JP5102889B2 - 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 lid material on the inner surface side of the container It is desired that the contents can be prevented from adhering to the back 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 technology can exert a very excellent effect in terms of the content adhesion prevention effect, the adhesion prevention layer is inferior in heat resistance, and the adhesion prevention effect is easily impaired when it receives an unfavorable heat history. There were difficulties. 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.

  Furthermore, the above-mentioned prior proposed technique has a heat sealability because the adhesion preventing layer composed of a fine hydrophobic inorganic fine particle layer becomes a contaminant that is interposed between the container main body and the heat sealing layer of the lid material in the heat sealing portion. There is a risk of damage. In this respect, in the description of the above-mentioned prior art document 6, the hydrophobic inorganic fine particles enter the heat-sealing layer that melts and softens during 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 to a high value so that the hydrophobic inorganic fine particles are completely taken into the heat sealing layer, the lid material is heated during heat sealing. The slight heat effect from the plate may increase, and the content adhesion prevention effect may be diminished. Especially, the content adhesion prevention effect in the region near the flange part of the container is relatively remarkable compared to other parts. We are anxious about it falling.

  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 aims to provide a new and improved technology that can seal at a relatively low temperature, has excellent sealing properties, and also exhibits excellent effects in the thermal stability of content adhesion prevention performance. .

  The present invention presents the following means [1] to [10] as a means for achieving the above object, with respect to the content adhesion preventing lid.

  In the following, the softening point is determined by the ring and ball method (based on JIS K6863), and the melting point is determined by the DSC method (based on JIS K7121).

[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 content adhesion preventing lid material, wherein the heat sealing layer is made of a resin composition having a softening point of 90 ° C or higher and a melt viscosity at 160 ° C of 4000 mPa · s or lower.

  [2] The content adhesion preventing lid material according to [1], wherein the heat sealing layer is made of a resin composition having a softening point of 100 ° C. or higher and a melt viscosity at 160 ° C. of 2000 to 4000 mPa · s. .

  [3] The content adhesion preventing lid material according to [1] or [2], wherein the resin composition contains an ethylene-unsaturated ester copolymer, a wax, and a tackifier as essential components.

  [4] The content adhesion preventing lid material according to [3], wherein the wax and the tackifier of the resin composition have a softening point or a melting point of 80 ° C. or higher.

[5] 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 softening point or melting point of the wax and tackifier is 80-130 ° C,
The content adhesion prevention lid | cover material characterized by the softening point of the said resin composition being 90-160 degreeC, and the melt viscosity in 160 degreeC being 2000-4000 mPa * s.

[6] The melting point of the ethylene-unsaturated ester copolymer is 75 to 95 ° C,
The softening point or melting point of the wax and tackifier is 90-120 ° C,
The softening point of the resin composition is 100 to 140 ° C., and the melt viscosity at 160 ° C. is 2000 to 3500 mPa · s.

  [7] The resin composition has a composition in which the ethylene-unsaturated ester copolymer is 20 to 80 wt%, the wax is 20 to 60 wt%, and the tackifier is 1 to 30 wt%. [3 ] The content adhesion prevention cover material of any one of [6].

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

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

  [10] The content adhesion prevention lid material according to any one of [1] to [9], wherein the adhesion prevention 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, since the heat sealing layer located on the lower surface side of the adhesion preventing layer uses a resin composition having a softening point of 90 ° C. or higher and a melt viscosity at 160 ° C. of 4000 mPa · s or less, the heat resistance of the adhesion preventing layer is increased. In addition to improving the sealing property by suppressing the increase in the melt viscosity of the heat sealing layer and improving the thermal stability of the anti-adhesion performance significantly, after sealing use to the container body The above-described excellent content adhesion preventing effect can be maintained well.

  According to the study by the present inventors, it is considered that the effect of improving the thermal stability of the adhesion preventing performance is achieved by the following phenomenon. In other words, 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 inorganic fine particles such as hydrophobic silica, the coating of the fine particle dispersion is applied. Low heat in the resin composition due to heat during drying after work, or radiant heat received from the hot plate during standby when the container is sealed after filling, and also due to the heat effect directly received from the hot plate during heat sealing It is possible to suppress or prevent the 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.

  Furthermore, the hydrophobic inorganic fine particles become a contaminant that is interposed between the container main body and the heat sealing layer of the lid, and the increase in the melt viscosity is kept low while increasing the softening point of the heat sealing layer. Specifically, the melt viscosity at 160 ° C. in consideration of the heat seal temperature is suppressed to 4000 mPa · s or less, so that the hydrophobic inorganic fine particles are formed in the heat seal layer after melting the heat seal layer at the time of heat sealing. Get inside easily and quickly. That is, it is easy to incorporate inorganic fine particles into the heat sealing layer. Therefore, the sealing performance is excellent, and sealing can be performed without having to raise the temperature at the time of sealing. That is, it does not hinder the low temperature sealing performance. As a result, this also makes it possible to maximize the effect of improving the thermal stability described above by setting the softening point of the heat sealing layer to 90 ° C. or higher.

