CA2053051A1

CA2053051A1 - Highly butadiene modified styrene bag

Info

Publication number: CA2053051A1
Application number: CA 2053051
Authority: CA
Inventors: Richard E. Sullivan; John E. Benson (Deceased)
Original assignee: AVP EXTRUSIONS Ltd; Bonar Inc Canada
Current assignee: AVP EXTRUSIONS Ltd; Bonar Inc Canada
Priority date: 1991-10-09
Filing date: 1991-10-09
Publication date: 1993-04-10

Abstract

ABSTRACT

A highly butadiene modified styrene (HBMS) material is made from a compounded blend of high impact polystyrene and styrene butadiene block copolymer with the cumulative polybutadiene rubber content in the compound ranging from about 15% to about 50% by weight. The HBMS material can be extruded into sheet or tubular film from which shipping bags, sacks or other containers can be made. Such containers are easily recyclable and have important advantages in the chemical, rubber, tire and plastics industries. The containers can be used in batch inclusion processes or they can be recycled in-house for use in end products. Problems of disposal are avoided by using containers of the new material.

Description

The present invention relates to polystyrene bags and to polystyrene films used in the production of such bags. In particular the invention relates to such films and bags that are recyclable and readily dispersible in batch applications.

BACKGROUND OF T~IE INVENTION
Heavy duty plastic shipping sacks are will known, particularly in the plastics industry itself, for the shipping and storage of resins ànd other materials.
Typically, such bags or sacks have been made from polyethylene (low density, linear low density, ultra low density, high density or blends thereoi), ethylene copolymer or polypropylene. Such materials have previously been recyclable only with considerable effort and expense and the tendency has been to throw such bags away rather than to attempt recycling. Needless to say, millions of such bags are produced and discarded each year, contributing to environmental prob]ems and increasing the cost of new product.

SUMMARY OF THE INV~ENTION
The present invention addresses the problems associated with prior art plastic shipping sacks, the result being a bag made ~rom material that is recyclable and readily dispersible in batch applications. The material can be extruded in sheet film or tubing configurations and formed into open mouth bottom seal or side weld ICI~l:jrC

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or side seal block bottom (square satchel type) bags, closed valved bags, or closed bags each having a filling sleeve incorporated therein.
The new material of the present invention may be briefly defined as "highly butadiene modified styrene", hereinafter "HBMS". Film made from HBMS
can be extruded to a thickness of 3 to 10 mil (7S-275 microns) on either a flat die or blown film extruder, in a conventional manner, so as to produce tubing or sheet film for bag production.
The HBMS of the present invention will typically involve a compounded blend with from about 15% to about 50% cumulative polybutadiene rubber content in the compound, the remainder being polystyrene. The resins usedin the compound include high impact polystyrene (a copolymer of about 95%
polystyrene and about 5% butadiene) and styrene butadiene block copolymer (a copolymer of about 60% styrene and about 40% butadiene rubber). General commercial colourants can be added, for example titanium dioxide (TIO2) can be added if the resulting material is to be opaque.
The HBMS material of this invention has a low softening point, in the region of 60C to 94C which makes it ideal for use as a batch inclusion package or it can be recycled in-house using grinders. The material also has value to compounders who will likely use it in the production of durable goods.
Broadly speaking therefore the present invention may be considered as providing a highly butadiene modified styrene resin for the manufacture of recyclable films comprising a compounded blend of high impact polystyrene and styrene butadiene block copolymer, the cumulative polybutadiene rubber content of the compounded blend being in the range of about 15% to about 50% by weight and the remainder being polystyrene.

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The present invention also encompasses bags and other containers made from the recyclable material of the present invention.

BRIEF DESCRIPTION OF T~IE DRAVVINGS
Figures 1 and 2 show perspective views of two typical shipping sacks 5 or bags that can be manufactured from the material of this invention.
Figures 3 and 4 illustrate schematically different recycle processes in which the material, and the products thereof, of this invention play a part.

