Abstract:
Paper release catalyst blends which are self-emulsifiable and form uniquely stable catalyst emulsions are disclosed. The blends, comprising compatible emulsifiers and organo tin catalysts, disperse in aqueous baths without colloidal milling and retain activity in storage longer than conventional catalyst emulsions.

Description:
This is a continuation of application Ser. No. 634,445, filed July 25, 1984, now abandoned, which is a continuation of application Ser. No. 356,797, filed Mar. 10, 1982 and now abandoned. 
    
    
     This invention relates to catalyst emulsions for use in silicone paper release coating compositions. More particularly, it relates to blends of emulsifiers and organo-tin catalysts which are self-dispersible in aqueous solutions and thus can be added to silicone paper release coating baths without pre-emulsification. 
     BACKGROUND OF THE INVENTION 
     Silicone compositions have long been used as release coatings, which render surfaces or materials comparatively nonadherent to other materials which would ordinarily adhere thereto. Silicone release compositions are widely used as coatings which release pressure-sensitive adhesives on labels, decorative laminates, transfer tapes, etc. Silicone release coatings on paper, polyethylene, Mylar®, and other such substrates are also employed to provide non-stick surfaces for food handling and industrial packaging applications. 
     Silicone paper release coatings are effeciently applied from an aqueous bath containing the emulsified silicone coating composition and a catalyst emulsion. Once coated, the paper or other substrate is exposed to heat in order to cure the coating. 
     Silanol-containing paper release compositions are catalyzed by organo tin compounds, as disclosed in U.S. Pat. No. 3,499,870 (Hadlock et al.), and extensive work has been performed in achieving the optimal combination of properties in these catalysts. See, e.g., U.S. application Ser. No. 356,796 filed Mar. 10, 1982, now U.S. Pat. No. 4,426,490 and commonly assigned. 
     Catalysts prepared for use in water base systems must be emulsified with such conventional emulsifiers as polyvinyl alcohol. A drawback to these catalyst emulsions has been that they can separate with time on storage, or they can break with exposure to temperature extremes, i.e., below about -15° C. or about 50° C. Some tin compounds may also undergo hydrolysis during prolonged storage and revert to catalytically inactive form. 
     It has now been discovered that these drawbacks can be overcome by novel blends including an emulsifier and an organo tin catalyst which are self-emulsifiable (i.e., water dispersible) and so can be added to paper release coating baths without pre-emulsification. The blends form uniquely stable catalyst emulsions which remain active longer when stored in emulsion form than known catalyst emulsions. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide novel organo tin catalyst/emulsifier blends which are self-dispersible in aqueous systems. 
     It is a further object of the present invention to provide catalyst emulsions which will remain catalytically active during prolonged shelf storage. 
     These and other objects are accomplished herein by a catalyst blend including: 
     (A) 13 to 50 parts by weight of an emulsifier, and 
     (B) 87 to 50 parts by weight of an organo tin catalyst of the formula R 2  SnQ 2 , wherein R is C 1  -C 8  alkyl and Q is selected from ##STR1##  --SR&#39;, or ##STR2##  where R&#39; is a monovalent hydrocarbon radical of from 1 to 18 carbon atoms; said components (A) and (B) being mutually soluble and said blend being water dispersible. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The self-emulsifiable catalyst blends of the present invention are prepared by emulsifying an organo tin catalyst with a compatible emulsifier so that a stable emulsion which is readily dispersible in aqueous systems is formed. Such catalyst emulsions are easier to use than catalysts requiring emulsification steps, such as colloidal milling, when introduced to water based systems such as paper release coating baths. They also remain catalytically active and in emulsion form during prolonged storage. 
     The typical catalyst emulsion blend of the present invention is composed of at least two components: an emulsifier, and an organo tin compound capable of catalyzing cross-linking in organosilicon polymer compositions, such as SiOH-containing paper release coating compositions. 
     Emulsifiers which are suitable for the purposes herein include any one of a number of organic compounds which is mutually soluble with at least one organo tin catalyst and which will render the catalyst readily dispersible in water without interfering with its catalytic activity in relation to organosilicon polymers. Emulsifiers already found which exhibit these properties include: 
     polyoxyethylene 20 sorbitan monooleate 
     polyoxyethylene 20 sorbitan mono stearate 
     polyoxyethylene 20 sorbitan trioleate 
     alkylphenoxypoly (ethyleneoxy) ethanol 
     polyoxyethylene 5 sorbitan monooleate 
     polyethylene glycol 400 monooleate 
     polyoxyethylene 4 ether lauryl alcohol 
     polyoxyethylene 10 oleyl ether p0 polyoxyethylene 10 cetyl ether 
     Polyoxyethylene 20 sorbitan trioleate and polyoxyethylene 20 sorbitan mono stearate are preferred. Simple experimentation will yield other suitable emulsifiers for a given tin catalyst and are intended to be included within the scope of this invention. Combinations of emulsifiers may also be used. 
