Patent Publication Number: US-4095013-A

Title: Reusable solar control film and method of making

Description:
BACKGROUND OF THE INVENTION 
     In one respect, this invention is related to solar control film adapted for bonding to windowpanes. In another aspect, the invention relates to a method of manufacturing solar control films. 
     It has long been recognized that a transparent or translucent film could be coated with a thin transparent-reflective metallic layer and used to control the solar radiation entering a room. For example, Lion U.S. Pat. No. 2,774,421 discloses roller-mounted window shades in which a transparent or translucent film is coated with a thin layer of vapor-deposited aluminum which may in turn be overcoated with a protective lacquer or varnish. While effective to a degree, Lion&#39;s window shade is spaced from the inner surface of a windowpane, thus permitting a considerable amount of heat to be admitted into the room. 
     Antonson et al U.S. Pat. No. 3,290,203 discloses a solar control film which, like Lion&#39;s, utilizes a transparent film which is metallized with a transparent-reflective aluminum layer on one face and provided with a protective overcoating. In the Antonson et al product, however, a water-activatible adhesive is employed to bond the solar control film directly to the inner surface of a windowpane, thereby greatly reducing the amount of solar energy which would otherwise enter the room, be absorbed by objects therein, and be re-emitted as heat. Another type of water-activated adhesive is shown in Theissen U.S. Pat. No. 3,681,179, where a normally tacky and pressure-sensitive adhesive is coated over the film and temporarily inacitivated by an overcoating of a water-soluble material. In both the Antonson et al and Theissen products, water is applied to the exposed coated surface, the windowpane (or both), the film placed in contact with the window and slid into position, and a squeegee thereafter being used to ensure intimate contact between the film and the windowpane. While both the Antonson et al and Theissen products have enjoyed widespread commercial success, there has been a desire for a solar control film product which could be utilized during the hot summer months and removed during the cold winter months. Although both the Antonson et al and Theissen solar control films can be removed, the process of removal is likely to destroy or distort them so that they cannot thereafter be easily reapplied. 
     For several years, various types of removable and replaceable solar control film have been available in the marketplace. In one embodiment, the solar control film has been simply a metallized biaxially oriented polyethylene terephthalate film in which the metallized layer is overcoated with a &#34;cling&#34; adhesive consisting essentially of a solvent-soluble polyester adhesive. In another embodiment, the &#34;cling&#34; adhesive is a plasticized vinyl film laminated to the structure by means of the soluble polyester adhesive. In the latter product, the structure adheres to a windowpane because of the plasticizer which exudes from the vinyl polymer and forms almost a monomolecular layer between the solar control film and the windowpane. While both types of product are easily applied and can be removed after being adhered to a windowpane for a comparatively short period of time, long-term exposure results in an adhesion buildup such that the solar control film is prone to distortion upon removal, effectively preventing it from being re-applied. Additionally, laminated products of the second type require both a coating and a laminating step, increasing the cost of manufacture. 
     SUMMARY OF THE INVENTION 
     The present invention provides a solar control film which is not tacky, which can be applied to a windowpane and allowed to remain in place for several months, removed at the end of the extended exposure to the rays of the sun without distortion, rolled on itself and stored until the next summer season, and again applied to the windowpane. Solar control films of the invention can be repeatedly applied, removed, and reapplied in this manner. 
     The solar control film of the invention is comparatively simple and inexpensive and is superior to the prior art solar control films incorporating plasticized vinyl films in that it does not increase in adhesion, even when exposed to temperatures on the order of 65° C for extended periods of time. 
     In accordance with the invention, a solar control film is provided with a thin, transparent &#34;cling&#34; adhesive stratum, or layer, of plasticized resin composition. This composition consists essentially of 100 parts by weight of plasticized solvent-soluble copolymer of vinyl monomers, consisting essentially of either (a) 80-97 parts by weight vinyl chloride and 3-20 parts by weight of monomers selected from the group consisting of vinyl acetate, vinyl alcohol and dibasic acid or (b) vinylidene chloride:acrylonitrile copolymer. The vinyl chloride copolymers are characterized by solubility of 20 parts by weight in 100 parts by weight of a 50:50 toluene:methylethyl ketone blend at room temperature, while the vinylidene chloride copolymers are similarly characterized by solubility of 20 parts by weight in 100 parts by weight of a 30:70 toluene:methylethyl ketone blend at room temperature. The vinyl copolymer may also contain small amounts of dibasic acid monomer. 
     In addition to the vinyl or vinylidene chloride copolymer, the coating contains 1-5 parts by weight of at least 1 lubricating, chlorine-scavenging light stabilizer for vinyl resins. This stabilizer is a liquid soap selected from the class consisting of (a) soaps having one or more metallic cations selected from the group consisting essentially of barium, cadmium and zinc and (b) tin soaps. 
     The &#34;cling&#34; adhesive layer also contains 5-100 parts by weight of at least one plasticizer for vinyl resin. 
     An especially important component of the &#34;cling&#34; adhesive layer is 5-200 parts by weight of at least one tack-controlling, adhesion buildup-inhibiting polymeric modifier selected from the class consisting of polymethylmethacrylate, polyethylmethacrylate, polyisobutylmethacrylate, poly-n-butylmethacrylate, poly-n-butylmethylmethacrylate, and n-butylmethacrylate:isobutylmethacrylate copolymer. 
     In accordance with the method of the invention, a reusable solar control sheet material is made by a process comprising the steps of (a) providing a self-supporting transparent film having a transparent-reflective layer of metal bonded to one face thereof, a layer of polymeric material protectively overlying the metal coat, (b) providing an organic solvent solution of the &#34;cling&#34; adhesive components mentioned in the preceding paragraphs, (c) applying a thin coating of the solution over the layer of protective polymeric material and (d) evaporating the solvent. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The single FIGURE of the drawing depicts a crosssectional view of a solar control product made in accordance with the invention. 
    
