JP2012180118A - Content attachment preventing cover material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cover material mainly applied to a container for yogurt packaging of a preliminary fermentation type that effectively prevents yogurt that is a content from sticking to the back surface of a cover and particularly prevents a reduction in the effect by the heat applied upon production of the cover material and filling/sealing while maintaining heat sealability and sealability well.SOLUTION: In the cover material having at least a base material layer, a heat sealing layer, and a content antisticking layer composed of water-repelling fine particles, the heat sealing layer is used which is made of a resin composition containing an acid denaturation polyolefin based resin and a wax and/or a tackifier as essential components and has melting points of 80°C or higher as the wax and the tackifier.

Description

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

  This type of heat sealing lid material is generally provided with a heat sealing layer, that is, a heat sealing layer, on an aluminum foil surface side of a base material layer made of a laminate of a base material film and an aluminum foil via an intermediate resin layer. In other words, a heat sealing layer is provided on the film surface of a base material layer made of a laminate of paper and a vapor deposition film. Then, the lid is placed on the upper surface opening of a cup-shaped container body filled with an object to be packaged such as yogurt, and the peripheral part is heat-sealed on the upper edge flange part of the container body to form a sealed package. It is supposed to be.

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

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

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

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

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

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

  Although this prior proposal technique can exert a very excellent effect in terms of content adhesion prevention effect, the adhesion prevention effect is impaired when the adhesion prevention layer is inferior in heat resistance and receives an undesirable heat history. was there. That is, as the 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 content adhesion prevention layer of the cover material having the most common hot melt type or lacquer type heat sealing layer, the fine particle dispersion is applied in the formation process of the adhesion prevention layer. 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.

  Further, when the heat sealing layer is of a lacquer type, the adhesion between the hydrophobic oxide fine particles and the heat sealing layer is poor, the adhesion preventing layer easily falls off, and the adhesion preventing effect may not be stable.

  The present inventors have conducted extensive experiments to elucidate the causes of the performance deterioration due to the thermal effect of such an adhesion preventing layer and the problem of poor adhesion between the hydrophobic fine particles and the heat sealing layer. As a result of repeated research, it has been found that there is one important cause in the composition of the heat sealing layer, which is the underlying layer, rather than due to the composition or structure of the anti-adhesion layer itself.

  That is, the above-described decrease in heat resistance, that is, the decrease in thermal stability of the anti-adhesion effect is due to heat received during drying, heat received directly from the hot plate during filling sealing, radiant heat received from the hot plate during standby, etc. When the heat-sealing layer melts due to the influence of the heat-sealing layer, fine hydrophobic oxide particles sink into the heat-sealing layer, or the molten component of the heat-sealing layer enters the gaps between the fine particles by capillarity and fills the space between the particles. Thus, it has been found that the effect of preventing the adhesion of contents cannot be obtained sufficiently by reducing the water-repellent surface area. In addition, it has been found that the problem of poor adhesion between the hydrophobic fine particles and the heat sealing layer can be improved epoch-makingly by configuring the heat sealing layer with a heat sealing agent comprising a specific component composition. The present invention has been completed based on the above.

  The present invention is intended to improve the above-described problems in the prior art, more specifically, good heat sealability, sealing performance, and easy peelability for opening, as well as an adhesion preventing layer. It aims at providing the new improvement technology which expresses the adhesion prevention performance of the content which was excellent in the adhesiveness improvement of this, and thermal stability.

  The present invention presents the following means [1] to [7] as a means for achieving the above object, with respect to the content adhesion preventing lid. Here, 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 provided with a content adhesion preventing layer containing hydrophobic inorganic fine particles as a main component on the outer surface of the heat sealing layer,
The heat sealing layer is composed of a resin composition containing an acid-modified polyolefin resin and a wax and / or tackifier as essential components,
A melting point of the wax and the tackifier is 80 ° C. or higher, and the content adhesion preventing lid material.

  [2] The content adhesion preventing lid material according to [1], wherein both the wax and the tackifier have melting points of 90 ° C. or higher.

