CA1299327C - Protective patch for shrinkable bag - Google Patents
Protective patch for shrinkable bagInfo
- Publication number
- CA1299327C CA1299327C CA 504830 CA504830A CA1299327C CA 1299327 C CA1299327 C CA 1299327C CA 504830 CA504830 CA 504830 CA 504830 A CA504830 A CA 504830A CA 1299327 C CA1299327 C CA 1299327C
- Authority
- CA
- Canada
- Prior art keywords
- patch
- vinyl acetate
- bag
- layer
- ethylene
- 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.)
- Expired - Lifetime
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/90—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in food processing or handling, e.g. food conservation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
Landscapes
- Laminated Bodies (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
- Materials For Medical Uses (AREA)
Abstract
64536-569(S) ABSTRACT
Disclosed is a protective patch for a biaxially heat shrinkable, thermoplastic vacuum bag for protecting the bag from puncture by sharp protruding bones in bone-in cuts of meat which are vacuum packaged within the bags. The patch is made from multi-layer film and preferably comprises outer layers of a blend of linear low density polyethylene and ethylene vinyl acetate copolymer and inner layers of ethylene vinyl acetate copolymer.
The patch is heat shrinkable with the bag. A method of making the patch is also disclosed.
Disclosed is a protective patch for a biaxially heat shrinkable, thermoplastic vacuum bag for protecting the bag from puncture by sharp protruding bones in bone-in cuts of meat which are vacuum packaged within the bags. The patch is made from multi-layer film and preferably comprises outer layers of a blend of linear low density polyethylene and ethylene vinyl acetate copolymer and inner layers of ethylene vinyl acetate copolymer.
The patch is heat shrinkable with the bag. A method of making the patch is also disclosed.
Description
~99;~
64536-569(S) PROTECTIVE PATCH FOR ~HRINKABLE BAG
FIELD OF THE INVENTION
This invention relates to the packaging of bone-in cuts of meat. In particular, this invention relates to a protective patch which prevents or reduces the likelihood that a bone will completely puncture and rupture a thermoplastic vacuum bag and patch combination.
BACKGROUND OF THE INVENTION
The use of heat shrinkable thermoplastics as flexible packaging materials for vacuum packaging various foodstuffs including meat is well-known. Such plastic materials, however, while in general quite successful for packaging meat understand-ably have difficulties in successfully packaging sharp or bony products. For example, attempts to package bone-in primal cuts of meat usually result in an unsatisfactorily large number of bag failures due to bone punctures The use of cushioning materials such as paper, paper laminates, wax impregnated cloth, and various types of plastic inserts have proved to be less than totally satisfactory in solving the problem. The preparation of special cuts of meat or close bone trim with removal of offending bones has also been attempted. However, this is at best only a limited solution to the problem since it does not offer the positive protection necessary for a wide variety of commercial bone-in types of meat. Furthermore, removal of the bone is a relatively expensive and time consuming procedure.
Accordingly, it is one object of the present invention to provide a patch material and method for making the patch which 3~ , ~Z99327 64536-569(S) will minimize or elimina-te the puncturing of flexible, heat shrinkable vacuum bags by sharp bones.
An example of a prior art method of protecting a thermoplastic bag from puncture is shown in United States Patent No. 2,891,870 which issued on June 23, 1959 to Meyer S. Selby et al. In the Selby patent the exposed bone in a bone-in cut of meat is covered with a wax impregnated cloth and the thus protected meat is placed in a heat shrinkable plastic bag. Accordingly, it is another object of the present invention to eliminate the neces-sity for having a separate packaging item such as a wax impregnat-ed cloth which must be carefully positioned over the bone and provide a protective patch which will not be as sensitive to or dependent upon the position of the bone within a vacuum bag.
Another object of the present invention is to provide a patch for a thermoplastic vacuum bag which is relatively strong and tough and which can be readily adhered to -the outer surface of a thermoplastic vacuum bag.
These and other objects of the present invention will be more readily understood from the summary of the invention, the drawings, and the description of the preferred embodiment which follow:
SUMMARY OF THE INVENTION
In one aspect, the subject invention is a method of making a multi-layer protective patch for a biaxially heat shrink-able thermoplastic bag comprising the steps of:
a) coextruding a multi-layer, thermoplastic tube, the inner wall of said tube comprising an ethylene vinyl acetate copolymer :LZ~327 64536-569(S) and the outer wall comprising linear low density polyethylene;
b) applying a sufficient amount cf an inert dust or powder to the interior tube walls so that upon collapsing, the tube will not self adhere;
c) collapsing the tube;
d) opening, inflating, heating, and stretching the tube to biaxially orient the tube material;
e) simultaneously cooling, collapsing and flattening the tube whereupon the tube adheres to itsel-f; and f) cutting the tube into at least one patch.
In another aspect, the present invention provides a protective multi-layer patch in combination with a biaxially heat shrinkable bag, wherein said patch comprises:
I) an o~ter layer comprising a linear low density poly-ethylene;
II) an inner layer comprising an ethylene-vinyl acetate copolymer;
wherein said patch is biaxially heat shrinkable, and is adhered to said bag; and wherein said patch will shrink with the bag, thereby reducing the tendency of the patch to delaminate from the bag.
In another aspect, the present invention is a protec-tive, biaxially heat shrinkable multi-layer patch for a biaxially heat shrinkable bag comprising: (I) an outer layer comprising (a) 80% to 100~ by weight linear low density polyethylene, and (b) 20%
to 0% by weight ethylene-vinyl acetate copolymer having a vinyl acetate content in the range of 7% to 12%; and (II) an inner layer comprising an ethylene vinyl ace-tate copolymer, preferably having -~Z993Z7 64536-569(S) 20% to 35% vinyl acetate content. In a particularly preferred embodiment the patch material has been cross-linked to the equivalent of a dosage level in the range between 4.5 and 13 MR.
The things or combinations that the applicant regards as new and in which an exclusive property or privilege is claimed are defined in the numbered claims forming part of this specification~
The claims also include some further and more particular embodi-ments of the invention.
DESCRIPTION OF THE D~AWINGS
In the drawings which are appended hereto and made a part of this disclosure, Figure 1 is a perspective view of meat enclosed in a heat shrunk bag with a patch of the present invention on the exterior thereof;
Figure 2 is a perspective view similar to that in Figure 1, but showing meat with a prior art patch in position;
Figure 3 is a sectional view taken along lines 3-3 of Figure 1;
Figure 4 is a fragmentary view showing the patch of the 2~ present invention adhered to a thermoplastic vacuum bag;
Figure 5 i6 a sectional view along lines 5-5 of Figure 4; and Figure 6 is an exaggerated sectional view of the patch material of the present invention showing a preferred arrangement of the layers.
DETAI~ED DESCRIPTION
Referring more specifically to the drawings and to Figs.
.~
~ ~9g3~7 64536-569(S) 1-6, there is provided a bone-in cut of meat 2, for example, a leg of lamb, having exposed bone portion 6. There is also provided patch 8 on bag 12 covering a substantial portion of the visible side of the package. Having the patch on the outside of the bag facilitates the step of loading the bag by eliminating the concern over dislodging a manually laid on cloth patch or a patch adhered to the inside of the bag. Loading can, therefore, take place more readily and easily. After a bone-in cut is loaded into the bag air is evacuated from the package and the bag neck 10 is gathered having the appearance as shown in Figure 1 and thereafter a clip 4 is applied to securely seal the bag. The bag can then be immersed in hot water and shrunken tightly against the meat thus providing a meat product in an evacuated atmosphere or aging and preserva-tion. The patch 8 shrinks with the bag thus reducing the tendenc~
to delaminate when the patch is not shrinkable in the same manner as the bag.
Figure 2 shows a prior art bag 12 and covering cloth patch 8 which requires careful positioning of the cloth 8 over the bone 6 and also requires care in positioning the bone within the bag so that the cloth 8 is not pushed out of position or dis-lodged.
Figure 3 shows t~e exposed bone portion 6 covered by bag 12 with the preferred pouch 8 adhered to the outside of the bag over the bone protrusion.
In Figure 4 patch 8 is shown adhered to one side of a wall of bag 12. Preferably patch 8 will cover substantially one side of a bag in its flattened, '~ `
~Z99327 64536-569(S) lay-flat position. In many applications it is desirable to adhere a patch to both sides o~ a bag.
Figure 5 is a cross-section view of Figure 4 showing patch 8 adhered to the one wall of bag 12.
Figure 6 shows a cross-section, in an exaggerated form, of patch 8 with outer layers 14 and 16 and inner layers 18 and 20.
In a preferred embodimen-t the composition of outer layers 14 and 16 comprises 87% by weight of linear low density pol~ethylene, 10%
by weight of e-thylene-vinyl acetate copolymer having 9~ vinyl acetate and 3% pigments and additives to aid in extrusion. The preferred linear low density polyethylene is Dowlex 2045* from Dow Chemical Company of Midland, Michigan and the preferred ethylene-vinyl acetate copolymer is ELVAX 3128* from the DuPont Company of Wilmington, Delware. The inner layers 18 and 20 comprise ethylene-vinyl acetate copolymer having 28~ vinyl acetate from the U.S.I. Division of National Distillers of New York, N.Y. All layers have been cross-linked by irradiation to the dosage level which is equivalent to 7 MR.
In one test bags were made with a 17.5 inches wide and 2Q 18 inches long patch of the protective material of the present invention on one side and a 17.5 inch wide and 10 inch long patch on the other. The lay flat dimensions of these bags were 18 inches wide by 30 inches long. In a larger bag (22" x 34") for blades a patch of 21.5 inches by 24 inches on one side and a patch of 21.5 inches by 8 inches on the other was used~ Various bone-in beef products were put up in bags with both the patch of the present invention as described and with cloth covered bones. The *Trade-mark `~t - 6 -~99327 64536~569(S) products ranged from rib ends -to blades and arms. Of the total of 1173 packages which used cloth to cover the protruding bones therewere a total of 55 bone punctures whereas in 2097 packages using the patches of the present invention as described there were only 18 bone punctures.
The embodiment as described is a preferred one but a satisfactory pouch can be made where the oute~ layers 14 and 16 comprise 15~ ethylene-vinyl acetate copolymer having 9~ vinyl acetate and 83.3~ linear low density polyethylene with the balance of 1.7% being a pigment. In addition, satisfactory pouches can be made with the outer layers comprising a blend of 90% linear low density polyethylene with 10~ vinyl acetate copolymer. Based on experience it is believed that the desirable composition range for the outer layer is 80% to 100% linear low density polyethylene and 20% to 0~ ethylene-vinyl acetate copolymer with the vinyl acetate content having a range from 7% to 12% vinyl acetate. The inner layer preferably comprises an ethylene-vinyl acetate copolymer having 20 to 35% vinyl acetate content.
It has been surprisingly found tha-t the increased strength and toughness of the patch according to the present invention is greatly enhanced by the use of linear low density polyethylene. The copolymers referred to as linear low density polyethylene generally have a density of 0.900 to 0.935 grams per cubic centimeter and a crystalline melting point in the range of 110C to 125C. These linear low density polyethylenes are not homopolymers although they are referred to generally as "poly-ethylene". In fact, they are copolymers of ethylene and an alpha-olefin having a carbon number less than 18, for instance, butene-~12993~
64536-569(S) 1, pentene-l, hexene-l, octene-l, etc. In the Dowlex* brand of linear low density polyethylene used in the above preferred embodiment it is understood that the alpha-olefin is octene-l.
Examples of patents showing the use of such polymers are U.S.
Patent No. 4,425,268 which issued on January 8, 1984 to Barry A.
Cooper; United States Paten-t No. 4,456,646 which issued on June 26, 1984 to ~ishimoto et al United Statés Patent No. 4,399,180 which issued on August 16, 1983 to William F. Briggs et al; and United States Patent No. 4,457,960 which issued on July 3, 1984 to David L. Newsome.
Typical vacuum bags and the vacuum bag of the type used in the test and example set forth above are made according to the process shown in United States Patent ~o. 3,741,253 which issued on June 26, 1973 to Harri J. Brax et al. The method of the Brax et al patent provides background for the description which follows for the method of making the patch of the present invention.
To make the patch of the present invention, a first ethylene-vinyl acetate copolymer having a vinyl-acetate content o~
approximately 28~ by weight is sent to a first extruder. This material forms layer 18 and 20. (Fig. 6). Also, a blend having a major proportion of linear low density polyethylene and a minor proportion of a second ethylene-vinyl acetate copolymer, one hav-ing a vinyl acetate content in the range of 7~ to 12%, is fed into a second extruder. This material forms layers 14 and 16. Both extruders feed a common coextrusion die of the type which is well-known in the art. The extrudate which issues from the die has an inner wall of the first ethylene-vinyl acetate copolymer and an *Trade-mark ~9~3Z~
~536-569(S) outer wall of the blend. This type of coextrusion essentially coextrudes two concentric tubes, one inside the other, and in this case the first vinyl acetate copolymer is the inner tube~
As the tube is extruded downwardly it is closed off and flattened by pinch rollers, but in order to keep the first vinyl acetate copolymer from adhering to itself the interior of the tube is coated with an inert dust or powder, preferably powdered corn-starch, in a surface concentration sufficient to prevent self-adherence. This flattened tubing is then fed through an irradia-tion vault where it will preferably receive a dosage of approx-imately 7 MR to cross-link the polymeric materials which comprise the tube. The preferred range is 4.5 MR to 13 MR with the most suitable range being between 6 and 8 MR. Chemical cross-linking using an organic peroxide is thought to be an alternate cross-linking method but irradiation cross-linking is preferred. After receiving the cross-linking dosage the tube is opened, inflated, heated, and stretched by the well-known bubble technique which is described in the above mentioned Brax et al patent. The biaxially stretching orients the tube material. After the material has been stretched to the desired diameter and wall thickness, it is then rapidly cooled and collapsed. This process results in a biaxially oriented patch material which is heat shrinkable at approximately the temperature at which it was oriented. When collapsed and flattened the tubing will now tend to adhere to itself as the stretching decreases the concentration of the cornstarch on the inner surface of the bubble or stretched tubing. This concentra-tion of the cornstarch now is low enough to permit self-adherence. The vinyl acetate content of the inner wall is approx-~2993;~
6~536-569(S) imately 28~ by weight. This is an ethylene-vinyl acetate copoly-mer in the range where the ethylene-vinyl acetate copolymer acts as an adhesive. Thus, a multi-layer tubular material is produced, in this instance, a four layer material as shown in Figure 6 is produced. This material can be cut into patches and adhered to one or both sides of the heat shrinkable bag to produce a protec-tive material which will greatly diminish the occurrence of bone punctures.
Many suitable adhesives to adhere the patch to the bag are available and can readily be selected by those skilled in the art, the tendency to delaminate having been greatly reduced as the patch shrinks biaxially as does the bag.
Having thus described my invention, ~ ,~ -- 10 --~-r .
64536-569(S) PROTECTIVE PATCH FOR ~HRINKABLE BAG
FIELD OF THE INVENTION
This invention relates to the packaging of bone-in cuts of meat. In particular, this invention relates to a protective patch which prevents or reduces the likelihood that a bone will completely puncture and rupture a thermoplastic vacuum bag and patch combination.
BACKGROUND OF THE INVENTION
The use of heat shrinkable thermoplastics as flexible packaging materials for vacuum packaging various foodstuffs including meat is well-known. Such plastic materials, however, while in general quite successful for packaging meat understand-ably have difficulties in successfully packaging sharp or bony products. For example, attempts to package bone-in primal cuts of meat usually result in an unsatisfactorily large number of bag failures due to bone punctures The use of cushioning materials such as paper, paper laminates, wax impregnated cloth, and various types of plastic inserts have proved to be less than totally satisfactory in solving the problem. The preparation of special cuts of meat or close bone trim with removal of offending bones has also been attempted. However, this is at best only a limited solution to the problem since it does not offer the positive protection necessary for a wide variety of commercial bone-in types of meat. Furthermore, removal of the bone is a relatively expensive and time consuming procedure.
Accordingly, it is one object of the present invention to provide a patch material and method for making the patch which 3~ , ~Z99327 64536-569(S) will minimize or elimina-te the puncturing of flexible, heat shrinkable vacuum bags by sharp bones.
An example of a prior art method of protecting a thermoplastic bag from puncture is shown in United States Patent No. 2,891,870 which issued on June 23, 1959 to Meyer S. Selby et al. In the Selby patent the exposed bone in a bone-in cut of meat is covered with a wax impregnated cloth and the thus protected meat is placed in a heat shrinkable plastic bag. Accordingly, it is another object of the present invention to eliminate the neces-sity for having a separate packaging item such as a wax impregnat-ed cloth which must be carefully positioned over the bone and provide a protective patch which will not be as sensitive to or dependent upon the position of the bone within a vacuum bag.
Another object of the present invention is to provide a patch for a thermoplastic vacuum bag which is relatively strong and tough and which can be readily adhered to -the outer surface of a thermoplastic vacuum bag.
These and other objects of the present invention will be more readily understood from the summary of the invention, the drawings, and the description of the preferred embodiment which follow:
SUMMARY OF THE INVENTION
In one aspect, the subject invention is a method of making a multi-layer protective patch for a biaxially heat shrink-able thermoplastic bag comprising the steps of:
a) coextruding a multi-layer, thermoplastic tube, the inner wall of said tube comprising an ethylene vinyl acetate copolymer :LZ~327 64536-569(S) and the outer wall comprising linear low density polyethylene;
b) applying a sufficient amount cf an inert dust or powder to the interior tube walls so that upon collapsing, the tube will not self adhere;
c) collapsing the tube;
d) opening, inflating, heating, and stretching the tube to biaxially orient the tube material;
e) simultaneously cooling, collapsing and flattening the tube whereupon the tube adheres to itsel-f; and f) cutting the tube into at least one patch.
In another aspect, the present invention provides a protective multi-layer patch in combination with a biaxially heat shrinkable bag, wherein said patch comprises:
I) an o~ter layer comprising a linear low density poly-ethylene;
II) an inner layer comprising an ethylene-vinyl acetate copolymer;
wherein said patch is biaxially heat shrinkable, and is adhered to said bag; and wherein said patch will shrink with the bag, thereby reducing the tendency of the patch to delaminate from the bag.
In another aspect, the present invention is a protec-tive, biaxially heat shrinkable multi-layer patch for a biaxially heat shrinkable bag comprising: (I) an outer layer comprising (a) 80% to 100~ by weight linear low density polyethylene, and (b) 20%
to 0% by weight ethylene-vinyl acetate copolymer having a vinyl acetate content in the range of 7% to 12%; and (II) an inner layer comprising an ethylene vinyl ace-tate copolymer, preferably having -~Z993Z7 64536-569(S) 20% to 35% vinyl acetate content. In a particularly preferred embodiment the patch material has been cross-linked to the equivalent of a dosage level in the range between 4.5 and 13 MR.
The things or combinations that the applicant regards as new and in which an exclusive property or privilege is claimed are defined in the numbered claims forming part of this specification~
The claims also include some further and more particular embodi-ments of the invention.
DESCRIPTION OF THE D~AWINGS
In the drawings which are appended hereto and made a part of this disclosure, Figure 1 is a perspective view of meat enclosed in a heat shrunk bag with a patch of the present invention on the exterior thereof;
Figure 2 is a perspective view similar to that in Figure 1, but showing meat with a prior art patch in position;
Figure 3 is a sectional view taken along lines 3-3 of Figure 1;
Figure 4 is a fragmentary view showing the patch of the 2~ present invention adhered to a thermoplastic vacuum bag;
Figure 5 i6 a sectional view along lines 5-5 of Figure 4; and Figure 6 is an exaggerated sectional view of the patch material of the present invention showing a preferred arrangement of the layers.
DETAI~ED DESCRIPTION
Referring more specifically to the drawings and to Figs.
.~
~ ~9g3~7 64536-569(S) 1-6, there is provided a bone-in cut of meat 2, for example, a leg of lamb, having exposed bone portion 6. There is also provided patch 8 on bag 12 covering a substantial portion of the visible side of the package. Having the patch on the outside of the bag facilitates the step of loading the bag by eliminating the concern over dislodging a manually laid on cloth patch or a patch adhered to the inside of the bag. Loading can, therefore, take place more readily and easily. After a bone-in cut is loaded into the bag air is evacuated from the package and the bag neck 10 is gathered having the appearance as shown in Figure 1 and thereafter a clip 4 is applied to securely seal the bag. The bag can then be immersed in hot water and shrunken tightly against the meat thus providing a meat product in an evacuated atmosphere or aging and preserva-tion. The patch 8 shrinks with the bag thus reducing the tendenc~
to delaminate when the patch is not shrinkable in the same manner as the bag.
Figure 2 shows a prior art bag 12 and covering cloth patch 8 which requires careful positioning of the cloth 8 over the bone 6 and also requires care in positioning the bone within the bag so that the cloth 8 is not pushed out of position or dis-lodged.
Figure 3 shows t~e exposed bone portion 6 covered by bag 12 with the preferred pouch 8 adhered to the outside of the bag over the bone protrusion.
In Figure 4 patch 8 is shown adhered to one side of a wall of bag 12. Preferably patch 8 will cover substantially one side of a bag in its flattened, '~ `
~Z99327 64536-569(S) lay-flat position. In many applications it is desirable to adhere a patch to both sides o~ a bag.
Figure 5 is a cross-section view of Figure 4 showing patch 8 adhered to the one wall of bag 12.
Figure 6 shows a cross-section, in an exaggerated form, of patch 8 with outer layers 14 and 16 and inner layers 18 and 20.
In a preferred embodimen-t the composition of outer layers 14 and 16 comprises 87% by weight of linear low density pol~ethylene, 10%
by weight of e-thylene-vinyl acetate copolymer having 9~ vinyl acetate and 3% pigments and additives to aid in extrusion. The preferred linear low density polyethylene is Dowlex 2045* from Dow Chemical Company of Midland, Michigan and the preferred ethylene-vinyl acetate copolymer is ELVAX 3128* from the DuPont Company of Wilmington, Delware. The inner layers 18 and 20 comprise ethylene-vinyl acetate copolymer having 28~ vinyl acetate from the U.S.I. Division of National Distillers of New York, N.Y. All layers have been cross-linked by irradiation to the dosage level which is equivalent to 7 MR.
In one test bags were made with a 17.5 inches wide and 2Q 18 inches long patch of the protective material of the present invention on one side and a 17.5 inch wide and 10 inch long patch on the other. The lay flat dimensions of these bags were 18 inches wide by 30 inches long. In a larger bag (22" x 34") for blades a patch of 21.5 inches by 24 inches on one side and a patch of 21.5 inches by 8 inches on the other was used~ Various bone-in beef products were put up in bags with both the patch of the present invention as described and with cloth covered bones. The *Trade-mark `~t - 6 -~99327 64536~569(S) products ranged from rib ends -to blades and arms. Of the total of 1173 packages which used cloth to cover the protruding bones therewere a total of 55 bone punctures whereas in 2097 packages using the patches of the present invention as described there were only 18 bone punctures.
The embodiment as described is a preferred one but a satisfactory pouch can be made where the oute~ layers 14 and 16 comprise 15~ ethylene-vinyl acetate copolymer having 9~ vinyl acetate and 83.3~ linear low density polyethylene with the balance of 1.7% being a pigment. In addition, satisfactory pouches can be made with the outer layers comprising a blend of 90% linear low density polyethylene with 10~ vinyl acetate copolymer. Based on experience it is believed that the desirable composition range for the outer layer is 80% to 100% linear low density polyethylene and 20% to 0~ ethylene-vinyl acetate copolymer with the vinyl acetate content having a range from 7% to 12% vinyl acetate. The inner layer preferably comprises an ethylene-vinyl acetate copolymer having 20 to 35% vinyl acetate content.
It has been surprisingly found tha-t the increased strength and toughness of the patch according to the present invention is greatly enhanced by the use of linear low density polyethylene. The copolymers referred to as linear low density polyethylene generally have a density of 0.900 to 0.935 grams per cubic centimeter and a crystalline melting point in the range of 110C to 125C. These linear low density polyethylenes are not homopolymers although they are referred to generally as "poly-ethylene". In fact, they are copolymers of ethylene and an alpha-olefin having a carbon number less than 18, for instance, butene-~12993~
64536-569(S) 1, pentene-l, hexene-l, octene-l, etc. In the Dowlex* brand of linear low density polyethylene used in the above preferred embodiment it is understood that the alpha-olefin is octene-l.
Examples of patents showing the use of such polymers are U.S.
Patent No. 4,425,268 which issued on January 8, 1984 to Barry A.
Cooper; United States Paten-t No. 4,456,646 which issued on June 26, 1984 to ~ishimoto et al United Statés Patent No. 4,399,180 which issued on August 16, 1983 to William F. Briggs et al; and United States Patent No. 4,457,960 which issued on July 3, 1984 to David L. Newsome.
Typical vacuum bags and the vacuum bag of the type used in the test and example set forth above are made according to the process shown in United States Patent ~o. 3,741,253 which issued on June 26, 1973 to Harri J. Brax et al. The method of the Brax et al patent provides background for the description which follows for the method of making the patch of the present invention.
To make the patch of the present invention, a first ethylene-vinyl acetate copolymer having a vinyl-acetate content o~
approximately 28~ by weight is sent to a first extruder. This material forms layer 18 and 20. (Fig. 6). Also, a blend having a major proportion of linear low density polyethylene and a minor proportion of a second ethylene-vinyl acetate copolymer, one hav-ing a vinyl acetate content in the range of 7~ to 12%, is fed into a second extruder. This material forms layers 14 and 16. Both extruders feed a common coextrusion die of the type which is well-known in the art. The extrudate which issues from the die has an inner wall of the first ethylene-vinyl acetate copolymer and an *Trade-mark ~9~3Z~
~536-569(S) outer wall of the blend. This type of coextrusion essentially coextrudes two concentric tubes, one inside the other, and in this case the first vinyl acetate copolymer is the inner tube~
As the tube is extruded downwardly it is closed off and flattened by pinch rollers, but in order to keep the first vinyl acetate copolymer from adhering to itself the interior of the tube is coated with an inert dust or powder, preferably powdered corn-starch, in a surface concentration sufficient to prevent self-adherence. This flattened tubing is then fed through an irradia-tion vault where it will preferably receive a dosage of approx-imately 7 MR to cross-link the polymeric materials which comprise the tube. The preferred range is 4.5 MR to 13 MR with the most suitable range being between 6 and 8 MR. Chemical cross-linking using an organic peroxide is thought to be an alternate cross-linking method but irradiation cross-linking is preferred. After receiving the cross-linking dosage the tube is opened, inflated, heated, and stretched by the well-known bubble technique which is described in the above mentioned Brax et al patent. The biaxially stretching orients the tube material. After the material has been stretched to the desired diameter and wall thickness, it is then rapidly cooled and collapsed. This process results in a biaxially oriented patch material which is heat shrinkable at approximately the temperature at which it was oriented. When collapsed and flattened the tubing will now tend to adhere to itself as the stretching decreases the concentration of the cornstarch on the inner surface of the bubble or stretched tubing. This concentra-tion of the cornstarch now is low enough to permit self-adherence. The vinyl acetate content of the inner wall is approx-~2993;~
6~536-569(S) imately 28~ by weight. This is an ethylene-vinyl acetate copoly-mer in the range where the ethylene-vinyl acetate copolymer acts as an adhesive. Thus, a multi-layer tubular material is produced, in this instance, a four layer material as shown in Figure 6 is produced. This material can be cut into patches and adhered to one or both sides of the heat shrinkable bag to produce a protec-tive material which will greatly diminish the occurrence of bone punctures.
Many suitable adhesives to adhere the patch to the bag are available and can readily be selected by those skilled in the art, the tendency to delaminate having been greatly reduced as the patch shrinks biaxially as does the bag.
Having thus described my invention, ~ ,~ -- 10 --~-r .
Claims (33)
1. A method of making a multi-layer protective patch for a biaxially heat shrinkable thermoplastic bag comprising the steps of:
a) coextruding a multi-layer, thermoplastic tube, the inner wall of said tube comprising an ethylene vinyl acetate copolymer and the outer wall comprising linear low density polyethylene;
b) applying a sufficient amount of an inert dust or powder to the interior tube walls so that upon collapsing, the tube will not self adhere;
c) collapsing the tube;
d) opening, inflating, heating, and stretching the tube to biaxially orient the tube material;
e) simultaneously cooling, collapsing and flattening the tube whereupon the tube adheres to itself; and f) cutting the tube into at least one patch.
a) coextruding a multi-layer, thermoplastic tube, the inner wall of said tube comprising an ethylene vinyl acetate copolymer and the outer wall comprising linear low density polyethylene;
b) applying a sufficient amount of an inert dust or powder to the interior tube walls so that upon collapsing, the tube will not self adhere;
c) collapsing the tube;
d) opening, inflating, heating, and stretching the tube to biaxially orient the tube material;
e) simultaneously cooling, collapsing and flattening the tube whereupon the tube adheres to itself; and f) cutting the tube into at least one patch.
2. The method of claim 1 wherein the inert dust or powder is powdered cornstarch.
3. The method of claim 1 wherein the inner wall of the thermoplastic tube comprises a first ethylene vinyl acetate co-polymer and the outer wall of said tube comprises a blend having a major proportion of linear low density polyethylene and a minor amount of a second ethylene vinyl acetate copolymer.
64536-569(S)
64536-569(S)
4. The method of claim 3 wherein the vinyl acetate content of the second copolymer is in the range of 7% to 12% and the vinyl acetate content of the first copolymer is in the range of 20 to 35%, and wherein the blend of linear low density polyethylene and the second ethylene-vinyl acetate copolymer comprises at least 80%
linear low density polyethylene, up to 20% ethylene-vinyl acetate copolymer, and up to 5% pigments and additives.
linear low density polyethylene, up to 20% ethylene-vinyl acetate copolymer, and up to 5% pigments and additives.
5. The method of claim 1, 2, 3 or 4 which comprises the additional step of irradiating the collapsed tube so as to cross-link polymer material thereof.
6. The method of claim 5 wherein the collapsed tube is irradiated in the dosage range of from 4.5 to 13.0 MR.
7. The method of claim 1, 2, 3, 4, or 6 includes the additional step of adhering the patch to a surface of a shrinkable thermoplastic bag thereby protecting the bag from puncture.
8. A method of making a multi-layer protective patch on a biaxially heat shrinkable thermoplastic bag comprising the steps of:
a) coextruding a multi-layer, thermoplastic tube, the inner wall of said tube comprising a first ethylene vinyl acetate co-polymer and the outer wall comprising a blend having a major pro-portion of linear low density polyethylene and a minor amount of a 64536-569(S) second ethylene vinyl acetate copolymer;
b) applying a sufficient amount of an inert dust or powder to the interior tube walls so that upon collapsing, the tube will not self adhere;
c) collapsing the tube, d) irradiating the collapsed tube to cross-link polymer material thereof;
e) opening, inflating, heating, and stretching the tube to biaxially orient the tube material f) simultaneously cooling, collapsing and flattening the tube whereupon the tube adheres to itself;
g) cutting the tube into at least one patch, and h) adhering the patch to a surface of the shrinkable thermo-plastic bag thereby protecting the bag from puncture, wherein said patch will, when adhered to said bag, shrink with the bay, thereby reducing the tendency of the patch to delaminate from the bag.
a) coextruding a multi-layer, thermoplastic tube, the inner wall of said tube comprising a first ethylene vinyl acetate co-polymer and the outer wall comprising a blend having a major pro-portion of linear low density polyethylene and a minor amount of a 64536-569(S) second ethylene vinyl acetate copolymer;
b) applying a sufficient amount of an inert dust or powder to the interior tube walls so that upon collapsing, the tube will not self adhere;
c) collapsing the tube, d) irradiating the collapsed tube to cross-link polymer material thereof;
e) opening, inflating, heating, and stretching the tube to biaxially orient the tube material f) simultaneously cooling, collapsing and flattening the tube whereupon the tube adheres to itself;
g) cutting the tube into at least one patch, and h) adhering the patch to a surface of the shrinkable thermo-plastic bag thereby protecting the bag from puncture, wherein said patch will, when adhered to said bag, shrink with the bay, thereby reducing the tendency of the patch to delaminate from the bag.
9. The method of claim 8 wherein the vinyl acetate content of the second copolymer is in the range of 7% to 12% and the vinyl acetate content of the first copolymer is in the range of 20 to 35%, and wherein the blend of linear low density polyethylene and the second ethylene-vinyl acetate copolymer comprises at least 80%
linear low density polyethylene, up to 20% ethylene-vinyl acetate copolymer, and up to 5% pigments and additives.
linear low density polyethylene, up to 20% ethylene-vinyl acetate copolymer, and up to 5% pigments and additives.
10. A protective, biaxially heat shrinkable, multi-layer patch having no barrier layer for a biaxially heat shrinkable bag 64536-569(S) comprising:
I) an outer layer comprising:
a) 80% to 100% by weight linear low density poly-ethylene, and b) 20% to 0% by weight ethylene-vinyl acetate copolymer having a vinyl acetate content in the range from 7% to 12%, and II) an inner layer comprising an ethylene-vinyl acetate copolymer.
I) an outer layer comprising:
a) 80% to 100% by weight linear low density poly-ethylene, and b) 20% to 0% by weight ethylene-vinyl acetate copolymer having a vinyl acetate content in the range from 7% to 12%, and II) an inner layer comprising an ethylene-vinyl acetate copolymer.
11. The patch of claim 10 wherein the polymer material of the patch has been cross-linked to the equivalent of an irradia-tion dosage level in the range between 4.5 to 13 MR.
12. The patch of claim 10 wherein the polymer material of the patch has been cross-linked by irradiation to a dosage in the range from 6 to 8 MR.
13. The patch of claim 10, 11, or 12 wherein the material of layer II comprises an ethylene-vinyl acetate copolymer having 20 -35% vinyl acetate content.
14. The patch of claim 10, 11, or 12 wherein the patch comprises four layers, the outer layers comprising the material of layer (I) and the inner layers comprising the material of layer (II).
15. The patch of claim 14 wherein the material of layer II
64536-569(S) comprises an ethylene-vinyl acetate copolymer having 20 - 35%
vinyl acetate content.
64536-569(S) comprises an ethylene-vinyl acetate copolymer having 20 - 35%
vinyl acetate content.
16. The patch of claim 14 wherein the material of layer (I) comprises 87% linear low density polyethylene blended with 10%
ethylene-vinyl acetate copolymer having 9% vinyl acetate content and 3% pigments and additives, and layer (II) comprises ethylene-vinyl acetate copolymer having 28% vinyl acetate.
ethylene-vinyl acetate copolymer having 9% vinyl acetate content and 3% pigments and additives, and layer (II) comprises ethylene-vinyl acetate copolymer having 28% vinyl acetate.
17. A protective multi-layer patch in combination with a biaxially heat shrinkable bag, wherein said patch comprises:
I) an outer layer comprising a linear low density poly-ethylene;
II) an inner layer comprising an ethylene-vinyl acetate co polymer;
wherein said patch is biaxially heat shrinkable, and is adhered to said bag, and wherein said patch will shrink with the bag, thereby reducing the tendency of the patch to delaminate from the bag.
I) an outer layer comprising a linear low density poly-ethylene;
II) an inner layer comprising an ethylene-vinyl acetate co polymer;
wherein said patch is biaxially heat shrinkable, and is adhered to said bag, and wherein said patch will shrink with the bag, thereby reducing the tendency of the patch to delaminate from the bag.
18. The patch-bag combination of claim 17, wherein the polymer material of the patch material has been cross-linked to the equivalent of an irradiation dosage level in the range between 4.5 to 13 MR.
19. The patch-bag combination of claim 17, wherein polymer material of the patch has been cross-linked by irradiation to a dosage in the range from 6 to 8 MR.
64536-569(S)
64536-569(S)
20. The patch-bag combination of claim 17, 18 or 19 wherein the patch comprises four layers, the outer layers comprising the material of layer (I) and the inner layers comprising the material of layer (II).
21. The patch-bag combination of claim 20 wherein the patch is adhered to a biaxially shrinkable, thermoplastic vacuum bag.
22. The patch-bag combination according to claim 17, 18 or 19 wherein the outer layer (I) comprises a blend of: (a) linear low density polyethylene, and (b) a second ethylene-vinyl acetate copolymer; and the inner layer (II) comprises a first ethylene-vinyl acetate copolymer.
23. The patch-bag combination of claim 22, wherein the patch comprises four layers, the outer layers comprising the material of layer (I) and the inner layers comprising the material of layer (II).
24. The patch-bag combination of claim 23 wherein the patch is adhered to a biaxially shrinkable, thermoplastic vacuum bag.
25. The patch-bag combination according to claim 17, 18 or 19 wherein the outer layer (I) comprises a blend of: (a) a major amount by weight of linear low density polyethylene; (b) a minor amount by weight of an ethylene-vinyl acetate having a vinyl 64536-569(S) acetate content in the range from 7% to 12% by weight; and (c) 0%
to 5% by weight pigments and additives; and the inner layer (II) comprises an ethylene-vinyl acetate copolymer having 20% to 35% by weight vinyl acetate content.
to 5% by weight pigments and additives; and the inner layer (II) comprises an ethylene-vinyl acetate copolymer having 20% to 35% by weight vinyl acetate content.
26. The patch-bag combination of claim 25, wherein the patch comprises four layers, the outer layers comprising the material of layer (I) and the inner layers comprising the material of layer (II).
27. The patch-bag combination of claim 26, wherein the patch is adhered to a biaxially shrinkable, thermoplastic vacuum bag.
28. The patch-bag combination of claim 17, 18 or 19, where-in: the outer layer (I) comprises a blend of: (a) 80% to 100% by weight linear low density polyethylene; (b) 20% to 0% by weight ethylene-vinyl acetate having a vinyl acetate content in the range from 7% to 12% by weight and (c) 5% to 0% by weight pigments and additives; and the inner layer (II) comprises an ethylene-vinyl acetate copolymer having 20% to 35% by weight vinyl acetate content.
29. The patch-bag combination of claim 28, wherein the patch comprises four layers, the outer layers comprising the material of layer (I) and the inner layers comprising the material of layer (II).
64536-569(S)
64536-569(S)
30. The patch-bag combination of claim 29, wherein the patch is adhered to a biaxially shrinkable, thermoplastic vacuum bag.
31. The patch-bag combination of claim 17, 18, or 19, where-in the material of layer (I) comprises 87% by weight linear low density polyethylene blended with 10% by weight ethylene-vinyl acetate copolymer having 9% by weight vinyl acetate content and 3%
by weight pigments and additives, and layer (II) comprises ethylene-vinyl acetate copolymer having 28% by weight vinyl acetate.
by weight pigments and additives, and layer (II) comprises ethylene-vinyl acetate copolymer having 28% by weight vinyl acetate.
32. The patch-bag combination of claim 31, wherein the patch comprises four layers, the outer layers comprising the material of layer (I) and the inner layers comprising the material of layer (II).
33. The patch-bag combination of claim 32, wherein the patch is adhered to a biaxially shrinkable, thermoplastic vacuum bag.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US74036085A | 1985-06-03 | 1985-06-03 | |
| US740,360 | 1985-06-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1299327C true CA1299327C (en) | 1992-04-28 |
Family
ID=24976173
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 504830 Expired - Lifetime CA1299327C (en) | 1985-06-03 | 1986-03-24 | Protective patch for shrinkable bag |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPH0649338B2 (en) |
| AU (2) | AU593252B2 (en) |
| CA (1) | CA1299327C (en) |
| NZ (1) | NZ215714A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NZ247940A (en) * | 1993-06-21 | 1995-05-26 | Grace W R & Co | Heat-shrinkable thermoplastics packaging film comprising at least two identical films |
| CN114083818A (en) * | 2021-11-24 | 2022-02-25 | 汪文瑞 | Processing technology of double-layer inner-adhesion flexible freight bag |
| CN114919200B (en) * | 2022-06-10 | 2023-12-26 | 浙江硕华生命科学研究股份有限公司 | Pipe fitting heating stretching tool and pipette cutting forming equipment |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3555604A (en) | 1965-03-12 | 1971-01-19 | Union Carbide Corp | Biaxial orientation |
| US3741253A (en) | 1971-03-30 | 1973-06-26 | Grace W R & Co | Laminates of ethylene vinyl acetate polymers and polymers of vinylidene chloride |
| US4136203A (en) | 1976-07-08 | 1979-01-23 | Swift & Company | Meat packaging |
| DE3114171A1 (en) * | 1981-04-08 | 1982-10-28 | Wolff Walsrode Ag, 3030 Walsrode | SEALABLE MULTILAYER FILMS |
| US4457960A (en) | 1982-04-26 | 1984-07-03 | American Can Company | Polymeric and film structure for use in shrink bags |
| US4448792A (en) * | 1982-07-26 | 1984-05-15 | W. R. Grace & Co., Cryovac Division | Pasteurizable and cook-in shrink bag constructed of a multilayer film |
| US4469742A (en) * | 1983-01-31 | 1984-09-04 | W. R. Grace & Co., Cryovac Div. | Pasteurizable, cook-in shrink film |
-
1986
- 1986-03-24 CA CA 504830 patent/CA1299327C/en not_active Expired - Lifetime
- 1986-04-07 NZ NZ21571486A patent/NZ215714A/en unknown
- 1986-05-26 AU AU57912/86A patent/AU593252B2/en not_active Expired
- 1986-05-26 JP JP11939586A patent/JPH0649338B2/en not_active Expired - Lifetime
-
1990
- 1990-06-29 AU AU57956/90A patent/AU622334B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| AU593252B2 (en) | 1990-02-08 |
| AU5791286A (en) | 1986-12-11 |
| AU622334B2 (en) | 1992-04-02 |
| AU5795690A (en) | 1991-04-18 |
| JPH0649338B2 (en) | 1994-06-29 |
| JPS61279533A (en) | 1986-12-10 |
| NZ215714A (en) | 1988-08-30 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |