JP4521807B2 - Heat-sealable composite film - Google Patents

Description

  The present invention relates to a heat-sealable composite film comprising at least a base material part and a heat-seal part, having easy peelability, and mainly used for packaging bags.

  Conventionally, composite films used for packaging bags that wrap articles typified by food consist of at least a base material part and a heat seal part. If necessary, the content is blocked by outside air in order to prevent the contents from being altered. It has a function to prevent oxidation of objects. Moreover, it has the function of preventing the deterioration by preventing light from being blocked by light shielding, the contents absorbing moisture during storage, and conversely drying.

  The packaging bag using this composite film generally employs a method of sealing by heat-sealing the heat-sealed portion on the inner surface side. Therefore, in order to achieve the above-mentioned purpose of the packaging bag, this heat seal part needs to have a sufficient sealing property, and a sufficient heat so that the sealed part is not peeled off in the process of transportation or the like. Seal strength is required. In general, in order to have sufficient bag resistance, the heat seal strength of the packaging bag is required to be 20 N / 15 mm width or more.

  However, excessive heat seal strength to protect the contents, on the contrary, cannot be easily opened by hand when used by consumers, and it is often necessary to use a device such as a bag. In addition, a large force is required at the time of opening, and even if it can be opened, the contents may jump out at the moment of opening. In general, when the heat seal strength exceeds 15 N / 15 mm width, it is difficult to open by hand peeling.

  In other words, the seal portion needs to have a strength of 20 N / 15 mm width or more in order to withstand bag breaking during transportation, but in order to be easily opened by hand, it is better not to exceed 15 N / 15 mm width. It is necessary to satisfy contradictory properties.

Conventionally, a composite film for a packaging bag has been proposed in which the heat seal strength is weakened to 15 N / 15 mm width or less so that it can be easily opened by hand while having sufficient sealing performance. However, in these films, the heat seal strength is uniformly less than 20 N / 15 mm width, so that when the contents are heavy, the sealed portion where the load is applied in the process of transportation or the like is peeled off. The properties were not sufficient (for example, see Patent Documents 1 to 3).
JP 2002-154555 A (0042 column) JP 2001-179907 A JP-A-8-267677

  The present invention has sufficient heat seal strength to prevent the seal from being peeled off in the process of transporting a packaging bag filled with the contents using one composite film. On the other hand, when the consumer opens the bag, the heat seal strength is partially changed in one bag according to the conditions at the time of bag making so that the scheduled opening portion can be easily opened by hand. An object of the present invention is to provide a composite film that can be used.

  As a result of intensive studies in order to solve the above problems, the inventors have made the present invention. The first aspect of the invention is a composite film comprising at least a base material portion and a heat seal portion, wherein the heat seal portion comprises at least two layers, and the two layers mainly comprise a high melting point resin having a melting point of 135 ° C. to 180 ° C. A layer (c) mainly composed of a mixed resin of a low melting point resin having a melting point of 80 ° C. to 135 ° C. and the high melting point resin, and the melting point of the high melting point resin and the low melting point The difference between the highest melting point of the resin is 20 ° C. or more, and the two layers are laminated in the order of (c) and (b) from the heat seal surface of the heat seal part. It is a film. With this configuration, one composite film can have two types of heat seal strength depending on heat seal conditions. Depending on the conditions at the time of bag making, a plurality of heat seal portions of one bag can be used depending on the application. Different heat seal strengths can be provided.

  A second aspect of the invention is a composite film comprising at least a base material portion and a heat seal portion, wherein the heat seal portion is composed of at least three layers, and the three layers mainly comprise a low melting point resin having a melting point of 80 ° C to 135 ° C. Layer (a), a layer (b) mainly composed of a high melting point resin having a melting point of 135 ° C. to 180 ° C., and a layer (c) mainly composed of a mixed resin of a low melting point resin and the high melting point resin, The low melting point resin of the layer (a) and the low melting point resin of the layer (c) are the same or compatible with each other when melted, and the melting point of the high melting point resin of the layer (b) and the low melting point of the layer (c) The difference between the melting point resin and the highest melting point is 20 ° C. or more, and the three layers are laminated in the order of (a), (c) and (b) from the heat seal surface of the heat seal part. It is a film. With this configuration, one composite film can have two types of heat seal strength depending on heat seal conditions. Depending on the conditions at the time of bag making, a plurality of heat seal portions of one bag can be used depending on the application. Different heat seal strengths can be provided.

  In the first or second aspect of the invention, preferably, the ratio of the high melting point resin contained in the layer (c) is in the range of 5 to 30% by weight, and the ratio of the low melting point resin is in the range of 30 to 95% by weight. It is a heat-sealable composite film characterized by being. Alternatively, the heat-sealable composite film is characterized in that the thickness ratio of the layer (b) and the layer (c) is 3: 1 to 1: 4. In the second aspect of the invention, preferably, the heat-sealable composite is characterized in that a low-melting point resin layer having a melting point of 80 ° C. to 135 ° C. is further laminated on the heat seal part following the layer (a). It is a film.

