CA1221059A - Infusion bag - Google Patents
Infusion bagInfo
- Publication number
- CA1221059A CA1221059A CA000468810A CA468810A CA1221059A CA 1221059 A CA1221059 A CA 1221059A CA 000468810 A CA000468810 A CA 000468810A CA 468810 A CA468810 A CA 468810A CA 1221059 A CA1221059 A CA 1221059A
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- Canada
- Prior art keywords
- vacuum
- thermoplastic film
- heat resistant
- dual layer
- film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
INFUSION BAG
Abstract of the Disclosure An infusion bag for particulated food products such as tear coffee and the like, constructed of a coextruded multilayer perforated thermoplastic film having a heat resistant outer layer of film forming resin and an outer layer of a somewhat less heat resistant film forming resin and having a multiplicity of minute uniform slots or rectangularly-shaped holes each of which is sufficiently small across the minor axis to prevent the migration of the particulated product therethrough and which are suffi-ciently large across the major axis and the minor axis to permit adequate fluid flow therethrough without a deleterious effect on the film. The heat resistant outer layer of the film forms the outside of the bag and the less heat resistant layer of the film forms the inside of the bag. The film is also substantially odorless and tasteless.
Abstract of the Disclosure An infusion bag for particulated food products such as tear coffee and the like, constructed of a coextruded multilayer perforated thermoplastic film having a heat resistant outer layer of film forming resin and an outer layer of a somewhat less heat resistant film forming resin and having a multiplicity of minute uniform slots or rectangularly-shaped holes each of which is sufficiently small across the minor axis to prevent the migration of the particulated product therethrough and which are suffi-ciently large across the major axis and the minor axis to permit adequate fluid flow therethrough without a deleterious effect on the film. The heat resistant outer layer of the film forms the outside of the bag and the less heat resistant layer of the film forms the inside of the bag. The film is also substantially odorless and tasteless.
Description
~221059 Case V-5203 INFUSION BAG
The present invention is directed to infusion bags, especially tea bags and the like, and more particularly to an infusion bag constructed of a non-woven, fiber-free, perforated thermoplastic film.
The invention is particularly concerned with an infusion bag constructed of a coextruded multilayer perforated thermo-plastic film having a plurality of uniform minute slotted holes or openings therein.
0 Thermoplastic films such as polyethylene and polypro-pylene are common packaging materials. ~ultilayer films of various types are also quite common packaging materials. The films are generally non-porous and impervious to water and other inert li~uids. At least one of the layers of film has strong adhesive qualities. Examples of such multilayer films may be seen in U.S. 4,254,169; U.S. 4,239,826; U.S. 4,233,367; U.S.
3,908,070; U.S. 3,423,231; u.S. 2,817,124 and u.s. 2,817,123.
Perforated thermoplastic films have many useful applica-tions, including packaging of food products such as cheese, gar-dening and farming to prevent growth of weeds while permi~tingmoisture to be transmitted through the film to the soil beneath and for making absorptive structures such as disposable diapers, for example, see U.S. 3,814,101.
~7 ~ZZ~59 Perforation of thermoplastic films is generally achieved by vacuum perforation of thin plastic films which involves the extrusion of molten polymeric materials such as polyethylene through a slot die. The hot melt web of film exiting the die impinges on a form through which a vacuum is drawn causing the film web to be perforated and holes formed therein. Depending upon the form used, films can be produced which have as few as 50 holes per square inch or which have thousands of holes per square inch. One of the earlier methods for vacuum perforation of plastic film is disclosed in U.S. 3,054,148. Perforations are generally round, oval, pentagonal or hexagonal.
Infusion-type tea bags are usually rectangular packets or sachets made from single or multiple pieces of paper folded in half and crimped or otherwise sealed along the edges. In another type, a single strip of paper is folded twice longitu-dinally to form an inner centrally disposed double fold joining the two meeting edges. In a type of flow-through tea bag, a triple transverse fold intermediate the length of the folded strip forms two pockets which are partially filled with tea before the open ends thereof are folded over and stapled to a strand of string usually having a tag on the end thereof.
Over the years, a wide variety of infusion packets or bags, usually for containing tea for subsequent brewing, have been develooed. The bags are usually constructed of filter paper or some other type of porous material such as cloth or the like.
~22~59 An infusion packet having two oppositely disposed, rigidly separated pockets of tea joined together by two tapering end portions which form a narrow, triangular shaped porous cup is shown in U.S. 3,597,222.
U.S~ 3,653,913 discloses an infusion bag made from a rectangular strip of porous fibrous material, the longitudinal margins of which are folded together so as to form a longitudinal joint consisting of three layers which are knurled together.
