JPH04502588A - resealable packaging materials - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Sealable Flexible packaging materials consisting of layers of thermoplastic polymers are used to package a wide variety of articles, especially foods. For example, cereals, potato chips and other snack foods is packaged in such material. Those packages are sealed using heated sealing jaws. is formed on a packaging machine where the packaging material is sealed to itself. However, pankey The first step is to pull off one of the heat seals, which are normally located at the top of the package. Therefore, once opened, the heat seal will not reseal unless heat and pressure are applied. 0 The present invention eliminates pressure in the area of the seal formed by the packaging machine. Provided is a flexible packaging material that can be resealed by applying pressure.

The material of the present invention comprises a base layer, a tacky adhesive layer adjacent to the base layer, and a tacky adhesive layer. Consists of the epidermal layer that covers the formed by sealing packaging material to itself When the seal is pulled apart, its sticky adhesive is exposed on the surface of the sealed area. , thus allowing the material to loosen in its sealing area by application of manual pressure alone. reseals itself to allow the package to be reclosed.

The base layer may be a flexible material, such as plastic film, metal foil, or a combination thereof. It may be made of any material commonly used for flexible packaging applications. plus The tick film base layer may be single layer or multilayer and may be oriented. It may also be unstretched. Films can be made of polyamide, polyester, or It can be a polymer or copolymer of lefins. A suitable base layer is poly(ethylene). (ethylene terephthalate) film, paper, stretched polypropylene film and nonwoven fabric Includes materials.

As used herein, the term "tacky adhesive" refers to Refers to adhesives that form resealable joints by application of only manual pressure at temperatures do. The reseal strength is preferably about 0.5 to 4 pounds per inch (0.5 to 4 pounds per inch). 1 to 0.7 kg/a*), more preferably about 1 to 2 per inch Bond (0.1B to 0.36kg/cs), such adhesives are usually Hot seals and adhesive lacquers may be included. Room-temperature seals are made of elastomer water-based rubber. Formed from tex emulsion. The adhesive is preferably an elastomer. It is a pressure-sensitive adhesive that is a blend of adhesive and tackifier. Pressure sensitive adhesives are preferably is about 40 to 80 percent thermoplastic elastomer, 20 to 60 percent tackifier, and up to about 15 percent other ingredients, such as fragrances. and customary additives such as antioxidants and oils.

If the adhesive layer in the packaging material contains a fragrance, the fragrance The fragrance is present in the packaging material until it is formed into a Since it is essentially included in the book, it cannot be thanked very much. package is opened The fragrance is then released - thus enhancing the attractiveness of the items in the panpackage.

Best results are obtained using oil-based fragrances that are absorbed by the elastomeric component of the adhesive. can be obtained.

A particularly suitable elastomer is manufactured by Firestone under the trademark 5tereon. Styrene-butadiene copolymer sold by Shell Chemical Company Styrene-isoprene copolymers sold under the trademark Kraton Including tyrene copolymers. Other suitable nylastomers are polyurethanes, and ethylene vinyl acetate with a vinyl acetate content of about 18 percent or more. Including copolymers.

Tackifiers are any compounds commonly used with elastomers to make pressure-sensitive adhesives. Any tackifier may be used. Suitable tackifiers are trademarked by Alicina Chemical Company. Terpene resins, such as those sold by Zonatac, and Exonke Resin-like petroleum hydrocarbons sold under the trademark Escorez by Michal Includes resins.

The pressure sensitive adhesive is preferably coextrudable. The coextrudability of pressure sensitive adhesives is low. By utilizing a thermoplastic elastomer with a melt index, and Strengthening can be achieved by increasing the proportion of elastomer in the adhesive. adhesive Melt index is preferred for coextrusion with conventional polyolefins. is less than 30, more preferably less than 10.