  In addition, as described in the above item [2], the effects as described above can be obtained by setting the softening point of the resin composition to 100 ° C. or higher and a melt viscosity at 160 ° C. of 2000 to 4000 mPa · s. It can be enjoyed more surely and satisfactorily.

  However, if the softening point is set too high, the viscosity at the time of melting becomes high, so it should be set to 140 ° C. or lower as described later, preferably 130 ° C. or lower, more preferably 120 ° C. or lower. desirable.

  The melt viscosity at 160 ° C. should be set to 4000 mPa · s or less, preferably 2000 to 4000 mPa · s, and more preferably 2000 to 3500 mPa · s.

  In addition, as described in the above item [3], the resin composition can be enjoyed more reliably and favorably by containing an ethylene-unsaturated ester copolymer, a wax, and a tackifier as essential components. .

  Moreover, as described in the above item [4], when the softening point or melting point of the wax and tackifier of the resin composition is 80 ° C. or higher, the resin composition can be enjoyed more reliably and better.

  In addition, as described in the above item [5], the ethylene-unsaturated ester copolymer having a melting point range of 70 to 100 ° C. is used, and the softening point or the melting point of 80 to 130 ° C. is compared for the wax and tackifier. The softening point of the resin composition constituting the heat-sealing layer is set in the range of 90 to 160 ° C., and the melt viscosity at 160 ° C. is in the range of 2000 to 4000 mPa · s. By setting to the above, it is possible to comprehensively and reliably achieve various effects according to the items [1] to [4] without impairing the low temperature heat sealability.

  In addition, as described in the above item [6], the above effect can be further improved by setting the temperature range of the melting point, the temperature range of the softening point, and the viscosity range at the time of melting in the above item [5] to more preferable ranges. Can be achieved.

  Moreover, as described in the above item [7], the resin composition constituting the heat sealing layer is composed of 20 to 80 wt% of ethylene-unsaturated ester copolymer, 20 to 60 wt% of wax, and 1 of tackifier. By having a composition of ˜30 wt%, it is possible to set the melt viscosity at 160 ° C. to 4000 mPa · s or less while keeping the melt viscosity low while achieving a high softening point of the heat sealing layer. Heat sealability, sealing performance, suitable easy peelability for opening, and improved thermal stability of content adhesion prevention effect can be achieved.

  In addition, when hydrophobic silica is selectively used for the hydrophobic inorganic fine particles as described in the above item [8], an excellent content adhesion preventing effect can be achieved with a relatively inexpensive material that is easily available from the market. Can do.

  In addition, by using hydrophobic inorganic fine particles having an average particle size as described in the above item [9], the content adhesion preventing effect as described above is often obtained using a relatively inexpensive material that is easily available from the market. Can be realized more reliably.

  Furthermore, as described in the above item [10], 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. 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 is composed of a resin composition having a softening point of 90 ° C. or higher and a melt viscosity at 160 ° C. of 4000 mPa · s or lower. The specific composition of this resin composition is not particularly limited. As an adhesive resin component, for example, an acid-modified polyolefin resin, an ethylene-unsaturated ester copolymer, polyethylene, polypropylene, acrylic resin, polyester resin, or the like can be used as a hot melt type or lacquer type resin composition. However, the most common and preferred resin composition contains an ethylene-unsaturated ester copolymer, a wax, and a tackifier as essential components, and further contains an anti-blocking agent, an antioxidant, and the like as necessary. A resin composition containing the additive as an optional component is recommended.

  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 softening point. For example, most commonly, a resin composition having a softening point of about 65 ° C to 75 ° C has been used. Moreover, the thing of the high softening point was high viscosity.

  Under such a technical background, in the present invention, the softening point of the resin composition is particularly 90 ° C. or higher, preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and the melt viscosity at 160 ° C. Is 4000 mPa · s or less, preferably 2000 to 4000 mPa · s, more preferably 2000 to 3500 mPa · s. By using such a resin composition having a relatively high softening point and a constant melt viscosity for the heat sealing layer, adhesion prevention by the hydrophobic inorganic fine particles additionally formed on the outer surface side of the heat sealing layer as described above The water repellency of the layer, and thus the thermal stability of the anti-adhesion property, can be remarkably improved.

However, use of a resin composition having an excessively high softening point may impair the low-temperature heat sealability and miscellaneous sealability of the heat-sealing layer. Therefore, a resin composition having a softening point of 140 ° C. or lower should be used. It is desirable to use a softening point of 130 ° C. or lower, more preferably 120 ° C. or lower.

  The setting of the softening point as described above and the setting of the melt viscosity of the resin composition used for the heat sealing layer are based on the selection and combination of the melting point or softening point of each component constituting the composition as described later, It can be easily performed by adjusting the composition ratio of each component. In particular, with respect to the unique request of the present invention that involves a dilemma in terms of technical common sense that the melt viscosity is kept as low as possible while increasing the softening point of the resin composition, the wax and tackifier are relatively By selecting and using those having a high melting point or softening point, setting their blending amount more than the general blending ratio in relation to the blending amount of resin components such as olefins that are adhesive components It can be easily handled.

  In the preferred resin composition used for the heat sealing layer, the essential component ethylene-unsaturated ester copolymer is, as the unsaturated ester monomer, methyl acrylate, ethyl acrylate, methyl methacrylate or the like. Unsaturated carboxylic acid esters, vinyl esters such as vinyl acetate, and the like can be used. Of these, vinyl acetate and methyl methacrylate are particularly preferable. Those having different unsaturated ester contents and molecular weights can be appropriately selected and used in combination of two or more.

  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. Polyethylene wax.

  Further, as tackifiers, rosin, rosin derivatives (hydrogenated rosin, nearby rosin, rosin ester), alicyclic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins or their water attachments are added. And terpene resins (α-pinene, β-pinene) and the like, but it is preferable to use an aromatic petroleum resin with water attached.

  The softening point or melting point of the wax and tackifier is desirably 80 ° C or higher, preferably 90 ° C or higher, more preferably 100 ° C or higher.

  The blending composition ratio of the essential components of the resin composition needs to be set in consideration of the softening point and melt viscosity required for the resin composition. Preferably, the ethylene-unsaturated ester copolymer is 20 -80 wt%, preferably 30-60 wt%, wax 20-60 wt%, preferably 30-50 wt%, tackifier 1-30 wt%, preferably 5-25 wt% It is possible to achieve improvement in heat stability such as sealing property, dust sealing property, sealing property, suitable peelability for opening and content adhesion preventing effect. That is, a sufficient sealing strength cannot be obtained with a resin composition having an ethylene-unsaturated ester copolymer content of less than 20 wt%. On the other hand, if it exceeds 80 wt%, the seal strength becomes too high and the easy-openability of the seal lid is impaired. If the blending amount of the wax is less than 20 wt%, the coating suitability (processing suitability) of the resin composition is impaired and the easy-openability is impaired. On the other hand, if it exceeds 60 wt%, sufficient seal strength cannot be obtained. Moreover, if the compounding amount is less than 1 wt%, it is difficult to obtain a sufficient seal strength. Conversely, if it exceeds 30 wt%, the adhesion preventing effect of the adhesion preventing layer may be reduced. There is.

  A plurality of these waxes, tackifiers, and ethylene-unsaturated ester copolymers may be appropriately selected and used in combination.

  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 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), hot melt 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 115 ° C.
WX (II): Polyethylene wax having a melting point of 108 ° C
WX (III): Microwax with a melting point of 94 ° C
WX (IV): Paraffin wax with a melting point of 75 ° C
WX (V): Paraffin wax having 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

Tackifier (TF)
TF (I) petroleum-based hydrogenated resin Melting point 105 ° C
TF (II) petroleum hydrogenated resin Melting point 115 ° C
TF (III) rosin softening point 68 ℃

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 fine particles (MP)
MP (I): ethylene-vinyl acetate copolymer (vinyl acetate 20%, ethylene 80%, average particle size 100 nm)
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 10 and 13 to 14 were set to 0.5 g / m ² (weight after drying). 11 and 12, it was 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 14 of the various lid materials shown in Table 1 obtained as described above, samples 1 to 10 were examined by changing the softening point and melt viscosity in the heat sealing layer.
In Samples 11 and 12, 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 13 and 14 were examined by changing the particle diameter of the hydrophobic inorganic fine particles.

(Evaluation test)
(1) Anti-adhesion performance Each sample No. Aloe yoghurt (Trademark “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 of 1 to 14, 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 14, 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) Adhesion prevention performance after container sealing Each lid material of 1 to 7 and 9 to 14 is combined with a container (caliber 88 mm), and 125 g of aloe yogurt (trademark “Morinaga Aloe Yogurt” manufactured by Morinaga Milk Industry Co., Ltd.) is added to the container, and then 140 ° C. × Heat sealing was performed on the flange surface of the container under sealing conditions of 90 kgf × 1.0 sec. On the other hand, under the same sealing conditions as above, the sample No. For No. 8, the lid material was heat sealed on the flange surface under sealing conditions of 150 ° C. × 90 kgf × 1.0 sec.

