Pressure-sensitive acoustic door tape

BACKGROUND OF THE INVENTION

This invention relates to a novel pressure-sensitive adhesive tape wound in a roll, which is capable of use as an acoustic door tape and also as a weatherstrip tape for doors and windows.

While a variety of strip materials (e.g., metal, wood, rubber, woven pile, felt) have been employed for weather stripping of doorways, these expedients have had only limited utility for acoustic sealing. Atmospheric sound vibrations are readily transmitted through relatively minute cracks or passageways between the perimeter of a closed door and its frame. An acceptable weather stripping, which efficiently restrains the movement of cold or warm air between a closed door and its frame, will not necessarily be effective as a sound barrier. Air vibrations can be transmitted via openings through which there is little or no flow of air. Acoustic and thermal sealing problems are different.

Attempts at modifying or redesigning conventional weatherstrip material to improve acoustic sealing efficiency, generally results in a strip material which lacks durability, especially When used with office doors which are frequently opened. In any event, there is likely to be an unacceptable increase in the effort needed for opening or closing the door. Contrariwise, modifications to reduce these problems lead to a loss of acceptable acoustic efficiency.

The well-known V-shaped brass weather strips are prone to quickly develop nicks or imperfections which provide airways and acoustic leaks. Any springy metal strip will be either too inflexible or too thin and flimsy. The problem is made even worse by the fact that oftentimes there is a variable or uneven spacing between a door and its frame.

For these reasons, resort has been made to other acoustic sealing systems of a more complicated nature. Thus use has been made of a rubberlike tube which is inflated in the space between the door and frame after the door is closed. This expedient is utterly impracticable for ordinary office and home use. Another expedient, which has enjoyed substantial commercial use, employs a flexible soft elastic foam rod having a fabric or plastic cover, provided with a continuous tab for fastening the strip to a door frame by nailing or by use of an adhesive coating on the tab. This type of sealing strip is too bulky or conspicuous for many applications, and it increases the door closure pressure to an undesirable degree in most CilSCS.

Surprisingly we have discovered a relatively simple pressure-sensitive adhesive sealing strip structure, that can be conveniently supplied in the form of a long length flat tape wound in a roll, which solves the aforesaid problem in a new way. This tape can be folded and can be readily cut with scissors to provide springy V-shaped plastic acoustic sealing strips which are easily installed, inconspicuous, long-lived, and add little to the effort required to close or open the door. This acoustic sealing strip also provides efficient weather stripping when installed in outer doorways or windows.

The practical success of this tape depends upon the fact that although the plastic strip is produced in a creased springy Vshaped state, it can be flattened and the adhesive tape wound into a roll wherein the tape stably maintains an undistorted flat condition until, whenever desired, tape is unwound and folded to restore the antecedent springy V-shape which is thereafter stably maintained during use as a door sealing strip even though subjected to innumerable flexings of the V.

A new and useful result is obtained that cannot be achieved with metal strips. The present plastic sealing strip is not a mere substitute for a metal weatherstrip.

SUMMARY OF THE INVENTION

The unique plastic-film sealing strip component of our adhesive tape product is provided by a flexible and springy but planar-rigid plastic tape of about 8 to 16 mils ( 0.2 to 0.4 mm.) thickness, which is axially folded and creased to a springy V shape and is then flattened. It has the ability to stably retain either a wound-in-a-roll flat condition or a V-shape when subsequently folded and used.

By “planar-rigid” it is meant that the plastic-film tape is not stretchy or extensible in its own plane, even though it is highly flexible. By “springy” it is meant that the tape springs back when bent or flexed and released, and that the V-shape is springy when compressed and released. “Plastic-film” designates that the tape is a thermoplastic melt-formed film (formed by extrusion or calendering) as distinguished, for instance, from metal strips and from woven pile or other fibrous strips.

A melt-extruded pigmented polypropylene film of about 8 to 16 mils (0.2 to 0.4 mm.) thickness, slit into tape having a width of about 1 inch (25 mm.), is illustrative of a tape suitable for such folding and flattening.

The flattened creased tape is coated along one leg or flange with a stripe of tacky pressure-sensitive adhesive which extends from the central crease line to or near the edge. The adhesive is on the ridged side of the tape, meaning the outer side which is to be adhered to a door or window frame (as distinguished from the grooved inner side) when the tape is subsequently folded to restore the V-shaped cross section preparatory to use. A thin dry-strippable release liner is applied over the adhesive coating as a temporary covering.