     Suitable organo tin catalysts for the present invention will have the general formula R 2  SnQ 2 , wherein R is an alkyl radical of 1 to 8 carbons and Q is carboxylate ##STR3## mercaptide (--SR&#39;), or thioacetic acid ester ##STR4## where R&#39; is a monovalent hydrocarbon radical of from 1 to 18 carbon atoms. Commercially obtainable such compounds include but are not limited to 
     Witco Formez® UL-1 (dibutyl tin mercaptide) 
     Witco Formez® UL-6 (dibutyl tin dithioacetic acid ester) 
     Witco Formez® UL-28 (dimethyl tin dineodeconate). 
     Witco Fomrez® UL-24 (dimethyl tin S,S&#39;-bis(isooctyl mercapto acetate) and 
     Witco Fomrez® UL-29 (di(n-octyl) tin S,S&#39;-bis(isooctyl mercapto acetate) 
     M&amp;T Thermolite® 831 [abbreviated T-831 hereinafter] (di(n-octyl) tin S,S,&#39; bis(isooctyl mercapto acetate) 
     M&amp;T Catalyst 20 (diorgano tin mercaptide, 17.5% tin) 
     The wide structural variety of catalysts which may be suitable for the self-emulsifiable catalyst blends of the present invention is a special advantage in that there is great flexibility in the class of tin catalysts that can be employed, and those skilled in the art may tailor a catalyst emulsion for their specific needs. 
     A further advantage of the present blends is that the tin catalyst content is upwards of 50%, which gives much higher solids content than conventional catalyst emulsions, which typically contain 20-33% tin catalyst. 
     In order that those skilled in the art may better understand how to practice the present invention, the following examples are provided by way of illustration, and not by way of limitation. 
     The following is a description of the catalysts and emulsifiers used in the formulations of the examples; the tradenames will be used hereinafter for brevity: 
     General Electric SM-2057, a silicone emulsion containing approximately 40% silanol-stopped polydimethylsiloxane fluids and a polyvinyl alcohol emulsifier. 
     Kelgin MV, medium viscosity (MV) hydrophilic derivative of algin (sodium alginate). 
     Hodag PSMO-20, polyoxyethylene sorbitan monooleate, nonionic emulsifier, HLB 15.0. 
     PSML-20, polyoxyethylene sorbitan monolurate, nonionic emulsifier, HLB 16.7. 
     Tween 80 (ICI Americas Inc.), polyoxyethylene (20) sorbitan monooleate, nonionic emulsifier, HLB 15.0. 
     Tween 81, polyoxyethylene (5) sorbitan monooleate, nonionic emulsifier, HLB 10.0. 
     Tween 85, polyoxyethylene (20) sorbitan trioleate (polysorbate 85), nonionic emulsifier, HLB 11.0. 
     Witconol H-31A (Witco Chemical Corp.), polyethylene glycol (400) monooleate nonionic oil-in-water emulsifier. 
     Witconol NP-40, ethoxylated nonylphenol (4 molar) emulsifier. 
     Witconol NP-80, ethoxylated nonylphenol (8 molar) emulsifier. 
     Glycosperse P-20 (Glyco Chemical, Inc.), polyoxyethylene (20) sorbitan monopalmitate emulsifier, HLB 15.6. 
     Glycosperse S-20, polyoxyethylene (20) sorbitan monostearate emulsifier, HLB 14.9. 
     Glycosperse O-20, polyoxyethylene (20) sorbitan monooleate emulsifier, HLB 15.0. 
     Glycosperse L-20, polyoxyethylene (20) sorbitan monolaurate emulsifier, HLB 16.7. 
     T-Maz-20 (Mazer Chemicals, Inc.), polyoxyethylene (20) sorbitan monolaurate, nonionic emulsifier, HLB 16.7. 
     Sorbax PMO-20 (Chemax, Inc.), polyoxyethylene (20) sorbitan monooleate, nonionic emulsifier. 
     Pegosperse 400 MOT (Glyco Chemical, Inc.), polyethylene Glycol (400) monotallate, nonionic emulsifier, HLB 11.0. 
     Aldo MOD (Glyco Chemicals, Inc.), glycerol monooleate (dispersible), nonionic emulsifier, HLB 5.6. 
     Ethosperse G-26 (Glyco Chemicals, Inc.), polyoxyethylene (26) ether of glycerine, HLB 18.4. 
     Ethosperse LA-4, polyoxyethylene (4) ether of lauryl alcohol, HLB 9.5. 
     Ethosperse SL-20, polyoxyethylene (20) ether of sorbitol, HLB 16.6. 
     Ethofat 242/25, (Armak Industrial Chemicals Division), ethylene oxide condensate of fatty acids, nonionic emulsifier. 
     Brij 56 (ICI Americas, Inc.), polyoxyethylene (10) cetyl ether, nonionic emulsifier, HLB 12.9. 
     Brij 93, polyoxyethylene (2) oleyl ether, nonionic emulsifier, HLB 4.9. 
     Brij 96, polyoxyethylene (10) oleyl ether, nonionic emulsifier, HLB 12.4. 
     Brij 98, polyoxyethylene (20) oleyl ether, nonionic emulsifier, HLB 15.3. 
     Nonionic E-4 (Hodag Chemical Corp.), nonyl phenoxy poly(ethyleneoxy) ethanol, nonionic wetting agent (4 moles etheyleneoxide), HLB 8.6. 
     Nonionic E-6, nonyl phenoxy polyethyleneoxy ethanol, nonionic wetting agent (6 moles ethylene oxide), HLB 10.6. 
     Nonionic E-10, nonyl phenoxy polyethyleneoxy ethanol, nonionic wetting agent (10 moles ethylenoxide), HLB 12.6. 
     Tetronic 304 &amp; 702 (BASF Wyandotte Industrial Chemicals Group), two of a serires of compounds formed by addition of propylene oxide of ethylene diamine, followed by the addition of ethylene oxide; nonionic wetting agents, HLB 17.0 &amp; 7.0, respectively. 
     Plurafac A-24 (BASF), oxyethylated straight-chain alcohol, nonionic emulsifier. 
     Plurafac D-25, modified oxyethylated straight-chain alcohol, nonionic emulsifier, HLB 11.0. 
     Pluronic L-35, L-42 &amp; L-61 (BASF), three Liquid Emulsifiers in a series of condensates of ethylene oxide with hydrophobic bases formed by condensing propylene oxide with propylene glycol, nonionic, HLB 8.0, 12.0 &amp; 7.0, respectively. 
     Pluronic 17R2 &amp; 17R4, two dispersants in a series of condensates of propylene oxide with hydrophilic bases formed by condensing ethylene oxide with ethylene glycol, liquid nonionic additives. 
     Arlamol E (Atlas Chemical Industries), fatty acid propoxylate, liquid nonionic emollient. 
     Mazol PGO-31 (Mazer Chemicals, Inc.), triglycerol monooleate polyol, HLB 6.2. 
     Mazol PGO-104, decaglycerol tetraoleate, HLB 6.2. 
    
    
     EXAMPLES 1-3 
     A silanol-containing paper release coating bath was prepared using the following ingredients: 
     
         ______________________________________Ingredient            Parts by Weight______________________________________silicone release emulsion                 20 parts by weight(General Electric SM-2057)catalyst emulsion      4 parts by weight(A) polyoxyethylene 20sorbitan monooleate(B) 82.9% di(n-octyl) tinS,S&#39; bis(isooctyl) mercaptoacetate)Kelgin MV solution (1% Kelgin MV)                 50 parts by weightwater                 26 parts by weight______________________________________ 
    
     The catalyst emulsion was transparent and was readily dispersed when added to the aqueous release emulsion and gently shaken. Mechanical energy as supplied by colloid milling was unnecessary to produce an emulsion. 
     The coating bath solution was coated on Riegal 42-pound bleached Kraft paper at 0.5 pounds per ream with the following results: 
     
         ______________________________________Release Value at 12 in/min. (Johnson &amp; Johnson Tape)Initial (20 hrs.)          1 week aged______________________________________5-11 gr./in.   6-14 gr./in.______________________________________ 
    
     The above experiment was repeated using a 25% and 50% levels of the emulsifier, polyoxyethylene 20 sorbitan monooleate, with comparable results. It was observed with the above catalyst blends that there was no smear or rub-off after one-hour conditioning of the coated sheet at room temperature and 50% relative humidity. Subsequent adhesion of the tape was found to be 70-90%, which compares to standard commercial paper release systems. 
     EXAMPLES 4-6 
     Several emulsifiers were tested for self-emulsification with a single catalyst, Thermolite® 831, i.e., di(n-octyl) tin S,S&#39; bis(isooctyl mercapto acetate), abbreviated T-831. 
     
