Patent Publication Number: US-2009233056-A1

Title: Polypropylene Laminate Wallcovering

Description:
FIELD OF THE INVENTION 
     The present invention relates to wallcoverings. More particularly, the present invention relates to a polypropylene laminate wallcovering. 
     BACKGROUND OF THE INVENTION 
     Polyvinyl chloride (PVC) is a standard material for producing commercial wallcoverings. PVC wallcoverings are relatively low cost, have high durability properties relative to weight, have good printing properties and embossing properties, and are flexible from an installation perspective. PVC wallcoverings, however, have drawbacks. The most serious drawback is the environmental hazard that polyvinyl chloride poses. PVC wallcoverings produce environmental hazards during the manufacturing stage, when the finished PVC wallcovering is installed, and when the PVC wallcoverings are eventually discarded. 
     Alternatives to PVC wallcoverings have failed in one or all of the following categories: Too expensive, poor print registration, poor grain capture (does not emboss well), does not meet Type II wallcovering protocol, which includes the ASTM E-84 Class A flammability requirements, and many other performance criteria as stated in CCC-W-408 A and CCC-W-408-D. 
     A need therefore exists for an improved, environmentally friendly wallcovering that is low cost, has good printing and embossing characteristics, and meets standard performance criteria, including flammability requirements. 
     SUMMARY OF THE INVENTION 
     The present invention answers this need by providing a wallcovering comprising a laminate of three layers including: (1) a scrim backing layer, (2) a specially formulated, oriented polypropylene (OPP) film forming a substrate layer that is printable, and (3) a top layer comprising either a clear, ultraviolet (UV) cured coating (an over print varnish (OPV)) or an oriented polypropylene film. The oriented polypropylene film used for the substrate layer has good print registration and excellent grain capture when embossed and is comparable in cost, if not less expensive, than standard Type II PVC film. The oriented polypropylene film used as a substrate in the laminate wallcovering of the present invention has been specially engineered to accept printing inks and adhesives for laminating purposes. 
     It is thus an object of the present invention to provide a polypropylene laminate wallcovering that has the look, feel, and performance characteristics of conventional PVC wallcoverings without the environmental drawbacks associated with PVC wallcoverings. The wallcovering, constructed in accordance with the present invention, also has a Class A flame rating. 
     Further objects, features and advantages will become apparent upon consideration of the following detailed description of the invention when taken in conjunction with the drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section view of the wallcovering in accordance with the present invention. 
         FIG. 2  is an exploded, cross-section view of the wallcovering in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning to  FIGS. 1 and 2 , a polypropylene laminate wallcovering  10  comprises a scrim backing layer  12 , a specially formulated, oriented polypropylene (OPP) film forming a substrate layer  14 , and a top layer  16  comprising either a UV cured, clear coating or a clear oriented polypropylene film. 
     The backing layer  12  of the laminate wallcovering  10  is a ‘scrim” or woven fabric. The backing layer  12  is conventional scrim fabric commonly used for wallcovering backing and is generally a 100% polyester, although polyester/cotton blends are commonly used as a backing for wallcoverings as well. Based on testing, the scrim construction that provided the best performance and finished weight was a scrim having 68 ends×38 picks. Lighter weight woven scrims can be utilized, depending on the finished weight that is required for the laminate wallcovering  10 . A range of woven scrim constructions and fiber combinations were tested in order to maximize the performance and weight of the finished laminate wallcovering  10 . Much of the tensile and tear performance of the laminate wallcovering  10  is predicated on the woven backing layer  12 , or scrim. Table 1 shows the range of wallcoverings tested. Ultimately, the 68×38 polyester scrim provided the best balance of weight, flexibility, performance, and cost, although the other scrims shown in Table 1 performed satisfactorily. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 Materials Tested: 
               
               
                   
               
            
           
           
               
               
            
               
                 A 
                 1.00 mil WHITE OPP (substrate layer 14) 
               
               
                 B 
                 2.20 mil WHITE OPP (substrate layer 14) 
               
               
                 C 
                 4.25 mil WHITE OPP (substrate layer 14) 
               
               
                 D 
                 8.00 mil WHITE OPP (substrate layer 14) 
               
               
                 E 
                 12.00 mil WHITE OPP (substrate layer 14) 
               
               
                 F(UV) 
                 0.35 mil CLEAR PROTECTIVE UV COATING (top layer 16) 
               
               
                 G(UV) 
                 0.50 mil CLEAR PROTECTIVE UV COATING (top layer 16) 
               
               
                 H(UV) 
                 0.60 mil CLEAR PROTECTIVE UV COATING (top layer 16) 
               
               
                 I(UV) 
                 1.30 mil CLEAR PROTECTIVE UV COATING (top layer 16) 
               
               
                 F(OPP) 
                 0.75 mil CLEAR PROTECTIVE OPP (top layer 16) 
               
               
                 G(OPP) 
                 2.20 mil CLEAR PROTECTIVE OPP (top layer 16) 
               
