Detailed Description
The substantially homogeneous polyurethane-polysiloxane resin mixture of the present invention results from the combination (i.e., mixing) of a two-part curable composition as will be more fully described hereinafter. The two components, which constitute the "first component" and the "second component" of the curable composition, respectively, have storage stability for an indefinite period (indefinition) when separated from each other, but cure rapidly upon combination, providing the resin mixture of the present invention.
A. First component of curable composition
The first component of the two-part curable composition of the invention comprises a Silylated Polyurethane (SPU) resin, a crosslinker for the diorganopolysiloxane in which the silicon atoms at each polymer chain end are silanol terminated ("silanol terminated diorganopolysiloxane" or SDPS), and optionally one or more other ingredients by which the entire curable composition can be adapted to act as a sealant, adhesive or coating, if desired.
Moisture-curable silylated polyurethanes useful in the first component of the curable composition are known materials and can generally be prepared by the following process: (a) reacting an isocyanate-terminated Polyurethane (PU) prepolymer with a suitable silane, for example, a hydrolysable functionality reactive towards isocyanate (specifically 1 to 3 alkoxy groups per silicon atom) and an active hydrogen functionality (e.g., mercapto, primary amine and preferably secondary amine), or (b) reacting a hydroxyl-terminated PU prepolymer with a suitable isocyanate-terminated silane, for example, having 1 to 3 alkoxy groups. Details of these reactions and the preparation of the isocyanate-terminated and hydroxyl-terminated PU prepolymers used can be found in: U.S. Pat. Nos. 4,985,491, 5,919,888, 6,197,912, 6,207,794, 6,303,731, 6,359,101 and 6,515,164 and published U.S. Pat. Nos. 2004/0122253 and 2005/0020706 (isocyanate-terminated PU prepolymers); U.S. Pat. nos. 3,786,081 and 4,481,367 (hydroxyl-terminated PU prepolymer); U.S. Pat. nos. 3,627,722, 3,632,557, 3,971,751, 5,623,044, 5,852,137, 6,197,912, 6,207,783 and 6,310,170 (moisture curable SPU resins derived from the reaction of isocyanate-terminated PU prepolymers with reactive silanes such as aminoalkoxysilanes); and U.S. Pat. Nos. 4,345,053, 4,625,012, 6,833,423 and published U.S. patent application 2002/0198352 (moisture-curable SPU resin derived from the reaction of a hydroxyl-terminated PU prepolymer with an isocyanatosilane). The entire contents of the above-mentioned U.S. patent documents are incorporated herein by reference.
(a) Moisture curable SPUR resins from isocyanate terminated PUR prepolymers
The isocyanate-terminated PU prepolymer is derived from the reaction of one or more polyols (preferably diols) with one or more polyisocyanates (preferably diisocyanates) in a ratio such that the resulting prepolymer is isocyanate-terminated. In the case of the reaction of the diol with the diisocyanate, a molar excess of diisocyanate is used.
Polyols useful in the preparation of the isocyanate-terminated PU prepolymer include polyether polyols, polyester polyols (e.g., hydroxyl-terminated polycaprolactones), polyetherester polyols (e.g., those derived from the reaction of a polyether polyol with epsilon-caprolactone), polyesterether polyols (e.g., those derived from the reaction of a hydroxyl-terminated polycaprolactones with one or more alkylene oxides (e.g., ethylene oxide and propylene oxide)), hydroxyl-terminated polybutadienes, and the like.
Specific suitable polyols include poly (oxyalkylene) ether diols (i.e., polyether diols), specifically poly (oxyethylene) ether diols, poly (oxypropylene) ether diols and poly (oxyethylene-oxypropylene) ether diols, poly (oxyalkylene) ether triols, poly (tetraethylene) ether diols, polyacetals, polyhydroxy polyacrylates, polyhydroxy polyester amides, polyhydroxy polythioethers, polycaprolactone diols and triols, and the like. In one embodiment of the present invention, the polyol used to prepare the isocyanate-terminated PU prepolymer is a poly (oxyethylene) ether glycol having an equivalent weight of about 500 to 25,000. In another embodiment of the present invention, the polyol used to prepare the isocyanate-terminated PU prepolymer is a poly (oxypropylene) ether glycol having an equivalent weight of about 1,000 to 20,000. Mixtures of polyols of various structures, molecular weights and/or functionalities may also be used.