The tube is divided by a transverse bend so as to form a pair of chambers for holding an infusible substance, and the opposite ends of the tube are connected to each other so as to close the bag.
An early type of tea bag or tea ball wherein the bag is a triangularly-shaped pocket formed from a rectangular strip of perforated aluminum foil is described in U.S. 1,581,578.
Other types of filter paper tea bags or the like with a variety of handles are illustrated in U.S. 2,328,017; U.S.
The present invention is directed to infusion bags, especially tea bags and the like, and more particularly to an infusion bag constructed of a non-woven, fiber-free, perforated thermoplastic film.
The invention is particularly concerned with an infusion bag constructed of a coextruded multilayer perforated thermo-plastic film having a plurality of uniform minute slotted holes or openings therein.
0 Thermoplastic films such as polyethylene and polypro-pylene are common packaging materials. ~ultilayer films of various types are also quite common packaging materials. The films are generally non-porous and impervious to water and other inert li~uids. At least one of the layers of film has strong adhesive qualities. Examples of such multilayer films may be seen in U.S. 4,254,169; U.S. 4,239,826; U.S. 4,233,367; U.S.
3,908,070; U.S. 3,423,231; u.S. 2,817,124 and u.s. 2,817,123.
Perforated thermoplastic films have many useful applica-tions, including packaging of food products such as cheese, gar-dening and farming to prevent growth of weeds while permi~tingmoisture to be transmitted through the film to the soil beneath and for making absorptive structures such as disposable diapers, for example, see U.S. 3,814,101.
~7 ~ZZ~59 Perforation of thermoplastic films is generally achieved by vacuum perforation of thin plastic films which involves the extrusion of molten polymeric materials such as polyethylene through a slot die. The hot melt web of film exiting the die impinges on a form through which a vacuum is drawn causing the film web to be perforated and holes formed therein. Depending upon the form used, films can be produced which have as few as 50 holes per square inch or which have thousands of holes per square inch. One of the earlier methods for vacuum perforation of plastic film is disclosed in U.S. 3,054,148. Perforations are generally round, oval, pentagonal or hexagonal.
Infusion-type tea bags are usually rectangular packets or sachets made from single or multiple pieces of paper folded in half and crimped or otherwise sealed along the edges. In another type, a single strip of paper is folded twice longitu-dinally to form an inner centrally disposed double fold joining the two meeting edges. In a type of flow-through tea bag, a triple transverse fold intermediate the length of the folded strip forms two pockets which are partially filled with tea before the open ends thereof are folded over and stapled to a strand of string usually having a tag on the end thereof.
Over the years, a wide variety of infusion packets or bags, usually for containing tea for subsequent brewing, have been develooed. The bags are usually constructed of filter paper or some other type of porous material such as cloth or the like.
~22~59 An infusion packet having two oppositely disposed, rigidly separated pockets of tea joined together by two tapering end portions which form a narrow, triangular shaped porous cup is shown in U.S. 3,597,222.
U.S~ 3,653,913 discloses an infusion bag made from a rectangular strip of porous fibrous material, the longitudinal margins of which are folded together so as to form a longitudinal joint consisting of three layers which are knurled together.
The tube is divided by a transverse bend so as to form a pair of chambers for holding an infusible substance, and the opposite ends of the tube are connected to each other so as to close the bag.
An early type of tea bag or tea ball wherein the bag is a triangularly-shaped pocket formed from a rectangular strip of perforated aluminum foil is described in U.S. 1,581,578.
Other types of filter paper tea bags or the like with a variety of handles are illustrated in U.S. 2,328,017; U.S.
2,359,292, U.S. 3,566,573; U.S. 4,153,153; and Great Britain 2,087,350. British Patent 2,053,668 discloses a tea bag having 2n a somewhat accordion fold.
Infusion bags with positioning means and flotation means are disclosed in U.S. 3,797,642 and U.S. 3,809,215, respectively.
The tea bags themselves may be made of various materials inclu-ding paper, plastics such as nylon, perforated plastic film, e.g., polyester, or woven or non-woven fabric of natural or synthetic origin.
12;~1059 A percolatable porous bag constructed of a blend of individualized textile or cellulosic fiber and a small amount of thermoplastic fiber is disclosed in Canadian patent 802,720.
Various degrees of success have been achieved with the foregoing infusion bags, with paper of fibrous bags presently dominating the market place. One of the problems with paper bags is lack of wet strength~ This is even more of a problem with the larger bags for tea brewing commonly used by the food service industries.