Pressure sensitive adhesives, or other tacky adhesives, can be used for applications other than extrusion, such as adhesive lamination, gravure, flexible Kison printing or silk screen printing, Meyer rond, spray It can also be applied to the base layer by methods such as laser coating or vacuum deposition.

Adhesives can be used in 100 percent solid form or with water or solvent as a vehicle. It can be used by using .

Adhesive adhesive is only needed in areas where the package will be opened, so The adhesive only needs to be applied in layers where it is needed, as well as on the epidermis. The layers are sequentially adhesive layer and skin layer against the base layer using a central contact press machine. It can be applied overlay only with adhesive, such as by subsequent printing. but, The skin layer is equally applicable to other surface areas, including the entire surface of the packaging material. You may be

The adhesive adhesive can also be applied to the base layer by transferring it from the support medium. . This technique uses a single layer of metal produced by vapor deposition during the production of metallized packaging materials. commonly used to transfer thin layers of metal from one substrate to another, such as Ru. The skin layer can also be transferred with adhesive by this technique. The supporting medium is Preferably it is a paper coated with a silicone release agent. Nizo base material is recycled and in a continuous process may be an endless belt. adhesive layer When the supporting paper is rolled up, it is Preferably, it is coated with a release agent.

The thickness of the adhesive adhesive layer is preferably about 0.1 to 2.0 mils (2.5 to 2.5 mils). 51 microns), more preferably about 0.3 to 0.7 mils (7.6 to 1 8 microns).

The epidermal layer serves two important functions. Firstly, it means that the packaging material is The surface of the packaging material is made to have a coefficient of friction that can be modified. Second, the seal The skin layer so that when pulled apart, the adhesive adhesive is exposed on the surface of the seal. can be torn. There are two mechanisms by which this occurs. In one mechanism (first mechanism) , the skin layer is ruptured by the shearing action of the sealing jaws in the packaging machine, and the packaging is thus This results in the presence of a tacky adhesive at the interface where the material is sealed to itself. epidermal layer is preferably ruptured over most of the area of the seal. This mechanism Therefore, the initial seal can be made using adhesive adhesive alone, which allows the seal job to be completed. This eliminates the need to apply heat to the In another mechanism (second mechanism), the table The cortical layer is sealed against itself, preferably by using flat sealing jaws. heat sealed, and force is first applied to pull the heat seal apart. It remains virtually intact until the epidermal layer ruptures down to the adhesive layer. It's stopped. The skin layer then expands to the edge of the seal when additional force is applied. delaminates from the base layer. Delamination occurs between the skin layer and the adhesive layer, between the adhesive layer and the base layer, Alternatively, it preferably occurs in the plane passing through the adhesive layer, thus allowing the adhesive to The seal can become present on both surfaces of the sealing area after it has been pulled apart. the latter type of delamination heats both seal jaws when the heat seal is formed This is facilitated by

When the second mechanism is employed, the adhesive adhesive is a coextrudable pressure sensitive adhesive. It is possible that it is co-extruded with the skin layer, with or onto the base layer. preferable. When the base layer is coextruded with the skin layer and the adhesive layer, the blown film Film coextrusion or cast film coextrusion may be employed. The extruded product is , may include multiple layers of pressure sensitive adhesive.

The skin layer is a thermoplastic film commonly used as a heat-sealing layer in packaging materials. It may be a layer of shaped polymer. This polymer, at the desired thickness of the skin layer, Heat sealing is facilitated, preferably with a force of about 0.4 to 0.9 kg/cv. It is preferable that the package has a tensile strength such that it can be opened easily. Also, polymers are preferable. preferably has a low elongation at break of less than 400 percent. The polymer is A group consisting of tyrene, carboxylic acids and esters, salts and anhydrides of carboxylic acids Preferably, it is a copolymer of ethylenically unsaturated comonomers selected from Examples of such comonomer components are acrylic acid, methacrylic acid, acrylic acid Methyl, ethyl acrylate, methyl methacrylate, vinyl acetate, and male anhydride This includes phosphoric acids. Such copolymers are suitable for heat sealing in flexible packaging materials. It is a well known commercially available polymer commonly used to form the layer. polyolefin Other polymers, such as polymers, may be blended with the above copolymers in small amounts.