DESCRIPTION OF T~E PREFERRED EMBODIMENT
Figure 1 shows an open mouth block bottom bag 10 made from the 10 material of this invention. The bag is made from a tube (seamless) or from a sheet film (seamed) of the HBMS material, the film thickness being in the order of 3 to 10 mil (75-275 microns). The bag 10 has side and end walls 12, 14 and a square satchel type bottom 16, also known as a block bottom. The bag can be used to ship and store any product imaginable, but it is particularly suitable for shipping and 15 storing plastics material such as resins. A cap of the same material can be adhered to the open mouth to close it off, if desired. Any seams or joints can be sealed or made by using an extruded bead of high impact polystyrene, a suitable adhesive material or a hot melt adhesive. A suitable adhesive could be a combination of an aromatic polyisocyanate, specifically toluene diisocyanate based adduct, with 20 methylene chloride (and small additions of ethyl acetate) as a carrier.
Figure 2 shows a valve style bag 20 which has both ends of the bag closed off and a sleeve 22, formed as a tube, extending from the bag upper end for filling or pouring purposes. The sleeve 22 is formed from the HBMS material in Icm:jrc 3 2 Q ~
a gauge of about 1 to 7 mil (25-175 microns). The sleeve is cut to length and placed in the folded square end of the bag. It can be flush cut with the edge of the finished bag or it can extend up to about 1~ cm past the edge of the bag. The sleeve is adhered to the bag using a suitable adhesive, hot melt adhesive, or extruded polystyrene resin. As with the open mouth bag the valve style bag can be closed by affixing an end cap (not shown) to the sleeve 22.
The material used for the bags 10,20 (and any other comparable container) is unique in that it lends itself to easy, inexpensive, recycling but it does not relinquish any of its strength or other attributes. The HBMS material of this invention is particularly suitable for bags or containers used in the resin, chemical, tire and rubber industries where many products are made from compounds that involve polystyrene and butadiene.
The HBMS material of this invention is compounded from two resins, namely high impact polystyrene and styrene butadiene block copolymer. The former is a copolymer of styrene and butadiene made from about 95% polystyrene and about 5% butadiene. The latter is a copolymer of about 60% styrene and about 40% butadiene rubber. Commercial colourants can be added, for example titanium dioxide (TIO2) can be included to render the material opaque. The compounded resins are mixed so that the cumulative polybutadiene rubber content in the resulting compound ranges from about 15% to about 50% by weight, the remainder being polystyrene (and titanium dioxide, if used). The HBMS resin is compounded using standard, well-established techniques.
The HBMS material of this invention has a range of specific gravity of 0.94 to 1.04, dependent on the formulation, as tested using ASTM 792. It has a range of Vicat Softening Points of 60C to 94C as tested using ASTM D 1525. It Icm:jrc 4 2 ~ 3 ~

has a melt index range of 7-12 and FDA compliance under 21CFR-177-1640.
Typical physical data is shown below.
PhYsicnl Data Guage Range 1 to 10 mil Tensiles Yield - psi MD 1400 to 5000 Ultimate Strength - psi MD 3200 to 5500 TD 1800 to 2500 Elongation %
MD 45 to 400 TD 120 to 500 Elmendorf tear gms/mil MD 8 to 25 TD 16 to 50 Slip C.O.F. (out to out) .28 to .800 Dart Impact (small dart) gmslmil 130 to 300 The tubing or sheet film material used to make the bags or sacks is extruded from the HBMS resin also by standard, well-established, techniques which need not be described in detail. For example, with flat die extrusion processes molten HBMS is extruded through a flat die and pulled down over cooling rollers to produce an unioriented uniform gauge film. In the blown film process a tube of the HBMS material is extruded, usually vertically, and air is admitted to the hot tube as it emerges from the extrusion die. The tube is continuously inflated by the Icm:jrc S

