Secondary backing for carpeting

Abstract

A secondary backing is provided for a carpet material. The secondary backing comprises a woven synthetic scrim with a layer of staple fibers needled onto the top surface of the scrim with portions of the fibers projecting through to the bottom surface of the scrim. The secondary backing will be laminated to the primary backing of a carpet with the top surface of the secondary backing engaging the back surface of the primary backing and the bottom surface of the secondary backing being covered with a latex and being ironed.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to the manufacture of a carpet structure, and more particularly, to a synthetic secondary backing for carpet material.

2. Description of the Prior Art

It is often desirable to apply a secondary backing to the bottom surface of a carpet material to add dimensional stability, weight and durability thereto. Secondary backing materials have traditionally been made of woven jute, but due to the difficulties in obtaining a reliable source of jute and its high variable cost and its lack of good dimensional stability, manufacturers have sought for some time to find a suitable replacement.

One material that has many of the requisite physical properties for a secondary backing and is available at a reasonable price is a woven synthetic scrim of the type now commonly used for primary backings. A number of factors have heretofore mitigated against the use of this material for secondary backings. For one thing, the synthetic filaments are smooth and slippery, making it difficult to bond the scrim to the underside of the carpeting. This same slipperiness makes woven synthetic scrims, particularly those with ribbon filaments, subject to edge raveling so that they are somewhat difficult to handle. Also, the shiny appearance and smoothness of the synthetic scrims distract from their marketability since customers are accustomed to the appearance of a jute backing or a latex backing on the carpet. Further, where high weight secondary backing is necessary or desirable, the synthetic scrim material can become quite expensive.

U.S. Pat. No. 3,542,632, issued Nov. 24, 1970, discloses a method for improving the hand and adherability of synthetic scrim material by needling or otherwise treating it to develop fibrils or splinters. While this does improve the characteristics of the scrim, there are still significant problems. For example, it is necessary to use a relatively heavy, and therefore expensive, material in order to have sufficient strength remaining after fibrilation and in order to give the desired final weight. Also, edge raveling may remain a problem unless the material is severely fibrilated and/or subjected to a heat treatment. Further, the fibrilated material retains much of the translucent, shiny appearance of the basic scrim.

U.S. Pat. No. 3,817,817, issued June 18, 1974, discloses another method for improving the hand and adherence of a synthetic scrim material which will be used as a secondary backing. A layer of staple fibers are needled onto the bottom surface of the scrim with portions of the fibers projecting through the top surface of the secondary backing. This is then bonded to the back of the carpet and the staple fibers needled onto the bottom surface of the scrim of the secondary backing provide a product which may give the appearance of being jute.

SUMMARY OF THE INVENTION

A conventional carpet material is provided with the carpet secondary backing invention herein. The secondary backing is formed from a woven scrim of synthetic fibers. On the top surface of the scrim is placed a web of fibers. The fibers are then needle bonded to the scrim. On the bottom of the scrim where the fibers are pushed through the scrim by the needling operation, a latex coating is applied to bond the fibers to the bottom surface of the scrim and the bottom surface is ironed. Adhesive is then applied to the back side of the carpet material and the secondary backing is then applied to the carpet material with the top side of the scrim being placed up against the back side of the primary backing of the carpet material. This then results in the fiber material which was needle bonded to the secondary backing being laminated between the scrim of the primary backing of the carpet material and the scrim of the secondary backing.

This will provide a carpet product which has good dimensional stability and good adherence between the primary backing and secondary backing. The bottom of the secondary backing is provided with a nonslip coating which will enable the carpet to better frictionally engage a floor surface.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an enlarged, somewhat schematic fragmentary view of a cross section of a piece of carpeting including a secondary backing formed according to the invention herein; and

Fig. 2 is a schematic view of the process for making the product of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The carpet material 2 shown in FIG. 1 is of the type shown in U.S. Pat. No. 3,605,666, issued on Sept. 20, 1971 to Kimmel et al and entitled "Tufted Carpet with Compatibly Dyeable Needlebonded Surface and Method of Manufacturing Same" to which reference may be had for a complete description thereof. The carpet shown as element 2 in FIG. 1 has not been shown with the layer of dyeable staple fibers which would be placed upon the top surface of the primary backing 4 of the carpet. The carpet face has a series of tufts 6 which extend through the primary backing 4. The base portions of the tuft are on the underside of the primary backing 4 and are preferably locked in place by a thin layer 8 of a suitable latex or other adhesive. The tufts 6 may be of any desirable length and density and may be looped as shown or cut. Any suitable materials may be used for the carpet face tufts 6 and normally they are nylon or acrylic materials.