Preferably, the copolymer is an ionomer. The term ionomer refers to olefins and A film-forming copolymer with an ethylenically unsaturated monocarboxylic acid, At least 10% of the acid groups are bound by metal ions, preferably zinc. Refers to something that has been neutralized. An olefin has the formula RCH=CH, where R is It is hydrogen or an alkyl group containing up to 8 carbon atoms. olefin is preferably ethylene. The carboxylic acid is preferably acrylic acid or methacrylic acid. Lylic acid or methyl methacrylic acid. Percentage of olefin units in the ionomer is at least 50 mole percent, preferably at least 80 mole percent It is. Suitable ionomers are described in U.S. Pat. No. 3,355,319. , commercially available under the trademark 5urlyn.

The skin layer is preferably relatively thin, and is thinner than the heat seal layer of conventional packaging materials. and therefore when the seal jaws are applied or when the seal is pulled apart. Preferably, the layer ruptures. The thickness of the epidermal layer is preferably no more than about 0.05 0.5 mil (1.3 to 13 microns), more preferably about 0.075 0.2 mil (1.9 to 5 microns).

If the first mechanism is adopted, the skin layer produces the desired coefficient of friction and the skin layer rupture sufficiently by the seal jaws so that adhesive is present at the seal interface. It can be any substance that can Not only that, but the material is talc or even finely divided solid particles (dust) such as starch particles. good. The particles can be prepared using conventional methods such as using a 0χydry™ device. Therefore, it can be applied to an adhesive layer.

The skin layer and the pressure sensitive adhesive layer are typically combined by conventional coextrusion coating methods. They may be coextruded together to form the packaging material of the present invention. The component of pressure sensitive adhesive is nitrogen acid at the extrusion temperature which causes decomposition and odor, maintained under an inert atmosphere such as It is preferable to reduce this as much as possible.

The packaging material is typically used to seal flexible packaging materials in packaging machines. It can be sealed by any method. If the first mechanism is adopted, the packaging material A seal job that applies shear to the skin layer, as described in Patent No. 4,582,555, preferably sealed by a Shearing causes rupture of the skin layer and opening of the seal Promote the exposure of adhesive when sticky. If the first mechanism is adopted, the sealing jaw The temperature is preferably lower than the melting point of the skin layer. In some specific examples, Now the material is effectively cold sealed instead of being heat sealed. at ambient temperature. If the second mechanism is adopted, the epidermal layer will be approximately 230℃ below (110℃ ) is heat sealed to itself at conventional temperatures. In either mechanism , the seal is sufficiently bonded to prevent the buff cage from being opened during normal handling. Has strength. The bond strength should be at least about 2 bonds per inch (0.4k g/am), but the seal can be pulled apart by hand. It is also desirable that the seal be easily opened, so the bond strength should be about 5 pounds per inch. It is preferably smaller than 0.9 kg/cm.

Until the epidermal layer is ruptured, the coefficient of friction of the epidermal layer depends on the material forming the epidermal layer. It is determined that Therefore, the material of the invention can be used in applications such as forming, filling and sealing machines. It can be used in conventional packaging machines in the same way as conventional flexible packaging materials. on its surface Materials with tacky adhesives are, of course, susceptible to such It could not be used in machines. How packaging materials can be used in packaging machines The material of the present invention has good machinability, which is referred to in the art as machinability.

In a preferred embodiment, each surface of the material is machined to stainless steel. It has a coefficient of friction of about 0.1 to 0.5, which is within the preferred range for its properties.

Example 1 The laminate was made by coextruding the skin layer and pressure sensitive adhesive onto the base layer.

