US3076588A

US3076588A - Peelable gummed tape

Info

Publication number: US3076588A
Application number: US12634A
Authority: US
Inventors: William E Conway; William N Thompson
Original assignee: Nashua Corp
Current assignee: Nashua Corp
Priority date: 1960-03-03
Filing date: 1960-03-03
Publication date: 1963-02-05
Anticipated expiration: 1980-02-05

Description

Feb- &1963" w. E. CONWAY EI'AL 3,075,533

PEELABLE ammo TAPE Filed March 3, 1960 SMOOTH INTERMEDIATE SURFACED LAYER OF REMOISTENABLE BACKING ELASTOMER ADHESIVE J in "HI-"3'1.

INVENTORS WILLIAM E. CONWAY EMILIEN DIONNE WILLIAM N. THOMPSON KEHWAY, JENNEY, WITTER & HILDRETH ATTO R N EYS United States Patent Oiiice 3,076,588 Patented Feb. 1963 3,076,588 PEELABLE GUMMED TAPE William E. Conway, Emilien Dionne, and William N.

Thompson, Nashua, N.H., assignors to Nashua Corporation, Nashua, N.H., a corporation of Delaware Filed Mar. 3, 1960, Ser. No. 12,634 12 Claims. (Cl. 229-35) This invention relates to gummed tapes and to packages sealed with gummed tapes, and provides a tape having a strongly adherent remoistenable adhesive from which the tape backing may be stripped to open the package it secures.

In opening cartons sealed with gumrned tape, it has been the practice either to cut or rip either the tape or carton. This is not only time consuming, requiring a knife or similar tool, but also results frequently in damage to the t packaged goods through cutting too deeply. The savings in both labor and casualty losses afforded by avoiding these practices are substantial. Numerous proposals have been advanced in this direction, such as to provide a tear strip in the carton to permit it to be slit by pulling the strip, or to slit the carton partially to permit it to be easily ripped. These damage the cartons so that they cannot be reused and also frequently fail as when the tear strip breaks or where the carton rips along a path different from the partial slitting.

Adhesive tapes are available that may be stripped or peeled from the underlying surface. One type has a tacky pressure sensitive adhesive coating which adheres with such limited strength between the adhesive face and underlying surface that the bond may be broken by peeling. Another type utilizes a backing material of fabric which is sufiiciently strong to permit a weakly adherent adhesive seal to be broken by stripping off the tape. With either type, if the adhesive bond is strong the underlying carton material is likely to be ripped. In both of these therefore stripping without damaging the underlying carton is achieved at a sacrifice of adhesive bond strength. With pressure sensitive tacky adhesives there is moreover a tendency for the adhesive bond to give way under a prolonged tension of much less than that required to dis rupt the bond under a force rapidly applied.

This invention provides an improved peelable tape which avoids the limitations of those heretofore available. It utilizes a backing of kraft, or similar inexpensive paper, and a conventional high tenacity glue having a high bonding strength for carton material such as boxboard and the like. It accordingly serves to provide a seal of high strength, which does not give way under prolonged tension and which does not require a backing of strength sufficient to pull a weak adhesive from the carton.

The adhesive tape of this invention utilizes a kraft or similar backing having a smooth, non-porous surface, which is provided typically by applying a layer of plastic to the paper, and an intermediate layer of a non-viscous, non-tacky, solid polymeric elastomer which is of a physical and chemical nature as to adhere to the smooth surface of the paper backing with only limited strength and is more cohesive than adhesive so as to permit it to be peeled fromthe backing. The glue is applied over the layer of solid polymeric elastomer, and the latter should therefore be capable of being wetted by the glue, solution.

A tape of this type provides a durable-unyielding bond far stronger than that provided by tapes carrying adhesives which can be stripped from the carton. The bond provided by the glue will in fact generally be so strong that stripping the glue from the carton would splitthe boxboard. However by providing an intermediate release layer of a polymeric elastomer over the smooth surface of the backing, the tape backing may be stripped from the adhesive, leaving the adhesive bonded to the carton entirely intact. The over-all strength of the bond is therefore governed by the adherence of the adhesive to the backing, through the intermediate layer, and is not limited to the strength of weakly adhesive materials which characterize early types of products.

The characteristics of a typical tap'e embodying this invention may be related to the cohesive strength of typical carton stock, as to the peeling force per unit length required to split the stock and the shear force per unit area, applied over a given width, required either to break the stock or cause it to split. As a representative example, 275 pound test corrugated kraft boxboard having facings of 69 pound Fourdrinier kraft over vertical B flute corrugation has been found to split under a peeling force of about 5000 grams per 2 inches, measured by gluing a strong tape 2 inches wide against the surface of the box board, leaving one end free, then pulling the free end until the board splits and measuring the force. The force required to pull a tape in shear from the same surface, causing splitting of the boxboard is about -120 pounds per square inch, measured by applying a strong tape 2 inches wide to the edge of a piece of boxboard, with a /2 inch overlap (thus providing one square inch of adhesively bonded area), then pulling the strip in the direction normal to its width until the tape tears free, splitting the carton, and measuring the force.

In accordance with this invention a suitable tape will have strength to resist shear which is high in relation to the strength of the carton, but will have strength to resist peeling which is low in relation to the peeling force required to split the carton. Since the carton is secured only by the shear tension of the tape, the tapes of this invention provide high strength for holding the carton closed while being readily peeled free. Peelability is attained without a corresponding loss of bond strength.

The nature of this invention is described in greater are given and reference is made to the drawings in which:

FIG. 1 is a fragmentary view showing the various layers constituting the tape of this invention;

FIG. 2 shows a carton having cover flaps sealed by a tape of this invention, with part of the tape being stripped free;

FIG. 3 is a fragmentary view showing in perspective a portion of tape being stripped to illustrate schematically one form of stripping action; and

FIG. 4 is similar to FIG. 3 but illustrates schematically another form of stripping action that may be encountered.

In making a tape 2 according to this invention, an intermediate layer 10 of a solid polymeric elastomer is first applied to a backing 12 having a smooth essentially nonporous, non-fibrous surface 14, and when the intermediate layer 1-9 of elastomer is dry, a coating of glue 16 or other remoistenable adhesive material is applied to it. The backing 12 is typically a kraft paper of from 45 pounds to pounds per ream (consisting of 500 sheets, 24 inches by 3 6 inches) to which has been applied a surface coating of a synthetic organic plastic capable of imparting a hard, smooth, nonporous, non-fibrous surface 14. Numerous plastic materials have been found to be suitable for this purpose including polyethylene, a latex formed of butadiene-acrylonitrile copolymer, ethyl cellulose, a copolymer of vinyl acetate and vinyl chloride, polyvinyl acetate, to name but a few. The backing 12 may also be formed of smooth surfaced plastic-impregnated papers, such as rope paper. In general it appearsthat any flexible sheet material having a hard, smooth surface to which may be applied a distinct, yet strongly adherent, intermediate coating of a polymeric elastomer may be used. The essential requisites of the backing surface 14 are its physical characteristics, and do not depend on particular chemical properties or compositions.

3 The intermediate layer 10 may be any of numerous polymeric elastomers including natural rubber and the elastomers commonly known as synthetic rubbers, and

should be applied in a manner preserving the integrity of the backing surface 14 such that the intermediate layer 10 forms a distinct elastic ply between the backing 12 and the adhesive 16. This ply should be impervious to the adhesive to provide complete separation from the backing 12. Preferably the intermediate layer 10 is deposited from a latex so as to avoid the presence of organic solvents likcly to soften the backing surface 14 and to prevent coalescence or fusion of the intermediate layer with the backing surface. In typical embodiments the intermediate layer will be from to 20 pounds per ream (500 sheets, 24 inches by 36 inches).

in the final operation a coating 16 of bone glue is applied over the intermediate layer and permitted to harden in conventional manner. Other remoistenable adhesive materials well known to the art, such as gelatin and polyvinyl alcohol, may also be used.

Thc-adhesive tape 2 thus formed may be applied to seal boxboard cartons in the usual manner as shown in FIG. 2 and will provide a strong, durable seal characteristic of conventional gummed papers. Typically the tape 2 will join opposite box flaps 20, forming a seal between them. When the seal is to be broken, the backing 12 may be pried free to provide a grip, and then stripped from the glue by a moderate peeling force, which will typically be less than 2000 grams for a tape 2 inches wide. This it will be noted is considerably less than the force of about 5000 grams required to split ordinary boxboard. Upon peeling the tape backing 12 from the underlying surface, the intermediate layer lti of elastorner will typically peel free from both the backing 12 and the adhesive 16, and lag behind the backing as it is pulled away. The stretching of. the elastomcr that occurs appears to help cause it to release from the adhesive film which remains intact on the underlying carton.

Most ideally the intermediate layer will strip free of the adhesive 16 and accompany the backing '12 as it is peeled away, as shown schematically in FIG. 3. In some cases however the intermediate layer 10 peels partially or entirely free from the backing 12 and may remain at least partially with the adhesive layer 16 as shown schematically in FIG. 4. In either case a clean separation of the backing from the adhesive is afforded to permit the carton to be opened, and where the intermediate layer peels free of the adhesive, the carton may be reused without the trouble of removing the intermediate layer.

The following examples describe in detail various preferred and representative tapes made in accordance with this invention. In the examples all weights given refer to pounds (dry weight) per ream of 500 sheets, 24 inches by 36 inches.

Example I A backing sheet of l20-p'ound kraft paper was provided with a surface coating of 20 pounds of polyethylene (Dow Alathon 1 6) extruded as a film of molten polyethylene. After the polyethylene coating had cooled and hardened a coating of 8 pounds of natural rubber latex (General 1856B) was applied and allowed to dry. An adhesive layer consisting of 20 pounds of bone glue (Baugh 220 gm.) was then applied over the dry latex coating, permitted to harden, and the paper is then slit into two-inch widths to form tape.

The peel resistance of the tape was determined by first activating the adhesive by water and sticking the tape to a boxboard surface. After drying thoroughly the two-inch Wide sample is peeled from the surface at an angle of between 135 and 155 at a constant rate of 72 inches per minute. The force required to peel the tape is measured in grams.

The tensile strength of the tape was determined by joining two abutting pieces of carton stock with a piece of tape 2 inches wide overlapping one of the blanks by one-half inch to provide an area of adhesion of 1 square inch. The tape was applied over a much greater area to the other blank. After the adhesive joints were thoroughly dry, the assembly was pulled apart in a Scott tensile tester and the force required to cause failure was noted. Measurements were made with the pull in the direction parallel to the machine direction of the tape and also in the direction parallel to the cross direction of the tape. The following results were obtained for the tape of Example 1: Feel resistance: 1800 grams Tensile:

Machine direction84 pounds per square inch Cross direction70 pounds per square inch Variations of the composition of the tape are illustrated in the following examples, each of which was prepared by applying the intermediate to the base and permitting it to dry or otherwise harden and then applying the adhesive.

Example II Backing: 50-pound bag kraft coated with 10 pounds of a butadiene-acrylonitrile copolymer latex (Goodrich Hycar 1571) Intermediate: 8 pounds natural rubber latex (General Adhesive: 20 pounds bone glue (Baugh 220 gm.)

Peel resistance: 1000 grams Tensile:

MD57 pounds per square inch CD48 pounds per square inch Example III Backing: 120-pound kraft paper coated with 18 pounds of ethyl cellulose (Dow 50 cps. Standard Ethoxy) applied as a 20 percent solution in toluol Intermediate: 8 pounds natural rubber latex (General Adhesive: 20-pound bone glue (Baugh 220 gm.)

Peel resistance: 1600 grams Tensile:

MD65 pounds per square inch CD6O pounds per square inch Example IV Backing: l20-pound kraft paper coated with 20 pounds of a copolymer of vinyl acetate and vinyl chloride (Bakelite VYLF) applied as a 20 percent solution in toluol Intermediate: 20 pounds natural rubber latex (General Adhesive: 20-pound bone glue (Baugh 220 gm.)

Peel resistance: 600 grams Tensile:

MD-56 pounds per square inch CD50 pounds per square inch Example V Backing: l20-pound kraft paper coated with 15 pounds of polyvinyl acetate (Shawinigan Gelva V7) applied as a 20 percent solution in a solvent consisting of parts toluol to 20 parts ethyl alcohol Intermediate: 20 pounds of natural rubber latex (General 1SS6E) Adhesive: 20 pounds of bone glue (Baugh 220 gm.)

Peel resistance: 1700 grams Tensile:

MD pounds per square inch CD-63 pounds per square inch Example VI Backing: Cambric cloth (68 x 72 weave) Intermediate: 10 pounds of a mixture consisting of 90 percent by weight of natural rubber latex (General 1556B) and 10 pounds by weight of polystyrene latex (Monsanto E600) Example VII Backing: 80-pound rope paper Intermediate: 10 pounds natural rubber latex (General 1S56E) Adhesive: 20 pounds bone glue (Baugh 220 gm.)

Peel resistance: 800 grams Tensile:

MD-45 pounds per square inch CD-30 pounds per square inch Example VIII Backing: 120-pound kraft paper having a surface coating of 20 pounds of polyethylene (Dow Alathon 16) extruded as a film of molten polyethylene Intermediate: 10 pounds of 60-40 styrene-butadiene coplymer latex (Dow 513) v Adhesive: 20 pounds bone glue (Baugh 220 gm.)

Peel resistance: r 1500 grams Tensile:

MD-lOO pounds per square inch CD-63 pounds per square inch Example IX Backing: 120'pound kraft paper having a surface coating of 20 pounds of polyethylene (Dow Alathon 16) extruded as a film of molten polyethylene Intermediate: 5 pounds natural rubber latex (General Adhesive: 20 pounds corn dextrine Peel resistance: 500 grams Tensile:

(JD-48 pounds per square inch CD-38 pounds per square inch Example X Backing: 120-pound kraft paper having a surface coating of 20 pounds of polyethylene (Dow Alathon 16) extruded as a film of molten polyethylene Intermediate: 5 pounds natural rubber latex (General Adhesive: 20 pounds converted starch (Stein-Hall Tenace Peel resistance: 1500 grams Tensile:

MD50 pounds per square inch CD37 pounds per square inch Of the tapes described in the foregoing examples, those of Examples I, II, VI, VII, IX, and X peeled with separation occurring at the interface between the adhesive and the intermediate layer, with those of Examples I, II, IX, and X showing a pronounced off-setting of the intermediate layer in the manner shown in FIG. 3. The intermediate layer followed the backing but separated from it before separating from the adhesive coating, separating from the latter only after the intermediate layer was stretched. It appears that this distortion of the intermediate layer contributes to its separation from the adhesive.

In the tapes of Examples VI and VII, the intermediate layer was pulled free of the adhesive without apparent olfsetting of the intermediate occurring. With reference to Example VII, it will be noted that although the same intermediate and adhesive were used as in Example I, neither the peel resistance nor the tensile strength is as great as in Example I. The reason for this is not known but it is suggested that the less tenacious bonding of the intermediate of the base in Example I actually contributes to an over-all increased strength in the final product.

In the tapes of Examples III and IV, peeling of the tape from the surface occurred with the intermediate layer being stripped from the base, with a partial separation of the intermediate from the adhesive in the manner suggested by FIG. 4 The bulk of the intermediate layer remained with the adhesive layer.

From the examples given herein it will be noted that the tapes of this invention provide bonds of high tensile strength, in all cases greater than 30 pounds per square inch determined as described in Example I, while the peel resistance is less than 2,000 grams over 2 inch width, determined as described in Example I. They are accordingly well suited for joining boxboard panels in a manner holding the panels securely together while being peelable from them without causing damage.

The foregoing examples have been selected as being representative of the scope of this invention. Although specific compositions are described, it is believed apparent that obvious modifications to these preferred formulations will readily occur to those skilled in the art and familiar with this disclosure, and that such may be made without departing from the scope of this invention.

Having thus disclosed our invention and described in detail preferred embodiments thereof, We claim and desire to secure by Letters Patent:

1. A remoistenable adhesive tape which may be peeled from an underlying surface to which the remoistened adhesive is applied, comprising a flexible backing having a smooth, non-fibrous, non-porous surface, a distinct intermediate layer of a polymeric elastomer releasably adhered in direct contact with said surface, and a coating of a water-remoistenable adhesive applied directly to said intermediate layer, said intermediate layer providing a bond between said backing and said adhesive permitting said backing to be peeled away intact from said adhesive.

2. A remoistenable adhesive tape which may be peeled from an underlying surface to which the remoistened adhesive is applied, comprising a kraft paper backing having a smooth, hard plastic surface, a distinct intermediate layer of a polymeric elastomer releasably adhered in direct contact with said plastic surface, and a coating of a water-remoistenable adhesive applied directly to said intermediate layer, said intermediate layer providing a bond between said backing and said adhesive permitting said backing to be peeled away intact from said adhesive.

3. The adhesive tape defined by claim 2 wherein the intermediate layer is a film of dried latex of the elastomer.

4. A remoistenable adhesive tape which may be peeled from an underlying surface to which the remoistened adhesive is applied, comprising a flexible backing having a smooth, non-fibrous, nonporous surface, a distinct intermediate layer of a polymeric elastomer of dried latex releasably adhered in direct contact with said surface, and a coating of a water-remoistenable adhesive applied directly to said intermediate layer, said intermediate layer providing a bond between said backing and said adhesive permitting said backing to be peeled away intact from said adhesive.

5. A remoistenable adhesive tape which may be peeled from an underlying surface to which the remoistened adhesive is applied, comprising a kraft paper backing having a smooth, hard plastic surface of polyethylene, a distinct intermediate layer of a polymeric elastomer releasably adhered in direct contact with said plastic surface, and a coating of a water-remoistenable adhesive applied directly to said intermediate layer, said intermediate layer providing a bond between said backing and said adhesive permitting said backing to be peeled away intact from said adhesive.

6. A remoistenable adhesive tape which may be peeled from an underlying surface to which the remoistened adhesive is applied, comprising a kraft paper backing having a smooth, hard, plastic surface of polyethylene, a distinct intermediate layer of a polymeric elastomer of dried latex releasably adhered in direct contact with said plastic surface, and a coating of a water-remoistenable adhesive applied directly to said intermediate layer, said intermediate layer providing a bond between said backing and said adhesive permitting said backing to be peeled away intact from said adhesive.

7. A package comprising a container having folding portions for closing the same, said folding portions being secured by a remoistenable adhesive tape which comprises a flexible backing having a smooth, non-fibrous, nonporous surface, a distinct intermediate layer of a polymeric elastomer releasably adhered in direct contact with said surface, and a coating of a water-remoistenable adhesive applied directly to said intermediate layer, said intermediate layer providing a bond between said backing and said adhesive permitting said backing to be peeled away intact from said folding portions.

8. A package comprising a container having folding portions for closing the same, said folding portions being secured by a rernoistena'ole adhesive tape which comprises a flexible backing having a smooth, hard plastic surface, a distinct intermediate layer of a polymeric elastomer releasably adhered in direct contact with said plastic surface, and a coating of a water-moistenable adhesive applied directly to said intermediate layer, said intermediate layer providing a bond between said backing and said adhesive permitting said backing to be peeled away intact from said folding portions.

9. The method of making a remoistenable tape comprising applying a layer of a polymeric elastomer directly to a flexible backing having a smooth, non-fibrous, nonporous surface, said elastomer being relcasably adherent to said surface, and applying a water-remoistenable adhesivc to said layer.

10. The method defined by claim 9 wherein the polymeric elastomer is applied as a latex.

11. The method of making a remoistenable tape comprising applying a coating of plastic to the surface of a kraft paper backing and causing said coating to harden to form a smooth, hard plastic surface, applying a latex of a polymeric elastomer directly to said surface and causing said latex to dry to form a directly adhering intermediate layer over said surface, and applying a waterremoistenable adhesive to said intermediate layer.

12. The method of making a remoistenable tape comprising applying a coating of polyethylene to the surface of a kraft paper backing and causing said coating to harden to form a smooth, hard plastic surface, applying a latex of a polymeric elastomer directly to said surface and causing said latex to dry to form a directly adhering intermediate layer over said surface, and applying a waterremoistenable adhesive to said intermediate layer.

References Cited in the file of this patent UNITED STATES PATENTS 2,295,613 Stillwell Sept. 15, 1942 2,358,831 Schieman Sept. 26, 1944 2,541,498 Calvert Feb. 13, 1951 2,795,515 Lavanchy June 11, 1957

Claims

7. A PACKAGE COMPRISING A CONTAINER HAVING FOLDING PORTIONS FOR CLOSING THE SAME, SAID FOLDING PORTIONS BEING SECURED BY A REMOISTENABLE ADHESIVE TAPE WHICH COMPRISES A FLEXIBLE BACKING HAVING A SMOOTH, NON-FIBROUS, NON-