Another problem with fibrous or paper bags is that as they become wet, the fibers expand or swell. Such expansion or swelling closes the openings in the bag material and removes the permeability thereof. When placed in a water containing vessel such as a cup or pot, the bags tend to float since the fibrous structure is so closed or porosity so diminished that air is trapped inside the bag.
An infusion bag for items such as tea, coffee or similar food products for brewing must have a number of qualities. It must have an inability to impart a taste factor to the liquid product after brewing. In effect, it must be substantially odor-less and tasteless. It must also be sufficiently strong to con-tain the brewing product in boiling water, e.g., in the steeping of tea, coffee, and similar liquid beverages. The bag must also be porous enough to permit liquid diffusion therethrough, but the pores or openings must be of such size that migration of the lZ210~9 beverage material therethrough is inhibited, both when the bag is dry and when the bag has been immersed in a liquid.
It is also important that infus;`on begins to take place within a few seconds and be completed within a few minutes. It is further desirable that a sachet, such as a tea sachet, retain sufficient stability that it can be compressed after brewing is completed without destruction of the container.
The present invention provides an infusion bag or sachet which meets all of these requirements.
~ore particularly, the present invention provides an infusion bag for particulated or granular products such as tea and coffee constructed of a vacuum perforated coextruded dual layer thermoplastic film having a base thickness of about 0.25 mil to 2 mils and having an outer heat resistant layer of film forming resin, and a less heat resistant inner sealant layer of fil~ forming resin, the vacuum perforated coextruded dual layer thermoplastic film having about 1800 to 4200 uniform substantially rectangularly shaped perforations or holes per square inch of film, the substantially rectangularly shaped perforations or holes having been formed by vacuum perforation of the thermoplastic film, said substantially rectangularly shaped vacuum formed perforations or holes being about 1 mil to about 4 mils across the minor axis, the vacuum formed perfora-tions or holes of the vacuum perforated coextruded dual layer thermoplastic film being tapered capillaries, with the larger capillary opening being in the outer heat resistant layer of the vacuum perforated coextruded dual layer thermoplastic film and the smaller capillary opening being in the inner less heat resistant layer of the vacuum perforated coextruded dual layer thermoplastic film, and the vacuum perforated dual layer co-extruded thermoplastic film having a porosity of about 100 to about 500 cubic feet per minute.
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Fig. 1 is a top plan view of one embodiment of the invention;
Fig. 2 is a side view of the embodiment of Fig. l;
~ Fig. 3 is an end view of the embodiment of Fig. l;
Fig. 4 is an enlarged sectional view across line 4-4 oE
Fig. 1;
Fig. 5 is an enlarged top view of a portion of the thermoplastic film of which the embodiment of ~ig. 1 is constructed: and, Fig. 6 is a view similar to that of Fig. 5 illustrating an alternate embodiment of the film of the invention.
Referring now to the drawings, an infusion bag of the present invention is illustrated gen_rally at 10. The bag or packet 10 is constructed of a rectangular strip of a perforated plastic film 11 which is described in more detail hereinafter.
The strip of film 11 is folded at 12, sealed at edges 13 and 14 and filled with a particulated product P which can be seen through the film 11. After the product P is inserted in the sachet 10, the edge 15 is sealed, thereby encasing the product P
within the bag 10.
As best seen in Figs. 4 and 5, the infusion bag 10 is constructed of a coextruded multilayer thermoplastic film 11 comprising an outer layer 21 of a heat resistant film forming thermoplastic resin, such as polyester, polyolefin, polycarbonate or nylon with polyester being preferred, and an inner sealant lZ2~059 layer 22 of a somewhat less heat resistant film forming thermoplastic resin, such as polyethylene, polyester, polycarbonate or nylon, with polyethylene being preferred. The film ll has a multiplicity of fine slots or rectangularly-shaped capillaries 23 which are of a somewhat tapered construction, being more or less in the form of a truncated box.
The slots 23 are illustrated in alternate rows in a uniform, pre-determined pattern and represent an ideally shaped slot. The slots are rectangularly shaped with somewhat rounded ends. In actual construction, they may have slight bulges at their center. The slots are of such a size that particulate matter is inhibited from passing therethrough. The size of the slot can be adjusted by changing either the major axis or the minor axis. By changing the minor axis, the slot can control the size particulate matter that can be passed or sifted through the film. By changing either the major axis or the minor axis, the liquid infusion rate can be controlled. It is important that the slots be sufficiently large in size and in sufficient number to provide a desired rate of liquid infusion and yet be sufficiently small in size to prevent the migration of particles therethrough such as the particulated product P.
A perforated thermoplastic film 31 is illustrated in Fig. 6 which has slots 33 which are arranged in somewhat diagonal lines. It can be appreciated that the slots can be arranged in a variety of patterns as desired.
