JP5908707B2 - Content adhesion prevention lid - Google Patents

Description

  The present invention relates to a heat-sealing lid material mainly applied to containers for packaging foods, more specifically, cups for packaging coffee beverages such as cafe latte, portion milk, yogurt, jelly, pudding, jam and the like. It is related with the lid | cover material provided with the content adhesion prevention property applied to a container.

  This type of lid material for liquid containers such as coffee drinks is generally provided by laminating a heat sealing layer made of a heat sealing agent on one surface of an aluminum foil. In addition, a lid for a container of gelled or viscous food such as yogurt is provided with a heat sealing layer by applying a primer to the film surface of the base material layer composed of a laminate of paper and a vapor deposition film as necessary. It has been made. Then, these lid materials are put on the upper surface opening of a cup-shaped container body filled with a packaged item such as a coffee beverage or yogurt, and the peripheral portion is sealed by heat-sealing on the upper edge flange portion of the container body. It is supposed to form a package.

  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. 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 prior art according to this prior proposal is to form a porous layer having a three-dimensional network structure with very fine hydrophobic oxide particles such as hydrophobic silica on the outer surface of the heat sealing layer, and prevent the adhesion of contents. Although the effect can be excellent, the adhesion preventing layer is inferior in thermal stability (heat resistance), and there is a problem that the adhesion preventing effect is easily impaired when receiving an unfavorable heat 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 the contents such as yogurt are sealed after being filled into the container, the effect of preventing the adhesion of the contents may be impaired due to the severe heat effect that the lid member 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.

  Further, the anti-adhesion layer was formed on the heat sealing layer as a porous layer made of hydrophobic oxide fine particles by applying hydrophobic oxide fine particles as a dispersion using a dispersion medium such as alcohol and then drying. As a result, the bonding force or adhesion to adjacent heat sealing layers is generally weak, and particularly when the heat sealing layer is of lacquer type, there is a strong lack of bonding power to the hydrophobic oxide fine particles and the heat sealing layer. As a result, there was a fear that the adhesion preventing layer could easily fall off and the adhesion preventing effect was not stable.

  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 still inferior, and the improvement of this point was a place where the improvement was strongly calculated | required for practical use.

Japanese Patent No. 4348401 Japanese Patent No. 4668352

  In view of the above-described problems in the prior art, the present invention is intended to further improve them, specifically, while maintaining stable and good heat sealing performance, content adhesion prevention performance, particularly heat. Adhesion with the heat-sealing layer of hydrophobic particles having good heat resistance that can maintain excellent content adhesion prevention performance even when exposed to a high temperature at which the sealing layer melts, and exhibiting the adhesion prevention effect An object of the present invention is to provide an improvement technique capable of improving the stability and improving the stability and sustainability of the content adhesion preventing effect.

  In the above-mentioned object, the inventors of the present invention are particularly responsible for the problem of performance deterioration due to the thermal influence of the adhesion preventing layer as described above and the problem of poor adhesion between the hydrophobic inorganic fine particles and the heat sealing layer. As a result of further research and investigation, we have conducted intensive experiments and research to find out that there is one important cause in the composition of the heat-sealing layer, which is the underlayer of the anti-adhesion layer. The heat sealing layer is made of a resin composition having a specific composition, and it has been found that the problem of poor adhesion between the hydrophobic oxide fine particles and the heat sealing layer can be dramatically improved while improving the thermal stability. The present invention has been completed.

  Therefore, the present invention provides an anti-adhesion lid material having the following constitution, which is mainly characterized in that the heat sealing layer is composed of a mixed resin composition having a specific composition.

  In the present invention, 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] In a lid material having at least a base material layer and a heat sealing layer, and a content adhesion preventing layer containing hydrophobic inorganic fine particles as a main component on the outer surface of the heat sealing layer,
The content adhesion preventing lid material, wherein the heat sealing layer is made of a resin composition containing, as an essential component, a styrenic block copolymer (A) having an organic acid group.

  [2] The heat sealing layer is made of a resin composition containing, as essential components, a styrenic block copolymer (A) having an organic acid group, a wax (C) and / or a tackifier (D). The content adhesion prevention lid material according to the preceding item [1].

  [3] A styrene block copolymer (A) in which the heat sealing layer has an organic acid group, a styrene block copolymer (B) having no organic acid group, a wax (C) and / or a tackifier ( The content adhesion preventing lid material according to the above item [1] or [2], comprising a resin composition containing D) as an essential component.

  [4] The content adhesion prevention according to [2] or [3] above, wherein the wax (C) and / or the tackifier (D) each have a melting point or softening point of 80 ° C. or higher. Lid material.

  [5] Any one of [2] to [4] above, wherein the wax (C) and / or tackifier (D) has a melting point or softening point of 90 ° C. or higher. The contents adhesion prevention lid material.

  [6] The heat sealing layer is 5 to 90% by weight of a styrene block copolymer (A) having an organic acid group, 5 to 90% by weight of a styrene block copolymer (B) having no organic acid group, The content adhesion prevention lid material according to any one of [3] to [5] above, comprising a resin composition having a blending composition of 5 to 40% by weight of wax (C) and / or tackifier (D) .

  [7] The content adhesion preventing lid material according to [6], wherein the resin composition includes 0 to 20% by weight of wax and 0 to 30% by weight of a tackifier.

  [8] The content adhesion preventing lid material according to any one of [1] to [7], wherein the hydrophobic inorganic fine 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 preventing lid material according to any one of [1] to [9], wherein the adhesion preventing layer is composed of a mixed composition of hydrophobic inorganic fine particles and thermoplastic resin fine particles.

  According to the present invention, in the configuration of the above item [1], a content adhesion preventing layer made of hydrophobic oxide fine particles such as hydrophobic silica is formed on the outer surface of the heat sealing layer. 1 and 2 have unique excellent contents adhesion prevention performance.

  Moreover, the heat sealing layer located on the lower surface side of the adhesion preventing layer is a resin composition containing a styrenic block copolymer (A) having an organic acid group as an essential component, so that it can be directly applied to an aluminum foil substrate. By doing so, a heat sealing layer can be formed. That is, since the polystyrene-based block copolymer (A) having an organic acid group has good adhesion to a metal such as aluminum, a lid material using an aluminum foil as a base material does not use an anchor coating agent. Even if the heat sealing layer is provided directly on the aluminum foil surface, sufficient adhesion strength can be ensured, which is advantageous for simplifying the laminated structure of the lid. Of course, when a polyethylene terephthalate film is used for the base material of the lid material, sufficient adhesion to the base material can be ensured by using an anchor coating agent. In addition, the polystyrene block copolymer (A) having an organic acid group has good adhesion to the hydrophobic inorganic fine particles forming the anti-adhesion layer due to its excellent adhesion to different types of adherends. Can be obtained. Therefore, the anti-adhesion layer does not fall off and does not partially peel, and the anti-adhesion effect can be stably maintained, and the hydrophobic oxide fine particles detached from the anti-adhesion layer are taken into the contents for hygiene purposes. There is no risk of problems.

  In addition, as described in the above item [2], by forming a heat sealing layer with a resin composition further containing at least one of wax and tackifier or both, adhesion to the base material layer side can be improved. Adhesion with the hydrophobic inorganic fine particles forming the adhesion preventing layer can be further improved without damaging, and good heat-sealability with respect to the container, sealing performance, and appropriate ease for opening. Peelability can be obtained with certainty.

  Furthermore, as described in the item [3], the heat sealing layer further includes a styrene block copolymer (A) having an organic acid group, and a styrene block copolymer (B) having no organic acid group. , By comprising a composition containing wax (C) and / or tackifier (D) as essential components, adhesion to the substrate side and good heat-sealing properties, sealing properties, and opening of the container It is possible to obtain even better and more reliable easy peelability for the time.

