JP5283090B2 - Lid material - Google Patents

Description

  The present invention relates to a lid member, and more particularly to a lid member that seals the container by heat-sealing at a mouth portion of a container for storing food or the like, particularly a glass container.

  To prevent the contents from touching air or moisture before opening in containers containing foods such as instant coffee, creaming powder, seasonings, sprinkles, and other medicines, cosmetics, etc. In addition, it is widely practiced to heat-seal and seal the lid at the container mouth. As such a lid member, there are known two types, for example, a lid member of the type disclosed in Patent Document 1 and a lid member of the type disclosed in Patent Document 2, for example. Any type of lid material has a hot melt adhesive layer at the lowest layer, which is heat sealed to the container mouth to seal the container and prevent alteration of the contents. The material is peeled and removed entirely from the container mouth when opened, whereas the latter type of lid material has a reseal layer and a seal layer between them when the container cap is removed. After delamination, the reseal layer is left inside the cap and the seal layer is left attached to the container mouth, and then the seal layer is peeled and removed during opening. In the case of this latter type, even after the seal layer is removed, when the cap is closed, the reseal layer left inside the cap closes the container mouth, so that a certain alteration preventing effect can be obtained. .

  In such a lid material, the hot melt adhesive layer provided in the lowermost layer is mainly composed of a thermoplastic resin such as ethylene-vinyl acetate copolymer (EVA), and has good sealing properties (peel strength, sealing strength). A hot melt adhesive composition prepared by blending a predetermined ratio of a tackifier (pressure-sensitive adhesive) for reducing the viscosity and softening point of a thermoplastic resin, such as gravure roll coating, etc. It is formed by applying by an appropriate method (for example, see paragraph 0021 of Patent Document 1 and paragraph 0010 of Patent Document 2).

JP 2000-118546 A JP 11-138680 A JP 2004-331199 A JP-A-60-76586 Microfilm of Japanese Utility Model No. 58-130213 (Japanese Utility Model Application No. 60-38264)

By the way, the lid member has a sealing strength of a predetermined value or more in order to maintain the inside of the container in an airtight state when it is used as a lid member, and to prevent the contents from being deteriorated over a long period of time. Of course, the peel strength is required to be a predetermined value or less in order to make it easy to peel off when opening the container in use. Another important performance requirement is that the material does not stick when stored in a state in which a large number of materials are stacked (blocking resistance). However, the lid material according to the prior art is not always satisfactory in this respect. For example, in the hot melt adhesive layer in the lid material of Patent Document 1 , 15 to 30% by weight of a tackifier such as hydrogenated rosin is blended with 30 to 50% by weight of thermoplastic resin (EVA), Such a lid material is likely to cause blocking due to the influence of a highly blended tackifier when stored in a state where a large number of the lid materials are stacked.

  In particular, inorganic containers such as glass bottles change significantly over time, and in glass bottles that have been left for a long time, sodium silicate, calcium silicate, etc. may precipitate on the glass surface, reducing adhesion to the lid. It is regarded as a problem. In order to solve this problem, a technique (Patent Document 3) is proposed in which the mouth portion of the glass container is covered with a resin film in advance and the hot melt adhesive layer of the lid material is heat sealed thereon. However, processing into glass bottles is necessary and not only is cost and process wasteful, but it is also difficult to perform such processing with a glass container with a complicated mouth shape, which is a fundamental solution. Has not reached. Tackifiers commonly used in conventional hot melt adhesive layers for lids provide good sealing strength for glass bottles immediately after manufacture, but sealing strength for aged weathered glass containers. Further, after sealing, the sealing strength is significantly lowered when left for a long period of time under high temperature and high humidity conditions, and the hermeticity of the contents cannot be maintained over a long period of time (see the test results described later).

  Therefore, the problem to be solved by the present invention is to improve the blocking resistance, exhibit a good sealing strength not only for a resin container such as a polyester resin but also for a glass container, particularly an aged weathered glass container, and It is to provide a novel lid that can be maintained.

