JPH05319441A - Tear-open type envelope and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide a tear-open type envelope that cannot be opened unexpectedly although it can easily be open by means of a tearing strip. CONSTITUTION: A tear-open envelope is made of a tear-resistant sheet material. A pair of closely spaced parallel weakening lines 16, 17 is formed on a sheet material. A long reinforcing tape 18 that readily tears longitudinally while being highly resistant to traverse tearing is bonded covering the weakening lines 16, 17. In order to open the envelope, only a strip of the reinforcing tape 18 between a pair of the weakening lines 16, 17 is peeled off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tear envelope and a method for manufacturing the same. More particularly, the present invention relates to envelopes having tear strips on the sheet material from which the envelope is made.

[0002]

BACKGROUND OF THE INVENTION Presently preferred sheet materials for tear resistant envelopes are spunbonded polyolefins such as e.g. Eye. Sold under the registered trademark Tyvek by DuPont Numor. It is very tear resistant, so you have to form a line of weakness to tear it into a strip and open the envelope, but the line of weakening can be easily separated so that you can secretly open flaps or seams. Will leave visual evidence of such attempts.

What we know about tear strips for Tyvek type sheet material is US Pat. No. 4,781,296 (Morris et al.). It discloses that the application of ultrasonic waves causes the fibers to transform into a film along a pair of weakening lines extending in parallel at closely spaced intervals. Such a device is shown in FIGS. 3 and 4 of the Morris et al. Patent, which describes in order to provide a bag with the robustness of the bag's raw materials and with an easy opening tape system. Disclosed is a long thermoplastic tape having a pressure sensitive adhesive on its surface, wherein the fibers are converted into a film and adhered by adhesive over the lines of weakness surrounding the surface of the bag. Further, as a backing of the reinforcing tape, a tear strip having a reinforcing filament and a pressure-sensitive adhesive applied on one surface are provided so that the reinforcing tape is adhered to a position between the weak lines.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tear envelope which is made of a tear resistant sheet material and which can be easily opened by a tear strip, but which is not opened abruptly. Is to provide. Compared to the Morris et al. Patent bag, the tear-open feature of the present invention is more economical to manufacture because it uses a single tape instead of two. Is. Moreover, the edges of the opening will be smoother. Here, the term "envelope" includes not only a mail envelope but also a shipping bag and other shipping contents made of a tear-resistant sheet material such as Tyvek spunbond polyolefin.

[0005]

Briefly stated, the tear-open envelope of the present invention, like Morris et al., Has a pair of weakenings extending parallel to each other in close proximity to a tear resistant sheet material. A line is formed and a long, flexible stiffening tape is secured over the weakening line. In addition to employing a single stiffening tape, the tear envelope of the present invention, unlike Morris et al., Has an impact value of at least 300 N / dm (defined later), at least 1500 N / dm. It has a longitudinal breaking strength (ASTM D-3759), is easily torn in the longitudinal direction, and has high tear resistance in the lateral direction,
And has a tear value (defined later) of less than 4 oz (1N), whereby only the strip portion extending between the pair of weakening lines of the reinforcing tape is peeled to open the envelope. become able to.

Here, the line of weakness means any line such that a sheet material having tear resistance can be easily and clearly separated at the line of weakness, for example, melting line of a razor cut line or Morris. It should include score lines.
For some tear-resistant sheet materials, it is sufficient to provide perforations or partial cuts at close intervals, but the sheet material of the tear envelope of the preferred embodiment of the present invention, Tyvek When using spunpond polyolefins, it is necessary to ensure that the line of weakening extends completely uninterrupted through the thickness of the sheet material. Tyvek spunpond polyolefins are available in thicknesses of 0.1 to 0.2 mm, all of which have sufficient tear resistance to be used as tear-open envelopes of the present invention. There is.

[0007] Preferably, a long reinforcing tape is provided so as to cover the inner surface of the envelope. One end of this long stiffening tape is cut a short distance along the line of weakening, and the end portion of the stiffening tape can be used as a pull tab if the weakening line is not yet cut. When you pull this pull tab with your finger, the strips that extend between the pair of weakening lines of the reinforcing tape easily separate from the rest of the reinforcing tape, opening the envelope between the pair of weakening lines. Acts as a tear strip through the envelope to do so. Alternatively, one end of the long stiffening tape can be left unattached at the opening of the envelope, thereby grasping the tab to initiate the opening.

As the reinforcing tape for the envelope, any flexible tape having the above-mentioned properties can be used. A preferred reinforcing tape is disclosed in EPC Patent No. 343896 (Reseman), issued November 29, 1989. The backing of the stiffening tape is a polymer film with polymeric ribs on one surface, which provides easy longitudinal tear and excellent lateral tear resistance. Preferably, an adhesive layer is carried on the other surface of the backing, and the reinforcing tape is adhered to the envelope by the adhesive layer. Thereby, the ribs split the film of polymer as the tear strip is pulled through the envelope, leaving a smooth edge in the opening. Also useful as a reinforcing tape is, for example, US Pat. No. 2753.
A filament reinforced tape as described in No. 294 (Paul et al.), Which has a kraft paper backing and leaves a smooth edge when the tear strip is pulled through the envelope. However, care should be taken when choosing a filament reinforced tape, as the line of weakening is not bridged by the film backing of the reinforcing tape after the tearing action has ended. That is, when the filaments are pulled through the line of weakness, they cut the film backing of the reinforcing tape. Tapes having a polymeric film backing with a high degree of longitudinal tension are also useful as reinforcing tapes. Such backings can be longitudinally embossed or engraved to enhance both transverse strength and longitudinal tearing.

The strip of tape that opens the envelope is reinforced by the sheet material underneath it, and thus has greater strength and toughness than unreinforced tape of the same width, thus opening the envelope. Significantly reduces the risk of pulling strips breaking in between.

Preferably, the spacing between the weakening lines is 3 to 1.
It is 0 mm. Substantially smaller spacing makes it more difficult to grasp the tear strip and can injure a person's finger. Further, the narrow spacing reduces the amount of reinforcement imparted by the sheet material to the strips of tape, making them more susceptible to breakage. On the other hand, when the distance is substantially larger than 10 mm, it is necessary to increase the width of the reinforcing tape, which increases the cost without the corresponding advantage.

The long stiffening tape preferably has sufficient width to extend laterally beyond each side of the line of weakness by at least 6 mm to adequately resist the inadvertent opening of the envelope in use. On the other hand, it would be economically wasteful for the long stiffening tape to be wide enough to extend substantially 12 mm or more across each side of the line of weakening.

Envelopes are typically formed from long rolls of sheet material using equipment that continuously cuts, folds and seals the sheet material. Preferably, such a device simultaneously forms an envelope with the tear-splitting feature of the present invention either before or after placing the stiffening tape in place. In order to be able to achieve this without reducing the production, the line of weakening is preferably razor cut, because slowing down the production line when ultrasonically generating the line of weakening is recommended. Request. In order to simplify the equipment of the production line forming the weakening lines, they are adjacent to the edge of the envelope, in the direction of movement of the sheet material, typically perpendicular to the edge carrying the flap of the envelope. Is preferably extended.

For simplicity, the long stiffening tape covering the weakening line is provided with an adhesive whereby the stiffening tape is secured to the envelope. Most conveniently, the adhesive is pressure sensitive, but may be heat or solvent activated. If you use the same adhesive that is used to sew seams, or to flap envelopes,
Flexible tapes will exhibit similar resistance to unobtrusive pranks as seams and flaps.

It is conceivable to provide only one weakening line on the tear envelope and to form a score on the reinforcing tape on each side of this weakening line to initiate the tearing action. When such a single line of weakening is created by ultrasound, it should be wide enough to allow the strips of tape to be pulled without damaging the human finger.
Forming such wide widths can only be done very slowly, which is a waste of energy. When forming a relatively wide weakening line by cutting, the adhesive of the reinforcing tape is exposed, and the tear strips of the reinforcing tape cannot be reinforced by the sheet material of the envelope, thus causing accidental damage. It will be easier.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The tear-type envelope 10 of the embodiment of FIGS.
It is formed from a tear-resistant spunbonded polyolefin sheet material. The flap 12 is provided with a pressure sensitive adhesive layer 13, which is protected by a removable liner 14. The flap 12 is formed with a pair of weakening lines 16 and 17 extending in parallel at closely spaced intervals. In the weakening lines 16 and 17, spunbonded polyolefin fibers are transformed into a film by an ultrasonic method. The long reinforcing tape 18 has an adhesive layer 20, which covers the weakening lines 16, 17 and is permanently adhered to the flap 12 by this adhesive layer 20. One end of the reinforcing tape 18 is cut by a short distance at a portion 21 corresponding to the weakening lines 16 and 17 extending downward, and the weakening lines 16 and 17 are also cut by the same distance, as shown in FIG. Pull tab 22
To form.

The liner 14 has been removed and the flap 12 has been removed.
After the adhesive has been adhered to the body of the envelope 10 by the adhesive layer 13, the pull tab 22 can be pulled with a fingertip. This separates the strip of reinforcing tape 18 between the weakening lines 16, 17 from the reinforcing tape 18, which tape strip acts as a tearing strip, by pulling it between the weakening lines 16,17. You can open the envelope with.

The tear-type envelope 30 shown in FIGS. 3 and 4 is also formed of a sheet material having tear resistance. A pair of cuts 33, 34 extending in parallel at close intervals are formed in the edge portion of the envelope 30 in the direction perpendicular to the edge portion provided with the flap 32. The long stiffening tape 36 has an adhesive layer 37 which covers the cuts 33, 34.
To be permanently adhered to the envelope 30. Reinforcing tape 36
One end of is cut a short distance in line with the cuts 33, 34 of the envelope to form a pull tab 39.

[0018]

【test】

(Impact value) Two 2 x 6 inches (5.1 x 15.2c
Samples were prepared using rectangular Tibeck spunbonded polyolefin sheet material of m). The 1/4 inch (6 mm) gap between the long sides of the Tyvek polyolefin sheet material is bridged with 6 inch (15.2 cm) long and 1 inch (2.54 cm) wide reinforcing tape to be tested. Was done. This assembly is mounted between the jaws of the Instron Tensile Tester (CRE),
These jaws are 1.5 inches (3.8 cm) wide and 2
He was isolated for an inch (5.1 cm). The jaws were separated at a speed of 1000 inches (2.54 m) / minute. Impact value is peak resistance, N (of width of jaw)
/ Dm.

Tear Value The long reinforcing tape to be tested was slit with a razor along the length of about 4 cm at the center. The free ends on each side of the slit were gripped by an Instron Tensile Tester (CRE) jaw, which was then longitudinally separated at a rate of 50 inches (127 cm) / minute. The average resistance is the tear value.

Example 1 A two pound parcel courier envelope was obtained from the United States Postal Service and was made from 18 pound Tyvek Spunbond polyolefin sheet material and was 39 cm long and 31 cm wide. It had a flap. The weak line is 2mm wide and spaced 6mm apart, and the second flap is located 3mm from the first edge of the flap.
It was provided so as to pass through the edge portion and penetrate the thickness of the sheet material. The center of the line of weakness is 1 inch wide (2.54c
m), a pressure sensitive adhesive reinforcing tape, was adhered by its own adhesive as shown in FIG. This stiffening tape was made as disclosed in the Resemann EPC patent. This reinforcing tape has an impact value of 490N
/ Dm, and the breaking strength in the longitudinal direction is 3150 N / dm
And the tear value was 0.75N.

Then to provide a pull tab,
Razor slits were provided in each weak line and the reinforcing tape above it at a distance of 1.3 cm from the second edge of the reinforcing tape. When the pull tab is pulled, the tear strip is pulled out from the middle of the reinforcing tape and the sheet material of the envelope below it until it reaches the first edge of the pull tab of the reinforcing tape and reaches the first edge of the pull tab. It then stopped abruptly, causing the pull tab to slip from the finger. Thus, the torn portion of the flap and the tear strip remain attached to the envelope and can be discarded as a unit after the material is removed from the envelope.

Example 2 An envelope equivalent to that of FIG. 1 is Example 1
It had the same tear-opening characteristics as those of No. 1, except that the line of weakness was formed with a razor slit. Pulling on the pull tab with a person's finger removes the strip of reinforcing tape between the razor slits, thus opening the flap, which leaves the torn portion and tear strip of the flap attached to the envelope. The edge of the tear was smooth.

[Brief description of drawings]

1A and 1B are views showing a cleaving envelope according to a first embodiment of the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a partially enlarged view.

2 is an enlarged cross-sectional view taken along line 2-2 of FIG.

FIG. 3 is a perspective view showing a cleaving envelope according to a second embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view taken along line 4-4 of FIG.

[Explanation of symbols]

 10 ... Envelope 12 ... Flap 16, 17 ... Weak line 18 ... Reinforcing tape 22 ... Tensile tab 30 ... Envelope 33, 34 ... Notch 36 ... Reinforcing tape 39 ... Tensile tab

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Donald John Klassen Minnesota 55144-1000, St. Paul, 3M Center, USA (no address) (72) Inventor Richard Lawrence Sheehan, Junia 55144-1000, St. Minnesota USA Paul, 3M Center (No street number)

Claims (10)

[Claims] 1. A tear-open envelope made of a sheet material having tear resistance, wherein a pair of weakening lines extending in parallel at closely spaced intervals are formed in the sheet material and easily tearable in a longitudinal direction. A long reinforcing tape having a high tear resistance in the lateral direction is secured over the weakening line, and a strip portion extending between the pair of weakening lines of the reinforcing tape to open the envelope. A tear-open envelope that allows only the chisel to be peeled off. 2. The tear-open envelope according to claim 1, wherein the sheet material is a spunbonded polyolefin. 3. The tear-open envelope according to claim 1, wherein the line of weakness extends completely in the thickness direction of the sheet material without interruption. 4. The split envelope of claim 1, wherein the long reinforcing tape is adhered to the inner surface of the envelope. 5. The tear envelope of claim 4, wherein the long stiffening tape is cut a short distance along the line of weakening to allow the end portion of the stiffening tape to be used as a pull tab. 6. The long reinforcing tape comprises a polymeric film backing having polymeric ribs on one surface and an adhesive layer on the other surface, the reinforcing tape being adhered to the envelope by the adhesive layer. Item 2. The cleaving envelope according to Item 1. 7. A method for manufacturing a tear-open envelope comprising a sheet material having tear resistance, comprising: (a) forming a pair of weakening lines extending in parallel at closely spaced intervals on the sheet material; A long reinforcing tape which is easily torn in the longitudinal direction but has a high tear resistance in the lateral direction is fixed to the sheet material by covering the weakening line, and (c) the sheet material is formed to form an envelope. A method for manufacturing a tear-open envelope comprising the steps of cutting, bending and sealing. 8. The method for producing a tear-open envelope according to claim 7, wherein the sheet material is bent in the step (c) so that the long reinforcing tape covers the inner surface of the envelope. 9. The cleaving system according to claim 8, wherein in the step (c), the step of forming the weakening line completely cuts the sheet material by a distance substantially equal to the length of the long reinforcing tape. Envelope manufacturing method. 10. The method of making a tear envelope of claim 9 including the step of cutting one end of the long stiffening tape a short distance along the line of weakness to provide a pull tab.