         ______________________________________Sample Composition             Solubility______________________________________4      25% Nalco ® non-ionic ethoxylated                          soluble  alkylphenol, HLB 9, in T-831#      25% Nalco  ® non-ionic polyoxyethylated                          not soluble  vegetable oil, HLB 14+, in T-8315      25% Nalco ® non-ionic ethoxylated                          soluble  alkylphenol, HLB 14, in T-8316      25% Nalco ® non-ionic ethoxylated                          soluble  alkylphenol, HLB 10-11, in T-831______________________________________Self-Emulsification                         Freeze-ThawSample Initial    After 20 Hrs.                         (16 Hrs. at -15° C.)______________________________________4      emulsified broke rapidly                         no haze or ppt.5      &#34;          some separation                         frozen6      &#34;          no separation                         no haze or ppt.______________________________________ 
    
     Of the three compositions which were initially self-emulsifiable, Sample 6 is seen to have the most stable emulsion, lasting&gt;20 hours without separation and showing no haze or precipitation after freeze-thaw testing. 
     EXAMPLES 7-9 AND COMPARATIVE TRIALS 
     A wide variety of catalyst-emulsifier combinations were tested for compatibility [emulsifiers and catalysts identified by tradename]: 
     [See Table A] 
     
                                           TABLE A__________________________________________________________________________Sample    Sn Catalyst       Amount Emulsifier                       Amount Comments__________________________________________________________________________A.  Witco UL 1       24 parts/wt.              Hodag PSMO-20                        6 parts/wt.                              not soluble hazeB.  Witco UL 6       24 parts/wt.              Hodag PSMO-20                        6 parts/wt.                              not soluble hazeC.  Catalyst 120       24 parts/wt.              Hodag PSMO-20                        6 parts/wt.                              not soluble haze7.  Catalyst 120        3 parts/wt.              Tween 85  1 parts/wt.                              soluble8.  Catalyst 120        3 parts/wt.              Witconal H31A                        1 parts/wt.                              solubleF.  Catalyst 120        3 parts/wt.              Glycosperse 520                        1 parts/wt.                              not soluble haze (S)G.  Catalyst 120        3 parts/wt.              Glycosperse 0.20                        1 parts/wt.                              not soluble haze (S)9.  Catalyst 120        3 parts/wt.              Tween 85  1/2 parts/wt.                              soluble              Witconal H31A                        1/2 parts/wt.                              --I.  Witco UL-6        3 parts/wt.              Tween 85  1 parts/wt.                              solubleJ.  Witco UL-6        3 parts/wt.              Glycosperse O20                        1 parts/wt.                              solubleK.  Witco UL-6        3 parts/wt.              Glycosperse S20                        1 parts/wt.                              solubleL.  Witco UL-6        3 parts/wt.              Witconal H31A                        1 parts/wt.                              solubleM.  Witco UL-24        3 parts/wt.              Tween 85  1 parts/wt.                              solubleN.  Witco UL-29        3 parts/wt.              Glycosperse S20                        1 parts/wt.                              solubleO.  Witco UL-29        3 parts/wt.              Glycosperse S20                        1 parts/wt.                              solubleP.  Witco UL-29        3 parts/wt.              Witconal H31A                        1 parts/wt.                              solubleQ.  Catalyst T-831       71/2 parts/wt.              TMAZ-20  21/2 parts/wt.                              not solubleR.  Catalyst T-831       71/2 parts/wt.              Glycosperse S20                       21/2 parts/wt.                              solubleS.  Catalyst T-831       71/2 parts/wt.              Glycosperse L20                       21/2 parts/wt.                              (S)T.  Catalyst T-831       71/2 parts/wt.              Glycosperse O20                       21/2 parts/wt.                              solubleU.  Catalyst T-831       71/2 parts/wt.              Hodag PSMO-20                       21/2 parts/wt.                              (S)V.  Catalyst T-831       71/2 parts/wt.              Hodag PSMO-20                       21/2 parts/wt.                              (S)W.  Catalyst T-831       71/2 parts/wt.              Tween 80 21/2 parts/wt.                              solubleX.  Catalyst T-831       71/2 parts/wt.              Tween 85 21/2 parts/wt.                              solubleY.  Catalyst T-831       71/2 parts/wt.              Sortux PMO-20                       21/2 parts/wt.                              (S)Z.  Catalyst T-831       71/2 parts/wt.              Witconal H31A                       21/2 parts/wt.                              solubleAA. Catalyst T-831       71/2 parts/wt.              Tween 81 21/2 parts/wt.                              hazeAB. Catalyst T-831       71/2 parts/wt.              Pegosperse 400                       21/2 parts/wt.                              not solubleAC. Catalyst T-831       71/2 parts/wt.              MOT      21/2 parts/wt.                              (S)              Aldo MODAD. Catalyst T-831       71/2  parts/wt.              Ethosperse G-26                       21/2 parts/wt.                              (S)__________________________________________________________________________ (S) = separated on standing at room temperature. 
    