The secondary backing of this invention is particularly suitable for the above particular type of tufted carpet material, but it is obvious that it can be used with any other tufted carpet, woven carpet or other type of carpet material. The particular type of carpet material 2 used is not part of the invention herein.

The secondary backing 10 is normally conventionally bonded to the underside of the carpet material usually as the last step in the manufacture of the end product. The secondary backing 10 is usually bonded to the back of the conventional carpet material by the use of an adhesive layer 12 which may be any suitable type of adhesive, such as the normally used commercially available latex adhesives. It is obvious that the adhesive layer 8 and adhesive layer 12 must be compatible and any number of conventional backing adhesives can be utilized to secure the bond of the secondary backing to the primary backing.

The secondary backing 10 includes a scrim 14 and a backing face 16 of needled staple fibers. The scrim 14 is preferably a woven polypropylene ribbon scrim which is basically similar to the scrim 4 which forms the primary backing of the carpet 2 and this is the same as the scrim of U.S. Pat. Nos. 3,605,666 and 3,817,817. The scrim 14 can be of a somewhat lighter weight than the scrim 4. In the preferred embodiment, the scrim 14 is made up of warp and weft ribbons 18 and 20 which are of a generally uniform size and spaced apart a slight distance. Specifically, in the preferred embodiment, the weft ribbons are made up with a uniform size and cross section and are slightly spaced apart at about six ribbons per inch. The warp ribbons are also of a uniform size and cross section and they are tightly spaced together at about 24 ribbons to inch. The resultant 24 .times. 6 construction weighs approximately 2.7 ounces per square yard. It is obvious that a heavier woven polypropylene scrim could be used. It is of a particular advantage for the invention herein that this above type of structure be used, but it is obvious that scrims made of different polyolefins or other materials and having other various configurations can be substituted for the above preferred embodiment.

The backing face 22 is applied to the top surface of the scrim 14, said top surface corresponds to the surface of the scrim which will be facing the primary backing of the carpet in the assembled carpet structure forming the end product. The backing face 22 is attached to the secondary backing 14 by a conventional needling process such as is well known in the art. In the preferred embodiment, the staple fibers used are nylon 66 and have a weight of 3 denier with an average length of 21/2 inches. It is possible to also use polyester, polypropylene, and other fibers as blends. The fibers are deposited uniformly across the top of the scrim 14 at the rate of 1.5 to 2 ounces per square yard. The needling of the face 22 to the scrim 14 is accomplished by the use of standard barbed needles which are used to punch from the top surface of the secondary backing through to the back surface of the secondary backing. The back surface of the secondary backing is that portion of the backing which will be against the floor when the carpet end product is in use. In the preferred embodiment, the needling is performed by the use of a suitable needle loom set at about 134 punches per square inch with a punch penetration of 21/32 of an inch. The needles are preferably barbed needles of 32 gauge. It will be obvious that variations are possible in the types of fibers used, the rates at which they are applied, and the extent to which they are needled, bearing in mind the desired results discussed more fully below.

The needling step causes the staple fibers to be interlaced to bond the backing face 16 to the scrim 14. The staple fibers may be fire retardant or have other specialty features. The weight of the fiber deposited can be easily controlled in order to control the weight of the secondary backing. During the needling step, the needles extend through the scrim 14 and cause fibers to project through to the bottom side of the scrim. Those portions 24 of the fibers which extend below the scrim will be locked to the bottom surface of the scrim to improve the adherability of the face layer 16 to the scrim 14.

Adherence of the fibers 24 which extend to the bottom surface of the scrim 14 is accomplished by the following technique. A conventional filled latex is sprayed upon the bottom surface of the scrim to apply 1.25 to 1.5 ounces of filled latex to the bottom of the scrim 14. This is then ironed with a calender roll heated to 260.degree.F. This tends to flatten and push down the fibers 24 and embed them within the latex coating 26. The ironing operation can also be carried out by passing the bottom surface of the scrim over a series of rollers heated to 220.degree.F to 260.degree.F. This latex coating can be any conventional latex adhesive and specifically is a carboxylated styrene-butadiene latex of the following formulation:

Material % By Weight ______________________________________ Styrene-butadiene latex 33 (50% solids) Water 49.0 Tri-sodium Polyphosphate 0.7 (wetting agent) Alumina Trihydrate 16.0 (fire retardant) Sodium Polyacrylate 1.3 (thickener) 100.0%