The resultant flat adhesive tape is wound upon a core in a roll of desired length. It is important that the tape be wound such that the liner-protected adhesive-coated ridged side is on the inside (facing the axis of the roll). The grooved side of the tape (which will be on the inside of the V when the tape is subsequently folded to a V-shape thus faces outwardly in the wound roll. This results in a roll wherein the adhesive tape will indefinitely maintain a stable undistorted flat condition. If the tape is wound “inside out” with the ridged side on the outside of the roll, the tape will tend to triangulate and resume its original folded shape, thereby bunching up and distorting the roll. A straight piece of tape lying unrestrained will tend to twist or distort. Hence the importance of providing and keeping the tape wound in roll form. A stable roll of flat tape has the further advantage of enabling a long length of tape (even as long as 100 yards or 100 meters) to be supplied in a single compact roll. A stable undistorted roll is also desirable in facilitating mounting in dispenser or applicator devices.

The tape roll can be kept from spontaneously loosening or unwinding by fastening down the free end of the tape with a piece of removable and reuseable pressure-sensitive adhesive tape (such as a piece of paper masking tape).

The tape can be easily unwound and cut with hand scissors to provide strips of any desired length. It can be folded at any convenient stage to restore the antecedent V-shape. The liner is peeled off to expose the tacky adhesive as the strip is being laid down in position on a door frame to serve as an acoustic barrier. The resultant V-shaped sealing strip will indefinitely retain its springy action. It will compress when the door is closed and press against the door with elastic force to effect a good sealing action; and it will spring open when released by the opening of the door; despite innumerable closings of the door. Yet this springy sealing action does not materially or objectionably increase the force needed for closing or opening the door.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying schematic drawings:

FIG. 1 shows a roll of the pressure-sensitive adhesive tape wound convolutely upon a core, the end portion of the tape being unwound and the end of the liner strip being peeled back to expose the adhesive.

FIG. 2 shows in perspective an end portion of a strip of the adhesive tape which has been removed from the roll and axially folded at the central crease so as to restore a stable Vshape, the liner being partially peeled back to expose the underlying adhesive (which is on the outer side of one leg of the

3,581,884 tape). In this embodiment (unlike that of FIG. 1), the liner strip extends past the edge of the tape to provide an edge tab to facilitate finger grasping when the liner is to be peeled off.

FIG. 3 is a sectional view showing a piece of the V-shaped tape adhesively attached to the jamb of a door frame as an acoustic barrier sealing strip.

FIG. 4 is a similar view but with the V-shaped piece of tape attached to the stop of the door frame.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As illustrated in FIG. 1, a roll 1 of our pressure-sensitive adhesive door-sealing tape 2, as supplied to a user, consists of a desired length of flattened creased tape wound convolutely upon a core. As previously explained, the adhesive-coated ridged side must face inwardly in the wound roll in order to avoid subsequent distortion. The slightly indented axial crease line 3 is visible as a centerline on the other, outwardly facing, side of the plastic-film tape 4. The wound tape in such case remains indefinitely in a flat condition and hence, as shown, it is flat when unwound. The end of the tape can be held down on the roll, to prevent uncoiling, by using a piece of tacky adhesive tape (Such as a pressure-sensitive masking tape) which can be peeled off whenever desired to free the end of the tape for removal of a desired strip.

In FIG. 1 a short length of the tape has been unwound and lies flat in both the lengthwise and crosswise directions. The ridged side is shown, having a central crease line 5 dividing the two legs or flanges of the plastic-film tape, one of which 6 is adhesive-free, and the other of which 7 is coated with a stripe of tacky pressure-sensitive adhesive 8. A dry-strippable liner strip 9, consisting of a thin film having a release type surface, covers and adheres to the adhesive coating with a low degree of adherency to enable it to be easily peeled off whenever desired. (Such liners are referred to as “dry-strippable” because they can be peeled off dry without being moistened.)

In this particular embodiment, the liner strip is coextensive with the adhesive stripe and they extend from the center crease line to or near to the edge of the underlying plastic-film tape. This would be the case where the adhesive is initially coated on a web of the liner film material, which is slit to provide adhesive coated liner strips of appropriate width, and such a strip is laminated by means of its tacky adhesive to one leg or flange of the flattened plastic-film tape during manufacture. In this case the liner-supported pressure-sensitive adhesive is transfer coated” in a dry condition upon the plastic tape film surface.

FIG. 2 shows in perspective an end portion of adhesivecoated tape (similar to but not identical with that of FIG. 1) which has been unwound from its roll and subjected to folding about its axial crease line so as to restore the original crosssectional V-shape (which, during manufacture, had been imparted to the plastic-film tape by folding and creasing, and then eliminated for the time being by flattening out).

Using the same reference numerals as in FIG. 1, except for the liner, the V-shaped strip has a sharp central ridge whose apex is the crease line 5, the uncoated leg 6 and the adhesivecoated leg 7 of the plastic-film strip being flat and converging at an acute included angle (preferably about 60°). The pressure-sensitive adhesive coating 8 is on the outside surface and is covered by the dry-strippable liner strip 9 (which is shown peeled back to expose the adhesive).

