Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/541—Silicon-containing compounds containing oxygen
  • C08K5/5415—Silicon-containing compounds containing oxygen containing at least one Si—O bond
  • C08K5/5419—Silicon-containing compounds containing oxygen containing at least one Si—O bond containing at least one Si—C bond
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
  • C08G77/16—Polysiloxanes containing silicon bound to oxygen-containing groups to hydroxyl groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
  • C08G77/18—Polysiloxanes containing silicon bound to oxygen-containing groups to alkoxy or aryloxy groups
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S528/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S528/901—Room temperature curable silicon-containing polymer

Definitions

• This invention relates to novel polyorganosiloxane cross-linkers or chain extenders for room temperature vulcanizable (RTV) sealants, and to novel RTV sealant compositions containing same.
• the invention further relates to novel methods of production of the claimed cross-linkers or chain extenders.
• the major polymer component was a linear or moderately branched silicone with silanol terminal groups.
• Alkyl silicates or alkylpolysilicates typically tetraethyl orthosilicate or partially hydrolyzed and condensed products therefrom, were used as crosslinking agents.
• Catalysts typically employed were tin compounds, e.g., stannous octoate, dibutyltindilaurate. Fillers, color pigments and other ancillary materials were also used.
• the system was usually prepared in two parts, thereby maintaining separation of the siloxanol polymer and the catalyst. At point of use, the two parts were mixed, thereby initiating crosslinking of the siloxanol.
• RTN silicones The next major development in RTN silicones was the one-part system in which a mixture of all components (except water) remained workable in a sealed container until exposed to moisture, such as that present in the atmosphere.
• the major polymer component was a linear or lightly branched silicone having reactive groups that readily underwent hydrolytic polymerization to form siloxanes.
• the reactive groups, that readily underwent hydrolytic polymerization, could be present in terminal or non-terminal positions or both.
• a large number of reactive groups were reported in the prior art to be effective.
• the crosslinking agents usually possessed three or more identical reactive groups are present per molecule.
• a wide variety of catalysts are used; the choice depending on the nature of the functional group that readily underwent hydrolytic polymerization. Metal and amino carboxylate salts are often useful.
• cross-linkers of this type are highly effective, they do possess limitations. For instance, polyfunctional silane monomers represent highly concentrated sites of functionality. They are therefore usually not well suited as means for modifying the properties of the cured sealant.
• the presence of identical functional groups upon the cross-linker also poses problems concerning workability of the sealant composition since gellation times and curing times vary little. This may be remedied by employing sealants containing mixtures of cross-linkers. However, problems associated with proper distribution of the cross-linkers within the sealant composition then occur.
• crosslinking is accomplished by hydrosilylation.
• the major polymer components is usually a linear or lightly branched silicone with vinyl or other olefinic groups in terminal or nonterminal positions.
• the crosslinker is usually a low molecular weight siloxane with three or more hydridosiloxane units per molecule.
• Catalysts are typically platinum compounds that are effective at parts per million (pp ) levels.
• Compositions of this type that are active at room temperature are two-part systems. One-part systems are made with inhibited catalysts but require elevated temperatures for at least brief periods to activate the catalyst and are therefore not true RTN systems.
• a drawback of this kind of crosslinking system is that the platinum catalyst can be poisoned by many substances. This type of curing mechanism has a significant advantage in that no undesirable reaction products are formed.
• crosslinking occurs by oxidation of mercaptoalkyl substituents upon contact with molecular oxygen.
• the major polymer components is a linear or lightly branched silicone having mercaptoalkyl substituents, such as a 3- mercaptopropyl bonded directly to the silicon.
• Crosslinker components are optional and are usually low molecular weight silicones having three or more mercaptoalkyl substituents per molecule.
• Catalysts are organic compounds of pro-oxidant metals such as cobalt.
• the major by-product is water which is considered to be relatively innocuous and which can usually be tolerated or, if necessary, removed in many applications.
• side reactions may result in the formation of small amounts of malodorous and toxic hydrogen sulfide.
• unreacted mercaptoalkyl groups may have undesirable interactions.
• compositions containing disulfide linkages can degenerate with formation of corrosive sulfur compounds such as sulfurous and sulfuric acids on exposure to moisture and air at elevated temperatures.
• RTN sealant compositions often also contain non-reactive silicone oils as viscosity modifiers.
• these oils do indeed aid in the formulation of the sealant, their presence in the crude product is often undesirable since their non-reactive nature allows them to bleed out of the cured material.
• Acetoxysilanes are well known cross-linking agents for one-part room temperature vulcanizable silicone rubber compositions.
• a common type of such an acetoxysilane cross-linking agent is methyltriacetoxysilane.
