Zipper tape and container equipped with zipper tape

Abstract

Provided is an elongated zipper tape including, in a cross-sectional shape, a pair of base parts and engaging parts that protrude from mutually facing surfaces of the pair of base parts and can be engaged with each other. At least the engaging parts are formed of a resin composition that contains polyethylene and a modifier.

Description

Zipper tape and container with zipper tape

[0001] The present invention relates to a zipper tape and a container with the zipper tape.

[0002] Generally, the manufacturing process for zipper tape-attached bags includes a side sealing step in which films to which zipper tapes are bonded are placed face to face and the ends of the bag are sealed together with the zipper tapes. Since poor bonding at the engaging portions of the zipper tapes protruding from the inner surface of the film can cause pinholes and reduce the sealing performance of the bag, a point sealing step is carried out to flatten the engaging portions of the zipper tapes before the side seals are formed.

[0003] However, this point sealing process can sometimes limit the speed of the manufacturing process. While increasing the temperature of the point sealing process can shorten the time required for the process, there is a limit to how much the temperature can be increased because wrinkles will occur if the film has low heat resistance. In recent years, in order to improve the recyclability of resin products, there has been a demand for mono-materialization, where most of the materials are made from a single compound. For example, as described in Patent Document 1, it has been proposed to form zipper tape, including an engaging portion, from polyethylene to match the material of the film. However, even in this case, the point sealing process takes time, which can sometimes limit the speed of the manufacturing process.

[0004] JP 2023-150830 A

[0005] Therefore, an object of the present invention is to provide a zipper tape and a container with the zipper tape that make it possible to shorten or omit the point sealing process at the side seal portion when the engaging portion of the zipper tape is formed from a resin containing polyethylene.

[0006] [1] A long zipper tape having a cross-sectional shape including a pair of base portions and engaging portions projecting from opposing surfaces of the pair of base portions and capable of engaging with each other, wherein at least the engaging portions are formed of a resin composition containing polyethylene and a modifier. [2] The zipper tape according to [1], wherein the polyethylene in the resin composition has a melting point of less than 125°C in differential scanning calorimetry (DSC). [3] The zipper tape according to [1] or [2], wherein the modifier includes an ethylene-based elastomer or an ethylene-based plastomer. [4] The zipper tape according to any one of [1] to [3], wherein the content of the modifier in the resin composition is 5% or more, where the total of the polyethylene and the modifier is taken as 100%, in mass %. [5] The zipper tape according to any one of [1] to [4], wherein the resin composition has a melting enthalpy ΔH of less than 125 J / g over the entire temperature range in differential scanning calorimetry (DSC). [6] The zipper tape according to any one of [1] to [5], wherein at least a part of the base is formed of a resin composition different from the resin composition forming the engaging portion. [7] A container with zipper tape, comprising the zipper tape according to any one of [1] to [6] and a container body to which the zipper tape is joined. [8] The container with zipper tape according to [7], wherein the container body is formed of a resin composition containing polyethylene. [9] The container with zipper tape according to [7] or [8], wherein the container body is bag-shaped.

[0007] According to the above configuration, the crushability of the engaging portion of the zipper tape is improved, so that when the engaging portion is formed of a resin containing polyethylene, the point sealing process at the side seal portion can be shortened or omitted.

[0008] Fig. 1 is a plan view of a bag with zipper tape according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view of the bag with zipper tape taken along line II-II of the bag with zipper tape shown in Fig. 1. Fig. 3 is a graph for explaining the melting enthalpy ΔH and melting point Tm of a resin composition. Fig. 4 is a cross-sectional view of a bag with zipper tape according to a second embodiment of the present invention.

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0010] (First embodiment) Fig. 1 is a plan view of a bag with zipper tape according to a first embodiment of the present invention, and Fig. 2 is a cross-sectional view of the bag with zipper tape shown in Fig. 1 taken along line II-II. As shown in Figs. 1 and 2, the bag with zipper tape 1 according to the first embodiment includes a bag-shaped film 10 having a first surface 11A and a second surface 11B, and zipper tape 20.

[0011] The film 10 is the container body in this embodiment and is formed, for example, from a single-layer or multi-layer thermoplastic resin. When recycling the film 10 without separating the zipper tape 20 from it, it is preferable to form the film 10 from a resin composition containing polyethylene, more specifically, low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE), similar to the zipper tape 20, from the viewpoint of mono-materialization. When recycling the zipper tape 20 by separating it from the film 10 or when the zipper tape 20 is used in common for films 10 made from different raw materials, the thermoplastic resin forming the film 10 is not limited to polyethylene and may be polypropylene such as homopolypropylene (HPP), random polypropylene (RPP), or block polypropylene (BPP). Furthermore, when the film 10 is a multilayer film, the surface substrate may be biaxially oriented polypropylene (OPP), biaxially oriented polyethylene terephthalate (OPET), or biaxially oriented nylon (ONy). Furthermore, the film forming the film 10 may include a layer of a metal material such as aluminum or a layer of an inorganic material. The resin composition forming the film 10 may be an environmentally friendly bioplastic, or a mixture of a fossil fuel-derived resin and a biomass plastic such as biopolyethylene.

[0012] In this embodiment, two sheets of film 10 are joined together at the bottom seal 12 and the side seal 13 to form a bag-shaped container body having a first surface 11A and a second surface 11B. However, in another embodiment, the first surface 11A and the second surface 11B may be formed by folding back a single sheet of film 10 at a portion corresponding to the side seal 13. Alternatively, a portion where the film 10 is folded inward, a so-called gusset, may be formed at a portion corresponding to the bottom seal 12 or the side seal 13 in the example of FIG. 1 . In this case, the gusset may be formed by the film 10, or by another film joined to the film 10. The zipper tape-equipped bag 1 may also be a standing pouch that can be placed upright by forming a gusset at the bottom.

[0013] Furthermore, in the present embodiment, the opening 14 of the zipper tape-attached bag 1 is formed by forming the bottom seal 12 and the side seal 13 but not the top seal. However, in another embodiment, a top seal may be formed in addition to the bottom seal 12 and the side seal 13, and the opening 14 may be formed in the zipper tape-attached bag 1 later by cutting between the top seal and the zipper tape 20. In yet another embodiment, the bottom seal 12 may not be formed, i.e., the zipper tape-attached bag 1 may be provided without being sealed on the side opposite the zipper tape 20. In this case, the bottom seal 12 is formed after the zipper tape-attached bag 1 is filled with contents. Additionally, zipper tape can be joined to bags of various known configurations and containers other than bags, as long as the zipper tape can be fused thereto, to form the zipper tape-attached container according to the present invention.

[0014] 2, the zipper tape 20 is a long member having a cross-sectional shape including a pair of base portions 21A, 21B joined to the first surface 11A and the second surface 11B of the film 10, respectively, and engaging portions 22A, 22B protruding from the opposing surfaces of the base portions 21A, 21B and engageable with each other. In the illustrated example, the engaging portion 22A has a male cross-sectional shape, and the engaging portion 22B has a female cross-sectional shape. The engaging portions 22A, 22B engage with each other to close the zipper tape 20 and seal the opening 14 of the zipper tape-attached bag 1. Note that the shapes of the engaging portions of various known zipper tapes, such as a combination of claws, hooks, or knobs, are not limited to male and female shapes, and may be applied to the engaging portions 22A, 22B in the above example.

[0015] In this embodiment, the base portions 21A, 21B and the engaging portions 22A, 22B of the zipper tape 20 are formed from a resin composition containing polyethylene and a modifier. Specifically, the polyethylene contained in the resin composition is low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE). The resin composition forming the zipper tape 20 may be an environmentally friendly bioplastic, or a mixture of a fossil fuel-derived resin and a biomass plastic such as biopolyethylene. The modifier may be, for example, an ethylene-based modifier, specifically an ethylene-based elastomer or ethylene-based plastomer, more specifically, ethylene-propylene rubber (EPR), ethylene-butene-1 (EBR), or ethylene-1-octene copolymer. The inclusion of an ethylene-based modifier lowers the melting point of the resin composition and improves the crushability of the engaging portions 22A, 22B. Other modifiers, such as propylene-butene-1 (PBR), terpolymers, or petroleum resins, may also be used in combination within acceptable limits from the perspective of monomaterialization. The resin composition forming the zipper tape 20 may further contain known additives, such as a stabilizer, an antioxidant, a lubricant, an antistatic agent, or a colorant, as necessary. A sealing layer made of, for example, metallocene LLDPE may be laminated on the surface of the bases 21A, 21B opposite to the engaging portions 22A, 22B.

[0016] The content of the modifier in the resin composition forming the zipper tape 20 is preferably 5% by mass or more, and more preferably 10% by mass or more, when the total of the polyethylene and the modifier is 100%. The upper limit of the content of the modifier in the resin composition forming the zipper tape is not particularly limited, but is typically 60% by mass or less. As shown in the examples described below, the crushability of the engaging portions 22A, 22B can be improved by forming the zipper tape 20 from a resin composition containing LDPE, which has a relatively low melting point among polyethylenes, and an appropriate amount of modifier. The polyethylene contained in the resin composition forming the engaging portions 22A, 22B preferably has a melting point Tm of less than 125°C as measured by differential scanning calorimetry (DSC). For example, when using a low-melting-point LDPE with a melting point Tm of 110°C or less, sufficient crushability can be obtained with a relatively small amount of modifier, specifically, for example, 5% by mass or more, which can be advantageous from the standpoints of productivity and cost. On the other hand, when a relatively large amount of modifier, specifically, for example, 20% by mass or more, can be contained, sufficient crushability can be obtained even with ordinary LDPE that does not have a low melting point, which can be advantageous from the viewpoint of cost.

[0017] The resin composition forming the zipper tape 20 in this embodiment preferably has a melting enthalpy ΔH of less than 125 J / g over the entire temperature range in differential scanning calorimetry (DSC) described below. ΔH is more preferably 115 J / g or less, and even more preferably 110 J / g or less. By setting ΔH to less than 125 J / g, the crushability is improved. The lower limit of ΔH is not particularly limited, but ΔH is usually 5 J / g or more.

[0018] FIG. 3 is a graph illustrating the melting enthalpy ΔH and melting point Tm of a certain resin composition. In the following description, the DSC measurement and analysis methods are based on JIS K7121, "Method for Measuring Transition Temperature of Plastics." The melting enthalpy ΔH in DSC is determined as the area between the DSC curve at the peak and the baseline, with temperature T as the horizontal axis. JIS K7121 defines the peak of a DSC curve as "the portion from when the curve deviates from the baseline until when it returns to the baseline," and the baseline is defined as "the temperature region (omitted) of the DSC curve where no transition or reaction occurs in the test specimen." In other words, the peak is the temperature region from when the DSC curve reaches the baseline and when transition or reaction begins to occur until it ceases to occur. However, in this embodiment, the peak onset temperature is fixed at 20°C, considering that it may be difficult to identify the peak onset temperature depending on the composition of the resin composition. In this case, the peak of the DSC curve is "the portion from a temperature of 20°C to the point where transition and reaction no longer occur in the test piece," and the baseline for determining the melting enthalpy ΔH is "the line segment connecting a temperature of 20°C to the end point of the peak, i.e., the point where transition and reaction no longer occur in the test piece." The melting point Tm in DSC is determined as the temperature at which the peak of the DSC curve, with the temperature T on the horizontal axis, is maximum.

[0019] In this embodiment, the entire zipper tape 20 is formed from the above-described resin composition, thereby improving the crushability of the engaging portions 22A, 22B. The improved crushability of the engaging portions 22A, 22B, which are irregularly shaped portions protruding from the base portions 21A, 21B, enables the point sealing step of flattening the engaging portions 22A, 22B of the zipper tape 20 before forming the side seal portions 13 to be performed at a lower temperature, thereby shortening or even eliminating the step.

[0020] Second Embodiment Fig. 4 is a cross-sectional view of a zipper tape-attached bag according to a second embodiment of the present invention. As shown in Fig. 4, the zipper tape-attached bag 2 according to the second embodiment includes a film 10 and a zipper tape 30. The configuration of the film 10 is the same as that of the first embodiment, and therefore a duplicated description will be omitted below.

[0021] The zipper tape 30 includes a pair of base portions 31A, 31B bonded to the first surface 11A and the second surface 11B of the film 10, respectively, and engaging portions 22A, 22B protruding from the opposing surfaces of the base portions 31A, 31B. The engaging portions 22A, 22B are configured similarly to those in the first embodiment and are engageable with each other. The engaging portions 22A, 22B are formed of a resin composition containing polyethylene and a modifier, similar to the zipper tape 20 in the first embodiment. The resin composition forming the engaging portions 22A, 22B preferably has a melting enthalpy ΔH of less than 125 J / g in a temperature range measured by differential scanning calorimetry (DSC). ΔH is more preferably 115 J / g or less, and even more preferably 110 J / g or less. A ΔH of less than 125 J / g improves crushability. The lower limit of ΔH is not particularly limited, but ΔH is typically 5 J / g or greater.

[0022] On the other hand, in the second embodiment, the base portions 31A, 31B of the zipper tape 30 are formed of a resin composition different from that of the engaging portions 22A, 22B. The resin composition forming the base portions 31A, 31B does not necessarily have to be a resin composition containing polyethylene and a modifier like the resin composition forming the engaging portions 22A, 22B, and does not have to satisfy the conditions regarding the melting point and melting enthalpy ΔH. The zipper tape 30 is formed, for example, by co-extrusion molding the resin composition forming the engaging portions 22A, 22B and the resin composition forming the base portions 31A, 31B. The base portions 31A, 31B may be further divided into several portions, and each portion may be formed of a different resin composition. For example, the bases 31A, 31B may have a laminated structure including layers made of different types of polyethylene. More specifically, the layer on the side of the bases 31A, 31B facing the engaging portions 22A, 22B and the layer on the side opposite the engaging portions 22A, 22B may be made of LDPE (which may contain a modifier like the engaging portions 22A, 22B), with an intermediate layer made of HDPE interposed between them. Also, a sealing layer made of, for example, metallocene LLDPE may be laminated on the surface of the bases 31A, 31B opposite the engaging portions 22A, 22B.

[0023] In this embodiment, as in the first embodiment, the crushability of the engaging portions 22A, 22B of the zipper tape 30 is improved, so that the point sealing process of the side seal portion 13 can be performed at a lower temperature, thereby shortening or eliminating the process.

[0024] Examples of the present invention will be described below. In each example and comparative example, a "Diamond DSC" manufactured by PerkinElmer Japan Co., Ltd. was used as the DSC. A test piece of the resin composition was isothermally held at 0°C for 5 minutes, and then heated to 220°C at a rate of 10.00°C / min (first run). From the DSC curve, the melting enthalpy ΔH over the entire temperature range was calculated according to the definitions of peak and baseline as described above. The calculation of the melting enthalpy ΔH was in accordance with JIS K7121 except for the above conditions.

[0025] In the Examples and Comparative Examples shown in Table 1, the resin composition forming the engaging portion and base portion of the zipper tape contains either low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE) as polyethylene. The melting points of each material were calculated by the DSC described above for zipper tapes made from each material. The modifier used was a polyethylene with a density of 0.875 g / cm. ３ An ethylene-1-octene copolymer with a melt flow rate of 3 g / 10 min was used. In all Examples and Comparative Examples, a metallocene LLDPE seal layer was laminated on the side of the zipper tape opposite the engaging portion. The seal layer was present between the zipper tape and the laminate film. LDPE-I: melting point 107°C, melt flow rate 3.5 g / 10 min LDPE-II: melting point 111°C, melt flow rate 1.9 g / 10 min LLDPE-I: melting point 123°C, melt flow rate 3.5 g / 10 min Metallocene LLDPE: melting point 98°C, melt flow rate 3.8 g / 10 min

[0026] The raw material composition was extruded and then cooled with water to produce zipper tapes. In Comparative Example 3, an intermediate layer made of 100% high-density polyethylene (HDPE; melting point 130°C, melt flow rate 5 g / 10 min) was formed on the base by coextrusion.

[0027] For each example and comparative example, the measurement results of the fusion enthalpy ΔH and the results of evaluating the crushability at the lowest point sealing temperature (minimum crushing temperature) at which pinholes do not occur are shown in Table 1. The evaluation method is as follows.

[0028] Using a Totani Giken Co., Ltd. three-sided press seal automatic bag making machine "BH-60HV," a laminate film of MDOPE #25 / LLDPE #100 was used. For the zipper tape and laminate film of each Example and Comparative Example, the following common sealing conditions were used: two-stage point seal, two-stage side seal, and two-stage side cooling, with a sealing time of 0.4 seconds, acceleration of 0.3 G, waiting time of 0 seconds, feed length of 160 mm, zipper seal temperature of 150 ° C, and side seal temperature of 170 ° C. Evaluation samples were obtained by appropriately varying the point seal temperature. The crushability of these evaluation samples was evaluated based on the minimum crush temperature. In Table 1, the minimum crush temperature of Comparative Example 1, in which the entire zipper tape was formed from 100% "LDPE-I," was used as the standard. When the minimum crush temperature was lower than the standard and the crushability improved, the decrease was less than 10 ° C., and when the decrease was 10 ° C. or more, the evaluation sample was evaluated. In addition, a case where the minimum crushing temperature was the same as the standard and no improvement in crushability was observed was rated "C", and a case where the minimum crushing temperature was higher than the standard and crushability was reduced was rated "D".

[0029]

[0030] 1, 2...bag with zipper tape, 10...film, 12...bottom seal portion, 13...side seal portion, 14...opening, 20, 30...zipper tape, 21A, 21B, 31A, 31B...base portion, 22A, 22B...engagement portion.

Claims

1. A long zipper tape having a cross-sectional shape including a pair of base portions and engaging portions that protrude from the opposing surfaces of the pair of base portions and are capable of engaging with each other, wherein at least the engaging portions are formed from a resin composition containing polyethylene and a modifier.

2. The zipper tape according to claim 1, wherein the polyethylene in the resin composition has a melting point of less than 125°C as measured by differential scanning calorimetry (DSC).

3. The zipper tape of claim 1 or claim 2, wherein the modifier comprises an ethylene-based elastomer or an ethylene-based plastomer.

4. A zipper tape according to any one of claims 1 to 3, wherein the content of the modifier in the resin composition is 5% or more by mass when the total of polyethylene and the modifier is 100%.

5. The zipper tape according to any one of claims 1 to 4, wherein the resin composition has a melting enthalpy ΔH of less than 125 J / g over the entire temperature range as measured by differential scanning calorimetry (DSC).

6. The zipper tape according to any one of claims 1 to 5, wherein at least a portion of the base is formed from a resin composition different from the resin composition forming the engaging portion.

7. A container with zipper tape comprising: the zipper tape according to any one of claims 1 to 6; and a container body to which the zipper tape is joined.

8. The zipper tape-equipped container according to claim 7, wherein the container body is formed from a resin composition containing polyethylene.

9. A container with zipper tape according to claim 7 or claim 8, wherein the container body is bag-shaped.

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