  In order to solve this problem, the present inventors paid attention to blending a silane coupling agent in the hot melt adhesive layer of the lid material instead of the conventional tackifier. The silane coupling agent is composed of two types of reactive groups having different reactivity in one molecule, that is, a hydrolyzable group “OR” chemically bonded to an inorganic material and an organic reactive group chemically bonded to an organic material. An organosilicon compound having “X”. Silane coupling agents are used in various applications as they can strongly bond inorganic materials and organic materials that are usually difficult to bond due to greatly different chemical properties, improving the adhesion to glass. Therefore, it has also been proposed to blend in the hot melt adhesive layer of the lid (Patent Documents 4 and 5). However, there are various silane coupling agents in which vinyl, epoxy, styryl, methacryl, acrylic, amino, mercapto, sulfide, isocyanate and the like are used as the organic reactive group “X”. When various tests were conducted by adding these various silane coupling agents to the hot melt adhesive layer of the lid, only the silane coupling agent having a specific organic reactive group was able to solve the above problems. It was confirmed that it acted significantly. In other words, in a specific application where the hot-melt adhesive layer of the lid material is formulated in place of the conventional tackifier, not all silane coupling agents are uniformly useful, but some silanes. Only coupling agents are useful. The inventors have found this as a result of many tests and studies, and have completed the present invention.

That is, the present invention relates to a lid material in which a hot melt adhesive layer is provided on the lower surface of a base material and is attached to a container mouth portion with a high frequency seal , wherein the hot melt adhesive layer is a thermoplastic resin adhesive. And a wax having a softening point of 90 to 160 degrees (Fahrenheit) and a silane coupling agent having an amino group as an organic reactive group, and a thermoplastic resin adhesive / wax blending ratio of 30/70 to 70/30 The silane coupling agent is added in an amount of 0.3% by weight or more based on the total of the thermoplastic resin adhesive and the wax .

  According to the present invention, the anti-blocking property is greatly improved, so that the storage stability and storage stability are good, and good sealing strength is long-termed not only for synthetic resin containers but also for inorganic containers such as glass bottles. A lid member that can be stably maintained over a wide range is provided. Therefore, it is optimal for use as a lid regardless of the material of the container.

It is sectional drawing which shows an example of the cover material by this invention. It is sectional drawing which shows the other example of the cover material by this invention.

  The lid according to the present invention is provided as a lid of the type illustrated in FIG. 1 or a lid of the type illustrated in FIG.

The lid member 10 in FIG. 1 has a configuration in which a hot melt adhesive layer 12 is provided on the back surface of a substrate 11. The material and configuration of the base material 11 are arbitrary. For example, a sheet obtained by laminating a polyethylene sheet on the back side of an aluminum foil or a composite sheet obtained by sand-laminating polyethylene on both sides of an aluminum foil is layered on the back side of the paper. Can be used. The hot melt adhesive layer 12 can be provided on the back surface of the base material 11 in a spot shape by gravure coating at an application amount of 20 g / m ² , for example. This lid material 10 is the same type as the lid material described in Patent Document 1, and the container contents are exposed to air and moisture by being heat sealed to the container mouth portion via the hot melt adhesive layer 12. It is prevented from being altered, and when it is opened for use, the whole is peeled and removed from the container mouth. Note that the heat seal is a high-frequency seal in order to suppress the heating of the container contents as much as possible.

On the other hand, the lid member 20 of FIG. 2 has a configuration in which the reseal layer 21 and the seal layer 22 are provided so as to be peelable through the peel layer 23. For example, the reseal layer 21 is obtained by laminating a polyethylene 21b having a thickness of 60 μm on the back surface of a paper 21a having a basis weight of 480 g / m ² . The sealing layer 22 is formed by forming a release layer 23 by applying a release agent on the surface of a base material 24 and providing a hot melt adhesive layer 25 on the back surface thereof. The material and configuration of the base material 24 are arbitrary. For example, a polyethylene film 24b having a thickness of 15 to 30 μm and a glassine paper 24c having a thickness of 30 g / m ² are sequentially layered on the back surface of an aluminum foil 24a having a thickness of 9 to 30 μm. Can be used. Moreover, the hot-melt-adhesive agent layer 25 can be provided on the back surface of the base material 24 (the back surface of the glassine paper 24c) by the gravure coating with the application amount of 20 g / m < ² >, for example. The lid member 20 is the same type as the lid member described in Patent Document 2, and is heat-sealed to the container mouth portion through the hot melt adhesive layer 25 as an integral unit having the reseal layer 21 and the seal layer 22. Therefore, the container contents are prevented from being deteriorated by contact with air or moisture. When the container cap is removed, the reseal layer 21 and the seal layer 22 are delaminated at the release layer 23, and the reseal layer 21 is located inside the cap. The seal layer 22 is left in a state of being attached to the container mouth. After that, the seal layer 22 is peeled and removed in use, but when the cap is closed, the reseal layer 21 left inside the cap closes the container mouth, so that a certain quality-preventing effect is maintained even after opening. There are advantages that can be done.

