Classifications

• • 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
  • 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
• • 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
  • C08G77/80—Siloxanes having aromatic substituents, e.g. phenyl side groups
• • 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
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
• • 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
  • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59

Definitions

• This invention is generally related to silicone compositions for structural glazing and weatherseal applications. More specifically, this invention relates to silicone rubber compositions possessing rapid deep-section cure.
• One-part systems generally comprise, inter alia, a silicone polymer having hydrolyzable silyl functionality and a catalyst.
• a silicone polymer having hydrolyzable silyl functionality Upon exposure to a moist atmosphere, the silyl groups react with water to form silanol groups which, in turn, condense to form a cured siloxane network, the condensation being facilitated by the catalyst.
• silicone polymers systems typically cure slowly, i.e., after a few days to a few weeks of exposure to a moist atmosphere.
• Prior art solutions to the undesirably slow deep-section cure rate of silicone and hydrocarbon based compositions include the addition of various catalysts and other ingredients as optional components.
• U.S. Pat. No. 4,435,536 to Kato et al. discloses one-pack, moisture-curable comp.ositi ⁇ n ⁇ [ased on hydrolyzable silyl group containing vinyl polymers wherein the inclusion of a splvent imparts storage stability and "workability" to the compositions. When cured, the compositions are said to have excellent surface hardness and weather resistance.
• the only specific limitation on the solvent is that it does not lead to precipitation when combined with the vinyl ether or ester, inter alia.
• Preferred solvents include alcohols and hydrolyzable esters, methanol, methyl orthoformate, ethyl orthoformate, methyltrimethoxilane and ethyl silicate being specifically illustrated.
• the systems illustrated appear to be cured at elevated temperatures as thin films and are not shown to provide deep-section cure. Additionally, the solvents illustrated either react into the network, or are too volatile to be retained in the composition as it cures.
• long-chain alkyl alcohols which are also suggested as solvents would tend to undergo an exchange reaction with the hydrolyzable groups on silicon to effectively cap the polymer with a long-chain alkoxy group which is not readily hydrolyzed, thereby interfering with the intended moisture cure.
• Fig. 1 is a graphical representation of the "tack-free time" of Comparative
• Fig. 2 is a graphical representation of the "deep-section cure" rates of
• Fig. 3 is a graphical representation of the "deep-section cure" rates of
• the present invention discloses blends of siloxane polymers and zinc oxide and their uses in sealant formulations possessing rapid deep-section cure. More particularly, the present invention provides a curable sealant composition comprising: a) at least one silanol-terminated diorganopolysiloxane; b) at least one crosslinker for the silanol-terminated diorganopolysiloxane(s); c) at least one catalyst for the crosslinking reaction; d) a rapid deep-section curing amount zinc oxide; and, optionally, e) at least one additional component selected from the group consisting of alkyl-terminated diorganopolysiloxane, filler, UV stabilizer, antioxidant, adhesion promoter, cure accelerator, thixotropic agent, plasticizer, moisture scavenger, pigment, dye, surfactant, solvent and biocide.
• a curable sealant composition comprising: a) at least one silanol-terminated diorganopolysiloxan
• the room-temperature curable one and two part sealant compositions of the present invention inventively provides rapid deep-section cure.
• the present invention discloses blends of siloxane polymers and zinc oxide and their uses in sealant formulations.
• the presence of zinc oxide in silicone systems to provide high thermal conductivity and prolonged surface oil on room temperature vulcanizable (RTV) silicone sealant has been reported in U.S. Patents Nos. 5,292,606 and 5,733,960, respectively.
• Tack-free time or ⁇ suf face curing and “deep-section cure” or curing along the sealant's thickness.
• Tack-free time is tested by spreading a sealant to a desired thickness (e.g., 6.35 mm) on a Teflon mold and placing a 1Og stainless steel (SS) weight on the sealant at different intervals of time.
• the tack free time is the time when no material sticks to the surface of the weight.
• the curable composition of the present invention includes at least one silanol-terminated diorganopolysiloxanes (a).
• Suitable silanol-terminated diorganopolysiloxanes (a) include those of the general formula:
• R 1 and R 2 each independently is a monovalent hydrocarbon group up to 60 carbon atoms; D is
• R 3 and R 4 each independently is a monovalent hydrocarbon group up to 60 carbon atoms; and D' is
• R 5 R 6 SiO 2 A 2 wherein R and R each independently is a monovalent hydrocarbon group up to 60 carbon atoms.
• the level of incorporation of the diorganopolysiloxane wherein the silicon atom at each polymer chain end is silanol terminated (a) ranges from about 5 weight percent to, about 95 weight percent of the total composition. In another embodiment of the invention, the level of incorporation of the diorganopolysiloxane polymer or blends of diorganopolysiloxane polymers (a) ranges from about 20 weight percent to about 85 weight percent of the total composition. In yet another embodiment of the present invention, the diorganopolysiloxane polymer or blends of diorganopolysiloxane polymers (a) ranges from about 30 weight percent to about 60 weight percent of the total composition.
