GB2322097A

GB2322097A - Hot-melt adhesive

Info

Publication number: GB2322097A
Application number: GB9805953A
Authority: GB
Inventors: J Michael Eshleman
Original assignee: Armstrong World Industries Inc
Current assignee: Armstrong World Industries Inc
Priority date: 1995-11-27
Filing date: 1996-11-26
Publication date: 1998-08-19
Anticipated expiration: 2016-11-26
Also published as: GB2322096A; GB2322096B; GB2322097B; GB9805952D0; GB9805953D0

Abstract

A hot-melt stick comprises an ethylene/vinyl acetate copolymer and an additive selected from a group consisting of ethylene/(meth)acrylic acid, propylene/(meth)acrylic acid, and calcium carbonate, wherein the calcium carbonate may pass through a sieve opening of 0.044 mm. The hot-melt stick may further comprise a tackifier which is optionally a hydrogenated aromatic or aliphatic hydrocarbon, an alpha-methylstyrene polymer, poly iso-butene or poly n-butene.

Description

SEAM SEALING METHOD, PRODUCT, & DEVICE 2322097 This invention relates to a

method for the sealing and bonding of seams or joints of floor coverings. More particularly, the invention relates to a hot-melt seaming or bonding process. The invention also relates to the floor covering system produced by the method and a device used in the method.

Seams and joints of floor coverings are sealed and bonded to keep out moisture and dirt and to impart strength. Seam sealing or bonding systems presently used involve the use of environmentally unacceptable chemicals, expensive high temperature equipment, or porous grouting materials.

Most floors have seams or joints at regular intervals. These seams may be bonded or sealed or not. Bonding or sealing of seams is preferable because dirt, spills and cleaning solutions are prevented from penetrating the seam. Foreign matter which penetrates into the seam can interfere with the adhesion of the floor covering to the substrate, produce an undesirable appearance, and foster bacterial growth.

The sealing methods most commonly used are the grouting of rigid tile, the bonding of resilient floors to the subfloor with strong impervious adhesives, the welding of poly(vinyl chloride) (PVC) based resilient floors using very high temperatures and threads of PVC - 2 inserted into specially cut grooves, and the use of PVC resin solutions forming lacquers that partially dissolve the PVC flooring forming a solvent weld. Each of these systems has its drawbacks and the floor covering industry is always looking for faster, easier, less expensive, and less dangerous ways to seal or bond seams.

According to the present invention, seams of floor covering materials are sealed or bonded using a hot-melt sealer applied with a heated gun or applicator, advantageously one employing a specially designed tip.

The present invention provides a floor covering system comprising first and second floor covering elements and a hot-melt material having a composition different from the composition of the floor covering elements; the first floor covering element and the second floor covering element each having substantially parallel first and second major surfaces and an edge portion extending from the first to the second major surfaces; the edge portions of the first and second elements being bonded together with a layer of the hot-melt material; the hot-melt material being disposed between the edge portions of the first and second elements and preferably extending from the first major surface to the second major surface of the two elements.

The floor covering elements are advantageously resilient floor covering elements.

3 - The present invention also provides a method of installing a floor covering system comprising laying up a first and a second floor covering element, each element having a first major surface, a substantially parallel second major surface and an edge portion extending from the first to the second major surface, the edge portions of the first element and the second element being adjacent to one another, and bonding the adjacent edge portions of the first element and the second element together, advantageously from the first major surface to the second major surface, with a layer comprising a hot-melt material, the composition of the hot-melt material being different from the compositions of the material forming the first and second floor covering elements.

Normally, the composition of the first and second floor covering elements will be the same. If they are different, however, the hot-melt material composition may be different from only one or both of the two compositions. The difference may lie in any characteristic of the compositions, e.g, chemical constitution, melting point, or melt viscosity.

The present invention further provides a hot-melt applicator tip comprising a tubular shaft portion and a distal end portion having a slot, the slot having a width of about 0.25 mm to about 0.70 mm and a length of about 0.38 cm to about 1.3 cm, the distal end portion 4 comprising two beveled surfaces, the slot being disposed between the two beveled surfaces, the angle between the two beveled surfaces being about 800 to about 1000, a portion of the two beveled surfaces intersecting along a line, the line forming an angle of about 400 to about 600 from a line perpendicular to the axis of the tubular shaft portion.

The present invention further provides a hot-melt stick comprising an ethylene/vinyl acetate copolymer and an additive selected from the group consisting of ethylene/(meth)acrylic acid, propylene/(meth)acrylic acid, and calcium carbonate, wherein the calcium carbonate may pass through a sieve opening of 0.044 mm (325 U.S. mesh).

Various embodiments of the invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of two floor covering elements being hotmelt seam sealed by one method in accordance with the present invention.

Figure 2 is a sectional view, taken substantially along line 2-2 of Figure 1.

Figure 3 is a side view of a hot-melt gun tip in accordance with the present invention.

Figure 4 is a front view of the hot-melt gun tip shown in Figure 3.

Figure 5 is a back view of the hot-melt gun tip shown in Figure 3.

Figure 6 is a bottom view of the hot-melt gun tip shown in Figure 3.

Figure 7 is a sectional view, taken substantially along line 7-7 of Figure 2.

Figure 8 is a perspective view of the hot-melt gun tip shown in Figure 3.

The invention is described with respect to floor coverings and particularly resilient poly(vinylchloride) floor coverings. However, the invention may be used in connexion with all resilient floor coverings, e. g., rubber floor coverings, although its application to carpeting, for example, is not at present envisaged. Further, the invention is not limited to monolithic resilient floor coverings, but may also be used with multi-layered laminates including those with felt or fiber backings. The hot-melt seam sealing system is applicable also to bonding surface covering elements other than floor coverings.

Hot-melt seam sealing is best performed by, but not limited to, employing an ethylene-vinyl acetate (EVA) copolymer hot-melt material. EVA material, particularly when mixed with an aliphatic hydrocarbon, is flexible, has a low viscosity, bonds well, has good light stability, and does not discolor with exposure to heat.

6 The bond strength of the EVA material improves substantially when an ethylene/(meth)acrylic acid copolymer, a propylene/(meth)acrylic acid copolymer, or calcium carbonate is added to the composition. (Meth)acrylic acid means acrylic acid or methacrylic acid. The calcium carbonate should be able to pass through 325 U.S. mesh sieve opening (0044 mm sieve opening).

Other hot-melt materials which may be used include polyamides, and polyethylene or polypropylene modified by the addition of a tackifier. If desired the hot-melt material may include a pigment or pigments to form a colored seam.

In one preferred embodiment the hot-melt material is an ethylene/vinyl acetate copolymer or other resin to which a tackifier is added. The primary purpose of the tackifier is to improve adhesion, but it also improves flexibility.

Advantageously the tackifier is an optionally hydrogenated aromatic or aliphatic hydrocarbon, an alphamethylstyrene polymer, poly iso-butene or poly n-butene.

Typical hot-melt guns operate at about 193.30C (3800F) which, especially with the tip designed in accordance with the invention, can pass a significant amount of heat to the edges of the flooring elements which are being seam sealed, thereby enhancing the bond. The hot-melt material advantageously has a melt viscosity 7 - such that it flows through the gun and the tip with only moderate effort when molten and is advantageously fluid enough to fill the seam from the bottom of the floor covering elements to slightly overflowing.

As shown more especially in Figures 1 and 2, the seam is formed by placing the flooring elements 1, such as tile or sheet goods, a set distance apart using a gauge. An advantageous spacing is, but is not limited to, a range of about 0.38 cm to about 1.02 cm. The flooring materials are preferably affixed to the subfloor 2 when the seam width is set and the seams may then be sealed as a separate operation rather than sealing the seams as they are laid on the subfloor.

The molten hot-melt material 3 fills the seam from the subfloor 2 to the surface 4 of the flooring elements. Flooring elements welded in accordance with the prior art have weld material filling approximately the top half of the seam only. The adjacent edge portions which form the seam groove do not need to be cut or trimmed as is necessary portions elements The if they were to be welded. The adjacent edge are straight as formed when the flooring are cut to size and are substantially parallel. hot-melt material sets up quickly eliminating problems that can occur while waiting for adhesives to cure or solvents to evaporate. The small bead 5 of excess material which is extruded above the top of the seam is easily skived (sliced off) with a spatula-style knife.

8 - The bead 5, which is shown in Figure 2 and in phantom in Figure 7, is only slightly wider than the space between the floor elements. The beads of vinyl welded seams are 125 mils (about 3.2 mm) wide and are advantageously a plasticized poly(vinylchloride) resin.

As shown in Figure 1, the specially designed hot-melt gun tip 6 is inserted into the groove of the seam 7 and the hot-melt material is caused to flow into the seam filling the area under the tip to slightly overflowing by hot-melt gun 8. As overflow begins to occur, the tip is drawn along the seam maintaining a flow rate that produces the small bead of overflow 5. The rate of movement along the seam is controllable with the flow rate of the hot-melt material 9.

If for some reason the seal should be broken, it may be re-established by inserting the hot-melt gun tip into the area of the broken seal and applying fresh hot-melt material. The excess is skived off and the seam sealed. When sealing intersecting seams, the heat of the applicator tip melts through the already sealed seam with little effort and the new bead of hot-melt material knits the opening after the tip passes through.

Tip design is important for efficient seam sealing. The tip of the hotmelt gun must direct the molten hot-melt material accurately into the seam. The hotmelt gun should transmit some heat through the tip of the hot-melt gun to the edge portions of the floor covering 9 elements which form inside of the seam to enhance adhesion with the hot- melt material. The tip should be sized so that it is highly manoeuvrable and controllable.

A tip as shown in Figures 3 to 8 is highly advantageous, but performance of the method is not limited to the use of such a design. The tip 6 is preferably made of bronze, but other metals have performed very well and engineering grade plastics have been used successfully.

The tip is made from a tubular piece of heat conducting material and includes a shaft portion 10 and a distal end portion 11. The proximal end portion 12 is threaded and has a faceted portion 13 to enable easy attachment to the hot-melt gun. The distal end has a slot 14 which is about 0.25 mm to about 0.76 mm wide and about 0.38 cm to about 1.3 cm in length. The distal end portion has two beveled surfaces 15, the slot being disposed between the two beveled surfaces. The angle between the two beveled surfaces is about 800 to about 1000. A portion of the two beveled surfaces intersects along a line which forms an angle of about 400 to about 600 with a line perpendicular to the axis of the tubular shaft portion.

The beveled surfaces help guide the tip within the seam groove without penetrating too deeply into the groove and causing excessive drag or making it difficult to fill the seam with hot-melt material. The angle between the intersection of the beveled surfaces and the axis of the tubular shaft portion enables the slot to be substantially parallel to the surface of the floor covering when the handle of the hot-melt gun is resting on the floor covering, as shown in Figure 2.

Many formulations have been tried with varying success using a variety of polymers that are frequently incorporated into hot-melt coatings or adhesives. Some polyamides were tried with moderate success. Polyethylene wax based formulations were not as strong as desired when used alone but were of considerable use as modifiers in other formulations. Block copolymer rubbers and polyesters also make good modifiers but their melt index is generally too low for use in a typical hot-melt gun. Ethylene acrylic acid copolymers produced some useful formulations. The preferred formulation comprises an ethylene vinyl acetate copolymer, with or without a modifier.

The following are some of the formulations used for hot-melt seam sealing: EVA Resin (18% vinyl acetate, melt index = 500) EVA Resin (9% vinyl acetate, melt index = 7) Hydrogenated aliphatic hydrocarbon resin (melt point = 850C) 4 0. 0 % 10.0 50.0 100.0 The above formulation has good strength and skiving characteristics along with fair soil resistance.

EVA Resin (14% vinyl acetate, melt index = 2500) Ethylene-methacrylic and copolymer resin (melt point = 510C) 10.0 Alpha-Methylstyrene resin (melt point = 1200C) 20.0 100.0 The above formulation has good strength, good skiving characteristics and fair to good soil resistance.

EVA Resin (18% vinyl acetate, melt index = 500) EVA Resin (28% vinyl acetate, melt index = 6) Hydrogenated aliphatic hydrocarbon resin (melt point = 1300C) 25.0 100.0 The above formulation has good strength, good skiving characteristics and fair to good soil resistance.

EVA Resin (14% vinyl acetate, melt index = 2500) 33.3 % EVA Resin (33% vinyl acetate, melt index = 400) EVA Resin (18% vinyl acetate, melt index = 500) 70.0 % 60.0 % 15.0 33. 3 33. 3 99.9 12 The above formulation has good strength, good skiving characteristics and fair soil resistance.

EVA Resin (18% vinyl acetate, melt index = 600) Ethylene methacrylic acid Resin (melt index = 312) Hydrogenated aliphatic hydrocarbon resin (melt point = 1300C) 23.0 100.0 The above formulation has good strength, good skiving characteristics, and good soil resistance. EVA Resin (18% vinyl acetate, melt index = 500) Hydrogenated aliphatic hydrocarbon resin (melt point = 851C) 68.0 9.0 50.0% 50.0 100.0 The above formulation had fair strength but poor skiving and soiling characteristics. The amount of hydrocarbon resin was too high and the resin had too low a melt point for use in this formulation. EVA Resin (18% vinyl acetate, melt index = 500) EVA Resin (9% vinyl acetate, melt index = 7) Hydrogenated aliphatic hydrocarbon resin (melt point = 1300C) 50. 0 % 25.0 25.0 100.0 13 - The above formulation had poor strength and poor skiving characteristics because of too high a melt index and a hydrocarbon resin with too high a melt point for use in this formulation. Amorphous Polypropylene Hydrogenated aliphatic hydrocarbon resin (melt point = 1000C) Polyethylene Homopolymer (melt point = 1060C) 50.0 % 20.0 30.0 100.0 The above formulation was tacky and lacked strength.

Ethylene-vinyl acetate resin (18% vinyl acetate, melt index 500-600) 68.0 Hydrogenated aliphatic hydrocarbon resin (melt point = 1300C) Calcium carbonate (< 0.044 mm mesh sieve) 23.0 9.0 100.0 14 181811

Claims

1. A hot-melt stick comprising an ethylene/vinyl acetate copolymer and an additive selected from the group consisting of ethylene/(meth)acrylic acid, propylene/(meth)acrylic acid, and calcium carbonate, wherein the calcium carbonate is capable of passing through a sieve of 0.044 mm.

2. The hot-melt stick of claim 1, further comprising a tackifier.