Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
  • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
  • B29C65/04—Dielectric heating, e.g. high-frequency welding, i.e. radio frequency welding of plastic materials having dielectric properties, e.g. PVC
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/01—General aspects dealing with the joint area or with the area to be joined
  • B29C66/05—Particular design of joint configurations
  • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
  • B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
  • B29C66/112—Single lapped joints
  • B29C66/1122—Single lap to lap joints, i.e. overlap joints
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/40—General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
  • B29C66/41—Joining substantially flat articles ; Making flat seams in tubular or hollow articles
  • B29C66/43—Joining a relatively small portion of the surface of said articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
  • B29C66/71—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
  • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
  • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/10—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of paper or cardboard
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
  • B32B27/306—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl acetate or vinyl alcohol (co)polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
  • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
  • B29C65/08—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using ultrasonic vibrations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
  • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
  • B29C65/18—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated tools
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
  • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
  • B29C65/38—Impulse heating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/40—General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
  • B29C66/41—Joining substantially flat articles ; Making flat seams in tubular or hollow articles
  • B29C66/43—Joining a relatively small portion of the surface of said articles
  • B29C66/431—Joining the articles to themselves
  • B29C66/4312—Joining the articles to themselves for making flat seams in tubular or hollow articles, e.g. transversal seams
  • B29C66/43121—Closing the ends of tubular or hollow single articles, e.g. closing the ends of bags
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
  • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
  • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
  • B29C66/7232—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a non-plastics layer
  • B29C66/72327—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a non-plastics layer consisting of natural products or their composites, not provided for in B29C66/72321 - B29C66/72324
  • B29C66/72328—Paper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
  • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
  • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
  • B29C66/7234—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a barrier layer
  • B29C66/72341—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a barrier layer for gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
  • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
  • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
  • B29C66/7234—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a barrier layer
  • B29C66/72343—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a barrier layer for liquids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
  • B29K2023/04—Polymers of ethylene
  • B29K2023/08—Copolymers of ethylene
  • B29K2023/086—EVOH, i.e. ethylene vinyl alcohol copolymer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2009/00—Layered products
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/30—Properties of the layers or laminate having particular thermal properties
  • B32B2307/304—Insulating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2323/00—Polyalkenes
  • B32B2323/04—Polyethylene
  • B32B2323/046—LDPE, i.e. low density polyethylene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2331/00—Polyvinylesters
  • B32B2331/04—Polymers of vinyl acetate, e.g. PVA
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2439/00—Containers; Receptacles
  • B32B2439/70—Food packaging

Definitions

• This invention relates to structural materials used in the formation of packaging for consumer products, particularly food products, and more particularly liquid food products such as juices, and the methods for heat sealing these structural materials. Commonly, the products are packaged under aseptic conditions.
• Shelf life of a packaged product is of importance in the many consumer products. Much effort has been expended in the development of packaging materials and packaging methods and apparatus to achieve extended shelf lives for the products contained within the package. Packaging the product under aseptic conditions has been employed to extend shelf life of certain products, particularly food products, and more particularly liquid food products. Choice of the packaging material for the package also has been extensively examined.
• FFS form, fill and sealing technology
• FFS machines are widely used, particularly in the food packaging industry.
• FFS machines of the prior art perform heat sealing by means of (a) induction heat generation using low frequency, e.g.
• FFS presents at least three major concerns with respect the suitability of the packaging material which can be used in the FFS machine.
• the packaging material used in FFS machines (a) must provide barrier protection of the packaged product as will permit the product to withstand the normal conditions to which it is exposed between the time of its packaging and its consumption by a consumer, (b) must be compatible with the mechanical forces imposed on the packaging material in the course of its being folded and sealed in the course of its processing through the FFS machine, and (c) must be capable of repeatedly forming effective sealing of the formed and filled packages at high production rates such as up to about 15,000 packages per hour. Since FFS machines are designed to provide automatic and substantially continuous operation, the speed with which the folding, and particularly the sealing operation, is carried out is of critical importance .
• the laminate includes a substrate and at least an outer heat sealable layer.
• other layers of differing materials may be added to the laminate.