  The composite film of the present invention can realize two stable heat seal strengths with one film. At that time, the heat seal strength can be changed by a simple means of changing the heat seal condition. When the composite film is used to fill the contents and make a bag, the seal part that is loaded during transportation has sufficient heat seal strength to prevent the seal from being peeled off, while the consumer opens it. The heat seal portion can be easily opened by hand while maintaining a low heat seal strength.

  The present invention will be specifically described below. FIG. 1 is a schematic sectional view of an embodiment of the composite film of the present invention. The composite film 7 includes at least a base material portion 11 and a heat seal portion 8. Further, the heat seal portion 8 is composed of at least two layers, which are a layer (b) 22 mainly composed of a high melting point resin and a layer (c) 23 mainly composed of a mixed resin of a low melting point resin and a high melting point resin. Yes, layers (c) 23 and (b) 22 are laminated in this order from the heat seal surface 9 of the heat seal portion 8. In addition, a heat seal surface means the surface on the opposite side to the surface where a heat seal part and a base-material part contact | connect with respect to a heat seal part.

  Further, the heat seal portion may be composed of at least three layers as shown in FIG. 2, and these three layers are a layer (a) 21 mainly composed of a low melting point resin, a layer mainly composed of a high melting point resin ( b) 22, a layer (c) 23 mainly composed of a mixed resin of a low melting point resin and a high melting point resin. The layer (a) 21, the layer (c) 23, the layer ( b) The layers may be laminated in the order of 22.

  In the composite film, the base material part 11 is a part responsible for the strength of the film and other functions. When carrying the strength of the film, generally, a stretched film made of polypropylene (hereinafter referred to as PP) (hereinafter referred to as OPP), a stretched film made of nylon resin (hereinafter referred to as Ny) (hereinafter referred to as ONy), a stretched film made of polyethylene terephthalate (hereinafter referred to as PET) (hereinafter referred to as PET film), etc. Are preferably used, but other films may be used as necessary.

  As a function other than strength, for example, there is a gas barrier property, particularly an oxygen barrier property. Examples of methods for imparting barrier properties include the above-mentioned OPP, ONy, PET film surfaces, polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA), PVA mixed with scaly inorganic material, organosiloxane, etc. A film coated with a layer having a property can be used. Further, a film obtained by laminating and stretching PP and ethylene-vinyl alcohol copolymer resin (hereinafter EVOH) instead of OPP, or a film obtained by laminating and stretching Ny and metaxylene adipamide resin instead of ONy, A film obtained by laminating and stretching Ny and EVOH can be used. Moreover, the film etc. which vapor-deposited aluminum, aluminum oxide, silicon oxide etc. on the surface of the said OPP, ONy, and PET film can be used. Furthermore, a film having gas barrier properties such as a PVDC film, an EVOH film, an aluminum foil, or the like can be laminated on the OPP, ONy, or PET film.

  In addition, in order to find a desire to purchase or to display information related to the contents on the packaging bag, printing can be performed on a film constituting the base portion such as the OPP, ONy, or PET film described above.

  Furthermore, if necessary, the above-mentioned various films and films other than the above can be laminated and used. There is no restriction | limiting in particular in the method of laminating | stacking a film, A well-known technique can be utilized. For example, there are a method of applying and bonding an adhesive on the film surface, a method of extruding a molten resin between two films to form an intervening layer, and the like. FIG. 3 is a schematic cross-sectional view of an example in the base material portion of the composite film. The OPP layer 12, the printing layer 13, the intervening layer 14, the vapor deposition aluminum layer 15, and the PET layer 16 are laminated in order from the outer surface side when the bag is made.

  In the composite film, the heat seal part 8 or 20 is used so as to be on the inner surface side of the bag when bag-making is performed using this, and a bag is formed by heat-sealing the opposite surfaces in contact with each other. It is the part that bears the function of sealing after filling the contents. In an actual packaging bag, there are a method of forming a bag having an opening on one side and then filling the contents to seal the opening, and a method of simultaneously forming the bag and filling the contents.

  The heat seal part of the composite film is composed of at least two layers. These two layers are a layer (b) 22 mainly composed of a high melting point resin having a melting point of 135 ° C. to 180 ° C., a low melting point of 80 ° C. to 135 ° C. A layer (c) 23 mainly composed of a mixed resin of the melting point resin and the high melting point resin, and the difference between the melting point of the high melting point resin of the layer (b) and the highest melting point of the low melting point resin of the layer (c) is 20 The layer (c) 23 and the layer (b) 22 are laminated in this order from the heat seal surface. Note that “mainly” means containing 50% by weight or more. The difference between the melting point of the high melting point resin of the layer (b) and the highest melting point of the low melting point resin of the layer (c) is preferably 23 ° C. or more, and more preferably 25 ° C. or more.