  Further, as described in the above item [4], the melting point or softening point of the wax and / or tackifier is 80 ° C. or higher, so that the hydrophobic inorganic fine particles and the heat-sealing agent are sealed as described above. In addition to being able to improve adhesion to the layer and prevent the adhesion prevention layer from falling off and preventing partial peeling, the heat resistance of the adhesion prevention layer can be improved, and the thermal stability of the adhesion prevention performance can be improved. Even after heat-sealing to the main body, the excellent content adhesion preventing effect is maintained well. The wax component in the heat-sealing layer plays an important role in improving the adhesion to the hydrophobic inorganic fine particles, but the wax generally used in the past has a problem in the heat stability of the adhesion preventing effect. . On the other hand, according to the study by the present inventors, it is considered that the thermal stability of the adhesion preventing effect according to the present invention, that is, the heat resistance improving effect, 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 melting point in the resin composition due to heat at the time of drying after the work or radiant heat from the hot plate received during standby when the container is sealed after filling the contents, and further due to the heat effect directly received from the hot plate at the time of heat sealing It is possible to suppress or prevent the component from being melted early and excessively and exhibiting high fluidity. That is, since the melting point or the softening point of the wax and tackifier of the resin composition are both high, their melting 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.

  The effect of improving the heat resistance as described above can be enjoyed more surely and satisfactorily by setting the melting point or softening point of the wax and / or tackifier to 90 ° C. or higher as described in the above item [5]. can do.

  Moreover, as described in the above item [6], the resin composition constituting the heat sealing layer is 5 to 90% by weight of the styrene-based block copolymer (A) having an organic acid group, and does not have an organic acid group. It has a blend composition of 5 to 90% by weight of a styrenic block copolymer (B), 5 to 40% by weight of a wax (C) and / or a tackifier (D), and preferably described in the above item [7]. As described above, by including 0 to 20% by weight of wax and 0 to 30% by weight of the tackifier, good heat sealability, sealing property, suitable peelability for opening, and even better hydrophobicity As a result, it is possible to reliably achieve the effect of improving the thermal stability of the adhesion of the conductive inorganic fine particles and the content adhesion preventing effect. In particular, it is foreseen that the anti-adhesion layer consisting of hydrophobic inorganic fine particles will inherently impair the heat sealability by interposing as a contaminant between the heat sealing layer and the adherend surface on the container body side where it is heat sealed. A composition comprising the above styrene block copolymer (A) having an organic acid group, a styrene block copolymer (B) having no organic acid group, a wax (C), and a tackifier (D). By optimizing the composition ratio of each component of the product, it is possible to easily adjust the heat seal characteristics considering the effect of the anti-adhesion layer, good heat sealability, sealability, and appropriate ease for opening It is possible to reliably achieve the effect of improving the releasability and the better adhesiveness of the hydrophobic inorganic fine particles, as well as the thermal stability of the content adhesion preventing effect.

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

  In addition, by using hydrophobic 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 (4) is provided on the surface facing the inside of the container body when the lid is used. The above laminated structure is the same as that of the conventional lid material, and the laminated body including the base material layer (1) and the heat sealing layer (4) will be referred to as “lid material body” herein.

  The content adhesion preventing lid according to the present invention further has an adhesion preventing layer (5) on the outer surface of the heat sealing layer (4) of the lid body.

  The base film layer (2) is arranged on the front side of the packaging container, and the material thereof is a single layer such as polyester, polyethylene, polypropylene, polyamide, polyacrylate, polycarbonate, polyvinyl chloride, cellulose acetate, cellophane, etc. Alternatively, a composite film, or a film obtained by laminating or coating these films and resin on paper or the like can be exemplified. The base film layer (2) is usually appropriately printed (6) 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 coffee beverage or yogurt container, an aluminum foil having a thickness of about 5 to 100 μm is preferably used 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). . In that case, a primer layer may be provided in order to obtain adhesion between the metal vapor-deposited film and the heat sealing layer (4). Any material can be used for forming the primer layer as long as it provides adhesion between the base material layer (1) and the heat sealing layer (4).

  The heat sealing layer (4) must have good adhesion to the metal foil layer (3) or primer layer and the container side. In the present invention, the heat sealing layer is composed of a resin composition containing the styrene block copolymer (A) having an organic acid group as an essential component. Preferably, a resin composition further comprising a wax (C) and / or a tackifier (D) as essential components, that is, a resin comprising at least one of the wax (C) and the tackifier (D) or both. It consists of a composition. More preferably, the styrene block copolymer (A) having an organic acid group, the styrene block copolymer (B) having no organic acid group, a wax (C) and / or a tackifier (D). And a mixed resin composition containing as essential components. And as for the said wax and / or tackifier, those whose melting | fusing point or softening point is 80 degreeC or more, Preferably it is 90 degreeC or more. In addition to the above essential components, inorganic fillers such as silica, mica, talc, clay, calcium carbonate and the like can be included as necessary as the filler (E). Of these, silica and talc are particularly preferable. Furthermore, additives such as antioxidants are included as optional components as necessary.

  By the way, the styrenic block polymer (A) having an organic acid group, which is an essential component of the heat sealing layer (4), has good adhesion to the metal foil (3) on the substrate (1) side serving as a base surface. Contribute to ensuring On the other hand, the styrenic block polymer (B) having no organic acid group mainly plays a role of ensuring good heat sealability. Accordingly, the blending ratio of the base material (1) depends on the kind of the base material (1) and the laminated structure, and the kind of the container body as the adherend, particularly the material of the sealing surface, and the adhesion strength and the sealing strength with the base material. The relative ratio is determined for good harmony.

  The styrenic block copolymer (A) having an organic acid group is obtained by adding an organic acid group to a styrene block copolymer (B) having no organic acid group, and does not have an organic acid group. Styrene block copolymer (B) includes styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-isobutylene-styrene block copolymer, styrene-butadiene-styrene block copolymer. Styrene-ethylenebutylene-styrene block copolymer, which is a hydrogenated product of merging, and styrene-ethylenepropylene-styrene block copolymer, which is a hydrogenated product of styrene-isoprene-styrene block copolymer. Instead of styrene that constitutes the block copolymer, α-methylstyrene , 3-methylstyrene, 4-propyl styrene, block copolymer of styrene derivatives has been configured and 4-cyclohexyl styrene can also be used. Examples of the organic acid of the organic acid group added to the styrenic block copolymer (B) having no organic acid group include itaconic acid and maleic anhydride.

  A polymer selected from an acrylic polymer and a styrene polymer may be added as a vinyl polymer to the resin composition constituting the heat sealing layer. The vinyl polymer is a polymer of a compound that is a polymerizable vinyl group-containing monomer, and examples of the polymerizable vinyl group-containing monomer include acrylic compounds, styrene compounds, vinyl glycidyl ether, (meth) allyl glycidyl ether, and vinyl acetate. , Vinyl propionate, butadiene, isoprene, chloroprene, olefins, unsaturated esters and the like. An acrylic polymer that is a polymer of these acrylic compounds and a styrene polymer that is a polymer of the above styrene compounds are particularly preferable. The vinyl polymer is not limited to one type, and two or more types can be used.

  Examples of the wax that is one of the optional optional components in the resin composition include paraffin wax, microcrystalline wax, montan wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, carnauba wax, and modified wax. However, polyethylene wax is more preferable.

  Furthermore, it is preferable to use a tackifier according to the required level of heat seal strength.

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

  By the way, the use of a resin composition containing a heat-adhesive resin component and a wax or tackifier as a heat-sealing layer is known per se, but the resin composition that has been generally used in general is an essential component. A wax having a relatively low melting point was used. For example, paraffin wax having a melting point of about 65 ° C. is most commonly used, and a polyethylene wax having a relatively high melting point of at most about 75 ° C. has been used. Also, for the low-temperature sealing properties, the resin composition generally has a softening point of about 65 ° C to 90 ° C.

  Under such a technical background, in a preferred embodiment of the present invention, the wax that is one of the selectively contained components in the resin composition, in particular, a melting point of 80 ° C. or higher, preferably 90 ° C. or higher, more preferably Those having a temperature of 100 ° C. or higher are used. Further, as a tackifier which is another selective component, a melting point of 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher is used. It is characterized by that. By using such a resin composition containing a wax having a relatively high melting point or softening point and / or a tackifier for the heat sealing layer (4), it is additionally formed on the outer surface side of the heat sealing layer as described above. The water repellency of the anti-adhesion layer (5) by the hydrophobic inorganic fine particles, and consequently the thermal stability of the anti-adhesion property, can be significantly improved.

