Abstract:
Methods for elastifying and extending polymers with EVA copolymers, PVC homopolymers or PVC copolymers in gel form are described. The elastified and extended polymers are useful as sealing materials, adhesives and sealants.

Description:
FIELD OF THE INVENTION 
     This invention relates to a method for elastifying and extending polymers with EVA copolymers, PVC or PVC copolymers in gel form and to the use of thusly produced compositions. 
     BACKGROUND OF THE INVENTION 
     Molding and joint sealing materials based on mixtures of acrylate copolymer dispersions with fillers, pigments and plasticizers have only minimal elastic properties, and the tackiness of the molding materials produced from these mixtures increases with increasing plasticizer fraction. Such molding and joint sealing materials are useful only for a total deformation of about 10%, so that they are unsuitable for sealing a large number of joints in building construction despite their advantageous price. 
     Furthermore, moisture-curing one-component molding and sealing materials based on MS polymers (from Kaneka) are known. These sealing materials contain as prepolymers the aforementioned MS polymers which are crosslinkable by atmospheric humidity and which are compounds having silyl end groups with at least one hydrolyzable substituent on the silicon atom. Such prepolymers and molding and sealing materials produced therefrom are known from DE-A-40 19 074 and DE-A-38 16 808. The latter specification describes molding and sealing materials produced from these MS polymers at length with reference to further publications. The disclosure content of the two aforementioned specifications is hereby incorporated in full by reference. 
     Molding and sealing materials based on MS polymers react with moisture from the air to form elastomers, the surface of which is very frequently highly tacky. Therefore, the use of such materials is not possible wherever soiling with dust takes place or is likely. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to reduce this surface tackiness of molding and sealing materials to such an extent that in the event of contact with dusts of various kinds permanent soiling can be ruled out. 
     The invention provides the achievement of this object which is discernible in the claims. It consists essentially in adding to the aforementioned molding and sealing materials a gel based on an ethylene-vinyl acetate copolymer (EVA), a polyvinyl chloride homopolymer (PVC) or a vinyl chloride/vinyl acetate copolymer (PVC copolymer and a lasticizer and wax. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The use of vinyl acetate homo- and/or copolymers in adhesives and sealants is known per se. For instance, JP 07197010 A/95 describes a two-component sealant composition consisting of an isocyanate component and a low molecular weight hydroxyl-functional acrylate copolymer which contains vinyl acetate as comonomer. This sealant has low surface tackiness. The use of an ethylene-vinyl acetate gel is not disclosed. 
     JP-A-87/64881 describes a nontacky contact adhesive containing a thermoplastic resin and a plasticizer; the thermoplastic resin may be an ethylene-vinyl acetate copolymer. 
     EP-A-295 727 describes latices of interpolymers of vinyl acetate, ethylene and a vinyl ester of a tertiary aliphatic carboxylic acid in which the carboxylic acid component contains 9 carbon atoms. These films are notable for low tackiness. 
     A method for elastifying and extending polymer compositions selected from the group consisting of acrylate copolymer dispersions, reactive polyurethane polymers, MS polymers, polysulfides and silicone rubbers through the addition of EVA gels is not mentioned in any of the aforementioned documents. 
     The method of the invention is carried out by initially fabricating a gel from EVA, PVC or PVC copolymer, plasticizer and wax and also, optionally, benzoyl chloride or TI additive (from Bayer). The total amount of the plasticizer needed is initially charged to a stirred tank, and then EVA, PVC or PVC copolymer and wax are added with stirring. This mixture is then heated with stirring to about 125° C. and stirred until a clear homogeneous solution is obtained. Stirring is then continued at this temperature for 30 minutes. Subsequently, if desired, 0.1% by weight of benzoyl chloride or TI additive are added. For intermediate storage, this gel is filled into a vessel to be sealed airtight and the intermediate product is then cooled down to room temperature. 
     In a second operation, the thusly fabricated gel is mixed with the other constituents of the molding or sealing material in a planetary dissolver until homogeneous. These constituents of the molding and sealing materials customarily comprise polymer compositions selected from the group of MS polymers (from Kaneka) or acrylate copolymer dispersions. However, polyurethane polymers, polysulfide polymers or silicone rubbers can be used as well. Suitable MS polymers are described in DE-A-40 19 074 and DE-A-38 16 808 with reference to further publications. The disclosure content of the two last-mentioned documents is hereby incorporated in full by reference. 
     The molding and sealing materials further contain inorganic fillers such as carbon black, calcium carbonate and pigments such as titanium dioxide and the like and also plasticizers, especially phthalic esters such as diisononyl phthalate or alkylsulfonic acid esters of phenol such as MESAMOLL (from Bayer) or phosphoric esters such as tricresyl phosphate. The materials may finally include customary UV stabilizers and aging inhibitors and also organofunctional silanes, for example 3-glycidyloxypropyl- or 3-aminopropyl-trimethoxysilane or vinyltrimethoxysilane, especially to improve the adhesion to glass, metals, etc. 
     Particularly the moisture-reactive one-component materials further contain organometallic tin compounds to accelerate the curing, and also moisture scavengers such as carbonyl chlorides, for example benzoyl chloride or TI additive (from Bayer). 
     The molding and sealing materials based on MS polymers and incorporating the gels of the invention surprisingly exhibit an appreciable reduction in surface tackiness, and this tackiness decreases with increasing EVA copolymer, PVC or PVC copolymer content, despite the associated high plasticizer content. Additionally, an appreciable economic advantage is obtained, since up to about 45% of the original MS polymer fraction can be replaced with the less costly gel. 
     As mentioned at the beginning, mixtures of acrylate copolymer dispersions with fillers, pigments and plasticizers have only minimal elastic properties, and the tackiness of molding materials produced from these mixtures increases with increasing plasticizer fraction. By adding the inventive EVA, PVC or PVC copolymer gels, optionally in combination with emulsifiers, it is possible to produce elastic molding materials which achieve a total deformation of 25%. Compared with the otherwise customary total deformation of about 10% for acrylate dispersion molding materials, this is an unexpectedly great improvement. Compared with the customary elastic molding materials based on polysulfides, modified silicone rubber, polyurethanes and silicone rubber, such molding materials based on acrylate copolymer dispersions with EVA, PVC or PVC copolymer gels are significantly more economical, given that the other properties such as modulus of elasticity, total deformation and aging resistance are comparable. 
     The invention is more particularly described by the nonlimiting examples hereinbelow. 
    