• HF high frequency
• Foil layers in packaging material laminates are undesirable due to the cost of the foil, but more importantly, because foil-containing laminates, when folded, tend to develop breaks or ruptures at the locations of the folds due to the unyielding nature of the foil, with consequential loss of the protective nature of the foil layer.
• Ethylene vinyl alcohol has also been used heretofore as an effective oxygen barrier, particularly for providing extended shelf life for packaged food products.
• EVOH as used in the prior art as an oxygen barrier layer has not been heretofore employed as an RF susceptor for heat sealing purposes. But rather, in the prior art, when using EVOH as the oxygen barrier layer, it has been necessary to incorporate into the laminate a different material as the RF or HF susceptor for heat sealing.
• Figure 1 is a schematic representation, taken in cross-section, of a fragment of a laminated packaging material embodying various of the features of the present invention.
• Figure 2 is a schematic representation, taken in cross-section, of a fragment of two portions of a laminated packaging material disposed in facing relationship to define a seal interface therebetween and depicting the application of RF electric energy to the two portions.
• the present inventors have discovered a combination of laminated materials which provide a non-foil packaging material having enhanced sealability employing RF energy.
• the relatively low, and otherwise inadequate, RF susceptibility of one or more layers of the laminate is enhanced to a value which provides fast and efficient heat sealing of the laminate to itself.
• This enhancement is accomplished through the incorporation within the laminate, in a selected order of lamination, of one or more layers which tend to direct the heat generated by one or more inner layers to that outer layer of the laminate which is to be heated to an effective heat sealing temperature.
• Ethylene vinyl alcohol (EVOH) has been found to particularly suitable as a primary RF susceptor in the combination of the present invention.
• the interfacial sealing temperatures of contiguous layers of the present laminated packaging material is a function of the internal heat generation of the polymeric layer or layers and dissipation of this generated heat by conductive heat transfer.
• RF active polymers possess polar molecules that respond to time varying electric energy field excitation by the dissipation of the energy as heat via molecular rotations. The degree to which the polymer responds to the RF electric energy field is dependent upon material properties such as the dissipation factor (i.e., the product of the dielectric constant and the loss tangent) , as well as the strength and frequency of the electric field.
• the present inventors have observed that the heat sealing properties of the laminated material also vary with temperature as heat is generated. DETAILED DESCRIPTION OF INVENTION
• two layers of a non-foil, RF susceptible composite material are brought into intimate contact (sealing surface to sealing surface facing relationship) , as in the FFS process of liquid packaging, held together under adequate contact pressure and then exposed to a RF electric energy field for a specified time period (with the electric field perpendicular to the plane of the composite material) .
• heat is generated through energy losses due to the thermal motions of molecular dipoles in the polar components of the composite structure.
• a temperature gradient is established across the thickness of each of the composites (of particular interest in the direction of the RF field) .
• a substrate layer which exhibits a first thermal conductivity and which is laminated with at least one polymeric layer which exhibits a thermal ⁇ conductivity which is higher than the thermal conductivity of the substrate layer, thereby providing that heat generated within the polymeric layer when it is subjected to RF electric energy tends to flow away from the substrate layer and toward the area of desired heat sealing.
• the degree to which fusion occurs is dependent upon the clamping pressure within the seal area and the duration of the RF electric energy application.
• the clamping pressure is held after fusion of the interface to allow both the interface and the inner composite layers to cool below the melt phase to ensure adequate seal strength for the specific packaging application.
• a p area of each layer perpendicular to the applied electric field
• thk 1 thickness of each layer in plane to the applied electric field
• V 0 voltage drop across the laminate structure induced by the applied electric field
• ⁇ ' dielectric constant
• tan( ⁇ ) dissipation factor
• the product of (T)» c ab ⁇ orb (T,f) describes the ability for a polymer to absorb the RF electric energy and transfer the heat to the seal inter ace. The higher the value, the more desirable the material is for the incorporation in the present packaging material structure.
• the product of ⁇ (T)» c ⁇ bso ⁇ ;b (T,f) may also be treated in differential forms and integrated over appropriate temperature & frequency ranges to obtain an overall maximum value for a given layer.