The base layer is a poly(ethylene tetraphthalate) film with a thickness of 112 microns. The skin layer, which was extruded at 218°C, was a polyamide film (DuPont Myler). Comprised of Listyrene (Dow Tyron 625), extruded at approximately 163°C. The pressure-sensitive adhesive is a 60 percent styrene-isoprene-styrene block. Lycium copolymer (Shell Kraton D-1107), 30 percent aliphatic Petroleum hydrocarbon resin (Exxon Escorez 1310) and 2 percent Fe It consisted of a nol-based antioxidant (Ciba Geigy 1rganox 1010). , the hydrocarbon resin was injected into the barrel of an extruder. The thickness of the polystyrene layer is approximately 0. ．． 1 mil (2.5 microns) and the thickness of the pressure sensitive adhesive layer is approximately 0.5 mil. (12.7 microns). The laminate is manufactured by U.S. Patent No. 4.582.55. Using the heat seal jaws described in No. 5, 80psi (5.6kg/C The seal is applied to itself by applying a pressure of I) for 2 seconds at a temperature below 110°C. I did it.

A force of 3.3 pounds (0.59 kg/cm) per inch of width is applied to the heat seat. Required for le opening. The opened heat seal is then resealed and 14 psi (0,99 kg/sq. It was resealed by applying the pressure in step 1). Average reseal strength per 1 inch width The weight was 1.03 bond (184 g/Cl).

This example demonstrates that the packaging material of the present invention can be easily resealed after each intermediate use. It is particularly suitable for packaging cereals and snack foods as packaging materials. This is to clarify.

Example λ Apply a coat of molten pressure sensitive adhesive onto the base layer, allow the adhesive to cool, and then By applying a coat of polyvinylidene chloride (PVDC) to the surface of the adhesive. , made a laminate. These coats are applied using a Meyer rod. clothed.

Laminated with 1 mil (25 micron) thick poly(ethylene terephthalate) It was a film. Pressure-sensitive adhesive is heated to about 150°C and produces about 14 bons per series. It was applied at a coat weight of 23 grams per square meter. findlay The pressure sensitive adhesive, commercially available from (Findley) Adhesives, has a It has a viscosity of about 42,000 centipoise at 0°C. PVDC is a series of Apply at a coat weight of approximately 4 bonds (7g per square meter) and heat at approximately 93°C. Dry. This laminate is then self-sealed using sealing jaws that provide high shear. I sealed it on my body. The jaws were heated to 71°C and 80 psi (5,6k A pressure of 1 g/sq. 3.2 per inch to open that seal. A force of bond (0,57 kg/cm) was required. The opened seal is then Reseal and open 20 times within 1 second at room temperature to 14 psi (0, It was resoled by applying a pressure of 99 kg/sq. Average reseal strength was 0.53 pounds per inch (95 grams per 1c+a).

This example describes the production of the packaging material of the invention employing a first mechanism. This material is , cereals and snack foods in pan cages that can be easily resealed after each intermediate use. It can be used to package products.

Example 1 Skin on a 2 mil (51 micron) thick high density polyethylene film. The laminate was made by coextruding the layers and pressure sensitive adhesive. Press at 230°C The skin layer released consisted of an ionomer commercially available from DuPont.

Pressure sensitive adhesives extruded at 196°C are commercially available from Findlay Adhesives. It is. This adhesive has a viscosity of more than 100 cm at 177°C. have The adhesive weighs 4 pounds per strip (7 grams per square meter). It was.

This laminate was heated at 40 psi (2.8 kg/c) for 1 second using flat seal jaws. by applying a pressure of i+), it sealed itself, but one jaw It was at room temperature and the other jaw was at 116°C. Open this heat seal A force of 2.4 bonds per inch (0.43 kg/cf) was required to This heat seal was opened again 20 times and left at room temperature for less than 1 second. by applying a pressure of 14 psi (0,99 kg/sq C11). I sealed it. Average reseal strength is 1.03 pounds per inch (1.03 pounds per IC). 84 grams).