The polyether polyol may have a functionality of up to about 8, but preferably has a functionality of 2 to 4, and more preferably a functionality of 2 (i.e., diol). Particularly suitable are polyether polyols prepared in the presence of Double Metal Cyanide (DMC) catalysts, alkali metal hydroxide catalysts or alkali metal alkoxide catalysts; see, for example, U.S. Pat. nos. 3,829,505, 3,941,849, 4,242,490, 4,335,188, 4,687,851, 4,985,491, 5,096,993, 5,100,997, 5,106,874, 5,116,931, 5,136,010, 5,185,420, and 5,266,681, the entire contents of which are incorporated herein by reference. Polyether polyols prepared in the presence of these catalysts tend to have high molecular weights and low unsaturation, which are believed to result in improved properties of retroreflective articles of the present invention. Preferably, the polyether polyols have a number average molecular weight of from about 1,000 to about 25,000, more preferably from about 2,000 to about 20,000, and still more preferably from about 4,000 to about 18,000. Examples of commercially available diols suitable for use in preparing the isocyanate-terminated PU prepolymer include ARCOL R-1819 (number average molecular weight of 8,000), E-2204 (number average molecular weight of 4,000) and ARCOL E-2211 (number average molecular weight of 11,000).
Any of numerous polyisocyanates, preferably diisocyanates, and mixtures thereof may be used to provide the isocyanate-terminated PU prepolymer. In one embodiment, the polyisocyanate may be diphenylmethane diisocyanate ("MDI"), polymethylene polyphenylene polyisocyanate ("PMDI"), p-phenylene diisocyanate, naphthylene diisocyanate, liquid carbodiimide modified MDI and derivatives thereof, isophorone diisocyanate, dicyclohexylmethane-4, 4' -diisocyanate, toluene diisocyanate ("TDI"), particularly the 2, 6-TDI isomer, as well as various other aliphatic and aromatic polyisocyanates well-established in the art, and combinations thereof.
The silylating reactants used in the reaction with the isocyanate-terminated PUR prepolymers described above must contain functionality reactive with isocyanates and at least one readily hydrolyzable and subsequently crosslinkable group (e.g., alkoxy). Particularly useful silylation reactants are silanes having the general formula:
X-R1-Si(R2)x(OR3)3-x
wherein X is an active hydrogen-containing group reactive with isocyanates, e.g. -SH or-NHR4Wherein R is4Is H, a monovalent hydrocarbon radical having up to 8 carbon atoms or-R5-Si(R6)y(OR7)3-y，R1And R5Each being the same or different divalent hydrocarbon radical having up to 12 carbon atoms optionally containing one or more heteroatoms, each R2And R6Are identical or different monovalent hydrocarbon radicals having up to 8 carbon atoms, each R3And R7Are identical or different alkyl radicals having up to 6 carbon atoms, x and y are each independently of the other 0,1 or 2.
Specific silanes useful in the present invention include various mercaptosilanes such as 2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltripropoxysilane, 2-mercaptoethyltri-sec-butoxysilane, 3-mercaptopropyltri-tert-butoxysilane, 3-mercaptopropyltriisopropoxysilane, 3-mercaptopropyltrioctyxysilane, 2-mercaptoethyltri-2' -ethylhexoxysilane, 2-mercaptoethyldimethoxyethoxysilane, 3-mercaptopropylmethoxyethoxyethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethoxydimethylsilane, 3-mercaptopropyltrimethoxysilane, and the like, 3-mercaptopropylethoxydimethylsilane, 3-mercaptopropyldiethoxymethylsilane, 3-mercaptopropylcyclohexyloxydimethylsilane, 4-mercaptobutyltrimethoxysilane, 3-mercapto-3-methylpropyltrimethoxysilane, 3-mercapto-3-methylpropyl-tripropoxysilane, 3-mercapto-3-ethylpropyl-dimethoxymethylsilane, 3-mercapto-2-methylpropyltrimethoxysilane, 3-mercapto-2-methylpropyldimethoxyphenylsilane, 3-mercaptocyclohexyl-trimethoxysilane, 12-mercaptododecyltrimethoxysilane, 12-mercaptododecyltriethoxysilane, 18-mercaptooctadecyltrimethoxysilane, 