• Selection of the present laminated packaging material structure involves determining the dielectric and thermal properties of each RF susceptible layer of the laminate as a function of temperature and frequency.
• the present invention exploits the combined electrical and barrier characteristics of EVOH in particular to provide a simple, inexpensive, easily manufactured composite packaging material while providing functional RF electric heat sealability and barrier characteristics necessary for extended shelf life product containment.
• a sealant layer 14 which defines a first outermost layer of the depicted laminate and includes first and second planar surfaces 16 and 18.
• This sealant layer is disposed in facing relationship to, and bonded to a first planar surface 20 of a tie layer 22 , which, in turn, has its second planar surface 24 disposed in facing relationship to, and bonded to a first planar surface 26 of a RF susceptor layer 28.
• the opposite and second planar surface 30 of the susceptor layer is disposed in facing relationship to, and bonded to, a first planar surface 32 of a second tie layer 34.
• the opposite and second planar surface 36 of the second tie layer 34 is disposed in facing relationship to, and bonded to, a first planar surface 38 of a substrate layer 40.
• the opposite and second planar surface 42 of the substrate layer is disposed in facing relationship to, and bonded to, a first planar surface 44 of a gloss layer 46 (i.e., print surface).
• This gloss layer defines a second outermost layer of the depicted laminate.
• the laminate depicted in Figure 1 may be manufactured employing techniques well known in the industry such as extrusion or common lamination employing various bonding enhancing practices such as ozone treatment or corona discharge treatment of the facing surfaces of one or more of the layers of the laminate.
• outermost layer 46 comprises gloss low density polyethylene (LDPE) and is intended to be that surface of the laminate which forms the outside exposed surface of the finished package. This surface preferably is printable and sufficiently tough to withstand normal treatment occurring during manufacture, boxing, transport and storage of a packaged product.
• LDPE gloss low density polyethylene
• a suitable gloss LDPE layer may be within the weight range of between about 5 and about 10 lbs/3000 ft 2 .
• the LDPE layer is disposed in facing relationship and bonded to a substrate layer 40 comprising paperboard.
• the substrate layer provides structural integrity to the packaging material, hence to the finished package.
• the material of construction of the substrate layer is also chosen for its low heat transfer characteristics so that it tends to retard the transfer of heat therethrough.
• Other materials of construction of the substrate layer may include like-functioning materials or similar materials, or combinations of these and/or other like-functioning materials.
• a suitable paperboard for the substrate layer may have a weight of between about 70 and about 350 lbs/3000 ft 2 .
• a layer of ethylene vinyl alcohol (EVOH) 28 is bonded to the substrate 40.
• This tie layer 34 preferably is relatively thin and serves primarily to bond the EVOH layer to the substrate.
• EVOH ethylene vinyl alcohol
• One suitable resin for use as a tie layer between the paperboard substrate and the EVOH layer is Tymor 1220 E, available from Morton Chemicals.
• a suitable weight range of a resin tie layer is between about 0.25 and about 15 lbs/3000 ft 2 -
• the EVOH layer 28 of the depicted laminate functions as an oxygen barrier, and as discovered by the present inventors, as a suitable primary RF susceptor for heat sealing purposes .
• the actual EVOH coating weight necessary for barrier protection is shelf-life dependent. Typically about 5 lbs/3000 ft 2 of EVOH (at 29% by mole % ethylene content) is adequate for most long shelf-life applications.
• the maximum coat weight is dependent upon, but not limited to, RF electric energy heat generation requirements as dictated by the selection equations set forth hereinabove .
• the ethylene content of the EVOH may be chosen to provide adequate heat generation response to an RF field.
• the ethylene content of the EVOH may range from about 10 to about 70 mole %.
• the ethylene is a homogeneous component of the copolymer.
• the lower mole percentages of ethylene provide greater barrier characteristics and enhanced RF susceptibility. Because processibility of the copolymer through an extruder degrades as the ethylene content decreases, ethylene mole percentages below about 27 mole % are not currently available in commercial quantities, so that at the present time 29 mole % ethylene is preferred for commercial application of the present invention.
