JP6454663B2 - Contents adhesion prevention lid material and manufacturing method thereof - Google Patents

Description

  The present invention is mainly applied to heat-sealing lid materials applied to food packaging containers, and more specifically to cup-shaped containers for packaging yogurt, jelly, pudding, jam, milk portion, coffee beverages and the like. The present invention relates to a lid member having a content adhesion preventing property and a manufacturing method thereof.

  This type of heat sealing lid is generally provided with a heat sealing layer, that is, a heat sealing layer, on the film surface of a base material layer made of a laminate of paper and a metal vapor-deposited film. A heat sealing layer is provided on an aluminum foil surface side of a base material layer made of a laminate with an aluminum foil through an intermediate resin layer as necessary. Then, the lid is placed on the upper surface opening of a cup-shaped container body made of polystyrene or paper filled with an object to be packaged such as yogurt, and the peripheral edge portion is heat-sealed on the upper edge flange portion of the container body. Thus, a sealed package is formed.

  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.

  In response to such a request, conventionally, a proposal as shown in the following Patent Document 1 (Japanese Patent No. 4348401) has been made as means for imparting or improving contents adhesion prevention performance.

  The known technique according to this prior proposal is to form a porous layer having a three-dimensional network structure with extremely fine hydrophobic oxide particles such as hydrophobic silica on the outer surface of the heat sealing layer. Although an excellent effect can be obtained in terms of the prevention effect, the adhesion prevention layer is inferior in thermal stability (heat resistance), and there is a problem that the adhesion prevention effect is easily impaired when it receives an unfavorable thermal history. That is, as the hydrophobic oxide fine particles, those using ultrafine hydrophobic oxide fine particles having an average primary particle diameter of 3 to 100 nm, typically synthetic fine silica, especially silica fine particles produced by a dry method, are used. When this is applied to the most common lacquer-type or hot-melt type heat sealing layer cover content adhesion prevention layer, after the application of the fine particle dispersion in the adhesion prevention layer formation process At the time of drying, if the heating temperature is too high or the drying time is long, the content adhesion preventing effect is significantly impaired. Also, due to the difference in the dry state due to uneven application of the fine particle dispersion, the area with a small amount of application is heated excessively until the part with a large amount of application is dried. There was a possibility that the object adhesion preventing effect was partially impaired.

  Furthermore, even when sealing after filling containers such as yogurt, jelly, and pudding, the effect of preventing the adhesion of the contents is impaired due to the severe heat effect that the lid receives from the hot plate during standby or heat sealing. There is a fear that the content adhesion preventing effect is particularly remarkably lowered in the vicinity of the heat seal portion, that is, in the vicinity of the flange portion of the container 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.

  On the other hand, the present invention is an improved technique that can further ensure non-adhesiveness while solving the problem of the prior art, particularly the thermal stability problem of Patent Document 1 as described above. The inventors previously proposed the invention described in Patent Document 2 (Japanese Patent No. 4668352).

This prior proposed technique is mainly characterized by using hydrophobic wet silica particles instead of the conventionally known hydrophobic dry silica as a material for forming the adhesion preventing layer. According to the mechanism described in paragraphs [0023] and [0037] of the above, it is possible to improve the content adhesion preventing effect while simultaneously improving the thermal stability (heat resistance).

  However, on the other hand, since the wet silica particles have a relatively large particle size of micron size, there are few contacts to the adjacent heat sealing layer, and dry silica particles made of aggregates of ultrafine primary particles are used. Compared with the case where it does, there exists a difficulty that the adhesiveness with respect to a heat sealing layer is comparatively inferior, and the improvement of this point was still strongly calculated | required for practical use.

Japanese Patent No. 4348401 Japanese Patent No. 4668352

  The present invention uses hydrophobic wet silica particles that express the unique excellent content adhesion prevention performance in response to the above-described improvement request of the prior art, and at a high temperature at which the heat sealing layer temporarily melts. While ensuring good thermal stability (heat resistance) that does not damage the anti-adhesion performance even when exposed, the adhesion or adhesion of the hydrophobic particles exhibiting the anti-adhesion effect to the heat-sealing layer is enhanced. It aims at providing the improvement technique which can improve the stability sustainability of the content adhesion prevention effect.

  In order to achieve the above object, the present inventors have conducted various experiments and researches. As a result, hydrophobic wet silica particles and hydrophilic dry silica particles are used in combination, and they are used as a mixed composition of a predetermined ratio. By doing so, the inherent disadvantages of each silica particle can be compensated by the advantages of the other silica particle, and as a result, the problems of the prior art can be solved at once by mutual complementation and further by a synergistic effect. Has been completed based on such unique knowledge.

  Therefore, the present invention presents the content adhesion preventing lid material described in the following [1] to [12] and a method for producing the same as specific technical means for achieving the above object.

[1] In a lid having at least a base material layer and a heat sealing layer,
Content adhering prevention characterized in that a particle coating layer for preventing content adhering comprising a mixed composition of hydrophobic wet silica particles and hydrophilic dry silica particles is formed on the outer surface of the heat sealing layer. Lid material.