18-mercaptooctadecylmethoxydimethylsilane, 2-mercapto-2-methylethyl-tripropoxysilane, 2-mercapto-2-methylethyl-trioctyoxysilane, 2-mercaptophenyltrimethoxysilane, 2-mercaptophenyltriethoxysilane, 2-mercaptotolyltrimethoxysilane, 2-mercaptotolyltriethoxysilane, 1-mercaptomethyltolyltrimethoxysilane, 1-mercaptomethyltolyltriethoxysilane, 2-mercaptoethylphenyltrimethoxysilane, 2-mercaptoethylphenyltriethoxysilane, 2-mercaptoethyltolyltrimethoxysilane, 2-mercaptoethyltolyltriethoxysilane, 3-mercaptopropylphenyltrimethoxysilane and 3-mercaptopropylphenyltriethoxysilane; and various aminosilanes such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 4-aminobutyltriethoxysilane, N-methyl-3-amino-2-methylpropyltrimethoxysilane, N-ethyl-3-amino-2-methylpropyldiethoxymethylsilane, N-ethyl-3-amino-2-methylpropyltriethoxysilane, N-ethyl-3-amino-2-methylpropyl-methyldimethoxysilane, N-butyl-3-amino-2-methylpropyltrimethoxysilane, N-tert, 3- (N-methyl-2-amino-1-methyl-1-ethoxy) -propyltrimethoxysilane, N-ethyl-4-amino-3, 3-dimethyl-butyldimethoxymethylsilane, N-ethyl-4-amino-3, 3-dimethylbutyltrimethoxy-silane, N- (cyclohexyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, Aminopropyltriethoxysilane, bis- (3-trimethoxysilyl-2-methylpropyl) amine and N- (3' -trimethoxysilylpropyl) -3-amino-2-methylpropyltri-methoxysilane.
Catalysts are generally used for the preparation of isocyanate-terminated PU prepolymers. Condensation catalysts are preferably used, since these also catalyze the curing (hydrolysis followed by crosslinking) of the SPU resin component of the curable composition of the invention. Suitable condensation catalysts include dialkyltin dicarboxylates (e.g., dibutyltin dilaurate and dibutyltin acetate), tertiary amines, stannous salts of carboxylic acids (e.g., stannous octoate and stannous acetate), and the like. In one embodiment of the present invention, dibutyltin dilaurate catalyst is used in the preparation of the PUR prepolymer. Other useful catalysts include zirconium-and bismuth-containing complexes (e.g., KAT XC6212, K-KAT XC-A209, and K-KAT 348, available from King Industries, Inc.), aluminum chelates (e.g., aluminum chelates)Type, available from DuPont company; and KRs available from KenrichPetrochemical, Inc.) and other organometallic catalysts (e.g., catalysts comprising metals such as Zn, Co, Ni, Fe), and the like.
(b) Moisture curable SPUR resins from hydroxyl terminated PUR prepolymers
As previously mentioned, the moisture-curable SPU resin of the first component of the curable composition of the present invention may be prepared by the reaction of a hydroxyl-terminated PU prepolymer with an isocyanatosilane. The hydroxyl-terminated PU prepolymer may be prepared in substantially the same manner as described above for the isocyanate-terminated PU prepolymer, using substantially the same materials, i.e., polyol, polyisocyanate, and optionally catalyst (preferably a condensation catalyst), with the primary difference being that the ratio of polyol to polyisocyanate results in hydroxyl termination in the resulting prepolymer. Thus, for example, in the case of a diol reacted with a diisocyanate, a molar excess of the diol is used, thereby producing a hydroxyl-terminated PU prepolymer.
Useful silylating reactants for the hydroxyl-terminated SPU resin are those containing isocyanate-terminated and readily hydrolyzable functionality (e.g., 1 to 3 alkoxy groups). Suitable silylation reactants are isocyanatosilanes having the general formula:
wherein R is8Is alkylene having up to 12 carbon atoms, optionally containing one or more heteroatoms, each R9Are identical or different alkyl or aryl radicals having up to 8 carbon atoms, each R10Are identical or different alkyl radicals having up to 6 carbon atoms, and y is 0,1 or 2. In one embodiment, R8Having 1 to 4 carbon atoms, each R10Identical or different, is methyl, ethyl, propyl or isopropyl, and y is 0.
