Patent Application
20060073346
The present invention relates in general to composites, and more specifically, to polyester-polyurethane composites in which adhesion between an unsaturation containing polyester matrix and a polyurethane matrix is greatly enhanced by the inclusion in the polyurethane matrix of at least one polyether containing both hydroxyl-functionality and unsaturation-functionality.
Shen et al., in U.S. Pat. No. 5,854,386, disclose polyethers which contain both hydroxyl-functionality and unsaturation-functionality. These bi-functional compounds are prepared by oxyalkylating an unsaturated monomer having at least one oxyalkylatable hydrogen in the presence of an effective amount of a double metal cyanide complex catalyst, optionally, when necessary, in the presence of a free radical polymerization inhibitor. Although the resulting polyethers are said to be suitable for such uses as polymer polyol stabilizers or stabilizer precursors, and both in situ and ex situ impact modifiers for thermoplastics, no suggestion is made in Shen et al. of using these polyethers as adhesion promoters between polyurethanes and unsaturated polyesters.
U.S. Pat. No. 6,461,732, issued to Wittmann et al., teaches composites of at least two different plastics materials joined directly to one another. One plastic is a thermoplastic polymer or a thermoplastic mixture of polymers which contains at least one polar compound of at least one metal as an extremely finely divided powder and the other plastic is polyurethane.
Therefore, a need continues to exist in the art for polyester-polyurethane composites having improved adhesion between the polyester and polyurethane layers.
Accordingly, the present invention provides a composite made from an unsaturation-containing polyester matrix and a polyurethane matrix including at least one polyether containing both hydroxyl-functionality and unsaturation-functionality. The inventive composites exhibit markedly improved adhesion between the polyurethane and polyester matrices.
These and other advantages and benefits of the present invention will be apparent from the Detailed Description of the Invention herein below.
The present invention will now be described for purposes of illustration and not limitation. Except in the operating examples, or where otherwise indicated, all numbers expressing quantities, percentages, molecular weights and so forth in the specification are to be understood as being modified in all instances by the term “about.” Equivalent weights and molecular weights given herein in Daltons (Da) are number average equivalent weights and number average molecular weights respectively, unless indicated otherwise.
The present invention provides a composite made from an unsaturation-containing polyester matrix and a polyurethane matrix including at least one polyether containing both hydroxyl-functionality and unsaturation-functionality, wherein the at least one polyether containing both hydroxyl-functionality and unsaturation-functionality promotes adhesion between the polyester and polyurethane matrices
The present invention further provides a process for producing a polyurethane-polyester composite involving applying a polyurethane matrix including a polyether containing both hydroxyl-functionality and unsaturation-functionality to a partially cured unsaturation-containing polyester matrix and curing the matrices.
The present invention involves the incorporation of the hydroxyl terminus of a polyether containing both hydroxyl-functionality and unsaturation-functionality into a polyurethane polymer matrix. Without wishing to be limited to any theory, the inventors herein speculate that the unsaturated group of this polyether is chemically integrated into an unsaturation-containing polyester matrix during application of the polyurethane polymer matrix to the polyester matrix. The polyether containing both hydroxyl-functionality and unsaturation-functionality is thus chemically bonded to both polymer matrices, thereby greatly improving the adhesion between the two different matrices. Without this unsaturation-containing polyether, tensile adhesion values in such polyurethane-polyester composites are typically below 100 psi. In the inventive composites, at levels as low as 3 parts by weight (“pbw”) of the polyether containing both hydroxyl-functionality and unsaturation-functionality, adhesion values of greater than 400 psi can be achieved.
As mentioned above, the salient feature of the present invention is that the polyurethane is formed containing a polyether containing both hydroxyl-functionality and unsaturation-functionality having e.g., an acrylate functional group as one end group and a hydroxyl functional group as the other end group. This polyurethane is applied onto an unsaturation-containing polyester gel coat. The polyurethane is preferably applied before this polyester gel coat has completely cured (which occurs via a free radical cure mechanism) so that the acrylate-containing polyether can react with both the polyester gel coat (via the acrylate moiety) and with the isocyanate of the polyurethane via the hydroxyl moiety.