[2] In a lid having at least a base material layer and a heat sealing layer,
On the outer surface of the heat sealing layer, a particle coating layer for preventing adhesion of contents is formed, which is composed of a mixed composition of hydrophobic wet silica particles and hydrophilic dry silica particles,
An impregnation adhesion strengthening layer in which a molten component of the heat sealing layer enters at least a gap between the wet and dry silica particles is formed on a part of the particle covering layer on the heat sealing layer side. The content adhesion prevention lid | cover material by which the adhesion prevention layer which the surface of at least the said wet silica particle exposed at least remains formed in the outermost surface side of this.

  [3] The content according to [1] or [2], wherein the mixed composition of silica particles includes 50 wt% or more and less than 99 wt% of hydrophobic wet silica particles, and the rest is composed of hydrophilic dry silica particles. Adhesion prevention lid.

  [4] Any one of [1] to [3] above, wherein the wet silica particles have an average particle size of 0.5 to 7.0 μm, and the dry silica particles have an average particle size of primary particles of 3 to 50 nm. The content adhesion prevention cover material of Claim 1.

  [5] The heat sealing layer includes an adhesive resin component composed of one or more of acid-modified polyolefin resin, ethylene-unsaturated ester copolymer, acrylic resin, polyester resin, and styrene resin. The content adhesion preventing lid material according to any one of [1] to [4] above, comprising a resin composition containing, as an essential component, at least one of wax, a tackifier, and the like.

  [6] The content adhesion preventing lid material according to [5], wherein the total blending amount of the wax and tackifier of the resin composition is 1 to 70% by weight.

  [7] The content adhesion prevention lid material according to [5] or [6] above, wherein the melting point or softening point of the wax and tackifier of the resin composition is 80 ° C. or higher.

  [8] Prepared by dispersing a mixed composition of hydrophobic wet silica particles and hydrophilic dry silica particles in an organic dispersion medium on the outer surface of the heat sealing layer of the cover material having at least a base material layer and a heat sealing layer. A method for producing a content adhesion preventing lid material, wherein the dispersion liquid is applied and dried to form a particle coating layer for preventing content adhesion.

[9] Prepared by dispersing a mixed composition of hydrophobic wet silica particles and hydrophilic dry silica particles in an organic dispersion medium on the outer surface of the heat sealing layer of a cover material having at least a base material layer and a heat sealing layer. The dispersion liquid is applied and dried to form a particle coating layer for preventing adhesion of the content comprising the mixed composition,
And, by performing heat treatment at a temperature higher than the melting start temperature (softening point) of the heat sealing layer forming component, at least part of the wet and dry silica particles are partly on the heat sealing layer side of the particle coating layer. An impregnation adhesion reinforcing layer in which the molten component of the heat sealing layer has entered the gap between the particles is formed, and an adhesion preventing layer having at least the surface of the wet silica particles exposed on the outermost surface side of the particle coating layer. A method for producing a content adhesion preventing lid material, wherein the lid material is formed to remain.

  [10] The content according to [8] or [9], wherein the mixed composition of silica particles contains 50 wt% or more and less than 99 wt% of hydrophobic wet silica particles, and the remainder is hydrophilic dry silica particles. A method for manufacturing an anti-adhesion lid.

  [11] The wet silica particles have an average particle diameter of 0.5 to 7.0 μm, and the dry silica particles have any one of the primary particles having an average particle diameter of 3 to 50 nm. A method for producing the content adhesion preventing lid material according to claim 1.

  [12] The method for manufacturing a content adhesion preventing lid material according to any one of [9] to [11], wherein the heat treatment is performed under a heat treatment condition of a temperature of 85 to 220 ° C. and a time of 3 to 120 seconds.

  In the invention described in the above item [1], the particle coating layer for preventing adhesion of contents is a mixed composition of hydrophobic wet silica particles obtained by imparting hydrophobicity to wet silica particles and hydrophilic dry silica particles. It is made up of. Therefore, while taking advantage of each particle's inherent advantages, the other particle compensates for the disadvantages. As a result, not only the excellent anti-adhesion performance is ensured, but also the thermal stability is improved, and the adhesion of the particle layer to the heat sealing layer In addition, a lid material excellent in adhesion stability can be obtained.

  That is, the hydrophobic wet silica particles have relatively superior contents adhesion prevention performance as compared with the hydrophobic dry silica particles as described in the above-mentioned Patent Document 2 or as described later, On the other hand, it is excellent in thermal stability, and is relatively inferior in terms of adhesion to the underlying heat sealing layer due to its large particle size. On the other hand, dry silica particles have ultra-fine primary particles on the order of several nanometers to several tens of nanometers, and therefore have a high cohesive force. When the dispersion medium is removed in the coating process, the porous silica particles are porous. Since it has the feature of forming an agglomerated layer and has many contacts with the heat sealing layer, it has excellent adhesion and bonding strength to the heat sealing layer, but it has an anti-adhesion performance when affected by heat. It is inferior in stability maintenance, that is, heat stability or heat resistance.

  Here, in the present invention, by using hydrophobic wet silica particles and hydrophilic dry silica particles in combination, while securing the required anti-adhesion performance and thermal stability mainly by the former hydrophobic wet silica particles, The wet silica particles can be constrained by the dry silica particles, and the adhesion to the heat sealing layer can be supplemented. As a result, the adhesion prevention, thermal stability and adhesion are further improved as described above. A lid member provided with a particle coating layer for use can be obtained.