Specific isocyanatosilanes which may be employed in the present invention to react with the above-described hydroxyl-terminated PU prepolymers to provide the moisture-curable SPU resin include isocyanatopropyltrimethoxysilane, isocyanatoisopropyltrimethoxysilane, isocyanaton-butyltrimethoxysilane, isocyanatot-butyltrimethoxysilane, isocyanatopropyltriethoxysilane, isocyanatoisopropyltriethoxysilane, isocyanaton-butyltriethoxysilane, isocyanatot-butyltriethoxysilane, and the like.
(c) Crosslinking agent
The crosslinker component in the first component of the curable composition is a material effective for crosslinking silanol terminated diorganopolysiloxane (SDPS), which is a component of the second component of the curable composition. In one embodiment, the crosslinking agent is an alkyl silicate having the general formula:
(R11O)(R12O)(R13O)(R14O)Si
wherein R is11、R12、R13And R14Is an independently selected monovalent hydrocarbon radical having up to about 60 carbon atoms.
The crosslinking agents useful in the present invention include tetra-N-propyl silicate (NPS), tetraethyl orthosilicate, methyltrimethoxysilane, and similar alkyl-substituted alkoxysilane compositions.
B. Second component of curable composition
The silanol terminated diorganopolysiloxane polymer (SDPS) in the second component of the curable composition is preferably selected from the group of materials having the general formula:
MaDbD′c
subscript a ═ 2, b equal to or greater than 1, and subscript c is zero or a positive number, where
M＝(HO)3-x-yR15xR16ySiO1/2；
Subscript x is 0,1 or 2 and subscript y is 0 or 1, subject to the following limitations: x + y is less than or equal to 2, wherein R15And R16Is independently selected monovalent C1-C60A hydrocarbyl group; wherein
D＝R17R18SiO1/2，
Wherein R is17And R18Is independently selected monovalent C1-C60A hydrocarbyl group; wherein
D′＝R19R20SiO2/2；
Wherein R is19And R20Is an independently selected monovalent hydrocarbon radical having up to about 60 carbon atoms.
The above-described SDPS polymers and their crosslinking with alkyl silicate crosslinkers (such as those described above) are disclosed in more detail in published U.S. patent application 2005/0192387, the entire contents of which are incorporated herein by reference.
C. Optional ingredients
Optionally, the first component and/or the second component of the curable composition may comprise one or more further ingredients, such as fillers, UV stabilizers, antioxidants, adhesion promoters, cure accelerators, thixotropic agents, plasticizers, moisture scavengers, pigments, dyes, surfactants, solvents and antimicrobial agents, which are present in the first component and/or the second component, whichever component is compatible. Thus, for example, the filler, when present, may be in the first component and/or the second component; the u.v. stabilizer, when present, is typically in the first component; the antioxidant, when present, is typically in the first component; the adhesion promoter, when present, is in the first component; the cure accelerator, when present, is typically in the second component; thixotropic agents, when present, are typically included in the first component; the plasticizer, when present, is in the first component and/or the second component; the moisture scavenger, when present, is in the first component; the pigment, when present, may be in the first component and/or the second component; the dye, when present, may be in the first component and/or the second component; the surfactant, when present, may be in the first component and/or the second component; the solvent, when present, may be in the first component and/or the second component; and antimicrobial agents, when present, are typically incorporated in the second component.
The following examples illustrate the two-part curable compositions of the present invention and the substantially homogeneous polyurethane-polysiloxane resin mixtures prepared therefrom.
Example 1
This example illustrates the preparation of a moisture-curable SPU resin derived from the reaction of an isocyanate-terminated PU prepolymer with an aminosilane. SPU resin was used to prepare the first part of the two-part composition of examples 2-5 and one-part composition (one-part composition) of comparative example 1.
The SPU resin is prepared in a two-step reaction sequence substantially as described in U.S. patent No. 6,602,964, the entire contents of which are incorporated herein by reference. In a first step, an isocyanate-terminated PU prepolymer was prepared by reacting a polypropylene ether glycol (Acclaim 4200, 400g) with isophorone diisocyanate (IPDI, 34.8g) in the presence of a trace of a tin catalyst (dibutyltin dilaurate, 3.5 ppm). The reaction to form the prepolymer is carried out at 70-75 ℃ until the NCO concentration has dropped to 0.8% as determined by titration. In the second step (silylation of the prepolymer), 17.6g N-isobutylaminopropyl-trimethoxysilane was added to the prepolymer and reacted with all remaining NCO until no NCO was detected by titration. The resulting moisture-curable SPU resin had a viscosity of about 100,000cps at 25 ℃.