~L2Z~059 In the packaging of an item such as tea, a preerred slot size is from one to four mils across the minor axis, with a size of two to four mils being most preferred. The major axis is four to 10 mils across, with about four to six mils being preferred. The film has a thickness of 0.25 mil to two mils and about 500 slots per square inch or more. From 1800 to 4200 slots per square inch are preferred, with about 2900 slots per square inch being most preferred. The porosity of the film is 100 to 500 cubic feet per minute (CFM).
The outer layer of the coaxial or coextruded perforated thermoplastic film of the bag is preferably a heat resiskant polyester film having a melting temperature of 425F to 600F
witb about 525F being most preferred. The inner sealant layer of the coextruded perforated thermoplastic film of the bag is preferably a somewhat less heat resistant polyethylene film having a melting temperature of 180F to 250F with 220F being most preferred. The use of an outer polyester layer enables a sealing/melting temperature differential of about 150F to be obtained. The film has a desired seal strength of 3/4 lb. per inch width.
A temperature of about 240F is required to melt the polyethylene film for sealing. To prevent sticking of the outer layer of thermoplastic film to the steel jaws of the sealing device or heat sealing machine, it is important that the melting temperature of the polyethylene be kept below about 260F. It ~Z2:1~5~
can be appreciated that 2articular polyolefin resins or other film forming resins may have higher or lower melting tempera-tures; however, it is essential that a melting temperature dif-ferential be obtained between each layer to achieve the desired seal without a deleterious effect on the film.
For example, a heat resistant polypropylene film layer has a melting temperature of 230F to 350F with about 320F
being 2referred. The melting temperature of 180F to 250F
of the somewhat less heat resistant polyethylene film layer provides the necessary melting temperature differential.
The edges of the film are heat sealed to complete the package. The melting temperature of the outer layer of the bag must be sufficiently high to prevent the film from sticking to the sealant jaws. The melting temperature of the inner sealant layer of the bag must be less than the melting temperature of the outer layer.
The edges of the bags may be readily heat sealed using standard sealing and automatic bag making machines. The edges may also be effectively sealed with use of impulse or band type sealers, hot wires, hot air or other suitable apparatuses or techniques.
For the packaging of a typical commercial tea for brew-ing, a perforated thermoplastic film suitable for constructing the infusion bag is a coextruded polypropylene/polyethylene slot perforated thermoplastic film formed from a high density poly-~221059 ethylene resin and a polypropylene resin. The resins are odor-less and tasteless and approved for food packaging.
The female side or surface of the thermoplastic film to be on the outside of the bag is also preferably flame or corona discharge treated. Such treatment enhances the flow of water into the bag and thus accelerates the infusion process.
Although a coextruded multilayer polyester/polyethylene film is preferred, other combinations of multilayer films are suitable. ~sing the following designations:
Polypropylene PP
Polyethylene PE
Crystalline polyester CPE
Amorphous polyester APE
Polycarbonate PC
Nylon N
some examples of other suitable multilayer films are as follows:
PP/PE PC/PE N/PP
CPE/PP PC/PP ~/PE
CPE/APE PC/APE N/APE
It can readily be appreciated that other film forming resins can be used providing they can be effectively perforated and provided that there is an adequate melt differential between the outer layer and the inner sealant layer.
With some resins, it may be necessary to provide multi-layer films of more than two layers. ~or example, a triple layer ~Z~059 film is suitable. Regardless of the number of layers of film, it is essential that the melting temperature differential be maintained between the outer layer of the bag and the inner sealant layer of the bag. The layers of a sheet of film must also, of course, not be subject to separation or delamination.
The film is preferably clear in color, but may be manu-factured in its natural color or a variety of colors as desired or permitted.
The film has a dry surface and has no tendency to stick, 0 cling or ~block~.
In the construction of infusion bags, the male surface of the film is on the inside of the bag.
The invention is illustrated in its simplest form, and as a typical smal~ size infusion bag for the packaging of in-dividual servings of tea for brewing. Larger size packages,such as those customarily used in the food services industry can also be constructed. Such larger bags can be similarly con-structed or constructed of two rectangular strips of film and sealed on all four edges. The bags or packages of the invention can be constructed in other geometrical configurations as desired. Rectangularly shaped packages are generally more suit-able for boxing or other type of group packaging and can usually be more easily fabricated.
The infusion bags of the present invention have excel-lent wet strength and will not deteriorate in boiling water.
12ZlOS9 The bags themselves are odorless and tasteless and do not impart any foreign taste to the item being packaged. They are, in effect, substantially inert.