• Suitable cross-linkers (b) of the present invention include an alkylsilicate of the general formula:
• R 7 , R 8 , R 9 and R 10 are independently chosen monovalent Ci to Ceo hydrocarbon radicals.
• crosslinkers include, but are not limited to, tetra-N- propylsilicate (NPS), tetraethylortho silicate and methyltrimethoxysilane (MTMS), vinyltrimethoxysilane (VTMS) and similar alkyl substituted alkoxysilane compositions, and the like.
• the level of incorporation of the alkylsilicate (crosslinker) ranges from about 0.3 weight percent to about 5 weight percent of the total composition.
• the level of incorporation of the alkylsilicate (crosslinker) ranges from about 0.5 weight percent to about 1.5 weight percent of the total composition.
• Suitable catalysts (c) for use herein can be any of those known to be useful for facilitating crosslinking in silicone sealant compositions.
• the catalyst may include metal and non-metal catalysts.
• the metal portion of the metal condensation catalysts useful in the present invention include tin, titanium, zirconium, lead, iron cobalt, antimony, manganese, bismuth and zinc compounds.
• tin compounds useful for facilitating crosslinking in silicone sealant compositions include: tin compounds such as dibutyltindilaurate, dibutyltindiacetate, dibutyltindimethoxide, tinoctoate, isobutyltintriceroate, dibutyltinoxide, solubilized dibutyl tin oxide, dibutyltin bis-diisooctylphthalate, bis-tripropoxysilyl dioctyltin, dibutyltin bis-acetylacetone, silylated dibutyltin dioxide, carbomethoxyphenyl tin tris-uberate, isobutyltin triceroate, dimethyltin dibutyrate, dimethyltin di-neodecanoate, triethyltin tartarate, dibutyltin dibenzoate, tin oleate,
• the catalyst for the crosslinking reaction is a metal catalyst.
• the metal catalyst is selected from the group consisting of tin compounds, and in yet another embodiment of the invention, the metal catalyst is solubilized dibutyl tin oxide.
• titanium compounds useful for facilitating crosslinking in silicone sealant compositions include:
• the catalyst for the crosslinking reaction is Di(isopropoxide) Titanium bis(ethylacetoacetate).
• the level of incorporation of the catalyst ranges from about 0.001 weight percent to about 1 weight percent of the total composition. In another embodiment off the invention, the level of incorporation of the catalyst, ranges from about 0.003 weight percent to about 0.5 weight percent of the total composition. In yet another embodiment of the invention, the level of incorporation of the catalyst, ranges from about 0.005 weight percent to about 0.2 weight percent of the total composition.
• the curable sealant composition of the present invention provides room- temperature curable silicone sealant composition, which cures to provide rapid deep- section cure.
• This rapid deep-section cure is provided by the presence of particulate zinc oxide (d) in the room temperature-curable silicone sealant composition when present in an amount of at least about 1 parts by weight per 100 parts by weight of the total composition of the room-temperature curable silicone sealant composition.
• the zinc oxide is present in amounts from about 2 to about 30 parts by weight per 100 parts by weight of the total composition, and in a more specific embodiment from about 5 to about 20 parts by weight per 100 parts by ⁇ weight'of:the totahcomposition:
• the particulate zinc oxide (d) of the present invention possesses an average particle size of less than about 1 micron, from about 50 to about 70 nm, and a surface area from about 5 to about 30 m /g.
• the zinc oxide (d) possesses a purity of from about 80 to about 99.9 percent and a pH that ranges from about 7.0 to about 9.0.
• the zinc oxide of the present invention is commercially available as White Seal (IP 100) (available from MLA group of Industries, Kanpur, India); Zincosil NK-T-150 (available
• the room- temperature curable silicone sealant composition is obtained as a "one-part" composition, wherein all the ingredients are contained in one package and curing occurs upon exposure to atmospheric air.
• the room-temperature curable silicone sealant composition is obtained using a "two-part" composition, such compositions are well known in the art.
• the first part comprises polydiorganosiloxane as described herein, and zinc oxide
• a second part comprises a crosslinker, such as the one described herein above.
• the second part can also contain filler and a curing catalyst for the room-temperature curable silicone composition.
• the particulate zinc oxide can be added to either the first or second part.
• the "parts" of these two-part compositions are stored in separate packages to prevent premature curing which can occur if all the ingredients are mixed for too long a time period before the use of the composition.
• compositions of the present invention can be prepared using either batch or continuous modes of manufacture.