  [3] The content described in [1] or [2] above, wherein the amount of the unsaturated carboxylic acid or anhydride thereof contained in the acid-modified polyolefin resin is 0.001 to 3% by weight. Material adhesion prevention lid.

  [4] The heat sealing layer includes any one of [1] to [3] described above having a composition of 30 to 90% by weight of an acid-modified polyolefin resin, 1 to 50% by weight of a wax, and 1 to 40% by weight of a tackifier. The content adhesion prevention cover material of Claim 1.

  [5] The content adhesion preventing lid material according to any one of [1] to [4], wherein the hydrophobic inorganic fine particles are hydrophobic silica.

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

  [7] The content adhesion prevention lid material according to any one of [1] to [6], wherein the adhesion prevention layer is composed of a mixed composition of hydrophobic inorganic fine particles and thermoplastic resin fine particles.

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

  Moreover, the heat sealing layer located on the lower surface side of the adhesion preventing layer is composed of a resin composition containing an acid-modified polyolefin resin and a wax and / or tackifier as essential components, and the melting point of the wax and tackifier Since both are made at 80 ° C. or higher, first, the adhesion between the hydrophobic fine particles and the heat sealing layer can be drastically improved, and the adhesion prevention layer does not fall off or cause partial peeling. Of course, there is no possibility that the hydrophobic inorganic fine particles of the adhesion preventing layer are taken into the contents and the adhesion preventing effect is impaired. In addition to the wax component, the tackifier component greatly contributes to enhancing the adhesion of the hydrophobic inorganic fine particles as described above.

  Further, the above composition of the heat sealing layer can improve the heat resistance of the adhesion preventing layer, and can significantly improve the thermal stability of the adhesion preventing performance, and the above excellent after heat sealing to the container body. Maintains good adhesion prevention effect. 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. That is, the coating of the fine particle dispersion is applied in relation to the fact that the content adhesion preventing layer provided in addition to the outer surface of the heat sealing layer is formed by a layer of hydrophobic fine particles such as hydrophobic silica. Low heat in the resin composition due to heating during subsequent drying or axial radiant heat from the hot plate that is 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 during heat sealing It is possible to suppress or prevent the melting point component from being melted early and excessively and exhibiting high fluidity. That is, since the melting point of the wax and / or tackifier of the resin composition is high, melting thereof can be delayed and suppressed. As a result, the hydrophobic inorganic fine particles of the anti-adhesion layer unintentionally sink into the heat sealing layer, or the molten component of the heat sealing layer enters the gaps between the fine particles by capillary action and fills the gaps. Can be prevented. Therefore, it is considered that an extreme decrease in the exposed area of the hydrophobic surface of the fine particles can be prevented and a good content adhesion preventing effect can be maintained.

  The effect of improving the heat resistance as described above can be enjoyed more surely and satisfactorily by setting the melting point of the wax and tackifier to 90 ° C. or higher as described in the above item [2]. it can.

  In addition, as described in [3] above, the amount of unsaturated carboxylic acid or anhydride thereof contained in the acid-modified polyolefin resin is 0.001 to 3% by weight, so that the container is good. Can exhibit excellent heat seal characteristics. 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. However, by optimizing the modification rate with the unsaturated carboxylic acid or its anhydride, it is possible to easily adjust the heat seal characteristics in consideration of the influence of the anti-adhesion layer, and the best sealing state can be realized.

  Moreover, as described in the above item [4], the resin composition constituting the heat sealing layer is composed of 30 to 90% by weight of acid-modified polyolefin resin, 1 to 50% by weight of wax, and 1 to 40% by weight of a tackifier. By having the composition of the above, good heat-sealing property, sealing property, suitable easy peelability at the time of opening, better adhesion of hydrophobic fine particles, in addition to heat of content adhesion prevention effect The stability improvement effect can be achieved reliably.

  In addition, as described in the above item [5], when hydrophobic silica is selectively used for the hydrophobic inorganic fine particles, an excellent content adhesion preventing effect is achieved with a relatively inexpensive material that is easily available from the market. be able to.