This example describes the production of the packaging material of the present invention employing a second mechanism. This material is Cereals and snack foods in packages that can be easily resealed after each intermediate use It can be used for packaging.

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Claims (20)

[Claims] 1. a base layer, a layer of adhesive adhesive adjacent to the base layer, and a layer of adhesive adhesive overlying the base layer; a flexible packaging material consisting of a skin layer; each surface of the packaging material is The material has a coefficient of friction that allows it to be machined in a packaging machine; sealed against itself by the jaws and remains closed during normal handling Has some initial bond strength, but can be easily pulled apart by hand for opening. A package with a seal can be formed; the skin layer is separated by the seal. When the adhesive is removed, the tacky adhesive is exposed at the surface of the seal area and allows the packaging material to brace itself in the area of the seal by applying only hand pressure. said flexible packaging material, wherein said flexible packaging material is capable of being sealed to reclose the package; fee. 2. Claims having a coefficient of friction against stainless steel between about 0.1 and 0.5. Packaging materials in Box 1. 3. 2. The packaging material of claim 1, wherein the adhesive includes a fragrance. 4. The packaging material according to claim 1, wherein the adhesive adhesive is a pressure sensitive adhesive. 5. The skin layer and the pressure sensitive adhesive layer are pressed together, with or onto the base layer. and the skin layer is removed all the way down to the adhesive layer when the seal is pulled apart. rupture and then rupture by delamination from the base layer, thereby causing damage in the seal area. 5. The packaging material of claim 4, wherein the pressure sensitive adhesive is exposed. 6. The pressure sensitive adhesive is about 40 to 80 percent thermoplastic elastomer and about 20 percent thermoplastic elastomer. 6. The packaging material of claim 5, comprising from 60 percent to 60 percent tackifier. 7. The skin layer is heat-sealed when the jaws have a temperature of 230°F (110°C). 6. The packaging material of claim 5, wherein the packaging material is a layer of thermoplastic film-forming polymer capable of forming a film. 8. 8. The packaging material according to claim 7, wherein the skin layer is made of an ionomer. 9. Heat seals approximately 2 to 5 pounds per square inch (0.4 to 0.9k) 8. The packaging material of claim 7, having an initial bond strength of (g/cm). 10. The strength of resealable joints formed by pressure-sensitive adhesives is approximately 0.0 mm per inch. The packaging of claim 9 which is 5 to 4 pounds (0.1 to 0.7 kg/cm) material. 11. The thickness of the epidermal layer is approximately 0.05 to 0.5 mil (1.3 to 13 microns) ) The packaging material according to claim 7. 12. The thickness of the pressure sensitive adhesive layer is approximately 0.1 to 2.0 mils (2.5 to 51 mils). 12. The packaging material according to claim 11, wherein the packaging material is 13. The skin layer is an adhesive bond at the interface where the material is sealed to itself. The skin layer breaks through the seal jaw so that the adhesive is present. The packaging material of claim 1 which is damaged by -. 14. The temperature of the seal jaw is lower than the melting point of the material forming the skin layer. Range 13 packaging materials. 15. The seal is about 2 to 5 pounds per inch (0.4 to 0.9 kg/cm) 14. The packaging material of claim 13, having an initial bond strength of ). 16. The strength of the resealable bond formed by the tacky adhesive is approximately 0.0 mm per inch. The package of claim 15 having a weight of 5 to 4 pounds (0.1 to 0.7 kg/cm) packaging material. 17. 14. The packaging material according to claim 13, wherein the skin layer is composed of finely divided granules. 18. 18. The packaging material of claim 17, wherein the granules are talc or starch particles. 19. 14. The method of claim 13 comprising transferring a layer of adhesive from a support medium to a base layer. Method of forming packaging materials. 20. The skin layer is transferred to the adhesive base layer and the support medium is a silicone release layer. 19. The method of claim 18, wherein the paper is coated with a release agent.