               
                 H(OPP) 
                 4.25 mil CLEAR PROTECTIVE OPP (top layer 16) 
               
               
                 I(OPP) 
                 7.00 mil CLEAR PROTECTIVE OPP (top layer 16) 
               
               
                 K 
                 68 × 38 Polyester Scrim (backing layer 12) 
               
               
                 L 
                 39 × 26 Polyester Scrim (backing layer 12) 
               
               
                 M 
                 54 × 42 Polyester/Cotton Scrim (backing layer 12) 
               
               
                   
               
            
           
           
               
            
               
                 Combinations Tested: 
               
            
           
           
               
               
               
            
               
                   
                 TOP LAYER 16 
                   
               
               
                 SUBSTRATE 
                 (UV COATING or OPP 
               
               
                 LAYER 14 
                 FILM) 
                 BACKING LAYER 12 
               
               
                 White OPP Layer 
                 Clear Protective Layer 
                 Woven Scrim Layer 
               
               
                   
               
               
                 A 
                 F(UV) or F(OPP) 
                 K-L-M 
               
               
                 A 
                 G(UV) or G(OPP) 
                 K-L-M 
               
               
                 A 
                 H(UV) or H(OPP) 
                 K-L-M 
               
               
                 A 
                 I(UV) or I(OPP) 
                 K-L-M 
               
               
                 B 
                 F(UV) or F(OPP) 
                 K-L-M 
               
               
                 B 
                 G(UV) or G(OPP) 
                 K-L-M 
               
               
                 B 
                 H(UV) or H(OPP) 
                 K-L-M 
               
               
                 B 
                 I(UV) or I(OPP) 
                 K-L-M 
               
               
                 C 
                 F(UV) or F(OPP) 
                 K-L-M 
               
               
                 C 
                 G(UV) or G(OPP) 
                 K-L-M 
               
               
                 C 
                 H(UV) or H(OPP) 
                 K-L-M 
               
               
                 C 
                 I(UV) or I(OPP) 
                 K-L-M 
               
               
                 D 
                 F(UV) or F(OPP) 
                 K-L-M 
               
               
                 D 
                 G(UV) or G(OPP) 
                 K-L-M 
               
               
                 D 
                 H(UV) or H(OPP) 
                 K-L-M 
               
               
                 D 
                 I(UV) or I(OPP) 
                 K-L-M 
               
               
                 E 
                 F(UV) or F(OPP) 
                 K-L-M 
               
               
                 E 
                 G(UV) or G(OPP) 
                 K-L-M 
               
               
                 E 
                 H(UV) or H(OPP) 
                 K-L-M 
               
               
                 E 
                 I(UV) or I(OPP) 
                 K-L-M 
               
               
                   
               
            
           
         
       
     
     The substrate layer  14  of the laminate wallcovering  10  is a white oriented polypropylene film, ranging in thickness from 1.00 mil to 12.00 mil with a preferred thickness of 8.00 mil. Oriented polypropylene film inherently repels foreign matter, like dirt and stains. This repellency characteristic of oriented polypropylene film normally includes printing inks. The oriented polypropylene film of the present invention is specially formulated to bond permanently with a variety of printing media (inks)  18  and the adhesives used for lamination. Both the face and back surfaces of the oriented polypropylene film forming substrate layer  14  are given a functional treatment to specifically capture and hold ink and adhesive. The process used to enhance the bonding property of the oriented polypropylene film of substrate layer  14  involves both an oxidative treatment and a surface primer applied to the film after the extrusion stage. This process alters the dyne level of the surface of the oriented polypropylene film, allowing inks and adhesive to bond permanently to the treated oriented polypropylene film. The oriented polypropylene film used in connection with the present invention as the substrate layer  14  also has excellent grain capture when embossed. 
     In connection with the present invention, substrate layers  14  having the following thicknesses were tested: 1.0 mil, 2.20 mil, 4.25 mil, 8.00 mil and 12.00 mil thickness. (See Table 1.) The lesser thicknesses of the oriented polypropylene films for the substrate layer  14  exhibited somewhat reduced “hiding” properties when installed and somewhat reduced resistance to impact. The higher thicknesses (12.00 mil) of the oriented polypropylene film exhibited increased stiffness requiring the wallcovering installer to “fight” the wallcovering to get it on the wall. The 8.00 mil thick oriented polypropylene film provided good performance while maintaining an acceptable hand, enabling the paper hanger to install the wallcovering with ease. The thicknesses for the oriented polypropylene film for the substrate layer  14  shown in Table 1, however, are all considered within the scope of the invention. The source for the oriented polypropylene film used for the substrate layer  14  is Applied Extrusion Technologies, Inc. (AET), located at 115 Read&#39;s Way, New Castle, Del. 19720. AET is the only independent global supplier dedicated solely to the manufacturing of oriented polypropylene films, and it currently provides 25% of North America&#39;s oriented polypropylene film needs. The specific AET 8.00 mil film is sold by AET under the product designation 8SPM. 
     The top layer  16  of the wallcovering  10  is a 0.35 mil to 1.30 mil ultra violet (UV) cured clear coating with a matte or gloss outer finish. This UV clear coating has been formulated by Environmental Inks &amp; Coatings, 31 Quality Products Road, Morganton, N.C. 28655 and sold under the product designations Matte UF 170689, UV 175 Matte OPV and Gloss UF 170690, UV 80gloss OPV. This UV clear coating has been formulated to provide chemical and abrasion resistance that exceeds standard Type II PVC wallcovering finishes currently being offered in the market. This coating also provides dry erase properties. 
     A range of coating weights for the UV cured top layer  16  were tested on different weights of the oriented polypropylene film substrate layer  14  as noted in Table 1. The same qualifications (performance, hand, and cost) were used to determine that the UV coating at the 0.35 mil thickness, applied with a 200 anilox cylinder provided a good balance of performance, hand, and value. Suitable performance, however, was achieved with coating weights from 0.35 mil to 1.30 mil. 
     In an alternative embodiment, the top layer  16  of the wallcovering  10  is a 0.75 mil-7.00 mil clear oriented polypropylene film with a matte outer finish. The oriented polypropylene film used for the top layer  16  protects the finished laminate wallcovering  10 . The oriented polypropylene film for the top layer  16  is supplied by AET under the designation RLS Mat XZ811. The back side of the clear oriented polypropylene film top layer  16 , facing the substrate layer  14 , has been given an oxidative treatment to enhance the oriented polypropylene film&#39;s acceptance of adhesives used for laminating purposes. The face (matte) side of the oriented polypropylene film has been treated with a blend of polymers that create a release property. 
     A range of weights for the oriented polypropylene film top layer  16  were tested on different weights of the oriented polypropylene film substrate layer  14  as noted in Table 1. The same qualifications (performance, hand, and cost) were used to determine that the 0.75 mil oriented polypropylene film provided a good balance of performance, hand, and value although the other thicknesses, 0.075 mil to 7.00 mil, provided adequate performance. 
     In order to construct the polypropylene laminate wallcovering  10 , the oriented polypropylene film substrate layer  14  is first printed on its outer surface with the desired ink pattern  18 . Where the oriented polypropylene film is used for the top layer  16  instead of the UV clear coating, the desired pattern can be printed on the inner surface of the clear, oriented polypropylene film top layer  16 . Better printing results, however, were achieved by printing the oriented polypropylene film substrate layer  14  as compared to printing of the oriented polypropylene film top layer  16 . The oriented polypropylene film substrate layer  14  can be printed on existing gravure printing equipment using standard water based ink systems, or digitally printed using UV cured ink systems, and laminate wallcovering  10  can be embossed on equipment like that currently used for standard PVC wallcovering production. 
     Once the polypropylene film substrate layer  14  has been printed, the UV cured clear coating is applied over the printed oriented polypropylene film substrate layer  14 . The scrim layer  12  is then laminated by means of heat and/or adhesive to the oriented polypropylene film substrate layer  14 . After the layers been laminated, the entire laminate wallcovering  10 , now consisting of a) the woven scrim backing layer  12 , b) the printed polypropylene film substrate layer  14 , and c) the UV cured clear coating top layer  16 , is run through an embossing roller imparting the pattern of choice to the top surface of the laminate wallcovering  10 . Because polypropylene has a relatively low melt temperature, a balance of heat and pressure is required in the embossing process to maximize the grain capture. Although not considered critical to the present invention, the good embossing results were achieved within the following ranges of temperature, speed, and pressure: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Web temperature: 
                 240 F.-250 F. 
               
               
                   
                 Line Speed: 
                 35-40 yds/minute 
               
               
                   
                 Pressure: 
                 2800-3100 PSI 
               
               
                   
                   
               
            
           
         
       
     
     With the alternative embodiment using the clear oriented polypropylene film for the top layer  16 , the clear oriented polypropylene film top layer  16  is wet laminated to the printed polypropylene film substrate layer  14 . The scrim layer  12  is then laminated by means of heat and/or adhesive to the oriented polypropylene film substrate layer  14 . After the layers been laminated, the entire laminate wallcovering  10 , now consisting of a) the woven scrim backing layer  12 , b) the printed polypropylene film substrate layer  14 , and c) the clear oriented polypropylene film top layer  16 , is run through an embossing roller imparting the pattern of choice to the top surface of the laminate wallcovering  10 . 
     With either embodiment of top layer  16 , the finished laminate wallcovering  10  has the appearance and hand of standard Type II PVC wallcovering, and can be produced at a lower cost than the PVC wallcovering. The performance properties of the polypropylene laminate wallcovering  10  exceed those of the PVC based product, in particular the abrasion and stain resistance properties. A substantial advantage of the polypropylene laminate wallcovering  10  is the energy and labor savings compared to that required for production of conventional PVC wallcoverings. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principals and applications of the present invention. Accordingly, while the invention has been described with reference to the structures and processes disclosed, it is not confined to the details set forth, but is intended to cover such modifications or changes as may fall within the scope of the following claims.