• Methyltriacetoxysilane is known to have a melting point of 40°C, and has a disadvantage in that it must be melted or blended with another silane in order to be able to add it to a continuous extruder.
• Blends of methyltriacetoxysilane and ethyltriacetoxysilane have been used as cross-linking agent in acetoxy cure RTVs.
• the present invention provides for a one part moisture curable room temperature vulcanizable silicone composition comprising an alkylalkoxyacyloxysilane selected from the group consisting of and
• R 1 , R 4 and R 7 are independently selected from the group of alkyl radicals having the formula (CH 2 ) n X, where n has 1 to 10 carbon atoms, and X is selected from the group consisting of hydrogen, amino, epoxy, cyano, thiocyano, allyl, and vinyl;
• R 2 R 5 and R s are independently selected from the group of acyloxy radicals having the formula OC(0)(CH 2 ) m H, where m has 1 to 8 carbon atoms;
• R 3 , R 6 and R 9 are independently selected from the group of alkoxy radicals or mixture of alkoxy radicals of 1 to 10 carbon atoms wherein the subscripts a, b and c are subject to the following limitations: 0 ⁇ a ⁇ 3; 0 ⁇ b ⁇ 3; and 0 ⁇ c ⁇ 3 wherein said alkylalkoxyacyloxysilane is a liquid at a temperature above 0 °C.
• the present invention further provides for a moisture curable room temperature vulcanizable silicone composition thacomprises:
• R 1 , R 4 and R 7 are independently selected from the group of alkyl radicals having the formula (CH2)nX, where n has 1 to 10 carbon atoms, and X is selected from the group consisting of hydrogen, amino, epoxy, cyano, thiocyano, allyl, and vinyl;
• R 2 R 5 and R 8 are independently selected from the group of acyloxy radicals having the formula OC(0)(CH 2 ) m H, where m has 1 to 8 carbon atoms;
• R 3 , R 6 and R 9 are independently selected from the group of alkoxy radicals or mixture of alkoxy radicals of 1 to 10 carbon atoms wherein the subscripts a, b and c are subject to the following limitations: 0 ⁇ a ⁇ 3; 0 ⁇ b ⁇ 3; and 0 ⁇ c ⁇ 3 wherein said alkylalkoxyacyloxysilane is a liquid at a temperature above 0 °C; (D) from about 0.01 to
• the present invention provides for silicone RTV compositions, containing a crosslinking agent that is reactive in the presence of moisture and a Sn 4+ catalyst.
• the present invention further provides for a crosslinking agent that is a liquid at temperatures above zero degrees Celsius.
• the present invention further provides for a synthesis of the catalyst that does not produce hazardous waste, such as acetyl chloride in its syntheses.
• the present invention further provides for silicone RTV sealants made using this crosslinking agent having excellent primerless adhesion, without the addition of an adhesion promoter.
• the present invention relates to a 1-component, room temperature vulcanized silicone sealant compositions that are fast curing, have excellent primerless adhesion, and are shelf-stable. More particularly, the present invention relates to the discovery of the use of a new family of alkylalkoxyacyloxysilane based crosslinking agents which together with polyhydroxy terminated polydimethlysiloxane (PDMS) polymers, reinforcing fillers, plasticizing oils, and Sn +4 condensation cure catalysts, provide fast curing, self bonding, shelf stable, low temperature stable, 1-part, RTV silicone sealants. Further, these new alkylalkoxyacyloxysilane based crosslinking agents are liquid at ambient temperature, i.e.
• PDMS polyhydroxy terminated polydimethlysiloxane
• alkylalkoxyacyloxysilane based crosslinking agents of the present invention are selected from the group consisting of
• R 1 , R 4 and R 7 are independently selected from the group of alkyl radicals having the formula (CH2) n X, where n has 1 to 10 carbon atoms, and X is selected from the group consisting of hydrogen, amino, epoxy, cyano, thiocyano, allyl, and vinyl and is most preferably hydrogen;
• R 2 R 5 and R 8 are independently selected from the group of acyloxy radicals having the formula OC(0)(CH 2 ) m H, where m has 1 to 8 carbon atoms and is most preferably 1.
• R 3 , R 6 and R 9 are independently selected from the group of alkoxy radicals or mixture of alkoxy radicals of 1 to 10 carbon atoms, and is most preferably 2-propyl, 2-butyl, or 1 butyl.
