Flame retardant tufted carpet tile and method of preparing same

Abstract

A flame-resistant carpet tile having low smoke values and improved flame resistance which carpet tile comprises a primary backing having a fibrous face and a fibrous back, a barrier layer adjacent to fibrous back to an acrylic polymer heavily loaded with a metallic flame-retardant salt filler material which acrylic polymer is compatible with a vinyl chloride polymer layer and a relatively thick vinyl chloride polymer backing layer adhering to the barrier layer.

The method of preparing a flame-resistant carpet tile which comprises pre-coating the back of a carpet with an acrylic polymer latex containing a metallic salt flame-retardant filler material, coating the latex material with a PVC layer, thereafter laying the latex PVC coated carpet into the top surface of a liquid PVC backing layer, heating the laid-in carpet to fuse the PVC layers, cooling the carpet and cutting the carpet into carpet tile.

Description

BACKGROUND OF THE INVENTION

Carpet tiles are typically composed of a fibrous or wear-type surface and an undersurface secured to a primary backing and containing a thick layer of a thermoplastic backing material, such as for example, of polyvinyl chloride resin as a solid or a foam, bitumen or atactic polypropylene. Often glass fiber scrim or tissue is employed with the primary backing and embedded in the backing layer in order to impart dimensional stability to the carpet tile. Typical carpet tiles and carpet tile production methods are described for example in U.S. Pat. No. 4,582,554 issued Apr. 15, 1986 hereby incorporated by reference.

It is desirable to provide for a carpet tile which has a low flame resistance and low smoke value. Flame-resistant carpets have been prepared by applying a carboxylated cross-linkable vinyl chloride resin composition to the back surface of a thermoplastic backing sheet which serves as the primary backing and then heating the vinyl chloride composition to cross-link the vinyl chloride resin and to bond the tufted yarns to the base of the primary backing. In such a method, the temperature of the cross-linking in heating is maintained below the shrinkable temperature of the polymeric fibrous primary backing is then laminated to the surface of the cross-linked vinyl chloride resin composition (see for example U.S. Pat. No. 3,661,691 issued May 9, 1972 hereby incorporated by reference).

The flame-retardant, vinyl-foam carpet and method of the patent provides for improved flame resistance by bonding the surface of the primary backing coated with a cross-linked vinyl resin to a secondary backing wherein the primary and secondary backing are prevented from shrinking and separating when exposed to open-flame conditions. This improvement is related to flame-retardant vinyl-foam backing carpet and not to carpet tile, which requires a very thick, heavy thermoplastic backing layer to secure a free-lay, dimensionally stable carpet tile.

SUMMARY OF THE INVENTION

The invention relates to a flame-resistant, low smoke value carpet tile and to the method of preparing the same. In particular, the invention concerns a flame-resistant carpet tile having low smoke values in which a pre-coat barrier layer is employed which is compatible with the backing layer and which barrier layer contains flame-retardant filler material.

It has been found that the application of a pre-coat latex barrier layer containing a flame-retardant filler material as a pre-coat for plastic-backed carpet tiles provides for a unique flame-resistant, low smoke value carpet tile. In particular, it has been discovered that the employment of a vinyl, particularly an acrylic-type pre-coating latex, which contains a metallic salt, and more particularly aluminum trihydrate, when employed as a pre-coat for a vinyl chloride resin carpet tile backing layer, provides for an improved flame-resistant, low-smoke value carpet tile. Carpet tile, so prepared, will typically register 0.5 or more on flame retardance when tested in accordance with the Flooring Radiant Panel Test ASTM E-648. This ASTM test essentially measures the watt density which is required to ignite the carpet in that the higher the test number, the more flame-resistant the carpet. In addition, the carpet tile typically has a value of less than about 400, e.g. 200 or less, on the smoke density value test with a PVC backing layer is as follows:

The carpet tile had a flame retardance on the radiant panel test of about 0.5 or more, e.g. 0.7 to 0.9, and a smoke value of about 300 or less, e.g. 225 to 275.

______________________________________
VINYL LATEX PRE-COAT FORMULATION
Ingredients         Parts by Weight
______________________________________
1. UNOCAL 761  200
a styrene-acrylic latex (latex)
2. Water             15
3. Aluminum trihydrate (ATH)
150
(smoke and flame retardant
4. CELLOID2 211
1
(dispersing agent for ATH)
5. ACRYSOL3 ASE 60
1.5 (as needed)
(polyacrylate salts as thickener)
6. Aqueous ammonia  To pH 8.5
Brookfield viscosity 4/20
3 groups
solids 68%
______________________________________
1 a trademark of Union Oil Company
2 a trademark of North Chemical Company, Inc. of Marietta, Georgia
3 a trademark of Rohm & Haas Company

FIG. 2 illustrates a block form diagram of a method of preparing a flame-resistant carpet tile as shown in FIG. 1. The method of the process is to cast or coat a layer of about 35 to 50 mils thick of a fibrous polyvinyl chloride (PVC) plastisol as the first coating on a flouro-carbon-coated endless belt. This first PVC layer forms the back surface of the carpet and normally contains fillers therein, such as calcium carbonate or other particulate inert filler-type material, to provide weight thereto and lower cost. Glass fiber tissue sheet material is then laid onto the top surface of the first PVC plastisol layer, and this first layer is then heated in an oven, for example, from the bottom using heated platens beneath the endless belt, such as by circulating hot oil through the plates adjacent to the bottom of the endless belt, to gel the first layer and to fix the glass fiber tissue on or about the top surface. Then a second coat, a PVC plastisol coat, of about 25 to 50 mils, which may be the same of a different PVC plastisol, is applied over the first gel layer and the tissue sheet therein in order to bury the glass fiber tissue sheet intermediate the two PVC layers.

A carpet composed of a primary backing to which has been tufted a fibrous material to form a fibrous-face wear surface and a back loop or a back fibrous surface is pre-coated with an the a latex pre-coat formulation containing a high amount of aluminum trihydrate and heated to form a thin barrier layer. A PVC vinyl precoat that is a plastisol is then applied by a lick roller over the barrier layer. The carpet containing the barrier layer and the PVC pre-coat is then passed through a laying-in station and the back surface laid directly onto the top liquid plastisol of the second PVC backing layer. Typically, the laying-in station is very close to the second layer coating, the second layer PVC coating station. After the laying-in, the carpet is then sent though a fusing oven whereby the PVC layers are then fused to form an integral PVC backing layer. The carpet is then cooled and then cut into carpet tiles. The process thus involves a pre-coating station for pre-coating the latex then heating the latex at a station for pre-coating the latex layer with a pre-coat PVC layer and two stations for coating PVC to form the bulk of the backing layer.

The carpet tile so produced thus has a good bond between the vinyl-styrene barrier layer and the thermoplastic backing layer. The backing layer not only helps to lock in the fibers, but more importantly serves to improve the flame resistance and reduce the smoke values.

Claims

1. A carpet tile having improvide flame resistance, which carpet tile comprises:

(a) a primary backing having a fibrous face and a fibrous back;

(b) a barrier layer adjacent the fibrous back which barrier layer comprises a non-halogenated latex vinyl polymer and a metal salt, flame retardant filler material in an amount sufficient to provide a flame-retardant barrier layer, which filler material comprises a compound selected from the group consisting of (i) a metal salt hydrate which generates water upon heating; and (ii) a metal salt of a borate, oxide, carbonate, phosphate, or sulfate of aluminum, barium, magnesiu, or zinc, and which latex vinyl polymer is compatible with a theromoplastic polymer vinyl chloride resin backing layer; and

(c) a vinyl polyvinyl chloride resin backing layer bonded to the barrier layer, to impart stability and free-laying properties to the carpet tile.

2. The carpet tile of claim 1 wherein the metal salt filler comprises aluminum trihydrate.

3. The carpet tile of claim 1 wherein the carpet tile includes a fiberglass or polyester tissue or scrim sheet material in the backing layer.

4. The carpet tile of claim 1 wherein the carpet tile is characterized by an ASTM E-62 E-662 smoke value of about 400 of less.

5. The carpet tile of claim 1 wherein the carpet tile is characterized by a flame-resistance ASTM E-648 value of about 0.5 or higher.

6. The carpet tile of claim 1 wherein the latex vinyl polymer comprises a butadiene-acrylonitrile polymer having an excess of about 50% or more by weight of acrylontrile.

7. The carpet tile of claim 1 wherein the barrier layer comprises from about 10 to 50 ounces per square yard, and the backing layer is a solid layer and has a thickness of from about 50 to 150 mils.

8. The carpet tile of claim 1 wherein the carpet tile is a tufted carpet tile.

9. The carpet tile of claim 1 wherein the backing layer is a vinyl chloride foam layer.

10. The carpet tile of claim 1 wherein the backing layer comprises a polyvinyl chloride polymer layer.

11. The carpet tile of claim 1 wherein the barrier layer comprises from about 100 to 250 parts by weight of the flame-retardant filler material per 100 parts by weight of the vinyl polymer.

12. The carpet tile of claim 1 wherein the flame-retardant filler material comprises an oxide, sulfate, borate, phosphate or carbonate of zinc, barium, magnesium or aluminum.

13. The carpet tile of claim 1 wherein the fibrous face and fibrous back comprises a polyamide fiber.

14. The carpet tile of claim 1 wherein the latex vinyl polymer is selected from the group consisting of: copolymer of acrylic and methacrylic acid and alkyl acrylates; acrylic-styrene copolymers; acrylonitrile-styrene copolymers; ethylene-vinyl acetate copolymers; polyvinyl acetate; and vinylidene chloride-acrylonitrile copolymers and combinations thereof.

15. The carpet tile of claim 1 wherein the backing layer is a solid layer of from about 50 to 200 mils in thickness.

16. The carpet tile of claim 1 wherein the backing layer is a foam layer of from about 100 to 350 mils in thickness.

17. A carpet tile having low smoke values by ASTM E-62 E-662 of 300 of less and improved flame resistance by ASTM E-648 of 0.5 or more, which carpet tile comprises a primary backing, having a tufted fibrous face and a fibrous back fiber;

(a) a barrier layer adjacent to fibrous back which barrier layer comprises a non-halogenated latex vinyl-styrene copolymer containing from about 50 to 350 parts per 100 parts of the vinyl polymer of aluminum trihydrate and which barrier layer is compatible with a vinyl chloride resin backing layer; and

(b) a solid vinyl polyvinylchloride resin backing layer directly bonded to the barrier layer to impart stability and free-laying properties to the carpet tile.