  Further, the heat seal part may be composed of at least three layers. The three layers are a layer (a) 21 mainly composed of a low melting point resin having a melting point of 80 ° C to 135 ° C, and a melting point of 135 ° C to 180 ° C. A layer (b) 22 mainly composed of a high melting point resin, a layer (c) 23 mainly composed of a mixed resin of a low melting point resin and the high melting point resin, and the low melting point resin and the layer (c) of the layer (a) ) Are the same or compatible with each other when melted, and the difference between the melting point of the high melting point resin of the layer (b) and the highest melting point of the low melting point resin of the layer (c) is 20 ° C. or more. Yes, it is preferable that the layer (a) 21, the layer (c) 23, and the layer (b) 22 are laminated in this order from the heat seal surface.

  As the low melting point resin of the layer (a), a thermoplastic resin having a melting point of 90 ° C. to 130 ° C. is preferably used, particularly low density polyethylene (hereinafter referred to as LDPE), ethylene-α olefin copolymer, ethylene-vinyl acetate copolymer. A polymer (hereinafter referred to as EVA), an ethylene-acrylic acid copolymer, and an ethylene-acrylic acid ester copolymer can be suitably used. Moreover, each said resin may be used individually, respectively, and 2 or 3 types or more may be mixed and used for it. The layer (a) preferably contains 50% by weight or more mainly composed of a low melting point resin, and may contain other components as long as the object of the present invention is not impaired. For example, a slip agent, an antiblocking agent, an antistatic agent, an antifogging agent, etc. can be included as needed.

  As the high melting point resin of the layer (b), a thermoplastic resin having a melting point of 135 ° C. to 165 ° C. is more preferably used, and PP is particularly preferably used. For PP, ethylene or butene may be copolymerized for the purpose of imparting cold resistance and flexibility. Moreover, each said resin may be used individually, respectively, and 2 or 3 types or more may be mixed and used for it. For example, a PP homopolymer having a melting point of 160 ° C. and a PP copolymer having a melting point of 140 ° C. can be mixed and used. However, when a mixed resin is used, the difference between the lowest melting point of the melting points of each resin and the highest melting point of the low melting point resin of the layer (c) described later is preferably 20 ° C. or higher. By doing in this way, easy peelability can be implement | achieved comparatively easily. Preferably it is 23 degreeC or more, More preferably, it is 25 degreeC or more.

  As long as the layer (b) contains 50% by weight or more mainly composed of a high melting point resin, the layer (b) may contain other components as long as the object of the present invention is not hindered. For example, in order to impart flexibility, polybutene, ethylene-propylene rubber, or the like can be mixed.

  The layer (c) is mainly composed of a mixed resin of a low melting point resin and a high melting point resin. The low melting point resin of the layer (c) may be the same as that used when the layer (a) is provided, or is compatible with the low melting point resin of the layer (a) when melted. Another resin may be used. For example, when the low melting point resin of the layer (a) is EVA, the low melting point resin of the layer (c) may be EVA or LDPE. For example, the low melting point resin of the layer (a) may be EVA, and the low melting point resin of the layer (c) may be a mixed resin of EVA and an ethylene-α-olefin copolymer. Of course, even when the layer (a) is not provided, the resin exemplified here can be used for the layer (c).

  More preferably, the proportion of the high melting point resin contained in the layer (c) is in the range of 5 to 30% by weight, and the proportion of the low melting point resin is in the range of 30 to 95% by weight. When the ratio of the high melting point resin contained in the layer (c) is 5% by weight or more, a sufficient sealing strength is obtained when heat sealing is performed at a temperature higher than the melting point of the high melting point resin. Further, when the ratio of the high melting point resin contained in the layer (c) is 30% by weight or less, the fusion between the layer (b) and the layer (c) at the time of forming the heat seal portion hardly occurs, When heat-sealed at a temperature lower than the melting point of the high-melting point resin, more stable and easy peelability is exhibited. Further, when the ratio of the low melting point resin contained in the layer (c) is 30% by weight or more, the interlayer adhesive strength between the layer (a) and the layer (c) is sufficiently stable, and the composite film is wound or fed out. When peeling, almost no peeling occurs. In addition, the layer (c) should just contain 50 weight% or more of the mixed resin of the said low melting point resin and high melting point resin as a main body, and may contain the other as long as the objective of this invention is not disturbed. In other words, the proportion of the others is 0 to less than 50% by weight. For example, in order to further improve the transparency of the composite film, a polyolefin-based elastomer (hereinafter sometimes referred to as TPO) or the like can be mixed as a compatibilizer. Moreover, when adding a slip agent, an antistatic agent, an antifogging agent, etc. to a layer (a), the same additive can be added to a layer (c) in order to assist the effect.

  The thickness ratio of the layer (b) and the layer (c) in the heat seal part of the composite film is preferably 3: 1 to 1: 4. There is a case where the thickness ratio between the layer (b) and the layer (c) is related to the heat-seal strength showing easy peelability. In such a case, when the thickness ratio of the layer (b) is increased, the heat seal strength is decreased, and when the thickness ratio is decreased, the heat seal strength is increased. And when the thickness ratio of the layer (b) and the layer (c) is 3: 1 or less, the heat seal strength showing easy peelability is sufficiently stable. When this happens, it is easier to prevent troubles such as opening this part easily. In addition, when the thickness ratio of the layer (b) and the layer (c) is 1: 4 or more, the heat seal strength showing easy peelability does not easily exceed 15 N / 15 mm width, It may be easy to obtain stable easy peelability.

  As for the thickness of the heat seal part of a composite film, 8 micrometers or more are more preferable. When the thickness of the heat-sealed part is 8 μm or more, the heat-sealing is more satisfactory for foreign matters such as steps due to overlapping of the films, film wrinkles, and contents adhered to the place to be sealed. Sex is likely to become more complete. Although there is no element which prescribes | regulates the upper limit of thickness, when the ease of handling of a film and economical efficiency are considered, 100 micrometers or less are preferable.

  The heat seal part of the composite film may have four or more layers as necessary as long as the above-described conditions are satisfied. For example, in order to prevent curling of the film, it may be a symmetric configuration, may be a configuration in the order of (c) (b) (c) from the heat seal surface, or (a) (c) from the heat seal surface. It can also be set as the structure by the order of (b) (c) (a). In the former, since the effect of the composite film is manifested in the second layer from the heat seal surface, the preferred range of the thickness ratio of the layer (b) and the layer (c) described above is the second layer from the heat seal surface, respectively. And the thickness ratio of the first layer is applicable. In the latter, since the effect of the composite film is manifested in the third layer from the heat seal surface, the preferred range of the thickness ratio of the layer (b) and the layer (c) described above is the third layer and the third layer from the heat seal surface, respectively. This corresponds to the thickness ratio of the second layer.

  The heat seal strength of such a composite film changes rapidly when the heat seal temperature is near the melting point of the high melting point resin, and the heat seal strength is 15 N / 15 mm width or less when the heat seal temperature is lower than the melting point. It shows easy peelability, and when the heat seal temperature is higher than the melting point, the heat seal strength is 20 N / 15 mm width or more, and a strong seal is possible. Therefore, if the above-mentioned composite film is used, when forming a packaging bag, the portion to be opened can be easily opened by heat sealing at a temperature lower than the melting point of the high melting point resin. Sealing other than the above high melting point resin at a temperature higher than the melting point of the high melting point resin results in a strong packaging bag, so that even if the contents are heavy, the sealed part is difficult to peel off during transportation and other processes. A packaging bag having bag characteristics can be realized.

  It should be noted that the heat seal strength is stable in each of the regions where the heat-seal strength is easy to peel and the region where the heat-seal strength is high and the region where the heat-seal strength is high is around the melting point of the high-melting point resin. Thus, it hardly changes depending on the heat seal temperature or the heat seal pressure. For this reason, even if the temperature and pressure at the time of heat sealing are slightly changed, the performance of the bag is hardly affected, and can be stably used for any bag making system and filling system. Furthermore, the heat seal strength in the region where the heat seal strength is low can be arbitrarily set by changing the thickness ratio of the layer (b) and the layer (c).

  As a method for forming the heat seal portion of the composite film, a known multilayer film manufacturing method can be used. For example, coextrusion and extrusion from a T die, cooling and film formation by a cooling roll, coextrusion and extrusion from a circular die There are a method of cooling and film formation by inflation, a method of sequentially extruding each layer and laminating. Moreover, after forming a multilayer film once, you may extend | stretch further. In particular, a method of forming a film to be a heat seal part by further stretching after co-extrusion film formation is preferable because it is easy to control the adhesive strength between the layers of the heat seal part to an appropriate range.

  In the composite film, the innermost layer (a) can be laminated on the heat seal surface of the heat seal part, and the melting point is 80 ° C. to 135 ° C. on the heat seal surface side of this layer (a). A melting point resin layer can be laminated. Thereby, for example, it becomes easy to provide an antistatic function. For such a low melting point resin layer, low density polyethylene, ethylene-α olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer are particularly suitable. is there. The resin layer may contain other materials as long as the object of the present invention is not hindered. If necessary, for example, a slip agent, an antiblocking agent, an antistatic agent, an antifogging agent and the like can be contained.

  FIG. 4 is a schematic cross-sectional view in an example in which a resin layer is further laminated on the heat seal surface side of the layer (a) of the heat seal portion of the composite film. An LDPE layer 24 is further laminated on the heat seal surface 25 side of the layer (a) 21 of the composite film 10 composed of the base material portion 11 and the heat seal portion 20. There is no particular limitation on the lamination method. For example, after forming a composite film, there is a method of performing extrusion lamination on the heat seal surface side of the layer (a) of the heat seal portion.

  There is no restriction | limiting in particular in the method of laminating | stacking a base material part and a heat seal part, A well-known technique can be utilized. For example, there are a method of applying and bonding an adhesive on the film surface, a method of extruding a molten resin between two films to form an intervening layer, and the like. FIG. 5 is a schematic cross-sectional view of an embodiment in which a base material portion and a heat seal portion are bonded to each other by applying an adhesive 31, and FIG. 6 is an illustration of extruding a molten resin 32 between two films. It is a schematic sectional drawing in one Example used as an intervening layer. The method of extruding a molten resin between two films to form an intervening layer is an application of extrusion lamination. Therefore, as in the case of extrusion lamination, an anchor coating agent can be applied to the film surface as necessary to improve the adhesive strength. The resin used for the intervening layer may be a resin used for extrusion lamination, for example, LDPE, ethylene-α olefin copolymer, EVA, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer. There are coalescence, PP, etc.

  The composite film configured in this way exhibits completely different heat seal strengths (the heat seal strength jumps) depending on whether the heat seal temperature is above or below a certain threshold value, and the heat seal temperature changes within each range. However, it exhibits a certain heat seal strength. The reason for such an effect is considered as follows. When the heat seal surfaces of the composite film are put together and sealed at a relatively low temperature, the layers (c) on the heat seal surface (if the layers (a) are provided, the layers (a) are welded), the layers ( b) remains unmelted. As a result, when the sealed portion is peeled off, a weak seal is obtained in which the interface between the layer (b) and the layer (c) is peeled off. On the other hand, when sealing at a relatively high temperature, the layer (b) also melts, and as a result, the sealing strength increases at any interface of the composite film, resulting in a strong seal.

  About the form of the packaging bag using a composite film, there is no restriction | limiting in particular, For example, the 4-way seal bag shown in FIG. 7, the barracuda bag shown in FIG. 8, the pillow bag shown in FIG. 9, the pillow gazette bag shown in FIG. There are a four-corner seal gusset bag shown in FIG. 11, a standing bag shown in FIG. If at least one of the above-mentioned bag seal portions is heat-sealed at a heat seal temperature lower than the melting point of the high-melting point resin in the layer (b) of the heat seal portion of the composite film, a seal portion exhibiting easy peelability is obtained. Becomes the part to be opened. If the remaining seal part is heat-sealed at a heat seal temperature higher than the melting point of the high melting point resin, it becomes a seal part with strong seal strength. Sufficient heat seal strength so that the sealed part does not peel off during transportation Thus, a packaging bag that can be easily opened by hand when used by a consumer can be obtained. The position of the seal part having easy peelability and the seal part having strong seal strength may be determined according to the purpose of the packaging bag.

  As described above, in forming a packaging bag, after forming a bag having an opening on one side once, filling the contents and sealing the opening, and simultaneously forming the bag and filling the contents And can be appropriately selected according to the purpose. Once a bag is formed, filled and sealed, the sealing part that forms the bag has strong sealing strength, and the sealing part that is sealed last is easily peelable to prevent bag breakage during filling. This is preferable. Hereinafter, the present invention will be described based on examples.

  First, as the heat seal part, a resin having a melting point of 140 ° C. and a density of 0.89 and a random PP (PF4334 manufactured by Sun Allomer) was used as the layer (b). The layer (c) is 70% by weight of low density polyethylene (F2225.2 manufactured by Asahi Kasei Corporation), 20% by weight of the same random PP used for the layer (b), and has a melting point of 67 ° C. and a density of 0.005. A resin prepared by adding 10% by weight of 865 polyolefin elastomer (engaged EG8150 manufactured by Dow) and mixing them was used. Using these, the layers are co-extruded in the order of layer (c), layer (b), layer (c) so that each layer has a thickness of 10 μm, and a three-layer film with a total thickness of 30 μm is created. did.

  Next, using a PET film “Embret PET” 25 μm manufactured by Unitika Co., Ltd. as the base material, a polyethyleneimine-based anchor coating agent was applied to the bonding surface of the PET film, and then the substrate was subjected to extrusion lamination using LDPE as an intervening layer. The material part and the heat seal part were laminated | stacked and the composite film was obtained. The thickness of the LDPE intervening layer was 20 μm, and the total thickness of the composite film was 75 μm. The heat seal strength and haze of the obtained composite film were evaluated. The evaluation results are shown in Table 1.

  The heat seal strength was evaluated as follows. First, the test pieces were heat-sealed with a heat seal tester TP-701S manufactured by Tester Sangyo Co., Ltd. at a heat seal time of 1 second and a heat seal pressure of 98 kPa. At that time, test pieces were prepared by changing the heat seal temperature from 100 ° C. to 200 ° C. in 6 levels every 20 ° C. The heat seal strength was measured in accordance with JIS-Z1707 in an environment of 23 ° C. and 50% relative humidity. However, the test speed was 300 ± 30 mm per minute. It measured about the flow direction (MD) and width direction (TD) of the film, respectively. The haze was evaluated according to ASTM D-1003.

  From Table 1, it can be seen that the heat seal strength jumps between the heat seal temperatures of 140 ° C. and 160 ° C., and before and after that, a constant heat seal strength is shown regardless of the heat seal temperature. . In other words, by a simple means of changing the heat seal temperature, using one film, the heat seal strength of the part to be opened is easily peelable with a width of 15 N / 15 mm or less, that is, the heat seal part with good openability, and the others It can be seen that the heat-sealing strength can be stably used separately for a heat-seal portion having a sufficient bag-breaking resistance of 20 N / 15 mm width or more. It can also be seen that the haze remains in a range where there is no particular problem.

  First, as a heat seal portion, layer (a) is EVA having a melting point of 92 ° C., layer (b) is a resin obtained by mixing 70% by weight of PP having a melting point of 160 ° C. and 30% by weight of polybutene resin, and layer (c). A resin prepared by mixing 60% by weight of the EVA, 25% by weight of the PP, and 15% by weight of a polyolefin elastomer having a density of 0.87 was used. Using these, the layers are coextruded so that the layer structure is in the order of layer (a), layer (c), layer (b), layer (c), layer (a), and further tripled in the film flow direction. , Stretched 2.5 times in the width direction, layer (a) 1 μm, layer (c) 2 μm, layer (b) 5 μm, layer (c) 2 μm, layer (a) 1 μm in order and thickness, total thickness 11 μm A five-layer film was prepared. Next, using a PET film “Embret PET” 25 μm manufactured by Unitika Co., Ltd. as the base material, a polyethyleneimine-based anchor coating agent was applied to the bonding surface of the PET film, and then the substrate was subjected to extrusion lamination using LDPE as an intervening layer. The material part and the heat seal part were laminated | stacked and the composite film was obtained. The thickness of the LDPE intervening layer was 15 μm, and the total thickness of the composite film was 51 μm. The obtained composite film was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  In this film, there is a jump in heat seal strength between the heat seal temperature of 160 ° C. and 180 ° C., and before and after that, the heat seal strength is constant regardless of the heat seal temperature as in Example 1. I understand. Moreover, the haze showed a favorable value.

  First, as a heat seal portion, layer (a) is EVA having a melting point of 92 ° C., layer (b) is a resin obtained by mixing 70% by weight of PP having a melting point of 160 ° C. and 30% by weight of polybutene resin, and layer (c). A resin in which 60% by weight of the EVA, 25% by weight of the PP, and 15% by weight of a polyolefin-based elastomer having a density of 0.87 are mixed, and the layer constitution is layer (a), layer (c), layer (b), Layer (c) and layer (a) are co-extruded in the order, and further stretched 3 times in the film flow direction and 2.5 times in the width direction, layer (a) 1 μm, layer (c) 2 μm, A five-layer film having a total thickness of 10 μm was prepared in the order and thickness of layer (b) 4 μm, layer (c) 2 μm, and layer (a) 1 μm. Next, using a PET film “Embret PET” 12 μm manufactured by Unitika Co., Ltd. as the base material, a polyethyleneimine-based anchor coating agent was applied to the bonding surface of the PET film, and then the substrate was subjected to extrusion lamination using LDPE as an intervening layer. The material part and the heat seal part were laminated | stacked and the composite film was obtained. The thickness of the LDPE intervening layer was 20 μm, and the total thickness of the composite film was 42 μm. Table 2 shows the evaluation results of the heat seal strength of the obtained composite film.

  The heat seal strength was evaluated as follows. First, the test pieces were heat-sealed with a heat seal tester TP-701S manufactured by Tester Sangyo Co., Ltd. with a heat seal time of 2 seconds. At that time, the heat seal temperature was changed from 100 ° C. to 200 ° C. to 6 levels every 20 ° C., and the heat seal pressure was further changed to 2 levels of 98 kPa and 196 kPa, respectively, to prepare test pieces. . The heat seal strength was measured in accordance with JIS-Z1707 in an environment of 23 ° C. and 50% relative humidity. However, the test speed was 300 ± 30 mm per minute. The film flow direction and the width direction were measured, and the average value was defined as the heat seal strength of the film.

  From Table 2, by a simple means of changing the heat seal temperature, using one film, the heat seal strength of the part to be opened is 15N / 15 mm width or less easily peelable, that is, a heat seal part with good openability, It can be seen that the other heat seal strength can be stably used separately for a heat-seal portion having a sufficient bag resistance that has a width of 20 N / 15 mm or more.

  First, as a heat seal portion, layer (a) is EVA having a melting point of 92 ° C., layer (b) is a resin obtained by mixing 70% by weight of PP having a melting point of 160 ° C. and 30% by weight of polybutene resin, and layer (c). A resin in which 70% by weight of the EVA, 10% by weight of the PP and 20% by weight of a polyolefin-based elastomer having a density of 0.87 are mixed, and the layer constitution is layer (a), layer (c), layer (b), Coextruded in the order of layer (c) and layer (a), and further stretched 3 times in the film flow direction and 2.5 times in the width direction, layer (a) 1 μm, layer (c) 3. A five-layer film having a total thickness of 10 μm was prepared in the order and thickness of 5 μm, layer (b) 1 μm, layer (c) 3.5 μm, and layer (a) 1 μm. Next, a unit film made of Unitika Co., Ltd. “Embret PET” 12 μm was used as the base material, and the base material and the heat seal part were laminated by extrusion lamination using LDPE as an intervening layer in the same manner as in Example 1. A film was obtained. The thickness of the LDPE intervening layer was 20 μm, and the total thickness of the composite film was 42 μm. The heat seal strength was evaluated in the same manner as in Example 3 using the obtained composite film. The evaluation results are shown in Table 2. Similar to Example 3, two types of heat seal strength were obtained using one film.

  First, as a heat seal portion, layer (a) is EVA having a melting point of 92 ° C., layer (b) is a resin obtained by mixing 70% by weight of PP having a melting point of 160 ° C. and 30% by weight of polybutene resin, and layer (c). A resin in which 30% by weight of the EVA, 50% by weight of an ethylene-octene copolymer having a melting point of 120 ° C. and 20% by weight of the PP is mixed, has a layer constitution of layer (a), layer (c), layer (b ), Layer (c) and layer (a) are co-extruded, and further stretched 3.5 times in the film flow direction and 3 times in the width direction, and layer (a) 1 μm, layer (c) A five-layer film having a total thickness of 10 μm was prepared in the order and thickness of 2.5 μm, layer (b) 3 μm, layer (c) 2.5 μm, and layer (a) 1 μm. Next, a unit film made of Unitika Co., Ltd. “Embret PET” 12 μm was used as the base material, and the base material and the heat seal part were laminated by extrusion lamination using LDPE as an intervening layer in the same manner as in Example 1. A film was obtained. The thickness of the LDPE intervening layer was 20 μm, and the total thickness of the composite film was 42 μm. The heat seal strength was evaluated in the same manner as in Example 3 using the obtained composite film. The evaluation results are shown in Table 2. Similar to Example 3, two types of heat seal strength were obtained using one film.

  First, as a heat seal portion, layer (a) is EVA having a melting point of 92 ° C., layer (b) is a resin obtained by mixing 70% by weight of PP having a melting point of 160 ° C. and 30% by weight of polybutene resin, and layer (c). A resin in which 30% by weight of the EVA, 50% by weight of an ethylene-octene copolymer having a melting point of 120 ° C. and 20% by weight of the PP is mixed, has a layer constitution of layer (a), layer (c), layer (b ), Layer (c) and layer (a) are co-extruded, and further stretched 3.5 times in the film flow direction and 3 times in the width direction, and layer (a) 1.5 μm, layer ( c) Five layers of films having a total thickness of 15 μm were prepared in the order and thickness of 4 μm, layer (b) 4 μm, layer (c) 4 μm, and layer (a) 1.5 μm. Next, a unit film made of Unitika Co., Ltd. “Embret PET” 12 μm was used as the base material, and the base material and the heat seal part were laminated by extrusion lamination using LDPE as an intervening layer in the same manner as in Example 1. A film was obtained. The thickness of the LDPE intervening layer was 20 μm, and the total thickness of the composite film was 47 μm. Using the obtained composite film, the heat seal strength as in Example 3 was evaluated. The evaluation results are shown in Table 2. Similar to Example 3, two types of heat seal strength were obtained using one film.

  First, as a heat seal portion, layer (a) is EVA having a melting point of 92 ° C., layer (b) is a resin obtained by mixing 70% by weight of PP having a melting point of 160 ° C. and 30% by weight of polybutene resin, and layer (c). A resin in which 30% by weight of the EVA, 50% by weight of an ethylene-octene copolymer having a melting point of 120 ° C. and 20% by weight of the PP is mixed, has a layer constitution of layer (a), layer (c), layer (b ), Layer (c) and layer (a) are co-extruded, and further stretched 3.5 times in the film flow direction and 3 times in the width direction, and layer (a) 1.5 μm, layer ( c) Five layers of films having a total thickness of 15 μm were prepared in the order and thickness of 4 μm, layer (b) 4 μm, layer (c) 4 μm and layer (a) 1.5 μm. Next, the PET film “Embret PET” 12 μm manufactured by Unitika Co., Ltd. was used as the base material portion, and the base material portion and the heat seal portion were laminated by extrusion lamination using LDPE as an intervening layer in the same manner as in Example 1. The thickness of the LDPE intervening layer was 20 μm. Furthermore, 20 μm of LDPE having a melting point of 106 ° C. was laminated on the surface of the layer (a) of the heat seal part by extrusion lamination to obtain a composite film. The total thickness of the composite film was 67 μm. The heat seal strength was evaluated in the same manner as in Example 3 using the obtained composite film. The evaluation results are shown in Table 2. Similar to Example 3, two types of heat seal strength were obtained using one film.

    [Comparative example 1] Unitika Co., Ltd. PET film “Embret PET” 12 μm was used as the base part, and Tosero Co., Ltd. linear low density polyethylene film “TUX-FCD” 25 μm was used as the heat seal part. Similarly to Example 1, the base material portion and the heat seal portion were laminated by extrusion lamination using LDPE as an intervening layer to obtain a composite film. The thickness of the LDPE intervening layer was 20 μm, and the total thickness of the composite film was 57 μm. The heat seal strength was evaluated in the same manner as in Example 3 using the obtained composite film. The evaluation results are shown in Table 2.

  Even when the pressure and temperature of the heat seal were changed, the heat seal strength was slightly changed but remained high. Since it was not easily peelable, the opening performance was poor when it was made into a bag.

    [Comparative Example 2] Using a PET film “Embret PET” 12 μm manufactured by Unitika Co., Ltd. as a base material part, and using an easily peelable film “IMX” 35 μm manufactured by J Film Co., Ltd. as a heat seal part, Example 1 Similarly, the base material portion and the heat seal portion were laminated by extrusion lamination using LDPE as an intervening layer to obtain a composite film. The thickness of the LDPE intervening layer was 20 μm, and the total thickness of the composite film was 67 μm. The heat seal strength was evaluated in the same manner as in Example 3 using the obtained composite film. The evaluation results are shown in Table 2.

  Even if the pressure and temperature of the heat seal were changed, the heat seal strength was slightly changed but remained low.

It is a schematic sectional drawing in an example of the composite film of this invention. It is a schematic sectional drawing in the other example of the composite film of this invention. It is a schematic sectional drawing of an example in the base-material part of the composite film of this invention. It is a schematic sectional drawing in the further another example of the composite film of this invention. It is a schematic sectional drawing in the further another example of the composite film of this invention. It is a schematic sectional drawing in the further another example of the composite film of this invention. It is a schematic diagram of a 4-way seal bag. It is a schematic diagram of a barracuda bag. It is a schematic diagram of a pillow bag. It is a schematic diagram of a pillow gazette bag. It is a schematic diagram of a four-corner seal gusset bag. It is a schematic diagram of a standing bag.

Explanation of symbols

DESCRIPTION OF SYMBOLS 7 Composite film 8 Heat seal part 9 Heat seal surface 10 Composite film 11 Base material part 12 OPP layer 13 Print layer 14 Interposition layer in a base material part 15 Deposition aluminum layer 16 PET layer 20 Heat seal part 21 Mainly with low melting point resin Layer (a)
22 Layer mainly composed of high melting point resin (b)
23 Layer mainly composed of mixed resin of low melting point resin and high melting point resin (c)
24 Low melting point resin layer other than layer (a) 25 Heat seal surface 31 Adhesive layer for laminating base material portion and heat seal portion 32 Intervening layer for laminating base material portion and heat seal portion 41 Seal part 42 4-way seal bag 43 Camas bag 44 Pillow bag 45 Pillow gusset bag 46 Four corner seal gusset bag 47 Standing bag

Claims (5)

A composite film sealing method comprising at least a base material portion and at least two heat seal portions , wherein the two layers are a layer (b) mainly composed of a high melting point resin having a melting point of 135 to 180 ° C., and a melting point Is a layer (c) mainly composed of a mixed resin of a low-melting resin having a melting point of 80 to 135 ° C. and a high-melting resin having a melting point of 135 to 180 ° C., and having a melting point of 135 to 180 ° C. A composite film in which the difference between the melting point and the highest melting point of the low melting point resin is 20 ° C. or more, and the two layers are laminated in the order of (c) and (b) from the heat seal surface of the heat seal part , After laminating so that the heat sealing surfaces face each other, a part of the composite film is sealed at a temperature higher than the melting point of the high melting point resin, and the other part is sealed at a temperature lower than the melting point of the high melting point resin. Characteristic composite Sealing method of Irumu. A composite film sealing method comprising at least a base material part and a heat seal part, wherein the heat seal part comprises at least three layers, and the three layers mainly comprise a low melting point resin having a melting point of 80 ° C to 135 ° C. Layer (a), a layer (b) mainly composed of a high melting point resin having a melting point of 135 ° C. to 180 ° C., a layer (c) mainly composed of a mixed resin of a low melting point resin and the high melting point resin, The low melting point resin of the layer (a) and the low melting point resin of the layer (c) are the same or compatible with each other when melted, and the melting point of the high melting point resin of the layer (b) and the layer (c) A composite film in which the difference from the highest melting point of the low melting point resin is 20 ° C. or more, and the three layers are laminated in the order of (a), (c), and (b) from the heat seal surface of the heat seal part. After stacking so that the heat seal surfaces face each other, Sealing method of the composite film is partially sealed at a temperature above the melting point of the high melting point resin, the other part, characterized in that the sealing at temperatures below the melting point of the high melting point resin film. The ratio of the high melting point resin contained in the layer (c) is in the range of 5 to 30% by weight, and the ratio of the low melting point resin is in the range of 30 to 95% by weight. Or the sealing method of the composite film of 2. The method for sealing a composite film according to any one of claims 1 to 3, wherein the thickness ratio of the layer (b) to the layer (c) is 3: 1 to 1: 4. 5. The composite film according to claim 2, wherein a low melting point resin layer having a melting point of 80 ° C. to 135 ° C. is further laminated on the heat seal portion following the layer (a) . Sealing method .

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