Polyurethane Matrix
The polyurethane matrix of the inventive composite is produced by the reaction of a polyisocyanate with an isocyanate-reactive component. The isocyanate-reactive component includes at least one polyether containing both hydroxyl-functionality and unsaturation-functionality. This reaction preferably occurs at an isocyanate index of greater than 100 and more preferably at an isocyanate index of between 103 and 107.
Isocyanate
Any of the known organic isocyanates, modified isocyanates or isocyanate-terminated prepolymers made from any of the known organic isocyanates may be used to produce the polyurethane matrix of the inventive composites. Suitable isocyanates include aromatic, aliphatic, and cycloaliphatic polyisocyanates and combinations thereof. Useful isocyanates include, but are not limited to, diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,6-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, hexahydro-toluene diisocyanate and its isomers, isophorone diisocyanate, dicyclo-hexylmethane diisocyanates, 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate and 3,3′-dimethyl-diphenylpropane-4,4′-diisocyanate; triisocyanates such as 2,4,6-toluene triisocyanate; and polyisocyanates such as 4,4′-dimethyl-diphenylmethane-2,2′,5,5′-tetraisocyanate and the polymethylene polyphenylpolyisocyanates.
Undistilled or a crude polyisocyanate may also be used in producing the polyurethane matrix of the inventive composite. The crude toluene diisocyanate obtained by phosgenating a mixture of toluene diamines and the crude diphenylmethane diisocyanate obtained by phosgenating crude diphenylmethanediamine (polymeric MDI) are examples of suitable crude polyisocyanates. Suitable undistilled or crude polyisocyanates are disclosed in U.S. Pat. No. 3,215,652.
Modified isocyanates are obtained by chemical reaction of diisocyanates and/or polyisocyanates. Modified isocyanates useful in the practice of the present invention include isocyanates containing ester groups, urea groups, biuret groups, allophanate groups, carbodiimide groups, isocyanurate groups, uretdione groups and/or urethane groups. Preferred examples of modified isocyanate include prepolymers containing NCO groups and having an NCO content of from 25 to 35 wt %, preferably from 28 to 32 wt %, particularly those based on polyether polyols or polyester polyols and diphenylmethane diisocyanate. Processes for the production of these prepolymers are known in the art. Polyisocyanate adducts containing biuret groups may be prepared from the previously mentioned diisocyanates by processes such as those disclosed in U.S. Pat. Nos. 3,124,605; 3,358,010; 3,644,490; 3,862,973; 3,903,126; 3,903,127; 4,051,165; 4,147,714 or 4,220,749 by using co-reactants such as water, tertiary alcohols, primary and secondary monoamines, and primary and/or secondary diamines. The preferred diisocyanate to be used in these processes is 1,6-diisocyanato-hexane.
Polyisocyanate adducts containing allophanate groups may be prepared from diisocyanates by any of the processes disclosed in U.S. Pat. Nos. 3,769,318 and 4,160,080; British Patent 994,890; and German Offenlegungsschrift 2,040,645.
Polyisocyanate adducts containing isocyanurate groups may be prepared by trimerizing diisocyanates in accordance with the processes disclosed in U.S. Pat. Nos. 3,487,080; 3,919,218; 4,040,992; 4,288,586; and 4,324,879; German Auslegeschrift 1,150,080; German Offenlegungsschrift 2,325,826; and British Patent 1,465,812. The preferred diisocyanates to be used for producing such adducts are 2,4 diisocyanatotoluylene, 2,6-diisocyanatotoluene and mixtures of these isomers; 1,6-diisocyanatohexane; isophorone diisocyanate and mixtures of 1,6-diisocyanatohexane and isophorone diisocyanate.
Isocyanate-Reactive Component
Although any isocyanate-reactive compound may be used to produce the polyurethane matrix of the inventive composite, polyether polyols are preferred as isocyanate-reactive components. Suitable methods for preparing polyether polyols are known and are described, for example, in EP-A 283 148, U.S. Pat. Nos. 3,278,457; 3,427,256; 3,829,505; 4,472,560; 3,278,458; 3,427,334; 3,941,849; 4,721,818; 3,278,459; 3,427,335; and 4,355,188.