     The combinations which were mutually soluble in the above trials were tested for freeze-thaw stability of the emulsion and water dispersability. The following results were observed: 
     
         ______________________________________   Freeze-Thaw Results                    Self-Sample  (16 hrs below -15° C.)                    Emulsifiable Results______________________________________7.      Clear            initial &amp; 16 hrs.8.      Haze             initial &amp; 16 hrs.9.                       initial &amp; 16 hrs.I.      ClearJ.      HazeK.      Slight HazeL.      HazeM.      ClearN.      Haze &amp; Slight SeparationO.      Slight HazeP.      HazeR.      HazeT.      Slight HazeW.      ClearX.      ClearZ.      Haze______________________________________ 
    
     Samples 7, 8 and 9 were the samples that were self-emulsifiable for this invention. 
     EXAMPLES 10-17 AND COMPARATIVE TRIALS 
     A large number of emulsifiers were tested for compatability with a single catalyst, Catalyst 120® (M &amp; T Chemicals, Inc.), an organo tin mercaptide containing 17.5% by weight tin. All emulsifiers were added to 25% by weight of the emulsifier/Catalyst 120 blend [emulsifiers identified by tradename]. 
     
         ______________________________________              &gt;Catalyst&lt;Sample Emulsifier   Solubility at r.t.                           Water Dispersible______________________________________10    Brij 93      soluble      initially,                           then separatedBB    Brij 98      haze11    Nonionic L-4 soluble      initiallyBD    Nonionic E-6 hazeBE    Nonionic E-10              haze12    Ethosperse LA-4              soluble      initially13    Witconal NP-40              soluble      initiallyBH    Witconal NP-80              hazeBI    Tetronic 304 hazeBJ    Tetronic 702 haze14    Plurafac A-24              soluble      initiallyBL    Plurafac D-25              hazeBM    Pluronic 17R2              hazeBN    Pluronic 17R4              hazeBO    Pluronic L-35              hazeBP    Pluronic L-42              hazeBQ    Pluronic L-61              haze15    Arlamal E    soluble      initially,                           then separatedBS    Ethofat 242/25              hazeBT    Ethosperse SL-20              hazeBU    Mazol PGO-3  soluble      not dispersibleBV    Mazol PGO-104              soluble      not dispersible16    Brij 96      slight haze  initially17    Brij 56      soluble      initially______________________________________ 
    
     The catalyst emulsions which were initially water dispersible were observed over 20 hours for stability and subjected to freeze-thaw testing. The following results were observed: 
     
         ______________________________________                  Freeze-ThawSample    Emulsion Stability                  (16 hrs. at -15° C.)______________________________________10        creamy, separated                  O.K.11        stable at 20 hrs.                  freeze through but                  fast thaw12        stable at 20 hrs.                  freeze through but                  fast thaw13        fully separated                  OK14        stable at 20 hrs.                  freeze through                  moderately fast thaw15        fully separated                  OK16        stable at 20 hrs.                  freeze through,                  slow thaw17        stable at 20 hrs.                  freeze through,                  slow thaw______________________________________ 
    
     It can be seen from the above data that the Samples 11 and 12 have mutually soluble components and form very stable emulsions.