In this particular embodiment (unlike that of FIG. 1), the pressure-sensitive adhesive coating solution was initially applied to one leg of the flattened plastic-film tape, dried, and covered by a dry-strippable liner film strip having a width somewhat greater than the adhesive stripe such as to project beyond the edge of the tape leg to provide an edge tab 10. This tab thus extends along the edge of the V-shaped sealing strip and permits the liner to be easily grasped between thumb nail and forefinger for stripping off the liner when the sealing strip is to be adhesively affixed to a door or window frame.

This V-shaped plastic-film sealing strip is springy and when the legs have been compressed or pinched, they will upon release return to approximately the same angle. The elasticrestoring force, coupled with the flexibility of the tape, makes for good door-sealing action and yet is not so strong as to materially increase the effort needed for closing and opening.

The permanently springy characteristic of our V-shaped sealing strip clearly distinguishes from plastic-film strips which have been folded and creased to provide a relatively inelastic hinge intended for fastening to the edges of two swingable members (such as the stiff covers of a folder).

As to each of the preferred embodiments described above, the plastic-film is therefore a planar-rigid springy film which is selected with reference to its capability to be folded and creased to a V-shape, to be flattened to a stable flat condition, and to be restored to a V-shape that is permanently springy despite innumerable squeezings. A preferred strip material is a melt-extruded pigmented isotactic polypropylene film having a thickness of about 12 mils (0.3 mm.) and which is slit to provide a plastic-film tape of desired width. A width of about seven-eighths inch (22 mm.) is suitable for most door installations in the U.S.A, but other widths obviously can be employed when appropriate. The polypropylene film is preferably given an adhesion-promoting electrical treatment on the side to which the pressure-sensitive adhesive coating will ultimately be applied, so as to cause a stronger interbonding. (Such treatment is described, for instance, in U.S. Pat. No. 3,118,534.)

The pressure-sensitive adhesive is viscoelastic and is of a type which is aggressively tacky, has high internal strength (cohesive or shear strength), and is of a long-lasting or “permanent” nature which will strongly anchor the tape to a door frame. A presently preferred adhesive is of the known class of viscoelastic acrylate polymers which inherently possess the requisite combination of tackiness and internal strength and are stable against deterioration. The preferred polyacrylate adhesive is a copolymer of an acrylate ester containing an average of 4—12 carbon atoms, and a minor proportion by weight of acrylic acid, as taught in Ulrich’s U.S. Pat. No. Re. 24,906 (reissue of U.S. Pat. No. 2,884,126.)

A suitable dry-strippable release liner is a thin pigmented white polyethylene film, having a thickness of about 4 mils (0.1 mm.). The surface of this film has a relatively low adhesion to the pressure-sensitive polyacrylate adhesive coating when applied thereover. Another suitable liner is a matte finish nonpigmented polypropylene film which appears to be white due to the frosty surface.

FIGS. 3 and 4 are horizontal sectional diagrammatic views illustrating door-sealing usages of the V-shaped adhesive strip of FIG. 2 (after cutting to length and removal of the liner).

In FIG. 3 the V-shaped strip is adhesively secured along the jamb 11 of the door frame with the apex facing outwardly toward the door 12 as the door comes into the frame upon swinging to a closed position. The interposed tacky pressuresensitive adhesive coating 8 serves to adhesively and resiliently unite the leg 7 to the jamb, the open leg 6 extending out at an angle. It will be apparent that as the door closes, the springy V-shaped strip will be squeezed or compressed between the door edge and the jamb and that the flexible leg 6 of the strip will elastically press against the edge of the closed door, to effect an air seal. When the door is opened, the legs will spread to restore the normal V-shape.

To determine whether a door can be feasibly stripped, insert a piece of compressed strip in the gap between door and jamb and move it about. If it can be moved with reasonable ease, the door can be stripped without unduly increasing the force needed for door closure. If the fit is too tight, the gap should be increased, as by planing the edge of the door.

In FIG. 4, the V-shaped strip is adhesively secured along the stop 13 of the door frame with the apex facing into the doorway. The leg 7 is thus resiliently bonded by the adhesive coating 8 to the stop, the open leg 6 extending out from the stop. As the door closes, the springy V-shaped strip is squeezed

3,581,884 between the marginal face of the door and the stop to effect an air seal.

In either situation, the stripping installation procedure is as follows:

1. The flat adhesive tape is unwound from the roll and folded to the V-shape. This can be done manually, or by pulling through a V-shaped slot, or by making use of a known type of pressure-sensitive tape dispenser which includes a device for folding tape down the center as it is drawn from the roll (such dispensers being used to fold “edging” tapes).

2. The V-shaped tape is cut to desired length by means of a scissors so that it will fit the door frame. Ordinarily, the frame will be stripped along both vertical sides and across the top.

3. Clean and dry the surfaces that are to be contacted by the pressure-sensitive adhesive.

4. Remove the white liner film to expose the tacky adhesive surface, and apply the V-shaped strip so that the adhesive contacts the frame (see FIGS. 3 and 4). Miter the corner joints with scissors.

5. Using a rubber-covered roller, or fingers, press the strip 20 firmly against the frame to obtain good continuous adhesive contact.

6. Open the V by running the finger inside it so that it is more open than normal. Close and open the door several times to bring the V to normal condition.

MANUFACTURING PROCEDURE

A presently preferred procedure for manufacturing rolls of the flattened adhesive door tape as supplied for sale and use is as follows: ’

Use is made of a suitable extrusion grade of isotactic polypropylene resin which includes a dispersed pigment so that the sealing strips as installed by the user will be inconspicuous. Preferred polypropylene resins have a melt index value in the range of approximately 0.4 to 4 (I₂ at 230° C according to A.S.T.M. Test Method D -1238). For example,' use can be made of Profax 6723E” isotactic polypropylene resin, melt index of 0.8 sold by Hercules Powder Co., Wilmington, Del., blended in a mixer with a few percent of compatible brown metal oxide pigment adapted to impart a dark brown ⁴⁰opaque appearance to the ultimate film product. This blend is melt extruded to provide a film which is 12 mils (0 3 mm ) thick.

The film is given a known type of electrical treatment on one side, as previously indicated, which is adapted to modify ⁴⁵the surface so that it will adhere more strongly to the adhesive when later applied. The film is then slit to provide plastic-film strips of seven-eighths inch (22 mm.) width which are wound into supply rolls for subsequent processing.

The folding-creasing device includes a right-angled openended aluminum trough or channel which is faced with “Teflon” (PTFE) film (for easy slidability) and mounted horizontally with the flanged opening facing upwardly. The flanges have a width of about 1.5 inches (3.75 cm.). Each flange has a guide which holds down and centers the tape as it moves toward a heated creasing blade. This is a heated springloaded rectangular brass creasing blade mounted about 6 inches (15 cm.) downstream from the front end of the trough, so as to resiliently press down into the right-angled vertex of the channel, the blade edge and the channel vertex being parallel to each other. The upstream bottom comer of the blade is rounded to facilitate entry of the plastic-film strip between the edge of the blade and the vertex groove. The blade is 5¼ inches (13 cm.) long, three-fourths inch (2 cm.) wide, and 0.06 inch (1.5 mm.) thick. The bottom edge is beveled but the edge being rounded to prevent cutting of the film. An electrical heating device is joined along the upper portion of the blade and can be regulated to adjust the tem6 perature reached by the lower (creasing) edge of the blade.

A roll of the polypropylene strip is mounted on a spindle located ahead of the trough, and the withdrawn strip passes around a tensioning roll and through guide rolls to enter the trough. As the strip is pulled downwardly toward the creasing blade edge, it is gradually folded by interaction with the flanged walls and overlying guides. It is then pulled between the edge of the heated creasing blade and the right-angled vertex of the trough. Sufficient plastic flow occurs in the thermoplastic polypropylene film to result in a permanent crease and a sharp ridge, but there is no scoring and no impairment of the desired permanent springy characteristic. The temperature and time factors are adjusted by trial and error so that the folded film strip acquires a V-angle of approximately 60°.

The creased V-shaped strip then leaves the trough and is drawn through the nip of the rubber-covered pull rolls which have served to pull the strip through the creasing device. These rolls unfold and flatten the strip to a flat tape and, as previously pointed out, the flat condition can be stably maintained when the tape is wound in roll form.

The flattened tape is now drawn through an adhesive coater where a stripe of pressure-sensitive adhesive solution is applied along one leg, between the axial crease line and the edge of the tape, on the ridged side of the tape. This side had been 25 given an adhesion-promoting electrical treatment, as previously mentioned. The coated tape then passes around a series of rolls in a drying oven so as to eliminate the solvent from the adhesive.

The dried adhesive-coated tape is then drawn between 30 rubber-covered rolls together with a release liner strip, which is thereby removably adhered to cover the tacky adhesive stripe and extend about one-sixteenth inch (2 mm.) beyond the edge of the tape to provide an edge tab.

This flat adhesive tape product is then wound upon cores to provide tape rolls of desired length for sale. A typical length is 36 yards (32 meters), although rolls of tape 100 yards or 100 meters in length can be provided. As earlier mentioned in connection with FIG. 1, it is essential that the adhesive-coated ridged-side of the tape be on the inside in the wound roll.