  In addition, as in the above item [2], for example, an appropriate heat treatment is performed to form an impregnated adhesion reinforcing layer on a part of the particle coating layer, thereby entering the gap between the particles and solidifying. The particle coating layer itself can be fixed to the heat-sealing layer by an anchor effect while the wet silica particles are often firmly restrained and fixed by the constituent components of the layer, particularly the low viscosity and low molecular weight components. Moreover, an adhesion prevention layer with at least hydrophobic wet silica particles exposed on the outer surface side remains, so that it forms on the outer surface of the particle coating layer in addition to the good water repellency inherent to hydrophobic wet silica particles. Due to the slightly rough concavo-convex structure due to the arrangement of the wet silica particles and the fine concavo-convex structure on the surface of the porous wet silica particles themselves, excellent adhesion prevention performance is often expressed.

  Here, by using hydrophilic silica particles as the dry silica particles, it is easy to form the impregnated adhesion reinforcing layer, and further improvement in adhesion with the heat sealing layer can be expected.

  In addition, as shown in the blending ratio described in [3] above, by forming a particle coating layer using a mixed composition mainly composed of hydrophobic wet silica particles, it is possible to ensure good adhesion prevention performance. can do. The blending amount of the dry silica particles represents an effect of improving the adhesiveness commensurate with the amount thereof, and is appropriately determined in the range of at least 1% by weight to less than 50% by weight in consideration of the required adhesive strength. sell.

  Further, by using wet and dry silica particles having an average particle size as described in the above item [4], the above-mentioned effects can be reliably achieved with a relatively inexpensive material that is easily available from the market. .

  Further, as described in the above item [5], the heat sealing layer is made of a resin composition containing an adhesive resin component and at least one of a wax and a tackifier as essential components. The above effects can be achieved while ensuring good heat-sealing properties, sealing properties, and easy peelability at the time of opening.

  Further, as described in the items [6] and [7], the resin composition contains a predetermined amount of at least one of a wax and a tackifier, preferably further their softening point or melting point. In addition to the effect of the above item [5], the thermal stability or heat resistance of the particle coating layer for preventing adhesion can be further improved in addition to the effect of the above item [5]. When the impregnated adhesion reinforcing layer is formed as described in item 2], the adhesion reinforcing layer can be reliably formed and the effect can be achieved more reliably.

  Moreover, according to the manufacturing method as described in said [8] item, not only can the lid | cover material which has the effect of said [1] item be obtained, but especially formation of a particle coating layer is carried out to hydrophobic wet silica particle. And a dry composition prepared by dispersing a mixed composition of silica and hydrophilic dry silica particles in an organic dispersion medium, and drying, so that a uniform particle coating layer can be formed relatively easily and dispersed during the drying process. As the medium is volatilized, dry silica particles having a small particle diameter gather on the heat sealing layer side below the particle coating layer and sink to increase the distribution density, thereby forming a porous aggregated layer. As a result, the layer of the dry silica particles surrounds and restrains a part of the wet silica particles having a relatively large particle size. That is, wet silica particles form a structure in which they are partially embedded in an aggregate layer of dry silica particles, and as a result, the effect of further improving the adhesion of the particle coating layer is exhibited.

  In addition, as described in the above item [9], in the case of forming an impregnated adhesion reinforcing layer, a lid material having various characteristics that have both the effects of the item [2] and the previous item [8] is provided. It can be manufactured relatively easily.

  In particular, when the heat-sealing layer is melted by heat treatment, the porous aggregated layer composed of dry silica particles tends to have low viscosity and low molecular weight components entering the voids between the particles. On the other hand, since the hydrophobic wet silica particles having a large particle size are in contact with the heat sealing layer at points, there are few contacts from which the heat sealing layer component originally enters, but the layer formation is performed as a mixed composition with the dry silica particles. This increases the number of indirect contact points between the wet silica particles and the heat sealing layer through the porous layer of the dry silica particles, so that the heat sealing layer components can easily enter the wet silica particles. As a result, a sufficiently strong adhesive force can be ensured over the entire particle coating layer containing wet silica particles.

  Further, in the case of hydrophobic wet silica particles, when the resin component of the heat sealing layer enters from the above direct or indirect contact, the voids inside the particles are uniform and relatively easy to enter the whole, but adjacent to each other. Resin components are less likely to enter the gaps between the wet silica particles. This is presumably because the gap between particles is large and capillary action is unlikely to occur. As a result, it is possible to easily and reliably form an adhesion preventing layer that is exposed without covering at least the surface of the hydrophobic wet silica particles with the resin component on the outermost surface side of the particle coating layer.

  Moreover, the lid | cover material which show | plays the effect of said [3] term and [4] term can be obtained by selection of the silica particle of the mixture ratio and average particle diameter as described in said [10] term and [11] term.

  Furthermore, by applying the heat treatment under the conditions described in the above item [12], the adhesion preventing layer can be used in any case under the selective use of various materials for the heat sealing layer exhibiting good heat sealing properties. It is possible to form the impregnated adhesion reinforcing layer while reliably forming the residual.

FIG. 1 is a cross-sectional view showing an outline of an example of a laminated structure of a content adhesion preventing lid material according to the present invention. FIG. 2 is a schematic cross-sectional view schematically showing the structure of the particle coating layer for preventing adhesion according to the present invention, which is shown upside down with respect to FIG.

  The content adhesion preventing lid according to the present invention is, as an example of a lid suitable for a yogurt packaging container, for example, a coated paper (2) with a coated (7) surface protected by a coating agent (2a) as shown in FIG. ) And a metal vapor-deposited film (3) bonded with a general adhesive to form a base material (1), and an anchor coat (on the metal vapor-deposited film (3) side outer surface of the base material (1) A heat sealing layer (5) is provided via 4). This laminated structure is the same as that of a conventionally known lid material, and the laminated body including the base material (1) and the heat sealing layer (5) is referred to as a “lid material body” herein.

  Said metal vapor deposition film (3) provides gas barrier property, light-shielding property, etc., and an aluminum vapor deposition polyester film is used in many cases. Particularly in the case of a lid for a yogurt container, an aluminum vapor-deposited polyester film having a thickness of about 12 to 16 μm is suitably used as a light-shielding property and light weight. In addition, a general adhesive is used for laminating and bonding with the coated paper (2).

  In the case of a lid material using a hot melt agent for the heat sealing layer (5), the lid body is composed of a base material layer formed by laminating a lid material film layer and a metal foil layer, and the base material layer. A heat sealing layer is provided on the outer surface of the metal foil side through an intermediate layer as necessary.

  By the way, the content adhesion preventing lid material according to the present invention is such that a particle coating layer (6) for preventing adhesion is additionally formed on the outer surface of the heat sealing layer (5) of the lid body. .

  The material of the heat sealing layer (5) is not particularly limited as long as it has good adhesion to the container side. For example, a lacquer type heat sealant, a hot melt agent, or a known sealant film can be used. Preferably, an adhesive resin component composed of one or more of acid-modified polyolefin resin, ethylene-unsaturated ester copolymer, acrylic resin, polyester resin, and styrene resin, and wax and tackifier What consists of a resin composition which contains at least any one of an agent as an essential component can be used. Further, in this case, the wax and tackifier in the resin composition are set such that their total blending amount is set to 1 to 70% by weight and their melting point or softening point is 80 ° C. or higher. It is desirable to do. When the blending amount is less than 1% by weight, the effect of adding them cannot be fully enjoyed. When the content exceeds 70% by weight, the particle coating is caused by heat treatment or heat influence during heat sealing. There exists a possibility that the adhesion prevention performance of a layer (6) may be impaired. Further, if the melting point or softening point thereof is less than 80 ° C., the water repellency of the particle coating layer (6) and thus the thermal stability of the adhesion preventing effect may be impaired. That is, the low melting point component of the heat-sealing layer (5) is melted early and excessively due to the heat effect received during heat sealing or the like, and exhibits high fluidity, covering the surface of the silica particles through the gaps between the silica particles. The exposed area is reduced, and as a result, the adhesion preventing effect may be impaired. Preferably, the blending amount is set in a range of 10 to 40% by weight, and a melting point or a softening point of 90 to 120 ° C. is preferably selected and used.

  Now, the particle coating layer (6) for preventing adhesion, which is the main feature of the present invention, is composed of a mixed composition of hydrophobic wet silica particles (A) and hydrophilic dry silica particles (B). Yes.

  The blending ratio of the hydrophobic wet silica particles (A) and the hydrophilic dry silica particles (B) in the above mixed composition is to ensure good water repellency and non-adhesiveness on the surface of the particle coating layer (6). The wet silica particles are relatively contained. That is, the blending amount of the wet silica particles (A) is set to 50 wt% or more and less than 99 wt%, and the blending amount of the dry silica particles is set to the remaining 1 to 50 wt%. Particularly preferably, the blending ratio of the former hydrophobic wet silica particles is 60 to 80% by weight, and the remaining 20 to 40% by weight is based on the latter dry silica particles. When the blending amount of the hydrophobic wet silica particles (A) is less than 50% by weight, good adhesion prevention performance and thermal stability cannot be obtained. On the other hand, if it exceeds 99% by weight, the amount of the dry silica particles is relatively small, so that the effect of improving the adhesion of the particle coating layer (6) cannot be obtained. A preferable blending ratio is a range of 60-80: 40-20 blending ratio in wet silica particles (A): dry silica particles (B).

  The hydrophobic wet silica fine particles (A) are particles obtained by chemically reacting an organic silicon compound with a hydroxyl group on the surface of wet silica particles, which are synthetic amorphous silica produced by a wet method, to impart hydrophobicity. is there.

  Wet silica has more surface silanol groups than dry silica, and even in hydrophobic particles after the surface has been hydrophobized with silanes or silicones, it has superior water repellency and hydrophobicity compared to dry silica. Indicates. Further, as described above, wet silica particles not only have a large particle diameter, but also have a larger particle size than the dry silica particles whose primary unit is the aggregate of primary particles having no pores. Large specific surface area, large pore volume and oil absorption. These facts are also considered to greatly contribute to the improvement of the performance of the adhesion preventing layer.

  Hydrophobic wet silica particles can be produced in various sizes at the production stage, but in the application of the present invention, the average particle size is in the range of 0.5 to 7.0 μm. Things should be used.

  When fine particles having an average particle size of less than 0.5 μm are used, it is generally impossible to obtain a good content adhesion preventing effect within a range of coating amount and adhesion amount that does not adversely affect heat sealability. On the other hand, when coarse particles exceeding 7.0 μm are used, not only the adhesion to the heat sealing layer (5) is deteriorated, but also the heat sealing property is hindered. Preferably, the average particle diameter is 1.0 to 5.0 μm, more preferably 2.0 to 5.0 μm.

  On the other hand, the dry silica particles (B) are produced as an aggregate of very fine primary particles by a flame method or the like, and those having an average primary particle size of 3 to 50 nm can be suitably used. Ultrafine particles having an average particle size of less than 3 nm are difficult to obtain from the market and are disadvantageous in terms of cost. On the other hand, coarse dry silica having an average primary particle size of more than 50 nm is poor in improving the adhesion of the particle coating layer (6). Particularly preferred are dry silica particles having an average primary particle size of 5 to 30 nm.

  Further, when the dry silica particles (B) are hydrophilic to this, particularly when the impregnated adhesion reinforcing layer (6a) is formed on the particle coating layer (6) by heat treatment as described later, Rather, it is useful for forming the impregnated adhesion-strengthening layer (6a) without significantly hindering the adhesion prevention performance, and can contribute to the improvement of adhesion.

  The particle coating layer (6) is formed by uniformly dispersing a predetermined amount of a mixed composition of hydrophobic wet silica particles (A) and hydrophilic dry silica particles (B) in a liquid dispersion medium to prepare a dispersion. This can be suitably carried out by applying it to the outer surface of the heat sealing layer (5) of the lid body and drying it.

  The dispersion is prepared by dispersing the mixed composition of silica particles using water or an organic liquid dispersion medium to obtain a colloidal solution having a predetermined concentration. The dispersion medium particularly has an organic dispersion medium having a polar group. Is preferably used. 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.

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

The coating amount of the dispersion may be set according to the required thickness of the particle coating layer (6), but is preferably about 0.3 to 3.0 g / m ² in terms of weight after drying. 2 g / m ² is more preferable.

  It may be naturally dried as well as dried after application, but is preferably dried by heating in order to enhance productivity and adhesion to the heat sealing layer. As drying conditions in that case, it is desirable to set the temperature in the range of 80 to 140 ° C. and the time of 5 to 30 seconds.

  The particle coating layer (6) formed by the above-described coating, that is, the coating and drying process, already has an excellent surface water repellency by itself, and of course has the expected anti-adhesion performance. It also has excellent thermal stability and adhesion.

  That is, by containing a large amount of hydrophobic wet silica particles (A) as a main component, in addition to the inherent good water repellency of the hydrophobic wet silica particles, as shown in FIG. Excellent non-adhesiveness due to the rough concavo-convex structure formed by protruding the wet silica particles (A) on the surface of the particle coating layer (6) and the fine concavo-convex structure of the surface of the porous wet silica particles themselves, Adhesion prevention effect is secured.

  And this content adhesion prevention performance is excellent in thermal stability, and even if it is exposed to high temperature, high adhesion prevention performance can be maintained well. The reason is considered as follows. That is, the wet silica particles are large in micron size, and in the present invention, those having an average particle size of 0.5 to 7.0 μm are used. Silica particles are unlikely to sink into the adhesive layer. In addition, unlike the case of dry silica, wet silica particles are inherently porous, have a high specific surface area, and have a large pore volume and oil absorption. For this reason, when the heat sealing layer is melted, the low melting point and low molecular weight components such as wax and rosin contained therein are rapidly adsorbed by the wet silica particles themselves, and the gaps between the particles are filled with the molten hot melt adhesive. To prevent it. Therefore, it is considered that the gap between the particles is maintained, and by extension, the exposed area of the hydrophobic surface of the particles is prevented from being extremely reduced, and a good content adhesion preventing effect is maintained.

  On the other hand, the particle coating layer (6) contains a predetermined amount of hydrophilic dry silica particles (B). The dry silica particles (B) are fine particles having a particle size of at most about 300 nm or less even in the primary aggregate particles in which the primary particles are randomly fused and bonded in the production stage. Accordingly, as the dispersion medium is volatilized and removed in the drying step after the dispersion of the particles is applied, the dry silica particles (B) having a small particle size are heat sealed together with the strong cohesive force of the particles themselves. A porous aggregate layer is formed on the surface of the layer (5). As a result, the agglomerated layer is bonded to the heat sealing layer (5) at many points of contact and exhibits good adhesion, while the hydrophobic wet silica particles (A) having a relatively large particle size are particularly heat sealed. A portion close to the layer (5) side is partially embedded in the aggregated layer. For this reason, the wet silica particles (A) are restrained and fixed by the dry silica particles (B) surrounded by a part of the wet silica particles (A), and as a result, particles adhering to a mixture composition of the wet and dry silica particles (A) and (B). The layer (6) itself has good adhesion to the heat sealing layer (5).

  In the best mode of the present invention, after the formation of the particle coating layer (6) according to the above, a predetermined heat treatment is further performed, so that the particle coating layer (6) is formed as shown in a schematic diagram in FIG. An impregnation adhesion strengthening layer in which a molten component of the heat sealing layer (5) enters at least a gap between the wet and dry silica particles (A) and (B) at a part of the heat sealing layer (5) side. (6a) is formed, and an adhesion preventing layer (6b) in which at least the surface of the wet silica particles is exposed is formed on the outermost surface side of the particle coating layer.