• the ingredients such as silicone polymer, zinc oxide, cure catalyst, crosslinker, adhesion promoter, plasticizers, filler, process aids, and other additives are combined in a continuous compounding extruder to produce the desired sealant composition.
• Both the "first part” and the "second part” are prepared in this manner.
• the continuous compounding extruder can be any continuous compounding extruder such as the twin screw Wemer- Pfleiderer extruder, or a Buss, or P.B. Kokneader extruder.
• ingredients may be mixed in the continuous compounding extruder, that is silicone polymer, zinc oxide, plasticizer, a. condensation catalyst and an adhesion promoter, ⁇ etc ⁇ __ In_s ⁇ ch .
• a process ⁇ whicMs ⁇ continuous ⁇ theiextrudemssoperate ⁇ afcairangejOf ⁇ Ho- ⁇ fe € ⁇ butTmore ⁇ zz ⁇ preferably in the range of 25° to 50° C and the extruder is operated at a partial vacuum so as to remove volatiles during the mixing process.
• the silicone compositions of the present invention further comprise an alkoxysilane or blend of alkoxysilanes as an adhesion promoter.
• the adhesion promoter may be a combination blend of n-2-aminoethyl-3-aminopropyltrimethoxysilane and 1,3,5- tris(trimethoxysilylpropyl)isocyanurate.
• adhesion promoters useful in the present invention include but are not limited to n-2-aminoethyl-3-aminopropyltriethoxysilane, ⁇ - aminopropyltriethoxysilane, ⁇ -aminopropyltrimethoxysilane, aminopropyltrimethoxysilane, Z?£s- ⁇ -trimethoxysilypropyl)amine, N-Phenyl- ⁇ - aminopropyltrimethoxysilane, triaminofunctionaltrimethoxysilane, ⁇ - aminopropylmethyldiethoxysilane, y- aminopropylmethyldiethoxysilane, methacryloxypropyltrimethoxysilane, methylaminopropyltrimethoxysilane, ⁇ - glycidoxypropylethyldimethoxysilane, ⁇ -glycidoxypropyltrimethoxysilane, ⁇ - glycidoxyethyl
• the level of incorporation of the alkoxysilane ranges from about 0.1 weight percent to about 20 weight percent. In one embodiment of the invention, the adhesion promoter ranges from about 0.3 weight percent to about 10 weight percent of the total composition. In another embodiment of the invention, the adhesion promoter ranges from about 0.5 weight percent to about 2 weight percent of the total composition.
• the composition of the present invention includes a plasticizer to reduce the modulus of the cured elastomer.
• the plasticizer can be polydimethylsiloxane having terminal trioganosiloxy units where the organo groups are methyl, vinyl or phenyl or combinations of these groups.
• the polydimethylsiloxanes used as plasticizers or modulus reducing agents can normally have a viscosity of from 100 to 100,000 mpa.s measured at 25° C and can be used in amounts up to 80 parts by weight per 100 parts by weight of the polymeric material.
• the silicone composition of the present invention may also comprise a filler.
• Suitable fillers of the present invention include, but are not limited to, ground, precipitated and colloidal calcium carbonates which is treated with compounds such as stearate or stearic acid, reinforcing silicas such as fumed silicas, precipitated silicas, silica gels and hydrophobized silicas and silica gels; crushed and ground quartz, alumina, aluminum hydroxide, titanium hydroxide, diatomaceous earth, iron oxide, carbon black and graphite or clays such as kaolin, bentonite or montmorillonite, talc, mica, and the like.
• the filler is a calcium carbonate filler, silica filler or a mixture thereof.
• zinc oxide (d) is added directly to the filler.
• the type and amount of filler added depends upon the desired physical properties for the cured silicone composition.
• the amount of filler is from 0 weight percent to
• the amount of filler is from about 5 weight percent to about 60 weight percent of the total composition. In still another embodiment of the invention, the amount of filler is from about 10 weight percent to about 40 weight percent of the total composition.
• the filler may be a single species or a mixture of two or more species.
• compositions of the present invention may optionally comprise non- ionic surfactant compound selected from the group of surfactants consisting of polyethylene glycol, polypropylene glycol, ethoxylated castor oil, oleic acid ethoxylate, alkylphenol ethoxylates, copolymers of ethylene oxide (EO) and propylene oxide (PO) and copolymers of silicones and polyethers (silicone polyether copolymers), copolymers of silicones and copolymers of ethylene oxide and propylene oxide and mixtures thereof in an amount ranging from slightly above 0 weight percent to about 10 weight percent, more preferably from about 0.1 weight percent to about 5 weight percent, and most preferably from about 0.5 weight percent to about 0.75 weight percent of the total composition.