    
     DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS 
     As an aid to understanding the invention, a series of tabulated examples will be shown below. In each of these examples, a 2-mil (50-micron) biaxially oriented polyethylene terephthalate film was vapor-coated with aluminum to achieve a visible light transmission of approximately 20%. Over the aluminum vapor coating was then knife-coated through a 2-mil (50-micron) opening, a solution of the following components: 
     
         ______________________________________                                    
COMPONENT            PARTS BY WEIGHT                                      
______________________________________                                    
Soluble polyester resin                                                   
(&#34;Vitel&#34; PE222, commercially                                              
available from Goodyear                                                   
Chemical Company)    26.95                                                
Ultraviolet light absorber                                                
(&#34;Cyasorb&#34; U.V. 24, commer-                                               
cially available from                                                     
American Cyanamid Company)                                                
                     0.14                                                 
Methylethyl ketone   37.00                                                
Toluene              35.91                                                
                     100.00                                               
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     The coating was dried by exposing it for 10 minutes to the radiation from a 230-watt infrared lamp at a distance of 8 inches (20 centimeters), leaving a dried coating which weighed approximately 5.5 grams/m 2  and had a thickness of approximately 0.15 mil (4microns). The purpose of this coating is to provide a protective layer over the aluminum coating and inhibit its oxidation, all as is disclosed more fully in the aforementioned Antonson et al U.S. Pat. No. 3,290,203. 
     In each of the examples (unless otherwise noted), the following &#34;cling&#34; adhesive solution was then coated over the polyester protective coating: 
     
         ______________________________________                                    
COMPONENT            PARTS BY WEIGHT                                      
______________________________________                                    
Vinyl or vinylidene chloride                                              
copolymer            100                                                  
Plasticizer for vinyl resins                                              
                     as shown                                             
Tack-controlling, adhesion                                                
buildup-inhibiting polymeric                                              
modifier             as shown                                             
Stabilizer for vinyl resins                                               
                     as shown                                             
Solvent (1:1 toluene:methyl-                                              
ethyl ketone blend for vinyl                                              
chloride copolymer or 3:7                                                 
toluene:methylethyl ketone                                                
blend for vinylidene chloride                                             
copolymer)           500                                                  
______________________________________                                    
 
    
     The adhesive solution was applied with a knife coater having a 2-mil (50-micron) opening and the solvent evaporated to leave a dry coating which weighed approximately 5.5 grams/m 2  and had a thickness of about 0.15 mil (4 microns). 
     Test Procedure 
     Each of the tabulated examples was tested as follows: 
     Adhesion Buildup. 
     A sheet of solar control film approximately 6 cm × 18 cm was applied to cleaned, moistened plate glass and a squeegee used to remove excess water. The glass-solar control film laminate was then dried, film-side up, for at least 4 days at approximately 20° C, 20% relative humidity. Adhesion of the solar control film to the glass was measured by slitting a portion of the film between razor blades spaced 1 inch (about 2.5 cm) apart, doubling the 1-inch (2.5 cm) strip of film back of itself at 180°, and measuring the force required to remove it at a rate of 4 cm/second. 
     A second glass-solar control film laminate was prepared and dried in the same manner as the first and thereafter heated for 16 hours at 65° C and 20% relative humidity. Adhesion of the film to glass was then measured in the same way as for the first sample. (It has been found empirically that this heating process subjects the solar control film to conditions similar to those encountered inside a recreational vehicle parked in summer sunshine.) 
     Peel Resistance. 
     To measure the ability of the solar control film of the invention to cling to the surface of glass to which it is applied and resist being inadvertently peeled therefrom -- or even falling off the windowpane shortly after being applied thereto -- an additional test was run on the film of some examples. In this test, a 2-inch × 7-inch (51 mm × 178 mm) sample of the product was applied to 3/8-inch (9.5 mm) plate glass and allowed to dry, all as described above. A 1-inch (2.5 cm) strip of strongly adherent normally tacky and pressure-sensitive adhesive tape was then adhered to the exposed surface of the solar control film, the strip extending across the 2-inch (51-mm) dimension of the solar control film parallel to and 1 inch (2.5 cm) from one end. A paper clip was inserted over the top of the adhesive tape so that it extended between the tape and the solar control film. To the opposite end of the paper clip was then attached a 500-gram weight. The glass-solar control film laminate was then positioned so that it was mounted at 30° to the vertical, with the solar control film being on the upper surface and the adhesive tape at the upper end. The time required for the solar control film to pull away from the glass was then determined. 
     Components of Cling Adhesive Composition 
     To simplify the presentation of examples in tabular form, individual components of the &#34;cling&#34; adhesive are designated by abbreviations; the component indicated by each abbreviation is shown below: 
     
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VINYL CHLORIDE COPOLYMER                                                  
                        Intrinsic                                         
Weight % of Comonomers  viscosity in                                      
Abbrev- Vinyl    Vinyl            cyclohexanone                           
iation  Chloride Acetate  Other   at 20° C.                        
______________________________________                                    
VAGH    91       3        6       0.54                                    
                          (vinyl                                          
                          alcohol)                                        
VMCH    86       13       1       0.50                                    
                          (dibasic                                        
                          acid)                                           
VYHD    86       14       0       0.42                                    
VYHH    87       13       0       0.50                                    
VYLF    87       13       0       0.24                                    
VYNS    90       10       0       0.80                                    
VYNW    97       3        0       1.07                                    
______________________________________                                    
 
    
     
         ______________________________________                                    
VINYLIDENE CHLORIDE COPOLYMER                                             
Abbreviation                                                              
          Description                                                     
______________________________________                                    
F220      80:20 vinylidene chloride:acrylonitrile                         
          copolymer, a 20% methylethylketone solution                     
          having a Brookfield viscosity of about 80                       
          cps at 25° C., commercially available from               
          Dow Chemical Company under the trade desig-                     
          nation &#34;Saran&#34; F220                                             
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         ______________________________________                                    
PLASTICIZERS                                                              
Abbre-                                                                    
viation                                                                   
       Description                                                        
______________________________________                                    
A 562  Medium molecular weight polyester, formed by                       
       reacting approximately 2.1 mols adipic acid,                       
       1.1 mols propylene glycol, 1.5 moles 1,4-                          
       butanediol and 1.0 mole C-12 fatty acid, having                    
       a viscosity of approximately 15 stokes at                          
       about 25° C.; commercially available from                   
       Ashland Chemical Company under the trade                           
       designation &#34;Admex&#34; 562                                            
A761   Medium molecular weight polyester formed                           
       by reacting approximately 2.3 moles adipic                         
       acid, 0.8 mole phthalic acid, 2 moles pro-                         
       pylene glycol, 1.6 moles of 1,4-butanediol,                        
       and 1.0 mole C-12 fatty acid; commercially                         
       available from Ashland Chemical Company                            
       under the trade designation &#34;Admex&#34; 761                            
A770   Medium molecular weight polyester, having a                        
       viscosity of 38 stokes at 25° C.; commercially              
       available from Ashland Chemial Company under                       
       the trade designation &#34;Admex&#34; 770                                  
G-25   Sebacic acid:propylene glycol polyester,                           
       molcular weight about 8000, viscosity                              
       2200 poises at 25° C.; commercially avail-                  
       able from Rohm and Haas Company under the                          
       trade designation &#34;Paraplex&#34; G-25                                  
G-40   Adipic acid:propylene glycol polyester                             
       plasticizer, molecular weight about 6000,                          
       viscosity 2000 poises at 25° C.; commercially               
       available from Rohm and Haas Company under                         
       the trade designation &#34;Paraplex&#34; G-40                              
G-54   Aliphatic polyester plasticizer, molecular                         
       weight about 3300, viscosity 53 poises at                          
       25° C.; commercially available from Rohm                    
       and Haas Company under the trade designation                       
       &#34;Paraplex&#34; G-54                                                    
G-62   Epoxidized soybean oil, molecular weight                           
       about 1000, viscosity 3.4 poises at 25° C.;                 
       commercially available from Rohm and Haas                          
       Company under the trade designation &#34;Para-                         
       plex&#34; G-62                                                         
P9750  Medium molcular weight polymeric plasticizer,                      
       typically having an acid volume of 1.9, a                          
       hydroxyl value of 19.0, a specific gravity                         
       of 1.06 at 25° C., and a viscosity at 100° F.        
       (38° C.) of 8.57 strokes; commercially avail-               
       able from Emery Industries, Inc. under the                         
       trade designation &#34;Plastolein&#34; 9750                                
S79TM  Trialkyl trimellitate (essentially linear                          
       7-9 carbon linear alcohol), molecular weight                       
       560, visocisty 5460 stokes at 25° C.; commer-               
       cially available from Monsanto Chemical Company                    
       under the trade designation &#34;Santicizer&#34;                           
       79-TM                                                              
S409   Medium molecular weight liquid aliphatic poly-                     
       ester having a specific gravity of 1.082-                          
       1.084 and viscosity of approximately 3.2                           
       stokes at 25° C.; commercially available from               
       Monsanto Chemical Company under the trade                          
       designation &#34;Santicizer&#34; 409 permanent                             
       plasticizer                                                        
S711   Liquid modified polyester formed by reacting                       
       phthalic acid with a combination of 7-, 9-,                        
       and 11-carbon alcohols, having a viscosity                         
       of 44 centistokes at 25° C.; commercially                   
       available from Monsanto Chemical Company                           
       under the trade designation &#34;Santicizer&#34;                           
       711                                                                
V7191  Epoxidized triglyceride containing 9.0-                            
       9.1% oxirane oxygen, having a specific                             
       gravity of 1.02 at 25° C. and a viscosity                   
       of 6.5-8.5 stokes; commercially available                          
       from Viking Chemical Company under the trade                       
       designation &#34;Vikoflex&#34; 7191                                        
X-100  Polyester formed from sebacic acid and, it                         
       is believed, propylene glycol; commercially                        
       available from Rohm and Haas Company under                         
       the trade designation &#34;Paraplex&#34; X-100                             
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         ______________________________________                                    
STABILIZER FOR VINYL RESINS                                               
Abbre-                                                                    
viation                                                                   
       Description                                                        
______________________________________                                    
180    Liquid barium-cadmium stabilizer having a                          
       specific gravity of 1.022 at 25° C.; commer-                
       cially available from Argus Chemical Corp-                         
       oration under the trade designation &#34;Mark 180&#34;                     
462    Liquid barium-cadmium composition having a                         
       specific gravity of 1.033 at 25° C.; commer-                
       cially available from Argus Chemical Corp-                         
       oration under the trade designation &#34;Mark 462&#34;                     
462A   Liquid barium-cadmium-zinc stabilizer con-                         
       taining low zinc level, having a specific                          
       gravity of 0.988 at 25° C.; commercially avail-             
       able from Argus Chemical Corporation under                         
       the trade designation &#34;Mark 462A&#34;                                  
462B   Liquid barium-cadmium-zinc stabilizer con-                         
       taining medium zinc level, having a specific                       
       gravity of 0.993 at 25° C.; commercially avail-             
       able from Argus Chemical Corporation under                         
       the trade designation &#34;Mark 462B&#34;                                  
462C   Liquid barium-cadmium-zinc stabilizer con-                         
       taining high zinc level, having the specific                       
       gravity of 0.984 at 25° C.; commercially avail-             
       able from Argus Chemical Corporation under                         
       the trade designation &#34;Mark 462C&#34;                                  
1414A  Organotin compound, having a specific gravity                      
       of 1.208 at 25° C.; commercially available                  
       from Argus Chemical Corporation under the                          
       trade designation &#34;Mark 1414A&#34;                                     
A-101  40% methylethyl ketone solution of polymethyl-                     
       methacrylate, a 35% solids solution having a                       
       Brookfield viscosity in the range of 700-1400                      
       cps at 25° C., commercially available from Rohm             
       and Haas Company under the trade designation                       
       &#34;Acryloid&#34; A-101                                                   
B-66   40% toluene solution of 1:1 n-butylmethacrylate:                   
       methylmethacrylate, having a Brookfield vis-                       
       cosity of 235-325 cps at 25° C.; commercially               
       available from Rohm and Haas Company under the                     
       trade designation &#34;Acryloid&#34; B-66                                  
DINP   Diisononylphthalate                                                
DMP    Dimethylphthalate                                                  
DOP    Dioctylphthalate                                                   
DOA    Dioctyladipate                                                     
E-2041 Polymethylmethacrylate having a typical inherent                   
       viscosity of 1.20; commercially available from                     
       E. I. Du Pont de Nemours &amp; Company under the                       
       trade designation &#34;Elvacite&#34; 2041                                  
E-2043 Polyethylmethacrylate having a typical inherent                    
       viscosity of 0.20, commercially available from                     
       E. I. Du Pont de Nemours &amp; Company under the                       
       trade designation &#34;Elvacite&#34; 2043                                  
E-2044 High molecular weight poly-n-butylmethacrylate                     
       having a typical inherent viscosity of 0.53;                       
       commercially available from E. I. Du Pont de                       
       Nemours &amp; Company under the trade designation                      
       &#34;Elvacite&#34; 2044                                                    
E-2045 High molecular weight polyisobutylmethacrylate                     
       having a typical inherent viscosity of 0.66;                       
       commercially available from E. I. Du Pont de                       
       Nemours &amp; Company under the trade designation                      
       &#34;Elvacite&#34; 2045                                                    
E-2046 1:1 (mole ratio) n-butylmethacrylate:isobutyl-                     
       methacrylate having a typical inherent viscosity                   
       of 0.61; commercially available from E. I. Du                      
       Pont de Nemours &amp; Company under the trade desig-                   
       nation &#34;Elvacite&#34; 2046                                             
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     In the following examples, all parts are by weight. 
     EXAMPLES 1-10 
     Vinyl Copolymer 
     These examples all incorporate 100 parts of vinyl polymer, 40 parts G-40 plasticizer, 5 parts G-62 plasticizer, 2 parts 462 stabilizer and 25 parts A-101 modifier. Only the type of vinyl copolymer is varied. 
     
         ______________________________________                                    
             Adhesion                                                     
             g/cm, after Time to fail in                                  
             conditioning                                                 
                         cling test, hours at                             
Vinyl        at          indicated temperature                            
Ex.  Copolymer   20° C                                             
                         65° C                                     
                               4° C                                
                                     21° C                         
                                           49° C                   
______________________________________                                    
--               2       40                                               
Comparison example                                                        
based on prior art                                                        
commercial product                                                        
of polyvinyl chlor-                                                       
ide plasticized                                                           
with a X-100 and lami-                                                    
nated to metallized                                                       
polyester film                                                            
             2       80       2      1    2                               
1    VYHH        2       10    120   &gt;120  168                            
It will be observed that the commercial prior art product                 
displays the simultaneous disadvantages of (1) being                      
excessively difficult to remove from a windowpane after                   
exposure to high temperatures and (2) perversely failing                  
to adhere as firmly to a windowpane during normal use -conditions as      
would be desired.                                                         
1a*  VYHH        2       2                                                
2    VYNS        4       14                                               
3    VYNW        2       40                                               
4    VYLF        10      12                                               
5    VYHD        10      14                                               
6    1:1         6       20                                               
     VYHH:VYNS                                                            
7    1:1         2       20                                               
     VYHH:VAGH                                                            
8    1:1         6       20                                               
     VYHH:VYNS                                                            
9    1:1         2       14                                               
     VYHH:VYNW                                                            
10   1:1         2       20                                               
     VYHH:VAGH                                                            
______________________________________                                    
  *Contains 0.5 pats 2,2&#39;,4,4&#39; tetrahydroxybenzophenone, a UV absorber    
 which is commonly used in compositions based on polyvinyl chloride.      
 
    
     EXAMPLES 11 and 12 
     Vinylidene Chloride Copolymer 
     These examples incorporate 100 parts F220, 40 parts G-40 plasticizer, 5 parts G-62 plasticizer, 2 parts 462 stabilizer and the indicated amounts of A-101 modifier. 
     
         ______________________________________                                    
                     adhesion, g/cm,                                      
                     after                                                
       Parts A-10    conditioning at                                      
Example  Modifier        20° C.                                    
                                   65° C.                          
______________________________________                                    
11       25              4         20                                     
12       100             8         20                                     
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     EXAMPLES 13 - 37 
     Variations in plasticizer for vinyl resins 
     Each composition listed below is identical to that of Example 1 except for (a) the use of a different plasticizer system and (b) variations in the amount of detackifier. 
     
         ______________________________________                                    
               Parts    Adhesion, g/cm,                                   
Plasticizer    A-101    after conditioning at                             
Example                                                                   
       Type    Parts   modifier                                           
                              20° C.                               
                                      65° C.                       
______________________________________                                    
13     P9750   40                                                         
       G-62    5       25     8       20                                  
14     A770    40                                                         
       G-62    5       25     8       20                                  
15     V7191   40                                                         
       G-62    5       25     2       40                                  
16     G-25    40                                                         
       G-62    5       25     6       &gt;100                                
17     G-25    40                                                         
       G-62    5       100    2       10                                  
18     DOP     40                                                         
       G-62    5       25     10      100                                 
19     DOP     40                                                         
       G-62    5       100    8       8                                   
20     A562    40                                                         
       G-62    5       25     4       &gt;100                                
21     A562    40                                                         
       G-62    5       100    2       18                                  
22     S111    40                                                         
       G-62    5       25     30      &gt;100                                
23     S111    40                                                         
       G-62    5       100    4       6                                   
24     DIN     40                                                         
       G-62    5       25     10      &gt;100                                
25     DIN     40                                                         
       G-62    5       100    10      10                                  
26     S79TM   40                                                         
       G-62    5       25     2       &gt;100                                
27     S79TM   40                                                         
       G-62    5       100    2       4                                   
28     DMP     40                                                         
       G-62    5       25     2       &gt;100                                
29     DMP     40                                                         
       G-62    5       100    8       6                                   
30     G-62    40      25     2       10                                  
31     S409    40      25                                                 
       G-62    5              2       12                                  
32     G-54    40      25                                                 
       G-62    5              2       20                                  
33     DOA     40                                                         
       G-62    5       100    2       4                                   
34     A562    40                                                         
       G-62    5       100    2       18                                  
35     S111    40                                                         
       G-62    5       100    4       6                                   
36     A761    40                                                         
       G-62    5       100    2       8                                   
37     G-40    40                                                         
       V7191   5       100    20      40                                  
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     EXAMPLES 38 - 43 
     Stabilizer for Vinyl Resins 
     The following examples are all identical to Example 1 except for the use of a different stabilizer for the vinyl resins: In each example, however, the total amount of stabilizer employed was 2 parts, as in Example 1. 
     
         ______________________________________                                    
               Adhesion, g/cm,                                            
               after conditioning at                                      
Example Stablizer    20° C.                                        
                                 65° C.                            
______________________________________                                    
38      180          20          20                                       
39      462A         10          20                                       
40      462B         10          20                                       
41      462C         2           10                                       
42      1414A        2           30                                       
43      Equal amounts                                                     
        of 1414A &amp;                                                        
        462          2           10                                       
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     EXAMPLES 44 - 52 
     Variations in tack-controlling, adhesion buildup-inhibiting polymeric modifier 
     Each of the following examples is identical to Example 1 except for varying the type and amount of modifier. 
     
         ______________________________________                                    
                  Adhesion, g/cm,                                         
Modifier           after conditioning at                                  
Ex.  Type    Parts by Weight                                              
                          20° C.                                   
                                   65° C.                          
______________________________________                                    
44   E2041   40           2        8                                      
45   E2043   40           2        100                                    
46   E2043   60           2        8                                      
47   E2043   100          2        4                                      
48   E2044   40           2        20                                     
49   E2045   40           2        100                                    
50   E2045   60           2        2                                      
51   E2046   100          2        2                                      
52   B-66    50           2        20                                     
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     The examples set forth above, while numerous, do not purport to be exhaustive. It is believed, however, that they illustrate the types of variation which can be made in the &#34;cling&#34; adhesive coatings employed in the practice of the invention. Numerous other compositions can also be made to function effectively by making suitable adjustments in the ratios of individual components.