AU593252B2 - Protective patch for shrinkable bag - Google Patents

Description

r K -Yi-; COMMONWEALTH OF AUSTRALIA PATENT ACT 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE Class Int. Class Application Number: S11 Lodged: Complete Specification Lodged.

Accepted: Published: Priority: Related Art: t t 1 I1 4414 4t* t Ntiame of Applicant: SAddress of Applicant: 9 Actual Iwentor(s) i *.ddress for Service: W. R. GRACE CO. 1114 Avenue ot the Americas, D AT SUB-01*MC4 New York, N.Y. 10036, UNITED STATES OF AMERICA. 6 M W6 I e J3FERGUe Daniel J. FERGUSON c t 2: i 19 DAVIES COLLISON, Patent Attorneys, 1 Little Collins ;treet, Melbourne, 3000.

Complete Specification for the invention entitlek.

"PROTECTIVE PATCH FOR SHRINKABLE BAG" The following statement is a full description of this invention, including the best method of performing it known to us -1- PROTECTIVE PATCH FOR SHICNKABLE BAG FIELD OF THE INVENTION This invention relates to the packaging of bone-in cuts of weak'. In particular, this invention relates to protective patch which prevents or reduces the likelihood that a bone will completely purketure and rupture a thermoplastic vacuum bag and patch combination.

4. BACKGROUN~D OF THlE INVENTION The use of heat shrinkable thermoplastics as flexible packaging materials fo vacuum packaging various foodstuffs including meat is well-known.

Such plastic mnaterials, however, while in general quite successful, for packaging meat understandably 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 c uts of meat or close bone trim with removal of offending bones has also been attempted. However, this is at best ox,\y a limited solution to the problem since it does not offer the positive protection necessary for a wide variety of rconme'rcial bone-in types of meat. Furthermore, removal of the bong, is a relAtively expensive and time consuming procedure.

9/053085/7A/l /9 ~4~j 9 9 .9 *9 99 .9,9 9 a, 9, 9 *9.

9 9 999 9 9 *999 I~t

I

Ir 4 9 9.

a a. 0 9# 9* -2- Accordingly, it is one object of the present invention to provide a patch material and method for making the patch which will minimize and eliminate 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 wtth 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 necessity for havi.ng a separate packaging item such as a wax impregnated cloth which must be carefully positioned over the bone and provide a protective patch which will not be as sansitive to or depcndent 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 'Feadily 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 des.cription of the preferred embodiment which follow: SUTMMARY OF THE INVENTION multi-layer protective patch for a heat shrinkable thermoplastic omprising the steps of: coextruding a multi-layer thermoplas ube, the inner wall of said tube comprising a first ethyle nyl acetate copolymer and the outer wall comprising a ,be aving a major proportion of linear low density ,io miiitt a ln iycoads-hlneto~y a aepelymer,'N >2

I

4 2a- 1 The present invention provides a protective multi-layer 2 patch in combination with a biaxially heat shrinkable bag, 3 said patch comprising: 4 an outer layer comprising a blend of: 80% to 100% linear low density polyethylene: 6 20:; to 0% ethylene-vinyl acetate having a 7 vinyl acetate content in the range from 7% to 12%; 8 (II) an inner layer comprising an ethylene-vinyl 9 acetate copolymer having 20% to 35% vinyl acetate content; (III) said patch being biaxially heat shrinkable, 11 and being adhered to said bag; 12 (IV) wherein said patch will shrink with the bag, 13 thereby reducing the tendency of the patch to delaminate 14 from the bag.

16 The present invention also provides a method of making S. 17 a multi-layer protective patch for a biaxially heat 18 shrinkable bag comprising the steps of: S 19 coextruding a multi-layer, thermoplastic tube, the S 20 outer wall comprising a linear low density polyethylene 21 and the (II) inner wall of said tube comprising an ethylene- 22 vinyl acetate copolymer; 23 applying a sufficient amount of an inert dust or 24 powder to the interior tube walls so that upon collapsing, S 25 the tube will not self adhere; 94 26 collapsing the tube; S27 irradiating the collapsed tube to cross-link the 28 materials thereof; S 29 opening, inflating, heating, and stretching the tube to biaxially orient the tube material; 31 cooling, collapsing and flattening the tube 32 whereupon the tube adheres to itself; and 33 cutting the tObe into at least one patch.