18. The carpet tile of claim 15 wherein which includes a tissue or scrim-type sheet material imbedded in the vinyl chloride polymer backing layer.

19. The carpet tile of claim 17 wherein the fibrous face and back comprise a nylon fiber, and the latex ep vinyl polymer comprises a styrene-acrylic polymer.

20. In a method of preparing a flame-resistant carpet tile, which method comprises: applying a polyvinyl chloride resin backing layer to the back surface of a primary backing having a fibrous wear face surface and a fibrous back surface to form a carpet tile materials, the improvement which comprises:

(a) pre-coating the back surface of the primary backing with a thin precoat layer of a non-halogenated vinyl polymer latex composition; and heating the precoat layer to form a barrier layer, which vinyl polymer is compatible with the vinyl chloride resin backing layer and which pre-coat latex composition contains a flame-retardant amount of a metal sale, flame-resistant filler compound, which compound is selected from the group consisting of (i) a metal salt hydrate which generates water upon heating; and (ii) a metal salt of a borate, oxide, carbonate, phosplhate, or sulfate of aluminum, varium, magnesium, or zinc.

21. The method of claim 20 wherein the flame-resistant carpet tile comprises:

(a) the barrier layer comprising from about 100 to 250 parts by weight of a flame-retardant filler material per 100 parts by weight of the latex vinyl polymer;

(b) the flame-retardant filler material comprises an oxide, sulfate, borate, phosphate or carbonate of zinc, barium, magnesium or aluminum; and

(c) a fibrous face and fibrous back comprise a polyamide fiber.

22. The carpet tile produced by the method of claim 20.

23. The method of claim 20 wherein the latex vinyl polymer is selected from the group consisting of: copolymer of acrylic and methacrylic acid and alkyl acrylates; acrylic-styrene copolymers; acrylonitrile-styrene copolymers, ; ethylene-vinyl acetate copolymers; polyvinyl acetate; vinylidene chloride-acrylonitrile copolymers and combinations thereof.

24. The method of claim 20 which includes pre-coating the vinyl latex composition onto the back surface in an amount of from about 15 to 50 ounces per square yard.

25. The method of preparing a flame-resistant carpet tile, which method comprises:

(a) coating a first layer of a polyvinyl chloride resin plastisol on a support surface;

(b) placing a dimensionally stable sheet material onto the top surface of the first layer and heating the layer to gel the layer and position the sheet material; p1 (c) applying a second layer of a polyvinyl chloride plastisol onto the gelled surface of the first layer;

(d) pre-coating the back of a primary backing having a fibrous wear-resistant face surface and a fibrous back surface, with a non-halogenated vinyl polymer latex composition, the latex composition containing a flame retardant amount of a metal salt filler comound compound, which compound is selected from the group consisting of i) a metal salt hydrate which generates water upon heating; and (ii) a metal salt of a borate, oxide, carbonate, phosphate, or sulfate of aluminum, barium, magnesium, or zinc, and wherein the vinyl latex polymer is compatible with the polyvinyl chloride, and heating the pre-coated layer to form a barrier layer;

(e) coating a thin, polyvinyl chloride liquid plastisol layer over the barrier layer;

(f) laying the coated barrier layer carpet onto the top surface of the plastisol of the second polyvinyl chloride layer;

(g) heating the carpet so formed to fuse the polyvinyl chloride layers into an integrally-fused backing layer;

(h) cooling the carpet; and

(i) cutting the carpet into carpet tile.

26. The carpet tile produced by the method of claim

27. The method of claim 25 wherein the metal salt filler compound comprises aluminum trihydrate, the vinyl latex polymer comprises a styrene-acrylic latex polymer, and the fibrous face and back surface comprise a nylon fiber.

28. The carpet tile produced by the method of claim 27.

29. The carpet tile of claim 1, wherein the non-halogenated latex vinyl polymer comprises ethylene vinyl acetate copolymer. 30. The carpet tile of claim 1, wherein the fibrous face comprises nylon, and the non-halogenated latex vinyl polymer comprises ethylene vinyl acetate

copolymer. 31. The carpet tile of claim 1, wherein the fibrous face comprises nylon, the non-halogenated latex vinyl polymer comprises ethylene vinyl acetate copolymer, and the primary backing comprises polypropylene. 32. The carpet tile of claim 1, wherein the fibrous face comprises nylon, the non-halogenated latex vinyl polymer comprises ethylene vinyl acetate copolymer, and the metal salt

comprises an aluminum salt. 33. The carpet tile of claim 1, wherein the fibrous face comprises nylon, the non-halogenated latex vinyl polymer comprises ethylene vinyl acetate copolymer, and the metal salt comprises a magnesium salt.