• a, b and c are independently either 1 or 2 but for mixtures of these crosslinker compounds, which may be mixtures of formula I compounds, formula II compounds or mixtures of formula I and formula II compounds, 0 ⁇ a ⁇ 3; 0 ⁇ b ⁇ 3; and 0 ⁇ c ⁇ 3; with a preferably varying from about 1.50 to about 2.95, more preferably from about 2.20 to about 2.90, and most preferably varying from about 2.75 to about 2.85; with b preferably varying from about 0.50 to about 1.95, more preferably varying from about 1.60 to about 1.95, and most preferably from about 1.75 to about 1.85; and with c preferably varying from about 0.50 to about 1.95, more preferably varying from about 1.
• the present invention also provides for a moisture curable RTV sealant composition
• a moisture curable RTV sealant composition comprising:
• a tin condensation cure catalyst selected from the group consisting of dibutyltindilaurate, dibutyltindiacetate, dibutyldibutoxytin, dibutyldimethoxytin, and dibutyldineodecanoatetin.
• the RTV sealant may optionally contain from about 01 to about 40 weight percent, preferably from about 0.5 to about 30 weight percent, more preferably from about 1 to about 20 weight percent and most preferably from about 5 to about 15 weight percent, of a reinforcing filler selected from the group consisting of fumed silica, precipitated silica, and calcium carbonate.
• the RTV sealant may optionally contain from about 0 to about 40 weight percent, preferably from about 0.5 to about 30 weight percent, more preferably from about 1 to about 20 weight percent and most preferably from about 5 to about 15 weight percent, of a plasticizing fluid being a polydiorganosiloxane (e.g. polydimethylsiloxane) having a viscosity ranging from about 1 to about 3,000 centipoise at 25 °C, preferably from about 1 to about 1,000 centipoise at 25 °C, more preferably from about 1 to about 500 centipoise at 25 °C and most preferably from about 1 to about 350 centipoise at 25 °C.
• a plasticizing fluid being a polydiorganosiloxane (e.g. polydimethylsiloxane) having a viscosity ranging from about 1 to about 3,000 centipoise at 25 °C, preferably from about 1 to about 1,000 centipo
• an RTV composition comprising: (A) 69 parts by weight of a silanol stopped polydimethylsiloxane having a viscosity of 22,000 centipoise (cps) at 25. degree. C;
• Example 1 describes the preparation of (1- butoxy)methyldiacetoxysilane. This crosslinker was synthesized by mixing the following ingredients under anhydrous conditions.
• reaction mixture was stirred for 15 minutes followed by evaporation of acetic acid under reduced pressure.
• Example 2 describes the preparation of a mixture of (1- butoxy)methyldiacetoxysilane and methyltriacetoxysilane.
• This crosslinker was synthesized by mixing the following ingredients under anhydrous conditions.
• This catalyst mixture is a liquid at 20°C
• reaction mixture was stirred for 15 minutes followed by evaporation of acetic acid under reduced pressure.
• Example 3 describes the preparation of a mixture of methyltriacetoxysilane and butoxymethyldiacetoxysilane. This crosslinker was synthesized by mixing the following ingredients under anhydrous conditions. This catalyst mixture is a liquid a 20°C.
• Example 4 describes the preparation of a mixture of methyltriacetoxysilane, (2-propoxy)methylacetoxysilanes. This crosslinker was synthesized by mixing the following ingredients under anhydrous conditions. 15.3 g of 2-propanol
• reaction mixture was stirred for 15 minutes, followed by evaporation of acetic acid under reduced pressure.
• Example 4 describes the preparation of a mixture of methyltriacetoxysilane, (2-propoxy)methylacetoxysilanes and acetic acid. This crosslinker was synthesized by mixing the following ingredients under anhydrous conditions.
• the reaction mixture was stirred for 15 minutes, no removal of acetic acid.
• RTV sealant made with a crosslinking agent composed of a mixture of triacetoxysilane and (2-methyl 2-propoxy)methylacetoxysilanes. This sealant was mixed and extruded in a Werner-Pfleiderer extruder as described elsewhere.
• RTV sealant made with a crosslinking agent composed of a mixture of mixture of (l-butoxy)methyldiacetoxysilane and methyltriacetoxysilane. This sealant was mixed and extruded in a Werner-Pfliederer twin-screw extruder.
• RTV sealant made with a crosslinking agent composed of a mixture of methyltriacetoxysilane and (2-propoxy)methyldiacetoxysilane. This sealant was mixed and extruded in a WP extruder as described elsewhere.
• RTV sealant made with a crosslinking agent composed of a mixture of methyltriacetoxysilane, (2-propoxy)methyldiacetoxysilane, and acetic acid. This sealant was mixed and extruded in a WP extruder as described elsewhere. Preparation of a one component silicone sealant having the following composition:
• the advantage of this invention is that it is a simple way to product a low melting catalyst (will melt at room temperature), by a one step reaction, with or without stripping the acetic acid.

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• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Sealing Material Composition (AREA)

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