34 The present invention also provides a protective 36 multi-layer patch for a biaxially heat shrinkable bag 37 comprising: S38 an outer layer comprising a blend of: 0

°I

.t 8917,cmdt.066,grace2.1,2 I 4 1 1 j ^1 -2b- 1 80% to 100% linear low density polyethylene; 2 20% to 0% ethylene-vinyl acetate having a 3 vinyl acetate content in the range from 7% to 12%; and 4 5% to 0% pigments and additives; (11) an inner layer comprising an ethylene-vinyl 6 acetate copolymer having 20% to 35% vinyl acetate content 7 and, 8 (III)said patch being biaxially heat shrinkable.

9 Preferably the patch material has been cross-linked by 11 irradiation to the equivalent of a dosage level in the range 12 between 4.5 to 13 MR.

13 14 More preferably the patch material has been crosslinked by irradiation to a dosage in the range f rom 6 to 8 16 MR.

17 18 Preferably the patch comprises four layers, the outer layers 19 comprising the material of layer and the inner layers rf r 1 0 comprising the material of layer (II) and wherein the two 21 outer layers sandwich the two inner layers.

22 23 Preferably 24 the outer layer comprises a blend of: linear low density polyethylene, and 26 ethylene-vinyl acetate copolymer.

27 4 t tt 28 Preferably C, 29 the outer layer comprises a blend of a major C 30 amount by welght of linear low density polyethylene and a

C

31 minor amount by weight of ethylene-vinyl acetate copolym~er, 32Q wherein said ethylene-vinyl acetate has a vinyl acetate 33 content in the range f rom 7% to 12% by weight; and 34 (11) the inner layer comprises an ethylene-vinyl acetate copolymer having 20% to 35% by weight vinyl acetate 36 content.

rrLM 891117,cuSdat.066.grace2.1.3 ii ~rr.rj~ 1 -2c *i 9** *c 4 :9 1 9 i I 4 4 4 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 29 31 32 33 34 36 37 38 Preferably the outer layer comprises a blend of: 80% to 100% by weight linear low density polyethylene; 20% to 0% by weight ethylene-vinyl acetate having a vinyl acetate content in the range from 7% to 12% by weight and 5% to 0% by weight pigments and additives; (II) the inner layer comprises an ethylene-vinyl acetate copolymer having 20% to 35% by weight vinyl acetate content.

Most preferably the material of layer comprises 87% by weight linear low density polyethylene blended with 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.

891117 c _dat.066,grace2.1,4 1 46

I

~xXr~- -3ppying ,,ifrit-nt nmnt mf paprp corP-t-arrh- -Gr- ta like t rhe in.prior of the tubular extrudate so that upon collapsing, the tube will not self adhere; collapsing the tube; irradiating the col psed tube to cross-link the materials thereof; opening, heating, and st etching the tube to biaxially orient the tube material; collapsing and fl tening the oriented tube whereupon the tube adheres to itself; and cutti g the tube into at least one patch.

In another aspect, the pre nt invention is a protective, multi-layer patch for a heat shrinkable vacu bag comprising: an outer layer comprising a blend of 80% to 100% linear 1 density polyethylene, 20% to 0% ethylene-vinyl acetate copolymer having a inyl acetate content in the range of 7% to 12%, and 5% to 0% pigments and dditives; an inner layer comprising an ethylene vinyl S* acetate copolymer h ing 20% to 35% vinyl acetate content; and, said patch S being biaxially at shrinkable. In a particularly preferred embodiment the patch materia as been cross-linked to the equivalent of a dosage level in the *t tc -Mf~ge b-tw a 4.5 nd 12 4 e t DESCRIPTION OF THE DRAWINGS In the drawings which are appended hereto and made a part of this S disclosure, 4 Figure 1 is a perspective view of meat enclosed in a heat shrunk bag with the patch of the present invention on the exterior thereof; Fgure 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 present invention adhered to a thermoplastic vacuum bag; O(7 J 053085/7A/3 7u r JT- f All 9#4 4p 4 4. .4* 4e 4. V 4 -4- Figure 5 is 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.

DETAILED DESCRTPTION Referring more specifically to the drawings and to Figs. 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 faci~litates 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 athered having the appearance as shown in Figure I[ and thereafter a clip 4 is applied to securely seal the bag. The bag Qin then be immersed in hot watet and shrunken tightly against the meat thus providing a meat produa:t in an evacuated atmosphere for aging and preservation.

The patch 8 shrinks with the bag thus reducing the tendency 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 re4uires careful positioning of the cloth 8 over the bone 6 and also requires care in positioning the bone within .tha bag so that the cloth8.is iot pushed out of position or dislodged.

Figure 3 shows the exposed bone portion 6 covered by bag 12 with the preferred po'dch 8 adhered to the ouLIside of the bag over the bone protcusion.

In Figure 4 patch 8 !ts 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, tt *0 4 a *e 4 9/053085/7A/4 4 1, S Slay-flat position. In many applications it is desirable to adhere a patch to both sides of a bag.

Figure 5 is a crosz-section view of Figure 4 showing patch adhered to the one -,ll 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 embodiment the composition of outer layers 14 and 18 comprises 87% by weight of linear low density polyethylene, 10% by weight of ethylene-vinyl acetate I copolymer having 9% vinyl acetate and 3% pigments and additives to aid in S extrusion. The preferred linear low density polyethylene is Dowlex 2045 from S Dow Chemical Company of Midland, Michigan and the preferred ethylene-vinyl i acetate copolymer is ELVAX 3128 from the DuPont Company of Wilmington, S Delaware. The inner layers 18 and 20 comprise ethylene-vinyl acetate copolymer having 2%Z vinyl acetate from the U.S.I. Division of National Distillers of New Yozk, N.Y. All layers have been cross-linked by irradiation to the dosage level which is equivalent to 7 MR.

In f-,e test bags were made with a 17.5 inches wide and 18 inchbL long patch of the protective material of the present invettion on one side and a 17.5 inch wide and 10 inch long patch on the other. The-lay flat dimensions of Sthese bags were 18 inches wide by 30 inches long. In a larger bag (22" x 34") S for blades a patch of 21.5 inches by 24 inches on one side and a pa\tch 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 products ranged from rib ends to blades and arms. Of the total of 1173 packages which used cloth to cover the protruding bones there were a total of 55 bone punctures whereas in 2097 packages using 9/053085/7A/5 0CD -6the patches of the present invention as described there were ony 18 bone punctures.

The embodiment as described above is a preferred one but a satisfactory pouch can be made where the inner and outer layers 14 and 16 p comprise 15% ethylene-vinyl acetate copolymer having 9% vinyl acetate and 83.3% linear low density polyethylene with the balance zf 1.7% being a pigment. In addition, satisfactory pouches can be made with the outer layers comprising a I 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% S* S S' ethylene-vinyl acetate copolymer with the vinyl aceaate content having a range t from 7% to 12% vinyl acetate. The inner layer preferably comprises an ethylenevinyl acetate copolyser having 20 to 35% vinyl acetate content.