    
     EXAMPLES 1 TO 3 
     An EVA gel was prepared from 77 parts of MESAMOLL, 12 parts of EVA polymer (vinyl acetate fraction 40%) and 11 parts of microcrystalline wax by initially charging the entire plasticizer to a stirred tank and then adding EVA polymer and wax with stirring. The temperature was then raised to about 125° C. and the mixture was stirred until a clear homogeneous solution was obtained. This temperature was subsequently maintained for 30 minutes while the stirring was continued. To conclude, 0.1% by weight of TI additive was added, and the mixture was filled into a vessel to be sealed airtight and allowed to cool down to room temperature. 
     In the examples hereinbelow the commercially available sealant TERSOTAT 930 (total MS polymer and plasticizer content 42.25% by weight) was modified with the above-described EVA gel in such a way that the MS polymer content was replaced with the EVA gel according to the invention in a 5% by weight, 10% by weight and 15% by weight fraction of the polymer content. 
     
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Example 
                 Comp 1 
                 Inv 1 
                 Inv 2 
                 Inv 3 
                 Comp 2 
                 Comp 3 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 TEROSTAT 930 
                 100 
                 95 
                 90 
                 85 
                 90 
                 90 
               
               
                 Additional plasticizer 4)   
                 0 
                 0 
                 0 
                 0 
                 0 
                 10 
               
               
                 EVA gel 4)   
                 0 
                 5 
                 10 
                 15 
                 0 
                 0 
               
               
                 Wax mixture 
                 0 
                 0 
                 0 
                 0 
                 10 
                 0 
               
               
                 Spray value 1)  after 1 day 
                 50 
                 48 
                 32 
                 12 
                 67 
                 150 
               
               
                 Spray value 1)  after 1 week 
                 32 
                 38 
                 20 
                 10 
                 45 
               
               
                 40° C. 
               
               
                 Shore A hardness after 14 d 
                 26 
                 22 
                 18 
                 14 
                 15 
                 14 
               
               
                 Ball test 2)  after 1 d 
                 40 
                 14 
                 8 
                 0 
                 19 
                 48 
               
               
                 Hardening mm/d 
                 4 
                 4 
                 3.5 
                 3.4 
                 3.5 
                 3.6 
               
               
                 Tensile strength 3)  [N/mm 2 ] 
                 0.89 
                 0.74 
                 0.61 
                 0.47 
                 0.59 
                 0.57 
               
               
                 Stress value 3)  100% [N/mm 2 ] 
                 0.49 
                 0.42 
                 0.34 
                 0.27 
                 0.27 
                 0.27 
               
               
                 Breaking extension 3)  [%] 
                 399 
                 388 
                 364 
                 343 
                 411 
                 378 
               
               
                   
               
               
                 Notes:  
               
               
                   1) on the lines of DIN 52456, flow meter method, i.e., the amount of sealing material is determined which can be expressed from a standard cartridge at a given pressure, time and nozzle diameter (3 bar, 15 sec, 3 mm)  
               
               
                   2) as disclosed on page 8 of DE-A-40 19 074  
               
               
                   3) according to DIN 18545 E  
               
               
                   4) addition instead of an identical fraction of MS polymer  
               
             
          
         
       
     
     INVENTIVE EXAMPLES 4 to 6 
     Inventive Examples 1 to 3 were repeated to prepare a PVC copolymer gel from 85 parts of MESAMOLL, 8 parts of PVC copolymer (vinyl acetate fraction 5%) and 7 parts of microcrystalline wax, except that no TI additive was included. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Example 
                 Inv 4 
                 Inv 5 
                 Inv 6 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 TEROSTAT 930 
                 95 
                 90 
                 85 
               
               
                   
                 Additional plasticizer 4)   
                 0 
                 0 
                 0 
               
               
                   
                 EVA gel 4)   
                 5 
                 10 
                 15 
               
               
                   
                 Wax mixture 
                 0 
                 0 
                 0 
               
               
                   
                 Spray value 1)  after 1 day 
                 87 
                 102 
                 110 
               
               
                   
                 Shore A hardness after 14 d 
                 21 
                 16 
                 10 
               
               
                   
                 Ball test 2)  after 1 d 
                 1 
                 1 
                 3 
               
               
                   
                 Hardening mm/d 
                 3.1 
                 3.1 
                 2.7 
               
               
                   
                 Tensile strength 3)  [N/mm 2 ] 
                 0.58 
                 0.43 
                 0.64 
               
               
                   
                 Stress value 3)  100% [N/mm 2 ] 
                 0.45 
                 0.35 
                 0.52 
               
               
                   
                 Breaking extension 3)  [%] 
                 379 
                 311 
                 329 
               
               
                   
                   
               
               
                   
                 Notes:  
               
               
                   
                   1) on the lines of DIN 52456, flow meter method, i.e., the amount of sealing material is determined which can be expressed from a standard cartridge at a given pressure, time and nozzle diameter (3 bar, 15 sec, 3 mm)  
               
               
                   
                   2) as disclosed on page 8 of DE-A-40 19 074  
               
               
                   
                   3) according to DIN 18545 E  
               
               
                   
                   4) addition instead of an identical fraction of MS polymer  
               
             
          
         
       
     
     As Inventive Examples 1 to 6 reveal compared with the noninventive Comparative Example 1, increasing the fraction of gel in the composition lowers the surface tackiness more and more while the mechanical properties such as tensile strength, stress value and breaking extension remain within what is acceptable. The surface tackiness was determined according to the ball test disclosed on page 8 of DE-A-40 19 074. A high value indicates high tackiness, i.e., a ball of defined circumference will move an inclined plane (defined length) at height H. A sheet of partially cured molding material has been doctor-coated onto this inclined plane in a thickness of about 2 mm. 
     To examine possible effects of the wax in the EVA gel, Comparative Tests 2 and 3 were carried out. Comparative Test 2 utilizes a wax mixture consisting of 23 parts of wax and 77 parts of MESAMOLL instead of the EVA gel, while in Comparative Test 3 the EVA gel was replaced with an additional plasticizer fraction of 10 parts. In both cases, appreciable surface tackiness as measured by the ball test is observed. 
     In summary it is to be noted that the EVA or PVC copolymer gels in the abovementioned sealant formulations bring about the typical character of a plasticizer with regard to the mechanical properties, but effect exactly the opposite of an increased plasticizer fraction with regard to surface tackiness and processing viscosity. 
     INVENTIVE EXAMPLE 7 AND COMPARATIVE EXAMPLE 4 
     Inventive Example 1 was repeated to prepare a gel from 88 parts of diisobutyl phthalate (DIBP), 3 parts of EVA polymer (vinyl acetate fraction 28%) and 9 parts of PVC copolymer (vinyl acetate fraction 5%), but without addition of TI additive. 
     The commercially available sealant TEROSTAT 20 (total acrylic copolymer dispersion and plasticizer content 42% by weight) was modified according to the invention by adding the gel according to the invention in such an amount that 6% of the dispersion content and 20% of the chalk/pigment fraction were replaced. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Example 
                 Comp 4 
                 Inv 7 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 TEROSTAT 20 
                 100 
                 60 
               
               
                   
                 Acrylic dispersion/plasticizer 
                 42 
                 26 
               
               
                   
                 fraction 
               
               
                   
                 EVA/PVC copolymer gel 
                 0 
                 40 
               
               
                   
                 Total deformation 1)  [%] 
                 about 10 
                 25 
               
               
                   
                 Rebound from 150% extension 2)  [%] 
                 cohesive 
                 about 71 
               
               
                   
                   
                 fracture 
               
               
                   
                 Stress value 3)  100% [N/mm 2 ] 
                 0.15 
                 0.03 
               
               
                   
                 Extension [%] 
                 &lt;140 
                 &gt;150 
               
               
                   
                   
               
               
                   
                 Notes  
               
               
                   
                   1) on the lines of DIN 52455  
               
               
                   
                   2) on the lines of DIN 52458  
               
               
                   
                   3) according to DIN 18545 E  
               
             
          
         
       
     
     As Inventive Example 7 reveals in comparison with noninventive Comparative Example 4, the addition of the gel according to the invention improves the mechanical properties such as stress value, extension, rebound and total deformation to such an extent that the requirements of DIN 18540 (test conditions for building expansion joint sealants) are almost achieved. 
     In summary it is to be noted that the EVA/PVC copolymer gels in the sealant formulation as per Inventive Example 7 based on acrylic copolymer dispersion bring about the typical character of a plasticizer with regard to the mechanical properties, but do not exhibit any adverse effects with regard to surface tackiness in comparison with noninventive Comparative Example 4.