GB1575846A - Polyolefin packaging films - Google Patents

Polyolefin packaging films Download PDF

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Publication number
GB1575846A
GB1575846A GB1498177A GB1498177A GB1575846A GB 1575846 A GB1575846 A GB 1575846A GB 1498177 A GB1498177 A GB 1498177A GB 1498177 A GB1498177 A GB 1498177A GB 1575846 A GB1575846 A GB 1575846A
Authority
GB
United Kingdom
Prior art keywords
styrene
block copolymer
weight
packaging film
vinyl acetate
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
Application number
GB1498177A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
British Cellophane Ltd
Original Assignee
British Cellophane Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by British Cellophane Ltd filed Critical British Cellophane Ltd
Priority to GB1498177A priority Critical patent/GB1575846A/en
Priority to FR7810591A priority patent/FR2387169A1/en
Publication of GB1575846A publication Critical patent/GB1575846A/en
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
    • B65D65/38—Packaging materials of special type or form
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C08L23/08—Copolymers of ethene
    • C08L23/0846—Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
    • C08L23/0853—Vinylacetate
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
    • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes

Description

(54) POLYOLEFIN PACKAGING FILMS (71) We, BRITISH CELLOPHANE LIMITED, a British Company of Bath Road, Bridgwater, Somerset do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to polyolefin packaging films and in particular to films of ethylene/vinyl acetate copolymers having improved durability at low temperatures.
In the packaging of deep frozen foodstuffs, such as peas, brussel sprouts and similar loose products into bags, it is essential that the bags are capable of being handled at temperatures ranging from ambient to about -400C without risk of splitting or bursting. Bags manufactured from low density polyethylene are particularly susceptible to such splitting at sub-zero freezing temperatures. It is known that the addition of rubbery block copolymers of styrene and butadiene to the low density polyethylene reduces the tendency for splitting to occur at low temperatures, as indicated by impact strength measurements made on the film forming the bags, but below about -20 C the impact strength of the film falls below the level which is desirable.
It has now been found that films of ethylene/vinyl acetate copolymer with low vinyl acetate content blended with minor quantities of rubbery block copolymers have improved impact strength at temperatures below -20"C.
According to the present invention, a packaging film comprises an ethylene/vinyl acetate copolymer in which the vinyl acetate content lies in the range between 3 /O and 7% by weight blended with between 4% and 15% by weight of the blend of a styrene/diene rubber/styrene block copolymer having a minor proportion of styrene.
When the vinyl acetate content of the ethylene/vinyl acetate copolymer exceeds about 7% by weight, the film tends to become too "rubbery" for practical packaging purposes. Further when the vinyl acetate content is lower than about 3% the impact strength of the film tends to fall below a desirable value at temperatures below about -20"C.
In a preferred form of the invention, the vinyl acetate content of the ethylene/vinyl acetate copolymer is in the range between 5% and 6% by weight.
Preferably the styrene/diene rubber/styrene block copolymer is present in the range between 5% and 10% by weight of the blend.
The styrene/diene rubber/styrene block copolymer may be a styrene/butadiene/styrene or styrene/isoprene/styrene block copolymer such as is marketed by Shell Chemicals U.K. Limited of London, England under the trade mark "Cariflex".