Unlike bags constructed of fibrous materials, the poro-sity of the bags of this invention is unaffected by the brewingprocess. The slots in the thermoplastic film remain unchanged when submerged in water and the porosity of the film remains constant. The infusion bag of the invention is also not as prone to entrap air as a bag of fibrous material. Entrapped air causes 0 flotation of the bag and slows the brewing process.
Although the invention is particularly suitable for the packaging of tea, it can be used for packaging of other types of finely ground or particulated food products such as coffee and grits. The bags of the invention are also suitable for packaging items such as tobacco, snuff and the like. The bags may be used for packaging of any items in which infusion of liquids is desired.
The foregoing disclosure and description of the inven-tion is illustrative and explanatory thereof and various changes in the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.
Infusion bags with positioning means and flotation means are disclosed in U.S. 3,797,642 and U.S. 3,809,215, respectively.
The tea bags themselves may be made of various materials inclu-ding paper, plastics such as nylon, perforated plastic film, e.g., polyester, or woven or non-woven fabric of natural or synthetic origin.
12;~1059 A percolatable porous bag constructed of a blend of individualized textile or cellulosic fiber and a small amount of thermoplastic fiber is disclosed in Canadian patent 802,720.
Various degrees of success have been achieved with the foregoing infusion bags, with paper of fibrous bags presently dominating the market place. One of the problems with paper bags is lack of wet strength~ This is even more of a problem with the larger bags for tea brewing commonly used by the food service industries.
Another problem with fibrous or paper bags is that as they become wet, the fibers expand or swell. Such expansion or swelling closes the openings in the bag material and removes the permeability thereof. When placed in a water containing vessel such as a cup or pot, the bags tend to float since the fibrous structure is so closed or porosity so diminished that air is trapped inside the bag.
An infusion bag for items such as tea, coffee or similar food products for brewing must have a number of qualities. It must have an inability to impart a taste factor to the liquid product after brewing. In effect, it must be substantially odor-less and tasteless. It must also be sufficiently strong to con-tain the brewing product in boiling water, e.g., in the steeping of tea, coffee, and similar liquid beverages. The bag must also be porous enough to permit liquid diffusion therethrough, but the pores or openings must be of such size that migration of the lZ210~9 beverage material therethrough is inhibited, both when the bag is dry and when the bag has been immersed in a liquid.
It is also important that infus;`on begins to take place within a few seconds and be completed within a few minutes. It is further desirable that a sachet, such as a tea sachet, retain sufficient stability that it can be compressed after brewing is completed without destruction of the container.
The present invention provides an infusion bag or sachet which meets all of these requirements.
~ore particularly, the present invention provides an infusion bag for particulated or granular products such as tea and coffee constructed of a vacuum perforated coextruded dual layer thermoplastic film having a base thickness of about 0.25 mil to 2 mils and having an outer heat resistant layer of film forming resin, and a less heat resistant inner sealant layer of fil~ forming resin, the vacuum perforated coextruded dual layer thermoplastic film having about 1800 to 4200 uniform substantially rectangularly shaped perforations or holes per square inch of film, the substantially rectangularly shaped perforations or holes having been formed by vacuum perforation of the thermoplastic film, said substantially rectangularly shaped vacuum formed perforations or holes being about 1 mil to about 4 mils across the minor axis, the vacuum formed perfora-tions or holes of the vacuum perforated coextruded dual layer thermoplastic film being tapered capillaries, with the larger capillary opening being in the outer heat resistant layer of the vacuum perforated coextruded dual layer thermoplastic film and the smaller capillary opening being in the inner less heat resistant layer of the vacuum perforated coextruded dual layer thermoplastic film, and the vacuum perforated dual layer co-extruded thermoplastic film having a porosity of about 100 to about 500 cubic feet per minute.
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Fig. 1 is a top plan view of one embodiment of the invention;
Fig. 2 is a side view of the embodiment of Fig. l;
~ Fig. 3 is an end view of the embodiment of Fig. l;
Fig. 4 is an enlarged sectional view across line 4-4 oE
Fig. 1;
Fig. 5 is an enlarged top view of a portion of the thermoplastic film of which the embodiment of ~ig. 1 is constructed: and, Fig. 6 is a view similar to that of Fig. 5 illustrating an alternate embodiment of the film of the invention.
Referring now to the drawings, an infusion bag of the present invention is illustrated gen_rally at 10. The bag or packet 10 is constructed of a rectangular strip of a perforated plastic film 11 which is described in more detail hereinafter.
The strip of film 11 is folded at 12, sealed at edges 13 and 14 and filled with a particulated product P which can be seen through the film 11. After the product P is inserted in the sachet 10, the edge 15 is sealed, thereby encasing the product P
within the bag 10.