  The present invention can be applied to any of these types of lids, and the main feature is the composition of the hot melt adhesive layers 12 and 25. Hereinafter, the hot melt adhesive layers 12 and 25 will be described in detail.

The hot melt adhesive layer includes a thermoplastic resin adhesive, a wax, and a silane coupling agent having an amino group as an organic reactive group. As the thermoplastic resin adhesive, ethylene-vinyl acetate copolymer (EVA) is particularly preferably used. EVA preferably contains 19-35% vinyl acetate (VA). When the VA content is less than 19%, the adhesiveness is lowered, and when it exceeds 35%, the blocking resistance, water resistance and peel strength are lowered. As the wax , a paraffin wax having a softening point of 90 to 160 degrees (Fahrenheit, the same applies below) is used . When the softening point is smaller than 90 degrees, the blocking resistance is lowered, and when it is larger than 160 degrees, the peel strength and the sealing strength are lowered. Compounding ratio of EVA / wax is 30 / 70-70 / 30, the mixing ratio is reduced to be small and peel strength and seal strength, productivity in heat sealing process is decreased becomes larger.

As described above, the silane coupling agent has two types of reactive groups having different reactivity in one molecule, that is, a hydrolyzable group “OR” chemically bonded to an inorganic material, and a chemically bonded organic material. With an organic reactive group "X" attached. Here, the inorganic reactive group OR is an acryloyl group such as a methoxy group and an ethoxy group, and the organic reactive group X is a vinyl group, an epoxy group, a methacryloxy group, an amino group, a mercapto group, etc. Although a silane coupling agent is known, it was confirmed from a test result by the inventors described later that a silane coupling agent in which the organic reactive group X is an amino group acts significantly in the present invention. The inorganic reactive group OR is not particularly limited, and may be any of methoxy group, ethoxy group and the like. The mixing ratio of the silane coupling agent, a remarkable effect can be obtained when in the total of the thermoplastic resin adhesive and a wax and 0.3 wt% or more.

<Test>
Various silane coupling agents (X-Si- (OR) ₃ ) are added in the range of 0.1% to 30% with respect to the total of 50% EVA with 28% VA mixing ratio and 50% paraffin wax. A hot melt adhesive compound was prepared by adding the mixture in different amounts and uniformly kneading while heating using a heating and melting pot having a rotating blade, and this was prepared on the back surface of the base 11 (thickness 30 μm aluminum foil). A hot melt adhesive layer 12 is formed by applying a gravure coating at a coating amount of 20 g / m ² to form a hot melt adhesive layer 12 on the back surface of a polyethylene sheet layered to a thickness of 30 μm. Lid samples (Experiment Nos. 1 to 63) were obtained. Further, a lid material sample prepared in the same manner as described above except that 30% hydrogenated rosin was added as a tackifier instead of the silane coupling agent in the hot melt adhesive layer 12 was compared with a comparative example (experiment). No. 64).