The invention also includes a packaging film in accordance with the invention when formed into a bag and when the bag formed from the film contains frozen foodstuffs.
The invention further includes a method of manufacturing. a packaging film comprising blending an ethylene/vinyl acetate copolymer in which the vinyl acetate content lies in the range between 3% and 7% weight with between 4% and 15% by weight of the blend of a styrene/diene rubber/styrene block copolymer having a minor proportion of styrene and extruding the blend to form a film.
The invention will now be more specifically illustrated by the following example: EXAMPLE An ethylene/vinyl acetate copolymer in which the vinyl acetate content was 4% by weight was blended with a styrene/butadiene/styrene block copolymer having a minor proportion of styrene (marketed by Shell Chemicals U.K. Limited as "Cariflex" TR-l 102) in quantities ranging from 0% to 10% by weight of the blend and was then extruded through an annular die to form a tubular film by the conventional so-called "bubble" method.
The thickness of the various films obtained were about 65 microns.
Samples of the films were taken and the impact strength determined by the method described in British Standard No. 2782 Method 306F at a temperature of 21"C and at -250C.
The impact strength was determined in the number of grams weight of the falling dart capable of rupturing 50% of the specimens of the particular sample under test and was a measure of the likelihood of the film, when in bag form, bursting under stress.
The results obtained were as follows:- % by Weight Impact Impact Bag Bursting of Block Strengh Strength Resistance Copolymer at 21"C at -25 C Properties in Blend (grams) (grams) at -25"C 0 315 155 POOR 2 348 200 POOR 4 380 237 FAIR 5 395 260 GOOD 6 412 280 GOOD 8 440 320 GOOD 10 475 360 GOOD For films to be used in the manufacture of bags from ddep frozen foodstuffs a minimum impact strength of about 240 grams at -250C is required to secure the desired bag bursting resistance.
WHAT WE CLAIM IS: 1. A packaging film comprising an ethylene/vinyl acetate copolymer in which the vinyl acetate content lies in the range between 3% and 7% by weight blended with between 4% and 15% by weight of the blend of a styrene/diene rubber/styrene block copolymer having a minor proportion of styrene.
2. A packaging film as claimed in claim 1 in which the vinyl acetate content of the ethylene/vinyl acetate copolymer lies in the range between 5% and 6% by weight.
3. A packaging film as claimed in claim 1 or claim 2 in which the styrene/diene rubber/styrene block copolymer is present in the range between 5% and 10% by weight.
4. A packaging film as claimed in claim 1, claim 2 or claim 3 in which the styrene/diene rubber/styrene block copolymer is a styrene/butadiene/styrene block copolymer.
5. A packaging film as claimed in claim 1, claim 2 or claim 3 in which the styrene/diene rubber/styrene block copolymer is a styrene/isoprene/styrene block copolymer.
6. A packaging film as claimed in claim 1 substantially as described.
7. A packaging film as claimed in any one of the claims 1 to 6 when formed into a bag.
8. A packaging film as claimed in claim 7 when the bag contains frozen foodstuffs.
9. A method of manufacturing a packaging film comprising blending as ethylene/vinyl acetate copolymer in which the vinyl acetate content lies in the range between 3% and 7% by weight with between 4% and 15% by weight of the blend of a styrene/diene rubber/styrene block copolymer having a minor proportion of styrene and extruding the blend to form a film.
10. A method as claimed in claim 9 in which the styrene/diene rubber/styrene block copolymer is a styrene/butadiene/styrene block copolymer.
11. A method as claimed in claim 9 substantially as described.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