As best seen in Figs. 4 and 5, the infusion bag 10 is constructed of a coextruded multilayer thermoplastic film 11 comprising an outer layer 21 of a heat resistant film forming thermoplastic resin, such as polyester, polyolefin, polycarbonate or nylon with polyester being preferred, and an inner sealant lZ2~059 layer 22 of a somewhat less heat resistant film forming thermoplastic resin, such as polyethylene, polyester, polycarbonate or nylon, with polyethylene being preferred. The film ll has a multiplicity of fine slots or rectangularly-shaped capillaries 23 which are of a somewhat tapered construction, being more or less in the form of a truncated box.
The slots 23 are illustrated in alternate rows in a uniform, pre-determined pattern and represent an ideally shaped slot. The slots are rectangularly shaped with somewhat rounded ends. In actual construction, they may have slight bulges at their center. The slots are of such a size that particulate matter is inhibited from passing therethrough. The size of the slot can be adjusted by changing either the major axis or the minor axis. By changing the minor axis, the slot can control the size particulate matter that can be passed or sifted through the film. By changing either the major axis or the minor axis, the liquid infusion rate can be controlled. It is important that the slots be sufficiently large in size and in sufficient number to provide a desired rate of liquid infusion and yet be sufficiently small in size to prevent the migration of particles therethrough such as the particulated product P.
A perforated thermoplastic film 31 is illustrated in Fig. 6 which has slots 33 which are arranged in somewhat diagonal lines. It can be appreciated that the slots can be arranged in a variety of patterns as desired.
~L2Z~059 In the packaging of an item such as tea, a preerred slot size is from one to four mils across the minor axis, with a size of two to four mils being most preferred. The major axis is four to 10 mils across, with about four to six mils being preferred. The film has a thickness of 0.25 mil to two mils and about 500 slots per square inch or more. From 1800 to 4200 slots per square inch are preferred, with about 2900 slots per square inch being most preferred. The porosity of the film is 100 to 500 cubic feet per minute (CFM).
The outer layer of the coaxial or coextruded perforated thermoplastic film of the bag is preferably a heat resiskant polyester film having a melting temperature of 425F to 600F
witb about 525F being most preferred. The inner sealant layer of the coextruded perforated thermoplastic film of the bag is preferably a somewhat less heat resistant polyethylene film having a melting temperature of 180F to 250F with 220F being most preferred. The use of an outer polyester layer enables a sealing/melting temperature differential of about 150F to be obtained. The film has a desired seal strength of 3/4 lb. per inch width.
A temperature of about 240F is required to melt the polyethylene film for sealing. To prevent sticking of the outer layer of thermoplastic film to the steel jaws of the sealing device or heat sealing machine, it is important that the melting temperature of the polyethylene be kept below about 260F. It ~Z2:1~5~
can be appreciated that 2articular polyolefin resins or other film forming resins may have higher or lower melting tempera-tures; however, it is essential that a melting temperature dif-ferential be obtained between each layer to achieve the desired seal without a deleterious effect on the film.
For example, a heat resistant polypropylene film layer has a melting temperature of 230F to 350F with about 320F
being 2referred. The melting temperature of 180F to 250F
of the somewhat less heat resistant polyethylene film layer provides the necessary melting temperature differential.
The edges of the film are heat sealed to complete the package. The melting temperature of the outer layer of the bag must be sufficiently high to prevent the film from sticking to the sealant jaws. The melting temperature of the inner sealant layer of the bag must be less than the melting temperature of the outer layer.
The edges of the bags may be readily heat sealed using standard sealing and automatic bag making machines. The edges may also be effectively sealed with use of impulse or band type sealers, hot wires, hot air or other suitable apparatuses or techniques.
For the packaging of a typical commercial tea for brew-ing, a perforated thermoplastic film suitable for constructing the infusion bag is a coextruded polypropylene/polyethylene slot perforated thermoplastic film formed from a high density poly-~221059 ethylene resin and a polypropylene resin. The resins are odor-less and tasteless and approved for food packaging.
The female side or surface of the thermoplastic film to be on the outside of the bag is also preferably flame or corona discharge treated. Such treatment enhances the flow of water into the bag and thus accelerates the infusion process.
Although a coextruded multilayer polyester/polyethylene film is preferred, other combinations of multilayer films are suitable. ~sing the following designations:
Polypropylene PP
Polyethylene PE
Crystalline polyester CPE
Amorphous polyester APE
Polycarbonate PC
Nylon N
some examples of other suitable multilayer films are as follows:
PP/PE PC/PE N/PP
CPE/PP PC/PP ~/PE
CPE/APE PC/APE N/APE
It can readily be appreciated that other film forming resins can be used providing they can be effectively perforated and provided that there is an adequate melt differential between the outer layer and the inner sealant layer.