It has been surprisingly found that the increased strength and S 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 e 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 110'0 to 125°C. These linear-low density polyethylenes are not homopolymers although they are .eferred to generally as "polyethylene". In fact, they are 4.

copolyers of ethylene and an alpha-olefin having a carbon number lfs than 18, SI for instance, butene-1, pentene-1, hexene-1, octene-1, 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-1. 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 Patent No. 4,456,646 which it 9/0530857A/6 A 7 issued on June 26, 1984 to Nishimoto et al; United States Patent No. 4,399,180 I which issued on August 16, 1983 to William V. 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 Lie process shown in United States Patent No. 3,741,253 which issued on June 26, 1973 to Harri J. Brax et al. The method of the Brax et al patent is incorporated here in by reference S and provides background for the description which follows for the method of making the patch of the present invention.

S* To make the patch of the present invention, a first ethylene-vinyl 4, acetate copolymer having a vinyl-acetate content of approximately 28% by weight is sent to a first extruder. This material forms layers 18 and 20. (Fig. 6).

41 t Also, a: blend having a major proportion of linear low density polyethylene and a minor proportion of a second ethylene-vinyl acetate copolymer, one having 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 Scopolymer and an outer wall of the blend. This type of coextrusion essentially g 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 Spinch 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 cornstarch, in a surface concentration sufficient to prevent self-~dherence. This flattened tubing is then fed through an irradiation vault where it will preferably receive a dosage of approximately 7 9/053085/7A/7

I,

-8- 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 quite satisfactory results are obtained through use of irradiation cross-linking and 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 4 4 Sorients the tube material. After the material has been stretched to the desired diameter and wall thickness, it is then rapidly cooled and collapsed." a* S 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 te stretching decreases the concentration of the cornstarch on the inner surface S of the bubble or stretched tubing. This concen.ration of the cornstarch now is loi enough to permit self-adherence. The vinyl acetate content of the inner a 4 a wall is approximately 28% by veighti This is an ethyln,:-vinyl acetate copolymer in the range where the ethylne-vinyl acetate copolymer acts a an adhesive. Thus, a multi-layer tubular material is produced, in this instance, c. 4 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.protective material, which will greatly diminish the occurrence of bone punctures.

Many suitable adhesives to adhere the patch to the bag 4ar avaiiL, 4 and can readily be selected by those $killed in the art, the t delaminate having beren greatly reduced as the patch shrinks blai the. bag.

Having thus described my invention, 9/053085/7A/8 j~t'

Claims (3)

19. The patch of any one of claims 16-18, wherein the patch 21 comprises four layers, the outer layers comprising the 22 material of layer and the inner layers comprising the 23 material of layer (II) and wherein the two outer layers 24 sandwich the two inner layers. 26 20. The patch of any one of claims 16-19, wherein the 27 material of layer comprises 87% linear low density 28 polyethylene blended with 10% ethylene-vinyl acetate 29 copolymer having 9% vinyl acetate content and 3% pigments 30 and additives, and layer (II) comprises ethylene-vinyl 31 acetate copolymer having 28% vinyl acetate. S 32 33 21. A protective multi-layer patch in combination with a 34 biaxially heat shrinkable bag substantially as hereinbefore described with reference to any one of Figs. 1, 3, 4, 5 or 6 36 of the accompanying drawings. 37 38 22. A method of making a multi-layer protective patch for a 8 911170cdat066,aroce21.2 i 1, I -13 biaxially heat shrinkable bag substantially as hereinbefore described with reference to any one of Figs. 1, 3, 4, 5 or 6 of the accompanying drawings.

23. A protective multi-layer patch for a biaxially heat shrinkable bag substpntially as hereinbefore described with reference to any one of Figs. 1, 3, 4, 5 or 6 of the accompanying drawings. 99 9 0* 49 g 9.49 94 4. 4 *0 ~9 9 409 @9 9 9 9 4 49 99 4 .4 9. 9 9 .9 9 4 9*~.e9 9 9 S. IA 9 .9. 9 3S @499 4 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 29 31 32 33 34 3 36 37 38 DATED THIS 17th November, 1989 DAVIES COLLISON Fellows Institute of Patent Attorneys of Australia. Patent Attorn-eys for the Applicant W.R.GRACE CO. -,CON'N

891117.c_sdat.O66,qrs~Z.1,13 7'