  Further, by using hydrophobic inorganic fine particles having an average particle diameter as described in the above item [6], 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 [7], the adhesion preventing layer is made of a mixed composition of hydrophobic inorganic fine particles, which are main components, and thermoplastic resin fine particles. Compensates the bonding force between hydrophobic inorganic fine particles and improves adhesion to the heat sealing layer, and prevents the unintentional particles from falling off and the anti-adhesion layer from peeling off. Preventive effect can be maintained. In addition, the inclusion of the above-mentioned thermoplastic resin fine particles in the anti-adhesion layer acts to supplement the heat sealability of the heat seal layer, and it is good and stable against the container body of the lid regardless of the presence of hydrophobic inorganic fine particle groups. Therefore, it is possible to ensure a suitable heat sealing property, that is, a suitable sealing property in which easy opening and sealing properties are harmonized.

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

  FIG. 1 shows an example of a laminated structure of a content adhesion preventing lid according to the present invention. The lid material includes a base material layer (1) composed of a laminate of a base film layer (2) and a metal foil layer (3), and an outer surface of the base material layer (1) on the metal foil (3) side, A heat sealing layer (5) is provided on the surface facing the inside of the container body when the lid is used via an intermediate resin layer (4). The above laminated structure is the same as that of the conventional lid, and the laminated body including the base material layer (1) and the heat sealing layer (5) will be referred to as a “lid body” here.

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

  The base film layer (2) is 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 (7) to impart design properties.

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

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

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

  The heat sealing layer (5) must have good adhesion to the intermediate resin layer (4) and the container side. In the present invention, the heat sealing layer contains an acid-modified polyolefin resin and a wax and / or a tackifier as essential components, and further contains additives such as an anti-blocking agent and an antioxidant as necessary. It consists of the resin composition contained as. Therefore, the combination mode of the essential components includes a combination of an acid-modified polyolefin resin and a wax, a combination of an acid-modified polyolefin resin and a tackifier, and a three component of an acid-modified polyolefin resin, a wax and a tackifier. Are included, and most preferably a combination of the above three components.

  By the way, the use of a resin composition comprising a combination of essential components as described above as a heat-sealing layer is known per se as described in, for example, Patent Document 6, but is generally used conventionally. In the resin composition, a wax having a relatively low melting point was used as a wax which is an essential component. For example, paraffin wax having a melting point of about 65 ° C. is most commonly used, and a polyethylene wax having a relatively high melting point of at most about 75 ° C. has been used.

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

  Under such a technical background, in the present invention, the wax that is one of the optional essential components in the resin composition has a melting point of 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher. In addition, as a tackifier that is another optional essential component, a melting point of 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher is used. And By using such a resin composition containing a wax having a relatively high melting point and / or a tackifier for the heat sealing layer, as described above, the hydrophobic inorganic fine particles are additionally formed on the outer surface side of the heat sealing layer. The water repellency of the anti-adhesion layer, and hence the thermal stability of the anti-adhesion property, can be significantly improved.

  However, use of a wax having a melting point that is too high and a tackifier may increase the viscosity of the resin composition and reduce processability, and may impair stable and good heat sealability of the heat sealing layer. . For this reason, any of those having a melting point of 150 ° C. or lower should be used, and those having a melting point of 140 ° C. or lower are preferably used.

  Furthermore, in the present invention, the resin composition may be used as a heat-sealing layer forming material, as a lacquer type heat sealant dissolved or dispersed in a solvent, or from a solvent-free 100% solid content. It may be used as a hot melt resin composition.