With some resins, it may be necessary to provide multi-layer films of more than two layers. ~or example, a triple layer ~Z~059 film is suitable. Regardless of the number of layers of film, it is essential that the melting temperature differential be maintained between the outer layer of the bag and the inner sealant layer of the bag. The layers of a sheet of film must also, of course, not be subject to separation or delamination.
The film is preferably clear in color, but may be manu-factured in its natural color or a variety of colors as desired or permitted.
The film has a dry surface and has no tendency to stick, 0 cling or ~block~.
In the construction of infusion bags, the male surface of the film is on the inside of the bag.
The invention is illustrated in its simplest form, and as a typical smal~ size infusion bag for the packaging of in-dividual servings of tea for brewing. Larger size packages,such as those customarily used in the food services industry can also be constructed. Such larger bags can be similarly con-structed or constructed of two rectangular strips of film and sealed on all four edges. The bags or packages of the invention can be constructed in other geometrical configurations as desired. Rectangularly shaped packages are generally more suit-able for boxing or other type of group packaging and can usually be more easily fabricated.
The infusion bags of the present invention have excel-lent wet strength and will not deteriorate in boiling water.
12ZlOS9 The bags themselves are odorless and tasteless and do not impart any foreign taste to the item being packaged. They are, in effect, substantially inert.
Unlike bags constructed of fibrous materials, the poro-sity of the bags of this invention is unaffected by the brewingprocess. The slots in the thermoplastic film remain unchanged when submerged in water and the porosity of the film remains constant. The infusion bag of the invention is also not as prone to entrap air as a bag of fibrous material. Entrapped air causes 0 flotation of the bag and slows the brewing process.
Although the invention is particularly suitable for the packaging of tea, it can be used for packaging of other types of finely ground or particulated food products such as coffee and grits. The bags of the invention are also suitable for packaging items such as tobacco, snuff and the like. The bags may be used for packaging of any items in which infusion of liquids is desired.
The foregoing disclosure and description of the inven-tion is illustrative and explanatory thereof and various changes in the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An infusion bag for particulated or granular products such as tea and coffee constructed of a vacuum perforated coextruded dual layer thermoplastic film having a base thickness of about 0.25 mil to 2 mils and having an outer heat resistant layer of film forming resin, and a less heat resistant inner sealant layer of film forming resin, said vacuum perforated coextruded dual layer thermoplastic film having about 1800 to 4200 uniform substantially rect-angularly shaped perforations or holes per square inch of film, said substantially rectangularly shaped perforations or holes having been formed by vacuum perforation of the thermoplastic film, said substantially rectangularly shaped vacuum formed perforations or holes being about 1 mil to about 4 mils across the minor axis, said vacuum formed perforations or holes of said vacuum perforated coextruded dual layer thermoplastic film being tapered capillaries, with the larger capillary opening being in the outer heat resistant layer of said vacuum perforated coextruded dual layer therm-plastic film and the smaller capillary opening being in the inner less heat resistant layer of said vacuum perforated co-extruded dual layer thermoplastic film, and said vacuum perforated dual layer coextruded thermoplastic film having a porosity of about 100 to about 500 cubic feet per minute.
2. The infusion bag of claim 1, wherein the resin of the heat resistant outer layer of said vacuum perforated coextruded dual layer thermoplastic film is polyester.
dal/
dal/
3. The infusion bag of claim 1, wherein the resin of the less heat resistant inner sealant layer of said vacuum perforated coextruded dual layer thermoplastic film is polyethylene.
4. The infusion bag of claim 1, wherein said vacuum formed substantially rectangularly shaped perforations or holes in said vacuum perforated coextruded dual layer thermo-plastic film have somewhat rounded corners or ends.
5. The infusion bag of claim 1, wherein the distance across the major axis of each slot is about 2-10 mils.
6. The infusion bag of claim 1, wherein the distance across the minor axis of each vacuum formed substantially rectangularly shaped perforation or hole in said vacuum perforated coextruded dual layer thermoplastic film is about 3-4 mils.
7. The infusion bag of claim 1, wherein said vacuum formed substantially rectangularly shaped perforations or holes are arranged in alternating rows.
8. The infusion bag of claim 1, wherein said vacuum formed substantially rectangularly shaped perforations or holes are arranged in somewhat diagonal rows.
9. The infusion bag of claim 1, wherein said bag is substantially rectangularly shaped and is formed from a single strip or piece of said vacuum perforated coextruded dual layer thermoplastic film which has been folded to form one edge and which has been sealed on the other edges.