• a layer of low density polyethylene (LDPE) or linear low density polyethylene (LLDPE) 14 is bonded to the surface 26 of the EVOH layer.
• This tie layer may be substantially identical to the tie layer 34.
• This layer of LDPE or LLDPE is the outermost layer of the laminate opposite the gloss LDPE layer 46 and defines the heat sealable layer of the laminate.
• this layer 14 functions as a moisture barrier, which function, in part, dictates the desired minimum thickness of this layer. Typically, about 10 lbs/3000 ft 2 of either LDPE or LLDPE will provide an adequate moisture barrier.
• the moisture barrier property of this layer is to be taken in conjunction with the combined laminate tensile properties necessary to obtain pinhole prevention, resistance to distribution damage, and adequate seal strength, typically a maximum of about 35 lbs/3000 ft 2 .
• Normal manufacturing extrusion coat weight tolerances typically are up to about ⁇ 10%.
• first and second portions 60 and 62, respectively, of laminated packaging material of the present invention are disposed contiguously with the outermost heat sealing layers 14' and 14" thereof in facing relationship to form a seal interface 64.
• Pressure from a pair of sealing jaws 66 and 68 is applied to the facing portions 60 and 62 to urge these portions into intimate contact with one another.
• RF electric energy from a source thereof (not shown) is imposed across the contiguous layers including the seal interface.
• the lines 70 of the RF electric energy field are directed substantially perpendicular to the plane of the seal interface.
• the EVOH layers 28' and 28" are the primary RF susceptor layers of the two portions 60 and 62.
• the resin tie layers 22" and 22", 34' and 34" and the polyethylene-based layers 14' and 14" of each portion of the packaging material may contribute to the generation of heat when in the presence of the RF field. Because each of the substrate layers 40' and 40" has a low coefficient of heat conductivity relative to the EVOH layer, the tie layers and the heat sealing layers, the heat generated in these layers 40' and 40" tends to be transferred by conduction to the heat sealing layers 14' and 14".
• the sealing frequency range of the RF energy employed to effect a heat seal as depicted in Figure 2 typically will range between about 1 and about 300 MHZ depending upon the particular material structure of the laminated packaging material.
• the sealing range may be determined through use of the optimization equations provided hereinabove and will account for dielectric relaxation and thermal property changes of the materials of the laminated packaging material in the course of their exposure to the RF energy.
• About 65 MHZ has been found to be particularly suitable.
• a typical sealing cycle includes a time period to generate adequate heat to increase the temperature of the seal interface up to and above the melt point of the sealing layer and a time period for cooling of the sealing layer (and any other layers which have entered the melt phase) below the freeze points of the composite layers while they remain fixed under the clamping pressure of the sealing jaws. Sealing cycles typically are on the order of 50 to 500 milliseconds, employing the present invention.
• the order of lamination that is, relative positions of the several layers of the laminated packaging material, be chosen to enhance the transfer of heat from the primary RF electric energy susceptor layer (EVOH layer) to the heat sealing layer
• EVOH layer electric energy susceptor layer
• paperboard is preferred as the construction materials for the substrate layer, but other material having the required structural integrity and relatively low heat conductivity may be employed. Consequently, the thickness of the substrate layer may be varied.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Laminated Bodies (AREA)
• Wrappers (AREA)

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• 1997
  • 1997-08-18 ZA ZA9707410A patent/ZA977410B/xx unknown
  • 1997-09-16 PA PA19978438201A patent/PA8438201A1/es unknown
  • 1997-09-26 CO CO97056095A patent/CO4770856A1/es unknown
  • 1997-09-26 AR ARP970104453A patent/AR008644A1/es unknown
  • 1997-11-04 TW TW086116334A patent/TW369479B/zh active
  • 1997-11-13 WO PCT/US1997/020788 patent/WO1998022283A1/en not_active Application Discontinuation
  • 1997-11-13 AU AU54377/98A patent/AU5437798A/en not_active Abandoned
  • 1997-11-13 EP EP97948285A patent/EP1007356A4/en not_active Withdrawn

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