Container

Aug. 13, 1963

R. MCFEDRIES, JR

CONTAINER

Filed Jan. 30, 1967

3,396,901

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INVENTOR.

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AGENT

United States Patent Office 3,396,901 ________________ __________ Patented Aug. 13, 1968 olefin resin selected from the group consisting of ethylene polymers, propylene polymers and resinous copolymers of ethylene and propylene, the second or outer faces of the panels comprising a synthetic resinous material having a slip angle of at least 50°, the slip angle being determined by stretching a sheet of material to be evaluated on a flat surface, securing the material to the surface, overwrapping a block weighing one pound and having a rectangular face, measuring 2x2 inches with another portion of material to be tested, placing the covered 2x2 inch surface of the block in engagement with a portion of the film secured to the flat surface, subsequently raismg one end of the flat surface to cause the surface of the block to assume an increase in angle with respect to the horizontal and determining the angle of the flat surface to the horizontal at the time when the block commences to slide or move.

. Beneficially, bags in accordance with the present invention are prepared from multilayer sheet or film which comprises a first or inner layer of a polyolefin adhered directly or indirectly to the material having a slip angle of at least 50°. Such multi-layer film may be prepared by methods well known in the art, including hot lamination, extrusion lamination, simultaneous extrusion such as is ®^et f°^rth in Britist Patent 985,310 and Italian Patent 522,838. Advantageously, film having only two layers is beneficially used unless exceptional physical properties are desired wherein a high strength component may be disposed between the inner and outer surfaces. Such a high strength component may be biaxially oriented polypropylene of a non-fibrous nature, fabric, natural or synthetic, woven or non-woven, depending on the desired characteristics of the finished product. Materials which are eminently suited for the outer surface of such bags or 35 bodies are polyethylene, chlorinated polyethylene, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene acrylic acid copolymers including graft polymers, certain plasticized polyvinyl chlorides, as ^{as man}Y other extrudable synthetic resinous composi40 tions. .When polyethylene is employed for the outer surface, it must be without the slip additives which are customarily added to polyethylene formulations sold for extrusion into filament.

Particularly advantageous and beneficial for the preparation of such films as are used in the preparation of bags m accordance with the present invention is polymeric material obtained by chlorination of essentially linear finely divided polyethylene or interpolymers containing at least about 90 mole percent of ethylene in the polymer molecule, which polymers have a molecular weight of less than about 1,000,000 and preferably between about 20,000 and 300,000.

More specifically, the preferred chlorinated olefin polymers utilized contain from about 25 and 50, and preferably between about 30 and 40 weight percent of chemically combined chlorine. Particularly preferred chlorinated olefin polymers are those prepared by chlorination in aqueous suspension, which are further characterized by having a relative crystallinity of between about 15 and 28 percent when containing about 25 weight percent chlorine, and a relative crystallinity of less than about 10 percent when containing about 34 weight percent of chemically combined chlorine. Such preferred chlorinated poly^aJ^{e r},^eadily obtained by practice of a chlorination in an inert medium of finely divided polymers and interpolymers of ethylene to a desired total of combined chlorine content, wherein such polyolefin is first chlorinated at a temperature of up to about 110° C„ and preferably ₇₀ between about 65° C. and 110° C., for a period sufficient to provide a chlorine content of not more than about 23 weight percent chlorine, based on the total weight of

3,396,901 CONTAINER Robert McFedrles, Jr., Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich. Continuation-in-part of application Ser. No. 575,138, Aug. 25, 1966. This application Jan. 30, 1967, Ser. No. 629,042

Claims. (CI. 229—55)

ABSTRACT OF THE DISCLOSURE

Plastic bags are prepared from two layer plastic film employing as an outer layer on the bags a material having a high coefficient of friction, such as chlorinated polyethylene.

This application is a continuation-in-part of my copending patent U.S. application Ser. No. 575,138, filed Aug. 25, 1966, now abandoned.

This invention relates to an improved container, and more particularly relates to an improved plastic container of a bag-like configuration which is suitable to receive various bulk products.

Many products, particularly those of a granular and powdery nature, are advantageously shipped in bags, for example, synthetic resins both in pellet and powder form, flour, sugar, talc, fertilizer and the like. Usually, such bags contain from 50—100 pounds of packaged material. Considerable difficulty has been encountered in many instances wherein bags must be stacked one upon the other wherein the bags have been prepared from a synthetic resinous composition. Various multi-wall paper structures having a creped outer finish provide an adequate coefficient of friction to permit stacking of bags one on top of another on a pallet and subsequent handling of such a stacked pallet by means of a fork truck or crane or like loading device. However, employing the advantageous embodiment of a plastic or synthetic resinous bag, oftentimes the coefficient of friction of the material from which the bag is prepared is insufficient to permit advantageous stacking and shipping without undesired motion of the stacked bags relative to one another. Attempts to employ polyolefins as sand bags for the construction of dikes, levies, embankments and the like have met with limited success, as when bags are perforated, the sand is 45 lost and the empty bag is free to float on the water. Oftentimes, such floating causes difficulty with water intake pumps on ships and shore installations utilizing water containing such floating bags.

It is an object of the present invention to provide an 50 improved flexible container.

A further object of the present invention is to provide an improved plastic bag suitable for bulk shipment.

A further object of the invention is to provide a plastic bag having strong puncture resistance, tear resistance and 55 exposed surfaces having a coefficient of friction suitable to permit convenient stacking and handling.

Another object of the present invention is to provide a strong, puncture resistant, air tight plastic bag having a surface of a high coefficient of friction which is particu- 60 larly suited for use as a sand bag for water control purposes.

These benefits and other advantages in accordance with the present invention are achieved in a synthetic resinous , .,- - --------- — package, the synthetic resinous package comprising at ⁰⁵ P^rocedure which comprehends the suspension chlorination least a first panel and a second panel, the first and second ^f ’ panels being disposed in facing relationship, the first and second panels being joined in regions adjacent at least about three edge portions, the first and second panels defining inner faces and outer faces, the inner faces of the first and second panels comprising a non-blocking poly3,396,901 the polymer; followed by the sequential suspension chlorination of such polymer, in a substantially non-crystalline, particulate form, at a temperature above that employed for the herein described first chlorination and not more than about 150° C., for a period sufficient to provide a combined chlorine content of between about .25 and 50 weight percent, based on the total weight of the polymer.

Preferably, the polyolefinic materials to be chlorinated are those distinct species and varieties of essentially linear and unbranched, highly porous, finely divided polymers containing at least about 90 mol percent ethylene in the polymer molecule with any remainder being one or more ethylenically unsaturated comonomers. Exemplary of such comonomers are the non-aromatic hydrocarbon olefins having 3 or more carbon atoms such as propylene, butene-1 and butene-2, and 1,7-octadiene and the like, cyclooctadiene and the like; substituted olefins such as acrylic acid and its esters; conjugated diolefins such as butadiene and the like; and the alkenyl· aromatic compounds such as styrene and its derviatives, among many other polymerizable materials known to the art.

Advantageously, the polymers and interpolymers described herein are prepared under the influence of catalyst systems comprising admixtures of strong reducing agents such as triethyl aluminum and compounds of groups IV-B, V-B and VI-B metals of the Periodic System, such as titanium tetrachloride, and; the like, and are characterized by having molecular weights below about 1,000,000 and preferably from about 20,000 to 300,000. It is to be pointed out, however, that conventionally prepared, low density branched polyolefins may also be advantageously chlorinated by the process of the present invention, providing such materials are available in finely comminuted form.

It is further to be pointed out that other ingredients such as pigments, stabilizers, lubricants and the like may be incorporated in the chlorinated olefin polymers, if desired.

Exemplary of particularly useful stabilizers are those materials conventionally employed in the preparation of vinyl polymer and copolymer film compositions, e.g., organic complexes and/or salts of lead, barium, cadmium, zinc, sodium, etc., and particularly the sulfur containing organo tin compounds including the alkyl tin mercaptides as well as dibutyl tin maleate among others.

Further features and advantages of the present invention will become more apparent from the following specification when taken in connection with the drawing wherein:

FIGURE 1 schematically depicts a bag or container in accordance with the invention,

FIGURE 2 is an enlarged sectional view of a laminate suitable for the wall of the bag of FIGURE 1,.

In FIGURE 1 there is depicted a bag generally desig- ₅₅nated by the reference numeral 10. The bag 10 comprises a first panel 11. The first panel 11 has a first or outer face 12 and a second or inner face 13, The panel 11 has first, second, third and fourth edges 14, 15, 16 and 17, respectively. A similar panel 18 is disposed in facing relation- go ship to the first panel 11. The second panel 18 has an internal surface 19 and an external surface 20. The panel 18 has first, second, third and fourth edge portions 21, 22, 23 and 24, respectively. The first, second, third and fourth edge portions of the panel 11 are sealed to the gg first, second, third and fourth edge portions of the second panel 18 to form the bag 10 having a granular material 25 disposed therein.

In FIGURE 2 there is depicted an enlarged cross-sectional view of a laminate for a bag such as the bag 10, 70 the laminate being generally designated by the reference numeral 30. The laminate 30 comprises an outer layer 31 composed of a material having a slip angle of 50° or more, the inner layer 32 composed of a non-blocking polyolefin resin, the inner layer 32 defining an inner sur- 75 face 33, a reinforcing layer 34 firmly adhering the inner and outer layers 31 and 32, respectively, together.

The invention is further illustrated but not limited by the following examples:

Example 1

A sheet is prepared employing apparatus generally similar to that depicted in British Patent 985,310, providing a two layer sheet having a thickness of 10 mils having a first or outer layer of chlorinated polyethylene, the chlorinated polyethylene containing 30 weight percent chlorine. The thickness of the chlorinated polyethylene layer is three mils. The sheet also has a second or inner layer of low density polyethylene having a melt index of 0.45 and a density of 0.916 and having a thickness of about 7 mils. Portions of the sheet are folded to form bags generally as depicted in FIGURE 1 wherein the polyethylene layer forms the inner surface of the bag and the chlorinated polyethylene layer forms the outer surface of the bag. The edges are heat sealed to form a bag with an open mouth. To each of the bags is added 50 pounds of pelletized calcium chloride and the mouth of the bag closed by heat sealing. The bags are stacked one upon the other on a pallet and transported by a fork truck over a rough surface. Little or no tendency is observed for the bags to slide relative to one another.

Example 2

A three layer sheet is formed having a first or outer layer of chlorinated polyethylene containing 30 weight percent chlorine and having a thickness of 2.5 mils. An inner or second surface layer of low density polyethylene has a melt index of 0.45 and a density of 0.916. The center layer has a thickness of 5 mils. The center layer is formed of high density polyethylene having a melt index of 0.85 and a density of 0.964 and the sheet having a total thickness of about 10 mils. A plurality of bags are formed employing the procedure of Example 1. The bags are filled with 100 pounds of pelletized fertilizer, 40 stacked one on top of the other on a pallet and the bags and pallet transported by a fork truck over rough ground. No tendency was observed for the bags to slide relative to one another.

Example 3

In a manner similar to Example 1, a plurality of bags are fabricated from a composite sheet consisting of a first or outer layer of ethylene vinyl acetate copolymer containing 4 weight percent vinyl acetate polymerized therein and having a melt index of 2 and a density of 0.925. The thickness of the ethylene vinyl acetate layer is 3 mils. An inner or second layer of lower density polyethylene having a melt index of 0.45 and a density of 0.916 has a thickness of 7 mils. The bags are each filled with 98 pounds of portland cement, stacked one on top of the other on a pallet, transported by a fork truck over rough ground. No tendency is observed for the bags to shift relative to one another. The pallet containing the bags is placed within a box car and shipped for about 760 miles by rail. On opening the box car at the end of the journey, the bags are still stacked one on top of the other.

Example 4

A plurality of bags are fabricated generally in accordance with Example 1, the bags having an outer layer of chlorinated polyethylene 3 mils in thickness. The chlorinated polyethylene contains about 30 weight percent chlorine. The film forming the walls of the bag has a center layer of a copolymer of ethylene containing 8 weight percent acrylic acid polymerized therein having a thickness of about 3 mils and a 4 mil thick inner layer of high density polyethylene having a melt index of 0.85 and a density of 0.964. Each of the bags is filled with 100 pounds of granulated white sugar and sealed. The resultant bags are stacked one on top of the other on a pallet, the pallet transferred to a truck, the truck driven

3,396,901 a distance of 432 miles. On inspection of the truck after the journey, no shifting of the bags relative to one another is observed.

Example 5

A plurality of bags are fabricated from a 2 layer sheet ⁵having a thickness of 10 mils. The outer layer of the bags is chlorinated polyethylene containing about 36 weight percent chlorine and has a thickness of about 3 mils. The inner layer has a thickness of about 7 mils and is low density polyethylene having a melt index of 0.45 and a 10 density of 0.916. The bags are filled with 87 pounds of prilled ammonium nitrate, stacked one upon the other upon a pallet, the pallet and bags subsequently transported by a fork truck over rough ground. No tendency is observed for the bags to slide relative to one another. ¹⁵

Example 6

A plurality of multilayer film bags are fabricated from a two layer film prepared from polyethylene having a density of 0.916 and a chlorinated polyethylene having a ²⁰density of 1.15. The relative proportion of polyethylene to chlorinated polyethylene is 63 to 37 by volume. The resultant film has a density of 1.002 grams per cubic centimeter and does not float in fresh water. The bags prepared have a volume sufficient to contain about 80 ²⁵pounds of dry sand, and the chlorinated polyethylene layer forms the outer surface. A plurality of the bags are filled with about 80 pounds of dry sand and employed as a facing on an embankment adjacent a dock on a fresh water lake. Continued wave action does not dislodge or ³⁰cause shifting of one bag relative to the other. A temporary dam about 5 feet high and 20 feet in length is prepared employing similar sand-filled bags and is found eminently satisfactory. On perforation and removal of the sand from the bags, the bags sink in fresh water. ³⁵

Example 7

A tube having a diameter of about 12 inches is prepared having three layers, an outer layer of a copolymer of about 80 weight percent ethylene and 20 weight per- ⁴⁰cent vinyl acetate having a density of 0.943 and a melt index of about 2. The inner layer of the tube is polyethylene having a density of 0.925 and a melt index of 0.45. An intermediate layer of chlorinated polyethylene having a density of 1.15 and containing 36 weight per- ⁴⁵cent chlorine is disposed between the polyethylene layer and the ethylene vinyl acetate layer adhered thereto. The proportions of volume of polyethylene to chlorinated polyethylene to ethylene vinyl acetate are 60:30:10, re- _rspectively The tube is formed into a rectangular configuration and the end of the tube folded upon itself to form a bag having a rectangular bottom, the tube flattened and subsequently heat sealed to form a rectangular bottomed bag. As the heat sealing _r_ temperature of the ethylene vinyl acetate copolymer is ^J0about 100° below that of the polyethylene, heat sealing does not require the use of an internal mandrel within the bag and permits sealing in a flattened condition.

Bags prepared in the foregoing manner are eminently suitable for the purposes hereinbefore set forth. ^bu

In each of the foregoing examples, the outer layer of the bag had a slip angle of at least 50°. By way of comparison, bags fabricated of high density polyethylene having a slip angle of about 20° showed a marked tendency to shift relative to one another when treated in a com- ^bsparable manner.

various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. For this reason, it is to be fully understood that all of the foregoing is intended to be merely illustrative and is not to be construed or interpreted as being restrictive or otherwise limiting of the present invention, excepting as it is set forth and defined in the hereto-appended claims.