Suitable polyether polyols may be used such as those resulting from the polymerization of a polyhydric alcohol and an alkylene oxide. Examples of such alcohols include ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, glycerol, 1,1,1-trimethylolpropane, 1,1,1-trimethylolethane, or 1,2,6-hexanetriol. Any suitable alkylene oxide may be used such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, and mixtures of these oxides. Polyoxyalkylene polyether polyols may be prepared from other starting materials such as tetrahydrofuran and alkylene oxide-tetrahydrofuran mixtures, epihalohydrins such as epichlorohydrin, as well as aralkylene oxides such as styrene oxide. The polyoxyalkylene polyether polyols may have either primary or secondary hydroxyl groups. Included among the polyether polyols are polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, polytetramethylene glycol, block copolymers, for example, combinations of polyoxypropylene and polyoxyethylene glycols, poly-1,2-oxybutylene and polyoxyethylene glycols and copolymer glycols prepared from blends or sequential addition of two or more alkylene oxides. The polyoxyalkylene polyether polyols may be prepared by any known process.
Polyether Containing Both Hydroxyl-Functionality and Unsaturation-Functionality
The isocyanate-reactive component of the polyurethane matrix of the composite of the present invention includes one or more polyethers containing both hydroxyl-functionality and unsaturation-functionality. Such polyethers may be made by various methods as known in the art. The inventors herein prefer polyethers containing both hydroxyl-functionality and unsaturation-functionality made according to the methods disclosed in U.S. Pat. No. 5,854,386. Examples of suitable starters for such polyethers include, but are not limited to, hydroxyalkylacrylates and methacrylates such as hydroxyethylacrylate, hydroxypropylacrylate, hydroxybutylacrylate, hydroxyethylmethacrylate and hydroxypropylmethacrylate, unsaturated monocarboxylic acids, particularly α-unsaturated acids such as acrylic acid and methacrylic acid, half esters of unsaturated carboxylic acids such as maleic acid methyl half ester, maleic acid ethyl half ester, and fumaric acid methyl half ester; oligomeric reaction products of unsaturated dicarboxylic acids or acid anhydrides with diols or polyoxyalkylene oligomer glycols such as bis(2-hydroxyethyl)maleate and bis(2-hydroxyethyl)fumarate, unsaturated aromatic compounds such as 4-vinylphenol, and the like.
Particularly preferred are those polyethers based on monomethacrylic acid made according to U.S. Pat. Nos. 5,854,386 and 6,664,360, the entire contents of both patents are incorporated herein by reference thereto. The polyether containing both hydroxyl-functionality and unsaturation-functionality may preferably be present in the isocyanate-reactive component in an amount ranging from 0.5 to 10 pbw, more preferably from 1.5 to 8 pbw, based on the weight of the isocyanate-reactive component. The polyether containing both hydroxyl-functionality and unsaturation-functionality may be present in the isocyanate-reactive component of the polyurethane matrix of the inventive composite in an amount ranging between any combination of these values, inclusive of the recited values.
Polyester Matrix
The polyester matrix of the inventive composite is prepared from polycarboxylic acids and polyalcohols and contains ethylenically unsaturated functionality. The unsaturated functionality may be provided by the polycarboxylic acid itself or may result from the inclusion in the polyester matrix of copolymerizable compounds having ethylenically unsaturated functionality. Suitable unsaturated polycarboxylic acids such as maleic acid, fumaric acid, itaconic acid, maleic acid mono (meth)acryloyloxyethyl ester, succinic acid mono (meth)acryloyloxyethyl ester and phthalic acid mono (meth)acryloyloxyethyl ester may be used. Also suitable are polycarboxylic acids including terephthalic acid, isophthalic acid, phthalic acid, trimellitic acid, cycloaliphatic dicarboxylic acids, such as hexahydroterephthalic acid and hexahydrophthalic acid, and linear aliphatic dicarboxylic acids, such as succinic, glutaric, adipic, azelaic, sebacic and decanedicarboxylic acid or dimeric fatty acids. Compounds having ethylenically unsaturated groups, which are copolymerizable with the polycarboxylic acid include styrene, α-styrene, vinyltoluene, vinylpyrrolidone, vinylether, vinylester, divinylbenzene and di(meth)acrylic acid esters of diols, such as ethanediol, 1,3-propanediol and 1,4-butanediol. Most preferred are those polyesters containing styrene. Preferred are those polyesters containing up to 50 wt. %, more preferably from 10 to 50 wt. %, most preferably from 20 to 50 wt. %, based on the weight of the polyester matrix, of unsaturated functionality.
