 g / m ² .

40 parts by weight of wax
Polyethylene wax with a melting point of 104 ° C .: 40 parts by weight Ethylene-vinyl acetate copolymer (vinyl acetate content: 26%), melting point: 76 ° C.
Tackifier: 20 parts by weight Petroleum-based hydrogenated resin

  Next, an adhesion preventing layer (6) having various compositions and application amounts as shown in Table 1 below was formed on the outer surface of the heat sealing layer (5) of the lid body by using the following materials.

Hydrophobic inorganic fine particles (SP)
SP (I): Hydrophobic dry silica, primary particle average particle diameter 7 nm
SP (II): Hydrophobic wet silica average particle diameter 2700 nm
SP (III): Hydrophobic wet silica average particle size 3900 nm

Thermoplastic resin fine particles (MP)
MP (I): ethylene-vinyl acetate copolymer (vinyl acetate 20%, ethylene
80%, average particle size 100nm)
MP (II): Vinyl acetate-vinyl chloride copolymer (20% vinyl acetate, vinyl chloride
80%, average particle size 100nm)

  Here, the adhesion preventing layer (6) is formed by coating each of the hydrophobic inorganic fine particles (SP) or both of the hydrophobic inorganic fine particles (SP) and the thermoplastic fine particles (MP) uniformly in ethanol. A liquid was prepared, and the various coating liquids were applied to the outer surface of the heat sealing layer (5) of the lid main body by a gravure coating method, and then forcedly dried under a drying condition of 100 ° C. × 15 seconds.

(Preparation of container body (B))
Using a laminated material with cardboard as the base material (12) and coating the resin layers (13) and (14) on both the inside and outside, combine the bottom member (11) with the bottom of the barrel member (10) molded into a tapered cylinder A cup-shaped paper container body (B) was prepared.

Here, the outer surface resin layer (14) of the trunk member (10) and the outer surface resin layer of the bottom member (11) are both 20 μm thick with polyethylene having a density of 0.922 g / cm ³ , and the bottom member (11 The inner resin layer of) was also made of the same polyethylene with a thickness of 40 μm.

  In contrast to the above, for the resin layer (13) on the inner surface side constituting the innermost layer (13A) of the body member (10), the following various ethylene- having different vinyl acetate content, melt flow rate, and melting point: It consisted of a vinyl acetate copolymer. The thickness of each resin layer (13) was set to 40 μm.

Ethylene-vinyl acetate copolymer (EVA)
Vinyl acetate content MFR (g / 10 min: 190 ° C) Melting point (° C)
EVA1: 10 20 91
EVA2: 6 17 101
EVA3: 1.5 10 113
EVA4: 15 2 89
EVA5: 20 14 75

(Evaluation test)
(1) Adhesion prevention performance with container seal Sample No. After putting 125 g of aloe yogurt (Trademark “Morinaga Aloe Yogurt” manufactured by Morinaga Milk Industry Co., Ltd.) into a container of 1 to 3 and 5 to 9 (caliber 88 mm) and a lid, 140 ° C. × 90 kgf × The lid material was heat-sealed on the flange surface under a sealing condition of 1.0 sec. On the other hand, under the same sealing conditions as above, sample No. For No. 4, the lid material was heat-sealed on the flange surface under sealing conditions of 150 ° C. × 90 kgf × 1.0 sec.

Subsequently, each of these samples was stored upside down for 12 hours, and then opened to evaluate the state of attachment of yogurt on the back surface of the lid.
◎ ・ ・ ・ No yogurt adhesion ○ ・ ・ ・ Slight adhesion on the flange is observed × ・ ・ ・ Adhesion on the flange is observed

(2) Sealability (2) -1) Sealing strength Sample No. The lid material was heat-sealed on the flange surface of the container body under the sealing conditions of 140 ° C. × 90 kgf × 1.0 sec using a combination of the containers 1 to 9 (caliber 88 mm) and the lid material.

  The “sealing strength” is measured according to the sealing strength test method of the ministerial ordinance (Ministry of Health and Welfare Ordinance No. 17 of April 16, 1979) relating to the component standards of milk and dairy products, and the sealing strength is 13.3 kPa or more. Were determined as pass (◎) and less than 13.3 kPa as reject (x).

(2) -2) Opening strength Next, the “opening strength” is the above-mentioned heat-sealed lid material is pulled at an elevation angle of 45 ° and a speed of 100 mm / min, and the maximum load at the time of opening is defined as the opening strength (N). . And the range of the optimal opening strength was 8-15N, and the thing in this range was evaluated as a pass ((circle) mark), and the thing outside the range was evaluated as a disqualification (x mark).

(2) -3) Heat seal strength Sample No. A combination of containers 1 to 9 (caliber 88 mm) and a lid material was cut into a width of 15 mm, and both were heat-sealed under sealing conditions of 150 ° C. × 0.2 MPa × 1.0 sec. Next, the lid member was pulled in the direction of 180 ° at a speed of 100 mm / min, and the maximum load at the time of peeling was defined as the heat seal strength.

And, the heat seal strength (peeling resistance / sealing property of the cover material) in the cover material as it is without the adhesion prevention layer is used as a reference value, and the rate of decrease or increase in heat seal strength is as follows: It was judged and evaluated.
◎ ・ ・ ・ Reduced strength or increase less than 10% ○ ・ ・ ・ Reduced strength or increase 10% to less than 20% × ・ ・ ・ Reduced strength or increased 20% or more

  Table 2 shows the results of the evaluation tests (1) to (2).

  As shown in the test results of “Liquid adhesion prevention performance” in Table 2, in the heat seal container according to the present invention, the cover material after receiving a rather severe heat history due to the heat seal of the cover material to the container body. Also, almost no adhesion of yogurt to the back surface of the lid was observed. This means that the contents on the back side of the lid material are sealed against the contents even after the lid material is heat sealed in a container filled with contents containing viscous liquid components such as yogurt, pudding, and jelly. It shows that the adhesion prevention effect of an object can be maintained satisfactorily. In addition, as shown in the results of the “sealability” test, the presence of the anti-adhesion layer did not significantly impair the sealing strength, heat sealability (seal strength) and easy-openability, and was excellent in their stability. I was able to confirm that it was possible.

A ... Lid material B ... Container body 1 ... Base material layer 2 ... Base material film 3 ... Metal foil 5 ... Heat sealing layer 6 ... Adhesion prevention layer 10 ... Body member 10a ... Flange 11 ... Bottom member 12 ... Cardboard 13 ... Inner surface side resin layer 13A ... Innermost layer

Claims (6)

In a packaging container consisting of a combination of a container body and a heat seal lid,
The heat seal lid is a lid provided with a content adhesion preventing layer mainly composed of hydrophobic inorganic fine particles on the lower surface of the heat sealing layer,
The heat sealing layer is composed of an ethylene-unsaturated ester copolymer, a wax having a melting point of 80 to 130 ° C., and a resin composition having a softening point of 90 ° C. or higher, which contains a tackifier as essential components,
The container body has ethylene-vinyl acetate whose innermost layer of the barrel member has a vinyl acetate content of 1.0 to 10% by weight , a melt flow rate at 190 ° C. of 10 g / 10 min or more, and a melting point of 85 to 115 ° C. A heat seal container for packaging, comprising a copolymer. The packaging heat seal container according to claim 1, wherein the ethylene-vinyl acetate copolymer has a melt flow rate at 190 ° C of 15 g / 10 min or more. The heat-sealing container for packaging according to claim 1, wherein the ethylene-vinyl acetate copolymer has a melting point of 90 to 105 ° C. The packaging heat seal container according to any one of claims 1 to 3, wherein the hydrophobic inorganic fine particles in the content adhesion preventing layer are hydrophobic silica. The packaging heat seal container according to claim 4, wherein the hydrophobic inorganic particles are hydrophobic silica having an average particle diameter of 1 to 5,000 nm. The packaging heat seal container according to any one of claims 1 to 5, wherein the content adhesion preventing layer is composed of a mixed composition of hydrophobic inorganic fine particles and thermoplastic resin fine particles.

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