Next, each of these samples was inverted and stored for 12 hours, then opened, and the yogurt adhesion state on the back surface of the lid was visually observed and evaluated according to the following criteria.
◎ ・ ・ ・ No yogurt adhesion ○ ・ ・ ・ Slight adhesion is observed around the flange area × ・ ・ ・ Adhesion is observed around the flange area.

(4) Sealability (4) -1 Seal strength sample No. The lid materials 1 to 14 were heat-sealed on the flange surface of the container body (paper / polyethylene container) under sealing conditions of 150 ° C. × 90 kgf × 1.0 sec.
The “sealing strength” is 13.3 kPa or more in accordance with the sealing strength test method of the ministerial ordinance (Ministry of Health and Welfare Ordinance No. 17 on April 16, 1979) regarding the component standards of milk and dairy products. Those with a pass (◎) and those with less than 13.3 kPa were judged as unacceptable (×).

(4) -2 Opening strength 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).

(4) -3 Heat seal strength Sample No. The lid material of 1-14 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) under the 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

(5) Adhesion Sample No. A weight (500 g) wrapped with a black cloth was placed vertically on the surface of the adhesion preventing layer of each of the lid materials 1 to 14, and slowly rubbed by a length of 200 mm, and the presence or absence of fine particles adhered to the surface of the cloth was visually inspected. .

And it evaluated on the following reference | standard by the transfer adhesion amount (peeling amount) of the hydrophobic fine particle and thermoplastic resin fine particle in a 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 (5).

  As shown in the results of the “anti-adhesion performance” test in Table 2, in the contents anti-adhesion lid material according to the present invention, the yogurt droplet starts rolling and moving only by slightly tilting the sample. In addition, this adhesion prevention effect is maintained well with little deterioration after receiving a fairly severe thermal history at 100 ° C. for 15 minutes, as seen in the results of the “adhesion prevention performance after heat treatment” test. As shown in the results of the “adhesion prevention performance after container sealing” test, the lid was heat sealed in a container filled with contents containing viscous liquid components such as yogurt, pudding, and jelly. Later, it is guaranteed that the contents are excellent in the effect of preventing the contents from adhering to the back surface of the lid. In addition, as shown in the results of the “sealability” test, the presence of the anti-adhesion layer does not significantly impair both heat sealability (seal strength) and easy-openability, while maintaining appropriate sealability while preventing adhesion. Can give performance. In addition, as can be seen in the results of the “adhesion” test, the hydrophobic particles and the adhesion preventing layer containing them have good adhesion, and unintentional separation and removal of hydrophobic fine particles, etc., and partial peeling of the adhesion preventing layer There is no fear of such problems, 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 3 ... Metal foil 5 ... Heat sealing layer 6 ... Adhesion prevention layer

Claims (8)

A heat seal lid used for a packaging container for foods, 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 In the material,

The heat sealing layer is composed of a resin composition containing an ethylene-unsaturated ester copolymer, a wax, and a tackifier as essential components, and the softening point of the resin composition is 90 to 160 ° C. and melted at 160 ° C. A content adhesion preventing lid material having a viscosity of 2000 to 4000 mPa · s . 2. The content adhesion preventing lid material according to claim 1, wherein the resin composition has a softening point of 100 to 140 ° C. and a melt viscosity at 160 ° C. of 3500 mPa · s or less.
The melting point of the ethylene-unsaturated ester copolymer in the resin composition is 70 to 100 ° C.,
The content adhesion prevention cover material according to claim 1 or 2, wherein the wax and the tackifier have a softening point or a melting point of 80 to 130 ° C.
The melting point of the ethylene-unsaturated ester copolymer in the resin composition is 75 to 95 ° C.,
  The content adhesion prevention lid material according to claim 1 or 2, wherein the wax and the tackifier have a softening point or a melting point of 90 to 120 ° C. 5. The resin composition according to claim 1, wherein the ethylene-unsaturated ester copolymer has a composition of 20 to 80 wt%, a wax of 20 to 60 wt%, and a tackifier of 1 to 30 wt%. The content adhesion prevention cover material of any one of these. The content adhesion prevention lid material according to any one of claims 1 to 5, wherein the hydrophobic fine inorganic particles are hydrophobic silica. The content adhesion prevention lid material according to any one of claims 1 to 6, 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 7, 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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