  Each of these lid material samples was high-frequency sealed at a sealing speed of 200 bottles per minute using a 450 KHz high-frequency seal oscillator at the mouth of two types of glass bottles, a normal bottle and a weathered bottle. Here, the normal bottle is a glass bottle having an outer diameter of 46 mm and an inner diameter of 42 mm, and the weathered bottle is the normal bottle left for 12 hours at a temperature of 70 ° C. and a humidity of 90%. It corresponds to the state left for years. In the weathered bottle, components (such as sodium silicate and calcium silicate) that inhibit adhesion among the glass components were deposited on the surface due to changes over time. Then, the peel strength and sealing strength were measured in the initial state immediately after high-frequency sealing in each bottle and in the time-lapsed state after standing for 30 days under conditions of a temperature of 40 ° C. and a humidity of 90%.

  Peel strength is the peel strength against the adherend of the lid (container opening), and serves as an indicator of the ease with which the lid can be peeled off (easy peel) when the container is opened. In this test, after each lid material sample was high-frequency sealed and adhered to a glass bottle, the lid material sample was peeled off in a 90-degree direction from the adhered glass surface by a tensile tester, The initial peel value was defined as the peel strength. Measurement was repeated 20 times for each lid sample, and the average value was adopted, and in three stages: ○: 15 mm width 7 N or more, Δ: 15 mm width 3 N or more and less than 7 N, x: 15 mm width 3 N or less. evaluated.

  The sealing strength is an internal pressure value when air starts to leak in a test in which an internal pressure of 1.33 KPa / sec is applied to the sealed lid material, so that the contents of the container are not leaked to the outside. In this test, each lid material sample was sealed with a high-frequency seal on a glass bottle under the same conditions as described above, and left at room temperature for 1 hour, and then the sealing strength was measured with a sealing tester. It was measured. As described above, the lid material sample after change with time was left to stand at a temperature of 40 ° C./humidity of 90% for 30 days as described above, and then left at room temperature for one day, and the sealing strength was measured with a sealing tester in the same manner. did. Each lid material sample was measured 20 times repeatedly, and the average value was adopted and evaluated in three stages: ◯: 40 KPa or more, Δ: 10 KPa or more and less than 40 KPa, ×: less than 10 KPa.

  In addition, each lid material sample was punched to a diameter of 50 mm, 250 sheets were stacked and allowed to stand at room temperature for 30 days, and the state of ease of peeling was visually observed. ○: The lid materials were easily peeled off without being bonded, X: The blocking resistance was evaluated in two stages of maintaining the state in which the cover members were integrated without being separated from each other.

  In addition, each lid sample is sealed with high frequency in a normal bottle containing powdered food under the same conditions as above, and the seal part is completely immersed in pure water, and the time until the pure water penetrates the contents is visually observed. The water resistance was evaluated in three stages: ◯: not permeated for 24 hours or more, Δ: permeation for 2 hours or more and less than 24 hours, and x: penetration for less than 2 hours.

  Table 1 shows the types of silane coupling agents (or tackifiers) added to the hot melt adhesive layer 12 in each lid material sample and the test results.

  First, the comparative example (experiment number 64) corresponding to the prior art in which 30% of hydrogenated rosin is added as a tackifier to the hot melt adhesive layer 12 has insufficient sealing properties (peel strength and sealing strength) against weathered bottles. Yes, blocking resistance and water resistance were also poor.

  On the other hand, all of the lid material samples (experiment numbers 1 to 63) obtained by adding a silane coupling agent to the hot melt adhesive layer 12 have good blocking resistance, and the conventional hot melt adhesive for lid materials. It was found that blocking resistance was improved by using a silane coupling agent instead of a tackifier such as hydrogenated rosin added to the layer. In this respect, effectiveness was confirmed regardless of the type of silane coupling agent.