  The acid-modified polyolefin resin that is an essential component of the heat sealing layer is linear low density polyethylene (LLDPE), low density polyethylene (LDPE), very low density polyethylene (VLDPE), medium density polyethylene (MDPE), high density polyethylene. (HDPE), ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-propylene (block or random) copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene-α-olefin (4 to 4 carbon atoms) 20 α-olefin) A polyolefin-based resin such as a copolymer, polybutene, polypentene, or other olefin homopolymer or copolymer is modified with an acid such as an unsaturated carboxylic acid or its anhydride. Add saturated carboxylic acid or its anhydride to polyolefin resin Examples thereof include modified polyolefin resins containing a carboxyl group obtained by chemical bonding by a reaction or graft reaction. Particularly, acid graft modified polyolefin resins are preferred, and more specifically, maleic anhydride grafts. Modified polyethylene, maleic anhydride graft modified polypropylene, maleic anhydride graft modified ethylene-propylene (block or random) copolymer, maleic anhydride graft modified ethylene-ethyl acrylate copolymer, maleic anhydride graft modified ethylene-vinyl acetate copolymer One or a mixture of two or more selected from polymers and the like is preferred.

  The modification rate of the acid-modified polyolefin resin at this time, that is, the amount of unsaturated carboxylic acid or anhydride thereof contained in the acid-modified polyolefin resin is preferably in the range of 0.001 to 3% by weight. Preferably it is 0.01 to 2 weight%, Most preferably, it is 0.03 to 1 weight%. If the amount of modification in the modified polyolefin resin is small, the adhesiveness may be insufficient. On the other hand, if the amount is large, a crosslinking reaction may occur and the moldability may be deteriorated.

  Examples of the wax that is one of the optional essential components in the resin composition include paraffin wax, microcrystalline wax, montan wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, carnauba wax, and modified wax. More preferably, it is polyethylene wax.

  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.

  The composition ratio of the essential components of the resin composition must be set in consideration of the softening point, melt viscosity, low temperature heat sealability, heat seal strength, opening strength, etc. 30-90 wt% resin, preferably 40-80 wt%, 1-50 wt% wax, preferably 5-40 wt%, and optionally 1-40 wt% tackifier, preferably 5-50 wt%. By setting it to 40% by weight, it is possible to achieve good heat-sealability, sealability, appropriate easy peelability for opening and improved thermal stability of content adhesion prevention effect, heat-sealing layer and adhesion prevention An improvement in layer adhesion can also be achieved. That is, a sufficient sealing strength cannot be obtained with a resin composition in which the blend amount of the acid-modified polyolefin resin is less than 30% by weight. On the other hand, if it exceeds 90% by weight, the sealing strength becomes too high and the easy-openability of the sealing lid is impaired. On the other hand, when the amount of the wax is less than 1% by weight, the adhesion of the hydrophobic fine particles is impaired and the easy-openability is impaired. On the other hand, if it exceeds 40% by weight, sufficient seal strength cannot be obtained. Moreover, if the amount of the tackifier is less than 1% by weight, it is difficult to obtain a sufficient effect of improving the sealing strength. Conversely, if the content exceeds 40% by weight, the adhesion preventing layer is prevented from being adhered. The effect may be reduced.

  The thickness of the heat-sealing layer is not particularly limited, but is generally about 3 to 100 μm in thickness, preferably 5 to 50 μm from the viewpoint of cost, sealing performance, productivity, and the like. It is good to be in the range.

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

  The hydrophobic inorganic fine particles play a dominant role in the content adhesion prevention performance of the lid material, and the material is not particularly limited as long as it is made of a hydrophobic substance having a surface energy of 20 mN / m or more. Specific examples include hydrophobic inorganic fine particles such as hydrophobic silica, alumina, calcium oxide, calcium carbonate, calcium sulfate, and calcium silicate. Of these, the use of hydrophobic silica or alumina is preferred from the viewpoint of hydrophobic performance, cost, availability of ultrafine particle materials from the market, and the like. As the hydrophobic silica, any of dry process silica and wet process silica can be suitably used. The average particle diameter of the hydrophobic inorganic fine particles should be in the range of 1 to 5,000 nm. Ultrafine particles having an average particle size of less than 1 nm are difficult to obtain from the market and are disadvantageous in terms of cost. On the other hand, if the average particle size exceeds 5,000 nm, the heat sealability may be impaired, and the adhesion preventing effect may be reduced, which is not suitable. A preferred average particle size is in the range of 3 to 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 (5) and the hydrophobic inorganic fine particles, and has a good adhesion to the surface layer of the container body. It is desirable to select and use those containing at least the thermoplastic resin as a main component. Examples of such thermoplastic resins include homopolymers such as vinyl acetate resins, polyolefin resins, polyester resins, acrylic resins, styrene resins, or two or more types of copolymers. Since it is a thermoplastic resin, the use of waxes having a low molecular weight, which has been conventionally used as an anti-adhesion agent for lids, is excluded. As a particularly preferable type of thermoplastic resin, the most preferable result can be obtained by using a thermoplastic resin containing at least one or more olefinic resins as a main component.