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internal air pressure, then it is cooled, collapsed by pinch rolls and wo~lnd up on subsequent take-up rolls.
Figures 3 and 4 show schematically how bags made from the HBMS
material of this invention can be recycled and used to the benefit of a particular 5 industry.
In Figure 3 resins R are packaged for shipping and storing in bags B
made from the HBMS material of this invention. Then, when the resins are to be compounded and used, as for making tires, rubber belts, etcetera, the entire bag, filled with resin, is added to the batch K. The low softening point (60C to 94C) 10 of the HBMS material makes it ideal for such batch inclusion processes. The butadiene content makes the material more compatible with the batch compounds than polyethylene for many applications. There is no possibility of fiber contamination as with conventional multiwall paper bags (which are not added to the batch) and, of course, disposal and labour costs are greatly reduced.
Figure 4 shows the bag B storing resin material R, which material is poured from the bag for appropriate compounding as at step C. Thereafter, the bag B can be ground up at grinder G and compounded with the appropriate resins for production of plastic articles. The HBMS bags may be used by the resin end-user or they may be shipped, when empty, to other compounders who will use them 20 in their products, or even to make new HBMS bags or containers.
Clearly, the present invention represents an advance in the packaging art since a strong useful bag, sack or other container which can be easily recycled is now available. The cost of recycling is very low and problems of disposal of empty bags have been obviated. Of course, the HBMS material of this invention 25 is not restricted to the manufacture of bags or sacks. It can be used in a myriad of Icm:jrc 6 2Q~33~ 31 packaging applications, imparting all of its benefits thereto. The scope of protection to be afforded this invention should therefore be determined from theclaims appended hereto.

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Claims

1. A highly butadiene modified styrene resin for the manufacture of recyclable films comprising a compounded blend of high impact polystyrene and styrene butadiene block copolymer, the cumulative polybutadiene rubber content of the compounded blend being in the range of about 15% to about 50% by weight and the remainder being polystyrene.

2. The resin of Claim 1 wherein said high impact polystyrene is a copolymer of about 95% polystyrene by weight and about 5% butadiene by weight.

3. The resin of Claim 2 wherein said styrene butadiene block copolymer is a copolymer of about 60% styrene by weight and about 40% butadiene rubber by weight.

4. The resin of Claim 1, 2 or 3 including general colourants to colour the films.

5. An extruded sheet film made from the resin of Claim 1, 2 or 3, said sheet film being recyclable.

6. The sheet film of Claim 5 wherein said resin includes general colourants to colour the film.

7. An extruded seamless tube film made from the resin of Claim 1, 2 or 3, said tube film being recyclable.

8. The tube film of Claim 7 wherein said resin includes general colourants to colour the film.

9. An open mouth block bottom bag made from the sheet film of Claim 5.

10. An open mouth block bottom bag made from the tube film of Claim 7.

11. A bottom seal block bottom bag made from the sheet film of Claim 5.

12. A bottom seal block bottom bag made from the tube film of Claim 7.

13. A side weld block bottom bag made from the sheet film of Claim 5.

14. A side weld block bottom bag made from the tube film of Claim 7.

15. A side seal block bottom bag made from the sheet film of Claim 5.

16. A side seal block bottom bag made from the tube film of Claim 7.

17. A block bottom valve bag made from the sheet film of Claim 5.

18. A block bottom valve bag made from the tube film of Claim 7.

19. The bag of any one of Claims 9 to 15 or 16 wherein said film has a thicknessin the range of 3 to 10 mil (75-275 microns).

20. The bag of Claim 17 or 18 wherein said film has a thickness in the range of 3 to 10 mil (75-275 microns) and there is provided a tubular sleeve giving access to the bag, said sleeve being made from the film of Claim 5 or Claim 7 having a thickness in the range of 1 to 7 mil (25-175 microns).

21. The bag of any one of Claims 9 to 17 or 18 which has been rendered opaque by the addition of titanium dioxide to the resin from which the bag-forming film has been made.

22. The film of Claim 5 or 7 having a thickness in the range of 1 to 10 mil (25-275 microns) and a softening point as low as 65°C.

23. The film of Claim 6 or 8 having a thickness in the range of 1 to 10 mil (25-275 microns) and a softening point as low as 65°C.

24. The film of Claim 4, 6 or 8 wherein the colourant is titanium dioxide, rendering the film opaque.