JP5102882B2 - Content adhesion prevention lid - Google Patents

Description

  The present invention relates to a heat-sealing lid material mainly applied to containers for packaging foods, and more specifically, to prevent adhesion of contents applied to cup-shaped containers for packaging such as yogurt, jelly, pudding, jam, etc. It is related with the lid | cover material provided with.

  This type of heat sealing lid material is generally provided with a heat sealing layer, that is, a heat sealing layer, on an aluminum foil surface side of a base material layer made of a laminate of a base material film and an aluminum foil via an intermediate resin layer. A sealed package is formed by covering the top opening of a cup-shaped container body filled with an object to be packaged such as yogurt and heat-sealing the peripheral part on the upper edge flange part of the container body. It has been.

  Therefore, in such a lid material, good heat-sealing property, sealing property and appropriate easy peelability for opening are required, and at the same time, the non-adhesiveness of the contents, that is, the back surface of the lid material on the inner surface side of the container It is desirable that the content can be prevented from adhering to the surface. 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.

  Therefore, conventionally, various proposals as shown in Patent Documents 1 to 6 below have been made for cover materials having a content adhesion prevention performance.

JP 2002-37310 A JP 2007-153385 A JP 2008-1000073 A JP 2009-73523 A JP 2009-241943 A Japanese Patent No. 4348401

  The prior arts shown in Patent Documents 1 to 3 are those in which a nonionic surfactant or a hydrophobic additive having an adhesion preventing effect, a wax, or the like is added to the heat sealing layer on one side of the base material. Although the layer itself is intended to impart anti-adhesion performance, all of them are still unsatisfactory in terms of the expected content-preventing effect.

  Further, the prior arts of Patent Documents 4 to 5 are such that a content adhesion preventing layer is additionally formed on the outer surface (surface on the container side) of the heat sealing layer. The adhesion preventing layer is made of wax, And a composition with a solid fine particle filler dispersed in the composition. These prior arts are further improved in the content adhesion preventing effect as compared with the prior arts of Patent Documents 1 to 3, but they are still not sufficient, and in addition, a filler is dispersed in the wax. Therefore, there is a concern that the heat-sealing property of the heat-sealing layer is adversely affected and the sealing property tends to be unstable.

  Further, the prior art disclosed in Patent Document 6 is to form a porous layer having a three-dimensional network structure with very fine oxide particles such as hydrophobic silica on the outer surface of the heat sealing layer.

  Although this prior proposal technique can exert a very excellent effect in terms of content adhesion prevention effect, the adhesion prevention effect is impaired when the adhesion prevention layer is inferior in heat resistance and receives an undesirable heat history. was there. That is, as the fine hydrophobic particles, ultrafine hydrophobic oxide fine particles having an average primary particle diameter of 3 to 100 nm, typically synthetic silica, especially silica fine particles produced by a dry method, are used. When this is applied to the content adhesion prevention layer of the cover material having the most common hot-melt type heat sealing layer, heating is performed at the time of drying after application of the fine particle dispersion in the formation process of the adhesion prevention layer. If the temperature is too high or the drying time is long, the content adhesion preventing effect is significantly impaired. In addition, there is a difference in the drying state due to uneven application of the fine particle dispersion, and the area with a small amount of application is heated excessively until the portion with a large amount of application is dried. There was a risk of partial damage. Furthermore, even when filling and sealing containers such as yogurt, jelly, and pudding, the effect of preventing the adhesion of the contents may be impaired due to the slight thermal effect that the lid receives from the hot plate during standby or heat sealing. In particular, there has been a concern that the effect of preventing the adhesion of contents in the vicinity of the heat seal portion, that is, in the vicinity of the flange portion of the container, may be significantly reduced as compared with other portions. 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 existed a difficulty that handling was difficult.

  The inventors of the present invention have conducted extensive experiments and research to elucidate the cause of the performance degradation problem due to the thermal effect of the adhesion preventing layer. Rather than being caused by this, it has been found that there is one important cause in the composition of the heat sealing layer that is the underlayer.

  That is, the above-described decrease in heat resistance, that is, the decrease in thermal stability of the anti-adhesion effect is due to heat received during drying, heat received directly from the hot plate during filling sealing, radiant heat received from the hot plate during standby, etc. When the hot-melt adhesive in the heat-sealing layer melts due to the influence of fine particles, fine hydrophobic oxide fine particles sink into the hot-melt adhesive, or the melted component of the hot-melt adhesive capillarizes in the gaps between the fine particles. In order to fill the space between the particles and reduce the water-repellent surface area, it has been found that the content adhesion preventing effect cannot be obtained sufficiently, and the present invention has been completed based on such knowledge. It was possible.

  In view of the above-mentioned problems in the prior art, the present invention is intended to further improve them, more specifically, good heat sealability, sealability, and appropriate easy peelability for opening. At the same time, it is an object of the present invention to provide a new improvement technique that exhibits a content adhesion prevention performance excellent in thermal stability.

  The present invention presents the means of the following items [1] to [9] for the content adhesion preventing lid material as means for achieving the above object. Here, the softening point was determined by the ring and ball method (in accordance with JIS K6863 “soft melt adhesive softening point test method”), and the melting point was determined by the DSC method (in accordance with JIS K7121 “plastic transition temperature measurement method”). It is.

[1] Used for packaging containers for foods having at least a base material layer and a heat sealing layer, and having an outer surface of the heat sealing layer provided with a content adhesion preventing layer containing hydrophobic inorganic fine particles as a main component. In heat seal lid materials,
The heat sealing layer is composed of a resin composition containing an ethylene-unsaturated ester copolymer, a wax, and a tackifier as essential components,
The content adhesion preventing lid material, wherein the resin composition has a softening point of 90 ° C or higher and the wax has a melting point of 80 ° C or higher.

  [2] The content adhesion preventing lid material according to [1] above, wherein the softening point of the resin composition is 100 ° C. or higher and the melting point of the wax is 90 ° C. or higher.

  [3] The content adhesion preventing lid material according to [1] or [2], wherein the ethylene-unsaturated ester copolymer has a melting point of 70 to 100 ° C.

[4] In the lid member having at least a base material layer and a heat sealing layer, and provided with a content adhesion preventing layer containing hydrophobic inorganic fine particles as a main component on the outer surface of the heat sealing layer,
The heat sealing layer is composed of a resin composition containing an ethylene-unsaturated ester copolymer, a wax, and a tackifier as essential components,
The melting point of the ethylene-unsaturated ester copolymer is 70 to 100 ° C.,
The wax has a melting point of 80-130 ° C.,
The softening point of the said resin composition is set to 90-160 degreeC, The content adhesion prevention lid | cover material characterized by the above-mentioned.

[5] The melting point of the ethylene-unsaturated ester copolymer is 75 to 95 ° C,
The melting point of the wax is 90-120 ° C.,
The content adhesion preventing lid material according to [4], wherein a softening point of the resin composition is set to 100 to 140 ° C.

  [6] The resin composition has a composition in which the ethylene-unsaturated ester copolymer is 30 to 50 wt%, the wax is 30 to 50 wt%, and the tackifier is 5 to 25 wt%. ] The content adhesion prevention lid | cover material of any one of [5].

  [7] The content adhesion preventing lid material according to any one of [1] to [6], wherein the hydrophobic inorganic fine particles are hydrophobic silica.

  [8] The content adhesion preventing lid material according to any one of [1] to [7], wherein the hydrophobic inorganic fine particles have an average particle diameter of 1 nm to 5,000 nm.

  [9] The content adhesion preventing lid material according to any one of [1] to [8], wherein the adhesion preventing layer is made 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. Moreover, the heat sealing layer located on the lower surface side of the adhesion preventing layer comprises a resin composition containing an ethylene-unsaturated ester copolymer, a wax having a melting point of 80 ° C. or higher, and a tackifier, By using a resin composition with a softening point of 90 ° C or higher, the heat resistance of the adhesion preventing layer can be improved, and the thermal stability of the adhesion preventing performance can be remarkably improved. Even after this, the above-described excellent content adhesion preventing effect can be maintained satisfactorily.

  According to the study by the present inventors, it is considered that such an effect of improving the heat resistance is achieved by the following phenomenon. That is, the coating of the fine particle dispersion is applied in relation to the fact that the content adhesion preventing layer provided in addition to the outer surface of the heat sealing layer is formed by a layer of hydrophobic fine particles such as hydrophobic silica. In the resin composition due to the heating during the subsequent drying or the axial radiant heat from the hot plate that is received while waiting for the container to be sealed after filling the contents, or the thermal effect directly received from the hot plate during the heat sealing, etc. It is possible to suppress or prevent the low melting point component from being melted early and excessively and exhibiting high fluidity. That is, since the softening point of the resin composition is high, melting thereof can be delayed and 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, it is considered that 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.

  As described in [2] above, the effect of improving the heat resistance is that the melting point of the wax is set to 90 ° C. or higher, and the softening point of the resin composition is set to 100 ° C. or higher. By doing so, it can enjoy more reliably and favorably.

Further, the [3] as described in the item ethylene - unsaturated ester copolymers, by melting to adopt those 7 0 to 100 ° C., a good heat-sealing properties, sealing properties, at the time of unsealing Therefore, it is possible to ensure the content adhesion preventing performance with excellent thermal stability as well as appropriate easy peelability. Examples of the unsaturated ester monomer of the ethylene-unsaturated ester copolymer include unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, and methyl methacrylate, vinyl esters such as vinyl acetate, and the like. Preferred are an ethylene-vinyl acetate copolymer and an ethylene-methyl methacrylate copolymer.

  Further, as described in the above item [4], the wax having a relatively high melting point of 80 to 130 ° C. is used for the wax while the ethylene-unsaturated ester copolymer having a melting point of 70 to 100 ° C. is used. By setting the softening point of the resin composition constituting the heat-sealing layer in the range of 90 to 160 ° C., the above-mentioned items [1] to [3] are performed without impairing the low-temperature heat sealability. Various effects can be achieved comprehensively and reliably.

  Moreover, as described in the above item [5], by setting the temperature range of the melting point and the temperature range of the softening point in the item [4] to a more preferable range, the above effect can be achieved more satisfactorily. it can.

  Moreover, as described in the above item [6], the resin composition constituting the heat-sealing layer is composed of 30 to 50 wt% of the ethylene-unsaturated ester copolymer, 30 to 50 wt% of the wax, and 5 of the tackifier. By having a composition of ˜25 wt%, it is possible to achieve good heat sealability, sealability, suitable easy peelability for opening, and improved thermal stability of content adhesion prevention effect.

  In addition, as described in [7] above, 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.

  Further, by using the hydrophobic inorganic fine particles having the average particle diameter as described in the above item [8], the content adhesion preventing effect as described above is often obtained by using a relatively inexpensive material that is easily available from the market. Can be realized more reliably.

  Furthermore, as described in the above item [9], the adhesion preventing layer is made of a mixed composition of hydrophobic inorganic fine particles, which are the 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. 1 shows an example of a laminated structure of a content adhesion preventing lid according to the present invention. The lid material includes a base material layer (1) composed of a laminate of a base film layer (2) and a metal foil layer (3), and an outer surface of the base material layer (1) on the metal foil (3) side, A heat sealing layer (5) is provided on the surface facing the inside of the container body when the lid is used via an intermediate resin layer (4). 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 prevention lid material according to the present invention further has an adhesion prevention layer (6) on the outer surface of the heat sealing layer (5) of the lid material 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 the present invention, the heat sealing layer contains an ethylene-unsaturated ester copolymer, a wax, and a tackifier as essential components, and further contains additives such as an antiblocking agent and an antioxidant as necessary. It consists of the resin composition contained as.

  The use of a resin composition having such a composition as a heat-sealing layer is known per se, but the resin composition that has been generally used conventionally has a relatively low melting point as its essential component wax. It was done. 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 technical background, the present invention uses a wax that is one of the essential components of the resin composition, particularly those having a melting point of 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher. The softening point of the resin composition is 90 ° C. or higher, preferably 100 ° C. or higher, more preferably 105 ° 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. The water repellency of the adhesion preventing layer by the fine particles, and hence the thermal stability of the adhesion preventing property can be remarkably improved.

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

  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 an essential component of the heat-sealing layer, includes unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, and methyl methacrylate, and 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 an essential component in the resin composition include paraffin wax, microcrystalline wax, montan wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, carnauba wax, and modified wax, more preferably polyethylene. It is 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 the essential components 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 500 nm, particularly preferably 3 to 100 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 according to 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.

  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.

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

(Preparation of lid body)
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), resin compositions having various blends as shown in Table 1 below were prepared using the following materials.

Wax (WX)
WX (I): Polyethylene wax having a melting point of 108 ° C
WX (II): Polyethylene wax having a melting point of 104 ° C
WX (III): Polyethylene wax having a melting point of 94 ° C
WX (IV): Microwax with a melting point of 80 ° C
WX (V): Paraffin wax having a melting point of 75 ° C
WX (VI): Paraffin wax with a melting point of 67 ° C

Resin (EVA)
EVA (I): ethylene-vinyl acetate copolymer (vinyl acetate content 26%)
Melting point 76 ° C
EVA (II): ethylene-vinyl acetate copolymer (vinyl acetate content 20%)
Melting point 82 ° C
EVA (III): ethylene-vinyl acetate copolymer (vinyl acetate content 5%)
Melting point 105 ° C

Tackifier (TF)
TF (I) petroleum-based hydrogenated resin
TF (II) rosin

And the hot-melt resin composition of various compositions shown in Table 1 was applied by the gravure coating method at a coating amount of 18 g / m ² on the intermediate resin layer (4), and the heat sealing layer (5) Formed.

(Formation of adhesion prevention layer)
As materials for the adhesion preventing layer, the following hydrophobic inorganic fine particles and thermoplastic resin fine particles were prepared.

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)

  Each of the hydrophobic inorganic fine particles (SP) or both the hydrophobic inorganic fine particles (SP) and the thermoplastic fine particles (MP) were uniformly dispersed in ethanol to prepare a coating solution. Table 1 shows the blending amount of the hydrophobic inorganic fine particles or the blending ratio of the thermoplastic fine particles and the hydrophobic inorganic fine particles.

And these various coating liquids were apply | coated to the outer surface of the said heat sealing layer (5) of a lid | cover material main body (1) by the gravure coating method, and it forcedly dried and formed the adhesion prevention layer. The coating amount is the sample number. 1 to 14 and 17 to 21 were set to 0.5 g / m ² (weight after drying). 15 and 16 were set to 0.8 g / m ² (weight after drying). Moreover, all forced drying was performed on the drying conditions of temperature 100 degreeC x time 15 seconds.

(Type of preparation sample)
Among samples 1 to 21 of the various lid materials shown in Table 1 obtained as described above, samples 1 to 9 and 19 were examined by changing the wax, resin, and softening point in the heat sealing layer. Sample 10 was obtained by changing the tackifier and examining its influence. Samples 11 to 14 and 20 to 21 were examined by changing the blending ratio of each component of the heat sealing layer. In Samples 15 and 16, the adhesion preventing layer was made of a mixture of hydrophobic inorganic fine particles and thermoplastic fine particles, and the effect was examined by changing the coating amount to 0.8 g / m ² . Samples 17 and 18 were examined by changing the particle diameter of the hydrophobic inorganic fine particles.

(Evaluation test)
(1) Anti-adhesion performance Each sample No. Aloe yogurt (trade name “Morinaga Aloe Yogurt” manufactured by Morinaga Milk Industry Co., Ltd.) is dropped as a 0.5 cc droplet on the back surface of the lid material, that is, the outer surface of the adhesion preventing layer, and the sample is slowly tilted. When the above-mentioned droplet was measured, the “inclination angle when it started to roll” was measured and evaluated according to the following criteria.

◎ ・ ・ ・ 15 degrees or less ○ ・ ・ ・ 16 degrees or more and 30 degrees or less × ・ ・ ・ 31 degrees or more

(2) Adhesion prevention performance after heat treatment For each of the lid materials 1 to 21, the first heat resistance test was performed under the heating condition of “temperature 100 ° C. × time 30 seconds”, and the second heat resistance test was performed under the heating condition of “temperature 100 ° C. × time 10 minutes”. heat resistance test 3 the heating condition of "temperature 100 ° C. × time 15 minutes", after storage of each sample in a heated atmosphere, respectively, the same attachment preventing performance evaluation tests as described above for each sample was cooled (1) to room temperature Went.

(3) Sealability (sealing strength and opening strength)
Sample No. The lid | cover material of 1-21 was heat-sealed on the flange surface of a container main body (paper / polyethylene container) on the sealing conditions of 150 degreeCx90kgfx1.0sec.

  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).

  Next, “opening strength” was determined by pulling the lid member at an elevation angle of 45 ° and a speed of 100 mm / min, and setting the maximum load at the time of opening 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).

(Heat seal strength)
Sample No. The lid | cover material of 1-21 was cut out to 15 mm width, and it heat-sealed to the 15 mm width strip cut out from the container main body (paper / polyethylene container) on the sealing conditions of 150 degreeC * 0.2MPa * 1.0sec. 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

(4) Adhesiveness Sample No. A weight (500 g) wrapped with a black cloth was placed vertically on the surface of the anti-adhesion layer of each of the lid materials 1 to 21, and slowly rubbed by a length of 200 mm, and visually inspected for the presence of fine particles adhering to the cloth surface. .

  And it evaluated by the following evaluation criteria by the transfer adhesion amount (peeling amount) of the hydrophobic fine particles and the thermoplastic resin fine particles in the black cloth.

◎ ・ ・ ・ Almost no adhesion ○ ・ ・ ・ Slight adhesion that is considered acceptable range × ・ ・ ・ Clearly much adhesion

  Table 2 shows the results of the evaluation tests (1) to (4).

  As shown in the test results of “Adhesion prevention performance” in Table 2, in the contents adhesion prevention lid material according to the present invention, the yogurt droplet starts rolling and moving only by slightly tilting the sample. Moreover, this adhesion prevention effect is almost reduced after receiving a rather severe thermal history of 100 ° C. × 15 minutes, further 100 ° C. × 15 minutes, as seen in the results of the “adhesion prevention performance after heat treatment” test. Maintained well without. This is because the contents on the back surface 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 it has an excellent anti-adhesion effect. Moreover, as shown in the results of the “sealability” test, the presence of the adhesion preventing layer does not significantly impair the sealing strength, heat sealability (seal strength), and easy-openability, while maintaining an appropriate sealability, The adhesion preventing performance can be imparted. In addition, as seen in the results of the “adhesion” test, the hydrophobic inorganic particles and the adhesion preventing layer containing the same have good adhesion, and unintentional separation and removal of hydrophobic inorganic fine particles, etc. There is no possibility of partial peeling, etc., and the content adhesion preventing performance can be stably maintained over a long period of time, and there is no possibility of foreign matter mixing into the container.

DESCRIPTION OF SYMBOLS 1 ... Base material layer 2 ... Base film layer 3 ... Metal foil layer 4 ... Intermediate resin layer 5 ... Heat sealing layer 6 ... Adhesion prevention layer

Claims (5)

A heat seal used for food packaging containers, having at least a base material layer and a heat sealing layer, and having a content adhesion preventing layer containing hydrophobic inorganic fine particles as a main component on the outer surface of the heat sealing layer In the lid material,
The heat sealing layer is composed of a resin composition containing 30 to 50 wt% of an ethylene-unsaturated ester copolymer, 30 to 50 wt% of a wax, and 5 to 25 wt% of a tackifier,
The melting point of the ethylene-unsaturated ester copolymer is 70 to 100 ° C.,
The melting point of the wax is 80 ° C. or higher,
The content adhesion prevention lid | cover material characterized by the softening point of the said resin composition being 90 degreeC or more. The melting point of the ethylene-unsaturated ester copolymer is 75 to 95 ° C.,
The melting point of the wax is 90-120 ° C.,
The content adhesion prevention cover material according to claim 1 whose softening point of said resin composition is 100-140 ° C. The content adhesion prevention lid material according to claim 1 or 2, wherein the hydrophobic inorganic fine particles are hydrophobic silica. The content adhesion prevention lid material according to any one of claims 1 to 3, wherein the hydrophobic inorganic fine particles have an average particle diameter of 1 nm to 5,000 nm. The content adhesion prevention lid material according to any one of claims 1 to 4, wherein the adhesion prevention layer is composed of a mixed composition of hydrophobic inorganic fine particles and thermoplastic resin fine particles.

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