Abstract:
The incorporation of a vinyl chloride/vinyl acetate/maleic acid terpolymer in the pigment particle containing decorative layer of a floor covering improves the cohesive strength of the pigmented decorative layer and adhesion of the decorative layer to the adjacent layers. The use of this vinyl terpolymer as the binder in the printed or coated decorative layer imparts improved bond strength particularly with platey pigments like pearlescents and metallics or in highly filled decorative layers containing titanium dioxide or other pigments.

Description:
This is a continuation of application Ser. No. 78,487 filed on Jun. 21, 1993, now abandoned, which is a continuation of application Ser. No. 561,688 filed on Aug. 1, 1990, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to floor coverings having a decorative layer with improved cohesion within the decorative layer and improved adhesion of the decorative layer to the adjacent layers. More particularly, the decorative layer includes a vinyl chloride/vinyl acetate/maleic acid terpolymer binder in the decorative layer. 
     PRIOR ART 
     Floor coverings of the prior art include vinyl sheet, vinyl tile, linoleum, and rubber tile. Such floor coverings include thermoplastic and thermosetting wear layers. The exposed surface which is subjected to traffic wear may be a clear wear layer. Preferred wear layers include crosslinked thermosetting layers such as polyurethane or thermoplastic layers such as rigid or plasticized polyvinyl chloride or vinyl plastisols. Other floor coverings do not include wear layers but have through-color decorative layers which are exposed to the traffic. The base layer may be a conventional vinyl floor tile material, a conventional felt-backed vinyl composition sheet, plastisol saturated glass or solid vinyl plastisol. 
     The binder resin of choice for use in decorative layers of floor coverings has been an hydroxyl-modified vinyl chloride/vinyl acetate resin such as VAGH resin sold by Union Carbide. Coatings and inks based on this hydroxyl-modified vinyl resin have good adhesion to wash primers, metals, wood, and many plastic substrates. Under most manufacturing conditions, the hydroxyl-modified vinyl resin decorative layers have provided adequate cohesion within the decorative layer and adhesion between the decorative layer and base or wear layer. This cohesion and adhesion generally have proved to be sufficient to prevent delamination of the floor covering. However, with high filler loadings, particularly pearl platelets, delamination problems have occurred. The cohesion and adhesion have been improved by lowering the filler content of the decorative layer and increasing the vinyl binder content of the tile base. However, these solutions have not been entirely adequate. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide a decorative layer having improved cohesion and adhesion. 
     A further object is to improve the cohesion and adhesion sufficiently to permit increased filler loadings in the decorative layer which is cohesively stronger than the base to which it is adhered so that delamination failure occurs in the base. 
     These objects have been met by a decorative layer having a vinyl chloride/vinyl acetate/maleic acid terpolymer binder resin. The cohesion within the decorative layer and adhesion between the decorative layer and surrounding layers (i.e., wear and base layers) are such that upon being delaminated the failure occurs in the base near the interface of the decorative layer and base whereby portions of the base are separated from the base layer and are adhered to the decorative layer while substantially no decorative layer composition adheres to the base layer. 
     DETAILED DESCRIPTION 
     Low wear layer adhesion has occurred in tile patterns printed with an overall .pearl layer. The cohesion of the decorative layer and adhesion between layers are tested in a 180° delamination test on a tensile testing machine. A 1&#34;×6&#34; or 2&#34;×6&#34; specimen is cut with the long dimension in the machine direction. After conditioning in 23° C. water for ten minutes, the backing is scored about one inch from the end and peeled back 11/2 to 2&#34;. The sample is mounted in the tensile tester with a 1&#34; jaw distance and pulled at a machine speed of 6&#34; min with a 1&#34;/min chart speed. The results are reported in average pounds pull per inch width. 
     If delamination occurs within the decorative layer, the numerical result of the delamination test is a measure of cohesion within the decorative layer, and the adhesion between the decorative layer and the base layer, to which the decorative layer is adhered, is greater than the cohesion within the decorative layer. If the delamination occurs at the surface of the decorative layer adjacent the base layer, the numerical result of the delamination test is a measure of the adhesion between the decorative layer and the base layer, and the cohesion within the decorative layer is greater than the adhesion between the layers or the cohesion within the base layer. 
     The ink extender solutions used were made by adding the various vinyl resins to an isopropyl acetate solvent containing dibutyl tin maleate stabilizer. This was done by slowly adding the vinyl resin to the solvent and stabilizer in a high shear mixer until the resin was dissolved. While still mixing, an acrylic resin was added and mixed thoroughly. The weight percent of the components of the extender solutions used in the Examples is set forth in Table 1. 
     