  When the laminate is heated at a temperature equal to or higher than the melting start temperature of the heat sealing layer (5) after the formation of the particle coating layer (6), the low-melting component, low-viscosity component, low The molecular weight component is fluidized and enters the voids of the agglomerated layer of the dry silica particles (B) having a fine porous structure and the voids between the wet particles (A). The particles (A) enter the solids themselves and solidify to form the impregnated adhesion reinforcing layer (6a). Accordingly, the particle coating layer (6) is integrally bonded to the heat sealing layer (5) by the impregnated adhesion reinforcing layer (6a), thereby strengthening the adhesion.

  However, the formation of the adhesion strengthening layer (6a) by the heat treatment described above is such that at least the surface of the hydrophobic wet silica particles (A) is not covered with the molten component on the outermost surface portion of the particle coating layer (6). It must be performed under conditions that allow the exposed portion of the anti-adhesion layer (6b) to remain.

Moreover, the component composition of the heat sealing layer (5) and the particle coating layer (6) are such that the amount of residual particles forming the adhesion preventing layer (6b) is in the range of 0.1 to 1.2 g / m ^2. The heat treatment conditions should be determined in consideration of the correlation with the coating amount and the like. If the residual particle amount of the adhesion preventing layer (6b) is less than 0.1 g / m ² , the desired good adhesion preventing performance cannot be exhibited. On the contrary, when it exceeds 1.2 g / m ² , the adhesion of the particle coating layer (6) is deteriorated, and the possibility of the silica particles falling off and peeling off increases. A preferable range of the residual particle amount is approximately 0.3 to 1.0 g / m ² .

  Here, the measurement of the amount of the remaining particles forming the adhesion preventing layer (6b) is performed by wiping the surface of the sample covering layer cut out to a predetermined area with absorbent cotton soaked with alcohol or the like. It can be obtained from the weight difference between the sample pieces before and after wiping.

  In consideration of the relationship with the material used for the heat-sealing layer (5), the heat treatment is at least a temperature higher than the melting start temperature of the heat-sealing layer (5), preferably higher by 50 ° C. or more. It is necessary to carry out at temperature. Although this heating temperature correlates with the heating time, generally preferable heat treatment conditions are a temperature of 85 to 220 ° C. and a time of 3 to 120 seconds, and particularly preferably a temperature of 100 to 180 ° C. and a time of 10 to 60. Seconds.

  However, the outermost surface portion of the particle coating layer (6) has a large interval between adjacent wet particles (A) and (A) having a large particle size, so that a penetration phenomenon similar to a capillary phenomenon is unlikely to occur, thereby preventing adhesion. The layer (6b) is easily formed. This makes it possible to relax the heat treatment conditions during the heat treatment, thereby simplifying the management of the heat treatment step. As a result, the range of the formation region of each of the adhesion reinforcing layer (6a) and the adhesion preventing layer (6b) can be easily controlled by changing the mixing composition ratio of the hydrophobic silica particles (A) and the dry silica particles (B). Can be adjusted.

  There is a cover material in which the adhesion enhancement layer (6a) portion impregnated with the heat sealing layer component as described above is further formed on the particle coating layer (6) using the hydrophobic wet silica particles (A) and the dry silica particles (B) in combination. Therefore, the adhesion improving effect can be further improved as compared with the case where the layer (6a) is not formed.

  The above heat treatment for forming the impregnated adhesion reinforcing layer (6a) is performed as an independent separate process after applying and drying the dispersion of silica particles, thereby controlling the process under the most preferable conditions. Although it is easy, in order to simplify the work process, the drying process after application and the heat treatment process may be performed simultaneously or continuously.

  Next, in order to confirm the effect of the present invention, various examples thereof are shown in comparison with comparative examples and control examples.

(Preparation of lid body)
The lid main body uses a lacquer type heat sealing agent for its heat sealing layer (sample Nos. 1 to 10, 13 to 19 and 21), and uses a hot melt agent (samples No. 11, 12, and 20). ) And 2) were prepared as shown in a and b below.

a, Lid using a lacquer type heat sealant Coated paper (55 g / m ² ) and a 16 μm thick aluminum vapor-deposited polyethylene terephthalate film, which were laminated with a polyurethane-based dry laminate adhesive to form a base material layer .

Next, after applying an anchor coating agent to the aluminum vapor-deposited polyethylene terephthalate film of the base material layer, it is further subjected to a gravure coating method, and various compounding compositions as shown in Table 1 as being suitable for a lid for a container made of polystyrene. In each case, a heat sealing layer having a coating amount of 5 g / m ² was formed using the lacquer type heat sealing agent. The base material layer / anchor coating agent / heat sealing layer laminate thus obtained was used as a lid body.

b, Lid using a hot melt agent A polyethylene terephthalate film having a thickness of 12 μm was used as a substrate film, and an aluminum foil having a thickness of 30 μm was bonded to one surface thereof with a polyurethane dry laminate adhesive to form a substrate layer.

Next, an anchor coating agent is applied to the surface of the base material layer on the aluminum foil side, and a polyethylene resin is extruded and coated so as to have a thickness of 20 μm to form an intermediate resin layer. A heat sealing layer having an application amount of 18 g / m ² was formed using a hot melt agent having a composition as shown in Table 1. The base material layer / intermediate resin layer / heat sealing layer laminate thus obtained was used as a lid body.