  However, the use of a wax having a melting point (softening point) that is too high and a tackifier may increase the viscosity of the resin composition and reduce the processability, thereby hindering the stable and good heat sealability of the heat sealing layer. There is a fear. For this reason, any one having a melting point (softening point) of 150 ° C. or lower should be used, and it is desirable to use a melting point (softening point) of 140 ° C. or lower.

  Furthermore, in the present invention, the resin composition is preferably used as a lacquer-type heat sealant dissolved or dispersed in a solvent as a material for forming a heat-sealing layer, but consists of a solvent-free 100% solid content. It can also be used as a hot melt resin composition.

  The composition ratio of each component of the resin composition is set in consideration of the adhesive strength with the base material (1), the softening point of the composition, the melt viscosity, the low temperature heat sealability, the heat seal strength, the opening strength, and the like. Preferably, the styrene block copolymer (A) having an organic acid group is 5 to 90% by weight, preferably 10 to 80% by weight, and the styrene block copolymer having no organic acid group. (B) is 5 to 90 wt%, preferably 10 to 80 wt%, wax (C) is 0 to 20 wt%, preferably 3 to 15 wt%, and tackifier (D) is 0 to 30 wt%. , Preferably, by setting to 10 to 20% by weight, it is possible to achieve good heat sealability, sealing property, suitable easy peelability for opening and improved thermal stability of content adhesion prevention effect, Improvement in adhesion between the sealing layer and the adhesion preventing layer can also be achieved. That is, in the resin composition in which the blending amount of the styrene block copolymer (A) having an organic acid group is less than 5% by weight, sufficient adhesive strength with the metal foil layer cannot be obtained. On the other hand, when it exceeds 90% by weight, the adhesion of the hydrophobic inorganic fine particles is impaired. In addition, the addition of the styrene block copolymer (B) having no organic acid group contributes to the improvement of the sealing strength for the container, but if the addition amount is less than 5% by weight, the effect may not be sufficiently obtained. is there. Conversely, if it exceeds 90% by weight, sufficient adhesive strength with the metal foil layer cannot be obtained. The wax and tackifier are generally added to improve the coating suitability of the resin composition, but if the total distribution amount of one or both of them is less than 5% by weight, In addition to the above effects not being sufficiently obtained, the adhesion of the hydrophobic inorganic fine particles is impaired, and the easy-openability may be impaired. Moreover, when those total compounding quantities contain exceeding 40 weight%, there exists a possibility that sufficient sealing strength may not be acquired or the fall of the effect of an adhesion prevention layer may be caused. In particular, when the blending amount of the wax exceeds 20% by weight, sufficient seal strength cannot be obtained. On the other hand, if the tackifier is contained in excess of 30% by weight, the adhesion preventing effect of the adhesion preventing layer may be lowered.

  Although the thickness of the heat sealing layer is not particularly limited, it is generally about 1 to 50 μm in thickness, preferably 2 to 40 μm from the viewpoint of cost, sealing property, productivity, and the like. It is good to be in the range.

  The adhesion preventing layer (5) 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 3000 nm, particularly preferably 3 to 1000 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 (4) and the hydrophobic inorganic fine particles, and has 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, a thermoplastic resin containing at least one or more olefinic resins as a main component can be used.

  Specific examples of the olefin resin include polyethylene, polypropylene, ethylene-unsaturated ester copolymer, and polystyrene. 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 inorganic fine particles is 0 to 50% by weight: 100 to 50% by weight in the 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 (5) also has a significant influence on the content adhesion prevention performance of the lid.

  The anti-adhesion layer (5) 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 with 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, methanol and ethanol are preferred from the standpoints of cost, safety, water repellency, etc., and cyclohexane, methylcyclohexane, methylethylketone, toluene, etc. can also be used for the purpose of improving the adhesion between the heat sealing layer and the hydrophobic inorganic fine particles. It is possible to use a mixture of two or more of these organic solvents. Cyclohexane, methylcyclohexane, methyl ethyl ketone, toluene and the like may dissolve the heat sealing layer. However, the dispersion concentration of the fine particles in the dispersion medium and the time from application to drying of the coating liquid (heat of the liquid dispersion medium) By adjusting the contact time with the sealing layer, there is an advantage that the adhesion to the heat sealing layer can be further improved while maintaining the adhesion prevention property of the surface of the hydrophobic inorganic fine particles.