                                           TABLE 1__________________________________________________________________________                       DibutylVinyl Resin       Isopropyl                  Acryloid                       Tin  PercentExtenderVMCC    VAGH        VAGD Acetate                  A101.sup.1                       Maleate                            Nonvolatiles__________________________________________________________________________1    14.5    --  --   80.2 5.0  0.3  16.82    18.6    --  --   74.7 6.4  0.3  21.53    --  14.5        --   80.2 5.0  0.3  16.84    --  --  14.5 80.2 5.0  0.3  16.8__________________________________________________________________________ .sup.1 Acrylic resin supplied at 40% solids in methyl ethyl ketone (made by Rohm and Haas Company) 
    
     The inks were made by dispersing the pearlescent pigment into the extender with a low shear mixer and additional isopropyl acetate solvent was added to adjust to printing viscosity. Table 2 sets forth the weight percent of the ink components for Examples 1 and 2. 
     
                                           TABLE 2__________________________________________________________________________                     Additional                            Viscosity                     Isopropyl                            of ExtenderInk Extender Solution     Acetate                            Pearl, andInk  Extender No.  Pearl.sup.4                     Solvent                            AdditionalSample(Type) (Parts by w.sup.t.)              (Parts by wt.)                     (Parts by wt.)                            Solvent.sup.5__________________________________________________________________________1    1(VMCC.sup.2)       100    13.65  --     15&#34;2    2(VMCC).sup.       100    17.65  33     12&#34;3    2(VMCC).sup.       100    13.65  26     12&#34;C1   3(VAGH.sup.3)       100    13.65  12     20&#34;C2   4(VAGD.sup.3)       100    13.65  --     15&#34;C3   3(VAGH).sup.       100    13.65  26     12&#34;__________________________________________________________________________ .sup.2 Vinyl chloride/vinyl acetate/maleic acid terpolymer resin from Union Carbide .sup.3 Hydroxylmodified vinyl chloride/vinyl acetate resin from Union Carbide .sup.4 Superfine pearl platelets from the Mearl Corporation .sup.5 Measured on a #3 Zahn Cup Viscometer 
    
     The ink compositions of Examples 1 and 2 were applied in the laboratory to a 4-mil high modulus vinyl film, laminated under about 80 psi at about 310° F. for about 15 seconds to a vinyl tile base having a thickness of about 73 mils. These test samples were made only 1&#34; in width and were tested for 180° delamination on an Instron tensile tester. 
    
    
     EXAMPLE 1 
     As shown in Table 3, the vinyl chloride/vinyl acetate/maleic acid terpolymer resin (VMCC) showed a 21% improvement over the prior art system which consisted of a hydroxyl-modified vinyl chloride/vinyl acetate copolymer resin (VAGH) at the same percent pearl in the dried ink film (6.9 pounds per one inch width versus 5.7 pounds per one inch width). Even with a higher percent pearl in the wet ink, Sample 1 gave superior 180° delamination test results versus Sample C1. 
     
                       TABLE 3______________________________________Ink           Extender  % Pearl % Pearl PoundsSam- Pearl    No.       in Wet  in Dry  Pull Perple  Type     (Type)    Ink Film.sup.6                           Ink Film.sup.6                                   1&#34; Width______________________________________1    Mearl.sup.7         1(VMCC)   12.0    44.8    6.9SuperfineC1   Mearl.sup.7         3(VAGH)   10.9    44.8    5.7SuperfineC2   Mearl.sup.7         4(VAGD)   12.0    44.8    4.9Superfine______________________________________ .sup.6 Weight percent .sup.7 Mearl Corporation 
    
     Sample C2 was made with a lower molecular weight hydroxyl-modified vinyl chloride/vinyl acetate resin (VAGD) than the VAGH used in Sample C1. At the same percent pearl pigment in the wet and dry ink, Sample 1 gave superior 180° delamination test results versus Sample C2. 
     EXAMPLE 2 
     The results of Example 1 were confirmed in a similar test reported in Table 4. 
     
                       TABLE 4______________________________________         Extender  % Pearl % Pearl PoundsSam- Pearl    No.       in Wet  in Dry  Pull Perple  Type     (Type)    Ink Film                           Ink Film                                   1&#34; Width______________________________________3    Mearl    2(VMCC)   9.8     38.8    8.4Superfine2    Mearl    2(VMCC)   11.7    45.1    8.0SuperfineC3   Mearl    3(VAGH)   9.8     44.8    4.5Superfine______________________________________ 
    
     As shown in Example 2, the pearl ink extender of the present invention has been found to give improved cohesion and adhesion even with increased filler loading. The present extender (extender 2) has resin solids of 21.5% versus 16.8% for the prior art extender (extender 3). The solvent reduction to print viscosity is the same for Samples 3 and C3 due to the lower molecular weight resin used in the present extender. The combination of better cohesive properties of the present vinyl solution resin (VMCC) plus the higher solids gave superior cohesion and adhesion results compared to the prior art extender made with VAGH. On increasing the pearl pigment to 11.7% in Sample 2 to yield a % pearl in the dry ink of about 45, the cohesion and adhesion still remained high at 8.0 pounds when compared to Sample C3. 
     EXAMPLE 3 
     The present invention can be used to improve the appearance of metallic pearl pigments. Increased pearl pigment concentration in the ink, while maintaining good interlaminar adhesion, gives a more intense metallic pearlescent effect to the finished flooring product. Table 5 sets forth the type and parts by weight of ink extender and pearl pigment, parts by weight of additional solvent, ink viscosity, percent pearl in wet and dry compositions, and results of the 180° delamination test. 
     
                                           TABLE 5__________________________________________________________________________                   Additional    Ink Extender Solution                   Isopropyl                          Ink    Percent                                        Percent    (Parts by wt.)           Pearl Pigment                   Acetate                          Viscosity                                 Pearl  Pearl  PoundsInk Extender No. (Type)           (Parts by wt.)                   Solvent                          (in sec                                 in Wet in Dry Pull perSample    2(VMCC)     3(VAGH)           Silver.sup.8               Gold.sup.9                   (Parts by wt.)                          on #3 Zahn)                                 Composition                                        Composition                                               1&#34; Width__________________________________________________________________________   4A    100         13.65   40     12      8.9%  38.9%  7.0   4B    100         17.65   40     12     11.2%  45.1%  6.4   4C    100         21.65   40     12     13.4%  50.2%  5.1C4A       100   13.65   40     17      8.9%  44.8%  4.5C4B       100   17.65   40     18     11.2%  51.2%  3.4C4C       100   21.65   40     23     13.4%  56.3%  3.1   4D    100             13.65                   40     11      8.9%  38.9%  6.9   4E    100             17.65                   40     11     11.2%  45.1%  6.2   4F    100             21.65                   40     12     13.4%  50.2%  6.1C4D       100       13.65                   40     16      8.9%  44.8%  4.1C4E       100       17.65                   40     17     11.2%  51.2%  3.9C4F       100       21.65                   40     18     13.4%  56.3%  3.7__________________________________________________________________________ .sup.8 Silver A3, a mixture of Afflair pearlescent pigments sold by Functional Materials, Inc. of Paramus, N.J. .sup.9 Gold G4, a mixture of Afflair pearlescent pigments sold by Functional Materials, Inc. of Paramus, N.J. Afflair is a trademark of E. M. Industries, Inc. 
    
     Samples 4C and 4F were at a much higher percent pearl pigment loading in both the wet and dry ink when compared with Samples C4A and C4D. Yet Samples 4C and 4F with the present ink extender gave higher 180° delamination test results. 
     In each of the Examples 1 to 3, the 1&#34; wide comparative samples all yielded less than 6 lbs/1 inch in the 180° delamination test. The comparative samples delaminated within the decorative layer whereby some of the pearl pigment remained adhered to the base layer. Therefore, the cohesion within the decorative layer was less than the adhesion between the decorative layer and the base layer. In the samples of the present invention, the failure occurred at the surface of the decorative layer adjacent the base whereby substantially none of the decorative layer composition remained adhered to the base layer. Therefore, the adhesion between the decorative layer and the base layer was less than the cohesion within the decorative layer. 
     Union Carbide produces a family of vinyl chloride/vinyl acetate/maleic acid terpolymers including VMCH, VMCC, and VMCA. While the medium molecular weight resin was tested, the higher molecular weight and lower molecular weight resins would yield improved cohesion and adhesion. 
     While cohesion of the decorative layer including pearl platelets may be more critical due to the flat configurations of the platey material and improved cohesion may be more easily measured, cohesion and adhesion are improved in other highly filled decorative layers such as those including titanium dioxide particles. 
     The present ink extender can be used wherever ink extenders are presently used in flooring applications. The present ink extender may be used in rotogravure inks on vinyl tile and vinyl sheet goods. It can be printed directly on the flooring base or printed on film which will be adhered to the base, or printed on a release paper in a transfer process.