  The following materials were used as the constituent materials of the heat sealing layers a and b.

Heat sealing layer constituting material Acid-modified polyolefin resin Acid-modified PO: Acid-modified polypropylene resin (maleic anhydride graft-modified modification rate 1.0%)
Ethylene-unsaturated ester copolymer EVA: ethylene-vinyl acetate copolymer (190 ° C. MFR 20 g / 10 min, vinyl acetate content 20%)
Wax (WX)
WX (I): Polyethylene wax having a melting point of 125 ° C. WX (II): Polyethylene wax having a melting point of 75 ° C. Tackifier (TF)
TF (I): Petroleum-based hydrogenated resin Melting point 115 ° C

(Formation of anti-adhesion particle coating layer)
The following hydrophobic wet silica particles and hydrophilic dry silica particles were prepared as materials for the adhesion preventing particle coating layer.
Hydrophobic wet silica particles (A)
A (I): Hydrophobic wet silica average particle size 2.7 μm
A (II): Hydrophobic wet silica average particle size 3.9 μm
Hydrophilic dry silica (B)
B (I): hydrophilic dry silica primary particle average particle size 7 nm,
Specific surface area by BET method 220m ² / g
B (II): Hydrophilic dry silica Primary particle average particle size 12 nm
Specific surface area by BET method 200m ² / g

  The hydrophobic wet silica particles A (I) or A (II) and the hydrophilic dry silica particles B (I) or B (II) are mixed under various blending ratios shown in Table 1, and these These dispersion compositions were uniformly dispersed in ethanol to prepare various dispersions.

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

(Heat treatment)
Of the samples obtained above, No. The other samples except the two samples 15 and 16 were heat-treated under the heating conditions shown in Table 1.

(Type of preparation sample)
Sample Nos. Of various lid materials shown in Table 1 obtained above. 1-2, sample No. 1-4, 7-11, 13, 15, 18-21 are “hydrophilic dry silica particles B (I) as dry silica particles in the mixed composition of particles for forming the particle coating layer (6)”. ”And sample no. 5, 6, 12, 14, and 16 are those using “hydrophilic dry silica particles B (II)”. Sample No. For comparison, 17 is composed of only “hydrophobic wet silica particles A (I)” without using dry silica. Sample No. Nos. 15 and 16 are changes in performance such as adhesion when the impregnated adhesion reinforcing layer (6a) is not formed by heat treatment. Furthermore, sample no. Nos. 18 to 21 are the results of examining the effects when the composition of the heat sealing layer (5) is inappropriate as a control example.

(Evaluation test)
(1) SEM observation Sample No. About each lid | cover material of 1-21, when the cross-section of a particle coating layer was observed with the FE-SEM image, sample No.1. About the lid | cover material of 1-14, the heat sealing layer component entered into the space | gap or gap | interval between silica particles over the predetermined thickness range on the heat sealing layer (5) side of the particle coating layer (6), and solidified. It was confirmed that a layer that was recognized as an impregnation adhesion reinforcing layer (6a) was formed, and a thin adhesion preventing layer (6b) portion where the silica particles were exposed was formed thereon. Sample No. without heat treatment In the lid materials 15 and 16, the formation of a clear impregnated adhesion reinforcing layer as described above is not observed, but fine dry silica particles are densely distributed particularly in the lower part of the relatively large wet silica particles. A structural aspect that was perceived as surrounding was observed.

  On the other hand, no. Sample No. 17 containing no wax or tackifier in the cover material of No. 17 and the heat sealing layer (5). Regarding the cover materials of Nos. 18 and 19, no clear impregnation layer as recognized as the adhesion reinforcing layer was observed, and the heat sealing layer (5) contained excessive wax and tackifier. About 20 lid | cover materials, it was confirmed that residual formation of the adhesion prevention layer (6b) part is inadequate. Similarly, Sample No. containing a wax having a low melting point. It was also confirmed that the remaining formation of the adhesion preventing layer (6b) was insufficient with respect to the 21 cover material.

(2) Anti-adhesion performance Each sample No. Aloe yogurt (Trademark “Morinaga Aloe Yogurt” manufactured by Morinaga Milk Industry Co., Ltd.) is dropped on the back surface of the lid material 1 to 21, that is, on 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

(3) Heat seal strength Sample No. The lid material of 1 to 21 is cut out to a width of 15 mm, and the sample Nos. 1 to 10, 13 to 19, and 21 are sealed from the container main body (polystyrene container) under a sealing condition of 180 ° C. × 0.2 MPa × 1.0 seconds. The cut out 15 mm wide strip was heat sealed. Samples Nos. 11, 12, and 20 were heat-sealed into strips having a width of 15 mm cut out from the container body (paper / polyethylene container) under sealing conditions of 150 ° C. × 0.2 MPa × 1.0 seconds. 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 on the following evaluation criteria by the transfer adhesion amount (peeling amount) of the silica particle to 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 (3).

  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. 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 anti-adhesion layer does not significantly impair the heat sealability (seal strength), and provides the above anti-adhesion performance while maintaining an appropriate sealing performance. sell. In addition, as seen in the results of the “adhesion” test, the adhesion of the particle-preventing particle coating layer is good, and there is no risk of unintentional separation or dropping, partial peeling, etc. The prevention performance can be maintained stably, and there is no possibility of foreign matter entering the container.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Coated paper 3 ... Metal vapor deposition film 4 ... Anchor coating layer 5 ... Heat sealing layer 6 ... Particle coating layer 6a for adhesion prevention .... Adhesion reinforcement layer 6b ..Adhesion prevention layer A ... hydrophobic wet silica particles B ... hydrophilic dry silica particles

Claims (13)

In a lid having at least a base material layer and a heat sealing layer,
The base material layer is composed of a laminate obtained by laminating a coated paper and a metal vapor deposition film with an adhesive, and the heat sealing layer is formed by a lacquer heat sealant on the outer surface of the metal base film on the metal vapor deposition film side,
Content adhering prevention characterized in that a particle coating layer for preventing content adhering comprising a mixed composition of hydrophobic wet silica particles and hydrophilic dry silica particles is formed on the outer surface of the heat sealing layer. Lid material. In a lid having at least a base material layer and a heat sealing layer,
The base material layer is composed of a laminate obtained by laminating a coated paper and a metal vapor deposition film with an adhesive, and the heat sealing layer is formed by a lacquer heat sealant on the outer surface of the metal base film on the metal vapor deposition film side,
On the outer surface of the heat sealing layer, a particle coating layer for preventing adhesion of contents is formed, which is composed of a mixed composition of hydrophobic wet silica particles and hydrophilic dry silica particles,
An impregnation adhesion strengthening layer in which a molten component of the heat sealing layer enters at least a gap between the wet and dry silica particles is formed on a part of the particle covering layer on the heat sealing layer side. The content adhesion prevention lid | cover material by which the adhesion prevention layer which the surface of at least the said wet silica particle exposed at least remains formed in the outermost surface side of this.   The content adhesion prevention cover material according to claim 1 or 2, wherein the mixed composition of silica particles contains 50 wt% or more and less than 99 wt% of hydrophobic wet silica particles, and the rest is made of hydrophilic dry silica particles.   4. The wet silica particles according to claim 1, wherein the wet silica particles have an average particle size of 0.5 to 7.0 μm, and the dry silica particles have an average particle size of primary particles of 3 to 50 nm. Content adhesion prevention lid.   The heat sealing layer is an acid-modified polyolefin resin, an ethylene-unsaturated ester copolymer, an acrylic resin, a polyester resin, an adhesive resin component composed of two or more of a styrene resin, a wax and The content adhesion prevention lid | cover material of any one of Claims 1-4 which consists of a resin composition which contains at least any one of tackifier as an essential component.   The content adhesion prevention lid | cover material of Claim 5 whose total compounding quantity of the wax and tackifier of the said resin composition is 1 to 70 weight%.   The content adhesion prevention lid material according to claim 5 or 6, wherein the melting point or softening point of the wax and tackifier of the resin composition is 80 ° C or higher. The dry weight of the particle coating layer is 0.3 to 3.0 g / m ² The content adhesion prevention lid material according to any one of claims 1 to 7.   A cover material having at least a base material layer and a heat sealing layer, wherein the base material layer is composed of a laminate in which a coated paper and a metal vapor deposition film are bonded together with an adhesive, and the metal vapor deposition film side of the base material layer A mixture composition of hydrophobic wet silica particles and hydrophilic dry silica particles is used as an organic dispersion medium on the outer surface of the heat sealing layer of the cover material in which the heat sealing layer is formed on the outer surface of the lacquer heat sealant. A method for producing a content adhesion preventing lid material, comprising applying a dispersion prepared by dispersing and drying to form a particle coating layer for preventing content adhesion. A cover material having at least a base material layer and a heat sealing layer, wherein the base material layer is composed of a laminate in which a coated paper and a metal vapor deposition film are bonded together with an adhesive, and the metal vapor deposition film side of the base material layer A mixture composition of hydrophobic wet silica particles and hydrophilic dry silica particles is used as an organic dispersion medium on the outer surface of the heat sealing layer of the cover material in which the heat sealing layer is formed on the outer surface of the lacquer heat sealant. A dispersion prepared by dispersing is applied and dried to form a particle coating layer for preventing adhesion of the content comprising the mixed composition,
And, by performing heat treatment at a temperature higher than the melting start temperature (softening point) of the heat sealing layer forming component, at least part of the wet and dry silica particles are partly on the heat sealing layer side of the particle coating layer. An impregnation adhesion reinforcing layer in which the molten component of the heat sealing layer has entered the gap between the particles is formed, and an adhesion preventing layer having at least the surface of the wet silica particles exposed on the outermost surface side of the particle coating layer. A method for producing a content adhesion preventing lid material, wherein the lid material is formed to remain. The said heat processing is a manufacturing method of the content adhesion prevention lid | cover material of Claim 10 performed on the heat processing conditions of temperature 85-220 degreeC and time 3 to 120 second. The mixed composition of the silica particles according to any one of claims 9 to 11, wherein the mixed composition of silica particles contains 50 wt% or more and less than 99 wt% of hydrophobic wet silica particles, and the rest consists of hydrophilic dry silica particles. A method for manufacturing a prevention lid. The wet silica particles had an average particle size of 0.5～7.0Myuemu, dry silica particles have an average particle size of the primary particles according to any one of claims 9-12 is 3~50nm A method of manufacturing a content adhesion prevention lid.

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