10. The infusion bag of claim 1, wherein said bag is substantially rectangularly shaped and comprises two equally sized sheets or strips of said vacuum perforated coextruded dual layer thermoplastic film positioned one on top of the other and sealed on all edges.
11. The infusion bag of claim 1, wherein said vacuum perforated coextruded dual layer thermoplastic film has a male side or surface and a female side or surface and the male side is on the surface of the less heat resistant inner sealant layer of said vacuum perforated coextruded dual layer thermoplastic film and the female surface is on the heat resistant outer layer of said vacuum perforated coextruded dual layer thermoplastic film.
12. The infusion bag of claim 1, wherein the resin of said heat resistant outer layer of said vacuum perforated coextruded dual layer thermoplastic film is selected from the group consisting of polypropylene, polycarbonate and nylon.
13. The infusion bag of claim 1, wherein the resin of said less heat resistant inner sealant layer of said vacuum perforated coextruded dual layer thermoplastic film is an amorphous polyester.
14. The infusion bag of claim 1, wherein the resin of said heat resistant outer layer is polyester and the resin of said less heat resistant inner sealant layer is polyethylene.
15. The infusion bag of claim 1, wherein the resin of said less heat resistant inner sealant layer is a polyolefin.
16. The infusion bag of claim 1, wherein the resin of said heat resistant outer layer is polypropylene and the resin of said less heat resistant inner sealant layer is polyethylene.
17. The infusion bag of claim 1, wherein said vacuum perforated coextruded dual layer thermoplastic film has a liquid porosity of about 125 cubic feet per minute.
18. An infusion bag for particulated or granular products such as tea and coffee constructed of a vacuum perforated coextruded dual layer thermoplastic film having a base thickness of about 0.25 mil to 2 mils and having a heat resistant outer layer of polypropylene having a melting temperature of about 230°F to 350°F and a less heat resistant inner sealant layer of polyethylene having a melting temperature of about 180°F to about 250°F, said vacuum perforated coextruded dual layer thermoplastic film having about 1800 to 4200 uniform substantially rectangularly shaped perforations or holes per square inch of film, said substantially rectangularly shaped perforations or holes having been formed by vacuum perforation of said coextruded dual layer thermoplastic film, said vacuum formed substantially rectangularly shaped perforations or holes being about 1 mil to about 4 mils across the minor axis, said vacuum formed substantially rectangularly shaped perforations or holes in said vacuum perforated coextruded dual layer thermoplastic film being in the form of tapered capillaries, with the larger capillary opening being in the heat resistant polypropylene outer layer of said vacuum perforated coextruded dual layer thermoplastic film and the smaller capillary opening being in the less heat resistant polyethylene inner sealant layer of said vacuum perforated coextruded dual layer thermoplastic film, and said vacuum perforated coextruded dual layer thermoplastic film having a porosity of about 100 to about 500 cubic feet per minute.
19. An infusion bag for particulated or granular products such as tea and coffee constructed of a vacuum perforated coextruded dual layer thermoplastic film having a thickness of about 0.25 mil to 2 mils and having a heat resistant outer layer of polyester having a melting temper-ature of about 425°F to 600°F and a less heat resistant inner sealant layer of polyethylene having a melting temper-ature of about 180°F to about 250°F, said vacuum perforated coextruded dual layer thermoplastic film having about 1800 to 4200 uniform substantially rectangularly shaped perforations or holes per square inch of film, said substantially rect-angularly shaped perforations or holes having been formed by vacuum perforation, said vacuum formed substantially rect-angularly shaped perforations or holes being about 1 mil to about 4 mils across the minor axis, said vacuum formed substantially rectangularly shaped perforations or holes in said vacuum perforated coextruded dual layer thermoplastic film being in the form of tapered capillaries, with the larger capillary opening being in the heat resistant outer polyester layer of said vacuum perforated coextruded dual layer thermo-plastic film and the smaller capillary opening being in the less heat resistant inner sealant polyethylene layer of said vacuum perforated coextruded dual layer thermoplastic film, and said vacuum perforated coextruded dual layer thermoplastic film having a porosity of about 100 to about 500 cubic feet per minute.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US56182383A | 1983-12-15 | 1983-12-15 | |
| US561,823 | 1983-12-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1221059A true CA1221059A (en) | 1987-04-28 |
Family
ID=24243620
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000468810A Expired CA1221059A (en) | 1983-12-15 | 1984-11-28 | Infusion bag |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1221059A (en) |
-
1984
- 1984-11-28 CA CA000468810A patent/CA1221059A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |