Abstract:
A non-aqueous sealant composition particularly adapted for use in the installation or sealing of fixed glass in vehicles. The composition has a thermoplastic rubber base, suitably modified by plasticizers, tackifyers and a cationic surfactant to provide a sealant system which displaces water from a wetted substrate to which it is applied, permitting it to be utilized under either wet or dry conditions.

Description:
BACKGROUND OF THE INVENTION 
     The automotive repair and service industry is called upon to replace broken glass panels, such as windshields, in vehicles, as well as to find and seal water leaks which may occur in the joints or seams of the vehicles, particularly around the fixed glass installations and similar areas which tend to collect rain or wash water. 
     A variety of sealant compositions and sealant tapes are used in the automotive industry for original installation of windshields and the like. Such original installation occurs indoors or under cover on a scheduled production basis and under dry conditions. 
     The automotive repair industry has in its aftermarket activities in glass repair and replacement and in leak detection and sealing used the same variety of sealant compositions which are used by the automotive manufacturing industry. Vehicles are often brought in directly from the rain for immediate service by the customer; or the vehicle may be temporarily parked in an outside lot and be exposed to rain before being brought in for a scheduled repair; or a mobile repair unit may have to make the repair in rainy weather at a remote location. In such situations, the area to which sealant has to be applied is wet and the sealant composition cannot be applied until the area is dried or is permitted to air dry, as satisfactory bond cannot otherwise be achieved. 
     Similarly, when the repair involves the detection and sealing of a water leak in the vehicle, it is often necessary to spray the suspected joint or seam with water to locate the leak. The area then has to be dried before sealant can be applied thereto. After the sealant has set, a water spray is again used to determine whether the leak has been stopped. If the leak persists, the area again has to be dried, sealant applied, a test water spray applied, and the process repeated until the leak is sealed. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the invention to provide a nonaqueous rubber sealant composition which can be used on either wet or dry substrates with complete and satisfactory bond. 
     It is another object of the invention to provide a sealant composition having the ability and characteristic of displacing the underlying water from the substrate to which the sealant is applied so as to present a substantially water-free surface to which the sealant can adhere. 
     It is a further object of the invention to provide a sealant composition of the character described in a broad range of viscosity for different methods of application and use. 
     Other objects and advantages of the invention will become apparent during the course of the following description. 
     DESCRIPTION OF THE INVENTION 
     The sealant composition is a non-aqueous homogeneous mixture of the following constituents which are present in the composition as a percentage of the total weight of the listed composition in the range indicated in Table 1 below. 
     
                       Table 1______________________________________  Constituent      % by weight______________________________________(A)      thermoplastic rubber base                       5 - 20(B)      liquid plasticizer 0.5 - 12(C)      tackifying resin   1 - 20(D)      anti-oxidant       0.1 - 3(E)      cationic surfactant                       0.25 - 0.70(F)      inert filler       0 - 48(G)      bodying agent      0 - 5(H)      hydrocarbon solvent                       20 - 70______________________________________ 
    
     The thermoplastic rubber base constituent (A) is preferably one or more of the styrene block copolymers, such as styrene-butadiene-styrene or styrene-isoprene-styrene, but can be one of the other known rubbers such as butyl rubber or the like. It is utilized in particle form for better admixture and solution. Mixtures of different rubbers can be utilized for the base to achieve desired properties in the composition. 
     The plasticizer constituent (B) is preferably an oxidation-resistant balsamic resin or could be one of the heavy aromatic hydrocarbons derived from petroleum and suitable for the purpose. 
     The tackifyer constituent (C) is preferably a thermoplastic ester derived from pentarythiritol or a polyturpene resin. 
     The anti-oxidant (D) for the rubber will ordinarily be one of the hindered phenols known to the art for this purpose. 
     The cationic surfactant constituent (E) is an imidazoline derivative, preferably 1 -- hydroxyethyl -- 2 alkyl imidazoline. 
     The filler (F) can be any suitable inert inorganic constituent in powdered form which may be utilized, if desired, to add mass to the composition. Its use in the composition is optional, but is often desirable in attaining desired consistencies or achieving cost reduction of product, as long as its proportion in the composition does not reduce the performance characteristics of the composition below a quality level which will be satisfactory for the particular purpose intended. A commonly used filler is calcium carbonate, but others such as magnesium carbonate could also be used. 
     Whether or not a bodying agent (G) should be introduced into the composition will depend upon the consistency which is desired for the composition; the extent to which such desired consistency is achieved by other constituents of the composition; the manner and environment in which the composition is to be applied to the substrate; and other factors. A bodying agent which is suitable and commonly used for this purpose is coatings grade asbestos. Other bodying agents, such as fumed silica with thixotropic tendencies, could also be used. 
     The hydrocarbon solvent (H) is any one or a suitable mixture of aliphatic or aromatic hydrocarbon liquids, such as toluol, naphtha or kerosene. 
     In addition to the foregoing constituents, it is frequently desirable for the sake of appearance, particularly in the automotive field, that pigment or coloring be added to the composition to achieve a particular color. For example, carbon black or any of the commonly available coloring agents may be added to the composition in such minor proportions as required to achieve the color intensity desired. 
     All of the mandatory constituents of the composition, as well as those optional constituents selected for inclusion, are thoroughly mixed for a sufficient period of time to obtain complete solution of the soluble constituents and attain a homogeneous mixture of the desired consistency or viscosity. 
     The resulting sealant compositions can broadly be categorized as light-bodied or heavy-bodied. The light-bodied sealant compositions flow readily when brushed or flowed onto the joint or seam to be sealed and readily penetrate or seep into small openings, such as cracks and crevices, which could be a source of leakage through a substrate joint, for example between a windshield and the automobile pinchwell or molding or even between a windshield and its original bed of sealant. These light-bodied sealant compositions have a Brookfield viscosity ranging from above 100 to about 5000 cps. 
     The heavy-bodied compositions have a putty-like consistency and are considerably more viscous than the light-bodied sealants. They have a Brookfield viscosity ranging from above 75 thousand to about one million cps. They are generally applied by means of high-pressure dispensing devices to the substrate joint and tend to stay in situ rather than flow readily. After they set, these heavy-bodied compositions still retain an excellent degree of flexibility and resiliency; they have a Shore A Durometer hardness of no more than 50, ranging down to about 30. 
     It will be understood that the description of the light and heavy-bodied categories above is merely by way of illustration and that the invention also contemplates sealant compositions whose consistency or viscosity would be intermediate the values above given for each category. 
     The sealant compositions of the invention are themselves non-aqueous and have no significant water absorption tendency, but do have the novel ability to effectively displace the underlying water on the water-wetted substrate surfaces to which the composition is applied. This characteristic permits the sealant to be applied to water-wet surfaces in the joints or seams to be sealed, without the necessity of first drying them. The application of the sealant can be performed in the rain or upon wet surfaces with excellent results. After the sealant has been applied, the joint can be water-tested for leakage without fear of impairing the bond, and more sealant can be applied, if necessary, without waiting for the wet joint to dry. The water-displacing characteristic is independent of the specific gravity or relative density of the sealant composition. 
     The heavy-bodied sealants preferably have the composition and percentage by weight of constituents indicated in Table 2 below. 
     
                       Table 2______________________________________  Constituent      % by weight______________________________________(A)      thermoplastic rubber base                       5 - 13(B)      liquid plasticizer 0.5 - 7(C)      tackifying resin   1 - 15(D)      anti-oxidant       0.1 - 3(E)      cationic surfactant                       0.25 - 0.70(F)      inert filler       25 - 48(G)      bodying agent      3 - 5(H)      hydrocarbon solvent                       20 - 50______________________________________ 
    
     The light-bodied sealants preferably have the composition and percentage by weight of constituents indicated in Table 3 below. 
     
                       Table 3______________________________________  Constituent      % by weight______________________________________(A)      thermoplastic rubber base                       8 - 20(B)      liquid plasticizer 3 - 12(C)      tackifying resin   10 - 20(D)      anti-oxidant       0.1 - 3(E)      cationic surfactant                       0.25 - 0.70(F)      inert filler       0 - 25(G)      bodying agent      0 - 5(H)      hydrocarbon solvent                       50 - 70______________________________________ 
    
     As previously indicated, coloring agents in minor amounts may be added to the compositions of Tables 2 and 3. 
     It is to be noted that the range of the cationic surfactant is critical to achieve homogenity and effectiveness of the composition. Below 0.25% of constituent (E), the composition loses its water-displacing ability and will not satisfactorily perform on water-wetted substrates. When constituent (E) exceeds 0.7% by weight, the composition becomes water-absorbent and there is a precipitation effect causing constituent separation and destroying the homogeneous character of the composition. 
     In general the heavy-bodied sealant compositions of Table 2 contain higher proportions of filler (F) and bodying agent (G) and less solvent (H) than do the light-bodied sealants of Table 3. 
     Six specific examples of representative sealant compositions according to the invention are set forth in Table 4 below. 
     
                                           Table 4__________________________________________________________________________          Percentage by weight          Example Example Example Example Example ExampleConstituent    I       II      III     IV      V       VI__________________________________________________________________________(A)   Thermoplastic rubber          8.5     10.0    10.5    12.6    9.3     16.4   base(B)   Plasticizer 6.6     6.4     3.5     1.7     3.6     6.3(C)   Tackifying Resin          7.0     2.0     12.0    12.7    17.5    14.0(D)   Anti-oxidant          0.1     0.1     0.1     0.1     0.1     1.5(E)   Cationic surfactant          0.6     0.5     0.6     0.6     0.3     0.25(F)   Filler      37.8    40.5    44.1    46.7    --      --(G)   Bodying agent          3.8     5.0     3.4     3.6     --      2.7(H)   Solvent     35.6    30.8    23.7    22.0    68.7    58.85(I)   Pigment or coloring          --      4.7     2.1     --      0.5     --          100.0   100.0   100.0   100.0   100.0   100.0   Approximate Brookfield          100,000               cps                  150,000                       cps                          800,000                               cps                                  1,000,000                                       cps                                          135  cps                                                  400  cps   Viscosity   Approximate Shore A          45      48      50      50      --      --   Durometer__________________________________________________________________________ 
    
     Examples I through IV can be categorized as heavy-bodied. Examples III and IV are of a consistency and character particularly adapted for use where an entire windshield or other fixed glass insert has to be replaced and reset in a vehicle. Examples I and II are of a consistency and character particularly adapted for use in rehabilitating an existing joint where the sealant has suffered cracking, embrittlement or other general deterioration. 
     Examples V and VI can be categorized as extremely light-bodied. They can be flowed on easily for rapid penetration in localized areas of the joint, such as pin holes and the like, and can otherwise be utilized where relatively thin layers of flowable sealant are needed or desirable.