Abstract:
A process for the manufacturing of plastisol based synthetic coverings (e.g. floor or wall coverings) having improved resistance to soiling; and the product produced from the process is presented. The synthetic covering utilizes a wear layer formed from a mixture comprising at least one silicone polymer and a cross-linking agent. Preferably, this mixture also includes a catalyst. The mixture is deposited onto a conventional support as a wear layer. The silicone polymer is then cross-linked and the wear layer undergoes pre-gelling and gelling.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a process for the manufacture of plastisol based synthetic coverings (e.g., floor or wall coverings) having improved resistance to soiling. This invention also relates to a floor or wall covering obtained by means of this process. 
     One of the well known difficulties encountered in the use of plastisol based synthetic coverings, particularly plastisol based floor coverings, comprises soiling, particularly soiling by shoe heels. It is known that soiling can be reduced by increasing the slipperiness of the covering, thus avoiding heating caused by the friction of a heel on the covering. 
     An increase of slipperiness may be achieved by adding to the surface coating plastisol a silicone polymer, preferably a silicone polymer incompatible with the surface plastisol. This incompatibility is for the purpose of promoting migration of the silicone to the surface. However, the slipperiness effect quickly disappears during successive washings and/or cleanings of the covering by means of the washing and/or cleaning agents normally used. 
     SUMMARY OF THE INVENTION 
     The above-discussed and other problems and deficiencies of the prior art are overcome or alleviated by the process for the manufacture of plastisol based floor or wall coverings of the present invention comprising a wear layer having improved resistance to soiling, particularly to soiling by shoe heels. The present invention also provides a synthetic covering having a plastisol based wear layer of a novel type. This novel wear layer is formed from a mixture comprising at least one silicone polymer and a cross-linking agent. Preferably, this mixture also includes a catalyst. The mixture is deposited onto a conventional support as a wear layer. The silicone polymer is then cross-linked and the wear layer undergoes pre-gelling and gelling. 
     An important feature of the synthetic coverings of the present invention is the provision of a plastisol based wear layer possessing improved resistance to soiling, particularly to soiling due to shoe heels, even after repeated washings and/or cleanings. 
     The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In accordance with a first embodiment of the present invention, a process for the manufacture of plastisol based floor or wall coverings having improved resistance to soiling comprises the formation of a plastisol mixture containing a silicone polymer, a cross-linking agent, and optionally a catalyst. Next, this mixture is deposited on a decorative support to serve as a wear layer. The wear layer is then pre-gelled and gelled. The silicone polymer is preferably incompatible with the wear layer plastisol. 
     The cross-linking of the silicone polymer is preferably effected at the time as the gelling of the wear layer plastisol. Migration of the silicone polymer to the surface is permitted by control of the cross-linking of the polymer, which is preferably effected at the same time as the gelling of the plastisol, this being achieved through the appropriate choice of the catalyst and cross-linking agent pair; and by suitable proportioning of these two components. 
     In a particularly preferred emboiment of the present invention, the silicone polymer comprises a silicone gum containing --OH functional groups. The cross-linking agent may consist of a fluid based on silicone containing reactive --H groups. However, the cross-linking agent may also consist of an optionally blocked type isocyanate. When a blocked type isocyanate is used, the system and the liberation of --NCO groups permitting the cross-linking of the silicone polymer containing --OH groups is initiated at a relatively high temperature (which, however, is lower than the maximum working temperature, for example 130° C.). The surface migration of the silicone polymers is thus promoted. The utilization of a system comprising a silicone polymer and a blocked type isocyanate makes it possible to prepare a stable system which can be stored for a long time. 
     It is advantageous, in order to obtain a particularly preferable result, to mix from 0.1 to 10% of silicone polymer containing OH groups and permitting cross-linking in the wear layer plastisol. The ratio of silicone to cross-linking agent is between 10:10 and 10:0.1. Depending on the type of catalyst used (for example a tin or barium-zinc catalyst and for example a PVC stabilizer), the ratio of catalyst to silicone may be between 0.1 and 0.001. 
     According to another feature of the present invention, it is also contemplated that the floor or wall covering may include a decorative support obtained by processes known per se, covered with a wear layer based on a plastisol containing a cross-linked silicone polymer in accordance with the process of the present invention. 
     In order to improve still further the effect obtained, micronized polyethylene wax may be added to the plastisol mixture intended to form the wear layer. 
     It is also preferable for the cross-linked silicone polymer to have a high density at the surface then in the heart of the wear layer. 
    