  1. **WARNING** start of CLMS field may overlap end of DESC **.
    conventional so-called "bubble" method.
    The thickness of the various films obtained were about 65 microns.
    Samples of the films were taken and the impact strength determined by the method described in British Standard No. 2782 Method 306F at a temperature of 21"C and at -250C.
    The impact strength was determined in the number of grams weight of the falling dart capable of rupturing 50% of the specimens of the particular sample under test and was a measure of the likelihood of the film, when in bag form, bursting under stress.
    The results obtained were as follows:- % by Weight Impact Impact Bag Bursting of Block Strengh Strength Resistance Copolymer at 21"C at -25 C Properties in Blend (grams) (grams) at -25"C 0 315 155 POOR
    2 348 200 POOR
    4 380 237 FAIR
    5 395 260 GOOD
    6 412 280 GOOD
    8 440 320 GOOD
    10 475 360 GOOD For films to be used in the manufacture of bags from ddep frozen foodstuffs a minimum impact strength of about 240 grams at -250C is required to secure the desired bag bursting resistance.
    WHAT WE CLAIM IS: 1. A packaging film comprising an ethylene/vinyl acetate copolymer in which the vinyl acetate content lies in the range between 3% and 7% by weight blended with between 4% and 15% by weight of the blend of a styrene/diene rubber/styrene block copolymer having a minor proportion of styrene.
  2. 2. A packaging film as claimed in claim 1 in which the vinyl acetate content of the ethylene/vinyl acetate copolymer lies in the range between 5% and 6% by weight.
  3. 3. A packaging film as claimed in claim 1 or claim 2 in which the styrene/diene rubber/styrene block copolymer is present in the range between 5% and 10% by weight.
  4. 4. A packaging film as claimed in claim 1, claim 2 or claim 3 in which the styrene/diene rubber/styrene block copolymer is a styrene/butadiene/styrene block copolymer.
  5. 5. A packaging film as claimed in claim 1, claim 2 or claim 3 in which the styrene/diene rubber/styrene block copolymer is a styrene/isoprene/styrene block copolymer.
  6. 6. A packaging film as claimed in claim 1 substantially as described.
  7. 7. A packaging film as claimed in any one of the claims 1 to 6 when formed into a bag.
  8. 8. A packaging film as claimed in claim 7 when the bag contains frozen foodstuffs.
  9. 9. A method of manufacturing a packaging film comprising blending as ethylene/vinyl acetate copolymer in which the vinyl acetate content lies in the range between 3% and 7% by weight with between 4% and 15% by weight of the blend of a styrene/diene rubber/styrene block copolymer having a minor proportion of styrene and extruding the blend to form a film.
  10. 10. A method as claimed in claim 9 in which the styrene/diene rubber/styrene block copolymer is a styrene/butadiene/styrene block copolymer.
  11. 11. A method as claimed in claim 9 substantially as described.
GB1498177A 1977-04-12 1977-04-12 Polyolefin packaging films Expired GB1575846A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB1498177A GB1575846A (en) 1977-04-12 1977-04-12 Polyolefin packaging films
FR7810591A FR2387169A1 (en) 1977-04-12 1978-04-11 POLYOLEFIN PACKAGING FILMS

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1498177A GB1575846A (en) 1977-04-12 1977-04-12 Polyolefin packaging films

Publications (1)

Publication Number Publication Date
GB1575846A true GB1575846A (en) 1980-10-01

Family

ID=10050967

Family Applications (1)

Application Number Title Priority Date Filing Date
GB1498177A Expired GB1575846A (en) 1977-04-12 1977-04-12 Polyolefin packaging films

Country Status (2)

Country Link
FR (1) FR2387169A1 (en)
GB (1) GB1575846A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2139634A (en) * 1983-05-13 1984-11-14 Grace W R & Co Silent film for ostomy pouches

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5034078A (en) * 1985-05-08 1991-07-23 Exxon Chemical Patents Inc. Method of making an elastomeric film
DE4217470A1 (en) * 1992-05-27 1993-12-02 Buna Ag Thermoplastic molding compounds

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1342432A (en) * 1961-11-24 1963-11-08 Dow Chemical Co Ethylene Polymer Compositions
US3459832A (en) * 1965-09-24 1969-08-05 Monsanto Co Crystalline polystyrene having activity as a polymerization catalyst
DE2051024C3 (en) * 1970-10-17 1979-05-31 Basf Ag, 6700 Ludwigshafen Plastic film with improved transparency
FR2356694A1 (en) * 1976-07-01 1978-01-27 Siamp Cedap Reunies Extrudable polystyrene-polyolefin blend - including butadiene!-contg. block copolymer to give prod. of uniform appearance

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2139634A (en) * 1983-05-13 1984-11-14 Grace W R & Co Silent film for ostomy pouches

Also Published As

Publication number Publication date
FR2387169B1 (en) 1982-11-05
FR2387169A1 (en) 1978-11-10

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PS Patent sealed
PCNP Patent ceased through non-payment of renewal fee