  However, for other evaluation items, that is, peel strength, sealing strength and water resistance, a silane coupling agent having an amino group as an organic reactive group (hereinafter referred to as “amino-based silane coupling agent”, experiment numbers 1 to 14). Showed generally good results, but non-amino silane coupling agents (Experiment Nos. 15 to 63) were insufficient, and the performance tended to deteriorate rather than the comparative example (Experiment No. 64) corresponding to the prior art. It was seen. From this, not all kinds of silane coupling agents to be added to the hot melt adhesive layer of the lid material are uniformly useful, only the amino silane coupling agent acts significantly. I was able to confirm. In addition, there should be no significant difference in the test results between the lid material samples having methoxy groups as the inorganic reactive groups (experiment numbers 1 to 7) and the lid material samples having ethoxy groups (experiment numbers 8 to 14). From the results, it was confirmed that the inorganic reactive group of the silane coupling agent was not particularly limited. That is, a necessary and sufficient condition as a silane coupling agent to be added to the hot melt adhesive layer of the lid material is to have an amino group as an organic reactive group. If it is an amino-based silane coupling agent, it can not only greatly improve the blocking resistance by adding it to the hot melt adhesive layer of the lid material, but also the glass container, which is also a glass component due to aging Among them, it exhibits good sealing performance for glass containers where components that inhibit adhesion (sodium silicate, calcium silicate, etc.) are deposited on the surface, and also improves water resistance. It has been demonstrated that it can be done.

  Here, especially when an amino silane coupling agent is added to the hot-melt adhesive layer 12 among silane coupling agents, the reason why the peel strength, sealing strength, and water resistance are dramatically improved is not necessarily clear. However, since the adhesion-inhibiting component deposited on the surface of the weathered glass bottle is an inorganic substance such as sodium silicate or calcium silicate, an amino-based silane coupling agent that has good adhesion to the inorganic substance has a peel strength against the weathered glass bottle. It is thought that it acts significantly in improving the sealing strength. Further, the hot melt adhesive layer 12 to which an amino silane coupling agent is added drastically improves the water resistance of the lid material, so that it is not easily affected by humidity (moisture), and this is usually applied to glass bottles and weathered glass bottles. In any case, it is considered that a decrease in peel strength and sealing strength with time is suppressed to a minimum. In addition, the amino silane coupling agent exhibits good compatibility with other components (a thermoplastic resin such as EVA and a wax) in the hot melt adhesive layer 12, which contributes to the improvement of these physical properties. It is thought that there is.

  Regarding the addition amount of the silane coupling agent having an amino group as the organic reactive group, even when 0.1% by weight is added to the total of the thermoplastic resin adhesive and the wax (experiment numbers 1, 8). However, the above effect can be maximized by adding 0.3% by weight or more. The upper limit of the addition amount is not particularly limited, but it is not practical to add more than necessary in consideration of cost. As described above, for example, in the hot melt adhesive layer in the lid material of Patent Document 2, a tackifier such as hydrogenated rosin is 15 to 30% by weight with respect to 30 to 50% by weight of the thermoplastic resin (EVA). Compared to the fact that it is blended, a sufficient effect can be obtained by adding an amino-based silane coupling agent of 0.1% by weight or more in the present invention, and in a preferred embodiment of 0.3% by weight or more. It has been proved that it has a very high cost advantage.

  In this test, glass bottles were targeted, but this was selected to compare and demonstrate that the lid material according to the present invention exhibits particularly superior in peel strength and sealing strength. Application is not limited to glass containers, but can also be applied to resin containers and the like. Test data in this case is not particularly shown, but it should exhibit the same or higher peel strength and sealing strength as a conventional lid material having a hot melt adhesive layer to which a tackifier such as hydrogenated rosin is added. As shown in Table 1, the blocking resistance and water resistance are remarkably superior to those of the prior art lid materials.

10 Lid 11 Base 12 Hot Melt Adhesive Layer 20 Lid 21 Reseal Layer 21a Paper 21b Polyethylene 22 Seal Layer 23 Release Layer 24 Base 24a Aluminum Foil 24b Polyethylene 24c Glassine Paper 25 Hot Melt Adhesive Layer

Claims (1)

In a lid material in which a hot melt adhesive layer is provided on the lower surface of a base material and is attached to a container mouth by high frequency sealing, the hot melt adhesive layer is composed of a thermoplastic resin adhesive and a softening point of 90 degrees Fahrenheit. -160 degree (32.2-71.1 degreeC) and the silane coupling agent which has an amino group as an organic reactive group, and the compounding ratio of thermoplastic resin adhesive / wax is 30 / 70-70. / 30, and 0.3% by weight or more of a silane coupling agent is added to the total of the thermoplastic resin adhesive and the wax.

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