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

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

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

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

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

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

  The coating liquid is prepared by dispersing thermoplastic resin fine particles and hydrophobic inorganic fine particles 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 1.2 g / m. ² is more preferable, and it is optimal to set it in the range of 0.4 to 0.8 g / m ² . If it is less than 0.1 g / m ² , the content adhesion preventing effect may be insufficient. On the other hand, if it exceeds 5.0 g / m ² , the cost is increased and there is a risk that the fine particles may fall off.

  The drying process after application is also an important factor. Naturally, it may be naturally dried, but in order to improve productivity and adhesion to the heat sealing layer, it should be dried by heating. In this case, the drying conditions are a temperature of 80 to 140 ° C., a time of 5 to 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 140 ° 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 thereof has. The water repellency tends to be impaired.

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

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

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

  Here, as the heat sealing layer (5), resin compositions having various blends as shown in Table 1 below were prepared using the following materials.

Acid-modified polyolefin resin Acid-modified PO (I): acid-modified polypropylene resin (maleic anhydride graft modification)
Denaturation rate 0.5%)
Acid-modified PO (II): acid-modified polypropylene resin (maleic anhydride graft modification)
Denaturation rate 1.0%)
Acid-modified PO (III): acid-modified polypropylene resin (maleic anhydride graft modification)
Denaturation rate 2.0%)
Unmodified PO: Polypropylene resin (maleic anhydride graft modification)
Denaturation rate 0%)

Wax (WX)
WX (I): Polyethylene wax having a melting point of 125 ° C.
WX (II): Polyethylene wax having a melting point of 108 ° C
WX (III): Polyethylene wax with a melting point of 94 ° C
WX (IV): Microwax with a melting point of 80 ° C
WX (V): Paraffin wax having a melting point of 68 ° C

Tackifier (TF)
TF (I) petroleum hydrogenated resin Melting point 115 ° C
TF (II) petroleum hydrogenated resin Melting point 100 ° C
TF (III) Rosin Softening point 68 ℃

And the resin composition of the various composition shown in Table 1 is apply | coated by the gravure coating method in the ratio of the application quantity of 8 g / m < ² > all on the said intermediate resin layer (4), and a heat sealing layer (5) is formed. did.

(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, vinyl chloride
80%, average particle size 100nm)
Each of the hydrophobic inorganic fine particles (SP) or both the hydrophobic inorganic fine particles (SP) and the thermoplastic fine particles (MP) were uniformly dispersed in ethanol to prepare a coating solution. Table 1 shows the blending amount of the hydrophobic inorganic fine particles or the blending ratio of the thermoplastic fine particles and the hydrophobic inorganic fine particles.

And these various coating liquids were apply | coated to the outer surface of the said heat sealing layer (5) of a lid | cover material main body (1) by the gravure coating method, and it forcedly dried and formed the adhesion prevention layer. In addition, as for the coating amount, all are sample weights in the weight after drying. 1 to 16 and 19 to 20 are set to 0.5 g / m ² , and sample Nos. 17 and 18 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 to 20 of the various lid materials shown in Table 1 obtained as described above, samples 1 to 6 and 9 to 11 change the acid-modified polyolefin, wax, and tackifier in the heat-sealing layer, and examine their effects. It is a thing. Sample 10 was obtained by changing the tackifier and examining its influence. Samples 7, 8, and 12 to 16 were examined by changing the blending ratio of each component of the heat sealing layer. In Samples 17 and 18, the adhesion preventing layer was made of a mixture of hydrophobic inorganic fine particles and thermoplastic fine particles, and the effect was examined by changing the coating amount to 0.8 g / m ² . Samples 19 and 20 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 1-20, 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 substrates 1 to 20, the first heat test is performed under the heating condition of “temperature 100 ° C. × time 30 seconds”, and the second heat test is performed under the heating condition of “temperature 100 ° C. × time 10 minutes”. The heat resistance test of No. 3 was performed under the heating conditions of “temperature 100 ° C. × hour 30 minutes”, and each sample was stored in a heated atmosphere and then cooled to room temperature. Went.

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

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

(3) -2 Opening strength Next, “opening strength” was determined by pulling the lid member at an elevation angle of 45 ° and a speed of 100 mm / min, and setting the maximum load at the time of opening as the opening strength (N). And the range of the optimal opening strength was 8-15N, and the thing in this range was evaluated as a pass ((circle) mark), and the thing outside the range was evaluated as a disqualification (x mark).

(3) -3 Heat seal strength Sample No. The lid | cover material of 1-21 was cut out to 15 mm width, and it heat-sealed to the 15 mm width strip cut out from the container main body (paper / polyethylene container) on the sealing conditions of 150 degreeC * 0.2MPa * 1.0sec. Next, the lid member was pulled in the direction of 180 ° at a speed of 100 mm / min, and the maximum load at the time of peeling was defined as the heat seal strength.

  And, the heat seal strength (peeling resistance / sealing property of the cover material) in the cover material as it is without the adhesion prevention layer is used as a reference value, and the rate of decrease or increase in heat seal strength is as follows: It was judged and evaluated.

◎ ・ ・ ・ Reduced strength or increase less than 10% ○ ・ ・ ・ Reduced strength or increase 10% to less than 20% × ・ ・ ・ Reduced strength or increased 20% or more

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

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

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

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

  As shown in the test results of “Adhesion prevention performance” in Table 2, in the contents adhesion prevention lid material according to the present invention, the yogurt droplet starts rolling and moving only by slightly tilting the sample. Moreover, this adhesion prevention effect is almost reduced after receiving a 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 5 ... Heat sealing layer 6 ... Adhesion prevention layer

Claims (7)

In the lid member having at least a base material layer and a heat sealing layer, and provided with a content adhesion preventing layer containing hydrophobic inorganic fine particles as a main component on the outer surface of the heat sealing layer,
The heat sealing layer is composed of a resin composition containing an acid-modified polyolefin resin and a wax and / or tackifier as essential components,
A melting point of the wax and the tackifier is 80 ° C. or higher, and the content adhesion preventing lid material.   The content adhesion preventing lid material according to claim 1, wherein the melting points of the wax and the tackifier are both 90 ° C. or higher.   The content adhesion preventing lid material according to claim 1 or 2, wherein the amount of the unsaturated carboxylic acid or anhydride thereof contained in the acid-modified polyolefin resin is 0.001 to 3% by weight.   4. The heat sealing layer according to claim 1, wherein the heat sealing layer has a composition of 30 to 90% by weight of an acid-modified polyolefin resin, 1 to 50% by weight of a wax, and 1 to 40% by weight of a tackifier. Content adhesion prevention lid.   The content adhesion prevention lid material according to any one of claims 1 to 4, wherein the hydrophobic inorganic fine particles are hydrophobic silica.   The content adhesion prevention lid material according to any one of claims 1 to 5, wherein the hydrophobic inorganic fine particles have an average particle diameter of 1 nm to 5,000 nm.   The content adhesion prevention lid material according to any one of claims 1 to 6, wherein the adhesion prevention layer is made of a mixed composition of hydrophobic inorganic fine particles and thermoplastic resin fine particles.

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