Suitable polyalcohols for the polyester matrix include glycols, such as ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,4-cyclohexanedimethanol, and trifunctional alcohols such as trimethylolpropane and glycerol.
Fillers and Other Additives
Suitable fillers and reinforcing agents that may be included in the composite of the present invention include both organic and inorganic compounds, for example, compounds such as glass in the form of fibers, flakes, cut fibers, or microspheres; silica; aluminum silicates; mica, sand, wollastonite; carbon fibers; carbon black; carbon black paste; talc; calcium carbonate; barium sulfate, kieselguhr; whiting; liquid crystal fibers; aramide fibers; and coarse-grained filler, such as gravel; quarry material; slag; comminuted rubble; and foam concrete. The inventive composite may include up to 90 wt. % filler, more preferably from 15 to 90 wt. % filler, most preferably from 50 to 90 wt. % filler, based on the weight of the composite. The filler may be present in the inventive composite in an amount ranging between any combination of these values, inclusive of the recited values.
Depending upon the particular application, the composites of the present invention may also contain other additives commonly used in the art including, but not limited to, leveling agents, wetting agents, flow control agents, anti-skinning agents, anti-foaming agents, viscosity regulators, plasticizers, pigments, dyes and UV absorbers. Stabilizers against thermal and oxidative degradation may also be included as needed.
Among the preferred applications of the inventive compositions are as spas, bath tubs, shower stalls, tub surrounds, sinks, table tops, and kitchen counter tops.
The present invention is further illustrated, but is not to be limited, by the following example. All quantities given in “parts” and “percents” are understood to be by weight, unless otherwise indicated.
A propoxylated hydroxypropyl acrylate, 3 parts (prepared according to U.S. Pat. No. 6,664,360 and having an OH# of 56.9 and a viscosity @ 25° C. of 123 cP) was added to 219 parts of a mixture of polyol blend and calcium carbonate (CaCO3@ 60% in final mixture, therefore 100 parts polyol blend and 119 parts CaCO3). The polyol blend contained 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (available from Eastman as TXIB plasticizer).
The solution was well mixed. The resulting material was combined with isocyanate (polymeric MDI, available from Bayer MaterialScience as MONDUR MR having an NCO group content of about 31.5%, a functionality of about 2.8, and a viscosity of about 196 mPa·s at 25° C.) at an isocyanate index of 105 (98 parts), mixed for 15 seconds and poured into a mold. The mold had previously been sprayed with an unsaturated polyester gel coat, VIBRIN G309-LA (available from Alpha Owens Corning, 25-30 wt. % styrene content), and partially cured until the surface was still tacky, but not so tacky as to leave material on a test stick used to test the surface. The mold was clamped shut. The part was allowed to cure for about one minute and removed from the mold.
The adhesion of the polyester gel coat to the polyurethane was measured using a hand operated adhesion tester, in which testing elements were glued to the surface of the gel coat. After the glue had dried, the elements were pulled at a right angle to the surface until the element with attached gel coat was freed from the surface. The force required to remove the gel coat from the substrate was measured and recorded. The gel coat adhesion of a composite with no monocarboxylic acid based polyether was tested and found to be <10 psi. The gel coat adhesion of the inventive composite with polyether containing both hydroxyl-functionality and unsaturation-functionality was tested and found to be 400-450 psi.
The foregoing example of the present invention is offered for the purpose of illustration and not limitation. It will be apparent to those skilled in the art that the embodiments described herein may be modified or revised in various ways without departing from the spirit and scope of the invention. The scope of the invention is to be measured by the appended claims.