Comparative example 1; examples 2 to 5
In these examples, the following materials were used:
| materials/functions | Name (R) |
| SPU resin of example 1, moisture curable | SPU resin |
| Silanol terminated diorganopolysiloxane having a viscosity of about 3,000cps at 25 deg.C | SDPS-1 |
| Silanol terminated diorganopolysiloxane having a viscosity of about 30,000cps at 25 deg.C | SDPS-2 |
| Precipitated calcium carbonate (Filler) | P-CaCO3 |
| Surface-modified calcium carbonate (filler) | SM-CaCO3 |
| Titanium dioxide (pigment) | TiO2 |
| Fumed silica (thixotropic agent) | F-Sil |
| N-beta- (aminoethyl) -gamma-aminopropyl-trimethoxysilane (adhesion promoter) | Silane A |
| Tris- [3- (trimethoxysilyl) propyl]Isocyanurate (adhesion promoter) | Isocyanurates |
| tetra-N-propyl silicate (crosslinker for SDPS) | NPS |
| Methyltrimethoxysilane (moisture scavenger/crosslinker) | Silane B |
| Ciba-Geigy Tinuvin 213 | UV stabilizers |
| Ciba-Geigy Tinuvin 622L | UV stabilizers |
| Dibutyl tin oxide (condensation catalyst) | DBTO |
The two-part curable compositions of examples 2-5 and the one-part curable composition of comparative example 1 were prepared using the above materials using the following general procedure:
A. two-part curable compositions (examples 2-5)
Adding P-CaCO before use3、SM-CaCO3And F-Sil is dried in an oven at 120 ℃ for at least 12 hours.
The first component of each two-part curable composition was prepared by reacting P-CaCO3Diisodecyl phthalate plasticizer, F-Sil, TiO2Mixing at 2,000rpm on a Speed Mixer DAC 400 FV, followed by addition of SM-CaCO in the amount shown in Table 13SPU resin, antioxidant, UV stabilizer, silane a, isocyanurate and NPS until a well blended mixture is obtained.
The second component of each two-part curable composition was prepared by mixing SDPS-1, SDPS-2, and P-CaCO in the amounts shown in Table 1 below3Mix on a Speed Mixer at 2000rpm for about 2 minutes, then add additional DBTO condensation catalyst. The mixture was then blended on a Speed Mixer until a substantially homogeneous mixture was obtained.
B. One part curable composition (comparative example 1)
This one-part curable composition was prepared as described above for the first part of the two-part curable composition, but finally no NPS and no DBTO condensation catalyst were added.
The two-part curable composition described above was blended on a Speed Mixer for 1-2 minutes and subsequently cast into a film for mechanical testing and weathering testing. The cast film and the one-component curable composition provided in the form of the cast film are both cured under controlled conditions:
table 1: curable composition formulations
The results of the mechanical and weather resistance tests performed on the cured films are as follows:
table 2: results of the experiment
| Example 2 | Example 3 | Example 4 | Example 5 | Comparative example 1 |
| Tensile stress (psi) | 213 | 187 | 254 | 219 | 285 |
| Young's modulus (psi) | 442 | 239 | 416 | 304 | 511 |
| Elongation% | 94 | 112 | 125 | 124 | 126 |
| Hardness, Shore A | 47 | 43 | 46 | 43 | 55 |
| B value after aging in QUV weatherometer for 4400 hours | 12 | 12 | 10 | 9 | 15 |
| Visual appearance | Light beige, less chalky | Light beige, less chalky | Light beige, less chalky | Light beige, light chalky | White and white chalk |
From these data, it is shown that while the cured resin blends of the present invention (examples 2-5) have inferior tensile strength, Young's modulus, and percent elongation compared to the cured resin of comparative example 1, it is believed that any of these properties proved acceptable values due to their cured SPUR resin content. However, the cured resin of the present invention was significantly superior to the resin of comparative example 1 in weatherability, which is believed to be due to the crosslinked polysiloxane content of the resin.
While the method of the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention method, but that the invention will include all embodiments falling within the scope of the appended claims.