The calender roll is the conventional heated calender roll which is a well known structure in the art. The calender roll simply engages the bottom surface of the scrim and rotates in a direction opposite from the direction the scrim is moving so as to press down the fibers 24 into the latex coating 26. This then provides a bottom surface for the secondary backing which bottom surface then becomes the bottom surface of the composite carpet structure. This provides a structure which has good adherence to a floor structure underlying the carpet. It gives a visual effect which is completely different from that disclosed in U.S. Pat. No. 3,817,817 in that the product herein is provided with a latex coating on the back side of the carpet, whereas the product of the aforesaid patent is provided with a fibrous appearance on the back side of the carpet product.

Once the secondary backing is formed, it is applied to the back of the carpet structure 2 and is bonded thereto by the use of adhesive layer 12. The secondary backing 10 is bonded to the carpet structure with the backing face 16 facing the backside of the carpet structure 2. Adhesive coating 12 will be primarily engaging the backing face 16 and this face 16 will really be laminated between the primary backing scrim 4 and the secondary backing scrim 14. Use of the layer of fibers 16 at this point will secure a better bond of the two scrim layers 4 and 14 to each other.

FIG. 2 is a schematic showing of the process for forming the product of FIG. 1. A fiber face 16 is deposited on a woven scrim 14. A conventional needling machine 28 needles the fiber facing to the scrim. The bulk of the fiber facing is left on the upper face of the scrim, but some of the fiber is pushed to the back surface (bottom) of the scrim and exists there as fibers 24. An adhesive coating 26 is sprayed (or roll coated) on the bottom of the scrim where the fibers 24 project through the scrim. In FIG. 2 a spray nozzle 30 is shown coating the fibers 24 with a latex adhesive. A calender roll 32 then engages the bottom of the scrim and this flattens and pushes down the fibers 24 and embeds them in the latex adhesive coating 26 to form the finished secondary backing 10. A conventional carpet material 2 with adhesive on the back thereof is then secured to the top of the secondary backing 10 to form the finished product of FIG. 2.

Needle bonded secondary backing formed according to the invention herein has proven to be satisfactory from the standpoint of appearance, strength, cost, durability, and adherability. The process described for making the product herein involves a number of well known steps within the carpet art. While a preferred embodiment of the invention has been shown and described, it will be understood that various modifications might be made without departure from the spirit of the invention. The invention is not, therefore, intended to be limited by the showing or description herein, or in any other manner, except as may specifically be required.

Claims

What is claimed is:

1. A secondary backing designed for adherence to the underside of a carpet material, said secondary backing being secured to the underside of the carpet material by an adhesive layer, the improvement wherein the secondary backing comprises a woven synthetic scrim; a backing face comprising a layer of staple fibers needled onto the top surface of the scrim with portions of the fibers of the backing face extending downwardly through the scrim to the back surface of the scrim, said fibers on the back surface of the scrim being encapsulated in an adhesive layer and said last-mentioned fibers being bent over and flattened against the back surface of the scrim of the secondary backing.

2. A carpet structure comprising in combination: a carpet material consisting of a primary scrim having tufted thereinto a fibrous material with loops extending above the primary scrim to form the carpet face, the carpet face fibrous material extends partly to the opposite side of the primary scrim and an adhesive layer bonds this last-mentioned material to the primary scrim, and, a secondary backing comprising a secondary scrim and a fiber facing needle bonded to the top surface thereof, an adhesive layer bonding the secondary backing to the carpet material with the fiber facing on the secondary scrim being sandwiched in between the primary scrim of the carpet material and the secondary scrim and in engagement with the adhesive layer which is bonding the secondary backing to the carpet material, and said fiber facing having some fiber needled through the secondary scrim with this fiber being encapsulated in an adhesive and being inclined and flattened against the bottom of the secondary scrim.

3. The process for making a secondary carpet backing comprising the steps of depositing a fiber facing on a woven scrim, placing the fiber facing on the upper surface of the woven scrim, needling the fiber facing to the woven scrim by forcing some fibers of the fiber facing to the back surface of the woven scrim, depositing an adhesive coating on the back surface of the scrim to encapsulate those last-mentioned fibers forced through the scrim by the needling operation, and then ironing the fibers and adhesive to flatten down the fibers against the back surface of the woven scrim and to embed those fibers into the adhesive layer.