  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 1.5 g / m. ² is more preferable, and it is optimal to set it in the range of 0.4 to 1.0 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 200 ° C., a time of 5 to 60 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 200 ° C., or the time is set to a time exceeding 60 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 thereof are shown in comparison with comparative examples and control 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 50 μm was bonded to one surface thereof with a polyurethane-based dry laminate adhesive to form a substrate layer (1).

  Next, a heat sealing layer (4) was formed on the surface of the base material layer (1) on the aluminum foil (3) side by a gravure coating method. The base material layer (1) / heat sealing layer (4) laminate obtained in this manner was used as a lid body.

  Here, as the heat sealing layer (4), resin compositions having various blends as shown in Table 1 below were used according to the following materials.

Styrenic block copolymer having organic acid group (A)
Styrene-styrene butylene-styrene block copolymer (I):
Tuftec M1913 (trade name: Asahi Kasei Kogyo Co., Ltd.)
Styrenic block copolymer having no organic acid group (B):
Styrene-styrene butylene-styrene block copolymer (II):
Tuftec H1043 (Product name: Asahi Kasei Kogyo Co., Ltd.)
Wax (C)
C (I): Polyethylene wax having a melting point of 125 ° C.
C (II): Polyethylene wax having a melting point of 108 ° C.
C (III): Polyethylene wax having a melting point of 94 ° C.
C (IV): Micro wax having a melting point of 80 ° C.
C (V): Paraffin wax having a melting point of 68 ° C. Tackifier (D)
D (I): Petroleum hydrogenated resin Melting point 115 ° C
D (II): petroleum-based hydrogenated resin, melting point 100 ° C
D (III): Rosin Softening point 68 ° C
Filler (E)
talc

And the resin composition of the various composition shown in Table 1 was apply | coated by the gravure coating method in the ratio of the application quantity of 5 g / m < ² > all on the said aluminum foil, and the heat sealing layer (4) was formed.

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

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

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

  Each of the hydrophobic inorganic fine particles (SP) or both the hydrophobic inorganic fine particles (SP) and the thermoplastic resin 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 resin 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 (4) of a lid | cover material main body (1) by the gravure coating method, and it forcedly dried and formed the adhesion prevention layer.

In addition, as for application quantity, all are the weight after drying, sample No. 1 to 12 and 15 to 16 are set to 0.5 g / m ² , and sample nos. 13 and 14 were set to 0.8 g / m ² . Moreover, all forced drying was performed on the drying conditions of temperature 100 degreeC x time 15 seconds.

(Type of preparation sample)
Among samples 1-16 of the various lid materials shown in Table 1 obtained above, samples 1-12 are styrene block copolymers (A), (B), wax (C), and tackifier in the heat sealing layer. The effect of the agent (D) was investigated by changing the type and blending ratio of the agent (D). In Samples 13 and 14, the adhesion prevention layer was made of a mixture of hydrophobic inorganic fine particles and thermoplastic resin fine particles, and the coating amount was changed to 0.8 g / m ² to examine the influence. Samples 15 and 16 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 on the back of the lid material of 1 to 16, 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

(2) Adhesion prevention performance after heat treatment For each of the lid materials 1 to 16, the first heat resistance test was performed under the heating conditions of “temperature 100 ° C. × time 30 seconds”, and the second heat resistance test was performed under the heating conditions of “temperature 100 ° C. × time 10 minutes”. The heat resistance test of No. 3 is performed under the same heating prevention condition as “temperature 100 ° C. × hour 30 minutes”. Each sample was stored in a heated atmosphere and then cooled to room temperature. went.

(3) Sealing property (3) -1 Sealing strength Sample No. 1-16 lid materials were heat-sealed on the flange surface of a container main body (polystyrene container) under sealing conditions of 180 ° C. × 90 kgf (882 N) × 1.0 seconds.

  The “sealing strength” is measured in accordance with the sealing strength test method of the ministerial ordinance (Ministry of Health and Welfare Ordinance No. 17 of April 16, 1979) on the component standards of milk and dairy products, and the sealing strength is 13.3 kPa or more. Were determined as pass (◎) and less than 13.3 kPa as unacceptable (×).

(3) -2 Unsealing strength Next, the “unsealing strength” is the same as described above. The lid material heat-sealed as above is pulled at an elevation angle of 45 ° and a speed of 100 mm / min, and the maximum load at the time of opening is defined as the unsealing strength (N). did. 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).

(3) -3 Heat seal strength Sample No. The lid material of 1-16 was cut out to 15 mm width, and it heat-sealed to the 15 mm width strip cut out from the container main body (polystyrene container) on the sealing conditions of 180 degreeC x 0.2 MPa x 1.0 second. 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 16, and slowly rubbed by a length of 200 mm, and visually inspected for the presence of fine particles adhering to the cloth surface. .

And it evaluated by the following evaluation criteria by the transfer adhesion amount (peeling amount) of the hydrophobic inorganic fine particles and the thermoplastic resin fine particles in the black cloth.
◎ ・ ・ ・ No adhesion ○ ・ ・ ・ Slight adhesion recognized as an acceptable range × ・ ・ ・ Clearly much adhesion Table 2 shows the results of the evaluation tests (1) to (4) above. .

  As shown in the test results of “Adhesion prevention performance” in Table 2, in the contents adhesion prevention lid material according to the present invention, the yogurt droplet starts rolling and moving only by slightly tilting the sample. Moreover, this adhesion prevention effect is almost reduced after receiving a severe heat history of 100 ° C. × 10 minutes, and further 100 ° C. × 30 minutes, as seen in the results of the “adhesion prevention performance after heat treatment” test. Maintained well without. This is effective in preventing the contents from adhering to the back surface of the lid material even after heat-sealing the lid material in a container filled with contents containing viscous liquid components such as yogurt, pudding, and jelly. It shows that it is excellent. Moreover, as shown in the results of the “sealability” test, the presence of the adhesion preventing layer does not significantly impair the sealing strength, heat sealability (seal strength), and easy-openability, while maintaining an appropriate sealability, The adhesion preventing performance can be imparted. In addition, as seen in the results of the “adhesion” test, the hydrophobic inorganic particles and the adhesion preventing layer containing the same have good adhesion, and unintentional separation and removal of hydrophobic inorganic fine particles, etc. There is no possibility of partial peeling, etc., and the content adhesion preventing performance can be stably maintained over a long period of time, and there is no possibility of foreign matter mixing into the container.

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

Claims (9)

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 a styrene-based block copolymer having an organic acid group and (A), Ri Do wax (C) and / or resin composition comprising a tackifier and (D) as essential components,
The wax (C) and / or tackifier content adhesion preventing cover material melting or softening point, characterized in der Rukoto all being 80 ° C. of (D). 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 a styrene block copolymer (A) having an organic acid group, a styrene block copolymer (B) having no organic acid group, a wax (C) and / or a tackifier (D). A resin composition containing as an essential component,
The content adhesion prevention lid | cover material whose melting | fusing point or softening point of the said wax (C) and / or tackifier (D) are all 80 degreeC or more. The heat sealing layer is composed of 5 to 90% by weight of a styrenic block copolymer (A) having an organic acid group, 5 to 90% by weight of a styrenic block copolymer (B) having no organic acid group, and a wax (C ) and / or tackifier (D) contents adhesion preventing lid according to claim 2 comprising the resin composition having the composition of the 5 to 40 wt%. The said resin composition is a content adhesion prevention cover material of Claim 3 containing 0 to 20 weight% of waxes, and 0 to 30 weight% of tackifiers. The content adhesion prevention lid according to any one of claims 1 to 4, wherein the melting point or softening point of the wax (C) and / or the tackifier (D) is 90 ° C or higher. Wood. The content adhesion prevention lid material according to any one of claims 1 to 5 , wherein the hydrophobic inorganic fine 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 cover material according to any one of claims 1 to 7 , wherein the adhesion prevention layer is made of a mixed composition of hydrophobic inorganic fine particles and thermoplastic resin fine particles. The content adhesion prevention lid material according to any one of claims 1 to 8, wherein the melting point or softening point of the wax (C) and / or the tackifier (D) is 80 ° C or higher and 150 ° C or lower.

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