• non- ionic surfactant compound selected from the group of surfactants consisting of polyethylene glycol, polypropylene glycol, ethoxylated castor oil, oleic acid ethoxylate, alkylphenol
• compositions of the present invention may be prepared using other ingredients that are conventionally employed in room temperature vulcanizing (RTV) silicone compositions such as colorants and pigments as long as they do not interfere with the desired properties.
• RTV room temperature vulcanizing
• the rapid deep-section curing silicone sealant compositions of the present invention find numerous uses in applications where rapid deep-section curing is essential.
• the compositions are used for weather sealing and sealant composition in insulating glass units, or IG units, as elements of windows, skylights, doors and related products, including vehicles.
• Additional uses of the rapid deep-section curing silicone sealant compositions include conventional curtain wall cladding systems and adjacently jointed window panels, e.g., atrium skylights, glass window walls, and the like.
• the present compositions provide the necessary flexibility and resiliency, in the desired application, which provides for expansion and contraction due to various conditions, e.g., temperature variations and movement due to
• Comparative Examples 1 and 2 were prepared without zinc oxide and consisted of the various ingredients displayed in Table 1. Comparative Example 1 and 2 were prepared the same way in Ross mixer using the following procedure: 34g of silanol polymer was placed in the Ross mixer and 1Og of plasticizer was placed in a Ross kettle. Heat was applied to 100° C. 20 g of Omya CaCO 3 was slowly added while mixing. 2g of doubly treated fumed silica was also added. Mixing continued for 15 minutes. The dispersion was checked. Additional 15g of Omya CaCO 3 was slowly added along with 2g of doubly treated fumed silica and mixed for 30 minutes. The dispersion was again checked. Another 15g of Omya CaCO 3 slowly added to the mix, along with 2 more grams of doubly treated fumed silica and mixing continued for 2 hours. The mixture was transferred to an air-tight container.
• Comparative Example 2 was prepared exactly as Comparative Example 1 except that cross-linker vinyl trimethoxy silane (VTMS) and adhesion promoter Iso-T were used as displayed in Table 3:
• VTMS cross-linker vinyl trimethoxy silane
• adhesion promoter Iso-T adhesion promoter Iso-T
• Example 1 sealant formulation was prepared with zinc oxide and the
• Example 1 was prepared cross-linker MTMS and adhesion promoter Iso-T:
• Example 2 sealant formulation [0048] The ingredients of Example 2 sealant formulation are displayed in Table 6:
• Example 2 sealant formulation was prepared with zinc oxide and the various ingredients displayed in Table 6.
• Example 2 was prepared in Ross mixer using the following procedure: 34g of Silanol polymer was placed in a Ross mixer and 1Og of plasticizer was placed in a Ross kettle. Heat was applied to 100° C. 15 g of Omya CaC ⁇ 3 , 2g of doubly treated fumed silica, and 1Og of zinc oxide were slowly added while mixing. Mixing continued for 15 minutes. The dispersion was checked. An additional 1Og of Omya CaCO 3 and 2g of doubly treated fumed silica were slowly added to the mixture. Mixing proceeded for 30 minutes. The dispersion was checked. Another 15g of Omya CaCO 3 and 2g of doubly treated fumed silica were slowly added to the mixture. Mixing continued for 2 hours. The mixture was transferred in an air tight container.
• Example 2 was prepared with cross-linker vinyltrimethoxysilane (VTMS) and adhesion promoter Iso-T and the various ingredients of Table 7:
• VTMS cross-linker vinyltrimethoxysilane
• Iso-T adhesion promoter
• Examples 1-2 and Comparative Examples 1-2 in Teflon molds with 1 A" thickness the surface was made even with an aluminum spacer. Beginning at the time the material was first applied, the surface was checked with a 1Og weight to determine if the material is -tack-free-at4 ⁇ -minute-mter ⁇ als z (minimum)-untiHt-is-foundHo-be-tack-free.- ⁇ ack-free— time data of Examples 1-2 and Comparative Examples 1-2 is presented in Figure 1.
• Deep-section cure was determined by solvent swelling experiments as follows: A weighed portion of the resin in accordance with Examples 1-2 and Comparative Examples 1-2 was obtained from a cut along the thickness of the mold (a sample of about 5 grams from each of Examples 1-2 and Comparative Examples 1-2 was obtained) and allowed to swell in 100ml of toluene for 3 days. The samples from Example 1-2 and Comparative Examples 1-2 were removed from the toluene and kept for drying under ambient conditions for 3 days. Each sample was weighed again after drying. The difference in weight provides the amount of uncured sample from Example 1-2 and Comparative Examples 1-2 dissolved in toluene. This measurement was obtained at the 6 th , 24 th and 48 th hour after applying the sealant examples in the Teflon mold. The percentage of uncured example was plotted against time.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Sealing Material Composition (AREA)
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