    
     The following are non-limiting examples describing the present invention: 
     EXAMPLE 1 
     The cross-linking of the silicone was studied under the following conditions: 
     
         ______________________________________SILICONE    10     10    10  10   10  10  10  10   10CROSS-LINKINGAGENT       7      7     3   3    3   3   3   3    3Sn CATA-LYST        1      --    --  1    0.5 0.1 0.5 0.01 --(DOW CORNINGXY 176)Ba--Zn CA-TALYST      --     --    --  --   --  --  --  --   1______________________________________ 
    
     The silicone polymer used in a Dow Corning gum of the type Q 2 32 38 (trade name) containing --OH functional groups. The cross-linking agent is Dow Corning 1107 Fluid, which contains silicone containing --H groups. 
     The degree of cross-linking corresponding to temperatures of 150° C. and 190° C. were observed as follows: 
     
         ______________________________________150°1&#39;     3      0    0    3   2    1    1    1   02&#39;     3      0    0    3   3    2    1    1   13&#39;     3      0    0    3   3    3    2    1   1190°1&#39;     3      0    0    3   3    3    2    1   12&#39;     3      0    0    3   3    3    3    2   23&#39;     3      0    0    3   3    3    3    2   2______________________________________ 0 = zero crosslinking 1 = start of crosslinking 2 = middle of crosslinking 3 = complete crosslinking 
    
     Resistance to soiling by shoe heels with respect to washing and/or cleaning cycles, and also the unexpected effect of cross-linking are shown in the following table for various compositions used. 
     
         ______________________________________       T     1      2       3     4______________________________________PVC PLASTISOL 100     100    100   100   100SILICONE      --      3.14   1.85  2.41  2.41CROSS-LINKINGAGENT         --      --     1.29  0.72  0.72CATALYST (Sn) --      --     --    0.013 0.002IMMEDIATESOILING       3       0      0     0     0SOILING AFTER100 CLEANINGCYCLES (AJAX ®)         5       3      2     2     1NUMBER OFCYCLES NEEDEDTO ELIMINATESOILING       8       5      3     3     1______________________________________ 0 = no soiling 5  heavy soiling 
    
     Independent of the cleaning, a lack of resistance to soiling was found for the control (T). 
     The utilization of a non-cross-linked silicon gum (1) according to a conventional process avoids immediate soiling, but does not prevent relatively considerable soiling after a few cleaning cycles. This is due to the fact that the silicone is not cross-linked and is contained in an emulsifiable system washable with cleaning water. 
     Tests (2), (3) and (4) show that through the use of a cross-linking agent for the silicone polymer, the resistance to soiling is substantially improved, even after 100 washing cycles. 
     Particularly advantageous results are obtained in Test No. 4 because of the use of a catalytic system which adapts the cross-linking so as to permit the migration to the surface of a silicone polymer which is incompatible with the plastisol in which it is mixed. 
     EXAMPLE 2 
     In a second example, the cross-linking agent used was a polyaliphatic polyisocyanate in a solution containing about 8% of free isocyanate. Through the use of this cross-linking agent, the storability of the resulting product is improved and the migration of the silicones to the surface is promoted (in view of the fact that the liberation of the blocked --NCO groups starts only at a temperature on the order of 130° C.). 
     
         ______________________________________The composition used is:______________________________________PVC plastisol        100Silicone polymer     1.25(Q 2 32 38 Dow Corning)Micronized polyethylene wax                2Cross-Linking agent: HULS                0.35IPDI B 1370 (commercial name)Tin catalyst         0.001(Dibutyltin dilaurate).______________________________________ 
    
     The above plastisol mixture can be stored for a long time without undergoing cross-linking of the silicone system which is a particularly advantageous feature. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.